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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.
11

Performance of Hybrid LMS Control Algorithm for Smart Antennas

Dauga, Salah 04 October 2022 (has links)
No description available.
12

Apport de la chimiométrie et des plans d’expériences pour l’évaluation de la qualité de l’huile d’olive au cours de différents processus de vieillissement / Contribution of chemometrics and experimental designs for evaluating the quality of olive oil during different aging process

Plard, Jérôme 17 January 2014 (has links)
L'huile d'olive est un élément important de l'alimentation méditerranéenne. Cependant lorsqu'une huile vieillit, elle se dégrade et perd ses propriétés. Il est donc important de connaitre l'évolution de la composition de l'huile en fonction de ses conditions de stockage et de fabrication. Ce suivi a été effectué sur deux huiles de fabrication différente, une huile fruité vert et une huile fruité noir, obtenue à partir d'olive à maturité que l'on a laissé fermenter quelques jours. De manière à obtenir rapidement des vieillissements poussés, ces deux huiles ont été vieillies artificiellement, par procédé thermique , et par procédé photochimique. Ces vieillissements ont été réalisés sur des volumes différents de manière à déterminer l'impact du rapport surface/masse. En parallèle, des échantillons de chacune des deux huiles ont été conservés durant 24 mois dans des conditions de stockage différentes déterminées à l'aide d'un plan d'expériences. Les paramètres influençant le plus la conservation de l'huile d'olive sont l'apport en oxygène, la luminosité et la température. Ces influences ont été déterminées à partir du suivi des principaux paramètres de qualité La réponse des plans a permis de mettre en évidence des interactions entre ces différents paramètres. L'analyse de la composition de l'huile ainsi que de tous les critères de qualité demande beaucoup de temps et consomme une grande quantité de solvant. Afin de pallier à ces désagréments, les résultats ont également été utilisés pour construire des modèles chimiométriques permettant de déterminer ces grandeurs à partir des spectres proche et moyen infrarouge des échantillons. / Olive oil is an important component of the Mediterranean diet. When oil ages, it deteriorates and loses its properties. It is therefore important to know the evolution of the oil composition according to the conditions of storage and manufacturing. This monitoring was carried out on two different oils manufacturing, green fruity oil obtained from olives harvested before maturity, and black fruit oil obtained from olives harvest at maturity and fermented for few days under controlled conditions. To obtain quickly pushed aging, these two oils were artificially aged by heat process (heated to 180 °C under supply of O2), and photochemical process (under an UV lamp and under supply of O2). These aging were performed on different volumes to determine the impact of surface/weight ratio. In parallel, samples of both oils were stored for 24 months under different storage conditions determined using an experimental design. The parameters affecting the most the conservation of olive oil are oxygen, light and temperature. These influences were determined from the monitoring of key quality criteria. Response of experimental design helped to highlight the interactions between these different parameters. The analysis of the oil composition as well as all the quality criteria requires a large amount of solvents and a lot of time consumer. To overcome these inconveniences, chemometric models has been built to determine these criteria from the near and mid-infrared spectra of samples. Natural aging is very little advanced in comparison to accelerated aging, so predictive models were established from the results of natural aging and accelerated separately.
13

Inversion of Nonlinear Dispersive Wave and its Application in Determining Tsunami Wave Soure

Li, Lieh-Yu 13 April 2011 (has links)
In this study, the method of deciding the water level of the initial tsunami is proposed by using spatial-temporal focusing (Coalescence) theory and waveform inversion reciprocal with Green function. Tsunami and earthquake are so closely bonded that the current tsunami numerical model is dependent on the parameters of the fault and the initial tsunami water level by calculating the theory of half flexibility. But in fact, it is not easy to have the parameters of seabed fault so that the initial tsunami water level is very hard to get a accurate value. On the other hand, although the parameters of fault can be speculated by seismic waves, because ground is uneven medium, therefore, it is still a lot of improvement to get the parameters of fault by using seismic waves. For the tsunami simulation, if you have the value of the initial tsunami water level, the fault parameters can be estimated.Since the propagation of tsunami in the ocean is a linear behavior, the propagating process is affected by the topography of the ocean and the nonlinear effect so minimal that it is to satisfy the linear shallow water equations and the requirement of reversibility;However, in fact, the values of the water level measured by the tide stations on the coast are influenced by the shoaling effect so that the reversibility of linear system can not be directly applied to Coastal areas.Therefore, the overall Inversion procedure on this study consists of two parts; the first one is that the usage of variable coefficient Korteweg-de Vries (vKdV) equation and the Coalescence theory inverses the data gathered by the Coastal tide stations to the water level data where the depth is more than 50m on the linear region, and compares the above results with the stimulation and confirms the accuracy of the inversed waveform;The second one is that according to the reversibility of the linear system the use of least squares and least squares QR- decomposition (LSQR) method reproduce the initial tsunami wave source that compares with the initial tsunami wave source by stimulating and has a very good conformity. The seismic parameters can be easily decided by the above results.
14

Les relations entre l'innovation et la performance internationale pour les activités de service aux entreprises

Castro-Lucas de Souza, Cristina 28 November 2011 (has links)
Cette recherche vise à comprendre la relation existante entre l’innovation de services et l’internationalisation, à savoir, comment les entreprises obtiennent des avantages compétitifs sur les marchés internationaux grâce à l'innovation dans le secteur des services aux entreprises.Nous avons testé la relation entre l'innovation et la performance internationale, avons évalué l'impact de l'innovation par rapport à d'autres avantages internationaux. Symétriquement, nous avons également vérifié dans quelle mesure le processus d'internationalisation peut être un puissant moteur d'innovation pour les entreprises de services. Après le développement d'un modèle théorique, nous avons procédé à une enquête téléphonique auprès de 807 entreprises de services exportatrices. Les répondants cible de l'enquête étaient des cadres supérieurs de sociétés de services internationalisés en France. 51 réponses exploitables ont été reçues. Les données recueillies ont été analysées par Modélisation des Équations Structurelles (SEM), en utilisant la méthode Partial Least Square. Le modèle testé montre que l'innovation de service a une influence positive sur le développement international et que la compétence internationale, obtenue sur les marchés étrangers, stimule la dynamique de l'innovation dans les entreprises de services. Le modèle proposé met en évidence les capacités de R & D (organisationnelle), relationnelles, les TIC, la compétence internationale, l’innovation de service et l’expérience internationale comme facteurs qui influent les résultats des entreprises internationalisées, ou plus précisément, la performance international. / This research deals with service innovation and internationalization: how firms perform on international markets and get an edge thanks to innovation on service concept or service process. We tested the relationship between innovation and international performance, assessed the impact of innovation compared to other international advantages. Symmetrically, we also checked how far the internationalization process can be a powerful driver of innovation for service firms. After the development of a theoretical model, data were collected from a telephone survey. The target respondents of the survey were senior executives of internationalized service companies in France. Out of the 807 companies which were contacted, 51 usable responses were received. The data collected were analyzed by Structural Equation Modeling (SEM), using the Partial Least Square method. The tested model shows that service innovation has a positive influence on international development and that the international competence, obtained in foreign markets, drives the dynamics of innovation in services company. The model proposed highlights the capabilities for R & D (organizational), relational, ICT, international competence, service and international experience as factors that impact the final results of internationalized companies, or more specifically, the international performance.
15

Robust mixtures of regression models

Bai, Xiuqin January 1900 (has links)
Doctor of Philosophy / Department of Statistics / Kun Chen and Weixin Yao / This proposal contains two projects that are related to robust mixture models. In the robust project, we propose a new robust mixture of regression models (Bai et al., 2012). The existing methods for tting mixture regression models assume a normal distribution for error and then estimate the regression param- eters by the maximum likelihood estimate (MLE). In this project, we demonstrate that the MLE, like the least squares estimate, is sensitive to outliers and heavy-tailed error distributions. We propose a robust estimation procedure and an EM-type algorithm to estimate the mixture regression models. Using a Monte Carlo simulation study, we demonstrate that the proposed new estimation method is robust and works much better than the MLE when there are outliers or the error distribution has heavy tails. In addition, the proposed robust method works comparably to the MLE when there are no outliers and the error is normal. In the second project, we propose a new robust mixture of linear mixed-effects models. The traditional mixture model with multiple linear mixed effects, assuming Gaussian distribution for random and error parts, is sensitive to outliers. We will propose a mixture of multiple linear mixed t-distributions to robustify the estimation procedure. An EM algorithm is provided to and the MLE under the assumption of t- distributions for error terms and random mixed effects. Furthermore, we propose to adaptively choose the degrees of freedom for the t-distribution using profile likelihood. In the simulation study, we demonstrate that our proposed model works comparably to the traditional estimation method when there are no outliers and the errors and random mixed effects are normally distributed, but works much better if there are outliers or the distributions of the errors and random mixed effects have heavy tails.
16

台灣地區基金績效持續性之影響因素分析 / The Determining Factors of Mutual Fund’s Performance Persistence in Taiwan

黃鴻鈞 Unknown Date (has links)
共同基金是由投資信託公司向大眾募集資金,再轉投資到股票、債券、不動產等標的上,最後再分配投資收益的的一種工具。從自有共同基金開始至今已超越百年,而台灣地區方面,目前也是全民理財不可或缺的一項標的。 共同基金雖號稱是懶人投資,不用花費大量心思。但實際上,天下沒有白吃的午餐,投資人仍需投注精力了解趨勢,並從中挑選適當的標的。但儘管有許多理財專家提出經驗談,就一般投資大眾而言,如何挑選共同基金仍是具有挑戰性的工作。  為協助投資人以現有資訊,找出適當的投資標的,因此利用投信公會公布的資料,將基金依照Jensen值進行區分為大於零及小於零兩個群組,再以最小平方法探討兩個群組中,影響各種類型基金績效持續性的因素,以期能利用簡單的資訊,找出值得長期投資的標的。
17

ADVERTISING EFFECTIVENESS ON INTERNATIONAL TOURISM DEMAND IN ÅRE – AN ECONOMETRIC ANALYSIS

Kronenberg, Kai January 2013 (has links)
The objective of this study is to estimate advertising effects on international tourismdemand for the leading Swedish winter destination, Åre. The increasing share of foreigninbound tourists in this destination region creates a strong interest by shareholders toidentify the factors responsible for this trend. According to traditional micro-economictheory, economic factors, such as income and price, are considered as main determinantsfor tourism demand (Song and Witt 2000). However, according to advertising theories(Comanor and Wilson, 1974) and previous tourism research (Bhagwat and Debruine, 2008;Divisekera and Kulendran, 2006), this study additionally focuses on the brand awarenessof Åre as perceived by international tourists. More concretely, advertising theoriesdistinguish between the brand and the information function of advertising (Nelson, 1974).The former function follows the idea that advertising increases the level of productdifferentiation to build up a base of loyal customers. By contrast, the information functionimplies that advertising primarily provides information about products in order to increasethe market transparency. Accordingly, in order to estimate the impact of advertisingexpenditures for off- and online channels as well as promotional activities, furtherexplanatory variables, e.g. mega events, are considered in this study (Salman, 2003; Songet al., 2010). By applying ordinary least square (OLS) methods, demand elasticitycoefficients are estimated for each of the sending countries Norway, Finland, Russia,Denmark and the UK. Results show that advertising is the main significant driver oftourism demand from the UK, Russia and Finland, while a comparably weak advertisingleverage can be shown for Denmark and Norway. Interestingly, in contrast to microeconomictheories tested in previous research, income and tourism price levels reveal asbeing less significant drivers for demand in all analysed tourism markets. In turn, theresults provide evidence that the increased usage of online channels most significantlyaffects consumers’ buying behaviour. Finally, with respect to brand image perception,results reveal that the destination of Åre is perceived as a brand by tourists from Denmark.Moreover, for customers from the countries Norway and Finland, Åre indicates a weakbrand perception, while tourists from Russia and the UK don’t perceive Åre as a brand atall. The results gained by this research conducted at the level of the tourism destinationprovide useful hints about the factors influencing travel behaviour of tourists from maininternational markets. The study supports destination managers to appropriately adjustmarketing campaigns according to the predominant level of brand perception in respectivesending countries. / KK-Foundation project ‘Engineering the Knowledge Destination’ (no. 20100260; Stockholm, Sweden).
18

[en] RECONSTRUTION OF GEOMETRY BASED IN CONNECTIVITY AND MESH SAMPLES / [pt] RECONSTRUÇÃO DE GEOMETRIA A PARTIR DA CONECTIVIDADE DA MALHA E DE PONTOS DE CONTROLE

CATIUSCIA ALBUQUERQUE BENEVENTE BORGES 31 August 2007 (has links)
[pt] Este trabalho busca reconstruir a geometria de uma malha partindo de sua conectividade e de um conjunto esparso de pontos com geometria conhecida, denominados pontos de controle. O problema é formulado como a maximização da suavidade da superfície fixando a posição dos pontos de controle. Nessa formulação, o método consiste em resolver um sistema linear esparso aplicando-se mínimos quadrados. Diferentes propostas para a seleção de pontos de controle, o método de minimização e a construção do sistema linear são apresentadas e comparadas. / [en] This work aims at reconstructing the geometry of a mesh from its connectivity and a small set of control points, whose geometry is known.The problem is formulated as a maximization of the surface smoothness restricting the position of the control points. With this formulation, the method reduces to solving a sparse linear system using least squares minimization. Several proposals for the selection of the control points, the minimization method and the linear system construction are presented and compared .
19

An Improved Meta-analysis for Analyzing Cylindrical-type Time Series Data with Applications to Forecasting Problem in Environmental Study

Wang, Shuo 27 April 2015 (has links)
This thesis provides a case study on how the wind direction plays an important role in the amount of rainfall, in the village of Somi$acute{o}$. The primary goal is to illustrate how a meta-analysis, together with circular data analytic methods, helps in analyzing certain environmental issues. The existing GLS meta-analysis combines the merits of usual meta-analysis that yields a better precision and also accounts for covariance among coefficients. But, it is quite limited since information about the covariance among coefficients is not utilized. Hence, in my proposed meta-analysis, I take the correlations between adjacent studies into account when employing the GLS meta-analysis. Besides, I also fit a time series linear-circular regression as a comparable model. By comparing the confidence intervals of parameter estimates, covariance matrix, AIC, BIC and p-values, I discuss an improvement on the GLS meta analysis model in its application to forecasting problem in Environmental study.
20

Essays on semi-parametric Bayesian econometric methods

Wu, Ruochen January 2019 (has links)
This dissertation consists of three chapters on semi-parametric Bayesian Econometric methods. Chapter 1 applies a semi-parametric method to demand systems, and compares the abilities to recover the true elasticities of different approaches to linearly estimating the widely used Almost Ideal demand model, by either iteration or approximation. Chapter 2 co-authored with Dr. Melvyn Weeks introduces a new semi-parametric Bayesian Generalized Least Square estimator, which employs the Dirichlet Process prior to cope with potential heterogeneity in the error distributions. Two methods are discussed as special cases of the GLS estimator, the Seemingly Unrelated Regression for equation systems, and the Random Effects Model for panel data, which can be applied to many fields such as the demand analysis in Chapter 1. Chapter 3 focuses on the subset selection for the efficiencies of firms, which addresses the influence of heterogeneity in the distributions of efficiencies on subset selections by applying the semi-parametric Bayesian Random Effects Model introduced in Chapter 2.

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