Physical Sciences and Mathematics Commons^™

Specifying Interdatabase Dependencies In A Multidatabase Environment, Marek Rusinkiewicz, Amit P. Sheth, George Karabatis

Kno.e.sis Publications

The problem of interdatabase dependencies and the effect they have on applications updating interdependent data are addressed. A model that allows specifications of constraints among multiple databases in a declarative fashion is proposed. The separation of the constraints from the application programs facilitates the maintenance of data constraints and allows flexibility in their implementation. It allows investigation of various mechanisms for enforcing the constraints, independently of the application programs. By grouping the constraints together, it is possible to check their completeness and discover possible contradictions among them. The concepts of polytransactions, which use interdatabase dependencies to generate a series of …

On Compensation And Conductivity Models For Molecular-Beam-Epitaxial Gaas Grown At Low-Temperature, David C. Look

Physics Faculty Publications

Molecular‐beam‐epitaxial GaAs grown at 200 °C has an extremely high (≳10¹⁹ cm⁻³) concentration of As_Ga defects and, after an anneal at 550–600 °C, a high concentration of As precipitates. The relative roles of the As_Ga defects and As precipitates in compensation and conductivity is controversial. Here criteria are developed to distinguish between two existing models.

Boundary C1, Α Regularity For Variational Inequalities, Fang-Hua Lin, Yi Li

Mathematics and Statistics Faculty Publications

No abstract provided.

Analysis And Finite-Element Approximation Of Optimal-Control Problems For The Stationary Navier-Stokes Equations With Distributed And Neumann Controls, Max D. Gunzburger, L. Hou, Tom Svobodny

Mathematics and Statistics Faculty Publications

We examine certain analytic and numerical aspects of optimal control problems for the stationary Navier-Stokes equations. The controls considered may be of either the distributed or Neumann type; the functionals minimized are either the viscous dissipation or the L⁴-distance of candidate flows to some desired flow. We show the existence of optimal solutions and justify the use of Lagrange multiplier techniques to derive a system of partial differential equations from which optimal solutions may be deduced. We study the regularity of solutions of this system. Then, we consider the approximation, by finite element methods, of solutions of the …

Infrared Quenching And Thermal Recovery Of Thermally Stimulated Current Spectra In Gaas, Z-Q. Fang, David C. Look

Physics Faculty Publications

Thermally stimulated current (TSC) spectra stimulated by infrared (hν≤1.12 eV) light at 90 K have been used to study the photoquenching and thermal recovery of several dominant TSC peaks in Ga‐rich, semi‐insulating GaAs. The filling‐pulse‐length dependence of the quenching for these traps, and the temperature dependence of their recovery are clearly identified with the ground‐to‐metastable state transition of EL2. The data are consistent with the traps having a direct association with EL2 or EL2∗ rather than an indirect association which could result from a change in the dominant‐free carriers as EL2 transforms to EL2∗. If so, they likely …

Comparison Of Deep Centers In Semiinsulating Liquid-Encapsulated Czochralski And Vertical-Gradient Freeze Gaas, Z-Q. Fang, David C. Look

Physics Faculty Publications

Three‐inch, semi‐insulating (SI) GaAs, grown by the vertical gradient freeze (VGF) technique, has been studied by IR absorption, temperature‐dependent dark current and Hall‐effect, thermally stimulated current (TSC), and photoinduced current transient spectroscopy and has been compared with undoped, SI GaAs, both As‐rich and Ga‐rich, grown by the high‐pressure liquid‐encapsulated Czochralski method. The results clearly indicate that (1) the VGF GaAs contains less EL2, which suggests a less As‐rich crystal stoichiometry; (2) in some VGF samples activation energies of 0.43 or 0.46 eV are deduced from temperature‐dependent carrier concentration or resistivity measurements, respectively, and (3) VGF samples often show a thermal …

On-Wafer Hall-Effect Measurement System, P. D. Mumford, David C. Look

Physics Faculty Publications

A novel system capable of making on‐wafer Hall‐effect measurements of a patterned wafer during the fabrication sequence has been developed. A flat, powerful rare‐earth magnet provides the magnetic field required. The wafer need only have van der Pauw patterns available for on‐wafer measurement capability. Measurement of room temperature Hall mobility can quickly and easily be obtained, making possible detailed study of carrier concentration and mobility variations during wafer fabrication.

On The Relationship Between Parsimonious Covering And Boolean Minimization, Venu Dasigi, Krishnaprasad Thirunarayan

Kno.e.sis Publications

Minimization of Boolean switching functions is a basic problem in the design of logic circuits. The designer first comes up with a switching function expressed in terms of several binary input variables that satisfies the desired functionality, and then attempts to minimize the function as a sum of products or product of sums. It turns out that a sum of products form of a switching function that has no redundancy is a union of prime implicants of the function.

In this paper we would like to explicate some of the relationships of the boolean minimization problem to a formalization of …

On Serializability Of Multidatabase Transactions Through Forced Local Conflict, Dimitrios Georgakopoulos, Marek Rusinkiewicz, Amit P. Sheth

Kno.e.sis Publications

The main difficulty in enforcing global serializability in a multidatabase environment lies in resolving indirect transitive conflicts between multidatabase transactions. Indirect conflicts introduced by local transactions are difficult to resolve because the behavior or even the existence of local transactions is not known to the multidatabase system. To overcome these problems, we propose to incorporate additional data manipulation operations in the subtransactions of each multidatabase transaction. We show that if these operations create direct conflicts between subtransactions at each participating local database system, indirect conflicts can be resolved even if the multidatabase system is not aware of their existence. Based …

The Architecture Of Braid: A System For Bridging Al/Db Systems, Amit P. Sheth, Anthony B. O'Hare

Kno.e.sis Publications

We describe the design of BrAID (a Bridge between Artificial Intelligence and Database Management Systems), an experimental system for the efficient integration of logic based Artificial Intelligence (Al) and database (DB) technologies. Features provided by BrAID include (a) access to conventional DBMSs, (b) support for multiple inferencing strategies, (c) a powerful caching subsystem that manages views and employs subsumption to facilitate the reuse of previously cached data, (d) lazy or eager evaluation of queries submitted by the AI system, and (e) the generation of advice by the AI system to aid in cache management and query execution planning. To discuss …

The Jovian Ionospheric E Region, Y. H. Kim, Jane L. Fox

Physics Faculty Publications

We have constructed a model of the Jovian ionosphere that includes direct photoionization of hydrocarbon molecules. A high resolution solar spectrum was synthesized from Hinteregger's solar maximum spectrum (F79050N) and high resolution cross sections for photoabsorption by H₂ bands in the range 842 to 1116 Å were constructed. Two strong solar lines and about 30% of the continuum flux between 912 and 1116 Å penetrate below the methane homopause despite strong absorption by CH₄ and H₂. We find that hydrocarbons (mainly C₂H₂) are ionized at a maximum rate of 55 cm^{−3 …}

Analysis And Finite Element Approximation Of Optimal Control Problems For The Stationary Navier-Stokes Equations With Dirichlet Controls, M. D. Gunzburger, L. S. Hou, Tom Svobodny

Mathematics and Statistics Faculty Publications

Optimal control problems for the stationary Navier-Stokes equations are examined from analytical and numerical points of view. The controls considered are of Dirichlet type, that is, control is effected through the velocity field on (or the mass flux through) the boundary; the functionals minimized are either the viscous dissipation or the L4-distance of candidate flows to some desired flow. We show that optimal solutions exist and justify the use of Lagrange multiplier techniques to derive a system of partial differential equations from which optimal solutions may be deduced. We study the regularity of solutions of this system. The n, finite …

Student Fact Book, Fall 1991, 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, 1991.

The Venus Ultraviolet Aurora: A Soft Electron Source, Jane L. Fox, A. I. F. Stewart

Physics Faculty Publications

The Pioneer Venus Orbiter Ultraviolet Spectrometer has recorded continuous but variable emissions of atomic oxygen at 1304 and 1356 Å in images of the nightside of Venus. We show that the observed intensities are consistent with the presence of precipitation of soft electrons into the nightside thermosphere. Model calculations are presented in which upper and lower limits to the magnitude of the electron flux necessary to produce the observed intensities are derived. Constraints are imposed on the energy spectrum of the electrons by the measured ion densities and by the predicted intensities of other emissions that have not been detected.