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人群-桥梁耦合振动研究及参数分析 被引量:8
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作者 陈舟 颜全胜 +2 位作者 胡俊亮 黄仕平 余晓琳 《华南理工大学学报(自然科学版)》 EI CAS CSCD 北大核心 2014年第5期75-83,共9页
根据交通流和生物力学的研究成果,将人体视为具有质量、刚度、阻尼的两自由度系统,建立了人群过桥时人群-桥梁耦合系统的动力学模型,分析了人群对耦合系统动力特性的影响,研究了不同行走模式时人群-桥梁耦合系统的动力响应和人致振动参... 根据交通流和生物力学的研究成果,将人体视为具有质量、刚度、阻尼的两自由度系统,建立了人群过桥时人群-桥梁耦合系统的动力学模型,分析了人群对耦合系统动力特性的影响,研究了不同行走模式时人群-桥梁耦合系统的动力响应和人致振动参数敏感性.结果表明:人群使耦合系统产生了附加振型;人群集度和位置对耦合系统的动力特性影响较大;行走人群对桥梁动力响应的影响主要取决于人群行走的频率是否与结构竖向基频相接近,以及人群行走步调是否相接近;人群集度和行走速度对人群-桥梁耦合系统的动力特性均有不同程度的影响.文中模型避免了计算人群与桥梁的耦合振动时参数取值的任意性. 展开更多
关键词 人群流 行走特性 耦合振动 动态响应 参数分析
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Epidemiology of Hepatitis B and Associated Liver Diseases in China 被引量:17
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作者 Yao Zhang Hua Zhang +1 位作者 Au Elizabeth Xiao-qing Liu 《Chinese Medical Sciences Journal》 CAS CSCD 2012年第4期243-248,共6页
Hepatitis B virus (HBV) infection has long been a critical public health challenge in China. National surveys revealed a prevalence of approximate 10% for chronic HBV infection in general population. HBV has been the ... Hepatitis B virus (HBV) infection has long been a critical public health challenge in China. National surveys revealed a prevalence of approximate 10% for chronic HBV infection in general population. HBV has been the leading cause of chronic hepatitis, cirrhosis, and liver cancers in Chinese population and a common pathogen of acute viral hepatitis. Meanwhile, the epidemic provided important opportunities to research the natural history, public health impact, and therapeutic and preventive interventions for HBV in China. In this review, we summarized the selected key epidemiological studies since 1970s regarding HBV infection and its associated liver diseases in China, and provided considerations for future research, prevention and treatment of HBV. 展开更多
关键词 hepatitis B EPIDEMIOLOGY CIRRHOSIS hepatocellular carcinoma
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SEXUALLY TRANSMITTED DISEASES:INCIDENCE AND DISTRIBUTION
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作者 王千秋 《Chinese Medical Sciences Journal》 CAS CSCD 1996年第1期56-62,共7页
The incidence of sexually transmitted diseases(STDs) increased from 26. 04 per 100 000 in 1987 to 104. 81 per 100 000 in 1993 in selected areas of the country. Gonorrhea is by far the most common STD but its constitue... The incidence of sexually transmitted diseases(STDs) increased from 26. 04 per 100 000 in 1987 to 104. 81 per 100 000 in 1993 in selected areas of the country. Gonorrhea is by far the most common STD but its constituent ratio declined because of a rapid increase of nongonococcal uretheritis and genital warts during most recent years. The incidence of syphilis is relatively low and cases of congenital infection are noted. The wide spread of resistant Neisseria gonorrhoeae infection gives a challenge to the therapeutical and control strategies of STDs. Sexually transmitted Chlamydia trachomatis infections, an important cause of urethritis. cervicitis and pelvic inflammatory disease. is becoming common in our country. Attention has been drawn on viral hepatitis in their means of transmission by sexually behaviors, and also, on the homosexuals, assumed to be the high risk group to catch STDs. Coordinated national efforts to control STDs in China have been taken. 展开更多
关键词 sexually transmitted diseases EPIDEMIOLOGY
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