Methods of expressing the radiation patterns of phased arrays in closed form that include the effects of radiated mutual coupling are investigated. The two basic methods considered are the classical array analysis method and the active element pattern methods. The theoretical derivations of the active element pattern methods are presented and the various types of active element patterns are defined. Also, a new method based on active element patterns, the hybrid active element pattern method, is introduced which accurately predicts the patterns of small and moderately-sized arrays of equally-spaced elements. Arrays of center-fed dipoles are considered in this study since dipole arrays can be fully characterized, including mutual coupling, using modem numerical electromagnetic analysis codes, thus allowing verification of the array analysis methods presented here. The results are general, however, and may be applied to arrays of any type of element. The array patterns computed using the classical analysis method and the active element pattern methods are compared to those computed using ideal array analysis and the highly-accurate numerical codes. / Master of Science

Extensive research to determine the strength of steel deck reinforced concrete floor systems has been carried out on single-span, single panel width test specimens. Little of this research has considered the benefits that actual field conditions have on overall strength and stiffness. This experimental study investigates typical field details at intermediate supports and end spans. In particular, the influence of adjacent spans and typical pour stop details are considered. Additionally, this study illustrates the applicability of simple analytical models, which can be used to determine the strength and stiffness of steel deck reinforced concrete floor systems. / Master of Science

In the past forty years, much work has been done in the area of multiple scattering effects on the propagation of electromagnetic waves in a random particulate medium. This work is important to wave propagation in the atmosphere, the planetary sphere, and the ocean. Current research is aimed at high frequencies (gigahertz to terahertz). At these frequencies, multiple scattering effects become very important since the wavelength reduces to the size of a particle. The purpose of this thesis is to augment the Twersky theory of multiple scattering in a random particulate medium. Most applications of Twersky’s work use a far-field approximation and a point-particle assumption. At high frequencies, particle sizes may be large relative to a wavelength; therefore, the point-particle assumption is inaccurate. Under a low-density approximation, this thesis introduces a scattering operator, which defines closed equations for the fields due to multiple scattering. The low-density approximation holds for many media (e.g. clouds and rain). The scattering operator may be solved for various particle shapes, eliminating the need for the point-particle assumption. / Master of Science

Nearly periodic structures exhibit localized modes of vibration depending upon the ex· tent of the coupling and the disorder between their periodic components. These localized modes may cause excessive vibration amplitudes resulting in significantly higher stresses than the ones the structures have been designed to withstand. The Rayleigh-Ritz method, as employed earlier, for dynamic analysis for two-span beams could predict only the lower modes of vibration at prohibitive computational expense. A semi-analytical method which predicts even the higher modes at significantly reduced cost has been applied to the free vibration analysis of two-span beams. This method has been applied to the forced vibration analysis of a couple of mistuned turbine blades modeled as a two- span beam rotating in a turbulent flow field. It is shown that the maximum vibration amplitude of the mistuned structure may increase by several hundred percent as compared to that of the perfectly ordered structure. / Master of Science

Even with the performance of microprocessors expected to double within the next three to five years, the processing power increase offered by parallel processing has made multiprocessor systems very cost-effective. Each module in the multiprocessor systems will typically include a processor, coprocessor, cache, and main memory. This kind of architecture has generated the system-on-aboard distributed-intelligence concept, and the 32-bit multimaster buses thus come into play since these high-performance systems need to communicate with each other. During communication, commands and large blocks of data are transmitted across the bus. Along with the multiprocessor system, the single-CPU system continues to need a fast bus and wide data path to serve as a common I/O interface for terminals, disk storage devices, communication, and memory boards. With the board size limited, the trend toward distributed intelligence increases the need to place more functions on a single board, and therefore bus interface unit (BIU) integrated circuits (ICs) play an important role in the design of new boards. Spaceborn systems must be fault-tolerant due to their high susceptibility to transient faults and the high costs of repair and maintenance. Hence, a gate array fault-tolerant bus-interface IC based on modified NuBus protocols is designed to meet these requirements. The gate array IC design system HIGHLAND from United Technologies Microelectronics Center is used, along with other CAD tools such as the Berkeley VLSI Tool Set and LOGEN to generate a layout for the BIU. Two programs are written to interface the necessary CAD tools. All the circuits are designed and simulated on a VAXstation 3200 (Ultrix-32) and VAX11/785 (VMS). / Master of Science

Many structures are sensitive to initial imperfections, sometimes leading to a great decrease in buckling load. Koiter showed that the effect of initial imperfections is largely determined by the initial post-buckling behavior of the perfect structure. The present work seeks to implement Koiter’s method of asymptotic post-buckling analysis on a finite element program Engineering Analysis Language (EAL). EAL is based on engineering strain measures. It is shown via examples that the predicted post-buckling behavior of a structure for engineering strain measure is approximately the same as that for Green’s strain measure provided the strains are small. To characterize the post-buckling behavior by Koiter’s method in the finite element form, the linear and incremental stiffness matrices are required. These matrices comprise the tangent stiffness matrix. As EAL uses the modified Newton-Raphson procedure to solve nonlinear structures, it calculates the tangent stiffness. The first and second order incremental stiffnesses are extracted by partial differentiation of the tangent stiffness using a second order central difference scheme. The linear stiffness is directly given by the EAL processor ”K”. These stiffnesses are then used to get the post-buckling load-displacement behavior close to the bifurcation point. Numerical results for the initial post-buckling behavior are obtained for truss and frame structures using the Koiter’s analysis procedure on EAL. It is compared to the nonlinear load-displacement behavior of the structures with small initial imperfections. The post-buckling load-displacement behavior for a knee frame is also compared to the behavior obtained experimentally by Roorda [19] and analytically by Koiter [13]. The asymptotic analysis procedure has given good asymptotic post-buckling results. / Master of Science

The harmonic excitation of simply supported Euler plates is performed experimentally using arrays of piezoceramic patch pair actuators bonded to the plate surface. The experimental techniques used are presented, and the effects of patch location, relative actuator phasing, and excitation frequency on modal excitation are demonstrated. In addition, experimental results are compared to a previously developed closed-form solution which predicts the modal distribution due to such excitation. Finally, a finite element model of a simpler 2-D case of beam actuation is employed to illustrate the effects of the adhesive layers between the patches and structure on modal excitation. Results show that the closed-form solution is capable of predicting both the relative modal distribution and absolute modal amplitudes for different experimental configurations and indicate that with knowledge of the system resonant frequencies and nodal lines, experimental parameters such as excitation frequency, patch location, and relative patch phasing can be logically manipulated to produce a desired vibrational response. The results of the finite element analysis reveal that the net effect of the finite adhesive layer depends on both the stiffness and thickness of the layer, and that increasing either of these parameters can result in multiple consequences, which can combine to positively or negatively affect modal excitation levels. / Master of Science

The purpose of this thesis was a) to review the design process literature in architecture and urban planning, b) to develop a model of the interior design process, and c) to apply parts of the model in a case study. The genesis and evolution of design processes in fields allied with interior design was traced. The review of literature established that interior design has little documentation of the design process. Much of what exists is borrowed from architecture and urban planning. / Master of Science

Shape memory alloys (SMA) have the unique ability to recover large strains and generate large recovery stresses via a repeatable martensitic transformation. Stress-strain and shape memory effect characteristics are needed in order to develop SMA force actuator design methods. Moreover, constitutive models able to quantitatively predict these characteristics and thus be useful as engineering design tools are also needed. An experimental apparatus designed to characterize the mechanical behavior of SMA was built and utilized. The apparatus is used specifically to gather stress-strain and shape memory effect characteristics from nitinol wire whereby mechanical properties associated with the material are determined. Phenomena such as the R-phase and stress induced martensite serration are investigated. A one-dimensional constitutive model is presented that quantitatively predicts stress-strain and shape memory effect behavior and was developed with the intention of being an engineering design tool for SMA force actuators. Experimental stress-strain and shape memory effect results are compared against that predicted by the model with the intention of verifying the model. The model displays the ability to predict stress-strain behavior that is in good quantitative agreement with experiment. The model also displays the ability to predict hysteric shape memory effect behavior for free, controlled, and restrained recovery cases of selected prestrains that is in good quantitative agreement with experiment. The model is unable to predict shape memory effect behavior such as the R-phase. Demonstrating the ability to experimentally investigate a constitutive model will hopefully inspire further combined experimental and theoretical SMA research. / Master of Science

The responses of larval fish to toxicants in subchronic toxicity tests may be modified by events and stressors not associated with the toxicants themselves. In the following work, three potential modifying factors related to larval fish growth, survival, and response to toxicant stress were investigated. Using four-day acute cadmium toxicity tests and seven-day subchronic toxicity tests, differences in the responses of larvae based on the age of the larvae, their exposure to methylene blue, and changes in environmental pH were determined. The age of larvae chosen for toxicity tests, 1 to 24 h old, 24 to 48 h, or 48 to 72 h, did not significantly affect the cadmium (Cd) LC_50S in acute tests or the larval growth or survival in subchronic tests. Prior methylene blue (MB) exposure in larval fish was. not found to affect the Cd LC₅₀ compared to unexposed larvae. However, in subchronic tests with industrial effluents, prior MB exposure resulted in lowered survival or lowered growth, but did not increase sensitivity to the effluent. Lowered growth and survival was observed in blue- dyed individuals from larval populations exposed to MB during the interval from hatch to test commencement. At 20°C, the acute toxicity of MB, as indicated by the LC_10S, was apparent at concentrations greater than 44 mg MB/L in 24 h. At the suggested fathead minnow culture temperature, 25°C, concentrations greater than 5.0 ppm were acutely toxic in 96 h. Chronic toxicity, determined at 25°C, was found at levels greater than 2.12 mg MB/L. Light intensity negatively affected MB chronic toxicity. Chronic values estimated by larval fish growth response were significantly lower in the test done under normal lab light compared to that done under very subdued light. Larval fathead minnows were sensitive to low pH stress based on the acid used to lower test solution pH. Hydrochloric acid was found least toxic to larvae at low PH; phosphoric acid was found most toxic. Larvae tolerated instantaneous changes in pH 2.0 units lower and 1.5 units higher than their culture water without any significant decrease in growth and survival as measured in 7 d. These results indicate that the pH tolerance range for larval fathead minnows, where no effects are seen on growth or survival, is greater than pH 6.0 and less than pH 9.5. / Master of Science