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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.
51

Konstrukce rizikových prémií při obchodování v odchylce na OTE / The construction of the risk surcharges for the imbalances trading on OTE market

Maštalíř, Jakub January 2011 (has links)
This master thesis approaches the energy markets from the point of view of an electricity trader acting on the retail markets, in particular an electricity supplier to the end customers. The first part introduces the reader into the basic practices applied in the management process of the portfolio of end customers, which includes metering and evaluation of the real take-off, planning and prediction and, of course, final evaluation of the imbalances. Second part explains the principles of balance management in case of the entire ČEPS electrical grid, mechanics of the imbalances settlement and describes its actual setting with focus on the way it motivates the market participants for minimization of their own imbalances and therefore improvement of the overall electrical grid balance. The final part describes the basic construction of the risk surcharges, which the supplier adds to the commodity price to cover the costs caused by the existence of his end customers' imbalances. Furthermore, it is shown how the dependence on the system imbalance influences the size of the risk surcharge and the basic model is extended to include even this factor. Because the supplier does not set the surcharge at the level of individual end customer but for the entire portfolio, the functioning and power of the portfolio effect, which brings an extra savings in the imbalances settlement costs, is also explored in the final part. The possibility of dependence presence in the imbalances of individual end customers is also accounted for. For the first time in the Czech academic literature the economic problems that are faced by the electricity supplier to the end customers are examined and the analysis and solution of one important problem is provided in the full picture. However, the most important contribution of this master thesis lays in the opening of this topic to further examination on the academic ground.
52

Power/Thermal Interaction within an Adaptive Turbine Engine

DeSomma, Andrew K. 10 May 2019 (has links)
No description available.
53

Modelling a Novel Linear Transverse Flux Machine and Designing a Hysteresis Current Controller for Power Factor Correction

Alhaidari, Ahmed January 2019 (has links)
In this thesis, the basics of electromagnetic theory for wave-energy conversion are reviewed, some of the characteristics of the ocean wave are investigated, some of the power take-off (PTO) systems are introduced, and details about linear permanent magnetic machines, in particular, are discussed.  The thesis aims to model the novel linear transverse flux machine designed by Anders Hagnestål and to build hysteresis current controller for power factor correc- tion. Although this machine is expected to have high performance in terms of efficiency, it also exhibits a strong mutual interaction between the three phases of the machine. Thus, simplification of the actual model of the machine is im- posed to mitigate the complexity of the machine and facilitate the Simulink model. Four cases of the double band hysteresis control are studied. The cur- rents seem to be responding properly to the control scheme; however, software and hardware programming of a microprocessor would be preferable to ensurethe applicability of the control strategy in a real environment. / I detta examensarbete undersöks elektromagnetisk teori och havsvågors egenskaper. Några energiomvandlingssystem introduceras och permanentmagnetiserade maskiner diskuteras i detalj. Syftet med avhandlingen är att modelleraen ny linjär transversalflödesmaskin som är designad av Anders Hagnestål och att bygga en hysteresbaserad strömkontroll för denna. Även om maskinen förväntas prestera bra, uppvisar den också en stark ömsesidig magnetisk interaktion mellan de tre faserna. För att kunna hantera detta problem och därmed kunna genomföra simuleringar införs en förenklad elektromagnetisk modell av maskinen. En strömkontroller har implementerats i Simulink, där fyra fall av dubbelbandshystereskontroll studerats. Resultaten från simuleringarna visar att strömkontrollern fungerar. Nästa steg i projektet är att utföra mjukvaru och hårdvaruprogrammering av en mikrokontroller för att testa systemet i enverklig miljö.
54

Mängdavtagning från dynamisk BIM-modell, en fallstudie på NCC Montagebro / Model based quantity take off from a dynamic BIM-model, case study on NCC Montagebro

Fransson, Emelie January 2012 (has links)
Byggbranschen har flertalet gånger blivit kritiserad för att inte uppnå samma utveckling och produktivitet som andra sektorer. Visionen om ett effektivt samhällsbyggande är ändå positiv och en av de stora nämnarna för framgång är BIM, Building Information Modeling. Arbetsmetoden, som handlar om att effektivt tillhandahålla information, tillämpas redan i relativt stor utsträckning på hussidan. Samtidigt ligger bro- och anläggningssidan i startgroparna för att följa efter husbyggnad i utvecklingen. NCC Montagebro är en prefabricerad betongbro som utvecklades på 80-talet och som återigen lyfts fram för utveckling. De tidigare standardmåtten har avskaffats för att i högre grad möta kundens önskemål om längd och bredd. Problemet med de fritt valbara måtten är att det inte finns något underlag att utgå ifrån vid prissättning i ett anbud. Syftet med detta arbete var därför att undersöka möjligheten med att upprätta en parameterstyrd BIM-modell att använda för mängdavtagning. Genom att belysa hinder och möjligheter var målet att resultatet skulle kunna användas för fortsatt utveckling av produkten. Studien utfördes med hjälp av intervjuer med verksamma personer i branschen och en praktisk fallstudie. Resultaten från dessa diskuterades utifrån de uppställda frågeställningarna och den tidigare redovisade litteraturstudien. En viktig aspekt som framkommit under studien är att möjligheten att effektivisera och standardisera prissättningen går hand i hand med graden av standardisering för brokonceptet som helhet. För att kunna göra en generell och anpassningsbar modell måste det utredas vilka mått och parametrar som ska vara standard och vilka som kan justeras fritt för varje nytt projekt. Detta och alla övriga erfarenhetsdokument borde samlas i en egen tekniska plattform för NCC Montagebron. Studiens slutsats är att det går att effektivisera prissättningen av NCC Montagebro med hjälp av BIM men det är inte ett tillräckligt argument för att skapa en BIM-modell. Förslagsvis bör modellen uppdateras med mer information så att den kan utnyttjas i fler delprocessen för annars går en stor del av syftet med BIM förlorat. / The Construction Industry has been criticized several times for their slow development and for not being as productive as other industries. In orderto achieve an efficient Architecture, Engineering & Construction (AEC) Industry, Building Information Modeling, BIM, is one of the most debatedtopics in the field. The work process, which is about to efficiently provide information about a project, is already applied in the building construction. On the other hand, bridge and civil construction are just about to start the implementation of BIM. NCC Montagebro is a prefabricated concrete bridge which was developed in the 1980s and is once again up-to-date for product development. Theprevious standard dimensions have been removed in order to meet the customers’ requirements for length and width. A problem that occurs when allowing the customers to choose the dimensions is that there is no corresponding documentation to base the pricing on. The aim of this work was to investigate the possibility of establishing a parametric BIM model to use for quantity take off. A goal was to facilitate the continuing improvement of the product by highlighting obstacles and opportunities. The study was carried out through interviews and a practical case study. The results of these were discussed from the stated research questions andthe previously reported literature review. An important aspect emerging from the study is that the ability to rationalize and standardize the pricing depends on the degree of standardizationof the whole bridge concept. To make a general and flexible model it is necessary to examine which dimensions and parameters that should be set to default and which can be freely adjusted for each new project. These decisions and all other documents of experience should be gathered in a special technical platform for the NCC Montagebro. The study concludes that it is possible to rationalize the pricing of NCC Montagebro by using BIM but the arguments may not be enough to design a BIM model. The model should be provided with additional information so that it can be used in several sub-processes because otherwise, a large part of the purpose of BIM is lost.
55

Why is BIM not being used in a larger extent in the construction industry? : A study on BIM used for quantity take-off at medium-sized construction companies / Varför används inte BIM i större utsträckning inom byggbranschen? : En studie om BIM vid mängdavtagning hos medelstora entreprenadföretag

Sohlberg, Gabriella, Lorentzon, Henny January 2021 (has links)
Compared to other industries, the construction industry is slow to take advantage of the benefits of digitalization. There are many different parties involved in projects, which makes it a versatile but also fragmented industry, which in this case is not to its advantage. Building information modeling (BIM) is a tool that could improve the cooperation between these parties and which has many other benefits associated with it, such as time- and cost savings. Quantity take-off in BIM is something that can be carried out at a low degree of maturity and is considered to be one of the most useful working methods that BIM enables. Despite the many benefits that studies have shown, many companies in the construction industry have still not fully implemented a working method where BIM is used for quantity take-off.The purpose of the project is to investigate the BIM use among parties in the Swedish construction industry. More specifically, this study will examine the working methods of medium-sized construction companies with quantity take-off. Since the work with quantity take-off has been shown to be linked to more basic BIM use, this factor can be seen as a good indicator for the development of BIM within companies. Medium-sized construction companies have been chosen as they are a good representative of the large mass of parties in the construction industry who have both the capacity and the finances to implement BIM. Furthermore, this project also aims to locate the difficulties in using these digital working methods for quantity take-off.The study is performed as a qualitative case study where ByggDialog AB exemplified a medium-sized construction company in the construction industry. In semi-structured interviews, employees were asked to answer questions concerning the subject of the study.The results of the study have shown that the willingness to develop working methods with BIM at medium-sized construction companies exists, but that visions and ambitions are limited by the adjustment costs that a BIM-implementation would entail. The fact that there are no requirements or demands from customers is another factor that contributes why BIM is not used more today. As a result of the fact that the customers today are not prepared to finance a BIM-implementation, the development is not driven further within the studied company.In this case study, we have identified that the studied medium-sized construction company does not use BIM for quantity take-off. This is not due to that the contractors do not want to, but because it is difficult to motivate that a BIM-implementation would cover the costs involved. This study therefore indicates that in the short term it is not profitable to implement BIM as it entails large conversion costs for companies. / Byggbranschen är jämfört med andra branscher långsam på att utnyttja de fördelar som finns med digitalisering. Det är många olika aktörer inblandade i projekt vilket gör det till en mångsidig men även fragmenterad bransch, vilket i det här fallet inte är till dess fördel. Building information modeling (BIM) är ett verktyg som skulle kunna förbättra samarbetet mellan dessa aktörer och som har många andra fördelar kopplat till sig såsom tids- och kostnadsbesparing. Mängdavtagning i BIM är något som kan genomföras vid en låg mognadsgrad och anses vara en av de mest användbara arbetsmetoderna som BIM möjliggör. Trots de många fördelar som studier påvisat har många företag inom byggbranschen fortfarande inte fullt ut implementerat ett arbetssätt där BIM används vid mängdavtagning.Syftet med examensarbetet är att undersöka BIM-användningen hos aktörer i den svenska byggbranschen. Mer specifikt kommer detta examensarbete att granska medelstora entreprenörers arbetssätt med mängdavtagning. Eftersom mängdavtagning har visats vara kopplat till mer grundläggande BIM-användning kan denna faktor ses som en god indikator för utvecklingen av BIM inom företag. Medelstora entreprenadföretag har valts då dessa är en god representant för den stora massan av aktörer inom byggbranschen som både har kapaciteten och ekonomin att implementera BIM. Vidare syftar detta examensarbete också till att lokalisera svårigheterna vid användning av dessa digitala arbetssätt för mängdavtagning.Studien är utförd som en kvalitativ fallstudie där ByggDialog AB fått exemplifiera ett medelstort entreprenadföretag i byggbranschen. Medarbetare har i semistrukturerade intervjuer fått svara på frågor som berör studiens ämne.Resultatet i studien har visat att viljan att utveckla arbetssätt med BIM hos medelstora entreprenadföretag finns men att visioner och ambitioner begränsas av de omställningskostnader som en BIM-implementering skulle medföra. Att det inte finns någon efterfrågan eller krav från beställare är en annan faktor som spelar in i varför BIM inte används mer idag. Som en följd av att beställarna idag inte är beredda att finansiera en BIM-implementering så drivs inte utvecklingen vidare inom det studerade företaget.Vi har i denna fallstudie identifierat att det studerade medelstora entreprenadföretaget ej använder sig av BIM vid mängdavtagning. Detta beror inte på en ovilja hos entreprenörerna, utan för att det är svårt att argumentera för att en BIM-implementering skulle täcka de kostnader som det innebär. Denna studie indikerar därför att det på kort sikt inte lönar sig att implementera BIM då det innebär stora omställningskostnader för företagen.
56

Val av elektrisk motor till separat drivet kraftuttag för tunga fordon / Selection of Electric Motor To Separately Driven Power Take-Off For Heavy Vehicle

Sjöblom, Simon, Tidblom, Gustav January 2021 (has links)
I en tid kännetecknat av en strävan efter ett mer hållbart samhälle, med utformade långsiktiga klimatmål för förnyelsebara energikällor och minskade utsläpp, arbetar fordonsutvecklare med att ta fram alternativ till förbränningsmotorer. För att nå satta klimatmål och samtidigt förbättra arbetsmiljön med minskat buller anses en elektrisk drivlina som ett troligt alternativ. För tunga fordon såsom lastbilar som ofta utrustas med tillsatsutrustning som kranar, tippbara flak eller cementroterare är beroende av ett kraftuttag för att driva hydraulpumpar och generatorer. Vid en omställning till elektrisk drivlina är det inte längre säkert att möjligheten kvarstår att ta kraft från drivlinan. Detta har lett till en efterfrågan på elektriskt separat drivna kraftuttag uppstått på marknaden. Syftet med denna studie är att undersöka och få en förståelse för inom vilket effektområde och vilken typ av elektrisk motor som är bäst lämpad för att separat driva ett kraftuttag. Målet är att med denna kunskap utveckla en modell som förenklar valet av lämplig elektrisk motor för ett givet fall av kraftuttag. Modellen testas med en effekt på 60 kW vilket resulterade i att en lågvarvig axial flux BLDC-motor anses bäst lämpad. Detta då en lågvarvig elektrisk motor kräver lägre utväxling för att uppfylla krävt vridmoment, vilket ger en lägre totalvikt. Totalvikt för testad effekt hamnar på 78,6 kg, vilket är tre gånger det funktionella kravet. Studien ger en indikation på att det med givna krav enbart är försvarbart att driva kraftuttag med separata elektriska motorer vid låga effekter, runt 10 kW. / In a time characterized by an endeavor for a more sustainable society. With formulated long-term climate targets for renewable energy sources and reduced emissions, vehicle developers are working to develop alternatives to internal combustion engines. In order to achieve set climate targets and at the same time improve the working environment with reduced noise, an electric driveline is considered a likely alternative. For heavy vehicles such as trucks that are often equipped with auxiliary accessories such as cranes, tipper trucks or cement rotators are dependent on a power take-off to drive hydraulic pumps and generators. When switching to an electric driveline, it is no longer certain that the possibility remains to take power from the driveline. This has led to a demand for electrically driven power take-offs on the market. The purpose of this study is to investigate and gain an understanding of the power range and type of electric motor that is best suited to drive a power take-off separately. The goal is to use this knowledge to develop a model that simplifies the choice of a suitable electric motor for a given case of power take-off. The model is tested with an output of 60 kW, which resulted in a low-speed axial flux BLDC-motor being considered best suited. This is because a low-speed electrical motor requires a lower gear ratio to meet the required torque, which gives a lower total weight. The total weight for the tested effect ends up at 78,8 kg, which is three times the functional requirement. The study gives an indication that with given requirements it is only justified to operate power take-offs with separate electric motors at low powers, around 10 kW.
57

The effective use of multiple unmanned aerial vehicles in surface search and control

Berner, Robert Andrew 12 1900 (has links)
Approved for public release; distribution in unlimited. / This study analyzes the effective use of multiple unmanned aerial vehicles (UAVs) for the Navy's Surface Search and Control mission. In the future, the Navy hopes to leverage the capabilities of a family of UAVs to provide increased situational awareness in the maritime environment. This family of UAVs includes a Broad Area Maritime Surveillance (BAMS) UAV and Vertical Take-Off UAVs (VTUAVs). The concepts of operations for how these UAVs work together have yet to be determined. Questions exist about the best number of UAVs, types of UAVs, and tactics that will provide increased capabilities. Through modeling and agent-based simulation, this study explores the validity of future UAV requirements and provides insights into the effectiveness of different UAV combinations. For the scenarios modeled, the best UAV combination is BAMS plus two or three VTUAVs. However, analysis shows that small numbers of VTUAVs can perform as well without BAMS as they do with BAMS. For combinations with multiple UAVs, BAMS proves to be a valuable asset that not only reduces the number of missed classifications, but greatly improves the amount of coverage on all contacts in the maritime environment. BAMS tactics have less effect than the mere presence of BAMS itself. / Lieutenant, United States Navy
58

Nouveaux algorithmes efficaces de modélisation 2D et 3D : Temps des premières arrivées, angles à la source et amplitudes / New efficient 2D and 3D modeling algorithms to compute travel times, take-off angles and amplitudes

Belayouni, Nidhal 25 April 2013 (has links)
Les temps de trajet, amplitudes et angles à la source des ondes sismiques sont utilisés dans de nombreuses applications telles que la migration, la tomographie, l'estimation de la sensibilité de détection et la localisation des microséismes. Dans le contexte de la microsismicité, il est nécessaire de calculer en quasi temps réel ces attributs avec précision. Nous avons développé ici un ensemble d'algorithmes rapides et précis en 3D pour des modèles à fort contraste de vitesse.Nous présentons une nouvelle méthode pour calculer les temps de trajet, les amplitudes et les angles à la source des ondes correspondant aux premières arrivées. Plus précisément, nous résolvons l'équation Eikonal, l'équation de transport et l'équation des angles en nous basant sur une approche par différences finies pour des modèles de vitesse en 3D. Nous proposons une nouvelle méthode hybride qui bénéficie des avantages respectifs de plusieurs approches existantes de résolution de l'équation Eikonal. En particulier, les approches classiques proposent généralement de résoudre directement les équations et font l'approximation localement d'une onde plane. Cette approximation n'est pas bien adaptée au voisinage de la source car la courbure du front d'onde est importante. Des erreurs de temps de trajet sont alors générées près de la position de la source, puis propagées à travers tout le modèle de vitesse. Ceci empêche de calculer correctement les amplitudes et les angles à la source puisqu'ils reposent sur les gradients des temps. Nous surmontons cette difficulté en introduisant les opérateurs sphériques ; plus précisément nous reformulons les temps de trajet, amplitudes et angles à la source par la méthode des perturbations.Nous validons nos nouvelles méthodes pour différents modèles à fort contraste de vitesse en 2D et 3D et montrons notre contribution par rapport aux approches existantes. Nos résultats sont similaires à ceux calculés en utilisant la modélisation de la forme d'onde totale alors qu'ils sont bien moins coûteux en temps de calcul. Ces résultats ouvrent donc de nouvelles perspectives pour de nombreuses applications telles que la migration, l'estimation de la sensibilité de détection et l'inversion des mécanismes au foyer. / Traveltimes, amplitudes and take-off angles of seismic waves are used in many applications such as migration, tomography, detection sensitivity estimation and microseism location. In the microseismicty context it is necessary to compute in near real time accurately these attributes. Here we developed a set of fast and accurate algorithms in 3D for highly contrasted velocity models.We present a new accurate method for computing first arrival traveltimes, amplitudes and take-off angles; more precisely we solve the Eikonal, transport and take-off angle equations based on a finite difference approach for 3D velocity models. We propose a new hybrid method that benefits from the advantages of several existing Eikonal solvers. Common approaches that solve directly these equations assume that we are locally propagating a plane wave. This approximation is not well adapted in the neighborhood of the source since the wavefront curvature is important. Travel times errors are generated near the source position and then propagated through the whole velocity model. This prevents from properly calculating the amplitudes and the take-off angles since they rely on the travel time gradients that are not accurate. We overcome this difficulty by introducing spherical operators. Indeed we reformulate the traveltimes, amplitudes and take-off angles with the perturbation method.We validate our new methods on various highly contrasted velocity models in 2D and 3D and show our contribution compared to other existing approaches. Our results are similar to those computed using full waveform modeling while they are obtained in a much shorter CPU time. These results open thus new perspectives for several applications such as migration, detection sensitivity estimation and focal mechanism inversion.
59

Internationalization of Chinese Construction Equipment Firms : “Take-off Drivers & Entry Strategies”

Halak, Michael, Reinke, Charlene January 2011 (has links)
This master thesis investigates how Chinese construction equipment firms internationalize (i.e. how they enter new markets and how they are driven to exit their own). For this, the institutions of China and Brazil are comparatively analyzed, Porter’s five forces model is used to analyze the Chinese construction equipment industry, while distinct resources, capabilities and key success factors are defined and analyzed for Sany and Xuzhou Construction Machinery Group (XCMG). After careful analysis, the authors bring to light various take-off drivers, patterns and strategies of Chinese construction equipment firms when internationalizing or venturing abroad. Chinese construction equipment firms are beginning to follow their Western counterparts, focusing their efforts on product quality and extensive customer service. Warranties, parts centers, aftermarket service and strategically placed research and development facilities are becoming more greatly utilized, expanding the quality and offerings of Chinese firms, while adding to the customers perception of overall value.    These key insights expand the knowledge base associated with Chinese construction equipment firms in developing markets, while unlocking new theoretical perspectives for supplementary research.
60

Internationalization processes of small and medium-sized enterprises: Entering and taking off from emerging markets

Sandberg, Susanne January 2012 (has links)
The high economic growth of formerly closed markets such as China, Russia, Poland, and the Baltic states has created vast business and growth opportunities for small and medium-sized enterprises (SMEs). Although this international business expansion of SMEs occurs in highly dissimilar business contexts and fierce international competition, it remains overlooked by research. Therefore, the main aim of this thesis is to contribute to an enhanced understanding of internationalization processes of SMEs by studying the overarching research question: What are the main features of internationalization processes of SMEs in an emerging market context? Three sub-problems are researched with regard to SMEs entering and taking off from emerging markets, as well as differences and similarities between these processes, in order to identify what features characterize them. Empirically, two surveys of 116 and 203 Swedish SMEs, respectively, with experiences of entry into emerging markets were conducted through standardized questionnaires via mail and on-site visits. In addition, case studies were conducted through interviews and observations of five internationalizing Chinese SMEs and four Chinese wholesale and retail market platforms. Five essays are compiled within the thesis and major findings and conclusions provide theoretical and empirical contributions to research on the internationalization processes of SMEs. With regard to the overlooked internationally experienced manufacturing SMEs from mature markets such as Sweden, theoretical advancements are made identifying the main concepts of their entry into emerging markets: entry node (the establishment point into the foreign business network); market-specific experiential knowledge; and perceived institutional distance. With regard to the internationally novel Chinese SMEs, these were seen to diverge from traditional internationalization paths. Indications were found of a parallel expansion abroad and at home, even using foreign markets as a springboard for further growth at home. The take-off node concerns the departure from an emerging home market, where a paradox of knowledge was found: the use of indirect export via a domestic intermediary facilitates the take off, but hinders further international expansion since no international experience or relationships are built up. Moreover, institutional distance was reduced due to collective internationalization through co-locating abroad. Generally, degree of maturity of the home market; as well as degree of internationalization and type of firm; are the main features behind differences between internationalization processes of SMEs in an emerging market context.

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