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Anul XVIII (2011), Nr. 1

TABLE OF CONTENTS

ARTICLES

Gas Tank for Cars
Peter Lorenz, Valentina Ignat

In this work the development of a highly efficient pressure vessel for liquid petroleum gas (LPG) in integral design is described. The pressure vessel can be customized in an optimal available installation space and thus means that the suitable for everyday use of existing modified cars or trucks can be increased.

Keywords: pressure vessel, LPG, Liquefied Petroleum Gas, space optimization

Obtaining Target for Solar Cells with Unconventional Supports
Mariana Buga, Bogdan Maria, Costin Cepisca, Rares Medianu

The main technological aim is to develop experimental models of magnetron targets of CuInS2 and CuInSe2, controlled Ga doped in concen-trations ranging between 7% and 17%. Advantage of using CuInS2 in manufacturing of solar cells is the presence of nontoxic sulfur. The optimum concentration of Ga determine surely the best crystalline phase of CuInS2 and results are an improvement of the absorbtion band and therefore an increase of quantum efficiency of the quaternary mixture – CIGS in double thin layer.

Keywords: solar cells, unconventional supports, magnetron sputtering

Considerations Concerning the Dynamics of Vibratory Mills Used in Powders’ Mechanical Milling Process
Jevto Lučić, Nenad Zrnić

Air pollution as a consequence of a modern way of life contaminates the natural environment and brings us the global warming which poses a clear and present danger to civilization. The main causes of global warming are greenhouse gasses, which arise of reliance on fossil fuels, deforestation, agriculture, industrial processes and transport. The transport itself makes 14% of the main causes of greenhouse gasses. Its dependence on fossil fuels, together with the decrease of a world fossil fuels reserves, force us to look for alternative fuels and to develop alternative drive systems, which can stabilize and reduce the greenhouse effect, and at the same time offer us new technologies, in-dependent on a fossil fuels. This paper will try to present potential solutions for this problem, and to show the development of alternative drive systems.

Keywords: greenhouse gasses, vehicle emission, alternative drive systems

Determination of Optical Constants of Polystyrene Films from IR Reflection-Absorption Spectra
Simion Jitian

Determination of The transmittance values measured in IR reflection-absorption (RA) spectra were used to determine the optical constants of dielectric films laid on solid substrates. In order to obtain the optical constants of polystyrene films laid on steel we used dispersion analysis. In this case, the optical constants are obtained from IR spectrum recorded at a single incidence angle. The use of dispersion analysis offers the advantage of processing a large volume of data.

Keywords: reflexion-absorption, optical constants, IR spectra, dispersion analysis

Reducing Power Penalty Related to Post-Combustion CO2 Capture in Coal Power Plants
Ramona Mihaela Negoi, Adrian Badea, Cristian Dinca, Tiberiu Apostol, Norișor Mihaela

Considering the important role of coal in energy security and in the same time the growing need to reduce CO2 emissions, amine-based post-combustion CO2 capture is considered as one of the most proper technologies to be implemented in coal fired power plants as well in natural gas fired plants, reﬁnery gas, cement plants etc. The main challenge for CO2 post-combustion is reducing the energy demand of the process, especially for solvent regeneration. In this paper, the energy reduction potential when waste heat of flue gases is integrated in the CO2 capture configuration scheme is discussed. The results are compared with a conventional coal power plant configuration when low-steam pressure is extracted from the water-steam cycle of the power plant.

Keywords: CO2 capture, post-combustion, monoethanolamine

Microstructural Analysis of Al/Al2O3/Gr Powder Composites Produced by Mechanical Alloying
Gheorghe Iacob, Adina Uşurelu-Cristea, Gabriela Popescu, Mihai Buzatu, Florin Miculescu

Powder samples of Al/Al2O3/Gr hybrid composites with different weight percents were obtained by mechanical alloying in a high energy ball mill. The aim of this study is to investigate the effect of alumina and graphite particles content on the microstructure of Al/Al2O3/Gr hybrid composites. Results obtained using Scanning Electron Microscopy (SEM) as well as Energy-Dispersive X-ray Spectroscopy (EDS) show that the addition of alumina particles as the reinforcement has a drastic effect on the size and morphology of the composite powders. Also, the addition of graphite particles as one of the reinforcing components is presumed to improve tribological properties by forming a graphite-rich lubricant film between the sliding surfaces.

Keywords: composites, powder, microstructure, morphology

Stereomicroscopic Analysis of ECAE Processed Mg-Zn-Zr alloy
Florina-Diana Dumitru, Brânduşa Ghiban, Nicolae Ghiban, Gheorghe Gurău, Mihai Brânzei, Mihai Marin

Lately, a growing volume of research has been conducted on studying the effects of equal channel angular extrusion processing. Equal channel angular extrusion (ECAE) or equal channel angular pressing (ECAP) is a severe plastic deformation (SPD) technique, which presses the test materials through a die with two channels which are equal in cross section and intersecting at a certain angle. After the deformation, the test materials will still retain its original cross-section being able to repeat the process to many cycles. This method improves the mechanical properties of the processed materials because of the ultrafine grained structures resulted. Present paper intends to make a qualitative investigation of the Mg-Zn-Zr samples processed through ECAE.

Keywords: severe plastic deformation method, equal channel angular extrusion, magnesium alloys

On the Geometric Transformations and Auxetic Materials
Veturia Chiroiu, Petre P.Teodorescu, Ligia Munteanu

A new approach to obtain various architectures for auxetic foams by using the property of Helmholtz equation to be invariant under geometric transformations is described in this paper. The versatility of the geometric transformations is illustrated in order to obtain the auxetic version from the conventional foam.

Keywords: Geometric transformation, auxetic foams, Cosserat theory, chirality

Eco Issues in Bulk Materials Handling Technologies in Ports
Nenad Zrnić, Miloš Đorđević, Branislav Dragović, Srđan Bošnjak

This paper deals with eco issues in bulk materials handling in ports. Solid, free-flowing materials are said to be in bulk. Bulk materials handling is very difficult, because it incorporates all the features of liquids, gasses and mass solids. Energy efficiency, dust emissions in nearby environment, dust explosions, jamming, noise, handling of hazardous materials and protection of materials from contamination are issues that will be considered in this paper. Here are also presented possible solu-tions for some of these issues.

Keywords: Ports, bulk materials handling, eco issues, eco efficiency

Different Aspects of Cavitation Damages in Some Stainless Steels
Mădălina-Elena Mânzână, Brândușa Ghiban, Nicolae Ghiban, Ilare Bordeașu, Florin Miculescu, Mihai Marin

Cavitation is an important factor in many areas of science and engineering, including acoustics, chemistry and hydraulics. In this paper the authors analyze the manner of cavitation damages in different samples of stainless steels. Cavitation destruction was performed in a magnetostrictive vibrating apparatus in Laboratory of Polytechnic University of Timisoara, Romania. Cavitation erosion behaviour was appreciated considering macrostructural analysis (both quantitative and qualitative) made at stereomicroscope type OLYMPUS equipped with QuickMicrophoto 2.2 software and structural analysis at scaning electron microscope (SEM) at Philips SEM microscope. Finally conclu-sions regarding specific structural features of cavitation at stainless steels were revealed.

Keywords: cavitation-erosion, damages, stainless steels, chemical element

Structural Analysis of Cavitation for Different Stainless Steels
Mădălina-Elena Mânzână, Brândușa Ghiban, Nicolae Ghiban, Ilare Bordeașu, Florin Miculescu, Sorina Mitrea, Mihai Marin

The cavitation phenomenon is currently approaching all areas of technology and modern industry, where are fluid in motion. In this paper cavitational erosion was conducted on different samples of stainless steels. The cavitation were performed in magnetostrictive vibrating apparatus at Cavitation Laboratory (Polytechnic University of Timisoara). The present paper intends to identify specific structural features in stainless steels. Several investigations were done: macrostructural analysis (Olympus SZX57), scaning electron microscope (Philips SEM) and X-ray diffraction (D8 ADVANCE). After quantitative and qualitative investigations structural features were put in evidence on experimental stainless steels..

Keywords: cavitation, chemical composition, macrostructural analysis, stainless steels

Hysteresis Models, State of the Art
Octavian Tabără

Hysteresis represents a new challenge for scientists in last years. Several models of hysteresis were developed in order to understand the delay between input and output. This article does a classification of vectorial hysteresis models and presents simulation results obtained for some specimens using variable separation, and Preisach algorithm.

Keywords: vectorial hysteresis models, Preisach models, Stoner-Wohlfarth models, Preisach-Stoner-Wohlfarth models

Modelling of Corrugated Paper Board Boxes with FEM
Peter Lorenz, Valentina Ignat

The main aim of this project is the comparison between the experimental and FEM results of loaded corrugated paper boards. The corrugated paper boards have an orthotropic material behaviour, which means that the boards, depending on the direction of the corrugation, have different modules of elasticity. The research should give results about theses different material data of the plates. These results are the basis for further product designs with corrugated paper boards.

Keywords: corrugated paper board, FEM

Analysis of the Rollover Behavior of the Bus Bodies
Dan Alexandru Micu, Daniel Mihail Iozsa

When performing calculations using ANSYS software have been achieved so far, only a part of the requirements imposed by regulation on how to conduct computerized mathematical modeling, the paper presented only a first set of results in this area, following research should be conducted detail.

Keywords: analysis, bus, structural, rollover

Some Aspects of the Roll-over Protective Structures Evaluation, Using Shock Loading Simulation
Petru Dumitrache

The objective of this paper is the highlighting of the main aspects that be considered in numerical simulation of the behavior of roll-over protective structures that are included in mobile machinery cabs, using finite numerical simulation. In first part of the paper are presented, briefly, the legislative framework and the reference documents governing the mechanical protection of the human operator of machinery and equipment construction. Next, are analyzed the roll-over protective structures and the main aspects related to their evaluation by shock loading simulation. In this context, are given the necessary information to correctly model the real problem so that the results to have an im-posed accuracy.

Keywords: Roll-over protective structures, shock loading, numerical simulation

About Mechanical Shock Energy Dissipation by Deformation and Friction, with Applications to In-crease Performance of Protective Structures
Petru Dumitrache

Increasing the capacity of the mechanical shock's energy dissipation is the main objective in design of protective structures. Article brings to the forefront the idea of increasing the amount of energy dissipated by simultaneously deformation and friction of the structural elements. In this context, some experimental results are presented and some aspects of finite element modeling of the behavior of such systems. At the end of the article are drawn some conclusions on the implementation of such systems in protective structures.

Keywords: Shock energy, deformation, friction, protective structures

Experimental Investigation of Dynamic Behavior of Viaducts by Shock Loading
Adrian Leopa, Silviu Nastac, Gheorghe Panfiloiu

The viaducts are constructions designed to provide ground communication over different geographical barriers such as examples valleys (depressions). To avoid partial or total destruction that may occur after dynamic stress from road (or railroad) or seismic activity, in viaducts structure is placed systems for dynamic isolation. Thus, the viaduct deck is mounted on viscoelastic type systems designed to provide pro-tection from the shock loading. Over time, due to an intensive and var-ied of dynamic loadings, these isolation systems suffer degradation of viscoelastic links, something that leads to uncontrolled movements of the system. In this work, are established and quantified on experimen-tal way, kinematics parameters of the vibration of the viaduct deck loading by shocks, which will be monitored over time to establish the degree of normality in the functioning of viscoelastic systems.

Keywords: shock, vibration, bridge, damage

DFatigue Analysis of an Outer Bearing Bush of a Kaplan Turbine
Calin-Octavian Miclosina, Constantin Viorel Campian, Doina Frunzaverde, Vasile Cojocaru

The paper presents the fatigue analysis of an outer bearing bush of a Kaplan turbine. This outer bush, together with an inner one, bear the pin lever - trunion - blade subassembly of the runner blade operating mechanism. For modeling and simulation, SolidWorks software is used.

Keywords: Outer bearing bush, Kaplan turbine, fatigue analysis

Experimental Analysis of Residual Stresses in Samples of Austenitic Stainless Steel Welded on Martensitic Stainless Steel Used for Kaplan Blades Repairs
Vasile Cojocaru, Constantin Viorel Campian, Calin-Octavian Miclosina

Residual stresses occur in materials as a result of mechanical processes: welding, machining, grinding etc. If residual stresses reach high values they can accelerate the occurrence of cracks and erosion of material. An experimental research was made in order to study the occurrence of residual stresses in the repaired areas of hydraulic turbine components damaged by cavitation erosion. An austenitic stainless steel was welded in various layer thicknesses on a martensitic stainless steel base. The residual stresses were determined using the hole drilling strain gage method.

Keywords: residual stresses, austenitic stainless steel, martensitic stainless steel, cavitation erosion, Kaplan turbine

On Virtual Integrated Model of a 6DoF Manipulator Arm for Emergency Cases Interventions
Gigi Naidin, Silviu Nastac, Carmen Debeleac

This research deals with a virtual integrated model for a 6DoF manipulator arm dedicated to use for emergency situations intervention. The virtual model can simulates both the entire structural and mechanical configuration of the manipulator, and the driving system with automated command unit. The basic idea supposes to develop a complex simulator for kinematical and dynamic behavior analysis of 6DoF robot manipulator, and for facilely cross correlation and comparative evaluation between essential parameters and extremely bearing cases defining the manipulator working state. The analysis was developed in Matlab© - SimScape© software. The conclusions dignify the main functional capability of the manipulator supposing the capacity of driving system and mechanical structure.

Keywords: manipulator robot, integrated virtual model, emergency situations, dynamics, SimScape©

Finite Element Analysis of Collision Phenomenon that Occurs during the Manufacturing Process of Axial Bearings Rollers
Tiberiu Stefan Manescu, Tiberiu Manescu Jr., Vasile Cojocaru

The paper presents the analysis of the collision phenomenon that occurs during the manufacturing process of axial bearings rollers. The manufacture of rollers is made on automatic production centers. During the transport process on automated lines, collisions occur between rollers. A study on cylindrical rollers Φ16 x L24, in the simplified cases of head-head collision and head-circular surface collision, was made in Solid Works Simulation. Stress and deformation results are presented.

Keywords: elasto-plastic collision, stress, deformation, bearing rollers

Design of a Hydraulic Damper for Heavy Machinery
Emil Zaev, Gerhard Rath, Hubert Kargl

A hydraulic unit consisting of an accumulator as energy storage element and an orifice providing friction was designed to damp oscillations of a machine during operation. In the first step, a model for the gas spring was developed from the ideal gas laws for the dimensioning the elements. To model the gas process with a graphical simulation tool it is necessary to find a form of the gas law which can be integrated with a numerical solver, such as Tustin, Runge-Kutta, or other. For simulating the working condition, the model was refined using the van der Waals equations for real gas. A unified model representation was found to be applied for any arbitrary state change. Verifications were made with the help of special state changes, adiabatic and isothermal. After determining the dimensional parameters, which are the accumulator capacity and the orifice size, the operational and the limiting parameters were to be found. The working process of a damper includes the gas pre-charging to a predefined pressure, the nearly isothermal static loading process, and the adiabatic change during the dynamic operation.

Keywords: Vibration damping, hydraulic damping, gas laws

Modeling the Collision Phenomena of Ø11X19 Size Rolls
Tiberiu Manescu Jr., Michael Thurnes, Claudiu Iavornic, Ioan Ciorba

This paper presents a numerical comparison using dynamic modeling techniques, of physical phenomena occurring at collisions between two rollers in a lot of distinct situations: impact on the edge at angles of 0°, 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80° and impact on generator. These situations occur frequently in the manufacturing process of small cylindrical rollers.

Keywords: bearing, cylindrical rollers, collision

Stress and Deformation Analysis in Base Isolation Elements Using the Finite Element Method
Claudiu Iavornic, Gilbert-Rainer Gillich, Vasile Iancu, Zeno-Iosif Praisach, Ovidiu Vasile

In Modern tools as Finite Element Method can be used to study the behavior of elastomeric isolation systems. The simulation results obtained in this way provide a large series of data about the behavior of elastomeric isolation bearings under different types of loads and help in taking right decisions regarding geometrical optimizations needed for improve such kind of devices.

Keywords: elastomeric isolation systems, earthquake, safety, finite element method

Analysis of the CVT Efficiency by Simulation
Valerian Croitorescu, Jan Anthonis, Mircea Oprean, Eugen Negrus, Cristian Andreescu

All vehicle manufacturers desire an ideal vehicle that has the highest powertrain efficiency, best safety factor and ease of maintenance while being environmentally friendly. These highly valued vehicle development characteristics are only reachable after countless research hours. One major powertrain component to be studied in relation to these demands is the Continuous Variable Transmission that a Hybrid Electric Vehicle is equipped with. The CVT can increase the overall powertrain efficiency, offering a continuum variable gear ratios between established minimum and maximum limits. This paper aims to determine the losses of a CVT, operating on a HEV. Using simulation, the losses were computed and the fuel economy was analyzed. During various modes of operation, such as electric, regenerative braking, engine charge for maintaining the battery state of charge, the losses and their dependence with the control properties were analyzed. A relevant determination of precise losses is able to reduce them by using appropriate materials for their components and fluids, more efficient technical manufacturing and usage solutions and innovative control strategy.

Keywords:CVT, HEV, power loss, efficiency, simulation

Peculiar Aspects of Rotor-Bearing Systems Vibrations
Radu Panaitescu-Liess, Amelitta Legendi, Cristian Pavel

The rotor-bearing systems are marked both by an asymmetrical stiffness and by important damping properties, which are causing instability in their rotating motion. The asymmetrical properties presented in this paper are displayed in the rotor motion preferential direction due to the damping internal forces mainly, and also to forces in slide bearings.

Keywords:rotor; eigenfrequency; internal damping; instability

Numerical Analysis of Flow in Kaplan Turbine Runner Blades Anticavitation Lip with Modified Hydro-dynamic Profile
Vasile Cojocaru, Viorel Constantin Campian, Daniel Balint

In order to increase the lifetime of runner blades of Kaplan turbines damaged by cavitation erosion, an anticavitation lip is attached to the periphery of the runner blades on the suction side. The anticavitation lip overtakes the cavitation pitting which appears between the runner blades and the runner chamber. A blade with the original anticavitation lip was modeled using CAE. The numerical simulations showed the tip vortex position and the source of the cavitation erosion. Using these data, a modified profile of the anticavitation lip was designed.

Keywords:anticavitation lip, cavitation erosion, Kaplan turbine, runner blade, CAE

Attenuation Analysis and Acoustic Pressure Levels for Combined Absorptive Mufflers
Ovidiu Vasile, Darian Onchis-Moaca

The paper describes the pressure-wave propagation in a muffler for an internal combustion engine in case of two combined mufflers geometry. The approach is generally applicable to analyzing the damping of propagation of harmonic pressure waves. The paper purpose is to show finite elements analysis of both inductive and resistive damping in pres-sure acoustics. The main output is the attenuation and acoustic pressure levels for the frequency range 50 Hz–3000 Hz.

Keywords: attenuation, absorptive muffler, geometry of muffler, glass wool

Natural Frequencies Distribution on the Damaged Beams
Zeno-Iosif Praisach, Gilbert-Rainer Gillich, Peter Lorenz

This paper presents the natural frequencies distribution on the damaged beams. The frequencies distributions was analyzed for three types of beams: cantilever, double clamped and simple supported. The analysis was performed using the finite element method (FEM), for the undamaged beam and for the beam having damages at around 190 locations, considered one by one, and nine levels of depth. The authors deduced analytical relationships for damaged beam frequency shift and presents the results.

Keywords: natural frequencies distribution, damage, beam

On Methods for Estimating the Friction between the Tire and Tread
Cristina Opriţescu Amalia Ţîrdea, Polidor Bratu, Mihai Toader

The influence of the tire-road friction coefficient is studied in the work for the avoidance of collisions of traffic taking part vehicles. The part of the road surface state is made evident.

Keywords: friction, tire, rolling surface

Anul XVIII (2011), Nr. 2

TABLE OF CONTENTS

ARTICLES

Asymptotic Behavior of Distributions and the Short-time Fourier Transform
Katerina Saneva, Roza Aceska, Sanja Kostadinova

Asymptotic and quasi-asymptotic behavior of the wavelet transform has been studied by the first author in [20, 21, 19, 22]. Similar results are, as expected, derived for the STFT: we provide Abelian and Tauberian type results relating asymptotics of STFT and the quasiasymptotic behavior in the space. Even though it is probable that different behavior would occur with respect to different weight spaces, we have not clarifed the weight-asymptotics link yet. In other words, we still do not know if specifcasymptotic behavior of the STFT occurs only in certain modulation spaces.

Keywords: STFT, modulation spaces, asymptotic behavior, distributions, weight functions

Unsupervised Clustering of EO-1 ALI Panchromatic Data Using Multilevel Local Pattern Histograms and Latent Dirichlet Allocation Classification
Costăchioiu Teodor, Niță Iulian, Lăzărescu Vasile, Datcu Mihai

Over the last years huge amounts of remotely sensed data have been acquired. Among remote sensing satellites we can mention the EO-1 ALI mission, designed as a platform for testing and validation of new technologies that will be incorporated in the forthcoming Landsat LDCM satellite. In this paper we propose a method for unsupervised clustering of the panchromatic band of EO-1 data using multilevel local pattern histograms to capture local and spatial information by recording the size and distribution of bright, dark and homogenous area within a moving window. For classification task we propose the use of Latent Dirichlet Allocation, a method that can discover complex patterns in data, providing results with a high semantic meaning, close to expectations of the human user.

Keywords: EO1-ALI, Multilevel Local Pattern Histogram, Latent Dirichlet Allocation

Speaker Verification using Pole/Zero Estimates of Nasals
Ewald Enzinger, Peter Balazs

The acoustics of nasals are an important source of speaker-discriminating features. Nasal spectra contain poles and zeros dependent upon nasal cavities which are complex static structures which vary from person to person. Nasal spectra may therefore have low within-speaker and high between-speaker variability. This study applies a recent pole-zero model estimation technique based on a logarithmic criterion on nasal spectra to obtain pole/zero features for speaker verification. The robustness against two mismatch conditions, Lombard speech and studio versus GSM transmission channel, is evaluated and compared with an approach based on MFCC features. Furthermore, results of fusion of the nasal systems with a generic MFCC-based GMM-UBM speaker verification system are presented.

Keywords: Pole/Zero model, nasals, speaker verification

Vocal Tract Modeling: from Signal to Structure
Christian H. Kasess, Wolfgang Kreuzer

Tube models are very popular for the computational modeling of speech production. For nasals and nasalized vowels a minimum of two tubes is necessary to accurately model the spectral components of the speech signal. Typically, such models are estimated applying a pole-zero model as a first step and then estimate the tubes cross-sectional areas based on this model. Here, we introduce a method that estimates the tube areas without the necessity to estimate a pole-zero filter model. The algorithm is based on a variational Bayesian scheme under Gaussian assumptions. Probabilistic priors are used to enforce smoothness of the tubes. The method is tested on simulated data and results show that under strong smoothness prior the algorithm converges more reliably than an unconstrained method.

Keywords: vocal tract, two tube model, pole-zero model, variational Bayes

The Influence of Nonindividual Hrtf in Binaural Reproduction Using Headphones
Tudor Marcel Culda, Dumitru Stanomir, Cristian Negrescu

A 3D virtual surround sound environment can be created for a listener using headphone reproduction. For this purpose, a set of head related transfer functions are needed. These functions are convolved with audio signals of a sound source resulting in a 3D virtual spatialization of the source. Two of the most common problems in headphone reproduction are in-head-localization and front-back confusion. In the present paper we are concentrating on analysing the influence of a personal or not personal Hrtf use. For this task it has been measured and built a database with individual Hrtfs for more than one person and performed subjective audio listening tests. In these listening tests we have been evaluated the perfomance of the reduction of reversal confusion in localization when different nonindividual Hrtf in as compared to using individual Hrtf for different types of audio signals.

Keywords: Hrtf, front-back confusion, 3D audio

A Queuing Model Study of Port Performance Evolution
Branislav Dragović, Nenad Dj. Zrnić

The main purposes of the paper are to describe port performance evaluation by queuing models (QMs) based on the nature and applications of the models, state of the art survey based on the classification and identify considered problems and the applications of the existing QMs. There are number of benefits to be gained from QMs for port performance evaluation, among them are: faster development, greater flexibility, less data required and it is easier to understand and interpret the results.

Keywords: queuing models (QMs), port performance evaluation

An Effective Trajectory Optimization Method for Autonomous Mobile Robot Conducted by GPS Positioning using Kalman Filter Approach
Iulian Bățroș, Ovidiu Tomescu, Mihnea Beldescu

The maintenance and operational tasks on construction sites and warehouses are currently performed by human operators (moving stacked crates or debris, powering other devices, plucking products from shelves). This paper would like to highlight the use of a robot capable of performing these tasks using the GPS signals with differential corrections and an effective trajectory optimization method using a Kalman filter approach, also with the aim to identify strengths and weaknesses of this study work. In this paper is also proposed the localization algorithm of an autonomous robot using differential GPS and a Kalman filter approach to smooth the trajectory of the robot, with detailed explanation of the algorithmic approach.

Keywords: Kalman filter, robotics, differential GPS, UTM, real-time kinematics

HPipeline Analyzer using the Fractional Fourier Transform for Engine Control and Satellites Data
Darian M. Onchiș, Mihail Găianu, Ovidiu Vasile

The aim of this paper is to present an algorithm for computing the fractional Fourier transform integrated into the pipeline of processing multi-variate and distributed data recorded by the engine control unit (ECU) of a car and its satellites. The role of this transform is vital in establishing a time-variant filter and therefore it must be computed in a fast way. But for large scale time series, the application of the discrete fractional Fourier transform involves the computations of a large number of Hermite polynomials of increasingly order. The parallel algorithm presented will optimally compute the discrete Fourier-type transform for any given angle.

Keywords: ECU, fractional Fourier transform, pipeline, parallelization

The Level of Calculation Errors in the Case of Using the Weibull Distribution for Estimating the Eolian Potential According to the Real Potential Based on Effective Measurements of the Weather Characteristics
Ioan Ion, Doina Frunzăverde, Viorel Câmpian, Adrian Cuzmoş, Cosmin Dumbravă

The management of an investment program in wind power generators must consider the proper evaluation of the possibilities offered by the location where the park will be disposed and will operate: the available existing electric networks, access roads, the shape of relief, climate, extreme weather phenomena, the average wind speed, etc. Among the items listed above, the most important is wind potential of the area, quantified, measured mainly by multi-annual average wind speed. Evaluation, without special measurements, can be done based on general information such as measurements obtained from meteorological stations, using Weibull distribution for wind speed. When using the weather characteristics measurement results, the evaluation is closer to real multi- annual potential.

Keywords: wind, wind speed, wind potential, wind specific power, energy, Weibull distribution

Wigner Ville Distribution in Signal Processing, using Scilab Environment
Cristian Paul Chioncel, Petru Chioncel, Nicoleta Gillich, Ovidiu Gelu Tirian

The Wigner Ville distribution offers a visual display of quantitative information about the way a signal’s energy is distributed in both, time and frequency. Through that, this distribution embodies the fundamentally concepts of the Fourier and time-domain analysis. The energy of the signal is distributed so that specific frequencies are localized in time by the group delay time and at specifics instants in time the frequency is given by the instantaneous frequency. The net positive volum of the Wigner distribution is numerically equal to the signal’s total energy. The paper shows the application of the Wigner Ville distribution, in the field of signal processing, using Scilab environment.

Keywords: Wigner Ville distribution, Scilab, time - frequency analysis

Oversampling Operators: Frame Representation of Operators
Peter Balazs, Georg Rieckh

For a numerical solution of operator equations a discretization of the operators is necessary. In the well-known Boundary Element Method (BEM) the Galerkin approach uses bases to do that. Frames are often easier or faster to construct than bases. Here we look at the matrix representation of operators using frames. We give a survey over the basic results, with particular focus on the invertibility of the involved systems.

Keywords: Frames, matrix representation, discretization of operators, operator equations

Modern Solutions for Automation of Electrical Traction Power Supply Systems
Ana Mihaela Andreica

This paper presents modern solutions for the automation of the electrical traction power supply system used in urban public transport (trams, trolleybuses and subway trains). The monitoring and control of this process uses SCADA distributed architectures, grouped around a central point (dispatcher) who controls all field sensors, transmitters and actuators using programmable logical controllers. The presented applications refer to the Bucharest electrical transport infrastructure.

Keywords: automation, electrical traction, power supply, urban transport

Naval Power System Dynamics with Proportional Type Regulators
Florenţiu Deliu, Gheorghe Samoilescu, Beazit Ali

This work analyzes the dynamic behavior of naval power system using proportional type controllers, system which provides energy for consumers on the vessel so that the voltage and frequency is always in nominal value limits. Essential problems of the work relates to the tuning of controllers, because the system is nonlinear and we can’t apply known criteria. Analyzing type P controllers we found that oscillations known to occur in proportional type controller can put out the naval power system.

Keywords: naval power system, regulators, generator

The Dynamics of Naval Power System with Integrator Proportional and Derivative Integrator Proportional Regulators
Florenţiu Deliu, Gheorghe Samoilescu, Beazit Ali

The essay analyses the dynamics activity of the naval power system regulators using the integrator proportional and derivative integrator proportional regulators, system that provides the necessary energy for ship consumers so that the voltage and the frequency is always within nominal values.

Keywords: naval power system, regulators, generator

Improved Model for Blood Pressure Regulation in Post Cardiac Surgery Patients
Ciprian Sandu, Paul Dan Cristea

Including automatic control of blood pressure in post cardiac surgery patients has obvious benefits such as reduced costs, effort and enhanced level of safety for the patients. The focus of this study is on the model of a hypertensive patient which is improved relative to the detailed and realistic model proposed, successfully developed and implemented by Lee et al. (2005). This study will be used afterwards with the proven and widespread PID controller for the control of the blood pressure.

Keywords: Blood pressure regulation, patient model

Traffic Signal Green-Wave Control Strategy Based on Divers’ Behaviors
Ovidiu Tomescu, Vicente Ramón Tomás López, Florin Codruț Nemțanu, Iulian Bățroș

The behaviour of vehicles runing in urban areas depends on the driver behaviour and also, their are influenced by traffic control and environmental factors. On the basis of this context and the increase, year by year, of the number of vehicles in urban areas, the authors are focused on finding solutions to use the current road infrastructure in an intensive manner. The paper presents a new model for a bidirectional green wave traffic signal control which is improved by the results of analyzing the relation between vehicles/drivers behavior and the movement of the vehicles and groups of vehicles. The authors will model this dependency using MATLAB software and the paper is concluded with the results of testing of several measures on this functional model.

Keywords: urban arterial road, green-wave, drivers’ behaviors, offset

Improving Quay Cranes Exploitation by Implementing a Port Equipment Management System
Cristina Dragomir

Port operators use almost all type of port equipments, from a range of heavy equipments to light machines. Port activities efficiency can be achieved by improving the exploitation of the necessary port equipment for handling cargo. Objectives of research are based on establishing factors that influence management activities of quay cranes exploita-tion. A better exploitation management of quay cranes can be achieved by implementing a proper port equipment management system.

Keywords: exploitation, port equipments, quay cranes, management system

Systems Structure Based on Wireless Sensor Networks for Monitoring the Transportation Pipelines of Oil and Gas
Petru Junie

This paper presents some results of our own doctoral research on the structure of transportation systems for monitoring oil and gas pipelines using wireless sensors networks. Wireless sensor networks (WSN in English) are a new area of research which is growing rapidly due to the development of the new sensor technologies which are cheaper and cheaper. In this paper we analyze some linear structures and we propose a new hierarchical structure of WSN monitoring systems.

Keywords: Linear structures of WSN systems, pipeline oil and gas transportation monitoring systems, hierarchical structures of WSN monitoring systems

Programming Methods for Road Traffic Control Video Applications
Răzvan Ghiţă

This paper aims to present an application capable of detecting the road traffic load in urban areas using an infrastructure of video cameras in conjunction with a well known programming language: LabView. The presentation will highlight the role played by video detection technology, what advantages it offers and some examples of its successful use in the area of public transports. Developments in recent years clearly show that video systems certainly can, and will, establish themselves in the market. Also, an important aspect of the application consist of the advantage that it can determine the degree of occupation of a traffic link at certain hours, but it also can realize a traffic optimization by interconnecting this application with a traffic light adaptive, control system.

Keywords: road traffic load, video application, traffic optimization

Urban Road Traffic Simulation Techniques
Ana Maria Nicoleta Mocofan

For achieving a reliable traffic control system it is necessary to first establish a network parameter evaluation system and also a simulation system for the traffic lights plan. In 40 years of history, the computer aided traffic simulation has developed from a small research group to a large scale technology for traffic systems planning and development. In the following thesis, a presentation of the main modeling and simulation road traffic applications will be provided, along with their utility, as well as the practical application of one of the models in a case study.

Keywords: traffic, simulation, optimization

Rotor-Stator Air Gap Unevenness Influence on Vibrations in Operation of High Power Hydrogenerators
Valentin Nedelea, Ladislau Augustinov, Gheorghe Liuba

This paper refers to the determination of the influence of rotor-stator unevenness on operating performances in terms of vibration. All generators are generally characterized by certain unevenness which must be taken into account for stator centering. The paper presents the experimental verification method of unevenness influence on hydrogenerator’s vibrations.

Keywords: hydrogenerator, air gap, stator-rotor, vibration

Ballast Load Control of Turbine-Generator Sets in the Micro-Hydro Range with a Turbine that has no Flow Regulating Value
Valentin Nedelea, Ionel Dragomirescu, Ladislau Augustinov, Cosmin Laurian Ungureanu

This paper presents the effects of voltage and frequency variation on users load supplies from electrical supply system generated from small micro-hydro plants. Induction generators operate as stand-alone self excited by capacitors and turbine has no flow regulating valve. Many conventional and non conventional approaches are described to govern turbine-generator set to ensure a steady frequency and voltage level. A load controller increases or decreases a ballast load connected across the generator as the user load varies, to keep frequency and voltage variation in standard limits. To design a controller for self excited induction generator, researches were performed on asynchronous generator with double winding stator to analyse steady state open loop behaviour. The results on the behaviour of the unregulated turbine (DC motor) – generator system was presented.

Keywords: induction generator, voltage and frequency control, ballast load

Edusta 2011. Data processed Expert System for the Evaluation of Mast Security
Peter Lorenz, Valentina Ignat, Thomas Zielinski, Labinot Gashi, Sebastian Haffner, Immanuel Haffner

The expert system EDUSTA 2011 is a new software solution designed to determinate the stability of mast-systems, like lamp-posts and anchor masts. The operators, mainly the municipalities and the cities but also operating companies at airports for instance, are responsible for the stability of there masts and the traffic safety.

Keywords: Edusta 2011, LIMAtest

Anul XVIII (2011), Nr. 3

TABLE OF CONTENTS

ARTICLES

Optimal Solutioning Mode of the Assignment Problems
Olga Ioana Amariei, Codruţa Oana Hamat, Pascal Duval

In the present paper we are presenting an optimal way to solve the Asignment problems using the Network Modeling Module of the WinQSB software, by the Hungarian algorithm. Meantime, the given problem was solved also regarded as a transport problem, due to the fact that the assignment problems may be took in consideration as extensions of the transport problems.

Keywords: Hungarian algorithm, distribution, balanced problem, optimal solution

Velocity Domain Determination of a Waterline Plane Using Continuous Sources
Viorel Andrei, Nicoleta-Gabriela Rodicichin

A calculation algorithm of velocity domain using continuous sources method was developed from successive deduction of complex potential and current function for “n” continuous sources. This paper presents the applicability of this method to a ship waterline. For the waterline curve are known the widths, and the continuous sources are placed in the longitudinal plane of the ship. Result by calculations, the velocity components helps to determine the velocity module along the curve.

Keywords: velocity, continuous sources, waterline

An Oriented Object Application
Cornelia Victoria Anghel

This article presents the description of an Oriented Object Application functional inside an Expert System of an industrial Company. This application manages the company's employees, while working in various projects and program packages. With this application, the company can generate productivity reports for different departments, thus monitoring their efficiency and profitability.

Keywords: Oriented Object Application, C++ language, web programs, Expert System, industrial Company

Code description of a C++ Object Oriented Program
Cornelia Victoria Anghel

This article presents the description of a C++ Object Oriented Application functional in an industrial Company. Changes of the existing application were made on three levels, the result being very advantageous for employees and management of the company.

Keywords: object oriented program, C++ language, code programs, sequences

Methods of Manufacturing Technology for Active Compounds Plates of Stamps and Molds
Silviu Dan Avram, Ioan Ciorba

Industrial fields that assume series production of various assembly parts tend more and more to apply as manufacturing method cold stamping and moulding. At current level of development, this process-ing method compared to others comes with important advantages. Pre-sent paper describes methods applied in active boards manufacturing technology of moulds and stamps.

Keywords: active board, component, mold, stamping

Phonic Attenuation due to Screen-Barriers
Vasile Bacria, Nicolae Herişanu

The technique of noise decreasing admits two basic approaches: an active approach and a passive one. In the frame of passive method one can count the employment of screen-barriers. In this paper we present some considerations on sound attenuation due to screen-barriers emphasizing the elements which influence it. The elucidation of these elements is made by measurements. The obtained results can be applied in every other practical situation concerning the protection against noise.

Keywords: screen-barriers, noise attenuation

Experimental Studies and FEM Analysis Regarding the Influence of Geometric Parameters on Strain, Thickness Reduction and Forces in Incremental Forming Process
Adrian Blaga, Valentin Oleksik , Octavian Bologa, Radu Breaz

The purpose of this study was to investigate the influence of geometrical parameters on the distribution of the principal strains and relative thinning and determination of forces in two directions in single point incremental forming process. For this purpose we have chosen a straight grove piece type. The parameters were taken into account are the punch diameter and step down in z direction. Were conducted the tests on two thickness sheet metal of the same material but having different mechanical characteristics. To determine the distribution of strains we used an optical method and to determine the forces a dynamometer was used. We have made two types of FEM analyses, one to determine the strains distribution and another to determine the forces.

Keywords: single point incremental forming, experimental research, strain measurement, force measurement, FEM analysis

Mathematical Modelling and Experimental Investigation of Collector Efficiency of a Thermosyphonic Solar Water Heating System
Bukola Olalekan Bolaji

The collector efficiency of a thermosyphonic solar water heating system was investigated theoretically and experimentally. Mathematical models were developed and used to predict the system performance. The solar collector with water pipes spreading across its width was also developed, tested and the theoretical results obtained agreed well with the experimental results. The collector efficiency is high especially around mid-day when the solar collector receives the highest energy. The results also reveal the dependency of the system performance on intensity of solar radiation and mass flow rate. Increase in both solar radia-tion and mass flow rate increases the collector efficiency. Maximum ef-ficiencies of 72.8 and 70.4% were obtained from theoretical and ex-perimental analyses, respectively, at optimum mass flow rate of 0.098 kg/s.

Keywords: Solar, collector, efficiency, thermosyphonic, water heating

Increasing the Business Performances using Business Intelligence
Antoaneta Butuza, Ileana Hauer, Cornelia Muntean, Adina Popa

Business intelligence is a concept that arose twenty years ago from decision support, which were designed for directors, managers and their supporting analysts. Since then, organizations have come to realize that decision-makers at all levels in all parts of the organization need access to timely, relevant and accurate information, whether in a call centre, sales office, shop floor, retail outlet or logistics department. The paper explores the concepts of BI, its components, emergence of BI, benefits of BI, factors influencing BI, technology requirements, and various BI techniques.

Keywords: Business intelligence, decision-makers, business decisions

Overview of Classic and Modern Wind Measurement Techniques, Basis of Wind Project Development
Cristian P. Chioncel, Petru Chioncel, Nicoleta Gillich, Thomas Nierhoff

For an accurate prediction of the production for windpowerplants and to chose the rigth location for such investments, the main information are given through long time and punctual windmeasurements. That's why the accuracy of a proper wind resource assesment and the rigth data management give the necesary information about the wind shear, turbulance and variability (temporal and spatial). The paper presents the main windmeasurement technics to identify the vertical wind profil, wind speed, wind rose and the time distribution of those parameters.

Keywords: wind measurement, anemometer, LIDAR

Research on the Calculus of the Equivalent Strain of an Elasto-Tactile System for the Monitoring of the Play / Joint during Welding
Lenuţa Cîndea, Cornel Haţiegan, Constantin Marta, Monica Roşu

The paper aims at bringing contributions to the optimisation of the cal-culus of the equivalent strain of an elasto-tactile system in order to monitor the welding joint or play. For this purpose one needs special-ised installations able to take into account the concrete conditions of the performance of welded seams. These installations are equipped with joint sensors which “see” the parts and the trajectories to follow.

Keywords: welded seams, strain, measurement, sensors

The Influence of Distance between Electrodes at Electrohydraulic Forming
Liviu Coman, Codruta Hamat

The paper presents the results of the author`s experimental research for the influence of electrode gap on the maximum drawing depth and shock wave pressure in the case of the electrohydraulic drawing, in the high voltage domain, between 20...50 kV, in which the studies are in small number and, in a large measure, incomplete or contradictories.

Keywords: drawing depth, electrohydraulic forming, electrode gap

Using the Initiation System of Electrical Discharge in the Case of Electrohydraulic Forming
Liviu Coman

The paper presents the results of the author experimental research in order to find the influence of exploding wire geometry on the pressure obtained in the discharge chamber, in the case of electrohydroimpulses drawing in the high voltage domain, between 20...50 kV. The fusible was made by Cu, being studied as follows: the influence of the diame-ter, of the discharge space length, of the developed length of the ex-ploding wire, of the distance between base electrodes and also of the different types and dimensions of the plane or spatial geometrical con-figuration of the exploding wire.

Keywords: pressure, electrohydraulic forming, wire initiation

Efficient Selection of Data Mining Method
Mirela Danubianu, Tiberiu Socaciu

Data mining tools can access large amounts of data and find patterns that can solve various problems, often with surprising solutions. We have analyzed the data mining methods, techniques and algorithms with their characteristics, with their advantages and weakness. Taking into account the tasks to be resolved in order to discover the different types of knowledge, the kind of databases to work on and the type of data, as well as the area for which on desire the implementation of the data mining system we have try to find a way to efficiently choose the proper methods in a given situation. ExpertDM system has the aim to find the best data mining methods for solving a task and specifying the transformation which need to be made for bringing the data at a proper form for applying these methods.

Keywords: data mining, expert system

The Control of Voltage and Frequency of Self-excited Three-Phase Induction Generator
Ionel Dragomirescu, Cosmin Laurian Ungureanu, Valentin Nedelea

In this work it is presented the control of voltage and frequency of three-phase induction generator in autonomous regime. It is adjusted the intensity of voltage and frequency at the terminals of the consumer by means of frequency converter, in conditions of driving the induction generator at constant speed. System testing and measurements were carried out by the Laboratory for Designing and Testing of Equipment Excitation and Automation of the Center for Research in Hydraulics, Automation and Thermal Processes (CCHAPT) within “Eftimie Murgu” University of Resita.

Keywords: voltage, frequency, bank of capacitors, induction generator, frequency converter

Virtual Product Development on Venturi Pump
Sava Ianici, Draghiţa Ianici, Milan Banić, Aleksandar Miltenović

Market globalization and increased customer demands are leading providers of low product series to the high cost of development and construction. To overcome noted challenges it is necessary to use process of virtual product development. In that way it is possible, even in early phases of product development, to assess the operational product behaviour. Even the specific customer demands are determined before the actual product design phase. The paper presents an up to date concept of virtual product development with application on assessment of operational behaviour of Venturi pumps.

Keywords: virtual product development, CFD, optimisation, Venturi pump

Adaptive Control Strategy for Dual–Fuel Stationary Spark Ignition Engines
Adrian Irimescu

Fuel availability is an issue that will become ever more important in the future. Therefore, fuel systems will be required to ensure proper operation with a variety of fuel types. The main idea of this study is to de-velop a control strategy that ensures high fuel conversion efficiency and low emissions levels when employing dual–fuel operation in a micro–cogeneration installation powered by a spark ignition engine. Biogas was considered as the main fuel, while liquid fuel is used to com-pensate for eventual variations in the gaseous fuel flow. Stoichiometric air-fuel ratio is required at all times so that a three way catalytic converter can be used to simultaneously reduce carbon monoxide, unburned hydrocarbon and nitrogen oxide emissions.

Keywords: biofuels, spark ignition engine, dual–fuel, emissions control

Typical Method of Connection of Electric Motor-gear Unit in the Frame of Universal Motor Gear Reducer
Siniša Kuzmanović, Sava Ianici, Milan Rackov, Draghiţa Ianici

Characteristic conceptual solutions of connection of electric motor and gear unit, in the frame of universal motor gear reducer with helical gears, are analyzed in this paper. The aim of this analysis is to highlight the importance and benefits of particular solutions. It is known that today almost all major manufacturers of universal motor gear reducer use special (reducer) motors. Smaller manufacturers commonly use standard (IEC) motors, although large manufacturers, sometimes, also use IEC motors, especially when the customer request. The both of electric motors have certain advantages which manufacturers of motor reducer, with suitable construction solutions, want to use in order to achieve some benefits in the market.

Keywords: sconnection, motor gear reducer, electric motor

Determining the Temperature Variation of the on the Wall of the Casting Mould during the casting of the Hadfield Steel
Constantin Marta, Ioan Ruja, Marius Tufoi, Viorel Bizau, Lenuta Suciu, Monica Rosu

The present paper approaches the analysis of the metal temperature variation during the filling and solidification of steel in the casting mould. Furthermore we made determinations upon the heat transfer through the wall of the casting mould. The casting temperature, the casting speed and the heat transfer through the walls of the mould have a remarkable impact upon the shrinkage process for the preven-tion of casting defects (heat cavities and cracks). These cavities are also development cores for the heat cracks and the concentration of strains, which reduce the chemical, physical and mechanical properties of the cast parts. The shrinkage cavities represent one of the main de-fects of the cast product, and their reduction should be made up to the limits of technical possibilities.

Keywords: casting, defects, shrinking cavity, acquisition, balls

First Law Analysis of a Two-stage Ejector-vapor Compression Refrigeration Cycle working with R404A
Feiza Memet, Daniela-Elena Mitu

The traditional two-stage vapor compression refrigeration cycle might be replaced by a two-stage ejector-vapor compression refrigeration cycle if it is aimed the decrease of irreversibility during expansion. In this respect, the expansion valve is changed with an ejector. The performance improvement is searched in the case of choosing R404A as a refrigerant. Using the ejector as an expansion device ensures a higher value for COP compared to the traditional case. On the basis of the ejector approach it possible to identify the highest COP value for a given condensation temperature, when the evaporation temperature varies.

Keywords: compression, ejector, performance, cycle

A Software Model Proposed for the Contact Stress Calculation of Xylan 1052-coated Toothed Wheels
Ion-Cornel Mituletu, Ion Vela, Daniel Gheorghe Vela, Virgil Dan Caramidaru

We are proposing a software simulation model that could be used for the contact stress determination in the case of a new type of Xylan 1052-coated cylindrical toothed wheel gearing. It shows the contact stress distribution and displacements into the Xylan 1052 fluoropolymer coating that was applied to the surfaces of tooth flank. It represents a necessity due to the fact that, as it's well known, the strength of plastic material is much less than the strength of steel material.

Keywords: contact stress, displacement, simulation model

Catalysts Efficiency Evaluation by using CC Analysis Test
Arina Negoitescu, Adriana Tokar

The study emphasizes the necessity of the catalysts efficiency testing. Diagnosis systems using lambda probes are based on the capacity of the catalyst oxygen storage. Comparing the lambda probe signals upstream and downstream of catalyst provides an indication on catalyst activity, although the correlation between oxygen storage capacity and catalyst efficiency is still difficult. Diagnosis for the 1.4 Renault Clio Symbol was accomplished in the Road Vehicles Lab at the Politehnica University of Timisoara using AVL Dicom 4000. The tests showed that the engine worked with lean mixture being necessary a fuel mixture correction calculated by the control unit ECU. A compensation of 0.14 % vol is required for the engine correct operation and emissions integration within permissible limits.

Keywords: catalyst, fuel mixture, lambda sensor, diagnosis, pollutant emissions

Connecting the Web Pages to Databases
Florica Novăcescu

In this paper, it tried to make a presentation of the concepts underlying the operation of the Internet, how to transfer information, and interfaces client - server. The concepts presented in this paper have not only a teaching purpose, but they refer both to the advantages of using technologies to connect the Web pages to databases and the problems that can occur in implementing these technologies.

Keywords: Web pages, databases, client-server architecture, MySQL

High-performance Scientific Computing using Parallel Computing to Improve Performance Optimization Problems
Florica Novăcescu

HPC (High Performance Computing) has become essential for the acceleration of innovation and the companies’ assistance in creating new inventions, better models and more reliable products as well as obtaining processes and services at low costs. The information in this paper focuses particularly on: description the field of high performance scientific computing, parallel computing, scientific computing, parallel computers, and trends in the HPC field, presented here reveal important new directions toward the realization of a high performance computational society. The practical part of the work is an example of use of the HPC tool to accelerate solving an electrostatic optimization problem using the Parallel Computing Toolbox that allows solving computational and data-intensive problems using MATLAB and Simulink on multicore and multiprocessor computers.

Keywords: HPC, parallel supercomputers, parallel computing, scientific computing

Voltage Fluctuations Synchronous Hydro Autonomous in a Concrete Building
Ion Piroi, Elisabeta Spunei

The paper presents a concrete situation appeared at a micro hydro-autonomous central. The central consists of two similar turbines, which train a synchronous self-excited generator, respectively an induction generator operating at constant load. The two generators feed two not interconnected groups of consumers. When the two generators are operating simultaneously, in the synchronous generator appearce a voltage fluctuation with low frequency (0,5÷2 Hz). This fluctuation is shown in a disturbing change in luminous flux of light sources. When the synchronous generator is operating alone, this fluctuation of voltage is not present. In the presented work we analyzed the mentioned situation end, have established the causes of these fluctuations and proposed solutions to eliminate it.

Keywords: voltage fluctuations, autonomous synchronous generator autoexcitate

Power System Fault on Modern Numerical Relays
Andrei Romanescu, Adrian-Ioan Toma

Modern digital protections, provides comprehensive data in the event of a defect in equipment, data that can be used for the analysis of defects and to remove weaknesses in the system, namely the primary apparatus. Development of numerical protection systems and putting them in power system protection systems enables improved operation in terms of increasing complexity of events.

Keywords: fault, modern digital terminal equipment, software

Study Regarding the Identification of the Induction Motor
Ioan Ruja, Ladislau Augustinov, Ion-Cornel Mituletu

In the framework of the paper, we analyze some theoretical and practical aspects regarding the identification of the induction motor. The problem is important in the synthesis of different driving systems with automatic induction motors, usually with variable speed of rotations. The performances in the transitory and stationary regime of these quick adjustment systems are influenced by the precision of the mathematical model of the chosen driving motor. We present different mathematical models of the induction motor, obtained in an experimental way.

Keywords: identification, induction motor, driving system, transitory regime, stationary regime

Rapid Calculation Program of Certain Sizes used in design of Synchronous Generators
Elisabeta Spunei, Ion Piroi

This paper presents a program of rapid determination of certain sizes required in the design of synchronous machines using Mathcad software. During the design of electrical machines are phases in which certain sizes are extracted from different tables depending on certain variables. This operation is difficult and sometimes hard to do. To eliminate this problem and greatly shorten the time of determination of sizes and to ensure accurate values we have designed a program allowing even interpolation between two known values. The program developed applied, in this paper, to quickly determine the value of the voltage form factor kB and the value of the ideal polar coverage coefficient αi of polar step τ.

Keywords: voltage form factor, the ideal polar coverage coefficient, interpolation

The Importance of Thermal Heat Bridges in Civil Engineering
Adriana Tokar, Arina Negoitescu

Based on the heat transfer characteristics of a construction, the expected temperatures along interior surfaces must be evaluated in order to predict (and avoid) areas of potential moisture condensation. Beyond preventing damage to building materials caused by mould growth, adequate surface temperatures are also a relevant factor in the thermal comfort of an interior environment. An agreable climate in a room can be obtained, when relative humidity is between 40 and 60%. As the air in a room is warmer, the more vapor can absorb (and vice versa), influencing the thermal comfort index. Heat losses are influenced largely by thermal bridges of construction. The importance of the thermal heat bridges is strongly increasing today. In new developments the thermal optimization of junctions in today common low energy constructions receives very special standing. The subject of avoiding thermal bridges in passive houses became predominant.

Keywords: thermal heat bridges, heat flow, vapor diffusion, humidity, condens, dew point

Improving the Quality of Electric Energy to Electric Arc Furnace
Adrian-Ioan Toma, Andrei Romanescu

This paper presents a study of power quality problems created by an electric arc furnace (EAF) with eccentric bottom tap (EBT) at power system. The analysis have been done to EAF of 100 t capacity used for steel melting. Experimental results show this EAF is substantial source of electric disturbances, such as voltage fluctuations, flicker, harmonics, and unbalance between phases. Improvement of the quality of electric energy at EAF imposes a careful technical and economical analysis. Of all possible solutions for improvement of the power quality for an EAF (passive filter, STATCOM or SVC), SVC is the ideal solution.

Keywords: electric arc furnace, power quality, static var compensator

Model for the Study of Automating a System of Pumping Water from Upstream to Downstream Hydropower Plant Using Siemens S7-200 PLC
Marius Tufoi, Ion Vela, Constantin Marta, Cornel Mituletu, Viorel Bizau

This work presents design methods, optimization and realization of me-chanical for continuous casting plants using modern techniques: CAD,CAM and CAE. These current techniques refer to techniques CAD (Computer-Aided Design), CAE (Computer-Aided Engineering) and CAM (Computer-Aided Manufacturing). Techniques mentioned above are ar-eas of information technology aimed at helping engineering a variety of areas to be faster, more efficient and creative. A synthesis of the works published in the last 15 years shows that computer aided design and manufacturing are two areas which have developed simultaneously be-ing treated in a common vision based on the natural links that exist be-tween the activities of design and production or manufacturing. The paper will present a practical case application of techniques CAD, CAE and CAM.

Keywords: CAD, CAE, CAM, simulation, finite element

WidetheSEE – Gateway for Solar Thermal Energy Exploitation
Gino Stefano Verrocchi, Daniel Amariei, Athanasios Kalogeras

The present paper intends to present the partial results obtained by implementation of the first project pilot of the WidetheSEEbySuccMod project, a project financed by European Union through South East Europe Transnational Cooperation Program. “Let the Sun Shine In!” campaign started in February 2011 in Romania, aiming to raise aware-ness of population from Caras Severin County and enlarge it to West-ern part of Romania regarding the use of this friendly source of energy in general and the DHW installations in particular.

Keywords: solar thermal, domestic hot water, renewable energy, environmental impact