消声水池声场特性的测量

本文描述了消声水池的数学模型，介绍了相对声压－距离法消声水池声场特性测量装置的组成，分析了声场特性的测量不确定度，并利用此装置对消声水池的声场情况进行了实际测试。     

全国环境样品中总α／β测量概况

中国计量科学研究电离辐射处于2000年初组织的全国总α/β测量工作，截止到10月底，全国共有60多个单位参加，这次的主要是辐射环境监测系统，自来水系统，卫生防疫系统，核电站，商检系统以及工厂和研究所等。共收到测量比对结果60多份，现对2000年总α/β测量概况作一介绍。     

消声水池中弹性球回声的测量与标定

在消声水池中对直径范围为2cm～5cm的钢球进行了回声测量。对长脉冲和短脉冲入射声信号的回声信号进行了分析比较。研究了目标的弹性作用在这两种情况下对回声的影响。通过对标准钢球回声测量结果与解析计算结果的比较,检验了消声水池目标回声测量的精度,并为其他非标准目标回声测量提供对比标定的依据。     

高压消声水池端部松木尖劈吸声性能研究

本文介绍了高压消声水池端部用松木尖劈的实验研究,根据尖劈总长度、基础部分长度和过渡部分长度的变化分成四组样品,并在声管中进行测量,文中从松木尖劈的吸声机理出发研究分析了长度变化以及浸润处理对尖劈吸声性能的影响。     

钢筋混凝土水池设计中的裂缝的处理方法

钢筋混凝土水池的渗漏多由裂缝开始，裂缝的预防和控制，是钢筋混凝土水池设计中的要点。文中介绍了裂缝的成因及设计中控制裂缝的方法，并结合工程实例对此进行了进一步的阐述。     

基于USMN的大型操纵性水池基础轨道空间位置测量方法研究

在进行大型工程测量时,单台、单站测量仪器通常不能完成全部的测量任务,需要使用多站或多台仪器在不同的位置实施测量。本文介绍了一种基于统一空间测量网络(Unified Spatial Metrology Network,USMN)的测量方法,该方法对多台多站的测量数据的处理,相比传统的拟合拼接法不会引入较大的累积误差。基于USMN的测量方法通过重新分配拟合要素的权重,来降低多次拼接引入的累积误差,提高多站测量方法的精度,为大型工程测量精度的提高提供了有效的方法。通过对两种方法的多站数据拼接并观测末站数据和首站数据的闭环性及拟合圆的径向跳动,显著地观察到本文介绍的方法闭环性更好,拟合的圆径向跳动更小,相较传统方法更加接近测量的真实情况。     

水压爆破拆除钢筋混凝土水池

本文详述了利用水压爆破拆除复杂环境中的钢筋混凝水池的施爆方案，参数设计，装药结构及安全防护，并对爆破效果进行了分析。     

回水池液位的简易控制

1引言在输液生产中，洗瓶和漂膜工序使用后的大量去离子水先流回中间水池，再由水泵陆续拍往水站重新利用。中间水池是去离子水回收系统中一个重要的缓冲环节。实际使用中发现人工难以控制水池液位，抽干和溢流现象频繁出现，去离子水大量浪费，水泵经常损坏。我们根据回水池瞬时回水流量和回水时间都不易确定的特点，采用了三位控制仪表与原有电气线路相结合的改造方案，实现了回水池液位的自动控制。2系统构成系统由液位变送器，数显控制仪和水泵电控线路组成。系统可将池内液位控制在上、下设定值之间，同时具有超水位报警和自动、手动选…     

专利发布

<正>海洋波浪能发电系统专利号:200810228018专利权人:高占山本发明涉及一种动能转换技术,特别是一种利用海洋波浪能发电系统。海洋波浪能发电系统,由吸能器、压力缸、活塞、轨道、高位水池、低位水池、水轮发电机、波高测量装置、潮位测量装置、摄像监控装置、管道、     

水压爆破拆除复杂结构水池

对筒形水池水压爆破拆除的药量计算，布药方式及安全校核等作了详尽介绍和分析，希望对同类工程有所借鉴。     

混响的感知及其评价

回顾了近年来国内外关于混响的主观感知和客观评价方面的研究,着重总结了声能衰变的时间特性、空间特性、频率特性以及听音信号强度等因素对混响感知的影响。     

Decaying Counterflow Turbulence in He II

No Heading Systematic investigations of the counterflow turbulence and its decay in three channels of different geometry have been performed using the second sound attenuation technique. The steady-state counterflow turbulence is generated by applying power to the heater placed in the closed end of the channel; when switched-off, the measured temperature difference across the channel quickly decays, in accord with the developed simple model. At all investigated temperatures, after the fast initial decay the second sound amplitude indicates a net increase of the observed vortex line density, which can be understood in terms of depolarization of the vortex tangle. After saturation time, the decay closely follows the classical –3/2 power law and for high enough initial vortex line density the decaying turbulence can be approximated here as homogeneous and isotropic and characterized by an effective kinematic viscosity. The influence of the channel geometry on the form of the observed decay is discussed.     

Multiphonon Decay of Solitons in Bose–Einstein Condensates

The stability of the Jones–Roberts (JR) solitary waves in Bose–Einstein condensates with respect to quantum decay into several phonons is investigated. The conservation laws permits such a decay for the upper branch of JP dispersion curve and for the part of lower branch which lies above the sound line. The minimal number of phonons in which an excitation with given energy and momentum can decay is estimated. This number depends of the gas parameter of the fluid.     

室内扩散声场的Monte Carlo模拟方法

本文介绍了ＭｏｎｔｅＣａｒｌｏ方法模拟室内扩散声场的原理，模拟计算了混响室声场中的能量密度衰减曲线、能量脉冲响应、平均自由程及吸声系数等。该方法原理简单，占用内存少，适应于模拟室内声场分布。     

Bandpass Filter Comparator for Confirming the Absence of Serious Internal Voids in Wood Poles

Structural timber is frequently exposed to weather and is thus subject to decay and consequential strength loss which eventually requires the replacement of the affected member. When decay is internal, destructive investigation is the only direct way of detecting it. This is obviously undesirable and a frequently used alternative is to tap each member with a hammer. A conclusion is reached by listening to the sound emitted. Because this sound is composed of many different frequencies which vary in magnitude and spectrum from one member to another, the result of the test is uncertain. Research has revealed that a definite sonic frequency range exists for a class of members such as poles used for electricity distribution purposes. Part of this range is common to all members regardless of condition, but there is another part which is greatly affected by the presence of hollowness or decay. A double bandpass filter arrangement has been constructed to register the presence and magnitude of frequencies relating to hollowness or decay and to measure this magnitude against the magnitude of frequencies always present. The member under test is excited by a series of blows of equal force and a ratio established between the signals from each filter, the A low ratio indicates a solid section. A high ratio indicates that the section may be hollow or decayed.     

Quantum Spinodal Decay of a Metastable Liquid at Low Temperatures

No Heading The theory is given for the decay from a metastable liquid by a quantum mechanism involving the relaxation and high frequency properties of a medium. It is our purpose to estimate the effect of relaxation time on the quantum decay rate. The theory predicts a strong dependence of nucleation regime, rate and thermal-quantum crossover temperature on both the relaxation time and the ratio of the high frequency sound velocity to the low frequency one. The shorter the relaxation time, the smaller the quantum decay rate and thermal-quantum crossover temperature. The decay rate can display a minimum in the region of the thermal-quantum crossover. The recent experiments on cavitation in normal³ He and superfluid⁴ He at negative pressures are discussed. The distinction in the properties of high frequency sound mode near the spinodal and in the temperature behavior of relaxation time results in a different picture of quantum cavitation in ³He and ⁴He.PACS numbers: 67.40.Fd, 67.55.–s, 64.60.Qb, 47.55.Bx     

Superfluid Vortex Reconnections

After reviewing recent theoretical results on superfluid vortex reconnections and their effects, we interpret measurements of the decay of superfluid turbulence at very low temperatures. We estimate the fraction of the vortex length lost whose energy is transformed into sound bursts during reconnection events.     

Defect-Free Sound Insulator Using Single Metal-Based Friction Stir Process Array

Metals are excellent conductors for phonon transportation such as vibration, sound, and heat. Generally, metal sound insulators require multimaterial structure or defects and unimetal sound insulators are challenging. Therefore, a design of a defect-free sound insulator made by single alloys with multiple friction stir processes (FSPs) is proposed. Periodic friction stir processing can induce superlattice-like local mechanical properties’ modifications. By experimental acoustic characterization, it is observed that FSP can introduce clear acoustic–elastic property contrast on an aluminum plate by the presence of stir zone and heat-affected zones. In numerical simulations, the signature FSP-induced property profile is periodically and parallelly arranged on a long aluminum plate. The transmission gap frequencies are present on the frequency spectrum with the sound propagation direction perpendicular to the FSP paths. Disorder offsets on FSP periodicity are further introduced. Anderson localization is found on a resonance frequency, which provides −11 dB sound reduction by an exponential decay. Due to the finite design length, the slight disorder can also enhance sound insulation in the periodic transmission gap frequency. With analysis and comparison with different configurations, the best performance in the models can achieve −30 dB sound insulation in the 350 mm-long aluminum alloy plate with 14 parallel FSPs.     

高速列车“通过噪声”的测试分析

为了评估高速列车运行时对轨道周围环境的噪声污染程度,对高速列车以不同速度工况通过时的车外辐射噪声(称为"通过噪声")进行了测试,得到了以最大A声级和1/3倍频程A声级标志的列车通过噪声的测量数据。分析了通过噪声的频谱特性、及其与列车速度的关系。测试数据表明高速列车通过噪声是宽频噪声,最大A声级在标准规定测试点上的值达到约90 dB,对铁路附近的噪声污染比较大;通过噪声随着列车速度增大而增大,在时速370 km以上增幅变大。     

乐罩对剧院音质参量的影响分析

乐罩是有自然声演出功能剧场舞台表演区的重要组成部分,其作用是防止有限的自然声能被舞台吸收和逸散,并。文章分析了24座剧院加乐罩前后音质参量实测数据,研究了加乐罩前后音质参量的统计特性。加乐罩后的剧院,在混响时间、早期衰变时间、强度因子、舞台支持度等音质参量上均有显著的提升。