Contrary to the aliasing defect between the adjacent intrinsic model functions(IMFs) existing in empirical model decomposition(EMD), a new method of detecting dynamic unbalance with cardan shaft in high-speed train wa...Contrary to the aliasing defect between the adjacent intrinsic model functions(IMFs) existing in empirical model decomposition(EMD), a new method of detecting dynamic unbalance with cardan shaft in high-speed train was proposed by applying the combination between EMD, Hankel matrix, singular value decomposition(SVD) and normalized Hilbert transform(NHT). The vibration signals of gimbal installed base were decomposed through EMD to get different IMFs. The Hankel matrix constructed through the single IMF was orthogonally executed through SVD. The critical singular values were selected to reconstruct vibration signs on the basis of the key stack of singular values. Instantaneous frequencys(IFs) of reconstructed vibration signs were applied to detect dynamic unbalance with shaft and eliminated clutter spectrum caused by the aliasing defect between the adjacent IMFs, which highlighted the failure characteristics. The method was verified by test data in the unbalance condition of dynamic cardan shaft. The results show that the method effectively detects the fault vibration characteristics caused by cardan shaft dynamic unbalance and extracts the nature vibration features. With comparison to the traditional EMD-NHT, clarity and failure characterization force are significantly improved.展开更多
Dear Editor, The influenza viruses cause continual epidemics in human society. As is reported by the World Health Organization （WHO）, each year the seasonal influenza viruses, i.e., human influenza A （H1N1）, A （H...Dear Editor, The influenza viruses cause continual epidemics in human society. As is reported by the World Health Organization （WHO）, each year the seasonal influenza viruses, i.e., human influenza A （H1N1）, A （H3N2） and B viruses, infected 5%- 15% of the world＇s population, leading to about 3 to 5 million cases of severe illness and about 250000 to 500000 deaths worldwide （WHO, 2014）. Vaccination is currently the most effective way to fight against it. Due to the frequent mutations on the HA protein, the virus often changes its antigen, which may lead to the ineffectiveness of the influenza vaccines （Carrat and Flahault, 2007; Taubenberger and Kash, 2010）.展开更多
Plug-in electric vehicle (PHEV) technology is seen as promising technology for reducing oil use, improving local air quality, and/or possibly reducing GHG emissions to support a sustainable transportation system. This...Plug-in electric vehicle (PHEV) technology is seen as promising technology for reducing oil use, improving local air quality, and/or possibly reducing GHG emissions to support a sustainable transportation system. This paper examines the usage of household vehicles to support assessment of the market potential of plug-in hybrid electric vehicles (PHEVs), the higher purchase price of which requires high usage rates to pay off the investment in the technology. According to the 2009 National Household Travel Survey (NHTS), about 40% of household vehicles were not used on the survey travel day [1]. This study analyzed household vehicle use and non-use by vehicle type, age, area type (metropolitan statistical area [MSA] and non-MSA), and population density. Vehicles used on survey day with or without a reported travel time and distance in the survey are considered “vehicles used”. All others are referred to as “vehicles not used”. We divided the “vehicles not used” into three categories: 1) left at home while other household vehicles were used;2) not used because travelers used other modes;and 3) no household trips. The “vehicle used” consists of two categories: 1) those with distance and time data and 2) those with no travel data. Within these five categories, vehicles were subdivided according to four vehicle types: car, van, SUV, and pickup. Each vehicle type was further subdivided in two age groups: 10 years or less (≤10) and more than 10 years (>10). In addition, vehicle usage was compared in both MSAs and non-MSAs and during weekdays and weekends. Results indicate that most vehicles—especially pickups—are not used because the households own and use other vehicles. Moreover, SUVs—especially newer SUVs (≤10 years)—are the most utilized vehicle type and should be strongly considered as a primary vehicle type for PHEVs, in addition to cars.展开更多
一年一度的CES大展结束了，展会的最后一个高潮是Best of CES奖的揭晓。这是CES诸多奖项中含金量最高的一个，其中高级音响类(Ultimte Audio)的获奖名单更是音响爱好者们最关心的。Best of CES的评奖方法是先从所有同类展品中筛选出三...一年一度的CES大展结束了，展会的最后一个高潮是Best of CES奖的揭晓。这是CES诸多奖项中含金量最高的一个，其中高级音响类(Ultimte Audio)的获奖名单更是音响爱好者们最关心的。Best of CES的评奖方法是先从所有同类展品中筛选出三款作为Finalist(进入决赛的选手)，然后三中选一，作为年度获胜者(Winner)。获胜者将被授予该类别的Best of CES奖，另两款则授予Best of CES Finalist奖。在获奖名单中看到中国血统的惠威，仿佛又体验了一次《藏龙卧虎》获得奥斯卡奖时的心情。不错，Best of CES就是音响业的奥斯卡，能够获得这个奖，证明中国人有能力在强手如林的西方音响业中争得一席之地。这些获奖产品能从CES浩如烟海的展品中脱颖而出，必非等闲之辈。它们究竟有什么与众不同的“神功秘技”呢?读者们想必也会希望了解，本文想从技术角度来简单介绍一下它们的特色。展开更多
基金Projects(61134002,51305358)supported by the National Natural Science Foundation of ChinaProject(PIL1303)supported by the Open Project of State Key Laboratory of Precision Measurement Technology and Instruments,ChinaProject(2682014BR032)supported by the Fundamental Research Funds for the Central Universities,China
文摘Contrary to the aliasing defect between the adjacent intrinsic model functions(IMFs) existing in empirical model decomposition(EMD), a new method of detecting dynamic unbalance with cardan shaft in high-speed train was proposed by applying the combination between EMD, Hankel matrix, singular value decomposition(SVD) and normalized Hilbert transform(NHT). The vibration signals of gimbal installed base were decomposed through EMD to get different IMFs. The Hankel matrix constructed through the single IMF was orthogonally executed through SVD. The critical singular values were selected to reconstruct vibration signs on the basis of the key stack of singular values. Instantaneous frequencys(IFs) of reconstructed vibration signs were applied to detect dynamic unbalance with shaft and eliminated clutter spectrum caused by the aliasing defect between the adjacent IMFs, which highlighted the failure characteristics. The method was verified by test data in the unbalance condition of dynamic cardan shaft. The results show that the method effectively detects the fault vibration characteristics caused by cardan shaft dynamic unbalance and extracts the nature vibration features. With comparison to the traditional EMD-NHT, clarity and failure characterization force are significantly improved.
基金supported by the National Natural Science Foundation(31500126 and 31371338)National Key Plan for Scientific Research and Development of China(2016YFD0500300 and 2016YFC1200200)the Young Teacher’s Development Plan of Hunan University to YS(531107040720)
文摘Dear Editor, The influenza viruses cause continual epidemics in human society. As is reported by the World Health Organization （WHO）, each year the seasonal influenza viruses, i.e., human influenza A （H1N1）, A （H3N2） and B viruses, infected 5%- 15% of the world＇s population, leading to about 3 to 5 million cases of severe illness and about 250000 to 500000 deaths worldwide （WHO, 2014）. Vaccination is currently the most effective way to fight against it. Due to the frequent mutations on the HA protein, the virus often changes its antigen, which may lead to the ineffectiveness of the influenza vaccines （Carrat and Flahault, 2007; Taubenberger and Kash, 2010）.
文摘Plug-in electric vehicle (PHEV) technology is seen as promising technology for reducing oil use, improving local air quality, and/or possibly reducing GHG emissions to support a sustainable transportation system. This paper examines the usage of household vehicles to support assessment of the market potential of plug-in hybrid electric vehicles (PHEVs), the higher purchase price of which requires high usage rates to pay off the investment in the technology. According to the 2009 National Household Travel Survey (NHTS), about 40% of household vehicles were not used on the survey travel day [1]. This study analyzed household vehicle use and non-use by vehicle type, age, area type (metropolitan statistical area [MSA] and non-MSA), and population density. Vehicles used on survey day with or without a reported travel time and distance in the survey are considered “vehicles used”. All others are referred to as “vehicles not used”. We divided the “vehicles not used” into three categories: 1) left at home while other household vehicles were used;2) not used because travelers used other modes;and 3) no household trips. The “vehicle used” consists of two categories: 1) those with distance and time data and 2) those with no travel data. Within these five categories, vehicles were subdivided according to four vehicle types: car, van, SUV, and pickup. Each vehicle type was further subdivided in two age groups: 10 years or less (≤10) and more than 10 years (>10). In addition, vehicle usage was compared in both MSAs and non-MSAs and during weekdays and weekends. Results indicate that most vehicles—especially pickups—are not used because the households own and use other vehicles. Moreover, SUVs—especially newer SUVs (≤10 years)—are the most utilized vehicle type and should be strongly considered as a primary vehicle type for PHEVs, in addition to cars.
文摘一年一度的CES大展结束了，展会的最后一个高潮是Best of CES奖的揭晓。这是CES诸多奖项中含金量最高的一个，其中高级音响类(Ultimte Audio)的获奖名单更是音响爱好者们最关心的。Best of CES的评奖方法是先从所有同类展品中筛选出三款作为Finalist(进入决赛的选手)，然后三中选一，作为年度获胜者(Winner)。获胜者将被授予该类别的Best of CES奖，另两款则授予Best of CES Finalist奖。在获奖名单中看到中国血统的惠威，仿佛又体验了一次《藏龙卧虎》获得奥斯卡奖时的心情。不错，Best of CES就是音响业的奥斯卡，能够获得这个奖，证明中国人有能力在强手如林的西方音响业中争得一席之地。这些获奖产品能从CES浩如烟海的展品中脱颖而出，必非等闲之辈。它们究竟有什么与众不同的“神功秘技”呢?读者们想必也会希望了解，本文想从技术角度来简单介绍一下它们的特色。
