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Full-Text Articles in Engineering
Comparison Of Timing Jitter In External And Monolithic Cavity Mode-Locked Semiconductor Lasers, Dennis J. Derickson, P. A. Morton, J. E. Bowers, R. L. Thornton
Comparison Of Timing Jitter In External And Monolithic Cavity Mode-Locked Semiconductor Lasers, Dennis J. Derickson, P. A. Morton, J. E. Bowers, R. L. Thornton
Electrical Engineering
A comprehensive timing jitter comparison is made for mode-locked semiconductor lasers using active, passive, and hybrid mode-locking techniques in both external and monolithic cavity configurations. Active mode locking gives the lowest residual rms timing jitter of 65 fs (150 Hz-50 MHz), followed by the hybrid and passive mode-locking techniques. It is found that monolithic cavity devices with all active waveguides have higher timing jitter levels than the comparable external cavity case.
Evaluation Of Torsional Provisions In Seismic Codes, Anil K. Chopra, Rakesh K. Goel
Evaluation Of Torsional Provisions In Seismic Codes, Anil K. Chopra, Rakesh K. Goel
Civil and Environmental Engineering
The effects of plan asymmetry on the earthquake response of code-designed, one-story systems are identified with the objective of evaluating how well these effects are represented by torsional provisions in building codes. The earthquake-induced deformations and ductility demands on resisting elements of asymmetric-plan systems, designed according to several different codes, are compared with their values if the system plan were symmetric. The presented results demonstrate that the design eccentricity in building codes should be modified in order to achieve the desirable goal of similar ductility demands on asymmetric-plan and symmetric-plan systems. The design eccentricity should be defined differently for elastic …
Unsteady Flow In Vertical, Converging Tubes, Hamid Johari, William W. Durgin
Unsteady Flow In Vertical, Converging Tubes, Hamid Johari, William W. Durgin
Office of the Provost Scholarship
The discharge of liquids from vertical tubes with various contraction geometries was studied via the unsteady Bernoulli equation. The temporal variations of the exit velocity and fluid level in the tube were found from the numerical integration of nonlinear differential equations. Sudden, quadratic, and exponential contraction geometries were considered. For inlet to exit area ratios greater than two, the flow initially accelerates to a maximum speed and then it decelerates for the geometries studied. The exponential contraction has the shortest discharge time. The solutions also reveal that the largest possible velocity and the shortest discharge time are achieved in a …
Improved Efficiency In Semiconducting Polymer Light-Emitting Diodes, David Braun, A. J. Heeger, H. Kromer
Improved Efficiency In Semiconducting Polymer Light-Emitting Diodes, David Braun, A. J. Heeger, H. Kromer
Electrical Engineering
We report visible light emission from metal-polymer diodes made from semiconducting polymers, with indium-tin oxide as the “ohmic” contact, and a variety of metals as the barrier metal. Our results, which confirm the discovery by the Cambridge group [Nature347, 539 (1990)], demonstrate that light-emitting diodes can be fabricated by casting the polymer film on indium-tin oxide from solution with no subsequent polymer processing or heat treatment required. Electrical characterization reveals diode behavior with rectification ratios greater than 105 at sufficiently high voltages. Use of an electrode material with low work function leads to more than an order of magnitude improvement …
Efficient Single-Heterojunction Al0.27Ga0.73As/Gaas P-I-N Photodiodes With 22-Ghz Bandwidths, C. Johnson, S. Sloan, D. M. Braun, J. L. Russell, M. Zurakowski, M. Lightner, F. Kellert, G. Patterson, R. Koo, Dennis J. Derickson, J. E. Bowers
Efficient Single-Heterojunction Al0.27Ga0.73As/Gaas P-I-N Photodiodes With 22-Ghz Bandwidths, C. Johnson, S. Sloan, D. M. Braun, J. L. Russell, M. Zurakowski, M. Lightner, F. Kellert, G. Patterson, R. Koo, Dennis J. Derickson, J. E. Bowers
Electrical Engineering
A report is presented on the design, fabrication, testing, and modeling of single-heterojunction Al0.27Ga0.73As/Ga p-i-n photodiodes for use as components in optical receivers. The photodiodes are grown by molecular beam epitaxy and fabricated as 1100-μm2 mesa structures. At 5-V reverse bias and 850 nm, 100 fF of capacitance, 90 pA of leakage current, 73% external quantum efficiency, <2% reflectivity, and 22-GHz bandwidths are typically measured.
Tardiness Heuristic For Scheduling Flexible Manufacturing Systems, Ali S. Kiran, Sema E. Alptekin, A. Celal Kaplan
Tardiness Heuristic For Scheduling Flexible Manufacturing Systems, Ali S. Kiran, Sema E. Alptekin, A. Celal Kaplan
Industrial and Manufacturing Engineering
This paper evaluates the tardiness performance of a sampling-based adaptive heuristic in a dynamic manufacturing environment. A test bed, following a real world manufacturing system, has been developed. The proposed algorithm has been implemented in this simulated environment. After fine tuning the algorithm, it has been tested in various shop conditions. The results of these simulation studies are summarized.
The Use Of A High Level Cfd Code In Engineering Education, J.E.S. Venart, P. Lemieux, A.C.M. Sousa, D. Tatchell
The Use Of A High Level Cfd Code In Engineering Education, J.E.S. Venart, P. Lemieux, A.C.M. Sousa, D. Tatchell
Mechanical Engineering
An advanced multipurpose Computational Fluid Dynamics (CFD) code, FloSYS, developed for use in a CAD/CAE environment has been utilized in undergraduate and graduate courses in heat transfer. Problems are introduced at an introductory level in: -steady 2- and 3-dimensional conduction, -transient 1-, 2-, and 3-dimensional conduction, -free convective cavity flow with conjugate heat transfer, and -turbulent flows with heat transfer. More sophisticated problems, related to the use of porous media concepts for modelling heat exchangers, and compartment fire modelling are introduced at a more senior level. After one year's experimental use, the CFD code is being recommended for use in …
High-Frequency Electrooptic Fabry-Perot Modulators, R. J. Simes, R. H. Yan, C. C. Barron, Dennis J. Derickson, D. G. Lishan, Judy R. Karin, L. A. Coldren, M. Rodwell, S. Elliott, B. Hughes
High-Frequency Electrooptic Fabry-Perot Modulators, R. J. Simes, R. H. Yan, C. C. Barron, Dennis J. Derickson, D. G. Lishan, Judy R. Karin, L. A. Coldren, M. Rodwell, S. Elliott, B. Hughes
Electrical Engineering
Electrooptic modulators built from GaAs/AlxGa1-xAs Fabry-Perot cavities operating up to 6.5 GHz are reported. The measured frequency response agrees well with the one predicted using an equivalent circuit model derived from high-speed electrical measurements. The parasitic capacitances have been reduced to approximately 30 fF by fabricating the devices on semi-insulating GaAs substrates and integrating them with on-wafer bound pads which have dimensions compatible with microwave coplanar probes.
Apparatus And Method For Automatically Identifying Chemical Species Within A Plasma Reactor Environment, Richard N. Savage
Apparatus And Method For Automatically Identifying Chemical Species Within A Plasma Reactor Environment, Richard N. Savage
Materials Engineering
A method and apparatus to control the plasma environment in a semiconductor or thin-film fabrication chamber. The apparatus and method include a means for measuring an optical emission spectrum of the chemical species in the plasma and a library containing a multiplicity of predefined spectral patterns. A processor automatically correlates the spectrum with the predefined spectral patterns in the library, and yields a correlation value for all the correlations. A subset of the predefined spectral patterns based upon the highest correlation values are selected and used to identify the chemical species and abundances thereof in the plasma. A comparator compares …
Visible Light Emission From Semiconducting Polymer Diodes, David Braun, A. J. Heeger
Visible Light Emission From Semiconducting Polymer Diodes, David Braun, A. J. Heeger
Electrical Engineering
We report visible light emission from Shottky diodes made from semiconducting polymers, confirming the discovery by the Cambridge group [Nature 347, 539 (1990)]. Our results demonstrate that light-emitting diodes can be fabricated by casting the polymer film from solution with no subsequent processing or heat treatment required. Electrical characterization reveals diode behavior with rectification ratios greater than 104. We propose that tunneling of electrons from the recitifying metal contact into the gap states of the positive polaron majority carriers dominates current flow and provides the mechanism for light emission.
Effects Of Plan Asymmetry In Inelastic Seismic Response Of One-Story Systems, Rakesh K. Goel, Anil K. Chopra
Effects Of Plan Asymmetry In Inelastic Seismic Response Of One-Story Systems, Rakesh K. Goel, Anil K. Chopra
Civil and Environmental Engineering
The effects of plan asymmetry on the earthquake response of one-story systems are identified by comparing the dynamic response of an asymmetric-plan system and the corresponding symmetric-plan system for a wide range of system parameters—uncoupled lateral vibration period, uncoupled torsional-to-lateral frequency ratio, stiffness eccentricity, and yield factor. Elastic as well as inelastic systems are studied. For the latter, two values of the strength eccentricity are considered: equal to the stiffness eccentricity and zero; the latter is representative of code-designed buildings. Based on the response results for a wide range of system parameters, this paper identifies how the structural response is …
The Evolution Of The Wpi Advanced Space Design Program - An Evolving Program Of Technical And Social Analysis Using The Nasa Space Shuttle For Engineering Education, Fred J. Looft, Robert C. Labonte, William W. Durgin
The Evolution Of The Wpi Advanced Space Design Program - An Evolving Program Of Technical And Social Analysis Using The Nasa Space Shuttle For Engineering Education, Fred J. Looft, Robert C. Labonte, William W. Durgin
Office of the Provost Scholarship
In December of 1982, Worcester Polytechnic Institute, with the cooperation and support of the MITRE Corporation, initiated a primarily undergraduate educational program to develop experiments to be flown onboard a NASA Space Shuttle. Christened the MITRE WPI Space Shuttle Program, it sponsored the development of five educationally meritorious experiments over a period of four years. Although the experiments were ready to fly in early 1986, the Challenger disaster delayed their flight until the Spring of 1991. The delay notwithstanding, the benefits of the first program were sufficient to justify the development of a second set of experiments. More comprehensive in …
The Production Data-Based Similarity Coefficient Versus Jaccard's Similarity Coefficient, Hamid Seifoddini, Manocher Djassemi
The Production Data-Based Similarity Coefficient Versus Jaccard's Similarity Coefficient, Hamid Seifoddini, Manocher Djassemi
Industrial Technology and Packaging
This paper compares the performance of Jaccard's similarity coefficient with the production data-based similarity coefficient. A number of machine-component charts taken from the literature or randomly generated are used to form machine-component groups. Then, the sum of intercellular and intracellular material handling costs for each machine-component group is calculated and used as a basis for performance evaluation of the two similarity coefficients.
In-Situ Film Thickness Measurements For Real-Time Monitoring And Control Of Advanced Photoresist Track Coating Systems, Richard N. Savage, Thomas E. Metz, Horace O. Simmons
In-Situ Film Thickness Measurements For Real-Time Monitoring And Control Of Advanced Photoresist Track Coating Systems, Richard N. Savage, Thomas E. Metz, Horace O. Simmons
Materials Engineering
This paper explores the methodologies of real-time measurement of photoresist film thickness on silicon wafers using multi-wavelength reflection interferometry. Reflected light from the wafer's surface, containing the interference profile, is collected in-situ via a fiber optic cable and film thickness is determined in real-time via a pattern recognition algorithm. The instrumentation used to make this measurement and its application toward optimizing track performance during spin-coating and back are discussed. Data demonstrating basic thickness versus spin-time and thickness versus bake-time profiles acquired on-line without process disruption are presented along with its utilization toward minimizing process set-up and machine qualification. Moreover, the …
Tailwater Recovery Demonstration Program Study, Doug Welch, Tim O'Halloran, Stuart Styles
Tailwater Recovery Demonstration Program Study, Doug Welch, Tim O'Halloran, Stuart Styles
BioResource and Agricultural Engineering
No abstract provided.