BEPCII横向束流反馈系统前端电子学

选择了一台商业化的前端电子学RFTF（radio frequency front-end for transverse feedback system）用于BEPCII横向束流反馈系统, 这是跟进世界先进加速器技术的具体实施。在BEPC同步运行模式下对RFTF的性能进行了测试实验，结果表明使用RFTF可以得到理想的波形，能够满足BEPCII横向反馈系统的需要，但是，当储存环出现不稳性时，系统无法正常工作，这就要求BEPCII纵向不稳定很小或者用纵向反馈系统来抑制存在的纵向不稳定。     

SiO2分子的基态(X1A1)结构与分析势能函数

应用群论及原子分子反应静力学方法推导了SiO₂分子的电子态及其离解极限，采用B3P86方法，在6-311G^**水平上,优化出SiO₂基态分子稳定构型为单重态的C_2V构型，其平衡核间距R_e=R_Si—O=0.1587 nm,∠OSiO＝111.2°,能量为-440.4392 a.u..同时计算出基态的简正振动频率:对称伸缩振动频率ν(B₂)=945.4cm^-1，弯曲振动频率ν(A₁)=273.5 cm^-1和反对称伸缩振动频率ν(A₁)=1362.9cm^-1.在此基础上，使用多体项展式理论方法，导出了基态SiO₂分子的全空间解析势能函数，该势能函数准确再现了SiO₂(C_2V)平衡结构.     

热膨胀动态过程的理论和实验研究

 本文列出了一维点阵非谐振动的非线性微分方程组，并求出了这组方程在相应边值条件下的解析解。据此算出了该点阵的热膨胀系数和热膨胀动态过程的特征时间，同时说明了它的物理意义。关于金属箔的实验结果，可以作为这一理论预言的一个验证。这些结果还告诉我们，在高速加热时，即使温度均匀而且膨胀自由，热应力仍然存在，不过将很快弛豫。     

干涉法测量液体膨胀系数的讨论

液体的折射率和液体的密度有直接关系,液体密度又与温度有关,根据已有关于透明介质的折射率公式,可得液体的膨胀系数的测量方法.迈克耳孙干涉法是测量液体折射率的温度系数的简捷的手段.用此方法得出了液体的膨胀系数,进而讨论了关于液体折射率的2个不同公式的精确程度.     

Theoretical study of structure and analytic potential energy function for the ground state of PO2 molecule

In this paper, the energy, the equilibrium geometry, and the harmonic frequency of the ground electronic state of PO₂ are computed using B3LYP, B3P86, CCSD(T), and QCISD(T) methods in conjunction with 6-311++G(3df, 3pd) and cc-pVTZ basis sets. A comparison between the computational results and the experimental values indicates that the B3P86/6-311++G(3df, 3pd) method can give better energy calculation results for the PO₂ molecule. It is shown that the ground state of the PO₂ molecule has C_2v symmetry and its ground electronic state is X²A₁. The equilibrium parameters of the structure are R_P-O=0.1465 nm, d=19.218 eV. The bent vibrational frequency ν₁=386 cm^-1, the symmetric stretching frequency ν₂=1095 cm^-1, and the asymmetric stretching frequency ν₃=1333 cm^-1 are obtained. On the basis of atomic and molecular reaction statics, the reasonable dissociation limit for the ground state of the PO₂ molecule is determined. Then the analytic potential energy function of the PO₂ molecule is first derived by using the many-body expansion theory. The potential curves correctly reproduce the configurations and the dissociation energy for the PO₂ molecule.     

The phase transition, hygroscopicity, and thermal expansion properties of Yb2-xAlxMo3O12

Materials with the formula Yb2-xAlxMo3O12 （x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, 0.9, 1.0, 1.1, 1.3, 1.5, and 1.8） were synthesized and their structures, phase transitions, and hygroscopicity investigated using X-ray powder diffraction, Raman spectroscopy, and thermal analysis. It is shown that Yb2-xAlxMo3012 solid solutions crystallize in a single monoclinic phase for 1.7 〈 x 〈 2.0 and in a single orthorhombic phase for 0.0 〈 x 〈 0,4, and exhibit the characteristics of both monoclinic and orthorhombic structures outside these compositional ranges. The monoclinic to orthorhonlbic phase transition temperature of A12Mo3012 can be reduced by partial substitution of A13＋ by Yb3＋, and the Yb2-zAlxMo3012 （0.0 〈 x 〈 2.0） materials are hydrated at room temperature and contain two kinds of water species. One of these interacts strongly with and hinders the motions of the polyhedra, while the other does not. The partial substitution of A13＋ for Yb3＋ in Yb2Mo3012 decreases its hygroscopicity, and the linear thermal expansion coefficients after complete removal of water species are measured to be -9.1 x 10-6/K, -5.5 x 10-6/K, 5.74 x 10-6/K, and 9.5 x 10 6/K for Ybl.sAlo.2（MoO4）3, Yb1.6Alo.4（MoO4）3, Ybo.4All.6（Mo04）3, and Ybo.2Al1.8（MoO4）3, respectively.     

Estimation of the Covariance Matrix in Hierarchical Bayesian Spatio-Temporal Modeling via Dimension Expansion

Ozone concentrations are key indicators of air quality. Modeling ozone concentrations is challenging because they change both spatially and temporally with complicated structures. Missing data bring even more difficulties. One of our interests in this paper is to model ozone concentrations in a region in the presence of missing data. We propose a method without any assumptions on the correlation structure to estimate the covariance matrix through a dimension expansion method for modeling the semivariograms in nonstationary fields based on the estimations from the hierarchical Bayesian spatio-temporal modeling technique (Le and Zidek). Further, we apply an entropy criterion (Jin et al.) based on a predictive model to decide if new stations need to be added. This entropy criterion helps to solve the environmental network design problem. For demonstration, we apply the method to the ozone concentrations at 25 stations in the Pittsburgh region studied. The comparison of the proposed method and the one is provided through leave-one-out cross-validation, which shows that the proposed method is more general and applicable.     

An extended stochastic response surface method for random field problems

An efficient and accurate uncertainty propagation methodology for mechanics problems with random fields is developed in this paper. This methodology is based on the stochastic response surface method (SRSM) which has been previously proposed for problems dealing with random variables only. This paper extends SRSM to problems involving random fields or random processes fields. The favorable property of SRSM lies in that the deterministic computational model can be treated as a black box, as in the case of commercial finite element codes. Numerical examples are used to highlight the features of this technique and to demonstrate the accuracy and efficiency of the proposed method. A comparison with Monte Carlo simulation shows that the proposed method can achieve numerical results close to those from Monte Carlo simulation while dramatically reducing the number of deterministic finite element runs. The project supported by the National Natural Science Foundation of China (10602036). The English text was polished by Yunming Chen.     

节块内嵌离散纵标(SN)方法的算法研究及程序开发

介绍节块内嵌离散纵标(S_N)方法求解三维堆芯中子输运/扩散方程的算法框架.在基于扩散理论的三维粗网节块展开方法(NEM)的算法体系中,用基于输运理论的径向二维细网节块离散纵标方法(NDOM)的内迭代过程,替代节块展开方法(NEM)内迭代的径向求解过程.该算法充分考虑了核电厂反应堆堆芯的三维结构特点,另一方面,也充分利用了已经成熟的三维粗网节块展开方法(NEM)和二维离散纵标方法(S_N)的研究成果,同时有效避免了利用离散纵标方法(S_N)求解三维中子输运方程所面临的计算内存和计算时间的瓶颈问题.编制开发二维多群节块离散纵标方法(NDOM)模块程序NS_NM和三维多群节块展开方法(NEM)模块程序MGNEM,并以此为基础编制开发节块内嵌S_N方法的模块程序HANWIND;其中,NS_NM为HANWIND求解两维问题的功能模块.针对OECD/NEA-2D C5G7MOX基准问题以及两环路核电厂三维堆芯的数值验算结果表明,节块内嵌S_N方法的算法开发及程序编制有效、切实可行.     

Information Theoretic Methods for Variable Selection—A Review

We review the principal information theoretic tools and their use for feature selection, with the main emphasis on classification problems with discrete features. Since it is known that empirical versions of conditional mutual information perform poorly for high-dimensional problems, we focus on various ways of constructing its counterparts and the properties and limitations of such methods. We present a unified way of constructing such measures based on truncation, or truncation and weighing, for the Möbius expansion of conditional mutual information. We also discuss the main approaches to feature selection which apply the introduced measures of conditional dependence, together with the ways of assessing the quality of the obtained vector of predictors. This involves discussion of recent results on asymptotic distributions of empirical counterparts of criteria, as well as advances in resampling.