Self-adaptive optical systems for long-distance flying optics

The focusing characteristics of long-distance flying optics were studied systemically for TEMmn Gaussian beams. The results show that the ABCD law of parameter q can be extended to Gaussian modes of any order when waist radius w in the imaginary part of parameter q is replaced by Rayleigh range Z(R) of a certain resonator in the equation. The difference between the real focal length and the geometric focal length, defined as Delta f, was calculated for laser applications. A novel self-adaptive optical system was demonstrated for precisely controlling the focusing characteristics of long-distance flying optics, Theoretical analyses and experimental results were consistent. (c) 2006 Optical Society of America.

表面热透镜薄膜吸收测量灵敏度提高方法

为提高表面热透镜薄膜吸收测量仪的灵敏度，在表面热透镜衍射理论基础上，通过数值模拟给出了探测激光腰斑半径、探测激光腰斑到样品表面距离、样品到探测光纤端面距离等仪器参数的优化方法．经优化调整后该仪器能达到优于0．1ppm量级的薄膜吸收率测量灵敏度．

Anisotropic radiation pattern from InGaAlP quantum well mesa-like microdisks

To overcome the isotropic directional emission of an ideal circular microdisk, two kinds of cylindrical mesa-like InGaAlP single quantum well (SQW) microdisks emitting at a visible red wavelength of 0.66 mu m have been fabricated. An anisotropic luminescence pattern was revealed by the microscopic fluorescence (FL) image. FL intensity, preferentially enhanced with twofold symmetry, appeared at the circumference of the InGaAlP SQW microdisks. Our results demonstrated that anisotropic radiation can be achieved by geometry shaping of the disks on the top view two-dimensional boundary slightly deformed from circular shape and/or on the side-view cross-section of the circular mesa by wet etching anisotropic undercut. (C) 2000 Elsevier Science Ltd. All rights reserved.

Giant Goos-Hanchen displacement enhanced by dielectric film in frustrated total internal reflection configuration

It is predicted that the Goos-Hanchen displacement in the usual frustrated total internal reflection configuration can be resonantly enhanced greatly by coating a dielectric thin film onto the surface of the first prism when the angle of incidence is larger than the critical angle for total reflection at the prism-vacuum interface and is smaller than but close to the critical angle for total reflection at the prism-film interface. Theoretical analysis shows that the displacement of transmitted beam is about half the displacement of reflected beam in the thick limit of the vacuum gap between the two prisms. This is to be compared with the relation in the usual symmetric double-prism configuration that the displacement of transmitted beam is equal to the displacement of reflected beam. Numerical simulations for a Gaussian incident beam of waist width of 100 wavelengths reveal that when the dielectric thin film is of the order of wavelength in thickness, both the reflected and transmitted beams maintain well the shape of the incident beam in the thick limit of the vacuum gap. So largely enhanced displacements would lead to applications in optical devices and integrated optics. (c) 2007 American Institute of Physics.

Uniaxial anisotropy and novel magnetic behaviors of CoFe2O4 nanoparticles prepared in a magnetic field

CoFe2O4 nanoparticles prepared by chemical coprecipitation method in a magnetic field exhibit novel magnetic properties. The average particle diameter was about 2 nm and larger depending on the post annealing temperature. Magnetization measurements indicate that smaller nanoparticles are superparamagnetic above their respective blocking temperatures. In the blocked state, these nanoparticles exhibit interesting behaviors in the magnetic hysteresis measurements. Constricted, or wasp waisted with extremely narrow waist, hysteresis curves have been observed in the magnetization versus field sweeps. For larger nanoparticles, the room temperature hysteresis is typical of a ferromagnet with an open loop, but the loop closes at lower temperature. The novel magnetic behavior is attributed to the directional order of Co ions and vacancies in CoFe2O4 established during the coprecipitation of the nanoparticles under an applied field.

Capillary electrophoresis coupled with electrochemiluminescence detection using porous etched joint

A new setup to couple capillary electrophoresis (CE) with electrochemiluminescence (ECL) detection is described in which the electrical connection of CE is achieved through a porous section at a distance of 7 mm from the CE capillary outlet. Because the porous capillary wall allowed the CE current to pass through and there was no electric field gradient beyond that section, the influence of CE high-voltage field on the ECL procedure was eliminated. The porous section formed by etching the capillary with hydrofluoric acid after only one side of the circumference of 2-3 mm of polyimide coating of the capillary was removed, while keeping the polyimide coating on the other part to protect the capillary from HF etching makes the capillary joint much more robust since only a part of the circumference of it is etched. A standard three-electrode configuration was used in experiments with Pt wire as a counter electrode, Ag/AgCl as a reference electrode, and a 300-mum diameter Pt disk as a working electrode. Compared with CE-ECL conventional decoupler designs, the present setup with a porous joint has no added dead volume created.

Molecular characterization of beef liver catalase by scanning tunneling microscopy

Beef liver catalase molecules can stick tenaciously to the highly oriented pyrolytic graphite (HOPG) surface which has been activated by electrochemical anodization. The immobilized sample is stable enough for high resolution scanning tunneling microscope (STM) imaging. When the anodized conditions are controlled properly, the HOPG surface will be covered with a very thin oxide layer which can bind the protein molecules. Individual molecules of native beef liver catalase are directly observed in detail by STM, which shows an oval-shape structure with a waist. The dimensions of one catalase molecule in this study are estimated as 9.0 x 6.0x 2.0 nm(3), which are in good agreement with the known data obtained from X-ray analysis, except the height can not be exactly determined from STM. Electrochemical results confirm that the freshly adsorbed catalase molecules maintain their native structures with biological activities. However, the partly unfolding structure of catalase molecules is observed after the sample is stored for 15 days, this may be caused by the long-term interaction between catalase molecules and the anodized HOPG surface.

仿人机器人腰部机构的动力学建模、控制与仿真

本文介绍的仿人机器人具有差动腰部机构,它除了受自身的动力学影响以外,还受到手臂和车体运动以及外力、外力矩等对腰部机构关节力矩的影响。笔者利用高效牛顿-欧拉算法完成了仿人机器人的整体建模;在不考虑各关节间耦合运动的情况下,对整体动力学模型进行适当简化,得到了腰部机构的动力学模型。简化后的动力学模型既反映了机器人车体、腰部及双臂的动力学关系,又大大地减小了计算量,易于实现基于动力学的控制算法。基于动力学模型,给出了腰部机构PD伺服轨迹跟踪控制算法,并结合计算力矩方法用于补偿腰部机构两关节受到的力矩扰动。仿真分析表明,该控制方法可以明显提高腰部机构的位置跟踪精度,并提高仿人机器人的整体作业精度。

轮式移动仿人机器人的动力学建模与分析

利用高效迭代牛顿-欧拉方法对一个21自由度的轮式移动仿人机器人进行了整体动力学建模,该模型虽然维数较高,但消除了分块建模中需要对模块之间相互作用力进行建模的难点问题,并且由于机器人双臂的对称结构,当合理规划双臂运动时,动力学模型将得到部分简化。本文还对某关节运动时在各个关节所产生的力或力矩进行了仿真分析。解析及仿真结果表明,合理规划上臂各关节的协调运动,将极大地削弱车体及腰部各关节所受的力或力矩扰动,为基于动力学的机器人运动控制以及稳定性分析提供理论依据。

仿人机器人发展现状及其腰部机构研究

仿人机器人目前已成为机器人领域的研究热点问题之一。本文对仿人机器人目前的发展现状进行了综述,介绍了腰部机构在仿人机器人的作用以及具有不同结构特点的腰部机构。介绍了一种新型的两个自由度的并联差动驱动的腰部机构,并进行了运动学分析及PID控制下的响应特性分析。实验结果表明,该机构具有较快的响应速度和较好稳态精度。

宜人化双臂操作型服务机器人建模、控制和协调

为宜人化双臂操作型服务机器人建立了动力学模型,该模型的特点是独立的机理建模技术结合黑箱技术共同描述出完整的模型;结合建立的模型,提出一种基于NN的自适应鲁棒控制器,并证明了其渐近稳定性.最后,在分析宜人化双臂操作型服务机器人运动特征的基础上,提出一种基于事件的在线协调的策略.

仿人机器人发展现状及其腰关节的作用

仿人机器人是研究人类智能的高级平台,是综合多种学科的复杂智能机械,其研制和开发涉及到各学科、多方面问题,目前已成为机器人领域的研究热点问题之一.本文对仿人机器人目前的发展现状进行了综述,分析了多种仿人机器人的自由度分布,介绍了具有不同结构特点的腰机构,分析了腰关节在仿人机器人的稳定动态步行、全身协调运动及有情感步行等方面的重要作用.本文还指出了仿人机器人目前的主要研究方向.

仿人机器人腰机构控制及分析实验平台研究

介绍了一种新型的仿人机器人两自由度腰部结构,给出了该机构两个伺服电机的PID控制策略,建立了基于PC机CAN卡的网络控制平台,该平台可实现腰部机构的实时控制及实时机构控制响应特性分析,该平台还具有扩展性强、成本低的特点。

轮式移动宜人机器人技术研究

轮式移动宜人机器人项目研究的主要目的是开发自主式仿人机器人样机 ,探索先进的机器人理论和技术。轮式移动宜人机器人由正交轮式移动平台、腰部、躯干及头部和双臂组成 ,共 2 1个自由度。整体结构包括 :电源系统、机械系统、控制系统和传感系统。电源系统采用车载电池供电。机械系统包括变刚度结构 ,提高了机器人与人交互作业的安全性。控制系统分为中央协调层和执行层结构。传感系统主要实现关节位置检测、姿态检测、力检测和视觉。文章讨论了此机器人的研究进展。

仿人机器人柔性腰部机构研究

仿人机器人腰部的构成对仿人机器人的运动学、动力学性能起着重要的作用。本文着重分析了目前仿人机器人腰部机构存在的问题,提出了一种具有柔性特征的仿人机器人腰部设计方案,并分析了此腰部机构对机器人的运动稳定性、操作柔顺性的影响,本设计使仿人机器人具有良好的柔顺性,提高了机器人与人协作时的安全性、稳定性和抗干扰能力。