| 1. |
- Alayon Glazunov, Andres
(author)
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On the Antenna-Channel Interactions: A Spherical Vector Wave Expansion Approach
- 2009
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Doctoral thesis (other academic/artistic)abstract
- The main focus of this thesis is the analysis of the interactions between antennas and channels where electromagnetic fields play a central role. Our goal has been to devise a general framework to enable a clear separation of the properties of the propagation channel from the influence of the antennas at the same time as it provides a common ground for a joint characterization of their properties. For this we have taken help of two tools: 1) a solution to Maxwell's equations, i.e., a spherical vector wave (svw) multi-modal expansion of the electromagnetic field and 2) the scattering matrix representation of an antenna that provides a full description of all its properties as a transmitting, receiving or scattering device. These tools offer a natural characterization of the polarizational, directional, and spatial properties of multiple-input multiple-output (MIMO) antenna systems. In this thesis we first show that under some assumptions the propagation channel and the antenna are equivalent. The equivalence is in the sense that the impact of the channel cross-polarization ratio (XPR) and the antenna effective cross-polarization discrimination (XPD) on the mean effective gain (MEG) of an antenna are symmetrical. We also find bounds on the MEG in a wireless channel. Then we provide closed form expressions for the covariance of the field multi-modes as a function of the Power Angle Spectrum (PAS) and the channel XPR. A new interpretation of the MEG of antennas in terms of field multi-modes is also provided where the maximum MEG is obtained by conjugate mode matching between the antennas and the channel. We also show the (intuitive) result that the optimum decorrelation of the antenna signals is obtained by the excitation of orthogonal spherical vector wave modes. The cross-correlation coefficient between signals at two antenna branches (ports) in the presence of spatially selective interference and additive white gaussian noise is also investigated showing that spatial interference can also be readily modeled in terms of the svw mode expansion. We further devise a correlation model for co- and cross-polarized field components and introduce the concept of mode-to-mode channel mapping, the M-matrix, between the receive and transmit antenna modes. The M-matrix maps the modes excited by the transmitting antenna to the modes exciting the receive antennas and vice versa. The covariance statistics of this M-matrix are expressed as a function of the double-directional power-angular spectrum (PAS) of co- and cross-polarized components of the electromagnetic field. We finally derive physical limitations on the interactions of antennas exciting TM or TE modes (but not both) and wireless propagation channels. Rather than maximizing antenna gain in a single direction we obtain physical limitations on the antenna gain pattern, which is directly translated to more condensed parameters, i.e. the instantaneous effective gain Gi and the mean effective gain Ge if instantaneous realizations or correlation statistics of the expansion coefficients of the electromagnetic field are known, respectively. The obtained limitations are on the maximum of Gi/Q and Ge/Q, which establish a trade-off between link gain and the antenna quality factor Q.
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| 2. |
- Eneberg, Magnus
(author)
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Beyond the Product – Enabling design services in small and medium sized enterprises
- 2015
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Doctoral thesis (other academic/artistic)abstract
- While the design industry is moving into new domains, it seems that potential customers do not always understand how the designer can contribute beyond the aesthetically appealing product. The overall purpose of this thesis is to expand our understanding of design as an enabling service in the context of small and medium sized enterprises. Enabling design services have the potential to result in organizational learning and change. The co-creation of new knowledge and competencies can in turn enable the customer organization to become more innovative and able to deal with an ambiguous environment. The first part of the research consisted of interviews and workshops with the major industrial design consultancies in Sweden and Finland and some smaller American consultancies. A conceptual business model canvas based on service dominant logic is presented in the thesis to increase our understanding of the business of the industrial design consultancy. During the study, we observed several changes in the organization of the industrial design consultancy. We also noticed self-confidence among the industrial design consultancies in respect to their skills in methods to orchestrate collaboration and contribute to strategic development in customer organizations. An analysis of the initial interviews and workshops together with a literature study helped me to summarize the characteristics of the methods and processes designers are educated in as being integrative, collaborative and explorative. They are integrative in that they incorporate hands with thought, and theory with practice. They are collaborative in that interaction between individuals is a necessity to solve the wicked, ambiguous and open-ended problems the designer usually faces. This has resulted in designers being educated in methods involving a broad range of stakeholders such as users in development processes. Finally, the methods and processes are explorative in that they aim at ingenuity and focus on how things ought to be rather than on the present state. The second part of the research consisted of interviews and observations and had a focus on shared activities between design students and participants from small and medium sized companies. Design methods and processes were put into the context of organizational learning and change theories that centered on knowing as embodied and encultured. An activity theoretical model was applied to enrich the analysis of the diversity of perspectives that may lead to conflicting interpretation and negotiation in shared activities. The concepts of place and space were used to highlight the dynamics between how structures and human desires and needs motivated participants in the shared activities. Place is characterized by stability and is the strategy of the prevailing and often connected to identity. Space is practiced place and connected to change and human agency. The thesis presents how design services enabled individuals and organizations to be introduced to and to strengthen a given place, such as a discipline or organization. It also provides examples of the opposite, with individuals distancing themselves from a place, such as a discipline. Mediating artifacts and the integration of doing and reflection created experiences that evoked emotional involvement and enactment among the participants. Most activities resulted in creating space for change and learning and the outcome can be characterized as business and organizational development.
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| 3. |
- Henriksson, Greger
(author)
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Stockholmarnas resvanor – mellan trängselskatt och klimatdebatt
- 2008
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Doctoral thesis (other academic/artistic)abstract
- This thesis examines the concept of travel habits, public responses to large-scale traffic congestion regulations and how travel patterns of urban dwellers can be made environmentally sustainable in the long term. It also examines the interrelationships of different scientific disciplines dealing with urban travel. The main conclusions relate to the scientific concept of habit. This concept and the associated behaviours are not well-studied in the social and cultural sciences. Indeed, in some contexts the concept is bereft of meaning, e.g. when the notion of travel habits is used to represent the travel patterns of an entire population. This study demonstrated the (traffic and environmental policy) significance of non-habitual travel, but also showed habitual travel to have inherent resistance to change, i.e. with habits acting as a buffer between experience and response. Case studies revealed travel habits to be a cultural phenomenon, since acceptable travel habits are expressed in a restricted local and social context. People develop their (travel) habits in mutual and only partly conscious interactions with each other and their material surroundings. The case studies also showed how changes occurring during critical points in the course of a life (primarily as regards housing, employment and household composition) brought about particularly clear changes in individual travel habits. Stability and sustainability in urban travel patterns could be achieved through the promotion and gradual spread (geographical, between age classes, etc.) of certain types of travel habits that are already in use at the individual level. Thus habits should be regarded less as an obstacle and more as an opportunity for sustainable development. A case study of the Stockholm congestion charge trial showed wide variation and ingenuity in how Stockholmers dealt with this new feature of their daily lives. For example, many stopped many stopped driving into the charging zone in order to demonstrate, to themselves and others, their disagreement with the charge and the political circumstances surrounding its introduction. Interestingly (and paradoxically), this probably contributed to the overall major reduction in traffic, perceived at a societal level as evidence of the success of congestion charging. However, regarding the scope for sustainable development of urban travel, the conclusion from this appraisal of the Stockholm trial was that environmental, congestion-reducing and possibly traffic-controlling political measures appear to be in public demand. Efforts in this thesis to interrelate the scientific perspectives of the different disciplines studying the various levels of urban travel (e.g. sociology, human geography and ethnology in relation to transport economics and psychology) indicated that further collaboration is required. As with the concept of travel habits, there are numerous concepts that could benefit from being developed and tested through interdisciplinary collaboration.
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| 4. |
- Hrastinski, Stefan
(author)
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Participating in Synchronous Online Education
- 2007
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Doctoral thesis (other academic/artistic)abstract
- There is an increasing need for education since the workforce of today is expected to be highly educated and continuously learn. Distance education is a powerful response to meet the growing need for education. Online education, here concisely defined as distance education mediated online, is the most common type of distance education. It mainly relies on asynchronous communication although it is well known that many students regard the lack of synchronous communication as disadvantageous. This thesis aims to achieve a deeper understanding of how, why and when synchronous communication, as a complement to asynchronous communication, affects student participation in online education. In order to study the complex phenomenon of online student participation, various qualitative and quantitative data collection methods for assessing both perceived participation and actual participation were used. The aim was investigated in two offerings of an online undergraduate course and two series of online discussions on master level, and by conducting focus group interviews with experienced practitioners. The findings indicate that synchronous communication has the potential to enhance online student participation. Light was shed on two dimensions of participation, which were labelled personal participation and cognitive participation. The thesis suggests that synchronous communication, as a complement to asynchronous communication, may better support personal participation. This is likely to induce arousal and motivation, and increased convergence on meaning, especially in smaller groups. Synchronous communication seems particularly beneficial for supporting task and social support relations, and to exchange information with a lower degree of complexity. By drawing on the studies of the thesis and previous research, propositions on when to support synchronous communication in online education were suggested.
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| 5. |
- Högselius, Per
(author)
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The Dynamics of Innovation in Eastern Europe -Lessons from Estonia
- 2005
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Doctoral thesis (other academic/artistic)abstract
- The overall interest pursued in this thesis is how the former socialist economies of Central and Eastern Europe can build strong and dynamic systems of innovation. The purpose of the thesis is to investigate the dynamics and evolution of the telecommunications system of innovation in Estonia from the late Soviet period to Estonia's EU accession, and to provide an in-depth explanation of how innovation has been enabled to occur in the system. Underlying the study is the empirical observation that the transition from socialism to capitalism in Central and Eastern Europe is a simultaneous process of, on the one hand, a transformation of the old Soviet-era structures into something new, and on the other hand, a reorientation from being deeply integrated economically with other Central and East European countries towards a new integration with the global capitalist system. From a systems-theoretical perspective these two processes can be expected to be closely interrelated. In order to understand and explain the emergence of new East European systems of innovation, the thesis therefore takes into account both system-internal processes of change in Estonia as well as the relationships between the Estonian system and its foreign environment. Based on a case-study methodology and recent theorizing on systems of innovation, the thesis shows that the socialist historical heritage, and in particular inherited competencies, have been used in highly creative ways for generating dynamic innovation in post-socialist Estonia. The thesis also uncovers the complex and multifaceted ways in which the geographical and cultural proximity to Sweden and Finland has been creatively used as a powerful resource in the pursuit of building the Estonian system of innovation in telecommunications. Moreover, the thesis demonstrates that it has been possible for an East European system of innovation to develop highly creative domestic dynamics without necessarily imitating Western system trajectories or styles of innovation. The results are also shown to have important theoretical implications for the study of systems of innovation.
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| 6. |
- Kopsch, Fredrik, 1982-
(author)
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Essays on Regional Economics
- 2013
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Doctoral thesis (other academic/artistic)abstract
- This thesis is, to its nature, somewhat wide in scope. The common denominator for theincluded essays is regional economics. Within this very wide area of research, the thesis isdivided rather sharply between one part regarding trading of emission permits in theinternational aviation sector and another part concerned with real estate markets. The basis ofthis thesis is five essays all written for the purpose of peer reviewed publication.The first topic includes three essays; the first provides an overview of previous emissionstrading schemes which allow us to learn for future policy designs when including new sectorsor creating new trading schemes. The second essay aims at estimating elasticities for domesticair travel in Sweden. The third essay, takes an analytical approach to scrutinizing theproposed barrier of trade between the international aviation sector and the stationary sourceswithin the EU ETS.The second topic is motivated by the structural relocations that two municipalities in thenorthern part of Sweden are currently undergoing. The first essay on this topic, the fourthessay of this thesis, concerns redistributions of wealth that occur when moving a city center.The fifth and final essay approaches the problem of measuring an effect of information onhouse values with small quantities of data, such as is the case for Gällivare municipality.
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| 7. |
- Mihaescu, Mihai
(author)
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Computational Aeroacoustics Based on Large Eddy Simulation and Acoustic Analogies
- 2005
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Doctoral thesis (other academic/artistic)abstract
- The thesis presents a numerical method developed by the author and its applications for computing the generated sound by an unsteady flow field and its propagation. The full equations of motion for compressible and unsteady flows describe both flow field and sound generation and propagation. It is assumed that the flow variables can be decomposed into semi-compressible / incompressible components and inviscid, irrotational acoustic components. The present method is based on Large Eddy Simulation (LES) to compute the turbulent flow and an approach based on an inhomogeneous wave equation to compute the radiated acoustic field. In this way one can avoid the necessity for a very large computational effort associated with direct simulation of the near- and specially far- field sound generated by a turbulent flow. The governing equations are written in the form of a non-homogeneous wave equation for the acoustic fluctuation with acoustic sources on the right-hand side. The thesis includes the details of the coupling between the flow solver and the acoustic one, as well as the results for test cases employed to validate the numerical algorithm and the implemented boundary conditions. The method has been successfully applied to compute the near- and far- acoustic fields generated by various unsteady flows such as a round hot turbulent jet ejected from a pipe close to a solid boundary, coaxial turbulent non-isothermal jets (separate exhaust system), or the flow around a wind-turbine.
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| 8. |
- Rauhut, Daniel
(author)
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Fattigvård, socialbidrag och synen på fattigdom i Sverige 1918-1997
- 2002
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Doctoral thesis (other academic/artistic)abstract
- The purpose of the study is to analyse the poverty norm for single adults without children in Sweden between 1918 - 1997. The study analyses the full norm, not support given as an income supplement. The poverty norm is defined as the minimum level of a socially acceptable standard of living. The study investigates two problems: how has the poverty norm changed during the period 1918-1997 and why has the norm changed during this period? To examine the changes of the poverty norm in Sweden 1918-1997 a hypothesis is tested: the poverty norm is linked to the standard of living of the low-income earners. By linking different forms of compensation rates it is possible to estimate the poverty norm for the studied period. This study has its theoretical point of departure in the social affinity hypothesis. Social affinity is seen as a subjective feeling of social solidarity with other individuals based on income. Given that the subjective feeling of social solidarity is formed around income, the gap between the low-income earners and the middle-income rank and the gap between the middle-income ranks and the high-income earners play a central role. Thus, this assumes that the poverty norm is determined by the changes in the income situation of the low-income earners. The hypothesis tests positive for the periods 1940-1972 and 1985-1997. During the first part of the period the poverty norm is determined by market related factors, such as income and wage. But at for the period 1985-1997 the poverty norm became a political-administrative budget line determined by politicians and bureaucrats. The poverty norm has also been the subject of ideological changes during the whole period of study. During the Inter-war period the view on poverty is determined by an absolute view on poverty. Since 1939 poverty has been regarded as something relative, which has had an impact on the poverty norm. The political left advocate a relative view on poverty.
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| 9. |
- Sandberg, Henrik
(author)
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Model Reduction for Linear Time-Varying Systems
- 2004
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Doctoral thesis (other academic/artistic)abstract
- The thesis treats model reduction for linear time-varying systems. Time-varying models appear in many fields, including power systems, chemical engineering, aeronautics, and computational science. They can also be used for approximation of time-invariant nonlinear models. Model reduction is a topic that deals with simplification of complex models. This is important since it facilitates analysis and synthesis of controllers. The thesis consists of two parts. The first part provides an introduction to the topics of time-varying systems and model reduction. Here, notation, standard results, examples, and some results from the second part of the thesis are presented. The second part of the thesis consists of four papers. In the first paper, we study the balanced truncation method for linear time-varying state-space models. We derive error bounds for the simplified models. These bounds are generalizations of well-known time-invariant results, derived with other methods. In the second paper, we apply balanced truncation to a high-order model of a diesel exhaust catalyst. Furthermore, we discuss practical issues of balanced truncation and approximative discretization. In the third paper, we look at frequency-domain analysis of linear time-periodic impulse-response models. By decomposing the models into Taylor and Fourier series, we can analyze convergence properties of different truncated representations. In the fourth paper, we use the frequency-domain representation developed in the third paper, the harmonic transfer function, to generalize Bode's sensitivity integral. This result quantifies limitations for feedback control of linear time-periodic systems.
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| 10. |
- Östlund, Britt, 1956-
(author)
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Gammal är äldst : En studie om teknik i äldre människors liv
- 1995
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Doctoral thesis (other academic/artistic)abstract
- This thesis deals with the role of technology in elderly peoples everydaylife, to what extent technology can facilitate or prevent them from havinga social life. The intension is to describe the role of technology from olderpeoples own perspective. Four activities in everyday life in which technology is involved are emphasised: social contacts, security, information and distribution of services and goods. Technology related to these activities are telephones, televisions, safety alarms and homeshopping-terminals. The aim of the study is to describe how these fourtechnologies are used by the elderly and what function and meaning theygive to the technology; and to describe old peoples attitudes to newtechnology in general and to the home shopping-terminals specificallyand how this technology affects their everyday life contacts and routins.The main emphirical work consists of recurrent interviews andobservations of a group of old people living in a city (Malmo) and in a rural district (Kinda).The results show that the function of technologies such as the telephoneand the television becomes more specific and even more important to connect the home with the outside world. By this kind of technology the interviewees remain socially integrated but, which is one of their expressed preferences, with no demands on social participation. A growing need of privacy is succesfully combined with an increased need of security and help. Technology is not used to establish new contacts but relations to relatives and friends are maintained. The attitude and acceptance of new technology in general is positive due to their lifelong experiences of improvements. The difference is that they are not that interested anymore, referring to an increased pragmatic vue towards modernity, to a limited future-perspective and to their basic values.
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