Physical Sciences and Mathematics Commons^™

Ga-Doped Zno Films Grown On Gan Templates By Plasma-Assisted Molecular-Beam Epitaxy, H. J. Ko, Yanfang Chen, S. K. Hong, H. Wenisch, T. Yao, David C. Look

Physics Faculty Publications

We have investigated the structural and optical properties of Ga-doped ZnO films grown on GaN templates by plasma-assisted molecular-beam epitaxy. The carrier concentration in Ga-doped ZnO films can be controlled from 1.33×10¹⁸/cm³ to 1.13×10²⁰/cm³. Despite high Ga incorporation, the linewidth of (0002) ω-rocking curves of Ga-doped ZnO films still lies in the range from 5 to 15 arc min. Photoluminescence (PL) spectra of Ga-doped ZnO films show dominant near-bandedge emission with negligibly weak deep-level emission, independent of carrier concentration. The PL spectrum exhibits a new emission line at 3.358 eV, which corresponds to …

Commuting Self-Adjoint Extensions Of Symmetric Operators Defined From The Partial Derivatives, Palle Jorgensen, Steen Pedersen

Mathematics and Statistics Faculty Publications

We consider the problem of finding commuting self-adjoint extensions of the partial derivatives {(1/i)(∂/∂x_j):j=1,...,d} with domain C^∞_c(Ω) where the self-adjointness is defined relative to L²(Ω), and Ω is a given open subset of R^d.

The Expected Wet Period Of Finite Dam With Exponential Inputs, Eui Yong Lee, Kimberly Kinateder

Mathematics and Statistics Faculty Publications

We use martingale methods to obtain an explicit formula for the expected wet period of the finite dam of capacity V, where the amounts of inputs are i.i.d exponential random variables and the output rate is one, when the reservoir is not empty. As a consequence, we obtain an explicit formula for the expected hitting time of either 0 or V and a new expression for the distribution of the number of overflows during the wet period, both without the use of complex analysis.

Combined Effects Of Screening And Band Gap Renormalization On The Energy Of Optical Transitions In Zno And Gan, D. C. Reynolds, David C. Look, B. Jogai

Physics Faculty Publications

The energy positions of the optical transitions in both GaN and ZnO were investigated when the samples were excited simultaneously with a HeCd laser and an Ar⁺ ion laser. The increased number of free electrons excited by the Ar⁺ ion laser will effectively screen both the free exciton and bound exciton transitions, resulting in a blueshift. The increased number of free electrons also produces many-body effects, which lead to a reduction of the band gap energy and thus a redshift. The resultant of screening and renormalization results in a redshift of the optical transitions in ZnO but a …

Classes Of Logic Programs Which Possess Unique Supported Models, Anthony K. Seda, Pascal Hitzler

Computer Science and Engineering Faculty Publications

Logic programming is concerned with the use of logic as a programming language. The main manifestation of this computing paradigm is in the various versions of Prolog which are now available, in which computation is viewed as deduction from sets of Horn clauses, although there is also growing interest in the related form known as answer set programming, see [10]. The reference [1] contains a good survey of the growth of logic programming over the last twenty-five years both as a stand-alone programming language and as a software component of large information systems. One advantage a logic program P has …

Student Fact Book, Fall 2000, Twenty-Fourth 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, 2000.

Student Fact Book, Fall 2000, 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, 2000.

Electron Beam And Optical Depth Profiling Of Quasibulk Gan, L. Chernyak, A. Osinsky, G. Nootz, A. Schulte, J. Jasinski, M. Benamara, Z. Liliental-Weber, David C. Look, Richard J. Molnar

Physics Faculty Publications

Electron beam and optical depth profiling of thick (5.5–64 μm) quasibulk n-type GaN samples, grown by hydride vapor-phase epitaxy, were carried out using electron beam induced current (EBIC), microphotoluminescence (PL), and transmission electron microscopy (TEM). The minority carrier diffusion length, L, was found to increase linearly from 0.25 μm, at a distance of about 5 μm from the GaN/sapphire interface, to 0.63 μm at the GaN surface, for a 36-μm-thick sample. The increase in L was accompanied by a corresponding increase in PL band-to-band radiative transition intensity as a function of distance from the GaN/sapphire interface. We attribute …

Identification Of The Gamma(5) And Gamma(6) Free Excitons In Gan, D. C. Reynolds, David C. Look, B. Jogai, A. W. Saxler, Seong-Ju S. Park, J. Y. Hahn

Physics Faculty Publications

The Γ₅ and Γ₆ free excitons have been identified in GaN from emission measurements. Another emission peak is also observed which we believe to be the longitudinal free exciton. These measurements along with electrical measurements, which show the sample to have very high peak mobility, attest to the high quality of the sample.

Semantic Web And Information Brokering: Opportunities, Commercialization, And Challenges, Amit P. Sheth

Kno.e.sis Publications

From the chairs' report published in SIGMOD record: The keynote address entitled 'Semantic Web and Information Brokering: Opportunities, Early Commercializations, and Challenges' was delivered by Amit Sheth (University of Georgia and Taalee Corp). Sheth characterized semantics as the next step in the evolution of the WWW and stressed the importance of semantically organized information for supporting ubiquitous, powerful, accurate and efficient access to this information. Sheth also reviewed proposals for semantic interoperability frameworks such as the DAML(DARPA Agent Mark-Up Language), the Oingo family of tools for defining concepts and extracting knowledge from large databases, as well as several scenarios on …

A >130,000-Year-Long Pollen Record From Pittsburg Basin, Illinois, Rebecca Teed

Earth and Environmental Sciences Faculty Publications

Pittsburg Basin, in south-central Illinois, contains a sediment record extending from the present back to the end of the late Illinoian glaciation, when central Illinois was covered with Picea/Pinus forest. During the last interglaciation, a temperate deciduous forest more diverse than Holocene Quercus/Carya forest replaced the Illinoian late-glacial boreal forest. Prairie pollen types and the charcoal/pollen ratio, indicating fire frequency, temporarily increased. Then forest, with high Juniperus percentages, became dominant once more, as the charcoal/pollen ratio dropped. After the last interglaciation, the charcoal/pollen ratio increased again and prairie and wetland surrounded Pittsburg Basin through the entire Wisconsinan glacial age. The …

A Nonlinear Parabolic Equation Modelling Surfactant Diffusion, Xinfu Chen, Chaocheng Huang, Jennifer Zhao

Mathematics and Statistics Faculty Publications

An initial-boundary value problem for nonlinear parabolic equations modelling surfactant diffusions is investigated. The boundary conditions are of nonlinear adsorptive types, and the initial value has a single point jump. We study the well-posedness of the problem, the convergence of a numerical scheme, and the regularity as well as quantitative behaviour of solutions.

Photoluminescence Measurements From The Two Polar Faces Of Zno, R. E. Sherriff, D. C. Reynolds, David C. Look, B. Jogai, J. E. Hoelscher, T. C. Collins, G. Cantwell, W. C. Harsch

Physics Faculty Publications

The crystal structure of ZnO is wurtzite and the stacking sequence of atomic layers along the “c” axis is not symmetric. As a result, a ZnO crystal surface that is normal to the c axis exposes one of two distinct polar faces, with (0001̄) being considered the O face and (0001) the Zn face. Photoluminescence (PL) measurements on the two faces reveal a striking difference. Two transitions are observed in PL that are dominant from the O face and barely observed in PL from the Zn face. These lines are identified as phonon replicas of a particular D …

Exception Handling In Workflow Systems, Zongwei Luo, Amit P. Sheth, Krzysztof J. Kochut, John A. Miller

Kno.e.sis Publications

In this paper, defeasible workflow is proposed as a framework to support exception handling for workflow management. By using the “justified” ECA rules to capture more contexts in workflow modeling, defeasible workflow uses context dependent reasoning to enhance the exception handling capability of workflow management systems. In particular, this limits possible alternative exception handler candidates in dealing with exceptional situations. Furthermore, a case-based reasoning (CBR) mechanism with integrated human involvement is used to improve the exception handling capabilities. This involves collecting cases to capture experiences in handling exceptions, retrieving similar prior exception handling cases, and reusing the exception handling experiences …

Properties Of Semi‐Insulating Gaas:Fe Grown By Hydride Vapor Phase Epitaxy, E. Rodríguez Messmer, D. Söderström, P. Hult, S. Marcinkevicius, S. Lourdudoss, David C. Look

Physics Faculty Publications

In this paper we analyze GaAs grown by hydride vapor phase epitaxy (HVPE) and doped with four different iron concentrations between and . From temperature dependent current‐voltage measurements we observed the highest resistivity in the lowest doped sample. We also quantified the activation energy. These results together with those of time resolved photoluminescence measurements indicate that in the sample with the lowest Fe concentration, EL2 may be dominant. From the analysis of the time resolved photoluminescence measurements, the intrinsic EL2 concentration and the electron and hole capture cross sections of Fe in GaAs were estimated. © 2000 The Electrochemical Society. …

Strain Variation With Sample Thickness In Gan Grown By Hydride Vapor Phase Epitaxy, D. C. Reynolds, David C. Look, B. Jogai, J. E. Hoelscher, R. E. Sherriff, Richard J. Molnar

Physics Faculty Publications

High quality GaN crystals can be grown on sapphire by hydride vapor phase epitaxy. The thermal expansion mismatch between sapphire and GaN produces strain in the GaN crystal as it is cooled from the growth temperature to room temperature. The strain is evidenced by shifts in the photoluminescence and reflectance line positions. By analyzing the surface strain as the crystal thickness is increased, the thickness required to obtain zero surface strain can be estimated. This structure might provide a lattice matched and thermally matched substrate for further epitaxial growth of GaN.

Time-Resolved Photoluminescence Lifetime Measurements Of The Gamma(5) And Gamma(6) Free Excitons In Zno, D. C. Reynolds, David C. Look, B. Jogai, J. E. Hoelscher, R. E. Sherriff, M. T. Harris, M. J. Callahan

Physics Faculty Publications

Time-resolved photoluminescence spectroscopy at 2 K was used to measure the radiative recombination lifetime of the allowed (Γ₅) and forbidden (Γ₆) free excitons in ZnO. The measurements were made on a sample containing internal strain, which altered the sample symmetry, and resulted in relaxed selection rules, allowing the Γ₆ exciton to be observed. A radiative recombination lifetime of 259 ps was measured for the Γ₅ exciton and 245 ps for the Γ₆ exciton. The decay of the free excitons was of single-exponential form, and the decay times were obtained using a least-squares fit …

Electrical Properties Of Boron-Doped P-Sigec Grown On N(-)-Si Substrate, M. Ahoujja, Y. K. Yeo, R. L. Hengehold, G. S. Pomrenke, David C. Look, J. Huffman

Physics Faculty Publications

Electrical properties of fully strained boron-doped Si_0.90−yGe_0.10C_y/n⁻–Si grown by low pressure chemical vapor deposition have been investigated as a function of carbon content (0.2%–1.5%), using the variable temperature (25–650 K) Hall-effect technique. The results of Hall-effect measurements show that the Si substrate and the SiGeC/Si interfacial layer affect significantly the electrical properties of the SiGeC epitaxial layer. Thus, a three-layer conducting model has been used to extract the carrier concentration and mobility of the SiGeC layer alone. At room temperature, the hole carrier concentration decreases from 6.8×10¹⁷ to 2.4×10 …

Dimensionality Reduction Using Genetic Algorithms, Michael L. Raymer, William F. Punch, Erik D. Goodman, Leslie A. Kuhn, Anil K. Jain

Kno.e.sis Publications

Pattern recognition generally requires that objects be described in terms of a set of measurable features. The selection and quality of the features representing each pattern affect the success of subsequent classification. Feature extraction is the process of deriving new features from original features to reduce the cost of feature measurement, increase classifier efficiency, and allow higher accuracy. Many feature extraction techniques involve linear transformations of the original pattern vectors to new vectors of lower dimensionality. While this is useful for data visualization and classification efficiency, it does not necessarily reduce the number of features to be measured since each …

A New Fixed-Point Theorem For Logic Programming Semantics, Anthony K. Seda, Pascal Hitzler

Computer Science and Engineering Faculty Publications

We present a new fixed-point theorem akin to the Banach contraction mapping theorem, but in the context of a novel notion of generalized metric space, and show how it can be applied to analyse the denotational semantics of certain logic programs. The theorem is obtained by generalizing a theorem of Priess-Crampe and Ribenboim, which grew out of applications within valuation theory, but is also inspired by a theorem of S.G. Matthews which grew out of applications to conventional programming language semantics. The class of programs to which we apply our theorem was defined previously by us in terms of operators …

Dissociation Of Al2o3(0001) Substrates And The Roles Of Silicon And Oxygen In N-Type Gan Thin Solid Films Grown By Gas-Source Molecular Beam Epitaxy, J. E. Van Nostrand, J. Solomon, A. Saxler, Q. H. Xie, D. C. Reynolds, David C. Look

Physics Faculty Publications

Unintentionally doped and silicon doped GaN films prepared by molecular beam epitaxy using ammonia are investigated. Hall, secondary ion mass spectroscopy (SIMS), photoluminescence, and x-ray data are utilized for analysis of sources of autodoping of GaN epitaxial films in an effort to identify whether the n-type background electron concentration is of impurity origin or native defect origin. We identify and quantify an anomalous relationship between the Si doping concentration and free carrier concentration and mobility using temperature dependent Hall measurements on a series of 2.0-μm-thick GaN(0001) films grown on sapphire with various Si doping concentrations. SIMS is used to …

On-Line Bayesian Speaker Adaptation By Using Tree-Structured Transformation And Robust Priors, Shaojun Wang, Yunxin Zhao

Kno.e.sis Publications

This paper presents new results by using our previously proposed on-line Bayesian learning approach for affine transformation parameter estimation in speaker adaptation. The on-line Bayesian learning technique allows updating parameter estimates after each utterance and it can accommodate flexible forms of transformation functions as well as prior probability density functions. We show through experimental results the robustness of heavy tailed priors to mismatch in prior density estimation. We also show that by properly choosing the transformation matrices and depths of hierarchical trees, recognition performance improved significantly.

Zno Diode Fabricated By Excimer-Laser Doping, Toru Aoki, Yoshinori Hatanaka, David C. Look

Physics Faculty Publications

A ZnO diode was fabricated by using a laser-doping technique to form a p-type ZnO layer on an n-type ZnO substrate. A zinc-phosphide compound, used as a phosphorous source, was deposited on the ZnO wafer and subjected to excimer-laser pulses. The current–voltage characteristics showed a diode characteristic between the phosphorous-doped p-layer and the n-type substrate. Moreover, light emission, with a band-edge component, was observed by forward current injection at 110 K.

Local Properties Of Query Languages, Guozhu Dong, Leonid Libkin, Limsoon Wong

Kno.e.sis Publications

In this paper we study the expressiveness of local queries. By locality we mean — informally — that in order to check if a tuple belongs to the result of a query, one only has to look at a certain predetermined portion of the input. Examples include all relational calculus queries. We start by proving a general result describing outputs of local queries. This result leads to many easy inexpressibility proofs for local queries. We then consider a closely related property, namely, the bounded degree property. It describes the outputs of local queries on structures that locally look “simple.” Every …

On The Main Irradiation-Induced Defect In Gan, L. Polenta, Z-Q. Fang, David C. Look

Physics Faculty Publications

We show that the usual Arrhenius analysis of the main electron-irradiation-induced defect trap in n-type GaN, observed by deep-level transient spectroscopy (DLTS), is not sufficiently accurate. Instead, an exact fitting of the DLTS spectrum for this trap reveals two components, each of which has a thermal energy near 60 meV, not the apparent 140–200 meV, as given in other DLTS studies. This result resolves the discrepancy between Hall-effect and DLTS determinations of the thermal energy of this defect center.

The Space Of Jumping Emerging Patterns And Its Incremental Maintenance, Jinyan Li, Kotagiri Ramamohanarao, Guozhu Dong

Kno.e.sis Publications

The concept of jumping emerging patterns (JEPs) has been proposed to describe those discriminating features which only occur in the positive training instances but do not occur in the negative class at all; JEPs have been used to construct classifiers which generally provide better accuracy than the state-of-the-art classifiers such as C4.5. The algorithms for maintaining the space of jumping emerging patterns (JEP space) are presented in this paper. We prove that JEP spaces satisfy the property of convexity. Therefore JEP spaces can be concisely represented by two bounds: consisting respectively of the most general elements and the most specific …

Der Kontraktionssatz Auf Metrischen Raumen Und Verallgemeinerungen, Pascal Hitzler

Computer Science and Engineering Faculty Publications

No abstract provided.

Separation Property Of Solutions For A Semilinear Elliptic Equation, Yi Liu, Yi Li, Yinbin Deng

Mathematics and Statistics Faculty Publications

In this paper, we study the following elliptic problem[formula]where K(x) is a given function in C^α(ⁿ\0) for some fixed α∈(0, 1), p>1 is a constant. Some existence, monotonicity and asymptotic expansion at infinity of solutions of (*) are discussed.

Optimization Techniques For Data Intensive Decision Flows, Richard Hull, Francois Llirbat, Bharat Kumar, Gang Zhou, Guozhu Dong, Jianwen Su

Kno.e.sis Publications

For an enterprise to take advantage of the opportunities afforded by electronic commerce it must be able to make decisions about business transactions in near-real-time. In the coming era of segment-of-one marketing, these decisions will be quite intricate, so that customer treatments can be highly personalized, reflecting customer preferences, the customer's history with the enterprise, and targeted business objectives. This paper describes a paradigm called “decision flows” for specifying a form of incremental decision-making that can combine diverse business factors in near-real-time.

This paper introduces and empirically analyzes a variety of optimization strategies for decision flows that are “data-intensive”, i.e. …

Separating Auxiliary Arity Hierarchy Of First-Order Incremental Evaluation Using (3+1)-Ary Input Relations, Guozhu Dong, Louxin Zhang

Kno.e.sis Publications

Presents a first-order incremental evaluation system that uses first-order queries to maintain a database view defined by a non-first-order query. Reduction of the arity of queries to understand the power of foies; Use of a key lemma for proving a query which encodes the multiple parity problem.