Digital Commons Network^™

Direct Simulation Monte Carlo For Thin Film Bearings, Alejandro Garcia, B. Alder, F. J. Alexander

Faculty Publications

The direct simulation Monte Carlo (DSMC) scheme is used to study the gas flow under a read/write head positioned nanometers above a moving disk drive platter (the slider bearing problem). In most cases, impressive agreement is found between the particle-based simulation and numerical solutions of the continuum hydrodynamic Reynolds equation which has been corrected for slip. However, at very high platter speeds the gas is far from equilibrium, and the load capacity for the slider bearing cannot be accurately computed from the hydrodynamic pressure.

Primary Decomposition Of Torsion R[X]-Modules, William A. Adkins

Faculty Publications

This paper is concerned with studying hereditary properties of primary decompositions of torsion R[X]-modules M which are torsion free as R-modules. Specifically, if an R[X]-submodule of M is pure as an R-submodule, then the primary decomposition of M determines a primary decomposition of the submodule. This is a generalization of the classical fact from linear algebra that a diagonalizable linear transformation on a vector space restricts to a diagonalizablc linear transformation of any invariant subspace. Additionally, primary decompositions are considered under direct sums and tensor product. © 1994, Hindawi Publishing Corporation. All rights reserved.

Extended Loops: A New Arena For Nonperturbative Quantum Gravity, Cayetano Di Bartolo, Rodolfo Gambini, Jorge Griego, Jorge Pullin

Faculty Publications

We propose a new representation for gauge theories and quantum gravity. Alternatively, it can be viewed as a new framework for doing computations in the loop representation. It is based on the use of a novel mathematical structure that extends the group of loops into a Lie group. This extension allows the use of functional methods to solve the diffeomorphism and Hamiltonian constraint equations. It puts in a precise framework some of the regularization problems of the loop representation. It has practical advantages in the search for quantum states. Making use of it we are able to find a new …

Late-Time Behavior Of Stellar Collapse And Explosions. Ii. Nonlinear Evolution, Carsten Gundlach, Richard H. Price, Jorge Pullin

Faculty Publications

We compare the predictions of linearized theory for the radiation produced in the collapse of a spherically symmetric scalar field with a full numerical integration of the Einstein equations. We find power-law tails and quasinormal ringing remarkably similar to predictions of linearized theory even in cases where nonlinearities are crucial. We also show that power-law tails develop even when the collapsing scalar field fails to produce a black hole. © 1994 The American Physical Society.

Colliding Black Holes: The Close Limit, Richard H. Price, Jorge Pullin

Faculty Publications

The problem of the mutual attraction and joining of two black holes is of importance as both a source of gravitational waves and as a testbed of numerical relativity. If the holes start out close enough that they are initially surrounded by a common horizon, the problem can be viewed as a perturbation of a single black hole. We take initial data due to Misner for close black holes, apply perturbation theory, and evolve the data with the Zerilli equation. The computed gravitational radiation agrees with and extends the results of full numerical computations. © 1994 The American Physical Society.

Several Considerations Regarding The Variable Length Blade Rotor, Bogdan Popescu, Victor Giurgiutiu

Faculty Publications

No abstract provided.

A Comparison Of Pedagogical Knowledge Structures Of Preservice Students And Teacher Educators In Two Institutions, Judith E. Rink, Karen E. French, Amelia M. Lee, Melinda A. Solomon, Susan K. Lynn

Faculty Publications

Understanding how the knowledge structures of preservice teachers develop as expertise is acquired would seem to be an important aspect of teacher preparation. The purpose of this study was to compare the pedagogical knowledge structures about effective teaching of preservice teachers and teacher educators in the professional preparation programs of two different institutions. Two groups of preservice teachers at two different points in their preparation program at each of the two institutions were asked to complete a concept map (Roehler et al., 1987) about effective teaching. One group completed the concept map just after the first teaching methods course, and …

Tao Of Jurisprudence: Chaos, Brain Science, Synchronicity, And The Law, Thomas Geu

Faculty Publications

No abstract provided.

United States Supreme Court: 1993-94 Term, Paul C. Giannelli

Faculty Publications

No abstract provided.

Paying For The Deal: An Analysis Of Analysis Of Wire Transfer Law And International Financial Market Interest Groups, Raj Bhala

Faculty Publications

No abstract provided.

Effect Of Proton Diffusion, Electron Conductivity, And Charge-Transfer Resistance On Nickel Hydroxide Discharge Curves, John W. Weidner, Paul Timmerman

Faculty Publications

Constant-current discharge curves for the nickel hydroxide electrode are simulated assuming resistances due to diffusion of protons and conduction of electrons through the nickel hydroxide film, and charge-transfer resistance at the film/electrolyte interface contribute to the polarization losses of the electrode. Good qualitative agreement is observed between the model predictions and experimental discharge curves. The results suggest that polarization losses due to diffusional limitations of protons is a critical factor in determining the characteristics of the discharge curve. Ohmic resistance has a significant effect on the discharge curves at the end of discharge, and charge-transfer resistance is a minor contributor …

Theoretical Analysis Of The Discharge Performance Of A Niooh/H2 Cell, Z. Mao, P. De Vidts, Ralph E. White, John Newman

Faculty Publications

A mathematical model is presented for the discharge of a NiOOH/H₂ cell. This model includes diffusion and migration in the electrolyte phase as well as proton diffusion and ohmic drop across the solid active material in the porous nickelelectrode. A theoretical analysis of the cell performance is presented for different design parameters using this model. It is predicted that proton diffusion in the solid active material is the main factor in limiting the cell voltage and the utilizationof the active material. It is also predicted that use of a thick nickel electrode is an effective method for increasing electrode …

Toil Of The Firestarters, Peter A. Alces

Faculty Publications

No abstract provided.

Presenting Italian Comparative And Superlative Forms Of Adjectives To College L2 Beginners, Ilona Klein

Faculty Publications

This study treats the necessity to de-emphasize the focus on grammar teaching alone in L2, and to introduce methods which are not teacher-centered, so as to enable students to interact more among each other.

By using comparative and superlative forms of adjectives – but in reality using a sequence of teaching techniques that could be applied to other grammatical situations – this article presents the use of sea shells as a visual and tactile aid which allows students to shift their L2 efforts from an abstract notion to a concrete usage.

This study offers a tool to attempt a balance …

The Bespeaks Caution Doctrine: Revisiting The Application Of Federal Securities Law To Opinions And Estimates, Royce De R. Barondes

Faculty Publications

Disclosure of estimates and opinions, which are often referred to as ‘soft information,‘ has presented a number of difficult issues to courts, the Securities and Exchange Commission (SEC) and companies issuing offering materials or required to file periodic reports with the SEC. Although this type of information often consists of projections, historical financial statements also include this type of information to varying degrees. For example, a bank's statement of financial position requires specification of loan loss reserves and is therefore dependent on an assessment of future events (the timing and extent of repayment). Similarly, determination of the timing of a …

Microscopic Simulation Of Dilute Gases With Adjustable Transport Coefficients, Alejandro Garcia, F. Baras, M. Malek Mansour

Faculty Publications

The Bird algorithm is a computationally efficient method for simulating dilute gas flows. However, due to the relatively large transport coefficients at low densities, high Rayleigh or Reynolds numbers are difficult to achieve by this technique. We present a modified version of the Bird algorithm in which the relaxation processes are enhanced and the transport coefficients reduced, while preserving the correct equilibrium and nonequilibrium fluid properties. The present algorithm is found to be two to three orders of magnitude faster than molecular dynamics for simulating complex hydrodynamical flows.

Oscillator Strengths For Fe Ii Transitions At 224.918 And 226.008 Nanometers, Scott D. Bergeson, K. L. Mullman, J. E. Lawler

Faculty Publications

We report accurate experimental absorption oscillator strengths (f-values) for transitions out of the ground level of Fe II to the z⁴D^o_7/2 and z⁴D^o_9/2 levels at 224.918 and 226.008 nm (air wavelengths) to be 0.00182(14) and 0.00244(19), respectively. The number in parenthesis is the uncertainty in the last digits. These two lines are important for studying Fe abundances and grain depletions in the interstellar medium. These f-values are determined by combining emission branching fractions with radiative lifetimes. Branching fractions are measured using classical spectroradiometry on an optically thin source. Radiative lifetimes are from …

Using Computer Conferencing Technology To Assist Collaboration Between Higher Education Faculty; Student Teachers And K-12 Practitioners, Richard Stahlhut, Richard R. Hawkes

Faculty Publications

The College of Education at the University of Northern Iowa (UNI) created collaborative partnerships with nine major school districts in Iowa in order to establish several kinds of relationships between practitioners and university faculty which computer networks facilitated. A new "Cobra" computer conference system was expanded to the nine regional off-campus centers where UNI student teachers were working; and modem-equipped portable computers were linked to the campus through a WATTS telephone line. Personnel; including field-based personnel and practitioners; were then able to communicate with nearly all offices on UNI campus through E-mail and computer conferences. Further programs have recruited teachers …

What Educators Want In A Master's Program: A Practitioner's Perspective, Mary J. Selke

Faculty Publications

A constructivist practitioner's masters program in professional development (PDMA) was designed and piloted at the University of Northern Iowa. The program provides an option for pursuing a master's in education structured upon the following constructivism-focused framework of components: (1) the program is designed for experienced educators; and all coursework is applicable to the classroom; (2) classrooms serve as field-based learning laboratories; (3) students progress through the program in cohort groups; (4) professors collaborate in teaching teams to deliver an articulated curriculum; (5) electives; seminars; and practice foster individualization within a community of learners; (6) exit outcomes reflect the linkage of …

Development Of Strength Theories For Random Fiber Composites, Victor Giurgiutiu

Faculty Publications

A ressessment of existing theories for calculating the strength of random and quasi-random fiber composites is presented. Fundamental aspects regarding the physical model, macromechanics analysis, fiber distribution functions, generalized failure criterion, and progressive versus sudden failure models are covered first. Progressive ductile failure, progressive brittle failure, and sudden brittle failure are treated in detail. In each case, the original theory is briefly reviewed, and then its extensions accompanied by numerical examples are presented. Several limitations originally imposed by Hahn, such as the monotonically nonincreasing requirement on the failure strain curve, are lifted and the mathematical formulations are generalized. Some common …

Plate Motions In The North Andean Region, Jeffrey T. Freymueller, James N. Kellogg, Victor Vega

Faculty Publications

Repeated geodetic measurements with the Global Positioning System (GPS) provide direct measurements of displacements due to plate motions and active crustal deformation in Central America and northern South America, an area of complex interaction of the Nazca, Cocos, Caribbean and South American plates. The displacement rates for the period 1988-1991, obtained from the results of the first three Central And South America (CASA) GPS campaigns, are in general agreement with the predictions of the NUVEL-1 plate motion model, but there are differences in detail between the observations and the model. The Nazca-North Andes convergence rate vector measured by GPS is …

On Stationary And Moving Interface Cracks With Frictionless Contact In Anisotropic Bimaterials, Xiaomin Deng

Faculty Publications

The asymptotic structure of near-tip fields around stationary and steadily growing interface cracks, with frictionless crack surface contact, and in anisotropic bimaterials, is analysed with the method of analytic continuation, and a complete representation of the asymptotic fields is obtained in terms of arbitrary entire functions. It is shown that when the symmetry, if any, and orientation of the anisotropic bimaterial is such that the in-plane and out-of-plane deformations can be separated from each other, the in-plane crack-tip fields will have a non-oscillatory, inverse-squared-root type stress singularity, with angular variations clearly resembling those for a classical mode II problem when …

Neutron Reflection Interferometry: Physical Principles Of Surface Analysis With Phase Information, Vladimir Gudkov, G. I. Opat, A. G. Klein

Faculty Publications

It is shown that the analysis of surface layers by neutron reflection interferometry is considerably enhanced by performing the reflectometry with phase information. We discuss two methods of providing such information. One method involves physically adding an extra reference layer, whose amplitude and phase are known theoretically. The other uses the Lloyd's mirror configuration, in which a directly propagating ray that interferes with the reflected ray supplies the phase information. The methods have much in common with holography.

Seismic Evidence For Blind Thrusting Of The Northwestern Flank Of The Venezuelan Andes, Bruno De Toni, James N. Kellogg

Faculty Publications

Surface geology and seismic and well data from the northwestern flank of the Venezuelan Andes indicate overthrusting of Andean basement rocks toward the adjacent Maracaibo Basin along a blind thrust fault. The frontal monocline is interpreted as the forelimb of a northwestward verging fault-related fold deformed over a crustal-scarle map. The Andean block has been thrust 20 km to the northwest and uplifted 10 km on a ramp that dips about 20^o-30^o southeastward. The thrust fault ramps up through crystalline basement rocks to a decollement horizon within the shaly units of the Cretaceous Colon-Mito Juan formations. Backthrusts …

The Importance Of Using Multiple Styles Of Generalization, Tony R. Martinez, D. Randall Wilson

Faculty Publications

There are many ways for a learning system to generalize from training set data. There is likely no one style of generalization which will solve all problems better than any other style, for different styles will work better on some applications than others. This paper presents several styles of generalization and uses them to suggest that a collection of such styles can provide more accurate generalization than any one style by itself. Empirical results of generalizing on several real-world applications are given, and comparisons are made on the generalization accuracy of each style of generalization. The empirical results support the …

Towards A General Distributed Platform For Learning And Generalization, Brent W. Hughes, Tony R. Martinez

Faculty Publications

Different learning models employ different styles of generalization on novel inputs. This paper proposes the need for multiple styles of generalization to support a broad application base. The Priority ASOCS model (Priority Adaptive Self-organizing Concurrent System) is overviewed and presented as a potential platform which can support multiple generalization styles. PASOCS is an adaptive network composed of many simple computing elements operating asynchronously and in parallel. The PASOCS can operate in either a data processing mode or a learning mode. During data processing mode, the system acts as a parallel hardware circuit. During leaming mode, the PASOCS incorporates rules, with …

Purification And Characterization Of A Gamma-Like Dna-Polymerase From Chenopodium Album L., K. Meißner, Sabine Heinhorst, Gordon C. Cannon, T. Börner

Faculty Publications

A DNA polymerase activity from mitochondria of the dicotyledonous angiosperm Chenopodium album L. was purified almost 9000 fold by successive column chromatography steps on DEAE cellulose, heparin agarose and ssDNA cellulose. The enzyme was characterized as a gamma-class polymerase, based on its resistance to inhibitors of the nuclear DNA polymerase alpha and its preference for poly(rA).(dT)12-18 over activated DNA in vitro. The molecular weight was estimated to be 80,000 - 90,000. A 3' to 5' exonuclease activity was found to be tightly associated with the DNA polymerase activity through all purification steps. This is the first report of an association …

Driven Diffusion Of Particles, First-Passage Front, And Interface Growth, R. Bidaux, Ras B. Pandey

Faculty Publications

We study a computer-simulation model for driven particles on a discrete lattice where a fraction p of the lattice sites is randomly occupied by frozen impurities (barriers), and an imposed bias governs the particles’ hopping through the lattice. These particles (the carriers) are initially released from a source of wetting fluid from one end of the lattice in order to wet and the dry lattice on their trails. We study the transport of particles, frontier of their trail, and the growth of the interface between the wet and dry regions as a function of the biased field and the number …

Matrices Over Differential Fields Which Commute With Their Derivative, William A. Adkins, Jean Claude Evard, Robert M. Guralnick

Faculty Publications

A theorem is proved concerning the diagonalizability of a matrix over a differential field by means of a similarity transformation from the field of constants of the differential field. This result contains, as a special case, known results concerning the diagonalizability over the complex numbers of a Hermitian matrix of analytic functions under the hypothesis that the matrix commutes with its derivative. © 1993.

Classification Of The Tor-Algebras Of Codimension Four Almost Complete Intersections, Andrew R. Kustin

Faculty Publications

Let (R, m, k) be a local ring in which 2 is a unit. Assume that every element of k has a square root in k . We classify the algebras Tor'(R/J, k) as J varies over all grade four almost complete intersection ideals in R. The analogous classification has already been found when J varies over all grade four Gorenstein ideals [21], and when J varies over all ideals of grade at most three [5, 30]. The present paper makes use of the classification, in [21], of the Tor-algebraso f codimension four Gorenstein rings, as well as the (usually …