四阶Colpitts混沌振荡器

提出了一种新的四阶Colpitts混沌振荡器.理论设计与电路实验表明,在三阶Colpitts混沌振荡器中的电感两端并联一个电容器C₃,可构建出一种四阶Colpitts混沌振荡器.当C₃的取值变化时,电路的谐振频率随之改变,从而使该振荡器经过倍周期分岔进入混沌状态.对四阶Colpitts混沌振荡器的平衡点、分岔和李氏指数等基本动力学问题进行了分析.最后通过数值仿真和电路实验证实了这一方法的可行性. 关键词： 四阶Colpitts混沌振荡器 混沌吸引子 电路实现     

Scheme for Remote Implementation of Partially Unknown Quantum Operation of Two Qubits in Cavity QED

By constructing the recovery operations of the protocol of remote implementation of partially unknown quantum operation of two qubits [An-Min Wang： Phys. Rev. A 74 （2006） 032317] with two-qubit Cnot gate and single qubit logic gates, we present a scheme to implement it in cavity QED. Long-lived Rydberg atoms are used as qubits, and the interaction between the atoms and the field of cavity is a nonresonant one. Finally, we analyze the experimental feasibility of this scheme.     

A stabilized finite element predictor–corrector scheme for the incompressible Navier–Stokes equations using a nodal‐based implementation

A finite element model to solve the incompressible Navier–Stokes equations based on the stabilization with orthogonal subscales, a predictor–corrector scheme to segregate the pressure and a nodal based implementation is presented in this paper. The stabilization consists of adding a least‐squares form of the component orthogonal to the finite element space of the convective and pressure gradient terms, which allows to deal with convection‐dominated flows and to use equal velocity–pressure interpolation. The pressure segregation is inspired in fractional step schemes, although the converged solution corresponds to that of a monolithic time integration. Finally, the nodal‐based implementation is based on an a priori calculation of the integrals appearing in the formulation and then the construction of the matrix and right‐hand side vector of the final algebraic system to be solved. After appropriate approximations, this matrix and this vector can be constructed directly for each nodal point, without the need to loop over the elements and thus making the calculations much faster. Some issues related to this implementation for fractional step and our predictor–corrector scheme, which is the main contribution of this paper, are discussed. Copyright © 2004 John Wiley & Sons, Ltd.     

NLPQL: A fortran subroutine solving constrained nonlinear programming problems

NLPQL is a FORTRAN implementation of a sequential quadratic programming method for solving nonlinearly constrained optimization problems with differentiable objective and constraint functions. At each iteration, the search direction is the solution of a quadratic programming subproblem. This paper discusses the organization of NLPQL, including the formulation of the subproblem and the information that must be provided by a user. A summary is given of the performance of different algorithmic options of NLPQL on a collection of test problems (115 hand-selected or application problems, 320 randomly generated problems). The performance of NLPQL is compared with that of some other available codes.     

一个超混沌Lorenz吸引子及其电路实现

通过在三阶Lorenz系统中引入一个外加的状态变量构造了一个新的超混沌系统.对系统的一些基本特性，如耗散性、平衡点、稳定性、Hopf分叉进行了详细分析，且观察到了从周期到混沌、超混沌的演化.系统超混沌的存在性通过Lyapunov指数谱得到了验证.还设计了一个模拟电子电路，从电路实验中观察到了各种超混沌吸引子. 关键词： Lorenz系统 超混沌吸引子 电路实现     

A Three-Dimensional Hybrid LES-Acoustic Analogy Method for Predicting Open-Cavity Noise

A three-dimensional (3D) hybrid LES-acoustic analogy method for computational aeroacoustics (CAA) is presented for the prediction of open-cavity noise. The method uses large-eddy simulation (LES) to compute the acoustic source while the Ffowcs Williams-Hawkings (FW-H) acoustic analogy is employed for the prediction of the far-field sound. As a comparison, a two-dimensional (2D) FW-H analogy is also included. The hybrid method has been assessed in an open-cavity flow at a Mach number of 0.85 and a Reynolds number of Re=1.36×10⁶, where some experimental data are available for comparison. The study has identified some important technical issues in the application of the FW-H acoustic analogy to cavity noise prediction and CAA in general, including the proper selection of the integration period and the modes of sound sources in the frequency domain. The different nature of 2D and 3D wave propagation is also highlighted, which calls for a matching acoustic solver for each problem. The developed hybrid method has shown promise to be a feasible, accurate and computationally affordable approach for CAA.     

基于化学学科理解的“化学平衡常数”教学设计与实施研究*

基于化学学科理解,凝练了化学平衡主题的学科本原性问题,抽提了认识视角,建构了概念的层级结构。从教学目标和教学思路、教学实施、学生收获、教师反思及专家评价等方面,系统呈现了基于化学学科理解的“素养为本”的课堂教学研究过程。     

细观结构对复合材料热膨胀系数的影响研究

基于应力为未知量的通用单胞模型改进算法在保证计算精度的前提下，可以提高计算效率，本文利用该方法计算了纤维细观结构对纤维增强复合材料热膨胀系数的影响。计算结果表明，热膨胀系数随体积比的增加而减小，纵向热膨胀系数受纤维的形状和排列方式的影响不大，而横向热膨胀系数受纤维形状以及排列方式的影响较为明显。复合材料的纵向热膨胀系数并不是随温度上升而上升的．它与各组分的弹性模量和热膨胀系数等有关．     

Heterogeneous dual memristive circuit: Multistability,symmetry, and FPGA implementation

An improved heterogeneous dual memristive circuit (DMC) is proposed based on Chua's circuit, which shows good symmetry and multistablility. For the difficulty in controlling the initial conditions, which restricts the engineering applications, the 3rd-order model (3OM) in flux-charge domain is derived from the 5th-order model (5OM) in volt-ampere domain by using the flux-charge analysis method (FCAM). The consistence of symmetry and multistability before and after dimensionality decreasing is meticulously investigated via bifurcation diagram, Lyapunov exponents, and especially attraction basins. The comparative analysis validates the effectiveness of reduction model and improves the controllability of the circuit. To avoid the noise in the analog circuit, a field-programmable gate array (FPGA) is utilized to realize the reduction model, which is rarely reported and valuable for relevant research and application.     

Access mechanisms in block structured environments

Statistics from dynamic analysis of programs are used to compare the efficiency of different methods to access global variables. The method where static links are used for access is shown to be at least as efficient as the display method. The use of the linked list method also leads to a simpler runtime system and allows separately compiled modules to execute at any level in the resulting program. The results of the dynamic analysis are presented in a form which allows comparison of the access methods in language implementations on specific computers. Experience with using two different access methods in an implementation of Simula67 concludes the paper.