A Simple Configuration for Discontinuous Wavelength-tuning Optical Pulse Source

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Optimal control for Multi-Conjugate Adaptive Optics

Classic adaptive optics (AO) is now a proven technique that provides a closed loop real time correction of the turbulence. It is generally based on simple and efficient control algorithms. The next AO generation (Multi-Conjugate AO (MCAO) in its various forms and Extreme AO (XAO)) will require more sophisticated control approaches, especially in the case of wide field AO. We present here the concepts behind optimal control. The advantages compared to more standard approaches are stressed. A first experimental validation is presented. To cite this article: C. Petit et al., C. R. Physique 6 (2005).     

Fractional Motion Control: Application to an XY Cutting Table

In path tracking design, the dynamic of actuators must be taken intoaccount in order to reduce overshoots appearing for small displacements.A new approach to path tracking using fractional differentiation isproposed with its application on a XY cutting table. It permits thegeneration of optimal movement reference-input leading to a minimum pathcompletion time, taking into account both maximum velocity, accelerationand torque and the bandwidth of the closed-loop system. Fractionaldifferentiation is used here through a Davidson–Cole filter. Amethodology aiming at improving the accuracy especially on checkpointsis presented. The reference-input obtained is compared with splinefunction. Both are applied to an XY cutting table model and actuatoroutputs compared.     

A Novel Fabrication for Method Long PeriodFiber Grating

A new method of fabricating all-fiber broadband-rejection filter based on long period fiber grating (LPFG) is proposed. The principle in the method is to make periodic asymmetrical deformation in the core of fiber without microbends by electrode discharging so as to induce periodic refractive index changes. Two kinds of filters whose rejection peak wavelength at 1550 nm and 1310 nm are obtained. The insertion loss is less than 0.6 dB and 1.4 dB respectively. The 20 dB bandwidth ranges from 10 nm to 39 nm. The backward reflection loss is extremely small (less than - 70 dB). Such devices can be used as isolation filters in 1310/1550 nm WDM system and other fields.     

An Iterative Formula for the Reflection Coefficient of Multi-layer Thin Film and Its Application in the Design of Optical All Pass Filter

In this paper, an iterative formula for the reflection coefficient of the multi-layer thin film is deduced and the design of multi-layer thin film gires-tournois interferometer optical all pass filter(GTI-OAPF) is discussed. The group delay τm ranges from 0. 06 to 460 ps and the bandwidth △ω ranges from 0.068 to 0.0000079 (1015 rad/s). By changing the incident angle θ0, the multi-channel dispersion compensation may be achieved.     

一种改进的基于分水岭的图像分割算法

针对分水岭算法过分割现象,提出一种综合分水岭算法、中值过滤算法和归一化割算法的改进算法。该算法首先应用改进型的中值过滤算法对图像进行适当的除噪;然后通过分水岭变换对图像进行了初步分割,最后使用归一化割算法进行图像精度分割。算法集合了分水岭算法、中值过滤算法及归一化割算法的优点,既较好地解决了分水岭算法中过度分割的问题,又降低了归一化割算法的时间复杂度。实验结果表明该算法是一种切实可行的图像分割方法。     

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设计并优化了一种新型多色仪。该方案中滤光片和探测器更加易于安装,缩短了光程长度,提高了对散射信号的探测本领,减少了透镜的使用数量,提高了多色光谱仪的传输率。通过数值计算,得到在200~20000eV温度范围内多色光谱仪的通道数为7是最优化结果。最后,对7通道多色仪的相关参数进行优化设计,使用模拟退火法计算优化各通道干涉滤光片的波长范围。     

Speech enhancement in dual-microphone mobile phones using Kalman filter

In this paper, a dual-microphone speech enhancement algorithm for the mobile phones is proposed. The adopted method exploits the coherence function algorithm and the Kalman filter. This algorithm has a simple implementation that does not need a prediction of interfering signals statistics. In addition, this algorithm can be used in small devices with so closely distance between the two microphones. Moreover, the use of such algorithm allows reducing multiple noise sources at many azimuths positions. Finally, the new algorithm proves its performances referring to the perceptual evaluation of speech quality and the time domain waveforms.     

Filtration characteristics of fibrous filter following an electrostatic precipitator

This study presents the results of investigations of a hybrid electrostatic filtration system (HEFS), which combines an electrostatic precipitator (ESP) and a fibrous filter installed downstream of the ESP. The particles escaping from the ESP carry large amount of charge and this can increase the filtration efficiency of the fibrous filter. The filtration characteristics, including the efficiency, pressure drop and ozone generation, were investigated experimentally. The influence of system parameters, including the filter type, applied voltage, and distance between the ESP and fibrous filter on the overall efficiency were also studied. The measured results show that utilizing the non-high-efficient fibrous filter to remove the charged particle could provide a much higher efficiency without adding the pressure drop due to the electrostatic force. If the efficiency was similar, the ozone generated by HEFS was much lower than that of the single ESP. The results proved that filter efficiency increased with a higher applied voltage and higher initial mechanical filtration efficiency. The distance between the filter and ESP had no influence on the system filtration efficiency. The efficiency of filter in HEFS supplied with the positive voltage was slightly lower than for the negative voltage. In addition, the mathematical model was utilized to model the air filter efficiency in HEFS. The modeled and measured results agreed reasonably. Overall conclusion is that the HEFS could operate at a high efficiency with the lower applied voltage, ozone generation and pressure drop.     

流动注射在线预富集-高效液相色谱法测定水中的4-壬基酚和双酚A

建立了以香烟过滤嘴作吸附剂,在线固相萃取(SPE)与高效液相色谱(HPLC)联用测定水中双酚A(bisphenol A,BPA)和4-壬基酚(4-nonylphenol,4-NP)的方法。对于高效液相(HPLC)在线固相萃取而言,采用内置香烟过滤嘴的预富集圆形柱来代替传统的高效液相仪中的注射管进样环用于在线固相萃取。通过流动注射仪将样品分析物负载加入到预富集柱中,随后采用V(甲醇):V(H2O)=93:7混合液为洗脱剂对富集的样品分析物进行洗脱。采用Eclipse XDB-C18色谱柱,V(甲醇):V(H2O)=93:7混合液为流动相,流速为1.0mL/min,紫外检测波长为227nm,保留时间定性,外标法定量。双酚A在0.005～0.8mg/L、4-壬基酚在0.04～8.0mg/L范围内,两者峰面积与浓度呈线性关系,相关系数分别为0.9985和0.9983,检出限(S/N=3)分别为2.1和10.0μg/L,富集倍数分别为816和346倍。对标准混合物(BPA:0.2mg/L;4-NP:2.0mg/L)重复测量11次的相对标准偏差为2.3%和1.5%。本方法用于当地河流水样中BPA和4-NP的测定,回收率为93.2%～105.4%。