煤矿常见隐蔽致灾因素及其探查技术分析

煤矿隐蔽致灾因素是影响当前煤矿安全生产和生产效率的主要因素之一,查明影响煤矿安全生产的各种隐蔽致灾因素是煤矿地质工作的主要任务,也是保证煤矿安全生产的关键。通过对煤矿隐蔽致灾特点、灾害分布以及常用探查方法技术的分析,发现:煤矿隐蔽致灾因素具有极强的隐蔽性、时变性、突发性,但在宏观上具有一定的区域性和继承性,进行排查时必须全面收集区域致灾因素资料,综合考虑。采空区积水、底板突水、煤与瓦斯突出、顶板冒落、冲击地压是煤矿较为常见的五种致灾因素。其中,采空区积水主要发生在在掘进工作面,底板突水是由断裂构造引发,地质构造、煤层赋存条件、应力集中是煤与瓦斯突出常见致灾因素。支护系统不合理是顶板冒落事故的常见原因。岩性条件、地质构造、工作面“见方”和煤柱应力集中是煤矿冲击地压发生的常见原因。地面调查-物探先行-化探跟进-钻探验证-综合探测是煤矿隐蔽致灾因素的常见探查方法。其中调查主要用来定性和半定量判断,地面物探和井下物探是隐蔽致灾最常用的探查手段,前者主要在矿井建设过程中,后者主要为煤矿安全生产服务。化探和钻探主要用于对物探结果进行验证。     

Bio‐Inspired Multifunctional Metallic Foams Through the Fusion of Different Biological Solutions

Nature is a school for scientists and engineers. Inherent multiscale structures of biological materials exhibit multifunctional integration. In nature, the lotus, the water strider, and the flying bird evolved different and optimized biological solutions to survive. In this contribution, inspired by the optimized solutions from the lotus leaf with superhydrophobic self‐cleaning, the water strider leg with durable and robust superhydrophobicity, and the lightweight bird bone with hollow structures, multifunctional metallic foams with multiscale structures are fabricated, demonstrating low adhesive superhydrophobic ­self‐cleaning, striking loading capacity, and superior repellency towards different corrosive solutions. This approach provides an effective avenue to the development of water strider robots and other aquatic smart devices floating on water. Furthermore, the resultant multifunctional metallic foam can be used to construct an oil/water separation apparatus, exhibiting a high separation efficiency and long‐term repeatability. The presented approach should provide a promising solution for the design and construction of other multifunctional metallic foams in a large scale for practical applications in the petro‐chemical field. Optimized biological solutions continue to inspire and to provide design idea for the construction of multiscale structures with multifunctional integration.     

振动对于吸收式制冷影响的实验研究

利用已搭建的装有电动振动系统的溴化锂吸收式制冷实验台,对溴冷机各主要部件的性能进行实验分析。主要分析振动对于吸收式制冷过程中传热和制冷性能的影响。通过实验数据的处理和分析可以看出：在低频振动状态下,蒸发器、吸收器内的换热效果均优于静止的情形,表明低频振动有利于强化换热,同时增加了机组制冷量,提高了机组COP值。     

影响间接接入式直流电能表计量准确性的相关研究

间接接入式直流电能表是直流充电、轨道交通等领域进行贸易结算不可或缺的器具,其通常搭配直流分流器使用。本文对该类型表的单独检定与整体检定试验进行了分析,得出了其误差受引线电阻与输入阻抗的影响较大的结论。提出了应将直流小信号输入阻抗纳入该类型表的型式评价考核项目,并最大限度地降低引线误差,以确保直流电能计量的准确性。     

多源/多负荷直流微电网的能量管理和协调控制方法

低压直流微电网的能量管理与协调控制是保证其可靠运行需要解决的关键问题之一。基于直流母线电压信号的传统控制方法在不同工作模式将引起直流母线电压存在偏差,对恒功率负载造成不利影响,进而引起系统不稳定。针对这一问题,提出一种基于本地信息的能量管理和协调控制方法。详细分析并网运行、变流器限流运行以及孤岛运行模式下的能量管理、切换条件和协调控制方法。在系统孤岛运行模式下采用一种开环桨距角控制方法并结合恒压控制,消除直流电压波动,提高电能质量和系统稳定性。最后进行仿真研究,仿真结果验证了所提出方法的有效性。     

235/75R17.5低滚动阻力子午线轮胎的设计优化

介绍235/75R17.5低滚动阻力子午线轮胎的设计优化。结构设计参数不变,即外直径　794 mm,断面宽　236 mm,行驶面宽度　188 mm,行驶面弧度高　6 mm,胎圈着合直径　443.5 mm,胎圈着合宽度　184 mm,断面水平轴位置（H/₁/H/₂）　1.002 86。采取优化措施为：采用低滚动阻力胎面胶和胎侧胶配方,胎面采用胎冠胶＋小翼胶复合形式挤出,胎体采用3×0.24/9×0.225CCST钢丝帘线替代3＋9×0.22＋0.15NT钢丝帘线,带束层采用2＋7×0.30ST钢丝帘线替代4＋3×0.33ST和3＋9＋15×0.22＋0.15NT钢丝帘线,优化胎圈部位材料分布,采用低温硫化工艺。成品性能试验结果表明,优化轮胎的耐久性能提高,高速性能达到企业标准要求,滚动阻力系数为6.12 N·kN^-1 ,满足市场要求。     

新型硅烷偶联剂在轿车子午线轮胎胎面胶中的应用

研究新型硅烷偶联剂在轿车子午线轮胎胎面胶中的应用。结果表明：新型硅烷偶联剂的硫含量与硅烷偶联剂Si75接近,硫分布与硅烷偶联剂Si69接近;与采用硅烷偶联剂Si75的胶料相比,采用新型硅烷偶联剂的胶料的硫化效率相对较高,但加工安全性相对较差,胶料的物理性能相当,滞后损失较低,有利于降低胎面胶的滚动阻力,提高轮胎综合性能。     

Effects of rotational speed and fill level on particle mixing in a stirred tank with different impellers

The particle mixing was studied in a cylindrical stirred tank with elliptical dished bottom by experiments and simulations.The impeller types used were double helical ribbon(HR) + bottom HR,pitched blade ribbon + bottom HR,inner and outer HR + bottom HR,and pitched blade ribbon + Pfaudler + bottom HR labeled as impellers Ⅰ to Ⅳ,respectively.The quantitative correlations among the rotational speed,fill level and power consumption for impeller Ⅰ and impeller Ⅱ were obtained by experiments to validate the discrete element method(DEM) simulations.The particle mixing at different operating conditions was simulated via DEM simulations to calculate the mixing index using the Lacey method,which is a statistical method to provide a mathematical understanding of the mixing state in a binary mixture.The simulation results reveal that as the rotational speed increases,the final mixing index increases,and as the fill level increases,the final mixing index decreases.At the same operating conditions,impeller Ⅲ is the optimal combination,which provides the highest mixing index at the same revolutions.     

组合螺带桨搅拌槽内粉体的混合性能

在直径0.48 m的立式搅拌槽内研究了4种组合式螺带搅拌桨的粉体混合性能,考察了搅拌转速、粉体物料装填高度和搅拌桨型对粉体混合性能的影响,分析了径向与轴向上的粉体混合情况. 结果表明,搅拌转速是影响粉体混合的重要因素,增加搅拌转速能明显缩短混合时间,转速44.0 r/min时的混合因子π3比转速8.7及26.5 r/min时下降50%及30%以上;在搅拌桨内部附加较小的内桨使功率略有增加,但可显著缩短混合时间,转速44.0 r/min时能使π3下降50%,提高混合效率.     

Effect of rare earth on the performance of Ru/MgAl-LDO catalysts for ammonia synthesis

A series of MgAl-layered double oxides (LDO) doped with different rare-earth elements (Y, La, and Ce) were synthesized by the calcination of Mg–Al layered double hydroxides, and Ru, which were used to prepare ammonia synthesis catalysts. The as-obtained oxides and catalysts were characterized by XRD, TEM, TPD, TPR and XPS to understand their catalytic performances in ammonia synthesis. The H₂-TPR and HRTEM studies reveal that Ru/Y-LDO catalyst possesses more active Ru metal and small particle size. The XPS demonstrates that the electronic interaction between Y and Ru metals is stronger, which can be tentatively explained by most of Y inserted into the hydrotalcites structure. CO₂-TPD demonstrates that Ru/Y-LDO catalyst shows stronger basic site densities than catalysts doped with Ce and La. Higher activity of the Ru/Y-LDO catalyst can be attributed to smaller particle size, more active metal (Ru) and strong Ru–support interaction.