Electro-elastic fields of piezoelectric materials with an elliptic hole under uniform internal shearing forces

The existing investigations on piezoelectric materials containing an elliptic hole mainly focus on remote uniform tensile loads. In order to have a better understanding of the fracture behavior of piezoelectric materials under different loading conditions, theoretical and numerical solutions are presented for an elliptic hole in transversely isotropic piezoelectric materials subjected to uniform internal shearing forces based on the complex potential approach. By solving ten variable linear equations, the analytical solutions inside and outside the hole satisfying the permeable electric boundary conditions are obtained. Taking PZT-4 ceramic into consideration, numerical results of electro-elastic fields along the edge of the hole and axes, and the electric displacements in the hole are presented. Comparison with stresses in transverse isotropic elastic materials shows that the hoop stress at the ends of major axis in two kinds of material equals zero for the various ratios of major to minor axis lengths; If the ratio is greater than 1, the hoop stress in piezoelectric materials is smaller than that in elastic materials, and if the ratio is smaller than 1, the hoop stress in piezoelectric materials is greater than that in elastic materials; When it is a circle hole, the shearing stress in two materials along axes is the same. The distribution of electric displacement components shows that the vertical electric displacement in the hole and along axes in the material is always zero though under the permeable electric boundary condition; The horizontal and vertical electric displacement components along the edge of the hole are symmetrical and antisymmetrical about horizontal axis, respectively. The stress and electric displacement distribution tends to zero at distances far from the elliptical hole, which conforms to the conclusion usually made on the basis of Saint-Venant’s principle. Unlike the existing work, uniform shearing forces acting on the edge of the hole, and the distribution of electro-elastic fields     

河流护岸多孔生态材料对水体中硝态氮去除试验

为进一步提升护岸材料对面源污染物的净化能力,采用骨料交联法制备了具有较高透水率的多孔生态砌块,研究骨料粒径与砌块透水率的关系,并采用动水挂膜法对不同透水率的生态砌块进行反硝化细菌表面负载,在此基础上,研究所制备的不同骨料粒径的生态砌块的透水率、比表面积等对水体中硝态氮去除率的耦合效应。结果表明:在相同孔隙率条件下生态砌块的透水率随比表面积的增加而降低,且随着骨料粒径的增大而提高;生态砌块对水体中硝态氮的去除率随透水率的增加呈现先增大再减小的趋势,其中骨料粒径为7~11 mm,透水率为6.6 m L/(s.cm~2)的多孔生态砌块对硝态氮的去除率可达90.3%。     

气爆卸压增透防治井筒揭穿煤层突出的数值模拟研究

爆破震动卸压增透抽采瓦斯是消除井筒揭穿低透气性煤层煤与瓦斯事故的根本措施。采用有限差分数值模拟的方法,研究了气爆冲击震动卸压范围对井筒揭穿煤层卸压增透防突效果的影响。结果表明:当冲击震动卸压范围较小时,井筒揭穿卸压煤层后,煤层无支承压力增高区的出现;当卸压范围较大时,则依次出现支承压力三区,且支承压力增高区的宽度有随卸压范围的增大而增加的趋势;冲击震动卸压存在一临界卸压范围,当卸压范围超过该临界范围时,煤层支承压力曲线由单峰特征转变为内外双峰特征,且外峰值小于内峰值,内峰值还明显小于无卸压和不超过该临界范围卸压范围时支承压力单峰值,还能使支承压力增高区向煤岩体深部转移,显著降低井筒揭穿瓦斯煤层发生煤与瓦斯突出动力灾害发生的频度及强度,为气爆冲击卸压防治井筒揭穿煤层突出的工程应用提供参考。     

透气性多孔陶瓷材料制备工艺的研究

以硅酸乙脂水解液为粘结剂,以莫来石、铁粉为原料,通过粉浆浇注、干燥及烧结等工艺过程,制备了多孔透气性莫来石基陶瓷材料。研究了成型及干燥工艺对成型坯体质量及烧结体性能的影响。     

鄂尔多斯盆地北部中生界延安组、延长组渗透性砂层反演、解释方法及研究应用

针对黄土塬地区（以新城-红柳沟地区为例）地震测线以弯线为主，充分利用有效的地震信息对目的层开展地震储层横向预测，尤其是对目的层渗透性砂岩的识别总结提炼出5种方法，在平面上编制渗透性砂岩展布范围图，为井位布署提供了一定的依据；通过后期完钻井考核，其渗透性砂层厚度预测符合率达80％以上。     

粘土固化浆液在强透水层中防渗试验

防渗用粘土浆液中加入少量粘土浆液固化剂,被注浆的透水地层,其结石强度和渗透系数值达到防渗要求。用粘土固化浆与水泥浆在坝基强透水地层做了高喷截渗时比试验。     

Fe基非晶合金的恒导磁性能研究

研究了Fe基非晶合金在不同热处理工艺条件下的恒导磁性能.结果表明,通过简单的横向磁场热处理工艺,可将具有高饱和磁感应强度的Fe基非晶合金制成无间隙的恒导磁磁芯,并且具有良好的综合磁特性.合金在350℃处理时,恒磁范围达到400A/m,磁导率约为3.14×10-3T·m/A,随保温时间的延长,恒磁场范围提高到600A/m以上,但磁导率降低,约为1.25×10-3T@m/A.在晶化温度以下,提高横向磁场热处理温度有利于提高材料的恒导磁性能.     

机械化学与同步热激活法结合制备SrCoO2.5+δ透氧膜及其分离性能

采用机械化学激活与同步热激活相结合的固相反应法制备SrCoO2.5 δ(SC)透氧膜材料.借助热失重分析方法优化出反应物同步活化反应的温度条件:当以10 ℃/min升温到950 ℃进行固相反应时,参加反应的成份会同时被激化到活性状态,使合成SC产物的转化率提高,且所获得SC陶瓷膜样品的稳定性增加.氧渗透实验结果表明:氧空位无序的SC具有较高的透氧性能,随温度降低出现氧空位有序时,SC基本失去透氧性能;并且在升降温过程中,上述转变过程具有明显的回滞现象.     

In-group members' perceptions of a social mobility attempt: Effects of boundary permeability and outcome.

This study examined in-group members' impressions of a fellow member who attempted to join a higher power group, along with the interactive effects of the permeability of group boundaries and relative success of this social mobility attempt on impressions. Because groups with less permeable boundaries are typically more cohesive, a group member's relative success in achieving mobility should have meaning for these groups, as opposed to those with more permeable boundaries. Thus, it was predicted that the effect of success versus failure on in-group members' evaluations would be stronger when group boundaries were less permeable. The results showed that a member successful at social mobility was evaluated more positively than one who was unsuccessful, and this difference was larger when boundaries were less permeable. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evaluation of polyaromatic hydrocarbon removal from aqueous solutions using activated carbon and hyper‐crosslinked polymer (Macronet MN200)

BACKGROUND: Sorption of polycyclic aromatic hydrocarbons (PAHs) on activated carbon and the Macronet polymeric sorbent MN200 was investigated to determine the effectiveness of each sorbent for removal of pollutants from aqueous solution and their possible use as sorbent materials for groundwater. Experiments were carried out to determine the loading capacities of a family of PAHs (acenaphthene, anthracene, fluoranthene, fluorene, naphthalene and pyrene). RESULTS: Activated carbon was the more effective sorbent, with maximum loadings of PAHs between 90 and 230 g kg^?1, while MN200 resin showed values of 25–160 g kg^?1. Loading isotherms based on the Langmuir, Freundlich and Redlich–Peterson models were determined. The hydrophobic character of the pollutants appeared as an important parameter related to the sorption process. Equilibrium and kinetic parameters were used to determine the retardation factors for each PAH. CONCLUSION: The calculated values for the simulation of barrier thickness using both sorbents, taking into account EU requirements for PAHs in groundwater effluent, were perfectly reasonable as a first estimate. The better kinetic properties of MN200 are evident in lower hydraulic residence times and consequently in a lower barrier thickness. Copyright © 2008 Society of Chemical Industry