A Note on the Pair Excitation Across Major Shell in Deformed Nuclei

Valence nucleons usually play a dominant role in low energy nuclear spectra. The original version of the Interacting Boson Model[1](IBM) with the assumption that all degrees of freedom arise from the valence shell reproduces well large amount of experimental data. However this assumption does not work well in some cases, for instance, in the even isotopes of Sn, Cd, and Hg, Pb rather well developed intruder bands121 lie outside the IBA model space. K. Heyde et al. attributed these low lying intruder states to the pair excitation (PE) across major shell131. In the well deformed nuclei one can hardly think of the closed shell core as being spherical and inert. The rapid change of Nilsson levels with deformation seems to indicate that there should be excitations of nucleons across major shells in the well deformed nuclei.     

公交车调度问题的数学模型

对 2 0 0 1年全国大学生数学建模竞赛的 B题——公交车调度问题进行了分析 ,建立了调度的目标规划模型及 0— 1规划模型 .在假设各站上、下车人数服从均匀分布的条件下 ,通过对模型的求解 ,求出了公交公司的最小运行车辆数 5 2辆 ,并给出了发车时刻表 ,其中上行方向运行 2 2 5班次 ,下行方向运行 2 2 0班次 .该模型简单 ,求解容易 ,能较好地考虑各方利益     

非饱和土的非线性固结模型和弹塑性固结模型及其应用

把作者最近提出的非饱和土的增量非线性本构模型及由作者改进的Alonso等人提出的非饱和土弹塑性模型引入陈正汉建立的非饱和土的固结理论,得到非饱和土的非线性固结模型和弹塑性固结模型,设计了有关程序,求解了地基在分级加载条件下的固结过程和塑性区的动态扩展,从而把非饱和土固结问题的研究推到了一个新水平。     

On AdS/CFT correspondence of EYM fields

In the compactized Minkowski space, which is equivalent to the conformal spaceM ₄, we introduced a Lorentz metric d σ² and a Yang-Mills field θ. Later, we proved that dσ² and θ together satisfy the EYM (Einstein-Yang-Mills) equation. In this paper, it is proved that θ onM ₄ (which is the boundary of the anti-de-Sitter space AdS₅) can be extended to be a Yang-Mills field [^(q)]\hat \theta on AdS₅ such that Hua’s metric ds² on AdS₅, together with [^(q)]\hat \theta satisfies the EYM equation on AdS₅.     

Effect of SnI2 on the thermal and optical properties of Ge–Se–Te glasses

A systematic series of (Ge₂₀Se₁₅Te₆₅)_1?x–(SnI₂)_x (x = 0, 0.05, 0.1, 0.15) chalcogenide glasses have been prepared. The amorphous nature can be confirmed by XRD and SEM. With the SnI₂ content increasing, the indirect optical band gaps are decreased from 0.662 to 0.622 eV according to Tauc laws. The introduction of SnI₂ makes the glasses much easier to prepare and more stable against crystallization, making them drawable as optical fibers. The highest ΔT (130 °C) value for (Ge₂₀Se₁₅Te₆₅)_0.9–(SnI₂)_0.1 glass composition can be obtained. A slight red-shifting of the long-wavelength cutting-off edge from 18.4 to 19.4 μm was shown and it seems that SnI₂ in these glasses offers the improvement in the far-infrared properties.     

Study of q and η' physics at BES-Ⅲ

Decays of both η and η' provide very useful information in our understanding of low-energy QCD,and experimental signatures for these decays would be extremely helpful at BES-Ⅲ.The rare decays of the η and η' mesons could serve as a low-energy test of the Standard Model and its beyond.The sensitivities of the measurements of η and η' decays are discussed at BES-Ⅲ,in which the η and η' mesons are produced in the ψ decays.     

Tuning for the first 9-cell TESLA cavity of PKU

A method based on circuit model is used to tune the first home-made 9-cell TESLA type superconducting niobium cavity at Peking University.After tuning,a flat field profile with a final π-mode frequency within 3 kHz of target frequency is achieved.The field flatness is measured by a bead-pull method,and the relative electric field is calculated from the frequency shift perturbed by the bead stepping along the axis of the cavity.     

逐步增加的Ⅱ型截尾下冷贮备串联系统可靠性指标的Bayes估计

在逐步增加的Ⅱ型截尾模型下,运用Bayes方法,研究部件寿命服从双参数指数分布的冷贮备串联系统可靠性指标的近似置信区间问题.在两个参数均未知的情形下,给出了失效率,系统可靠度及平均寿命的Bayes近似置信区间的计算公式;对于超参数的确定,给出一种新的方法;最后进行了随机模拟,并对近似置信区间的精度进行了讨论.     

Unexpected Chemisorption State of CO2 on the Si(100)-2×1 Surface Predicted by Theory

Li the past decade, the reactivity of carbon containing confounds with single crystal silicon surfaces has received extensive attention from both experimental and theoretical sides owing to its compact relevance to the growth of silicon carbide and diamond films. While considerable interest has been focused on the adsorptions of alkenes, alkanes and some other small organic molecules^[1], very few experiments^[2,3] can be found in the literature regarding the adsorption of CO₂,a greenhouse gas, on Si surfaces. We report herein the results of our recent theoretical study concerning CO₂ adsorption on the reconstructed Si(100)-2×l surface. The methods employed in our calculations are the hybrid density functional B3LYP method and a two-layer ONIOM (CCSD(T):B3LYP) approach^[4].