线性光采样模拟前端研制与128Gb/s信号测试

面对100 Gb/s光纤传输系统性能监测需求,自主研制完成高速线性光采样模拟前端。其内部由1个被动锁模光纤激光器产生脉宽为2 ps、重复频率为96.25 MHz的采样光脉冲,待测偏振复用四相移键控(PDM-QPSK)信号和采样光脉冲进入光混频器后完成偏振相位分集探测,利用模拟带宽为400 MHz的平衡探测器完成光电转换后,将4路模拟信号传入主机进行数字化处理,获得高速光信号时域分析结果。通过优化设计,实现被动锁模光纤激光器的脉冲功率、中心波长、重复频率稳定输出。利用商用128 Gb/s PDM-QPSK信号对工程样机和安捷伦调制信号分析仪N4391A展开对比测试,测试结果表明工程样机可获得相同的时域参数分析结果。     

基于CEEMD特征提取的无绝缘轨道电路补偿电容故障诊断

本文利用电路网络理论和传输线理论构建ZPW-2000A轨道电路传输模型,仿真并分析了补偿电容故障对轨面电压的影响,提出基于互补的总体经验模式分解(CEEMD)特征提取的补偿电容故障诊断方法。实验结果表明,相比于传统经验模式分解(EMD)和总体经验模式分解(EEMD),基于CEEMD特征提取的补偿电容故障诊断方法可以有效地克服EMD方法引起的模态混叠和能量泄露现象,减少EEMD方法在信号重构过程中的白噪声残留,为补偿电容的故障诊断提供了一种快速准确的方法,为保证信号传输质量提供了参考依据。     

测量微秒量级脉宽方波信号的电容分压器

为了解决测量脉宽达到μs量级的方波信号的平顶衰落问题,设计了改进的双端匹配电容分压器。对采取双端匹配方式的电容分压器进行了频域和时域仿真。仿真结果表明,双端匹配方式的中频段幅频特性不平坦,方波响应波形也存在过冲。通过仿真计算调整了始端电阻以及对应的末端电容,实现了双端匹配方式的优化设计。实验结果表明:当低压臂电容为2 nF的情况下,使用电长度为50 ns的电缆的改进双端匹配电容分压器可以得到过冲小于2%,无平顶衰落的波形。     

长征六号运载火箭动力测发控系统仿真测试平台的设计

针对长征六号运载火箭动力测发控系统射前仿真测试需求,结合短周期快速发射及方舱操作的特点,设计了一种仿真测试平台;该测试平台使用电气信号模拟动力配气台阀门、压力传感器及箭体连接器硬件接口信号,形成硬件接口层;采用软件模拟配气台工作原理,仿真箭体连接器通断,并模拟基地加注间通讯系统与动力测发控系统进行信息交互,形成软件模型层;硬件接口层与软件模型层之间通过RS422总线和PC104总线连接,实现仿真测试平台的模块化和组合化设计;该仿真测试平台为长征六号运载火箭动力测发控系统提供了闭环测试环境;实际情况表明,该仿真测试平台可覆盖动力测发控系统的全部工作状态,满足短周期快速发射的测试需求,提高了动力测发控系统仿真测试的效率。     

基于LabVIEW的振动信号分析系统设计

针对机械故障监测的需求,开发了振动信号分析系统。采用LabVIEW图形化开发工具,系统实现了振动信号分析流程和基本的信号分析方法,能够对振动信号进行预处理,并从时域、频域和时频域角度对其进行特征提取。完成了基于仿真信号和实测的公开振动数据集进行验证,实验结果表明,所开发的振动信号分析系统具备参数配置灵活、结果显示直观、扩展性强的优势,为基于振动测试的机械故障监测提供了基础平台。     

时频域独立元分析方法实现超声兰姆波的多模式分离

为方便兰姆波信号分析与模式定征,提出一种将短时傅里叶变换(Short-Time Fourier Transform,STFT)与独立元分析(Independent Component Analysis,ICA)相结合的多模式超声兰姆波识别方法。首先通过STFT将兰姆波时域信号投影至时频域,基于各模式信号在时频域相对独立的特点,利用ICA实现混叠模式分离。根据分离模式时频能量脊提取各模式群速度曲线,进而估计板厚。将方法运用于时域有限差分(Finite-Difference Time-Domain,FDTD)法仿真与钢板实验,分离得到A0、A1和S0三种模式。仿真与实验中平均群速度估计误差约为1.5%和2.0%,板厚估计误差约为0.3%和2.0%。仿真结果表明,在信噪比(Signal-to-Noise Ratio,SNR)不小于0 dB的情况下,时频域独立元分析方法均可实现兰姆波多模式分离、群速度曲线提取及板厚估计。      

基于简正波理论的浅海低频混响时间序列仿真

混响场时域信号序列的数值实现对主动声纳目标模拟器研制具有重要意义。本文所述适用于水平变化浅海环境混响时间序列的一种实现方法,基于现有的浅海简正波相干混响理论。所述方法的思路是通过相干散射场随机序列与发射信号的离散卷积来构成混响时域序列,文中以Pekeris均匀浅海环境为例,给出了相应的混响时间序列仿真结果,并对仿真结果的频谱特性、统计特性、强度衰减以及垂直相关特性等进行了系统检验。结果表明,由仿真混响时间序列所获得的混响特性与理论结果相符,可用于浅海混响序列的仿真。     

航空重力仪稳定平台机电联合建模仿真

航空重力仪是一款对地球重力进行测量的精密仪器,为了使重力仪在工作状态下隔离飞机飞行过程中的各种扰动,始终保持竖直稳定状态,设计了一款高精度航空重力仪惯性稳定平台。同时为了缩短稳定平台设计周期,并保证所设计的稳定平台系统结构方面的性能能够满足设计指标的要求,对所设计的高精度航空重力仪惯性稳定平台进行机电联合建模仿真,建立了基于Adams和Simulink的机电联合仿真模型,对机电联合仿真模型进行了时域和频域仿真分析,得到稳定平台时域与频域的基本性能指标,并把仿真结果和实际测试结果进行了对比。结果表明:在开环的条件下,时域与频域仿真结果和实际测试结果基本一致,俯仰轴幅频匹配度在83%,相频匹配度在79.2%,横滚轴幅频匹配度在92.9%,相频匹配度在86.1%,2个轴的时域匹配基本类似,验证了仿真模型的正确性和有效性。该模型可对稳定平台的伺服性能进行预测,为平台的实际测试与调试打下基础。     

基于X射线脉冲星导航的模拟调制仿真源研究

为实现X射线脉冲星导航系统在地面的演示验证, 提出并设计了一种高精度X射线脉冲星仿真源. 该仿真源由模拟调制信号发生器和栅控X射线球管组成. 模拟调制信号发生器根据脉冲星标准脉冲轮廓数据和栅控球管特性曲线, 利用直接数字频率合成技术产生模拟调制信号, 加载在X射线球管控制栅极, 从而控制轰击阳极靶的高速电子数目来实现X射线的调制, 产生与脉冲星标准脉冲轮廓高吻合度的X射线光子统计分布. 在X射线脉冲星地面仿真系统中对Crab脉冲星仿真源的性能进行测试, 测试结果为: 采集脉冲轮廓与标准脉冲轮廓时域相关度和频率相关度分别达到0.9774和0.9853, 辐射流量为1. 90 ph·cm^-2·s^-1, 脉冲辐射流量与总辐射流量之比为76.15%, 脉冲半宽度为1.879 ms. 结果表明: 该仿真源具有符合度高, 成本低, 操作简单灵活, 对X 射线脉冲星导航关键技术的攻关具有重要的意义. 关键词： X射线脉冲星导航 仿真源 栅控X射线球管 直接数字频率合成     

基于光纤中四波混频效应光逻辑门的信号同步提取与擦除

设计并演示了一种新型的光信号全光提取与擦除方案。将两个时域上同步,强度反相的矩形光脉冲作为控制信号,通过光纤中四波混频效应所形成的逻辑门(与门和非门),可以对一段时隙上的光数据进行同步的提取和擦除。对10Gb/s非归零信号的仿真和实验验证了方案的可行性。方案可在更高速率的系统下工作,并对波长和码型透明。     

Chinese speech intelligibility at different speech sound pressure levels and signal-to-noise ratios in simulated classrooms

The speech intelligibility in classroom can be influenced by background-noise levels, speech sound pressure level (SSPL), reverberation time and signal-to-noise ratio (SNR). The relationship between SSPL and subjective Chinese Mandarin speech intelligibility and the effect of different SNRs on Chinese Mandarin speech intelligibility in the simulated classroom were investigated through room acoustical simulation, auralisation technique and subjective evaluation. Chinese speech intelligibility test signals recorded in anechoic chamber were convolved with the simulated binaural room impulse responses, and then reproduced through the headphone by different SSPLs and SNRs. The results show that Chinese Mandarin speech intelligibility scores increase with increasing of SSPLs and SNRs within a certain range in simulated classrooms. Chinese Mandarin speech intelligibility scores have no significant difference with SNRs of no less than 15 dBA under the same reverberation time condition.     

一种新的X射线脉冲星信号模拟方法

由于无法在地面直接观测到X射线脉冲星信号, 且空间飞行探测耗时长, 成本高, 模拟具有真实物理特征的X射线脉冲星信号对X射线脉冲星信号处理方法及导航方案的验证具有重要意义. 本文提出了一种利用太阳系质心处脉冲星信号模型和航天器轨道信息, 建立航天器处实时光子到达速率函数, 再利用尺度变换法产生光子到达时间序列的脉冲星信号模拟新方法. 该方法真实还原了脉冲星信号的频率缓变特性, 考虑了动态探测环境下的相对论效应, 且避免了现有模拟航天器处光子序列方法中的迭代过程, 产生非齐次泊松光子到达时间序列的运算量也低于常用的齐次泊松过程筛选法和反函数递推法. 数值仿真从频率特性、流量特性、轮廓相似度及与实测数据的接近程度四个方面验证了该模拟方法的正确性.     

导爆管起爆器瞬态电火花温度的光谱法测定

应用双谱线原子发射光谱测温法的原理，建立了一套石英光导纤维传输的瞬态实时双谱线测温系统，它的时间分辨率最高可达0.1цs，所采用的两条谱线的波长分别为Cu I 510.5和Cu I 521.8nm。利用该套装置，研究了在不同电压下导爆管起爆器的放电火花温度随时间的变化，以及不同放电条件下的电火花持续时间。试验表明：对给定的起爆器火花的温度，是在2100-4200K范围内变化，放电时间随充电电压的提高而增长。     

生态水体景观视觉影响下道路交通声评价的实验研究

采用里克特5级量表(1:非常不舒适;5:非常舒适)实验研究了不同声级的道路交通声评价在生态水体景观视觉影响下的规律。分析发现:与单听觉测试条件相比,生态水体景观将道路交通声级与声评价的相关系数由-0.91降低至-0.81~-0.57,其中30 dBA的道路交通声评价值下降0.13~0.68,而70 dBA的道路交通声评价值升高0.10~0.22。在一定声级范围内景观要素对道路交通声评价的影响不同:人工要素比自然要素影响下的道路交通声评价值高0.33/10 dBA;自然水体远景比近景影响下的道路交通声评价值高0.33/10 dBA;人的活动要素比动物活动要素影响下的道路交通声评价值高0.28/10 dBA,      

上下并联轴流风机室外机气动声学预测模型

本文基于CFD模拟方法,分析了空调器室外机上下并联轴流风机系统噪声源分布,建立了室外机气动声学预测方法.研究发现,上下并联轴流风机系统由宽频和离散频率噪声组成,宽频噪声是影响室外机噪声总声压级的重要因素.涡声分析表明,涡脱落噪声是宽频噪声的主要影响因素.基于CFD的叶片尾缘涡脱落噪声预测方法计算得到宽频声压误差为2 dB,考虑离散频率影响时,室外机A计权总声压级预测误差小于2 dBA.基于CFD的点源时域预测模型,捕捉到了上下并联轴流风机系统的离散频率噪声峰值,且在上下叶轮前二阶谐波处预测值与实验值吻合较好.     

Soundscape evaluation in Han Chinese Buddhist temples

In this study, surveys were conducted at four typical Han Chinese Buddhist temples. These surveys were then analyzed to identify the subjective and objective factors of soundscape evaluation. Field measurements of the four temples’ sound levels were taken over the course of an entire day, and the representative sounds in temples were recorded. Soundscape evaluation questionnaire surveys were distributed at the temples. The analytical results of the questionnaire and measurement data showed that the sound preferences in temples are significantly correlated with sharpness value of the sounds in terms of psychoacoustic parameters, and the average sound levels at the four temples over the course of an entire day were between 47.0 and 52.7 dBA, and approximately 70% of those surveyed tended to evaluate the temples’ soundscapes as comfortable and harmonious. Regarding the objective factors, there was a significant correlation between the measured sound levels and the soundscape evaluations. When the sound level of a temple was higher than 60 dBA, respondents were more likely to feel uncomfortable, and the correlation between the sound level and the evaluation of acoustic comfort substantially increased. Regarding the subjective factors, the respondent’s age, occupation, religious belief, purpose, frequency of visiting the temples, and educational level significantly correlated with the soundscape evaluation with correlation coefficients ranging from 0.13 to 0.35.     

Electric ignition energy evaluation and the energy distribution structure of energy released in electrostatic discharge process

Ignition energy is one of the important parameters of flammable materials, and evaluating ignition energy precisely is essential to the safety of process industry and combustion science and technology. By using electric spark discharge test system, a series of electric spark discharge experiments were conducted with the capacitor-stored energy in the range of 10 J, 100 J, and 1000 J, respectively. The evaluation method for energy consumed by electric spark, wire, and switch during capacitor discharge process has been studied respectively. The resistance of wire, switch, and plasma between electrodes has been evaluated by different methods and an optimized evaluation method has been obtained. The electric energy consumed by wire, electric switch, and electric spark-induced plasma between electrodes were obtained and the energy structure of capacitor-released energy was analyzed. The dynamic process and the characteristic parameters(the maximum power, duration of discharge process) of electric spark discharge process have been analyzed. Experimental results showed that, electric spark-consumed energy only accounts for 8%–14% of the capacitor-released energy. With the increase of capacitor-released energy, the duration of discharge process becomes longer, and the energy of plasma accounts for more in the capacitor-released energy. The power of electric spark varies with time as a damped sinusoids function and the period and the maximum value increase with the capacitor-released energy.     

Humidity and aggregate content correction factors for air-coupled ultrasonic evaluation of concrete

This paper describes the use of non-contact ultrasound for the evaluation of concrete. Micromachined capacitance transducers are used to transmit ultrasonic longitudinal chirp signals through concrete samples using air as the coupling medium, and a pulse compression technique is then employed for measurement of time of flight through the sample. The effect on the ultrasonic wave speed of storing concrete samples, made with the same water/cement ratio, at different humidity levels is investigated. It is shown that there is a correlation between humidity and speed of sound, allowing a correction factor for humidity to be derived. A strong positive linear correlation between aggregate content and speed of sound was then observed; there was no obvious correlation between compressive strength and speed of sound. The results from the non-contact system are compared with that from a contact system, and conclusions drawn concerning coupling of energy into the samples.     

水中针-板结构小能量脉冲火花放电特性北大核心CSCD

开展了J量级系统储能下电脉冲参数对水中火花放电特性影响研究。驱动源采用参数可调的固态重频纳秒脉冲电源,放电负载为水中针-板结构(间距1 mm),在低重频条件(约5 Hz)下进行实验。通过调节放电参数、拍摄高速阴影图像、光谱诊断以及声信号测量,研究水中脉冲放电的物理特性,得到不同放电参数下放电演化规律及其对声学、光谱特性影响。实验发现:在J量级储能下,放电通道连通两极后,回路电流在几百ns内快速上升至10 A左右,随后缓慢下降,持续50~60μs。发现预设脉宽对放电影响较大,短脉宽条件下放电会被电源固态开关强制截断出现反向放电,而长脉宽条件下放电通道在后期变得不稳定甚至熄弧中断,出现气泡中二次放电现象。辐射光谱揭示了更多等离子体信息,推断通道电子密度在1018 cm-3量级,随着脉宽增加,特征谱线强度增加,表明活性粒子数密度增加,但粒子种类不变。短脉冲(<150μs)作用下产生的脉冲声波的特征宽度在110~150μs,而当脉宽继续增大,声波脉宽并不继续增加而是保持不变,保持在150μs左右。研究结果对水中小能量火花放电的机理研究有一定参考价值,为水声学、液相等离子体等领域的应用提供思路。     

空调室外机钣金结构辐射噪声分析与优化

针对空调室外机背面位置处在压缩机5280 r/min转速下的出现两倍频(176 Hz)噪声峰值异常高的问题,基于双转子压缩机工作原理,计算双转子压缩机吸排气过程的两倍频转动力矩;建立空调室外机整机有限元模型,施加两倍频转动力矩,应用模态线性叠加法计算整机的频率响应,经过模态测试确定在176 Hz附近整机钣金存在共振,导...