Reactive Recoil and Pressure Pulsations with 1/ f Power Spectrum under Conditions of Explosion Boiling of Jets of Superheated Liquid

The results are given of an experimental investigation of the reactive recoil of jets of boiling up liquids in a thermodynamically highly nonequilibrium mode of efflux. The experimental data are given in the dimensionless form using the thermodynamic similarity methods. The correlation is discussed between the abrupt decrease in the reactive power with a complete disintegration of the jet under conditions of explosion boiling. Local measurements are performed of pressure pulsations in a jet of superheated liquid with different mechanisms of vaporization. It is found that, under conditions of explosion boiling, the power spectrum of pulsations depends inversely proportionally on frequency (1/f or flicker noise). This form of power spectrum implies the possibility of strong low-frequency pulsations of reactive recoil of boiling up flows.     

Critical Behavior in the Low-Energy Spin Fluctuations in High-Tc Superconductors

We study the spin fluctuations of pure and Zn-substituted La_{2 – x} Sr _x CuO₄ using the muon spin relaxation technique. Superconductivity is found to coexist with low-frequency spin fluctuations over a large region of the superconducting phase diagram. The characteristic temperature of spin fluctuations detected by SR decreases with increasing x and vanishes above a critical doping x _c 0.19. This value of x _c coincides with the doping at which the normal state pseudogap extrapolates to zero. These results are discussed in terms of a quantum transition that separates the superconducting phase diagram of high-temperature superconductors into two distinct ground states.     

Temperature Dependence of Spin-Density Fluctuations in Liquid 3He

The dynamic structure factor S(Q,E) in normal liquid ³ He, which contains information on both density and spin-density fluctuations, has been measured by inelastic neutron scattering both well below and close to the Fermi temperature. The data extend to smaller wave vectors and energies than covered in earlier experiments, and give a much better determination of the line shape of the spin-density response. Together with the temperature dependence, this allows to discriminate between different theoretical models for the nuclear spin fluctuations, and provides information on the quasiparticle dispersion and effective mass.     

Critical Fluctuations of Membranes: Spectroscopy Meets Thermodynamics

Broadband ultrasonic spectra (100 kHz to 2 GHz) of aqueous solutions of liposomes from phospholipids without and with cholesterol or with a peptide added are analyzed near the main phase-transition temperatures of the bilayer systems. All spectra reveal a critical term due to domain structure fluctuations and up to three relaxation terms with discrete relaxation times. By analogy with critically demixing binary fluids, the former is evaluated within the framework of the Bhattacharjee–Ferrell dynamic scaling theory. The relaxation rates of fluctuations and the critical amplitudes resulting from this analysis are discussed briefly. Consistency with and differences to critically demixing systems are demonstrated. The terms with discrete relaxation times are related to short-scale liposome deformation, rotational diffusion of phospholipid molecules, and conformational isomerization of alkyl chains within the bilayers, respectively.     

HL-1M装置边缘扰动和流速的实验研究

利用一组马赫探针研究HL-1M装置刮离层和边缘等离子体流在欧姆放电、壁硼化、偏压抽气孔栏、偏压电极、低混杂波电流驱动、电子回旋共振加热、弹丸注入、分子束注入、激光吹气和补充送气等情况下的平行流马赫数、离子饱和电流扰动、平行流速度剪切和极向流速度的分布。实验中发现局部等离子体电位快速变化，改变了电场分布，改变了边缘等离子体的流速和方向。从而改善了等离子体约束性能。     

Density of Superheated and Undercooled Liquid Alumina by a Contactless Method

The density of liquid alumina drops maintained in levitation with an aerodynamic device and heated with CO₂ lasers is determined by analysis of high-speed video digital images between 2000 and 3100 K in various gases. It is shown that consistent results can be achieved for the lighter drops (m<100 mg) which do not depend on the nature of the gas. Experiments performed with lasers impinging the drop surface or during free cooling of the preheated drop gave similar results. The density is represented by the following expression: d=(2.79±0.01)(l–(T–2500)) g·cm^–3, where =(4.22 ±0.14) × 10^–5K^–1.     

Long-Lived Magneto-dynamic Modes in Liquid 3He

We present NMR spectra of liquid ³He, confined to a cylindrical cell, in the temperature range from 2.3 to 1000 mK for a static field of 11.33 tesla and range of applied field gradients. The spectra are generated by taking the Fourier transform of the free induction decay (FID) following NMR tipping pulses. For small tipping angles, the spectra exhibit sharp lines which correspond to long-lived modes with decay times greater than 100 ms. The cause of these magneto-dynamic modes is oscillation of the transverse magnetisation in the applied magnetic field and the demagnetising field. The frequencies of the modes for a given field gradient are independent of temperature, but their damping depends on the effective spin diffusion coefficient which is determined by the Leggett-Rice effect. We also investigate how the spectrum changes with the magnetisation. We are able to simulate the spectra using a model that includes the demagnetising field. The predicted spectral-line frequencies are in reasonable agreement with experiment when there is an applied field gradient. The damping of the modes is due to diffusion, but because of the finite size of the matrices used in the calculation, we have found it necessary to increase the effective diffusion coefficient in the model above the experimental value in order to obtain a spectrum which resembles the experimental one.     

Critical Behavior in the Low-Energy Spin Fluctuations in High-T c Superconductors

We study the spin fluctuations of pure and Zn-substituted La_{2 ? x} Sr _x CuO₄ using the muon spin relaxation technique. Superconductivity is found to coexist with low-frequency spin fluctuations over a large region of the superconducting phase diagram. The characteristic temperature of spin fluctuations detected by μSR decreases with increasing x and vanishes above a critical doping x _c ≈ 0.19. This value of x _c coincides with the doping at which the normal state pseudogap extrapolates to zero. These results are discussed in terms of a quantum transition that separates the superconducting phase diagram of high-temperature superconductors into two distinct ground states.     

Analysis of Non-Equilibrium Fluctuations In A Ternary Liquid Mixture

From the benchmark values of the diffusion and thermodiffusion coefficients of the tetralin, isobutylbenzene and n-dodecane ternary mixture, and the published optical contrast factors, we have evaluated the theoretical amplitudes of the two composition modes of the refractive-index fluctuations. Shadowgraph experiments have been performed on ground, where the current theory is expected to be correct only for large wave vectors. Two decay times have been observed experimentally. The fastest one being related to the thermal diffusivity of the mixture, while the slower one to mass diffusion. Hence, it has not been possible to distinguish the two eigenvalues of the mass diffusion matrix, a problem also encountered in traditional light-scattering with ternary mixtures of similar-size molecules. Thus, to compare the measured Intermediate Scattering Function with theory, we fix the amplitudes and decay rates to the benchmark values, use the wave number as a fitting parameter, and compare it to the experimental wave number. The good agreement between theory and experiments for the larger wave numbers validates the theory developed for the microgravity conditions.     

液相对流对固液界面稳定性的影响

以模型合金丁二腈－乙醇的强制性晶体生长为基础，利用自行研制的液相对流驱动装置，详细考查了液相自然对流及强迫对流作用下，模型合金平界面失稳的动态生长过程，证实了液相的流动加快了液相温度与浓度分布的均匀化，从而增强了液／固界面的稳定性。并且随流动速度的增加，界面稳定性提高。     

Surface Factor in Incompressible Liquid Film Flow

The results of investigation of the influence of a solid surface on the film flow of a viscous incompressible liquid in a gravitational field are analyzed. Using the dimensional method, a generalized similarity criterion for a film flow has been obtained. The laboratory facility and the method for investigating the film flow for various types of packing elements are described.     

Visualisation of Convective Flow Patterns in Liquid Helium

The advantages of using liquid helium as the investigative fluid in Rayleigh-Bénard experiments are reviewed. A low temperature shadowgraphy apparatus is described that permits convective flow pattern visualisation in liquid helium, thus overcoming the main disadvantage until now of using quantum fluids. The factors involved in maximising the optical resolution for both the shadowgraph and schlieren methods are examined for several fluids and this discussion is applied to the low temperature apparatus in assessing its performance. Some preliminary results on pattern formation in liquid helium are presented.     

两种不锈钢在单相流和液/固两相流中冲刷与腐蚀的交互作用

用质量损失法研究了65Mn和316L及其Ni-P镀层的冲刷腐蚀行为.结果表明:在试样表面与流体间相对运动距离相同的条件下,65Mn和316L在单相流和两相流中的冲刷腐蚀速率随着介质温度的升高和理论流速的减小而增大.在20%H2sO4单相流和20%H2S04+20 g/L黄砂两相流(50℃,L88 m/s)中,冲刷与腐蚀...     

Quality and 1/f noise of electronic components

Classification rules of electronic components based on their 1/f noise measurements are presented. It is proposed to classify electronic components into four groups with different quality: high, good, low, poor. The results of investigations of type BF 414 transistors are reported.     

1/f noise in a model of intersecting phase transitions

A mathematical model for the appearance of fluctuations with a spectrum inversely proportional to the frequency (flicker or 1/f noise) upon the intersection of phase transitions is proposed. A system with a two-valley potential, whose dynamics are described by two coupled nonlinear Langevin equations that transform Gaussian δ-correlated noise (white noise) into two modes of stochastic fluctuations with spectra having 1/f ^μ and 1/f ^v frequency distributions, where μ ≈ 1 and 1.5 ? v ? 2, is considered.     

Experimental Study of Rewetting of a Superheated Plate with Structured Capillary-Porous Coating by Flowing Liquid Film

The experimental results on rewetting of the surface of a superheated vertical copper heater and a heater with a structured capillary-porous coating (applied by means of directed plasma spraying) by liquid nitrogen film are presented. It is shown that presence of the capillary-porous coating fundamentally influences the temperature variation and reduces the duration of overall plate cooling by more than three times. The high-speed videofilming of the transient processes was carried out and data on the character and structure of the rewetting front were obtained. Analysis of the synchronized measurements of the plate temperature and the high-speed video of transient processes shows that the higher cooling rate in the presence of structured capillary-porous coating is related to the development of intensive boiling in the rewetting front at sufficiently higher plate temperature.     

基于气液两相流的聚合物气辅挤出数值模拟

为了更准确地反映气辅挤出中气体对熔体成型的影响机理,建立了气液两相流模型,对不同气压作用下的熔体挤出成型进行了有限元数值模拟,得到了气辅作用下熔体的流速、压力降和第一法向应力差等分布。与完全滑移边界条件的模拟结果对比发现,基于气液两相流的气辅挤出,熔体的流速、压力降和第一法向应力差等物理场均存在较大变化。实验也验证了熔体挤出成型受气压的影响较大。对模拟和实验结果分析表明,气体的辅助作用对熔体产生的第一法向应力差,是造成熔体流速、压力降和成型产生变化的主要原因。而这些是以完全滑移边界条件气辅模拟方法无法体现出来的。因此,气辅挤出模拟需要考虑气体层对熔体成型的影响,并且在实际气辅挤出加工中,需要合理地设置气压等工艺参数。     

再论1/f噪声的动力学统计理论

在《1/f噪声的动力学统计理论》一文中,为了突出重点,攻克主要矛盾,因而对1/f噪声的某些特点,如实验上发现的1/f噪声的功率谱S(f)为什么总是1/fM能谱和功率谱S(f)为何是同一函数等等,当时未能深入追究,本文除了弥补这些不足之外,还从“零点能”与“暗物质”而引发的“背景能量的涌动”这个深层次上来解释普适关系式:S(f)∝logf/f。     

Plasma Modes of the Three-Chain Electron System Over Liquid Helium

We simulate the surface electron system over liquid helium subjected to a confinement potential in the electron layer plane. In the solid phase, the two-dimensional system is observed to transform first into a multi-chain system and, finally, into a three chain, a zigzag structure and a single chain. Both longitudinal and transversal plasma oscillations of the three-chain electron system are determined. One of the longitudinal oscillation modes is acoustic, whereas the other two are optical. On turn, all transversal oscillations branches are optical. The theoretical results obtained can be used to identify experimentally the configurations of the low-dimensional electron system over helium under confinement potential.