Inverse spectral problems for differential pencils on the half-line with turning points

The inverse spectral problem of recovering pencils of second-order differential operators on the half-line with turning points is studied. We establish properties of the spectral characteristics, give a formulation of the inverse problem, prove a uniqueness theorem and provide a constructive procedure for the solution of the inverse problem.     

不可压缩流动的移动粒子半隐式法数值模拟

介绍了一种新的移动粒子半隐式方法。该方法采用Lagrange描述,用一系列离散粒子代替流体,通过半隐式求解和时间推进法来进行计算,弥补了传统网格法对复杂形状、大变形、高速撞击等情况下网格划分和重构过于繁琐的缺点,在模拟不可压缩流动问题中得到了较好的效果。     

沿垂等温平板的自然对流问题的近似解析解

本文用加权残值得到了沿垂等温平板的自然对流问题的近似解析解。和已有准确解的比较表明，在平板表面附近，近似解有很好的精度，而且速度场的精度比温度场更好一些。文末还对配域法的准收敛问题作了说明。     

三阶非线性发展方程的线性化有理逼近方法

研究了三阶非线性发展方程的初边值问题的解。采用基于Sinc函数的微分求积法发展了线性化有理逼近方法。通常的配点法不适用于上述三阶问题的求解。本文把提出的方法用于求解KdV方程,取得了良好的效果。     

准静态离散元方法和线性粘弹性问题的模拟

离散元方法是近年发展起来的一种新数值方法,但原则上只能用于动态问题。从静力平衡条件出发建立了离散元系统的准静态演化方程并证明了系数矩阵具有对称正定、稀疏、带状分布等特点,适用于“有效列”方法求解,该解法比高斯消去法节省更多的内存和机时。通过引入广义Maxwell体的元间作用模型建立起线性粘弹性材料准静态响应的离散元模拟方法。该方法独立于传统动态离散元方法,是传统动态离散元方法的拓展,可望在更多领域获得应用。     

Pressurised liquid extraction and quantification of fat-oil in bread and derivatives products

A pressurised liquid extraction (PLE) method for extraction and quantification of total fat and oil in bread and derivatives products has been proposed. Parameters implied in the extraction process; such us temperature, static time, number of extraction cycles, purge time and flush volume; have been optimised using a formal methodology based on statistical experimental design in order to obtain the best results. Moreover, this method has been validated using homemade bread elaborated in the laboratory which contained 9.64 g of olive oil in 100 g dry weight. The production and use of an “ad hoc” in-house reference material is just one of the most relevant aspects of this study. The uncertainty estimation has been carried out taking into account all the uncertainty components of the process and it was stated as 4.2%. Finally, the proposed method has been applied to six different Spanish bread derivatives products with different olive oil contents (5-20%) to determine the fat content.     

Ce-EU-1分子筛的合成和表征

采用水热法,以溴化六甲双铵（HMBr2）为模板剂,硅溶胶、偏铝酸钠为硅铝源,以六水硝酸铈为铈源合成了稀土Ce-EU-1分子筛,并通过XRD、FTIR、紫外-可见漫反射光谱、热重分析（TG-DTG）和氮气吸附-脱附等测试手段对合成样品的孔道结构、物化性能及Ce的存在状态进行了表征。XRD结果表明,合成样品不仅具有很高的纯度和结晶度,为典型的立方有序排列的EU-1结构,而且部分Ce已取代Si或Al进入微孔分子筛的骨架。样品的FTIR图谱在980cm-1附近有明显的Si—O—Ce特征吸收峰,证明Ce存在于分子筛的骨架中。紫外-可见漫反射图谱显示,在253nm附近出现O—Ce之间的电子跃迁特征峰,进一步证明了Ce进入了分子筛骨架。氮气吸附-脱附结果表明了Ce的掺入对分子筛的物化性能和孔道结构产生了影响。同时考察了镧系其他金属离子（Ln：La、Nd、Sm和Gd）对EU-1分子筛的影响,发现随着镧系离子半径的减小,Ln-EU-1分子筛的相对结晶度逐渐降低,晶胞体积减小。     

毛细管电泳分离-激光诱导荧光检测血清中的巴氯芬

首次将新合成的柱前衍生试剂6-氧-（N-琥珀酰亚胺乙酸酯）-9-（2′-甲氧羰基）荧光素（SAM F）用于巴氯芬（B aclofen）的衍生标记,并采用毛细管电泳分离-激光诱导荧光（CE-L IF）法分离检测衍生物。研究表明,在磷酸盐缓冲溶液（pH=7.5）介质中,30℃下10m in即可完成衍生反应。反应物在pH 5.6,35mm o.lL-1的磷酸盐缓冲溶液中12m in内达到分离,检出限为6×10-10m o.lL-1。本法用于血清中巴氯芬的分析测定,回收率为95.8%—101.0%。     

罗替戈汀微球体外释放度的检查方法

分别采用摇床法和流通池法测定罗替戈汀微球的体外释放度,并通过与体内药动学曲线拟合进行选择.结果表明,摇床法和流通池法测定的体外释放度均与体内吸收具有明显相关性,相关系数r分别为0.9937和0.9978,且流通池法可检测到微球存在的较小突释.摇床法和流通池法均可用于罗替戈汀微球的体外释放度检查,流通池法作为一种新型溶出...     

Physalis method for heterogeneous mixtures of dielectrics and conductors: Accurately simulating one million particles using a PC

Prosperetti’s seminal Physalis method, an Immersed Boundary/spectral method, had been used extensively to investigate fluid flows with suspended solid particles. Its underlying idea of creating a cage and using a spectral general analytical solution around a discontinuity in a surrounding field as a computational mechanism to enable the accommodation of physical and geometric discontinuities is a general concept, and can be applied to other problems of importance to physics, mechanics, and chemistry. In this paper we provide a foundation for the application of this approach to the determination of the distribution of electric charge in heterogeneous mixtures of dielectrics and conductors. The proposed Physalis method is remarkably accurate and efficient. In the method, a spectral analytical solution is used to tackle the discontinuity and thus the discontinuous boundary conditions at the interface of two media are satisfied exactly. Owing to the hybrid finite difference and spectral schemes, the method is spectrally accurate if the modes are not sufficiently resolved, while higher than second-order accurate if the modes are sufficiently resolved, for the solved potential field. Because of the features of the analytical solutions, the derivative quantities of importance, such as electric field, charge distribution, and force, have the same order of accuracy as the solved potential field during postprocessing. This is an important advantage of the Physalis method over other numerical methods involving interpolation, differentiation, and integration during postprocessing, which may significantly degrade the accuracy of the derivative quantities of importance. The analytical solutions enable the user to use relatively few mesh points to accurately represent the regions of discontinuity. In addition, the spectral convergence and a linear relationship between the cost of computer memory/computation and particle numbers results in a very efficient method. In the present paper, the accuracy of the method is numerically investigated by example computations using one dielectric particle, one isolated conductor particle, one conductor particle connected to an external source with imposed voltage, and two conductor/dielectric particles with strong interactions. The efficiency of the method is demonstrated with one million particles, which suggests that the method can be used for many important engineering applications of broad interest.