巨高巷道巷帮稳定机理及支护技术

以山西某矿5203轨道巷的巨高巷道为研究对象,采用对比分析方法,描述了巨高巷道巷帮水平位移和下沉特征及塑性区的分布特征。通过分析巷帮片帮力学模型、巷帮锚固墙的对深部围岩约束原理、巨高巷道金属支架腿部易产生压杆失稳等,最终采用高强锚杆、带、网、索支护方式加固巷帮并确定了合理支护参数。实践结果表明,巨高巷道巷帮稳定原理适用于巨高巷道巷帮支护。     

云南有色金属产业关联程度及影响分析

本文基于投入产出分析方法及可计算一般均衡模型,定量分析了云南有色金属产业与其他各个产业的关联程度,并在此基础上模拟了价格波动下该产业对各关联产业的影响程度,确定了云南有色金属产业的关联产业包括电气、机械和器材,电力、热力生产和供应,通用设备等共23个关联产业。有色金属产品价格变动时,受影响最大的分别为电气、机械和器材,电力、热力生产和供应,煤炭采选产品等部门,且影响情况和关联程度的关系较为密切。有色金属产品价格下跌在合理范围内,对经济产生的积极影响随着价格下跌的幅度逐渐增大,但当有色金属产品价格下跌幅度在40%以上时,GDP将受到极大的负面影响;有色金属产品价格上涨对GDP有一定的负面影响,负面影响一定范围内随价格的上涨幅度逐渐增大。     

Investigation of breakdown conditions in drift chambers

The electrostatic conditions for which breakdown occurs in multiwire chambers are investigated as a function of wire thickness and the total gain in the system.     

Ultralight polymer-derived ceramic aerogels with wide bandwidth and effective electromagnetic absorption properties

In this work, ultralight polymer-derived ceramic aerogels (PDCA) were prepared by a facile method of hydrosilylation crosslink and freeze drying. The electromagnetic absorption properties of ultralight PDCA were investigated for the first time. The PDCA pyrolyzed at 1000 °C shows a uniform three-dimensional (3D) framework with a low bulk density of ∼0.19 g/cm³ and high surface area of 134.48 m²/g. The electromagnetic properties of PDCA were characterized by a vector network analyzer. The minimum reflection and absorption bandwidth of PDCA pyrolyzed at 1000 °C, 1200 °C and 1400 °C are −43.37 dB @ 7.6 GHz, −42.01 dB@12.5 GHz, and −31.69 dB@17.3 GHz and 3.8 GHz, 6.6 GHz and 4.2 GHz, respectively, at the frequency range of 2–18 GHz. The strong electromagnetic absorption and wide bandwidth features of PDCA could be attributed to the multiple reflections of microwaves in the 3D framework, as well as the high dielectric loss and proper conductivity.     

Ka波段相控阵雷达TR组件幅相控制芯片的大功率微波非线性效应研究

采用实验测试和理论分析的方法研究了幅相控制芯片的大功率微波非线性效应.该芯片应用于Ka波段相控阵雷达收发组件中.测试平台利用固态源和脉冲磁控管来产生Ka波段大功率微波.随着输入功率幅值的提高,在实验中很明显地观测到了芯片的降级和毁伤现象.通过一系列的实验测试得到了芯片的全态相移特性和降级阈值,并通过图片给出了实验结果.最后,通过理论分析给出了该芯片的毁伤机理.     

同心层状土体柱孔扩张弹塑性解

考虑到目前多在均质土中应用圆孔扩张理论,提出同心层状土体中柱形孔扩张的弹塑性解析解。该解答基于统一强度理论和非相关联流动准则,采用应力跌落模型模拟岩土材料的软化特性并引入对数应变考虑土体大变形效应。通过对比不同弹性模量组合、软化程度、土层界面半径以及统一强度理论参数,分析扩张压力和柱形孔扩张引起的应力场的影响规律。结果表明：同心层状土体的弹性模量组合对扩张压力影响显著,对于内层弹性模量较大的组合,极限扩张压力比峰值扩张压力小;相同扩张压力作用下,土体软化程度越高扩张率越大;土层界面半径存在需要考虑两种土体相互作用的临界值;统一强度理论参数对扩张压力有一定影响,极限扩张压力随统一强度理论参数的增大而增大。     

环形UV消毒器流场模拟及湍流模型的研究

为了预测紫外反应器的流场特性,利用CFD技术,分别采用标准k-ε模型、Realizablek-ε模型、低雷诺k-ε模型和雷诺应力模型(RSM)进行了水力特性的模拟.结果表明:在x=0,z=1 cm以及x=0,z=83 cm处,4种湍流模型对z向流速的模拟结果都较符合PIV实验数据,在x=0,z=15 cm处,Realizable k-ε模型的模拟结果偏差较大,在x=0,z=64cm处,标准k-ε模型的模拟偏差较其他3种模型大.综合比较,低雷诺k-ε模型和RSM模型的模拟结果较为理想.     

Failure analysis of a pull rod actuator of an ATOX raw mill used in the cement production process

A failure analysis of a forged and machined pull rod made of a quenched and tempered high strength steel – namely DIN 34CrNiMo6 – is presented in this paper. The pull rod under study is one of the three rods that connect the three existing hydraulic cylinders to the roller mill and it is used to exert grinding pressure on the roller in an ATOX raw mill. The study of the failure involved the mechanical system's simulation, as well as the fatigue damage assessment based on the application of the Rainflow Method and Fracture Mechanics principles. The pull rod's stress state was determined from in situ strain gages rosettes measurements, and system's simulation showed that the pull rod was designed to support axial loadings only. To ensure this stress state, a proper functioning of the plain bearings and a good condition of the elastomers of the horizontal rod buffer are required. According to the stress-life approach given in the FKM guideline, the current design solution should provide a useful life of 50 years to the pull rod. However, fatigue crack growth calculations made with the strain spectra registered demonstrated that the presence of an initial surface crack is extremely harsh to the lifespan of the rod, which will reach a critical value in a much shorter period of time. Surface finish, corrosion protection and maintenance actions to ensure the correct functioning of the plain bearings, could be important to ensure the desired longevity of the pull rod.     

Current flat roof bituminous membranes waterproofing systems – inspection,diagnosis and pathology classification

In this paper, a classification system for flat roof waterproofing inspection is presented. The main anomalies liable to be detected in waterproofing systems are listed and classified. All the direct and indirect possible causes of the potential defects, as well as the repair techniques, are also catalogued and classified. The practical use of the system is exemplified with anomalies and repair forms.