CMMB中MFS码流分析及实现

针对CMMB在视音频解码播放及码流检测等应用的需要,对CMMB系统帧结构、码流复用标准等进行分析,提出了MFS码流分析解复用的一套方案,并且应用嵌入式系统进行了实现,提出了硬件实现框图、系统软件的设计及实现流程等关键内容.     

Sound Propagation Analysis on Sonic Crystal Elastic Structures using the Method of Fundamental Solutions (MFS)

The study of periodic structures, namely sonic crystals, for sound attenuation purposes has been a topic of intense research in the last years. Some efficient methods are available in literature to solve the problem of sound propagation in the presence of this kind of structures such as those based in the Multiple Scattering Theory (MST) or the Finite Element Method (FEM). In this paper a solution based on the Method of Fundamental Solutions (MFS) which presents advantages, namely in computational discretization and calculation costs, is presented. The proposed formulation considers the presence of elastic ring shaped scatterers, correctly accounting for their interaction with the host fluid. The model accuracy is tested by comparing it to FEM in an exemplificative case. A set of numerical examples is then presented and the results compared with the ones given by a MFS approach where the structure is considered as rigid. The results showed that in the case of low-contrasting between solid/fluid properties, the elastic behavior of the structure could not be neglected.     

Major Facilitator Superfamily Transporter Gene FgMFS1 Is Essential for Fusarium graminearum to Deal with Salicylic Acid Stress and for Its Pathogenicity towards Wheat

Wheat is a major staple food crop worldwide, due to its total yield and unique processing quality. Its grain yield and quality are threatened by Fusarium head blight (FHB), which is mainly caused by Fusarium graminearum. Salicylic acid (SA) has a strong and toxic effect on F. graminearum and is a hopeful target for sustainable control of FHB. F. graminearum is capable of efficientdealing with SA stress. However, the underlying mechanisms remain unclear. Here, we characterized FgMFS1 (FGSG_03725), a major facilitator superfamily (MFS) transporter gene in F. graminearum. FgMFS1 was highly expressed during infection and was upregulated by SA. The predicted three-dimensional structure of the FgMFS1 protein was consistent with the schematic for the antiporter. The subcellular localization experiment indicated that FgMFS1 was usually expressed in the vacuole of hyphae, but was alternatively distributed in the cell membrane under SA treatment, indicating an element of F. graminearum in response to SA. ΔFgMFS1 (loss of function mutant of FgMFS1) showed enhanced sensitivity to SA, less pathogenicity towards wheat, and reduced DON production under SA stress. Re-introduction of a functional FgMFS1 gene into ∆FgMFS1 recovered the mutant phenotypes. Wheat spikes inoculated with ΔFgMFS1 accumulated more SA when compared to those inoculated with the wild-type strain. Ecotopic expression of FgMFS1 in yeast enhanced its tolerance to SA as expected, further demonstrating that FgMFS1 functions as an SA exporter. In conclusion, FgMFS1 encodes an SA exporter in F. graminearum, which is critical for its response to wheat endogenous SA and pathogenicity towards wheat.     

Stable Boundary and Internal Data Reconstruction in Two-Dimensional Anisotropic Heat Conduction Cauchy Problems Using Relaxation Procedures for an Iterative MFS Algorithm

We investigate two algorithms involving the relaxation of either the given boundary temperatures (Dirichlet data) or the prescribed normal heat fluxes (Neumann data) on the over-specified boundary in the case of the iterative algorithm of Kozlov91 applied to Cauchy problems for two-dimensional steady-state anisotropic heat conduction (the Laplace-Beltrami equation). The two mixed, well-posed and direct problems corresponding to every iteration of the numerical procedure are solved using the method of fundamental solutions (MFS), in conjunction with the Tikhonov regularization method. For each direct problem considered, the optimal value of the regularization parameter is chosen according to the generalized cross-validation (GCV) criterion. The iterative MFS algorithms with relaxation are tested for over-, equally and under-determined Cauchy problems associated with the steady-state anisotropic heat conduction in various two-dimensional geometries to confirm the numerical convergence, stability, accuracy and computational efficiency of the method.     

Regularized MFS-Based Boundary Identification in Two-Dimensional Helmholtz-Type Equations

We study the stable numerical identification of an unknown portion of the boundary on which a given boundary condition is provided and additional Cauchy data are given on the remaining known portion of the boundary of a two-dimensional domain for problems governed by either the Helmholtz or the modified Helmholtz equation. This inverse geometric problem is solved using the method of fundamental solutions (MFS) in conjunction with the Tikhonov regularization method. The optimal value for the regularization parameter is chosen according to Hansen's L-curve criterion. The stability, convergence, accuracy and efficiency of the proposed method are investigated by considering several examples.     

Wave Propagation around Thin Structures using the MFS

This paper presents a strategy for using the Method of Fundamental Solutions (MFS) to model the propagation of elastic waves around thin structures, like empty cracks or thin rigid screens, located in a homogeneous elastic medium. The authors make use of a simple approach for modeling these propagation conditions using the MFS together with decomposition of the domain into distinct regions. This approach makes it possible to avoid the undetermined system of equations that arises from imposing boundary conditions at both sides of a thin structure. The numerical implementation of the MFS is performed in the frequency domain, making use of the Fundamental Solutions defined by Tadeu and Kausel (2000) for the propagation of elastic waves generated by a 2.5D load located in an unbounded domain. Using this formulation, it is then possible to model 3D structures which have a constant cross-section in the z direction. This calculation is performed by decomposing the 3D response into a sequence of 2D responses computed for different wave-numbers along z.
The first part of the paper describes the formulation of the method in detail, also presenting the Fundamental Solutions used. Then, the method is verified by comparing its results against those given by a frequency domain formulation of the Traction Boundary Element Method (TBEM). \newline A final section of the paper presents a sample application which illustrates the applicability of the method to study the wave propagation around a thin rigid screen, embedded in a fluid medium. For this case, time domain responses are computed and presented in the form of snapshots.     

罗丹明B的荧光猝灭法测定钢铁中微量钨

本文研究了在酸介质中,NaCl存在的条件下,罗丹明B与钨酸根WO_4~_(2-)络合生成三元络合物使罗丹明B试剂荧光猝灭。以365 nm为最大激发波长,测定594 nm最大发射荧光强度。用钠型Dowex50W—X4离子交换树脂胶柱交换分离溶液中共存的磷酸根、重铬酸根、Cr~(3+)、Fe~(3+)等干扰离子,利用罗丹明B荧光强度减弱的程度和钨含量呈线性关系,测定钢样中微量钨。     

MOSIX集群系统中DFSA机制研究

MOSIX是基于Linux的集群计算系统,它通过抢占式进程迁移使负载在集群节点间达到均衡。DFSA(DirectFileSystemAccess)是一种能够提高集群文件系统性能的机制,它允许迁移的进程直接访问当前节点上的文件。MOSIX通过其文件系统MFS(MOSIXFileSystem)引入了对DFSA的支持,实现了把进程迁移到数据的策略。文中简要介绍了MOSIX系统,然后对DFSA机制进行了分析,最后研究了MOSIX中DFSA机制的实现。     

基于流形特征相似度的感知图像质量评价

图像质量评价（Image quality assessment, IQA）的目标是利用设计的计算模型得到与主观评价一致的结果,而人类视觉感知特性是感知图像质量评价的关键.大量研究发现,认知流形和拓扑连续性是人类感知的基础即人类感知局限在低维流形之上.基于图像低维流形特征分析,本文提出了基于流形特征相似度（Manifold feature similarity, MFS）的全参考图像质量评价方法.首先,利用正交局部保持投影算法来模拟大脑的视觉处理过程获取最佳映射矩阵进而得到图像的低维流形特征,通过流形特征的相似度来表征两幅图像的结构差异,从而反映感知质量上的差异.其次,考虑亮度失真对人眼视觉感知的影响,通过图像块均值计算亮度相似度并用于评价图像的亮度失真;最后,结合两个相似度得到图像的客观质量评价值.在四个公开图像测试库上的实验结果表明,所提出方法与现有代表性的图像质量方法相比总体上具有更好的评价结果.     

Theoretical studies of the capacitance‐voltage characteristics of metal‐ferroelectric‐GaN structures

We have simulated the capacitance versus voltage characteristics (C‐V) of metal‐ferroelectric‐gallium nitride (GaN metal‐ferroelectric‐semiconductor) structures and found useful design rules for improving the devices' performance. The thickness effects of ferroelectric film on the C‐V are studied. When the ferroelectric Pb(Zr, Ti)O3 thickness is no more than 100 nm, the GaN metal‐ferroelectric‐semiconductor structures can approach inversion just under 5 V, which is the generally applied voltage used in semiconductor‐based integrated circuits. This marked improvement of C‐V behaviors is mainly due to the high dielectric constant and large polarization of the ferroelectric gate oxide. Copyright © 2011 John Wiley & Sons, Ltd.