顶空固相微萃取-气质联用测定刺柏成分

为分析刺柏的挥发性成分,采用顶空固相微萃取技术捕集香气成分,气相色谱-质谱联用法进行定性分析,并通过面积归一化法确定各成分的相对质量分数。刺柏样品共鉴定出31种挥发性成分,具有复杂丰富的化学成分。分析结果表明,该方法能较好地分析刺柏挥发性物质的组成,为分析刺柏挥发性成分提供了新方法,对刺柏的研究及进一步开发有推动作用。国家自然科学基金项目(21406185);;厦门大学校长基金项目(20720170027

一种番茄红素中间体的制备

本文介绍一种番茄红素中间体(3E,5E,7E)-8-碘-4-甲基-1,3,5,7-壬四烯的制备方法。本方法的原料来源方便,路线简单可行,成本低廉,可以用于工业化生产。本中间体也同样可作为其它类胡萝卜素的合成原料,因此具有很好的应用价值和发展潜力。国家自然科学基金项目(21406185);;厦门大学校长基金项目(20720170027

Numerical investigation of flow structures resulting from the interaction between an oblique detonation wave and an upper expansion corner

Wedge-induced oblique detonation waves (ODWs) have been studied widely, but their interactions with complicated geometries have not been fully addressed. In this study, we investigate ODW interaction with a deflected upper corner due to confinement change upstream of the ODW. Numerical simulations are conducted using the reactive Euler equations with a two-step induction-reaction kinetic model. Two ODWs without the upper wall deflection are first simulated to resolve the basic structures with inflow Mach numbers M-0 = 6 and 7. Thereafter, we introduce a deflected upper confinement, resulting in a new wave configuration. This wave is characterized by a post-turning, triangular recirculation zone coupled with a gaseous wedge connecting the deflection point and ODW surface. A parametric study is performed to analyse the effects of the deflection location, deflection angle and activation energy of the heat release reaction. The results reveal that the wave configuration is due to the evolution of ODW decoupling in an expanded supersonic flow. We further study the surface stability and structural unsteadiness arising for M-0 = 6. Upstream-travelling transverse waves are observed for the first time, and effects of different parameters on the surface instability are analysed via fast Fourier transforms. Two destabilizing mechanisms of ODW structures are proposed, one from the post-surface thermal choking and the other from the enhanced surface instability

Numerical study of oblique detonation initiations with chain-branching kinetics

Oblique detonations induced by semi-infinite wedge are simulated by solving Euler equations with chain branching kinetics. Numerical results show the initiation can be triggered by either the abrupt transition or smooth transition, dependent on incident Ma Minand wedge angle 胃, and then their effects on the oblique detonation angle 尾 and initiation length Liniare analyzed. When 胃 increases, Linidecreases monotonically but 尾 has a minimum value, corresponding to 胃 = 29掳 in this study. When Min decreases, both Liniand 尾 increases monotonically until Mindecreases below certain critical value, Min= 9.2 in this study. Then low inflow Ma effects generate the maximum Lini, with the complex of ODW (oblique detonation wave), SODW (secondary oblique detonation wave) and SIDW (self-ignition deflagration wave). The transient process is observed, demonstrating the structure can self-adjust to find a proper position. The wave structure suggests two wave/heat release process determining the detonation initiation. In the cases with high Minfeatured by SIDW, the oblique-shock induced self-ignition dominates, and Liniincreases when Mindecreases. In the cases with low Minfeatured by SODW, the interaction of ODW and SODW dominates, and Linidecreases when Min decreases. 漏 2017 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.</p

Al2O3含量对PVDF/PVC/Al2O3共混中空纤维膜的影响

以聚偏氯乙烯(PVDF)、聚氯乙烯(PVC)和纳米氧化铝(Al2O3)三元共混,制备中空纤维膜,探讨Al2O3含量对膜性能的影 响。结 果表明,由于 适量Al2O3的加入,中空纤维膜膜孔结构明显改善,大孔减少,微孔增多;亲水性明显提高。Al2O3为最佳含量3%时,水通量和截留率分别达到了301L/(h·m2)和77.2%

Reverse Microemulsion Synthesis and Characterization of The Nanocatalysts

本论文以微乳技术为核心合成手段，以LaMgxMn1-xAl11O19和CexBa1-xMnyAl11Oz六铝酸盐催化剂为主要研究对象，以廉价、无毒的无机盐为前驱物，结合超临界干燥技术，制备了高稳定性、高活性的纳米结构的甲烷燃烧催化剂；同时，组装、合成了核/壳型CdS/SiO2纳米粒子及SiO2空心球。并通过相应的物理、化学表征手段，研究了催化剂性能与制备条件之间的关系，深入研究了制备方法对最终材料的影响，得到如下一些结论： 反相微乳合成技术，在纳米材料制备中具有独特的应用价值。通过控制或调节粒子的成核、生长过程，可以有效地控制一次粒子的形貌和尺寸，最终控制催化剂颗粒的形貌与大小；并可以显著地提高前驱体组分的混合均匀性，促进六铝酸盐相在较低的温度下结晶，有利于制备大比表面、高活性的催化剂

区块链技术在数字货币中的应用态势分析

在经济危机和技术变革的双重压力下，全球货币金融体系发生重大变革。本文利用文献计量学，对区块链技术在数字货币的应用进行发展态势研究，旨在掌握数字货币的现状和主要发展方向。结果表明，数字货币研究处于快速发展阶段并且区域特征明显；数字货币的安全和隐私、区块链技术共识算法、区块链在开采过程中的能源消耗、基于以太网智能合约的交易安全、数字货币的金融监管、机器学习在数字货币中的应用是区块链技术在数字货币应用中的六个主要研究内容。未来区块链技术在加密技术的研究、智能合约的安全开发、共识机制、可扩展性、金融监管等方面面临严峻挑战。通过本文研究及展望，希望对未来区块链技术在数字经济中的发展和政策制定提供指导建议。</p

斜爆轰流动燃烧现象及其机理

斜爆轰是高速可燃气体中激波与释热紧密耦合形成的流动现象，在高超声速推进中有潜在的工程应用价值。第1章介绍爆轰的**理论和研究前沿，以及几个重要工程应用，从气相爆轰视角下引入斜爆轰这一*特的研究方向。第2章和第3章分别讲述起爆区和波面特征的研究成果，从基础研究角度揭示斜爆轰及其相关的复杂流动结构。第4章和第5章分别讲述来流扰动和受限空间对斜爆轰流动与燃烧的影响，源于工程研制遇到的实际问题，具有鲜明的应用指向。第6章和第7章从理论、数值和实验角度，介绍常用的研究方法，同时介绍了一些重要结果。第8章从高超声速推进工程应用的角度进行探讨，分析斜爆轰在应用中面临的主要问题。 [1]</p