城市休闲方式的若干现象及规划面临的挑战

首先阐释城市休闲的基本概念,然后分析了当前我国城市休闲方式中存在的三个现象:户外休闲活动所占比重较低、与社区疏远、休闲获取方式过度货币化,并对这些问题的成因做了探讨。在此基础上,阐述了当前城市规划应从几个方面出发,应对城市休闲发展带来的挑战。     

发扬特别能战斗精神打造第二个百年焦煤

焦作煤矿从1898年开始大工业开采煤炭，已经走过108年的光荣历程。早在1925年12月1日，焦作煤矿工人为声援上海“五卅”运动举行大罢工，尚未结束之时，毛泽东同志就在《中国社会各阶级的分析》一文中，高度赞扬焦作煤矿工人“他们特别能战斗”。特别能战斗精神从此成为焦作煤矿工人，乃至全国煤矿工人宝贵的精神财富。     

人参三醇组甙对雄性大鼠阿片肽与免疫功能的辐射防护作用

采用５ＧｙＸ射线全身照射雄性大鼠模型，大鼠于照射前２４ｈ及照射后，每天腹腔注射５ｍｇ／０．２ｍｌ人参三醇组甙，共注射１４ｄ，观察人参三醇组甙对其阿片肽与免疫功能的辐射防护作用。结果表明，照射组下丘脑阿片肽含量及胸腺和脾脏免疫参数均降低；而在照射加人参组下丘脑阿片肽组水平，所有的免疫参数虽降低但却高于照射组。结果提示，人参三醇组甙可减轻下丘脑网片肽含量及含量接近对照胸腺和脾脏免疫参数的降低，具有辐射防护作用。     

Protein Iodination by Click Chemistry

Two steps to click iodine : We have developed a two‐step reaction for protein iodination using click chemistry. With this method, which is summarized in the scheme, covalent attachment of a stable iodine‐containing aromatic azide moiety to an alkyne‐containing protein was achieved.

     

微通道中液氮的流动沸腾——两相流动压降分析

对液氮在直径为0.531 mm,加热长度为250mm的圆管中的流动沸腾压降和传热特性进行研究.作为第一部分,主要对微通道中液氮的两相流动压降进行试验研究与分析.结果表明:在核态沸腾起始时,质量流量迅速降低,而压降突然增大,并伴随着明显的温度滞后,幅度约为4.0～5.0 K.由于压降很大,在微通道内液氮的两相流动中会出现闪蒸,从而对质量干度产生重要影响.最后,利用均相模型和三个两相流动模型(L-M模型,Chisholm B系数模型和Friedel模型)对微通道沿程压降进行分析和比较.不同于常规通道的是,均相模型可以很好地预测压降试验结果,而三个两相流动模型的预测偏差较大,这是由于在微小通道中的高速流动情况下,汽相和液相混合比较均匀;同时液氮的液汽密度比很小,这也有利于均相模型的预测.     

A General Method for the Chemical Synthesis of Large‐Scale,Seamless Transition Metal Dichalcogenide Electronics

The capability to directly build atomically thin transition metal dichalcogenide (TMD) devices by chemical synthesis offers important opportunities to achieve large‐scale electronics and optoelectronics with seamless interfaces. Here, a general approach for the chemical synthesis of a variety of TMD (e.g., MoS₂, WS₂, and MoSe₂) device arrays over large areas is reported. During chemical vapor deposition, semiconducting TMD channels and metallic TMD/carbon nanotube (CNT) hybrid electrodes are simultaneously formed on CNT‐patterned substrate, and then coalesce into seamless devices. Chemically synthesized TMD devices exhibit attractive electrical and mechanical properties. It is demonstrated that chemically synthesized MoS₂–MoS₂/CNT devices have Ohmic contacts between MoS₂/CNT hybrid electrodes and MoS₂ channels. In addition, MoS₂–MoS₂/CNT devices show greatly enhanced mechanical stability and photoresponsivity compared with conventional gold‐contacted devices, which makes them suitable for flexible optoelectronics. Accordingly, a highly flexible pixel array based on chemically synthesized MoS₂–MoS₂/CNT photodetectors is applied for image sensing.     

三峡工程大坝混凝土长龄期耐久性能试验研究

混凝土的耐久性能直接影响混凝土结构的使用寿命。本文通过对三峡工程大坝混凝土进行龄期长达10年的耐久性能试验研究,分析了混凝土抗冻性能、抗渗性能以及混凝土碳化深度,抗冻性能随龄期的变化规律,不同养护条件对混凝土耐久性能随龄期发展规律的影响。研究表明,自然养护对混凝土长龄期耐久性能不利。研究结论可为长期工作条件下大坝混凝土的真实性能和结构安全性评价提供参考。     

Tailor‐made controlled rheology polypropylenes from metallocene and Ziegler–Natta resins

Production of controlled rheology polypropylenes (CRPPs) is practiced industrially by modifying existing commodity Ziegler–Natta resins through peroxide‐induced β‐scission reactions, resulting in materials with controlled rheological properties and accompanying narrower molecular weight distributions (MWDs). In this work, this methodology was studied using both metallocene‐based polypropylenes (mPPs) and Ziegler–Natta‐based polypropylenes (ZN‐PPs). Numerical simulations based on a previously proposed kinetic model indicated that the nature of the starting resin has a significant effect on the control of MWD polydispersity index (PDI) and weight‐average molecular weight ( ${\overline{M}}_W$) of the resulting CRPP. Based on these observations, experiments were carried out to demonstrate the feasibility of producing CRPP with targeted molecular and rheological characteristics. Commercial mPP and ZN‐PP resins were selected to produce CRPP with similar ${\overline{M}}_W$ or melt flow rates (MFRs) but varying PDIs. The rheological properties and MWDs of these materials were evaluated through oscillatory shear and gel permeation chromatography (GPC) measurements and their extrusion behavior was briefly studied and assessed with respect to these properties. POLYM. ENG. SCI., 59:1114–1121 2019. © 2019 Society of Plastics Engineers     

基于功率特征的抗密集多假目标干扰跟踪技术

针对密集多假目标干扰下,真假目标识别困难、跟踪精度低的问题,提出了基于功率特征的抗干扰技术。首先,对干扰条件下的雷达量测进行信号似然比预处理,剔除杂波;然后,进行角度卡方检验及同源量测融合,以充分利用虚假目标信息;最后,根据真假目标功率特征构建“分贝数冶加权因子,并结合位置信息,实现真实目标的功率/ 位置双重加权,从而大大削弱干扰信号的影响,达到抗干扰的目的。仿真实验表明,该技术能较好地适应密集多假目标干扰环境,并取得较高的跟踪精度。     

ECEF坐标系弹道导弹跟踪研究

针对单模型跟踪算法无法实现对弹道导弹连续精确跟踪的问题,提出了一种地心地固坐标系下弹道导弹全阶段连续跟踪的交互式多模型(IMM)算法。根据导弹不同飞行阶段的受力情况建立IMM算法的两个滤波模型集:助推段采用恒轴向力模型,中段、再入段采用被动段跟踪模型,两个模型都利用滤波精度高、数值稳定性较好的求容积卡尔曼滤波算法进行滤波。针对该IMM算法在混合估计过程中引入偏差的问题,采用无偏混合的方法,以两种典型的跟踪场景进行仿真校验,实验结果验证了该文算法的优越性。