Synthesis of efficient Vulcan–LaMnO3 perovskite nanocomposite for the oxygen reduction reaction

In situ autocombustion has been developed as a novel and efficient route for the synthesis of perovskite–carbon nanocomposites for the oxygen reduction reaction (ORR) in alkaline media. We demonstrate the synthesis of crystalline LaMnO_3 + δ perovskite–Vulcan composite with a high accessibility of active sites and high electronic conductivity required for efficient electrocatalysis. The rotating disc electrode measurements evidenced an excellent activity of the composite for the ORR.     

Identification of metabolites of rupestonic acid in rat urine by liquid chromatography combined with electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry

Rupestonic acid, a potential anti‐influenza agent, is an important and characteristic compound in Artemisia rupestris L., a well‐known traditional Uighur medicine for the treatment of colds. In the present study, high‐performance liquid chromatography combined with electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry was used to detect and identify the metabolites in rat urine after oral administration of rupestonic acid. A total of 10 metabolites were identified or partially characterized. The structure elucidations of the metabolites were performed by comparing the changes in accurate molecular masses and fragment ions with those of the parent compound. The results showed that the main metabolites of rupestonic acid in rat urine were formed by oxidation, hydrogenation and glucuronidation. A metabolism pathway was proposed for the first time based on the characterized structures. This metabolism study can provide essential information for drug discovery, design and clinical application of rupestonic acid. Copyright © 2014 John Wiley & Sons, Ltd.     

演化算法求解桁架多目标拓扑优化的收敛速度研究

演化算法能够同时满足结构拓扑优化的前沿领域对全局优化、黑箱函数优化、组合优化和多目标优化的需求,但采用此类算法的可行性与必要性由其收敛性与计算效率决定。本文以应力约束桁架多目标拓扑优化问题为求解对象,致力于揭示在收敛性与计算效率两方面具有竞争力的算法。首先提出评估演化算法求解拓扑优化问题收敛性与计算效率的通用方法,采用穷举法严格推导了典型桁架多目标拓扑优化问题的全局最优解,并采用超体积指标定义了多层次收敛性能准则。最后通过比较研究得到不同收敛性需求下具有最快收敛速度的演化算法,并揭示了具有竞争力的算法机制。本研究为演化算法求解多目标拓扑优化问题的收敛速度奠定了理论基础,同时为高效求解实际工程拓扑优化问题提供算法支持。     

开放式多体系统动力学仿真算法软件研发(Ⅱ)DAEs求解算法对比

研究求解微分-代数方程组(DAEs)的高效率、高精度和高稳定性数值积分方法一直是多体系统动力学领域的热点问题之一。本文将求解结构动力学方程的Bathe数值积分策略应用于DAEs的求解,并基于SiPESC平台开发了开放式多体系统动力学仿真算法软件,综合比较研究了Newmark法、HHT-I3法、Generalizedα方法、Bathe方法和祖冲之类Symplectic方法。通过复摆、刚-柔耦合双摆和对称陀螺三个数值算例研究了算法参数与数值阻尼的关系。数值实验表明,Newmark方法在特定参数下引入的数值阻尼通常不可控,HHT-I3方法、Generalizedα方法和Bathe方法通过选择特定步长和参数可引入可控的数值阻尼,祖冲之类Symplectic方法无数值阻尼。在求解真实高频和低频耦合问题以及高速旋转的陀螺问题时,采用祖冲之类Symplectic方法或者无耗散的Newmar方法能够对系统的高频成分进行准确模拟。     

An identification method to estimate surface shortwave fluxes on temperature and thickness observations of sea ice in CHINARE 2006

In this paper, a parameter identification method to determine surface shortwave fluxes using temperature and thickness measurements of sea ice in CHINARE 2006 is presented. Adopting a new standard for the calculation of the thermodynamic properties of seawater named TEOS‐10, the surface shortwave fluxes are calculated by the temperature and thickness observations that were measured at Nella Fjord around Zhongshan Station, Antarctica. New simulations for temperature profiles in a different measurement period are performed by three parameterization schemes including the present method, Zillman and Shine. All numerical results are compared with in situ measurements. Results show that better simulations of the surface shortwave radiations and temperature distributions are possible with the identification method than Zillman and Shine. Therefore this method is valid, and the obtained shortwave radiation function can be applied in sea ice modeling. Copyright © 2015 John Wiley & Sons, Ltd.     

A coupled immersed boundary‐lattice Boltzmann method with smoothed point interpolation method for fluid‐structure interaction problems

The immersed boundary‐lattice Boltzmann method has been verified to be an effective tool for fluid‐structure interaction simulation associated with thin and flexible bodies. The newly developed smoothed point interpolation method (S‐PIM) can handle the largely deformable solids owing to its softened model stiffness and insensitivity to mesh distortion. In this work, a novel coupled method has been proposed by combining the immersed boundary‐lattice Boltzmann method with the S‐PIM for fluid‐structure interaction problems with large‐displacement solids. The proposed method preserves the simplicity of the lattice Boltzmann method for fluid solvers, utilizes the S‐PIM to establish the realistic constitutive laws for nonlinear solids, and avoids mesh regeneration based on the frame of the immersed boundary method. Both two‐ and three‐dimensional numerical examples have been carried out to validate the accuracy, convergence, and stability of the proposed method in consideration of comparative results with referenced solutions.