The transformation method to control waves has received widespread attention in electromagnetism and acoustics. However, this machinery is not directly applicable to the control of elastic waves, because it has been s...The transformation method to control waves has received widespread attention in electromagnetism and acoustics. However, this machinery is not directly applicable to the control of elastic waves, because it has been shown that the Navier＇s equation does not usually retain its form under coordinate transformation. In this letter, we prove the form invariance of the Navier＇s equation under the conformal mapping based on the Helmholtz decomposition method. The needed material parameters are provided to manipulate elastic waves. The validity of this approach is confirmed by an active stealth device which can disguise the signal source by changing its position. Experimental verifications and potential applications may be expected in nondestructive testing, structural seismic design and other fields.展开更多
On the basis of analyzing the shortages of present studies on plant disease model for autonomous phenomenon, and considering the actual situation, this paper applies the joint factors of environmental change and the i...On the basis of analyzing the shortages of present studies on plant disease model for autonomous phenomenon, and considering the actual situation, this paper applies the joint factors of environmental change and the infectivity for latent plants into the system;therefore we deal with a non-autonomous plant disease model with roguing. Some sufficient conditions are established for extinction of diseases and permanence of the system in this paper.展开更多
Summary What is already known about this topic?In recent decades,work-related musculoskeletal disorders(WMSDs)have become increasingly prominent and have become an important issue that is of universal concern and an u...Summary What is already known about this topic?In recent decades,work-related musculoskeletal disorders(WMSDs)have become increasingly prominent and have become an important issue that is of universal concern and an urgent need to be solved in all countries of the world.What is added by this report?The top three industries or occupational groups with the highest standardized prevalence rate of WMSDs were flight attendants,medical staff,and vegetable greenhouses in that order.Women workers were 1.5 times more likely to suffer from WMSDs than men workers.展开更多
What is already known about this topic?Work-related musculoskeletal disorders(WMSDs)have a high prevalence and seriously harmful,which has attracted extensive attention in various countries in the world.Currently,the ...What is already known about this topic?Work-related musculoskeletal disorders(WMSDs)have a high prevalence and seriously harmful,which has attracted extensive attention in various countries in the world.Currently,the occurrence and rules of WMSDs in key industries are not known in China.What is added by this report?The prevalence of WMSDs is relatively high among professional populations in key industries in China,with the most commonly affected body parts concentrated in neck,shoulders,and low back and increasing with age and working years.What are the implications for public health practice?This study determined the prevalence and distribution characteristics of WMSDs in key industries in China and provided scientific evidence to recommend for inclusion of WMSDs in the new revision of the list of occupational diseases in China.展开更多
What is already known about this topic?The burden of illness and economic losses due to upper-limb work-related musculoskeletal disorders(UL-WMSDs)is high;thus,they have become a major global public health problem.At ...What is already known about this topic?The burden of illness and economic losses due to upper-limb work-related musculoskeletal disorders(UL-WMSDs)is high;thus,they have become a major global public health problem.At present,the epidemiological characteristics of UL-WMSDs in China's occupational population are still unknown.What is added by this report?The incidence of UL-WMSDs among key occupational groups in China is 22.5%,with distinct occupational characteristics.What are the implications for public health practice?This study has primarily determined the occurrence and potential risk factors of UL-WMSDs in key industries in China and provided data support for recommending prevention and control of the occurrence of such diseases in key industries in China,and in facilitating the addition into the China’s List of Legal Occupational Diseases.展开更多
基金supported by the National Natural Science Foundation of China (90916007 and 91116008)
文摘The transformation method to control waves has received widespread attention in electromagnetism and acoustics. However, this machinery is not directly applicable to the control of elastic waves, because it has been shown that the Navier＇s equation does not usually retain its form under coordinate transformation. In this letter, we prove the form invariance of the Navier＇s equation under the conformal mapping based on the Helmholtz decomposition method. The needed material parameters are provided to manipulate elastic waves. The validity of this approach is confirmed by an active stealth device which can disguise the signal source by changing its position. Experimental verifications and potential applications may be expected in nondestructive testing, structural seismic design and other fields.
文摘On the basis of analyzing the shortages of present studies on plant disease model for autonomous phenomenon, and considering the actual situation, this paper applies the joint factors of environmental change and the infectivity for latent plants into the system;therefore we deal with a non-autonomous plant disease model with roguing. Some sufficient conditions are established for extinction of diseases and permanence of the system in this paper.
基金The Project of Occupational Health Risk Assessment and National Occupational Health Standard Formulation of National Institute of Occupational Health and Poison Control(Project No.131031109000150003).
文摘Summary What is already known about this topic?In recent decades,work-related musculoskeletal disorders(WMSDs)have become increasingly prominent and have become an important issue that is of universal concern and an urgent need to be solved in all countries of the world.What is added by this report?The top three industries or occupational groups with the highest standardized prevalence rate of WMSDs were flight attendants,medical staff,and vegetable greenhouses in that order.Women workers were 1.5 times more likely to suffer from WMSDs than men workers.
基金funded by the Project of Occupational Health Risk Assessment and National Occupational Health Standard Formulation of National Institute of Occupational Health and Poison Control(Project No.:131031109000150003).
文摘What is already known about this topic?Work-related musculoskeletal disorders(WMSDs)have a high prevalence and seriously harmful,which has attracted extensive attention in various countries in the world.Currently,the occurrence and rules of WMSDs in key industries are not known in China.What is added by this report?The prevalence of WMSDs is relatively high among professional populations in key industries in China,with the most commonly affected body parts concentrated in neck,shoulders,and low back and increasing with age and working years.What are the implications for public health practice?This study determined the prevalence and distribution characteristics of WMSDs in key industries in China and provided scientific evidence to recommend for inclusion of WMSDs in the new revision of the list of occupational diseases in China.
基金Funded by the Project of Occupational Health Risk Assessment and the National Occupational Health Standard Formulation of the National Institute of Occupational Health and Poison Control(Project No.131031109000160004)National Key R&D Program of China(2022YFC2503205).
文摘What is already known about this topic?The burden of illness and economic losses due to upper-limb work-related musculoskeletal disorders(UL-WMSDs)is high;thus,they have become a major global public health problem.At present,the epidemiological characteristics of UL-WMSDs in China's occupational population are still unknown.What is added by this report?The incidence of UL-WMSDs among key occupational groups in China is 22.5%,with distinct occupational characteristics.What are the implications for public health practice?This study has primarily determined the occurrence and potential risk factors of UL-WMSDs in key industries in China and provided data support for recommending prevention and control of the occurrence of such diseases in key industries in China,and in facilitating the addition into the China’s List of Legal Occupational Diseases.
