(Ga,Fe)Sb is a promising magnetic semiconductor(MS)for spintronic applications because its Curie temperature(T_(C))is above 300 K when the Fe concentration is higher than 20%.However,the anisotropy constant Ku of(Ga,F...(Ga,Fe)Sb is a promising magnetic semiconductor(MS)for spintronic applications because its Curie temperature(T_(C))is above 300 K when the Fe concentration is higher than 20%.However,the anisotropy constant Ku of(Ga,Fe)Sb is below 7.6×10^(3)erg/cm^(3)when Fe concentration is lower than 30%,which is one order of magnitude lower than that of(Ga,Mn)As.To address this issue,we grew Ga_(1-x-y)Fe_(x)Ni_(y)Sb films with almost the same x(≈24%)and different y to characterize their magnetic and electrical transport properties.We found that the magnetic anisotropy of Ga_(0.76-y)Fe_(0.24)Ni_(y)Sb can be enhanced by increasing y,in which Ku is negligible at y=1.7%but increases to 3.8×10^(5)erg/cm^(3)at y=6.1%(T_(C)=354 K).In addition,the hole mobility(μ)of Ga_(1-x-y)Fe_(x)Ni_(y)Sb reaches 31.3 cm^(2)/(V∙s)at x=23.7%,y=1.7%(T_(C)=319 K),which is much higher than the mobility of Ga_(1-x)Fe_(x)Sb at x=25.2%(μ=6.2 cm^(2)/(V∙s)).Our results provide useful information for enhancing the magnetic anisotropy and hole mobility of(Ga,Fe)Sb by using Ni co-doping.展开更多
High-purity germanium(HPGe)detectors,which are used for direct dark matter detection,have the advantages of a low threshold and excellent energy resolution.The surface passivation of HPGe has become crucial for achiev...High-purity germanium(HPGe)detectors,which are used for direct dark matter detection,have the advantages of a low threshold and excellent energy resolution.The surface passivation of HPGe has become crucial for achieving an extremely low energy threshold.In this study,first-principles simulations,passivation film preparation,and metal oxide semiconductor(MOS)capacitor characterization were combined to study surface passivation.Theoretical calculations of the energy band structure of the -H,-OH,and -NH_(2) passivation groups on the surface of Ge were performed,and the interface state density and potential with five different passivation groups with N/O atomic ratios were accurately analyzed to obtain a stable surface state.Based on the theoretical calculation results,the surface passivation layers of the Ge_(2)ON_(2) film were prepared via magnetron sputtering in accordance with the optimum atomic ratio structure.The microstructure,C-V,and I-V electrical properties of the layers,and the passivation effect of the Al/Ge_(2)ON_(2)/Ge MOS were characterized to test the interface state density.The mean interface state density obtained by the Terman method was 8.4×10^(11) cm^(-2) eV^(-1).The processing of germanium oxynitrogen passivation films is expected to be used in direct dark matter detection of the HPGe detector surface passivation technology to reduce the detector leakage currents.展开更多
The paper presents GEneral ReadOut (GERO), a general readout ASIC based on a switched capacitor array for micro-pattern gas detectors. It aims at providing general readout electronics for low-to-medium event-rate gas ...The paper presents GEneral ReadOut (GERO), a general readout ASIC based on a switched capacitor array for micro-pattern gas detectors. It aims at providing general readout electronics for low-to-medium event-rate gas detectors with high sampling frequency, configurable storage depth, and data digitalization. The first prototype GERO chip integrates 16 channels and was fabricated using a 0.18-lm CMOS process. Each channel consists of a sampling array working in a ping-pong mode, a storage array with a 1024-cell depth, and 32 Wilkinson analog-todigital converters. The detailed design and test results are presented in the paper.展开更多
Polytetrafluoroethylene(PTFE)is a low-background polymer that is applied to several applications in rare-event detection and underground low-background experiments.PTFE-based electronic substrates are important for re...Polytetrafluoroethylene(PTFE)is a low-background polymer that is applied to several applications in rare-event detection and underground low-background experiments.PTFE-based electronic substrates are important for reducing the detection limit of high-purity germanium detectors and scintillator calorimeters,which are widely applied in dark matter and 0υββdetection experiments.The traditional adhesive bonding method between PTFE and copper is not conducive to working in liquid nitrogen and extremely low-temperature environments.To avoid adhesive bonding,PTFE must be processed for surface metallization owing to the mismatch between the PTFE and copper conductive layer.Low-background PTFE matrix composites(m-PTFE)were selected to improve the electrical and mechanical properties of PTFE by introducing SiO_(2)/TiO_(2) particles.The microstructures,surface elements,and electrical properties of PTFE and m-PTFE were characterized and analyzed following ion implantation.PTFE and m-PTFE surfaces were found to be broken,degraded,and cross-linked by ion implantation,resulting in C=C conjugated double bonds,increased surface energy,and increased surface roughness.Comparably,the surface roughness,bond strength,and conjugated double bonds of m-PTFE were significantly more intense than those of PTFE.Moreover,the interface bonding theory between PTFE and the metal copper foil was analyzed using the direct metallization principle.Therefore,the peel strength of the optimized electronic substrates was higher than that of the industrial standard at extremely low temperatures,while maintaining excellent electrical properties.展开更多
Spectral computed tomography(CT) based on photon counting detectors(PCDs) is a well-researched topic in the field of X-ray imaging. When PCD is applied in a spectral CT system, the PCD energy thresholds must be carefu...Spectral computed tomography(CT) based on photon counting detectors(PCDs) is a well-researched topic in the field of X-ray imaging. When PCD is applied in a spectral CT system, the PCD energy thresholds must be carefully selected, especially for K-edge imaging, which is an important spectral CT application. This paper presents a threshold selection method that yields better-quality images in K-edge imaging. The main idea is to optimize the energy thresholds ray-by-ray according to the targeted component coefficients, followed by obtaining an overall optimal energy threshold by frequency voting. A low-dose pre-scan is used in practical implementations to estimate the line integrals of the component coefficients for the basis functions. The variance of the decomposed component coefficients is then minimized using the Cramer–Rao lower bound method with respect to the energy thresholds. The optimal energy thresholds are then used to take a full scan and gain better image reconstruction with less noise than would be given by a full scan using the non-optimal energy thresholds. Simulations and practical experiments on imaging iodine and gadolinium solutions, which are commonly used as contrast agents in medical applications, were used to validate the method. The noise was significantly reduced with the same dose relative to the non-optimal energy thresholds in both simulations and in practical experiments.展开更多
Anti-perovskite solid-state electrolyte Li_(2)OHCl usually exhibits orthorhombic phase and low ionic conductivity at room temperature.However,its ionic conductivity increases greatly when the temperature is up to 40℃...Anti-perovskite solid-state electrolyte Li_(2)OHCl usually exhibits orthorhombic phase and low ionic conductivity at room temperature.However,its ionic conductivity increases greatly when the temperature is up to 40℃,while it goes through an orthorhombic-to-cubic phase transition.The cubic Li_(2)OHCl with high ionic conductivity is stabilized at room temperature and even lower temperature about 10℃ by a simple synthesis method of wet mechanical milling.The cubic Li_(2)OHCl prepared by this method performs an ionic conductivity of 4.27×10^(-6) S/cm at room temperature,about one order of magnitude higher than that of the orthorhombic Li_(2)OHCl.The phase-transition temperature is decreased to around 10℃.Moreover,it can still remain cubic phase after heat treatment at 210℃.This work delivers a huge potential of fabricating high ionic conductivity phase antiperovskite solid-state electrolyte materials by wet mechanical milling.展开更多
Recently, neural implicit function-basedrepresentation has attracted more and more attention,and has been widely used to represent surfacesusing differentiable neural networks. However, surfacereconstruction from poin...Recently, neural implicit function-basedrepresentation has attracted more and more attention,and has been widely used to represent surfacesusing differentiable neural networks. However, surfacereconstruction from point clouds or multi-view imagesusing existing neural geometry representations stillsuffer from slow computation and poor accuracy. Toalleviate these issues, we propose a multi-scale hashencoding-based neural geometry representation whicheffectively and efficiently represents the surface asa signed distance field. Our novel neural networkstructure carefully combines low-frequency Fourierposition encoding with multi-scale hash encoding. Theinitialization of the geometry network and geometryfeatures of the rendering module are accordinglyredesigned. Our experiments demonstrate that theproposed representation is at least 10 times faster forreconstructing point clouds with millions of points.It also significantly improves speed and accuracyof multi-view reconstruction. Our code and modelsare available at https://github.com/Dengzhi-USTC/Neural-Geometry-Reconstruction.展开更多
The Jiangmen Underground Neutrino Observatory(JUNO)is a large liquid scintillator detector designed to explore many topics in fundamental physics.In this study,the potential of searching for proton decay in the p→νK...The Jiangmen Underground Neutrino Observatory(JUNO)is a large liquid scintillator detector designed to explore many topics in fundamental physics.In this study,the potential of searching for proton decay in the p→νK^(+)mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification.Moreover,the excellent energy resolution of JUNO permits suppression of the sizable background caused by other delayed signals.Based on these advantages,the detection efficiency for the proton decay via p→νK^(+)is 36.9%±4.9%with a background level of 0.2±0.05(syst)±0.2(stat)events after 10 years of data collection.The estimated sensitivity based on 200 kton-years of exposure is 9.6×1033 years,which is competitive with the current best limits on the proton lifetime in this channel and complements the use of different detection technologies.展开更多
We report the first results on ^(76)Ge neutrinoless double beta decay from stage one of the China dark-matter experiment(CDEX).A p-type point-contact high-purity germanium detector with a mass of 994 g has been instal...We report the first results on ^(76)Ge neutrinoless double beta decay from stage one of the China dark-matter experiment(CDEX).A p-type point-contact high-purity germanium detector with a mass of 994 g has been installed to detect neutrinoless double beta decay events, as well as to directly detect dark matter particles. An exposure of 304 kg d has been analyzed over a wide spectral band from 500 keV to 3 MeV. The average event rate obtained was about 0.012 counts per keV per kg per day over the 2.039 MeV energy range. The half-life of ^(76)Ge neutrinoless double beta decay derived based on this result is T^(0ν)1/2>6.4×10^(22) yr(90% C.L.). An upper limit on the effective Majorana-neutrino mass of 5.0 eV has been achieved.展开更多
Machine-learned interatomic potentials based on local environment descriptors represent a transformative leap over traditional potentials based on rigid functional forms in terms of prediction accuracy.However,a chall...Machine-learned interatomic potentials based on local environment descriptors represent a transformative leap over traditional potentials based on rigid functional forms in terms of prediction accuracy.However,a challenge in their application to ionic systems is the treatment of long-ranged electrostatics.Here,we present a highly accurate electrostatic Spectral Neighbor Analysis Potential(eSNAP)for ionicα-Li3N,a prototypical lithium superionic conductor of interest as a solid electrolyte or coating for rechargeable lithium-ion batteries.We show that the optimized eSNAP model substantially outperforms traditional Coulomb–Buckingham potential in the prediction of energies and forces,as well as various properties,such as lattice constants,elastic constants,and phonon dispersion curves.We also demonstrate the application of eSNAP in long-time,large-scale Li diffusion studies in Li3N,providing atomistic insights into measures of concerted ionic motion(e.g.,the Haven ratio)and grain boundary diffusion.This work aims at providing an approach to developing quantum-accurate force fields for multi-component ionic systems under the SNAP formalism,enabling large-scale atomistic simulations for such systems.展开更多
We present weakly interacting massive particles(WIMPs) search results performed using two approaches of effective field theory from the China Dark Matter Experiment(CDEX), based on the data from both CDEX-1B and CDEX-...We present weakly interacting massive particles(WIMPs) search results performed using two approaches of effective field theory from the China Dark Matter Experiment(CDEX), based on the data from both CDEX-1B and CDEX-10 stages. In the nonrelativistic effective field theory approach, both time-integrated and annual modulation analyses were used to set new limits for the coupling of WIMP-nucleon effective operators at 90% confidence level(C.L.) and improve over the current bounds in the low mχregion. In the chiral effective field theory approach, data from CDEX-10 were used to set an upper limit on WIMP-pion coupling at 90% C.L. We for the first time extended the limit to the m_(χ)<6 GeV/c^(2) region.展开更多
The CDEX-10 experiment searches for light weakly interacting massive particles, a form of dark matter, at the China Jinping Underground Laboratory, where approximately 10 kg of germanium detectors are arranged in an a...The CDEX-10 experiment searches for light weakly interacting massive particles, a form of dark matter, at the China Jinping Underground Laboratory, where approximately 10 kg of germanium detectors are arranged in an array and immersed in liquid nitrogen. Herein, we report on the experimental apparatus, detector characterization, and spectrum analysis of one prototype detector. Owing to the higher rise-time resolution of the CDEX-10 prototype detector as compared with CDEX-1 B, we identified the origin of an observed category of extremely fast events. For data analysis of the CDEX-10 prototype detector, we introduced and applied an improved bulk/surface event discrimination method. The results of the new method were compared to those of the CDEX-1 B spectrum. Both sets of results showed good consistency in the 0-12 ke Vee energy range, except for the 8.0 keV K-shell X-ray peak from the external copper.展开更多
The Jiangmen Underground Neutrino Observatory(JUNO)features a 20 kt multi-purpose underground liquid scintillator sphere as its main detector.Some of JUNO's features make it an excellent location for^8B solar neut...The Jiangmen Underground Neutrino Observatory(JUNO)features a 20 kt multi-purpose underground liquid scintillator sphere as its main detector.Some of JUNO's features make it an excellent location for^8B solar neutrino measurements,such as its low-energy threshold,high energy resolution compared with water Cherenkov detectors,and much larger target mass compared with previous liquid scintillator detectors.In this paper,we present a comprehensive assessment of JUNO's potential for detecting^8B solar neutrinos via the neutrino-electron elastic scattering process.A reduced 2 MeV threshold for the recoil electron energy is found to be achievable,assuming that the intrinsic radioactive background^(238)U and^(232)Th in the liquid scintillator can be controlled to 10^(-17)g/g.With ten years of data acquisition,approximately 60,000 signal and 30,000 background events are expected.This large sample will enable an examination of the distortion of the recoil electron spectrum that is dominated by the neutrino flavor transformation in the dense solar matter,which will shed new light on the inconsistency between the measured electron spectra and the predictions of the standard three-flavor neutrino oscillation framework.IfDelta m^(2)_(21)=4.8times10^(-5);(7.5times10^(-5))eV^(2),JUNO can provide evidence of neutrino oscillation in the Earth at approximately the 3sigma(2sigma)level by measuring the non-zero signal rate variation with respect to the solar zenith angle.Moreover,JUNO can simultaneously measureDelta m^2_(21)using^8B solar neutrinos to a precision of 20% or better,depending on the central value,and to sub-percent precision using reactor antineutrinos.A comparison of these two measurements from the same detector will help understand the current mild inconsistency between the value of Delta m^2_(21)reported by solar neutrino experiments and the KamLAND experiment.展开更多
Anti-perovskites X3BA,as the electrically inverted derivatives of perovskites ABX3,have attracted tremendous attention for their good performances in multiple disciplines,especially in energy storage batteries.The Li/...Anti-perovskites X3BA,as the electrically inverted derivatives of perovskites ABX3,have attracted tremendous attention for their good performances in multiple disciplines,especially in energy storage batteries.The Li/Na-rich antiperovskite(LiRAP/NaRAP)solid-state electrolytes(SSEs)typically show high ionic conductivities and high chemical/electrochemical stability toward the Li-metal anode,illustrating their great potential for applications in the Limetal batteries(LMBs)using nonaqueous liquid electrolyte or all-solid-state electrolyte.The antiperovskites have been studied as artificial solid electrolyte interphase for Li-metal anode protection,film SSEs for thin-film batteries,and low melting temperature solid electrolyte enabling melt-infiltration for the manufacture of all-solid-state lithium batteries.Transition metal-doped LiRAPs as cathodes have demonstrated a high discharge specific capacity and good rate capability in the Li-ion batteries(LIBs).Additionally,the underlying scientific principles in antiperovskites with flexible structural features have also been extensively studied.In this review,we comprehensively summarize the development,structural design,ionic conductivity and ion transportation mechanism,chemical/electrochemical stability,and applications of some antiperovskite materials in energy storage batteries.The perspective for enhancing the performance of the antiperovskites is also provided as a guide for future development and applications in energy storage.展开更多
JUNO is a multi-purpose neutrino observatory under construction in the south of China.This publication presents new sensitivity estimates for the measurement of the △m_(31)^(2),△m_(21)^(2),sin^(2)θ_(12),and sin^(2)...JUNO is a multi-purpose neutrino observatory under construction in the south of China.This publication presents new sensitivity estimates for the measurement of the △m_(31)^(2),△m_(21)^(2),sin^(2)θ_(12),and sin^(2)θ_(13) oscillation parameters using reactor antineutrinos,which is one of the primary physics goals of the experiment.The sensitivities are obtained using the best knowledge available to date on the location and overburden of the experimental site,the nuclear reactors in the surrounding area and beyond,the detector response uncertainties,and the reactor antineutrino spectral shape constraints expected from the TAO satellite detector.It is found that the △m_(21)^(2) and sin^(2)θ_(12) oscillation parameters will be determined to 0.5%precision or better in six years of data collection.In the same period,the △m_(31)^(2) parameter will be determined to about 0.2%precision for each mass ordering hypothesis.The new precision represents approximately an order of magnitude improvement over existing constraints for these three parameters.展开更多
Introduction Time projection chamber(TPC)with micropattern gaseous detectors(MPGDs)as readout has been one of the research hotspots in recent years.MPGD-based TPC has been applying to many experiments due to its high ...Introduction Time projection chamber(TPC)with micropattern gaseous detectors(MPGDs)as readout has been one of the research hotspots in recent years.MPGD-based TPC has been applying to many experiments due to its high spatial and energy resolutions in 3D track measurement.Purpose A novel sampling TPC detector based on thick gaseous electron multiplier(THGEM)was developed to measure the low-energy electron tracks online from 0.1 to 50 MeV with a 100μm spatial resolution in a vacuum tank.The tracks will be extrapolated to determine the hit positions on a target about 200mm behind the TPC.Methods and materials A new type of self-developed THGEM detector was chosen as the TPC readout unit.The field cage has two 50×50mm2 windows welded by Gold-plated tungsten wires for low-energy electrons passing through.The front-end electronics was designed with a self-developed application specific integrated circuit chip,i.e.,CASA-GEM.Seven columns of readout pads were used to equidistantly sample the electron tracks in a length of 75mm.Each column has 72 pads of 0.56×0.56mm2 and two additional strips along each column for drift time measurement.Both Geant4 and Garfield++were chosen to simulate and optimize the detector,such as the penetration efficiency,electric field in field cage and operating gas pressure.Results The design and the preliminary performances of the TPC detector were verified by beam test andβsource test.A drift velocity of 3.415±0.103 cm/μs was measured at 125 V/cm in Ar+iC4H10(97:3)forπ−.The electron detection efficiency is about 88%forβsource.And the gain of the double THGEM reached more than 1.0×10^(4).展开更多
Background The Multi-Wire Drift Chamber(MWDC)is among the significant detectors for CSR External Target Experiment(CEE).We require the MWDC detector’s front-end readout circuits to have a high integration,high count r...Background The Multi-Wire Drift Chamber(MWDC)is among the significant detectors for CSR External Target Experiment(CEE).We require the MWDC detector’s front-end readout circuits to have a high integration,high count rate,and big dynamic range in order to measure the tracks of fore-angle products.Purpose In this paper,MWDC readout electronics verification system is shown,which is based on the front-end amplifier chip and Switched Capacitor Array(SCA)chip independently established by the project team.Results In the dynamic input range of 14 fC–950 fC,the readout electronics’energy measurement linearity is greater than 1%.The test results with MWDC illustrate that with a 55Fe source an energy resolution of 22.4%was acquired,and with cosmic rays the residual error is less than 400um.展开更多
Aiming at the low recognition accuracy of non-negative matrix factorization(NMF)in practical application,an improved spare graph NMF(New-SGNMF)is proposed in this paper.New-SGNMF makes full use of the inherent geometr...Aiming at the low recognition accuracy of non-negative matrix factorization(NMF)in practical application,an improved spare graph NMF(New-SGNMF)is proposed in this paper.New-SGNMF makes full use of the inherent geometric structure of image data to optimize the basis matrix in two steps.A threshold value s was first set to judge the threshold value of the decomposed base matrix to filter the redundant information in the data.Using L2 norm,sparse constraints were then implemented on the basis matrix,and integrated into the objective function to obtain the objective function of New-SGNMF.In addition,the derivation process of the algorithm and the convergence analysis of the algorithm were given.The experimental results on COIL20,PIE-pose09 and YaleB database show that compared with K-means,PCA,NMF and other algorithms,the proposed algorithm has higher accuracy and normalized mutual information.展开更多
基金This work is supported by the National Key R&D Program of China(No.2021YFA1202200)the CAS Project for Young Scientists in Basic Research(No.YSBR-030)+1 种基金the National Natural Science Foundation Program of China(No.12174383)H L Wang also acknowledges the support from the Youth Innovation Promotion Association,Chinese Academy of Sciences(No.2021110).
文摘(Ga,Fe)Sb is a promising magnetic semiconductor(MS)for spintronic applications because its Curie temperature(T_(C))is above 300 K when the Fe concentration is higher than 20%.However,the anisotropy constant Ku of(Ga,Fe)Sb is below 7.6×10^(3)erg/cm^(3)when Fe concentration is lower than 30%,which is one order of magnitude lower than that of(Ga,Mn)As.To address this issue,we grew Ga_(1-x-y)Fe_(x)Ni_(y)Sb films with almost the same x(≈24%)and different y to characterize their magnetic and electrical transport properties.We found that the magnetic anisotropy of Ga_(0.76-y)Fe_(0.24)Ni_(y)Sb can be enhanced by increasing y,in which Ku is negligible at y=1.7%but increases to 3.8×10^(5)erg/cm^(3)at y=6.1%(T_(C)=354 K).In addition,the hole mobility(μ)of Ga_(1-x-y)Fe_(x)Ni_(y)Sb reaches 31.3 cm^(2)/(V∙s)at x=23.7%,y=1.7%(T_(C)=319 K),which is much higher than the mobility of Ga_(1-x)Fe_(x)Sb at x=25.2%(μ=6.2 cm^(2)/(V∙s)).Our results provide useful information for enhancing the magnetic anisotropy and hole mobility of(Ga,Fe)Sb by using Ni co-doping.
基金supported by the National Natural Science Foundation of China(No.12005017).
文摘High-purity germanium(HPGe)detectors,which are used for direct dark matter detection,have the advantages of a low threshold and excellent energy resolution.The surface passivation of HPGe has become crucial for achieving an extremely low energy threshold.In this study,first-principles simulations,passivation film preparation,and metal oxide semiconductor(MOS)capacitor characterization were combined to study surface passivation.Theoretical calculations of the energy band structure of the -H,-OH,and -NH_(2) passivation groups on the surface of Ge were performed,and the interface state density and potential with five different passivation groups with N/O atomic ratios were accurately analyzed to obtain a stable surface state.Based on the theoretical calculation results,the surface passivation layers of the Ge_(2)ON_(2) film were prepared via magnetron sputtering in accordance with the optimum atomic ratio structure.The microstructure,C-V,and I-V electrical properties of the layers,and the passivation effect of the Al/Ge_(2)ON_(2)/Ge MOS were characterized to test the interface state density.The mean interface state density obtained by the Terman method was 8.4×10^(11) cm^(-2) eV^(-1).The processing of germanium oxynitrogen passivation films is expected to be used in direct dark matter detection of the HPGe detector surface passivation technology to reduce the detector leakage currents.
基金supported by the National Natural Science Foundation of China(Nos.11675197 and 11775242)
文摘The paper presents GEneral ReadOut (GERO), a general readout ASIC based on a switched capacitor array for micro-pattern gas detectors. It aims at providing general readout electronics for low-to-medium event-rate gas detectors with high sampling frequency, configurable storage depth, and data digitalization. The first prototype GERO chip integrates 16 channels and was fabricated using a 0.18-lm CMOS process. Each channel consists of a sampling array working in a ping-pong mode, a storage array with a 1024-cell depth, and 32 Wilkinson analog-todigital converters. The detailed design and test results are presented in the paper.
基金supported by the National Natural Science Foundation of China(Nos.12141502 and 12005017).
文摘Polytetrafluoroethylene(PTFE)is a low-background polymer that is applied to several applications in rare-event detection and underground low-background experiments.PTFE-based electronic substrates are important for reducing the detection limit of high-purity germanium detectors and scintillator calorimeters,which are widely applied in dark matter and 0υββdetection experiments.The traditional adhesive bonding method between PTFE and copper is not conducive to working in liquid nitrogen and extremely low-temperature environments.To avoid adhesive bonding,PTFE must be processed for surface metallization owing to the mismatch between the PTFE and copper conductive layer.Low-background PTFE matrix composites(m-PTFE)were selected to improve the electrical and mechanical properties of PTFE by introducing SiO_(2)/TiO_(2) particles.The microstructures,surface elements,and electrical properties of PTFE and m-PTFE were characterized and analyzed following ion implantation.PTFE and m-PTFE surfaces were found to be broken,degraded,and cross-linked by ion implantation,resulting in C=C conjugated double bonds,increased surface energy,and increased surface roughness.Comparably,the surface roughness,bond strength,and conjugated double bonds of m-PTFE were significantly more intense than those of PTFE.Moreover,the interface bonding theory between PTFE and the metal copper foil was analyzed using the direct metallization principle.Therefore,the peel strength of the optimized electronic substrates was higher than that of the industrial standard at extremely low temperatures,while maintaining excellent electrical properties.
基金supported by Grants from National key research and development program(No.2016YFF0101304)the National Natural Science Foundation of China(Nos.61771279,11435007)
文摘Spectral computed tomography(CT) based on photon counting detectors(PCDs) is a well-researched topic in the field of X-ray imaging. When PCD is applied in a spectral CT system, the PCD energy thresholds must be carefully selected, especially for K-edge imaging, which is an important spectral CT application. This paper presents a threshold selection method that yields better-quality images in K-edge imaging. The main idea is to optimize the energy thresholds ray-by-ray according to the targeted component coefficients, followed by obtaining an overall optimal energy threshold by frequency voting. A low-dose pre-scan is used in practical implementations to estimate the line integrals of the component coefficients for the basis functions. The variance of the decomposed component coefficients is then minimized using the Cramer–Rao lower bound method with respect to the energy thresholds. The optimal energy thresholds are then used to take a full scan and gain better image reconstruction with less noise than would be given by a full scan using the non-optimal energy thresholds. Simulations and practical experiments on imaging iodine and gadolinium solutions, which are commonly used as contrast agents in medical applications, were used to validate the method. The noise was significantly reduced with the same dose relative to the non-optimal energy thresholds in both simulations and in practical experiments.
基金supported by the Guangdong Basic and Applied Basic Research Foundation(Grant No.2021A1515011784)the Key Program of the National Natural Science Foundation of China(Grant No.51732005)+2 种基金the Shenzhen Science and Technology Program(Grant No.KQTD20200820113047086)21C Innovation Laboratory,Contemporary Amperex Technology Ltd(Grant No.C-ND-21C LAB-210044-1.0)the Guangdong-Hong Kong-Macao Joint Laboratory for Neutron Scattering Science and Technology。
文摘Anti-perovskite solid-state electrolyte Li_(2)OHCl usually exhibits orthorhombic phase and low ionic conductivity at room temperature.However,its ionic conductivity increases greatly when the temperature is up to 40℃,while it goes through an orthorhombic-to-cubic phase transition.The cubic Li_(2)OHCl with high ionic conductivity is stabilized at room temperature and even lower temperature about 10℃ by a simple synthesis method of wet mechanical milling.The cubic Li_(2)OHCl prepared by this method performs an ionic conductivity of 4.27×10^(-6) S/cm at room temperature,about one order of magnitude higher than that of the orthorhombic Li_(2)OHCl.The phase-transition temperature is decreased to around 10℃.Moreover,it can still remain cubic phase after heat treatment at 210℃.This work delivers a huge potential of fabricating high ionic conductivity phase antiperovskite solid-state electrolyte materials by wet mechanical milling.
基金supported by the National Natural Science Foundation of China(Nos.62122071 and 62272433)the Fundamental Research Funds for the Central Universities(No.WK3470000021)the Alibaba Innovation Research Program(AIR).
文摘Recently, neural implicit function-basedrepresentation has attracted more and more attention,and has been widely used to represent surfacesusing differentiable neural networks. However, surfacereconstruction from point clouds or multi-view imagesusing existing neural geometry representations stillsuffer from slow computation and poor accuracy. Toalleviate these issues, we propose a multi-scale hashencoding-based neural geometry representation whicheffectively and efficiently represents the surface asa signed distance field. Our novel neural networkstructure carefully combines low-frequency Fourierposition encoding with multi-scale hash encoding. Theinitialization of the geometry network and geometryfeatures of the rendering module are accordinglyredesigned. Our experiments demonstrate that theproposed representation is at least 10 times faster forreconstructing point clouds with millions of points.It also significantly improves speed and accuracyof multi-view reconstruction. Our code and modelsare available at https://github.com/Dengzhi-USTC/Neural-Geometry-Reconstruction.
基金supported by the Chinese Academy of Sciencesthe National Key R&D Program of China+22 种基金the CAS Center for Excellence in Particle PhysicsWuyi Universitythe Tsung-Dao Lee Institute of Shanghai Jiao Tong University in Chinathe Institut National de Physique Nucléaire et de Physique de Particules (IN2P3) in Francethe Istituto Nazionale di Fisica Nucleare (INFN) in Italythe Italian-Chinese collaborative research program MAECI-NSFCthe Fond de la Recherche Scientifique (F.R.S-FNRS)FWO under the "Excellence of Science-EOS" in Belgiumthe Conselho Nacional de Desenvolvimento Científico e Tecnològico in Brazilthe Agencia Nacional de Investigacion y Desarrollo in Chilethe Charles University Research Centrethe Ministry of Education,Youth,and Sports in Czech Republicthe Deutsche Forschungsgemeinschaft (DFG)the Helmholtz Associationthe Cluster of Excellence PRISMA+ in Germanythe Joint Institute of Nuclear Research (JINR)Lomonosov Moscow State University in Russiathe joint Russian Science Foundation (RSF)National Natural Science Foundation of China (NSFC) research programthe MOST and MOE in Taiwan,Chinathe Chulalongkorn UniversitySuranaree University of Technology in Thailandthe University of California at Irvine in USA
文摘The Jiangmen Underground Neutrino Observatory(JUNO)is a large liquid scintillator detector designed to explore many topics in fundamental physics.In this study,the potential of searching for proton decay in the p→νK^(+)mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification.Moreover,the excellent energy resolution of JUNO permits suppression of the sizable background caused by other delayed signals.Based on these advantages,the detection efficiency for the proton decay via p→νK^(+)is 36.9%±4.9%with a background level of 0.2±0.05(syst)±0.2(stat)events after 10 years of data collection.The estimated sensitivity based on 200 kton-years of exposure is 9.6×1033 years,which is competitive with the current best limits on the proton lifetime in this channel and complements the use of different detection technologies.
基金supported by the National Natural Science Foundation of China(Grant Nos.11275107,11475117,11475099,and 11675088)the National Key Basic Research Program of China(Grant No.2010CB833006)
文摘We report the first results on ^(76)Ge neutrinoless double beta decay from stage one of the China dark-matter experiment(CDEX).A p-type point-contact high-purity germanium detector with a mass of 994 g has been installed to detect neutrinoless double beta decay events, as well as to directly detect dark matter particles. An exposure of 304 kg d has been analyzed over a wide spectral band from 500 keV to 3 MeV. The average event rate obtained was about 0.012 counts per keV per kg per day over the 2.039 MeV energy range. The half-life of ^(76)Ge neutrinoless double beta decay derived based on this result is T^(0ν)1/2>6.4×10^(22) yr(90% C.L.). An upper limit on the effective Majorana-neutrino mass of 5.0 eV has been achieved.
基金This work was supported by the Office of Naval Research(ONR)Young Investigator Program(YIP)under Award No.N00014-16-1-2621
文摘Machine-learned interatomic potentials based on local environment descriptors represent a transformative leap over traditional potentials based on rigid functional forms in terms of prediction accuracy.However,a challenge in their application to ionic systems is the treatment of long-ranged electrostatics.Here,we present a highly accurate electrostatic Spectral Neighbor Analysis Potential(eSNAP)for ionicα-Li3N,a prototypical lithium superionic conductor of interest as a solid electrolyte or coating for rechargeable lithium-ion batteries.We show that the optimized eSNAP model substantially outperforms traditional Coulomb–Buckingham potential in the prediction of energies and forces,as well as various properties,such as lattice constants,elastic constants,and phonon dispersion curves.We also demonstrate the application of eSNAP in long-time,large-scale Li diffusion studies in Li3N,providing atomistic insights into measures of concerted ionic motion(e.g.,the Haven ratio)and grain boundary diffusion.This work aims at providing an approach to developing quantum-accurate force fields for multi-component ionic systems under the SNAP formalism,enabling large-scale atomistic simulations for such systems.
基金supported by the National Key Research and Development Program of China(Grant No.2017YFA0402200)the National Natural Science Foundation of China(Grant Nos.11725522,11675088,11475099U1865205)。
文摘We present weakly interacting massive particles(WIMPs) search results performed using two approaches of effective field theory from the China Dark Matter Experiment(CDEX), based on the data from both CDEX-1B and CDEX-10 stages. In the nonrelativistic effective field theory approach, both time-integrated and annual modulation analyses were used to set new limits for the coupling of WIMP-nucleon effective operators at 90% confidence level(C.L.) and improve over the current bounds in the low mχregion. In the chiral effective field theory approach, data from CDEX-10 were used to set an upper limit on WIMP-pion coupling at 90% C.L. We for the first time extended the limit to the m_(χ)<6 GeV/c^(2) region.
基金supported by the National Key Research and Development Program of China(Grant No.2017YFA0402201)the National Natural Science Foundation of China(Grant Nos.11475092,11475099,11675088,and 11725522)
文摘The CDEX-10 experiment searches for light weakly interacting massive particles, a form of dark matter, at the China Jinping Underground Laboratory, where approximately 10 kg of germanium detectors are arranged in an array and immersed in liquid nitrogen. Herein, we report on the experimental apparatus, detector characterization, and spectrum analysis of one prototype detector. Owing to the higher rise-time resolution of the CDEX-10 prototype detector as compared with CDEX-1 B, we identified the origin of an observed category of extremely fast events. For data analysis of the CDEX-10 prototype detector, we introduced and applied an improved bulk/surface event discrimination method. The results of the new method were compared to those of the CDEX-1 B spectrum. Both sets of results showed good consistency in the 0-12 ke Vee energy range, except for the 8.0 keV K-shell X-ray peak from the external copper.
基金This work was supported by the Chinese Academy of Sciences,the National Key R&D Program of China,the CAS Center for Excellence in Particle Physics,the Joint Large Scale Scientific Facility Funds of the NSFC and CAS,Wuyi University,and the Tsung-Dao Lee Instiute of Shanghai Jiao Tong University in China,the In stiut National de Physique Nucleaire et de Physique de Particules(IN2P3)in France,the Istituto Nazionale di Fisica Nucleare(INFN)in Italy,the Fond de la Recherche Scintifique(F.R.S-FNRS)and FWO under the"Excellence of Science-EOS"in Belgium,the Conselho Nacional de Desenvolvimento Cientificoce Tecnologico in Brazil,the Agencia Nacional de Investigacion y Desrrollo in Chile,the Charles University Research Centre and the Ministry of Education,Youth,and Sports in Czech Republic,the Deutsche Forschungsgemeinschaft(DFG),the Helmholtz Association,and the Cluster of Exellence PRISMA+in Germany,the Joint Institute of Nuclear Research(JINR),Lomonosov Moscow State University,and Russian Foundation for Basic Research(RFBR)in Russia,the MOST and MOE in Taiwan,the Chu-lalongkorm University and Suranaree University of Technology in Thailand,and the University of aliformia at Irvine in USA.
文摘The Jiangmen Underground Neutrino Observatory(JUNO)features a 20 kt multi-purpose underground liquid scintillator sphere as its main detector.Some of JUNO's features make it an excellent location for^8B solar neutrino measurements,such as its low-energy threshold,high energy resolution compared with water Cherenkov detectors,and much larger target mass compared with previous liquid scintillator detectors.In this paper,we present a comprehensive assessment of JUNO's potential for detecting^8B solar neutrinos via the neutrino-electron elastic scattering process.A reduced 2 MeV threshold for the recoil electron energy is found to be achievable,assuming that the intrinsic radioactive background^(238)U and^(232)Th in the liquid scintillator can be controlled to 10^(-17)g/g.With ten years of data acquisition,approximately 60,000 signal and 30,000 background events are expected.This large sample will enable an examination of the distortion of the recoil electron spectrum that is dominated by the neutrino flavor transformation in the dense solar matter,which will shed new light on the inconsistency between the measured electron spectra and the predictions of the standard three-flavor neutrino oscillation framework.IfDelta m^(2)_(21)=4.8times10^(-5);(7.5times10^(-5))eV^(2),JUNO can provide evidence of neutrino oscillation in the Earth at approximately the 3sigma(2sigma)level by measuring the non-zero signal rate variation with respect to the solar zenith angle.Moreover,JUNO can simultaneously measureDelta m^2_(21)using^8B solar neutrinos to a precision of 20% or better,depending on the central value,and to sub-percent precision using reactor antineutrinos.A comparison of these two measurements from the same detector will help understand the current mild inconsistency between the value of Delta m^2_(21)reported by solar neutrino experiments and the KamLAND experiment.
基金Key Program of the National Natural Science Foundationof China,Grant/Award Number:51732005Guangdong Basic and Applied Basic Research Foundation,Grant/Award Number:2021A1515011784+1 种基金Key Laboratory of Energy Conversion and Storage Technologies(Southern University of Science and Technology),Ministry of EducationShenzhen Science and Technology Program,Grant/Award Number:KQTD20200820113047086。
文摘Anti-perovskites X3BA,as the electrically inverted derivatives of perovskites ABX3,have attracted tremendous attention for their good performances in multiple disciplines,especially in energy storage batteries.The Li/Na-rich antiperovskite(LiRAP/NaRAP)solid-state electrolytes(SSEs)typically show high ionic conductivities and high chemical/electrochemical stability toward the Li-metal anode,illustrating their great potential for applications in the Limetal batteries(LMBs)using nonaqueous liquid electrolyte or all-solid-state electrolyte.The antiperovskites have been studied as artificial solid electrolyte interphase for Li-metal anode protection,film SSEs for thin-film batteries,and low melting temperature solid electrolyte enabling melt-infiltration for the manufacture of all-solid-state lithium batteries.Transition metal-doped LiRAPs as cathodes have demonstrated a high discharge specific capacity and good rate capability in the Li-ion batteries(LIBs).Additionally,the underlying scientific principles in antiperovskites with flexible structural features have also been extensively studied.In this review,we comprehensively summarize the development,structural design,ionic conductivity and ion transportation mechanism,chemical/electrochemical stability,and applications of some antiperovskite materials in energy storage batteries.The perspective for enhancing the performance of the antiperovskites is also provided as a guide for future development and applications in energy storage.
基金Supported by the Chinese Academy of Sciencesthe National Key R&D Program of China+18 种基金the CAS Center for Excellence in Particle Physics,Wuyi Universitythe Tsung-Dao Lee Institute of Shanghai Jiao Tong University in Chinathe Institut National de Physique Nucléaire et de Physique de Particules(IN2P3)in Francethe Istituto Nazionale di Fisica Nucleare(INFN)in Italythe Italian-Chinese collaborative research program MAECI-NSFCthe Fond de la Recherche Scientifique(F.R.S-FNRS)FWO under the“Excellence of Science-EOS in Belgium”the Conselho Nacional de Desenvolvimento Científico e Tecnològico in Brazilthe Agencia Nacional de Investigacion y Desarrollo and ANID-Millennium Science Initiative Program-ICN2019_044 in Chilethe Charles University Research Centre and the Ministry of Education,Youth,and Sports in Czech Republicthe Deutsche Forschungsgemeinschaft(DFG)the Helmholtz Associationthe Cluster of Excellence PRISMA+in Germanythe Joint Institute of Nuclear Research(JINR)and Lomonosov Moscow State University in Russiathe joint Russian Science Foundation(RSF)National Natural Science Foundation of China(NSFC)research programthe MOST and MOE in Taiwanthe Chulalongkorn University and Suranaree University of Technology in Thailand,University of California at Irvinethe National Science Foundation in USA。
文摘JUNO is a multi-purpose neutrino observatory under construction in the south of China.This publication presents new sensitivity estimates for the measurement of the △m_(31)^(2),△m_(21)^(2),sin^(2)θ_(12),and sin^(2)θ_(13) oscillation parameters using reactor antineutrinos,which is one of the primary physics goals of the experiment.The sensitivities are obtained using the best knowledge available to date on the location and overburden of the experimental site,the nuclear reactors in the surrounding area and beyond,the detector response uncertainties,and the reactor antineutrino spectral shape constraints expected from the TAO satellite detector.It is found that the △m_(21)^(2) and sin^(2)θ_(12) oscillation parameters will be determined to 0.5%precision or better in six years of data collection.In the same period,the △m_(31)^(2) parameter will be determined to about 0.2%precision for each mass ordering hypothesis.The new precision represents approximately an order of magnitude improvement over existing constraints for these three parameters.
基金National Natural Science Foundation of China(11205173,11305190,11565004)in part by the State Key Laboratory of Particle Detection and Electronics(H929420JTD).
文摘Introduction Time projection chamber(TPC)with micropattern gaseous detectors(MPGDs)as readout has been one of the research hotspots in recent years.MPGD-based TPC has been applying to many experiments due to its high spatial and energy resolutions in 3D track measurement.Purpose A novel sampling TPC detector based on thick gaseous electron multiplier(THGEM)was developed to measure the low-energy electron tracks online from 0.1 to 50 MeV with a 100μm spatial resolution in a vacuum tank.The tracks will be extrapolated to determine the hit positions on a target about 200mm behind the TPC.Methods and materials A new type of self-developed THGEM detector was chosen as the TPC readout unit.The field cage has two 50×50mm2 windows welded by Gold-plated tungsten wires for low-energy electrons passing through.The front-end electronics was designed with a self-developed application specific integrated circuit chip,i.e.,CASA-GEM.Seven columns of readout pads were used to equidistantly sample the electron tracks in a length of 75mm.Each column has 72 pads of 0.56×0.56mm2 and two additional strips along each column for drift time measurement.Both Geant4 and Garfield++were chosen to simulate and optimize the detector,such as the penetration efficiency,electric field in field cage and operating gas pressure.Results The design and the preliminary performances of the TPC detector were verified by beam test andβsource test.A drift velocity of 3.415±0.103 cm/μs was measured at 125 V/cm in Ar+iC4H10(97:3)forπ−.The electron detection efficiency is about 88%forβsource.And the gain of the double THGEM reached more than 1.0×10^(4).
基金supported by the National Natural Science Foundation of China(Nos.E11927901 and E911530101).
文摘Background The Multi-Wire Drift Chamber(MWDC)is among the significant detectors for CSR External Target Experiment(CEE).We require the MWDC detector’s front-end readout circuits to have a high integration,high count rate,and big dynamic range in order to measure the tracks of fore-angle products.Purpose In this paper,MWDC readout electronics verification system is shown,which is based on the front-end amplifier chip and Switched Capacitor Array(SCA)chip independently established by the project team.Results In the dynamic input range of 14 fC–950 fC,the readout electronics’energy measurement linearity is greater than 1%.The test results with MWDC illustrate that with a 55Fe source an energy resolution of 22.4%was acquired,and with cosmic rays the residual error is less than 400um.
基金This work was supported by the National Natural Science Foundation of China(Grant No.61501005)the Anhui Natural Science Foundation(Grant No.1608085 MF 147)+2 种基金the Natural Science Foundation of Anhui Universities(Grant No.KJ2016A057)the Industry Collaborative Innovation Fund of Anhui Polytechnic University and Jiujiang District(Grant No.2021cyxtb4)the Science Research Project of Anhui Polytechnic University(Grant No.Xjky2020120).
文摘Aiming at the low recognition accuracy of non-negative matrix factorization(NMF)in practical application,an improved spare graph NMF(New-SGNMF)is proposed in this paper.New-SGNMF makes full use of the inherent geometric structure of image data to optimize the basis matrix in two steps.A threshold value s was first set to judge the threshold value of the decomposed base matrix to filter the redundant information in the data.Using L2 norm,sparse constraints were then implemented on the basis matrix,and integrated into the objective function to obtain the objective function of New-SGNMF.In addition,the derivation process of the algorithm and the convergence analysis of the algorithm were given.The experimental results on COIL20,PIE-pose09 and YaleB database show that compared with K-means,PCA,NMF and other algorithms,the proposed algorithm has higher accuracy and normalized mutual information.