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71.
72.
Jia Rong Li~* Li Jun Zhang Xi Quan Yang Qing Li Dong Wang Chun Xia Wang Da Xin Shi Qi Zhang School of Chemical Engineering Environment Beijing Institute of Technology Beijing China 《中国化学快报》2008,(1)
Two different skeletons of heterocyclic compounds,quinoline and quinazolinone analogs could be obtained by a novel one-pot synthesis from substituted 3-amino-1 H-benzo[f]chromene-2-carbonitrile derivatives and cyclohexanone in DMF in the catalyst of anhydrous zinc chloride under reflux.A plausible mechanism was proposed. 相似文献
73.
Zhi Hui Zhou Jian Hua Yang* Li Feng Chang Yan Zhang Wei Guo Sun Jin Qu Wang* State Key Laboratory of Fine Chemicals Institute of Adsorption Inorganic Membrane Dalian University of Technology Dalian PR China 《中国化学快报》2007,18(4):455-457
Novel NaA/carbon nanocomposite thin films were successfully prepared on a porous a-Al2O3 substrate by incorporatingnanosized NaA zeolite into novolak-type phenolic resin.The prepared films were characterized by XRD,SEM and single gaspermeation tests.The NaA zeolite/carbon nanocomposite thin films exhibited that the ideal separation factor of CO2/CH4 was 28.4and the carbon dioxide flux was 3.39*10-7mol/(Pa m2s)at room temperature and under a pressure difference of 100 kPa,whichwas two orders of magnitude higher than that of pure carbon membrane prepared at the same procedures and conditions as those ofcomposite films.From the SEM images,the films were continuous and highly intergrown.Compared with carbon membranes,thethickness of nanocomposite films was drastically decreased,which was helpful to reduce the diffusion resistance and increase theflux of gas permeance. 相似文献
74.
针对SURF(speeded-up robust features)算法计算量大、图像拼接效率低的不足,以FAST (features from accelerated segment test)角点取代SURF斑点在图像重合区域提取特征点,使用SURF描述子进行特征点描述,通过描述子降维、自适应最近邻与次近邻比值法、几何约束法剔除错误匹配点,提高匹配的准确性。匹配完成后,通过减少样本集的个数和舍弃不合理参数模型来改进RANSAC(random sample consensus)方法,获取单应性矩阵,最后进行图像变换、融合和拼接。实验结果显示,该图像拼接算法与传统的SURF算法相比,图像拼接总时间减少了12%,拼接效率得到了显著提高。 相似文献
75.
在碱性介质中,K3Fe(CN)6氧化鲁米诺产生化学发光,黄芩苷对该体系化学发光具有强烈的抑制作用。利用该化学发光的抑制体系,结合反相流动注射技术,建立了测定黄酮类药物黄芩苷含量的新方法。在优化的条件下,黄芩苷浓度在1.0×10-8~1.0×10-7和3.0×10-7~4.0×10-6mol/L范围内与化学发光抑制强度ΔI呈良好的线性关系,检出限为1.0×10-9mol/L,对3.0×10-7mol/L的黄芩苷进行平行测定10次,得相对标准偏差(RSD)为1.7%。该方法可应用于银黄口服液中黄芩提取物(黄芩苷计)的含量测定。 相似文献
76.
77.
研究了可分离二次背包问题的一种直接算法.此类背包问题的目标函数是二次的,且含有严格的一次项,其不等式约束是线性的.给出所求模型的一般形式,经过预处理该模型,最终归为求解两类问题(P1)和(P2).重点是求解(P2)问题的最优解,通过分析(P2)问题的结构特点,假设固定一次项后问题的最优解和相应不等式的拉格朗日乘子已求出,通过比较拉格朗日乘子和(P2)问题的一次项系数来调节λ的大小,从而求出(P2)问题的最优解.对于(P1)问题,改进了Bretthauer和Shetty给出的算法(Bretthauer K M,Shetty B.A pegging algorithm for the nonlinear resource allocation problem.Computers and Operations Research,2002,29(5):505-527).此算法的计算复杂性为O(n).数值算例表明,将这种固定变量算法和文中的定理5结合起来,能够快速有效地求解此类更一般的二次背包问题. 相似文献
78.
Cui Hua XUE Qi Ming MU Shu Hua CHEN* The Faculty of chemistry Sichuan University Chengdu 《中国化学快报》2001,(5)
Molecular tweezers is a novel type of artificial receptors, which not only offer the advantage of efficient construction but also their surfaces can be tailored for specific applications. The clefts of molecular tweezers are particularly effective in regard to complementarity with substrates since functional groups attached to the interior of the cleft converge on substrates held inside1. So, in recent years, the molecular tweezers receptors have attracted more and more attention in molecular … 相似文献
79.
Gang ZHOU Xiao Lei GAO Yu Kun GUAN Wei Dong LI Yu Lin LI* National Laboratory of Applied Organic Chemistry Institute of Organic Chemistry Lanzhou University Lanzhou 《中国化学快报》2001,(5)
Sesquiterpenic compounds of the Eudesmane family have attracted considerable attention due to their intriguing biological properties1,2, particularly significant antifeedant activity, cell growth inhibitory and plant growth regulating activities.In 1996, J. Hu and co-workers3 had isolated eudesmane sesquiterpene 5?-hydroxy-isopterocarpolone 1 from the aerial parts of chinese folk medicine Artemisia eriopoda and elucidated its structure by spectropic methods. Herein, we reported the first tota… 相似文献
80.
Our group have explored the reaction of allylsamarium bromide with a variety of substrates, such as N-(2-aminoalkyl)benzotriazoles1, imines2, nitriles3, diorgano diselenides4, disulfides5, isocyanates6 and nitroalkenes7. Here we wish to report the monoallylation of gem-diacetates with allylsamarium bromide. Gem-diacetates are stable in neutral and basic media, thus they are frequently used to protect aldehydes8. However, the presence of two leaving groups at the same carbon may make carbon … 相似文献