Download Buletin Stiintific - UPB - Seria C - numar 4 - 2008

U. P. B. Sci. Bull., Series C, Vol. 70, Iss. 4, 2008
ISSN 1454-234x
Contents
ELECTRONICS AND TELECOMMUNICATIONS
Cătălin Ungurean, Dragoş Burileanu, Vladimir Popescu, Cristian Negrescu, Aurelian
Derviş
Automatic diacritic restoration for a TTS-based e-mail reader application
3
AUTOMATIC CONTROL AND COMPUTERS
Sergiu St. Iliescu, Ioana Fgărăşan, Victor Popescu, Călin Soare
Gas turbine modeling for load-frequency control
13
Nidal Turab, Florica Moldoveanu
The impact of various security mechanisms on the WLAN performances
21
Florin Stratulat
Linear systems’ stabilization by using dynamic compensation
37
Carmen Niculescu-Faida, Adrian Niculescu-Faida
Vehicle dynamics modeling during moving along a curved path. Mathematical
model usage on studying the robust stability
49
Janetta Culiţă, Dan Ştefănoiu, Florin Ionescu
Semi-empirical methods for bearings diagnosis
61
Dan Popescu, Radu Dobrescu, Nicoleta Angelescu
Statistical texture analysis of road for moving objectives
75
Elena Uleia
OSSim: a switched packets network simulator
Ciprian Lupu, Cătălin Petrescu, Alexandru Ţiclea, Catalin Dimon, Andreea Udrea,
Bogdan Irimia
Multi-model system with nonlinear compensator blocks
87
97
Messaouda Azzouzi
Identification and optimal control of blowing system
115
George Matei, Dan Mihoc
IEC 61850 Standard – A new step in the future of the communication protocols
123
U. P. B. Sci. Bull., Series C, Vol. 70, Iss. 4, 2008
ISSN 1454-234x
ELECTRICAL ENGINEERING
Arif Mammadov, Neculai Galan
The axial air-gap three-phased asynchronous motor
Dan Floricǎu
The balancing of total losses in three-levels voltage source converters
137
153
U. P. B. Sci. Bull., Series C, Vol. 70, Iss. 4, 2008
ISSN 1454-234x
AUTOMATIC DIACRITIC RESTORATION
FOR A TTS-BASED E-MAIL READER APPLICATION
Cătălin UNGUREAN, Dragoş BURILEANU, Vladimir POPESCU,
Cristian NEGRESCU, Aurelian DERVIŞ
Speech synthesis technology is becoming more important for network-based
applications. However, an e-mail or SMS reader application based on TTS (text-tospeech) technology, for example, needs to face many difficulties, one of them being
the requirement for restoring missing diacritics to text, as a common problem for
many languages that use the Latin alphabet. The paper proposes an efficient
automatic diacritic restoration algorithm for a TTS system in Romanian used in an
e-mail reader application. The algorithm is essentially based on a statistical
strategy that uses n-gram similarity measures, relies on limited linguistic knowledge
and needs a medium-sized training corpus.
Keywords: Text-to-speech synthesis, diacritic restoration, n-grams
GAS TURBINE MODELING FOR LOAD-FREQUENCY
CONTROL
Sergiu St. ILIESCU, Ioana FĂGĂRĂŞAN, Victor POPESCU, Călin SOARE
The traditional role of the gas turbine as fast response unit, ideal for
improving primary control response of the power system, has been to a certain
extent lost, due to relatively high constraints in ramping up and down the power
output during the normal operation. This trend must be fully reflected in the
modeling and simulation of the gas turbines in power system analysis programs. The
paper is a contribution to the systematic analysis of power-frequency control
concepts for multi shaft high power gas turbines and the enhancement of their
modeling in conventional power system analysis software.
Keywords: gas turbines, modeling, frequency and load control, power plants
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U. P. B. Sci. Bull., Series C, Vol. 70, Iss. 4, 2008
ISSN 1454-234x
THE IMPACT OF VARIOUS SECURITY MECHANISMS ON
THE WLAN PERFORMANCES
Nidal TURAB, Florica MOLDOVEANU
Various security techniques were developed to improve the security of the
communication in a WLAN. Their usage in a WLAN can degrade the network
performances.
This paper presents the results of experiments conducted by the authors
regarding the capability of a WLAN to transfer data files of different sizes, under
normal and congested traffic loads, while various security mechanisms are used.
Two levels of communication were chosen to carry out the measurements:
TCP/UDP and FTP/ HTTP.
Keywords: network throughput, congested network, IEEE 802.11g , WEP, WPA,
TKIP, EAP-TLS
LINEAR SYSTEMS’ STABILIZATION BY USING DYNAMIC
COMPENSATION
Florin STRATULAT
The automatic systems are projected so that they should ensure the
fulfillment of some performance indexes of the stationary and dynamical regime. In
this article is presented a stabilization procedure of a multivariable linear system by
using dynamical compensation. The projection of the stabilizer dynamic
compensatory (SDC) is realized in two ways: SDC with Kalman (unitary) state
estimator and SDC with state estimator of Luenberger (minimal) type. The
validation of the solutions obtained is realized by Matlab-Simulink simulation, by
presenting both the Matlab program and the simulation’s result.
Keywords: controllability, observability, control law, allocability, state
estimators, stabilizability, detectability, stabilizer dynamic
compensatory
U. P. B. Sci. Bull., Series C, Vol. 70, Iss. 4, 2008
ISSN 1454-234x
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VEHICLE DYNAMICS MODELING DURING MOVING
ALONG A CURVED PATH. MATHEMATICAL MODEL
USAGE ON STUDYING THE ROBUST STABILITY
Oana-Carmen NICULESCU-FAIDA, Adrian NICULESCU-FAIDA
The problem of the motion of an automobil on a curved path represents a
subject of high interest, in the strive of the profile engineers and automatists to
design the proper control system. First of all rigorous knowledge is compulsory,
about the vehicle dynamics on a circular motion, in order to express as accurate as
possible the physical reality into mathematical equations. The mathematical model
must contain all the defining elements for the specified process, so that a
compromise can be done, between the complexity of the equations and the
computing power needed. This paperwork presents a mathematical nonlinear model
with six freedom degrees, based on which the influence of different parameters over
the stability of the vehicle on a curved path is studied (brackage angle, velocity and
acceleration of the vehicle a.s.o.).From the study based on the Liapunov meaning
stability criterion, we conclude that, at speed exceeding 120 km/h, small brakeage
angles can destabilize the vehicle.
The obtained results can be shown to advantage through a control system.
Keywords: brackage angle, speed, robust stability
SEMI-EMPIRICAL METHODS FOR BEARINGS DIAGNOSIS
Janetta CULIŢĂ, Dan ŞTEFĂNOIU, Florin IONESCU
Vibrations, especially generated by mechanical systems, exhibit a fortunate
and extremely useful feature in fault diagnosis: encoding information about the
health state of the system that produced them. In order to decode that information,
the main properties of vibration yielding identification and isolation of faults have to
a priori be known. The paper goal is to review such properties and to present some
elementary methods of automatic fault diagnosis by vibrations processing.
Keywords: vibrations processing, spectral analysis, bearings fault diagnosis
U. P. B. Sci. Bull., Series C, Vol. 70, Iss. 4, 2008
ISSN 1454-234x
STATISTICAL TEXTURE ANALYSIS OF ROAD FOR
MOVING OBJECTIVES
Dan POPESCU, Radu DOBRESCU, Nicoleta ANGELESCU
The paper objective is to identify and localize significant regions in textured
images for navigating an autonomous agent. Two types of statistic texture features
are used. The first type features are the histograms, and the edge density. The
second type features derive from the medium co-occurrence matrices, which is a
notion introduced by the authors. The algorithms are implemented in MATLAB. The
basic texture is considered the asphalt and the different textures are considered the
grass and the pebble. The experimental results indicate that the features, which
derive from medium co-occurrence matrices, have a good discriminating power
both for texture classification and region localization.
Keywords: texture, statistic features, medium co-occurrence matrix, edge
densities, grey level histogram
OSSIM: A SWITCHED PACKETS NETWORK SIMULATOR
Elena ULEIA
The OSSim software package is a development environment created for
supporting network simulation and analysis, in particular, and any stochastic
processes of discrete systems, in general. It makes use of technologies from the area
of distributed computing, client-server architectures and object oriented
programming. One of the key issues of the design is high performance of the overall
system, making possible the modelling and the simulation of complex networks.The
OSSim toolset is a brand new implementation, based on UNIX open source, not
making use of any existent source code from any other simulators.
Keywords: simulation, protocol modelling, queuing systems, performance
analysis, hierarchical models, distributed computing
U. P. B. Sci. Bull., Series C, Vol. 70, Iss. 4, 2008
ISSN 1454-234x
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MULTI-MODEL SYSTEM WITH NONLINEAR
COMPENSATOR BLOCKS
Ciprian LUPU, Cătălin PETRESCU, Alexandru ŢICLEA, Cătălin DIMON,
Andreea UDREA, Bogdan IRIMIA
The multi-model control structures represent real solutions to control the
systems with important nonlinearities or different functioning regimes. One of
structure’s specific problems is determination of models number. An increased
number determine superior performance and very complex structure. The paper
proposes a original methodology for reducing the model number without
performance decreasing.
This solution has practical importance being facile to be implemented on
PLC and process computers. Experimental results prove structure’s performances.
Keywords: multi-model, control, nonlinearities, compensator block, real-time
IDENTIFICATION AND OPTIMAL CONTROL OF BLOWING
SYSTEM
Messaouda AZZOUZI
The major efforts regarding this analysis, on algorithmic development, and
on computations deal with the flow and temperature control and their optimization.
This study treats the steady state in order to avoid the unsteady problems.
The paper’s analyses, i.e. the numerical analyses, and computations have
addressed two important types of controls which are the air flow and the
temperature. The principal object of this paper is to control several important
characteristics of a chemical process by using an automatic device for optimization
and system identification; in each case one intends to control the temperature
degrees and the air pressure values in the same time, starting from a mechanical
apparatus connected at a computer where there are installed the respective control
software; this apparatus gives the possibility to set the temperature values at a
specified pressure which can produce cold air.
Keywords: air flow control, temperature control, ELWE, ADAPTECH,
optimization
U. P. B. Sci. Bull., Series C, Vol. 70, Iss. 4, 2008
ISSN 1454-234x
IEC 61850 STANDARD – A NEW STEP IN THE FUTURE OF
THE COMMUNICATION PROTOCOLS
George MATEI, Dan MIHOC
The appearance of the IEC 61850 communication standard open new
perspectives for evolution of the protection and control systems from electrical
substations because the integration of existing equipment with the latest generation
equipment from different manufacturers can be possible now. In the authors
opinion, represent a personal contribution presenting of way, which this standard
evaluated, the clear advantages which offer and the perspectives which result
following of the communication developing for protection and control systems. In
the paper was presented the new protocols for data acquisition and communication.
Also the authors insisted on the advantages for IEC 61850 unitary adopting at
National Power Grid level, taking in consideration frequent implementation of
protection and control system in the electrical substations.
Keywords: IEC 61850, communication protocols, protections and control
systems, IEDs (Intelligent Electronic Devices), SCL (Substation
Configuration description Language), GOOSE (Generic Object
Oriented Substation Event)
THE AXIAL AIR-GAP THREE-PHASED ASYNCHRONOUS
MOTOR
Arif MAMMADOV, Neculai GALAN
It presents a motor with axial air-gap which has been manufactured
practically. The new elements concern the two stators poles disposition as well as
the winding building and some technological elements. One has presented the
building manner, the operating mode, and the elaborating mathematical model
where the electrical parameters calculation way becomes concrete for this new
motor. The motor we have proposed gets real advantages: less material; less energy
for variable load; opportunity to be manufactured with two synchronism speeds on
the condition the two stators not be supplied simultaneously; possibility of
successive brakes. The equivalent circuit are presented in the general reference K
and one shows the manner they can be particularized in other reference systems.
Keywords: axial motor, mathematical model, electrical parameters
U. P. B. Sci. Bull., Series C, Vol. 70, Iss. 4, 2008
ISSN 1454-234x
THE BALANCING OF TOTAL LOSSES IN THREE-LEVELS
VOLTAGE SOURCE CONVERTERS
Dan FLORICǍU
Static converters design has to ensure that in all specific operating
conditions the junction temperature of power devices does not exceed admitted
limits. The temperature of different components depends on the losses distribution
and on the number of switches in IGBT modules. This paper investigates the
balancing of total losses in four 3L-VSI (Voltage Source Inverters): 3L-Stacked
Cells, 3L-Neutral Point Clamped (NPC), 3L-Active NPC and 3L-Stacked NPC. The
3L-Stacked NPC concept allows the natural doubling of the apparent switching
frequency and leads to a better balancing of total losses.
Keywords: multilevel converters, conduction losses, switching losses.
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