Mass concentration calculation with the pulse height distribution of aerosols and system calibration

The pulse height distribution of aerosols, which was measured by an optical particle counter, was applied to inverse aerosol mass concentration. Using the conceptions of equivalent diameters, the feasibility that the pulse height distribution was used to inverse mass concentration was verified theoretically, and then the definition of average mass was introduced. According to the Mie scattering theory, considering particle shape and non-uniformity of intensity distribution in the optical sensing volume, a novel algorithm for mass concentration was proposed based on the theoretical analysis. In this algorithm, we only need to calibrate two coefficients. The Gauss-Newton and the two-step calibration methods were presented. The former method revealed that calibration coefficients calculated with nonlinear regression are related to the range of mass concentration, leading to the instability of the calibration coefficients. Furthermore, though detailed analysis of the problem, the latter method was put forward. The experimental results indicate mass concentrations inversed by the algorithm have high precision.     

基于平均质量的悬浮颗粒物的质量密度算法

基于米氏(Mie)散射理论得到了粒子计数器测量球形颗粒物质量密度的计算公式。考虑非球形颗粒,从颗粒群粒度分布概念出发,提出了统计意义上的平均质量概念,推导了非球形颗粒物质量密度的理论公式。运用理论公式证明了粒子计数器测量非球形颗粒物质量密度计算公式的合理性,进而给出了基于平均质量的悬浮颗粒物的质量密度算法,该算法只需对两个系数进行标定。实验表明,该算法的质量密度计算值与实际值十分吻合,两者拟合直线的斜率为0.9713,相关系数为0.9998。该算法为实现粒子计数器在线测量悬浮颗粒物的质量密度提供了一种可行途径。     

基于二阶滤波器的消光起伏谱颗粒测量结果

消光起伏频谱法是一种新的测量两相流系统中颗粒粒径分布和浓度的方法,装置简单,操作方便,适合实时、在线测量。采用二阶低通滤波器对起伏的透射率信号分析,得到消光起伏频谱实验数据,并利用改进的Chahine循环方法计算得到颗粒的粒径分布和浓度信息。重点讨论高浓度情况,包括对特征函数频率响应的修正和对其阶高修正两个方面,得到修正参量并运用到反演算法中从而得到正确的测量结果。测量结果表明,通过高浓度修正,消光起伏频谱法可以在很大的颗粒浓度动态范围得到合理的测量结果,其可测颗粒最大体积分数视颗粒的大小而定。     

White-light Detection for Nanoparticle Sizing with the TSI Ultrafine Condensation Particle Counter

Several of the most common methods for measuring nanoparticle size distributions employ the ultrafine condensation particle counter (UCPC) for detection purposes. Among these methods, the pulse height analysis (PHA) technique, in which the optical response of the UCPC detector is related to initial particle diameter in the 3–10nm range, prevails in applications where fast sampling is required or for which concentrations of nanoparticles are frequently very low. With the PHA technique, white light is required for particle illumination in order to obtain a monotonic relationship between initial particle diameter and optical response (pulse height). However, the popular, commercially available TSI Model 3025A UCPC employs a laser for particle detection. Here, we report on a novel white-light detection system developed for the 3025A UCPC that involves minimal alteration to the instrument and preserves normal counting operation. Performance is illustrated with pulse height spectra produced by differential mobility analyzer (DMA) – generated calibration aerosols in the 3–50nm range.     

PM2.5质量浓度廓线的激光雷达反演研究

针对PM2.5质量浓度在空间不同高度上的分布测量较难这一问题,采用激光雷达和大气透射仪以及粒径谱仪进行联合探测,反演PM2.5质量浓度廓线.考虑相对湿度等因素的影响,通过大气透射仪和粒径谱仪建立地面PM2.5质量浓度与大气透过率之间的函数关系.以大气透射仪所测地面大气透过率值为基准,修正激光雷达大气透过率在高空的边界值,结合Fernald后向积分法反演出大气透过率的垂直分布.依据建立的函数关系和大气透过率垂直分布,得到PM2.5质量浓度廓线,并采用HYSPLIT后向轨迹分析不同高度层气溶胶的输送和动态变化.通过激光雷达、大气透射仪和粒径谱仪的联合探测实验,结果表明:经大气透射仪修正后,大气透过率垂直分布精度得到了提高,PM2.5质量浓度廓线很好的反映了气溶胶垂直分布的微物理变化特征.     

基于水动力学的水体组分垂直结构对遥感信号的影响

基于水动力模型和辐射传输模型,模拟不同风速条件下水体组分(浮游植物和悬浮颗粒物)垂直分布对遥感反射率的影响,对比分析现有的两种水体光学均一函数(Zaneveld权重函数和Gordon权重函数)在不同层化程度水体中的应用。结果表明,悬浮颗粒物垂直分布对500～650nm范围内的遥感反射率(Rrs)影响较大,随着参考深度悬浮颗粒物质量浓度增加(由5～70mg/L),悬浮颗粒物垂直分布对Rrs的影响不断减小(变异系数由27.46%减小到3.38%),同时Rrs受到悬浮颗粒物影响的最大波长位置向长波方向移动(由585nm逐渐移动到685nm);在浮游植物垂直分布影响下,400～725nm范围内的Rrs值随着风速的增加呈现先增加再逐渐减小趋势,400～450nm范围内的Rrs受浮游植物垂直分布影响较小,变异系数仅为1%;500～600nm范围内的Rrs受浮游植物垂直分布影响较大,最大变异系数可达27.18%。在水体组分层化较弱水体中,Zaneveld与Gordon权重函数对水体光学均一处理效果较为相似;但在水体组分层化较为严重的水体中,Zaneveld权重函数光学均一处理效果要好于Gordon权重函数。     

Localized subharmonic waves in a circularly vibrated granular bed

Localized period-doubling waves arise in circularly shaken granular beds contained in an annular channel. These solitary wave packets are accompanied by a locally increased particle density. The width and velocity of the granular wave pulse are measured as a function of the bed height. A continuum model for the material distribution, based on the measured granular transport velocity as a function of the bed thickness, captures the essence of the experimental findings.     

A proposed semiconductor laser pump-probe source

A model is presented which determines the output from a semiconductor laser as a function of the direct current (d.c.) and radio frequency (r.f.) current applied to the laser. It is shown that by adjusting these two components the output optical pulse from a laser can be shifted in time without change to the pulse shape or height. Experimental results are presented which support the model. It is suggested how these results can be used to produce a semiconductor pump-probe source, which is essential for the development of optical probing.     

用脉冲激光全息术测量喷雾场中粒子的分布和运动速度

本文叙述了用脉冲激光全息术测量喷雾场中粒子的分布和运动速度的原理，阐明了同轴全息和离轴全息在测量雾场的应用范围，重点讨论了离轴全息。测量光学系统是４Ｆ系统，它可以测量粒子浓度大的雾场中大于５μｍ的粒子分布和运动速度。在平行光场区段，可进行不同装置、不同景深的喷雾研究，使每个粒子具有相同的放大倍数，它给再现、数据处理、粒子大小的标定都有很大的好处。文中还分析了在底片上形成干涉的各种情况；粒子直径ｄ，远场数Ｎ和从底片到粒子的距离Ｚ的关系。给出脉冲间隔为５μｓ；１０μｓ粗度为±０．１μｓ时不同直径粒子的分布和运动速度在电视屏幕上显示出来的照片。在上述实验结果的基础上讨论了粒子的识别，噪音的消除等问题。     

基于多轴差分光学吸收光谱探测的北京春季气溶胶垂直廓线

气溶胶垂直廓线是评估污染物来源、输送等途径的必要手段。气溶胶污染对环境和人体健康带来直接的影响。该研究于2019年4-5月,利用中国科学院大气物理研究所（39.98°N,116.39°E）的地基多轴差分光学吸收光谱（MAX-DOAS）仪,对北京地区春季大气光谱垂直廓线进行了观测。凭借MAX-DOAS实时、在线、连续的观测优势,能有效的对气溶胶进行监测。MAX-DOAS基于最优估算法（OEM）以及最小二乘光谱拟合法,并以辐射传输模型SCIATRAN作为前向模型,利用海德堡廓线（HEIPRO）算法反演得到气溶胶消光系数的垂直廓线,通过对气溶胶消光系数在其路径的积分获得气溶胶光学厚度（AOD）。利用地基太阳光度计观测的AOD和高塔观测的颗粒物质量浓度垂直廓线,分别与MAX-DOAS观测的AOD和气溶胶消光系数垂直廓线进行对比,验证MAX-DOAS算法的适用性。研究结果表明,MAX-DOAS与太阳光度计观测AOD结果,相关系数为0.92,斜率为0.89。三层气溶胶消光系数与PM_2.5质量浓度的皮尔森相关系数从低处到高处分别达到0.69（60 m）,0.77（160 m）和0.75（280 m）。并且,将气溶胶平均消光系数和对应三层（60,160和280 m）的PM_2.5平均质量浓度对比,发现两者趋势一致。同样的,为了验证MAX-DOAS是否具备准确识别污染物的长距离输送的能力,我们通过Angstrom指数确定沙尘天气,通过计算梯度理查森数和边界层高度确定静稳天气,分析了在特殊天气条件下,MAX-DOAS能够对沙尘和静稳天气做出及时、准确的响应。分析气溶胶平均消光系数,发现气溶胶垂直廓线随高度升高呈现指数衰减变化的趋势,并且气溶胶消光系数均值在1.5 km高度处约为近地面的50%左右,而在1.5 km以上消光系数会随着高度的增加而快速减小。当高度达到2 km左右时,气溶胶消光系数均值下降到了0.1 km-1。以上结果表明MAX-DOAS探测大气气溶胶垂直廓线具有较高的适用性。     

炉顶凸起对6分离器CFB气固流动的影响

本文在6分离器CFB冷态试验台上,研究了炉顶凸起空间对气固流动的影响。利用差压法测量炉膛颗粒浓度轴向分布,采用光纤探针测量不同位置的颗粒浓度和速度的径向分布,通过积料法测量6分离器的颗粒循环流率。通过试验结果的分析,得到炉顶凸起空间内的颗粒运动特性,以及不同凸起高度时的炉膛环核流动特性和颗粒外循环特性。本文的研究对大型多分离器布置CFB锅炉的结构优化设计具有参考意义。     

空气击穿效应对粒子全息像的影响

 在粒子场全息实验中,研究了4F光学成像系统不抽真空时,其内部实焦点处由于光脉冲能量聚焦引起的空气击穿现象。发现在这种情况下得到的同轴和离轴全息粒子再现像,与实焦点未被击穿时得到的正常全息再现像相比,其强度分布发生了反转。理论分析表明,这种情况是由于实焦点处空气击穿引起的空间滤波效应造成的。研究发现:在离轴粒子场全息实验中,合理调整曝光强度,利用4F系统中的空气击穿效应可以获得高清晰度的全息再现象。     

水色要素垂直分布对其遥感反演算法精度的影响

基于辐射传输模型模拟得到叶绿素和悬浮颗粒物在不同垂直分布条件下的遥感反射率数据集,利用该数据集对现有叶绿素、悬浮颗粒物浓度和固有光学量模型进行检验,研究了垂直分布对遥感反演算法反演精度的影响。结果表明：在悬浮颗粒物垂直分布、叶绿素及其垂直分布的影响下,悬浮颗粒物波段比值模型高估的悬浮颗粒物浓度要大于单波段模型;叶绿素波段比值模型和三波段模型能够较好地降低由叶绿素垂直分布、悬浮颗粒物及其垂直分布引起的叶绿素浓度高估的程度。悬浮颗粒物和叶绿素及其垂直分布对固有光学量反演具有双重效应,悬浮颗粒物垂直分布将使得吸收系数和后向散射系数被高估,而叶绿素垂直分布将使得吸收系数和后向散射系数被低估。在悬浮颗粒物和叶绿素共同作用下,固有光学反演结果具有较大的不确定性。     

台风对沿海地区气溶胶光学特性的影响分析

利用CE317太阳辐射计对2005年第19号台风登陆前后期问(9月29 H至10月6日)进行观测实验,采用Langley法分析台风对中国大陆沿海地区气溶胶光学特性的影响.指出台风过后气溶胶光学特性明显发生改变,气溶胶大粒子数增多,小粒子数减小.气溶胶光学厚度、Angstr(o)m波长指数α和大气混浊度系数β为测量期间最低分别为0.132(550 nm处),0.861和0.079.同时利用实验期间APS3321空气动力学粒度仪分析的气溶胶单位体积数粗细质粒所占比重、气溶胶粒子尺度谱分布和实测的日际气溶胶粒子数浓度对实验分析结果.α,β进行对比,发现它们之间的一致性很好.     

Measurement of Solid-gas Two-phase Flow using Optical Fiber Sensor

ＭｅａｓｕｒｅｍｅｎｔｏｆＳｏｌｉｄ┐ｇａｓＴｗｏ┐ｐｈａｓｅＦｌｏｗｕｓｉｎｇＯｐｔｉｃａｌＦｉｂｅｒＳｅｎｓｏｒＦＡＮＨｕａＣＨＥＮＹｕａｎｄｉＴＡＮＹｕｓｈａｎ（ＩｎｓｔｉｔｕｔｅｏｆＬａｓｅｒ＆ＩｎｆｒａｒｅｄＡｐｐｌｉｃａｔｉｏｎｓｉｎＸｉ...     

Generating a quasiellipsoidal electron beam by 3D laser-pulse shaping

A generic 3D laser-pulse-shaping scheme is proposed towards the generation of a uniform ellipsoidal particle distribution, an ideal distribution due to the linear dependence of the space-charge force on the particle position. The shaping is accomplished via spatiotemporal coupling of the laser dynamics via chromatic aberration in an optical lens. Particle tracking simulations show that the electron beam initiated by such a laser pulse in a high-gradient radio-frequency photoinjector delivers very low emittance, ideal for beam-based light sources such as the x-ray free-electron laser.     

Theoretical study of the trapping efficiency of an optical tweezers array system

Optical tweezers have been a valuable research tool since their invention in the 1980s. One of the most important developments in optical tweezers in recent years is the creation of two-dimensional arrays of optical traps. In this paper, a method based on interference is discussed to form gradient laser fields, which may cause the spatial modulation of particle concentration. The parameters related to the optical tweezers array are discussed in detail and simulated by the Matlab software to show the influence of important parameters on the distribution of particle concentration. The spatial redistribution of particles in a laser interference field can also be predicted according to the theoretical analysis.     

Day-side auroral signatures based on simultaneous, coordinatedobservations at Svalbard and Greenland

The height distribution of the dayside cusp aurora and the relation between optical emissions and net downward electron energy flux are discussed. These two important characteristics of day-side cusp aurora are still unknown. It is instructive to compare particle flux and optical luminosity because these two quantities should be proportional if the cusp aurora is caused by electron impact, as has been found for nighttime aurora in the oval. Furthermore, there should then be a direct relation between auroral altitudes and particle energy. Based on coordinated auroral observations at Svalbard and Greenland, together with simultaneous, overhead F-9 satellite measurements, these quantities have been evaluated     

混沌信号在光纤传输过程中的非线性演化

对光纤混沌传输理论及混沌信号与光纤传输媒介相互作用的物理机制进行了理论研究. 通过耦合激光混沌系统和光纤传输信道，提出光纤混沌信号传输的非线性演化物理模型. 着重分析光纤自相位调制对激光混沌信号传输与演化的作用. 结果表明：自相位调制不影响混沌信号脉冲的形状，但能产生非线性相移使混沌信号频谱展宽；自相位调制不影响混沌信号脉冲的功率分布和场强分布，但能影响混沌信号脉冲的功率频谱分布，影响混沌信号光场以及慢变场的变化. 提出混沌信号在光纤传输中的非线性演化频率啁啾和形式，数值模拟了混沌信号在光纤传输过程中的相位、频谱、场以及场的慢变部分的相空间等演化形式和特点. 关键词： 混沌 光纤 传输 演化     

抛光颗粒尺度均匀性对射流去除特性的影响

基于单喷嘴射流抛光去除机理,研究了抛光颗粒尺度分布理想均匀时,颗粒直径和抛光液质量分数变化对冲击去除分布的影响。在此基础上,考虑到实际加工过程中,抛光粉颗粒不可避免地存在分布不均匀的情况,在非理想不均匀条件下,提出了一种分析颗粒尺度的材料去除特性模型,重点研究了不同颗粒尺度分布范围对材料去除特性的影响。结果表明:在理想状态下,冲击去除随着抛光颗粒直径的增大而减小,随着抛光液质量分数的增大而增大。当颗粒直径随机分布时,材料去除量将出现明显的波动,抛光液质量分数的增大使去除量波动也增加,去除量波动的大小与抛光粉颗粒的平均直径直接相关,且与理想均匀状态下的去除特性相比,颗粒分布不均匀性使得材料的去除量有所增大。