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Missouri University of Science and Technology

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1994

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Articles 1 - 30 of 110

Full-Text Articles in Engineering

Vortex Lattice Symmetry And Electronic Structure In Yba₂Cu₃O₇, Bernhard Keimer, Wan Y. Shih, Ross W. Erwin, Jeffrey W. Lynn, Fatih Dogan, Ilhan A. Aksay Dec 1994

Vortex Lattice Symmetry And Electronic Structure In Yba₂Cu₃O₇, Bernhard Keimer, Wan Y. Shih, Ross W. Erwin, Jeffrey W. Lynn, Fatih Dogan, Ilhan A. Aksay

Materials Science and Engineering Faculty Research & Creative Works

We report a small angle neutron scattering study of the vortex lattice in YBa2Cu3O7 in magnetic fields of 0.5≤H≤5 T applied along and close to the c axis. Over the entire field range, the vortices form an oblique lattice with two nearly equal lattice constants and an angle of 73°between primitive vectors. Numerical calculations suggest that variations of the superconducting order parameter near the vortex core are important in stabilizing this structure. An analysis that accounts for the fourfold symmetry of the vortex core qualitatively explains both the symmetry and the orientation of the observed …

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A Contactless Method For Measuring The Bulk Resistance Of Ii-Vi Compound Semiconductors, Edward D. Wheeler, Jack L. Boone, James L. Drewniak Dec 1994

A Contactless Method For Measuring The Bulk Resistance Of Ii-Vi Compound Semiconductors, Edward D. Wheeler, Jack L. Boone, James L. Drewniak

Electrical and Computer Engineering Faculty Research & Creative Works

A radio frequency measurement technique for measuring the bulk resistivity of II-VI compound semiconductors is described. Wafers of n-type CdS are used to demonstrate the technique. An equivalent circuit model is introduced which predicts a frequency dependence for the CdS wafer impedance which agrees well with the experiment. The model assumes a broad distribution of relaxation times associated with the polarization. The radio frequency method gives values for the resistivity within 15% of four point probe measurements for the lower resistivity wafers, and within 5% for the higher resistivity wafers.

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Identification And Robust Control Of Smart Structures Using Artificial Neural Networks, R. Damle, R. Lashlee, Vittal S. Rao, Frank J. Kern Dec 1994

Identification And Robust Control Of Smart Structures Using Artificial Neural Networks, R. Damle, R. Lashlee, Vittal S. Rao, Frank J. Kern

Electrical and Computer Engineering Faculty Research & Creative Works

This paper describes an integrated approach to design and implement robust controllers for smart structures. To demonstrate this procedure, we have designed and fabricated a structural test article incorporating shape memory alloy (SMA) actuators, strain gauge sensors, signal-processing circuits and digital controllers with flexible structures. A neural-network-based structural identification method to determine a state space model of the system from its experimental input/output data is presented. To reduce the learning time required to train a neural network significantly, we have developed an accelerated adaptive learning-rate algorithm. The mathematical model derived using neural networks is compared with models obtained by more …

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Computer-Aided Instruction In Dynamics: Does It Improve Learning?, Ralph E. Flori Nov 1994

Computer-Aided Instruction In Dynamics: Does It Improve Learning?, Ralph E. Flori

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Since 1992, the authors have been developing and testing BEST Dynamics software (Basic Engineering Software for Teaching Dynamics) with the goal of transforming how engineering dynamics is taught at the University of Missouri-Rolla, USA. This paper introduces the "BEST" Dynamics and its classroom implementation, raises questions concerning the cognitive impact of the software, attempts to classify the type of learning environment used in BEST Dynamics, and gives some new directions that are being taken based on the authors'' observations and experiences.

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Performance Of Bandlimited Gaussian Noise As A Spreading Code In Awgn And Single Tone Interference Channels, Tze-Yu Chu, Kurt Louis Kosbar Nov 1994

Performance Of Bandlimited Gaussian Noise As A Spreading Code In Awgn And Single Tone Interference Channels, Tze-Yu Chu, Kurt Louis Kosbar

Electrical and Computer Engineering Faculty Research & Creative Works

This paper examines the bit error rate (BER) of a direct sequence spread spectrum (SS) system that uses bandlimited white Gaussian noise (BLWGN) as a spreading code. The performance of this "bandlimited-SS" system is examined in both additive white Gaussian noise (AWGN) and single tone jamming environments. The BLWGN spreading code is inferior to conventional codes in AWGN channels, but is more robust when a narrow band interference signal is present.

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Two-Dimensional Current Transient And Trap-State Filling Of Amorphous Silicon Thin-Film Transistors, J. S. Huang, Cheng-Hsiao Wu Nov 1994

Two-Dimensional Current Transient And Trap-State Filling Of Amorphous Silicon Thin-Film Transistors, J. S. Huang, Cheng-Hsiao Wu

Electrical and Computer Engineering Faculty Research & Creative Works

Two-dimensional simulations of amorphous silicon thin-film transistors are presented for the case when source-drain voltage is turned on long before gate voltage is turned on. Discrepancies between these results and the one-dimensional results of M. F. Willums, M. Hack, P. G. LeComber, and J. G. Shaw [MRS Symp. Proc. 258, 985 (1992)] are discussed. Valid reasons for drain current decay are provided, and occupation dynamics for the trap states are shown in order to distinguish these from the one-dimensional results of C. van Berkel, J. R. Hughes, and M. J. Powell [J. Appl. Phys. 66, 4488 (1989)] where …

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Correlative Tracking Of Pseudo-Noise Codes Using A Phase Shifted Reference, Kurt Louis Kosbar, Hettiachchi Upul Gunawardana Nov 1994

Correlative Tracking Of Pseudo-Noise Codes Using A Phase Shifted Reference, Kurt Louis Kosbar, Hettiachchi Upul Gunawardana

Electrical and Computer Engineering Faculty Research & Creative Works

This work investigates a first-order correlation loop for tracking pseudo-noise (PN) codes. The local reference is produced by a PN sequence generator in series with a Hilbert transform filter. The tracking performance of this non-linear loop is compared with conventional early-late delay-lock loops (ELDLL). Using a conservative definition of bandwidth, the new loop was found to be superior at moderate to low signal-to-noise ratios (SNR). Another advantage of the new structure is that it has a very large (arguably infinite) lock range.

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Method Of Manufacture Of Multiple-Element Piezoelectric Transducer, Lawrence J. Busse, Jeffry W. Stevenson, Wayne Huebner Nov 1994

Method Of Manufacture Of Multiple-Element Piezoelectric Transducer, Lawrence J. Busse, Jeffry W. Stevenson, Wayne Huebner

Materials Science and Engineering Faculty Research & Creative Works

An improved method for fabrication of a multiple-element piezoelectric transducer and the transducer produced thereby. A green precursor tape is produced by doctor-blade tape-casting of a slurry containing lead zirconate-titanate (PZT) powder. After drying, individual strips of the tape are stacked between flat plates of previously sintered PZT, and sintered to form PZT strips; Pb from the previously sintered PZT plates makes up any Pb lost from the surfaces of the tape strips during sintering. The PZT strips are stacked interposed by layers of a thermoplastic polymer, and heated to a temperature above the melting point of the polymer, forming …

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Nature Of The Ferroelectric Phase Transition In Pbtio₃, Noam Sicron, Bruce D. Ravel, Yitzhak Yacobi, Edward A. Stern, Fatih Dogan, John J. Rehr Nov 1994

Nature Of The Ferroelectric Phase Transition In Pbtio₃, Noam Sicron, Bruce D. Ravel, Yitzhak Yacobi, Edward A. Stern, Fatih Dogan, John J. Rehr

Materials Science and Engineering Faculty Research & Creative Works

We have measured quantitatively the temperature dependence of the local distortions of PbTiO3 crystals below and above the structural ferroelectric phase transition, using x-ray absorption fine-structure (XAFS) measurements. Two probe atoms, Pb and Ti, were used. The results were analyzed by fitting parametrized theoretical XAFS spectra to the experimental results. These measurements provide quantitative distortion parameters defined as the difference between the distance of the probe to its nearest neighbor measured in the actual structure and that in a centrosymmetric structure with the same unit cell dimensions. At low temperatures the Pb-edge spectra were fit using four shells and …

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A Novel Microwave Method For Detection Of Long Surface Cracks In Metals, Chin-Yung Yeh, R. Zoughi Oct 1994

A Novel Microwave Method For Detection Of Long Surface Cracks In Metals, Chin-Yung Yeh, R. Zoughi

Electrical and Computer Engineering Faculty Research & Creative Works

A novel microwave technique for detecting long surface cracks in metals is described. This technique utilizes an open-ended waveguide to probe the surface of a metal. In the absence of a crack the metal surface is seen as a relatively good short-circuit load. However, in the presence of a crack higher order modes are generated which in turn change the reflection properties at the waveguide aperture. This change brings about a perturbation in the standing wave characteristics which is then probed by a diode detector. The experimental and theoretical foundations of this technique are given, along with several examples. It …

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Effect Of Additives On Anomalous Deposition In Zinc-Cobalt Alloy Electrogalvanizing, H. M. Wang, Thomas J. O'Keefe Sep 1994

Effect Of Additives On Anomalous Deposition In Zinc-Cobalt Alloy Electrogalvanizing, H. M. Wang, Thomas J. O'Keefe

Materials Science and Engineering Faculty Research & Creative Works

Alloys of Zn-Co were deposited from sulphate electrolytes containing various additives to study their influence on the anomalous behavior of the reactions. The effects of antimony, germanium and arsenic on the Zn-Co alloy composition and structure were examined. The results showed that the composition and structure of Zn-Co alloys deposited could be dramatically changed by antimony, and to a lesser extent by germanium and arsenic. A concentration of Sb(III) as low as 5 mg dm-3 increased the cobalt content by a factor of approximately 3; however, the deposit morphology was very dendritic. Germanium additions nearly doubled the cobalt content and …

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Orientation Induced Scattering Asymmetry, Jee-Ching Wang, Ronald E. Olson Aug 1994

Orientation Induced Scattering Asymmetry, Jee-Ching Wang, Ronald E. Olson

Chemical and Biochemical Engineering Faculty Research & Creative Works

Projectile angular scattering is investigated following electron capture by protons from circular Rydberg atoms oriented along a quantization axis perpendicular to the incident projectile direction. We find strong left-right scattering asymmetry as a function of the orientation angle at collision speeds comparable to the electron orbital speed. The capture cross section is dramatically enhanced due to velocity matching when the angular momenta of the proton and the electron are aligned. The scattering asymmetry exhibits characteristic impact parameter dependencies suitable for studying three-body dynamics influenced by both long and short range forces of comparable strength. © 1994 IOP Publishing Ltd.

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Ccfss Technical Bulletin August 1994, Wei-Wen Yu Center For Cold-Formed Steel Structures Aug 1994

Ccfss Technical Bulletin August 1994, Wei-Wen Yu Center For Cold-Formed Steel Structures

CCFSS Technical Bulletins (1993 - 2020)

No abstract provided.

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Ccfss News August 1994, Wei-Wen Yu Center For Cold-Formed Steel Structures Aug 1994

Ccfss News August 1994, Wei-Wen Yu Center For Cold-Formed Steel Structures

CCFSS Newsletters (1999 - 2008)

No abstract provided.

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Identifying And Quantifying Printed Circuit Board Inductance, Todd H. Hubing, Thomas Van Doren, James L. Drewniak Aug 1994

Identifying And Quantifying Printed Circuit Board Inductance, Todd H. Hubing, Thomas Van Doren, James L. Drewniak

Electrical and Computer Engineering Faculty Research & Creative Works

The concepts of inductance and partial inductance play a key role in printed circuit board (PCB) modeling. The inductance of the signal path is an important parameter in high-speed signal integrity calculations. Delta_I noise modeling, crosstalk calculations, and common-mode source identification all rely heavily on accurate estimations of the partial inductance associated with traces, vias, and signal return paths on printed circuit boards. The paper begins by identifying and quantifying the parameters that affect the inductance of typical PCB geometries. Closed-form equations are provided for estimating the partial inductances of simple trace, via, and ground plane configurations. Finally, the issue …

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Common Mode Currents Induced On Wires Attached To Multilayer Printed Wire Boards With Segmented Ground Planes, R. Lee Hill, Thomas Van Doren, Todd H. Hubing, James L. Drewniak, Franz Gisn Aug 1994

Common Mode Currents Induced On Wires Attached To Multilayer Printed Wire Boards With Segmented Ground Planes, R. Lee Hill, Thomas Van Doren, Todd H. Hubing, James L. Drewniak, Franz Gisn

Electrical and Computer Engineering Faculty Research & Creative Works

An investigation has been undertaken to further study the fundamental mechanisms responsible for inducing high frequency common mode currents on wires attached to multilayer printed wire boards (PWBs). Previous work reported in the EMC literature has demonstrated that the presence of unintended common mode currents on the external cables of electronic equipment is often the primary source of radiated EMI at frequencies above 30 MHz. In an attempt to reduce the magnitude of these currents to yield `quieter' electronic products, many EMC engineers have implemented segmented or `gapped' ground plane geometries in mulilayer PWB designs. The objective of this study …

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The Multirate Method For Simulation Of Power System Dynamics, J. G. Chen, Mariesa Crow Aug 1994

The Multirate Method For Simulation Of Power System Dynamics, J. G. Chen, Mariesa Crow

Electrical and Computer Engineering Faculty Research & Creative Works

In this paper, the multirate method is introduced to analyse power system behavior for systems with widely varying time constants. Estimates for computational speed-up are derived based on a linear system approach. The method is applied to a small power system example and the results, both in terms of accuracy and computation time, are compared to traditional simulation methods

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Modeling Power Bus Decoupling On Multilayer Printed Circuit Boards, James L. Drewniak, Todd H. Hubing, Thomas Van Doren, P. Baudendistal Aug 1994

Modeling Power Bus Decoupling On Multilayer Printed Circuit Boards, James L. Drewniak, Todd H. Hubing, Thomas Van Doren, P. Baudendistal

Electrical and Computer Engineering Faculty Research & Creative Works

Power bus decoupling designs on multilayer printed circuit boards must adequately account for the power bus interplane capacitance and its consequences for the design. Lumped element models for a power bus on a multilayer printed circuit board where an appreciable or entire portion of a layer is devoted to power and ground have been developed. The models are applicable below the distributed resonances of the board. Analytical, circuit simulation, and experimental studies have been conducted to test the models, investigate the effects of the distributed interplane capacitance of the power bus, and the effect of interconnect inductance associated with surface-mount …

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Investigation Of Fundamental Mechanisms Of Common-Mode Radiation From Printed Circuit Boards With Attached Cables, James L. Drewniak, Todd H. Hubing, Thomas Van Doren Aug 1994

Investigation Of Fundamental Mechanisms Of Common-Mode Radiation From Printed Circuit Boards With Attached Cables, James L. Drewniak, Todd H. Hubing, Thomas Van Doren

Electrical and Computer Engineering Faculty Research & Creative Works

Fundamental mechanisms leading to common-mode radiation from printed circuit boards with attached cables have been studied. Two primary mechanisms have been identified, one associated with a differential-mode voltage that results in a common-mode current on an attached cable, and another associated with a differential-mode current that results in a common-mode current on the cable. The two mechanisms are demonstrated through numerical and experimental results.

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Simulation Of Communication Systems, William H. Tranter, Kurt Louis Kosbar Jul 1994

Simulation Of Communication Systems, William H. Tranter, Kurt Louis Kosbar

Electrical and Computer Engineering Faculty Research & Creative Works

When both a complex system and a complex channel model are encountered, the result is typically a design or analysis problem that cannot be solved using traditional (pencil and paper) mathematical analysis. Computer-aided techniques, which usually involve some level of numerical simulation, can be a very valuable tool in these situations. The purpose of this article is to provide a tutorial review of some of the basic techniques of communication system simulation. The authors consider the basic techniques used to represent signals, generate signals, and model linear systems, nonlinear systems, and time-varying systems within a simulation. They consider the important …

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Detection Optimization Of Disbond In Layered Composites With Varying Thicknesses Using An Open-Ended Rectangular Waveguide, Stoyan I. Ganchev, Nasser N. Qaddoumi, R. Zoughi Jul 1994

Detection Optimization Of Disbond In Layered Composites With Varying Thicknesses Using An Open-Ended Rectangular Waveguide, Stoyan I. Ganchev, Nasser N. Qaddoumi, R. Zoughi

Electrical and Computer Engineering Faculty Research & Creative Works

The detection of air disbond in layered dielectric composite, which is an important practical issue in many industries, is studied both theoretically and experimentally. Sensitivity of disbond detection depends on certain parameters, like the frequency of operation, the distance between the sensor and the first dielectric layer, and the layered composite geometry (conductor backed or terminated by an infinite half-space of air). The impact of all these parameters is investigated theoretically and then verified experimentally.

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A Novel Microwave Fatigue Crack Detection Technique Using An Open-Ended Coaxial Line, Nasser N. Qaddoumi, Stoyan I. Ganchev, R. Zoughi Jul 1994

A Novel Microwave Fatigue Crack Detection Technique Using An Open-Ended Coaxial Line, Nasser N. Qaddoumi, Stoyan I. Ganchev, R. Zoughi

Electrical and Computer Engineering Faculty Research & Creative Works

Surface crack detection on metallic structures (aircraft fuselage, turbine blades and nuclear power plant steam generator turbines) is of utmost importance. The use of an open-ended coaxial line for this purpose is very attractive because it offers advantages such as a wide frequency band of operation, small aperture (sensing) area, and excellent sensitivity.

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Analysis Of Radiation From An Open-Ended Coaxial Line Into Stratified Dielectrics, Sasan Bakhtiari, Stoyan I. Ganchev, R. Zoughi Jul 1994

Analysis Of Radiation From An Open-Ended Coaxial Line Into Stratified Dielectrics, Sasan Bakhtiari, Stoyan I. Ganchev, R. Zoughi

Electrical and Computer Engineering Faculty Research & Creative Works

Radiation from an open-ended coaxial transmission line into an N-layer dielectric medium is studied in application to nondestructive evaluation of materials. Explicit formulations for two cases of layered media, one terminated into an infinite half-space and the other into a conducting sheet are addressed in general form. In the theoretical derivations it is assumed that only the fundamental TEM mode propagates inside the coaxial line. The terminating admittance of the line is then formulated using the continuity of the power flow across the aperture. The admittance expressions for specific cases of two-layer dielectric composite with generally lossy dielectric properties, and …

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Simple Apparatus For Producing Single Liquid Drops, Dhiren Panda, D. G. C. Robertson Jul 1994

Simple Apparatus For Producing Single Liquid Drops, Dhiren Panda, D. G. C. Robertson

Materials Science and Engineering Faculty Research & Creative Works

A simple experimental apparatus has been used to produce individual mercury and sodium amalgam drops in the size range of 0.3-2.5 mm diam. A high resistance to the flow of liquid was provided by a capillary tube. The cross section consisted of a 0.20 mm o.d. tungsten wire placed in a 0.25 mm capillary bore. By this method, flow rates of 1 μl/s and lower were obtained, which enabled the formation of drops as small as 1 mm diam in a time interval of 20 s. The drops were formed at a plastic tip, and on reaching the desired size, …

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The Response Of Dispersion-Strengthened Copper Alloys To High Fluence Neutron Irradiation At 415⁰C, Danny J. Edwards, Joseph William Newkirk, Frank A. Garner, Margaret L. Hamilton, A. Nadkarni, P. Samal Jun 1994

The Response Of Dispersion-Strengthened Copper Alloys To High Fluence Neutron Irradiation At 415⁰C, Danny J. Edwards, Joseph William Newkirk, Frank A. Garner, Margaret L. Hamilton, A. Nadkarni, P. Samal

Materials Science and Engineering Faculty Research & Creative Works

Various oxide-dispersion-strengthened copper alloys have been irradiated to 150 dpa at 415°C in the Fast Flux Test Facility (FFTF). The Al2O3-strengthened GlidCop™ alloys, followed closely by a HfO2-strengthened alloy, displayed the best swelling resistance, electrical conductivity, and tensile properties. The conductivity of the HfO2-strengthened alloy reached a plateau at the higher levels of irradiation, instead of exhibiting the steady decrease in conductivity observed in the other alloys. A high initial oxygen content resulted in significantly higher swelling for a series of castable oxide-dispersion-strengthened alloys, while a Cr2O3 -strengthened alloys …

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Identification Of Cutting Force In End Milling Operations Using Recurrent Neural Networks, Q. Xu, K. Krishnamurthy, Bruce M. Mcmillin, Wen Feng Lu Jun 1994

Identification Of Cutting Force In End Milling Operations Using Recurrent Neural Networks, Q. Xu, K. Krishnamurthy, Bruce M. Mcmillin, Wen Feng Lu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The problem of identifying the cutting force in end milling operations is considered in this study. Recurrent neural networks are used here and are trained using a recursive least squares training algorithm. Training results for data obtained from a SAJO 3-axis vertical milling machine for steady slot cuts are presented. The results show that a recurrent neural network can learn the functional relationship between the feed rate and steady-state average resultant cutting force very well. Furthermore, results for the Mackey-Glass time series prediction problem are presented to illustrate the faster learning capability of the neural network scheme presented here

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A Recursive Least Squares Training Algorithm For Multilayer Recurrent Neural Networks, Q. Xu, K. Krishnamurthy, Bruce M. Mcmillin, Wen Feng Lu Jun 1994

A Recursive Least Squares Training Algorithm For Multilayer Recurrent Neural Networks, Q. Xu, K. Krishnamurthy, Bruce M. Mcmillin, Wen Feng Lu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Recurrent neural networks have the potential to perform significantly better than the commonly used feedforward neural networks due to their dynamical nature. However, they have received less attention because training algorithms/architectures have not been well developed. In this study, a recursive least squares algorithm to train recurrent neural networks with an arbitrary number of hidden layers is developed. The training algorithm is developed as an extension of the standard recursive estimation problem. Simulated results obtained for identification of the dynamics of a nonlinear dynamical system show promising results.

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Work Measurement Decision Diagram Development And Application At Nasa's Kennedy Space Center, Susan L. Murray, Amanda M. Mitskevich, Joseph J. Pignatiello Jr., Timothy S. Barth, William W. Swart May 1994

Work Measurement Decision Diagram Development And Application At Nasa's Kennedy Space Center, Susan L. Murray, Amanda M. Mitskevich, Joseph J. Pignatiello Jr., Timothy S. Barth, William W. Swart

Engineering Management and Systems Engineering Faculty Research & Creative Works

This paper presents a decision flow diagram developed at NASA's Kennedy Space Center for the selection of the appropriate work measurement methodologies for Space Shuttle processing.

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Automation Of Process Data Management, Stephen C. Chadwick May 1994

Automation Of Process Data Management, Stephen C. Chadwick

Opportunities for Undergraduate Research Experience Program (OURE)

The project goal is to create an automated system for managing data that describes a chemical process. The data is both graphical, such as piping and instrumentation diagrams, and numerical, such as pipe schedule and diameter. AutoLisp and C++ programs were developed and tested to simplify the creation of the automated system.

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The Reduction Of Dielectric Constant By Shaped Porosity, Weiping Cai May 1994

The Reduction Of Dielectric Constant By Shaped Porosity, Weiping Cai

Opportunities for Undergraduate Research Experience Program (OURE)

In multi-layer circuits, the reduction of the dielectric constant in substrate materials is becoming increasingly important, as the heat emission of the circuits increases with an increasing number of layers. One way to achieve a lower dielectric constant is to create porosity in the material. In this project, two types of substrate samples were made with coin-shaped porosity. One had holes of 8.0mm in diameter, and the other had holes of 2.5mm in diameter. The total vacuum area was 250mm2, or 7.7% of the total area, in either case. It was hoped to discover a relationship between aspect …

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