利用深部岩爆模拟试验系统对花岗岩进行室内瞬时岩爆模拟试验,同时利用声发射系统采集试验过程中声发射信号,得到试验全过程应力和声发射波形信息时域图。结合声发射累计能量曲线特征,找到5个关键拐点,即花岗岩初始加载能量激增后产生...利用深部岩爆模拟试验系统对花岗岩进行室内瞬时岩爆模拟试验,同时利用声发射系统采集试验过程中声发射信号,得到试验全过程应力和声发射波形信息时域图。结合声发射累计能量曲线特征,找到5个关键拐点,即花岗岩初始加载能量激增后产生的第一个拐点A、岩爆发生前两次明显的上升台阶处拐点B和C、岩爆发生时的能量突跃点D、最终峰值点E。将关键点处波形信号从全时域波形中提取出来并进行快速傅里叶变换,得到各关键点二维功率谱图,结果表明:花岗岩声发射主频值在加载初期时为106 k Hz,随着荷载的增加,频率由低频向高频过渡,频带变宽且由单峰向多峰转化,频率成分复杂预示多种破裂模式的发生。岩爆前和最终岩爆时刻频带又变窄并恢复单峰,主频值降低至与初始加载时一致,约为106 k Hz,预示着岩爆时刻花岗岩岩石高能量的释放。展开更多
AIM: To conduct a systematic review relating myocardial strain assessed by different imaging modalities for prognostication following ST-elevation myocardial infarction(STEMI).METHODS: An online literature search was ...AIM: To conduct a systematic review relating myocardial strain assessed by different imaging modalities for prognostication following ST-elevation myocardial infarction(STEMI).METHODS: An online literature search was performed in Pub Med and OVID® electronic databases to identify any studies that assessed global myocardial strain parameters using speckle-tracking echocardiography(STE) and/or cardiac magnetic resonance imaging(CMR) techniques [either myocardial tagging or feature tracking(FT) software] in an acute STEMI cohort(days 0-14 post-event) to predict prognosis [either development of major adverse cardiac events(MACE)] or adverse left ventricular(LV) remodelling at follow-up(≥ 6 mo for MACE,≥ 3 mo for remodelling). Search was restricted to studies within the last 20 years. All studies that matched the pre-defined search criteria were reviewed and their results interpreted. Due to considerable heterogeneity between studies,metaanalysis was not performed.RESULTS: A total of seven studies(n = 7) were identified that matched the search criteria. All studies used STE to evaluate strain parameters- five(n = 5) assessed global longitudinal strain(GLS)(n = 5),one assessed GLS rate(GLS-R)(n = 1) and one assessed both(n = 1). Three studies showed that GLS independently predicted the development of adverse LV remodelling by multivariate analysis- odds ratio between 1.19(CI: 1.04-1.37,P < 0.05) and 10(CI: 6.7-14,P < 0.001) depending on the study. Four studies showed that GLS predicted the development of MACE- hazard ratio(HR) between 1.1(CI: 1-1.1,P = 0.006) and 2.34(1.10-4.97,P < 0.05). One paper found that GLS-R could significantly predict MACEHR 18(10-35,P < 0.001)- whilst another showed it did not. GLS <-10.85% had sensitivity/specificity of 89.7%/91% respectively for predicting the development of remodelling whilst GLS <-13% could predict the development of MACE with sensitivity/specificity of 100%/89% respectively. No suitable studies were identified that assessed global strain by CMR tagging or FT tech展开更多
文摘利用深部岩爆模拟试验系统对花岗岩进行室内瞬时岩爆模拟试验,同时利用声发射系统采集试验过程中声发射信号,得到试验全过程应力和声发射波形信息时域图。结合声发射累计能量曲线特征,找到5个关键拐点,即花岗岩初始加载能量激增后产生的第一个拐点A、岩爆发生前两次明显的上升台阶处拐点B和C、岩爆发生时的能量突跃点D、最终峰值点E。将关键点处波形信号从全时域波形中提取出来并进行快速傅里叶变换,得到各关键点二维功率谱图,结果表明:花岗岩声发射主频值在加载初期时为106 k Hz,随着荷载的增加,频率由低频向高频过渡,频带变宽且由单峰向多峰转化,频率成分复杂预示多种破裂模式的发生。岩爆前和最终岩爆时刻频带又变窄并恢复单峰,主频值降低至与初始加载时一致,约为106 k Hz,预示着岩爆时刻花岗岩岩石高能量的释放。
基金funded by the University of Leicester and the National Institute for Health Research (NIHR) in the United Kingdom
文摘AIM: To conduct a systematic review relating myocardial strain assessed by different imaging modalities for prognostication following ST-elevation myocardial infarction(STEMI).METHODS: An online literature search was performed in Pub Med and OVID® electronic databases to identify any studies that assessed global myocardial strain parameters using speckle-tracking echocardiography(STE) and/or cardiac magnetic resonance imaging(CMR) techniques [either myocardial tagging or feature tracking(FT) software] in an acute STEMI cohort(days 0-14 post-event) to predict prognosis [either development of major adverse cardiac events(MACE)] or adverse left ventricular(LV) remodelling at follow-up(≥ 6 mo for MACE,≥ 3 mo for remodelling). Search was restricted to studies within the last 20 years. All studies that matched the pre-defined search criteria were reviewed and their results interpreted. Due to considerable heterogeneity between studies,metaanalysis was not performed.RESULTS: A total of seven studies(n = 7) were identified that matched the search criteria. All studies used STE to evaluate strain parameters- five(n = 5) assessed global longitudinal strain(GLS)(n = 5),one assessed GLS rate(GLS-R)(n = 1) and one assessed both(n = 1). Three studies showed that GLS independently predicted the development of adverse LV remodelling by multivariate analysis- odds ratio between 1.19(CI: 1.04-1.37,P < 0.05) and 10(CI: 6.7-14,P < 0.001) depending on the study. Four studies showed that GLS predicted the development of MACE- hazard ratio(HR) between 1.1(CI: 1-1.1,P = 0.006) and 2.34(1.10-4.97,P < 0.05). One paper found that GLS-R could significantly predict MACEHR 18(10-35,P < 0.001)- whilst another showed it did not. GLS <-10.85% had sensitivity/specificity of 89.7%/91% respectively for predicting the development of remodelling whilst GLS <-13% could predict the development of MACE with sensitivity/specificity of 100%/89% respectively. No suitable studies were identified that assessed global strain by CMR tagging or FT tech
