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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.
91

Statistical methods for knowledge discovery in adverse drug reaction surveillance

Norén, G. Niklas January 2007 (has links)
<p>Collections of individual case safety reports are the main resource for early discovery of unknown adverse reactions to drugs once they have been introduced to the general public. The data sets involved are complex and based on voluntary submission of reports, but contain pieces of very important information. The aim of this thesis is to propose computationally feasible statistical methods for large-scale knowledge discovery in these data sets. The main contributions are a duplicate detection method that can reliably identify pairs of unexpectedly similar reports and a new measure for highlighting suspected drug-drug interaction.</p><p>Specifically, we extend the hit-miss model for database record matching with a hit-miss mixture model for scoring numerical record fields and a new method to compensate for strong record field correlations. The extended hit-miss model is implemented for the WHO database and demonstrated to be useful in real world duplicate detection, despite the noisy and incomplete information on individual case safety reports. The Information Component measure of disproportionality has been in routine use since 1998 to screen the WHO database for excessive adverse drug reaction reporting rates. Here, it is further refined. We introduce improved credibility intervals for rare events, post-stratification adjustment for suspected confounders and an extension to higher order associations that allows for simple but robust screening for potential risk factors. A new approach to identifying reporting patterns indicative of drug-drug interaction is also proposed. Finally, we describe how imprecision estimates specific to each prediction of a Bayes classifier may be obtained with the Bayesian bootstrap. Such case-based imprecision estimates allow for better prediction when different types of errors have different associated loss, with a possible application in combining quantitative and clinical filters to highlight drug-ADR pairs for clinical review.</p>
92

Analys av ledtid för volymprodukter till en nyckelkund hos Fredriksons Verkstads AB.

Johansson, Frida January 2010 (has links)
No description available.
93

Utvärdering av ett optimeringsprogram för produktionsplanering

Smedh, Hanna January 2009 (has links)
<p>Målet med detta examensarbete är att utvärdera det program, baserat på dynamisk programmering, som tidigare skrivits för att efterlikna TSS:s produktionsplanering. Till att börja med återfinns i arbetet ett kapitel om programmets uppbyggnad, en kortare beskrivning av vart och ett av delprogrammen samt en förteckning över in- och utdata i respektive program. DP-programmet består av 6 sammankopplade exekverbara m-filer som tillsammans räknar ut den optimerade produktionsplaneringen för var och en av planeringsgrupperna. Programmet läser in och formaterar om data och optimerar sedan produktionen för var och en av artiklarna i en planeringsgrupp. Till sist sätter programmet ihop planeringsgruppens alla artikelplaneringar och får då ut ett produktionsalternativ. När genomgången av programmet var klar återstod körningar på nya data. För att få tillgång till dessa nya data gjordes ett besök hos TSS och efter detta utfördes körningar på den kommande periodens planerade tillverkning. Resultatet från dessa körningar visar, likt tidigare resultat, på att man skulle kunna minska sina kostnader ganska rejält genom att dra ner på lagerhållningen. Överlag skulle man enligt programmet kunna minska sina kostnader med drygt 50 %, vilket ändå måste anses som en rejäl vinst.</p> / <p>The aim of this thesis is benchmarking of the program, based on dynamic programming, that earlier was written to imitate the production planning at TSS. This thesis starts with a chapter about the construction of the DP-program, a shorter description of one and each of the program parts and also a list over the in- and output data in each program part. The DP-program consists of six linked MATLAB-files that together produce an optimized production plan for the different planning groups at TSS. The program reads in and reformat the given data and optimize the production of the articles in one group. Finally it compounds all article production plans and give us a production alternative. After running the program with new data the result shows, resembling with previous results, that TSS could be able to make some distinct cost-savings. According to the program, a 50 % decrease of TSS production costs is possible.</p>
94

Skattning av antal träd baserat på data från flygburen laserskanning

Hjelmér, Minna January 2009 (has links)
<p>För att skatta skogsegenskaper utifrån data baserade på flygburen laserskanning används framförallt två olika metoder. Den första (areametoden) bygger uteslutande på höjden där laserpulserna reflekterats och en uppskattning av vilka pulser som reflekterats på marken och vilka som reflekterats i vegetationen. Den andra metoden (segmentmetoden) använder en segmentering av punkterna där laserpulserna reflekterats till enskilda träd. Detta är dock svårt att praktiskt genomföra, därför innehåller varje segment mellan 0 och cirka 10 träd. För att kunna utveckla och utvärdera resultaten insamlas även exakt information från ett antal provytor genom fältstudier. I denna rapport föreslås en icke-parametrisk modell för att skatta antalet träd i ett segment med segmentens area och art som förklarande variabler. Modellen skattas med hjälp av alla segment som finns inom en provyta, även de som inte helt ligger inom provytan. Modellen valideras på tre olika sätt och det visar sig att antalet träd i princip skattas väntevärdesriktigt. Dessutom förbättras inte resultatet nämnvärt med trädart som förklarande variabel.</p> / <p>To estimate forest characteristics based on airborne laser scanning data, two methods are used. The first one is on a raster cell level and uses solely the height of where the laser pulse is reflected and whether it is reflected on the ground or not. The second one is on an individual tree level and uses segmentation of the reflection points into individual trees. However, since it is difficult to segment into individual trees, every segment contains between 0 and about 10 trees. To be able to develop and validate the results, exact information about the trees in different field plots is gathered. In this report a nonparametric model is suggested to predict the number of trees in a segment, with area and species of the segments as predictors. In the estimation of the model, all segments within the field plots are used, even those only partly within. The model is validated in three different ways and estimates the number of trees with very small bias. Also the predictor, species of the segments, does not improve the results much.</p>
95

Linear regression analysis of economic time series /

Koopmans, Tjalling Charles, January 1936 (has links)
Thesis--Universiteit te Leyden. / Summaries in English, Dutch, French and German. Includes bibliographical references (p. [130]-132).
96

Stochastic Epidemic Models : Different Aspects of Heterogeneity

Lindholm, Mathias January 2008 (has links)
This thesis is concerned with the study of stochastic epidemic models for infectious diseases in heterogeneous populations. All diseases treated are of SIR type, i.e. individuals are either Susceptible, Infectious or Recovered (and immune). The transitions between these states are according to S to I to R. The thesis consists of five papers. Papers I and II treat approximations for the distribution of the time to extinction. In Paper I, a sub-community version of the SIR model with demography is considered. The interest is in how the distribution of the time to extinction is affected by varying the degree of interaction between the sub-communities. Paper II is concerned with a two-type version of Bartlett's model. The distribution of the time to extinction is studied when the difference in susceptibility/infectivity between the types of individuals is varied. Papers III and IV treat random intersection graphs with tunable clustering. In Paper III a Reed-Frost epidemic is run on such a random intersection graph. The critical parameter R_0 and the probability of a large outbreak are derived and it is investigated how these quantities are affected by the clustering in the graph. In Paper IV the interest is in the component structure of such a graph, i.e. the size and the emergence of a giant component is studied. The last paper, Paper V, treats the situation when a simple epidemic is running in a varying environment. A varying environment is in this context any external factor that affects the contact rate in the population, but is itself unaffected by the population. The model treated is a term-time forced version of the stochastic general epidemic where the contact rate is modelled by an alternating renewal process. A threshold parameter R_* and the probability of a large outbreak are derived and studied.
97

Existence and convergence of moments of Student’s t-statistic

Jonsson, Fredrik January 2008 (has links)
No description available.
98

On two classic problems in statistics

Thulin, Måns January 2012 (has links)
No description available.
99

Markov Chains, Renewal, Branching and Coalescent Processes : Four Topics in Probability Theory

Nordvall Lagerås, Andreas January 2007 (has links)
This thesis consists of four papers. In paper 1, we prove central limit theorems for Markov chains under (local) contraction conditions. As a corollary we obtain a central limit theorem for Markov chains associated with iterated function systems with contractive maps and place-dependent Dini-continuous probabilities. In paper 2, properties of inverse subordinators are investigated, in particular similarities with renewal processes. The main tool is a theorem on processes that are both renewal and Cox processes. In paper 3, distributional properties of supercritical and especially immortal branching processes are derived. The marginal distributions of immortal branching processes are found to be compound geometric. In paper 4, a description of a dynamic population model is presented, such that samples from the population have genealogies as given by a Lambda-coalescent with mutations. Depending on whether the sample is grouped according to litters or families, the sampling distribution is either regenerative or non-regenerative.
100

Theoretical and Practical Applications of Probability : Excursions in Brownian Motion, Risk Capital Stress Testing, and Hedging of Power Derivatives

Lindell, Andreas January 2009 (has links)
The thesis treats three different areas; (i) Ranked increments of stable processes and ranked excursions of Brownian motion, (ii) Sufficient capital levels for banks, and (iii) Trading strategies for reduction of the fluctuations of revenues for power plants. The first part is a theoretcial investigation involved with the calculation of distribution functions concerning special properties of stable processes. The second part is a description of a framework in which the sufficiency of capital levels for banks can be evaluated. The third part is a typical example of how financial mathematics can be used to derive practical methods applicable in risk management of energy derivatives and real options. Altogether, five papers are presented.

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