音乐厅中后期反射声对空间感的影响

空间感是音乐厅音质中很重要的主观感觉.起初人们对空间感的研究主要集中在与早期侧向反射声有关的空间响应上,近年的研究结果使人们更多地了解到后期反射声也对空间感有所影响.文章将主要介绍音乐厅中后期反射声对空间感主要是听者环绕感(LEV)的影响.     

声屏障缩尺模型试验研究

通过声屏障原型试验和声屏障模型试验结果对比分析,得出倒L型声屏障对低频声降噪效果不明显,对中、高频声有较好的降噪效果.在160Hz-4000Hz的频带范围内,声屏障原型试验和声屏障模型试验有较好的相关性,证明缩尺模型试验是开展降噪声屏障研究的有效方法,对今后开展降噪声屏障的设计和研究具有参考价值.     

音乐厅中后期反射声对空间感的影响

空间感是音乐厅音质中很重要的主观感觉。起初人们对空间感的研究主要集中在与早期侧向反射声有关的空间响应上，近年的研究结果使人们更多地了解到后期反射声也对空间感有所影响。文章将主要介绍音乐厅中后期反射声对空间感主要是听者环绕感（LEV）的影响。     

双层复合道路噪声分布及其控制

近几年来，随着市政建设的发展，地面－高架相结合的双层复合道路在国内各大城市相继兴建，由于车流量大，加上地面和高架底部的多次反射声，使道路两侧的交通噪声污染十分严重。据对上海市内环线复合道路噪声的实测，高峰小时的等效声级可达８０ｄＢ（Ａ），引起临近居民的强烈反应。本文通过理论计算和缩尺声模型试验结果的分析，根据声场分布的特点，对控制复合道路交通噪声的有关措施及其效果进行了探讨。对于多车道、多种车型的单层复合车流，可采用分车道、分车流的方法分别计算各种车流、各车道在测点产生的声级，再用途加方法求得总…     

双层复合道路声缩尺模型试验新方法的探讨

在道路边设置声屏障是降低道路交通噪声的主要措施之一。声屏障的应用日益增多，对声屏障进行理论和实验以及应用研究具有重要的现实意义。缩尺模型试验是声屏障实验研究的主要手段。但是传统的模型试验需用空气喷射声源，这就要使用空气压缩机和压力控制等专用设备，实验所需投入很高，虽有文献提出可用高频扬声器做点声源，用点声源组成线声源作为试验声源，但这一方法所实现的线声源精度和有效范围均不够理想。要解决上述问题，需增加点声源数目。此外，为避免各点声源间的声干涉，点声源必须使用各自独立的噪声发生器和功率放大器系统，…     

音响系统设计安装与调试（三）

声源发出的声音在空间传播到达声音接收点，这时，声音接收点上听到的声音称为“直达声”。之后声音越过接收点继续传播，由于周围墙壁或其它物件的反射，接收点将听到反射声。反射声中最早到达的一些是“早期反射声”，它们的方向较明显，间隔也较流；再后到达的反射声多是经过墙壁和物体多次反射的声波，它们的间隔很密，方向很乱，是多方向、多次的反射声的混合声。由于人的听觉延时效应，人们对直达声和早期反射声是分不开的，而人们那些间隔很密，方向很乱，多方向、多次的反射声的混合声则会把它与直达声分开。这种混合声就称为“混响…     

房间内早期反射声方向分布的声强法测量

早期反射声的方向分布,对空间感音质参量的评价具有重要意义。室内音质不仅与反射声到达的时间、能量有关,而且与反射声到达的方向特性具有密切的关系,反映反射声方向特性的客观音质参量在音质评价中得到了越来越多的应用。根据声强测量的互谱法原理,论文提出采用不在同一平面上的任意四只传声器进行瞬时声强的测量,经合成得到各频带早期反射声方向分布特性的方法。该测量方法弱化了常规传声器阵列测试方法中对传输器位置的严格要求,同时也可有效降低由于传输器之间的相位不匹配带来的测量误差,因而更适合于现场测量。运用该测量方法,在消声中对单入射声条件下的入射方向进行了实验测量验证,表明其具有较高的准确性,同时对一实际房间中早期反射声的方向分布进行了测量,给出了直角坐标系中三个相互垂直平面上的反射声能量与入射方向的分布图。测量结果表明该测试方法可应用于实际房间中早期反射声方向分布的测量。     

有关音质模型试验的讨论

一、前言 采用声学方法进行音质模型试验,已有二十多年的历史。五十年代苏联发表过几篇文章,讨论模型试验的模拟条件,以及柴可夫斯基音乐厅的1/40模型试验情况,测量频率采用20千赫(对应实物500赫),主要测量反射声的分布和混响时间,六十年代西德 Spandock采用 1/10模型进行试验,测量频率从1250赫～40千赫(对应实物125赫～4千赫),测量的参量包括有混响时间,反射声分布,声场分布和方向性扩散,并在模型中把空气的相对湿度降低至3%,进行主观评价试验。七十年代日本橘秀树提出1/10模型中充氮气将氧分子排除,减少空气中氧分子对高频声波的吸收。木…     

两个水景剧院的建声设计与音质模拟

概述了建于远香湖湖畔的上海嘉定保利大剧院和建于小东海与鹿回头湾交汇处的三亚半岛音乐厅两个水景剧院的建筑概况,重点介绍了保利剧院1500座歌剧厅和半岛音乐厅1300座歌剧厅的音质设计思想、技术指标及建声措施,并对两个水景剧场进行了厅堂音质计算机模拟分析,同时还完成了保利1500座歌剧厅1：10声学缩尺模型试验,最后依据计算机空满场模拟结果对两个剧场的音质进行了初步评估。     

钢筋混凝土立柱爆破后钢筋骨架承载特征研究

钢筋混凝土立柱爆破后通常会残留钢筋骨架,钢筋骨架的承载特性是判断结构局部失稳的重要前提,同时也是确定立柱爆破高度的理论依据。基于立柱爆后实际形态,开展了具有初弯曲形态的立柱钢筋骨架缩尺模型试验,模拟了顶部有水平向约束和无水平向约束两种工况。试验结果表明:立柱钢筋骨架的承载力随着其高度和初始挠度的增加而显著降低;顶部无水平约束钢筋骨架的失稳形态主要表现为侧向倾斜,顶部有水平约束钢筋骨架的失稳形态主要表现为竖向压缩和钢筋外凸。模型试验实测承载力远低于欧拉等直压杆模型计算值,而高于初弯曲压杆模型计算结果,且实测值与初弯曲压杆模型计算值存在线性关系。根据试验结果,给出了初弯曲压杆失稳模型的修正建议。     

The measuring method of early lateral energy fraction in the scale model experiments

This paper introduces a measuring method of early lateral energy fraction in the scale model experiments. According to the interference principle of half wave length making the high frequency figure-8 directional microphone. With the signal-processing technique, a receiving and analyzing system, for the measurements of lateral energy fraction in the scale model is realized.     

Modeling 1-3 composite piezoelectrics: thickness-mode oscillations

A simple physical model of 1-3 composite piezoelectrics is advanced for the material properties that are relevant to thickness-mode oscillations. This model is valid when the lateral spatial scale of the composite is sufficiently fine that the composite can be treated as an effective homogeneous medium. Expressions for the composite's material parameters in terms of the volume fraction of piezoelectric ceramic and the properties of the constituent piezoelectric ceramic and passive polymer are derived. A number of examples illustrate the implications of using piezocomposites in medical ultrasonic imaging transducers. While most material properties of the composite roughly interpolate between their values for pure polymer and pure ceramic, the composite's thickness-mode electromechanical coupling can exceed that of the component ceramic. This enhanced electromechanical coupling stems from partially freeing the lateral clamping of the ceramic in the composite structure. Their higher coupling and lower acoustic impedance recommend composites for medical ultrasonic imaging transducers. The model also reveals that the composite's material properties cannot be optimized simultaneously; tradeoffs must be made. Of most significance is the tradeoff between the desired lower acoustic impedance and the undesired smaller electromechanical coupling that occurs as the volume fraction of piezoceramic is reduced.     

A more general investigation for the longitudinal stress waves in microrods with initial stress

In the present work, the propagation of longitudinal stress waves along a nanoscale bar with initial stress is investigated by using a unified nonlocal model with two length scale parameters. In principle, the analysis of wave motion is based on Love rod theory including the effects of lateral deformation. However, here are not ignored the contribution of shear stress components due to lateral deformations in the calculation of total elastic strain energy. By applying Hamilton’s principle, the explicit general solution is obtained, and comparative results containing the different effects are presented and discussed.     

粘弹性复合材料的有效三维阻尼矩阵预报与能耗计算

提出了一种计算纤维增强复合材料粘弹性阻尼和能耗的新方法。在层片的层次上,基于各向异性粘弹性理论导出以阻尼矩阵表示的材料能耗计算公式。在层板的层次上由能量等效原理得到有效阻尼矩阵。由此,可由层板的有效应力和有效应变计算出其能量耗散进而得到比阻尼。其中的关键点是有效阻尼矩阵的推导,最终得到的有效阻尼矩阵是各单层阻尼系数、体积分数、刚度系数以及层合板有效刚度系数的函数。用有效阻尼矩阵计算能耗可以适用于任意复合材料的应力应变状态,这对于粘弹性复合材料结构能耗的数值分析尤其重要。最后将该理论应用于几种情况下的复合材料的能耗和比阻尼分析,算例表明与其它的理论预测和试验相比吻合良好,证实了该方法的合理性。      

Modeling 1-3 composite piezoelectrics: hydrostatic response

A simple physical model of 1-3 composite piezoelectrics that was advanced for the material properties relevant to thickness-mode oscillations is extended to address the hydrostatic response. The model is valid when the lateral spatial scale of the composite is sufficiently fine that the composite can be treated as an effective homogeneous medium. Expressions are derived for the composite's material parameters in terms of the volume fraction of piezoelectric ceramic and the properties of the constituent piezoelectric ceramic and passive polymer. The results are similar to those derived by Haun and Newnham (1983, 1986) using a parallel-series connectivity model. The model is illustrated by analyzing composites made from conventional PZT5 and anisotropic modified lead titanate piezoelectric ceramics. For PZT5, the composite structure enhances its hydrostatic charge coefficient, hydrostatic voltage coefficient, hydrophone figure of merit, and hydrostatic coupling coefficient, while three of these quantities fall short of their pure ceramic values in the modified lead titanate composites. The shortfall is due to an enhanced composite that arises from lateral stress on the polymer being transferred to a longitudinal stress along the ceramic rods by the Poisson effect in the polymer, thus producing a charge through the ceramic's d(33).     

A theory for the formation of tetrahedral amorphous carbon including deposition rate effects

A theoretical model is presented to describe the effect of ion beam bombardment rate on the formation of tetrahedral amorphous carbon (ta-C) films. The critical ion energy, E_c, corresponding to a 50% sp³ content in the films, is found to be dependent on both the effective thermal resistance and the ion beam bombardment rate. In the model, the ‘window’ width in the ion energy scale for the formation of ta-C material increases with decreasing deposition rate and with a reduction in the effective thermal resistance, until limited by lower and upper boundary thresholds. Experimental data are reproduced by the model. The plasmon energy, which correlates with sp³ fraction, is found experimentally of be higher for lower deposition rate and smaller effective thermal resistance. Data points for high sp³ content ta-C films deposited on silicon substrates at room temperature occupy a region in the ion energy-deposition rate (E-r) diagram similar to that predicated from the theory.     

钢筋混凝土框架-纤维增强混凝土耗能墙结构抗震性能试验研究

高性能纤维增强混凝土（HPFRC）具有受拉应变硬化和多裂缝开展性能,是一种理想的耗能材料。将HPFRC耗能墙装配于钢筋混凝土（RC）框架,形成RC框架-HPFRC耗能墙新型抗震结构。设计制作了2个1/2比例RC框架-HPFRC耗能墙结构模型,对其进行了拟静力试验,研究其破坏机理、变形和耗能性能等;分析了RC框架和HPFRC耗能墙在峰值荷载点的有效刚度。结果表明:RC框架-HPFRC耗能墙结构可实现“大震可修”的抗震设防目标;1个框架单元内装配2片与1片耗能墙相比,其水平承载力提高了38.3%,初始侧向刚度提高了1.78倍,但后期侧向刚度仅提高20%~30%,不同损伤状态的耗能能力提高了10%~175%,侧向变形能力基本相同;RC框架和HPFRC耗能墙在峰值荷载点的有效刚度系数分别为0.11和0.13。     

大跨度球面网壳结构表面风压间歇特性研究

在同济大学TJ-3风洞试验室对大跨度球面网壳结构进行刚性模型测压试验。通过对结构表面风压信号进行连续及离散小波变换,得到各尺度小波系数时程。对结构表面测点信号的尺度能量比率,间歇能量比率及间歇因子三个参数进行比较性分析,得到以下结论：（1）尺度11处,环向测点尺度能量随位置的变化很小,而在尺度12处侧向测点1－7和1－19的尺度能量明显大于其他区域,约为迎风及背风区域测点1－1和1－13的2倍;（2）测点1－7和1－19的间歇能量主要集中在尺度11处,而测点1－1和1－13的间歇能量在各尺度分布较为均匀;（3）测点1－1,1－7,1－13和1－19的间歇因子随尺度的变化趋势相似,在低尺度区变化平缓而在高尺度区域迅速增大。上述说明,结构表面不同区域的风压信号间歇特性不尽相同,可以进一步为结构风压基本特性的精细化分析提供帮助。     

Simulated pulsed flow of gas and particles in a horizontal oppose-pulsed gas jets of bubbling fluidized bed

Flow behavior of gas and particles with a horizontal oppose-pulsed gas jets are simulated by means of a three dimensional Computational Fluid Dynamics (CFD) model with the kinetic theory of granular flow in a gas-particles bubbling fluidized bed. The effects of amplitudes and frequencies on the hydrodynamics of gas and particles are analyzed. The simulation results are presented in terms of phase velocity vector plot, volume fraction of phases, granular temperature, power spectrum and Reynolds stresses in the bed. Results show that the impingement caused by the oppose-pulsed gas jets oscillates with the variation of pulsed gas velocity. The impingement zone with the high solid volume fraction reciprocates from the left side to the right side through the bed center with the variation of pulsed jet gas velocities. The lateral velocity and gas turbulent kinetic energy, granular temperature and Reynolds stresses of gas and particles are larger near the pulsed gas jets than that at the center of the bed. The large dispersion coefficients of particles using the horizontal oppose-pulsed gas jets enhance the mixing of particles in gas-solid fluidized bed.     

Modelling of microstructure evolution during hot rolling of AA5083 using an internal state variable approach integrated into an FE model

Hot rolling, a critical process in the manufacturing of aluminum sheet products, can significantly impact the final properties of the cold rolled sheet. In this research, a mathematical model was developed to predict the through-thickness thermal and deformation history of a sheet undergoing single stand hot rolling using the commercial finite element (FE) package, ABAQUS^™. A physically based internal state variable microstructure model has been incorporated into the FE simulation for an AA5083 aluminum alloy to predict the evolution of the material stored energy and the subsequent recrystallization after deformation is complete. The microstructure predictions were validated against experimental measurements conducted using the Corus pilot scale rolling facility in IJmuiden, the Netherlands for an AA5083 aluminum alloy. The model was able to predict the fraction recrystallized as well as the recrystallized grain size reasonably well under a range of industrially relevant hot deformation conditions. A sensitivity analysis was carried out to determine the influence of changing the material constants in the microstructure model and deformation conditions on the predicted recrystallization behaviour. The analysis showed that the entry temperature was the most sensitive process parameter causing significant changes in the predicted driving force for recrystallization, nucleation density, fraction recrystallized, and recrystallized grain size.