Simultaneously manipulating multiple physical fields plays an important role in the increasingly complex integrated systems,aerospace equipment,biochemical productions,etc.For on-chip systems with high integration lev...Simultaneously manipulating multiple physical fields plays an important role in the increasingly complex integrated systems,aerospace equipment,biochemical productions,etc.For on-chip systems with high integration level,the precise and efficient control of the propagation of electromagnetic waves and heat fluxes simultaneously is particularly important.In this study,we propose a graphical designing method(i.e.,thermal-electromagnetic surface transformation)based on thermal-electromagnetic null medium to simultaneously control the propagation of electromagnetic waves and thermal fields according to the pre-designed paths.A thermal-electromagnetic cloak,which can create a cloaking effect on both electromagnetic waves and thermal fields simultaneously,is designed by thermal-electromagnetic surface transformation and verified by both numerical simulations and experimental measurements.The thermal-electromagnetic surface transformation proposed in this study provides a new methodology for simultaneous controlling on electromagnetic and temperature fields,and may have significant applications in improving thermal-electromagnetic compatibility problem,protecting of thermal-electromagnetic sensitive components,and improving efficiency of energy usage for complex onchip systems.展开更多
Developing advanced oxygen reduction reaction(ORR)electrocatalysts with rapid mass/electron transport as well as conducting relevant kinetics investigations is essential for energy technologies,but both still face ong...Developing advanced oxygen reduction reaction(ORR)electrocatalysts with rapid mass/electron transport as well as conducting relevant kinetics investigations is essential for energy technologies,but both still face ongoing challenges.Herein,a facile approach was reported for achieving the highly dispersed Co nanoparticles anchored hierarchically porous N-doped carbon fibers(Co@N-HPCFs),which were assembled by core-shell MOFs-derived hollow polyhedrons.Notably,the unique one-dimensional(1D)carbon fibers with hierarchical porosity can effectively improve the exposure of active sites and facilitate the electron transfer and mass transfer,resulting in the enhanced reaction kinetics.As a result,the ORR performance of the optimal Co@N-HPCF catalysts remarkably outperforms that of commercial Pt/C in alkaline solution,reaching a limited diffusion current density(J)of 5.85 m A cm^(-2)and a half-wave potential(E_(1/2))of 0.831 V.Particularly,the prepared Co@N-HPCF catalysts can be used as an excellent air-cathode for liquid/solid-state Zn-air batteries,exhibiting great potentiality in portable/wearable energy devices.Furthermore,the reaction kinetic during ORR process is deeply explored by finite element simulation,so as to intuitively grasp the kinetic control region,diffusion control region,and mixing control region of the ORR process,and accurately obtain the relevant kinetic parameters.This work offers an effective strategy and a reliable theoretical basis for the engineering of first-class ORR electrocatalysts with fast electronic/mass transport.展开更多
Image detection based on machine learning and deep learning currently has a good application prospect for railway fault diagnosis,with good performance in feature extraction and the accuracy of image localization and ...Image detection based on machine learning and deep learning currently has a good application prospect for railway fault diagnosis,with good performance in feature extraction and the accuracy of image localization and good classification results.To improve the speed of locating small target objects of fasteners,the YOLOv5 framework model with faster algorithm speed is selected.To improve the classification accuracy of fasteners,YOLOv5-based heavy-duty railway rail fastener detection is proposed.The anchor size is modified on the original basis to improve the attention to small targets of fasteners.The CBAM(Convolutional Block Attention Module)module and TPH(Transformer Prediction Head)module are introduced to improve the speed and accuracy issues.The rail fasteners are divided into 6 categories.Experiment comparisons show that before the improvement,the MAP@0.5 value of all categories are close to the peak of 0.989 after the epoch of 150,and the F1 score approaches 1 with confidence in the interval(0.2,0.95).The improved mAP@0.5 value approached the highest value of 0.991 after the epoch of 75,and the F1 score approached 1 with confidence in the interval(0.01,0.95).The experiment results indicate that the improved YOLOv5 model proposed in this paper is more suitable for the task of detecting rail fasteners.展开更多
In this study,we proposed a self-healing conductive hydrogel based on polysaccharides and Li+to serve as flexible sensors.At first,the oxidized sodium alginate(OSA)was obtained through the oxidation reaction of sodium...In this study,we proposed a self-healing conductive hydrogel based on polysaccharides and Li+to serve as flexible sensors.At first,the oxidized sodium alginate(OSA)was obtained through the oxidation reaction of sodium alginate(SA).Then OSA,carboxymethyl chitosan(CMC),and agarose(AGO)were dissolved in LiCl solution,respectively.Finally,the hydrogel was obtained through heating,mixing,and cooling processes.Because of the Schiff base structure and hydrogen bonding,the hydrogel demonstrates good mechanical and self-healing properties.The presence of Li+provides good conductivity for the hydrogel.In addition,we demonstrated the application of the hydrogel as the flexible sensors.It can perceive the process of pressing Morse code with the index finger as a pressure sensor and monitor sliding movement of the thumb as the strain sensor to browse the web with the mobile phone.Thus,the selfhealing conductive hydrogel may have potential applications in flexible wearable sensors.展开更多
In this work,a novel NiP_(2)/g-C_(3)N_(4)heterojunction via homogeneous precipitation method assisted by thermal phosphorization reaction was designed and constructed,and the optimized sample showed the excellent phot...In this work,a novel NiP_(2)/g-C_(3)N_(4)heterojunction via homogeneous precipitation method assisted by thermal phosphorization reaction was designed and constructed,and the optimized sample showed the excellent photocatalytic H_(2)evolution activity under visible-light irradiation,which was nearly 112 times higher than that of pristine g-C_(3)N_(4)sample.Experimental characterizations and DFT calculations demonstrated that the NiP_(2)nanoparticles covered on the g-C_(3)N_(4)surface can form a built-in electric field at the interface to accelerate the transfer of photoexcited electrons from g-C_(3)N_(4)to NiP_(2),crucial for hindering the recombination of electron-hole pairs.Moreover,the energy barrier of hydrogen evolution reaction can also vastly reduce when combined NiP_(2)and g-C_(3)N_(4)to construct NiP_(2)/g-C_(3)N_(4)heterojunction.This work represents a method through combing experimental and theoretical tools to thoroughly investigate the mechanism of photocatalytic process.展开更多
Chemodivergent reactions of 2,2-dimethoxyacetaldehyde and anilines were described,which were established on the basis of either a C—C bond cleavage or a rearrangement process of a reaction inte rmediate.These reactio...Chemodivergent reactions of 2,2-dimethoxyacetaldehyde and anilines were described,which were established on the basis of either a C—C bond cleavage or a rearrangement process of a reaction inte rmediate.These reactions proceeded in a condition-determined manner with good functional group tolerance.In the first model,2,2-dimethoxyacetaldehyde reacted with aniline to form a new C—N bond,in the presence of O_(2),via a C—C bond cleavage reaction.However,in the second model,by performing the reaction in the absence of O_(2),Heyns rearrangement occurred and generated a new C—O bond to form methyl phenylglycinate.Such condition-determined reactions not only offered the new way for valueadded conversion of biomass-derived platform molecule,2,2-dimethoxyacetaldehyde,but also provided efficient methods for the synthesis of N-arylformamides and methyl phenylglycinates.展开更多
Adjusting the electronic structure of graphitic carbon nitride(g-C_(3)N_(4))photocatalyst throughπ-πconju-gation is an effective method to achieve efficient photogenerated carrier separation.One key challenge ofπ-...Adjusting the electronic structure of graphitic carbon nitride(g-C_(3)N_(4))photocatalyst throughπ-πconju-gation is an effective method to achieve efficient photogenerated carrier separation.One key challenge ofπ-πconjugation control is to tune the degree of such conjugation without destroying the g-C_(3)N_(4)struc-ture.Herein we report a conceptual design that achieves a coplanar heterojunction by enhancing theπ-πconjugation via the doping of crystalline g-C_(3)N_(4)using a conjugated double bond ring molecule,1,3,5-benzenetriol,during calcination process.The selection of the dopant enables the facile creation of a unique coplanar heterojunction which not only retains the pristine network structure of g-C_(3)N_(4),but remarkably promotes separation and transfer of photogenerated carriers through the enhancedπ-conjugated endogenous electric field.As a result,the new g-C_(3)N_(4)photocatalyst efficiently photocatalyti-cally produces hydrogen from water under visible light irradiation with a high H 2 production rate up to 94.94μmol/h,and a notable external quantum efficiency of 16.4%at 420 nm.展开更多
Quantum secure direct communication(QSDC)that allows people to directly transmit confidential information through insecure channels is an important branch of quantum communication.The widespread adoption of the QSDC d...Quantum secure direct communication(QSDC)that allows people to directly transmit confidential information through insecure channels is an important branch of quantum communication.The widespread adoption of the QSDC demands the development of simple and stable systems.However,most of the existent QSDC systems involve a complex self-alignment process at the initial stage and additional hardware to compensate environmental disturbance.In this study,we present a fiber-based QSDC system without active polarization compensation.Our system comprises a stable transmitter and a novel Sagnac-Mach-Zehnder interferometer for security detection.This robust system simplifies the self-alignment and is immune to environmental disturbance.The robustness of the system was theoretically and experimentally verified,and low bit error rates in a 12 min continuous operation with an active polarization scrambler were attained.In addition,we performed a proof-of-principle QSDC demonstration,and a secrecy capacity of 3.43 kbps over a 5 km fiber with a detection bit error rate of 0.85%±0.07%and a quantum bit error rate of 0.42%±0.05%were achieved.Experimental results confirm the viability of the proposed QSDC system for practical applications.展开更多
To meet the emerging demands for thermal protection materials for hypersonic aircraft,developing porous ultrahigh-temperature ceramics with both robust mechanical properties and superior thermal insulation performance...To meet the emerging demands for thermal protection materials for hypersonic aircraft,developing porous ultrahigh-temperature ceramics with both robust mechanical properties and superior thermal insulation performance is a critical challenge.Herein,we report novel porous(Ta_(0.2)Nb_(0.2)Ti_(0.2)Zr_(0.2)Hf_(0.2))C high-entropy carbide(PHEC)ceramics fabricated by a self-foaming method using commercially available metal chloride and furfuryl alcohol(FA)as precursors.The PHEC ceramics are constructed of microspheres with a size of 2µm,leading to a high porosity of 91.3%and an interconnected frame.These microspheres consist of high-entropy carbide grains(20 nm),resulting in abundant interfaces and nanosized pores in the PHEC ceramics.Due to its unique hierarchical structure,the prepared PHEC ceramics have outstanding compressive strength(28.1±2 MPa)and exceptionally low thermal conductivity(κT,0.046 W·m^(-1)·K^(-1))at room temperature.This makes it a promising thermal insulation materials for ultrahigh temperature applications.This work provides a cost-effective and facile strategy for producing porous ultrahigh-temperature ceramics.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 61971300, 12274317, 12374277, 61905208)Open Foundation of China-Belarus Belt and Road Joint Laboratory on Electromagnetic Environment Effect (No. ZBKF2022031202)+1 种基金Scientific and Technological Innovation Programs (STIP) of Higher Education Institutions in Shanxi (Nos. 2019L0159 and 2019L0146)2022 University Outstanding Youth Foundation of Taiyuan University of Technology
文摘Simultaneously manipulating multiple physical fields plays an important role in the increasingly complex integrated systems,aerospace equipment,biochemical productions,etc.For on-chip systems with high integration level,the precise and efficient control of the propagation of electromagnetic waves and heat fluxes simultaneously is particularly important.In this study,we propose a graphical designing method(i.e.,thermal-electromagnetic surface transformation)based on thermal-electromagnetic null medium to simultaneously control the propagation of electromagnetic waves and thermal fields according to the pre-designed paths.A thermal-electromagnetic cloak,which can create a cloaking effect on both electromagnetic waves and thermal fields simultaneously,is designed by thermal-electromagnetic surface transformation and verified by both numerical simulations and experimental measurements.The thermal-electromagnetic surface transformation proposed in this study provides a new methodology for simultaneous controlling on electromagnetic and temperature fields,and may have significant applications in improving thermal-electromagnetic compatibility problem,protecting of thermal-electromagnetic sensitive components,and improving efficiency of energy usage for complex onchip systems.
基金The financial support of the Natural Science Foundation of China(21802079 and 22075159)the Postdoctoral Science Foundation of China(2018 M642605)+1 种基金the Youth Innovation Team Project of Shandong Provincial Education Department(2019KJC023)the Taishan Scholar Program for L.Zhang(202103058)are appreciated。
文摘Developing advanced oxygen reduction reaction(ORR)electrocatalysts with rapid mass/electron transport as well as conducting relevant kinetics investigations is essential for energy technologies,but both still face ongoing challenges.Herein,a facile approach was reported for achieving the highly dispersed Co nanoparticles anchored hierarchically porous N-doped carbon fibers(Co@N-HPCFs),which were assembled by core-shell MOFs-derived hollow polyhedrons.Notably,the unique one-dimensional(1D)carbon fibers with hierarchical porosity can effectively improve the exposure of active sites and facilitate the electron transfer and mass transfer,resulting in the enhanced reaction kinetics.As a result,the ORR performance of the optimal Co@N-HPCF catalysts remarkably outperforms that of commercial Pt/C in alkaline solution,reaching a limited diffusion current density(J)of 5.85 m A cm^(-2)and a half-wave potential(E_(1/2))of 0.831 V.Particularly,the prepared Co@N-HPCF catalysts can be used as an excellent air-cathode for liquid/solid-state Zn-air batteries,exhibiting great potentiality in portable/wearable energy devices.Furthermore,the reaction kinetic during ORR process is deeply explored by finite element simulation,so as to intuitively grasp the kinetic control region,diffusion control region,and mixing control region of the ORR process,and accurately obtain the relevant kinetic parameters.This work offers an effective strategy and a reliable theoretical basis for the engineering of first-class ORR electrocatalysts with fast electronic/mass transport.
基金supported by the National Key R&D Program of China(Grant 2021YFF0501102)National Natural Science Foundation of China(Grant U1934219)+1 种基金National Science Fund for Excellent Young Scholars(Grant 52022010)National Natural Science Foundation of China(Grant 52202392,Grant 62120106011).
文摘Image detection based on machine learning and deep learning currently has a good application prospect for railway fault diagnosis,with good performance in feature extraction and the accuracy of image localization and good classification results.To improve the speed of locating small target objects of fasteners,the YOLOv5 framework model with faster algorithm speed is selected.To improve the classification accuracy of fasteners,YOLOv5-based heavy-duty railway rail fastener detection is proposed.The anchor size is modified on the original basis to improve the attention to small targets of fasteners.The CBAM(Convolutional Block Attention Module)module and TPH(Transformer Prediction Head)module are introduced to improve the speed and accuracy issues.The rail fasteners are divided into 6 categories.Experiment comparisons show that before the improvement,the MAP@0.5 value of all categories are close to the peak of 0.989 after the epoch of 150,and the F1 score approaches 1 with confidence in the interval(0.2,0.95).The improved mAP@0.5 value approached the highest value of 0.991 after the epoch of 75,and the F1 score approached 1 with confidence in the interval(0.01,0.95).The experiment results indicate that the improved YOLOv5 model proposed in this paper is more suitable for the task of detecting rail fasteners.
基金support from National Natural Science Foundation of China(51873009)Beijing Natural Science Foundation(2192042).
文摘In this study,we proposed a self-healing conductive hydrogel based on polysaccharides and Li+to serve as flexible sensors.At first,the oxidized sodium alginate(OSA)was obtained through the oxidation reaction of sodium alginate(SA).Then OSA,carboxymethyl chitosan(CMC),and agarose(AGO)were dissolved in LiCl solution,respectively.Finally,the hydrogel was obtained through heating,mixing,and cooling processes.Because of the Schiff base structure and hydrogen bonding,the hydrogel demonstrates good mechanical and self-healing properties.The presence of Li+provides good conductivity for the hydrogel.In addition,we demonstrated the application of the hydrogel as the flexible sensors.It can perceive the process of pressing Morse code with the index finger as a pressure sensor and monitor sliding movement of the thumb as the strain sensor to browse the web with the mobile phone.Thus,the selfhealing conductive hydrogel may have potential applications in flexible wearable sensors.
基金supported by the National Natural Science Foundation of China(Grant Nos.U1862105,22108214,22050410267)Natural Science Basic Research Plan in Shaanxi Province of China(Grant Nos.2017JZ001,2018KJXX-008)+3 种基金Fundamental Research Funds for the Central Universities(Grant No.cxtd2017004)China Postdoctoral Science Foundation(Grant No.2021TQ0262)the Promotion Plan for Young People of Shaanxi Association for Science and Technology(20210605)K.C.Wong Education Foundation,Hong Kong,China。
文摘In this work,a novel NiP_(2)/g-C_(3)N_(4)heterojunction via homogeneous precipitation method assisted by thermal phosphorization reaction was designed and constructed,and the optimized sample showed the excellent photocatalytic H_(2)evolution activity under visible-light irradiation,which was nearly 112 times higher than that of pristine g-C_(3)N_(4)sample.Experimental characterizations and DFT calculations demonstrated that the NiP_(2)nanoparticles covered on the g-C_(3)N_(4)surface can form a built-in electric field at the interface to accelerate the transfer of photoexcited electrons from g-C_(3)N_(4)to NiP_(2),crucial for hindering the recombination of electron-hole pairs.Moreover,the energy barrier of hydrogen evolution reaction can also vastly reduce when combined NiP_(2)and g-C_(3)N_(4)to construct NiP_(2)/g-C_(3)N_(4)heterojunction.This work represents a method through combing experimental and theoretical tools to thoroughly investigate the mechanism of photocatalytic process.
基金partly supported by the National Natural Science Foundation of China(61922004 and 62135001)the National Key Research and Development Program of China(2020YFB1806405)+4 种基金the Major Key Project of PCL(PCL2021A14)the Open Fund of the State Key Laboratory of Integrated OptoelectronicsUS National Science Foundation through the University of Pennsylvania Material Research Science and Engineering Center(DMR-1720530)US Office of Naval Research(ONR)Multidisciplinary University Research Initiative(MURI)Grant N00014-20-1-2325 on Robust Photonic Materials with High-Order Topological Protectionthe US Army Research Office under award contract W911-NF-19-1-0087。
基金the National Natural Science Foundation of China for financial support(Nos.2171101076,21872060 and 21902054)Fundamental Research Funds for the Central Universities(No.2019kfyXJJS072)Natural Science Foundation of Hubei Province(No.2019CFB219)。
文摘Chemodivergent reactions of 2,2-dimethoxyacetaldehyde and anilines were described,which were established on the basis of either a C—C bond cleavage or a rearrangement process of a reaction inte rmediate.These reactions proceeded in a condition-determined manner with good functional group tolerance.In the first model,2,2-dimethoxyacetaldehyde reacted with aniline to form a new C—N bond,in the presence of O_(2),via a C—C bond cleavage reaction.However,in the second model,by performing the reaction in the absence of O_(2),Heyns rearrangement occurred and generated a new C—O bond to form methyl phenylglycinate.Such condition-determined reactions not only offered the new way for valueadded conversion of biomass-derived platform molecule,2,2-dimethoxyacetaldehyde,but also provided efficient methods for the synthesis of N-arylformamides and methyl phenylglycinates.
基金supported by the National Natural Science Foundation of China (Nos. U1862105, 22078256)Natural Science Basic Research Plan in Shaanxi Province of China (Nos. 2017JZ001, 2018KJXX-008)+2 种基金Fundamental Research Funds for the Central Universities (No. cxtd2017004)K.C. Wong Education Foundation, Hong Kong, Chinafinancial support from Australian Research Council are appreciated
文摘Adjusting the electronic structure of graphitic carbon nitride(g-C_(3)N_(4))photocatalyst throughπ-πconju-gation is an effective method to achieve efficient photogenerated carrier separation.One key challenge ofπ-πconjugation control is to tune the degree of such conjugation without destroying the g-C_(3)N_(4)struc-ture.Herein we report a conceptual design that achieves a coplanar heterojunction by enhancing theπ-πconjugation via the doping of crystalline g-C_(3)N_(4)using a conjugated double bond ring molecule,1,3,5-benzenetriol,during calcination process.The selection of the dopant enables the facile creation of a unique coplanar heterojunction which not only retains the pristine network structure of g-C_(3)N_(4),but remarkably promotes separation and transfer of photogenerated carriers through the enhancedπ-conjugated endogenous electric field.As a result,the new g-C_(3)N_(4)photocatalyst efficiently photocatalyti-cally produces hydrogen from water under visible light irradiation with a high H 2 production rate up to 94.94μmol/h,and a notable external quantum efficiency of 16.4%at 420 nm.
基金supported by the National Natural Science Foundation of China(Grant Nos.62171144,and 11905065)Guangxi Science Foundation(Grant Nos.2021GXNSFAA220011,and 2021AC19384)+1 种基金Open Fund of IPOC(BUPT)(Grant No.IPOC2021A02)Innovation Project of Guangxi Graduate Education(Grant No.YCSW2022040)。
文摘Quantum secure direct communication(QSDC)that allows people to directly transmit confidential information through insecure channels is an important branch of quantum communication.The widespread adoption of the QSDC demands the development of simple and stable systems.However,most of the existent QSDC systems involve a complex self-alignment process at the initial stage and additional hardware to compensate environmental disturbance.In this study,we present a fiber-based QSDC system without active polarization compensation.Our system comprises a stable transmitter and a novel Sagnac-Mach-Zehnder interferometer for security detection.This robust system simplifies the self-alignment and is immune to environmental disturbance.The robustness of the system was theoretically and experimentally verified,and low bit error rates in a 12 min continuous operation with an active polarization scrambler were attained.In addition,we performed a proof-of-principle QSDC demonstration,and a secrecy capacity of 3.43 kbps over a 5 km fiber with a detection bit error rate of 0.85%±0.07%and a quantum bit error rate of 0.42%±0.05%were achieved.Experimental results confirm the viability of the proposed QSDC system for practical applications.
基金This research was supported by the National Natural Science Foundation of China(Nos.52173299 and 52372087)the Natural Science Foundation of Shaanxi Province(No.2021JZ-51).
文摘To meet the emerging demands for thermal protection materials for hypersonic aircraft,developing porous ultrahigh-temperature ceramics with both robust mechanical properties and superior thermal insulation performance is a critical challenge.Herein,we report novel porous(Ta_(0.2)Nb_(0.2)Ti_(0.2)Zr_(0.2)Hf_(0.2))C high-entropy carbide(PHEC)ceramics fabricated by a self-foaming method using commercially available metal chloride and furfuryl alcohol(FA)as precursors.The PHEC ceramics are constructed of microspheres with a size of 2µm,leading to a high porosity of 91.3%and an interconnected frame.These microspheres consist of high-entropy carbide grains(20 nm),resulting in abundant interfaces and nanosized pores in the PHEC ceramics.Due to its unique hierarchical structure,the prepared PHEC ceramics have outstanding compressive strength(28.1±2 MPa)and exceptionally low thermal conductivity(κT,0.046 W·m^(-1)·K^(-1))at room temperature.This makes it a promising thermal insulation materials for ultrahigh temperature applications.This work provides a cost-effective and facile strategy for producing porous ultrahigh-temperature ceramics.
