水中微气泡光散射偏振特性的研究

在Mie散射理论的基础上，建立气泡光散射模型，计算水中微小气泡与固体微粒在不同的粒径参数和散射角条件下的光散射偏振特性，并对两者进行比较．结果表明，水中气泡及微粒对入射光散射后偏振状态的改变十分复杂．总体上气泡的退偏振效应比固体微粒强25％，微小气泡与固体微粒对偏振状态的影响在粒径域和散射角上具有选择性．     

存在内外质量交换的声空化泡动力学模型

对于空化微气泡的动力学研究多基于气泡内外无质量交换的Rayleigh模型。考虑了气泡内外的物质交换,泡内气体分子数量,即气泡平衡半径成为变量,进而将Rayleigh模型推广到有质量交换的情形。通过数值计算,获得稳定平衡半径,以及它与驱动声压的相关性。结果表明:在低声压驱动下,气泡稳定平衡半径随驱动声压增大而减小;而在高声压下,气泡稳定平衡半径随驱动声压增大而增大,稳定平衡半径-声压曲线存在一个转折点。     

超声作用下刚性壁面附近的双气泡脉动

在实际应用时,空化泡可能位于刚性壁附近。对刚性壁附近的空化泡脉动进行研究有利于更好地利用声空化。文章研究了刚性壁附近双气泡的动力学规律。研究结果表明,当两气泡与刚性壁距离相同时,气泡与壁之间的距离越大,刚性壁对辐射声波的反射越小,气泡脉动时能够达到的最大半径与最小半径的比值(即压缩比)也越大。若改变单个气泡与刚性壁的距离,则当两个气泡距离接近时,位置固定的气泡压缩比会减小。增大单个气泡的平衡半径,会使得两气泡脉动时的压缩比变小。此外,文章还对两气泡间距固定情况下,气泡压缩比与两气泡中心连线和壁面所成夹角之间的关系进行了讨论。     

基于AUTODYN的乳化炸药水下爆炸能量分布的数值研究

基于AUTODYN软件建立了水下爆炸一维楔形模型,对空气不耦合装药结构下爆炸能量的输出进行研究。首先获得炸药冲击波压力以及气泡脉动随时间的变化曲线,进一步获知径向不耦合状态下水下爆炸的冲击波峰值压力、气泡最大半径以及脉动周期等数据,并最终得到了不耦合系数下冲击波能以及气泡能的变化情况。将计算结果与已有的水下爆炸实验结果进行了比较分析。结果表明,该计算结果与实验数据吻合较好,证明了利用数值计算手段可以实现定量化表征炸药输出能量随不耦合装药结构的变化规律。     

基于AUTODYN的乳化炸药水下爆炸能量分布的数值研究

基于AUTODYN软件建立了水下爆炸一维楔形模型,对空气不耦合装药结构下爆炸能量的输出进行研究。首先获得炸药冲击波压力以及气泡脉动随时间的变化曲线,进一步获知径向不耦合状态下水下爆炸的冲击波峰值压力、气泡最大半径以及脉动周期等数据,并最终得到了不耦合系数下冲击波能以及气泡能的变化情况。将计算结果与已有的水下爆炸实验结果进行了比较分析。结果表明,该计算结果与实验数据吻合较好,证明了利用数值计算手段可以实现定量化表征炸药输出能量随不耦合装药结构的变化规律。     

单泡声致发光中泡内气体含量参数实验研究

液体中的含气量是单泡声致发光相空间的重要参数，对声致发光气泡的运动及发光有重要影响本文给出了一种使用插入式荧光光谱含氧量计测量稳态单泡声致发光的液体中气体含量参数的方法，并对这父键性参数与气泡平衡半径R0和声压Pa的关系进行了具体的研究，再次验证了扩散平衡、化学分解假设理论。     

单泡声致发光——气泡的动力学特性

单泡声致发光现象中，气泡动力学特性的研究是十分重要的。文章由简单的振子模型及能量守恒定律，导出了不可压缩、弱粘滞流体中纯径向振动气泡的Rayleigh—Plesset方程，利用龙格-库塔法计算了不同驱动声压下的R(t)曲线，并对崩溃相气泡的聚能效应做了讨论。     

考虑热效应的液氢气泡生长特性研究北大核心CSCD

根据单个气泡的生长特点,考虑液氢的热效应和气泡内部温度分布,通过联立求解热平衡方程、热扩散方程、Rayleigh-Plesset方程和半无限大空间的导热方程构建了单个气泡生长的数理模型。通过液氮工质中气泡的生长实验结果验证了模型的正确性,进而对比了几种典型低温工质中气泡半径的热力学生长过程,分析了不同工质热效应参数对气泡半径和半径临界时间的影响。此外还研究了液氢中单个气泡的半径生长过程和半径临界时间随环境压力和过热度的变化规律。     

喷管内临界泡状流计算分析

基于均质混合流模型,引入Rayleigh-Plesset方程考虑气泡动力学作用,采用拉格朗日有限体积法,进行喷管内非稳态泡状流计算。分析临界泡状流的特性,并把流场计算结果与相关实验数据对比,吻合较好。将不同边界条件下的临界泡状流计算结果进行对比分析,得到了入口含气率、压力及初始气泡半径对临界泡状流动的影响。结果表明:临界入口速度随着入口含气率的增大而减小,而随入口压力、初始气泡半径的增大而增大。     

水下爆炸气泡脉动的数值研究磁

利用AUTODYN软件模拟PETN药柱和TNT球形装药水下爆炸气泡脉动的过程,分析了脉动周期与最大半径随装药量、爆炸深度的变化规律。结果表明：当炸药所处的爆炸深度一定时,气泡膨胀最大半径与初始半径的比值、气泡脉动周期与初始半径的比值均为一个定值;一定质量的TNT装药水下爆炸时,气泡最大半径随爆炸深度呈指数形式变化且该变化规律与装药量无关;在不考虑重力的影响下,装药的爆炸深度一定时,当装药的初始半径成倍增加时,气泡脉动最大半径亦成相同倍数增加。     

Magnetic bubble logic

Although the literature on the bubble logic devices is limited, the concepts and device configurations are diverse. In conductor-access devices, logic can be performed by bubble transfer operations. In field-access devices, logic can be performed by providing alternative paths which are selected by interaction between bubbles. Examples include the conjugate logic gates, the resident-bubble cellular logic, and the chevron 3-3 circuits. Logic can also be performed by counting bubbles, such as in the symmetric switching function implementation. The various mechanisms for implementing bubble logic are all described by truth tables. To assess their efficiency, they are compared in terms of space and delay when they are used to implement the same logic element - a full adder. They are all comparable except for the resident-bubble cellular logic which requires excessive space and delay. However, it is important to point out that only the symmetric switching function devices offer rewrite-ability to eliminate the part number problem, and accommodation for a large number of inputs to ease interconnection and delay equalization problems.     

Characterisation of bubble materials

The rapid development of magnetic bubble technology has required growth to exacting specifications of a large number of magnetic films of garnets and some amorphous binary and ternary alloys of rare-earth and transition metals. The characterisation of these films is an essential part in the search for newer materials which hold out promise for better device performance and cost viability. Many methods of films characterisation have been reported from time to time. By and large, these methods can be divided into two groups: one, bulk measurements made on the film and two, measurements made on the domains. We have attempted to collate and briefly introduce various techniques to characterise magnetic bubble materials in this review.     

Separation of a vapor bubble and calculation of the critical bubble radius

On the basis of the solution to the equation of motion of a variable mass, a formula is derived for analytically calculating the critical radius of a vapor bubble in a boiling liquid during free flow of the latter.Translated from Ihzhenerno-Fizicheskii Zhurnal, Vol. 24, No. 5, pp. 831–835, May, 1973.     

舰船气泡尾流场气泡数密度衰减模型研究

为探究舰船气泡尾流场中气泡的数密度衰减特性,通过港内海况条件下冲锋舟航行实验,以高速摄像机采集实验测得的不同螺旋桨转速下的真实气泡尾流场数据,对舰船气泡尾流场中不同螺旋桨转速工况下气泡的数密度衰减特性进行分析,得出舰船气泡尾流场中气泡数密度随时间呈指数衰减,最大气泡数密度可达8×105/m3,且衰减情况受螺旋桨转速的影响,转速越高衰减越快,并构建舰船气泡尾流场中考虑螺旋桨转速的气泡数密度衰减模型,模型与实验结果吻合良好,表明模型的正确性和应用价值,对舰船气泡尾流场微观气泡探测和鱼雷制导等研究应用具有参考价值。     

Magnetic bubble mass memory

An experimental magnetic bubble mass memory module complete with all control function and detection electronics has been built and operated. The module contains twenty-eight 16 448-bit mass memory chips and operates at a nominal rotating field frequency of 100 kHz. The module has an average access time of 2.7 ms, a read/write cycle time of 5.14 ms, and a data rate of 700 kbit/sec. A read error rate of <1.6 × 10¹²and error-free propagation in excess of 8.4 × 10¹⁵bubble cycles have been demonstrated.     

The magnetooptic bubble display

The various factors that affect the properties of magneto-optic (M/O) bubble displays which use bismuth substituted iron garnets are discussed. A composite bias magnet-ferrite drive coil assembly is described which allows optical access to the display chip. The drive coils required 300 mW to produce an in-plane field of 30 Oe when operated at 10 kHz, and the bias field was uniform to ± 1.5% over an area of radius equal to 1/10 that of the bias magnet. Also discussed is the brightness and heating of the display. A screen brightness of 160 candelas/m²is possible using a X20 projection lens, and the temperature rise of the display chip could be less than 1°C if adequate heat sinking were used. Finally a prototype hand-held display is described which contains a 1.3 k bit capacity display chip. Examples of characters written into that chip are given.     

Contiguous-disk bubble domain devices

Contiguous-disk bubble devices are an approach to higher bit density through the use of coarse overlay patterns in manipulating small bubbles to relax device lithography requirements. As a first step towards such an objective, a fully processed chip using ion-implanted devices has been tested, showing the feasibility of all required memory functions with 5-μm bubbles and 25-μm period overlay patterns. A critique of permalloy versus implanted contiguous-disk devices is made, pointing out their basic difference in magnetization reversal processes and explaining the superiority of the latter over the former in achieving a good edge affinity of bubbles. The requirements for a good implanted device are reviewed, including the selection of garnet material parameters (K1, λ111), of implantation parameters (ion energy and dosage) and of device pattern geometry (thickness and shape of implanted layer). An understanding of these requirements has made it possible to demonstrate 1-μm bubble propagation in several contiguous-disk type circuits with 4.5-μm periods, yielding an areal density of over 3 × 10⁷bit/in²made by conventional photolithography.     

Optical thermocapillary bubble trap

The phenomenon of thermocapillary trapping of gas bubbles by a laser beam in a layer of absorbing liquid confined between two plates is demonstrated. In this system, the laser beam is capable of trapping gas bubbles occurring at a distance of up to ten beam diameters. Acceleration of a trapped bubble was observed, and the bubble velocity was determined as a function of the distance to the beam projection on the layer plane. The force developed by a thermocapillary trap exceeds 10 nN.     

Magnetic bubble counting circuits

A new group of magnetic circuits that can count the number of magnetic bubbles and display them in any binary, ternary, ..., decimal basis is proposed. Feasibility of the concept was demonstrated by successful operation of a binary counter circuit. A design of a decimal counter is given.     

Eight-micron period bubble devices

Magnetic bubble shift register devices of 68 121- and 266 473-bit capacity have been fabricated and tested. The epitaxial garnet bubble films were nominally 1.7 μm thick, supported nominally 1.7-μm diameter bubbles, and had collapse fields of about 260 Oe. The storage area per bit was 64 μm², which was realized with a minimum coded feature dimension of 1 μm and contact photolithography using EBES chrome masters. Initial yields obtained in two experimental batches each of the two chip capacities are discussed. Parametric test results are presented for generator current, transfer current and phase, and rotating field intensity. Nominal values have been established to be 130-mA generate current, 21-mA transfer current, and 60-Oe drive. The detector signals were about half as large as normally obtained from 3.3-μm bubble devices with comparable resistance and conventional design.