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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.
11

Statistical methods to study heterogeneity of treatment effects

Taft, Lin H. 25 September 2015 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / Randomized studies are designed to estimate the average treatment effect (ATE) of an intervention. Individuals may derive quantitatively, or even qualitatively, different effects from the ATE, which is called the heterogeneity of treatment effect. It is important to detect the existence of heterogeneity in the treatment responses, and identify the different sub-populations. Two corresponding statistical methods will be discussed in this talk: a hypothesis testing procedure and a mixture-model based approach. The hypothesis testing procedure was constructed to test for the existence of a treatment effect in sub-populations. The test is nonparametric, and can be applied to all types of outcome measures. A key innovation of this test is to build stochastic search into the test statistic to detect signals that may not be linearly related to the multiple covariates. Simulations were performed to compare the proposed test with existing methods. Power calculation strategy was also developed for the proposed test at the design stage. The mixture-model based approach was developed to identify and study the sub-populations with different treatment effects from an intervention. A latent binary variable was used to indicate whether or not a subject was in a sub-population with average treatment benefit. The mixture-model combines a logistic formulation of the latent variable with proportional hazards models. The parameters in the mixture-model were estimated by the EM algorithm. The properties of the estimators were then studied by the simulations. Finally, all above methods were applied to a real randomized study in a low ejection fraction population that compared the Implantable Cardioverter Defibrillator (ICD) with conventional medical therapy in reducing total mortality.
12

Generator maintenance scheduling models in power systems : integrated cost models for generator maintenance strategy under market environment

Al-Arfaj, Khalid Abdulaziz January 2009 (has links)
Change from a regulated to deregulated structure means that, the centralized maintenance system is not valid any more. In the surveyed published literature, there is not a single model which incorporates all maintenance cost components to analyze the effect of different maintenance strategies for generator companies (GENCOs). The work enclosed in this thesis demonstrates that there is a considerable requirement for accurately modelling cost components of the maintenance model, to be used in maintenance scheduling for deregulated power system, in order to attain a superior schedule with major financial and operational impact. This research investigates and models most cost factors that affect the maintenance activities of the deregulated GENCOs, and demonstrates the utilization of the developed cost models in maintenance scheduling. It also presents the data gathering process for the developed maintenance cost model. A generator maintenance scheduling model that considers direct and indirect maintenance costs, opportunity costs (i.e. loss of customer goodwill), effective maintenance strategies, failures, and interruptions is developed. A Genetic Algorithm (GA) based approach is employed to achieve maintenance schedules to various generators maintenance scenarios. An Analytical Hierarchy Process (AHP) approach is proposed for modelling customer goodwill. The maintenance model was redeveloped under the Reliability Centred Maintenance (RCM) strategy to analyze the effect of a maintenance strategy on maintenance costs. Case studies are presented to demonstrate the utilisation of the developed models.The investigation shows that the market prices, opportunity costs and maintenance strategy have an effect on the final maintenance schedule. The research demonstrates that the cost components are critical factors to achieve an effective maintenance schedule, and they must be considered and carefully modelled in order to reflect more realistic situation for maintenance scheduling of generator units in deregulation environment.
13

Access to Education in Conflict Crises : The Impact of Education in Emergencies Interventions in Armed Conflict

Hanon, Maëlig January 2022 (has links)
Conflict crises have a devastating impact on education. In response, international organisations have increasingly implemented Education in Emergencies (EiE) interventions in seeking to improve the access to education. However, little is known about the impact of these interventions in the context of armed conflict. The literature has mostly focused on the physical barriers that conflict brings to educational access and most of the previous research on the effectiveness of EiE interventions comes from stable low- and middle-income countries. By answering the question ‘How do Education in Emergencies interventions affect the access to education in conflict crises?’, this study seeks to contribute to this understudied field by first discussing the non-physical ‘opportunity costs’ conflict barriers to educational access. Subsequently, this study moves on to demonstrate the significance of particular components that EiE interventions may hold that are able to address these specific conflict barriers. The argument is tested through a qualitative comparative study of two international organisations that implement EiE programmes in Colombia. The empirical findings demonstrate the importance of a variety of different components of EiE interventions in improving access to education in conflict contexts, with indeed many of these addressing ‘opportunity costs’.
14

Generator Maintenance Scheduling Models in Power Systems. Integrated Cost Models for Generator Maintenance Strategy under Market Environment.

Al-Arfaj, Khalid A. January 2009 (has links)
Change from a regulated to deregulated structure means that, the centralized maintenance system is not valid any more. In the surveyed published literature, there is not a single model which incorporates all maintenance cost components to analyze the effect of different maintenance strategies for generator companies (GENCOs). The work enclosed in this thesis demonstrates that there is a considerable requirement for accurately modelling cost components of the maintenance model, to be used in maintenance scheduling for deregulated power system, in order to attain a superior schedule with major financial and operational impact. This research investigates and models most cost factors that affect the maintenance activities of the deregulated GENCOs, and demonstrates the utilization of the developed cost models in maintenance scheduling. It also presents the data gathering process for the developed maintenance cost model. A generator maintenance scheduling model that considers direct and indirect maintenance costs, opportunity costs (i.e. loss of customer goodwill), effective maintenance strategies, failures, and interruptions is developed. A Genetic Algorithm (GA) based approach is employed to achieve maintenance schedules to various generators maintenance scenarios. An Analytical Hierarchy Process (AHP) approach is proposed for modelling customer goodwill. The maintenance model was redeveloped under the Reliability Centred Maintenance (RCM) strategy to analyze the effect of a maintenance strategy on maintenance costs. Case studies are presented to demonstrate the utilisation of the developed models.The investigation shows that the market prices, opportunity costs and maintenance strategy have an effect on the final maintenance schedule. The research demonstrates that the cost components are critical factors to achieve an effective maintenance schedule, and they must be considered and carefully modelled in order to reflect more realistic situation for maintenance scheduling of generator units in deregulation environment.
15

Intertemporal Choice and Enrollment: Exploring the Influence of Latency on Enrollment Yield within the Recruitment Funnel

Guzman, Gregory A. January 2014 (has links)
No description available.
16

Overcoming logistical problems in organizations : The case of Elicom AB

Khaki Boukani, Farzad January 2007 (has links)
This paper presents an empirical case study of the company Elicom AB. Elicom AB is producing electrical devices that are mostly used in the telecom market where the main customers are. The data that was collected from this case was collected through observations, interviews and the study of company documents. This allowed the author to compare secondary and primary data, as well as quantitative and qualitative information. The problem, the company is facing in the logistical field, was discovered in the labeling production process. The production of the labels is unnecessarily complicated and inefficient due to incompatibility of the computer systems. Therefore some parts of the label design have to be made manually, even though the company has a scanning system. When analyzing the problem in detail it became clear to the author that it could be fixed easily and fast and that the key individuals involved in the process already knew the answer to the problem. Therefore the question of the underlying cause of the problem arose. Why has the company not yet fixed the problem if it is so obvious and also everybody in the organization is aware of it? When further reanalyzing the problem, the author discovered a second problem, which was not lying in the logistics of the production process, but had its roots in the organizational structure. The problem of interfering authorities and responsibilities made it impossible for the company to overcome the changes needed to solve the logistical problem in the labeling production process. Therefore this problem must be addressed first, together with overcoming the obstacles to change in the organization, to make a problem-solving-process in the logistical area possible. In general this paper shows the interrelation of logistics with organization and the highly complex environment manufacturing companies are facing when it comes to changes in the production process. / Denna uppsats är en empirisk fallstudie som gjordes på Elicom AB. Elicom AB är en tillverkare av elektrisk apparatur som till mestadels används inom Telecom-marknaden, vilket också är den marknad som de flesta av företagets kunder finns inom. Den data som författaren samlat in är igenom observationer, intervjuer samt analys av olika interna företagsdokument. Detta gjorde att författaren kunde jämföra sekundär-och primär-data samt kvalitativ-och kvantitativ-data. Problemet som företaget hade framför sig var av logistisk karaktär och upptäcktes i etikettproduktionsprocessen. Produktionen av etiketter är onödigt komplicerad och ineffektiv pga icke kompatibla datasystem. Därför sker visa delar av skapandet av etiketter manuellt, även om företaget har ett scanning system. Efter viss analys blev det dock klart för författaren att problemet var lätt att ordna upp och att huvudpersonerna som var involverade, i etikett hanteringen, visste om att problemet var lätt löst men gjorde inget åt situationen. Detta ledde till att författaren fråga sig vad den underliggande orsaken, till detta problem, kunde vara. Varför har inte företaget gjort något åt problemet om det har varit uppenbart för dem att problemet existerar? När all information sedan om analyserades, upptäckte författaren ett andra problem vilket inte var inom logistikområdet utan hade sina rötter i organisationens struktur. Problemet med överlappande auktoritet, samt ansvarsområden, gör det omöjligt för företaget att lösa deras logistiska problem inom etiketthanteringen. Därför måste detta problem ses över först, samtidigt som inställningen till förändring måste ändras för att göra det möjligt att skapa en ”problem-lösnings-process” i den logistiska delen. Generellt visar denna fallstudie på relationen mellan logistik- och organisation och på den mycket komplicerade miljön som tillverkande företag ställs inför vid en förändring av sina processer.
17

Overcoming logistical problems in organizations : The case of Elicom AB

Khaki Boukani, Farzad January 2007 (has links)
<p>This paper presents an empirical case study of the company Elicom AB. Elicom AB is producing electrical devices that are mostly used in the telecom market where the main customers are. The data that was collected from this case was collected through observations, interviews and the study of company documents. This allowed the author to compare secondary and primary data, as well as quantitative and qualitative information. The problem, the company is facing in the logistical field, was discovered in the labeling production process.</p><p>The production of the labels is unnecessarily complicated and inefficient due to incompatibility of the computer systems. Therefore some parts of the label design have to be made manually, even though the company has a scanning system. When analyzing the problem in detail it became clear to the author that it could be fixed easily and fast and that the key individuals involved in the process already knew the answer to the problem. Therefore the question of the underlying cause of the problem arose. Why has the company not yet fixed the problem if it is so obvious and also everybody in the organization is aware of it?</p><p>When further reanalyzing the problem, the author discovered a second problem, which was not lying in the logistics of the production process, but had its roots in the organizational structure. The problem of interfering authorities and responsibilities made it impossible for the company to overcome the changes needed to solve the logistical problem in the labeling production process. Therefore this problem must be addressed first, together with overcoming the obstacles to change in the organization, to make a problem-solving-process in the logistical area possible.</p><p>In general this paper shows the interrelation of logistics with organization and the highly complex environment manufacturing companies are facing when it comes to changes in the production process.</p> / <p>Denna uppsats är en empirisk fallstudie som gjordes på Elicom AB. Elicom AB är en tillverkare av elektrisk apparatur som till mestadels används inom Telecom-marknaden, vilket också är den marknad som de flesta av företagets kunder finns inom. Den data som författaren samlat in är igenom observationer, intervjuer samt analys av olika interna företagsdokument. Detta gjorde att författaren kunde jämföra sekundär-och primär-data samt kvalitativ-och kvantitativ-data. Problemet som företaget hade framför sig var av logistisk karaktär och upptäcktes i etikettproduktionsprocessen.</p><p>Produktionen av etiketter är onödigt komplicerad och ineffektiv pga icke kompatibla datasystem. Därför sker visa delar av skapandet av etiketter manuellt, även om företaget har ett scanning system. Efter viss analys blev det dock klart för författaren att problemet var lätt att ordna upp och att huvudpersonerna som var involverade, i etikett hanteringen, visste om att problemet var lätt löst men gjorde inget åt situationen. Detta ledde till att författaren fråga sig vad den underliggande orsaken, till detta problem, kunde vara. Varför har inte företaget gjort något åt problemet om det har varit uppenbart för dem att problemet existerar?</p><p>När all information sedan om analyserades, upptäckte författaren ett andra problem vilket inte var inom logistikområdet utan hade sina rötter i organisationens struktur. Problemet med överlappande auktoritet, samt ansvarsområden, gör det omöjligt för företaget att lösa deras logistiska problem inom etiketthanteringen. Därför måste detta problem ses över först, samtidigt som inställningen till förändring måste ändras för att göra det möjligt att skapa en ”problem-lösnings-process” i den logistiska delen.</p><p>Generellt visar denna fallstudie på relationen mellan logistik- och organisation och på den mycket komplicerade miljön som tillverkande företag ställs inför vid en förändring av sina processer.</p>
18

Ökonomische Analyse forstlicher Bestandesbehandlung / Economic Analysis of Forest Stand Management

Koster, Roman 11 September 2020 (has links)
No description available.
19

Optimal Portfolio Re-Balancing on Fixed Periods using a Cost/Risk Adaptation Model and Stochastic Optimization.

Ehn, Max, Jämte, Marcus January 2023 (has links)
In this thesis we investigate the problem of portfolio re-balancing for fixed periods using a cost/risk adaptation model and stochastic optimization. The cost/risk adaptation model takes theory of optimal liquidity costs and risk preference to build a universe in which we try to find better strategies than conventional ones. The results are focused on the comparison between the conventional execution strategies versus our developed model. We have found that our model outperforms the conventional methods for all assets that has been evaluated, and especially for investors whom value exposure to the markets higher.
20

Economic potential and sectoral impacts of forest-based climate change mitigation

Krause, Michael 04 June 2015 (has links)
Die vermiedene tropische Entwaldung und zusätzliche Aufforstungen sind von zentraler Bedeutung für die Klimawandelvermeidung, üben aber zusätzlichen Druck auf die globalen Landressourcen zur Produktion von Nahrungsgütern, Futtermittel, Fasern, Bioenergie und Rundholz dar. Die Ziele der Studie beziehen sich auf die Analyse der Verzichtskosten in der Land- und Forstwirtschaft sowie das Potential zur Klimawandelvermeidung in globalen Wäldern durch normative und marktbasierte Klimaschutzprogramme. Das globale ökonomische Landnutzungsmodell ''Model of Agricultural Production and its Impact on the Environment'' (MAgPIE) wurde um eine konsistente Landnutzungsdatenbank und den Forstsektor erweitert. Es simuliert die räumlich-explizite Landnutzung und deren Änderungen während die Kosten land- und forstwirtschaftlicher Produktion unter gegebener Nachfrage nach Gütern geschätzt werden. Szenarien zu Klimaschutzmaßnahmen werden verglichen mit Referenzszenarien über Zeithorizonte bis zum Jahr 2100. Die Ergebnisse verweisen auf ein begrenztes Mitigationspotential normativen tropischen Waldschutzes zu geringen zusätzlichen Kosten in der Landwirtschaft. Lateinamerika profitiert von ausreichenden Landreserven und geringem Anstieg in der Güternachfrage und geringer Referenzentwaldung. Die Verlagerung von Emissionen durch regionalen Waldschutz hat Auswirkungen auf die sektoralen Produktionskosten und verringert das globale ökonomische Potential. Die Schlussfolgerungen betreffen 1) den Bedarf an substantieller Ertragssteigerung in Sub-Sahara Afrika als Voraussetzung für die erfolgreiche Umsetzung vermiedener Entwaldung, 2) die erhöhte Gefahr der Verlagerung von Emissionen aus Entwaldung durch die Umsetzung regionaler Klimaschutzprogramme und der Liberalisierung des Holzhandels, 3) das hohe ökonomische Potential integrierter Klimaschutzprogramme zu moderaten Verzichtskosten, sowie 4) die Notwendigkeit zusätzlicher Forschung bezüglich der Unsicherheiten in Parametern und Modellprozessen. / Avoiding tropical deforestation and additional afforestation are of primary importance for climate change mitigation but exert additional pressure on global land resources for the production of food, feed, fibre, bioenergy and timber. The study objectives relate to the analysis of the foregone economic benefits, the opportunity costs, in agriculture and forestry and the climate change mitigation potential of global forests in normative and market-based programmes. The global economic ‘Model of Agricultural Production and its Impact on the Environment'' (MAgPIE) has been extended by a consistent land use database and the forestry sector. It simulates spatially-explicit land use and land use changes while estimating the costs of production in agriculture and forestry to satisfy a prescribed demand. Climate change mitigation scenarios are contrasted to baselines for time horizons up to the year 2100. The results show the limited mitigation potential of normative forest conservation in tropical regions at low additional costs in agriculture. Latin America benefits from sufficient land endowments and low increases in crop demand leading to relatively low baseline deforestation. The displacement of carbon emissions between regions impacts the regional agriculture and forestry production costs and reduces the global economic potential. The conclusions pertain to the 1) need for high rates of yield increase in Sub-Saharan Africa as a precondition for successfully avoided deforestation, 2) increased threat of regional carbon emission leakage from implementing mitigation programmes and liberalized trade of timber, 3) high economic potential of climate change mitigation from integrating afforestation and avoided deforestation at moderate costs, and 4) additional research needs to account for significant uncertainties from growth and cost parameters and model processes.

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