Motion planning in velocity affine mechanical systems

We address the motion planning problem in specific mechanical systems whose linear and angular velocities depend affinely on control. The configuration space of these systems encompasses the rotation group, and the motion planning involves the system orientation. Derivation of the motion planning algorithm for velocity affine systems has been inspired by the continuation method. Performance of this algorithm is illustrated with examples of the kinematics of a serial nonholonomic manipulator, the plate-ball kinematics and the attitude control of a rigid body.     

新颖的双馈风力发电机灭磁控制策略

电网电压突变会引起双馈发电机输出功率波动和电磁转矩振动。造成这些电磁振荡的根本原因是定子绕组中产生的定子磁链暂态直流分量。本文详细分析了定子磁链暂态分量并推导出定子磁链和转子电流之间的数学表达式,在此基础上提出了一种新颖的双馈风力发电机定子磁链定向矢量控制的灭磁控制方法。仿真结果表明,所提出的灭磁控制方法可以在电网电压跌落程度较轻的情况下有效减小双馈发电机定子磁链中暂态直流分量的影响,提高双馈风电控制系统的稳定性,有利于实现风电机组的低电压穿越。     

HJ1B星CCD相机内方位元素的在轨标定方法

为了获得内方位元素的在轨值,提高遥感影像的定位精度,利用线阵推扫传感器构象模型,提出了一种对HJ1B\|CCD相机内方位元素进行在轨标定的方法。首先,选取地面控制点,建立地面控制点和相应像点的共线方程组;其次,建立误差方程,估算未知参数的初值;最后,利用狭义岭估计的方法解算误差方程,获得内方位元素和外方位元素值。实验证明,用该方法对HJ1B\|CCD相机内方位元素进行在轨标定,具有较高的稳定性和精度。     

FUZZY MODELS OF UNIT OPERATIONS

A classical quantitative analysis is not appropriate for some ill-defined or/and very complex chemical engineering problems. An application of the fuzzy approach is therefore proposed. It is possible to build up a linguistic model. The specification of the grade of membership functions for linguistic values of the linguistic variables allows the use of a fuzzy model.     

Processing-property relationships of polycarbonate/graphene composites

Polycarbonate composites reinforced with graphite and functionalized graphene sheets (FGS) were produced using melt compounding. Composite samples with different degrees of graphite orientation were processed via injection, compression molding and long-term annealing. Electron microscopy and X-ray scattering revealed that FGS was nearly exfoliated. However, graphite remained multi-layer even after melt processing. Flow induced orientation of graphite was observed from both injection and compression molded samples. Graphite particles in samples after long-term annealing exhibited more random orientation. Composites with the exfoliated FGS required a smaller amount of reinforcement for rigidity and connectivity percolation, as determined by melt rheology and electrical conductivity measurements. FGS also showed better performance in suppressing gas permeability of polycarbonate. However, improvements by FGS dispersion in tensile modulus and dimensional stability were not as significant. This may be due to defects in the sheet structure formed during oxidation and pyrolysis used to exfoliate.     

253.7 nm 辐射源总辐射通量副基准的建立

简述了建立２５３．７ｎｍ辐射源总辐射通量副基准的原理和方法，提出了建立该副基准的关键问题并详细介绍了解决办法。     

A method of combined indirect measurement for object quality parameters

A method is considered for measuring object quality parameters that can arise through indirect parameters, and in particular electrophysical signals acting on the object. Methods are given for obtaining a mathematical model for the measurement procedure and examples are quoted of the method applied with the use of spectrometric characteristics of the object. __________ Translated from Izmeritel'naya Tekhnika, No. 8, pp. 13–16, August, 2008.     

建筑企业在后危机时代的管理取向

通过对建筑企业内外部环境的客观分析,明确提出集约化、精益化、标准化是企业管理在后危机时代背景下的必然取向,以指导建筑施工企业认清形势,及时调整方向,保持和增强自身竞争力。     

Speed limits: Orientation and semantic context interactions constrain natural scene discrimination dynamics.

The visual system rapidly extracts information about objects from the cluttered natural environment. In 5 experiments, the authors quantified the influence of orientation and semantics on the classification speed of objects in natural scenes, particularly with regard to object-context interactions. Natural scene photographs were presented in an object-discrimination task and pattern masked with various scene-to-mask stimulus-onset asynchronies (SOAs). Full psychometric functions and reaction times (RTs) were measured. The authors found that (a) rotating the full scenes increased threshold SOA at intermediate rotation angles but not for inversion; (b) rotating object or context degraded classification performance in a similar manner; (c) semantically congruent contexts had negligible facilitatory effects on object classification compared with meaningless baseline contexts with a matching contrast structure, but incongruent contexts severely degraded performance; (d) any object-context incongruence (orientation or semantic) increased RTs at longer SOAs, indicating dependent processing of object and context; and (e) facilitatory effects of context emerged only when the context shortly preceded the object. The authors conclude that the effects of natural scene context on object classification are primarily inhibitory and discuss possible reasons. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

基于矢量控制的电机参数辨识及自调整策略

矢量控制技术要使感应电机达到与直流电机相同的调速性能，准确获得磁场定向是关键，而磁场定向又依赖于电机模型参数的设定。解决这一问题的方法很多，文中对近年国内外一些有代表性的方法做了简单的介绍，并对每种方法的优缺点进行了分析。