Comprehensive assessment on dynamic roof instability under fractured rock mass conditions in the excavation disturbed zone

The damage process of fractured rock mass showed that the fracture in rocks induced roof collapse in Yangchangwan Coal Mine,China.The rock mass was particularly weak and fractured.There occurred 6 large-scale dynamical roof falls in the excavation disturbed zone (EDZ) with the collapsing volume of 216 m3.First,the field detailed geological environment,regional seismic dy-namics,and dynamic instability of roadways were generally investigated.Second,the field multiple-index monitoring measurements for detecting the deep delamination of the roof,convergence deformation,bolt-cable load,acoustic emission (AE) characteristic pa-rameters,total AE events,AE energy-releasing rate,rock mass fracture,and damage were arranged.Finally,according to the time-space-strength relations,a quantitative assessment of the influence of rock-mass damage on the dynamic roof instability was accomplished.     

废砂/PE废地膜复合材料热老化性能的研究

以聚乙烯(PE)废地膜和工业废砂为原料,制备了不同配比的废砂/PE废地膜复合材料,研究了PE基体和复合材料的热老化规律。研究发现,经80℃人工加速热老化处理后,复合材料的玻璃化转变温度(Tg)随老化时间的增加而降低;一定条件下的热老化有助于加强PE基体和废砂间的界面作用,使复合材料的力学性能先升高后降低;废砂的加入有利于PE废地膜热老化性能的提高。     

Synthesis and characterization of CdS nanocrystals embedded on solid electrolyte films

In this article nano‐sized CdS crystal embedded in a PEO matrix was successfully prepared by a complex transformation method that is universal for preparing nanosized compounds containing transition metals. The size of embedded CdS particles was in the nanoscale from 2 to 10 nm determined by X‐ray diffusion. The nanosized CdS displayed the expected blue shift of the onset absorbance in the UV spectrum. The amount of blue shift depends upon the dipping time of the PEO–cadmium complex film in a sodium sulfide solution as well as its concentration. The most effective means for adjusting the size of CdS nanocrystals is to change the ratio of the oxygen along with the PEO chain to the cadmium ion in the complex film. The alkali salt in the film would contribute to the conductivity of the composite film. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1263–1268, 2002; DOI 10.1002/app.10459     

三维编织复合材料编织工艺过程仿真研究

总结了四步编织工艺的运动规律。对纱线的空间坐标进行三次B样条曲线拟合得到拟合坐标;设计实现了纱线实体的静态模型算法,根据拟合坐标得到纱线空间网格坐标并建立了纱线实体的静态模型;实现了纱线轨迹的动态展示以及实体生成过程的动态展示;构建了GUI界面并编译成了可脱离Matlab环境的独立运行程序。     

Factors influencing magnetic polymer microspheres prepared by dispersion polymerization

Magnetic iron oxide (Fe₃O₄) was prepared by a coprecipitation method. Core–shell composite magnetic polymer microspheres with carboxyl groups were synthesized by the dispersion polymerization of styrene and acrylic acid in the presence of magnetic oxide, and dibenzoyl peroxide was used as an initiator. The synthesized magnetic polymer microspheres were characterized with X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and so forth. The results indicated that the product was single‐phase Fe₃O₄, and its average size was about 10 nm. The configuration of the microspheres, which contained carboxyl groups, was spherical, and the average size was about 2 μm. The results of vibrating sample magnetometry tests showed that the magnetic powders produced by different surfactants had different saturation magnetizations. When poly(ethylene glycol) with a weight‐average molecular weight of 4000 was used as a surfactant, the saturation magnetization of the samples reached 69.2 emu/g. The factors that affected the shape, magnetism, size, and distribution of the microspheres were also studied. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Virtual Model Reduction-based Control Strategy of Planar Three-link Underactuated Manipulator with Middle Passive Joint

This paper presents a position control strategy for a planar active-passive-active (APA) underactuated manipulator with second-order nonholonomic characteristics. According to the structural characteristics of the planar APA system, we divide the system into two parts: a planar virtual Pendubot (PVP) and a planar virtual Acrobot (PVA). For the PVP, we mainly fulfill the target angle of the first link, which is calculated through the geometry method, and make the system stable. In this stage, via keeping the states of the third link being zero, the system is reduced to the PVP. Meanwhile, we design an open-loop control law based on the nilpotent approximation (NA) model of the PVP to make the second link stable and the first link stabilize at its target angle. Then, the planar APA system is reduced to a PVA with all links’ angular velocities being zero. For the PVA, we mainly realize the other two links’ target angles obtained via the particle swarm optimization (PSO) algorithm. Thus, the control objective of the planar APA system is achieved. Finally, above control strategy is verified by simulation results.

     

Chaos-PSO-based Motion Planning and Accurate Tracking for Position-posture Control of a Planar Underactuated Manipulator with Disturbance

Unlike a fully-actuated manipulator, the position-posture control of a planar underactuated manipulator (PUM) is more difficult, but the research on it is significant due to the wide practical applications. The existing control methods consider no external disturbance and are involved in the staged control idea, bringing the problems of nonsmooth control torque and time-consuming. A novel one-stage control approach is proposed in this paper for the position-posture control of a three-link PUM with the first free joint under the external disturbance. By analyzing the coupling relationship between its active joints and free joint, the position-posture control is transformed into the trajectory tracking control. Unlike the general trajectory planning, the trajectories of the active joints are planned to include several parameters. Meanwhile, the parameters are solved using a chaos particle swarm optimization algorithm to guarantee that all joint angles can reach to their desired angles. Then, to obtain the high trajectory tracking accuracy at every moment under the external disturbance, the nonlinear disturbance observer is constructed and a nonlinear fast terminal sliding mode tracking controller is designed. Finally, the feasibility and superiority of this strategy are verified via two simulations.

     

基于光纤光栅的预应力碳纤维板加固钢梁抗弯性能试验研究

结合碳纤维增强复合材料(CFRP)的高强特性及光纤光栅(OFBG)的感知特性,研制开发CFRP-OFBG智能复合板,通过试验验证其应变传感性能.完成预应力CFRP-OFBG板加固钢梁静载试验,监测钢梁的应变和屈服破坏过程,研究预应力CFRP-OFBG智能碳纤维板加固钢梁的抗弯性能.结果表明:预应力CFRP-OFBG智能碳纤维板是一种集受力和传感于一体的新型土木工程材料,克服了光纤光栅埋设的工艺问题,并且能有效提高加固钢梁的抗弯性能,具有良好的推广价值和应用前景.     

单─银精矿提取银的技术

某单─银矿经浮选所得精矿（％）：Ａｇｌ～２，Ｃｕ≈１，Ｐｂ４～７，ＣａＯ＋ＭｇＯ３０～３５，Ｓ４～７，Ｃ８～９。研究了氰化、硫脲、氨浸等方案对该精矿浸出效果，并从浸出指标等因素进行比较，认为焙烧─预浸─氨浸方案较好，银浸出率＞９７％，铜浸出率９５％。