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研究了滑动弧放电过程中电参数的变化,并对滑动弧等离子体中的非平衡度和各个参数之间的关系进行了讨论。应用双通道电弧模型,对电弧在气流作用下运动规律进行了数值模拟,模拟所得的结果有助于分析滑动弧非平衡等离子体的产生机理。     

Evaluating fair premiums of equity-linked policies with surrender option in a bivariate model

We tackle the problem of computing fair periodical premiums of an equity-linked policy with a maturity guarantee and an embedded surrender option. We consider the policy as a Bermudan-style contingent claim that can be exercised at the premium payment dates. The evaluation framework is based on a discretization of a bivariate model that considers the joint evolution of the equity value with stochastic interest rates. To deeply reduce the computational complexity of the pricing problem we use the singular points framework that allows us to compute accurate upper and lower estimates of the policy premiums.     

Sufficient criteria are necessary for monotone control volume methods

Control volume methods are prevailing for solving the potential equation arising in porous media flow. The continuous form of this equation is known to satisfy a maximum principle, and it is desirable that the numerical approximation shares this quality. Recently, sufficient criteria were derived guaranteeing a discrete maximum principle for a class of control volume methods. We show that most of these criteria are also necessary. An implication of our work is that no linear nine-point control volume method can be constructed for quadrilateral grids in 2D that is exact for linear solutions while remaining monotone for general problems.     

Ueber die Haupttangentencurven derKummer' schen Fläche vierten Grades mit 16 Knotenpunkten

Ohne ZusammenfassungDer Berliner Academie am 15. December 1870 vorgelegt durch Herrn Kummer.     

Surface modification and submicron structure of carbon fibers through high current pulse

This paper investigated the behavior of carbon fibers subjected to a ∼20 kA, ∼5 μs high current pulse. It was found that the broken fibers and submicron particles were generated by electrical explosion process. After high current pulsed discharge, the fiber diameter increased significantly, from 5-7 μm to ∼13 μm. Also, the surface rupture of carbon fibers with valleys of hundreds of nanometers was observed. Most notably, the submicron particles appeared with two typical shapes (near-sphere and square). The high current pulsed discharge of carbon fibers can be divided into three stages, namely, heating stage, phase change stage, and explosion stage. Indeed, the electrical explosion process occurred in the last stage of ∼200 ns. The nature behind these results is closely related to the plasma development during the explosion process. The plasma expansion due to a large plasma thermal stress leads to the incomplete explosion. In the explosion stage, the current passing through the fibers exhibited a huge fluctuation, indicating plasma instabilities. Finally, the physical mechanisms, how to affect the surface morphology of carbon fibers, are presented.     

Design of Infrared Inverted Telephoto-Optical System with Double-Layer Harmonic Diffractive Element

A double-layer harmonic diffractive element （HDE） structure is investigated and the optimization procedure is given based on the equation of diffraction efficiency of the double-layer diffractive optical element. A new infrared double-layer inverted telephoto-optical system with an HDE is designed, which can work in the mid- and farinfrared wavebands. The diffraction efficiency of the system at each wavelength in the designed two wavebands is larger than 90%, which improves the image contrast and the imaging quality significantly.     

电感储能加速器运行中电磁辐射的实验研究

发现了一个被普遍忽视的问题,在电感储能加速器运行中产生很强的电磁辐射.这种电磁辐射在一定距离范围内可以对测量仪器造成破坏.通过多次测量,发现此辐射主频在75MHz左右,频谱较宽,是一低频电磁波.以同轴电缆作为测量仪器的替代物,测量辐射场对同轴电缆的作用,罗氏线圈测得电流幅值达217mA.辐射可能是由回路LC振荡或者加速器中的电爆炸丝开关引起的.基于LC振荡和电爆炸丝的工作原理,分别讨论了辐射产生的物理过程.我们更倾向于认为辐射来源于开关导通引起的回路LC振荡.此外,辐射强度受电流的变化率影响,初级回路电流变化慢,次级回路变化快,这样产生了一弱一强的两个辐射信号.这些为进一步研究电感储能加速器运行中的电磁辐射及防护提供实验支持.