目的:总结成人急性创伤病人院前急救中病情评估指标的文献证据,为构建急诊急救大平台下“零通道”启用指标提供循证依据。方法:检索BMJ Best Practice、the Cochrane Library、PubMed、美国指南网、中国知网等国内外循证数据库和指南网...目的:总结成人急性创伤病人院前急救中病情评估指标的文献证据,为构建急诊急救大平台下“零通道”启用指标提供循证依据。方法:检索BMJ Best Practice、the Cochrane Library、PubMed、美国指南网、中国知网等国内外循证数据库和指南网站中关于“零通道”、院前急救创伤评分以及创伤团队启用标准的专家共识、系统评价、相关指南、Meta分析和高质量临床研究等。检索时限为2010年1月—2021年10月。由2名研究者对纳入文献的质量进行评价,并对符合质量标准的文献进行证据提取及总结。结果:共纳入17篇相关文献,其中专家共识3篇、临床研究9篇、指南1篇、系统评价4篇,最终在意识状态、生命体征、创伤机制等方面总结了10条证据。结论:系统总结了成人急性创伤病人院前急救启用“零通道”指标的最佳证据,为构建急诊急救大平台下“零通道”启用指标提供了循证参考。展开更多
钙质砂的颗粒易碎性是造成其变形和强度特性不同于石英砂的重要性质。本文基于临界状态理论,通过一系列试验定量地描述钙质砂临界状态线随颗粒破碎的演化规律。本文试验分两个阶段进行:第1阶段研究了60~2000 k Pa围压条件下钙质砂的力...钙质砂的颗粒易碎性是造成其变形和强度特性不同于石英砂的重要性质。本文基于临界状态理论,通过一系列试验定量地描述钙质砂临界状态线随颗粒破碎的演化规律。本文试验分两个阶段进行:第1阶段研究了60~2000 k Pa围压条件下钙质砂的力学特性和颗粒破碎特征;第2阶段以不同破碎率的试样为母本重塑制样,在100~300 k Pa围压条件下,剪切至破碎临界状态线。试验结果表明:在较小围压(<300 k Pa)条件下,松砂和密砂均表现出明显的剪胀和应变软化特性;而高围压(>1 MPa)条件下,显著的颗粒破碎会造成试样的持续剪缩;颗粒破碎存在明显围压阈值,对于松砂而言,在围压小于300 k Pa条件下,颗粒基本不发生破碎;在e-lg p’平面内,破碎临界状态线的截距ΔeΓ和斜率λc均会随着修正相对破碎率Br*的增大而减小,即颗粒破碎会使临界状态线发生下移和逆时针转动;而在q-p’平面内,钙质砂的临界状态点落在同一条直线上,即存在唯一的临界状态应力比Mcr和临界摩擦角φcr。展开更多
A large number of breakwaters have been constructed along coasts to protect humans and infrastructures from tsunamis.There is a risk that foundation soils of these structures may liquefy,or partially liquefy during th...A large number of breakwaters have been constructed along coasts to protect humans and infrastructures from tsunamis.There is a risk that foundation soils of these structures may liquefy,or partially liquefy during the earthquake preceding a tsunami,which would greatly reduce the structures’capacity to resist the tsunami.It is necessary to consider not only the soil’s liquefaction behavior due to earthquake motions but also its post-liquefaction behavior because this behavior will affect the breakwater’s capacity to resist an incoming tsunami.In this study,numerical tests based on a sophisticated constitutive model and a soil-water coupled finite element method are used to predict the mechanical behavior of breakwaters and the surrounding soils.Two real breakwaters subjected to two different seismic excitations are examined through numerical simulation.The simulation results show that,earthquakes affect not only the immediate behavior of breakwaters and the surrounding soils but also their long-term settlements due to post-earthquake consolidation.A soil profile with thick clayey layers beneath liquefied soil is more vulnerable to tsunami than a soil profile with only sandy layers.Therefore,quantitatively evaluating the seismic behavior of breakwaters and surrounding soils is important for the design of breakwater structures to resist tsunamis.展开更多
文摘目的:总结成人急性创伤病人院前急救中病情评估指标的文献证据,为构建急诊急救大平台下“零通道”启用指标提供循证依据。方法:检索BMJ Best Practice、the Cochrane Library、PubMed、美国指南网、中国知网等国内外循证数据库和指南网站中关于“零通道”、院前急救创伤评分以及创伤团队启用标准的专家共识、系统评价、相关指南、Meta分析和高质量临床研究等。检索时限为2010年1月—2021年10月。由2名研究者对纳入文献的质量进行评价,并对符合质量标准的文献进行证据提取及总结。结果:共纳入17篇相关文献,其中专家共识3篇、临床研究9篇、指南1篇、系统评价4篇,最终在意识状态、生命体征、创伤机制等方面总结了10条证据。结论:系统总结了成人急性创伤病人院前急救启用“零通道”指标的最佳证据,为构建急诊急救大平台下“零通道”启用指标提供了循证参考。
文摘钙质砂的颗粒易碎性是造成其变形和强度特性不同于石英砂的重要性质。本文基于临界状态理论,通过一系列试验定量地描述钙质砂临界状态线随颗粒破碎的演化规律。本文试验分两个阶段进行:第1阶段研究了60~2000 k Pa围压条件下钙质砂的力学特性和颗粒破碎特征;第2阶段以不同破碎率的试样为母本重塑制样,在100~300 k Pa围压条件下,剪切至破碎临界状态线。试验结果表明:在较小围压(<300 k Pa)条件下,松砂和密砂均表现出明显的剪胀和应变软化特性;而高围压(>1 MPa)条件下,显著的颗粒破碎会造成试样的持续剪缩;颗粒破碎存在明显围压阈值,对于松砂而言,在围压小于300 k Pa条件下,颗粒基本不发生破碎;在e-lg p’平面内,破碎临界状态线的截距ΔeΓ和斜率λc均会随着修正相对破碎率Br*的增大而减小,即颗粒破碎会使临界状态线发生下移和逆时针转动;而在q-p’平面内,钙质砂的临界状态点落在同一条直线上,即存在唯一的临界状态应力比Mcr和临界摩擦角φcr。
基金National Natural Science Foundation of China under Grant Nos.51678369,41627801 and 41372284Technical Innovation Foundation of Shenzhen under Grant No.JCYJ20170302143610976+2 种基金Doctoral Fund of Shandong Province under Grant No.ZR2017BEE071China Postdoctoral Science Foundation under Grant No.2017M612227the Special Project Fund of Taishan Scholars of Shandong Province under Grant No.2015-212
文摘A large number of breakwaters have been constructed along coasts to protect humans and infrastructures from tsunamis.There is a risk that foundation soils of these structures may liquefy,or partially liquefy during the earthquake preceding a tsunami,which would greatly reduce the structures’capacity to resist the tsunami.It is necessary to consider not only the soil’s liquefaction behavior due to earthquake motions but also its post-liquefaction behavior because this behavior will affect the breakwater’s capacity to resist an incoming tsunami.In this study,numerical tests based on a sophisticated constitutive model and a soil-water coupled finite element method are used to predict the mechanical behavior of breakwaters and the surrounding soils.Two real breakwaters subjected to two different seismic excitations are examined through numerical simulation.The simulation results show that,earthquakes affect not only the immediate behavior of breakwaters and the surrounding soils but also their long-term settlements due to post-earthquake consolidation.A soil profile with thick clayey layers beneath liquefied soil is more vulnerable to tsunami than a soil profile with only sandy layers.Therefore,quantitatively evaluating the seismic behavior of breakwaters and surrounding soils is important for the design of breakwater structures to resist tsunamis.
