保留指数结合准确质量测定对鱼腥草挥发性成分的定性分析

采用顶空-气相色谱-四极质谱法和顶空-气相色谱-飞行时间质谱法对鱼腥草挥发性成分进行检测,运用保留指数结合准确质量测定,分别从鱼腥草茎和叶中鉴定出49、39种挥发性组分,并采用峰面积归一化法测定各组分的相对含量。鱼腥草茎和叶中的挥发性成分差别较大。鱼腥草茎以α-蒎烯(12.24%)、β-蒎烯(22.42%)、月桂烯(11.98%)、乙酸冰片酯(10.97%)、甲基正壬酮(10.83%)为主要成分,而鱼腥草叶则以月桂烯(39.48%)、(Z)-β-罗勒烯(26.52%)、癸醛(10.35%)、桧烯(4.43%)、甲基正壬酮(2.44%)为主。结合保留指数和准确质量测定能显著提高质谱定性的准确性,有利于解决质谱检索时定性不确定的问题。     

Optimal Runge–Kutta smoothers for the p-multigrid discontinuous Galerkin solution of the 1D Euler equations

This work presents a family of original Runge–Kutta methods specifically designed to be effective relaxation schemes in the numerical solution of the steady state solution of purely advective problems with a high-order accurate discontinuous Galerkin space discretization and a p-multigrid solution algorithm. The design criterion for the construction of the Runge–Kutta methods here developed is different form the one traditionally used to derive optimal Runge–Kutta smoothers for the h-multigrid algorithm, which are designed in order to provide a uniform damping of the error modes in the high-frequency range only. The method here proposed is instead designed in order to provide a variable amount of damping of the error modes over the entire frequency spectrum. The performance of the proposed schemes is assessed in the solution of the steady state quasi one-dimensional Euler equations for two test cases of increasing difficulty. Some preliminary results showing the performance for multidimensional applications are also presented.     

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.     

A stable and accurate projection method on a locally refined staggered mesh

In this paper, a robust projection method on a locally refined mesh is proposed for two‐ and three‐dimensional viscous incompressible flows. The proposed method is robust not only when the interface between two meshes is located in a smooth flow region but also when the interface is located in a flow region with large gradients and/or strong unsteadiness. In numerical simulations, a locally refined mesh saves many grid points in regions of relatively small gradients compared with a uniform mesh. For efficiency and ease of implementation, we consider a two‐level blocked structure, for which both of the coarse and fine meshes are uniform Cartesian ones individually. Unfortunately, the introduction of the two‐level blocked mesh results in an important but difficult issue: coupling of the coarse and fine meshes. In this paper, by properly addressing the issue of the coupling, we propose a stable and accurate projection method on a locally refined staggered mesh for both two‐ and three‐dimensional viscous incompressible flows. The proposed projection method is based on two principles: the linear interpolation technique and the consistent discretization of both sides of the pressure Poisson equation. The proposed algorithm is straightforward owing to the linear interpolation technique, is stable and accurate, is easy to extend from two‐ to three‐dimensional flows, and is valid even when flows with large gradients cross the interface between the two meshes. The resulting pressure Poisson equation is non‐symmetric on a locally refined mesh. The numerical results for a series of exact solutions for 2D and 3D viscous incompressible flows verify the stability and accuracy of the proposed projection method. The method is also applied to some challenging problems, including turbulent flows around particles, flows induced by impulsively started/stopped particles, and flows induced by particles near solid walls, to test the stability and accuracy. Copyright © 2010 John Wiley & Sons, Ltd.     

关于在已完成楼面上加设200t重水箱的结构处理分析

为改变现有建筑物的部分使用功能而需要增加设备的情况屡见不鲜。若需增加的设备质量较大,不能直接放在楼面上,就需要对原有结构进行加固修改。讨论了在已完成楼面上加设200t重水箱的结构处理问题。     

有限截面度对现浇混凝土空心楼盖内力的影响

介绍了现浇空心楼盖的技术优势,分析了有效截面度对现浇混凝土空心楼盖内力的影响,并得出了相应的结论。     

贺西煤矿3~#煤层瓦斯尾巷底鼓机理及控制技术研究

贺西煤矿3#煤层在回采过程中,瓦斯尾巷底鼓非常严重,严重影响下一工作面的正常使用,致使采掘衔接紧张,本文以3#煤层工作面瓦斯尾巷为背景,深入分析瓦斯尾巷底鼓量大的主要因素,剖析巷道底鼓机理,以FLAC3D数值模拟为主要手段,针对实际情况选择合理底鼓控制措施。工业性试验结果表明,工作面瓦斯尾巷巷道支护状况良好,底鼓问题基本得到了解决。     

具有中国特色的精确农业初探

介绍了精准农业的概念及其在国内外的发展状况，重点论述了具有中国特点的精准农业体系及实施步骤。     

用小量程电压表作精密测量实验研究

1 原理为了准确地测量直流稳压电源输出电压的微小变化△V_o,通常采用多位直流数字电压表测量.但直流数字电压表价值昂贵,在设备条件不许可的情况下,也可采用简便的补偿法来测量.补偿法的原理是用小量程的直流电压表借助参考电源来测量较高电压的微小变化     

低温热水地板辐射采暖技术

介绍了低温热水地板辐射采暖的系统形式、构造、特点，并简单阐述了其采暖热负荷计算和系统设计原则，指出它与传统的对流采暖方式相比，具有节能、节约占地空间，便于分户计量等特点。