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951.
R. S. Chen Z. B. Ye Edward K. N. Yung K. F. Tsang 《International Journal of Infrared and Millimeter Waves》2003,24(8):1325-1339
A gradient optimization technique along with a definition of cost function is applied to the CAD of the circulator with a magnetized ferrite sphere for millimeter wave communications. A three-dimensional Finite-Difference Time-Domain (FDTD) approach for the analysis of this ferrite sphere based microstrip circulator is presented. The topology of the structure is enforced at each step of optimization and its physical dimensions are used as optimization variables. The cost function is defined using location of zeros and poles of the circulator's transmission, isolation, and reflection functions. Numerical tests show that the optimization process converges from an arbitrarily selected starting point with the new definition of the cost function. 相似文献
952.
ChengBinCUI ChiXU QianQunGU ShiDongCHU HaiHongJI GangJING 《中国化学快报》2004,15(10):1191-1194
26-O-β-D-Glucopyranosyl-furost-5(6),20(22)-dien-3β,26-diol 1, a new furostanol saponin, was isolated from the water-extract of Dioscorea nipponica Mak., the raw material of a traditional Chinese herbal medicine Wei Ao Xin. The structure of 1 was determined on the basis of its spectral data especially by NMR spectroscopy. The result provides the first example of naturally occurring furostanol saponins with a single saccharide chain at the C-26 position. 相似文献
953.
954.
T.K. Liang L.R. Nunes K.S. Abedin D. Van Thourhout P. Dumon H.K. Tsang 《Optics Communications》2006,265(1):171-174
The switching speed of conventional silicon-based optical switching devices based on plasma dispersion effect is limited by the lifetime of free carriers which introduce either phase or absorption changes. Here we report an all-optical logic NOR gate which does not rely on free carriers but instead uses two-photon absorption. High speed operation was achieved using pump induced non-degenerate two-photon absorption inside the submicron size silicon wire waveguides. The device required low pulse energy (few pJ) for logic gate operation. 相似文献
955.
O. Cozar L. David V. Chiş C. Cosma V. Znamirovschi G. Damian I. Bratu Gh. Bora 《Applied magnetic resonance》1995,8(2):235-242
Powder ESR spectra of the [Cu2(Asp)4](H2O)2 complex show the existence of Cu(II) acetate like dimers characterized by a strong antiferromagnetic exchange interaction (J=?288 cm?1). In pyridine-dimethylformamide solutions the monomeric species prevail. Two different monomeric species, the Cu(DMF)4 of planar-distorted tetrahedral (Td) symmetry and the Cu(Asp)2(DMF)2 with elongated tetrahedral-octahedral symmetry were evidenced in DMF solution adsorbed on NaY zeolite. In 40 % Py+60 % DMF solution two monomeric species were also identified. These are Cu(Asp)2(DMF)2 and Cu(Asp)2(Py)2, the last species having a CuN2O2 chromophore in atrans squareplanar arrangement. In pyridine Cu(II)-aspirinate solution only the Cu(Py)4 monomeric species of CuN4 chromophore was evidenced. 相似文献
956.
E H Cao X J Fan S J Chi Y X Wang 《Journal of photochemistry and photobiology. B, Biology》1988,2(4):503-513
A new fluorescence band with an emission maximum at 460 nm was observed in S180 tumour cells and human cancer tissues photosensitized by Y-HPD. This fluorescence was the result of a photochemical reaction involving specific proteins and Y-HPD in the cells. 相似文献
957.
A near zero-dispersion regime, fundamental soliton with third-order dispersion is considered. There are three different waves radiated from the soliton. We find a threshold condition for the radiated waves. Below the threshold condition a stable soliton exists; an approximate soliton solution is obtained. 相似文献
958.
959.
960.
在室温下测量了GdoBr:Eu的常压和高压荧光谱,光谱范围在13 000~21 500 cm-1之间,压力至12 GPa。由光谱数据得到了Eu3+晶场能级随压力的变化曲线。7F0~5能级随压力的变化规律比较复杂,而5D0~2各能均随压力的升高几乎线性地降低。在基态谱项7F的49个状态上进行了晶场拟合计算,所得常压下的5个非零晶场参数分别为:B02=-1 124.0 cm-1,B04=-969.6 cm-1,B44=827.9 cm-1,B06=889.6 cm-1,B46=377.0 cm-1。高压下的计算结果表明,B04、B06这两个晶场参数随压力的增加而增大,B46随压力的增加而减小,而B02、B44随压力的变化有些起伏。晶场强度在8 GPa以下随压力增加而减小,其后开始变强。 相似文献