Download Zahn, M. and H.A. Haus, Contributions of Prof. James R. Melcher to Engineering Education, Journal of Electrostatics 34, pp. 109-162, March 1995

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Journal of Electrostatics 34 (1995) 109-162
Contributions of Prof. James R. Melcher to engineering
education
Markus Zahn*, Hermann A. Haus
Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology.
Cambridge, MA 02139, USA
Received 12 April 1993; accepted after revision 20 September 1993
Abstract
This paper reviews the teaching and research career of the late Professor James R. Melcher. It
describes his approach to the teaching of electric and magnetic fields bolstered by the lecture
demonstrations he had developed. He is considered the founder of the modern day field of
electrohydrodynamics. His undergraduate courses, reinforced by educational films which are
briefly described, gave students an introduction into the field. His graduate courses and
research extended more broadly into fluid mechanics, heat transfer, and physical chemistry. He
spoke and wrote on the need for a national energy policy and was concerned about the effect of
military expenditures on US commercial competitiveness.
1. Brief overview of career
Professor James R. Melcher, an engineer, scientist, and educator widely respected
for his practical applications of the principles of electromagnetism and continuum
electromechanics and a member of the Department of Electrical Engineering at the
Massachusetts Institute of Technology since 1962, died on 5 January 1991 at the age
of 54. At the time of his death, he was the director of the M I T L a b o r a t o r y for
Electromagnetic and Electronic Systems and was the Julius A. Stratton Professor of
Electrical Engineering and Physics. Considered an outstanding educator - he received
the Outstanding Teacher Award from the New England Section of the American
Society for Engineering Education in 1969 and the M I T Graduate Student Teaching
Award in 1978 - Prof. Melcher was noted for his dynamic lectures and as a leader in
teaching electromagnetic field theory and continuum electromechanics to both undergraduate and graduate students. Through his research and textbooks he is the founder
of the modern day field of electrohydrodynamics, the interaction of electric fields with
fluids. He was a critical judge of the quality of his students' work, but did not spare
* Corresponding author.
0304-3886/95/$09.50 © 1995 Elsevier Science B.V. All rights reserved.
SSDI O 3 0 4 - 3 8 8 6 ( 9 4 ) O O O 3 1 - X
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effort and concern in helping his students and colleagues reach the high standards that
he set for himself and them. He has deeply affected the lives, careers, and values of his
students and colleagues.
This paper will describe his major contributions to engineering education, as course
innovator and lecturer, and as research supervisor. It will also briefly describe his
personal qualities as an articulate, thoughtful, and intensely moral human being. A list
of his publications and of doctoral, engineers, masters, and bachelors theses that he
has supervised is given in the appendices.
James R. Melcher (JRM) was born in Giard, Iowa on 5 July 1936. He received
a BSEE in 1957 and a MS in Nuclear Engineering in 1958, both from Iowa State
University. He was a research assistant at the Ames Laboratory of the US Atomic
Energy Commission. His first journal paper, based on his master's thesis "A Useful
Analogy for Single-Group Neutron Diffusion Theory" [A.1] won the American
Nuclear Society's First Mark Mills Award. He came to MIT for his doctoral work in
electrical engineering, was a teaching assistant in the MIT Department of Electrical
Engineering, and received the Ph.D. in 1962. He was an Assistant Professor from
1962-1966, an Associate Professor from 1966-1969, and a Professor from 1969, all in
the Department of Electrical Engineering at MIT. He spent 1971-72 on sabbatical
with Sir Geoffrey I. Taylor at the Cavendish, Churchill College, Cambridge, England.
When a memorial was held in honor of Sir Geoffrey, JRM was invited as one of the
keynote speakers. They had first worked together at a MIT symposium on Electrohydrodynamics sponsored by the International Unions of Theoretical and Applied
Mechanics and of Pure and Applied Physics, from 31 March to 1-2 April 1969, where
Sir Geoffrey was Chairman and JRM was Secretary [A.32]. He was Director of the
MIT High Voltage Research Laboratory (HVRL) from 1980-1984, and then with the
merging of HVRL with the MIT Continuum Electromechanics Laboratory and the
MIT Electric Power Systems Energy Laboratory (EPSEL), to form the MIT Laboratory for Electromagnetic and Electronic Systems (LEES) he was briefly co-director
of LEES from September-December 1984 and then Director from January 1985 until
his death. Since 1981 he was also the first J.A. Stratton Professor in Electrical
Engineering and Physics, particularly appropriate because both he and Dr. Stratton
were inspired researchers and teachers of electromagnetism.
In his own words from his resume, he described his research interests as following:
"As an engineering science, continuum electromechanics draws upon the
areas of electromagnetics, fluid and solid mechanics, heat transfer, and physical
chemistry. Typically, electromagnetic fields are exploited for the control, sensing or augmentation of processes. Continuum electromechanics is interdisciplinary and has been shown to provide an overview that encourages the
development of techniques and viewpoints that are not only applicable to
systems coupled to electromagnetic fields, but to purely mechanical,
thermal and electrochemical systems as well. Some of these universal
viewpoints are described in the text Continuum Electromechanics I. Some
1J.R. Melcher,Continuum Electromechanics, MIT Press, 1981.
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
111
specific areas of research are electrohydrodynamics (augmentation of heat
transfer and mixing), magnetohydrodynamics (metals processing and hydromagnetic stability), continuum feedback control (continuum robotics),
sensors (electromechanical and electro-physiochemical), biophysical electromechanics (electromechanics of polymer membranes), microelectromechanical systems (for printing), electromechanical fluidized beds (airpollution control), macroscopic particle electromechanics in turbulent flows
(electrostatic precipitators, electrostatic paint spraying and insulator
contamination), insulation research (electrokinetics of liquid-insulator interfaces), electrically induced heating (for polymer processing) and electromechanical
energy conversion (including new types of rotating machines)."
His textbooks on both undergraduate and graduate levels had similar themes and
their content overlapped, although the material was presented at the appropriate
levels intended. Almost as valuable as the material presented are the problems at the
end of each chapter which greatly reinforce the text material and often provide
descriptions of practical applications. Homework problems were great learning experiences for his students. He took great care and effort in developing interesting and
solvable homework problems, for it was also a way to teach himself new material. He
did not feel that he completely understood a new concept until he could also formulate
an undergraduate level homework problem.
He received the following honors and awards:
1958
1969
1971
1971
1971
1977
1978
1981
1981
1982
First Mark Mills Award, American Nuclear Society
Outstanding Teaching Award, American Society for Engineering Education,
New England Section Western Electric Fund for Outstanding Teaching
Fellow, Churchill College, Cambridge, England
Young Alumnus Recognition, Iowa State University
Guggenheim Fellowship, Guggenheim Memorial Foundation
Fellow, Institute of Electrical and Electronic Engineers, "For contributions
to electrohydrodynamics and its practical application."
MIT Graduate Student Teaching Award, Electrical Engineering
Professional Achievement Citation in Engineering, Iowa State University
Julius A. Stratton Professorship in Electrical Engineering and Physics
National Academy of Engineering-for "applications of continuum electromechanical principles to engineering science advancements in electrohydrodynamics, magnetohydrodynamics and electrofluidized beds."
He was a member of the following professional societies: National Academy of
Engineering, Institute of Electrical and Electronic Engineers, American Physical
Society, American Chemical Society, American Society of Mechanical Engineers,
Electrostatics Society of America, Tau Beta Pi, Sigma Xi, and Eta Kappa Nu.
After his death, the Electrostatics Processes Committee of the IEEE Industrial
Applications Society named its Paper Recognition Awards the James R. Melcher
Prize Paper Awards, "in tribute to a truly great electrical engineering researcher and
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teacher of our times." Their statement included "Professor Melcher is known for his
contribution of several highly original papers to the electrostatic processes
technology, some of which were prize winning papers. The high quality of both
his written manuscripts and oral presentations established a level of technical
excellence that has served as a standard for the profession." Papers [A.76, A.77,
and A.91] listed in his resume in Appendix A won IEEE IAS Paper Recognition
Awards.
2. Undergraduate education
2.1. Electromagnetic fields
2.1.1. Educational approach
With the second author of this paper, JRM developed the junior level MIT course
and textbook Electromaonetic Fields and Energy [A.34, A.93, B.4] described in the
MIT catalog as follows:
Maxwelrs equations and the Lorentz force law. Quasistatic forms of Maxwell's equations. Studies of electroquasistatic fields and their sources through
solutions of Poisson's and Laplace's equations. Steady conduction and polarization. Charge relaxation. Magnetoquasistatic approximation; magnetic
boundary value problems, magnetization, induction, current induced in
stationary and moving conductors. Electric and magnetic forces derived from
energy. Electromagnetic waves. Extensive use of engineering examples.
The traditional approach emphasizes statics in order that students master mathematical methods. This approach permits the introduction of only few stimulating
engineering examples. By allowing fields to be time varying, many more interesting
examples can be brought in, and lecture demonstrations are more easily constructed.
For a major part of the course, the variation with time is "slow", so that the problems
can be treated as quasistatic; electroquasistatic if the electric fields predominate,
magnetoquasistatic when the magnetic fields predominate. At first, electromagnetic
waves are unimportant, yet the electric and magnetic fields are never static because of
time varying sources, typically sinusoidal, because of geometry changing with time, or
because media introduce their own dynamics. For example, in semiconductor devices
the inertia, mobility, and diffusion of charge carriers introduce their own important
dynamics, not the electromagnetic waves. The course teaches the student that electric,
magnetic, and electromagnetic devices and systems can often be described by either
neglecting the magnetic induction or the displacement current density in Maxwell's
equations. Recognition of these two limits is part of the art and science of modeling: of
making the simplifications necessary for physical insight, for formulating an analytic
or numerical treatment, or for extracting the essential features of a process as a guide
to invention. JRM drew almost all the figures for his papers and books. Fig. 1 shows
his sketch from the textbook [B.4] of a representative summary of how he viewed
applications of his work.
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M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
\ /
\
C
[3
\
.~
\
7~"~
F
Fig. 1. Melcher's drawing of quasistatic and electrodynamic fields in the physical world.
2.1.2. Lecture demonstrations
The acceptance of time-varying fields into an introductory course on electric and
magnetic fields allows for a wealth of lecture demonstrations to be used throughout
the course, described in the text, which makes the mathematical analysis take on
physical meaning. Based upon relatively simple configurations and arrangements of
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equipment, the demonstrations make a direct connection between what has been
analytically derived and what is observed. Often accompanied by a plot of the
theoretical predictions that can be compared to data taken in the classroom, they give
the opportunity to test the range of validity of the theory and to promulgate
a quantitative approach to dealing with the physical world. In the MIT classroom, the
demonstrations are presented "live", but many of the demonstrations have also been
videotaped, presenting enough overview of the theory, documentation of the experimental procedure and data, and summary graphics to stand alone from the textbook
[C.4]. These tapes are used to train new teaching staff and for review at the students
convenience and on campus cable television. The undergraduate students in the
course are urged to view the tapes as study aids before exams while graduate students
are urged to view the videotapes in their preparation for qualifying exams. These tapes
are used as supplements to the electromagnetism course at many universities throughout the world, and an abbreviated version with the most fundamental demonstrations
are given with the Software Book, Vol. I by the NSF/IEEE Center for Computer
Applications in Electromagnetics Education (CAEME) [A.99, 1].
Throughout the course, in lecture, recitation, tutorial, or homework, practical
applications are used as examples, typically including: vacuum tube and semiconductor diodes; drift/diffusion conduction in semiconductors; electric and capacitance
microphones; electrocardiograms; magnetic tape recording and playback; transformers, motors, generators, and power dissipation reducing laminations in AC
devices; induction and dielectric heating; driver for a dot matrix printer; dielectric
waveguides and optical fibers; Helmholtz coil; transmission lines, waveguides, and
antennas; superconductors; circuit elements of resistance, inductance, and
capacitance; binding energies in atoms and crystals; electric and magnetic forces;
electrostatic precipitation; electrostatic generators; high-voltage insulating bushings;
Hall effect probes; mass spectrograph; cyclotron and betatron; magnetohydrodynamic machines; and charged particle beams.
2.1.3. Connecting fields to circuits
The course builds on and reinforces an understanding of analog circuits. Dynamics
are typically illustrated with step and sinusoidal steady-state responses in linear ohmic
media of dielectric permittivity e, magnetic permeability/~, and ohmic conductivity a,
so that time-dependent quantities obey ordinary linear differential equations with
constant coefficients. The approximations inherent in the development of circuit
theory from Maxwelrs equations are brought out very explicitly, so that the student
appreciates under what conditions the assumptions implicit in circuit theory cease to
be applicable. Development begins with capacitors with charges and their associated
electric fields, equipotentials to represent perfect conductors and steady ohmic conduction to represent resistive losses. The student appreciates how EQS field dynamics
with the representative time scale Te = e/a are like resistor--capacitor (re = RC) dynamics. The same approach is used with inductors with currents and their associated
magnetic fields to show how MQS systems with the representative time scale
Tm= #trl z follow resistor-inductor dynamics (Zm = L/R) where l is a typical length
scale of the system.
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
115
~L
I Eos.1
L
r Mos-1
I
Te Tem
Co)
±
i
Tm
Tm Tem
I
±
Te
(0)
Fig. 2. As the angular frequency o) is raised, an electromagnetic system is first (a) EQS if z, > Zm and is (b)
M Q S if zm > re. The representative EQS system in (a) has a voltage source driving a pair of perfectly
conducting spheres having radius and spacing with the same typical length L. The representative MQS
system in (b) has a perfectly conducting loop driven by a current source having radius and width with the
same typical length L. For quasistatic systems, it is necessary that system dimensions be much smaller than
the radiating wavelength (L ,~ 2, 2 = 2~c/o.~ and c = [e/~]- 1/2 is the speed of electromagnetic waves).
In the quasistatic limits the course focuses on the use of superposition of sources
and on solutions to Laplace's equation for planar layers, cylinders and spheres. With
very simple geometries and general solutions to Laplace's equation, a wide range of
EQS and MQS problems, duals and anti-duals, are solved.
Electromagnetic waves in loss-free media are examined in their distributed inductive (L henries/meter)-capacitive (C farads/meter) circuit analog with representative
time-scale of zero--l[lal;'] 1/2 = I [ L C ' ] 1/2 equal to the wave propagation time across
a system of length I. Lossy material is then introduced as an analog to RLC circuits.
Drawing on EQS, MQS, and electrodynamic characteristic times and lengths, rem is
the geometric mean of the time constants re and Zm, Zero= [ZeZm]1/2. This is why the
world can often be either EQS or MQS, but not both as either re or Zmis smaller than
Zem. AS illustrated in Fig. 2(a) for large R (small or), EQS dynamics comes first as the
frequency co is raised, followed by electrodynamics. For small R (large a), Fig. 2(b)
shows that MQS dynamics comes first as the frequency is raised, followed by
electrodynamics. Implicit is the enormous difference between what is meant by
a perfect conductor in EQS (constant electric scalar potential) and MQS (constant
magnetic vector potential) systems. The condition when a system is neither EQS nor
MQS occurs when the system size is such that re = "lTm~--- "Cem SO that l* = [-g//2]1/2/o ".
As shown in Fig. 3, systems having a length I < l* are EQS while systems having I > l*
are MQS. The MQS and EQS regimes in Fig. 3 both reduce to quasistationary
conduction (QSC) at low frequencies such that both ogze ~ 1 and ~Orm~ 1.
Although most of JRM's professional research contributions were in quasistatic
limits, he was a ham radio operator and thus very knowledgeable about electrodynamics, both theory and practice. He carried on regular worldwide radio
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Qoq r
Icur6=l ~rern "-I
Fig. 3. With characteristicsize scale I* = [e//~]~/2/a,systemsare EQS if the system length scale I < l* and
are MQS if I > l*. The MQS and EQS regimes both become quasistationary conduction (QSC) at low
frequenciessuch that both o~Te~ 1 and o~r~,~ 1.
communications with his family and friends. His backyard hosted a tall antenna
tower, that his students often helped install, maintain, and improve with a home
barbecue as the payoff. This hobby attracted students who were already hams to work
with him, as well as encouraged other students to become hams. He performed some
consulting work concerning high frequency electrical signal propagation through the
mud surrounding an oil well. He verified key assumptions of his model by performing
experiments in his backyard swimming pool. JRM devoted a major amount of time to
the successful development of electrodynamic demonstrations, even though his course
only briefly introduced this material. He did this in part for use in the subsequent
course Electrodynamics, but mainly it deepened his understanding of radio phenomena.
2.1.4. Magnetization: the Chu formulation
Another distinction in the course presentation was the use of paired magnetic
charges, magnetic dipoles, rather than Amp6rian currents as the source of magnetization. In this approach, when polarization and magnetization are incorporated into
Maxwell's equations, they become essentially symmetric (except for some minus
signs). L.J. Chu exploited the symmetry in order to facilitate the introduction of
magnetization by analogy with polarization [2]. This approach was criticized because
the dipole moment of the electron, the main source of ferromagnetism, is associated
with the spin of the electron, and thus seems more appropriately pictured as a circulating current.
Tellegen I-3] took issue with this approach and gave a derivation of the force on
a current loop (the Amp6rian model of a magnetic dipole) and showed that it gave
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
117
a different answer from that on a magnetic dipole. The difference was small, relativistic
in nature occurring only in the presence of a time-varying electric field, and thus
difficult to detect in macroscopic measurements. However, if the criticism was valid,
the treatment in terms of magnetic dipoles would be suspect.
It turned out that Tellegen's analysis was in error because the time-varying electric
field produces changes in a constant circulating current that causes an additional force
that cancels the critical term [4]. Both models of a magnetic dipole yield the same force
expression and thus are a matter of taste. The magnetic charge model is simpler, because
a dipole at rest has no moving parts, whereas a current loop contains moving charges.
2.1.5. Computers and fields
JRM encouraged the use of computer instruction to improve the teaching of
concepts and for exposure to practical examples. He was especially interested in
computer animated dynamic presentations where the field distributions evolve, using
the screen to represent the spatial distributions and real time to represent evolution in
time. He used computer animation of evolving dispersion relations in synchronism
with experiments in his films Complex Waves I and II [A.31, C.1, C.2]. With the
advent of the MIT computer network, Project Athena, he incorporated the use of the
computer into the classroom and for use with homework assignments. The field
concepts introduced in the course were a natural basis for numerical approaches using
the method of moments as the superposition integral approach to boundary value
problems, and energy methods for the finite element approach. With improvements to
computer capabilities, it was possible to take detailed account of geometric effects in
routine engineering design. However, he stressed that even with these computer tools,
a firm conceptual base was essential to the engineer to attack nonstandard problems.
Even with numerical analysis, the engineer must comprehend the physical phenomena
at work.
2.2. Electromechanical dynamics
2.2.1. Educational approach
JRM's development of the electromagnetism course came from his mature understanding of the fundamentals. His course and textbook developments began in the
mid 1960s with the MIT course Fields, Forces, and Motion and the associated three
volume text, Electromechanical Dynamics lB.2, A.28], co-authored with H.H. Woodson, his doctoral thesis supervisor.
The course description that Jim wrote for the MIT catalog provides
an accurate summary:
Fields, Forces, and Motion
Electromechanical interactions in lumped-parameter and continuum systems. Integral and differential electromagnetic laws, including motion. Lumped electrical and mechanical elements; thermodynamics of discrete electromechanical coupling, equations of motion. Synchronous and induction
rotating machines. Linear and nonlinear transducers, transient and steady-
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
118
state dynamics; electromechanical time constants. Field transformations, dc
rotating machines, magnetic diffusion and charge relaxation in moving conductors. Electromagnetic force densities and stress tensors.
The course and text begins with a fields viewpoint of capacitive and inductive
geometries, but where one or more of the surfaces could move. If the geometry is
a function of position x, and if this position is a function of time, then the capacitance,
C(x(t)) and inductance, L(x(t)), are also functions of time and the usual linear
constitutive laws relating charge q to voltage v and flux 2 to current i are:
q-- C(x)v;
(1)
2 = L(x)i,
so that the voltage/current relationships become
i = dq/dt = d[C(x(t))v]/dt;
v = d2/dt = d [ L ( x ( t ) ) i ] / d t .
(2)
Upon expansion of the derivatives, the extra terms over the usual circuit descriptions,
proportional to the speed of the moveable members, dx/dt, are due to the electromechanical coupling. An energy method description like that used in thermodynamics is developed and applied to various actuators and rotating machinery. The
effects of ohmic loss are included with charge relaxation and magnetic diffusion.
A formulation of electric and magnetic forces culminates in the teaching of the
Maxwell stress tensor. Then the course concludes with applications of electric and
magnetic forces on charged and current carrying strings, membranes, and jets, tying
together elastic waves and the issues of wave propagation, evanescence, absolute
instability and convective instability (amplifying waves). Using such simple electromechanical systems, he teaches and demonstrates the physics of such analogous
complex systems as elastic, acoustic, and electromagnetic waveguides, gaseous and
solid-state plasmas, lasers, electron beam oscillators and amplifiers, microwave magnetics, supersonic flows of gases, and supercritical flow of rivers.
The course covers the first two volumes. The third volume of the text has hardly
been used in courses, but is a valuable reference for electromechanical coupling to
bulk elastic waves, and the thermodynamics of magnetohydrodynamic machines.
Associated with this course, JRM produced three educational films:
(a) Complex Waves I: Propagation, Evanescence and Instability [-C.1, A.31];
(b) Complex Waves II: Instability, Convection and Amplification [C.2, A.31];
(c) Electric Fields and Moving Media [C.3, A.39].
2.2.2. Complex waves (the films)
Using elastic waves on a simple string, the dispersion relation between complex
frequency o9 and wave number k, is demonstrated by allowing the string to carry
current in a magnetic field or to be charged in an electric field. String deflections are
taken to be of the form
6(x, t) = Re oeexp [j (ogt - kx)].
(3)
The dispersion relation, o9(k), evolves by computer animation on the bottom half
screen in synchronism with changes in the physical phenomenon in the top half screen
as shown in Fig. 4. Such simple configurations model more complex physical systems
Fig. 4. (a) Coils on either side of a centered string carry equal currents in the same direction so that the magnetic field in the center is zero increasing
approximately linearly to either side of the string. The string also carries a current I in the direction opposite to the currents in the coils. A deflection of the string
results in a magnetic restoring force; (b) With I = 0 and the frequency and amplitude of a displacement drive on the right fixed, ordinary waves propagate here
shown with the string nearly in resonance;(c) As 1 is increased beyond a cutoff value, evanescent waves result and the string displacement decreases exponentially
from the source; (d) If the current I is reversed to be in the same direction as the coil currents, the magnetic force is destabilizing, here shown with I greater than
required for instability and the string bows to one side or the other.
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but by keeping the mathematical development simple by reducing the governing
partial differential wave equations to linear constant coefficient ordinary differential
equations, it became possible to understand complex physics without obstruction by
difficult mathematics.
For ordinary elastic waves on a string under tension, described by the wave
equation, waves of all frequencies have the same velocity and any disturbance
propagates without changing shape in either direction. He developed the familiar
notion of dividing the response into two parts - one due to the drive, the driven
response, and one due to initial conditions, consisting of a superposition of natural
modes.
(a) Evanescent waves. Evanescent waves, the phenomenon of spatial decay without
dissipation, are illustrated by making the elastic string carry a current in a nonuniform magnetic field so that any string deflection results in a restoring Lorentz force
that tends to exert a force in the direction opposite to the string deflection as in Fig.
4(a), with the dispersion relations shown in Figs. 4(b)-(d). The natural response is
found by assuming the string of length l is fixed at both ends, so that the natural
modes require wave numbers given by k = mr/l, where n is an integer, so that the
magnetic restoring force raises the natural frequencies. For one end of the string
driven at a sinusoidal frequency below a critical value, the resulting wave number is
imaginary representing a spatial distribution that decays exponentially away from the
source, Fig. 4(c). These cut-off waves are common in acoustic and electromagnetic
waveguides.
(b) Absolute instability. An absolute instability results by reversing the direction of
current as now the magnetic force on the string also reverses so that any string
deflection results in a force in the same direction of the deflection, tending to increase
the deflection further. The resonant frequencies are lowered by the magnetic force. If
the magnetic force is large enough, a resonant frequency is driven through zero to
imaginary values, representing exponential growth in time rather than sinusoidal
oscillations for real frequencies. In the experiment, the current is first below the
threshold for instability and a plucked string vibrates in its lowest natural mode,
reduced from the value with no current. With the current increased beyond the
threshold, no matter how carefully the string is released from a centered position
where the magnetic force is zero, it deflects to one side or the other, Fig. 4(d).
The EQS analog is also demonstrated in Fig. 5, where a conducting string is
centered between plane, parallel electrodes each at potential V with respect to the
grounded string. With the string centered, surface charges are induced on both sides of
the string and the net force on the string is zero. However, a slight deflection of the
string leads to a charge excess on one side, so that the net electric force acts to further
increase the deflection, again leading to an absolute instability.
Absolute instabilities are typically found in plasmas and fluids as they interact with
electric and magnetic fields, most widely known in fusion machines.
(c) Moving media. The elastic string is replaced by a moving jet of water with
surface tension, which can be modeled as a moving, perfectly conducting elastic string.
If the jet velocity, U, is less than the wave phase velocity, v, the effects of evanescence
and absolute instability are similar to that described in (a) and (b) with the wave
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
121
(a)
(b)
Fig. 5. (a) A conducting string that is grounded is placed between two electrodes each at voltage V: (b) As
the voltage V is increased, the static equilibrium becomes unstable.
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traveling in the same direction as the convection having its phase velocity increased to
U + v, and the wave traveling in the opposite direction to the convection having
reduced phase velocity, U - v. Because the wave equation is second order in space,
the solution at any point is determined by two boundary conditions, one upstream
and one downstream. However, if the jet is "supersonic" so that its velocity U is
greater than the wave phase velocity v, both waves travel in the direction of convection, and the waves interfere spatially to form a stationary sinusoidal envelope or
"beats". Now both boundary conditions must be specified upstream to determine the
solution at downstream locations.
Material convection and instability are brought together by centering the grounded
jet between parallel plate electrodes at potential V in Fig. 6(a). For a real frequency,
the wave number is complex, with one root growing exponentially in space-wave
amplification, as shown in Fig. 6(b).
The art of electron-beam engineering, with its traveling wave tube amplifiers and
backward wave oscillators, uses space charge waves on a streaming electron beam to
interact with a fixed transmission line. Such a graphic impression is produced in the
film using a charged water jet coupled to a fixed string to make an oscillator, shown in
Fig. 7.
2.2.3. Electric fields and moving media
In the teaching of fundamental field theory, case studies comparing theory and an
experiment are rare. Jim gave a "sparkle" to his lectures by letting the student see the
consequences of the field and charge distributions, in otherwise lack-luster examples,
such as a cylindrical conductor or insulator in a uniform electric field. With the
expenditure of a very few minutes during a class, an experimental demonstration turns
an academic discussion into a highly motivating experience. The experiments presented in "Electric Fields and Moving Media" [A.39, C.3-I were intended to be used as
demonstrations and electromechanics subjects together with analytical models. In the
EQS demonstrations in the film, magnetic induction is unimportant and the phenomena were due to free charge and polarization forces in ohmic media.
The crucial role played by charge relaxation is illustrated with a conducting sphere
bouncing between parallel plate electrodes, comparing the use of slightly conducting
and highly insulating oils described by conductivity tr and permittivity e. The application of high-voltage charges the sphere when it rests on the lower electrode. The
resulting Coulomb force causes the sphere to rise but the slightly conducting oil
causes the charge on the sphere to leak away and the sphere returns to the lower
electrode by gravity where the process repeats. Particle motions are also shown to
lead to electrical breakdown, a major factor in limiting the performance of highvoltage insulation.
The electric field induces a force which causes a motion resulting in the convection
of charge. The electric Reynold's number, Re = ~v/trl, describes when charge convection is important for material moving with a characteristic velocity v to move
a characteristic distance I.
The effect of charge convection on the electric field is illustrated by a series of
experiments using charged water drops as the charge carriers. Grounded jets of water
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
123
(a)
(b)
Fig. 6. (a) The string of Fig. 5 is replaced by a jet of water with surface tension; (b) The experiment and
dispersion relation show an amplifying wave with complex k for real co.
124
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
Fig. 7. (a) The jet interacting with a fixed string between electrodes;(b) spontaneous oscillatoryinstability
similar to that found in an improperly terminated traveling-wavetube, with the jet playing the role of the
electron beam and the string playing the role of the slow-wavestructure.
break into drops as they pass through a metal "inducer" ring at a potential. The drops
break away with a net charge which they carry to an insulated pail below. One
kilovolt on the ring results in a generated voltage of about 10 kV on the water in the
pail. This is similar to the operation of a van de Graaffgenerator, where a moving belt
replaces the falling water drops. By connecting two such drop generators together,
a self-excited dynamo, first due to Lord Kelvin, generates about 20 kV [5]. Then using
three water drop generators, as in Fig. 8, three phase AC is spontaneously generated.
Similar processes of drop charging may be present in atmospheric electric phenomena.
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
125
Fig. 8. A high-voltage AC water dynamo of 3 streams which generalizes Kelvin's original 2 stream DC
dynamo. The droplet streams pass through induction charging rings and are then collected in barrels. Each
ring is connected to the water in a neighboring barrel. The spontaneous buildup of low frequency
alternating charge on the streams is evident from their oscillatory spreading and collapse.
Free charge accumulates at interfaces between conductors of different uniform
conductivities. In an electric field, such charged interfaces can move as illustrated by
Taylor's pump in Fig. 9 [A.20]. Similarly, a cylinder placed within a slightly conducting fluid in a uniform electric field similarly acquires surface charge, as in yon
Quincke's rotor of Fig. 10. If the cylinder has dielectric relaxation time longer than
that of the surrounding fluid, at a critical DC voltage, it spontaneously rotates. The
surface charge distribution has positive charge near the positive electrode and negative charge near the negative electrode. Such a charge distribution is unstable, similar
to a compass needle oriented backwards in a magnetic field. The rotor tends to rotate
to try to reverse the orientation of the dipolar surface charge. Steady rotation develops
as the electrical relaxation compensates for the transport of surface charge by
rotation. Cellular motions on fluid interfaces as in Fig. 11 are due to similar interplays
between convection and conduction currents.
The electric Reynolds number relates relaxation, re = e/a, and transport times,
rt = l/v. The period of an alternating sinusoial voltage provides another dynamical
time. With a traveling wave voltage, surface charge is induced on a nearby interface.
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
126
,
2
l ~,e'E,Ey]]
: "-__'
~
x
[
I
h
(
I
y
i.b'il::;:i:.:::".::.;i
:
:
;:".; i .:ii:.i::~.:
I
Y=O
n. Vo
~
;_L-.-J.:
'.
.,.,~v; tp,,. - "
'/ax
~
7
)
o
:..:.
I":!.";L;
::.:.":i :.::."i-.-".".:
".;.:)i.;;:.:.::i :::i :.:.!i( ;": !--i": :: i i!-':'."";'. ~;.i;.!::": :.
(o)
y: q.
Fig. 9. Taylor's pump showing conducting liquid layer with contacting electrodes at left and right and slanted
electrode to induce a uniform distribution of surface charge on the interface. The uniform electric field in the
liquid exerts a shearing surface force on the charged interface to the left and causes the cellular convection.
At very low frequencies, the electrical shear force is small because the tangential
electric field is small while at high frequencies, the surface charge does not have time to
significantly form on the interface over the course of a sinusoidal cycle. If the region
between the traveling wave voltage and the interface has longer relaxation time than
the fluid layer, the force is in the same direction as the traveling wave motion. If the
intervening m e d i u m has shorter dielectric relaxation time than the fluid layer, then the
force is in the opposite direction. With the fluid more insulating than the intervening
region, positive charges at a given point on the electrode structure induce charges of
the same sign in their local n e i g h b o r h o o d on the nearby interface, resulting in a force
of repulsion and driving the fluid in the opposite direction to the traveling wave.
This interfacial m o t i o n can also occur in the fluid bulk if the conductivity is
a distributed function of position, such as is the case with a fluid with a temperature
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
I
127
I
corn
electrodes,
----
--"
Eo
Eo
oil
teflon
/
(a)
..E-
(b)
!
+
3-
~P"
-
D
Fig. 10. (a) Von Quincke's rotor consisting of a highly insulating cylinder, free to rotate, that is placed in
slightly conducting oil between parallel plate electrodes. As DC voltage is raised, at a critical voltage the
rotor spontaneously rotates in either direction; (b) The motion occurs because the rotor charges like
a capacitor with positive surface charge near the positive electrode and negative surface charge near the
negative electrode. Any slight displacement of the cylinder in either direction results in an electrical torque
in the same direction as the initial displacement.
gradient and whose conductivity varies with temperature. A conductivity gradient
leads to a volume charge distribution and a volume C o u l o m b force with an electric
field [-A.21].
Polarization forces can exist even in the absence of net free charge. An experiment
involving polarization forces is shown in Fig. 12. C o n d u c t i n g transparent electrodes
are used as diverging capacitor plates and dipped into a dielectric fluid [A.36]. T h e
electrodes impose an essentially tangential electric field to the fluid interface so that
there is no free surface charge on the interface, yet the fluid rises between the
electrodes as the voltage is raised. The high dielectric constant fluid is most attracted
where the electric field is highest, that is, at the left where the capacitor gap is smallest.
C o m b i n e d free charge and polarization forces act on the current carrying jet of
Fig. 13 I-A.30]. T h e surrounding plates at a constant potential induce the opposite
polarity surface charge on the jet. T h e electric field in the jet exerts a tangential surface
force on the jet via the free surface charge and a n o r m a l force due to the difference in
permittivities on either side of the jet interface. If the shear electrical force accelerates
the flow, the jet necks down, as in Fig. 13(a). Reversing either the polarity of the
128
M. Zahn, H.A. Hausf.lournal of Electrostatics 34 (1995) 109-162
(a)
A
B
x
,,
k',-
; , . -,~,,
j.
I+~-v
L L-v
,,.
L½v
d
I
2 Tr/kr d
.......'!
-:..
,-~..
.. " " "
1"-~_
-
"
.:'-"
::'~::'..
k:.::i:(t.::1.:.:.(-);.:{":7.:::::::-77~1(:::!::.;.::~7:;7~ 7:~"::i1{:7:x: ;..:;v.:...:..:~.Ti:7:-..:.::.-.i..;..t.::.~1..: ,7~~.~
'
: ,•. . l , . . u
'
i
".-..
: , : . t 4 . . , . : , ""...': : . . : ' . . : - . : , . , ' , :•: :.,"
.......
'
"":..." '.' .'." .'"b ".'. ;'"
+~V
external flow(l)
')"
• . . ...,-.-."
'., i:..::~
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.,, . ...-
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.
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interaction,
/ region ,
. ,.' . .: .,. -.. . '. - . . ,:. . : .',...',:::,-
. . . .
-'W
external flow(r)
".
. ,. [ .b . : : ..". ' i l l
i
I
(/
r(y)
~\
7-:.:5".:.'
9
:-.
~
~:.::.!.!--7:-:...;:: ....:.-...- Uoeoskyy
P (z)17.':::'..:t::..:: . ~ ! pr...:.,':%.~
pr(z)
• ;)i~iii!:.::.~~!/
I:'::':~." ".'." " :.
I'r'.'.,:.:::" "...,:::
......
'.:.':':.';',
!.:::
:1
.'.': ".
,~i.:..:7:):::..:- .:{.':.::.:-;i
i ::,::,:.: • ...) .u.-
:': .. :'.'~".'.:7
+;v ~ - - . v
(b}
Fig. 11. (a) A layer of slightly conducting liquid bounded from above by air and below by strip electrodes
of alternate polarities. (b) Electrical shear stresses at the interface tend to pump the liquid in a cellular
pattern, here seen looking down on the interface.
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
129
7
lg
,,~Ir)
"-
Fig. 12. Diverging transparent conducting plates stressed by a DC voltage draws dielectric liquid upwards,
with a height proportional to the square of the electric field so that the height is greatest where the electrode
gap is least.
Fig. 13. Current driven jet of glycerin results from imposing high voltage between orifice at top and
electrode at bottom. Ring electrodes around the jet control the sign of surface charge induced on the jet
surface. (a} Jet accelerated by downwards electric shearing force and (b) with reversal of polarity of either
ring voltage or orifice voltage the electric force is also reversed to decelerate the jet.
130
M. Zahn, H.A. Haus/dournal of Electrostatics 34 (1995) 109-162
~corn
(a)
(b)
(c)
Fig. 14. (a) Heavy liquid above lighter liquid is stabilized against gravity by means of polarization forces
induced by applying a non-uniform tangential electric field to the interface by using diverging transparent
electrodes. (b) Electric field on and (c) Rayleigh-Taylor instability when electric field is turned off.
surrounding electrodes or of the electric field in the jet, but not both, will reverse the
electrical shear force and decelerate the jet thereby increasing its diameter, as in Fig. 13(b).
An example of non-uniform electric field stabilization is shown in Fig. 14 where for
stabilization of a more dense fluid over a less dense fluid, the upper fluid in the strong
field region must have a higher dielectric constant than the lower fluid. When
the voltage is removed, the more dense fluid falls because of the Rayleigh-Taylor
gravitational instability. This experiment is shown in the film Complex Waves II as an
example of an absolute instability.
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
131
3. Graduate teaching
3.1. Continuum electromechanics
3.1.1. Educational approach
JRM developed a two semester graduate course sequence and textbook to teach
widely applicable basic laws of electromagnetism interacting with solid and fluid
media, together with models and mathematical techniques for analysis [B.3]. It
started out as an introduction to the subject of electrohydrodynamics, to reflect his
research interests, but during his 1971-72 sabbatical as a Guggenheim Fellow and
a Fellow of Churchill College, Cambridge University, England, the objective was
broadened toward the disciplines of continuum mechanics. JRM achieved great
satisfaction and motivation from seeing his ideas serve the needs of industry. His
consulting activities for more than 30 companies provided many useful examples
and he was happy to see the concepts presented in his book and course applied
to the development of new energy systems and to the problems of environmental
control.
The course descriptions in the MIT catalog provide a concise summary of topics
covered in the courses:
Continuum Electromechanics I
Quasistatic field dynamics. Transfer relations as an approach to field
descriptions. Electromagnetic forces, force densities, and stress tensors, including magnetization and polarization. Classification of energy-conversion
processes. Charge migration and relaxation, and magnetic diffusion and
induction interactions with material motion. Introduction to electromechanics of continua. Temporal and spatial modes. Spectral numerical
techniques. Method of characteristics. Varied applications.
Continuum Electromechanics II
Laws, approximations, and relations of continuum mechanics. Mechanical and electromechanical transfer relations. Statics and dynamics of electromechanical systems having a static equilibrium. Electromechanical flows.
Field coupling with thermal and molecular diffusion. Electrokinetics.
Streaming interactions. Applications to materials processing, magnetohydrodynamics and electrohydrodynamic pumps and generators, physiochemical
systems, heat transfer, continuum feedback control, electron beam devices,
and plasma dynamics. Emphasis on microfabricated systems.
3.1.2. Physical and mathematical modeling
In addition to developing physical understanding of diverse phenomena, the course
and text emphasized the need to develop approximate mathematical models and their
analytical solutions if possible, and numerical solutions if necessary. He believed in
quantitative as well as qualitative understanding with three classes of approximations:
time-rate, space-rate, and amplitude parameter expansions.
132
M. Zahn, H.A. Haus/dournal o f Electrostatics 34 (1995) 109-162
Table 1
Characteristic time constants for systems having a typical length l
Time
Nomenclature
Electromagnetic
Ter n =
"C©=
Electromagnetic wave transit time
Charge relaxation time
Magnetic diffusion time
Particle migration time
l/c
g/O"
Zm = #tTl 2
Zmtg= l/bE
Mechanical and thermal
Acoustic wave transit time
Viscous diffusion time
Viscous relaxation time
Molecular diffusion time
Thermal diffusion time
Za = I/a
zv = pl2/tl
zc = ~l/pa 2
TD = 12/x
rr = 12pcv/kr
Electromechanical
Electroviscous time
Magnetoviscous time
Electroinertial time
Magnetoinertial time
ZEv = tl/eE 2
ZMv = tl/#H 2
z~t = IV/~/~E 2
zMi = I x / - ~ H 2
Table 2
Dimensionless numbers as ratios of characteristic times. The material transit or residence time is ~ = l/U,
where U is a typical material velocity
Number
Symbol
Nomenclature
Re
Rm
Electric Reynolds number
Magnetic Reynolds number
Za/Z = U/a
Zv/Z = plU/tl
ZD/Z = IU/x
zr/z = pcvlU/kx
M
Rr
RD
R~
"CD/Tv :
Po
Mach number
Reynolds number
Molecular Peclet number
Thermal Peclet number
Molecular-viscous Prandtl number
Thermal-viscous Prandtl number
Electromagnetic
ze/z = ~U/la
z~/z = l~alU
Mechanical and thermal
rl/Pko
zr/rv = %tl/kv
PT
Electromechanical
~JZEv;
"rd*Ev
z~/zv = qlltr/p
He
Pm
Magnetic Hartmann number
Electric Hartmann number
Magnetic-viscous Prandtl number
T i m e - r a t e e x p a n s i o n s a r e u s e d w h e n t e m p o r a l rates o f c h a n g e o f i n t e r e s t a r e s l o w
c o m p a r e d to o n e o r m o r e c h a r a c t e r i s t i c t i m e s d e s c r i b i n g s u c h d y n a m i c a l p r o c e s s e s as
in T a b l e 1. I m p o r t a n t d i m e n s i o n l e s s n u m b e r s f o r m e d as r a t i o s o f t i m e c o n s t a n t s , as in
T a b l e 2, d e f i n e i m p o r t a n t r e g i m e s w h e r e s i m p l i f y i n g a p p r o x i m a t i o n s c o u l d be m a d e .
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
133
Space-rate expansions lead to quasi-one or two-dimensional spatial models, also
known as long-wave models. Here fields or deformations in a "transverse" direction
can be approximated as being slowly varying with respect to a "longitudinal" direction.
Amplitude parameter expansions are carried to first order in linearized models. Often
they are used to describe dynamics departing from a static or steady equilibrium.
The course begins with Maxwell's equations in the Chu formulation, in integral and
differential form, with magnetization, polarization, and material motion. He formally
derives the conditions for the EQS and MQS limits, develops the Galilean transformations between inertial frames, and derives generalized boundary conditions
including electrical double-layer effects so that the tangential component of electric
field can be discontinuous, being proportional to the surface gradient of the surface
double-layer density.
He derives the lumped parameter EQS element of capacitance and MQS element of
inductance, generalized to elements with deformable geometry, and then develops an
energy conservation formulation with the thermodynamics of discrete electromechanical coupling to find forces. He then generalizes the analysis to find the
force densities and stress tensors in continuous media. He considers and compares
force density and stress tensor descriptions using microscopic models and energy
conservation principles. He shows that for an isolated object in free space, the total
force is the same for all models as the free space stress tensors are the same for all
models. He also shows that for incompressible media, that force density terms described
by a gradient of a scalar have no effect on the motion, only on the pressure distribution.
A major technique that JRM pioneered for multi-layered systems, was the use of
generalized prototype layers relating pertinent interfacial variables at two interfaces in
planar, circular cylindrical, and concentric spherical geometries, such as those shown
in Fig. 15. Since these variables appear in the boundary conditions at the interfaces
between layers, analysis of multi-layered systems is greatly simplified by splicing
together generalized interfacial relations thereby avoiding the redundancy of solving
the same bulk equations in each layer. Many different boundary value problems,
could be essentially solved simultaneously, only requiring specification of the pertinent boundary conditions. This generalized approach was used to relate interfacial
variables in many diverse coupled systems such as relating tangential and normal
electric and magnetic field components to interfacial scalar and vector potentials;
relating perturbation pressures and viscous stresses to interfacial fluid velocities in
inviscid and viscous, incompressible and compressible fluids; and relating heat fluxes
to interfacial temperatures.
In many practical situations, excitations are periodic in one or two spatial directions, and in time. Throughout the course sources and fields are represented with
complex Fourier amplitudes and Fourier transforms, with simple formulas for the
time and space averages of field products in terms of the complex amplitudes, a great
simplification in finding forces and torques.
3.1.3. Applications
(a) Electromechanical kinematics. In source free regions of dielectric or magnetic
media, the electric and magnetic fields are irrotational and thus describable by electric
134
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
Planar la~er
RI x
[~~x~]=~
:J
i
5~
¢
Iict](a)
1
-1
sinh (yA) coth (yA)
Y
-J (kyy + kzZ)
= Re ¢ ( x , t )
-coth(yA)
B
e
7 =-~k2 + k2
y
z
(a)
~/
/
Ct Ct
r,¢~)
¢ = Re¢(r,t)e -j(=e + kz)
(b)
,= Re ~(r,t)pn~(cos O)e-Jm~
(c)
Fig. 15. Laplacian flux-potential relations for (a) a planar prototype layer, (b) a cylindrical annulus, and
(c) a spherical shell.
and magnetic scalar potentials that obey Laplace's equation. Generalized prototype
layers relate the normal component of fields to interfacial potentials.
Solenoidal fields, such as the magnetic flux density B, the current density in the
steady state Jr, or the displacement field D with no volume charge, can be represented
M. Zahn, H.A. Haus /Journal of Electrostatics 34 (1995) 109-162
135
by a vector potential. It is shown how the vector potential is related to a flux variable,
and generalized prototype relations are derived relating the tangential field components to interracial vector potentials. It is also shown that in two dimensions that
solenoidal field lines are given by constant values of vector potential which is directed
in the third direction.
These relations are first applied to electromechanical kinematics where the mechanical motions, charges, and currents are known from the outset. The mechanics
involves rigid-body translations or rotations while charges and currents are constrained by electrodes and wires. Stress, force, and torque relations in spatially
periodic systems are developed and applied to synchronous and DC machines,
magnetic and electric types. The synchronous machines involve periodically distributed surface currents for the magnetic case and periodic electrode voltages or a periodic space charge distribution for the electric case. The DC cases are those of
a standard brush/commutator magnetic machine and a Van de Graaff electrostatic
generator.
(b) Charge migration, convection and relaxation. The kinematic case is generalized
to allow the prescribed material deformations to vary in time and space. Electrodes
and wires are no longer used to constrain the sources, rather the distribution of free
charge and current is determined by the fields themselves. Charge conservation with
material convection for bipolar conduction by migration and diffusion with recombination and generation is treated.
When electric potentials greatly exceed the thermal voltage, about 25 mV at room
temperature, diffusion is generally negligible. Furthermore, if the net charge density is
small, the electric field E has approximately no divergence and is thus describable by
a vector potential. In this "imposed field" approximation, the electric field is essentially determined by charges outside of the region of interest, typically on boundaries. For
incompressible fluids, the velocity field v also has no divergence and thus also has
a vector potential. Melcher converts the governing partial differential equation of
charge conservation to a pair of ordinary differential equations, using the method of
characteristics. The approximate result is that in the frame of reference of the charged
particle moving at velocity v + bE, where b is the charge mobility, the charge density
remains approximately constant. Because of the solenoidal character of v and E, the
charged particle trajectories follow the net vector potential of v + bE. The results are
applied to an ion-drag anemometer and the Whipple and Chalmers model of impact
charging of macroscopic particles, important for modeling the charging of raindrops
in thunderstorms as well as particle charging for electrostatic copying, printing,
painting, and pollution control systems.
Then the self fields from the space charge distribution are included to show that the
mutual Coulomb self repulsion causes a self-precipitation of the charge to boundaries,
so that the charge density decreases with time. Results are applied to electrostatic
precipitators and an electrohydrodynamic energy converter that can be operated as
a pump or generator.
Unipolar dynamics are then generalized to bipolar conduction and applied to ions
in a gas, aerosol particles, ionized liquids, and dissociated salts in solvents with many
case studies developed using the method of characteristics.
136
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
Then the treatment considers charge relaxation dynamics of deforming ohmic
conductors and considers operation as a generator or pump. General prototype layer
relations are used to analyze an electroquasistatic induction motor and tachometer.
(c) Magnetic diffusion and induction interactions. With the same viewpoint as the
previous EQS section, magnetoquasistatic systems are treated where material deformations are prescribed (kinematic) while the magnetic field sources, distributions of
currents or magnetization, evolve in a dynamical manner that is self-consistent with
the magnetic field distribution. In practical terms, the subject takes leave of the
windings, slip rings, and commutators used to constrain current distributions in
moving elements and takes up conductors in which the currents seek a distribution
consistent with the MQS field laws.
Analysis begins with the ohmic constitutive law with moving media applied to
Ampere's and Faraday's laws to give the magnetic diffusion equation. For thin
translating sheets or rotating shells, boundary conditions are derived and applied to
magnetic induction motors and a tachometer. For thick regions, the generalized
prototype layer is used again to relate the tangential magnetic field components to the
interfacial vector potentials and applied to an induction motor with a deep conductor
as a magnetic diffusion study. Applications of the nonlinear magnetization characteristic are demonstrated with a hysteresis motor.
(d) Fluid mechanics. This section considers the field sources to assume distributions consistent with deformations of the media, but also allows the medium to
respond to the associated electric and magnetic forces. This limit is appropriate for
gases and liquids, as well as fluid-like continua such as certain plasma models and
electron beams.
The conservation laws of mass and momentum are elegantly derived using integral
theorems earlier derived. JRM first considers motions of an inviscid fluid and
develops an Eulerian description of the fluid interface with surface tension. A very
useful result is Bernoulli's equation generalized to include irrotational force densities.
Generalized prototype relations are derived for the pressure-velocity relations for
inviscid fluids which are incompressible and for slightly compressible fluids to describe acoustic waves, guides, and transmission lines. Then the development is
extended for viscous fluids to derive viscous diffusion transfer relations to relate shear
and normal stresses to interracial velocities. The thermodynamics and energy conservation laws of highly compressible fluids are also covered.
This physical and mathematical development is applied to many diverse coupled
problems of fluids with electric or magnetic forces. The static equilibrium for polarizable and magnetizable fluids is used with the extended Bernoulli's law to solve for
equilibrium fluid shapes. Magnetoacoustic waves in perfectly conducting fluids have
an increased wave phase velocity while an electric potential conserving fluid has an
electroacoustic wave phase velocity that is reduced. Fluid layer problems are solved
for dual dielectric and magnetic fluid geometries for stabilization of the
Rayleigh-Taylor instability using tangential fields and destabilization using perpendicular fields. Other interfacial problems solved include the z-O plasma pinch of
a cylindrical jet with and without magnetic diffusion, the stability of a charged drop,
and the stability of charged aerosols.
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
137
Smoothly inhomogeneous systems and their internal modes are solved for bulk
internal waves and instabilities, reciprocity and energy conservation, and spatial and
temporal modes.
(e) Electromechanicalflows. The dynamics of fluids perturbed from static equilibria
illustrated electromechanical rate processes with characteristic times short compared
to the representative time constants of a source, such as the period of a sinusoidal
excitation. Now another important time constant is the transport time z = l/U for
a fluid moving at characteristic velocity U over a length I.
An irrotational force density interacts with a flow of a homogeneous incompressible
fluid to alter the pressure distribution but not the flow pattern, as illustrated by an
electrolyte flowing through a uniform magnetic field perpendicular to the flow.
Fully developed flows are established after either a temporal or a spatial transient
as illustrated by problems with a charge monolayer driven convection, magnetic
induction pumping, and cellular creep flow. Also considered are magnetic- and
electric-type Hartmann flows where there is a competition between viscous and
magnetic or electric forces for power generation, pumping, or dissipation. Magnetohydrodynamic and electrohydrodynamic energy conversion with gas flows are
described with isentropic subsonic and supersonic flow through nozzles and diffusers.
(f) Electromechanics with thermal and molecular diffusion. The three-way coupling
between thermal or molecular subsystems with mechanical and electromagnetic
subsystems is first developed with the laws, relations, and parameters of convective
diffusion. Thermal transfer relations are derived for a planar layer between heat fluxes
and temperatures at upper and lower interfaces and applied to electrical dissipation
due to alternating currents induced in a moving conducting layer. Because the
dissipated power is proportional to the square of the current density, the temperature
response has dc and double frequency parts. Other applications are thermally induced
pumping and electrical augmentation of heat transfer, a rotor model for natural
convection in a magnetic field, and a hydromagnetic B6nard-type instability of
cellular convection.
Molecular diffusion is illustrated with unipolar ion charging of macroscopic particles; the competition between migration and diffusion that creates a double layer of
charge at an interface; an electrokinetic shear flow model to describe electroosmosis,
streaming potential, streaming current, particle electrophoresis, and sedimentation
potential; and electrocapillarity.
(g) Streamin9 interactions. Charged particle beams in vacuum are described for
magnetron electron flow and the paraxial ray equation is used to describe magnetic
and electric lenses. Nonlinear magnetoacoustic dynamics, shocks and nonlinear
electron beam dynamics are described using the method of characteristics. Linear
dynamics are described in terms of complex waves, identifying criteria for propagating, evanescent, absolutely unstable, and convectively unstable waves.
3.2. Research achievements
JRM's research activity of continuum electromechanics was concerned with the
interactions between macroscopic media and electromagnetic fields. Its interdisciplinary
138
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
nature combined electromagnetic field theory with other disciplines such as fluid or
solid mechanics, heat transfer, insulation engineering, physical chemistry, or bioengineering. His research was applied to diverse situations: polymer and glass processing, electronic devices, sensors, transducers, printing, copying, painting, stack gas
cleaning, image processing, metal and dielectric liquid mixing and pumping, motors,
generators, and biomedical products.
Appendix B gives a list of doctoral, engineer's, master's, and bachelor's theses
supervised by JRM. A major clue that students were very happy with his thesis
supervision is to note that many students did two or more theses with him. Many of
JRM's students went on to become university professors, some others to found
companies, others to work in the military and industry. The following briefly summarizes the major research areas that JRM focussed on with his students.
3.2.1. Electrohydrodynamics, magnetohydrodynamics, and ferrohydrodynamics
JRM's doctoral thesis resulted in his first book, Field-Coupled Surface Waves [B.1]
which treated the stability and dynamics of the electromechanics of incompressible
and inviscid fluids. Electrohydrodynamics (EHD) research [A.2-7, A.9-19] initially
considered polarization forces on perfectly insulating dielectrics and Coulomb forces
on interfacial surface charge on perfectly conducting fluids. His early research was
funded by NASA to develop space applications of electromechanical forces to act as
artificial gravity [A.12, A.18, A.24].
Ferrohydrodynamics (FHD) of linearly magnetizable fluids was the direct analog to
polarization forces on dielectrics but at the time of his analysis such fluids did not yet
exist. When they were first synthesized in 1965 by other researchers [6], his analysis
could be directly applied to these new fluids. He supervised a number of theses on
ferrohydrodynamics [A.25] and worked with these first researchers in the field, and
helped the fledgling company Ferrofluidics, Corp. in its early years as a technical
advisor to understand ferrofluid behavior and their practical application.
JRM's magnetohydrodynamic (MHD) research generally concerned perfectly conducting fluids and could be applied to plasma systems and liquid metals [A.29, A.66].
Because such EHD, FHD, and M H D systems are generally inherently unstable, much
of his early research focussed on feedback control in time and space to stabilize
otherwise unstable systems [A.5, A.7, A.10, A.11, and A.29].
It was natural for his following research to continue these themes but to relax some
of the simplifying assumptions. With his students, he extended his EHD research to
include space-varying fluid viscosity, gradients in mass density, dielectric permittivity,
and temperature and to include volume space charge and conduction as better models
of real dielectrics [A.21, A.35, A.47]. His major new contributions were to develop
true physical and mathematical models of liquid dielectrics so that he is considered to
be the modern day father of electrohydrodynamics, but often via duality principles he
also contributed to magnetohydrodynamic and ferrohydrodynamic research.
He applied this research to novel energy conversion systems [A.33]; power systems
[A.43, A.68, A.71]; improved heat transfer and fluid mixing [A. 14, A.26, A.47, A.55];
electrostatic precipitation and charged droplet scrubbers for air and water pollution
control [A.48, A.51-53, A.58-62]; electrostatic processes of printing, copying and
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
grounded
p
shield~ ~ [
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/
insulating
tube
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,
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Fig. 16. Apparatus for an electrical standing wave capacitive interaction with an imposed flow that
convects part of the electrical double-layercharge distribution. With the liquid stationary, the charging
currents, i2 and i3, a r e balanced by bridge adjustments. With flow,the standing wave distribution of charge
near the interfaceis displaced relative to the sensing electrodesand the currents i2 and i3 change.
painting [A.81, 82, A.90-92]; electrokinetics [A.38, A.49, 50]; electrical insulation
measurements, monitoring, and improvements [A.88, 89, A.94, 95, A.97, 98]; and
sensors for continuous measurements of material properties [A.101, 102]. Notable
were his contributions to understanding audible noise from water droplets on power
lines [A.43], insulation problems in HVDC systems [A.68, A.71], AC electrostatic
precipitation [A.76, 77, A.79], improvements to electrostatic paint spraying [A.81,
82], and traveling wave transport of tribo-electrified particles for application to
electrostatic copying [A.90-92].
3.2.2. Fundamental electrokinetics
JRM's interest in electrokinetic systems grew from his observations of mercury/electrolyte interfaces [A.65], where the electromechanical responses were large
even though the applied voltages were of order of volts as opposed to tens of kilovolts for
electromechanical interactions with dielectrics. This work continued on his sabbatical at
the Cavendish and through collaboration with his student and then colleague Grodzinsky
to the electromechanical and physiochemical nature of connective tissue [A.49, A.50].
Articular cartilage is an example of a biphasic medium in which electromechanical
coupling at the double-layer scale can be important. It is composed of an ionic interstitial
fluid and an organic matrix of collagen and other biological constituents. The streaming
currents and electrical stresses associated with articular stresses and deformations
may be related to degenerative changes such as arthritis. Practical motivation for
understanding these effects also comes from the need for a membrane-based transport
system in which an electric field is applied across a biological polymer membrane and
used to control permeability, perhaps useful for controlled drug delivery.
An engineering application utilizing the electrical double layer in dielectrics is
shown in Fig. 16, where a standing wave of potential is imposed around an insulating
140
M. Zahn, H.A. Haus/Journal o f Electrostatics 34 (1995) 109-162
tube by a distributed electrode structure. Direct liquid/electrode contact is avoided by
using capacitive coupling of the AC voltage through highly insulating tubing. With
imposed flow, convected double-layer charge results in a spatial phase shift of charge
that gives an imbalance in image charges on the electrode structure that is detected as
a difference in charging currents, iz and i3. Such measurements were used to study
natural double-layer processes in flow electrifying systems [7].
Fig. 17 shows the inverse problem where a mechanical response of driven flow
is obtained by an imposed traveling wave of potential that gives rise to electric
field components both tangential and normal to the tubing interface. The tangential
field component on the double-layer charge causes a Coulomb force that convects the
fluid in either direction depending on voltage amplitude and frequency [7, A.96].
3.2.3. Electropacked and electrofluidized beds
JRM's research with electrostatic precipitation led to major improvements to
conventional technology using electropacked and electrofluidized beds to greatly
improve the efficiency and ability to capture smaller particles with a greatly decreased
volume [A.45, A.48, A.51-53, A.58-62]. In a conventional electrostatic precipitator,
the collection takes place on electrodes several stories high, with much of the interior
volume not used for collection. His concept was to fill the interior volume with
particles, each of which could capture smaller particles, as small as 0.1 ~tm, particles
too small to be captured by conventional precipitators, yet the size range that
penetrate into the lungs. JRM demonstrated that a bed of sand a few inches deep
could clean smoke as efficiently as an electrostatic precipitator several stories high.
The beds of particles could also be powered with alternating voltage rather than the
required DC for conventional precipitators simplifying the power requirements.
JRM was proud that his students could make the transition from complex physics
and mathematics of mass transfer in the presence of electric fields to wearing hard
hats in a plant that applied these ideas to making the recycling of asphaltic concrete
environmentally acceptable. Upon graduation some of his students founded the
company EFB, Inc. to apply bed technology to air pollution control equipment. JRM
was in part motivated in controlling the fine particles in the insulating ash from
western coals and from diesel engine emissions.
3.2.4. Flow electrification
In transformers and high-voltage direct-current (HVDC) substations, the flow of
liquid coolant can cause charge accumulation and buildup of electric fields beyond
design limits leading to spark discharges [7, 8, A.89]. This has resulted in failures of
a HVDC substation and of about two-dozen power transformers world-wide. The
problem originates with the entrainment from the liquid side of the diffuse doublelayer charge at pressboard/oil interfaces in transformers and at the tefzel insulating
tube/liquid Freon interface in the substation [7]. This charge can accumulate on
insulating surfaces, causing the electric potential to rise in the same fashion as voltage
build-up in a van de Graaff generator. The potential builds up until the rate of charge
accumulation equals the rate of charge leakage, or until spark discharges occur.
Similar processes also occur in fuel pump/gasoline systems.
M. Zahn, H.,4. Haus/Journal of Electrostatics 34 (1995) 109-162
~rl°~ie~v°ir
....
~
.....
141
n~a~
Ivv
(a)
/
~ = VoCOS(COt - kz)
T
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insulating
2a
wall
• = VoCOS(Wt - kz)
(b)
displacement
(arbitrary
units)
12.5
/
KV
2.O KV
1.5 KV
forward
pumping
~
\
I0
15
2O
!
I backward
pumping
frequency
(Hz)
(c)
Fig. 17. (a) A multiple winding around an insulating tube excited by a polyphase high voltage results in
a traveling wave high voltage that has an electric field component within the liquid electrical double layer
tangential to the tube surface; (b) Planar model showing a representative flow profile; (c) Representative
measurements show that as a function of voltage amplitude and frequency, the liquid can be pumped in the
same direction (forward pumping) or opposite direction (backward pumping) to the traveling wave
direction.
142
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
Fig. 18. The Couette Charger distributes interfacialelectricaldouble layer chargethroughout the turbulent
core betweencylinderswith rotation of the inner cylinderthat is measured by the Absolute Charge Sensor.
The electricalterminals across the cylinderscan be connectedfor measuring open circuit voltage or short
circuit current resulting from the core charge density or can be used to apply DC or AC high voltages to
enhance the charge density.
Understanding of flow electrification requires coupling the laws of electroquasistatics, fluid mechanics, heat, and electro-chemistry to describe the generation, transport, accumulation, and leakage of charge and to relate how these factors are affected
by temperature, moisture, flow rate and turbulence, contaminants and surface active
agents, material and surface condition, and energization [A.883. JRM's research
developed physical modelling and experimental measurement techniques with well
instrumented laboratory models that monitored solid and liquid conductivity and
moisture levels, flow conditions, and temperature.
The apparatus included flow loop models with conducting and insulating sections
[A.89] and a Couette flow facility [A.88, A.98, A.103], shown in Fig. 18, where
transformer oil or gasoline fills the annulus between coaxial cylindrical electrodes
which could be bare metal or covered with pressboard or polymers and could be
energized with DC or AC high voltages. The Couette facility rotated the inner cylinder
at speeds to give controlled laminar, secondary cellular convection, or turbulent flows,
to bring electric charge to the volume from the double layer at liquid/solid interfaces.
This compact apparatus allowed flexibility in testing various liquid/solid combinations at controlled temperatures and moisture levels to simulate physical processes at
work in power apparatus.
He invented the Absolute Charge Sensor (ACS) [A.97], shown in Fig. 18 and more
fully illustrated in Fig. 19, which could measure the volume charge density in a liquid
by bringing a sample of fluid into a Faraday cage, independent of the fluid's electrical
properties, velocity, and any electrification processes within the instrument. The ACS
overcame the ambiguity in current or voltage measurements of probes placed into the
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
sampling
.
::i.
•
.
"
:
.
.
. . . . .
i
:~
<
. .-
.,
./
, :
samplingprobe.~:
. f.-:.
•
.
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.
.
:
.
:
probe
143
:
.::.
-..
:
. :
triax (
to ele
ded
(a)
Fig. 19. Schematicsof the Absolute Charge Sensor (ACS) that measures fluid charge density by bringing
a sample of charged fluid into a Faraday cage.
fluid flow where it is impossible to separate contributions from impacting charge in
the flow from charge separated at the probe interface by the very charge generation
and transport processes that were being studied.
3.2.5. Imposed frequency-wavenumber sensors
JRM was the principal investigator of a 4-year research program aimed at developing sensors and computerized trend analysis to continually monitor the health of
power transformers and to take corrective action in the event of imminent problems.
At the same time, other MIT research had developed microdielectrometry sensors
which measured the complex permittivity of a medium, with application to monitoring the state of cure of epoxies [9]. The sensor was like that in Fig. 20(a), where one set
of interdigitated electrodes are driven at a sinusoidal voltage over the frequency range
of 0.005 to 10 000 Hz, while a second set of interdigitated electrodes were floating, and
would rise to a voltage magnitude and phase as a function of frequency that depended
on the dielectric permittivity and ohmic conductivity of the surrounding dielectric
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
144
y
•/.
_
(b)
Fig. 20. (a) Interdigital electrode structure for dielectrometry measurements of the complex permittivity of
adjacent material and (b) analogous meandering winding magnetometer for measurements of magnetic
permeability and conductivity of adjacent media.
[A.94, 95]. Working backward from the measured voltage gain and phase of the
floating electrodes, the dielectric constant and ohmic conductivity of the adjacent
medium could be calculated.
The applied frequency was imposed by the voltage source and the spatial dependence was imposed by the periodic array of electrodes. JRM modelled the dielectric
medium as a continuum driven by a voltage periodic in time and space. The potential
obeyed Laplace's equation so that being periodic along the sensor, each Fourier
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
145
component of the potential decayed exponentially into the dielectric with a characteristic decay length equal to the electrode spacing divided by the mode number. He
applied this sensor to monitoring the complex permittivity of transformer oil and
developed the concept of selectively absorbing coatings to also measure moisture and
gas contents. To measure dielectric properties of thick regions, such as pressboard, it
was necessary to increase the electrode periodicity to make macro-sensors. To
measure nonuniform distributions, such as moisture penetrating into pressboard,
multiple wavelength sensors were developed [A.102]. If the dielectric properties are
known functions of other variables, such as moisture level, these sensors could be used
to monitor those variables also. These sensors and similar structures can also be used
to measure electrical double-layer properties.
Again, by duality, the capacitive sensors for dielectrometry have their eddy current
inductive counterpart for measuring the magnetization and conductivity of magnetizable metals, as in Fig. 20(b). JENTEK Sensors, Inc., founded by Goldfine, Melcher's
last doctoral student, is developing such new magnetometers for material property
characterization.
4. Social and political activism
JRM's last days were spent writing a paper describing what he perceived as the
major problems in American society [A.104]. The time also coincided with the
buildup preceding the Persian Gulf War. He used the interesting writing style of
alternating between his own deteriorating health to describing his view of the deteriorating health of the country that was leading to war in order to have "cheap oil",
because the country had avoided a national energy policy.
His view that America was on the wrong path began while he was on sabbatical in
England in 1971-72 where he was able to see from abroad America's involvement in
Vietnam and also Britain's involvement in Northern Ireland. He searched for ways to
make his teaching and research have an impact on America's course so that the basic
engineering science taught at MIT could have an impact on the practical "real world".
4.1. Bicycling
Shortly after his return from sabbatical to MIT came the first Arab oil boycott with
lines of cars at gas stations and his growing awareness of America's vulnerability. He
sold his family's second car and committed himself to year-round bicycle commuting.
For 45 min each way, 9 miles, he contemplated the American transportation system
from the point of view of the lowest class on the road. All together he bicycled the
equivalent of more than four times around the world on essentially the same route
each day.
He became active in promoting bicycling, joining the Boston Area Bicycle Coalition
and the League of American Wheelmen. He did not present bicycling as a sacrifice,
but rather as fun providing exercise and satisfaction of having done useful work,
and a way to greatly reduce air pollution. Student bicyclists were attracted to his
146
M. Zahn, H.A. Haus/Journal o f Electrostatics 34 (1995) 109-162
Continuum
Electromechanics
Fig. 21. Bicycle with electromechanical variables was the logo for Melcher's Continuum Electromechanics
Laboratory which appeared on tee-shirts and sweat-shirts of laboratory students and staff.
laboratory, resulting in a bicycle annotated with electromechanical variables as the
laboratory symbol, as illustrated in Fig. 21. With his students, he became good
enough to be competitive, drafting a student who won the Great Commuter Race
from City Hall in Wellesley, MA to the State House in Boston, and he with two other
students placed first for a team in one of MIT's bi-yearly 30 mile intramural races.
JRM recognized the obvious dangers of sharing the road with automobiles, buses
and trucks. He had bicycle breakdowns, was hit by cars about 6 times, and as
a diabetic, fainted on his bike due to his miscalculating his blood-sugar level.
In 1985, JRM and colleague Richard Tabors wrote a proposal for a MacArthur
Foundation grant to MIT for disarmament studies. The proposal "In Pursuit of
Policies Designed to Create Socio-Economic Conditions That Minimize Incentives
for Arming: A Feasibility Study on the Allocation by Beneficiary of the Costs of
Military Services", pointed out that because oil (gasoline) is made cheap by being
subsidized through taxes for the military, people see arming as being in their economic
interest. The proposal explored ways of restoring free-market incentives by having the
true cost be paid by the consumer, for example, by putting a tax on imported oil to
pay the appropriate portion of the military budget. The proposal was not funded.
4.2. Opposition to the strategic defense initiative (SDI)
JRM did not fit the image of an anti-war protester, but he became one after the
Vietnam War period. He fought against energy dependence and militarism. He made
his views known in many rallies, seminars, and other public forums. He was greatly
disturbed by the extent to which the military both directly and indirectly dictated the
nation's research agenda. He noted that the best scientists and industries were turning
away from research and manufacturing of civilian goods such as airplanes and
automobiles, where money is tight and the market competition is stiff, and toward
military hardware, where research money is plentiful and profits assured. He came to
believe that the nations priorities were misguided.
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
147
JRM was one of four scientists at a news conference in Washington, DC to present
a petition signed by more than 3700 senior science professors and senior researchers
pledging to do no research on the strategic defense initiative program. He signed the
pledge because he thought SDI was an escalation in the arms race and a pretext for
putting weapons in space. He was not for unilateral disarmament because he was
aware of the Soviet threat. He was against SDI because he felt that it had no chance to
succeed, being easily defeated with "a bucket of sand in a retrograde orbit". He
advocated that human creative talents could be better applied to human needs and to
help America's competiveness. He used John Trump as an example, his predecessor as
Director of the MIT High Voltage Research Laboratory. Trump could make megavolt beams of ions and electrons. He did not apply his work to weapons, but rather to
cancer research and sterilizing sludge.
The Wall Street Journal editorialized that the petitioners were "Intellectuals In
Isolation". JRM responded by sending his press release as part of a letter to the editor,
but it was not published. It is reprinted here:
"We have no meaningful defense without a healthy economy. The dollars
we spend for SDI are from a deficit budget. Pursuit of SDI implies even
larger contributions to the deficit in the future. This alone puts our economic
future in jeopardy. But, as our balance of payments becomes increasingly
negative, it becomes more evident that military spending compounds the
economic tragedy by suffocating our capitalistic base. Our industry can
either hide from foreign competition by cultivating the Pentagon as a customer or use its capital and human resources to make a profit in products
that are competitive at home and abroad. SDI is industries' Pied Piper. As it
becomes difficult to buy many US manufactured products even in the US, it
is becoming clear that time is running out on the US economic miracle.
While the SDI escalates the confrontation with our military adversary, it
makes us even less able to compete economically with friends who do not
share our obsession for arming."
Despite his strong opposition to SDI, as laboratory director he would sign a proposal to SDI from individual laboratory faculty, of which there was only one, but he
tried to find and encourage alternatives. He led major research efforts sponsored by
many individual electrical utilities, the Electric Power Research Institute, Empire
State Electric Energy Research Corporation, Lord Corporation, and IBM.
Even though he tried to justify his views on matters of economics and common
sense, his experiences gave him the feeling that the basic issue was moral. He felt that
there was a large group that abhorred the society we would become if we continued to
use our military to obtain more than our fair share.
Acknowledgements
This paper was written while the first author (MZ) was on sabbatical at the
Centre National de la Recherche Scientifique, Laboratoire d'Electrostatique et de
148
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
Materiaux Dielectriques and at l'Universit~ Joseph Fourier, Grenoble, France.
It was also partially supported by the National Science Foundation, G r a n t
No. ECS-8913605.
References
[1] For information about purchasing the videotapes, contact M. Zahn.
[2] R.M. Fano, L.H. Chu and R.B. Adler, Electromagnetic Fields, Energy, and Forces, Wiley, New York,
! 960.
[3] D.B.H. Tellegen, Magnetic-dipole models, Amer. J. Phys., vol. 30, pp. 650-652, Sept. 1962.
[4] H.A. Haus and P. Penfield, Jr., Force on a current loop, Phys. Lett., 26A (1968) 412-413.
[5] M. Zahn, Self-excited AC high voltage generation using water droplets, Amer. J. Phys., 41 (1973)
196-202.
[61 R.E. Rosensweig, Ferrohydrodynamics, Cambridge University Press, Cambridge, 1985.
[71 S.M. Gasworth, J.R. Melcher and M. Zahn, Electrification Problems Resulting from Liquid Dielectric
Flow, Electric Power Research Institute Report EL-4501, April, 1986.
[8] M. Zahn, Guest Editor, Special Issue on Flow Electrification in Electric Power Apparatus, IEEE
Trans. Electrical Insulation, 23(1)(1988) 101-176.
[9] N.F. Sheppard, D.R. Day, H.L. Lee and S.D. Senturia, Microdielectrometry,Sensors and Actuators,
2(3) (1982) 263-274.
Appendix A. Resume of Prof James R. Melcher
J.A. Stratton Professor of Electrical Engineering and Physics Director, Laboratory
for Electromagnetic and Electronic Systems Massachusetts Institute of Technology
Cambridge, MA 02139
Born: July 5, 1936 - Giard, Iowa
Education: B.S.E.E., 1957, Iowa State University
M.S., Nu.E., 1958, Iowa State University
Ph.D., E.E., 1962, Massachusetts Institute of Technology
Professional Experience:
1957-1958
1959-1961
1962-1966
1966-1969
1969-until
1980-1984
Sept.-Dec.
terns, M I T
Jan. 1985
MIT.
Research Assistant, Ames L a b o r a t o r y of U.S.A.E.C.
Teaching Assistant, Dept. of Electrical Engineering, M I T
Assistant Professor, Dept. of Electrical Engineering, M I T
Associate Professor, Dept. of Electrical Engineering, M I T
his death, 1991 Professor, Dept. of Electrical Engineering, M I T
Director, High Voltage Research Laboratory, M I T
1984 Co-director, L a b o r a t o r y for Electromagnetic and Electronic SysDirector, L a b o r a t o r y for Electromagnetic and Electronic Systems,
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
149
Publications
A. Journal articles
[-1] Melcher, J.R., A useful analogy for single-group neutron diffusion theory, Nucl.
Sci. Eng., 1 (1960) 235-239. (Paper won American Nuclear Society's First
Mark Mills Award.)
[2] Melcher, J.R., Electrohydrodynamic surface resonators, Phys. Fluids, 5(9)
(1962).
[3] Melcher, J.R., Electrohydrodynamic and magnetohydrodynamic surface waves
and instabilities, Phys. Fluids, 4(11) (1961) 1348-1354.
[4] Melcher, J.R., Electrohydrodynamic and magnetohydrodynamic nonlinear
surface waves, Phys. Fluids, 5(9) (1962) 1037-1043.
[5] Melcher, J.R., Stabilization of a continuum electromechanical instability, Proc.
Inst. Electrical and Electronics Eng. (IEEE) (1965) 460-473.
[6] Devitt, E.E. and J.R. Melcher, Surface electrohydrodynamics with high frequency fields, Phys. Fluids, 8(6) (1965).
[7] Melcher, J.R., An experiment to stabilize an electromechanical continuum,
IEEE Trans. Automat. Control, AC-10 (1965) 466-469.
[8] Melcher, J.R. and E.P. Warren, Demonstration of magnetic flux constraints
and a lumped-parameter Alfven wave, IEEE Trans. Education, E-8 (1965)
41--47.
[9] Melcher, J.R., Traveling-wave-induced electroconvection, Phys. Fluids, 9(8)
(1966) 1548-1555.
[10] Melcher, J.R., Continuum feedback control of instabilities on an infinite fluid
interface, Phys. Fluids, 9(10) (1966) 1973-1982.
[11] Melcher, J.R. and E.P. Warren, Continuum feedback control of a RayleighTaylor type instability, Phys. Fluids, 9(11) (1966) 2085-2094.
[12] Melcher, J.R. and M. Hurwitz, Gradient stabilization of electrohydro-dynamically oriented liquids, J. Spacecraft Rockets, 4(7) (1967) 864-881.
[13] Melcher, J.R., Charge relaxation on a moving liquid interface, Phys. Fluids,
10(2) (1967) 325-332.
[14] Melcher, J.R. and M.S. Firebaugh, Traveling-wave bulk electro-convection induced across a temperature gradient, Phys. Fluids, 10(6) (1967)
1178-1185.
[15] Smith, C.V., Jr. and J.R. Melcher, An electrohydrodynamically induced, spatially periodic cellular stokes flow, Phys. Fluids, 10(11) (1967) 2315-2322.
[16] Ketterer, F.D. and J.R. Melcher, Electromechanical costreaming and counterstreaming instabilities, Phys. Fluids, 11(10) (1968) 2179-2191.
[17] Melcher, J.R. and W.J. Schwarz, Jr., Interfacial relaxation overstability in
a tangential electric field, Phys. Fluids, 11(12) (1968) 2604-2616.
[18] Melcher, J.R., D.S. Guttman and M. Hurwitz, Dielectrophoretic orientation, J.
Spacecraft Rockets, 6(1) (1969) 25-32.
[19] Ketterer, F.D. and J.R. Melcher, Electromechanical stream-structure instabilities, Phys. Fluids, 12(1) (1969) 109-119.
150
M. Zahn, H..A. Haus/Journal of Electrostatics 34 (1995) 109-162
[20] Melcher, J.R. and G.I. Taylor, Electrohydrodynamics: A review of the role of
interfacial shear stresses, Chapter in the First Review of Fluid Mechanics,
Annual Reviews, Palo Alto, CA, 111-146.
[21] Turnbull, R.J. and J.R. Melcher, Electrohydrodynamic Rayleigh-Taylor bulk
instability, Phys. Fluids, 12(6) (1969) 1160-1166.
[22] Calvert, R.T. and J.R. Melcher, Stability and dynamics of rotating dielectrophoretic equilibria, J. Fluid Mech., 38, Part 4 (1969) 721-742.
[23] Melcher, J.R. and C.V. Smith, Jr., Electrohydrodynamic charge relaxation and
perpendicular-field interfacial instability, Phys. Fluids, 12(4) (1969) 778-790.
[24] Melcher, J.R., M. Hurwitz and R.G. Fax, Dielectrophoretic liquid expulsion, J.
Spacecraft Rockets, 6(9) (1969) 961-967.
[25] Zelazo, R.E. and J.R. Melcher, Dynamics and stability of ferrofluids: Surface
interactions, J. Fluid Mech., 39, Part 1 (1969) 1-24.
[26] Wong, J. and J.R. Melcher, Thermally induced electroconvection, Phys. Fluids,
12(11) (1969) 2264-2269.
[27] Jolly, D.C. and J.R. Melcher, Electroconvective instability in a fluid layer, Proc.
Roy. Soc. (London), A314 (1970) 269-283.
[28] Woodson, H.H. and J.R. Melcher, Electromechanics in the undergraduate
curriculum, IEEE Trans. Education, E-13 (1970) 167-175.
[29] Melcher, J.R., Feedback stabilization of hydromagnetic continua: Review and
prospects, in: T.K. Chu, H.W. Hendel (Eds.), Proc. Symp. on Feedback and
Dynamic Control of Plasmas, American Institute of Physics, New York, 1970,
pp. 38-53.
[30] Melcher, J.R. and E.P. Warren, Electrodynamics of a current-carrying semiinsulating jet, J. Fluid Mech., 47, Part 1 (1971) 127-143.
[31] Melcher, J.R., Complex waves, IEEE Spectrum (1968) 86-101.
[32] Melcher, J.R., Review of the IUTAM-IUPAP symposium on electrohydrodynamics, J. Fluid Mech., 40, Part 3 (1970) 641-655.
[33] Melcher, J.R. and T.C. Cheng, Prospects of electrogasdynamic power generation, invited paper, Paper No. 70 CP 210-PWR, IEEE Winter Power Meeting,
New York, NY, January 25-30, 1970.
[34] Haus, H.A. and J.R. Melcher, Electric and magnetic fields, Proc. IEEE, 59(6)
(1971) 887-894.
[35] Zahn, M. and J.R. Melcher, Space-charge dynamics of liquids, Phys. Fluids,
15(7) (1972) 1197-1206.
[36] Jones, T.B. Jr. and J.R. Melcher, Dynamics of electromechanical flow structures, Phys. Fluids, 16(3) (1973).
[37] Jones, T.B. Jr., M.P. Perry and J.R. Melcher, Dielectric siphons, Science, 174
(1971) 1232-1233.
[38] Melcher, J.R., Dynamics of charge monolayers on insulating liquid interfaces,
J. Fluid Mech., 60, Part 3 (1973) 417-431.
[39] Melcher, J.R., Electric fields and moving media, IEEE Trans. Education, E-17
(2) (1974) 100-110.
[40] Zelazo, R.E. and J.R. Melcher, Dynamic interactions of monomolecular films
with imposed electric fields, Phys. Fluids, 17 (1974) 61-72.
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
151
[41] Melcher, J.R., Electrohydrodynamics, in: E. Becker and G.K. Mikhailov (Eds.),
Proc. 13th lnternat. Congr. of Theoretical and Applied Mechanics, 1972, Springer, New York, NY, 1973, pp. 240-263; (in Russian) Magnetohydrodynamics,
2 (1974) 3-30.
[42] Hoburg, J.F. and J.R. Melcher, Observations on 'slot effect' transducer analysis, IEEE Trans. Acoust. Speech, Signal Process., ASSP-23 (1975) 500-501.
[43] Hoburg, J.F. and J.R. Melcher, Current-driven, corona-terminated water jets
as sources of charge droplets and audible noise, IEEE Trans. Power Apparatus
Systems, PAS-94 (1975) 128-136.
[44] Dietz, P.W. and J.R. Melcher, Field controlled charge and heat transfer involving
macroscopic charged particles in liquids, J. Heat Transfer, 97 (1975) 429-434.
[45] Johnson, T.W. and J.R. Melcher, Electromechanics of electrofluidized beds,
Ind. Eng. Chem. Fundam. 14 (1975) 146-152.
[46] Melcher, J.R., Electric fields and forces in semi-insulating liquids, J. Electrostat., 2 (1976) 121-132.
[47] Hoburg, J.F. and J.R. Melcher, Internal electrohydrodynamic instability and
mixing of fluids with orthogonal field and conductivity gradients, J. Fluid
Mech., 73 (1976) 333 351.
[48] Zahedi, K. and J.R. Melcher, Electrofluidized beds in the filtration of submicron aerosols, J. Air Pollut. Control, 26 (1976) 345.
[49] Grodzinsky, A.J. and J.R. Melcher, Electromechanics of deformable charged
polyelectrolyte membranes, Proc. 27th Ann. Conf. Eng. Med. Biology, 16
(1974) Paper 53.2.
[50] Grodzinsky, A.J. and J.R. Melcher, Electromechanical transduction with
charge polyelectrolyte membranes, IEEE Trans. Biomed. Eng., BME-23(6)
(1976) 421-433.
[51] Zahedi, K. and J.R. Melcher, Collection of submicron particulate in bubbling
electroftuidized beds, Presented at 82nd Meeting of American Institute of
Chemical Engineers, August 1976 and published in I & EC Fundamentals, 16
(1977) 248-254.
[52] Dietz, P.W. and J.R Melcher, Momentum transfer in electrofluidized beds,
AIChE Symposium Series, Control and Dispersion of Air Pollutants: Emphasis on NOx and Particulate Emissions, 74 (1978) 175, 168-174.
[53] Alexander, J.C. and J.R. Melcher, Alternating field electrofluidized beds in the
collection of submicron aerosols, Presented at the 82nd Meeting of American
Institute of Chemical Engineers, August 1976, and published in I & EC
Fundamentals, 16 (1977) 311-317.
[54] Melcher, J.R. and J.F. Hoburg, Electrohydrodynamic mixing, Presented at the
82nd Meeting of American Institute of Chemical Engineers, invited paper,
August 1976.
[553 Lang, J.H., J.F. Hoburg and J.R. Melcher, Field induced mixing across a diaphragm, Phys. Fluids, 19(6) (1976) 917--918.
[56] Melcher, J.R., Oscillations and traveling wave induced streaming of charge
monolayers on insulating liquid surfaces, Proc. Conf. on Electrical Insulation
and Dielectric Phenomena, October 1976, pp. 233-241.
152
M. Zahn, 1t..4. Haus/Journal o f Electrostatics 34 (1995) 109-162
[57] Hoburg, J.F and J.R. Melcher, Electrohydrodynamic mixing and instability
induced by co-linear fields and conductivity gradients, Phys. Fluids, 20(6)
(1977) 903-911.
[58] Zieve, P.B., K. Zahedi, J.R. Melcher and J.F. Denton, Electrofluidized beds in
the filtration of smoke emissions from an asphaltic pavement recycling process,
Env. Sci. Tech., (12) (1978) 96.
[59] Melcher, J.R., Electrofluidized beds for industrial scale air pollution
control, Presented at Novel concepts, methods and advanced technology
in particulate-gas separation workshop, University of Notre Dame, April
1977.
[60] Dietz, P.W. and J.R. Melcher, Interparticle electrical forces in packed and
fluidized beds, I&EC Fundam., 17 (1978) 28.
[61] Melcher, J.R., K. Sachar and E.P. Warren, Overview of electrostatic devices for
control of submicron particles, IEEE Proc., 65(12) (1977) 1659-1669.
[62] Dietz, P.W. and J.R. Melcher, Momentum transfer in electrofluidized beds,
AIChE Syrup. Ser. (175), 74 (1978) 166-174.
[63] Melcher, J.R., The electrohydrodynamics of G.I. Taylor, J. Electrostat., 5 (1978)
1-9.
[64] Withers, R.S., J.R. Melcher, and J.W. Richmann, Charging, migration
and electrohydrodynamic transport of aerosols, J. Electrostat., 5 (1978),
225-239.
[65] Zuercher, J. and J.R. Melcher, Double-layer transduction at a mercury-electrolyte interface with imposed temporal and spatial periodicity, J. Electrostat.,
(1978) 21-31.
[66] McHale, E.J. and J.R. Melcher, Hydromagnetic instability of liquid metals in
AC magnetic fields and augmentation of heat transfer, Electric Mach. Electromech., 3 (1979) 197-207.
[67] Davey, K.R. and J.R. Melcher, Numerical determination of potential and flux
conserving static equilibria of liquids, Electric Mach. Electromech., 5 (1980)
237-245.
[68] Horenstein, M.N. and J.R. Melcher, Particle contamination of high voltage DC
insulators below corona threshold, IEEE Trans., EI-14(6) (1979) 297-305.
[69] Davey, K.R. and J.R. Melcher, Electromagnetic precipitation and ducting of
particles in turbulent boundary layers, in: Gary R. Hough (Ed.) Viscous Flow
Drag Reduction Vol. 72, Progress in Astronautics and Aeronautics, 1980.
[70] McHale, E.J. and J.R. Melcher, Instability of a planar liquid layer in an
alternating magnetic field, J. Fluid Mech., 114 (1982) 27-40.
[71] Radun, A.V. and J.R. Melcher, DC power line charging of macroscopic particles and associated electrical precipitation on insulators, IEEE Trans. Insulation, EI-16(3) (1981) 165-179.
[72] Alexander, J.C., K.R. Davey and J.R. Melcher, Comparative study of direct and
alternating current electric and magnetic precipitation from laminar and
turbulent flows, I & EC Fundam., 20 (1981) 207-216.
[73] Withers, R.S. and J.R. Melcher, Space-charge effects in aerosol charging and
migration, J. Aerosol Sci., 12 (1981) 307-331.
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
153
[74] Ehrlich, R.M. and J.R. Melcher, Bipolar model for traveling-wave induced
nonequilibrium double-layer streaming in insulating liquids, Phys. Fluids, 25
(1982) 1785-1793.
[75] Melcher, J.R., Electrohydrodynamic surface waves, Chapter in Waves on Fluid
Interfaces, Academic Press, New York, pp. 167-200.
1-76] Ehrlich, R.M. and J.R. Melcher, AC corona charging of particles, IEEE Trans.
Ind. Appl., IA-23(1) (1987). (Technical Paper Recognition Award of the
IEEE/IAS Electrostatic Processes Committee.)
[77] Ehrlich, R.M. and J.R. Melcher, AC electrostatic precipitation, IEEE Trans.
Ind. Appl. 24(4) (1988). (Technical Paper Recognition Award of the IEEE/IAS
Electrostatic Processing Committee, 1989. Also, IAS Prize Papers Committee
Second Place paper published in the IAS Transactions in 1988-1989.)
[78] Inkpen, S.L. and J.R. Melcher, Smoothing the electromagnetic heating pattern
in polymers, Polymer Eng. Sci., 25(25) (1985) 289-294.
[79] Ehrlich, R.M. and J.R. Melcher, Turbulent diffusion of a traveling-wave of
charged aerosol, Ind. Eng. Chem. Fundam. Res., 26(3) (1987).
[80] Von Guggenburg, P., Porter, A.J. and Melcher, J.R., Field-mediated hydraulic
deformation and transport of magnetically solidified magnetizable particles,
IEEE Trans. Magnetics, MAG-22(5) (1986) 614-619; also LEES Technical
Report #TR86-016, May 1986.
1,81] Inkpen, S.L. and Melcher, J.R., Dominant mechanisms for color differences in
the mechanical and the electrostatic spraying of metallic paints. Ind. Eng.
Chem. Res., 26 (1987) 1645-1653.
[82] Inkpen, S.L., LR. Melcher and P.K. Jeganathan, Electrical induction of patterns in metallic paints, I&EC Amer. Chem. Soc., (1988) 58-64.
[83] Withers, R.S. and J.R. Melcher, Augmentation of single-stage electrostatic
precipitation by electrohydrodynamic instability, I&EC Amer. Chem. Soc.,
(1988) 170-179.
1-84] Bart, S.F., J.R. Melcher and R.M. Ehrlich, AC collection efficiency of precharged particulate in turbulent flows, I&EC Amer. Chem. Soc., (1988)
123-131.
[85] Melcher, J.R., Noninvasive ion-drag velocimeter, J. Electrostat., 24 (1989)
67 -77.
[86] Zaretsky, M.C., L. Mouayad and J.R. Melcher, Continuum properties from
interdigital electrode dielectrometry, IEEE Trans. Electrical Insulation, 23(6)
(1988) 897-917.
[87] Melcher, J.R., Lyon, D. and Zahn, M., Flow electrification in transformer
oil/cellulosic systems, Annual Report of Conf. on Electrical Insulation and
Dielectric Phenomena, IEEE Dielectrics and Electrical Insulation Society,
1986 (IEEE Service Center, Single Pub. Sales Dept. 445 Hoes Lane, Piscataway, NJ 08854) pp. 257-265.
[88] Lyon, D.J., J.R. Melcher and M. Zahn, Couette charger for measurement of
equilibrium and energization flow electrification parameters: Application to
transformer insulation, IEEE Trans. Electrical Insulation, 23(1) (1988)
159-176.
154
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
[89] Gasworth, S.M., J.R. Melcher and M. Zahn, Flow-induced charge accumulation in thin insulating tubes, IEEE Trans. Electrical Insulation, 23(1) (1988)
103-115.
[90] Melcher, J.R., E.P. Warren and R.H. Kotwal, Theory for finite-phase traveling-wave boundary guided transport of tribo-electrified particles, IEEE Trans.
on Industrial Applications, 25(5) (1989) 949-955.
[91] Melcher, J.R., E.P. Warren and R.H. Kotwal, Traveling-wave delivery of single
component developer, IEEE Trans. Ind. Appl., 25(5) (1989) 956-961. (1990
Technical Paper Recognition Award from IEEE Industrial Applications Society Electrostatic Processes Committee).
[92] Melcher, J.R., E.P. Warren and R.H. Kotwal, Theory for pure-traveling-wave
boundary-guided transport of tribo-electrified particles, Particle Science and
Technology.
[93] Haus, H.A. and Melcher, J.R., Fields that are always dynamic, IEEE J.
Education, 33(I) (1990) 35-46.
[94] Zaretsky, M.C., Li, P. and Melcher, J.R., Estimation of thickness, complex bulk
permittivity and surface conductivity using interdigital dielectrometry, IEEE
Trans. Electrical Insulation, EI-24(6) (1989) 1159-1166.
[95] Zaretsky, M.C., Melcher, J.R. and Cooke, C.M., Moisture sensing in transformer oil using thin film microdielectrometry, IEEE Trans. Electrical Insulation, EI-24(6) (1989) 1167-1176.
[96] Washabaugh, A.P., M. Zahn and J.R. Melcher, Electrohydrodynamic traveling-wave pumping of homogeneous semi-insulating liquids, IEEE Trans. Electrical Insulation, 24(5) (1989) 807-834.
[97] Morin, A.J., II, M. Zahn, J.R. Melcher and D. Otten, An absolute charge sensor
for fluid electrification measurements, IEEE Trans. Electrical Insulation, EI-26
(1991) 181-199.
[98] Morin, A.J., II, M. Zahn and J.R. Melcher, Fluid electrification measurements
of transformer pressboard/oil insulation in a couette charger, IEEE Trans.
Electrical Insulation, EI-26 (1991) 870-901.
[99] Zahn, M., J.R. Melcher and H.A. Haus, Experimental demonstrations for
teaching electromagnetic fields and energy, in: NSF/IEEE Center for Computer Applications in Electromagnetics Education (CAEME), Software Book,
Vol. I, Chapter 7, 1992.
[lOO] Washabaugh, A.P., M. Zahn and J.R. Melcher, Enhanced electrification charge
densities due to recirculatory flow, 3rd Internat. Conf. on Properties and
Applications of Dielectric Materials, July, 1991, Tokyo, Japan, pp. 272-275.
[lO1] von Guggenberg, P.A. and J.R. Melcher, An immersible relative saturation
moisture sensor with application to transformer oil, 3rd Internat. Conf. on
Properties and Applications of Dielectric Materials, July, 1991, Tokyo, Japan,
pp. 1258-1261.
[1023 von Guggenberg, P.A. and J.R. Melcher, A three-wavelength flexible sensor for
monitoring the moisture content of transformer pressboard, 3rd Internat.
Conf. on Properties and Applications of Dielectric Materials, July, 1991,
Tokyo, Japan, pp. 1262-1265.
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
155
[103] Washabaugh, A.P., P.A. von Guggenberg, M. Zahn and J.R. Melcher, Temperature and moisture transient flow electrification measurements of transformer
pressboard/oil insulation using a couette facility, 3rd Internat. Conf. on Properties and Applications of Dielectric Materials, July, 1991, Tokyo, Japan, pp.
867-870.
[104] Melcher, J.R., America's Perestroika, Technology Review Alumni Section,
April, 1991, pp. 4-11.
[105] von Guggenberg, P.A. and J.R. Melcher, Moisture dynamics in paper/oil
systems subject to thermal transients, in: Proc. of the PSE & G/EPRI Workshop: Static Electrification in Power Transformers, Electric Power Research
Institute, Princeton, N J, November 15-17, 1989, Paper No. 3-4; EPRI Technical Report EL-6918, July, 1990.
[106] von Guggenberg, P.A., M. Zahn and J.R. Melcher, Diagnostic methods for
moisture detection in tranformer insulation, in Proc. 3rd EPRI Workshop:
Static Electrification in Power Tranformers, Electric Power Research Institute,
San Jose, CA, January 23-24, 1992.
B. BooKs'
[-1] Melcher, J.R., Field-Coupled Surface Waves, MIT Press Monograph, Cambridge, MA, 1963.
[2] Woodson, H.H. and J.R. Melcher, Electromechanical Dynamics, text published in three separately bound volumes, Wiley, New York, 1968; also published in Japanese and Chinese.
[3] Melcher, J.R., Continuum Electromechanics, The MIT Press, Cambridge, MA,
1981, including Solutions Manual.
[4] Haus, H.A. and J.R. Melcher, Electromagnetic Fields and Energy, PrenticeHall, Englewood Cliffs, N J, 1989 and Solutions Manual: Electromagnetic
Fields and Energy.
C. Films
[1] Melcher, J.R., Complex Waves, I: Propagation, Evanescence and Instability, 26
minutes, produced by Education Development Center, Newton, MA, for the
National Committee on Electrical Engineering Films.
[2] Melcher, J.R., Complex Waves, II: Instability, Convection and Amplification,
23 minutes, produced by Education Development Center, Newton, MA, for
the National Committee on Electrical Engineering Films.
[3] Melcher, J.R., Electric Fields and Moving Media, 30 minutes, produced by
Education Development Center, Newton, MA, for the National Committee on
Engineering Education Films.
[4] Zahn, M., J.R. Melcher and M.L. Silva, Video Tapes of Selected Demonstrations of Electromagnetic Fields and Energy, MIT, 1989; and also Fundamental
Demonstrations of Electromagnetic Fields and Energy, Center for Computer
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
156
Applications in Electromagnetic Education (CAEME), Salt Lake City, UT,
1991.
D. Pamn~
[1] Electrohydrodynamic apparatus and method, US Patent # 3,463,944, August
26, 1969.
[2] Sheet glass thickness control method and apparatus, US Patent # 3,496,736,
February 24, 1970 (with M. Hurwitz).
[3] Electrohydrodynamic induction flowmeter and conductivity measuring device,
US Patent #3,528,287, September 15, 1970.
[4] Electrohydrodynamic generator, US Patent #3,529,186, September 15, 1970.
[5] Method for inducing agglomeration of particulate in a fluid flow, US Patent
# 3,755,122, 1973.
[6] Apparatus for electrical support and stabilization of static packed and fluidized
beds, US Patent #4,038,052, 1977.
[7] Electrofluidized beds for collection of particulate, US Patent # 4,038,049, 1977.
[8] Fluid mixing apparatus, US Patent #4,174,907, 1979.
[9] Method for inducing color shift in metallic paint and product, US Patent
#4,911,947 (with S. Inkpen).
[10] Apparatus and methods for measuring permittivity in materials, US Patent
#4,814,690, 1989 (with M. Zaretsky).
[11] Instrument for measurement of charge entrained in fluids, US Patent
#4,873,489, Oct. 10, 1989 (with A.J. Morin, II and M. Zahn).
[ 12] Apparatus and methods for measuring permeability and conductivity in materials using multiple wavenumber magnetic interrogations, US Patent
#5,015,951, May 14, 1991.
[13] Apparatus and methods for obtaining increased sensitivity, selectivity and
dynamic range in property measurement using magnetometers, US Patent
Application Serial Number 07/803,504 (with N. Goldfine), 1992.
Appendix B. Theses Supervised by Prof. James R. Melcher
1. Doctoral Theses
1965
J.M. Crowley, Feedback control of a convective instability.
R. Holland, Application of Green's functions and eigenmodes in the design of
piezoelectric ceramic devices.
F.D. Ketterer, Electromechanical streaming instabilities.
1966
M.J. Schaffer, Hydromagnetic surface waves with an alternating magnetic field.
R.J. Turnbull, Electroconvective instabilities in a fluid with a stabilizing temperature gradient.
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
157
1968
C.V. Smith, Jr., Electrohydrodynamically induced deformation of a planar fluidfluid interface.
1970
T.B. Jones, Jr., Polarization surface electrohydrodynamics.
M. Zahn, Space charge dynamics of liquids.
1971
J.L. Dressier, Video techniques in the feedback control of an electromechanical
continuum.
R.E. Zelazo, Dynamic interactions of monomolecular films with imposed electric
fields.
J.C. Zuercher, Electromechanical interactions based on the electrocapillary phenomenon.
1972
A.R. Millner, Nonlinear feedback control of a continuum (co-supervised with R.R.
Parker).
1973
E.B. Devitt, Electrogaskinematic flows of charged particles.
1974
A.J. Grodzinsky, Electromechanics of deformable polyelectrolyte membranes (cosupervised with I.V. Yannas).
K.S. Sachar, Charged droplet scrubbing of submicron particles.
1975
J.F. Hoburg, Electrohydrodynamic mixing.
1976
P.W. Dietz, Electrofluidized bed mechanics.
K. Zahedi, Electrofluidized bed filtration: fundamentals and applications.
1977
J.C. Alexander, Electrofluidized beds in the control of fly ash.
E.J. McHale, AC Magnetohydrodynamic instability.
1978
M. Horenstein, Particle contamination of high voltage DC insulators.
R.S. Withers, Transport of charged aerosols.
1979
K.R. Davey, Flow of magnetizable particles in turbulent air streams.
J.H. Lang, Computer control of stochastic distributed systems with applications
to very large electrostatically figured satellite antennas (co-supervised with
D.H. Staelin).
1981
A.V. Radun, Charging of particles in the turbulent air around D.C. power lines.
1984
R.M. Ehrlich, AC electrostatic precipitation.
1985
S.M. Gasworth, Electrification by liquid dielectric flow (co-supervised with M.
Zahn).
158
M. Zahn, I-£A. Haus/Journal of Electrostatics 34 (1995) 109-162
1986
S.L. Inkpen, Discoloration mechanisms in electrostatic spraying of metallic paints.
1987
M.C. Zaretsky, Theory and applications of measuring complex permittivities of
insulating media using microdielectrometry.
1990
N.J. Goldfine, Uncalibrated, absolute property estimation and measurement optimization for conducting and magnetic media using imposed ~ - k magnetometry.
2. Master's and Engineer's Theses
1962
H.T. Ochs III, The stabilization of a Rayleigh-Taylor instability by a rotating
electric field.
1963
J.M. Crowley, Excitation and growth rate of electrohydrodynamic instabilities.
1965
R. Canales, Stability of the hydromagnetic pinch with ideal feedback.
M. Nannetti-Valencia, Continuum feedback control of electromechanical instabilities in a thin metal plate.
1966
J.V. Burchett, A magnetoaeroelastic energy conversion scheme.
E.B. Devitt, Surface coupled electromechanics in time varying fields.
J.L. Dressier, Active electromechanical control of fourth-order continua.
M.S. Firebaugh, Electrohydrodynamic induction pumping in a closed conduit.
W.J. Schwarz, Jr., Electrohydrodynamic relaxation surface instability.
R.H. Thomas, Stability of a distributed parameter system controlled by spatially
and temporally sampled feedback.
1967
S. Grodzinsky, Stability of electrohydrodynamic waves in rotational systems.
D.S. Guttman, Bang-bang electrohydrodynamic stabilization.
L. Herold, Traveling-wave charged particle generation.
D.L. Luck, An electrohydrodynamic wick.
R.J. Tove, Problems in plated wire fabrication.
R.E. Zelazo, Interfacial ferrohydrodynamics.
1968
R.T. Calvert, Stability and dynamics of simple rotating dielectrophoretic orientation systems.
W.F. Reeve, Traveling-wave synchronous electrohydrodynamic power generation.
J.P. Regan, Loading characteristics of a charge-constrained synchronous generator.
J. Wong, Thermally induced electroconvection in D.C. fields.
1969
B.E. Bennett, An AC electrostatic precipitator.
F.A. Centanni, Asynchronous traveling wave electrohydrodynamics.
C.W. Kirkwood, A nonlinear quasistatic model for piezoelectric solids.
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
159
1970
R.R. Burn, Electromechanical peristaltic pumping and detection.
T.C. Cheng, Electrogasdynamic flows and related shock phenomena.
D. Pearson, Nonlinear aspects of electrohydrodynamic surface instability.
K.S. Sachar, Double layer transduction mechanisms.
1971
J.O. Dodson, An interactive computer aid for teaching.
D.M. Dudley, The electrodynamics of pendant drops.
A.J. Grodzinsky, Elastic electrocapillary transduction.
J.F. Hoburg, Modes of behavior of water of high voltage transmission lines.
1974
P.W. Dietz, Heat, charge, and momentum transfer in a zero-flow electrofluidized
bed.
T.W. Johnson, The electromechanics of a fluidized bed of insulating particles.
1975
K. Zahedi, Electrofluidized beds in the filtration of submicron particles.
1976
J.C. Alexander, Frequency characteristics of electrofluidized beds in the collection
of submicron particulate.
S.D. Bonner, A technique for the measurement of surface conductivity.
1977
D.T. Ching, Anomalous mobility and electrophoretic deposition of polyvinyl chloride particles in liquid dioctyl phthalate.
H.R. Simkovits, Control of a variable shaftspeed wind energy conversion and
battery storage system.
1978
P.M. Osterberg, Deformable membrane spatial light modulator: A charge-coupled
approach.
1979
R.M. Ehrlich, Non-equilibrium electrokinetic pumping of a semi-insulating
liquid.
P.B. Zieve, New England utilities air pollution retrofit study.
1980
R. McLay, An electromechanical model for a permanent magnet dot matrix
solenoid.
A.M. Presser, The collection of fine particles at high temperature.
1982
L.A. MacGinitie, Electromechanics and filtration efficiency of spouted beds subject
to corona discharge.
M.C. Zaretsky, Design strategy for and implementation of electrostatic control of
diesel exhaust.
1983
K.G. Rhoads, Ion source designs for high temperature precipitators.
1984
S.L. Inkpen, Methods for obtaining uniform electromagnetic heating.
160
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
1985
S.F. Bart, Back corona in AC electrostatic precipitation; two-stage efficiency and
single-stage effects of highly resistive particulates in AC precipitators.
K.A. Delin, Low frequency acoustic methods for leak location in underground
oil-filled conduits.
Y. Kisler, Pressure wave pothead failure.
L. Mouayad, Monitoring of transformer oil using microdielectric sensors.
1986
A.H. Kotwal, A xerographic development system using electrostatic travelling wave
pumping of single component developer.
1987
P. Li, A new approach to on-line monitoring of transformer oil using dielectrometry.
D. Lyon, Couette flow measurement of equilibrium and energization charging in
transformer insulation (co-supervised with M. Zahn).
3. Bachelor's Theses
1962
W.H. Childs, Electrohydrodynamic shocks and anti-shocks.
1963
R.H. Jansen, Stabilizing an electrically stressed plate.
1964
R.J. Aldana, A low output impedance D.C. power amplifier.
E.B. Devitt, Electrohydrodynamic surface waves with alternating bias fields.
K.L. Doty, Effects of electrical losses on resonances of field-coupled surface waves.
R.A. Grant, Jr., Magnetization surface waves.
E. Lombrozo, A high impedance, high Q, low frequency electromechanical bandpass filter.
E.P. Warren, A synthetic Alfven shear wave.
1965
F. Herba, Experimental study of two stream electromechanical instabilities.
J.I. Steele, The excitation and detection of magnetic-coupled surface waves.
1966
F.A. Centanni, Jr., The dynamics of electrified sheets of fluid.
D.M. Espenshade, An experiment with alternating fields in an electrohydrodynamic
system.
J.G. Paglia, Jr., An electro-mechanical analog to viscosity.
G. Prado, The dynamic behavior of charged water droplets.
J. Wong, Resonance frequencies of a rotating electrohydrodynamic system.
1967
G.L. Blankenship, Bang-bang stabilization in one dimension.
R.R. Crout, Mechanical effects of polarization forces.
R.L. Goldstein, Electric field gradient stabilization of the Kelvin-Helmholtz instability.
M. Zahn, H.A. Haus/Journal of Electrostatics 34 (1995) 109-162
161
R.W. Landley, Electrohydrodynamic instability of perfect dielectrics.
1969
P.J. Abbas, Experimental investigation of interfacial relaxation overstability.
M.P. Perry, A dielectrophoretic siphon.
G.A. Tripoli, On the design and operation of an electrohydrodynamic power
generator.
F. Westhoff, Measuring conductivity by induction.
1971
T.H. Tate, Properties of a dielectric interface stressed by a perpendicular electric field.
1972
F. Ahmad, Charged droplet production via electrohydrodynamic sprayers.
1973
T.W. Johnson, Dynamics of a conducting sphere between capacitor plates.
T. Mitchell, Electrically controlled chemical to mechanical transduction at a mercury double layer.
1974
C.K.-K. Yue, Electrohydrodynamical behavior of a system of convecting charged
droplets under oscillation.
1975
J. Gordon, Oscillations of a charged sheet of water droplets.
A.A. Merab, Traveling-wave induced electroconvection for a circular geometry.
1976
S.M. Gasworth, Ferrohydrodynamic stability in cylindrical geometry.
D.P. Hinson, Synchronous pumping of a highly conducting fluid by an electric field.
P.B. Zieve, Electrofluidized bed in filtration of asphaltic smoke emissions.
1977
A. Barnett, A particle mobility analyzer.
1978
R.S. Colby, Electrohydrodynamics of charged aerosol flows.
P.G. Huber, High temperature particulate using a combustion ion source.
P.A. Martin, Removal of magnetic particles from a turbulent gas.
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