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The overall purpose of this dissertation is to develop a multi-scale framework that can simulate radiation defect accumulation across a broad range of time and length scales in metals. In order to accurately describe defect accumulation in heterogeneous microstructures and under complex irradiation conditions, simulation methods are needed that can explicitly account for the effect of non-homogeneous microstructures on damage accumulation. In this dissertation, an advanced simulation tool called spatially resolved stochastic cluster dynamics (SRSCD) is developed for this purpose. The proposed approach relies on solving spatially resolved coupled rate equations of standard cluster dynamics methods in a kinetic Monte Carlo scheme. Large-scale simulations of radiation damage in polycrystalline materials are enabled through several improvements made to this method, including a pseudo-adaptive meshing scheme for cascade implantation and implementation of this method in a synchronous parallel kinetic Monte Carlo framework. The performance of the SRSCD framework developed in this dissertation is assessed by comparison to other simulation methods such as cluster dynamics and object kinetic Monte Carlo and experimental results including helium desorption from thin films and defect accumulation in neutron-irradiated bulk iron. The computational scaling of the parallel framework is also investigated for several test cases of irradiation conditions. SRSCD is next used to investigate radiation damage in three main types of microstructures, using α-iron as a test material: iron thin films, coarse-grained bulk iron, and nanocrystalline iron. SRSCD is used to investigate the mechanisms involved with defect accumulation in irradiated materials, such as effective diffusivity of helium in thin films and the effect of grain boundary sink strength on defect accumulation in nano-grained metals, and to predict defect populations in irradiated materials for comparison with experiments. Particular emphasis is placed on the role of microstructural features such as free surfaces and grain boundaries in influencing damage accumulation. Finally, the methodology developed in this dissertation is applied in the context of multiscale modeling and experimental design. To complete the multi-scale transition between defect-level behavior and macroscopic material property changes caused by irradiation, the relationship between mechanical loading and radiation damage is investigated. The impact of radiation damage on hardening of irradiated materials is investigated by using the results of SRSCD as inputs into polycrystalline crystal plasticity simulations. This is carried out in bulk iron by fitting hardening models to experimental data from neutron irradiation of iron and then used to predict hardening under irradiation conditions beyond what has already been accomplished in experimental studies. In addition, SRSCD is used to demonstrate the temperature shift required to achieve equivalent damage accumulation in irradiation conditions with significantly differing dose rates, such as in the case of using ion irradiation to simulate damage from neutron irradiation. In this dissertation, the development of SRSCD and its application in a multi-scale framework to predict macroscopic material property changes in metals represents a significant improvement over the state of the art due to improved simulations of defect accumulation and direct upscaling of results into polycrystalline plasticity models. The tools and understanding of defect behavior developed here will allow predictive modeling of metal degradation in reactor-relevant damage environments, including the defected microstructure and macroscopic material property changes due to irradiation.

This dissertation offers a platform to understand the nature of cluster initiatives as a socio-economic phenomenon combining cluster, entrepreneurship and intermediary features. They are particular types of ventures facilitating networks and dialog platforms adjusted to local contexts and offering a way to enhance regional development. The success of clusters and regions is shaped by the degree they are based on and involve entrepreneurial activity, which is viewed here under the prism of cluster initiatives. This dissertation uses both qualitative and quantitative approaches to study various organizational aspects of cluster initiatives and their intermediary role as well as providing recommendations for the management and support of these organizations. It is based on five papers written by the author of the dissertation solely and in collaboration with other scholars where the level of analysis is focused on cluster initiatives. Based on empirical material from the papers this dissertation brings together both the structural and organizational content of cluster initiatives by providing evidence in the areas of actors and relationships, mode of organization and intermediary specific, assessment and management as well as policy. This work has generated the following conclusions: firstly, cluster initiatives represent organizations bringing together a four-faceted constellation of interrelated actors (i.e. the initiative itself, key player, support and target group), through organization of intermediary activities. Secondly, these organizations are organized as temporary projects, but being able to attract many members and to satisfy their needs through diversified and innovative activities can help them to achieve longevity. The longevity of initiatives can also be supported by policy, which in order to become effective, should include a long-term perspective and bottom-up approach. And finally, the study proposes a model of five central qualitative success factors to be used for the assessment and management of the initiatives, which together depict a holistic picture of their functioning. This model contains elements such as idea, driving forces, activities, organization and critical mass. The two models of interrelated actors and of success factors form the main contribution of this work. Extending the stream of studies this dissertation raises awareness and calls for recognition of cluster initiatives as important actors working in-between the boundaries of other organizations and institutions. / PIE/HELIX

This research study is based on the cluster system model for effective management of schools in Namibia. with special reference to Erongo Education Region. The cluster system introduces a new perspective on the way the schools arc managed. It radically differs from the historically isolated school, employing individualistic approaches and management practices characterised by strong hierarchical structures and top down decision-making. The cluster system advocates shared decision-making, teamwork, collaboration. integration and networking. In other words clustering provides a superb climate for teachers, principals, parents and learners to interface with one another within a legitimate framework. Clustering is an effective management model that has also been implemented in developed countries such as England, the Netherlands and the United States of America. The research study involved 60 principals as respondents to a questionnaire on the cluster system, its problems and prospects. The major findings indicate that clustering enhances the quality of education through sharing of resources, exchange of ideas among teachers, and closer cooperation between schools. The study identifies numerous challenges in the implementation of the cluster system. These challenges include disparity between schools in the rural and urban areas, lack of reliable transport, lack of facilities and teaching materials in most schools, large distances between schools, teacher isolation and increased workload among personnel. However, if the challenges and prospects of clustering are put on a simple scale, the latter would probably outweigh the former completely. This means that clustering holds encouraging prospects for the education system in Namibia in general and Erongo Education Region in particular. An important finding in this regard is that the majority of the principals in the Erongo Education Region agree that the cluster system has the potential to champion and transcend in effective management of all schools within cluster centres. / Thesis (M.Ed.)--North-West University, Potchefstroom Campus, 2006.

Calculations have been carried out to investigate the stability and electronic structure of aluminum iodide clusters using first principles gradient-corrected density functional theory. Analysis of A113Ix-, A114Ix-, and A17I- clusters reveals that their stability is governed by the geometrically unperturbed A113-, A1142+, and A17+ units, respectively, that are demonstrated to constitute the compact cores of the clusters upon significant iodine content. The compact, icosahedral A113, icosahedral-like A1 14, and capped square bi-pyramid A17 superatom structures of the stable aluminum cores have an analogous electronic configuration to that of halogen, alkaline-earth, and alkaline atoms, respectively. Novel chemistry is demonstrated in superatoms, arising from two primary sources. Firstly, the calculations demonstrate the preference to break molecular I2 bonds in favor of iodine atoms individually adsorbing onto the aluminum sites of the central aluminum core surface. Secondly, the calculation show that observations of alternating stability trends dependent on the number of iodine ligands are connected to the formation and quenching of active sites. The significance of the induced active centers on aluminum iodide clusters upon association to alkenes is addressed, demonstrating a method towards predicting the location and extent of binding hydrocarbons. The novel chemistry of superatoms allows for a host of possible applications that integrate their unique properties in original ways and some key examples are described. Superatoms are the analogs to atoms and subsequently, just as the periodic table of elements lists atoms that can assemble into molecules and lattice structures, there exists the fathomable possibility to incorporate superatoms into extended structures such that they maintain their unique properties and result in a new class of materials. Initiation of such cluster-materials insinuates that cluster-mediated periodic table may be a proper extension to allow for a simple means for conveying fundamental information about clusters.

Notre recherche a pour objet de discuter les stratégies d'alliance entre prestataires de services logistiques (PSL) dans un cluster logistique chinois. Nous nous focalisons sur les impacts des caractéristiques d'un cluster sur le maintien d'une alliance. En utilisant la méthodologie qualitative, nous avons mené les entretiens avec les acteurs dans quatre clusters logistiques de la province de Guangdong qui est la plus développée en Chine. Les résultats de cette thèse nous ont permis d'abord d'avoir un premier panorama des motivations des PSL d'entrer dans un cluster logistique, ainsi également des motivations et des défis d'une stratégie d'alliance entre PSL. Nous mettons en évidence ensuite que la proximité géographique entre PSL favorise le choix de partenaires fiables et compétents et la coordination d'une alliance. De plus, les réseaux sociaux « Guanxi » permettent un contrôle informel des comportements opportunistes et aussi la construction de la confiance dans l'alliance. Enfin, l'attention portée par les pouvoirs publics sur le cluster logistique a un impact positif indirect sur le contrôle informel d'une alliance entre PSL. Nos contributions enrichissent le corps théorique de l'alliance horizontale entre PSL et du cluster logistique, et offrent des arguments pour aider des PSL à choisir d'entrer dans les clusters logistiques et à former des alliances au sein de ces clusters logistiques. En prenant compte les caractéristiques culturelles et politiques de la Chine, nous avons réalisé une recherche exploratoire sur ce sujet qui manque encore dans les études spécialisées. / The present research aims to discuss the strategies of alliance between logistics service providers (LSP) in a Chinese logistics cluster. The study focus on the impact of the characteristics of a cluster on the maintain of an alliance. With the principe of qualitative methodology, we conducted interviews with principal actors in four logistics clusters of Guangdong Province which is the most developed province in China. There are several results of this thesis. First of all, it gives an overview of the motivations of LSP to enter a logistics cluster, also the motivations and challenges of a strategic alliance between LSP. Then the results show that geographical proximity between LSP promotes coordination of an alliance and the choice of reliable and competent partners. In addition, the social networks "Guanxi" could be source of informal control of opportunistic behavior and build confidence. Finally, the attention paid by the government on the logistics cluster has an indirect positive impact on the informal control of an alliance between LSP. As theoretical contributions, this research enrichs the aspect of alliance between LSP and logistics cluster and offers arguments to help LSP choose logistics cluster and form strategies alliances within these logistics clusters. Taking into account the cultural and political characteristics of China, an exploratory research was conducted on this topic which is still lacking in the literature.

In this dissertation, we consider the problem of partitioning a set of k population with respect to a control population. For this problem some multistage methodologies are proposed and their properties are derived. Using the Monte Carlo simulation techniques, the small and moderate sample size performance of the proposed procedure are studied. We have also considered at statistical surveillance of various cancers in Louisiana.

A combined experimental and computational study on the reversible ortho-metalation exhibited by the triosmium cluster Os3(CO)10(dppm) (dppm = 1,1-bis(diphenylphosphino)methane is reported. The conversion of nonacarbonyl cluster HOs3(CO)9[-PhP(C6H4)CH2PPh2] to Os3(CO)10(dppm) is independent of added CO and exhibits a significant inverse equilibrium isotope effect (EIE). Reductive coupling of the C-H bond in HOs3(CO)9[-PhP(C6H4)CH2PPh2] leads to the formation of agostic C-H and two distinct aryl-π species prior to the rate-limiting formation of the unsaturated cluster Os3(CO)9(dppm). Heating the unsaturated dimer H2Re2(CO)8 with Cp*Rh(CO)2 (Cp* = 1,2,3,4,5-pentamethylcyclopentadiene) at elevated temperature affords the new trimetallic clusters H2RhRe2Cp*(CO)9 and HRh2ReCp*2(CO)6, and the spiked-triangular cluster HRhRe3Cp*(CO)14. H2Re2(CO)8 reacts with Cp*2Rh2(CO)2 under identical conditions to furnish H2RhRe2Cp*(CO)9 and HRh2ReCp*2(CO)6 as the principal products, in addition to the tetrahedral cluster H2Rh2Re2Cp*2(CO)8. H2RhRe2Cp*(CO)9 undergoes facile fragmentation in the presence of halogenated solvents and the thiols RSH (where R = H, C6H4Me-p) to afford the structurally characterized products Cp*Rh(-Cl)3Re(CO)3, S2Rh3Cp*(CO)4, Cp*Rh(-Cl)(-SC6H4Me-p)2Re(CO)3, and Cp*Rh(-SC6H4Me-p)3Re(CO)3. The new hydrazido-substituted compounds TaCl(NMe2)3[N(TMS)NMe2] (TMS = tetramethylsilyl) and Ta(NMe2)4[N(TMS)NMe2] have been synthesized and their structures established by X-ray crystallography. The latter product represents the first structurally characterized octahedral tantalum(V) complex containing a single hydrazido(I) ligand in an all-nitrogen coordinated environment about the metal center. The fluxional properties of the amido and hydrazido ligands in these new compounds have been established by VT 1H NMR spectroscopy (VT = variable temperature). Preliminary data using Ta(NMe2)4[N(TMS)NMe2] as an ALD (ALD = atomic layer deposition) precursor for the preparation of tantalum nitride and tantalum oxide thin films are presented.

Firstly, we have developed a Tensor Contraction Engine-based implementation of the BW-MRCCSD approach. The scalability tests have been performed across thousand of cores. We have further developed a novel two-level parallel algorithm for Hilbert-space MRCC methods which uses the processor groups. In this approach, references are distributed among processor groups (reference-level parallelism) and tasks of each reference are distributed inside of a given processor group (task-level parallelism). We have shown that our implementation scales across 24000 cores. The usability of our code was demonstrated on larger systems (dodecane, polycarbenes and naphthyne isomers). Finally, we present novel universal state- selective (USS) corrections to the state-specific MRCC methods. The USS-corrected MRCC results were compared with the full configuration interaction (FCI) results.

O diamante, juntamente com o germânio e o silício, é um importante material para área de tecnologia de semicondutores e sua superfície C(100) é considerada a de maior interesse devido às várias possibilidades de aplicações tecnológicas. Neste trabalho, seguindo uma linha similar de estudos teóricos envolvendo clusters de silício, já estudados em nosso grupo, e utilizando o estado da arte em termos de cálculos de estrutura eletrônica, realizou-se uma investigação detalhada englobando aspectos estruturais e energéticos do aglomerado C9H12 nos estados singleto e tripleto, bem como as novas características dos mesmos frente à incorporação de átomos de oxigênio e enxofre. Para o sistema limpo, C9H12 , foi dado grande enfoque à ligação dímera bem como ao processo de reconstrução que a envolve. Esta forma limpa, preferencialmente, sofre reconstrução adquirindo característica de uma dupla ligação C=C. Para os sistemas C9H12 + O e C9H12 + S foram estudados duas estruturas principais, a bridge e a top, também enfocando seus aspectos estruturais e energéticos e em cada estado de spin abordado. Para a estrutura mais estável dos sistemas, bridge-singleto, foi explorada a energia de quimissorção envolvida no processo, bem como as restrições necessárias para descrevê-la corretamente. Concluiu-se que o átomo de oxigênio interage de maneira mais efetiva com a superfície exigindo uma energia maior para se dissociar. Para a forma oxigenada, os cálculos CASSCF e MRCI forneceram um valor de 140,67 kcal.mol-1 e 150,78 kcal.mol-1, respectivamente; para a estrutura contendo enxofre, estes resultados foram de 102,45 e 112,49 kcal.mol-1, respectivamente / Diamond, like germanium and silicon, is an important material in the semiconductor area, and its C (100) surface is considered the most interesting, due to the various possibilities of technological applications. In this work, following a similar line of theoretical studies involving silicon clusters, also studied in our group, and using a high level of electronic structure calculations, we carried out a detailed investigation on structural and energetic aspects of the C9H12 cluster both in singlet and triplet states, as well as, their new characteristics arising from incorporation of oxygen and sulfur atoms. For the clean system, C9H12, a great emphasis was given to the dimer bond, as well as its reconstruction process. This clean structure undergoes reconstruction acquiring a double bond C = C character. For the systems C9H12 + O and C9H12 + S, we studied two main structures, bridge and top, also focusing on their structures and energetic, for each spin state. For the most stable structure described, bridge-singlet, we also estimated the energy involved in the chemisorption process and the restrictions necessary to carry out the calculations. We found out that the oxygen atom interacts more effectively with the surface requiring a greater energy to dissociate. For the oxygenated form, the CASSCF and MRCI calculations have provided values of 140.67 kcal.mol-1 and 150.78 kcal.mol-1, respectively; for the structure containing sulfur, these results are 102.45 kcal.mol-1 and 112.49 kcal.mol-1, respectively