NDZ-20医用电子直线加速器的注入系统

文章介绍了NDZ-20医用电子直线加速器的束流注入系统的结构和特性。电子枪为轰击型的皮尔斯电子枪。漂移管上的预聚焦线圈、偏掉线圈、导向线圈和束流前沿切割线圈用来实现对电子束的多种控制,实现加速器的ARC,ADC和BLC运用,以保证加速器运行的稳定性和可靠性,改善反馈加速器的能谱。     

基于皮尔斯符号三元关系的洛阳文创产品设计

目的致力于建立体验经济时代下的洛阳文创产品设计模型,提出具有创新性的洛阳文创产品设计方法,从而提升产品文化内涵,弘扬洛阳文化。方法基于皮尔斯符号三元关系衍生出洛阳文创产品设计模型,采用了文献研究与实地调研相结合的方法,对洛阳文化元素进行整理,提出洛阳文化的八大主题及其子集并进行符号解析。运用产品设计方法对文化元素符号进行编码,采用用户故事地图法对用户进行产品体验解码,指导洛阳文创设计。结论提出了洛阳文创产品设计模型中的三要素——元素、产品、用户,元素是洛阳文创设计模型的基础,产品是洛阳文创设计模型的重点,用户是洛阳文创设计模型的难点和最终目标。选取了石辟邪文化元素对洛阳文创设计模型进行实践验证,设计出了符合用户需求、独具特色的洛阳文创产品。     

Boolean representation of bounded BCK-algebras

We define the Boolean center and the Boolean skeleton of a bounded BCK-algebra, and we use the Boolean skeleton to obtain a representation of bounded BCK-algebras, called (weak) Pierce -representation, as (weak) Boolean products of bounded BCK-algebras. We analyze the cases in which the stalks in these representations are directly indecomposable, finitely subdirectly irreducible or simple algebras. We give some examples of algebras and relative subvarieties of bounded BCK-algebras to illustrate the results.     

基于Spindt冷阴极的行波管电子枪设计

针对X波段小型化Spindt冷阴极螺旋线行波管进行了电子枪设计.基于皮尔斯型电子枪结构,联合PPM高频聚焦系统,以电子注聚焦特性为优化目标,采用CST粒子工作室对电子枪结构和工作参数进行了优化设计,获得了 30 mA工作电流下电子注填充比为0.68的良好电子注聚焦.在此电子枪结构和高频结构下,分析了特定电流下电子注聚焦...     

Pierce point minimization and optimal torch path determination in flame cutting

This paper addresses the problem of sequencing a torch for the cutting of a stock sheet nested with regular or irregular parts. The image of the nesting is reduced to an equivalent graph, and the objective is to traverse this graph with a minimum number of pierce points, or blowthroughs. If the graph has $\text{2k}$ vertices of odd degree, then $\text{k}$ pierce points are necessary and sufficient to traverse the graph. The torch path problem formulation includes manufacturing cost, efficiency, and distortion considerations. We present three algorithms for the problem. The first algorithm shows how to determine the $\text{k}$ torch paths, and is optimal in run time complexity. The second algorithm uses trim margin edges to investigate further reduction in the number of pierce points. The third algorithm guarantees that for the special case where a torch path has no vertices of odd degree, no piece will be dropped that needs further interior cuts. Some possible extensions to this work are also addressed.     

The naming of photography

Abstract

Photography now seems so natural a word for the process to which it refers that we tend to forget that the naming of this process was a matter of intense debate during the years leading up to 1839. Indeed photography's pioneers showed almost as much interest in the medium's nomenclature as in its invention, and almost all of them proposed one or more possible names. Given the importance attached to language at the time, it is reasonable to assume that the choice of name for their inventions was in each case indicative of their general thinking about photography and its character. In many cases the word actually came before the invention, or at least before the invention was fully operational. The choice of name therefore reflected not so much what photography was as what photography might be. It was a one-word summation of the idea of photography, and of the desires and aspirations that induced each of its various inventors to undertake their experiments. A history of photography's naming represents a useful insight into these desires, useful because it gives us one more glimpse into the manner of the medium's conception and early development.     

Simulation of Mannesmann piercing process by the three-dimensional rigid-plastic finite-element method

Simulation of the Mannesmann piercing process is performed for the first time by the three-dimensional rigid-plastic finite-element method. Firstly, a method of analysis is proposed for the steady-state formulation in the case that the sides of the finite elements cannot be made to coincide with the streamline of the material flow. Secondly, the simulation of the Mannesmann piercing process is performed under the variation of rolling conditions such as the feed angle, the minimum roll gap, the maximum plug diameter, the plug advance and the guide shoe diameter, and the effects of the rolling conditions on various rolling properties such as the outer diameter, the inner diameter, the roll force, the mandrel force, the equivalent strain distribution and the equivalent strain rate distribution are demonstrated. Finally, the results of the analysis are compared with the results of an experiment using Plasticine. The dimension in the rolling condition of the experiment is scaled to one-third of the dimension in the rolling condition in an actual Mannesmann piercing process. The analytical results agree with the experimental results and the validity of the method of analysis is confirmed.     

一种谐振器型单端SAW湿度传感器测试系统

声表面波(SAW)传感器已经广泛应用在各个领域.本文介绍了一种基于改进皮尔斯振荡器,中心频率为433.92MHz的谐振器型单端SAW(SAWR)湿度传感器的测试系统,经测试该办法可有效抑制同频点传统SAW振荡器所产生的87MHz附近的谐波,并能有效提高输出信号的功率.本文采用有机复合材料酞菁铜(CuPc)掺杂聚乙烯吡咯烷酮(PVP)作为SAW传感器敏感膜进行了湿度测试,并讨论了膜层厚度对传感器特性的影响.     

体声波谐振器质量负载等效电感的量化方法

体声波(BAW)谐振器受到质量负载时,谐振器的Butterworth Van Dyke(BVD)电路模型中会增加1个质量负载等效电感,为得到该电感与负载质量的量化关系,以便对BAW传感器进行系统行为仿真,该文提出了3D多物理场-等效电路仿真对比建模的方法。通过对比COMSOL Multiphysics软件的3D多物理场仿真结果与ADS的等效电路仿真结果得到质量负载等效电感和负载质量的量化关系。以一个薄膜体声波谐振器(FBAR)为例,介绍了该方法的详细过程,并得到案例中的量化关系为:质量负载等效电感每增加1nH,负载质量增加0.1ng。最后将该量化关系应用于基于Pierce振荡器的BAW传感器检测电路的系统级行为仿真。仿真结果表明,质量负载等效电感每增加1nH,振荡频率减小6 MHz,即振荡频率的变化情况与等效电路仿真结果相吻合,从而验证了该检测电路能用于BAW传感器的频率信号的检测。该量化方法同样适用于石英晶体微天平(QCM)。     

碳纳米管冷阴极Pierce电子枪

为发展场致发射冷阴极毫米波电真空辐射源器件, 对利用大面积碳纳米管冷阴极产生大电流、高电流密度电子注的电子光学系统进行了研究.通过在Pierce电子枪阴极表面引入栅网结构, 解决了碳纳米管冷阴极场致发射所需的强电场和电子聚束问题.在碳纳米管冷阴极实验测试数据的基础上, 采用粒子模拟软件对上述电子光学系统进行了仿真.研究了栅网对注电流、注腰半径和电子注散射的影响, 分析了阳极电压和外加轴向磁场对电子注的聚束作用.优化后的仿真结果表明在阴极发射面为3.03 cm2时, 该电子光学系统能够产生210 mA、60 kV, 电流密度为6.7 A/cm2, 最大注半径为1mm的电子注.