New construction of mattress springs

It is commonly believed that spring systems in upholstered furniture are considerably more durable as well as friendlier in usage than foam systems. The objective of this study was to design and develop new constructions of hybrid springs for mattresses and to compare their stiffness with the stiffness of typical springs used in production of furniture for lying. The performed investigations comprised attempts to numerical modelling of new spring constructions, making their physical prototypes and carrying out laboratory tests of uniaxial compression. It was demonstrated on the basis of the performed investigations and the analysis of their results that the new hybrid spring for mattresses has desired progressive stiffness characteristics and, from the point of its usage, it can effectively replace the traditional bonnell spring.     

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.     

Optical operation of a magnetic bubble

A magnetic bubble domain is generated on liquid-phase epitaxial (LPE) garnet film by focusing laser light. It is possible to write with only a few milliwatts light power on a thin film with a low anisotropy field. Because the Bi-containing LPE films used have a high Faraday rotation angle, a written bit or bubble can be read out with a high contrast ratio. Because of its low coercivity, the bubble moves along the temperature gradient to the region heated by the light beam and is then stabilized at a corner of a square formed on the film by etching or ion-implantation. Erasure is possible selectively or all together by increasing the bias field. These optical operations of a magnetic bubble are discussed in connection with the material parameters.     

Analytical model of a bubble switch

A model is presented for a bubble switch based on the Y-bar propagation element. Good correlation of the predictions of the model with experimental results is found for 8 μ bubbles. The heuristically derived scaling law, which predicts that the switching current must remain constant as the bubble diameter decreases, is confirmed by direct calculation with the model. The model shows that it will be increasingly difficult to design switches as the bubble diameter is reduced below 1 μ.     

High speed imaging of bubble clouds generated in pulsed ultrasound cavitational therapy--histotripsy

Our recent studies have demonstrated that mechanical fractionation of tissue structure with sharply demarcated boundaries can be achieved using short (< 20 micros), high intensity ultrasound pulses delivered at low duty cycles. We have called this technique histotripsy. Histotripsy has potential clinical applications where noninvasive tissue fractionation and/or tissue removal are desired. The primary mechanism of histotripsy is thought to be acoustic cavitation, which is supported by a temporally changing acoustic backscatter observed during the histotripsy process. In this paper, a fast-gated digital camera was used to image the hypothesized cavitating bubble cloud generated by histotripsy pulses. The bubble cloud was produced at a tissue-water interface and inside an optically transparent gelatin phantom which mimics bulk tissue. The imaging shows the following: (1) Initiation of a temporally changing acoustic backscatter was due to the formation of a bubble cloud; (2) The pressure threshold to generate a bubble cloud was lower at a tissue-fluid interface than inside bulk tissue; and (3) at higher pulse pressure, the bubble cloud lasted longer and grew larger. The results add further support to the hypothesis that the histotripsy process is due to a cavitating bubble cloud and may provide insight into the sharp boundaries of histotripsy lesions.     

Breakaway of a bubble from a heating surface

In this paper we solve the problem of determining the breakaway, diameter of the vapor bubble in the case of a large number of active vapor-forming centers. The motion of the liquid is discussed. The dynamic pressure of the liquid surrounding the vapor bubble and the radius of the bubble on breakaway from the heating surface are determined.     

Formation of a gas bubble on a vibrating capillary immersed in a liquid

The formation of a train of bubbles in a low-viscosity liquid is investigated. The dependence of the gas flow rate during formation of the bubble train on the vibrational acceleration of the capillary is determined.Deceased.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 30, No. 4, pp. 665–670, April, 1976.     

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。     

固化压力对一种纸基摩擦材料摩擦性能的影响

基于本实验室制备的一种炭纤维增强纸基摩擦材料, 研究了固化压力对材料孔隙率, 动摩擦系数, 静动摩擦系数之比, 摩擦力矩曲线的影响。研究结果表明: 孔隙率随固化压力增加而下降; 动摩擦系数随制动压力的增加均呈下降趋势; 静动摩擦系数比值随制动压力的增加分布趋势较为复杂: 较低的固化压力条件下, 静动摩擦系数之比略有上升, 而较高的固化压力条件下静动摩擦系数之比则略有下降趋势; 摩擦力矩曲线随固化压力升高有轻微翘曲出现。综合考虑固化压力对动摩擦系数、 静动摩擦系数比值以及摩擦力矩曲线的影响, 在这种纸基摩擦材料成分不变的条件下, 其对应较为合适的固化压力约为3.4MPa。      

复合材料薄膜充气床垫的多物质ALE数值模拟

某型充气床垫是典型的气囊结构,该床垫由新型柔性薄膜材料制成,力学性能复杂。目前,国内外气囊仿真研究多采用两种方法,一种是控制体积方法(CV),该方法比较简便计算需求较少,但计算精度只能满足一般的工程需要;另一种方法是基于有限元技术的ALE方法,该方法计算精度高,可用于气囊的详细仿真。针对充气床垫充气爆破工况和载人工况的复杂性,采用多物质ALE方法对其进行了详细数值模拟。充气爆破工况通过与物理试验对比,判断出床垫结构的薄弱位置,同时提出结构改进方案。载人工作工况通过参数分析方法,分析不同充气内压时床垫变形和应力状况,并判断出床垫最佳工作内压。最终的仿真结果可作为该型产品设计定型的重要依据,也为同类问题提供了参考。     

Temperature distributions in a megabit bubble chip

For a large-capacity large-size bubble chip, various operating parameter nonuniformities across the chip as well as garnet material and device processing inhomogeneities could be a source of considerable bias margin loss. An example is chip temperature nonuniformity due to detector heating. In an attempt to estimate the chip margin loss due to local temperature nonuniformities, temperature distributions in a Mbit chip have been mapped as a function of detector current amplitude. Temperatures at several regions in the chip were monitored by measuring the resistance of active device components, such as transfer-in gate and replicate/transfer-out gate conductors, and detectors themselves that are of full-shorted 200-element chevron stretchar type. A simple physical model has been developed which, together with various measured local temperatures, provides complete two-dimensional mapping of temperature distributions in the chip. Nonnegligible temperature differences are shown to exist among minor loops (especially at the replicate/transfer-out gate), and those minor loops located close to the detectors are shown to suffer considerable margin losses even at moderate detector-current amplitudes. Operating margin measurements of the minor loops have confirmed the finding.     

A two-dimensional bubble near a free surface

A boundary integral technique is used in conjunction with a conformal map to examine the motion of a two-dimensional bubble near a free surface. For small times, the results are shown to compare well with a first-order perturbation expansion for the problem of the response of a free surface to a deeply submerged dipole. For a large bubble, far from the free surface the bubble deformation is found to agree with previous theoretical and experimental results for a two-dimensional bubble in an infinite fluid.     

The pressure inside a suspended gas bubble

Summary. An integral representation is derived for the pressure inside an inviscid, compressible or incompressible bubble suspended in a Newtonian fluid, in terms of the instantaneous bubble shape and structure of the ambient velocity field. The starting point in deriving this representation is the reciprocal theorem for Navier-Stokes flow, applied for the flow around the bubble and the flow due to a point source situated inside the bubble. The integral representation is used to evaluate the pressure inside a spherical bubble in potential flow to leading order with respect to the Weber number, and the pressure inside a circular bubble in Stokes flow to leading order with respect to the capillary number. The results are consistent with and generalize numerical and analytical solutions derived by previous authors.     

Detonation waves in a multicomponent bubble liquid

The features of evolution of detonation waves in bubble liquid containing bubbles, some of which consist of combustible gas mixture and others of which contain inert gas, have been considered. The dynamics of inert bubbles against the background of a detonation wave appearing because of bubbles of the combustible gas mixture has been studied.     

Cavitation bubble dynamics in a polar liquid

It is suggested to introduce a new term into the equation describing the cavitation bubble dynamics in a polar liquid that takes into account a finite relaxation rate of dipole molecules of the liquid during rapid collapse of the bubble. It is shown that solutions of the modified equation provide significantly lower values of the thermodynamic parameters of the gas at the end of the collapse, so that thermal mechanisms of the high-energy processes accompanying cavitation cannot be operative. A substantial difference between commonly accepted notions and the proposed physical mechanism of accumulation of the acoustic field energy is demonstrated, whereby the energy is concentrated in the electrostatic field of oriented dipoles rather than in the form of the energy of compressed gas in the cavitation bubble. Experimental data are presented that confirm the proposed model.     

Phase velocity in a gas-liquid bubble flow

An experimental method and some results are presented for measurement of gas phase velocity and slip velocity in an ascending gas-liquid flow in a vertical tube.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 57, No. 1, pp. 12–15, July, 1989.     

Steady motion of a gas bubble in a liquid

A method is proposed for calculating the velocity of a gas bubble during a steady lift in a liquid, on the assumption that the bubble transmits to the medium an array of weak waves.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 25, No. 4, pp. 656–662, October, 1973.     

Effect of surface tension on the collapse of a cavitation bubble

By means of numerical calculations on the BéSM6 computer, we study the effect of surface tension on the size and rate of collapse of a cavitation bubble for the entire region of surface tensions of real liquids =(160)·10 ^-2 N/m (at temperatures 290 K). The effect of two parallel solid walls bounding the liquid is taken into account.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 60, No. 1, pp. 41–46, January, 1991.