• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 34
  • 22
  • 12
  • 7
  • 6
  • 4
  • 4
  • 4
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 107
  • 24
  • 16
  • 11
  • 10
  • 10
  • 8
  • 8
  • 7
  • 7
  • 7
  • 7
  • 6
  • 6
  • 6
  • 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.
41

Marshallian sources of growth and interdependent location of Swedish firms and households

Sörensson, Robert January 2010 (has links)
This thesis consists of three papers that examine Marshallian sources of growthand interdependent location of Swedish firms and households. Paper [I] examines the impact of static and dynamic knowledge externalitiesand their impact on Swedish market operating firms growth pattern between1997 and 2005. The three types of externalities are: (i) Marshall-Arrow-Romer(MAR), (ii) Jacobs, and (iii) Porter. My empirical findings for the 40 industriescan briefly be summarized in the following points: (i) static MAR, Jacobsand/or Porter externalities are present in all but nine industries; (ii) except for five cases all industries are exposed to one or more of the MAR, Jacobs and/orPorter type of dynamic externalities; (iii) contrary to previous studies but inline with theoretical predictions, we do find positive and significant effects forstatic as well as dynamic Jacobs externalities. Paper [II] focuses on the presence of agglomeration economies in the form of labor pooling and educational matching and their impact on economic growth in Swedish manufacturing and service industries from 1997 to 2005. To accomplish this I employ a translog production function that enables me to decompose the total agglomeration elasticities into returns that accrue to: direct agglomeration effects, an indirect effect of agglomeration at given input levels, a cross agglomeration effect of matching on labor pooling and vice versa. Household services is the single industry where both the labor pooling and matching hypothesis is supported by our data. Publishing is the sole instance of betterinput usage due to matching consistent with the theoretical claim. Paper [III] studies the interdependent location choices of households and firms expressed as population and employment in Swedish municipalities. Using a model of the Carlino-Mills type to investigate the impact of various location attributes such as differences in public revenue and spending patterns, accessibility to jobs and potential workforce, quality of the labor pool, concentration ofcommercial, private and public services. The findings suggest that fiscal factors significantly alters the impact of housing and accessibility attributes compared to exiting studies on Swedish data. Another finding, in line with previous studies, indicate that there is a significant degree of inertia in household and firm location choices.
42

Mixed integer bilinear programming with applications to the pooling problem

Gupte, Akshay 10 August 2012 (has links)
Solution methodologies for mixed integer bilinear problems (MIBLP) are studied in this dissertation. This problem class is motivated using the pooling problem, a multicommodity network flow problem that typically arises in chemical engineering applications. Stronger than previously known results are provided to compare the strengths of polyhedral relaxations of the pooling problem. A novel single node flow relaxation, defined by a bilinear equality constraint and flow balance, is proposed for the pooling problem. Linear valid inequalities in the original space of variables are derived using a well-known technique called lifting. Mixed integer linear (MILP) formulations are proposed for generating feasible solutions to the pooling problem. Some of these MILP models arise from variable discretizations while others possess a network flow interpretation. The effectiveness of these MILP models is empirically validated on a library of medium and large-scale instances. General MIBLPs, not necessarily pooling problems, are solved using extended MILP reformulations. The reformulation is obtained by writing binary representation for each general integer variable. Facet-defining inequalities are provided for the reformulation of each bilinear term. New valid inequalities are also proposed for bilinear terms with a nontrivial upper bound. The proposed reformulation and cutting planes are compared against a global solver on five different classes of MIBLPs.
43

Tools for Maximizing the Efficiency of Protein Engineering

Polizzi, Karen Marie 14 November 2005 (has links)
Biocatalysts offer advantages over their chemical counterparts in terms of their high enantioselectivity and the opportunity to develop more environmentally friendly processes. However, the widespread adoption of biocatalytic processes is hampered by the long development times for enzymes with novel and sufficient activity and adequate stability under operating conditions. Protein engineering, while extremely useful for modifying the properties of protein catalysts in select cases, still cannot be performed rapidly enough for many applications. In order for biocatalysts to become a competitive alternative to chemical catalysts, new tools to make the tailoring of biocatalysts by protein engineering methods speedier and more efficient are necessary. The aim of this work was to develop methods to aid in the faster production of novel biocatalysts. Protein engineering involves two steps: the generation of diversity and the screening or selection of variants with the desired properties. Both of these must be targeted to create a faster protein engineering process. In the case of the former, this work sought to clone and overexpress some template enzymes which would create smaller, more manageable libraries of mutants with a higher likelihood of function by the manipulation of a few focused amino acid residues. For the latter, this work developed and validated a Monte-Carlo simulation model of pooling to increase screening throughput and created a set of vectors to aid in high-throughput screening by eliminating unwanted mutants from the assay procedure entirely.
44

Spatial pooling strategies for image quality assessment

Moorthy, Anush Krishna 03 September 2009 (has links)
Recent image quality assessment (IQA) metrics achieve high correlation with human perception of image quality. Naturally, it is of interest to produce even better results. One promising method is to weight image quality measurements by visual importance. To this end, we describe three strategies - visual fixation-based weighting, quality-based weighting and weighting based on distribution of local quality scores about the mean. By contrast with some prior studies we find that these strategies can improve the correlations with subjective judgment significantly. We demonstrate improvements on the SSIM index in both its multi-scale and single-scale versions, using the LIVE database as a test-bed. / text
45

The Benefit of Capacity Pooling for Repairable Spare Parts

Sahba, Pedram 16 August 2013 (has links)
Capacity pooling in production systems, in the form of production capacity or inventory pooling, has been extensively studied in the literature. While production capacity pooling has been proven to be beneficial, the impact of inventory pooling has been less significant. These results cannot be easily extended to repairable systems due to fundamental differences between repairable and production systems. For one thing, in repairable systems, the demand rate is a function of the number of operational machines, whereas it is exogenous and constant in production systems. In this Thesis, to serve different fleets of machines possibly at different locations, we study whether repair shop pooling is more cost effective than having dedicated on-site repair shops for each fleet. In the first model, we consider transportation delays and related costs, which have been traditionally ignored in the literature. We include on-site spare-part inventories that operate according to a continuous-review base-stock policy. Our numerical findings indicate that when transportation costs are reasonable, repair shop pooling is a better alternative. Next, we model a pooled repair shop that fixes failed components from different k-out-of-n:G systems. We permit a shared spare parts inventory serving all systems and/or reserved spare parts inventories for each system; we call this a hybrid model. The destination for a repaired component can be chosen either on a first-come-first-served basis or by following a static priority rule. Our findings show that both hybrid policies are more cost effective than having separate repair shops and inventories for each system. We propose implementing the multilevel rationing (MR) policy in systems with shared inventory. The MR policy prioritizes classes, and stops serving a class from inventory if the inventory level is below the inventory threshold identified for that class. When there is no inventory, the repaired component is sent to the highest priority class among those with down machines. To approximate the cost of the MR policy, we study an M/G/1//N queueing system serving multiple classes of customers with an unreliable server. Our numerical findings indicate that the MR policy performs as well as the epsilon-optimal policy and outperforms the hybrid policies.
46

The Benefit of Capacity Pooling for Repairable Spare Parts

Sahba, Pedram 16 August 2013 (has links)
Capacity pooling in production systems, in the form of production capacity or inventory pooling, has been extensively studied in the literature. While production capacity pooling has been proven to be beneficial, the impact of inventory pooling has been less significant. These results cannot be easily extended to repairable systems due to fundamental differences between repairable and production systems. For one thing, in repairable systems, the demand rate is a function of the number of operational machines, whereas it is exogenous and constant in production systems. In this Thesis, to serve different fleets of machines possibly at different locations, we study whether repair shop pooling is more cost effective than having dedicated on-site repair shops for each fleet. In the first model, we consider transportation delays and related costs, which have been traditionally ignored in the literature. We include on-site spare-part inventories that operate according to a continuous-review base-stock policy. Our numerical findings indicate that when transportation costs are reasonable, repair shop pooling is a better alternative. Next, we model a pooled repair shop that fixes failed components from different k-out-of-n:G systems. We permit a shared spare parts inventory serving all systems and/or reserved spare parts inventories for each system; we call this a hybrid model. The destination for a repaired component can be chosen either on a first-come-first-served basis or by following a static priority rule. Our findings show that both hybrid policies are more cost effective than having separate repair shops and inventories for each system. We propose implementing the multilevel rationing (MR) policy in systems with shared inventory. The MR policy prioritizes classes, and stops serving a class from inventory if the inventory level is below the inventory threshold identified for that class. When there is no inventory, the repaired component is sent to the highest priority class among those with down machines. To approximate the cost of the MR policy, we study an M/G/1//N queueing system serving multiple classes of customers with an unreliable server. Our numerical findings indicate that the MR policy performs as well as the epsilon-optimal policy and outperforms the hybrid policies.
47

The validity of a three-part criteria for differentiating between delayed pharyngeal swallow and premature spillage secondary to poor oro-lingual control on videofluoroscopy

Flanagan, Liana January 2007 (has links)
Background and Aims The accurate differentiation between a delayed pharyngeal swallow (sensory impairment) and premature spillage secondary to poor oro-lingual control (motor impairment) is essential to effective dysphagia management. However both physiologic abnormalities result in an identical radiographic sign, that of pre-swallow pooling of the bolus in the pharynx. The dysphagia literature does not provide satisfactory guidelines for making this distinction on videofluoroscopy. The purpose of this study was to assess the validity of a three-part rating scale for differentiating between these two impairments. Methods Videofluoroscopy was used to evaluate the swallowing of 29 participants presenting with dysphagia following stroke. Sensory thresholds for these participants were established by electrical stimulation of the anterior faucial pillars. The videofluoroscopic swallowing studies were analysed using the three-part rating scale and results from this were compared to sensory thresholds using Pearson's product moment correlation. Results There was no significant correlation between the three-part criteria and sensory thresholds. Inter-rater reliability for some measures was poor. Conclusions The three-part criteria was not shown to be a valid measure for differentiating between delayed pharyngeal swallow and premature spillage secondary to poor oro-lingual control. Possible explanations for these findings are discussed, including the relevance of faucial pillar sensation to swallowing.
48

La gestion des entrepôts mutualisés et leurs impacts dans les chaînes logistiques / Pooled warehouses management and their impact in supply chain

Makaci, Mourad 02 July 2018 (has links)
La mutualisation des entrepôts est l’une des approches de la logistique collaborative récemment initiée par différents acteurs afin d’améliorer la performance des chaînes logistiques. Les exigences de la grande distribution et l’augmentation des coûts logistiques relatifs aux activités d’entreposage et de transport obligent les entreprises à revoir leurs stratégies de distribution. S’inscrivant dans un paradigme post-positiviste, cette thèse permet de répondre à deux principales questions de recherche issues d’une revue de littérature sur la logistique collaborative : quelles sont les caractéristiques des entrepôts mutualisés ? Quel est l’impact de la présence de l’entrepôt mutualisé dans la chaîne logistique ? Nous avons développé une approche mixant une méthode qualitative de type exploratoire sur sept cas situés en France, complétée par une méthode quantitative de type simulation des flux. L’étude qualitative a permis d’identifier les principales spécificités des entrepôts mutualisés et de proposer une typologie d’entrepôts mutualisés basée sur deux dimensions : le degré de collaboration et le degré de dynamique. Elle a permis également d’identifier les nouveaux indicateurs de performance, les facteurs clés de succès, les principales sources d’incertitude et les risques associés à la mise en place d’entrepôts mutualisés. L’impact de l’entrepôt mutualisé sur la performance de la chaîne logistique a été étudié plus précisément sur un des sept cas précédents, en comparant quatre configurations de flux avec deux politiques de réapprovisionnement, pour lesquelles nous avons proposé une hybridation, et deux profils de demande. Les résultats des simulations montrent que la mutualisation des entrepôts prend tout son intérêt si elle est associée à la mutualisation du transport. Il apparaît également que la politique d’approvisionnement hybride est plus avantageuse que les politiques classiques de point de commande et de recomplètement calendaire. Finalement, cette thèse montre que le contexte de l’entrepôt mutualisé offre d’intéressantes perspectives de recherche autour du lien entre pratique et recherche, de la création de connaissance en gestion des opérations, et de l’impact de la mutualisation sur la performance des chaînes logistiques. / The warehouse pooling is one of the collaborative logistics’ research field, recently introduced by various actors to improve the performance of supply chains. The mass-market retailing requirements as well as the increase logistic costs, relative to the activities of storing and transport, oblige companies to review more in detail their distribution strategies. Consisting of a post-positivist paradigm, this thesis answers two main research questions: What are the characteristics of pooled warehouses? What is the impact of the presence of a pooled warehouse in the supply chain? We have developed an approach combining a qualitative exploratory method on seven cases located in France, supplemented by a quantitative method based on flow simulation. The qualitative study allowed to identify the main specificities of pooled warehouses and proposed a typology of pooled warehouses based on two dimensions: collaboration degree and dynamics degree. Our study also allowed identifying new performance indicators, the key success factors, the main sources of uncertainty and the risks related to pooled warehouse implementation. The impact of a pooled warehouse on the supply chain performance was analyzed more specifically in one of the seven previous cases, comparing four flow configurations with two replenishment policies, for which we proposed hybridization, and two demand profiles. The simulation results show that the pooled warehouse takes all its interest if it is associated with transport pooling. Furthermore, the hybrid procurement policy seems to be more advantageous than the classical policies of traditional reorder point and calendar replenishment. Finally, this thesis shows that the context of the shared warehouse offers interesting research perspectives on the link between practice and research, the creation of knowledge in operations management, and the impact of pooling on the performance of logistics chains.
49

Reformeringen av Försvarsmakten - på vilka grunder? : En fallstudie av Sveriges försvars- och säkerhetspolitiska utveckling under åren 1999 - 2009

Kjellman, Peter January 2012 (has links)
Undersökningen är en fallstudie av de uttalade motiven för reformeringen av den svenska Försvarsmakten under åren 1999-2009, med nedslag i tre försvarspropositioner.Syftet med denna undersökning har varit att analysera de svenska regeringarnas argumentation för den försvarsreform som successivt genomförts under 2000-talet.Detta har studerats med fokus på en förändrad hotbild och förändrad inställning till multilateralt försvarssamarbete genom två olika teorier, det vidgade säkerhetsbegreppet och Pooling and Sharing.Resultatet visar att influenserna av teorierna har ökat, vilket kan förklara delar av reformeringen av försvarspolitiken.
50

Limited liability and non-responsiveness in moral hazard and adverse selection problems

Pires, Henrique Brasiliense de Castro 21 March 2016 (has links)
Submitted by Henrique Brasiliense de Castro Pires (henrique.brasiliense2014@fgvmail.br) on 2016-05-04T18:32:36Z No. of bitstreams: 1 Limited Liability and Non-responsiveness in Moral Hazard and Adverse Selection Problems (1).pdf: 525295 bytes, checksum: 0463596c60f1218d5dfffa8108178df6 (MD5) / Approved for entry into archive by GILSON ROCHA MIRANDA (gilson.miranda@fgv.br) on 2016-05-10T19:09:38Z (GMT) No. of bitstreams: 1 Limited Liability and Non-responsiveness in Moral Hazard and Adverse Selection Problems (1).pdf: 525295 bytes, checksum: 0463596c60f1218d5dfffa8108178df6 (MD5) / Approved for entry into archive by Marcia Bacha (marcia.bacha@fgv.br) on 2016-05-16T19:27:56Z (GMT) No. of bitstreams: 1 Limited Liability and Non-responsiveness in Moral Hazard and Adverse Selection Problems (1).pdf: 525295 bytes, checksum: 0463596c60f1218d5dfffa8108178df6 (MD5) / Made available in DSpace on 2016-05-16T19:28:10Z (GMT). No. of bitstreams: 1 Limited Liability and Non-responsiveness in Moral Hazard and Adverse Selection Problems (1).pdf: 525295 bytes, checksum: 0463596c60f1218d5dfffa8108178df6 (MD5) Previous issue date: 2016-03-21 / This work analyses the optimal menu of contracts offered by a risk neutral principal to a risk averse agent under moral hazard, adverse selection and limited liability. There are two output levels, whose probability of occurrence are given by agent’s private information choice of effort. The agent’s cost of effort is also private information. First, we show that without assumptions on the cost function, it is not possible to guarantee that the optimal contract menu is simple, when the agent is strictly risk averse. Then, we provide sufficient conditions over the cost function under which it is optimal to offer a single contract, independently of agent’s risk aversion. Our full-pooling cases are caused by non-responsiveness, which is induced by the high cost of enforcing higher effort levels. Also, we show that limited liability generates non-responsiveness.

Page generated in 0.108 seconds