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介绍了传统蜂窝夹层结构,它是由蜂窝芯材耦合面板/薄膜组合而成,具有优异的降噪特性。为进一步提升蜂窝夹层结构的降噪性能,结合多孔吸声原理及“吸/隔声结构功能一体化”概念,将多孔吸声材料填充至蜂窝芯中,形成了基于多孔吸声的蜂窝夹层结构,但中、低频降噪性能较差。结合微穿孔板、亥姆霍兹共振理论,开发了基于共振吸声的单自由度蜂窝夹层结构,由蜂窝芯材耦合穿孔面板/薄膜组合而成,提升了中、低频降噪特性,但是依旧存在降噪频带过窄的问题,只能在某段特定频率范围内表现出良好的降噪特性。为此,研发了基于共振吸声的多自由度蜂窝夹层结构,利用各层穿孔面板/薄膜和蜂窝结构特性,实现了不同频率噪声控制。最后总结了蜂窝夹层结构在国内外直升机被动噪声控制上的应用情况,展望了新型蜂窝夹层结构的发展趋势。 相似文献
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锅炉鼓风机噪声控制有许多方法,真正达到效果不十分理想,如何把噪声控制措施进步完善,结合水暖厂锅炉房鼓,引风机治理实践,探索出锅炉鼓风机噪声控制的条件和有效的措施。 相似文献
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本文对球磨机噪声进行了测试分析,对现有的噪声控制方法进行了评估。在此基础上,提出了以砂作为阻尼吸声材料,集缓冲,阻尼,吸声,隔声于一体的噪声控制方法。 相似文献
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通过对城市环境噪声控制目的的反思,提出将声景学引入城市环境噪声控制。论述了声景学与噪声控制的关系,并从声景观的创造性、关联性、社会性三个方面提出噪声控制的新思路,给城市环境噪声控制的研究提供了崭新的研究方法。 相似文献
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高速铁路噪声污染及其防治 总被引:2,自引:0,他引:2
噪声污染是高速铁路的主要环境问题之一,通过对高速铁路噪声声源和噪声水平的分析以及日本、欧洲国家有关高速铁路噪声控制标准和法规的实践,提出了高速铁路的声源控制,传播途径及管理等3方面的噪声控制措施。 相似文献
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《Environmental Science & Policy》2003,6(3):261-269
Voluntary contributions to biodiversity conservation efforts in private forests of Austria have a long tradition which dates back to the 19th century. The most important remnants of undisturbed forests of the Alps today owe their existence to these voluntary initiatives by forest owners. In this earlier period the protection of forest areas by decree or biodiversity conservation initiatives on public owned forests, did not play such a prominent role. But as well as national parks, Natura 2000 areas and other programmes based on protection by decree, significant new voluntary approaches have emerged recently. The Austrian Forest Reserves Programme started in 1995, as a specific approach to voluntary participation in biodiversity conservation by private landowners is discussed in detail. This programme is based on the concept of nature conservation by contracts under private law, agreed between the forest owners and the Republic of Austria. The main characteristics of the programme are presented and experiences gained during the establishment and the maintenance of the network are discussed. Other voluntary initiatives, such as an Austrian network of gene conservation forests, as well as an initiative of a forest owner’s association, are also presented and discussed. 相似文献
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以国际腐殖质协会(IHSS)推荐的胡敏酸提取方法为基础,以去有机质土壤中添加胡敏酸所配制的土壤为研究对象,引入超声作为胡敏酸提取的辅助条件,采用批次试验优化了土壤中胡敏酸的提取方法。结果表明,基于胡敏酸提取回收率和精密度,在室温下获得的优化提取方法为:液土比为8:1、提取次数为3次、Na OH溶液浓度为0.05 mol/L、超声功率为120 W、超声时间为30 min;在此优化条件下,胡敏酸的回收率为94.73%±1.50%,显著大于IHSS推荐方法的回收率64.76%±0.28%,变异系数CV为1.59%、小于10%。相对于IHSS提取法,此优化提取法具有胡敏酸提取回收率高、资源节约、胡敏酸变性小、提取时间短等优点。 相似文献
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This study measures productive inefficiency within the context of multi-environmental pollution (eco-efficiency) in the Chinese industrial sector. The weighted Russell directional distance model is applied to measure eco-efficiency using production technology. The objective is to clarify how external factors affect eco-efficiency. The major findings are that both foreign direct investment and investment for pollution abatement improve eco-efficiency as measured by air pollutant substances. A levy system for wastewater discharge improves eco-efficiency as measured by wastewater pollutant substances. However, an air pollutant levy does not significantly affect eco-efficiency as measured by air pollutants. 相似文献
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This study measures productive inefficiency within the context of multi-environmental pollution (eco-efficiency) in the Chinese industrial sector. The weighted Russell directional distance model is applied to measure eco-efficiency using production technology. The objective is to clarify how external factors affect eco-efficiency. The major findings are that both foreign direct investment and investment for pollution abatement improve eco-efficiency as measured by air pollutant substances. A levy system for wastewater discharge improves eco-efficiency as measured by wastewater pollutant substances. However, an air pollutant levy does not significantly affect eco-efficiency as measured by air pollutants. 相似文献
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Global nitrogen (N) emission and deposition have been increased rapidly due to massive mobilization of N which may have longreaching
impacts on ecosystems. Many agricultural and forest ecosystems have been identified as secondary N sources. In the present
study, the input-output budget of inorganic N in a small forested watershed of subtropical China was investigated. Inorganic N wet
deposition and discharge by stream water were monitored from March, 2007 to February, 2009. The concentrations and fluxes of
inorganic N in wet precipitation and stream water and net retention of N were calculated. Global N input by dry deposition and
biological fixation and N output by denitrification for forested watersheds elsewhere were reported as references to evaluate whether
the studied forested watershed is a source or a sink for N. The results show that the inorganic N output by the stream water is mainly
caused by NO3??-N even though the input is dominated by NH4
+-N. The mean flux of inorganic N input by wet precipitation and
output by stream water is 1.672 and 0.537 g N/(m2 yr), respectively, which indicates that most of inorganic N input is retained in the
forested watershed. Net retention of inorganic N reaches 1.135 g N/(m2 yr) considering wet precipitation as the main input and stream
water as the main output. If N input by dry deposition and biological fixation and output by denitrification are taken into account, this
subtropical forested watershed currently acts as a considerable sink for N, with a net sink ranging from 1.309 to 1.913 g N/(m2 yr)
which may enhance carbon sequestration of the terrestrial ecosystem. 相似文献
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改性凹凸棒土吸附处理PAM废水研究 总被引:1,自引:0,他引:1
以丙烯酰胺(PAM)为目标污染物,研究了改性凹凸棒土对PAM的吸附性能、吸附过程的影响因素以及吸附完成后的再生问题。研究表明,250mg/L的PAM溶液振荡吸附1h后,酸改性凹凸棒土的吸附效率高于提纯和热改性凹凸棒土,达90.08%。在250mg/L的PAM溶液投加酸改性凹凸棒土进行振荡吸附试验,吸附时间为45min,试验结果表明,酸改性凹凸棒土的最佳投加量为1g/L;吸附过程最佳pH范围是4~6;吸附过程为放热过程。以5%、10%和15%的氢氧化钠溶液作为脱附剂进行再生试验,随着氢氧化钠溶液浓度的提高,再生效率逐渐提高。但是,再生效率提高的幅度减小,浓度为10%和15%的氢氧化钠溶液的再生效率差别不大。以10%的氢氧化钠溶液作为脱附剂时,最经济的再生次数为5次。 相似文献
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