Engineering Commons^™

Exact Formula For Nondiagonal Green's Functions In Condensed-Matter Physics , T. Toyoda, Y. Takahashi, C. Zhang

Faculty of Engineering - Papers (Archive)

An exact formula for the nondiagonal part of the one-particle temperature Green’s function is obtained within the framework of the nonperturbative canonical formulation of the finite-temperature generalized Ward-Takahashi relation. It is shown that the Landau-level Green’s function for two-dimensional electrons has a nonvanishing nondiagonal part if the electron-electron interaction is included.

Use Of A Narrow-Gap Prewell For The Optical Study Of Charge Buildup And The Fermi-Energy Edge Singularity In A Double-Barrier Resonant-Tunneling Structure , T. A. Fisher, P. D. Buckle, Philip E. Simmonds, R. J. Teissier, M. S. Skolnick, C. R. White, D. M. Whittaker, L. Eaves, B. Usher, P. C. Kemeny, R. Grey, G. Hill, M. A. Pate

Faculty of Engineering - Papers (Archive)

A strained InyGa1-yAs layer is incorporated adjacent to the emitter barrier of an AlxGa1-xAs/GaAs/AlxGa1-xAs double-barrier resonant-tunneling structure (DBRTS), so that it forms a prewell for the electrons that accumulate prior to tunneling into the GaAs quantum well (QW). Observation of photoluminescence (PL) and photoluminescence excitation (PLE) from the prewell then enables a direct optical determination of the charging behavior in the emitter-accumulation region to be achieved. We show in addition that an optical probe of the prewell can, by consideration of the electrostatics, provide a reliable determination of the charge distribution in the whole DBRTS at the peak of the …

United States Patent: Ellipsometer, John A. Woollam, Blaine D. Johs, David W. Doerr, Reed A. Christenson

Department of Electrical and Computer Engineering: Faculty Publications

To sense characteristics of a sample, an ellipsometer includes a pivotal diffraction grating positioned to receive white light from the analyzer without further focusing of the light after the light leaves the sample. The diffraction grating is focused on the sensor at a predetermined angle with a precision of at least plus or minus one-half degree using an alignment-sensing means positioned between the analyzer and diffraction grating. The sensor includes an aperture through which the incident beam of light is transmitted, light-sensitive areas on opposite sides of said sensor and a comparator for comparing the signal from said light-sensitive areas. …

Radiative Transfer Of Ultrasound, Joseph A. Turner, Richard L. Weaver

Department of Engineering Mechanics: Faculty Publications

A radiative transfer equation is used to model the diffuse multiple scattering of ultrasound in a medium containing discrete random scatterers. An assumption of uncorrelated phases allows one to write an equation of energy balance for the diffuse intensity. This ultrasonic radiative transfer equation contains single-scattering and propagation parameters that are calculated using the elastic wave equation. Polarization effects are included through the introduction of an elastodynamic Stokes vector which contains a longitudinal Stokes parameter and four shear Stokes parameters similar to the four Stokes parameters used in optical radiative transfer theory. The theory is applied to a statistically homogeneous, …

Anthropometric Estimates For Colombian Adults, Orlando A. Corredor

FIU Electronic Theses and Dissertations

Knowledge of anthropometric dimensions is important for the design of workspaces and equipment. In a developing country, such as Colombia, no anthropometric survey for Colombian adults has yet been published. Therefore, the purpose of this study is to assemble a Colombian adult anthropometric data set sufficiently accurate for design applications. An anthropometric survey was conducted on 134 Colombian adults living in South Florida. Twenty body dimensions were measured. Moreover, an anthropometric estimation method was selected, described and validated to be used as a reference when measurement of the user population is not possible. Anthropometric estimates, using the scaling ratio method, …

Sixth U.S.-Japan Seminar On Polymer Synthesis: Macromolecular Design For Advanced Materials, Otto Vogl, Shiro Kobayashi

Emeritus Faculty Author Gallery

No abstract provided.

64. Tibor Kelen, Otto Vogl

Emeritus Faculty Author Gallery

No abstract provided.

Polymer Institute Slovak Academy Of Sciences Bratislava, Slovakia, Otto Vogl

Emeritus Faculty Author Gallery

No abstract provided.

Travelling Wave Electrode Optimization For High Speed Electro-Optic Modulators Using The Fourier Series Method, W. Boyu, X. Guangjun, Xiaomin Jin

Electrical Engineering

The performance of Z-cut Mach-Zehnder high speed LiNbO₃ amplitude modulators with a CPW traveling wave electrode, has been analyzed and optimally designed in detail by the Fourier series method. The effect of electrode and buffer layer thickness on the electric field distribution in the substract, effective micro- wave refractive index and characteristic impedance of CPW electrode, are discussed. Calculation shows that increasing the thickness of the electrode and SiO₂ buffer layer can improve the phase velocity mismatch between electric and optical waves, and the drive power required by the modulator with thin buffer layer and thick electrode is …

Radiative Transfer And Multiple Scattering Of Diffuse Ultrasound, Joseph A. Turner, Richard L. Weaver

Department of Engineering Mechanics: Faculty Publications

A model is presented fro the multiply scattered incoherent field in a continuous polycrystalline elastic medium. Unlike a previous development based upon energy conservation considerations [J. A. Turner and R.L. Weaver, J. Acoust. Soc. Am. 93, 2312 (A) (1993)] for a medium containing discrete random scatterers, the present model has been developed from the wave equation and first principles. Appropriate ensemble averaging of the wave equation leads to Dyson and Bethe-Salpeter equations which govern the mean Green’s function and the covariance of the Green’s function, respectively. These equations are expanded for weak heterogeneity and equations of radiative transfer are obtained. …

Nmr And Nqr Study Of The Electronic And Structural Properties Of Al-Cu-Fe And Al-Cu-Ru Quasicrystals, A. Shastri, F. Borsa, D.R. Torgeson, Jeffrey E. Shield, A.I. Goldman

Nebraska Center for Materials and Nanoscience: Faculty Publications

²⁷ Al and ^63.65Cu NMR measurements are reported for powder samples of stable Al-Cu-Fe and Al-Cu-Ru icosahedral quasicrystals and their crystalline approximants, and for an Al-Pd-Mn singlegrain quasicrystal. Furthermore, ²⁷Al NQR spectra at 4.2 K have been observed in the Al-Cu-Fe and Al-Cu-Ru samples. From the quadrupole-perturbed NMR spectra at different magnetic fields, and from the zero-field NQR spectra, a wide distribution of local electric-field gradient (EFG) tensor components and principal-axis-system orientations was found at the Al site. A model EFG calculation based on a 1/1 Al-Cu-Fe approximant was successful in explaining the observed NQR spectra. The average …

Acuta Enews December 1994, Vol. 23, No. 12

ACUTA Newsletters

In This Issue

Board report

President's message

George Mason University becomes "virtual campus"

Phone fraud at Salve Regina

Campus-wide network at James Madison

From ACUTA Headquarters

Instability In Self-Pulsation In Laser Diodes And Its Effect On All-Optical Synchonization, Jonathan Hyland, Gerald Farrell

Articles

The effect of short- and long-term frequency instability in self pulsation on all-optical synchronization using a twin-section laser diode is experimentally investigated. Short-term frequency instability broadens the unlocked full width at half maximum (FWHM) of the fundamental of the rf spectrum of the self-pulsating laser diode. We show experimentally that the value of the unlocked FWHM, and thus the level of short-term instability, has a direct effect on the optical power required to maintain synchronization. A novel means of reducing the FWHM is presented based on a reflective transmission line stub connected to the absorber of the twin-section self-pulsating laser …

Optical-Fiber Preamplifiers For Ladar Detection And Associated Measurements For Improving The Signal-To-Noise Ratio, Michael S. Salisbury, Paul F. Mcmanamon, Bradley D. Duncan

Electro-Optics and Photonics Faculty Publications

In an effort to increase achievable postdetection signal-tonoise ratios (SNRs) of continuous-wave, 1-gm all-solid-state ladar systems, a prototype rare-earth-doped optical-fiber amplifier has been included in the optical return signal path of both a heterodyne and a directdetection ladar system. We provide numerical predictions for SNR increases according to our previously developed theory. We also detail our experimental efforts and provide the results of SNR measurements for four distinct cases: direct ladar detection with and without a fiber amplifier, and heterodyne ladar detection with and without a fiber amplifier. Experimentally measured increases in SNRs for ladar systems incorporating an optical-fiber amplifier …

In Vitro Activities Of 2,2'-Bipyridyl Analogs Against Mycobacterium Leprae, Arvind Madhav Dhople, Maria Antonia Ibáñez, Anita A. Dhople

Biomedical Engineering and Sciences Faculty Publications

In vitro susceptibility of Mycobacterium leprae to two bipyridyl analogs was studied by using two biochemical parameters to measure the metabolic activity of the organism. VUF-8514 at 0.16 μg/ml, but not VUF-8842, completely inhibited the metabolic activity of M. leprae, and the action was bactericidal. When compared to rifampin (MIC 0.3 μg/ml), VUF-8514 was equally bactericidal against M. leprae.

An Overview Of Flexible Ac Transmission Systems, P. Asare, T. Diez, A. Galli, E. O'Neill-Carillo, J. Robertson, R. Zhao

Department of Electrical and Computer Engineering Technical Reports

FACTS or "flexible AC transmission systems" is a term that has been suggested for the use of solid state devices to control bulk power flow in transmission systems. The Electric Power Research Institute supported this idea, and many researchers have invested efforts on the value and potential of FACTS. At this time, it appears that the main value of FACTS lies in improving transmission capability; increasing the flexibility of power flow control (e.g., for wheeling or for economic dispatch); for controlling voltage (and var flow); and possibly additional advantages in lower voltage systems (e.g., distribution systems). This report is an …

Vortex Lattice Symmetry And Electronic Structure In Yba₂Cu₃O₇, Bernhard Keimer, Wan Y. Shih, Ross W. Erwin, Jeffrey W. Lynn, Fatih Dogan, Ilhan A. Aksay

Materials Science and Engineering Faculty Research & Creative Works

We report a small angle neutron scattering study of the vortex lattice in YBa₂Cu₃O₇ in magnetic fields of 0.5≤H≤5 T applied along and close to the c axis. Over the entire field range, the vortices form an oblique lattice with two nearly equal lattice constants and an angle of 73°between primitive vectors. Numerical calculations suggest that variations of the superconducting order parameter near the vortex core are important in stabilizing this structure. An analysis that accounts for the fourfold symmetry of the vortex core qualitatively explains both the symmetry and the orientation of the observed …

A Contactless Method For Measuring The Bulk Resistance Of Ii-Vi Compound Semiconductors, Edward D. Wheeler, Jack L. Boone, James L. Drewniak

Electrical and Computer Engineering Faculty Research & Creative Works

A radio frequency measurement technique for measuring the bulk resistivity of II-VI compound semiconductors is described. Wafers of n-type CdS are used to demonstrate the technique. An equivalent circuit model is introduced which predicts a frequency dependence for the CdS wafer impedance which agrees well with the experiment. The model assumes a broad distribution of relaxation times associated with the polarization. The radio frequency method gives values for the resistivity within 15% of four point probe measurements for the lower resistivity wafers, and within 5% for the higher resistivity wafers.

The Fat-Pyramid And Universal Parallel Computation Independent Of Wire Delay, Ronald I. Greenberg

Computer Science: Faculty Publications and Other Works

This paper shows that a fat-pyramid of area Θ(A) requires only O(log A) slowdown to simulate any competing network of area A under very general conditions. The result holds regardless of the processor size (amount of attached memory) and number of processors in the competing networks as long as the limitation on total area is met. Furthermore, the result is valid regardless of the relationship between wire length and wire delay. We especially focus on elimination of the common simplifying assumption that unit time suffices to traverse a wire regardless of its length, since the assumption becomes more and more …

Development Of Guidelines And Performance For Asphalt Concrete Containing Recycled Rubber, Kamyar C. Mahboub, Donn E. Hancher

Kentucky Transportation Center Research Report

The primary objective of this study was to investigate the feasibility of implementation of the crumb rubber technology in Kentucky. The impetus for this study was provided by the Intermodal Surface Transportation Efficiency Act of 1991 (lSTEA).

This study included an overview of existing literature on the subject from an implementation point of view for Kentucky's conditions. Upon completion of this phase of the study, guidelines were developed by the KTC research team and were submitted to the Transportation Cabinet for field implementation of the crumb rubber modifier (CRM) technology in Kentucky. From the ease of implementation point of view, …

Application Of Lawn Fertilizers And Pesticides In Salt Lake Valley Recharge Areas, Ghassan R. Musharrafieh, Larry Sager, Howard M. Deer, Richard C. Peralta

Civil and Environmental Engineering Faculty Publications

Homeowners, chemical applicators, and commercial lawncare companies apply chemicals to lawns and ornamentals overlying the recharge zone of Salt Lake Valley's principal aquifer. These applied fertilizers, herbicides, insecticides, and fungicides can potentially leach far enough to contaminate ground water. This report summarizes a study conducted in 1993-1994 to determine the type, rate, and frequency of applying chemicals to lawns and ornamentals in the recharge zone. Surveyed are lawncare companies, chemical applicators, schools, churches, hospitals, parks, homeowners, and government documents and community and state regulations. Results will help assess the potential impact of these applications on future ground water quality.

Development Of A Highway Safety Management System For Indiana: Phase 1, Omar Farooq, Kumares C. Sinha, John Nagle, Dwayne Stanley James, Yi Jiang

JTRP Technical Reports

This report presents the work plan for the development of a highway safety management system for Indiana. It identifies major activities and responsibilities for the development and implementation of a formal, statewide, interactive safety decision-making process. The safety management system of Indiana is perceived as a continuous process of considering all opportunities to improve highway safety in all phases of highway planning, design, construction, maintenance and operation. The primary emphasis is on coordination of activities at various levels and on the development of a common information data base that can be used for selecting and implementing effective highway safety strategies …

Evaluation Of Change Interval Treatments For Traffic Signals At High-Speed Intersections, Kenneth R. Agent, Jerry G. Pigman

Kentucky Transportation Center Research Report

A large number of traffic accidents at signalized intersections on high-speed roadways occur during or just after the change interval. The green extension system (GES) has been used extensively in Kentucky as a method of alleviating the problem related to the dilemma zone. An alternate method of handling this problem involves warning drivers that the signal indication is about to change from green to red using advance warning flashers (AWF). The objectives of this study were: 1) to evaluate the alternative methods (GES or AWF) which can be used to lessen the problem associated with the dilemma zone which occurs …

Sorption Of Chlorinated Organic Compounds By Sedimentary Rocks, Paul M. Mcginley, S. Kesaraju, Ronald D. Gruzesky

KWRRI Research Reports

The sorption of dichlorobenzene and trichlorobenzene on carbonate and shale rocks collected in Kentucky demonstrate that rock organic matter content is a good indicator of sorptive reactivity in rock systems. Although this is similar to soil systems, significant differences between sorption in rock and soil systems exist. Sorption isotherms on these rocks are nonlinear and sorption can be an order of magnitude higher than predicted using correlations from soils and their organic matter content. This sorption reaction could lead to significant concentration tailing during contaminant cleanup. Experimental elution of trichloroethylene from rock filled columns verified that cleanup times might be …

1994 Scholars And Artists Bibliography, Michael Schwartz Library, Cleveland State University, Friends Of The Michael Schwartz Library

Scholars and Artists Bibliographies

This bibliography was created for the annual Friends of the Michael Schwartz Library Scholars and Artists Reception, recognizing scholarly and creative achievements of Cleveland State University faculty, staff and emeriti

Modelling For Optimal Conjunctive Water Management: Irrigated Crop Production Versus Nps Pollution Prevention, O. H. Daza, Richard C. Peralta

Civil and Environmental Engineering Faculty Publications

Conjunctive water management{CWM)involves coordinating use of ground and surface water sources. Agricultural (A) and nonagricultural {NA)users compete for available water of adequate quality. A Simulation/Optimization (S/0) conjunctive water management model was developed to aid estimating the effects of water and environmental management decisions on crop yield and water quality. Included subsystems are groundwater, surface water, reservoir, delivery system, drainage, and A and NA water users. The nonlinear model addresses flows described by nonsmooth piecewise-linear functions which have discontinuous derivatives. Embedded constraints describe all significant subsystem flows. For example 1 deep percolation and runoff from surface irrigation are explicitly described as …

Broadband Rf Current Detector, George Cabrera

FIU Electronic Theses and Dissertations

The problems to be solved in this thesis were 1) development of a broadband RF preamplifier to be used with non-ferrous current probes so that the amplified signal exceeds the errors due to cable pickup, no detection is needed in this application, and 2) development of a self-contained device that amplifies and detects the output from a nonferrous current probe, providing a digital readout of the current. These instruments have been completed and are being tested for use by the National Institutes of Occupational Safety and Health (NIOSH). The self-contained current meter operates at frequencies up to 600 MHz, and …

A Prototype Computational Phantom To Create Digital Images For Research And Training In Diagnostic Radiology, Charles F. Babbs

Weldon School of Biomedical Engineering Faculty Working Papers

Research in the processing, compression, transmission, and interpretation of digital radiographic images require the testing and evaluation of a wide variety of images, varying both in format and in spatial resolution. If receiver operating characteristic (ROC) analysis or a related method is used to evaluate the performance of observers using novel vs. conventional displays, large numbers of test images containing known abnormalities are required. This report describes a convenient, inexpensive, and reproducible source of test images, having any desired resolution and containing precisely defined abnormalities of unlimited subtlety. The images are generated by computing x-ray transmission through mathematically defined, three …

Fault Tolerant Medical Network (Mednet), Hamid Ghassemi

FIU Electronic Theses and Dissertations

This investigation describes the development of a new fault tolerant Medical Network (MEDNET) model based on the existing Public Switch Telephone Network (PSTN), Integrated Services Digital Network (ISDN) and Intemetworking (Internet). This research includes the original design, development and testing of the required hardware and software interfaces to provide a complete Medical Network model. MEDNET ties the Doctor, the Patient, the Hospital, the Medical Lab, and the Pharmacy for near real time and fault tolerant exchange of medical information. The MEDNET model includes the following modules: 1 Central Database Server, 2. Remote Client Access, and 3. Communication Interface. This work …

Alternative Methods For Newborn Urine Sample Collection, Nancy Ann Burke

FIU Electronic Theses and Dissertations

This project investigated the accuracy of laboratory results of urine samples collected from cotton balls as compared with samples collected from catheterization, preemie pampers and newborn pampers. Also, it examined the cotton ball's effect on the infant's skin upon its removal. Comparisons in test results were made concerning the Directigen test for Group B strep (GBS) and labstick analysis, using descriptive and inferential statistical analysis. The infants (21) who were tested for GBS using catheter and cotton ball samples yielded the same results.

Urine samples subjected to labstick analysis were obtained from 30 infants, the urine being extracted from preemie …