Soft-bionic-fishtail structured triboelectric nanogenerator driven by flow-induced vibration for low-velocity water flow energy harvesting

To adapt to the low-velocity water flow closely related to human life,the natural energy can be efficiently harvested and used to power monitoring devices.Herein,a triboelectric soft fishtail(TE-SFT)driven by flow-induced vibration(FIV)effect is proposed based on the soft material synthesis technology.Specifically,inspired by the fishtail fin,a bluff body with the cross-section of fishtail-shaped is designed,and has a preferable vortex effect by fluid simulation.In power generation part,the triboelectric nanogenerator(TENG)is designed to act as an inertial pendulum structure by geometric method.Under the FIV effect,the TESFT driven by fishtail-shaped bluff body swings like a fish in the water and then brings the inertial pendulum to acquire the oscillation for harvesting energy from low-velocity water flow.The TE-SFT attains an open-circuit voltage(VOC)of 200 V to 313 V at the flow velocities of 0.24 to 0.89 m/s.Additionally,after 30 days of water immersion,the VOC of TE-SFT retains 96.81%.In demonstration,the TE-SFT is applied to power the temperature and humidity sensor through harvesting water flow energy.This work also provides a way for self-powered system based on the TENG and soft bionic fish in water environment.

3D fully-enclosed triboelectric nanogenerator with bionic fish-like structure for harvesting hydrokinetic energy

The hydrokinetic energy of river current,as one of the essential and widespread renewable energies,is difficult to be harvested in low flow velocity and shallow water areas.In this work,a three-dimensional(3D)fully-enclosed triboelectric nanogenerator(FETENG)with bionic fish-like structure for harvesting hydrokinetic energy is reported,which is comprised of the triboelectric powergeneration unit,bionic fish-like structure and connection unit.Through the bionic structure,the FE-TENG realizes zero head power generation in shallow water with low flow velocity.What’s more,the effect of external excitations and bionic structures on the electrical performance are systematically studied in this work.The FE-TENG can generate peak power density of 7 and 0.36 W/m^(3)respectively under the simulated swing state with frequency of 1.25 Hz and simulated river current with flow velocity of 0.81 m/s.In practical applications,due to the 3D fully-enclosed design,the FE-TENG immersed in water for 35 days demonstrates excellent immersion durability with undiminished electrical performance.Therefore,the work proposes an efficient method realizing zero head power generation,and provides a good candidate for long-term service in the river current.

The trends of migration in China, 1949-2019

Based on relevant policy documents and census data,the authors analyze the characteristics and trends of China’s population migration since the founding of People’s Republic of China(PRC)in 1949.The study finds that over the past 70 years,population migration in China has exhibited distinct stage-specific characteristics.From the founding of PRC to the period of reform and opening-up that got underway in 1978,China witnessed a shift from free population movement to restricted population movement,as well as a shift from population movement driven by the recovery of national economy to that driven by political reasons.With the launch of the reform and opening-up policy,China’s population migration entered an entirely new stage of development,exhibiting the following trends:(1)population migration was highly active,and there were changes in the size of the migrant population;(2)with regard to the direction of migration,rural to urban migration remained the dominant pattern,but the proportion of urban to urban migrants also rose;(3)with regard to the choice of destination,inter-provincial migrants were increasingly concentrated in the coastal areas of Eastern China,whilst the large cities in the Central and Western China were more favored by intra-provincial migrants;(4)the distances inter-provincial migrants traveled increased;(5)migration was motivated mainly by economic factors,yet the importance of social factors was on the rise;and(6)the educational level of migrants went up significantly and the sex ratio gradually became balanced.Accordingly,we must gain a deeper understanding of the trends and characteristics of population migration,taking into consideration the interrelationship between population migration and socioeconomic development.To begin,the equalization of basic public services and thorough-going reform of the household registration system can contribute to the development of a new urbanization strategy.