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Sökning: LAR1:cth > Högskolan i Gävle

  • Resultat 1-8 av 8
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1.
  • Amin, Shoaib, et al. (författare)
  • Behavioral Modeling and Linearization of Crosstalk and Memory Effects in RF MIMO Transmitters
  • 2014
  • Ingår i: Ieee Transactions on Microwave Theory and Techniques. - 0018-9480. ; 62:4, s. 810-823
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper proposes three novel models for behavioral modeling and digital pre-distortion (DPD) of nonlinear 2 x 2 multiple-input multiple-output (MIMO) transmitters in the presence of crosstalk. The proposed models are extensions of the single-input single-output generalized memory polynomial model. Three types of crosstalk effects were studied and characterized as linear, nonlinear, and nonlinear & linear crosstalk. A comparative study was performed with previously published models for the linearization of crosstalk in a nonlinear 2 x 2 MIMO transmitter. The experiments indicate that, depending on the type of crosstalk, the selection of the correct model in the transmitter is necessary for behavioral modeling and sufficient DPD performance. The effects of coherent and partially noncoherent signal generation on the performance of DPD were also studied. For crosstalk levels of 30 dB, the difference in the normalized mean square error and adjacent channel power ratio was found to be 3-4 dB between coherent and partially noncoherent signal generation.
2.
  • Glaumann, Mauritz, et al. (författare)
  • Miljöklassning av byggnader : Slutrapport
  • 2008
  • Rapport (övrigt vetenskapligt)abstract
    • Den här rapporten presenterar en metod för att miljöklassa byggnader med avseende på energi, innemiljö och kemiska ämnen. Rapporten presenterar också några särskilda miljökrav för byggnader med eget VA-system.Det övergripande syftet med ett nationellt miljöklassningssystem är att bidra till en hållbar bygg- och fastighetssektor. Arbetet ska resultera i en praktiskt tillämpbar metod för miljöklassning av byggnader som är väl förankrad i byggsektorn och hos myndigheterna. En allmänt accepterad miljöklassning av yggnader kan bli ett starkt incitament för byggherrar, fastighetsägare, fastighetsförvaltare och bebyggelsens användare att påskynda en utveckling mot en miljöanpassad och hälsoinriktad byggsektor.En av de viktigaste utgångspunkterna för arbetet med att ta fram ett miljöklassningssystem har varit Bygga-bo-dialogens1 mål att alla nya hus och 30 procent av det befintliga byggnadsbeståndet ska vara miljöklassade senast år 2009. Denna ambition har medfört att enkelhet har varit ett viktigt mål för miljöklassningsarbetet. Balansen mellan trovärdighet ochenkelhet har varit viktigt för arbetet.
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3.
  • Kazmierczak, Karolina, et al. (författare)
  • An integrated analysis of ergonomics and time consumption in Swedish 'craft-type' car disassembly
  • 2005
  • Ingår i: Applied Ergonomics. - 00036870. ; 36:3, s. 263-273
  • Tidskriftsartikel (refereegranskat)abstract
    • Car disassembly is at the edge of extensive rationalisations due to increased legislative demands for recycling. This study focused on (1) assessing Current mechanical exposures (physical work loads) for comparison with future rationalised systems, with particular emphasis on time aspects, (2) analysing disassembly work in terms of time consumption and exposures in constituent tasks as defined by a loss analysis technique, and (3) predicting the consequences of car disassembly rationalisation for mechanical exposures. The study showed that disassembly implied pronounced circulatory loads, and that more walking and higher lumbar peak loads were found than in studies of assembly work. Value-adding tasks comprised 30% of the total working time, and implied higher postural exposures for the head, arm, trunk and wrist, as well as less opportunities to recover, as compared to non-value-adding tasks. Organisational-type rationalisations can be expected to increase the time spent in value-adding work, thus increasing local exposures for the average worker, while a concurrent increase in mechanisation level might reduce circulatory exposures, the amount of walking, and peak lumbar loads.
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4.
  • Neumann, W. P., et al. (författare)
  • Production system design elements influencing productivity and ergonomics - A case study of parallel and serial flow strategies
  • 2006
  • Ingår i: International Journal of Operations & Production Management. - 0144-3577. ; 26:8, s. 904-923
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose - The purpose of this paper is to investigate a strategic change from parallel cell-based assembly (old) to serial-line assembly (new) in a Swedish company with special reference to how production system design elements affect both productivity and ergonomics. Design/methodology/approach - Multiple methods, including records and video analysis, questionnaires, interviews, biomechanical modelling, and flow simulation were applied. Findings - The new system, unlike the old, showed the emergence of system and balance losses as well as vulnerability to disturbances and difficulty handling all product variants. Nevertheless, the new system as realised partially overcame productivity barriers in the operation and management of the old system. The new system had impaired ergonomics due to decreased physical variation and increased repetitiveness with cycle times that were 6 per cent of previous thus increasing repetitiveness, and significantly reducing perceived influence over work. Workstations' uneven exposure to physical tasks such as nut running created a potential problem for workload management. The adoption of teamwork in the new system contributed to significantly increased co-worker support - an ergonomic benefit. Practical implications - Design decisions made early in the development process affect both ergonomics and productivity in the resulting system. While the time pattern of physical loading appeared to be controlled by flow and work organisation elements, the amplitude of loading was determined more by workstation layout. Psychosocial conditions appear to be affected by a combination of system elements including layout, flow, and work organisation elements. Strategic use of parallelisation elements in assembly, perhaps in hybrid forms from configurations observed here, appears to be a viable design option for improved performance by reducing the fragility and ergonomic problems of assembly lines. Originality/value - The interacting design elements examined here pose potential "levers" of control by which productivity and ergonomics could be jointly optimised for improved total system performance.
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5.
  • Sandén, Björn, et al. (författare)
  • A framework for analysis of multi-mode interaction among technologies with examples from the history of alternative transport fuels in Sweden
  • 2011
  • Ingår i: Research Policy. - 0048-7333. ; 40:3, s. 403-414
  • Tidskriftsartikel (refereegranskat)abstract
    • The relationship between technologies is a salient feature of the literature on technical change and terms like ’dominant design’ and ’technology lock-in’ are part of the standard vocabulary and put competition among technologies in focus. The aim of this paper is to provide an account of the wide range of interaction modes beyond competition that is prevalent in transition processes and to develop a conceptual framework to facilitate more detailed and nuanced descriptions of technology interaction. Besides competition, we identify five other basic modes of interaction: symbiosis, neutralism, parasitism, commensalism and amensalism. Further, we describe interaction as overlapping value chains. Defining a technology as a socio-technical system extending in material, organisational and conceptual dimensions allows for an even more detailed description of interaction. The conceptual framework is tested on and illustrated by a case study of interaction among alternative transport fuels in Sweden 1974-2004. © 2011 Elsevier B.V. All rights reserved.
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6.
  • Soltani Tehrani, Ali, 1982-, et al. (författare)
  • A Comparative Analysis of the Complexity/Accuracy Tradeoff in Power Amplifier Behavioral Models
  • 2010
  • Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480. ; 58:6, s. 1510-1520
  • Tidskriftsartikel (refereegranskat)abstract
    • A comparative study of state-of-the-art behavioral models for microwave power amplifiers (PAs) is presented in this paper. After establishing a proper definition for accuracy and complexity for PA behavioral models, a short description on various behavioral models is presented. The main focus of this paper is on the modeling accuracy as a function of computational complexity. Data is collected from measurements on two PAs—a general-purpose amplifier and a Doherty PA designed for WiMAX—for different output power levels. The models are characterized in terms of accuracy and complexity for both in-band and out-of-band error. The results show that, among the models studied, the generalized memory polynomial behavioral model has the best tradeoff for accuracy versus complexity for both PAs, and can obtain high performance at half of the computational cost of all other models analyzed.
7.
  • Törnström, T, et al. (författare)
  • Low-energy cooling for improved thermal comfort in offices
  • 2007
  • Konferensbidrag (refereegranskat)abstract
    • This study has explored the possibility and potential of using a thermal active mass system for reducing the temperature rise and increasing the thermal comfort in an office room. The Controlled Active Mass (CAM) will be used as a heat sink to absorb heat from the room in order to increase the thermal comfort. Physically, the CAM system was designed as a cubic-shaped tank filled with water, with the tank surfaces either polished or black. Full-scale laboratory measurements of the CAM system in an office room have been used to evaluate the temperature, air velocity and thermal comfort values, PMV, PPD and the equivalent temperature (t eq). The measurements showed that, although the CAM size is relatively small compared to the office room, and the temperature difference between the room air and the temperature of the CAM is quite modest, the influence on the thermal comfort and indoor environment is quite apparent. This is particularly so when the surfaces of the CAM system are black, since the tank is able to absorb more heat from the room surfaces than can the polished CAM system. The CAM system does not cause any uncomfortable draughts and, since it is a low-exergy system, it has a considerable potential for future energy-efficient systems in buildings.
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8.
  • Wells, R., et al. (författare)
  • Time - A key issue for musculoskeletal health and manufacturing
  • 2007
  • Ingår i: Applied Ergonomics. - 0003-6870. ; 38:6, s. 733-744
  • Tidskriftsartikel (refereegranskat)abstract
    • Time is a key issue for both ergonomists and engineers when they engage in production system interventions. While not their primary purpose, the actions of engineers have major effects on biomechanical exposure; possibly of much greater magnitude than many ergonomics interventions. This paper summarises the aims, actions and tools of engineers and ergonomists, emphasising time-related outcomes. Activities of the two groups when attempting to manipulate time aspects of work may be contradictory; engineers wishing to improve production and ergonomists aiming at better health as well as contributing to production. Consequently, tools developed by ergonomists for assessing time aspects of work describe rest patterns, movement velocities or daily duration of exposures, while engineering tools emphasise time-efficient production. The paper identifies measures that could be used to communicate time-relevant information between engineers and ergonomists. Further cooperation between these two stakeholders as well as research on the topic are needed to enable ergonomists to have a larger impact on the design of production systems.
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