Engineering Commons^™

Phase Separation In Glasses, N. J. Kreidl

Materials Science and Engineering Faculty Research & Creative Works

The detection, acceptance and further investigation of glass-glass phase separation was closely connected with the development of methods making detection possible, such as electron microscope technique pioneered and exploited by Werner Vogel, to whom this paper is dedicated on the occasion of his 65th birthday. Structures are not always found in agreement with rules derived from thermodynamic principles, and also depend on thermal history, as well as mode of preparation. The phenomenon is exemplified in many glass-forming systems. Among more recent applications are the control of crystallization by preceding phase separation as in glass-ceramics and semiconductor-doped glasses for non-linear optics. …

Preliminary Design Guide For Cold-Formed C- And Z-Members, Committee On Specifications For The Design Of Cold-Formed Steel Structural Members

American Iron and Steel Institute (AISI) Specifications, Standards, Manuals and Research Reports (1946 - present)

No abstract provided.

Effect Of Flange Restraint On Web Crippling Strength, Roger A. Laboube, Wei-Wen Yu, Bhavnesh H. Bhakta

CCFSS Library (1939 - present)

INTRODUCTION The web crippling limit states equations given in the AISI Specification were primarily developed based on the results in which the flange was not attached to the support beams. This may not accurately represent field practice, since flanges are typically fastened by bolts or welds to their support beam. Due to these fasteners, the Specification equations may be underestimating the web crippling strength of the member. Therefore, a pilot study was proposed to study the behavior of webs, and the load carrying capacity of the webs with restrained flanges.

Ccfss News February 1991, Wei-Wen Yu Center For Cold-Formed Steel Structures

CCFSS Newsletters (1999 - 2008)

No abstract provided.

The Synthesis Of Patterns Using A Series-Fed Array Of Annular Sector Radiating Line (Anserlin) Elements: Low-Profile, Circularly Polarized Radiators, James L. Drewniak, P. E. Mayes

Electrical and Computer Engineering Faculty Research & Creative Works

A series-fed, circularly polarized array of annular sector radiating-line elements that operates over a ground plane and has a low profile is presented. Pattern shaping can be achieved through control of the fraction of the incident power that is radiated by each element. This can be accomplished over a wide range by a simple adjustment in the geometry of each element. A synthesis technique is given, and experimental results are presented. The array is demonstrated to have a high return loss (good impedance match) and a low axial ratio

Quantum Network Theory Of Transport With Application To The Generalized Aharonov-Bohm Effect In Metals And Semiconductors, Cheng-Hsiao Wu, Gunter Mahler

Electrical and Computer Engineering Faculty Research & Creative Works

Quantum transport for resistor networks is developed with a general form factor, where each node point of the network is associated with a potential. The phase factor of the wave function in between two adjacent nodes is related to the reflection coefficient along that path. The exact transmission probability for a generalized Aharonov-Bohm ring is derived for a clean and cold crystal ring of arbitrary two-lead connections. The even- and odd-numbered rings have distinctly different transmission behaviors. The periodicity of the odd-numbered ring with respect to the threaded magnetic flux is shown to be double to that of an even-numbered …

Lrfd Cold-Formed Steel Design Manual, American Iron And Steel Institute

American Iron and Steel Institute (AISI) Specifications, Standards, Manuals and Research Reports (1946 - present)

No abstract provided.

Web Crippling Behavior Of Sections With Web Openings, Wei-Wen Yu, James E. Langan, Roger A. Laboube

CCFSS Library (1939 - present)

No abstract provided.

Instability And Collapse Behavior Of A Seismic Structure, Franklin Y. Cheng, Jeng Fuh Ger

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

The collapse behavior of a 22-story steel building during the September 19, 1985, Mexico earthquake is investigated by studying hysteretic behavior, ductility factors of individual structural components, and overall instability of the building. The hysteresis models for truss-type girders, bracing members, and box columns to be used in the inelastic analysis of this building are developed. A series of inelastic analyses have been performed for the building by using the multicomponent seismic input of actual Mexico City earthquake records. It was found that the structural response exceeds the original design ductility of this building because most girders in the building …

Analytical And Experimental Investigation On Vibration Control Of Piezoelectric Structures, M. J. Tzeng, W-Z Ben Wu

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

Active vibration control of smart structural materials (beam and plate) has been achieved by using distributed piezoelectric actuators. Numerical simulation and experimental testing have been conducted to investigate vibration suppression of the advanced structures. Results from simulation and testing are in satisfactory agreement.

Uplift Capacity Of Z-Purlins, Roger A. Laboube

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

Roof systems constructed using cold-formed steel components, i.e., Z-shaped purlins and interconnected roof panels, have become a very popular form of construction. This roof system is used extensively for single-story commercial and industrial buildings in the United States. The popularity of cold-formed steel members is due in part to their superior gravity load strength-to-weight ratio; however, because of their relatively light weight, a cold-formed member is very susceptible to wind uplift loading. The design specification in the United States for cold-formed steel construction does not provide a comprehensive analytical solution to the problem of wind uplift strength of a cold-formed …

Defect Structure, Nonstoichiometry, And Phase Stability Of Ca-Doped Ycro3, G. F. Carini, Harlan U. Anderson, M. M. Nasrallah, Don M. Sparlin

Materials Science and Engineering Faculty Research & Creative Works

The dependence of the defect structure of Ca-doped YCrO₃ on oxygen activity and temperature was investigated by high temperature thermogravimetric measurements. Defect models developed from electrical conductivity data obtained in a previous study were used to interpret the thermogravimetric data. A correlation was found between the electrical conductivity and the thermogravimetric data which suggested that these data were concomitantly dependent on the acceptor dopant and oxygen vacancy dependance of the thermodynamic parameters. Kröger-Vink type diagrams showing the regions of stability with respect to oxygen activity and temperature were constructed. The TGA data show that Ca-doped YCrO₃ is even …

Unreachable Roots For Global Homotopy Continuation Methods, Soo Hyoung Choi, Neil L. Book

Chemical and Biochemical Engineering Faculty Research & Creative Works

No abstract provided.

Adaptive Gain Control And Contrast Improvement For Medical Diagnostic Ultrasound B-Mode Imaging System Using Charge-Couples Devices, Alan W. Bryant, Thomas J. Herrick

Electrical and Computer Engineering Faculty Research & Creative Works

A B-mode ultrasound imaging system operates by transmitting a high-frequency sound pulse and measuring the strength and time of flight of the reflected signal. The ultrasound signal may be attenuated as much as 60 dB in its round trip to a target and must be normalized so that contrast is not lost in the far field. Manual controls for adjusting receiver gain versus depth are common in many clinical uses but are impractical in most surgical applications. The goal of this project was to design a circuit to automatically adjust the gain. A two-dimensional low-pass filter is used to approximate …

Linear Interpolation Lattice, Cameron K. Coursey, John A. Stuller

Electrical and Computer Engineering Faculty Research & Creative Works

The Well-Known Analysis and Synthesis Filters of Linear Prediction Theory Are Extended Here to Include Linear Interpolation. © 1991 IEEE

A Neural Architecture For Unsupervised Learning With Shift, Scale And Rotation Invariance, Efficient Software Simulation Heuristics, And Optoelectronic Implementation, Donald C. Wunsch, D. S. Newman, T. P. Caudell, R. A. Falk, C. David Capps

Electrical and Computer Engineering Faculty Research & Creative Works

A simple modification of the adaptive resonance theory (ART) neural network allows shift, scale and rotation invariant learning. The authors point out that this can be accomplished as a neural architecture by modifying the standard ART with hardwired interconnects that perform a Fourier-Mellin transform, and show how to modify the heuristics for efficient simulation of ART architectures to accomplish the additional innovation. Finally, they discuss the implementation of this in optoelectronic hardware, using a modification of the Van der Lugt optical correlator

Reduced Order H∞ Controller Design, Seng Chu Chow

Masters Theses

"The problem formulation and the development of the H_∞ optimal control theory are reviewed. Various H_∞ robust controller design techniques, including both state and output feedback cases, together with a brief comparison and some remarks on these methodologies arc presented. Also included are a review of the controller order reduction alternatives and various balanced truncation model reduction methods.

A new model reduction technique with reduced error bound is proposed. This proposed technique introduces a new parameter which can be used to select the spectral norm of the model reduction error at low and high frequency ranges according to …

Impact On Laminated Composite Materials, Serge Abrate

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Laminated composite materials are used extensively in aerospace and other applications. With their high specific modulus, high specific strength, and the capability of being tailored for a specific application, these materials offer definite advantages compared to more traditional materials. However, their behavior under impact is a concern, since impacts do occur during manufacture, normal operations, or maintenance. The situation is critical for impacts which induce significant internal damage, undetectable by visual inspection, that cause large drops in the strength and stability of the structure. Impact dynamics, including the motion of both the impactor and the target and the force developed …

Petri Net Modeling Of A Flexible Assembly Station For Printed Circuit Boards, M. Zhou, Ming-Chuan Leu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Petri net modeling approaches are presented for a flexible workstation for automatic assembly of printed circuit boards. In order to improve the productivity of such a system, the building of mathematical models is a crucial step. Concentrating on the operational aspects, the authors construct ordinary and temporal Petri net models for the AT&T FWS-200 physical flexible workstation. Three outcomes follow from such models. First, designers can have a better understanding of concurrency, synchronization, mutual exclusion, and sequential relations involved in the system control from the graphical representations of Petri nets. Second, the performance analysis of system operations under different settings …

A Commodity Trading Model Based On A Neural Network-Expert System Hybrid, K. Bergerson, Donald C. Wunsch

Electrical and Computer Engineering Faculty Research & Creative Works

Demonstrates a system that combines a neural network approach with an expert system to provide superior performance compared to either approach alone. Learning capability is provided in a software-based approach to commodity trading systems. The authors used the backpropagation network with some parameters selected experimentally. They used a human expert to implicitly define patterns, using hindsight, that an intelligent system might have been able to use for an accurate prediction. Desired outputs were found by a combination of observing the behavior of technical indices that normally precede a certain kind of market behavior, and by observing the actual market behavior …

A Hybrid Optoelectronic Art-1 Neural Processor, Donald C. Wunsch, T. P. Caudell

Electrical and Computer Engineering Faculty Research & Creative Works

Summary form only given. A new implementation of ART-1 (adaptive resonance theory) has been proposed that efficiently combines optical and electronic devices. All parallel computations are performed by the optics, while serial operations are performed in electronics.

A Laboratory Investigation Of Electro-Optic Kerr Effect For Detection Of Electric Transmission Line Faults, Badrul H. Chowdhury, E. Grigsby, T. J. Englert

Electrical and Computer Engineering Faculty Research & Creative Works

A prototype Kerr cell has been constructed and tested for detecting and identifying faults by monitoring high voltages such as are found in electric power delivery systems. Simulated faults were generated under laboratory conditions and monitored by the Kerr cell. Preliminary analysis was done using analog-to-digital conversion of the detected waveforms with a single board microprocessor serially interfaced with a personal computer. The occurrence of faults is readily observed and results indicate that identification of fault types can be accomplished within less than one cycle of a standard sixty-cycle-per-second delivery system. With a dedicated analysis system such a technique may …

A Nuclear Fragmentation Energy Deposition Model, John W. Wilson, D. M. Ngo, T. N. Forgarty, W. W. Buck

Mining Engineering Faculty Research & Creative Works

A formalism for target fragment transport is presented with application to energy loss spectra in thin silicon devices. A nuclear database is recommended that agrees well with the measurements of P.J. McNulty et al. (1980) using surface barrier detectors. High-energy events observed by P.J. McNulty et al. (1981), which are not predicted by intranuclear cascade models, are well represented by this work

Compensation Modes In Counterdoped Rutile, M. M. Nasrallah, Harlan U. Anderson

Materials Science and Engineering Faculty Research & Creative Works

Thermogravimetric measurements were conducted on undoped, Nb⁵⁺ or Ta⁵⁺ donor-doped, and Al³⁺ acceptor doped rutile at 1000°C and 105-10-7 Pa oxygen activity. Nb⁵⁺ or Ta⁵⁺ doped rutile was counter doped by Al³⁺ in order to identify the role of Al³⁺ acceptor and its effect on donor doped rutile. Our results show that both dopants enter the lattice substitutionally for Ti⁴⁺, that Al³⁺ is as effective an acceptor as Nb⁵⁺ or that Ta⁵⁺ is effective as a donor, and the compensation occurs on a one-to-one basis. Earlier reports indicate …

Positron Study Of Defects And Diffusion Induced Grain Boundary Migration In A Pb-Sn System, A. Belaidi, Hollis P. Leighly, H. Aourag, B. Khelifa, M. Oubadi, A. Elias

Materials Science and Engineering Faculty Research & Creative Works

The Pb-Sn system discloses a remarkable effect at the intermediate α → α + β phase boundary. The observation of the sharp transient peak in the S-parameter curve which is analogous to those found in thermal capacity curves is, as far as the authors are aware, unique in such positron measurements. This effect is interpreted in terms of positron trapping in defects associated with the strains accompanying the initial stage of transformation. This short note offers a new approach to the underlying phenomenon published in J. Phys. F. Met. Phys., 12 (1982) 813 by A. Belaidi, H. P. Leighly Jr. …

Electrical Conductivity, Seebeck Coefficient And Defect Chemistry Of Ca-Doped Ycro3, G. F. Carini, Harlan U. Anderson, Don M. Sparlin, M. M. Nasrallah

Materials Science and Engineering Faculty Research & Creative Works

The electrical transport behavior and defect structure of Ca-doped YCrO₃ were studied using electrical conductivity and Seebeck coefficient measurements as a function of oxygen activity and temperature. Defect models derived from the electrical conductivity data were found to adequately relate the concentration of charge carriers to the acceptor dopant and oxygen vacancy concentrations. Thermodynamic properties were calculated and found to be consistent with the model. Activation energy and carrier mobility data were also obtained. The analysis of the electrical conductivity, Seebeck and mobility data suggest that the conduction process in Ca-doped YCrO₃ occurs via the small polaron hopping …

Occupation Dynamics Of Trap States In An A-Si:H Thin-Film Transistor, J. N. Bullock, Cheng-Hsiao Wu

Electrical and Computer Engineering Faculty Research & Creative Works

We calculate the dynamical behavior of a-Si:H thin-film transistors with an emphasis on the occupation dynamics of trap states. The appropriate rate equation for the occupation function of trap states is included. We show the relations of filling the trap states with the switch-on time and of emptying the trap charges with the switch-off time. The occupation functions in both cases are non-Fermi distribution. The quasi-equilibrium approximation underestimates those two time constants. Thus, transit time theory cannot describe the speeds of transistors made from disordered materials.

Matrix Cracking In Laminated Composites: A Review, Serge Abrate

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This article presents an overview of the problem of matrix cracking in laminated composite materials. The parameters governing the onset and accumulation of internal damage under several types of loadings are reviewed. The analysis of laminates with matrix cracks can be performed using a shear-lag model, variational, elasticity, finite element or finite difference approaches. Prediction of further cracking is based on either a fracture mechanics approach or a probabilistic failure strength theory. Continuum damage mechanics are used by some investigators to model the behavior of the cracked laminate. Recent developments in this area are summarized here, and suggestions for future …

Design Of Robust Controllers For Gas Turbine Engines, D. E. Moellenhoff, Vittal S. Rao, C. A. Skarvan

Electrical and Computer Engineering Faculty Research & Creative Works

This paper describes robust controller design methodologies for gas turbine engines. A linear state variable model for the engine is derived using partial derivatives. The Linear Quadratic Gaussian with Loop Transfer Recovery (LQG/LTR) and the Parameter Robust Linear Quadratic Gaussian (PRLQG) robust controller design methodologies have been used to design a controller for gas turbine engines. A new method is proposed by combining the features of LQG/LTR and PRLQG methods and yields good robustness properties with respect to both unstructured uncertainties in the frequency domain and structured parameter variations in the time domain. The new procedure is illustrated with the …

A Technological Development Model For Strategy Formation, Halvard E. Nystrom

Engineering Management and Systems Engineering Faculty Research & Creative Works

Summary form only given, as follows. The author presents a technological development model for product and company development based on a distinction between explicit and implicit technologies. Implicit technologies are evolving technologies while explicit technologies are established technologies. Based on empirical data from Swedish companies, a number of strategic dimensions are discussed such as network interaction and combining knowledge from various sources. These concepts are then used to present an integrated model of strategy formation and product and company development. It is argued that this view of technological development facilitates the understanding and analysis of innovation and entrepreneurship in highly …