固体火箭包覆层脱粘调制红外热波检测法的数值模拟

调制红外热波无损检测是一种可以检测材料内部缺陷的先进技术,在固体火箭发动机包覆层脱粘的诊断中有一定的应用前景.以有限元法对固体火箭发动机包覆层脱粘的调制红外热波检测法进行数值模拟,研究加热条件和结构对可检测性的影响.得出可检信息参数(表面过余温度幅值、相位和相位差)随热波激励条件(调制频率、热流强度)和结构参数(材料、...     

Mechanical(compressive)form of driving force triggers the phase transformation from βto ω&α"phases in metastable β phase-field Ti-5553 alloy

Most of the structural alloys'applications are under static,dynamic,and cyclic forms of loading.Ti-5553 alloy in the beta phase field is being investigated to confirm the mechanism of deformation and phase transformation upon quasi-static and dynamic compression.The Ti-5553 alloy was heat-treated at 900 C(almost 50℃above beta transus temperature)for one hour of soaking time followed by air quenching to achieve a fully β phase field.After that,Dynamic compression(DC)by Split Hopkinson Pressure Bar(SHPB)and Quasi-static compression(QSC)were performed at a strain rate of～103/s and 10-3/s,respectively.Recovered specimens were thoroughly examined by using different tools,such as an Optical microscope(OM),Scanning electron microscope(SEM),High-resolution transmission electron microscope(HRTEM),and Electron backscatter diffraction(EBSD)to get the reliable data for justification of logical conclusions.It is found that the dominating mode of deformation was dislocation slip along with twinning({332}〈113〉)to some extent in both of QSC and DC,but sliding&spalling of the grain boundary is observed more in the former.Stress-induced phase transformation,i.e.,β to α"and 3 toω,took place in the grains saturated with dislocation slips,where the former transformation occurred simultaneously with{332}〈113〉twinning,while β to ω transformation was completed when a set of two adjacent(110)β planes covered±1/6th of the total separation distance between two(next to each other)(111)β planes,by equal but opposite shear in(111)β direction,and it caused 3％shrinkage of two closed packed(110)β planes after transformation.     

Accelerating Photogenerated Charge Kinetics via the Synergetic Utilization of 2D Semiconducting Structural Advantages and Noble‐Metal‐Free Schottky Junction Effect

Although photocatalysis is one of the most promising technologies for environmental and energy issues, the irreconcilable contradiction between the absorption of the visible light and the strong redox capability of the photocatalyst and the low photocatalytic reaction kinetics result in the poor efficiency. Here, a composite photocatalyst is reported with high redox capability and accelerated reaction kinetics synergistically utilizing 2D semiconducting structural advantages and the noble‐metal‐free Schottky junction effect. The 2D structure can not only increase the bandgap of the photocatalyst but also improve the transfer and separation of the photogenerated charge carriers. Furthermore, the introduction of the noble‐metal‐free Schottky junction effect accelerates the photocatalytic reaction kinetics. The Schottky barrier can also prevent the photogenerated charges trapped by the electron acceptor from flowing back to the semiconductor, which can further boost the photocatalytic performance. The transfer process of the photogenerated charge carriers is also researched in detail by the comprehensive characterization methods, which enable the photocatalytic mechanism to be revealed.     

α-Fe2O3/alkalinized C3N4 heterostructure as efficient electrocatalyst for oxygen reduction reaction

Journal of Materials Science - A nanocomposite of α-Fe2O3/alkalinized C3N4 (α-Fe2O3/A-C3N4) electrocatalyst for oxygen reduction reaction (ORR) was synthesized by a simple in situ...     

金属钠——乙醇还原酯的机理

本文介绍了一种较为合理的纳在乙醇中还原酯的机理     

基于灵敏度分析的直流输电接地极优化选址方法研究

为了最大程度避免直流输电工程单极大地运行方式造成的变压器直流偏磁问题,提出了一种直流输电接地极的优化选址方法。研究了直流接地极选址时需要考虑的大地电性参数、电力规划需求、周边交流电网的结构与参数等因素,建立了直流接地极位置与变压器直流偏磁风险之间的关联度模型。对此模型进行了灵敏度分析,并以此为依据,提出了高压直流输电接地极选址优化方法。以一个交直流混联电网为例研究了优化选址的效果。优化方法对避免交流电网变压器直流偏磁风险有理论参考作用。     

城镇燃气管道随桥设计的分析与研究

本文介绍了目前合肥市燃气管道的随桥敷设方式,总结和分析了不同随桥敷设方式的特点及其存在的问题和难点,针对问题和难点提出了相应的解决方案.同时给出了不同燃气管道过桥方式需要采取的安全保护措施.为今后燃气管道随桥敷设提供了重要的参考价值.     

中国对外承包工程法律保障初步研究

本文初步研究了中国对外承包工程法律保障现状及存在的问题,提出了完善中国对外承包工程法律保障的基本原则及对策.