Comparison of thermodynamic properties of coarse-grained and atomic-level simulation models.

Thermodynamic data are often used to calibrate or test amomic-level (AL) force fields for molecular dynamics (MD) simulations. In contrast, the majority of coarse-grained (CG) force fields do not rely extensively on thermodynamic quantities. Recently, a CG force field for lipids, hydrocarbons, ions, and water, in which approximately four non-hydrogen atoms are mapped onto one interaction site, has been proposed and applied to study various aspects of lipid systems. To date, no extensive investigation of its capability to describe salvation thermodynamics has been undertaken. In the present study, a detailed picture of vaporization, solvation, and phase-partitioning thermodynamics for liquid hydrocarbons and water was obtained at CG and AL resolutions, in order to compare the two types or models and evaluate their ability to describe thermodynamic properties in the temperature range between 263 and 343 K. Both CG and AL models capture the experimental dependence of the thermodynamic properties on the temperature, albeit a systematically weaker dependence is found for the CG model. Moreover, deviations are found for solvation thermodynamics and for the corresponding enthalpy-entropy compensation for the CG model. Particularly water/oil repulsion seems to be overestimated. However, the results suggest that the thermodynamic properties considered should be reproducible by a CG model provided it is reparametrized on the basis of these liquid-phase properties.     

基于参考光栅的光纤光栅应变传感器温度补偿

为解决光纤布拉格光栅（FBG）应变测量时的应变、温度交叉敏感问题，利用FBG便于构成传感网络的优点，将温度补偿参考FBG与应变测量FBG串联在一路光纤上，根据2只FBG布拉格波长相对漂移获得被测结构应变。双FBG波长相对漂移对温度的灵敏度仅为0．12pm／℃，较好地实现FBG应变测量的温度补偿。参考FBG法原理简单，可操作性强，为FBG应变传感器的实际工程应用奠定了基础。     

SOI基光学电流传感器的设计与仿真

将光纤与微电子机械系统(MEMS)技术相结合,设计了一种新颖的检测50Hz高压交流电的光学电流传感器(OCS)。用ANSYS软件分析了器件的模态、动态响应与热膨胀特性,并通过Matlab软件模拟了器件的工作性能。模拟计算表明:ANSYS与理论公式得到的结果基本一致;传感器的量程为100~3600A,对于大电流下的灵敏度可达到0.02dB/A,温度变化±50K时传感器相应的测试误差为0.2%。     

异步电动机直接转矩控制中的死区效应的仿真研究

逆变器是直接转矩控制系统主电路中的关键部件。逆变器死区的设置虽然防止了逆变器器件的直通,同时也带来了死区效应,特别是对直接转矩控制系统的影响更是明显。本文通过分析异步电动机直接转矩控制系统中死区的生成及死区对电动机和整个系统的影响,定义了偏差电压矢量,并在此基础上,提出了一种死区补偿分析算法。该方法不需附加硬件,只需对原控制软件进行修改。仿真结果显示,在直接转矩控制系统中加入死区补偿,能有效改进电动机定子电流波形,使转矩脉动减小,整个系统的运行性能得到了一定的改善。     

Evaluation of the pole expressions of nano-scale multistage amplifiers based on equivalent output impedance

Several frequency compensation schemes have been proposed to stabilize multistage amplifiers with negative feedback. The performance of these amplifiers can be analyzed by inspecting their input-output transfer function as representation of their frequency response. With many circuit elements affecting the output response, it is relatively difficult to obtain the real transfer function of multistage amplifiers based on only the original small-signal expressions. Instead, certain techniques such as Miller’s theorem are used to approximate important parameters such as DC gain and dominant pole. These methods are not generally helpful for approximating the nondominant poles which have a critical role on the loop stability of nano-scale amplifiers. With this issue in mind, this work proposes a systematic methodology to achieve the pole expressions of multistage amplifiers with frequency compensation. The key in the proposed technique is to model the equivalent impedance of the compensation loop at the output. The effectiveness of the proposed approach has been verified through comparison between the transfer functions obtained from theory and those transfer functions found in the literature.     

补偿强反光体表面红外测温误差的算法研究

针对运动强反光体表面温度实时测量困难、精度低这一难点,本文从红外测温原理入手,分析并揭示了红外测温精度易受到被测物体反射率、测量距离、测量环境、红外入射角等因素的影响。根据铝板材加工设备轧辊表面测温实际需要设计了一种利用红外传感器实现对强反光体表面温度点对点测量的方案。通过对测量数据的研究分析建立了一种基于斯忒藩定律的红外入射角度补偿算法,以此减小因红外入射角度变化产生的测温误差。实验结果证明本方法能较好地弥补红外入射角度变化产生的测温误差,提高测温精度。该补偿算法运算简单,适应性强,为改善入射角度变化对测温精度影响提供了新的方法。     

采用一维物理光学法的天线罩瞄准误差补偿

针对雷达天线罩瞄准误差的补偿问题，提出了一种适用于各向同性的天线罩瞄准误差修正方法。构建了基于一维物理光学法的天线罩瞄准误差的数学模型，推导了雷达导引头测量目标角度和角速度的误差修正公式。试验结果表明，该方法有效降低了天线罩瞄准误差对目标角速度性能的影响。