Theoretical model of warping deformation during self-rotating grinding of YAG wafers

YAG wafers are the most host laser crystals used for high-power lasers, which are usually machined by grinding to meet the required accuracy for laser components. Warping deformation induced by the residual stress is one of the main damages for YAG wafers after the grinding process, which will seriously decrease the service accuracy and life of the lasers. Developing theoretical model of warping deformation is of great significance to achieving the ultra-precision machining of YAG wafers. The cutting depth of single abrasive and grinding force in self-rotating grinding were investigated by considering the kinematic trajectory of abrasives, brittle-to-ductile transition, elastic mechanics, elastic deformation of the grinding wheel and strain rate effect. A theoretical model of warping deformation in self-rotating grinding of YAG wafers was developed based on the cutting depth and grinding force. The influence of subsurface damage and residual stress on warping deformation was analyzed based on the theoretical model and finite element simulation. Self-rotating grinding tests of YAG wafers were performed, and the results showed that the warping deformation decreased as the wheel rotational speed increased, and increased as the abrasive size, workpiece rotational speed and feed speed increased. The experimental results agreed well with the simulated results of the theoretical model, indicating that the theoretical model can accurately predict the warping deformation induced by self-rotating grinding process. This work will not only enhance the understanding of the essence of the wafer warping induced by ultra-precision machining, but also provide a guide for optimizing the processing parameters in self-rotating grinding of YAG wafers.     

砖烟囱折叠爆破拆除的研究

随着城市的改造和集中供暖的实现,许多砖烟囱需拆除。结合工程实例,对烟囱折叠爆破进行了研究。分析了折叠爆破的影响因素,对爆破切口的高度和起爆时间差进行了理论探索。理论计算与实际基本相符,对类似的烟囱爆破具有一定的指导意义。     

Generalized differential quadrature analysis of electro-magneto-hydrodynamic dissipative flows over a heated Riga plate in the presence of a space-dependent heat source: The case for strong suction effect

The importance of including an electromagnetic actuator as a moving boundary on the dissipative flows of weakly conducting fluids had led to many published facts. But, nothing is known on the generalized differential quadrature analysis of magnetohydrodynamics over a Riga plate with emphasis on the case of viscous dissipation and space-dependent heat source. After deriving the simplified boundary layer equation that models the transport phenomenon, appropriate variables were used to non-dimensionalize and parameterize the partial differential equations. Thereafter, the resulting set of ordinary differential equations was solved numerically by applying a powerful differential quadrature algorithm. Based on the outcome of the simulation, it can be concluded that the viscous frictional effect can be minimized at the Riga plate either by weakening the suction process or by heightening the magnetic parameter. Moreover, the Lorentz forces have a hastening effect on the fluid motion, in the case when those magnetic causes are directed in the same sense of the developed flow.     

输水管道水平定向钻进关键节点设计

本文主要结合输水管道事故现状,分析水平定向钻进在国内外的现状及技术水平,进而提出输水管道水平定向钻进在设计中的关键节点及应对措施,为规范的修订及类似工程设计提供参考。     

Charge and non-radiative energy transfer in P3HT-CdSe nanocomposite

A theoretical model based on the rate equation is used in the calculation of the light intensity and the exciton density profile. Interesting numerical results have been presented for low and high concentration of CdSe nanoparticles. We have found that the significant reduction of the electroluminescence intensity is related to the exciton density profiles which exhibit a monotonic decrease with the increase of the Förster energy transfer between host polymer (donor) and guest CdSe nanoparticles (acceptors). Moreover our calculations were found to be in good agreement with the experimental data.     

A Novel Mathematical Framework for Similarity-based Opportunistic Social Networks

In this paper we study social networks as an enabling technology for new applications and services leveraging, largely unutilized, opportunistic mobile encounters. More specifically, we quantify mobile user similarity and introduce a novel mathematical framework, grounded in information theory, to characterize fundamental limits and quantify the performance of sample knowledge sharing strategies. First, we introduce generalized, non-temporal and temporal profile structures, beyond geographic location, as a probability mass function. Second, we examine classic and information-theoretic similarity metrics using data in the public domain. A noticeable finding is that temporal metrics give lower similarity indices on the average (i.e., conservative) compared to non-temporal metrics, due to leveraging the wealth of information in the temporal dimension. Third, we introduce a novel mathematical framework that establishes fundamental limits for knowledge sharing among similar opportunistic users. Finally, we show numerical results quantifying the cumulative knowledge gain over time and its upper bound, the knowledge gain limit, using public smartphone data for the user behavior and mobility traces, in the case of fixed as well as mobile scenarios. The presented results provide valuable insights highlighting the key role of the introduced information-theoretic framework in motivating future research along this ripe research direction, studying diverse scenarios as well as novel knowledge sharing strategies.     

短程硝化反硝化理论及工艺研究进展

介绍了SCND理论研究进展，对影响亚硝酸积累的温度、pH、分子态游离氨、DO、泥龄等因素进行了分析，阐述了近年来国内外主要的SCND理论研究成果，并得出了相关结论，以期促进短程硝化反硝化理论研究。     

Do research literatures give correct answers?

The rationale for insisting on properly designed studies is to ensure the construction of research literatures that are not influenced by biases of any sort. Once a literature is established, however, whatever answers it gives (usually via meta-analysis) are accepted as valid. The results of our favored statistical techniques are understood best when significant relationships are present while the meaning of null results are unclear. Thus, significant findings are more likely to be published. This file drawer problem has been known for many years. However, the effect that the file drawer has on research literatures has never been probed empirically. A new method is described that tests the impact a file drawer has on a research literature. The results of the file drawer on four separate psychological research literatures are presented. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

对北一区断西三元复合驱若干问题的认识

结合北一区断断元复合驱试验进展及效果，分析了三元复合驱过程中窜流和结垢对试验的影响，在提高三元复合驱开采效果配套技术方面取得了一些认识，并提出了下步研究方向。     

不同应力路径对红土三轴剪切试验成果的影响

红土作为一种特殊土类，其物理力学性质不同于一般粘性土。本文从红土的基本物理力学性质出发，对红土在不同应力路径不同试验方法下的三轴剪切试验成果进行分析研究，指出红土的应力－应变－体变曲线出现特殊现象，同时还分析了两种应力路径对试验成果的影响。