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Articles 13951 - 13980 of 21750

Full-Text Articles in Engineering

Al2o3-Ni Composites With High Strength And Fracture Toughness, William Fahrenholtz, Donald T. Ellerby, Ronald E. Loehman Jan 2000

Al2o3-Ni Composites With High Strength And Fracture Toughness, William Fahrenholtz, Donald T. Ellerby, Ronald E. Loehman

Materials Science and Engineering Faculty Research & Creative Works

Al2O3-Ni Composites Were Prepared by the Reactive Hot Pressing of Al and NiO. the Composites Had a Two-Phase, Interpenetrating Microstructure and Contained Approx. 35 Vol% Ni. They Exhibited an Impressively High Combination of Strength and Toughness at Room Temperature; the Four-Point Bending Strength Was in Excess of 600 MPa with a Fracture Toughness of More Than 12 MPa·m1/2 . Examination of Fracture Surfaces Showed that Ni Ligaments Underwent Ductile Deformation during Fracture. SEM Analysis Revealed Knife-Edge Ni Ligaments with a Limited Amount of Debonding Around their Periphery (I.e., at the Ni-Al2O3 Interface), …

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Midcourse Guidance Law With Neural Networks, Dongchen Han, S. N. Balakrishnan Jan 2000

Midcourse Guidance Law With Neural Networks, Dongchen Han, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A neural network-based synthesis of an optimal midcourse guidance law is presented in this study. We use a set of two-neural networks; the first network called 'a critic' outputs the Lagrange's multipliers arising in an optimal control formulation and second network called 'an action network' outputs the optimal guidance/control. In this so-called 'adaptive critic' approach, the inputs to the networks are the current values of the states. This approach needs no external training. System equations, optimality conditions and the costate equations are used in conjunction with the network outputs to provide the targets for the neural networks. When the critic …

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Carryover For Hypersonic '+' And 'X' Configuration Delta Fin Missiles, Harlan F. Nelson Jan 2000

Carryover For Hypersonic '+' And 'X' Configuration Delta Fin Missiles, Harlan F. Nelson

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The Zonal Euler Solver code (ZEUS) is used to predict hypersonic missile flow fields and to determine the carryover factors for the effect of the body on wing lift, Kw(B), and for the effect of the wing on body lift, KB(w). Results are presented for Mach 4, 6, 8, and 10 at an angle of attack of 2 deg. The missile has a conical nose and a cylindrical fuselage with a 1-degree flair angle. Both 'x' and '+' fin configurations are considered. Results are given for 20 and 30 deg semi vertex angles as a function of fur span to …

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Robust Adaptive Critic Based Neurocontrollers For Systems With Input Uncertainties, S. N. Balakrishnan, Zhongwu Huang Jan 2000

Robust Adaptive Critic Based Neurocontrollers For Systems With Input Uncertainties, S. N. Balakrishnan, Zhongwu Huang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A two-neural network approach to solving optimal control problems is described in this study. This approach called the adaptive critic method consists of two neural networks: one is called the supervisor or critic, and the other is called an action network or controller. The inputs to both these networks are the current states of the system to be controlled. Each network is trained through an output of the other network and the conditions for optimal control. When their outputs are mutually consistent, the controller network output is optimal. The optimality is limited to the underlying model. Hence, we develop a …

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Degradation And Uptake Of Benzene In Laboratory Phytoremediation Studies, Carla Ross, Lisa M. Harrison, Adrian Marsh, Lars Zetterstrom, Joel Gerard Burken Jan 2000

Degradation And Uptake Of Benzene In Laboratory Phytoremediation Studies, Carla Ross, Lisa M. Harrison, Adrian Marsh, Lars Zetterstrom, Joel Gerard Burken

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

In Whole-Plant Laboratory Studies, Hybrid Poplar Trees Were Shown to Impact a Variety of Fate and Transport Mechanisms for Benzene. Laboratory Experiments Investigated the Distribution of the Contaminant in the Plant Tissues, Degradation in the Soil Profile, and Volatilization from Both the Soil and Leaf Tissues. a New Testing System Was Developed that Allowed for Rapid Testing that is More Field-Representative Than Earlier Studies. Whole Plants Were Utilized in a Reactor Design that Included Both a Saturated and a Vadose Zone. the Continuous Feed Reactors Were Supplied with a Steady Influent Benzene Stream to Mimic Plume Conditions. the Presence of …

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Cellular Automata Study Of The Feasibility Of A Parallel Optical Computer, Jason Robert Lane Jan 2000

Cellular Automata Study Of The Feasibility Of A Parallel Optical Computer, Jason Robert Lane

Masters Theses

"The speed of modern electronic computers has inherent design limitations which will soon be reached. A possible substitute is the optical computer. In this project, the feasibility of the optical computer is explored by designing and building a parallel optical system. This system is used to test the basic principles that would govern a parallel optical computer. The system is based on the principle of cellular automata, which is a simulation technique used to study interactions of objects in a system. The following goals were set. The system would be based on cellular automata. A one-dimensional array with nine cells, …

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Reconstitution And Characterization Of Membrane Proteins, Sarah Mia Pates Jan 2000

Reconstitution And Characterization Of Membrane Proteins, Sarah Mia Pates

Masters Theses

“A membrane protein, cytochrome c reductase, was crystallized and examined using transmission electron microscopy. Two-dimensional crystals were prepared by two methods. In Method 1, the protein was solubilized in 50 mM Tris-Acetate (pH 6.0)/0.5 mM EDTA70.05% (w/v) Triton X-100 and reconstituted into a mixture of phosphatidylcholine and phosphatidylserine (4:1), dissolved in the same buffer. The Triton X-100 was removed from the mixture by dialysis in the presence of Bio-beads (SM-2) at approximately 25-30 °C. Method 2 was the same as Method 1, except that the vesicles were fractionated before reconstitution, and the pH and temperature for crystallization were 7.0 and …

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Investigation Of Pattern Classification And Feature Selection Of Gaussian Processes, Vivek Ramaprasad Jan 2000

Investigation Of Pattern Classification And Feature Selection Of Gaussian Processes, Vivek Ramaprasad

Masters Theses

"This thesis focuses on the application of statistical techniques for pattern classification where the patterns are power spectra of the recorded acoustic signals of occluded objects. Different approaches used to classify are : The Bayes linear and piece-wise linear classifiers, the correlation classifier, classification using error spectra and the clustering algorithm. Classifiers were designed and experiments were conducted to investigate the performance. The performance is evaluated in terms of the percentage efficiency by counting the number of vectors identified correctly and the number of vectors which were misclassified. The feature vectors from primitive measurement space is then reduced to lesser …

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Two Separate Continually Online Trained Neurocontrollers For Excitation And Turbine Control Of A Turbogenerator, Ganesh K. Venayagamoorthy, Ronald G. Harley Jan 2000

Two Separate Continually Online Trained Neurocontrollers For Excitation And Turbine Control Of A Turbogenerator, Ganesh K. Venayagamoorthy, Ronald G. Harley

Electrical and Computer Engineering Faculty Research & Creative Works

This paper presents the design of two separate continually online trained (GOT) artificial neural network (ANN) controllers for excitation and turbine control of a turbogenerator connected to the infinite bus through a transmission line. These neurocontrollers augment/replace the conventional automatic voltage regulator and the turbine governor of a generator. A third COT ANN is used to identify the complex nonlinear dynamics of the power system. Results are presented to show that the two COT ANN controllers can control turbogenerators under steady state as well as transient conditions and thus allow turbogenerators to operate more closely to their steady state stability …

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Analysis Of Intangible Factors In Waste Minimization Projects, Halvard E. Nystrom, William Ralph Kehr Jan 2000

Analysis Of Intangible Factors In Waste Minimization Projects, Halvard E. Nystrom, William Ralph Kehr

Engineering Management and Systems Engineering Faculty Research & Creative Works

Continual population growth and rising standards of living that accelerate the consumption of limited resources, are forcing society to encourage conservation of these resources. These resources not only include raw material, but also the areas to dispose of the wastes. As a result, communities are driving industries towards waste minimization by limiting waste generation and landfill availability. Firms'' environmentally friendly strategies can gain competitive advantage by leading in environmental practices. This advantage emanates from the reduction of risk of environmental regulatory overreaction, as well as improved asset utilization and landfill utilization. However, these intangible benefits are difficult to identify and …

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Exercising Real Unit Operational Options Under Price Uncertainty, Chung-Li Tseng Jan 2000

Exercising Real Unit Operational Options Under Price Uncertainty, Chung-Li Tseng

Engineering Management and Systems Engineering Faculty Research & Creative Works

In this paper, we use the real options framework to value the operation flexibility of a power plant. The power plant operation is formulated as a multi-stage stochastic problem. We assume that there are hourly spot markets for both electricity and the fuel used by the generator, and that their prices follow some Ito processes. At each hour, the power plant operator must decide whether or not to run the unit so as to maximize expected profit. However, the unit operation is subject to decision lead times and minimum uptime and downtime constraints, so the commitment decision must take into …

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Simple Ensemble-Averaging Model Based On Generalized Regression Neural Network In Financial Forecasting Problems, Cihan H. Dagli, Parinya Disorntetiwat Jan 2000

Simple Ensemble-Averaging Model Based On Generalized Regression Neural Network In Financial Forecasting Problems, Cihan H. Dagli, Parinya Disorntetiwat

Engineering Management and Systems Engineering Faculty Research & Creative Works

Introduces an ensemble-averaging model based on a GRNN (generalized regression neural network) for financial forecasting. The model trains all input individually using GRNNs and uses a simple ensemble-averaging committee machine to improve the accuracy performance. In a financial problem, there are many different factors that can effect the asset price movement at different times. An experiment is implemented in two different data sets, S&P 500 index and currency exchange rate. The predictive abilities of the model are evaluated on the basis of root mean squared error, standard deviation and percent direction correctness. The study shows a promising result of the …

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Strategy Planning For Technological Discontinuities In A Changing Regulatory Environment, William Ralph Kehr, Halvard E. Nystrom Jan 2000

Strategy Planning For Technological Discontinuities In A Changing Regulatory Environment, William Ralph Kehr, Halvard E. Nystrom

Engineering Management and Systems Engineering Faculty Research & Creative Works

This paper describes an approach to the analysis of publicly available financial data for individual industries. These methods enable the analyst to assess past practices and the historical rate of technological diffusion during the transition period of discontinuous technological change. This assessment can provide a basis of comparison for current changes in their industry. These methods are applied to small rural telephone companies during the period of 1960 to 1996. Annual data is presented detailing the change from aerial distribution cable to buried cable by the roughly 600 rural telephone companies financed through loans from the Rural Utilities Services, a …

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Integration Of Battery Energy Storage With Flexible Ac Transmission System Devices, Zhiping Yang Jan 2000

Integration Of Battery Energy Storage With Flexible Ac Transmission System Devices, Zhiping Yang

Doctoral Dissertations

"This dissertation, consisting of five papers, presents the results of research on the incorporation of battery energy storage into a Static Synchronous Compensator (StatCom). The main contribution of this body of work is the establishment of the modeling and control of the StatCom/BESS in power system dynamic applications. The first paper is focused on the steady state characteristics of the StatCom and StatCom/BESS. The characteristic curves of output voltage and output power were proposed and used in comparing the functionality of the StatCom and StatCom/BESS. In the second paper, a StatCom model was proposed and used in power flow analysis. …

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The Anomalous Behavior Of Al³⁺ In Nickel Electrowinning From Sulfate Electrolytes, Michael Holm, Thomas J. O'Keefe Jan 2000

The Anomalous Behavior Of Al³⁺ In Nickel Electrowinning From Sulfate Electrolytes, Michael Holm, Thomas J. O'Keefe

Materials Science and Engineering Faculty Research & Creative Works

The effect of varying concentrations of Al3+ on the morphology and current efficiency of electrodeposited nickel from an acid-sulfate electrolyte was studied. Concentrations of Al3+ of 20 to 100 ppm significantly degraded the nickel-cathode morphology and current efficiency. However, it was found that higher concentrations of Al3+, in the range of 1 to 5 g/L, depending on the electrolyte parameters and operating conditions, improved the deposit morphology compared to deposition from a pure electrolyte. However, the current efficiency remained low. Physical characterization of the nickel revealed that a smoother, more uniform surface resulted from deposition in …

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Modeling And Characterization Of Electrical Transport In Oxygen Conducting Solid Electrolytes, Igor Kosacki, Vladimir Petrovsky, Harlan U. Anderson Jan 2000

Modeling And Characterization Of Electrical Transport In Oxygen Conducting Solid Electrolytes, Igor Kosacki, Vladimir Petrovsky, Harlan U. Anderson

Materials Science and Engineering Faculty Research & Creative Works

A model for the electrical conductivity in acceptor-doped oxides which involves an association between the acceptor-dopants and oxygen vacancies resulting in donor centers is considered. The model relates the behavior of the electrical conductivity with the temperature, ambient atmosphere and band structure. The predictions of the model are compared to experimental data for ZrO2:16% Y and SrCeO3:5% Yb oxygen conductors and some band structure parameters have been determined.

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Evaluation Of Lsco Electrodes For Sensor Protection Devices, Robert W. Schwartz, M. T. Sebastian Jan 2000

Evaluation Of Lsco Electrodes For Sensor Protection Devices, Robert W. Schwartz, M. T. Sebastian

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We have evaluated lanthanum strontium cobalt oxide (La0.50Sr0.50CoOx; LSCO 50/50) as a candidate “transparent” electrode for use in an electrostatic shutter-based infrared sensor protection device. The device requires that the electrode be transparent (80% transmission) and have moderate sheet resistance (300 - 500 Ω/sq.). To meet these needs, the effects of postdeposition annealing on the resistivity and optical absorption characteristics of sputter deposited LSCO thin films were studied. The as-deposited films were characterized by an absorption coefficient of ~ 12,500 cm-1 and resistivities of ~ 0.08 to 0.5 Ω-cm. With annealing at 800°C, the resistivity decreased to 350 μΩ-cm, while …

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Convergence Analysis Of Adaptive Critic Based Optimal Control, S. N. Balakrishnan, Xin Liu Jan 2000

Convergence Analysis Of Adaptive Critic Based Optimal Control, S. N. Balakrishnan, Xin Liu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Adaptive critic based neural networks have been found to be powerful tools in solving various optimal control problems. The adaptive critic approach consists of two neural networks which output the control values and the Lagrangian multipliers associated with optimal control. These networks are trained successively and when the outputs of the two networks are mutually consistent and satisfy the differential constraints, the controller network output produces optimal control. In this paper, we analyze the mechanics of convergence of the network solutions. We establish the necessary conditions for the network solutions to converge and show that the converged solution is optimal.

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An Analog Front-End Speech Processor Using The Ratio Spectrum, John G. Harris, Shao Jen Lim Jan 2000

An Analog Front-End Speech Processor Using The Ratio Spectrum, John G. Harris, Shao Jen Lim

Electrical and Computer Engineering Faculty Research & Creative Works

We have combined the standard front-end filter bank with a feature extraction process to produce a model that requires dramatically less hardware (or software). This new model, based on the frequency-sampled ratio spectrum, can be interpreted as a small set of constant-Q filters whose center frequencies adapt to locations of high signal energy. The resulting feature vectors are shown to outperform several competing techniques for phoneme recognition. Results from fabricated CMOS analog VLSI circuits illustrate a hardware efficient method to sample the ratio spectrum.

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A Probabilistic Analysis Of The Ratio Spectrum, M. D. Skowronski, J. G. Harris Jan 2000

A Probabilistic Analysis Of The Ratio Spectrum, M. D. Skowronski, J. G. Harris

Electrical and Computer Engineering Faculty Research & Creative Works

Recently, Lim and Harris (see IEEE International Symposium on Circuits and Systems, p.277-80, June 1998) developed a novel spectral representation called the ratio spectrum. The ratio spectrum is formed by taking the ratio of the power of a low pass filtered signal to the power of the original unfiltered signal for all filter cutoff frequencies. Features extracted from the ratio spectrum have proven to be promising for phoneme recognition and speech compression. In this work we have shown that the ratio spectrum feature sets are competitive with standard feature sets used for automatic speech recognition. To understand the underlying properties …

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A Silicon Olfactory Bulb Oscillator, Vitor M.Grade Tavares, Jose C. Principe, John G. Harris Jan 2000

A Silicon Olfactory Bulb Oscillator, Vitor M.Grade Tavares, Jose C. Principe, John G. Harris

Electrical and Computer Engineering Faculty Research & Creative Works

This paper presents a low power MOS-VLSI implementation of an oscillator proposed by Freeman to model a very important component of the olfactory cortex. The model dynamics has time constants in the order of 1/220 (s). To accomplish the long-time constants a new filtering technique recently proposed was utilized. All the blocks involving information processing were designed to operate below threshold (weak inversion).

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A Novel Fpga-Based Master/Slave Pci Interface Core, Chris Brueggen, Hardy J. Pottinger Jan 2000

A Novel Fpga-Based Master/Slave Pci Interface Core, Chris Brueggen, Hardy J. Pottinger

Electrical and Computer Engineering Faculty Research & Creative Works

Current high-density, high-speed devices such as Xilinx's Virtex FPGAs are more than capable of implementing a 64-bit, 66 MHz PCI bus interface and associated application specific logic. This paper presents a novel design for an FPGA-based PCI bus interface, which is being used in the development of a medical ultrasound instrument.

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Automated Identification Of The Operational Modes Of Switched Electric Circuits, J. Jatskevich, O. Wasynczuk, E. A. Walters, C. E. Lucas, Steven Pekarek, P. T. Lamm Jan 2000

Automated Identification Of The Operational Modes Of Switched Electric Circuits, J. Jatskevich, O. Wasynczuk, E. A. Walters, C. E. Lucas, Steven Pekarek, P. T. Lamm

Electrical and Computer Engineering Faculty Research & Creative Works

In the analysis of power-electronic-based energy conversion systems, it is important to identify the operational modes of the associated converters and inverters. However, as the number of switching elements increases, it becomes more difficult to analytically establish all possible modes of operation. In this paper, a modelling technique is described wherein a state-space representation of the overall system is generated automatically and updated dynamically as each new topology is encountered. Utilizing this approach, it becomes possible to identify the operational modes of converters and inverters based upon the cyclically repeated sequences of topologies that can be observed during steady-state operation. …

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Editorial, Ahmed Noor, Victor Birman Jan 2000

Editorial, Ahmed Noor, Victor Birman

Mechanical and Aerospace Engineering Faculty Research & Creative Works

No abstract provided.

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Development Of A Functional Basis For Design, Robert B. Stone, Kristin L. Wood Jan 2000

Development Of A Functional Basis For Design, Robert B. Stone, Kristin L. Wood

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Functional models represent a form independent blueprint of a product. As with any blueprint or schematic, a consistent language or coding system is required to ensure others can read it. This paper introduces such a design language, called a functional basis, where product function is characterized in a verb-object (function-flow) format. The set of functions and flows is intended to comprehensively describe the mechanical design space. Clear definitions are provided for each function and flow. The functional basis is compared to previous functional representations and is shown to subsume these attempts as well as offer a more consistent classification scheme. …

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Experimental Characterization Of Hygrothermal And Aging Effects In Textile Composites, Lokeswarappa R. Dharani, Samit Roy, V. Gupta, Weiqun Xu, N. Dixon Jan 2000

Experimental Characterization Of Hygrothermal And Aging Effects In Textile Composites, Lokeswarappa R. Dharani, Samit Roy, V. Gupta, Weiqun Xu, N. Dixon

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper summarizes the hygrothermal and physical aging tests that were conducted on AS4/PR500 5HS textile composite laminates. The objectives of the hygrothermal tests were to determine the diffusivity and maximum moisture content of the laminate. Three temperatures and three relative humidity levels (RH) were used in combination to create seven test conditions. In addition, three stress levels and three damage levels were imposed to examine the combined effects of stress and damage on moisture absorption. Short-term creep tests were performed on neat resin at different test temperatures to characterize physical aging of the resin matrix. In addition, creep and …

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A Heuristic Method For Identifying Modules For Product Architectures, Robert B. Stone, Kristin L. Wood, Richard H. Crawford Jan 2000

A Heuristic Method For Identifying Modules For Product Architectures, Robert B. Stone, Kristin L. Wood, Richard H. Crawford

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Developing product architectures is a key phase in design and development processes. It encompasses the transformation of product function to alternative product layouts. In this paper, we describe a new approach for identifying modules for product architectures. We begin by reviewing the terminology and motivation for modular products. The new concepts of a functional basis and time ordered function chains are used to formally derive functional models of products. Then, three heuristic methods for identifying modules from functional models are presented. Using the formal functional decomposition and heuristic methods, modular design can be executed earlier in the product development process, …

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Tuning Parameter Tolerance Design: Foundations, Methods, And Measures, Daniel A. Mcadams, Kristin L. Wood Jan 2000

Tuning Parameter Tolerance Design: Foundations, Methods, And Measures, Daniel A. Mcadams, Kristin L. Wood

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this paper, a novel technique is presented to solve tolerance design problems. To achieve the desired performance tolerance, the technique uses a subtle, but significant, change in the design: the addition of a tuning parameter in place of an increase in component precision. Statistical models are used to develop a framework for the tuning parameter design method. Also developed is a new, dimensionless design metric which ranks candidate tuning parameters. A step-by-step method is developed for the application of tuning parameters using this metric. The step-by-step tuning parameter design method is applied to a heavy-duty manual stapler as a …

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Using Quantitative Functional Models To Develop Product Architectures, Robert B. Stone, Kristin L. Wood, Richard H. Crawford Jan 2000

Using Quantitative Functional Models To Develop Product Architectures, Robert B. Stone, Kristin L. Wood, Richard H. Crawford

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Developing product architectures is a key phase in design and development processes. It encompasses the transformation from functional model to alternative product layouts. In this paper, we introduce a methodology for representing a functional model of a product in a quantitative manner. In addition to describing product functionality, the quantitative functional model also incorporates customer need ratings. Product design knowledge can be archived and transmitted in databases using this novel representation. Numerical manipulations of such a database assist in developing product architectures. In particular, product families and customer need ratings for modules are easily computed. Prior to the methodology, a …

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Integration Of Csab And Abet, Lee W. Saperstein, Kenneth Martin, Doris K. Lidtke Jan 2000

Integration Of Csab And Abet, Lee W. Saperstein, Kenneth Martin, Doris K. Lidtke

Mining Engineering Faculty Research & Creative Works

The Accreditation Board for Engineering and Technology, Inc. (ABET) and the Computing Sciences Accreditation Board (CSAB) signed a Memorandum of Agreement in November 1998 to integrate CSAB''s accreditation services with ABET, with a transition time of approximately two years. During the interim period, the operations of the Computer Science Accreditation Commission (CSAC) are contracted by CSAB to ABET. A committee with CSAC, CSAB, and ABET representation is working to set up the new commission for accrediting programs in the computing sciences. This new commission will probably be called the Computing Accreditation Commission (CAC). Other activities are underway to try to …

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