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Three-dimensional (3D) shape measurement techniques play an increasingly important role in the quality control proceedures of industry, such as aerospace, bioengineering, information security, automobile, integrated circuits and so on. Additive manufacturing (AM) provide significant advantages over conventional subtractive manufacturing techniques in terms of the wide range of part geometry that can be obtained. The key metal AM technology is powder bed processing. During the AM process, powder delivery occurs thousands of times. Therefore, the assessment of delivery quality would be advantageous for the process to provide feedback for process control. After the energy source melts the powder bed, the detection of the machined surface is also a critically important criterion for the evaluation of the manufacturing quality. This thesis presents an in-situ quantitative inspection technique for the powder bed post raking and printed surface after melting, the technique uses fringe projection profilometry. In this thesis, system calibration methods, phase analysis algorithms, and error correction methods are investigated. A novel surface fitting algorithm is employed to reduce the influence of phase error and random noise during system calibration. A novel intelligent fringe projection technique using a support-vector-machine (SVM) algorithm is proposed to measure the 3D topography of high dynamic range surfaces on a layer by layer basis within the EBAM machine. A simple calibration method is used to eliminate phase errors during system calibration. The proposed in-situ inspection technique has been installed on a commercial electron beam melting (EBM) AM machine. Exemplar powder beds with defects and printed surfaces, are measured with the proposed technique. The whole inspection process lasts less than 5 seconds. Experimental results showed that the powder and the melting surface defects could be efficiently inspected using the proposed system and the measurement result could be fed back to the build process to improve the processing quality. For the inspection of highly reflective surface geometries that have been further machined post AM, phase measuring deflectometry (PMD) has been widely studied for the 3D form measurement. This thesis presents a new direct PMD (DPMD) method that measures the full-field 3D shape of complicated specular objects. A mathematical model is derived to directly relate an absolute phase map to depth data, instead of the gradient. The 3D shape of a monolithic multi-mirror array having multiple specular surfaces was measured. Experimental results show that the proposed DPMD method can obtain the full-field 3D shape of specular objects having isolated and/or discontinuous surfaces accurately and effectively. In this thesis, the fringe projection and the deflectometry techniques are studied. Two different measurement systems were used to measure different roughness surfaces. The experimental results shows the rough surfaces, reflective surfaces, and the highly reflective specular surfaces can be measured and reconstructed by the proposed methods.

An overarching goal of multisensory research is to understand multisensory behaviour in a wider context but still within a unified framework. Modelling has been a useful tool to understand how information from different senses is combined to produce behaviour. For example, different models have been used to understand the improvement in speed or precision of multisensory relative to unisensory decisions (Ernst & Banks, 2002; Raab, 1962). However, these modelling approaches are limited to address a single measure of multisensory decisions, for example, models of speed cannot explain precision and models of precision cannot explain speed. The field is still working towards developing a unified modelling framework that can link the different aspects of multisensory decisions together. In aim of this, I addressed three gaps in research on multisensory decision making, which I believe is essential to address the missing linkage between studies of multisensory behaviour. Firstly, most multisensory modelling work has used an implicit assumption, which states that processing of a unisensory signal and processing of the corresponding unisensory component of a multisensory signals are identical. However, the validity of this assumption, has not been tested. I offered a way to understand this assumption under experimental settings and proved that it is most likely violated. This suggests that studies of multisensory behaviour should rather consider the influence of context in modelling work. Secondly, I addressed that multisensory response at neuronal and behavioural level can be linked. The spatial principle, which is found in neuronal studies, can be mapped to behaviour and accounted for by a race model. Thirdly, I attempt to address the link between speed and precision of multisensory behaviour. In the past, the two have rarely been studied within a unified paradigm. I found that when both measures were required, participants are far from achieving optimality in either speed or precision, and it is possible that they are switching strategies towards favouring one of the measures in such decisions. The race model is a strong candidate to be refined and developed in future research to incorporate more aspects of multisensory decisions, as I have address it is not limited to explain speedup in simple detection task, but also influence of context, space, and precision in more complex experimental tasks.

During the long evolutionary process, amphibians have developed their unique defence mechanisms. Among these, bioactive peptides in special skin secretions produced by frogs have been considered to be one of the rich natural sources for developing new drugs in the future. In this thesis, several bioactive peptides were identified from the skin secretions of frogs by using RP-HPLC and molecular cloning. Then these peptides were synthesised by solid phase peptide synthesis (SPPS) for researching their biological functions. In Chapter 3, a novel peptide, phylloseptin-PV1, was discovered and identified from the defensive skin secretion of the White-lined leaf frog, Phyllomedusa vaillantii. It was found not only to demonstrate potent antimicrobial activity against planktonic ESKAPE strains and the yeast, C. albicans, but also inhibited and eradicated the biofilm of S. aureus and MRSA. Therefore, a mice model was used for evaluating its further in vivo antimicrobial activity. In Chapter 4, a novel dermaseptin peptide, QUB-2522, was identified from the defensive skin secretion of the Northern orange-legged leaf frog, Phyllomedusa hypochondrialis. It exhibited antimicrobial activity against the bacteria, S. aureus and E. coli, at 32 μM concentration, and this activity was not affected by temperatures below 100°C. In order to improve its antimicrobial activity, three analogue peptides, QUB-2534, QUB-2648 and QUB-2574, were modified according to the sequence of QUB-2522 and studied in addition. In Chapter 5, Frenatin 1.1 and Frenatin 3 from the skin secretion of the Australasian giant white-lipped tree frog, Litoria infrafrenata, and Caeridin-1 from the Australian White’s tree frog, Litoria caerulea, and the designed analogue of this, QUB-1128, were studied for a range of bioactivities. These four peptides showed varying degrees of effect on rat smooth muscle.

This thesis investigates the torque production mechanism of rotor permanent magnet synchronous machines (PMSMs), with emphasis on the contribution of magnetic gearing effect. Fractional slot concentrated winding (FSCW) and Vernier permanent magnet synchronous machines (VPMSMs) will be used as examples for investigation. Then, the torque production mechanism of all existing rotorPM machine types will be unified and new slot/pole number combinations are proposed. For both FSCW PMSMs and VPMSMs, the torque production mechanisms are analysed from the perspective of the air-gap field harmonics modulation and the magnetic gearing effect, accounting for slotting effect. It is found that for both machine types, the average torque is produced by both the principle of conventional PMSM torque production and the magnetic gearing effect. A finite element analysis (FEA)-based equivalent current sheet model (ECSM) and a harmonic restoration method are firstly applied to a 12-slot/8-pole FSCW PMSM and a 12-slot/22-pole VPMSM, respectively, to quantify the respective contributions of the conventional principle and the magnetic gearing effect. Hence, the magnetic gearing effect in both machine types are revealed and the expressions of gear ratios are derived. The influence of gear ratio on different performance metrics are analysed and it shows that it can act as an index for a quick overall performance comparison in each machine type. The influence of slot opening on the torque production of all existing Ns-slot/2pr-pole rotor-PM machine types are analysed from the perspectives of both energy conversion and magnetic gearing effect. It shows that for large torque production, all rotor-PM machines with 2pr < Ns should have small slot openings to enlarge the torque produced via the conventional principle, since the contributions from the magnetic gearing effect are weak. For those with 2pr > Ns, there exists an optimal slot opening for the best trade-off between the conventional principle and magnetic gearing effect. The higher the PM pole number is, the larger the optimal slot opening will be. VPMSM can be regarded as a kind of conventional rotor-PM machine of special slot/pole number combinations, whose slot opening plays a critical role in the torque production. For FSCW PMSMs, a machine with 2pr > Ns can also be seen as a Vernier counterpart of one with 2pr < Ns. In this way, the torque production mechanisms of all kinds of rotor-PM machines are unified. Finally, a series of high power factor VPMSMs with coil-pitch of two slot pitches are developed, expanding the selections of slot/pole number combinations of rotor-PM machines. All theoretical analyses have been validated experimentally.

The introduction of synthetic fuels produced from various alternative approaches has led to the concern over their compatibility with elastomeric seals used in current aircraft engines. The aim of this research is to investigate into this compatibility issue of alternative aviation fuels with typical elastomeric sealing materials. Experimental methodologies employed were the stress relaxation test (under both isothermal and temperature cycling conditions) and the Fourier Transform Infrared (FTIR) spectroscopy. A wide range of valuable data was collected and detailed analysis was carried out using statistical method and the Hansen Solubility Parameters (HSPs). The outcome of this research establishes the fundamental stress relaxation characteristics of typical sealing materials in jet fuels produced via various sources. It demonstrates different impacts that individual fuel species may have on seals. A correlation has been found between the stress relaxation and the molecular structure changes of the O-rings. The HSP analysis suggests a good non-linear correlation between the equilibrium compression force and the RED number generated from the ‘triangle’ test data. It is proved that temperature is an influential factor in terms of the sealing performance of an O-ring. Generally, the stress relaxation process slows down (accelerates) as the temperature decreases (increases). At extremely low temperatures, seals become very inert and the relaxation process would stop. Temperature cycling tests show the relationship between seals’ ability to recovery from thermal contraction and the aromatic content in the fuel. Based on the knowledge gained here, recommendations have been given on the potential future work related to this topic.

Using a large sample of about 1,900 M&A deals from 1993 to 2005, and data on more than 3,100 CEOs, I explore merger and acquisition activities from a psychological perspective, and provide another explanation for M&A motives and associated firm stock performance. Specifically, I empirically test if highly narcissistic CEOs are more likely to conduct mergers or acquisitions than lowly narcissistic CEOs. I also examine the impact of high level of CEO narcissism on the market reaction to firm M&A announcements, and also long run post-M&A stock returns. In addition, I empirically investigate the impact of the parallel CEO narcissistic tendency of target firm on acquiring firm M&A performance. Three proxies for CEO narcissism are used in this study: Holder67, a CEO option exercise-based measure, CEO media portrayal, and a third new measure based on the formal content analysis of actual CEO speech. I find empirical evidence that CEOs with high level of narcissism are more likely to conduct mergers and acquisitions than other CEOs. My results also suggest that a high level of acquiring firm CEO narcissism has a significantly negative impact on acquiring firm short run M&A performance. Post-acquisition, I find that deals conducted by highly narcissistic CEOs significantly underperform those by lowly narcissistic CEOs. Moreover, my results show that a high level of target firm CEO narcissism similarly negatively affects acquiring firm short run M&A performance. In an additional analysis, I find that the positive link between CEO narcissism and the likelihood of a CEO conducting an M&A deal is stronger and the impact of CEO narcissism on firm M&A performance is more negative in large firms than that in smaller firms. My results also show that the negative impact of CEO narcissism on firm short run M&A performance is strongest when both acquiring firm and target firm CEO narcissism coexist concurrently. However, I find that the level of CEO narcissism is negatively associated with the quality of corporate governance, and the positive link between CEO narcissism and the likelihood of a CEO conducting an M&A deal is weaker in firms with good corporate governance than that in firms with poorer corporate governance, which may suggest that effective corporate governance mechanisms might play positive roles in curbing CEO narcissistic tendencies and in helping to ameliorate, to some extent, the adverse impact of high level of CEO narcissism on firm M&A decision making.

Tuberculosis remains the world’s deadliest infectious disease caused by a single agent. Although tuberculosis is curable, treatment success is limited by our narrow understanding of genetic factors allowing its causative agent, Mycobacterium tuberculosis (Mtb), to evade antibiotic clearance. Large-scale sequencing of clinical Mtb populations revealed ongoing selection on genetic variants that could confer fitness advantages in the presence of drug pressure. This unbiased approach allowed identification of genes with no previous link to drug resistance, including two essential genes dnaA and resR. Although initially investigated independently, DnaA and ResR share a common binding site at the Rv0010c-Rv0011c intergenic region (IGR) and this IGR itself is one of the highly mutated non-coding regions on Mtb genome. Clinical IGR variants overlap with DnaA and ResR binding sites and phenocopy dnaA and resR variants, revealing a genetic pathway under selection. Yet this genetic pathway and the function of Rv0010c-Rv0011c IGR remains uncharacterized. Isogenic variants in the Rv0010c-Rv0011c IGR phenocopy dnaA and resR variants, showing similar increases in cell length, antibiotic resilience, and low-level isoniazid resistance. We found that DnaA and ResR bind at neighboring sites in the most conserved regions of this IGR, which paradoxically are where more recent clinical mutations accumulate. Knockout of the entire the Rv0010c-Rv0011c operon, including its 155bp IGR, resulted in shorter cells with increased sensitivity to isoniazid. This defect can only be complemented with the entire operon, though this complementation does not require translation of the two coding genes. Complementation with the intact operon carrying clinically relevant IGR variants recapitulates isogenic variant phenotypes. Meanwhile, complementation with the intact operon carrying DnaA or ResR binding site deletions failed, highlighting the requirement of protein binding in its downstream function. To understand the functional consequence of protein binding, we used biochemical approaches and found that DnaA and ResR bind cooperatively at this IGR. Clinical IGR variants increase the binding affinity of two proteins and binding site deletions reduce their affinity. Using transcriptomics, we identified genes that are differentially expressed in strains with clinical IGR variants versus strains with binding site deletions to pinpoint transcriptional changes correlating with divergent phenotypes in these strains. These genes included whiB2 and its regulon of division related genes. Notably, the promoter of whiB2 is a known direct target of ResR and is also highly mutated in clinical Mtb populations. We propose a model where clinical variations sequester ResR through its interaction with DnaA at the Rv0010c-Rv0011c IGR. This sequestration reduces ResR’s ability to activate division related genes and alter division dynamics, resulting in morphology and drug phenotypes. Together, the data in this dissertation provide functional insight into an essential and previously uncharacterized genetic pathway under selection in clinical Mtb populations. We propose that clinical mutations in this pathway alter dynamics of cell cycle events and contribute to changes in Mtb morphology and drug response. Understanding non-canonical drug determinants is critical to elucidate other mechanisms Mtb use to evade antibiotics killing and we hope to inspire future studies on intergenic regions and unknown genetic pathways to better understand Mtb biology and improve treatment design.

Cellular senescence refers to a state in which cells enter a permanent cell cycle arrest without undergoing cell death. Cells become senescent after being exposed to replicative, genotoxic, oncogenic, and/or oxidative stress. Senescence has long been considered a tumor-suppressive mechanism that prevents the malignant transformation and uncontrollable proliferation of cells carrying an unstable genome and/or activated oncogenes. Therapy-induced senescence (TIS), the induction of senescence in tumors through radiation and/or certain chemotherapy treatments, is thought to contribute to the anti-tumor effects of cancer treatments. Various mechanisms that induce tumor cell senescence are extensively examined in this thesis. I first demonstrated the DNA repair-independent role of DNA-PKcs and detailed how inhibition of DNA-PKcs accelerates senescence by resulting in persistent DNA damage foci and mitotic slippage in response to radiation. Then I explored the roles of telomerase catalytic activity in DNA damage response and senescence. According to the results, using a novel covalent TERT inhibitor NU-1 and the well-established antagonists BIBR-1532 and MST-321 to target telomerase catalytic activity enhanced cellular senescence by delaying end-joining repair of DNA double-strand breaks induced by radiation. In the syngeneic CT26 murine colon carcinoma tumor model, NU-1 did not affect the host or reduce tumor growth on its own, but it significantly enhanced activated immune infiltrate and exhibited immunogenic radiosensitization over radiation alone. This study points to TERT as an attractive target for overcoming intrinsic resistance to genotoxic therapy and potentiating anti-tumor immune response. In the next chapter, I discussed the possibility of using senescent tumor cells as a cancer vaccine for controlling tumor growth and metastasis, including how the senescence vaccine synergizes radiation and immune checkpoint inhibitors. Senescent tumor cells have been shown to promote dendritic cell maturation/activation and T cell priming, thereby enabling dendritic cells activated by senescent tumor cells to serve as cancer vaccines for treating both local and metastatic tumors. This work may offer translational benefits from using senescent tumor cells to enhance anti-tumor immunity and improve cancer treatment. Paradoxically, a growing body of preclinical studies indicates that accumulated senescent cells in tumors may also promote tumor recurrence, metastasis, and resistance to therapy. The utilization of senolytics, a class of chemical compounds that specifically eliminate senescent cells, might be a promising approach to inhibit senescence-mediated detrimental effects. Senolytic compounds such as ABT263, a BCL-2 inhibitor, were commonly used following senescence induction in preclinical studies, referred to as the "one-two punch" strategy. Here, I demonstrated that senescent tumor cells induced by various inducers displayed varying sensitivity to ABT263-induced apoptosis. Interestingly, senescent cells displayed bystander effects, causing neighboring non-senescent cells to become more sensitive to senolytic treatment, whereas the degree of bystander effect was positively correlated with senescent cells' sensitivity to senolytic compounds. This work suggested that evaluating senescence hallmarks and/or manipulating therapy-induced senescence might be necessary to improve the efficacy of "one-two punch" cancer therapy.

The brain operates in a world with rich dynamics across a wide range of timescales, including those on the order of seconds and above. Behavioral experiments on memory and timing reveal striking similarities in the behavioral patterns across a range of timescales from seconds to minutes. To subserve these behavioral patterns and adapt to natural statistics, the collective activity of the large of number of neurons in the brain should exhibit dynamics over these macroscopic timescales as well. Most established results in systems neuroscience concern the short-term responses of single neurons to static features of the world. Recently, new techniques for large-scale and chronic measurements of neural activity open up the opportunity to investigate neural dynamics across different macroscopic timescales. This dissertation presents work that reveals the temporal patterns of neural activity across a range of macroscopic timescales and explores their mechanistic basis. Chapter 1 briefly surveys the relevant empirical evidence, biophysical processes and modeling techniques. Chapter 2 presents a biophysically-realistic neural circuit model that combines a detailed simulation of a calcium-activated membrane current with the mathematical formalism of the inverse Laplace transform to produce sequential neural activity with a scale-invariant property. Chapter 3 is a theoretical analysis of the ability of linear recurrent neural networks to generate scale-invariant neural activity. It is shown that the network connectivity matrix should have a geometric series of eigenvalues and translated eigenvectors if the eigenvalues are real and distinct. Chapter 4 presents an empirical analysis of neural data motivated by the hypothesis that robust neural dynamics should simultaneously exist on multiple timescales. The analysis reveals the existence of repeatable neural dynamics on the timescale of both seconds and minutes in multiple neural recordings of rodents performing various cognitive tasks. Chapter 5 of the dissertation presents an initial effort to characterize the changes in the neural population activity during learning on the timescale of tens of minutes by analyzing neural recordings from monkeys while they learn associations between visual stimuli.

My work comes from my understanding and perception of historical fragments. I think imperfection is a natural beauty, which exists everywhere in our lives. My perspective was influenced by a Buddhist theory called “Wabi-sabi”, and I referred to the method of “architecture renovation” to create my jewelry work. During the creation, I was also inspired by a jewelry artist named John Iverson, with his work influencing the many forms and techniques I used for this project. I also adopted a different method of constructing material to represent my interpretation of my observation of “fragments.” In my heart, fragments not only belong to the past— they also belong to our current selves.

Power is a fundamental concept in social science (Russell 1938), which has gained much academic attention in various disciplines. Two essays of this dissertation examine the theoretical and practical implications of power effects on donation decisions and material/experiential consumption. The first essay demonstrates power's moderating effect on the relationship between publicity and donation. Specifically, it is proposed that powerful people tend to donate more in public (vs. private) situation, whereas powerless people do not show such a difference. This effect is driven by people's concern about self-presentation in a donation scenario. Additionally, this effect only holds when people strongly believe that high donation enhances others' positive impression of them, but dilutes when such belief is not held. The theorizing is supported across four studies. The second essay focuses on how power influences consumers' preferences for material and experiential products. It is predicted that those who feel powerless tend to spend more of their discretionary money on material products than experiential products. This effect occurs through feelings of resourcefulness caused by possessing material or experiential goods. In addition, this effect is further moderated by implicit theory, such that the impact of power on material versus experience product choice persists for incremental theorists but dissipates for entity theorists. Three experiments provide support to this proposition. Overall, by investigating how power influences people's donation behavior and choice of material/experiential products, this dissertation strengthens the understanding of power's effects on consumer behavior and provides practical implications on how power status can influence consumers' well-being.

Recently, transition metal dichalcogenides and black phosphorus (BP) emerged as new 2D semiconductors due to the advantages of moderate energy band gap, high carrier mobility, ultra thin film and high anisotropy. Together with graphene, 2D materials have been utilized in the development of biomedical devices, touch screen and display technologies, and flexible applications such as wearable electronics and IoT devices. They also open up new opportunities in research fields including spintronics, optoelectronics and next generation post-silicon transistor. In this dissertation, we present theoretical modeling for several topics related to 2D materials. Starting with the fundamental tight-binding theory of graphene, we review electronic properties for graphene including massless 2x2 Dirac Hamiltonian and pseudo-spin wave function. Followed by discussion of ballistic transport, a detailed analysis on graphene diffusive transport is provided. Ionized impurity scattering and carrier screening effect is considered in the model. The momentum relaxation time and mobility for graphene is modeled. A non-linear Thomas Fermi screening is introduced to improve the simulation accuracy. Taking the real spin into account, the new Hamiltonian is a 4x4 matrix. An external field perpendicular to the graphene breaks the reflection symmetry and introduces a Rashba spin-orbit interaction, which couples pseudo-spin and real spin. The relevant charge carrier states are no longer spin eigenstates. Rashba interaction is found to be quite small compared to Coulomb impurity scattering. To characterize the spin-polarized electrons tunneling from electrodes and transport in graphene, a spin valve device modeling and magnetoresistance calculation is developed. Black phosphorus possesses excellent properties like other 2D materials for high performance nanoelectronic applications. Moreover, there is a uniquely high in-plane anisotropy in BP due to its puckered crystal structure. To model the anisotropic transport, a model based on the BTE is developed, considering the full anisotropic electronic structure. For zero temperature calculation with ionized impurity limited scattering, anisotropy ratio 3-4 can be obtained from the model. Due to the dominating effect of screening, mobility is found to decrease weakly with increasing temperature. For , a smaller anisotropy ratio of 1.8-3.5 matching experimental measurements indicates that impurity scattering is an important mechanism for black phosphorus.

Infrastructureless Delay Tolerant Networks (DTNs) composed of commodity mobile devices have the potential to support communication applications resistant to blocking and censorship, as well as certain types of surveillance. In this thesis we study the utility, practicality, robustness, and security of these networks. We collected two sets of wireless connectivity traces of commodity mobile devices with different granularity and scales. The first dataset is collected through active installation of measurement software on volunteer users' own smartphones, involving 111 users of a DTN microblogging application that we developed. The second dataset is collected through passive observation of WiFi association events on a university campus, involving 119,055 mobile devices. Simulation results show consistent message delivery performances of the two datasets. Using an epidemic flooding protocol, the large network achieves an average delivery rate of 0.71 in 24 hours and a median delivery delay of 10.9 hours. We show that this performance is appropriate for sharing information that is not time sensitive, e.g., blogs and photos. We also show that using an energy efficient variant of the epidemic flooding protocol, even the large network can support text messages while only consuming 13.7% of a typical smartphone battery in 14 hours. We found that the network delivery rate and delay are robust to denial-of-service and censorship attacks. Attacks that randomly remove 90% of the network participants only reduce delivery rates by less than 10%. Even when subjected to targeted attacks, the network suffered a less than 10% decrease in delivery rate when 40% of its participants were removed. Although structurally robust, the openness of the proposed network introduces numerous security concerns. The Sybil attack, in which a malicious node poses as many identities in order to gain disproportionate influence, is especially dangerous as it breaks the assumption underlying majority voting. Many defenses based on spatial variability of wireless channels exist, and we extend them to be practical for ad hoc networks of commodity 802.11 devices without mutual trust. We present the Mason test, which uses two efficient methods for separating valid channel measurement results of behaving nodes from those falsified by malicious participants.

With the increasing popularity of mobile devices and their apps, mobile technologies have changed the nature of travel significantly. With numerous travel apps available today, many tourists can become confused with which one to select and use. Another important factor is that a majority of travel applications are designed for everyone traveling everywhere, not specifically for one kind of tourist and one subject matter. The goal of this thesis is to create an effective and efficient user experience system. The project is a travel planner for people to pursue an art tour of their own interest. It focuses on designing an effective user navigation system to guide tourists making their travel plans, and provides comprehensive tours to help people appreciate and learn more about art. To achieve this project, this thesis focuses on interaction design, information design, multimedia technology, as well as user experience design. Considering the independent choice of different tourists, this design provides various ways for them to make their own travel plans and discover art they are interested in. The final design is presented as an interactive prototype which demonstrates the functionality of the user interface and experience and is used for usability testing.

Ultra-fine grained materials with sub-micrometer grain size exhibit superior mechanical properties when compared with conventional fine-grained material as well as coarse-grained materials. Severe plastic deformation (SPD) techniques have been shown to be an effective way to modify the microstructure in order to improve the mechanical properties of the material. Crystalline materials require dislocations to accommodate plastic strain gradients and maintain lattice continuity. The lattice curvature exists due to the net dislocation that left behind in material during deformation. The characterization of such defects is important to understand deformation accumulation and the resulting mechanical properties of such materials. However, traditional techniques are limited. For example, the spatial resolution of EBSD is insufficient to study materials processed via SPD, while high dislocation densities make interpretations difficult using conventional diffraction contrast techniques in the TEM. A new technique, precession electron diffraction (PED) has gained recognition in the TEM community to solve the local crystallography, including both phase and orientation, of nanocrystalline structures under quasi-kinematical conditions. With the assistant of precession electron diffraction coupled ASTARÔ, the structure evolution of equal channel angular pressing processed commercial pure titanium is studied; this technique is also extended to two-phase titanium alloy (Ti-5553) to investigate the existence of anisotropic deformation behavior of the constituent alpha and beta phases.

In the first chapter of this thesis, we propose a penalized splines (P-splines) estimator for random effects panel data model. While being a nonparametric technique, one of the most attractive properties of splines methods is their analogous setup to parametric regression model. Compared to kernel-based methods, however, splines methods are far less developed at least for econometric models. The asymptotic results of our P-splines estimator are established in this chapter. Monte Carlo simulation is conducted to compare the performance of our P-splines estimator with different kernel-based estimators proposed in recent literature. It turns out that the P-splines estimator consistently performs well and is computationally efficient. In the second chapter, we develop a general procedure to derive the asymptotic variance-covariance matrices of two-stage estimators that can be used to estimate simultaneous equation systems with a mixture of any number of binary and continuous dependent variables. To demonstrate the usefulness of our procedure, we apply our formulas to empirical data with one continuous and two binary dependent variables in the simultaneous equations system. Our results are expected to be of tremendous help to numerous practitioners of econometrics using two-stage procedures to estimate their simultaneous equations models.

Myopia or nearsightedness is a condition in which the axial length of the eye is too long relative to its optical focal length. This condition is reaching epidemic levels worldwide, and has become a tremendous public health burden. Myopia is one of the leading causes of vision loss and high myopia significantly increases the risk of permanent blindness. Consequently, myopia cannot be considered as a benign condition and early interventions aimed at slowing down or even stopping the progression of myopia rather than merely correcting the associated optical focusing error is of great importance. The consistent evidence from animal model studies showing that imposed hyperopic defocus, if sustained, comprises an effective myopogenic stimulus, accelerating eye growth, while imposed myopic defocus slows ocular elongation, has motivated clinical studies using bifocal and progressive addition spectacles for myopia control. While these studies, reviewed in Chapter 2 of this dissertation, failed to provide convincing evidence for a clinically significant treatment effect, i.e., slowed myopia progression; smaller scale, non-randomized studies using multifocal soft contact lenses and orthokeratology lenses have shown much more promising effects in terms of slowing myopia progression. However, the mechanism(s) underlying the latter anti-myopia treatment effects are poorly understood, thereby limiting their further refinement. In addition to the aforementioned systematic review of relevant clinical evidence for optical interventions for myopia control, this dissertation described 3 other studies using chick model, representing efforts to further understand how multifocal optical environments affect normal ocular development, specifically the process of emmetropization. These manipulations have also been used as a tool to investigate the mechanism underlying the myopia controlling effect of the novel contact lens applications referred above. Chapter 2 describes a systematic review and meta-analysis performed on randomized controlled trials investigating the effects of three traditional optical interventions, bifocal and progressive addition spectacles, and rigid contact lenses, all believed to control myopia progression, based on anecdotal evidence. The overall treatment effect was estimated to be only small and clinically insignificant. A number of reasons were proposed to explain the discrepancy between the results of related animal studies and these clinical trials - strong support for optical control of myopia from the former studies and inconclusive results from the latter studies. Poor compliance to the spectacle corrections in clinical studies, inaccurate measurement of adherence to the treatments, inadequate and potentially, ambiguous classification systems for clinical myopia, and potential flaws in the optical designs are likely to have contributed to the discouraging results from the clinical trials. Chapter 3 describes the first of three studies in which the chick model was used to test the effects on ocular growth of a series of custom-designed 2-zone multifocal "spectacle" lenses. This and the two follow-up studies using this model have the following merits; they made use of standardized experimental paradigms and objective methods of measurement to track ocular changes. The first study applied the lenses in a simple experimental paradigm, in which monocular lenses were attached to the normal eyes of young chickens. The 2-zone lenses included a plano zone, either in the center or peripheral surround, with either positive or negative power (+5 or -5 D) incorporated into the other zone. The size of the central zone was also allowed to vary, to control the size of the unifocal central and peripheral retinal areas, and intermediate multifocal zone, as was the placement of the powered zone, i.e. in the center or periphery of the lenses. Single vision lenses were included as a control treatment. Two important observations from this study were that 1) peripheral optical defocus can influence both peripheral (off-axis) and central (on-axis) refractive error development and 2) the inhibitory effect on axial ocular growth of myopic defocus imposed using 2-zone lenses (positive zones) could exceed that induced by single vision lenses of the same power. These results suggested complex interactions between adjacent retinal regions, with the peripheral retina apparently able to decode optical defocus, as well as complex interactions between the eyes own optical aberrations and those of the 2-zone lenses, which introduced large amounts of spherical aberration. Chapter 4 described a closely related study in which subsets of the same 2-zone lenses were tested on eyes that had undergone surgical manipulations (sectioning of the ciliary nerve, CNX or iridectomy, ID) to investigate the influence of the pupil size of the eye as well as accommodation on the effects of the 2-zone lenses. Both were uncontrolled in the first study; yet create a dynamic optical system on which the multifocal optical environment was imposed. The ID surgery produced a fixed dilated pupil without any effect on accommodation (confirmed in another study, reported in Appendix I), while the CNX surgery produced a similarly enlarged pupil while also eliminating accommodation. This study revealed pupil size to be a critical factor in the treatment effects of 2-zone lenses, likely to reflect at least in part, its influence on the optical experience of various retinal zones (center to periphery), and also suggested a significant role of accommodation in the decoding of imposed optical defocus stimuli, in this case, complex multifocal optical stimuli. Chapter 5 described a third study which attempted to develop a clinically more relevant scenario; specifically, 2-zone lenses that incorporated two different negative powers (-5 & -10 D) in two optical zones (center & periphery or vice versa), were tested on both normal eyes and eyes made myopic before being fitted with one of the 2-zone lenses. The latter combination was intended to simulate the ocular conditions created when concentric multifocal contact lenses, i.e. with a near addition, are prescribed to human myopes, one of the novel, myopia control treatments currently being explored. When the 2-zone lenses were fitted to normal eyes, they induced myopia, of a magnitude falling between the values expected, had single vision lenses of the same powers been used. However, on myopic eyes, the lenses had a strong myopia inhibiting effect with the already induced myopia undergoing substantial regression. This result supports the further investigation of appropriately designed concentric multifocal contact lenses for the control of myopia progression. In summary, the studies reported in this dissertation indicate complex interactions between central and peripheral retinal regions in decoding and responding to complex defocus signals as well as critical influences of pupil size and accommodation on these processes. The strong and consistent inhibitory effects on ocular growth of concentric 2-zone lenses incorporating a zone of either positive power or a near addition, 2-zone designs lend plausibility to the notion of using custom-designed novel optical treatments for the control of myopia progression.

Since the rediscovery, LDPC codes attract a large amount of research efforts. In 1998, nonbinary LDPC codes were firstly investigated and the results shown that they are better than their binary counterparts in performance. Recently, there is always a requirement from the industry to design applied nonbinary LDPC codes. In this dissertation, we firstly propose a novel class of quasi-cyclic (QC) LDPC codes. This class of QC-LDPC codes embraces both linear encoding complexity and excellent compatibility in various degree distributions and nonbinary expansions. We show by simulation results that our proposed QC-LDPC codes perform as well as their comparable counterparts. However, this proposed code structure is more flexible in designing. This feature may show its power when we change the code length and rate adaptively. Further more, we present two algorithms to generate codes with short girth and better girth distribution. The two algorithms are designed based on progressive edge growth (PEG) algorithm and they are specifically designed for quasi-cyclic structure. The simulation results show the improvement they achieved. In this thesis, we also investigate the believe propagation based iterative algorithms for decoding of nonbinary LDPC codes. The algorithms include sum-product (SP) algorithm, SP algorithm using fast Fourier transform, min-sum (MS) algorithm and complexity reduced extended min-sum (EMS) algorithm. In particular, we present the proposed modified min-sum algorithm with threshold filtering which further reduces the computation complexity.

This thesis consists of three studies on corporate governance issues of Chinese listed companies. In the first study, I investigate the role of board secretaries in management earnings forecasts. Individuals in this senior executive position are responsible for coordinating information disclosure. I find that their legal and accounting expertise and foreign experience help improve management earnings forecast quality. The quality of forecasts, as indicated by forecast occurrence, frequency, precision and accuracy, is positively associated with board secretaries' duality role and equity holdings, whereas it is negatively associated with their political connections. The quality of forecasts is found to increase the compensation of board secretaries. Finally, I show that the equity holdings of board secretaries reduce litigation risks and increase corporate philanthropic giving. Based on the notion that women cooperate more with women than with men, my second study examines the gender interaction effect between female top managers and female board directors in Chinese firms. I show that this gender interaction is positively associated with the firm's accounting return but negatively associated with its stock price return. Earnings management, which can lead to overstated accounting numbers but unfavourable stock market reactions, partly explains the opposite results. Furthermore, I find that only the newly appointed female top managers engage in this earnings management. Overall, the findings suggest that the pressure on women to perform leads to 'women helping women', which is detrimental to shareholders' value. Women are underrepresented on corporate boards. By employing the large variation in socioeconomic development across provinces of China, the third study shows that the barriers to board gender diversity are deeply rooted in societal gender role attitudes. I find that corporate boards tend to be more gender diverse in a province where there is a smaller gender difference in educational achievement in STEM disciplines, where there is a stronger belief that women and men possess equal intrinsic abilities, or where female political leaders are present in the provincial government or communist party. However, I find little evidence that female labour force participation or childcare provision would affect board gender diversity. Collectively, the findings suggest that it is the gender equality attitudes rather than the supply of average female labour that contribute to gender-diverse corporate boards.