Дисертації з теми "Context refinement"

Twelve step organizations such as Alcoholics Anonymous and Narcotics Anonymous are free, community-based fellowships. Such organizations are the most widely sought recovery management options, surpassing professional treatment. The emerging evidence base suggests that involvement in such organizations is associated with positive substance-related outcomes (e.g., abstinence). Relatively speaking, however, far less is known about whether or not involvement is associated with other meaningful psychosocial constructs. The current study examined gratitude, meaning in life, life satisfaction, personal growth, and various other recovery and psychosocial constructs in a sample of self-identified NA members (N = 128) from 26 U.S. states, ranging in age from 22 to 64 years. The primary aim of the present study was to psychometrically evaluate and refine four distinct positive psychology instruments (i.e., Gratitude Questionnaire (GQ – 6), Meaning in Life Scale (MLQ), Satisfaction With Life Scale (SWLS), Personal Growth Initiative Scale (PGIS)). The current study contained three phases. First, the psychometric properties of each instrument were examined within an Item Response Theory measurement framework. The Rating Scale Model was used to evaluate the each instrument using WINSTEPS 3.74.01. With the exception of the Meaning in Life Questionnaire (which did not conform to an IRT measurement model), each instrument was iteratively refined based on statistical and clinical considerations, resulting in the collapse of response options and the removal of poorly fitting items. These refinements improved the psychometric properties of each instrument, resulting in a more reliable, accurate, and efficient way to measure gratitude, life satisfaction, and personal growth in clinical samples. Second, items from the GQ – 6, SWLS, and PGIS were examined concurrently using the PROC IRT procedure in SAS to explore whether the constructs were distinct from one another. Results provide support that gratitude, life satisfaction, and personal growth are unique and distinct constructs. Last, the study examined several recovery-related correlates of gratitude, life satisfaction, and personal growth. Hierarchical regression models assessed whether abstinence duration and other recovery-related variables accounted for significant incremental variance in gratitude, life satisfaction, and personal growth, over and above several covariates. As a block, abstinence duration and recovery predictors accounted for significant incremental variance in all of the constructs. These data suggest ongoing recovery involvement in 12-step organizations may be associated with positive outcomes beyond abstinence. Limitations and directions for future research are discussed.

This study identified the common factors that influence social care practice across disciplines (such as social work and psychology), practice fields, and geographical contexts and further developed the Practice Domain Framework as an empirically-based conceptual framework to assist practitioners in understanding practice complexities. The framework has application in critical reflection, professional supervision, interdisciplinary understanding, teamwork, management, teaching and research. A mixed-methods design was used to identify the components and structure of the refined framework. Eighteen influential factors were identified and organised into eight domains: the Societal, Structural, Organisational, Practice Field, Professional Practice, Accountable Practice, Community of Place, and Personal.

This thesis investigates the properties of generic refinements of behavioral specifications. At the base of this investigation stands the view from algebraic specification that abstract data types can be modeled as algebras. A specification of a data type is formed from a syntactic part, i.e. a signature detailing the interface of the data type, and a semantic part, i.e. a class of algebras (called its models) that contains the valid implementations of that data type. Typically, the class of algebras that constitutes the semantics of a specification is defined as the class of algebras that satisfy some given set of axioms. The behavioral aspect of a specification comes from relaxing the requirements imposed by axioms, i.e. by allowing in the semantics of a specification not only the algebras that literally satisfy the given axioms, but also those algebras that appear to behave according to those axioms. Several frameworks have been developed to express the adequate notions of what it means to be a behavioral model of a set of axioms, and our choice as the setting for this thesis will be Bidoit and Hennicker’s Constructor-based Observational Logic, abbreviated COL. Using specifications that rely on the behavioral aspects defined by COL we study the properties of generic refinements between specifications. Refinement is a relation between specifications. The refinement of a target specification by a source specification is given by a function that constructs models of the target specification from the models of the source specification. These functions are called constructions and the source and target specifications that they relate are called the context of the refinement. The theory of refinements between algebraic specifications, with or without the behavioral aspect, has been well studied in the literature. Our analysis starts from those studies and adapts them to COL, which is a relatively new framework, and for which refinement has been studied only briefly. The main part of this thesis is formed by the analysis of generic refinements. Generic refinements are represented by constructions that can be used in various contexts, not just in the context of their definition. These constructions provide the basis for modular refinements, i.e. one can use a locally defined construction in a global context in order to refine just a part of a source specification. The ability to use a refinement outside its original context imposes additional requirements on the construction that represents it. An implementer writing such a construction must not use details of the source models that can be contradicted by potential global context requirements. This means, roughly speaking, that he must use only the information available in the source signature and also any a priori assumption that was made about the contexts of use. We look at the basic case of generic refinements that are reusable in every global context, and then we treat a couple of variations, i.e. generic refinements for which an a priori assumption it is made about the nature of their usage contexts. In each of these cases we follow the same pattern of investigation. First we characterize the constructions that ensure reusability by means of preservation of relations, and then, in most cases, we show that such constructions must be definable in terms of their source signature. Throughout the thesis we use an informal analogy between generic (i.e. polymorphic) functions that appear in second order lambda calculus and the generic refinements that we are studying. This connection will enable us to describe some properties of generic refinements that correspond to the properties of polymorphic functions inferred from their types and named “theorems for free” by Wadler. The definability results, the connection between the assumptions made about the usage contexts and the characterizing relations, and the “theorems for free” for behavioral specifications constitute the main contributions of this thesis.

Smoothed Particle Hydrodynamics (SPH) is a relatively new, simple and effective numerical method that can be used to solve a variety of difficult problems in computational mechanics. It is a fully Lagrangian meshless method ideal for solving large deformation problems such as complex free surface fluid flows. This research was carried out with the support of BAE Systems and falls into two distinct areas. Firstly to investigate new methods for treating fixed boundaries and secondly to investigate refinement algorithms which allow for both sparsely and densely populated regions of particles within the same computational domain. Much work has been done in the modelling of particle-boundary interactions in SPH since the governing equations do not naturally incorporate essential boundary conditions. In this research a new technique for calculating boundary contact forces is developed. The forces are obtained from a variational principle and as such conserve both the linear and angular momentum of the system. The boundaries are explicitly defined using this new approach and so the need for additional boundary particles is removed. In the past most SPH derivations have been based on a uniform distribution of particles of equal mass. This leads to large simulations with many particles and long run times. In other mesh based schemes it has become common place to use mesh adaptivity to improve numerical results and reduce computation times. With a corresponding refinement strategy SPH can gain these same advantages. In this research a refinement strategy based upon particle splitting is developed. Candidate particles are split into several 'daughter' particles according to a given refinement pattern centred about the original particle position. Through the solution of a non-linear minimisation problem the optimal mass distribution for the daughter particles is obtained so as to reduce the errors introduced into the underlying density field. This procedure necessarily conserves the mass of the system. The unique daughter particle velocity configuration that conserves the linear and angular momentum of the system is also identified. The conclusion of the research was the successful implementation of these improvements into the existing SPH framework. As a result the capability and flexibility of the code is greatly increased and the computational expense needed for running large simulations has been reduced.

Hypereutectic Al-Si alloys are of increasing interest for applications that require a combination of light weight and high wear resistance, such as pistons, liner-less engine blocks and pumps. The wear resistance of this class of alloys is due to the presence of hard primary Si particles formed during casting. The objective of this work was to develop one or more methods of refining primary silicon in cast hypereutectic Al-Si alloys to compete with the conventional process of adding phosphorous and to achieve the simultaneous modification of silicon in the Al-Si eutectic. A robust sampling/casting technique was developed to minimise macro-segregation of primary silicon during solidification of hypereutectic Al-Si alloys by using water cooled steel mould with cooling rate in excess of 15 K/s. The morphology of silicon phases was found to change with increasing melt temperature and cooling rate. The high cooling rate and superheat temperature produces a good distribution of polyhedral primary silicon particles in a refined lamellar eutectic matrix in solidification of commercial purity Al-Si alloys. Removing Ca by fluxing with K2SiF6 prior to casting can improve the refinement and modification effect of Mg and Sb respectively. Effects of various inoculants were studied. Microstructural analysis showed that Mg and ZnS refined primary Si whereas MgO, CaO and Na2S coarsened the primary Si together with a modification effect on the eutectic Si. Adding Zn had no effect on morphology of Si phases. Refinement of both primary and eutectic silicon phases was observed for the Al-15Si alloy with Mg content ≤ 0.3 wt%. P-doped γ-Al2O3 was found to be a potent substrate to nucleate primary silicon whilst good modification of the eutectic matrix is retained during solidification of hypereutectic Al-Si alloys. On using P-doped γ-Al2O3 could be a perfect and clean source of P without additional impurities. A new solid-liquid duplex casting process was devised to achieve simultaneous refinement and modification of Si phases in hypereutectic Al-Si alloys with improvement in mechanical properties. The static mechanical properties of Al-Si produced by the solid-liquid duplex casting process are significantly better than conventionally cast untreated Al-Si and slightly better than conventionally cast Al-Si treated with P and/or Sr. A novel Al-ZnS master alloy was developed by in situ reaction of Zn and Na2S in the Al melt. The results from this study leave little doubt that this novel Al-ZnS master alloy is a promising refiner in solidification of hypereutectic Al-Si alloys. It refines primary silicon to the same extent as that achieved by adding P via Cu-P following the same refinement mechanism.

Cette thèse s'intéresse à la conception et à l'analyse de méthodes de discrétisation hybrides pour les inégalités variationnelles non linéaires apparaissant en mécanique des fluides et des solides. Les principaux avantages de ces méthodes sont la conservation locale au niveau des mailles, la robustesse par rapport à différents régimes de paramètres et la possibilité d’utiliser des maillages polygonaux / polyédriques avec des nœuds non coïncidants, ce qui est très intéressant dans le contexte de l’adaptation de maillage. Les méthodes de discrétisation hybrides sont basées sur des inconnues discrètes attachées aux faces du maillage. Des inconnues discrètes attachées aux mailles sont également utilisées, mais elles peuvent être éliminées localement par condensation statique. Deux applications principales des discrétisations hybrides sont abordées dans cette thèse. La première est le traitement par la méthode de Nitsche du problème de contact de Signorini (dans le cas scalaire) avec une non-linéarité dans les conditions aux limites. Nous prouvons des estimations d'erreur optimales conduisant à des taux de convergence d'erreur d'énergie d'ordre (k + 1), si des polynômes de face de degré k >= 0 sont utilisés. La deuxième application principale concerne les fluides à seuil viscoplastiques. Nous concevons une méthode de Lagrangien augmenté discrète appliquée à la discrétisation hybride. Nous exploitons la capacité des méthodes hybrides d’utiliser des maillages polygonaux avec des nœuds non coïncidants afin d'effectuer l’adaptation de maillage local et mieux capturer la surface limite. La précision et la performance des schémas sont évaluées sur des cas tests bidimensionnels, y compris par des comparaisons avec la littérature
This thesis is concerned with the devising and the analysis of hybrid discretization methods for nonlinear variational inequalities arising in computational mechanics. Salient advantages of such methods are local conservation at the cell level, robustness in different regimes and the possibility to use polygonal/polyhedral meshes with hanging nodes, which is very attractive in the context of mesh adaptation. Hybrid discretizations methods are based on discrete unknowns attached to the mesh faces. Discrete unknowns attached to the mesh cells are also used, but they can be eliminated locally by static condensation. Two main applications of hybrid discretizations methods are addressed in this thesis. The first one is the treatment using Nitsche's method of Signorini's contact problem (in the scalar-valued case) with a nonlinearity in the boundary conditions. We prove optimal error estimates leading to energy-error convergence rates of order (k+1) if face polynomials of degree k >= 0 are used. The second main application is on viscoplastic yield flows. We devise a discrete augmented Lagrangian method applied to the present hybrid discretization. We exploit the capability of hybrid methods to use polygonal meshes with hanging nodes to perform local mesh adaptation and better capture the yield surface. The accuracy and performance of the present schemes is assessed on bi-dimensional test cases including comparisons with the literature

Ce travail de thèse s’inscrit dans le cadre de l’étude de l’Interaction mécanique Pastille-Gaine (IPG) se produisant dans les crayons combustibles des réacteurs à eau pressurisée. Ce mémoire porte sur le développement de méthodes de raffinement de maillage permettant de simuler plus précisément le phénomène d’IPG tout en conservant des temps de calcul et un espace mémoire acceptables pour des études industrielles. Une stratégie de raffinement automatique basée sur la combinaison de la méthode multi-grilles Local Defect Correction (LDC) et l’estimateur d’erreur a posteriori de type Zienkiewicz et Zhu est proposée. Cette stratégie s’appuie sur l’erreur fournie par l’estimateur pour détecter les zones à raffiner constituant alors les sous-grilles locales de la méthode LDC. Plusieurs critères d’arrêt sont étudiés afin de permettre de stopper le raffinement quand la solution est suffisamment précise ou lorsque le raffinement n’apporte plus d’amélioration à la solution globale.Les résultats numériques obtenus sur des cas tests 2D élastiques avec discontinuité de chargement permettent d’apprécier l’efficacité de la stratégie proposée.Le raffinement automatique de maillage dans le cas de problèmes de contact unilatéral est ensuite abordé. La stratégie proposée dans ce travail s’étend aisément au raffinement multi-corps à condition d’appliquer l’estimateur d’erreur sur chacun des corps séparément. Un post-traitement est cependant souvent nécessaire pour garantir la conformité des zones de raffinement vis-à-vis des frontières de contact. Une variété de tests numériques de contact entre solides élastiques confirme l’efficacité et la généricité de la stratégie proposée
This Ph.D. work takes place within the framework of studies on Pellet-Cladding mechanical Interaction (PCI) which occurs in the fuel rods of pressurized water reactor. This manuscript focuses on automatic mesh refinement to simulate more accurately this phenomena while maintaining acceptable computational time and memory space for industrial calculations. An automatic mesh refinement strategy based on the combination of the Local Defect Correction multigrid method (LDC) with the Zienkiewicz and Zhu a posteriori error estimator is proposed. The estimated error is used to detect the zones to be refined, where the local subgrids of the LDC method are generated. Several stopping criteria are studied to end the refinement process when the solution is accurate enough or when the refinement does not improve the global solution accuracy anymore.Numerical results for elastic 2D test cases with pressure discontinuity shows the efficiency of the proposed strategy.The automatic mesh refinement in case of unilateral contact problems is then considered. The strategy previously introduced can be easily adapted to the multibody refinement by estimating solution error on each body separately. Post-processing is often necessary to ensure the conformity of the refined areas regarding the contact boundaries. A variety of numerical experiments with elastic contact (with or without friction, with or without an initial gap) confirms the efficiency and adaptability of the proposed strategy

Des travaux scientifiques récents ont ouvert de nouveaux champs d’application aux traitements mécaniques tels que le grenaillage. Il a été montré que de tels traitements, réalisés avant un traitement de nitruration à la surface d’alliage ferreux, permettaient d’abaisser les températures de traitement et d’augmenter significativement les cinétiques de diffusion. Nous avons entrepris de tester les performances de cette combinaison de traitements mécanique et thermochimique sur des aciers inoxydables et des alliages à base nickel austénitiques. Des essais ont été réalisés à partir d’une technique de grenaillage mécanique appelée « Surface Mechanical Attrition Treatment » (SMAT). Des billes en métal ou en céramique sont introduites dans l’enceinte et mises en mouvement par la sonotrode. Les billes percutent et introduisent donc une déformation plastique à la surface des échantillons. Après cette étape, les échantillons subissent un traitement thermochimique de nitruration assisté plasma. La comparaison des résultats obtenus après nitruration sur des échantillons traités mécaniquement avec ceux n’ayant pas été pré-traités mécaniquement a permis de quantifier les effets des traitements combinés. Les analyses par diffraction des rayons X, les mesures de microdureté, les observations au microscope optique/électronique à balayage/électronique en transmission, les analyses de texture par EBSD (Electron BackScatered Diffraction) et la mesure des profils de concentration en azote par SIMS (Secondary Ion Mass Spectrometry) et SDL (Spectroscopie à Décharge Luminescente) ont montré l’importance de la nature de la couche transformée mécaniquement sur la diffusion de l’azote
Recent scientific work has opened new fields of application to mechanical treatments such as shot blasting or peening. Indeed, it has been shown that this treatment, performed before a nitriding treatment on the surface of ferrous alloy, lowers processing temperatures and significantly increases the diffusion kinetics. We undertook to test this combination of mechanical and thermochemical treatments on stainless steels and nickel-based alloys. The mechanical treatments were done by Surface Mechanical Attrition Treatment (SMAT). This method is implemented in a box where metal or ceramic balls were introduced and set in motion by an ultrasound system in order to impact the surface of the pieces. The treated samples were then nitrided at low temperature by using a remote plasma. The comparison of the results obtained after nitriding treatments on mechanically treated samples and those not mechanically treated allows quantifying the effects of the combined treatments. Analyses by X-ray diffraction, microhardness measurement, observations by optical and scanning and transmission electron microscopy, texture analysis by EBSD (Electron Diffraction BackScatered) and measurement of nitrogen concentration profiles by SIMS (Secondary Ion Mass Spectrometry) show the importance of the nature of the deformed layer

碩士
國立臺灣科技大學
資訊管理系
102
The aim of this research is to cluster the context patterns of the query and resolve the relevant topics of documents according the most discriminative context words for the clusters. First, context patterns are extracted from documents and converted into feature space by latent semantic indexing, in which pattern clustering is conducted. These clusters are then refined to remove the patterns close to the boundary, and the words for the remaining patterns within each cluster are extracted and sorted so as to obtain the most discriminative context words. These words are further used to re-ranking the documents and the purities of the top 20 documents are evaluated. Experimental results based on the context patterns of the query “apple” shows, GMM-based clustering can achieve significantly better clustering performance (F-measure) than K-means or agglomerative clustering, since GMM is based on parametric model that has better generalization capability and takes into account the distance normalization by covariance. In addition, the discriminative context words added into the query individually can improve the retrieval performance (purity of top 20 documents) from 0.85 to 0.96, and cluster refinement can further improve the purity to 0.973. When the proposed scheme was used to analyze the clusters of the context patterns for such queries as “rocket”, “Eva”, “expired” and “Philippine”, the relevant topics can be resolved effectively, which may help to induce the word senses or track the events of various topics.

No
Abstract: In periodic manner the analysts teams are in the process of designing, updating and verifying the situational awareness SWA system. Initially, at the designing stage the risk assessment model has little information about the dynamic environment. Hence, any missing information can directly impact the situational assessment capabilities. With this in mind, researchers relied on various performance metrics in order to verify how well they were doing in assessing different situations. In fact, before measuring the ranking capabilities of the SWA system, the underlying performance metrics should be examined against its intended purpose. In this paper, we have conducted quality based evaluations for the performance metrics, namely "The Ranking Capability Score". The results obtained showed that the proposed performance metrics have scaled well over a number of scenarios. Indeed, from the data fusion perspectives the underlying metrics have adequately satisfied different SWA system needs and configurations.

This thesis presents the conceptualization, formulation, development and demonstration of Omnispective Analysis and Reasoning (OAR), an epistemic framework for managing intellectual concerns in scientific workflows. Although scientific workflows are extensively used to support the management of experimental and computational research, intellectual concerns are not adequately handled in current practice owing to the focus on low-level implementation details, limited context support, issues in developing shared semantics across disciplines and lack of support for verification and validation of the underlying science of the workflow. The management of intellectual concerns in scientific workflows can be improved by developing a framework for providing a layer of abstraction to lift focus from low-level implementation details, adding context as a workflow parameter, introducing localized ontologies and abstracting and mapping intellectual concerns in the research-domain to workflow specification and execution semantics. Following an examination of typical definitions of scientific workflow offered in literature, the Scientific Method is applied to develop an enhanced definition of a scientific workflow. This definition, which extends the scope of ordered analysis and investigation to a generic problem scenario, is utilized in the OAR framework. The design of OAR is modular like the Domain of Science Model (DoSM). The structure and working of OAR incorporate the evolving nature of science, hierarchy of conceptualization, omnispection, and the logical processes of analysis, reasoning and abstraction. These form the Foundation and Theory of OAR. Abstracting concerns in terms of unit knowledge entities (ukes) and groups of ukes (recipes), use of context to identify relation between recipes, the management of recipes in shelves, and the processes of concern refinement and context refinement constitute the Methodology. A comprehensive and simple example of the application of OAR to the abstraction, analysis, formulation and orchestration of a scientific workflow at different levels of granularity is provided by applying it to the problem of origami paper folding. The use of OAR in capturing the rationale of design decisions and mapping them to desired outcomes is demonstrated by applying OAR for contextualizing course design. Another example illustrates the use of OAR in the analysis, understanding and management of complex systems. Localized ontologies enable the exposure of side-effects and emergent behavior in large-scale systems due to the choice of any particular solution specification. These examples constitute a first step in building the Applications block of OAR. While OAR may be manually applied even to large-scale problems, it is expedient to avail of tool support. Soma - a simple and illustrative tool prototype is developed to indicate directions for a reference tool implementation. The thesis concludes with a consideration of ideas for future work. The contribution in this thesis corresponds to an instance of the DoSM for scientific workflow management. The OAR framework has great potential for further development as a well-formed Science of Workflows.

A high-order central essentially non-oscillatory (CENO) finite-volume scheme in combination with a block-based adaptive mesh refinement (AMR) algorithm is proposed for solution of hyperbolic and elliptic systems of conservation laws on body- fitted multi-block mesh. The spatial discretization of the hyperbolic (inviscid) terms is based on a hybrid solution reconstruction procedure that combines an unlimited high-order k-exact least-squares reconstruction technique following from a fixed central stencil with a monotonicity preserving limited piecewise linear reconstruction algorithm. The limited reconstruction is applied to computational cells with under-resolved solution content and the unlimited k-exact reconstruction procedure is used for cells in which the solution is fully resolved. Switching in the hybrid procedure is determined by a solution smoothness indicator. The hybrid approach avoids the complexity associated with other ENO schemes that require reconstruction on multiple stencils and therefore, would seem very well suited for extension to unstructured meshes. The high-order elliptic (viscous) fluxes are computed based on a k-order accurate average gradient derived from a (k+1)-order accurate reconstruction. A novel h-refinement criterion based on the solution smoothness indicator is used to direct the steady and unsteady refinement of the AMR mesh. The predictive capabilities of the proposed high-order AMR scheme are demonstrated for the Euler and Navier-Stokes equations governing two-dimensional compressible gaseous flows as well as for advection-diffusion problems characterized by the full range of Peclet numbers, Pe. The ability of the scheme to accurately represent solutions with smooth extrema and yet robustly handle under-resolved and/or non-smooth solution content (i.e., shocks and other discontinuities) is shown for a range of problems. Moreover, the ability to perform mesh refinement in regions of smooth but under-resolved and/or non-smooth solution content to achieve the desired resolution is also demonstrated.