随机四参数法生成多孔介质及渗流模拟

本文基于多孔介质内流动的广泛应用背景,模拟了多孔介质渗流。采用随机四参数生长法生成了多孔介质模型,并对模型中的微小固相进行了过滤处理。将随机四参数生长法生成的多孔介质结合格子玻尔兹曼方法D2Q9模型模拟了压力驱动的多孔介质中的渗流。通过将模拟结果与著名的CK理论公式的计算结果进行比较,发现在孔隙率高时误差较小(φ=0.9时,误差约为6%)。研究表明在高孔隙率时采用文中的方法得到的多孔介质渗透率及孔隙尺度的流动结果较为准确。     

多环芳烃与不饱和自由基氢提取反应类的动力学研究

对2~6个环的多环芳烃的氢提取反应类进行了系统研究, 提取氢原子的不饱和自由基包括丙炔基自由基（C₃H₃）、 烯丙基自由基（C₃H₅）、 丁二烯基自由基（nC₄H₅, iC₄H₅）、 环戊二烯基自由基（C₅H₅）以及苯基自由基（C₆H₅）. 采用M06-2X/cc-pVTZ方法得到了多环芳烃的电子结构信息, 利用过渡态理论并结合Eckart隧道校正, 计算了所有反应在500~2500 K范围内的反应速率常数.考察了多环芳烃的大小、 结构对反应速率常数的影响, 对比了不同氢提取自由基及不同氢提取反应类型的速率常数. 结果表明, 多环芳烃的大小对反应速率常数影响不大, 但是多环芳烃的环结构对反应速率常数影响较大. 将不同的氢提取反应类简化为发生在五元环上的C₅类和发生在六元环上的C₆类两类, 结果表明, C₆类的反应活性高于C₅类. 研究了nC₄H₅, iC₄H₅以及C₆H₅自由基与多环芳烃的氢提取反应, 它们的氢提取反应活性大小顺序为C₆H₅>nC₄H₅>iC₄H₅. 通过对每类典型反应的速率常数取平均值, 总结出相应类型的速率规则, 可用于构建多环芳烃和碳烟机理.     

Enhanced Euler's method to a free boundary porous media flow problem

We study an ODE‐based iterative method, the residual velocity method, for steady state free boundary problems. The convergence analysis of the method, as well as the numerical implementation based on Euler's method were provided by Donaldson and Wetton (J Appl Math 71 (2006), 877–897). In this article, we develop an enhanced Euler's method which is nearly as simple as the modified Euler's method but can achieve a rapid convergence rate similar to the fourth‐order Runge‐Kutta method. Numerical results are also provided to verify the validity of our method. © 2011 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2012     

Enhancing the thermal stability of poly(methyl methacrylate) by removing the chains with weak links in a continuous polymerization

A novel method is proposed to produce PMMA with excellent thermal stability by a continuous process composed of polymerization and devolatilization steps. It is based on the fact that free radical polymerized PMMA is a mixture of polymer chains with different structure, a small fraction of which, containing head-to-head linkages or unsaturated ends, is less thermally stable and the major portion without those defect structures which is much more stable. Our idea is selectively remove the unstable chains from this mixture by pre-decomposing them at suitable temperatures in a continuous process, leaving the stable portion as the final PMMA product. The results showed that during the continuous process, the chains with head-to-head linkages were eliminated by conducting the polymerization at 155 °C, and then the chains with unsaturated ends were removed by devolatilization at 300 °C. The final PMMA was thermally stable up to 313 °C.     

水位下降对均质土坝边坡稳定性的影响

对均质土坝在水位下降时坝体的渗流和坝坡稳定性进行了分析，坝体渗流分析时采用有限单元法．坝坡稳定性分析时采用条分法．发挥有限单元法和条分法两个方法的长处，并结合运用，可供工程设计人员参考使用．     

Eichinvariante Berechnung des Diamagnetismus und der chemischen Verschiebung

The procedure derived in^1–4 was used to calculate the magnetic susceptibilities of a series of unsaturated hydrocarbons (propene, isobutene, 1-butene, cyclohexene, butadiene,trans-1,3,5-hexatriene). The difference between the measured and computed susceptibilities of these molecules is discussed. The discussion shows, that there is no correlation existing between the difference and the presumed delocalisation effects.

Die Ergebnisse sind Bestandteil einer der letzten Arbeiten, die von dem von uns hochverehrten, leider zu früh verstorbenen, Prof. Dr.W. Haberditzl betreut wurden.     

On unsteady dispersion flow in porous media

The generalising dispersion equations of flow through porous media have been investigated. The Laplace transform has been applied to obtain the solution to dispersion problem as a result of adsorption. The generalised closed form solution for dispersion has been presented and the different types of variations in concentration have been graphically discussed. When the steady state occurs, the concentration becomes constant but for small value of time (say 0.5) the concentration tends to zero as distance increases.     

Acetylene chemistry,part 32: Alkinylation and cyclic rearrangement of theophylline with unsaturated alcohols by Mitsunobu reaction

Summary The reaction of theophylline (1) with 2-methyl-3-butyn-2-ol and 1-butyn-3-ol under Mitsunobu conditions gave the respective 9-substituted derivatives 9-[2-(2-methyl-3-butynyl)]-theophylline (2) and 9-[2-(3-butynyl)]-theophylline (3). On reaction with 2-methyl-3-buten-2-ol, theophylline yielded in addition to the 9-[2-(2-methyl-3-butenyl)]-theophylline (4), two more cyclic products, identified as 1,5,5a,8-tetrahydro-1,3,8,8-tetramethyl-2H-pyrrolo[1,2-e]purine-2,4(3H)-dione (5) and 8a,9-dihydro-1,3,6,6-tetramethyl-1H-pyrrolo[2,1-f]purine-2,4(3H,6H)-dione (7).

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Acetylenchemie, 32. Mitt.: Alkinylierung und cyclische Umlagerung von Theophyllin mit ungesättigten Alkoholen mittels Mitsunobu-Reaktion

Zusammenfassung Die Reaktion von Theophyllin (1) mit 2-Methyl-3-butin-2-ol und 1-Butin-2-ol unter Mitsunobu-Bedingungen führte zu den 9-substituierten Derivaten 9-[2-(2-Methyl-3-butinyl)]-theophyllin (2) bzw. 9-[2-(3-Butinyl)]-theophyllin (3). Bei der Reaktion mit 2-Methyl-3-buten-2-ol ergab Theophyllin außer 9-[2-(2-Methyl-3-butenyl)]-theophyllin (4) noch zwei weitere cyclisierte Produkte, die als 1,3,8,8-Tetramethyl-1,5,5a,8-tetrahydro-pyrrolo[1,2-e]purin-2,4(3H)-dion (5) und 1,3,6,6-Tetramethyl-8a,9-dihydro-1H,6H-pyrrolo[2,1-f]purin-2,4-dion (7) identifiziert wurden.

     

Chemistry and Biochemistry of Unsaturated Fatty Acids

Although unsaturated fatty acids have long been known to accompany saturated fatty acids in most lipids, qualitative and quantitative determination of fatty acid patterns only became possible with the advent of modern analytical methods. Present day knowledge of the chemical structure, physical properties, and metabolism of unsaturated fatty acids provides the basis for the development of new concepts of their function. Thus unsaturated fatty acids crucially determine the properties of biological membranes. Moreover, essential fatty acids are precursors of prostaglandins.     

Quantitative Analysis of aliphatic aldehydes by headspace SPME sampling and ion-trap GC-MS

Summary A fast and simple headspace SPME sampling method has been developed for quantification of volatile aliphatic aldehydes in sunflower oil. Analysis has been performed by gas chromatography, on a 30m×0.25 mm i.d. ×0.25 μm CP-Wax 52CB column, with mass spectrometric detection. Carryover from the SPME fiber could be eliminated by heating the fiber in the injection port between runs. Response factors of all the compounds were linear for concentrations up to 100 ng μL⁻¹. The slopes of the calibration curves decrease with the amount of saturation of the aldehydes. The average responses for unsaturated aldehydes were twice as high as those for the saturated variety. Responses for dienes were approximately one order of magnitude higher than for saturated aldehydes. Depletion of the analyte was examined by repeated extraction from the same vial. SPME was optimized—after 30 min extraction most components were found to have reached equilibration. The detection limit for the compounds studied varied between 0.1 and 1 ng μL⁻¹. Distribution constants were determined for ten different aldehydes and Henry's constants were calculated for unsaturated aldehydes. There was a definite relationship between the response factors and the amount of saturation of the aldehydes. Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997