8阶群速度控制格式及其应用

构造了8阶精度的群速度控制型差分格式.根据激波捕捉能力及对小尺度分辨能力对格式系数进行了优化.采用该格式对可压缩均匀各向同性湍流进行了直接数值模拟,所计算的最大湍流马赫数达到0.95.相同计算条件下的结果与他人结果吻合较好,说明了格式在捕捉激波的同时对湍流小尺度有较好的分辨能力.

Influences of Al doping concentration on structural, electrical and optical properties of Zn0.95Ni0.05O powders

Nanocrystalline Zn0.95 - xNi0.05AlxO (x = 0.01, 0.02, 0.05 and 0.10) diluted magnetic semiconductors have been synthesized by an auto-combustion method. X-ray diffraction measurements indicate that all Al-doped Zn0.95Ni0.05O samples have the pure wurtzite structure. Transmission electron microscope analyses show that the as-synthesized powders are of the size 40 - 45 nm. High-resolution transmission electron microscope, energy dispersive spectrometer and X-ray photoemission spectroscope analyses indicate that Ni2+ and Al3+ uniformly substitute Zn2+ in the wurtzite structure without forming any secondary phases. The Al doping concentration dependences of cell parameters (a and c), resistance and the ratio of green emission to UV emission have the similar trends. (c) 2007 Elsevier B.V. All rights reserved.

维生素B_(12)对萼花臂尾轮虫种群的影响

温度为15℃时,添加20,40,80和100μg/mL维生素B12后,萼花臂尾轮虫(Brachionuscalyciflorus)种群密度随时间增加而增长,其回归方程依次为:y=e(0.1757+0.2974x),y=4.6765x1.2079,y=7.7798x1.0175和y=e(0.6117+0.3469x),密度显著高于对照组(t=4.56,8.15,8.53和9.86;P<0.01)。对照组和添加组最大混交雌体百分率依次为57.69,76.09,73.81,60.00和45.15%,最大卵雌比依

Absorption spectra of Se-8-ring clusters in zeolite 5A

Samples with different weight ratio of Se to zeolite 5A (Se concentration) have been prepared by loading Se into the pores of zeolite 5A, and the measuerments of the absorption and Raman spectra have been carried out for the prepared samples. The measured absorption edges of the samples are close to the value for monoclinic Se containing Se-8-ring, suggesting the formation of Se-8-ring clusters(1) in the pores. The continuous and broadening features of the absorption spectra are interpreted by the strong electron-nucleus coupling in the Se-8-ring cluster. The absorption edges are red shifted with the increase of the Se concentration. It is tentatively attributed to two reasons. One is the existence of the double Se-8-ring cluster in the high Se concentration samples, and the other is that for the strong electron-nucleus coupling cluster, the absorption edge of the clusters system will be red shifted with the increase of the cluster concentration in the clusters system. A single broad band at about 262 cm(-1) is observed in the Raman spectra, which further supports the formation of Se-8-ring clusters. (C) 1997 Published by Elsevier Science S.A.

A ternary supramolecular compound of p-sulfonatocalix[8]arene with 1D channels

A ternary supramolecular complex of [Ni(bipy)(2)(H2O)](4)(C8AS)center dot 17.6(H2O) (bipy=4,4'-dimethyl-2,2'-bipyridine and C8AS = p-sulfonatocalix[8]arene) has been synthesized by a hydrothermal method and characterized by FT-IR spectroscopy, TG-DTA analysis and single crystal X-ray diffraction. In the structure. the water-soluble p-sulfonatocalix[8]arene molecule adopts a double partial cone conformation and is coordinated by four nickel atoms each of which is bonded by two 4,4'-dimethyl-2,2'-bipyridine molecules and one water molecule at the same time. The tetranuclear Subunits are stacked into an extended 3D structure with 1D water-filled channels via hydrogen bonds and C-H center dot center dot center dot pi interactions.

Improvement of amplified spontaneous emission performance by doping tris(8-hydroxyquinoline) aluminum (Alq3) in dye-doped polymer thin films

A well-known red fluorescent dye 4-(dicy-anomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)4H-pyran (DCJTB) was codoped with an electron transport organic molecule tris(8-hydroxyquinohne) aluminum (Alq3) in a host matrix of polystyrene (PS), and the amplified spontaneous emission (ASE) was studied by optically pumping. It was found that the ASE performance was significantly improved by the introduction of Alq3. The Alq3:DCJTB:PS blending thin films showed a low threshold (2.4 mu J/pulse) and a high net gain coefficient (109.95 cm(-1)) compared with the pure DCJTB:PS system (threshold of 15.2 mu J/pulse and gain of 35.94 cm(-1)). The improvement of the ASE performance was considered to be attributable to the effective Foster energy transfer from Alq(3) to DCJTB. Our results demonstrate that the Alq(3):DCJTB could be a promising candidate as gain medium for red organic diode lasers.

95-2重穗型小麦品系生长动态分析

对重穗型小麦品系95－2生长动态分析结果表明，95－2较一般概念上的栽培品系株型粗壮、高大．在整个生育期保持较高的有效光合面积，形成较高的生物学产量，根系发达，形成大穗大粒，体现了源大、库大的特点，茎拜系统也具良好的输导性能。在下一步超高产、稳产品种培育中，植株叶型及其合理配置是一个着重要考虑和解决的问题。