基于双面质点振速测量的声场分离技术

现有的声场分离技术或是基于双面声压测量或是基于单面声压和质点振速测量。本文以二维空间傅里叶变换法作为声场分离算法,提出一种基于双面质点振速测量的声场分离技术。论文首先推导出了该方法的理论模型,随后通过仿真研究验证了该方法的有效性,并通过与基于双面声压测量的声场分离方法的比较说明了其优越性。结果表明:采用基于双面质点振速测量的声场分离方法可以有效实现声场分离;基于双面质点振速测量的声场分离方法可以获得更高的质点振速分离精度,而基于双面声压测量的声场分离方法可以获得更高的声压分离精度。     

Hydrodynamic lubrication in fully plastic asperity contacts

A line contact inlet zone analysis is carried out for the hydrodynamic lubrication in a fully plastic asperity contact. A governing equation of the central film thickness i.e. the film thickness in the fully plastic contact area is derived. An equation predicting this film thickness is also derived. It is found that for the fully plastic contact, under relatively light loads the prediction accuracy for the central film thickness is good, while at the load heavy enough the prediction equation greatly overestimates the central film thickness and the central film thickness solved from the analytical governing equation is significantly low showing the asperity in boundary layer lubrication. For the fully plastic contact, the central film thickness is nearly half of that obtained based on the elastic contact assumption for relatively light loads or even lower for heavier loads. The hydrodynamic lubrication is found difficult to form in the fully plastic asperity contact for the carried load heavy enough or the significantly low sliding speed between the asperities. To achieve a high hydrodynamic lubrication film thickness in the fully plastic asperity contact it is recommended to employ a high sliding speed or a high fluid viscosity. However, in the fully plastic asperity contact, the potential hydrodynamic load-carrying capacity is limited and much smaller than that based on the elastic contact assumption or predicted by conventional line contact elasto-hydrodynamic lubrication theory.     

Boundary film shear elastic modulus effect in hydrodynamic contact. Part II: influence of operational parameters

The present paper is the subsequent research of the first part (Theor Comput Fluid Dyn, 2009). It investigates the boundary film shear elastic modulus effect in a hydrodynamic contact in different operating conditions. The hydrodynamic contact is one-dimensional, composed of two parallel plane surfaces, which are respectively rough rigid with rectangular micro projections in profile periodically distributed on the surface and ideally smooth rigid. The whole contact consists of cavitated area and hydrodynamic area. The hydrodynamic area consists of many micro Raleigh bearings which are discontinuously and periodically distributed in the contact. The hydrodynamic contact in a micro Raleigh bearing consists of boundary film area and fluid film area which, respectively, occur in the outlet and inlet zones. In boundary film area, the film slips at the upper contact surface due to the limited shear stress capacity of the film–contact interface, while the film does not slip at the lower contact surface due to the shear stress capacity of the film–contact interface large enough. In boundary film area, the viscosity, density, and shear elastic modulus of the film are varied across the film thickness due to the film–contact interactions, and their effective values are used in modeling which depends on the film thickness. In fluid film area, the film does not slip at either of the contact surfaces, and the shear elastic modulus of the film is neglected. It is found from the simulation results that the boundary film shear elastic modulus influences are normally negligible on the mass flow through the contact, the carried load of the contact and the overall film thickness of the contact, and the boundary film shear elastic modulus would normally influence the local film thickness in an elastic contact when the local film thickness is on the film molecule diameter scale. It is also found that the boundary film shear elastic modulus effect has the tendency of being increased with the reduction of the width of a micro contact. It is increased with the reduction of the boundary film–contact interfacial shear strength or with the increase of the critical boundary film thickness, while it is strongest at certain values of the contact surface roughness, the width ratio of fluid film area to boundary film area, and the lubricant film shear elastic modulus.

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Fabrication and characterization of Bi2Te3 nanoplates via a simple solvothermal process

Bi₂Te₃ nanoplates have been successfully obtained by a novel solvothermal method in the presence of hexadecyltrimethylammonium bromide (CTAB). Various techniques such as X-ray diffraction (XRD), field-emission scanning electron microscope (FESEM), transmission electron microscope (TEM), selected area electron diffraction (SAED), and Fourier transform infrared spectrometry (FT-IR) have been used to characterize the obtained products. The results show that the as-synthesized samples are rhombohedral-structured Bi₂Te₃ single-crystal nanoplates about 70–200 nm in diagonal and 30 nm in thickness, and the growth direction is perpendicular to c-axis. The existence of CTAB is vital to the formation of the plate-like morphology. In addition, the reaction solvents also have important influence on the shape-control of final products.     

流化床燃烧器中气泡相和密相氧浓度的理论预测与实验验证Ⅰ．理论模型

基于流态化两相理论，建立了描述流化床燃烧器中煤焦间歇燃烧过程的数学模型。该模型只有一个可调参数（△Ｔ），能够预测煤焦的烧失时间以及气泡相和密相氧浓度随时间的变化。对模型输入参数的敏感性分析表明，煤焦加入量、探头位置以及过剩空气速度是影响气泡相和密相氧浓度的主要操作因素。     

利用表面活性剂介导的方法制备AgrC蛋白脂质体

膜蛋白AgrC是金黄色葡萄球菌双组分信号转导系统的感受激酶. 其信号转导机制的阐明对于解决细菌耐药问题具有重要意义. 目前膜蛋白研究的主要瓶颈是难以获得大量高纯度和功能稳定的蛋白. 将目标蛋白表达在大肠杆菌体内,利用表面活性剂将其从细胞膜上溶解,纯化,这一系列步骤容易引起膜蛋白不稳定和功能损失. 本文报道了用表面活性剂介导的方法将膜蛋白AgrC镶嵌到脂质体上,即形成蛋白脂质体. 脂质体和蛋白脂质体的结构、形貌以及平均粒径分别用透射电镜和动态光散射仪表征. 蔗糖密度梯度离心的结果表明蛋白重构效率达80%. 硫醇试剂标记实验确定AgrC的细胞质域在脂质体中取向于内侧. 体外磷酸化实验表明AgrC蛋白在脂质体中的自我磷酸化活性远远高于表面活性剂中的活性,且其自我磷酸化活性在2周内几乎没有损失. 蛋白脂质体的构建不仅解决了膜蛋白的不稳定性问题,也为体外研究AgrC蛋白的结构、功能和信号转导机制提供了新的思路.     

六苯基苯衍生物分子内光化学关环反应

研究了六苯基苯衍生物的分子内光化学关环脱氢反应,与热化学关环脱氢反应不同,光化学关环脱氢反应只生成关一个环的产物。光化学关环脱氢反应过程中,氧化剂种类、用量以及溶剂对关环脱氢产物的产率具有显著影响,在正己烷溶剂中,以单质碘为氧化剂进行光化学关环脱氢反应,关环产物产率可达91%。     

Preparative purification of anti-tumor derivatives of honokiol by high-speed counter-current chromatography

In our program to synthesize a series of novel derivatives as potential analogs of honokiol for anti-tumor treatment, we have found that at least three of the derivatives of honokiol showed more potency to inhibit the proliferation of K562 leukemia cells and SPC-A1 adenocarcinoma cells. As a critical step to our further series synthesis of derivatives of honokiol, three derivatives of honokiol composed of two isomers and one compound with two formyl groups, which were hardly separated by common purification methods, needed to be rapidly separated and purified. The present work describes analytical and preparative high-speed counter-current chromatography (HSCCC) for the isolation and purification of these three C-formylation derivatives of honokiol, named 3'-formylhonokiol, 5-formylhonokiol and 3',5-diformylhonokiol, respectively. The solvent system for HSCCC separation was composed of hexane-ethyl acetate-methanol-water with the ratio of 1:0.4:1:0.4 (v/v). The one-step purification produced 157.8 mg, 121.6 mg and 21.2 mg of 3'-formylhonokiol, 5-formylhonokiol, 3',5-diformylhonokiol from crude sample of 400mg with purities of 98.6%, 99.2% and 99.6%, respectively, in an elution time of 2.5 h. The purities and structural identification were determined by HPLC, (1)H NMR, (13)C NMR and mass spectroscopy. Their anti-proliferation effects on K562, A549 and SPC-A1 cell lines were evaluated by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay.