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Articles 1741 - 1770 of 2906

Full-Text Articles in Physical Sciences and Mathematics

Zero-Inflated Censored Regression Models: An Application With Episode Of Care Data, Jonathan P. Prasad Jul 2009

Zero-Inflated Censored Regression Models: An Application With Episode Of Care Data, Jonathan P. Prasad

Theses and Dissertations

The objective of this project is to fit a sequence of increasingly complex zero-inflated censored regression models to a known data set. It is quite common to find censored count data in statistical analyses of health-related data. Modeling such data while ignoring the censoring, zero-inflation, and overdispersion often results in biased parameter estimates. This project develops various regression models that can be used to predict a count response variable that is affected by various predictor variables. The regression parameters are estimated with Bayesian analysis using a Markov chain Monte Carlo (MCMC) algorithm. The tests for model adequacy are discussed and …

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Evans Function Computation, Blake H. Barker Jul 2009

Evans Function Computation, Blake H. Barker

Theses and Dissertations

In this thesis, we review the stability problem for traveling waves and discuss the Evans function, an emerging tool in the stability analysis of traveling waves. We describe some recent developments in the numerical computation of the Evans function and discuss STABLAB, an interactive MATLAB based tool box that we developed. In addition, we verify the Evans function for shock layers in Burgers equation and the p-system with and without capillarity, as well as pulses in the generalized Kortweg-de Vries (gKdV) equation. We conduct a new study of parallel shock layers in isentropic magnetohydrodynamics (MHD) obtaining results consistent with stability.

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Numerical Solutions For Stochastic Differential Equations And Some Examples, Yi Luo Jul 2009

Numerical Solutions For Stochastic Differential Equations And Some Examples, Yi Luo

Theses and Dissertations

In this thesis, I will study the qualitative properties of solutions of stochastic differential equations arising in applications by using the numerical methods. It contains two parts. In the first part, I will first review some of the basic theory of the stochastic calculus and the Ito-Taylor expansion for stochastic differential equations (SDEs). Then I will discuss some numerical schemes that come from the Ito-Taylor expansion including their order of convergence. In the second part, I will use some schemes to solve the stochastic Duffing equation, the stochastic Lorenz equation, the stochastic pendulum equation, and the stochastic equations which model …

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Properties Of The Zero Forcing Number, Kayla Denise Owens Jul 2009

Properties Of The Zero Forcing Number, Kayla Denise Owens

Theses and Dissertations

The zero forcing number is a graph parameter first introduced as a tool for solving the minimum rank problem, which is: Given a simple, undirected graph G, and a field F, let S(F,G) denote the set of all symmetric matrices A=[a_{ij}] with entries in F such that a_{ij} doess not equal 0 if and only if ij is an edge in G. Find the minimum possible rank of a matrix in S(F,G). It is known that the zero forcing number Z(G) provides an upper bound for the maximum nullity of a graph. I investigate properties of the zero forcing number, …

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Meta-Analysis Using Bayesian Hierarchical Models In Organizational Behavior, Michael David Ulrich Jul 2009

Meta-Analysis Using Bayesian Hierarchical Models In Organizational Behavior, Michael David Ulrich

Theses and Dissertations

Meta-analysis is a tool used to combine the results from multiple studies into one comprehensive analysis. First developed in the 1970s, meta-analysis is a major statistical method in academic, medical, business, and industrial research. There are three traditional ways in which a meta-analysis is conducted: fixed or random effects, and using an empirical Bayesian approach. Derivations for conducting meta-analysis on correlations in the industrial psychology and organizational behavior (OB) discipline were reviewed by Hunter and Schmidt (2004). In this approach, Hunter and Schmidt propose an empirical Bayesian analysis where the results from previous studies are used as a prior. This …

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Musical Query-By-Content Using Self-Organizing Maps, Kyle B. Dickerson Jul 2009

Musical Query-By-Content Using Self-Organizing Maps, Kyle B. Dickerson

Theses and Dissertations

The ever-increasing density of computer storage devices has allowed the average user to store enormous quantities of multimedia content, and a large amount of this content is usually music. Current search techniques for musical content rely on meta-data tags which describe artist, album, year, genre, etc. Query-by-content systems, however, allow users to search based upon the actual acoustical content of the songs. Recent systems have mainly depended upon textual representations of the queries and targets in order to apply common string-matching algorithms and are often confined to a single query style (e.g., humming). These methods also lose much of the …

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Modeling Temperature Reduction In Tendons Using Gaussian Processes Within A Dynamic Linear Model, Richard David Wyss Jul 2009

Modeling Temperature Reduction In Tendons Using Gaussian Processes Within A Dynamic Linear Model, Richard David Wyss

Theses and Dissertations

The time it takes an athlete to recover from an injury can be highly influenced by training procedures as well as the medical care and physical therapy received. When an injury occurs to the muscles or tendons of an athlete, it is desirable to cool the muscles and tendons within the body to reduce inflammation, thereby reducing the recovery time. Consequently, finding a method of treatment that is effective in reducing tendon temperatures is beneficial to increasing the speed at which the athlete is able to recover. In this project, Bayesian inference with Gaussian processes will be used to model …

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A Sophisticated Library Search Strategy Using Folksonomies And Similarity Matching, William Lund, Yiu-Kai D. Ng, Maria Soledad Pera Jul 2009

A Sophisticated Library Search Strategy Using Folksonomies And Similarity Matching, William Lund, Yiu-Kai D. Ng, Maria Soledad Pera

Faculty Publications

Libraries, private and public, offer valuable resources to library patrons. As of today the only way to locate information archived exclusively in libraries is through their catalogs. Library patrons, however, often find it difficult to formulate a proper query, which requires using specific keywords assigned to different fields of desired library catalog records, to obtain relevant results. These improperly formulated queries often yield irrelevant results or no results at all. This negative experience in dealing with existing library systems turn library patrons away from library catalogs; instead, they rely on Web search engines to perform their searches first and upon …

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Finding Alternatives To The Hard Disk Drive For Virtual Memory, Bruce Albert Embry Jul 2009

Finding Alternatives To The Hard Disk Drive For Virtual Memory, Bruce Albert Embry

Theses and Dissertations

Current computer systems fill the demand of operating systems and applications for ever greater amounts of random access memory by paging the least recently used data to the hard disk drive. This paging process is called "virtual memory," to indicate that the hard disk drive is used to create the illusion that the computer has more random access memory than it actually has. Unfortunately, the fastest hard disk drives are over five orders of magnitude slower than the DRAM they are emulating. When the demand for memory increases to the point that processes are being continually saved to disk and …

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Radio Determination On Mini-Uav Platforms: Tracking And Locating Radio Transmitters, Braden Russell Huber Jun 2009

Radio Determination On Mini-Uav Platforms: Tracking And Locating Radio Transmitters, Braden Russell Huber

Theses and Dissertations

Aircraft in the US are equipped with Emergency Locator Transmitters (ELTs). In emergency situations these beacons are activated, providing a radio signal that can be used to locate the aircraft. Recent developments in UAV technologies have enabled mini-UAVs (5-foot wingspan) to possess a high level of autonomy. Due to the small size of these aircraft they are human-packable and can be easily transported and deployed in the field. Using a custom-built Radio Direction Finder, we gathered readings from a known transmitter and used them to compare various Bayesian reasoning-based filtering algorithms. Using a custom-developed simulator, we were able to test …

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Improving The Separability Of A Reservoir Facilitates Learning Transfer, David Norton, Dan A. Ventura Jun 2009

Improving The Separability Of A Reservoir Facilitates Learning Transfer, David Norton, Dan A. Ventura

Faculty Publications

We use a type of reservoir computing called the liquid state machine (LSM) to explore learning transfer. The Liquid State Machine (LSM) is a neural network model that uses a reservoir of recurrent spiking neurons as a filter for a readout function. We develop a method of training the reservoir, or liquid, that is not driven by residual error. Instead, the liquid is evaluated based on its ability to separate different classes of input into different spatial patterns of neural activity. Using this method, we train liquids on two qualitatively different types of artificial problems. Resulting liquids are shown to …

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Music Recommendation And Query-By-Content Using Self-Organizing Maps, Kyle B. Dickerson, Dan A. Ventura Jun 2009

Music Recommendation And Query-By-Content Using Self-Organizing Maps, Kyle B. Dickerson, Dan A. Ventura

Faculty Publications

The ever-increasing density of computer storage devices has allowed the average user to store enormous quantities of multimedia content, and a large amount of this content is usually music. Current search techniques for musical content rely on meta-data tags which describe artist, album, year, genre, etc. Query-by-content systems allow users to search based upon the acoustical content of the songs. Recent systems have mainly depended upon textual representations of the queries and targets in order to apply common string-matching algorithms. However, these methods lose much of the information content of the song and limit the ways in which a user …

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A Functional Framework For Content Management, Robert Emer Broadbent Jun 2009

A Functional Framework For Content Management, Robert Emer Broadbent

Theses and Dissertations

This thesis proposes a functional framework for content management. This framework provides concepts and vocabulary for analysis and description of content management systems. The framework is derived from an analysis of eight content management systems. It describes forty-five conceptual functions organized into five functional groups. The functionality derived from the analysis of the content management systems is described using the vocabulary provided by the functional framework. Coverage of the concepts in the existing systems is verified. The utility of the framework is validated through the creation of a prototype that implements sufficient functionality to support a set of specific use …

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Novel Cinchona Alkoloid Derived Ammonium Salts As Phase-Transfer Catalysts For The Asymmetric Synthesis Of Beta-Hydroxy Alpha-Amino Acids Via Aldol Reactions And Total Synthesis Of Celogentin C., Bing Ma Jun 2009

Novel Cinchona Alkoloid Derived Ammonium Salts As Phase-Transfer Catalysts For The Asymmetric Synthesis Of Beta-Hydroxy Alpha-Amino Acids Via Aldol Reactions And Total Synthesis Of Celogentin C., Bing Ma

Theses and Dissertations

Project I. Cinchona alkaloid-derived quaternary ammonium salts have been successfully used as phase-transfer catalysts, particularly in asymmetric alkylations. Our group applied this type of catalyst in the synthesis of β-hydroxy α-amino acids via aldol reactions and discovered that the Park-Jew catalyst afforded good yields and good enantiomeric excess of the syn diasteromers, but negligible diastereoselectivity. This project was therefore focused on the synthesis of novel cinchonidine-derived catalysts with the Park-Jew catalyst as the lead structure. The C3 position of cinchonidine nucleus was modified to achieve dimers and catalysts possessing electron-deficient alkyne and alkene moieties. Synthesized catalysts were tested in the …

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Fusion Of The Parastrophic Matrix And Weak Cayley Table, Nathan C. Perry Jun 2009

Fusion Of The Parastrophic Matrix And Weak Cayley Table, Nathan C. Perry

Theses and Dissertations

The parastrophic matrix and Weak Cayley Tables are matrices that have close ties to the character table. Work by Ken Johnson has shown that fusion of groups induces a relationship between the character tables of the groups. In this paper we will demonstrate a similar induced relationship between the parastrophic matrices and Weak Cayley Tables of the fused groups.

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Super-Resolution Via Recapture And Bayesian Effect Modeling, Bryan S. Morse, Kevin Seppi, Neil Toronto, Dan A. Ventura Jun 2009

Super-Resolution Via Recapture And Bayesian Effect Modeling, Bryan S. Morse, Kevin Seppi, Neil Toronto, Dan A. Ventura

Faculty Publications

This paper presents Bayesian edge inference (BEI), a single-frame super-resolution method explicitly grounded in Bayesian inference that addresses issues common to existing methods. Though the best give excellent results at modest magnification factors, they suffer from gradient stepping and boundary coherence problems by factors of 4x. Central to BEI is a causal framework that allows image capture and recapture to be modeled differently, a principled way of undoing downsampling blur, and a technique for incorporating Markov random field potentials arbitrarily into Bayesian networks. Besides addressing gradient and boundary issues, BEI is shown to be competitive with existing methods on published …

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Coalition Robustness Of Multiagent Systems, Nghia Cong Tran May 2009

Coalition Robustness Of Multiagent Systems, Nghia Cong Tran

Theses and Dissertations

Many multiagent systems are environments where distinct decision-makers compete, explicitly or implicitly, for scarce resources. In these competitive environments, itcan be advantageous for agents to cooperate and form teams, or coalitions; this cooperation gives agents strategic advantage to compete for scarce resources. Multiagent systems thus can be characterized in terms of competition and cooperation. To evaluate the effectiveness of cooperation for particular coalitions, we derive measures based on comparing these different coalitions at their respective equilibria. However, relying on equilibrium results leads to the interesting question of stability. Control theory and cooperative game theory have limitations that make it hard …

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Genetic Analysis Of Ribosome Stalling And Rescue, Douglas Ray Tanner May 2009

Genetic Analysis Of Ribosome Stalling And Rescue, Douglas Ray Tanner

Theses and Dissertations

In eubacteria, ribosome stalling on broken messenger RNA transcripts can lead to cell death. The trans-translation quality control mechanism rescues many of these stalled ribosomes. In this process, tmRNA enters stalled ribosomes by mimicking a transfer RNA, accepting the stalled nascent peptide. The ribosome then releases the broken mRNA and resumes translation on a coding region within tmRNA itself. Translation of tmRNA marks the nascent peptide for destruction by the addition of a short proteolysis tag and the ribosome is released at a stop codon within the tmRNA open reading frame. An intriguing aspect of trans-translation is that …

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An Exploration Of Topologies And Communication In Large Particle Swarms, Matthew Gardner, Andrew Mcnabb, Kevin Seppi May 2009

An Exploration Of Topologies And Communication In Large Particle Swarms, Matthew Gardner, Andrew Mcnabb, Kevin Seppi

Faculty Publications

Particle Swarm Optimization (PSO) has typically been used with small swarms of about 50 particles. However, PSO is more efficiently parallelized with large swarms. We formally describe existing topologies and identify variations which are better suited to large swarms in both sequential and parallel computing environments. We examine the performance of PSO for benchmark functions with respect to swarm size and topology. We develop and demonstrate a new PSO variant which leverages the unique strengths of large swarms. “Hearsay PSO” allows for information to flow quickly through the swarm, even with very loosely connected topologies. These loosely connected topologies are …

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Easemail: Easy Accessible Secure Email, Ryan B. Segeberg May 2009

Easemail: Easy Accessible Secure Email, Ryan B. Segeberg

Theses and Dissertations

Traditional email encryption methods are difficult to set up, as they require senders to obtain a message recipient's public key before a secure communication can be sent. Easy Accessible Secure Email (EASEmail) addresses the key establishment and exchange issues of encrypted email by using a lightweight symmetric key server. Users can send a secure email without establishing or exchanging keys with the recipient in advance. With usability as its primary goal, EASEmail strives to bring usable secure email communication to the masses.

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Synthesis And Evaluation Of Stimulatory Properties Of Glycolipids For Natural Killer T Cells, Xiangtian Long May 2009

Synthesis And Evaluation Of Stimulatory Properties Of Glycolipids For Natural Killer T Cells, Xiangtian Long

Theses and Dissertations

Natural killer T cells (NKT cells) are a subset of T cells. They regulate a wide range of diseases including infection, tumor growth, and autoimmune diseases, through recognizing glycolipid antigens in the context of CD1d. An understanding of the scope of glycolipid antigens would facilitate use of this cell type in controlling immune responses. Till today, a lysosomal glycolipid, isoglobotrihexosylceramide (iGb3), is the only natural glycolipid that has been found to be recognized by both human and mouse NKT cells. To elucidate the molecular basis of this specific recognition, iGb3 variants were designed and prepared: i) replacement of the C26 …

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Ionic Selectivity In L-Type Calcium Channels By Electrostatics And Hard-Core Repulsion, Dezso Boda, Douglas Henderson, Monika Valisko, Bob Eisenberg, Dirk Gillespie Apr 2009

Ionic Selectivity In L-Type Calcium Channels By Electrostatics And Hard-Core Repulsion, Dezso Boda, Douglas Henderson, Monika Valisko, Bob Eisenberg, Dirk Gillespie

Faculty Publications

A physical model of selective "ion binding" in the L-type calcium channel is constructed, and consequences of the model are compared with experimental data. This reduced model treats only ions and the carboxylate oxygens of the EEEE locus explicitly and restricts interactions to hard-core repulsion and ion–ion and ion–dielectric electrostatic forces. The structural atoms provide a flexible environment for passing cations, thus resulting in a self-organized induced-fit model of the selectivity filter. Experimental conditions involving binary mixtures of alkali and/or alkaline earth metal ions are computed using equilibrium Monte Carlo simulations in the grand canonical ensemble. The model pore rejects …

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Uav Intelligent Path Planning For Wilderness Search And Rescue, Rongbin Lin Apr 2009

Uav Intelligent Path Planning For Wilderness Search And Rescue, Rongbin Lin

Theses and Dissertations

In Wilderness Search and Rescue (WiSAR), the incident commander (IC) creates a probability distribution map of the likely location of the missing person. This map is important because it guides the IC in allocating search resources and coordinating efforts, but it often depends almost exclusively on prior experience and subjective judgment. We propose a Bayesian model that utilizes publicly available terrain features data to help model lost-person behaviors. This approach enables domain experts to encode uncertainty in their prior estimations and also make it possible to incorporate human-behavior data collected in the form of posterior distributions, which are used to …

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Development Of An Adaptive Equalization Algorithm Using Acoustic Energy Density, Panu Tapani Puikkonen Apr 2009

Development Of An Adaptive Equalization Algorithm Using Acoustic Energy Density, Panu Tapani Puikkonen

Theses and Dissertations

Sound pressure equalization of audio signals using digital signal processors has been a subject of ongoing study for many years. The traditional approach is to equalize sound at a point in a listening environment, but because of its specific dependence on the room frequency response between a source and receiver position, this equalization generally causes the spectral response to worsen significantly at other locations in the room. This work presents both a time-invariant and a time-varying implementation of an adaptive acoustic energy density equalization filter for a one-dimensional sound field. Energy density equalization addresses the aforementioned challenge and others that …

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Progressive Spatial Networks, Samuel Curren Apr 2009

Progressive Spatial Networks, Samuel Curren

Theses and Dissertations

Digital street and trail maps are typically represented by an interconnected network of path segments. These spatial networks are used in map creation, route planning, and geo-location. Consumer GPS devices have become popular as a method of collecting data for use in spatial networks. Existing methods for creating spatial networks either require extensive hand editing or use inefficient algorithms that require re-computation when adding new data to an existing network. I demonstrate a method for creating and maintaining spatial networks that allows for incremental updates without complete re-computation. I also demonstrate how spatial limits on data set growth allows networks …

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Synthesis Of 2,4,5-Triaminocyclohexane Carboxylic Acid As A Novel 2-Deoxystreptamine Mimetic, Sarah Elizabeth Roberts Apr 2009

Synthesis Of 2,4,5-Triaminocyclohexane Carboxylic Acid As A Novel 2-Deoxystreptamine Mimetic, Sarah Elizabeth Roberts

Theses and Dissertations

RNAs have become increasingly recognized as possible drug targets due to their involvement in important biochemical functions, as well as their unique but well-defined structures. Recently published crystal structures depict the binding of a series of aminoglycosides- or more specifically- 2-deoxystretamine (2-DOS), the most preserved central scaffold of aminoglycosides, to a conserved 5'-GU-3'region on their target RNAs. A novel unnatural γ-amino acid, 1, has been synthesized using 2-deoxystreptamine as a template through structure-based rational design. The unnatural amino acid has been designed to replace a glycosidic linkage with an amide bond, which may limit the promiscuous binding characteristics of aminoglycosides …

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State Of Secure Application Development For 802.15.4, Janell Armstrong Apr 2009

State Of Secure Application Development For 802.15.4, Janell Armstrong

Theses and Dissertations

A wireless sensor network consists of small, limited-resource embedded systems exchanging environment data and activating controls. These networks can be deployed in hostile environments to monitor wildlife habitats, implemented in factories to locate mobile equipment, and installed in home environments to optimize the use of utilities. Each of these scenarios requires network security to protect the network data. The IEEE 802.15.4 standard is designed for WSN communication, yet the standard states that it is not responsible for defining the initialization, distribution, updating, or management of network public keys. Individuals seeking to research security topics will find that there are many …

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Xprime: A Method Incorporating Expert Prior Information Into Motif Exploration, Rachel Lynn Poulsen Apr 2009

Xprime: A Method Incorporating Expert Prior Information Into Motif Exploration, Rachel Lynn Poulsen

Theses and Dissertations

One of the primary goals of active research in molecular biology is to better understand the process of transcription regulation. An important objective in understanding transcription is identifying transcription factors that directly regulate target genes. Identifying these transcription factors is a key step toward eliminating genetic diseases or disease susceptibilities that are encoded inside deoxyribonucleic acid (DNA). There is much uncertainty and variation associated with transcription factor binding sites, requiring these sites to be represented stochastically. Although typically each transcription factor prefers to bind to a specific DNA word, it can bind to different variations of that DNA word. In …

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Role Of Molecular Chaperones In G Protein B5-Regulator Of G Protein Signaling Dimer Assembly And G Protein By Dimer Specificity, Alyson Cerny Howlett Apr 2009

Role Of Molecular Chaperones In G Protein B5-Regulator Of G Protein Signaling Dimer Assembly And G Protein By Dimer Specificity, Alyson Cerny Howlett

Theses and Dissertations

In order for G protein signaling to occur, the G protein heterotrimer must be assembled from its nascent polypeptides. The most difficult step in this process is the formation of the Gβγ dimer from the free subunits since both are unstable in the absence of the other. Recent studies have shown that phosducin-like protein (PhLP1) works as a co-chaperone with the cytosolic chaperonin complex (CCT) to fold Gβ and mediate its interaction with Gγ. However, these studies did not address questions concerning the scope of PhLP1 and CCT-mediated Gβγ assembly, which are important questions given that there are four Gβs …

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Test Case Generation Using Model Checking For Software Components Deployed Into New Environments, Tonglaga Bao, Michael D. Jones Apr 2009

Test Case Generation Using Model Checking For Software Components Deployed Into New Environments, Tonglaga Bao, Michael D. Jones

Faculty Publications

In this paper, we show how to generate test cases for a component deployed into a new software environment. This problem is important for software engineers who need to deploy a component into a new environment. Most existing model based testing approaches generate models from high level specifications. This leaves a semantic gap between the high level specification and the actual implementation. Furthermore, the high level specification often needs to be manually translated into a model, which is a time consuming and error prone process. We propose generating the model automatically by abstracting the source code of the component using …

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