基于振动筛同步相位角测试系统设计及试验研究

振动筛实现由不同步到自同步的物理过程中,相位差角是衡量自同步能力的重要参量。为了定量描述相位角的时间历程变化,针对于相位角测试系统的设计是非常有必要的。基于振动筛样机模型为实验研究对象,采用PCI-1780数据采集卡作为测试系统信号采集硬件,同时在Visual Basic设计环境下结合Active DAQ显示控件联合开发测试系统。实验结果表明所得数据与理论值基本吻合。对此,振动筛相位角测试系统可以为同步性理论研究提供实验依据。     

数字中频幅相检测仪设计

介绍了基于T1公司高性能16位定点数宇信号处理器TMS320VC5416的幅相检测系统设计。对系统组成模块进行了详细的描述。该仪器同时测量两路信号的幅度和相位。与传统测量方法相比,具有较强的抗干扰能力和较高的精度。应用前景广阔。     

Re-evaluation of differential phase contrast (DPC) in a scanning laser microscope using a split detector as an alternative to differential interference contrast (DIC) optics

In this paper, differential phase imaging (DPC) with transmitted light is implemented by adding a suitable detection system to a standard commercially available scanning confocal microscope. DPC, a long‐established method in scanning optical microscopy, depends on detecting the intensity difference between opposite halves or quadrants of a split photodiode detector placed in an aperture plane. Here, DPC is compared with scanned differential interference contrast (DIC) using a variety of biological specimens and objective lenses of high numerical aperture. While DPC and DIC images are generally similar, DPC seems to have a greater depth of field. DPC has several advantages over DIC. These include low cost (no polarizing or strain‐free optics are required), absence of a double scanning spot, electronically variable direction of shading and the ability to image specimens in plastic dishes where birefringence prevents the use of DIC. DPC is also here found to need 20 times less laser power at the specimen than DIC.     

Improving energy resolution of EELS spectra: an alternative to the monochromator solution

In this paper, we propose a numerical method which can routinely improve the energy resolution down to 0.2-0.3eV of electron energy-loss spectra acquired in a transmission electron microscope. The method involves measurement of the point-spread function (PSF) corresponding to the spectrometer aberration and to the incident energy spread, and then an inversion of this PSF so as to restore the spectrum. The chosen algorithm is based on an iterative calculation of the maximum likelihood solution known to be very robust against small errors in the PSF used. Restorations have been performed on diamond and graphite C-K edges acquired with an initial energy resolution of around 1eV. After reconstruction, the sharp core exciton lines become clearly visible for both compounds and the final energy resolution is estimated to be about 200-300meV. In the case of graphite, restorations involving both energy resolution and angular resolution have been successfully conducted. Finally, restorations of Fe L(2,3) and O-K edges measured for various iron oxides will be shown.     

Physical randomization of tissue architecture: an alternative to systematic sampling

A method is described for the rapid and accurate quantitation of tissue morphology using rat thyroid as a model. Perfused-fixed rat thyroid was diced into approximately thirty small pieces which were then randomly embedded in epon. Sections were taken at 500 μm intervals and stained with toluidine blue. Epithelial, follicular lumen and stromal components were quantified by a point counting technique. An analysis of variance was then performed on the data to determine whether there was any significant variation in the distribution of components between sections cut at different levels. No significant variation in any component was seen between sections for normal diced thyroid. This was also the case for diced thyroids of animals chronically treated with goitrogen to create a different physiological state. The method is therefore reliable even when marked changes in component distribution are induced. The physical randomization of tissue architecture by dicing, prior to embedding, greatly reduces the number of sections needed for the accurate morphometry of non-randomly distributed tissues.     

17.1 nm波段光电成像系统分辨率的实验研究

设计了17.1 nm波段光电成像系统,用于对波长为17.1 nm的极紫外光进行成像。该成像系统分为三大部分:光源、单色仪和探测系统。一个调Q的Nd∶YAG激光器(Continuum 9000)用来产生激光等离子体,掠入射单色仪由2块球面聚焦镜和1块600 L/mm的球面掠入射光栅组成,经单色仪分光后得到波长为17.1 nm的单色光,探测器是微通道板(MCP)和荧光屏组件共同组成,Kodak400型胶卷被用于记录狭缝的像。结果获得了一宽度为3 mm的狭缝的像,实验测得130 μm的成像系统的空间分辨率,好于相同条件下文献[6]的结果。     

同步带传动系统横向振动的分析研究

建立了同步带传动横向振动的运动方程式，导出了静态时（带的运动速度为零）同步带横向振动的目振频率，并对同步带在运动时横向振动的自振频率进行了修正。     

The Large-Scale Digital Cell Analysis System: an open system for nonperturbing live cell imaging

The Large-Scale Digital Cell Analysis System (LSDCAS) was designed to provide a highly extensible open source live cell imaging system. Analysis of cell growth data has demonstrated a lack of perturbation in cells imaged using LSDCAS, through reference to cell growth data from cells growing in CO₂ incubators. LSDCAS consists of data acquisition, data management and data analysis software, and is currently a Core research facility at the Holden Comprehensive Cancer Center at the University of Iowa. Using LSDCAS analysis software, this report and others show that although phase-contrast imaging has no apparent effect on cell growth kinetics and viability, fluorescent image acquisition in the cell lines tested caused a measurable level of growth perturbation using LSDCAS. This report describes the current design of the system, reasons for the implemented design, and details its basic functionality. The LSDCAS software runs on the GNU/Linux operating system, and provides easy to use, graphical programs for data acquisition and quantitative analysis of cells imaged with phase-contrast or fluorescence microscopy (alone or in combination), and complete source code is freely available under the terms of the GNU Public Software License at the project website ( http://lsdcas.engineering.uiowa.edu ).     

转角相位差对双点压力机精度的影响及同步校正方法

曲柄转角相位差是影响闭式双点压力机精度的一个重要因素,对转角相位差影响压力机精度的原理进行分析,并阐述一种实用的同步校正方法.     

NATALIE: a 32 detector integrated acquisition system to characterize laser produced energetic particles with nuclear techniques

We present a stand-alone system to characterize the high-energy particles emitted in the interaction of ultrahigh intensity laser pulses with matter. According to the laser and target characteristics, electrons or protons are produced with energies higher than a few mega electron volts. Selected material samples can, therefore, be activated via nuclear reactions. A multidetector, named NATALIE, has been developed to count the β(+) activity of these irradiated samples. The coincidence technique used, designed in an integrated system, results in very low background in the data, which is required for low activity measurements. It, therefore, allows a good precision on the nuclear activation yields of the produced radionuclides. The system allows high counting rates and online correction of the dead time. It also provides, online, a quick control of the experiment. Geant4 simulations are used at different steps of the data analysis to deduce, from the measured activities, the energy and angular distributions of the laser-induced particle beams. Two applications are presented to illustrate the characterization of electrons and protons.     

上海音乐厅顶升和平移工程的液压同步系统

本文以上海音乐厅的平移为例，介绍了顶升和平移工程的液压同步系统。该系统建立在力和位移双闭环控制的基础上．由59个高压液压缸精确地按照各点建筑的实际荷重，平稳地项举建筑物，使顶升过程中建筑物的内应力下降到最低，并使顶升、平移过程中由于建筑物重量分布不均而造成的基础沉降大部分得到抵消。     

基于Matlab和LabVIEW的永磁同步电机控制系统设计

针对永磁同步电机控制系统设计时,单独采用Matlab建模仿真方式多参数整定繁琐的问题,提出了一种基于Matlab与LabVIEW相结合的混合仿真方法。首先,理论分析了永磁同步电机在多坐标系中的数学模型,利用该数学模型在Matlab/Simulink环境中搭建了底层电机控制模型,并基于LabVIEW设计了电机系统测试界面。然后,利用仿真接口工具包—SIT使Matlab和LabVIEW保持同步通讯,在LabVIEW上层测试界面上对电机系统仿真参数进行整定。最后,为验证该混合仿真方法的可靠性,分别建立传统Matlab仿真模型与混合仿真模型,对电机进行了仿真实验。研究结果表明,该混合仿真模型与Matlab单独仿真模型的结果具有较高的吻合性,并符合理论计算结果。这种混合仿真方法在保证实验结果的正确性下,简化了永磁同步电机控制系统的参数整定;同时能从LabVIEW界面上直接查看仿真波形,进一步缩短了调试时间,提高了系统仿真效率。     

物流机器人调度系统及其双向同步跳点搜索算法设计

针对物流机器人在物料配送中对路径规划的安全性、实时性与高效性要求逐步提升的问题,本文提出了一种物流机器人调度系统及其双向同步跳点搜索算法。首先,分析物流机器人调度系统的功能需求并设计总体实现方案。其次,采用正六边形栅格地图取代传统栅格地图,并在此基础上提出改进的双向同步跳点搜索算法(JPS)。该算法调整了传统JPS算法的节点拓展规则以适应新地图,并引入灰狼优化算法指导扩展的相对方向,确保两侧搜索能够相遇。通过仿真测试对比所提算法与传统算法,所提算法比正四边形栅格图传统JPS算法快34%,比正六边形栅格图传统JPS算法快23%,结果表明所提算法的规划效率与安全性更高。此外,实物实验显示本文提出的双向同步JPS算法相较对比方法路径长度更优,在调度系统监控下物流机器人行走更加安全。     

同步串行扩展总线接口在单片机测控系统中的应用

简要论述了当前单片机测控领域常见的几种同步串行扩展总线的基本原理，给出了它们典型的应用接口方式，同时对单片机测控系统的总线选择提出一些建议。     

Going green: plants' alternative way to position the Ran gradient

Ran is a multi-functional small GTPase of the Ras super-family involved in nucleocytoplasmic transport, mitotic spindle assembly, cell cycle control and nuclear envelope (NE) formation. Its roles are accomplished by the asymmetric distribution of its GTP- and GDP-bound forms, enabled by the specific localization of Ran accessory proteins, the Ran GTPase-activating protein RanGAP and the nucleotide exchange factor RCC1. Mammalian RanGAP1 is targeted to the NE during interphase and to the spindle and kinetochores during mitosis via a SUMOylated C-terminal domain and interaction with the nucleoporin Nup358/RanBP2. Arabidopsis RanGAP1 (AtRanGAP1) lacks the SUMOylated C-terminal domain of vertebrate RanGAP, but contains a plant-specific N-terminal domain (WPP domain), which is necessary and sufficient for its targeting to the NE in interphase. AtRanGAP1 has a mitotic trafficking pattern uniquely different from that of vertebrate RanGAP, which includes targeting to the outward-growing rim of the cell plate. The WPP domain is necessary and sufficient for this targeting. Now, a novel family of plant-specific, nuclear pore-associated proteins has been identified in Arabidopsis, which is essential for anchoring RanGAP to the Arabidopsis nuclear envelope at the root meristem. This suggests that RanGAP anchoring to the nuclear pore has been solved in two fundamentally different ways in animals and plants. These findings support a separate evolution of RanGAP targeting mechanisms in different kingdoms, possibly related to different functional geometries of the Ran gradient in animal and higher plant cell division.     

高性能可编程模数转换器及其在测温系统中的应用

在测试、控制领域中,测试结果的精确程度在相当大的程度上与模拟信号/数字信号的转换精度有关.模/数转换电路的性能好坏将严重影响测量精度,本文介绍了一种24位∑-△高精度可编程模/数转换器AD7731,并给出了AD7731与常用8位单片机89C51的接口方法以及相关的程序,并将其应用到一种以铂电阻进行高精确度的测温系统中,保证了0.001℃的测量分辨率,使系统的测量误差小于0.055%.     

Signal strength and noise in confocal microscopy: Factors influencing selection of an optimum detector aperture

In confocal microscopy, several factors influence the selection of an optimum size and geometry of detector aperture. These include (1) strength of signal from the specimen, (2) noise level in the system, (3) optical configuration of the microscope (e.g., reflection or fluorescence), (4) time available for signal accumulation, (5) specimen thickness, and (6) amount of reduction in axial and transverse resolution (from the theoretical maximum) that can be tolerated. It is shown both theoretically and experimentally that the size of the detector aperture critically influences the type and amount of system noise that is detected along with the specimen signal. It is also demonstrated that increasing the size of the detector pinhole does not appreciably increase the signal strength from any single thin plane, but only increases the sampling depth, enhancing brightness at the cost of a reduction in axial resolution. As a result, it is shown that there is no advantage, from the standpoint of signal strength, to using a slit aperture rather than a circular detector pinhole. Finally, it is concluded that all confocal microscopes should be designed to allow the user the capability of selecting ah optimum compromise detector aperture setting based on the particular specimen properties, type of microscopy (e.g., fluorescence or reflection) and resolution required.     

海洋风电吊装运输专用船液压同步控制系统研究

以海洋风电吊装运输专用船液压控制系统为研究对象,针对该船桩腿升降系统实际工况需要的同步升降,分析其液压系统的工作特性.分别应用泵控和阀控的控制方式,实现同步控制.利用仿真分析的方法对两种控制方式的特性进行比较,确定采用阀泵联控的控制方案,实现了大功率、动态特性好的同步控制.     

Focused ion beam milling of vitreous water: prospects for an alternative to cryo-ultramicrotomy of frozen-hydrated biological samples

The feasibility of using a focused ion beam (FIB) for the purpose of thinning vitreously frozen biological specimens for transmission electron microscopy (TEM) was explored. A concern was whether heat transfer beyond the direct ion interaction layer might devitrify the ice. To test this possibility, we milled vitreously frozen water on a standard TEM grid with a 30‐keV Ga⁺ beam, and cryo‐transferred the grid to a TEM for examination. Following FIB milling of the vitreous ice from a thickness of approximately 1200 nm to 200–150 nm, changes characteristic of heat‐induced devitrification were not observed by TEM, in either images or diffraction patterns. Although numerous technical challenges remain, it is anticipated that ‘cryo‐FIB thinning’ of bulk frozen‐hydratred material will be capable of producing specimens for TEM cryo‐tomography with much greater efficiency than cryo‐ultramicrotomy, and without the specimen distortions and handling difficulties of the latter.