Electric ignition energy evaluation and the energy distribution structure of energy released in electrostatic discharge process

Ignition energy is one of the important parameters of flammable materials, and evaluating ignition energy precisely is essential to the safety of process industry and combustion science and technology. By using electric spark discharge test system, a series of electric spark discharge experiments were conducted with the capacitor-stored energy in the range of 10 J, 100 J, and 1000 J, respectively. The evaluation method for energy consumed by electric spark, wire, and switch during capacitor discharge process has been studied respectively. The resistance of wire, switch, and plasma between electrodes has been evaluated by different methods and an optimized evaluation method has been obtained. The electric energy consumed by wire, electric switch, and electric spark-induced plasma between electrodes were obtained and the energy structure of capacitor-released energy was analyzed. The dynamic process and the characteristic parameters(the maximum power, duration of discharge process) of electric spark discharge process have been analyzed. Experimental results showed that, electric spark-consumed energy only accounts for 8%–14% of the capacitor-released energy. With the increase of capacitor-released energy, the duration of discharge process becomes longer, and the energy of plasma accounts for more in the capacitor-released energy. The power of electric spark varies with time as a damped sinusoids function and the period and the maximum value increase with the capacitor-released energy.     

一种无虚通道NoC负载均衡容错路由算法

随着芯片复杂度的不断增大,设计一个高效的片上网络容错路由算法面临着巨大的挑战。由于芯片面积开销的限制,拥有低面积开销的无虚通道片上网络路由器受到学术界的广泛关注。但目前对无虚通道片上网络容错路由算法的研究却停留在容错性能上,而忽略了容错路由算法的路由路径过于单一所造成的负载不均、数据包平均延迟较大等问题。文章在借鉴已有的奇偶转向容错路由算法的基础上,对算法的故障模型和故障绕行策略进行优化,并在算法中融入负载均衡策略,以形成新的容错算法缓解上述问题。在9x9的2D mesh网络中对新提出的算法和参考算法的仿真结果表明：与参考算法相比,新算法在降低数据延迟和吞吐量方面有着明显的优势,在最优情况下能减少8.92%数据延迟和增加10.46%的吞吐量。     

Fractal dynamics in the ionization of helium Rydberg atoms

We study the ionization of helium Rydberg atoms in an electric field above the classical ionization threshold within the semiclassical theory.By introducing a fractal approach to describe the chaotic dynamical behavior of the ionization,we identify the fractal self-similarity structure of the escape time versus the distribution of the initial launch angles of electrons,and find that the self-similarity region shifts toward larger initial launch angles with a decrease in the scaled energy.We connect the fractal structure of the escape time plot to the escape dynamics of ionized electrons.Of particular note is that the fractal dimensions are sensitively controlled by the scaled energy and magnetic field,and exhibit excellent agreement with the chaotic extent of the ionization systems for both helium and hydrogen Rydberg atoms.It is shown that,besides the electric and magnetic fields,core scattering is a primary factor in the fractal dynamics.     

化学沉淀法制备BaTiO3纳米粉体的研究

以正钛酸(H₄TiO₄)、硝酸钡[Ba(NO₃)₂]为原料, 以双氧水、氨水为溶剂, 采用化学沉淀法制备出晶粒尺寸约20 nm的钛酸钡粉体. 研究了原料种类、煅烧温度、加料方式、反应温度对钛酸钡粉体性能的影响, 确定了最佳的制备条件. 结果表明: 当正钛酸(g)∶双氧水(mL)∶氨水(mL)＝1∶5∶3, 且采用正钛酸的双氧水-氨水溶液缓慢滴加到硝酸钡溶液中的加料方式时, 溶解完全, 制得的BaTiO₃粉体粒径小、纯度高. 用X射线衍射(XRD)和扫描电子显微镜(SEM)表征了颗粒的晶体结构、晶型转变机理以及颗粒的形貌|结果显示: 前驱体的起始晶型转变温度为500, 800 ℃煅烧获得的粒子晶型完整, 形貌呈规则的球形, 当煅烧温度升高到900 ℃时, 粉体晶体结构由立方相转变为四方相.     

“乙醇”教学设计

1指导思想与理论依据新理念下的化学教学强调"以学生的发展为本",注重学生的可持续发展。建构主义理论认为"学习不应该被看成是对于教师授予知识的被动接受,而是学习者以自身已有的知识和经验为基础主     

胶束电动力学毛细管色谱法测定尿中核苷

用胶束电动力学毛细管色谱法测定尿中核苷.通过苯基硼酸亲和色谱柱对尿中核苷进行纯化,以十二烷基磺酸钠(SDS)-十水合四硼酸钠-磷酸二氢钠为缓冲液(pH=6.96),在未涂层石英毛细管上,于7kV恒压,29℃下进行电泳分离,检测波长为254nm.此方法用于28个正常人尿中14种核苷的测定,确定了正常成年人(汉族)尿中核苷的排放范围.     

利用无网格法进行几何非线性热固耦合柔性机构拓扑优化设计

将无网格伽辽金法引入到拓扑优化中,利用其进行了几何非线性热固耦合柔性机构的优化设计研究.利用无网格法离散和求解了热固耦合场的控制方程.基于SIMP模型和无网格法,建立了柔性机构的优化模型,利用MMA方法求解.研究了基于无网格法的伴随敏度分析方法,并提出了解决拓扑结构出现不连续散乱点同题的敏度过滤方法.求解经典算例,表明本文方法的正确性和有效性.     

波导内脏超声推挤的试验研究

本文从实验和理论分析两个方面研究了超声推挤过程中推挤力和因负载变化等因素上起的声学系统谐振频率的变化,提出了超声推挤机理,为提高加工精度,降低表面粗糙度建立了基础。     

多孔体内插物强化蒸汽凝结换热实用计算关联式

根据多孔体内插物显著影响凝结液膜流动状态并导致液膜波动的特性,提出了用于大空隙率多孔体内插物强化蒸汽凝结换热计算的半经验准则关联式,用实验结果对关联式的正确性进行了验证,并通过数值模拟计算结果与该关联式结果的比较,证明了提出的半经验关联式可以应用到实验范围以外。     

光阴极微波电子枪优化设计的考虑

对光阴极微波电子枪进行了优化设计 ,给出了光阳极微波腔的形状、电参数和电场分布 .电子束团初始参数对束流横向发射度的影响 ,用 Parmela程序对其进行了优化 ,得到了一组最优参数 .考虑了补偿线圈对束流发射度的影响 ,对线圈的位置和电流的大小做了优化 .经过优化后得到腔出口处的横向发射度为 1 .39πmm.mrad,达到了设计时的要求. A 1.3 GHz photocathode RF gun is under study in peking University. The photocathode RF gun, composed of gun cavity, photocathode and Laser system, is expected to deliver a electron beam with a normalized transverse rms emittance of 1π mm·mrad at a charge of 1nC. Its performance has been studied by the space-charge tracking code PARMELA. The influences of the initialized electron beam were also studied. The emittance compensation technique is employed. After optimization of the parameters was...