Co?N graphene encapsulated cobalt catalyst for H2O2 decomposition under acidic conditions

Hydrogen peroxide (H₂O₂) has been listed as one of the 100 most important chemicals in the world. However, huge amount of residual H₂O₂ is hard to timely decomposed into O₂ and H₂O under acidic condition, easily resulting in explosion hazard. Here, we reported a core–shell structure catalyst, that is graphene with Co N structure encapsulated Co nanoparticles. Co N graphene shell serves as the active site for the H₂O₂ decomposition, and Co core further enhance this decomposition. Benefiting from it, the H₂O₂ decomposition were close to 100% after 6 cycles without pH adjustment, which increased 6 orders of magnitude compared with no catalyst. At the same time, the O₂ generation reached 99.67% in 2 h with little metal leaching, and ·OH has been greatly inhibited to only 0.08%. This work can cleanly remove H₂O₂ with little deep oxidation and protect the process of H₂O₂ utilization to achieve a safer world.     

矿用履带式运输车在复杂开采条件下的应用

为了方便煤炭的运输，某矿使用了矿用履带式搬运车。履带运输车解决了轮式运输车在恶劣道路条件下不能行走的问题，这种履带车是一种新型的运输工具，其特点是体积小、转弯灵活、动力强大，可在不受场地限制的情况下轻松通过狭窄的地方，能有效解决山区、土壤、陡坡等恶劣条件下物料的运输问题，适合普通运输车辆无法通行的地方。介绍了矿用履带式搬运车的主要结构以及工作原理，并给出了实际应用中应注意的事项。     

Braking behaviours of C/C–SiC mated with iron/copper-based PM in dry,wet and salt fog conditions

C/C–SiC composites have enormous potential as a new generation of brake materials. It is worth studying the friction and wear behaviours of these materials in special environments to ensure the safe and effective braking of trains in practical applications. In this study, the braking behaviours and wear mechanisms of C/C–SiC mating with iron/copper-based PM in dry, wet and salt fog conditions are compared in detail. The results show that the coefficient of friction (COF) in the wet condition is reduced by 14.13% compared with that under the dry condition. The COF value of the first braking under salt fog condition is increased by 12.27% and 30.75% compared to the dry and wet conditions, respectively. Additionally, the tail warping phenomenon of the braking curve disappears in wet condition, which is attributed to the weak adhesion of friction interfaces and the lubrication of the water film. The main wear mechanisms of C/C–SiC mating with iron/copper-based PM under dry condition are adhesive, fatigue and oxidation wear. However, the dominant wear in wet condition is abrasive wear. The cooling and lubrication of water reduce the tendency of thermal stress, and weaken adhesive and fatigue wear. Furthermore, salt fog can accelerate the corrosion of alloy friction film, leading to the damage of friction film. Meanwhile, the third body particles formed in salt fog condition participate in the braking process. The wear mechanisms in salt fog condition are dominated by abrasive and delamination wear.     

Modelling of mechanical properties of five maize varieties at critical processing conditions in the production of fermented slurry-ogi

This research work was conducted to investigate the impact of critical processing conditions on the selected mechanical properties of maize in the production of fermented ogi slurry. Five varieties of maize (A4W, C3Y, D8W, B2Y, and E9W) were soaked at 28 ^ºC and average hot soaking at 65^ºC, respectively, for 96 h at 12-h interval. Selected mechanical properties were evaluated based on a 5 × 2 × 9 factorial design (varieties× soaking methods× soaking periods). Force (FB) and energy required to break (EB) maize grains decreased significantly (p < 0.05) up to the 12th hour. The EB reduced from 873.3 to 70.0 N mm and from 873.3 to 77.8 N mm for variety E9W at soaking conditions of 28^ºC and 65^ºC, respectively. Similar trends were observed for other maize varieties. Modulus of elasticity and resilience decreased significantly (p < 0.05) with increase in soaking period and moisture content. The EB to break maize grains was directly proportional to the product of Young’s modulus and area (E_m A^1.5), the FB and area (F_m A°^.5) and force required to break and geometric mean diameter (F D_g²) of maize grains with a high R² (0.9610.999). This study suggested that the duration of soaking between 12 and 24 h should be enough to significantly (p > 0.05) reduce the hardness, force, and energy required to break whole maize grains in the production of this fermented product and relevant for predicting minimum required energy for a large-scale operation.     

碱铝硅酸盐玻璃化学强化关键影响因素概述

化学强化是一种玻璃机械强度增强方法,适用于异型、超薄、高碱、高膨胀玻璃增强,因新型超薄显示产品的屏幕保护玻璃发展需要,化学强化技术重新在碱铝硅酸盐玻璃品种掀起研究热潮。本文对化学强化本质及铝硅酸盐玻璃在屏幕保护玻璃应用进行了回顾,基于玻璃化学强化的高CS、DOL和低CT诉求,归纳总结了关键影响因素,第1,碱铝硅酸盐玻璃的成分及结构是基础,氧化铝有利玻璃网络孔隙增大创造交换通道,氧化钠或氧化锂是离子交换关键物质;第2,对于玻璃组成和结构设计,要求玻璃网络键合度R=O/Si或O/(Si+Al)满足2.15~2.40,碱金属氧化物质量分数大于13%且膨胀系数大于6×10^-6/℃;第3,在化学强化工艺方面,化学强化温度决定离子扩散系数,化学强化时间决定DOL,一步法仅能获得相对较大的CS,而DOL不很理想,只有两种离子参与交换的二步法才有利于CS和DOL同步提高。     

车用有机朗肯循环系统中计量泵的性能研究

在模拟车用有机朗肯循环(organic Rankine cycle,ORC)系统的工作环境下,设计并搭建以R123作为工质的液压隔膜计量泵性能测试平台。在额定转速(2900 r/min)下,通过调节液压隔膜计量泵的冲程(25%、50%、75%、100%)和出口压力,得到变工况下液压隔膜计量泵的特性曲线,并分析液压隔膜计量泵的关键参数对车用ORC系统性能的影响情况。结果表明:液压隔膜计量泵的流量受冲程影响,与出口压力基本无关。其输入功率和实际运行效率均随着冲程的增加而升高,最高分别可达523.91 W、88.27%。应用该液压隔膜计量泵的模拟车用ORC系统吸热量变化范围较广,系统热效率最高可达12.81%。液压隔膜计量泵可应用于车用ORC系统,通过调节液压隔膜计量泵的冲程和出口压力,可实现提高车用ORC系统热效率、增加系统净输出功率的目的。     

交错巷道巷间围岩承载结构稳定性分析

针对普遍存在的矿井交错巷道围岩体稳定性及支护问题,运用极限平衡分析和弹塑性力学建立交错巷道巷间围岩稳定性分析判别方程,探讨了交错巷道巷间围岩稳定性主要影响因素,并进行了工业性试验。结果表明:交错巷道巷间围岩体受围岩水平应力集中叠加影响,围岩破坏自巷间围岩体上下表面向中部延伸,加之巷间围岩体尺寸有限,一旦破坏贯通将致使巷间围岩承载存在失稳隐患;交错巷道巷间距越小,越近乎平行布置都会加剧巷间围岩破坏且诱发巷间围岩破坏贯通,合理设计断面尺寸及下方巷道合理支护强度可有效控制并维持围岩稳定;现场采用交错巷道联合支护方案后,交错位置上巷道断面完整无较明显变形且下巷道围岩最大变形量小于100 mm,支护效果显著。     

非平稳条件下基于贝叶斯网络的内涝风险评估和管理方法

受非平稳条件因素(如气候变化、城市化)的影响,近几年内涝灾害频发。以Z市某地块为研究区域,借助地理信息系统(ArcGIS)和暴雨雨洪管理模型(SWMM)实现研究区排水管网的水动力模拟。在不同降雨情境下,比较分析现状系统及不同改造方案下的系统溢流量等信息,计算内涝风险指数。采用贝叶斯网络分析工具(Bayes Server)对引发内涝风险的主要因素进行推理、识别和分析,进而构建内涝风险评估模型。该模型便于决策者根据设计需求,结合各因素的不确定性范围和发生概率值,综合选取最适合的改造措施,优化市政排水防涝规划,为市政基础设施建设提供了依据。     

Vipulanandan model for the rheological properties with ultimate shear stress of oil well cement modified with nanoclay

In this study, the effect of clay nanoparticles (NC) and temperature on the rheological properties with ultimate shear stress and weight loss of the oil well cement (class H) modified with NC was investigated. The NC content was varied between 0 and 1% by the weight of the cement. The total weight loss at 800 °C for the oil well cement decreased from 6.10% to 1.03%, a 83% reduction when the cement was mixed with 1% of NC. The results also showed that 1% of NC increased the rheological properties of the cement slurry. The NC modification increased the yield stress (τ_o) and plastic viscosity (PV) by 5%–65% and 3%–16% respectively based on the NC content and the temperature of the cement slurry. The shear thinning behavior of the cement slurry with and without NC has been quantified using the Vipulanandan rheological model and compared with the Herschel-Bulkley model. The Vipulanandan rheological model has a maximum shear stress limit were as the Herschel-Bulkley model did not have a limit on the maximum shear stress. Based on the Vipulanandan rheological model the maximum shear stress produced by the 0% and 1% of NC at the temperature of 25 °C were 102 Pa and 117 Pa respectively hence an increase of 15% in the ultimate shear stress due to the addition of NC. The addition of 1% of NC increased the compressive strength of the cement by 12% and 43% after 1 day and 28 days of curing respectively. The modulus of elasticity of the cement increased with the additional of 1% NC by 6% and 76% after 1 day and 28 days of curing respectively. Effects of NC content and the temperature on the model parameters have been quantified using a nonlinear model (NLM). The NLM quantified the effect of NC treatment on all the model parameters.