埋入式光纤法布里—珀罗温度和应变传感器模型研究

研究了埋入式内置和外置型法布里－珀罗光纤传感器模型，这一框蒋 传感器中应变和温度的变化同反射光强联系起来，其中；子模型Ⅰ建立了传感器内的温度与应变同传感器长度变化及传感器光学性质变化的函数关系；子模型Ⅱ建立了传感器长度和光学性质的变化同反射光强变化的函数关系。     

基于p偏振光双面反射的薄膜传感器光学参数的优化

ｐ偏振光在镀膜平板玻璃上、下表面反射光强比γ的角度调制曲线的性状与膜层光学参数密切相关。分析了γ与膜层折射率、消光系数及膜厚的相对梯度随光参数变化的着急为基于ｐ偏振光双面反射的薄膜传感器选择最佳参数提供了理论依据,计算表明该类型传感器对膜层折射率的测量分辨率高达１０＾－７。对不同工艺条件下得到的溶胶－凝胶ＳｎＯ２膜进行光学参数测定及初步气敏实验,结果表明ｐ偏振光双面反射可作为高灵敏度光化学传感器的     

纳米纤锌矿氮化硼的同步辐射真空紫外反射光谱与光学性质

对冲击波法合成的纳米纤锌矿氮化硼（ｗＢＮ）进行了同步辐射真空紫外区的反射光谱测量，得到波长范围１００一２４０ｎｍ区间的反射光谱．利用Ｋｒａｍｅｒｓ－Ｋｒｏｎｉｇ关系计算获得了它的光学常数和介电函数谱，并导出了光电导谱．获得了纳米ｗＢＮ的光学禁带宽度实验值，为８．７±０．５ｅＶ．将以上结果和最新的理论计算进行了比较．观察到了经不同退火温度处理的纳米ｗＢＮ样品结构及尺寸变化对反射光谱和光学性质的影响． 关键词：     

玻璃表面层光学参数分布的研究

利用并改进平板玻璃两面Ｐ偏振光反射光强比的测量来确定玻璃表面光学参数的方法，测量了平板玻璃两面Ｐ偏振光反射光强比γ与入射角θｉ的关系曲线，运用新的表面层模型进行数据模拟，获得了表面层的光学参数分布。     

带宽调制型单光纤光栅温变无补偿位移传感

报道了利用反射谱带宽调制和光强差分探测技术实现单一光纤光栅温变无补偿位移精确测量的新方法。设计了一种结构新颖的曲臂梁位移传感装置,结合光波导理论与材料力学原理分析了光纤光栅在高斯应变作用下光栅反射谱侧向梯度展宽的成因,理论推导了特殊结构梁在外力作用下光栅反射谱带宽/反射光强与压力之间的响应关系。光栅反射谱侧向梯度展宽的同时反射光强线性增加,利用光强差分检测方法消除光源出光抖动的影响,提高了位移测量精度。基于带宽调制的光纤光栅位移传感方法免受温度变化的影响,在-10℃~80℃的温度变化范围内,测量误差小于1.2%,实现了单光纤光栅温变无补偿位移测量。     

基于FBG反射谱特征的修补结构裂纹扩展监测

为了提高飞行器壁板裂纹修补结构的安全性,对基于光纤布拉格光栅(FBG)反射谱特征的航空铝合金修补结构疲劳裂纹扩展长度及角度监测方法进行了研究。修补结构在疲劳载荷的作用下,裂纹发生扩展,其尖端附近会产生不均匀应变场,在其作用下FBG传感器反射谱发生变形,通过检测反射谱变形达到监测裂纹扩展的目的。建立了实验样件的模型,使用有限元方法计算得到不同角度下裂纹扩展到不同长度时的应变分布,使用传输矩阵数值计算方法得到相应的FBG反射谱。提取反射谱的主峰偏移、反射谱面积、次峰峰值和三峰峰值等变形特征,建立并训练人工神经网络(ANN),通过ANN建立反射谱变形特征同裂纹扩展情况的关系,实现了对修补结构裂纹扩展的精确监测,监测裂纹长度误差在0.5 mm之内,角度误差在5°之内。解决了修补结构的裂纹扩展精确监测问题,对提高飞行器安全以及节约维护成本有着重要意义。     

Cd_xHg_(1-x)Te混晶的远红外反射光谱和多振子模型

在温度4.2—300K和波数15—450cm~(-1)范围内研究了x=0.18到0.45的不同组份的Cd_xHg_(1-x)Te样品的远红外反射光谱。实验观察到了类CdTe光学声子反射带的精细结构和低组份样品类HgTe反射带的复杂结构,研究了这些结构对组份和温度的关系,并用多振子模型讨论了反射光谱的这种精细结构。 对实验反射光谱用经典的振子匹配方法进行了拟合计算,并从这种拟合运算获得了Cd_(x~-)Hg_(1-x)Te的远红外介电函数谱及其它光学常数和频率的关系。     

小斜率近似在粗糙面激光散射BRDF计算中的应用

基于小斜率近似法建立了粗糙面激光散射双向反射分布函数的数学模型,采用该模型计算了粗糙度参量已知的合金铝样片的双向反射分布函数值,计算结果与实测结果吻合良好,验证了模型的正确性.研究了粗糙度参量和样片光学常量对双向反射分布函数的影响,结果表明,粗糙面激光散射的双向反射分布函数与表面高度起伏均方根、自相关长度及样片光学常量相关.当入射波长一定时,高度起伏均方根越大,或者自相关长度越小,粗糙面粗糙度越大,入射激光的漫反射特性越强,双向反射分布函数峰值越小且分布越分散;当粗糙度一定时,样片光学常量对双向反射分布函数影响较大,粗糙面对入射激光复折射率的虚部越大,样片双向反射分布函数的峰值越小,当粗糙度参量增大时,样片光学参量对双向反射分布函数的影响逐步减弱.     

保偏微结构光纤啁啾光栅折射率传感特性分析

将有限元法和传输矩阵法相结合,系统地研究了保偏微结构光纤(PM-MOF)啁啾布拉格光栅的折射率传感特性。仿真研究了光纤空气孔中充入不同折射率被测物时啁啾光栅的反射谱,结果表明随着被测物折射率的增加,反射谱的面积出现明显变化,由此得到了光栅反射谱面积与被测物折射率的关系。分析了中心孔直径、啁啾系数、切趾函数等光栅结构参数对反射谱的影响。分析表明由于光纤两个方向的偏振模对温度、噪声等干扰响应相似,因此利用两个偏振模式反射谱的相对变化进行监测能够有效地降低干扰,提高传感器的稳定性;其次,由于反射谱面积正比于光强,这一方法将光栅的光谱解调转化为光强解调,简化了解调系统,便于现场实时测量。研究结果为保偏微结构光纤光栅在折射率传感器及其生物传感器方面的应用提供了理论依据。     

光强检测型光纤光栅温变不敏感动态压力传感研究

报道了基于光纤光栅反射谱带宽调制和光强差分检测技术实现单一光纤光栅温变不敏感动态压力传感的新方法。设计了一种结构新颖的双孔梁压力传感装置,依据双孔梁有限元受力分析将光纤光栅准确定位于线性梯度应变区,压力作用下光纤光栅反射谱对称展宽,反射光强线性正比于压力变化。基于光波导理论和材料力学原理推导了线性梯度应变场作用下光栅反射谱带宽、反射光强与压力之间的响应关系。利用光强差分检测技术取代传统波长解调方法,简化解调过程的同时传感系统免受温变影响。实验表明,在-10~80℃的温度变化范围内,系统测量误差小于总量程(120kPa)的1.8%,动态响应速度约80Hz,重复测量系统输出稳定,具有较好的应用价值。     

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.