In the process of human behavior recognition, the traditional dense optical flow method has too many pixels and too much overhead, which limits the running speed. This paper proposed a method combing YOLOv3 (You Only ...In the process of human behavior recognition, the traditional dense optical flow method has too many pixels and too much overhead, which limits the running speed. This paper proposed a method combing YOLOv3 (You Only Look Once v3) and local optical flow method. Based on the dense optical flow method, the optical flow modulus of the area where the human target is detected is calculated to reduce the amount of computation and save the cost in terms of time. And then, a threshold value is set to complete the human behavior identification. Through design algorithm, experimental verification and other steps, the walking, running and falling state of human body in real life indoor sports video was identified. Experimental results show that this algorithm is more advantageous for jogging behavior recognition.展开更多
Aiming at the problem that the average recognition degree of the moving target line is low with the traditional motion target behaviour recognition method, a motion recognition method based on deep convolutional neura...Aiming at the problem that the average recognition degree of the moving target line is low with the traditional motion target behaviour recognition method, a motion recognition method based on deep convolutional neural network is proposed in this paper. A target model of deep convolutional neural network is constructed and the basic unit of the network is designed by using the model. By setting the unit, the returned unit is calculated into the standard density diagram, and the position of the moving target is determined by the local maximum method to realize the behavior identification of the moving target. The experimental results show that the multi-parameter SICNN256 model is slightly better than other model structures. The average recognition rate and recognition rate of the moving target behavior recognition method based on deep convolutional neural network are higher than those of the traditional method, which proves its effectiveness. Since the frequency of single target is higher than that of multiple recognition and there is no target similarity recognition, similar target error detection cannot be excluded.展开更多
The selective oxidation of methanol to methyl formate is one of the most attractive processes to obtain value-added methanol-downstream products.The development of highly efficient and stable catalysts is critical for...The selective oxidation of methanol to methyl formate is one of the most attractive processes to obtain value-added methanol-downstream products.The development of highly efficient and stable catalysts is critical for this transformation.In this study,a series of MIL-88B(Fe_(x),Co_(1‒x))bimetallic catalysts with different Fe/Co molar ratios were prepared through a one-pot hydrothermal method.X-ray diffraction,scanning electron microscopy,high-resolution transmission electron microscopy,energy dispersive spectroscopy,Fourier transform infrared spectroscopy,X-ray photoelectron spectroscopy,N2 adsorption-desorption,and inductively coupled plasma-mass spectrometry characterization were performed to elucidate the structure of the catalysts.The activity of the catalysts were assessed in the one-step oxidation of methanol to methyl formate with H_(2)O_(2)in a liquid-phase batch reactor.The results show that the MIL-88B(Fe_(x),Co_(1‒x))catalysts exhibit uniform needle-like morphologies with an average length and width of 400-600 nm and 100-150 nm,respectively.Co^(2+)is incorporated into the framework by partially replacing Fe^(3+)in MIL-88B.Moreover,the catalyst efficiently promoted the conversion of methanol to methyl formate.When MIL-88B(Fe_(0.7),Co_(0.3))catalyst was used with a molar ratio of H_(2)O_(2)to methanol of 0.5 at 80℃for 60 min,34.8%methanol conversion was achieved,and the selectivity toward methyl formate was 67.6%.The catalysts also showed great stability with a steady conversion and selectivity even after four cycles.The preliminary oxidation mechanism was also studied.It was determined that H_(2)O_(2)is first adsorbed on the Fe^(3+)sites and subsequently activates these sites.Methanol is adsorbed by the O atoms of the framework through hydrogen bonding and is gradually oxidized to formic acid.Subsequently,formic acid reacts with the residual methanol at the Fe^(3+)and Co^(2+)Lewis acid sites to form methyl formate.展开更多
The resistance of cancer cells to the anti-cancer drugs is the most important reason that affecting the efficacy of the non-small cell lung cancer(NSCLC)chemotherapy;thus,to explore the underlyingmechanismof drug resi...The resistance of cancer cells to the anti-cancer drugs is the most important reason that affecting the efficacy of the non-small cell lung cancer(NSCLC)chemotherapy;thus,to explore the underlyingmechanismof drug resistance ofNSCLC medications is urgently needed for improving the therapeutic efficacy of current anti-NSCLC chemotherapies.The aim of the present study is to explore the roles of exosomes in the chemosensitivity of A549 cells and the related mechanism.A549 cells and cisplatin resistant cell line A549/DDP derived exosomes were isolated,and the expressions of CXCR4 were compared.Then,after cisplatin treatment,A549 cells were treated with exosomes,and the proliferation,apoptosis,migration,and invasion of the cells were examined.Finally,the tumorigenic effect of A549/DDP derived exosomes were also evaluated by cisplatin treated xenograft tumor mice models in vivo.We found that A549/DDP derived exosomes increased the proliferation,migration,and invasion,and inhibited the apoptosis and cisplatin sensitivity of A549 cells.CXCR4 was also significantly increased in cells treated with A549/DDP derived exosomes.Furthermore,A549/DDP derived exosomes may also decrease the chemosensitivity of NSCLC cells to cisplatin in vivo.Our data suggested that A549/DDP derived exosomes can affect the chemosensitivity of A549 cells to cisplatin,possibly by transporting CXCR4 to A549 cells.Our data may provide novel evidence for the investigation of drug resistance of NSCLC.展开更多
This paper aims to make a comparison between good and poor language learners in the use of vocabulary learning strategies. It will introduce some helpful vocabulary learning strategies to help those frustrated Chinese...This paper aims to make a comparison between good and poor language learners in the use of vocabulary learning strategies. It will introduce some helpful vocabulary learning strategies to help those frustrated Chinese college non-English major learners.展开更多
In this work,the advantage of Coulomb repulsion in the intermolecular forces experienced by molecules on the solid–liquid nanosized contact interface is taken,and the superior friction-reducing property of Cu_(3)(PO_...In this work,the advantage of Coulomb repulsion in the intermolecular forces experienced by molecules on the solid–liquid nanosized contact interface is taken,and the superior friction-reducing property of Cu_(3)(PO_(4))2·3H_(2)O(CuP)oil-based additives has been confirmed for titanium alloy.Three-dimensional(3D)CuP nanoflowers(CuP-Fs)with a strong capillary absorption effect are prepared to achieve the homogeneous mixing of solid CuP and lubricating oil.Lubrication by CuP-Fs additives for titanium alloy,friction coefficient(COF)can be reduced by 73.68%,and wear rate(WR)reduced by 99.69%.It is demonstrated that the extraordinary friction-reducing property is due to the repulsive solid–liquid interface with low viscous shear force originating from Coulomb repulsion between polar water molecules in CuP and non-polar oil molecules.However,any steric hindrance or connection between this repulsive solid–liquid interface will trigger the adhesion and increase the viscous shear force,for example,dispersant,hydrogen bondings,and shaky adsorbed water molecules.Besides,the lamellar thickness of CuP and the molecular size of lubricant both have a great influence on tribological properties.Here the lubrication mechanism based on interface Coulomb repulsion is proposed that may help broaden the scope of the exploration in low-friction nanomaterial design and new lubricant systems.展开更多
The condition of the motor oil in civilian cars is difficult to monitor;hence,we propose a method to evaluate the degree of degradation of motor oil using an on‐board diagnostic(OBD)system.Three civilian cars and fou...The condition of the motor oil in civilian cars is difficult to monitor;hence,we propose a method to evaluate the degree of degradation of motor oil using an on‐board diagnostic(OBD)system.Three civilian cars and four motor oils(containing mineral oils and synthetic oils)were subjected to five groups of road tests under urban traffic and high‐way conditions.The operation information,oil service time,mileage,engine operation time,idle time of the engine,and number of start‐ups of the engine were obtained using the proposed OBD system.Physiochemical properties and changes in the components of motor oils during road tests were analyzed in laboratory.The theoretical model of the comprehensive indicators of driving parameters and oil properties were established.The proposed method was successfully applied to different cars,motor oils,and operating conditions in road tests.All the theoretical models had high accuracy and precision.Herein,we provide a method to monitor the oil condition with real‐time driving parameters and provide a reference for end users to change their motor oil reasonably.展开更多
Ag nanowire(NW)film is the promising next generation transparent conductor.However,the residual long-chain polyvinylpyrrolidone(PVP,introduced during the synthesis of Ag NWs)layer greatly deteriorates the carrier tran...Ag nanowire(NW)film is the promising next generation transparent conductor.However,the residual long-chain polyvinylpyrrolidone(PVP,introduced during the synthesis of Ag NWs)layer greatly deteriorates the carrier transport capability of the Ag NW film and as well its long-term stability.Here,we report a one-step I−ion modification strategy to completely replace the PVP layer with an ultrathin,dense layer of I^(−)ions,which not only greatly diminishes the resistance of the Ag NW film itself and that at interface of the Ag NW film and a functional layer(e.g.,a current collect electrode)but also effectively isolates the approaching of corrosive species.Consequently,this strategy can simultaneously improve the carrier transport properties of the Ag NW film and its long-term stability,making it an ideal electric component in diverse devices.For example,the transparent heater and pressure sensor made from the I^(−)-wrapped Ag NW film,relative to their counterparts made from the PVP-wrapped Ag NW film,deliver much improved heating performance and pressure sensing performance,respectively.These results suggest a facile post treatment approach for thin Ag NW film with improved carrier transport properties and long-term stability,thereby greatly facilitating its downstream applications.展开更多
Several civilian vehicles in China operate in urban traffic conditions and have their motor oil changed every 5,000 km.This study investigates the variations in oil properties after servicing at 5,000 km,based on syst...Several civilian vehicles in China operate in urban traffic conditions and have their motor oil changed every 5,000 km.This study investigates the variations in oil properties after servicing at 5,000 km,based on systematic road tests(including a repeated test,a parallel test,and a new vehicle test).The physicochemical properties,changes in components,oxidation stability,detergent‐dispersant performance,and tribological properties of motor oils were analyzed.The results showed that the total acid number(TAN)of oils increased with the operation mileage,by up to 1.41 mgKOH/g.The total base number(TBN)decreased after the road tests were completed,and the decrease was less than 44.6%.The kinematic viscosity(KV)of most oils decreased initially and then stabilized in the middle stage,before starting to increase later in the experiment.The change in KV at 100℃was less than 15.96%.The oxidation onset temperature(OOT)of the oils diminished gradually with the operation mileage.All OOT values of the used oils were higher than 210℃.A spot test indicated that the used oils retained their detergentdispersant performance to an appropriate extent.The four‐ball wear scar diameters and friction coefficient of the used oils did not increase significantly after the road tests were completed.This study can serve as a reference for end‐users when changing motor oils.展开更多
Three-dimensional(3D)nanoporous gold(NPG)shows promising applications in various fields.However,its most common fabrication strategy(i.e.,dealloying)faces the problems of high energy consumption,resource waste,the use...Three-dimensional(3D)nanoporous gold(NPG)shows promising applications in various fields.However,its most common fabrication strategy(i.e.,dealloying)faces the problems of high energy consumption,resource waste,the use of corrosive solvent,and residue of the sacrificial component.Here,we report a general bottom-up nanowelding strategy to fabricate high-purity NPG from Au nanoparticles(NPs),accomplished via interfacial self-assembly of the Au NPs into monolayer Au NP film,its subsequent layer-by-layer transfer onto a solid substrate,and direct current(DC)nanowelding.We show that the DC nanowelding process can gradually evolve the layered Au NP film into NPG at low temperatures within 10 s,while not damaging their spherical structure.This is because during the nanowelding,electrons are preferred to be localized at the high-resistance NP/NP junctions,whose electrostatic repulsion in turn strengthens their surface atom diffusion to initiate a mild solid-state diffusion nanowelding.Furthermore,when using differently sized Au NPs as the starting building blocks,this strategy allows readily tuning the thickness,ligament size,and pore size,thereby offering great flexibility to create functional porous nanomaterials,e.g.,electrocatalyst for methanol electrooxidation.Surely,low-temperature nanowelding can play a role for the production of diverse nanoporous materials from other NPs beyond Au NPs.展开更多
The accomplishment of nanowelding typically requires the input of high energy,possibly causing appreciable damages to the brittle nanomaterial.Herein,we report an external field(EF,i.e.,light,direct current(DC),and al...The accomplishment of nanowelding typically requires the input of high energy,possibly causing appreciable damages to the brittle nanomaterial.Herein,we report an external field(EF,i.e.,light,direct current(DC),and alternating current(AC))-strengthened Ostwald nanowelding(ONW)strategy to enable low-temperature nanowelding of Au nanoparticles(NPs)with nanoscale spacing in solution and propose an electron localization mechanism to understand it.We reveal that the EF-derived local electrons not only greatly strengthen the dissolution of surface atoms and the reduction of Au3+ions dissolved,but also confine(together with ordered water molecules)the transport of Au^(3+)ions within the nanogap.Consequently,the electrochemical Ostwald ripening(OR)process of the Au NPs is actively strengthened,which,along with the local electron-strengthened surface atom diffusion(as a result of the strong electrostatic repulsion created),enables feasible ONW for solution processing of interdigital electrodes(IDEs)from Au NPs and high-performance transparent conductor(TC)from Ag nanowires(NWs).Our low-temperature nanowelding strategy offers an efficient interconnection technique for the processing of functional nanodevices from individual nanomaterials.展开更多
A new precision rotary piezoelectric(PZT)actuator is proposed to improve its drive performance.Based on piezoelectric technology,the actuator adopts the principle of bionics,with a new method of stator inner anchor/lo...A new precision rotary piezoelectric(PZT)actuator is proposed to improve its drive performance.Based on piezoelectric technology,the actuator adopts the principle of bionics,with a new method of stator inner anchor/loosen/rotor outer drive and a distortion structure of a thin shelf flexible hinge.This structure improves the stability of the anchor/loosen and step rotary.Its characteristics are evaluated by finite element analysis.The experiment shows that the new rotary PZT actuator works with higher frequency(40 Hz),higher speed(325 mrad/s),wider movement(360u),high resolution(1 mrad/step)and high torque(30 N?cm).The novel actuator can be applied in wide movement and high resolution driving devices such as those for optics engineering,precision positioning and some other micro-manipulation fields.展开更多
文摘In the process of human behavior recognition, the traditional dense optical flow method has too many pixels and too much overhead, which limits the running speed. This paper proposed a method combing YOLOv3 (You Only Look Once v3) and local optical flow method. Based on the dense optical flow method, the optical flow modulus of the area where the human target is detected is calculated to reduce the amount of computation and save the cost in terms of time. And then, a threshold value is set to complete the human behavior identification. Through design algorithm, experimental verification and other steps, the walking, running and falling state of human body in real life indoor sports video was identified. Experimental results show that this algorithm is more advantageous for jogging behavior recognition.
文摘Aiming at the problem that the average recognition degree of the moving target line is low with the traditional motion target behaviour recognition method, a motion recognition method based on deep convolutional neural network is proposed in this paper. A target model of deep convolutional neural network is constructed and the basic unit of the network is designed by using the model. By setting the unit, the returned unit is calculated into the standard density diagram, and the position of the moving target is determined by the local maximum method to realize the behavior identification of the moving target. The experimental results show that the multi-parameter SICNN256 model is slightly better than other model structures. The average recognition rate and recognition rate of the moving target behavior recognition method based on deep convolutional neural network are higher than those of the traditional method, which proves its effectiveness. Since the frequency of single target is higher than that of multiple recognition and there is no target similarity recognition, similar target error detection cannot be excluded.
文摘The selective oxidation of methanol to methyl formate is one of the most attractive processes to obtain value-added methanol-downstream products.The development of highly efficient and stable catalysts is critical for this transformation.In this study,a series of MIL-88B(Fe_(x),Co_(1‒x))bimetallic catalysts with different Fe/Co molar ratios were prepared through a one-pot hydrothermal method.X-ray diffraction,scanning electron microscopy,high-resolution transmission electron microscopy,energy dispersive spectroscopy,Fourier transform infrared spectroscopy,X-ray photoelectron spectroscopy,N2 adsorption-desorption,and inductively coupled plasma-mass spectrometry characterization were performed to elucidate the structure of the catalysts.The activity of the catalysts were assessed in the one-step oxidation of methanol to methyl formate with H_(2)O_(2)in a liquid-phase batch reactor.The results show that the MIL-88B(Fe_(x),Co_(1‒x))catalysts exhibit uniform needle-like morphologies with an average length and width of 400-600 nm and 100-150 nm,respectively.Co^(2+)is incorporated into the framework by partially replacing Fe^(3+)in MIL-88B.Moreover,the catalyst efficiently promoted the conversion of methanol to methyl formate.When MIL-88B(Fe_(0.7),Co_(0.3))catalyst was used with a molar ratio of H_(2)O_(2)to methanol of 0.5 at 80℃for 60 min,34.8%methanol conversion was achieved,and the selectivity toward methyl formate was 67.6%.The catalysts also showed great stability with a steady conversion and selectivity even after four cycles.The preliminary oxidation mechanism was also studied.It was determined that H_(2)O_(2)is first adsorbed on the Fe^(3+)sites and subsequently activates these sites.Methanol is adsorbed by the O atoms of the framework through hydrogen bonding and is gradually oxidized to formic acid.Subsequently,formic acid reacts with the residual methanol at the Fe^(3+)and Co^(2+)Lewis acid sites to form methyl formate.
基金supported by The Fundamental Research Funds for the Central Universities[No.WK9110000071]Youth Fund of Anhui Cancer Hospital[Nos.2018YJQN019,2020YJQN007].
文摘The resistance of cancer cells to the anti-cancer drugs is the most important reason that affecting the efficacy of the non-small cell lung cancer(NSCLC)chemotherapy;thus,to explore the underlyingmechanismof drug resistance ofNSCLC medications is urgently needed for improving the therapeutic efficacy of current anti-NSCLC chemotherapies.The aim of the present study is to explore the roles of exosomes in the chemosensitivity of A549 cells and the related mechanism.A549 cells and cisplatin resistant cell line A549/DDP derived exosomes were isolated,and the expressions of CXCR4 were compared.Then,after cisplatin treatment,A549 cells were treated with exosomes,and the proliferation,apoptosis,migration,and invasion of the cells were examined.Finally,the tumorigenic effect of A549/DDP derived exosomes were also evaluated by cisplatin treated xenograft tumor mice models in vivo.We found that A549/DDP derived exosomes increased the proliferation,migration,and invasion,and inhibited the apoptosis and cisplatin sensitivity of A549 cells.CXCR4 was also significantly increased in cells treated with A549/DDP derived exosomes.Furthermore,A549/DDP derived exosomes may also decrease the chemosensitivity of NSCLC cells to cisplatin in vivo.Our data suggested that A549/DDP derived exosomes can affect the chemosensitivity of A549 cells to cisplatin,possibly by transporting CXCR4 to A549 cells.Our data may provide novel evidence for the investigation of drug resistance of NSCLC.
文摘This paper aims to make a comparison between good and poor language learners in the use of vocabulary learning strategies. It will introduce some helpful vocabulary learning strategies to help those frustrated Chinese college non-English major learners.
基金the National Natural Science Foundation of China(Nos.51975421,52075405,and 51975420)Hubei Longzhong Laboratory Independent Innovation Research Project(No.2022ZZ-05).
文摘In this work,the advantage of Coulomb repulsion in the intermolecular forces experienced by molecules on the solid–liquid nanosized contact interface is taken,and the superior friction-reducing property of Cu_(3)(PO_(4))2·3H_(2)O(CuP)oil-based additives has been confirmed for titanium alloy.Three-dimensional(3D)CuP nanoflowers(CuP-Fs)with a strong capillary absorption effect are prepared to achieve the homogeneous mixing of solid CuP and lubricating oil.Lubrication by CuP-Fs additives for titanium alloy,friction coefficient(COF)can be reduced by 73.68%,and wear rate(WR)reduced by 99.69%.It is demonstrated that the extraordinary friction-reducing property is due to the repulsive solid–liquid interface with low viscous shear force originating from Coulomb repulsion between polar water molecules in CuP and non-polar oil molecules.However,any steric hindrance or connection between this repulsive solid–liquid interface will trigger the adhesion and increase the viscous shear force,for example,dispersant,hydrogen bondings,and shaky adsorbed water molecules.Besides,the lamellar thickness of CuP and the molecular size of lubricant both have a great influence on tribological properties.Here the lubrication mechanism based on interface Coulomb repulsion is proposed that may help broaden the scope of the exploration in low-friction nanomaterial design and new lubricant systems.
基金financial support from the National Natural Science Foundation of China(No.51575402)
文摘The condition of the motor oil in civilian cars is difficult to monitor;hence,we propose a method to evaluate the degree of degradation of motor oil using an on‐board diagnostic(OBD)system.Three civilian cars and four motor oils(containing mineral oils and synthetic oils)were subjected to five groups of road tests under urban traffic and high‐way conditions.The operation information,oil service time,mileage,engine operation time,idle time of the engine,and number of start‐ups of the engine were obtained using the proposed OBD system.Physiochemical properties and changes in the components of motor oils during road tests were analyzed in laboratory.The theoretical model of the comprehensive indicators of driving parameters and oil properties were established.The proposed method was successfully applied to different cars,motor oils,and operating conditions in road tests.All the theoretical models had high accuracy and precision.Herein,we provide a method to monitor the oil condition with real‐time driving parameters and provide a reference for end users to change their motor oil reasonably.
基金support from the National Natural Science Foundation of China(Nos.21872047,21673070,and 22072039)Hunan Key Laboratory of Two-Dimensional Materials(No.2018TP1010).
文摘Ag nanowire(NW)film is the promising next generation transparent conductor.However,the residual long-chain polyvinylpyrrolidone(PVP,introduced during the synthesis of Ag NWs)layer greatly deteriorates the carrier transport capability of the Ag NW film and as well its long-term stability.Here,we report a one-step I−ion modification strategy to completely replace the PVP layer with an ultrathin,dense layer of I^(−)ions,which not only greatly diminishes the resistance of the Ag NW film itself and that at interface of the Ag NW film and a functional layer(e.g.,a current collect electrode)but also effectively isolates the approaching of corrosive species.Consequently,this strategy can simultaneously improve the carrier transport properties of the Ag NW film and its long-term stability,making it an ideal electric component in diverse devices.For example,the transparent heater and pressure sensor made from the I^(−)-wrapped Ag NW film,relative to their counterparts made from the PVP-wrapped Ag NW film,deliver much improved heating performance and pressure sensing performance,respectively.These results suggest a facile post treatment approach for thin Ag NW film with improved carrier transport properties and long-term stability,thereby greatly facilitating its downstream applications.
基金The authors are grateful for the financial support from the National Natural Science Foundation of China(51575402)the National Natural Science Foundation of Hunan Province of China(No.2020JJ5217).
文摘Several civilian vehicles in China operate in urban traffic conditions and have their motor oil changed every 5,000 km.This study investigates the variations in oil properties after servicing at 5,000 km,based on systematic road tests(including a repeated test,a parallel test,and a new vehicle test).The physicochemical properties,changes in components,oxidation stability,detergent‐dispersant performance,and tribological properties of motor oils were analyzed.The results showed that the total acid number(TAN)of oils increased with the operation mileage,by up to 1.41 mgKOH/g.The total base number(TBN)decreased after the road tests were completed,and the decrease was less than 44.6%.The kinematic viscosity(KV)of most oils decreased initially and then stabilized in the middle stage,before starting to increase later in the experiment.The change in KV at 100℃was less than 15.96%.The oxidation onset temperature(OOT)of the oils diminished gradually with the operation mileage.All OOT values of the used oils were higher than 210℃.A spot test indicated that the used oils retained their detergentdispersant performance to an appropriate extent.The four‐ball wear scar diameters and friction coefficient of the used oils did not increase significantly after the road tests were completed.This study can serve as a reference for end‐users when changing motor oils.
基金supported by the National Natural Science Foundation of China (21872047 and 21673070)Hunan Key Laboratory of Two-Dimensional Materials (2018TP1010)。
文摘Three-dimensional(3D)nanoporous gold(NPG)shows promising applications in various fields.However,its most common fabrication strategy(i.e.,dealloying)faces the problems of high energy consumption,resource waste,the use of corrosive solvent,and residue of the sacrificial component.Here,we report a general bottom-up nanowelding strategy to fabricate high-purity NPG from Au nanoparticles(NPs),accomplished via interfacial self-assembly of the Au NPs into monolayer Au NP film,its subsequent layer-by-layer transfer onto a solid substrate,and direct current(DC)nanowelding.We show that the DC nanowelding process can gradually evolve the layered Au NP film into NPG at low temperatures within 10 s,while not damaging their spherical structure.This is because during the nanowelding,electrons are preferred to be localized at the high-resistance NP/NP junctions,whose electrostatic repulsion in turn strengthens their surface atom diffusion to initiate a mild solid-state diffusion nanowelding.Furthermore,when using differently sized Au NPs as the starting building blocks,this strategy allows readily tuning the thickness,ligament size,and pore size,thereby offering great flexibility to create functional porous nanomaterials,e.g.,electrocatalyst for methanol electrooxidation.Surely,low-temperature nanowelding can play a role for the production of diverse nanoporous materials from other NPs beyond Au NPs.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.21872047,21673070,and 91750205)lHunan Key Laboratory of Two-Dimensional Materials(No.2018TP1010).
文摘The accomplishment of nanowelding typically requires the input of high energy,possibly causing appreciable damages to the brittle nanomaterial.Herein,we report an external field(EF,i.e.,light,direct current(DC),and alternating current(AC))-strengthened Ostwald nanowelding(ONW)strategy to enable low-temperature nanowelding of Au nanoparticles(NPs)with nanoscale spacing in solution and propose an electron localization mechanism to understand it.We reveal that the EF-derived local electrons not only greatly strengthen the dissolution of surface atoms and the reduction of Au3+ions dissolved,but also confine(together with ordered water molecules)the transport of Au^(3+)ions within the nanogap.Consequently,the electrochemical Ostwald ripening(OR)process of the Au NPs is actively strengthened,which,along with the local electron-strengthened surface atom diffusion(as a result of the strong electrostatic repulsion created),enables feasible ONW for solution processing of interdigital electrodes(IDEs)from Au NPs and high-performance transparent conductor(TC)from Ag nanowires(NWs).Our low-temperature nanowelding strategy offers an efficient interconnection technique for the processing of functional nanodevices from individual nanomaterials.
基金supported by the Hi-Tech Research and Development Program of China (No.2002AA423150)the National Natural Science Foundation of China (Grant No.50475010).
文摘A new precision rotary piezoelectric(PZT)actuator is proposed to improve its drive performance.Based on piezoelectric technology,the actuator adopts the principle of bionics,with a new method of stator inner anchor/loosen/rotor outer drive and a distortion structure of a thin shelf flexible hinge.This structure improves the stability of the anchor/loosen and step rotary.Its characteristics are evaluated by finite element analysis.The experiment shows that the new rotary PZT actuator works with higher frequency(40 Hz),higher speed(325 mrad/s),wider movement(360u),high resolution(1 mrad/step)and high torque(30 N?cm).The novel actuator can be applied in wide movement and high resolution driving devices such as those for optics engineering,precision positioning and some other micro-manipulation fields.
