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1
المؤلفون: Persson, Peter
المصدر: eSSENCE: The e-Science Collaboration.
مصطلحات موضوعية: vibration reduction, finite element method, coupled problems, vibration measurements, wave propagation, ground vibration, soil dynamics, wave barrier, shaped landscape, soil stabilisation, liquid-filled pipes, model order reduction, Teknik, Samhällsbyggnadsteknik, Husbyggnad, Engineering and Technology, Civil Engineering, Building Technologies, Infrastrukturteknik, Infrastructure Engineering, Geoteknik, Geotechnical Engineering
الوصف: Vibrations in a built environment can exceed the requirements for sensitive equipment in a building or can cause annoyance to residents. Hence, there is often a need for reducing such vibrations. The vibrations can originate from ambient sources such as motorway traffic, or from internal sources such as people walking inside the building. Disturbing vibrations can be reduced by reduction measures. Vibration-reduction measures can be evaluated numerically, with for instance the finite element method, to avoid construction of expensive mock-ups. In the thesis, large finite element models involving several physical domains (e.g. road, soil, bedrock, and building parts) were developed to study the effect of vibration-reduction measures.Ground vibrations can be reduced by installing a wave barrier between an external source and a receiver. As concluded in the thesis, an empty barrier (i.e. a trench) installed in the soil has the ability to reduce the ground-vibration level by approximately 60%. If the barrier contains a solid material, however, the level of reduction is reduced to approximately 30%. At long distances, at around 500 m and longer, from the vibration source, an amplification in vibration is observed. At such distances, moreover, the ground motion follows the motion of the bedrock. Another example of a wave obstacle that is studied in the thesis involves shaping the landscape surrounding a building. The topsoil that is usually transported from the construction site can be used to construct hills and valleys that constitute the shaped landscape. However, this can result in anything from an appreciable reduction to an appreciable amplification in the ground-vibration levels, depending on how the landscape is formed. If constructed properly, the reduction in the level of vibration can reach approximately 35%. Vibrations from both external and internal sources can be reduced by modifying the properties of the concrete slabs and the soil underneath. The soil properties can be improved by mixing the soil with a binder, in order to stiffen the soil. Is is shown in the thesis that by using stabilised soil underneath a concrete slab, vibrations originating from motorway traffic can be reduced by almost 60%, and up to 80% for an internal pedestrian load. By using a time-efficient numerical model developed in the thesis, the effect by using different positions for the supports of a water-pipe system on vibrations transmitted to other parts of buildings was studied. Because frequency peaks can be avoided, a marked change of vibration characteristics can be achieved. A reduction of more than 60% in the transmitted vibrations was observed. The general methods and measures presented in the thesis are exemplified by the conceptual design process of the MAX IV Laboratory, a vibration-sensitive research facility. This laboratory exhibited the phenomena needed for selecting it as a comprehensive example case.
وصف الملف: electronic
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2تقرير
المساهمون: Ladell, Lars
وصف الملف: Medium: ED; Size: Pages: 45
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3تقرير
المساهمون: Witalis, E.
وصف الملف: Medium: ED; Size: Pages: 23
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4رسالة جامعية
المؤلفون: Fors, Karina
مصطلحات موضوعية: Dynamisk simulering, kanalens impulssvar, RPS, Radio Wave Propagation, tidsinvariant impulssvar, vågutbredning, stadsmiljö, urban miljö, Datatransmission
الوصف: Militära insatser i urban miljö kommer troligen att öka alltmer. Detta kräver soldater till fots eftersom dessa lättare kan förflytta sig via och mellan byggnader. Varje deltagande soldat kommer att behöva egen radioutrustning. Då stadsmiljö är ett relativt outforskat område vad gäller militär radiokommunikation är det viktigt att öka förståelsen för radiovågors utbredning i stadsmiljö. Härtill har institutionen för Informationsöverföring på FOI köpt in programmet Radiowave Propagation Simulator (RPS). RPS används i det här examensarbetet för att genomföra en beräkning för ett statiskt scenario, och till beräkningen infoga påverkan från sändares och mottagares mobilitet. Detta utförs genom att rumsligt extrapolera kanalens impulssvar till att gälla i andra positioner än de ursprungligen var beräknade för. Kanalens impulssvar blir då modifierat så att impulssvarets utbredningsvägar får nya fördröjningstider och dess komplexa signal får ny fas. Metoden, som har tagits fram i det här arbetet, för den rumsliga extrapoleringen har implementerats och utvärderats för ett litet scenario. Det extrapolerade resultatet har sedan jämförts med beräknade resultat från RPS. Analysen visade att metoden ger ett tillförlitligt resultat. Ett annat syfte med examensarbetet har varit att visa hur forskningsresultat (från radiokanalen) kan användas effektivare för att ge högre kvalité på forskningsresultat, både på länk- och på nätnivå.
وصف الملف: application/pdf
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5رسالة جامعية
المؤلفون: Forsberg, Nicklas, Säfholm, Johan
مصطلحات موضوعية: Datorteknik, Link budget, radio wave propagation, antennas, radio system, radio coverage, flying platforms, Computer Engineering
الوصف: There exist several known methods for calculation of radio coverage for ground-based systems. As far as we know there are no equivalent methods for the case of flying platforms when the altitudes and speeds are significantly different to those of ground-based systems. This thesis describes the theoretical concepts behind calculations of radio coverage for flying platforms. An investigation is made to sort out what is important and possible to employ in a model for simulations. A method is described and implemented in a program for evaluation of flying radio systems. Two typical cases of flight missions are simulated and discussed. It is found that the free space model is valid most of the mission time. The contribution from the antennas is found to be small in comparison to the path loss. Further investigations suggested are e.g. better ground reflection models and a better model for the flight mechanics.
وصف الملف: application/pdf
العلاقة: LiTH-ISY-Ex, ; 3218
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6
المؤلفون: Forsberg, Nicklas, Säfholm, Johan
مصطلحات موضوعية: Link budget, radio system, radio wave propagation, flying platforms, Computer Engineering, antennas, radio coverage, Datorteknik
الوصف: There exist several known methods for calculation of radio coverage for ground-based systems. As far as we know there are no equivalent methods for the case of flying platforms when the altitudes and speeds are significantly different to those of ground-based systems. This thesis describes the theoretical concepts behind calculations of radio coverage for flying platforms. An investigation is made to sort out what is important and possible to employ in a model for simulations. A method is described and implemented in a program for evaluation of flying radio systems. Two typical cases of flight missions are simulated and discussed. It is found that the free space model is valid most of the mission time. The contribution from the antennas is found to be small in comparison to the path loss. Further investigations suggested are e.g. better ground reflection models and a better model for the flight mechanics.
وصف الملف: application/pdf
الوصول الحر: https://explore.openaire.eu/search/publication?articleId=dedup_wf_001::11873b092d6c43ef5714fbc43ea0aaefTest
http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-1080Test -
7تقرير
المساهمون: Ryhming, I
المصدر: Other Information: UNCL. Orig. Receipt Date: 31-DEC-70
وصف الملف: Medium: X; Size: Pages: 80
الوصول الحر: http://www.osti.gov/scitech/biblio/4167694Test
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8رسالة جامعية
المؤلفون: Forsberg, Nicklas, Säfholm, Johan
مصطلحات موضوعية: Datorteknik, Link budget, radio wave propagation, antennas, radio system, radio coverage, flying platforms, Computer Engineering
الوصف: There exist several known methods for calculation of radio coverage for ground-based systems. As far as we know there are no equivalent methods for the case of flying platforms when the altitudes and speeds are significantly different to those of ground-based systems. This thesis describes the theoretical concepts behind calculations of radio coverage for flying platforms. An investigation is made to sort out what is important and possible to employ in a model for simulations. A method is described and implemented in a program for evaluation of flying radio systems. Two typical cases of flight missions are simulated and discussed. It is found that the free space model is valid most of the mission time. The contribution from the antennas is found to be small in comparison to the path loss. Further investigations suggested are e.g. better ground reflection models and a better model for the flight mechanics.
وصف الملف: application/pdf
العلاقة: LiTH-ISY-Ex; 3218; http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-1080Test
