Open-channel turbulent flow over non-uniform gravel beds

the measurements of flow over non-uniform gravel open channel have been conducted with Laser Doppler Velocimetry (LDV). The experimental results indicate that the distribution of mean velocity agrees well with the Nikuradse's law. From the distributions of resistance coefficient, reference level and turbulence intensity, the classification of small scale roughness case is obtained.Project supported by the National Science Foundation of China     

含水砂层对堆积体稳定性的影响研究

受复杂地质环境的影响,我国西南岷江上游沿岸普遍发育一种前缘多分布有一层或多层具一定厚度含水砂层的特殊堆积体。大量工程实践表明,工程开挖的扰动可导致砂层出现明显侧向变形,进而导致整个堆积体的失稳破坏。本文采用数值计算的方法,结合某典型堆积体对开挖条件下砂层影响其整体稳定性的作用机理进行了较为深入的分析和探讨。     

Magnetically stabilized bed reactor for selective hydrogenation of olefins in reformate with amorphous nickel alloy catalyst

A magnetically stabilized bed （MSB） reactor for selective hydrogenation of olefins in reformate was developed by combining the advantages of MSB and amorphous nickel alloy catalyst. The effects of operating conditions, such as temperature, pressure, liquid space velocity, hydrogen-to-oil ratio, and magnetic field intensity on the reaction were studied. A mathematical model of MSB reactor for hydrogenation of olefins in reformate was established. A reforming flow scheme with a post-hydrogenation MSB reactor was proposed. Finally, MSB hydrogenation was compared with clay treatment and conventional post-hydrogenation.     

Der Einfluß des Zusatzes von Hemicellulosen auf die Fließeigenschaften von Weizenmehlteig

The water adsorption capacity of a dough consisting of wheat flour was increased linearly by the addition of water-insoluble hemicelluloses (xylane, mannane etc.) extracted from beech-wood pulp using soda lye (a by-product of viscose fiber production). The investigation of this finding by viscosity measurements revealed two reasons for the higher water uptake: 1) a higher kneading resistance of the dough, and 2) a gel-regeneration of the kneaded dough during the dough-rest.

Herrn Prof. Dr. Josef Schurz zum 60. Geburtstag gewidmet.     

铝材轧制过程中润滑添加剂吸附特性研究

依据铝材轧制过程中润滑油添加剂浓度对摩擦因数的影响，同时以Ｔｅｍｋｉｎ吸附理论为基础，设定添加剂分子在摩擦表面的覆盖率与摩擦因数的联系，提出了铝材轧制过程中润滑添加剂吸附有的求解方法，还定义了铝材轧制时润滑添加剂饱和吸附最低浓度的概念，通过二辊轧机测定了在不同添加剂浓度时纯铝材轧制过程中的摩擦因数，并且计算了相应的润滑添加剂的吸附自由能及其饱和吸附最低浓度，表明理论分析结果与实测结果具有良好的一致     

硼原子掺杂对碳纳米管吸附Ne原子影响的第一性原理计算

采用基于第一性原理的密度泛函理论(DFT)和局域密度近似(LDA)方法,优化计算得到碳纳米管(CNT),硼原子取代碳原子及其吸附氖原子前后系统的几何结构,能量,电子能带和态密度.结果显示,碳纳米管的能带结构与石墨的层状几何结构相似,能量的变化只在kz=0和kz=0.5平面之间沿着c轴方向出现.B原子取代C原子使价带和导带分别分裂为两个和三个能带.对Ne原子的吸附使价带能量沿着c轴方向升高并导致Fermi面附近的态密度下降.Ne原子的吸附在谷位H最稳定,顶位A其次.C-C间σ键的弯曲使Ne原子吸附在桥位b1比桥位b2处更为稳定.Ne原子在管外的吸附均为放热过程,而管内则为吸热过程.结构分析表明Ne原子对C原子有排斥作用,对B原子却具有吸引作用.B原子取代C原子的位置略凸出于CNT的管壁之外,使Ne原子的吸附能增加.     

增殖剂球床载气体流动特性

增殖剂球床是聚变堆或混合堆产氚包层可选结构之一,准确把握增殖剂球床中载带气体的流动特性有助于提高对球床载氚过程的认识并优化包层设计。采用离散元程序PFC3D模拟增殖剂小球的填充行为,在球床内不同位置随机截取不同尺寸的控制体,利用布尔运算中的"差集"得到孔隙范围,建立孔隙分布的三维几何模型,进一步划分网格并用计算流体力学(CFD)方法求解,得出控制体上单位长度的压降以及单元体内的速度分布特征,计算结果发现载带气体速度分布与γ分布很类似,且只要选取恰当的控制体,通过计算流体力学方法可以较好地分析整个球床孔隙内流体的流动,有利于进一步研究载氚及相关过程。     

面向丙烯/丙烷吸附分离的金属有机骨架材料的高通量计算筛选

丙烯、丙烷作为分子尺寸相近的共沸物,其分离一直是化工领域研究热点。金属有机骨架(MOFs)材料因其高度可调的孔道结构,在丙烯/丙烷分离应用上已展现出诱人潜能。本文基于Core MOF 2019数据库,采用巨正则蒙特卡洛基高通量计算筛选技术,获得了分离性优异的MOFs结构,发现其拥有适中的丙烯吸附量和较弱的丙烷吸附能力,且骨架孔径为3.70～4.10?、孔隙率中等(0.35～0.44),并揭示了孔道中心吸附位的选择性与丙烯/丙烷分离系数间关系。本研究阐明了高丙烯/丙烷分离性的骨架材料的结构和性能特征,为设计MOFs实现丙烯/丙烷的高效分离提供理论指导和数据支撑。     

Inorganics distribution in bio oils and char produced by biomass fast pyrolysis: The key role of aerosols

Fast pyrolysis of biomass is a promising process for the preparation of bio-oil dedicated to energy production. Inorganic species originally present in biomass are known to induce problems such as bio-oil instability or deposits and fouling. However the mechanisms of inorganic species release during biomass pyrolysis into the raw bio-oils still remain unclear. The present work focuses on the determination of inorganic distribution in the products from wheat straw and beech wood fast pyrolysis performed in a fluidized bed. More specifically, the bio-oils are fractionated by using a series of condensers. The results show that more than 60 wt.% of the inorganic content of the overall bio-oil is contained in the aerosols. Several possible interpretations for this observation are discussed. It is likely that the inorganics are transported within the aerosols droplets and solid particles which are recovered in the bio-oils, either by mechano-chemical processes, or by entrainment of submicron intermediate liquid compound formed in the first steps of biomass fast pyrolysis.     

Adsorption and dissociation of NH3 on clean and hydroxylated TiO2 rutile (110) surfaces: a computational study

The adsorption and dissociation of NH(3) on the clean and hydroxylated TiO(2) rutile (110) surfaces have been investigated by the first-principles calculations. The monodentate adsorbates such as H(3)N-Ti(a), H(2)N-Ti(a), N-Ti(a), H(2)N-O(a), HN-O(a), N-O(a) and H-O(a), as well as the bidentate adsorbate, Ti-N-Ti(a) can be formed on the clean surface. It is found that the hydroxyl group enhances the adsorption of certain adsorbates on the five-fold-coordinated Ti atoms (5c-Ti), namely H(2)N-Ti(a), HN-Ti(a), N-Ti(a) and Ti-N-Ti(a). In addition, the adsorption energy increases as the number of hydroxyl groups increases. On the contrary, the opposite effect is found for those on the two-fold-coordinated O atoms (2c-O). The enhanced adsorption of NH(x) (x = 1-2) on the 5c-Ti is due to the large electronegativity of the OH group, increasing the acidity of the Ti center. This also contributes to diminish the adsorption of NH(x) (x = 1-2) on the two-fold-coordinated O atoms (2c-O) decreasing its basicity. According to potential energy profile, the NH(3) dissociation on the TiO(2) surface is endothermic and the hydroxyl group is found to lower the energetics of H(2)N-Ti(a)+H-O(a) and HN-Ti(a)+2{H-O(a)}, but slightly raise the energetic of Ti-N-Ti(a)+3{H-O(a)} compare to those on the clean surface. However, the dissociation of NH(3) is found to occur on the hydroxylated surface with an overall endothermic by 31.8 kcal/mol and requires a barrier of 37.5 kcal/mol. A comparison of NH(3) on anatase surface has been discussed. The detailed electronic analysis is also carried out to gain insights into the interaction nature between adsorbate and surface.