This study focuses on the spatiotemporal distribution,urban-rural variations,and driving factors of ammonia Vertical Column Densities(VCDs)in China’s Yangtze River Delta region(YRD)from 2008 to 2020.Utilizing data fr...This study focuses on the spatiotemporal distribution,urban-rural variations,and driving factors of ammonia Vertical Column Densities(VCDs)in China’s Yangtze River Delta region(YRD)from 2008 to 2020.Utilizing data from the Infrared Atmospheric Sounding Interfer-ometer(IASI),Generalized Additive Models(GAM),and the GEOS-Chem chemical transport model,we observed a significant increase of NH_(3)VCDs in the YRD between 2014 and 2020.The spatial distribution analysis revealed higher NH_(3)concentrations in the northern part of the YRD region,primarily due to lower precipitation,alkaline soil,and intensive agricul-tural activities.NH_(3)VCDs in the YRD region increased significantly(65.18%)from 2008 to 2020.The highest growth rate occurs in the summer,with an annual average growth rate of 7.2%during the period from 2014 to 2020.Agricultural emissions dominated NH_(3)VCDs during spring and summer,with high concentrations primarily located in the agricultural areas adjacent to densely populated urban zones.Regions within several large urban areas have been discovered to exhibit relatively stable variations in NH_(3)VCDs.The rise in NH_(3)VCDs within the YRD region was primarily driven by the reduction of acidic gases like SO_(2),as emphasized by GAM modeling and sensitivity tests using the GEOS-Chem model.The concentration changes of acidic gases contribute to over 80%of the interannual variations in NH_(3)VCDs.This emphasizes the crucial role of environmental policies targeting the reduction of these acidic gases.Effective emission control is urgent tomitigate environmental hazards and secondary particulate matter,especially in the northern YRD.展开更多
Studying the contribution of regional transport to ultrafine particles(UFPs)and the deposition effect of nanoscale particles in human respiratory system is conducive to exploring the impact of atmospheric particles on...Studying the contribution of regional transport to ultrafine particles(UFPs)and the deposition effect of nanoscale particles in human respiratory system is conducive to exploring the impact of atmospheric particles on the environment and human health.Based on the data set of number concentration spectrum in the particle size range of 5.6–560 nm in the spring of Hefei,the Yangtze River Delta region obtained by a fast mobility particle sizer,the explosive growth characteristics,potential source identification and deposition flux analysis of UFPs were systematically studied.The results showed that the frequency of new particle formation(NPF)events during spring was 31.5%.SO_(2) and O_(3) contribute to NPF events.Daytime,higher temperature,stronger solar radiation and lower humidity were more conducive to the explosive growth of UFPs.In addition,regional transport of pollutants from the cities around Hefei played an important role in the accumulation mode particles,which were mainly affected by the land-source air mass from northwest Jiangsu(23.64%)and the sea-source air mass from the Yellow Sea(23.99%).It was worth noting that approximately 10,406 ng of UFPs enters the human respiratory system every day.Themain deposition area of 5.6–560 nm nanoscale particles was alveolar,5.6–400 nm is more likely to be deposited on alveolar,while nanoscale particles with particle size between 400 and 560 nm is more likely to be deposited on head airways.This study identified the deposition risk of nanoscale particles in the respiratory system under different particle sizes.展开更多
Minimally invasive interventional surgery techniques using guidewire-based catheters are widely adopted to treat vascular diseases.However,commonly used interventional catheters lack active guidance.The use of guidewi...Minimally invasive interventional surgery techniques using guidewire-based catheters are widely adopted to treat vascular diseases.However,commonly used interventional catheters lack active guidance.The use of guidewires is associated with risks,including increased exposure to X-rays and potential vascular damage during withdrawal from complex vessels.Herein,we developed sub-millimeter microtubular ionic actuators(0.6-0.8 mm outer diameter)integrated into steerable interventional catheters.These actuators can generate large deformations(>10 mm)under 7 V direct current due to enhanced ion migration,enabling precise navigation without the need for guidewires.The designed catheters achieved active bending and accurate positioning in complex arterial vascular branches within a human model.They were also able to navigate within different arterial locations(e.g.,the innominate,subclavian,and carotid arteries)in pigs without the use of guidewires,and even access the ventricle and deliver contrast medium,indicating their great potential for future endovascular therapy.展开更多
In this paper, a carangiform robotic fish with 4-DoF （degree of freedom） tail has been developed. The robotic fish has capability of swimming under two modes that are radio control and autonomous swimming. Experimen...In this paper, a carangiform robotic fish with 4-DoF （degree of freedom） tail has been developed. The robotic fish has capability of swimming under two modes that are radio control and autonomous swimming. Experiments were conducted to investigate the influences of characteristic parameters including the frequency, the amplitude, the wave length, the phase difference and the coefficient on forward velocity. The experimental results shown that the swimming performance of the robotic fish is affected mostly by the characteristic parameters observed.展开更多
Diverse natural organisms possess stimulus-responsive structures to adapt to the surrounding environment.Inspired by nature,researchers have developed various smart stimulus-responsive structures with adjustable prope...Diverse natural organisms possess stimulus-responsive structures to adapt to the surrounding environment.Inspired by nature,researchers have developed various smart stimulus-responsive structures with adjustable properties and functions to address the demands of ever-changing application environments that are becoming more intricate.Among many fabrication methods for stimulus-responsive structures,femtosecond laser direct writing(FsLDW)has received increasing attention because of its high precision,simplicity,true three-dimensional machining ability,and wide applicability to almost all materials.This paper systematically outlines state-of-the-art research on stimulus-responsive structures prepared by FsLDW.Based on the introduction of femtosecond laser-matter interaction and mainstream FsLDW-based manufacturing strategies,different stimulating factors that can trigger structural responses of prepared intelligent structures,such as magnetic field,light,temperature,pH,and humidity,are emphatically summarized.Various applications of functional structures with stimuli-responsive dynamic behaviors fabricated by FsLDW,as well as the present obstacles and forthcoming development opportunities,are discussed.展开更多
In this paper,we present the design,fabrication,locomotion and bionic analysis of a Soft Robotic Fish Actuated by Artificial Muscle(SoRoFAAM).As a carangiform swimmer,the most important part of SoRoFAAM-1,on the motio...In this paper,we present the design,fabrication,locomotion and bionic analysis of a Soft Robotic Fish Actuated by Artificial Muscle(SoRoFAAM).As a carangiform swimmer,the most important part of SoRoFAAM-1,on the motion point of view,is its tail designed around a bidirectional flexible bending actuator by layered bonding technology.This actuator is made of two artificial muscle modules based on Shape Memory Alloy(SMA)wires.Each artificial muscle module has four independent SMA-wire channels and is therefore capable of producing four different actuations.This design allows us to implement an adaptive regulated control strategy based on resistance feedback of the SMA wires to prevent them from overheating.To improve the actuation frequency to 2 Hz and the heat-dissipation ratio by 60%,we developed a round-robin heating strategy.Furthermore,the thermomechanical model of actuator is built,and the thermal transformation is analysed.The relationships between the actuation parameters and SoRoFAAM-1’s kinematic parameters are analysed.The versatility of the actuator endows SoRoFAAM-1 with cruise straight and turning abilities.Moreover,SoRoFAAM-1 has a good bionic fidelity;in particular,a maneuverability of 0.15,a head swing factor of 0.38 and a Strouhal number of 0.61.展开更多
Recently,air pollution especially fine particulate matters(PM_(2.5))and ozone(O_(3))has become a severe issue in China.In this study,we first characterized the temporal trends of PM_(2.5) and O_(3) for Beijing,Guangzh...Recently,air pollution especially fine particulate matters(PM_(2.5))and ozone(O_(3))has become a severe issue in China.In this study,we first characterized the temporal trends of PM_(2.5) and O_(3) for Beijing,Guangzhou,Shanghai,andWuhan respectively during 2018-2020.The annual mean PM2.5 has decreased by 7.82%-33.92%,while O_(3) concentration showed insignificant variations by-6.77%-4.65%during 2018-2020.The generalized additive models(GAMs)were implemented to quantify the contribution of individual meteorological factors and their gas precursors on PM_(2.5) and O_(3).On a short-term perspective,GAMs modeling shows that the daily variability of PM_(2.5) concentration is largely related to the variation of precursor gases(R=0.67-0.90),while meteorological conditions mainly affect the daily variability of O_(3) concentration(R=0.65-0.80)during 2018-2020.The impact of COVID-19 lockdown on PM_(2.5) and O_(3) concentrations were also quantified by using GAMs.During the 2020 lockdown,PM_(2.5) decreased significantly for these megacities,yet the ozone concentration showed an increasing trend compared to 2019.The GAMs analysis indicated that the contribution of precursor gases to PM_(2.5) and O_(3) changes is 3-8 times higher than that of meteorological factors.In general,GAMsmodeling on air quality is helpful to the understanding and control of PM2.5 and O3 pollution in China.展开更多
With the coming of the“14th Five-Year Plan,”the coordinated control of particulate matter with an aerodynamic diameter no greater than 2.5 lm(PM_(2.5))and O_(3) has become a major issue of air pollution prevention a...With the coming of the“14th Five-Year Plan,”the coordinated control of particulate matter with an aerodynamic diameter no greater than 2.5 lm(PM_(2.5))and O_(3) has become a major issue of air pollution prevention and control in China.The stereoscopic monitoring of regional PM_(2.5) and O_(3) and their precursors is crucial to achieve coordinated control.However,current monitoring networks are currently inadequate for monitoring the vertical profiles of both PM_(2.5) and O_(3) simultaneously and support air quality control.The University of Science and Technology of China(USTC)has established a nationwide ground-based hyperspectral stereoscopic remote sensing network based on multi-axis differential optical absorption spectroscopy(MAX-DOAS)since 2015.This monitoring network provides a significant opportunity for the regional coordinated control of PM_(2.5) and O_(3) in China.One-year vertical profiles of aerosol,NO_(2) and HCHO monitored from four MAX-DOAS stations installed in four megacities(Beijing,Shanghai,Shenzhen,and Chongqing)were used to characterize their vertical distribution differences in four key regions,Jing–Jin–Ji(JJJ),Yangtze River Delta(YRD),Pearl River Delta(PRD),and Sichuan Basin(SB),respectively.The normalized and yearly averaged aerosol vertical profiles below 400 m in JJJ and PRD exhibit a box shape and a Gaussian shape,respectively,and both show exponential shapes in YRD and SB.The NO_(2) vertical profiles in four regions all exhibit exponential shapes because of vehicle emissions.The shape of the HCHO vertical profile in JJJ and PRD was Gaussian,whereas an exponential shape was shown in YRD and SB.Moreover,a regional transport event occurred at an altitude of 600–1000 m was monitored in the southwest–northeast pathway of the North China Plain(NCP)by five MAX-DOAS stations(Shijiazhuang(SJZ),Wangdu(WD),Nancheng(NC),Chinese Academy of Meteorological Sciences(CAMS),and University of Chinese Academy of Sciences(UCAS))belonging to the above network.The aerosol optical depths(AOD)in these five stations decreased in the order of SJZ>WD>NC>CAMS>UCAS.The short-distance regional transport of NO2 in the 700–900 m layer was monitored between WD and NC.As an important precursor of secondary aerosol,the peak of NO_(2) air mass in WD and NC all occurred 1 h earlier than that of aerosol.This was also observed for the short-distance regional transport of HCHO in the 700–900 m layer between NC and CAMS,which potentially affected the O_(3) concentration in Beijing.Finally,CAMS was selected as a typical site to determine the O_(3)–NO_(x)–volatile organic compounds(VOCs)sensitivities in vertical space.We found the production of O_(3) changed from predominantly VOCs-limited conditions to mainly mixed VOCs–NO_(x)-limited condition from the 0–100 m layer to the 200–300 m layer.In addition,the downward transport of O_(3) could contribute to the increase of ground surface O_(3) concentration.This ground-based hyperspectral stereoscopic remote sensing network provide a promising strategy to support management of PM_(2.5) and O_(3) and their precursors and conduct attribution of sources.展开更多
The coupling vibration of a hydraulic pipe system consisting of two pipes is studied.The pipes are installed in parallel and fixed at their ends,and are restrained by clips to one bracket at their middle points.The pi...The coupling vibration of a hydraulic pipe system consisting of two pipes is studied.The pipes are installed in parallel and fixed at their ends,and are restrained by clips to one bracket at their middle points.The pipe subjected to the basement excitation at the left end is named as the active pipe,while the pipe without excitation is called the passive pipe.The clips between the two pipes are the bridge for the vibration energy.The adjacent natural frequencies will enhance the vibration coupling.The governing equation of the coupled system is deduced by the generalized Hamilton principle,and is discretized to the modal space.The modal correction is used during the discretization.The investigation on the natural characters indicates that the adjacent natural frequencies can be adjusted by the stiffness of the two clips and bracket.The harmonic balance method(HBM)is used to study the responses in the adjacent natural frequency region.The results show that the vibration energy transmits from the active pipe to the passive pipe swimmingly via the clips together with a flexible bracket,while the locations of them are not node points.The adjacent natural frequencies may arouse wide resonance curves with two peaks for both pipes.The stiffness of the clip and bracket can release the vibration coupling.It is suggested that the stiffness of the clip on the passive pipe should be weak and the bracket should be strong enough.In this way,the vibration energy is reflected by the almost rigid bracket,and is hard to transfer to the passive pipe via a soft clip.The best choice is to set the clips at the pipe node points.The current work gives some suggestions for weakening the coupled vibration during the dynamic design of a coupled hydraulic pipe system.展开更多
Formaldehyde(HCHO)and glyoxal(CHOCHO)are important oxidization intermediates of most volatile organic compounds(VOCs),but their vertical evolution in urban areas is not well understood.Vertical profiles of HCHO,CHOCHO...Formaldehyde(HCHO)and glyoxal(CHOCHO)are important oxidization intermediates of most volatile organic compounds(VOCs),but their vertical evolution in urban areas is not well understood.Vertical profiles of HCHO,CHOCHO,and nitrogen dioxide(NO_(2))were retrieved from ground-based Multi-Axis Differential Optical Absorption Spectroscopy(MAXDOAS)observations in Hefei,China.HCHO and CHOCHO vertical profiles prefer to occur at higher altitudes compared to NO_(2),which might be caused by the photochemistry-oxidation of longer-lived VOCs at higher altitudes.Monthly means of HCHO concentrations were higher in summer,while enhanced amounts of NO_(2)were mainly observed in winter.CHOCHO exhibited a hump-like seasonal variation,with higher monthly-averaged values not only occurred in warm months(July-August)but also in cold months(November-December).Peak values mainly occurred during noon for HCHO but emerged in the morning for CHOCHO and NO_(2),suggesting that HCHO is stronger link to photochemistry than CHOCHO.We further use the glyoxal to formaldehyde ratio(GFR)to investigate the VOC sources at different altitudes.The lowest GFR value is almost found in the altitude from 0.2 to 0.4 km,and then rises rapidly as the altitude increases.The GFR results indicate that the largest contributor of the precursor VOC is biogenic VOCs at lower altitudes,while at higher altitudes is anthropogenic VOCs.Our findings provide a lot more insight into VOC sources at vertical direction,but more verification is recommended to be done in the future.展开更多
Unmanned vehicle has attracted wide attention and interests throughout the world since it first deputed in the 1960s. However, the experimental methods for unmanned vehicle＇s intelligent behavior, such as semi-physic...Unmanned vehicle has attracted wide attention and interests throughout the world since it first deputed in the 1960s. However, the experimental methods for unmanned vehicle＇s intelligent behavior, such as semi-physical simulation and motion subsystem, have not been widely explored. First, the requirements of the motion subsystem in unmanned vehicle semi-physical facility are analyzed, and a six DOF parallel manipulator is selected to reproduce the pose of the vehicle. The link lengths of the motion subsystem are worked out under the given rotational angles of the vehicle. According to the geometric properties of tetrahedron, three joint positions of the top platform are determined, and the rest are obtained from the first three position vectors. Six constraint equations are set up based on the vertices on the top platform and the link lengths. In order to solve the six angle variables, a numerical algorithm built on the Newton-Raphson iterative method is presented, which is based on Taylor series expansion of six constraint equations. The pose of the top platform is ultimately calculated. The eigenvalues of the top platform are solved to obtain the natural frequencies of the motion subsystem. The coordinates of six joint centers on the top platform and six constraint equations can be realized by simple algebraic manipulation, which allows significant abbreviation in the formulation and provides a systematic way of obtaining the kinematic solution of the parallel manipulator. A numerical example is given and its efficacy is demonstrated by the inverse kinematics. The computation strategy based on tetrahedron method and Newton-Raphson iterative method provide a simple and cost-effective method for solving forward kinematics of six DOF parallel manipulators, and this method sheds light on other parallel manipulators.展开更多
Atomic force microscopy(AFM)is increasingly being used as a fundamental tool for dimensional measurements at the nanoscale in the laboratory and in industry.Since the environmental temperature is not controlled in man...Atomic force microscopy(AFM)is increasingly being used as a fundamental tool for dimensional measurements at the nanoscale in the laboratory and in industry.Since the environmental temperature is not controlled in many measurements,or is even varied on purpose,quantification of its effects on AFM dimensional measurements is needed.In this paper,the influences of the temperature in the entire environment of the AFM(excluding only the controller and computer)and that in the local environment around the tip–sample are investigated.The results show that lateral dimensional measurements are affected mainly by the entire environmental temperature.However,vertical measurements are influenced by the temperature of both the entire environment and the local environment.The effects become significant for temperatures higher than some threshold,here between 35 and 40 XC.展开更多
Three series of amorphous copolymers containing azobenzene groups with various substituents and certain amounts of crosslinkable acrylic groups were prepared. The cross-linked polymer films were obtained by thermal po...Three series of amorphous copolymers containing azobenzene groups with various substituents and certain amounts of crosslinkable acrylic groups were prepared. The cross-linked polymer films were obtained by thermal polymerization of the acrylic groups in the copolymers, during which, by controlling the time of cross-linking reaction, the films can be made with different cross-linking degree （from 0 to 32%, which was monitored by FT-IR spectra measurement）. Photo-induced alignment process of the films was performed under irradiation with linearly polarized light at 442 nm, and the effect of cross-linking degree on the photo-induced alignment rate was investigated. The dynamics of the photo-induced alignment was analyzed with biexponential curve fitting. The photo-induced alignment rate and the maximum transmittance of the films decreased because of the cross-linking. Furthermore, for the cross-linked samples, it was found that their saturated value of transmittances keep constant after repeated ＂writing＂ and ＂erasing＂ cycles. The findings reveal that the cross-linking of the film can effectively restrain the phototactic mass transport of azopolymer during irradiation by polarized light. The relationship between the cross-linking degree and the photo-induced alignment behavior of azopolymer is discussed in detail.展开更多
基金supported by the Joint Funds of the National Natural Science Foundation of China(No.U21A2027)the New Cornerstone Science Foundation through the XPLORER PRIZE(2023-1033).
文摘This study focuses on the spatiotemporal distribution,urban-rural variations,and driving factors of ammonia Vertical Column Densities(VCDs)in China’s Yangtze River Delta region(YRD)from 2008 to 2020.Utilizing data from the Infrared Atmospheric Sounding Interfer-ometer(IASI),Generalized Additive Models(GAM),and the GEOS-Chem chemical transport model,we observed a significant increase of NH_(3)VCDs in the YRD between 2014 and 2020.The spatial distribution analysis revealed higher NH_(3)concentrations in the northern part of the YRD region,primarily due to lower precipitation,alkaline soil,and intensive agricul-tural activities.NH_(3)VCDs in the YRD region increased significantly(65.18%)from 2008 to 2020.The highest growth rate occurs in the summer,with an annual average growth rate of 7.2%during the period from 2014 to 2020.Agricultural emissions dominated NH_(3)VCDs during spring and summer,with high concentrations primarily located in the agricultural areas adjacent to densely populated urban zones.Regions within several large urban areas have been discovered to exhibit relatively stable variations in NH_(3)VCDs.The rise in NH_(3)VCDs within the YRD region was primarily driven by the reduction of acidic gases like SO_(2),as emphasized by GAM modeling and sensitivity tests using the GEOS-Chem model.The concentration changes of acidic gases contribute to over 80%of the interannual variations in NH_(3)VCDs.This emphasizes the crucial role of environmental policies targeting the reduction of these acidic gases.Effective emission control is urgent tomitigate environmental hazards and secondary particulate matter,especially in the northern YRD.
基金supported by the National Natural Science Foundation of China(Nos.U21A2027,42207113,and 42407141)。
文摘Studying the contribution of regional transport to ultrafine particles(UFPs)and the deposition effect of nanoscale particles in human respiratory system is conducive to exploring the impact of atmospheric particles on the environment and human health.Based on the data set of number concentration spectrum in the particle size range of 5.6–560 nm in the spring of Hefei,the Yangtze River Delta region obtained by a fast mobility particle sizer,the explosive growth characteristics,potential source identification and deposition flux analysis of UFPs were systematically studied.The results showed that the frequency of new particle formation(NPF)events during spring was 31.5%.SO_(2) and O_(3) contribute to NPF events.Daytime,higher temperature,stronger solar radiation and lower humidity were more conducive to the explosive growth of UFPs.In addition,regional transport of pollutants from the cities around Hefei played an important role in the accumulation mode particles,which were mainly affected by the land-source air mass from northwest Jiangsu(23.64%)and the sea-source air mass from the Yellow Sea(23.99%).It was worth noting that approximately 10,406 ng of UFPs enters the human respiratory system every day.Themain deposition area of 5.6–560 nm nanoscale particles was alveolar,5.6–400 nm is more likely to be deposited on alveolar,while nanoscale particles with particle size between 400 and 560 nm is more likely to be deposited on head airways.This study identified the deposition risk of nanoscale particles in the respiratory system under different particle sizes.
基金the National Natural Science Foundation of China(No.52375293)the Research Fund of State Key Laboratory of Mechanics and Control for Aerospace Structures(Nanjing University of Aeronautics and astronautics,Nos.1005-IZD2300225 and IZD2400217)+2 种基金the Nanjing Life and Health Technology Special Project(No.202305031)the Clinical Competence Enhancement Project in Healthcare(No.JSPH-MB-2022-4)the Medical Engineering Translational Fund of Jiangsu Province Hospital(No.NM202402).
文摘Minimally invasive interventional surgery techniques using guidewire-based catheters are widely adopted to treat vascular diseases.However,commonly used interventional catheters lack active guidance.The use of guidewires is associated with risks,including increased exposure to X-rays and potential vascular damage during withdrawal from complex vessels.Herein,we developed sub-millimeter microtubular ionic actuators(0.6-0.8 mm outer diameter)integrated into steerable interventional catheters.These actuators can generate large deformations(>10 mm)under 7 V direct current due to enhanced ion migration,enabling precise navigation without the need for guidewires.The designed catheters achieved active bending and accurate positioning in complex arterial vascular branches within a human model.They were also able to navigate within different arterial locations(e.g.,the innominate,subclavian,and carotid arteries)in pigs without the use of guidewires,and even access the ventricle and deliver contrast medium,indicating their great potential for future endovascular therapy.
文摘In this paper, a carangiform robotic fish with 4-DoF （degree of freedom） tail has been developed. The robotic fish has capability of swimming under two modes that are radio control and autonomous swimming. Experiments were conducted to investigate the influences of characteristic parameters including the frequency, the amplitude, the wave length, the phase difference and the coefficient on forward velocity. The experimental results shown that the swimming performance of the robotic fish is affected mostly by the characteristic parameters observed.
基金supported by the National Natural Science Foundation of China (Nos. 52122511, 52105492, and 62005262)the National Key Research and Development Program of China (No. 2021YFF0502700)+2 种基金the Students’ Innovation and Entrepreneurship Foundation of USTC (Nos. CY2022G32 and XY2022G02CY)the USTC Research Funds of the Double First-Class Initiative (No. YD2340002009)CAS Project for Young Scientists in Basic Research (No. YSBR-049)
文摘Diverse natural organisms possess stimulus-responsive structures to adapt to the surrounding environment.Inspired by nature,researchers have developed various smart stimulus-responsive structures with adjustable properties and functions to address the demands of ever-changing application environments that are becoming more intricate.Among many fabrication methods for stimulus-responsive structures,femtosecond laser direct writing(FsLDW)has received increasing attention because of its high precision,simplicity,true three-dimensional machining ability,and wide applicability to almost all materials.This paper systematically outlines state-of-the-art research on stimulus-responsive structures prepared by FsLDW.Based on the introduction of femtosecond laser-matter interaction and mainstream FsLDW-based manufacturing strategies,different stimulating factors that can trigger structural responses of prepared intelligent structures,such as magnetic field,light,temperature,pH,and humidity,are emphatically summarized.Various applications of functional structures with stimuli-responsive dynamic behaviors fabricated by FsLDW,as well as the present obstacles and forthcoming development opportunities,are discussed.
基金The authors gratefully acknowledge financial support from the National Science Foundation of China(Nos.61773358)and Cyrus Tang Foundation.
文摘In this paper,we present the design,fabrication,locomotion and bionic analysis of a Soft Robotic Fish Actuated by Artificial Muscle(SoRoFAAM).As a carangiform swimmer,the most important part of SoRoFAAM-1,on the motion point of view,is its tail designed around a bidirectional flexible bending actuator by layered bonding technology.This actuator is made of two artificial muscle modules based on Shape Memory Alloy(SMA)wires.Each artificial muscle module has four independent SMA-wire channels and is therefore capable of producing four different actuations.This design allows us to implement an adaptive regulated control strategy based on resistance feedback of the SMA wires to prevent them from overheating.To improve the actuation frequency to 2 Hz and the heat-dissipation ratio by 60%,we developed a round-robin heating strategy.Furthermore,the thermomechanical model of actuator is built,and the thermal transformation is analysed.The relationships between the actuation parameters and SoRoFAAM-1’s kinematic parameters are analysed.The versatility of the actuator endows SoRoFAAM-1 with cruise straight and turning abilities.Moreover,SoRoFAAM-1 has a good bionic fidelity;in particular,a maneuverability of 0.15,a head swing factor of 0.38 and a Strouhal number of 0.61.
基金supported by the National Key Research and Development Program of China(Nos.2018YFC0213104 and 2017YFC0210002)the National Natural Science Foundation of China(Nos.41977184,41941011,and 51778596)+5 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA23020301)the Major Projects of High Resolution Earth Observation Systems of National Science and Technology(No.05-Y30B01-9001-19/20-3)the Youth Innovation Promotion Association of CAS(No.2021443),the Young Talent Project of the Center for Excellence in Regional Atmospheric Environment,CAS(CERAE202004)the China Postdoctoral Science Foundation(Nos.2020TQ0320 and 2021M693068)Anhui Provincial Natural Science Foundation(No.2108085QD178)the Fundamental Research Funds for the Central Universities.
文摘Recently,air pollution especially fine particulate matters(PM_(2.5))and ozone(O_(3))has become a severe issue in China.In this study,we first characterized the temporal trends of PM_(2.5) and O_(3) for Beijing,Guangzhou,Shanghai,andWuhan respectively during 2018-2020.The annual mean PM2.5 has decreased by 7.82%-33.92%,while O_(3) concentration showed insignificant variations by-6.77%-4.65%during 2018-2020.The generalized additive models(GAMs)were implemented to quantify the contribution of individual meteorological factors and their gas precursors on PM_(2.5) and O_(3).On a short-term perspective,GAMs modeling shows that the daily variability of PM_(2.5) concentration is largely related to the variation of precursor gases(R=0.67-0.90),while meteorological conditions mainly affect the daily variability of O_(3) concentration(R=0.65-0.80)during 2018-2020.The impact of COVID-19 lockdown on PM_(2.5) and O_(3) concentrations were also quantified by using GAMs.During the 2020 lockdown,PM_(2.5) decreased significantly for these megacities,yet the ozone concentration showed an increasing trend compared to 2019.The GAMs analysis indicated that the contribution of precursor gases to PM_(2.5) and O_(3) changes is 3-8 times higher than that of meteorological factors.In general,GAMsmodeling on air quality is helpful to the understanding and control of PM2.5 and O3 pollution in China.
基金This research is supported by grants from the National Key Research and Development Program of China(2018YFC0213104)Project supported by the Presidential Foundation of the Hefei Institutes of Physical Science,Chinese Academy Sciences,China-“Spark”(YZJJ2021QN06)+6 种基金National Natural Science Foundation of China(41722501,91544212,51778596,41575021,41977184,and 41875043)National Key Research and Development Program of China(2017YFC0210002,2016YFC0203302,and 2017YFC0212800)Anhui Science and Technology Major Project(18030801111)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA23020301)the National Key Project for Causes and Control of Heavy Air Pollution(DQGG0102 and DQGG0205)the National High-Resolution Earth Observation Project of China(05-Y30B01-9001-19/20-3)Civil Aerospace Technology Advance Research Project(Y7K00100KJ).From 0-100 and 200-300 m layers,the production of O_(3) changed from predominantly VOCs-limited condition to mainly mixed VOCs-NOx-limited condition.
文摘With the coming of the“14th Five-Year Plan,”the coordinated control of particulate matter with an aerodynamic diameter no greater than 2.5 lm(PM_(2.5))and O_(3) has become a major issue of air pollution prevention and control in China.The stereoscopic monitoring of regional PM_(2.5) and O_(3) and their precursors is crucial to achieve coordinated control.However,current monitoring networks are currently inadequate for monitoring the vertical profiles of both PM_(2.5) and O_(3) simultaneously and support air quality control.The University of Science and Technology of China(USTC)has established a nationwide ground-based hyperspectral stereoscopic remote sensing network based on multi-axis differential optical absorption spectroscopy(MAX-DOAS)since 2015.This monitoring network provides a significant opportunity for the regional coordinated control of PM_(2.5) and O_(3) in China.One-year vertical profiles of aerosol,NO_(2) and HCHO monitored from four MAX-DOAS stations installed in four megacities(Beijing,Shanghai,Shenzhen,and Chongqing)were used to characterize their vertical distribution differences in four key regions,Jing–Jin–Ji(JJJ),Yangtze River Delta(YRD),Pearl River Delta(PRD),and Sichuan Basin(SB),respectively.The normalized and yearly averaged aerosol vertical profiles below 400 m in JJJ and PRD exhibit a box shape and a Gaussian shape,respectively,and both show exponential shapes in YRD and SB.The NO_(2) vertical profiles in four regions all exhibit exponential shapes because of vehicle emissions.The shape of the HCHO vertical profile in JJJ and PRD was Gaussian,whereas an exponential shape was shown in YRD and SB.Moreover,a regional transport event occurred at an altitude of 600–1000 m was monitored in the southwest–northeast pathway of the North China Plain(NCP)by five MAX-DOAS stations(Shijiazhuang(SJZ),Wangdu(WD),Nancheng(NC),Chinese Academy of Meteorological Sciences(CAMS),and University of Chinese Academy of Sciences(UCAS))belonging to the above network.The aerosol optical depths(AOD)in these five stations decreased in the order of SJZ>WD>NC>CAMS>UCAS.The short-distance regional transport of NO2 in the 700–900 m layer was monitored between WD and NC.As an important precursor of secondary aerosol,the peak of NO_(2) air mass in WD and NC all occurred 1 h earlier than that of aerosol.This was also observed for the short-distance regional transport of HCHO in the 700–900 m layer between NC and CAMS,which potentially affected the O_(3) concentration in Beijing.Finally,CAMS was selected as a typical site to determine the O_(3)–NO_(x)–volatile organic compounds(VOCs)sensitivities in vertical space.We found the production of O_(3) changed from predominantly VOCs-limited conditions to mainly mixed VOCs–NO_(x)-limited condition from the 0–100 m layer to the 200–300 m layer.In addition,the downward transport of O_(3) could contribute to the increase of ground surface O_(3) concentration.This ground-based hyperspectral stereoscopic remote sensing network provide a promising strategy to support management of PM_(2.5) and O_(3) and their precursors and conduct attribution of sources.
基金Project supported by the National Natural Science Foundation of China(No.12002195)the Pujiang Project of Shanghai Science and Technology Commission of China(No.20PJ1404000)。
文摘The coupling vibration of a hydraulic pipe system consisting of two pipes is studied.The pipes are installed in parallel and fixed at their ends,and are restrained by clips to one bracket at their middle points.The pipe subjected to the basement excitation at the left end is named as the active pipe,while the pipe without excitation is called the passive pipe.The clips between the two pipes are the bridge for the vibration energy.The adjacent natural frequencies will enhance the vibration coupling.The governing equation of the coupled system is deduced by the generalized Hamilton principle,and is discretized to the modal space.The modal correction is used during the discretization.The investigation on the natural characters indicates that the adjacent natural frequencies can be adjusted by the stiffness of the two clips and bracket.The harmonic balance method(HBM)is used to study the responses in the adjacent natural frequency region.The results show that the vibration energy transmits from the active pipe to the passive pipe swimmingly via the clips together with a flexible bracket,while the locations of them are not node points.The adjacent natural frequencies may arouse wide resonance curves with two peaks for both pipes.The stiffness of the clip and bracket can release the vibration coupling.It is suggested that the stiffness of the clip on the passive pipe should be weak and the bracket should be strong enough.In this way,the vibration energy is reflected by the almost rigid bracket,and is hard to transfer to the passive pipe via a soft clip.The best choice is to set the clips at the pipe node points.The current work gives some suggestions for weakening the coupled vibration during the dynamic design of a coupled hydraulic pipe system.
基金the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA23020301)the National Natural Science Foundation of China(Nos.51778596,41977184,and 41941011)+5 种基金the Key Research and Development Project of Anhui Province(202104i07020002)the Anhui Science and Technology Major Project(No.18030801111)the Major Projects of High Resolution Earth Observation Systems of National Science and Technology(05-Y30B01-9001-19/20-3)the Youth Innovation Promotion Association of CAS(2021443)the Young Talent Project of the Center for Excellence in Regional Atmospheric Environment,CAS(CERAE202004)the Fundamental Research Funds for the Central Universities(No.JUSRP12042)。
文摘Formaldehyde(HCHO)and glyoxal(CHOCHO)are important oxidization intermediates of most volatile organic compounds(VOCs),but their vertical evolution in urban areas is not well understood.Vertical profiles of HCHO,CHOCHO,and nitrogen dioxide(NO_(2))were retrieved from ground-based Multi-Axis Differential Optical Absorption Spectroscopy(MAXDOAS)observations in Hefei,China.HCHO and CHOCHO vertical profiles prefer to occur at higher altitudes compared to NO_(2),which might be caused by the photochemistry-oxidation of longer-lived VOCs at higher altitudes.Monthly means of HCHO concentrations were higher in summer,while enhanced amounts of NO_(2)were mainly observed in winter.CHOCHO exhibited a hump-like seasonal variation,with higher monthly-averaged values not only occurred in warm months(July-August)but also in cold months(November-December).Peak values mainly occurred during noon for HCHO but emerged in the morning for CHOCHO and NO_(2),suggesting that HCHO is stronger link to photochemistry than CHOCHO.We further use the glyoxal to formaldehyde ratio(GFR)to investigate the VOC sources at different altitudes.The lowest GFR value is almost found in the altitude from 0.2 to 0.4 km,and then rises rapidly as the altitude increases.The GFR results indicate that the largest contributor of the precursor VOC is biogenic VOCs at lower altitudes,while at higher altitudes is anthropogenic VOCs.Our findings provide a lot more insight into VOC sources at vertical direction,but more verification is recommended to be done in the future.
基金supported by National Natural Science Foundation of China (Grant No. 50908222)
文摘Unmanned vehicle has attracted wide attention and interests throughout the world since it first deputed in the 1960s. However, the experimental methods for unmanned vehicle＇s intelligent behavior, such as semi-physical simulation and motion subsystem, have not been widely explored. First, the requirements of the motion subsystem in unmanned vehicle semi-physical facility are analyzed, and a six DOF parallel manipulator is selected to reproduce the pose of the vehicle. The link lengths of the motion subsystem are worked out under the given rotational angles of the vehicle. According to the geometric properties of tetrahedron, three joint positions of the top platform are determined, and the rest are obtained from the first three position vectors. Six constraint equations are set up based on the vertices on the top platform and the link lengths. In order to solve the six angle variables, a numerical algorithm built on the Newton-Raphson iterative method is presented, which is based on Taylor series expansion of six constraint equations. The pose of the top platform is ultimately calculated. The eigenvalues of the top platform are solved to obtain the natural frequencies of the motion subsystem. The coordinates of six joint centers on the top platform and six constraint equations can be realized by simple algebraic manipulation, which allows significant abbreviation in the formulation and provides a systematic way of obtaining the kinematic solution of the parallel manipulator. A numerical example is given and its efficacy is demonstrated by the inverse kinematics. The computation strategy based on tetrahedron method and Newton-Raphson iterative method provide a simple and cost-effective method for solving forward kinematics of six DOF parallel manipulators, and this method sheds light on other parallel manipulators.
基金the National Natural Science Foundation of China(No.51675504)the Fundamental Research Funds for the Central Universities(No.WK2090000022).
文摘Atomic force microscopy(AFM)is increasingly being used as a fundamental tool for dimensional measurements at the nanoscale in the laboratory and in industry.Since the environmental temperature is not controlled in many measurements,or is even varied on purpose,quantification of its effects on AFM dimensional measurements is needed.In this paper,the influences of the temperature in the entire environment of the AFM(excluding only the controller and computer)and that in the local environment around the tip–sample are investigated.The results show that lateral dimensional measurements are affected mainly by the entire environmental temperature.However,vertical measurements are influenced by the temperature of both the entire environment and the local environment.The effects become significant for temperatures higher than some threshold,here between 35 and 40 XC.
基金This work was supported by the National Natural Science Foundation of China （No.50573071, No.50533040, No.50703038, No.50773075, and No.50640420265）, the National Basic Research Program of China （No.2006cb302900）, and the Chinese Academy of Sciences （No.kjcx2.yw.H02）.
文摘Three series of amorphous copolymers containing azobenzene groups with various substituents and certain amounts of crosslinkable acrylic groups were prepared. The cross-linked polymer films were obtained by thermal polymerization of the acrylic groups in the copolymers, during which, by controlling the time of cross-linking reaction, the films can be made with different cross-linking degree （from 0 to 32%, which was monitored by FT-IR spectra measurement）. Photo-induced alignment process of the films was performed under irradiation with linearly polarized light at 442 nm, and the effect of cross-linking degree on the photo-induced alignment rate was investigated. The dynamics of the photo-induced alignment was analyzed with biexponential curve fitting. The photo-induced alignment rate and the maximum transmittance of the films decreased because of the cross-linking. Furthermore, for the cross-linked samples, it was found that their saturated value of transmittances keep constant after repeated ＂writing＂ and ＂erasing＂ cycles. The findings reveal that the cross-linking of the film can effectively restrain the phototactic mass transport of azopolymer during irradiation by polarized light. The relationship between the cross-linking degree and the photo-induced alignment behavior of azopolymer is discussed in detail.
