体积分数对基于沸石和硅油的悬浮液的电流变性能的影响

用 HAAKE RV2 0型流变仪 ,在不同外加电场强度和不同颗粒体积分数下测试了基于沸石和硅油的电流变液的剪切应力变化 .结果表明 :随着外加电场强度升高 ,电流变液的零电场粘度急剧增加 ,电流变液的剪切屈服应力增加 ;随着电流变液中沸石颗粒体积分数升高 ,电流变液的剪切屈服强度急剧上升 .这种变化可以用颗粒间作用力与颗粒间距的关系、单位面积的颗粒链数目变化以及多体作用对电流变液性能的影响来解释     

Ductile fracture criteria for simulating shear by node separation method

This study is concerned with the mechanics of ductile fracture in bulk metal forming processes by a finite-element analysis and experiments. Developed is a computer program using conventional finite-element method such that the behavior of crack propagation after ductile fracture can be analyzed. The phenomenon of a material separating into two pieces upon shearing and tensile tests has been simulated using the developed computer program. Special attention is focused on the effect of various ductile fracture criteria on crack initiation and propagation during shearing and tensile tests.     

Long-term strength of metals and creep equations based on the Coulomb-Mohr criterion

It is proposed to construct long-term strength and creep relations for metals on the basis of the Coulomb-Mohr criterion. The creep equations and the long-term strength criterion for plane stress are analyzed in detail. Results of long-term strength calculations are compared with data of experiments with metallic materials. It is established that theoretical and experimental results are in satisfactory agreement. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 6, pp. 115–123, November–December, 2007.     

Exact solution for compressive flow of viscoplastic fluids under perfect slip wall boundary conditions

Based on the perfect slip condition between rigid walls and fluids, the compressive flow of Herschel-Bulkley fluids and biviscous fluids was studied. The explicit expressions of stresses and fluid velocity were given. To move the rigid walls for a Herschel-Bulkley fluid with the yield stress (τ₀), the mean pressure applied onto the rigid wall should be larger than 2τ₀/. No yield surface exists in the interior of the fluids when flow occurs. For a biviscous fluid, a critical load was given. The fluid behaves like the Bingham fluid when the external applied load onto the wall is larger than the critical load, otherwise the fluid is Newtonian. Received: 10 June 1997 Accepted: 22 September 1997     

MODELING HARVEST SCHEDULING IN MULTIFUNCTIONAL PLANNING OF FORESTS FOR LONGTERM WATER YIELD OPTIMIZATION

In this study, wood production and hydrologic functions of forests were accommodated within a planning procedure for separate working circles (areas dedicated to certain forest functions) that were delineated according to an Ecosystem‐Based Functional Planning approach. Mixed integer goal programming was used as the optimization technique. The timing and scheduling of a maintenance cutting (partial harvest) was the decision variable in the modeling effort, and an original formulation was developed as a multiobjective planning procedure. Four sample planning strategies were developed and model outputs were evaluated according to these strategies. Spatial characteristics of stands were considered, and used to prohibit the regeneration of adjacent stands during the same time period. Because of the positive relationship between qualified water production and standing timber volume in the forest, the model attempts to maximize qualified water production levels by increasing standing volume stocks in the forest through the delay of regeneration activities.     

高能电子辐照绝缘厚样品的表面电位动态特性

采用数值计算和实验测量相结合的方法, 阐明了高能电子束照射下绝缘厚样品的表面电位和电子产额动态特性. 结果表明: 由于电子在样品内部的散射和输运, 沿着深度方向, 空间电位先缓慢下降到最小值, 然后逐渐升高并趋近于零; 随着电子束照射, 样品的表面电位逐渐下降, 可至负千伏量级, 电子总产额逐渐增大至一个接近于1的稳定值; 电子束停止照射后, 长时间放置下, 表面电位将逐渐升高, 但带电并不会消除; 表面电位随电子束能量的升高近似线性下降, 随入射角的增大而升高, 而随样品厚度的增大仅略有下降.     

Xe~(26+)入射Au靶离子L壳层空穴的产生与退激辐射

基于两体碰撞过程的能量与角动量守恒,推导出Xe26+离子与Au原子碰撞过程,单离子的L壳层空穴产额与离子动能的理论关系.实验测定了动能2.4-3.6Me V的Xe26+离子入射Au靶,产生的Xe的L-X射线谱,获得了射线产额与离子入射动能的实验关系.结果表明,碰撞过程产生Xe L壳层空穴的同时,产生了一定数目的 M壳层空穴,导致L壳层空穴平均荧光产额显著变大,在实验能量范围,空穴产额的理论值与射线产额的实验值存在较好的一致性.     

Quantitative analysis of oxidative DNA damage induced by high-voltage pulsed discharge with cavitation

Pulsed discharge is used for sterilization and disinfection, but the details of the molecular mechanisms remain largely unknown. Since pulsed discharge generates reactive oxygen species (ROS), we analyzed the oxidative DNA damages after pulsed discharge treatment to consider the involvement of ROS in the damaging process. We applied pulsed discharge with cavitation to plasmid DNA molecules and estimated the yields of the damages by agarose gel electrophoresis. The treated DNA contained various oxidative DNA damages, including single and double strand breaks and base lesions. The yields of the damages increased in response to the energy used for pulsed discharge. We also measured the yield of 8-hydroxyguanine (8-OH-G), one of the major oxidative base lesions, in the treated plasmid DNA by mass spectrometry quantitatively and found that the yield of the oxidative base lesion corresponded to the increment of the applied energy. In addition, we observed the involvement of mutM gene, which is responsible for repair of 8-OH-G, in the increased sensitivity of Escherichia coli to pulsed discharge. Therefore, ROS seem to mediate the sterilization ability of pulsed discharge.     

Elastic modulus and yield stress of suspensions

A recent technique, developed to measure yield stress has here also been used to determine the elastic modulus of a suspension. Temperature effects have been measured.     

Head-flow and npsh performance of an axial piston pump working with organic fluids at different temperatures

A modified version of the standard axial piston pump, normally used with fuels, has been tested with organic fluids R11 and R113. Head-flow characteristics, volumetric and global efficiency, and npsh curves, have been determined at different speeds and fluid temperatures and the results compared with those obtained with kerosene. Pump efficiencies remain satisfactory with high density, very low viscosity and high vapour pressure fluids. In the absence of cavitation, pump performance seems to be a function of kinematic viscosity, while the npsh curves appear to be a complex function of density, viscosity and vapour pressure