Precipitate coarsening and its effects on the hot deformation behavior of the recently developedγ’-strengthened superalloys

Recently,theγ’-strengthened superalloys are of great interests in high temperature applications due to their excellent high temperature strength which is derived from theγ’strengthening phase.For theseγ’-strengthened superalloys,the changes in morphology,size and distribution ofγ’precipitates due to coarsening during thermal exposure have a significant impact on the properties of alloys.This article briefly summarizes the recent advances on the coarsening behavior of gamma prime precipitates in the recently-developedγ’-strengthened superalloys and its effects on the hot deformation behavior of superalloys,drawing specific examples on Allvac^■718 Plus TM and Ni3 Al-based intermetallic superalloys.It is found that the particle size plays an important role in morphological evolution ofγ’precipitates.For instance,the morphology ofγ’precipitates evolves from cuboidal to strip-like or other complex structures in Ni3 Al-based intermetallic alloys,while theγ’precipitates in Allvac^■718 Plus alloy always present nearspherical morphology due to the relatively small initial particle size.The Lifshitz-Slyozof-Wagner(LSW)theory and its modifications,as well as Trans-Interface Diffusion Controlled(TIDC)theory have been applied to describing the coarsening kinetics ofγ’precipitates.Additionally,the hot deformation behavior ofγ’-strengthened superalloy is found to be greatly influenced by the coarsening ofγ’precipitates.     

金纳米阵列薄膜的制备及在表面增强拉曼光谱中的应用EI北大核心CSCD

表面增强拉曼光谱(SERS)是一种灵敏度很高的分析技术,可以给出分子水平的光谱信息,常被用于痕量分析检测。金纳米颗粒(AuNPs)由于其可控制备、独特的光学特性,是最常用的SERS基底材料之一。然而,如何经济、高效地制备出一种性质稳定、耐保存的拉曼基底材料,仍是亟待解决的问题。文中通过静电纺丝工艺,将修饰了β-环糊精的AuNPs聚合液制备成静电纺丝薄膜;将此薄膜用作SERS基底材料,以罗丹明6G作为探针分子,获得了优异的SERS效果,增强因子约为10~5,检测限达到10^(-6)级以下,且基底材料的重复性优越。     

一种以普朗尼克为大分子交联剂的强韧型凝胶制备

对商用普朗尼克(Pluronic)进行修饰,使其形成外层带可聚合基团的胶束,参与2-丙烯酸甲氧基乙酯(MEA)的聚合反应,得到一种强韧型的胶束凝胶(Pluronic/PMEA gel)。对制备的凝胶进行了形貌、热力学、力学强度的表征。结果显示,含水平衡的凝胶在压缩形变85%时压缩强度在1.1 MPa以上,压缩不破碎且形变可回复。凝胶干燥之后变得更加柔韧,不同胶束凝胶拉伸断裂强度在550~1200 k Pa之间;压缩强度在25 MPa以上。     

Stability enhancement of PbS quantum dots by site-selective surface passivation for near-infrared LED application

Infrared lead chalcogenide quantum dots(QDs)suffer fast degradation due to the easy oxidation of surface chalcogen atoms.Here,we report a trioctylphosphine-mediated surface passivation method to improve the air stability of PbS QDs.Surface mechanism study reveals an in situ surface reaction,which leads to site-selective passivation of surface S atoms with lead mono-carboxylate.The surface capping motif sufficiently protects PbS QDs from oxygen and improves their stability as well as quantum efficiency regardless of the QD size and original ligands on surface cations.The modified PbS QDs display no obvious fluorescence quenching and surface oxidization after 30 days of air exposure.The robust surface capping also provides high compatibility of PbS QDs with polymers for optoelectronic device fabrication.The near-infrared LEDs based on the modified PbS QDs display a slight degradation of only 1.47%from the maximum intensity after continuous operation in air for 250 hours(lifetime>10,000 h)at 0.5 W/cm² power density,indicating the surface passivation route is promising strategy for promoting practical optoelectronic application of PbS QDs.     

基于物联网技术的二次供水智能管理平台的设计与实现

本文中主要提出一种以物联网技术为基础,通过应用传感器技术、MQTT协议以及GIS服务等技术为核心,并通过可视化泵房管理、网络化告警管理以及智能化运维管理等方式,构建起能够实现二次供水全过程智能管理的平台,为提升我国二次供水管理水平作出积极的贡献,希望为相关人员带来一些参考。     

Modeling and analysis of pointing error for non-landing vehicle-mounted photoelectric theodolite

In order to achieve high accuracy measurement for non-landing vehicle-mounted photoelectric theodolite (NVPT) with continuous zoom optical system, a theoretical model of pointing error is presented. Starting with the working mode, the error source of the whole closed loop which affects the pointing error is analyzed. The measurement equation is derived using a coordinate transformation. The pointing error model is then obtained with the help of Monte Carlo method. The error of an NVPT prototype is measured, showing that the pointing error can be predicted accurately. A high precision NVPT with continuous zoom optical system is successfully designed and analyzed, with an accuracy of 11.9″ at azimuth and 10.9″ at elevation, when the optical focal length is set between 1 000 mm and 4 000 mm.     

大比值r／t弯曲回弹的计算及其补偿

一、引言由于材料的弹性变形，使成形后零件的角度和圆角半径与模具相应形状不一样。材料的相对弯曲半径r/t越大，回弹也越大。如果对回弹不加以补偿或校正，就会影响产品质量。本文主要论述相对弯曲半径r/t＞10时回弹的计算及其补偿。二、传统补偿方法的有限性图1所示的零件为批量生产，材料为Q235。其特点是零件弯曲内侧半径r与材料厚度t之比值r／t较大，因而弯曲回弹值凸a也比较大，见图2。以前我厂按照传统工艺方法采取了以下措施，见图3。1．将凸模两侧的形状进行修正，使其两侧各内顿2”。2．凸模的底平面铣浅槽，槽深为O．15mm。这…     

二项式分布在种群平衡模型模拟粒度分布中的应用

提出了一种适用于几何网格的子粒子二项式分布函数,并应用于种群平衡模型模拟活性污泥絮凝后的粒度分布。结果表明：与二元分布相比,该二项式分布可以得到更准确的粒度分布和平均粒度模拟值;通过校核二项式分布参数C_p的取值,可以提高粒度分布和平均粒度的模拟精度。相比于二元分布或正态分布只能描述一种类型的子粒子分布,该二项式分布具有较强的适应性,调整参数C_p的取值,可以得到更多可能的子粒子分布;参数C_p还可以表征粒子的破碎方式--较小的C_p值表征粒子具有较强的稳定性,易破碎生成较大的子粒子;较大的C_p值表征粒子具有较弱的稳定性,易破碎生成较小的子粒子。     

基于标准的大数据互连技术综述

介绍了大数据概念、特征及其对互连技术的影响和要求,提出了大数据时代下标准化的作用及其与互连技术和互连产品的关系,展望了大数据时代的产品、技术和标准的发展趋势,就国内连接器企业如何应对大数据时代的变革、抓住机遇展开了讨论。     

堵塞对复合垂直流湿地水力特征的影响

复合垂直流人工湿地系统(IVCW)堵塞后其水力特征会发生变化，通过示踪剂对小试和中试系统堵塞前后的水力特征进行了研究。结果表明，堵塞后IVCW出水流量减小，小试系统实际停留时间由堵塞前21．3h延长至32．5h，中试系统实际停留时间从19.4h延长至26．8h。IVCW堵塞后容易造成下行池表面积水，既恶化了卫生条件又降低了系统的处理能力。