Motorway noise modelling based on perpendicular propagation analysis of traffic noise

A model for motorway traffic noise has been obtained from measurements along the the Bangkok-Chonburi motorway. The model’s parameters include traffic volume and combination, the average spot speed of each type of vehicle and the physical conditions of the motorway in terms of right-of-way width, number of lanes, lane width, shoulder width, and median width for both of the main carriageways and frontage roads. The noise level that is generated by each type of vehicle has been analyzed according to the propagation in the direction perpendicular to the center line of motorway’s carriageway. The total traffic noise is then analyzed from traffic volume of all vehicle types on both sides of carriageways and frontage roads. The basic noise levels used in the motorway traffic noise model are modified according to the effective ground effect along the propagation path. The final result of this study is that a motorway traffic noise model based on the perpendicular propagation analysis technique performs well in a statistical goodness-of-fit test against the field data, and therefore, can be used effectively in traffic noise prediction for related or similar motorway projects.     

热粘性对发动机排气管道中噪声传播的影响

声波在气体中传播时,气体的热粘性效应会使声波产生一定程度的衰减,且气体的声吸收系数随温度的升高而增大。由于发动机的排气温度较高,热粘性效应引起的排气管道中的噪声衰减应加以考虑。基于准平面波理论,首次计算了考虑热粘性效应时不同温度、流速和管道尺寸下排气管道中的传递损失,分析了各参数对管道中噪声衰减的影响。结果表明,随着温度和频率的升高热粘性声衰减增强,而气流流速和管道直径的增加会降低直管中的热粘性声衰减。对于简单膨胀腔,传递损失的预测结果表明,热粘性效应使通过频率处的声衰减有所改善。     

An empirical model for the noise propagation in open cast mines - A case study

Data obtained from 312 measurement stations of sound propagation in panel 48 of the Tuncbilek open cast mine, Western Lignite Corporation, Turkey have been used to create an empirical model for such propagation. As well as the noise level recorded at these stations, atmospheric conditions were recorded also by the meteorological station located at the same panel. A total of 95,000 noise values were recorded at these stations. In addition the distances of the measurement stations to the effective source of noise and to the working slope, the meteorological effects and the number of noise sources were defined for each of 312 measurement stations. Using these data, the proposed model was tested against the noise measurements.     

Electromagnetic wave propagation in rain and polarization effects

This paper summarizes our study on microwave and millimeter-wave propagation in rain with special emphasis on the effects of polarization. Starting from a recount of our past findings, we will discuss developments with these and how they are connected with subsequent research.     

Numerical Investigation and Wind Tunnel Validation on Near-Wake Vortical Structures of Wind Turbine Blades

Computational fluid dynamics (CFD) has been used by numerous researchers for the simulation of flows around wind turbines. Since the 2000s, the experiments of NREL phase VI blades for blind comparison have been a de-facto standard for numerical software on the prediction of full scale horizontal axis wind turbines (HAWT) performance. However, the characteristics of vortex structures in the wake, whether for modeling the wake or for understanding the aerodynamic mechanisms inside, are still not thoroughly investigated. In the present study, the flow around NREL phase VI blades was numerically simulated, and the results of the wake field were compared with the experimental ones of a one-to-eight scaled model in a low-speed wind tunnel. A good agreement between simulation and experimental results was achieved for the evaluation of overall performances. The simulation captured the complete formation procedure of tip vortex structure from the blade. Quantitative analysis showed the streamwise translation movement of vortex cores. Both the initial formation and the damping of vorticity in near wake field were predicted. These numerical results showed good agreements with the measurements. Moreover, wind tunnel wall effects were also investigated on these vortex structures, and it revealed further radial expansion of the helical vortical structures in comparison with the free-stream case.     

Practical guidance for risk assessment of traffic noise effects on sleep

Environmental noise disturbs sleep and may impair well-being, performance and health. The European Union Directive 2002/49/EC (END) requires member states to generate noise maps and action plans to mitigate traffic noise effects on the population. However, practical guidance for the generation of action plans, i.e. for assessing the effects of traffic noise on sleep, is missing. Based on the current literature, we provide guidance on hazard identification, exposure assessment, exposure-response relationships and risk estimation: there is currently no consensus on both exposure and outcome variables that describe traffic noise effects on sleep most adequately. END suggests the equivalent noise level L_night as the primary exposure variable, and our own simulations of single nights with up to 200 noise events based on a field study on the effects of aircraft noise on sleep support using expert consensus L_night ranges (<30, 30-40, 40-55, >55 dB) for risk assessment. However, the precision of risk assessment may be considerably improved by adding information on the number of noise events contributing to L_night. The calculation of L_night should be extended to the shoulder hours of the day if traffic is busy during these periods. More data are needed on the combined effects of different traffic modes.     

Wave propagation in fluid-conveying viscoelastic single-walled carbon nanotubes with surface and nonlocal effects

In this paper, the transverse wave propagation in fluid-conveying viscoelastic single-walled carbon nanotubes is investigated based on nonlocal elasticity theory with consideration of surface effect. The governing equation is formulated utilizing nonlocal Euler-Bernoulli beam theory and Kelvin-Voigt model. Explicit wave dispersion relation is developed and wave phase velocities and frequencies are obtained. The effect of the fluid flow velocity, structural damping, surface effect, small scale effects and tube diameter on the wave propagation properties are discussed with different wave numbers. The wave frequency increases with the increase of fluid flow velocity, but decreases with the increases of tube diameter and wave number. The effect of surface elasticity and residual surface tension is more significant for small wave number and tube diameter. For larger values of wave number and nonlocal parameters, the real part of frequency ratio raises.     

尾波场与相对论效应对激光脉冲自相位调制及频移影响的比较研究

对共振和非共振情形下尾波场效应与相对论效应对强激光脉冲在稀薄等离子体中传输的影响 作了详细比较.尾波场效应导致脉冲自相位调制的不对称性，其大小与初始脉冲形状和脉宽 大小有关.在长脉冲极限下，尾波场效应远小于相对论效应，从而可以忽略；在短脉冲极限 下，尾波场效应可以抵消相对论效应.在共振情况下，尾波场效应导致脉冲内大部分光子减 速. 关键词： 脉冲传输 等离子体 相对论效应 尾波场效应 自相位调制     

Influence of strong noise on the decline and propagation of population in the delayed Malthus-Verhulst model

The effects of strong noise on the decline and propagation processes of a population in the Malthus-Verhulst model with time delay are investigated by a stochastic simulation. Time delays in two different processes are concurrent in ecosystems. The simulation results indicate that: The stability of the population is enhanced by the decreasing multiplicative noise intensity and the increasing delay time. The replacement of old individuals with young ones is accelerated by an increasing multiplicative noise intensity, an increasing additive noise intensity and a decreasing delay time. An increasing multiplicative noise intensity will drive the population of species to fluctuate more largely.     

人工电离层洞形态调制及其对短波传播的影响

本文在电离层中性气体点源扩散近似解的基础上,给出了多源释放动力学模型.分析了释放物质、释放高度、释放模式和释放量等因素对人工电离层洞形态调制的影响,并利用电离层短波三维数字射线追踪技术,对不同调制电离层洞的电波传播效应进行了数值模拟和分析. 关键词： 化学物质释放 人工电离层洞 形态调制 电波传播效应     

纳米网络中的太赫兹波大气传输和信道分析（英）

利用太赫兹大气传输衰减模型,比对太赫兹时域光谱系统的实验结果,结合最新的HITRAN数据库,发展了一个适用于纳米尺度的太赫兹信道分析模型。提出了一个0.1~5 THz宽的信道,分析了此信道在纳米尺度的传输损耗和最大传输数据率。研究结果表明,在纳米尺度0.1~5 THz宽的信道的传输数据率达几百Gbit/s,随着天线增益等硬件性能的不断提升,信道的最大传输数据率将达Tbit/s,此研究对于纳米器件之间的快速、大数据量的信息共享具有重要的参考价值。     

Estimation of directivity and sound power levels emitted by aircrafts during taxiing, for outdoor noise prediction purpose

Integrated noise model (INM) is the most internationally used software to calculate noise levels near airports. Take off, landing or pass by operations can be modeled by INM, but it does not consider aircrafts taxiing, which, in some cases, can be important to accurately evaluate and reduce airports’ noise assessment.Aircraft taxiing noise emission can be predicted using other prediction tools based on standards that describe sound attenuation during propagation outdoors. But these tools require data inputs that are not known: directivity and sound power levels emitted by aircraft during taxiing.This paper describes methods used to calculate directivity indexes and sound power levels, based on field measurements made in Madrid-Barajas Airport (Spain). Obtained results can be used as inputs for general purpose outdoor sound prediction software, which will be able to evaluate noise at airports vicinity as industrial noise.Directivity and sound power levels have been estimated in octave and third octave band terms, for several aircraft families.     

反馈有源噪声控制系统水床效应的分析与改善

本文依据反馈有源噪声控制原理分析了水床效应存在机理,以一模拟反馈有源噪声控制系统作为实例介绍了水床效应的分析方法,提出了通过展宽噪声放大频段和均匀噪声放大频段内的噪声放大量来优化反馈控制器,改善水床效应的方法。采用数字反馈控制器实现了水床效应的改善,给出了具体设计过程,并且考虑了数字时延对系统性能影响。仿真和实验表明了所提出方法的有效性。     

Coupled FEM/BEM for control of noise radiation and sound transmission using piezoelectric shunt damping

In this paper, we present a coupled finite element/boundary element method (FEM/BEM) for control of noise radiation and sound transmission of vibrating structure by passive piezoelectric techniques. The system consists of an elastic structure (with surface mounted piezoelectric patches) coupled to external/internal acoustic domains. The passive shunt damping strategy is employed for vibration attenuation in the low frequency range. The originality of the present paper lies in evaluating the classically used FEM/BEM methods for structural–acoustics problems when taking account smart systems at the fluid–structure interfaces.     

The effects of tilt corrected residual aberration on the detection probability of single-photon propagation in a slant path turbulent atmosphere

Based on the assumption of a pulse laser beam with an initial Gaussian temporal shape and a collimated fundamental-model Gaussian beam, the Rytov approximation and Kolmogorov spectrum model for the index-of-refraction fluctuation of atmosphere, the effect of turbulence on the probability density, acquisition transmittance probability, transmittance probability density, acquisition probability of single-photon propagation in atmospheric communication channel with z-tilt and centroid-tilt aberration corrected are studied theoretically. The probability density, acquisition transmittance probability, transmittance probability density and acquisition probability models for single-photon propagation in uplink path and downlink path are derived. Our results shown that the detection probability and the acquisition transmittance probability of the single-photon are obvious increase, when the beams are propagation in the z-tilt corrected communication channel.     

Heat recirculation effects on flame propagation and flame structure in a mesoscale tube

Heat recirculation effects on flame propagation and flame structure are theoretically and experimentally examined in a mesoscale tube as the simplest model of heat-recirculating burners. Solutions for steady propagation are obtained using a one-dimensional two-temperature approximation. The results show that the low heat diffusivities of common solid materials permit significant heat recirculation through the wall only for a slowly-propagating condition, otherwise the flame behaves almost like a freely-propagating nonadiabatic flame. This limited heat recirculation sharply pinches and stretches two well-known branches of the freely-propagating nonadiabatic flame, resulting in the appearance of two slow-propagation branches. On the upper slow-propagation branch flames can reach superadiabatic temperatures and on the lower one, which is stretched from the classical unstable lower branch, flames can be stable. As the tube inner diameter decreases, another burning regime appears where flames are barely sustained by the heat recirculation. Further reduction of the tube inner diameter makes no flame exist. It is also revealed that a flame in a mesoscale tube has two length scales, i.e. the conventional flame thickness and a convective preheat zone thickness, and that the latter should be much larger than the former for significant heat recirculation. It is theoretically predicted that a heat-recirculating, even superadiabatic, flame with positive propagation velocity against the gas flow can exist in a mesoscale tube. It is also found that a flame transition from one branch to another in a given tube is well described by only one dimensionless parameter. Finally, these theoretical results show good qualitative agreements with experiments, especially for the transition behaviours.     

迈克尔逊风场探测干涉仪探测温度不确定度分析

根据迈克尔逊风场探测干涉仪探测原理,所探测的温度不确定度是由装置调制度不确定度和发射线的表观调制度不确定度所决定的.通过它们之间的定量关系,求出了对应于一定温度不确定度的调制度不确定度的允许范围,并进行了模拟计算.最后针对影响因素提出了提高温度不确定度的方法, 明显提高了温度测试准确度.     

Theoretical and experimental investigation of fluid rheology effects on modulated ultrasound propagation

A mathematical model is developed and presented to capture the effect of viscoelastic nature of a material on modulated ultrasound (US) pulses. The model is established by considering perturbation of material elements subject to modulated US pulses and by introducing the exponential relaxation of the perturbed fluid elements with a spectrum of time constants. Both the model and experimental findings revealed that consecutive perturbation of a material via the modulated US pulses enabled to probe the relaxation times of similar order of magnitudes to the frequency of the US modulation while filtering out the impact of other relaxation times on the US measurement. The US experimental results were verified by those of a conventional rheometer. Hence carrying out measurements at different US modulation frequencies in the Hz ranges seems to allow one to obtain the relaxation time spectrum of the investigated material in the time scales of milliseconds to seconds.     

换流变压器噪声预测模型及其简化研究

换流变压器作为高压直流换流站主要噪声源,其噪声预测精度和控制方法的选择将直接影响换流站整体噪声预测水平及治理效果。通过对换流变压器噪声的产生机理、噪声频谱及常见治理方案等方面进行系统研究,重点推出了换流变压器噪声控制方法BOX-IN技术,并就BOX-IN装置的噪声预测模型进行了简化和对比验证。通过对降噪量进行现场测试,结果表明,BOX-IN装置降噪量达到20dB(A)左右,与理论计算值近似,为进一步提高高压直流换流站噪声预测精度提供了理论依据。     

基于XRD与SEM研究风淬渣微粉用于重金属污染土壤的修复机理

钢渣是冶金工业中产生的主要固体废弃物,其产量约为每年粗钢产量的15%~20%。由于技术的局限,导致我国钢渣利用率较低,仅为年钢渣产量的10%,同时加之管理制度的不健全,导致钢渣大量露天堆放,对土地资源、地下水源,以及空气质量形成严重影响。面对上述问题,利用钢渣开发一种价格低廉的固化药剂用于重金属污染土壤的修复,既是冶金固体废弃物可持续发展的重要途径之一,也是大幅降低重金属污染土壤修复成本的重要途径之一。该研究创新性是用风淬渣微粉作为固化药剂对含有Cd,Cu,Pb,Ni和Zn的重金属污染土壤进行修复。研究了风淬渣粉磨时间、风淬渣微粉掺量和养护时间对修复重金属污染土壤效果的影响。利用激光粒度分析仪测试风淬渣微粉的粒度分布、比表面积与孔隙度吸附仪测试风淬渣微粉的孔结构、扫描电子显微镜测试风淬渣微粉-重金属污染土壤混合物的微观形貌、X-射线衍射仪测试风淬渣微粉的矿物成分,分析风淬渣微粉修复重金属污染土壤的机理。结果表明,风淬渣的性质安全,对生态环境不存在污染,可以用于修复重金属污染土壤的固化技术。当风淬渣粉磨时间为100 min、风淬渣微粉掺量为20%、养护时间为14 d时,风淬渣微粉对重金属污染土壤中Cu,Cd,Ni,Zn和Pb的固化效果均达到91%以上。随着风淬渣粉磨时间的延长,风淬渣微粉的粒径尺寸减小、粒度分布趋向均匀。风淬渣的多孔结构破坏、比表面积提高,有利于提高风淬渣微粉对重金属污染土壤的修复效果。随着风淬渣微粉掺量的增加,风淬渣微粉形成的水化凝胶（C-S-H）数量增加,有利于提高风淬渣微粉包裹重金属污染土壤的效果,以达到固化重金属污染土壤中Cd,Cu,Pb,Ni和Zn的目的。风淬渣微粉对固化重金属污染土壤中Cu,Cd,Ni,Zn和Pb具有选择性,在不同养护时间下,重金属分别以Cd₂SiO₄,Cu(OH)₂·2H₂O,PbCO₃,3Ni(OH)₂·2H₂O,Ni₂SiO₄,Zn(OH)₂和Zn₂SiO₄形式存在。