木质阻尼复合结构隔声性能的研究现状

利用木质复合材料作为室内隔声材料,是控制室内噪声的重要手段。与钢质板材料的隔声性能相比较,木质材料的隔声性能较差。然而隔声性能好的高分子阻尼材料由于刚度较低不能单独使用,因此将木质材料与高分子阻尼材料复合制成层合复合材料,研究结果表明:通过提高木质和阻尼材料的厚度、密度或者改变木质板材与阻尼层合的层数,均可以提高复合材料的隔声性能,这种材料被应用在木质门、木质墙等室内装修中,是未来的一个发展方向。     

Manufacture and properties of low-density binderless particleboard from kenaf core

Low-density binderless particleboards from kenaf core were successfully developed using steam injection pressing. The target board density ranged from 0.10 to 0.30g/cm³, the steam pressure used was 1.0MPa, and the steam treatment times were 7 and 10min. The mechanical properties, dimensional stability, and thermal and sound insulation performances of the boards were investigated. The results showed that the low-density kenaf binderless particleboards had good mechanical properties and dimensional stability relative to their low board densities. The board of 0.20g/cm³ density with a 10-min treatment time produced the following values: modulus of rupture 1.1MPa, modulus of elasticity 0.3GPa, internal bond strength 0.10MPa, thickness swelling in 24h water immersion 6.6%, and water absorption 355%. The thermal conductivity of the low-density kenaf binderless particleboards showed values similar to those of insulation material (i.e., rock wool), and the sound absorption coefficient was high. In addition, the boards are free from formaldehyde emission. Kenaf core appears to be a potential raw material for low-density binderless panels suitable for sound absorption and thermally resistant interior products.Part of this report was presented at the 52th Annual Meeting of the Japan Wood Research Society, Gifu, Japan, April 2002     

Factors influencing densities of non‐indigenous species in the ballast water of ships arriving at ports in Puget Sound,Washington, United States

• 1. Oceanographic characteristics and the presence of international shipping in Puget Sound, Washington, USA contribute to its vulnerability to non‐indigenous species (NIS) invasions. To evaluate NIS arriving in ballast water, zooplankton was sampled in 380 ballast tanks of ships after they entered Puget Sound.
• 2. Taxa were classified into a higher risk group of coastal organisms (including known NIS), and a lower risk group of largely oceanic species. Most ships reported conducting mid‐ocean ballast water exchange (BWE). However, despite state regulations requiring BWE, and apparent compliance by ship operators, most sampled tanks from both transpacific and coastal routes had coastal zooplankton densities exceeding internationally proposed discharge standards.
• 3. BWE efficiency models and controlled before‐and‐after BWE experiments indicate that BWE consistently removes most coastal zooplankton. However, this study found that although the empty–refill method of BWE significantly reduced coastal plankton compared with un‐exchanged tanks, the flow‐through method did not, and in either case remaining coastal plankton densities presented appreciable risks of introducing NIS.
• 4. Densities of high risk taxa were consistently and significantly higher from US domestic trips dominated by tank ships carrying ballast water from California, and lower in samples from trans‐Pacific trips dominated by container ships and bulk carriers with ballast from Asia. These findings are probably a result of the dense and diverse NIS assemblages present in California and other US west coast estuaries and the comparatively short transit times between them and Puget Sound.
• 5. While it appears that BWE can effectively replace NIS with less risky ocean species, new reporting, verification, and operational procedures may be necessary to enhance BWE efficacy. In the long‐term, the introduction of ballast water treatment technologies may be required to significantly reduce the discharge of risky organisms from commercial ships if BWE practices do not become more effective.

Copyright © 2008 John Wiley & Sons, Ltd.     

泵站噪声采集系统的软硬件设计

介绍了一种用于泵站等工业现场的噪声采集装置的软硬件设计。该装置由工控机、精密声级计、数据采集卡以及相应的采集和分析软件构成。在软件设计上，该装置采用了DMA采集和数据传送方式，通过使用环行缓存的内存调度方法，保证了在Windows下噪声数据采集的实时性。通过多线程工作方式充分发挥了硬件的性能。经过在某水电站现场使用证明该装置具有较强的抗干扰能力，能够用于存在较强电磁干扰的工业现场。     

利用超声无损检测对木质材料的特性研究

使用超声换能器,利用一发一收2个超能换能器对射式检测方式,对橡木指接板、中密度纤维板、细木工板、刨花板4种木质材料的频谱和声速进行了分析研究。研究表明在500 kHz的超声波时,均会产生"频移"现象,并且频移程度按以上顺序依次增加,细木工板和刨花板的"频移"现象尤其剧烈,500 kHz的超声波成分基本已经消失。结合超声波信号比较,能清晰地区分4种木质材料。     

汽车噪声源识别技术及发展

随着汽车工业的发展,汽车噪声已成为影响人们生活质量的重要污染源,如何控制汽车噪声成为世界汽车工业的一个重要课题,而对汽车噪声源准确的识别是有效控制汽车噪声的重要前提。本文介绍了汽车噪声的来源及汽车噪声源识别方法,探讨了每种方法的特点、适用范围及存在问题,并对如何做好汽车声源识别提出了一些建议,为不同的方法在工程中的应用提供了参考。     

轻型木结构建筑减振降噪试验研究

为促进木结构建筑减振降噪研究,以一栋普通轻型木结构建筑和一栋葡萄牙软木优化轻型木结构建筑为研究对象,采用瞬态激励法和现场声压级法,分别测试两栋建筑的动力参数(频率、峰值加速度、阻尼比)和隔声量,并进行相关分析。结果表明:两种轻型木结构建筑均符合舒适度要求,同时软木优化轻型木结构建筑的平均阻尼比比普通轻型木结构建筑高1.6%;在关闭门窗,交通噪声源和扬声器噪声源共同作用情况下,软木优化结构建筑的平均隔声量比普通结构高4.6 dB(A);其中软木优化结构的减振降噪性能好于普通轻型木结构建筑,可以明显改善木结构建筑楼盖振动特性和隔声效果。上述以期为轻型木结构建筑的减振降噪优化设计工作提供技术支撑,具有工程应用价值。     

复合地板撞击声隔声性能的预测

给出了一种通过小型隔声箱的测量结果推测在国家建筑隔声标准条件下测量的复合地板撞击声隔声性能的方法。与实际测量结果相比，预测数据的撞击声倍频程声压级误差在各频段内均小于4dB。此方法在复合地板研制过程中，用较低的成本，可大致了解复合地板的撞击声隔声性能，具有重要的实用价值。     

Ecosystem controls of juvenile pink salmon (Onchorynchus gorbuscha) and Pacific herring (Clupea pallasi) populations in Prince William Sound,Alaska

Five years of field, laboratory, and numerical modelling studies demonstrated ecosystem‐level mechanisms influencing the mortality of juvenile pink salmon and Pacific herring. Both species are prey for other fishes, seabirds, and marine mammals in Prince William Sound. We identified critical time‐space linkages between the juvenile stages of pink salmon and herring rearing in shallow‐water nursery areas and seasonally varying ocean state, the availability of appropriate zooplankton forage, and the kinds and numbers of predators. These relationships defined unique habitat dependencies for juveniles whose survivals were strongly linked to growth rates, energy reserves, and seasonal trophic sheltering from predators. We found that juvenile herring were subject to substantial starvation losses during a winter period of plankton diminishment, and that predation on juvenile pink salmon was closely linked to the availability of alternative prey for fish and bird predators. Our collaborative study further revealed that juvenile pink salmon and age‐0 herring exploit very different portions of the annual production cycle. Juvenile pink salmon targeted the cool‐water, early spring plankton bloom dominated by diatoms and large calanoid copepods, whereas young‐of‐the‐year juvenile herring were dependent on warmer conditions occurring later in the postbloom summer and fall when zooplankton was composed of smaller calanoids and a diversity of other taxa. The synopsis of our studies presented in this volume speaks to contemporary issues facing investigators of fish ecosystems, including juvenile fishes, and offers new insight into problems of bottom‐up and top‐down control. In aggregate, our results point to the importance of seeking mechanistic rather than correlative understandings of complex natural systems.     

后桥噪声检测与故障诊断试验台控制系统

基于声强法测量声功率原理,设计了后桥噪声检测与故障诊断试验台,阐述了该试验台检测后桥噪声的工艺和试验台控制系统的方案选型、硬件设计和软件设计,并解决了控制中较为重要的上位机、下位机通讯问题。