Gels from mixed ligand silver(I) carboxylates: a promising approach for gel formation utilizing surface modifications

Mixtures of Ag(hexanoate) and Ag(palmitate) give thermoreversible gels at very low concentration in toluene. The framework of the gel is composed of the branched nanosized fibers, contrary to the microsized wire precipitates of silver(I) carboxylates. The randomness of mixed-ligand silver(I) carboxylate polymeric chains hinders the crystallization process, resulting in very thin fibrils. This may be a new approach to design and control the properties of materials, which do not have properties involving gels or nanostructures in a conventional process.     

High energy heavy ion tracks in bubble detectors

Bubble detectors which are commonly used as neutron detectors have been demonstrated through this study to be good detectors for registration of high energy heavy ion tracks. Large size bubble detectors made in China Institute of Atomic Energy were irradiated to heavy ions Ar and C up to 650 MeV/u and 400 MeV/u, respectively. Very clear features of stringy tracks of high energy heavy ions and their fragmentations are manifested and distinguishable. A single track created by a specific high energy heavy ion is composed of a line of bubbles, which is visible by naked eyes and retained for months wihhout reduction in size. The creation of heavy ion tracks in bubble detectors is governed by a threshold whose essence is approximately a critical value of energy loss rate (dE/dX)_c similar to that of etch track detectors. Ranges of heavy ions in bubble detectors are apparent and predictable by existing formulas. Identification of high energy heavy ions and the applications to heavy ion physics, cosmic rays, exotic particles and cancer therapy monitoring are obviously promising. The experimental and theoretical aspects of high energy heavy ion tracks in bubble detectors as well as the expectable applications are presented and discussed.     

Concise synthesis of dopexamine dihydrochloride via benzyl protecting protocol

Benzyl protecting protocol was first employed in two routes for the concise synthesis of dopexamine dihydrochloride.This protecting group could be cleanly removed under mild condition and no unacceptable ion was brought to the final product.The total yield of route I was 43.8% from phenylacetic acid,while it was 54.1% of route II from 2-(3,4-bis(benzyloxy)phenyl)acetic acid.The titration purity of the final product was more than 99.5%,while any single or total impurities met the known standard of the drug by HPLC analysis.The measured residual palladium met an acceptable limit(<1 ppm) as an API for injection.     

考虑公交港湾式停靠的多速混合城市交通流元胞自动机模型研究

在Nagel-Schreckenberg提出的元胞自动机模型基础上,建立了考虑公交车辆和港湾式公交停靠站的多速混合车辆单车道城市交通流元胞自动机模型.通过计算机模拟,给出了随机减速概率、混合车流密度、公交车辆平均停靠时间、公交车辆占有率和港湾式公交车站间距对混合车流速度和流量的影响图.对混合车流的特性进行了分析和讨论. 关键词： 元胞自动机 港湾式公交停靠站 混合交通流模型 计算机模拟     

Au/SiO2纳米多层薄膜的制备及其性质表征

利用多靶磁控溅射技术制备了Au/SiO₂纳米颗粒分散氧化物多层复合薄膜.研究了在保持Au单层颗粒膜沉积时间一定时薄膜厚度一定、变化SiO₂的沉积时间及SiO₂的沉积时间一定而改变薄膜厚度时，多层薄膜在薄膜厚度方向的微观结构对吸收光谱的影响.研究结果表明：具有纳米层状结构的Au/SiO₂多层薄膜在560 nm波长附近有明显的表面等离子共振吸收峰，吸收峰的强度随Au颗粒的浓度增加而增强，在Au颗粒浓度相同的情况下，复合薄膜 关键词： 2纳米复合薄膜')" href="#">Au/SiO₂纳米复合薄膜 多靶磁控溅射 吸收光谱 有效介质理论     

不同滤波方法对揭示全球海洋条带结构的比较

海洋条带结构是近年物理海洋学研究的一个新热点. 在海洋中, 条带结构往往被大尺度环流过程所掩盖. 把这种隐蔽的海水运动现象显现出来的办法是对时间平均的速度场进行空间滤波. 利用全球简单海洋资料同化分析系统资料和中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室的气候系统海洋模式模拟数据对三种一维滤波方法进行了比较, 分别是常用的高斯和汉宁滤波方法, 以及本文引入的切比雪夫滤波方法. 结果表明, 尽管三种方法均可获得条带结构, 但以切比雪夫方法为最佳; 另外, 设计高通滤波器时需设定截断频率, 而它的选定取决于对具体数据的频谱分析, 当选取的归一化的截断频率值在0.1和0.4之间时, 可以有效地揭示出条带结构在全球海域内的分布. 因此本文的研究方法为海洋条带结构的深入研究提供了一个有力工具.     

地表反照率对短波红外探测大气CO2的影响

在卫星短波红外遥感二氧化碳的过程中, 表征地表特征的地表反照率是影响探测精度的重要参数之一. 针对温室气体二氧化碳高精度探测的需求, 本文研究了地表反照率对正演模拟光谱和反演近地面二氧化碳平均柱浓度XCO₂的影响. 模拟计算结果显示, 地表反照率数值增大时, 观察的光谱强度也相应增大, 并且在O₂-A波段造成的光谱差异比1.6 μm波段高出一个数量级, 即地表反照率在O₂-A波段的影响比较大. 选取了两个不同地表类型的实际观测光谱, 仅改变O₂-A波段和1.6 μm波段地表反照率数值, 得出草地点在O₂-A波段地表反照率达到0.25的误差时, 会给XCO₂的反演结果造成大于1%的相对误差, 而1.6 μm波段的地表反照率变化对XCO₂的反演结果造成的误差可以忽略不计, 说明了地表反照率在反演XCO₂过程中的重要性主要来自对O₂-A波段的影响. 此研究表明了地表反照率在卫星遥感温室气体过程中的重要性, 为提高遥感探测二氧化碳的精度提供了重要的理论依据和指导.     

Dimethoxycarbonyl Groups Surrounding a Symmetric Diaminobistetrazole Ring: Exploring New Green Energetic Materials

A novel oxygen‐containing dimethoxycarbonyl diaminobistetrazole ( 1 ) was synthesized via a facile strategy. The sodium salt ( 2 ) based on this ligand was prepared and these two compounds were fully characterized by using elemental analysis, IR and mass spectrometry and single‐crystal X‐ray diffraction. Their density, heats of formation, thermal stability and sensitivity, as well as the energetic properties from EXPLO5 code were investigated. These newly synthesized compounds possess high positive heats of formation and detonation heats. Compound 1 exhibits good detonation performance and acceptable stability, and might be a potential eco‐friendly alternative of lead azide. The present study contributes to the development of tetrazole derivatives as new energetic materials.     

Contact-pair neighborhood theorem for submanifolds in symplectic pairs

Let M be a 2n-dimensional smooth manifold associated with the structure of symplectic pair which is a pair of closed 2-forms of constant ranks with complementary kernel foliations. Let Q⊂Mbe a codimension 2 compact submanifold. We show some sufficient and necessary conditions on the existence of the structure of contact pair (α,β) on Q,which is a pair of 1-forms of constant classes whose characteristic foliations are transverse and complementary such that α and β restrict to contact forms on the leaves of the characteristic foliations of βand α,respectively. This is a generalization of the neighborhood theorem for contact-type hypersurfaces in symplectic topology.     

多极化MIMO信道特性与天线设计*

多极化MIMO技术在高频谱效率和紧凑型MIMO通信系统中具有较大的应用潜力,其信道特性与天线辐射特性和环境散射特性以及它们之间的相互作用密切相关,目前紧凑型、低耦合的多极化MIMO天线设计仍存在很大挑战。本文简要介绍和总结了多极化MIMO信道建模理论、多极化天线实现方式和信道特性测量实验等,并指出存在的一些问题和未来的研究方向。