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  • 121951.
    Zeraatpisheh, Milad
    et al.
    Sharif Univ Technol, Dept Mech Engn, Tehran 79417, Iran..
    Arababadi, Reza
    Grad Univ Adv Technol, Inst Sci & High Technol & Environm Sci, Dept Energy, Kerman 76169, Iran..
    Pour, Mohsen Saffari
    KTH.
    Economic Analysis for Residential Solar PV Systems Based on Different Demand Charge Tariffs2018In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 11, no 12, article id 3271Article in journal (Refereed)
    Abstract [en]

    It is well known that the use of photovoltaic (PV) systems helps to preserve the environment, produce lower levels of greenhouse gases (GHGs), and reduce global warming, however, whether it is economically profitable for customers or not is highly debatable. This paper aims to address this issue. To be comprehensive, three different types of buildings are considered as case studies. Then, these three buildings are modeled in EnergyPlus to determine the rate of energy consumption. Afterward, comparisons of various solar system sizes based on economic parameters such as the internal rate of return, the net present value, payback period and profitability indexing for various-sized PV systems are carried out. The results show that by the demand charge tariffs, using PV systems has no economic justification. It has been shown that even with neglecting further costs of the PV system like maintenance, by demand charge tariffs, it is not economically beneficial for customers to use the PV systems. Profitability index of all three buildings with various PV power systems is between 0.2 to 0.8, which are by no means is desirable. Moreover, it was found that bigger solar systems are less cost-effective in the presence of demand charges.

  • 121952. Zerbst, J.
    et al.
    Pietre-Cambacedes, L.
    Dondossola, G.
    Mcdonald, J.
    Ekstedt, Mathias
    KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
    Torkilseng, Åge
    Cyber attack modelling and security graded approach: Key elements when designing security architecture for Electric Power Utilities (EPUs)2012In: 44th International Conference on Large High Voltage Electric Systems 2012, 2012, p. 1-8Conference paper (Refereed)
    Abstract [en]

    The multiplication of access interfaces and technologies in Electric Power Utilities (EPUs) communication architectures and the smart grid developments, which will enable numerous new services with new traffic patterns, will change radically both network accesses and core architectures. This evolution could introduce new vulnerabilities to the reliability of electricity supply, based on the introduction and exposure of vulnerabilities in digital systems, architectures, and communications. This situation calls for new security requirements for digital systems and the underlying architecture used in EPUs. Security requirements have to be derived from appropriate risk assessments and general architectural decisions. Numerous existing cyber security standards provide guidance and use-cases which represent valuable inputs for the development of such requirements. The proliferation of standards suggests, however, that the existing documents either do not meet completely the needs of EPUs or are difficult to combine together. This paper focuses on two weak points of the existing cyber security standards in the area. Initially, the paper addresses the characterization, categorization and modeling of malicious cyber threats, which represent key steps in a risk assessment process. The paper presents a conceptual model expressing the meaning and the links between the key concepts of cyber security risks. Following this, the work examines attack modeling, addressing some pertinent technical and architectural issues. In addition, the paper explains why attack modeling is central to risk assessment and present graphical approaches to attack modeling. The second part the paper addresses the use of security architecture principles, notably the graded security approach as a fundamental framework to classify and structure a process of risk mitigation by security controls in both current and future EPU architectures. This discussion starts with the clarification of the terminology related to a graded security approach and then gives a general overview of the characteristics of known standards and best practices of graded security architectures. Following this, the paper presents an outlook of classification criteria to enable the implementation of a graded security approach in a real world environment and then illustrates the effectiveness and adaptability of a graded security approach in a real-world attack case.

  • 121953.
    Zerdesti, Tavga
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Urban and Regional Studies.
    Konceptualisering och Operationalisering av Social Hållbarhet: Fallstudie av Täby kommun2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 121954.
    Zerkak, Omar
    et al.
    Paul Scherrer Institut.
    Gajev, Ivan
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
    Manera, Annalisa
    Paul Scherrer Institut.
    Kozlowski, Tomasz
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
    Gommlich, Andre
    Helmholtz-Zentrum Dresden-Rossendorf.
    Zimmer, Stéphanie
    Commissariat à l’Energie Atomique.
    Kliem, Sören
    Helmholtz-Zentrum Dresden-Rossendorf.
    Crouzet, Nicolas
    Commissariat à l’Energie Atomique.
    Zimmermann, Martin A.
    Paul Scherrer Institut.
    Revisiting Temporal Accuracy in Neutronics/THCode Coupling Using the NURESIM LWRSimulation Platform2011In: The 14th Internation Topical Meetingon Nuclear Reactor Thermalhydraulics (NURETH-14), 2011Conference paper (Refereed)
    Abstract [en]

    The first part of this paper reviews the different temporal coupling methodologies that are currentlyemployed for the transient simulation of LWR cores. The second part shows preliminary resultsfrom the implementation of some suggested coupling improvements, including high-ordercorrections to the exchanged coupling fields and a dynamic time step control technique, for thesimulation of an exemplary reactivity insertion transient analysed using the European NURESIMLWR simulation platform.

  • 121955. Zerkak, Omar
    et al.
    Kozlowski, Tomasz
    Gajev, Ivan
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
    Review of multi-physics temporal coupling methods for analysis of nuclear reactors2015In: Annals of Nuclear Energy, ISSN 0306-4549, E-ISSN 1873-2100, Vol. 84, p. 225-233Article in journal (Refereed)
    Abstract [en]

    The advanced numerical simulation of a realistic physical system typically involves multi-physics problem. For example, analysis of a LWR core involves the intricate simulation of neutron production and transport, heat transfer throughout the structures of the system and the flowing, possibly two-phase, coolant. Such analysis involves the dynamic coupling of multiple simulation codes, each one devoted to the solving of one of the coupled physics. Multiple temporal coupling methods exist, yet the accuracy of such coupling is generally driven by the least accurate numerical scheme. The goal of this paper is to review in detail the approaches and numerical methods that can be used for the multi-physics temporal coupling, including a comprehensive discussion of the issues associated with the temporal coupling, and define approaches that can be used to perform multi-physics analysis. The paper is not limited to any particular multi-physics process or situation, but is intended to provide a generic description of multi-physics temporal coupling schemes for any development stage of the individual (single-physics) tools and methods. This includes a wide spectrum of situation, where the individual (single-physics) solvers are based on pre-existing computation codes embedded as individual components, or a new development where the temporal coupling can be developed and implemented as a part of code development. The discussed coupling methods are demonstrated in the framework of LWR core analysis.

  • 121956.
    Zerouali, Mehdi
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    VoIP Communications over WLANs: Implementation of a new downlink transmission protocol2010Report (Other academic)
    Abstract [en]

    Voice over IP (VoIP) is becoming more and more popular every day. The number of VoIP service providers is continuously increasing along with the number of customers they serve. Moreover, the latest generation of smartphones and mobile devices now incorporate VoIP support. This enables users within a wireless local area network (WLAN) cell to exchange VoIP traffic with other peers.

    This new traffic potentially poses a problem for WLANs, as the WLAN access point could be required to handle a large number of small packets of encoded speech. Since the access to the media can only be made by one node at a time, all of the devices must contend to access it. If there are multiple calls between nodes in the WLAN and nodes in the fixed network, then all of these packets must go to and from the access point. Moreover the access point needs to transmit the downlink traffic for all of these nodes. Because the Access Point has the same probability of getting access to the media as any other node, this can lead to high delays, and limits the maximum number of simultaneous calls to a rather small number, despite the increasing data rates that the WLAN interfaces are capable of.</p>This project implements and evaluates a new solution that consists of aggregating downlink packets at the access point and transmitting a large multicast packet containing a set of voice frames that need to be sent to nodes within the cell. A demultiplexing process at node extracts the appropriate RTP content from the multicast packet and delivers it locally.

  • 121957. Zerva, K.
    et al.
    Kourtit, Karima
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Urban and Regional Studies. A. Mickiewicz University, Poland.
    Nijkamp, P.
    Tourism and voyeurism in Heterotopia’s: The role of perception and information in the behaviour of visitors to Amsterdam2016In: Impact Assessment in Tourism Economics, Springer, 2016, p. 247-273Chapter in book (Other academic)
    Abstract [en]

    Tourists are not only regular visitors of important distinct places of interest. In making their decisions what or where to visit, they are also influenced by the (expected or realized) observed behaviour of others. A particularly interesting case of such social externalities is formed by so-called ‘voyeurism’, the phenomenon that visitors are visibly interested in-and attracted by-the preservice and spatial motives and behaviours of other visitors. Essentially, voyeurists derive their visitor utility from the observable behaviour of others, e.g. by watching them or speculating on their motives when they pass by. The present paper offers a novel empirical approach to these issues; it focuses on tourist voyeurism in the Red Light District of Amsterdam, with an emphasis on two well-known characteristic phenomena in this area, viz. prostitution and soft drugs. On the basis of existing literature that has demonstrated the importance of tours as an educative tool for tourists, we analyse if and how the perceptions of visitors have changed, through a panel study of 29 foreign students, and identify changes in their perceptions, after they have been exposed to real-world and site-specific factual information on this area, inter alia through a professionally guided field tour. Tools used in the present paper to analyse the voyeurism phenomenon-based on a before and after experiment-are multivariate analysis and regression techniques, while as a start a content cloud analysis is employed as an introductory exploratory tool. It turns out that information provision by a tour may change the site perceptions of voyeurists, but less so their value systems on the objects or people observed.

  • 121958.
    Zervens, Mikaela
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Samverkansgrundläggning - en sättningsuppföljning av två objekt i Uppsala2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 121959. Zervos, T.
    et al.
    Alexandridis, A.
    Peppas, K.
    Lazarakis, F.
    Dangakis, K.
    Soras, C.
    Lindmark, Björn
    KTH, Superseded Departments, Signals, Sensors and Systems.
    The influence of MIMO terminal user's hand on channel capacity2006Conference paper (Refereed)
    Abstract [en]

    In this paper the impact of user's hand holding a Multiple-Input-Multiple- Output (MIMO) terminal on the system performance is investigated. A 4×4 MIMO system is considered with a Personal Digital Assistant (PDA) terminal equipped with a compact array of 4 patch elements. The radiation patterns of the antenna elements are simulated in the presence of the other elements and in the presence of a user's hand. The obtained patterns are used to evaluate the covariance matrix of the receive antenna which is incorporated in a correlation-based MIMO channel model. MIMO channel capacity is calculated to demonstrate the capacity degradation caused by the user's hand.

  • 121960.
    Zetoun, Mirella
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematical Statistics.
    Pricing With Uncertainty: The impact of uncertainty in the valuation models ofDupire and Black&Scholes2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Theaim of this master-thesis is to study the impact of uncertainty in the local-and implied volatility surfaces when pricing certain structured products suchas capital protected notes and autocalls. Due to their long maturities, limitedavailability of data and liquidity issue, the uncertainty may have a crucialimpact on the choice of valuation model. The degree of sensitivity andreliability of two different valuation models are studied. The valuation models chosen for this thesis are the local volatility model of Dupire and the implied volatility model of Black&Scholes. The two models are stress tested with varying volatilities within an uncertainty interval chosen to be the volatilities obtained from Bid and Ask market prices. The volatility surface of the Mid market prices is set as the relative reference and then successively scaled up and down to measure the uncertainty.The results indicates that the uncertainty in the chosen interval for theDupire model is of higher order than in the Black&Scholes model, i.e. thelocal volatility model is more sensitive to volatility changes. Also, the pricederived in the Black&Scholes modelis closer to the market price of the issued CPN and the Dupire price is closer tothe issued Autocall. This might be an indication of uncertainty in thecalibration method, the size of the chosen uncertainty interval or the constantextrapolation assumption.A further notice is that the prices derived from the Black&Scholes model areoverall higher than the prices from the Dupire model. Another observation ofinterest is that the uncertainty between the models is significantly greaterthan within each model itself.

  • 121961.
    Zetterberg, Andreas
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Environmental Management and Assessment.
    Connecting the dots: Network analysis, landscape ecology, and practical application2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Humans have a profound impact on ecosystems, and land-use change constitutes a primary driving force in the loss of biodiversity. Habitat loss and fragmentation are key factors in this process by seriously impeding the habitat availability and movement of species, leading to a significant decrease in population viability. Landscape connectivity management able of crossing administrative and ecological spatial and temporal scales has been identified as one of the most important measures to counteract these negative impacts. The use of graph-theory and network-based landscape-ecological tools has become established as a promising way forward to address these issues. Despite urgent needs to adapt and implement such tools in planning, assessment and decision-making, surprisingly little attention has been paid to developing approaches for their effective practical application. This thesis presents the development of a toolbox with network-based, landscape-ecological methods and graph-theoretic indicators, which can be effectively implemented by practitioners within environmental assessment, physical planning and design, to analyze landscape connectivity. Recent advances in network analysis and landscape ecology are brought together and adapted for practical application, bridging the gap between science and practice. The use of participatory approaches was identified as key to successful development, and several workshops, meetings, interviews, as well as prototype testing of the developed software were conducted throughout the study. Input data and selection of species were based on the experience gained through seven real-world cases, commissioned by different governmental organizations within Stockholm County. The practitioners’ perspectives on effective practical application of the proposed toolbox were then assessed through an interview-study. The respondents anticipated improved communication with other actors in addition to being able to better assess critical ecological structures within the landscape. The toolbox was finally tested in a large-scale network analysis of impacts of the regional development plan (RUFS 2010), leading to important insights on the planning of connectivity in an urbanizing region.

  • 121962.
    Zetterberg, Andreas
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Network Based Tools and Indicators for Landscape Ecological Assessments, Planning, and Design2009Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Land use change constitutes a primary driving force in shaping social-ecological systems world wide, and its effects reach far beyond the directly impacted areas. Graph based landscape ecological tools have become established as a promising way to efficiently explore and analyze the complex, spatial systems dynamics of ecological networks in physical landscapes. However, little attention has been paid to making these approaches operational within ecological assessments, physical planning, and design. This thesis presents a network based, landscape-ecological tool that can be implemented for effective use by practitioners within physical planning and design, and ecological assessments related to these activities. The tool is based on an ecological profile system, a common generalized network model of the ecological infrastructure, graph theoretic metrics, and a spatially explicit, geographically defined representation, deployable in a GIS. Graph theoretic metrics and analysis techniques are able to capture the spatio-temporal dynamics of complex systems, and the generalized network model places the graph theoretic toolbox in a geographically defined landscape. This provides completely new insights for physical planning, and environmental assessment activities. The design of the model is based on the experience gained through seven real-world cases, commissioned by different governmental organizations within Stockholm County. A participatory approach was used in these case studies, involving stakeholders of different backgrounds, in which the tool proved to be flexible and effective in the communication and negotiation of indicators, targets, and impacts. In addition to successful impact predictions for alternative planning scenarios, the tool was able to highlight critical ecological structures within the landscape, both from a system-centric, and a site-centric perspective. In already being deployed and used in planning, assessments, inventories, and monitoring by several of the involved organizations, the tool has proved to effectively meet some of the challenges of application in a multidisciplinary landscape.

  • 121963.
    Zetterberg, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630).
    Mörtberg, Ulla
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630).
    Balfors, Berit
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630).
    Making graph theory operational for landscape ecological assessments, planning, and design2010In: Landscape and Urban Planning, ISSN 0169-2046, E-ISSN 1872-6062, Vol. 95, no 4, p. 181-191Article in journal (Refereed)
    Abstract [en]

    Graph theory and network analysis have become established as promising ways to efficiently explore and analyze landscape or habitat connectivity. However, little attention has been paid to making these graph-theoretic approaches operational within landscape ecological assessments, planning. and design. In this paper, a set of both theoretical and practical methodological developments are presented to address this issue. In highly fragmented landscapes, many species are restricted to moving among small, scattered patches of different resources. instead of one, large patch. A life-cycle based approach is therefore introduced, in which a metapatch is constructed, spanning over these resources, scattered across the landscape. The importance of spatially explicit and geographically defined representations of the network in urban and regional planning and design is stressed, and appropriate, context-dependent visualizations of these are suggested based on experience from real-world planning cases. The study moves beyond the issue of conservation of currently important structures, and seeks to identify suitable redesigns of the landscape to improve its social-ecological qualities, or increase resilience. By introducing both a system-centric and a site-centric analysis, two conflicting perspectives can be addressed. The first answers the question "what can I do for the network", and the second, "what can the network do for me". A method for typical planning strategies within each of these perspectives is presented. To illustrate the basic principles of the proposed methods, an ecological study on the European common toad (Bufo bufo) in Stockholm. Sweden is presented, using the betweenness centrality index to capture important stepping-stone structures.

  • 121964.
    Zetterberg, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Environmental Management and Assessment.
    Mörtberg, Ulla
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Environmental Management and Assessment.
    Bodin, Örjan
    Stockholm Resilience Centre, Stockholm University.
    Saura, Santiago
    Dept. of Forest Management and Economics, E.T.S.I. Montes, Universidad Politécnica de Madrid.
    Sprawl or dense?: Assessing impacts of regional development plans on landscape network connectivityManuscript (preprint) (Other academic)
    Abstract [en]

    The management of landscape connectivity has been identified as one of the most important measures to counteract negative impacts on biodiversity by habitat loss and fragmentation. Such management must be able to cross spatial and temporal administrative and ecological scales. The use of graph-theory and network-based landscape-ecological tools has gained considerable interest as a promising way forward to address these issues. However, despite urgent needs to adapt and implement network-based connectivity analysis in planning, assessment and decision-making, surprisingly little attention has been paid to developing approaches for their effective practical application. In this paper, a large-scale assessment of the Regional Development Plan for the Stockholm Region (RUFS 2010) was carried out, argued to be the first graph-theoretic assessment of landscape connectivity for real proposed planning alternatives. In addition, it is the first time where the analysis of connectivity was an integral part in the planning process. Three planning alternatives were compared with the current situation for four different habitat types and one hundred different dispersal capacities. Three families of network metrics representing different underlying processes were selected, that have previously been shown to capture the variability of a larger set of metrics. The sprawl alternative emerged as having the largest negative impact while the dense alternative had the smallest. However, when comparing the impact with the amount of habitat consumed, the sprawl alternative emerged as being the most efficient in several situations. In order to achieve a better understanding of the underlying processes, a spatial study was carried out. The analysis leads to important insights on the planning of connectivity in an urbanizing region, argued to be applicable within a broad set of urbanizing regions throughout the world.

     

  • 121965. Zetterberg, C
    et al.
    Hemphälä, H
    Nylén, Per
    KTH, School of Technology and Health (STH), Health Systems Engineering, Ergonomics.
    Workshop in visual ergonomics2013Conference paper (Refereed)
    Abstract [en]

    Increased use of computers is common across many work sectors. Prolonged near work at a computer screen is associated with both visual discomfort and neck/shoulder discomfort and pain. Inadequate visual ergonomics at a computer workstation can also influence both visual and neck/shoulder discomfort. The new provision from the Swedish Work Environment Authority on prevention of musculoskeletal disorders includes risk assessment of occupational visual conditions. These assessments require practitioners to have knowledge of the topic, as well as experience with practical assessment tools.

    The first part of the workshop proposed here will involve a presentation of the theories underlying visual ergonomic practices and a discussion of the most important factors to assess at a computer workstation. These factors include contrast, font size, resolution, glare, reflexion, non-visual flicker, and edge sharpness. The second part of the workshop, will allow participants hands-on practice in measuring and evaluating visual ergonomics at a computer workstation.

  • 121966. Zetterberg, Charlotta
    et al.
    Edvardsson Björnberg, Karin
    Philosophy and History, KTH, School of Architecture and the Built Environment (ABE), Philosophy and History of Technology, Philosophy.
    Time for a New EU Regulatory Framework for GM Crops?2017In: Journal of Agricultural and Environmental Ethics, ISSN 1187-7863, E-ISSN 1573-322X, Vol. 30, no 3, p. 325-347Article in journal (Refereed)
    Abstract [en]

    In recent years, the EU legislation on genetically modified (GM) crops has come under severe criticism. Among the arguments are that the present legislation is inconsistent, disproportionate, obsolete from a scientific point of view, and vague in terms of its scope. In this paper, the EU GM legislation (mainly the "Release Directive", 2001/18/EC) is analysed based on five proposed criteria: legal certainty, non-discrimination, proportionality, scientific adaptability, and inclusion of non-safety considerations. It is argued that the European regulatory framework does not at present satisfy the criteria of legal certainty, non-discrimination, and scientific adaptability. Two ways of reforming the present legislation toward greater accommodation of the values expressed through the proposed criteria are briefly introduced and discussed.

  • 121967.
    Zetterberg, Daniel
    KTH, School of Architecture and the Built Environment (ABE), Architecture.
    Stadshus i Stadshagen2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A solid draped in fabrics. Light and heavy curtains, protecting and filtering the outside, defining space and privacy. An open, circulating composition of rooms along the facades. Larger, connected rooms for socializing, smaller podlike rooms for rest and study. An imagined life, inspired by the Japanese or Turkish ways of living. A maximum of windows. French balconys and sliding doors. A close connection between the outside climate and the interior. Light, wind, wheather.

    The building houses mainly larger appartments, 70 - 120 sqm. The central stairwell is shared by both the appartments and the offices, and from it, arms holding practical and social functions such as a laundry room, a gym and a party/meeting room spread. The roof functions as the buildings garden.

    The building is situated on top of a subway station, in the northern end of a park. The rooftop garden allows for the building to make a smaller footstep in the park. The ground floor has spaces for smaller businesses and a garage. It's an urban building facing the street, situated in a park.

  • 121968.
    Zetterberg, Lena
    et al.
    Uppsala University.
    Aquilonius, Sten-Magnus
    Uppsala University.
    Lindmark, Birgitta
    Uppsala University.
    Lundström, Erik
    Uppsala University.
    Stokes, Virgil
    Uppsala University.
    Färnstrand, Catarina
    Uppsala University.
    Halvorsen, Kjartan
    The Swedish School of Sport and Health Sciences.
    Objective assessment in cervical dystonia2004In: Proceedings from ESMAC 13th Annual Meeting of European Society of Movement Analysis of Adult and Children, 2004Conference paper (Refereed)
  • 121969.
    Zetterberg, Lena
    et al.
    Uppsala University.
    Halvorsen, Kjartan
    Swedish School of Sports and Health Sciences.
    Färnstrand, Catarina
    Uppsala University.
    Aquilonius, Sten-Magnus
    Uppsala University.
    Lindmark, Birgitta
    Uppsala University.
    Physiotherapy in cervical dystonia: six experimental single-case studies2008In: Physiotherapy Theory and Practice, ISSN 0959-3985, E-ISSN 1532-5040, Vol. 24, no 4, p. 275-290Article in journal (Refereed)
    Abstract [en]

    The aim of the study was to explore the outcome of a physiotherapy program targeted to improve the quality of life of people with cervical dystonia (CD) by reducing pain, improving awareness of postural orientation, increasing muscle strength, and reducing the effort of moving the head and neck. In six single case studies, the primary outcome measure for each case was the Cervical Dystonia Questionnaire (CDQ) to measure the impact of the program on the individuals' quality of life. Secondary outcome measures were identified for the different components of the physiotherapy program: Visual Analogue Scale (pain); Postural Orientation Index (postural orientation awareness); and Movement Energy Index (effort of moving head and neck). Each of the cases had the severity of their problems scored on the Toronto Western Spasmodic Torticollis Scale. The study period was 26 weeks: 2 weeks' baseline period, 4 weeks' treatment period, and 20 weeks' follow-up. All measures except the Movement Energy Index (MEI) and CDQ-24 were taken three times per week for the first 6 weeks of the study and then once at 3 and 6 months. The MEI was taken once a week during the pretreatment and the treatment periods and during the first 2 weeks of follow-up and also after 3 and 6 months of follow-up. The CDQ-24 was taken once in the pretreatment period, once after completion of treatment, once 2 weeks after treatment, and once at 3 and 6 months of follow-up. Five of the six case studies reported an increase in quality of life at 6-month follow-up, as measured on the CDQ-24. Three of the six cases reported a reduction in pain and severity of the dystonia and had improved scores on the postural orientation measure at 6-month follow-up. All six patients had a reduction in the movement energy scores, but this was not significant. The outcomes of the six case studies would suggest that further investigation is required to show the effectiveness of physiotherapy programs in the management of CD.

  • 121970.
    Zetterberg, Lena
    et al.
    Uppsala University.
    Halvorsen, Kjartan
    Swedish School of Sports and Health Sciences.
    Färnstrand, Catarina
    Uppsala University.
    Lundström, Erik
    Uppsala University.
    Lindmark, Birgitta
    Uppsala University.
    Aquilonius, Sten-Magnus
    Uppsala University.
    Objective assessment of cervical dystonia: a pilot study2005In: Acta Neurologica Scandinavica, ISSN 0001-6314, E-ISSN 1600-0404, Vol. 112, no 4, p. 248-253Article in journal (Refereed)
    Abstract [en]

    Objectives - The aims were to characterize the movements in cervical dystonia (CD) by using an estimate of the mechanical power and work involved in the movements and to describe this through a movement energy index (MEI). Materials and methods - The subjects (patients n = 6, controls n = 6) were seated in front of a screen with a laser pointer attached to a headband while they performed standardized movements. A three-dimensional motion capture system was used and a test-retest was performed. Results - The mean value of MEI was significantly higher for the patients than for the controls. There was no significant difference between MEI from test to retest for the patients but there was a significant difference between MEI from test to retest for the controls. Conclusion - This study suggests that MEI could be a useful measure for the quantification of movement dysfunction in CD and thus an objective outcome measure in comparison of different therapies.

  • 121971.
    Zetterberg, Mikaela
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    A critical overview of machining simulations in ABAQUS.2014Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Metal cutting is one of the most commonly occurring manufacturing processes in the industry and major effort is made to improve its processes. Cutting tools are expensive and have a life length measured in minutes, why predictions of tool wear are of great interest. Finite Element (FE) simulations have a central role in the development of tools and cutting processes, but performing simulations of metal cutting is not easy. The method chosen for the chip formation has a large impact on the result of the simulations. The scope of this work includes a survey on important parameters and different possibilities to form a chip in simulations of metal cutting in ABAQUS/Explicit. Particular emphases are placed the on  prediction of flank wear and how the hardening implemented in the material model effects this. The approach has been to start with a literature study and thereafter make simulations in ABAQUS/Explicit. FE simulations, of cutting, with different damage criteria and simulations with SPH (Smooth Particle Hydrodynamics)- method are presented. None of the possibilities to form a chip in ABAQUS/Explicit, as implemented today, seems to be sufficient for simulations of cutting to predict flank wear. The SPH-method will be a good alternative for simulations of metal cutting in ABAQUS/Explicit if temperature dependency is implemented. The material model in general, the type of hardening in specific, has an impact on the chip-form and the stress state in the chip and workpiece. And thereby effects the flank wear.

  • 121972.
    Zetterberg, Mikaela
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Kastby, Claes
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Vibrationsmätningar på handhållna pneumatiska verktyg.2011Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The current guidelines on how to assess and classify the health risk with exposure of the hand-arm system to vibrations is based on a simple frequency weighting curve. The problem with today's existing standard is that it doesn’t take into consideration all the factors influencing the risk of vibrating hand held power tools. For example factors such as impact of transients in vibration and the amount of energy absorbed by the hand are not taken into account. One way to more accurately evaluate the contribution of these factors is to use methods others than those imposed by the current standard, such as vibration power absorption or analytical wavelet transform. Another problem with today’s standard is that the characterization seems to be depending on the method chosen. Two of the recommended methods of analysis in the standard, weighting filter for narrowband and weighting factors in one third octave bands was tested, to determine if there is a difference depending on the analysis method chosen, and thus see how arbitrary the characterization is. This was done by applying both methods on each of the two recorded time signals, one with a strong tone and one with strong transients. The test confirmed that there is a difference between weighting factors in one third octave bands and narrow bands and that this affects the total hand weighted accelerations, ( ) especially if the vibration contains strong tones. The character of the vibration and the frequency of the tones are likely factors behind these results. The results can be used to optimize the outcome when selecting the method of analysis. It should be noted however that further research and investigation should be conducted to find how the locations of the tones within the third octave band, in the frequency domain, as well as how the selection of frequencies for summation of the affects the outcome of .

  • 121973.
    Zetterberg, Per
    KTH, Superseded Departments, Signals, Sensors and Systems.
    A Smart Antenna Concept for 4G and Transceiver Cost2004In: Proceedings of Nordic Radio Symposium, 2004Conference paper (Other academic)
  • 121974.
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Comparison of angle-spread in outdoor-to-outdoor and outdoor-to-indoor cases in an urban macro-cesll2005In: Wireless Personal Multimedia Communications (WPMC), Aalborg, Denmark, 2005Conference paper (Refereed)
  • 121975.
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Signal Processing.
    Experimental Investigation of TDD Reciprocity-Based Zero-Forcing Transmit Precoding2011In: EURASIP J ADV SIGNAL PROCESS, ISSN 1687-6172, p. 137541-Article in journal (Refereed)
    Abstract [en]

    We describe an implementation of TDD reciprocity based zero-forcing linear precoding on a wireless testbed. A calibration technique which self-calibrates the base-station without the need for help from other nodes is described. Performance results in terms of downlink channel estimation error as well as bit error rate (BER) and signal to interference noise and distortion ratio (SINDR) are presented for a scenario with two base-stations and two mobile stations, with two antennas at the base-stations and a single antenna at the mobile-station. The results show considerable performance improvements over reference schemes (such as maximum ratio transmission). However, our analysis also reveals that the hardware impairments significantly limit the performance achieved. We further investigate how to model these impairments and attempt to predict the SINDR, such as what would be needed in a coordinated multipoint (CoMP) scenario where scheduling is performed jointly over the two cells. Although the results are obtained for a MISO scenario the general conclusions are relevant also for MIMO scenarios.

  • 121976.
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Interference alignment (IA) and coordinated multi-point (CoMP) overheads and RF impairments: Testbed results2014In: 2014 IEEE 80th Vehicular Technology Conference (VTC Fall), 2014, p. 1-7Conference paper (Refereed)
    Abstract [en]

    In this work we investigate the network MIMO techniques of interference alignment (IA) and joint transmission coordinated multipoint (CoMP) in an indoor very small cell environment. Our focus is on the overheads in a system with quantized channel state feedback from the receiver to the transmitter (based on the 802.11ac standard) and on the impact of non-ideal hardware. The indoor office scenario should be the most favorable case in terms of the required feedback rates due to the large coherence bandwidth and coherence time of the channel.The evaluations are done using a real-world wireless testbed with three BSs and three MSs all having two antennas. The signal to noise ratio in the measurements is very high, 35-60dB, due to the short transmission range. Under such conditions radio hardware impairments becomes a major limitation on the performance. We quantify the impact of these impairments. For a 23ms update interval the overhead is 2.5% and IA and CoMP improves the sum throughput 25% and 50% in average (over the reference schemes e.g. TDMA MIMO), under stationary conditions. When two people are walking in the measurement area the throughput improvements drops to 17% and 45%, respectively.

  • 121977.
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    INTERFERENCE ALIGNMENT (IA) AND COORDINATED MULTI-POINT (COMP) WITH IEEE802.11AC FEEDBACK COMPRESSION: TESTBED RESULTS2014In: Proceedings of the IEEE International Conference on Acoustics, Speech and Signal Processing, ISSN 1520-6149, p. 6854791-Article in journal (Refereed)
    Abstract [en]

    We have implemented interference alignment (IA) and joint transmission coordinated multipoint (CoMP) on a wireless testbed using the feedback compression scheme of the new 802.11ac standard. The performance as a function of the frequency domain granularity is assessed. Realistic throughput gains are obtained by probing each spatial modulation stream with ten different coding and modulation schemes. The gain of IA and CoMP over TDMA MIMO is found to be 26% and 71%, respectively under stationary conditions. In our dense indoor office deployment, the frequency domain granularity of the feedback can be reduced down to every 8th subcarrier (2.5MHz), without sacrificing performance.

  • 121978.
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Method for Decreasing Fading in a Telecommunication System1998Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    The present invention provides a method for decreasing fading and more particularly the down-link fading in a mobile telecommunication system having transmit lobe diversity. The telecommunication system comprises at least one base station having an antenna array providing lobe diversity, and communicating with mobile terminal units. According to the invention, the average path-loss between the base station and a mobile terminal unit is measured by the base station in order to select a set of alternative lobes. The instantaneous down-link path-loss of the alternative lobes between the base station and the mobile terminal unit is also measured by the mobile in order to select a communication lobe from said set of alternative lobes, such that the communication is effected in the communication lobe.

  • 121979.
    Zetterberg, Per
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Mobile cellular communications with base station antenna arrays1997Doctoral thesis, monograph (Other scientific)
    Abstract [en]

    This thesis deals with the problem of increasing thespectrum efflciency of cellular systems by the use of antennaarray base stations. The focus of the thesis is on downlinktransmission in frequency division duplex systems. i.e.,systems with different up and downlink carrier frequency. In ashort summary the thesis:

        Proposes five reasonable propagation models.

        Uses these models to design and analyze three differentbeamformers: The maximum desired power (MDP), the summedinterference to carrier ratio minimizing (SCIR) and thegeneralized-SCIR beam-former

        Introduces three capacity enhancement approaches: samesector frequency reuse (SSFR), reduced cluster size withoutnulling (RCS-WON) and reduced cluster size with nulling(RCS-WIN).

        Proposes channel allocation, power control. andbeamforming algorithms for these approaches.

        Estimates the "outage probability" {probability ofinsufficient quality), for SICR-SSFR. SICR-RCS-WON andSICR-RCS-WIN. using simulations as well as analyticalanalysis, as a function of critical parameters.

        Investigates the capacity enhancement achieved with thebase station antenna array as a function of angular spreadingand the number of antennas for SICR-SSFR. SICR-RCS-WON andSICR-RCS-WIN.

        Partially verifies the system simulation assumptionsusing real data.

        Combines simulation and experimental results to makelikely that three to tenfold capacity enhancement isrealistic using 3 - 18 antenna elements per 120-degree sector(in comparison with a system employing a single antenna persector). The higher capacity enhancements are obtained usingthe more complex approaches

        Makes a detailed proposal of a simple and robust downlinkbeamforming algorithm for realizing RCS-WON in GSM (the MDPbeamformer

        Simulates this beamformer under realistic networkconditions, using simulated as well as real data

    Keywords:antenna arrays, base station, downlink,spectrum efficiency

  • 121980.
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Performance of Antenna Tilting and Beamforming in an Urban Macrocell2009In: 2009 1ST INTERNATIONAL CONFERENCE ON WIRELESS COMMUNICATION, VEHICULAR TECHNOLOGY, INFORMATION THEORY AND AEROSPACE & ELECTRONIC SYSTEMS TECHNOLOGY, VOLS 1 AND 2, NEW YORK: IEEE , 2009, p. 197-202Conference paper (Refereed)
    Abstract [en]

    In this paper we investigate the use of very high gain antenna columns (up to twelve stacked 8dBi elements) in an urban macro-cell. We also investigate electrical downtilt, and horizontal beamforming using an array of very high gain antenna columns. In particular we investigate simultaneous beamforming and electrical downtilt. The results show that the vertical gain is close to the theoretical frees-space gain, while electrical downtilt increases the effective path-loss slope. Interestingly, the electrical downtilt also increases the azimuth RMS-angle-spread and thereby decreases the horizontal gain achievable with beamforming.

  • 121981. Zetterberg, Per
    Performance of narrow beams in an suburban environment2000In: Vehicular Technology Conferance (VTC 2000-Spring), 2000, p. 1235-1239Conference paper (Refereed)
  • 121982.
    Zetterberg, Per
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Performance of three, six, nine and twelve sector sites in CDMA: Based on measurements2004In: IEEE International Symposium on Spread Spectrum Techniques and Applications, 2004, p. 394-399Conference paper (Refereed)
    Abstract [en]

    In this paper we investigate the performance improvement achieved by increasing the number of sectors on a W-CDMA or CDMA2000 site by increasing the number of sectors from today's typical three to six, nine or twelve. The radio propagation environment determines if the narrow beams can be created and kept separated or if they blur together, which in turn determines the sector-to-sector isolation and the soft-handoff populations. The rate of change in signal strength of the beams also determines whether the handover mechanisms are sufficiently fast to allocate the correct beam. In this paper we analyze these issues based on simultaneous measurements of two antenna panels placed on the top of a building overlooking a typical European urban environment of mostly six to eight stories high buildings. Based on these measurements and simulations we find that a nine-sector site has more than double the capacity of a conventional three-sector site.

  • 121983.
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Simulation of Spatially Correlated Large-Scale Parameters and Obtaining Model Parameters from Measurements2008Report (Other academic)
  • 121984.
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    WIreless DEvelopment LABoratory(WIDELAB) Equipment Base2013Report (Other academic)
    Abstract [en]

    This paper documents some of the hard- and soft-ware used by the signal- processing group at KTH, in it’s experimental work on wireless systems. We call these items collectively WIreless DEvelopment LABoratory (WIDELAB), and this paper aims to document the most important pieces and some of the knowledge needed to understand, operate and develop them further. To access the hard and software described contact perz@s3.kth.se

  • 121985.
    Zetterberg, Per
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Signal Processing.
    McNamara, Darren
    Karlsson, Peter
    Beach, Mark A.
    Downlink beamforming with delayed channel estimates under total power, element power and equivalent isotropic radiated power (EIRP) constraints2001In: IEEE 54TH VEHICULAR TECHNOLOGY CONFERENCE, VTC FALL 2001, 2001, p. 516-520Conference paper (Refereed)
    Abstract [en]

    A WLAN-type scenario where a base-station (access point) equipped with multiple antennas is transmitting and a mobile with only a single antenna is receiving, is considered. Three approaches are investigated: Grid-of-beams (GOB), Maximal-Ratio (MR) and equal-gain (EG) each with one of the following constraints 1) Total transmit power over all antenna elements, 2) Maximum power on any antenna element 3) Equivalent isotropic radiated power (EIRP). The median diversity gain for the MR approach was estimated to be 14.8dB, 10.6dB, and 11.4dB using constraint 1-3, respectively at 5.2GHz in a modern University building at 5-50 meter range. For GOB corresponding numbers are 9.4dB,9.4dB,2.3dB and for EG 13.9dB,13.9dB,10.3dB, respectively. These results were virtually independent of delay between channel estimation and use of the same estimate, when the delay is less than 130ms. This result was obtained although there were people moving in the environment. The diversity gain under the EIRP constraint is encouraging and shows that coverage improvements are possible even under EIRP limitations.

  • 121986.
    Zetterberg, Per
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Bengtsson, Mats
    KTH, Superseded Departments, Signals, Sensors and Systems.
    McNamara, Darren P.
    Karlsson, Peter C.
    Beach, Mark A.
    Performance of multiple-receive multiple-transmit beamforming in WLAN-type systems under power or EIRP constraints with delayed channel estimates2002In: IEEE 55TH VEHICULAR TECHNOLOGY CONFERENCE, VTC SPRING 2002, VOLS 1-4, PROCEEDINGS, 2002, p. 1906-1910Conference paper (Refereed)
    Abstract [en]

    Downlink beamforming in a WLAN-type system employing access points and mobiles equipped with multiple antennas and associated receivers and transmitters are considered. The beamforming aims at maximizing the performance under constraints on transmit power or equivalent isotropic radiated power (EIRP). Solutions for the two constraints are derived and investigated using simulated and measured channels. Our simulation and experimental results shows that performance gains of 8-10dB when using four directional transmitter antennas and two receive antennas (as compared with a base-line one-transmit two-receive), are possible under both constraints. For simulated channels, a delay between channel estimation and use of the same channel of up to 10% of the (inverse of the) Doppler frequency only degrades performance some tenths of a dB. In our measurements, very small degradations are seen with delays of up to 130ms. The measurements were made under relatively stationary conditions with only occasionally moving people Two different strategies for updating the beamforming vectors: sounding and ping-pong, are also considered in the paper.

  • 121987.
    Zetterberg, Per
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Fardi, Ramin
    Open Source SDR Frontend and Measurements for 60-GHz Wireless Experimentation2015In: IEEE Access, E-ISSN 2169-3536, Vol. 3, p. 445-456Article in journal (Refereed)
    Abstract [en]

    This paper aims to make 60-GHz experimentation possible for a wider range of research groups. We do this by describing a low-cost front-end that can be used in combination with any baseband processing platform. We provide detailed instructions and software for connection with the USRP N200/N210, including general classes for controlling the board and example single-input single-output and 2 x 2 Multiple-Input Multiple Output applications. In addition, we provide measurements to assess the impact of phase noise and other hardware impairments in low-cost millimeter-wave systems for hybrid measurement and simulation studies. Finally, we also perform performance measurements on the hardware. All our materials, such as the hardware design, the software, and the measurements, are freely available.

  • 121988.
    Zetterberg, Per
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Jaldén, Joakim
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Lundin, Henrik
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Samuelsson, David
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Svedman, Patrick
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Zhang, Xi
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Implementation of SM and RxTxIR on a DSP-Based Wireless MIMO Test-Bed2004In: Proceedings of the European DSP Education and Research Symposium EDERS, 2004Conference paper (Refereed)
    Abstract [en]

    In this paper we describe the implementation of two smart-antenna strategies and associated signal processing algorithms on a common DSP-based wireless MIMO test-bed. The test-bed supports single cell and two-cell configurations. All nodes (MS andBS) have two antennas (either two transmit or tworeceive) and there are feedback links (via cable) from the receivers to all transmitters.These possibilities has been utilized differently in the two techniques: spatial multiplexing (SM) and joint receiver transmitter and interference rejection (RxTxIR).The SM technique targets a single-link low-mobility scenario and boosts throughput using two parallel spatially multiplexed modulation streams. The RxTxIR scheme utilizes the two-cell configuration of the testbed to demonstrate the possibility of suppressing intercell interference in transmitter as well as the receiver beamforming.

  • 121989.
    Zetterberg, Per
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Jaldén, Niklas
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Analysis of Multi-Cell MIMO Measurements in an Urban Macrocell Environment2005In: General Assembly of Internation Union of Radio Science (URSI), 2005Conference paper (Other academic)
  • 121990.
    Zetterberg, Per
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Jaldén, Niklas
    Ottersten, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Investigation of Simple Algorithms for Estimation of Delay-Spread and Angle-Spread2012Report (Other academic)
    Abstract [en]

    In this paper we describe two simple methods for estimation of delay-spread and angle-spread, re-spectively. The algorithms are simple in the sense that the transmitted signal may consist of only threesuperimposed CW tones -and the receiver need only two antennas. The algorithms are also simple in thesense that the computational cost is very low. We verify the algorithms by applying them to wideband andmulti-antenna measurement data, respectively.

  • 121991.
    Zetterberg, Per
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Jaldén, Niklas
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Yu, Kai
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Analysis of MIMO Multi-Cell Correlations and Other Propagation Issues Based on Urban Measurements2005In: IST Mobile and Wireless Communications Summit, 2005Conference paper (Refereed)
  • 121992.
    Zetterberg, Per
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Mavrokefalidis, C.
    Lalos, A. S.
    Matigakis, E.
    Experimental Investigation of Cooperative Schemes on a Real-Time DSP-Based Testbed2009In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499Article in journal (Refereed)
    Abstract [en]

    Experimental results on the well-known cooperating relaying schemes, amplify-and-forward (AF), detect-and-forward (DF), cooperative maximum ratio combining (CMRC), and distributed space-time coding (DSTC), are presented in this paper. A novel relaying scheme named "selection relaying" (SR), in which one of two relays are selected base on path-loss, is also tested. For all schemes except AF receive antenna diversity is as an option which can be switched on or off. For DF and DSTC a feature "selective" where the relay only forwards frames with a receive SNR above 6 dB is introduced. In our measurements, all cooperative relaying schemes above increase the coverage area as compared with direct transmission. The features "antenna diversity" and "selective" improve the performance. Good performance is obtained with CMRC, DSTC, and SR.

  • 121993.
    Zetterberg, Per
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Mavrokefalidis, Christos
    Lalos, Aris
    Emmanouil, Matigakis
    Implementation and Testing of Co-Operative Schemes on a Real-Time DSP-Based Testbed2009In: ICT-MobileSummit 2009 Conference Proceedings / [ed] Paul Cunningham and Miriam Cunningham, 2009Conference paper (Refereed)
    Abstract [en]

    Experimental and simulation results on well-known co-operating relayingschemes such as: amplify-and-forward (AF), detect-and-forward (DF), co-operativemaximum-ratio combining (CMRC), and distributed space-time coding (DSTC) arepresented in this paper. A novel relaying scheme named “selection relaying” (SR), inwhich one of two relays are selected base on path-loss, is also tested.We also implement the modes “Selective” and “Antenna Diversity”. The “Selective”option is designed to avoid forwarding of erroneous frames.In our measurements, all co-operative relaying schemes above increase the coveragearea as compared with direct transmission. The features “Antenna diversity” and “Selective”improve the performance. Good performance is obtained with CMRC, DSTCand SR.

  • 121994.
    Zetterberg, Per
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Moghadam, Nima N.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    An experimental investigation of SIMO, MIMO, interference-alignment (IA) and coordinated multi-point (CoMP)2012In: 2012 19th International Conference on Systems, Signals and Image Processing, IWSSIP 2012, 2012, p. 211-216Conference paper (Refereed)
    Abstract [en]

    In this paper we present experimental implementations of interference alignment (IA) and coordinated multi-point transmission (CoMP). We provide results for a system with three base-stations and three mobile-stations all having two antennas. We further employ OFDM modulation, with high-order constellations, and measure many positions both line-of-sight and non-line-of-sight under interference limited conditions. We find the CoMP system to perform better than IA at the cost of a higher back-haul capacity requirement. During the measurements we also logged the channel estimates for offline processing. We use these channel estimates to calculate the performance under ideal conditions. The performance estimates obtained this way is substantially higher than what is actually observed in the end-to-end transmissions - in particular in the CoMP case where the theoretical performance is very high. We find the reason for this discrepancy to be the impact of dirty-RF effects such as phase-noise and non-linearities. We are able to model the dirty-RF effects to some extent. These models can be used to simulate more complex systems and still account for the dirty-RF effects (e.g., systems with tens of mobiles and base-stations). Both IA and CoMP perform better than reference implementations of single-user SIMO and MIMO in our measurements.

  • 121995.
    Zetterberg, Per
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Ottersten, Björn
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Experiments Using an Antenna Array in a Mobile Communications Environment1994In: IEEE Seventh SP Workshop on Statistical Signal and Array Processing, 1994, p. 137-140Conference paper (Refereed)
    Abstract [en]

    The goal of this paper is to obtain knowledge about spatial characteristics of the mobile channel seen through an antenna array. Particular interest is paid to the effect of local scattering. i.e large number of rays in the vicinity of the mobile.

  • 121996.
    Zetterberg, Per
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Ottersten, Björn
    KTH, Superseded Departments, Signals, Sensors and Systems.
    The Spectrum Efficiency of a Base Station Antenna Array System for Spatially Selective Transmission1995In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 44, no 3, p. 651-660Article in journal (Refereed)
    Abstract [en]

    In this paper we investigate the spectrum efficiency gain using  ransmittingantenna arrays at the base stations of a mobile cellular  etwork. The proposedsystem estimates the angular positions of the mobiles from the received data, and allows multiple mobiles to be allocated to the same channel within a cell. This is possible by applying a transmit scheme which directs nulls against co-channel users within the cell. It is shown that multiple mobiles per cell is an efficient way of increasing capacity in comparison with reduced channel reuse distance and narrow beams (without directed nulls). The effect of the spatial spread angle of the locally scattered rays in the vicinity of the mobile is also investigated

  • 121997.
    Zetterberg, Per
    et al.
    KTH, School of Electrical Engineering (EES).
    Ottersten, Björn
    KTH, School of Electrical Engineering (EES).
    The spectrum efficiency of a base station antenna array system for spatially selective transmission2009In: Adaptive Antennas for Wireless Communications, John Wiley and Sons Inc. , 2009, p. 471-480Chapter in book (Other academic)
    Abstract [en]

    In this paper we investigate the spectrum efficiency gain using transmitting antenna arrays at the base stations of a mobile cellular network. The proposed system estimates the angular positions of the mobiles from the received data, and allows multiple mobiles to be allocated to the same channel within a cell. This is possible by applying a transmit scheme which directs nulls against co-channel users within the cell. It is shown that multiple mobiles per cell is an efficient way of increasing capacity in comparison with reduced channel reuse distance and narrow beams (without directed nulls). The effect of the spatial spread angle of the locally scattered rays in the vicinity of the mobile is also investigated.

  • 121998.
    Zetterberg, Per
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Ottersten, Björn
    KTH, Superseded Departments, Signals, Sensors and Systems.
    The Spectrum Efficiency of a Base-Station Antenna Array System for Spatially Selective Transmission1994In: IEEE 44th Vehicular Technology Conference, IEEE , 1994, p. 1517-1521Conference paper (Refereed)
    Abstract [en]

    The goal of this paper is to estimate the gain, in terms of system capacity at a given outage probability, which can be obtained by applying antenna arrays in the base stations of a mobile cellular network. For this purpose apropagation model which incorporates the angular distribution of the rays in the vicinity of the mobile is postulated. Also included in the model is the interference from co-channel cells. With the aid of the model, aweight selection algorithm is derived. The proposed system is simulated with different numbers of mobiles per channel in each cell and different numbers of antenna elements in the arrays. Also varied is the cluster size. This is done to determine the optimal trade-off between reduced cluster size and multiple mobiles per channel in each cell. The results show that it is possible to increase capacity between two and twelve times depending on thenumber of antennas in the arrays and the spread of the local scattering.

  • 121999. Zetterberg, T.
    et al.
    Astrom, B. T.
    Backlund, J.
    Burman, Magnus
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    On design of joints between composite profiles for bridge deck applications2001In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 51, no 1, p. 83-91Article in journal (Refereed)
    Abstract [en]

    Techniques for joining of pultruded composite profiles for bridge-deck applications are designed and analyzed. It is shown that both adhesively bonded and bolted joints can be designed to fulfill stringent requirements, but it is clear that the former is the preferred alternative. The methodology used to analyze a large composite structure composed of modular construction elements and to determine the load transfer between composite profiles is described.

  • 122000.
    Zetterberg Wallin, Georg
    KTH, School of Engineering Sciences (SCI).
    System architectural interfaces forautonomous trucks2014Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis evaluates a proprietary interface developed by Scania that connects a third party developed autonomy solution to the electrical system of a Scania truck. The autonomy solution is developed for a mining application. While evaluating the interface the focus of the thesis narrows down to how to make the interface scalable and future proof. The content of this thesis is mainly based upon interviews and internal Scania documentation. In summary, the two main conclusions that could be drawn from this evaluation study are, that the interface needs to support a larger amount of requests from an external control to support that the interface is applicable in many areas. Secondly the idea of a modular electrical system must be carried on to autonomous applications as well and interface logic must be separated from core functionality of the electrical system.

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