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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.
1

Použití metody bootstrap v časových řadách / Applications of bootstrap methods to time series

Baumová, Tereza January 2018 (has links)
Práce se vìnuje studiu variant metody bootstrap vhodných pro vy¹etøování vlastností autoregresních procesù s náhodnými koe cienty. Ètenáø je nejprve se- známen s pùvodní metodou bootstrap navr¾enou pro nezávislé stejnì rozdìlené náhodné velièiny a se základními variantami této metody bì¾nì pou¾ívanými pro analýzu èasových øad. Poté je pøedstaven autoregresní proces s náhodnými koe - cienty øádu p (RCA(p)). Jsou popsány základní vlastnosti tohoto procesu a blí¾e prozkoumány vlastnosti procesu RCA(1). V dal¹í èásti jsou uvedeny varianty me- tody bootstrap, které jsou v pøípadì procesu RCA(1) konzistentní, a pro metodu wild bootstrap je odvozena konzistence pro proces RCA(2). V poslední kapitole jsou na simulovaných datech ovìøeny vlastnosti popsaných metod. 1
2

Estimation of gusty winds in RCA / Beräkning av byiga vindar i RCA

Nordström, Maria January 2005 (has links)
In this study a new wind gust estimate (WGE) method proposed by Brasseur (2001) is implemented in a limited area climate model (RCA, Rossby Centre regional Atmospheric model). The WGE method assumes that wind gusts develop when air parcels higher up in the boundary layer deflect down to the surface by turbulent eddies. The method also gives an interval of possible gusts by estimating an upper and lower bound of a bounding interval. Two separate storms (December 3-4, 1999 and January 8-9, 2005) and a three month period (November 1, 2004 - January 31, 2005) are simulated with RCA. The results are compared to direct observations and to gridded analysis (MESAN). The result is highly dependent on how well the meteorological fields are represented in RCA. Since the storm of December 1999 was not well captured by RCA, the wind gusts were consequently not correctly estimated. The storm of January 2005 was well captured by the RCA and the wind gusts relatively well described. Both the storm of January 2005 and the simulation over a three month period give rather good estimated gusts over sea areas, while over land there is an obvious overestimation of the calculated gusts. A correction to the estimated gust is necessary in order to make the parameterisation useful. Such a correction is tested in this study. It shows significant improvement over most land areas and also gives a certain underestimation in other areas. / Sammanfattning av ”Beräkning av byiga vindar i RCA” En ny metod (WGE-metoden) för att bestämma byvindar har i den här studien implementerats i en regional klimatmodell (RCA, Rossby Centre regional Atmospheric model). WGE-metoden utgår från att vindbyar genereras när luftpaket högre upp i gränsskiktet förs ner till marken av stora turbulenta virvlar. Ett intervall av möjliga byvindar erhålls genom att en övre och undre gräns för detta intervall beräknas. Två stormar (3-4 december 1999 och 8-9 januari 2005) och en tremånaders period (1 november 2004 – 31 januari 2005) har simulerats, och resultaten har jämförts med mätdata och MESAN. Resultatet är till stor del beroende av hur väl de meteorologiska fälten representeras av RCA. Stormen i december 1999 simulerades dåligt av RCA, vilket medförde att byvinden inte heller simulerades korrekt. Både stormen januari 2005 och simuleringen över tre månader ger en tämligen korrekt byvind över hav, samtidigt som man över land får kraftiga överskattningar av den beräknade byvinden. För att byvind-parametriseringen ska vara användbar krävs korrigeringar för att komma till rätta med överskattningen över land. En korrigering testades i den här studien med resultatet att ett förbättrat resultat över land samtidigt leder till en viss underskattning av byvinden i andra områden.
3

The accuracy of the wind stress over ocean of the Rossby Centre Atmospheric model (RCA)

Ohlsson, Alexandra January 2006 (has links)
The aim of this study is to investigate how well the wind stress is described in the regional climate model RCA (Rossby Centre Atmospheric model). The model data is compared with measurements taken at Östergarnsholm, an island located east of Gotland in the Baltic Sea. The investigation covers the period October 1997 to September 2000. Compared with the measurements RCA underestimates the wind speed over ocean in most cases. When the wind speed is studied in monthly mean it was found that the wind speed is consistently underestimated in the model, especially during summer and early winter. The wind stress is also underestimated during the year except during late winter and in October when it is overestimated. When wind speed from the model and measurements were studied it was found that lower wind speed is overestimated in the model. This contributes to overestimation of the wind stress for lower wind speeds. For higher wind speeds both wind speed and wind stress is underestimated in RCA. If the model would have a correct wind speed the wind stress would be overestimated with 20-30 % for all wind speeds compared to the measured. This is probably due to miscalculations of wind stress in the model. RCA fail to capture the stability in a satisfactory way. The model describes most of the times a different stratification than the measurements do. Separate studies over modeled and measured wind speed and wind stress was made. RCA is found to represent stable condition well. During unstable stratification modeled wind speed and wind stress are underestimated. Investigation of the measured wave age shows that the model underestimates both wind speed and wind stress for growing sea and mature sea. For the situations when the measured wave age was defined as swell the model overestimated wind speed and wind stress.2 / Den här studien tar upp hur väl friktionen över havsytan beskrivs i den regionala klimatmodellen RCA (Rossby Centre Atmospheric model). Modelldata jämförs med mätningar gjorda på Östergarnsholm, en ö belägen öster om Gotland i Östersjön. Studien spänner över tidsperioden oktober 1997 till september 2000. RCA underskattar i många fall vindhastigheten på 10 m över havsytan jämfört med mätningarna. Då månadsmedelvärden studeras visar det sig att modellen genomgående underskattar vindhastigheten, särskilt på sommaren och på vintern. Friktionen överskattas under sen vinter och för oktober månad. För alla andra månader underskattas friktionen. Studier över vindhastigheterna visar på att de lägre vindhastigheterna överskattas i modellen. Detta bidrar till överskattning av friktionen för de lägre vindhastigheterna. För högre vindhastigheter underskattar RCA vindhastigheterna och därmed även friktionen. Om modellen skulle ge en korrekt vindhastighet skulle resultatet istället visa på en överskattning av friktionen med 20-30 % för alla vindhastigheter. Detta beror troligen på felaktigheter i beräkningen av friktionen i modellen. Stabiliteten visar sig vara dåligt beskriven i RCA. I de flesta fall är skiktningen i modellen och mätningarna helt olika. Jämförelser mellan separata studier mellan modelldata och mätningar visar att vindhastigheten och friktionen beskrivs bra under stabila förhållanden, men i samband med instabil skiktning underskattas vindhastigheten och friktionen i modellen. Studier över den uppmätta vågåldern visar att modellen underskattar både vindhastigheten och friktionen för växande och fullvuxen sjö. Då det råder dyning överskattar modellen både vindhastigheten och friktionen.
4

Multidimensionale Darstellung der proximalen RCA in 3D4D- Technik im Vergleich zur Koronarangiographie

Lange, Katharina 30 June 2014 (has links) (PDF)
Das Ziel der vorliegenden Studie war die Analyse der Detektierbarkeit von Stenosen und Lumenverschlüssen im proximalen Bereich der rechten Koronararterie mit konventioneller 2D- und 3D- Echokardiographie von transthorakal. Zusätzlich wurden die Befunde der 3D-Echoloops mit den Untersuchungsergebnissen der Koronarangiographie verglichen. Methodisch wurden daher bei Patienten mit bestehender Indikation zur Koronarangiographie vorhergehende zweidimensionale parasternale Lang- (n=91) und Kurzachsenaufnahmen (n=76), sowie parasternale dreidimensionale (n=91) echokardiographische Aufnahmen des Ostiums und der proximalen Region der rechten Herzkranzarterie durchgeführt. Durch zusätzliche Schnittebenen der proximalen Abschnitte der rechten Koronararterie sollte die konventionelle zweidimensionale Echokardiographie für eine Stenosendetektion ergänzt werden. Diese ermöglichten eine genaue Darstellung der rechtskoronaren Morphologie im proximalen Gefäßbereich. Maximal konnten die proximalen 35mm der rechten Koronararterie untersucht werden. Die Ergebnisse der einzelnen verschiedenen echokardiographischen Dokumentationen wurden miteinander und mit denen der Koronarangiographie verglichen. Insgesamt zeigten sich keine signifikanten Unterschiede zwischen den Ergebnissen der 2D Echokardiographie und der Koronarangiographie. Die Diameter der Streckenmessungen an der rechten Koronararterie in der 3D-Echokardiographie und der Koronarangiographie sind hingegen in ihren Mittelwerten signifikant verschieden. Dies ist durch häufigere Sekantenanschnitte der Gefäße mittels Echokardiographie bedingt. Die höchste Sensitivität konnte mittels 3D-Echokardiographie (98%) nachgewiesen werden, wohingegen die zweidimensionale Technik bessere Spezifitäten (91% in 2D-Langachsen- und 92% in 2D-Kurzachsen-Aufnahmen) aufweist. Diese Ergebnisse zeigen den Nutzen der Echokardiographie im klinischen Alltag zur intravasalen Stenosendetektion der rechten Koronararterie.
5

Efficacité d’interventions de prévention, basées sur une meilleure prise en compte des besoins perçus et vécus des HSH en République Centrafricaine

Mbeko Simaleko, Marcel 21 December 2020 (has links) (PDF)
Résumé français :Problématique :les hommes qui ont des rapports sexuels avec des hommes (HSH) constituent les populations les plus à risque d’infection au VIH dans différents pays d’Afrique subsaharienne. A ce jour, très peu d’interventions sont menées pour réduire le risque d’infection en influant sur les facteurs de risque, en Afrique Centrale et particulièrement en République Centrafricaine. Les objectifs de cette thèse visent à démontrer que les HSH sont identifiables et sont à risque des IST/VIH, que leur simple suivi médical ne permet pas un changement de comportements sexuels et réduire la fréquence des IST/VIH, mais que la combinaison d’interventions comportementale, biomédicale et structurelle permet, même en période de crise humanitaire, le changement de comportement sexuel et la réduction de la fréquence des IST/VIH. Méthodologie :Les HSH ont été enrôlés progressivement depuis 2010 pour atteindre un nombre de 220 en 2014. L’étude préliminaire sur les caractéristiques sociodémographiques et pratiques sexuelles à risque a concerné les 103 premiers HSH enrôlés en 2010. En 2012, la cohorte atteint le nombre de 170 HSH parmi lesquels 99 qui avaient un dossier médical complet ont fait l’objet de la deuxième étude du suivi sur deux ans.En 2013, alors que la cohorte des HSH avait atteint 200, 20 HSH ont été interviewés dans le cadre de l’étude qualitative. En 2014, la cohorte des HSH a atteint le nombre de 220. L’étude d’intervention a concerné 40 HSH sélectionnés sur les 220 et s’est poursuivie jusqu’en 2016.Résultats :L’analyse des caractéristiques socio démographiques des 103 HSH relève la présence de HSH jeunes. L’âge varie entre 15 et 40 ans, avec une médiane à 23 ans. Les pratiques sexuelles à risque sont fréquentes, notamment les premiers rapports sexuels avant 16 ans et sans préservatifs (70%) ;7% n’ont jamais utilisé les préservatifs, 56 % sont bisexuels, 98% pratique la pénétration anale. 31 HSH soit 24 %, étaient séropositifs pour le VIH ;22 soit 17% étaient infectés par le virus de l'hépatite B (VHB), dont 6 cas étaient coinfectés par le VIH et le VHB (M.B. Simaleko, et al.- Médecine d'Afrique Noire 6010 - Octobre 2013 - 409-414).En 2012, après deux ans de suivi médical et de counseling, il n’y a pas eu de changement de comportement et de pratiques sexuelles à risque, notamment en ce qui concerne la fréquence des rapports non protégés et la moyenne du nombre de partenaires occasionnels. La fréquence des principales IST a augmenté. Les prévalences du VIH, de la syphilis et de l’hépatite ont augmenté de manière significative et respectivement de 29% à 41%, de 12% à 21% de 14% à 23%. (Mbeko Simaleko M. et al. Pan Afr Med J. 2018; 29: 132).L’entretien avec les HSH a révélé plusieurs obstacles à l’utilisation des préservatifs, notamment, les ruptures, leur disponibilité, les fausses croyances, les pressions de l’entourage. (Mbeko Simaleko M. et al. Médecine et Santé Tropicale 2018 ;28 :424-429). De 2014 à 2016, l’étude d’interventions sur 40 HSH choisis de manière aléatoire et basée sur la combinaison des interventions comportementale, biomédicale et structurelle a permis d’améliorer le comportement et pratiques sexuelles des HSH par la réduction significative du nombre de partenaires sexuels occasionnels et l’augmentation significative de la fréquence des rapports sexuels protégés. À cet effet, il a été noté un seul cas de nouvelle infection par le VIH parmi les séronégatifs des 40 HSH contre 9 cas dans le groupe témoin. Aucune nouvelle infection au virus de l’hépatite B dans le groupe intervention contre 18, dans le groupe témoin. Il y a une augmentation significative de séropositifs dans le groupe témoin comparativement au groupe intervention en ce qui concerne la sérologie de la syphilis. (Mbeko Simaleko M. et al. Health Sci. Dis. 2020; 21: 94-99). Conclusion :les HSH sont identifiables et à risque. Le simple suivi médical associé au counseling ne permet pas d’améliorer le comportement sexuel et réduire la fréquence des IST. Cependant la combinaison des interventions a permis d’améliorer le comportement et la prise de risques des HSH mais également de réduire la fréquence des IST, même en période de crise humanitaire. Au vu du faible nombre de HSH inclus dans l’étude, il serait nécessaire d’étendre celle-ci, afin de conforter les résultats obtenus.Abstract Issue: Men who have sex with men (MSM) are the most at risk populations of HIV infection in different countries of sub-Saharan Africa. To date, very few interventions have been carried out to reduce the risk of infection by influencing on risk factors in Central Africa and particularly in the Central African Republic. The objectives of this research are to demonstrate that MSM are identifiable and at risk of STI/HIV, that the medical follow-up does not cause a change in sexual behavior and a reduction in the frequency of STI/HIV but that the combination of behavioral, biomedical and structural interventions allows, even in times of humanitarian crisis, behavioral change and reduction in the frequency of STI/HIV. Methodology: MSM have been progressively enrolled since 2010 to reach a number of 220 in 2014. The preliminary study on sociodemographic characteristics and sexual risk practices involved the first 103 MSM recruited until 2011. In 2012, 99 MSM who had a complete medical record were the subject of the second study on a two-year follow-up. In 2013, when the MSM cohort reached 200, 20 MSM were interviewed in the context of the qualitative study. In 2014, the MSM cohort reached 220. The intervention study involved 40 selected MSM out of the 220 and was continued during 2016.Results: MSM are predominantly young Their age varied between 15 and 40 years, with a median of23 years. Risky sexual practices were frequent, including first sexual intercourse before the age of 16 and without condoms (70%); 7% never used condoms, 56% are bisexual, 98% practice anal penetration. 31 MSM, or 24%, were HIV-positive; 22, or 17%, were infected with hepatitis B virus (HBV), of which 6 cases were co-infected with HIV and HBV (M.B. Simaleko, Set al. - Médecine d'Afrique Noire 6010 - Octobre 2013 - 409-414). In 2012, after two years of medical follow-up and counselling, there was no change in risk behavior and sexual practices, including the frequency of unprotected sex and the average number of occasional partners.The incidence of major STIs increased. The prevalence of HIV, syphilis and hepatitis increased significantly and respectively from 29% to 41%, from 12% to 21%, from 14% to 23%, respectively (Mbeko Simaleko M. et al. Pan Afr Med J. 2018; 29: 132). Interviews with MSM revealed several barriers to condom use, including condom breaks, condom availability, false beliefs, and peer pressure (Mbeko Simaleko M. et al. Médecine et Santé Tropicale 2018; 28: 424-429). From 2014 to 2016, the intervention study of 40 randomly selected MSM based on a combination of behavioral, biomedical, and structural interventions improved the sexual behavior and practices of MSM by significantly reducing the number of occasional sexual partners and significantly increasing the frequency of safer sex. Only 1 case of new HIV infection was noted among the 40 HSH HIV-negative compared to 9 cases in the control group. There were no new hepatitis B virus infections in the intervention group versus 18 in the control group. There was a significant increase in seropositivity in the control group compared to the intervention group with respect to syphilis serology (Mbeko Simaleko M. et al. Health Sci. Dis: Vol 21 (7) July 2020 pp 94-99). Conclusion: MSM were identifiable and most of them were at HIV risk. Simple medical follow-up combined with counselling does not allow to improve sexual behavior or to reduce the frequency of STIs. However, the combination of interventions has made it possible to improve the behavior and risk-taking of MSM and also to reduce the frequency of STIs, even in times of humanitarian crisis. In view of the low number of MSM included in the sample study and in order to consolidate the results obtained, it would be necessary to carry out a more in-depth study with a larger sample of MSM. / Doctorat en Santé Publique / info:eu-repo/semantics/nonPublished
6

A Radical Conjugate Addition Approach to the Total Synthesis of Celogentin C

Capps, Steven G. 11 August 2008 (has links) (PDF)
The synthesis of five chiral DBFOX (dibenzofuran-oxazoline) ligands with either aryl or benzyl substituents will be presented. The requisite amino alcohols were obtained with high enantioselectivity either commercially (DBFOX/Bn), via Sharpless asymmetric aminohydroxylation (DBFOX/Nap, DBFOX/t-BuPh, DBFOX/Pip), or via phase-transfer catalyzed asymmetric alkylation (DBFOX/MeNap). These ligands, complexed with Mg(NTf2)2, were used as Lewis acid promoters of enantioselective radical conjugate additions to α/β-unsaturated nitro-amides/esters. A summary of these results is presented and discussed. These findings led us to believe that our initial binding model between metal, ligand, and substrate was flawed. Thus, we figured that if we started with a functionality known to bind to both nitro groups and carbonyls, and then introduced a chiral element for control, we may be able to improve the beta-carbon enantioselectivity. We have tried to accomplish this via hydrogen-bonding ligands (ureas and thioureas). Initial studies on achiral versions of this concept are discussed.
7

Detekce změn v RCA modelech / Change detection in RCA models

Biolek, Jiří January 2019 (has links)
The thesis describes Random Coefficient Autoregressive time series mo- dels (RCA models). In first chapter we introduce different types of estimati- ons for coefficients of RCA model. Main part is in second chapter, where we describe detection changes procedures for all methods mentioned in chapter one, here the thesis expands the current theory about change detection of wei- ghted least square method and functional estimation. In last chapter we sum- marize results of simulation study. 1
8

Effect of Recycled Concrete Aggregate Properties on the Behaviour of New Concrete

Ahimoghadam, Faraz 04 May 2018 (has links)
Application of recycled concrete aggregates (RCA) has increased recently as a sustainable alternative in concrete construction. Although application of RCA has substantially grown over the past decades, issues related to its structural performance and long-term behaviour still prevent its widespread application, especially in structural purposes. In this study, a new mixture proportioning method called the “Equivalent Volume (EV)” method is proposed for RCA concrete, which is developed on the assumption that the RCA mix is based on a companion conventional concrete mix having the same volume of “cement paste and aggregates” as the companion mixture. RCA mixes containing different aggregate types and mechanical properties were designed using the EV method. Chemical, mechanical and non-destructive tests were performed and their performance was investigated. Finally, a quality control protocol for evaluating the suitability of RCA sources for structural applications is proposed. Results show that the EV method seems a promising approach to mix-proportion eco-friendly recycled concrete mixes. Moreover, the RCA type and properties seem to influence in the behaviour of RCA concrete and thus should be accounted in the mix- design.
9

台灣與韓國在金磚四國的競爭力:1997-2007

陳穗瑛 Unknown Date (has links)
高盛證券曾預言,2050年世界經濟強權將重新洗牌,屆時現有六大工業國家只剩美國與日本,金磚四國(中國、巴西、俄羅斯、印度)將取代英國、德國、法國、義大利成為新的經濟強權。由於金磚四國未來在能源、天然資源、資本三大市場將扮演要角,且成為全球最重要的消費市場,未來勢必影響全球經濟板塊的移動。 台灣與韓國貿易型態相近,製造業產品的市場性質與產品定位也較相似。因此,台灣與韓國在金磚四國的崛起這場經濟板塊大挪移之下,兩國能在金磚四國市場上占有一席之地?而又台灣與韓國產品的競爭力變化趨勢為何?在在都是非常値得注意與探討的重要議題。 本文透過顯示性比較利益指標、集中程度指標、競爭力移轉指標、持續性指標以及Michaely指標,將台灣與韓國從1997年到2007年對金磚四國的貿易情況加以量化,以利於比較與評估。 由這些指標結果顯示,台灣與韓國近十年來在金磚四國的競爭力逐漸減弱,但台灣在金磚四國的競爭力又較韓國強。另外,由於金磚四國的經濟尚處於快速成長的不穩定階段。因此,台灣與韓國面對金磚四國的貿易時常出現大幅度的波動。又由台灣與韓國對金磚四國最具優勢與最不具優勢前五大產業的結果,我們發現台灣與韓國最具優勢的產業大不相同,甚至幾乎沒有可以相互競爭的產業。因此,我們推論台灣與韓國出口結構是不大相同的。
10

Near threshold operation of 16-bit adders in 65nm CMOStechnology

Maddula, Ravi January 2014 (has links)
The main objective of the thesis is to implement different architectures of 16-bit adders such as; Ripple CarryAdder (RCA), Manchester Carry Chain Adder (MCCA) and Kogge Stone Adder (KSA), in 65nm CMOS technology and to study their performance in terms of power, operating frequency and speed at near threshold operating regions. The performance of these adders are evaluated and compared with each other and a final conclusion is made as to which adder structure is more suitable for implementation in a 65nmtechnology for low power applications. Several optimisation techniques are performed for the adders to reduce the delay and power consumption. Propagation delay is the most critical or essential parameter to be considered, hence, to minimise the delay of the adder, a technique called sizing and ordering are required for the transistors. The purpose of the thesis is to make a fair comparison among adders over several metrics which include linearity, delay and power. Simulation results of MCCA achieved a greater significant performance upon or over RCA and KSA, and proved it is the best suitable adder for low power applications.

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