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141.
GUO Qiao-Linga GUO Jin-Changb LI Si-Dianb② a 《结构化学》2008,27(6):651-658
A density functional theory investigation on the geometries, electronic structures, and electron detachment energies of BS, BS2, B(BS)2 and B(BS)3 has been performed in this work. The linear ground-state structures of BS (C∞v, ^1∑^+) and BS2^- (O∞h, ^1∑g^+) prove to be similar to the previously reported BO and BO2 with systematically lower electron detachment energies. Small boron sulfide clusters are found to favor the formation of -B=S groups which function basically as a-radicals and dominate the ground-state structures of the systems. The perfect linear B(BS)2^-(D∞h, ^3∑g) and beautiful equilateral triangle B(BS)3^- (D3h,^2A1”) turn out to be analogous to the well-known C2v BH2 and O3h BH3, respectively. The electron affinities of BS, BS2, B(BS)2 and B(BS)3 are predicted to be 2.3, 3.69, 3.00 and 3.45 eV, respectively. The electron detachment energies calculated for BS^-, BS2^-, B(BS)2^-, and B(BS)3^- may facilitate future photoelectron spectroscopy measurements to characterize the geometrical and electronic structures of these anions. 相似文献
142.
Morphology Control of SrCO3 Crystals using Complexons as Modifiers in the Ethanol-water mixtures 总被引:1,自引:0,他引:1
ZHAGN Ming-Xuana HUO Ji-Chuana② YU Yong-Shengb CUI Cai-Pinga LEI Yong-Lina a 《结构化学》2008,27(10):1223-1229
Using SrC12-6H2O and Na2CO3 as the main raw materials and adding different complexons as modifiers with simple co-precipitation method, SrCO3 crystals with distinct morphologies like spherical, bundle-like, overlapping plate-like, hexagonal star-like, dumbbell-like, etc. can be synthesized in the ethanol-water mixtures. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectrograph (FT-IR). The interrelated effect mechanism is presented in the end. Results show that the modifier carboxyl groups play a significant role in controlling the SrCO3 crystal morphologies, which can alter the crystal growth unit (Sr^2+) supply mode and induce the crystal formation with the morphologies matching their spatial configurations. 相似文献
143.
平板流固耦合振动的数值分析 总被引:2,自引:0,他引:2
采用了一种基于紧耦合的流固耦合算法,对流场与柔性平板之间的耦合运动进行了数值模拟.流场部分通过有限体积法求解任意拉格朗日 欧拉描述下的不可压缩N-S方程,而结构则由有限元法离散求解拉格朗日坐标下的弹性动力学方程.在一个时间步内,流场与结构计算区域的交界面上进行多次的数据传递和插值,以保证满足耦合面边界条件.计算了在静止流场中弹性板的自由振动和方柱后部平板的涡激振动现象,监测了平板的振幅和频率以及水动力载荷.通过与前人结果的比较,验证了所采用的流固耦合算法的可靠性.同时,分析了不同的材料参数对于平板耦合运动的影响.流体黏性越大对平板振动的阻尼作用越明显,而流体密度的增加会加速振动的衰减,并降低振动的频率.对于具有较低固有频率的结构,在耦合运动中的振动幅度和频率也较小.
相似文献
144.
针对采用码相位循环移位获得的M元扩频需要额外同步信息的问题,提出一种改进型扩频通信算法.该算法采用m序列及其倒序序列构成系统扩频码集;在同相支路上利用扩频码的码极性调制进行传输,同时在正交支路利用扩频码码相位调制,实现M元扩频.该算法利用2种扩频方式的自身特点可快速准确地获取载波相位信息,具有不需要额外提供同步资源的优势.仿真结果表明,该算法可有效提高系统资源的利用率. 相似文献
145.
146.
Ren Y Acuña UM Jiménez F García R Mejía M Chai H Gallucci JC Farnsworth NR Soejarto DD Carcache de Blanco EJ Kinghorn AD 《Tetrahedron》2012,68(12):2671-2678
Six new (1-6) and eight known germacranolide-type sesquiterpene lactones, along with several known phenylpropanol coumarates and methylated flavonoids, were isolated from the leaves of Piptocoma rufescens, collected in the Dominican Republic. The new compounds were identified by analysis of their spectroscopic data, with the molecular structure of 3 being established by single-crystal X-ray diffraction. The absolute configurations of the sesquiterpene lactones isolated were determined from their CD and NOESY NMR spectra, together with the analysis of Mosher ester reactions. Bioassay screening results showed the majority of the sesquiterpene lactones isolated (1-13) to be highly cytotoxic toward the HT-29 human colon cancer cell line, with the most potent compound being 15-deoxygoyazensolide (10, IC(50), 0.26 μM). In addition, several of the sesquiterpene lactones exhibited NF-κB (p65) inhibitory activity. 相似文献
147.
The effect of oxidation pretreatment temperature(500 ~ 1 000 ℃) on the catalytic activity of Kovar applied on hydrocarbon CO2reforming was examined. Catalytic performance evaluation using tetradecane at 800 ℃ with 70 μmol/s CO2revealed 700 and 1 000 ℃ as the best pre-oxidation temperature in producing CO and H2,respectively. XRD and SEM-EDX analyses showed that a separate metal oxide layer composed of iron oxide(Fe2O3and F3O4),nickel,cobalt,and possibly their respective oxides started to form when oxidation was conducted at 700 ℃ or higher.The presence of iron enhanced the stability of nickel in the structure while the compact structure of Fe3O4resulted into the formation of a thick and rigid metal oxide layer on the surface of the Kovar tube. The strong physical bond between the metal oxide layer and Kovar tube provided the catalyst good mechanical strength and consequently good catalytic activity. 相似文献
148.
149.
Sapienza R García PD Bertolotti J Martín MD Blanco A Viña L López C Wiersma DS 《Physical review letters》2007,99(23):233902
In this Letter we demonstrate Mie resonances mediated transport of light in randomly arranged, monodisperse dielectric spheres packed at high filling fractions. By means of both static and dynamic optical experiments we show resonant behavior in the key transport parameters and, in particular, we find that the energy transport velocity, which is lower than the group velocity, also displays a resonant behavior. 相似文献
150.
Kleemans NA Bominaar-Silkens IM Fomin VM Gladilin VN Granados D Taboada AG García JM Offermans P Zeitler U Christianen PC Maan JC Devreese JT Koenraad PM 《Physical review letters》2007,99(14):146808
We report the direct measurement of the persistent current carried by a single electron by means of magnetization experiments on self-assembled InAs/GaAs quantum rings. We measured the first Aharonov-Bohm oscillation at a field of 14 T, in perfect agreement with our model based on the structural properties determined by cross-sectional scanning tunneling microscopy measurements. The observed oscillation magnitude of the magnetic moment per electron is remarkably large for the topology of our nanostructures, which are singly connected and exhibit a pronounced shape asymmetry. 相似文献