• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 59
  • 57
  • 20
  • 18
  • 12
  • 5
  • 5
  • 4
  • 3
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 208
  • 47
  • 43
  • 35
  • 19
  • 18
  • 16
  • 15
  • 15
  • 12
  • 12
  • 11
  • 10
  • 10
  • 9
  • 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.
101

Network Security Analysis and Summary in Taiwan

Fang, Jia-Ching 30 July 2003 (has links)
With the increasing reliance on the Internet and computers, threats also increase. More and more foundations, companies and tools of computer network security emerge to defense the Internet. To prevent the attacks form crackers, plenty of resources about network security were developed on the Internet and people can get the resource they want as long as they know where the professional network security information is. But from another point of view, too much information would become a great burden to general users on the Internet, because they have no idea what information is the most important. This make them confuse, and the only thing they can do is do nothing. They need summarized security information and the advise for his own system and services, instead of all system security information. In this research, we integrate the systems in TWCERT/CC and discover the most helpful information to those who access the Internet in Taiwan, such as, the most threatened vulnerabilities in Taiwan. The information is like the SANS TOP 20. The unity of the entire system in TWCERT/CC could give administrators more specific and summarized information and their prior job is to fix the most vulnerable holes according to the information offered. Key words: network security, critical Internet security vulnerabilities, incident report, SAS, Security Auditing System, TWCERT/CC
102

Globalisering och miljöarbete inom multinationella företag / Globalization and environmental work within multinational companies

Sangby, Katarina January 2002 (has links)
<p>The environment became an established issue on the international political agenda after World War 2. How to preserve natural resources became an issue that concerned several powerful participants, affected by changed conditions in the environmental legislation. This paper is a study of the growing environmental work within the multinational Swedish corporations Boliden, IKEA and SAS and how it was affected by the globalization. The material studied is environmentally related information produced by the companies and also interviews with the Environmental Managers. The information provided has been analyzed and compared with well-known opinions of globalization, trying to find out how the process of globalization has affected the handling of environmental work within the companies. The conclusion is the globalization brings several disadvantages, but it also results in an international legislation and co-operation between different participants, something that does have a positive effect on the environment.</p>
103

Emerging Tendencies in the European Airline Industry : an investigation of SAS and Ryanair -

Jacob, Mandy, Jakesova, Zuzana January 2003 (has links)
<p>Background: The airline industry is unique and fascinating. It was protected through government controls until the early 1980s. However, due to deregulation policy the industry opened to free competition. As a result, collaborations and alliances were formed and low budget airlines were able to enter the market. </p><p>Purpose: The purpose of this thesis is to present the current stage of the European airline industry by investigating the strategies of Ryanair and SAS with the help of strategic management tools. </p><p>Procedure: Two companies were chosen, Ryanair as a low budget airline and SAS as a mature airline. The investigation was based on secondary data found in financial -, annual -, business - and company reports as well as in independent analyst reports and on the Internet. </p><p>Results: Ryanair’s and SAS’ strategies differ a lot. While Ryanair is focusing on lowest costs it is able to offer low fare tickets but also puts effort into increasing service. On the other hand, SAS’ complicated situation in the weak industry leads to many strategic adjustments. Its diverse choice of prices and services underlines its current instability. Concerning the European airline industry, moves toward consolidation are observable. The industry is reshaped</p>
104

Traditionella flygbolags åtgärder efter lågprisflygets inträde på marknaden : En fallstudie av SAS &amp; Finnair

Massaro, Rosa Maria, Witmarker, Lisette January 2006 (has links)
The de-regulation of commercial air traffic in the early 1990’s lead to that many new airline companies entered the market. Many of these new actors were low budget airlines which meant that the traditional airlines met a new type of competition. This situation contributed to the fact that ticket prices dropped in many countries. It has become more and more common that the traveller prefers to fly with low budget airlines rather than with the traditional airlines. That this is causing a major problem becomes quite evident when reading about their economic losses as they appear in the reports handed in by many of the worldwide traditional airline companies in the last few years. This essay deals with the effects that resulted among the traditional airline companies from the entrance of low budget airlines. The purpose was to examine what issues the traditional airlines actively had to meet in order to stay competitive. We were also interested in finding out what measures they actually had taken. This essay is based on a qualitative method, a casestudy in the form of deep interviews. The objects of the study chosen were persons working for the airline companies SAS and Finnair. The bases for the study are theories about competitive strategies, positioning, quality of service, marketing mix and segmentation. In the light of these theories we put together sufficient questions to ask at the interviews to ensure a solid result that answered the purpose and problem of this essay. The result of the study showed that both SAS and Finnair at all times work in a number of ways to adjust themselves to the current market situation. The results clearly shows that both SAS and Finnair have been forced to adapt to the changes in the price development to remain competitive. The most noticeable measure implemented by SAS and Finnair is that they have lowered their ticket prices in order to maintain their customers. Our conclusion states that the effects that has resulted among the traditional airlines are changes of their pricing and quality of service. Even positioning and the competitive strategies of the companies have been affected. / Avregleringen av flygmarknaden i början av 1990-talet ledde till att många flygbolag äntrade marknaden. Många av dessa nya aktörer är lågprisflygbolag vilket har lett till en ökad konkurrens mot de traditionella flygbolagen. Denna situation har även bidragit till att biljettpriserna har sjunkit i många länder. Det blir allt vanligare att resenärerna väljer att flyga med lågprisflygbolag i stället för att välja att resa med de traditionella flygbolagen. Detta torde vara ett stort problem för de traditionella flygbolagen. Inte minst tydligt blir det i beaktande av de förluster som många av dessa flygbolag, världen över, redovisat de senaste åren. Denna uppsats behandlar de faktorer som har påverkats hos de traditionella flygbolagen efter lågprisflygets inträde på marknaden. Syftet med vår studie var att ur ett företagsperspektiv undersöka vilka åtgärder som vidtagits av de traditionella flygbolagen samt om deras strategier ändrats till följd av lågprisflygets inträde på marknaden. Uppsatsen bygger på en kvalitativ metod där det har gjorts en fallstudie i form av djupintervjuer. Undersökningsobjekten som valdes är flygbolagen SAS och Finnair. Till grund för undersökningen ligger teorier om konkurrensstrategier, positionering, tjänstekvalitet, marknadsföringsmixen och segmentering. Utifrån teorierna har intervjufrågor utformats vilka har gett ett relevant underlag för att kunna besvara syftet och problemformuleringen. Undersökningen visade att både SAS och Finnair arbetar med en rad olika strategier för att hela tiden vara anpassade till den rådande marknadssituationen. Resultatet visar tydligt att både SAS och Finnair har tvingats följa med i prisutvecklingen för att vara fortsatt konkurrenskraftiga. Den mest konkreta åtgärd som vidtagits av SAS och Finnair är att de båda flygbolagen har sänkt sina priser för att inte tappa alltför många kunder. I slutsatsen framkommer det att en av de faktorer som har påverkats till följd av den nya konkurrensutsatta marknadssituationen är prissättningen. Ytterligare faktorer som påverkats är tjänstekvalitet och konkurrensstrategier.
105

Analysis of Dependently Truncated Sample Using Inverse Probability Weighted Estimator

Liu, Yang 01 August 2011 (has links)
Many statistical methods for truncated data rely on the assumption that the failure and truncation time are independent, which can be unrealistic in applications. The study cohorts obtained from bone marrow transplant (BMT) registry data are commonly recognized as truncated samples, the time-to-failure is truncated by the transplant time. There are clinical evidences that a longer transplant waiting time is a worse prognosis of survivorship. Therefore, it is reasonable to assume the dependence between transplant and failure time. To better analyze BMT registry data, we utilize a Cox analysis in which the transplant time is both a truncation variable and a predictor of the time-to-failure. An inverse-probability-weighted (IPW) estimator is proposed to estimate the distribution of transplant time. Usefulness of the IPW approach is demonstrated through a simulation study and a real application.
106

Strategiska beteenden inom den europeiska flygindustrin

André, Madeleine, Ericson, Katja, Rautila, Malin January 2010 (has links)
<p>Syftet är att skapa en förståelse för strategiska beteenden hos flygbolag i Europa, under en tid som präglas utav finansiell oro, detta då människor i allt högre grad använder sig utav flyg som transportmedel. Vid utförandet av denna uppsats har en kvalitativ forskningsmetod använts samtidigt som den präglats av en induktiv ansats, då utgångspunkten är empirin för att sedan tillämpa passande teorier på det empiriska materialet. Insamlandet av det empiriska materialet har genomförts med hjälp av en tvärsnittsstudie utav sex olika flygbolag, vi har då valt att enbart använda oss av sekundära källor, då vi anser att detta är passande för denna uppsats. När valet av flygbolag gjordes var kravet att bolagen skulle finnas inom Europa och bedriva flygtrafik till och från Sverige.</p><p><strong> </strong></p>
107

Comparação de ajustes do modelo de Gompertz a dados de crescimento

Sallum Neto, Farid [UNESP] 07 February 2013 (has links) (PDF)
Made available in DSpace on 2014-08-13T14:50:46Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-02-07Bitstream added on 2014-08-13T18:00:39Z : No. of bitstreams: 1 000756908.pdf: 521999 bytes, checksum: c92d8043980849d8b21f239dd04dac21 (MD5) / Em análise de modelo de crescimento com o objetivo de representar o desenvolvimento de organismos vivos por um período maior que sua fase inicial, utiliza-se, frequentemente, modelos não lineares. O objetivo deste trabalho foi ajustar o modelo não-linear de Gompertz utilizando o software SAS através de três estruturas diferentes: 1) modelo de efeitos fixos; 2) modelo autorregressivo de primeira ordem e 3) modelo de efeito misto a um conjunto de dados de crescimento em peso de ratos da linhagem Rattus norvegicus e para um conjunto de dados de crescimento em peso de vacas de três raças: Flamengas, Guernsey-Gir e Holandesas, para verificar o melhor modelo para os conjuntos de dados obtidos. Para tal, optou-se por seis critérios estatísticos como avaliadores de ajuste. Os critérios foram: Quadrado médio do resíduo, critério de informação de Akaike (AIC), critério de informação Bayesiano (BIC), erro de predição médio (EPM), resíduos nos pontos iniciais, chamadores 0, usado para avaliar o ajuste nas primeiras observações e um índice sendo um valor considerado como avaliador no final do ajuste (calculado pela razão entre os 20% dos maiores valores estimados e a assíntota estimada). Além destes, foram feitos testes de Durbin-Watson e Breusch-Pagan para verificar a independência dos resíduos e a heteroscedasticidade, respectivamente. Os resultados mostram que, em muitas repetiçõees, onde havia a necessidade de correção da autocorrelação e heterocedasticidade, o modelo autorregessivo de primeira ordem foi o melhor ajuste. Já em relação ao ajuste único, nos casos em que a autocorrelação foi significativa, o modelo autorregressivo foi o melhor segundo os critérios e, quando a autocorrelação foi não significativa, o modelo de efeitos fixos foi o melhor modelo / In growth model analyzing to represent the development of organisms for a larger period than its initial phase, it nonlinear models are often used . The aim of this work was to adjust the nonlinear Gompertz model using the software SAS by three different structures: 1) fixed effects model, 2) first-order autoregressive model and 3) mixed-effects model to a data of growth of female and male rats Rattus norvegicus and to a data of growth of three breeds cow to verify the best model for the data obtained. To attach the objective, six criteria was chosen as evaluators of statistical adjustment. The criteria were: residual mean square, Akaike information criterion (AIC), Bayesian information criterion (BIC), mean prediction error (EPM), residues in starting points, called res 0, used to assess the fit in the first observations and an index value being considered as an evaluator at the end of adjustment (calculated as the ratio between 20% of the largest estimated values and estimated asymptote). In addition, Durbin-Watson and Breusch-Pagan tests were performed to verify the independence of waste and heteroscedasticity, respectively. The results show that in many repetitions, where was need a correction of autocorrelation and heteroscedasticity, the first order autoregressive model was the best fit. In relation to the single adjustment, where the autocorrelation was significant, the autoregressive model was the best, according to the criteria utilized, and when the autocorrelation was not significant, the fixed effects model was the best model
108

Comparação de ajustes do modelo de Gompertz a dados de crescimento /

Sallum Neto, Farid. January 2013 (has links)
Orientador: Lídia Raquel de Carvalho / Banca: Jose Silvio Govone / Banca: Silvio Sandoval Zocchi / Resumo: Em análise de modelo de crescimento com o objetivo de representar o desenvolvimento de organismos vivos por um período maior que sua fase inicial, utiliza-se, frequentemente, modelos não lineares. O objetivo deste trabalho foi ajustar o modelo não-linear de Gompertz utilizando o software SAS através de três estruturas diferentes: 1) modelo de efeitos fixos; 2) modelo autorregressivo de primeira ordem e 3) modelo de efeito misto a um conjunto de dados de crescimento em peso de ratos da linhagem Rattus norvegicus e para um conjunto de dados de crescimento em peso de vacas de três raças: Flamengas, Guernsey-Gir e Holandesas, para verificar o melhor modelo para os conjuntos de dados obtidos. Para tal, optou-se por seis critérios estatísticos como avaliadores de ajuste. Os critérios foram: Quadrado médio do resíduo, critério de informação de Akaike (AIC), critério de informação Bayesiano (BIC), erro de predição médio (EPM), resíduos nos pontos iniciais, chamadores 0, usado para avaliar o ajuste nas primeiras observações e um índice sendo um valor considerado como avaliador no final do ajuste (calculado pela razão entre os 20% dos maiores valores estimados e a assíntota estimada). Além destes, foram feitos testes de Durbin-Watson e Breusch-Pagan para verificar a independência dos resíduos e a heteroscedasticidade, respectivamente. Os resultados mostram que, em muitas repetiçõees, onde havia a necessidade de correção da autocorrelação e heterocedasticidade, o modelo autorregessivo de primeira ordem foi o melhor ajuste. Já em relação ao ajuste único, nos casos em que a autocorrelação foi significativa, o modelo autorregressivo foi o melhor segundo os critérios e, quando a autocorrelação foi não significativa, o modelo de efeitos fixos foi o melhor modelo / Abstract: In growth model analyzing to represent the development of organisms for a larger period than its initial phase, it nonlinear models are often used . The aim of this work was to adjust the nonlinear Gompertz model using the software SAS by three different structures: 1) fixed effects model, 2) first-order autoregressive model and 3) mixed-effects model to a data of growth of female and male rats Rattus norvegicus and to a data of growth of three breeds cow to verify the best model for the data obtained. To attach the objective, six criteria was chosen as evaluators of statistical adjustment. The criteria were: residual mean square, Akaike information criterion (AIC), Bayesian information criterion (BIC), mean prediction error (EPM), residues in starting points, called res 0, used to assess the fit in the first observations and an index value being considered as an evaluator at the end of adjustment (calculated as the ratio between 20% of the largest estimated values and estimated asymptote). In addition, Durbin-Watson and Breusch-Pagan tests were performed to verify the independence of waste and heteroscedasticity, respectively. The results show that in many repetitions, where was need a correction of autocorrelation and heteroscedasticity, the first order autoregressive model was the best fit. In relation to the single adjustment, where the autocorrelation was significant, the autoregressive model was the best, according to the criteria utilized, and when the autocorrelation was not significant, the fixed effects model was the best model / Mestre
109

Modélisation de la prévision de défaillance des entreprises par des approches statiques et dynamiques : réseaux de neurones, réseaux bayésiens, modèles de durée et dichotomiques / Modeling of business failure prediction by statistic and dynamic approaches : neural networks, Bayesian networks, duration and dichotomous models

Abid, Ilyes 15 November 2011 (has links)
L'objectif de cette thèse est d’étudier différentes méthodes de prévision de la défaillance d'entreprises aussi bien en statique qu'en dynamique. Plus précisément, dans l'approche statique, nous avons recouru aux méthodes de sélection des variables discriminantes en utilisant les réseaux de neurones. Nous avons ainsi proposé deux nouvelles procédures relevant de ces méthodes.La première, fondée sur le critère HVS, intitulée HVS-AUC, nous a permis i) de construire un modèle plus parcimonieux par rapport à l’ADL ; ii) de dégager un ensemble de variables stables à la fois non conjoncturelles et avec un fort pouvoir explicatif. A l'inverse, la seconde technique est basée sur la procédure forward ou plus exactement sur forward-AUC. Cette méthode fait apparaître des résultats comparables à l'ADL mais avec moins de variables explicatives. Elle permet notamment de détecter les ratios jugés les plus pertinents selon ADL et HVS-AUC.Nous avons de plus utilisé des méthodes d'apprentissage de structure de réseaux bayésiens pour essayer d'améliorer la performance de classification des entreprises. Nous avons mobilisé une technique intitulée "Max-Min Hill-Climbing" ou MMHC. Nous avons analysé les performances de classification d'un algorithme combiné entre MMHC et le modèle de base d'un réseau bayésien naïf (BN). Cette nouvelle méthode a été nommée BN-MMHC (Bayes naïf augmentée par MMHC). Les résultats obtenus confirment néanmoins l'opinion dominante : pour ce qui est du pouvoir discriminant, aucune structure ne semble à même de concurrencer BN de manière significative.Dans la deuxième approche dynamique, nous avons mis plus l'accent sur les facteurs non mesurables a priori et sur des facteurs explicatifs impossibles à appréhender dans un cadre statique. Nous avons mobilisé dans un premier volet les variables macroéconomiques pour mieux estimer le risque de défaut. Dans un second volet, nous avons utilisé une modélisation alternative permettant d'appréhender correctement les chocs que peuvent subir les entreprises au cours du temps. De ce fait, nous avons évalué ainsi l'effet de la propagation de ces chocs. / The objective of this thesis is to study bankruptcy prediction models from both static and dynamic viewpoints. More precisely, in the static approach, we used the methods of selecting discriminating variables using the neural networks. We thus proposed two new procedures relating to these methods. The first one is based on the criterion HVS called HVS-AUC and allowed to 1) build a more parsimonious model compared to the LDA, 2) identify a set of variables both static and non-cyclical with a strong explanatory power. Conversely, the second technique is based on the forward procedure, more precisely on forward-AUC. This method shows results comparable to the LDA but with fewer variables. It allows the detection of ratios considered as the most relevant according to LDA and HVS-AUC. We have also used methods of structure learning of Bayesian networks to improve the performance of classification of firms. We have mobilized a technique called "Max-Min Hill-Climbing" or MMHC. Specifically, we plan to analyze the performance of classification of an algorithm that mixes both MMHC and the canonical model of a naive Bayes network (NB). This new method could be called NB-MMHC (naive Bayes augmented by MMH C). The results confirm the prevailing view: as for the discriminatory power, no structure seems to be able to significantly compete with NB. In the second dynamic approach, we put more emphasis on factors not measurable a priori and also on explanatory factors impossible to capture within a static framework. In the first phase, we used the macroeconomic variables to better estimate the risk of default. In the second part, we used an alternative model to better estimate the shocks that firms could undergo over time. We therefore evaluate the propagation effects of theses shocks
110

Vliv vybraných agrotechnických faktorů na strukturní stav půdy při dlouhodobém pěstování jarního ječmene

Pásler, Adam January 2016 (has links)
The thesis deals with the influence of selected agro-technical factors on the structural condition of the soil in the long-term cultivation of spring barley. Assesses the impact of different tillage and crop rotation on the coefficient of structure (KS). Additionally, for selected variants is assessed water stability of soil aggregates. First is a review, which presents characteristic of spring barley and its growing demands, describes the soil structure and its dynamics. Next part consists of statistical evaluation of long-term field experiment in terms of sugar beet growing region. In 2014, it was determined statistically highly significant difference in variants of crop rotation. Crop rotation with a representation of 33.3% cereals showed a higher rate of KS than crop rotation with 66.6 % cereals. Statistically higher KS was observed at a depth of 0-0.15 m, in both years. There was not determined statistically significant difference among the variants of different tillage in both years. Year 2014 in comparison with year 2015 showed a higher coefficient of structure and showed a statistically significant difference. The highest value of water stability of soil aggregates was identified in 2014 at shallow tillage variant, with high significance. In 2015, statistical significance was found at a depth effect only. The outer layer of 0-0.15 m showed higher stability of soil aggregates. With reduction of tillage intensity has been reported to increase the content of agronomically valuable aggregates and also increase their water stability.

Page generated in 0.0344 seconds