Damage and permeability in tape-laid thermoplastic composite cryogenic tanks

This work presents a combined experimental and numerical approach to the design and analysis of tape-laid thermoplastic composite cryogenic tanks. A detailed material and defect characterisation of automated tape-laid CF/PEEK is undertaken using optical micrography and 3D X-ray CT (computed tomography) as well as cryogenic testing to investigate damage formation. Resulting material data is used as input for a novel XFEM (extended finite element method)–cohesive zone methodology which is used to predict intra- and inter-ply damage in an internally pressurised cryogenic tank. An optimised tank lay-up is presented and analysed using the numerical method to ensure resistance to microcrack formation and fuel leakage through the tank walls under operating loads.     

基于非接触式IC卡的信息管理系统

基于非接触式IC卡的信息管理系统由软硬件组成。硬件主要包括3部分，读写部分，读出或写入射频卡中的数据，其功能主要由SHC1702读写模块完成；显示部分，使用TMl2232A显示芯片以点阵显示代替LED段显示；串口通信部分：负责计算机和刷卡装置之间的通信，使用MAX485芯片以保证足够的通信距离；此外采用的X5043芯片带有4kB的闪存，能在单片机“死机”或掉电的情况下，及时保存重要数据，并尽快使之恢复正常工作状态。软件部分包括单片机的下位机程序，PC机的上位机程序，数据库，实现通信、管理等工作。     

Computational model generation and RVE design of self-healing concrete

Computational homogenization is a versatile tool that can extract effective properties of heterogeneous or composite material through averaging technique. Self-healing concrete (SHC) is a heterogeneous material which has different constituents as cement matrix, sand and healing agent carrying capsules. Computational homogenization tool is applied in this paper to evaluate the effective properties of self-healing concrete. With this technique, macro and micro scales are bridged together which forms the basis for multi-scale modeling. Representative volume element (RVE) is a small (microscopic) cell which contains all the microphases of the microstructure. This paper presents a technique for RVE design of SHC and shows the influence of volume fractions of different constituents, RVE size and mesh uniformity on the homogenization results.     

Specific heat capacity of molten salt-based alumina nanofluid

There is no consensus on the effect of nanoparticle (NP) addition on the specific heat capacity (SHC) of fluids. In addition, the predictions from the existing model have a large discrepancy from the measured SHCs in nanofluids. We show that the SHC of the molten salt-based alumina nanofluid decreases with reducing particle size and increasing particle concentration. The NP size-dependent SHC is resulted from an augmentation of the nanolayer effect as particle size reduces. A model considering the nanolayer effect which supports the experimental results was proposed.     

硬质与超硬涂层在印制电路板微型刀具上的应用（三）——超硬SHC涂层在挠性板微钻上的应用

通过物理气相沉积方法,在挠性印制电路板微钻上沉积超硬SHC涂层,对涂层的硬度、结合强度等力学性能进行了研究,并进行了超硬SHC涂层微钻与未涂层微钻对比加工测试。实验结果表明,超硬SHC涂层的硬度高,与硬质合金基材结合良好,涂层的摩擦系数低;在本实验中,超硬SHC涂层钻头加工柔性PCB板材时,使用寿命是未涂层钻头的2倍。     

基于虚拟阻抗的两级式逆变器二次纹波电流传播特性及抑制策略

两级式单相逆变器的输出瞬时功率包含2倍于输出电压频率的脉动功率,致使前级DC/DC变换器的输入存在二次纹波电流。前级DC/DC变换器控制环路的优化是解决该问题有效且低成本的方法。通过环路等效,给出了单环控制以及双环控制的等效电路模型,基于虚拟阻抗的概念分析了电压外环以及电流内环在二次纹波电流传递过程中的作用。在此基础之上,解释并归纳了现有控制策略的抑制原理,指出其中存在的局限性,并给出了2种优化方案。最后,构建了1.5 kVA两级式单相逆变器原理样机进行了仿真及试验验证,验证了分析方法的可行性以及控制策略优化的有效性。