溢流阀常见压力故障的原因及处理办法

分析了溢流阀常见压力故障的原因,并指出了各种故障的一些消除措施。     

软粘土中单桩承载力时间效应的研究

采用静力触探资料估算单桩竖向承载力的方法经大量的工程实践证明是行之有效的 ,它可以充分发挥地基土的潜力 ,节省工程投资。但对于某些处于深厚软粘土中的桩 ,按规范规定的休止时间进行试桩时 ,实测的单桩极限承载力有时与理论计算结果相去甚远 ,本文结合具体工程实例详细说明了在工程中遇到此类问题的几种的处理措施 ,提出了此类地层中确定单桩竖向承载力的一些建议。     

静力触探探头传感器线性度的有限元分析

采用有限元法对静力触探探头传感器的弹性元件进行分析。用此法不仅可以得到弹性元件的应变分布特性,确定应变片的最佳贴片位置,而且可以得到不同载荷下相应节点的应变值。由电压与应变之间的关系式最终可以得到输入载荷与输出电压之间的关系,从而分析出传感器的线性性能。分析结果表明．此传感器的线性度很好,能满足使用要求。     

基于净能力及二阶锥规划的分布式光储多场景协同优化策略

针对现有配电网中分布式光储调度模型存在资源协同不足、求解复杂等问题,提出了一种基于净能力及二阶锥规划的分布式光储多场景协同优化调度策略。通过引入储能接入配电网后的功率转移分布因子,提出一种基于系统净能力的储能最优选址计算方法;综合考虑储能的运行特性和分布式光伏的出力不确定性,建立以系统日综合成本和削峰填谷为目标的分布式光储多场景协同优化调度模型;利用二阶锥松弛和Big-M法对潮流约束、储能运行约束进行处理,将原规划模型转化为混合整数二阶锥规划问题。以IEEE 33节点系统和西北某实际系统为算例进行仿真分析,结果表明所提方法能在降低负荷峰谷差和日综合成本、平抑负荷波动的同时,显著提高对分布式光伏的消纳能力,验证了所提方法的有效性和可行性。     

A bi-objective DC-optimal power flow model using linear relaxation-based second order cone programming and its Pareto Frontier

The DC optimal power flow (DC-OPF) plays an important role in the operation and planning of modern power systems. In this paper, a bi-objective DC-OPF model minimizing both network losses and generation costs is introduced, which can further be converted into a single objective model via the weighted sum method. Furthermore, the Pareto Frontier is employed to solve this problem. In the mathematical view, the model is a special non-convex quadratic constraints quadratic programming problem. In order to obtain a continuous Pareto Frontier, the original non-convex feasible region is relaxed to its convex hull using a linear relaxation-based second order cone programming method. Compared with the semi-definite relaxation method, the proposed method can greatly reduce the number of dummy variables and the complexity of solutions. Finally, simulations on eight small systems and four practical, large systems are performed, in addition to the comparison of a Monte Carlo simulation. The results verify the effectiveness of the proposed algorithm.     

Electronic transport properties of phosphorene/graphene(silicene/germanene) bilayer heterostructures: A first-principles exploration

Recently, new researches on van der Waals (vdW) two-dimensional bilayer heterostructures have been carried out owing to their unique properties different from single-layer materials. Herein, three types of bilayer heterostructures, phosphorene/graphene, phosphorene/silicene and phosphorene/germanene are constructed and their electronic transport properties are calculated based on the first-principle method. The results show that their I-V curves are totally different that the phosphorene/graphene devices have higher electron transmission probability, resulting in higher current values. Furthermore, we calculate their band structures to explore the internal mechanism of current difference. The graphene-like Dirac cones are found in the bilayer phosphorene/graphene heterostructures. However, the positions of their Dirac cones in the Brillouin zone are markedly different from that of graphene. But when the silicene or germanene is combined with the phosphorene together, the Dirac cones of the silicene or germanene disappear, instead, there are band gaps of about 0.2?eV around the Fermi level. Our results suggest that the Dirac cone can be mainly retained by the weak hybridization between monolayer phosphorus and 2D Dirac materials. Due to the existence of the Dirac cone, the overlap between the source and drain electrodes increases, which leads to a larger current value. This discovery of the Dirac cones in the bilayer heterostructures is applicable in designing Dirac materials and understanding their electronic transport properties.     

纳米水滑石/氧化锌/氧化镁复合改性聚氯乙烯的燃烧特性

采用原位悬浮聚合制备了聚氯乙烯/纳米水滑石（PVC/HT）复合材料,并进一步与ZnO、MgO复合。采用锥形量热仪分析了PVC/HT/ZnO/MgO复合材料的燃烧特性。结果表明,HT、ZnO、MgO在PVC基体中分散良好,HT/ZnO/MgO对降低PVC燃烧过程中的热释放速率和烟雾释放速率有良好的协同作用。PVC/HT/ZnO/MgO(95/5/3/3)复合材料的最大热释放速率和最大烟雾释放速率比纯PVC降低了50 %以上,残留率明显提高。PVC/HT/ZnO/MgO复合材料的拉伸强度和缺口冲击强度均大于PVC/ZnO/MgO复合材料。     

煅烧时间对水泥浆体流变性的影响

采用电炉模拟预分解窑热工制度煅烧水泥熟料,并用旋转黏度计和微型坍落度仪等测定水泥浆体的流变性,又利用扫描电镜、水化热等近代测试方法,分析相关的作用机理,研究熟料煅烧时间对水泥浆体流变性的影响。研究结果表明：煅烧熟料的保温时间过短,矿物晶体来不及充分长大,颗粒细小,发育不完善,加快水泥的水化速度,使水泥浆体的流变性变差。     

锥角对水力旋流器压力场和速度场的影响

针对所建立的静态水力旋流器结构模型进行了简要的分析,采用CFD软件中基于各相异性的雷诺应力湍流模型,应用PC-SIMPLEC算法,对双锥水力旋流器内部流场进行了的三维数值模拟,得到了旋流器内部流场的压力分布特性和速度分布特性.结合流体力学及旋流器理论分析验证模拟结果的正确性.研究发现:在一定范围内,水力旋流器内部压力降...     

RF30802旋转下料阀减速器输出轴锥套失效分析

聚丙烯装置RF30802旋转下料阀在运行过程中发生减速器输出轴端的锁紧锥套断裂失效,从而造成传动链轮松动,减速器输出轴键槽磨损。文章通过分析锥套材质的化学成分、金相显微组织、断口,查找出锥套失析原因,并制订了相应措施,以确保设备正常运行。