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Conference on electrical Insulation and Dielectric Phenomena, (CEIDP)

作者： A. Ostundag T.J. Gung M. Zahn Dept. of Electr. Eng. & Comput. Sci. MIT Cambridge MA USA Department of Electrical Engineering and Computer Science Laboratory for Electromagnetic and Electronic Systems Massachusetts Institute of Technology Cambridge MA USA

Recently we used the onion peeling method to reconstruct the axisymmetric electric field distribution of point/plane electrodes from Kerr electro-optic measurements. The method accurately reconstructed the electric field from numerically generated data. However in the presence of experimental noise the performance was less satisfactory. The measurements were especially noisy and unstable near the needle tip which is also the most interesting region since most charge injection occurs here. In this paper we propose a new algorithm for Kerr electro-optic reconstruction of space charge in arbitrary geometries. The algorithm is built on the finite element method for Poisson's equation and will be called the finite element based Kerr electro-optic reconstruction (FEBKER) hereafter. FEBKER is tested on a point/plane like simple artificial axisymmetric geometry. Research is underway for application of the method to actual axisymmetric point/plane experiments. The method is readily extendible to arbitrary three dimensional geometries.

关键词： Reconstruction algorithms Geometry Finite element methods Electrodes Electric variables measurement Current measurement Charge measurement Needles Space charge Poisson equations

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A Region-Based Representation of Images in MARS

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Journal of VLSI Signal Processing Systems for Signal, Image, and Video Technology 1998年第1-2期20卷 137-150页

作者： Servetto, Sergio D. Rui, Yong Ramchandran, Kannan Huang, Thomas S. Beckman Inst. Adv. Sci. and Technol. Univ. Illinois at Urbana-Champaign Urbana IL 61801 United States Universidad Nacional de La Plata Argentina Univ. Illinois at Urbana-Champaign United States Comp. Res. Adv. Applications Group IBM Argentina Argentina Image Formation and Processing Group Beckman Institute UIUC United States Department of Computer Science UNLP Argentina Dept. of Elec. and Comp. Engineering UIUC United States Multimedia Commun. Res. Department Bell Laboratories Murray Hill NJ United States Info. Sciences Research Department AT and T Labs. Florham Park NJ United States Department of Computer Science UIUC United States Southeast University China Tsinghua University China University of Illinois Urbana-Champaign IL United States Image Formation and Processing Group Beckman Inst. Advance Sci. Technol. UIUC United States Vis. Technol. Grp. of Microsoft Res. Redmond WA United States City College of New York United States Columbia University United States AT and T Bell Labs. United States Ctr. for Telecommunications Research Columbia University United States Elec. and Comp. Eng. Department United States Beckman Institute Coordinated Science Laboratory IL United States IEEE Signal Processing Society United States IEEE IMDSP Technical Committee United States IEEE Transactions on Image Proc. United States National Taiwan University Taipei Taiwan Massachusetts Inst. of Technology Cambridge MA United States Department of Electrical Engineering MIT United States School of Electrical Engineering United States Lab. for Info. and Signal Processing Purdue University United States Dept. of Elec. and Comp. Engineering United States Coordinated Science Laboratory United States Image Formation and Processing Group Beckman Inst. Adv. Sci. and Technol. United States MIT Lincoln Laboratory IBM Thomas J. Watson Research Center Rheinishes Landes Museum Bonn Germany Swiss Institutes of Technology Zurich Switzerland Swiss Institutes of Technology Lausanne S

We study the problem of representing images within a multimedia Database Management System (DBMS), in order to support fast retrieval operations without compromising storage efficiency. To achieve this goal, we propose new image coding techniques which combine a wavelet representation, embedded coding of the wavelet coefficients, and segmentation of image-domain regions in the wavelet domain. A bitstream is generated in which each image region is encoded independently of other regions, without having to explicitly store information describing the regions. Simulation results show that our proposed algorithms achieve coding performance which compares favorably, both perceptually and objectively, to that achieved using state-of-the-art image/video coding techniques while additionally providing region-based support.

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Rotationally invariant, geometrically uniform trellis codes

Rotationally invariant, geometrically uniform trellis codes

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1997 IEEE International Symposium on Information Theory, ISIT 1997

作者： Sarvis, James P. Trott, mitchell D. Laboratory for Information and Decision Systems Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology MIT 35-316 77 Massachusetts Ave Cambridge MA 02139 United States

Given a group trellis and a partitioned signal set, we show how to find all geometrically uniform mappings from the trellis branches to the partition cells. The result is a procedure for constructing geometrically uni... 详细信息

ISBN: (纸本)0780339568

关键词： Trellis codes

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Sub-optimal power spectra for colored Gaussian channels

Sub-optimal power spectra for colored Gaussian channels

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IEEE International Symposium on Information Theory

作者： B. Schein M. Trott Laboratory for Information and Decision Systems Department of Electrical Engineering and Computer Science MIT Cambridge MA USA

We consider a particular approximate "water-pouring" scheme applied to an additive, colored Gaussian noise channel. The scheme allocates power uniformly over an optimized band of frequencies. Within the set of all noise power spectral densities yielding a fixed water-pouring capacity, we find the noise spectrum yielding the smallest mutual information between input and output when the transmitter is restricted to use the sub-optimal scheme. The loss at high SNR is a fraction of a bit per Hz; the relative loss at low SNR is less than 15%.

关键词： Gaussian channels Frequency Gaussian noise Signal to noise ratio Mutual information Legged locomotion Additive noise Propagation losses Laboratories Helium

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Optical Coherence Tomography for Biomedical Imaging and Diagnostics 12

Optical Coherence Tomography for Biomedical Imaging and Diag...

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12th International Conference on Optical Fiber Sensors, OFS 1997

作者： Fujimoto, J.G. Bouma, B.E. Tearney, G.J. Boppart, S.A. Pitris, C. Herrmann, J. Swanson, E.A. Southern, J.F. Brezinski, M.E. Department of Electrical Engineering and Computer Science Research Laboratory of Electronics Massachusetts Institute of Technology CambridgeMA02139 United States MIT Lincoln Laboratory LexingtonMA02173 United States Massachusetts General Hospital Harvard Medical School BostonMA02114 United States

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A simulation methodology for assessing the impact of spatial/pattern dependent interconnect parameter variation on circuit performance

A simulation methodology for assessing the impact of spatial...

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International Electron Devices Meeting (IEDM)

作者： B.E. Stine V. Mehrotra D.S. Boning J.E. Chung D.J. Ciplickas Department of Electrical Engineering and Computer Science MIT Cambridge MA USA PDF Solutions Inc.orporated San Jose CA USA

In this paper, we illustrate a methodology for determining the impact of interconnect pattern dependent variation on circuit performance. The methodology helps enable first pass prediction and can handle large layouts using methods which are reasonably compatible with existing CAD tools. We illustrate the relative utility of the methodology using two case studies. Both studies are drawn from industrial relevant problems: unwanted skew in a balanced clock tree and capacitance variation of a critical net in an SRAM array.

关键词： Capacitance Circuit simulation Geometry Focusing Lenses Manufacturing processes Electromagnetic coupling Equations Coupling circuits Periodic structures

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A sealed cavity TFR process for RF bandpass filters

A sealed cavity TFR process for RF bandpass filters

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1996 International Electron Devices Meeting

作者： Lutsky, JJ Naik, RS Reif, R Sodini, CG MIT Microsystems Technology Laboratories Department of Electrical Engineering and Computer Science Cambridge 02139 MA United States

ISBN: (纸本)0780333942

Thin film bulk acoustic wave resonators(TFRs) show considerable promise as a silicon compatible integrated solution for RF bandpass filters with center frequencies in the 1-2 GHz range. This paper presents a VLSI compatible sealed cavity TFR process using reactively sputtered AlN as the piezoelectric film. The devices are free-standing and have a fundamental longitudinal resonance at 1.36 GHz with an insertion loss of 3.5 dB, a K-eff(2) of .4%, and a Q(series) of 210.

关键词： Bandpass filters

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A method of moments model for VHF propagation

A method of moments model for VHF propagation

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Antennas and Propagation Society International Symposium

作者： J.T. Johnson R.T. Shin J. Eidson L. Tsang J.A. Kong Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA USA Lincoln Laboratory MIT Lexington MA USA Electromagnetics and Remote Sensing Laboratory University of Washington Seattle WA USA

Site specific VHF propagation models remain a subject of continuing interest. A number of approximate methods exist and have been applied successfully in specific cases, but the limitations of the approximations of these models remain unclear. A numerically exact model based on the banded matrix iterative approach (BMIA) to the method of moments is presented which enables the solution of practical propagation problems. Although this model remains computationally complex, use of the iterative method along with parallel computing techniques enables large scale propagation problems to be solved within reasonable amounts of computational time. A typical VHF propagation problem involves predicting the power measured by a receiver as a function of altitude at a given distance away from a like polarised transmitter and above an inhomogeneous terrain profile.

关键词： Moment methods Iterative methods Concurrent computing Numerical models Computational modeling Parallel processing Large-scale systems Power measurement Polarization Transmitters

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Kerr electro-optic measurement technique for determination of nonuniform electric fields

Kerr electro-optic measurement technique for determination o...

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International Conference on Conduction and Breakdown in Dielectric Liquids

作者： A. Ustundag T.J. Gung M. Zahn Dept. of Electr. Eng. & Comput. Sci. MIT Cambridge MA USA Department of Electrical Engineering and Computer Science Labomtoy for Electromagnetic and Electronic Systems Massachusetts Institute of Technology Cambridge MA USA Massachusetts Institute of Technology Cambridge MA US

Use of the ac modulation technique which has an ac high voltage superposed onto a dc high voltage has increased the sensitivity of Kerr electro-optic measurements. The technique has been used when the electric field magnitude and direction have been constant along the light path. Recently the technique was extended with use of the Abel transformation to recover the non-uniform axisymmetric electric field magnitude along the ground plane and along the needle axis of a point/plane electrode geometry. In these measurements the direction of light propagation is constant along the light path. The experimental results were in good agreement with analysis for the space charge free case. In this work we extend the technique to also allow the electric field direction to vary along the light path. We show that it is possible to measure three "characteristic parameters", analogous to non-uniform photo-elastic stress analysis, that allow determination of the electric field magnitude and direction. These three parameters are related to the electric field through the matricant of the differential equations that govern the Kerr media and reduce to the electric field direction and light phase retardation proportional to the electric magnitude squared for the case where the electric field direction is constant.

关键词： Measurement techniques Voltage Electric fields Nonuniform electric fields Electrooptic modulators Needles Electrodes Geometry Optical propagation Space charge

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GENERIC RANK-ONE CORRECTIONS FOR VALUE-ITERATION IN MARKOVIAN DECISION-PROBLEMS

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OPERATIONS RESEARCH LETTERS 1995年第3期17卷 111-119页

作者： BERTSEKAS, DP Department of Electrical Engineering and Computer Science MIT Cambridge MA 02139 USA

Given a linear iteration of the form x := F(x), we consider modified versions of the form x := F(x + gamma d), where d is a fixed direction, and gamma is chosen to minimize the norm of the residual \\x + gamma d - F(x + gamma d)\\. We propose ways to choose d so that the convergence rate of the modified iteration is governed by the subdominant eigenvalue of the original. In the special case where F relates to a Markovian decision problem, we obtain a new extrapolation method for value iteration. In particular, our method accelerates the Gauss-Seidel version of the value iteration method for discounted problems in the same way that MacQueen's error bounds accelerate the standard version. Furthermore, our method applies equally well to Markov Renewal and undiscounted problems.

关键词： DYNAMIC PROGRAMMING MARKOVIAN DECISION PROBLEM VALUE ITERATION STOCHASTIC SHORTEST PATH JACOBI METHOD GAUSS-SEIDEL METHOD

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