| 1. |
- Brandt, Anders, et al.
(author)
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A Digital Filter Method for Forced Response Computation
- 2003
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Conference paper (peer-reviewed)abstract
- Transient forced response of mechanical structures is usually computed using time domain integration. This is often computationally costly, and the numerical precision and stability are concerns. In the present paper, a novel method based on modal superposition, using a new digital filter implementation, is presented. Poles and residues of the model are used as input data, which allows for using data from a finite element model, a lumped parameter model, or from experimental modal analysis. Modal damping can be used if the damping matrix is unknown. With the proposed method, the frequency dependant error can easily be computed, and can be chosen arbitrarily small by selecting proper sampling frequency (time increment). The method is applicable to all linear structures and can be used for stationary or transient input data. Simulation results show that the new method is superior to the alternative methods, at less computational cost.
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| 2. |
- Andersson, Roger, et al.
(author)
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Large Housing Estates in Sweden. Overview of developments and problems in Jönköping and Stockholm
- 2003
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Reports (other academic/artistic)abstract
- All over Europe massive numbers of people live in large-scale housing estates built after the Second World War. The estates were carefully planned, but now often manifest a mulitude af problems. They house large numbers of low-income households, the unemployment rates are above average and in some countries they have become concentration areas for ethnic minorities. Many estates are becoming increasingly associated with crime and social exclusion. The circumstances on the estates and policy initiatives associated with these are focus of the RESTATE-project. RESTATE is the acronym for Restructuring Large-scale Housing Estates in European Cities: Good Practices and New Visions for Sustainable Neighbourhoods and Cities. The study draws on estates in ten European countries: France, Germany, Hungary, Italy, the Netherlands, Poland, Slovenia, Spain, Sweden and the United Kingdom. The present report deals specifically with large housing estates in two cities in Sweden: Jönköping och Stockholm. The basic questions are about physical structure, demographic-, economic- and socio-cultural developments. The same kind of information for estates in other countries in the RESTATE-project can be found in the parallel reports
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| 3. |
- Andrén, Linus, et al.
(author)
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Identification of Dynamic Properties of Boring Bar Vibrations in a Continuous Boring Operation
- 2004
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In: Mechanical systems and signal processing. - : Academic Press. - 0888-3270 .- 1096-1216. ; 18:4, s. 869-901
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Journal article (peer-reviewed)abstract
- Vibrations in internal turning operations are usually a cumbersome part of the manufacturing process. This article focuses on the boring bar vibrations. Boring bar vibrations in alloyed steel, stainless steel and cast iron have been measured in both the cutting speed direction and the cutting depth direction with the aid of accelerometers. The dynamic response of a boring bar seem to be a time varying process that exhibits non-linear behaviour. The process is influenced by non-stationary parameters that are not under the control of the operator or experimenter. The vibrations are clearly dominated by the first resonance frequency in one of the two directions of the boring bar. The problem with force modulation in rotary machinery, which appears as side band terms in the spectrum, is also addressed. Furthermore, the resonance frequencies of the boring bar are correlated to an Euler-Bernoulli beam model.
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| 4. |
- Andrén, Linus, et al.
(author)
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Identification of Motion of Cutting Tool Vibration in a Continuous Boring Operation : Correlation to structural Properties
- 2004
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In: Mechanical systems and signal processing. - : Academic Press, UK. - 0888-3270 .- 1096-1216. ; 18:4, s. 903-27
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Journal article (peer-reviewed)abstract
- The internal turning operation has a history of being a cumbersome metal working process as vibration in boring operations is usually inevitable. In this article, the deflection shapes and/or mode shapes as well as the resonance frequencies of a boring bar have been put under scrutiny. Three methods have been used in order to investigate dynamic properties of a clamped boring bar: a theoretical Euler-Bernoulli beam model, an experimental modal analysis and an operating deflection shape analysis. \\ The results indicate a correlation between the shapes of the deflection shapes and/or mode shapes produced by the three different analysis methods. On the other hand, the orientation of the forced deflection shapes and/or mode shapes and the resonance frequencies demonstrates differences between the three methods. During continuous cutting, it is demonstrated that the bending motion of the first two resonance frequencies is to a large extent in the cutting speed direction.
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| 5. |
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| 6. |
- Fai, Cedric Yiu Ka, et al.
(author)
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A New Design Method for Broadband Microphone Arrays for Speech Input in Automobiles
- 2002
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In: IEEE Signal Processing Letters. - : IEEE. - 1070-9908 .- 1558-2361. ; 9:7, s. 222-224
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Journal article (peer-reviewed)abstract
- A new design method for broadband microphone arrays is presented. Using sequences of calibration signals, the method is able to design finite-impulse response (FIR) filters with specific performance. The method can control and adjust the speech distortion, noise suppression, and echo cancellation directly. It turns out that a significantly shorter filter length can be applied to achieve better overall performance than the least-squares method or the signal-to-noise plus interference method.
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| 7. |
- Kao-Walter, Sharon
(author)
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On the Fracture of Thin Laminates
- 2004
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Doctoral thesis (other academic/artistic)abstract
- This thesis concerns mechanical and fracture properties of a thin aluminium foil and polymer laminate that is widely used as packaging material. The possibility of controlling the path of the growing crack propagation by adjustment of the adhesion level and the property of the polymer layer is investigated. First, the fracture process of the aluminium foil is investigated experimentally. It is found that fracture occurs at a much lower load than what is suggested by standard handbook fracture toughness. Observations in a scanning electron microscope with a tensile stage show that small-scale stable crack growth occurs before the stress intensity factor reaches its maximum. An examination using an optical profilometric method shows almost no plastic deformation except for in a small necking region at the crack tip. However, accurate predictions of the maximum load are obtained using a strip yield model with a geometric correction. Secondly, the mechanical and fracture properties of the laminate are studied. A theory for the mechanics of the composite material is used to evaluate a series of experiments. Each of the layers forming the laminate is first tested separately. The results are analysed and compared with the test results of the entire laminate with varied adhesion. The results show that tensile strength and strain at peak stress of the laminate, with or without a crack, increase when the adhesion of the adhesive increases. It is also found that a much larger amount of energy is consumed in the laminated material at tension compare with the single layers. Possible explanations for the much higher toughness of the laminate are discussed. Finally, the behaviour of a crack in one of the layers, perpendicular to the bimaterial interface in a finite solid, is studied by formulating a dislocation superposition method. The stress field is investigated in detail and a so-called T stress effect is considered. Furthermore, the crack tip driving forces are computed numerically. The results show that the analytical methods for an asymptotically small crack extension can also be applied for a fairly large amount of crack growth. By comparing the crack tip driving force of the crack deflected into the interface with that of the crack penetrating into the polymer layer, it is shown how the path of the crack can be controlled by selecting a proper adhesion level of the interface for different material combinations of the laminate.
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| 8. |
- Ketola, Katja
(author)
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I mötet mellan projekt och process. Om samverkan
- 2000
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Licentiate thesis (other academic/artistic)abstract
- This thesis for the degree of Licentiate of Architecture is an inquiry into the possibilities and obstacles for a communicative planning practice in the regeneration of neighbourhoods. Focusing on the planning process it discusses the commonly used concept of collaboration and trust as a prerequisite of collaboration. It draws on communicative planning theory and the institutionalist approach in social science. The study includes a qualitative case study of a regeneration project in the neighbourhood Navestad in Norrköping. The regeneration project was officially described as a continuous process based on a participatory approach and collaboration between different planning levels. The project aimed to break the pattern of prior regeneration projects in the neighbourhood; projects with an ad hoc character based on an instrumental and objective planning approach. The thesis highlights two aspects of trust relations as momentous for collaboration in the regeneration project: the reciprocity in trust and the significance of prior experiences in the judgement of the risk in showing trust in the relationships between different stakeholders in the planning process. Different styles of planning governance within the regeneration project are identified. The analysis of the planning process shows that collaboration was obstructed by differences in the rationality of means between stakeholders acting in different governance styles. The thesis emphasizes that the institutional basis for developing governance forms that facilitate a communicative planning practice is too weak for breaking the pattern of objective and instrumental planning of the previous regeneration projects in the neighbourhood.
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| 9. |
- Nordholm, Sven, et al.
(author)
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Performance Limits in Subband Beamforming
- 2003
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In: IEEE transactions on speech and audio processing. - : IEEE. - 1063-6676 .- 1558-2353 .- 2329-9290. ; 11:3, s. 193-203
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Journal article (peer-reviewed)abstract
- This paper analyzes subband beamforming schemes mainly aimed at speech enhancement and acoustic echo suppression applications such as hands-free telephony for both mobile and office environments, internet telephony and video conferencing. Analytical descriptions of both causal finite-length and noncausal infinite-length subband microphone array structures are given. More specifically, this paper compares finite Wiener filter performance with the noncausal Wiener solution, giving a comprehensive theoretical suppression limit. It is shown that even short filters will yield a good approximation of the infinite solution, provided that the element spacing and temporal sampling is matched to the frequency band of interest. Typically, 10-20 FIR taps are sufficient in each subband.
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| 10. |
- Vuorio, Tuomas
(author)
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Information on recreation and tourism in spatial planning in the Swedish mountains : methods and need for knowledge
- 2003
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Licentiate thesis (other academic/artistic)abstract
- The Swedish mountain region makes up about one third of the country but includes less than 2 per cent of the population. It stretches for over 1000 km and includes 90 per cent of the total nature conservation area in Sweden. With its 8000 km of hiking trails and 100 mountain huts and lodges it is one of the most important areas for outdoor recreation and tourism - visited by one fourth of the Swedish adult population every year. With the current decline of the extractive industries tourism has become an important development issue in the area. Effective spatial planning in the mountains presupposes good information on tourism and outdoor recreation. Municipalities need adequate data to base planning on. One precondition for more effective information supply to spatial planning is research and development of methods. It must be possible to follow developments, predict environmental effects and effects on user attitudes, satisfaction etc. There are big differences between visitors in the mountains. Their needs and interest in different nature experiences, their tolerance towards crowding and contacts with other users vary a lot. It is important for planning and management to find out which qualities users are looking for and appreciating and to have a clear picture of the variance between different users. Management of recreation areas is normally combined with conservation and often has two goals: i) to maintain “natural conditions” and ii) to provide recreation opportunities. These two goals will often be contradictory. Resolving this conflict is both a theoretical and practical problem. The discourse within spatial planning differs from the nature conservation discourse. While the nature conservation discourse comes from a tradition of “calculating rationality” and a scientific, central view that points out the foremost values – “national interests”, national parks, world heritage areas – the basis of the spatial planning ideology in Sweden is a conception of local, political decision making. The Swedish planning system with a planning monopoly and veto of the municipalities is in theory a system with deliberative or communicative rationality: the plan is supposed to express citizens’ will and needs expressed through their representatives. How to provide the planning system with relevant information on different levels, i.e. information that can be used for predicting different reactions to different management actions in order to be able to handle conflicts will be one of the central questions in the thesis. Special attention will be paid to different methods of measuring nature tourism and outdoor recreation. Self registration combined with satisfactory studies on non participation can give a relatively good synoptic picture of the use of the area. At the same time it is obvious that the non participation varies too much geographically and between different points of time for self registration alone to be used for studying frequencies and patterns of use. Flight observations carried out as a part of the study in Södra Jämtlandsfjällen (article II) proved to be a good method of studying the patterns of camping. They were also important for conflict analysis and studying divergences. The indirect methods for estimating the total number of visitors have to be calibrated often, which can be difficult (for example number of visitors in a car or a buss). The indirect methods risk missing factors that make it possible to get indications of possible tendencies in the use of an area. In situations where conflicts exist, it is important that the picture of the present situation is well established and legitimate. This means that both methods and the actors participating in the study have to be experienced as legitimate by all parties taking part in the planning process. A general conclusion is that there are not any good shortcuts to useful knowledge about outdoor recreation and tourism for planning as a whole, for management or for EIA. Need for predictions is far too big to make indirect data useful alone. Three studies are presented: i) a national screener study on current tourism patterns in the Swedish mountain region, ii) a case study among the visitors in Södra Jämtlandsfjällen and iii) a case study among the residents in Södra Jämtlandsfjällen.
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