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Textile sound absorbents are getting more and more popular on the market as noise reduction is a major requirement for human comfort today. In this paper we focus on a new textile material for sound absorption, by investigating the acoustic characteristics of nanofibers. Through impedance tube method we measured the sound absorption coefficients of multiple layers of nanofiber webs and compared those with microfiber materials per fabric weight. We also examined the effect of layers of nanofiber webs on regularfiber knitted fabric on sound absorption. The test results showed that the sound absorption coefficients of nanofiber layers were superior that of microfiber fabrics in the frequency range 1000–4000 Hz. In this range, the sound absorption of nanofiber webs improved with numbers of layers. Also, adding nanofiber web plies to regularfiber fleece increased the sound absorption coefficient with 85 % at 4000 Hz. From our results we could observe differences in the sound absorption coefficients between two test methods, which are higher absorbance coefficients through the reverberation room method than impedance tube method. 相似文献
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Since 1947, the development of greater Copenhagen has followed a plan that divided the city into a centre and five urban ‘fingers’. The ‘Finger Plan’ has constituted an important part of the planning framework, albeit informally. Under this plan, four green wedges and three green rings, located between the urban ‘fingers’, form a multifunctional recreational landscape of high value to the citizens. In 2006, the Greater Copenhagen Authority put forward a proposal for the enlargement of the existing green wedges and the addition of a new fourth green ring. In order to achieve this plan, detailed mapping of recreational opportunities was needed. Based on existing planning approaches combined with theoretical and empirical studies on preferences, use, and composition of green spaces, a method for monitoring and analyzing recreational experiences using seven specific categories was adapted and further developed to Danish conditions and applied to land use categories in greater Copenhagen. Areas that comprised one or more recreational experience values were designated by use of GIS techniques and map-based indicators for each of the seven ‘experience classes’ (wilderness; feeling of the forest; panoramic views, water, and scenery; biodiversity and land form; cultural history; activity and challenge; service and gathering). For incorporation into the regional and municipal planning policy, the seven experience classes were transformed into GIS, creating a decision support system for use at municipal and regional levels in order to facilitate future planning of the recreational landscape in greater Copenhagen. The method proved capable of pointing out important areas for recreational development in the enlarged but not yet developed areas. Further, the division of the recreational potential into seven classes makes possible site-specific development that utilizes existing potential. 相似文献
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P Hjorth 《Nordisk veterinaermedicin》1971,23(5):260-262
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