Coherent sets for nonautonomous dynamical systems

We describe a mathematical formalism and numerical algorithms for identifying and tracking slowly mixing objects in nonautonomous dynamical systems. In the autonomous setting, such objects are variously known as almost-invariant sets, metastable sets, persistent patterns, or strange eigenmodes, and have proved to be important in a variety of applications. In this current work, we explain how to extend existing autonomous approaches to the nonautonomous setting. We call the new time-dependent slowly mixing objects coherent sets as they represent regions of phase space that disperse very slowly and remain coherent. The new methods are illustrated via detailed examples in both discrete and continuous time.     

Level mixing resonances on oriented nuclei

The level crossing and level mixing resonance methods have been developed in order to enable the measurement of quadrupole interaction frequencies of nuclei with lifetimes between microseconds and minutes in solids. Both methods are shown to be better suited for application 1n this lifetime region than the existing ones. Only the level mixing resonance method can be applied to nuclei with lifetimes up to several minutes. A review of our level crossing and level mixing experiments is also given in this paper.     

水下干式储存取样的乏燃料破损检测技术

介绍了通用的乏燃料破损检测方法, 分析了已有的乏燃料破损检测技术存在的缺陷, 针对其缺陷以及根据自身的需求设计了新的乏燃料破损检测工艺与工作流程, 并介绍了检测样品的测量及样品与乏燃料包壳状态的判断依据。 实际应用结果表明: 该技术可以在水下实现一次对一批乏燃料进行逐个取样, 每个样品对应一盒确定的乏燃料, 检测效率高; 该采样系统对乏燃料的操作在水下进行, 现场辐射防护容易满足。 In the present article, several previous methods for damage detection of spent fuel assembly, as well as the existing limitations of these methods are reviewed. A new sampling system, including the working procedure and operating schedule, was developed in order to meet the practical demands and to solve the disadvantages mentioned. The measurement method for sampling and the criterion practical results provided evidence that, in this system, each operating process could successfully achieve a sample for a single certain spent fuel assembly with high precision. Moreover, all the operations were carried out under water, which made the radiation protection much easier.     

Construction of broadband homonuclear TOCSY sequences via numerical optimization

Some new isotropic mixing sequences have been designed via numerical optimization procedure. The performance of the isotropic mixing sequences generated here, has been assessed and compared with other existing sequences by computer simulation. The global quality factors for some of the present sequences are better, when compared to the sequences that are routinely used in the literature for TOCSY experiments.     

建立微尺度蒸发冷凝的通用准则

蒸发冷却模式以及微换热器,是最具有潜力的冷却高热流密度电子器件的方法之一。总结和研究微尺度蒸发冷凝相变机理,是本文研究目的。我们在参阅大量文献和提取大量精确数据的基础上,发现了新的区分常规通道与微通道的临界准则Bo×Re1^0.5=200;在此基础上,我们归纳出了新的预测微通道压降、传热系数和临界热流量的关联式,与以前...     

The prediction of flow-induced noise in heat exchanger tube arrays

A number of methods for the prediction of flow-induced acoustic standing waves in heat exchangers are recommended in the literature. The source for this noise has been assumed to be vortex shedding, turbulent buffeting or broadband turbulence and a variety of methods based on these have been proposed for predicting the occurrence of these standing wave resonances. Furthermore, parameters which estimate the capacity of a heat exchanger unit to dissipate acoustic energy and thus suppress such resonances have been suggested. As there has been no direct comparison of these various techniques, there is confusion as to the applicability of each. In this paper the merits of the techniques for predicting resonance are compared, with use of data from four independent sources, and a method for estimating the limit conditions for avoidance of resonance is recommended. In addition, the parameters for estimating the “damping capacity” of a tube bank are examined and shown to have limitations. A modified damping criterion is suggested and appears to correlate existing data well.     

Generalized Correntropy Criterion-Based Performance Assessment for Non-Gaussian Stochastic Systems

Control loop performance assessment (CPA) is essential in the operation of industrial systems. In this paper, the shortcomings of existing performance assessment methods and indicators are summarized firstly, and a novel evaluation method based on generalized correntropy criterion (GCC) is proposed to evaluate the performance of non-Gaussian stochastic systems. This criterion could characterize the statistical properties of non-Gaussian random variables more fully, so it can be directly used as the assessment index. When the expected output of the given system is unknown, generalized correntropy is used to describe the similarity of two random variables in the joint space neighborhood controlled and take it as the criterion function of the identification algorithms. To estimate the performance benchmark more quickly and accurately, a hybrid-EDA (H-EDA) combined with the idea of “wading across the stream algorithm” is proposed to obtain the system parameters and disturbance noise PDF. Through the simulation of a single loop feedback control system under different noise disturbances, the effectiveness of the improved algorithm and new indexes are verified.     

Stability of non-degenerate parametric soliton in quadratic media

The non-degenerate solitons due to three-wave mixing in a quadratic medium are analyzed. A new stability criterion for these solitons is found and verified numerically. The influence of the non-paraxial terms on the instability threshold is also discussed.     

Synchronization of chaotic Lur'e systems with delayed feedback control using deadzone nonlinearity

In this paper we present a synchronization method for chaotic Lur'e systems by constructing a new piecewise Lyapunov function. Using a delayed feedback control scheme, a delay-dependent stability criterion is derived for the synchronization of chaotic systems that are represented by Lur'e systems with deadzone nonlinearity. Based on the Lyapunov--Krasovskii functional and by using some properties of the nonlinearity, a new delay-dependent stabilization condition for synchronization is obtained via linear matrix inequality (LMI) formulation. The criterion is less conservative than existing ones, and it will be verified through a numerical example.     

Experimental Results on Neutrino Masses and Lepton Mixing

The experimental status of measrerments of neutrino masses and lepton flavour mixing is summarised. Limits of mass and mixing parameters obtained by different experimental techniques are given and the possibilities and limits of the different methods are discussed. Future projects are presented and their ability to verify existing results or to explore further regions of the mass and mixing parameter space is discussed.     

A Criterion to Identify Maximally Entangled Four-QubitState

Paolo Facchi, et al. [Phys. Rev. A77 (2008) 060304(R)] presented a maximally multipartite entangled state (MMES). Here, we give a criterion for the identification of maximally entangled four-qubit states. Using this criterion, we not only identify some existing maximally entangled four-qubit states in the literature, but also find several new maximally entangled four-qubit states as well.     

Approximation of joint PDFs by discrete distributions generated with Monte Carlo methods

A new method for the approximation of multivariate scalar probability density functions (PDFs) in turbulent reacting flow by means of a joint presumed discrete distribution (jPDD) is presented. The jPDDs can be generated with specified mean values and variances as well as covariances. Correlations between variables – e.g. fluctuating mixture fractions and/or reaction progress – can thereby be taken into account. In this way the new approach overcomes an important limitation of ordinary presumed PDF methods, where statistical independence between the variables is often assumed. Different methods are presented to generate discrete distributions, based either on biased random number generators or on mixing models familiar from PDF transport models.

The new approach is extensively validated on a turbulent flow configuration with simultaneous mixing and reaction. Large eddy simulation data as well as results from a transported PDF model are used for the validation of the jPDD approach. The comparison shows that in particular distributions generated with mixing models are able to predict mean reaction rates accurately. For the configuration considered, the neglect of correlations results in significant underestimation of reaction rates. Moreover it is found that higher statistical moments (e.g. the skewness) can influence reaction rates. The consequences for the generation of jPDDs are discussed.

In summary, the new jPDD model has the potential to be significantly more accurate than established presumed PDF methods, because correlations between fluctuating variables can be taken into account. At the same time, the new approach is nearly as efficient as standard presumed PDF formulations, since mean rates are computed in a pre-processing step and stored in look-up tables as a function of the first and second moments of the relevant variables.     

Projective synchronization of hyperchaotic system via periodically intermittent control

We further study the projective synchronization of a new hyperchaotic system. Different from the most existing methods, intermittent control is applied to chaotic synchronization in the present paper. We formulate the intermittent control system that governs the dynamics of the projective synchronization error, then derive the sufficient conditions for the exponential stability of intermittent control system by using Lyapunov stability theory, and finally establish the periodically intermittent controller according to the stability criterion by which the projective synchronization is expected to be achieved. The analytical results are also demonstrated by several numerical simulations.     

Projective synchronization of a hyperchaotic system via periodically intermittent control

We further study the projective synchronization of a new hyperchaotic system. Different from the most existing methods, intermittent control is applied to chaotic synchronization in the present paper. We formulate the intermittent control system that governs the dynamics of the projective synchronization error, then derive the sufficient conditions for the exponential stability of intermittent control system by using the Lyapunov stability theory, and finally establish the periodically intermittent controller according to the stability criterion by which the projective synchronization is expected to be achieved. The analytical results are also demonstrated by several numerical simulations.     

A novel knowledge-based potential for RNA 3D structure evaluation

Ribonucleic acids(RNAs) play a vital role in biology, and knowledge of their three-dimensional(3D) structure is required to understand their biological functions. Recently structural prediction methods have been developed to address this issue, but a series of RNA 3D structures are generally predicted by most existing methods. Therefore, the evaluation of the predicted structures is generally indispensable. Although several methods have been proposed to assess RNA 3D structures, the existing methods are not precise enough. In this work, a new all-atom knowledge-based potential is developed for more accurately evaluating RNA 3D structures. The potential not only includes local and nonlocal interactions but also fully considers the specificity of each RNA by introducing a retraining mechanism. Based on extensive test sets generated from independent methods, the proposed potential correctly distinguished the native state and ranked near-native conformations to effectively select the best. Furthermore, the proposed potential precisely captured RNA structural features such as base-stacking and base-pairing. Comparisons with existing potential methods show that the proposed potential is very reliable and accurate in RNA 3D structure evaluation.     

A new efficient two-channel backward algorithm for speech intelligibility enhancement: A subband approach

This paper addresses the problem of speech intelligibility enhancement by adaptive filtering algorithms employed with subband techniques. The two structures named the forward and backward blind source separation structures are extensively used in the speech enhancement and source separation areas, and largely studied in the literature with convolutive and non-convolutive mixtures. These two structures use two-microphones to generate the convolutive/non-convolutive mixing signal, and provide at the outputs the target and the jammer signal components. In this paper, we focus our interest on the backward structure employed to enhance the speech signal from a convolutive mixture. Furthermore, we propose a subband implementation of this structure to improve its behavior with speech signal. The new proposed subband-Backward BSS (SBBSS) structure allows a very important improvement of the convergence speed of the adaptive filtering algorithms when the subband-number is selected high. In order to improve the robustness of the proposed subband structure, we have adapted then applied a new criterion that combines the System Mismatch and the Mean-Errors criterion minimization. The proposed subband backward structure, when it is combined with this new criterion minimization, allows to enhance the output speech signal by reducing the distortion and the noise components. The performance of the proposed subband backward structure is validated through several objective criteria which are given and described in this paper.     

反应堆高阶κ本征方程数值计算方法的改进

针对反应堆高阶κ-本征方程数值计算问题，提出了提高计算效率和计算精度的改进方法，并以一维问题为例，对该方法进行了验证。The solution methods for the higher order oped yet in the nuclear reactor engineering. Based on harmonics and higher order eigenvalues are not well develthe analysis of the convergence process of power iteration, a new approach for setting the starting values of higher order harmonic flux has been proposed. The results of numerical tests demonstrate that the proposed method could effectively improve the efficiency of calculations of higher order harmonics. In addition, a new type of criterion that judges the convergence of higher order harmonics dynamically has been proposed, it has been verified that the new convergence criterion could effectively prevent the buildup of numerical errors introduced in the solution of lower order harmonics in the solution of higher order harmonics.     

基于声压振速联合信息处理的声矢量阵相干信号子空间方法

为解决水下宽带源的远程测向问题,提出了一种基于声压P与振速V的互谱矩阵的声矢量阵相干信号子空间方法。与现有的将声矢量传感器的振速信息仅仅作为独立阵元来处理的声矢量阵测向方法不同,新方法完全基于声压与振速联合信息处理,充分利用了声矢量阵中P-V互谱的抗噪能力,能将相干信号子空间方法的宽带高分辨能力及去相干能力与声矢量阵的抗噪能力有机地结合起来,实现对宽带源的远程、高分辨方位估计。理论分析给出了基于P-V互谱矩阵的宽带聚焦原理和特征分解原理,以及信源数检测准则。基于湖试数据的仿真实验结果显示,采用3元声矢量阵,在信噪比为-10dB和观测时间为20s时,新方法方位估计的均方根误差约为5°,明显强于现有方法。     

Dynamic Scaling in Miscible Viscous Fingering

We consider dynamic scaling in gravity driven miscible viscous fingering. We prove rigorous one-sided bounds on bulk transport and coarsening in regimes of physical interest. The analysis relies on comparison with solutions to one-dimensional conservation laws, and new scale-invariant estimates. Our bounds on the size of the mixing layer are of two kinds: a naive bound that is sharp in the absence of diffusion, and a more careful bound that accounts for diffusion as a selection criterion in the limit of vanishingly small diffusion. The naive bound is simple and robust, but does not yield the experimental speed of transport. In a reduced model derived by Wooding [20], we prove a sharp upper bound on the size of the mixing layer in accordance with his experiments. Woodings model also provides an example of a scalar conservation law where the entropy condition is not the physically appropriate selection criterion.