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1994

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Full-Text Articles in Engineering

Mat Forming Apparatus, Bernard C. H. Sun Dec 1994

Mat Forming Apparatus, Bernard C. H. Sun

Michigan Tech Patents

Mat forming apparatus comprising, in combination, a hollow material transporting member, drive structure for producing a pressure differential across spaced portions of the transporting member so that material is propelled from one of the spaced portions to the other within the hollow transporting member, material directing structure communicating with the drive structure for receiving material from the hollow transporting structure and, responsive to the drive structure, operative to direct the received material in a predetermined path, the hollow transporting member having a non-linear inner surface so that flow in the hollow transporting member is turbulent causing the material being transported ...


Exact Formula For Nondiagonal Green's Functions In Condensed-Matter Physics , T. Toyoda, Y. Takahashi, C. Zhang Dec 1994

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 Dec 1994

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 ...


United States Patent: Ellipsometer, John A. Woollam, Blaine D. Johs, David W. Doerr, Reed A. Christenson Dec 1994

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

Faculty Publications from the Department of Electrical and Computer Engineering

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 ...


On Modeling Of A Mobile Multipath Fading Channel, Heng Xiao Dec 1994

On Modeling Of A Mobile Multipath Fading Channel, Heng Xiao

Dissertations and Theses

Multipath fading is one of the major practical concerns in wireless communications. A multipath transmission takes place when a transmitted signal arrives at a receiver by two or more paths of different delay. Such multiple paths may be due to atmospheric reflection or refraction, or reflections from buildings or other objects. A multipath fading channel is usually modeled as a time-variant tapped delay system. RAKE receiver can be used to detect the signal from the multipath fading channel. However, the number of delay taps, the time delay of each path, and the tap weight for each delay path need to ...


Methodology For Accurate Speedup Prediction, Aruna Chittor Dec 1994

Methodology For Accurate Speedup Prediction, Aruna Chittor

Dissertations and Theses

The effective use of computational resources requires a good understanding of parallel architectures and algorithms. The effect of the parallel architecture and also the parallel application on the performance of the parallel systems becomes more complex with increasing numbers of processors. We will address this issue in this thesis, and develop a methodology to predict the overall execution time of a parallel application as a function of the system and problem size by combining simple analysis with a few experimental results. We show that runtimes and speedup can be predicted more accurately by analyzing the functional forms of the sequential ...


Radiative Transfer Of Ultrasound, Joseph A. Turner, Richard L. Weaver Dec 1994

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

Faculty Publications from the Department of Engineering Mechanics

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 Dec 1994

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 ...


Predicting Solute Transport In Natural Streams - A Stochastic Approach, Xueqing Zhou Dec 1994

Predicting Solute Transport In Natural Streams - A Stochastic Approach, Xueqing Zhou

Dissertations and Theses

The existing theories for predicting longitudinal dispersion in straight open channels have long been recognized as inadequate when applied to natural rivers. These theories tend to grossly underestimate dispersion in real streams since an important mixing mechanism due to nonuniform river cross-section variations is not explicitly taken into account. Recognizing the important role of stream irregularities on solute transport and the analytical difficulties of classical deterministic analysis, we develop a stochastic approach for analyzing solute transport in natural streams. Variations in river width and bed elevation are conveniently represented as one-dimensional random fields, characterized by their autocorrelation functions. Advection and ...


Polymer Institute Slovak Academy Of Sciences Bratislava, Slovakia, Otto Vogl Dec 1994

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

Emeritus Faculty Author Gallery

No abstract provided.


Sixth U.S.-Japan Seminar On Polymer Synthesis: Macromolecular Design For Advanced Materials, Otto Vogl, Shiro Kobayashi Dec 1994

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 Dec 1994

64. Tibor Kelen, Otto Vogl

Emeritus Faculty Author Gallery

No abstract provided.


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 ...


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

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


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 Dec 1994

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 ...


The Kinetics Of Volatile Lead Compound Formation During Simulated Hazardous Waste Incineration, Joel Thomas Shor Dec 1994

The Kinetics Of Volatile Lead Compound Formation During Simulated Hazardous Waste Incineration, Joel Thomas Shor

Doctoral Dissertations

Air pollution from fine metal-containing particles (and vapors) formed during hazardous waste incineration has attracted less attention than other incinerator emissions. Recently, however, metal pollution has become subject to more stringent regulations. The U.S. Environmental Protection Agency has announced limitations on the emissions of ten toxic metals. Pollution control systems that will effectively remove fine (submicron) metal-containing particles from flue gases are difficult to construct. Incinerators have not been designed or operated to minimize the formation of such particles. Industrial-scale incineration testing has produced anomalous results for air emissions of lead and other metals.

To gain a better fundamental ...


Airport Security Checkpoint Screener: An Analytical Study Of Job Retention And Attrition Factors, Norman Mark St. Laurent Dec 1994

Airport Security Checkpoint Screener: An Analytical Study Of Job Retention And Attrition Factors, Norman Mark St. Laurent

Theses - Daytona Beach

The proposed research seeks to identify the factors contributing to job retention and job attrition in terms of why an airport security checkpoint screener would try or want to stay on the job or leave the job. By identifying the causes of employee satisfaction and dissatisfaction, and by understanding the integral components of employee turnover can develop appropriate interventions that curb existing retention problems (exceeding 70% annually in most facilities). Aside from the obvious costs affiliated with recruiting, selecting, and training replacement employees, there is likely to be a detrimental impact on the effectiveness of airline passenger screening when a ...


The Effects Of The Proposed Larger Aircraft On Airport Capacity In The United States, Kerwin S. Mckenzie Dec 1994

The Effects Of The Proposed Larger Aircraft On Airport Capacity In The United States, Kerwin S. Mckenzie

Theses - Daytona Beach

The problem of airport capacity is one that has been around for some time. With air travel projected to increase into the year 2000, Airbus Industrie, Boeing Corporation and McDonnell Douglas are making plans or are in the process of building large transports. Airbus has built the A340/A330 and is planning the now named A3XX, a 600 plus seater. Boeing is currently flying the 747-400 which holds up to 570 passengers. In addition, Boeing rolled out the 777 in June 1994, which holds up to 550 passengers. Douglas is planning the MD-12 with a 700 plus passenger load. The ...


Airbus A320/321 Quick Change Market Analysis - A Case Study, Till Christian Mommsen Dec 1994

Airbus A320/321 Quick Change Market Analysis - A Case Study, Till Christian Mommsen

Theses - Daytona Beach

The purpose of this thesis is to evaluate and compare the Boeing B737 QC to the Airbus A320/321 QC aircraft, and to determine their relative market within a sample airline. The technical design of the two Airbus aircraft in a mixed QC operation were considered with respect to the requirements of a particular airline. Direct operating costs and payload range data for all three aircraft were calculated.

To evaluate the competitiveness of the A320/321 QC under actual conditions, a linear programming fleet planning model was developed that considers more than the direct operating costs of a particular aircraft ...


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 Dec 1994

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

Faculty Publications from Nebraska Center for Materials and Nanoscience

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 ...


Instability In Self-Pulsation In Laser Diodes And Its Effect On All-Optical Synchonization, Jonathan Hyland, Gerald Farrell Dec 1994

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 ...


An Evolutionary Approach To Allocating Tasks In Hard Real-Time Distributed Systems, Christian Lang Dec 1994

An Evolutionary Approach To Allocating Tasks In Hard Real-Time Distributed Systems, Christian Lang

Master's Theses

In real-time systems, correctness not only depends on the result of the computation but also on the time at which this result is available. The violation of timing constraints in hard real-time systems can be critical to human life or environment. Therefore, the scheduling algorithm for distributed systems has to allocate tasks to processing nodes so that no timing constraints can be violated. In addition to timing constraints, tasks have precedence and fault-tolerance constraints.

Static scheduling allocates tasks to processing nodes before the tasks are executed. Static scheduling problems are known to be NP-hard [4]. Therefore, heuristic techniques are necessary ...


A Pc-Based Signal Validation System For Nuclear Power Plants, Ali Seyfettin Erbay Dec 1994

A Pc-Based Signal Validation System For Nuclear Power Plants, Ali Seyfettin Erbay

Masters Theses

The safe operation and efficient control of a nuclear power plant requires reliable information about the state of the process. Therefore the validity of sensors which measure the process variables is of great importance. Signal validation is the detection, isolation and characterization of faulty signals. Properly validated process signals are also beneficial from the standpoint of increased plant availability and reliability of operator actions.

In recent years, several methods have been developed for signal validation (SV). Some of these methods include generalized consistency checking (GCC) , process empirical modeling (PEM) for prediction, multi-dimensional process hypercube (PHC), univariate and multivariate autoregression modeling ...


The Positive Impact Of Agricultural Professionals On Health And Safety Changes Among Farmers, Carol J. Lehtola Dec 1994

The Positive Impact Of Agricultural Professionals On Health And Safety Changes Among Farmers, Carol J. Lehtola

Proceedings of the Integrated Crop Management Conference

This workshop presents examples of program results and applications that indicate farmers are willing to purchase safety equipment and develop safer working practices. Many of these interventions for improving farmers' safety have been promoted and endorsed by the ag professionals who work directly with farmers. Case study examples show how ag professionals are playing a positive and active role towards improving the safety and health of Iowa's farm families.


Lighting And Marking Farm Equipment, H. Mark Hanna, Charles V. Schwab, Carol J. Lehtola, Richard W. Steffen Dec 1994

Lighting And Marking Farm Equipment, H. Mark Hanna, Charles V. Schwab, Carol J. Lehtola, Richard W. Steffen

Proceedings of the Integrated Crop Management Conference

Agriculture is one of the most hazardous occupations in the United States as determined by death rates. Excluding persons under 14 years of age, the National Safety Council (1993) estimates there were 37 deaths per 100,000 agricultural workers in 1992. Farm machinery and motor vehicles being used for farm related purposes are often involved in accidental agricultural deaths. The classes of injury causing agent with the greatest frequency of accidental occupational farm fatalities during 1992 in Iowa were tractors, machinery, and motor vehicles {IDPH, 1993). Together these three classes accounted for 64 percent of 83 recorded fatalities. Thirty-one percent ...


Using Crop Growth Models For Soybean And Corn Management, William D. K. Batchelor Dec 1994

Using Crop Growth Models For Soybean And Corn Management, William D. K. Batchelor

Proceedings of the Integrated Crop Management Conference

Corn and soybeans are the two primary row-crops grown in Iowa. In 1993, 11 million acres of corn was planted, with an average yield of 149 bu/ ac. In the same year, 8.1 million acres of soybean was planted, with an average yield of 44 bu/ ac (Iowa Crop Report, 1994). Growers are under increasing pressure to produce crops with minimum effects to the environment. This must be done without compromising the economic sustainability of the farm. It is becoming more difficult to determine the optimum crop production strategy because the system constraints continue to increase. In the future ...


Yield Monitoring And Mapping, Steven C. Borgelt Dec 1994

Yield Monitoring And Mapping, Steven C. Borgelt

Proceedings of the Integrated Crop Management Conference

The monitoring and mapping of yield variations have captured the interest of many producers. The ability to monitor grain yield on-the-go and map the in-field variations for use in management decisions has come from a dream to near-reality. The paper and presentation will discuss the recent past, the present, and the near future of crop yield monitoring and mapping. An attempt to provide accurate, correct, and current information was made. However, some information may have changed and may be outdated. This paper is not an endorsement of the products or technologies.


Residue Removal When Planting No-Till Corn, Donald C. Erbach, Thomas C. Kaspar Dec 1994

Residue Removal When Planting No-Till Corn, Donald C. Erbach, Thomas C. Kaspar

Proceedings of the Integrated Crop Management Conference

Plant residues from the previous crop are very effective in reducing soil erosion. However, if not properly managed, surface plant residues increase the risk of poor stand establishment for com (Zea mays. L.) and reduce yield potential of com when grown, especially following com, with conservation tillage production systems. A series of field studies evaluated residue management when planting com in no-tillage systems. Com planted by use of planters with residue clearing attachments emerges more rapidly than com planted with use of rolling coulter attachments. Row cleaners not only reduce plant residue above the seed row, but also result in ...


Effectiveness Of Buffer Strips In Reducing Herbicide Losses, Steven K. Mickelson, James L. Baker, Kapil Arora, Akhilesh Misra Dec 1994

Effectiveness Of Buffer Strips In Reducing Herbicide Losses, Steven K. Mickelson, James L. Baker, Kapil Arora, Akhilesh Misra

Proceedings of the Integrated Crop Management Conference

In an effort to reduce the amount of herbicide lost with sediment and water in runoff from a field, farmers are considering using best management practices (BMP's) related to land, crop, and pesticide management. Conservation tillage, pesticide incorporation, contour farming, filter strips and setbacks from water, terraces, contour farming, and pesticide application timing are just a few of the BMP's that could be considered. These practices allows farmers to be competitive in the market, as well as allowing them to effectively use fertilizers and pesticides with minimal losses to the environment. One BMP being strongly recommended today is ...


Radiative Transfer And Multiple Scattering Of Diffuse Ultrasound, Joseph A. Turner, Richard L. Weaver Dec 1994

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

Faculty Publications from the Department of Engineering Mechanics

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 ...