| 1. |
- Andrén, Linus
(författare)
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Active suppression of vibration and noise in industrial applications
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Today, active control technology is about to emerge from the research labs into products in various areas. It has become an attractive method where passive techniques have low impact at low frequencies and adding active control to that part is often an attractive solution. The active control technique has been enabled by the rapid development of digital signal processors over the last decades. The focal point in this thesis is active vibration and noise suppression. Two different industrial applications have been subjected to active control to reduce unwanted disturbances. In cutting operations, active vibration suppression has been applied to both external turning and boring operations with successful results. Turning operations, and in particular boring operations, are typical examples of chatter prone machining. In order to implement active vibration control in boring operations a thourough investigation of the boring process has been made in the first two parts in this thesis. The following two parts of the thesis treat active vibration suppression in external turning operations and in boring operations. The second industrial application treats the noise in a fork-lift truck. In the final part of the thesis, active noise suppression has been implemented in the cabin of a fork-lift truck.
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| 2. |
- Bengtsson, PerOlof
(författare)
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Architecture-Level Modifiability Analysis
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cost, quality and lead-time are three main concerns in software engineering projects. The quality of developed software has traditionally been evaluated on completed systems. Evaluating the product quality at completion introduces a great risk of wasting effort on software products with inadequate system qualities. It is the objective of this thesis to define and study methods for assessment, evaluation and prediction of software systems’ modifiability characteristics based on their architecture designs. Since software architecture design is made early in the development, architecture evaluation helps detect inadequate designs and thus reduces the risk of implementing systems of insufficient quality. We present a method for architecture-level analysis of modifiability (ALMA) that analyses the modifiability potential of a software system based on its software architecture design. The method is scenario-based and either compares architecture candidates, assesses the risk associated with modifications of the architecture, or predicts the effort needed to implement anticipated modifications. The modification prediction results in three values; a prediction of the modification effort and the predicted best- and worst-case effort for the same system and change scenario profile. In this way the prediction method provides a frame-of-reference that supports the architect in the decision whether the modifiability is acceptable or not. The method is based on the experiences and results from one controlled experiment and seven case-studies, where five case studies are part of this thesis. The experiment investigates different ways to organize the scenario elicitation and finds that a group of individually prepared persons produce better profiles than individuals or unprepared groups.
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| 3. |
- Björkman, Christina
(författare)
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Crossing Boundaries, Focusing Foundations, Trying Translations : Feminist Technoscience Strategies in Computer Science
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis I explore feminist technoscience strategies in computer science, starting in “the gender question in computer science”, and ending up in communication and translation between feminist technoscience research and computer science educational practice. Necessary parts in this work concern issues of boundary crossings between disciplines, and focusing on the foundations of computer science: what it means to “know computer science”. The point of departure is in computer science (CS), in particular CS education. There are at this starting point two intertwined issues: the gender question in computer science (often formulated as “what to do about the situation of women in computer science?”) and the foundation question: “what does it mean to know computer science?”. These are not primarily questions looking for answers; they are calls for action, for change and transformation. The main focus and goal of this thesis concerns how to broaden the meaning of “knowing computer science”; to accommodate epistemological pluralism and diversity within the practices and among the practitioners of CS. I have identified translation as fundamental, to make feminist research and epistemological perspectives communicable into the community of computer science practitioners. In this, questions of knowledge and how knowledge is perceived and talked about are central. Communication and translation also depend on the ability and willingness to cross boundaries, to engage in “world- travelling” (Lugones). Additional issues of importance are asking questions open enough to invite to dialogues, and upholding critical (self) reflection. An important goal for feminist research is transformation. Because of this, interventions have been part of my research, interventions in which I myself am implicated. The work has been based in feminist epistemological thinking, where the concepts of positioning and partial perspectives (Haraway) have been of particular importance. After an introduction, the thesis consists of three parts, each part relating to one of the three issues in the title, issues identified as important for feminist technoscience work in computer science. In part A, I investigate and discuss what it means to be simultaneously an engineer/computer scientist and a feminist technoscience researcher. What boundary crossings, challenges, conflicts, negotiations and issues of being inside and outside are involved? This part also focuses on what the implications of these boundary crossings and different “mind-sets” are for transformatory work in science and engineering education, as well as a discussion of what feminist technoscience research can be and how it can be used for interventions and transformations. Part B focuses on foundations of computer science. This part consists of studies of texts, which I critically read and query from a feminist technoscience perspective, in order to challenge existing approaches and concepts within computer science. The texts are about the gender question in computer science; foundational topics of “what is computer science”, as well as epistemological questions concerning approaches to knowledge in computer science: “what does it mean to know computer science”? Part C deals with a concrete intervention project aiming at establishing conversations with computer science faculty. In this project, the issues of communication and translation appear as central. The focus in this part is communication between computer science educational practice and feminist technoscience research, language as a carrier of epistemology, and a discussion of translation.
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| 4. |
- Broberg, Magnus
(författare)
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Performance Prediction and Improvement Techniques for Parallel Programs in Multiprocessors
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The performance of a computer system is important. One way of improving performance is to use multiprocessors with several processors that can work in parallel. Where multiprocessors are used, the programs must also be parallel in order to achieve high performance. However, it is not always easy to write parallel programs for multiprocessors; program developers need support in this area. Such support includes, for example, information regarding how well the parallel program scales-up when the number of processors increases and identification of performance bottlenecks; ideally, the result should be presented graphically. Bottlenecks arise both as a result of parallelization as well as traditional (sequential) code. Further, the developer may need to predict performance on other systems than the one used for development, since the development environment often is the (uni-processor) workstation on the developer's desk. One way of increasing the performance may be to bind threads on processors statically. Finding the optimal allocation is NP-hard and it is necessary to resort to heuristic algorithms. When heuristic algorithms are used we do not know how near/far we are from the optimal allocation. Finding a bound for the program's completion time shows what should be achievable using a heuristic algorithm. In this thesis, I present techniques how to simulate a multiprocessor execution of a parallel program based on a monitored execution on a uni-processor. The result of the (simulated) multiprocessor execution is graphically presented in order to give feedback to the developer. The techniques can be used for heuristic algorithms to find an allocation of threads to processors. Further, I show an algorithm that identifies the critical path of the parallel program on a multiprocessor, thereby identifying the segments that are worthwhile optimizing. I also show how to calculate a tight bound on the minimal completion time for the optimal allocation of threads to processors. Finally, I discuss the implications of the choice of simulation model. The techniques and algorithms described have been manifested in a prototype tool which I have used to perform empirical studies. The tool has been validated using a real multiprocessor.
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| 5. |
- Carlsson, Bengt
(författare)
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Conflicts in Information Ecosystems
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main topic of this thesis concerns the study of how conflicting interests of software agents within an information ecosystem may cause cooperative behavior. Since such agents act on the behalf of their human owners, which often act in their own interest, this will sometimes result in malignant acts. Different types of models, often inspired by biological theories such as natural selection, will be used to describe various aspects of such information ecosystems. We begin by adopting a game theoretic approach where a generous and greedy model is introduced. Different agent strategies for iterated games are compared and their ability to cooperate in conflicting games are evaluated in simulation experiments. The conclusion is that games like the chicken game favor more complex and generous strategies whereas in games like the prisoner’s dilemma, the non-generous strategy tit-for-tat often is the most successful. We then use models based on a surplus value concept to explain antagonistic group formations. The focus is on systems that consist of exploiter agents and agents being exploited. A dynamic protection model of access control is proposed, where a chain of attacks and countermeasures concerning the access are measured. This process can be described as an arms race. It is argued that arms race is a major force in the interaction between antagonistic agents within information ecosystems. Examples of this are given in several contexts such as peer-to-peer tools concerning anonymity and non-censorship, using agents for sending or filtering out mass distributed advertisement e-mails, and finally for describing the fight against viruses or spywares.
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| 6. |
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| 7. |
- Elovaara, Pirjo
(författare)
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Angels in Unstable Sociomaterial Relations : Stories of Information Technology
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- I have explored spaces, where negotiations of border transgressions take place and where issues of technology and politics mingle. We meet a diversity of actors in the world of information technology (IT): political texts, people and technology participating in numerous sociomaterial relations. Time is the end of the 1990s and the beginning of the new millennium, 2000. Years, when IT occupied the western world and created its own fuzzy discourse. Years, when IT stole the biggest newspaper headlines and years, when IT became a mundane everyday part of our work practices. Years, when we learned to live in heterogeneous worlds. Actor-Network Theory (ANT) and Actor-Network Theory and After (ANTa) provide analytical and methodological perspectives when working with the empirical material. I present a chronological exposé of some of the key concepts of ANT and ANTa. I also discuss how the classical ANT perspective has changed during the last few years from being a theory of networks to become a methodological and analytical approach to other kinds of spaces such as fluid and fire. The heart of the thesis consists of six empirical cases. My aim of writing stories of information technology has been to investigate the black box of information technology. Investigating includes also efforts of opening. Concepts that are taken for granted, such as the very notion of information technology in my case, can be explored, questioned, transgressed, blurred and opened up. Each of the diffracted stories is specific and unique, with its own actors, context, location and situatedness. But the stories are also connected through ANT, and feminist technology and technoscience studies. Case number one, ‘Discourses and Cracks – A Case Study of Information Technology and Writing Women in a Regional Context ’, is about a project, where questions concerning discourses of information society with a special focus on citizenship are discussed and where global and national politics are translated to local and situated practices. Case number two, ‘Translating and Negotiating Information Technology ’, consists of two main parts. The fi rst one is about a regional library project. The analysis of the project is based on the classical Actor Network Theory (ANT) approach that invites the study of the heterogeneous and negotiable shaping of IT. The second part is about librarians developing web-based services. The analysis is inspired by the later development of ANT (called ANTa in the thesis) in order to include more invisible actors, relations and negotiations. Case number three, ‘Negotiating Information Technology: Politics and Practices of The Public Sector Web Production’, is about work practices of a municipal web developer, through which creation of sociotechnical relations of everyday information technology practices is analysed and also mirrored to national and local IT politics. Case number four, ‘Making e-Government Happen – Everyday Co-Development of Services, Citizenship and Technology’, is presenting the same web developer as in the third case, but now his everyday practices are connected with an expanded and wider circuit of co-constructors of information technology. The text is a co-production of a multidisciplinary research group aiming to describe, analyse and problematise connections when creating practices, where technology and society collaborate. Case number fi ve, ‘Citizenship at the Crossroads of Multiple Layers of Sociotechnical Relations’, enrols technology as an active actor in the construction of citizenship in an IT context in Sweden. The perspective emphasising the active agency of non-humans both enhances and challenges the Scandinavian approach of systems development by suggesting a direction towards a cyborgian approach towards technology design. Case number six, ‘Between Stability and Instability – a Project about e-Democracy ’, takes its point of departure from a small-scale project having as its goal the development of e-democracy in a municipal context. In the text the focus is on the stabilisation processes in shaping the technology (‘e’) and democracy parts of the project. I also discuss what kinds of spaces exist in between (the hyphen in e-democracy) and ask if integration between technology and democracy is possible as a whole. Finally, my intention is to step further into stories and practices not yet existing. Inspired by the French philosopher Michel Serres, I introduce the fi guration of an angel as a cartographer, intermediator and (co-) constructor of sociomaterial relations. Angels are needed to sew the separate fi elds of technology, politics and everyday practices to a rich seamless tapestry. They are the ‘artful integrators’ (Suchman).
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| 8. |
- Fredriksson, Martin
(författare)
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Online engineering : On the nature of open computational systems.
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Computing has evolved from isolated machines, providing calculative support of applications, toward communication networks that provide functional support to groups of people and embedded systems. Perhaps, one of the most compelling feature and benefit of computers is their overwhelming computing efficiency. Today, we conceive distributed computational systems of an ever-increasing sophistication, which we then apply in various settings – critical support functions of our society just to name one important application area. The spread and impact of computing, in terms of so-called information society technologies, has obviously gained a very high momentum over the years and today it delivers a technology that our societies have come to depend on. To this end, concerns related to our acceptance of qualities of computing, e.g., dependability, are increasingly emphasized by users as well as vendors. An indication of this increased focus on dependability is found in contemporary efforts of mitigating the effects from systemic failures in critical infrastructures, e.g., energy distribution, resource logistics, and financial transactions. As such, the dependable function of these infrastructures is governed by means of more or less autonomic computing systems that interact with cognitive human agents. However, due to intricate system dependencies as well as being situated in our physical environment, even the slightest – unanticipated – perturbation in one of these embedded systems can result in degradations or catastrophic failures of our society. We argue that this contemporary problem of computing mainly is due to our own difficulties in modeling and engineering the involved system complexities in an understandable manner. Consequently, we have to provide support for dependable computing systems by means of new methodologies of systems engineering. From a historical perspective, computing has evolved, from being supportive of quite well defined and understood tasks of algorithmic computations, into a disruptive technology that enables and forces change upon organizations as well as our society at large. In effect, a major challenge of contemporary computing is to understand, predict, and harness the involved systems’ increasing complexity in terms of constituents, dependencies, and interactions – turning them into dependable systems. In this thesis, we therefore introduce a model of open computational systems, as the means to convey these systems’ factual behavior in realistic situations, but also in order to facilitate our own understanding of how to monitor and control their complex interdependencies. Moreover, since the critical variables that govern these complex systems’ qualitative behavior can be of a very elusive nature, we also introduce a method of online engineering, whereby cognitive agents – human and software – can instrument these open computational systems according to their own subjective and temporal understanding of some complex situation at hand.
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| 9. |
- Gislén, Ylva
(författare)
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Rum för handling. Kollaborativt berättande i digitala medier
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Avhandlingen fokuserar på kollaborativt berättande i digitala medier, och tar avstamp i relativt detaljerade beskrivningar av de designprojekt som utgör avhandlingsarbetets ryggrad. Kännetecknande för dessa designprojekt är att de kombinerar fysiska och virtuella rum och/eller flera medieplattformar. Utifrån kritiska läsningar av designval och bruk av de koncept och prototyper som designprojekten utmynnat i presenteras argument för föreslagna "sätt att se" på design av berättande i digitala medier och centrala kvaliteter i miljöer för kollaborativt berättande. Grundläggande är att se berättande som en överenskommelse, som måste springa ur den berättarsituation, den fysiska och sociala verklighet, som utgör en oavvislig del av allt berättande. Denna överenskommelse upprättar ett "rum" för att undersöka och värdera möjlig mänsklig handling, ett rum vars estetiska egenskaper inte kan skiljas från de etiska och politiska frågeställningar som sätts i rörelse av allt berättande. Utifrån detta grundläggande synsätt diskuteras frågan om utformandet av handlingsutrymme i relation till interaktivitet i digitala medier, begrepp som roll, karaktär, samarbete och konflikt samt rytm, poesi och mångtydighet. Argumenten och resonemangen grundas, utöver i den kritiska läsningen av designprojekten, också i en bredare översikt av narrativitetsbegreppets utveckling inom human- och samhällsvetenskaperna de senaste två decennierna samt i en diskussion av teorier, synsätt och vanliga grundantaganden kring berättande i digitala media. Utrymme i avhandlingen ges också åt en kunskapsteoretisk diskussion kring frågan om design som forskning, främst ur ett perspektiv grundat i STS-fältet men också i relation till förda resonemang ifråga om praxisbaserad forskning i allmänhet och designforskning och designteori i synnerhet.
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| 10. |
- Grbic, Nedelko
(författare)
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Optimal and Adaptive Subband Beamforming
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The increased use of personal communication devices, personal computers and wireless cellular telephones enables the development of new inter-personal communication systems. The merge between computers and telephony technologies brings up the demand for convenient hands-free communications. In such systems the users wish to lead a conversation in much the same way as in a normal person-to-person conversation. The advantages of hands-free telephones are safety, convenience and greater flexibility. In many countries and regions, hand held telephony in cars is prohibited by legislation. By placing the microphone far away from the user a number of disadvantages are introduced, which results in substantial speech distortion and poor sound quality. These disturbances are mainly caused by room reverberation and background noise. Furthermore, acoustic feedback generated at the near-end side is a problem for the far-end side talker, who will hear his/her own voice echoed with 100-200 ms delay, making speech conversation substantially more difficult. Digital filtering may be used to obtain a similar sound quality as for hand held telephony. Three major tasks must be addressed in order to improve the quality of hands-free communication systems; noise suppression, room reverberation suppression, and acoustic feedback cancellation of the hands-free loudspeaker. The filtering operation must perform the above mentioned tasks without causing severe near-end speech distortion. A properly designed broad-band microphone array is able to perform all the given tasks, i.e. speech enhancement, echo cancellation and reverberation suppression, in a concise and effective manner. This is due to the fact that the spatial domain may be utilized as well as the temporal domain. This thesis deals with the problem of specification and design of beamformers used to extract the source signal information. A new subband adaptive beamforming algorithm is proposed, where many of the drawbacks embedded in conventional adaptive beamforming are eliminated. Evaluation in a car hands-free situation show the benefits of the proposed method. Blind signal separation is discussed and a new structure based on frequency domain inverse channel identification and time domain separation, is proposed. Further, filter-bank properties and design are discussed together with performance limitations in subband beamforming structures.
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