Vibration transmission between coupled plates using finite element methods and statistical energy analysis. Part 2: The effect of window apertures in masonry flanking walls

Part 1 of this paper demonstrated the validity of predictions of vibration transmission across junctions of masonry walls using Finite Element Methods (FEM). Part 2 uses numerical experiments with FEM to calculate the vibration transmission between masonry walls with window apertures at different positions in the flanking wall(s). Results from the numerical experiments are used to assess a simple “rule-of-thumb” estimate for calculating the change in the coupling parameters due to the introduction of an aperture into a flanking wall. Conclusions are drawn concerning use of the “rule-of-thumb” estimate for the coupling loss factor in Statistical Energy Analysis and the vibration reduction index in European standard EN 12354.     

用虚量子理论研究重离子束—靶相互作用

本文将虚量了理论用于重离子束与靶相互作用过程中靶原子的Ｋ壳层电子的离子化以及入射重离子的Ｋ壳层电子的激发与离化，这一简单模型所提供的理论结果与实验符合得很好。     

A BEM approach to validate a model for predicting sound propagation over non-flat terrain

A two-dimensional boundary element model for sound propagation in a homogeneous atmosphere above non-flat terrain has been constructed. An infinite impedance plane is taken into account in the Green's function in the underlying integral equation, so that only the non-flat parts of the terrain need to be discretised in the boundary element model. This Green's function is undefined for points below the impedance plane, and therefore valleys and hollows are taken into account by coupling the exterior domain above the ground with one or several interior domains below the ground, as suggested in a recent paper [J. Sound Vibrat. 223 (1999) 355]. The resulting BEM model, which can handle arbitrary combinations of barriers and hollows, has been used for validating a ray model for various difficult configurations, including combinations of valleys and barriers.     

Development of multiple drywall with high sound insulation performance

Experimental studies for the development of multiple drywalls with a high sound insulation performance are performed. Firstly, a means of preventing the sound insulation deterioration due to the coincidence effect at high frequencies is investigated by layering two plasterboards with different physical characteristics. Based on the results, a double drywall with a sound insulation performance of R_w = 61 is developed. Further more, a double drywall of R_w = 64 , a triple drywall of R_w = 86 and a quadruple drywall of R_w = 90 are developed.     

Colour, design and virtual reality at JET

Joint European torus (JET) is the world's largest nuclear fusion research facility investigating the use of nuclear fusion, the process that powers the stars, as a source of clean, limitless electrical energy.The JET machine undergoes an on-going program of upgrades and modifications facilitating a broad scientific program of experimentation. Maintenance of the JET machine is carried out remotely using telemanipulators mounted on a robotic Boom, employing a ‘man in the loop’ approach. The system relies on the use of real time 3D computer graphic models in a ‘virtual reality’ environment for preparation and support of remote-handling operations. Colour is used in this virtual environment to emphasise robots from the vessel environment and to highlight materials, components and systems requiring special care.     

新型虚阴极振荡器的研究

 采用小信号理论，在考虑到透射、反射束电子不同作用下，分析了虚阴极振荡器产生微波的机制，获得了计算微波主频的方法，讨论了增强束波作用效率的方法，并提出一种新型结构的虚阴极振荡器。该振荡器的阳极后放置了一个谐振腔，谐振腔长度很小，虚阴极不能在其中形成，谐振腔受到反射电子束激励并建立强场，场对入射电子进行调制，同时采用同轴结构引出微波。利用2.5D PIC 程序对新型的结构进行了数值模拟，验证了理论分析的正确性。在入射电子束电子能量为520keV和电子束流12.5kA的条件下，获得微波平均功率为1GW，频率为3.66GHz，平均束波转换效率为15.3%。     

声强探头相位误差的电补偿技术

以双传声器技术为基础的声强测量方法对两个传声通道的相位特性非常敏感，本文介绍了对声强探头进行相位匹配以及使用精密相位计进行测量的方法和实例，通过在声强探头后级电路中采用一种称相网络进行相位补偿，在大部分频段上减少了相位误差，可以改善声强测量的精度。文中提供了基本的电路原理图和典型的实验数据。     

水声声强测量分析系统及其在水下噪声鉴别中的应用

本文将空气中能形成测量分析系统的声强测量技术引入到水介质中，建立了一套水声声强测量分析系统，讨论了此套水声声强测量分析系统的硬，软件组成及特征，实验验证了本系统的可靠性，利用此声强分析系统对水下双噪声源的近场作了平面扫描测量，可以定位和鉴别这两个噪声源。     

A simplified method to calculate the field distribution of pistonlike source

I.IntroductionThesoundfieldproducedbyanidealbaflledplanartransducerhasbeenoneofthemostfundamentalproblernsinacousticsforaverylongtime.TheproblemcanbereducedtothewellknownRayleighintegralorKing'sintegral.Inmostcases,however,theirsolutionsarenotanalyticalandcdnnotberepreselltedinclosedformbygeneralorspecialfunctions.AsanexaInPleoftheuniformpistonsource)todescribethesoundbeamdistributionsinthenearandtransitionzones,itisnecessarytomakecalculationsbyusingthenumericalintegrations(point-by-poillt)o…     

电声技术近年进展

本文讨论近年电声技术的进展，综述电声器件概况，介绍高保真立体声中的环境声和数字声频，并总结迅速发展的声场电声控制技术，最后讨论了主观电声测量方面的动态．