不确定环境下的再制造闭环物流网络优化

考虑废旧产品回收数量、回收质量、再生产品需求量的不确定性以及废弃处理中心的选址等多重因素,构建单产品、多周期的再制造闭环物流网络优化设计模型,运用云遗传算法来确定物流网络中各设施的数量、位置、规模以及各设施间的合理物流分配量,使得在整个运营周期的净收益最大。通过算例来验证该模型的有效性。     

基于气体润滑技术的MEMS透平研究进展

高能密度和微型化已经成为动力设备发展的必然趋势,然而,润滑技术的发展直接制约着高速透平的极限转速。微机电系统(MEMS)中的高速透平内轴承与转子间最小间隙为微米量级甚至更小,必然会给装置的设计和制造带来一些新问题。文中简要介绍了基于气体润滑技术的MEMS透平国内外发展状况,并对相关领域的研究进展进行了展望。     

Impacts of urea-formaldehyde resin residue on recycling and reconstitution of wood-based panels

Recycling and reuse of wood-based panels has been attracting great attention since it is an environmentally friendly means of managing wood waste. The recycled wood-based panels usually still contain adhesive residue. In the current research, the impact of urea-formaldehyde (UF) resin, one of the most widely used adhesives, on recycling and reconstitution of wood-based products has been evaluated by adding cured UF resin particles into a new adhesive system. The morphology, chemical structure, curing behavior, and bonding quality of an adhesive system containing 0–6% previously cured resin particles of varied sizes (< 600 μm) were investigated and compared to those properties of a regular adhesive without any impurity. Three-ply plywood glued with a UF adhesive containing 0–10 wt% previously cured resin of varied particle sizes (< 600 μm) were prepared and characterized. The results indicated that the resin residue could significantly affect the curing behavior and bonding quality of the new adhesive system. Higher content and greater size of the particles caused more severe deterioration in the bonding strength.     

VR技术在农业高校教育教学中的应用研究

VR技术即虚拟现实技术,本文结合其技术特征和农业高校教学特点,通过对农业高校学习特征及内容进行研究后,分析了VR技术在农业高校教育教学中的多种应用场景,设计了"基于VR"的教学模式。     

Matrix microstructure deteriorations resulting from diamond incorporation in electroplated metal-diamond composites

Because of their desirable hardness and wear resistance, diamond composite coatings have been widely studied. This article first reports our observation results about the impact of diamond incorporation on the matrix microstructure, and then gives explanations. It is shown that the incorporation significantly worsens the microstructure, like coarsening matrix grain, inducing gaps between matrix and diamond, and promoting emergence of nodules, valleys and over-plating cases on matrix surface. These deterioration phenomena are aggravated by an increase in ‘troublesome’ diamond grain number, current density, or deposit thickness. All the facts are found to result from Lorentz forces generated by the interaction of electric current (moving cations) and magnetic fields produced by magnetic diamond grains that contain metallic inclusions. The interaction not only forces a magnetic diamond grain to stand on one of its corners, also forces a nearby cation that moves from anode to cathode (i.e., from the diamond top to the bottom) to rotate counterclockwise around the grain with an increasing radius (due to a repelling Lorentz force) before it passes the diamond middle, and then to rotate clockwise with a decreasing radius (due to an attracting Lorentz force) after passing the middle.     

固相微萃与GC/MS联用分析水蜜桃挥发性成分

采用固相微萃取技术萃取新鲜和腐败的水蜜桃挥发性成分,并通过气相色谱质谱联用法来分析、鉴定水蜜桃中的气味成分。经NIST质谱数据库检索和文献对照,新鲜水蜜桃检测出32种成分,占总峰面积的81.48%;腐败的水蜜桃检测出27种成分,占总峰面积的86.56%。相同成分有辛酸乙酯、4-癸酸乙酯、辛酸己酯、1,2-苯二羧基酸丁辛酯、异丙基棕榈酸酯、4-(2,6,6-三甲基)-2-丁酮、5-乙二氢基-2(3H)呋喃酮、十五烷、十六烷、十七烷等20种物质,但其相对含量存在很大差异。结果表现出水蜜桃不同品质果实气味成分的不同,可应用于果实的质量鉴定。     

Potentials of bio-hydrogen and bio-methane production from diseased swines

Diseased swines can be utilized as substrate for anaerobic fermentation after proper pretreatment. The cumulative bio-hydrogen and bio-methane production yields were taken as targets, the effects of different initial pH values and enzyme concentration on bio-hydrogen and bio-methane production characteristics by anaerobic fermentation from diseased swines were investigated. Results showed that the highest cumulative hydrogen yield reached up to 175.84 mL/L when pH value and enzyme concentration are of 8.0 and 2.5% respectively. While the maximum cumulative bio-methane-production yield of 104.59 mL/L was obtained when the enzyme concentration and pH value are of 1.0% and 8.0 respectively. The effects of enzyme on cumulative bio-hydrogen yield was greater than that of the initial pH while it is opposite for cumulative bio-methane yield. The potential of bio-hydrogen production from diseased swines is higher than that of bio-methane production.     

Secondary air distribution in a 600 MWe multi-injection multi-staging down-fired boiler: A comprehensive study

Multi-injection multi-staging combustion technology was designed to provide high boiler efficiency together with low pollutant emissions when employing hard-to-burn coal, and showed good application prospects. In this technology, to achieve the first staged air and more flexible combustion regulation on the arches, the secondary air employs a more complicated distribution surrounding the coal/air flows. This design concept significantly affects the flow and combustion characteristics of the actual boiler. Elucidating the underlying mechanisms by which the various secondary air parameters affect the boiler operation requires a comprehensive analysis of the secondary air distribution on the arches. In this work, small-scale cold modeling tests combined with industrial-scale trials using two actual 600 MW_e down-fired boilers were conducted. The results show that the secondary air distribution can significantly affect the near-burner flow and mixing as well as the decay of the downward airflow velocity. High velocity secondary air, especially the secondary air surrounding the fuel-rich flow, evidently promotes the advanced mixing of fuel-rich and fuel-lean flows. Increasing the secondary air flux around the fuel-rich flow and raising the secondary air velocity decrease the pulverized coal heating rate, while a decreased inner secondary air velocity advances the coal ignition. Adjusting the secondary air also greatly affects the downward flame depth and the unburnt coal proportion in the near wall region of the furnace hopper, such that the flame kernel location and the temperatures near the hopper wall are modified. In addition, NO_x formation can be accelerated by a high secondary air flux near the fuel-rich flow or a large contact area between the secondary air and the fuel-rich flow.     

制备电镀金刚石工具时外加交变磁场的作用

引入外加交变磁场以期提高电镀金刚石工具的性能。SEM观察结果表明:与无磁场影响的镀层相比,外加电压为200V时,胎体晶粒尺寸得到细化,镀层的显微硬度提高1 060MPa。磨削实验表明:外加电压为200V时,所制得的金刚石工具与传统无磁场影响下所制得的金刚石工具相比,使用寿命为其1.5倍,工作效率提高了20.21%。     

采用汽油与甲醇燃料的C级车CO2排放对比分析

随着我国社会与经济的进步与发展及汽车保有量的不断增加,能源与环境等诸多问题日趋严峻。结合我国近几年CO₂排放量的变化趋势,本文简要分析了采用甲醇燃料和传统汽油燃料对碳排放的影响。结果显示:研究用某C级车消耗1L/100km甲醇燃料,产生尾气中CO₂为10.9g/km,消耗1L/100km汽油,产生尾气中CO₂为23g/km。相对于传统燃油汽车,合理优化车用能源结构对实现节能减排,降低大气中CO₂具有十分重要的意义。