Engineering A-site cation deficiency into LaCoO3 thin sheets for improved microwave absorption performance

Journal of Materials Science - Rationally designing microwave absorption materials with highly efficient and tunable bandwidth is in great demand but remains a huge challenge. In this study,...     

A DFT study on enhanced adsorption of H2 on Be-decorated porous graphene nanosheet and the effects of applied electrical fields

The adsorption of the hydrogen molecule on the pure porous graphene nanosheet (P-G) or the one decorated with Be atom (Be-G) was investigated by the first-principle DFT calculations. The Be atom was adsorbed on the P-G with a binding energy of ?1.287 eV to successfully establish the reasonable Be-G. The P-G was a poor substrate to interact weakly with the H₂, whereas the Be-G showed a high affinity to the adsorbed H₂ with an enhanced adsorption energy and transferred electrons of ?0.741 eV and 0.11 e, respectively. A molecular dynamics simulation showed that the H₂ could also be adsorbed on the Be-G at room temperature with a reasonable adsorption energy of ?0.707 eV. The interaction between the adsorbed H₂ and the Be-G was further enhanced with the external electrical fields. The applied electrical field of ?0.4 V/Å was found to be the most effective to enhance the adsorption of H₂ on the Be-G with the modified adsorption energy and the improved transferred electrons being ?0.708 eV and 0.17 e, respectively. Our study shows that the Be-G is a promising substrate to interact strongly with the H₂ and could be applied as a high-performance hydrogen gas sensor, especially under the external electrical field.     

某水利枢纽基坑降水开挖有限元分析研究

结合某水利枢纽基坑工程,采用弹塑性有限单元法分析基坑工程在不同设计方案条件下,支护条件和开挖降水对周围地面沉降及建筑物的影响;分析基坑底部位移分布以及不同方案下的支护结构的特性变化,并根据计算分析结果,针对可能出现的问题,提出相应的处理措施。     

荆江大堤杨家湾险段地下水渗流场特征的模拟研究

采用美国地质调查局(USGS)的Visual Modflow软件,通过对荆江大堤监利县杨家湾险段不同水位条件下的模拟和在高水位下(10 m水头差)不同处理模式的模拟(减压井模式、防渗墙模式、压浸模式和改变人工填土渗透系数模式、渊塘模式),结果表明:(1) 人工填土的性质对渗透破坏的影响显著;(2) 减压井有利于降低含水层中的水头,但由于减压井中的混合水位为地表高程,与同点无减压井条件下基本相同,其出流带的减压效果不显著;(3) 由于该剖面防渗墙处岩层的渗透性较小,与防渗墙体的渗透性差异不大,防渗墙的作用不明显;(4) 当存在渊塘或天窗时,渊塘及其周边是发生渗透破坏的重点区域,可以通过减压处理防止渗透破坏。     

带并联间隙地线复合绝缘子直流覆冰闪络特性

架空地线融冰已成为一个亟需解决的问题,目前通常对架空地线进行改造加装带间隙的绝缘子并采用直流融冰,其融冰电压受到地线绝缘子放电电压的制约,进而也影响了地线融冰的长度。对耐张型和悬垂型两种地线绝缘子在严重覆冰条件下并联间隙大小与地线绝缘子直流冰闪电压间的关系进行了试验研究。结果表明:两种地线绝缘子表面清洁、未覆冰情况下,其直流50%放电电压U50%与并联间距d呈幂指数关系,随着并联间距d增大,U50%增大,且增速逐渐减小;覆冰条件下,耐张型并联间隙地线复合绝缘子并联间距的选择与覆冰厚度di相关,可以选为(10+2di)mm;悬垂型地线绝缘子在严重覆冰地区建议选择80~100mm的并联间距。在保证融冰期间地线与杆塔保持良好绝缘的条件下,应选择较小间距来提高其防雷性能。     

模块化生态声屏障简介

介绍了模块化生态声屏障的结构、植物搭配、土壤配比等方面的特点,并对生态声屏障的发展趋势进行了论述。     

灌注桩桩侧泥皮性质对桩承载性状影响研究

灌注桩桩侧泥皮的存在对桩承载力影响很大,分析泥皮性状对桩承载性状影响具有非常重要的实用价值。本文采用折减桩土接触面系数方法进行考虑泥皮对钻孔灌注桩承载性状的数值分析。研究结果表明:通过折减桩土接触面模拟泥皮性状是可行的;当泥皮效应比值α在0.3~0.8时,极限承载力损失约在10%~50%;对桩侧某一点,α值和剪应力呈线性关系;对同一加载条件下,α值越大,剪应力越大,相应竖向位移越小。因此,分析钻孔灌注桩受力特征和工程安全时,应充分考虑泥皮作用影响。     

活塞顶面热障涂层对活塞热负荷的影响

活塞顶面热障涂层可以有效降低活塞工作热负荷、提高活塞使用寿命。以一款非道路高压共轨柴油机铝合金活塞为研究对象,采用硬度塞测温法试验测试了无热障涂层活塞在最大转矩工况下表面19个特征点的温度值,同时采用等参法建立了活塞有限元仿真分析模型,对比分析了活塞顶面热障涂层对活塞温度场和热应力场的影响。研究结果表明：活塞顶面热障涂层能有效降低活塞头部和环槽区域的工作温度,活塞头部顶面区域温度下降幅度为20~32 ℃,一环和二环的环槽区域温度下降幅度为15~18 ℃;但活塞顶面采用热障涂层后,活塞基体顶面黏结层区域的热应力会急剧升高,活塞基体顶面、喉口区域以及边缘棱角处热应力集中现象明显,在活塞顶面喉口黏结层区域最大热应力达到291MPa,易导致热障涂层的剥落失效。     

Enhanced voltage endurance capability of Ba(Zr0.2Ti0.8)O3 thin films induced by atomic-layer-deposited Al2O3 intercalations and the application in electrostatic energy storage

Ultrathin Al₂O₃ insulating intercalations with different thicknesses and numbers, prepared by atomic layer deposition technology, were introduced into Ba(Zr_0.2Ti_0.8)O₃ (BZT) relaxor ferroelectric films as the dielectric for electrostatic energy storage capacitors. The phase structure, microstructure and electrical properties were investigated in detail. Due to the insertion of insulating layers, the films show less leakage current and enhanced voltage endurance capability when the thickness of single Al₂O₃ intercalation exceeds a threshold (0.45–0.9 nm). The voltage endurance capability can be more enhanced by increasing the number of Al₂O₃ intercalations. For energy storage applications, the energy storage density and efficiency obtained from the polarization-electric field loops are significantly improved owing to the suppressed leakage and enhanced voltage endurance ability. The results promote the application of BZT-based films in electrostatic energy storage. It is demonstrated that the introduction of atomic-layer-deposited insulating intercalations with controllable thickness, such as those fabricated by ALD method, is an effective way to improve the electrical performance of devices based on composite materials.     

基于矢量图形的G代码自动生成软件路径优化算法的研究

分析矢量图形的数据格式,并对矢量图形有效数据提取及G代码自动生成软件的路径优化算法进行研究。实践证明,该算法切实可行。