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Gas-kinetic numerical study of complex flow problems covering various flow regimes

COMPUTERS & mathematics WIth APPLICATIONS 2011年第12期61卷 3653-3667页

作者： Li, Zhi-Hui Bi, Lin Zhang, Han-Xin Li, Lin Natl Lab Computat Fluid Dynam Beijing 100191 Peoples R China China Aerodynam Res & Dev Ctr Hyperveloc Aerodynam Inst Mianyang 621000 Peoples R China

the Boltzmann simplified velocity distribution function equation, as adapted to various flow regimes, is described on the basis of the Boltzmann-Shakhov model from the kinetic theory of gases in this study. the discrete velocity ordinate method of gas-kinetic theory is studied and applied to simulate complex multi-scale flows. On the basis of using the uncoupling technique on molecular movements and collisions in the DSMC method, the gas-kinetic finite difference scheme is constructed by extending and applying the unsteady time-splitting method from computational fluid dynamics, which directly solves the discrete velocity distribution functions. the Gauss-type discrete velocity numerical quadrature technique for flows with different Mach numbers is developed to evaluate the macroscopic flow parameters in the physical space. As a result, the gas-kinetic numerical algorithm is established for studying the three-dimensional complex flows with high Mach numbers from rarefied transition to continuum regimes. On the basis of the parallel characteristics of the respective independent discrete velocity points in the discretized velocity space, a parallel strategy suitable for the gas-kinetic numerical method is investigated and, then, the HPF (High Performance Fortran) parallel programming software is developed for simulating gas dynamical problems covering the full spectrum of flow regimes. To illustrate the feasibility of the present gas-kinetic numerical method and simulate gas transport phenomena covering various flow regimes, the gas flows around three-dimensional spheres and spacecraft-like shapes with different Knudsen numbers and Mach numbers are investigated to validate the accuracy of the numerical methods through HPF parallel computing. the computational results determine the flow fields in high resolution and agree well with the theoretical and experimental data. this computing, in practice, has confirmed that the present gas-kinetic algorithm probably provides

关键词： Boltzmann model equation Velocity distribution function discrete velocity ordinate method Finite difference computation three-dimensional complex flows Parallel computing

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Energy aware routing protocols for Wireless Sensor Networks using discrete transmission energies

Energy aware routing protocols for Wireless Sensor Networks ...

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Int Joint conference of 10th IEEE Int Conf on Trust, Security and Privacy in Computing and Communications (TrustCom) / 8th IEEE Int Conf on Embedded Software and Systems (ICESS) / 6th Int Conf on Frontier of Computer Science and Technology (FCST)

作者： Balazs, Karlocai Andras, Bojarszky Janos, Levendovszky Pazmany Peter Katolikus Egyet Informacios Technol Kar Prater U 50-A H-1086 Budapest Hungary Budapesti Muszaki & Gazdasatud Egyet H-1117 Budapest Hungary

ISBN: (纸本)9780769546001

In this paper three novel routing algorithms are proposed which facilitate energy aware routing and provide reliable packet transfer to the BS. All the three methods take into account that transmission energy cannot be chosen arbitrarily on the nodes but from a set of discrete energy levels. As will be demonstrated the new protocols can outperform LEACH and Directed Diffusion as far life span and reliability is concerned.

关键词： algorithm energy aware packet transfer protocol routing wsn

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Evaluation of the mean cycle time in stochastic discrete event dynamic systems 11

Evaluation of the mean cycle time in stochastic discrete eve...

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6th international conference on Queueing theory and Network Applications, QTNA 2011

作者： Krivulin, Nikolai St. Petersburg State University Faculty of Mathematics and Mechanics 28 Universitetsky Avenue St. Petersburg 198504 Russia

ISBN: (纸本)9781450307581

We consider stochastic discrete event dynamic systems that have time evolution represented with two-dimensional state vectors through a vector equation that is linear in terms of an idempotent semiring. the state transitions are governed by second-order random matrices that are assumed to be independent and identically distributed. the problem of interest is to evaluate the mean growth rate of state vector, which is also referred to as the mean cycle time of the system, under various assumptions on the matrix entries. We give an overview of early results including a solution for systems determined by matrices with independent entries having a common exponential distribution. It is shown how to extend the result to the cases when the entries have different exponential distributions and when some of the entries are replaced by zero. Finally, the mean cycle time is calculated for systems with matrices that have one random entry, whereas the other entries in the matrices can be arbitrary nonnegative and zero constants. the random entry is always assumed to have exponential distribution except for one case of a matrix with zero row when the particular form of the matrix makes it possible to obtain a solution that does not rely on exponential distribution assumptions. © 2011 ACM.

关键词： Stochastic systems

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Packing of Polydispersed Discs into Containers of Regular Shape

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PARTICULATE SCIENCE AND TECHNOLOGY 2011年第1期29卷 28-39页

作者： Belevicius, Rimantas Kacianauskas, Rimantas Markauskas, Darius Sesok, Dmitrij Vilnius Gediminas Tech Univ Vilnius Univ Fac Fundamental Sci Syst Anal DeptInst Math & Informat LT-10223 Vilnius Lithuania

A geometric algorithm for the packing of a given sequence of polydispersed circular particles into containers of regular polygon shape is suggested. the proposed algorithm aims for a twofold goal: obtaining the maximum packing density and following the prescribed homogeneity distribution laws of polydispersed particles. When seeking for maximum density, the obtained packing is further optimized by several heuristic and stochastic optimization algorithms. the objective function for the optimization algorithm is supplied by the oblack-boxo routine, which can either determine the best possible place in the packing for each particle or allow arbitrary narrowing of the placement domain, thus accelerating the computations. the quality of packing rendered by the packing routine depends only on the initial sequence of the particles in a set. the obtained packing is stable with respect to gravitational effects. the performance of optimization methods was studied using benchmark tests of periodic and non-periodic packing of mono- and poly-sized assemblies of circular particles. Simulation quality is controlled by packing density and computational efficiency. the stability of the generated packing is proved using a discrete element method.

关键词： container of regular shape discrete element method packing plane spherical particles

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Research on Reverse Design of the Cam Mechanism

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6th China-Japan international conference on Mechatronics (CJCM 2010)

作者： Liu Minfei Qian Zhiliang Soochow Univ Coll Mech & Elect Engn Suzhou 215021 Jiangsu Peoples R China

ISBN: (纸本)9783037850008

In view of the reverse design of planar cam mechanism, the measurements of cam contour are smoothed by the discrete energy law in order to ensure the dynamic performance. the cam profile is fitted by three non-uniforms B-spline according to the features that cam contour is a closed curve and its measurements are distributed non-uniformly. Based on the above, the expressions of displacement, speed, and acceleration of the follower in form of polar radius of profile and its first and second derivative are derived. Finally, a reverse design example is given, the effectiveness of the method is verified.

关键词： Cam Mechanism Reverse Design B spline discrete energy law

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discrete TIME INTEGRATION OF OBSERVERS WIth CONTINUOUS FEEDBACK BASED ON TUSTIN'S MEthOD WIth VARIABLE PREWARPING

DISCRETE TIME INTEGRATION OF OBSERVERS WITH CONTINUOUS FEEDB...

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IET international conference on Power Electronics, Machines and Drives

作者： Christopher Korlinchak Mihai Comanescu Penn State Altoona

ISBN: (纸本)9781622761456

the paper discusses the problem of integrating the equations of state observers associated with direct field orientation (DFO) of motor drives and presents a method to improve the integration accuracy when the drive operates at high frequency. In a typical implementation, observer equations are integrated based on the Euler method (forward rectangular rule). Euler method is simple;however, integration is accurate only at low/medium speed. As the speed (frequency) increases, the integration process becomes more and more inaccurate because the rectangular approximation starts losing more and more area from under the curve. theoretically, the problem could be alleviated by increasing the sampling frequency;however, this cannot always be done because it has implications related to the switching frequency of the power converter. Another idea is to use a more accurate integration method, for example, trapezoidal integration (Tustin method). At high frequency, trapezoidal integration performs better than the Euler method and the resulting estimates are closer to the expected values (in both magnitude and phase). In DFO drives, this leads to a more accurate field orientation angle. the paper presents an improvement to trapezoidal integration - the state equations of observers are integrated using a discrete-time filter that is prewarped as a function of the drive's operating frequency. the algorithm estimates the applied frequency, prewarps the continuous-time transfer function used in practical integration and obtains a discrete-time filter with frequency dependent coefficients. It is shown that the method produces an improvement over trapezoidal integration in the high-speed region. the implications related to DFO are studied by considering a full-order observer for the PMSM - integration with prewarping is compared with the classic Tustin method. the theoretical development is supported with simulation results.

关键词： Euler method Tustin method Trapezoidal integration Permanent magnet synchronous motor Rotor position estimation

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Gaussian noise and discrete cosine transform image compression on transmission of dermatological images

Gaussian noise and discrete cosine transform image compressi...

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6th international conference on Mass Data Analysis of Signals and Images in Medicine, Chemistry, Biotechnology and Food Industry, MDA 2011

作者： Dimililer, Kamil Kavalcioglu, Cemal Electrical and Electronic Engineering Department Near East University Lefkosa Mersin 10 Turkey

ISBN: (纸本)9783942952026

Telemedicine provides medical information and services using telecommunication technologies. Teledermatology is a subspecialty in the medical field of dermatology and probably one of the most common applications of telemedicine and e-health. In Teledermatology, telecommunication technologies are used to exchange medical information over a distance using audio, visual and data communication. Medical images require compression, before transmission or storage due to constrained bandwidth and storage capacity. An ideal image compression system must yield high quality compressed image with high compression ratio;this ratio can be achieved using transform-based image compression, however the contents of the image affects the choice of an optimum compression ratio and the optimum compression method. this paper suggests that discrete cosine transform based image compression is suitable for the dermatology images to be applied before the transmission through a communication channel. the Peak-Signal-to-Noise Ratio results shows that the suggested system gives better results than *** © 2011 ibai-publishing.

关键词： Image compression

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Packing of Polydispersed Discs into Containers of Regular Shape

Packing of Polydispersed Discs into Containers of Regular Sh...

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6th international conference on Conveying and Handling of Particulate Solids/ 10th international conference on Bulk Materials Storage, Handling and Transportation

关键词： container of regular shape discrete element method packing plane spherical particles

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Modelling dynamic bottlenecks in production networks

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international JOURNAL OF COMPUTER INTEGRATED MANUFACTURING 2011年第5期24卷 391-404页

作者： Scholz-Reiter, Bernd Windt, Katja Liu, Huaxin Univ Bremen BIBA Bremen Inst Ind Technol & Appl Work Sci D-28359 Bremen Germany Jacobs Univ Sch Engn & Sci D-28759 Bremen Germany Int Grad Sch Dynam Logist IGS D-28359 Bremen Germany

Bottlenecks, as the key ingredients for improving the performances of the production networks, have been profoundly studied. However, the major definitions of bottlenecks are derived in terms of the throughput and based on the theory of constraints (TOC). Moreover, before the specific measures can be applied on them, it is not straightforward to localise dynamic bottlenecks due to their complex dynamic characteristics. Distinguishing from the traditional view at the bottlenecks, this article therefore develops a systematic and comprehensive definition of dynamic bottlenecks of the production networks based on both the TOC and the bottleneck-oriented logistic analysis. Afterwards, the defined dynamic bottlenecks are modelled by means of discrete simulation using practical data, aiming at visualising them in the production network. By applying the logistic operating curves, the practical application of the proposed research and its procedures is discussed as well.

关键词： dynamic bottlenecks production networks discrete simulation, TOC, BOLA, LOCs

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3-axis NC Rough Tool-path Generation from discrete Data Points of Reliefs

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6th China-Japan international conference on Mechatronics (CJCM 2010)

作者： Liu Wei Zhou Laishui An Luling Nanjing Univ Aeronaut & Astronaut Coll Mech & Elect Engn Nanjing 210016 Jiangsu Peoples R China

ISBN: (纸本)9783037850008

this paper presents an algorithm through which 3-axis NC rough tool-paths can be directly generated from discrete data points. Based on Inverse Tool Offset (ITO) method, the algorithm generates direction-parallel (DP) tool paths for relief point clouds. the algorithm includes four steps: dividing data points into 3D cell grids;constructing inverse tool model and calculating the grids intersecting the surface of inverse tool;obtaining the grids containing cutter location points;calculating tool paths. the experiment results indicate that the algorithm of the rough tool paths is efficient.

关键词： NC machining tool path discrete data points 3D cell grid

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