Physical Sciences and Mathematics Commons^™

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 12, Number 10, December 1996, 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.

Algorithms For Adapting Materialised Views In Data Warehouses, Mukesh Mohania, Guozhu Dong

Kno.e.sis Publications

In this paper we consider the problem of materialised view adaptation in data warehouses. Materialised views are important in data warehousing where they are used to speed up query processing on large amounts of data. User requirements change over time, which may change the definitions of views dynamically. For such situations, the question arises whether the materialised views should be recomputed from scratch for every change in the definition or they should be obtained by adapting old materialised views. Changes to a view definition may be expensive, if the view is recomputed from scratch. Therefore, it is worthwhile to examine …

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 12, Number 9, November 1996, College Of Engineering And Computer Science, Wright State University

BITs and PCs Newsletter

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

Effect Of Multistep Wafer-Annealing On Main Traps In Czochralski-Grown Semi-Insulating Gaas, Z-Q. Fang, David C. Look, H. Yamamoto, H. Shimakura

Physics Faculty Publications

Both multistep wafer‐annealed (MWA) and ingot‐annealed semi‐insulating (SI) GaAs wafers, grown by the Czochralski technique, are characterized by using normalized thermally stimulated current (NTSC) spectroscopy. Two main NTSC traps, T₃ at 200 K and T₅ at 140 K, which are thought to be related to arsenic vacancy defects, are found to be largely suppressed by MWA processes, especially by a new MWA process. Concomitant with a decrease of these traps, a significant increase of the threshold electrical field for both the thermal quenching of T₅ and the low‐temperature photocurrent saturation has been observed

Student Fact Book, Fall 1996, Wright State University, Office Of Student Information Systems, Wright State University

Wright State University Student Fact Books

The student fact book has general demographic information on all students enrolled at Wright State University for Fall Quarter, 1996.

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 12, Number 8, October 1996, College Of Engineering And Computer Science, Wright State University

BITs and PCs Newsletter

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

On The Portability Of Behavioral Vhdl-93, Krishnaprasad Thirunarayan, Robert Ewing

Kno.e.sis Publications

Goossens defined a structural operational semantics for a subset of VHDL-87 and proved that the parallelism present in VHDL is benign. We extend this work to include shared variables in VHDL-93 that changes the underlying semantic model. In the presence of shared variables, non-deterministic execution of VHDL-93 processes destroys the unique meaning property. We identify and characterize a class of portable VHDL-93 descriptions for which unique meaning property can be salvaged.

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 12, Number 7, September 1996, 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.

Existence And Bifurcation Of The Positive Solutions For A Semilinear Equation With Critical Exponent, Yinbin Deng, Yi Li

Yi Li

In this paper, we consider the semilinear elliptic equation[formula]Forp=2N/(N−2), we show that there exists a positive constantμ*>0 such that (∗)_μpossesses at least one solution ifμ∈(0, μ*) and no solutions ifμ>μ*. Furthermore, (∗)_μpossesses a unique solution whenμ=μ*, and at least two solutions whenμ∈(0, μ*) and 2<NN⩾6, under some monotonicity conditions onf((1.6)) we show that there exist two constants 0<μ_**⩽μ**<μ* such that problem (∗)_{μ …}

Existence And Bifurcation Of The Positive Solutions For A Semilinear Equation With Critical Exponent, Yinbin Deng, Yi Li

Mathematics and Statistics Faculty Publications

In this paper, we consider the semilinear elliptic equation[formula]Forp=2N/(N−2), we show that there exists a positive constantμ*>0 such that (∗)_μpossesses at least one solution ifμ∈(0, μ*) and no solutions ifμ>μ*. Furthermore, (∗)_μpossesses a unique solution whenμ=μ*, and at least two solutions whenμ∈(0, μ*) and 2<NN⩾6, under some monotonicity conditions onf((1.6)) we show that there exist two constants 0<μ_**⩽μ**<μ* such that problem (∗)_{μ …}

Simple Measurement Of 300 K Electron Capture Cross Section For El2 In Gaas, David C. Look, Z-Q. Fang

Physics Faculty Publications

A simple experiment involving only the measurement of dark current I_dark and 1.1 μm photocurrent I_PC in semi‐insulating (SI) GaAs allows an accurate determination of the electron capture cross section σ_n for the important defect EL2 in GaAs. For 45 SI GaAs samples, from 12 different boules, grown by three different techniques, we find that I_PC/I_dark=1.96±0.05 at 300 K. This relationship gives σ_n=1.4±0.4×10⁻¹⁶ cm², which is compared to previously estimated values.

Deep-Center Hopping Conduction In Gan, David C. Look, D. C. Reynolds, W. Kim, Ö. Aktas, A. Botchkarev, A. Salvador, H. Morkoç

Physics Faculty Publications

Molecular‐beam‐epitaxial GaN layers change from strongly conductive (ρ≂10⁻² Ω cm at 300 K) to semi‐insulating (ρ≂10⁶ Ω cm) as the N flux is increased. Layers grown at low fluxes show strong n‐type conduction, with transport in the conduction band at high temperatures and in a shallow donor band at low temperatures. For layers grown at high N fluxes, the Hall coefficients become too small to measure, suggesting hopping conduction among deep centers. The temperature‐dependent resistivity data are most consistent with multiphonon, rather than single‐phonon, hopping.

Managing Multiple Information Sources Through Ontologies: Relationship Between Vocabulary Heterogeneity And Loss Of Information, Eduardo Mena, Vipul Kashyap, Arantza Illarramendi, Amit P. Sheth

Kno.e.sis Publications

The ability to deal with a huge number of independent and heterogeneous repositories is the most critical problem in Global Information Systems. One approach to enable efficient query processing is by utilizing semantic descriptions (organized as ontologies) of such repositories whenever available.

In this context semantic relationships among ontologies can be used Query Processors. Three kind of relationships are considered: synonyms and hypernyms. Using synonyms the semantic of the query is preserved; however, when synonyms are not available and hypernyms or hyponyms are used there exists some loss of information that must be measured.

Self-Consistency: A Fundamental Concept In Statistics, Thaddeus Tarpey, Bernard Flury

Mathematics and Statistics Faculty Publications

The term ''self-consistency'' was introduced in 1989 by Hastie and Stuetzle to describe the property that each point on a smooth curve or surface is the mean of all points that project orthogonally onto it. We generalize this concept to self-consistent random vectors: a random vector Y is self-consistent for X if E[X|Y] = Y almost surely. This allows us to construct a unified theoretical basis for principal components, principal curves and surfaces, principal points, principal variables, principal modes of variation and other statistical methods. We provide some general results on self-consistent random variables, give …

On Hall Scattering Factors For Holes In Gaas, David C. Look, C. E. Stutz, J. R. Sizelove, K. R. Evans

Physics Faculty Publications

Hall scattering factors for electrons and holes in molecular beam epitaxial GaAs layers have been determined by comparing carrier concentrations measured by the Hall effect with those measured by the electrochemical capacitance–voltage technique. The conclusion is that both the electron and hole scattering factors are near unity for n ranging from 2×10¹⁶ to 7×10¹⁷ cm⁻³, and p ranging from 5×10¹⁶ to 4×10¹⁹ cm⁻³. This conclusion is consistent with the present theory for electrons, but not with that for holes.

Ground And Excited State Exciton Spectra From Gan Grown By Molecular-Beam Epitaxy, D. C. Reynolds, David C. Look, W. Kim, Ö. Aktas, A. Botchkarev, A. Salvador, H. Morkoç, D. N. Talwar

Physics Faculty Publications

The emission and reflection spectra of GaN have been investigated in the intrinsic region and the data have been interpreted in terms of the wurtzite crystal band structure. Three intrinsic exciton transitions have been observed, one associated with each of the valence bands. Exciton excited states associated with the two top valence bands were also observed. The exciton binding energies, the band-gap energies, and the exciton Bohr radii are all reported along with the dielectric constant and the spin-orbit and crystal-field parameters for GaN.

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 12, Number 6, June 1996, College Of Engineering And Computer Science, Wright State University

BITs and PCs Newsletter

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

Thermally Stimulated Current Trap In Gan, David C. Look, Z-Q. Fang, W. Kim, Ö. Aktas, A. Botchkarev, A. Salvador, H. Morkoç

Physics Faculty Publications

A thermally stimulated current peak, occurring at 100 K for a heating rate of 0.4 K/s, has been found in semi‐insulating GaN grown by molecular beam epitaxy. This peak has contributions from two traps, with the main trap described by the following parameters: emission thermal activation energy E≂90±2 meV, effective capture cross‐section σ≂3±1×10⁻²² cm⁻², and Nμτ≂3±1 × 10¹⁴ cm⁻¹ V ⁻¹, where N is the trap concentration, μ the mobility, and τ the free‐carrier lifetime. This trap is much deeper than the typical shallow donors in conducting GaN, but shallower than any …

Observer: An Approach For Query Processing In Global Information Systems Based On Interoperation Across Pre-Existing Ontologies, Eduardo Mena, Vipul Kashyap, Amit P. Sheth, Arantza Illarramendi

Kno.e.sis Publications

The huge number of autonomous and heterogeneous data repositories accessible on the “global information infrastructure” makes it impossible for users to be aware of the locations structure/organization, query languages and semantics of the data in various repositories. There is a critical need to complement current browsing, navigational and information retrieval techniques with a strategy that focuses on information content and semantics. In any strategy that focuses on information content, the most critical problem is that of different vocabularies used to describe similar information across domains. We discuss a scalable approach for vocabulary sharing. The objects in the repositories are represented …

Proof Strategies For Hardware Verification, Robert Eastham, Krishnaprasad Thirunarayan

Kno.e.sis Publications

Ascertaining correctness of digital hardware designs through simulation does not scale-up for large designs because of the sheer combinatorics of the problem. Formal verification of hardware designs holds promise because its computational complexity is of the order of number of different types of components (and not number of components in the design). This approach requires the specification of the behavior and the design in a formal language, and reason with them using a theorem prover. In this paper we attempt to develop a methodology for writing and using these specifications for some important classes of hardware circuits. We examine digital …

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 12, Number 5, May 1996, 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.

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 12, Number 4, April 1996, College Of Engineering And Computer Science, Wright State University

BITs and PCs Newsletter

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

Stability Analysis Of A Model For The Defect Structure Of Yba2cu3ox, Gregory Kozlowski, Tom Svobodny

Physics Faculty Publications

Unusual microstructures of YBa₂Cu₃O_x (123) crystals have been observed. These structures have been shown to pass very high transport currents. A model of the solidification of 123 from a melt with Y₂BaCuO₅ (211) inclusions indicates that the stability of the 123 interface can depend on the sizes of the 211 inclusions. The observed formations are interpreted in the light of this instability.

Electron Impact Vibrational Excitation Cross Sections Of Sif4, R. Nagpal, A. Garscadden, Jerry D. Clark

Physics Faculty Publications

Electron drift velocities in mixtures of SiF₄ and Ar have been measured using a pulsed‐Townsend type drift tube. A set of vibrational excitation cross sections of electron scattering in SiF₄ has been subsequently determined by the swarm analyses of measured transport data in highly dilute SiF₄−Ar mixtures. The derived cross sections are consistent with the electron transport properties over an order of magnitude in SiF₄ concentration in gas mixtures, thus providing evidence that the main features of their near threshold behavior, and of their absolute magnitude have been captured.

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 12, Number 3, March 1996, College Of Engineering And Computer Science, Wright State University

BITs and PCs Newsletter

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

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 12, Number 2, February 1996, College Of Engineering And Computer Science, Wright State University

BITs and PCs Newsletter

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

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 12, Number 1, January 1996, 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.

Spieltheorie, Alexander Chocholaty, Pascal Hitzler

Computer Science and Engineering Faculty Publications

No abstract provided.

Exact Multiplicity Results For Boundary Value Problems With Nonlinearities Generalizing Cubic, Philip Korman, Yi Li, Tiancheng Ouyang

Mathematics and Statistics Faculty Publications

No abstract provided.

A Center-Unstable Manifold Theorem For Parametrically Excited Surface Waves, Larry Turyn

Mathematics and Statistics Faculty Publications

When fluid in a rectangular tank sits upon a platform which is oscillating with sufficient amplitude, surface waves appear in the ''Faraday resonance.'' Scientists and engineers have done bifurcation analyses which assume that there is a center manifold theory using a finite number of excited spatial modes. We establish such a center manifold theorem for Xiao-Biao Lin's model in which potential flow is assumed but an artificial dissipation term is included in the system of partial differential equations on the free surface. We use interpolation spaces developed by da Prate and Grisvard, establish maximal regularity for a family of evolution …