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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.
61

Optimizing Communication Cost in Distributed Query Processing / Optimisation du coût de communication des données dans le traitement des requêtes distribuées

Belghoul, Abdeslem 07 July 2017 (has links)
Dans cette thèse, nous étudions le problème d’optimisation du temps de transfert de données dans les systèmes de gestion de données distribuées, en nous focalisant sur la relation entre le temps de communication de données et la configuration du middleware. En réalité, le middleware détermine, entre autres, comment les données sont divisées en lots de F tuples et messages de M octets avant d’être communiqués à travers le réseau. Concrètement, nous nous concentrons sur la question de recherche suivante : étant donnée requête Q et l’environnement réseau, quelle est la meilleure configuration de F et M qui minimisent le temps de communication du résultat de la requête à travers le réseau?A notre connaissance, ce problème n’a jamais été étudié par la communauté de recherche en base de données.Premièrement, nous présentons une étude expérimentale qui met en évidence l’impact de la configuration du middleware sur le temps de transfert de données. Nous explorons deux paramètres du middleware que nous avons empiriquement identifiés comme ayant une influence importante sur le temps de transfert de données: (i) la taille du lot F (c’est-à-dire le nombre de tuples dans un lot qui est communiqué à la fois vers une application consommant des données) et (ii) la taille du message M (c’est-à-dire la taille en octets du tampon du middleware qui correspond à la quantité de données à transférer à partir du middleware vers la couche réseau). Ensuite, nous décrivons un modèle de coût permettant d’estimer le temps de transfert de données. Ce modèle de coût est basé sur la manière dont les données sont transférées entre les noeuds de traitement de données. Notre modèle de coût est basé sur deux observations cruciales: (i) les lots et les messages de données sont communiqués différemment sur le réseau : les lots sont communiqués de façon synchrone et les messages dans un lot sont communiqués en pipeline (asynchrone) et (ii) en raison de la latence réseau, le coût de transfert du premier message d’un lot est plus élevé que le coût de transfert des autres messages du même lot. Nous proposons une stratégie pour calibrer les poids du premier et non premier messages dans un lot. Ces poids sont des paramètres dépendant de l’environnement réseau et sont utilisés par la fonction d’estimation du temps de communication de données. Enfin, nous développons un algorithme d’optimisation permettant de calculer les valeurs des paramètres F et M qui fournissent un bon compromis entre un temps optimisé de communication de données et une consommation minimale de ressources. L’approche proposée dans cette thèse a été validée expérimentalement en utilisant des données issues d’une application en Astronomie. / In this thesis, we take a complementary look to the problem of optimizing the time for communicating query results in distributed query processing, by investigating the relationship between the communication time and the middleware configuration. Indeed, the middleware determines, among others, how data is divided into batches and messages before being communicated over the network. Concretely, we focus on the research question: given a query Q and a network environment, what is the best middleware configuration that minimizes the time for transferring the query result over the network? To the best of our knowledge, the database research community does not have well-established strategies for middleware tuning. We present first an intensive experimental study that emphasizes the crucial impact of middleware configuration on the time for communicating query results. We focus on two middleware parameters that we empirically identified as having an important influence on the communication time: (i) the fetch size F (i.e., the number of tuples in a batch that is communicated at once to an application consuming the data) and (ii) the message size M (i.e., the size in bytes of the middleware buffer, which corresponds to the amount of data that can be communicated at once from the middleware to the network layer; a batch of F tuples can be communicated via one or several messages of M bytes). Then, we describe a cost model for estimating the communication time, which is based on how data is communicated between computation nodes. Precisely, our cost model is based on two crucial observations: (i) batches and messages are communicated differently over the network: batches are communicated synchronously, whereas messages in a batch are communicated in pipeline (asynchronously), and (ii) due to network latency, it is more expensive to communicate the first message in a batch compared to any other message that is not the first in its batch. We propose an effective strategy for calibrating the network-dependent parameters of the communication time estimation function i.e, the costs of first message and non first message in their batch. Finally, we develop an optimization algorithm to effectively compute the values of the middleware parameters F and M that minimize the communication time. The proposed algorithm allows to quickly find (in small fraction of a second) the values of the middleware parameters F and M that translate a good trade-off between low resource consumption and low communication time. The proposed approach has been evaluated using a dataset issued from application in Astronomy.
62

Riadenie nákladov na IS/ICT vo vybranej spoločnosti / Management of IS/ICT costs in selected company

Gazda, Štefan January 2013 (has links)
The thesis is focused on IS/ICT cost management. The purpose of this thesis is to create an IS/ICT cost model based on the principles of managerial method ABC (Activity Based Costing) for business informatics of selected company. The theoretical part is focused on costs in IS/ICT, their classification and management, with the analyze of the reasons for continuous growth of IS/ICT cost management. A significant part of this section is a characteristic of ABC method and a description of different phases in creation of ABC model. The practical part of the thesis presents a selected company, its business informatics and an organizational structure. Subsequently the current state of IS/ICT cost management is described and analyzed. Based on the analysis and with regard to objectives of the company in the future, a new IS/ICT cost allocation model is designed. For the purpose of calculating and determining of intradepartmental prices for ICT services, a process of allocating and calculating costs is simulated on the new designed model, with the use of current and historical data of the company. At the end of the practical part, the results achieved through the designed model and the results of the current method of allocation and calculation costs are compared.
63

Systemunterstützung für den Abgleich von Geschäftsobjekten zwischen Anwendungsservern über WebServices: Systemunterstützung für den Abgleich von Geschäftsobjekten zwischen Anwendungsservern über WebServices

Ameling, Michael 07 September 2009 (has links)
Geschäftsanwendungen wie Supply Chain Management (SCM) oder Customer Relationship Management (CRM) werden repliziert, um eine hohe Skalierbarkeit und schnellen lokalen Zugriff zu erreichen. Die Geschäftsobjekte als Datencontainer der Anwendungen müssen infolge von Änderungen synchronisiert werden. Diese Arbeit leistet einen Beitrag zur Effizienzsteigerung des Synchronisationsprozesses durch die Reduzierung der Anzahl der Synchronisationsnachrichten sowie der zu übertragenden Datenmenge - auch unter Berücksichtigung des entstehenden Mehraufwands durch zusätzliche Verarbeitungsprozesse. / Business applications such as supply chain management (SCM) or customer relationship management (CRM) are replicated in order to reach high scalability and fast local access. The business objects representing the data containers have to be synchronized to stay consistent across the application servers. This thesis provides a contribution to reach more efficiency during the synchronization process by reducing the amount of synchronization messages and the amount of data to be transmitted. The additional effort due to further processing steps is taken into account via a proper cost model.
64

Tillverkningsekonomisk utvärdering av återvinning och återanvändning av blyfri mässing

Aco, Dekan January 2018 (has links)
Detta examensarbete är en del av ett större projekt (Evochip) som bedrivs på Lunds tekniska högskola, avdelningen för industriell produktion (iProd) och med samarbete med bland annat AB Markaryds metallarmatur och Mistra innovation. I detta arbete har en dynamisk kostnadsmodell tagits fram för att beräkna tillverkningskostnaderna av komponenter tillverkade av återanvända spånor av blyfri mässing från de egna tillverkningsprocesserna hos AB Markaryds metallarmatur (MMA). Idag skickas alla kasserade detaljer och materialspill ner till materialleverantörer i Sydeuropa för återvinning. Transporterna sker med lastbil och återvinningsprocessen utgår från ett energikrävande nedsmältningssteg. Idag pågår utvecklingsprojekt med målet att återanvända spånorna utan nedsmältning hos MMA, men kostnadsbilden per detalj har varit hittills okänd. Med hjälp av detta examensarbete ska detaljpriset tas fram. Tillverkningsprocessen delas in i totalt 11 olika förädlingsstationer. För att kartlägga kostnaderna används Jan-Eric Ståhls dynamiska kostnadsmodell. Nödvändig data och information har samlats in med hjälp av intervjuer på företaget och genom företagets egna dokumentationer. För att minska felmarginalen i resultaten har lämpliga Monte Carlo simuleringar utförts. Arbetet utgår även från ett hållbarhetsperspektiv. Förutom elimineringen av lastbilstransporter och energikrävande nedsmältningsprocesser för grundmaterialet, främjar arbetet även användning och återanvändning av blyfri mässing genom att kompaktera spånor till nya grönkroppar. Detta då forskare länge har varnat för blyade detaljers negativa hälsoeffekter.  Detaljen som undersöks i detta arbete är en ventil som har benämningen EVO 10, vilken återfinns i företagets blyfria standardsortiment. Kostnadsmodellen är dynamisk till den grad att den i framtiden skulle kunna appliceras på övriga blyfria mässingkomponenter hos MMA.      En jämförelse mellan två olika koncept presenteras i resultatdelen. Koncept ett representerar dagens tillverkningssystem, och koncept två framtidens kompakteringsteknik. Då många av förädlingsstegen är desamma för båda systemen, valdes en jämförelse mellan framtagningen av grönkropparna genom de två olika koncepten. Resultaten visar att kutsar, framtagna enligt dagens tillverkningssystem, kostar 12,75 SEK/detalj, och kutsar framtagna enligt koncept två kostar 9,61 SEK/detalj. Då koncept två är beroende av spånor från dagens tillverkningssystem, kan MMA inte helt gå över till att kompaktera spånor till nya kutsar. Mer arbete måste utföras för att hitta en balanserad modell mellan de två olika tillverkningssystemen för bästa möjliga resultat. Monte Carlo-simuleringarna visar att kostnaden per detalj uppgår till 12.96 SEK, detta med de på förhand valda konstanter och variabler i systemet. / This master thesis is part of a larger project (Evochip), conducted at Lund University, faculty of engineering, Industrial Production Department (iProd). The project is in collaboration with AB Markaryds metallarmatur and Mistra innovation. In this work, a dynamic cost model has been developed to calculate the manufacturing costs of components made from recycled chips of lead-free brass from the manufacturing processes of AB Markaryds metallarmatur (MMA). In the current situation, all rejected details and waste materials are sent to the material supplier in southern Europe for recycling. The transport takes place by trucks and the recycling process is based on an energy-intensive melting step. Development projects are currently underway to reuse the chips without melting at sight at MMA´s facilities, but the cost per detail has been unknown for the company. With the help of this thesis, the manufacturing price will be presented. The manufacturing process is divided into a total of 11 different processing stations. To estimate the costs, Jan-Eric Ståhl's dynamic cost model is used. Necessary data and information have been collected using interviews with the employees of the company and through the company's own documentation regarding the production lines. In order to reduce the error margin in the results, suitable Monte Carlo simulations have been performed. The work is also based on a sustainability perspective. In addition to eliminating transportations by trucks and energy-intensive melting processes for the products, the work also promotes the use and reuse of lead-free brass by pressing metal chips to form new bars. All this in order to avoid leaded brass components due to the negative health effects caused by the lead. The component investigated in this work is a radiator valve called EVO 10. The valve is found in the company's lead-free standard range. The cost model in this project is dynamic to the extent that it could be applied in the future to other lead-free brass components at MMA. A comparison of two different concepts is presented in the results section. Concept one represents the current manufacturing system, and concept two, the future compacting technology. Since many of the processing steps are the same for both systems, a comparison was made between the productions of the pellet through the two different concepts. The results show that pellets made according to today's manufacturing system cost 12.75 SEK / detail, and pellets manufactured according to concept two costs 9.61 SEK / detail. As concept two is dependent on chips from today's manufacturing system, MMA cannot completely switch to compacting chips to new pellets. More work must be done to find a balanced model between the two different manufacturing systems for the best possible results.The results from the Monte Carlo-simulations shows that the manufacturing cost with the chosen parameters and variables is 12.96 SEK/detail.
65

Conception et pilotage d'un atelier intégrant la fabrication additive / Design and management of a workshop integrating additive manufacturing

Antomarchi, Anne-Lise 27 September 2019 (has links)
La fabrication additive est un domaine en plein essor. Cependant, les industriels sont aujourd’hui dans une phase d’interrogation sur l’utilisation de ce procédé dans le cadre d’une production de masse. La problématique posée dans le cadre de ces travaux de recherche est : Comment rendre viable, industriellement, le procédé de fusion sur lit de poudre ? Nos travaux abordent la conception et le pilotage d’ateliers intégrant la fabrication additive et le processus complet d’obtention de la pièce selon les trois niveaux de décision : stratégique, tactique et opérationnel. D’un point du vue stratégique, des décisions fortes d’investissement, de sélection de machines et de choix d’organisation sont à prendre avec des enjeux économiques importants. L’objectif est de définir une méthode d’optimisation multicritère pour la conception modulaire d’un système de production intégrant la fabrication additive en présence de données incertaines, optimale sur le long terme et sur le court terme. D’un point de vue tactique, toutes les pièces ne sont pas forcément des candidates pertinentes pour la fabrication additive. Dans ces travaux, nous avons développé un outil d’aide à la décision qui évalue la pertinence ou non de la fabrication additive pour l’obtention des pièces dans une approche globale des coûts. Au niveau opérationnel, nous proposons un outil basé sur la simulation de flux qui permet de passer des commandes aux ordres de fabrication et leur ordonnancement de manière à garantir l’efficience de l’atelier. Ces travaux de recherche sont développés en lien avec des acteurs du monde industriel : AddUp, MBDA et Dassault qui alimentent nos travaux et nous permettent de confronter nos outils à une réalité industrielle. / The additive manufacturing is a field on the rise. However, companies wonder about the use of additive manufacturing for mass production. The problem raised in the context of this thesis is: How to make the process of sintering laser melting industrially viable? Our work focuses on the design and on the management of workshops integrating the additive manufacturing and of the complete process to obtain part according to three levels of decision: strategic, tactic and operational. About the strategic level, strong decisions of investment, machines selection and organization choice are taken with important economic issues. The aim is to define a multicriteria optimization method for the modular design of a production system integrating the additive manufacturing in the presence of uncertain data, optimal in the long term and the short term. From a tactical point of view, not all parts are necessarily relevant candidates for additive manufacturing. In this work, we developed a decision support tool that evaluates the relevance or not of additive manufacturing to obtain parts in a global cost approach. At the operational level, we offer a tool based on flow simulation that allows orders to be placed to production orders and their scheduling in order to guarantee the efficiency of the workshop. This research work is developed in collaboration with companies: AddUp, MBDA and Dassault, who contribute to our work and enable us to compare our tools with an industrial reality.
66

Framtagning av en konceptuell kostnadsmodell för sökmotoroptimerade webbapplikationer : Ett förslag på kostnadsmodell som beskriver uppkomna kostnader utifrån centrala aktiviteter / Development of a conceptual cost model for search engine optimized web applications : An alternative cost model that describes expenses based on key activities

Rosvall, Oliver January 2021 (has links)
Den digitala utvecklingen har förändrat sättet människor kommunicerar och lever sina liv. Idag är det möjligt att boka ett möte, beställa mat eller köpa en resa online. Den moderna människans konsumtionsvanor gör det livsviktigt för företag att etablera en digital närvaro. Som ett resultat av detta väljer allt fler företag att utveckla nya webbapplikationer för att sälja och marknadsföra sina produkter. För att synas finns det idag många olika marknadsföringsstrategier men under de senaste åren har det visat sig vara populärt att använda sig av sökmotorer. Sökmotormarknadsföring kan utföras med hjälp av sökmotoroptimering (SEO) och sökmotorannonsering. Båda metoderna behandlar olika områden som gör att en webbsida syns bland sökresultaten på sökmotorer såsom Google, Yahoo och Bing. Som ett resultat har det blivit vanligt att dessa två metoder används i symbios med varandra för att skapa ett konstant inflöde av användare. Att räkna ut priset för sökmotorannonsering är enkelt eftersom webbägaren betalar ett pris för varje annonsklick. Att räkna ut priset för SEO är något mer komplicerat eftersom kostnaden beror på vilket optimeringsarbete som utförs. Problemet är att det inte finns en känd kostnadsmodell som presenterar uppkomna kostnader vid framtagning och underhåll av en sökmotoroptimerad webbapplikation. Denna rapport syftar därför till att ta fram och presentera en konceptuell kostnadsmodell som ökar förståelsen för uppkomna kostnader vid centrala aktiviteter. Rapportens mål är däremot att ta fram en modell som kan användas av företag, organisationer, forskargrupper och individer för att identifiera och kategorisera uppkomna kostnader vid skapande och underhåll av en sökmotoroptimerad webbapplikation. Framtagandet av den konceptuella kostnadsmodellen genomfördes via en kvalitativ studie vilket innebär att studiens resultat bygger på observationer, upplevelser och sinnesintryck. Insamling av data gjordes med hjälp av en utforskningsmodell som består av två forskningskriterier. Arbetet inleddes med att utforska (1) centrala aktiviteter som påverkar kostnaden och därefter studerades (2) initiala och löpande kostnader. En fallstudie och fyra stycken intervjuer har använts som rapportens forskningsinstrument. De data som samlats in har analyserats med en tematisk analys där samband och olikheter identifieras. Utifrån upptäckterna i analysen skapades sedan en primär kostnadsmodell. Den primära kostnadsmodellen utvärderades med hjälp av arbetets utvärderingsmodell som präglades av tre forskningskriterier. Utvärderingen gjordes med en av intervjupersonerna och fokus låg på att studera hur bra modellen speglar verkligheten. Under intervjun utvärderades modellens övergripande (1) struktur, (2) aktiviteter och (3) kostnadsslag. Resultatet från utvärderingen resulterades sedan i en slutgiltig kostnadsmodell vid namn SEOCM (Search Engine Optimization Cost Model). Modellen tar och beskriver centrala aktiviteter som påverkar tillverkningskostnader och underhållskostnader för en sökmotoroptimerad webbapplikation. / The rise of technology has changed the way people communicate and live their lives. Nowadays, people can book a meeting, order food, or buy a trip online. The change in consumption habits makes it vital for companies to establish a digital presence. As a result, more companies are choosing to develop web applications to sell and market their product. To be visible, there are many different marketing strategies, but in recent years it has proven popular to use search engines. Search engine marketing can be done with search engine optimization (SEO) and search engine advertising. Both methods deal with different areas that make a web application visible on search engines such as Google, Yahoo and Bing. As a result, both methods are usually combined to generate a higher number of visitors. Calculating the price of search engine advertising is easy because the web owner pays a price for each ad clicked. Calculating the price for SEO is somewhat more complicated as the cost depends on the optimization work performed. The problem is that there is no known cost model that presents costs categories during development and maintenance of a search engine optimized web application. This purpose of the report, is therefore, to develop and present a conceptual cost model that demonstrates costs incurred in key activities. The goal of the report, however, is to develop a model that can be used by companies, organizations, research groups, and individuals to identify and categorize the cost incurred in creating a web application that applies search engine optimization. The development of the conceptual cost model has been carried out via a qualitative study, which means that the results are based on observations, experiences, and sensory impressions. Data collection has been done using an exploration model that consists of two research criteria. The work began with exploring (1) key activities that affect the cost and then studied (2) initial and running costs. A case study and four interviews have been used as the report's research instruments. The data collected have been analyzed with a thematic analysis where similarities and differences are identified. Based on the findings, a primary cost model was created. The primary cost model has been evaluated with an evaluation model, which carried three research criteria. The evaluation was made with one of the interviewees and the focus was on studying how well the model reflects reality. During the interview, the model's overall (1) structure, (2) activities, and (3) cost categories were evaluated. The results of the evaluation then resulted in a final cost model called SEOCM (Search Engine Optimization Cost Model). The model captures and describes key activities that affect manufacturing costs and maintenance costs for search engine optimized web applications.
67

Optimizing Notifications of Subscription-Based Forecast Queries

Fischer, Ulrike, Böhm, Matthias, Lehner, Wolfgang, Pedersen, Torben Bach 27 January 2023 (has links)
Integrating sophisticated statistical methods into database management systems is gaining more and more attention in research and industry. One important statistical method is time series forecasting, which is crucial for decision management in many domains. In this context, previous work addressed the processing of ad-hoc and recurring forecast queries. In contrast, we focus on subscription-based forecast queries that arise when an application (subscriber) continuously requires forecast values for further processing. Forecast queries exhibit the unique characteristic that the underlying forecast model is updated with each new actual value and better forecast values might be available. However, (re-)sending new forecast values to the subscriber for every new value is infeasible because this can cause significant overhead at the subscriber side. The subscriber therefore wishes to be notified only when forecast values have changed relevant to the application. In this paper, we reduce the costs of the subscriber by optimizing the notifications sent to the subscriber, i.e., by balancing the number of notifications and the notification length. We introduce a generic cost model to capture arbitrary subscriber cost functions and discuss different optimization approaches that reduce the subscriber costs while ensuring constrained forecast values deviations. Our experimental evaluation on real datasets shows the validity of our approach with low computational costs.
68

Comportements d'investissement et performances des exploitations agricoles selon la position dans le cycle de vie / Investment decisions of french dairy farms : the case of Brittany

Levi, Loïc 12 December 2018 (has links)
L'investissement et l'innovation jouent un rôle important dans le secteur agricole, permettant aux exploitations de s'adapter aux changements de politiques et aux conditions du marché. Au cours des dernières décennies, les exploitations agricoles de l'Union européenne (UE) ont été confrontées à des changements substantiels à travers la politique agricole commune (PAC). C'est notamment le cas du secteur laitier, qui a vu la fin du régime de quotas laitiers et également vu une volatilité accrue des prix. De tels changements pourraient affecter la productivité et l’efficacité des exploitations agricoles, la compétitivité du secteur laitier et les changements structurels. Comprendre les mécanismes sous-jacents au comportement d’investissement des exploitations pourrait permettre d’identifier les principaux facteurs qui influent sur les tendances observées. Cela pourrait aider à anticiper les futurs changements structurels, prévoir les besoins des exploitations et aider les décideurs publicet les autres acteurs du secteur agricole à adapter leurs politiques. La thèse contribue à cet objectif en analysant pour les exploitations laitières d'une sous-région de Bretagne (Ille-et-Vilaine) en France, (i) l'impact de la suppression du quota laitier sur les décisions d'investissement des agriculteurs et l'hétérogénéité de leurs réactions (ii) le lien entre la performance agricole et les décisions d'investissement des agriculteurs, (iii) le rôle des interactions sociales liées aux effets de voisinage sur la décision d'investissement des agriculteurs. Les résultats montrent que la fin / : Investment and innovation play an important role in the agricultural sector, allowing farms to adapt to policy changes and market condition changes. In the last decades, farms in the European Union (EU) have faced substantial changes in the Common Agricultural Policy (CAP). This is particularly the case of the dairy sector, which has seen the end of milk quota regime and increased price volatility. Such changes could affect farm productivity and efficiency, the dairy sector’s competitiveness and structural change. Understanding the mechanisms underlying farms’ investment behaviour could allow identifying key drivers that influence the observed trends. This could help anticipate future structural changes, predict farms’ needs and help policy makers and other stakeholders in farming to adapt their policy. The thesis contributes to this objective by analysing for dairy farms in a sub-region of Brittany (Ille-et-Vilaine) in France, (i) the impact of the termination of the milk quota onfarmers’ investment decisions and the heterogeneity of farm investment behaviour, (ii) the link between farm performance and farmers’ investment decisions, (iii) the role of social interactions related to neighbourhood effects on farmers' investment decision. Findings show that the termination of the dairy quota policy increased farmers’ incentive to invest, contributing to the trend towards larger, more capital intensive and more specialised dairy farms. In addition, the thesis underlines the need to take into account farmers’ heterogeneity in modelling investment behaviour. Doing so allows
69

Integrated design and control optimization of hybrid electric marine propulsion systems based on battery performance degradation model

Chen, Li 13 September 2019 (has links)
This dissertation focuses on the introduction and development of an integrated model-based design and optimization platform to solve the optimal design and optimal control, or hardware and software co-design, problem for hybrid electric propulsion systems. Specifically, the hybrid and plug-in hybrid electric powertrain systems with diesel and natural gas (NG) fueled compression ignition (CI) engines and large Li-ion battery energy storage system (ESS) for propelling a hybrid electric marine vessel are investigated. The combined design and control optimization of the hybrid propulsion system is formulated as a bi-level, nested optimization problem. The lower-level optimization applies dynamic programming (DP) to ensure optimal energy management for each feasible powertrain system design, and the upper-level global optimization aims at identifying the optimal sizes of key powertrain components for the powertrain system with optimized control. Recently, Li-ion batteries became a promising ESS technology for electrified transportation applications. However, these costly Li-ion battery ESSs contribute to a large portion of the powertrain electrification and hybridization costs and suffer a much shorter lifetime compared to other key powertrain components. Different battery performance modelling methods are reviewed to identify the appropriate degradation prediction approach. Using this approach and a large set of experimental data, the performance degradation and life prediction model of LiFePO4 type battery has been developed and validated. This model serves as the foundation for determining the optimal size of battery ESS and for optimal energy management in powertrain system control to achieve balanced reduction of fuel consumption and the extension of battery lifetime. In modelling and design of different hybrid electric marine propulsion systems, the life cycle cost (LCC) model of the cleaner, hybrid propulsion systems is introduced, considering the investment, replacement and operational costs of their major contributors. The costs of liquefied NG (LNG), diesel and electricity in the LCC model are collected from various sources, with a focus on present industrial price in British Columbia, Canada. The greenhouse gas (GHG) and criteria air pollutant (CAP) emissions from traditional diesel and cleaner NG-fueled engines with conventional and optimized hybrid electric powertrains are also evaluated. To solve the computational expensive nested optimization problem, a surrogate model-based (or metamodel-based) global optimization method is used. This advanced global optimization search algorithm uses the optimized Latin hypercube sampling (OLHS) to form the Kriging model and uses expected improvement (EI) online sampling criterion to refine the model to guide the search of global optimum through a much-reduced number of sample data points from the computationally intensive objective function. Solutions from the combined hybrid propulsion system design and control optimization are presented and discussed. This research has further improved the methodology of model-based design and optimization of hybrid electric marine propulsion systems to solve complicated co-design problems through more efficient approaches, and demonstrated the feasibility and benefits of the new methods through their applications to tugboat propulsion system design and control developments. The resulting hybrid propulsion system with NG engine and Li-ion battery ESS presents a more economical and environmentally friendly propulsion system design of the tugboat. This research has further improved the methodology of model-based design and optimization of hybrid electric marine propulsion systems to solve complicated co-design problems through more efficient approaches, and demonstrated the feasibility and benefits of the new methods through their applications to tugboat propulsion system design and control developments. Other main contributions include incorporating the battery performance degradation model to the powertrain size optimization and optimal energy management; performing a systematic design and optimization considering LCC of diesel and NG engines in the hybrid electric powertrains; and developing an effective method for the computational intensive powertrain co-design problem. / Graduate
70

The development and application of a freight transport flow model for South Africa

Havenga, Jan H. 12 1900 (has links)
Thesis (DPhil (Logistics))--University of Stellenbosch, 2007. / South Africa currently experiences the double jeopardy problem of catching up to global economic competitiveness whilst at the same time feeling the pressures of sustainability management spearheaded by a global agenda. Global sustainability is defined as growth that is shared without depleting natural resources or damaging the environment. Academic disciplines are challenged to make a contribution and economics as such should contribute by providing the lead and lag indicators for the planning and measurement of scarce resources usuage. This integrative view includes economic sub-disciplines, such as logistics. This integrative view is an acknowledged part of the economics discipline, except that the macro-economic context of some sub-disciplines, such as logistics, often receives less attention during the course of academic activities. The distribution of resources and outputs in the economy is a logistics controlled cross-cutting factor, but suffers from a lack of macro-economic perspective, and lead and lag orientated measurement. This state of the affairs is a historic backlog of logistics and its specific position within economics. During the primary economic era the world began to configure networks and markets, which became more pronounced and settled with the dawn and settling of the industrial era. Logistics then was a “given” and did not receive much thought even as industrial, market economies developed. Transport was regarded as an administered cost, i.e. inefficiencies in logistics systems were evenly distributed between competitors, not giving any specific entity an advantage. With the advent of global competition and the diminishing returns on other cost saving measures, companies began to collaborate and integrate logistics functions within value chains, but the administered part of transport costs failed to receive the attention it required. In this way, global competitors did begin to experience disadvantages on a national level as whole economies suffered from inefficiencies in logistics and specifically transport systems.

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