弹性支撑斑海豹胡须模型单自由度流致振动实验研究

斑海豹依靠其具有波状外形的胡须,可感知猎物尾迹流场中的涡流,进而循迹追踪.对斑海豹胡须感知涡流特征的机制进行研究具有重要的科学意义和应用价值.本文根据斑海豹胡须的外形参数,制作了1:30的实验模型,在水槽中研究了均匀流场和尾迹流场中单个胡须模型和胡须模型阵列的单自由度流致振动特性,分析了模型振动响应与涡流特征的关联.结...     

Study of linearity for a high dynamic range calorimeter

A high dynamic range calorimeter has been designed for the DArk Matter Particles Explore(DAMPE) satellite. It consists of 308 BGO crystals, multi-dynode readout PMTs and front end electronics system. We have built on previous research to show that BGO fluorescence should not be saturated by high electron energy density under DAMPE's energy range. A BGO fluorescence simulator is set up to calibrate the energy range of the dynodes, while a cosmic-ray unit is used to calibrate 1 MIP with the ADC count in dynode 8. Linearity is achieved for the dynamic range from 0.5 MIPs to 1.26×105MIPs. The requirements of DAMPE can thus be satisfied.     

开放的V型三能级系统中原子注入和退出速率对位相相关的无反转激光增益和强度空间演化的调制作用

利用数值计算结果, 研究了具有自发辐射诱导相干的开放V 型三能级原子系统中的传播效应. 研究表明: 改变探测场和驱动场之间的相对位相对无反转激光(LWI)增益和 强度随传播距离的变化即空间演化具有重要的影响; 而原子的注入速率比(S)和退出速率(r₀)的改变将对位相相关的LWI增益和强度的空间演化产生明显的调制作用. 在S(r₀)的一定取值范围内, S(r₀)的值越大, LWI增益和强度越大且强度达到极大值需要的传播距离越长; 相应封闭系统中LWI增益和强度的最大值及能产生增益的传播距离都小于开放系统. Doppler效应对LWI增益和强度的空间演化也具有明显的影响, 存在Doppler效应时得到的LWI增益和强度明显小于无Doppler效应时的值.     

循环电场下钙钛矿铁电薄膜的极化疲劳机制

将循环电场引起电荷注入并产生局部相分解的理论引入到氧空位模型中,建立了一个解析形式的钙钛矿结构铁电薄膜极化疲劳模型.结合该模型讨论了铁电薄膜与金属电极间的低介电常数界面层对疲劳特性的影响,认为界面层对疲劳的产生起关键作用.运用该模型分析了不同松弛时间、电压、温度下的疲劳特性,并与已报道的实验结果进行了对比,模型计算结果与实验数据具有很好的一致性.     

用改进的十进制遗传算法确定土质边坡最危险滑面

基于瑞典圆弧法和简化Bishop条分法分析土质边坡的稳定性,以圆弧滑裂面与边坡面的左右交点的两个横坐标和以滑裂面圆心的纵坐标作为优化变量,采用了一种改进的十进制遗传算法对优化变量进行优化。这种改进的遗传算法是以简单的十进制遗传算法为基础,结合优体克隆操作、子体优生操作和多代调环操作。通过计算ACADS考核题验证,该方法有较强的自适应能力,具有收敛速度快、解的精度高和避免出现早熟等优点。     

Molecular Dynamic Simulation on the Absorbing Process of Isolating and Coating of α-olefin Drag Reducing Polymer

The absorbing process in isolating and coating process of α-olefin drag reducing polymer was studied by molecular dynamic simulation method, on basis of coating theory of α-olefin drag reducing polymer particles with polyurethane as coating material. The distributions of sodium laurate, sodium dodecyl sulfate, and sodium dodecyl benzene sulfonate on the surface of α-olefin drag reducing polymer particles were almost the same, but the bending degrees of them were obviously different. The bending degree of SLA molecules was greater than those of the other two surfactant molecules. Simulation results of absorbing and accu-mulating structure showed that, though hydrophobic properties of surfactant molecules were almost the same, water density around long chain sulfonate sodium was bigger than that around alkyl sulfate sodium. This property goes against useful absorbing and accumulating on the surface of α-olefin drag reducing polymer particles; simulation results of interactions of different surfactant and multiple hydroxyl compounds on surface of particles showed that, interactions of different surfactant and one kind of multiple hydroxyl compound were similar to those of one kind of surfactant and different multiple hydroxyl compounds. These two contrast types of interactions also exhibited the differences of absorbing distribution and closing degrees to surface of particles. The sequence of closing degrees was derived from sim-ulation; control step of addition polymerization interaction in coating process was absorbing mass transfer process, so the more closed to surface of particle the multiple hydroxyl com-pounds were, the easier interactions with isocyanate were. Simulation results represented the compatibility relationship between surfactant and multiple hydroxyl compounds. The isolating and coating processes of α-olefin drag reducing polymer were further understood on molecule and atom level through above simulation research, and based on the simulation, a referenced theoretical basis was provided for practical optimal selection and experimental preparation of α-olefin drag reducing polymer particles suspension isolation agent.     

核物理中的π介子

在强子层次上,原子核或强子物质的基本组元是核子和介子.弄清这些强子的结构,并由基本原理出发研究它们的性质,是当代核物理的重要课题.在各种介子中,π介子是最轻且最重要的介子.关于自由空间中π介子的结构与性质、核介质内π介子的性质、π 核子相互作用与π 核相互作用等问题,始终受到相当多的关注.π介子在核物理中的作用直接联系着手征对称性,汤川秀树关于π介子的最初概念已经大大发展了.有清楚的实验证据表明,核内存在π介子的集体模式,这种集体模式与以前观测到的所有核集体运动模式截然不同.拟对π 核物理的研究现状及值得进一步研究的主要问题予以简要评述. At the hadronic level, nucleons and mesons are constituents of nuclei and hadronic matter. Understanding the structures of hadrons, finding the physics of how the properties of these particles arise from the first principle, are major interests in modern nuclear physics. Among mesons, the lightest and most important one is certainly the pion, thus it is no accident that its structure, properties (both in free space and in nuclear matter) and interactions with nucleons and nuclei have gotten considerable ...     

含面桥基磷硫配体的新颖三核和四核钌羰合簇

[Ru₃(CO)₁₂]与Lawesson试剂[(MeOC₆H₄PS₂)₂]反应,合成、分离并用谱学表征了产物三核钌羰合簇[(μ-H)₂Ru₃(CO)₉(μ₃-P)](Ⅰ)和四核钌羰合簇[(Ru₄(CO)₁₀(μ₃-S)(μ₃-PC₆H₄OMe)](Ⅰ).X射线衍射测定了的晶体分子结构,表明含有1个裸磷原子作为面桥基配体,并具有颇短的Ru-Ru键距,该价电子数为49e的簇合物对氧和水稳定.谱学分析表明,化合物具有四面体型的Ru₄簇心,其三角形面上分别具有面桥基μ₃-S和μ₃-PC₆H₄OMe基配体.     

邻苯二酚紫-示波计时电位法测定天然水中不同形态铝

报道邻苯二酚紫-示波计时电位法分别在酸性和碱性条件下直接检测天然水中的无机单核铝和总单核铝浓度。并用该法测定了水样中的总铝,有机单核铝和酸溶态铝,从而实现了天然水中5种Al形态的电化学测定。测定了20多个实际水样,与Driscoll方法进行了对照,结果基本一致。     

环境与生物样品中铝测定的吸光光度和荧光光度分析方法进展

本文评述了九十年代以来环境与生物样品分析中测铝的吸光光度和荧光光度分析方法的进展。对不同的方法进行了详尽的比较和讨论