Electron lenses of hyperbolic field structure

Increasing lens voltage, higher than the incident electron voltage, at first blocks the beam and then converts the electron lens into a curved mirror, the focal properties of which are analyzed.The embodiment of hyperbolic lenses is discussed by means of the boundary conditions which may be rigorously or approximately satisfied in actual designs. The effects of lateral apertures and windows on the imaging qualities of the field are considered in detail.Expressions are derived for velocity-, angular- and aperture-defects, the latter being merely a surface effect of the hyperbolic field. They all depend on a few parameters only of the lens field and are relatively small in magnitude. An experi- mental verification of the field structure with partial compensation of the defects shows favorable imaging qualities.Two-dimensional fields, constituting electron cylinder lenses, are considered in a similar way, leading to analogous formulations for the cardinal properties.     

Micro-optofluidic Lenses: A review

This review presents a systematic perspective on the development of micro-optofluidic lenses. The progress on the development of micro-optofluidic lenses are illustrated by example from recent literature. The advantage of micro-optofluidic lenses over solid lens systems is their tunability without the use of large actuators such as servo motors. Depending on the relative orientation of light path and the substrate surface, micro-optofluidic lenses can be categorized as in-plane or out-of-plane lenses. However, this review will focus on the tunability of the lenses and categorizes them according to the concept of tunability. Micro-optofluidic lenses can be either tuned by the liquid in use or by the shape of the lens. Micro-optofluidic lenses with tunable shape are categorized according to the actuation schemes. Typical parameters of micro-optofluidic lenses reported recently are compared and discussed. Finally, perspectives are given for future works in this field.     

On electron optics

For many experiments in physics and in some engineering applications, it is necessary to produce electron bundles, or as they are often called, “electron beams” of considerable intensities.Various methods have been used for directing a cloud of electrons evaporated from an emitting surface into a beam and then concentrating this beam to a desired degree. The concentration of electron beam in high vacuum depends entirely upon fields of force, either electric or magnetic, while in low vacuum or in rarified rare gas it depends also upon the action of the field of ionized gas molecules.In high vacuum the fields of force act upon the electron beam in a manner similar to the action of lenses upon a beam of light. An improperly shaped field produces effects similar to spherical aberration in poorly corrected lenses; non-uniform velocity of electrons in the beam results in effects similar to chromatic aberration of light.This optical analogy is not perfect.In the case of the electron beam the velocity varies continuously throughout most of the path and indices of refraction employed usually are greater than in the optical case. Moreover, space charge in beams of high intensity limits the concentration attainable; consequently, even theoretically, an electron beam can never be brought up to a mathematical point as in the case of light optics. Many secondary effects are present which complicate the problem still further.In focusing electron beams, both electrostatic and electromagnetic methods have been used extensively. The electrostatic method, however, seems to be preferable, especially when the beam is to be deflected. Precautions should be taken not to destroy the focusing of the beam during deflection.     

Photometric determination of camera exposures for motion picture work

A photometric method for the determination of camera exposures in motion picture work is described. The relation of exposure, object brightness and lens stop number is derived, and the proportionality constant empirically determined for “Pan Astro” lenses of two- and three-inch focal length. A nomographic chart of the exposure relation is given to simplify the determination of the lens stop number to be used for a given object brightness.     

Miniaturization of dielectric liquid microlens in package

This study presents packaged microscale liquid lenses actuated with liquid droplets of 300-700 μm in diameter using the dielectric force manipulation. The liquid microlens demonstrated function focal length tunability in a plastic package. The focal length of the liquid lens with a lens droplet of 500 μm in diameter is shortened from 4.4 to 2.2 mm when voltages applied change from 0 to 79 V(rms). Dynamic responses that are analyzed using 2000 frames∕s high speed motion cameras show that the advancing and receding times are measured to be 90 and 60 ms, respectively. The size effect of dielectric liquid microlens is characterized for a lens droplet of 300-700 μm in diameter in an aspect of focal length.     

用类比法探究圆锥曲线切线的性质

1）双当线约任意一条切线与切点处的两一条焦半径所成的角相等。2）在圆锥曲线中,从一个焦点出发的一束光线经圆性曲线反刘后总经过另一个焦点（或双曲线中是反射光线的反向延长线经过另一个焦点）。     

Magnetic Field Diffusion Through Infinite Conducting Media

The diffusion of the magnetic field due to a step current in an infinitely long ideal conductor, through infinite media is discussed. An analytical solution of the field diffusion through two concentric cylinders of different conductivity is derived using a generalized Ohm's law which considers both solid and fluid conductors. A rigorous mathematical treatment which can be generalized to any number of conducting cylinders is presented.The limiting case of an external superconducting medium is discussed and it is shown that with all the other parameters fixed it represents a lower limit in diffusion time.     

自旋极化电子源装置研究

自旋极化电子在许多研究领域有着广泛用途，目前国际上普遍采用光电离GaAs晶体产生自旋极化电子。本文介绍自旋极化电子产生的原理及一种设计简洁、结构简单的极化电子源装置。该十字型四通道装置内有一非常简单的900静电偏转器，新型的用于固定晶片的弹簧夹子可保证晶片加热均匀。用波长780nm圆偏振激光激活GaAs光电阴极可以产生极化电子，然后通过900静电偏转器及一组静电透镜将极化电子引、到反应区。     

Journal clustering using a bibliographic coupling method

The classification of journal titles into fields or specialties is a problem of practical importance in library and information science. An algorithm is described which accomplishes such a classification using the single-link clustering technique and a novel application of the method of bibliographic coupling. The novelty consists in the use of two-step bibliographic coupling linkages, rather than the usual one-step linkages. This modification of the similarity measure leads to a marked improvement in the performance of single-link clustering in the formation of field or specialty clusters of journals. Results of an experiment using this algorithm are reported which grouped 890 journals into 168 clusters. This scope is an improvement of nearly an order of magnitude over previous journal clustering experiments. The results are evaluated by comparison with an independently derived manual classification of the same journal set. The generally good agreement indicates that this method of journal clustering will have significant practical utility for journal classification.     

The electron mechanics of induction acceleration

The radial and axial motions of electrons in the betatron are described by means of a potential function of forces. Previously reported conditions of equilibrium, stability and damping of oscillations are derived for the region of parabolic variation of the potential. Extension of the analysis to, non-parabolic regions gives an account of the injection in conventional instruments in better agreement with experiment, particularly in regard to higher voltages of injection.Space charge limitations are discussed with the help of the Laplacian of the potential of forces.By means of an additional radial electric field electrons can be introduced as in the magnetron, without any asymmetry inherent in the conventional betatron circumferential injector. The analysis of the conditions of equilibrium and stability, greatly facilitated in this case by the notion of potential, shows that no substantial improvement in space charge limitations can be expected and that the required variations between the flux linking the electron orbits and the magnetic and electric fields at the orbits are difficult to realize on account of their complexity and narrow tolerances. The X-ray output of a small experimental double yoke instrument was measured by a phototube multiplier viewing an irradiated fluorescent screen and gave evidence of multiple group electron capture.     

中职生职业生涯规划教育的思考

中职生在校时期既是人格形成的时期,也是自我意识蓬勃发展、社会生活领域迅速扩大并走向成人的重要时期。引导中职生合理有序就业,做好农村职业学校的职业生涯规划教育,一直是我国职业教育的焦点,也是目前农村中职教育的一个重点。     

大企业衍生创业对创业集群形成的影响研究

提出"大企业衍生创业"的概念,并构建以创业能力形成为中心环节的衍生创业的过程模型;在文献分析基础上通过定性分析并辅以案例验证,认为大企业衍生创业是产业相关企业不断创建产生并最终推动集群形成的重要动因;建立以大企业衍生创业为核心的集群形成解释模型,并据此提出通过创业-集群的方法来促进区域经济成长和创新发展的政策建议。     

组织间资源影响因素实证研究

近年来,组织的资源基础随着竞争形态的变化也发生了深刻的变革,组织间网络中的资源对企业的竞争制胜愈发关键。尽管组织间资源的重要性得到了学者和企业界的一致认同,组织间资源的构建受到哪些因素的影响却是一个悬而未决的问题。本文在综合现有研究基础上,构建了组织间资源影响因素模型,并运用大样本问卷调查和回归分析的方法对理论假设进行了验证。研究发现,总体看来企业自身吸收能力、合作伙伴的资源禀赋水平以及双方的关系特征对组织间资源的构建有显著影响,各要素的影响因素和作用效果又存在一定的差异。     

Closed plane curves described by finite and infinite sums of rotating vectors

A large group of closed plane curves may be classified as roulettes, including epicycloids, hypocycloids, and related epitrochoids and hypotrochoids. The equation for the roulette in complex polar form shows that any roulette may be described by the vector sum of two vectors of specified constant magnitudes rotating with constant angular velocities. Methods for plotting, and for electronic display of roulettes are described. An equation is derived for a roulette approximation for an N-sided regular polygon. In particular, an application to two-dimensional potential theory is described and illustrated by consideration of the roulette approximation for a square as an equipotential curve, with derivation of equations for equipotential curves in the field surrounding the square. General equations are derived for given closed plane curves with points whose x and y coordinates may separately be expanded in Fourier series as functions of the polar angle, assuming these expansions are valid. It is shown that, in general, a closed plane curve may be considered as being described by an infinite sum of vectors, each rotating in a circle. Simplifying effects of symmetry about a polar axis and/or about the origin are discussed, and methods for harmonic analysis of a given closed plane curve with aid of an electronic calculator are described.     

基于共词分析的国内文献传递领域可视化研究

以共词分析为研究方法,结合聚类分析、多维尺度分析等多元统计方法,对CNKI数据库中1999-2011年国内文献传递领域的研究主题进行可视化分析。从363篇文献中提炼出11大类主题,其中馆际互借与资源共享主题是该领域的研究核心,高频词图书馆、馆际互借和读者服务是持续性的研究热点,研究者对文献传递服务体系、传输软件等主题的探索则是今后的研究趋势。     

Characterization of a microflow cytometer with an integrated three-dimensional optofluidic lens system

Flow cytometry is a standard analytical method in cell biology and clinical diagnostics and is widely distributed for the experimental investigation of microparticle characteristics. In this work, the design, realization, and measurement results of a novel planar optofluidic flow cytometric device with an integrated three-dimensional (3D) adjustable optofluidic lens system for forward-scattering∕extinction-based biochemical analysis fabricated by silicon micromachining are presented. To our knowledge, this is the first planar cytometric system with the ability to focus light three-dimensionally on cells∕particles by the application of fluidic lenses. The single layer microfluidic platform enables versatile 3D hydrodynamic sample focusing to an arbitrary position in the channel and incorporates integrated fiber grooves for the insertion of glass fibers. To confirm the fluid dynamics and raytracing simulations and to characterize the sensor, different cell lines and sets of microparticles were investigated by detecting the extinction (axial light loss) signal, demonstrating the high sensitivity and sample discrimination capability of this analysis system. The unique features of this planar microdevice enable new biotechnological analysis techniques due to the highly increased sensitivity.     

Adaptive-observer-based formation tracking of networked uncertain underactuated surface vessels with connectivity preservation and collision avoidance

This paper investigates an adaptive output-feedback formation tracking problem for ensuring connectivity preservation and collision avoidance among networked uncertain underactuated surface vessels (USVs) with different communication ranges. An adaptive observer using neural networks is designed to estimate the velocity information of USVs where neural networks estimate unknown nonlinearities of USVs. Especially, contrary to the existing related work of USVs, a new state transformation technique for the adaptive observer design is presented to relax the condition requiring the boundedness of the yaw velocity of USVs. Then, the recursive tracker design strategy is established by using a unified error function for connectivity-preserving and collision-avoiding formation tracking, without employing any potential functions. The proposed formation tracker does not require additional neural networks to estimate unknown nonlinearities derived from the tracker design procedure. The proposed theoretical result is proved in the sense of Lyapunov.     

行为供应链决策模型研究文献综述

回顾行为供应链决策模型的研究进程,对在供应链决策模型中影响决策的行为因素方面的研究进行深入分析,梳理本领域的研究热点与重点,进而总结现有研究的局限,并对未来的研究进行展望。     

Determinants of satisfaction among social entrepreneurs in e-Government services

Information Technology–enabled e-Governance outlets are being increasingly used in developing economies to facilitate the delivery of e-Government services. These outlets are managed by social entrepreneurs who serve as an intermediary between the citizen and the government. With social entrepreneurship and stakeholder theories as underpinnings and model validation with data from 232 respondents, the current work suggests that social entrepreneurs' satisfaction is derived from a positive public image and satisfaction with stakeholders. The two factors fulfill the entrepreneur’s communion motives and are derived from their economic well-being, an agency motive, which itself is an outcome of the e-Government website service quality. This study also establishes the intervening role of process and the government support for enhancing the social entrepreneur’s economic wellbeing. The study brings the unique perspectives of social entrepreneurship to e-Government service delivery and provides recommendations for policymakers to focus on the satisfaction of such intermediaries for sustainable inclusion into the digital mainstream.     

企业创新生态系统参与者创新研究

通过对海尔集团创新生态系统构建的案例研究,打开平台焦点企业如何协调各参与者参与互补性创新的过程黑箱。研究先从资源禀赋程度和生态系统位置两个维度分析了不同类型参与者的角色特征和对焦点企业创新的作用,并关注他们与焦点企业进行资源互补时的互动过程,着重探讨了焦点企业与不同类型参与者进行前置资源化过程的协调行为。研究发现,不同资源禀赋程度的生态系统参与者会分别通过三种不同类型的前瞻资源化过程互补于焦点企业的创新活动,而焦点企业针对不同资源禀赋程度和生态系统中位置的参与者会采取不同的协调机制。由此,本研究归纳出创新生态系统参与者角色、前瞻资源化类型和焦点企业协调机制的匹配逻辑关系,最终得到一个整合框架。