《计算机网络基本原理》课程学习指南

计算机网络基本原理是计算机网络专业(独立本科段)的一门专业基础课，教材一共分为九章，由浅入深地介绍了计算机网络的基本原理，同时课程内容以介绍网络基本理论和网络最新实用技术为主，强调理论和实际相结合。

浅谈潮流计算在电力系统中的应用

潮流计算在电力系统分析中一直是其基本和核心的算法,应用于对电力系统各个部分的运行状态和运行参数的分析中。在电力系统的设计中,我们需要采用潮流计算来帮助选择合适的电气设备和接线方式,其计算的结果也可以用来判断电力系统中现存或计划运行方式是否合理,同时也可以评价其经济性。了解掌握潮流计算的基本原理,对我们的电力系统分析和计算会有很大帮助。

First-principles local density approximation (LDA) + U and generalized gradient approximation(GGA) + U studies of plutonium oxides

The electronic structures and properties of PuO 2 and Pu 2 O 3 have been studied according to the first principles by using the all-electron projector-augmented-wave (PAW) method.The local density approximation (LDA)+U and the generalized gradient approximation (GGA)+U formalisms have been used to account for the strong on-site Coulomb repulsion among the localized Pu 5f electrons.We discuss how the properties of PuO 2 and Pu 2 O 3 are affected by choosing the values of U and exchange-correlation potential.Also,the oxidation reaction of Pu 2 O 3,leading to the formation of PuO 2,and its dependence on U and exchange-correlation potential have been studied.Our results show that by choosing an appropriate U it is possible to consistently describe structural,electronic,and thermodynamic properties of PuO 2 and Pu 2 O 3,which enable the modelling of the redox process involving Pu-based materials.

First-principles calculation of phase equilibria and phase separation of the Fe-Ni alloy system

Theoretical investigation of the phase equilibria of the Fe-Ni alloy has been performed by combining the FLAPW total energy calculations and the Cluster Variation Method through the Cluster Expansion Method. The calcula- tions have proved the stabilization of the L12 phase at 1:3 stoichiometry, which is in agreement with the experimental result, and predicted the existence of L10 as a stable phase below 550 K; this L10 phase has been missing in the conventional phase diagram. The calculations are extended to the Fe-rich region that is characterized by a wide range phase separation and has drawn considerable attention because of the intriguing Invar property associated with a Fe concentration of 65%. To reveal the origin of the phase separation, a P-V curve in an entire concentration range is derived by the second derivative of free energy functional of the disordered phase with respect to the volume. The calculation confirmed that the phase separation is caused by the breakdown of the mechanical-stability criterion. The newly calculated phase separation line combined with the L10 and L12 order-disordered phase boundaries provides phase equilibria in the wider concentration range of the system. Furthermore, a coefficient of thermal expansion (CTE) is attempted by incorporating the thermal vibration effect through harmonic approximation of the Debye–Gruneisen model. The Invar behavior has been reproduced, and the origin of this anomalous volume change has been discussed.

First-principles investigations on elastic and thermodynamic properties of zinc-blende structure BeS

In this paper the elastic and thermodynamic properties of the cubic zinc-blende structure BeS at different pressures and temperatures are investigated by using ab initio plane-wave pseudopotential density functional theory method within the generalized gradient approximation (GGA).The calculated results are in excellent agreement with the available experimental data and other theoretical results.It is found that the zinc-blende structure BeS should be unstable above 60GPa.The thermodynamic properties of the zinc-blende structure BeS are predicted by using the quasi-harmonic Debye model.The pressure-volume-temperature (P V T) relationship,the variations of the thermal expansion coefficient α and the heat capacity C V with pressure P and temperature T,as well as the Gru¨neisen parameter-pressure-temperature (γ P T) relationship are obtained systematically in the ranges of 0-90GPa and 0-2000K.

Phase transition and thermodynamic properties of SrS via first-principles calculations

The phase transition of SrS from NaCl structure (B1) to CsCl structure (B2) is investigated by means of ab initio plane-wave pseudopotential density functional theory,and the thermodynamic properties of the B1 and the B2 structures are obtained through the quasi-harmonic Debye model.It is found that the transition phase from the B1 to the B2 structures occurs at 17.9 GPa,which is in good agreement with experimental data and other calculated results.Moreover,the thermodynamic properties (including specific heat capacity,the Debye temperature,thermal expansion and Gru¨neisen parameter) have also been obtained successfully.

Pressure and Temperature Induced Phase Transition of ZnS from First-Principles Calculations

压力从 wurtzite ( WZ )和到岩石盐( RS )的结构组织的锌闪锌矿( ZB )导致了 ZnS 的阶段转变，温度从 ZB 结构导致了阶段转变到 ab initio 飞机波浪调查的 WZ 结构斧子假潜在的密度功能的理论(I)英尺)，和伪泛音 Debye 模型。从到 RS-ZnS 的 WZ-ZnS 和 ZB-ZnS 的零温度的转变压力分别地是 17.20 和 17.37 GPa，这被发现。到 WZ-ZnS 的从 ZB-ZnS 的零压力的转变温度是 1199 K。所有这些结果与可得到的试验性的数据一致。而且，压力和热扩大系数高山上的规范的原始房间体积 V/V-0 的依赖哈在温度上也成功地被获得。

Magnetic properties of Mn-doped ZnO diluted magnetic semiconductors

A series of Mn-doped ZnO films have been prepared in different sputtering plasmas by using the inductively coupled plasma enhanced physical vapour deposition.The films show paramagnetic behaviour when they are deposited in an argon plasma.The Hall measurement indicates that ferromagnetism cannot be realized by increasing the electron concentration.However,the room-temperature ferromagnetism is obtained when the films are deposited in a mixed argon-nitrogen plasma.The first-principles calculations reveal that antiferromagnetic ordering is favoured in the case of the substitution of Mn 2+ for Zn 2+ without additional acceptor doping.The substitution of N for O (N O) is necessary to induce ferromagnetic couplings in the Zn-Mn-O system.The hybridization between N 2p and Mn 3d provides an empty orbit around the Fermi level.The hopping of Mn 3d electrons through the empty orbit can induce the ferromagnetic coupling.The ferromagnetism in the N-doped Zn-Mn-O system possibly originates from the charge transfer between Mn 2+ and Mn 3+ via N O.The key factor is the empty orbit provided by substituting N for O,rather than the conductivity type or the carrier concentration.

First-Principles Calculation for the Electron-Phonon Coupling Constant of Superconducting MgB2

We use a first-principles plane wave method with the new relativistic analytic pseudopotential of the Hartwigsen,Goedecker and Hurter (HGH) scheme and the pseudopotential of the Troullier-Martins scheme to calculate the eleetron-phonon coupling constant λ of superconducting MgB2. The calculated results show that there is a peak at about 300-350cm^-1 in the eleetron-phonon spectral functional α2F(ω), duo to the coupling of the electrons to the acoustic phonon, and the relativistic effect appears in the high frequencies zone. All the results agree well with the present and previous experimental data,