嵌入到Fabry-Perot谐振腔的双晶约瑟夫森结阵列的阻抗匹配和相位锁定研究

在He等人所做的嵌入到Fabry-Perot谐振腔中约瑟夫森结阵列的微波辐照研究基础上,提出了同时实现约瑟夫森结阵列阻抗匹配和相位锁定的方法,进行了相关的电磁仿真和数值计算.双晶约瑟夫森结阵列被制作在YSZ双晶基片上,同时被嵌入到Fabry-Perot谐振腔内.通过在基片上制作与结阵列集成的串联馈电半波偶极天线阵,并对其结构进行优化实现了结与天线的匹配,数值计算表明结的辐射效率达到94%;利用天线阵辐射场的特征和对模型合理的设计,使Fabry-Perot谐振腔和基片同时谐振在合适的模式下,从而使结阵列与谐 关键词： 约瑟夫森结阵列 阻抗匹配 相位锁定 Fabry-Perot谐振腔     

Efficient exponential-time algorithms for edit distance between unordered trees

The edit distance problem for rooted unordered trees is known to be NP-hard. Based on this fact, this paper studies exponential-time algorithms for the problem. For a general case, an $O(\min ({1.26}^{n_1+n_2},2^{b_1+b_2}\cdot \text{<mi mathvariant="italic" is="true">poly</mi>}(n_1,n_2)))$ time algorithm is presented, where $n_1$ and $n_2$ are the numbers of nodes and $b_1$ and $b_2$ are the numbers of branching nodes in two input trees. This algorithm is obtained by a combination of dynamic programming, exhaustive search, and maximum weighted bipartite matching. For bounded degree trees over a fixed alphabet, it is shown that the problem can be solved in $O({(1+ϵ)}^{n_1+n_2})$ time for any fixed $ϵ>0$. This result is achieved by avoiding duplicate calculations for identical subsets of small subtrees.     

Large deviation properties for patterns

Deciding whether a given pattern is over- or under-represented according to a given background model is a key question in computational biology. Such a decision is usually made by computing some p-values reflecting the “exceptionality” of a pattern in a given sequence or set of sequences. In the simplest cases (short and simple patterns, simple background model, small number of sequences), an exact p-value can be computed with a tractable complexity. The realistic cases are in general too complicated to get such an exact p-value. Approximations are thus proposed (Gaussian, Poisson, Large deviation approximations). These approximations are applicable under some conditions: Gaussian approximations are valid in the central domain while Poisson and Large deviation approximations are valid for rare events. In the present paper, we prove a large deviation approximation to the double strands counting problem that refers to a counting of a given pattern in a set of sequences that arise from both strands of the genome. In that case, dependencies between a sequence and its reverse complement cannot be neglected. They are captured here for a Bernoulli model from general combinatorial properties of the pattern. A large deviation result is also provided for a set of small sequences.     

Reduced order fully coupled structural–acoustic analysis via implicit moment matching

A reduced order model is developed for low frequency, undamped, fully coupled structural–acoustic analysis of interior cavities backed by flexible structural systems. The reduced order model is obtained by applying a projection of the coupled system matrices, from a higher dimensional to a lower dimensional subspace, whilst preserving essential properties of the coupled system. The basis vectors for projection are computed efficiently using the Arnoldi algorithm, which generates an orthogonal basis for the Krylov Subspace containing moments of the original system. The key idea of constructing a reduced order model via Krylov Subspaces is to remove the uncontrollable, unobservable and weakly controllable, observable parts without affecting the transfer function of the coupled system. Three computational test cases are analyzed, and the computational gains and the accuracy compared with the direct inversion method in ANSYS.     

有限元计算中疏密网格过渡方法研究

工程计算中出于节省计算量的目的,往往需要在一个有限元模型中布置粗细不同的网格。为保证计算结果的准确性,必须保证网格突变情况下的位移协调问题。本文工作之一是在强天驰界面过渡单元的基础上,引入虚拟节点和子单元,在子单元中应用节理元思想,提出了基于最小势能原理的弹簧节理单元法。简化了积分运算,避免了精度要求极高的坐标转换,从而提高了方法的精度和实用性;二是提出了基于位移约束的主从自由度法,简便实用,只需简单的矩阵运算即可实现。两种方法均实现了不同尺寸网格间位移的协调性和刚度的匹配,从而使之满足有限元收敛准则,且生成的刚度阵具有对称性及带状性。算例证明两种方法精度良好,并可方便地应用于求解大规模工程问题。     

基于重力场特征参数信息熵的适配区选择方法

针对当前重力统计特征参数类别繁多,选择标准复杂而导致错选有效匹配区域的问题,利用信息熵具有能够整合多种统计参数且算法计算量小的特点,提出了一种基于特征参数信息熵的重力辅助导航适配区的选择方法。首先,在DTU10模型下将该方法与传统单一特征参数的方法进行比较,确定了传统方法的确会错误选择可匹配区,从而也反映了所提出方法的优越性;其次,在该方法划分出的匹配区和非匹配区中分别设计了8条仿真航线,匹配区中仿真航线的匹配效果明显优于非匹配区中的匹配效果。仿真结果表明了该方法的有效性。     

Convection laminaire forcée dans le sillage d'une plaque chaude placée dans un canal

In this Note, a numerical investigation of laminar convection wake above a heated plate placed in a channel is carried out. An analytical study based on a three region structure is proposed in the immediate neighbourhood of the trailing edge. Velocity and temperature at the centerline channel as well as the pressure gradient are presented in asymptotic expressions. Comparison of these results with numerical solutions enhances the analytical study. To cite this article: Z. Doulfoukar, A. Achiq, C. R. Mecanique 333 (2005).     

大陀螺零偏条件下的快速传递对准算法

针对某些某些微机械陀螺零偏重复性差的特点,提出了滤波反馈修正和陀螺零偏粗对准预处理两种方法,使“速度＋姿态”快速传递对准算法在大陀螺零偏条件下能够不损失估计精度。在简要介绍“速度＋姿态”．决速传递对准算法数学模型的基础上,探讨了大陀螺零偏导致的惯导系统非线性误差。为减小上述非线性误差的影响,提出用每一步滤波估计值修正子掼导状态的反馈修正方法,和在进行卡尔曼滤波前直接测量比较主、子惯导陀螺输出的陀螺零偏粗对准预处理方法。仿真结果表明,采用上述两种方法,快速传递对准算法可在陀螺零偏过大的情况下保持算法的有效性和估计精度。     

基于激光陀螺自适应补偿的船体变形测量方法

基于长期变形、动态挠曲变形以及陀螺随机零偏的状态方程,构建了激光陀螺测量的惯性姿态匹配最优滤波器,可以实时地估计出船体变形角。针对实时估计的长期变形角具有偏置误差的问题,推导了惯性姿态匹配的误差方程,指出动态挠曲变形角与船体惯性姿态角之间具有长时间的交叉相关耦合作用导致了长期变形角估计具有偏置误差,并提出了对输入到最优滤波器的激光陀螺角增量进行自适应补偿的方法来抑制偏置误差。实验结果表明,补偿后俯仰角、横滚角和艏挠角的偏置误差均方根均小于5″,较补偿前降低均方根误差约为5″,该自适应补偿方法可有效地抑制偏置误差,提高惯性姿态匹配方法在船体变形测量应用中的有效性。     

基于初始位置的高速公路快速地图匹配算法

针对车辆行驶在高速公路过程中,传统地图匹配算法存在大量冗余检索时间,且消除垂直误差后仍存在水平误差等问题,设计了一种基于初始定位信息的快速地图匹配算法。该算法首先利用初始定位点到候选路段的距离与夹角确定车辆所行驶道路,然后考虑道路网拓扑结构和连通性,将后续定位点直接投影到初始确定的道路上,减少检索道路的时间;同时为提高算法的精确度,在引用初始定位信息时,通过设置距离阈值剔除定位数据漂移点,并利用一元线性方程建立HP模型以消除水平误差。经理论计算和实际测试表明,该算法利用初始获得的7个连续定位点,能准确检索出车辆正在行驶的道路,节省36%的检索时间,借助HP模型可以减少定位点与车辆实际位置之间45%的投影误差。因此,与连续匹配算法和垂直投影方式相比,该算法具有检索过程简单、检索准确率高、误差消除大的优势。