Physical Sciences and Mathematics Commons^™

Si Doping Of High-Al-Mole Fraction Alxga1-Xn Alloys With Rf Plasma-Induced Molecular-Beam-Epitaxy, Jeonghyun Hwang, William J. Schaff, Lester F. Eastman, Shawn T. Bradley, Leonard J. Brillson, David C. Look, J. Wu, Wladek Walukiewicz, Madalina Furis, Alexander N. Cartwright

Physics Faculty Publications

Very high levels of n-type doping of Al_xGa_1−xN alloys were recently achieved by rf plasma-induced molecular-beam epitaxy on sapphire substrates and Si as a dopant. Electron concentrations were obtained up to 1.25×10²⁰ cm⁻³ when the Al mole fraction was 50%, and 8.5×10¹⁹ cm⁻³ electrons were measured even when the Al mole fraction was 80%. Other material properties were determined by optical absorption, photoluminescence, cathodoluminescence, x-ray diffraction, and atomic force microscopy measurements and high optical and morphological qualities were shown.

Recombination Of Excitons Bound To Oxygen And Silicon Donors In Freestanding Gan, A. Wysmolek, K. P. Korona, R. Stepniewski, J. M. Baranowsky, J. Bloniarz, M. Potemski, R. L. Jones, David C. Look, J. Kuhl, S. S. Park, S. K. Lee

Physics Faculty Publications

The neutral donor bound exciton recombination processes in freestanding GaN have been studied. The photoluminescence spectrum shows emission lines related to silicon and oxygen donors. Time-resolved luminescence allows us to correlate the principal donor bound exciton lines with their two-electron satellites. The magnetic field splitting of the two-electron lines is well described by the theory of the hydrogen atom in a magnetic field. For the oxygen donor a 1.5 meV chemical shift and a 30.8 meV effective Rydberg have been evaluated. Two-electron satellites involving excitations to the 2p and 2s donor states are separated by an energy of 1.0 and …

On Computing Condensed Frequent Pattern Bases, Jian Pei, Guozhu Dong, Wei Zou, Jiawei Han

Kno.e.sis Publications

Frequent pattern mining has been studied extensively. However, the effectiveness and efficiency of this mining is often limited, since the number of frequent patterns generated is often too large. In many applications it is sufficient to generate and examine only frequent patterns with support frequency in close-enough approximation instead of in full precision. Such a compact but close-enough frequent pattern base is called a condensed frequent patterns-base.

In this paper, we propose and examine several alternatives at the design, representation, and implementation of such condensed frequent pattern-bases. A few algorithms for computing such pattern-bases are proposed. Their effectiveness at pattern …

Web Service Technologies And Their Synergy With Simulation, Senthilanand Chandrasekaran, Gregory S. Silver, John A. Miller, Jorge Cardoso, Amit P. Sheth

Kno.e.sis Publications

The World Wide Web has had a huge influence on the computing field in general as well as simulation in particular (e.g., Web-Based Simulation). A new wave of development based upon XML has started. Two of the most interesting aspects of this development are the Semantic Web and Web Services. This paper examines the synergy between Web service technology and simulation. In one direction, Web service processes can be simulated for the purpose of correcting/improving the design. In the other direction, simulation models/components can be built out of Web services. Work on seamlessly using simulation as a part of Web …

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 19, Number 2, November 2002, 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.

Microcathodoluminescence And Electron Beam Induced Current Observation Of Dislocations In Freestanding Thick N-Gan Sample Grown By Hydride Vapor Phase Epitaxy, A. Y. Polyakov, A. V. Govorkov, N. B. Smirnov, Z-Q. Fang, David C. Look, Seong-Ju S. Park, J. H. Han

Physics Faculty Publications

Microcathodolumunescence (MCL) spectra measurements, MCL and electron beam induced current (EBIC) imaging of the freestanding n-GaN samples grown by hydride vapor phase epitaxy were made. Dark-spot defects in plan-view EBIC and MCL images and dark line defects in MCL images taken on the cleaved surface of the samples could be associated with dislocations. MCL spectra measurements in the vicinity of dislocations and in the matrix do not reveal specific luminescence bands that could be attributed to dislocations but rather suggest that dislocation regions have higher density of deep nonradiative traps.

Deep Electron And Hole Traps In Freestanding N-Gan Grown By Hydride Vapor Phase Epitaxy, A. Y. Polyakov, N. B. Smirnov, A. V. Govorkov, Z-Q. Fang, David C. Look, Seong-Ju S. Park, J. H. Han

Physics Faculty Publications

Deep level electron and hole traps were studied by means of deep level transient spectroscopy with electrical and optical injection on a freestanding thick n-GaN sample with low dislocation density. It is shown that at both the upper and the lower surface of the sample there exists a thin, ∼0.5 μm layer of damaged material with lowered concentration of electrons and enhanced density of deep centers. Deep in the bulk of the film the densities of the majority of the electron and hole traps are shown to be very low, but measurably higher on the lower face (N face), …

Student Fact Book, Fall 2002, Twenty-Sixth Annual Edition, 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, 2002.

Student Fact Book, Fall 2002, Wright State University Lake Campus, 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 Lake Campus for Fall Quarter, 2002.

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 19, Number 1, October 2002, College Of Engineering And Computer Science, Wright State University

BITs and PCs Newsletter

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

Semantic Web Services And Processes: Semantic Composition And Quality Of Service, Jorge Cardoso, Chistoph Bussler, Amit P. Sheth, Dieter Fensel

Kno.e.sis Publications

Web Services are increasingly being adapted by Enterprises as the new approach to component-based solutions for enterprise applications. They hold potential to transform Web from a collection of information resources to a distributed computing platform. Many enterprise applications, including those supporting e-commerce take a form of processes, which need to be created from individual Web Services and other software components.

Thermoelectric Effect Spectroscopy Of Deep Levels In Semi-Insulating Gan, U. V. Desnica, M. Pavlovic, Z-Q. Fang, David C. Look

Physics Faculty Publications

The report of thermoelectric effect spectroscopy (TEES) applied on semi-insulating GaN was presented. The type of TEES setup, especially suitable for film-on-substrate samples, was devised. TEES enabled determination of sign of observed deep traps. Using TEES and thermally stimulated current spectroscopy measurements in combination with the simultaneous multiple peak analysis formalism all important trap parameters were determined. The shallowest identified electron and hole traps had activation energies E_c−0.09 eV and E_v+0.167 eV, respectively. Results indicate that both these traps, oppositely charged are present in the studied material in relatively high concentrations causing the electrical compensation and …

Matroid Duality From Topological Duality In Surfaces Of Nonnegative Euler Characteristic, Dan Slilaty

Mathematics and Statistics Faculty Publications

Let G be a connected graph that is 2-cell embedded in a surface S, and let G* be its topological dual graph. We will define and discuss several matroids whose element set is E(G), for S homeomorphic to the plane, projective plane, or torus. We will also state and prove old and new results of the type that the dual matroid of G is the matroid of the topological dual G*.

Representation Of A Quantum Ensemble As A Minimal Set Of Pure States, Thomas E. Skinner, Steffen J. Glaser

Physics Faculty Publications

The density matrix ρ for an n-level system is decomposed into the minimum number of pure states necessary to calculate physical observables. The corresponding physical system is first represented by a set B of n pure states |β_i〉, together with their statistical weights. The time evolution of the system is therefore calculated as B(t)=UB(t₀), with the propagator U operating on each member of the set, in contrast to the more laborious ρ(t)=Uρ(t₀)U^†. At least one of the states can be eliminated from the set by reducing its weight to zero via a …

Characterization Of Homoepitaxial P-Type Zno Grown By Molecular Beam Epitaxy, David C. Look, D. C. Reynolds, C. W. Litton, R. L. Jones, D. B. Eason, G. Cantwell

Physics Faculty Publications

An N-doped, p-type ZnO layer has been grown by molecular beam epitaxy on an Li-diffused, bulk, semi-insulating ZnO substrate. Hall-effect and conductivity measurements on the layer give: resistivity = 4×10¹ Ω cm; hole mobility = 2 cm²/V s; and hole concentration = 9×10¹⁶ cm⁻³. Photoluminescence measurements in this N-doped layer show a much stronger peak near 3.32 eV (probably due to neutral acceptor bound excitons), than at 3.36 eV (neutral donor bound excitons), whereas the opposite is true in undoped ZnO. Calibrated, secondary-ion mass spectroscopy measurements show an N surface concentration of about …

Applying Xml/Xslt Technology: A Case Study, Krishnaprasad Thirunarayan

Kno.e.sis Publications

Typically, paper-based semi-structured documents are used to communicate technical requirements in the industry. One approach to improving the efficiency and flexibility of searching and manipulating these documents is to obtain them in electronic form, and then make explicit the technical content in a form amenable to pattern matching and symbol manipulation. This paper explores the role of XML Technology for these purposes: the use of XML language to make explicit the content of a document in a standard fashion, and the use of XSLT to manipulate the content and mediate between applications that need this content. In order to recognize …

Implementing Qos Management For Workflow Systems, Jorge Cardoso, Amit P. Sheth, Krzysztof J. Kochut

Kno.e.sis Publications

Workflow management systems (WfMSs) have been used to support various types of business processes. As organizations adopt new working models, such as e-commerce, new challenges arise for workflow systems. One such challenge is that of quality of service (QoS) management. QoS management includes mechanisms that specify, compute, monitor, and control the quality of service of the products or services to be delivered. A good management of QoS directly impacts the success of organizations participating in e-commerce activities by better fulfilling customer expectations and achieving customer satisfaction. In this paper we present an implementation of a comprehensive QoS model for workflows …

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 18, Number 9, June 2002, 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.

Semi-Automatic Content Extraction From Specifications, Krishnaprasad Thirunarayan, Aaron Berkovich, Dan Z. Sokol

Kno.e.sis Publications

Specifications are critical to companies involved in complex manufacturing. The constant reading, reviewing, and analysis of materials and process specifications is extremely labor-intensive, quality impacting, and time-consuming. A conceptual design for a tool that provides computer-assistance in the interpretation of specification requirements has been created and a strategy for semantic-markup, which is the overlaying of abstract syntax (“the essence”) on the text, has been developed. The solution is based on the techniques for Information Extraction and the XML technology, and it captures the specification content within a semantic ontology. The working prototype of the tool being built will serve as …

Towards Peer-To-Peer Semantic Web: A Distributed Environment For Sharing Semantic Knowledge On The Web, Madhan Arumugam, Amit P. Sheth, I. Budak Arpinar

Kno.e.sis Publications

The real value of Semantic Web vision can be demonstrated if people and applications can create and discover new and interesting knowledge and share this knowledge in a transparent manner similar to the way data is exchanged today. Therefore, we believe that Semantic Web will consist of a distributed environment of shared and interoperable ontologies, which have emerged as common formalisms for knowledge representation. The users will need to discover new ontologies, which are not known to them before and use them to either annotate the content or to formulate their information requests. This requires an environment that supports creating, …

On The Existence Of Multiple Positive Solutions For A Semilinear Problem In Exterior Domains, Yinbin Deng, Yi Li

Yi Li

In this paper, we study the existence and nonexistence of multiple positive solutions for problem where Ω=^N\ω is an exterior domain in ^N, ω⊂^N is a bounded domain with smooth boundary, and N>2. μ⩾0, p>1 are some given constants. K(x) satisfies: K(x)∈C^α_loc(Ω) and ∃C, ϵ, M>0 such that |K(x)|⩽C |x|^l for any |x|⩾M, with l⩽ −2−ϵ. Some existence and …

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 18, Number 8, May 2002, 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.

On The Existence Of Multiple Positive Solutions For A Semilinear Problem In Exterior Domains, Yinbin Deng, Yi Li

Mathematics and Statistics Faculty Publications

In this paper, we study the existence and nonexistence of multiple positive solutions for problem where Ω=^N\ω is an exterior domain in ^N, ω⊂^N is a bounded domain with smooth boundary, and N>2. μ⩾0, p>1 are some given constants. K(x) satisfies: K(x)∈C^α_loc(Ω) and ∃C, ϵ, M>0 such that |K(x)|⩽C |x|^l for any |x|⩾M, with l⩽ −2−ϵ. Some existence and …

Deep Hole Traps In N-Gan Films Grown By Hydride Vapor Phase Epitaxy, A. Y. Polyakov, N. B. Smirnov, A. V. Govorkov, Z-Q. Fang, David C. Look, Richard J. Molnar, A. V. Osinsky

Physics Faculty Publications

Concentrations of deep hole traps were measured in a set of hydride vapor phase epitaxy grown samples with thicknesses varying from 2.6 to 68 μm. Results were obtained from low temperature capacitance–voltage measurements before and after illumination and from deep level transient spectroscopy measurements with optical injection (ODLTS). The former revealed the presence of high densities (∼10¹⁵ to 10¹⁶ cm⁻³) of hole traps whose concentration decreased with sample thickness in a manner similar to that found for the dislocation density. Capacitance versus temperature measurements in the dark and after illumination suggested that these traps form a …

Depth-Dependent Investigation Of Defects And Impurity Doping In Gan/Sapphire Using Scanning Electron Microscopy And Cathodoluminescence Spectroscopy, X. L. Sun, S. H. Goss, L. J. Brillson, David C. Look, Richard J. Molnar

Physics Faculty Publications

Cathodoluminescence (CL) imaging and temperature-dependent cathodoluminescence spectroscopy (CLS) have been used 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 imaging, CLS, and CL imaging show systematic variations in defect emissions with 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 out-diffusion from Al₂O₃ into GaN over hundreds of nanometers. Low-temperature CL spectra exhibit a new donor level …

Modeling Quality Of Service For Workflows And Web Service Processes, Jorge Cardoso, John A. Miller, Amit P. Sheth, Jonathan Arnold

Kno.e.sis Publications

Workflow management systems (WfMSs) have been used to support various types of business processes for more than a decade now. In workflows for e-commerce and Web-services applications, suppliers and customers define a binding agreement or contract between the two parties, specifying Quality of Service (QoS) items such as products or services to be delivered, deadlines, quality of products, and cost of services. The management of QoS metrics directly impacts the success of organizations participating in e-commerce. Therefore, when services or products are created or managed using workflows, the underlying workflow system must accept the specifications and be able to estimate, …

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 18, Number 7, April 2002, 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.

Topology Tracking For The Visualization Of Time-Dependent Two-Dimensional Flows, Xavier Tricoche, Thomas Wischgoll, Gerik Scheuermann, Hans Hagen

Computer Science and Engineering Faculty Publications

The paper presents a topology-based visualization method for time-dependent two-dimensional vector fields. A time interpolation enables the accurate tracking of critical points and closed orbits as well as the detection and identification of structural changes. This completely characterizes the topology of the unsteady flow. Bifurcation theory provides the theoretical framework. The results are conveyed by surfaces that separate subvolumes of uniform flow behavior in a three-dimensional space–time domain.

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 18, Number 6, March 2002, 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 18, Number 5, February 2002, 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.