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Parallel MCMC methods and their applications in inverse problemsRussell, Paul January 2018 (has links)
In this thesis we introduce a framework for parallel MCMC methods which we call parallel adaptive importance sampling (PAIS). At each iteration we have an ensemble of particles, from which PAIS builds a kernel density estimate (KDE). We propose a new ensemble, using this KDE, that is weighted according to standard importance sampling rules. A state-of-the art resampling method from the optimal transportation literature, or alternatively our own novel resampling algorithm, can be used to produce an equally weighted ensemble from this weighted ensemble. This equally weighted ensemble is approximately distributed according to the target distribution and is used to progress the algorithm. The PAIS algorithm outputs a weighted sample. We introduce an adaptive scheme for PAIS which automatically tunes the scaling parameters required for efficient sampling. This adaptive tuning converges rapidly for the target distributions we have experimented with and significantly reduces the burn-in period of the algorithm. PAIS has been designed to work well on computers with parallel processing units available, and we have demonstrated that a doubling of the number of processing units available more than halves the number of iterations required to reach the same accuracy. The numerical examples have been implemented on a shared memory system. PAIS is incredibly flexible in terms of the proposal distributions and resampling methods we can use. Throughout the thesis we introduce a number of these proposal schemes, and highlight when they may be of use. Of particular interest is the transport map based proposal scheme introduced in Chapter 7 which, while more expensive than the other schemes, allows us to sample efficiently from a wide range of complex target distributions.
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Balancing integration and responsiveness in case of the sales function within the FMCG industry : a study of foreign subsidiaries in GermanyReichstein-Scholz, Harriet January 2017 (has links)
Significant structural changes in the retail sector, due to retailer consolidation within and across countries as well as retailer internationalisation, lead to significant changes of the sales function within the FMCG industry. Whilst formally sales functions acted traditionally predominantly locally, manufacturers are recently pressured to act more integrated, i.e. centrally, regarding its sales function. From an IB perspective this study strives to investigate into the result of the competing forces for integration and responsiveness at the manufacturers side in the special context of Germany, being a pivotal market for this industry. Identifying the potential division of strategic sales activities between subsidiary and HQ, the study investigates into how such division impacts on the subsidiary market performance. Using the I/R framework as a starting point, network theory and the concept of subsidiary importance are utilized to understand the interrelationships a subsidiary is embedded in and its potential strategic importance to the wider MNE. The framework connects the antecedents of the division of strategic sales activities between HQ and subsidiary, to subsidiary market performance. The research follows a mixed-method approach using contextualising interviews and a quantitative survey. The data analysis has been conducted with PLS SEM reflecting both the more explorative character of the study and the relatively small sample size. Empirical evidence showed that most strategic sales decisions are still made at subsidiary level, pointing at a low level of division between HQ and subsidiary. The results show that strong customer relationships as well as the positive impact of a formalised sales strategy, which ideally follows a global strategic framework, seem to be the main contributors to subsidiary market performance. Unexpectedly, subsidiary importance, the visibility and relevance of sales capabilities to other subsidiaries, fails to be a driver for the subsidiary strategic role within the MNE, mainly due to the functional (sales competencies stay rather local) and country (sheer importance of the German market) context of the study. The key contributions of this study are related to the area of IB and the sales literature. This study adds to the extant IB literature from a downstream value chain perspective supporting existing findings regarding the network theory and subsidiary market performance. The irrelevance of the concept of subsidiary importance highlights the importance of the empirical context in IB research. Finally, the study sheds light on the sales function from a strategic perspective in the IB context and thus adds to the sparse literature regarding the sales strategy as well as it starts bridging both fields.
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Kriging-based Approaches for the Probabilistic Analysis of Strip Footings Resting on Spatially Varying SoilsThajeel, Jawad 08 December 2017 (has links)
L’analyse probabiliste des ouvrages géotechniques est généralement réalisée en utilisant la méthode de simulation de Monte Carlo. Cette méthode n’est pas adaptée pour le calcul des faibles probabilités de rupture rencontrées dans la pratique car elle devient très coûteuse dans ces cas en raison du grand nombre de simulations requises pour obtenir la probabilité de rupture. Dans cette thèse, nous avons développé trois méthodes probabilistes (appelées AK-MCS, AK-IS et AK-SS) basées sur une méthode d’apprentissage (Active learning) et combinant la technique de Krigeage et l’une des trois méthodes de simulation (i.e. Monte Carlo Simulation MCS, Importance Sampling IS ou Subset Simulation SS). Dans AK-MCS, la population est prédite en utilisant un méta-modèle de krigeage qui est défini en utilisant seulement quelques points de la population, ce qui réduit considérablement le temps de calcul par rapport à la méthode MCS. Dans AK-IS, une technique d'échantillonnage plus efficace 'IS' est utilisée. Dans le cadre de cette approche, la faible probabilité de rupture est estimée avec une précision similaire à celle de AK-MCS, mais en utilisant une taille beaucoup plus petite de la population initiale, ce qui réduit considérablement le temps de calcul. Enfin, dans AK-SS, une technique d'échantillonnage plus efficace 'SS' est proposée. Cette technique ne nécessite pas la recherche de points de conception et par conséquent, elle peut traiter des surfaces d’état limite de forme arbitraire. Toutes les trois méthodes ont été appliquées au cas d'une fondation filante chargée verticalement et reposant sur un sol spatialement variable. Les résultats obtenus sont présentés et discutés. / The probabilistic analysis of geotechnical structures involving spatially varying soil properties is generally performed using Monte Carlo Simulation methodology. This method is not suitable for the computation of the small failure probabilities encountered in practice because it becomes very time-expensive in such cases due to the large number of simulations required to calculate accurate values of the failure probability. Three probabilistic approaches (named AK-MCS, AK-IS and AK-SS) based on an Active learning and combining Kriging and one of the three simulation techniques (i.e. Monte Carlo Simulation MCS, Importance Sampling IS or Subset Simulation SS) were developed. Within AK-MCS, a Monte Carlo simulation without evaluating the whole population is performed. Indeed, the population is predicted using a kriging meta-model which is defined using only a few points of the population thus significantly reducing the computation time with respect to the crude MCS. In AK-IS, a more efficient sampling technique ‘IS’ is used instead of ‘MCS’. In the framework of this approach, the small failure probability is estimated with a similar accuracy as AK-MCS but using a much smaller size of the initial population, thus significantly reducing the computation time. Finally, in AK-SS, a more efficient sampling technique ‘SS’ is proposed. This technique overcomes the search of the design points and thus it can deal with arbitrary shapes of the limit state surfaces. All the three methods were applied to the case of a vertically loaded strip footing resting on a spatially varying soil. The obtained results are presented and discussed.
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John SpaghotteSchuler, Peter C 01 June 2015 (has links)
Author Peter Schuler discusses his thoughts on how ideas of creativity, literature, and pedagogy helped to develop into his first novel, John Spaghotte of Crumb. Schuler is a native of the Coachella Valley in Southern California and writes from a middle-class appreciation of working and living in an area where everything is catered to the wealthy class. Through personal injury and his experience in undergraduate and graduate studies he fought to develop a healthy critical mind and a grasp as to the true nature of identity. As a result, his riveting debut novel about a young, nerdy California version of Don Quixote becomes a cautionary tale about the dangers of failing to recognize oneself among a world full of materialistic pleasures and grandiose, fictional heroes. In the formulation of his novel Schuler argues that artistic creation, appreciation, study, and the development of a critical scope to see the world with lead to a better understand his own identity while his protagonist suffers from the lack of such a development.
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Effcient Monte Carlo Simulations for the Estimation of Rare Events Probabilities in Wireless Communication SystemsBen Issaid, Chaouki 12 November 2019 (has links)
Simulation methods are used when closed-form solutions do not exist. An interesting simulation method that has been widely used in many scientific fields is the Monte Carlo method. Not only it is a simple technique that enables to estimate the
quantity of interest, but it can also provide relevant information about the value to be
estimated through its confidence interval. However, the use of classical Monte Carlo
method is not a reasonable choice when dealing with rare event probabilities. In fact,
very small probabilities require a huge number of simulation runs, and thus, the computational time of the simulation increases significantly. This observation lies behind the main motivation of the present work. In this thesis, we propose efficient importance sampling estimators to evaluate rare events probabilities. In the first part of
the thesis, we consider a variety of turbulence regimes, and we study the outage probability of free-space optics communication systems under a generalized pointing error model with both a nonzero boresight component and different horizontal and vertical jitter effects. More specifically, we use an importance sampling approach,based on the exponential twisting technique to offer fast and accurate results. We also
show that our approach extends to the multihop scenario. In the second part of the
thesis, we are interested in assessing the outage probability achieved by some diversity techniques over generalized fading channels. In many circumstances, this is related to the difficult question of analyzing the statistics of the sum of random variables.
More specifically, we propose robust importance sampling schemes that efficiently evaluate the outage probability of diversity receivers over Gamma-Gamma, α − µ, κ − µ, and η − µ fading channels. The proposed estimators satisfy the well-known bounded relative error criterion for both maximum ratio combining and equal gain
combining cases. We show the accuracy and the efficiency of our approach compared
to naive Monte Carlo via some selected numerical simulations in both case studies.
In the last part of this thesis, we propose efficient importance sampling estimators
for the left tail of positive Gaussian quadratic forms in both real and complex settings. We show that these estimators possess the bounded relative error property.
These estimators are then used to estimate the outage probability of maximum ratio
combining diversity receivers over correlated Nakagami-m or correlated Rician fading
channels
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An Investigation of the Influence of Cooperating Teachers on the Educational Goal Ranking Behavior of Student TeachersJones, Susan Myrna 01 May 1979 (has links)
The purpose of the study was to identify the effects of the influence of cooperating teachers on how student teachers prioritize particular goals of education. This was accomplished by administering a predetermined list of eighteen educational goals to a group of student teachers prior and subsequent to their quarter-long student teaching experience, and to their respective cooperating teachers during their student teaching quarter. The list enabled the teacher groups to rank the goals in order of priority. In this way the cooperating teachers' goal rankings were compared to both the student teachers' pre and post student teaching goal rankings.
Twenty-three student teachers and their respective cooperating teachers in secondary and special education served as subjects. The Phi Delta Kappa Goal Setting Instrument was used as the goals list in the study. The questions explored were: 1) are there differences between the relative importance as signed to selected educational goals by student teachers prior to the student teaching experience and the relative importance assigned to the same goals by the cooperating teachers; 2) are there differences in the relative importance assigned to selected educational goals by student teachers before their student teaching experience as compared to their assigned rankings after their student teaching experience; and 3) is there a relationship between any changes in the relative importance assigned by the student teachers prior and subsequent to the student teaching experience and the relative importance assigned by the cooperating teachers. To test the hypotheses under investigation, eighteen one-way analyses of variance with repeated measures were computed. Significant F ratios were found for two of the eighteen goals; the remaining F ratios were not statistically significant.
The results suggest some tentative support for student teachers' goal prioritizations of two goals changing after the student teaching experience. Some tentative support was also suggested on these two goals for the student teachers' goal prioritizations changing after the student teaching experience to become more similar to the cooperating teacher' s goal prioritizations. However, the lack of significant change in sixteen of the eighteen goals more strongly suggested that the influence of a) the experience of the student teaching activity and b) the cooperating teachers' own goals prioritization biases upon the student teachers did not markedly affect student teacher goal prioritization behavior. The possibilities that the teacher groups had initial general agreement on goal priorities, that the goals may represent stable educational values, and that instrumentation concerns may have affected the results were then discussed.
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Bear River Heritage Area: A Study of Recreation Specialization and Importance-PerformanceBaird, Tyler A. 01 May 2013 (has links)
Heritage tourism is a fast growing sector in the recreation arena. Research into multiple aspects of heritage tourism has increased during the last few decades as it has been recognized as a distinct form of tourism and promoted around the globe. This study was conducted in an effort to better understand multiple aspects of heritage tourism in the Bear River Heritage Area of northern Utah and southeastern Idaho. The following aims to provide Bear River Heritage Area leadership with baseline data on their visitors and build upon the base of literature in the areas of recreation specialization, and importance-performance analysis. Attempts to apply the recreation specialization continuum in the context of heritage tourism were relatively unsuccessful in this case. Potential problems with applying recreation specialization to heritage tourism are discussed and implications for future studies are explored. In addition, emerging trends in importance-performance research are applied to respondent ratings of attribute importance and satisfaction in order to provide the best possible suggestions for Bear River Heritage Area management improvements and build upon existing research. Specifically, traditional importance-performance analysis is compared to analyses that incorporate grand means, segmentation, and confidence intervals.
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Quantitative methods for hydrological spatial field comparisonWealands, Stephen Russell Unknown Date (has links)
This thesis addresses the current lack of comprehensive, quantitative methods for comparing hydrological spatial fields. Comparison of spatial fields is needed for assessing hydrological models and for data assimilation. The methods that are currently used for quantitative comparison generally fail to consider the spatial arrangement of element values within spatial fields. Instead, there is a dependence on qualitative methods (e.g. visual comparison) to undertake comparison of many aspects (e.g. intermediate scale features), but such methods are non-repeatable, often biased and difficult to report on. This thesis advances the comparison methods available for use with hydrological spatial fields. (For complete abstract open document)
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Quantitative methods for hydrological spatial field comparisonWealands, Stephen Russell Unknown Date (has links)
This thesis addresses the current lack of comprehensive, quantitative methods for comparing hydrological spatial fields. Comparison of spatial fields is needed for assessing hydrological models and for data assimilation. The methods that are currently used for quantitative comparison generally fail to consider the spatial arrangement of element values within spatial fields. Instead, there is a dependence on qualitative methods (e.g. visual comparison) to undertake comparison of many aspects (e.g. intermediate scale features), but such methods are non-repeatable, often biased and difficult to report on. This thesis advances the comparison methods available for use with hydrological spatial fields. (For complete abstract open document)
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Livsviktigt : -en undersökning om pedagogiskt drama / The importance of life : – a study of creative drama.Gustafsson-Brown, Annika, Jonsson Lindahl, Catarina January 2007 (has links)
Syftet med studien är att utvärdera och undersöka pedagogers inställningen till det pedagogiska dramat utifrån materialet Livsviktigt. Från syftet har vi formulerat följande frågeställningar:- I vilka situationer används pedagogiskt drama?- Hur anser pedagogerna att eleven utvecklas i samband med det pedagogiska dramat?- Vilken inställning har pedagogerna till pedagogiskt drama?För att besvara frågeställningarna har vi använt oss av en undersökande enkät med både öppna och fasta svarsalternativ. Enkäten besvarades av 102 pedagoger från Värnamo kommuns grundskolor.Resultatet av studien visar att pedagogiskt drama i undervisningen styrker barns självkänsla. Den visar också på en positiv inställning av pedagogerna till det pedagogiska dramat. / The objective of this study is to evaluate the attitude of a teacher in regard to creative drama related to material referred to as Livsviktigt. (The importance of life). The following questions have been formulated from the result of the study: - What are the situations in which creative drama can be used? - How does the teacher consider the development of a student in relation to creative drama? - What is the attitude of a teacher in regard to creative drama? A questionnaire that invited both specific and non-specific answers has been used as a means of considering the formulation of the listed questions. The questionnaires have been completed by a total of 102 teachers representing all of the Elementary Schools in the Värnamo area. The result of the study provides a clear indication that the inclusion of drama in the education of children serves to strengthen their self confidence. There is also an indication that a teacher will develop a more positive attitude toward creative drama.
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