低频噪声有调度计算模型分析

对于低频噪声,信号中心频率附近声压级较高的有调音部分发生变化时,包括谱峰的声压级增高和谱峰的形状变尖,会使主观有调感明显提高。因此在考虑有调度计算模型时,一定要充分考虑峰值信号部分产生的影响。现有的有调度计算模型虽然在此部分有所考虑,但是由于模型中的带宽计权因子不能恰当描述这一特征,因而不能准确描述相应的主观感觉,并且计算模型不稳定。通过实验研究与分析得到影响主观有调感最大的因素是有调音部分的声压级大小和谱峰形状,据此进一步从纯音的窄带频率调制信号的主观评价实验出发,通过实验所得的有调度评分值反演出有调度的带宽计权因子,从而对现有模型中的带宽计权因子进行了修正,增加了峰值尖锐程度对有调度的影响,提高了有调度模型的准确性,而且增强了计算的鲁棒性。     

A new compact circuit-level model of semiconductor lasers: investigation of relative intensity noise and frequency noise spectra

We introduce a new compact noise equivalent circuit model of semiconductor lasers (SLs) from the rate equation including Langevin noise sources. The noise sources are described in terms of the spectral properties of the relative intensity noise (RIN) and frequency/phase noise (FN). Unlike the previous noise equivalent circuit models, which are based on two different DC and small-signal circuit models, using only a single circuit model, the static and dynamic responses and also the noise characteristics of SLs, can be investigated. We examine the validity of the presented noise circuit model by comparing the simulated results with the analytical and numerical results available in the literatures.     

某型蛙人运载器辐射噪声测量与特征分析

蛙人是港口和水下设施的重要威胁,蛙人运载器产生的辐射噪声是对依靠运载器执行任务的水下蛙人实施警戒探测的重要依据,目前利用声学系统被动探测是发现水下蛙人的有效手段之一。文章针对某型蛙人运载器的实际探测问题设计了声学测量实验,实验包括消声水池测量和海上测量两部分,目的是获取蛙人运载器的有效声学特征,包括声源级、指向性、功率谱、LOFAR谱和DEMON谱等,获得有效的轴频、叶频及其各次谐波簇。在实验测量的基础上,系统分析了某型蛙人运载器辐射噪声的典型时频变化特征,为水下蛙人运载器的警戒探测提供实测数据支撑。     

Features of the analysis of low-frequency noise by the discrete fourier transformation method

The choice of the optimum weighting function of the window for the mathematical processing of low-frequency noise experimental research data is discussed. Experimental low-frequency noise spectra are obtained using automated equipment. __________ Translated from Izmeritel’naya Tekhnika, No. 12, pp. 47–50, December 2005.     

太阳能半导体制冷的实验研究与数值分析

建立了以水为热交换媒介的太阳能光伏半导体制冷模块实验系统.制冷装置模块化,用以适应制冷功率变化较大的不同空间布局,通过太阳能光电半导体制冷实验获得了不同工作状态下电流、制冷量、制冷系数等重要参数,该参数可为确定系统最佳工作区域提供可靠依据.给出了太阳能热电制冷系统组合方案,介绍了一种新型组合式半导体制冷器和半导体热电发电装置,其数值计算的结构参数、最大制冷系数和制冷率等重要参数以及热电器件最佳工作区域和结构参数的最优范围,可为系统优化设计的配置提供理论上的指导.     

船舶螺旋桨叶片与艉部湍流场互作用噪声的预报研究

低噪声特性是螺旋桨设计者所追求的目标之一。当船尾的螺旋桨周期性旋转在空间和瞬时随机的非均匀流场中时,在螺旋桨叶片上就会产生升力脉动,从而辐射出离散谱噪声和低频宽带噪声。利用湍流谱和FfowcsWilliams-Hawkings方程可以获得低频宽带噪声级。这种方法可用于实船螺旋桨噪声预报和低噪声设计,这对提高舰船安静化程度有重要的现实意义。     

Determination of tolerance limits for the reliability of semiconductor devices using longitudinal data

Design and production of semiconductor devices for the automotive industry are characterized by high reliability requirements, such that the proper functioning of these devices is ensured over the whole specified lifetime. Therefore, manufacturers let their products undergo extensive testing procedures that simulate the tough requirements their products have to withstand. Such tests typically are highly accelerated, to test the behavior of the products over the whole lifetime. In case of drift of electrical parameters, manufacturers then need to find appropriate tolerance limits for their final electrical product tests, such that the proper functioning of their devices over the whole specified lifetime is ensured. In this study, we present a statistical model for the determination of tolerance limits that minimize yield loss. The model considers longitudinal measurements of continuous features, based on censored data from stress tests. The tolerance limits are derived from multivariate distributions where the dependence structure is described by different copulas. Based on extensive numerical testing, we are able to provide insights into the properties of our model for different drift behaviors of the devices.     

风机盘管机组低频噪声故障分析及改善

为了降低风机盘管机组的低频噪声水平,采用鱼骨刺图、专家判断、Scatter plots,Two-Sample TTest,One-way ANOVA和仿真分析等方法对FCU03机组的低频噪声进行分析。结果表明,低频噪声不会随机外静压的变化而变化;机组的低频噪声与风速相关,低速档工作时,低频噪声问题更明显;提高风机座板的刚度,能够有效地降低风机盘管机组的低频噪声水平,提高产品质量。     

红外探测技术对多目标弹道参数的测量

在对多目标探测所用传感器的选择、目标提取和数据处理等三方面技术问题进行分析论证的基础上,提出了一种新的多、弱、小、暗目标近地弹道参数测量方法。采用红外热像仪合理布站,对运动的多个目标进行空间定位;采集多目标近地区域的下落图像,拟合出相应的轨迹,然后根据多条轨迹得到诸如目标空间坐标、轨迹、速度等弹道参数。这种方法可用于测量靶场落点和近地轨迹等;尤其是在对子母弹子弹群的近地弹道参数及落点的测量中,通过后期处理,可快速精确地报出各子弹的落点坐标。     

社会生活环境噪声排放标准实施

GB22337-2008《社会生活环境噪声排放标准》的实施,标志着我国将社会生活环境噪声排放纳入到国家法律的范围。本文指出制冷空调设备生产企业所面临的挑战,企业应积极对产品进行技术创新改进,以达到国家标准的要求。     

高架轻轨箱梁噪声辐射现场实测分析

对武汉轻轨一号线某高架段25 m跨单箱单室预应力钢筋混凝土简支箱梁的噪声辐射进行了现场测试。将采集的噪声信号利用快速傅里叶变换技术通过相干函数进行一定程度的净化,从而获得真实的结构辐射噪声。绘制了箱梁结构表面辐射声压级等值线图。比较分析了综合噪声和结构辐射噪声的A声级。分析结果表明:近轨时箱梁结构各部位的辐射噪声明显大于远轨时箱梁结构各部位的辐射噪声。在近轨和远轨两种工况下,底板和翼缘的辐射噪声都大于腹板。箱梁各部位的辐射声压级在跨长方向和桥宽度方向上都表现出非单一的变化规律,需结合列车运行工况具体分析。轻轨箱梁结构辐射噪声级在61~66 d B(A)之间,实际工程中为了获得真实的结构辐射噪声级需将测得的综合噪声级减去约2 d B(A)(背景噪声影响)。实测分析结果可让工程技术人员了解箱梁噪声辐射情况,为后期箱梁的降噪设计提供参考依据。     

声强测量法在汽车空调噪声测量中的应用

分析声强测量法的原理与优点，介绍声强测量法在汽车空调噪声声功率级测试中的应用。通过比较声强法与普通方法的测量结果，证明声强测量法在空调噪声测试中具有足够高的精度，有很高的实用价值。     

Computer-aided system for measuring the static parameters of semiconductor devices

A computer-aided system for measuring the static parameters of semiconductor devices is described. The system is controlled by a personal computer. A hierarchy of models is formed from the results of the measurements from the simplest behavioral models to the accurate physical models used in computer-aided design systems. Translated from Izmeritel'naya Tekhnika, No. 12, pp. 49–52, December, 1996.     

半导体器件引线框架材料的现状与发展

本文评述了半导体器件引线框架材料国内外研究开发的现状 ,对引线框架材料性能和材料设计进行了分析 ,并讨论了随着计算机和信息工业的迅猛发展 ,引线框架材料今后的发展趋势。     

500kV变电站厂界低频噪声控制指标适用性调查分析

随着电网设施的发展,变电站的低频噪声问题越来越受到关注。为分析500 kV变电站厂界低频噪声控制指标的适用性,基于实测数据对9座变电站厂界低频噪声进行了分析,并选取2座变电站分别对其实体围墙上下方和主变附近采取降噪措施前后的厂界噪声进行了比较。结果表明,变电站厂界低频噪声在中心频率为100 Hz的1/3倍频带上的峰值最为明显。厂界低频噪声样本低频段声能量比例θ_low和L_Ceq-L_Aeq平均值分别为87.2%和11.0 dB,并且呈现出L_Aeq较低的声样本的θ_low和L_Ceq-L_Aeq却较大的规律。围墙下方的厂界噪声L_Aeq和L_{100 Hz}通常小于围墙上方,但θ_low和L_Ceq-L_Aeq却可能更大。通过主变附近采取降噪措施使厂界噪声L_Aeq和L_{100 Hz}得到有效控制的情况下,θ_low和L_Ceq-L_Aeq也可能比原来更大。可见,直接引入θ_low和L_Ceq-L_Aeq指标来评价变电站厂界低频噪声存在一定缺陷。分析结果可为变电站厂界低频噪声排放控制指标选取和限值确定提供参考。     

Automatic measurement of galvanomagnetic parameters of narrow-gap semiconductor devices

Translated from Izmeritel'naya Tekhnika, No. 8, pp. 42–43, August, 1991.     

Correlation between 1/f noise and semiconductor laser degradation

The origin of the increase in residual spectral linewidth during device degradation is experimentally and theoretically clarified in a multiple quantum well (MQW) distributed feedback (DFB) laser. Non-radiative recombination current increases during device degradation and causes 1/f noise to increase. This current 1/f noise is the origin of the increase in the residual spectral linewidth. Through these degradation behaviours, a model showing a correlation between 1/f noise and the semiconductor laser degradation is proposed.     

低频噪声主观感知与频谱特征关系研究

低频噪声对人的主观影响越来越引起人们的重视,本文采用正交分析方法,研究了低频噪声频谱中不同频率下降点,不同下降斜率,不同频率调制因子和用于调制信号的窄带噪声不同截止频率四个因素对主观低沉度、有调感、粗糙感和烦恼度的影响.主观评价采用了分组成对比较法和参考语义细分法.研究结果表明,不同频率调制因子对粗糙感的影响较大.不同截止频率对有调感和低沉度的影响比较明显.在进行主观烦恼度的统计分析时,需要考虑人群分类的影响,对于不同的人群烦恼度的影响因素会有所不同.     

Relating concrete pavement noise and friction to three-dimensional texture parameters

The objectives of this research were to characterise concrete pavement surface texture using three-dimensional (3D) surface texture indicators, to explore the relationship between pavement noise/friction and texture parameters. A newly constructed Portland cement concrete pavement with 13 types of textures was selected as test site. Pavement texture heights were recovered using photometric stereo technique. A comparative study was conducted between proposed 3D texture parameters and other established two-dimensional texture measurements, i.e. the circular track meter and the high-speed texture profiler. Correlation analysis between 3D texture parameters and noise/friction data were also carried out to explore relationship between pavement texture and noise/friction. In addition to texture amplitude, the direction and distribution of pavement texture have strong impacts on pavement noise and friction. It is possible to have a better understanding of surface texture and pavement noise/friction using combinations of the proposed 3D texture parameters.