期刊文献+
共找到22,299篇文章
< 1 2 250 >
每页显示 20 50 100
GaP/GaPN核壳纳米线阵列修饰的硅光阴极的光电化学制氢反应 预览
1
作者 谢关才 Saad Ullah Jan +10 位作者 董泽健 代亚雯 Rajender Boddula 魏玉轩 赵唱 辛琪 王娇娜 杜银芳 马兰 郭北斗 宫建茹 《催化学报》 SCIE EI CAS CSCD 北大核心 2020年第1期2-8,共7页
能够大规模同时提升电极的催化效率和稳定性对光电化学分解水系统的开发具有重要意义.硅是一种地球储量丰富且成熟的工业材料,由于其合适的带隙(1.1 eV)和优异的导电性,已被广泛用于光电化学制氢反应.然而,缓慢的表面催化反应和在电解... 能够大规模同时提升电极的催化效率和稳定性对光电化学分解水系统的开发具有重要意义.硅是一种地球储量丰富且成熟的工业材料,由于其合适的带隙(1.1 eV)和优异的导电性,已被广泛用于光电化学制氢反应.然而,缓慢的表面催化反应和在电解液中的不稳定性限制了其在太阳能制氢中的实际应用.III-IV族半导体材料也具有较高的载流子传输特性且被广泛用于光电器件.其中,GaP的直接带隙和间接带隙分别为2.78和2.26 eV,可与硅组成串联型光电极用于光电化学分解水.然而,GaP的光腐蚀电位位于禁带中,很容易在光电催化过程中发生光腐蚀而导致性能大幅下降.本文报道了一种新型的GaP/GaPN核/壳纳米线修饰的p型硅(p-Si)串联型光阴极,同未修饰的p-Si相比,其光电化学制氢性能更高.这可归因于以下几点:(1)p-Si和GaP纳米线之间形成的p-n结促进了电荷分离;(2)GaPN相对于GaP具有更低的导带边位置,进一步促进了光生电子向电极表面的转移;(3)纳米线结构既缩短了光生载流子的收集距离,又增加了比表面积,从而加快了表面反应动力学.此外,在GaP中引入氮元素还提高了体系的光吸收和稳定性.我们所提出的高效、简便的改进策略可应用于其他的太阳能转换体系.利用简单的化学气相沉积法制备GaP/GaPN核/壳纳米线修饰的p-Si光阴极.首先在p-Si衬底上利用Au纳米颗粒作为催化剂生长GaP纳米线;然后,去除Au催化剂,并在氨气中退火便形成了GaP/GaPN核壳纳米线.高分辨透射电子显微镜,拉曼光谱和X射线光电子谱的表征结果均证实了氨气退火使得GaP纳米线表面形成了GaPN的薄壳层,同时证明了GaP/GaPN核壳纳米线具有可调的核壳结构.在模拟太阳光下作为光阴极用于光解水制氢反应时,GaP/GaPN核壳纳米线修饰的p-Si光阴极的起始电位为~0.14 V,而未修饰的p-Si电极的起始电位大约在?0.77 V.而且,GaP/GaPN核/� 展开更多
关键词 核壳纳米线 GAP GaPN 制氢 光解水 串联结构
在线阅读 下载PDF
脱空缺陷对钢管混凝土压弯扭构件力学性能的影响研究
2
作者 张传钦 廖飞宇 +2 位作者 王静峰 阮锦发 陈宇峰 《工业建筑》 CSCD 北大核心 2019年第10期19-24,共6页
为研究脱空缺陷对钢管混凝土试件在压弯扭复合作用下力学性能的影响,对14根(包括6根带脱空缺陷试件、6根无脱空试件以及2根空钢管试件)压弯扭复合作用下的试件进行试验研究。以轴压比、弯扭比为主要试验参数,考察带缺陷试件的破坏模式... 为研究脱空缺陷对钢管混凝土试件在压弯扭复合作用下力学性能的影响,对14根(包括6根带脱空缺陷试件、6根无脱空试件以及2根空钢管试件)压弯扭复合作用下的试件进行试验研究。以轴压比、弯扭比为主要试验参数,考察带缺陷试件的破坏模式和脱空缺陷对荷载-位移关系曲线、扭矩-转角关系曲线的影响。试验结果表明:脱空缺陷的存在对试件的破坏模式影响并不显著,但会降低试件的承载力;对于带脱空缺陷的试件,轴压比和弯扭比的增加均导致试件承载力系数有所降低。 展开更多
关键词 钢管混凝土 脱空缺陷 压弯扭复合受力 脱空率 极限承载力
HNIW/GAP混合物燃速的实验研究与数值模拟 预览
3
作者 李恒 赵凤起 +6 位作者 裴庆 李猛 徐司雨 姚二岗 姜菡雨 郝海霞 马晓迅 《火炸药学报》 CAS CSCD 北大核心 2019年第2期152-159,I0003共9页
制备了HNIW/GAP二元混合物,在6~15MPa压强范围测试了其静态燃速,研究了HNIW含量和压强对混合物燃速的影响;分析了HNIW粒径与预热层厚度对HNIW/GAP混合物燃速的影响规律;基于Relay-Race模型对燃速进行了模拟;分析了燃速控制机理,并采用DS... 制备了HNIW/GAP二元混合物,在6~15MPa压强范围测试了其静态燃速,研究了HNIW含量和压强对混合物燃速的影响;分析了HNIW粒径与预热层厚度对HNIW/GAP混合物燃速的影响规律;基于Relay-Race模型对燃速进行了模拟;分析了燃速控制机理,并采用DSC对HNIW/GAP混合物进行了热分析研究。结果表明,Relay-Race模型可以预测HNIW低含量时的部分燃速,在6~9MPa下,混合物燃速随HNIW含量的增加而增大,在12~15MPa下,混合物燃速随HNIW含量增加先减小后增大;在压强低于约0.2MPa下,粒径62μm的HNIW颗粒低于预热层厚度,不经历自持燃烧,增大HNIW粒径可以促进混合物燃烧;在HNIW与GAP质量比为1∶1条件下,模拟的燃速增幅会随着粒径的增大而减小。当HNIW质量分数在0~30%时,混合物燃烧过程的反应控制区域由GAP转移至HNIW燃烧区域,从而导致燃速变化。 展开更多
关键词 物理化学 HNIW GAP 粒径 预热层厚度 燃烧机理 CL-20 自持燃烧
在线阅读 下载PDF
Comparative study on breakdown characteristics of trigger gap and overvoltage gap in a gas pressurized closing switch
4
作者 翟戎骁 黄涛 +4 位作者 丛培天 罗维熙 王志国 张天洋 尹佳辉 《等离子体科学与技术:英文版》 SCIE EI CAS CSCD 2019年第1期87-92,共6页
Gas pressurized closing switches are one of the most important elements in FLTD-based systems. Improving the trigger performance of gas switches is useful for optimizing the output parameters and the reliability of th... Gas pressurized closing switches are one of the most important elements in FLTD-based systems. Improving the trigger performance of gas switches is useful for optimizing the output parameters and the reliability of the FLTD. In this paper, the breakdown characteristics of the trigger gap and the overvoltage gap are studied experimentally. The reasons for the different breakdown performance of the two gaps are also investigated. The results show that the breakdown delay of the trigger gap is more influenced by the trigger voltage, while the breakdown delay of the overvoltage gap is more influenced by the working coefficient and always higher than that of the trigger gap. The jitter of the trigger gap is more influenced by the trigger voltage and accounts more than 60% of the total switch jitter, while the jitter of the overvoltage gap is hardly changed with the trigger voltage as well as the working coefficient and maintains less than 1.4 ns. It is proved that the discharging product from the trigger gap can effectively reduce the breakdown delay and jitter of the overvoltage gap. Based on that, the effect and improvement of pre-ionization on the two gaps are also studied. It is concluded that the jitter of the trigger gap reduces obviously when the pre-ionization is added, while the pre-ionization almost has no effect on the jitter of the overvoltage gap. The jitter of the overvoltage gap is about two times higher than the trigger gap in the pre-ionizing switch. 展开更多
关键词 gas SWITCH BREAKDOWN characteristic pre-ionization TRIGGER GAP OVERVOLTAGE GAP
How does Helicobacter pylori cause gastric cancer through connexins: An opinion review 预览
5
作者 Huan Li Can-Xia Xu +3 位作者 Ren-Jie Gong Jing-Shu Chi Peng Liu Xiao-Ming Liu 《世界胃肠病学杂志:英文版》 SCIE CAS 2019年第35期5220-5232,共13页
Helicobacter pylori (H. pylori) is a Gram-negative bacterium with a number of virulence factors, such as cytotoxin-associated gene A, vacuolating cytotoxin A, its pathogenicity island, and lipopolysaccharide, which ca... Helicobacter pylori (H. pylori) is a Gram-negative bacterium with a number of virulence factors, such as cytotoxin-associated gene A, vacuolating cytotoxin A, its pathogenicity island, and lipopolysaccharide, which cause gastrointestinal diseases. Connexins function in gap junctional homeostasis, and their downregulation is closely related to gastric carcinogenesis. Investigations into H. pylori infection and the fine-tuning of connexins in cells or tissues have been reported in previous studies. Therefore, in this review, the potential mechanisms of H. pylori-induced gastric cancer through connexins are summarized in detail. 展开更多
关键词 Helicobacter pylori CONNEXIN GAP JUNCTIONAL INTERCELLULAR communications GAP junction proteins Gastric cancer Transcription factors DNA methylation Proliferation Apoptosis
在线阅读 免费下载
端丙炔基聚丁二烯预聚物的贮存稳定性 预览
6
作者 高文博 李永辉 +1 位作者 何吉宇 杨荣杰 《火炸药学报》 CAS CSCD 北大核心 2019年第5期460-464,I0003共6页
为确定端丙炔基聚丁二烯(PTPB)在常温下的贮存稳定性,通过跟踪测试研究了PTPB在室温(15~30℃)、5℃他-10℃下的贮存稳定性。采用13 C-NMR、FT-IR、TG、GPC和黏度测试对贮存在不同温度下、不同时间的PTPB的化学结构和性质进行了表征分析... 为确定端丙炔基聚丁二烯(PTPB)在常温下的贮存稳定性,通过跟踪测试研究了PTPB在室温(15~30℃)、5℃他-10℃下的贮存稳定性。采用13 C-NMR、FT-IR、TG、GPC和黏度测试对贮存在不同温度下、不同时间的PTPB的化学结构和性质进行了表征分析,并将贮存的PTPB预聚物分别与聚叠氮缩水甘油醚(GAP)制成PTPB弹性体,采用FTIR、DMA和力学测试对弹性体进行表征。结果表明,在室温下贮存4个月的PTPB,与在5℃和-10℃贮存4个月的PTPB化学结构及性质一致,未发生聚合、交联、断链、氧化反应,黏度也未发生变化;由其制成的PTPB弹性体在3种温度下贮存4个月后,其分子结构、动态力学性能及室温力学性能也保持一致。因此PTPB能够在常温下稳定贮存,不需在低温贮存。 展开更多
关键词 分析化学 端丙炔基聚丁二烯 PTPB 弹性体 贮存稳定性 GAP
在线阅读 下载PDF
影响阀门高温上阀盖焊接质量的研究和分析 预览
7
作者 刘兰 谢远奉 +1 位作者 段大军 尚洪宝 《仪器仪表用户》 2019年第8期22-25,38共5页
在石油化工领域选择铬钼钢作为阀门高温上阀盖的重要材质,其焊接质量直接影响生产运行的安全,合理的焊接工艺和焊接坡口设计有利于保证焊缝的使用性能。针对某石化现场运行的阀门高温上阀盖出现的问题进行了研究分析,根据试验数据探讨... 在石油化工领域选择铬钼钢作为阀门高温上阀盖的重要材质,其焊接质量直接影响生产运行的安全,合理的焊接工艺和焊接坡口设计有利于保证焊缝的使用性能。针对某石化现场运行的阀门高温上阀盖出现的问题进行了研究分析,根据试验数据探讨了合理的焊接工艺要求和坡口设计方案,对行业中此类材质的焊接方式具有重要的指导作用。 展开更多
关键词 上阀盖 V型 坡口 焊接 焊缝 失效 对比试验 间隙 裂纹 拉伸
在线阅读 下载PDF
Discovering unusual structures from exception using big data and machine learning techniques
8
作者 Jianshu Jie Zongxiang Hu +9 位作者 Guoyu Qian Mouyi Weng Shunning Li Shucheng Li Mingyu Hu Dong Chen Weiji Xiao Jiaxin Zheng Lin-Wang Wang Feng Pan 《科学通报:英文版》 SCIE EI CSCD 2019年第9期612-616,共5页
Recently, machine learning(ML) has become a widely used technique in materials science study. Most work focuses on predicting the rule and overall trend by building a machine learning model. However,new insights are o... Recently, machine learning(ML) has become a widely used technique in materials science study. Most work focuses on predicting the rule and overall trend by building a machine learning model. However,new insights are often learnt from exceptions against the overall trend. In this work, we demonstrate that how unusual structures are discovered from exceptions when machine learning is used to get the relationship between atomic and electronic structures based on big data from high-throughput calculation database. For example, after training an ML model for the relationship between atomic and electronic structures of crystals, we find AgO2 F, an unusual structure with both Ag3+and O22à, from structures whose band gap deviates much from the prediction made by our model. A further investigation on this structure might shed light into the research on anionic redox in transition metal oxides of Li-ion batteries. 展开更多
关键词 Machine learning GRADIENT BOOSTING decision tree Band gap UNUSUAL STRUCTURES
Distinct Superconducting Gap on Two Bilayer-Split Fermi Surface Sheets in Bi2Sr2CaCu2O8+δ Superconductor
9
作者 艾平 高强 +13 位作者 刘静 张玉晓 李聪 黄建伟 宋春尧 闫宏涛 林赵 刘国东 顾根大 张丰丰 杨峰 彭钦军 许祖彦 周兴江 《中国物理快报:英文版》 SCIE CAS CSCD 2019年第6期66-74,共9页
High resolution laser-based angle-resolved photoemission measurements are carried out on an overdoped superconductor Bi2Sr2CaCu2O8+with ac of 75 K.Two Fermi surface sheets caused by bilayer splitting are clearly ident... High resolution laser-based angle-resolved photoemission measurements are carried out on an overdoped superconductor Bi2Sr2CaCu2O8+with ac of 75 K.Two Fermi surface sheets caused by bilayer splitting are clearly identified with rather different doping levels:the bonding sheet corresponds to a doping level of 0.14,which is slightly underdoped while the antibonding sheet has a doping of 0.27 that is heavily overdoped,giving an overall doping level of 0.20 for the sample.Different superconducting gap sizes on the two Fermi surface sheets are revealed.The superconducting gap on the antibonding Fermi surface sheet follows a standard d-wave form while it deviates from the standard d-wave form for the bonding Fermi surface sheet.The maximum gap difference between the two Fermi surface sheets near the antinodal region is~2 meV.These observations provide important information for studying the relationship between the Fermi surface topology and superconductivity,and the layer-dependent superconductivity in high temperature cuprate superconductors. 展开更多
关键词 DISTINCT Superconducting Gap Bilayer-Split FERMI Surface SHEETS Bi2Sr2CaCu2O8+δSuperconductor
Effects of Hot Wire Temperature on Properties of GeSi:H Films with High Hydrogen Dilution by Hot-Wire Chemical Vapor Deposition
10
作者 TAI Xin LI Xingbing +3 位作者 ZHEN Huang SHEN Honglie LI Yufang HUANG Haibin 《武汉大学学报:自然科学英文版》 CAS CSCD 2019年第5期405-408,共4页
GeSi:H films are prepared by hot-wire chemical vapor deposition(CVD) with high hydrogen dilution, DH=98%. Effects of hot wire temperature(Tw) on deposition rate, structural properties and bandgap of GeSi:H films are s... GeSi:H films are prepared by hot-wire chemical vapor deposition(CVD) with high hydrogen dilution, DH=98%. Effects of hot wire temperature(Tw) on deposition rate, structural properties and bandgap of GeSi:H films are studied with surface profilemeter, Raman spectroscopy, Fourier transformed infrared spectroscopy, and UV-VIS-NIR spectrophotometer. It is found that the deposition rate(Rd) goes up with increasing of Tw, but increasing rate of Rd declines when Tw≥1 550 ℃. High Tw is beneficial to the formation of Ge-Si, but it has little effect on relative contents of the hydrogen bonds(Ge-H, Si-H, etc.) in the films. In the Tw range of 1 400-1 850 ℃, the maximum bandgap of the GeSi:H films is 1.39 eV at Tw =1 450 ℃ and the band gap decreases with Tw increasing when Tw≥1 450 ℃. 展开更多
关键词 GeSi:H FILMS HOT-WIRE chemical vapor deposition(CVD) DEPOSITION rate structural properties band gap hot wire TEMPERATURE
Application of the hybrid RANS/LES method on the hydraulic dynamic performance of centrifugal pumps 预览
11
作者 Zheng-chuan Zhang Hong-xun Chen +4 位作者 Zheng Ma Qun Wei Jian-wu He Hui Liu Chao Liu 《水动力学研究与进展:英文版》 SCIE EI CSCD 2019年第3期637-640,共4页
The nonlinear hybrid RANS/LES method has been developed considering the simulation efficiency and accuracy to simulate the hydraulic dynamic characteristics of the centrifugal pump. It has been proved that the nonline... The nonlinear hybrid RANS/LES method has been developed considering the simulation efficiency and accuracy to simulate the hydraulic dynamic characteristics of the centrifugal pump. It has been proved that the nonlinear hybrid RANS/LES method could effectively capture the unsteady flow structure and pressure pulsation in 2?D centrifugal pumps. To further investigate the hydraulic dynamic performance of a redesigned 3-D-gap drainage centrifugal pump, the nonlinear hybrid RANS/LES method is employed. Both numerical simulation and experimental results show that the hydraulic performance and pressure pulsation characteristics of the 3-D-gap drainage impeller centrifugal pump are significantly enhanced. 展开更多
关键词 3-D GAP drainage BLADES nonlinear hybrid RANS/LES METHOD pressure PULSATION
在线阅读 下载PDF
不同受荷条件下脱空缺陷对钢管混凝土构件的承载力和刚度的影响分析
12
作者 高献 《工业建筑》 CSCD 北大核心 2019年第10期43-47,53,共6页
为了解脱空缺陷对钢管混凝土在不同受荷条件下的力学性能影响,将已有报道中不同受荷条件下(压弯、拉弯、压弯扭等)带脱空缺陷试件的承载力和刚度折减系数的变化规律进行比较,并对脱空的影响规律进行探讨。结果表明:在承受压弯荷载时,偏... 为了解脱空缺陷对钢管混凝土在不同受荷条件下的力学性能影响,将已有报道中不同受荷条件下(压弯、拉弯、压弯扭等)带脱空缺陷试件的承载力和刚度折减系数的变化规律进行比较,并对脱空的影响规律进行探讨。结果表明:在承受压弯荷载时,偏心受压为最不利荷载条件;轴压比和轴拉比分别为压弯荷载和拉弯荷载加载路径下影响带缺陷试件承载力的重要因素;滞回作用能加剧压弯荷载加载路径下的承载力折减;轴压比为0.3时,脱空对压弯构件承载力和刚度的影响最小;压弯荷载对带缺陷构件承载力的影响比压弯扭荷载更为不利。 展开更多
关键词 脱空缺陷 钢管混凝土 不同受荷条件 承载力 刚度
2000—2015年我国省、市、县域3 种尺度下城乡收入差距的时空格局演化 预览
13
作者 张改素 丁志伟 《河南科学》 2019年第10期1708-1720,共13页
以城乡收入比为指标,采用变异系数、莫兰指数与空间分析方法,基于省域、市域、县域3种尺度对2000—2015年中国城乡收入差距的时空格局特征进行分析.研究表明:①从内部差异看,不同尺度下全国、两大经济带、四大板块基本上表现出城乡收入... 以城乡收入比为指标,采用变异系数、莫兰指数与空间分析方法,基于省域、市域、县域3种尺度对2000—2015年中国城乡收入差距的时空格局特征进行分析.研究表明:①从内部差异看,不同尺度下全国、两大经济带、四大板块基本上表现出城乡收入差距缩小且差异程度降低的趋势特征,这一特征在县域尺度下表现得尤为明显;从省域尺度看,中东部多数省区表现出逐步下降或波动下降的趋势,但一些欠发达,尤其是地处西部的省区表现出相反的趋势特点.②从空间自相关与集聚现象看,全国、两大经济带、四大板块在不同尺度下表现为较强的正相关,虽然近期有所下降,但整体上仍呈现出不同集聚程度的增强;而从各省区看,县域尺度下表现出不断增强的正相关且集聚效应明显,市域尺度下差异较大且部分省区规律性不明显.③从空间分异格局演化看,极高、高、较高等类型区在西部地区明显减少而中等及其以下差距区个数逐渐增多是其主要的格局演变特点,在西部县域尺度下变化最为明显;东部除极少数较高差距区外,其他均处于中等及其以下类型区,逐渐向低层次、均衡化空间格局转化;中部格局变化相对不大,大多单元均处于较高、中等或较低差距区.由较高、高、极高组成的“楔子”型的大范围集聚连片区在县域尺度下凸显,但空间集聚的程度有所下降.④从空间关联类型看,以HH区、LL区为主导且总体表现出HH区增加、LL区下降的趋势,但各尺度的差异化特征不同.从空间演化看,显著HH区主要分布在西部地区并产生大范围连绵分布区,近期向中部扩展的趋势明显;显著LL区虽在中东部城市群核心区、城镇化高水平区集聚分布,但在东北、西北集聚的范围较大且连绵态势明显;显著HL区与显著LH区分布数量少且未形成集聚分布,显示出极化与塌陷效应均不明显. 展开更多
关键词 城乡收入 差距 时空格局 演化 多尺度 中国
在线阅读 下载PDF
恶性肿瘤中GAPLINC的调控作用及其与患者预后的关系
14
作者 周原世 徐书婉 +2 位作者 关沧海 胡增涛 姜兴明 《中华病理学杂志》 CAS CSCD 北大核心 2019年第11期902-905,共4页
长链非编码RNA(long non-coding RNAs,lncRNA)是一类长度超过200个核苷酸且因缺乏开放性阅读框架而丧失蛋白编码能力的转录本,但是lncRNA能够在转录以及转录后等不同水平以诸多方式调控肿瘤的发生发展。GAPLINC(gastric adenocarcinoma ... 长链非编码RNA(long non-coding RNAs,lncRNA)是一类长度超过200个核苷酸且因缺乏开放性阅读框架而丧失蛋白编码能力的转录本,但是lncRNA能够在转录以及转录后等不同水平以诸多方式调控肿瘤的发生发展。GAPLINC(gastric adenocarcinoma associated,positive CD44 regulator,long intergenic non-coding RNA)定位于人类染色体18p11.31,在多种恶性肿瘤(胃癌、结直肠癌、胆管癌等)中异常高表达并能够通过不同的作用机制调控肿瘤细胞的增殖、抗凋亡、侵袭和转移。此外,GAPLINC还可作为生物标志物在肿瘤的早期诊断、靶向治疗及患者的预后评估等方面具有重要的应用前景。该文就GAPLINC在恶性肿瘤中的调控作用及应用前景作一综述。 展开更多
关键词 胆管癌 人类染色体 恶性肿瘤 靶向治疗 CD44 抗凋亡 GAP
Enhancing coupling coefficient in a hybrid nanotoroid–nanowire system
15
作者 张淇 任娟娟 +3 位作者 段雪珂 郝赫 龚旗煌 古英 《中国光学快报:英文版》 SCIE EI CAS CSCD 2019年第3期86-90,共5页
Enhancing light–matter interaction in cavity quantum electrodynamics has aroused widespread interests in on-chip quantum information processing. Here, we propose a hybrid nanotoroid–nanowire system to enhance photon... Enhancing light–matter interaction in cavity quantum electrodynamics has aroused widespread interests in on-chip quantum information processing. Here, we propose a hybrid nanotoroid–nanowire system to enhance photon–exciton interaction. A nanoscale gap is formed by placing a dielectric nanowire close to a dielectric nanotoroid, where the coupling coefficient between photon and emitter can achieve 5.55 times of that without nanogap. Meanwhile, the cavity loss and spontaneous emission of the emitter will remain at a small value to guarantee the realization of strong coupling. The method might hold promise for the research of nanophotonics,quantum optics, and novel optical devices. 展开更多
关键词 PHOTON optical TIMES HAS GAP can
Synchronization of home departure and arrival times in dual earner households with children:Panel regression model of time gaps
16
作者 Bilin Han Harry Timmermans 《交通运输工程学报(英文版)》 CSCD 2019年第5期504-513,共10页
Organizing schedules and allocating time to different activities is always a challenge in dual-earner households,especially when they have children.Parents may need to link their schedule to those of their children to... Organizing schedules and allocating time to different activities is always a challenge in dual-earner households,especially when they have children.Parents may need to link their schedule to those of their children to allow them escorting their children to school or to take care or be with their children at home.This paper reports the results of an analysis of the degree of synchronization of home departure and arrival times in dual earner households with children,where the degree of synchronization is defined as the gap between departure and arrival times of a parent and child.Using activity-travel diary data of different household members,a random parameters regression model is estimated to examine differences in time gaps in home departure and arrival times between parents and children as a function of gender,day of the week,age of the youngest child,and other socio-demographic characteristics.The results of the analysis provide insight into factors influencing the degree of synchronization and coordination of double activity-travel scheduling decisions in households with children.Findings indicate that gender,number of children in the household,age of the youngest child,travel within or outside peak hours,day of the week,transport mode used for the work commute and household income level significantly affect time gaps,especially arrival time gaps. 展开更多
关键词 HOME DEPARTURE and ARRIVAL TIMES SYNCHRONIZATION Time gap Dual-earner households RANDOM parameters panel regression model
给水泵振动原因分析及对策 预览
17
作者 薛大强 《冶金动力》 2019年第4期36-39,共4页
锅炉给水泵是锅炉安全稳定运行的基础,由于设备老化和检修安装技术水平等原因。造成在试运行时,会出现各种常见的缺陷,其中轴承振动偏大是工作中的一个难点,针对给水泵振动这个问题,通过联轴器中心调整、轴承检查间隙调整、转子扬度调整... 锅炉给水泵是锅炉安全稳定运行的基础,由于设备老化和检修安装技术水平等原因。造成在试运行时,会出现各种常见的缺陷,其中轴承振动偏大是工作中的一个难点,针对给水泵振动这个问题,通过联轴器中心调整、轴承检查间隙调整、转子扬度调整等3个事例实践总结分析出3种切实可行的解决方案。 展开更多
关键词 给水泵 振动 中心 间隙 扬度
在线阅读 下载PDF
优衣库×KAWSIP潮流文化的力量 预览
18
作者 陆杨 《时尚北京》 2019年第7期108-111,共4页
今年6月初,优衣库推出KAWS联名款系列,网店上线3秒即售罄,线下门店则出现哄抢,话题一度盘踞热搜数日。与此同时,与优衣库同属一梯队的Zara、H&M、Gap等国际快时尚品牌却频频遭遇业绩滑铁卢。优衣库的财报不仅显示净利润大增,更是助... 今年6月初,优衣库推出KAWS联名款系列,网店上线3秒即售罄,线下门店则出现哄抢,话题一度盘踞热搜数日。与此同时,与优衣库同属一梯队的Zara、H&M、Gap等国际快时尚品牌却频频遭遇业绩滑铁卢。优衣库的财报不仅显示净利润大增,更是助力创始人柳井正登上日本首富宝座。 展开更多
关键词 文化 潮流 时尚品牌 GAP 净利润 创始人 度盘
在线阅读 下载PDF
Weakened interlayer coupling in two-dimensional MoSe2 flakes with screw dislocations
19
作者 Xiangzhuo Wang Huixia Yang +13 位作者 Rong Yang Qinsheng Wang Jingchuan Zheng Lu Qiao Xianglin Peng Yongkai Li Dongyun Chen Xiaolu Xiong Junxi Duan Guangyu Zhang Jie Ma Junfeng Han Wende Xiao Yugui Yao 《纳米研究:英文版》 SCIE EI CAS CSCD 2019年第8期1900-1905,共6页
The screw dislocations are intriguing defects that are often observed in natural and artificial materials. The dislocation spirals break the reflection and inversion symmetries of the lattices and modify the interlaye... The screw dislocations are intriguing defects that are often observed in natural and artificial materials. The dislocation spirals break the reflection and inversion symmetries of the lattices and modify the interlayer coupling in layer-structured materials, inducing additional complexity in layer stacking and thus novel properties in materials. Here, we report on the interlayer coupling of two-dimensional (2D) MoSe2 flakes with screw dislocations by atomic force microscopy (AFM), Raman spectra and photoluminescence (PL) spectra. By controlling the supersaturation conditions, 2D MoSe2 flakes with screw dislocations are grown on amorphous SiO2 substrates by chemical vapor deposition (CVD). AFM measurements reveal that the interlayer spacing in such 2D MoSe2 flakes with screw dislocation is slightly widened with respect to the normal AA- or AB-stacked ones due to the presence of the screw dislocations. Raman and PL spectra show that the interlayer coupling is weaker and thus the band gap is wider than that in the normal AA- or AB-stacked ones. Our work demonstrates that the interlayer coupling of 2D transition metal dichalcogenides (TMDCs) flakes can be tuned by the induction of screw dislocations, which is very helpful for developing novel catalysts and electronic devices. 展开更多
关键词 TRANSITION-METAL DICHALCOGENIDES MOLYBDENUM SELENIDE screw dislocations INTERLAYER coupling band gap
酒钢西沟矿绿色矿山建设规划方案探讨与研究
20
作者 任毅 陈佳 +2 位作者 许守信 张士全 乔敏 《矿山机械》 2019年第10期1-4,共4页
为保证西沟矿达到国家级绿色矿山建设标准,早日进入国家级绿色矿山建设名录,按照《非金属矿行业绿色矿山建设规范》和《水泥灰岩绿色矿山建设规范》的要求,逐项比对,深层剖析西沟矿绿色矿山建设现状和短板,甄别西沟矿与国家绿色矿山标... 为保证西沟矿达到国家级绿色矿山建设标准,早日进入国家级绿色矿山建设名录,按照《非金属矿行业绿色矿山建设规范》和《水泥灰岩绿色矿山建设规范》的要求,逐项比对,深层剖析西沟矿绿色矿山建设现状和短板,甄别西沟矿与国家绿色矿山标准的差距,最终确定为矿区环境治理和修复、资源综合利用、节能减排、科技创新与智能矿山、企地和谐共建和企业规范管理六方面,梳理出西沟矿绿色矿山建设的重点任务,编制西沟矿西沟矿绿色矿山建设规划和可行性研究报告,分期推进西沟矿绿色矿山建设工作。 展开更多
关键词 绿色矿山 名录 差距 分期推进
上一页 1 2 250 下一页 到第
使用帮助 返回顶部 意见反馈