Estimation of dynamic behavior and energy efficiency of thrust hybrid bearings with active control
|
|
- Christina Norton
- 5 years ago
- Views:
Transcription
1 INTERNATIONAL JOURNAL OF MECHANICS Volume 1 18 Estimation of dynamic behavior and energy efficiency of thrust hybrid bearings with active control Alexander Babin Sergey Majorov Leonid Savin Abstract The resent aer considers analysis of world tendencies of alication of bearings with feedback control systems in various tyes of rotor machines. A ossibility of qualitative imrovement of oerational characteristics has been highlighted for bearings with integrated additional functions of automated diagnostics and active control of geometric rheological and force arameters. The resent aer features a mathematical model its imlementation in a form of an algorithm and numerical results including ressure and temerature distribution in a bearing in question load caacity and rotor s axial trajectories. A quality index has been formulated for thrust taered land hybrid bearings with a central feeding chamber that is based on a combination of minimum ower loss due to friction and stability of motion of a rotor. Various combinations of roughness and axial gas have been taken into account. Keywords mechatronics active control fluid-film bearings thrust bearings dynamic behavior energy efficiency. I. INTRODUCTION NTEREST in modelling and exerimental investigation of Iactive bearings arose with the evolution of what is commonly referred to as Industry 4. [1]. Synergy-based technological overla of mechanical engineering electrical engineering and information technologies enable smart machines and many cases emerge where traditional arts of machines could be relaced with mechatronic devices that extend functionality and enhance erformance of these machines. In the field of rotating machinery fluid-film bearings used to carry the load of a shaft are the most vital elements and thus become subjected to various enhancements including the ossibility to introduce active control systems. This work was suorted by the Ministry of Education and Science of the Russian Federation under Project no /4.6 (develoment and modernization of the test rig) and by the Russian Science Foundation under Project no (formulation and solution of the roblem in all sections of the resent aer). Alexander Babin is with the research lab Modelling of Hydro and Mechanical Systems at the Orel State University Orel Naugorskoe sh. 9 3 Russia (tel.: alex.mech.osu@gmail.com). Sergey Majorov is with the research lab Modelling of Hydro and Mechanical Systems at the Orel State University Orel Naugorskoe sh. 9 3 Russia ( sergeyostu@yandex.ru). Leonid Savin is with the deartment of Mechatronics Mechanics and Robotics at the Orel State University Orel Naugorskoe sh. 9 3 Russia ( savin@ostu.ru). The idea behind these enhancements is to not only rovide a stable oerational regime but also and very imortantly to increase energy efficiency of a machine. And ower loss in rotating machinery mainly occurs in bearings due to both friction and vibration. Machines subjected to loads varying in time or vibrations due to oerational regimes require certain sets of dynamic characteristics of bearings these sets are unique in each case making design of bearings a challenge. Investigation in the field of rotor s dynamic behaviour control in fluid-film bearings is carried out in the following fields: study of the ossibility of rofile adjustment of a ga between a rotor and a sleeve or a thrust disk of a bearing e.g. tilting-ad and some foil bearings [ 3]; study of the ossibility of alication of lubricants with adjustable arameters such as viscosity or density e.g. ferromagnetic fluids [4 5]; and study of hybrid fluid-film bearings [6 7] where load caacity is generated as a combination of hydrodynamic forces in the film and hydrostatic force from the lubricant sulied into a bearing under ressure where rotor s osition can be adjusted by means of electrohydraulic devises like servovalves. Alication of servovalves roved feasible in many alications with journal bearings [8-1]. There are however very few studies regarding the ossibility to aly the same aroach to thrust bearings. The urose of the resent aer is to introduce active control system to a traditional thrust taered land bearing and to estimate feasibility to use active control to enhance the erformance of the bearing in question. II. MATHEMATICAL MODEL OF AN ACTIVE THRUST HYBRID BEARING The oerational rincile of an ATHB (Figure 1) is as follows: the um (1) located in the tank with the fluid (water oil etc.) sulies the lubricant into the housing () of the bearing (3) which suorts the rotor (4) in the axial direction. The ressure data is acquired with the sensor (8). The data on the resent osition of the rotor is acquired with the roximity sensor (7). Data from the sensors is analogue and is acquired with the analogue inut modules of a DAQ system (5). This system also controls the servovalve (6) by means of adjusting the oening rate ξ generating an analogue voltage signal and the um (discrete outut module). ISSN:
2 INTERNATIONAL JOURNAL OF MECHANICS Volume 1 18 Fig. 1 rincile diagram of an ATHB To simulate the oeration of an ATHB one has to ay close attention to two basic roblems: a roblem of hydrodynamic lubrication theory based on the Reynolds equation and the energy balance equation and a roblem of theory of automatic control. Merging a model of a hybrid bearing with a model of the control system yields a model of an active bearing. Here the controlled variable is the axial ga between the rotor s thrust disk and the bearing in question. By means of controlled suly of lubricant under ressure one could change the ressure distribution in the bearing thus controlling the value of the ga. The first stage is consequently modelling a assive thrust hybrid bearing (THB). The hoto and calculation diagram of a THB are resented in the Fig.. the following form: 1 F 1 h F rf r + r r + r r ω F (1) t where ω angular velocity of the shaft (rθ) local ressure F F 1 F Dowson s functions determined as in [11]: h dy h h ydy y F F F1 µ µ 1 F y dy µ F where h(θ) axial ga function µ(rθ) local viscosity which is determined as a distributed scalar value and is a function of temerature: µ µ e λ ( T T s ) where µ viscosity of the sulied fluid T s temerature of the sulied fluid λ temerature/viscosity coefficient. Here it has to be noted that the shae of the axial ga is modelled using Bezier curves that allow higher calculation accuracy of ressure gradient in the circumferential direction. In the Fig. 3 results of modelling and actual ga measurement are resented along with the hoto of the measuring setu. Fig. hoto of a THB (a) calculation diagram of a THB (b) Here R in and Rout are inner and outer radiuses of the bearing accordingly V r V θ and V y are velocity comonents in the olar coordinate system h minimum film thickness Θ angular extent of a single ad α angle of inclination of a ad. To obtain the ressure distribution the generalized Reynolds equation is derived to be solved iteratively with the energy balance equation which allows taking into account ossible viscosity variation in the fluid film due to temerature rise that occurs as a result of action of friction between the layers of the fluid. The generalized Reynolds equation takes Fig. 3 hoto of the rofile measurement system (a) comarison between rofile measurement and modelling (b) It could be seen that modelling results are accurate enough however there is a slight deviation due to mechanical treatment of the surface of the THB. In order to obtain the temerature distribution the energy equation taking into account the action of dissiation forces in the fluid is derived in the following form: ISSN:
3 INTERNATIONAL JOURNAL OF MECHANICS Volume 1 18 h T h ωr T ρc µ r r µ r r () 1 1 h h ωr µ µ r µ r h where ρ density of the fluid c heat caacity of the fluid Т(rθ) local temerature. Equations (1) and () and the additional exressions are solved iteratively using a finite difference method with the following boundary conditions for ressure and temerature: T r Rout θ T T a θ Θ T r Rin T T θ θ r Rin s θ θ Θ θ s θ Θ θ Θ where s suly ressure a ambient ressure. The iteration rocess is then considered converged if the convergence criterion based on difference in load caacity of a bearing on the resent and the revious iteration. Character ressure and temerature distributions in thrust hybrid bearings are resented in the Fig. 4. Fig. 5 rotor-bearing dynamic system Under steady conditions the rotor takes the equilibrium osition when the hydrodynamic forces counterbalance the inertia forces i.e. R Y mg where m rotor s mass g freefall acceleration. When the rotor s osition changes under the influence of some imulse some additional forces start acting on the rotor so assuming these dislacements are relatively small the reaction force of a bearing could be linearized using Taylor series. The reaction force of the bearing could be determined as follows: Ry RY KY Y BY Y and consequently the motion law of the system is as follows: my B Y Y KYY F(t) (3) where F(t) is some external force as a function of time t. (3) is solved using the Runge-Kutta method of the 4 th order. In order to introduce the model of the control system to the develoed model of the bearing the structure of the named system has to be considered (Fig. 6). Fig. 6 Structure of the control system of an ATHB Fig. 4 ressure (a) and temerature (b) distribution in a THB Load caacity of a bearing is obtained by means of integration of ressure distribution over the area of the bearing: R Y z Θ Rout Rin ( r θ ) rdθdr where z number of fixed ads. To estimate dynamic behavior of a rotor on the ATHB a model of a dynamic system has to be develoed. The diagram is resented in the Fig. 5 The control system consists of a module that sets the value of a set oint (SP) and the data channel (D) the obtained data is comared to the set oint and the error ε is the used to generate a control signal by means of alication of a PID controller based regulator (R). The signal is then amlified (A) and sent to the actuator servovalve (SV) thus changing the suly ressure. These actions affect the osition of a rotor in the bearing (B) that could be subjected to some external force F(t). The aim of control is to maintain a desired value of the axial ga between the rotor and the THB. The control rincile is essentially regulation of in-flow ressure to increase or decrease the bearing s reaction force which results in increase or decrease of the axial ga. Here the regulator is the core element of the control system and is based on the PID control law where the outut signal is a function of the current error and the desired osition Ys (set oint): t ε ( t) u( t) K ε ( t) + K i ε ( t) dt + K d t where u(t) outut signal from the regulator K Ki Kd roortional integral and differential comonents of the regulator accordingly ε(t) error function. ISSN:
4 INTERNATIONAL JOURNAL OF MECHANICS Volume 1 18 The kind of electrohydraulic actuators used in the resent research is simulated using the known relation between the ressure it sulies the lubricant with and the voltage on the inut of the valve. The most imortant term here is the time constant of the valve T SV i.e. the time it takes for a fully closed valve to fully oen. This is a crucial characteristic for systems subjected to high-frequency eriodic loads. The exression that allows simulation of a servo valve is as follows: d( t) TSV + ( t) K SV u( t) (4) dt where K SV gain coefficient of a servo valve u(t) control signal i.e. voltage on the servo valve s inut. The given equations (1) () (3) and (4) with additional exressions such as function of viscosity make a mathematical model of an ATHB which is going to subjected to study in the resent aer. III. NUMERICAL RESULTS AND DISCUSSION Problems of stability are the rimary roblems that are solved when develoing bearings for high-seed rotating machinery. Axial stability is considered in various tyes of ums for oil extraction aircraft and sacecraft engines etc. The urose of the resent study is to estimate the influence of the control system on the axial stability and energy efficiency of an ATHB. Stability analysis is based on estimation of the magnitude of oscillations of a rotor under comlex external axial loading and relies on the remise that the desired osition should be as close to the set oint as ossible. Energy efficiency estimation is based on calculation of ower loss due to friction: N FR M FRω Rout Θ where h ωrµ M FR r + rdθdr - friction torque. r h Rin Oeration of the ATHB has been modelled under the influence of a following external axial force: ωt π ωt π F( t) AD sin + sin + AD 1 5 where A D amlitude taken as N. In the Fig. 7 results of calculation of rotor s trajectories are shown for various A D settings. Fig. 7 results of rotor s trajectories calculation under various axial load (a) - A D 5 b) - A D 35 c) - A D 5 d) - A D 75) First the regulator has been tuned manually based on minimum transition eriod and control error. Chosen regulator arameters are: K 7.5 Ki15 Kd.5. Throughout this art the following modelling arameters were used : Rout.6 m Rin.3 m α.5 z 6 ISSN:
5 INTERNATIONAL JOURNAL OF MECHANICS Volume 1 18 lubricant H 3⁰C ω 5 rad/s Tsv.5 s rotor s mass is 5.5 kg. In the Fig. 8 comarison results are shown for THB and ATHB regarding the stability and energy efficiency enhancement. case a machine is subjected to changing loads and needs to be designed with a sufficient level of rotor s ositioning accuracy it could be seen that introduction of a relatively simle in terms of simulation and execution control system greatly imroves the erformance of the bearing and the machine at a whole. IV. EXPERIMENTAL SETUP In order to verify the resented model and ossibly identify some new or unaccounted for effects a test rig has been develoed. A series of exeriments has been lanned for carrying out in the nearest future to suort the idea of an ATHB. A hoto of the test rig is resented in the Fig. 9 and in more detail in the Fig. 1. The main advantage of the develoed test rig is ossibility to study both radial and thrust active bearings at the same time. For verification uroses within the resent research it is lanned to only focus on ATHBs so instead of sliding journal bearings two rolling element bearings are installed so that there is such radial ga that the rotor could erform axial motion without restraining friction in these bearings. These bearings also rovide higher stability in radial direction. An ATHB is installed in its housing where one side is made of lexiglass in order to rovide some visual information like observable cavitation or turbulence etc. In Fig. 1a and Fig. 1b more detailed hotos of the servovalve setu and the ATHB are resented. Fig. 8 comarison results of oeration of THB and ATHB During simulations magnitude of oscillations has been calculated for comarison uroses and at frequency of 1 Hz the data on ower loss has been collected. Then a mean value of ower loss due to friction has been determined. It could be seen that alication of ATHB significantly decreases the magnitude of oscillations thus enhancing stability (Fig. 6a). With a ractically constant magnitude in the case of an ATHB magnitude of oscillations of a rotor increases in the case of a assive THB with the increase of the amlitude of the external axial force. Decrease of magnitude by the ATHB in this case is u to 85 % and the resulting trajectories are considered stable in comarison to a assive THB. Moreover the osition of the rotor only slightly deviates from the set oint which is very imortant in terms of ositioning accuracy. Comarison of ower loss due to friction (Fig. 6b) shows a 4% decrease in the case of the ATHB. And once more the value of ower loss remains constant in the whole range of simulated amlitudes whereas in the THB the ower loss increases with the increase of the amlitude of the axial external force. Based on the obtained numerical results it could be highlighted that the alication of ATHBs significantly increases stability and energy efficiency of a rotor machine. In Fig. 9 test rig with an ATHB (general view) ISSN:
6 INTERNATIONAL JOURNAL OF MECHANICS Volume 1 18 the height of the axial ga rovides less friction and enough hydrodynamic force allows energy efficiency to be significantly increased. Finally a test rig has been develoed to verify the obtained numerical results. Exerimental studies are the first ste of future research as it rovides initial data about the accuracy of the resented model. Possible identification of effects that have not been accounted for allows develoment of a more accurate model. ACKNOWLEDGMENTS This work was suorted by the Ministry of Education and Science of the Russian Federation under Project no /4.6 (develoment and modernization of the test rig) and by the Russian Science Foundation under Project no (formulation and solution of the roblem in all sections of the resent aer). Fig. 1 a) servovalve setu b) ATHB in more detail As shown in the Fig. 1a ressure is controlled right before the fluid enters the feeding chamber and it is ossible to also determine the temerature of the inflow. In order to determine whether radial oscillations occur that influence the erformance of the ATHB and to ossible determine shae deviation of the rotor s thrust disk four dislacement sensors are mounted around the thrust disk (Fig. 1b). One of these sensors is used to acquire data about rotor s osition for the control system to be used as current rotor s osition. V. RESULTS AND DISCUSSION Results resented in the resent aer show feasibility of alication of active ressure control to increase axial stability of rotors with thrust hybrid bearings. Numerical results show a more than 8% decrease of amlitude of vibration if active control is alied. It has also been determined that with varying amlitude of the external force the actual rotor s dislacement on the ATHB is more stable while amlitude of vibrations of the rotor on the assive THB increases. It has also been determined that energy efficiency of the rotor system increases in terms of decreased ower loss due to friction in the bearing. Along with decreased amount of energy dissiated due to vibrations ositioning of the rotor so that REFERENCES [1] E.A Lee Cyber Physical Systems: Design Challenges 11th IEEE International Symosium on Object Oriented Real-Time Distributed Comuting (ISORC) [] A. M. Haugaard Modeling of Flexible Tilting Pad Journal Bearings With Radial Oil Injection Proceedings of the STLE/ASME International Joint Tribology Conference [3] G. Aguirre Dynamic stiffness comensation with active aerostatic thrust bearings Proceedings of ISMA [4] H. Urreta Hydrodynamic bearing lubricated with magnetic fluids Journal of Physics Conference Series vol [5] A. Albagachiev Magnetic fluid in the regime of hydrodynamic lubrication Bulletin of the Bryansk Technical University vol [6] P. Kytka Alication of Feedforward-Disturbance-Comensation and Inut-Shaing to a Machine z-axis in Active Hydrostatic Bearings Proceedings of the 9th International Conference on Motion and Vibration Control [7] L.A. Savin Rotor trajectories in fluid-film bearings adjustment of them and energy efficiency arameters Proceedings of ICMMR MATEC Web of Conferences vol [8] F. G. Pierart Active lubrication alied to radial gas journal bearings. Part : Modelling imrovement and exerimental validation Tribology International vol [9] A. Chasalevri Imroving stability and oeration of turbine rotors using adjustable journal bearings Tribology Int vol. 14 (1) [1] D. C. Deckler Simulation and Control of an Active Tilting-Pad Journal Bearing STLE Tribol. Trans. vol [11] I. Chatzisavvas On the influence of thrust bearings on the nonlinear rotor vibrations of turbochargers Proceedings of ASME Turbo Exo 16: Turbomachinery Technical Conference and Exosition GT ISSN:
Feedback-error control
Chater 4 Feedback-error control 4.1 Introduction This chater exlains the feedback-error (FBE) control scheme originally described by Kawato [, 87, 8]. FBE is a widely used neural network based controller
More informationPrediction of the Excitation Force Based on the Dynamic Analysis for Flexible Model of a Powertrain
Prediction of the Excitation Force Based on the Dynamic Analysis for Flexible Model of a Powertrain Y.S. Kim, S.J. Kim, M.G. Song and S.K. ee Inha University, Mechanical Engineering, 53 Yonghyun Dong,
More informationOil Temperature Control System PID Controller Algorithm Analysis Research on Sliding Gear Reducer
Key Engineering Materials Online: 2014-08-11 SSN: 1662-9795, Vol. 621, 357-364 doi:10.4028/www.scientific.net/kem.621.357 2014 rans ech Publications, Switzerland Oil emerature Control System PD Controller
More informationMultivariable Generalized Predictive Scheme for Gas Turbine Control in Combined Cycle Power Plant
Multivariable Generalized Predictive Scheme for Gas urbine Control in Combined Cycle Power Plant L.X.Niu and X.J.Liu Deartment of Automation North China Electric Power University Beiing, China, 006 e-mail
More informationPosition Control of Induction Motors by Exact Feedback Linearization *
BULGARIAN ACADEMY OF SCIENCES CYBERNETICS AND INFORMATION TECHNOLOGIES Volume 8 No Sofia 008 Position Control of Induction Motors by Exact Feedback Linearization * Kostadin Kostov Stanislav Enev Farhat
More informationThe Numerical Simulation of Gas Turbine Inlet-Volute Flow Field
World Journal of Mechanics, 013, 3, 30-35 doi:10.436/wjm.013.3403 Published Online July 013 (htt://www.scir.org/journal/wjm) The Numerical Simulation of Gas Turbine Inlet-Volute Flow Field Tao Jiang 1,
More informationTRIBOLOGICAL BEHAVIOR OF THRUST BEARING USING STRUCTURED SURFACES PART 1 THEORETICAL BACKGROUND
SISOM 007 and Homagial Session of the Commission of Acoustics, ucharest 9-31 May TRIOLOGICAL EHAVIOR OF THRUST EARING USING STRUCTURED SURFACES PART 1 THEORETICAL ACKGROUND Gabriel-Arin MIHALCEA *, Octavian
More informationJournal of System Design and Dynamics
Vol. 5, No. 6, Effects of Stable Nonlinear Normal Modes on Self-Synchronized Phenomena* Hiroki MORI**, Takuo NAGAMINE**, Yukihiro AKAMATSU** and Yuichi SATO** ** Deartment of Mechanical Engineering, Saitama
More informationDevelopment of self-adaptively loading for planetary roller traction-drive transmission
Available online www.jocr.com Journal of Chemical and Pharmaceutical Research, 013, 5(9):498-506 Research Article ISSN : 0975-7384 CODEN(USA) : JCPRC5 Develoment of self-adatively loading for lanetary
More informationUniversity of North Carolina-Charlotte Department of Electrical and Computer Engineering ECGR 4143/5195 Electrical Machinery Fall 2009
University of North Carolina-Charlotte Deartment of Electrical and Comuter Engineering ECG 4143/5195 Electrical Machinery Fall 9 Problem Set 5 Part Due: Friday October 3 Problem 3: Modeling the exerimental
More informationRadar Dish. Armature controlled dc motor. Inside. θ r input. Outside. θ D output. θ m. Gearbox. Control Transmitter. Control. θ D.
Radar Dish ME 304 CONTROL SYSTEMS Mechanical Engineering Deartment, Middle East Technical University Armature controlled dc motor Outside θ D outut Inside θ r inut r θ m Gearbox Control Transmitter θ D
More informationMODELING OF THE DYNAMIC RESPONSE OF A FRANCIS TURBINE
MODELING OF THE DYNAMIC RESPONSE OF A FRANCIS TURBINE Paolo PENNACCHI, Steven CHATTERTON *, Andrea VANIA Politecnico di Milano, Deartment of Mechanical Engineering - Via G. La Masa, - 256 - Milano, Italy.
More informationMODELLING, SIMULATION AND ROBUST ANALYSIS OF THE TEMPERATURE PROCESS CONTROL
The 6 th edition of the Interdiscilinarity in Engineering International Conference Petru Maior University of Tîrgu Mureş, Romania, 2012 MODELLING, SIMULATION AND ROBUST ANALYSIS OF THE TEMPERATURE PROCESS
More informationu y
VO., NO., FEBRUARY 8 ISSN 89-668 6-8 Asian Research Publishing Network (ARPN). All rights reserved. NON-NEWTONIAN EFFECTS OF OAD CARRYING CAPACITY AND FRICTIONA FORCE USING RABINOWITS FUID ON TE PERFORMANCE
More informationTORSIONAL VIBRATION SUPPRESSION IN AUTOMATIC TRANSMISSION POWERTRAIN USING CENTRIFUGAL PEN- DULUM VIBRATION ABSORBER
TORSIONAL VIBRATION SUPPRESSION IN AUTOMATIC TRANSMISSION POWERTRAIN USING CENTRIFUGAL PEN- DULUM VIBRATION ABSORBER Takashi Nakae and Takahiro Ryu Oita University, Faculty of Engineering, Deartment of
More information16. CHARACTERISTICS OF SHOCK-WAVE UNDER LORENTZ FORCE AND ENERGY EXCHANGE
16. CHARACTERISTICS OF SHOCK-WAVE UNDER LORENTZ FORCE AND ENERGY EXCHANGE H. Yamasaki, M. Abe and Y. Okuno Graduate School at Nagatsuta, Tokyo Institute of Technology 459, Nagatsuta, Midori-ku, Yokohama,
More informationMagnetostrictive Dynamic Vibration Absorber (DVA) for Passive and Active Damping
aer : 59 /. Magnetostrictive ynamic Vibration Absorber (VA) for Passive and Active aming C. May a,. uhnen b, P. Pagliarulo b and H. Janocha b a Centre for nnovative Production (ZP), Saarbrücken, ermany,
More informationMeasurement of cyclone separator
Measurement of cyclone searator. Aim of the measurement Cyclones are widely used in industry (in food and chemical industry, in energy technology and in buildings) to remove dust and other articles from
More informationTheory of turbomachinery. Chapter 1
Theory of turbomachinery Chater Introduction: Basic Princiles Take your choice of those that can best aid your action. (Shakeseare, Coriolanus) Introduction Definition Turbomachinery describes machines
More informationMODULAR LINEAR TRANSVERSE FLUX RELUCTANCE MOTORS
MODULAR LINEAR TRANSVERSE FLUX RELUCTANCE MOTORS Dan-Cristian POPA, Vasile IANCU, Loránd SZABÓ, Deartment of Electrical Machines, Technical University of Cluj-Naoca RO-400020 Cluj-Naoca, Romania; e-mail:
More informationA Simple Fuzzy PI Control of Dual-Motor Driving Servo System
MATEC Web of Conferences 04, 0006 (07) DOI: 0.05/ matecconf/07040006 IC4M & ICDES 07 A Simle Fuzzy PI Control of Dual-Motor Driving Servo System Haibo Zhao,,a, Chengguang Wang 3 Engineering Technology
More informationAn Investigation on the Numerical Ill-conditioning of Hybrid State Estimators
An Investigation on the Numerical Ill-conditioning of Hybrid State Estimators S. K. Mallik, Student Member, IEEE, S. Chakrabarti, Senior Member, IEEE, S. N. Singh, Senior Member, IEEE Deartment of Electrical
More informationANALYTIC APPROXIMATE SOLUTIONS FOR FLUID-FLOW IN THE PRESENCE OF HEAT AND MASS TRANSFER
Kilicman, A., et al.: Analytic Aroximate Solutions for Fluid-Flow in the Presence... THERMAL SCIENCE: Year 8, Vol., Sul.,. S59-S64 S59 ANALYTIC APPROXIMATE SOLUTIONS FOR FLUID-FLOW IN THE PRESENCE OF HEAT
More informationModelling a Partly Filled Road Tanker during an Emergency Braking
Proceedings of the World Congress on Engineering and Comuter Science 217 Vol II, October 25-27, 217, San Francisco, USA Modelling a Partly Filled Road Tanker during an Emergency Braking Frank Otremba,
More informatione eccentricity; δ radial clearance, m;
International Journal of Alied Engineering Research ISSN 973-456 Volume, Number 9 (7). 98-937 Research India Publications. htt://www.riublication.com Radial Plain Bearings Oerating on Viscoelastic Lubricant
More informationCFD AS A DESIGN TOOL FOR FLUID POWER COMPONENTS
CFD AS A DESIGN TOOL FOR FLUID POWER COMPONENTS M. BORGHI - M. MILANI Diartimento di Scienze dell Ingegneria Università degli Studi di Modena Via Cami, 213/b 41100 Modena E-mail: borghi@omero.dsi.unimo.it
More informationElectromagnetic Levitation Control of Contactless Linear Synchronous Drive for Flexible Vertical Transportation
Electromagnetic Levitation Control of Contactless Linear Synchronous Drive for Flexible Vertical Transortation Toshiyuki NAKAI*, Daisuke TATEISHI**, Takafumi KOSEKI*, and Yasuaki AOYAMA*** (*)Deartment
More informationDamage Identification from Power Spectrum Density Transmissibility
6th Euroean Worksho on Structural Health Monitoring - h.3.d.3 More info about this article: htt://www.ndt.net/?id=14083 Damage Identification from Power Sectrum Density ransmissibility Y. ZHOU, R. PERERA
More informationIndirect Rotor Field Orientation Vector Control for Induction Motor Drives in the Absence of Current Sensors
Indirect Rotor Field Orientation Vector Control for Induction Motor Drives in the Absence of Current Sensors Z. S. WANG *, S. L. HO ** * College of Electrical Engineering, Zhejiang University, Hangzhou
More informationOptimisation of Pressure Loss and Flow Distribution at Pipe Bifurcation
ISSN 9 86 Volume, Issue 9 Setember 07 Otimisation of Pressure Loss and Flow Distribution at Pie Bifurcation Dr. Nagaraj Sitaram Professor, Deartment of Civil Engineering,School of Engineering Technology,
More informationHomogeneous and Inhomogeneous Model for Flow and Heat Transfer in Porous Materials as High Temperature Solar Air Receivers
Excert from the roceedings of the COMSOL Conference 1 aris Homogeneous and Inhomogeneous Model for Flow and Heat ransfer in orous Materials as High emerature Solar Air Receivers Olena Smirnova 1 *, homas
More informationPreliminary Uncertainty Estimation of the Pressure Distortion Coefficient of a Pressure. Balance by FEM Calculations
Preliminary Uncertainty Estimation of the Pressure Distortion Coefficient of a Pressure Balance by FEM Calculations G. Molinar*, M. Bergoglio*, G. Mosso*,G. Buonanno**, M. Dell Isola** * Istituto di Metrologia
More informationSTUDY ON OIL FILM CHARACTERISTICS OF SLIPPER WITHIN AXIAL PISTON PUMP UNDER DIFFERENT WORKING CONDITION
STUDY ON OIL FILM CHAACTEISTICS OF SLIPPE WITHIN AXIAL PISTON PUMP UNDE DIFFEENT WOKING CONDITION Yi Sun, Jihai-Jiang. Harbin Institute o Technology, School o Mechtrionics Engineering, China ABSTACT In
More informationMeshless Methods for Scientific Computing Final Project
Meshless Methods for Scientific Comuting Final Project D0051008 洪啟耀 Introduction Floating island becomes an imortant study in recent years, because the lands we can use are limit, so eole start thinking
More informationDeformation Effect Simulation and Optimization for Double Front Axle Steering Mechanism
0 4th International Conference on Comuter Modeling and Simulation (ICCMS 0) IPCSIT vol. (0) (0) IACSIT Press, Singaore Deformation Effect Simulation and Otimization for Double Front Axle Steering Mechanism
More informationOn Line Parameter Estimation of Electric Systems using the Bacterial Foraging Algorithm
On Line Parameter Estimation of Electric Systems using the Bacterial Foraging Algorithm Gabriel Noriega, José Restreo, Víctor Guzmán, Maribel Giménez and José Aller Universidad Simón Bolívar Valle de Sartenejas,
More informationTHE 3-DOF helicopter system is a benchmark laboratory
Vol:8, No:8, 14 LQR Based PID Controller Design for 3-DOF Helicoter System Santosh Kr. Choudhary International Science Index, Electrical and Information Engineering Vol:8, No:8, 14 waset.org/publication/9999411
More informationFLOW RATE CONTROL OF VARIABLE DISPLACEMENT PISTON PUMP USING GENETIC ALGORITHM TECHNIQUE
FLOW RATE CONTROL OF VARIABLE DISPLACEMENT PISTON PUMP USING GENETIC ALGORITHM TECHNIQUE Ayman A. Aly 1,2 and A. Al-Marakeby 1,3 1) Mechatronics Section, Mech. Eng. Det., Taif University, Taif, 888, Saudi
More informationTime Domain Calculation of Vortex Induced Vibration of Long-Span Bridges by Using a Reduced-order Modeling Technique
2017 2nd International Conference on Industrial Aerodynamics (ICIA 2017) ISBN: 978-1-60595-481-3 Time Domain Calculation of Vortex Induced Vibration of Long-San Bridges by Using a Reduced-order Modeling
More informationAll-fiber Optical Parametric Oscillator
All-fiber Otical Parametric Oscillator Chengao Wang Otical Science and Engineering, Deartment of Physics & Astronomy, University of New Mexico Albuquerque, NM 87131-0001, USA Abstract All-fiber otical
More informationFlow Velocity Measurement Principles of Hot Film Anemometry
Flow Velocity Measurement Princiles of Hot Film Anemometry The hot film anemometer (HFA) is made of a thin, structured, metallic resistive film ( heater ) which is deosited onto a substrate. In the oerating
More informationActual exergy intake to perform the same task
CHAPER : PRINCIPLES OF ENERGY CONSERVAION INRODUCION Energy conservation rinciles are based on thermodynamics If we look into the simle and most direct statement of the first law of thermodynamics, we
More informationNumerical Study on the Oil Pump System of Rotary Compressor
Purdue University Purdue e-pubs International Comressor Engineering Conference School of Mechanical Engineering 2012 Numerical Study on the Oil Pum System of Rotary Comressor Chunhui Liu yuanym@shec.com.cn
More informationHOW TO PREDICT THE VIBRATION EFFECT DUE TO MACHINE OPERATION ON ITS SURROUNDINGS
ICSV14 Cairns Australia 9-1 July, 007 HOW TO PREDICT THE VIBRATION EFFECT DUE TO MACHINE OPERATION ON ITS SURROUNDINGS Alexandre Augusto Simões 1, Márcio Tadeu de Almeida and Fabiano Ribeiro do Vale Almeida
More informationSimulation of 3-Phase 2- Stator Induction Motor Using MATLAB Platform
International Journal of Alied Engineering Research ISSN 0973-456 Volume 3, Number (08). 9437-944 Simulation of 3-Phase - Stator Induction Motor Using MATLAB Platform Pallavi R.Burande Deartment of Electrical
More information645. Active control of the process and results of treatment
645. Active control of the rocess and results of treatment V. Gichan 1 1 Vilnius Gediminas echnical University, Basanaviciaus 28, L-10223, Vilnius, Lithuania E-mail: vladimir@zebra.lt (Received 10 March
More informationRobust Performance Design of PID Controllers with Inverse Multiplicative Uncertainty
American Control Conference on O'Farrell Street San Francisco CA USA June 9 - July Robust Performance Design of PID Controllers with Inverse Multilicative Uncertainty Tooran Emami John M Watkins Senior
More informationSimulation of the PIR detector active function
04036 (016) DOI: 10.1051/ matecconf/0167604036 CSCC 016 Simulation of the PIR detector active function Rudolf Drga 1,a, Dagmar Janacova and Hana Charvatova 3 1 Tomas Bata University in Zlín, Faculty of
More informationLecture 13 HYDRAULIC ACTUATORS[CONTINUED]
Lecture 1 HYDRAULIC ACTUATORS[CONTINUED] 1.5Acceleration and Deceleration of Cylinder Loads Cylinders are subjected to acceleration and deceleration during their oeration. Cylinders are decelerated to
More informationENERGY-EFFICIENT MOTION CONTROL OF A DIGITAL HYDRAULIC JOINT ACTUATOR
ENERGY-EFFICIEN MOION CONROL OF DIGIL HYDRULIC JOIN CUOR Matti LINJM and Matti VILENIUS Institute of Hydraulics and utomation amere University of echnology.o.ox 89, FIN-3311 amere, Finland (E-mail: matti.linjama@tut.fi)
More informationOptimization of Gear Design and Manufacture. Vilmos SIMON *
7 International Conference on Mechanical and Mechatronics Engineering (ICMME 7) ISBN: 978--6595-44- timization of Gear Design and Manufacture Vilmos SIMN * Budaest Universit of Technolog and Economics,
More informationPRELIMINARY SELECTION OF BASIC PARAMETERS OF DIFFERENT TORSIONAL VIBRATION DAMPERS INTENDED FOR USE IN MEDIUM-SPEED DIESEL ENGINES
Ivan Filiović Dževad Bibić Aleksandar Milašinović Almir Blažević Adnan Pecar ISSN 333-4 PRELIMINARY SELECTION OF BASIC PARAMETERS OF DIFFERENT TORSIONAL VIBRATION DAMPERS INTENDED FOR USE IN MEDIUM-SPEED
More informationDetermination of Pressure Losses in Hydraulic Pipeline Systems by Considering Temperature and Pressure
Paer received: 7.10.008 UDC 61.64 Paer acceted: 0.04.009 Determination of Pressure Losses in Hydraulic Pieline Systems by Considering Temerature and Pressure Vladimir Savi 1,* - Darko Kneževi - Darko Lovrec
More informationInternational Association of Scientific Innovation and Research (IASIR) (An Association Unifying the Sciences, Engineering, and Applied Research)
International Association of ientific Innovation and Research (IASIR) (An Association Unifying the iences, Engineering, and Alied Research) International Journal of Emerging Technologies in Comutational
More informationThe extreme case of the anisothermal calorimeter when there is no heat exchange is the adiabatic calorimeter.
.4. Determination of the enthaly of solution of anhydrous and hydrous sodium acetate by anisothermal calorimeter, and the enthaly of melting of ice by isothermal heat flow calorimeter Theoretical background
More informationTopology Optimization of Three Dimensional Structures under Self-weight and Inertial Forces
6 th World Congresses of Structural and Multidiscilinary Otimization Rio de Janeiro, 30 May - 03 June 2005, Brazil Toology Otimization of Three Dimensional Structures under Self-weight and Inertial Forces
More informationError Analysis for Gyroscopic Force Measuring System
Proceedings of the 7 th International Conference on Force, Mass, Torque and Pressure Measurements, IMEKO TC3, 7- Set., Istanbul, Turkey Error Analysis for Gyroscoic Force Measuring System Shigeru Kurosu
More informationRobust Predictive Control of Input Constraints and Interference Suppression for Semi-Trailer System
Vol.7, No.7 (4),.37-38 htt://dx.doi.org/.457/ica.4.7.7.3 Robust Predictive Control of Inut Constraints and Interference Suression for Semi-Trailer System Zhao, Yang Electronic and Information Technology
More informationRoots Blower with Gradually Expanding Outlet Gap: Mathematical Modelling and Performance Simulation Yingjie Cai 1, a, Ligang Yao 2, b
2nd International Conference on Advances in Mechanical Engineering and Industrial Informatics (AMEII 216) Roots Bloer ith Gradually Exanding Outlet Ga: Mathematical Modelling and Performance Simulation
More informationA High Precision Double Tubed Hydrostatic Leveling System for Accelerator Alignment Applications
9th International Worksho on Accelerator Alignment, Setember 6-9, 6 A High Precision Double Tubed Hydrostatic Leveling System for Accelerator Alignment Alications S. Singatulin, J. olk,. Shiltsev Fermilab,
More informationShadow Computing: An Energy-Aware Fault Tolerant Computing Model
Shadow Comuting: An Energy-Aware Fault Tolerant Comuting Model Bryan Mills, Taieb Znati, Rami Melhem Deartment of Comuter Science University of Pittsburgh (bmills, znati, melhem)@cs.itt.edu Index Terms
More informationDual-Halbach Array Permanent Magnet Tubular Generator for Free-Piston Generator
Journal of Magnetics 0(4), 405-41 (015) ISSN (Print) 16-1750 ISSN (Online) 33-6656 htt://dx.doi.org/10.483/jmag.015.0.4.405 Dual-Halbach Array Permanent Magnet Tubular Generator for Free-Piston Generator
More informationDesign of NARMA L-2 Control of Nonlinear Inverted Pendulum
International Research Journal of Alied and Basic Sciences 016 Available online at www.irjabs.com ISSN 51-838X / Vol, 10 (6): 679-684 Science Exlorer Publications Design of NARMA L- Control of Nonlinear
More informationHigh speed wind tunnels 2.0 Definition of high speed. 2.1 Types of high speed wind tunnels
Module Lectures 6 to 1 High Seed Wind Tunnels Keywords: Blow down wind tunnels, Indraft wind tunnels, suersonic wind tunnels, c-d nozzles, second throat diffuser, shocks, condensation in wind tunnels,
More informationMODELING THE RELIABILITY OF C4ISR SYSTEMS HARDWARE/SOFTWARE COMPONENTS USING AN IMPROVED MARKOV MODEL
Technical Sciences and Alied Mathematics MODELING THE RELIABILITY OF CISR SYSTEMS HARDWARE/SOFTWARE COMPONENTS USING AN IMPROVED MARKOV MODEL Cezar VASILESCU Regional Deartment of Defense Resources Management
More informationThermal Propellant Gauging System for BSS 601
5th AIAA International Communications Satellite Systems Conference (organized by APSCC) AIAA 007-3149 Thermal Proellant Gauging System for BSS 601 T. Narita. 1 JSAT Cor, 9-1 Miho-Cho, Midori-ku, Yokohama
More informationAn Active-Passive Variable Stiffness Elastic Actuator for Safety Robot Systems
The 1 IEEE/RSJ International Conference on Intelligent Robots and Systems October 18-, 1, Taiei, Taiwan An Active-Passive Variable Stiffness Elastic Actuator for Safety Robot Systems Ren-Jeng Wang, Han-Pang
More informationwhich is a convenient way to specify the piston s position. In the simplest case, when φ
Abstract The alicability of the comonent-based design aroach to the design of internal combustion engines is demonstrated by develoing a simlified model of such an engine under automatic seed control,
More informationWolfgang POESSNECKER and Ulrich GROSS*
Proceedings of the Asian Thermohysical Proerties onference -4 August, 007, Fukuoka, Jaan Paer No. 0 A QUASI-STEADY YLINDER METHOD FOR THE SIMULTANEOUS DETERMINATION OF HEAT APAITY, THERMAL ONDUTIVITY AND
More informationChapter 1 Fundamentals
Chater Fundamentals. Overview of Thermodynamics Industrial Revolution brought in large scale automation of many tedious tasks which were earlier being erformed through manual or animal labour. Inventors
More informationChurilova Maria Saint-Petersburg State Polytechnical University Department of Applied Mathematics
Churilova Maria Saint-Petersburg State Polytechnical University Deartment of Alied Mathematics Technology of EHIS (staming) alied to roduction of automotive arts The roblem described in this reort originated
More informationNonlinear superheat and capacity control of a refrigeration plant
Nonlinear suerheat and caacity control of a refrigeration lant Henrik Rasmussen Deartment of Electronic Systems Aalborg University DK-92 Aalborg, Denmark Email: hr@es.aau.dk Lars F. S. Larsen Danfoss A/S,
More informationEffect of an hourglass shaped sleeve on the performance of the fluid dynamic bearings of a HDD spindle motor
DOI 10.1007/s00542-014-2136-5 Technical Paper Effect of an hourglass shaped sleeve on the performance of the fluid dynamic bearings of a HDD spindle motor Jihoon Lee Minho Lee Gunhee Jang Received: 14
More informationCOMPUTER SIMULATION OF A LABORATORY HYDRAULIC SYSTEM WITH MATLAB-SIMULINK
DVNCED ENGINEERING 4(20101, ISSN 1846-5900 COMPUTER SIMULTION OF LORTORY HYDRULIC SYSTEM WITH MTL-SIMULINK Grego, G. & Siminiati, D. bstract: The article resents some selected roblems related to modeling
More informationSession 5: Review of Classical Astrodynamics
Session 5: Review of Classical Astrodynamics In revious lectures we described in detail the rocess to find the otimal secific imulse for a articular situation. Among the mission requirements that serve
More information5 Diagnosis of diesel engines
5 Diagnosis of diesel engines In order to develo advanced fault-detection and diagnosis systems for diesel engines a modular structure is used, which is based on the available inut and outut signals from
More informationLateral Dynamics of Flexible Rotors Supported by Controllable Gas Bearings Theory & Experiment
Downloaded from orbit.dtu.dk on: Apr, 19 Lateral Dynamics of Flexible Rotors Supported by Controllable Gas Bearings Theory & Experiment Pierart Vásquez, Fabián Gonzalo; Santos, Ilmar Published in: Proceedings
More informationRecursive Estimation of the Preisach Density function for a Smart Actuator
Recursive Estimation of the Preisach Density function for a Smart Actuator Ram V. Iyer Deartment of Mathematics and Statistics, Texas Tech University, Lubbock, TX 7949-142. ABSTRACT The Preisach oerator
More informationSpin Diffusion and Relaxation in a Nonuniform Magnetic Field.
Sin Diffusion and Relaxation in a Nonuniform Magnetic Field. G.P. Berman, B. M. Chernobrod, V.N. Gorshkov, Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 V.I. Tsifrinovich
More informationAdvance Publication by J-STAGE. Mechanical Engineering Journal
Advance Publication by J-STAGE Mechanical Engineering Journal DOI:10.199/mej.15-00033 Received date : 9 January, 015 Acceted date : 1 May, 015 J-STAGE Advance Publication date : 1 May, 015 Alication of
More informationINTERACTIONS among power converters, input/output filters,
IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 55, NO. 4, APRIL 8 795 Reaching Criterion of a Three-Phase Voltage-Source Inverter Oerating With Passive and Nonlinear Loads and Its Imact on Global Stability
More informationVisualizing Free and Forced Harmonic Oscillations using Maple V R5*
Int. J. Engng Ed. Vol. 15, No. 6,. 437±455, 1999 0949-149X/91 $3.00+0.00 Printed in Great Britain. # 1999 TEMPUS Publications. Visualizing Free and Forced Harmonic Oscillations using Male V R5* HARALD
More informationCompressor Surge Control Design Using Linear Matrix Inequality Approach
Comressor Surge Control Design Using Linear Matrix Inequality Aroach Nur Uddin Det. of Electrical Engineering Universitas Pertamina Jakarta, Indonesia Email: nur.uddin@universitasertamina.ac.id Jan Tommy
More informationPHYSICAL REVIEW LETTERS
PHYSICAL REVIEW LETTERS VOLUME 81 20 JULY 1998 NUMBER 3 Searated-Path Ramsey Atom Interferometer P. D. Featonby, G. S. Summy, C. L. Webb, R. M. Godun, M. K. Oberthaler, A. C. Wilson, C. J. Foot, and K.
More informationCHAPTER 1 INTRODUCTION Hydrodynamic journal bearings are considered to be a vital component of all the rotating machinery. These are used to support
CHAPTER 1 INTRODUCTION Hydrodynamic journal bearings are considered to be a vital component of all the rotating machinery. These are used to support radial loads under high speed operating conditions.
More informationThe Motion Path Study of Measuring Robot Based on Variable Universe Fuzzy Control
MATEC Web of Conferences 95, 8 (27) DOI:.5/ matecconf/27958 ICMME 26 The Motion Path Study of Measuring Robot Based on Variable Universe Fuzzy Control Ma Guoqing, Yu Zhenglin, Cao Guohua, Zhang Ruoyan
More informationMethods for detecting fatigue cracks in gears
Journal of Physics: Conference Series Methods for detecting fatigue cracks in gears To cite this article: A Belšak and J Flašker 2009 J. Phys.: Conf. Ser. 181 012090 View the article online for udates
More informationNonlinear Dynamic Analysis of a Hydrodynamic Journal Bearing Considering the Effect of a Rotating or Stationary Herringbone Groove
G. H. Jang e-mail: ghjang@hanyang.ac.kr J. W. Yoon PREM, Department of Mechanical Engineering, Hanyang University, Seoul, 133-791, Korea Nonlinear Dynamic Analysis of a Hydrodynamic Journal Bearing Considering
More informationINTRODUCING THE SHEAR-CAP MATERIAL CRITERION TO AN ICE RUBBLE LOAD MODEL
Symosium on Ice (26) INTRODUCING THE SHEAR-CAP MATERIAL CRITERION TO AN ICE RUBBLE LOAD MODEL Mohamed O. ElSeify and Thomas G. Brown University of Calgary, Calgary, Canada ABSTRACT Current ice rubble load
More informationShape and Failure Control of Composite Laminates using Piezoelectric Actuators
Excert from the Proceedings of the COMSOL Conference 00 Boston Shae and Failure Control of Comosite Laminates using Piezoelectric Actuators Zeaid Hasan * Texas A&M University, College Station, Texas *Corresonding
More informationEffect of accumulators on cavitation surge in hydraulic systems
Effect of accumulators on cavitation surge in hydraulic systems Donghyuk Kang, Satoshi Yamazaki, Shusaku Kagawa, Byungjin An, Motohiko Nohmi, Kazuhiko Yokota ISROMAC 6 International Symosium on Transort
More informationJ. Electrical Systems 13-2 (2017): Regular paper
Menxi Xie,*, CanYan Zhu, BingWei Shi 2, Yong Yang 2 J. Electrical Systems 3-2 (207): 332-347 Regular aer Power Based Phase-Locked Loo Under Adverse Conditions with Moving Average Filter for Single-Phase
More informationPulse Propagation in Optical Fibers using the Moment Method
Pulse Proagation in Otical Fibers using the Moment Method Bruno Miguel Viçoso Gonçalves das Mercês, Instituto Suerior Técnico Abstract The scoe of this aer is to use the semianalytic technique of the Moment
More informationInternational Journal of Mathematics Trends and Technology- Volume3 Issue4-2012
Effect of Hall current on Unsteady Flow of a Dusty Conducting Fluid through orous medium between Parallel Porous Plates with Temerature Deendent Viscosity and Thermal Radiation Harshbardhan Singh and Dr.
More informationMICROPOLAR FLUID LUBRICATION OF FINITE PARTIAL ROUGH POROUS JOURNAL BEARINGS WITH SQUEEZE EFFECT
International Journal of Mechanical Engineering and Technology (IJMET) Volume 6 Issue 11 Nov 015. 58-79 Article ID: IJMET_06_11_08 Available online at htt://www.iaeme.com/ijmet/issues.as?jtye=ijmet&vtye=6&itye=11
More informationContinuous Steel Casting System Components
CCC Annual Reort UIUC, August 9, 5 Caturing and Suressing Resonance in Steel Casting Mold Oscillation Systems Oyuna Angatkina Vivek Natarjan Zhelin Chen Deartment of Mechanical Science & Engineering University
More informationAalborg Universitet. Nonlinear superheat and capacity control of a refrigeration plant Rasmussen, Henrik; Larsen, Lars F. S.
Aalborg Universitet Nonlinear suerheat and caacity control of a refrigeration lant Rasmussen, Henrik; Larsen, Lars F. S. Published in: 17th Mediterranean Conference on Control and Automation DOI (link
More informationImpact Damage Detection in Composites using Nonlinear Vibro-Acoustic Wave Modulations and Cointegration Analysis
11th Euroean Conference on Non-Destructive esting (ECND 214), October 6-1, 214, Prague, Czech Reublic More Info at Oen Access Database www.ndt.net/?id=16448 Imact Damage Detection in Comosites using Nonlinear
More informationNUMERICAL ANALYSIS OF THE IMPACT OF THE INLET AND OUTLET JETS FOR THE THERMAL STRATIFICATION INSIDE A STORAGE TANK
NUMERICAL ANALYSIS OF HE IMAC OF HE INLE AND OULE JES FOR HE HERMAL SRAIFICAION INSIDE A SORAGE ANK A. Zachár I. Farkas F. Szlivka Deartment of Comuter Science Szent IstvÆn University Æter K. u.. G d llı
More information