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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
281

Thermal Assessment of a Latent-Heat Energy Storage Module During Melting and Freezing for Solar Energy Applications

Ramos Archibold, Antonio Miguel 06 November 2014 (has links)
Capital investment reduction, exergetic efficiency improvement and material compatibility issues have been identified as the primary techno-economic challenges associated, with the near-term development and deployment of thermal energy storage (TES) in commercial-scale concentrating solar power plants. Three TES techniques have gained attention in the solar energy research community as possible candidates to reduce the cost of solar-generated electricity, namely (1) sensible heat storage, (2) latent heat (tank filled with phase change materials (PCMs) or encapsulated PCMs packed in a vessel) and (3) thermochemical storage. Among these the PCM macro-encapsulation approach seems to be one of the most-promising methods because of its potential to develop more effective energy exchange, reduce the cost associated with the tank and increase the exergetic efficiency. However, the technological barriers to this approach arise from the encapsulation techniques used to create a durable capsule, as well as an assessment of the fundamental thermal energy transport mechanisms during the phase change. A comprehensive study of the energy exchange interactions and induced fluid flow during melting and solidification of a confined storage medium is reported in this investigation from a theoretical perspective. Emphasis has been placed on the thermal characterization of a single constituent storage module rather than an entire storage system, in order to, precisely capture the energy exchange contributions of all the fundamental heat transfer mechanisms during the phase change processes. Two-dimensional, axisymmetric, transient equations for mass, momentum and energy conservation have been solved numerically by the finite volume scheme. Initially, the interaction between conduction and natural convection energy transport modes, in the absence of thermal radiation, is investigated for solar power applications at temperatures (300 - 400°). Later, participating thermal radiation within the storage medium has been included in order to extend the conventional natural convection-dominated model and to analyze its influence on the melting and freezing dynamics at elevated temperatures (800 - 850°). A parametric analysis has been performed in order to ascertain the effects of the controlling parameters on the melting/freezing rates and the total and radiative heat transfer rates at the inner surface of the shell. The results show that the presence of thermal radiation enhances the melting and solidification processes. Finally, a simplified model of the packed bed heat exchanger with multiple spherical capsules filled with the storage medium and positioned in a vertical array inside a cylindrical container is analyzed and numerically solved. The influence of the inlet mass flow rate, inner shell surface emissivity and PCM attenuation coefficient on the melting dynamics of the PCM has been analyzed and quantified.
282

An analysis of late-developing learning and memory systems in rats: fear-potentiated startle and context-specific latent inhibition and extinction

Yap, Carol Sue Lynn, Psychology, Faculty of Science, UNSW January 2006 (has links)
Eleven experiments examined two late-developing learning and memory systems in rats: fear-potentiated startle (FPS) and the contextual regulation of latent inhibition and extinction. The first study was based on three previous developmental findings on FPS: (1) FPS to an odour CS emerges at postnatal day (PN) 23; Rats conditioned at PN16 to an odour CS express freezing but not FPS when tested at PN23, and (3) FPS to an odour CS trained at PN16 is activated if rats are also trained to a difference odour at PN23 (Yap, Stapinski, & Richardson, 2005). Yap et al. (2005) hypothesised that the activation effect only occurs if rats are given training to the second odour at an age when FPS has emerged. Study 1 assessed this hypothesis and trained the second odour CS at either PN23 or PN20. Contrary to expectations, the results of this study showed the activation effect for both groups of rats. Surprisingly, the results also revealed a significant FPS effect to the odour CS trained at PN20. Subsequent experiments examined this unexpected result, and found that learning to odour 1 at PN16 facilitated the age of onset for FPS at PN20. The results of Study 1 are discussed in relation to past findings on enrichment, cumulative learning, and neurobiological models of conditioned fear. The second section of this thesis (Studies 2 and 3) examined the context-specificity of two memory interference paradigms, latent inhibition and extinction, in developing rats. The studies found that both phenomena were context-specific at PN23-25 but not at PN16-18. Moreover, the results suggest that the context-specificity of both latent inhibition depended on the age of the rat during the second phase of training, but not their age during the first phase of training or their age at test. The implications of these findings for theoretical and neural models of learning, as well as the occurrence of latent inhibition and extinction during development are discussed.
283

潛在群體分析與對應分析關係之探討

林錦鈺 Unknown Date (has links)
潛在群體分析及對應分析是在探討多個類別變數間關係常用的兩種分析方法,因其運用之領域不同,解說之方式不一,以致過去常被認為是兩種不相關的分析方法,然而實際卻非如此。本研究之目的係就雙變數及多變數的情況,針對這兩種分析方法間之關係作詳細的探討,並說明其對等及不對等的時機。 / Latent class analysis and correspondence analysis are two well-known methods that can be used to study the relationship between categorical variables. Since the two were developed and applied in two different fields in the past, they were never thought to be related. In this study, we examine the relationship between the two in more details. We further point out the situations where they are equivalent, and where they are not.
284

Analysis of the latency associated transcripts of Herpes simplex virus type 1 / Jane Louise Arthur.

Arthur, Jane Louise January 1994 (has links)
Bibliography: leaves 92-118. / xii, 118, [20] leaves, [12] leaves of plates : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Reports a method for the study of HSV-1 transcripts during latency. High resolution non-isotopic in situ hybridization (ISH) is used to study the intracellular location of HSV-1 latency associated transcripts (LATs) in primary sensory neurons of latently infected mice and humans. / Thesis (Ph.D.)--University of Adelaide, Dept. of Microbiology and Immunology, 1995?
285

Mesures de champs et identification de modèles de plasticité cristalline

Gérard, Céline 25 April 2008 (has links) (PDF)
L'identification des lois de comportement multi-échelles des matériaux polycristallins est étudiée. Une méthode couplant calculs par léments finis et modèles en champs moyens est développée. La description des interactions entre systèmes de glissement est améliorée par confrontation des réponses expérimentales et issues de la simulation du comportement d'un cuivre OFHC, sous chargements complexes.<br />La localisation de la déformation est analysée grâce à des mesures de champs réalisées, sous microscope électronique à balayage. Une microstructure synthétique tridimensionnelle représentative est développée à partir des cartographies EBSD.<br />Par ailleurs, on effectue la confrontation, sur microstructure périodique, entre plusieurs modèles en champs moyens et les simulations par éléments finis, à l'échelle des états moyens par phase. Le volume élémentaire représentatif est défini aux échelles globales et locales.
286

Bayesian Regression Inference Using a Normal Mixture Model

Maldonado, Hernan 08 August 2012 (has links)
In this thesis we develop a two component mixture model to perform a Bayesian regression. We implement our model computationally using the Gibbs sampler algorithm and apply it to a dataset of differences in time measurement between two clocks. The dataset has ``good" time measurements and ``bad" time measurements that were associated with the two components of our mixture model. From our theoretical work we show that latent variables are a useful tool to implement our Bayesian normal mixture model with two components. After applying our model to the data we found that the model reasonably assigned probabilities of occurrence to the two states of the phenomenon of study; it also identified two processes with the same slope, different intercepts and different variances. / McAnulty College and Graduate School of Liberal Arts; / Computational Mathematics / MS; / Thesis;
287

Data augmentation for latent variables in marketing

Kao, Ling-Jing, January 2006 (has links)
Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 215-219).
288

Model Specification Searches in Latent Growth Modeling: A Monte Carlo Study

Kim, Min Jung 2012 May 1900 (has links)
This dissertation investigated the optimal strategy for the model specification search in the latent growth modeling. Although developing an initial model based on the theory from prior research is favored, sometimes researchers may need to specify the starting model in the absence of theory. In this simulation study, the effectiveness of the start models in searching for the true population model was examined. The four possible start models adopted in this study were: the simplest mean and covariance structure model, the simplest mean and the most complex covariance structure model, the most complex mean and the simplest covariance structure model, and the most complex mean and covariance structure model. Six model selection criteria were used to determine the recovery of the true model: Likelihood ratio test (LRT), DeltaCFI, DeltaRMSEA, DeltaSRMR, DeltaAIC, and DeltaBIC. The results showed that specifying the most complex covariance structure (UN) with the most complex mean structure recovered the true mean trajectory most successfully with the average hit rate above 90% using the DeltaCFI, DeltaBIC, DeltaAIC, and DeltaSRMR. In searching for the true covariance structure, LRT, DeltaCFI, DeltaAIC, and DeltaBIC performed successfully regardless of the searching method with different start models.
289

Correcting for CBC model bias. A hybrid scanner data - conjoint model.

Natter, Martin, Feurstein, Markus January 2001 (has links) (PDF)
Choice-Based Conjoint (CBC) models are often used for pricing decisions, especially when scanner data models cannot be applied. Up to date, it is unclear how Choice-Based Conjoint (CBC) models perform in terms of forecasting real-world shop data. In this contribution, we measure the performance of a Latent Class CBC model not by means of an experimental hold-out sample but via aggregate scanner data. We find that the CBC model does not accurately predict real-world market shares, thus leading to wrong pricing decisions. In order to improve its forecasting performance, we propose a correction scheme based on scanner data. Our empirical analysis shows that the hybrid method improves the performance measures considerably. (author's abstract) / Series: Report Series SFB "Adaptive Information Systems and Modelling in Economics and Management Science"
290

Semantic represenations of retrieved memory information depend on cue-modality

Karlsson, Kristina January 2011 (has links)
The semantic content (i.e., meaning of words) is the essence of retrieved autobiographical memories. In comparison to previous research, which has mainly focused on phenomenological experiences and age distribution of memory events, the present study provides a novel view on the retrieval of event information by addressing the semantic representation of memories. In the present study the semantic representation (i.e., word locations represented by vectors in a high dimensional space) of retrieved memory information were investigated, by analyzing the data with an automatic statistical algorithm. The experiment comprised a cued recall task, where participants were presented with unimodal (i.e., one sense modality) or multimodal (i.e., three sense modalities in conjunction) retrieval cues and asked to recall autobiographical memories. The memories were verbally narrated, recorded and transcribed to text. The semantic content of the memory narrations was analyzed with a semantic representation generated by latent semantic analysis (LSA). The results indicated that the semantic representation of visually evoked memories were most similar to the multimodally evoked memories, followed by auditorily and olfactorily evoked memories. By categorizing the semantic content into clusters, the present study also identified unique characteristics in the memory content across modalities.

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