The throughput results for file transfers using file sizes ranging from 1 Kbytes through 1 Mbytes using both the standard TCP/IP and SCPS protocol stacks over a PPP link are reported. Channel properties were simulated...
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ISBN:
(纸本)0780365992
The throughput results for file transfers using file sizes ranging from 1 Kbytes through 1 Mbytes using both the standard TCP/IP and SCPS protocol stacks over a PPP link are reported. Channel properties were simulated using a space channel simulator with a range of balanced and unbalanced link speeds and channel error rates. The throughput results show the effects of link configuration and channel error rate on file transfer time. The host computer configuration options for the protocols are factored into the comparison. The throughput reporting shows the effects of header compression and selection of congestion algorithm upon the results. The TCP/IP ftp and SCPS-FP using the VJ congestion control algorithm results give similar results and better results than SCPS-FP with the Vegas congestion control algorithm in these experiments. No noticeable delay effects were noted with links delays corresponding to GEO orbits with file transfers of 1 Mbytes.
The problem of robust H/spl infin/ filtering for continuous-time uncertain linear systems with multiple time-varying delays in the state variables is investigated. The uncertain parameters are supposed to belong to a ...
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The problem of robust H/spl infin/ filtering for continuous-time uncertain linear systems with multiple time-varying delays in the state variables is investigated. The uncertain parameters are supposed to belong to a given convex bounded polyhedral domain. The aim is to design a stable linear filter assuring asymptotic stability and a prescribed H/spl infin/ performance level for the filtering error system, irrespective of the uncertainties and the time delays. Sufficient conditions for the existence of such a filter are established in terms of linear matrix inequalities, which can be efficiently solved by means of powerful convex programming tools with global convergence assured. An example illustrates the proposed methodology.
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 perform...
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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.
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. ...
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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.
We use a model for the ionization coefficients to calculate the frequency response characteristics and the avalanche breakdown voltage in thin layers. Notably, calculations based on the dead-space theory for the APD t...
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We use a model for the ionization coefficients to calculate the frequency response characteristics and the avalanche breakdown voltage in thin layers. Notably, calculations based on the dead-space theory for the APD time response reveal that in addition to a reduction in the excess noise factor, thin layers benefit from reduced spectral fluctuations in the buildup-time limited photocurrent.
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 d...
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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.
In multi-converter power electronic systems, different power electronic converters are integrated together to form a complex and extensively interconnected system. In general, there are two kinds of loads in these sys...
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In multi-converter power electronic systems, different power electronic converters are integrated together to form a complex and extensively interconnected system. In general, there are two kinds of loads in these systems. One group is conventional loads, which have positive incremental impedance characteristics. They are mainly considered as constant voltage loads that require regulated voltage for their operation. The other group is tightly regulated power electronic converters and motor drives sinking constant power from their input buses. The purpose of this paper is to present an assessment of the dynamic interactions between these loads in the multi-converter DC power electronic systems. Furthermore, a nonlinear robust stabilizing controller based on the feedback linearization technique for DC/DC PWM converters is presented.
In multi-converter power electronic systems, different converters such as DC/DC choppers, DC/AC inverters, and AC/DC rectifiers are used in source, load, and distribution subsystems to provide power at different volta...
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In multi-converter power electronic systems, different converters such as DC/DC choppers, DC/AC inverters, and AC/DC rectifiers are used in source, load, and distribution subsystems to provide power at different voltage levels and forms. Most of the loads are also in the form of power electronic converters and motor drives. The most popular examples of these systems are automotive systems and more electric/hybrid electric vehicles. These systems have unique characteristics, dynamics, and stability problems that are just beginning to be appreciated. In this paper, we take a closer look at multiconverter power electronic systems and address the fundamental problems faced in these systems.
The problem of robust H∞ state-feedback control design for a class of continuous-time linear systems with Markovian jumping parameters and multiple time-varying delays at the states, and subject to uncertain paramete...
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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 ...
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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.
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