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Determination of grain-size distribution from ultrasonic attenuation: Transformation and inversion

JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 1997年第2期101卷 686-689页

作者： Nicoletti, D Anderson, A Electrical and Computer Engineering Department Worcester Polytechnic Institute 100 Institute Road Worcester Massachusetts 01609

Although researchers often describe a particular medium with only a single grain size or an average grain size, distributions of grain sizes can have significant effects on the physical characteristics of the material. Ultrasonic attenuation due to energy scattered at the grain boundaries depends on the ultrasonic wavelength, the grain size, and certain material properties such as elastic constants. This paper examines the relationship between the wavelength dependency of ultrasonic attenuation and grain-size distributions. A transformation is developed which solves a general class of Fredholm equations of the first kind. The equation relating attenuation to grain-size distributions belongs to this class of equations. The transformation allows attenuation to be calculated by discrete convolution, and provides a method for estimating the grain-size distribution directly from attenuation measurements. (C) 1997 Acoustical Society of America.

关键词： wavelengths Particle size distribution size distribution Material properties Physical characteristics Ultrasonic attenuation Researchers

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ON ADAPTIVE REFINEMENT FOR BOUNDARY INTEGRAL METHODS IN ELECTROSTATICS

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IEEE TRANSACTIONS ON DIELECTRICS AND electrical INSULATION 1994年第6期1卷 963-974页

作者： SPASOJEVIC, M LEVIN, PL Computational Fields Laboratory Department of Electrical and Computer Engineering Worcester Polytechnic Institute Worcester MA USA

Numerical techniques based upon boundary integral methods like charge simulation or Galerkin boundary elements are still warmly received in the HV community because they are relatively easy to implement and use, and because they are accurate. However, the results can be sensitive to the quality of the discretization. In this work we introduce an efficient refinement scheme that automatically chooses the sections of conducting and dielectric boundaries where new nodes should be placed. The numerical results compare favorably to canonical solutions, and the method is shown to be effective on more complicated practical geometries.

关键词： Integral equations Electrostatics Geometry Computational modeling Costs Interpolation Laboratories computer simulation Moment methods Dielectrics

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Improved High-Speed Thermal Analysis Based on Two-Step Simulation for High-Frequency Transformers

Improved High-Speed Thermal Analysis Based on Two-Step Simul...

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Annual IEEE Conference on Applied Power Electronics Conference and Exposition (APEC)

作者： Zheyuan Yi Kai Sun Qiang Li Zengyang Liu Department of Electrical Engineering State Key Laboratory of Power System Tsinghua University Beijing China Delta Electronics Shanghai Co. Ltd. Shanghai China The Bradley Department of Electrical and Computer Engineering Virginia Polytechnic Institute and State Center for Power Electronics Systems University Blacksburg Virginia USA

ISBN: (数字)9798331516116

ISBN: (纸本)9798331516123

Thermal analysis is a crucial and time-consuming step in the optimization design process of high-frequency transformers (HFTs). This paper proposes an improved thermal analysis method based on heat dissipation-conduction two-step simulation, significantly reducing the computation time while ensuring the accuracy of thermal analysis. Simulation results validate the accuracy and of the proposed method and demonstrate that the proposed method saves 82% of computation time for a single thermal analysis case compared to direct CFD. Experimental results further verify the accuracy of the proposed method. An exemplary application of the proposed method in the optimization design of the HFT illustrates a 98% reduction in computation time for thermal analysis during the optimization process.

关键词： Heating systems Temperature distribution Accuracy Simulation Computational modeling Thermal analysis High-frequency transformers Optimization Surface treatment Heat transfer

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Flexible Full-Stokes Polarization engineering by Disorder-Scrambled Metasurfaces

arXiv

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arXiv 2025年

作者： Cheng, Zhi Zhou, Zhou Wang, Zhuo Wang, Yue Yu, Changyuan Department of Electrical and Electronic Engineering The Hong Kong Polytechnic University China Department of Electrical and Computer Engineering NUS Graduate School National University of Singapore Singapore117583 Singapore Guangdong Provincial Key Laboratory of Nanophotonic Functional Materials and Devices School of Optoelectronic Science and Engineering South China Normal University Guangzhou510006 China The Hong Kong Polytechnic University Shenzhen Research Institute Shenzhen China

The ability to arbitrarily and flexibly control the polarization of light, including both the state of polarization (SoP) and the degree of polarization (DoP), is highly important for quantum optics, polarization imaging, and coherent optical communications. Although metasurfaces have shown promise in polarization control, the few studies focusing on the DoP often lack flexibility in manipulation. Here, we propose a novel approach using a disordered metasurface to flexibly convert natural light into partially polarized light, enabling independent and flexible control over all Stokes parameters. The metasurface is composed of two types of meta-atoms, uniformly distributed with specific quantity ratios, decoupling the design parameters in the process of polarization control, and allowing a one-to-one correspondence between metasurface and polarization spaces. The azimuthal and elevation angles of the SoP on the Poincaré sphere are independently controlled by the meta-atom rotation and size, while the DoP is governed by the quantity ratio. A developed algorithm determines the disordered metasurface arrangement, with theoretical calculations showing an average error of less than 3° for both the azimuthal and elevation angles and a control accuracy of ±0.05 for the DoP. Copyright © 2025, The Authors. All rights reserved.

关键词： Quantum optics

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EMBEDDED INSTRUMENTATION FOR EVALUATING TASK SHARING PERFORMANCE IN A DISTRIBUTED COMPUTING SYSTEM

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IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT 1992年第2期41卷 316-321页

作者： ROTITHOR, HG Department of Electrical Engineering Worcester Polytechnic Institute Worcester MA USA

In this paper, an example of application level performance measurement on a distributed computing system using software-based instrumentation is considered. Embedded software instrumentation for measuring the performance of a decentralized adapative task-sharing algorithm in a distributed computing system is described. For our application, simplicity and flexibility provided by software-based instrumentation are demonstrated, and its limitations are discussed. Quantitative results obtained from the implementation on an experimental distributed computing system consisting of VAX stations connected by a local area network are presented.

关键词： EMBEDDED INSTRUMENTATION DISTRIBUTED COMPUTING PERFORMANCE MEASUREMENT TASK SHARING

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THEORETICAL BASIS FOR A UNIFIED CONSERVATION LAW DESCRIPTION OF THE ELECTROMAGNETIC ACOUSTIC TRANSDUCTION PROCESS

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IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL 1992年第4期39卷 476-480页

作者： LUDWIG, R Department of Electrical and Computer Engineering Worcester Polytechnic Institute Worcester MA USA

A unified theoretical formulation describing the electro-acoustic transduction processes governing an electromagnetic acoustic transducer is presented. This new approach establishes separate electrical, mechanical and material subsystem descriptions based on the momentum conservation forms of Maxwell's field equations in the quasi-static limit and Cauchy's law of motion. Instead of accounting for the electromagnetic acoustic material interaction by direct linkage of mechanical stress and magnetic flux through constitutive relations, the coupling of the field tensors is achieved as part of an additional material subsystem. As a result, the complete set of governing equations and associated boundary conditions can be derived from first principles in a concise way that lends itself to a quantitative numerical implementation in the time domain. Aspects of the numerical formulation and the subsequent computer model predictions are discussed in a companion paper.

关键词： Magnetic materials Magnetic flux Tensile stress Magnetostriction Maxwell equations Electromagnetic fields Acoustic materials Acoustic transducers Electromagnetic coupling Surface acoustic waves

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SHALLOW LEVEL RECOMBINATION CURRENT DOMINANCE IN TRANSISTOR BETAS

IEEE ELECTRON DEVICE LETTERS

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IEEE ELECTRON DEVICE LETTERS 1993年第2期14卷 49-50页

作者： LANYON, HPD Department of Electrical and Computer Engineering Worcester Polytechnic Institute Worcester MA USA

A new recombination mechanism, via the high density of shallow donor and acceptors present in the base-emitter junction of integrated circuit transistors, is suggested. In contrast to the recombination via deep centers, this mechanism has an ideal voltage dependence, leading to a beta essentially independent of the base-emitter voltage. It appears to be the dominant component to the base current of integrated circuit transistors. The temperature dependence of the beta of the transistors arises from the ionization energy of the donors and acceptors. The rate-setting capture cross section by neutral acceptor and donors is 1.3(5) x 10(-15) cm2.

关键词： Voltage Spontaneous emission Charge carrier processes Electron traps Silicon Temperature dependence Energy capture Ionization Doping Diodes

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IMAGE COMPRESSION USING ADDRESS-VECTOR QUANTIZATION

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IEEE TRANSACTIONS ON COMMUNICATIONS 1990年第12期38卷 2166-2173页

作者： NASRABADI, NM FENG, YS Department of Electrical Engineering Worcester Polytechnic Institute Worcester MA USA

Memoryless vector quantizers exploit the high correlation and the spatial redundancy between neighboring pixels, but they totally ignore the spatial redundancy between the neighboring blocks. In this paper, a new vector quantization scheme called the address-vector quantizer (A-VQ) is proposed. It is based on exploiting the interblock correlation by encoding a group of block together using an address-codebook. The address-codebook consists of a set of address-codevectors where each codevector represents a combination of addresses (indexes). Each element of this codevector is an address of an entry in the LBG-codebook, representing a vector quantized block. The address-codebook consists of two regions, one is the active (addressable) region, and the other is the inactive (nonaddressable) region. During the encoding process the codevectors in the address-codebook are recordered adaptively in order to bring the most probable address-codevectors into the active region. When encoding an address-codevector the active region of the address-codebook is checked, if such an address combination exists its index is transmitted to the receiver, otherwise the address of each block is transmitted individually. The quality (SNR value) of the images encoded by the proposed A-VQ method is the same as that of a memoryless vector quantizer, but the bit rate would be reduced by a factor of approximately two when compared to a memoryless vector quantizer.

关键词： Image coding Clustering algorithms Partitioning algorithms Iterative algorithms Vector quantization Image storage Bit rate Digital images Speech Distortion measurement

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AN IMPROVEMENT TO THE RYTOV APPROXIMATION IN DIFFRACTION TOMOGRAPHY

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IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL 1986年第4期33卷 394-401页

作者： SOUMEKH, M Department of Electrical Engineering Worcester Polytechnic Institute Worcester MA USA

A method for reducing the approximation errors introduced in the Rytov inversion of the inhomogeneous wave equation is presented. The approach is based on the filtering of the Rytov function components at the receiver line that correspond to the Rytov distortion term. Signal processing issues associated with the implementation of the scheme are discussed. Reconstruction results for simulated soft-scattering cylinders are presented. Copyright © 1986 by The institute of electrical and Electronics Engineers, Inc.

关键词： Tomography Testing Acoustic scattering Partial differential equations Signal processing Approximation error Filtering Image reconstruction Acoustic diffraction Acoustic refraction

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APPLICATIONS OF TENSOR THEORY TO OBJECT RECOGNITION AND ORIENTATION DETERMINATION

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IEEE TRANSACTIONS ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE 1985年第6期7卷 662-673页

作者： CYGANSKI, D ORR, JA Department of Electrical Engineering Worcester Polytechnic Institute Worcester MA 01609

A method is developed by which images resulting from orthogonal projection of rigid planar-patch objects arbitrarily oriented in three-dimensional (3-D) space may be used to form systems of linear equations which are solved for the affine transform relating the images. The technique is applicable to complete images and to unlabeled feature sets derived from images, and with small modification may be used to transform images of unknown objects such that they represent images of those objects from a known orientation, for use in object identification. No knowledge of point correspondence between images is required. Theoretical development of the method and experimental results are presented. The method is shown to be computationally efficient, requiring O(N) multiplications and additions where, depending on the computation algorithm, N may equal the number of object or edge picture elements.","doi":"10.1109/TPAMI.1985.4767722","publicationTitle":"IEEE Transactions on Pattern Analysis and Machine Intelligence","startPage":"662","endPage":"673","rightsLink":"http://***/AppDispatchServlet?publisherName=ieee&publication=0162-8828&title=Applications+of+Tensor+Theory+to+Object+Recognition+and+Orientation+Determination&isbn=&publicationDate=Nov.+1985&author=David+Cyganski&ContentID=10.1109/TPAMI.1985.4767722&orderBeanReset=true&startPage=662&endPage=673&volumeNum=PAMI-7&issueNum=6","displayPublicationTitle":"IEEE Transactions on Pattern Analysis and Machine Intelligence","pdfPath":"/iel5/34/4767715/***","keywords":[{"type":"IEEE Keywords","kwd":["Tensile stress","Object recognition","Position measurement","Fourier transforms","Image processing","Image recognition","Equations","Image sequence analysis","Pattern recognition","Manufacturing automation"]},{"type":"Author Keywords ","kwd":["tensor applications","Affine transformation","image processing","image sequence analysis","pattern recognition"]}],"allowComments":false,"pubLink":"/xpl/***

关键词： Tensile stress Object recognition Position measurement Fourier transforms Image processing Image recognition Equations Image sequence analysis Pattern recognition Manufacturing automation Author Keywords tensor applications Affine transformation image processing image sequence analysis pattern recognition

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