Engineering Commons^™

Two-Dimensional Ferroelectric Films, Alexander V. Bune, Vladimir M. Fridkin, Stephen Ducharme, Lev M. Blinov, Serguei P. Palto, Alexander V. Sorokin, S. G. Yudin, A. Zlatkin

Stephen Ducharme Publications

Ultrathin crystalline films offer the possibility of exploring phase transitions in the crossover region between two and three dimensions. Second- order ferromagnetic phase transitions have been observed in monolayer magnetic films [1,2], where surface anisotropy energy stabilizes the two-dimensional ferromagnetic state at finite temperature [3]. Similarly, a number of magnetic materials have magnetic surface layers that show a second-order ferromagnetic–paramagnetic phase transition with an increased Curie temperature [4]. Ferroelectricity is in many ways analogous to ferromagnetism, and bulk-like ferroelectricity and finite-size modifications of it have been seen in nanocrystals as small as 250 Å in diameter [5], in perovskite films …

Incommensurate Magnetic Fluctuations In Yba2⁢Cu3⁢O6.6, Pengcheng Dai, Herbert A. Mook, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

We use inelastic neutron scattering to demonstrate that the low-frequency magnetic fluctuations in YBa₂Cu₃O_6.6 (T_c= 62.7 K) change from commensurate to incommensurate on cooling with the incommensurability first appearing at temperatures above T_c. For the energies studied, the susceptibility at incommensurate positions increases on cooling below T_c, accompanied by a suppression of the spin fluctuations at the commensurate points. These results suggest that incommensurate spin fluctuations may be a common feature for all cuprate superconductors.

Incommensurate Magnetic Fluctuations In Yba2cu3o6.6, Pengcheng Dai, Hernert A. Mook, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

We use inelastic neutron scattering to demonstrate that the low-frequency magnetic fluctuations in YBa₂Cu ₃O_6.6 (T_c=62.7 K) change from commensurate to incommensurate on cooling with the incommensurability first appearing at temperatures above T_c. For the energies studied, the susceptibility at incommensurate positions increases on cooling below T_c, accompanied by a suppression of the spin fluctuations at the commensurate points. These results suggest that incommensurate spin fluctuations may be a common feature for all cuprate superconductors.

Dai Et Al. Reply:, Pengcheng Dai, Mohana Yethiraj, Herbert A. Mook, Terrence B. Lindemer, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

Phase Equilibria Of A Nematic And Smectic-A Mixture, Hao-Wen Chiu, Thein Kyu

College of Polymer Science and Polymer Engineering

A phase diagram of a mixture consisting of nematic and smectic liquid crystals has been calculated self-consistently by combining Flory-Huggins (FH) theory for isotropic mixing and Maier-Saupe-McMillan (MSM) theory for smectic-A ordering. However, the MSM theory can be deduced to the original Maier-Saupe (MS) theory for nematic ordering. To describe the phase transitions involving induced smectic phase and nematic + smectic equilibrium, two nematic and two smectic order parameters for the nematic/smectic mixtures have been coupled through the normalized partition function and the orientation distribution function. Self-consistent numerical solution has been sought in establishing nematic/smectic phase diagrams involving (i) phase …

Comments On Response Errors Of Non-Proportionally Lightly Damped Structures, W. Gawronski, Jerzy T. Sawicki

Mechanical Engineering Faculty Publications

Letters to the editor authors reply

Design, Performance, And Applications Of A Coherent Ultra-Wideband Random Noise Radar, Ram M. Narayanan, Yi Xu, Paul D. Hoffmeyer, John O. Curtis

Department of Electrical and Computer Engineering: Faculty Publications

A novel coherent ultra-wideband radar system operating in the 1- to 2-GHz frequency range has been developed recently at the University of Nebraska. The radar system transmits white Gaussian noise. Detection and localization of buried objects is accomplished by correlating the reflected waveform with a time-delayed replica of the transmitted waveform. Broadband dual-polarized log-periodic antennas are used for transmission and reception. A unique signal-processing scheme is used to inject coherence into the system by frequency translation of the ultrawideband signal by a coherent 160-MHz phase-locked source prior to performing heterodyne correlation. The system coherence allows the extraction of a target’s …

A Model For Calculating Acoustic Gravity Wave Energy And Momentum Flux In The Mesosphere From Oh Airglow, Gary R. Swenson, Alan Z. Liu

Physical Sciences - Daytona Beach

Acoustic gravity and tidal waves propagating in the mesosphere/lower thermosphere (80-110 km) perturb the airglow layer intensities. The OH airglow has recently been modeled to determine the relationship between the relative perturbed atmospheric density and temperature (ρ’/ ρ, T’/T) to the OH intensity ( I’_OH/I_OH ) at the OH emission altitudes [Swenson and Gardner, 1997]. A model is presented here which relates wave perturbed OH airglow to the wave energy and momentum flux as they propagate through the emission layer. The model is dependent on the wave horizontal and vertical wavelengths (or phase speed as related through …

Frontal Chromatography Of Proteins. Effect Of Axial Dispersion On Column Performance, G. A. Heeter, Athanasios I. Liapis

Chemical and Biochemical Engineering Faculty Research & Creative Works

A mathematical model describing the dynamic adsorption of proteins in columns packed with spherical porous adsorbent particles is used to study the effect of axial dispersion on the performance of chromatographic systems. The values of the axial dispersion coefficient, D(L), are estimated from a correlation based on a model describing axial dispersion in packed beds that provides satisfactory results when compared with experiment. Simulations of frontal chromatography in systems including axial dispersion and in systems without axial dispersion are made and compared to determine the effect of axial dispersion on the efficiency of the adsorption process; also, the system parameters …

Tractor Test Museum Committee February 10, 1998, Tractor Museum

Lester F. Larsen Tractor Museum: Planning and Development Documents

Heating Issues Handouts for visitors Big Red Club

Computer Simulations Of Branched Alkanes: The Effect Of Side Chain And Its Position On Rheological Behavior, Richard L. Rowley, Tapani A. Pakkanen, Maija Lahtela, Mikko Linnolahti

Faculty Publications

Nonequilibrium molecular dynamics simulations have been performed on model fluids representing eicosane isomers in order to investigate the effect of branching and side chain position on fluid rheology. A heterogeneous, united-atom model with 20 Lennard-Jones interaction sites located at carbon centers was used to model the fluids. Vibrations and bond rotations were frozen, but torsional rotation was included. It was found that viscosity increases significantly from the n-alkane structure to a branch on carbon 2, but the movement of the branch along the carbon backbone has a smaller increasing than decreasing effect. The size of the group in a branched …

Ccfss Technical Bulletin February 1998, Wei-Wen Yu Center For Cold-Formed Steel Structures

CCFSS Technical Bulletins (1993 - 2020)

No abstract provided.

Acuta Enews February 1998, Vol.27, No. 2

ACUTA Newsletters

In This Issue

Call for Nominations

ACUTA Board of Directors 1998-1999

Board Report

ACUTA 1998 EVENTS

International Project Aims to Determine What IT Services Really Cost

DC at a Glance

Positions Available

Welcome New Members

Encryption Algorithms Made (Somewhat) More Natural (A Pedagogical Remark), Misha Kosheleva, Vladik Kreinovich, Luc Longpre

Departmental Technical Reports (CS)

Modern cryptographic algorithms, such as DES, IDEA, etc., are very complex and therefore difficult to learn. Textbooks explain in detail how these algorithms work, but they usually do not explain why these algorithms were designed as they were. In this paper, we explain why, and thus, hopefully, make cryptographic algorithms easier to learn.

Design Of Automotive Structural Components Using High Strength Sheet Steels Transformed Section Method For The Calculation Of Yield Moment Of Cold-Formed Steel Hybrid Beams, Chi-Ling Pan, Wei-Wen Yu

CCFSS Library (1939 - present)

INTRODUCTION It has been recognized that material properties and stress-strain relationships of sheet steel can be influenced by the strain rate. Because the member strength is also influenced by dynamic loading, a large number of research projects were conducted for a variety of structural members under specified loading conditions during past three decades. In cold-formed steel design, local buckling is one of the major design features because of the use of large width-to-thickness ratios for compression elements. For the purpose of determining the load-carrying capacity of automotive components, the effective width approach has been used. In view of the fact …

Ccfss News February 1998, Wei-Wen Yu Center For Cold-Formed Steel Structures

CCFSS Newsletters (1999 - 2008)

No abstract provided.

An Operationalistic Reformulation Of Einstein's Equivalence Principle, Vladik Kreinovich, R. R. Zapatrine

Departmental Technical Reports (CS)

No abstract provided.

Derivation Of An Analytical Model To Calculate Junction Depth In Hgcdte Photodiodes, Stacy H. Gleixner, H. G. Robinson, C. R. Helms

Faculty Publications

Presents an enhanced analytical model to calculate junction depth and Hg interstitial profile during n-on-p junction formation in HgCdTe photodiodes. Detailed information on the enhanced model; Function of the model; Information on HgCdTe; Detailed information on how the model was obtained.

Factors Affecting The Room-Temperature Mechanical Properties Of Ticr2-Base Laves Phase Alloys, Katherine C. Chen, Samuel M. Allen, James D. Livingston

Materials Engineering

Various effects on the room-temperature mechanical properties of TiCr₂-base alloys have been assessed in efforts to improve the toughness of Laves phase intermetallics (AB₂). Systematic studies were performed on: (i) single-phase stoichiometric and nonstoichiometric TiCr₂, (ii) TiCr₂-base ternary Laves phases, and (iii) two-phase binary alloys containing TiCr₂. In order to make quantitative comparisons among the different alloys, Vickers indentation was used to obtain hardness and fracture toughness values. Within the single-phase field, constitutional defects accounted for the compositional dependencies of properties, and may aid the synchroshear deformation process. Ternary Laves …

Water Level Sensor And Datalogger Testing And Demonstration, A. Burt, Mike Lehmkuhl, Charles M. Burt, Stuart W. Styles

BioResource and Agricultural Engineering

Electronic water level sensing equipment is becoming increasingly important for the implementation of water conservation programs in irrigation districts. A need has risen for information on costs, advantages/disadvantages, required support equipment, and required maintenance for the various options. ITRC conducted a yearlong study on water level sensors and dataloggers and produced this report.

Effects Of Supplemental Viscous Damping On Seismic Response Of Asymmetric-Plan Systems, Rakesh K. Goel

Civil and Environmental Engineering

Coupling between lateral and torsional motions may lead to much larger edge deformations in asymmetric‐plan systems compared to systems with a symmetric plan. Supplemental viscous damping has been found to be effective in reducing deformations in the symmetric‐plan system. This investigation examined how supplemental damping affects the edge deformations in asymmetric‐plan systems. First, the parameters that characterize supplemental viscous damping and its plan‐wise distribution were identified, and then the effects of these parameters on edge deformations were investigated. It was found that supplemental damping reduces edge deformations and that reductions by a factor of up three are feasible with proper …

Three-Dimensional Dynamic Analysis Of Wheelchair Propulsion, Mary M. Rodgers, Srinivas Tummarakota, Junghsen Lieh

Mechanical and Materials Engineering Faculty Publications

A three-dimensional (3-D) inverse dynamic model of wheelchair propulsion was developed using the Newton-Euler method based on body coordinate systems. With this model, the arm was assumed to be three rigid segments (hand, forearm, and upper arm) connected by the wrist, elbow, and shoulder joints. A symbolic method was adopted to generate the equations of motion. The model was used to compute the joint forces and moments based on the inputs obtained from a 3-D motion analysis system, which included an instrumented wheelchair, video cameras, and a data acquisition system. The linear displacements of markers placed on the joints were …

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 14, Number 2, February 1998, 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.

Worst-Case Error Probability Of A Spread-Spectrum System In Energy-Limited Interference, Murad Hizlan, Brian L. Hughes

Electrical and Computer Engineering Faculty Publications

We consider a communication channel corrupted by thermal noise and by an unknown and arbitrary interference of bounded energy. For this channel, we derive a simple upper bound to the worst-case error probability suffered by a direct sequence (DS) communication system with error-correction coding, pseudorandom interleaving, and a correlation receiver. This bound is exponentially tight as the block length of the error correcting code becomes large. Numerical examples are given that illustrate the dependence of the bound on the choice of error correcting code, the type of interleaving used, and the relative energy of the Gaussian noise and arbitrary interference

Seismic Code Analysis Of Multi-Storey Asymmetric Buildings, Anthony P. Harasimowicz, Rakesh K. Goel

Civil and Environmental Engineering

Static torsional provisions in most seismic codes require that the lateral force at each floor level be applied at some distance from the reference centre at that floor. However, codes do not specify how to determine the locations of these centres. As a result, several different definitions of the reference centres are being used to implement the code analysis. This investigation examined how the results using various reference centres differ and which of these centres would lead to results that are in agreement with those of dynamic analysis. For this purpose three different buildings ranging form torsionally stiff to torsionally …

Bs News

Building Services Engineering

No abstract provided.

An Expert System For Service Industries Towards High Performance, Sherif Samir Abou Seif

Archived Theses and Dissertations

The thesis in hand deals with the problem of quality assessment in the service industry. Service quality measurement is an essential step towards high quality performance in these firms. Service industry plays an important role in the economy , it is currently realized that services are not luxurious activities but , rather an integral part of the economy since it employs the majority of employees and embraces more than half of the Gross National Product in most developed and under developed countries. The aim of this work is to construct a model for problem diagnosis and maintenance in the service …

Mechanical Behavior Of Al-Al2o3 Particulate Metal Matrix Composites Manufactured By Powder Metallurgy Techniques, Abdirahman Youssef Ahmed

Archived Theses and Dissertations

Metal matrix composite (N[MC) materials were manufactured using powder metallurgy (PM) techniques. Pure aluminum, Al, powder of mean particle size of 51 pm and alumina, AhO3, powder of 4 pm particle size were used as matrix and reinforcement, respectively. MNICs with four different weight fractions of reinforcement (e.g; Al-0wt.% AhO3, AI-2.5wt.% AhO3, Al-5wt.% AI2O3, and Al-1 0wt. %AhO3 ) were investigated The specimens were manufactured using hot compaction followed hot extrusion. Based on a preliminary study and on data published in the literature, two sets of processing parameters, designated as Scheme I and Scheme II, were used. The processing parameters …

Mechanical Properties, Structure, And Corrosion Characteristics Of Al And Al-Zn Coated Steel Sheets, Farraj El Shammari

Archived Theses and Dissertations

No abstract provided.

A Cooperative Expert System-Explanation Architecture, Samhaa R Adel El-Beltagy

Archived Theses and Dissertations

During the last few years, expert system explanation has become an active research area after recognizing chat its role goes beyond expert system verification as assumed by early systems. After examining current systems, it has been found that only a few of these meet the requirements of an end user interested in learning more about the domain being addressed by an expert system and understanding why it has reached a certain conclusion. It was also found that systems that address these requirements, do so at a very high cost) since they embed unmense amounts of knowledge in a system without …