A practical reliability assessment approach and its application for pile-stabilized slopes using FORM and support vector machine

Bulletin of Engineering Geology and the Environment - Many uncertainties exist in pile-stabilized slopes which make their design substantially complicated. In this paper, a first-order reliability...     

一锅法制备纳米纤维素及其性能研究

采用一种操作简单、绿色环保的以对甲苯磺酸为催化剂对竹纤维进行水热处理制备纳米纤维素(NCC)的方法。考察了反应时间、反应温度和超声作用对纳米纤维素得率和性能的影响。结果表明,在反应温度110℃、反应时间45 min、超声时间120 min的条件下,纳米纤维素得率最高。     

The dehydrogenation kinetics and reversibility improvements of Mg(BH4)2 doped with Ti nano-particles under mild conditions

Magnesium borohydride, Mg(BH₄)₂, is ball-milled with Ti nano-particles. Such catalyzed Mg(BH₄)₂ releases more hydrogen than pristine Mg(BH₄)₂ does during isothermal dehydrogenation at 270, 280, and 290 °C. The catalyzed Mg(BH₄)₂ also exhibits better dehydrogenation kinetics than the pristine Mg(BH₄)₂. Based on kinetics model fitting, the activation energy (E_a) of the catalyzed Mg(BH₄)₂ is calculated to be lower than pristine Mg(BH₄)₂. During partial dehydrogenation, the catalyzed Mg(BH₄)₂ releases 4.23 wt % (wt%) H₂ for the second dehydrogenation at 270 °C, comparing to 4.05, and 3.75 wt% H₂ at 280, and 290 °C. The reversibility of 4.23 wt% capacity is also one of the highest for Mg(BH₄)₂ dehydrogenation under mild conditions such as 270 °C as reported. 4 cycles of Mg(BH₄)₂ dehydrogenation are conducted at 270 °C. The capacities degrade during 4 cycles and tend to be stable at about 3.0 wt% for the last two cycles. By analyzing the hydrogen de/absorption products of the catalyzed sample, Mg(BH₄)₂ is found to be regenerated after rehydrogenation according to Fourier Transform Infrared (FTIR) spectroscopy. Ti nano-particles can react with Mg(BH₄)₂ during ball-milling and de/rehydrogenation. The products include TiH_1.924, TiB, and TiB₂, which can improve the dehydrogenation properties of Mg(BH₄)₂ from a multiple aspect.     

A distributed energy system integrating SOFC-MGT with mid-and-low temperature solar thermochemical hydrogen fuel production

Solar thermochemical hydrogen production with energy level upgraded from solar thermal to chemical energy shows great potential. By integrating mid-and-low temperature solar thermochemistry and solid oxide fuel cells, in this paper, a new distributed energy system combining power, cooling, and heating is proposed and analyzed from thermodynamic, energy and exergy viewpoints. Different from the high temperature solar thermochemistry (above 1073.15 K), the mid-and-low temperature solar thermochemistry utilizes concentrated solar thermal (473.15–573.15 K) to drive methanol decomposition reaction, reducing irreversible heat collection loss. The produced hydrogen-rich fuel is converted into power through solid oxide fuel cells and micro gas turbines successively, realizing the cascaded utilization of fuel and solar energy. Numerical simulation is conducted to investigate the system thermodynamic performances under design and off-design conditions. Promising results reveal that solar-to-hydrogen and net solar-to-electricity efficiencies reach 66.26% and 40.93%, respectively. With the solar thermochemical conversion and hydrogen-rich fuel cascade utilization, the system exergy and overall energy efficiencies reach 59.76% and 80.74%, respectively. This research may provide a pathway for efficient hydrogen-rich fuel production and power generation.     

Effects of particle sizes on performances of the multi-zone steam generator using waste heat in a bio-oil steam reforming hydrogen production system

Hydrogen production by bio-oil steam reforming is an advanced production technology. It is a good method of coupling waste heat utilization with bio-oil steam reforming to produce hydrogen, which increases the cleaning ability of the bio-oil steam reforming system. A multi-zone steam generator using waste heat has been proposed, which can produce the heat source and steam source of the hydrogen system. The DEM model of the multi-zone steam generator was set up. The model has been used to investigate the effects of particle sizes (40 mm–80 mm). With increasing particle size, the flow index and the flow uniformity gradually decrease, the vertical velocity gradient increases in the area on both side with the zone steam generator, and the vertical velocity fluctuation amplitude gradually increases. So, the hydrogen production decreases from the particle size increasing.     

Predicting elastic modulus of porous La0.6Sr0.4Co0.2Fe0.8O3-δ cathodes from microstructures via FEM and deep learning

In this work, a deep learning accelerated homogenization framework is developed for prediction of elastic modulus of porous materials directly from their inner microstructures. The finite element method (FEM) and the homogenization theory are used to obtain the macroscopic properties of materials based on their microstructures. Based on a large dataset consisting of various microstructures and corresponding elastic properties via FEM, a deep convolutional neural network (CNN) is trained to capture the nonlinear functional relationship between the microstructure features and their macroscopic elastic properties. The deep learning model is finally well validated against extra new samples with excellent predictive performances. This demonstrates that the CNN deep learning model can be trusted as a surrogate model for the FEM based homogenization method, with the computation time being reduced by several orders of magnitude. The proposed deep learning framework is highly extendable for prediction of various macroscopic properties from microstructures.     

Investigating the influence mechanism of hydrogen partial pressure on fracture toughness and fatigue life by in-situ hydrogen permeation

In this work, we investigate the influence mechanism of hydrogen partial pressure on fracture toughness and fatigue life of a high strength pipeline steel. Both fracture toughness test and fatigue life test are carried out under different hydrogen partial pressure. The experimental results show that with the increasing of hydrogen partial pressure, fracture toughness and fatigue life decrease and the decrease trends gradually flatten out. Hydrogen has a larger effect on fatigue life than fracture toughness. Only 3% hydrogen gas can cause a 67.7% decrease of fatigue life. The in-situ hydrogen permeation test is performed respectively in 2 MPa, 5 MPa and 8 MPa hydrogen partial pressure. With the increasing of hydrogen partial pressure, the increase trend of hydrogen permeation current gradually tends to be gentle, which indicates that the hydrogen atoms entering into the material gradually become saturated. This result can be used to clarify the influence mechanism of hydrogen partial pressure on fracture toughness and fatigue life.     

基于火灾动力学模拟的广府祠堂建筑性能化防火评估

为评估建筑遗产的防火性能,以广东广府地区典型祠堂建筑——广州陈氏书院为例,采用火灾动力学模拟(FDS)软件PyroSim计算其中厅堂建筑的火灾烟气流动与热量传递,进而评估山墙和青云巷等传统防火构造性能.结果 表明:传统坡屋顶下火灾烟气沿水平方向流动速度比沿垂直方向更快,容易在山墙部位形成高温,以致烧穿屋顶;山墙和青云巷可使相邻建筑外墙入射热通量降低约3/4;火灾蔓延除与山墙垂脊高度和青云巷宽度相关外,还取决于风速.因此,祠堂类高大厅堂建筑室内应设置纵向挡烟垂壁与自然排烟天窗,控制初始火场面积,减少火灾危害;当环境风速大于4m/s时,祠堂建筑应警惕屋顶飞火的远距离引燃风险,避免风环境恶化是建筑遗产防火保护的一项重要内容.     

Synthetic copolymer (AM/AMPS/DMDAAC/SSS) as rheology modifier and fluid loss additive at HTHP for water-based drilling fluids

In the petroleum industry, high temperature and high pressure (HTHP) would dramatically worsen rheological properties and increase fluid loss volumes of drilling fluids. Synthetic polymer as an indispensable additive has attracted more and more attention recently. In this article, a new copolymer (named AADS) of 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, dimethyl diallyl ammonium chloride, and sodium styrene sulfonate was synthesized through aqueous solution polymerization. The chemical structure of the copolymer was characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance. Moreover, its thermal stability was simultaneously analyzed using a differential scanning calorimetry. The results showed that the synthetic polymer contained all the designed functional groups, and its structure was consistent to the desired one. Under contamination of sodium chloride, AADS solution maintained relatively high viscosity in high concentration brine, showing a good antisalt capacity. Furthermore, the effect of AADS content and temperature on rheological behavior and fluid loss volume of the water-based drilling fluid (WBDF) containing the synthesized product were investigated according to the American Petroleum Institute standard. Results showed that the rheological and filtration properties of the prepared WBDF were improved with the increase in the AADS concentration before and after the thermal aging test. In addition, in the temperature range of 80–240 °C, a reversible rheological behavior was observed during the heating–cooling process, and the HTHP fluid loss was controlled within 22.5 mL, suggesting that the copolymer AADS was suitable for making WBDF s with high temperature resistance. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47813.     

多氢酸酸化反应特征及动力学

利用自制多氢酸液XS-1进行静态岩粉溶蚀与岩心流动实验,通过SEM、ICP等实验考察了多氢酸的缓速性与预防二次沉淀性能,并研究了多氢酸与岩心反应动力学特性。结果表明,XS-1多氢酸液具有良好的缓速与预防二次沉淀性能,反应后残酸的极限浓度为0.296 1 mol/L,酸液有效作用时间为6~7 h。在该多氢酸体系下岩心渗透率提高至4.15倍,在此条件下以酸岩反应动力学参数模型建立动力学方程,反应速率比同条件下普通酸液小,进一步证明多氢酸具有一定的缓速性。