超临界二氧化碳中布洛芬响应因子的研究

应用高压紫外检测器在线测定了布洛芬在超临界二氧化碳中的响应因子。 考察了温度、压力和CO2密度等参数对它的影响。在温度298-333K、压力9-17MPa范围内超临界CO2中布洛芬的响应因子随CO2密度的增加而线性递减。建立了布洛芬在超临界CO2中响应因子的经验计算式(回归系数r=0．97)，其理论计算结果与实验数据吻合良好，最大误差≤10％。     

Detection of C,H, N,and O in capillary gas chromatography by atomic emission

Using a new atomic emission detector for gas chromatography, the quantitative and qualitative aspects of selective elemental detection of carbon, hydrogen, nitrogen, and oxygen were investigated. Sensitivity, precision, degree of tailing, and response variation between compounds are reported for capillary applications. Earlier atomic emission detectors reported poor sensitivity and selectivity for the analysis of oxygen. These problems have been greatly reduced due to lower interactions between elements in the sample and the silica wall of the water-cooled discharge tube. Using near-optimal sample amounts and chromatographic conditions, area precision was found to be very good with little variation in response factors among different compounds. For the compounds tested, response factors varied over a span of 2% to 3% for carbon, hydrogen, and nitrogen, and over 7% for oxygen. For quantitative analysis, area ratios were calibrated directly from the area ratios of two elements of an internal standard, and yielded better precision and compound independence than the individual calibrated response of each element. Empirical formulas were calcualted using one peak as a qualitative internal standard. Unambiguous formulas were determined for some, but not all, of the compounds tested. Further increases in precision and/or compound independence is needed before empirical formula determination can be used as a routine tool.     

氨基苯磺酸和氨基萘磺酸在反相色谱中的保留行为

本文考察了冲洗剂中强组分浓度、无机盐浓度和酸度对保留值的影响,结果表明在溶质的 lnk 与 C_b 间线性关系中不能包括 C_b=0时的实验点。同时还观察到线性回归的 a 值与C_b=0时实测的 lnk′值存在较好的线性关系,酸度对 k′值的影响较复杂;溶质的保留值随无机盐浓度的增加而增大。     

纤维素酶降解纤维素机理的研究

纤维素是自然界中含量最多的一类碳水化合物,同时它也是地球上数量最大的可再生资源。纤维素酶是一种高活性生物催化剂,在纤维素类资源的利用方面发挥重要的作用。本文综述了纤维素、纤维素酶的分子结构和纤维素酶对纤维素的降解机理,影响酶解的主要因素以及提高酶解效率的主要措施,并对纤维素酶研究存在的问题以及今后的发展作了进一步展望。     

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分析了机械通风房间气流分岔的原因和主要影响参数. 首先根据射流理论,结 合数值模拟结果,通过分析Coanda效应在平面射流和集中射流中的作用,解释了平面射流相 对出射时可能出现分岔、而集中射流一般不出现分岔的原因,得出Coanda效应是引起分岔的 主要机理. 然后采用正交试验理论和方差分析法分析了影响分岔的参数,找到显著性因子, 并得出分岔强度和主要影响因子之间的关系.     

ANALYSIS OF A CRACK IN A FUNCTIONALLY GRADED STRIP WITH A POWER FORM SHEAR MODULUS

The plane strain problem of a crack in a functionally graded strip with a power form shear modulus is studied. The governing equation in terms of Airy＇s stress function is solved exactly by means of Fourier transform. The mixed boundary problem is then reduced to a system of singular integral equations and is solved numerically to obtain the stress intensity factor at crack-tip. The maximum circumferential stress criterion and the strain energy density criterion are both employed to predict the direction of crack initiation. Numerical examples are given to show the influence of the material gradation models and the crack sizes on the mode-I and mode-II stress intensity factors. The dependence of the critical kink-angle on the crack size is examined and it is found that the crack kink-angle decreases with the increase of the normalized crack length, indicating that a longer crack tends to follow the original crack-line while it is much easier for a shorter crack to deviate from the original crack-line.     

Analysis of dynamic stress intensity factors of thick-walled cylinder under internal impulsive pressure

Dynamic stress intensity factors are evaluated for thick-walled cylinder with a radial edge crack under internal impulsive pressure. Firstly, the equation for stress intensity factors under static uniform pressure is used as the reference case, and then the weight function for a thick-walled cylinder containing a radial edge crack can be worked out. Secondly, the dynamic stresses in uncracked thick-walled cylinders are solved under internal impulsive pressure by using mode shape function method. The solution consists of a quasi-static solution satisfying inhomogeneous boundary conditions and a dynamic solution satisfying homogeneous boundary condi- tions, and the history and distribution of dynamic stresses in thick-walled cylinders are derived in terms of Fourier-Bessel series. Finally, the dynamic stress intensity factor equations for thick-walled cylinder containing a radial edge crack sub- jected to internal impulsive pressure are given by dynamic weight function method. The finite element method is utilized to verify the results of numerical examples, showing the validity and feasibility of the proposed method.     

各向异性双材料界面裂纹扩展裂尖场

应用界面断裂力学理论和Stroh方法,研究了广义平面变形下动态裂纹沿着各向异性双材料界面扩展时的裂尖奇异应力及动态应力强度因子.双材料界面的动态裂尖区域特性主要由两个实矩阵W和D确定,且裂尖奇异应力和动态应力强度因子可以由包含这两个矩阵的柯西奇异积分方程确定,同时给出了动态应力强度因子和能量释放率的显示表达式.算例得出当裂纹以小速度扩展时,裂尖振荡因子ε与静态时几乎相同,当界面裂纹扩展速度接近瑞利波速时,ε趋于无穷大;同时得出应力强度因子及能量释放率随裂纹扩展速度的变化关系.     

扩展有限元裂尖场精度研究

论述了扩展有限元方法和基本原理,研究了单元类型(四边形单元和三角形单元、线性单元和二次单元)、网格密度、J积分区域半径等因素对裂尖局部应力场(应力强度因子)计算精度的影响。研究发现,上述因素对裂尖应力强度因子计算的收敛速度与稳定性影响不大,证实了XFEM可以用较少的节点获得较高的裂尖场精度,并提出了通过固定裂尖附加区半径可以进一步改善XFEM的收敛速度。