Water samples were collected in 120 stations in the Bohai Sea of China to analyze the distribution of dissolved nutrients and assess the degree of eutrophication in August 2002. The result shows that the average conce...Water samples were collected in 120 stations in the Bohai Sea of China to analyze the distribution of dissolved nutrients and assess the degree of eutrophication in August 2002. The result shows that the average concentration of DIN increased and the PO4-P concentration sharply decreased compared to the previous data of corresponding period. The high concentrations of DIN and PO4-P occurred in coastal waters, especially in the bays and some river estuaries, while the high concentrations of SiO3-Si in the surface and middle depth occurred in the central area of the Bohai Sea. The average ratio of DIN/PO4-P was much higher than the Redfield Ratio (16:1). Apparently, PO4-P was one of the limiting nutrient for phytoplankton growing in the sea. The average concentrations of DON and DOP were higher than their inorganic forms. The results of eutrophication assessment show that 22.1% of all stations were classified as violating the concentration levels of the National Seawater Quality Standard (GB 3097-1997) for DIN and only 3.9% for PO4-R The average eutrophication index in the overall area was 0.21±0.22 and the high values occurred in Bohai Bay, Liaodong Bay and near the Yellow River estuary. This means that the state of eutrophication was generally mesotrophic in the Bohai Sea, but relatively worse in the bays, especially some river estuaries.展开更多
Continuous deforming always leads to the performance degradation of a flexible triboelectric nanogenerator due to the Young’s modulus mismatch of different functional layers.In this work,we fabricated a fiber-shaped ...Continuous deforming always leads to the performance degradation of a flexible triboelectric nanogenerator due to the Young’s modulus mismatch of different functional layers.In this work,we fabricated a fiber-shaped stretchable and tailorable triboelectric nanogenerator(FST-TENG)based on the geometric construction of a steel wire as electrode and ingenious selection of silicone rubber as triboelectric layer.Owing to the great robustness and continuous conductivity,the FST-TENGs demonstrate high stability,stretchability,and even tailorability.For a single device with ~6 cm in length and ~3 mm in diameter,the open-circuit voltage of ~59.7 V,transferred charge of ~23.7 nC,short-circuit current of ~2.67 μA and average power of ~2.13 μW can be obtained at 2.5 Hz.By knitting several FST-TENGs to be a fabric or a bracelet,it enables to harvest human motion energy and then to drive a wearable electronic device.Finally,it can also be woven on dorsum of glove to monitor the movements of gesture,which can recognize every single finger,different bending angle,and numbers of bent finger by analyzing voltage signals.展开更多
Disposable medical protective clothing for 2019-nCoV mainly consists of stacked layers with nanopore films,polymer coated nonwoven fabrics and melt-blown nonwoven fabrics against anti-microbial and anti-liquid penetra...Disposable medical protective clothing for 2019-nCoV mainly consists of stacked layers with nanopore films,polymer coated nonwoven fabrics and melt-blown nonwoven fabrics against anti-microbial and anti-liquid penetration.However,such structures lack moisture permeability and breathability leading to an uncomfortable,stuffy wearing experience.Here,we propose a novel medical protective clothing material with a superabsorbent layer to enhance moisture absorption.Poly(acrylic acid-co-acrylamide)/polyvinyl alcohol superabsorbent fibers(PAAAM/PVA fibers)were prepared via wet spinning.And the superabsorbent composite layer was stacked from PAAAM/PVA fibers,bamboo pulp fibers(BPF)and ethylene-propyl-ene side by side fibers(ESF).The novel disposable medical protective composite fabric was obtained through gluing the superabsorbent layer to the inner surface of strong antistatic polypropylene nonwoven fabric.The resultant composite fabric possesses excellent absorption and retention capacity for sweat,up to 12.3 g/g and 63.8%,and a maximum hygroscopic rate of 1.04 g/h,higher than that of the conventional material(only 0.53 g/h).The moisture permeability of the novel material reached 12,638.5 g/(m^(2) d),which was 307.6%of the conventional material.The novel material can effectively reduce the humidity inside the protective clothing and significantly improve the comfort of medical staff.展开更多
The article explores the issue of designing a new design of a loading cylinder with a casing filled with vulcanized rubber for pneumomechanical spinning machines. The theoretical calculation of the deformed state of a...The article explores the issue of designing a new design of a loading cylinder with a casing filled with vulcanized rubber for pneumomechanical spinning machines. The theoretical calculation of the deformed state of a cylindrical shell filled with vulcanized rubber is given. Deflections and stresses in the rubber layer are determined, which we use approximately for the Ritz methods. The theory of the radial and axial moving rubber layer was analyzed. The specific energy of deformation of a cylindrical layer of a compound cylinder is determined. The statics of the case and the loading cylinder of spinning machines are thoroughly studied.展开更多
Multi-robot systems can be applied to patrol a concerned environment for security purposes.According to different goals,this work reviews the existing researches in a multi-robot patrolling field from the perspectives...Multi-robot systems can be applied to patrol a concerned environment for security purposes.According to different goals,this work reviews the existing researches in a multi-robot patrolling field from the perspectives of regular and adversarial patrolling.Regular patrolling requires robots to visit important locations as frequently as possible and a series of deterministic strategies are proposed,while adversarial one focuses on unpredictable robots’moving patterns to maximize adversary detection probability.Under each category,a systematic survey is done including problem statements and modeling,patrolling objectives and evaluation criteria,and representative patrolling strategies and approaches.Existing problems and open questions are presented accordingly.展开更多
Carbon-based metal-free catalysts are a promising substitute for the rare and expensive platinum (Pt) used in the oxygen reduction reaction. We herein report N-doped graphene (NG) that is exquisitely integrated in...Carbon-based metal-free catalysts are a promising substitute for the rare and expensive platinum (Pt) used in the oxygen reduction reaction. We herein report N-doped graphene (NG) that is exquisitely integrated into highly conductive frameworks, simultaneously providing more active sites and higher conductivity. The NG was in situ grown on carbon fibers derived from silk cocoon (SCCf) using a simple one-step thermal treatment. The resulting product (NG-SCCf), possessing a meso-/macroporous structure with three-dimensional (3D) interconnected networks, exhibits an onset potential that is only 0.1 V less negative than that of Pt/C and shows stability and methanol tolerance superior to those of Pt/C in alkaline media. Moreover, in the absence of Pt as co-catalyst, NG-SCCf shows a photocatalytic H2 production rate of 66.0 ~tmol-h l.g 1, 4.4-fold higher than that of SCCf. This outstanding activity is intimately related to the in situ grown NG, hierarchically porous structure, and 3D interconnected networks, which not only introduce more active sites but also enable smooth electron transfer, mass transport, and effective separation of electron-hole pairs. Considering the abundance of the green raw material in combination with easy and low-cost preparation, this work contributes to the development of advanced sustainable catalysts in energy storage/conversion fields, such as electro- and photocatalysis.展开更多
The urgent demand for portable electronics has promoted the development of high-efficienc)9 sustainable, and even stretchable self-charging power sources. In this work, we propose a flexible self-charging power unit ...The urgent demand for portable electronics has promoted the development of high-efficienc)9 sustainable, and even stretchable self-charging power sources. In this work, we propose a flexible self-charging power unit based on folded carbon (FC) paper for harvesting mechanical energy from human motion and power portable electronics. The present unit mainly consists of a triboelectric nanogenerator (FC-TENG) and a supercapacitor (FC-SC), both based on folded carbon paper, as energy harvester and storage device, respectively. This favorable geometric design provides the high Young's modulus carbon paper with excellent stretchability and enables the power unit to work even under severe deformations, such as bending, twisting, and rolling. In addition, the tensile strain can be maximized by tuning the folding angle of the triangle-folded carbon paper. Moreover, the waterproof property of the packaged device make it washable, protect it from human sweat, and enable it to work in harsh environments. Finally, the as-prepared self-charging power unit was tested by placing it on the human body to harvest mechanical energy from hand tapping, foot treading, and arm touching, successfully powering an electronic watch. This work demonstrates the impressive potential of stretchable self-charging power units, which will further promote the development of high Young's modulus materials for wearable/portable electronics.展开更多
Wearable electronics offer incredible benefits in mobile healthcare monitoring,sensing,portable energy harvesting and storage,human-machine interactions,etc.,due to the evolution of rigid electronics structure to flex...Wearable electronics offer incredible benefits in mobile healthcare monitoring,sensing,portable energy harvesting and storage,human-machine interactions,etc.,due to the evolution of rigid electronics structure to flexible and stretchable devices.Lately,transition metal carbides and nitrides(MXenes)are highly regarded as a group of thriving two-dimensional nanomaterials and extraordinary building blocks for emerging flexible electronics platforms because of their excellent electrical conductivity,enriched surface functionalities,and large surface area.This article reviews the most recent developments in MXene-enabled flexible electronics for wearable electronics.Several MXeneenabled electronic devices designed on a nanometric scale are highlighted by drawing attention to widely developed nonstructural attributes,including 3D configured devices,textile and planer substrates,bioinspired structures,and printed materials.Furthermore,the unique progress of these nanodevices is highlighted by representative applications in healthcare,energy,electromagnetic interference(EMI)shielding,and humanoid control of machines.The emerging prospects of MXene nanomaterials as a key frontier in nextgeneration wearable electronics are envisioned and the design challenges of these electronic systems are also discussed,followed by proposed solutions.展开更多
Outdoor passive heating to maintain a constant human body temperature is critical for human activities.However,most traditional energy-exhausted heating systems and inefficient passive heating technologies are incapab...Outdoor passive heating to maintain a constant human body temperature is critical for human activities.However,most traditional energy-exhausted heating systems and inefficient passive heating technologies are incapable of dealing with the cold outdoor environment.Developing fabrics with low thermal radiation and conduction to passively heat the human body is a viable way to overcome the constraints of existing passive heating strategies.Herein,a multimaterial aerogel fabric was developed to realize passive personal heating without any energy input.The multimaterial aerogel fabric was fabricated by coating an Ag layer on an aerogel composite fabric.The lightweight aerogel composite fabric,woven from aerogel composite fibers with multi-scale porous structure,exhibits excellent thermal insulation,self-cleaning,mechanical and thermal stability.Furthermore,by coating with an Ag layer,the multimaterial aerogel fabric exhibits both low thermal conductivity and low infrared emissivity at 7–14μm,demonstrating superior thermal insulating performance.As a result,the proposed multimaterial aerogel fabric with a thickness of only 1.29 mm is capable of improving the human body temperarure of 5.7℃ in a cold environment without energy input.This strategy offers a potential energy-saving alternative for future outdoor passive heating.展开更多
Water splitting,as an advanced energy conversion technology,consists of two half reactions,including oxygen evolution reaction(OER)and hydrogen evolution reaction(HER).However,the ideal electrocatalysts are noble meta...Water splitting,as an advanced energy conversion technology,consists of two half reactions,including oxygen evolution reaction(OER)and hydrogen evolution reaction(HER).However,the ideal electrocatalysts are noble metal based catalysts.Their high cost and scarcity in earth seriously restrict the large deployments.Ni Fe-based materials have attracted great attention in recent years due to their excellent catalytic properties for OER and HER.Nevertheless,their conductivity and electrochemical stability at high current density are unsatisfactory,resulting in ineffective water splitting due to high impedance and low stability.Recently,a series of catalysts coating Ni Fe-based materials on 3 D nickel foam were found to be extremely stable under the circumstance of high current density.In this review,we summarized the recent advances of NiFe-based materials on nickel foam for OER and HER,respectively,and further provided the perspectives for their future development.展开更多
Smart textiles with high sensitivity and rapid response for various external stimuli have gained tremendous attentions in human healthcare monitoring,personal heat management,and wearable electronics.However,the curre...Smart textiles with high sensitivity and rapid response for various external stimuli have gained tremendous attentions in human healthcare monitoring,personal heat management,and wearable electronics.However,the current smart textiles only acquire desired signal passively,regularly lacking subsequent on-demand therapy actively.Herein,a robust,breathable,and flexible smart textiles as multi-function sensor and wearable heater for human health monitoring and gentle thermotherapy in real time is constructed.The composite fiber as strain sensor(CFY@PU)was fabricated via warping carbon fiber yarns(CFY)onto polyurethane fibers(PU),which endowed composite fiber with high conductivity,excellent sensitivity(GF=76.2),and fantastic dynamic durability(7500 cycles)in strain sensing.In addition,CFY@PU can detect various degrees of human movements such as elbow bending,swallowing and pulse,which can provide effective information for disease diagnosis.More surprisingly,weaving CFY@PU into a fabric can assemble highly sensitive pressure sensor for remote communication and information encryption.Warping CFY onto Kevlar would obtain temperature-sensitive composite fiber(CFY@Kevlar)as temperature sensor and wearable heater for on-demand thermotherapy,which provided unique opportunities in designing smart textiles with ultrahigh sensitivity,rapid response,and great dynamic durability.展开更多
Global climate change,growing population,and environmental pollution underscore the need for a greater focus on providing advanced water treatment technologies.Although electrochemical basedprocesses are becoming prom...Global climate change,growing population,and environmental pollution underscore the need for a greater focus on providing advanced water treatment technologies.Although electrochemical basedprocesses are becoming promising solutions,they still face challenges owing to mass transport and upscaling which hinder the exploitation of this technology.Electrode design and reactor configuration are key factors for achieving operational improvements.The electroactive membrane has proven to be a breakthrough technology integrating electrochemistry and membrane separation with an enhanced mass transport by convection.In this review article,we discuss recent progress in environmental applications of electroactive membranes with particular focus on those composed of carbon nanotubes(CNT)due to their intriguing physicochemical prope rties.Their applications in degradation of refractory contaminants,detoxification and sequestration of toxic heavy metal ions,and membrane fouling alleviations are systematically reviewed.We then discuss the existing limitations and opportunities for future research.The development of advanced electroactive systems depends on interdisciplinary collaborations in the areas of materials,electrochemistry,membrane development,and environmental sciences.展开更多
Conventional firefighting clothing and fire masks can protect firemen’s safety to a certain extent,whereas cannot perceive environmental hazards and monitor their physical status in real time.Herein,we fabricated two...Conventional firefighting clothing and fire masks can protect firemen’s safety to a certain extent,whereas cannot perceive environmental hazards and monitor their physical status in real time.Herein,we fabricated two kinds of Janus graphene/poly(pphenylene benzobisoxazole)(PBO)fabrics by laser direct writing approach and evaluated their performance as intelligent firefighting clothes and fire masks.The results showed that the Janus graphene/PBO fabrics were virtually non-combustible and achieved the highest thermal protection time of 18.91 s ever reported in flame,which is due to the intrinsic flame-retardant nature of PBO fibers.The graphene/PBO woven fabrics-based sensor showed good repeatability and stability in human motion monitoring and NO_(2)gas detection.Furthermore,the piezoelectric fire mask was assembled with graphene/PBO nonwoven fabric as electrode layer and polyvinylidene fluoride(PVDF)electrostatic direct writing film as piezoelectric layer.The filtration efficiency of the fire mask reaches 95%for PM_(2.5)and 100%for PM_(3.0),indicating its effective filtration capability for smoke particles in fires.The respiratory resistance of the piezoelectric fire mask(46.8 Pa)was lower than that of commercial masks(49 Pa),showing that it has good wearing comfort.Besides,the piezoelectric fire mask can be sensitive to the speed and intensity of human breathing,which is essential for indirectly reflecting the health of the human body.Consequently,this work provides a facile approach to fabricate next-generation intrinsic flame-retardant smart textiles for smart firefighting.展开更多
Piezoelectric nanogenerators(PENGs)are promising for harvesting renewable and abundant mechanical energy with high efficiency.Up to now,published research studies have mainly focused on increasing the sensitivity and ...Piezoelectric nanogenerators(PENGs)are promising for harvesting renewable and abundant mechanical energy with high efficiency.Up to now,published research studies have mainly focused on increasing the sensitivity and output of PENGs.The technical challenges in relation to practicability,comfort,and antibacterial performance,which are critically important for wearable applications,have not been well addressed.To overcome the limitations,we developed an all-nanofiber PENG(ANF-PENG)with a sandwich structure,in which the middle poly(vinylidene fluoride-co-hexafluoropropylene(P(VDF-HFP))/ZnO electrospun nanofibers serve as the piezoelectric layer,and the above and below electrostatic direct-writing P(VDF-HFP)/ZnO nanofiber membranes with a 110 nm Ag layer on one side that was plated by vacuum coating technique serve as the electrode layer.As the ANF-PENG only has 91μm thick and does not need further encapsulating,it has a high air permeability of 24.97 mm/s.ZnO nanoparticles in ANF-PENG not only improve the piezoelectric output,but also have antibacterial function(over 98%).The multifunctional ANF-PENG demonstrates good sensitivity to human motion and can harvest mechanical energy,indicating great potential applications in flexible self-powered electronic wearables and body health monitoring.展开更多
Wearable tensile strain sensors have attracted substantial research interest due to their great potential in applications for the real-time detection of human motion and health through the construction of body-sensing...Wearable tensile strain sensors have attracted substantial research interest due to their great potential in applications for the real-time detection of human motion and health through the construction of body-sensing networks.Conventional devices,however,are constantly demonstrated in non-real world scenarios,where changes in body temperature and humidity are ignored,which results in questionable sensing accuracy and reliability in practical applications.In this work,a fabric-like strain sensor is developed by fabricating graphene-modified Calotropis gigantea yarn and elastic yarn(i.e.Spandex)into an independently crossed structure,enabling the sensor with tunable sensitivity by directly altering the sensor width.The sensor possesses excellent breathability,allowing water vapor generated by body skin to be discharged into the environment(the water evaporation rate is approximately 2.03 kg m^(-2) h^(-1))and creating a pleasing microenvironment between the sensor and the skin by avoiding the hindering of perspiration release.More importantly,the sensor is shown to have a sensing stability towards changes in temperature and humidity,implementing sensing reliability against complex and changeable wearable microclimate.By wearing the sensor at various locations of the human body,a full-range body area sensing network for monitoring various body movements and vital signs,such as speaking,coughing,breathing and walking,is successfully dem-onstrated.It provides a new route for achieving wearing-comfortable,high-performance and sensing-reliable strain sensors.展开更多
This work was dedicated to performing surface oxidation and coating treatments on carbon fibers (CF) and investigating the changes of fiber surface properties after these treatments, including surface composition, r...This work was dedicated to performing surface oxidation and coating treatments on carbon fibers (CF) and investigating the changes of fiber surface properties after these treatments, including surface composition, relative volume of functional groups, and surface topography with X-ray photoelectron spectroscopy (XPS) and atom force microscopy (AFM) technology. The results show that, after oxidation treatments, interfacial properties between CF and non-polar polyarylacetylene (PAA) resin are remarkably modified by removing weak surface layers and increasing fiber surface roughness. Coating treatment by high char phenolic resin solution after oxidation makes interface of CF/PAA composites to be upgraded and the interfacial properties further bettered.展开更多
Inspired by the overlapping structure of snake scales,a reinforced scale-like knitted fabric(R-SLKF)was created in this work.To achieve this,short carbon fibers in an epoxy resin(ER)matrix were incorporated into the s...Inspired by the overlapping structure of snake scales,a reinforced scale-like knitted fabric(R-SLKF)was created in this work.To achieve this,short carbon fibers in an epoxy resin(ER)matrix were incorporated into the scales of an SLKF.The resulting textile is a highly stable protective composite that is flexible,warm,and thermally insulated.In addition,supe-rior stab-resistance is ensured through rigid protective blocks in the R-SLKF,making up a hard overlapping scale region,besides satisfactory flexibility via soft twisted ultra-high-molecular-weight polyethylene yarn-based textiles.The R-SLKF achieves high stab resistance(peak load of approximately 600 N for a single scale thickness of 2 mm),good flexibility(~290 mN cm),and breathability(100 MPa,423 mm/s),coupled with good warmth retention and thermal insulation prop-erties(0.28℃/s),which are superior to previously reported protective composite textiles.From the results,the combination of desirable individual protection,excellent wearability and comfort enables human beings to survive in extremely danger-ous environments.Finite element simulations provided valuable insights into the factors influencing the stab resistance of R-SLKF and elucidated the underlying anti-puncture mechanism in accordance with the experimental findings.This study presents a novel strategy for the facile industrial fabrication of flexible and lightweight protective composite textiles,which is expected to enhance the structure and material design for future innovations and provide advantages for personal protec-tive equipment in various industrial fields.展开更多
With the increasing demand for smart wearable clothing, the textile piezoelectric pressure sensor (T-PEPS) that can harvest mechanical energy directly has attracted significant attention. However, the current challeng...With the increasing demand for smart wearable clothing, the textile piezoelectric pressure sensor (T-PEPS) that can harvest mechanical energy directly has attracted significant attention. However, the current challenge of T-PEPS lies in remaining the outstanding output performance without compromising its wearing comfort. Here, a novel structural hierarchy T-PEPS based on the single-crystalline ZnO nanorods are designed. The T-PEPS is constructed with three layers mode consisting of a polyvinylidene fluoride (PVDF) membrane, the top and bottom layers of conductive rGO polyester (PET) fabrics with self-orientation ZnO nanorods. As a result, the as-fabricated T-PEPS shows low detection limit up to 8.71 Pa, high output voltage to 11.47 V and superior mechanical stability. The sensitivity of the sensor is 0.62 V·kPa−1 in the pressure range of 0–2.25 kPa. Meanwhile, the T-PEPS is employed to detect human movements such as bending/relaxation motion of the wrist, bending/stretching motion of each finger. It is demonstrated that the T-PEPS can be up-scaled to promote the application of wearable sensor platforms and self-powered devices.展开更多
The paper presents a detailed analysis of ordinary and dark energy density of the cosmos based on two different but complimentary theories. First, and starting from the concept of the speed of light being an average o...The paper presents a detailed analysis of ordinary and dark energy density of the cosmos based on two different but complimentary theories. First, and starting from the concept of the speed of light being an average over multi-fractals, we use Magueijo-Smolin’s ingenious revision of Einstein’s special relativity famous formula E = mc2 to a doubly special formula which includes the Planck energy as invariant to derive the ordinary energy density E(O) = mc2/22 and the dark energy density E(D) = mc2(21/22) wheremis the mass andcis the speed of light. Second we use the topological theory of pure gravity to reach the same result thus confirming the correctness of the theory of varying speed of light as well as the COBE, WMAP and Type 1a supernova cosmological measurements.展开更多
Depleting fossil energy sources and conventional polluting power generation pose a threat to sustainable development.Hydroelectricity generation from ubiquitous and spontaneous phase transitions between liquid and gas...Depleting fossil energy sources and conventional polluting power generation pose a threat to sustainable development.Hydroelectricity generation from ubiquitous and spontaneous phase transitions between liquid and gaseous water has been considered a promising strategy for mitigating the energy crisis.Fibrous materials with unique flexibility,processability,multifunctionality,and practicability have been widely applied for fibrous materials-based hydroelectricity generation(FHG).In this review,the power generation mechanisms,design principles,and electricity enhancement factors of FHG are first introduced.Then,the fabrication strategies and characteristics of varied constructions including 1D fiber,1D yarn,2D fabric,2D membrane,3D fibrous framework,and 3D fibrous gel are demonstrated.Afterward,the advanced functions of FHG during water harvesting,proton dissociation,ion separation,and charge accumulation processes are analyzed in detail.Moreover,the potential applications including power supply,energy storage,electrical sensor,and information expression are also discussed.Finally,some existing challenges are considered and prospects for future development are sincerely proposed.展开更多
基金Supported by the National Natural Science Foundation of China (No. 40136020)Key International Technology Cooperation Plan (No. 2004DFA03600)the National Basic Research Program of China (973 Program, No. 2005CB422305)
文摘Water samples were collected in 120 stations in the Bohai Sea of China to analyze the distribution of dissolved nutrients and assess the degree of eutrophication in August 2002. The result shows that the average concentration of DIN increased and the PO4-P concentration sharply decreased compared to the previous data of corresponding period. The high concentrations of DIN and PO4-P occurred in coastal waters, especially in the bays and some river estuaries, while the high concentrations of SiO3-Si in the surface and middle depth occurred in the central area of the Bohai Sea. The average ratio of DIN/PO4-P was much higher than the Redfield Ratio (16:1). Apparently, PO4-P was one of the limiting nutrient for phytoplankton growing in the sea. The average concentrations of DON and DOP were higher than their inorganic forms. The results of eutrophication assessment show that 22.1% of all stations were classified as violating the concentration levels of the National Seawater Quality Standard (GB 3097-1997) for DIN and only 3.9% for PO4-R The average eutrophication index in the overall area was 0.21±0.22 and the high values occurred in Bohai Bay, Liaodong Bay and near the Yellow River estuary. This means that the state of eutrophication was generally mesotrophic in the Bohai Sea, but relatively worse in the bays, especially some river estuaries.
基金supported by National Natural Science Foundation of China (NSFC) (No. 61804103)National Key R&D Program of China (No. 2017YFA0205002)+8 种基金Natural Science Foundation of the Jiangsu Higher Education Institutions of China (Nos. 18KJA535001 and 14KJB 150020)Natural Science Foundation of Jiangsu Province of China (Nos. BK20170343 and BK20180242)China Postdoctoral Science Foundation (No. 2017M610346)State Key Laboratory of Silicon Materials, Zhejiang University (No. SKL2018-03)Nantong Municipal Science and Technology Program (No. GY12017001)Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University (KSL201803)supported by Collaborative Innovation Center of Suzhou Nano Science & Technology, the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)the 111 ProjectJoint International Research Laboratory of Carbon-Based Functional Materials and Devices
文摘Continuous deforming always leads to the performance degradation of a flexible triboelectric nanogenerator due to the Young’s modulus mismatch of different functional layers.In this work,we fabricated a fiber-shaped stretchable and tailorable triboelectric nanogenerator(FST-TENG)based on the geometric construction of a steel wire as electrode and ingenious selection of silicone rubber as triboelectric layer.Owing to the great robustness and continuous conductivity,the FST-TENGs demonstrate high stability,stretchability,and even tailorability.For a single device with ~6 cm in length and ~3 mm in diameter,the open-circuit voltage of ~59.7 V,transferred charge of ~23.7 nC,short-circuit current of ~2.67 μA and average power of ~2.13 μW can be obtained at 2.5 Hz.By knitting several FST-TENGs to be a fabric or a bracelet,it enables to harvest human motion energy and then to drive a wearable electronic device.Finally,it can also be woven on dorsum of glove to monitor the movements of gesture,which can recognize every single finger,different bending angle,and numbers of bent finger by analyzing voltage signals.
基金This work was supported by the Science and technology guidance project plan of China National Textile And Apparel Council(2017006)Natural Science Foundation of Shandong Province of China(ZR2018QEM004)+2 种基金Research and Development Program of Shandong Province of China(Grant Nos.2019GGXI02022,2019JZZY010340,and 2019JZZY010335)Anhui Province Special Science and Technology Project(201903a05020028)Shandong provincial universities youth innovation technology plan innovation team(2020KJA013).
文摘Disposable medical protective clothing for 2019-nCoV mainly consists of stacked layers with nanopore films,polymer coated nonwoven fabrics and melt-blown nonwoven fabrics against anti-microbial and anti-liquid penetration.However,such structures lack moisture permeability and breathability leading to an uncomfortable,stuffy wearing experience.Here,we propose a novel medical protective clothing material with a superabsorbent layer to enhance moisture absorption.Poly(acrylic acid-co-acrylamide)/polyvinyl alcohol superabsorbent fibers(PAAAM/PVA fibers)were prepared via wet spinning.And the superabsorbent composite layer was stacked from PAAAM/PVA fibers,bamboo pulp fibers(BPF)and ethylene-propyl-ene side by side fibers(ESF).The novel disposable medical protective composite fabric was obtained through gluing the superabsorbent layer to the inner surface of strong antistatic polypropylene nonwoven fabric.The resultant composite fabric possesses excellent absorption and retention capacity for sweat,up to 12.3 g/g and 63.8%,and a maximum hygroscopic rate of 1.04 g/h,higher than that of the conventional material(only 0.53 g/h).The moisture permeability of the novel material reached 12,638.5 g/(m^(2) d),which was 307.6%of the conventional material.The novel material can effectively reduce the humidity inside the protective clothing and significantly improve the comfort of medical staff.
文摘The article explores the issue of designing a new design of a loading cylinder with a casing filled with vulcanized rubber for pneumomechanical spinning machines. The theoretical calculation of the deformed state of a cylindrical shell filled with vulcanized rubber is given. Deflections and stresses in the rubber layer are determined, which we use approximately for the Ritz methods. The theory of the radial and axial moving rubber layer was analyzed. The specific energy of deformation of a cylindrical layer of a compound cylinder is determined. The statics of the case and the loading cylinder of spinning machines are thoroughly studied.
基金supported in part by the International Collaborative Project of the Shanghai Committee of Science and Technology(16510711100)National Natural Science Foundation of China(61603090,61806051)+2 种基金the Fundamental Research Funds for the Central Universities(2232017D-08,2232017D-13)Shanghai Sailing Program(17YF1426100)by FDCT(Fundo para o Desenvolvimento das Ciencias e da Tecnologia)(119/2014/A3)
文摘Multi-robot systems can be applied to patrol a concerned environment for security purposes.According to different goals,this work reviews the existing researches in a multi-robot patrolling field from the perspectives of regular and adversarial patrolling.Regular patrolling requires robots to visit important locations as frequently as possible and a series of deterministic strategies are proposed,while adversarial one focuses on unpredictable robots’moving patterns to maximize adversary detection probability.Under each category,a systematic survey is done including problem statements and modeling,patrolling objectives and evaluation criteria,and representative patrolling strategies and approaches.Existing problems and open questions are presented accordingly.
基金The work was financially supported by National Natural Science Foundation of China (Nos. 51203182 and 51173202), Foundation for the Author of Excellent Doctoral Dissertation of Hunan Province (No. YB2014B004), Aeronautical Science Foundation of China (No. 20143188004), Key Laboratory of Advanced Textile Materials and Manufacturing Technology (Zhejiang Sci-Tech University), Ministry of Education (No. 2015001), Key Laboratory of Lightweight and Reliability Technology for Engineering Vehicle, College of Hunan Province (No. 2016kfjj01), Research Project of NUDT. We thank Tengyuan Wang for help in ORR experiment and helpful discussions.
文摘Carbon-based metal-free catalysts are a promising substitute for the rare and expensive platinum (Pt) used in the oxygen reduction reaction. We herein report N-doped graphene (NG) that is exquisitely integrated into highly conductive frameworks, simultaneously providing more active sites and higher conductivity. The NG was in situ grown on carbon fibers derived from silk cocoon (SCCf) using a simple one-step thermal treatment. The resulting product (NG-SCCf), possessing a meso-/macroporous structure with three-dimensional (3D) interconnected networks, exhibits an onset potential that is only 0.1 V less negative than that of Pt/C and shows stability and methanol tolerance superior to those of Pt/C in alkaline media. Moreover, in the absence of Pt as co-catalyst, NG-SCCf shows a photocatalytic H2 production rate of 66.0 ~tmol-h l.g 1, 4.4-fold higher than that of SCCf. This outstanding activity is intimately related to the in situ grown NG, hierarchically porous structure, and 3D interconnected networks, which not only introduce more active sites but also enable smooth electron transfer, mass transport, and effective separation of electron-hole pairs. Considering the abundance of the green raw material in combination with easy and low-cost preparation, this work contributes to the development of advanced sustainable catalysts in energy storage/conversion fields, such as electro- and photocatalysis.
文摘The urgent demand for portable electronics has promoted the development of high-efficienc)9 sustainable, and even stretchable self-charging power sources. In this work, we propose a flexible self-charging power unit based on folded carbon (FC) paper for harvesting mechanical energy from human motion and power portable electronics. The present unit mainly consists of a triboelectric nanogenerator (FC-TENG) and a supercapacitor (FC-SC), both based on folded carbon paper, as energy harvester and storage device, respectively. This favorable geometric design provides the high Young's modulus carbon paper with excellent stretchability and enables the power unit to work even under severe deformations, such as bending, twisting, and rolling. In addition, the tensile strain can be maximized by tuning the folding angle of the triangle-folded carbon paper. Moreover, the waterproof property of the packaged device make it washable, protect it from human sweat, and enable it to work in harsh environments. Finally, the as-prepared self-charging power unit was tested by placing it on the human body to harvest mechanical energy from hand tapping, foot treading, and arm touching, successfully powering an electronic watch. This work demonstrates the impressive potential of stretchable self-charging power units, which will further promote the development of high Young's modulus materials for wearable/portable electronics.
文摘Wearable electronics offer incredible benefits in mobile healthcare monitoring,sensing,portable energy harvesting and storage,human-machine interactions,etc.,due to the evolution of rigid electronics structure to flexible and stretchable devices.Lately,transition metal carbides and nitrides(MXenes)are highly regarded as a group of thriving two-dimensional nanomaterials and extraordinary building blocks for emerging flexible electronics platforms because of their excellent electrical conductivity,enriched surface functionalities,and large surface area.This article reviews the most recent developments in MXene-enabled flexible electronics for wearable electronics.Several MXeneenabled electronic devices designed on a nanometric scale are highlighted by drawing attention to widely developed nonstructural attributes,including 3D configured devices,textile and planer substrates,bioinspired structures,and printed materials.Furthermore,the unique progress of these nanodevices is highlighted by representative applications in healthcare,energy,electromagnetic interference(EMI)shielding,and humanoid control of machines.The emerging prospects of MXene nanomaterials as a key frontier in nextgeneration wearable electronics are envisioned and the design challenges of these electronic systems are also discussed,followed by proposed solutions.
基金This work was supported by the National Natural Science Foundation of China(62175082)。
文摘Outdoor passive heating to maintain a constant human body temperature is critical for human activities.However,most traditional energy-exhausted heating systems and inefficient passive heating technologies are incapable of dealing with the cold outdoor environment.Developing fabrics with low thermal radiation and conduction to passively heat the human body is a viable way to overcome the constraints of existing passive heating strategies.Herein,a multimaterial aerogel fabric was developed to realize passive personal heating without any energy input.The multimaterial aerogel fabric was fabricated by coating an Ag layer on an aerogel composite fabric.The lightweight aerogel composite fabric,woven from aerogel composite fibers with multi-scale porous structure,exhibits excellent thermal insulation,self-cleaning,mechanical and thermal stability.Furthermore,by coating with an Ag layer,the multimaterial aerogel fabric exhibits both low thermal conductivity and low infrared emissivity at 7–14μm,demonstrating superior thermal insulating performance.As a result,the proposed multimaterial aerogel fabric with a thickness of only 1.29 mm is capable of improving the human body temperarure of 5.7℃ in a cold environment without energy input.This strategy offers a potential energy-saving alternative for future outdoor passive heating.
基金financially supported by the National Natural Science Foundation of China(Nos.51473081 and 51672143)Taishan Scholars Program,Outstanding Youth of Natural Science in Shandong Province(JQ201713)+1 种基金Natural Science Foundation of Shandong Province(ZR2017MEM018)ARC Discovery Project(No.170103317)
文摘Water splitting,as an advanced energy conversion technology,consists of two half reactions,including oxygen evolution reaction(OER)and hydrogen evolution reaction(HER).However,the ideal electrocatalysts are noble metal based catalysts.Their high cost and scarcity in earth seriously restrict the large deployments.Ni Fe-based materials have attracted great attention in recent years due to their excellent catalytic properties for OER and HER.Nevertheless,their conductivity and electrochemical stability at high current density are unsatisfactory,resulting in ineffective water splitting due to high impedance and low stability.Recently,a series of catalysts coating Ni Fe-based materials on 3 D nickel foam were found to be extremely stable under the circumstance of high current density.In this review,we summarized the recent advances of NiFe-based materials on nickel foam for OER and HER,respectively,and further provided the perspectives for their future development.
基金supported by Outstanding Youth Project of Zhejiang Provincial Natural Science Foundation(LR22E030002)the Key Research and Development Program of Zhejiang Province(2022C01049)+1 种基金Zhejiang Provincial Natural Science Key Foundation of China(LZ20E030003)National Natural Science Foundation of China(52273095).
文摘Smart textiles with high sensitivity and rapid response for various external stimuli have gained tremendous attentions in human healthcare monitoring,personal heat management,and wearable electronics.However,the current smart textiles only acquire desired signal passively,regularly lacking subsequent on-demand therapy actively.Herein,a robust,breathable,and flexible smart textiles as multi-function sensor and wearable heater for human health monitoring and gentle thermotherapy in real time is constructed.The composite fiber as strain sensor(CFY@PU)was fabricated via warping carbon fiber yarns(CFY)onto polyurethane fibers(PU),which endowed composite fiber with high conductivity,excellent sensitivity(GF=76.2),and fantastic dynamic durability(7500 cycles)in strain sensing.In addition,CFY@PU can detect various degrees of human movements such as elbow bending,swallowing and pulse,which can provide effective information for disease diagnosis.More surprisingly,weaving CFY@PU into a fabric can assemble highly sensitive pressure sensor for remote communication and information encryption.Warping CFY onto Kevlar would obtain temperature-sensitive composite fiber(CFY@Kevlar)as temperature sensor and wearable heater for on-demand thermotherapy,which provided unique opportunities in designing smart textiles with ultrahigh sensitivity,rapid response,and great dynamic durability.
基金the Natural Science Foundation of Shanghai,China(No.18ZR1401000)the Shanghai Pujiang Program(No.18PJ1400400)Donghua University for the start-up grant(No.113-07-005710)。
文摘Global climate change,growing population,and environmental pollution underscore the need for a greater focus on providing advanced water treatment technologies.Although electrochemical basedprocesses are becoming promising solutions,they still face challenges owing to mass transport and upscaling which hinder the exploitation of this technology.Electrode design and reactor configuration are key factors for achieving operational improvements.The electroactive membrane has proven to be a breakthrough technology integrating electrochemistry and membrane separation with an enhanced mass transport by convection.In this review article,we discuss recent progress in environmental applications of electroactive membranes with particular focus on those composed of carbon nanotubes(CNT)due to their intriguing physicochemical prope rties.Their applications in degradation of refractory contaminants,detoxification and sequestration of toxic heavy metal ions,and membrane fouling alleviations are systematically reviewed.We then discuss the existing limitations and opportunities for future research.The development of advanced electroactive systems depends on interdisciplinary collaborations in the areas of materials,electrochemistry,membrane development,and environmental sciences.
基金the National Natural Science Foundation of China(Nos.52073224 and 52202111)the Textile Vision Basic Research Program of China(No.J202110)+4 种基金the Key Research and Development Program of Xianyang Science and Technology Bureau,China(No.2021ZDYF-GY-0035)the Key Research and Development Program of Shaanxi Province,China(No.2022SF-470)the Key Research and Development Program of Shaanxi Province,China(No.2022GY-377)the Natural Science Foundation of Shaanxi Province(No.2021JQ-685)the Scientific Research Project of Shaanxi Provincial Education Department,China(No.22JC035).
文摘Conventional firefighting clothing and fire masks can protect firemen’s safety to a certain extent,whereas cannot perceive environmental hazards and monitor their physical status in real time.Herein,we fabricated two kinds of Janus graphene/poly(pphenylene benzobisoxazole)(PBO)fabrics by laser direct writing approach and evaluated their performance as intelligent firefighting clothes and fire masks.The results showed that the Janus graphene/PBO fabrics were virtually non-combustible and achieved the highest thermal protection time of 18.91 s ever reported in flame,which is due to the intrinsic flame-retardant nature of PBO fibers.The graphene/PBO woven fabrics-based sensor showed good repeatability and stability in human motion monitoring and NO_(2)gas detection.Furthermore,the piezoelectric fire mask was assembled with graphene/PBO nonwoven fabric as electrode layer and polyvinylidene fluoride(PVDF)electrostatic direct writing film as piezoelectric layer.The filtration efficiency of the fire mask reaches 95%for PM_(2.5)and 100%for PM_(3.0),indicating its effective filtration capability for smoke particles in fires.The respiratory resistance of the piezoelectric fire mask(46.8 Pa)was lower than that of commercial masks(49 Pa),showing that it has good wearing comfort.Besides,the piezoelectric fire mask can be sensitive to the speed and intensity of human breathing,which is essential for indirectly reflecting the health of the human body.Consequently,this work provides a facile approach to fabricate next-generation intrinsic flame-retardant smart textiles for smart firefighting.
基金The authors acknowledge the financial support from the National Natural Science Foundation of China(No.52073224)Textile Vision Basic Research Program of China(No.J202110)+3 种基金Advanced manufacturing technology project of Xi’an Science and Technology Bureau,China(21XJZZ0019)Scientific Research Project of Shaanxi Provincial Education Department,China(No.22JC035)Key Research and Development Program of Xianyang Science and Technology Bureau,China(No.2021ZDYF-GY-0035)Research Fund for the Doctoral Program of Xi’an Polytechnic University(No.BS202006).
文摘Piezoelectric nanogenerators(PENGs)are promising for harvesting renewable and abundant mechanical energy with high efficiency.Up to now,published research studies have mainly focused on increasing the sensitivity and output of PENGs.The technical challenges in relation to practicability,comfort,and antibacterial performance,which are critically important for wearable applications,have not been well addressed.To overcome the limitations,we developed an all-nanofiber PENG(ANF-PENG)with a sandwich structure,in which the middle poly(vinylidene fluoride-co-hexafluoropropylene(P(VDF-HFP))/ZnO electrospun nanofibers serve as the piezoelectric layer,and the above and below electrostatic direct-writing P(VDF-HFP)/ZnO nanofiber membranes with a 110 nm Ag layer on one side that was plated by vacuum coating technique serve as the electrode layer.As the ANF-PENG only has 91μm thick and does not need further encapsulating,it has a high air permeability of 24.97 mm/s.ZnO nanoparticles in ANF-PENG not only improve the piezoelectric output,but also have antibacterial function(over 98%).The multifunctional ANF-PENG demonstrates good sensitivity to human motion and can harvest mechanical energy,indicating great potential applications in flexible self-powered electronic wearables and body health monitoring.
基金National Key R&D Program of China(2021YFE0111100)Ministry of Science and Technology of the People’s Republic of China(KY202201002)+3 种基金Jiangsu Provincial Department of Science and Technology(BZ2022017)Shanghai Science and Technology Committee(21015800600)We would like to thank the China National Textile and Apparel Council(J202002)Jiangsu Advanced Textile Engineering Technology Center(XJFZ/2021/7),projects with number 2021-fx010104 for their support.
文摘Wearable tensile strain sensors have attracted substantial research interest due to their great potential in applications for the real-time detection of human motion and health through the construction of body-sensing networks.Conventional devices,however,are constantly demonstrated in non-real world scenarios,where changes in body temperature and humidity are ignored,which results in questionable sensing accuracy and reliability in practical applications.In this work,a fabric-like strain sensor is developed by fabricating graphene-modified Calotropis gigantea yarn and elastic yarn(i.e.Spandex)into an independently crossed structure,enabling the sensor with tunable sensitivity by directly altering the sensor width.The sensor possesses excellent breathability,allowing water vapor generated by body skin to be discharged into the environment(the water evaporation rate is approximately 2.03 kg m^(-2) h^(-1))and creating a pleasing microenvironment between the sensor and the skin by avoiding the hindering of perspiration release.More importantly,the sensor is shown to have a sensing stability towards changes in temperature and humidity,implementing sensing reliability against complex and changeable wearable microclimate.By wearing the sensor at various locations of the human body,a full-range body area sensing network for monitoring various body movements and vital signs,such as speaking,coughing,breathing and walking,is successfully dem-onstrated.It provides a new route for achieving wearing-comfortable,high-performance and sensing-reliable strain sensors.
文摘This work was dedicated to performing surface oxidation and coating treatments on carbon fibers (CF) and investigating the changes of fiber surface properties after these treatments, including surface composition, relative volume of functional groups, and surface topography with X-ray photoelectron spectroscopy (XPS) and atom force microscopy (AFM) technology. The results show that, after oxidation treatments, interfacial properties between CF and non-polar polyarylacetylene (PAA) resin are remarkably modified by removing weak surface layers and increasing fiber surface roughness. Coating treatment by high char phenolic resin solution after oxidation makes interface of CF/PAA composites to be upgraded and the interfacial properties further bettered.
基金supported by the National Natural Science Funds of China(52373085 and 11972172)Natural Science Foundation of Hubei Province(2023AFB828)+5 种基金Innovative Team Program of Natural Science Foundation of Hubei Province(2023AFA027)the Fundamental Research Funds for the Central Universities(JUSRP22026)a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAP)Open Fund for Hubei Key Laboratory of Digital Textile EquipmentWuhan Textile University(No.DTL 2023022)National Local Joint Laboratory for Advanced Textile Processing and Clean Production(17).
文摘Inspired by the overlapping structure of snake scales,a reinforced scale-like knitted fabric(R-SLKF)was created in this work.To achieve this,short carbon fibers in an epoxy resin(ER)matrix were incorporated into the scales of an SLKF.The resulting textile is a highly stable protective composite that is flexible,warm,and thermally insulated.In addition,supe-rior stab-resistance is ensured through rigid protective blocks in the R-SLKF,making up a hard overlapping scale region,besides satisfactory flexibility via soft twisted ultra-high-molecular-weight polyethylene yarn-based textiles.The R-SLKF achieves high stab resistance(peak load of approximately 600 N for a single scale thickness of 2 mm),good flexibility(~290 mN cm),and breathability(100 MPa,423 mm/s),coupled with good warmth retention and thermal insulation prop-erties(0.28℃/s),which are superior to previously reported protective composite textiles.From the results,the combination of desirable individual protection,excellent wearability and comfort enables human beings to survive in extremely danger-ous environments.Finite element simulations provided valuable insights into the factors influencing the stab resistance of R-SLKF and elucidated the underlying anti-puncture mechanism in accordance with the experimental findings.This study presents a novel strategy for the facile industrial fabrication of flexible and lightweight protective composite textiles,which is expected to enhance the structure and material design for future innovations and provide advantages for personal protec-tive equipment in various industrial fields.
基金This study was supported by National First-Class Discipline Program of Light Industry Technology and Engineering(No.LITE2018-21)the National Key Research and Development Program of China(Nos.2018YFC2000903 and 2019YFC1711701)+2 种基金the National Natural Science Foundation of China(Nos.21975107,61803364,and U1913216)the Fundamental Research Funds for the Central Universities(No.JUSRP51724B)the Shenzhen Fundamental Research and Discipline Layout Project(No.JCYJ20180302145549896).
文摘With the increasing demand for smart wearable clothing, the textile piezoelectric pressure sensor (T-PEPS) that can harvest mechanical energy directly has attracted significant attention. However, the current challenge of T-PEPS lies in remaining the outstanding output performance without compromising its wearing comfort. Here, a novel structural hierarchy T-PEPS based on the single-crystalline ZnO nanorods are designed. The T-PEPS is constructed with three layers mode consisting of a polyvinylidene fluoride (PVDF) membrane, the top and bottom layers of conductive rGO polyester (PET) fabrics with self-orientation ZnO nanorods. As a result, the as-fabricated T-PEPS shows low detection limit up to 8.71 Pa, high output voltage to 11.47 V and superior mechanical stability. The sensitivity of the sensor is 0.62 V·kPa−1 in the pressure range of 0–2.25 kPa. Meanwhile, the T-PEPS is employed to detect human movements such as bending/relaxation motion of the wrist, bending/stretching motion of each finger. It is demonstrated that the T-PEPS can be up-scaled to promote the application of wearable sensor platforms and self-powered devices.
文摘The paper presents a detailed analysis of ordinary and dark energy density of the cosmos based on two different but complimentary theories. First, and starting from the concept of the speed of light being an average over multi-fractals, we use Magueijo-Smolin’s ingenious revision of Einstein’s special relativity famous formula E = mc2 to a doubly special formula which includes the Planck energy as invariant to derive the ordinary energy density E(O) = mc2/22 and the dark energy density E(D) = mc2(21/22) wheremis the mass andcis the speed of light. Second we use the topological theory of pure gravity to reach the same result thus confirming the correctness of the theory of varying speed of light as well as the COBE, WMAP and Type 1a supernova cosmological measurements.
基金funding support from the National Key Research and Development Program of China(No.2022YFB3805800)the National Natural Science Foundation of China(52173059)+1 种基金The Major Basic Research Project of the Natural Science Foundation of the Jiangsu Higher Education Institutions(21KJA540002)Jiangsu Funding Program for Excellent Postdoctoral Talent(2022ZB555).
文摘Depleting fossil energy sources and conventional polluting power generation pose a threat to sustainable development.Hydroelectricity generation from ubiquitous and spontaneous phase transitions between liquid and gaseous water has been considered a promising strategy for mitigating the energy crisis.Fibrous materials with unique flexibility,processability,multifunctionality,and practicability have been widely applied for fibrous materials-based hydroelectricity generation(FHG).In this review,the power generation mechanisms,design principles,and electricity enhancement factors of FHG are first introduced.Then,the fabrication strategies and characteristics of varied constructions including 1D fiber,1D yarn,2D fabric,2D membrane,3D fibrous framework,and 3D fibrous gel are demonstrated.Afterward,the advanced functions of FHG during water harvesting,proton dissociation,ion separation,and charge accumulation processes are analyzed in detail.Moreover,the potential applications including power supply,energy storage,electrical sensor,and information expression are also discussed.Finally,some existing challenges are considered and prospects for future development are sincerely proposed.