Forecasting stock prices using deep learning models suffers from pro-blems such as low accuracy,slow convergence,and complex network structures.This study developed an echo state network(ESN)model to mitigate such pro...Forecasting stock prices using deep learning models suffers from pro-blems such as low accuracy,slow convergence,and complex network structures.This study developed an echo state network(ESN)model to mitigate such pro-blems.We compared our ESN with a long short-term memory(LSTM)network by forecasting the stock data of Kweichow Moutai,a leading enterprise in China’s liquor industry.By analyzing data for 120,240,and 300 days,we generated fore-cast data for the next 40,80,and 100 days,respectively,using both ESN and LSTM.In terms of accuracy,ESN had the unique advantage of capturing non-linear data.Mean absolute error(MAE)was used to present the accuracy results.The MAEs of the data forecast by ESN were 0.024,0.024,and 0.025,which were,respectively,0.065,0.007,and 0.009 less than those of LSTM.In terms of con-vergence,ESN has a reservoir state-space structure,which makes it perform faster than other models.Root-mean-square error(RMSE)was used to present the con-vergence time.In our experiment,the RMSEs of ESN were 0.22,0.27,and 0.26,which were,respectively,0.08,0.01,and 0.12 less than those of LSTM.In terms of network structure,ESN consists only of input,reservoir,and output spaces,making it a much simpler model than the others.The proposed ESN was found to be an effective model that,compared to others,converges faster,forecasts more accurately,and builds time-series analyses more easily.展开更多
Thermochromic smart windows have gained increasing popularity in light modulation and energy management in buildings.However,the fabrication of flexible thermochromic smart windows with high luminous transmittance(Tlu...Thermochromic smart windows have gained increasing popularity in light modulation and energy management in buildings.However,the fabrication of flexible thermochromic smart windows with high luminous transmittance(Tlum),tailorable critical temperature(τc),strong solar modulation ability(ΔTsol),and long-term durability remains a huge challenge.In this study,hydrogel-based thermochromic smart windows are fabricated by sandwiching thermochromic hydrogels of polyallylamine hydrochloride,polyacrylic acid,and carbonized polymer dots(CPDs)complexes between two pieces of transparent substrates.Benefiting from the incorporation of nanosized CPDs,the thermochromic hydrogel has an ultrahigh Tlum of~98.7%,a desirableτc of~24.2℃,aΔTsol of~89.3%and a rapid transition time of~3 s from opaque state to transparent state.Moreover,the thermochromic hydrogel exhibits excellent anti-freezing ability,tight adhesion toward various substrates,and excellent self-healing capability.The self-healing capability enables the fabrication of large-area smart windows by welding multiple hydrogel pieces.The smart windows retain their original thermochromic properties after being stored under ambient conditions for at least 147 days or undergoing 10,000 uninterrupted heating/cooling cycles.The model houses with smart windows can achieve a temperature reduction of 9.2℃,demonstrating the excellent indoor temperature modulation performance of the smart windows.展开更多
Noncovalentlycross-linkedpolymermaterials through healing,recycling,and reprocessing can reduce materials consumption and alleviate environmental pollution.However,it remains a huge challenge to fabricate super-strong...Noncovalentlycross-linkedpolymermaterials through healing,recycling,and reprocessing can reduce materials consumption and alleviate environmental pollution.However,it remains a huge challenge to fabricate super-strong noncovalently cross-linked polymer materials with mechanical strength comparable to high-performance engineering polymers.Herein,healable and reprocessable noncovalently cross-linked polymer compositeswith an unprecedented mechanical strength are fabricated by complexation of polyacrylic acid(PAA),polyvinylpyrrolidone(PVPON),and carbonized polymer dots(CPDs)(denoted as PAA-PVPON-CPDs).The incorporation of 15 wt%CPDs generates PAA-PVPON-CPDs compositeswith a tensile strength of∼158 MPa and Young’s modulus of∼8.2GPa.Servingas nanofillers,theCPDs can establish strong interactions with polymers in PAA-PVPON composites.The CPDs and the in situ-formed PAAPVPON nanoparticles work in concert to significantly strengthen the PAA-PVPON-CPDs composites to an unprecedented strength.The PAA-PVPON-CPDs composites exhibit excellent impact resistance and damage tolerance because of the high mechanical strength of the composites and the energy dissipation mechanism of the CPDs and PAA-PVPON nanoparticles.Moreover,the fractured PAA-PVPON-CPDs composites can be healed to restore their original mechanical strength.展开更多
It is a long-term pursuit,and also,a challenge to significantly improve the mechanical strength of thermoplastic polymers using readily dispersed polymers as nanofillers.In this study,we demonstrated that in situ form...It is a long-term pursuit,and also,a challenge to significantly improve the mechanical strength of thermoplastic polymers using readily dispersed polymers as nanofillers.In this study,we demonstrated that in situ formed carboxylic acid-functionalized poly(aryl ether sulfone)(PAES-COOH)/polyvinylpyrrolidone(PVPON)complex nanoparticles can significantly enhance the mechanical strength of PAES-COOH by mixing PAES-COOH with a small fraction of PVPON.The PAES-COOH/PVPON10%composite,which contained∼10 wt%PVPON,exhibited a tensile strength of∼104.8 MPa and Young’s modulus of∼932.2 MPa,which were∼2.0 and∼1.7 times higher than those of the PAES-COOH,respectively.The PAES-COOH/PVPON nanoparticles which were uniformly dispersed in PAES-COOH matrices and had strong hydrogen-bonding interactions with PAES-COOH,served as nanofillers to reinforce the mechanical strength of the PAES-COOH.The PAES-COOH/PVPON_(10%)composites possessed excellent solvent-assisted healability,and the fractured composites could be healed to restore their original mechanical strength.Meanwhile,the PAES-COOH/PVPON_(10%)composites could be recycled multiple times,and yet retained their shape integration and their original mechanical strength.展开更多
Highly durable and stretchable ionic conductors are indispensable components of flexible electronics.However,fabricating such ionic conductors that are also non-toxic and biodegradable remains a challenge.In this stud...Highly durable and stretchable ionic conductors are indispensable components of flexible electronics.However,fabricating such ionic conductors that are also non-toxic and biodegradable remains a challenge.In this study,highly stretchable,elastic,healable,and ultra-durable ionic conductors capable of non-hazardous disposal are conveniently fabricated by complexation of vanillin-grafted polyvinyl alcohol(VPVA)and ionic liquids(ILs)(denoted as VPVA-IL).展开更多
The fabrication of smart films with reversible wettability enabled by the stimulus-induced morphology changes has attracted growing interest but remains a challenge. Here we report a smart film that can reversibly cha...The fabrication of smart films with reversible wettability enabled by the stimulus-induced morphology changes has attracted growing interest but remains a challenge. Here we report a smart film that can reversibly changes its wettability between transparent hydrophobicity to translucent superhydrophobicity through the humidity-induced wrinkling/de-wrinkling process.The film was fabricated by depositing hydrophobic SiO2 nanoparticles(NPs) on poly(acrylic acid)(PAA)/poly(allylamine hydrochloride)(PAH) films, followed by partially exfoliating the films from the underlying substrates. The partially exfoliated PAA/PAH film can reversibly wrinkle and de-wrinkle when being alternately subjected to humid and dry environments. The deposition of hydrophobic SiO2 NPs on the wrinkling PAA/PAH film does not hinder the humidity-enabled wrin-kling/de-wrinkling ability of the composite film. The hydrophobic SiO2 NPs and the underlying humidity-wrinkling PAA/PAH film enable the composite film to spontaneously change from hydrophobic and transparent to superhydrophobic and translucent with the rise of environmental humidity.展开更多
It is a formidable challenge to fabricate healable polymeric materials with high mechanical strength and stiffness due to the highly suppressed diffusion of their polymer chains.Herein,a high-strength,highly stiff,and...It is a formidable challenge to fabricate healable polymeric materials with high mechanical strength and stiffness due to the highly suppressed diffusion of their polymer chains.Herein,a high-strength,highly stiff,andrepairable/healable supramolecular polymercomposite was fabricatedby complexingpoly(acrylic acid)(PAA)and poly(allylamine hydrochloride)(PAH)in aqueous solutions,followed by molding into desired shapes.Exquisitely tuning the electrostatic and H-bonding interactions between PAA and PAH led to associative phase-separation and in situ formation of nanostructures in the resultant PAA–PAH composites.展开更多
It is highly desirable to develop a solar-driven interfacial water evaporatorwith a self-healing ability and high-efficiency water evaporation performance for water distillation and desalination;however,this process i...It is highly desirable to develop a solar-driven interfacial water evaporatorwith a self-healing ability and high-efficiency water evaporation performance for water distillation and desalination;however,this process is considerably challenging.Herein,by exploiting the advantages of a self-healing hydrophilic polymer,a self-healing hydrophilic porous photothermal(SHPP)membrane was fabricated by curing a mixture of the polymer,carbon black,and NaCl,followed by removal of the NaCl from water.Since the SHPP membrane could serve as a photothermal layer and water transportation channel simultaneously,a solar-driven interfacial evaporator could be fabricated readily by assembling the SHPP membrane with polyethylene foam.We have shown that the SHPP membrane-based evaporator exhibited a water evaporation rate of 1.68 kg m^(−2) h^(−1) and an energy efficiency of 97.3%.These values are superior to those obtained using solar-driven interfacial evaporators with self-healing capability.Notably,by hydrogen bonds reformation between the fracture surfaces,the SHPP membrane could regain its structural integrity after breaking,making the SHPPmembrane-based evaporator the first to heal entirely and repeatedly from physical damage to sustain itswater evaporation capacity.Therefore,the potential of using SHPP membranes to develop stable,long-last ing,andhigh-efficiency solar-driven interfacial water evaporators is highlighted.展开更多
Mechanical performances are among the most fundamental properties that dictate the applicability and durability of polymeric materials.Reinforcement of polymeric materials is eternally pursued to broaden the applicati...Mechanical performances are among the most fundamental properties that dictate the applicability and durability of polymeric materials.Reinforcement of polymeric materials is eternally pursued to broaden the applications of polymers with light-weight,low-cost and easy-processing advantages.Noncovalent aggregates of biomacromolecules have been found to play a significant role in the mechanical properties of many natural materials,such as the spider silk.Increasing numbers of reports have demonstrated that the in situ formed noncovalent aggregates of polymer chains in polymeric systems are highly effective for enhancing the mechanical properties of artificial polymeric materials,in terms of strength,stiffness,toughness,and/or elasticity.The in situ formed noncovalent aggregates act as additional crosslinking domains and well-dispersed“hard”nanofillers in the polymer networks,significantly strengthening,stiffening and/or toughening the polymeric materials.Moreover,the noncovalent crosslinking of polymer chains favors the development of healable and recyclable polymeric materials,thanks to the reversible and dynamic properties of noncovalent bonds.This review provides an overview of the recent advances on the enhancement of the mechanical properties of different polymeric materials by the in situ formed noncovalent aggregates of polymer chains.It is expected to arouse inspirations for the development of novel polymeric materials with extraordinary mechanical performances and functionalities.展开更多
基金supported by the National Natural Science Foundation of China(No.72073041)Open Foundation for the University Innovation Platform in Hunan Province(No.18K103)+2 种基金2011 Collaborative Innovation Center for Development and Utilization of Finance and Economics Big Data Property,Universities of Hunan Province,Open Project(Nos.20181901CRP03,20181901CRP04,20181901CRP05)2020 Hunan Provincial Higher Education Teaching Reform Research Project(Nos.HNJG-2020-1130,HNJG-2020-1124)2020 General Project of Hunan Social Science Fund(No.20B16).
文摘Forecasting stock prices using deep learning models suffers from pro-blems such as low accuracy,slow convergence,and complex network structures.This study developed an echo state network(ESN)model to mitigate such pro-blems.We compared our ESN with a long short-term memory(LSTM)network by forecasting the stock data of Kweichow Moutai,a leading enterprise in China’s liquor industry.By analyzing data for 120,240,and 300 days,we generated fore-cast data for the next 40,80,and 100 days,respectively,using both ESN and LSTM.In terms of accuracy,ESN had the unique advantage of capturing non-linear data.Mean absolute error(MAE)was used to present the accuracy results.The MAEs of the data forecast by ESN were 0.024,0.024,and 0.025,which were,respectively,0.065,0.007,and 0.009 less than those of LSTM.In terms of con-vergence,ESN has a reservoir state-space structure,which makes it perform faster than other models.Root-mean-square error(RMSE)was used to present the con-vergence time.In our experiment,the RMSEs of ESN were 0.22,0.27,and 0.26,which were,respectively,0.08,0.01,and 0.12 less than those of LSTM.In terms of network structure,ESN consists only of input,reservoir,and output spaces,making it a much simpler model than the others.The proposed ESN was found to be an effective model that,compared to others,converges faster,forecasts more accurately,and builds time-series analyses more easily.
基金supported by the National Natural Science Foundation of China (No.21935004).
文摘Thermochromic smart windows have gained increasing popularity in light modulation and energy management in buildings.However,the fabrication of flexible thermochromic smart windows with high luminous transmittance(Tlum),tailorable critical temperature(τc),strong solar modulation ability(ΔTsol),and long-term durability remains a huge challenge.In this study,hydrogel-based thermochromic smart windows are fabricated by sandwiching thermochromic hydrogels of polyallylamine hydrochloride,polyacrylic acid,and carbonized polymer dots(CPDs)complexes between two pieces of transparent substrates.Benefiting from the incorporation of nanosized CPDs,the thermochromic hydrogel has an ultrahigh Tlum of~98.7%,a desirableτc of~24.2℃,aΔTsol of~89.3%and a rapid transition time of~3 s from opaque state to transparent state.Moreover,the thermochromic hydrogel exhibits excellent anti-freezing ability,tight adhesion toward various substrates,and excellent self-healing capability.The self-healing capability enables the fabrication of large-area smart windows by welding multiple hydrogel pieces.The smart windows retain their original thermochromic properties after being stored under ambient conditions for at least 147 days or undergoing 10,000 uninterrupted heating/cooling cycles.The model houses with smart windows can achieve a temperature reduction of 9.2℃,demonstrating the excellent indoor temperature modulation performance of the smart windows.
基金supported by the National Natural Science Foundation of China(NSFC grant no.21935004).
文摘Noncovalentlycross-linkedpolymermaterials through healing,recycling,and reprocessing can reduce materials consumption and alleviate environmental pollution.However,it remains a huge challenge to fabricate super-strong noncovalently cross-linked polymer materials with mechanical strength comparable to high-performance engineering polymers.Herein,healable and reprocessable noncovalently cross-linked polymer compositeswith an unprecedented mechanical strength are fabricated by complexation of polyacrylic acid(PAA),polyvinylpyrrolidone(PVPON),and carbonized polymer dots(CPDs)(denoted as PAA-PVPON-CPDs).The incorporation of 15 wt%CPDs generates PAA-PVPON-CPDs compositeswith a tensile strength of∼158 MPa and Young’s modulus of∼8.2GPa.Servingas nanofillers,theCPDs can establish strong interactions with polymers in PAA-PVPON composites.The CPDs and the in situ-formed PAAPVPON nanoparticles work in concert to significantly strengthen the PAA-PVPON-CPDs composites to an unprecedented strength.The PAA-PVPON-CPDs composites exhibit excellent impact resistance and damage tolerance because of the high mechanical strength of the composites and the energy dissipation mechanism of the CPDs and PAA-PVPON nanoparticles.Moreover,the fractured PAA-PVPON-CPDs composites can be healed to restore their original mechanical strength.
基金This work was supported by the National Natural Science Foundation of China(NSFC grant 20935004 and 21774049).
文摘It is a long-term pursuit,and also,a challenge to significantly improve the mechanical strength of thermoplastic polymers using readily dispersed polymers as nanofillers.In this study,we demonstrated that in situ formed carboxylic acid-functionalized poly(aryl ether sulfone)(PAES-COOH)/polyvinylpyrrolidone(PVPON)complex nanoparticles can significantly enhance the mechanical strength of PAES-COOH by mixing PAES-COOH with a small fraction of PVPON.The PAES-COOH/PVPON10%composite,which contained∼10 wt%PVPON,exhibited a tensile strength of∼104.8 MPa and Young’s modulus of∼932.2 MPa,which were∼2.0 and∼1.7 times higher than those of the PAES-COOH,respectively.The PAES-COOH/PVPON nanoparticles which were uniformly dispersed in PAES-COOH matrices and had strong hydrogen-bonding interactions with PAES-COOH,served as nanofillers to reinforce the mechanical strength of the PAES-COOH.The PAES-COOH/PVPON_(10%)composites possessed excellent solvent-assisted healability,and the fractured composites could be healed to restore their original mechanical strength.Meanwhile,the PAES-COOH/PVPON_(10%)composites could be recycled multiple times,and yet retained their shape integration and their original mechanical strength.
基金supported by the National Natural Science Foundation of China(NSFC grant nos.21935004 and 21774049).
文摘Highly durable and stretchable ionic conductors are indispensable components of flexible electronics.However,fabricating such ionic conductors that are also non-toxic and biodegradable remains a challenge.In this study,highly stretchable,elastic,healable,and ultra-durable ionic conductors capable of non-hazardous disposal are conveniently fabricated by complexation of vanillin-grafted polyvinyl alcohol(VPVA)and ionic liquids(ILs)(denoted as VPVA-IL).
基金supported by the National Natural Science Foundation of China(21225419)
文摘The fabrication of smart films with reversible wettability enabled by the stimulus-induced morphology changes has attracted growing interest but remains a challenge. Here we report a smart film that can reversibly changes its wettability between transparent hydrophobicity to translucent superhydrophobicity through the humidity-induced wrinkling/de-wrinkling process.The film was fabricated by depositing hydrophobic SiO2 nanoparticles(NPs) on poly(acrylic acid)(PAA)/poly(allylamine hydrochloride)(PAH) films, followed by partially exfoliating the films from the underlying substrates. The partially exfoliated PAA/PAH film can reversibly wrinkle and de-wrinkle when being alternately subjected to humid and dry environments. The deposition of hydrophobic SiO2 NPs on the wrinkling PAA/PAH film does not hinder the humidity-enabled wrin-kling/de-wrinkling ability of the composite film. The hydrophobic SiO2 NPs and the underlying humidity-wrinkling PAA/PAH film enable the composite film to spontaneously change from hydrophobic and transparent to superhydrophobic and translucent with the rise of environmental humidity.
基金the National Key R&D Program of China(2018YFC1105401)and China’s Thousand Talent Plan,L.Y.thanks the National Natural Science Foundation of China(NSFC grant no.21704067)J.S.thanks the National Natural Science Foundation of China(NSFC grant no.21774049)for financial support.
文摘It is a formidable challenge to fabricate healable polymeric materials with high mechanical strength and stiffness due to the highly suppressed diffusion of their polymer chains.Herein,a high-strength,highly stiff,andrepairable/healable supramolecular polymercomposite was fabricatedby complexingpoly(acrylic acid)(PAA)and poly(allylamine hydrochloride)(PAH)in aqueous solutions,followed by molding into desired shapes.Exquisitely tuning the electrostatic and H-bonding interactions between PAA and PAH led to associative phase-separation and in situ formation of nanostructures in the resultant PAA–PAH composites.
基金financially supported by the National Natural Science Foundation of China(grant no.21971083)the Science and Technology Department of Jilin Province(grant no.20190103019JH).
文摘It is highly desirable to develop a solar-driven interfacial water evaporatorwith a self-healing ability and high-efficiency water evaporation performance for water distillation and desalination;however,this process is considerably challenging.Herein,by exploiting the advantages of a self-healing hydrophilic polymer,a self-healing hydrophilic porous photothermal(SHPP)membrane was fabricated by curing a mixture of the polymer,carbon black,and NaCl,followed by removal of the NaCl from water.Since the SHPP membrane could serve as a photothermal layer and water transportation channel simultaneously,a solar-driven interfacial evaporator could be fabricated readily by assembling the SHPP membrane with polyethylene foam.We have shown that the SHPP membrane-based evaporator exhibited a water evaporation rate of 1.68 kg m^(−2) h^(−1) and an energy efficiency of 97.3%.These values are superior to those obtained using solar-driven interfacial evaporators with self-healing capability.Notably,by hydrogen bonds reformation between the fracture surfaces,the SHPP membrane could regain its structural integrity after breaking,making the SHPPmembrane-based evaporator the first to heal entirely and repeatedly from physical damage to sustain itswater evaporation capacity.Therefore,the potential of using SHPP membranes to develop stable,long-last ing,andhigh-efficiency solar-driven interfacial water evaporators is highlighted.
基金National Key Research and Development Program of China,Grant/Award Number:2018YFC1105401National Natural Science Foundation of China,Grant/Award Number:21935004。
文摘Mechanical performances are among the most fundamental properties that dictate the applicability and durability of polymeric materials.Reinforcement of polymeric materials is eternally pursued to broaden the applications of polymers with light-weight,low-cost and easy-processing advantages.Noncovalent aggregates of biomacromolecules have been found to play a significant role in the mechanical properties of many natural materials,such as the spider silk.Increasing numbers of reports have demonstrated that the in situ formed noncovalent aggregates of polymer chains in polymeric systems are highly effective for enhancing the mechanical properties of artificial polymeric materials,in terms of strength,stiffness,toughness,and/or elasticity.The in situ formed noncovalent aggregates act as additional crosslinking domains and well-dispersed“hard”nanofillers in the polymer networks,significantly strengthening,stiffening and/or toughening the polymeric materials.Moreover,the noncovalent crosslinking of polymer chains favors the development of healable and recyclable polymeric materials,thanks to the reversible and dynamic properties of noncovalent bonds.This review provides an overview of the recent advances on the enhancement of the mechanical properties of different polymeric materials by the in situ formed noncovalent aggregates of polymer chains.It is expected to arouse inspirations for the development of novel polymeric materials with extraordinary mechanical performances and functionalities.