基于听觉感知的不同航速稳态舰船噪声合成

声纳人员培训和人耳辨识舰船声实验中常需要完备的敌我舰船辐射噪声样本,但实录各国舰船噪声几乎是不可能的。因此,合成与真实水下声样本听觉感知相同的舰船辐射噪声十分必要。研究了舰船航速对其辐射噪声的影响及人耳听音的临界带通特性,通过已知的零散舰船噪声样本合成目标舰船在其它未知状态下的辐射噪声。采用临界带通滤波和线谱迭加方法,分别合成了目标舰船在低、中、高三种不同航速下的稳态辐射噪声。为了验证合成声的有效性,进行了主观评价实验,采用成对比较法验证了15组不同航速状态下的合成舰船噪声样本。结果表明,合成舰船噪声样本能够被人耳有效识别,准确率达93%。     

船舶水下辐射噪声抑制的声振相关性方法

船舶水下辐射噪声与船体振动的耦合关系是非常复杂的,识别水下辐射噪声与船体振动相关性较高的部位,确定影响水下辐射噪声的关键因素,对降低噪声具有重要工程意义。基于声振耦合分析原理,提出船舶水下辐射噪声抑制的声振相关性方法,探讨了船舶水下辐射噪声与结构振动特性、船上振源的频谱和船体振动响应等的相关性定量评价指标,厘清各因素对水下辐射噪声的影响规律。舱段及拖轮降噪设计示例表明,相关性定量评价指标的计算量小,根据指标值可以高效确定与水下辐射噪声相关性高的结构及影响参数,实现船舶水下辐射噪声的高效抑制设计;通过调整振源附近湿表面的板厚,舱段和拖轮的声功率总级分别降低了5.66 dB和4.84 dB,但振动减小幅度与噪声降低幅度并不是线性的。     

国外舰船声特征信号预测软件简介

舰船声特征信号的预测和评价是当前国内外的前沿课题，也是迫切需要发展的研究领域。迄今推广运用了国外的三种软件：辐射噪声估算软件--NDES、声目标强度估算软件--ARTES、综合辐射噪声与自噪声建模软件--FNVNOISE。以上方法将声特征信号预测建立在理论计算基础上，对于复杂问题均建立了各种专门用来帮助设计人员进行重要计算的数据库。研究人员可通过不断增加和核对新的数据，使数据库和计算方法得到不断改进和完善，从而为将来在解决设计中遇到的问题提供更有效的支持。     

表面速度法在变速箱噪声检测中的应用

基于结构表面振动速度与结构辐射声能的关系，针对以结构声为主的变速箱现场噪声评价问题，提出根据结构表面单点振动速度和工作振型来计算结构辐射声能的方法，此法大大简化了变速箱现场噪声检测的过程，提高了检测效率。通过实验证明这种方法在一定条件下是可行的。     

印刷装备振动噪声特性研究综述

目的 综述印刷装备振动噪声特性及其在故障诊断方面的研究进展。方法 通过文献调研,了解当前学术界对印刷装备振动噪声特性的认知情况,包括印刷企业噪声危害、印刷装备结构振动特性、印刷机噪声辐射,以及基于结构振动及噪声辐射的印刷装备故障诊断等方面的研究现状,并展望其发展前景。结果 目前对印刷装备的结构及声辐射特性的研究还处于初级阶段,尚未系统地对印刷设备的声振特性进行分析,针对印刷设备的降噪技术尚未起步。探讨印刷装备声振特性的研究进展将有助于研究者更好地了解及开展印刷装备降噪技术,以及推进印刷装备故障诊断技术研究的发展。结论 针对印刷机结构声振机理的研究和分析具有较高的学术意义和应用价值,该项研究会成为印刷装备降噪技术及故障诊断技术的基础。     

轨道交通轮轨噪声机理分析

近年来，随着我国铁路列车提速、快速客运专线的建设、高速铁路以及城市轨道交通的发展，轮轨噪声在国内开始受到关注。根据车辆一轨道耦合动力学理论及声辐射与传播理论，分析了列车运行过程中产生轮轨噪声的机理。在此基础上，分析了轮轨噪声辐射的基本规律。     

叶片出口角影响离心泵噪声辐射数值研究

运用FEM\BEM声振耦合计算方法分析叶片出口角对离心泵在水动力激励下泵壳振动辐射噪声影响。采用大涡模拟方法模拟离心泵内部瞬态流场,获得蜗壳壁面偶极子声源;对泵壳体结构进行模态分析获得结构模态响应;利用LMS Virtual Lab间接边界元IBEM声振耦合模块计算非定常流动引起的离心泵内部噪声,并与实验数据对比,验证基于LES、声振耦合的噪声数值模拟方法可行性。计算离心泵外场噪声及声辐射,研究叶片出口角度对离心泵外场噪声辐射影响。结果表明,离心泵叶片通过频率BPF处的辐射声功率随叶片出口角的增大而增大;外场噪声声压级指向性分布显示叶片出口角存在合适范围,使泵在小流量工况运行时噪声较小。     

表面振速法在干式变压器噪声测量中的应用

变压器是变电站的主要噪声源,由于变电站实际声学环境的限制,传统的声压法和声强法已不能满足测量精度要求,而振速法是基于声振耦合建立结构表面振动和噪声的关系,不受现场环境的影响,因此研究振速法在电力变压器噪声测量中的应用具有一定的实际意义。根据结构声辐射理论推导有限平面结构的表面声辐射计算方法,通过测量干式变压器的表面振动量级和测量其声功率级,以实验的方法求得干式变压器的声辐射比。着重分析了从测量表面振动来估计干式变压器的噪声的可行性。     

全特解场边界元方法在声辐射逆向问题中的应用研究

采用全特解场边界元方法求解声辐射逆问题，这种方法不需要变量插值、积分求解及奇性处理，因而计算量大幅度减少，且计算精度高。本文还从辐射声场的情况来探知声源的振动特性，这对噪声的主动控制及低噪声结构优化设计有着很大的意义，为噪声诊断提供直接的依据。     

基于径向基神经网络的水下振动物体辐射噪声级别分类研究

运用径向基神经网络，利用水下振动物体内表面加速度信号对其辐射噪声级别进行分类．达到判断其声隐身性的目的，该方法的运算量较传统方法大大降低，极大地提高了计算速度。实例表明，该方法能较准确地对水下振动物体辐射声场声压级别进行分类。进而对其推广应用于潜艇提供了较好的依据。     

The spectrum of cosmic-ray electrons measured with H.E.S.S.

The measurement of very-high-energy cosmic-ray electrons is intrinsically difficult due to the very steep electron spectrum with low fluxes and an enormous background of hadronic cosmic rays. The large collection areas needed for such a measurement can be provided by ground-based imaging atmospheric Cherenkov telescopes. The High Energy Stereoscopic System (H.E.S.S.) has performed the first ground-based cosmic-ray electron measurement and thereby extended the measured range of the spectrum to several TeV. Here the H.E.S.S. measurement is presented, as well as an extension of the H.E.S.S. spectrum towards lower energies. At these energies, H.E.S.S. can probe recent ATIC measurements, which have been interpreted in terms of dark matter scenarios.     

基于A.C.T.模型的灯具情感化设计

目的 对灯具产品的情感化设计方法进行研究。方法 以“情感”的心理学研究成果为基础,结合情感化设计理念与情感化设计模型——A.C.T.模型进行灯具产品设计方法研究。结论 总结归纳了具体、可广泛应用于灯具设计实践的情感化设计的有效方法——即从用户需求角度出发,运用A.C.T.模型以满意度、易用性、可用性为设计目标建立满足目标受众的产品个性,从而触发用户有意识或无意识的情感反应。     

Effect of hemodialysis and hemofiltration on plasma C.E.R.A. concentrations

C.E.R.A., a continuous erythropoietin receptor activator, is a long-acting erythropoiesis-stimulating agent approved for the treatment of anemia in patients with chronic kidney disease. Although the large molecular weight and the carbohydrate chain make it unlikely that C.E.R.A. could be removed during hemodialysis or hemofiltration, no such data have been published. In vitro studies were performed to assess the removal of C.E.R.A. during hemodialysis and hemofiltration, using both low-flux and high-flux membranes and parameters very similar to those used in clinical practice. Clinical pharmacokinetic studies of plasma C.E.R.A. concentrations in patients undergoing hemodialysis were also performed following subcutaneous injection of C.E.R.A. In the in vitro studies, plasma C.E.R.A. concentrations were not significantly different from baseline values in the primed blood reservoir over a 4-hour period during hemodialysis (P = 0.12). C.E.R.A. concentrations in the plasma obtained from the venous end of the hemofilter increased proportionally with the plasma total protein concentrations, reflecting the consequence of hemoconcentration and suggesting that C.E.R.A and plasma total proteins were retained by hemofiltration membranes to a similar degree. These in vitro studies showed that C.E.R.A. was not removed by simulated hemodialysis or hemofiltration either via transmembrane transport or adsorption to the membrane. The results were corroborated by the clinical pharmacokinetic data, which showed no detectable changes in plasma C.E.R.A. concentrations during hemodialysis using either low-flux or high-flux dialyzers. These results suggest that C.E.R.A. can be administered to patients at any time during hemodialysis or hemofiltration without appreciable loss in the extracorporeal circuit.     

p.V.T.t法气体流量标准装置的建立

p.V.T.t；气体流量；正压；常压；不确定度     

Thermoplastic filament winding with online-impregnation. Part B. Experimental study of processing parameters

In part A of this paper, a novel process technology was presented which allows to combine thermoplastic filament winding with online melt impregnation of fibre bundles. In this part, a comprehensive study of process parameters was conducted. Circular glass fibre (GF) reinforced polypropylene (PP) or polyamide 12 (PA12) tubes were produced as sample component. Processing speeds of up to 15 m/min could be achieved in case of GF/PP before a drop in quality of the parts had to be accepted. The present limitation in winding speed is not attributed to impregnation problems but to an excessive rise in force required to pull the fibre tow off the impregnation device. Measures for process improvement and increase in productivity were proposed.     

Influence of various parameters on the a.c. diamagnetic susceptibility of Bi-based superconductors

We present some results of a.c. susceptibility measured on pure and doped with indium and potassium Bi-compounds. For both the 80K and 110K phases, we follow the χ′ and χ″ variations as a function of (a) the annealing treatment, (b) the Sr/Ca ratio and (c) the doping. Indium doping has either a positive or a negative effect on the 80K material, depending on the Sr/Ca ratio. It induces an important increase of the superconductive volume of the 110K material. Effects due to potassium are opposite. The experimental results agree with the fact thatT _c goes through a maximum as the hole density increases.     

凯里卡特公式的修正

针对凯里卡特公式使用过程中,计算值与测量值有较大偏差的现象,并且未考虑纵横比对抗压力强度的影响,在箱高大于２５ｃｍ的条件下,提出了一个修正因了,Ｋ＝－０．１２１７Ａ＾２＋０．３２２８Ａ＋０．８５６,凯里卡特公式乘以Ｋ所得到的修正公式不但反映了纵横比Ａ的影响,而且经实验和资料数据验证,修正后的公式比原公式的计算结果更符合实际测量结果。对恺里卡特公式使用过程中英制、公式制转换常数不变的现象进行了纠正,     

Die drawn wood polymer composites. I. Mechanical properties

Oriented wood polymer composites (WPC) have been prepared by the Leeds die drawing process. Softwood and hardwood powder were used at 40% weight concentration (32% volume concentration) and in both cases materials with significantly increased stiffness (from 1.9 to 8.2 GPa) and strength (from 13 to 127 MPa) were obtained. Although the moduli of the drawn filled composites were lower than the equivalent unfilled polypropylene, the specific moduli, which take into account the lower density of the die drawn materials due to void formation were very similar. The type of wood particles and the use of polypropylene grafted with maleic anhydride had only a marginal influence on the mechanical properties of the die drawn composites. The morphology of the wood composites was studied by electron microscopy.     

Die drawn wood polymer composites. II. Micromechanical modelling of tensile modulus

The Cox–Krenchel micromechanical model was applied to give predictions for the tensile moduli of isotropic and oriented wood polymer composites (WPC). The oriented WPC were produced by the Leeds die-drawing process using polypropylene filled with softwood and hardwood powders. The wood particles were extracted from the composites to determine their density and aspect ratio by dissolving in hot decalin. To measure particle shape and size, image analysis was employed. These experimental parameters were then introduced to the Cox–Krenchel model which was found to give prediction of tensile modulus in very good agreement with the experimental values.     

美国进口食品进境口岸查验制度简介

美国是我国主要的食品出口国。为了促进我国食品更好地对美国出口,很有必要了解美国的进境口岸查验制度。本文主要介绍了美国食品药品监督管理局(FDA)、食品安全检验局(FSIS)进口食品的进境口岸查验制度,以帮助加强政府监管工作和输美食品顺利通关。