Legacy Theses and Dissertations (1940-2009)

Permanent URI for this collectionhttps://hdl.handle.net/10657/6771

This collection gathers digitized University of Houston theses and dissertations dating from 1940.


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    Availability of morphine sulfate and meperidine hydrochloride in total parenteral nutrition
    (1984) Macias, Jean M.; Martin, William J.; Lloyd, Charles W.; Driever, Carl W.; Gupta, V. Das
    At a comprehensive cancer center, patients experiencing severe chronic pain are managed by continuous infusion of narcotics via their TPN solutions. In some cases, patients have reported recurrence of pain when their narcotics were added to their TPN solutions shortly after titration in D5W. The purpose of this study was to evaluate the compatibility, stability and availability of two narcotics (morphine sulfate and meperidine hydrochloride) prepared in TPN and D5W. For this study a usual dose (300 mg) of each narcotic was mixed in the same types of products utilized with these patients (0.25 L bags of D5W and 3 L bags of TPN). Visually, each solution was examined immediately post-addition of drug to the bag and then every 12 hours for 36 hours. By high performance liquid chromatography (HPLC), the narcotic concentrations for each solution were determined prior to addition of drug to the bag, immediately post-addition of drug to the bag, and continuing every 4 hours for 36 hours. Results demonstrated no significant loss of morphine sulfate or meperidine hydrochloride due to adsorption to the polyvinyl chloride (PVC) bags. In addition, both narcotics were physically and chemically compatible, as well as, stable and available for at least 36 hours when stored at 21.5[degrees] C with no protection from environmental light.
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    Benzylamine oxidase activity in pathological states
    (1984) Hayes, Barbara Elaine; Clarke, David E.; Lokhandwala, Mustafa F.; McCalden, Thomas A.; Miller, Harold H.; Ostrow, Peter T.
    Benzylamine oxidase (BzAO) is an amine oxidase of unknown physiological significance. However, clinical studies show that BzAO activity is elevated in the serum of patients with fibrotic disorders and during growth spurts in children. Some workers have suggested, therefore, a functional association of BzAO in the biochemistry of connective tissue. The objective of the present research was to test this proposed association by measuring BzAO activity in conditions exhibiting enhanced connective tissue growth and proliferation. BzAO activity was measured in cellular systems as well as in serum, utilizing both human and animal tissues (human atherosclerotic aortae, bleomycin-induced lung fibrosis in rats, spontaneously hypertensive rats, and the hormonally manipulated rat uterus). No specific relationship between the activity of BzAO and connective tissue growth was found. BzAO activity was decreased significantly in plaque regions of atherosclerotic aortae, but this decrease was due to a reduced cell population density compared with nonplaque areas and normal aortae. In bleomycin-treated lungs, lysyl oxidase activity increased markedly, but again BzAO activity showed no specific change (lung and serum). Overall, similar negative results were found in hypertensive rats and in the rat uterus. In rat uteri (ovariecto-mized and estrogen-treated), BzAO activity was found to follow passively organ weight changes and, unlike monoamine oxidase, was unresponsive to direct hormonal influences. Since BzAO may be located predominantly in association with the smooth muscle cells of uterine blood vessels, changes in the activity of uterine BzAO may reflect changes in the vascularity of this organ (number of blood vessels per unit weight or wall thickness or both). An organ specific, disease dependent change in BzAO activity was found in diabetic rats where the activity of the serum and kidney enzyme was elevated in association with hyperglycemia. BzAO activity of lung, aorta and pancreas did not change significantly. Studies showed a different substrate profile for BzAO in the serum and kidney from that in aorta, lung and pancreas, indicating a possible heterogeneity of BzAO activity. It is speculated that elevations in the activity of serum BzAO may be reflective of renovascular damage associated with diabetes mellitus.
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    Effect of selected drugs on in vitro blood glucose determinations
    (1984) Rice, Gary K.; Galt, Kimberly O Bey; Driever, Carl W.; Martin, William J.; Lloyd, Charles W.
    Accurate determinations of urine and/or blood glucose are essential for the insulin dependent diabetic who is using these determinations to assess diabetic control. [...]
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    An investigation of factors influencing the perception accuracy of college recruiters
    (1983) Coverdale, Susan Hammond; Arvey, Richard D.; Campion, James E.; Rozelle, Richard M.; Blakeney, Roger N.; Sparks, C. Paul
    This study investigated the influence of various factors on the ability of college recruiters to accurately perceive the importance of intrinsic and extrinsic job characteristics to candidates interviewed. These factors included the interaction of recruiter and candidate sex, race and age as well as recruiter job familiarity and implicit personality theory. Data were collected at 14 college campuses throughout the country in conjunction with the recruitment program of a large petrochemical company. The sample consisted of 23 recruiters and 182 candidates. The results indicate that recruiter-candidate similarity on sex, race and age has no significant effect on perception accuracy. The same was true of recruiter job familiarity. There was some evidence that accurate and less accurate recruiters were differentiated by their implicit personality theory. These results are interpreted and discussed in the light of some statistical problems encountered. The design of future research in the area is suggested.
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    Physical modeling studies of thin beds
    (1983) Marhadi; Sheriff, Robert E.; Gardner, Gerald H. F.; McDonald, John A.
    This thesis describes a physical modeling study of seismic reflections from thin beds. Three models representing common thin bed situation were used in the study. In the first model, we studied the reflections from a homogeneous thinning bed embedded in a low velocity material, to determine amplitude and waveshape changes associated with changes in the bed thickness. In the second model, we studied the reflections from a thin bed which is composed of interlayering of high and low velocity materials of the same thickness, to investigate how reflections from a series of strata differ from reflection from a massive bed. In the third model, we extended the second model to study the reflections when the layers composing the thin bed are not of the same thickness, to verify the conclusion of numerical modeling that reflection amplitude and waveshape are not sensitive to how layers are distributed as long as the overall interval is thin. The results from the first model mostly agree with theoretical predictions published in the literature. In the second and third models the results show that not only interference but also other factors are important in constructing the reflection when the overall interval is thin. We also found that the waveshape is affected by the distribution of the layers in the thin bed, in contrast to the conclusion of numerical modeling published in the literature. We extended models two and three to model a concept of transgressive sands onlapping onto an unconformity, which relates to the question as to whether seismic reflections follow time or facies lines. The seismic sections show the attitude of most reflections are those of time lines.
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    The influence of substrate material on thermal stability of selective solar absorbing black chrome
    (1982) Bacon, Debra Ann; Ignatiev, Alex L.; Wood, Lowell T.; Chu, Paul C. W.; Wolfe, John C.
    The role of the substrate in optical degradation of solar absorbing black chrome films has been investigated. Past work in establishing the optical properties, microstructure, and optical degradation characteristics of these electroplated coatings has used nickel as the substrate. For temperatures less than 450[degrees]C the primary mode of degradation was believed to be changes in the film. It was later found that the thermally activated mechanism of substrate diffusion and oxidation existed for temperatures as low as 400[degrees]C. These results led to a consideration of other materials in the hope of finding a more thermally stable substrate. The metals to be considered here as substrates are copper, gold, nickel, chromium and stainless steel #304. The experimental techniques incorporate hemispherical reflectivity, normal emissivity, scanning electron microscopy, and Auger electron spectroscopy. Black chrome coating on each substrate candidate undergoes equivalent analyses (1) in the "as-prepared" case, (2) after air heating to 300[degrees]C for 24 hours, and (3) air heating to 450[degrees]C for 24 hours. In this work, diffusion at 450[degrees]C was shown to exist for all of the substrate materials considered. Stainless steel #304 however, demonstrated a selective diffusion and oxidation mechanism which significantly reduced optical degradation of the black chrome for temperatures up to 450[degrees]C. Of the candidates considered, this alloy substrate was found to be the most suitable for enhancement of thermal stability of black chrome.
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    Study of the morphology, toxicity and sterol composition of marine tropical benthic dinoflagellates, family ostreopsidaceae
    (1982) Besada, Eulogio G.; Loeblich, Alfred R., III; Alam, Maktoob; Jurtshuk, Peter, Jr.; Klass, Michael R.
    Cultures of Coolia monotis, Gambierdiscus toxicus and Ostreopsis ovata were initiated fron intertidal areas from the Caribbean Sea and G. toxicus from the Florida Keys. This is the first report of these three species from the Caribbean Sea; overwintering of G. toxicus in the Florida Keys is also documented. Photomicrography of thecae and scanning electron microscopy of cells of O. ovata revealed the following thecal plate tabulation: 1pp, 4', 6'', 6c, 8s, 5''', and 2''''. Variations in thecal plate numbers and tehcal fission lines are reported for O. ovata. Thecal plate assignments, based on interpretations of plate homologies, demonstrated gonyaulocoid affinities of these three genera and a sufficiently close relationship among them to place them in the family Ostreopsidaceae. Transmission electron micrographs of each of the three species revealed a unique cytoplasmic feature: vesicle-bound, spirally coiled, fibrous material. An astral aggregation of these vesicles (=pusule) occurred near the sulcal region. The tethered habit of these species is discussed in relation to the spiral bodies. Bioassays for toxicity in C. monotis and O. ovata and G. toxicus (Florida isolate) revealed the presence of toxic activity only in the lipid soluble fraction of G. toxicus. The minimal amount of residue that was lethal in less than 24h was 101 [micrograms] per g of mouse tissue, or 510 mouse units per 10[superscript 6] cells. Sterols were analysed by gas chromatography-mass spectrometry. For C. monotis and O. ovata, only cholesterol and dinosterol were detected (ration 2:1). An additional sterol, 24-methylcholesterol, was present in G. toxicus. The relative percentage of sterols in G. toxicus were 47% cholesterol, 20% dinosterol and 33% 24-methylcholesterol. Qualitative and quantitative similarities in the sterol fractions from members of these genera suggest they form a natural group (family Ostreopsidaceae). The sterol pattern of this family closely resembles that r eported for members of the family Gonyaulacaceae; confirming the conclusion, from morphological studies, that they are close relatives.
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    Marital satisfaction and communication skill : a cross-lagged panel correlation study
    (1982) Harris, Gerald Evan; Vincent, John P.; Brady, C. Patrick; Cook, Nancy Illback; Mariotto, Marco J.
    Marital discord is an extremely pervasive mental health problem and has been related to a wide variety of other health problems. Previous research comparing distressed and nondistressed couples has identified communication as a central discriminating factor, yet there is a lack of investigation of the relationship between marital satisfaction and communication behavior over time. The present study directly addresses this relationship by examining longitudinal data on 40 couples concerning their communication skills and marital satisfaction. Data were collected both before and after the birth of the couples' first child, an event presumed to call upon their coping responses in order to maintain marital satisfaction. Cross-lagged panel correlation analysis was used to examine the relationship between behavior and satisfaction across a four-month time span. Results indicated that communication and satisfaction within the marriage interact in different ways, depending on the context of the behavior. In an emotional support and under standing context, marital happiness appears to influence later negative verbal behavior such that initially happier couples later use fewer negative verbal behaviors. However, in a problem-solving context the opposite seems to be true; negative verbal behavior apparently influences later marital satisfaction. Theoretical and practical implications of the results and methods are discussed.
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    Design and analysis of a continous belt oil skimmer control system using the classical approach
    (1982) Barassamian-Azargen, Andranik; Schneider, William P.; Whitaker, Thomas N.; McInnis, Bayliss C.; Michalopoulos, Constantine D.; Long, Stuart A.; Prengle, Herman William, Jr.
    Mechanical devices for the removal of oil from the surface of water are known collectively as "skimmers". One type that shows excellent recovery performance consists of a continuous belt deployed between the sea surface and an oil collection point. For proper operation, the skimming material should have zero relative velocity to the oil surface. Consequently the most important consideration in the design of this system is to maintain the speed of the belt at the same speed as the oiled surface passing the vessel; that is, between the sea surface and the continuous belt is zero velocity. A design of a control system to automatically provide zero relative velocity for the desired range of skimmer speeds is presented in this thesis.
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    Modeling and migration by the fourier transform method
    (1982) Baysal, Edip; Sherwood, John W. C.; McDonald, John A.; Butler, John C.; Gardner, Gerald H. F.; Sheriff, Robert E.
    A Fourier or pseudo-spectral forward modeling algorithm for solving the two-dimensional acoustic wave equation is presented. Time derivatives which appear in the wave equation are calculated by second order finite differencing, whereas spatial derivatives are calculated by Fast Fourier Transforms (FFT). The scheme requires fewer spatial grid points than finite difference methods to achieve the same accuracy. This method is tested against known analytic solutions and physical modeling results. The "Exploding Reflector" concept (Loewenthal et al., 1976) is examined for the modeling of zero source-to-receiver offset sections. The acoustic wave equation is compared with a one-way wave equation which represents the upgoing wavefield only. The one-way wave equation used is not derived through an expansion and, therefore, can represent dips up to 90 degrees. There is apparently no simple counterpart of this equation in the space domain and it can be conveniently implemented only by a Fourier method. The inverse problem (migration) is investigated using the complementary version of the one-way wave equation employed for modeling. Also a novel alternative of carrying out the migration through a reverse time extrapolation is examined. This method is tested using synthetic data. A new two way "non-reflecting" wave equation is derived, which gives highly reduced reflection coefficients at material boundaries. This new equation is used in both zero source to receiver offset modeling and "reverse time" depth migration. The examples show that this equation is capable of simulating raypaths which bend beyond the horizontal due to refraction associated with large velocity gradients. It should be useful for the modeling or migration of primary reflections from the underside of complex structures such as overhanging salt domes or steep thrust faults.
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    High pressure study on some unusual magnetic and superconducting materials
    (1982) Wu, Maw-Kuen; Chu, Paul C. W.; Moss, Simon C.; Ting, Chin-Sen; Kevan, Larry
    A series of high pressure studies on several different and yet related materials with unusual magnetic and superconducting properties are made. The results suggest that (1) the competition among different interactions in a single system dictates the observed physical phenomena, and (2) novel superconducting mechanism may exist in some unusual superconducting materials. These are exemplified by the following compound or alloy systems: (1) From the study on the random magnetic alloys, we propose that the paramagnetic -> ferromagnetic -> spin-glass transition observed in several alloys on cooling is due to the delicate balance among the ferromagnetic, antiferromagnetic and a third unknown freezing mechanism present in the systems. And in a two stage process, the balance between the ferromagnetic interaction and the antiferromagnetic interaction determines the appearance or the disappearance of the ferromagnetic order, while the freezing mechanism causes the spins to freeze randomly and the formation of spin-glass state. (2) The Chevrel phase ternary Ce1.2Mo6S8 is found to behave like a dilute Kondo system, in spite of the large concentration of the Ce-atom locate periodically in the lattice. The results also show that the magnetic behavior in this compound is determined by the competition between an antiferromagnetic state and a Kondo state and the system can be treated as a Kondo lattice system. (3) The high pressure effects on the itinerant ferromagnets TiBe2-xCux and ZrZn2 compounds are found to be in agreement with the idea proposed by Enz and Matthias that the magnetism in these compounds originate from the electron-phonon interaction, which is also responsible for the superconductivity observed in the constituent elements. However, the predicted appearance of the p-pairing superconductivity after the complete suppression of magnetism is not found in the study. (4) The pressure-induced superconductivity observed in the Chevrel ternaries Eu1.2Mo6S8 and BaMo6S8 is rather intriguing. The non-monotonic variations of the superconducting signal and the superconducting transition temperature with pressure, and the non-bulk superconductivity suggest that the superconductivity observed may be due to some non-conventional superconducting mechanism. Based on the experimental data, the interface superconductivity is proposed as a plausible candidate. (5) In the study of the perovskite oxide BaPb0.8Bi0.2O3 compound, we found that the relatively high superconducting transition temperature in the system may also originate from a novel superconducting mechanism. Although a strong electron-phonon coupling mechanism can account for some of the recent observations, our results suggest the presence and importance of the grain boundaries in the compound. From these studies, we have not only provided some clues for the better understanding of different physical phenomena, but also directions for the synthesis of materials with novel properties.
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    Laser desorption mass spectrometry of nonvolatile biomolecules
    (1981) Hardin, Ernest Dwayne; Vestal, Marvin L.; Middleditch, Brian S.; Wentworth, Wayne E.; Deming, Stanley N.; Wendlandt, Wesley W.
    A new approach for mass analysis of nonvolatile, thermally labile biomolecules by laser desorption mass spectrometry (LDMS) has been developed. [...]
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    Analysis of the mini-pantograph/fixed rail sliding-contact current collector as used on transit systems
    (1980) Lott, J. Sam; Waldron, Kenneth J.; Shoup, Terry E.; Anderson, Wallace L.; Finch, Robert D.
    The method of current collection by a mini-pantograph which forms a sliding electrical contact with a fixed power rail is evaluated for use on a guided vehicle transit system. In order to establish the constraints on the problem of current collection at high speeds, the general theory of sliding electrical contacts is examined and conclusions are made on its application in terms of contact wear at the brush/rail interface. The "state of the art" in mini-pantograph current collectors is established by a discussion of the mechanical configurations of guided transit systems in this class and a review of the published material on the dynamic analysis of current collection. Finally, this background of information is applied to a conceptual actively controlled current collector and the results of a digital computer simulation lead to conclusions on the practicality of the active current collector concept.
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    The use of the temperature dependence of ultrasonic velocity in the measurements of residual stresses in aluminum and A533B steel
    (1981) Wang, Jen Jo; Salama, Kamel; Cook, Bill D.; Long, Stuart A.
    The effects of applied stress on the temperature dependence of 10 MHz ultrasonic longitudinal velocity have been studied in aluminum and steel. The study was made on the three aluminum alloys, 6061-T4, 2024- T351, and 3003-T251, and the steel alloy type A533B. In all measurements, the ultrasonic velocity is found to decrease linearly with temperature, and the slope of the linear relationship varies considerably when the specimen is subjected to stress. This slope is also found to change linearly as a function of applied stress. The results obtained on the aluminum alloys show that the temperature dependence of ultrasonic velocity increases as the amount of applied stress is increased for both tensile and compressive stresses. These results also indicate that the relative changes in the temperature dependence of ultrasonic velocity due to applied stress are insensitive to composition and texture, and the data obtained on the three types of alloys can be represented by a single relationship. Using this relationship, the sensitivity in determining unknown residual stresses in these alloys is estimated to be [plus-minus]10 MPa. The results obtained on type A533B steel, however, show that the slope of the linear relationship between velocity and temperature increases or decreases according to whether the stress is applied in tension or in compression respectively. The results also indicate that the relative change in the temperature dependence of the velocity is a linear function of applied stress, and the slope of this linear relationship is the same for both tensile and compressive stresses. These results were used to determine the value of the temperature dependence of the ultrasonic velocity at zero residual stress. They were further used to obtain a relationship between the temperature dependence and the residual stress. This relationship represents the calibration which can be utilized for the determination of unimown residual stresses in type A533B steel. The sensitivity of this method in the determination of residual stresses in this steel is estimated to be [plus-minus]34 MPa.
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    Prediction of component survival time by application of the asymptotic theory of extreme order statistics
    (1982) Abdallah, Mohamed G.; Wheeler, Lewis T.; Marshek, Kurt M.; Tait, Robert A.; VanArsdale, William E.; Han, Kye J.
    Previous applications of fracture mechanics theories to predict component life during crack propagation have been developed without consideration of the statistical nature of fracture mechanics parameters. The statistical approach to fracture mechanics has been concerned mainly with the study of the size effect of brittle fracture strength distribution. This study, however, presents for the first time an approach to link the statistical approach to fracture mechanics and the laws of crack propagation to predict component survival time in order to investigate the effect of size temperature and strain rate on the expected component life. The asymptotic theory of extreme order statistics of the third kind for the smallest values (Weibull model) was used to study the effect of size, temperature, and strain rate on the fracture strength of identical specimens for both uniform and uniaxial bending stress fields. Then, these results were combined with crack propagation laws to develop the required relationships to predict component survival time and to investigate the effect of size, temperature and strain rate. These relationships were developed for the following cases: 1. The component subjected to uniaxial static uniform and bending stress fields. 2. The component subjected to constant amplitude, uniaxial, dynamic, uniform and bending stress fields with and without the mean stress effect. 3. The component subjected to a random uniaxial stress field. This study also presents a discussion of this approach to the following: a). The limitation of this statistical approach. b). The application to predict survival time in an aggressive environment. c). The application to predict survival time under a multiaxial stress field. d). The required experimental testing programs to support the validity of this statistical approach for studying the effects of size, temperature and strain rate on the mean fracture strength and the mean survival time for the uniaxial static uniform and bending stress fields.
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    A synthesis of automotive suspension with numerical analysis
    (1988) Yook, Bok Soo; Schneider, William P.; Shieh, Leang-San; Cook, Bill D.
    The passive, active, and semi-active suspension systems of passenger cars are synthesized with numerical analysis methods to compare the ride comfort and road holding performances. The suspension systems of a quarter car are modeled, using the typical numeric values of its components, to derive practical system dynamics (differential) equations and frequency domain transfer functions. By formulating a reasonable performance index function and using an optimization algorithm developed by Schittkowsky, optimum parameters are found for each type of suspension. The optimum systems are reviewed in the frequency domain and simulated in the time domain to provide analyses of the characteristics of the systems. The conventional passive suspension system has limitations in improving present performance. The active suspension system can provide the "best" performance by the application of external power. It is found that the optimum performance index function value of the active system is about 41 [percent] of that of the passive system. In order to improve the performance index of the passive system, it is required to lower the spring stiffness, which however needs to be kept large enough to support the static weight of the car. However, by adding an active unit to a passive system, the spring stiffness can be lowered to accommodate the dynamics of the system and yet maintain the same static suspension as the passive system thus providing a performance index close to the active system.
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    High resolution ultrasonic frequency demodulation and analysis
    (1988) Wu, Hong-Nan; Anderson, Wallace L.; Smither, Miles A.; Cook, Bill D.
    The thermal derivative, dV/dT, of ultrasonic velocity is investigated as a parameter for determining the location and magnitude of stress in metal when a time-varying thermal gradient is made to occur within the region of interest. A PPLL(Pulse Phase-Locked Loop) instrument and ultrasonic transducer is used to transmit an ultrasonic signal into the specimen, receive the echo and maintain phase lock between the VCO and the echo's waveform. The frequency of the VCO is then a measure of the velocity of the ultrasound in the specimen. One technique for frequency measurement uses a high resolution frequency counter. Another technique requires mixing the signal with a local oscillator to get a difference frequency in a range of a few kHz and determining frequency deviation by time interval measurement. Interpretation of frequency deviation for stress estimation requires solution of the heat diffusion equation with appropriate boundary conditions. Formulation in terms of Laplace transforms is found to permit application of a numerical inversion technique which has negligible error in the time range needed for our analysis. In summary, techniques involving hardware, software and numerical analysis have been developed in support of a new method for estimation of subsurface stress in metals. Results obtained demonstrate the efficacy of these techniques.
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    Complex seismic trace attributes from theoretical and scaled physical model data
    (1983) Fisher, David Arthur; Sheriff, Robert E.; Gardner, Gerald H. F.; McDonald, John A.
    Complex seismic trace attributes including the amplitude of the envelope, instantaneous phase, instantaneous frequency, and apparent polarity are computed and displayed from theoretical and scaled physical model data. The models were chosen so the seismic data from them could demonstrate the utility of attribute displays and their analysis when developing an interpretation. Vertical and horizontal attribute sections are presented which show their possible uses for delineating unconformities and fault blocks and generating isochron contour maps. The instantaneous frequency attribute is shown to be sensitive to waveform interference and produces characteristic patterns for "pinch out" models. The importance of source wavelets, color codes and threshold parameters are demonstrated. Evaluation of elastic wave equation modeling programs is carried out by comparing complex trace attributes from synthetic and scaled physical model data. Lithologies of exploration interest are modeled using an elastic modeling program and their complex trace attributes are examined. Attribute displays are shown to aid the analysis of waveshape variation with angle of incidence in pre-stack common midpoint gathers. These variations might be able to be used for predicting lithologies and porefill material.
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    Digital redesign and pseudo-continuous-time suboptimal regulators for large-scale discrete systems
    (1988) Zhang, Jianliang; Shieh, Leang-San; Schneider, William P.; Sinkhorn, Richard D.
    A multi-stage pseudo-continuous-time state-space method is developed for designing a large-scale discrete system, which does not exhibit explicitly a structure with multiple time-scales. The designed pseudo-continuous-time regulator places the eigenvalues of the closed-loop discrete system near the common region of a circle (concentric within the unit circle) and a logarithmic spiral in the complex z-plane, without explicitly utilizing the open-loop eigenvalues of the given system. The proposed method requires the solutions of small order Riccati equations only at each stage of the design. Based on matching all the states at all the sampling instants, a new digital redesign technique is presented for finding the pseudo-continuous-time quadratic regulator. Also, a new optimal digital redesign technique is developed for finding a dynamic digital control law from the available analog counterpart and simultaneously minimizing a quadratic performance index. The proposed technique can be applied to a system with a more general class of reference inputs, and the developed digital regulator can be implemented via low cost microcomputers.
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    Planar transmission line excitation of dielectric resonator antennas
    (1988) Kranenburg, Roger A.; Long, Stuart A.; Williams, Jeffery T.; Auchmuty, J. F. Giles
    An approximate theory is derived for all the modes in a cylindrical dielectric resonator antenna. The air-dielectric interface is approximated as a perfect magnetic conductor and expressions for the resonant frequency and radiation from the equivalent surface magnetic currents are presented. A broad beam with a maximum normal to the ground plane is obtained for the lowest mode. A more directive beam or a beam with a single sharp null is obtained for the next mode depending on the cylinder geometry. Good agreement is obtained between theory and experiment. An experimental investigation was also undertaken to demonstrate the microstrip transmission line and the coplanar waveguide as effective excitation mechanisms for the cylindrical dielectric resonator antenna. Results showing the coupling behavior and the radiation patterns for various cylinder aspect ratios, dielectric constants, and feed positions are presented. The results show these feed structures result in efficient and practical antenna systems.