Experimental study on two-phase gas-liquid flow patterns at normal and reduced gravity conditions

Experimental studies have been performed for horizontal two-phase air-water flows at normal and reduced gravity conditions in a square cross-section channel. The experiments at reduced gravity are conducted on board the Russian IL-76 reduced gravity airplane. Four flow patterns, namely bubble, slug, slug-annular transition and annular flows, are observed depending on the liquid and gas superficial velocities at both conditions. Semi-theoretical Weber number model is developed to include the shape influence on the slug-annular transition. It is shown that its prediction is in reasonable agreement with the experimental slug-annular transition under both conditions. For the case of two-phase gas-liquid flow with large value of the Froude number, the drift-flux model can predict well the observed boundary between bubble and slug flows.

Experimental Characterization Of Electrical Current Leakage In Poly(Dimethylsiloxane) Microfluidic Devices

Poly(dimethylsiloxane) (PDMS) is usually considered as a dielectric material and the PDMS microchannel wall can be treated as an electrically insulated boundary in an applied electric field. However, in certain layouts of microfluidic networks, electrical leakage through the PDMS microfluidic channel walls may not be negligible, which must be carefully considered in the microfluidic circuit design. In this paper, we report on the experimental characterization of the electrical leakage current through PDMS microfluidic channel walls of different configurations. Our numerical and experimental studies indicate that for tens of microns thick PDMS channel walls, electrical leakage through the PDMS wall could significantly alter the electrical field in the main channel. We further show that we can use the electrical leakage through the PDMS microfluidic channel wall to control the electrolyte flow inside the microfluidic channel and manipulate the particle motion inside the microfluidic channel. More specifically, we can trap individual particles at different locations inside the microfluidic channel by balancing the electroosmotic flow and the electrophoretic migration of the particle.

Field and laboratory studies on pathological and biochemical characterization of microcystin-induced liver and kidney damage in the phytoplanktivorous bighead carp

Field and experimental studies were conducted to investigate pathological characterizations and biochemical responses in the liver and kidney of the phytoplanktivorous bighead carp after intraperitoneal (i.p.) administration of microcystins (MCs) and exposure to natural cyanobacterial blooms in Meiliang Bay, Lake Taihu. Bighead carp in field and laboratory studies showed a progressive recovery of structure and function in terms of histological, cellular, and biochemical features. In laboratory study, when fish were i.p. injected with extracted MCs at the doses of 200 and 500 mu g MC- LReq/kg body weight, respectively, liver pathology in bighead carp was observed in a time dose-dependent manner within 24 h postinjection and characterized by disruption of liver structure, condensed cytoplasm, and the appearance of massive hepatocytes with karyopyknosis, karyorrhexis, and karyolysis. In comparison with previous studies on other fish, bighead carp in field study endured higher MC doses and longer-term exposure, but displayed less damage in the liver and kidney. Ultrastructural examination in the liver revealed the presence of lysosome proliferation, suggesting that bighead carp might eliminate or lessen cell damage caused by MCs through lysosome activation. Biochemically, sensitive responses in the antioxidant enzymes and higher basal glutathione concentrations might be responsible for their powerful resistance to MCs, suggesting that bighead carp can be used as biomanipulation fish to counteract cyanotoxin contamination.

利用射流泵输送油水两相管流的实验研究

研究了应用射流泵输送油水两相管流时泵对下游管道中流型和压降的影响。实验管线为内径50mm的透明有机玻璃管，管线从入口到分离器长约35m，实验段由一个垂直倒U型管和一个长3m水平管组成。分别给出了不同入口条件下实验管段的流型图和压降图。结果表明：采用射流泵输送油水两相流动，对下游管道流型和油水乳化速度有着显著的影响，但对下游管道内的压降随混合流速和体积份额的变化趋势影响很小。

金属长杆撞击带薄盖板约束炸药的引爆现象研究

通过实验的方法研究了金属长杆撞击带薄盖板约束炸药的引爆现象。观察带有随机偏航角的金属长杆以不同速度撞击炸药的响应情况。找出了金属长杆在不同入射角度和炸药约束条件下，炸药的冲击爆轰阈值。讨论了判别未知炸药发生爆轰、延迟爆轰、非爆轰性爆炸、点火后淬熄和不反应的试验测量手段和方法。结果表明：冲击引爆阈值速度，对于不覆板的裸炸药，随入射角度（0、30、45）的增加而增加；随着覆板厚度的增加而增加。炸药的侧向约束情况对发生延迟爆轰有影响。射弹偏航也是影响炸药引爆的因素之一。Jacobs 判据是关于炸药冲击引爆阈值的经验判据，它可以适用于8701 炸药，文中给出了对平头钢弹、钢覆板情况下,用实验数据拟合的Jacobs公式。由于其它机理引发延迟爆轰（XDT）的现象是存在的，Jacobs 判据对这类现象不适用。

Viscosity, Surface Tension, and Atomization of Water-Methanol and Diesel Emulsions

This article is the result of experimental studies of the rheologv, viscosities, surface tensions, and atomization of water-methanol and diesel emulsions. The Span 80 and Tween 60 are employed to make three emulsifying agents, Y01, Y02, and Y03, with viscosity of 1.32-1.5 Pa s and HLB values of 5.36, 4.83, and 4.51, respectively. In the water-in-oil emulsions, the aqueous phase is between 10% and 50%; the agent concentration added is 0.8-8.0%. The viscosity of the emulsions is 0.003-0.02 Pa s, and the surface tens ion is 0.04-0.1 N/m. The types and concentrations of agents significantly influence the viscosity of the emulsions, and the higher concentration of the aqueous phase (<50%) in creases the viscosities of the emulsions, especially for higher agent concentration. Interfacial membrane and HLB values of the agents can explain all these phenomena. Higher aqueous phase concentration and agent viscosity results in larger Sauter mean diameter.

Multi-scale analysis of AFM tip and surface interactions

Thoroughly understanding AFM tip-surface interactions is crucial for many experimental studies and applications. It is important to realize that despite its simple appearance, the system of tip and sample surface involves multiscale interactions. In fact, the system is governed by a combination of molecular force (like the van der Waals force), its macroscopic representations (such as surface force) and gravitational force (a macroscopic force). Hence, in the system, various length scales are operative, from sub-nanoscale (at the molecular level) to the macroscopic scale. By integrating molecular forces into continuum equations, we performed a multiscale analysis and revealed the nonlocality effect between a tip and a rough solid surface and the mechanism governing liquid surface deformation and jumping. The results have several significant implications for practical applications. For instance, nonlocality may affect the measurement accuracy of surface morphology. At the critical state of liquid surface jump, the ratio of the gap between a tip and a liquid dome (delta) over the dome height (y(o)) is approximately (n-4) (for a large tip), which depends on the power law exponent n of the molecular interaction energy. These findings demonstrate that the multiscale analysis is not only useful but also necessary in the understanding of practical phenomena involving molecular forces. (c) 2007 Elsevier Ltd. All rights reserved.

冲击载荷下纤维复合材料裂纹起裂的实验研究

采用SHTB技术对纤维增强复合材料裂纹动态起裂行为进行了实验研究。使用应变片方法确定了裂纹的起裂时间，结合有限元数值模拟得到了裂纹的起裂韧性；同时观察了裂纹在冲击载荷作用下的裂纹起裂和扩展方式，分析了纤维的铺层角度对裂纹起裂和扩增的影响。

The Influence of Viscosity and Surface Tension on Atomization of Water/Methanol and Diesel Emulsions

This paper shows the result of experimental studies of the influence of viscosities, surface tensions on atomization characteristics of water/methanol and diesel emulsions. Three emulsifying agents Y01, Y02 and Y03, with viscosity of 1.32 ～ 1.5 Pa·s and HLB values of 5.36, 4.83 and 4.51 respectively was produced by Span 80 and Tween 60. In the W/O emulsions, the aqueous phase is between 10% and 50%; the agent concentration added is 0.8 ～ 8.0%. The viscosity of the emulsions is 0.003 ～ 0.02 Pa·s, and the surface tension is 0.04 ～ 0.1 N/m. The types and concentrations of agents and the aqueous phase ( < 50%) significantly influence the viscosity of the emulsions and the Sauter Mean Diameter, measured by Malvern Particle Analyzer SERIES 2600.

中国微重力流体科学的空间实验研究

微重力流体物理是微重力科学的重要组成部分,包括简单流体的许多新体系、气/液两相流动和传热以及复杂流体力学.微重力流体物理除其本身学术和应用的重要意义外,还与微重力燃烧学、空间生物技术和空间材料科学密切结合,促进了交叉学科的发展.利用我国返回式卫星和神舟飞船,进行了一批微重力科学的空间实验,使我国微重力科学迅速进展.本文主要介绍近10年来我国微重力流体科学的空间实验研究和主要学术成果.

利用皮秒脉冲激光驱动瞬态X射线激光

报道了利用皮秒激光驱动产生瞬态类镍银X射线激光的实验结果．采用一路脉冲宽度为数百皮秒的激光作为预脉冲，配合另一路皮秒激光作为主脉冲联合驱动平面靶，获得了一定强度的类镍银X射线激光输出，输出能量约为5-10nJ．

Photoelectron angular distributions from above threshold ionization of hydrogen atoms in strong laser fields

We apply a scattering theory of nonperturbative quantum electrodynamics to study the photoelectron angular distributions (PADs) of a hydrogen atom irradiated by linearly polarized laser light. The calculated PADs show main lobes and jetlike structure. Previous experimental studies reveal that in a set of above-threshold-ionization peaks when the absorbed-photon number increases by one, the jet number also increases by one. Our study confirms this experimental observation. Our calculations further predict that in some cases three more jets may appear with just one-more-photon absorption. With consideration of laser-frequency change, one less jet may also appear with one-more-photon absorption. The jetlike structure of PADs is due to the maxima of generalized phased Bessel functions, not an indication of the quantum number of photoelectron angular momentum states.

两种三光子吸收染料光限幅性能的实验研究

研究了两种新型D-π-D结构的芴类衍生物4-{7-[4-（二甲基胺）苯基]-9，9-二（2-乙基己基）-9H-芴-2-}-N，N-二甲基苯胺[缩写为B（DMAP）F]和4-{2-[7-（4-氨基苯乙烯基）-9，9-二（2-乙基己基）-9H-芴-2-]乙烯基}苯胺（缩写为BASF）在四氢呋喃（THF）和N，N-二甲基甲酰胺（DMF）中的线性吸收和单光子荧光行为，用脉冲宽度为38ps，重复频率为10Hz的1064nmNd；YAG脉冲激光研究了两种化合物的三光子吸收性质，结果表明：受溶剂效应的影响，两种化合物在

内蒙古温带草原生态系统过程对气候变化响应的实验研究

羊草草原、大针茅草原和草甸草原是内蒙古温带典型草原地区的三种主要植被类型，本文以此为研究对象，应用时空替代、温室、网室、自然降水接移、养分添加等多种方法模拟未来可能发生的气候变化，研究了这些变化对上述草原植物群落和生态系统过程的直接和间接影响。主要研究结果如下： 1. 气候变暖及其诱导的土壤养分释放速率增加对植物群落有明显的影响，表现在种种植物群落在高度、盖度、密度和生物量等都有不同程度的变化。说明我国温带草原生态系统对气候变化反应敏感。 2. 在群落说平上，气候变暖直接或间接使地上生物量提高17%～90%，但在种群水平，不同种群对模拟气候变化的响应具有很强的个性，而不具普遍性，不同种群反应的大小、方向不同。因此由在不同群落进行研究得出的推论只有部分是可能的，并且即使观测到相类似的反应，它们内在的机制也很可能是不同的。 3. 气候变化显著地影响着凋落物的分解特征。但不同的气候变化情景下，凋落物分解过程的响应不同。在温度升高降水变化不大或升高的情景下，凋落物的分解速率将加快;在气温上升，降水明显下降的情景下，凋落物的分解速率将降低。 4. 草甸草原土壤碳素释放过程和氮素矿化过程对气候变暖有明显的响应。气候变暖将促进土壤有机碳的释放，使草甸草原土壤成为碳源，同时加速氮素矿化速率，在一定程度上提高土壤有效养分的浓度。 5. 在中小尺度上，海拔样带所是应用时空替代原理，研究陆地生态系统与气候变化的理想平台，生物量是综合反应气候变化对土壤-植物系统影响的敏感指标。 6. 草原土壤有机碳和氮在2m～3m的小尺度上存在空间自相关性，其空间自相关尺度受人类活动的影响。

Statistical analysis of sequence features of introns with positive transcriptional regulation in yeast genes

A great deal of experimental studies have shown that many introns of eukaryotic genes function as regulators of transcription. However, comprehensive studies of this problem have not yet been conducted. After checking the transcription frequencies of some Saccharomyces cerevisiae (yeast), genes and their introns, a remarkable phenomenon was discovered that generally the introns of the genes with higher transcription frequencies are longer, and the introns of the genes with lower transcription frequencies are shorter. This suggests that the longer introns of genes with higher transcription frequencies may contain some characteristic sequence structures, which could enhance the transcription of genes. Therefore, two sets of introns of yeast genes were chosen for further study. The transcription frequencies of the first set of genes are higher (>30), and those of the second set of genes are lower (less than or equal to10). Some oligonucleotides are detected by statistically comparative analyses of the occurrence frequencies of oligonucleotides (mainly tetranucleotides and pentanucleotides), whose occurrence frequencies in the first set of introns; are significantly higher than those in the second set of introns, and are also significantly higher than those in the exons flanking the introns of the first set. Some of these extracted oligonucleotides are the same as the regulatory elements of transcription revealed by experimental analyses. Besides, the distributions of these extracted oligonucleotides in the two sets of introns and the exons show that the sequence structures of the first set of introns are favorable for transcription of genes.