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Articles 3331 - 3360 of 3840

Full-Text Articles in Physical Sciences and Mathematics

Convergence Classes And Spaces Of Partial Functions, Anthony K. Seda, Roland Heinze, Pascal Hitzler Oct 2001

Convergence Classes And Spaces Of Partial Functions, Anthony K. Seda, Roland Heinze, Pascal Hitzler

Computer Science and Engineering Faculty Publications

We study the relationship between convergence spaces and convergence classes given by means of both nets and filters, we consider the duality between them and we identify in convergence terms when a convergence space coincides with a convergence class. We examine the basic operators in the Vienna Development Method of formal systems development, namely, extension, glueing, restriction, removal and override, from the perspective of the Logic for Computable Functions. Thus, we examine in detail the Scott continuity, or otherwise, of these operators when viewed as operators on the domain (X → Y) of partial functions mapping X into …

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Solar Activity Variations Of The Venus Thermosphere/Ionosphere, Jane L. Fox, K. Y. Sung Oct 2001

Solar Activity Variations Of The Venus Thermosphere/Ionosphere, Jane L. Fox, K. Y. Sung

Physics Faculty Publications

We present models of the low and high solar activity thermospheres and ionospheres of Venus for a background atmosphere based largely on the VTS3 model of Hedin et al. [1983]. Our background model consists of 12 neutral species, and we compute the density profiles of 13 ions and 7 minor neutrals. We find that the peak production rates of some ions, such as CO2+ and N2+, vary approximately as the solar flux and that some, whose parent neutrals are photochemically produced, such as O+, N+, and C+, show variations …

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Photochemical Escape Of Atomic Carbon From Mars, Jane L. Fox, F. M. Bakalian Oct 2001

Photochemical Escape Of Atomic Carbon From Mars, Jane L. Fox, F. M. Bakalian

Physics Faculty Publications

We have modeled the escape fluxes of atomic carbon from the Martian atmosphere for low and high solar activities due to various photochemical escape mechanisms, including photodissociation of CO, dissociative recombination of CO+, electron impact dissociation and dissociative ionization of CO, photodissociative ionization of CO, and dissociative charge transfer of O++ to CO. Only photodissociation of CO and dissociative recombination of CO+ are found to be important, and the time-averaged escape flux is predicted to be controlled by the high solar activity values. The computed global average escape fluxes of C due to photodissociation of CO …

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Hot Carbon Densities In The Exosphere Of Mars, Andrew F. Nagy, Michael W. Liemohn, Jane L. Fox, Jhoon Kim Oct 2001

Hot Carbon Densities In The Exosphere Of Mars, Andrew F. Nagy, Michael W. Liemohn, Jane L. Fox, Jhoon Kim

Physics Faculty Publications

Theoretical results of hot carbon densities in the exosphere of Mars are presented. The calculation is a two-step process: First a two-stream transport code is used to solve for the distribution function at the exobase, and then these results are used in a Liouville equation solution above the exobase. It is found that photodissociation of carbon monoxide is the largest source of hot carbon atoms in the upper atmosphere of Mars, larger than dissociative recombination of CO+ and much larger than the creation of hot carbon through collisions with hot oxygen atoms. It is also found that the high …

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Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 18, Number 1, September 2001, College Of Engineering And Computer Science, Wright State University Sep 2001

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 18, Number 1, September 2001, College Of Engineering And Computer Science, Wright State University

BITs and PCs Newsletter

A twelve page newsletter created by the Wright State University College of Engineering and Computer Science that addresses the current affairs of the college.

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Online Bayesian Tree-Structured Transformation Of Hmms With Optimal Model Selection For Speaker Adaptation, Shaojun Wang, Yunxin Zhao Sep 2001

Online Bayesian Tree-Structured Transformation Of Hmms With Optimal Model Selection For Speaker Adaptation, Shaojun Wang, Yunxin Zhao

Kno.e.sis Publications

This paper presents a new recursive Bayesian learning approach for transformation parameter estimation in speaker adaptation. Our goal is to incrementally transform or adapt a set of hidden Markov model (HMM) parameters for a new speaker and gain large performance improvement from a small amount of adaptation data. By constructing a clustering tree of HMM Gaussian mixture components, the linear regression (LR) or affine transformation parameters for HMM Gaussian mixture components are dynamically searched. An online Bayesian learning technique is proposed for recursive maximum a posteriori (MAP) estimation of LR and affine transformation parameters. This technique has the advantages of …

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Control Of Error Rates In Adaptive Analysis Of Orthogonal Saturated Designs, Weizhen Wang, Daniel T. Voss Aug 2001

Control Of Error Rates In Adaptive Analysis Of Orthogonal Saturated Designs, Weizhen Wang, Daniel T. Voss

Mathematics and Statistics Faculty Publications

Individual and simultaneous confidence intervals using the data adaptively are constructed for the effects in orthogonal saturated designs under the assumption of effect sparsity. The minimum coverage probabilities of the intervals are equal to the nominal level 1 - α.

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Predicted Maximum Mobility In Bulk Gan, David C. Look, J. R. Sizelove Aug 2001

Predicted Maximum Mobility In Bulk Gan, David C. Look, J. R. Sizelove

Physics Faculty Publications

A 300 K bulk (three-dimensional) mobility of 1245 cm2/V s has been measured in free-standing GaN. Temperature-dependent Hall-effect data on this particular sample are fitted to obtain unknown lattice-scattering parameters, as well as shallow donor (ND) and acceptor (NA) concentrations, which are ND = 6.7×1015 and NA = 1.7×1015 cm−3. Realistic values of the maximum mobility attainable in bulk GaN are then obtained by assuming two-orders-of-magnitude lower values of ND and NA, leading to a maximum 300 K mobility of 1350 cm2 …

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Characterization Of Near-Surface Traps In Semiconductors: Gan, David C. Look, Z-Q. Fang Jul 2001

Characterization Of Near-Surface Traps In Semiconductors: Gan, David C. Look, Z-Q. Fang

Physics Faculty Publications

We present a simple a criterion, based on deep-level transient spectroscopy peak heights S(Vr) at two or more values of reverse bias Vr, to unequivocally determine whether or not a particular semiconductor trap is of bulk or near-surface nature. Moreover, we present an expression for S(Vr) with fitting parameters ϕB, the Schottky barrier height; δ, the trap penetration depth; and NT, the trap density. Application of the method to a thick, high-quality, epitaxial GaN layer, reveals two common traps which penetrate only 2700±300 Å into the …

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Semantic Operators And Fixed-Point Theory In Logic Programming, Anthony K. Seda, Pascal Hitzler Jul 2001

Semantic Operators And Fixed-Point Theory In Logic Programming, Anthony K. Seda, Pascal Hitzler

Computer Science and Engineering Faculty Publications

We consider rather general operators mapping valuations to (sets of) valuations in the context of the semantics of logic programming languages. This notion generalizes several of the standard operators encountered in this subject and is inspired by earlier work of M.C. Fitting. The fixed points of such operators play a fundamental role in logic programming semantics by providing standard models of logic programs and also in determining the computability properties of these standard models. We discuss some of our recent work employing topological ideas, in conjunction with order theory, to establish methods by which one can find the fixed points …

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Microcathodoluminescence Of Impurity Doping At Gallium Nitride/Sapphire Interfaces, S. H. Goss, X. L. Sun, A. P. Young, L. J. Brillson, David C. Look, Richard J. Molnar Jun 2001

Microcathodoluminescence Of Impurity Doping At Gallium Nitride/Sapphire Interfaces, S. H. Goss, X. L. Sun, A. P. Young, L. J. Brillson, David C. Look, Richard J. Molnar

Physics Faculty Publications

We have used low-temperature cathodoluminescence spectroscopy (CLS) to probe the spatial distribution and energies of electronic defects near GaN/Al2O3 interfaces grown by hydride vapor phase epitaxy (HVPE). Cross sectional secondary electron microscopy CLS shows systematic variations in impurity/defect emissions over a wide range of HVPE GaN/Sapphire electronic properties. These data, along with electrochemical capacitance–voltage profiling and secondary ion mass spectrometry, provide a consistent picture of near-interface doping by O diffusion from Al2O3 into GaN, over a range 100–1000 nm.

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Query Processing With An Fpga Coprocessor Board, Jack S. Jean, Guozhu Dong, Hwa Zhang, Xinzhong Guo, Baifeng Zhang Jun 2001

Query Processing With An Fpga Coprocessor Board, Jack S. Jean, Guozhu Dong, Hwa Zhang, Xinzhong Guo, Baifeng Zhang

Kno.e.sis Publications

In this paper, a commercial FPGA coprocessor board is used to accelerate the processing of queries on a relational database that contains texts and images. FPGA designs for text searching and image matching are described and their performances summarized. A potential design for a database JOIN operator is then studied. A query optimization preprocessor is then proposed.

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Summarizing Data Sets For Classification, Christopher W. Kinzig, Krishnaprasad Thirunarayan, Gary B. Lamont, Robert E. Marmelstein Jun 2001

Summarizing Data Sets For Classification, Christopher W. Kinzig, Krishnaprasad Thirunarayan, Gary B. Lamont, Robert E. Marmelstein

Kno.e.sis Publications

This paper describes our approach and experiences with implementing a data mining system using genetic algorithms in C++. In contrast with earlier classification algorithms that tended to “tile” the data sets using some pre-specified “shapes”, the proposed system is based on Marmelstein’s work on determining natural boundaries for class homogeneous regions. These boundaries are further refined to construct a compact set of simple data mining rules for classification.

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Fine Structure On The Green Band In Zno, D. C. Reynolds, David C. Look, B. Jogai Jun 2001

Fine Structure On The Green Band In Zno, D. C. Reynolds, David C. Look, B. Jogai

Physics Faculty Publications

An emission band at 2.4 eV, called the green band, is observed in most ZnO samples, no matter what growth technique is used. Sometimes this band includes fine structure, which consists mainly of doublets, repeated with a longitudinal-optical-phonon-energy spacing (72 meV). We have developed a vibronic model for the green band, based on transitions from two separate shallow donors to a deep acceptor. The donors, at energies 30 and 60 meV from the conduction-band edge, respectively, are also found from Hall-effect measurements.

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Evidence For Shallow Acceptors In Gan, D. C. Reynolds, David C. Look, B. Jogai, Richard J. Molnar Jun 2001

Evidence For Shallow Acceptors In Gan, D. C. Reynolds, David C. Look, B. Jogai, Richard J. Molnar

Physics Faculty Publications

Two low-temperature photoluminescence lines in GaN, in the region of energies commonly interpreted as longitudinal optical-phonon replicas of free excitons, donor-bound excitons, or acceptor-bound excitons, are reinterpreted as acceptor-bound excitons (A0X’s) collapsing to n=2 and n=3 excited states, respectively, of the acceptors involved. Application of this model to two sets of A0X-related lines in hydride-vapor-phase-grown GaN gives acceptor energies of 85±1, and 115±1 meV, respectively. The existence of such shallow acceptor states, if confirmed, is of great technological importance.

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Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 17, Number 9, June 2001, College Of Engineering And Computer Science, Wright State University Jun 2001

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 17, Number 9, June 2001, College Of Engineering And Computer Science, Wright State University

BITs and PCs Newsletter

An eight page newsletter created by the Wright State University College of Engineering and Computer Science that addresses the current affairs of the college.

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Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 17, Number 8, May 2001, College Of Engineering And Computer Science, Wright State University May 2001

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 17, Number 8, May 2001, College Of Engineering And Computer Science, Wright State University

BITs and PCs Newsletter

An eight page newsletter created by the Wright State University College of Engineering and Computer Science that addresses the current affairs of the college.

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Making Use Of The Most Expressive Jumping Emerging Patterns For Classification, Jinyan Li, Guozhu Dong, Kotagiri Ramamohanarao May 2001

Making Use Of The Most Expressive Jumping Emerging Patterns For Classification, Jinyan Li, Guozhu Dong, Kotagiri Ramamohanarao

Kno.e.sis Publications

Classification aims to discover a model from training data that can be used to predict the class of test instances. In this paper, we propose the use of jumping emerging patterns (JEPs) as the basis for a new classifier called the JEP-Classifier. Each JEP can capture some crucial difference between a pair of datasets. Then, aggregating all JEPs of large supports can produce a more potent classification power. Procedurally, the JEP-Classifier learns the pair-wise features (sets of JEPs) contained in the training data, and uses the collective impacts contributed by the most expressive pair-wise features to determine the class labels …

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Deep Centers In A Free-Standing Gan Layer, Z-Q. Fang, David C. Look, P. Visconti, D. F. Wang, C. Z. Lu, F. Yun, H. Morkoç, Seong-Ju S. Park, K. Y. Lee Apr 2001

Deep Centers In A Free-Standing Gan Layer, Z-Q. Fang, David C. Look, P. Visconti, D. F. Wang, C. Z. Lu, F. Yun, H. Morkoç, Seong-Ju S. Park, K. Y. Lee

Physics Faculty Publications

Schottky barrier diodes, on both Ga and N faces of a ∼300-μm-thick free-standing GaN layer, grown by hydride vapor phase epitaxy (HVPE) on Al2O3 followed by laser separation, were studied by capacitance–voltage and deep level transient spectroscopy (DLTS) measurements. From a 1/C2 vs V analysis, the barrier heights of Ni/Au Schottky contacts were determined to be different for the two polar faces: 1.27 eV for the Ga face, and 0.75 eV for the N face. In addition to the four common DLTS traps observed previously in other epitaxial GaN including HVPE-grown GaN a new trap …

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Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 17, Number 7, April 2001, College Of Engineering And Computer Science, Wright State University Apr 2001

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 17, Number 7, April 2001, College Of Engineering And Computer Science, Wright State University

BITs and PCs Newsletter

An eight page newsletter created by the Wright State University College of Engineering and Computer Science that addresses the current affairs of the college.

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Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 17, Number 6, March 2001, College Of Engineering And Computer Science, Wright State University Mar 2001

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 17, Number 6, March 2001, College Of Engineering And Computer Science, Wright State University

BITs and PCs Newsletter

An eight page newsletter created by the Wright State University College of Engineering and Computer Science that addresses the current affairs of the college.

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High Mobility In N-Type Gan Substrates, A. Saxler, David C. Look, S. Elhamri, J. R. Sizelove, William C. Mitchel, C. M. Sung, S. S. Park, K. Y. Lee Mar 2001

High Mobility In N-Type Gan Substrates, A. Saxler, David C. Look, S. Elhamri, J. R. Sizelove, William C. Mitchel, C. M. Sung, S. S. Park, K. Y. Lee

Physics Faculty Publications

No abstract provided.

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Survivability Architecture For Workflow Management Systems, Jorge Cardoso, Zongwei Luo, John A. Miller, Amit P. Sheth, Krzysztof J. Kochut Mar 2001

Survivability Architecture For Workflow Management Systems, Jorge Cardoso, Zongwei Luo, John A. Miller, Amit P. Sheth, Krzysztof J. Kochut

Kno.e.sis Publications

The survivability of critical infrastructure systems has been gaining increasing concern from the industry. The survivability research area addresses the issue of infrastructure systems that continues to provide pre-established service levels to users in the face of disorders and react to changes in the surrounding environment. Workflow management systems need to be survivable since they are used to support critical and sensitive business processes. They require a high level of dependability and should not allow process instances to be interrupted or aborted due to failures. Moreover, due to their sensitivity, business process should reflect any change in the environment. In …

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Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 17, Number 5, February 2001, College Of Engineering And Computer Science, Wright State University Feb 2001

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 17, Number 5, February 2001, College Of Engineering And Computer Science, Wright State University

BITs and PCs Newsletter

An eight page newsletter created by the Wright State University College of Engineering and Computer Science that addresses the current affairs of the college.

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Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 17, Number 4, January 2001, College Of Engineering And Computer Science, Wright State University Jan 2001

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 17, Number 4, January 2001, College Of Engineering And Computer Science, Wright State University

BITs and PCs Newsletter

An eight page newsletter created by the Wright State University College of Engineering and Computer Science that addresses the current affairs of the college.

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A "Converse" Of The Banach Contraction Mapping Theorem, Pascal Hitzler, Anthony K. Seda Jan 2001

A "Converse" Of The Banach Contraction Mapping Theorem, Pascal Hitzler, Anthony K. Seda

Computer Science and Engineering Faculty Publications

We prove a type of converse of the Banach contraction mapping theorem for metric spaces: if X is a T1 topological space and f: X -> X is a function with the unique fixed point a such that fn(x) converges to a for each x is a member of X, then there exists a distance function d on X such that f is a contraction on the complete ultrametric space (X,d) with contractivity factor 1/2. We explore properties of the resulting space (X,d).

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Generalized Metrics And Topology In Logic Programming Semantics, Pascal Hitzler Jan 2001

Generalized Metrics And Topology In Logic Programming Semantics, Pascal Hitzler

Computer Science and Engineering Faculty Publications

Many fixed-point theorems are essentially topological in nature. Among them are the Banach contraction mapping theorem on metric spaces and the fixed-point theorem for Scott-continuous mappings on complete partial orders. The latter theorem is fundamental in denotational semantics since semantic operators in most programming language paradigms satisfy its requirements. The use of negation in logic programming and non-monotonic reasoning, however, renders some semantic operators to be non-monotonic, hence discontinuous with respect to the Scott topology, and therefore invalidates the standard approach, so that alternative methods have to be sought. In this thesis, we investigate topological methods, including generalized metric fixed-point …

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Evolution Of Topology In Axi-Symmetric And 3-D Viscous Flows, Gerik Scheuermann, W. Kollmann, Xavier Tricoche, Thomas Wischgoll Jan 2001

Evolution Of Topology In Axi-Symmetric And 3-D Viscous Flows, Gerik Scheuermann, W. Kollmann, Xavier Tricoche, Thomas Wischgoll

Computer Science and Engineering Faculty Publications

No abstract provided.

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Parallel Detection Of Closed Streamlines In Planar Flows, Thomas Wischgoll, Gerik Scheuermann, Hans Hagen Jan 2001

Parallel Detection Of Closed Streamlines In Planar Flows, Thomas Wischgoll, Gerik Scheuermann, Hans Hagen

Computer Science and Engineering Faculty Publications

No abstract provided.

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Unique Supported-Model Classes Of Logic Programs, Pascal Hitzler, Anthony K. Seda Jan 2001

Unique Supported-Model Classes Of Logic Programs, Pascal Hitzler, Anthony K. Seda

Computer Science and Engineering Faculty Publications

We study classes of programs, herein called unique supported-model classes, with the property that each program in the class has a unique supported model. Elsewhere, the authors examined these classes from the point of view of operators defined relative to certain three-valued logics. In this paper, we complement our earlier results by considering how unique supported-model classes fit into the framework given by various classes of programs in several well-known approaches to semantics.

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