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Articles 32581 - 32610 of 40977

Full-Text Articles in Engineering

Agents For Integrating Distributed Data For Complex Computations, Ahmed M. Khedr, Raj Bhatnagar Jan 2006

Agents For Integrating Distributed Data For Complex Computations, Ahmed M. Khedr, Raj Bhatnagar

Turkish Journal of Electrical Engineering and Computer Sciences

Algorithms for many complex computations assume that all the relevant data are available on a single node of a computer network. In the emerging distributed and networked knowledge environments, databases relevant for computations may reside on a number of nodes connected by a communication network. These data resources cannot be moved to other network sites due to privacy, security, and size considerations. The desired global computation must be decomposed into local computations to match the distribution of data across the network. The capability to decompose computations must be general enough to handle different distributions of data and different participating nodes …

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State Of The Art For Differential Circuits In Wireless Transceivers: A New Wideband Active Balun In Sige Bicmos Technology, Balwant Godara, Alain Fabre Jan 2006

State Of The Art For Differential Circuits In Wireless Transceivers: A New Wideband Active Balun In Sige Bicmos Technology, Balwant Godara, Alain Fabre

Turkish Journal of Electrical Engineering and Computer Sciences

The aim of this paper is 3-fold: firstly, to provide a comprehensive overview of the use of differential circuits for analogue signal processing in wireless transceivers; secondly, to describe, in detail, single-ended signal to differential conversion, and the corresponding theory of such devices, their characterisation, various methods of implementation, and comparative analyses of their performance; lastly, to propose a new transistor-based solution for wideband baluns. This novel solution is based on the current conveyor and has been modelled using the transistor parameters of a 0.35 \mu m SiGe BiCMOS technology. The salient features of the new implementation are: (a) stable …

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Digital Fractional Frequency Synthesizer Based On Counters, Milan Stork Jan 2006

Digital Fractional Frequency Synthesizer Based On Counters, Milan Stork

Turkish Journal of Electrical Engineering and Computer Sciences

This paper describes the architecture of a new pure digital frequency synthesizer based on pulse generators, counters and a register. The technique described here is much simpler than other methods. The synthesizer presented is suitable for the design of VLSI architectures or for programmable large-scale integration circuits.

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Statistical Model Of Hot-Carrier Degradation And Lifetime Prediction For P-Mos Transistors, Firat Kaçar, Ayten Kuntman, Hakan Kuntman Jan 2006

Statistical Model Of Hot-Carrier Degradation And Lifetime Prediction For P-Mos Transistors, Firat Kaçar, Ayten Kuntman, Hakan Kuntman

Turkish Journal of Electrical Engineering and Computer Sciences

Along with advances in microelectronics, and computer and space technologies, device dimensions are becoming smaller; as a result, hot-carrier effect, lifetime prediction, and reliability become more important concepts for MOS transistors. In this paper, the degradation in the drain current and threshold voltage of P-MOS transistors are observed by operating the devices under voltage stress conditions. Using the observation results, the effect of hot-carriers was investigated statistically and a new statistical method for modeling was proposed as an alternative to those given in the literature. The linear regression method is used to estimate the power, Weibull, and logarithmic parameters, and …

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The Effect Of Collector Doping On Inp-Based Double Heterojunction Bipolar Transistors, Serkan Topaloğlu, Jörn Driesen, Werner Prost, Franz Josef Tegude Jan 2006

The Effect Of Collector Doping On Inp-Based Double Heterojunction Bipolar Transistors, Serkan Topaloğlu, Jörn Driesen, Werner Prost, Franz Josef Tegude

Turkish Journal of Electrical Engineering and Computer Sciences

High current effects on double heterojunction bipolar transistor (DHBT) performance were investigated. Three DHBTs with different collector doping densities were grown and processed. DC and RF measurements were performed to evaluate the influence of collector doping and the related Kirk effect on HBT performance. In addition to these samples, the Kirk effect was proven on SHBTs and the delay of this effect on submicron HBTs was investigated.

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An Adaptive Feedforward Amplifier Application For 5.8 Ghz, Engi̇n Kurt, Osman Palamutçuoğullari Jan 2006

An Adaptive Feedforward Amplifier Application For 5.8 Ghz, Engi̇n Kurt, Osman Palamutçuoğullari

Turkish Journal of Electrical Engineering and Computer Sciences

In this study, a 5.8 GHz power amplifier is linearized by an adaptive feedforward technique. A DSP-based control scheme is applied to reduce the intermodulation distortion of this amplifier. A two-tone test is used to verify the design.

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Artificial Neural Design Of Microstrip Antennas, Nurhan Türker, Fi̇li̇z Güneş, Tülay Yildirim Jan 2006

Artificial Neural Design Of Microstrip Antennas, Nurhan Türker, Fi̇li̇z Güneş, Tülay Yildirim

Turkish Journal of Electrical Engineering and Computer Sciences

A general design procedure is suggested for microstrip antennas using artificial neural networks and this is demonstrated using rectangular patch geometry. In this design procedure, synthesis is defined as the forward side and then analysis as the reverse side of the problem. Worked examples are given using the most efficient materials.

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Wind Power, Distributed Generation: New Challenges, New Solutions, Vladimiro Miranda Jan 2006

Wind Power, Distributed Generation: New Challenges, New Solutions, Vladimiro Miranda

Turkish Journal of Electrical Engineering and Computer Sciences

This paper discusses some issues related with the growing importance of wind power and in modern power systems and some challenges raised by the emergence of distributed generation, and how computational intelligence and other modern techniques have been able to provide valuable results in solving the new problems. It presents some solutions obtained with a number of computational intelligence techniques and their application to real cases.

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Controlling Rail Potential Of Dc Supplied Rail Traction Systems, Mehmet Turan Söylemez, Süleyman Açikbaş, Adnan Kaypmaz Jan 2006

Controlling Rail Potential Of Dc Supplied Rail Traction Systems, Mehmet Turan Söylemez, Süleyman Açikbaş, Adnan Kaypmaz

Turkish Journal of Electrical Engineering and Computer Sciences

Most modern DC electrified mass transit systems use a totally floating earth as their grounding strategy. A well-known problem related with totally floating systems is that the touch potentials can be dangerously high. In order to reduce the voltages on rails, several devices exist. Most of these devices allow a direct connection to earth when a certain voltage threshold is exceeded. In this paper, the working principles of these devices are given and the effect of certain parameters related with these devices on the minimum achievable touch potentials is investigated.

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Perceptually Meaningful Image Editing: Depth, Reynold J. Bailey, Cindy Grimm Jan 2006

Perceptually Meaningful Image Editing: Depth, Reynold J. Bailey, Cindy Grimm

All Computer Science and Engineering Research

We introduce the concept of perceptually meaningful image editing and present two techniques for manipulating the apparent depth of objects in an image. The user loads an image, selects an object and specifies whether the object should appear closer or further away. The system automatically determines target values for the object and/or background that achieve the desired depth change. These depth editing operations, based on techniques used by traditional artists, manipulate either the luminance or color temperature of different regions of the image. By performing blending in the gradient domain and reconstruction with a Poisson solver, the appearance of false …

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Design Of A Diversified Network Substrate, Jonathan Turner Jan 2006

Design Of A Diversified Network Substrate, Jonathan Turner

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A diversified network substrate enables multiple end-to-end metanetworks to co-exist within a shared physical infrastructure. Metanetworks are implemented by metarouters, hosted by substrate routers, and metarouters are connected by metalinks. The substrate allocates resources (both link bandwidth and processing resources) to metarouters based on advance reservations received from metanetwork planning systems. It also enables dynamic creation of access metalinks, connecting end systems to metarouters, and supports mobility of end systems under the control of their metanetworks. This report defines a model for a diversified internet and presents a detailed design of the substrate that enables metanetworks to co-exist. The design …

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Mobiwork: Mobile Workflow For Manets, Gregory Hackmann, Rohan Sen, Mart Haitjema, Gruia-Catalin Roman, Gill Jan 2006

Mobiwork: Mobile Workflow For Manets, Gregory Hackmann, Rohan Sen, Mart Haitjema, Gruia-Catalin Roman, Gill

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The workflow model is well suited for scenarios where many entities work collaboratively towards a common goal, and is used widely today to model complex business processes. However, the fundamental workflow model is very powerful and can be applied to a wider variety of application domains. This paper represents an initial investigation into the possibility of using workflows to model collaboration in an ad hoc mobile environment. Moving to a mobile setting introduces many challenges as the mobility of the participants in a workflow imposes constraints on allocation of workflow tasks, coordination among participants, and marshaling of results. We present …

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Discovering Weak Community Structures In Large Biological Networks , Jianhua Ruan, Weixiong Zhang Jan 2006

Discovering Weak Community Structures In Large Biological Networks , Jianhua Ruan, Weixiong Zhang

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Identifying intrinsic structures in large networks is a fundamental problem in many fields, such as biology, engineering and social sciences. Motivated by biology applications, in this paper we are concerned with identifying community structures, which are densely connected sub-graphs, in large biological networks. We address several critical issues for finding community structures. First, biological networks directly constructed from experimental data often contain spurious edges and may also miss genuine connections. As a result, community structures in biological networks are often weak. We introduce simple operations to capture local neighborhood structures for identifying weak communities. Second, we consider the issue of …

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Design And Evaluation Of A Blast Ungapped Extension Accelerator, Master's Thesis, Joseph M. Lancaster Jan 2006

Design And Evaluation Of A Blast Ungapped Extension Accelerator, Master's Thesis, Joseph M. Lancaster

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The amount of biosequence data being produced each year is growing exponentially. Extracting useful information from this massive amount of data is becoming an increasingly difficult task. This thesis focuses on accelerating the most widely-used software tool for analyzing genomic data, BLAST. This thesis presents Mercury BLAST, a novel method for accelerating searches through massive DNA databases. Mercury BLAST takes a streaming approach to the BLAST computation by offloading the performance-critical sections onto reconfigurable hardware. This hardware is then used in combination with the processor of the host system to deliver BLAST results in a fraction of the time of …

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Activepdf-Toolk, Washington University In St. Louis Computer Science Engineering Department Jan 2006

Activepdf-Toolk, Washington University In St. Louis Computer Science Engineering Department

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This document provides information for deploying activePDF Toolkit Professional in a development environment. This document is organized into four sections: Getting Started, Tutorials, Technical Reference and the Toolkit Appendices. The Getting Started section covers setup and installation, includes a product overview and information related to operating Toolkit Professional. Tutorials includes examples of many Toolkit features, including PDF generation and form filling. All of the tutorials can be used with activePDF Toolkit. Technical Reference provides detailed information on Toolkit’s objects, subobjects, methods and properties.

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Fast Packet Classification Using Bloom Filters, Sarang Dharmapurikar, Haoyu Song, Jonathan Turner, John Lockwood Jan 2006

Fast Packet Classification Using Bloom Filters, Sarang Dharmapurikar, Haoyu Song, Jonathan Turner, John Lockwood

All Computer Science and Engineering Research

While the problem of general packet classification has received a great deal of attention from researchers over the last ten years, there is still no really satisfactory solution. Ternary Content Addressable Memory (TCAM), although widely used in practice, is both expensive and consumes a lot of power. Algorithmic solutions, which rely on commodity memory chips, are relatively inexpensive and power-efficient, but have not been able to match the generality and performance of TCAMs. In this paper we propose a new approach to packet classification, which combines architectural and algorithmic techniques. Our starting point is the well-known crossproducting algorithm, which is …

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Smooth Surface Reconstruction Using Charts For Medical Data, Cindy Grimm, Tao Ju Jan 2006

Smooth Surface Reconstruction Using Charts For Medical Data, Cindy Grimm, Tao Ju

All Computer Science and Engineering Research

We present a surface reconstruction technique that constructs a smooth analytic surface from scattered data. The technique is robust to noise and both poorly and non-uniformly sampled data, making it well-suited for use in medical applications. In addition, the surface can be parameterized in multiple ways, making it possible to represent additional data, such as electromagnetic potential, in a different (but related) coordinate system to the geometric one. The parameterization technique also supports consistent parameterizations of multiple data sets.

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An Improved Analysis For A Greedy Remote-Clique Algorithm Using Factor-Revealing Lps, Benjamin E. Birnbaum, Kenneth J. Goldman Jan 2006

An Improved Analysis For A Greedy Remote-Clique Algorithm Using Factor-Revealing Lps, Benjamin E. Birnbaum, Kenneth J. Goldman

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Given a complete graph with nonnegative edge weights satisfying the triangle inequality and a positive integer p, the remote-clique problem is to find a subset of p vertices having a maximum-weight induced subgraph. A simple greedy algorithm for the problem has been shown to have an approximation ratio of 4, but a tight example has not been provided. In this paper, we use the technique of factor revealing linear programs to prove that this algorithm actually achieves an approximation ratio of 2, matching the best-known ratio for the problem. The greedy algorithm's running time of O(pn) makes it the fastest …

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The Design, Modeling, And Implementation Of Group Scheduling For Isolation Of Computations From Adversarial Interference, Terry Tidwell, Noah Watkins, Venkita Subramonian, Douglas Niehaus, Armando Gill, Migliaccio Jan 2006

The Design, Modeling, And Implementation Of Group Scheduling For Isolation Of Computations From Adversarial Interference, Terry Tidwell, Noah Watkins, Venkita Subramonian, Douglas Niehaus, Armando Gill, Migliaccio

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To isolate computations from denial of service (DoS) attacks and other forms of adversarial interference, it is necessary to constrain the effects of interactions among computations. This paper makes four contributions to research on isolation of computations from adversarial interference: (1) it describes the design and implementation of a kernel level scheduling policy to control the effects of adversarial attacks on computations’ execution; (2) it presents formal models of the system components that are involved in a representative DoS attack scenario; (3) it shows how model checking can be used to analyze that example scenario, under default Linux scheduling semantics …

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Efficient Mapping Of Virtual Networks Onto A Shared Substrate, Jing Lu, Jonathan Turner Jan 2006

Efficient Mapping Of Virtual Networks Onto A Shared Substrate, Jing Lu, Jonathan Turner

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Virtualization has been proposed as a vehicle for overcoming the growing problem of internet ossification [1]. This paper studies the problem of mapping diverse virtual networks onto a common physical substrate. In particular, we develop a method for mapping a virtual network onto a substrate network in a cost-efficient way, while allocating sufficient capacity to virtual network links to ensure that the virtual network can handle any traffic pattern allowed by a general set of traffic constraints. Our approach attempts to find the best topology in a family of backbone-star topologies, in which a subset of nodes constitute the backbone, …

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Adaptive Embedded Roadmaps For Sensor Networks, Gazihan Alankus, Nuzhet Atay, Chenyang Lu, Burchan Bayazit Jan 2006

Adaptive Embedded Roadmaps For Sensor Networks, Gazihan Alankus, Nuzhet Atay, Chenyang Lu, Burchan Bayazit

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In this paper, we propose a new approach to wireless sensor network assisted navigation while avoiding moving dangers. Our approach relies on an embedded roadmap in the sensor network that always contains safe paths. The roadmap is adaptive, i.e., it adapts its topology to changing dangers. The mobile robots in the environment uses the roadmap to reach their destinations. We evaluated the performance of embedded roadmap both in simulations using realistic conditions and with real hardware. Our results show that the proposed navigation algorithm is better suited for sensor networks than traditional navigation field based algorithms. Our observations suggest that …

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Multimodal Congestion Control For Low Stable-State Queuing, Maxim Podlesny, Sergey Gorinsky Jan 2006

Multimodal Congestion Control For Low Stable-State Queuing, Maxim Podlesny, Sergey Gorinsky

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To discover an efficient fair sending rate for a flow, Transmission Control Protocol (TCP) saturates the bottleneck link and its buffer until the router discards a packet. Such TCP-caused queuing is detrimental for interactive and other delay-sensitive applications. In this paper, we present Multimodal Control Protocol (MCP) which strives to maintain low queues and avoid congestion losses at network links. The multimodal MCP engages routers and hosts in limited explicit communication. A distinguishing property of MCP is stable transmission after converging to efficient fair states. To ensure convergence to fairness, MCP incorporates an innovative mechanism that enables a flow to …

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A Comprehensive Analysis Of The Effect Of Microarray Data, Monika Ray, Johannes Freudenberg, Weixiong Zhang Jan 2006

A Comprehensive Analysis Of The Effect Of Microarray Data, Monika Ray, Johannes Freudenberg, Weixiong Zhang

All Computer Science and Engineering Research

Background: Microarray data preprocessing, such as differentially expressed (DE) genes selection, is performed prior to higher level statistical analysis in order to account for technical variability. Preprocessing for the Affymetrix GeneChip includes background correction, normalisation and summarisation. Numerous preprocessing methods have been proposed with little consensus as to which is the most suitable. Furthermore, due to poor concordance among results from cross-platform analyses, protocols are being developed to enable cross-platform reproducibility. However, the effect of data analysis on a single platform is still unknown. The objective of our study is two-fold: first to determine whether there is consistency in the …

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Three Dimensional Panoramic Fast Flourescence Imaging Of Cardiac Arryhtymias In The Rabbit Heart, Fujian Qu, Vladimir P. Nikolski, Cindy Grimm, Igor R. Efimov Jan 2006

Three Dimensional Panoramic Fast Flourescence Imaging Of Cardiac Arryhtymias In The Rabbit Heart, Fujian Qu, Vladimir P. Nikolski, Cindy Grimm, Igor R. Efimov

All Computer Science and Engineering Research

Cardiac high spatio-temporal optical mapping provides a unique opportunity to investigate the dynamics of propagating waves of excitation during ventricular arrhythmia and defibrillation. However, studies using single camera imaging systems are hampered by the inability to monitor electrical activity from the entire surface of the heart. We have developed a three dimensional panoramic imaging system which allows high-resolution and high-dynamic-range optical mapping from the entire surface of the heart. Rabbit hearts (n=4) were Langendorff perfused and imaged by the system during sinus rhythm, epicardial pacing, and arrhythmias. The reconstructed 3D electrical activity provides us with a powerful tool to investigate …

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Knuth-Bendix Completion With Modern Termination Checking, Master's Thesis, August 2006, Ian Wehrman Jan 2006

Knuth-Bendix Completion With Modern Termination Checking, Master's Thesis, August 2006, Ian Wehrman

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Knuth-Bendix completion is a technique for equational automated theorem proving based on term rewriting. This classic procedure is parametrized by an equational theory and a (well-founded) reduction order used at runtime to ensure termination of intermediate rewriting systems. Any reduction order can be used in principle, but modern completion tools typically implement only a few classes of such orders (e.g., recursive path orders and polynomial orders). Consequently, the theories for which completion can possibly succeed are limited to those compatible with an instance of an implemented class of orders. Finding and specifying a compatible order, even among a small number …

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A View-Based Deformation Tool-Kit, Master's Thesis, August 2006, Nisha Sudarsanam Jan 2006

A View-Based Deformation Tool-Kit, Master's Thesis, August 2006, Nisha Sudarsanam

All Computer Science and Engineering Research

Camera manipulation is a hard problem since a graphics camera is defined by specifying 11 independent parameters. Manipulating such a high-dimensional space to accomplish specific tasks is difficult and requires a certain amount of expertise. We present an intuitive interface that allows novice users to perform camera operations in terms of the change they want see in the image. In addition to developing a natural means for camera interaction, our system also includes a novel interface for viewing and organizing previously saved views. When exploring complex 3D data-sets a single view is not sufficient. Instead, a composite view built from …

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Acceleration Of Gapped Alignment In Blastp Using The Mercury System, Brandon B. Harris Jan 2006

Acceleration Of Gapped Alignment In Blastp Using The Mercury System, Brandon B. Harris

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Protein databases have grown exponentially over the last decade. This exponential growth has made extracting valuable information from these databases increasingly time consuming. This project presents a new method of accelerating a commonly used program for performing similarity searching on protein databases, BLASTP. This project describes the design and implementation of Mercury BLASTP, a customized hardware accelerated variant of BLASTP. This project focuses on the gapped alignment stage of Mercury BLASTP and provides design details and implementation results.

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Design And Analysis Of An Accelerated Seed Generation Stage For Blastp On The Mercury System - Master's Thesis, August 2006, Arpith Jacob Jan 2006

Design And Analysis Of An Accelerated Seed Generation Stage For Blastp On The Mercury System - Master's Thesis, August 2006, Arpith Jacob

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NCBI BLASTP is a popular sequence analysis tool used to study the evolutionary relationship between two protein sequences. Protein databases continue to grow exponentially as entire genomes of organisms are sequenced, making sequence analysis a computationally demanding task. For example, a search of the E. coli. k12 proteome against the GenBank Non-Redundant database takes 36 hours on a standard workstation. In this thesis, we look to address the problem by accelerating protein searching using Field Programmable Gate Arrays. We focus our attention on the BLASTP heuristic, building on work done earlier to accelerate DNA searching on the Mercury platform. We …

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Auto-Pipe And The X Language: A Toolset And Language For The Simulation, Analysis, And Synthesis Of Heterogeneous Pipelined Architectures, Master's Thesis, August 2006, Eric J. Tyson Jan 2006

Auto-Pipe And The X Language: A Toolset And Language For The Simulation, Analysis, And Synthesis Of Heterogeneous Pipelined Architectures, Master's Thesis, August 2006, Eric J. Tyson

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Pipelining an algorithmis a popularmethod of increasing the performance of many computation-intensive applications. Often, one wants to form pipelines composed mostly of commonly used simple building blocks such as DSP components, simple math operations, encryption, or pattern matching stages. Additionally, one may desire to map these processing tasks to different computational resources based on their relative performance attributes (e.g., DSP operations on an FPGA). Auto-Pipe is composed of the X Language, a flexible interface language that aids the description of complex dataflow topologies (including pipelines); X-Com, a compiler for the X Language; X-Sim, a tool for modeling pipelined architectures based …

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Preserving Performance Of Byzantine Fault Tolerant Replica Groups In The Presence Of Malicious Clients, Sajeeva L. Pallemulle, Haraldur D. Thorvaldsson, Kenneth J. Goldman Jan 2006

Preserving Performance Of Byzantine Fault Tolerant Replica Groups In The Presence Of Malicious Clients, Sajeeva L. Pallemulle, Haraldur D. Thorvaldsson, Kenneth J. Goldman

All Computer Science and Engineering Research

The Castro and Liskov Byzantine Fault Tolerance protocol for replicated state machines (CLBFT) provides a practical means of tolerating arbitrary replica failures in replicated passive data servers. For better performance, CLBFT uses Message Authentication Codes (MAC) instead of public Key cryptography to authenticate messages and preserves replica consistency even in the presence of malicious clients. However, CLBFT is susceptible to potential attacks by malicious clients using corrupted MACs to force replica groups into expensive configuration changes repeatedly. While not affecting correctness, this vulnerability can seriously impair the performance of the replica group. We propose modifications to CLBFT that address this …

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