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Simulation of wave focusing in cavities

Computational Mathematics and Modeling 2002年第3期13卷 249-262页

作者： Bazarov, S.B. Naboko, I.M.

Simulation results are presented for the focusing of shock waves in conical and wedge-shaped cavities. Results are reported for plane waves and explosion waves. The distribution of parameters in the focusing zone is f... 详细信息

关键词： Conical Simulation results WAVE FOCUSING Plane waves simulating distributed parameter

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Model of mechanical wear based on Markov processes

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Soviet Applied Mechanics 1977年第3期13卷 258-262页

作者： Strel'nikov, V.P. Tatsii, V.G.

1. An analytical expression was obtained for the distribution of the working life for mechanical wear;the parameters of the distribution have specific physical significance and are determined by a special experiment. 2. The diffusional distribution of the life, as shown by preliminary estimates, does not disagree with experimental data and, together with other distributions, may be used for the treatment of statistical data on the life of couplings. Since the diffusional distribution was obtained on the basis of an analysis of wear kinetics, its use in estimating wear resistance is preferable to the use of other distributions based on different considerations (Weibull distribution, gamma distribution, normal distribution, etc.). 3. In the procedure proposed for determining the distribution law of the life, active use was made of a priori information on failure (the steady character of failure, i.e., the linear variation of the mean value and the dispersion), so that data on the lifetime can be extrapolated. Thus, the model of wear proposed may serve as the basis for the development of methods and means of accelerated testing for wear resistance. 4. By means of the mathematical model of wear proposed, it is fairly simple to obtain all the statistical characteristics of the reliability of coupling components necessary for engineering calculations. © 1977 Plenum Publishing Corporation.

关键词： mean value Basis wear life career failures Statistical Data ACCELERATED TESTING Couplings Markov chain distributed parameter abrasion

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Short-circuit current calculation on DC side of MMC-HVDC system with long distance transmission lines 3

Short-circuit current calculation on DC side of MMC-HVDC sys...

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3rd International Conference on Electrical Engineering and Control Science, IC2ECS 2023

作者： Wang, Zhuoya Hao, Liangliang He, Jinghan College of Electrical Engineering Beijing Jiaotong University Beijing China

ISBN: (纸本)9798350382426

The development of DC side faults in flexible DC transmission systems is rapid, and the short-circuit current rises very quickly. With the gradual expansion of flexible DC transmission technology to long-distance and long transmission line scenarios, the calculation of short-circuit current considering distributed parameter lines urgently needs attention. This article is based on the MMC DC side short-circuit current calculation universal model, studies the transmission line structure, establishes a long-distance transmission line mathematical model considering the distribution parameter characteristics and line frequency variation characteristics, and proposes a DC side short-circuit current calculation method for flexible DC transmission systems containing long-distance transmission lines. The comparison between simulation and calculation results verified the correctness of the theoretical model and the effectiveness of the calculation method. © 2023 IEEE.

关键词： distributed parameter modular multilevel converter short-circuit current calculation transmission lines model

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Study on multi scattering point modeling for target in fuze RF simulation and its application 3

Study on multi scattering point modeling for target in fuze ...

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3rd Asia-Pacific Conference on Antennas and Propagation, APCAP 2014

作者： Qian, Chen Jun, Gu ChunHua, Zhou XiaoBing, Wang Beijing Institute of Technology Beijing100094 China Science and Technology on Electromagnetic Scattering Laboratory Shanghai200438 China Shanghai Radio Equipment Reaearch Institute Shanghai200438 China

ISBN: (纸本)9781479943548

This article acquires the microwave imagery of target through simulation, bases on ISAR imagery of complex target, and adopts the CLEAN method to extract the strong scattering point of target imagery;meanwhile, combine the non-uniform illumination under missile-target encounter conditions, respectively obtain the distribution parameters of target scattering points at various miss distance, providing input data source for fuse RF simulation. © 2014 IEEE.

关键词： Atmospheric modeling Data models Electromagnetic scattering Fuses Radio frequency Vectors multi scattering point radio frequency simuation research of application Fuses radiofrequency Atmospheric models data models Electromagnetic scattering microwave images Targets distributed parameter broadcasting Scattering simulating Cloning Vectors

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Optimal configuration of microstructure in ferroelectric materials by stochastic optimization

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JOURNAL OF APPLIED PHYSICS 2010年第2期108卷 024101-024101页

作者： Jayachandran, K. P. Guedes, J. M. Rodrigues, H. C. Univ Tecn Lisboa IDMEC Inst Super Tecn P-1049001 Lisbon Portugal

An optimization procedure determining the ideal configuration at the microstructural level of ferroelectric (FE) materials is applied to maximize piezoelectricity. Piezoelectricity in ceramic FEs differs significantly from that of single crystals because of the presence of crystallites (grains) possessing crystallographic axes aligned imperfectly. The piezoelectric properties of a polycrystalline (ceramic) FE is inextricably related to the grain orientation distribution (texture). The set of combination of variables, known as solution space, which dictates the texture of a ceramic is unlimited and hence the choice of the optimal solution which maximizes the piezoelectricity is complicated. Thus, a stochastic global optimization combined with homogenization is employed for the identification of the optimal granular configuration of the FE ceramic microstructure with optimum piezoelectric properties. The macroscopic equilibrium piezoelectric properties of polycrystalline FE is calculated using mathematical homogenization at each iteration step. The configuration of grains characterized by its orientations at each iteration is generated using a randomly selected set of orientation distribution parameters. The optimization procedure applied to the single crystalline phase compares well with the experimental data. Apparent enhancement of piezoelectric coefficient d(33) is observed in an optimally oriented BaTiO3 single crystal. Based on the good agreement of results with the published data in single crystals, we proceed to,apply the methodology in polycrystals. A configuration of crystallites, simultaneously constraining the orientation distribution of the c-axis (polar axis) while incorporating ab-plane randomness, which would multiply the overall piezoelectricity in ceramic BaTiO3 is also identified. The orientation distribution of the c-axes is found to be a narrow Gaussian distribution centered around 45 degrees. The piezoelectric coefficient in such a ceramic is fou

关键词： Optimization Procedure crystalline phase Solution space homogenization iterative methods Piezoelectricity GTF2E1 gene Iron distributed parameter single crystals self-potential methods

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NMR investigation of mechanically milled nanostructured GaF₃ powders

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JOURNAL OF PHYSICS-CONDENSED MATTER 1999年第40期11卷 L423-L431页

作者： Bureau, B Guérault, H Silly, G Buzaré, JY Grenèche, JM Univ Maine UPRESA CNRS 6087 Lab Phys Etat Condensee F-72085 Le Mans 9 France

High-energy ball milling is suitable for the preparation of nanostructured powders. First, high-resolution, solid-state nuclear magnetic resonance (NMR) investigations of F-19, Ga-69 and Ga-71 in ball-milled ionic GaF3 are presented. The quadrupolar parameter and the isotropic chemical shift distributions are determined for the three nuclei. The quadrupolar parameter distributions give clear evidence of two main structurally different phases in mechanically milled GaF3. A discussion based upon molecular dynamics simulations allows us to distinguish these two phases according to the size of the distortion of the GaF6 octahedral units: the lowest distortion is related to crystalline grains and the highest one to grain boundaries. It is thus concluded that NMR is a technique well adapted to the quantification and characterization of these two phases.

关键词： abnormal shapes TWO-PHASE Ball milling Nuclear Magnetic Resonance High energy milling distortion Cereal Grain Molecular Dynamics Simulation distributed parameter Grain boundaries

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Fault location for general AC/DC transmission lines: Multi-phase, non-homogeneous, partially mutually coupled and multi-terminal lines

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ELECTRIC POWER SYSTEMS RESEARCH 2023年第1期222卷

作者： Lu, Dayou Liu, Yu ShanghaiTech Univ Sch Informat Sci & Technol Shanghai 201210 Peoples R China Minist Educ Key Lab Control Power Transmiss & Convers SJTU Shanghai 200240 Peoples R China

The complexity of a general AC/DC transmission line is mainly caused by the components such as multi-phase line, non-homogeneous line, partially mutually coupled line and multi-terminal line. This paper proposes a systematic methodology to accurately locate faults in a general complex AC/DC transmission line. Instantaneous measurements only at line terminals are required. First, the modeling methodologies of symmetrical/asym-metrical multi-phase line, non-homogeneous (including partially mutually coupled) line and multi-terminal line are proposed. The distributed parameter line model is fully considered with partial differential equations (PDEs) in time domain. Second, the voltage distribution along the entire line is obtained via numerical solutions. Third, the faulted segment and fault location is determined based on the calculated voltage distribution. The proposed method is carefully designed to ensure applicability for a general AC/DC transmission line, independent of the numbers of phases/poles, non-homogeneous (including partially mutually coupled) sections, terminals, and joint points. Numerical experiments in two example complex transmission lines prove that the proposed method can accurately identify faulted segments and locate faults under different fault conditions. The method works with a relatively low sampling rate of 20k samples/sec and a data window of 5 ms after the fault occurs.

关键词： Fault location Multi-phase line Non-homogeneous line Partially mutually coupled line Multi-terminal line Time domain distributed parameter Partial differential equations (PDEs)

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Structural Damage Detection and Localization with Unknown Postdamage Feature Distribution Using Sequential Change-Point Detection Method

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JOURNAL OF AEROSPACE ENGINEERING 2019年第2期32卷 4018149.1-4018149.10页

作者： Liao, Yizheng Kiremidjian, Anne S. Rajagopal, Ram Loh, Chin-Hsuing Stanford Univ Dept Civil & Environm Engn 473 Via Ortega Stanford CA 94305 USA Natl Taiwan Univ Dept Civil Engn 1Sect 4Roosevelt Rd Taipei 106 Taiwan

The high structural deficient rate poses serious risks to the operation of many bridges and buildings. To prevent critical damage and structural collapse, a quick structural health diagnosis tool is needed during normal operation or immediately after extreme events. In structural health monitoring (SHM), many existing methods will have limited usefulness in the quick damage identification process because (1) the damage event needs to be identified quickly, and (2) postdamage information is usually unavailable. To address these drawbacks, we propose a new damage detection and localization approach based on stochastic time series analysis. Specifically, damage sensitive features, which are extracted from vibration signals, follow different distributions before and after a damage event. Hence, we use optimal change-point detection theory to find the time of damage occurrence. Because existing change-point detectors require the postdamage feature distribution, which is unavailable in SHM, we propose a maximum likelihood method for learning the distribution parameters from the time-series data. The proposed damage detection using estimated parameters achieves optimal performance. Also, we utilize the detection results to find damage location without any further computation. Validation results show highly accurate damage identification in American Society of Civil Engineers benchmark structures and two shake table experiments.

关键词： Simple harmonic motion time series analysis Not Available structural damage detection maximum likelihood Damage detection SHAKING TABLE American Society of Civil Engineers (ASCE) inspection methods distributed parameter damage assessment normal operation

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Drop-size distribution characteristics in tropical mesoscale convective systems

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JOURNAL OF APPLIED METEOROLOGY 2000年第6期39卷 760-777页

作者： Cifelli, R Williams, CR Rajopadhyaya, DK Avery, SK Gage, KS May, PT Univ Maryland Baltimore Cty Joint Ctr Earth Syst Technol Baltimore MD 21228 USA Univ Colorado Cooperat Inst Res Environm Sci Boulder CO 80309 USA NOAA Aeron Lab Boulder CO 80303 USA Bur Res Meteorol Ctr Melbourne Vic Australia

Drop-size distribution characteristics were retrieved in eight tropical mesoscale convective systems (MCS) using a dual-frequency (UHF and VHF) wind profiler technique. The MCSs occurred near Darwin, Australia, during the 1993/94 wet season and were representative of the monsoon (oceanic) regime. The retrieved drop-size parameters were compared with corresponding rain gauge and disdrometer data, and it was found that there was good agreement between the measurements, lending credence to the profiler retrievals of drop-size distribution parameters. The profiler data for each MCS were partitioned into a three-tier classification scheme (i.e., convective, mixed convective-stratiform, and stratiform) based on a modified version of Williams et al. to isolate the salient microphysical characteristics in different precipitation types. The resulting analysis allowed for an examination of the drop-size distribution parameters in each category for a height range of about 2.1 km in each MCS. In general, the distributions of all of the retrieved parameters showed the most variability in convection and the least in stratiform, with the mixed convective-stratiform category usually displaying intermediate characteristics. Although there was significant overlap in the range of many of the parameter distributions, the mean profiles were distinct. In the stratiform region, there was minimal vertical structure for all of the drop-size distribution parameters. This result suggests an equilibrium between depletion (e.g., evaporation) and growth (e.g., coalescence) over the height range examined. In contrast, the convective parameter distributions showed a more complicated structure, probably as a consequence of the complex microphysical processes occurring in the convective precipitation category. Reflectivity-rainfall (Z-R) relations of the form Z = AR(B) were developed for each precipitation category as a function of height using linear regressions to the profiler retrievals of R and

关键词： drop-size distribution tropical mesoscale convective systems mesoscale convective systems (MCS) wind profiler technique Drop size distribution height profiler Category MCS gene distributed parameter

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DYNMIC MODEL OF A FLUIDIZED BED DRYER

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Drying Technology 1993年第3期11卷 589-602页

作者： R. C. Panda[a] V. S. Ramachandra IIao[a] [a] Department of Chemlcal Englneerlng Indian Institute of Technology Madras India

ABSTRACTABSTRACTAn axially dlstrlbuted dynamlc model of a gas-solldcontlnuous fluldlzed bed dryer 1s *** steady state formof the model 1s compared with the exlstlng models. Throughslmulatlon profiles of the molsture content and temperature of thebed are obtalned. The transient analysis of the developed model 1sstudled ulth reference to step changes in the air inlet temperature, superficial air *** residence *** molsture content of the feed and dryer-wall *** results are useful in developlng preclse control strategies to implement on the fluidized bed dryer.

关键词： automatic control distributed parameter dynamic characteristics moisture and temperature profiles

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