Improving the detection accuracy of rail internal defects and the generalization ability of detection models are not only the main problems in the field of defect detection but also the key to ensuring the safe operat...Improving the detection accuracy of rail internal defects and the generalization ability of detection models are not only the main problems in the field of defect detection but also the key to ensuring the safe operation of high-speed trains.For this reason,a rail internal defect detection method based on an enhanced network structure and module design using ultrasonic images is proposed in this paper.First,a data augmentation method was used to extend the existing image dataset to obtain appropriate image samples.Second,an enhanced network structure was designed to make full use of the high-level and low-level feature information in the image,which improved the accuracy of defect detection.Subsequently,to optimize the detection performance of the proposed model,the Mish activation function was used to design the block module of the feature extraction network.Finally,the pro-posed rail defect detection model was trained.The experimental results showed that the precision rate and F1score of the proposed method were as high as 98%,while the model’s recall rate reached 99%.Specifically,good detec-tion results were achieved for different types of defects,which provides a reference for the engineering application of internal defect detection.Experimental results verified the effectiveness of the proposed method.展开更多
A series of ballistic experiments were performed to investigate the damage behavior of high velocity reactive material projectiles(RMPs) impacting liquid-filled tanks,and the corresponding hydrodynamic ram(HRAM) was s...A series of ballistic experiments were performed to investigate the damage behavior of high velocity reactive material projectiles(RMPs) impacting liquid-filled tanks,and the corresponding hydrodynamic ram(HRAM) was studied in detail.PTFE/Al/W RMPs with steel-like and aluminum-like densities were prepared by a pressing/sintering process.The projectiles impacted a liquid-filled steel tank with front aluminum panel at approximately 1250 m/s.The corresponding cavity evolution characteristics and HRAM pressure were recorded by high-speed camera and pressure acquisition system,and further compared to those of steel and aluminum projectiles.Significantly different from the conical cavity formed by the inert metal projectile,the cavity formed by the RMP appeared as an ellipsoid with a conical front.The RMPs were demonstrated to enhance the radial growth velocity of cavity,the global HRAM pressure amplitude and the front panel damage,indicating the enhanced HRAM and structural damage behavior.Furthermore,combining the impact-induced fragmentation and deflagration characteristics,the cavity evolution of RMPs under the combined effect of kinetic energy impact and chemical energy release was analyzed.The mechanism of enhanced HRAM pressure induced by the RMPs was further revealed based on the theoretical model of the initial impact wave and the impulse analysis.Finally,the linear correlation between the deformation-thickness ratio and the non-dimensional impulse for the front panel was obtained and analyzed.It was determined that the enhanced near-field impulse induced by the RMPs was the dominant reason for the enhanced structural damage behavior.展开更多
Global interest in lithium-sulfur batteries as one of the most promising energy storage technologies has been sparked by their low sulfur cathode cost,high gravimetric,volumetric energy densities,abundant resources,an...Global interest in lithium-sulfur batteries as one of the most promising energy storage technologies has been sparked by their low sulfur cathode cost,high gravimetric,volumetric energy densities,abundant resources,and environmental friendliness.However,their practical application is significantly impeded by several serious issues that arise at the cathode-electrolyte interface,such as interface structure degradation including the uneven deposition of Li_(2)S,unstable cathode-electrolyte interphase(CEI)layer and intermediate polysulfide shuttle effect.Thus,an optimized cathode-electrolyte interface along with optimized electrodes is required for overall improvement.Herein,we comprehensively outline the challenges and corresponding strategies,including electrolyte optimization to create a dense CEI layer,regulating the Li_(2)S deposition pattern,and inhibiting the shuttle effect with regard to the solid-liquid-solid pathway,the transformation from solid-liquid-solid to solid-solid pathway,and solid-solid pathway at the cathode-electrolyte interface.In order to spur more perceptive research and hasten the widespread use of lithium-sulfur batteries,viewpoints on designing a stable interface with a deep comprehension are also put forth.展开更多
We report an extraordinary sound absorption enhancement in low and intermediate frequencies achieved by a thin multi-slit hybrid structure formed by incorporating micrometer scale micro-slits into a sub-millimeter sca...We report an extraordinary sound absorption enhancement in low and intermediate frequencies achieved by a thin multi-slit hybrid structure formed by incorporating micrometer scale micro-slits into a sub-millimeter scale meso-slit matrix. Theoretical and numerical results reveal that this exotic phenomenon is attributed to the noticeable velocity and temperature gradients induced at the junctures of the micro- and meso-slits, which cause significant loss of sound energy as a result of viscous and thermal effects. It is demonstrated that the proposed thin multi-slit hybrid structure with micro-scale configuration is capable of controling low frequency noise with large wavelength, which is attractive for applications where the size and weight of a sound absorber are restricted.展开更多
The femtosecond pulse shaping technique has been shown to be an effective method to control the multi-photon absorption by the light–matter interaction. Previous studies mainly focused on the quantum coherent control...The femtosecond pulse shaping technique has been shown to be an effective method to control the multi-photon absorption by the light–matter interaction. Previous studies mainly focused on the quantum coherent control of the multi-photon absorption by the phase, amplitude and polarization modulation, but the coherent features of the multi-photon absorption depending on the energy level structure, the laser spectrum bandwidth and laser central frequency still lack in-depth systematic research. In this work, we further explore the coherent features of the resonance-mediated two-photon absorption in a rubidium atom by varying the energy level structure, spectrum bandwidth and central frequency of the femtosecond laser field. The theoretical results show that the change of the intermediate state detuning can effectively influence the enhancement of the near-resonant part, which further affects the transform-limited （TL）-normalized final state population maximum. Moreover, as the laser spectrum bandwidth increases, the TL-normalized final state population maximum can be effectively enhanced due to the increase of the enhancement in the near-resonant part, but the TL-normalized final state population maximum is constant by varying the laser central frequency. These studies can provide a clear physical picture for understanding the coherent features of the resonance-mediated two-photon absorption, and can also provide a theoretical guidance for the future applications.展开更多
As a promising cathode material for aqueous zinc-ion batteries,1T-MoS_(2)has been extensively investigated because of its facile two-dimensional ion-diffusion channels and high electrical conductivity.However,the limi...As a promising cathode material for aqueous zinc-ion batteries,1T-MoS_(2)has been extensively investigated because of its facile two-dimensional ion-diffusion channels and high electrical conductivity.However,the limited number of available Zn storage sites,i.e.,limited capacity,hinders its application because the inserted Zn^(2+),which form strong electrostatic interactions with 1T-MoS_(2),preventing subsequent Zn^(2+)insertion.Currently,the approach of enlarging the interlayer distance to reduce electrostatic interactions has been commonly used to enhance the capacity and reduce Zn^(2+)migration barriers.However,an enlarged interlayer spacing can weaken the van der Waals force between 1T-MoS_(2)monolayers,easily disrupting the structural stability.Herein,to address this issue,an effective strategy based on Fe doping is proposed for 1T-MoS_(2)(Fe-1T-MoS_(2)).The theoretical calculations reveal that Fe doping can simultaneously moderate the rate of decrease in the adsorption energy after gradually increasing the number of stored atoms,and enhance the electron delocalization on metal-O bonds.Therefore,the experiment results show that Fe doping can simultaneously activate more Zn storage sites,thus enhancing the capacity,and stabilize the structural stability for improved cycling performance.Consequently,Fe-1T-MoS_(2)exhibits a larger capacity(189 mAh·g^(-1)at 0.1 A·g^(-1))and superior cycling stability(78%capacity retention after 400 cycles at 2 A·g^(-1))than pure 1T-MoS_(2).This work may open up a new avenue for constructing high-performance MoS_(2)-based cathodes.展开更多
Depression refers to a series of mental health issues characterized by loss of interest and enjoyment in everyday life,low mood and selected emotional,cognitive,physical and behavioral symptoms.Depression is a common ...Depression refers to a series of mental health issues characterized by loss of interest and enjoyment in everyday life,low mood and selected emotional,cognitive,physical and behavioral symptoms.Depression is a common disorder,affecting 5–15%of the general population.When diagnosed as major depressive disorder（MDD）,patients are currentlytreated with pharmacological agents such as serotonin or noradren- aline uptake inhibitors （SSRI or SNRI） or tricyclics.展开更多
In this study, pool boiling test results are provided for the structured enhanced tubes having pores with connecting gaps. The surface geometly of the present tube is similar to that of Turbo-B. Three tubes with diffe...In this study, pool boiling test results are provided for the structured enhanced tubes having pores with connecting gaps. The surface geometly of the present tube is similar to that of Turbo-B. Three tubes with different pore size (0.20 mm, 0.23 mm and 0.27 mm) were manufactured and tested using R-11, R-123 and R-134a. The pore size which yields the maximum heat transfer coefficient varied depending on the refrigerant. For R-134a, the maximum heat transfer coefficient was obtained for the tube having 0.27 nun pore size. For R-11 and R- 123, the optimum pore size was 0.23 mm. One novel feature of the present tubes is that their boiling curves do not show a cross-over characteristic, which existing pored tubes do. The connecting gaps of the present tube are believed to serve an additional route for the liquid supply and delay the dry-out of the tunnel. The present tubes yield the heat transfer coefficients approximately equal to those of the existing pored enhanced tubes. At the heat flux 40 kW/m2 and saturation temperature 4.4° C, the heat transfer coefficients of the present tubes are 6.5 times larger for R-11, 6.0 times larger for R-123 and 5.0 times larger for R-134a than that of the smooth tube展开更多
In recent years, semiconductor quantum dots （QDs） have been widely used as photon sources in quantum optics due to their special properties, such as high quantum effi- ciency, narrow and tunable emission spectrum, e...In recent years, semiconductor quantum dots （QDs） have been widely used as photon sources in quantum optics due to their special properties, such as high quantum effi- ciency, narrow and tunable emission spectrum, easy manipulation, and so on. The spontaneous emission of QDs also depends on the surrounding environment.展开更多
Lithium metal stands out as an exceptionally promising anode material,boasting an extraordinarily high theoretical capacity and impressive energy density.Despite these advantageous characters,the issues of dendrite fo...Lithium metal stands out as an exceptionally promising anode material,boasting an extraordinarily high theoretical capacity and impressive energy density.Despite these advantageous characters,the issues of dendrite formation and volume expansion of lithium metal anodes lead to performance decay and safety concerns,significantly impeding their advancement towards widespread commercial viability.Herein,a lithium-rich Li-B-In composite anode with abundant lithophilic sites and outstanding structural stability is reported to address the mentioned challenges.The evenly distributed Li-In alloy in the bulk phase of anodes act as mixed ion/electron conductors and nucleation sites,facilitating accelerated Li ions transport dynamics and suppressing lithium dendrite formation.Additionally,these micron-sized Li-In particles in LiB fibers framework can enhance overall structural integrity and provide sufficient interior space to accommodate the volume changes during cycling.The electrochemical performance of Li-B-In composite anode exhibits long-term cyclability,superior rate performance and high-capacity retention.This work confirms that the synergy between a 3 D skeleton and hetero-metallic lithiophilic sites can achieve stable and durable lithium metal anodes,offering innovative insights for the practical deployment of lithium metal batteries.展开更多
基金Supported by National Natural Science Foundation of China(Grant No.61573233)Guangdong Provincial Natural Science Foundation of China(Grant No.2021A1515010661)Guangdong Provincial Special Projects in Key Fields of Colleges and Universities of China(Grant No.2020ZDZX2005).
文摘Improving the detection accuracy of rail internal defects and the generalization ability of detection models are not only the main problems in the field of defect detection but also the key to ensuring the safe operation of high-speed trains.For this reason,a rail internal defect detection method based on an enhanced network structure and module design using ultrasonic images is proposed in this paper.First,a data augmentation method was used to extend the existing image dataset to obtain appropriate image samples.Second,an enhanced network structure was designed to make full use of the high-level and low-level feature information in the image,which improved the accuracy of defect detection.Subsequently,to optimize the detection performance of the proposed model,the Mish activation function was used to design the block module of the feature extraction network.Finally,the pro-posed rail defect detection model was trained.The experimental results showed that the precision rate and F1score of the proposed method were as high as 98%,while the model’s recall rate reached 99%.Specifically,good detec-tion results were achieved for different types of defects,which provides a reference for the engineering application of internal defect detection.Experimental results verified the effectiveness of the proposed method.
基金supported by the Youth Foundation of State Key Laboratory of Explosion Science and Technology (Grant No.QNKT22-12)the State Key Program of National Natural Science Foundation of China (Grant No.12132003)。
文摘A series of ballistic experiments were performed to investigate the damage behavior of high velocity reactive material projectiles(RMPs) impacting liquid-filled tanks,and the corresponding hydrodynamic ram(HRAM) was studied in detail.PTFE/Al/W RMPs with steel-like and aluminum-like densities were prepared by a pressing/sintering process.The projectiles impacted a liquid-filled steel tank with front aluminum panel at approximately 1250 m/s.The corresponding cavity evolution characteristics and HRAM pressure were recorded by high-speed camera and pressure acquisition system,and further compared to those of steel and aluminum projectiles.Significantly different from the conical cavity formed by the inert metal projectile,the cavity formed by the RMP appeared as an ellipsoid with a conical front.The RMPs were demonstrated to enhance the radial growth velocity of cavity,the global HRAM pressure amplitude and the front panel damage,indicating the enhanced HRAM and structural damage behavior.Furthermore,combining the impact-induced fragmentation and deflagration characteristics,the cavity evolution of RMPs under the combined effect of kinetic energy impact and chemical energy release was analyzed.The mechanism of enhanced HRAM pressure induced by the RMPs was further revealed based on the theoretical model of the initial impact wave and the impulse analysis.Finally,the linear correlation between the deformation-thickness ratio and the non-dimensional impulse for the front panel was obtained and analyzed.It was determined that the enhanced near-field impulse induced by the RMPs was the dominant reason for the enhanced structural damage behavior.
基金supported by the National Natural Science Foundation of China(Grant Nos.52102302,22409161 and 52472249)the Young Talent Support Plan of Xi’an Jiaotong University(Grant No.DQ6J011)+4 种基金the Natural Science Foundation of Shaanxi Province(2023-JC-QN-0115)the China Postdoctoral Science Foundation(2022M712499)Beilin District Science and Technology Plan(GX2328)the support from Young Elite Scientists Sponsorship Program by Chinese Association for Science and Technologythe“High-Level Talent Introduction Plan”of Shaanxi Province and Siyuan Scholar of Xi’an Jiaotong University。
文摘Global interest in lithium-sulfur batteries as one of the most promising energy storage technologies has been sparked by their low sulfur cathode cost,high gravimetric,volumetric energy densities,abundant resources,and environmental friendliness.However,their practical application is significantly impeded by several serious issues that arise at the cathode-electrolyte interface,such as interface structure degradation including the uneven deposition of Li_(2)S,unstable cathode-electrolyte interphase(CEI)layer and intermediate polysulfide shuttle effect.Thus,an optimized cathode-electrolyte interface along with optimized electrodes is required for overall improvement.Herein,we comprehensively outline the challenges and corresponding strategies,including electrolyte optimization to create a dense CEI layer,regulating the Li_(2)S deposition pattern,and inhibiting the shuttle effect with regard to the solid-liquid-solid pathway,the transformation from solid-liquid-solid to solid-solid pathway,and solid-solid pathway at the cathode-electrolyte interface.In order to spur more perceptive research and hasten the widespread use of lithium-sulfur batteries,viewpoints on designing a stable interface with a deep comprehension are also put forth.
基金Supported by the National Basic Research Program of China under Grant No 2011CB610300the National Natural Science Foundation of China under Grant Nos 11102148 and 11321062the Fundamental Research Funds for Central Universities of China
文摘We report an extraordinary sound absorption enhancement in low and intermediate frequencies achieved by a thin multi-slit hybrid structure formed by incorporating micrometer scale micro-slits into a sub-millimeter scale meso-slit matrix. Theoretical and numerical results reveal that this exotic phenomenon is attributed to the noticeable velocity and temperature gradients induced at the junctures of the micro- and meso-slits, which cause significant loss of sound energy as a result of viscous and thermal effects. It is demonstrated that the proposed thin multi-slit hybrid structure with micro-scale configuration is capable of controling low frequency noise with large wavelength, which is attractive for applications where the size and weight of a sound absorber are restricted.
基金Supported by the National Natural Science Foundation of China under Grant Nos 51132004,11474096 and 11604199the Science and Technology Commission of Shanghai Municipality under Grant No 14JC1401500the Higher Education Key Program of He'nan Province under Grant Nos 17A140025 and 16A140030
文摘The femtosecond pulse shaping technique has been shown to be an effective method to control the multi-photon absorption by the light–matter interaction. Previous studies mainly focused on the quantum coherent control of the multi-photon absorption by the phase, amplitude and polarization modulation, but the coherent features of the multi-photon absorption depending on the energy level structure, the laser spectrum bandwidth and laser central frequency still lack in-depth systematic research. In this work, we further explore the coherent features of the resonance-mediated two-photon absorption in a rubidium atom by varying the energy level structure, spectrum bandwidth and central frequency of the femtosecond laser field. The theoretical results show that the change of the intermediate state detuning can effectively influence the enhancement of the near-resonant part, which further affects the transform-limited （TL）-normalized final state population maximum. Moreover, as the laser spectrum bandwidth increases, the TL-normalized final state population maximum can be effectively enhanced due to the increase of the enhancement in the near-resonant part, but the TL-normalized final state population maximum is constant by varying the laser central frequency. These studies can provide a clear physical picture for understanding the coherent features of the resonance-mediated two-photon absorption, and can also provide a theoretical guidance for the future applications.
基金supported by the National Natural Science Foundation of China(No.52102318)the Fellowship of China Postdoctoral Science Foundation(Nos.2021TQ0287 and 2022M722855)Xingdian Talent Support Foundation of Yunnan Province(2020).
文摘As a promising cathode material for aqueous zinc-ion batteries,1T-MoS_(2)has been extensively investigated because of its facile two-dimensional ion-diffusion channels and high electrical conductivity.However,the limited number of available Zn storage sites,i.e.,limited capacity,hinders its application because the inserted Zn^(2+),which form strong electrostatic interactions with 1T-MoS_(2),preventing subsequent Zn^(2+)insertion.Currently,the approach of enlarging the interlayer distance to reduce electrostatic interactions has been commonly used to enhance the capacity and reduce Zn^(2+)migration barriers.However,an enlarged interlayer spacing can weaken the van der Waals force between 1T-MoS_(2)monolayers,easily disrupting the structural stability.Herein,to address this issue,an effective strategy based on Fe doping is proposed for 1T-MoS_(2)(Fe-1T-MoS_(2)).The theoretical calculations reveal that Fe doping can simultaneously moderate the rate of decrease in the adsorption energy after gradually increasing the number of stored atoms,and enhance the electron delocalization on metal-O bonds.Therefore,the experiment results show that Fe doping can simultaneously activate more Zn storage sites,thus enhancing the capacity,and stabilize the structural stability for improved cycling performance.Consequently,Fe-1T-MoS_(2)exhibits a larger capacity(189 mAh·g^(-1)at 0.1 A·g^(-1))and superior cycling stability(78%capacity retention after 400 cycles at 2 A·g^(-1))than pure 1T-MoS_(2).This work may open up a new avenue for constructing high-performance MoS_(2)-based cathodes.
基金funded by Ministry of Education,University and Research(MIUR)ex-60% research fund University of Brescia,Italy
文摘Depression refers to a series of mental health issues characterized by loss of interest and enjoyment in everyday life,low mood and selected emotional,cognitive,physical and behavioral symptoms.Depression is a common disorder,affecting 5–15%of the general population.When diagnosed as major depressive disorder（MDD）,patients are currentlytreated with pharmacological agents such as serotonin or noradren- aline uptake inhibitors （SSRI or SNRI） or tricyclics.
基金theR &D Management Center for Energy and Resources ofKorea
文摘In this study, pool boiling test results are provided for the structured enhanced tubes having pores with connecting gaps. The surface geometly of the present tube is similar to that of Turbo-B. Three tubes with different pore size (0.20 mm, 0.23 mm and 0.27 mm) were manufactured and tested using R-11, R-123 and R-134a. The pore size which yields the maximum heat transfer coefficient varied depending on the refrigerant. For R-134a, the maximum heat transfer coefficient was obtained for the tube having 0.27 nun pore size. For R-11 and R- 123, the optimum pore size was 0.23 mm. One novel feature of the present tubes is that their boiling curves do not show a cross-over characteristic, which existing pored tubes do. The connecting gaps of the present tube are believed to serve an additional route for the liquid supply and delay the dry-out of the tunnel. The present tubes yield the heat transfer coefficients approximately equal to those of the existing pored enhanced tubes. At the heat flux 40 kW/m2 and saturation temperature 4.4° C, the heat transfer coefficients of the present tubes are 6.5 times larger for R-11, 6.0 times larger for R-123 and 5.0 times larger for R-134a than that of the smooth tube
基金supported by the National Natural Science Foundation of China(Nos.11374289 and 61590932)the National Key R&D Program(No.2016YFA0301700)+2 种基金the Innovation Funds from the Chinese Academy of Sciences(No.60921091)the Fundamental Research Funds for the Central Universitiesthe Open Fund of the State Key Laboratory on Integrated Optoelectronics(No.IOSKL2015KF12)
文摘In recent years, semiconductor quantum dots （QDs） have been widely used as photon sources in quantum optics due to their special properties, such as high quantum effi- ciency, narrow and tunable emission spectrum, easy manipulation, and so on. The spontaneous emission of QDs also depends on the surrounding environment.
基金Project(2023YFC3905904)supported by the National Key Research and Development Program,ChinaProject(2220197000221)supported by the Team of Foshan National Hi-Tech Industrial Development Zone Industrialization Entrepreneurial Teams Program,ChinaProject(2024ZZTS0373)supported by the Central South University Graduate Student Autonomous Exploration Innovative Programme,China。
文摘Lithium metal stands out as an exceptionally promising anode material,boasting an extraordinarily high theoretical capacity and impressive energy density.Despite these advantageous characters,the issues of dendrite formation and volume expansion of lithium metal anodes lead to performance decay and safety concerns,significantly impeding their advancement towards widespread commercial viability.Herein,a lithium-rich Li-B-In composite anode with abundant lithophilic sites and outstanding structural stability is reported to address the mentioned challenges.The evenly distributed Li-In alloy in the bulk phase of anodes act as mixed ion/electron conductors and nucleation sites,facilitating accelerated Li ions transport dynamics and suppressing lithium dendrite formation.Additionally,these micron-sized Li-In particles in LiB fibers framework can enhance overall structural integrity and provide sufficient interior space to accommodate the volume changes during cycling.The electrochemical performance of Li-B-In composite anode exhibits long-term cyclability,superior rate performance and high-capacity retention.This work confirms that the synergy between a 3 D skeleton and hetero-metallic lithiophilic sites can achieve stable and durable lithium metal anodes,offering innovative insights for the practical deployment of lithium metal batteries.
