Relationship between the diffusiophoresis rate, evaporation coefficient, and size of a large volatile drop

A new theory of diffusiophoresis of large volatile spherical aerosol drops that is an extension of investigations [1–8] is developed. The influence of the radius of the drop, the surface tension coefficient varying over the surface of the drop, the evaporation coefficient α of the liquid, and the flows inside the drop on the diffusiophoresis rate are taken into account. Expressions obtained allow for direct determination of the velocity of large individual aerosol drops in a binary gas mixture nonuniform in component concentration. It is shown that both the magnitude and the direction of the diffusiophoresis velocity depend on α and the size of the drop. It is assumed that the size of the drop varies but remains considerably greater than the mean free path of gas molecules.     

On the mechanism of carbon nanotube formation: I. The thermodynamics of formation of carbon molten drops in a metallic catalyst

Carbon molten drops in a metallic catalyst are known to be nucleation centers for carbon nanotubes. The problem of the kinetics of condensation of such drops in wide concentration ranges of carbon and metal vapors is considered. The equilibrium distribution of the drops over the size and mole fraction of the components is obtained. The main result is the calculation of the quasi-steady-state rate of condensation of the molten drops in a supersaturated carbon vapor. This result forms the basis for the calculation of the characteristics of explosive and rapid condensation of the vapor upon its cooling. This calculation is performed in the next part of this work.     

内源性蛋白质分子成像的研究进展

酰氨质子转移（amide proton transfer, APT）成像是一种新的分子MRI技术,它可用来测量组织中内源性蛋白质. 理论上,APT-MRI信号强度主要取决于游离蛋白质的酰氨质子浓度以及交换速度,而酰氨质子交换速度与组织pH有关. 因此,APT-MRI技术已经被用于无创性中风pH成像（通常pH降低）和肿瘤蛋白质含量成像（通常蛋白质量提高）. 近期对大鼠的实验表明,APT-MRI技术可用来区分放射性坏死和胶质瘤. 该综述文章简要地介绍了APT成像的基本原理以及它在动物模型与临床中风和肿瘤成像中的应用.     

Detonation waves in bubble-drop media

Wave processes in chemically active multicomponent media: liquid — gas bubbles — liquid drops have been studied experimentally. Existence of detonation waves in multicomponent (bubble-drop) media has been proved. Structure of detonation waves in bubble-drop and bubble media is qualitatively identical: detonation waves are solitary waves with pulsation profile the pressure behind which is close in value to the one in unperturbed medium. Propagation velocity of detonation waves in bubble and bubble-drop media drops with the increase in medium gas phase concentration and with the decrease in carrier liquid viscosity. Presence of liquid drops decreases detonation wave velocity compared with bubble medium that does not contain liquid drops. Detonation wave propagation in multicomponent media causes gas bubbles fragmentation as well as fragmentation of individual liquid drops. The work was financially supported by the Russian Foundation for Basic Research (Grant No. 04-03-33106).     

On the mechanism of carbon nanotube formation: II. The kinetics of explosive condensation of carbon molten drops in a metallic catalyst

The preliminary stage of the formation of carbon nanotubes by the vapor-liquid-drop mechanism is considered as applied to the condensation of drops from carbon and metal vapors. The problem of the condensation of molten drops is solved for a wide concentration range for both vapors at a condensation temperature. It is shown that, at very high concentrations of the metal vapor (10¹⁸–10¹⁹ cm⁻³) and high temperatures (about 0.3 eV), peculiar heterogeneous condensation of the drops can occur at huge supersaturation of the carbon vapor and the saturated metal vapor. This problem of the condensation of the binary vapor is of methodical interest. This condensation is shown to be unrealizable in real experiment at the parameters of the carbon and metal vapors; it virtually merges with the homogeneous condensation of the metal vapor. The maximum concentration of the carbon vapor below which carbon condenses into drops and above which carbon condenses into amorphous soot particles is calculated. The calculation makes it possible to propose a new approach to the controlled growth of carbon nanotubes.     

Accurate measurement of the work function of electron-hole drops in germanium

The work function of electron-hole drops in Ge relative to free excitons is measured by an extremely simple and accurate technique. The threshold excitation power for drop condensation is determined as a function of temperature by observation of the sharp increase in shot noise associated with the drops in a collector junction. The resulting value of the work function is φ = 17.2 ± 1.0 K.     

Shape oscillations of microparticles on an optical microscope stage

A modulated acoustic radiation pressure technique to produce quadrupole shape oscillations of drops ranging in diameter from 50-220 micron has been used by us. These drops have been suspended by acoustic levitation in a small chamber mounted on a stage of an optical microscope, which allowed easy viewing. The fission of drops and the deformation of sea urchin eggs were also observed.     

Spreading of liquid drops on Agar gels

We study the spreading of pure water drops or water drops with surfactine (surfactant produced by bacteria Bacillus Subtilis) on gels (Agar/Water gel). We find that, surprisingly, the drops do not spread indefinitely, but remain in a state of partial wetting. Eventually the liquid diffuses into the gel on a time scale short with respect to evaporation times. The drops containing surfactant show a complex dynamics: at first the spreading velocity decreases, until the front stops and starts receding at about constant velocity. Concurrently, a second front detaches from the rim of the drop if the agar concentration is sufficiently low, and continues to move outwards.     

珍珠明目滴眼液中微量钙的共沉淀分离原子吸收光谱分析

采用硝酸锶-碳酸钾共沉淀分离富集珍珠明目滴眼液中的微量钙,用原子吸收分光光度法测定其含量。进样溶液钙浓度在0.0～20.0μg·mL-1范围内与其422.7 nm处的吸光度成良好线性关系,检出限为0.06 μg·mL-1。该法用于珍珠明目滴眼液中钙的测定,具有灵敏、简便、快速、准确、重复性好,平均回收率为97.0%～98.3%,相对标准偏差RSD为0.4%。     

The variation of defect damage with depth in molybdenum irradiated with 2MeV nitrogen ions

Transmission electron microscopy has been used to examine the damage produced in specimens of high purity molybdenum following irradiation with 2 MeV nitrogen ions in the Van de Graaff accelerator. A simple electropolishing technique was developed to allow the defect damage to be examined at different depths on a single specimen. Some results are presented here for specimens irradiated in the range 600–800°C, together with theoretical predictions of the nitrogen range and the variation of displacement damage with range, The experimental results show that the defect damage to the lattice results in a structure of dislocation loops, interstitial in nature, whose size drops with distance from the bombarded surface and whose concentration increases. Nevertheless the retained defect damage, measured by integrated loop area, agrees reasonably with the theoretical variation of displacement damage with range while the increase in loop concentration with depth coincides with the variation in ratio of nitrogen concentration to displacement damage. This latter result agrees with the hypothesis that the nucleation of damage is controlled to a large extent by the ratio of impurity atoms to displaced atoms.     

Self-propulsion of nematic drops: novel phase separation dynamics in impurity-doped nematogens

We report a novel phase separation dynamics, mediated by self-propelled motion of the nucleated drops, in a mixture of a nematogen and an isotropic dopant. We show that surface flow, induced by the gradient in the concentration of the dopant expelled by the growing drops, provides the driving force for the propulsion of nematic droplets. While the liquid crystal-isotropic transition is used here to demonstrate the phenomenon, self-propulsion should be observable in many other systems in which the dynamics of a conserved order parameter is coupled to a nonconserved order parameter.     

油水两相分散流的相界面浓度输运方程研究

通过对连续相湍流导致的油滴聚合和破裂现象的合理模化,本文建立了适用于垂直上升管油水两相分散流的相界面浓度输运方程.其中对连续相湍流驱动油滴随机碰撞引起的聚合现象模化时,考虑了两油滴间连续相液膜排出过程中的凹面膜效应.而在描述油滴与湍流涡随机碰撞导致的破裂现象时,考虑了破裂过程所产生油滴的大小不等的因素.利用所建立的相界面浓度输运方程对沿实验段轴向的相界面浓度变化进行了预测,结果与实验数据比较表明吻合很好.     

基于虚拟示波器动态判别溶液浓度

根据液滴对光具有会聚的特点以及溶液浓度与其折射率有定量的对应关系，设计了基于虚拟示波器动态判别溶液浓度的光电测量方法．     

Temperature dependence of the radius of electron-hole drops in Ge

The temperature dependence of the radius of electron-hole drops in Ge is determined from measurements of the number of particles in the drops using the p-n junction technique. The drop radius is found to increase from 5.5μ at 1.7 K to 10μ at 3.2 K for an excitation intensity of 160 mWatt/mm². As a function of excitation level at 1.8 K the drop radius is found to increase from 2.9μ at 8 mWatt/mm² to 6.5μ at 300 mWatt/mm². Our data are compared to results available in this field.     

基于可调谐激光吸收光谱技术的柴油机排放NO浓度瞬态测量

NO_x是柴油机排放的主要污染物质,它对人体和环境的危害极大,其中NO含量又占NO_x总量的90％以上,因此合理准确的检测柴油机排放物中NO的含量对NO_x含量的检测尤为关键。现有的测试方法由于采用采样分析法,不能及时反映真实情况,光学检测方法作为一种新型的测试技术,在很多领域都有应用。结合光学检测方法对稳态和瞬态过程下的NO浓度用TLAS技术开展研究,通过模拟NO浓度的变化情况,验证这种方法在柴油机上应用的可行性,选择一台中心波长为5 263 nm的带间级联激光器用于检测,为获得不同浓度的混合气体设计一套配气混合系统,用高纯度的ＮＯ作为被测气体,N₂作为背景气体,配比不同浓度的测试样气,在稳态测量时,分别配比浓度为500,1 000,2 000 ppm的样气进行试验,得到相对误差小于1%,最大绝对误差为11.5 ppm。在瞬态测量中,分别对浓度增加与减少过程进行试验,实时测量气室内的浓度变化情况,在1 ms时间分辨率的情况下可实现5.2%的最大相对误差。通过设计的系统,可以实现NO浓度的瞬态测量,能将此方法应用到柴油机上,这种方法有利于研究柴油机的排放物含量。     

Ultrafast x-ray phase-contrast imaging of the initial coalescence phase of two water droplets

We report an ultrafast x-ray phase-contrast imaging study of the early merging dynamics of two water drops in air. Owing to the edge-enhancement capability, the high penetrability, and the unprecedented temporal and spatial resolutions offered by this new x-ray technique, the coalescence singularity of two water drops was revisited. A finite initial contact radius was identified and the evolvement of the trapped toroidal air bubble was studied for the first time. Despite the existence of this finite initial contact radius, the subsequent meniscus radius followed power laws which agree with theoretical predictions for the inviscid regime.     

Droplet Size Distribution and Sphericity Measurements of Low‐Density Sprays Through Image Analysis

An image analysis technique has been developed in order to determine the drop size distributions of sprays produced by low‐velocity plain cylindrical jets. The particle sizing method is based on incoherent backlight images. Each drop is analyzed individually in the image. The two‐dimensional image resulting from the projection of the three‐dimensional object shape (the drop) on a screen (the video sensor surface) is modeled. The model, based on the point spread function formulation, has been developed to derive a relation between contrast and relative width of individual drops. This relation is used to extend the domain of validity of drop size in terms of size range, out of focus and image resolution. The shape parameter is determined for each drop image through morphological analysis. Spherical and non‐spherical droplets are then sorted on the basis of this parameter. Non‐spherical drops are regarded as non‐fully atomized liquid bulks or coalesced drops. Finally, the droplet size distribution of true spherical droplets is established for a low‐velocity plain cylindrical liquid jet.     

Fabrication and analysis of ZnO thin film bulk acoustic resonators

This study employs RF magnetron sputter technique to deposit high C-axis preferred orientation ZnO thin film on silicon substrate, which is then used as the piezoelectric thin film for a thin film bulk acoustic resonator (FBAR). Electrical properties of the FBAR component were investigated by sputtering a ZnO thin film on various bottom electrode materials, as well as varying sputter power, sputter pressure, substrate temperature, argon and oxygen flow rate ratio, so that structural parameters of each layer were changed. The experimental results show that when sputter power is 200 W, sputter pressure is 10 mTorr, substrate temperature is 300 °C, and argon to oxygen ratio is 4:6, the ZnO thin film has high C-axis preferred orientation. The FBAR component made in this experiment show that different bottom electrode materials have great impact on components. In the experiment, the Pt bottom electrode resonant frequency was clearly lower than the Mo bottom electrode resonant frequency, because Pt has higher mass density and lower acoustic wave rate. The component resonant frequency will decrease as ZnO thin film thickness increases; when top electrode thickness is higher, its resonant frequency also drops, due to top electrode mass loading effect and increased acoustic wave path. Therefore, ZnO thin film and top/bottom electrode thickness can be fine-tuned according to the required resonant frequency.     

苯在光滑铂电极上的电化学还原行为的共焦显微拉曼研究

本文利用共焦显微拉曼仪系统研究了苯在光滑铂电极上的电化学还原。研究结果表明:苯在电化学体系中可直接还原为不溶于水的环己烷液滴,附在电极表面构成第三相,随着电位的正移,表面液滴中苯和环己烷的相对含量会发生变化。     

Deconvolution with Maximum Entropy Solution to Determine Local Extinction Coefficient and Local Volume Concentration Values from Laser Diffraction Data

The traditional use of the laser diffraction technique provides line‐of‐sight liquid spray drop‐size distribution. However, deconvolution of the measurements can be performed for axisymmetric spray in order to determine local spray characteristics. In a previous publication, a new deconvolution technique making use of the maximum entropy principle was established and applied to determine the local drop‐size distributions. The entire approach was experimentally validated. In this work, the technique is employed to determine local extinction coefficient values. As in the previous investigation, the measurement procedure consists of scanning a laser beam through the spray cross‐section from the center to the edge of the spray. By use of the transmittance theory, the local extinction coefficients allow the local volume concentrations to be calculated. This theory introduces the mean scattering coefficient. The results show that this coefficient must be determined as a function of the Sauter mean diameter in order to avoid overestimation of the volume concentration. Although no proper validation is presented, the coherence of the overall approach is discussed in detail and solutions for improving the spatial resolution are presented. Finally, the local volume concentrations are combined with the local drop‐size distribution to provide local volume‐weighted, drop‐size distributions. These distributions provide information on the localization of the drops according to their diameter as well as on the spatial liquid distribution. This work illustrates applications and performances of laser diffraction technique that are rarely used.