气泡长大技术测定表面活性剂溶液的动表面张力

在理论分析的基础上,采用计算机图像采集技术,实时记录气泡的长大过程,用图像分析技术确定气泡边缘形状,即采用局部阈值的边缘跟踪算法识别气泡的边缘井进行优化,建立了根据气泡图像测定动表面张力的实验装置,可直接测量动表面张力随时间的变化.测定了十二烷基硫酸钠溶液的动表面张力.     

塔板上气泡直径的模拟计算

塔板上气液泡沫层传质面积对传质速率影响很大.传质面积由气泡的直径、大小分布和浓度所决定.气泡大小受塔板上流体力学状况影响,要对塔板上的气泡直径和分布进行可靠的模拟计算,就要对板上泡沫层的流体力学状况有着透彻了解,而板上流体力学状况十分复杂,因此,气泡直径的模拟计算和测定都很困难.气泡直径的模拟计算有两类方法--局部法和总体法.先简介局部法模拟计算气泡直径方法,然后进行总体法模拟计算气泡直径研究.通过建立一个数学模型,对塔板上泡沫层的气泡直径进行模拟计算,模拟计算结果和文献报道的实验测定结果基本一致.     

环流反应器的研究 Ⅱ.气泡大小分布与气相停留时间分布的关系

用照相法测定了气泡大小的分布,进行拟合的结果为:气泡的直径近似服从于Γ分布,气泡的体积近似服从于正态分布。用示踪的方法测定了气相停留时间分布,并与由气泡大小的分布推导出的气相停留时间分布的表达式相比较,符合较好。同时,还用传递函数法计算了气相返混并讨论了此法的可靠性。通过一个新设的参数λ,沟通了气泡大小分布、气含率和气相停留时间分布之间的联系,从而对从气泡这个半微观的尺度出发研究反应器的特性和工程放大问题进行了理论上的探索。     

气泡长大法测定表面活性剂溶液的表面扩展黏度

在理论分析的基础上 ,采用计算机图像采集技术 ,实时记录气泡的长大过程 ,用图像分析技术确定气泡边缘形状 ,建立了根据气泡图像测定表面扩展黏度的实验装置 .直接测量动表面张力随时间的变化 ,并通过动表面张力与气泡表面积变化率的关系 ,确定溶液的表面扩展黏度 .测定了十二烷基硫酸钠溶液的表面扩展黏度 ,并与不同表面变形速率下的文献值进行比较 ,说明了表面活性剂溶液的表面流变现象 .     

气-固流化床的气泡参数测定——直射式光纤探头在流化床研究中的应用

在鼓泡域中,从直射式光纤探头在二维床的测试与图像分析的结果得到气泡的平均直径与平均刺穿长度的关系为:d_b=1.6E[l]气泡的球形度为0.96。通过反射式和直射式光纤探头信号的比较表明,直射式探头的信号便于处理,并可用来测定气泡内的粒子含量。直射式光纤探头在二维床和三维床的测定结果对比表明,两种塔内的气泡行为规律一致但有明显的差异。     

气-液-固三相流化床中气泡大小分布的随机模型

本文利用马尔柯夫过程理论,建立了一个包括气泡上升速率、气泡大小以及气泡在床内出现位置的随机模型.利用热力学理论分析了模型参数.同时,本文利用四组元组合电导探针测定了气泡大小及其分布密度,验证了随机模型.结果表明,模型值与实验拟合很好.     

通过气泡成分分析解决超白浮法玻璃生产中的气泡缺陷

气泡是玻璃生产中最常见的玻璃缺陷之一,由于它的大小、密度、位置的不确定性,增加了对气泡缺陷来源诊断的难度。超白浮法玻璃生产中气泡更是影响玻璃质量的主要缺陷,通过测定气泡中气体的组成含量,可以较准确、快速地判断该缺陷产生的根源,从而采取有效措施消除缺陷。     

三相循环流化床中气泡上升速度的实验研究

开发了一种新型的光纤探头多相流气泡测试系统,可用于气－液两相和气－液－固三相体系中气泡参数的测定。应用此系统研究了三相循环流环化床中不同径同位置气泡的上升速度分布,气泡上升速度均值的径向布以及操作条件对这现任中分布的影响。     

纤维毡波折前后初始气泡点变化规律

纤维毡波折变形后孔径发生变化,引起初始气泡点变化.用过滤器渗透性试验仪测定了不同孔径纤维毡波折前后初始气泡点的变化情况.结果表明,纤维毡单重越大,纤维丝径越细,波折后初始气泡点变化越大;相同孔径的纤维毡,在细面形成波峰时比在细面形成波谷时初始气泡点变化大;纤维毡厚度越小,初始气泡点变化越大.     

水下爆炸能量测试中炸药入水深度的确定

研究了试样入水深度和气泡脉动周期的关系，并对测定的气泡脉动周期与计算值进行了比较，确定了有限水域炸药试样的合理入水深度。     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

Novel polyurethane coating technology through glycidyl carbamate chemistry

Glycidyl carbamate chemistry combines the excellent properties of polyurethanes with the crosslinking chemistry of epoxy resins. Glycidyl carbamate functional oligomers were synthesized by the reaction of polyfunctional isocyanate oligomers and glycidol. The oligomers were formulated into coatings with several amine functional crosslinkers at varying stoichiometric ratios and cured at different temperatures. Properties such as solvent resistance, hardness, and impact resistance were dependent on the composition and cure conditions. Most coatings had an excellent combination of properties. Studies were carried out to determine the kinetics of the curing reaction of the glycidyl carbamate functional oligomers with multifunctional and model amines. Detailed kinetic analysis of the curing reactions was also undertaken. The results indicated that the glycidyl carbamate functional group is more reactive than a glycidyl ether group. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, on October 27–29, 2004, in Chicago, IL.     

Highly moisture-proof polysilsesquioxane coating prepared via facile sol-gel process

A highly moisture-proof polysilsesquioxane coating was obtained from a new bis-silylated precursor, which was synthesized from 3-aminopropyltriethoxysilane (APTES) and m-xylylene diisocyanate (m-XDI) in tetrahydrofuran (THF) and verified by ¹H MAS NMR. For direct comparison purposes, an SiO₂ coating was also prepared by the Stöber method using tetraethoxysilane (TEOS) as the reactant. Interestingly, the coating obtained from the polysilsesquioxane sol exhibited a much higher moisture resistance capability than its counterpart, which was attributed to its more compact feature between nanoparticles as characterized by N₂ absorption experiment and transmission electron microscopy (TEM). Furthermore, its high transparency of about 92% showed potential for application in the protection of optical crystals.