模糊目标信息系统的属性约简

利用粗糙模糊集的概念定义了模糊目标信息系统的α下(上)分配约简,并讨论了它们同下(上)近似约简、下(上)最大分布约简的关系.相应于下(上)近似约简、下(上)最大分布约简和α下(上)分配约简给出了把模糊目标信息系统变换成对应的一致目标信息系统的方法.证明了变换前的模糊目标信息系统的下(上)近似约简、下(上)最大分布约简和α下(上)分配约简同变换后的对应的一致目标信息系统的属性约简是相同的,从而求模糊目标信息系统的属性约简可转化为求一致目标信息系统的约简.     

Pu2O3晶体结构、弹性和电子性质的 密度泛函理论研究

采用基于密度泛函理论的全势能线性缀加平面波方法(FLAPW),在局域自旋密度近似(LSDA:local spin density approximation)和广义梯度近似(GGA:generalized gradient approximation)及LSDA/GGA+U下,系统研究了强关联5f电子体系Pu_2O_3的晶体结构,弹性参数,电子态密度和电荷密度.优化计算结果表明,LSDA+U的晶格参数a0和c/a与实验值吻合最好,同时也在不同的近似下计算了Pu_2O_3的弹性参数.与此同时,LSDA/GGA+U计算的态密度在费米能级处分别出现约1.8和2.2eV能隙,而LSDA/GGA的计算结果在费米能级处并无能隙,所以对Pu_2O_3的Pu-5f加U能使体系从导体转变为绝缘体,这与实验测定Pu_2O_3是绝缘性很好吻合.此外,电荷密度计算结果表明,与LSDA相比,LSDA+U计算的Pu-O间电荷密度增加且有明显的成键特征.     

论煤矸石代替粘土生产水泥

本文从理论上分析了利用煤矸石代替粘土生产水泥的可行性,并通过生产证明:以矸石代粘土生产水泥是利用工业废料的有效途径。     

求解广义含时振子严格波函数的新方法

采用尝试波函数的方法精确求解了广义含时振子的严格波函数，并证明其为压缩Fock态。     

OⅡ空位对PbTiO3晶体影响的第一性原理研究

在广义梯度近似(GGA)下,利用超软赝势(USP)对理想PbTiO3晶体(以下简称理想晶体)和OⅡ空位PbTiO3晶体(以下简称OⅡ晶体)的电子云重叠布局数、态密度和能带分布等进行自洽计算.结果显示:OⅡ晶体与理想晶体相比能带向低能方向移动,而且在费米面附近O原子的2p轨道和Ti原子的3d轨道存在明显杂化,这种杂化是PbTiO3晶体保持铁电性的主要原因.氧空位使OⅠ空位PbTiO3晶体(以下简称OⅠ晶体)的氧八面体发生畸变[1],但并没有改变OⅡ晶体的结构,说明OⅡ晶体结构更加稳定.     

一维简单晶格声子非线性局域态

利用量子相干态表象和多重尺度与准连续近似方法，研究了考虑格点间相互作用势展开至4阶项的一维简单晶格模型，求得了该晶格系统脉冲与扭结2种包络形式的声子非线性局域态，与用经典方法研究同一系统所得结果一致。     

Synthesis, growing processes and physical properties of CdS nanoclusters in Y-zeolite studied by positron annihilation

Direct synthesis of CdS nanoclusters within the pore structure of Y zeolite was made. The location of CdS nanoclusters inside Y zeolite hosts was confirmed by the blue-shifted reflection absorption spectra with respected to that of bulk CdS materials. In this paper, we conducted Positron Annihilation Lifetime Spectrum (PALS) measurements on a series of CdS/Y zeolite samples and concluded that CdS clusters were not located in supercages but in smaller sodalite cages; as the CdS loading concentration increases to 5 wt%, the discrete CdS cubes begin to form bigger superclusters through interaction. The stability of CdS clusters inside the sodalite units is due to the coordination of Cd atoms with the framework oxygen atoms of the double six-ring windows. Moreover, PALS reveals some important information of surface states existing on the interfacial layers between CdS clusters and Y zeolite. Foundation item: Supported by the National Natural Science Foundation of China (19871074) Biography: Peng Hao (1978-), male, Ph. D candidate, research interest: semiconductor nanoclusters.     

Electronic structure, chemical bond and thermal stability of hydrogen absorber Li_2MgN_2H_2

The lowest total energy crystal structure of Li2MgN2H2 was identified by the first principle calculation with RPBE exchange-correlation function. Furthermore, the fine structure parameters of this crystal structure were calculated with PBE and PW91 exchange-correlation function. In a further step, the density of states, electron density, charge density difference on (0 0 1) plane and heat of formation of Li2MgN2H2 hydrogenation were computed with PW91 exchange-correlation function. Consequently, the electro...     

论中越宗藩关系下的“安全互保”

为了保证国家的稳定与安全，历朝历代越南国王都向中国朝延寻求保护；为保证边疆的稳定，防止外敌入侵，历朝历代中国君主也都推行“保藩固边”的政策。两者相结合便形成了独具东方色彩、又带有安全互保性质的“宗藩关系”。近千年的宗藩关系使得中越两国结成了“唇亡齿寒、共存共亡”的兄弟之邦，成为古代友好周边关系的典型范例。