背景中医药治疗脓毒症性急性肺损伤(ALI)/急性呼吸窘迫综合征(ARDS)的疗效确切,但大多数已发表的临床试验设计中缺乏标准、统一的结局指标,造成同类研究结果难以合并、对比,无法产生高质量的循证证据指导临床决策。目的分析2017—2022...背景中医药治疗脓毒症性急性肺损伤(ALI)/急性呼吸窘迫综合征(ARDS)的疗效确切,但大多数已发表的临床试验设计中缺乏标准、统一的结局指标,造成同类研究结果难以合并、对比,无法产生高质量的循证证据指导临床决策。目的分析2017—2022年中医药治疗脓毒症性ALI/ARDS临床试验结局指标的使用情况。方法检索中国知网(CNKI)、万方数据知识服务平台、中国生物医学文献服务系统、PubMed、Web of Science、Embase、Cochrane Library数据库中有关脓毒症性ALI或ARDS的随机对照试验,其中干预组措施为中医药联合其他药物或常规治疗方案,对照组不做限制。采用Cochrane研发的ROB.2工具进行文献质量评价并总结结局指标分类情况。结果经筛选后纳入39篇文献,其中文献偏倚风险评估为低风险1篇(2.56%),高风险3篇(7.69%),可能存在风险35篇(89.74%)。5篇(12.82%)文献结局指标报告质量评分≥5分,为结局指标报告完整。共报告106种结局指标,累计使用443次,包括理化检测(55种,51.89%)、中医症状/证候(2种,1.89%)、症状/体征(13种,12.26%)、远期预后(19种,17.92%)、生活质量(7种,6.60%)、安全性事件(8种,7.55%)和经济学评估(2种,1.89%)。使用率>50%的结局指标有4个,分别是氧合指数(82.05%)、急性生理与慢性健康状况评分系统Ⅱ(58.97%)、机械通气时间(51.28%)和白介素6(51.28%)。21篇文献使用有效率和/或中医证候疗效的复合结局指标,包括总有效率12次,中医证候积分8次和中医症状疗效6次。由于各结局指标差异较大,对106种指标进行合并和依次归类,最终总结出3个大类,分别为:整体评价指标(36种,33.96%)、共性指标(36种,33.96%)及不同关注重点指标(34种,32.08%)。结论目前中医药治疗脓毒症性ALI/ARDS临床试验结局指标的选择尚不规范,主要表现为主次结局指标区分不明确、复合结局指标标准不统一、轻视终点指标、缺少随访数据和中医特色指标等。未来应构建脓毒症性ALI/ARDS的中医药核心结局指标集,推动中医药的高质量发展。展开更多
This paper studies the dynamic responses of SDOF system under pulse-dominant excitations.The purpose of the study is to prepare for scrutiny of some near-field pulse-dominantground motions and their potential to cause...This paper studies the dynamic responses of SDOF system under pulse-dominant excitations.The purpose of the study is to prepare for scrutiny of some near-field pulse-dominantground motions and their potential to cause structural damage.Extending the single pulse dynamics,we consider the effect of pulse sequences.This kind of excitation was particularly obvious in some of previous earthquakes such as Northridge (1994) and Chi-Chi (1995).Based on the duration, peak and rise and decay era of the main pulse as well as its relationship with the predecessor and successor pulses,we propose a classification for the pulse sequences.Consequent studies have been canied out for acceleration,velocity and displacement response spectra of the main pulse with either a predecessor or a successor pulse.The analysis also includes general response behaviors in different fundamental period segments and special aspects of response at certain points (e.g.,the corresponding peak points).展开更多
Major earthquakes of last 15 years （e.g., Northridge 1994, Kobe 1995 and Chi-Chi 1999） have shown that many near-fault ground motions possess prominent acceleration pulses. Some of the prominent ground acceleration ...Major earthquakes of last 15 years （e.g., Northridge 1994, Kobe 1995 and Chi-Chi 1999） have shown that many near-fault ground motions possess prominent acceleration pulses. Some of the prominent ground acceleration pulses are related to large ground velocity pulses, others are caused by mechanisms that are totally different from those causing the velocity pulses or fling steps. Various efforts to model acceleration pulses have been reported in the literature. In this paper, research results from a recent study of acceleration pulse prominent ground motions and an analysis of structural damage induced by acceleration pulses are summarized. The main results of the study include： （1） temporal characteristics of acceleration pulses; （2） ductility demand spectrum of simple acceleration pulses with respect to equivalent classes of dynamic systems and pulse characteristic parameters; and （3） estimation of fundamental period change under the excitation of strong acceleration pulses. By using the acceleration pulse induced linear acceleration spectrum and the ductility demand spectrum, a simple procedure has been developed to estimate the ductility demand and the fundamental period change of a reinforced concrete （RC） structure under the impact of a strong acceleration pulse.展开更多
In a viscous damping device under cyclic loading, after the piston reaches a peak stroke, the reserve movement that follows may sometimes experience a short period of delayed or significantly reduced device force outp...In a viscous damping device under cyclic loading, after the piston reaches a peak stroke, the reserve movement that follows may sometimes experience a short period of delayed or significantly reduced device force output. A similar delay or reduced device force output may also occur at the damper＇s initial stroke as it moves away from its neutral position. This phenomenon is referred to as the effect of ＂deadzone＂. The deadzone can cause a loss of energy dissipation capacity and less efficient vibration control. It is prominent in small amplitude vibrations. Although there are many potential causes of deadzone such as environmental factors, construction, material aging, and manufacture quality, in this paper, its general effect in linear and nonlinear viscous damping devices is analyzed. Based on classical dynamics and damping theory, a simple model is developed to capture the effect ofdeadzone in terms of the loss of energy dissipation capacity. The model provides several methods to estimate the loss of energy dissipation within the deadzone in linear and sublinear viscous fluid dampers. An empirical equation of loss of energy dissipation capacity versus deadzone size is formulated, and the equivalent reduction of effective damping in SDOF systems has been obtained. A laboratory experimental evaluation is carried out to verify the effect of deadzone and its numerical approximation. Based on the analysis, a modification is suggested to the corresponding formulas in FEMA 3 5 6 for calculation of equivalent damping if a deadzone is to be considered.展开更多
文摘背景中医药治疗脓毒症性急性肺损伤(ALI)/急性呼吸窘迫综合征(ARDS)的疗效确切,但大多数已发表的临床试验设计中缺乏标准、统一的结局指标,造成同类研究结果难以合并、对比,无法产生高质量的循证证据指导临床决策。目的分析2017—2022年中医药治疗脓毒症性ALI/ARDS临床试验结局指标的使用情况。方法检索中国知网(CNKI)、万方数据知识服务平台、中国生物医学文献服务系统、PubMed、Web of Science、Embase、Cochrane Library数据库中有关脓毒症性ALI或ARDS的随机对照试验,其中干预组措施为中医药联合其他药物或常规治疗方案,对照组不做限制。采用Cochrane研发的ROB.2工具进行文献质量评价并总结结局指标分类情况。结果经筛选后纳入39篇文献,其中文献偏倚风险评估为低风险1篇(2.56%),高风险3篇(7.69%),可能存在风险35篇(89.74%)。5篇(12.82%)文献结局指标报告质量评分≥5分,为结局指标报告完整。共报告106种结局指标,累计使用443次,包括理化检测(55种,51.89%)、中医症状/证候(2种,1.89%)、症状/体征(13种,12.26%)、远期预后(19种,17.92%)、生活质量(7种,6.60%)、安全性事件(8种,7.55%)和经济学评估(2种,1.89%)。使用率>50%的结局指标有4个,分别是氧合指数(82.05%)、急性生理与慢性健康状况评分系统Ⅱ(58.97%)、机械通气时间(51.28%)和白介素6(51.28%)。21篇文献使用有效率和/或中医证候疗效的复合结局指标,包括总有效率12次,中医证候积分8次和中医症状疗效6次。由于各结局指标差异较大,对106种指标进行合并和依次归类,最终总结出3个大类,分别为:整体评价指标(36种,33.96%)、共性指标(36种,33.96%)及不同关注重点指标(34种,32.08%)。结论目前中医药治疗脓毒症性ALI/ARDS临床试验结局指标的选择尚不规范,主要表现为主次结局指标区分不明确、复合结局指标标准不统一、轻视终点指标、缺少随访数据和中医特色指标等。未来应构建脓毒症性ALI/ARDS的中医药核心结局指标集,推动中医药的高质量发展。
基金US NSF Under Grant No.CMS-0202846National Natural Science Foundation of China Under Grant No.50278092
文摘This paper studies the dynamic responses of SDOF system under pulse-dominant excitations.The purpose of the study is to prepare for scrutiny of some near-field pulse-dominantground motions and their potential to cause structural damage.Extending the single pulse dynamics,we consider the effect of pulse sequences.This kind of excitation was particularly obvious in some of previous earthquakes such as Northridge (1994) and Chi-Chi (1995).Based on the duration, peak and rise and decay era of the main pulse as well as its relationship with the predecessor and successor pulses,we propose a classification for the pulse sequences.Consequent studies have been canied out for acceleration,velocity and displacement response spectra of the main pulse with either a predecessor or a successor pulse.The analysis also includes general response behaviors in different fundamental period segments and special aspects of response at certain points (e.g.,the corresponding peak points).
基金U.S. National Science Foundation Under Grant CMS-0202846
文摘Major earthquakes of last 15 years （e.g., Northridge 1994, Kobe 1995 and Chi-Chi 1999） have shown that many near-fault ground motions possess prominent acceleration pulses. Some of the prominent ground acceleration pulses are related to large ground velocity pulses, others are caused by mechanisms that are totally different from those causing the velocity pulses or fling steps. Various efforts to model acceleration pulses have been reported in the literature. In this paper, research results from a recent study of acceleration pulse prominent ground motions and an analysis of structural damage induced by acceleration pulses are summarized. The main results of the study include： （1） temporal characteristics of acceleration pulses; （2） ductility demand spectrum of simple acceleration pulses with respect to equivalent classes of dynamic systems and pulse characteristic parameters; and （3） estimation of fundamental period change under the excitation of strong acceleration pulses. By using the acceleration pulse induced linear acceleration spectrum and the ductility demand spectrum, a simple procedure has been developed to estimate the ductility demand and the fundamental period change of a reinforced concrete （RC） structure under the impact of a strong acceleration pulse.
文摘In a viscous damping device under cyclic loading, after the piston reaches a peak stroke, the reserve movement that follows may sometimes experience a short period of delayed or significantly reduced device force output. A similar delay or reduced device force output may also occur at the damper＇s initial stroke as it moves away from its neutral position. This phenomenon is referred to as the effect of ＂deadzone＂. The deadzone can cause a loss of energy dissipation capacity and less efficient vibration control. It is prominent in small amplitude vibrations. Although there are many potential causes of deadzone such as environmental factors, construction, material aging, and manufacture quality, in this paper, its general effect in linear and nonlinear viscous damping devices is analyzed. Based on classical dynamics and damping theory, a simple model is developed to capture the effect ofdeadzone in terms of the loss of energy dissipation capacity. The model provides several methods to estimate the loss of energy dissipation within the deadzone in linear and sublinear viscous fluid dampers. An empirical equation of loss of energy dissipation capacity versus deadzone size is formulated, and the equivalent reduction of effective damping in SDOF systems has been obtained. A laboratory experimental evaluation is carried out to verify the effect of deadzone and its numerical approximation. Based on the analysis, a modification is suggested to the corresponding formulas in FEMA 3 5 6 for calculation of equivalent damping if a deadzone is to be considered.
