Physical Sciences and Mathematics Commons^™

A Fast Scan Submillimeter Spectroscopic Technique, Douglas T. Petkie, Thomas M. Goyette, Ryan P. A. Bettens, Sergei P. Belov, Sieghard Albert, Paul Helminger, Frank C. De Lucia

Physics Faculty Publications

A new fast scan submillimeter spectroscopic technique (FASSST) has been developed which uses a voltage tunable backward wave oscillator (BWO) as a primary source of radiation, but which uses fast scan (~10⁵ Doppler limited resolution elements/s) and optical calibration methods rather than the more traditional phase or frequency lock techniques. Among its attributes are (1) absolute frequency calibration to ~1/10 of a Doppler limited gaseous absorption linewidth (<0.1 MHz, 0.000 003 cm^-1), (2) high sensitivity, and (3) the ability to measure many thousands of lines/s. Key elements which make this system possible include the excellent short term spectral purity of the …

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 13, Number 4, April 1997, 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.

Microscopic Nature Of Thermally Stimulated Current And Electrical Compensation In Semi-Insulating Gaas, S. Kuisma, K. Saarinen, P. Hautojarvi, Z-Q. Fang, David C. Look

Physics Faculty Publications

No abstract provided.

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 13, Number 3, March 1997, 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.

Some Relationships Between Foies And Sigma 1 1 Arity Hierarchies, Guozhu Dong, Limsoon Wong

Kno.e.sis Publications

No abstract provided.

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 13, Number 2, February 1997, 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.

Optical Properties Of Gan Grown On Zno By Reactive Molecular Beam Epitaxy, F. Hamdani, A. Botchkarev, W. Kim, H. Morkoç, M. Yeadon, J. M. Gibson, S.-C. Y. Tsen, David J. Smith, Donald C. Reynolds, David C. Look, K. R. Evans, Cole W. Litton, William C. Mitchel, P. Hemenger

Physics Faculty Publications

High quality wurtzite GaN epilayers have been grown on ZnO(0001) substrates by reactive molecular beam epitaxy. Photoluminescence and reflectivity measurements point to high quality presumably due to the near match of both the crystal lattice parameter and the stacking order between GaN and ZnO. In addition, the good films lack the characteristic yellow photoluminescence band. Any misorientation of the GaN epilayer planes with respect to the ZnO substrate is not detectable with polarized reflectivity. The x-ray double crystal diffraction measurements indicate this misorientation is much smaller than those for GaN epilayers on SiC and Al₂O₃ . © …

Structural Issues In Active Rule Systems, James Bailey, Guozhu Dong, Kotagiri Ramamohanarao

Kno.e.sis Publications

Active database systems enhance the functionality of traditional databases through the use of active rules or ‘triggers’. There is little consensus, though, on what components should be included in a rule system. In this paper, the expressive power of some simple active database rule systems is examined and the effect of choosing different features studied. Four important parameters of variation are presented, namely the rule language, the external query language, the meta rule language and the pending rule structure. We show that each of these is highly influential in determining the expressiveness of the rule system as a whole, and …

An Error Handling Framework For The Orbwork Workflow Enactment Service Of Meteor, Davasish Worah, Amit P. Sheth, Krzysztof J. Kochut, John A. Miller

Kno.e.sis Publications

Workflow Management Systems (WFMSs) can be used to re-engineer, streamline, automate, and track organizational processes involving humans and automated information systems. However, the state-of-the-art in workflow technology suffers from a number of limitations that prevent it from being widely used in large-scale mission critical applications. Error handling is one such issue. What makes the task of error handling challenging is the need to deal with errors that appear in various components of a complex distributed application execution environment, including various WFMS components, workflow application tasks of different types, and the heterogeneous computing infrastructure.

In this paper, we discuss a top-down …

Topology And Logic Programming Semantics, Pascal Hitzler

Computer Science and Engineering Faculty Publications

Logic programming employs logic as a programming language. Thus a logic program consists of a set of clauses of a certain form most often a subset of the clauses of first order logic viewed as axioms. Computation in this paradigm is deduction from these axioms via some interpreter.

Logic programming semantics is concerned with background theory for logic programming. It tries to provide models for logic programs to give them their intended meaning and to connect them with practically implementable interpreters.

Travelling Fronts In Cylinders And Their Stability, Jerrold W. Bebernes, Comgming Li, Yi Li

Mathematics and Statistics Faculty Publications

No abstract provided.

Depth Measurement Of Doped Semiconductors Using The Hall Technique, G. C. Desalvo, David C. Look, Christopher A. Bozada, J. L. Ebel

Physics Faculty Publications

No abstract provided.

Identification Of Electron-Irradiation Defects In Semi-Insulating Gaas By Normalized Thermally Stimulated Current Measurements, David C. Look, Z-Q. Fang, Joseph W. Hemsky, P. Kengkan

Physics Faculty Publications

No abstract provided.

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 13, Number 1, January 1997, 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.

Eigenfunction And Harmonic Function Estimates In Domains With Horns And Cusps, Michael Cranston, Yi Li

Mathematics and Statistics Faculty Publications

No abstract provided.

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

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 …}

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.

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.

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.