目的:对北京大学第一医院心血管内科与国际同行学术论文发表情况进行量化对比分析,揭示其在科研产出、研究热点和国际合作等方面的现状与不足,为进一步完善学科建设提供科学依据和改进方向。方法:基于Web of Science 2015-2024年论文数...目的:对北京大学第一医院心血管内科与国际同行学术论文发表情况进行量化对比分析,揭示其在科研产出、研究热点和国际合作等方面的现状与不足,为进一步完善学科建设提供科学依据和改进方向。方法:基于Web of Science 2015-2024年论文数据,选取“2025年世界最佳医院”榜单中心脏病学领域排名前10的国际医疗机构作为对标机构,使用CiteSpace 6.4 R1从论文数量与增长率、研究关键词、机构合作、引文情况多维度进行比较分析。结果:与对标机构相比,北京大学第一医院心血管内科发文增长率较高,研究热点与国际接轨,合作网络呈现“国内集中、国际分散”特点,引文突现分析体现“诊疗并进”的趋势。结论:北京大学第一医院心血管内科发展势头较好,但与国际领先机构相比,在论文数量、国际学术影响力、国际合作等方面仍存在一定差距。未来应加快推动科研高质量发展,深化国际合作,关注临床前沿技术,激发创新活力,不断提升国际影响力。展开更多
岩石-混凝土界面是工程结构的薄弱环节,对结构整体的强度和稳定性有重要影响。为反映岩-混界面天然粗糙状态,基于内聚力模型(cohesive zone model,简称CZM),建立了具有随机生成粗糙界面的岩石-混凝土复合巴西圆盘试件数值模型,通过不同...岩石-混凝土界面是工程结构的薄弱环节,对结构整体的强度和稳定性有重要影响。为反映岩-混界面天然粗糙状态,基于内聚力模型(cohesive zone model,简称CZM),建立了具有随机生成粗糙界面的岩石-混凝土复合巴西圆盘试件数值模型,通过不同加载角度下的巴西劈裂物理试验验证了该方法的可靠性,并探究了界面粗糙度、加载角度对试件峰值荷载和破坏特征的影响。结果表明:不同加载角度下,试件存在3种典型破坏模式:界面黏结破坏、复合破坏、双材料拉伸开裂破坏;加载角度对试件力学行为的影响以70°为界,加载角度小于70°时影响显著,大于70°后影响不显著;界面粗糙度的影响随加载角度的不同有较大差异,当加载角度在15°~65°范围内,提高界面粗糙度可显著提高试件峰值荷载,增强岩-混结构的承载能力;界面处应力状态的差异决定了试件破坏模式的不同,但粗糙的界面可以增强混凝土与岩石之间的黏结和互锁效应,对试件破坏模式产生影响。研究结果将加深对岩石-混凝土界面破坏机制的认识,对工程建设具有指导意义。展开更多
The two kinds of rigid polyurethane(PU)foams were prepared with respectively adding the refined alkali lignin and alkali lignin modified by 3-chloro-1,2-epoxypropane to be instead of 15%of the polyether glycol in weig...The two kinds of rigid polyurethane(PU)foams were prepared with respectively adding the refined alkali lignin and alkali lignin modified by 3-chloro-1,2-epoxypropane to be instead of 15%of the polyether glycol in weight.The indexes of mechanical performance,apparent density,thermal stability and aging resistance were separately tested for the prepared PU foams.The results show that the mechanical property,thermal insulation and thermal stability for PU foam with modified alkali lignin are excellent among two kinds of PU foams and control samples.The additions of the refined alkali lignin and modified alkali lignin to PU foam have little effect on the natural aging or heat aging resistance except for decreasing hot alkali resistance apparently.Additionally,the thermal conductivity of modified alkali lignin PU foam is lowest among two kinds of PU foams and control samples.The alkali lignin PU foam modified by 3-chloro-1,2-epoxypropane could be applied in the heat preservation field.展开更多
文摘岩石-混凝土界面是工程结构的薄弱环节,对结构整体的强度和稳定性有重要影响。为反映岩-混界面天然粗糙状态,基于内聚力模型(cohesive zone model,简称CZM),建立了具有随机生成粗糙界面的岩石-混凝土复合巴西圆盘试件数值模型,通过不同加载角度下的巴西劈裂物理试验验证了该方法的可靠性,并探究了界面粗糙度、加载角度对试件峰值荷载和破坏特征的影响。结果表明:不同加载角度下,试件存在3种典型破坏模式:界面黏结破坏、复合破坏、双材料拉伸开裂破坏;加载角度对试件力学行为的影响以70°为界,加载角度小于70°时影响显著,大于70°后影响不显著;界面粗糙度的影响随加载角度的不同有较大差异,当加载角度在15°~65°范围内,提高界面粗糙度可显著提高试件峰值荷载,增强岩-混结构的承载能力;界面处应力状态的差异决定了试件破坏模式的不同,但粗糙的界面可以增强混凝土与岩石之间的黏结和互锁效应,对试件破坏模式产生影响。研究结果将加深对岩石-混凝土界面破坏机制的认识,对工程建设具有指导意义。
文摘The two kinds of rigid polyurethane(PU)foams were prepared with respectively adding the refined alkali lignin and alkali lignin modified by 3-chloro-1,2-epoxypropane to be instead of 15%of the polyether glycol in weight.The indexes of mechanical performance,apparent density,thermal stability and aging resistance were separately tested for the prepared PU foams.The results show that the mechanical property,thermal insulation and thermal stability for PU foam with modified alkali lignin are excellent among two kinds of PU foams and control samples.The additions of the refined alkali lignin and modified alkali lignin to PU foam have little effect on the natural aging or heat aging resistance except for decreasing hot alkali resistance apparently.Additionally,the thermal conductivity of modified alkali lignin PU foam is lowest among two kinds of PU foams and control samples.The alkali lignin PU foam modified by 3-chloro-1,2-epoxypropane could be applied in the heat preservation field.
