Imaging dislocations in ice

Three techniques have been used to study dislocations in ice: etch pitting-replication, transmission electron microscopy, and X-ray topography (XT). It is shown that, because ice is a weak absorber of X-rays and can be produced with a low dislocation density, allowing relatively thick specimens to be studied, the most useful technique is XT. The observations that have been made with conventional XT are briefly outlined. However, the introduction of high-intensity synchrotron radiation, with its concomitant short exposure times, showed that images obtained through conventional XT observations were of dislocations that had undergone recovery. The important dynamic observations and measurements that have been made using synchrotron X-ray topography are presented. Dynamic synchrotron X-ray topography observations of ice single crystals undergoing deformation in situ have shown that slip mainly occurs by the movement of screw and 60 degrees (1/3) [1120] dislocations on the basal plane, although non-basal slip by edge dislocations can also occur. The operation of Frank-Read and other dislocation multiplication sources have been clearly demonstrated and dislocation velocities have been measured. In contrast, in polycrystals, dislocation generation occurred at grain boundaries where there are stress concentrations before lattice dislocation generation mechanisms operate. Faulted dislocation loops have been determined to be mainly interstitial in both polycrystals and single crystals.     

Charging phenomena in PEEM imaging and spectroscopy

Spectromicroscopy with the imaging technique of X-ray photoelectron emission microscopy (X-PEEM) is a microchemical analytical tool installed in many synchrotron radiation laboratories, and which is finding application in diverse fields of research. The method of sample analysis, X-ray absorption spectroscopy, does not encounter the same problems as X-ray photoemission spectroscopy when sample charging occurs, hence even good insulators may often be analyzed without any apparent artifacts in images or spectra. We show, however, that charging effects cannot be neglected. We model the effect of surface charge formation on the secondary electron yield from uniform samples to demonstrate that surface charge primarily reduces the yield of electrons which may contribute to the detected signal. We illustrate that on non-uniform insulating samples, localized centers of charge may substantially affect microscope imaging and resolution as the electrostatic field close to the surface is distorted. Finally, in certain circumstances non-uniform surface charge may lead to unexpected lineshapes in X-ray absorption spectra causing, in some extreme cases, negative spectra. These negative spectra are explained, and several strategies are reviewed to minimize the impact of sample charging when analyzing poorly conducting samples of any nature.     

运动鞋发电充电装置

日常生活中,小型电器都是靠锂或镍电池等作为电力供应,在远离电源的山区、沙漠、草原等地区常因电源耗尽而使电子产品无法工作。针对这种情况,设计制造了一种运动鞋发电充电装置。     

新型便携式MIC充气阀

介绍了一种便携式摩托车轮胎充气阀,主要用于摩托车驾驶员外出途中对轮胎应急充气时使用。     

智能仪表收费管理系统

文章根据网络数据库的最新技术,设计了智能仪表收费管理系统。该系统采用客户机/服务器模式,既方便用户续卡充值,又为收费部门集中管理、合理调度资源、提高经济效益奠定了良好的基础。     

井下装药车及其应用前景

随着我国经济的快速发展，对矿产品的需求越来越大，国内各大中型矿山都在通过不断提高自身的机械化、数字化来提高采矿产能。在我国地下开采的钻、爆、铲、运四个主要环节中，爆破的机械化水平远远落后于其它几个环节．已经成为制约矿山提高产能的一个瓶颈。介绍了国内外井下装药机械的发展以厦发展前景，并对一种新型的井下装药车进行了详细的介绍。     

导爆管装药高度自动测量技术研究

介绍了导爆管装药高度自动测量装置,该装置主要由测量系统和机械系统两部分组成.测量系统采用几何光栅线位移传感器,通过对光栅常数进行细分提高测量装置的分辨率.机械系统的机构运动学设计应用阿贝原则,据此设计了定位机构和瞄准机构,提高了测量装置的精度和可靠性,从而实现了对导爆管装药高度的自动测量.     

冰球结冰蓄冷过程的研究

采用摄动方法对冰球结冰蓄冷过程进行了计算;对冰于蓄冷时间、冰于外换热、冰球大小、壁厚和材料影响蓄冷过程的特性进行了分析,得到一些有益的结论,可以指导冰球的设计和系统的蓄冷控制。     

节能太阳能充电鞋设计

为完成能量的转化使用,介绍了一种节能太阳能充电鞋,将普通的电热鞋与太阳能充电系统结合在一起,利用安装于鞋面上的柔性薄膜太阳能板以及鞋底内的直流太阳能充电控制器,将太阳能转化为电能,并储存在鞋内的锂电池中,再利用储存在锂电池中的电能,为碳纤维电热鞋垫加热,从而完成电热鞋的足部保暖功用.考虑到目前太阳能转换系统充电效率不高...     

快速充电技术发展迅速

正据了解,电动汽车能源效率已超过汽油机汽车。特别是在城市运行,汽车走走停停,行驶速度不高,电动汽车更加适宜。电动汽车停止时不消耗电量,在制动过程中,电动机可自动转化为发电机,实现制动减速时能量的再利用。然而,电动汽车充电时间长,充电难是电动汽车推广应用的一个难题。因此,快速充电技术的研究对电动汽车的发展影响重大,意义深远。一直以来,电动客车的发展面临电池技术的挑战,而电池技术所面临的瓶颈主要集中在充电时间长短和续航里程的长短上。充电     

超级电容充电策略研究

超级电容是一种绿色环保的电化学电容器,其充电过程受内阻和有效电容等诸多因素的影响,对其充电方法进行研究,在以后的工程应用中具有重要的意义。采用二阶段充电模式对其充电,控制电路以TMS32芯片为核心,通过检测超级电容的端电压,送入DSP进行分析和处理,得到相对应的PWM控制信号来控制主回路开关管（IGBT）的开通和关断,从而改变充电电流的大小,实现超级电容的智能充电。     

Structural changes in electron-irradiated paraffin crystals at < 15K and their relevance to lattice imaging experiments

The process of electron beam irradiation of orthorhombic monolamellar microcrystals of the n-paraffin n-tetratetracontane cooled < 15K is monitored by changes in the crystal structure to give a much clearer view of the beam damage process than is afforded by plots of diffraction intensity variation. The observed structural change in the chains, observed in the projection down the chain axes as an increasingly circular cross-section, is consistent with previous structural analyses of structural damage in an orthogonal view and also other observations of conformational flexibility of long chains induced by trans-vinylene groups. Nevertheless, within the 2.5 Å resolution available for direct lattice images (reported elsewhere), there is virtually no detectable structural change at the 10 e A^-2 electron dose used for these exposures.     

智能热量表计费系统研究

智能IC卡热水表的使用已相当普遍,它的使用虽然解决了传统的人工抄表和收费困难的问题,但是却存在着用水收费的不公平性,笔者对目前水表按流量计费方式进行改进,并设计出按热量计费的智能水表系统。     

An ice lithography instrument

We describe the design of an instrument that can fully implement a new nanopatterning method called ice lithography, where ice is used as the resist. Water vapor is introduced into a scanning electron microscope (SEM) vacuum chamber above a sample cooled down to 110 K. The vapor condenses, covering the sample with an amorphous layer of ice. To form a lift-off mask, ice is removed by the SEM electron beam (e-beam) guided by an e-beam lithography system. Without breaking vacuum, the sample with the ice mask is then transferred into a metal deposition chamber where metals are deposited by sputtering. The cold sample is then unloaded from the vacuum system and immersed in isopropanol at room temperature. As the ice melts, metal deposited on the ice disperses while the metals deposited on the sample where the ice had been removed by the e-beam remains. The instrument combines a high beam-current thermal field emission SEM fitted with an e-beam lithography system, cryogenic systems, and a high vacuum metal deposition system in a design that optimizes ice lithography for high throughput nanodevice fabrication. The nanoscale capability of the instrument is demonstrated with the fabrication of nanoscale metal lines.     

Electron scattering in ice and organic materials

Scattering cross-sections for the interpretation of the scattering-absorption contrast of microscopical images of amorphous biological specimens are calculated. The constituent atoms are treated as independent particles and their atomic potential is approximated by a modified Lenz-Wentzel potential. Both elastic and inelastic scattering processes are considered. Formulas of the effective elastic and inelastic atom scattering cross-sections are derived for both a CTEM with hollow-cone illumination and a STEM using an annular detector. The scattering-absorption contrast is plotted as a function of the atomic number for a CTEM applying parallel illumination and a STEM using a dark-field detector with maximum collection efficiency. The presented results are valid for acceleration voltages U in the range 20 kV<U<150 kV. Employing these data the ‘angular mass thicknesses’ of representative constituents of biological materials are determined. The application of the listed data is demonstrated by means of a special example.     

Sublimation rates of ice in a cryo-ultramicrotome

Sublimation rates of ice in the nitrogen-filled cryochamber of an ultramicrotome have been measured. The values are four to five orders of magnitude smaller than vacuum sublimation rates at the same temperatures. This is a consequence of the much shorter mean free path length of water molecules in nitrogen at atmospheric pressure, as compared to freeze drying under vacuum. The partial pressure at the phase boundary and gas diffusion and convection determine the rate of freeze drying. This has implications for section handling and the design of transfer equipment. Generally, it means that the danger of even partial dehydration of semi-thick (0·5–1 μm) sections used mainly for X-ray microanalysis is less serious than commonly assumed.     

智能立体充电车库设计分析

充电设施的发展没有与新能源汽车的发展相适应,从而导致了城市停车难》汽车充电难等问题,严重影响城市交通秩序和居民的生活质量,这已成为制约城市发展的障碍之一.设计了一种能自动存取车辆并智能控制充电的立体车库,对停车机构及其主要部件进行了设计分析.利用UG建立了虚拟样机模型,并对立体车库的停车装置进行了运动学仿真,分析了升降...     

增大传动比提高上料能力

针对某厂上料卷扬机由于设计配套不合理,严重影响生产的正常运行的问题,阐述了改造上料卷扬机传动比,提高上料能力,达到理想效果的设计经验.     

高频充电振荡器的参数计算

振荡器的种类很多,功能各异,应用也十分广泛。在实际使用的调试过程中往往需要对振荡器的频率、周期、占空比参数及相应保护电路参数进行计算。本文以555振荡器为核心组成的高频充电器为例,对实际电路的典型参数进行计算,为参数的选择提供理论依据。