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91.
高密度烃化合物的合成 总被引:5,自引:0,他引:5
92.
The analysis of loss characteristics for groove guide is one of the most practically important problems in millimeter wave system consisting of groove guide. In this paper, the calculation of the skin loss for the modes in the groove guide is ended to the solution of an active equivalent transmission line equation. The effectiveness and the reliability of the present method are verified by comparison between the present results and those given in the literature. 相似文献
93.
A dielectric grating leaky wave antenna with a substrate consisted of left handed material (LHM) is presented in this paper,
the case where the n = −1 space harmonic of TM mode radiating into the space is carefully investigated through the improved
perturbation analysis, which tremendously simplifies the analysis procedure with good calculation accuracy and brings considerable
physical insight into the overall behavior of the dielectric grating antenna. It has been found that the new leaky wave antenna
is of larger leakage constant than that of the traditional antenna with substrate of the right handed material (RHM). As a
result the dimension of the antenna could be largely reduced, which is of practical significance for some applications. Extensive
numerical results of the radiation characteristics are given to establish useful guidelines for the design of the new grating
antenna. 相似文献
94.
Yongmei Pan Shanjia Xu Kiyotoshi Yasumoto 《International Journal of Infrared and Millimeter Waves》2005,26(2):189-200
Loss and dispersion characteristics of groove guide are two practically important factors in the design for millimeter wave system consisting of groove guide. In this paper, a new method is presented for analyzing loss and dispersion characteristics of the groove guides with arbitrary groove cross-sections. The method is based on the combination of an equivalent active transmission line equation and the staircase approximation. Numerical results of dispersion and attenuation properties for some groove guides with different groove profiles are given. The effectiveness and practicality of the present analysis are confirmed by the data given in the literature.*Supported by the National Natural Science Foundation of China (No. 60171019)
and (No. 60371010) 相似文献
95.
Kang JH Siddiqui MA Sigano DM Krajewski K Lewin NE Pu Y Blumberg PM Lee J Marquez VE 《Organic letters》2004,6(14):2413-2416
[structure: see text] Commercially available 2-methylenepropane-1,3-diol was converted to chiral epoxide (R)-2 via Sharpless asymmetric epoxidation in >96% ee. Regiospecific epoxide ring opening and reduction of the intermediate alkyne set the stage for a one-pot lactonization to give (R)-6, a convenient precursor for all functionalized chiral DAG-lactones used as potent PK-C ligands. The synthesis of the most potent DAG-lactones known to date, (Z)-10 and (E)-10, served to confirm PK-C's exclusive preference for the (R)-stereochemistry in this class of compounds. 相似文献
96.
脯氨酸催化的不对称有机反应 总被引:1,自引:0,他引:1
脯氨酸作为一种结构简单、商品化的、廉价小分子手性催化剂,在多种不对称催化反应中表现出非常好的催化性能,本文综述了近年来脯氨酸直接催化的不对称有机反应涉及Aldol反应,Mannich反应,Michael反应,Diels-Alder反应,直接α-胺化反应,α-氧胺化反应,Baylis-Hillman反应,还原反应和氧化反应的进展并展望了其应用前景。 相似文献
97.
Ming Liu Shijun Ma Zhiqing Tian Hao Wu Lulu Wu Xiufang Xu Yaodong Huang Yongmei Wang 《Tetrahedron: Asymmetry》2013,24(12):736-743
A new series of bipyridine ligands coupled with Cinchona alkaloids were prepared in relatively high yields in only one step starting from commercially or readily available materials, and have been developed as chiral ligands for copper(II)-catalyzed asymmetric Henry reactions. The catalytic system works well with a wide range of aromatic, aliphatic, and heteroaromatic aldehydes to afford the corresponding nitroalkanols with high enantioselectivity (up to 92%) in good yields (up to 89%). A transition state model was proposed based on 1H NMR spectroscopy, X-ray structure, and computational calculations. 相似文献
98.
甲醛为公认的致癌物质,本文针对目前甲醛分析需使用专用仪器和试剂盒的不便现状,合成了分子探针(km2bn),通过晶体结构分析发现其苯并二氮杂卓基团与水自组装为一维分子线材料(km2bn·H2O),可与甲醛分子发生固-气相Hantzsch反应,生成具有更大共轭体系二氢吡啶杂环结构,双官能团反应使其生成一维伸展的线性聚合物,共轭体系得到更大的拓展,具有深色与光谱红移效应,其颜色坐标与甲醛浓度具有线性关系,兼具检测选择性,因而可通过该可视显色反应检测甲醛,并可制成试纸,方便普通家庭使用。 相似文献
99.
100.