硅衬底上纳米晶金刚石生长

研究了蚀刻气体对生长在硅衬底上纳米晶金刚石合成的影响.合成方法为热丝化学气相沉积法,衬底温度为550 oC,反应压力为4 kPa. 其中甲烷和氢气分别作为源气体和稀释气体. 氮气、氢气和氨气用作蚀刻气体. 结果表明,仅氢气作为蚀刻气体可获得最佳工艺条件.     

用可移动电流丝方法重建HL-2A等离子体边界的研究

根据Shafranov电流密度矩理论，给出了用可移动电流丝方法重建HL-2A装置等离子体边界的具体计算方法，研究了用可移动电流丝方法(VCF法)重建边界的可行性.VCF法与固定电流丝方法(FCF法)和有限电流元法(FCE法)相比，最大的优点就是用1—3个可移动电流丝就可以准确地重建位置和小半径快速变化的等离子体位形，这正好弥补了FCF法的不足.将可移动电流丝方法和FCF法相结合，可以实现全程等离子体放电的边界实时显示和等离子体的位形控制. 关键词： 可移动电流丝方法 边界识别     

The use of the isotropic orientation factor in fluorescence resonance energy transfer (FRET) studies of the actin filament

A Dale-Eisinger style analysis (R. E. Daleet al., Biophys. J. 26, 161, 1979) is used to produce three-dimensional plots that display the limits on the average orientation factor k ² that is required to calculate molecular distances in F-actin from fluorescence resonance energy transfer measurements. Maxima and minima plots are generated for the transfer of energy from a donor to a single acceptor and for transfer to multiple acceptors that are related by F-actin helical symmetry. The analysis is performed in terms of dipole cone half-angles rather than depolarization factors, in order to facilitate the modeling of the multiple acceptor problem. Calculations are carried out under the restrictive condition of a single electric dipole moment per fluorophore. In addition, both surface and volume averaging of the donor and acceptor dipoles are considered. Comparisons between the plots show that for the multiple acceptor cases with F-actin symmetry, there is a great reduction in the range for maxima and minima limits on k ². The calculations also suggest guidelines for the choice of fluorescence label that will result in an average orientation factor occurring within acceptable limits, i.e., inside the limits for which k ²=2/3 may be employed. Thus, without having detailed knowledge of the mean donor or acceptor dipole relative orientations, the use of k ²=2/3 in radial coordinate studies of F-actin is more than reasonable and is fairly assured of being correct.     

Detection of large cluster ions by time-of-flight mass spectrometry with a conversion dynode

A linear time-of-flight mass spectrometer (TOF-MS) has been constructed to measure mass distribution of negatively-charged clusters formed in the hot filament diamond chemical vapor deposition (CVD) process and in the metal evaporation. A conversion dynode made of CsI was employed to enhance detection efficiency of the large clusters greater than 10 000 amu. An atomic peak from the tungsten evaporation was used for the mass calibration of the carbon clusters. The carbon clusters produced in the CVD diamond process was loosely bound so that they were easily fragmented during passage through accelerating electric fields. The mass distribution measured with the TOF-MS system showed much less abundance of large clusters than those measured previously with the energy analyzer and Wien filter.     

Motion of a vortex filament with axial flow in the half space

We consider a nonlinear third order dispersive equation which models the motion of a vortex filament immersed in an incompressible and inviscid fluid occupying the three dimensional half space. We prove the unique solvability of initial–boundary value problems as an attempt to analyze the motion of a tornado.     

A Remark on the Global Existence of a Third Order Dispersive Flow into Locally Hermitian Symmetric Spaces

We prove time-global existence of solutions to the initial value problem for a third order dispersive flow into compact locally Hermitian symmetric spaces. The equation under consideration generalizes two-sphere-valued completely integrable systems modeling the motion of vortex filament. Unlike one-dimensional Schrödinger maps, our third order equation is not completely integrable under the curvature condition on the target manifold in general. The idea of our proof is to exploit two conservation laws and an “almost conserved quantity” which prevents the formation of a singularity in finite time.     

Organizing Filament of Small Amplitude Scroll Waves

We theoretically analyze the organizing filament of small amplitude scroll waves in general excitable media by perturbation method and explicitly give the expressions of coefficients in Keener theory.In particular for the excitable media with equal diffusion,we obtain a close system for the motion of the filament.With an example of the Oregonator Model,our results are in good agreement with those simulated by Windree.     

High-density silicon and silicon nitride cones

High-density cone-shaped silicon and silicon nitride have been synthesized on Si(1 0 0) substrates via plasma-assisted hot-filament chemical vapor deposition using a gas mixture of nitrogen, hydrogen and methane. Aligned silicon cones containing 3–10 at% C and N have been formed with less than 1 h growth. Further growth can lead to the increase of cone size and density, as well as to the formation of polycrystalline silicon nitride films on the tip and surface. The formation of these materials is thought to be due to the remodification of Si substrates under the effect of plasma and active C and N species. Different nucleation and growth styles were obtained under different growth conditions and reactive gas mixtures.     

水中流光放电流光丝的再发光和暂停行为

水中流光放电是研究水中放电基本物理、化学过程的主要研究对象.本文利用四分幅超高速相机、采用针-板电极结构、在20—800μS/cm水电导率范围内研究了水中微秒脉冲流光放电流光丝的再发光和暂停行为,探讨了高水电导率下观测不到流光丝的再发光的原因.结果发现:再发光在不同的流光丝之间交替发生并存在两种模式:一种为整根丝熄灭后再发光;一种为只有先端部分发光熄灭随后恢复发光.随着水电导率的增大,观测到流光丝的再发光现象的频度急剧减小, 540μS/cm水电导率时降到零;在20—800μS/cm水电导率条件下都可观测到流光丝伴生冲击波串分段现象,冲击波串分段现象的出现频度在65%以上,表明在20—800μS/cm水电导率条件下流光丝的暂停是一种普遍行为.通过测量两段冲击波的半径差得到流光的暂停时间平均为157 ns,几乎不受水电导率的影响;随着水电导率的增大,流光丝的发光强度显著增大,水电导率大于350μS/cm时,流光丝暂停期间内流光丝的光强度无法衰减到相机分辨水平以下,在相机获得的发光图像上看上去是持续发光的,难以分辨出流光丝"熄灭-再发光"过程.