BEM SOLUTION FOR THE PROBLEM OF FLUX OF A MULTICOMPONENT MIXTURE OF GASES OUT OF A MULTILAYER LANDFILL

A two-dimensional numerical model for convection–diffusion flow of a multigas mixture through a multilayer porous medium was developed with the aim to be used for evaluation of emissions of gases from landfills. The proposed model is based on the boundary element–dual reciprocity method. Time-independent one-dimensional analytical solutions for a multilayer domain were found for the cases of a single gas and a two-gas mixture and used to verify the accuracy of the model. Although the proposed technique is a simple one, consisting only of boundary integrals, it was found that the technique can be applied with satisfactory accuracy to the problem at which it was initially aimed.     

The influence of the carrier gas on retention in capillary gas-solid chromatography

In capillary gas-solid chromatography where interactions between solute and carrier gas and adsorption of the solute on the surface of the adsorbent are considered to be imperfect, it has been shown that chromatographic retention is determined largely by adsorption processes. It has been established that correlation relationships k(P₂)=A k(P₁) + B, where k is the retention factor, and A and B are equation constants, was valid for use of different carrier gases P₁ and P₂. Column efficiency could be improved by use of carbon dioxide. The advantages of using carbon dioxide as the carrier gas were investigated.     

Effects of Thermally Induced Roton-Like Excitation on the Superfluid Density of a Quasi-2D Dipolar Bose Condensed Gas

Using the Green's function approach, the density–density correlation function and the dielectric function in the random-phase approximation for a quasi-two-dimensional (quasi-2D) dipolar Bose gas are derived. From the pole of the density correlation function, by considering thermally induced roton-like excitations, the excitation spectrum of the system is calculated. It is shown that the position and depth of the roton minimum of the excitation spectrum are tunable by changing the temperature. To show how the position of the roton minimum influences the phenomenon of superfluidity, the superfluid density of the system is obtained and it is shown that the interplay of the thermal rotonization, contact and dipole–dipole interaction (DDI) can affect the superfluid fraction of a quasi-2D Bose gas. It is found that contact, DDI interactions, and thermally induced rotons enhance the fluctuations and reduce the superfluid density. In the absence of DDI and thermally induced rotons, the usual T³ dependence of superfluid density in 2D is obtained and the correction T⁴ term arises from DDI. It is shown that if the roton minimum is close to zero, the thermally induced rotons change the linear temperature dependence of the superfluid fraction, leading to a transition to nontrivial supersolid phase.     

Adsorption Equilibrium of Binary Mixtures in Zeolites and State of Adsorbed Phase

The criterion of ideal behavior of a mixture of a few molecules within a separate zeolite cavity is formulated on the basis of the statistical thermodynamics. The criterion determines the dependence of the Helmholtz free energy, internal energy, and entropy of a molecular aggregate on the ratio of the number of molecules of components 1 and 2. The similarity between this criterion and the criterion of ideal behavior for bulk solutions is shown. Expressions of excess thermodynamic functions of the molecular mixture in a cavity are obtained. The negative magnitude of these excess functions is proposed to be due to rearrangement of molecules under influence of energetic heterogeneity. The calculation procedure of the excess functions has been demonstrated for the system CO₂-C₂ H₆-zeolite NaX, the information of both isotherms and isosteric adsorption heats being used simultaneously. The approach offered allows the state of adsorbed mixture in a separate cavity to be analyzed from pure-component and multicomponent experimental data.     

日本产在线气相色谱仪柱填料的国产化

介绍了用于监测环氧丙烷生产车间原料气组成的日本产在线气相色谱仪柱填料国产化的研制工作。经大量的测试与比较,选出了４种固定相用以代替原进口柱内填充物,经模拟与现场测试,效果好。     

石墨炉原子吸收光谱法测定纯金中痕量铋

以乙酸乙酯萃取样品中基体金,将萃取样品后的含金的乙酸乙酯作为基体改进剂加入到铋标准溶液中,使得标准与样品的基体组成匹配,用石墨炉原子吸收法测定水相样品中的铋.并对石墨炉加热程序中的干燥时间、灰化温度及原子化温度进行了考察,探讨基体改进剂、介质酸度、萃取效率及共存的离子对测定的影响.方法特征量为8.3pg,检出限为2.26μg/L,相对标准偏差为1.89%-3.69%,回收率在93%-106%之间.该方法的精密度高,回收率好,且具有快速、简便的特点.     

中药无患子中金属元素的测定

本文采用火焰原子吸收光谱法和石墨炉原子吸收光谱法对中草药无患子茎部的Fe、Cu、Zn、Mn、Ca、Pb的含量进行了测定,方法简单、精密度好、回收率在94.34%-104.60%之间,结果令人满意.     

石墨炉原子吸收光谱法和ICP-AES测定水中镍的比较研究

通过对比石墨炉原子吸收光谱法和ICP-AES测定水中痕量镍的含量,发现ICP-AES具有直接进样、测量稳定、校准曲线线性范围宽等特点;而石墨炉原子吸收法需要较高的原子化温度,容易损坏石墨管.该方法经过t检验证明与标准方法无显著性差异,加标回收率为96.2%-105%,可以代替石墨炉原子吸收光谱法.