Shape optimization of bi-directional flow passage components based on a genetic algorithm and computational fluid dynamics

The inlet/outlet is an important part of a water conveyance system in a pumped storage power station (PSPS). Its hydraulic characteristics are directly related to the operation and economic benefit of the PSPS. Frequent changes between inflow and outflow operations pose significant challenges in the design of the inlet/outlet diffusion segment shape. In this study, an effective optimization method, including three-dimensional parametric modelling, computational fluid dynamics and a genetic algorithm, is introduced and coupled to the design of the diffusion segment shape. The hydraulic characteristics of bi-directional flow, including the head loss, velocity uneven distribution and uneven discharge distribution, are selected as the objective function in the optimization method. Using this method, the recommended shape of the inlet/outlet is studied and its hydraulic characteristics are discussed. The results indicate that the optimized inlet/outlet has better performance.     

Locally one-dimensional-alternating segment explicit–implicit and locally one-dimensional-alternating segment Crank–Nicolson methods for two-dimension parabolic equations

In the paper two new locally one-dimensional alternating segment schemes for solving the 2-D parabolic problems are developed. The parabolic problems can be solved efficiently over decomposed sub-domains. Two schemes are proved to be unconditionally stable and numerical experiments show the validity of the schemes.     

旋挖钻机设备油液智能分析与健康监测

为了对直升机盒段件入水载荷进行分析，开展了模型垂直入水冲击试验，同时采用有限元-光滑粒子流体动力学（finite element method-smooth particle hydrodynamics，简称FEM-SPH）耦合数值方法进行仿真分析，计算了不同材料构型和速度下的过载、压力及应变结果。与试验结果进行对比表明，仿真结果与试验值吻合较好，预测的结构失效破坏模式与试验结果基本一致，可为真实直升机入水冲击的结构设计提供参考。     

Effect of the composition and degree of crosslinking on the properties of poly(l‐lactic acid)/crosslinked polyurethane blends

Poly(l ‐lactic acid)/crosslinked polyurethane (PLLA/CPU) blends which were prepared via reactive blending of PLLA with poly(?‐caprolactone) (PCL), glycerol and 4,4′‐methylenediphenyl diisocyanate showed excellent toughness. The effects of the composition of the mixture and degree of crosslinking of CPU on the toughness of the PLLA/CPU blends (80/20 w/w) were studied in detail. Dynamic mechanical analysis and rheological measurements were used to characterize the structure of the in situ formed CPU in the PLLA matrix. A novel netlike phase structure was observed when the average molecular weight of PCL and degree of crosslinking were 1 kDa and 10%, respectively. The impact strength of the blend was enhanced from 2.2 kJ m^?2 for pure PLLA to 62.4 kJ m^?2; meanwhile, the elongation at break was increased to 489.8%. Therefore, the mechanical properties of PLLA/CPU blends can be easily tailored by tuning the composition of the mixture and the degree of crosslinking of CPU. © 2018 Society of Chemical Industry     

双圆弧齿轮端面齿廓方程及其啮合过程

详尽而又简明地推导了分阶式双圆弧齿轮的端面齿廓方程。通过插图来展示各坐标系的相互关系 ,介绍如何具体的在计算机上绘出双圆弧齿轮端面图及模拟齿轮的啮合过程。     

切削力监测刀具磨损的一种方法

刀具磨损的在线监测是柔性制造系统研究工程的一个重要课题。从理论上分析切削力与刀具磨损的相关性 ,提出切削的波动周期与系统振动周期是相同的。经过刀具磨损对切削力影响的理论计算 ,通过实验提出一种刀具磨损监测方法—频段均方值法。     

MAPGIS中使用结点平差操作的问题分析及改进建议

主要介绍应用MAPGIS制图过程中，使用结点平差操作所产生的误差，如：改变了原线段的方向，区分割时。使弧段产生变形，从而使结点平差后的弧段，分割后的区的属性未接要求进行改变，并提出了消除这些误差的方法与建议。     

新型弧形齿扁平接链环的研制

扁平接链环是各种刮板输送机中连接刮板链条用的连接环，有锯齿式、梯齿式和弧齿式等型式。其中锯齿式接链环拆装困难；梯齿式接链环拆装较容易，但齿形易变；弧齿式接链环是配合面为弧形的接链环，改善了齿面受力状态，强度高、连接可靠、拆装容易，因此，这种接链环正逐步替代锯齿式和梯齿式接链环。     

城市地铁盾构法区间隧道的设计

广州地铁二号线越秀公园一三元里区间盾构隧道已于2002年建成并投入试运营。阐述了该隧道的设计概况，主要内容包括：盾构隧道的线路拟合，衬砌环的构造形式，管片的结构设计和结构防水。总结了广州盾构隧道设计中的成功经验，并对当前盾构隧道设计中有关问题提出了建议。     

秦岭Ⅰ线隧道仰拱预制块施工技术

介绍了秦岭Ⅰ线隧道仰拱预制块的施工生产,对仰拱块的安装标准、安装方向的控制进行了初步探讨,供类似工程施工参考.