A generalized flexibility–based objective function utilized for structure damage identification is constructed for solving the constrained nonlinear least squares optimized problem. To begin with, the generalized fle...A generalized flexibility–based objective function utilized for structure damage identification is constructed for solving the constrained nonlinear least squares optimized problem. To begin with, the generalized flexibility matrix (GFM) proposed to solve the damage identification problem is recalled and a modal expansion method is introduced. Next, the objective function for iterative optimization process based on the GFM is formulated, and the Trust-Region algorithm is utilized to obtain the solution of the optimization problem for multiple damage cases. And then for computing the objective function gradient, the sensitivity analysis regarding design variables is derived. In addition, due to the spatial incompleteness, the influence of stiffness reduction and incomplete modal measurement data is discussed by means of two numerical examples with several damage cases. Finally, based on the computational results, it is evident that the presented approach provides good validity and reliability for the large and complicated engineering structures.展开更多
Organic thermoelectric generators(TEGs)are flexible and lightweight,but they often have high electrical resistance,poor output power,and low mechanical durability,because of which their thermoelectric performance is p...Organic thermoelectric generators(TEGs)are flexible and lightweight,but they often have high electrical resistance,poor output power,and low mechanical durability,because of which their thermoelectric performance is poor.We used a facile and rapid solvent evaporation process to prepare a robust carbon nanotube/Bi0.45Sb1.55Te3(CNT/BST)foam with a high thermoelectric figure of merit(zT).The BST sub-micronparticles effectively create an electrically conductive network within the three-dimensional porous CNT foam to greatly improve the electrical conductivity and the Seebeck coefficient and reinforce the mechanical strength of the composite against applied stresses.The CNT/BST foam had a zT value of 7.8×10^(−3)at 300 K,which was 5.7 times higher than that of pristine CNT foam.We used the CNT/BST foam to fabricate a flexible TEG with an internal resistance of 12.3Ωand an output power of 15.7μW at a temperature difference of 21.8 K.The flexible TEG showed excellent stability and durability even after 10,000 bending cycles.Finally,we demonstrate the shapeability of the CNT/BST foam by fabricating a concave TEG with conformal contact on the surface of a cylindrical glass tube,which suggests its practical applicability as a thermal sensor.展开更多
This paper proposes a two-parameter block triangular splitting(TPTS)preconditioner for the general block two-by-two linear systems.The eigenvalues of the corresponding preconditioned matrix are proved to cluster aroun...This paper proposes a two-parameter block triangular splitting(TPTS)preconditioner for the general block two-by-two linear systems.The eigenvalues of the corresponding preconditioned matrix are proved to cluster around 0 or 1 under mild conditions.The limited numerical results show that the TPTS preconditioner is more efficient than the classic block-diagonal and block-triangular preconditioners when applied to the flexible generalized minimal residual(FGMRES)method.展开更多
Polymer-based thermoelectric(TE)films feature several prominent merits,involving available multi-component composi-tions,versatile patterning fabrication,and readily integration.Therefore,these materials hold a huge p...Polymer-based thermoelectric(TE)films feature several prominent merits,involving available multi-component composi-tions,versatile patterning fabrication,and readily integration.Therefore,these materials hold a huge potential as the con-tinuous power supply for wearable devices.Herein,we reported the preparation of a series of vinylene-linked triazole-cored covalent organic frameworks(COFs)by Knoevenagel condensation of 2,4,6-trimethyl-1,3,5-triazine as the core monomer.The as-prepared COFs tend to generate the nano-or micro-fiber morphologies with tunable lengths and diameters through changing the polyphenylene building blocks.Accordingly,these COF fibers could be readily composited with single-walled carbon nanotubes(SWCNTs)to form the flexible free-standing films upon a simple vacuum filtration method.A film sample containing 30 wt%g-C_(18)N_(3)-COF exhibited the highest power factor of 68.93μW/(m K^(2))at 420 K.The manipulated 4-leg flexible thermoelectric generator(f-TEG)released a maximum output power and power density of 343.5 nW and 0.32 W/m^(2)at a temperature difference of 35 K.After bending for 1000 times at a radius of 15 mm,the resistance change rate of the as-fabricated f-TEGs was less than 5%,exhibiting excellent stability and flexibility.This work might not only broaden the potential application scope of COF materials but also provide a new fabrication strategy towards energy harvesting.展开更多
Emerging freestanding membrane technologies,especially using inorganic thermoelectric materials,demonstrate the potential for advanced thermoelectric platforms.However,using rare and toxic elements during material pro...Emerging freestanding membrane technologies,especially using inorganic thermoelectric materials,demonstrate the potential for advanced thermoelectric platforms.However,using rare and toxic elements during material processing must be circumvented.Herein,we present a scalable method for synthesizing highly crystalline CuS membranes for thermoelectric applications.By sulfurizing crystalline Cu,we produce a highly percolated and easily transferable network of submicron CuS rods.The CuS membrane effectively separates thermal and electrical properties to achieve a power factor of 0.50 mW m^(-1) K^(-2) and thermal conductivity of 0.37 W m^(-1) K^(-1) at 650 K(estimated value).This yields a record-high dimensionless figure-of-merit of 0.91 at 650 K(estimated value)for covellite.Moreover,integrating 12 CuS devices into a module resulted in a power generation of4μW atΔT of 40 K despite using a straightforward configuration with only p-type CuS.Furthermore,based on the temperature-dependent electrical characteristics of CuS,we develop a wearable temperature sensor with antibacterial properties.展开更多
Flexible thermoelectric generators(FTEGs)offer a promising solution for powering wearable electronics,while their practical applications are mainly obstructed by the moderate properties of flexible thermoelectric(TE)m...Flexible thermoelectric generators(FTEGs)offer a promising solution for powering wearable electronics,while their practical applications are mainly obstructed by the moderate properties of flexible thermoelectric(TE)materials.Here,flexible Ag_(2)Se nanowire(NW)/methyl cellulose(MC)composite films were developed via facile screen-printing technology combined with cold pressing and annealing treatment,and a highest power factor of 1,641.58μW m^(-1)K^(-2)at 360 K was achieved.The reasons for the high TE performance of the Ag_(2)Se NW/MC composite films were because,after the annealing treatment,the Ag_(2)Se NWs were sintered to form conductive network structures,the crystallinity of Ag_(2)Se was markedly enhanced,and the content of insulating phase MC in the composite film was decreased.The Ag_(2)Se NW/MC composite film held appreciable flexibility,as its room-temperature power factor(1,312.08μW m^(-1)K^(-2))can retain~93%after bending for 1,000 cycles at a radius of 4 mm.Furthermore,the assembled FTEG consisting of 4 strips can generate a maximal power density of 3.51 W m^(-2)at a temperature difference of 14.1 K.Our results open an effective and large-scale strategy for fabricating high-performance flexible TE materials and energy-harvesting devices.展开更多
Flexible thermoelectric generators(f-TEGs)are of importance for self-powered,portable,and wearable electronics.The materials’thermoelectric(TE)performance is one of the factors that affect the conversion efficiency o...Flexible thermoelectric generators(f-TEGs)are of importance for self-powered,portable,and wearable electronics.The materials’thermoelectric(TE)performance is one of the factors that affect the conversion efficiency of f-TEGs.Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)as a kind of conducting polymers has low thermal conductivity and good processability in solution;however,its TE properties are still much lower than those of the inorganic TE materials,which limits its wide applications in f-TEGs.Two-dimensional(2D)inorganic nanosheets(NSs)exfoliated from their corresponding powders are promising filler materials for enhancing the TE properties of PEDOT:PSS.This paper provides a brief review on the research progress of flexible 2D inorganic NS/PEDOT:PSS composite films fabricated by vacuum filtration,drop casting,and spin coating.The challenges,perspectives,and outlooks of flexible 2D inorganic NS/PEDOT:PSS composite films are further discussed.展开更多
Organic thermoelectric(OTE)materials have been considered to be promising candidates for large area and low‐cost wearable devices owing to their tailorable molecular structure,intrinsic flexibility,and prominent solu...Organic thermoelectric(OTE)materials have been considered to be promising candidates for large area and low‐cost wearable devices owing to their tailorable molecular structure,intrinsic flexibility,and prominent solution processability.More importantly,OTE materials offer direct energy conversion from the human body,solid‐state cooling at low electric consumption,and diversified functions.Herein,we summarize recent developments of OTE materials and devices for smart applications.We first review the fundamentals of OTE materials from the viewpoint of thermoelectric performance,mechanical properties and bionic functions.Second,we describe OTE devices in flexible generators,photothermoelectric detectors,self‐powered sensors,and ultra‐thin cooling elements.Finally,we present the challenges and perspectives on OTE materials as well as devices in wearable electronics and fascinating applications in the Internet of Things.展开更多
文摘A generalized flexibility–based objective function utilized for structure damage identification is constructed for solving the constrained nonlinear least squares optimized problem. To begin with, the generalized flexibility matrix (GFM) proposed to solve the damage identification problem is recalled and a modal expansion method is introduced. Next, the objective function for iterative optimization process based on the GFM is formulated, and the Trust-Region algorithm is utilized to obtain the solution of the optimization problem for multiple damage cases. And then for computing the objective function gradient, the sensitivity analysis regarding design variables is derived. In addition, due to the spatial incompleteness, the influence of stiffness reduction and incomplete modal measurement data is discussed by means of two numerical examples with several damage cases. Finally, based on the computational results, it is evident that the presented approach provides good validity and reliability for the large and complicated engineering structures.
文摘Organic thermoelectric generators(TEGs)are flexible and lightweight,but they often have high electrical resistance,poor output power,and low mechanical durability,because of which their thermoelectric performance is poor.We used a facile and rapid solvent evaporation process to prepare a robust carbon nanotube/Bi0.45Sb1.55Te3(CNT/BST)foam with a high thermoelectric figure of merit(zT).The BST sub-micronparticles effectively create an electrically conductive network within the three-dimensional porous CNT foam to greatly improve the electrical conductivity and the Seebeck coefficient and reinforce the mechanical strength of the composite against applied stresses.The CNT/BST foam had a zT value of 7.8×10^(−3)at 300 K,which was 5.7 times higher than that of pristine CNT foam.We used the CNT/BST foam to fabricate a flexible TEG with an internal resistance of 12.3Ωand an output power of 15.7μW at a temperature difference of 21.8 K.The flexible TEG showed excellent stability and durability even after 10,000 bending cycles.Finally,we demonstrate the shapeability of the CNT/BST foam by fabricating a concave TEG with conformal contact on the surface of a cylindrical glass tube,which suggests its practical applicability as a thermal sensor.
基金the National Natural Science Foundation of China under Grant Nos.61273311 and 61803247.
文摘This paper proposes a two-parameter block triangular splitting(TPTS)preconditioner for the general block two-by-two linear systems.The eigenvalues of the corresponding preconditioned matrix are proved to cluster around 0 or 1 under mild conditions.The limited numerical results show that the TPTS preconditioner is more efficient than the classic block-diagonal and block-triangular preconditioners when applied to the flexible generalized minimal residual(FGMRES)method.
基金supported by the Science and Technology Commission of Shanghai Municipality(20JC1414900)the National Natural Science Foundation of China(22271188,22075178,22005189)+1 种基金the China Postdoctoral Science Foundation(2020M681277)the Natural Science Foundation of Shanghai(23ZR1481100,21ZR1462300).
文摘Polymer-based thermoelectric(TE)films feature several prominent merits,involving available multi-component composi-tions,versatile patterning fabrication,and readily integration.Therefore,these materials hold a huge potential as the con-tinuous power supply for wearable devices.Herein,we reported the preparation of a series of vinylene-linked triazole-cored covalent organic frameworks(COFs)by Knoevenagel condensation of 2,4,6-trimethyl-1,3,5-triazine as the core monomer.The as-prepared COFs tend to generate the nano-or micro-fiber morphologies with tunable lengths and diameters through changing the polyphenylene building blocks.Accordingly,these COF fibers could be readily composited with single-walled carbon nanotubes(SWCNTs)to form the flexible free-standing films upon a simple vacuum filtration method.A film sample containing 30 wt%g-C_(18)N_(3)-COF exhibited the highest power factor of 68.93μW/(m K^(2))at 420 K.The manipulated 4-leg flexible thermoelectric generator(f-TEG)released a maximum output power and power density of 343.5 nW and 0.32 W/m^(2)at a temperature difference of 35 K.After bending for 1000 times at a radius of 15 mm,the resistance change rate of the as-fabricated f-TEGs was less than 5%,exhibiting excellent stability and flexibility.This work might not only broaden the potential application scope of COF materials but also provide a new fabrication strategy towards energy harvesting.
基金supported by the Korea Research Institute of Chemical Technology(KRICT)of the Republic of Korea(KS2321-10,BSK23-440,KK2351-10)supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(Ministry of Science and ICT)(RS-2024-00421857)supported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP)grant funded by the Ministry of Trade,Industry and Energy(MOTIE)(2021202080023D).
文摘Emerging freestanding membrane technologies,especially using inorganic thermoelectric materials,demonstrate the potential for advanced thermoelectric platforms.However,using rare and toxic elements during material processing must be circumvented.Herein,we present a scalable method for synthesizing highly crystalline CuS membranes for thermoelectric applications.By sulfurizing crystalline Cu,we produce a highly percolated and easily transferable network of submicron CuS rods.The CuS membrane effectively separates thermal and electrical properties to achieve a power factor of 0.50 mW m^(-1) K^(-2) and thermal conductivity of 0.37 W m^(-1) K^(-1) at 650 K(estimated value).This yields a record-high dimensionless figure-of-merit of 0.91 at 650 K(estimated value)for covellite.Moreover,integrating 12 CuS devices into a module resulted in a power generation of4μW atΔT of 40 K despite using a straightforward configuration with only p-type CuS.Furthermore,based on the temperature-dependent electrical characteristics of CuS,we develop a wearable temperature sensor with antibacterial properties.
基金supported by the Shuguang Program of Shanghai Education Development Foundation and Shanghai Municipal Education Commission(22SG54)the Natural Science Foundation of Shanghai(23ZR1481100 and 21ZR-1462300)+2 种基金support from the Knut and Alice Wallenberg Foundation through the Wallenberg Academy Fellows program(grant no.KAW 2020.0196)the Swedish Research Council under project grant no.2021-03826the Swedish Energy Agency under project 46519-1.
文摘Flexible thermoelectric generators(FTEGs)offer a promising solution for powering wearable electronics,while their practical applications are mainly obstructed by the moderate properties of flexible thermoelectric(TE)materials.Here,flexible Ag_(2)Se nanowire(NW)/methyl cellulose(MC)composite films were developed via facile screen-printing technology combined with cold pressing and annealing treatment,and a highest power factor of 1,641.58μW m^(-1)K^(-2)at 360 K was achieved.The reasons for the high TE performance of the Ag_(2)Se NW/MC composite films were because,after the annealing treatment,the Ag_(2)Se NWs were sintered to form conductive network structures,the crystallinity of Ag_(2)Se was markedly enhanced,and the content of insulating phase MC in the composite film was decreased.The Ag_(2)Se NW/MC composite film held appreciable flexibility,as its room-temperature power factor(1,312.08μW m^(-1)K^(-2))can retain~93%after bending for 1,000 cycles at a radius of 4 mm.Furthermore,the assembled FTEG consisting of 4 strips can generate a maximal power density of 3.51 W m^(-2)at a temperature difference of 14.1 K.Our results open an effective and large-scale strategy for fabricating high-performance flexible TE materials and energy-harvesting devices.
基金supported by the Natural Science Foundation of Shanghai(23ZR1481100)Shuguang Program of Shanghai Education Development Foundation,and Shanghai Municipal Education Commission(22SG54)+2 种基金support from the Knut and Alice Wallenberg Foundation through the Wallenberg Academy Fellows program(grant no.KAW 2020.0196)the Swedish Research Council under project grant no 2021-03826the Swedish Energy Agency under project 46519-1.
文摘Flexible thermoelectric generators(f-TEGs)are of importance for self-powered,portable,and wearable electronics.The materials’thermoelectric(TE)performance is one of the factors that affect the conversion efficiency of f-TEGs.Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)as a kind of conducting polymers has low thermal conductivity and good processability in solution;however,its TE properties are still much lower than those of the inorganic TE materials,which limits its wide applications in f-TEGs.Two-dimensional(2D)inorganic nanosheets(NSs)exfoliated from their corresponding powders are promising filler materials for enhancing the TE properties of PEDOT:PSS.This paper provides a brief review on the research progress of flexible 2D inorganic NS/PEDOT:PSS composite films fabricated by vacuum filtration,drop casting,and spin coating.The challenges,perspectives,and outlooks of flexible 2D inorganic NS/PEDOT:PSS composite films are further discussed.
基金supported by the National Key Research and Development Program of China(2017YFA0204700 and 2018YFE0200700)the National Natural Science Foundation of China(21805285,22021002,21905276,61971396)+2 种基金the Natural Science Foundation of Beijing(4202077)Beijing National Laboratory for Molecular Sciences(BNLMS201912)UCAS(Y954011XX2)and CAS(ZDBS‐LY‐SLH034).
文摘Organic thermoelectric(OTE)materials have been considered to be promising candidates for large area and low‐cost wearable devices owing to their tailorable molecular structure,intrinsic flexibility,and prominent solution processability.More importantly,OTE materials offer direct energy conversion from the human body,solid‐state cooling at low electric consumption,and diversified functions.Herein,we summarize recent developments of OTE materials and devices for smart applications.We first review the fundamentals of OTE materials from the viewpoint of thermoelectric performance,mechanical properties and bionic functions.Second,we describe OTE devices in flexible generators,photothermoelectric detectors,self‐powered sensors,and ultra‐thin cooling elements.Finally,we present the challenges and perspectives on OTE materials as well as devices in wearable electronics and fascinating applications in the Internet of Things.
