Ⅳ.工业钒催化剂的内部表面利用率

<正>当传质与传热过程影响催化反应速度时,利用化学动力学方程式严格地计算反应的总速度是一个极其复杂的课题。实际上一般多采用某些简化的假定,作近似计算,以满足工业设计上的需要。利用毛细管模型与催化剂内部表面利用率的概念来计算二氧化硫在工业钒催化剂上的氧化速度,给工业设计提供了一个简单有用的计算方法。     

TREOR多晶X射线衍射图指标化程序的适用性

多晶Ｘ射线衍射图指标化的ＴＲＥＯＲ程序已被普遍采用，特别是在硅酸盐矿物等材料的晶体结构研究工作中应用很多。然而，实际上它存在着一定的缺陷，有可能得出错误的结果。本文对这一程序作了详细的检验，发现即使在理想条件下它都不适用于低对称晶系的指标化。在对程序作改进以后，该程序可适用于高对称晶系多晶衍射的指标化     

二氧化硫在钒催化剂上氧化动力学的研究——Ⅲ.几种工业钒催化剂的动力学方程式的比较

<正>作者等过去的工作已经证实,由于扩散过程的影响、温度范围的不同、或化学组成的差异,二氧化硫在钒催化剂上的氧化动力学方程式可能具有不同的形式。反应物及生成物与催化剂之间的相互作用,可能使催化剂具有不同的颜色与活性,因而即使温度相同,由于催化剂在层内所处的部位不同,其催化活性可能并不一致。这些复杂性给工业设计带来了很大的困难。因此,合理的简化是完全必要的。 作者等选取了几种不同的工业钒催化剂,用实验方法求得了适用于它们的动力学方程式,进行比较和讨论,提出了一个简便的、合理的、可以用作设计基础的动力学方程式。     

Effects of buffer layer materials and process conditions on growth mechanisms of forming networks of SWNTs by microwave plasma chemical vapor deposition

This study investigates the growth mechanism of IC compatible processes and to the feasibility of synthesizing networks of single-walled carbon nanotubes (SWNTs) at lower temperatures (610 °C) on Si wafer using microwave plasma chemical vapor deposition (MPCVD) with CH₄ and H₂ as source gases. The effects of the buffer layer materials (ZnS–SiO₂, Al₂O₃, AlON, and AlN ) and process conditions on growth of carbon nanostructures with Co as catalyst were also examined, where the buffer layers and Co catalyst were deposited in sequence by physical vapor deposition (PVD), followed by H-plasma pretreatment before deposition of carbon nanostructures. Additionally, the morphologies and bonding structures of carbon nanostructures were characterized by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), and Raman Spectroscopy. Analytical results demonstrate that networks of SWNTs are more favorable to be synthesized by selecting proper buffer layer material (e.g., AlON), and under higher temperatures, thinner catalyst thickness (e.g., 5 nm) and lower CH₄ / H₂ ratio (e.g., 5 / 100 sccm/sccm). The networks of SWNTs can be fabricated at temperatures as low as 610 °C by manipulating these parameters. In conclusion, the growth mechanism determines the conditions for the formation of nano-sized extrusions on catalyst particles surface.     

Rapid Formation of Active Mesoporous TiO2 Photocatalysts via Micelle in a Microwave Hydrothermal Process

Rapid formation of active, mesoporous, and crystalline TiO₂ photocatalysts via a novel microwave hydrothermal process is presented. Crystalline anatase mesoporous nanopowders 100–300 nm in size with worm hole-like pore sizes of 3–5 nm were prepared by a modified sol–gel of titanium tetra-isopropoxide, accelerated by a microwave hydrothermal process. The organic surfactant, tetradecylamine, which is used as a self-assembly micelle in the sol–gel and microwave hydrothermal process, enables to harvest crystallized mesoporous anatase nanoparticles with a high-surface area. Mesoporous worm hole-like and crystalline powders with surface areas of 243–622 m²/g are obtained. X-ray diffraction, N₂-adsorption isotherms (Barrett–Joyner–Halenda and Brunauer–Emmet–Teller method), scanning electron microscope, and transmission electron microscope are used to identify the characteristics and morphologies of the powders. It is shown that crystallization by calcination at 400°C/3 h inevitably reduced the surface area, while the microwave hydrothermal process demonstrated a rapid formation of crystalline mesoporous TiO₂ nanopowders with a high-surface area and excellent photocatalytic effects.     

Preparation and application of fluorocarbon polymer/SiO2 hybrid materials,part 1: Preparation and properties of hybrid materials

For this study, we first prepared a fluorocarbon polymer and its hybrid materials. We found that fluorocarbon copolymers can produce hydrogen bonds with SiO₂ to form hybrid materials. We also used thermogravimetric analyzer and tested the thermostabilities of the four products, which were ranked as follows: fluorocarbon copolymer/SiO₂ hybrid material > fluorocarbon polymer/SiO₂ hybrid material > fluorocarbon copolymer > fluorocarbon polymer. In addition, we found that, due to the inorganic SiO₂ used, the number of pores and the specific surface areas of the hybrid materials both increased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1140–1145, 2007     

Soy protein combined with copper and boron compounds for providing effective wood preservation

Chromated copper arsenate (CCA), an arsenicbased wood preservative, is toxic to human health and the environment. Although CCA is stable in seasoned wood, there are potential dangers during CCA manufacture, lumber treatment, and waste disposal. This research was conducted to study the effectiveness of soy products to replace toxic chromium and arsenic compounds in wood preservative formulations. Three soy product (Arpro 2100, HM 90, and Supro 760) were used as fixative agents in preservative solutions containing anhydrous CuSO₄ and Na₂B₄O₇·10H₂O. The decay resistance of treated wood blocks was measured by a soil-block culture method. Despite the large molecular sizes of copper-protein and copper-boron-protein complexes, southern pine sapwood was treatable with these preservative formulations. Wood samples treated with >6 kg°m⁻³ CuSO₄ and 7.5 kg·m⁻³ soy product, and subsequently leached for 3 d and exposed to the decay fungus Gloeophyllum trabeum (Fr.) Mur., sustained only 0.5% weight loss over 12 wk. Wood samples needed 40 kg·m⁻³ CuSO₄ and 50 kg·m⁻³ soy protein to resist the copper-tolerant decay fungus Postia placenta (Fr.) M. Lars. & Lomb. These results suggest that soy-based wood preservatives can prevent wood products from fungal attack and can replace CCA.     

An efficient mode decision algorithm for H.264/AVC intra prediction

Multimedia Tools and Applications - Rate distortion optimization technique is adopted by H.264/AVC to select the best intra and inter prediction modes. It achieves remarkable improvement in...     

Authorized workflow schemas: deciding realizability through \mathsf{LTL }(\mathsf{F }) model checking

Many business processes are modeled as workflows, which often need to comply with business rules, legal requirements, and authorization policies. Workflow satisfiability is the problem of determining whether there exists a workflow instance that realizes the workflow specification while simultaneously complying with such constraints. This problem has already been studied by the computer security community, with the development of algorithms and the study of their worst-case complexity. These solutions are often tailored to a particular workflow model and are, therefore, of little or no use in analyzing different models; their worst-case complexities are likely to be an unreliable judge of their feasibility; and they lack support for other forms of analysis such as the determination of the smallest number of users required to satisfy a workflow specification. We propose model checking of an NP-complete fragment $\mathsf{LTL }(\mathsf{F })$ of propositional linear-time temporal logic as an alternative solution. We report encodings in LTL(F) that can compute a set of solutions (thus deciding satisfiability), compute minimal user bases and a safe bound on the resiliency of satisfiability under the removal of users. These theoretical contributions are validated through detailed experiments whose results attest to the viability of our proposed approach.     

海洋数据质量检验方案中残差优化选择算法磁

随着信息化的快速发展,海洋数据的获取手段变得多种多样,海洋数据的“量”急剧增大,如何保证海洋大数据的质量问题成为热点。抽样检验是一个较成熟的课题,但适用于海洋数据特性的抽样方案研究较少。结合海洋数据的特点,利用 Skyline 的思想,提出了分批排序的优化抽样检验方案选择算法。通过各抽样检验方案残差的 Skyline 集合,选择优化的质量检验方案,提高海洋数据质量检验精度的同时保证海洋数据的检验费用。