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Articles 11461 - 11490 of 12809

Full-Text Articles in Physical Sciences and Mathematics

A Pi Controller Based On Gain-Scheduling For Synchronous Generator, Alireza Sedaghati Jan 2006

A Pi Controller Based On Gain-Scheduling For Synchronous Generator, Alireza Sedaghati

Turkish Journal of Electrical Engineering and Computer Sciences

In this paper a gain- scheduling scheme of a proportional integral (GSPI) controller is proposed for a synchronous generator. In presented scheme, both proportional and integral gains are allowed to vary within a predetermined range. In order to validate the effectiveness of GSPI controller, simulation studies for a single-machine infinite bus power system are used .The results verify improved performance of GSPI controller comparing to conventional AVR under various operating conditions.

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Adaptive 3d Visual Servo Control Of Robot Manipulators Via Composite Camera Inputs, Türker Şahi̇n, Erkan Zergeroğlu Jan 2006

Adaptive 3d Visual Servo Control Of Robot Manipulators Via Composite Camera Inputs, Türker Şahi̇n, Erkan Zergeroğlu

Turkish Journal of Electrical Engineering and Computer Sciences

This paper considers the problem of position control of robot manipulators via visual servoing in the presence of uncertainty associated with the robot dynamics and the vision system. Specifically, an adaptive controller is designed to compensate for the uncertainties associated with the mechanical parameters of the robot manipulator and the intrinsic parameters of the cameras. The 3D visual information is obtained from the composite inputs of two separate cameras placed in the robot work space. Despite the uncertainties associated with the camera system and robot dynamics the proposed adaptive controller achieves asymptotic end effector position tracking. A Lyapunov based approach …

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Uplink Practical Capacity And Interference Statistics Of Wcdma Cigar-Shaped Microcells For Highways In Rural Zones With Non-Uniform Spatial Traffic Distribution And Imperfect Power Control, Bazil Taha Ahmed, Miguel Calvo Ramon, Leandro De Haro-Ariet Jan 2006

Uplink Practical Capacity And Interference Statistics Of Wcdma Cigar-Shaped Microcells For Highways In Rural Zones With Non-Uniform Spatial Traffic Distribution And Imperfect Power Control, Bazil Taha Ahmed, Miguel Calvo Ramon, Leandro De Haro-Ariet

Turkish Journal of Electrical Engineering and Computer Sciences

The capacity (the maximum number of users per sector that the system can support) and the interference statistics (expected value and variance) of sectors composed of cigar-shaped WCDMA microcells are studied. A model of 5 microcells is used to analyze the uplink capacity and interference statistics. The microcells are assumed to exist in rural zone highways. The capacity and the interference statistics of the microcells are studied for different non-uniform spatial traffic distributions. As user density decreases away from the base station, the capacity of the sector increases due to the reduced total power transmitted by the interfering users.

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An Ann Based Approach To Improve The Distance Relaying Algorithm, Hassan Khorashadi Zadeh, Zuyi Li Jan 2006

An Ann Based Approach To Improve The Distance Relaying Algorithm, Hassan Khorashadi Zadeh, Zuyi Li

Turkish Journal of Electrical Engineering and Computer Sciences

This paper presents an artificial neural network- (ANN) based approach to improve the performance of the distance relaying algorithm. The proposed distance relay uses magnitudes of voltages and currents as input signals to find fault locations. In this approach, an ANN has been included in the protection algorithm as an extension of the existing methods, which improves the reliability of the protection operation. The design procedure of the proposed relay is presented in detail. Simulation studies are performed and the influence of changing system parameters, such as fault resistance and source impedance, is studied. Performance studies show that the proposed …

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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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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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Pocket Deformable Mirror For Adaptive Optics Applications, Leonid A. Beresnev, Mikhail Vorontsov, Peter Wangsness Jan 2006

Pocket Deformable Mirror For Adaptive Optics Applications, Leonid A. Beresnev, Mikhail Vorontsov, Peter Wangsness

Electrical and Computer Engineering Faculty Publications

Adaptive/active optical elements are designed to improve optical system performance in the presence of phase aberrations. For atmospheric optics and astronomical applications, an ideal deformable mirror should have sufficient frequency bandwidth for compensation of fast changing wave front aberrations induced by either atmospheric turbulences or by turbulent air flows surrounding a flying object (air optical effects). In many applications, such as atmospheric target tracking, remote sensing from flying aircraft, boundary layer imaging, laser communication and laser beam projection over near horizontal propagation paths the phase aberration frequency bandwidth can exceed several kHz. These fast-changing aberrations are currently compensated using relatively …

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Fedcor: An Institutional Cordra Registry, Giridhar Manepalli, Henry Jerez, Michael L. Nelson Jan 2006

Fedcor: An Institutional Cordra Registry, Giridhar Manepalli, Henry Jerez, Michael L. Nelson

Computer Science Faculty Publications

FeDCOR (Federation of DSpace using CORDRA) is a registry-based federation system for DSpace instances. It is based on the CORDRA model. The first article in this issue of D-Lib Magazine describes the Advanced Distributed Learning-Registry (ADL-R) [1], which is the first operational CORDRA registry, and also includes an introduction to CORDRA. That introduction, or other prior knowledge of the CORDRA effort, is recommended for the best understanding of this article, which builds on that base to describe in detail the FeDCOR approach.

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Observed Web Robot Behavior On Decaying Web Subsites, Joan A. Smith, Frank Mccown, Michael L. Nelson Jan 2006

Observed Web Robot Behavior On Decaying Web Subsites, Joan A. Smith, Frank Mccown, Michael L. Nelson

Computer Science Faculty Publications

We describe the observed crawling patterns of various search engines (including Google, Yahoo and MSN) as they traverse a series of web subsites whose contents decay at predetermined rates. We plot the progress of the crawlers through the subsites, and their behaviors regarding the various file types included in the web subsites. We chose decaying subsites because we were originally interested in tracking the implication of using search engine caches for digital preservation. However, some of the crawling behaviors themselves proved to be interesting and have implications on using a search engine as an interface to a digital library.

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Addressing Cheating And Workload Characterization In Online Games, Christopher Chambers Jan 2006

Addressing Cheating And Workload Characterization In Online Games, Christopher Chambers

Dissertations and Theses

The Internet has enabled the popular pastime of playing video games to grow rapidly by connecting game players in disparate locations. However, with popularity have come the two challenges of hosting a large number of users and detecting cheating among users. For reasons of control, security, and ease of development, the most popular system for hosting on-line games is the client server architecture. This is also the most expensive and least scalable architecture for the game publisher, which drives hosting costs upwards with the success of the game. In addition to the expense of hosting, as a particular game grows …

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The Formal Laplace-Borel Transform Of Fliess Operators And The Composition Product, Yaqin Li, W. Steven Gray Jan 2006

The Formal Laplace-Borel Transform Of Fliess Operators And The Composition Product, Yaqin Li, W. Steven Gray

Electrical & Computer Engineering Faculty Publications

The formal Laplace-Borel transform of an analytic integral operator, known as a Fliess operator, is defined and developed. Then, in conjunction with the composition product over formal power series, the formal Laplace-Borel transform is shown to provide an isomorphism between the semigroup of all Fliess operators under operator composition and the semigroup of all locally convergent formal power series under the composition product. Finally, the formal Laplace-Borel transform is applied in a systems theory setting to explicitly derive the relationship between the formal Laplace transform of the input and output functions of a Fliess operator. This gives a compact interpretation …

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Virtualizing Network Processors, Ben Wun, Jonathan Turner, Patrick Crowley Jan 2006

Virtualizing Network Processors, Ben Wun, Jonathan Turner, Patrick Crowley

All Computer Science and Engineering Research

This paper considers the problem of virtualizing the resources of a network processor (NP) in order to allow multiple third-parties to execute their own virtual router software on a single physical router at the same time. Our broad interest is in designing such a router capable of supporting virtual networking. We discuss the issues and challenges involved in this virtualization, and then describe specific techniques for virtualizing both the control and data-plane processors on NPs. For Intel IXP NPs in particular, we present a dynamic, macro-based technique for virtualization that allows multiple virtual routers to run on multiple data plane …

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Tuple Space Coordination Across Space & Time, Gruia-Catalin Roman, Radu Handorean, Chenyang Lu Jan 2006

Tuple Space Coordination Across Space & Time, Gruia-Catalin Roman, Radu Handorean, Chenyang Lu

All Computer Science and Engineering Research

CAST is a coordination model designed to support interactions among agents executing on hosts that make up a mobile ad hoc network (MANET). From an application programmer’s point of view, CAST makes it possible for operations to be executed at arbitrary locations in space, at prescribed times which may be in the future, and on remote hosts even when no end-to-end connected route exists between the initiator and target(s) of the operation. To accomplish this, CAST assumes that each host moves in space in accordance with a motion profile which is accurate but which at any given time extends into …

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Agilla: A Mobile Agent Middleware For Sensor Networks, Chien-Liang Fok, Gruia-Catalin Roman, Chenyang Lu Jan 2006

Agilla: A Mobile Agent Middleware For Sensor Networks, Chien-Liang Fok, Gruia-Catalin Roman, Chenyang Lu

All Computer Science and Engineering Research

Agilla is a mobile agent middleware for sensor networks. Mobile agents are special processes that can migrate across sensors. They increase network flexibility by enabling active in-network reprogramming. Neighbor lists and tuple spaces are used for agent coordination. Agilla was originally implemented on Mica2 motes, but has been ported to other platforms. Its Mica2 implementation consumes 41.6KB of code and 3.59KB of data memory. Agents can move five hops in less than 1.1s with over 92% success. Agilla was used to develop multiple applications related to fire detection and tracking, cargo container monitoring, and robot navigation.

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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

All Computer Science and Engineering Research

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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Acceleration Of Profile-Hmm Search For Protein Sequences In Reconfigurable Hardware - Master's Thesis, May 2006 , Rahul Pratap Maddimsetty Jan 2006

Acceleration Of Profile-Hmm Search For Protein Sequences In Reconfigurable Hardware - Master's Thesis, May 2006 , Rahul Pratap Maddimsetty

All Computer Science and Engineering Research

Profile Hidden Markov models are highly expressive representations of functional units, or motifs, conserved across protein sequences. Profile-HMM search is a powerful computational technique that is used to annotate new sequences by identifying occurrences of known motifs in them. With the exponential growth of protein databases, there is an increasing demand for acceleration of such techniques. We describe an accelerator for the Viterbi algorithm using a two-stage pipelined design in which the first stage is implemented in parallel reconfigurable hardware for greater speedup. To this end, we identify algorithmic modifications that expose a high level of parallelism and characterize their …

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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

All Computer Science and Engineering Research

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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The Meta-Theory Of Q_0 In The Calculus Of Inductive Constructions, Master's Thesis, May 2006, Li-Yang Tan Jan 2006

The Meta-Theory Of Q_0 In The Calculus Of Inductive Constructions, Master's Thesis, May 2006, Li-Yang Tan

All Computer Science and Engineering Research

The notion of a proof is central to all of mathematics. In the language of formal logic, a proof is a finite sequence of inferences from a set of axioms, and any statement one yields from such a finitistic procedure is called a theorem. For better or for worse, this is far from the form a traditional mathematical proof takes. Mathematicians write proofs that omit routine logical steps, and details deemed tangential to the central result are often elided. These proofs are fuzzy and human-centric, and a great amount of context is assumed on the part of the reader. While …

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The Remote-Clique Problem Revisited, Benjamin E. Birnbaum Jan 2006

The Remote-Clique Problem Revisited, Benjamin E. Birnbaum

All Computer Science and Engineering Research

Given a positive integer k and a complete graph with non-negative edge weights that satisfy the triangle inequality, the remote-clique problem is to find a subset of k vertices having a maximum-weight induced subgraph. A greedy algorithm for the problem has been shown to have an approximation ratio of 4, but this analysis was not shown to be tight. In this thesis, we present an algorithm called d-Greedy Augment that generalizes this greedy algorithm (they are equivalent when d = 1). We use the technique of factor-revealing linear programs to prove that d-Greedy Augment, which has a running time of …

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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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Dynamic Conflict-Free Query Scheduling For Wireless Sensor Networks, Octav Chipara, Chenyang Lu, John Stankovic Jan 2006

Dynamic Conflict-Free Query Scheduling For Wireless Sensor Networks, Octav Chipara, Chenyang Lu, John Stankovic

All Computer Science and Engineering Research

With the emergence of high data rate sensor network applications, there is an increasing demand for high-performance query services in such networks. To meet this challenge, we present Dynamic Conflict-free Query Scheduling (DCQS), a novel scheduling technique for queries in wireless sensor networks. In contrast to earlier TDMA protocols designed for general-purpose networks and workloads, DCQS is specifically designed for query services supporting in-network data aggregation. DCQS has several important features. First, it optimizes the query performance and energy efficiency by exploiting the temporal properties and precedence constraints introduced by data aggregation. Second, it can efficiently adapt to dynamic workloads …

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Reusable Models For Timing And Liveness Analysis Of Middleware For Distributed Real-Time And Embedded Systems, Venkita Subramonian, Christopher Gill, Cesar Sanchez, Henny Sipma Jan 2006

Reusable Models For Timing And Liveness Analysis Of Middleware For Distributed Real-Time And Embedded Systems, Venkita Subramonian, Christopher Gill, Cesar Sanchez, Henny Sipma

All Computer Science and Engineering Research

Distributed real-time and embedded (DRE) systems have stringent constraints on timeliness and other properties whose assurance is crucial to correct system behavior. Formal tools and techniques play a key role in verifying and validating system properties. However, many DRE systems are built using middleware frameworks that have grown increasingly complex to address the diverse requirements of a wide range of applications. How to apply formal tools and techniques effectively to these systems, given the range of middleware configuration options available, is therefore an important research problem. This paper makes three contributions to research on formal verification and validation of middleware-based …

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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

All Computer Science and Engineering Research

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

All Computer Science and Engineering Research

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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Sliver: A Bpel Workflow Process Execution Engine For Mobile Devices, Gregory Hackmann, Mart Haitjema, Christopher Gill, Catalin-Gruia Roman Jan 2006

Sliver: A Bpel Workflow Process Execution Engine For Mobile Devices, Gregory Hackmann, Mart Haitjema, Christopher Gill, Catalin-Gruia Roman

All Computer Science and Engineering Research

The Business Process Execution Language (BPEL) has become the dominant means for expressing traditional business processes as workflows. The widespread deployment of mobile devices like PDAs and mobile phones has created a vast computational and communication resource for these workflows to exploit. However, BPEL so far has been deployed only on relatively heavyweight server platforms such as Apache Tomcat, leaving the potential created by these lower-end devices untapped. This paper presents Sliver, a BPEL workflow process execution engine that supports a wide variety of devices ranging from mobile phones to desktop PCs. We discuss the design decisions that allow Sliver …

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Hail: An Algorithm For The Hardware Accelerated Identification Of Languages, Master's Thesis, May 2006, Charles M. Kastner Jan 2006

Hail: An Algorithm For The Hardware Accelerated Identification Of Languages, Master's Thesis, May 2006, Charles M. Kastner

All Computer Science and Engineering Research

This thesis examines in detail the Hardware-Accelerated Identification of Languages (HAIL) project. The goal of HAIL is to provide an accurate means to identify the language and encoding used in streaming content, such as documents passed over a high-speed network. HAIL has been implemented on the Field-programmable Port eXtender (FPX), an open hardware platform developed at Washington University in St. Louis. HAIL can accurately identify the primary languages and encodings used in text at rates much higher than what can be achieved by software algorithms running on microprocessors.

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