A ship is operated under an extremely complex environment, and waves and winds are assumed to be the stochastic excitations. Moreover, the propeller, host and mechanical equipment can also induce the harmonic response...A ship is operated under an extremely complex environment, and waves and winds are assumed to be the stochastic excitations. Moreover, the propeller, host and mechanical equipment can also induce the harmonic responses. In order to reduce structural vibration, it is important to obtain the modal parameters information of a ship. However, the traditional modal parameter identification methods are not suitable since the excitation information is difficult to obtain. Natural excitation technique-eigensystem realization algorithm （NExT-ERA） is an operational modal identification method which abstracts modal parameters only from the response signals, and it is based on the assumption that the input to the structure is pure white noise. Hence, it is necessary to study the influence of harmonic excitations while applying the NExT-ERA method to a ship structure. The results of this research paper indicate the practical experiences under ambient excitation, ship model experiments were successfully done in the modal parameters identification only when the harmonic frequencies were not too close to the modal frequencies.展开更多
After the Industrial Revolution,with the deterioration of the environment,the ecological thought based on the harmonious coexistence of man and nature came into being.Due to the outbreak of COVID-19,people are beginni...After the Industrial Revolution,with the deterioration of the environment,the ecological thought based on the harmonious coexistence of man and nature came into being.Due to the outbreak of COVID-19,people are beginning to re-examine the relationship between man and nature,and ecological landscapes are gaining attention again.Through the overview of ecological landscapes,this paper analyzed the design ideas and design principles of ecological landscapes,sorted out the main ecological landscape architects and their thoughts at home and abroad,and put forward ecological thinking on landscape design under the background of COVID-19.展开更多
基金Supported by the National Natural Science Foundation of China（51079027）
文摘A ship is operated under an extremely complex environment, and waves and winds are assumed to be the stochastic excitations. Moreover, the propeller, host and mechanical equipment can also induce the harmonic responses. In order to reduce structural vibration, it is important to obtain the modal parameters information of a ship. However, the traditional modal parameter identification methods are not suitable since the excitation information is difficult to obtain. Natural excitation technique-eigensystem realization algorithm （NExT-ERA） is an operational modal identification method which abstracts modal parameters only from the response signals, and it is based on the assumption that the input to the structure is pure white noise. Hence, it is necessary to study the influence of harmonic excitations while applying the NExT-ERA method to a ship structure. The results of this research paper indicate the practical experiences under ambient excitation, ship model experiments were successfully done in the modal parameters identification only when the harmonic frequencies were not too close to the modal frequencies.
文摘After the Industrial Revolution,with the deterioration of the environment,the ecological thought based on the harmonious coexistence of man and nature came into being.Due to the outbreak of COVID-19,people are beginning to re-examine the relationship between man and nature,and ecological landscapes are gaining attention again.Through the overview of ecological landscapes,this paper analyzed the design ideas and design principles of ecological landscapes,sorted out the main ecological landscape architects and their thoughts at home and abroad,and put forward ecological thinking on landscape design under the background of COVID-19.
