一种基于非线性降维求正常星系红移的新方法

提出了一种确定正常星系红移的有效方法,该方法分为以下3个步骤:(1)利用四阶小波系数作为正常星系的特征表示,它能较好地反映吸收线、跳变点和吸收带的信息;(2)利用非线性降维方法LLE(locally linear embedding)将特征数据映射到三维空间中一维流形;(3)由一维流形上的红移分布数据,根据最近邻方法得到正常星系的红移值.实验表明,文中所给的方法较文献中通常使用的PCA方法对于红移的确定具有更高的精度.     

辐射骚扰整改方法与案例

辐射骚扰超标通常是电磁兼容测试中最常见也是最难对付的.本文通过案例清楚说明了一般整改思路及每一步骤,特别强调超标原因的正确分析,并就此指出几个关键注意事项.     

高速时钟电路的信号完整性设计

电子技术的发展日新月异,高速数字电路(即高时钟频率及快速边沿)的设计成为主流,给PCB设计带来许多问题和挑战.阐述了高速时钟电路设计过程中遇到的信号完整性问题,同时也给出了这些问题的解决方法.     

存在近场辐射源情况下的阵列流形建模及分辨性能分析

当辐射源位于天线阵列的近场区域时,信号波阵面在天线阵列的孔径渡越无法忽略,此时电磁波信号到达阵列的波前需要用球面波模型进行描述。本文针对这种情况,研究了传感器阵列的一项固有属性——近场阵列流形,首先构建了任意N元阵列的近场阵列流形数学模型,其次利用微分几何对近场阵列流形的局部特性进行了分析,推导出了近场阵列流形弧长和一阶曲率的数学表达式,并利用这两种局部特性参数分析了近场辐射源参数估计的精度及分辨性能。     

兰州燃气LNG调峰装置技术分析

JA工艺流程和设备方面详细分析了兰州燃气LNG调峰装置主工艺区各个单元包括预处理单元、液化单元、冷剂补充单元、蒸发气单元、储存单元、火炬单元及公用工程、仪表自控方面的技术特点,给出了主要设备的技术参数,总结了其在工艺和主要设备选择上的优越性.实际运行表明,兰州燃气LNG调峰装置在技术和经济上是非常可行的.     

Metal-Organic Frameworks for C6 Alkane Separation

The separation of alkane isomers is an important yet challenging process in the petrochemical industry. Being a crucial step to produce premium gasoline components as well as optimum ethylene feed, the current industrial separation by distillation is extremely energy intensive. Adsorptive separation based on zeolite is limited by insufficient adsorption capacity. Metal-organic frameworks (MOFs) hold enormous promise as alternative adsorbents due to their diverse structural tunability and exceptional porosity. Precise control of their pore geometry/dimensions has led to superior performance. In this minireview, we highlight the recent progresses in developing MOFs for the separation of C6 alkane isomers. Representative MOFs are reviewed based on their separation mechanisms. Emphasis is put on the material design rationale for achieving optimal separation capability. Finally, we briefly discuss the existing challenges, possible solutions, and future directions of this important field.     

Comparison of two liquid crystals as stationary phases in capillary gas chromatography

Summary The comparative gas chromatographic behavior has been investigated for two new liquid-crystal stationary phases, 2-(3-chlorobenzyloxy)-3-hexanoxy-4-(4-chlorobenzoyloxy)-4′-(4-methylbenzoyloxy)azobenzene (denoted 3-Cl) and 2-(3-methylbenzyloxy)-3-hexanoxy-4-(4-chlorobenzoyloxy)-4′-(4-methylbenzoyloxy)azobenzene (denoted 3-CH₃). The structures of the main core of the two liquid crystals are the same but they differ by lateral aromatic branch— 3-chlorobenzyloxy and 3-methylbenzoyloxy. Their thermal properties were established by use of differential scanning calorimetry (DSC) and their chromatographic separation properties by use of glass capillary columns. Interesting analytical performance was obtained in the separation of isomeric aromatic compounds, polyaromatic compounds, volatile aroma compounds, andcis andtrans isomers. Separation efficiency was higher for 3-Cl, especially for volatile aroma compounds, light aromatic compounds, and polyaromatic compounds, although the phases were similar in otherways.     

Enzyme-mediated enantioselective hydrolysis of poly(ethylene glycol)-supported carbonates

Kinetic resolution of poly(ethylene glycol)(PEG)-supported carbonates by enzymatic hydrolysis is discussed. Water-soluble carbonates are prepared by immobilization of racemic secondary alcohols onto low-molecular weight monomethoxy PEG (MPEG) through a carbonate linker. Porcine pancreas lipase (PPL) enantioselectively catalyzes the hydrolysis of the substrates to give optically active compounds. In this system, the separation of the resulting alcohols and the remaining substrates is achieved by an extraction process without laborious column chromatography. The carbonates are easily hydrolyzed with K₂CO₃ to afford the corresponding alcohols.     

渗透汽化膜分离研究的新进展

渗透汽化膜分离技术是当前分离膜研究领域的前沿课题之一.作为化学分离中的重要组成部分,近年来受到高度重视.本文按渗透汽化膜分离的三大类混合液体系有机液脱水、从水相中分离有机物和有机混合液的分离,综述了近几年渗透汽化膜分离技术研究的新进展.其中,又重点报道了有机混合液分离的最新研究成果,将其分为:极性/非极性化合物、芳香烃/脂肪烃体系、芳香烃/脂环烃体系、同分异构体、多元体系和汽油脱硫等六部分进行了详细叙述.文章最后还对渗透汽化膜分离研究进行了展望.     

水动力色谱及其在高分子科学中的应用

综述了水动力色谱的理论研究及三种主要水动力色谱方法,即微毛细管ＨＤＣ,毛细管ＨＤＣ和填充柱ＨＤＣ,并着重介绍了ＨＤＣ在胶体颗粒及聚合物大分子的分析与分离方面的应用。