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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.
71

Avalia??o de m?todos de an?lises para determina??o da contagem de c?lulas som?ticas no leite cru, mantido em tanque de resfriamento / Evaluation of methods of analysis to determine the somatic cell count in raw milk, kept in the cooling tank

Pereira Neto, Manoel 27 June 2012 (has links)
Made available in DSpace on 2014-12-17T15:34:44Z (GMT). No. of bitstreams: 1 ManoelPN_DISSERT.pdf: 1337463 bytes, checksum: aaed50bece00427adf0672e0a99b898a (MD5) Previous issue date: 2012-06-27 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / We analyzed the quality of raw milk from eight dairy farms in Rio Grande do Norte stored in a cooling tank , in order to evaluate methods for determining somatic cell counts (SCC). The Somaticell? kit and a portable Direct Cell Counter (DCC) were compared with each other and with the MilkoScanTM FT+ (FOSS Denmark), which uses Fourier Transform Infrared (FTIR) spectroscopy). Direct cell counter data were processed for somatic cell scores (log-transformed somatic cell count) and analyzed with the SAS?, statistical package , Statistical Analysis System, (SAS, INSTITUTE, 1998). Comparison of means and correlation of somatic cell scores were conducted using Pearson s correlation coefficient and the Tukey Test at 1 %. No significant difference was observed for comparison of means. The correlation between somatic cell scores was significant, that is, 0.907 and 0.876 between the MilkoScanTM FT+ and the Somaticell? kit and Direct Cell Count (DCC) respectively, and 0.943 between the Somaticell? kit and Direct Cell Count (DCC). The methods can be recommended for monitoring the quality of raw milk kept in a cooling tank in the production unit / A qualidade do leite cru mantido em tanque de resfriamento de oito propriedades do Rio Grande do Norte foi analisada, com o objetivo de avaliar m?todos para determina??o da contagem de c?lulas som?ticas (CCS). Foram usados o kit Somaticell? e o equipamento port?til Direct Cell Counter (DCC), sendo comparados entre si e com o MilkoScanTM FT+ (FOSS Denmark) que usa a metodologia do Infravermelho com Transformada de Fourier (IVTF). Os dados de CCS foram transformados para escore de c?lulas som?ticas ECS log (CCS) e analisados pelo pacote estat?stico SAS? Statical Analisys System, (SAS, INSTITUTE, 1998). Foram feitas a compara??o das m?dias e a correla??o dos escores de c?lulas som?ticas por meio do coeficiente de correla??o de Pearson, sendo aplicado o Teste de Tukey a 1%. N?o foi observada diferen?a significativa para a compara??o das m?dias. A correla??o entre os escores de c?lulas som?ticas foi significativa, sendo de 0,907 e 0,876 entre o MilkoScanTM FT+ e o kit Somaticell? e o Direct Cell Count (DCC) respectivamente, e de 0,943 entre o kit Somaticell? e o Direct Cell Count (DCC). Os m?todos avaliados podem ser recomendados para o monitoramento da qualidade do leite cru refrigerado mantido em tanque de resfriamento em n?vel de unidade produtiva
72

Caractérisation de SER Basse Fréquence et Modes Caractéristiques / Low Frequency RCS Measurement and Characteristic Modes

Cognault, Aurore 28 April 2009 (has links)
La SER, est la grandeur qui permet de quantifier le pouvoir réflecteur d'un objet, ou a contrario sa discrétion électromagnétique. Maîtriser la SER, voire la diminuer, est un enjeu majeur dans le domaine aéronautique de défense. C'est en particulier un gage de survivabilité pour les aéronefs. Historiquement, les fréquences RADAR d'intérêt étaient celles de la bande Super Haute Fréquence, ce qui équivaut à des longueurs d'onde de 2 à 30 centimètres. Des outils d'analyse adaptés ainsi que des moyens de mesure ou de caractérisation de la SER ont été mis au point. Ils se sont révélés extrêmement performants. On peut citer par exemple la chambre anéchoïque CAMELIA du CESTA. En revanche, dans le domaine des basses fréquences, il est plus délicat de réaliser des mesures précises. Pour des longueurs d'onde de 1 à 5 mètres, l'épaisseur des absorbants est souvent trop faible ; même les dimensions des chambres anéchoïques ne représentent que quelques longueurs d'onde. Notre objectif, lors de cette thèse, était de proposer et d'étudier des algorithmes nouveaux permettant d'améliorer ou de faciliter la caractérisation de la SER en basse fréquence. La notion de courants caractéristiques, introduite par Harrington et Mautz dans les années 70, puis reprise par Y. Morel dans le cas d'objets parfaitement conducteurs, permet la décomposition d'un courant induit quelconque en courants élémentaires. Les modes caractéristiques sont obtenus en faisant rayonner ces courants caractéristiques. Cependant, il n'existe pas d'outil de détermination des modes lorsque l'objet n'est plus parfaitement conducteur. Nous nous sommes donc dotés d'un tel outil, que nous avons construit et validé. Pour cela, nous avons repris dans un premier temps le cadre mathématique qui permet de définir l'opérateur de Perturbation, ses propriétés mathématiques et sa décomposition en éléments propres. Nous avons montré que cet opérateur discrétisé conserve ses propriétés mathématiques. Nous avons ensuite validé notre méthode de calcul direct des modes caractéristiques, issus de la diagonalisation de l'opérateur de perturbation discrétisé. Dans un deuxième temps, nous avons mené des études phénoménologiques. Nous avons tout d'abord observé l'évolution des éléments propres de l'opérateur de perturbation en fonction de l'impédance, et nous nous sommes intéressés au cas particulier de l'impédance égale à 1. Nous avons ensuite observé les phénomènes lorsque la fréquence évolue. En nous concentrant sur les valeurs propres, nous avons pu différencier deux types de modes. Enfin, nous avons détaillé quelques exemples d'applications concrètes de cette méthode de détermination des modes, qui permettent d'améliorer ou de faciliter la caractérisation de la SER en basse fréquence. L'outil ORFE (Outil de Reformulation, Filtrage et Extrapolation de données) permet d'atténuer les termes d'erreurs inhérents à toute caractérisation, et d'extrapoler des données existantes à des cas de figure non acquis ou non accessibles en mesure. Il a donné lieu à un brevet. Un outil d'interpolation de SER en basse fréquence a aussi été construit. Il permet d'obtenir de meilleurs résultats que l'interpolation linéaire de la SER. Nous avons aussi mis en place une méthode d'imagerie basse fréquence. Elle permet de localiser d'éventuels défauts de métallisation de l'objet considéré, en utilisant la base des courants caractéristiques. Enfin, nous avons présenté une méthodologie de caractérisation de SER qui intègre les limites des moyens de mesure. Nous avons mis en évidence que cette caractérisation donne une information absolue sur la SER de l'objet, dans un périmètre de validité. Un brevet a été déposé sur cette méthode. / This work focuses on RADAR Cross Section (RCS) measurements in the low frequency domain. Radar Cross Section (RCS) is a description of how an object reflects an incident electromagnetic wave. Quantitatively, RCS is the effective surface area that intercepts the incident wave and isotropically scatters the energy. Controlling RCS is a real challenge for aeronautic defence. In the past, RCS interest frequencies used to be in the Super High Frequency domain (wavelengths between 2 and 30 centimetres). RCS is mastered in this frequency domain, due to the use of bright point model and large anechoic chamber. On the other hand, RCS measurements cannot be entirely and accurately obtained in the low frequency domain because of experimental constraints. Indeed, absorbing coatings are too thin (compared to the wavelength) to be efficient, and the anechoic chamber is too small. The aim of the thesis was to suggest new algorithms that improve RCS low frequency characterization. The Characteristic Currents were first introduced by Harrington and Mautz in the early 70's and then studied by Y. Morel in his PhD thesis. This work highlights that the current of any Perfectly Electrically Conducting (PEC) object can be split into elementary currents. The characteristic modes are obtained by radiating the characteristic currents. However, there is no tool to determine the characteristic modes for non PEC object. In this thesis, such a tool has been built and validated. We _rst needed to set the mathematical framework. We defined the Perturbation Operator, its eigenvalues decomposition and its mathematical properties. We proved that the discrete Perturbation Operator keeps its properties. This method of modes determination has then been validated. We then presented two phenomenology studies. The first one deals with the impact of impedance on the eigenvalues and eigenvectors of the perturbation operator. We get particularly interested in the case of the impedance equal to 1. The second focuses on the impact of frequency, which led us to distinguish two kinds of modes. When finally listed some concrete applications of our method of modes determination, that led to improve RCS characterizations. The first tool named ORFE (it stands for Reformulation, Filtering and Extrapolation Tool), consists in reducing errors that are inherent in RCS measurements, and extrapolating data out of measurement range. This tool has been patented. A RCS frequency interpolation algorithm has also been built. We then implemented a low frequency imagery method. It consists in localizing some perturbation of metallization, by using the characteristic current basis. We finally presented a way to characterize RCS while taking low frequency experimental constraints into account. We show that this characterization gives information of the RCS of the object in a validity perimeter. This method has been patented too.
73

Dynamic covalent surfactants for the controlled release of bioactive volatiles / Tensio-actifs covalents dynamiques pour le relargage contrôlé de composés bio-actifs volatiles

Lutz, Eric 15 October 2014 (has links)
Ce projet consiste à fabriquer et à étudier des micelles à la fois biocompatibles et capables de relarguer des molécules volatiles bioactives à partir d’une solution aqueuse sous l’influence de stimuli extérieurs tel que le pH, la température ou la concentration. Pour atteindre ce but, nous avons étudiés un nouveau type d’objets micellaires qui sont formés par l’auto-assemblage d’amphiphiles covalents dynamiques (DCAs), des surfactants peu onéreux formés de l’association moléculaire réversible d’un bloc hydrophile et d’un bloc hydrophobe. Ces systèmes peuvent relarger une large gamme de fragrances à partir d’une solution, que cela soit à partir du coeur hydrophobe de la micelle ou alors à partir de l’amphiphile (profragrance). Ils ont aussi été capables de stabiliser en solution des aldéhydes sensibles à l’hydrolyse. / This project relies on the simple design and the study of biocompatible responsive micelles, capable of releasing a hydrophobic bioactive volatile from an aqueous solution and that, depending on the modulation of external factors such as pH, temperature, and concentration. To reach this goal, we have taken advantages of a new kind of micellar objects that are formed by the efficient self-assembly of biodegradable Dynamic Covalent Amphiphiles (DCAs), low cost surfactants that are made by the reversible molecular association of one hydrophilic and one hydrophobic block. These systems can release a broad variety of fragrances from solution, both from the hydrophobic micellar core or directly from the amphiphile (profragrance). It also proved able to stabilise some sensitive aldehydes in solution.
74

Garantované investiční fondy / Capital protected funds

Houdek, Ondřej January 2012 (has links)
This thesis is mainly focused on pricing securities of selected capital protected funds. In its theoretical part, there are summarized approaches and principals that are generally used for derivatives pricing because capital protected funds' securities contain embedded options. Emphasis is put on risk-neutral pricing using Monte Carlo simulation at that point because complicated pay-off functions of these funds are hard to be evaluated analytically. There are also presented main approaches to constructions and portfolio management of these funds from their portfolio manager's viewpoint. Finally, there is made an overview of basic types of capital protected funds issued both in The Czech republic and Europe. Analytical part is focused on evaluation of selected capital protected funds. There is applied a standard approach that is based on a simulation of Geometric Brownian Motion with constant conditional variance and correlation in contrast with an advanced approach where the conditional variance and conditional correlation matrix are simulated as well. That is accomplished with GARCH-in-mean and DCC-GARCH models. Estimated prices are compared with real market prices and there is also performance of the standard models compared with performance of advanced ones.
75

Tux fährt Bahn

Sontag, Ralph 12 November 2007 (has links)
Modelleisenbahnen können Kinderspielzeug oder anspruchsvolles Hobby sein. Heute fahren viele Bahnen digital und werden mittels Digital Command Control (DCC) gesteuert. Im Vortrag sollen die Grundlagen des Protokolls erläutert und die Grundfunktionen mittels des Decoder Programmers SPROG II unter Linux ausprobiert werden.
76

An investigation of Sustainable Assets, Equitiesand the Bond market during the Globalpandemic, COVID-19

Rahm, Vincent, de la Rosa, Frej January 2022 (has links)
ESG investing has been a hot topic during several years and there have been numerousstudies examining the relationship between sustainable assets and non-sustainable assetsincluding green bonds, social bonds, environmental bonds, ESG-bonds and ESG indices;conventional bonds, S&P 500, common stocks and non-ESG indices. During negative marketshocks several ESG stocks and indices have been shown to outperform common stocks andindices. Green bonds demonstrated an asymmetric relationship to other assets providinginvestors with an opportunity for diversification. We’ve looked at the relationship andperformance of sustainable assets and non-sustainable assets by using Markowitz portfoliometrics and Engle Rs’ DCC-GARCH. Our findings propose green bonds and treasuries toprovide hedging and diversification opportunities during crises but demonstrate sustainablefixed income assets to underperform non-sustainable fixed income assets during the COVID19 market shock as opposed to previous studies.
77

Swedish Equity Sectors Risk Management with Commodities : Revisiting dynamic conditional correlations and hedge ratios

Engström, Daniel, Gustafsson, Niklas January 2017 (has links)
The purpose of this study is to investigate changes in dynamic conditional correlations between Swedish equity sector indices and commodities using oil, gold, copper and a general commodity index. Additionally the purpose is to evaluate which of the two methods, DCC- GARCH or GO-GARCH that is more efficient in estimating correlation for hedge ratio calculation. Daily data on the FTSE30 index of Sweden and its sector indices have been studied between the years 1994 and 2017. A DCC-GARCH (1,1) and GO-GARCH (1,1) model with one autoregressive term AR(1) using multivariate Student t- and Multivariate Affine Negative Inverse Gaussian distribution were used to estimate conditional correlations. Correlations between Swedish FTSE30, its sector indices and commodities are considerably lower than previous research has found American or emerging markets correlation with commodities to be. This suggests better diversification opportunities with commodities for the Swedish market. Optimal hedge ratios (OHR) was calculated and back tested using a rolling window analysis with 1000 days forecast length and 20 days re-estimation window and evaluated using a calculated hedge effectiveness index (HE). Determined by HE, copper is the best hedge for the Swedish composite FTSE30 and sector indices using conditional correlation from the GO-GARCH during the data period. Gold is considered as a semi-strong safe haven due to its negative correlation with all sectors. Additionally, this study identifies a temporarily large increase in the correlation between the Swedish equities sectors and composite index with commodities around the years 2015/2016. This study also emphasizes the difference between stressful and calm periods in the market.
78

Interactions interhémisphériques dans le contrôle du mouvement unilatéral

Beaulé-Bulman, Vincent 02 1900 (has links)
L’exécution d’un mouvement purement unilatéral nécessite le recrutement d’un vaste réseau de régions corticales et sous-corticales, qu’il est possible de regrouper sous le terme de réseau de transformation non-miroir. Ce réseau doit contrer la tendance naturelle du cerveau à exécuter des mouvements de manière bilatérale et synchronisée, en miroir. Malgré l’efficacité de ce réseau, une activité miroir subtile est observée au niveau de la main qui doit demeurer inactive lors de mouvements unilatéraux chez l'humain en santé. Ce débordement moteur doit être inhibé grâce aux interactions interhémisphériques transitant par le corps calleux (CC), la plus grande commissure du cerveau servant de pont entre les hémisphères. Ainsi, la commande motrice peut être acheminée efficacement du cortex moteur primaire (M1) controlatéral à la main devant exécuter une l’action par l’entremise de la voie corticospianle (VCS). En plus du CC, le cortex prémoteur (CPM) joue un rôle important dans ce réseau puisque son interférence via la stimulation magnétique transcrânienne (SMT) entraîne une augmentation de l’activité miroir dans la main devant normalement demeurer inactive lors d’un mouvement unilatéral. Ainsi, toute modification dans ce réseau ou dans les processus interhémisphériques peut provoquer l’augmentation des mouvements miroirs (MM). À ce jour, aucune étude n’a tenté de moduler ces interactions pour réduire la présence de MM. Ainsi, les études cliniques et méthodologiques qui composent la présente thèse comportent deux objectifs principaux : (1) déterminer si la stimulation électrique transcrânienne à courant direct (SÉTcd) permet l'étude du réseau de transformation non-miroir, et si cette technique est en mesure de diminuer l’intensité des MM chez des individus en santé; (2) caractériser l'anatomie et le fonctionnement du cerveau dans deux populations d’individus porteurs de mutations génétiques affectant le développement de structures impliquées dans la latéralisation du mouvement, le CC et la VCS. L’article 1 décrit les assisses théoriques de la présente thèse grâce à une revue de la littérature portant sur les interactions interhémisphériques dans le mouvement unilatéral. L’article 2 suggère que la SÉTcd est un outil efficace dans l'étude du réseau de transformation non-miroir puisque le protocole de stimulation bilatérale a permis d’augmenter la présence et l’intensité des MM physiologiques (MMp) chez des individus en santé. Cependant, il n’a pas été possible de moduler à la baisse les MMp malgré différents protocoles de stimulation. Dans l’article 3, l'étude d’individus nés sans CC a mis en lumière une augmentation de l’épaisseur corticale au niveau des aires somatosensorielles (S1) et visuelles (V1) primaires, de même qu’au niveau de la représentation de la main dans M1. Ces différences demeurent toutefois légères considérant l’importance du CC. L’article 4 a démontré que les individus porteurs d’une mutation sur le gène DCC présentent un phénotype similaire à celui de porteurs d'une mutation sur le gène RAD51. Ces mutations affectent la migration de la VCS au niveau des pyramides. La VCS projette ainsi aux deux mains, causant des mouvements miroirs congénitaux (MMC). Cette pathologie est également accompagnée d’anomalies neurophysiologiques, telle qu’une inhibition interhémisphérique (IIH) réduite. En somme, les études composant cette thèse ont permis d’approfondir notre connaissance de certaines structures responsables de la latéralisation adéquate du mouvement, tout en décrivant de nouvelles méthodes pour en étudier le fonctionnement. / The execution of purely unilateral hand movements requires the recruitment of vast cortical and subcortical brain areas known as the non-mirroring network. This network counteracts the natural tendency of the brain, which tends to execute movements in a bilateral and synchronized manner. Despite the efficacy of the non-mirroring network in restricting motor output to contralateral limbs, subtle mirroring can be observed in the inactive hand of healthy individuals when performing a unilateral task. This motor overflow needs to be inhibited through interhemispheric projections coursing through the corpus callosum (CC), the biggest white matter tract of the brain. This mechanism makes it possible for motor commands originating from the primary motor cortex (M1) to reach the contralateral hand performing an action via the corticospinal tract (CST). It has been suggested that the premotor cortex (PMC) is an important component of the non-mirroring network since its interference with transcranial magnetic stimulation (TMS) enhances mirror activity in the inactive, mirror hand when a unilateral hand movement is performed. Indeed, modulation of parts of the non-mirroring network and interhemispheric projections can result in enhanced mirror movements (MM). It is not known whether specific interventions can decrease MM. The clinical and methodological studies that compose the present thesis have two main objectives: (1) Determine whether transcranial direct-current stimulation (tDCS) can be used to assess non-mirroring network function and reduce MM intensity in healthy individuals; (2) Characterize brain function and anatomy in two clinical populations presenting specific genetic mutations that affect the development of structures involved in the lateralization of movement (the CC and CST). Article 1 provides a theoretical basis for the present essay through a review of the literature pertaining to interhemispheric interactions in the production of unilateral movements. Article 2 shows that tDCS can be used to study the non-mirroring network since a bilateral stimulation protocol significantly increased the intensity of physiological MM (pMM) in healthy individuals. However, despite different stimulation protocols, it was not possible to reduce pMM. In article 3, anatomical MRIs performed in individuals born without a CC revealed increases in cortical thickness in primary somatosensory (S1) and visual (V1) cortex, as well as in the hand representation of M1. Taken together, however, the data suggest that anatomical differences between acallosal patients and healthy participants are relatively subtle considering the size and function of the CC. Article 4 showed that individuals presenting a mutation on the DCC gene display a phenotype similar to that of individuals presenting a mutation on the RAD51 gene. DCC mutations affect the crossing of the CST at the pyramidal level, resulting in a CST that projects to both hands simultaneously, causing congenital mirror movements (CMM). This pathological condition is accompanied by neurophysiological anomalies that include reduced interhemispheric inhibition (IHI). In summary, the studies comprised in the present thesis significantly increase our knowledge of the specific brain structures that enable the proper lateralization of movements. It also describes novel methods that can be used to investigate the non-mirroring network.
79

Quantitative Portfolio Construction Using Stochastic Programming / Kvantitativ portföljkonstruktion med användning av stokastisk programmering : En studie inom portföljoptimering

Ashant, Aidin, Hakim, Elisabeth January 2018 (has links)
In this study within quantitative portfolio optimization, stochastic programming is investigated as an investment decision tool. This research takes the direction of scenario based Mean-Absolute Deviation and is compared with the traditional Mean-Variance model and widely used Risk Parity portfolio. Furthermore, this thesis is done in collaboration with the First Swedish National Pension Fund, AP1, and the implemented multi-asset portfolios are thus tailored to match their investment style. The models are evaluated on two different fund management levels, in order to study if the portfolio performance benefits from a more restricted feasible domain. This research concludes that stochastic programming over the investigated time period is inferior to Risk Parity, but outperforms the Mean-Variance Model. The biggest aw of the model is its poor performance during periods of market stress. However, the model showed superior results during normal market conditions. / I denna studie inom kvantitativ portföljoptimering undersöks stokastisk programmering som ett investeringsbeslutsverktyg. Denna studie tar riktningen för scenariobaserad Mean-Absolute Deviation och jämförs med den traditionella Mean-Variance-modellen samt den utbrett använda Risk Parity-portföljen. Avhandlingen görs i samarbete med Första AP-fonden, och de implementerade portföljerna, med era tillgångsslag, är därför skräddarsydda för att matcha deras investeringsstil. Modellerna utvärderas på två olika fondhanteringsnivåer för att studera om portföljens prestanda drar nytta av en mer restrektiv optimeringsmodell. Den här undersökningen visar att stokastisk programmering under undersökta tidsperioder presterar något sämre än Risk Parity, men överträffar Mean-Variance. Modellens största brist är dess prestanda under perioder av marknadsstress. Modellen visade dock något bättre resultat under normala marknadsförhållanden.
80

美國次級房貸風暴對全球股價走勢的衝擊與影響-以DCC模型分析 / Using DCC Model to Analyze the Impact of the Subprime Mortage Crisis on the Global Stock Market

賴彥君, Lai Yen-Chun Unknown Date (has links)
摘要 2007年初美國發生次級房貸大量違約, 陸續有銀行倒閉, 進而撼 動整個美國與歐洲股市。一向與美國有密切貿易關係的台灣,在此事 件中到底受到多大的影響? 本文利用DCC模型探討次貸風暴前後,台 美股價間的關係是否有發生顯著的變化? 實證結果發現: 台灣與美國 的動態相關係數在次級房貸之後, 反而變小, 可見台灣的股市並未受 到很大的衝擊, 而亞洲地區的大多數國家也都與台灣相似,與美國的 動態相關係數變小,可見亞洲地區在次貸風暴中扮演著避風港的角色。

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