Application of BP neural networks in non-linearity correction of optical tweezers

The back-propagation (BP) neural network is proposed to correct nonlinearity and optimize the force measurement and calibration of an optical tweezer system. Considering the low convergence rate of the BP algorithm, the Levenberg-Marquardt (LM) algorithm is used to improve the BP network. The proposed method is experimentally studied for force calibration in a typical optical tweezer system using hydromechanics. The result shows that with the nonlinear correction using BP networks, the range of force measurement of an optical tweezer system is enlarged by 30% and the precision is also improved compared with the polynomial fitting method. It is demonstrated that nonlinear correction by the neural network method effectively improves the performance of optical tweezers without adding or changing the measuring system. __________ Translated from Optics and Precision Engineering, 2008, 16(1): 6–10 [译自: 光学精密工程]     

碎石桩复合地基桩土应力比的试验研究

该文简要阐述了碎石桩复合地基桩体与桩间土压缩变形之间的关系,通过工程实例介绍了复合地基桩土应力比的测试方法,并分析了桩土应力比与荷载、置换率、桩土模量比之间的关系,进而得出一些有益的结论。     

对比度因素对彩色CRT视觉工效的影响

作者用实验方法研究了CRT彩色显示中对比度因素与视觉工效的关系。实验的自变量为彩色目标一背景的亮度对比度．取值范畴为-0.68-14.1。实验的因变量为视觉通道容量。实验的刺激材料为8个不同开口方向的兰道环。实验结果表明：对比度是影响彩色CRT视觉工效的重要因素。当目标一背景的亮度对比度值小于-0．3(暗目标／亮背景)或大于 1．3(亮目标／暗背景)时，视觉工效较高．继续增大反差，视觉工效改善不明显；当对比度值从负端增大至-0．13或从正端减小至 1．3时，视觉工教急剧下降，而后继续减小反差，视觉工效的降低也不明显。     

基于SAW表面气液相效应和GC分离柱的气敏传感器的研究

限于传统涂敷敏感膜的声表面波（SAW）气敏传感器存在成膜困难和选择性差、重复性差以及再生性差等问题，本研究提出一种基于压电基底表面气体气液相转换效应机理的瑞利波传感器。首先建立了挥发性有机气体(VOCs)液相凝聚体薄层负载下的SAW波传模型，并仿真计算了其波传频散和波传衰减。然后在此基础上开发了一种基于瑞利声表面波传感器和气相色谱（GC）分离柱的便携式气体检测系统。最后实验论证了方案的可行性，初步的实验结果表明该系统具有分析时间短、选择性好、灵敏度高（可检测ppb浓度的混合VOCs）以及成本低等优势，因此其在痕量挥发性有机气体检测和分析应用上有良好的潜力和前景。