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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

From quantum many body systems to nonlinear Schrödinger Equations

Xie, Zhihui 06 November 2014 (has links)
The derivation of nonlinear dispersive PDE, such as the nonlinear Schrödinger (NLS) or nonlinear Hartree equations, from many body quantum dynamics is a central topic in mathematical physics, which has been approached by many authors in a variety of ways. In particular, one way to derive NLS is via the Gross-Pitaevskii (GP) hierarchy, which is an infinite system of coupled linear non-homogeneous PDE. In this thesis we present two types of results related to obtaining NLS via the GP hierarchy. In the first part of the thesis, we derive a NLS with a linear combination of power type nonlinearities in R[superscript d] for d = 1, 2. In the second part of the thesis, we focus on considering solutions to the cubic GP hierarchy and we prove unconditional uniqueness of low regularity solutions to the cubic GP hierarchy in R[superscript d] with d ≥ 1: the regularity of solution in our result coincides with known regularity of solutions to the cubic NLS for which unconditional uniqueness holds. / text
2

The Identification and Measurement of Conditional and Unconditional Self-Liking

Splendlove, Alan 01 May 1999 (has links)
The concept of unconditional self-love is fundamental to many theoretical perspectives in social science and is referred to periodically in the literature. This study addressed the problem that scientific literature refers to unconditional self-love, but does not clearly define it, differentiate it from other types of feelings that comprise self-esteem, measure it, or even attempt to substantiate its existence. The purpose of this study was to define, describe, and measure unconditional self-love so that it may be used in the treatment of problems caused by low self-esteem. To achieve this purpose, the concept of self-love was defined in relation to self-liking, separated from the other components of self-esteem, and operationalized through the creation of the Unconditional Self-Liking (USL) model and the Unconditional Self-Liking (USL) scale. The USL scale is a self-report questionnaire that simultaneously measures two variables in relation to one another. This was done using the intersect of the variables of personal success and self-liking as a measure of unconditionality across nine areas of self-identity. The USL model allows for the measurement and description of four primary types of self-liking: (a) conditional self-likers who like themselves only when they succeed, (b) unconditional self-dislikers who dislike themselves even when they succeed, (c) conditional self-dislikers who dislike themselves when they fail, and (d) unconditional self-likers who like themselves even when they fail. The USL scale was administered to a convenience sample of 164 undergraduate university students who also completed the Modified Barrett-Lennard Relationship Inventory (BLRI) and the 10-question Rosenberg Self-Esteem (RSE) scale. The subjects' responses on the three scales were compared. Major findings indicated that individual levels of self-liking varied between areas of self-identity. Moreover, the level of self-liking was not necessarily dependent on their level of success. Each of the corresponding measures of the three instruments showed positive correlations, except the measures of unconditionality. Finally, each of the four primary patterns of self-liking described by the USL model characterized some subjects. Findings support the concept of unconditional self- liking, which suggests that high levels of self-liking arc not limited to only the most capable, intelligent, talented, or attractive people.
3

Perturbations of selfadjoint operators with discrete spectrum

Adduci, James 19 October 2011 (has links)
No description available.
4

Enhancing understanding of tourist spending using unconditional quantile regression

Rudkin, Simon, Sharma, Abhijit 22 June 2017 (has links)
yes / This note highlights the value of using UQR for addressing the limitations inherent within previous methods involving conditional parameter distributions for spending analysis (QR and OLS). Using unique data and robust analysis using improved methods, our paper clearly demonstrates the over-importance attached to length of stay and the inadequate attention given to business travelers in previous research. There are clear benefits from UQR’s methodological robustness for assessing the multitude of variables related to tourist expenditures, particularly given UQR’s ability to inform across the spending distribution. Given tourism’s importance for the UK it is critical for expensive promotional activities to be targeted efficiently for ensuring effective policy making.
5

The Impact of Football Attendance on Tourist Expenditures for the United Kingdom

Rudkin, Simon, Sharma, Abhijit 14 September 2017 (has links)
Yes / We employ unconditional quantile regression with region of origin fixed effects, whereby we find that attending live football matches significantly increases expenditures by inbound tourist in the UK, and surprisingly we find that such effects are strongest for those who overall spend the least. Higher spending individuals spend significantly more than those who do not attend football matches, even when such individuals are otherwise similar. We analyse the impact of football attendance across the tourism expenditure distribution which is a relatively neglected aspect within previous research.
6

Live football and tourism expenditure: match attendance effects in the UK

Sharma, Abhijit, Rudkin, Simon 14 May 2019 (has links)
Yes / The inbound tourist expenditure generating role of football (soccer), particularly the English Premier League 15 (EPL) is evaluated. An enhanced economic and management understanding of the role of regular sporting fixtures emerges, as well as quantification of their impact. Expenditure on football tickets is isolated to identify local economic spillovers outside the stadium walls. Using the UK International Passenger Survey, unconditional quantile regressions (UQR) is used to evaluate the distributional impact of football attendance on tourist expenditures. Both total expenditure and a new measure which adjusts expenditures for football ticket prices are considered. UQR is a novel technique which is as yet underexploited within sport economics and confers important methodological advantages over both OLS and quantile regressions. Significant cross quantile variation is found. High spending football fans spend more, even after ticket prices are excluded. Surprisingly, spending effects owing to attendance are strongest for those who overall spend the least, confirming the role of sport as a generator of tourist expenditure unlike most others. Though the attendance effect is smaller for higher aggregate spenders, there is nevertheless a significant impact across the distribution. Distributional expenditure impacts highlight clear differentials between attendance by high and low spenders. Similar analysis is applicable to other global brands such as the National Football League (NFL) in the United States (American football) and the Indian Premier (cricket) League. The EPL’s global popularity can be leveraged for achieving enhanced tourist expenditure.
7

Unconditional quantile regression analysis of UK inbound tourist expenditures

Sharma, Abhijit, Woodward, R., Grillini, Stefano 09 December 2019 (has links)
Yes / Using International Passenger Survey (2017) data, this paper employs unconditional quantile regression (UQR) to analyse the determinants of tourist expenditure amongst inbound tourists to the United Kingdom. UQR allows us to estimate heterogeneous effects at any quantile of the distribution of the dependent variable. It overcomes the econometric limitations of ordinary least squares and quantile regression based estimates typically used to investigate tourism expenditures. However, our results reveal that the effects of our explanatory variables change across the distribution of tourist expenditure. This has important implications for those tasked with devising policies to enhance the UK’s tourist flows and expenditures.
8

Examining GARCH forecasts for Value-at-Risk predictions

Lindholm, Dennis, Östblom, Adam January 2014 (has links)
In this thesis we use the GARCH(1,1) and GJR-GARCH(1,1) models to estimate the conditional variance for five equities from the OMX Nasdaq Stockholm (OMXS) stock exchange. We predict 95% and 99% Value-at-Risk (VaR) using one-day ahead forecasts, under three different error distribution assumptions, the Normal, Student’s t and the General Error Distribution. A 500 observations rolling forecast-window is used on the dataset of daily returns from 2007 to 2014. The empirical size VaR is evaluated using the Kupiec’s test of unconditional coverage and Christoffersen’s test of independence in order to provide the most statistically fit model. The results are ultimately filtered to correspond with the Basel (II) Accord Penalty Zones to present the preferred models. The study finds that the GARCH(1,1) is the preferred model when predicting the 99% VaR under varying distribution assumptions.
9

Unconditionally Secure Cryptographic Protocols from Coding-Theoretic Primitives / Protocoles avec Sécurité Inconditionnelle issus de Techniques de la Théorie des Codes

Spini, Gabriele 06 December 2017 (has links)
Le sujet de cette thèse est la cryptographie et son interconnexions avec la théorie des codes. En particulier, on utilise des techniques issues de la théorie des codes pour construire et analyser des protocoles cryptographiques avec des propriétés nouvelles ou plus avancées. On se concentre d'abord sur le partage de secret ou secret sharing, un sujet important avec de nombreuses applications pour la Cryptographie actuelle. Dans la variante à laquelle on s'intéresse, un schéma de partage de secret reçoit en entrée un élément secret, et renvoie en sortie n parts de telle façon que chaque ensemble de parts de taille suffisamment petite ne donne aucune information sur le secret (confidentialité), tandis que chaque ensemble de taille suffisamment grande permet de reconstituer le secret (reconstruction). Un schéma de partage de secret peut donc être vu comme une solution à un problème de communication où un émetteur Alice est connectée avec un destinataire Bob par n canaux distincts, dont certains sont contrôlés par un adversaire Ève. Alice peut utiliser un schéma de partage de secret pour communiquer un message secret a Bob de telle façon qu'Ève n'apprenne aucune information sur le secret en lisant les données transmises sur les canaux qu'elle contrôle, tandis que Bob peut recevoir le message même si Ève bloque ces dits canaux. Notre contributions au partage de secret concernent ses liens avec la théorie des codes ; comme les deux domaines partagent un même but (récupérer des données à partir d'informations partielles), ce n'est pas surprenant qu'ils aient connu une interaction longue et fertile. Plus précisément, Massey commença une analyse fructueuse à propos de la construction et de l'étude d'un schéma de partage de secret à partir d'un code correcteur. L'inconvénient de cette analyse est que la confidentialité d'un schéma de partage de secret est estimé grâce au dual du code sous-jacent ; cela peut être problématique vu qu'il pourrait ne pas être possible d'obtenir des codes avec des propriétés souhaitables qui aient aussi un bon code dual. On contourne ce problème en établissant une connexion nouvelle entre les deux domaines, telle que la confidentialité d'un schéma de partage de secrets n'est plus contrôlée par le dual du code sous-jacent. Cela nous permet d'exploiter complètement le potentiel de certaines constructions récentes de codes pour obtenir des meilleurs schémas; on illustre ceci avec deux applications. Premièrement, en utilisant des codes avec codage et décodage en temps linéaire on obtient une famille de schémas de partage de secret où le partage (calcul des parts issues du secret) tout comme la reconstruction peuvent s'effectuer en temps linéaire ; pour des seuils de confidentialité et de reconstruction croissants, ceci restait jusqu'à présent un problème ouvert. Deuxièmement, on utilise des codes avec décodage en liste pour construire des schémas de partage de secret robustes, c'est-à-dire des schémas qui peuvent reconstituer le secret même si certaines parts sont incorrectes, sauf avec une petite probabilité d'erreur. etc... / The topic of this dissertation is Cryptography, and its connections with Coding Theory. Concretely, we make use of techniques from Coding Theory to construct and analyze cryptographic protocols with new and/or enhanced properties. We first focus on Secret Sharing, an important topic with many applications to modern Cryptography, which also forms the common ground for most of the concepts discussed in this thesis. In the flavor we are interested in, a secret-sharing scheme takes as input a secret value, and produces as output n shares in such a way that small enough sets of shares yield no information at all on the secret (privacy), while large enough sets of shares allow to recover the secret (reconstruction). A secret-sharing scheme can thus be seen as a solution to a secure communication problem where a sender Alice is connected to a receiver Bob via $n$ distinct channels, some of which are controlled by an adversary Eve. Alice can use a secret-sharing scheme to communicate a secret message to Bob in such a way that Eve learns no information on the message by eavesdropping on the channels she controls, while Bob can receive the message even if Eve blocks the channels under her control. Our contributions to Secret Sharing concern its connection with Coding Theory; since the two fields share the goal of recovering data from incomplete information, it is not surprising that Secret Sharing and Coding Theory have known a long and fruitful interplay. In particular, Massey initiated a very successful analysis on how to construct and study secret-sharing schemes from error-correcting codes. The downside of this analysis is that the privacy of secret-sharing schemes is estimated in terms of the dual of the underlying code; this can be problematic as it might not be possible to obtain codes with desirable properties that have good duals as well. We circumvent this problem by establishing a new connection between the two fields, where the privacy of secret-sharing schemes is no longer controlled by the dual of the underlying code. This allows us to fully harness the potential of recent code constructions to obtain improved schemes; we exemplify this by means of two applications. First, by making use of linear-time encodable and decodable codes we obtain a family of secret-sharing schemes where both the sharing (computation of the shares from the secret) and the reconstruction can be performed in linear time; for growing privacy and reconstruction thresholds, this was an hitherto open problem. Second, we make use of list-decodable codes to construct robust secret-sharing schemes, i.e., schemes that can recover the secret even if some of the shares are incorrect, except with a small error probability. The family we present optimizes the trade-off between the extra data that needs to be appended to the share to achieve robustness and the error probability in the reconstruction, reaching the best possible value. etc...
10

Aktuální otázky nepodmíněného trestu odnětí svobody / Selected Questions of Unconditional Imprisonment

Jirsová, Kamila January 2019 (has links)
- Selected Questions of Unconditional Imprisonment The presented diploma thesis dealing with current issues of unconditional imprisonment is led by an effort to analyze problems that are conncted with the imprisonment and to outline possible solutions. The introduction is devoted to the concept of punishment and its purpose. In order to better understanding the current concept of unconditional imprisonment, the second part briefly discusses the historical development of this punishment and the origin of penological systems. This section also includes legislative regulation at both international and national level. The third part examines the unconditional imprisonment in terms of length, while the author concludes that the greatest risk of negative effects is linked to both very short sentences and penalties of over 10 years. The pivotal part of the thesis is the fourth part, which deals with selected actual issues, which must be discussed in connection with the unconditional imprisonment. The author calls for the priority to be given to the problems of prison overcrowding, because without the solution of this problem it is not possible to face other negative phenomenons and effort to reform convicts are often void. The author sees the solution partly in the construction of new prison facilities....

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