The thesis examines the dynamic impact of capital structure on firm performance in Nigeria. The aims of this thesis are; first, to investigate the impact of capital structure of firms on their performance in a dynamic framework. This is unlike previous studies in the capital structure literature that have used static analysis. Second, to examine the dynamic feedback from performance to capital structure using the two-step system generalized method of moment estimator. Third, to explore the determinants or variables that influence capital structure choice of firms in Nigeria and the rate of adjustment to achieve optimal debt position. Fourth, to assess the possibility of non-monotonicity effect of capital structure on firm performance and non-monotonicity effect of performance on capital structure. The second chapter discusses the theoretical framework and review the empirical literatures on capital structure and firm performance. Also, the chapter review empirical literature on firm performance and capital structure as well as on determinants of capital structure. The study find much evidence in support of the theoretical prediction of the agency cost theory of capital structure. The stuudy observed that there are limited empirical studies on the franchise value and efficiency-risk hypotheses of reverse causality from performance to capital structure. The empirical literatures on determinants of capital structure suggests that both firm specific and country factors are important variables that drive capital structure choice of firms. The thrid chapter examines the methodology of the study. The population, sampling and sampling size, estimation methods were discussed in this chapter. The fourth chapter analysis and described the data employed in the study. Specifically, the results of the dynamic relationship between capital structure and firm performance were presented in this chapter. The results indicate that capital structure has non-monotonic effect on firm performance thereby supports the agency cost theory of capital structure. The fifth chapter provides results on the reverse causality between performance and capital structure. The findings indicate that there is reverse causality between performance and capital structure. This is evidence in the statistically significant negative finding between performance and capital structure. This finding support the franchise value hypothesis. The findings of this study also reveal that non-monotonic relationship exist between performance and capital structure. The sixth chapter provides results on the determinants of capital structure of Nigerian firms. The findings indicate that both firm specific variables (return on equity, risk, profitablity, age, size, tangibility, growth opportunities, dividend, ownership) and country variables (inflation, interest rates, credit to private sector as percentage of gross domestic product, institutional quality) jointly influence capital structure choice of firms in Nigeria. The findings equally indicate that firms in Nigeria adjust to their optimal debt target relatively faster with lower cost of adjustment because of better access to private debt that public debt. Conclusions from the empirical chapters indicate that firm specific and country factors are major determinants of capital structure of firms in Nigeria and that capital structure choice of firms influence their performance. Equally, there is evidence that indicate that there is reverse causality from performance to capital structure of firms. The study therefore contend that the agency cost theory of capital structure and franchise value hypothesis are portable in the Nigerian context. Full portability of these theories in emerging market like Nigeria may require modifications to accommodate specific peculiarities of operating and business environment of Nigeria.

This thesis documents the design and analysis of a low-power integrated ultra-wideband (UWB) receiver that is well suited for usage in medium to low rate, location aware communication systems. For the first time, this receiver design explores and exploits the unique properties of UWB pulse technology. By exploiting low emission power limit and pulse based communication, RF circuits have been designed with reduced linearity to achieve low-power operation and better circuit performance. The receiver design in this thesis follows a top-down approach which begins by focusing on UWB-specific issues such as signal characteristics, modulation schemes, potential advantages, and design challenges. Next, different receiver architectures are evaluated in terms of their circuit complexity, power consumption, and levels of integration. The impact of various analog non-idealities on the performance of UWB systems is also analysed in detail. After evaluating the performance of UWB systems operating with non-linear frontends, the use of pulse doublets is introduced, for the first time, to mitigate nonlinearityinduced distortion. Simulation results demonstrate that under non-linear operating conditions, significant BER improvements can be achieved by using filtering, pulse doublet, and direct sequence spread spectrum techniques. When ADC quantization effects are included in the receiver, analysis shows that quantization noise dominates distortion-induced BER degradation when two or three bits ADCs are employed. Consequently, reduced front-end linearity requirements can be tolerated in exchange for improvements in the more critical circuit parameters of the UWB receiver. By adopting the sub-linear circuit design approach, a direct-conversion receiver prototype is implemented in the 0.5 um SOS CMOS technology according to specifications determined from system-level Simulink simulations. This highly integrated receiver prototype contains a low-noise amplifier, a 4-GHz frequency synthesizer, mixers, baseband amplifiers and filters, and 2-GSps two-bit analog-to-digital converters. The receiver prototype consumes 75-mW of power, the lowest amount for reported UWB receivers operating in the 3.1 to 10.6-GHz band. Complete end-to-end simulations of the system are performed in Simulink, revealing an achievable BER of approximately 8x10e-4 Finally, a novel 79-uW 5.6-GHz CMOS frequency divider with on-chip temperature and processing compensation have been designed. The divider, designed in a 0.25 um SOS-CMOS technology, occupies 35 x 25 um2 and achieves an operating frequency of 5.6-GHz while consuming 79-uW at a supply voltage of 0.8V. The power efficiency of 143-GHz/mW is one of the highest achieved among conventional CMOS dividers. When combined with a simple and effective compensation submodule, the proposed divider is shown to achieve process and temperature-insensitive operation in a 5-GHz UNII band frequency synthesizer.

The objective of my dissertation work was to provide a better understanding of consumer choices related to these two important tradeoffs that consumers are often confronted with in the marketplace. Drawing upon regulatory focus theory, I investigated how consumers choose between price and quality or price and quantity, in each of two essays, thereby shedding light on the role of consumer goals in purchase decisions. In the first essay, I propose that quality is predominantly a promotion feature whereas price is predominantly a prevention feature. Therefore, promotion oriented consumers should be more attentive to differences in product quality whereas prevention oriented consumers should be more attentive to differences in product price. Three studies demonstrate that quality (price) is more strongly associated with a promotion (prevention) orientation, that promotion (prevention) oriented consumers prefer products with higher quality (cheaper prices), and that these preferences are mitigated when consumers do not need to prioritize between price and quality and are mediated by relative attention to quality versus price. In the second essay, I investigate the manner in which consumers' goal orientations affect their preferences for monetary versus nonmonetary promotional offers, such as bonus packs and price discounts. I propose that consumers with a promotion (vs. prevention) orientation are more likely to prefer a bonus pack offer over an economically equivalent price discount offer. Two pretests and one study provide empirical support for this key prediction. I also identify theoretically defensible and managerially actionable boundary conditions for this effect that are related to price levels and product types.

Physical layer security (PLS) is a new paradigm aiming at securing communications between legitimate parties at the physical layer. Conventionally, achieving confidentiality in communication networks relies on cryptographic techniques such as public-key cryptography, secret-key distribution and symmetric encryption. Such techniques are deemed secure based on the assumption of limited computational abilities of a wiretapper. Given the relentless progress in computational capacities and the dynamic topology and proliferation of modern wireless networks, the relevance of the previous techniques in securing communications is more and more questionable and less and less reliable. In contrast to this paradigm, PLS does not assume a specific computational power at any eavesdropper, its premise to guarantee provable security via employing channel coding techniques at the physical layer exploiting the inherent randomness in most communication systems. In this dissertation, we investigate a particular aspect of PLS, which is secret-key agreement, also known as secret-sharing. In this setup, two legitimate parties try to distill a secret-key via the observation of correlated signals through a noisy wireless channel, in the presence of an eavesdropper who must be kept ignorant of the secret-key. Additionally, a noiseless public channel is made available to the legitimate parties to exchange public messages that are also accessible to the eavesdropper. Recall that key agreement is an important aspect toward realizing secure communications in the sense that the key can be used in a one-time pad scheme to send the confidential message. In the first part, our focus is on secret-sharing over Rayleigh fading quasi-static channels. We study the fundamental relationship relating the probability of error and a given target secret-key rate in the high power regime. This is characterized through the diversity multiplexing tradeoff (DMT) concept, that we define for our model and then characterize it. We show that the impact of the secrecy constraint is to reduce the effective number of transmit antennas by the number of antennas at the eavesdropper. Toward this characterization, we provide several schemes achieving the DMT and we highlight disparities between coding for the wiretap channel and coding for secret-key agreement. In the second part of the present work, we consider a fast-fading setting in which the wireless channels change during each channel use. We consider a correlated environment where transmit, legitimate receiver and eavesdropper antennas are correlated. We characterize the optimal strategy achieving the highest secret-key rate. We also identify the impact of correlation matrices and illustrate our analysis with various numerical results. Finally, we study the system from an energy-efficiency point of view and evaluate relevant metrics as the minimum energy required for sharing a secret-key bit and the wideband slope.

Decisions among alternatives that do not fit rigorous numerical frameworks are common. Such decisions, in which the various aspects of the alternatives are considered simultaneously, are called a tradeoff studies. Tradeoff studies may be more common than optimization problems, but are not generally formalized in written form.Tradeoff studies are broadly recognized and mandated as the method for considering many criteria simultaneously. They are the primary method for making a decision among alternatives listed in the Software Engineering Institute's Capability Maturity Model Integration (CMMI) Decision Analysis and Resolution (DAR) process.The field of Decision Making can explain why the mechanics of tradeoff studies are approached with underconfidence, and can also help eliminate biases from the tradeoff process. Many conclusions obtained from Judgment and Decision Making (JDM), Cognitive Science and Experimental Economics can be used to shed light on various aspects of the tradeoff process. Of course, since many experiments were designed to reveal truths about choice at a basic level, they do not exactly model the processes of tradeoff studies. The technique used to compare the basic experiments and tradeoff studies will be abstraction.Abstraction noun 1. a general concept formed by extracting common features from specific examples, 2. the process of extracting the underlying essence.What follows is a union of the fields of tradeoff studies and cognitive decision making. Because these two areas have never before been explicitly unified, I have produced some unfinished areas in which specific research needs to be done. At this stage, the work of unification must necessarily be conducted at an abstract level.

No description available.

Spectral efficiency (SE), energy efficiency (EE), and transmission reliability are basic parameters to measure the performance of a cellular network. In this paper, spectral efficiency and energy efficiency tradeoff is considered keeping in mind the transmission reliability, where all the three are function of signal to noise ratio (SNR). SNR, in turn is a function of constellation size (or the number of bits per symbol) and data rate. Then, we propose a new power model which is as function of this SNR. Based on the power model, SE-EE trade-off function is evaluated taking transmission reliability in to consideration. Results confirmed that increasing constellation size results an increase in SNR and leads to a significant increase in energy efficiency without changing the transmit power. To demonstrate the validity of our analysis, channel gain and constellation size are varied keeping transmit power constant. The results also indicate that securing transmission reliability, the EE-SE trade-off is optimized by increasing the constellation size.

No description available.

The present manuscript discusses the performance and emission benefits due to two diesel injections in diesel-ignited methane dual fuel Low Temperature Combustion (LTC). A Single Cylinder Research Engine (SCRE) adapted for diesel-ignited methane dual fuelling was operated at 1500 rev/min and 5 bar BMEP with 1.5 bar intake manifold pressure. The first injection was fixed at 310 CAD. A 2nd injection sweep timing was performed to determine the best 2nd injection timing (as 375 CAD) at a fixed Percentage Energy Substitution (PES 75%). The motivation to use a second late injection ATDC was to oxidize Unburnt Hydrocarbons (HC) generated from the dual fuel combustion of first injection. Finally, an injection pressure sweep (550-1300 bar) helped achieve simultaneous reduction of HC (56%) and CO (43%) emissions accompanied with increased IFCE (10%) and combustion efficiency (12%) w.r.t. the baseline single injection (at 310 CAD) of dual fuel LTC.

Deep generative models when utilized in lossy image compression tasks can reconstruct realistic looking outputs even at extremely low bit-rates, while traditional compression methods often exhibit noticeable artifacts under similar conditions. As a result, there has been a substantial surge of interest in both the information theoretic aspects and the practical architectures of deep learning based image compression. This thesis makes contributions to the emerging framework of rate-distortion-perception theory. The main results are summarized as follows: 1. We investigate the tradeoff among rate, distortion, and perception for binary sources. The distortion considered here is the Hamming distortion and the perception quality is measured by the total variation distance. We first derive a closed-form expression for the rate-distortion-perception tradeoff in the one-shot setting. This is followed by a complete characterization of the achievable distortion-perception region for a general representation. We then consider the universal setting in which the encoder is one-size-fits-all, and derive upper and lower bounds on the minimum rate penalty. Finally, we study successive refinement for both point-wise and set-wise versions of perception-constrained lossy compression. A necessary and sufficient condition for point-wise successive refinement and a sufficient condition for the successive refinability of universal representations are provided. 2. Next, we characterize the expression for the rate-distortion-perception function of vector Gaussian sources, which extends the result in the scalar counterpart, and show that in the high-perceptual-quality regime, each component of the reconstruction (including high-frequency components) is strictly correlated with that of the source, which is in contrast to the traditional water-filling solution. This result is obtained by optimizing over all possible encoder-decoder pairs subject to the distortion and perception constraints. We then consider the notion of universal representation where the encoder is fixed and the decoder is adapted to achieve different distortion-perception pairs. We characterize the achievable distortion-perception region for a fixed representation and demonstrate that the corresponding distortion-perception tradeoff is approximately optimal. Our findings significantly enrich the nascent rate-distortion-perception theory, establishing a solid foundation for the field of learned image compression. / None / Doctor of Philosophy (PhD)