Static Magnetic Flux Dynamics in One-Dimensional (1D) Josephson Lattices

We investigated static magnetic flux dynamical properties of one-dimensional lattices of Josephson junctions. The discretized wave equations of the Josephson junction lattice were solved using a generalized relaxation iteration algorithm. Numerical simulations indicated that transitions between periodic state and chaotic state will occur as the physical parameters and geometric parameters such as external current y _n, magnetic field h ₀, h, and the length of Josephson junction _n and d _n , varied. A shot length of the Josephson junction favors stable periodic states.     

约瑟夫森结Nb电极的实验研究

通过溅射Nb膜张力与氩（Ar）压强的关系，超导转变温度Tc，室温阻扰与液氮温度阻抗比RRT／RLN2，沉积中Ar浓度CAr与负偏压关系的测量和扫描电子显微镜的观察分析，对约瑟夫森结Nb电极作了研究。发现Ar压强在1．1Pa时，Nb膜呈现无应力状态；低负偏压下沉积的Nb膜晶粒结构是由致密膜到圆柱状。在偏压Ub＝－50V时，获得表面致密均匀、晶粒结构合适的Nb膜。对Nb膜用阳极氧化电压谱图（AVS）分析，证实沉积的Nb膜内不存在氧化物、寄生结和分层界面。     

用于量子电压基准中约瑟夫森结阵列的CMP平整化工艺研究

化学机械平坦化(chemical mechanical planarization,CMP)工艺处理Si02绝缘层是一种获得高度集成化超导电路的关键技术,尤其适合于多层堆叠约瑟夫森结阵列器件的平整化.设计了应用于热氧化生长的Si02薄膜和化学气象沉积生长的Si02薄膜的CMP工艺,得出两种薄膜的抛光速率分别为2 nm/...     

Detecting Current Noise with a Josephson Junction in the Macroscopic Quantum Tunneling Regime

We discuss the use of a hysteretic Josephson junction to detect current fluctuations with frequencies below the plasma frequency of the junction. These adiabatic fluctuations are probed by switching measurements observing the noise-affected average rate of macroscopic quantum tunneling of the detector junction out of its zero-voltage state. In a proposed experimental scheme, frequencies of the noise are limited by an on-chip filtering circuit. The third cumulant of current fluctuations at the detector is related to an asymmetry of the switching rates.      

Numerical Simulations of the Fluxon Dynamics of a Two-Dimensional Josephson Junction System

A direct perturbation method applied to a long Josephson junction molded by one-dimensional sine-Gordon equation is presented and the modulation of perturbations on fluxon velocity and stable state is studied. Simulations of a two-dimensional Josephson junction with dc bias current in an external magnetic field provide an I–V characteristic curve for the system and determine the various dynamic behaviors, including the periodic, quasiperiodic, and chaotic motions. Physical explanations for the behaviors are presented. The numerical results are in good agreement with the energetic analysis.     

The Bradbury Butterfly Effect in Long Josephson Junctions

In a well-known science fiction novel by Ray Bradbury, a butterfly in the pre-historic past is accidentally crushed by time travelers and this seemingly insignificant event radically changes history. We will call this the “Bradbury Butterfly” Effect (BBE). We know that such an effect occurs in Long Josephson Junctions as described by a time-dependent nonlinear sine-Gordon equation. This equation states that any alteration within the initial perturbation fundamentally changes the asymptotic state of the system. The actual manifestation of this effect is proven by a numerical simulation of the time-dependent sine-Gordon equation.     

Ground States of Two-Component Bose-Einstein Condensates with an Internal Atomic Josephson Junction

In this paper, we prove existence and uniqueness results for the ground states of the coupled Gross-Pitaevskii equations for describing two-component Bose-Einstein condensates with an internal atomic Josephson junction, and obtain the limiting behavior of the ground states with large parameters. Efficient and accurate numerical methods based on continuous normalized gradient flow and gradient flow with discrete normalization are presented, for computing the ground states numerically. A modified backward Euler finite difference scheme is proposed to discretize the gradient flows. Numerical results are reported, to demonstrate the efficiency and accuracy of the numerical methods and show the rich phenomena of the ground sates in the problem.     

Excitation of Josephson junction by an electromagnetic field in the nonlinear process formalism

The numerical analysis of the excitation of the Josephson junction (Jj) by an external electromagnetic field has been reported. The fully nonlinear approach requires using the quasiperiodic solutions of the sine-Gordon equation (sGe) which are expressed by the Riemann theta functions. Their local soliton approximation of the nondissipative Jj is presented. Using the self-consistent phenomenological model of a long Jj, the influence of the external electromagnetic field on the volt-ampere characteristics is considered.     

Duality in the Quantum Dissipative Villain Model and Application to Mesoscopic Josephson Junction Circuits

We study exact self-duality in the model of a Brownian particle in a washboard (WB) potential which describes a Josephson junction (JJ) coupled to an environment, for arbitrary temperature and arbitrary form of the spectral density of the environment. To this end we introduce the quantum dissipative Villain model (QDVM), which models tunneling of a degree of freedom coupled to a linear quantum environment through an infinite set of states. We derive general exact mappings on various dual discrete representations (one-dimensional Coulomb gases or surface-roughening models) which are exactly self-dual. Then we show how the QDVM maps exactly onto the WB model and use duality relations to calculate the leading terms of the total impedance of a JJ circuit, for general frequency dependence of the spectral density of the environment and arbitrary temperature.     

碰撞阻尼器系统的分岔、混沌与控制

对碰撞阻尼器振动系统推导了周期解存在的条件，并利用Poincare映射和数字仿真进行了分岔与混沌运动的研究。计算结果表明，这种非线性碰撞振动系统在特定的参数条件下，除了稳定的周期运动形态外，还会沿着倍周期分岔、HOPF分岔及拟周期环面破裂等分岔进入混沌运动。因此，为了有效地利用碰撞阻尼器特性控制振动，在设计和使用碰撞阻尼器时应考虑参数满足周期运动的条件，避免由于自身的非线性特性而产生的混沌运动。     

机动车车室内复合主动噪声控制系统的设计

本文在系统研究主动噪声控制技术和机动车辆内噪声来源的基础上,提出利用复合主动噪声控制思想,改善机动车辆室内噪声环境的方案及其算法实现。具体地说,就是利用反馈主动噪声控制系统,抵消低频噪声对车室内的总噪声辐射;利用前馈主动噪声控制系统,抵消发动机噪声的基频分量及其多次谐波分量。分析表明：该方案具有较好的除噪效果和较高的实用价值。     

Leading Chaos to Period by Two Unfeedback Methods in a Two-degree-of-freedom Vibrating System with Two Rigid Constraints

The equations of the asymmetrical periodic motion in a two-degree-of-freedom vibrating system with two rigid constraints are constructed analytically.Its Poincaré mapping equation is established too.Periodic motions of the system and their routes to chaos are also illustrated by numerical simulation.The ranges of the system excited frequency from periodic motions to chaotic motions are obtained.The chaotic motions of the system are shown by diagrams of Poincaré mapping,phase portraits and diagrams of bifurcation.The chaos controlling methods by the addition of constant load and the addition of phase are dissertated and analyzed numerically by the numerical solution.The chaos of the system is controlled by the two methods.The allowable range controlling variables and the steady orbits of the controlled system are obtained.     

输液管道颤振失稳的时滞控制

采用时滞主动控制方法对输液管道的颤振失稳进行控制,以提高输液管道系统的临界流速.首先构造时滞控制策略并建立时滞控制的偏微分方程;然后利用伽辽金法离散时滞偏微分方程将其转化为时滞微分方程组,从理论上分析时滞微分方程的稳定性,并通过Matlab Biftool软件包对时滞控制系统的特征根分布情况进行模拟,与稳定性理论分析结果相当吻合;最后通过有限差分法对时滞偏微分方程进行数值模拟,与稳定性理论分析结果基本吻合.结果表明:通过时滞主动控制输液管道的颤振,控制策略简单,而且效果较好.     

管道有源消声次源声反馈问题研究与实验分析

有源消声是一种有效的低频噪声控制方法.而次源声反馈问题一直是影响管道有源消声系统的关键问题之一.从传递函数的角度分析了管道有源消声的次源声反馈问题,并提出了解决上述问题的方法.通过实验验证,此方法效果良好.     

建筑室内给排水管道噪声的分析与控制

分析了建筑室内给水排水管道噪声产生与传播的原因,探讨了控制建筑室内给排水管道噪声的相应措施。从设计和施工两方面出发,论述了给排水管道的布置、给排水管材的选用及给水泵房的减振隔声等内容     

Exploring the Use of Design of Experiments in Industrial Processes Operating Under Closed‐Loop Control

Industrial manufacturing processes often operate under closed‐loop control, where automation aims to keep important process variables at their set‐points. In process industries such as pulp, paper, chemical and steel plants, it is often hard to find production processes operating in open loop. Instead, closed‐loop control systems will actively attempt to minimize the impact of process disturbances. However, we argue that an implicit assumption in most experimental investigations is that the studied system is open loop, allowing the experimental factors to freely affect the important system responses. This scenario is typically not found in process industries. The purpose of this article is therefore to explore issues of experimental design and analysis in processes operating under closed‐loop control and to illustrate how Design of Experiments can help in improving and optimizing such processes. The Tennessee Eastman challenge process simulator is used as a test‐bed to highlight two experimental scenarios. The first scenario explores the impact of experimental factors that may be considered as disturbances in the closed‐loop system. The second scenario exemplifies a screening design using the set‐points of controllers as experimental factors. We provide examples of how to analyze the two scenarios. © 2017 The Authors Quality and Reliability Engineering International Published by John Wiley & Sons Ltd     

Numerical experiments with the Bloch–Floquet approach in homogenization

This paper deals with a numerical study of classical homogenization of elliptic linear operators with periodic oscillating coefficients (period εY). The importance of such problems in engineering applications is quite well‐known. A method introduced by Conca and Vanninathan [SIAM J. Appl. Math. 1997; 57 :1639–1659] based on Bloch waves that homogenize this kind of operators is used for the numerical approximation of their solution u^ε. The novelty of their approach consists of using the spectral decomposition of the operator on ?^N to obtain a new approximation of u^ε—the so‐called Bloch approximation θ^ε—which provides an alternative to the classical two‐scale expansion u^ε(x)=u*(x)+Σε^ku_k(x,x/ε), and therefore, θ^ε contains implicitly at least the homogenized solution u* and the first‐ and second‐order corrector terms. The Bloch approximation θ^ε is obtained by computing, for every value of the Bloch variable η in the reciprocal cell Y′ (Brillouin zone), the components of u* on the first Bloch mode associated with the periodic structure of the medium. Though theoretical basis of the method already exists, there is no evidence of its numerical performance. The main goal of this paper is to report on some numerical experiments including a comparative study between both the classical and Bloch approaches. The important conclusion emerging from the numerical results states that θ^ε is closer to u^ε, i.e. is a better approximation of u^ε than the first‐ and second‐order corrector terms, specifically in the case of high‐contrast materials. Copyright © 2005 John Wiley & Sons, Ltd.