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Articles 2071 - 2100 of 2496

Full-Text Articles in Physical Sciences and Mathematics

Combustion Synthesis And Doping Of Titanium Dioxide, Walter Alexander Morales Aug 2007

Combustion Synthesis And Doping Of Titanium Dioxide, Walter Alexander Morales

Chemistry & Biochemistry Theses

A novel combustion technique was used for the preparation and doping of titanium dioxide (TiO2). This metal oxide of titanium is a large band gap semiconductor (3.0 - 3.2 eV) that primarily absorbs in the ultraviolet region of the electromagnietic spectrum. However, the combustion synthesized TiO2 (CS-TiO2) prepared here, presented a shift in the absorption of light to the visible region of the spectrum and a high photocatalytic activity toward the reduction of Cr(VI). The final product was characterized using X-ray powder difraction (XRD), difuse reectance spectroscopy, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Comparison to a commercial …

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Building Energy-Efficient Broadcast Trees Using A Genetic Algorithm In Wireless Sensor Networks, Min Kyung An Aug 2007

Building Energy-Efficient Broadcast Trees Using A Genetic Algorithm In Wireless Sensor Networks, Min Kyung An

Computer Science and Engineering Theses

In wireless broadcast environment, data can be transmitted to several nodes by a single transmission. The nodes in that environment have limited energy resources; therefore we need to reduce the energy consumption when they broadcast data to all nodes to prolong the lifetime of the networks. We call this problem the MPB (minimum power broadcast) problem, and solving the problem has been shown to be an NP-Complete problem [2], [11]. We focus on finding 'near-optimal' solutions for the problem. An algorithm for constructing the minimum power broadcast trees, named BIP (broadcast incremental power) algorithm, was first proposed by Wieselthier et …

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M-Infosift : A Graph-Based Approach For Multiclass Document Classification, Aravind Venkatachalam Aug 2007

M-Infosift : A Graph-Based Approach For Multiclass Document Classification, Aravind Venkatachalam

Computer Science and Engineering Theses

With the increase in the amount of data being introduced into the Internet on a daily basis, the problem of managing large amount of data is an unavoidable problem. The area of document classification has been examined, explored and experimented as a technique for organizing and managing vast repositories of electronic documents such as emails, text and web pages. Over the past decade, several approaches such as machine learning, data mining, information retrieval and others have been proposed for addressing this problem of classifying electronic documents. While a majority of these techniques rely on extracting high-frequency keywords, they ignore the …

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Resource Adaptive Agent Based Fault Tolerant Architecture, Shreyas Shetty Aug 2007

Resource Adaptive Agent Based Fault Tolerant Architecture, Shreyas Shetty

Computer Science and Engineering Theses

Pervasive environment consists of increasing number of mobile, tiny and heterogeneous devices communicating through interconnected network. As ubiquitous computing has seeped into various aspects of everyday life, there has been an increasing demand for dependable systems. However providing reliability demands fault tolerance mechanisms that require substantial time and resources. The dynamic nature and the uncertainty associated with pervasive systems coupled with the energy constraints of the devices involved makes fault tolerance a challenging task. In general, the techniques used to provide fault-tolerance are based on having redundancy and duplication of the user tasks. However the additional cost and the low …

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Incremental Retrieval And Ranking Of Complex Patterns From Text Repositiories, Jayakrishna Thathireddy Aug 2007

Incremental Retrieval And Ranking Of Complex Patterns From Text Repositiories, Jayakrishna Thathireddy

Computer Science and Engineering Theses

As the volume of information accessible via the electronic medium (such as the Internet) is staggeringly large and growing rapidly, users have to sift through vast reservoirs of information to retrieve relevant data of their choice. It has been estimated that, the Internet consists of 2.5 billion unique, publicly accessible web-pages and this figure is growing at an alarming rate of 7.3 million pages per day. Currently, the only way to wade through such colossal information is by using search engines (such as Google, Live, Yahoo, etc.). Although the popularity of search engines has increased manifold due to -- simplicity …

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Sequence Alignment Editor - A New Tool To Assist With Inferring Phylogenetic And Functional Relationships In Biological Data, Ramya Raghukumar Aug 2007

Sequence Alignment Editor - A New Tool To Assist With Inferring Phylogenetic And Functional Relationships In Biological Data, Ramya Raghukumar

Computer Science and Engineering Theses

Biologists study evolution, discover functional and structural information in genomic or protein data through the extensive use of sequence alignments. It is very difficult to manually align long regions, so development of methods for this task continues to be an active area of research. Alignment construction algorithms, based on dynamic programming, approach the problem from a mathematical perspective. The optimal alignment is computed relative to a scoring scheme. The resulting layout is guaranteed to be mathematically optimal, though not necessarily biologically meaningful. Sequence alignments usually account only for single letter substitutions and relatively short indels, representing the latter as gaps. …

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Top K Query Processing In Distributed Database, Amrita Tamrakar Aug 2007

Top K Query Processing In Distributed Database, Amrita Tamrakar

Computer Science and Engineering Theses

Today's data is rarely stored in centralized location due to the enormous amount of information that needs to be stored and also to increase reliability, availability and performance of the system. Same data is stored in different format into different company's database as well as they may be partitioned or replicated. We consider various scenarios of distributed database such as horizontal, vertical fragmentation and attribute overlapping. Allowing access to integrated information from these multiple datasets can provide accurate and wholesome information to the end-user. We research on efficient querying to these distributed databases to get top k elements matching the …

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Performance Analysis Of Caching Effect On Real Time Packet Processing In A Multi-Threaded Processor, Miao Ju Aug 2007

Performance Analysis Of Caching Effect On Real Time Packet Processing In A Multi-Threaded Processor, Miao Ju

Computer Science and Engineering Theses

Caching has been time proven to be a very effective technique to improve memory access speed and average performance for general processors. Based on the real-world trace simulation, earlier research showed that cache can help improve the route lookup and packet classification performance in a Network Processor (NP). However, the existing studies did not take the packet delay/loss constraints into account. As a result, how effective the caching technique is, in dealing with traffic under stringent delay/loss constraints (as is the case for router interface using an NP for packet processing), is still an open issue. In this thesis, we …

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Rate Control Algorithms For Ieee 802.11 Wireless Networks, Bodhisatwa Chakravarty Aug 2007

Rate Control Algorithms For Ieee 802.11 Wireless Networks, Bodhisatwa Chakravarty

Computer Science and Engineering Theses

This thesis evaluates software driven rate selection algorithms used in IEEE 802.11 wireless network interface cards. The motive of the bit-rate selection techniques is to optimize the throughput over the wireless network out of the many rates that are supported by the IEEE 802.11 link. The decision to switch from one rate to another with the changing link conditions to optimize the throughput is the primary focus of the bit-rate selection algorithms. Due to the uncertainty in the channel quality, it is a challenge to make the correct decision so as to minimize the wastage of network resources and achieve …

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Dynamic Push And Pull Strategy Based On Data Interpolation For Web Sensor Networks, Rohita Mohan Aug 2007

Dynamic Push And Pull Strategy Based On Data Interpolation For Web Sensor Networks, Rohita Mohan

Computer Science and Engineering Theses

Sensor Web, a new trend has been developed recently to effectively network large scale deployed heterogeneous sensors with Internet to make sensor data discoverable, accessible and controllable via World Wide Web. Since sensor nodes are highly resource constrained, continuous back hauling of a large amount of data is not feasible. In this paper, we propose a dynamic push/pull service architecture where sensory quality is dynamically monitored and controlled. The architecture is implemented in a web proxy residing at the gateway of the network. As data is being pushed continuously from the network for effective sketching of the sensing field, interpolation …

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Qualitative Behavior Of Dynamical Vector Fields, Roger Dale Kirby Aug 2007

Qualitative Behavior Of Dynamical Vector Fields, Roger Dale Kirby

Mathematics Dissertations

Differential Equations come in two classes, deterministic and stochastic. The first part of this analysis establishes the stable properties of the set of all trajectories converging on a critical point in the real plane defined by two distinct negative eigenvalues. Also in the deterministic class I offer a method for finding closed-form primitives for a great variety of differential forms, through a reduction process facilitated by a Lyapunov-type Energy function. Many of these forms lie in classes which heretofore have not been shown to be solvable in closed form. The last part of this work outlines the appropriate procedures for …

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Quartic: An Ultra-Fast Time-Of-Flight Counter, Pedro Miguel Duarte Jul 2007

Quartic: An Ultra-Fast Time-Of-Flight Counter, Pedro Miguel Duarte

Physics Theses

Fast time-of-flight counters are planned to dramatically decrease backgrounds to events with a massive central system and forward/backward protons at the LHC. By using timing to confirm that the protons originated from the same vertex as the central system. QUARTIC's design uses an array of fused silica (quartz-like) bars aligned at an angle with respect to the beam. The protons pass through the bars and emit Cherenkov photons which are detected by a micro-channel plate photomultiplier tube at the end of the bars. In this work I present the results of the first stage of R&D efforts for the QUARTIC …

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Game Theoretical Data Replication Techniques For Large-Scale Autonomous Distributed Computing Systems, Samee Ullah Khan Jul 2007

Game Theoretical Data Replication Techniques For Large-Scale Autonomous Distributed Computing Systems, Samee Ullah Khan

Computer Science and Engineering Dissertations

Data replication in geographically dispersed servers is an essential technique for reducing the user perceived access time in large-scale distributed computing systems. A majority of the conventional replica placement techniques lack scalability and solution quality. To counteract such issues, this thesis proposes a game theoretical replica placement framework, in which autonomous agents compete for the allocation or reallocation of replicas onto their representative servers in a self-managed fashion. Naturally, each agent's goal is to maximize its own benefit. However, the framework is designed to suppress individualism and to ensure system-wide optimization. Using this framework as an environment, several cooperative and …

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Late-Type Near-Contact Eclipsing Binary [Hh97] Fs Aur-79, Jeff W. Robertson, R. K. Honeycutt, S. J. Austin, C. Tycner, T. Campbell May 2007

Late-Type Near-Contact Eclipsing Binary [Hh97] Fs Aur-79, Jeff W. Robertson, R. K. Honeycutt, S. J. Austin, C. Tycner, T. Campbell

Faculty Publications - Physical & Earth Sciences

The secondary photometric standard star number 79 for the FS Aur field (Henden & Honeycutt 1997), designated as [HH97] FS Aur-79 (GSC 1874-399), is a short-period (0.2508 days) eclipsing binary whose light curve is a combination of the β Lyr and BY Dra type variables. High signal-to-noise ratio multicolor photometry was obtained using the US Naval Observatory 1 m telescope. These light curves show asymmetry at quadrature phases (the O'Connell effect), which can be modeled with the presence of starspots. A low-resolution spectrum obtained with the 3.5 m Wisconsin-Indiana-Yale-NOAO telescope at orbital phase 0.76 is consistent with a spectral type …

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Qcd Equation Of State With 2+1 Flavors Of Improved Staggered Quarks, James E. Hetrick, C. Bernard May 2007

Qcd Equation Of State With 2+1 Flavors Of Improved Staggered Quarks, James E. Hetrick, C. Bernard

All Faculty Articles - School of Engineering and Computer Science

We report results for the interaction measure, pressure, and energy density for nonzero-temperature QCD with 2+1 flavors of improved staggered quarks. In our simulations, we use a Symanzik improved gauge action and the Asqtad O (a2) improved staggered quark action for lattices with temporal extent Nt = 4 and 6. The heavy quark mass ms is fixed at approximately the physical strange quark mass and the two degenerate light quarks have masses mud ≈ 0.1ms or 0.2ms. The calculation of the thermodynamic observables employs the integral method where energy density and pressure are obtained by integration over the interaction measure.

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Information Theoretic, Probabilistic And Maximum Partial Substructure Algorithms For Discovering Graph-Based Anomalies, William Fred Eberle May 2007

Information Theoretic, Probabilistic And Maximum Partial Substructure Algorithms For Discovering Graph-Based Anomalies, William Fred Eberle

Computer Science and Engineering Dissertations

The ability to mine data represented as a graph has become important in several domains for detecting various structural patterns. One important area of data mining is anomaly detection, particularly for fraud. However, less work has been done in terms of detecting anomalies in graph-based data. While there has been some previous work that has used statistical metrics and conditional entropy measurements, the results have been limited to certain types of anomalies and specific domains. In this work we present graph-based approaches to uncovering anomalies in domains where the anomalies consist of unexpected entity/relationship alterations that closely resemble non-anomalous behavior. …

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Automatic Content Analysis Of Endoscopy Video (Endoscopic Multimedia Information System), Sae K. Hwang May 2007

Automatic Content Analysis Of Endoscopy Video (Endoscopic Multimedia Information System), Sae K. Hwang

Computer Science and Engineering Dissertations

Advances in video technology are being incorporated into today's healthcare practice. For example, various types of endoscopes are used for colonoscopy, upper gastrointestinal endoscopy, enteroscopy, bronchoscopy, cystoscopy, laparoscopy, and some minimal invasive surgeries (i.e., video endoscopic neurosurgery). These endoscopes come in various sizes, but all have a tiny video camera at the tip of the endoscopes. During an endoscopic procedure, the tiny video camera generates a video signal of the interior of the human organ, for example, the internal mucosa of the colon. The video data are displayed on a monitor for real-time analysis by the physician. Diagnosis, biopsy and …

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Wildcat: An Integrated Stealth Environment For Dynamic Malware Analysis, Amit Vasudevan May 2007

Wildcat: An Integrated Stealth Environment For Dynamic Malware Analysis, Amit Vasudevan

Computer Science and Engineering Dissertations

Malware -- a term that refers to viruses, trojans, worms, spyware or any form of malicious code -- is widespread today. Given the devastating effects that malware have on the computing world, detecting and countering malware is an important goal. Malware analysis is a challenging and multi-step process providing insight into malware structure and functionality, facilitating the development of an antidote. To successfully detect and counter malware, malware analysts must be able to analyze them in binary, in both a coarse- (behavioral) and fine-grained (structural) fashion. However, current research in coarse- and fine-grained code analysis (categorized into static and dynamic) …

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Investigations Of The Mechanism Of Dna Cleavage Using Ruthenium Polypyridyl Complexes, Fiona Ongeri May 2007

Investigations Of The Mechanism Of Dna Cleavage Using Ruthenium Polypyridyl Complexes, Fiona Ongeri

Chemistry & Biochemistry Theses

We have synthesized a ruthenium complex, [(phen)2Ru(tatpp)Ru(phen)2]4+ (P4+), which has been shown to undergo various redox and protonation steps to form different species that can be monitored by UV-Vis spectroscopy. In Chapter 2, the photochemistry of P4+ in the presence and absence of DNA was studied. It was hypothesized that the lifetime (t1/2) of the excited state of P4+, P*, would be extended in the presence of DNA. However, studies conducted showed that the lifetime of P* was diminished in the presence of DNA as compared to P4+ alone. Experiments have also shown that P4+ is capable of damaging DNA …

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New Applications Of The Pauson-Khand Reaction And Studies Towards The Synthesis Of The Hamigerans, Christian Emeka Madu May 2007

New Applications Of The Pauson-Khand Reaction And Studies Towards The Synthesis Of The Hamigerans, Christian Emeka Madu

Chemistry & Biochemistry Dissertations

This dissertation is divided into two parts. The first part describes the dicobalt octacarbonyl mediated synthesis of medium sized rings via intramolecular Pauson-Khand (IMPK) reaction. The cyclization of 1,8-enynes has proved to be difficult via the IMPK reaction due to entropy reasons. To overcome thid limitation we attempted this cyclization in the presence of an ortho- buttressing group (t-butyl group) on the aromatic ring so as to reduce the conformationally allowed volume of the alkene arm of the substrate. The construction of the substrates started with O-alkenylation of the commercially available 3,5 di-tert-butyl-2-hydroxylbenzaldehyde and then the O-alkenylation products were alkynylated …

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Study Of Oxide Surfaces Using Time Of Flight Positron Annihilation Induced Auger Electron Spectroscopy, Manori Prasadika Nadesalingam May 2007

Study Of Oxide Surfaces Using Time Of Flight Positron Annihilation Induced Auger Electron Spectroscopy, Manori Prasadika Nadesalingam

Physics Dissertations

Transition metal oxides (TMOs) exhibit a rich collection of interesting and intriguing properties which can be used for wide variety of applications. In this dissertation, I will discuss the first PAES measurements on vacuum anneal induced changes in the surface layers of Cu2O/Ta, Cu 2O/TCO and oxidized Cu(100) prepared by spray coated, electrochemically deposition and thermal oxidation techniques respectively. PAES measurements on Cu2O/TCO shows that the a very large increase in the intensity of the Cu (M2,3 VV) Auger peak after annealing at 250°C. Similar but significantly smaller changes were observed in the EAES spectra consistent with the fact that …

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Case Studies Of The Circular Restricted Three Body Problem, William Jason Eberle May 2007

Case Studies Of The Circular Restricted Three Body Problem, William Jason Eberle

Physics Theses

In this thesis, the onset of instability for a planet which is part of a stellar binary system is investigated by running numerical simulations of the circular restricted three body problem. This study also makes use of a rotating (synodic) coordinate system keeping both binary stars at rest. This allows the definition of a constant of motion (Jacobi's constant), which in turn sets a permissible region of motion for the planet. As the initial conditions are varied, the boundary of the permissible region of motion passes through each of the three collinear equilibrium points with significant changes to the orbit …

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Alfvénic Accelerated Electrons And Short Burst Auroral Kilometric Radiations Observed By The Fast Satellite, Lun Ma May 2007

Alfvénic Accelerated Electrons And Short Burst Auroral Kilometric Radiations Observed By The Fast Satellite, Lun Ma

Physics Theses

This investigation is motivated by previous study of short burst radiations (S-bursts) reported by Ergun et al. [2006], who suggested two generation mechanisms of S-bursts: one is the electron cyclotron maser instability due to an unstable ring distribution; the other is an upward electron beam generating upper hybrid resonance. The simulation results reported by Su et al. [2007] support the former mechanism. Only one Earth-based S-burst event was reported prior to our study. A systematic study was performed on particle and field observations from the FAST spacecraft to search for events of S-bursts and Alfvén waves. Eight events involving coexistence …

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Efficient Multi-View Video Coding Scheme Based On Dynamic Video Object Segmentation, Xiaohui Wei May 2007

Efficient Multi-View Video Coding Scheme Based On Dynamic Video Object Segmentation, Xiaohui Wei

Computer Science and Engineering Dissertations

Multi-view video, which simultaneously acquires multiple video sequences from multiple viewpoints or view directions, is poised to become the next generation video technology. Exploiting redundancy is the hallmark of traditional video coding but is even more essential in multi-view video coding (MVC) where the data size is extremely large. The exploitation of additional redundancies, however, incurs extra computational overhead, thereby counteracting the benefits gained from coding efficiency. This dissertation proposes an efficient MVC scheme that provides a complete encoding solution with low complexity. This includes exploitation of inter- and intra-view redundancies for achieving high coding efficiency, and exploitation of inter-view …

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Flash Crowd Mitigation System, Dongchul Kim May 2007

Flash Crowd Mitigation System, Dongchul Kim

Computer Science and Engineering Theses

Flash crowd means that a web server suffers a sudden surge of traffic since a large number of Internet users access the web server simultaneously. Once a flash crowd occurs in a web server, the response rate for the HTTP requests decreases rapidly, or the web server may even crash. To protect the web server from such flash crowds, in this paper, we propose the Flash Crowd Mitigation System (FCMS) which is based on the cooperation of the web servers and the redirection of the HTTP request. In FCMS, when a flash crowd is predicted by the traffic monitoring module …

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Heros: A Patient-Centered Goal-Directed Electronic Medical Record System For The Homeless, Kallol Silas Mahata May 2007

Heros: A Patient-Centered Goal-Directed Electronic Medical Record System For The Homeless, Kallol Silas Mahata

Computer Science and Engineering Theses

Homelessness is a growing problem in the United States. Numerous barriers keep the street homeless from obtaining healthcare. Medical Street Outreach (MSO) programs are designed to reach out to the homeless. Gathering relevant clinical information on the streets is difficult, and carrying paper records in MSO is cumbersome and inefficient. Several complex healthcare record systems have been developed for hospitals, but no such system exists for collecting health data on the streets. In this thesis, we describe a light weight Electronic Medical Record (EMR), called HEROS (Homeless Electronic RecOrd System) that we have built to address the process of healthcare …

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Medical Decision Support System Using Augmentable Guideline Engine, Adetayo Afolabi Aiyedun May 2007

Medical Decision Support System Using Augmentable Guideline Engine, Adetayo Afolabi Aiyedun

Computer Science and Engineering Theses

Increasing life expectancy accompanied by existing growth of wireless infrastructure and ubiquitous computing technologies has given healthcare providers access to vital information within their healthcare networks. Medical decision support systems (MDSS) play an increasingly important role in medical practice by assisting physicians with making clinical decisions. MDSS are interactive computer programs, which are designed to assist physicians and other health professionals with decision making. Currently, the strategies for providing MDSS has failed, in part, because they have not provided a secure, timely access to information that is current, ability to modify their knowledge base without hard coding them in their …

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Efficient Visualization Of Streaming Sensor Network Data Using Approximation Technique, Sunil Pai May 2007

Efficient Visualization Of Streaming Sensor Network Data Using Approximation Technique, Sunil Pai

Computer Science and Engineering Theses

By commanding a large number of wireless sensor nodes capable of sensing, communicating, and computing, wireless sensor networks have revealed their vast potential in a plethora of applications. However, due to the stringent resources limitations on each sensor node ranging from energy and computation to network bandwidth and storage, efficient and light weight systems must be designed in order to accommodate the resource limited environment. Furthermore, due to the potentially large number of sensor nodes deployed, the amount of sensory data gathered therein can be overwhelming for processing and visualizing in a resource limited central controller, such as mobile devices. …

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Hiearchical Overlay For Service Composition In Pervasive Environments, Aparna Kailas May 2007

Hiearchical Overlay For Service Composition In Pervasive Environments, Aparna Kailas

Computer Science and Engineering Theses

The objective of pervasive computing is to allow users to perform their tasks in a transparent way regardless of device features. Resources on devices should be exploited to provide services in order to perform user tasks. When there is no exact match for the user task in the environment, the capabilities of available devices should be combined to perform the user task. Seamless Service Composition (SeSCo) abstracts device capabilities as services and leverages existing work on graph algorithms to perform service composition. A lightweight framework, PerSON (Service Overlay Network for Pervasive Environments) was developed to provide a service overlay network …

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A Dynamic Framework For Testing The Synchronization Behavior Of Java Monitors, Andres Yanes May 2007

A Dynamic Framework For Testing The Synchronization Behavior Of Java Monitors, Andres Yanes

Computer Science and Engineering Theses

A Java monitor is a specialized class that is used to synchronize the behavior of threads in a Java program. The monitors in a Java program must be adequately tested to ensure the correctness of the program. In this thesis we propose a dynamic framework in which a Java monitor is tested by exploring its state space in a depth-first manner. The state exploration procedure consists of dynamically creating method sequences to exercise the possible synchronization behavior of the monitor. During exploration, new threads will be created on the fly to simulate different scenarios that result from threads reaching the …

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