Criticality condition of the fully anisotropic Ising model with next-nearest neighbour interaction

We derive an analytical expression for the criticality condition of the fully anisotropic Ising model with next-nearest neighbour interaction. For that behalf a recently published method [H.J.W. Zandvliet, Eur. Phys. Lett. 73 (2006) 747] to calculate the free energy of a boundary between two areas of opposite magnetisation is generalised to systems without reflection symmetry with respect to the boundary line. For the anisotropic triangular model and related special cases without crossing bonds the method provides the exact criticality conditions in polynomial form, which is shown to be a factor of the exactly known criticality condition. The other factor is related to the first one by a reciprocal transformation. For systems with crossing bonds the method is not exact, but it may be useful as a closed form approximation in a wide parameter range.     

Photoinduced multi-mode quantum dynamics of pyrrole at the – conical intersections

The photoinduced dynamics of pyrrole at the – S₀ and – S₀ conical intersections has been investigated by multi-mode time-dependent quantum wave-packet calculations. Diabatic potential-energy surfaces have been constructed for both conical intersection using accurate multi-reference ab initio electronic-structure calculations. In addition to the NH stretching coordinate, the three (four) symmetry-allowed coupling modes of A₂ (B₁) symmetry have been considered for the – S₀ (– S₀) conical intersections. Wave-packet dynamics calculations have been performed for three-dimensional models, taking account of the two dominant coupling modes of each conical intersection. The electronic population-transfer processes at the conical intersections, the branching ratio for the dissociation to the ground and excited states of the pyrrolyl radical, and their dependence on the initial preparation of the system have been investigated. It is shown that the excitation of the NH stretching mode strongly enhances the photodissociation rate, while the excitation of the strongest coupling mode has a pronounced effect on the branching ratio of the photodissociation process. Although the inclusion of the second (weaker) coupling mode has little effect on the electronic population dynamics, it leads to interesting changes of the nodal pattern of the wave packet at the conical intersections. The calculations provide insight into the effect of the multiple coupling modes on the process of direct photodissociation through a conical intersection.     

Generalization of matching extensions in graphs (III)

Proposing them as a general framework, Liu and Yu (2001) [6] introduced (n,k,d)-graphs to unify the concepts of deficiency of matchings, n-factor-criticality and k-extendability. Let G be a graph and let n,k and d be non-negative integers such that n+2k+d+2?|V(G)| and |V(G)|−n−d is even. If on deleting any n vertices from G the remaining subgraph H of G contains a k-matching and each k-matching can be extended to a defect-d matching in H, then G is called an (n,k,d)-graph. In this paper, we obtain more properties of (n,k,d)-graphs, in particular the recursive relations of (n,k,d)-graphs for distinct parameters n,k and d. Moreover, we provide a characterization for maximal non-(n,k,d)-graphs.     

Locating a competitive facility in the plane with a robustness criterion

A new model for locating a competitive facility in the plane in a robust way is presented and embedded in the literature on robustness in facility location. Its mathematical properties are investigated and new sharp bounds for a deterministic method that guarantees the global optimum are derived and evaluated.     

Common hypercyclic vectors for the conjugate class of a hypercyclic operator

Given a separable, infinite dimensional Hilbert space, it was recently shown by the authors that there is a path of chaotic operators, which is dense in the operator algebra with the strong operator topology, and along which every operator has the exact same dense Gδ set of hypercyclic vectors. In the present work, we show that the conjugate set of any hypercyclic operator on a separable, infinite dimensional Banach space always contains a path of operators which is dense with the strong operator topology, and yet the set of common hypercyclic vectors for the entire path is a dense Gδ set. As a corollary, the hypercyclic operators on such a Banach space form a connected subset of the operator algebra with the strong operator topology.     

Carbon Nitride Thin Films Deposited by Plasma Assisted Nd∶YAG Laser Ablation of Graphite in N2+H2 Atmosphere

Carbon nitride thin films are deposited on silicon wafers by 532 nm Nd∶YAG laser ablation of graphite in the N2+H2 atmosphere assisted by a dc glow discharge plasma at a higher gas pressure of about 4.0 kPa. The properties of the thin films are investigated by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and X-ray diffraction (XRD). The results show that the deposited films are composed of α-C3N4, β-C3N4 phase and have the N/C atomic ratio of 2.01. The optical emission spectroscopy (OES) studies indicate that the introduction of a dc glow discharge and the adoption of a higher gas pressure during the film deposition are favorable to the net generation of the atomic N, CN radicals and N+2 in B2Σ+u excited state in the plasma, which are considered to play a major role in the synthesis of carbon nitride.     

H2对N2直流辉光放电电子行为的影响

通过用Monte Carlo方法模拟N₂-H₂ 混合气体直流辉光放电等离子体快电子行为，从不同H₂浓度的电子能量分布函数，电子密度以及e_f-N₂碰撞率等方面，研究了加H₂对氮辉光放电等离子体过程的影响. 研究结果表明: 随着H₂浓度的升高，电子的平均能量增加, 电子密度及e_f-N₂的各种非弹性碰撞率减小; 但在 关键词： 2-H₂辉光放电')" href="#">N₂-H₂辉光放电 Monte Carlo模拟 2碰撞率')" href="#">e-N₂碰撞率     

红外光学材料透过率温度特性测量方法

提出了一种变温条件下红外光学材料透过率测量评价方法。研究内容包括使用准直反射镜将红外光源变为平行光,通过斩波器变为脉冲光,再经滤光片选择波长;使用平面反射镜组与精密温控炉来获得变温条件下的双光路:测试光路与参考光路。使用前置放大电路和锁相放大器对红外微弱信号进行检测,根据两个光路的测量电压计算样品的透过率及透过率温度系数。计算机实现自动控制、采集与相关运算。该方法解决了变温条件下红外光学材料透过率测量中的实际应用问题,使光学材料参数检测从常规检测扩展到高温等极端条件,更接近于材料的实际使用条件,蓝宝石材料在波长5195 nm处,透过率高于10%,温度从室温到700℃的范围内,重复性优于0.2%。     

Structure of odd–odd La at high spin

The high spin states in the N=79 odd–odd ¹³⁶La nucleus have been investigated by in-beam γ-spectroscopic techniques following the ¹³⁰Te(¹¹B, 5n)¹³⁶La reaction at E=52 MeV using an array, consisting of eight Compton-suppressed clover germanium detectors. Thirty nine new γ rays have been assigned to ¹³⁶La on the basis of γ ray singles and γγ-coincidence data. The level scheme of ¹³⁶La has been extended above the known 115 ms isomer upto an excitation energy of 4.6 MeV and spin 18. Thirty one new levels have been proposed and spin-parity assignments for most of the newly proposed levels have been made on the basis of the deduced asymmetry ratios and polarisation information for the de-exciting transitions. The observed positive parity yrast band has been compared with the theoretical calculation, done within the framework of particle rotor coupling model (PRM) where the two odd quasi-particles are coupled to an axially symmetric core. The level structure has been discussed in the light of the known systematics of the neighbouring N=79 isotonic nuclei.     

Production of ultrafine particles of high-temperature tetragonal WO<Subscript>3</Subscript> by dc arc discharge in Ar–O<Subscript>2</Subscript> gases

Ultrafine particles of WO₃ are successfully produced by dc arc discharge in Ar-O₂ gases. Particle sizes are distributed from 10 nm to 1 m depending on production conditions: gas pressure, collection position and discharge current. Observations of the cooled particles by electron microscopy indicate that the WO₃ particles are tetragonal, a phase that is usually only stable above 725 °C. The octahedral crystals are bounded by eight {1 0 1} faces and occasionally truncated by {1 0 0} and/or {0 0 1} faces. This method of producing WO₃ by dc arc discharge therefore affords a high-temperature phase that is preserved upon cooling to room temperature.