Pulse pile-up is a problem in nuclear spectroscopy and nuclear reaction studies that occurs when two pulses overlap and distort each other,degrading the quality of energy and timing information.Different methods have ...Pulse pile-up is a problem in nuclear spectroscopy and nuclear reaction studies that occurs when two pulses overlap and distort each other,degrading the quality of energy and timing information.Different methods have been used for pile-up rejection,both digital and analogue,but some pile-up events may contain pulses of interest and need to be reconstructed.The paper proposes a new method for reconstructing pile-up events acquired with a neutron detector array(NEDA)using an one-dimensional convolutional autoencoder(1D-CAE).The datasets for training and testing the 1D-CAE are created from data acquired from the NEDA.The new pile-up signal reconstruction method is evaluated from the point of view of how similar the reconstructed signals are to the original ones.Furthermore,it is analysed considering the result of the neutron-gamma discrimination based on charge comparison,comparing the result obtained from original and reconstructed signals.展开更多
Metal matrix self-lubricating materials lie at the core of cutting-edge aerospace,mechanical,and electrical industries,which demand technological performances that cannot be met by traditional liquid lubricants.Rapid ...Metal matrix self-lubricating materials lie at the core of cutting-edge aerospace,mechanical,and electrical industries,which demand technological performances that cannot be met by traditional liquid lubricants.Rapid innovation in nanocarbon materials in recent years enabled rapid development of advanced nanocomposites for applications in structural engineering and functional devices.Carbonous materials(e.g.,graphite,graphene and carbon nanotubes),exhibit a wide range of unique electrical,mechanical,and thermal properties,which are also considered ideal lubricating reinforcements for metal matrix nanocomposites(MMCs)with superior mechanical and tribological properties.In this review,we first showcase the distinctive features of the constituents commonly employed in self-lubricating MMCs,encompassing the high-strength metallic matrix and nano-carbonous reinforcement.Then,we present a comprehensive overview of the recent advancements in preparation techniques for these advanced MMCs,followed by an in-depth discussion on their corresponding tribological properties and wear mechanisms.We close this review by outlining key problems to be solved and the future trend of the development in self-lubricating MMCs.展开更多
Lorentz force electrical impedance tomography （LFEIT） combines ultrasound stimulation and electromagnetic field detection with the goal of creating a high contrast and high resolution hybrid imaging modality. In thi...Lorentz force electrical impedance tomography （LFEIT） combines ultrasound stimulation and electromagnetic field detection with the goal of creating a high contrast and high resolution hybrid imaging modality. In this study, pulse compression working together with a linearly frequency modulated ultrasound pulse was investigated in LFEIT. Experiments were done on agar phantoms having the same level of electrical conductivity as soft biological tissues. The results showed that：（i） LFEIT using pulse compression could detect the location of the electrical conductivity variations precisely; （ii） LFEIT using pulse compression could get the same performance of detecting electrical conductivity variations as the traditional LFEIT using high voltage narrow pulse but reduce the peak stimulating power to the transducer by 25.5 dB; （iii） axial resolution of 1 mm could be obtained using modulation frequency bandwidth 2 MHz.展开更多
Understanding mechanical relaxation, such as primary（α） and secondary（β） relaxation, is key to unravel the intertwined relation between the atomic dynamics and non-equilibrium thermodynamics in metallic glasses....Understanding mechanical relaxation, such as primary（α） and secondary（β） relaxation, is key to unravel the intertwined relation between the atomic dynamics and non-equilibrium thermodynamics in metallic glasses. At a fundamental level, relaxation, plastic deformation, glass transition, and crystallization of metallic glasses are intimately linked to each other, which can be related to atomic packing, inter-atomic diffusion, and cooperative atom movement. Conceptually, βrelaxation is usually associated with structural heterogeneities intrinsic to metallic glasses. However, the details of such structural heterogeneities, being masked by the meta-stable disordered long-range structure, are yet to be understood. In this paper, we briefly review the recent experimental and simulation results that were attempted to elucidate structural heterogeneities in metallic glasses within the framework of β relaxation. In particular, we will discuss the correlation amongβ relaxation, structural heterogeneity, and mechanical properties of metallic glasses.展开更多
Full quantum mechanical calculations are performed to determine the broadening in the far wings of the cesium D1 and D2 line shapes arising from elastic collisions of Cs atom with inert helium atoms. The potential ene...Full quantum mechanical calculations are performed to determine the broadening in the far wings of the cesium D1 and D2 line shapes arising from elastic collisions of Cs atom with inert helium atoms. The potential energy curves of the low-lying CsHe molecular states, as well as the related transition dipole moments, are carefully computed from ab initio methods based on state-averaged complete active space self-consistent field-multireference configuration interaction(SACASSCF-MRCI) calculations, involving the spin-orbit effect, and taking into account the Davidson and BSSE corrections.The absorption and emission reduced coefficients are determined in the temperature and wavelength ranges of 323-3000 K and 800-1000 nm, respectively. Both profiles of the absorption and the emission are dominated by the free-free transitions,and exhibit a satellite peak in the blue wing near the wavelength 825 nm, attributed to B^2Σ1/2^+→ X^2Σ1/2^+/transitions. The results are in good agreement with previous experimental and theoretical works.展开更多
Background:In Mediterranean mountain socio-ecosystems,both grazing by livestock and the dry season may influence tree regeneration.However,the relative contributions of these drivers are poorly known,even though prese...Background:In Mediterranean mountain socio-ecosystems,both grazing by livestock and the dry season may influence tree regeneration.However,the relative contributions of these drivers are poorly known,even though present and future canopy composition might result from past and present variations in climate and herbivore density.This study aims to test how semi-feral cattle presence and season affect tree regeneration.Methods:The study was conducted using permanent plots inside and outside a cattle exclosure in an old-growth Mediterranean forest.Saplings and seedlings were counted five times per year(winter,early spring,middle spring,summer,fall)and monitored over 7 yrs.Results:Semi-feral cattle exclusion increased Acer,Fagus,Ilex,Pinus,Prunus and Quercus sapling densities and increased Acer,Fraxinus,Ilex,Quercus and Sorbus seedling densities.Interestingly,the dry season did not exert any noticeable effects on the sapling or seedling densities of any of the studied taxa.Discussion:Semi-feral cattle presence may limit tree regeneration through taxon-dependent effects,which suggests that the current decrease in grazing livestock across the Mediterranean basin will modify recruitment processes and,likely,future forest composition.Conclusions:Semi-feral cattle presence acts as a selective driver of tree community composition.展开更多
基金partially supported by MICIU MCIN/AEI/10.13039/501100011033Spain with grant PID2020-118265GB-C42,-C44,PRTR-C17.I01+1 种基金Generalitat Valenciana,Spain with grant CIPROM/2022/54,ASFAE/2022/031,CIAPOS/2021/114the EU NextGenerationEU,ESF funds,and the National Science Centre (NCN),Poland (grant No.2020/39/D/ST2/00466)
文摘Pulse pile-up is a problem in nuclear spectroscopy and nuclear reaction studies that occurs when two pulses overlap and distort each other,degrading the quality of energy and timing information.Different methods have been used for pile-up rejection,both digital and analogue,but some pile-up events may contain pulses of interest and need to be reconstructed.The paper proposes a new method for reconstructing pile-up events acquired with a neutron detector array(NEDA)using an one-dimensional convolutional autoencoder(1D-CAE).The datasets for training and testing the 1D-CAE are created from data acquired from the NEDA.The new pile-up signal reconstruction method is evaluated from the point of view of how similar the reconstructed signals are to the original ones.Furthermore,it is analysed considering the result of the neutron-gamma discrimination based on charge comparison,comparing the result obtained from original and reconstructed signals.
基金support by the National Key Research and Development Program of China(2022YFB3809000)the Natural Science Foundation of China(No.52175188)+2 种基金Key Research and Development Program of Shaanxi Province(2023-YBGY-434)the Open Fund of Liaoning Provincial Key Laboratory of Aero-engine Materials Tribology(Grant No.LKLAMTF202301)State Key Laboratory for Mechanical Behavior of Materials(20222412).
文摘Metal matrix self-lubricating materials lie at the core of cutting-edge aerospace,mechanical,and electrical industries,which demand technological performances that cannot be met by traditional liquid lubricants.Rapid innovation in nanocarbon materials in recent years enabled rapid development of advanced nanocomposites for applications in structural engineering and functional devices.Carbonous materials(e.g.,graphite,graphene and carbon nanotubes),exhibit a wide range of unique electrical,mechanical,and thermal properties,which are also considered ideal lubricating reinforcements for metal matrix nanocomposites(MMCs)with superior mechanical and tribological properties.In this review,we first showcase the distinctive features of the constituents commonly employed in self-lubricating MMCs,encompassing the high-strength metallic matrix and nano-carbonous reinforcement.Then,we present a comprehensive overview of the recent advancements in preparation techniques for these advanced MMCs,followed by an in-depth discussion on their corresponding tribological properties and wear mechanisms.We close this review by outlining key problems to be solved and the future trend of the development in self-lubricating MMCs.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51137004 and 61427806)the Scientific Instrument and Equipment Development Project of Chinese Academy of Sciences(Grant No.YZ201507)the China Scholarship Council(Grant No.201604910849)
文摘Lorentz force electrical impedance tomography （LFEIT） combines ultrasound stimulation and electromagnetic field detection with the goal of creating a high contrast and high resolution hybrid imaging modality. In this study, pulse compression working together with a linearly frequency modulated ultrasound pulse was investigated in LFEIT. Experiments were done on agar phantoms having the same level of electrical conductivity as soft biological tissues. The results showed that：（i） LFEIT using pulse compression could detect the location of the electrical conductivity variations precisely; （ii） LFEIT using pulse compression could get the same performance of detecting electrical conductivity variations as the traditional LFEIT using high voltage narrow pulse but reduce the peak stimulating power to the transducer by 25.5 dB; （iii） axial resolution of 1 mm could be obtained using modulation frequency bandwidth 2 MHz.
基金supported by the National Natural Science Foundation of China(Grant Nos.51401192 and 51611130120)the Natural Science Foundation of Shaanxi Province,China(Grant No.2016JM5009)+5 种基金the Fundamental Research Funds for the Central Universities of China(Grant Nos.3102015ZY027 and 3102015BJ(Ⅱ)JGZ019)the Aeronautical Science Foundation of China(Grant No.2015ZF53072)supported by the Hong Kong Scholar Program of China(Grant No.XJ2015056)the support of MINECO(Grant No.FIS2014-54734-P)Generalitat de Catalunya(Grant No.2014SGR00581)supported by the Research Grant Council,the Hong Kong City of China,through the General Research Fund(Grant No.City U11214914)
文摘Understanding mechanical relaxation, such as primary（α） and secondary（β） relaxation, is key to unravel the intertwined relation between the atomic dynamics and non-equilibrium thermodynamics in metallic glasses. At a fundamental level, relaxation, plastic deformation, glass transition, and crystallization of metallic glasses are intimately linked to each other, which can be related to atomic packing, inter-atomic diffusion, and cooperative atom movement. Conceptually, βrelaxation is usually associated with structural heterogeneities intrinsic to metallic glasses. However, the details of such structural heterogeneities, being masked by the meta-stable disordered long-range structure, are yet to be understood. In this paper, we briefly review the recent experimental and simulation results that were attempted to elucidate structural heterogeneities in metallic glasses within the framework of β relaxation. In particular, we will discuss the correlation amongβ relaxation, structural heterogeneity, and mechanical properties of metallic glasses.
文摘Full quantum mechanical calculations are performed to determine the broadening in the far wings of the cesium D1 and D2 line shapes arising from elastic collisions of Cs atom with inert helium atoms. The potential energy curves of the low-lying CsHe molecular states, as well as the related transition dipole moments, are carefully computed from ab initio methods based on state-averaged complete active space self-consistent field-multireference configuration interaction(SACASSCF-MRCI) calculations, involving the spin-orbit effect, and taking into account the Davidson and BSSE corrections.The absorption and emission reduced coefficients are determined in the temperature and wavelength ranges of 323-3000 K and 800-1000 nm, respectively. Both profiles of the absorption and the emission are dominated by the free-free transitions,and exhibit a satellite peak in the blue wing near the wavelength 825 nm, attributed to B^2Σ1/2^+→ X^2Σ1/2^+/transitions. The results are in good agreement with previous experimental and theoretical works.
基金the Observatoire des Sciences de l’Univers OREME at Montpellier,France(INSU-CNRS).
文摘Background:In Mediterranean mountain socio-ecosystems,both grazing by livestock and the dry season may influence tree regeneration.However,the relative contributions of these drivers are poorly known,even though present and future canopy composition might result from past and present variations in climate and herbivore density.This study aims to test how semi-feral cattle presence and season affect tree regeneration.Methods:The study was conducted using permanent plots inside and outside a cattle exclosure in an old-growth Mediterranean forest.Saplings and seedlings were counted five times per year(winter,early spring,middle spring,summer,fall)and monitored over 7 yrs.Results:Semi-feral cattle exclusion increased Acer,Fagus,Ilex,Pinus,Prunus and Quercus sapling densities and increased Acer,Fraxinus,Ilex,Quercus and Sorbus seedling densities.Interestingly,the dry season did not exert any noticeable effects on the sapling or seedling densities of any of the studied taxa.Discussion:Semi-feral cattle presence may limit tree regeneration through taxon-dependent effects,which suggests that the current decrease in grazing livestock across the Mediterranean basin will modify recruitment processes and,likely,future forest composition.Conclusions:Semi-feral cattle presence acts as a selective driver of tree community composition.
