关键词： 机械式动筛排矸机   动力学   运动学   仿真   UG  

摘要： 机械式动筛排矸机作为当前综采工作面选煤的关键设备,其工作的稳定性和可靠性直接影响最终的产煤质量。因此,基于UG和WorkBench仿真软件,以机械式动筛排矸机为研究对象,着重分析其在标准工况下的运动学和动力学特性,并对其关键部件进行校核,为进一步优化机械式动筛排矸机的结构提供一定的指导意义。

关键词： 农业机械化   农村   劳动力转移  

摘要： 我国在农业方面有着数千年的历史,是当之无愧的农业大国,而农村是我国基本单位,在机械化技术的推动下,农业重新焕发了生机。随着近年来我国经济结构的改革,由传统经济发展中的重速度转变为了重质量,使得农业也在积极转型,以待进一步的对经济发展、农民生活水平的提高作出应有的贡献。在当前思想意识的推动下,农村大量劳动力出现了外出转移的趋势,使得农业现代化与劳动力转移形成了一定的矛盾。本文就以农业机械化对农村劳动力转移贡献之间的联系进行了详细探讨,望可以对我国农业的发展出一份力。

关键词： 林业机械   液压   四轮独立驱动   设计  

摘要： 液压传动具有结构可靠、发展成熟、传动效率高且运转平稳等众多优点,在各种林业机械中的应用越来越广泛。针对目前林业机械轮式伐木机四轮驱动系统所存在的问题,设计了一种适用于伐木机械四轮独立驱动的液压动力系统,对其工作性能进行了分析。

关键词： 工程机械液压系统   动力匹配   控制技术  

摘要： 随着我国工业的快速发展,机电一体化已经逐渐应用到工业的各个方面。为了能够有效地提高工程机械液压系统动力的控制技术,对工程机械液压系统动力匹配与其控制技术进行了分析,并针对其工作中所存在的问题提供了一系列的解决方案。

关键词： 动力头式钻机   机械卸扣   防松器   技术方案  

摘要： 为确保动力头式钻机掘进工作的质效,缩短钻杆装卸周期,实现动力头式钻机的快速入场以及检修维护。文章从多个角度出发,梳理动力头式钻机机械卸扣的特点以及相关流程,全面分析机械卸扣的基本方法,构建起动力头式钻机机械卸扣机制,满足现阶段动力头式钻机机械卸扣的相关要求。

关键词： Natural rubber   Chlorobutyl rubber   Nanocomposites   Vulcanization kinetics   Mechanical modeling  

摘要： The curing kinetics, vulcanizate properties, mechanical reinforcement and chemical interactions of organically modified nanoclay filled natural rubber (NR) and chlorobutyl (CIIR) rubbers have been studied. From the vulcanization studies, it is observed that nanoclays are more intercalated in NR matrix rather than CIIR matrix. To understand the exact mechanism operating in the vulcanization behavior of NR and CIIR, autocatalytic model was applied. The vulcanization kinetic studies revealed that the nanoclay distribution at high temperature (190 degrees C) in CIIR matrix is somewhat intercalated in nature. Highly pronounced reversion behavior was observed in NR matrix. The mechanical reinforcement of vulcanizates was examined using the change in modulus values at 100% and 300% elongation. The mechanical properties were modeled using different kind of models such as Guth-Smallwood, Halpin-Tsai, modified Halpin-Tsai and Mod-Tanaka models. Finally, the dispersion of nano clay platelets in CIIR and NR matrix was confirmed by the phase images obtained from AFM technique.

关键词： Pressure-sensitive adhesives (PSAs)   Polydispersity   Molecular dynamics   Coarse-graining  

摘要： Amorphous polymers are one of the primary materials used in pressure sensitive adhesives (PSAs). Their design can be aided by a better understanding of the mechanisms governing the molecular and mesoscopic scale behavior. This work presents a molecular dynamics study of the toughness and failure modes of a coarse-grained polydisperse PSA model in probe peel tests, achieved by varying the crosslinking density and locations. Generally, the toughness of polydisperse PSAs increases at a crosslinking density of 0.5%, compared to the non-crosslinked structure, and declines at higher crosslinking densities, which also changes the failure mode from cohesive to adhesive. The performance is affected by the length of the polymer chains that form crosslinks, although high crosslinking densities make the system less sensitive to effects related to its polydispersity. The results herewith presented display an optimal performance when 35-45% of the particles in the system belong to the giant component of the PSA network. This is achieved at crosslinking densities of 0.5-1.0%, depending on the length of the chains that are allowed to crosslink.

关键词： Molecular dynamics   Laser nano-structured diamond abrasive   Mechanical polishing   Subsurface damage  

摘要： In the present study, a newly proposed mechanical polishing method of single-crystal silicon with nano-structured diamond abrasives fabricated by laser was investigated, using molecular dynamics (MD) simulations. The results were compared to conventional mechanical polishing under the same machining parameters. Polishing forces, atomic displacement, development of hydrostatic and von Mises stresses in the subsurface zone, temperature distribution, and polished surface morphologies during nano-polishing were investigated. An analysis model was also built to explore the subsurface damage mechanism in terms of examining the hydrostatic and shear stress distributions during nano-polishing. The analyses demonstrated that structured abrasives in silicon polishing lead to lower polishing forces, thinner subsurface damage layer, lower hydrostatic stresses, lower defect atom numbers, and less compressive normal stresses. Nevertheless, structured nanoscale abrasive polishing leads to lower material removal rates. Additionally, more Si-II forms from Si-I, when polishing with #-shaped groove abrasive is performed.

关键词： Dynamic tensile fracture   High-rate stretching   Solid aluminum   Aluminum melt   Molecular dynamics   Mechanical model  

摘要： Construction of the mechanical model for dynamic tensile (spall) fracture is one of the cornerstone problems in the mechanical description of the material behavior under dynamic loading. The spall fracture takes place for both solid and liquid substances, typically referred as cavitations in the latter case. We perform larger-scale MD simulation of the uniform triaxial stretching of molten and solid Al with the strain rate of 3/ns at different temperatures. Formation of multiple pores under used conditions of loading allows us to obtain detailed information about the evolution of pore ensemble at dynamic tensile fracture. This information can be used for verification of the mechanical models of dynamic tensile fracture. We formulate the mechanical models for the pore ensemble evolution in both liquid and elastic-plastic mater. The common part of the model describes the random nucleation of pores in the sample bulk. The size variation part of the model for liquid uses the Rayleigh-Plesset equation. The corresponding part of the model for elastic-plastic solid takes into account the dislocation activity in the pore vicinity. The detailed comparison of the model predictions with the MD data shows their adequacy in description of both the pore ensemble evolution and the general behavior of system parameters for room and elevated temperatures. The collapse of small pores after the relaxation of pressure from strong negative to close to zero values takes place for both molten and solid Al. In the case of melt, the larger and larger pores become collapsing with time, and the number of survived pores tends to one. In the case of solid, the elastic resistance of the surrounding material suppresses the collapse of the middle-sized pores, and only small pores disappear after the pressure relaxation. This feature does not allow one to use simple viscous growth models for pores in plastic solids. MD simulations show the nucleation of secondary voids in the vicinity of the primar

关键词： Sulfite electrooxidation   Kinetics   Palladium   Reaction mechanism  

摘要： Electrochemical oxidation of sulfite ions offers an efficient and profitable approach to the conversion of sulfur dioxide, a harmful air pollutant, into valuable by-products via flue gas desulfurization. Here, the electrochemical oxidation of sulfite in near-neutral pH electrolytes is studied in order to determine kinetic parameters and a reaction mechanism. Sulfite electrooxidation on palladium is demonstrated at pH 7.5 and 8.5, the latter being comparable to platinum. Anodic charge transfer coefficients and non-linear reaction orders are linked to a mechanism which involves sulfite adsorption at low potentials. This study proves that sulfite electrooxidation on palladium at near-neutral pH is a useful approach for sulfur dioxide exploitation.