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81.
四溴双酚A锑铝双金属化合物的合成及其阻燃性能 总被引:1,自引:0,他引:1
以四溴双酚A(TBA)合成了在水和空气中稳定的四溴双酚A合锑铝双金属化合物(TBASA).通过IR、1HNMR和元素分析予以表征,并研究了其对聚乙烯(PE)和聚环氧乙烷(PEO)的阻燃性能.结果表明,这种分子中含有溴、锑和铝的化合物,对聚乙烯和聚环氧乙烷等高聚物材料有高的阻燃性能与消烟效果. 相似文献
82.
ErWeiLI KunGAO ZhongJianJIA 《中国化学快报》2004,15(4):425-427
Two new acetylxylosides,ent-manool-13-O-β-D-2′-acetylxylopyranoside(1)and entmanool-13-O-β-D-2′,4′-diacetylxylopyranoside(2)were isolated from Aster veitchianus.Their structures were elucidated by spectroscopic methods. 相似文献
83.
For any Sturm-Liouville problem with a separable boundary condition and whose leading coefficient function changes sign (exactly once), we first give a geometric characterization of its eigenvalues λn using the eigenvalues of some corresponding problems with a definite leading coefficient function. Consequences of this characterization include simple proofs of the existence of the λn's, their Prüfer angle characterization, and a way for determining their indices from the zeros of their eigenfunctions. Then, interlacing relations among the λn's and the eigenvalues of the corresponding problems are obtained. Using these relations, a simple proof of asymptotic formulas for the λn's is given. 相似文献
84.
Guo Qing LI Zhong Jiao JIA 《中国化学快报》2003,14(1):62-65
Two new ionone derivatives,named rhododendrone and rhododendronside,were isolated from the alcohoilc extract of the aerial parts of Rhododendron przwalskii Maxim.Their structures were elucidated on the basis of spectroscopic analysis. 相似文献
85.
Bai-suo JIN~ 《中国科学A辑(英文版)》2007,50(9):1303-1315
In the factor analysis model with large cross-section and time-series dimensions,we pro- pose a new method to estimate the number of factors.Specially if the idiosyncratic terms satisfy a linear time series model,the estimators of the parameters can be obtained in the time series model. The theoretical properties of the estimators are also explored.A simulation study and an empirical analysis are conducted. 相似文献
86.
Stimulated Raman adiabatic passage (STIRAP) has been successfully extended to multilevel system. During the STIRAP process, the intermediate levels have notable population which is detrimental if these levels could decay to other levels through spontaneous emission. This paper proposes a novel method to reduce the intermediate level population during the STIRAP process. A complete population transfer can be achieved in this modified STIRAP even if the intermediate level decays to other levels. 相似文献
87.
88.
不确定市场条件下的稳健最优投资组合 总被引:1,自引:0,他引:1
本文假设风险资产和无风险资产收益的相关参数属于某个已知的凸多面体,分别讨论了在市场不存在无风险资产和存在无风险资产的情况下稳健最优投资组合问题,给出了问题的解析解,从而推广了Markowitz均值-方差模型的结果. 相似文献
89.
Z.J. Liu H.H. Long W.C. Ye X.X. Zou Z.L. Qin E.P. Li J.S. Chen 《Journal of magnetism and magnetic materials》2006
In this paper, specific issues related to high-density perpendicular magnetic recording processes, such as transition noise properties and cross-track correlation lengths, were investigated with the help of micromagnetic analysis. The effects of media parameters were taken into consideration, including intergranular exchange coupling, and exchange distribution, irregular grain shapes, magnetization saturation distribution, and anisotropy distribution. The micromagnetic simulation results showed that the effect of anisotropy distribution on transition noise is more significant than magnetization saturation distribution, and it is crucial to reduce this effect to achieve a high signal-to-noise ratio. Additionally, a new method to further estimate the partial erasure threshold was proposed to approximate the partial erasure effects, and the relation between the microtrack jitter and total track jitter was investigated. 相似文献
90.
Instability of Solitary Waves in Nonlinear Composite Media 总被引:1,自引:0,他引:1
Ye Zhao 《应用数学学报(英文版)》2007,23(2):311-318
In this paper,we investigate a class of Hamiltonian systems arising in nonlinear composite media.By detailed analysis and computation we obtain a decaying estimates on the semigroup and prove the orbitalinstability of two families of explicit solitary wave solutions (slow family in anisotropic case and solitary wavesin isotropic case),which theoretically verify the related guess and numerical results. 相似文献