Engineering Commons^™

Explanation Of Timing Jitter Mechanisms In Multisegment Mode-Locked Semiconductor Lasers, Dennis J. Derickson

Electrical Engineering

Multisegment mode-locked semiconductor lasers offer a simple, high performance solution for short pulse generation. Six mode-locking techniques used in multisegment mode-locked semiconductor lasers are shown. This paper concentrates on a theoretical explanation of the timing jitter mechanisms in these lasers with supporting experimental measurements. The analysis covers passive, hybrid, and active mode-locking techniques for both monolithic and external cavity devices. Timing jitter is a very important system consideration for most applications of mode-locked lasers.

High Power Edge-Emitting Light Emitting Diodes At 1.5Μ With Extremely Low Back Facet Feedback, J. E. Fouquet, G. R. Trott, W. V. Sorin, M. J. Ludowise, D. M. Braun, Dennis J. Derickson

Electrical Engineering

This paper describes novel semiconductor sources for optical low coherence reflectometry (OLCR), a measurement technique for characterizing device and fiber reflections with high sensitivity and high spatial resolution. Lasers and conventional superluminescent LEDs are not suitable for OLCR because strong reflections from the back facets mask weak reflection signals from the device or fiber under test. Even standard edge emitting LEDs (EELEDs) show significant reflections, which have limited the dynamic range of previous measurements. Low source output powers have also limited sensitivity. In order to obtain high power while minimizing internal reflections, a high single pass gain device is required. …

Local Needs Implementation For All Programs, James G. Harris, Madeleine M. Johnson, Norm Rogers, Jay Waddell

Electrical Engineering

SYNTHESIS is one of four ex1sting NSF Engineering Education Coalitions (there are apparently plans to add two others this year to bring the total number to six). SYNTHESIS consists of eight universities: Cal Poly, Cornell. Hampton, Iowa State, Southern, Stanford, Tuskgekee, and UC-Berkeley. It has been supported by NSF for over three years, being one of the first two-the other being ECSEL. The other two existing coalitions are GATEVI/AY and SUCCEED. One 9f the main goals of the 'SYNTHESIS coalition is the development of the National Engineering Education Dehvery System (NEEDS). After giving a brief overv1ew of the NEEDS, we …

National Engineering Education Delivery System (Needs), Alice M. Agogino, Sheri Sheppard, Kate Mink, James G. Harris, Lawrence Genalo, Jaya Krishnagopalan, Dave Martin, John Saylor

Electrical Engineering

The Synthesis Coalition, supported by the National Science Foundation and industrial partners, is comprised of the following eight educational institutions: California Polytechnic State University at San Luis Obispo, Comell, Hampton, Iowa State, Southern, Stanford, and Tuskegee Universities, and the University of California at Berkeley (1].

The National Engineering Education Delivery System (NEEDS) is an entirely new courseware development and distribution system which will provide Widespread, rapid, electronic access to an almost arbitrarily large number of diverse instructional modules (2-4). Curricular material in the NEEDS database are organized by a diverse range of indices. Links across disciplines are provided in the …

Set-Up Saving Schemes For Printed Circuit Boards Assembly, Oded Z. Maimon, Ezey M. Dar-El, Tali F. Carmon

Industrial and Manufacturing Engineering

Focusing on a basic printed circuit board (PCB) assembly line configuration characterized by very long set-up times, we examine two scheduling methods that can significantly reduce the set-up. Both methods -the Grouped Set-Up (GSU) method that has been recently introduced in the literature and the Sequence Dependent Scheduling (SDS) method, which has not been studied in this context -are based on component commonality among PCB types. Using the typical traditional scheduling method as a benchmark, the GSU and the SDS methods are compared in terms of three performance measures: line throughput, average work-in-process (WIP) inventory level, and implementation complexity. Guidelines …

Seismic Code Analysis Of Buildings Without Locating Centers Of Rigidity, Rakesh K. Goel, Anil K. Chopra

Civil and Environmental Engineering

Static force procedures of most building codes require that the lateral earthquake force at each floor level of an asymmetric-plan building be applied eccentrically from the centers of rigidity. To implement such procedures, it seemed necessary in the past to determine the locations of the centers of rigidity, an often confusing and cumbersome process. This paper presents a new approach for code lateral force analysis of asymmetric-plan buildings without locating the centers of rigidity. This procedure combines the results from three static analyses, which can be implemented directly on most commercially available computer programs for analysis of multistory buidings. The …

A Dynamic Part Assignment Procedure In Machine Cell Formation, Hamid Seifoddini, Manocher Djassemi

Industrial Technology and Packaging

A major contributing factor to the under utilization of machines in cellular manufacturing is the development of long queues in front of some machines in machine cells. This paper presents a procedure which identifies such machines and redistributes their loads to alternative machines whenever feasible.

Vinyl Chloride Biodegradation With Methanotrophic Attached Films, Yarrow M. Nelson, William J. Jewell

Civil and Environmental Engineering

Methanotrophic degradation of vinyl chloride (VC) is investigated using a laboratory-scale methanotrophic attached-film expanded-bed (MAFEB) bioreactor. This study provides a basis for applying a microbial cometabolizing reaction to practical treatment of toxic chlorinated compounds. The MAFEB reactor was operated at 20°C with influent VC concentrations ranging from 1,800 to 9,600 µg/L and bed hydraulic retention times ranging from 3.7 to 7.6 h. VC effluent concentrations during steady continuous operation ranged from 3 to 140 µg/L, with most values less than 26 µg/L, resulting in removal efficiencies of 96.3% to 99.8%. The maximum continuous-flow VC degradation rate observed at 20°C was …

Numerical Prediction Of Transition Of The F-16 Wing At Supersonic Speeds - Final Report, Russell M. Cummings, Joseph A. Garcia

Aerospace Engineering

No abstract provided.

Integration Of Simulation Modeling And Computer Aided Production Management In Computer Integrated Enterprise, Emine Persentili, Sema E. Alptekin

Industrial and Manufacturing Engineering

Designing efficient and integrated manufacturing systems is the first step in attaining computer integrated enterprises (CIE). Integration of planning and implementation phases of manufacturing is essential for taking full advantage of the CIE. In order to design reliable and efficient manufacturing systems, the designers must consider the impacts of planning decisions made by computer aided production management (CAPM) modules on implementations held in manufacturing cells. This paper focuses on two issues. The first issue is importance and necessity of integrating CAPM modules with manufacturing cells. The second issue includes major features of the object-oriented approach and their relevance to our …

Transient Flowmeter Calibration Facility, Paul J. Lefebvre, William W. Durgin

Office of the Provost Scholarship

An apparatus for defining the free surface of a moving column of a fluid in a vertical pipe to enhance the accuracy of measurements of transient rate of flow of the fluid using electromagnetic flowmeter is described. It provides a neutrally buoyant plug which stays in contact with the free surface of the column of the fluid at all times and thus defines the free surface of the fluid moving in the vertical pipe accurately and reduces the oscillations of the free surface of the fluid.

Advanced Aeronatics Design: Project Based Engineering Education At Wpi, D. J. Olinger, William W. Durgin, Andreas N. Alexandrou

Office of the Provost Scholarship

One element of WPI's project-based curriculum is its interdisciplinary Advanced Aeronautics Design Program. Students participating in the program are involved in the design, construction, and flight testing of non-traditional aircraft such as an ultralight solar-powered vehicle, microwave-powered long endurance aircraft, or a flying oblique wing. The WPI project philosophy and character are described and illustrated using examples from the AAD program.

Gis Utilization For Analysis Of District Drainage Water Recycling, Charles M. Burt, Robert E. Walker

BioResource and Agricultural Engineering

An ARC-INFO GIS system was used to identify physical drainage facilities in a 32,000 ha area of the San Joaquin Valley of California. Once the drainage facilities and linkages were established, it was possible to characterize the strategies used by various irrigation districts to control drainage outflows to the San Joaquin River. The motivation behind the study was the reduction of salt and selenium flows, via agricultural drainage, into the River.

Cal Poly Model Canal, John B. Parrish, Iii, Charles M. Burt

BioResource and Agricultural Engineering

The Cal Poly Model Canal, located at the Water Delivery Facility. Irrigation Training and Research Center, California Polytechnic State University, San Luis Obispo, Calif., was built to accommodate the study and promotion of automated downstream control. Being a large, fully functional scale model of a canal, it was used to collect data for use by the Irrigation Canal System Hydraulic Modeling Task Committee of the ASCE Irrigation and Drainage Division. The data was used by Task Committee members to help evaluate numerical models for simulation of unsteady free-surface flow. The Model Canal and the collected data are discussed. This paper …

Irrigation-Canal - Simulation Model Usage, Charles M. Burt, Gregory Gartrell

BioResource and Agricultural Engineering

Unsteady canal-simulation model usage requires serious investments of time and personnel. The reasons for deciding to invest in a model, as well as reasons not to invest, are discussed. For most cases, it is better to invest in the improvement of an existing model than the writing of a new model. Many excellent models are available, although very few can be considered user-friendly for the average design engineer. Unsteady flow-simulation models are not recommended for real-time control, but are key tools for the study of various control scenarios. Canal models can simulate an actual canal, but the user must input …

Reduced Bandwidth For Remote Vehicle Operations, Timothy E. Noell, Fred W. Depiero

Electrical Engineering

Oak Ridge National Laboratory staff have developed a video compression system for low-bandwidth remote operations. The objective is to provide real-time video at data rates comparable to available tactical radio links, typically 16 to 64 thousand bits per second (kbps), while maintaining sufficient quality to achieve mission objectives. The system supports both continuous lossy transmission of black and white (gray scale) video for remote driving and progressive lossless transmission of black and white images for remote automatic target acquisition. The average data rate of the resulting bit stream is 64 kbps. This system has been demonstrated to provide video of …

The Naval Reserve Civil Engineer Corps Environmental Engineering Program, William A. Heine, Samuel A. Vigil

Civil and Environmental Engineering

The Navy is engaged in a national effort to bring its shore facilities into compliance with all applicable local, state, and federal environmental regulations. This work is being completed by civil service employees, consultants, and contractors under the supervision of Navy Civil Engineer Corps officers. To supplement these active duty and civilian resources, the Reserve Division of the Naval Facilities Engineering Command (RDNAVFAC) has identified Reserve officers with substantial environmental engineering skills who are being assigned to assist Navy shore activities all over the world in this essential task. The Naval Reserve Civil Engineer Corps (CEC) is composed of over …

Light-Emitting Diodes From Partially Conjugated Poly(P-Phenylene Vinylene), C. Zhang, David Braun, A. J. Heeger

Electrical Engineering

We report the effect of conversion conditions on the device characteristics of poly(p-phenylene vinylene) (PPV) light-emitting diodes. Both electroluminescence and photoluminescence intensities decrease with increasing degree of conversion. Partial conjugation enhances the electroluminescence intensity and gives an efficiency (with Ca as electron-injecting contact) as high as 0.75% photons per electron, about two orders of magnitude more efficient than from similar devices prepared from fully converted PPV. The results of constant current stress measurements suggest that the partially conjugated PPV diode is relatively stable at room temperature.

Analysis Of Laser Pulse Chirping In Mode-Locked Vertical-Cavity Surface-Emitting Lasers, Wenbin Jiang, Dennis J. Derickson, John E. Bowers

Electrical Engineering

Mode-locked vertical cavity lasers have a large cross-sectional area and consequently a large saturation energy and large peak powers. The authors analyze excess optical bandwidth generation in these lasers and find that self-phase modulation due to optical pumping and gain saturation is the dominant factor in inducing laser pulse chirping. The large magnitude of the chirp makes intracavity prism-pair compensation difficult. Adjustment of the cavity length has a major impact on the pulse chirping, as observed experimentally. Proper adjustment can result in a large linear frequency chirp which can be compensated using external pulse compression techniques

Measurement Of The Nonsteady Flow Field In The Opening Of A Resonating Cavity Excited By Grazing Flow, Hans R. Graf, William W. Durgin

Office of the Provost Scholarship

Flow past the opening of a cavity can excite acoustic resonance. The periodic velocity field in the region of the cavity opening has been measured for various flow conditions and the vorticity distribution has been computed from the measured data using numerical differentiation. The results indicate that the shear layer rolls up into discreet vortices, which travel across the cavity opening. Two resonances were found. The first is characterized by a single vortex being present and results in the greatest amplitude. The second is characterized by the presence of two vortices which excite a distinct but lesser amplitude resonance. As …

Evaluation Of Us Seismic Code Provisions For Asymmetric-Plan Systems, Rakesh K. Goel, Anil K. Chopra

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 US building codes. The earthquake-induced deformations and ductility demands on resisting elements of asymmetric-plan systems, are compared with their values if the system plan were symmetric. The presented results demonstrate that the design eccentricity in US 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 depending on the design value of …

Numerical Prediction Of Transition Of The F-16 Wing At Supersonic Speeds, Russell M. Cummings

Aerospace Engineering

No abstract provided.

Semiconducting Polymer-Buckminsterfullerene Heterojunctions: Diodes, Photodiodes, And Photovoltaic Cells, N. S. Sariciftci, David Braun, C. Zhang, V. I. Srdanov, A. J. Heeger, G. Stucky, F. Wudl

Electrical Engineering

The characterization of rectifying heterojunctions (diodes) fabricated from a semiconducting polymer, a soluble derivative of poly(phenylene-vinylene), and buckminsterfullerene, C₆₀, are reported. Rectification ratios in the current versus voltage characteristics exceed 10⁴. When illuminated, the devices exhibit a large photoresponse as a result of photoinduced electron transfer across the heterojunction interface from the semiconducting polymer (donor) onto C₆₀ (acceptor). The photodiode and photovoltaic responses are characterized. Photoinduced electron transfer across the donor-accepted rectifying heterojunction offers potential for photodetector and for solar cell applications.

Low Gravity Environment On-Board Columbia During Sts-40, M. J.B. Rogers, C. R. Baugher, R. C. Blanchard, R. Delombard, William W. Durgin, D. H. Matthiesen, W. Neupert, P. Roussel

Office of the Provost Scholarship

The first NASA Spacelab Life Sciences mission (SLS-1) flew 5 June to 14 June 1991 on the orbiter Columbia (STS-40). The purpose of the mission was to investigate the human body's adaptation to the low gravity conditions of space flight and the body's readjustment after the mission to the 1 g environment of earth. In addition to the life sciences experiments manifested for the Spacelab module, a variety of experiments in other scientific disciplines flew in the Spacelab and in Get Away Special (GAS) Canisters on the GAS Bridge Assembly. Several principal investigators designed and flew specialized accelerometer systems to …

Irrigation Methods For Drainage Reduction Subsurface Drip Vs. Furrow Irrigation, J.. D. Oster, R. B. Smith, C. Phene, A. Fulton, S. W. Styles, T. Fernandes

BioResource and Agricultural Engineering

No abstract provided.

A Comparison Of Low-Gravity Measurements On-Board Columbia During Sts-40, M. J.B. Rogers, C. R. Baugher, R. C. Blanchard, R. Delombard, William W. Durgin, D. H. Matthiesen, W. Neupert, P. Roussel

Office of the Provost Scholarship

The first NASA Spacelab Life Sciences mission (SLS-1) flew 5 June to 14 June 1991 on the orbiter Columbia (STS-40). The purpose of the mission was to investigate the human body's adaptation to the low-gravity conditions of space flight and the body's readjustment after the mission to the 1 g environment of earth. In addition to the life sciences experiments manifested for the Spacelab module, a variety of experiments in other scientific disciplines flew in the Spacelab and in Get Away Special (GAS) Canisters on the GAS Bridge Assembly. Several principal investigators designed and flew specialized accelerometer systems to better …