A collision algorithm for anisotropic disperse flows based on ellipsoidal parcel representations

In this study, a new approach to the prediction of collision probabilities is proposed, which is specifically derived for Lagrangian Monte Carlo simulations of highly anisotropic disperse flows. The collision probability formulation eliminates the influence of the collision mesh by introduction of a parcel diameter. Two non-parametric parcel diameter estimators are given, an isotropic parcel diameter estimator for homogeneous droplet clouds, and an anisotropic parcel diameter estimator for inhomogeneous droplet clouds of reduced dimensionality, which obtains an ellipsoidal parcel representation from a weighted principal component analysis of the parcel population. The new formulation effectively reduces the parameters for spatial resolution from two (mesh size, number of parcels) to one (number of parcels only). For validation, simple synthetic test cases are run that allow a comparison of the collision probability formulation to purely stochastic and purely deterministic schemes. Dependence on numerical parameters is tested exemplary with a highly anisotropic hollow-cone spray for gasoline direct injection.     

电感耦合等离子体质谱法检测氧化镓中杂质元素

建立了电感耦合等离子体质谱法(ICP-MS)测定氧化镓中杂质元素的检测方法,采用微波消解技术溶样,以5 ng/mL Rh为内标补偿校正镓基体的抑制效应,采用碰撞室技术(CCT)消除多元素分子离子的干扰.方法的检出限为0.10～1.0 ng/mL,加标回收率在85%～110%之间,RSD为0.6%～7.1%.该方法能满足99.95%～99.995%氧化镓中杂质元素的分析要求.     

电感耦合等离子体串联质谱法测定野生皂荚中多种微量元素

采用电感耦合等离子体串联质谱(ICP-MS/MS)法测定野生皂荚中多种微量元素的含量。皂荚样品以HNO₃+H₂O₂+HCl为混合消解试剂经微波消解后直接测定。在MS/MS模式下向碰撞反应池中通过氧气或氨气,分别利用氧气质量转移、氧气原位质量和氨气质量转移消除多原子离子质谱干扰。通过分析国家标准参考物质绿茶(GBW10052)和芹菜(GBW10048)验证方法的准确性和精密度,所测定结果与参考值基本一致,RSD≤7.8%。采用所建立的方法分别分析了来自中国云南和重庆武陵山区野生皂荚中的12种微量元素(V,Cr,Co,Cu,Zn,Fe,Mn,Ni,As,Cd,Hg,Pb),12种微量元素的检出限为0.29～21.36 ng·L-1。结果显示,野生皂荚12种分析元素中Fe含量最高,其次为元素Zn,重金属元素As,Cd,Hg和Pb的含量远低于《中国药典》限量标准。该研究为野生皂荚中微量元素的安全评价和监管提供了科学方法和数据。     

Collision Dynamics of an Energetic Carbon Ion Impinging on the Stone-Wales Defect in a Single-walled Carbon Nanotube

By employing atomistic simulations based on an empirical potential model and a self-consistent-charge density-functional tight-binding method, the collision dynamics process of an energetic carbon ion impinging on the Stone-Wales defect in a single-walled carbon nanotube was investigated. The outwardly and inwardly displacement threshold energies for the primary knock-on atom in the Stone-Wales defect were calculated to be 24.0 and 25.0 eV, respectively. The final defect configuration for each case was a 5-1DB-T(DB=dangling bond) defect formed in the front surface of the nanotube. Moreover, the minimum incident energy of the projectile prompting the primary knock-on atom displacement was predicted to be 71.0 eV, and the time evolutions of the kinetic and potential energies of the projectile and the primary knock-on atom were both plotted to analyze the energy transfer process.     

Electron density of the magnesium XII doublet in the solar corona by use of a collision excitation model

For accurate spectroscopic diagnostics in the solar corona, the principle of spectral diagnostics of electron density is discussed by collision excitation model. Variation in electron density in the solar corona is calculated by this method using the observed signal ratio of spectral lines produced by the magnesium XII ion in the solar corona. Results show that with increasing signal ratio, the electron density will decrease; furthermore, the electron density is on the order of 10¹⁰?cm^?3, which is a reasonable value in the solar corona. Finally, variation in temperature with different signal ratio is discussed. This investigation will be significant for solar plasma diagnostics and study on the solar coronal.     

电感耦合等离子体串联质谱法分析麻疯树油中的多元素

工业化和现代化进程的加快消耗了大量能源,对能源的高度依赖性导致了全球化石能源需求的快速增长,随着非再生化石能源的日渐枯竭,迫切需要大力发展可再生能源以调整现有能源结构。作为国际上研究最多的生物柴油,麻疯树油是国内外公认的最有可能替代化石能源的再生能源,具有极大的开发潜力。麻疯树油中的微量元素在燃烧过程中会影响发动机的性能,并在尾气排放过程中决定了对环境所造成的污染程度。本文以获得麻疯树油中多元素的含量为目的,建立应用电感耦合等离子体串联质谱(ICP-MS/MS)法准确测定麻疯树油中低水平Na,Si,P,S,Cl,K,Ti,V,As含量的分析方法。采用微波密闭消解系统,依次向麻疯树油样品中加入硝酸和双氧水进行消解。详细地研究了各待测元素在不同分析模式下检出限(DL)和背景等效浓度(BEC)的变化情况,在MS/MS模式下,通过向碰撞/反应池(CRC)中加入反应气可以完全消除质谱干扰。选择O₂为反应气,P+,S+,Ti+,V+,As+与O₂的反应均为放热过程,能发生质量转移自发生成PO+,SO+,TiO+,VO+,AsO+,利用O₂质量转移法消除质谱干扰;选择H₂为反应气,Cl+与H₂反应能自发生成ClH+₂,利用H₂质量转移法消除质谱干扰,而Na+,Si+,K+均不能与H₂发生质量转移反应,利用H₂原位质量法消除质谱干扰。选择Sc为内标元素校正了分析过程中的基体效应。通过考察不同反应气流速下各元素的BEC变化,优化了反应气流速,O₂的最佳流速为0.45 mL·min-1,H₂的最佳流速为7.5 mL·min-1。在优化的实验条件下获得Na,Si,P,S,Cl,K,Ti,V,As的检出限分别为6.41,37.3,24.6,118,530,7.96,7.61,0.34,3.20 ng·L-1,各元素在0～50 μg·L-1范围内的线性相关系数(R2)≥0.999 8,方法具有良好的线性关系。采用三水平加标回收实验来验证方法的准确性和精密度,所有元素的加标回收率在91.2%～108%之间,相对标准偏差(RSD)为1.9%～4.6%,表明所建立的方法准确性好,精密度高。通过对来自中国不同地区的4个麻疯树油样品进行测定,结果显示,4个麻疯树油样品中P含量≤164 ng·g-1,S含量≤2310 ng·g-1,碱(Na+K)含量≤1 690 ng·g-1,三项指标均达到了中国生物柴油调和燃料国家标准,欧Ⅳ生物柴油标准,德国生物柴油标准和美国生物柴油标准。这项研究为麻疯树油中多种微量元素的准确分析提供了一种方便可行的新方法,为麻疯树油的质量控制和安全应用提供了科学的理论依据。     

Studies on Fragmentation of Peptide by Nano-electrospray Ionization Fourier Transform Ion Cyclotron Resonance Multi-stage Tandem Mass Spectrometry

The sequence analysis of peptides was performed by nano-electrospray ionization Fourier transform ion cyclotron resonance tandem mass spectrometry(Nano-ESI-FT-ICR-MSn) and several peptides were chosen as examples. With the aid of the collision induced dissociation(CID), FT-ICR provides not only precise mass/charge ratio, but also structure information of the selected peptides. The fragment ions were identified according to the observed molecular weights and peptide sequence was determined successfully. So Nano-ESI-FT-ICR-MSn is a useful tool for identification of the amino acid sequence of peptides with high confidence. Besides, a pathway for the dehydration of y ions without amino acids containing carboxylic acid under sustained off-resonance irradiation collision-induced dissociation(SORI-CID) condition was proposed.     

Construction of Discrete Kinetic Models with Given Invariants

We consider the general problem of the construction of discrete kinetic models (DKMs) with given conservation laws. This problem was first stated by Gatignol in connection with discrete models of the Boltzmann equation (BE) and it has been addressed in the last decade by several authors. Even though a practical criterion for the non-existence of spurious conservation laws has been devised, and a method for enlarging existing physical models by new velocity points without adding non-physical invariants has been proposed, a general algorithm for the construction of all normal (physical) discrete models with assigned conservation laws, in any dimension and for any number of points, is still lacking in the literature. We introduce the most general class of discrete kinetic models and obtain a general method for the construction and classification of normal DKMs. In particular, it is proved that for any given dimension d≥2 and for any sufficiently large number N of velocities (for example, N≥6 for the planar case d=2) there exists just a finite number of distinct classes of DKMs. We apply the general method in the particular cases of discrete velocity models (DVMs) of the inelastic BE and elastic BE. Using our general approach to DKMs and our results on normal DVMs for a single gas, we develop a method for the construction of the most natural (from physical point of view) subclass of normal DVMs for binary gas mixtures. We call such models supernormal models (SNMs) (they have the property that by isolating the velocities of single gases involved in the mixture, we also obtain normal DVMs).     

等离子体的三频点微波透射衰减诊断方法

 依据微波在等离子体中的传播特性,并利用微波透射非磁化等离子体时在三个相邻频率点的透射能量衰减值,可同时诊断等离子体中的电子密度和电子碰撞频率。使用该方法对100～700 Pa范围内氦气辉光放电等离子体进行了诊断,选择6.2,6.8和7.4 GHz三个频率点,并与使用双探针诊断的诊断结果进行比较。结果表明：两种诊断方法所得碰撞频率基本一致;微波透射衰减法诊断出的电子密度值与探针法的诊断结果在同一数量级(1016 m^-3),但前者约是后者的1.67倍。最后对造成这一差异的原因进行了分析。三频点微波透射衰减诊断方法可用于较高气压及其它静电探针使用受限的环境下,并且可以采用能量较小的微波,不会对等离子体本身造成显著影响,适用于等离子体的初步诊断。     

线型离子阱中冷却离子所需高纯度氦气的渗透与实验

利用氦的渗透性质,向超高真空系统中充入高纯度氦缓冲气体,可以降低离子阱中囚禁离子的运动速度,减小二级多普勒频移,增加离子的存储时间,提高线型离子阱微波频标的稳定度.实验上得到了氦气渗透的实验参数、特性以及对系统真空度的影响、实现了用温度调节精确的控制充入氦气的分压强.