On the decay rates of Timoshenko system with second sound

In this work, we study the well‐posedness and the asymptotic stability of a one‐dimensional linear thermoelastic Timoshenko system, where the heat conduction is given by Cattaneo's law and the coupling is via the displacement equation. We prove that the system is exponentially stable provided that the stability number χ_τ=0. Otherwise, we show that the system lacks exponential stability. Furthermore, in the latter case, we show that the solution decays polynomially. Copyright © 2015 John Wiley & Sons, Ltd.     

Spatial resonance and Turing–Hopf bifurcations in the Gierer–Meinhardt model

Gierer–Meinhardt system as a molecularly plausible model has been proposed to formalize the observation for pattern formation. In this paper, the Gierer–Meinhardt model without the saturating term is considered. By the linear stability analysis, we not only give out the conditions ensuring the stability and Turing instability of the positive equilibrium but also find the parameter values where possible Turing–Hopf and spatial resonance bifurcation can occur. Then we develop the general algorithm for the calculations of normal form associated with codimension-2 spatial resonance bifurcation to better understand the dynamics neighboring of the bifurcating point. The spatial resonance bifurcation reveals the interaction of two steady state solutions with different modes. Numerical simulations are employed to illustrate the theoretical results for both the Turing–Hopf bifurcation and spatial resonance bifurcation. Some expected solutions including stable spatially inhomogeneous periodic solutions and coexisting stable spatially steady state solutions evolve from Turing–Hopf bifurcation and spatial resonance bifurcation respectively.     

Zero Expectile Processes and Bayesian Spatial Regression

We introduce new classes of stationary spatial processes with asymmetric, sub-Gaussian marginal distributions using the idea of expectiles. We derive theoretical properties of the proposed processes. Moreover, we use the proposed spatial processes to formulate a spatial regression model for point-referenced data where the spatially correlated errors have skewed marginal distribution. We introduce a Bayesian computational procedure for model fitting and inference for this class of spatial regression models. We compare the performance of the proposed method with the traditional Gaussian process-based spatial regression through simulation studies and by applying it to a dataset on air pollution in California.     

Efficient Spatial Modeling Using the SPDE Approach With Bivariate Splines

Gaussian fields (GFs) are frequently used in spatial statistics for their versatility. The associated computational cost can be a bottleneck, especially in realistic applications. It has been shown that computational efficiency can be gained by doing the computations using Gaussian Markov random fields (GMRFs) as the GFs can be seen as weak solutions to corresponding stochastic partial differential equations (SPDEs) using piecewise linear finite elements. We introduce a new class of representations of GFs with bivariate splines instead of finite elements. This allows an easier implementation of piecewise polynomial representations of various degrees. It leads to GMRFs that can be inferred efficiently and can be easily extended to nonstationary fields. The solutions approximated with higher order bivariate splines converge faster, hence the computational cost can be alleviated. Numerical simulations using both real and simulated data also demonstrate that our framework increases the flexibility and efficiency. Supplementary materials are available online.     

Volumetric behaviour of the (2,2,4-trimethylpentane + methylbenzene + butan-1-ol) ternary system and its binary sub-systems within the temperature range (298.15–328.15) K

Densities and speeds of sound of the (2,2,4-trimethylpentane + methylbenzene + butan-1-ol) ternary system as well as all its binary sub-systems were measured at four temperatures, namely 298.15 K, 308.15 K, 318.15 K, and 328.15 K at atmospheric pressure by a vibrating-tube densimeter DSA 5000. The binary (isooctane + toluene) system was studied previously. Excess quantities (molar volume, adiabatic compressibility, and isobaric thermal expansivity) of the mixtures studied were calculated from the experimental densities and speed of sounds. The excess molar volume data were correlated using the Redlich–Kister equation. Both the positive and S-shaped excess molar volume curves were found for the systems studied. The excess molar volumes versus concentration of binary systems differed in the shape and temperature dependence. The experimental binary data were compared with literature data. The experimental excess molar volumes were analyzed by means of the Extended Real Associated Solution (ERAS) model. The experimental data and the ERAS model can help to estimate real behaviour of the systems studied.     

基于大科学装置的空间金属组学和单细胞/单颗粒金属组学

金属组学是综合研究生命体内（(特别是细胞内）)自由或络合的全部金属原子的分布、含量、化学种态及其功能的一门学科,而大科学装置为金属组学研究提供了强有力的工具。本综述本文首先介绍了金属组学发展简史,然后介绍了基于大科学装置的同步辐射技术、中子技术、质子技术及缪子技术等,最后概述了基于大科学装置的空间金属组学、单细胞/单颗粒金属组学的应用示例。基于大科学装置的中子活化技术（NAA）NAA、X-射线荧光光谱（XRF）以及质子激发X射线谱（PIXE ）等技术是开展非原位空间金属组学研究的有力手段,而XRF、PIXE以及缪子X射线荧光谱（MXA）为开展原位空间金属组学提供了有力工具,特别是基于XRF的技术,其空间分辨率可低至10 nm级别,是开展原位单细胞/单颗粒金属组学的利器。 新一代同步辐射光源、质子源及缪子源将为空间金属组学、特别是时空金属组学研究提供更强有力工具。     

A stationary population model with an interior interface-type boundary

We propose a stationary system that might be regarded as a migration model of some population abandoning their original place of abode and becoming part of another population, once they reach the interface boundary. To do so, we show a model where each population follows a logistic equation in their own environment while assuming spatial heterogeneities. Moreover, both populations are coupled through the common boundary, which acts as a permeable membrane on which their flow moves in and out. The main goal we face in this work will be to describe the precise interplay between the stationary solutions with respect to the parameters involved in the problem, in particular the growth rate of the populations and the coupling parameter involved on the boundary where the interchange of flux is taking place.     

基于等效密度流体模型的地声参数分析

目前的地声参数反演多采用液态海底模型,但是实际海底为多孔弹性海底。该文在等效密度流体模型基础上,通过计算液态海底和多孔弹性海底的反射系数及传播损失,给出了等效密度流体模型和液态海底模型的等效性分析。数值仿真结果表明在低频情况下,多孔弹性海底给出的快纵波声速与等效密度流体模型给出的声速以及等效密度流体的实部与真实的海底密度基本一致。将等效密度流体模型近似看作液态海底模型进行反射系数和传播损失计算,在小掠射角和远距离时,计算结果表明与多孔弹性海底计算结果具有较好一致性,从而以此为依据确定海底为液态,进行地声参数反演。     

新型列车侧墙内装板声学分析、优化及应用*

为了开发与应用新型列车车体降噪内装结构,基于混合FE-SEA法对轨道车辆用新型橡胶泡棉夹芯板进行隔声与声辐射预测建模,并进行了试验验证,进而利用该模型分析了橡胶泡棉孔隙率与芯皮厚度比对其隔声性能、声辐射性能的影响规律,并通过敷设阻尼层优化了其声学性能。最后,在侧墙组合结构的声学设计中评价了其实际应用效果。结果表明：随着孔隙率的逐步下降,橡胶泡棉夹芯板隔声量上升趋势较为明显,而辐射声功率持续降低;随着芯皮厚度比的逐步提高,夹芯板隔声量呈略微上升趋势,辐射声功率则相应降低。在远离声源一侧的橡胶泡棉蒙皮外侧敷设阻尼层的效果最优,优化后夹芯板计权隔声量提高0.7dB,总声功率级降低0.7dB;相较于传统木质胶合板和铝蜂窝板,橡胶泡棉夹芯板相较于传统内装板材在结构隔声设计中具有轻量化优势。