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- Överstam, Henrik, 1975-
(författare)
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The interdependence of plastic behaviour and final properties of steel wire, analysed by the finite element method
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The finite element method (FEM) has been used in order to study the interdependence of plastic behaviour and final properties in steel wire. Three processes metal forming have been studied: billet forging, wire rod rolling, and cold drawing. The forging study focuses on the possibilities to eliminate voids, pores and pipes by altering the bite ratio in open die forging. Forging is used in wire manufacturing when dealing with materials that are difficult or impossible to roll, e.g. tool steels like high-speed steels, and powder metallurgically manufactured materials like tungsten-molybdenum filament wire. The elimination of inner defects by forging were successfully simulated by the FEM. The rolling study focuses on the problems due of the extreme finish rolling velocities in modern wire rod mills and modern technologies such as thermo-mechanical rolling and sizing. A design for a high-speed laboratory mill for studies of material behaviour at extreme strain rates was made. With a combination of two-high stands and three-roll units is it possible to obtain a smoother temperature distribution in the bar cross section. Two studies of the cold drawing process were made. The first describes the distribution of the plastic deformation due to the die geometry. It was found that the influence of the die angle on the amount of inhomogeneous deformation decreases with increasing area reduction. The frictional behaviour was also studied. The second study describes how the bearing geometry affects the residual stress-state in the wire. It was found that a small taper could change the residual stress state in the surface immensely. This was shown with FE simulations and verified by X-ray diffraction measurements. The results in this paper gives a tool for control of the residual stress-state in the wire. This gives a possibility to increase e.g. the fatigue strength in the final product.
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| 2. |
- Abadei, S., et al.
(författare)
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Microwave properties of tunable capacitors basee on magnetron sputtered ferroelectric Na0.5K0.5NbO3 film on low and high resistivity silicon substrates
- 2001
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Ingår i: Integrated Ferroelectrics. - : Informa UK Limited. - 1058-4587 .- 1607-8489. ; 39:1-4, s. 359-366
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this work, small signal DC voltage dependent dielectric permittivity, loss tangent, and tuneability of magnetron sputtered epitaxial Na0.5K0.5NO3 films are studied experimentally. (100)-oriented Na0.5K0.5NbO3 films are deposited onto SiO2-buffered CMOS grade low resistivity (p = 10-20 cm) and high resistivity (p = 15-45 kcm) silicon substrates. Planar capacitors with 2 or 4 m gaps between electrodes have been fabricated on top of ferroelectric films. These devices have been characterized in the frequency range 1.0 MHz to 50 GHz at temperatures 30 - 300K. Na0.5K0.5NbO3/SiO2/Si structures on high resistivity silicon substrate exhibit C-V performances typical for Metal-Insulator- Semiconductor (MIS) capacitors. At low frequencies, f 1.0 GHz, the large tuneability and large losses are associated with the MIS structure, while at higher microwave frequencies the tuneability is mainly associated with the ferroelectric, film. At 1.0 MHz and room temperature, the tuneability of Na0.5K0.5NbO3/SiO2/Si structures more than 90%, reducing to 10-15 % at 50 GHz. The losses decrease with increasing the DC bias and frequency. A Q-factor more than 15 at 50 GHz is observed. The dielectric permittivity of the Na0.5K0.5NbO3 film is in the range 50-150 at frequencies 0.045-50 GHz. On low resistivity substrate the performance of Na0.5K0.5NbO3 films is completely screened by the high losses in silicon, and the tuneability is negligible. © 2001 Taylor and Francis.
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| 6. |
- Abugessaisa, Imad, et al.
(författare)
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Ontological Approach to Modeling Information Systems
- 2004
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Ingår i: Proceedings of the Fourth International Conference on Computer and information Technology (Cit'04), 14–16 September, Wuhan, China: IEEE Computer Society, Washington, DC. ; , s. 1122-1127
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In recent years, the use of formal tools in information system modeling and development represents a potential area of research in computer science. In 1967, the term ontology appeared for the first time in computer science literature as S. H. Mealy introduced it as a basic foundation in data modeling. The main objective of this paper is to discuss the concept of ontology (from a philosophical perspective) as it was used to bridge the gap between philosophy and information systems science, and to investigate ontology types that can be found during ontological investigation and the methods used in the investigation process. The secondary objective of this paper is to study different design and engineering approaches of ontology as well as development environments that are used to create and edit ontologies.
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| 7. |
- Ackermann, Thomas
(författare)
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Distributed Resources in a Re-Regulated Market Environment
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis analyses the value that distributed resources(DR) can contribute to an economically effcient operation of are-regulated electricity market and discusses the relevantchanges in the regulatory framework to allow the appropriatedevelopment of DR whenever DR may increase the economiceffciency of the electricity market. Distributed resources thereby combine two aspects:Distributed generation and demand-side resources. Distributedgeneration is defined as generation within the distributionsystem or on the customer side of the meter. Demand-sideresources are those load resources on the customer-side thatcan be used to shift electricity demand from peak to off-peakperiods, or to reduce the overall electricity demand. To gain a better understanding of the value that DR mayprovide in a re-regulated market, an analysis of there-regulation approaches in England andWales, Scandinavia,Australia, New Zealand as well as in two regions in the USA isperformed. The key findings of this analysis are that non ofthe re-regulation approaches put special emphasis on DR. Thecomparison also shows that despite very different approachesused in the various markets, the remaining re-regulationproblems are very similar. These key problems are mainlyrelated to market power in the various markets and littlecompetition in network services. The thesis shows that DR has the potential to improveoverall economic market effciency by reducing market powerissues and increasing competition in network services. Forinstance, many DR business schemes have no incentive toexercise market power, because withholding generation may havea negative impact on the complex revenue stream from differentincome sources. While this may not allow the general conclusionthat DR will always provide benefits to market operation, it isimportant to consider that not all DR need to provide suchbenefits, as it was also shown that already comparatively smallamounts of demand resources or distributed generation cansignificantlyreduce market power issues. In addition, it wasalso shown that DR can introduce competition into networkservices and therefore can provide incentives for distributionand transmission network companies to operate more costeffectively. It was also demonstrated that the potential of DR to improveoverall economic market effciency will only be realized if: 1. DR is developed in the correct size, i.e. DR should fitinto an existing distribution network and may increase networkutilization rate,2. DR is developed at the correct location in thenetwork, e.g. in areas with congestion problems,3. DR is in operation during the correct times, whenbeneficial to the market, e.g. during times when market powerissues may arise, and4. independent ownership of DR projects isencouraged. Market regulations therefore must provide the correctincentives for the correct siting and operation of DR as wellas for independent ownership. The thesis uses examples andempirical data to explain the relevant regulatory aspects indetail and provides suggestions for a regulatory framework thatconsiders the potential of DR to improve overall economiceffciency in an electricity market.
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| 9. |
- Adamsson, Niklas, 1977-
(författare)
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Interdisciplinary integration in complex product development : managerial implications of embedding software in manufactured goods
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Incorporating electronics and software systems into manufactured goods is becoming very common in manufacturing companies. New technical functions, increased flexibility, and compensation for mechanical design weaknesses are some key drivers of this technological change in our everyday products. The automotive industry exemplifies this trend, since approximately 80–90% of new functions in cars are based on electronics and software, and it is expected that at least a third of the total cost of a car will eventually be accounted for by electronics and software. However, one of the main downsides of this technological trend is the increasing number of quality issues related to these new technologies, something usually claimed to be a result of the increased product development complexity. Previous research into product development management has mainly concentrated on either physical products or software systems, but not concurrently on both. Additionally, much of the research has concentrated on issues of integrating marketing, R&D, and manufacturing in these companies, and has treated the engineering disciplines in R&D as a homogenous group. Motivated by this change in technology content and the lack of research into complex product development and especially into integration between engineering disciplines, the present work investigates how to increase operational performance in multidisciplinary engineering organizations. This work has especially focused on interdisciplinary integration and the feasibility of various so-called integration mechanisms, such as building common physical facilities, job rotation programs, the implementation and use of information and communications technology, and computer-aided engineering tools. Both qualitative and quantitative research has been performed, involving 11 different companies and over 300 respondents. Supported by the present findings, it is demonstrated that interdisciplinary integration is a crucial factor to consider, and it is concluded that certain integration mechanisms stand out as more important than others. Organizational structure, work procedures and methods, training, social systems, and computer-aided engineering were the five types of mechanisms that displayed the greatest potential for improvement. It is further concluded that the ability to successfully match the body of practices to current products is essential, since there is a high risk of current practices becoming out-dated with respect to the technology content. Furthermore, inadequate identification of or managerial ability to establish the currently most important interfaces complicate the choice of trade-offs between various technologies that are found to be essential to cope with the inherent dynamic complexity. The organizational powerbase is often re-positioned in the studied organizations, and the loss of decisive power can result in a demoralizing ignorance of newly established disciplines and their design practices. Additionally, rigid structures and counterproductive traditions can reduce the potential gains accruing from new boundary-spanning innovations, so organizational responsibilities and mandates must be declared unambiguously, in many cases differently from how they have been in the past. Based on these conclusions, it is suggested that managers in organizations like those studied must be able to do the following: cultivate software knowledge in all parts and levels of the product development organization; reassess their recruitment strategies; organize for interdisciplinary collaboration; articulate and communicate the technology fusion strategy to all disciplines; and realize and disseminate the fact that product launches do not only concern manufacturability.
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| 10. |
- Adamsson, Niklas, 1977-
(författare)
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Mechatronics engineering : New requirements on cross-functional integration
- 2005
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Several industrial sectors experience an increased reliance on mechatronic systems as electronics and software are being embedded into the traditional mechanical systems of these industries. Important challenges within mechatronics engineering comes from management of multi-disciplinary development project teams and the highly complex scope of problems, which in turn require extensive coordination and integration, both in terms of technical and organisational matters. The concept of cross-functional integration in product development research has in previous research mainly addressed integration of the functions marketing, R&D, and manufacturing, and whereas the present thesis is delimited to include only the R&D organization and the functions and engineering disciplines within such an organization. The purpose with thesis has been to investigate mechatronics engineering in order to understand and explain how co-operation, integration, and knowledge sharing between engineering disciplines can be supported. This research has been realized by empirical studies in mechatronic development settings in engineering companies, but also by taking part in industrial and academic research projects that develop and study computer-aided mechatronics engineering. Findings presented in this thesis show that mechatronics is a matter of integration at three organizational levels where the most substantial needs are found to be at the team-level and the individual level. Furthermore, it is identified that to be able to succeed in mechatronics engineering, managers and engineers must look beyond disciplinary needs. Subsequently, both teamwork and competence management become key issues for management of mechatronics engineering. Finally, computer-supported and model-based development of mechatronics show great potential for successful integration of engineering disciplines, even though such technological aids are still rather immature and needs further research and development. A tentative analysis model of organizational integration for mechatronics engineering is also presented and discussed in this thesis. Based on the presented findings, it is concluded that companies incorporating electronics and software in their mechanical products must effectively manage software and electronics development of these embedded systems. Despite the focus on cross-functional integration in engineering companies, this thesis shows examples of inadequate integration of software and electronics engineering with mechanical integration in organisations dominated by the latter. Future research studies are needed to investigate the relation between factors influencing the need for organizational integration and potential integration mechanisms. To further understand mechatronics engineering it is important to look deeper into research issues such as changed conditions for the engineering profession implied by multidisciplinary settings, social systems supporting integration of disciplines, changed work conditions due to implementation of technological aids for model-based system development, relationship between product and organizational complexity, organizational designs supporting integration of engineering disciplines, and cross-disciplinary training of highly specialized engineers.
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