Open Access. Powered by Scholars. Published by Universities.®

Engineering Commons™

Open Access. Powered by Scholars. Published by Universities.®

Purdue University

Discipline
Keyword
Publication Year
Publication
Publication Type
File Type

Articles 5371 - 5400 of 6327

Full-Text Articles in Engineering

Characterization Of Photon Recycling In Thin Crystalline Gaas Light Emitting Diodes, M. P. Patkar, M. S. Lundstrom, Michael R. Melloch Jan 1995

Characterization Of Photon Recycling In Thin Crystalline Gaas Light Emitting Diodes, M. P. Patkar, M. S. Lundstrom, Michael R. Melloch

Department of Electrical and Computer Engineering Faculty Publications

Gallium arsenide light emitting diodes (LEDs) were fabricated using molecular beam epitaxial films on GaAs substrates and removed by epitaxial lift-off (ELO). Lifted off devices were then mounted on a Si wafer using a Pd/Au/Cr contact layer, which also served as a back surface reflector. Devices were characterized by electrical and optical measurements, and the results for devices on the GaAs substrate were compared to those for EL0 devices. EL0 LEDs coated with a ZnS/MgF2 antireflection coating exhibited an optical output that was up to six times that of LEDs on GaAs substrates. At the same time, the measured current-voltage …

Go to article

Preliminary Results Of Deferoxamine And L1 Treatment Of Spinal Cord Ischemia, David G. Reuter, Willis A. Tacker Jr, Charles F. Babbs, Stephen F. Badylak, William D. Voorhees, Peter E. Konrad Jan 1995

Preliminary Results Of Deferoxamine And L1 Treatment Of Spinal Cord Ischemia, David G. Reuter, Willis A. Tacker Jr, Charles F. Babbs, Stephen F. Badylak, William D. Voorhees, Peter E. Konrad

Weldon School of Biomedical Engineering Faculty Publications

No abstract provided.

Go to article

Clinical Roc Studies Of Digital Stereo Mammography, Tarek Z. Elabbady, Charles F. Babbs, Valerie P. Jackson, Edward J. Delp, David M. Chelberg, Zygmunt Pizlo, Leslie A. Geddes Jan 1995

Clinical Roc Studies Of Digital Stereo Mammography, Tarek Z. Elabbady, Charles F. Babbs, Valerie P. Jackson, Edward J. Delp, David M. Chelberg, Zygmunt Pizlo, Leslie A. Geddes

Weldon School of Biomedical Engineering Faculty Working Papers

The objective of this study was to explore and document the diagnostic utility of digital stereo mammography for the detection of localized breast cancer in women. In it we character­ized the ability of experienced mammographers, general radiologists, and non-radiologists to detect three types of tumor masses embedded within a heterogeneous background of normal tis­sue elements in numerically simulated digital mammograms. The simulated mammograms were displayed to the subjects on a high resolution video display, both in stereo mode and in mono mode. Half of the mammograms contained a single tumor, ranging from 0.3 to 0.8 cm in maxi­mal diameter. Each …

Go to article

Stay-In Place Deck Panels - Part 1, Ariel Goldman, Menashi D. Cohen, J. A. Ramirez Jan 1995

Stay-In Place Deck Panels - Part 1, Ariel Goldman, Menashi D. Cohen, J. A. Ramirez

JTRP Technical Reports

The objective of this study was the evaluation of frost resistance of concrete bridge decks with stay-in-place galvanized steel deck forms. The evaluation included specific aspects related to the potential for D-cracking in concrete bridge decks with these forms. The experimental program has been set up so that the real parameters of the bridge deck overlays and the environmental conditions could have been modeled. The program included freezing-and-thawing testing of large concrete slab specimens (22 ¼” x 17 ¼” x 5 ¼”) situated in a computer-controlled environmental chamber and of small specimens (3” x 4” x 12”) immersed in water …

Go to article

Development Of A Highway Safety Management System For Indiana: Phase 1, Omar Farooq, Kumares C. Sinha, John Nagle, Dwayne Stanley James, Yi Jiang Dec 1994

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 …

Go to article

An Overview Of Flexible Ac Transmission Systems, P. Asare, T. Diez, A. Galli, E. O'Neill-Carillo, J. Robertson, R. Zhao Dec 1994

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 …

Go to article

A Prototype Computational Phantom To Create Digital Images For Research And Training In Diagnostic Radiology, Charles F. Babbs Nov 1994

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 …

Go to article

Resonant Tunneling Through Quantum Dot Arrays, Guanlong Chen, Gerhard Klimeck, Supriyo Datta, Guanhua Chen, William A. Goddard Iii Sep 1994

Resonant Tunneling Through Quantum Dot Arrays, Guanlong Chen, Gerhard Klimeck, Supriyo Datta, Guanhua Chen, William A. Goddard Iii

Birck and NCN Publications

We apply the Hubbard Hamiltonian to describe quantum-dot arrays weakly coupled to two contacts. Exact diagonalization is used to calculate the eigenstates of the arrays containing up to six dots and the linear-response conductance is then calculated as a function of the Fermi energy. In the atomic limit the conductance peaks form two distinct groups separated by the intradot Coulomb repulsion, while in the band limit the peaks occur in pairs. The crossover is studied. A finite interdot repulsion is found to cause interesting rearrangements in the conductance spectrum.

Go to article

The Impact Of Electronic Ballast Compact Fluorescent Lighting On Power Distribution Systems, Reid Iwao Sasaki Sep 1994

The Impact Of Electronic Ballast Compact Fluorescent Lighting On Power Distribution Systems, Reid Iwao Sasaki

Department of Electrical and Computer Engineering Technical Reports

Due to the high costs of expanding generation and transmission capacities, utilities have been initiating programs to reduce peak power demand by the customer. A number of these programs, which are commonly referred to as demand side management programs, have turned to the promotion of electronic ballast compact fluorescent lamps (CFLs) as an alternative to traditional incandescent lamps. These lamps provide a higher luminance and increased life as compared to their incandescent counterparts. Unfortunately, electronic ballast CFLs consume large amounts of harmonic current which may prove detrimental to the power distribution system. This thesis presents an introduction to the electronic …

Go to article

Pavement Management Workshop Series Reference Manual, Herpicc Aug 1994

Pavement Management Workshop Series Reference Manual, Herpicc

Indiana Local Technical Assistance Program (LTAP) Publications

This manual is provided to help instruct you in the basics of developing and using a roadway inventory in your agency.

Go to article

Conductance Spectroscopy In Coupled Quantum Dots, Gerhard Klimeck, Guanlong Chen, Supriyo Datta Jul 1994

Conductance Spectroscopy In Coupled Quantum Dots, Gerhard Klimeck, Guanlong Chen, Supriyo Datta

Birck and NCN Publications

We investigate the linear-response conductance through a pair of coupled quantum dots. The conductance spectrum under ideal conditions is shown to consist of two sets of twin peaks whose locations and amplitudes are determined by the interdot coupling and the intradot charging. We will show that the qualitative features of the spectrum survive against experimental nonidealities such as (1) detuning of the individual dots, (2) interdot charging, (3) inelastic scattering, and (4) multiple lateral states. The effect of higher lateral states depends strongly on the nature of the interaction potential, screening lengths, and exchange terms, but the lowest set of …

Go to article

Institutional Issues Related To The Application Of Intelligent Vehicle Highway Systems Technologies To Commercial Vehicle Operations In Indiana, James G. Kavalaris, Kumares C. Sinha May 1994

Institutional Issues Related To The Application Of Intelligent Vehicle Highway Systems Technologies To Commercial Vehicle Operations In Indiana, James G. Kavalaris, Kumares C. Sinha

JTRP Technical Reports

The study focused on potential barriers and opportunities to implementing Intelligent Vehicle-Highway System (IVHS) technologies to Commercial Vehicle Operations (CVO) in Indiana. Specific concepts included: (1) Automatic payment of tolls while driving at mainline speeds; (2) Pre-Clearance of vehicles and drivers past weigh stations; (3) "One-Stop-Shopping" for licenses, registrations, and permits; and (4) Transparent state borders. The study reviewed existing laws and policies applying to commercial vehicles operating in Indiana; prepared an inventory of the agencies responsible, their existing procedures, their physical facilities, and their human resources used to implement these regulations; itemized present impediments preventing the implementation of IVHS-CVO …

Go to article

Basic Resonant Topologies For Switching Power Supplies, Zacharias K. Vachaparambil Apr 1994

Basic Resonant Topologies For Switching Power Supplies, Zacharias K. Vachaparambil

Department of Electrical and Computer Engineering Technical Reports

The objective of this thesis is to study the basic resonant converter topologies for switching power supplies and to compare their performance under different operating conditions. The series and parallel resonant converters are analyzed in detail. The analysis uses the state plane method, which gives a good insight of the operation of the converter. It is found that these converters have more desirable characteristics when operated at a frequency above the resonant frequency rather than below it. Analytical results are verified by sinlulation and experiment.

Go to article

Development Of A Strategy For Compliance With Epa And Osha Regulation Application To Indot Facilities, Lynn A. Corson Jan 1994

Development Of A Strategy For Compliance With Epa And Osha Regulation Application To Indot Facilities, Lynn A. Corson

JTRP Technical Reports

Between March 1990 and November 1992, a sample of 27 field and support facilities operated by the Indiana Department of Transportation were visited by staff of the Environmental Management and education Program, School of Civil Engineering, Purdue University, for the purpose of conducting workplace assessments to ascertain the department’s compliance with federal and state environmental and worker protection regulations. Thirty-eight different department operations and nine different employee functions were observed and analyzed. There were compliance areas at every facility visited which needed strengthening. A total of 222 recommendations for strengthening those areas are included in the research report. The department …

Go to article

Multimedia Application Synthesis Study, Bob G. Mccullouch Jan 1994

Multimedia Application Synthesis Study, Bob G. Mccullouch

JTRP Technical Reports

Multimedia with its ability to involve various human faculties through the use of various media forms, provides a robust environment in which to learn in. Retention improves significantly when media exercises these various human faculties. Studies indicate that students complete training in one-third the time of the traditional instruction method while reaching up to 50 percent higher competency levels. Utilizing this technology can provide improved training tools and learning environments for the Department. Because of the many potential applications, technical and nontechnical, that may exist within the Department for utilizing this technology; a study was performed to answer questions about …

Go to article

Reviewer's Guide For Traffic Impact Studies, Soumya Sekhar Dey, Jon D. Fricker Jan 1994

Reviewer's Guide For Traffic Impact Studies, Soumya Sekhar Dey, Jon D. Fricker

JTRP Technical Reports

No abstract provided.

Go to article

Estimating Statewide Vehicle Miles Traveled In Indiana : Draft Final Report, Robert Kwasi Kumapley, Jon D. Fricker Jan 1994

Estimating Statewide Vehicle Miles Traveled In Indiana : Draft Final Report, Robert Kwasi Kumapley, Jon D. Fricker

JTRP Technical Reports

Two cross classification models have been developed in this study for use in the estimation of statewide VMT in Indiana. This is to provide INDOT with an independent source of improved statewide VMT estimates based on driver behavior to supplement the estimates obtained from the traffic count based HPMS method. The models are calibrated to produce VMT estimates for all functional classes in the state network, including combined statewide VMT estimates for functional classes that are not part of the state highway system. The results obtained in the model evaluation process indicate that the models are well calibrated. Model-generated VMT …

Go to article

Subgrade Resilient Modulus For Pavement Design And Evaluation : Implementation Report, Woojin Lee, Nihal Chand Bohra, A. G. Altschaeffl, Thomas D. White Jan 1994

Subgrade Resilient Modulus For Pavement Design And Evaluation : Implementation Report, Woojin Lee, Nihal Chand Bohra, A. G. Altschaeffl, Thomas D. White

JTRP Technical Reports

No abstract provided.

Go to article

An Evaluation Of The Strategic Highway Research Project Packing Handbook, Kenneth P. Cox, Charles F. Scholer, Menashi D. Cohen Jan 1994

An Evaluation Of The Strategic Highway Research Project Packing Handbook, Kenneth P. Cox, Charles F. Scholer, Menashi D. Cohen

JTRP Technical Reports

The objective of this research is to evaluate the use of the November 8, 1991 SHRP C-206 report entitled, “Packing Handbook – A Guide to the Optimal Gradation of Concrete Aggregates”. The purpose of the Packing Handbook is to determine the optimal combination of fine and coarse aggregates for concrete from available aggregate sources. Through the use of tables provided in the Packing Handbook, and given sources with known aggregate gradations and void contents, the relative proportion of each aggregate (coarse and fine) is obtained. Concretes made using the Packing Handbook recommendations of aggregate proportioning were compared to concretes used …

Go to article

Guidelines For Permitting Overloads, Part 2: Statistical Analysis Of Overload Vehicle Effects On Indiana Highway Bridges, Donald W. White, J. A. Ramirez, N Prasad, Thomas Kuczek Jan 1994

Guidelines For Permitting Overloads, Part 2: Statistical Analysis Of Overload Vehicle Effects On Indiana Highway Bridges, Donald W. White, J. A. Ramirez, N Prasad, Thomas Kuczek

JTRP Technical Reports

This report summarizes an analytical investigation carried out to develop a set of guidelines for regulation of overload vehicles in Indiana. A formula based first phase evaluation of overload permit requests is developed through statistical study of the rating of a representative sample of the highway bridges in Indiana using a representative sample of overload vehicles observed in the state in 1990 and 1991 plus the HS 20 design vehicle and the two Indiana Toll Road loadings. A sample of 148 bridges is chosen from a total population of 3700 Indiana highway bridges using a proportionate stratified random sampling process. …

Go to article

Guidelines For Permitting Overloads; Part 1: Effect Of Overloaded Vehicles On The Indiana Highway Network, Sameh Mohamed Zaghloul, Thomas D. White Jan 1994

Guidelines For Permitting Overloads; Part 1: Effect Of Overloaded Vehicles On The Indiana Highway Network, Sameh Mohamed Zaghloul, Thomas D. White

JTRP Technical Reports

Closed form analysis is commonly used to analyze pavement structures. This type of analysis assumes linear elastic material properties and static loading conditions. In reality, pavement materials are not linear elastic materials. For example, asphalt mixtures are viscoelastic materials and cohesive soils are elastic-plastic materials. Also truck loads are moving loads. The difference between the closed form analysis assumptions and the actual pavement conditions leads to significant differences between measured and predicted pavement response. A study has been conducted at Purdue University to develop a procedure for permitting overloaded trucks in Indiana. This study was funded by the Indiana Department …

Go to article

Implementation Of The Developed Quality Acceptance System For Steel Bridge Painting Construction, Luh M. Chang, Machine Hsie Jan 1994

Implementation Of The Developed Quality Acceptance System For Steel Bridge Painting Construction, Luh M. Chang, Machine Hsie

JTRP Technical Reports

The purpose of this research is to implement the steel bridge painting quality acceptance system developed in the Joint Highway Research Project HPR-2029-89-27 and to computerize the developed system into inspectors’ daily practice. A training program was conducted. Field experiment of the developed inspection system was initiated immediately right after the inspector training program. The new acceptance system was manually tested. Feedback from INDOT’s inspectors and other personnel were adopted to refine the inspection system. Meanwhile, an interactive computer graphic program was developed to assist the INDOT in designing the double sampling plan and deciding the sample size with controlled …

Go to article

The Computer Aided System For Planning Efficient Routes, J. R. Wright Jan 1994

The Computer Aided System For Planning Efficient Routes, J. R. Wright

JTRP Technical Reports

The Indiana Department of Transportation has sponsored the design and implementation of a decision support system for routing highway maintenance vehicles – the Computer Aided System for Planning Efficient Routes (CASPER). Designed for solving multiobjective route design problems, CASPER has been used by agency personnel to design routes for winter maintenance vehicles with significant results: cost savings of more than $9-million to the State of Indiana through more efficient use of materials, equipment, and personnel, while at the same time significant improvement in overall level of network and public service. CASPER integrates 1: an extensive spatial network database (GIS/CAD), 2) …

Go to article

1994 Directory Of Indiana State, County, City And Town Officials Responsible For Road And Street Work, Herpicc Jan 1994

1994 Directory Of Indiana State, County, City And Town Officials Responsible For Road And Street Work, Herpicc

Indiana Local Technical Assistance Program (LTAP) Directory

Contact information for agency officials and employees responsible for Indiana’s local road infrastructure.

Go to article

The Evolution Of Abdominal Compression In Cardiopulmonary Resuscitation, Charles F. Babbs Jan 1994

The Evolution Of Abdominal Compression In Cardiopulmonary Resuscitation, Charles F. Babbs

Weldon School of Biomedical Engineering Faculty Publications

Objective: To review the history of external abdominal compression as an adjunct to cardiopulmonary resuscitation (CPR), tracking the development of five major themes over the course of the 20th century: 1) augmentation of peripheral resistance by physical means, 2) risk of hepatic injury with abdominal compression, 3) counterpulsation vs. sustained compression, 4) the abdominal pump mechanism, and 5) contact compression techniques. Methods: Literature retrieved from successive MEDLINE English-language searches was reviewed with a special emphasis on work and concepts highlighted by participants at the First Purdue Conference on Interposed Abdominal Compression-CPR, September 1992. Results: External abdominal compression of one form …

Go to article

Numerical Modeling Of Cuinse2 An D Cdte Solar Cells, Jeffery L. Gray, Richard. J. Schwartz, Youn Jung Lee Jan 1994

Numerical Modeling Of Cuinse2 An D Cdte Solar Cells, Jeffery L. Gray, Richard. J. Schwartz, Youn Jung Lee

Department of Electrical and Computer Engineering Technical Reports

No abstract provided.

Go to article

Effective Bandgap Shrinkage In Gaas, E. S. Harmon, Michael R. Melloch, Mark S. Lundstrom Jan 1994

Effective Bandgap Shrinkage In Gaas, E. S. Harmon, Michael R. Melloch, Mark S. Lundstrom

Department of Electrical and Computer Engineering Faculty Publications

Electrical measurements of the equilibrium np product (n2ie) in heavily doped n‐ and p‐GaAs were performed. The n2ieDproduct (where D is the diffusivity) was measured by fitting the collector current‐voltage characteristic of a homojunction bipolar transistor to an ideal diode equation modified to account for transport in thin base transistors.The n2ie product was then extracted from n2ieD by utilizing diffusivity results obtained with the zero‐field time‐of‐flight technique. Our results show significant effective band‐gap shrinkage in heavily doped p‐GaAs, and very little effective band‐gap shrinkage …

Go to article

Thermal Velocity Limits To Diffusive Electron Transport In Thin‐Base Np+N Gaas Bipolar Transistors, E. S. Harmon, Michael R. Melloch, Mark S. Lundstrom, F. Cardone Jan 1994

Thermal Velocity Limits To Diffusive Electron Transport In Thin‐Base Np+N Gaas Bipolar Transistors, E. S. Harmon, Michael R. Melloch, Mark S. Lundstrom, F. Cardone

Department of Electrical and Computer Engineering Faculty Publications

We present experimental evidence that minority electron transport across a thin, quasineutral p+ GaAs region is limited by the thermal velocity of the electrons rather than by conventional diffusive transport. A set of GaAs homojunction np+n transistors with base widths of 4000, 2000, 1000, and 500 Å was fabricated and characterized. The diffusive modelpredicts that the dc collector current of the 500‐Å base width transistors should be eight times larger than the collector current of transistors with a 4000‐Å‐wide base. The experimental results, however, show only a factor of ~3.5 increase in collector current. The measured collector …

Go to article

Interposed Abdominal Compression As An Adjunct To Cardiopulmonary Resuscitation, Charles F. Babbs, Jeffrey B. Sack, Karl B. Kern Jan 1994

Interposed Abdominal Compression As An Adjunct To Cardiopulmonary Resuscitation, Charles F. Babbs, Jeffrey B. Sack, Karl B. Kern

Weldon School of Biomedical Engineering Faculty Publications

The addition of interposed abdominal compression (IAC) to otherwise standard CPR provides external pressure over the abdomen in counterpoint to the rhythm of chest compression. Interposed abdominal compression is a simple manual technique that can supplement the use of adrenergic drugs to increase both coronary perfusion pressure and total blood flow during CPR. Mechanistically, manual abdominal compressions induce both central aortic and central venous pressure pulses. However, owing to differences in venous versus arterial capacitance, the former are usually greater than the latter, so that systemic perfusion pressure is enhanced. Moreover, practical experience and theoretical analysis have suggested subtle refinements …

Go to article

A Study Of Dc Permanent Magnet Motor Noise Related To Line Current, Candace Rogers Suriano Jan 1994

A Study Of Dc Permanent Magnet Motor Noise Related To Line Current, Candace Rogers Suriano

Department of Electrical and Computer Engineering Technical Reports

Lightweight, compact and inexpensive DC permanent magnet motors are well suited for low cost high production use in industry. Unfortunately, the audible noise emanating from these motors can cause a false negative perception of the motor's quality. In cars, for example, fan motor noise can be a nuisance. The objective of this thesis is to examine the connection between motor noise and the line current wave form for a specific four pole DC permanent magnet motor. It is further concerned with identifying the underlying factors which influence the line current ripple. An audible noise to motor current transfer function is …

Go to article

First Prev Next Last