A Scheme for Atomic Entangled States and Quantum Gate Operations in Cavity QED

We propose a scheme for controllably entangling the ground states of five-state W-type atoms confined in a cavity and realizing swap gate and phase gate operations. In this scheme the cavity is only virtually excited and the atomic excited states are almost not occupied, so the produced entangled states and quantum logic operations are very robust against the cavity decay and atomic spontaneous emission.     

准连续调制激光吸收谱测量封闭室内O2浓度的研究

在开采煤矿的生产活动中,遇到煤矿爆炸或地震、地质等自然灾害,会导致坍塌、掩埋、堆积等情形,进而形成复杂的封闭环境。如果发生人员被困等突发情况,破灾救援、挽救生命工作显得至关重要。封闭环境中O₂的浓度随时间的变化直接威胁到被困人员的生命安全,及时掌握被困人员所处环境的O₂浓度变化对破灾救援机器人作业实施有着非常重要的指导意义。为准确测量O₂的浓度,以封闭室内O₂为研究对象,综合应用可调谐二极管激光吸收光谱(TDLAS)技术和波长调制光谱(WMS)技术,设计了一套准连续调制激光吸收谱实验测量O₂浓度系统,对24 h封闭室内O₂的浓度随时间变化情况进行测量研究。实验结果表明,封闭室内O₂的浓度受到室内人员活动的影响,准连续调制激光吸收谱测量方法可以准确测量封闭室内的氧气变化。     

硫在氧气中燃烧实验的新设计

利用吸滤瓶、玻璃棒、燃烧匙、气球等设计的封闭式实验装置,很好地解决了实验过程中可能存在的污染问题,保障了师生的健康,培养了学生的环保意识。     

有理三角Bézier曲线曲面光滑融合的构造

为了使自由曲线曲面在较为简单的条件下能够达到相对高阶的光滑拼接,并在不改变控制顶点的情况下自由调整曲线曲面的形状,构造了含多个形状参数的有理三角函数.基于该组基函数,定义了含多个形状参数的有理三角曲线曲面,并讨论了曲线曲面的光滑拼接条件.根据拼接条件,分别定义了由含多个形状参数的有理三角曲线曲面构成的分段组合曲线、分片组合曲面.这种新的曲线曲面能够自动保证组合曲线、曲面的连续性.数值实例的结果显示了该方法的有效性.     

一种用于分析封闭腔内湍流自然对流换热的k-ε新模型

由于目前用于求解湍流自然对流流动与传热的k-ε模型在应用过程中存在不足,结合高雷诺数k-ε模型需要借助壁面函数法来确定壁面上相关参数值和低雷诺数k-ε模型在近壁区布置更多节点以便获得粘性底层详细信息的特点,重新定义了湍流普朗特数σt的计算式,提出了一种修正的k-ε新模型;利用该模型对封闭方腔内的湍流自然对流流动与传热进行了数值分析。结果表明:与文献中数值模拟结果相比,当108≤Ra≤1014时本文模型所得壁面平均努塞尔特数更接近文献中的实验值,与实验值之间的相对误差在8%以内;壁面的局部努塞尔特数与文献中的实验值吻合得较好。这说明本文模型用于求解封闭腔内湍流流动与传热问题是合适的,比其它湍流模型更能准确地描述封闭腔内湍流自然对流换热中边界层发展与壁面传热特性之间的内在联系。     

Unique factorization of compositive hereditary graph properties

A graph property is any class of graphs that is closed under isomorphisms. A graph property P is hereditary if it is closed under taking subgraphs; it is compositive if for any graphs G1, G2 ∈ P there exists a graph G ∈ P containing both G1 and G2 as subgraphs. Let H be any given graph on vertices v1, . . . , vn, n ≥ 2. A graph property P is H-factorizable over the class of graph properties P if there exist P 1 , . . . , P n ∈ P such that P consists of all graphs whose vertex sets can be partitioned into n parts, possibly empty, satisfying: 1. for each i, the graph induced by the i-th non-empty partition part is in P i , and 2. for each i and j with i = j, there is no edge between the i-th and j-th parts if vi and vj are non-adjacent vertices in H. If a graph property P is H-factorizable over P and we know the graph properties P 1 , . . . , P n , then we write P = H [ P 1 , . . . , P n ]. In such a case, the presentation H[ P 1 , . . . , P n ] is called a factorization of P over P. This concept generalizes graph homomorphisms and (P 1 , . . . , P n )-colorings. In this paper, we investigate all H-factorizations of a graph property P over the class of all hered- itary compositive graph properties for finite graphs H. It is shown that in many cases there is exactly one such factorization.     

Finite-time stability with respect to a closed invariant set for a class of discontinuous systems

This paper discusses the problem of finite-time stability with respect to a closed, but not necessarily compact, invariant set for a class of nonlinear systems with discontinuous right-hand sides in the sense of the Filippov solutions. When the Lyapunov function is Lipschitz continuous and regular, the Lyapunov theorem on finite-time stability with respect to a closed invariant set is presented.     

具有封闭杆件的刚架在任意荷载作用下的精确解

对任意荷载作用下具有封闭杆件的刚架给出用分配系数和传递系数表示的精确解。刚架用变矩分配法求解时,将各结点用假设的刚臂固定,求得任意荷载引起的固端弯矩,然后求得结点不平衡力矩,从而将求任意荷载作用的问题转化为求任意的结点不平衡力矩作用的问题。用弯矩分配法求解时,将杆端弯矩,表示为无穷多次分配弯矩和传递弯矩之和,其表达式为公比小于1的无穷等比级数的和,为方便地求得该和的表达式,从而求得任意荷载作用下刚架结构的精确解。文中给出了算例。     

封闭空间有源弹性壁振动声辐射的鲁棒H∞控制研究

应用H∞控制原理,设计了封闭空间有源弹性壁声辐射有源力控制系统,折衷考虑了系统对外扰力噪声衰减问题和系统参数摄动的鲁棒问题,并对流体声速摄动这一常见情况进行了数值仿真,结果表明,系统对参数摄动具有较强的鲁棒性,同时能有效抑制外扰,与目前较先进的基于自适应滤波的前馈系统相比,具有不需要参考信号,系统相对简单,易于工程实现等优点。∞     

Partial wave scattering cross sectionsfor He--HBr collision

A new anisotropic potential is fitted to {\it ab initio} data. The close-coupling approach is utilized to calculate state-to-state rotational excitation partial wave cross sections for elastic and inelastic collisions of He atom with HBr molecule based on the fitted potential. The calculation is performed separately at the incident energies: 75, 100 and 200~meV.The tendency of the elastic and inelastic rotational excitation partial wave cross sections varying with total angular quantum number $J$ is obtained.