Research on data assimilation strategy of turbulent separated flow over airfoil

In order to increase the accuracy of turbulence field reconstruction, this paper combines experimental observation and numerical simulation to develop and establish a data assimilation framework, and apply it to the study of S809 low-speed and high-angle airfoil flow. The method is based on the ensemble transform Kalman filter(ETKF) algorithm, which improves the disturbance strategy of the ensemble members and enhances the richness of the initial members by screening high flow field sensitivity ...     

Comparison of chemometric methods for the screening of comprehensive two-dimensional liquid chromatographic analysis of wine

Two chemometric methods are compared for the rapid screening of comprehensive two-dimensional liquid chromatographic (LC × LC) analysis of wine. The similarity index and Fisher ratio methods were both found to be able to distinguish geographical variability and to determine potentially significant peaks for further quantitative and qualitative study. An experimental data set consisting of five different wine samples and multiple simulated data sets were analyzed in the investigation of the screening methods. Several statistical analyses are employed in the understanding and verification of the results from the similarity index and Fisher ratio methods. The sum rank difference (SRD) method was used to compare the rankings of the two different methods as applied to the different data sets and to determine the amount of variability associated with the ranking of the peak differences. The major advantage the similarity index method offers is that it is an unsupervised method; no a priori knowledge of the samples (i.e., class identification) is required, while the Fisher ratio method is supervised. Both methods are rapid and require little user intervention other than the determination of a threshold for inclusion/exclusion of compounds from further analysis.     

The exact likelihood for a multivariate ARMA model

A number of algorithms are presented for calculating the exact likelihood of a multivariate ARMA model. There are two aspects to the algorithms. Firstly, the parameterization is in terms of AR parameters and autocovariances. This obviates difficulties with initial MA estimates. Secondly, the algorithms explicitly account for specification of the lag structure of the multivariate time series. Additionally, an algorithm is presented to deal with missing data. The algorithms are, of themselves, not new but they have not been applied to likelihood construction in the manner discussed here.     

高消光比双通马赫-曾德尔干涉仪梳状滤波器

提出了一种新颖结构的高消光比双通马赫-曾德尔干涉仪梳状滤波器，将常规单通马赫-曾德尔干涉仪的两个输出端与光隔离器连接，构成一个双通马赫-曾德尔干涉仪梳妆滤波器，对滤波器的输出特性进行了理论分析和实验研究。数值模拟表明，与常规的单通马赫-曾德尔干涉仪相比，在相同参量的情况下该双通马赫-曾德尔干涉仪梳妆滤器的消光比得到了大大改善，消光比的提高取决于干涉仪的臂长差，当干涉仪的臂长差为0．7366mm时，消光比提高了20dB。实验结果表明，双通马赫-曾德尔干涉仪梳妆滤器的消光比为25．8dB，消光比提高了13dB。     

Hermite Interpolation in Loop Groups and Conjugate Quadrature Filter Approximation

A classical result of Weierstrass ensures that any continuous finite length trajectory in a vector space can be uniformly approximated by one whose coordinates are trigonometric functions. We derive an analogous result for trajectories in spheres and apply it to show that a continuous frequency response of a conjugate quadrature filter can be uniformly approximated by the frequency response of a finitely supported conjugate quadrature filter. We also extend this result, so as to preserve specified roots of the frequency response, and derive an approximation result for refinable functions whose integer translates are orthonormal. Our methods utilize properties of loop groups, jets, and the Brouwer topological degree. Mathematics Subject Classifications (2000) 22E67(Primary), 41A29(Secondary), 42A10, 42A11, 42C40, 47H10, 47H11.     

422.7nm法拉第反常色散滤光特性

对工作在第ｇ条夫朗和费暗线（４２２．６７４ｎｍ）的法拉第反常色散滤光器的滤光特性进行了理论分析和讨论。     

New approach to applying neural network in nonlinear dynamic model

In this work, radial basis function neural network (RBF-NN) is applied to emulate an extended Kalman filter (EKF) in a data assimilation scenario. The dynamical model studied here is based on the one-dimensional shallow water equation DYNAMO-1D. This code is simple when compared with an operational primitive equation models for numerical weather prediction. Although simple, the DYNAMO-1D is rich for representing some atmospheric motions, such as Rossby and gravity waves. It has been shown in the literature that the ability of the EKF to track nonlinear models depends on the frequency and accuracy of the observations and model errors. In some cases, just fourth-order moment EKF works well, but will be unwieldy when applied to high-dimensional state space. Artificial Neural Network (ANN) is an alternative solution for this computational complexity problem, once the ANN is trained offline with a high order Kalman filter, even though this Kalman filter has high computational cost (which is not a problem during ANN training phase). The results achieved in this work encourage us to apply this technique on operational model. However, it is not yet possible to assure convergence in high dimensional problems.     

Application of the Filter Diagonalization Method to One- and Two-Dimensional NMR Spectra

A new non-Fourier data processing algorithm, the filter diagonalization method (FDM), is presented and applied to phase-sensitive 1D and 2D NMR spectra. FDM extracts parameters (peak positions, linewidths, amplitudes, and phases) directly from the time-domain data by fitting the data to a sum of damped complex sinusoids. Grounded in a quantum-mechanical formalism, FDM shares some of the features of linear prediction and other linear algebraic approaches, but is numerically more efficient, scaling like the fast Fourier transform algorithm with respect to data size, and has the ability to correctly handle spectra with thousands or even millions of lines where the competing methods break down. Results obtained on complex spectra are promising.     

X射线荧光光谱成型滤纸片法测定生油岩抽提物中的钒和镍

本文提出以成型滤纸片作为标样与试样的支撑材料，点滴法制备样片，用钒和镍的有机金属标准试剂配制标准样品，以透空照射法直接测定生油岩抽提物中的钒和镍，方法检出限较低，制样与测量精度好于５％。方法简单、快速和实用。     

THz波段的F-P光子晶体滤波器

理论上设计了一系列一维非周期光子晶体，这些光子晶体具有超窄带滤波的特性.并利用成熟的半导体工艺制备出了具有此性能的滤波器.通过比对理论和实验上的透射光谱，得到了两者符合较好的结果. 关键词： THz波段 F-P滤波器 非周期 光子带隙