This dissertation deals with the design of bandwidth-efficient coding schemes with Low-Density Parity-Check (LDPC) for reliable wireless communications. Code design for wireless channels roughly falls into three categories: (1) when channel state information (CSI) is known only to the receiver (2) more practical case of partial CSI at the receiver when the channel has to be estimated (3) when CSI is known to the receiver as well as the transmitter. We consider coding schemes for all the above categories. For the first scenario, we describe a bandwidth efficient scheme which uses highorder constellations such as QAM over both AWGN as well as fading channels. We propose a simple design with LDPC codes which combines the good properties of Multi-level Coding (MLC) and bit-interleaved coded-modulation (BICM) schemes. Through simulations, we show that the proposed scheme performs better than MLC for short-medium lengths on AWGN and block-fading channels. For the first case, we also characterize the rate-diversity tradeoff of MIMO-OFDM and SISO-OFDM systems. We design optimal coding schemes which achieve this tradeoff when transmission is from a constrained constellation. Through simulations, we show that with a sub-optimal iterative decoder, the performance of this coding scheme is very close to the optimal limit for MIMO (flat quasi-static fading), MIMO-OFDM and SISO OFDM systems. For the second case, we design non-systematic Irregular Repeat Accumulate (IRA) codes, which are a special class of LDPC codes, for Inter-Symbol Interference (ISI) fading channels when CSI is estimated at the receiver. We use Orthogonal Frequency Division Multiplexing (OFDM) to convert the ISI fading channel into parallel flat fading subchannels. We use a simple receiver structure that performs iterative channel estimation and decoding and use non-systematic IRA codes that are optimized for this receiver. This combination is shown to perform very close to a receiver with perfect CSI and is also shown to be robust to change in the number of channel taps and Doppler. For the third case, we look at bandwidth efficient schemes for fading channels that perform close to capacity when the channel state information is known at the transmitter as well as the receiver. Schemes that achieve capacity with a Gaussian codebook for the above system are already known but not for constrained constellations. We derive the near-optimum scheme to achieve capacity with constrained constellations and then propose coding schemes which perform close to capacity. Through linear transformations, a MIMO system can be converted into non-interfering parallel subchannels and we further extend the proposed coding schemes to the MIMO case too.

The focus of this research was to create and characterize high temperature alumina and nitrate salt eutectic nanofluids for use in thermal energy storage (TES) systems. The nitrate eutectic was originally used in the TES system demonstrated as part of the Solar Two power tower and is currently employed as the TES material at Andasol 1 in Spain. Concentrations of alumina nanoparticles between 0.1% and 10% by weight were introduced into the base material in an effort to create nanofluids which would exhibit improved specific heat capacity to reduce the $/kWht thermal energy storage system costs. The composite materials were created using an aqueous mixing method in which both the nanoparticles and nitrate eutectic were placed into solution using acidic water. This solution was then sonicated in an ultrasonic bath in an effort to reduce nanoparticle agglomeration and to improve homogeneity. After boiling off the excess water, the nanoparticle-nitrate eutectic composite was recovered for characterization. The thermal properties of both the composite and base materials were characterized using the differential scanning calorimetry techniques outlined in ASTM E 1269. The created nanofluids were not stable and did not offer a cost-effective alternative to the current nitrate eutectic TES material. Despite these setbacks, a positive correlation between alumina concentration and nanofluid specific heat was demonstrated. Additionally, the specific heat capacities of the created nanofluids exceeded that predicted by the current theoretical models. These findings suggest that further work in the field of high temperature nanofluids for use in TES systems is warranted.

The objective of this research is to develop distributed approaches to optimizing network traffic. Two problems are studied, which include exploiting social networks in routing packets (coupons) to desired network nodes (users in the social network), and developing a rate based transport protocol, which will guarantee that all the flows in a network (e.g. Internet) meet a delay constraint per packet. Firstly, we will study social networks as a means of obtaining information about a system. They are increasingly seen as a means of obtaining awareness of user preferences. Such awareness could be used to target goods and services at them. We consider a general user model, wherein users could buy different numbers of goods at a marked and at a discounted price. Our first objective is to learn which users would be interested in a particular good. Second, we would like to know how much to discount these users such that the entire demand is realized, but not so much that profits are decreased. We develop algorithms for multihop forwarding of such discount coupons over an online social network, in which users forward coupons to each other in return for a reward. Coupling this idea with the implicit learning associated with backpressure routing (originally developed for multihop wireless networks), we would like to demonstrate how to realize optimal revenue. We will then propose a simpler heuristic algorithm and try to show, using simulations, that its performance approaches that of backpressure routing. As the second problem, we look at the traditional formulation of the total value of information transfer, which is a multi-commodity flow problem. Here, each data source is seen as generating a commodity along a fixed route, and the objective is to maximize the total system throughput under some concept of fairness, subject to capacity constraints of the links used. This problem is well studied under the framework of network utility maximization and has led to several different distributed congestion control schemes. However, this idea of value does not capture the fact that flows might associate value, not just with throughput, but with link-quality metrics such as packet delay, jitter and so on. The traditional congestion control problem is redefined to include individual source preferences. It is assumed that degradation in link quality seen by a flow adds up on the links it traverses, and the total utility is maximized in such a way that the quality degradation seen by each source is bounded by a value that it declares. Decoupling source-dissatisfaction and link-degradation through an ?effective capacity? variable, a distributed and provably optimal resource allocation algorithm is designed, to maximize system utility subject to these quality constraints. The applicability of our controller in different situations is illustrated, and results are supported through numerical examples.

The Psychrometric Testing Facility at the Riverside Energy Efficiency Laboratory at Texas AandM University has not been operational for several years. The goal of this project was to restore the testing facility to a fully operational condition for the purpose of supporting research and cooling capacity testing, with the latter following the appropriate standards. Numerous changes were made to the coolant piping system, the data acquisition system, instrumentation, and temperature and humidity control to update and improve the facility. In addition, a computer program was developed and implemented that allows for flexible control of the facility’s conditions and collection of data while showing real time performance and refrigerant and psychrometric calculations. The current program flexibility, along with the proper combination of instrumentation, allows the Psychrometric Facility to operate with separate steady state environmental conditions in each room, according to, and meeting, the AHRI 210/240 standard. Cooling capacity testing done on a split system residential unit was compared to the published AHRI rating to benchmark the state of the facility. Tested cooling capacity was about 3 percent below the published cooling capacity; tested EER was about 7 percent below the published EER; and finally, the calculated SEER based on the default degradation coefficient was about 10 percent below the published SEER. The difference in the calculated performance parameters to the published are expected due to unknown testing conditions used to calculate the published rating.

A superconducting microwave cavity has been designed to test advanced materials for use in the accelerating structures contained within linear colliders. The electromagnetic design of this cavity produces surface magnetic fields on the sample wafer exceeding the critical limit of Niobium. The ability of this cavity to push up to 4 times the critical field provides, for the first time, a short sample method to reproducibly test these thin films to their ultimate limit. In order for this Wafer Test cavity to function appropriately, the large sapphire at the heart of the cavity must have specific inherent qualities. A second cavity was constructed to test these parameters: dielectric constant, loss tangent, and heat capacity. Several tests were performed and consistent values were obtained. The consequences of these measurements were then applied to the Wafer Cavity, and its performance was evaluated for different power inputs. The Q_0 of the cavity could be as low as 10^7 because of the sapphire heating, therefore removing the ability to measure nano-resistances. However, with additional measurements in a less complex environment, such as the Wafer Test Cavity, the Q_0 could be higher than 10^9.

In this study, a reproducible spectrophotometric method was established and applied to measure reductive capacity of various nanomaterials. Reductive capacity had been implicated in the toxicity of nanomaterials, but a standardized measurement method had been lacking until this work. The reductive capacity of nanoparticles was defined as the mass of iron reduced from Fe3 to Fe2 by unit mass of nanoparticles, in an aqueous solution that initially contained ferric ions. To measure the reductive capacity, the nanomaterials were incubated in a ferric aqueous solution for 16 hours at 37 degrees C, and the reductive capacity of the nanoparticles was determined by measuring the amount of Fe3 reduced to Fe2 using a spectrophotometric method. The reagents 1,10-phenanthroline and hydroquinone were used as a Fe2 indicator and a reducing agent respectively for the assay. To standardize this method, various experiments were carried out. For the initial ferric solution, various Fe salts were tested, and Iron(III) sulfate was chosen as Fe salt for the standard method. The measured reductive capacity of nanoparticles was found to vary with the measurement conditions; the measured reductive capacity increased with increasing the Fe/nanoparticle ratio; the measured reductive capacity increased with incubation time and leveled off after 8 hours of incubation. For hydrophobic materials, the surfactant Tween-20 was added so that the particles could be wetted and suspended in the ferric aqueous solution. After incubation, the particles were removed from the solution by either filtration or centrifugation before applying the spectrophotometric method. In addition, optimal pH and minimum time to reach ultimate color intensity were also found. Carbon-based nanomaterials, standard reference material and metal oxides were measured for their reductive capacities with this method and characterized by transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDS), x-ray diffraction (XRD), BET measurement and Raman spectroscopy. For some nanoparticles, the reductive capacity was measured for both the pristine form and the form treated by oxidization or grinding. All carbon-based nanomaterials, except for pristine C60, have a significant reductive capacity while reductive capacity of metal oxides is very low. And it was found that reductive capacity can be increased by surface functional groups or structural defects and reduced by oxidization or heating (graphitization). The reductive capacity of a material can play an important role in its toxicology by synergistic toxic effects in the presence of transition metal ions through the Fenton reaction. Moreover, even without transition metal ions, the ability of a material to donate electrons can be involved in toxicity mechanisms via generation of reactive oxygen species.

This dissertation includes three studies, devoted to trying to understand inequality in health between people from different social groups in a democratic society. In the U.S., social inequality in health takes various forms and the key to understanding how democracy solves the problem of inequality lies in a complex set of political and social factors. I take an institutional approach and focus on examining how political and policy institutions, their administrative processes, and the policy implementation environment are linked to social inequality in health. The first essay, Whose Baby Matters More, uses a theoretical framework for evaluating heterogeneous group responses to public health policies and depicts how racial disparities in health are rooted in group heterogeneity in policy responses. The second essay, Anxious Girls and Inactive Boys, focuses on how state-level policy interventions and social capital interactively affect gender differences in health. The third essay, Responsibility for Equity, explores the link between publicness of state healthcare systems and social equity in healthcare access. In the first essay, I focus on racial disparities in infant mortality rates and pool state-level data from 1990 to 2006. The empirical analysis suggests that enhancing the capacity of state healthcare systems is critical to improving population health. Blacks and whites, nevertheless, exhibit different responses to the same policy. Racial disparities could be reduced only when policy interventions generate more relative benefits for Blacks. In the second essay, I find that social capital conditions the effect of public health policies with regard to managing childhood obesity. There are gender differences, moreover, in health outcomes and behavioral responses to state and local-level obesity policies. In the third essay, I find that different institutional factors exhibit different impact on inequality in healthcare access. While public finance resources may reduce inequality in healthcare access, public ownership and the public healthcare workforce do not have significant association with inequality in healthcare access. State Medicaid eligibility rules exhibit moderate impact on inequality in healthcare access.

Abstract A vast majority of the studies devoted to Lithium manganese oxide deals with their electrochemical characteristics in lithium batteries. The main project of this study is to realize the structure evolution upon electrochemical cycling. The phase transformations under the charge and discharge testing are an interesting project. Nitrate or oxide precursor calcined at 800¢XC can produce single phase stoichiometric LiMn2O4. The hypo-stoichiometric compositions (xLi2O¡Ñ4MnO, x < 1) synthesized by Li-poor situation contain LiMn2O4 and Mn2O3. The hyper- stoichiometric compositions (xLi2O¡Ñ4MnO, x > 1) synthesized by Li-rich situation contain non-stoichiometric spinel LixMn2O4 (such as Li4Mn5O12 or Li2Mn4O9) and Li2MnO3. The lattice parameter of LiMn2O4 increases slightly with increase of the lithium content at x < 1 (0.823 ~ 0.824 nm), but decreases sharply for x = 1.0 ~ 1.8 (0.824 to 0.817 nm). Differential thermal analysis showed at temperature higher than 935&#x00BA;C, rocksalt phase (with tetragonal symmetry), Mn3O4 will be produced. Above 1045&#x00BA;C, the crystallite phases contain cubic LiMn2O3 spinel, tetragonal Mn3O4 and orthorhombic symmetry LiMnO2. After high temperature annealing (> 935&#x00BA;C), the residual phase is lithium-deficient structure, Mn3O4. Apparent facets with {111}, {011}, and {001} (and {113}) planes are usually observed. The LiMn2O4 crystallite appears to be a truncated cubo-octahedron. The lowest surface energy gsv for LiMn2O4 spinel is located at the {111} planes. Lamellae domain and twinned structure are usually observed in LiMn2O4 particles. The occurrence of domain boundary and twin plane are {111} mostly. Forbidden reflections {200}, {420} in the initial powder and 1/2{311} and 1/3{422} superlattice reflections occurred after charging and discharging test reveal LiMn2O4 structure is a violation of space group. [311]/[111] peak ratio in the XRD traces is increase after electrochemical cycling. Fraction of inverse phase increased upon electrochemical cycling. The results for structure evolution under charging and discharging test can be divided into two parts for reversible and irreversible. First, unit cell of cubic spinel contracted upon charging and returned to original after discharging. The lattice constant varies back and forth between 0.824 nm to 0.814 nm for cycle between 3.3 and 4.3 V. LiMn2O4 transits to Li4Mn5O12 and l-MnO2 after fully charging to 4.3 V, which then recovers to cubic spinel LixMnyO4 after discharging to 3.3 V. The structure variations in the cycle of changing and discharging are LiMn2O4 ¡V (Li4Mn5O12 + l-MnO2) ¡V LixMnyO4. And metastable circular or rectangle LiMn2O4 particles observed in the surface can be extracted and inserted Li+ ion upon charging and discharging test. This process is reversible. Second, (1) tetragonal, rhombohedral and triclinic distorted within cubic spinel particles; (2) nanoscale regions of highly disordered lattices observed; (3) amorphous film observed in the powder particle surface; (4) crystalline phase Mn2O3 increased; (5) structure collapse inside the particle and the domain boundary; (6) inverse spinel structure. The structure of LixMn2O4 had distorted upon electrochemical cycling. These results are irreversible.

Since the Vietnamese Communist Party passed the resolution to implement the ¡§Doi Moi¡¨ policy in the sixth National Congress in December 1986, Vietnam¡¦s economy has transformed from state-controlled economic system to market and socialism-oriented economy. This change of economic system has contributed to the recent economic improvement in Vietnam, a key point of studying Vietnam¡¦s political development. On the perspective of political economy, modernization theory contends that economic development helps political democratization, whereas stably hegemony theory argues that economic achievement may bring about stability for authoritarian regimes. Based on state theory, this paper takes two dimensions, i.e. state autonomy and state capacity, to examine the issue whether the Vietnamese state will be influenced after Vietnam¡¦s political and economic reforms. This paper concludes that modernization theory is not able to explain the current political economy of Vietnam, because Vietnam did not change from a strong state to a weak state. Rather, Vietnam maintains a strong state, which fits the explanation of state theory.

In this study, the holding capacity of anchors and their design methodology are investigated. In general, three kinds of anchors have been used in cage aquaculture engineering, including embedment anchors, deadweight anchors, and pile anchors. The maximum holding capacity of embedment anchors was analyzed via the results of experiments by increasing the weight of anchors, while the best holding capacity of deadweight anchors was investigated by changing the types of shear keys. Moreover, the designs and considerations of pile anchors were also discussed in Appendix A. From the results of experiments, the maximum holding capacity of embedment anchors varies 12~19 times of their self-weight, and has the trend such as the holding capacity is in proportion to the weight of anchor. In the case of deadweight anchors, two methods were used to analyze the holding capacity, one is to consider the passive earth pressure behind each shear key of anchor block, and the other is to consider the net weight including the confined sand trapped inside of shear keys and its passive earth pressure at the outmost skirt key. It seems that the first method has more accurate than the second method until the number of keys equals 5 based on the experimental results. And, when the number of keys is greater and equal 6, the second method has better predictions than the first one. The main reason is that it is unable to fully develop the passive earth pressure in such a narrow space between the keys. Therefore, the interval between shear keys should at least equal 1 time of the key¡¦s penetration depth according to this study.