A theoretical scheme is proposed to enhance the sensitivity of force sensors with quantum nondemolition measurement(QND)in an optomechanical setup assisted by four-tone optical driving and an optical parametric amplif...A theoretical scheme is proposed to enhance the sensitivity of force sensors with quantum nondemolition measurement(QND)in an optomechanical setup assisted by four-tone optical driving and an optical parametric amplifier(OPA).With the help of special drive,the system can be simplified as the typical type of QND for force sensing,so that the backaction noise can be evaded to surpass the standard quantum limit.Besides,the added noise can be suppressed owing to the modified optical susceptibility resulting from the OPA.By introducing two oscillators coupling with two charged bodies respectively,the signal can be enhanced with the nonlinearity caused by Coulomb interaction,while the noise presents an exponential decrease.Moreover,considering the homodyne detection effect,the range of system parameters and frequency bands will be broadened.The present investigation may provide a route toward simultaneously evading backaction noise,reducing the mechanical thermal noise,and enhancing the external signal,which can be an alternative design for sensitive devices.展开更多
Force sensing provides a crucial physical-electrical channel within sensing technology.This study showcases the fabrication and characterization of force sensors by integrating a polydimethylsiloxane(PDMS)mechanical m...Force sensing provides a crucial physical-electrical channel within sensing technology.This study showcases the fabrication and characterization of force sensors by integrating a polydimethylsiloxane(PDMS)mechanical module and an optical channel formed by two ideal InGaN/GaN light-emitting diodes(LEDs)with transmit-receive characteristics.As an emitter,the InGaN/GaN device(5 mm×4 mm)exhibits electroluminescence at 469 nm with an on-voltage of 2.33 V.As a receiver,the response spectrum of InGaN/GaN devices spans from 350 to 480 nm,featuring a peak at 390 nm,rise time of~68.4 ms,and falling edge of~61.0 ms.The PDMS film can transform the force into deformation data and influence the signals in the optical receiver.The drive current,the gap between the emitter and receiver,and distance between the LED and PDMS mechanical module all significantly influence the receiver photocurrent.Distinct from the integrated design,our PDMS-assisted force sensing model uses discrete structures to allow signal intensity optimization.The finite element simulation and experimental results indicate that force of the designed PDMS film exhibits a linear relationship with z-axis displacement and photocurrent from 0 to 0.7 mm.The findings reveal that when the PDMS film height is 1.5 mm and the distance between the emitter and receiver is near,the photocurrent is higher.Meanwhile,Ag film with a thickness of 100 nm considerably enhances the photocurrent response and signal stability in the sensing channel.Finally,a weight measurement demonstration is employed to demonstrate force sensing.The system resolution is 1.23μA/N,and the measurement range is 0 to 0.7 N.展开更多
1,2-Dioxetane is a well-known chemiluminescent mechanophore allowing real-time monitoring of polymer chain scission,but usually suffers from fluorescence quenching in polar environments.Herein,a series of mechanochemi...1,2-Dioxetane is a well-known chemiluminescent mechanophore allowing real-time monitoring of polymer chain scission,but usually suffers from fluorescence quenching in polar environments.Herein,a series of mechanochemiluminescent waterborne polyurethanes/carbon dots composites(WPU-CDs)have been synthesized by incorporating fluorescent CDs to promote the energy transfer process in different environments.The resulting bulk WPUs,and in particular,their swollen films filled with a large amount of polar solvents(water and ionic liquid)emit intense mechanochemiluminescence.Thus force-induced covalent bond scission and stress distribution within these different WPU-CDs films can be sensitively visualized.Furthermore,the ionic liquid containing films exhibited both electrical and luminescent signal changes under stretching,which offer a new kind of force sensor responsive at a broad detecting strain range and for multi-mode strain analysis.This study is expected to stimulate new research endeavors in mechanistic insight on waterborne polyurethanes and the corresponding stretchable sensing devices.展开更多
The problems of attachment failure and detachment impact within gecko-like robots’ locomotion control are considered in this paper. A real-time foot-end force intelligent sensing module with integrated sensing and st...The problems of attachment failure and detachment impact within gecko-like robots’ locomotion control are considered in this paper. A real-time foot-end force intelligent sensing module with integrated sensing and structure is developed to help the robot get the foot-end force information in time and realize stable locomotion in an uncertain environment. Firstly,a structure/sensing integrated elastomer based on a Maltese cross/cantilever beam structure is completed by designing and finite element analysis. Secondly,a real-time data acquisition and transmission system is designed to obtain the foot-end reaction force which is miniaturized and distributed. Thirdly,based on this system,a force sensor calibration platform is built to complete the calibration,decoupling,and performance testing of the sensing module. Finally,the experiment of single-leg attachment performance is carried out. The results indicate that the three-axis sensing module can detect robot’s weight,measure the reaction force with high precision and provide real-time force from robot’s foot end.展开更多
Cavity magnomechanics,exhibiting remarkable experimental tunability,rich magnonic nonlinearities,and compatibility with various quantum systems,has witnessed considerable advances in recent years.However,the potential...Cavity magnomechanics,exhibiting remarkable experimental tunability,rich magnonic nonlinearities,and compatibility with various quantum systems,has witnessed considerable advances in recent years.However,the potential benefits of using cavity magnomechanical(CMM)systems in further improving the performance of quantum-enhanced sensing for weak forces remain largely unexplored.Here we show that,by squeezing the magnons,the performance of a quantum CMM sensor can be significantly enhanced beyond the standard quantum limit(SQL).We find that,for comparable parameters,two orders of magnitude enhancement in the force sensitivity can be achieved in comparison with the case without magnon squeezing.Moreover,we obtain the optimal parameter regimes of homodyne angle for minimizing the added quantum noise.Our findings provide a promising approach for highly tunable and compatible quantum force sensing using hybrid CMM devices,with potential applications ranging from quantum precision measurements to quantum information processing.展开更多
We theoretically investigate optomechanical force sensing via precooling and quantum noise cancellation in two coupled cavity optomechanical systems. We show that force sensing based on the reduction of noise can be u...We theoretically investigate optomechanical force sensing via precooling and quantum noise cancellation in two coupled cavity optomechanical systems. We show that force sensing based on the reduction of noise can be used to dramatically enhance the force sensing and that the precooling process can effectively improve the quantum noise cancellation. Specifically, we examine the effect of optomechanical cooling and noise reduction on the spectral density of the noise of the force measurement; these processes can significantly enhance the performance of optomechanical force sensing, and setting up the system in the resolved sideband regime can lead to an optimization of the cooling processes in a hybrid system. Such a scheme serves as a promising platform for quantum back-action-evading measurements of the motion and a framework for an optomechanical force sensor.展开更多
Force sensing is vital for situational awareness and safe interaction during minimally invasive surgery.Consequently,surgical robots with integrated force-sensing techniques ensure precise and safe operations.Over the...Force sensing is vital for situational awareness and safe interaction during minimally invasive surgery.Consequently,surgical robots with integrated force-sensing techniques ensure precise and safe operations.Over the past few decades,there has been considerable progress in force-sensing techniques for surgical robots.This review summarizes the existing electrically-and optically-based force sensors for surgical robots,including piezoresistive,piezoelectric,capacitive,intensity/phase-modulated,andfiber Bragg gratings.Their principles,applications,advantages,and limitations are also discussed.Finally,we summarize our conclusions regarding state-of-the-art force-sensing technologies for surgical robotics.展开更多
Weld seam inflection points are inevitable in tele-teaching process on many welding occasions. The inflection points identified accurately is one of the prerequisites of ensuring tele-teaching precision. On the basis ...Weld seam inflection points are inevitable in tele-teaching process on many welding occasions. The inflection points identified accurately is one of the prerequisites of ensuring tele-teaching precision. On the basis of the inflection point characters, the concept of inflection point direction coefficient is proposed, the human-simulation intelligent control model of inflection point is established. The algorithms above, the inflection point identifying of box workpiece can be well performed. The experimental results show that the identifying average error of inflection point can be reduced to less than O. 5 mm by using optimal treatment of robot off-line programming system. The identifying control can automatically identify weld seam inflection points which can meet tele-teaching requirements.展开更多
To effectively obtain the downforce of the gauge wheels in real time,mechanical models of the interaction among the ground,gauge wheels,gauge wheel arms,and depth adjustment lever were constructed.A measuring method w...To effectively obtain the downforce of the gauge wheels in real time,mechanical models of the interaction among the ground,gauge wheels,gauge wheel arms,and depth adjustment lever were constructed.A measuring method was proposed for monitoring the downforce through a two-dimensional radial sensing device,and a corresponding prototype was designed.Through simulation analysis of the sensing device with ANSYS,a 45°angle was determined to exist between the strain gauge axis and the sensing device axis,and the Wheatstone bridging circuit of R1+R3−R5−R7(R stands for resistance strain gauge,different figures represent the strain gauge number)and R2+R4−R6−R8 was adopted.According to performance and calibration tests for the sensing device,the maximum interaction effect between the X and Y axes was 2.52%,and the output signal was stable and consistent.The standard error of the slope of the fitting equation of the downforce calculation model is 0.008.According to the field test,the average downforce of the gauge wheels was 1148,1017,843,and 713 N,at different sowing speeds of 6,8,10,and 12 km/h,respectively.The coefficients of variation were 0.40,0.41,0.62,and 0.71,respectively.The results indicate that the downforce fluctuation of the gauge wheels became more severe with increasing planting speed.Both the strain simulation analysis and field test verified that the measurement method is accurate and reliable,the performance of the sensing device is stable,the measurement method and sensing device meet the application requirements and lay a foundation for the research of accurate and stable control of downforce of no-till planter.展开更多
Reclamation is one of the fastest-growing land use type developed in coastal areas and has caused degradation and loss of coastal wetlands as well as serious environmental problems. This paper was aimed at monitoring ...Reclamation is one of the fastest-growing land use type developed in coastal areas and has caused degradation and loss of coastal wetlands as well as serious environmental problems. This paper was aimed at monitoring the spatiotemporal patterns of coastal wetlands and reclamation in the Yangtze Estuary during the 1960s and 2015. Satellite images obtained from 1980 to 2015 and topography maps of the 1960 s were employed to extract changes of reclamation and coastal wetlands. Area-weight centroids were calculated to identify the movement trend of reclamation and coastal wetlands. The results show that from the 1960 s to 2015, the net area of natural wetlands declined by 574.3 km^2, while man-made wetlands and reclamation increased by 553.6 and 543.9 km^2, respectively. During the five study phases, the fastest areal change rate natural wetlands was –13.3 km^2/yr in the period of 1990–2000, and that of man-made areas was 24.7 km^2/yr in the same period, and the areal change rate of reclamation was 27.6 km^2/yr in the period of 2000–2010. Conversion of coastal wetlands mainly occurred in the Chongming Island, Changshu City and the east coast of Shanghai Municipality. Reclamation was common across coastal areas, and was mainly attributed to settlement and man-made wetlands in the Chongming Island, Lianyungang City and the east coast of Shanghai Municipality. Natural wetlands turned into farmlands and settlement, and man-made wetlands gained from reclamation of farmlands. The centroid of natural wetlands generally moved towards the sea, man-made wetlands expanded equally in all directions and inland, and the centroid of reclamation migrated toward Shanghai Municipality. Sea level rise, erosion-deposition changes, and reclamation activities together determine the dynamics of the Yangtze Estuary wetlands. However, reclamation activities for construction of ports, industries and aquaculture are the key causes for the dynamics. The results from this study on the dynamics of coastal wetlands and reclamation are valuable for local government to put forward sustainable land use and land development plans.展开更多
Forest disturbance plays a vital role in modulating carbon storage,biodiversity and climate change.Yearly Landsat imagery from 1986 to 2015 of a typical plantation region in the northern Guangdong province of southern...Forest disturbance plays a vital role in modulating carbon storage,biodiversity and climate change.Yearly Landsat imagery from 1986 to 2015 of a typical plantation region in the northern Guangdong province of southern China was used as a case study.A Landsat time series stack(LTSS) was fed to the vegetation change tracker model(VCT) to map long-term changes in plantation forests' disturbance and recovery,followed by an intensive validation and a continuous 27-yr change analysis on disturbance locations,magnitudes and rates of plantations' disturbance and recovery.And the validation results of the disturbance year maps derived from five randomly identified sample plots with 25 km^2 located at the four corners and the center of the scene showed the majority of the spatial agreement measures ranged from 60% to 83%.A confusion matrix summary of the accuracy measures for all four validation sites in Fogang County showed that the disturbance year maps had an overall accuracy estimate of 71.70%.Forest disturbance rates' change trend was characterized by a decline first,followed by an increase,then giving way to a decline again.An undulated and gentle decreasing trend of disturbance rates from the highest value of 3.95% to the lowest value of 0.76% occurred between 1988 and 2001,disturbance rate of 4.51% in 1994 was a notable anomaly,while after 2001 there was a sharp ascending change,forest disturbance rate spiked in 2007(5.84%).After that,there was a significant decreasing trend up to the lowest value of 1.96% in 2011 and a slight ascending trend from 2011 to 2015(2.59%).Two obvious spikes in post-disturbance recovery rates occurred in 1995(0.26%) and 2008(0.41%).Overall,forest recovery rates were lower than forest disturbance rates.Moreover,forest disturbance and recovery detection based on VCT and the Landsat-based detections of trends in disturbance and recovery(LandT rendr) algorithms in Fogang County have been conducted,with LandT rendr finding mostly much more disturbance than VCT.Overall,disturbances and recoveries in northern Guangdong were triggered mostly by timber needs,policies and decisions of the local governments.This study highlights that a better understanding about plantations' changes would provide a critical foundation for local forest management decisions in the southern China.展开更多
In recent years,conductive hydrogels have become a promising candidate for application in fields such as tissue engineering and flexible electronic devices because of their conductivity,soft and wet nature.However,the...In recent years,conductive hydrogels have become a promising candidate for application in fields such as tissue engineering and flexible electronic devices because of their conductivity,soft and wet nature.However,the preparation of tough and uniformly conductive hydrogels remains challenging because conductive nanofillers tend to aggregate during hydrogel formation.Herein,a hydrophilic polymer assistant dispersion strategy is proposed to fabricate a tough,conductive composite hydrogel with doublenetwork based on well-dispersed carbon nanotubes(CNTs).In particular,A@T_(2.0)/polyacrylamide(PAM)hydrogels showed a tensile strength of 332.9 kPa,elongation of 584.6%,Young’s modulus of 91.5 kPa,and conductivity of 2.765 S m^(-1),and a demonstration was performed to show the strain sensing for health monitoring and handwriting.Results showed that the fabricated conductive hydrogels offer promising and broad insights in the field of wearable sensors for health monitoring,innovative electronics,and human-machine interactions.展开更多
Spinal disease is an important cause of cervical discomfort,low back pain,radiating pain in the limbs,and neurogenic intermittent claudication,and its incidence is increasing annually.From the etiological viewpoint,th...Spinal disease is an important cause of cervical discomfort,low back pain,radiating pain in the limbs,and neurogenic intermittent claudication,and its incidence is increasing annually.From the etiological viewpoint,these symptoms are directly caused by the compression of the spinal cord,nerve roots,and blood vessels and are most effectively treated with surgery.Spinal surgeries are primarily performed using two different techniques:spinal canal decompression and internal fixation.In the past,tactile sensation was the primary method used by surgeons to understand the state of the tissue within the operating area.However,this method has several disadvantages because of its subjectivity.Therefore,it has become the focus of spinal surgery research so as to strengthen the objectivity of tissue state recognition,improve the accuracy of safe area location,and avoid surgical injury to tissues.Aside from traditional imaging methods,surgical sensing techniques based on force,bioelectrical impedance,and other methods have been gradually developed and tested in the clinical setting.This article reviews the progress of different tissue state recognition methods in spinal surgery and summarizes their advantages and disadvantages.展开更多
基金supported by the National Key Research and Development Program of China Grant No.2021YFA1400700National Natural Science Foundation of China Grant No.11974125。
文摘A theoretical scheme is proposed to enhance the sensitivity of force sensors with quantum nondemolition measurement(QND)in an optomechanical setup assisted by four-tone optical driving and an optical parametric amplifier(OPA).With the help of special drive,the system can be simplified as the typical type of QND for force sensing,so that the backaction noise can be evaded to surpass the standard quantum limit.Besides,the added noise can be suppressed owing to the modified optical susceptibility resulting from the OPA.By introducing two oscillators coupling with two charged bodies respectively,the signal can be enhanced with the nonlinearity caused by Coulomb interaction,while the noise presents an exponential decrease.Moreover,considering the homodyne detection effect,the range of system parameters and frequency bands will be broadened.The present investigation may provide a route toward simultaneously evading backaction noise,reducing the mechanical thermal noise,and enhancing the external signal,which can be an alternative design for sensitive devices.
基金supported by the Natural Science Foundation of Jiangsu Province(BK20210593)the National Natural Science Foundation of China(62204127,62404040)the Fundamental Research Funds for the Central Universities(No.NS2022096).
文摘Force sensing provides a crucial physical-electrical channel within sensing technology.This study showcases the fabrication and characterization of force sensors by integrating a polydimethylsiloxane(PDMS)mechanical module and an optical channel formed by two ideal InGaN/GaN light-emitting diodes(LEDs)with transmit-receive characteristics.As an emitter,the InGaN/GaN device(5 mm×4 mm)exhibits electroluminescence at 469 nm with an on-voltage of 2.33 V.As a receiver,the response spectrum of InGaN/GaN devices spans from 350 to 480 nm,featuring a peak at 390 nm,rise time of~68.4 ms,and falling edge of~61.0 ms.The PDMS film can transform the force into deformation data and influence the signals in the optical receiver.The drive current,the gap between the emitter and receiver,and distance between the LED and PDMS mechanical module all significantly influence the receiver photocurrent.Distinct from the integrated design,our PDMS-assisted force sensing model uses discrete structures to allow signal intensity optimization.The finite element simulation and experimental results indicate that force of the designed PDMS film exhibits a linear relationship with z-axis displacement and photocurrent from 0 to 0.7 mm.The findings reveal that when the PDMS film height is 1.5 mm and the distance between the emitter and receiver is near,the photocurrent is higher.Meanwhile,Ag film with a thickness of 100 nm considerably enhances the photocurrent response and signal stability in the sensing channel.Finally,a weight measurement demonstration is employed to demonstrate force sensing.The system resolution is 1.23μA/N,and the measurement range is 0 to 0.7 N.
基金financially supported by the National Natural Science Foundation of China(Nos.21905200,21975178 and 21734006)China Postdoctoral Science Foundation(No.2019M661006)。
文摘1,2-Dioxetane is a well-known chemiluminescent mechanophore allowing real-time monitoring of polymer chain scission,but usually suffers from fluorescence quenching in polar environments.Herein,a series of mechanochemiluminescent waterborne polyurethanes/carbon dots composites(WPU-CDs)have been synthesized by incorporating fluorescent CDs to promote the energy transfer process in different environments.The resulting bulk WPUs,and in particular,their swollen films filled with a large amount of polar solvents(water and ionic liquid)emit intense mechanochemiluminescence.Thus force-induced covalent bond scission and stress distribution within these different WPU-CDs films can be sensitively visualized.Furthermore,the ionic liquid containing films exhibited both electrical and luminescent signal changes under stretching,which offer a new kind of force sensor responsive at a broad detecting strain range and for multi-mode strain analysis.This study is expected to stimulate new research endeavors in mechanistic insight on waterborne polyurethanes and the corresponding stretchable sensing devices.
基金supported by the National Natural Science Foundation of China(Nos.31601870,51435008)Jiangsu Educational Innovation Program(No.KYLX16_0328)
文摘The problems of attachment failure and detachment impact within gecko-like robots’ locomotion control are considered in this paper. A real-time foot-end force intelligent sensing module with integrated sensing and structure is developed to help the robot get the foot-end force information in time and realize stable locomotion in an uncertain environment. Firstly,a structure/sensing integrated elastomer based on a Maltese cross/cantilever beam structure is completed by designing and finite element analysis. Secondly,a real-time data acquisition and transmission system is designed to obtain the foot-end reaction force which is miniaturized and distributed. Thirdly,based on this system,a force sensor calibration platform is built to complete the calibration,decoupling,and performance testing of the sensing module. Finally,the experiment of single-leg attachment performance is carried out. The results indicate that the three-axis sensing module can detect robot’s weight,measure the reaction force with high precision and provide real-time force from robot’s foot end.
基金supported by the National Natural Science Foundation of China(Grant No.11935006)supported by the National Natural Science Foundation of China(Grant No.12205054)+7 种基金the Science and Technology Innovation Program of Hunan Province(Grant No.2020RC4047)National Key R&D Program of China(Grant No.2024YFE0102400)Hunan Provincial Major Scitech Program(Grant No.2023ZJ1010)Ph.D.Research Foundation(BSJJ202122)supported by the Japan Society for the Promotion of Science(JSPS)Postdoctoral Fellowships for Research in Japan(No.P22018)Nippon Telegraph and Telephone Corporation(NTT)Research,the Japan Science and Technology Agency(JST)(via the Quantum Leap Flagship Program(Q-LEAP),and the Moonshot R&D(Grant No.JPMJMS2061))the Asian Office of Aerospace Research and Development(AOARD)(Grant No.FA2386-20-1-4069)the Office of Naval Research(ONR)Global(Grant No.N62909-23-1-2074)。
文摘Cavity magnomechanics,exhibiting remarkable experimental tunability,rich magnonic nonlinearities,and compatibility with various quantum systems,has witnessed considerable advances in recent years.However,the potential benefits of using cavity magnomechanical(CMM)systems in further improving the performance of quantum-enhanced sensing for weak forces remain largely unexplored.Here we show that,by squeezing the magnons,the performance of a quantum CMM sensor can be significantly enhanced beyond the standard quantum limit(SQL).We find that,for comparable parameters,two orders of magnitude enhancement in the force sensitivity can be achieved in comparison with the case without magnon squeezing.Moreover,we obtain the optimal parameter regimes of homodyne angle for minimizing the added quantum noise.Our findings provide a promising approach for highly tunable and compatible quantum force sensing using hybrid CMM devices,with potential applications ranging from quantum precision measurements to quantum information processing.
基金supported by the Arba Minch University Ethiopia,and the National Natural Science Foundation of China(Grant Nos.11574041,and 11475037)
文摘We theoretically investigate optomechanical force sensing via precooling and quantum noise cancellation in two coupled cavity optomechanical systems. We show that force sensing based on the reduction of noise can be used to dramatically enhance the force sensing and that the precooling process can effectively improve the quantum noise cancellation. Specifically, we examine the effect of optomechanical cooling and noise reduction on the spectral density of the noise of the force measurement; these processes can significantly enhance the performance of optomechanical force sensing, and setting up the system in the resolved sideband regime can lead to an optimization of the cooling processes in a hybrid system. Such a scheme serves as a promising platform for quantum back-action-evading measurements of the motion and a framework for an optomechanical force sensor.
基金the National Natural Science Foundation of China(No.62003209)the Natural Science Foundation of Shanghai(No.21ZR1429500)+2 种基金the Shanghai Rising-Star Program(No.22QC1401400)the Science and Technology Commission of Shanghai Municipality(No.20DZ2220400)the Open Project Fund from the Shenzhen Institute of Artificial Intelligence and Robotics for Society,China(No.AC01202005012)。
文摘Force sensing is vital for situational awareness and safe interaction during minimally invasive surgery.Consequently,surgical robots with integrated force-sensing techniques ensure precise and safe operations.Over the past few decades,there has been considerable progress in force-sensing techniques for surgical robots.This review summarizes the existing electrically-and optically-based force sensors for surgical robots,including piezoresistive,piezoelectric,capacitive,intensity/phase-modulated,andfiber Bragg gratings.Their principles,applications,advantages,and limitations are also discussed.Finally,we summarize our conclusions regarding state-of-the-art force-sensing technologies for surgical robotics.
文摘Weld seam inflection points are inevitable in tele-teaching process on many welding occasions. The inflection points identified accurately is one of the prerequisites of ensuring tele-teaching precision. On the basis of the inflection point characters, the concept of inflection point direction coefficient is proposed, the human-simulation intelligent control model of inflection point is established. The algorithms above, the inflection point identifying of box workpiece can be well performed. The experimental results show that the identifying average error of inflection point can be reduced to less than O. 5 mm by using optimal treatment of robot off-line programming system. The identifying control can automatically identify weld seam inflection points which can meet tele-teaching requirements.
基金supported by the State’s Key Project of Research and Development Plan of China(Grant No.2021YFD2000401)the Heilongjiang Province Engineering Science and Technology Major Project of China(Grant No.2020ZX17B01)the National Modern Agricultural Industry Technology System Project(Grant No.GARS-04).
文摘To effectively obtain the downforce of the gauge wheels in real time,mechanical models of the interaction among the ground,gauge wheels,gauge wheel arms,and depth adjustment lever were constructed.A measuring method was proposed for monitoring the downforce through a two-dimensional radial sensing device,and a corresponding prototype was designed.Through simulation analysis of the sensing device with ANSYS,a 45°angle was determined to exist between the strain gauge axis and the sensing device axis,and the Wheatstone bridging circuit of R1+R3−R5−R7(R stands for resistance strain gauge,different figures represent the strain gauge number)and R2+R4−R6−R8 was adopted.According to performance and calibration tests for the sensing device,the maximum interaction effect between the X and Y axes was 2.52%,and the output signal was stable and consistent.The standard error of the slope of the fitting equation of the downforce calculation model is 0.008.According to the field test,the average downforce of the gauge wheels was 1148,1017,843,and 713 N,at different sowing speeds of 6,8,10,and 12 km/h,respectively.The coefficients of variation were 0.40,0.41,0.62,and 0.71,respectively.The results indicate that the downforce fluctuation of the gauge wheels became more severe with increasing planting speed.Both the strain simulation analysis and field test verified that the measurement method is accurate and reliable,the performance of the sensing device is stable,the measurement method and sensing device meet the application requirements and lay a foundation for the research of accurate and stable control of downforce of no-till planter.
基金Under the auspices of National Program on Key Basic Research Project(No.2013CB430401)
文摘Reclamation is one of the fastest-growing land use type developed in coastal areas and has caused degradation and loss of coastal wetlands as well as serious environmental problems. This paper was aimed at monitoring the spatiotemporal patterns of coastal wetlands and reclamation in the Yangtze Estuary during the 1960s and 2015. Satellite images obtained from 1980 to 2015 and topography maps of the 1960 s were employed to extract changes of reclamation and coastal wetlands. Area-weight centroids were calculated to identify the movement trend of reclamation and coastal wetlands. The results show that from the 1960 s to 2015, the net area of natural wetlands declined by 574.3 km^2, while man-made wetlands and reclamation increased by 553.6 and 543.9 km^2, respectively. During the five study phases, the fastest areal change rate natural wetlands was –13.3 km^2/yr in the period of 1990–2000, and that of man-made areas was 24.7 km^2/yr in the same period, and the areal change rate of reclamation was 27.6 km^2/yr in the period of 2000–2010. Conversion of coastal wetlands mainly occurred in the Chongming Island, Changshu City and the east coast of Shanghai Municipality. Reclamation was common across coastal areas, and was mainly attributed to settlement and man-made wetlands in the Chongming Island, Lianyungang City and the east coast of Shanghai Municipality. Natural wetlands turned into farmlands and settlement, and man-made wetlands gained from reclamation of farmlands. The centroid of natural wetlands generally moved towards the sea, man-made wetlands expanded equally in all directions and inland, and the centroid of reclamation migrated toward Shanghai Municipality. Sea level rise, erosion-deposition changes, and reclamation activities together determine the dynamics of the Yangtze Estuary wetlands. However, reclamation activities for construction of ports, industries and aquaculture are the key causes for the dynamics. The results from this study on the dynamics of coastal wetlands and reclamation are valuable for local government to put forward sustainable land use and land development plans.
基金Under the auspices of the‘948’Project sponsored by the State Forestry Administration(SFA)of China(No.2014-4-25)National Natural Science Foundation of China(No.31670552,31270587)Doctorate Fellowship Foundation of Nanjing Forestry University,the PAPD(Priority Academic Program Development)of Jiangsu Provincial Universities,Graduate Research and Innovation Projects in Jiangsu Province(No.KYLX15_0908)
文摘Forest disturbance plays a vital role in modulating carbon storage,biodiversity and climate change.Yearly Landsat imagery from 1986 to 2015 of a typical plantation region in the northern Guangdong province of southern China was used as a case study.A Landsat time series stack(LTSS) was fed to the vegetation change tracker model(VCT) to map long-term changes in plantation forests' disturbance and recovery,followed by an intensive validation and a continuous 27-yr change analysis on disturbance locations,magnitudes and rates of plantations' disturbance and recovery.And the validation results of the disturbance year maps derived from five randomly identified sample plots with 25 km^2 located at the four corners and the center of the scene showed the majority of the spatial agreement measures ranged from 60% to 83%.A confusion matrix summary of the accuracy measures for all four validation sites in Fogang County showed that the disturbance year maps had an overall accuracy estimate of 71.70%.Forest disturbance rates' change trend was characterized by a decline first,followed by an increase,then giving way to a decline again.An undulated and gentle decreasing trend of disturbance rates from the highest value of 3.95% to the lowest value of 0.76% occurred between 1988 and 2001,disturbance rate of 4.51% in 1994 was a notable anomaly,while after 2001 there was a sharp ascending change,forest disturbance rate spiked in 2007(5.84%).After that,there was a significant decreasing trend up to the lowest value of 1.96% in 2011 and a slight ascending trend from 2011 to 2015(2.59%).Two obvious spikes in post-disturbance recovery rates occurred in 1995(0.26%) and 2008(0.41%).Overall,forest recovery rates were lower than forest disturbance rates.Moreover,forest disturbance and recovery detection based on VCT and the Landsat-based detections of trends in disturbance and recovery(LandT rendr) algorithms in Fogang County have been conducted,with LandT rendr finding mostly much more disturbance than VCT.Overall,disturbances and recoveries in northern Guangdong were triggered mostly by timber needs,policies and decisions of the local governments.This study highlights that a better understanding about plantations' changes would provide a critical foundation for local forest management decisions in the southern China.
基金supported by the Natural Science Foundation of Shanghai(Grant No.21ZR1400500)the National Natural Science Foundation of China(Grant Nos.52173029,51803022,51733002)+2 种基金the Fundamental Research Funds for the Central Universities(Grant Nos.2232021D-05,2232018A3-01)the Cooperative Project with Bestee(Grant No.106210232)the Graduate Student Innovation Fund of Donghua University(Grant No.CUSF-DH-D-2020038)。
文摘In recent years,conductive hydrogels have become a promising candidate for application in fields such as tissue engineering and flexible electronic devices because of their conductivity,soft and wet nature.However,the preparation of tough and uniformly conductive hydrogels remains challenging because conductive nanofillers tend to aggregate during hydrogel formation.Herein,a hydrophilic polymer assistant dispersion strategy is proposed to fabricate a tough,conductive composite hydrogel with doublenetwork based on well-dispersed carbon nanotubes(CNTs).In particular,A@T_(2.0)/polyacrylamide(PAM)hydrogels showed a tensile strength of 332.9 kPa,elongation of 584.6%,Young’s modulus of 91.5 kPa,and conductivity of 2.765 S m^(-1),and a demonstration was performed to show the strain sensing for health monitoring and handwriting.Results showed that the fabricated conductive hydrogels offer promising and broad insights in the field of wearable sensors for health monitoring,innovative electronics,and human-machine interactions.
基金This work was supported by the Beijing Natural Science Foundation(No.LI 82068)。
文摘Spinal disease is an important cause of cervical discomfort,low back pain,radiating pain in the limbs,and neurogenic intermittent claudication,and its incidence is increasing annually.From the etiological viewpoint,these symptoms are directly caused by the compression of the spinal cord,nerve roots,and blood vessels and are most effectively treated with surgery.Spinal surgeries are primarily performed using two different techniques:spinal canal decompression and internal fixation.In the past,tactile sensation was the primary method used by surgeons to understand the state of the tissue within the operating area.However,this method has several disadvantages because of its subjectivity.Therefore,it has become the focus of spinal surgery research so as to strengthen the objectivity of tissue state recognition,improve the accuracy of safe area location,and avoid surgical injury to tissues.Aside from traditional imaging methods,surgical sensing techniques based on force,bioelectrical impedance,and other methods have been gradually developed and tested in the clinical setting.This article reviews the progress of different tissue state recognition methods in spinal surgery and summarizes their advantages and disadvantages.
