光散射聚集速率测定中T矩阵方法的应用

聚集速率是评估胶体体系特性及稳定性的关键参数, 静态光散射和动态光散射则是测量聚集速率的两个重要方法. 然而, 用静态光散射和动态光散射测量聚集速率时, 需要知道有关单粒子和双粒子聚集体光散射特性的数据. 为此, 通常需要把动、静两种方法结合, 才能消去这个数据. 以前各种近似理论曾用来解决这个问题, 但因粒子尺寸和形状的限制, 结果并不理想. 而T矩阵方法可以不受粒子大小和形状的限制计算其光散射特性. 本工作用T矩阵方法直接计算静态光散射和动态光散射所必须的粒子散射特性, 并将该法得到的聚集速率与动静态光散射结合法得到的聚集速率进行了比较, 两者结果很接近. 本工作为简化静态光散射和动态光散射测量聚集速率, 扩展其应用范围开辟了新途径. 关键词： T矩阵')" href="#">T矩阵 光散射法 聚集速率     

基于反常衍射的红细胞变形研究及蒙特卡罗仿真

用反常衍射理论分析了人体血液中静态红细胞和在剪切力作用下变形为椭球形红细胞的前向光散射特点,建立等体积/等表面积（V/S）光散射模型,采用蒙特卡罗法对稀悬浮液中静态和变形红细胞的光散射过程进行仿真,并计算出红细胞的变形度及三轴参数.结果表明,该理论下进行的细胞光散射分析精度与夫朗和费衍射理论相比可提高约一倍.     

一种动-静态光散射颗粒折射率测量法

提出一种动静态光散射颗粒折射率测量方法.该方法分为三部分,一部分是用动态光散射技术测得颗粒样品的线宽分布函数,然后将此线宽分布连同一组折射率值代入静态光散射公式推算出不同折射率值下的散射光强空间分布;第二部分是用光电探测器测出实际的散射光空间分布;第三部分是将不同折射率下的推算值与实测值做均方偏差运算以做比较,取均方偏差最小时所对应的代入折射率值作为颗粒折射率的最终测量值.此方法对样品的分散度无要求,适用于微米到亚微米级的颗粒物.     

Ag-ZnO混合薄膜在聚合物太阳能电池中的应用

采用旋涂法研制了Ag浆SC100-ZnO混合薄膜,系统研究了不同混合比例SC100∶ZnO薄膜作为电子传输层或光散射层对聚合物太阳能电池器件性能的影响,并讨论了其中存在的物理机制。研究发现,采用少量SC100(1%和2.5%)混合的薄膜作为光散射层,可以提高器件的性能参数(短路电流密度和填充因子),器件的光电转换效率分别提高了4.4%和5%。     

光子计数模式下的目标探测与成像

 当光微弱到以单个光子发射时,成像系统只有利用光子计数模式才能探测到单光子信息。采用基于碰撞电离效应的全固态雪崩光电二极管作为探测元件,构成微光环境下的光子计数成像实验系统。该系统的硬件主要由雪崩光电二极管构成的单光子计数器、计算机、微光照度计、2维电控导轨、控制器、暗箱等组成。控制器的软件在Altera公司Quartus环境下设计,主要完成导轨运动的控制;上位机软件采用VC++编程实现系统的数据采集处理、系统功能控制和光子计数图像显示等。该系统为全固态结构,工作电压小于35 V,暗计数率小于4 Hz。所建光子计数成像系统在10－5 lx微光环境下实现了目标的探测成像。     

Nd：YAG固体脉冲激光器实验研究

介绍了Nd：YAG固体脉冲激光器相关的实验项目：静态和调Q状态的出光阈值、激光脉宽、倍频和激光光束形状等.采用普通相纸、红外相纸和激光能量计检测出不同的激光器静态和调Q出光阈值;采用散射、反射和透射方法研究了静态和调Q输出激光脉冲的宽度,发现用K9玻璃和多层膜镜测试的激光脉冲宽度比散射方法的大;采用激光能量计测试激光器静态和调Q的倍频效率和倍频激光能量与倍频晶体的位置关系;激光光束探测器表征激光器静态和调Q输出光的光斑形状.通过这些实验项目,学生将深入了解和掌握固体脉冲激光器的工作原理、性能参数,以及表征激光器性能参数的仪器设备,并深入地研究解决实验发现的问题,为今后激光相关领域的工作奠定坚实的基础.     

自由空间无衍射光通信模拟系统及其传输性能

无衍射光的中心光斑直径相对于高斯光束较小且发散角为零,在自由空间光通信领域具有良好的应用前景。介绍了一种自由空间无衍射光通信模拟实验系统,它通过串口连接上位机,应用微处理器进行信号的调制与解调,采用双头脉冲间隔调制,无衍射光的发生使用圆锥透镜法,在接收端使用PIN光电二极管将光信号转换为电信号,再经过放大电路、整形电路和微处理器的解调,最后通过串口将数据传输给上位机。上位机通过对发送数据与接收数据的对比计算出误码率,进而给出整个系统的传输性能评价。在无衍射光的最大传输距离内,当比特率为9 600 bps时,该系统的误码率优于610-5。     

基于STM32的汽车涂装线监控系统研究与实现

针对现有汽车电泳涂装线监控系统普遍存在信息采集不全面、分析处理时间长、共享程度低等问题,研究开发了基于STM32的涂装线设备状态监控系统。该系统采用高性能的STM32处理器,结合通用性好易开发的VC 6.0平台自主开发系统上位机软件,完成对设备数据的采集、处理分析及在线显示。首先,构建基于数据采集、中央处理、设备控制及通信的下位机硬件系统;然后,通过RS485总线技术实现各采集模块与中央处理模块的通讯,并通过串口及时将设备参数上传到上位机,实现涂装线设备的实时监控。     

基于光散射的火灾烟雾粒子激光图像探测技术研究

本文结合火灾探测领域的特点,分析了火灾烟雾粒子的光散射特性。通过与其他类型的光电感烟火灾烟雾探测技术的比较,阐述了基于光散射的火灾烟雾粒子激光图像探测技术的原理、特点和技术优势。     

α-LiIO3单晶中离子输运引起的高强度准弹性光散射

激光束通过加c向直流电压的α-LiIO₃单晶时,发生三种准弹性散射:散射光电位移矢量有特定取向且与入射光电位移矢量方向不一致者,散射光电位移矢量与入射光电位移矢量方向相同而散射带垂直c轴者以及散射光电位移矢量与入射光电位移矢量方向相同而散射带对c轴倾斜者,本文详细研究了这三种散射的空间频谱、精细结构、结构敏感性、弛豫规律以及光散射和晶体内电流密度与局部电场的关系,发现光散射发生于晶体内电流密度较大的区域,本文对三种散射的起因给予了说明:离子导体在直流电压作用下空间电荷的分布和运动引起 关键词：     

Self-organization of five species in a cyclic competition game

Cyclic competition game models, particularly the “rock–paper–scissors” model, play important roles in exploring the problem of multi-species coexistence in spatially ecological systems. We propose an extended “rock–paper–scissors” game to model cyclic interactions among five species, and find that two of the five can coexistent when biodiversity disappears, which is different from the “rock–paper–scissors” game. As the number of fingers is five, we named the new model the “fingers” game, where the thumb, forefinger, middle finger, ring finger, and little finger cyclically dominate their subsequent species and are dominated by their former species. We investigate the “fingers” model in two ways: direct simulations and nonlinear partial differential equations. An important finding is that the number of species in a cyclic competition game has an influence on the emergence of biodiversity. To be specific, the “rock–paper–scissors” model is in favor of maintaining biodiversity in comparison with the “fingers” model when the variables (population size, reproduction rate, selection rate, and migration rate) are the same. It is also shown that the mobility and reproduction rate can promote or jeopardize biodiversity.     

Contrastive analysis on tone between Putonghua and Taiwan Mandarin

The differences of the pitch and duration of Chinese syllables between Putonghua （PTH） and Taiwan Mandarin （TM） were studied. The speech materials to be used are not only isolated syllables, but also sentences. The results reveal that： For the isolated syllables, T1 and T2 in TM are influenced by Minnan dialect, therefore their pitch are lower than those in PTH. T3 is fall-rise in PTH, while it is fall in TM. Moreover, the syllable duration sequence for different tone is T3〉T2〉T1〉T4 in PTH, while it is T1〉T2〉T3〉T4 in TM. For the syllables in sentences, T2 is mid-rise in PTH, while it is mid-level in TM. And the T3 is longer than T4 but shorter than T1 or T2 in PTH, while it is the shortest in TM. Furthermore the effects of prosodic phrase boundary on duration for different tones are almost the same in PTH, but the lengthening part of T1 or T2 is longer than that of T3 or T4 in TM.     

Experimental study on downstep in Chinese intonation

Downstep in pitch contour of Chinese Putonghua is examined using subtly designed sentences by controlling tone combinations. The results show both automatic and nonautomatic downstep phenomena exist in Chinese. In non-automatic downstep, low tones compress downwards the pitch range of the following syllables. and the main influence of downstep is on topline. Low tone not only lower the topline behind it, but also raise the high tones before it, the effects are compatible with each other. In automatic downstep, the topline of pitch contour in intonational phrase is presented as a linear downtrend, but it differs among speakers due to the effect of personal stress practice. In comparison with downstep phenomenon in other tone or non-tone languages, the downstep ratio in Chinese is not constant, and the domain of downstep is not limited within the adjacent tones.     

Abelian-Higgs phase of SU(2) QCD and glueball energy

It is shown that SU(2) QCD admits an dual Abelian-Higgs phase, with a Higgs vacuum of a type-Ⅱ superconductor. This is done by using a connection decomposition for the gluon field and the random-direction approximation. Using a bag picture with soft wall, we presented a calculational procedure for the glueball energy based on the recent proof for wall-vortices [Nucl. Phys. B 741(2006)1].     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Signal generation in an isotropic medium in scanning electron acoustic microscope

Based on the research in Ref. [5][Materials Science and Engineering, 1989; A122： 57 63], an improved model of heat source is set up, the different modes of Lamb wave in an isotropic sample generated by a chopped electron beam at frequency f are obtained with integral transform and normal function expansion method, and the output signal of PZT coupled at the back surface of the sample is found out. The generation mechanism of SEAM （Scanning Electron Acoustic Microscopy） signal is discussed. It shows that the SEAM is a near field imaging technique with high spatial resolution and its best lateral spatial resolution is about 2√2α （α is the radius of the focused electron beam）. Some of experimental results of SEAM images are presented in the paper and it shows that the spatial resolution of SEAM is better than 0.5 μm and smaller than the thermal diffusion length of the sample. Therefore the character of near field imaging in SEAM is also proved experimentally.     

High efficiency filtering using two-dimensional photonic crystal coupled cavity structures

Transmission spectra of coupled cavity structures (CCSs) in two-dimensional (2D) photonic crystals (PCs) are investigated using a coupled mode theory, and an optical filter based on CCS is proposed. The performance of the filter is investigated using finite-difference time-domain (FDTD) method, and the results show that within a very short coupling distance of about 3λ, where λ is the wavelength of signal in vacuum, the incident signals with different frequencies are separated into different channels with a contrast ratio of 20 dB. The advantages of this kind of filter are small size and easily tunable operation frequencies.