具有特定光强分布的激光表面硬化技术

利用光束变换技术得到不同光斑形状和不同强度分布的光束,可满足表面硬化所需要的硬化层均匀性等要求.激光硬化在材料表面产生的实际效果与光强分布密切相关,利用特定光强分布的光束进行激光硬化可以得到所需要的温度场及组织分布,直接影响材料表面硬化的效果.对高斯光束圆光束、平顶矩形光束、曲边矩形光束、点阵光斑等不同强度分布的激光表面硬化(LSH)技术进行了介绍.硬化层特定的硬度分布及组织结构等硬化效果是特定光强分布激光束与材料相互作用的结果,要获得所需硬化效果,则需要利用反求方法设计与硬化效果相对应的特定光强分布的光斑.给出了特定光强分布的激光表面硬化技术的发展趋势.     

激光辐照皮肤组织模拟液的光子传输实验研究

通过实验测定了皮肤组织模拟液在632.8nm连续氦氖激光辐照下透射光场的光强分布,重点研究了模拟液浓度和容器厚度对光分布的影响.研究结果表明:皮肤组织模拟液透射光强与溶液浓度以及厚度密切相关;组织对激光的吸收和散射作用使得光强度下降;透射光强最高点在辐照中心处,并沿着径向衰减.     

多模光纤出射光束光强分布的研究

采用横向偏移法测量以LED为激励源的多模光纤纤芯截面光强分布和出射光束的传输特性，将光强分布从近距光强分布和远距光强分布两方面进行讨论，比较分析了理论曲线与实验曲线，指出LED作为光源的多模光纤光强分布非常有利于光耦合，并可通过测量多模光纤光强分布得到光纤数值孔径的大小。     

近红外光子在三维膝关节中传输的Monte Carlo模拟

提出一种检测早期膝骨性关节炎(ROA,knee osteoa rthritis)的方法。首 先建立光子在膝关节组织中的传输模型,利用蒙特卡洛(MC,monte carlo)方法模拟近红外光 子 在三维膝关节组织中的传输;在实验中,改变膝关节模型中软骨的 吸收系数和散 射系数,记录光子在膝关节表面的光强分布。结果表明,溢出膝关节表面的光子包括未碰撞 骨头组织直接 溢出的噪音光子和撞击骨头组织后溢出的有意义光子,吸收系数和散射系数的改变会导致膝 关节表面光强 分布发生变化,因此可通过膝关节表面光强分布变化判断膝关节的早期病变。     

光强均匀度与标准粒子信号分布关系研究

为了研究光敏区光强分布对粒子计数器标准粒子信号分布的影响,从理论上分析了光敏区光强概率分布和标准粒子信号幅度概率分布之间的关系,并建立了能统一描述光敏区光强分布均匀度和信号幅度分布均匀度的数学模型,此模型定量分析了光敏区光强均匀度对信号分布曲线的影响,同时也揭示了长期制约国产粒子计数器分辨能力的本质因素,并给出了实验验证.理论和实验结果表明,光敏区光强分布的不均匀性是影响计数器分辨能力的主要因素.     

激光辐照皮肤组织的光子传输解析计算研究

建立了激光与皮肤组织相互作用的二维非稳态光场模型,在柱坐标系下采用漫射近似法和格林函数法精确求解了高斯和平顶分布的连续激光辐照皮肤组织的光传输方程,得到瞬态光场分布,并以氦氖激光辐照皮肤组织为例,数值模拟了皮肤组织在激光作用下的光分布。研究结果表明：皮肤组织径向光分布规律与入射激光束的光强分布相似,激光与组织光效应在很大程度上取决于激光参数,主要有激光功率、焦斑半径等。     

一种测量激光光强按角度分布的新方法

提出了一种新的测量方法,用于测量近似点光源或线光源在相同半径处光强按角度的分布.测量系统由旋转装置、角度探测系统和光强探测系统三部分组成.利用该系统对多模光纤耦合激光器光强分布进行了实际测量.结果表明,采用高斯光束形式可以较好地描述该光束光强的远场分布,由拟合曲线得出的光强按角度分布规律与实验所用光纤数值孔径相符,进一步说明了该实验方法的可信性与可靠性.     

部分相干光束的聚焦特性

基于部分相干光的传输方程,研究了光强为高斯分布、空间相干度函数为零阶贝塞耳函数的部分相干光束的聚焦特性。研究结果表明,在几何焦点附近的光强分布不仅依赖于入射的部分相干光束的光强分布,而且还依赖于部分相干光束的空间相干度。当空间相干长度、焦距等参数取某些特定值时几何焦点附近的光强分布将出现平顶光束的分布形式;另外,当空间相干长度取值改变时几何焦点附近的光强分布将出现局域空心光束的分布形式。基于此,可以通过改变部分相干光束的空间相干度来实现对几何焦点附近光强分布的控制,从而获得需要的光强分布。     

高功率激光阵列探测器中光强分布复原方法

根据激光大气传输特性及衍射理论,提出一种对阵列探测器中相邻探测单元测量值之间进行插值的新方法——"高斯"插值法,并且对该方法获得的远场光强分布与"马赛克"及"线性"插值方法获得的光强分布进行了比较。结果表明:当焦平面处83.9%和63.2%环围能量半径上具有相同的探测单元时,"高斯"插值方法比其他两种方法复原的光强分布更为接近原始光斑的光强分布,其中"马赛克"方法复原的光强分布与原始的光强分布相比偏差较大。另外,从光斑大小考虑,"高斯"插值法也能够较好地复原出远场的空间光强分布。     

基于相位调制的激光多元相干阵列的远场光强分布研究

根据Fraunhofer衍射理论,建立了基于相位调制的二维M×N激光相干阵列的远场光强分布理论模型。结合应用实际,对5×5激光相干阵列的远场光强分布进行数值模拟,分析了不同调制相位对远场光强分布的影响。结果表明,远场光强分布的主极大(小)的位置随调制相位变化,相对强度也随之变化;不同阵列结构,光强分布不同,每列(行)相邻两阵元上加载的相位差为π时,出现较多的主极大和次极大且对称分布。这些结果可为应用相位调制去控制远场光强分布提供有益的参考。     

有限宽光束在生物组织中的传播

用ＭｏｎｔｅＣａｒｌｏ方法讨论了有限宽光束在生物组织中的传播,模拟了当无限细光束入射、高斯光束及平面圆光束入射到生物组织时的漫反射率及漫透射率等。模拟了有限宽光束在多层生物组织中的传播。     

近红外光谱范围生物组织表面漫反射率的研究

首先分析了近红外光在均匀生物组织中的传播过程，在此基础上提出一种计算分层生物组织表面漫反射率的理论模型。利用这种理论模型，讨论了两种不同组成的生物组织的表面漫反射率，得到双层介质表面漫反射率随探测距离的变化趋势与其他文献报道的研究结果一致。     

Directed emissive high efficient white transparent organic light emitting diodes with double layered capping layers

We report on white transparent organic light emitting diode (TOLED) with double layered capping layer (CL), 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) and ZnSe. By introducing the double layered CL, total efficiency was improved by 27% to have 90% of that of conventional bottom-emissive device. The achievement of highly improved efficiency was interpreted as the synergetic effect of constructive interference and maximized reflectance of CL. By adjusting the reflectance of the CL, it was possible to choose the emissions direction selectively and achieve spectral matching between top and bottom emissions as well as enhanced total efficiency in white TOLED.     

Inorganic Drug‐Delivery Nanovehicle Conjugated with Cancer‐Cell‐Specific Ligand

The surface of layered double hydroxide nanoparticles, a potential drug‐delivery nanovehicle, is modified with the cancer‐cell‐specific ligand, folic acid. The surface modification is successfully accomplished through step‐by‐step coupling reactions with aminopropyltriethoxysilane and 1‐ethyl‐3‐(3‐dimethyl aminopropyl)‐carbodiimide. In order to evaluate the cancer‐cell targeting effect of folic‐acid‐grafted layered double hydroxide utilizing fluorescence‐related assay, both layered double hydroxide with and without folic acid moiety are labeled with fluorescein 5′‐isothiocyanate. The uptake of layered double hydroxide and folic acid conjugated into KB and A549 cells is visualized using fluorescence microscopy and measured by flow cytometry. Both chemical and biological assay results demonstrate that the folic acid molecules are indeed conjugated to the surface of layered double hydroxide and thus the selectivity of nanovehicles to cancer cells overexpressing folate receptors increases. In this study, it is suggested that layered double hydroxide nanoparticles can be used as drug‐delivery carriers with a targeting function due to the chemical conjugation with specific ligand.     

Performance evaluation on a double‐layered satellite network

How to evaluate the performance of satellite networks is a prerequisite to the construction of satellite networks, and is also one of challenges in the researches on satellite networks. In this paper, generalized stochastic Petri net (GSPN) models are presented to carry out the performance analysis of a double‐layered satellite network. Firstly, the GSPN model of a double‐layered satellite network is simplified by proper analysis. Then, two sets of experiments are conducted to analyse the performance of the satellite networks, and show that the double‐layered satellite network outperforms single‐layered ones on the heavy traffic load. Finally, the feasibility and effectiveness of the proposed approach is verified by simulation experiments. Copyright © 2005 John Wiley & Sons, Ltd.     

双层费涅尔区板透镜的焦区场

采用改进的全波分析方法，分析了双层费涅尔区板透镜在平面波入射下的焦区场的分布，计算结果与文献的实验结果相符，进一步检出了平面波正投射与斜投射于单层ＦＺＰ透镜，双层ＦＺＰ透镜，双层ＦＺＰ透镜含不同介质层时，焦区场分布的计算结果，由此得出的结论为该类天线的设计提供一理论依据。     

Asynchronous Layered Modulation for High Spectral Efficiency Transmission with Lower Sensitivity to Phase Errors

In this paper, an asynchronous double layered modulation scheme is proposed to achieve high spectral efficiency transmission but has lower sensitivity to phase errors. By intentionally introducing a delay offset to the transmitted signals at each layer, the asynchronous double layered format can use lower level quadrature amplitude modulation (QAM) to achieve the same spectral efficiency as the conventional high level QAM modulation. The error probability performance of the asynchronous double layered format is analyzed in the presence of phase errors and the symbol error rate and the bit error rate are derived in the closed-form expression. Both the theoretical analysis and the simulation results show that the asynchronous layered format can achieve the same spectral efficiency as the conventional high level QAM modulation while has lower sensitivity to the phase errors.     

用于生物组织电特性重建的探头研究

对适用于分层生物组织电特性重建的宽带同轴贴片探头进行了研究.采用时域有限差分(FDTD)法分析了同轴贴片探头在三层生物组织中的场分布,结合遗传算法(GA)优化了探头的尺寸.优化设计出的圆形同轴贴片探头具有轴对称特点,辐射近场在生物组织中透入深、分布集中,反射系数的频率响应特性好,适用于局部分层生物组织电特性的重建,实验证明探头的设计优化是正确的.     

Size‐Dependent Optical Absorption of Layered MoS2 and DNA Oligonucleotides Induced Dispersion Behavior for Label‐Free Detection of Single‐Nucleotide Polymorphism

Size‐dependent optical absorption of semiconductive (2H) layered molybdenum disulfide (MoS₂), exhibiting great discrimination abilities to single‐ and double‐stranded DNA (ssDNA) and (dsDNA), is studied. In the presence of high concentration of salt, layered MoS₂ trends to aggregate rapidly, leading to the increases of sizes in both vertical and lateral dimensions of the nanosheets, which results from the interplay between van der Waals attraction and electrical double‐layer repulsion. Meanwhile, the aggregation behavior of layered MoS₂ is remarkably inhibited by the synergistic effects of DNA oligonucleotides. ssDNA can adsorb on the surface of layered MoS₂, resulting in a great dispersion, even in the presence of high concentration of salt, while the dispersion behavior is weakened when ssDNA is replaced by dsDNA. Whereas compared to graphene with zero bandgap energy, layered MoS₂, with semiconductive properties, exhibits great characteristic optical absorption in visible wavelength region devoted to exploring the aggregation behavior of layered MoS₂. Therefore, DNA oligonucleotides induced size control of layered MoS₂, contributing to the regular change of its characteristic absorption in visible region, is considered a label‐free bioassay for the detection of single‐nucleotide polymorphism. Due to its easy operation and high specificity, it is expected that the proposed assay holds great promise for further applications.     

Performance enhancement of multicrystalline silicon solar cells and modules using double‐layered SiNx:H antireflection coatings

Silicon nitride coating deposited by the plasma‐enhanced chemical vapor deposition method is the most widely used antireflection coating for crystalline silicon solar cells. In this work, we employed double‐layered silicon nitride coating consisting of a top layer with a lower refractive index and a bottom layer (contacting the silicon wafer) with a higher refractive index for multicrystalline silicon solar cells. An optimization procedure was presented for maximizing the photovoltaic performance of the encapsulated solar cells or modules. The dependence of their photovoltaic properties on the thickness of silicon nitride coatings was carefully analyzed. Desirable thicknesses of the individual silicon nitride layers for the double‐layered coatings were calculated. In order to get statistical conclusions, we fabricated a large number of multicrystalline silicon solar cells using the standard production line for both the double‐layered and single‐layered antireflection coating types. On the cell level, the double‐layered silicon nitride antireflection coating resulted in an increase of 0.21%, absolute for the average conversion efficiency, and 1.8 mV and 0.11 mA/cm² for the average open‐circuit voltage and short‐circuit current density, respectively. On the module level, the cell to module power transfer factor was analyzed, and it was demonstrated that the double‐layered silicon nitride antireflection coating provided a consistent enhancement in the photovoltaic performance for multicrystalline silicon solar cell modules than the single‐layered silicon nitride coating. Copyright © 2015 John Wiley & Sons, Ltd.