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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.
31

Application of electrical measurements to monitor the breakdown of organic coating systems applied to metallic substrates

Thompson, Ian January 1994 (has links)
No description available.
32

An integrated approach to fatigue cracking, reliability and inspection of offshore structures

Wolfram, Julian January 1985 (has links)
This thesis describes an integrated approach to fatigue cracking, reliability and inspection of offshore structures. The basis of the approach is statistical in nature and draws on recent experimental data and field measurements. It is intended as a working tool for those engaged in design, structural appraisal and sub-sea inspection of steel jacket structures. A review of current practice has been made and the requirements of an integrated approach are established. An approach is proposed comprising a series of compatible models dealing with fatigue cracking, the reliability of cracked joints and the inspection of welds for fatigue cracks. The primary linking parameter is the distribution of fatigue crack size which is considered as a time dependent variable. An integral part of the approach is a new statistically-based fatigue crack growth model. This is developed and the parameters involved in the model estimated from an analysis of experiment and oceanographic data. For any fatigue calculation the model allows the corresponding fatigue crack growth distribution to be estimated for any time during, or beyond, the nominal fatigue life. A number of example calculations are included; and using one of these a Bayesian procedure for revising fatigue lives in the light of inspection results is demonstrated. The effect of fatigue cracking upon the various modes of tubular joint failure is considered using linear statistical models. Example calculations are performed for a typical joint. An inspection strategy is proposed based on the concept of minimising life costs, including risk costs arising from the consequences of possible structural failure. This allows alternative inspection plans to be evaluated and compared, and a typical example calculation is included. The approach is discussed in the context of possible alternative approaches and areas for further related research are identified.
33

Transmission alternatives for grid connection of large offshore wind farms at large distance / Transmissionslösningar för nätanslutning av stora havsbaserade vindkraftsparker

Moberg, Désirée January 2013 (has links)
With the great possibility of offshore wind power that can be installed in the world seas, offshore wind power is starting to get and important source of energy. The growing sizes of wind turbines and a growing distance to land, makes the choice of transmission alternative to a more important factor. The profitability of the transmission solution is affected by many parameters, like investment cost and power losses, but also by parameters like operation & maintenance and lead time of the system. The study is based on a planned wind farm with a rated power of 1 200 MW and at a distance of 125 km to the connection point. Four models have been made for the transmission network with the technology of HVAC, HVDC and a hybrid of both. The simulation program used is EeFarm II, which has an interface in Matlab and Simulink. The four solutions have been compared technically, with difficulties and advantages pointed out and also economically, with the help of LCOE, NPV and IRR. Costs, power losses and availability of the wind turbines and intra array network are not included in the study. The result of the simulations implies that the HVAC solution is the most profitable with the lowest Levelized Cost of Energy and highest Net Price Value and Internal Rate of Return. The values are 25.11 €/MWh, 387.60 M€ and 15.32 % respectively. A HVDC model with just one offshore converter station, has a LCOE close to the HVAC solution, but with a more noticeable difference in NPV and IRR (25.71 €/MWh, 300.76 M€ and 14.84 % respectively). A sensitivity analysis has been done, where seven different parameters have been changed for analysing their impact on the economic result. The largest impact made was by a change in investment cost and lead times. The results imply that with a structure of the transmission network as for the models, and with similar input data, the break point where a HVDC solution is more profitable than a HVAC solution is not yet passed at a distance of 125 km from the connection point. With an evolving technology in the field of HVDC, a shorter lead time and lower investment cost could mean that a HVDC solution would be more profitable at this distance. Difficulties for a HVAC solution with more cable required, like bigger land usage and cable manufacturing as a bottle neck, could make an important factor tough while making a decision. / Med den stora potentialen hos världens hav, börjar havsbaserad vindkraft bli en betydande energikälla. Den ökande storleken på vindkraftsturbinerna tillsammans med de ökade avstånden mellan vindkraftsparkerna och land, gör att transmissionslösningen blir en mer betydelsefull komponent. Flera olika parametrar kan vara avgörande för transmissionslösningens lönsamhet, som investeringskostnad och effektförluster, men också saker som drift & underhåll och projektets ledtid. Studien är baserad på en planerad vindkraftspark med en märkeffekt på 1 200 MW och på ett avstånd på 125 km till anslutningspunkten. Fyra modeller av transmissionssnätet har gjorts, där tekniken har bestått av HVAC, HVDC samt en blandning av dessa. Simuleringarna har gjort i EeFarm II, ett program baserat på Matlab och Simulink. De fyra modellerna har jämförts tekniskt, med för- och nackdelar poängterade, och även ekonomiskt med hjälp av LCOE, NPV och IRR. Kostnader, effektförluster och tillgängligheten för vindkraftsturbinerna och internnätet i vindkraftsparken är inte inkluderade i studien. Resultaten av simuleringarna visar på att HVAC-lösningen är den mest lönsamma, med lägst Levelized Cost of Energy och högst Net Price Value och Internal Rate of Return. Värdena för dessa är 25,11 €/MWh, 387,60 M€ respektive 15,32 %. En HVDC-lösning med enbart en DC-plattform och likriktarstation för hela märkeffekten, har en LCOE inte långt ifrån HVAC-lösningen, men med en lite större skillnad i NPV och IRR (25,71 €/MWh, 300,76 M€ respektive 14,84 %). För att analysera påverkan av olika parametrar på de ekonomiska mätvärdena, har en osäkerhetsanalys gjort. Den största påverkan på resultatet syntes av förändringar av investeringskostnader och ledtider. Ovanstående resultat tyder på, med transmissionslösningar enligt modellerna i detta arbete, att brytpunkten där en HVDC-lösning är mer lönsam än en HVAC-lösning inte än är passerad vid ett avstånd på 125 km till anslutningspunkten. Med en fortfarande väldigt ung teknik för HVDC, kan den ständigt utvecklande tekniken i framtiden betyda kortare ledtider och en lägre investeringskostnad för en HVDC-lösning och möjligheten att vara en mer lönsam lösning. Komplikationer med en HVAC-lösning pga den extra landkabeln, som större landanvändning och med kabeltillverkningen som en flaskhals, kan ändå göra en HVDC-lösning mer praktisk.
34

Development of a composite repair system for reinforcing offshore risers

Alexander, Christopher Richard 15 May 2009 (has links)
A research program was conducted to investigate the application of composite materials in repairing corroded offshore risers, leading to the development of an optimized repair using a hybrid carbon/E-glass system. The objective of this research program was to investigate the feasibility of extending onshore composite repair techniques to offshore risers by developing integrated analytical and experimental methods. The study considered loads typical for offshore risers including internal pressure, tension, and bending. To fulfill this objective efforts included a state of the art assessment of current composite repair technology, designing a carbon-based composite repair system optimized by numerical simulation with prototype testing, and providing guidelines for industry in repairing and reinforcing offshore risers using composite materials. Research efforts integrated numerical modeling, as well as full-scale testing that included four composite repair manufacturers to assess the current state of the art on pipe samples with simulated corrosion reinforced with composite materials. Analysis and testing were also performed on the optimized carbon/E-glass system. The results of this program demonstrated that composite materials are a viable means for repairing corroded offshore steel risers as adequate reinforcement ensures that the steel risers are not loaded beyond acceptable design limits. For corroded risers, the results demonstrated through analysis and full-scale testing efforts that properly designed composite repair systems can provide adequate structural reinforcement to ensure that excessive strains are not induced in the steel when subjected to internal pressure, axial tension, and bending design loads. This was verified experimentally using strain gages placed beneath the composite repair. This program is the first of its kind and is thought to contribute significantly to the future of offshore riser repairs. It is likely that the findings of this program will foster future investigations involving operators by integrating their insights regarding the need for composite repair based on emerging technology. One of the most significant contributions to the existing body of work is the use of limit analysis in developing design limits for the repair of steel pipes using composite materials.
35

IS offshoring essays on project suitability and success /

Westner, Markus K. Strahringer, Susanne. January 1900 (has links)
Thesis (doctoral)--European Business School, International University Schloss Reichartshausen, 2009. / Includes bibliographical references.
36

Drilling for oil and gas in and near Florida lease sale 181 and beyond /

Dempsey, Angela C. Moore, Dennis D. January 2003 (has links)
Thesis (M.A.)--Florida State University, 2003. / Advisor: Dr. Dennis D. Moore, Florida State University, College of Arts and Sciences, Program in American and Florida Studies. Title and description from dissertation home page (viewed Mar. 2, 2004). Includes bibliographical references.
37

A computational procedure for three-dimensional simulation of nonlinear gravity wave propagation and response of floating structures

Hardjanto, Fauzi Adi. January 2002 (has links)
Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.
38

Strategic choices for business process sourcing

Ge, Ling, 1976- 12 October 2012 (has links)
Firms increasingly disaggregate business processes and source them on a global basis, either intra-firm or from external vendors. This dissertation examines two relevant strategic choices for business process sourcing: the choice of sourcing mechanisms and the choice of contract types. First a comprehensive choice model is proposed to incorporate different perspectives of transaction cost economics (TCE), resource-based view (RBV) and modular systems theory for the choice of sourcing mechanisms. The results indicate that modular design characteristics such as modularity and IT detachability of business processes have significant impact on firms’ sourcing choices. The findings show that at higher level of process modularity, domestic outsourcing is more likely while offshore outsourcing is more preferred at lower level of process modularity. Also domestic outsourcing is preferred over offshore outsourcing when processes are tightly coupled with the IT infrastructure. The results suggest that offshore outsourcing is a different governance mode from domestic outsourcing. It may be a viable choice for firms that are looking for capabilities and adaptation willingness to improve the modular design of a process and to meet firm-specific needs, but the nonmodular design of IT infrastructure may inhibit such attempts. The dissertation then examined how firms select appropriate types of contract once outsourcing decisions are made. Three types of contracts were considered: Fixedprice (FP), Cost-plus (CP) and Time & Materials (T&M), which provide different levels of cost-reduction incentive, completeness of contract design and flexibility to change. The findings suggest that business characteristics impact coordination and negotiation costs and thus the choice of contract types. Higher coordination costs (the costs of managing interdependence) lead to higher probability of selecting contracts with high incentives and detailed service descriptions such as FP contracts while high negotiation costs (the costs of opportunistic behavior in ex post adaptation) increase firms’ preference to contracts with more flexibility to change such as T&M contracts. Further, the selection bias of the choice of sourcing mechanism on the choice of contract types was identified. Firms that select outsourcing are more likely to adopt contracts with high level of incentive and contract completeness. / text
39

Two essays in environmental economics and offshoring

Zhou, Mohan., 周默涵. January 2013 (has links)
This dissertation consists of two independent studies. The first study belongs to the field of environmental economics and the second is on international trade, with a focus on offshoring. In the first study, we investigate firm investment in advanced abatement technology under a heterogeneous firms framework. In contrast to existing literature, we find that the optimal level of investment in advanced abatement technology is an inverted U-shaped function of firm productivity. More-productive firms have superior environmental performance, in the sense that they have lower emission per unit of output. Comparative statics shows that in response to a tighter environmental regulation, more-productive firms tend to raise their investment in advanced abatement technology while less-productive firms do the opposite. Key theoretical predictions are confirmed by Chinese data. The second study analyzes the decision of a multinational firm from a developed country to slice a production chain to allocate different tasks of the production chain globally. The process involves a wide range of tasks that varies from very routine jobs to very research and development (R&D) intensive work. We find that under certain conditions, a drop in offshoring costs (1) leads to more slicing (an increase in the length of production chain) and more offshoring, (2) stimulates R&D, and (3) raises employment in the developed country. / published_or_final_version / Economics and Finance / Doctoral / Doctor of Philosophy
40

Performance of suction caisson anchors in normally consolidated clay

El-Sherbiny, Rami Mahmoud 28 August 2008 (has links)
Not available / text

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