Computer Controlled AAS Scanning Method to Study Flame Atomization Processes

By slightly changing the optical and burner systems of the conventional atomic absorption spectrometer, a computer controlled scanning method has been developed, which enables us to get a picture of absorbance distribution over the entire cross section of the analytical flames quickly, reproducibly and in high resolution. The plotting of different distribution functions obtainable by computerized data processing and the conclusions drawn from them are illustrated with some examples of flame atomization of cobalt and magnesium salts. The newly discovered method, by its reliability and little demand on time, allows the extension of the general applicability of AAS in revealing analytical interference effects and in the study of flame-chemical processes.     

Resolution improvement for enhancing interference fringes of digital holograms with near infrared illuminance

A new resolution improving method of enhancing the interference stripes, which can achieve better reconstruction of the recorded object of infrared digital holography has been proposed in this paper. The experiment is conducted under near infrared illuminance. We create poor quality holograms with very low-resolution interference stripes and enhance it with our new method. The processed holograms have much higher-resolution interference stripes. This method is based on interpolation theory, and we make it works fast, stable and easy to apply. Both the forward and backward interpolation of the oriental and portrait direction of the source pixels have been calculated, and have been used to realize the final aim of resolution improvement. During the experiment, since the responsivity of the CCD is not satisfied with the illuminance laser, which is by design, we also give specific analysis on the experimental setup of our work to make sure the object information can be fully recorded by the optical setup but cannot be reconstructed because of the low-resolution and unobvious of the interference stripes. After the resolution improvement process of the original hologram, the object information can then be fully reconstructed, which is very clear in the paper. Figures and dataflow give evidence and demonstrate the good performance of our method.     

Cluster speckle structures through multiple apertures forming a closed curve

In this work, cluster-like speckle patterns are analyzed. These patterns are generated when a diffuser illuminated by coherent light is imaged by a lens having a pupil mask with multiple apertures forming a closed curve. We show that the cluster structure results from the complex modulation produced inside each speckle which is generated by multiple interferences of light through the apertures. In particular, when the apertures are uniformly distributed along a closed curve, the resulting image speckle cluster replicates the pupil aperture distribution. Experimental results and theoretical simulations show that cluster features depend on the apertures distribution and the size of the closed curves.     

基于非同步替代光谱定标的地表下垫面影响分析

对760nm附近的氧气吸收带,选用植被、枯萎植被、人工地物、沙地和雪地五种典型地表类型,基于模拟数据进行非同步替代光谱定标方法的误差分析,比较不同地表类型得到的光谱定标准确度,为高光谱成像仪的非同步替代光谱定标提供定标图像选择策略.结果表明:运用两种光谱匹配方法——光谱角度匹配和欧氏距离法得到的定标误差基本一致;730~800nm的地表反射率曲线标准差在0.05nm以内时,定标误差集中在±0.5nm范围内;人工地物类型中个别地物如橄榄绿光泽涂料和植被大面积覆盖的图像数据不适合用于非同步替代光谱定标.     

连动型抗干扰干涉具井下瓦斯浓度监测系统（英文）

针对井下甲烷浓度监控干扰大的问题,结合实时监测甲烷浓度的系统要求,设计角镜连动的自消震光学结构,构建了基于无线网络的实时数据通信系统.在干涉系统中,固定两个角镜位置,将两片半透半反镜用连杆结构同步旋转,由此产生光程差.由于采用了连杆结构,任意时刻引入的震动在两个分束镜上等量存在,其结果是差分值,可实现完全相消.由分析分束器的最大旋转范围计算得到系统的光程差变化范围.结合比尔朗伯定律,给出系统在井下工作的甲烷气体浓度最低检出限.分别在实验室及矿井主巷道中完成实验过程,通过化学反应法求得被测甲烷气体的标准浓度,与WQF530型光谱分析仪的测试结果作比较,结果表明:在实验室无干扰条件下,两种检测方法的相对误差均小于1.0%;在井下实验中,传统光学检测方法受环境影响明显,相对误差大幅增加,而本系统测试结果基本稳定,具有较强的抗干扰能力及较高的稳定性.     

基于U型弯曲光纤模间干涉的折射率传感

研究了去包层U型弯曲光纤的折射率传感特性.首先根据模间干涉理论,分析了U型光纤传感器的传感原理,指出干涉谱损耗峰波长与环境折射率和弯曲半径有关.利用单模光纤(SM-28)实验制作不同曲率半径的U型光纤传感器,把传感器的U型部分浸入不同折射率的液体中,研究其折射率传感特性.当U型光纤曲率半径为2.5~5.0mm时,传输光谱中均能观察到明显的模间干涉现象;当液体折射率从1.30RIU变到1.43RIU时,光谱损耗峰波长发生红移,且弯曲半径越大,折射率传感灵敏度越高;在曲率半径为5mm时灵敏度为207nm/RIU(折射率1.30~1.40RIU)和1 220nm/RIU(折射率1.40~1.42RIU).干涉峰的波形参量(半高宽、对比度)决定于包层模和纤芯导模之间的比例,当曲率半径为4mm时,损耗峰半高宽最小达3.2nm.综合半高宽和灵敏度两个参量,得出曲率半径4.5mm的U型光纤传感器品质因素最高,分别为43.1RIU-1(折射率1.30~1.40RIU)和191.2RIU-1(折射率1.40~1.42RIU),可直接由SM-28单模光纤制成,且制作工艺简单、成本低、机械强度高不需要任何特殊处理,具有很好的应用前景.     

QoS enhancement in OFDM based systems under transceiver impairments

Broadband wireless systems generally use orthogonal frequency division multiplexing (OFDM) with link adaptation (LA) to achieve high throughput while meeting bit error rate (BER) constraint. OFDM systems are known to be affected by non-linearity of high power amplifier (HPA) at transmitter, carrier frequency offset (CFO), symbol timing offset (STO) and channel estimation error at the receiver. The delay in feedback of channel state information (CSI) further affects the performance of LA procedures. The focus of this work is on performance analysis in presence of simultaneous affect of all these impairments on LA based OFDM systems. The results are found to be useful for threshold readjustment which is essential for successful implementation of LA scheme to counter the effects of change in operating conditions from ideal to as listed above.     

A study of multi-beam DICANNE system

I.IntroductionTheprob1cmofsuppressingstrongpointinterferencesourceisavcryimportantthesisinsonardesign.Fortheana1ogsonar,thesolutionofthisprob1emisquitedifficu1t.Untilthedevelopmentofdigitalsonar,thereissomerescarchreportsaboutsuppressingstrongpointin-terferencesource.Theear1ierworkin1969,dedicatcdbyV.C.Anderson,istheconccptofDICANNE(DigitalInterfcrcnceCance1lingAdaptiveNu1lNetworkEquipment)['l.Thisisadoublecompensatormulti-bcamsystcm.Oneisusedtoformintcrfercncebeamandanothcrisusedtofor…     

Partially coherent multiple-beam interference

The general formula for multiple-beam interference due to regular slit arrays illuminated with partially coherent quasi-monochromatic light is derived. The correlation functions chosen for partially coherent light assume Gaussian, sinc and besinc forms of correlation. The intensity distribution in the interference patterns is presented and discussed as a function of the spatial coherence condition. It is shown that spatial coherence of the illumination largely affects the features of multiple-beam interference patterns.     

用于投影显示的分色合色膜系的消偏振设计

由于斜入射时,光学薄膜存在一定的偏振效应,将产生S-和P-偏振光的光谱分离.在Philips棱镜系统中,分色合色膜系通常分色时对S-光应用,合色时则对P-光应用.从提高光能利用率、减少杂散光和增加系统对比度等因素综合考虑,要求分色合色膜系的S-和P-偏振光的分离尽可能小.新设计方法采用宽带法布里－珀罗薄膜干涉滤光片中心波长两侧的干涉带作为长波通或短波通截止滤光片,可实现S-和P-偏振分量的分离几乎为零.