Due to their potential properties unlike traditional materials and structures,elastic wave metamaterials have received significant interests in recent years.With the coupling between the acoustic and vibration,their m...Due to their potential properties unlike traditional materials and structures,elastic wave metamaterials have received significant interests in recent years.With the coupling between the acoustic and vibration,their mechanical characteristics can be tuned by the active feedback control system at low frequency ranges in which the traditional passive control is limited.This work illustrates that the superior performances of the effective mass density and sound pressure level(SPL)of an elastic wave metamaterial can be significantly changed by the active control,in which the periodic array of local resonators and orthogonal stiffeners are included.Significantly,based on the locally resonant mechanism,the negative density occurs over a frequency range.Due to the effects of lattice constant,structural damping and other parameters,the SPL with the function of fluid-solid coupling are illustrated and discussed.展开更多
Using the active feedback control system on the elastic wave metamaterial,this research concentrates on the sound transmission with the dynamic effective model.The metamaterial is subjected to an incident pressure and...Using the active feedback control system on the elastic wave metamaterial,this research concentrates on the sound transmission with the dynamic effective model.The metamaterial is subjected to an incident pressure and immersed in the external mean flow.The elastic wave metamaterial consists of double plates and the upper and lower four-link mechanisms are attached inside.The vertical resonator is attached by the active feedback control system and connected with two four-link mechanisms.Based on the dynamic equivalent method,the metamaterial is equivalent as a single-layer plate by the dynamic effective parameter.With the coupling between the fluid and structure,the expression of the sound transmission loss(STL)is derived.This research shows the influence of effective mass density on sound transmission properties,and the STL in both modes can be tuned by the acceleration and displacement feedback constants.In addition,the dynamic response and the STL are also changed obviously by different values of structural damping,incident angle(i.e.,the elevation and azimuth angles)and Mach number of the external fluid with the mean flow property.The results for sound transmission by two methods are compared,i.e.,the virtual work principle for double plates and the dynamic equivalent method corresponding to a single one.This paper is expected to be helpful for understanding the sound transmission properties of both pure single-and double-plate models.展开更多
Objective: To verify the existence of microRNAs(miRNAs) extracted from fresh ginseng decoction.Methods: Fresh ginseng was prepared into decoction according to the conventional method. The miRNA were extracted from the...Objective: To verify the existence of microRNAs(miRNAs) extracted from fresh ginseng decoction.Methods: Fresh ginseng was prepared into decoction according to the conventional method. The miRNA were extracted from the condensed ginseng decoction by plant microRNA extraction kit. Then miRNA were treated by DNase I and subjected to agarose gel electrophoresis and Agilent 2100 bioanalysis. Mi R-159 and mi R-6135, which were highly expressed in ginseng, were selected and verified by real-time quantitative PCR to detect the expression in the decoction.Results: Ginseng miRNA were successfully extracted from fresh decoction. Mi R-159 and mi R-6135 were expressed in fresh decoction with lower levels than those of fresh ginseng.Conclusion: miRNAs stably existed after processing, and retained some stability after high-temperature treatment. The findings provide a valuables basis for the further studies on ginseng miRNAs.展开更多
基金the supports by the National Natural Science Foundation of China(Grants 11922209,11991031 and 12021002)for this research work.
文摘Due to their potential properties unlike traditional materials and structures,elastic wave metamaterials have received significant interests in recent years.With the coupling between the acoustic and vibration,their mechanical characteristics can be tuned by the active feedback control system at low frequency ranges in which the traditional passive control is limited.This work illustrates that the superior performances of the effective mass density and sound pressure level(SPL)of an elastic wave metamaterial can be significantly changed by the active control,in which the periodic array of local resonators and orthogonal stiffeners are included.Significantly,based on the locally resonant mechanism,the negative density occurs over a frequency range.Due to the effects of lattice constant,structural damping and other parameters,the SPL with the function of fluid-solid coupling are illustrated and discussed.
基金The authors wish to express gratitude for the support provided by the National Natural Science Foundation of China(Grant Nos.11922209,11991031 and 12021002).
文摘Using the active feedback control system on the elastic wave metamaterial,this research concentrates on the sound transmission with the dynamic effective model.The metamaterial is subjected to an incident pressure and immersed in the external mean flow.The elastic wave metamaterial consists of double plates and the upper and lower four-link mechanisms are attached inside.The vertical resonator is attached by the active feedback control system and connected with two four-link mechanisms.Based on the dynamic equivalent method,the metamaterial is equivalent as a single-layer plate by the dynamic effective parameter.With the coupling between the fluid and structure,the expression of the sound transmission loss(STL)is derived.This research shows the influence of effective mass density on sound transmission properties,and the STL in both modes can be tuned by the acceleration and displacement feedback constants.In addition,the dynamic response and the STL are also changed obviously by different values of structural damping,incident angle(i.e.,the elevation and azimuth angles)and Mach number of the external fluid with the mean flow property.The results for sound transmission by two methods are compared,i.e.,the virtual work principle for double plates and the dynamic equivalent method corresponding to a single one.This paper is expected to be helpful for understanding the sound transmission properties of both pure single-and double-plate models.
基金supported by the National Natural Science Foundation for Young Scholars of China(no.81403195)Natural Science Foundation of Guangdong Province(no.S2013010015418)
文摘Objective: To verify the existence of microRNAs(miRNAs) extracted from fresh ginseng decoction.Methods: Fresh ginseng was prepared into decoction according to the conventional method. The miRNA were extracted from the condensed ginseng decoction by plant microRNA extraction kit. Then miRNA were treated by DNase I and subjected to agarose gel electrophoresis and Agilent 2100 bioanalysis. Mi R-159 and mi R-6135, which were highly expressed in ginseng, were selected and verified by real-time quantitative PCR to detect the expression in the decoction.Results: Ginseng miRNA were successfully extracted from fresh decoction. Mi R-159 and mi R-6135 were expressed in fresh decoction with lower levels than those of fresh ginseng.Conclusion: miRNAs stably existed after processing, and retained some stability after high-temperature treatment. The findings provide a valuables basis for the further studies on ginseng miRNAs.
