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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.
861

Mesure de la masse du quark top dans les canaux di-leptoniques auprès de l'expérience DØ au Tevatron

Croc De Suray, Aurélien 24 June 2011 (has links) (PDF)
Le quark top est le quark le plus lourd contenu dans le modèle standard. Découvert en 1995 par les deux expériences du Tevatron, il possède des caractéristiques atypiques telles qu'un temps de vie le plus court jamais observé qui le fait se désintégrer avant de pouvoir s'hadroniser et donne ainsi accès à sa masse dont sa mesure est alors d'une très grande précision. Les données accumulées par l'expérience DØ entre 2002 et 2009, représentant une luminosité intégrée de 5,4 fb⁻¹, sont utilisées pour effectuer cette mesure à partir de la méthode de l'élément de matrice dans les canaux di-leptoniques électron--électron, électron--muon et muon--muon. La valeur de la masse du quark top mesurée, 174.0 ± 1,8 (stat.) ± 2,4 (syst.) GeV, est en très bon accord avec les autres mesures effectuées. Sa précision est limitée, pour la première fois pour ces canaux, par les incertitudes systématiques. Dans cette thèse, plusieurs approches sont étudiées pour améliorer la précision de la mesure : l'utilisation d'informations sur l'identification de jets issus de quarks b afin d'optimiser la sélection des événements top--anti-top et une meilleure détermination des incertitudes systématiques principales. Une attention particulière est portée sur la simulation Monte-Carlo des muons à DØ : l'amélioration de l'ajustement de la résolution sur la mesure de l'impulsion transverse des muons simulés avec les données, discutée dans cette thèse, sera utilisée afin d'améliorer les prochaines mesures des propriétés du quark top ainsi que d'autres analyses menées dans l'expérience.
862

Recherche d'un boson de Higgs chargé avec le détecteur ATLAS : de la théorie à l'expérience

Weydert, Carole 05 September 2011 (has links) (PDF)
Cette thèse se situe à mi-chemin entre la phénoménologie et la physique de particules expérimentale. Dans la première partie, nous décrivons un calcul de section efficace à order supérieur en développement perturbatif, ainsi que son implementation dans un générateur d'événements Monte Carlo. Nous présentons les corrections au premier order en chromodynamique quantique pour la production de boson de Higgs chargé en association avec un quark top au LHC, en utilisant le formalisme de soustraction de Catani et Seymour. Notre code indépendant nous a permis de valider les résultats donnés par MC@NLO, et nous avons réalisé des études concernant diverses contributions aux erreurs systématiques dues à la simulation d'événements. L'implémention du processus a été réalisée pour le générateur POWHEG. En raison de la quantité de données insuffisante disponible fin 2010 (le détecteur ATLAS a accumulé 35 pb-1 de données de collisions proton-proton), le processus de production de Higgs chargé n'a pas pu être étudié et nous nous sommes tournés vers la caractérisation de bruits de fonds. Dans ce contexte, il s'avère que la production de boson W en association avec un quark top est importante à connaître. Dans la seconde partie de cette thèse, nous mettons en place une analyse spécifique au canal Wt semileptonique, en incluant les effets statistiques et systématiques, pour lesquels nous nous concentrons plus particulièrement sur l'effet dû aux différentes paramétrisations du contenu des protons. Le processus Wt étant inobservable au Tévatron, nous pouvons pour la première fois donner une limite à la setion efficace de production.
863

Complexity and Change in a Simple Food Web : Studies in the Baltic Sea (FAO Area 27.IIId)

Österblom, Henrik January 2006 (has links)
<p>An influence at one trophic level can result in dynamic impacts also on other components of a food web. These dynamics are known as trophic cascades, and can be both top-down and bottom-up. After a near-collapse of the Baltic cod <i>Gadus morhua</i> stock in the 1980s, its main prey sprat <i>Sprattus sprattus</i> increased dramatically. The main food of sprat, marine copepods, decreased during the same time period, likely a combined effect of increased predation pressure from sprat and decreasing salinities. This shortage of food for sprat resulted in decreasing quality of sprat as a food source for common guillemots <i>Uria aalge</i>. However, a recent increase in fishing for sprat has again resulted in better feeding conditions for guillemots.</p><p>Human impacts on this simple food web can be complex. In the early 20th century, marine mammals were abundant and nutrient levels were low in the Baltic Sea. This thesis illustrate that this situation corresponded to lower fish biomass. A reduction of seals early in the century led to reduced top-down control, which resulted in increasing fish stocks. Later, in the 1950s, the largest inflow of salt water during the century mobilized accumulated phosphorus from the deep sediments, which stimulated nitrogen fixation. Combined with increasing anthropogenic nutrient loads, this led to increased primary production and a rapid change from an oligotrophic to a eutrophicated state. This change can be termed a regime shift, which also stimulated fish production. Subsequent over-fishing of cod likely caused a second regime shift, from a cod- to a clupeid- dominated state, which led to the described effects on the common guillemots.</p><p>Several factors affect the life-history of this long-lived seabird. Bycatches in gillnet fisheries is one factor directly affecting guillemot survival, and the proportion of bycatches increased during a period of increasing fishing effort. Surprisingly, avian cholera, a previously undocumented disease in common guillemots, was found at times to cause considerable adult mortality. Common guillemot life-history information can communicate the diversity of factors influencing marine ecosystems – hopefully this can increase our understanding of how complex even "simple" food webs are.</p>
864

How to keep up with the war for talent? : A comparative study between talent management in Company X and literature suggestions for identification of talent

Rönnlund, Josefin January 2009 (has links)
<p><strong>Datum: </strong>2009-06-30</p><p><strong>Författare: </strong>Rönnlund Josefin</p><p><strong>Nivå/utbildning: </strong>Master Thesis, Management</p><p><strong>Handledare: </strong>Owe R. Hedström</p><p><strong>Titel: </strong> How to keep with the War for talent? A comparative study between talent management in Company X and literature suggestions for identification of talent</p><p><strong>Problem: </strong>The need for talent management and a company's assets in form of Human Capital creates the demand of consultant firms and their services. The problem for companies today is to keep their up with the war for talented workers, and the way leadership talent is managed in the company is crucial for gaining competitive advantage. The research problem in my study is to identify how companies can manage talent within their organization successfully and by doing a research within a specific company, compare findings in their different organizational levels.</p><p><strong>Syfte:</strong> To investigate talent management processes in one company known for their success in the area of talent management and compare different views on talent management that might exist in different levels. My paper aims to value their talent management processes, and if there are gaps that could be filled and methods that could be developed.</p><p><strong>Metod: </strong>Qualitative method through six interviews and by doing a comparison between empirical findings and theory</p><p><strong>Resultat/slutsatser:</strong> talent management processes are very well developed in this business line in Company X, and in some areas they are even better than what literature suggests. They need to keep encouraging their personnel to take challenges and rotate. They also need to have a clear understanding of the roles in the organization, the responsibility of top recruitment and development. The areas that are in need of further development are leadership development, learning and training. Even if they have grasped the importance of these factors, they have some difficulties implementing right methods for reaching their targets. The company should encourage their employees to take challenges to be able to discover who can learn the most from them.</p><p><strong>Sökord: </strong>talent management, key personnel, high flyers, top performers, human resource and human capital management, identification of potential, talent development and high performers.</p><p><strong>Omfång, sidor:</strong> 82</p><p><strong>Antal ref/källor:</strong> 43</p>
865

<em>Critical Success Factors for effective</em> <em>risk management procedures in financial industries</em> : A study from the perspectives of the financial institutions in Thailand

Na Ranong, Prapawadee, Phuenngam, Wariya January 2009 (has links)
<p>Risk management has become an important topic for financial institutes, especially since the business sector of financial services is related to conditions of uncertainty. The turmoil of the financial industry emphasizes the importance of effective risk management procedures. Consequently, this thesis studies<em> “</em><em>What are the critical success factors for effective risk management procedures in financial industries?</em><em>”</em> This research question was formulated in order to gain a better understanding of risk management procedures and to examine the critical success factors for effective risk management procedures.</p><p>To explore the importance of critical success factors in a practical context, we used the quantitative method of a self-completion questionnaire in order to collect data from a selection of financial institutions in Thailand. Financial institutions include banks, the stock exchange, insurance, stock securities, asset management and so on. Due to the fact that top-level management is directly responsible for risk management, the target groups included a range of positions from supervisors to board of directors.</p><p>This research found a set of seven critical success factors which can be used as a guideline on how to increase the effectiveness of risk management procedures. These factors are (1). Commitment and support from top management, (2) Communication, (3) Culture, (4) Information technology (IT), (5) Organization structure, (6) Training and (7) Trust. Because risk management is an important part of the financial industry, effectiveness is vital to increase project success. These seven factors can increase the effectiveness of risk management procedures from the perspective of the financial industry in Thailand.</p>
866

Payment Solutions for Services in Interactive TV : A Comparative Evaluation of Electronic Payment Systems / Betalningslösningar för tjänster i interaktiv TV : En jämförande utvärdering av elektroniska betalningssystem

Aminoff, Fredrik, Dettel, Johan January 2004 (has links)
<p>The market for digital TV is developing and some industry actors focus on interactive TV. Interactive content and services that previously only were able to use through a standard PC are now available to use through the TV set. To distribute the services to the TV a so called set top box with broadband connection needs to be used. Such a box can be described as a unit where a standard PC and a digital TV receptor are integrated.</p><p>This thesis aims to investigate the market for electronic payment solutions with a focus on payment for interactive content and services in digital TV. The presumptive services are many which lead to a relative complex analysis of how they should be paid for. What kind of service is it really to be paid for? </p><p>In order to conduct an appropriate analysis this thesis contains an identification of five different service-/content types. The grouping we have conducted is in so called On Demand services, Voice over IP, Shopping, Interactive TV and web services. In order to be able to conduct a relevant assessment of how the distributed services should be paid for the understanding of the market situation is utterly important. Therefore the thesis contains a pre study of the different market actors that can be related to a set top box and interactive TV. </p><p>The study of eight different actors on the Swedish market provides an overview of content providers’ as well as payment companies’ view on how interactive content and services should be paid for. The result from the thesis is a recommendation on how an electronic payment solution should be designed and important aspects to think of. One of the key outcomes is that different services needs different types of payment solutions which implies that you should first decide on what type of services that are to be provided before a decision is made on the payment solution. </p><p>A byproduct from the thesis is the analysis model that facilitates analysis of services as well as payment solutions and - methods related to electronic payments and interactive media.</p>
867

Implementation of Flash Analog-to-Digital Converters in Silicon-on-Insulator Technology

Säll, Erik January 2005 (has links)
<p>High speed analog-to-digital converters (ADCs) used in, e.g., read channel and ultra wideband (UWB) applications are often based on a flash topology. The read channel applications is the intended application of this work, where a part of the work covers the design of two different types of 6-bit flash ADCs. Another field of application is UWB receivers.</p><p>To optimize the performance of the whole system and derive the specifications for the sub-blocks of the system it is often desired to use a topdown design methodology. To facilitate the top-down design methodology the ADCs are modeled on behavioral level. The models are simulated in MATLAB®. The results are used to verify the functionality of the proposed circuit topologies and serve as a base to the circuit design phase.</p><p>The first flash ADC has a conventional topology. It has a resistor net connected to a number of latched comparators, but its thermometer-tobinary encoder is based on 2-to-1 multiplexers buffered with inverters. This gives a compact encoder with a regular structure and short critical path. The main disadvantage is the code dependent timing difference between the encoder outputs introduced by this topology. The ADC was simulated on schematic level in Cadence® using the foundry provided transistor models. The design obtained a maximum sampling frequency of 1 GHz, an effective resolution bandwidth of 390 MHz, and a power consumption of 170 mW.</p><p>The purpose of the second ADC is to demonstrate the concept of introducing dynamic element matching (DEM) into the reference net of a flash ADC. This design yields information about the performance improvements the DEM gives, and what the trade-offs are when introducing DEM. Behavioral level simulations indicate that the SFDR is improved by 11 dB when introducing DEM, but the settling time of the reference net with DEM will now limit the conversion speed of the converter. Further, the maximum input frequency is limited by the total resistance in the reference net, which gets increased in this topology. The total resistance is the total switch on-resistance plus the total resistance of the resistors. To increase the conversion speed and the maximum input frequency a new DEM topology is proposed in this work, which reduces the number of switches introduced into the reference net compared with earlier proposed DEM topologies. The transistor level simulations in Cadence® of the flash ADC with DEM indicates that the SFDR improves by 6 dB compared with when not using DEM, and is expected to improve more if more samples are used in the simulation. This was not possible in the current simulations due to the long simulation time. The improved SFDR is however traded for an increased chip area and a reduction of the maximum sampling frequency to 550 MHzfor this converter. The average power consumption is 92 mW.</p><p>A goal of this work is to evaluate a 130 nm partially depleted silicon-oninsulator (SOI) complementary metal oxide semiconductor (CMOS) technology with respect to analog circuit implementation. The converters are therefore implemented in this technology. When writing this the ADCs are still being manufactured. Since the technology evaluation will be based on the measurement results the final results of the evaluation are not included in this thesis. The conclusions regarding the SOI CMOS technology are therefore based on a literature study of published scientific papers in the SOI area, information extracted during the design phase of the ADCs, and from the transistor level circuit simulations. These inputs indicate that to fully utilize the potential performance advantages of the SOI CMOS technology the partially depleted SOI CMOS technology should be exchanged for a fully depleted SOI CMOS technology. The manufacturing difficulties regarding the control of the thin-film thickness must however first be solved before the exchange can be done.</p> / Report code: LiU-Tek-Lic-2005:68.
868

Kvinnliga yrkesmässiga nätverks betydelse för ledarskapet och karriären

Jantell, Frida, Dolfsdotter, Lina January 2008 (has links)
<p>In today’s society there is an ongoing debate concerning gender distribution amongst the top executives and there is a clear distinction between the men and women in leading positions. The reason for this can be because men and women to a certain degree conduct leadership differently. It is said that men are more focused on task oriented leadership while women seem to focus on a relation oriented and more interactive leadership. A leader’s success could be due to his or her ability to set up and use a network. Through professional networks a leader can get in touch with other people with similar life and work conditions and therefore this study was conducted to examine what effects the professional female network has contributed in the career developments of female top executives?</p><p>To answer the question the study begins with the collections of theoretical knowledge concerning the subject followed with in-depth interviews from picturing the real world. With the help of four female top executives, who all are active in the professional female network, empirical data could be collected to be compared with the theoretical references. The study showed that the professional female network had no major impact on the career advancement with the female top executives but that on the other hand it contributed to the personal development.</p><p>For women the work realm and the private realm are closely interconnected which means that family situations have constitute a problem for career advancement for female top executives. The opportunities female top executives encounter lies on the fact of being a woman as they then stand out on the claimed gender distribution.</p>
869

Den internationella kontextens påverkan över en nations demokratiseringsprocess under transitionen från ett auktoritärt styre till ett demokratiskt  -  En analytisk kategorisering

Hassan, Alexander January 2009 (has links)
<p><strong>Abstract</strong></p><p><em>Bachelor thesis in political science by Alexander Hassan, autumn 2008, “Effects of external factors on a nations democratisation process during the transition from authoritarian to electoral democratic rule – A categorical analysis”</em></p><p><em>Supervisor: Tomas Sedelius</em></p><p>In recent years globalization has become a hot topic in understanding the world we live in today. Globalization has indeed had a great impact on international relations and with it a great influence on the domestic conditions that determine a nation’s possibilities. It is therefore rational to hold true that this also would apply to a nation’s democratic process. This basic notion is what lies as a foundation for the thesis, where the purpose of the study is to examine the relatively new field of the international context and its significance on democratisation.</p><p>The aim of the study is to examine and determine, through a categorical analysis, the different forms and roles that the external factors can take during the process leading up to the transition and implementation of an electoral democracy, the most basic form of democracy.</p><p>The thesis thus has demanded the study and infusion of all discourses within the field of democratisation processes, as the only way to produce the roles and forms of the international contexts impact on the domestic process is through the study and determination of the different domestic spheres associated with the process.</p><p>The different forms of external influences have been studied within the confines of the third wave of democracy, and their roles in the democratic process determined depending on the respective domestic spheres they affect. The significant result of the studies where chiefly that all forms of external influence have the possibility to affect the democratisation process indirectly as well as directly. Where direct influence is exerted within the political sphere of the nation; where the actual transition takes place, and the indirect influence is exerted through the socio-economical and cultural sphere; which exerts its influence in the process through the political sphere. </p><p>The results thus show that it is hard to draw the conclusion that an indirect form of influence would be superior to the direct approach or vice versa, as both are prevalent in successful democratic transitions.</p>
870

Top-Quark and Charged Higgs Boson Production at Hadron Colliders : Data Analysis at the DØ Experiment and Simulations for the ATLAS Detector

Gollub, Nils January 2005 (has links)
<p>This thesis treats two different projects, both aiming at experimental tests at hadron colliders of some specific predictions of the Standard Model (SM) of particle physics and of its Minimal Supersymmetric extension (MSSM). The thesis is based on four papers.</p><p>Papers I-III study the discovery potential for a heavy charged Higgs boson of the ATLAS experiment at the Large Hadron Collider (LHC). Charged Higgs bosons are part of the Higgs sector in many extensions to the SM and their detection would be an unambiguous sign of new physics.</p><p>If the charged Higgs boson is heavier than the top quark, its dominant decay mode is into a top and a bottom quark. Searches in this decay channel at ATLAS are difficult mainly due to the large top-quark pair-production background. The possible gain obtained when requiring 4 b-tagged jets for the signal events is studied, but no significant improvement compared to an analysis requiring 3 b-tagged jets is found.</p><p>If the masses of supersymmetric particles are sufficiently small, heavy charged Higgs bosons can decay into a chargino-neutralino pair. We show that in this decay channel charged Higgs bosons can be detected, given a favourable choice of parameters governing the MSSM.</p><p>In a large-mass-splitting MSSM scenario, the charged Higgs decay into a W boson and a neutral Higgs can have a large branching fraction. We conclude, however, that charged Higgs searches in this decay channel are made difficult by a large, irreducible SM background.</p><p>Paper IV describes a measurement of the top-quark pair production cross-section performed with the DØ detector at the Tevatron collider. Signal events in the muon+jets decay channel are selected using topological event characteristics and a preliminary result of σ(ttbar)=3.8 +1.1-1.1(stat) +0.9-0.8(syst) +0.3-0.2(lumi) pb is obtained using an integrated luminosity of 363/pb.</p>

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