Traditional organic chromophores and polymers with disc-like, coplanar geometry tend to be highly emissive in the dilute solutions but become weakly luminescent in the concentrated solution and solid states. On the contrast, conventional chromophores (such as silole) with non-coplanar structure exhibit strong fluorescence in the concentrated states due to the aggregation-induced emission (AIE) or AIE enhancement (AIEE) effect originated from the restricted intramolecular rotation (RIR) inherent from the chemical structures of the luminescent materials. To verify the influence of RIR on the AIEE properties, four approaches were attempted in this research. First, copolymers PFN with alternative fluorene-naphthol unit was prepared through facile Suzuki coupling and was characterized to have AIEE properties due to the hydrogen-bond (H-bond) interactions among the inherent hydroxyl (OH) groups of the naphthol units. The H-bond interactions of PFN copolymer effectively restrict the molecular rotations and experimental variables (such as increasing solution concentration, introducing non-solvent water to solution, cooling and applying shearing forces during solvent evaporation stage etc.) effective in promoting the H-bond interactions result in the emission enhancement. Second, the fluorescent PFN was blended with poly(vinyl pyrrolidone) (PVR) through facile hydrogen-bond (H-bond) interactions. By the effective H-bond interactions between the OH groups of PFN and the carbonyl functions of PVR. The molecular rotations of PFN can be effectively locked by large amounts of carbonyl groups in PVR. With the efficient H-bond interactions, the PFN/PVR blend with the low content (2.33 wt%) of fluorescent PFN component actually has a high quantum efficiency of 0.93, comparatively higher than other blends containing higher fluorescent PFN. Third, novel vinyl polymer PTP with pendant AIE-effective tetraphenylthiophene (TP) group was prepared through radical polymerization. The resultant PTP polymer exhibits two discernible emission bands corresponding to monomer and aggregate emissions, respectively. The relative monomer to aggregate emission intensity of the PTP polymer in either the solution or the solid state depends strongly on the extent of aggregations. Increasing solution concentration results in the increasing extent of aggregation and the increasing aggregate/monomer emission ratio and also, the large emission enhancement due to the AIEE effect. Finally, the TP-derived ammonium (TP-NH3+) cations are complexed with poly(sodium vinylsulfonate) (PSV) polyanion to generate ionic PSV-TP(x/y) systems with long-range electrostatic interactions between the cationic ammonium of TP-NH3+ and the polyanion of PSV. The fluorophoric TP units are associated with each other to form large aggregate domains stabilized by the long-range interactions. Introduction of water into dilute solution of PSV-TP in THF resulted in self-aggregated nanoparticles and the accompanied emission enhancement due to AIEE effect. Introduction of excess PSV polyanions promoted the self-aggregation of the TP fluorophores and resulted in the fluorescence enhancement. Nevertheless, addition of NaCl electrolytes causes the dissociations of the TP aggregates and the corresponding emission reduction. By controlling the additive, the blended PSV-TP film containing excess PSV has a high quantum yield of £XF = 0.83. In addition, the ionic PSV-TP complex film possesses high spectral stability without spectral variations after annealing at a high temperature of 270 oC.

Topology optimization is commonly used to distribute a given amount of material to obtain the stiffest structure, with predefined fixed loads. The present work investigates the result of applying stress constraints to topology optimization, for problems with design-depending loading, such as self-weight and pressure. In order to apply pressure loading, a material boundary identification scheme is proposed, iteratively connecting points of equal density. In previous research, design-dependent loading problems have been limited to compliance minimization. The present study employs a more practical approach by minimizing mass subject to failure constraints, and uses a stress relaxation technique to avoid stress constraint singularities. The results show that these design dependent loading problems may converge to a local minimum when stress constraints are enforced. Comparisons between compliance minimization solutions and stress-constrained solutions are also given. The resulting topologies of these two solutions are usually vastly different, demonstrating the need for stress-constrained topology optimization.

Topology optimization is commonly used to distribute a given amount of material to obtain the stiffest structure, with predefined fixed loads. The present work investigates the result of applying stress constraints to topology optimization, for problems with design-depending loading, such as self-weight and pressure. In order to apply pressure loading, a material boundary identification scheme is proposed, iteratively connecting points of equal density. In previous research, design-dependent loading problems have been limited to compliance minimization. The present study employs a more practical approach by minimizing mass subject to failure constraints, and uses a stress relaxation technique to avoid stress constraint singularities. The results show that these design dependent loading problems may converge to a local minimum when stress constraints are enforced. Comparisons between compliance minimization solutions and stress-constrained solutions are also given. The resulting topologies of these two solutions are usually vastly different, demonstrating the need for stress-constrained topology optimization.

The behaviour of cohesionless soils is known to be influenced by the method of reconstitution. It is generally accepted in the literature that different reconstitution methods produce samples of varying fabric and thus samples of varying behaviour. Very little evidence has been presented to validate this statement. The main aim of this is thesis is firstly to observe the fabric of in situ and reconstituted gold tailings samples and secondly to investigate the difference in behaviour between these samples at the same state. The investigation focused on testing in situ and reconstituted gold tailings samples obtained from 3 positions on a tailings dam; pond, middle beach and upper beach. Laboratory reconstitution methods included moist tamping and slurry deposition. Fabric analysis involved the use of SEM images to classify the observed differences in the fabric of the undisturbed and reconstituted gold tailings samples. A particle interaction model based on the observed fabric was postulated to explain the differences or similarities in behaviour. The scope of behaviour investigated included sedimentation, collapse and swell, consolidation and compressibility, creep, stiffness and shear behaviour. The fabric analysis indicates that differences in the fabric of undisturbed and reconstituted gold tailings samples are visible. Moist tamping produces an aggregated fabric while slurry deposition yields a homogeneous fabric similar to that of the undisturbed samples. Comparison of behaviour indicates that neither moist tamping nor slurry deposition can replicate the behaviour of the undisturbed sample fully. Consolidation and compression is a function of the fabric while friction angle is independent of the fabric. Available shear strength and liquifaction potential is also affected by the preparation method and the resulting fabric. / Thesis (PhD)--University of Pretoria, 2009. / Civil Engineering / PhD / Unrestricted

This dissertation consists of three essays on different aspects of water management. The first essay focuses on the sustainability of freshwater use by introducing the notion that altruistic parents do bequeath economic assets for their offspring. Constructing a two-period, over-lapping generational model, an optimal ratio of consumption and pollution for old and young generations in each period is determined. Optimal levels of water consumption and pollution change according to different parameters, such as, altruistic degree, natural recharge rate, and population growth. The second essay concerns water sharing between countries in the case of trans-boundary river basins. The paper recognizes that side payments fail to forge water-sharing agreement among the international community and that downstream countries have weak bargaining power. An interconnected game approach is developed by linking the water allocation issue with other non-water issues such as trade or border security problems, creating symmetry between countries in bargaining power. An interconnected game forces two countries to at least partially cooperate under some circumstances. The third essay introduces the concept of virtual water (VW) into a traditional international trade model in order to estimate water savings for a water scarce country. A two country, two products and two factors trade model is developed, which includes not only consumers and producer’s surplus, but also environmental externality of water use. The model shows that VW trade saves water and increases global and local welfare. This study should help policy makers to design appropriate subsidy or tax policy to promote water savings especially in water scarce countries.

京都大学 / 0048 / 新制・課程博士 / 博士(情報学) / 甲第22586号 / 情博第723号 / 新制||情||124(附属図書館) / 京都大学大学院情報学研究科システム科学専攻 / (主査)教授 田中 利幸, 教授 石井 信, 教授 下平 英寿 / 学位規則第4条第1項該当 / Doctor of Informatics / Kyoto University / DFAM

In 2007, the Swedish payroll tax was reduced for youths in an attempt to suppress the perceived high unemployment among Swedish youths. The reform was rolled back later in 2016. For this period there is a rich supply of publicly available aggregated (macro) data. This thesis aims to examine: first, if the aggregated data is suitable for policy evaluation of the reform, and second, the effects of the reform introduction and repeal. This has been done by using both a conventional fixed effects model and a more unorthodox synthetic control method. Neither of the two methods could show any unbiased and consistent significant result of the treatment effects of the reform. Instead, the results of this thesis suggest that the publicly available aggregated data doesn’t contain enough information to evaluate such reforms.

In this paper, we show how to utilize the expectation-maximization (EM) algorithm for efficient and numerical stable parameter estimation of the batch Markovian arrival process (BMAP). In fact, effective computational formulas for the E-step of the EM algorithm are presented, which utilize the well-known randomization technique and a stable calculation of Poisson jump probabilities. Moreover, we identify the BMAP as an analytically tractable model of choice for aggregated traffic modeling of IP networks. The key idea of this aggregated traffic model lies in customizing the BMAP such that different lengths of IP packets are represented by rewards of the BMAP. Using measured traffic data, a comparative study with the MMPP and the Poisson process illustrates the effectiveness of the customized BMAP for IP traffic modeling by visual inspection of sample paths over several time scales, by presenting important statistical properties as well as by investigations of queuing behavior.

京都大学 / 新制・課程博士 / 博士(情報学) / 甲第23321号 / 情博第757号 / 新制||情||129(附属図書館) / 京都大学大学院情報学研究科数理工学専攻 / (主査)教授 太田 快人, 教授 山下 信雄, 教授 大塚 敏之 / 学位規則第4条第1項該当 / Doctor of Informatics / Kyoto University / DGAM

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