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Annual Symposium on Simulation

作者： A.B. McDonald T.F. Znati Department of Electrical and Computer Engineering Northeastern University Boston MA USA Department of Computer Science Telecommunica.tions Program University of Pittsburgh Pittsburgh PA USA

ISBN: (纸本)0769510922

Routing in ad-hoc networks is a difficult challenge that involves a tradeoff between efficiency and responsiveness. An ad-hoc network routing algorithm must adapt rapidly enough to topology changes to meet the performance demands of users, without over-utilizing network resources. This paper presents the (/spl alpha/,t) cluster framework which utilizes a distributed dynamic clustering strategy to organize nodes into clusters in which the probability of path failure due to node movement can be bounded over time. The objective of the clustering strategy is to achieve scalability and support robust, efficient routing subject to a wide range of mobility rates. Based on the (/spl alpha/,t) cluster scheme, routes within clusters are maintained on a proactive basis, whereas hierarchical routing between clusters is managed on a demand-basis. Simulation results show that the cluster organization can be effectively adapted to node mobility and that routing is both more robust and efficient than routing in fully proactive, reactive or fixed-hybrid schemes.

关键词： Algorithm design and analysis Clustering algorithms Heuristic algorithms Routing Ad hoc networks Network topology Robustness Telecommunication traffic Delay Telecommunication network topology

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A magnetically damped momentum transfer device to reduce chatter in a micro-mechanical switch

A magnetically damped momentum transfer device to reduce cha...

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IEEE International Conference on Micro Electro Mechanical Systems

作者： B. Chaudhuri K. Fischer H. Guckel Materials Science Program University of Wisconsin Madison WI USA Department of Electrical and Computer Engineering University of Wisconsin Madison WI USA

ISBN: (纸本)0780359984

A micro-mechanical switch has been designed and fabricated in which the bounce after contact closure has been reduced by using mechanical momentum transfer and magnetic damping, while maintaining high contact forces. The period of chatter has been reduced from 1.5 milliseconds to less than 0.3 milliseconds, while the switching speed is 5 millisecond. The switch has been fabricated using Permalloy (78% Ni and 22% Fe) and copper. The LIGA process was used in the fabrication of the switch. An improved copper process allowed the fabrication of high aspect ratio (20:1) structures which were subsequently freed and assembled.

关键词： Magnetic devices Magnetic moments Switches Contacts Copper Fabrication Magnetic switching Damping Iron Assembly

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Design of gyroscope-free navigation systems

Design of gyroscope-free navigation systems

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International Conference on Intelligent Transportation

作者： Chin-Woo Tan S. Park K. Mostov P. Varaiya Partners for Advanced Transit and Highways PATH Program University of California Berkeley USA Department of Electrical Engineering and Computer Science University of California Berkeley USA

We examine the feasibility of designing a gyroscope-free inertial navigation system (INS) that uses only accelerometers to compute the linear and angular motions of a rigid body. The accelerometer output equation is derived to relate the linear and angular motions of a rigid body relative to a fixed inertial frame. A sufficient condition is given to determine if a configuration of accelerometers is feasible. If the condition is satisfied, the angular and linear motions can be computed separately using two decoupled equations of an input-output (I/O) dynamical system; a state equation for angular velocity and an output equation for linear acceleration. This simple computation scheme is derived from the corresponding dynamical system equations for a special cube configuration for which the angular acceleration is expressed as a linear combination of the accelerometer outputs.

关键词： Gyroscopes Accelerometers Equations Acceleration Inertial navigation Angular velocity Sufficient conditions Aircraft navigation Rotation measurement Automobiles

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Segmentation and analysis of leg ulcers color images

Segmentation and analysis of leg ulcers color images

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International Workshop on Medical Imaging and Augmented Reality

作者： A.A. Perez A. Gonzaga J.M. Alves Computer Vision Laboratory Department of Electrical Engineering School of Engineering of São Carlos University of São Paulo Sao Paulo Brazil Department of Materials Aeronautic and Automotive Engineering School of Engineering of São Carlos University of São Paulo Bioengineering Graduate Program Sao Paulo Brazil

ISBN: (纸本)0769511139

This paper presents a methodology for the segmentation and analysis of the tissues in color images of leg ulcers. The segmentation is obtained through an automatic analysis made in the RGB and SI channels by changing from the RGB color space to the HSI color space. The aim is to determine which of the five channels have the characteristic that will make the segmentation process more efficient. After the analysis, the selected channel is segmented and used as a mask over the original image, allowing that only the inner tissues of the wound be analyzed. The analysis is done through predetermined functions that attribute membership grade for each processed pixel as well as its level of engagement in a specified tissue class. The article also shows the results obtained from both the segmentation and analysis of tissues using the proposed method.

关键词： Image segmentation Image analysis Image color analysis Leg Wounds Cameras Automotive engineering Colored noise Monitoring Video compression

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An information architecture for physiological models, clients and databases

An information architecture for physiological models, client...

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Annual International Conference of the IEEE engineering in Medicine and Biology Society (EMBC)

作者： C.F. Dewey B. Fu S. Zhang N. Dao W. Chuang Z. Li Mechanical Engineering Massachusetts Institute of Technology Cambridge USA Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge USA Health Sciences and Technology Massachusetts Institute of Technology Cambridge USA Department of Bioengineering University of Washington Seattle USA

Proposes an information system to support complex physiological information models. The system architecture requires three essential parts: a networked client that generates a request for information; a computation server that performs the calculation; and a model database that provides detailed parameters to the computation server to facilitate solution. The model database is organized as an object-oriented hierarchy following the design used to store medical images and their metadata in accordance with the international DICOM standard for medical images. A fourth critical component is also defined: a case database that archives the input data that has been used by the client to define the case to be computed, and archives the output from the solution. This system is applied to a complex contemporary model of the electrophysiology of cardiac myocyte cells.

关键词： Object oriented modeling computer architecture Biological system modeling Biology computing Image databases Object oriented databases Biomedical imaging DICOM Power system modeling computer networks

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Reflections on a candidate design of the user-interface for a wireless vital-signs monitor 00

Reflections on a candidate design of the user-interface for ...

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2000 Conference on Designing Augmented Reality Environments, DARE 2000

作者： McGarry, Ben Matthews, Ben Brereton, Margot Information Environments Program Department of Computer Science and Electrical Engineering University of Queensland St Lucia BrisbaneQLD4000 Australia

ISBN: (纸本)9781450373265

In this paper we present a case study of our candidate design for the user-interface of a wireless vital-signs monitor. We reflect on our design of the user-interface, and relate our design experience to theories of artefact design, evaluating from this case study how the theories apply to the broader design context of design for AR. Theories of 'good design' in artefact design literature do not unilaterally apply to the design for an augmented reality device. In many cases, design in AR fields requires the designer to create new cultural conventions by virtue of the fact that the designer is immersing the user in an unfamiliar environment. Thus, the designer is often unable to utilise affordances and existing cultural conventions because the functions and/or use of the object expands the environment in which affordances and cultural conventions currently have meaning. Copyright 2000 ACM.

关键词： User interfaces

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Signal Analysis of the Singing Voice: Low-Order Representations of Singer Identity 26

Signal Analysis of the Singing Voice: Low-Order Representati...

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26th International computer Music Conference, ICMC 2000

作者： Mellody, Maureen Wakefield, Gregory H. Applied Physics Program University of Michigan United States Department of Electrical Engineering and Computer Science University of Michigan United States

Signals from 12 soprano and mezzo-soprano singers are analyzed with the modal distribution, a high-resolution time-frequency analysis method, to obtain measures of instantaneous amplitude and frequency of the signals’ partial components. These estimates are used to construct singer-specific transfer functions for each vowel and pitch analyzed. An AR approximation to a residual representation of these transfer functions is determined. This low-order residual approximation is used in a hierarchical clustering experiment. Using this representation, functions from each singer for a given vowel tend to cluster into a single class before classes collapse across singers. This result suggests that the low-order residual approximation captures singer-specific features in the sung signals. © 2000 ICMC. All Rights Reserved.

关键词： Transfer functions

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Polarization effects and transport in AlGaN/GaN system

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 2000年第4期18卷 2322-2327页

作者： Yifei Zhang Yulia Smorchkova C. Elsass Stacia Keller James Ibbetson Steven DenBaars Umesh Mishra Jasprit Singh Applied Physics Program University of Michigan Ann Arbor Michigan 48109 Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor Michigan 48109-2122 Department of Electrical and Computer Engineering University of California Santa Barbara California 93106 Department of Electrical Engineering and Computer Engineering University of Michigan Ann Arbor Michigan 48109

The AlGaN/GaN heterostructure is important for both electronic and optoelectronic devices. In addition to having a large band gap, the heterostructure has a strong piezoelectric effect and a large spontaneous polarization. This allows one to incorporate a large electric field (>106 V/cm) and high sheet charge (>1013 cm−2) without doping. Theoretical studies are done to examine how polarization effects controls the sheet charge density. The studies also focus on how interface roughness, aluminum mole fraction in the barrier, impurity scattering, sheet charge density, and phonon scattering influence mobility. Results are compared with experimental studies on samples grown by both molecular beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD). We find that interface roughness is a dominant source of scattering in the samples reported. Due to the variation in growth techniques we find that the MBE samples have a smoother interface quality compared to the MOCVD samples. By carefully fitting the experimental data we present results on interface roughness parameters for MBE and MOCVD samples.

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Quantum Confinement in Nanocrystalline Si Superlattices

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MRS Online Proceedings Library 2000年第1期592卷 359-364页

作者： G. F. Grom P. M. Fauchet L. Tsybeskov J. P. McCaffrey H. J. Labbé D. J. Lockwood Department of Mechanical Engineering Materials Science Program USA Department of Electrical and Computer Engineering University of Rochester Rochester USA Institute for Microstructural Sciences National Research Council Ottawa Canada

Photoconductance spectroscopy was used to probe the effects of quantum confinement in nanocrystalline (nc)-Si/amorphous (a)-SiO2 superlattices (SLs). A Metal-Oxide-Semiconductor (MOS)-like structure with the nc-Si SL incorporated in the oxide was fabricated to study charging/discharging processes in Si nanocrystals. The fine structure observed in photoconductance spectra at low temperatures was interpreted in terms of singularities in the carrier density of states, possibly due to energy quantization. In addition, a low-resistance sample exhibited photocurrent oscillations with a frequency of several kHz, which could be a manifestation of sequential resonant carrier tunneling in the nc-Si/a-SiO2 SL.

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Investigation of NMR signal-to-noise ratio for RF scroll microcoils

Investigation of NMR signal-to-noise ratio for RF scroll mic...

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International Conference on Microtechnologies in Medicine and Biology

作者： B. Gimi S. Grant G. Friedman R. Magin Department of Bioengineering University of Illinois Chicago Chicago IL USA Department of Electrical Engineering and Computer Science University of Illinois Chicago Chicago IL USA

Although NMR has the ability to investigate biological systems non-destructively, it suffers from low sensitivity compared to other analytical techniques. Therefore, optimizing radio frequency (RF) coils to improve sensitivity is an area of significant focus in NMR Sensitivity can be improved for mass- and volume-limited samples by reducing, coil diameter, and adding sensing layers to the coil. This paper demonstrates that around skin depth, coil sensitivity can be increased with additional sensing layers, by using multilayered scroll coil geometries. While solenoids have demonstrated increased sensitivity over conventional coils (Helmholtz, Saddle, and Birdcage), their dimensions are limited by wire diameter, and difficulty in fabrication at reduced dimensions. The novel scroll geometry avails of microfabrication techniques to provide flexibility in manufacturing coils at very reduced dimensions.

关键词： Nuclear magnetic resonance Signal to noise ratio Radio frequency Coils Geometry Biological systems Skin Solenoids Wire Fabrication

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