Peak shear strength prediction for discontinuities between two different rock types using a neural network approach

The peak shear strength of discontinuities between two different rock types is essential to evaluate the stability of a rock slope with interlayered rocks. However, current research has paid little attention to shear strength parameters of discontinuities with different joint wall compressive strength (DDJCS). In this paper, a neural network methodology was used to predict the peak shear strength of DDJCS considering the effect of joint wall strength combination, normal stress and joint roughness. The database was developed by laboratory direct shear tests on artificial joint specimens with seven different joint wall strength combinations, four designed joint surface topographies and six types of normal stresses. A part of the experimental data was used to train a back-propagation neural network model with a single-hidden layer. The remaining experimental data was used to validate the trained neural network model. The best geometry of the neural network model was determined by the trial-and-error method. For the same data, multivariate regression analysis was also conducted to predict the peak shear strength of DDJCS. Prediction precision of the neural network model and multivariate regression model was evaluated by comparing the predicted peak shear strength of DDJCS with experimental data. The results showed that the capability of the developed neural network model was strong and better than the multivariate regression model. Finally, the established neural network model was applied in the stability evaluation of a typical rock slope with DDJCS as the critical surface in the Badong formation of China.

     

Design and construction of two new polymers featuring macrocyclic subunits based on a rigid clamp-like ligand

Reaction of a rigid conjugated clamp-like ligand N,N′-bis(pyridin-3-yl)-2,6-pyridinedicarboxamide (bppdca) with ZnSO₄·7H₂O or CoSO₄·7H₂O resulted in the formation of two new polymers, namely, {[Zn₂(bppdca)(SO₄)₂(DMF)₂]·(DMF)}_n (1) and {[Co(bppdca)(SO₄)(CH₃OH)(DMF)]·H₂O}_n (2). Both 1 and 2 feature one-dimensional double-chain structures with macrocyclic subunits, and the chains further self-assemble into a higher-dimensional framework via the hydrogen-bonding and π–π stacking interactions. Fluorescence studies show that the free ligand displays a strong fluorescence emission in solid state at room temperature, but in 1 and 2, the complexation of the ligand with metal ions and weak intermolecular interactions make the fluorescence emission partial quenching.     

浮选精煤掺粗对其脱水效果的影响

浮选精煤粒度过细会造成浮选消泡困难、浮选精煤水分高等问题,而合理的向浮选精煤中掺入粗颗粒,改善其粒度组成,有利于解决这些问题。通过试验论证了浮选精煤掺粗有利于浮选精煤消泡,并可有效降低浮选精煤水。     

基于流变学的CNTs/SBS复合改性沥青性能及储存稳定性研究

为了探究碳纳米管(CNTs)对苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)改性沥青的高低温性能及储存稳定性的改善效果,采用动态剪切流变试验(DSR)与弯曲梁蠕变试验(BBR)对CNTs/SBS复合改性沥青的流变特性进行评价,并基于软化点差值、流变学指数和荧光显微镜图像分析胶结料中聚合物分散状态。结果表明：CNTs加入后进一步增强了SBS改性沥青的高温抗车辙性能,且随CNTs掺量增加,高温性能逐步提升。CNTs的加入对改性沥青低温蠕变性能有不利影响,1.0%CNTs掺量下复合改性沥青更具性能效益。CNTs可以显著地提升SBS在沥青中的分布状态,CNTs与SBS形成均匀网状结构,在提升储存稳定性的同时具备增强沥青抗变形的能力,且CNTs的最佳掺量为1.0%。     

生产因素对橡胶沥青性能影响的研究

为了完善橡胶沥青的生产工艺,促进橡胶沥青大规模的推广应用,分别从搅拌方式、搅拌温度、胶粉规格、基质沥青种类、加工时间和胶粉掺量六个方面采用针入度、延度、软化点、弹性恢复和布氏旋转黏度等指标研究生产因素对橡胶沥青性能的影响.研究表明,在搅拌温度为180～190℃,40～60目的胶粉掺量为18％～20％时,高速搅拌1h生产的橡胶沥青综合性能较佳;基质沥青对橡胶沥青的性能有重要影响,与埃索90号基质沥青相比,SK70号基质沥青使橡胶沥青具有较好的高温性能,但低温性能略差.     

混杂纤维增强高强混凝土性能研究

为研究钢纤维、聚乙烯醇纤维混杂比例对高强混凝土性能的影响,通过合理设计坍落度试验、力学强度试验、收缩试验、抗裂试验、抗氯离子侵蚀试验,对比评价了纤维混杂比例对高强混凝土工作性、抗折强度、收缩性、抗裂性能以及氯离子渗透系数的影响。结果表明,钢纤维和聚乙烯醇纤维降低了新拌混合物的工作性。与单掺纤维相比,混杂纤维对高强混凝土力学性能改善效果不明显,但可明显改善混凝土抗裂性能,开裂面积抑制率最大为95.8%,同时能使高强混凝土收缩率和氯离子分别降低27.7%和66.5%,明显提高高强混凝土的耐久性能。通过扫描电镜试验分析探讨了纤维增强混凝土的作用机理,结果表明混杂纤维对基体内部结构的改善实现了对混凝土宏观性能的提升,最终推荐采用0.75%(体积分数)钢纤维和0.25%(体积分数)聚乙烯醇纤维。     

异步电机三电平矢量控制传动离线自整定

从异步电动机的状态方程出发,通过静止状态下对状态方程的简化和变形,采用特殊信号激励方法,对异步电动机三电平矢量控制系统进行离线参数估计,为传动系统调节器参数设计和参数在线估计做基础,仿真和实验结果验证了方法简单有效。     

发展循环经济是煤炭企业战略转型的契机

介绍了煤炭企业发展循环经济面临的挑战。提出了发展循环经济给煤炭企业带来的转型机遇、转型的方向和转型的关键问题。     

大规模风电接入对电网电压的影响及无功补偿研究

从静态电压稳定性的角度,研究了某地A风电接入C电网后系统运行方式、风机类型、风机控制策略和调峰策略的因素对系统电压稳定性的影响。针对某地A风电接入给C电网带来的电压控制问题,提出了相应的无功补偿方案及电压控制措施。仿真计算结果验证了所提无功补偿方案及电压控制措施的有效性,对大规模风电接入后对C电网安全、稳定运行具有一定的参考价值。     

超精密大尺寸光学玻璃平面磨床的研制

光学玻璃广泛应用于激光技术、光电通讯、航空航天以及国防工业等领域。上海机床厂有限公司开发了超精密大尺寸光学玻璃平面磨床,对该磨床的结构及相关技术进行了介绍。