表面纹理磁盘滑动接触的温度和应力及退磁临界条件的研究

采用应力场和温度场耦合的有限元方法,计算磁头/磁盘滑动接触下铝基磁盘磁层内瞬态温度场和应力场及退磁临界条件,分析接触压力、滑动速度、摩擦系数以及磁盘表面纹理对磁层内最大摩擦温升值和最大应力值的影响.结果表明:波形纹理表面瞬间滑动接触所产生的温度分布呈波形特征,表面纹理越尖锐,磁层内的温度和应力越大;滑动速度对磁层内温度的影响大于对应力的影响;当磁层最大应力小于1.2 GPa时,所对应的速度和压力为安全工况;当温升大于180 K时所对应的工况将导致磁盘退磁.     

范德华力对计算机磁头/磁盘超薄气膜承载性能的影响

在纳米间隙条件下,以楔型滑块和双轨式磁头为例,推导出楔型及双轨式磁头范德华力的计算公式,考察了范德华力对计算机磁头/磁盘超薄气膜承载性能的影响.结果表明,范德华力对计算机磁头/磁盘的承载性能影响很大,范德华力可以降低磁头的承载能力,尤其在最小空气间隙小于6 nm时;在相同尺寸的磁头中,双轨式磁头的范德华力小于楔型滑块的范德华力,而前者的承载力大于后者,双轨式磁头的范德华力对其承载性能影响较小.范德华力可以使飞行高度降低,为磁头设计和磁头/磁盘装配的重要依据.     

掺钇磁盘玻璃基板的研究

计算机大容量外部存储器最好的匹配是硬磁盘, 传统磁盘为在铝基板表面涂敷约10 μm金属磁厚膜, 近年几乎都使用表面致密、光滑、平直、硬度高、比重小、强度大、膨胀系数小、耐磨、便宜、与涂层附着力强、不易破坏的玻璃基板.其中大离子交换小离子的化学强化薄板玻璃基板虽然材质价廉、易加工,但其表面粗糙度只能达到2 nm, 为此研究用离子注入法制作磁盘玻璃基板,使其力学、电学、磁学性能都得到改善. 另外, 进一步利用玻璃成核析晶为理论基础研制出Y2O3-Li2O-SiO2-P2O5系统优质磁盘微晶玻璃基板,并揭示了Y2O3的作用机制. 该玻璃基板还可应用于光盘、光盘母盘、液晶显示器、光掩膜、IC等基板.     

Magnetic Instability in Accretion Disks with Anomalous Viscosity

Using the new model of anomalous viscosity, we investigate the magnetic instability in the accretion disks and give the dispersion formula. On the basis of the dispersion relation obtained, it is numerically shown that the instability condition of viscous accretion disk is well consistent with that of the ideal accretion disk, namely there would be magneto-rotational instability in the presence of a vertical weak magnetic field. For a given distance R from the centre of the disk, the growth rate in the anomalous case deviates from the ideal case more greatly when the vertical magnetic field is smaller. The large viscosity limits to the instability. In the two cases, the distributions of growth rate with wave number κ approach each other when the magnetic field increases. It greatly represses the effect of viscosity.     

Modelling Neutral Hydrogen Discs of Spiral Galaxies

We present an analytical model of a neutral hydrogen disc in a spiral galaxy.The gas disc of the spiral galaxy is assumed to have an exponential surface density profile and to be ionized by the cosmic ultraviolet background.To compare with observations,we consider the disc position angle and inclination angle for a line of sight going through the galaxy disc,The HI column densities depend on the strength of ionizing field and disc position and inclination.The model was applied to NGC 3198 and the results were compared with observational data.The Hi disc profile at large disc radii can be tested by further HI observations using radio telescopes with a larger aperture than the present facilities.This HI disc model can be used to predict quasar absorption line systems by galaxy discs if quasar lines of sight go through the discs.     

单自由度冲击扰动下模拟磁头／磁盘系统接触回复特性的实验研究

采用自制的试验装置研究了单自由度冲击扰动下磁头 /磁盘系统的接触回复特性 ,分析了不同载荷下球形模拟磁头跳跃振动回复系数和接触时间与输入速度之间的关系 .结果表明 :当载荷较小时 ,回复系数随着输入速度的减小而增加 ,而当载荷较大时 ,回复系数随着输入速度的减小而减小 .在不同载荷条件下 ,接触时间均随输入速度的减小而缩短 ,但小载荷下接触时间缩短的幅度较大 .球形模拟磁头的回复特性和接触时间与载荷、输入速度及润滑膜特性有关 ,增大载荷和选择合适的润滑剂均可抑制跳跃振动     

Neutron Star Motion in the Disk Galaxy

The neutron star motions are based on the undisturbed finitely thick galactic disk gravitational potential model. Two initial conditions, i.e. the locations and velocities, are considered. The Monte Carlo method is employed to separate rich diversities of the orbits of neutron stars into several sorts. The Poineare section has the potential to play an important role in the diagnosis of the neutron star motion. It has been observed that the increasing ratio of the motion range vertical to the galactic plane to that parallel to the galactic plane results in the irregularity of neutron star motion.     

Invariant Metrics and Laplacians on Siegel-Jacobi Disk

Let Dn be the generalized unit disk of degree n. In this paper, Riemannian metrics on the Siegel-Jacobi disk Dn × C（^m,n） which are invariant under the natural action of the Jacobi group are found explicitly and the Laplacians of these invariant metrics are computed explicitly. These are expressed in terms of the trace form.     

磁头-磁盘接触作用力对磁记录层信息强度影响规律的定量研究

磁存储密度的持续增长会导致磁头-磁盘的间距不断减小, 这样, 极有可能引起磁头-磁盘接触退磁的发生, 从而造成磁记录层存储数据的丢失. 为了明确退磁过程中的相应作用关系, 本文通过磁力显微镜的相位成像原理直接给出了磁盘退磁的定量测量方法. 并且依据此方法, 利用纳米划痕实验研究了磁头-磁盘接触作用力对磁记录层信息强度的影响规律. 结果表明:当磁头-磁盘接触作用力超过临界退磁载荷时, 磁记录层的信息强度与磁头-磁盘接触作用力之间存在减函数关系; 在低接触载荷区域中, 即使磁记录层表面没有划痕产生, 磁盘退磁现象仍旧可能发生; 对于任意磁头-磁盘接触作用力, 磁盘表面的破坏区域总是会大于磁记录层的退磁区域; 当磁头反复划刮磁盘的同一位置时, 磁记录层的表面划痕处将出现弹性安定状态, 对应地, 磁记录层的信息强度会趋近于某一定值.     

Novel magnetorheological figuring of KDP crystal

A new process of magnetorheological figuring(MRF) based on the deliquescence theory is proposed to finish KDP crystals.A novel,non-aqueous,and abrasive-free magnetorheological(MR) fluid is explored,and polishing experiments are performed on a self-developed MRF machine.The removal mechanism is reckoned to be the result of a combination of dominant chemical etching and accessorial mechanical drag.The results indicate that the surface roughness of I plate KDP of 80 × 80(mm) polished by MRF is 1.2 nm(root mean square(RMS)),and the tool marks are completely removed.The surface accuracy by MRF is 0.035λ(RMS),and the low/middle-frequency errors are significantly corrected after MRF.