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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.
41

Exploring item response theory in forced choice psychometrics for construct and trait interpretation in cross-cultural context

Huang, Teng-Wei 03 1900 (has links)
This thesis explores item response theory (IRT) in the Personal Profile Analysis (PPA) from Thomas International. The study contains two parts (Part 1 and Part II) for which two sample groups were collected. For Part I of the research 650 participants were collected via the old form (CPPA25/C7) in the Beijing office of Thomas International in China (male=323, Female=267, missing=60). Part II of the research used the amended form in the same area and collected a sample of 307 (male=185, female=119, missing=3). The study postulates that IRT methods are applicable to forced-choice psychometrics. The results of Part I showed that the current CPPA form functions, to some extent, according to PPA’s original constructs. Part I of the research identified 16 items that need to be amended (called Amend A in this research). The amended form was returned to China for the collection of samples for Part II, and the results are deemed acceptable. The study concludes with a research protocol for PPA-IRT research generated from the current research. The research protocol suggests four levels of analysis for forced choice (FC) psychometrics, namely: 1. Textual analysis, 2. Functional analysis, 3. Dynamic analysis, and 4. Construct analysis. / Psychology / M.A. (Psychology)
42

Impact of offtake mechanisms on wind turbine selection and design in North and Central Europe

Reiter, Gesa January 2023 (has links)
Wind power has become a major supplier of electricity in the European market in the last years. In 2020, 13% of electricity generated on the European continent was wind energy (onshore and offshore) and these shares are projected to increase in the next years due to reasons such as climate change and the energy security aspect. While an increased share of renewable electricity in the electricity mix has a lot of benefits, it also comes with challenges. One of these challenges are the electricity market design and the offtake mechanisms that find application. If national expansion goals for wind energy are to be achieved, wind power plants need to be profitable and hence be an attractive and competitive investment. If wind farms are running within the prevalent merit order system where the energy source with the highest marginal cost sets the electricity price, there is a risk of low or even negative income at times of high wind or solar irradiation. The unforeseeable and potentially low revenues also lead to worse conditions in the financing of wind projects, resulting in high financing costs. To counteract this challenge, governments have set up policy frameworks and subsidies and owners of wind farms have adopted different offtake mechanisms such as pay-as-produced PPAs (power purchase agreements) and baseload PPAs. Additionally, many operators hedge their assets, meaning that risks are reduced by deployment of different offtake mechanisms. All of this is where this study ties in. The objective was to evaluate how the design of markets and offtakes and their respective pricing level and predictability impact the best turbine fit in North and Central Europe. To get to an answer, two key onshore markets within the region have been chosen and characterized, namely Germany and Sweden. Two different turbine types, one with a low capacity factor but high rated power and one with a lower rated power but high capacity factor, have been examined in these markets in order to evaluate which turbine type performs better. A third turbine type which is a new concept in the technology demonstrator stage has been added to the study to assess its performance as compared to the existent turbines. The evaluation has been performed in form of a Use Case Analysis and Sensitivity Study. Finally, the results have been compared and generalized into key takeaways that can be transferred into other markets in the region of North and Central Europe. The study finds that different market characteristics and offtake mechanisms do in fact impact turbine selection and the best turbine fit. Important factors that have been found in this research are the key financial metric (NPV and IRR), market constraints such as a grid constraint, and offtake mechanisms and the predictability of revenues that comes with the offtake. The main impacts on wind turbine selection that can be tied to offtake mechanisms are the payment received per unit of electricity and the level of security that comes with the offtake mechanism. Constant incomes improve financing conditions, meaning that resources from crediting institutes are granted at better conditions if the income can be anticipated. For both markets, the optimal turbine fit varies depending on the boundary conditions. High capacity factor turbines have been found to be a better fit if the developing company considers the IRR as focal financial metric. If the NPV is the focal metric, the results are less clear: While low capacity turbines are a better fit for sites with low revenues from electricity pricing and lower wind conditions, turbines with high rated power benefit from high and secured electricity pricing and high wind speeds where rated power is reached. The German EEG as a special case promotes installation of high capacity turbines due to high and constant revenues per MWh. While the overall Value Pool (payment per MWh of electricity) is higher for Germany, business cases in Sweden benefit from higher turbine lifetimes. / Vindkraft har under de senaste åren blivit en viktig leverantör av el på den europeiska marknaden. År 2020 var 13 % av elproduktionen på den europeiska kontinenten vindkraft (på land och till havs) och dessa andelar förväntas öka under de kommande åren på grund av orsaker som klimatförändringar och energisäkerhet. Även om en ökad andel förnybar el i elmixen har många fördelar, kommer den också med utmaningar. En av dessa utmaningar är elmarknadens utformning och de uttagsmekanismer som tillämpas. Om de nationella utbyggnadsmålen för vindkraft ska kunna uppnås måste vindkraftverken vara lönsamma och därmed utgöra en attraktiv och konkurrenskraftig investering. Om vindkraftsparkerna drivs inom det rådande merit order-systemet, där den energikälla som har högst marginalkostnad sätter elpriset, finns det risk för låga eller till och med negativa intäkter vid tillfällen med mycket vind eller solinstrålning. De oförutsägbara och potentiellt låga intäkterna leder också till sämre villkor för finansiering av vindkraftsprojekt, vilket resulterar i höga finansieringskostnader. För att motverka denna utmaning har flera regeringar inrättat politiska ramverk och subventioner och ägare av vindkraftsparker har infört olika uppköpsmekanismer såsom PPA (Power Purchase Agreement) med betalning efter produktion och PPA för basbelastning. Dessutom säkrar många operatörer sina tillgångar, vilket innebär att riskerna minskas genom användning av olika upptagningsmekanismer. Målet var att utvärdera hur utformningen av marknader och upptag samt deras respektive prisnivå och förutsägbarhet påverkar den bästa turbinanpassningen i Nord- och Centraleuropa. För att komma fram till ett svar har representativa marknader inom regionen valts ut och karakteriserats, nämligen Tyskland och Sverige. Två olika turbintyper, en med låg kapacitetsfaktor men hög nominell effekt och en med lägre nominell effekt men hög kapacitetsfaktor, har undersökts på dessa marknader för att utvärdera vilken turbintyp som presterar bättre. En tredje turbintyp som är ett nytt koncept i teknikdemonstratorstadiet har lagts till i studien för att bedöma dess prestanda jämfört med de befintliga turbinerna. Utvärderingen har utförts i form av en användningsfallsanalys och en känslighetsstudie. Slutligen har resultaten jämförts och generaliserats till viktiga slutsatser som kan överföras till andra marknader i regionen Nord- och Centraleuropa. Studien visar att olika marknadsegenskaper och uppköpsmekanismer påverkar valet av turbin och vilken turbin som passar bäst. Viktiga faktorer som har hittats i denna forskning är det viktigaste finansiella måttet (NPV och IRR), marknadsbegränsningar som spetshöjd eller nätbegränsningar, och uppköpsmekanismer och förutsägbarheten av intäkter som kommer med uppköpet. De viktigaste faktorerna som påverkar valet av vindkraftverk och som kan kopplas till avsättningsmekanismer är den betalning som erhålls per enhet el och den säkerhetsnivå som följer med avsättningsmekanismen. Konstanta inkomster förbättrar finansieringsvillkoren, vilket innebär att resurser från kreditinstitut beviljas på bättre villkor om inkomsterna kan förutses. För båda marknaderna varierar den optimala turbinpassningen beroende på gränsvillkoren. Turbiner med hög kapacitet har visat sig passa bättre om utvecklingsföretaget betraktar internräntan som ekonomiska nyckeltal. Om NPV är det centrala måttet är resultaten mindre tydliga: Medan turbiner med låg kapacitet passar bättre för platser med låga intäkter från elpriser och lägre vindförhållanden, gynnas turbiner med hög nominell effekt av höga och säkra elpriser och höga vindhastigheter där nominell effekt uppnås. Det tyska EEG är ett specialfall som främjar installation av turbiner med hög kapacitet på grund av höga och konstanta intäkter per MWh. Medan den totala värdepoolen (betalning per MWh el) är högre för Tyskland, gynnas affärsfall i Sverige av högre livslängd för turbinerna.
43

Multiple Constant Multiplication Optimization Using Common Subexpression Elimination and Redundant Numbers

Al-Hasani, Firas Ali Jawad January 2014 (has links)
The multiple constant multiplication (MCM) operation is a fundamental operation in digital signal processing (DSP) and digital image processing (DIP). Examples of the MCM are in finite impulse response (FIR) and infinite impulse response (IIR) filters, matrix multiplication, and transforms. The aim of this work is minimizing the complexity of the MCM operation using common subexpression elimination (CSE) technique and redundant number representations. The CSE technique searches and eliminates common digit patterns (subexpressions) among MCM coefficients. More common subexpressions can be found by representing the MCM coefficients using redundant number representations. A CSE algorithm is proposed that works on a type of redundant numbers called the zero-dominant set (ZDS). The ZDS is an extension over the representations of minimum number of non-zero digits called minimum Hamming weight (MHW). Using the ZDS improves CSE algorithms' performance as compared with using the MHW representations. The disadvantage of using the ZDS is it increases the possibility of overlapping patterns (digit collisions). In this case, one or more digits are shared between a number of patterns. Eliminating a pattern results in losing other patterns because of eliminating the common digits. A pattern preservation algorithm (PPA) is developed to resolve the overlapping patterns in the representations. A tree and graph encoders are proposed to generate a larger space of number representations. The algorithms generate redundant representations of a value for a given digit set, radix, and wordlength. The tree encoder is modified to search for common subexpressions simultaneously with generating of the representation tree. A complexity measure is proposed to compare between the subexpressions at each node. The algorithm terminates generating the rest of the representation tree when it finds subexpressions with maximum sharing. This reduces the search space while minimizes the hardware complexity. A combinatoric model of the MCM problem is proposed in this work. The model is obtained by enumerating all the possible solutions of the MCM that resemble a graph called the demand graph. Arc routing on this graph gives the solutions of the MCM problem. A similar arc routing is found in the capacitated arc routing such as the winter salting problem. Ant colony optimization (ACO) meta-heuristics is proposed to traverse the demand graph. The ACO is simulated on a PC using Python programming language. This is to verify the model correctness and the work of the ACO. A parallel simulation of the ACO is carried out on a multi-core super computer using C++ boost graph library.
44

Modelling of input data uncertainty based on random set theory for evaluation of the financial feasibility for hydropower projects / Modellierung unscharfer Eingabeparameter zur Wirtschaftlichkeitsuntersuchung von Wasserkraftprojekten basierend auf Random Set Theorie

Beisler, Matthias Werner 24 August 2011 (has links) (PDF)
The design of hydropower projects requires a comprehensive planning process in order to achieve the objective to maximise exploitation of the existing hydropower potential as well as future revenues of the plant. For this purpose and to satisfy approval requirements for a complex hydropower development, it is imperative at planning stage, that the conceptual development contemplates a wide range of influencing design factors and ensures appropriate consideration of all related aspects. Since the majority of technical and economical parameters that are required for detailed and final design cannot be precisely determined at early planning stages, crucial design parameters such as design discharge and hydraulic head have to be examined through an extensive optimisation process. One disadvantage inherent to commonly used deterministic analysis is the lack of objectivity for the selection of input parameters. Moreover, it cannot be ensured that the entire existing parameter ranges and all possible parameter combinations are covered. Probabilistic methods utilise discrete probability distributions or parameter input ranges to cover the entire range of uncertainties resulting from an information deficit during the planning phase and integrate them into the optimisation by means of an alternative calculation method. The investigated method assists with the mathematical assessment and integration of uncertainties into the rational economic appraisal of complex infrastructure projects. The assessment includes an exemplary verification to what extent the Random Set Theory can be utilised for the determination of input parameters that are relevant for the optimisation of hydropower projects and evaluates possible improvements with respect to accuracy and suitability of the calculated results. / Die Auslegung von Wasserkraftanlagen stellt einen komplexen Planungsablauf dar, mit dem Ziel das vorhandene Wasserkraftpotential möglichst vollständig zu nutzen und künftige, wirtschaftliche Erträge der Kraftanlage zu maximieren. Um dies zu erreichen und gleichzeitig die Genehmigungsfähigkeit eines komplexen Wasserkraftprojektes zu gewährleisten, besteht hierbei die zwingende Notwendigkeit eine Vielzahl für die Konzepterstellung relevanter Einflussfaktoren zu erfassen und in der Projektplanungsphase hinreichend zu berücksichtigen. In frühen Planungsstadien kann ein Großteil der für die Detailplanung entscheidenden, technischen und wirtschaftlichen Parameter meist nicht exakt bestimmt werden, wodurch maßgebende Designparameter der Wasserkraftanlage, wie Durchfluss und Fallhöhe, einen umfangreichen Optimierungsprozess durchlaufen müssen. Ein Nachteil gebräuchlicher, deterministischer Berechnungsansätze besteht in der zumeist unzureichenden Objektivität bei der Bestimmung der Eingangsparameter, sowie der Tatsache, dass die Erfassung der Parameter in ihrer gesamten Streubreite und sämtlichen, maßgeblichen Parameterkombinationen nicht sichergestellt werden kann. Probabilistische Verfahren verwenden Eingangsparameter in ihrer statistischen Verteilung bzw. in Form von Bandbreiten, mit dem Ziel, Unsicherheiten, die sich aus dem in der Planungsphase unausweichlichen Informationsdefizit ergeben, durch Anwendung einer alternativen Berechnungsmethode mathematisch zu erfassen und in die Berechnung einzubeziehen. Die untersuchte Vorgehensweise trägt dazu bei, aus einem Informationsdefizit resultierende Unschärfen bei der wirtschaftlichen Beurteilung komplexer Infrastrukturprojekte objektiv bzw. mathematisch zu erfassen und in den Planungsprozess einzubeziehen. Es erfolgt eine Beurteilung und beispielhafte Überprüfung, inwiefern die Random Set Methode bei Bestimmung der für den Optimierungsprozess von Wasserkraftanlagen relevanten Eingangsgrößen Anwendung finden kann und in wieweit sich hieraus Verbesserungen hinsichtlich Genauigkeit und Aussagekraft der Berechnungsergebnisse ergeben.
45

Modelling of input data uncertainty based on random set theory for evaluation of the financial feasibility for hydropower projects

Beisler, Matthias Werner 25 May 2011 (has links)
The design of hydropower projects requires a comprehensive planning process in order to achieve the objective to maximise exploitation of the existing hydropower potential as well as future revenues of the plant. For this purpose and to satisfy approval requirements for a complex hydropower development, it is imperative at planning stage, that the conceptual development contemplates a wide range of influencing design factors and ensures appropriate consideration of all related aspects. Since the majority of technical and economical parameters that are required for detailed and final design cannot be precisely determined at early planning stages, crucial design parameters such as design discharge and hydraulic head have to be examined through an extensive optimisation process. One disadvantage inherent to commonly used deterministic analysis is the lack of objectivity for the selection of input parameters. Moreover, it cannot be ensured that the entire existing parameter ranges and all possible parameter combinations are covered. Probabilistic methods utilise discrete probability distributions or parameter input ranges to cover the entire range of uncertainties resulting from an information deficit during the planning phase and integrate them into the optimisation by means of an alternative calculation method. The investigated method assists with the mathematical assessment and integration of uncertainties into the rational economic appraisal of complex infrastructure projects. The assessment includes an exemplary verification to what extent the Random Set Theory can be utilised for the determination of input parameters that are relevant for the optimisation of hydropower projects and evaluates possible improvements with respect to accuracy and suitability of the calculated results. / Die Auslegung von Wasserkraftanlagen stellt einen komplexen Planungsablauf dar, mit dem Ziel das vorhandene Wasserkraftpotential möglichst vollständig zu nutzen und künftige, wirtschaftliche Erträge der Kraftanlage zu maximieren. Um dies zu erreichen und gleichzeitig die Genehmigungsfähigkeit eines komplexen Wasserkraftprojektes zu gewährleisten, besteht hierbei die zwingende Notwendigkeit eine Vielzahl für die Konzepterstellung relevanter Einflussfaktoren zu erfassen und in der Projektplanungsphase hinreichend zu berücksichtigen. In frühen Planungsstadien kann ein Großteil der für die Detailplanung entscheidenden, technischen und wirtschaftlichen Parameter meist nicht exakt bestimmt werden, wodurch maßgebende Designparameter der Wasserkraftanlage, wie Durchfluss und Fallhöhe, einen umfangreichen Optimierungsprozess durchlaufen müssen. Ein Nachteil gebräuchlicher, deterministischer Berechnungsansätze besteht in der zumeist unzureichenden Objektivität bei der Bestimmung der Eingangsparameter, sowie der Tatsache, dass die Erfassung der Parameter in ihrer gesamten Streubreite und sämtlichen, maßgeblichen Parameterkombinationen nicht sichergestellt werden kann. Probabilistische Verfahren verwenden Eingangsparameter in ihrer statistischen Verteilung bzw. in Form von Bandbreiten, mit dem Ziel, Unsicherheiten, die sich aus dem in der Planungsphase unausweichlichen Informationsdefizit ergeben, durch Anwendung einer alternativen Berechnungsmethode mathematisch zu erfassen und in die Berechnung einzubeziehen. Die untersuchte Vorgehensweise trägt dazu bei, aus einem Informationsdefizit resultierende Unschärfen bei der wirtschaftlichen Beurteilung komplexer Infrastrukturprojekte objektiv bzw. mathematisch zu erfassen und in den Planungsprozess einzubeziehen. Es erfolgt eine Beurteilung und beispielhafte Überprüfung, inwiefern die Random Set Methode bei Bestimmung der für den Optimierungsprozess von Wasserkraftanlagen relevanten Eingangsgrößen Anwendung finden kann und in wieweit sich hieraus Verbesserungen hinsichtlich Genauigkeit und Aussagekraft der Berechnungsergebnisse ergeben.

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