Sonochemically prepared hierarchical MFI-type zeolites as active catalysts for catalytic ethanol dehydration

In this paper, the ultrasonic-assisted desilication technique was reported as an attractive and efficient way for the preparation of hierarchical zeolites with MFI structure type. The prepared materials were used as active catalysts for the dehydration of ethanol into diethyl ether and ethylene. For all catalysts, the selectivity to diethyl ether was ca 95% or higher up to 210 °C, with catalytic activity in the range of 40–68%. In case of desilicated zeolites, at 270–290 °C, the conversion of ethanol was full with selectivity to ethylene ca 80%. MFI-type commercial zeolite was treated with a sodium and/or tetrabutylammonium hydroxide aqueous solutions (NaOH or NaOH/TBAOH) for 30 min. In the case of the application of ultrasounds, a QSonica Q700 sonicator (60 W and 20 kHz) equipped with a “1” diameter horn was used. In all cases, desilication was performed in an ice bath in order to keep the procedure conditions at low temperature.It was indicated that the use of ultrasounds during desilication procedure caused higher extraction of silicon and aluminum, which was connected with an elevated mesoporosity in relation to the samples modified in the absence of ultrasounds. Ultrasonic-assisted treatment of MFI-type zeolite caused also an apparent formation of numerous holes inside zeolite grains, resembling the look of “swiss cheese”. Furthermore, it was indicated that the samples prepared using ultrasonic irradiation exhibited enhanced catalytic properties in the dehydration of ethanol. For instance, MFI-type zeolite treated with NaOH/TBAOH alkaline mixture containing 10 mol% of TBAOH in the presence of ultrasounds (M−10 s) demonstrated higher both conversion of ethanol (59% vs. 47%) and selectivity to diethyl ether (95% vs. 93%) in comparison with zeolite modified conventionally (M−10c).The best catalyst was zeolite ultrasonically desilicated with NaOH/TBAOH solution of 70 mol% of TBAOH (M-70s). Generally, this catalyst indicated the highest conversion of ethanol, very high selectivity to diethyl ether (94-100%) at 150-210  °C and the highest selectivity to ethylene among investigated catalysts (21%, 66% and 84%) at 230  °C, 250 ^oC and 270  °C.     

HL-2M 真空室保温层设计及安装

基于 HL-2M 真空室烘烤保温要求,通过有限元分析和原型件实验确定采用陶瓷纤维与纳米级微孔材 料组合作为 HL-2M 真空室保温材料。在 30℃时,保温层的导热系数小于 0.027W⋅m⁻¹·℃⁻¹;300℃时,导热系数 小于 0.038W⋅m⁻¹·℃⁻¹。在保温层厚度 25mm、热面温度 300℃且达到稳态时,冷面可控制在 85℃以下,线圈侧的 温度低于 60℃,整体热损失小于 12kW,满足 HL-2M 真空室烘烤需求。      

非对称Halo异质栅应变Si SOI MOSFET的二维解析模型

为了进一步提高深亚微米SOI (Silicon-On-Insulator) MOSFET (Metal-Oxide Semiconductor Field Effect Transistor) 的电流驱动能力, 抑制短沟道效应和漏致势垒降低效应, 提出了非对称Halo异质栅应变Si SOI MOSFET. 在沟道源端一侧引入高掺杂Halo结构, 栅极由不同功函数的两种材料组成. 考虑新器件结构特点和应变的影响, 修正了平带电压和内建电势. 为新结构器件建立了全耗尽条件下的表面势和阈值电压二维解析模型. 模型详细分析了应变对表面势、表面场强、阈值电压的影响, 考虑了金属栅长度及功函数差变化的影响. 研究结果表明,提出的新器件结构能进一步提高电流驱动能力, 抑制短沟道效应和抑制漏致势垒降低效应, 为新器件物理参数设计提供了重要参考. 关键词： 非对称Halo 异质栅 应变Si 短沟道效应     

Preconcentration and Separation of Gold(III) from Ore Samples by Solid-Phase Extraction Prior to Its Catalytic Fluorescent Determination

ABSTRACT

A new catalytic kinetic fluorescent quenching method for the determination of trace gold(III) was investigated. The method was based on the catalytic effect of gold on oxidation of 3-(3′-methylphenyl)-5- (2′-arsenoxylphenylazo) rhodanine by hydrogen peroxide in potassium hydrogen phthalate–hydrochloric acid (pH = 3.4). Under the optimum conditions, the great decrease of fluorescence intensity has a linear relationship against the concentration of gold in the range of 0 to 12.0 µg·L^?1 with a detection limit of 6.0 × 10^?10g·L^?1. The coexistent metal ions can be separated, and gold can be enriched by TBP resin of solid-phase extraction, which greatly improves the selectivity and sensitivity of the system. The method can be used to determine trace amounts of gold in ore samples successfully with satisfactory results.     

Modified Bridgman anvils for high pressure synthesis and neutron scattering

ABSTRACT

A simple modified Bridgman design for large volume pressure anvils usable in the Paris-Edinburgh (PE) press has been demonstrated at Oak Ridge National Laboratory Spallation Neutron Source. The design shows advantages over the toroidal anvils typically used in the PE press, mainly rapid compression/decompression rates, complete absence of blow-outs upon drastic phase transitions, simplified cooling, high reliability, and relative low loads (～40 tons) corresponding to relatively high pressures (～20?GPa). It also shows advantages over existing large-volume diamond cells as sample volumes of ～2–3?mm³ can be easily and rapidly synthesized. The anvils thus allow sample sizes sufficient for in situ neutron diffraction as well as rapid synthesis of adequate amounts of new materials for ex situ analysis via total neutron scattering and neutron spectroscopy.     

On the scatter ranges for the elastic moduli of random aggregates of general anisotropic crystals

A randomly inhomogeneous material may have macroscopic properties (elasticity, conductivity) scattered over some uncertainty intervals, despite the idealistic uniqueness assumption of homogenization theory. Based on minimum energy principles and certain statistical isotropy-symmetry hypotheses, our partly third-order bounds on the effective properties of random polycrystals are expected to estimate those scatter ranges. Explicit expressions are given and calculated for the elastic moduli of the random aggregates of some known monoclinic and triclinic crystals, which yield results in agreement with those calculated for higher-symmetry crystals: the moduli are determinable within an accuracy of two or three significant digits in most cases. It is shown, however, that with some real-world exotic crystals the bounds may fall far apart, and further theoretical and experimental studies on them deserve attention.     

Using a pseudo-functionally graded interlayer in order to improve the static and dynamic behavior of wind turbine blade T-bolt root joints

The large wind turbines blades with multi-ton composite structures are mostly connected to the peach-bearings flanges using T-bolt joints which induce shear and bearing stress fields around the cross bolts. The significant differences between the modulus of elasticity of metallic bolts and composite surrounding materials cause stress concentration around interfaced zones and, also, limit the load capacity of the joints. In the present research, a pseudo functionally graded material (PFGM) as an interlayer is used around the cross bolts to examine the reduction of the stress concentration. Some radial variation of the mechanical properties would be considered for this interlayer. The finite element method is used to analyze the structures. Loadings are applied to the center of the cross bolts analogous to the real cases. Both the static and dynamic loadings are studied. For the finite element of the functionally graded material interlayer, a multilayer alternative material with constant properties in each layer is used. The results show that using an isotropic single layer with an average modulus of elasticity and specific thickness decreases the stress concentration of the composite part up to 47%. The various property models for the interlayer also show that an appropriated model can decrease the stress concentration up to 55%. Dynamic transient analyses would be implemented over the joint structure and improved considering to the practical cases. Using the PFGM interlayer decreases the constant and variable parts of the stresses up to 55% and also causes significant increasing of the joint fatigue life.     

应用Hotelling T~2检验评价学生学习成绩的探讨

本文简述了ＨｏｔｅｌｌｉｎｇＴ２检验法，并应用该法对某校学生的学习成绩进行了分析评价，发现其效果较为满意。认为对多变量资料进行分析评价需用ＨｏｔｅｌｌｉｎｇＴ２检验。     

一类不可压缩材料平面应力问题的裂纹尖端场

本文采用完全非线性弹性理论,研究了一类不可压缩橡皮类材料[1]在Ⅰ型荷载作用下的平面应力问题.指出裂尖变形由两个收缩区和一个扩张区三部分组成.裂纹尖端应力、应变分别具有R-1、R-1/n的奇异性,当趋近裂尖时,厚度以R1/4n的方式趋于零,n为材料常数.     

压电材料空间轴对称问题的通解及其应用

本文根据横观各向同性压电材料空间轴对称问题场方程的结构特点,利用逐次引进势函数的方法,最后得到将位移分量和电势函数用满足特定偏微分方程的单一势函数表示的所谓通解,推导过程表明这种形式的通解是完备的,作为应用举例,文中用通解求解了压电材料半无限体表面受集中力的问题,得到位移、应力、电位移分量及电势函数的解析表达式,本文所提供的通解可作为分析含空腔、夹杂或币形裂纹等缺陷的压电材料的机-电耦合行为的工具,算例所得结果可直接用于求解压电体相互间或压电体与普通弹性体间的接触问题。