The formation mechanism of heartwood is a scientific problem which has not been fully revealed in wood science.Effective regulation of heartwood formation is a scientific problem that is rarely studied and has not yet...The formation mechanism of heartwood is a scientific problem which has not been fully revealed in wood science.Effective regulation of heartwood formation is a scientific problem that is rarely studied and has not yet achieved a breakthrough in the field of forest cultivation.It is very beneficial to regulate the chemical properties of wood and directional and efficient cultivation of trees by fully understanding the formation mechanism of heartwood.Based on the author s research and practice,the recent research progress on the formation mechanism and regulation technology of heartwood is summarized,especially the research on the heartwood formation of Hongmu species.展开更多
Inspired by the fast,agile movements of insects,we present a 1.9 g,4.5 cm in length,piezoelectrically driven,quadrupedal microrobot.This microrobot uses a novel spatial parallel mechanism as its hip joint,which consis...Inspired by the fast,agile movements of insects,we present a 1.9 g,4.5 cm in length,piezoelectrically driven,quadrupedal microrobot.This microrobot uses a novel spatial parallel mechanism as its hip joint,which consists of two spatially orthogonal slider-crank linkages.This mechanism maps two inputs of two independent actuators to the decoupled swing and lift outputs of a leg,and each leg can produce the closed trajectories in the sagittal plane necessary for robot motion.Moreover,the kinematics of the transmission are analyzed,and the parameters of the flexure hinges are designed based on geometrical constraints and yield conditions.The hip joints,legs and exoskeletons are integrated into a five-layer standard laminate for monolithic fabrication which is composed of two layers of carbon fiber,two layers of acrylic adhesive and a polyimide film.The measured output force(15.97 mN)of each leg is enough to carry half of the robot’s weight,which is necessary for the robot to move successfully.It has been proven that the robot can successfully perform forward and turning motions.Compared to the microrobot fabricated with discrete components,the monolithically fabricated microrobot is more capable of maintaining the original direction of locomotion when driven by a forward signal and has a greater speed,whose maximum speed is 25.05 cm/s.展开更多
Proton exchange membrane fuel cells(PEMFCs)are recognized as potential environmentally friendly power sources owing to their high energy conversion efficiency and low pollutant emissions[1–4].However,the insufficient...Proton exchange membrane fuel cells(PEMFCs)are recognized as potential environmentally friendly power sources owing to their high energy conversion efficiency and low pollutant emissions[1–4].However,the insufficient electrocatalytic durability of Pt cathode catalysts remains one of the major obstacles for their wide applications[5–8].The Pt cathode catalyst is predominantly展开更多
基金Supported by National Natural Science Foundation of China(31270674)Zhaoqing Science and Technology Plan of Guangdong Province(2019N012)+2 种基金"Climbing Plan"of Special Fund for Science and Technology Innovation Cultivation of College Students in Guangdong(pdjh2020b0640)National Special Fund for Science and Technology Innovation Cultivation of College Students in Guangdong(202010580009)Provincial Special Fund for Science and Technology Innovation Cultivation of College Students in Guangdong(S202010580042).
文摘The formation mechanism of heartwood is a scientific problem which has not been fully revealed in wood science.Effective regulation of heartwood formation is a scientific problem that is rarely studied and has not yet achieved a breakthrough in the field of forest cultivation.It is very beneficial to regulate the chemical properties of wood and directional and efficient cultivation of trees by fully understanding the formation mechanism of heartwood.Based on the author s research and practice,the recent research progress on the formation mechanism and regulation technology of heartwood is summarized,especially the research on the heartwood formation of Hongmu species.
基金supported by the Shanghai professional technology service platform under Grant 19DZ2291103.
文摘Inspired by the fast,agile movements of insects,we present a 1.9 g,4.5 cm in length,piezoelectrically driven,quadrupedal microrobot.This microrobot uses a novel spatial parallel mechanism as its hip joint,which consists of two spatially orthogonal slider-crank linkages.This mechanism maps two inputs of two independent actuators to the decoupled swing and lift outputs of a leg,and each leg can produce the closed trajectories in the sagittal plane necessary for robot motion.Moreover,the kinematics of the transmission are analyzed,and the parameters of the flexure hinges are designed based on geometrical constraints and yield conditions.The hip joints,legs and exoskeletons are integrated into a five-layer standard laminate for monolithic fabrication which is composed of two layers of carbon fiber,two layers of acrylic adhesive and a polyimide film.The measured output force(15.97 mN)of each leg is enough to carry half of the robot’s weight,which is necessary for the robot to move successfully.It has been proven that the robot can successfully perform forward and turning motions.Compared to the microrobot fabricated with discrete components,the monolithically fabricated microrobot is more capable of maintaining the original direction of locomotion when driven by a forward signal and has a greater speed,whose maximum speed is 25.05 cm/s.
基金financially supported by the National Basic Research Program of China (2012CB215500 and 2012CB720300)the National Natural Science Foundation of China (21436003, 21573029 and 51272297)
文摘Proton exchange membrane fuel cells(PEMFCs)are recognized as potential environmentally friendly power sources owing to their high energy conversion efficiency and low pollutant emissions[1–4].However,the insufficient electrocatalytic durability of Pt cathode catalysts remains one of the major obstacles for their wide applications[5–8].The Pt cathode catalyst is predominantly
