The band gap and transmission characteristics investigation of local resonant quaternary phononic crystals with periodic coating

In this article, the investigation of the Lamb wave propagation in two-dimensional phononic crystals (PCs) composed of an array of periodic coating on a thin plate is presented. Compared with the traditional PCs usually consist of cylindrical scatters with uniform coatings in their exterior structure, the newly exterior coating structures with periodic alternant arrangement of two different materials are proposed. The band structures are calculated using finite element method. We discover that a complete band gap can be exhibited at low frequency. Furthermore, for a finite PCs plate, the computed transmission and resonance spectra shown an evident resonance nature which can be directly related to formation of the low-frequency gaps. The effects of different material parameters and arrangement mode of coating on the acoustic energy transmission and attenuation are also studied. Finally, the experimental transmission spectrum of the periodic coating PCs are also presented and compared with the numerical results. This study will provide useful support to the design of tuning band gaps and isolators in the low-frequency range.     

Novel matrix invariants for characterization of changes of proteomics maps

Previous studies on mathematical characterization of proteomics maps by sets of map invariants were based on the construction of a set of distance-related matrices obtained by matrix multiplication of a single matrix by itself. Here we consider an alternative characterization of proteomics maps based on a set of matrices characterizing local features of an embedded zigzag curve over the map. It is shown that novel invariants can well characterize proteomics maps. Advantages of the novel approach are discussed.     

甲硫醇在Cu(111)表面的解离吸附: 密度泛函理论研究

采用基于密度泛函理论的第一性原理方法和平板模型研究了CH₃SH分子在Cu(111)表面的吸附反应.系统地计算了S原子在不同位置以不同方式吸附的一系列构型, 第一次得到未解离的CH₃SH分子在Cu(111)表面顶位上的稳定吸附构型,该构型吸附属于弱的化学吸附, 吸附能为0.39 eV. 计算同时发现在热力学上解离结构比未解离结构更加稳定. 解离的CH₃S吸附在桥位和中空位之间, 吸附能为0.75-0.77 eV. 计算分析了未解离吸附到解离吸附的两条反应路径, 最小能量路径的能垒为0.57 eV. 计算结果还表明S―H键断裂后的H原子并不是以H₂分子的形式从表面解吸附而是以与表面成键的形式存在. 通过比较S原子在独立的CH₃SH分子和吸附状态下的局域态密度, 发现S―H键断裂后S原子和表面的键合强于未断裂时S原子和表面的键合.     

一种新的珍珠层厚度测量方法

珍珠层厚度是是珍珠价值最主要的衡量指标之一,目前珍珠层厚度的无损测量方法主要采用光学相干层析成像技术和X射线技术。光学相干层析成像技术在实际测量时精度较低。在研究X射线测量原理的基础上,提出了一种新的珠层厚度测量方法。首先介绍了灰度图像的边缘识别算法和珍珠核、珍珠外圆度拟合算法,其次提出了一种引入对照机制的珍珠层测量算法,最后还对算法的误差进行了分析,算法的误差可以控制在0.02%以内。实际的测量也验证了本测量方法具有很高的精度。     

Resonant equations with the Neumann p-Laplacian plus an indefinite potential

We consider a nonlinear Neumann problem driven by the p  -Laplacian plus an indefinite potential and a Carathéodory reaction which at ±∞ is resonant with respect to any nonprincipal variational eigenvalue of the differential operator. Using critical point theory and Morse theory (critical groups), we show that the problem has at least three nontrivial smooth solutions, two of which have constant sign. In the process we prove some results of independent interest concerning the unique continuation property of eigenfunctions and the critical groups at infinity of a C¹$C^1$-functionals.     

Pitfalls in X-ray absorption spectroscopy analysis and interpretation: A practical guide for general users

Despite the growing popularity of X-ray absorption spectroscopy (XAS) in scientific research, many researchers do not receive formalized training on this technique. Some of them learned from online resources, which only briefly introduce XAS and its applications. Here, this article aims to provide the overview of tips about the XAS analysis, general rules, as well as required information for presenting XAS data in publications, and some common mistakes in XAS data interpretations. Armed with these basics, the motivated aspiring XAS researchers will find existing resources more accessible and can progress much faster in understanding and using XAS.     

Measuring local pH in electrochemistry

Localized pH measurements are important in various areas of electrochemistry, from corrosion to bio-electrochemistry and electrocatalysis. Different techniques are available to perform these measurements and offer numerous possibilities in terms of spatial and temporal resolution, sensitivity, and precision. In this brief review we present the recent progress made and summarize the main techniques available for localized pH measurements in electrochemistry such as scanning probe techniques (SECM, SICM, SIET), laser (confocal) fluorescence microscopy, rotating ring-disc electrode (RRDE) voltammetry, and infra-red spectroscopy, among others.     

Research on application of polynomial fitting technique in rotary kiln infrared temperature measurement system

Aiming at the linear temperature compensation algorithm’s disadvantage of temperature measurement error in rotary kiln infrared scanning temperature measurement process, this paper proposes a precise nonlinear cubic polynomial fitting temperature compensation algorithm. The proposed algorithm compensates the temperature values of scanning points on rotary kiln surface by following steps: Calculating temperature difference between the real temperature value of rotary kiln and temperature value measured by infrared scanning temperature measurement system; Fitting the temperature difference data with cubic polynomial; Using the obtained function to compensate temperature. Experimental result shows that compared with the usual linear temperature compensation algorithm, the accuracy of proposed algorithm has raised about 2.25 times when cubic polynomial is used.     

Fitting of deuterium quadrupole echo spectra with multiple motional models

Dynamic information is generally extracted from deuterium quadrupole echo spectra by matching a spectrum calculated for a particular motional model to the experimental spectrum. In this work, a set of computer programs has been written to facilitate fitting of calculated spectra to experimental spectra that represent from one to five motional models. The fitting program requires pre-calculated libraries of spectra for the models of interest, and accomplishes the fitting either by a systematic method or by simulated annealing. The systematic method is convenient for fitting with one or two motional models, but the simulated annealing method is faster for two or more models, if the libraries are made up of hundreds of spectra. The parameter Q, with the standard deviation of the spectral points estimated as the standard deviation of the baseline noise, provides a stringent measure of goodness of fit. Acceptable fits of experimental data as judged by this criterion have not been found, even in the case of ring flip motion in phenylalanine-d(5) in which the fit may be judged acceptable by eye. An example of fitting with isotropic and methyl rotation motional models of alanine-d(3), which have distinct spectral patterns, shows that it is possible to obtain reasonably accurate estimates of the relative amounts of deuterium representing the different models, even from poorly fitted spectra.