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IEEE International Conference on Systems, Man and Cybernetics

作者： A.A. Farag Y. Cao D.M. Rose E.J. Delp Engineering Mathematics & Computer Science Department Speed Scientific School University of Louisville Louisville KY USA Computer Vision & Image Processing Laboratory School of Electrical Engineering Purdue University West Lafayette IN USA

The authors develop an empirical measure for the selection of the Gaussian filter that is commonly used for edge enhancement. The measure is based totally on the image at hand. Edge enhancement by a Gaussian filter has two distinct advantages: (1) the filter is fully described by a single parameter, the standard deviation sigma ; (2) the two-dimensional filter is separable and can be easily implemented. The filter's spatial support is a function of sigma . This support is normally in the range of +or-3.5 sigma . An empirical measure is described for the selection of the Gaussian filter's spatial support using the power spectrum density of the input image. Classic Fourier analysis is used to obtain a measure for the spatial support of the Gaussian filter given a particular image. Experimental results suggest that this measure can be used as an aid in deciding the Gaussian filter's spatial support needed to enhance the edges.< >

关键词： Parameter estimation Low pass filters Image edge detection Image segmentation Joining processes Smoothing methods Frequency estimation Density functional theory Shape Mathematics

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Comparative mobility degradation in modulation‐doped GaAs devices after e‐beam and x‐ray irradiation

Journal of Vacuum Science & Technology B: Microelectronics a...

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Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures processing, Measurement, and Phenomena 1992年第6期10卷 2890-2892页

作者： R. A. Ghanbari M. Burkhardt D. A. Antoniadis Henry I. Smith M. R. Melloch K. W. Rhee M. C. Peckerar Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge Massachusetts 02139 School of Electrical Engineering Purdue University West Lafayette Indiana 47907 Nanoelectronics Processing Facility U. S. Naval Research Laboratory Washington DC 20375

We report on measured Hall mobility versus temperature for high‐quality modulation‐doped AlGaAs/GaAs samples after exposure by electrons and x rays at doses and energies typically used in lithography. We find that bare samples exposed by 50 keV electrons suffered significant mobility degradation over the temperature range of 4.2–300 K (as much as a factor of 30). X‐ray‐exposed samples did not show any mobility degradation. Two‐dimensional electron densities were not dramatically affected by either exposure technique, although e‐beam exposed samples did show a slight decrease in carrier density. Our results are consistent with previous reports of mobility degradation in some e‐beam evaporators.

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Further Studies on Frozen-Time Eigenvalues in the Stability Analysis for Periodic Linear Systems

Further Studies on Frozen-Time Eigenvalues in the Stability ...

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Southeastern Symposium on System Theory

作者： J. Zhu S. Ray S.K. Vemula Remote Sensing and Image Processing Laboratory Louisiana State University Baton Rouge LA USA Electrical and Computer Engineering Department Louisiana State University Baton Rouge LA USA

In this paper we present some enlightening results to show why and how stability assessment for Linear Time-Varying (LTV) systems based solely on the location of the "frozen-time eigenvalues (FTE)" fails to be sufficient or necessary, using two classes of parametrized periodic LTV systems derived from two examples given by Markus-Yamabe [6] and Wu [11]. Exact domain of stability in the parameter space obtained using analytical or numerical solutions of the Floquet characteristic Exponents are presented, and compared to that predicted by FTEs. The results are useful in the study of robustness and stabilization of Linear Time Invariant (LTI) systems, as will be shown in this paper that an unstable LTI system maybe stabilized or destabilized by periodic structural perturbations (pumping) without any control input.

关键词： Eigenvalues and eigenfunctions Stability analysis Linear systems Stability criteria Upper bound Robust stability Remote sensing Image processing Laboratories Robust control

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Modification of a-Si(:H) by Thermally Generated Atomic Hydrogen: A Real Time Spectroscopic Ellipsometry Study of Si Bond Breaking

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MRS Online Proceedings Library 1992年第1期258卷 27-32页

作者： Ilsin An Youming Li C. R. Wronski R. W. Collins Materials Research Laboratory The Pennsylvania State University University Park USA Also with the Department of Physics The Pennsylvania State University University Park USA Also with the Department of Electrical and Computer Engineering and the Center for Electronic Materials and Processing The Pennsylvania State University University Park USA

We have applied real time spectroscopie ellipsometry (2.5≤h≤4.5 eV) to investigate in situ hydrogenation of thin film a-Si:H prepared by plasma-enhanced CVD. When a-Si:H is exposed to atomic H generated by a tungsten filament heated in H2, as many as ~5x1021 Si-Si bonds/cm3 can be converted to Si-H bonds in the top ~200 À of the film. We have determined the spectroscopie characteristics of Si-H bonds from optical to near-uv photon energies through an analysis of the changes in the dielectric function of the near-surface of the film upon hydrogenation. The conversion of Si-Si bonds to Si-H bonds is identified as reaction-limited to a depth of ~500 À. We find that a surface oxide a few monolayers in thickness acts as an effective diffusion barrier to H-incorporation.

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Conductance quantization in a GaAs electron waveguide device fabricated by x‐ray lithography

Journal of Vacuum Science & Technology B: Microelectronics a...

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Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures processing, Measurement, and Phenomena 1992年第6期10卷 2966-2969页

作者： W. Chu C. C. Eugster A. Moel E. E. Moon J. A. del Alamo Henry I. Smith M. L. Schattenburg K. W. Rhee M. C. Peckerar M. R. Melloch Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge Massachusetts 02139 Center for Space Research Massachusetts Institute of Technology Cambridge Massachusetts 02139 Nanoelectronics Processing Facility U.S. Naval Research Laboratory Washington DC 20375 School of Electrical Engineering Purdue University West Lafayette Indiana 47907

We report on the fabrication of AlGaAs/GaAs split‐gate electron waveguide devices of lengths between 0.1 and 2 μm using x‐ray lithography, and the measurements of these devices at liquid‐helium temperatures and up to 15 K. An x‐ray mask (parent mask) was fabricated using e‐beam lithography and replicated using proximity x‐ray lithography (λ=1.32 nm) to generate a replica (daughter) mask. The daughter mask was then aligned to patterns on a high‐mobility AlGaAs/GaAs sample and x ray exposed using a conformable mask fixture. The conductance of the electron waveguides was measured as a function of the split‐gate bias. Sharp 2e2/h conductance steps were observed in devices up to 0.75 μm long at T=2 K. The features in the conductance remain visible up to 15 K.

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Fabrication of parallel quasi‐one‐dimensional wires using a novel conformable x‐ray mask technology

Journal of Vacuum Science & Technology B: Microelectronics a...

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Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures processing, Measurement, and Phenomena 1992年第6期10卷 3196-3199页

作者： R. A. Ghanbari W. Chu E. E. Moon M. Burkhardt K. Yee D. A. Antoniadis Henry I. Smith M. L. Schattenburg K. W. Rhee R. Bass M. C. Peckerar M. R. Melloch Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge Massachusetts 02139 Center for Space Research Massachusetts Institute of Technology Cambridge Massachusetts 02139 Nanoelectronics Processing Facility U. S. Naval Research Laboratory Washington DC 20375 School of Electrical Engineering Purdue University West Lafayette Indiana 47907

We report on the fabrication of quasi‐one‐dimensional wires on modulation‐doped GaAs/AlGaAs using a novel conformable x‐ray mask technology which allows us to expose arbitrary sized samples, including samples much smaller than the membrane area, using our laboratory’s standard 31 mm‐diam silicon‐nitride x‐ray mask. After optical alignment, the sample and mask are brought into contact electrically, and then loaded into a specially designed cartridge which allows a vacuum to be pulled between mask and substrate. The vacuum causes the x‐ray mask to conform around the sample. We find that a vacuum hold down is necessary to allow easy separation of the sample from the mask with minimal risk to both.

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Use of PARADISE: A meta-tool for visualizing parallel systems 5

Use of PARADISE: A meta-tool for visualizing parallel system...

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5th International parallel processing Symposium, IPPS 1991

作者： Kohl, James Arthur Casavant, Thomas L. Parallel Processing Laboratory Department of Electrical and Computer Engineering University of Iowa Iowa CityIA52242 United States

ISBN: (纸本)0818691670

This paper addresses the problem of creating software tools for visualizing the dynamic behavior of parallel applications and systems. PARADISE (parallel Animated Debugging and Simulation Environment) approaches this problem by providing a meta-tool environment for generating custom visual analysis tools. PARADISE is a meta-tool because it is a tool which is utilized to create other tools. This paper focuses on the user's view of the use of PARADISE for constructing tools which analyze the interaction between parallel systems and parallel applications. An example of its use, involving the PASM parallel processing System, is given. © 1991 IEEE.

关键词： parallel processing systems

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PATH PLANNING FOR MOBILE MANIPULATORS FOR MULTIPLE TASK EXECUTION

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IEEE TRANSACTIONS ON ROBOTICS AND AUTOMATION 1991年第3期7卷 403-408页

作者： CARRIKER, WF KHOSLA, PK KROGH, BH Laboratory for Automated Systems and Information Processing Department of Electrical and Computer Engineering Carnegie Mellon University Pittsburgh PA USA

We consider the planning problem for a mobile manipulator system that must perform a sequence of tasks defined by position, orientation, force, and moment vectors at the end-effector. Each task can be performed in multiple configurations due to the redundancy introduced by mobility. We formulate the planning problem as an optimization problem in which the decision variables for mobility (base position) are separated from the manipulator joint angles in the cost function. The resulting numerical problem is nonlinear with nonconvex, unconnected feasible regions in the decision space. Simulated annealing is proposed as a general solution method for obtaining near-optimal results. The problem formulation and numerical solution by simulated annealing are illustrated for a manipulator system with three degrees of freedom mounted on a base with two degrees of freedom. These results are compared with results obtained by conventional nonlinear programming techniques customized for the particular example system.

关键词： Path planning Simulated annealing Cost function Numerical simulation Space stations Robotics and automation Manipulators Trajectory Constraint optimization Ear

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SYNTHESIS OF FEEDBACK-CONTROL LOGIC FOR DISCRETE MANUFACTURING SYSTEMS

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AUTOMATICA 1991年第4期27卷 641-651页

作者： KROGH, BH HOLLOWAY, LE Laboratory for Automated Systems and Information Processing Department of Electrical and Computer Engineering Carnegie Mellon University Pittsburgh PA 15213 United States

This paper concerns the supervisory coordination and control of concurrent activity cycles in automated manufacturing facilities. In contrast to commonly used simulation models which integrate the control policy with the system model, the state transition logic for the manufacturing equipment is represented by a class of controlled Petri nets (CtlPN) with external inputs to be determined by the control synthesis algorithm. We formulate the forbidden state control problem in the CtlPN context and present an algorithm for generating maximally permissive controls which guarantee the system will avoid the forbidden states while permitting a maximal amount of flexibility in the system operation. The problem formulation and control synthesis algorithm is illustrated for an example of AGV co-ordination, and several classes of manufacturing control problems which can be addressed within this framework are identified.

关键词： computer CONTROL CONTROL SYSTEM SYNTHESIS DISCRETE SYSTEMS MANUFACTURING PROCESSES SUPERVISORY CONTROL SYNTHESIS METHODS

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IMAGE SEQUENCE CODING BY SPLIT AND MERGE

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IEEE TRANSACTIONS ON COMMUNICATIONS 1991年第12期39卷 1845-1855页

作者： WILLEMIN, P REED, TR KUNT, M Signal and Image Processing Laboratory Swiss Federal Institute of Technology Lausanne Switzerland Department of Electrical Engineering and Computer Science University of California Davis CA USA

This paper describes a method for reducing the information contained in an image sequence, while retaining the information necessary for the interpretation of the sequence by a human observer. The method consists of first locating the redundant information, reducing the degree of redundancy, and coding the result. The sequence is treated as a single 3-D data volume, the voxels of which are grouped into several regions, obtained by a 3-D split and merge algorithm. To find these regions, we first obtain an initial region space by splitting the image sequence until the gray-level variation over each region can be approximated by a 3-D polynomial, to a specified accuracy. This results in a set of parallelepipedic regions of various sizes. To represent the gray-level variation over these regions, the coefficients of the approximating polynomial are used as features. The most similar regions are then merged, using a region adjacency graph. The information is coded by representing the borders of the regions using a pyramidal structure in the x, y, t space. The coefficients of the approximating polynomials are coded in a straightforward manner. For 256 x 256 pixel, 25 frames/s image sequences, compressions allowing transmission rates near 64 kbit/s are obtained.

关键词： Image sequences Image coding Pixel Bandwidth Layout Polynomials Image segmentation Humans Helium ISDN

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