猎豹汽车的降噪技术

汽车的噪声不仅是影响其舒适性指标的重要因素,而且也是评价其质量品质的重要指标之一。基于国家对汽车噪声控制标准的提升,文章系统地分析了长丰猎豹汽车噪声的产生源,阐述了长丰猎豹汽车降低噪声的控制方法。     

浅析环境噪声对城市人群的影响

城市是人们为了获得更美好的生活而聚集的地方,随着我国经济的高速增长,城市化进程得到了快速发展,近年来,我国随着老城区的改造,新城区的建设及农村城镇化建设步伐的加快,城市居住区面积及居民数量的不断增大,居住区噪声污染问题也日益严重,城市环境噪声对居住区居民的干扰和危害日益严重,不但干扰居民正常的工作、学习和睡眠质量,而且还对人在生理和心理上产生不可忽视的影响,甚至会危害到人的身体健康,从而引发各种疾病。     

Bayesian smooth-and-match inference for ordinary differential equations models linear in the parameters

Dynamic processes are crucial in many empirical fields, such as in oceanography, climate science, and engineering. Processes that evolve through time are often well described by systems of ordinary differential equations (ODEs). Fitting ODEs to data has long been a bottleneck because the analytical solution of general systems of ODEs is often not explicitly available. We focus on a class of inference techniques that uses smoothing to avoid direct integration. In particular, we develop a Bayesian smooth-and-match strategy that approximates the ODE solution while performing Bayesian inference on the model parameters. We incorporate in the strategy two main sources of uncertainty: the noise level of the measured observations and the model approximation error. We assess the performance of the proposed approach in an extensive simulation study and on a canonical data set of neuronal electrical activity.     

中型铣刨机噪声现状及噪声源识别

工程机械操作舒适性日渐成为评价一个产品好坏的重要指标,而噪声指标又是舒适性指标的重要组成部分。本文通过对某中型铣刨机进行噪声试验,研究了铣刨机的噪声源分布、频谱特性及噪声传递路径。试验结果表明:操作者位置上的噪声主要是由散热风扇和发动机排气噪声贡献,其能量主要集中在中心频率630Hz以下的中低频,且主要是从地板下方散热出风口传递过来。     

液压挖掘机机外辐射噪声分析与改进

液压挖掘机噪声直接影响整机舒适性,也是打开欧洲市场大门的关键钥匙之一;本文分析了液压挖掘机的主要噪声源及形成机理,通过频谱分析与试验,识别与定位了噪声源;针对不同噪声源,提出了合理的噪声治理措施,试验结果表明,某液压挖掘机机外辐射噪声降低3.7dB(A),证明该方法实用有效。     

谈高低频电路接地

在电子线路中,合理的接地方式能够有效抑制噪声和提高抗干扰能力。文章分析了电子线路中产生噪声干扰的一些原因,并讨论了一点接地及多点接地等接地方式消除噪声的方法。     

雷达接收机噪声特性研究分析

噪声是影响接雷达收机灵敏度的主要因素。接收机噪声越小,灵敏度就越高,所能够接收的信号就越弱,雷达的作用距离也就越远。本文首先对雷达接收机噪声进行分析,给出雷达接收机噪声系数与噪声温度的关系,最后提出了几种降低接收机噪声的具体方法。     

基于DSP的高斯白噪声的应用研究

基于浮点型DSP的结构特点,提出了一种实时高斯白噪声产生方案,核心算法采用斐波那契算法。应用时通过输入不同的方差值,可获得不同信噪比的数据流。     

燃机电厂厂区噪声治理与总平面布置研究

燃机电厂环保节能,大多建在城市近郊,但厂界噪声和周围声环境的达标却成了极其突出的问题。本文针对电厂噪声污染特点,分析了噪声源,结合总平面布置对不同区域噪声源采取了相应的噪声控制技术,以期达到国家环保要求,更好地解决燃机电厂的噪声污染问题。     

On statistics at level crossings by a stationary process

The main purpose of this paper is to indicate formal theorems and conditions for the extensions of Rice's Formula for intensities of crossings of a fixed level u by a stationary process X(t) in order to provide the conditional (Palm) distribution of an associated process Y(t) at the level crossing instants. Sections 1 and 2 provide brief background material on Rice's Formula and Palm distributions, while relevant historical comments and basic results are given in Section 3. These are stated with some indications of proof in Section 4 and calculation of the Palm distributions shown in Section 5. Two cases of importance in applications are considered: (a) where (roughly) X(t) , Y(t) and the derivative X'(t) have a joint density and (b) where Y(t) = X'(t) . The resulting Palm distributions are each absolutely continuous with readily calculable densities. These are evaluated for Gaussian processes in Section 6 and applications to motivating 2 structural safety questions indicated in Section 7.     

一种基于四分法噪声检测的开关中值滤波算法

为了精确的检测出图像中的脉冲噪声并滤除,提出一种基于四分法噪声检测的开关中值滤波算法。该算法使用一种新的检测方法将噪声检测窗口内的像素按灰度值大小进行排序,并且通过差分方法划分出高、低阶噪声块和高、低阶信号块四部分。当待测像素属于高、低阶信号块时将其视为信号点,否则,根据噪声块与信号块内像素比例关系就可认定其为噪声点或可能噪声点,若为可能噪声点,则需扩展检测窗口重新检测。对确定噪声点,取滤窗内信号点的中值作为滤波输出。实验证明该算法对脉冲噪声有较强的抑制作用。     

谈游乐园噪声污染防治措施——以南宁市凤岭儿童公园为例

文章对南宁市凤岭儿童公园环境影响评价实例进行分析,论述各类游乐园建设项目运营期噪声污染源及影响范围,并提出了切实可行的防治措施。     

济南某大剧院工程噪声及振动控制技术研究

当前,建筑业对我国市场经济的发展做出了十分重要的贡献。建筑工程的噪声和振动控制技术,也成为了建筑商日益关注的问题。结合最新的在不同空间所允许的背景噪音级别的声学设计标准,并对此进行定义,提供了如何满足声学要求的指导原则。采用隔声缝将房间在结构上分开,达到空间降噪的效果。在最终完成的剧院空间中,将不存在过度噪音。     

某通信生产大楼空调室外机的噪声分析及降噪措施探讨

文章阐述了噪声对人体产生的主要危害，分析了某通信生产大楼空调室外机噪声声源的特点及传播途径，有针对性地给出了一些降低空调室外机噪声的方法和措施。该生产大楼采用了目前环境污染治理行业前沿的减震、隔声、阻性消声等措施，使生产大楼厂界及周边环境达到相关的噪声标准。     

小行地铁站地面切割施工的噪声控制

针对施工过程中产生噪音的的实际问题,具体分析了噪声源,确定了在传播途径中控制噪声的方式并制作了拼装式可移动的隔声罩;通过实际测量,证明了该措施的有效性,在投入很小的情况下完全实现了噪声控制的预期效果,保证了工程的顺利开展实施,完全符合噪声控制设计应坚持的科学性、先进性和经济性原则。     

Distributional Effects of a Continuous Treatment with an Application on Intergenerational Mobility

This paper considers the effect of a continuous treatment on the entire distribution of outcomes after adjusting for differences in the distribution of covariates across different levels of the treatment. Our methodology encompasses dose-response functions, counterfactual distributions, and ‘distributional policy effects’ depending on the assumptions invoked by the researcher. We propose a three-step estimator that consists of (i) estimating the distribution of the outcome conditional on the treatment and other covariates using quantile regression; (ii) for each value of the treatment, averaging over a counterfactual distribution of the covariates holding the treatment fixed; (iii) converting the resulting counterfactual distribution into parameters of interest that are easy to interpret. We show that our estimators converge uniformly to Gaussian processes and that the empirical bootstrap can be used to conduct uniformly valid inference across a range of values of the treatment. We use our method to study intergenerational income mobility where we consider effects of parents’ income on features of their child's income distribution such as (i) the fraction of children with income below the poverty line; (ii) the variance of child's income; and (iii) the inter-quantile range of child's income–all as a function of parents’ income.     

Inference with non-Gaussian Ornstein–Uhlenbeck processes for stochastic volatility

Continuous-time stochastic volatility models are becoming an increasingly popular way to describe moderate and high-frequency financial data. Barndorff-Nielsen and Shephard (2001a) proposed a class of models where the volatility behaves according to an Ornstein–Uhlenbeck (OU) process, driven by a positive Lévy process without Gaussian component. These models introduce discontinuities, or jumps, into the volatility process. They also consider superpositions of such processes and we extend that to the inclusion of a jump component in the returns. In addition, we allow for leverage effects and we introduce separate risk pricing for the volatility components. We design and implement practically relevant inference methods for such models, within the Bayesian paradigm. The algorithm is based on Markov chain Monte Carlo (MCMC) methods and we use a series representation of Lévy processes. MCMC methods for such models are complicated by the fact that parameter changes will often induce a change in the distribution of the representation of the process and the associated problem of overconditioning. We avoid this problem by dependent thinning methods. An application to stock price data shows the models perform very well, even in the face of data with rapid changes, especially if a superposition of processes with different risk premiums and a leverage effect is used.     

THE INTERNALISATION OF ENVIRONMENTAL EXTERNALITIES AFFECTING DWELLINGS: A REVIEW OF COURT CASES IN HONG KONG

In 1960, Ronald Coase suggested that there are many methods to solve the problem of externalities apart from imposing Pigovian taxes. Internalisation is one of those noted in his classic paper, ‘The Problem of Social Cost’. This paper studies the possibility of residents receiving compensation from pollutant generators. Data collected from Hong Kong law reports over the past 20 years show that there is forty‐fold increase in number of water seepage court cases since the first case in 1994. The total amount of compensation has also increased greatly. There are, however, far fewer court cases where residents seek compensation from generators of noise and air pollution. This may reflect a combination of high transaction costs and low expected benefits from such cases.     

ASSESSING THE REGIONAL ECONOMIC IMPACTS OF DEFENSE ACTIVITIES: A SURVEY OF METHODS

Defense activities exercised in a specific region may alter the region's economic performance. An accurate assessment of the potential economic impacts of defense activities is a valuable undertaking to enable regional planners to prepare for changes. The variety in the methods (among others, input–output models, economic base models, Keynesian regional multipliers, fixed‐effects estimators, and case‐study approaches) inspired by geography, sociology, and political science can pose a dilemma. We detail the historical and theoretical background of each method, as well as select exemplary cases where these methods were applied. By examining old and “new” methods, we aim to construct a typology that could be valuable to all stakeholders. In this sense, defense economics can also contribute to the allied social sciences by outlining evaluation methods that may be applicable to other fields.     

Frequency domain estimation of temporally aggregated Gaussian cointegrated systems

This paper considers joint estimation of long run equilibrium coefficients and parameters governing the short run dynamics of a fully parametric Gaussian cointegrated system formulated in continuous time. The model allows the stationary disturbances to be generated by a stochastic differential equation system and for the variables to be a mixture of stocks and flows. We derive a precise form for the exact discrete analogue of the continuous time model in triangular error correction form, which acts as the basis for frequency domain estimation of the unknown parameters using discrete time data. We formally establish the order of consistency and the asymptotic sampling properties of such an estimator. The estimator of the cointegrating parameters is shown to converge at the rate of the sample size to a mixed normal distribution, while that of the short run parameters converges at the rate of the square root of the sample size to a limiting normal distribution.