Carbon fiber is one of the leading materials for high strength and modulus, and light weight applications. Improvements in carbon fiber properties are directly dependent on all aspects of manufacture, especially the process of stabilization. Therefore, it is the goal of this thesis to study the effects of the temperature and strain profile of the stabilization process, and the resulting carbon fiber tensile properties. In addition, the precursor fibers used were spun under two different draw ratios, to study the effects of the spinning parameters. Results indicated through DMA studies that completeness of stabilization reactions can be gauged by the peak and leveling of induced stress while fibers are stabilized in isostrain conditions. Through this method, carbon fiber tensile properties were maintained from the prior methods, but saved significant time for processing. Stress vs. strain tests throughout the stabilization process created a baseline for understanding the maximum capable strain on fibers throughout the stabilization process. Lastly, this information was summarized, combined, and basic mechanical engineering principles discussed for a continuous stabilization furnace with strain control, so that further research into the stabilization process can incorporate carbon fibers made with in situ stretch control.

Transient stability of electric energy grids is defined as the ability of the power system to remain in synchronism during large disturbances. If the grid is not equipped with controllers capable of transiently stabilizing system dynamics, large disturbances could cause protection to trigger disconnecting the equipment and leading further to cascading system-wide blackouts. Today’s practice of tuning controllers generally does not guarantee a transiently stable response because it does not use a model for representing system-wide dynamic interactions. To overcome this problem, in this thesis we propose a new systems modeling and control design for provable transient stabilization of power systems against a given set of disturbances. Of particular interest are fast power-electronically-controlled Flexible Alternating Current Transmission System (FACTS) devices which have become a new major option for achieving transient stabilization. The first major contribution of this thesis is a framework for modeling of general interconnected power systems for very fast transient stabilization using FACTS devices. We recognize that a dynamic model for transient stabilization of power systems has to capture fast electromagnetic dynamics of the transmission grid and FACTS, in addition to the commonly-modeled generator dynamics. To meet this need, a nonlinear dynamic model of general interconnected electric power systems is derived using time-varying phasors associated with states of all dynamic components. The second major contribution of this thesis is a two-level approach to modeling and control which exploits the unique network structure and enables preserving only relevant dynamics in the nonlinear system model. This approach is fundamentally based on separating: a) internal dynamics model for ensuring stable local response of components; b) system-level model in terms of interaction variables for ensuring stability of the system when the components are interconnected. The two levels can be controlled separately which minimizes the need for communication between controllers. Both distributed and cooperative ectropy-based controllers are proposed to control the interaction-level of system dynamics. Proof of concept simulations are presented to illustrate and compare the promising performance of the derived controllers. Some of the most advanced FACTS industry installations are modeled and further generalized using our approach.

This thesis examined the effect of continuous row-cropping on soil structure measured by bulk density and compaction ratings. Undisturbed core samples were collected from the selected sample sites to determine the bulk density. Compaction ratings were obtained by using a Proctor Penetrometer. A total of 192 soil samples were collected for this investigation. Comparisons of mean bulk densities, mean compaction ratings, and mean moisture percentages of the surface and Bt horizons of Blount and Pewamo soils in Delaware County, Indiana under three different field conditions: woods (untilled), field cultivated fields (continuous row-cropped), and plowed fields (continuous row-cropped) were made. This was done by calculating F-ratios and Bayesian Least Significant Difference ratios. Pearson's Product Moment Correlation' Coefficients were also calculated between selected parameters of the data. Conclusions drawn from these statistical analysis were discussed.

The immediate objectives of exchange-rate policy should be stability of output, stability of the rate of inflation and stability of the exchange rate itself. Moreover, exchange-rate policy is likely to be of some use in achieving these aims, as the modifications to the rational expectations theory which make monetary policy effective do so for exchange-rate policy as well, and additional channels of effectiveness operate in an open economy. There are various explanations for the volatility of exchange rates under free floating, but a more realistic picture of the reaction to external disturbances is obtained if step changes in interest rates are allowed for by considering the term structure of interest rates and the influence of the terms of trade on the demand for money. Capital is not in fact perfectly mobile internationally, which widens the range of policy options, and some modifications of the theory are required to study the determinants of capital flows in an imperfect world. One can use the correlation between deviations of output and inflation from trend to study the origin of disturbances. This is illustrated by a study of eighteen sub-Saharan African countries. Furthermore, the type and origin of disturbances have implications for whether some sort of dual exchange-rate or dual interest-rate system is desirable. Finally, a model of an open economy is presented in which exchange-rate policy can be analyzed whether specified in terms of exchange-rate targets or the degree of intervention, and with the possibility of a restricted forward foreign-exchange market. A variant of the model is estimated for South Africa for the period 1974-1981 and various exchange-rate policies are simulated.

No description available.

The quantitative effects of increasing the organic matter contents of three soils upon their susceptibility to compaction, the recovery of tilth after compaction and the fertility of the soils were investigated. These effects were further studied on the production of bush bean (Phaseolus vulgaris). / Soil consistency limits, soil water status, applied pressure and organic matter contents were used to predict shear strength, penetration resistance and water retention characteristics of compacted soils, with the aim of meeting the widespread demand for possible techniques of soil compaction prediction. / Soil compaction increased the ability of the soils to retain moisture, increased penetration resistance, shear strength and decreased the available water capacity of soils. On the other hand, organic matter increased the ability of the soils to retain moisture, expanded the available water capacity and decreased the penetration resistance and shear strength of compacted soils. / Although soil compaction increased the stem diameter of bush bean; the height, yields and root dry matter of the crop decreased with higher compaction levels. On the contrary, higher organic matter levels increased the plant and yield parameters of the crop.

The objective of this study is to remove turbidity originating from algae present in oxidation ponds effluents by an easy and inexpensive method. For this reason, a novel lab-scale Step Feed Dual Treatment (SFDT) process was constructed and the efficiency of trickling filter (TF) to remove algae and organic matter was investigated. SFDT process developed in this study is the unique, inexpensive and new system to scavenge algae from oxidation pond effluents. In this system, influent is first treated in a stabilization pond, and subsequently they directed to a TF, so as to provide a dual treatment. Moreover, some fraction of the raw influent was directly sent to TF to maintain a steady biofilm on the TF medium. Stabilization pond was not simulated in the experimental set-up as the main objective of the study is to observe TF ability to scavenge algae from pond effluent. To determine the magnitude of the effect of individual operational parameters (hydraulic loading rate, influent COD and chlorophyll-a concentration) and of their combinations on organics and particle removal efficacy an experimental design was followed. Experiments consistent with twolevel factorial design with three variables (23) were performed. Hydraulic loading rate (HLR) (0.5-2 m3/m2.day), influent COD (150-550 mg/l) and influent chlorophyll-a concentrations (Chl-a) (250-600 &micro / g/l) were selected as independent variables. The COD and algae removal (as Chl-a) were selected as dependent variables. Data obtained from the experiments showed that when HLR (m3/m2.day) was increased from 0.5 to 2, Chl-a, NTU, SS and COD removals were decreased, however, more than 85 % removal was attained in each case, except for COD. The lowest removal efficiencies were obtained for all the quality parameters when hydraulic loading was increased to 4 m3/m2.day. It was observed that in general removal percentages for turbidity, Chl-a, SS and COD increased considerably with the decreasing hydraulic loading rate. Highest removals were obtained at lowest HLR. The removal of algae in TF was presumably due to both flocculation (due to algal and bacterial EPS production) and degradation (through bacterial activity) of algae. In conclusion, trickling filter produced clear effluents, with less than 2 NTU, for most of the cases.

Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 3, 2008) Includes bibliographical references.

Thesis (M.S.)--Brigham Young University. Dept. of Civil and Environmental Engineering, 2006. / Includes bibliographical references (p. 45-47).

Thesis (Ph.D.)--University of Wollongong, 2004. / Typescript. Includes bibliographical references: leaf 243-252.