Engineering Commons^™

Nanosecond Transient Electroluminescene From Polymer Light-Emitting Diodes, David Braun, D. Moses, C. Zhang, A. J. Heeger

Electrical Engineering

The transient electroluminescence from polymer light-emitting diodes is reported. When the devices are mounted on a microstrip transmission line, the temporal response is limited by the electrode geometry, with rise and fall times below 50 ns. With low duty-cycle pulses (0.5%) the electroluminescence intensity remains proportional to the current at values up to 10 A/cm², two orders of magnitude greater than possible under direct current operation. Since the spectral blue-shift observed at high current levels (with power dissipation above 1 W/cm²) indicates significant sample heating, still higher levels should be possible with proper thermal management.

Stabilization Of Passively Mode-Locked Semiconductor Laser Repetition Frequency, Roger Helkey, Dennis J. Derickson, Alan Mar, John Wasserbauer, Robert L. Thornton

Electrical Engineering

No abstract provided.

Nsf Sponsored Innovation In Engineering And Cornputer Science, Jacob Abel, Patricia Daniels, James G. Harris, Harry Hedges

Electrical Engineering

No abstract provided.

Model For The Infrastructure Of Engineering Education, James G. Harris, Karen Frair, Win Aung, Susan T. Hill

Electrical Engineering

There are many ways to describe and model physical systems. The infrastructure of engineering education in the United States is an example of such a system, and it is the intent of this report to describe and model this infratructure. The means for doing this starts with the graduation statistics for the year 1989 given by the Computer Aided Science Policy Analysis & Research Database System (CASPAR) developed for the National Science Foundation by Quantum Research Corporation [1], and uses a simple categorization for the institutions that contribute to those statistics. This categorization sorts the post -secondary institutions in the …

Flow Excited Acoustic Resonance In A Deep Cavity: An Analytical Model, William W. Durgin, Hans R. Graf

Office of the Provost Scholarship

Flow past the opening of a deep cavity can excite and sustain longitudinal acoustic modes resulting in large pressure fluctuations and loud tone generation. An analytic model of the interaction of the free stream with the acoustic flow field using concentrated vortices in the shear layer is proposed. The model includes a computation of the power transferred by the traveling vortices to the acoustic oscillation in the cavity. Experimentally measured values for the vortex convection velocity and phase are used to enable calculation of the ensuing oscillation amplititude and frequency ratio. The radiated acoustic power is calculated using the model …

Spaceflight Payload Design, Flight Experience G-408, William W. Durgin, Fred J. Looft, Albert Sacco, Jr., Robert Thompson, Anthony G. Dixon, Dino Roberti, Robert Labonte, Larry Moschini

Office of the Provost Scholarship

Worcester Polytechnic Institute's first payload of spaceflight experiments flew aboard Columbia, STS-40, during June of 1991 and culminated eight years of work by students and faculty. The Get Away Special (GAS) payload was installed on the GAS bridge assembly at the aft end of the cargo bay behind the Spacelab Life Sciences (SLS-l) laboratory. The experiments were turned on by astronaut signal after reaching orbit and then functioned for 72 hours. Environmental and experimental measurements were recorded on three cassette tapes which, together with zeolite crystals grown on orbit, formed the basis of subsequent analyses.

The experiments were developed over …

Morphology, Deformation, And Defect Structures Of Ticr2 In Ti-Cr Alloys, Katherine C. Chen, Samuel M. Allen, James D. Livingston

Materials Engineering

The morphologies and defect structures of TiCr₂ in several Ti-Cr alloys have been examined by optical metallography, x-ray diffraction, and transmission electron microscopy (TEM), in order to explore the room-temperature deformability of the Laves phase TiCr₂. The morphology of the Laves phase was found to be dependent upon alloy composition and annealing temperature. Samples deformed by compression have also been studied using TEM. Comparisons of microstructures before and after deformation suggest an increase in twin, stacking faul4 and dislocation density within the Laves phase, indicating some but not extensive room-temperature deformability.

Waste-Surface Mapping Of The Fernald K-65 Silos Using A Structured Light Measurement System, B. L. Burks, Fred W. Depiero, M. A. Dinkins, J. C. Rowe, C. B. Selleck, D. L. Jacoboski

Electrical Engineering

During FY 1991, a remotely operated surface-mapping measurement system was developed by the Robotics & Process Systems Division at Oak Ridge National Laboratory for use in the K-65 waste-storage silos at Fernald, Ohio. The mapping system used three infrared line-generating laser diodes as illumination sources and three high-resolution, low-lux, calibrated, black-and-white, chargecoupled- device video cameras as receivers. These components were combined to form structured light source range and direction sensors with six different possible emitter-receiver pairs. A technology demonstration and predeployment tests were performed at Fernald during July and August 1991, using the empty Silo 4 into which was placed …

Short Pulse Generation Using Multisegment Mode-Locked Semiconductor Lasers, Dennis J. Derickson, R. J. Helkey, A. Mar, Judy R. Karin, J. G. Wasserbauer, J. E. Bowers

Electrical Engineering

No abstract provided.

Artificial Neural Networks For Robotics Coordinate Transformation, Stephen Aylor, Luis Rabelo, Sema E. Alptekin

Industrial and Manufacturing Engineering

Artificial neural networks with such characteristics as learning, graceful degradation, and speed inherent to parallel distributed architectures might provide a flexible and cost solution to the real time control of robotics systems. In this investigation artificial neural networks are presented for the coordinate transformation mapping of a two-axis robot modeled with Fischertechnik physical modeling components. The results indicate that artificial neural systems could be utilized for practical situations and that extended research in these neural structures could provide adaptive architectures for dynamic robotics control.

Repetition Frequency Stabilisation Of Passively Mode-Locked Semiconductor Lasers, R. J. Helkey, Dennis J. Derickson, A. Mar, J. G. Wasserbauer, J. E. Bowers, R. L. Thornton

Electrical Engineering

The repetition frequency of an external cavity mode-locked GaAs semiconductor diode laser has been stabilized by voltage controlled electrical feedback. The phase noise has been reduced by 40dB at 1 kHz offset from the carrier and timing jitter reduced from more than 30ps to 4ps. This technique can be used to stabilize millimetre-wave mode-locked lasers.

Mode-Locking Of High-Power Resonant-Optical-Waveguide Diode Laser Arrays, Alan Mar, Dennis J. Derickson, Roger Helkey, John Bowers, Dan Botez

Electrical Engineering

We report the first mode-locked operation of a resonant optical waveguide (ROW semiconductor laser array. Pulsewidths as short as 23 ps and peak powers of over 1W are generated in a single-lobed beam.

Automatic Recognition Of Tool Wear On A Face Mill Using A Mechanistic Modeling Approach, Daniel Waldorf, Shiv G. Kapoor, Richard E. Devor

Industrial and Manufacturing Engineering

A strategy is developed for identifying cutting tool wear on a face mill by automatically recognizing wear patterns in the cutting force signal. The strategy uses a mechanistic model development to predict forces on a lathe under conditions of wear and extends that model to account for the multiple inserts of a face mill. The extended wear model is then verified through experimentation over the life of the inserts. The predicted force signals are employed to train linear discriminant functions to identify the wear state of the process in a manner suitable for on-line application.

On The Creep Deformation Of A Cast Near Gamma Tial Alloy Ti-48al-1nb, R. W. Hayes, B. London

Materials Engineering

The steady-state creep deformation behavior of a cast two phase gamma TiAl alloy having the composition Ti---48Al---1Nb (at.%) has been studied. Tension creep tests using the stress increment technique (θθ2θ3) were conducted over the temperature range of 704–850°C at constant initial applied stress level of 103.4–241.3 MPa. The activation energy for creep over the temperature and stress regime of this study varied 317.5 kJ/mol (137.8 MPa) up to 341.0 kJ/mol (206.8 MPa) with an average value of 326.4 kJ/mol. This is well within the range of values previously measured for gamma TiAl alloys where creep controlled by volume diffusion has …

Methanotrophic Bacteria For Nutrient Removal From Wastewater: Attached Film System, William J. Jewell, Yarrow M. Nelson, Mark S. Wilson

Civil and Environmental Engineering

It was hypothesized that nutrient removal from wastewater could be achieved by using methane oxidizing bacteria (methanotrophs). Because methane is inexpensive. it can be used as an energy source to encourage bacterial growth to assimilate nitrogen and phosphorus and other trace elements. This initial feasibility study used synthetic nutrient mixtures and secondary sewage effluent as feed to a laboratory-scale methanotrophic attached-film expanded bed (MAFEB) reactor operated at 35°C and 20°C. The MAFEB system operated successfully at low nutrient concentrations under a variety of nutrient-limited conditions. Using a synthetic nutrient mixture with a nitrogen:phosphorus feed ratio (w/w) …

Remote Driving With Reduced Bandwidth Communication, Fred W. Depiero, Timothy E. Noell, Timothy F. Gee

Electrical Engineering

Oak Ridge National Laboratory has developed a real-time video transmission system for low-bandwidth remote operations. The system supports both continuous transmission of video for remote driving and progressive transmission of still images. Inherent in the system design is a spatiotemporal limitation to the effects of channel errors. The average data rate of the system is 64,000 bits/s, a compression of approximately 1000:1 for the black and white National Television Standard Code video. The image quality of the transmissions is maintained at a level that supports teleoperation of a high-mobility multipurpose wheeled vehicle at speeds up to 15 mph on a …

Integrated Optical Transmitters And Receivers Using Multi-Segment Laser Processes, J. G. Wasserbauer, Dennis J. Derickson, K. Giboney, R. J. Helkey, J. R. Karin, A. Mar, J. E. Bowers

Electrical Engineering

No abstract provided.

Electroluminescence And Electrical Transport In Poly(3-Octylthiophene) Diodes, David Braun, G. Gustafsson, D. Mcbranch, A. J. Heeger

Electrical Engineering

We report visible light emission from diodes made from poly(3-octylthiophene). Use of a soluble derivative of polythiophene allows fabrication of the light emitting diodes by casting the polymer film from solution with no subsequent processing or heat treatment required. The devices emit dim red-orange light with relatively low external quantum efficiencies, below 2.5×10⁻⁵ photons per electron at room temperature. Electrical characterization reveals diode behavior with rectification ratios greater than 10². The temperature dependence indicates that tunneling phenomena dominate the charge injection.

Application Of An Itô-Based Approximation Method To Random Vibration Of A Pinching Hysteretic System, Mohammad N. Noori, Mark D. Padua, Hamid Davoodi

Office of the Dean (CENG) Scholarship

In this paper, an extension of the Cumulant-Neglect closure scheme is utilized for the random vibration analysis of a single degree of freedom system with a general pinching hysteresis restoring force. The hysteresis element used in the system model can simulate commonly observed forms of stiffness, strength and pinching degradations. The second order statistics of the system response to a stationary Gaussian white noise input are derived using an Itô-based approximation technique. The validity of these response statistics are then verified by comparing them to Monte Carlo simulation results. The numerical studies performed for different combinations of degradation parameters and …

Microwave And Millimeter Wave Signal Generation Using Mode-Locked Semiconductor Lasers With Intra-Waveguide Saturable Absorbers, Dennis J. Derickson, R. J. Helkey, A. Mar, J. G. Wasserbauer, Y. G. Wey, J. E. Bowers

Electrical Engineering

Microwave and millimeter wave signals can be generated using mode-locked semiconductor lasers with intra-waveguide saturable absorbers. Monolithic and external cavity devices optimized for electrical and optical signal generation are discussed along with measurements of amplitude noise, phase noise, output power, and repetition rate tunability.

Development Of Solid Waste Management Courses At The Undergraduate And Graduate Level, Samuel A. Vigil, George Tchobanoglous

Civil and Environmental Engineering

Management of solid wastes in a cost effective and environmentally sensitive manner has become one of the most challenging infrastructure issues facing municipalities today. The problem is exacerbated by a shortage of qualified engineers. In this paper, both undergraduate and graduate courses in solid waste management that have been taught by the authors at their respective universities for over 20 years are described and available textbooks and reference materials are discussed.

Graphical Integrated Waste Management Model For Puerto Rico, Samuel A. Vigil, Hilary M. Theisen

Civil and Environmental Engineering

The application of STELLA, a commercially available, graphically based simulation language for the Macintosh computer, to solid waste facility planning is described. This paper discusses a STELLA model which was developed for the Commonwealth of Puerto Rico Solid Waste Management Authority (SWMA). The model simulates the existing solid waste management system in Puerto Rico and also the proposed system of regional landfills, transfer stations, and waste-to-energy plants. The model incorporates population projections for all 78 municipalities in Puerto Rico from 1990 to 2010, solid waste generation factors for all municipalities, data on remaining life for the existing landfills, and projected …

Suppression Of Multiple Pulse Formation In External-Cavity Mode-Locked Semiconductor Lasers Using Intrawaveguide Saturable Absorbers, Dennis J. Derickson, R. J. Helkey, A. Mar, Judy R. Karin, J. E. Bowers, R. L. Thornton

Electrical Engineering

Imperfect antireflection coatings in external-cavity mode-locked semiconductor lasers can cause multiple output pulse generation. The incorporation of an intrawaveguide saturable absorber segment into the laser suppresses this problem. Single pulse outputs of less than 2.8 ps and 0.7 pJ of energy are obtained using such devices with both quantum well and bulk active regions

Steady-State Creep Deformation Of Investment Cast Near-Gamma Titanium Aluminide, D. A. Wheeler, B. London, D. E. Larsen Jr.

Materials Engineering

No Abstract.

Computational Investigation Of Slot Blowing For Fuselage Forebody Flow Control, Scott M. Murman, Yehia M. Rizk, Russell M. Cummings, Lewis B. Schiff

Aerospace Engineering

This paper presents a computational investigation of a tangential slot blowing concept for generating lateral control forces on an aircraft fuselage forebody. The effects of varying both the jet width and jet exit velocity for a fixed location slot are analyzed. This work is aimed at aiding researchers designing future experimental and computational models of tangential slot blowing. The primary influence on the resulting side force of the forebody is seen to be the jet mass flow rate. This influence is insensitive to different combination of slot widths and jet velocities over the range of variables considered. Both an actuator …

Application Of Optical Emission Diagnostics And Control Related To Semiconductor Processing, Richard N. Savage, Greg C. Viloria

Materials Engineering

This paper discusses and shows applications of optical emission spectroscopy techniques and methods to monitor plasma emissions during semiconductor processing. A brief discussion of the instrumentation that was used and the software to control the instrumentation is presented. Optical emission spectroscopy techniques discussed include chemical species identification in plasma etching, process fingerprinting, contamination detection, endpoint analysis/control, and sputter/deposition plasma monitoring.

A Radiant Flow Reactor For High-Temperature Reactivity Studies Of Pulverized Solids, John C. Chen, Stephen Niksa

Mechanical Engineering

Our radiant two‐phase flow reactor presents several new possibilities for high‐temperature reactivity studies. Most importantly, the thermal histories of the suspension and entrainment gas can be independently regulated over wide ranges. At low suspension loadings, outlet temperatures can differ by hundreds of degrees and gas temperatures are low enough to inhibit hydrocarbon cracking chemistry, so primary products are quenched as soon as they are expelled. With coal suspensions, tars were generated with the highest H/C ratio and lowest proton aromaticity ever reported. Alternatively, particles and gas can be heated at similar rates to promote secondary chemistry by increasing particle loading. …

Suppressed Nitrogen Evolution From Coal-Derived Soot And Low-Volatility Coal Chars, John C. Chen, Stephen Niksa

Mechanical Engineering

This laboratory study uses a novel furnace to resolve nitrogen evolution during the three stages of pulverized coal combustion: primary devolatilization, secondary pyrolysis, and combustion. The behavior of six coals depicts continuous rank variations, as well as suppressed nitrogen evolution from low volatility coals. During primary devolatilization of any coal, aromatic compounds in tar and oils are virtually the only shuttles for nitrogen out of the coal matrix. The small amounts of HCN observed while primary devolatilization winds down probably come from the char, because char particles are significantly hotter than tar in these experiments. Secondary pyrolysis promotes additional HCN …

Broad-Crested Weir Application On 15,000-Acre Farm, Stuart W. Styles

BioResource and Agricultural Engineering

Growers in California have been subjected to increasing pressure to account for water used on the farm due to limited water supplies and increasing energy costs. Water measurement capability provides for equitable distribution of assigned costs and enables effective water management to be accomplished. Broad-crested weirs are proven water measurement devices, especially when applied to on-farm applications. The broad-crested weirs and published data were developed by the USDA Agricultural Research Service in Phoenix, Arizona. This paper is a discussion of an application of these weirs.

On Capacity Modeling For Production Planning With Alternative Machine Types, Robert C. Leachman, Tali F. Carmon

Industrial and Manufacturing Engineering

Analyzing the capacity of production facilities in which manufacturing operations may be performed by alternative machine types presents a seemingly complicated task. In typical enterprise-level production planning models, capacity limitations of alternative machine types are approximated in terms of some single artificial capacitated resource. In this paper we propose procedures for generating compact models that accurately characterize capacity limitations of alternative machine types. Assuming that processing times among alternative machine types are identical or proportional across operations they can perform, capacity limitations of the alternative machine types can be precisely expressed using a formulation that is typically not much larger …