基于线列阵传感器的射流冲击试验含气率分布研究

射流冲击是一种气-液两相流现象,既可作为一种除盐水混合硼酸的有效方法,也可用于研究压水堆（PWR）的承压热冲击（PTS）事故现象。当液体射流撞击水面时,发生气体夹带现象,并产生气泡,气泡夹带对混合过程起到关键的影响作用。研究了不同射流高度和流速下的含气率分布,设计了一种新型三层可移动线列阵传感器（WMS）测量瞬时二维局部空隙率,具有较高的空间分辨率（3 mm）和极高的时间分辨率（2500 Hz）,基于线列阵传感器测量的原始数据,获得了射流冲击中气体夹带的含气率分布,对比分析了不同射流高度和流速下的平均含气率分布。     

Enhanced performance of microbial electrolysis cells using microstructured electrodes

A microbial electrolysis cell is set up with the purpose to realize an efficient power-to-gas process. Both hydrogen production by electrolysis and biomethanization proceed in the same reactor cell. In particular, the formation of hydrogen bubbles is strongly governed by the surface properties of the used stainless steel electrodes. Here, we introduce surface topography modifications on the micron-scale to enhance the electrical transport in the cell and support charge conversion into hydrogen. Furthermore, it is analyzed if hydrogen bubble detachment can be supported to form smaller bubbles that can be efficiently converted into methane. A positive influence on the electrical transport is found and explained by a surface-controlled suppression of bio-film passivation.     

Enhanced Washburn Method (EWM): A comparative study for the contact angle measurement of powders

Washburn Method (WM) as a typical contact angle measurement (θ) method can be used for assessment of powder wettability (especially representative particle size range for flotation separation). However, as an indirect method, WM has several limitations. This investigation is going to introduce an Enhanced Washburn Method (EWM), which fills the gap of those WM obstacles, and can be applied for the meaningful indirect θ measurement of powders. For such a purpose, the wettability of quartz powders (d₈₀: 62 μm) was measured in the absence and in the presence of the cationic surfactant Flotigam®EDA at pH 10. EWM by using pre-conditioning of hydrophobized particles via unblock capillaries measured the θ of powders in different conditions. Statistical evaluations indicated that EWM could quite accurately measure θ of the hydrophobized powders, where there is a significant coefficient of determination (R² above 0.96) between EWM outcomes and other examined direct θ measurement methods (the captive bubble and sessile drop methods).     

逻辑函数的四种表示法

本文介绍了逻辑函数的四种表示方法,其中重点介绍了两种逻辑图及其联系与区别。     

房屋价格存在泡沫测定

近两年来，国内许多大众中城市特别是沿海一些城市的房屋价格大幅度上涨，房屋价格是否存在泡沫成为人们关注的焦点。通过对国内35个大中城市的近期房屋市场的价格情况进行分析，提出了测定房屋价格泡沫的基本方法，并对国内35个大中城市的房屋价格是否存在泡沫进行实证分析。     

EFFECTS OF LIQUID COMPRESSIBILITY ON RADIAL OSCILLATIONS OF GAS BUBBLES IN LIQUIDS

For forced radial oscillations of gas bubbles in liquids, a more rigorous expression of the acoustic damping constant based on Keller’s equation is developed. Comparison with those in published papers is also made. The expression offered in this paper will improve the predictions of total damping constant in particular for high frequencies and large bubbles, i.e., large ωR0/c1(ω is the frequency of driving sound field,R0 is the equilibrium bubble radius, c1 is the sound speed in the liquid). Examples in ultrasound imaging and acoustical oceanography are demonstrated.     

One- and two-equation turbulence models for the prediction of complex cascade flows using unstructured grids

One- and two-equation, low-Reynolds eddy-viscosity turbulence models are employed in the context of a primitive variable, finite volume, Navier-Stokes solver for unstructured grids. Through the study of the complex flow in a controlled-diffusion compressor cascade at off-design conditions, the ability of the models under consideration to predict the laminar separation bubble close to the leading edge and the boundary layer development is investigated. In order to control the unphysical growth of turbulent kinetic energy near the leading edge stagnation point, appropriate modifications to the conventional models are employed and tested. All of them improve the leading edge flow patterns and significantly affect the size of the predicted laminar separation bubble. The use of an adequately refined mesh around the airfoil, that is formed by triangles placed in a quasi-structured way, allows for the generation of grid elements of moderate aspect ratios. This helps to readily overcome any relevant problems of accuracy; a second-order upwind scheme without flux limiters or least squares approximations is successfully employed for the gradients. The test case includes quasi-3D effects by considering the streamtube thickness variation in the governing equations.     

注入氦不锈钢中氦泡热形核及长大研究

本文利用透射电镜观察了HR-2及SS321不锈钢注入He~+并在T<1023K不同温度退火后的He泡结构,发现T=0.45T_m是一个转变点,当0.3T_m0.45T_m时,He泡主要通过迁移和合并而长大,长大激活能的实验值分别为0.41eV和0.31eV,实验结果表明,HR-2钢中He泡数密度在整个测量温区内均大于SS321钢,并且材料迅速肿胀的开始温度也高于SS321钢,说明HR-2钢比SS321钢具有较好的抗氦性能     

金刚石刀头钎焊焊缝"冒泡"问题的分析与解决

通过对无过渡层金刚石刀头钎焊时出现的焊缝＂冒泡＂异常情况的分析,并结合分析而采取相应的措施,最终找到有效解决问题的方法.     

Validity of the first-order fluid model

The general validity of the first-order fluid model is considered. Conditions are established for which a first-order fluid represents an acceptable approximation to the integral viscoelastic fluid from which it was derived as a Taylor series approximation. The results are applied to two flow problems: generation of flow by the application of a pressure gradient and the growth or dissolution of bubbles in viscoelastic liquids. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 547–552, 1999