用频域法实现圆环形目标物的计数

研究了用频域法实现圆环形目标物计数的方法。对空域中含有圆环形目标物的二值图像，经傅里叶变换后在频域内进行滤波，再经傅里叶反变换后取一阈值进行处理，则对应于圆环形目标物即变为一个实心体，然后对实心体进行计数即可实现对圆环形目标物的计数。对该方法进行了数学描述，并分别用模拟图像和实际图像进行了实验。结果表明，该方法消除噪声的效果好，对部分封闭圆的检测同样有效，且可用于目标物有粘连的情况。该方法对圆环形目标物的尺寸相差不大的情况更为有效。     

Synthesis and optoelectronic properties of silole‐containing polyfluorenes with binary structures

2,5‐Bis(2‐bromofluorene‐7‐yl)silole was prepared by a modified one‐pot synthesis with a reverse addition procedure, from which novel silole‐containing polyfluorenes with binary random and alternating structures (silole contents between 4.5 and 25% and high M_w up to 509 kDa were successfully synthesized. The well‐defined repeating unit of the alternating copolymer comprises a terfluorene and a silole ring. Optoelectronic properties including UV absorption, electrochemistry, photoluminescence (PL), and electroluminescence (EL) of the copolymers were examined. The different excitation energy transfers from fluorene to silole of the copolymers in solution and in the solid state were compared. The films of the copolymers showed silole‐dominant green emissions with high absolute PL quantum yields up to 83%. EL devices of the copolymers with a configuration of ITO/PEDOT/copolymer/Ba/Al displayed exclusive silole emissions peaked at around 543 nm and the highest EL efficiency was achieved with the alternating copolymer. Using the alternating copolymer and poly(9,9‐dioctylfluorene) as the blend‐type emissive layer, a maximum external quantum efficiency of 1.99% (four times to that of the neat film) was realized, which was a high efficiency so far reported for silole‐containing polymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 756–767, 2007     

On Two Parallel Matched Gratings Demodulation Method of Fiber Grating Strain Sensor

The method of demodulation with two parallel matched fiber Bragg gratings( FBGs)system is introduced to enlarge the range of strain that can be detected by the FBG sensor system.     

La掺杂浓度对PLZT薄膜红外光学性质的影响

采用溶胶-凝胶法在Pt/Ti/SiO2/Si衬底上制备了不同La掺杂浓度PLZT(x/40/60)薄膜- x射线衍射分析表明制备的PLZT(x/40/60)薄膜是具有单一钙钛矿结构的多晶薄膜- 通过红外椭圆偏振光谱仪测量了波长为2-5—12-6μm范围内PLZT薄膜的椭偏光谱，采用经典色 散模型拟合获得PLZT薄膜的红外光学常数，同时也拟合获得PLZT薄膜的厚度- 随着La掺杂浓 度的增大，折射率逐渐减小- 而消光系数除PLZT(4/40/60)薄膜外，呈现逐渐增大的趋势- 分析表明这些差异主要与PLZ 关键词： PLZT薄膜 红外光学性质 红外椭圆偏振光谱     

Simplified analytic solutions and a novel fast algorithm for Yb-doped double-clad fiber lasers

In this paper, continuous wave Yb³⁺-doped double-clad fiber lasers (DCFLs) with linear-cavity are investigated theoretically and numerically using the rate equations. Under the steady state conditions, the simplified analytic solutions of Yb³⁺-doped DCFLs under considering the scattering loss are deduced in the strongly pump condition. Compared with the known analytic solutions in published literatures, our analytic solutions are more accurate, especially, at higher reflectivity of output mirror. In addition, a fast and stable algorithm based on the Newton-Raphson method is proposed to simulate numerically Yb³⁺-doped DCFLs. The results by simplified analytic solutions are in good agreement with those by the numerical simulation. Moreover, we have performed the optimization of an Yb³⁺-doped DCFL using the simplified analytic solutions and the numerical simulations, respectively.     

An approximate solution to the integral radiative transfer equation in an optically thick slab

We consider the problem of solving the integral form of the radiative transfer equation in an atmosphere with optical thickness τ₀?1. We propose two methods transforming this problem to a finite set of the independent problems of the same type set in an atmosphere with optical thickness much less then τ₀. The error estimates are derived. Copyright © 2007 John Wiley & Sons, Ltd.     

ZnSe/SiO2复合薄膜光学常数与荧光光谱的研究

采用溶胶-凝胶工艺与原位生长技术，制备了ZnSe/SiO₂复合薄膜.X射线衍射分 析表明薄膜中ZnSe晶体呈立方闪锌矿结构.X射线荧光分析结果显示薄膜中Zn与Se摩尔比为1 ∶1.01—1∶1.19.利用场发射扫描电子显微镜观察了复合薄膜的表面形貌，结果表明复合薄 膜表面既存在尺寸约为400nm的ZnSe晶粒，也存在尺寸小于100nm的ZnSe晶粒.利用椭偏仪测 量了薄膜椭偏角Ψ，Δ与波长λ的关系，采用Maxwell-Garnett有效介质理论对薄膜的光学 常数、厚度、气孔率、ZnS 关键词： 2复合薄膜')" href="#">ZnSe/SiO₂复合薄膜 光学性质 椭偏光度法 荧光光谱     

Optical bistability of planar metal/dielectric nonlinear nanostructures

We study theoretically a nonlinear response of the planar metal/dielectric nanostructures constituted from periodical array of ultra thin silver layers and the layers of Kerr-like nonlinear dielectric. We predict hysteresis-type dependences of the components of the tensor of effective dielectric permittivity on the field intensity allowing the change in material transmission properties from transparent to opaque and back at extremely low intensities of the light. It makes possible to control the light by light in all-optical nanoscale devices and circuits.     

拖曳线列阵用光纤水听器的研究

报道了光纤水听器用于拖曳线列阵的研究结果。在保证光纤水听器声相位灵敏度的前提下, 优化设计了光纤水听器的结构,降低了光纤水听器的加速度灵敏度36dB。实验测得在20-1600Hz 频段,该光纤水听器的相位灵敏度为-162．7dB,频段内灵敏度的起伏为±0．7dB,加速度灵敏度小于-30dB。     

掺铒光纤放大器中上转换过程的影响

掺杂浓度的提高影响了掺铒光纤放大器(EDFA)的性能,对经典Giles模型提出了新的要求。首先研究了高掺杂下铒离子距离较小引起的上转换过程的机理,通过优化速率方程模型分析了上转换过程对EDFA的影响,得出了在泵浦光和信号光远远大于ASE光的假设下泵浦光和信号光沿光纤长度变化的近似表达式,并将该近似分析解与解析解进行了比较。仿真结果表明上转换过程会降低随光纤传输的信号光和泵浦光,影响EDFA的放大性能,并得出了当掺铒浓度大于2.95×1025m-3时,上转换过程的影响不能忽略的结论。