To enable flexible and rapid aerodynamic performance evaluation in turbomachinery design,this paper proposes a panoramic performance prediction framework.Unlike most previous prediction models that directly predict th...To enable flexible and rapid aerodynamic performance evaluation in turbomachinery design,this paper proposes a panoramic performance prediction framework.Unlike most previous prediction models that directly predict the objective functions of interest,the approach first predicts the basic parameters of the Navier–Stokes equations,such as temperature,pressure,and density.Utilizing these basic physical quantities,it subsequently predicts key performance parameters of the turbine stage meridian plane.By adopting this methodology,the proposed panoramic performance prediction framework functions similarly to a CFD simulator,capable of predicting various objective of interest to the designers.To enhance prediction accuracy,a Transformer-enhanced Neural Operator(TNO)is introduced within this framework.Using the Rotor 37 blades as a reference,the proposed TNO is trained to predict the performance of a transonic compressor blade in the meridian plane.The TNO can accurately predict total quantities such as isentropic efficiency,mass flow,and distributions of total pressure ratio.Remarkably,the prediction error of TNO is observed to be smaller than that of state-of-the-art deep learning operators such as the Fourier Neural Operator(FNO)network and Deep Operator Network(DeepONet).Furthermore,the TNO is applied to downstream tasks,including sensitivity analysis and optimization of various objective functions.The results confirm that the TNO can operate almost like a CFD simulator,while reducing the computational cost of downstream tasks by four orders of magnitude.The effectiveness and reliability of the proposed TNO for solving different kinds of downstream tasks have been well demonstrated.展开更多
The in-flight instrumental background of the Follow-up X-ray Telescope(FXT)onboard Einstein Probe mis sion is analysed in this work by utilizing observations collected during the performance verification phase and sub...The in-flight instrumental background of the Follow-up X-ray Telescope(FXT)onboard Einstein Probe mis sion is analysed in this work by utilizing observations collected during the performance verification phase and subsequent dedicated filter wheel closed observations.The instrumental backgrounds of the two FXT modules are consistent with each other,with an average rate of~4×10^(-2)counts s^(-1)keV^(-1)in the 0.5-10 keV band for each module.The background is nearly uniformly distributed across the detector area,with a minor increase(<8%)observed along rows.The spatial distribution shows significant modulation by the geomagnetic field.The spectral shapes remain unchanged in 0.5-10 keV at different rates.The long-term temporal variation indicates a periodic change associated with the orbital precession(~57 days).The innovative design of FXT full-frame readout mode enables simultaneous recording of events in both the imaging area(IMG)and the frame store area(FSA)of the pnCCD.FSA event rates show a strong linear correlation with the IMG,based on which the IMG instrumental background modeling is established.展开更多
Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor(GECAM),consisting of two microsatellites,is designed to detect gamma-ray bursts associated with gravitational-wave events.Here,we introduce th...Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor(GECAM),consisting of two microsatellites,is designed to detect gamma-ray bursts associated with gravitational-wave events.Here,we introduce the real-time burst alert system of GECAM,with the adoption of the BeiDou-3 short message communication service.We present the post-trigger operations,the detailed ground-based analysis,and the performance of the system.In the first year of the in-flight operation,GECAM was triggered by 42 gamma-ray bursts.The GECAM real-time burst alert system has the ability to distribute the alert within~1 minute after being triggered,which enables timely follow-up observations.展开更多
We consider the existence of a neutron star magnetic field by the detected cyclotron lines. We collected data on nine sources of high-mass X-ray binaries with supergiant companions as a test case for our model, to dem...We consider the existence of a neutron star magnetic field by the detected cyclotron lines. We collected data on nine sources of high-mass X-ray binaries with supergiant companions as a test case for our model, to demonstrate their distribution and evolution. The wind velocity, spin period and magnetic field strength are studied under different mass loss rates. In our model, correlations between mass-loss rate and wind velocity are found and can be tested in further observations. We examine the parameter space where wind accretion is allowed, avoiding the barrier of rotating magnetic fields, with robust data on the magnetic field of neutron stars. Our model shows that most sources(six of nine systems) can be fed by the wind with relatively slow velocity, and this result is consistent with previous predictions. In a few sources,our model cannot fit the standard wind accretion scenario. In these peculiar cases, other scenarios(disk formation, partial Roche lobe overflow) should be considered. This would provide information about the evolutionary tracks of various types of binaries, and thus exhibit a clear dichotomy behavior in wind-fed X-ray binary systems.展开更多
We conduct a detailed analysis of an M1.3 limb flare occurring on 2017 July 3,which have the X-ray observations recorded by multiple hard X-ray telescopes,including Hard X-ray Modulation Telescope(Insight-HXMT),Ramaty...We conduct a detailed analysis of an M1.3 limb flare occurring on 2017 July 3,which have the X-ray observations recorded by multiple hard X-ray telescopes,including Hard X-ray Modulation Telescope(Insight-HXMT),Ramaty High Energy Solar Spectroscopic Imager(RHESSI),and the Fermi Gamma-ray Space Telescope(Fermi).Joint analysis has also used the extreme ultraviolet(EUV)imaging data from the Atmospheric Imaging Assembly(AIA)aboard the Solar Dynamic Observatory.The hard X-ray spectral and imaging evolution suggest a lower corona source,and the non-thermal broken power law distribution has a rather low break energy~15 keV.The EUV imaging shows a rather stable plasma configuration before the hard X-ray peak phase,and accompanied by a filament eruption during the hard X-ray flare peak phase.Hard X-ray image reconstruction from RHESSI data only shows one foot point source.We also determined the DEM for the peak phase by SDO/AIA data.The integrated EM beyond 10 MK at foot point onset after the peak phase,while the>10 MK source around reconnection site began to fade.The evolution of EM and hard X-ray source supports lower corona plasma heating after non-thermal energy dissipation.The combination of hard X-ray spectra and images during the limb flare provides the understanding on the interchange of non-thermal and thermal energies,and relation between lower corona heating and the upper corona instability.展开更多
The Bayesian Multi-Fidelity Surrogate(MFS)proposed by Kennedy and O’Hagan(KOH model)has been widely employed in engineering design,which builds the approximation by decomposing the high-fidelity function into a scale...The Bayesian Multi-Fidelity Surrogate(MFS)proposed by Kennedy and O’Hagan(KOH model)has been widely employed in engineering design,which builds the approximation by decomposing the high-fidelity function into a scaled low-fidelity model plus a discrepancy function.The scale factor before the low-fidelity function,ρ,plays a crucial role in the KOH model.This scale factor is always tuned by the Maximum Likelihood Estimation(MLE).However,recent studies reported that the MLE may sometimes result in MFS of bad accuracy.In this paper,we first present a detailed analysis of why MLE sometimes can lead to MFS of bad accuracy.This is because,the MLE overly emphasizes the variation of discrepancy function but ignores the function waviness when selectingρ.To address the above issue,we propose an alternative approach that choosesρby minimizing the posterior variance of the discrepancy function.Through tests on a one-dimensional function,two high-dimensional functions,and a turbine blade design problem,the proposed approach shows better accuracy than or comparable accuracy to MLE,and the proposed approach is more robust than MLE.Additionally,through a comparative test on the design optimization of a turbine endwall cooling layout,the advantage of the proposed approach is further validated.展开更多
Fast and reliable localization of high-energy transients is crucial for characterizing the burst properties and guiding the follow-up observations.Localization based on the relative counts of different detectors has b...Fast and reliable localization of high-energy transients is crucial for characterizing the burst properties and guiding the follow-up observations.Localization based on the relative counts of different detectors has been widely used for all-sky gamma-ray monitors.There are two major methods for this count distribution localization:χ^(2)minimization method and the Bayesian method.Here we propose a modified Bayesian method that could take advantage of both the accuracy of the Bayesian method and the simplicity of the χ^(2)method.With comprehensive simulations,we find that our Bayesian method with Poisson likelihood is generally more applicable for various bursts than the χ^(2)method,especially for weak bursts.We further proposed a location-spectrum iteration approach based on the Bayesian inference,which could alleviate the problems caused by the spectral difference between the burst and location templates.Our method is very suitable for scenarios with limited computation resources or timesensitive applications,such as in-flight localization software,and low-latency localization for rapidly follow-up observations.展开更多
The Gravitational wave burst high-energy Electromagnetic Counterpart All-sky Monitor(GECAM)is a dedicated mission for monitoring high-energy transients.Here we report the design of the GECAM Scientific Ground Segment(...The Gravitational wave burst high-energy Electromagnetic Counterpart All-sky Monitor(GECAM)is a dedicated mission for monitoring high-energy transients.Here we report the design of the GECAM Scientific Ground Segment(GSGS)in terms of the scientific requirements,including the architecture,the external interfaces,the main function,and workflow.Judging from the analysis and verification results during the commissioning phase,the GSGS functions well and is able to monitor the status of the payloads,adjust the parameters,develop the scientific observation plans,generate the scientific data products,analyze the data,etc.Thus,the on-orbit operation and scientific researches of GECAM are guaranteed.展开更多
To the Editor:Interstitial cystitis/bladder pain syndrome(IC/BPS)is a chronic inflammatory condition characterized by persistent pelvic pain,urinary urgency,frequency,and bladder fibrosis,which significantly diminishe...To the Editor:Interstitial cystitis/bladder pain syndrome(IC/BPS)is a chronic inflammatory condition characterized by persistent pelvic pain,urinary urgency,frequency,and bladder fibrosis,which significantly diminishes the quality of life of patients.[1]Despite its global prevalence of approximately 300 cases per 100,000 females,the condition remains poorly recognized and underdiagnosed in China,with reported incidences ranging from 21.8 to 100.0 per 100,000 individuals.Currently,IC/BPS diagnosis primarily relies on symptom evaluation and exclusion of bacterial infection,leading to frequent misdiagnoses.[2]While therapies such as antihistamines,amitriptyline,and pentosan polysulfate provide partial relief,their efficacy is limited,and adverse effects remain common.[3]Although the precise pathogenesis of IC/BPS remains unclear,accumulating evidence has suggested that immune dysregulation,chronic inflammation,and urothelial dysfunction may play pivotal roles.[4]Understanding the correlation between molecular mechanisms and clinical manifestations such as pain,fibrosis,and immune responses is crucial.The identification of phenotype-related genes associated with immune cell infiltration may uncover potential biomarkers,advancing diagnostic accuracy and targeted therapies.Recently,machine learning(ML)methods have provided powerful tools for identifying disease-associated biomarkers and gene expression signatures.[5]Utilizing ML algorithms to analyze transcriptomic data can reveal underlying molecular patterns,enhancing our understanding of complex diseases such as IC/BPS.展开更多
The chest X-ray(CXR)imaging has been the most frequently performed radiographic examination for decades,and its demand continues to grow due to their critical role in diagnosing various diseases.However,the image qual...The chest X-ray(CXR)imaging has been the most frequently performed radiographic examination for decades,and its demand continues to grow due to their critical role in diagnosing various diseases.However,the image quality of CXR has long been a factor limiting their diagnostic accuracy.As a post-processing procedure,image enhancement can cost-effectively improve image quality.Recently,the successful application of deep learning(DL)algorithms in medical image analysis has prompted researchers to propose and design DL-based CXR image enhancement algorithms.This review examines advancements in CXR image enhancement methods from 2018 to 2023,categorizing them into four groups:bone suppression,image denoising,super-resolution reconstruction,and contrast enhancement.For each group,the unique approaches,strengths,and challenges are analyzed.The review concludes by discussing shared challenges across these methods and proposing directions for future research.展开更多
In this paper,we present the current status of the enhanced X-ray Timing and Polarimetry mission,which has been fully approved for launch in 2030.eXTP is a space science mission designed to study fundamental physics u...In this paper,we present the current status of the enhanced X-ray Timing and Polarimetry mission,which has been fully approved for launch in 2030.eXTP is a space science mission designed to study fundamental physics under extreme conditions of matter density,gravity,and magnetism.The mission aims at determining the equation of state of matter at supra-nuclear density,measuring the effects of quantum electro-dynamics,and understanding the dynamics of matter in strong-field gravity.In addition to investigating fundamental physics,the eXTP mission is poised to become a leading observatory for time-domain and multi-messenger astronomy in the 2030s,as well as providing observations of unprecedented quality on a variety of galactic and extragalactic objects.After briefly introducing the history and a summary of the scientific objectives of the eXTP mission,this paper presents a comprehensive overview of:(1)the cutting-edge technology,technical specifications,and anticipated performance of the mission’s scientific instruments;(2)the full mission profile,encompassing spacecraft design,operational capabilities,and ground segment infrastructure.展开更多
We report the discovery of a peculiar X-ray transient,EP240408a,by Einstein Probe(EP)and follow-up studies made with EP,Swift,NICER,GROND,ATCA and other ground-based multiwavelength telescopes.The new transient was fi...We report the discovery of a peculiar X-ray transient,EP240408a,by Einstein Probe(EP)and follow-up studies made with EP,Swift,NICER,GROND,ATCA and other ground-based multiwavelength telescopes.The new transient was first detected with Wide-field X-ray Telescope(WXT)on board EP on April 8th,2024,manifested in an intense yet brief X-ray flare lasting for 12 s.The flare reached a peak flux of 3:9×10^(−9) erg cm^(−2) s^(−1) in 0.5-4 keV,∼300 times brighter than the underlying X-ray emission detected throughout the observation.Rapid and more precise follow-up observations by EP/FXT,Swift and NICER confirmed the finding of this new transient.Its X-ray spectrum is non-thermal in 0.5-10 keV,with a power-law photon index varying within 1.8-2.5.The X-ray light curve shows a plateau lasting for∼4 d,followed by a steep decay till becoming undetectable∼10 d after the initial detection.Based on its temporal property and constraints from previous EP observations,an unusual timescale in the range of 7-23 d is found for EP240408a,which is intermediate between the commonly found fast and long-term transients.No counterparts have been found in optical and near-infrared,with the earliest observation at 17 h after the initial X-ray detection,suggestive of intrinsically weak emission in these bands.We demonstrate that the remarkable properties of EP240408a are inconsistent with any of the transient types known so far,by comparison with,in particular,jetted tidal disruption events,gamma-ray bursts,X-ray binaries and fast blue optical transients.The nature of EP240408a thus remains an enigma.We suggest that EP240408a may represent a new type of transients with intermediate timescales of the order of∼10 d.The detection and follow-ups of more of such objects are essential for revealing their origin.展开更多
As China's first X-ray astronomy satellite,the hard X-ray modulation telescope(Insight-HXMT)carries three sets of X-ray telescopes.The high energy X-ray telescope(Insight-HXMT/HE)could serve as an all-sky gamma-ra...As China's first X-ray astronomy satellite,the hard X-ray modulation telescope(Insight-HXMT)carries three sets of X-ray telescopes.The high energy X-ray telescope(Insight-HXMT/HE)could serve as an all-sky gamma-ray monitor with a detection area of up to 5000 cm2and energy range from about 200 ke V to 3 Me V.These characteristics,together with the high orbital inclination angle(43°)of the satellite,make the HE very suitable for detecting terrestrial gamma-ray flashes(TGFs).In this work,we implemented a dedicated TGF search algorithm for Insight-HXMT/HE,and identified 282 bright TGFs in its first four years of operation.We made a systematic study on the properties of these TGFs,including trigger time,duration,intensity,as well as the lightning association.We found that TGFs detected in mid-latitude regions(30°to 43°)are rare and they do not exhibit significantly different properties compared with TGFs in low-latitude(within 30°).Interestingly,the hardness ratio of TGF measured by Insight-HXMT/HE seems to be independent of the TGF duration,which differs from previous studies.These results show that,despite the dedicated design for astronomical observation,Insight-HXMT/HE is a versatile instrument to study energetic radiation phenomena from the Earth.展开更多
Terrestrial gamma-ray flash(TGF)is intense and brief burst of gamma-rays originating in Earth's atmosphere.In this work,with a large sample of TGF observed by the Insight-HXMT from June 22,2017 to July 30,2024 and...Terrestrial gamma-ray flash(TGF)is intense and brief burst of gamma-rays originating in Earth's atmosphere.In this work,with a large sample of TGF observed by the Insight-HXMT from June 22,2017 to July 30,2024 and lightning sferics detected by the world wide lightning location network(WWLLN),we systematically investigated the temporal,spatial,and energetic relationships between the TGF and lightning sferics.More sferics associated with TGF are revealed using a novel two-step analysis method.We find that TGF always occurs in the initial stage(about 5 to 20 ms)of a lightning process(lasting about 800 ms)and that there is significant deficit in the lightning sferic during about 30 s before the TGF time.Based on the sferic-TGF time offset and the sferics rate,we identify,for the first time,that TGF-associated sferics are composed of three components:simultaneous sferics,adjacent sferics,and follow-up sferics.Compared to the average energy of background sferics(~2200 J),simultaneous sferics have much higher average energy(~8300 J),while adjacent sferics(~1700 J)and follow-up sferics(~1300 J)are somewhat lower.Interestingly,we find that as TGF becomes shorter in duration,the median energy of the simultaneous sferics increases.Moreover,based on the distance distribution,we conclude that TGF and all three components of the associated sferics should happen in a small region in the thunderstorm.These findings refresh our understanding of the TGF-lightning relation and thus have important implications on the TGF and lightning production mechanisms.展开更多
Charged particle precipitation typically manifests as a gradual increase and decrease of flux observed by space detectors.Cases with rapid flux variation are very rare,while periodic events are even more extraordinary...Charged particle precipitation typically manifests as a gradual increase and decrease of flux observed by space detectors.Cases with rapid flux variation are very rare,while periodic events are even more extraordinary.These oscillating particle precipitation(OPP)events are usually attributed to the bounce motion of electrons probably induced by lightning.However,the origin of these oscillation events is still on debate.Here we report three peculiar charged particle precipitation events detected by GECAM during a geomagnetic storm on March 21,2024,with two exhibiting significant periodicity.These events were observed around the same region during three consecutive orbits with a life time of more than 3.5 h.Through comprehensive temporal and spectral analyses,we find that one of the OPP events exhibited a transition in spectral lag of mini-pulses,shifting from“softer-earlier”to“softer-later”while showing no significant time evolution in overall frequency characteristics,and that there is no association found between these two OPP events and lightning activity nearby.Finally,we discussed possible scenarios to explain these GECAM-detected OPP events,and we found that they may represent a new type of particle precipitation event or a peculiar lightning-induced electron precipitation(LEP).展开更多
As China’s first X-ray astronomical satellite, the Hard X-ray Modulation Telescope (HXMT), which was dubbed as Insight-HXMT after the launch on June 15, 2017, is a wide-band(1-250 ke V) slat-collimator-based X-ray as...As China’s first X-ray astronomical satellite, the Hard X-ray Modulation Telescope (HXMT), which was dubbed as Insight-HXMT after the launch on June 15, 2017, is a wide-band(1-250 ke V) slat-collimator-based X-ray astronomy satellite with the capability of all-sky monitoring in 0.2-3 Me V. It was designed to perform pointing, scanning and gamma-ray burst(GRB)observations and, based on the Direct Demodulation Method (DDM), the image of the scanned sky region can be reconstructed.Here we give an overview of the mission and its progresses, including payload, core sciences, ground calibration/facility, ground segment, data archive, software, in-orbit performance, calibration, background model, observations and some preliminary results.展开更多
In this paper we present the enhanced X-ray Timing and Polarimetry mission—eXTP. eXTP is a space science mission designed to study fundamental physics under extreme conditions of density, gravity and magnetism. The m...In this paper we present the enhanced X-ray Timing and Polarimetry mission—eXTP. eXTP is a space science mission designed to study fundamental physics under extreme conditions of density, gravity and magnetism. The mission aims at determining the equation of state of matter at supra-nuclear density, measuring effects of QED, and understanding the dynamics of matter in strong-field gravity. In addition to investigating fundamental physics, eXTP will be a very powerful observatory for astrophysics that will provide observations of unprecedented quality on a variety of galactic and extragalactic objects. In particular, its wide field monitoring capabilities will be highly instrumental to detect the electro-magnetic counterparts of gravitational wave sources.The paper provides a detailed description of:(1) the technological and technical aspects, and the expected performance of the instruments of the scientific payload;(2) the elements and functions of the mission, from the spacecraft to the ground segment.展开更多
基金supported by the National Science and Technology Major Project,China(No.2019-II-0008–0028)。
文摘To enable flexible and rapid aerodynamic performance evaluation in turbomachinery design,this paper proposes a panoramic performance prediction framework.Unlike most previous prediction models that directly predict the objective functions of interest,the approach first predicts the basic parameters of the Navier–Stokes equations,such as temperature,pressure,and density.Utilizing these basic physical quantities,it subsequently predicts key performance parameters of the turbine stage meridian plane.By adopting this methodology,the proposed panoramic performance prediction framework functions similarly to a CFD simulator,capable of predicting various objective of interest to the designers.To enhance prediction accuracy,a Transformer-enhanced Neural Operator(TNO)is introduced within this framework.Using the Rotor 37 blades as a reference,the proposed TNO is trained to predict the performance of a transonic compressor blade in the meridian plane.The TNO can accurately predict total quantities such as isentropic efficiency,mass flow,and distributions of total pressure ratio.Remarkably,the prediction error of TNO is observed to be smaller than that of state-of-the-art deep learning operators such as the Fourier Neural Operator(FNO)network and Deep Operator Network(DeepONet).Furthermore,the TNO is applied to downstream tasks,including sensitivity analysis and optimization of various objective functions.The results confirm that the TNO can operate almost like a CFD simulator,while reducing the computational cost of downstream tasks by four orders of magnitude.The effectiveness and reliability of the proposed TNO for solving different kinds of downstream tasks have been well demonstrated.
基金supported by Strategic Priority Program on Space Science of Chinese Academy of Sciences,in collaboration with ESA,MPE and CNES(grant Nos.XDA15310303,XDA15310103 and XDA15052100)。
文摘The in-flight instrumental background of the Follow-up X-ray Telescope(FXT)onboard Einstein Probe mis sion is analysed in this work by utilizing observations collected during the performance verification phase and subsequent dedicated filter wheel closed observations.The instrumental backgrounds of the two FXT modules are consistent with each other,with an average rate of~4×10^(-2)counts s^(-1)keV^(-1)in the 0.5-10 keV band for each module.The background is nearly uniformly distributed across the detector area,with a minor increase(<8%)observed along rows.The spatial distribution shows significant modulation by the geomagnetic field.The spectral shapes remain unchanged in 0.5-10 keV at different rates.The long-term temporal variation indicates a periodic change associated with the orbital precession(~57 days).The innovative design of FXT full-frame readout mode enables simultaneous recording of events in both the imaging area(IMG)and the frame store area(FSA)of the pnCCD.FSA event rates show a strong linear correlation with the IMG,based on which the IMG instrumental background modeling is established.
基金supported by the National Key R&D Program of China(2021YFA0718500,2022YFF0711404)the Strategic Priority Research Program on Space Science,the Chinese Academy of Sciences(grant Nos.XDA15360300,XDA15052700 and E02212A02S)+1 种基金the National Natural Science Foundation of China(grant Nos.U2031205,12133007)supported by the Strategic Priority Research Program on Space Science,the Chinese Academy of Sciences,grant No.XDA15360000。
文摘Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor(GECAM),consisting of two microsatellites,is designed to detect gamma-ray bursts associated with gravitational-wave events.Here,we introduce the real-time burst alert system of GECAM,with the adoption of the BeiDou-3 short message communication service.We present the post-trigger operations,the detailed ground-based analysis,and the performance of the system.In the first year of the in-flight operation,GECAM was triggered by 42 gamma-ray bursts.The GECAM real-time burst alert system has the ability to distribute the alert within~1 minute after being triggered,which enables timely follow-up observations.
基金the Abdul Hamed Shoman Foundation (Grant No. 6/2017) for supporting this projectsupported by the JSPS KAKENHI (Grant No. 18K03706)+1 种基金supported by the National Key R&D Program of China (2016YFA0400801)the National Natural Science Foundation of China (Grant No. U1838201)
文摘We consider the existence of a neutron star magnetic field by the detected cyclotron lines. We collected data on nine sources of high-mass X-ray binaries with supergiant companions as a test case for our model, to demonstrate their distribution and evolution. The wind velocity, spin period and magnetic field strength are studied under different mass loss rates. In our model, correlations between mass-loss rate and wind velocity are found and can be tested in further observations. We examine the parameter space where wind accretion is allowed, avoiding the barrier of rotating magnetic fields, with robust data on the magnetic field of neutron stars. Our model shows that most sources(six of nine systems) can be fed by the wind with relatively slow velocity, and this result is consistent with previous predictions. In a few sources,our model cannot fit the standard wind accretion scenario. In these peculiar cases, other scenarios(disk formation, partial Roche lobe overflow) should be considered. This would provide information about the evolutionary tracks of various types of binaries, and thus exhibit a clear dichotomy behavior in wind-fed X-ray binary systems.
基金supported by the National Program on Key Research and Development Project(Grant Nos.2021YFA0718500 and 2021YFA0718503)the Fundamental Research Funds for the Central Universities(No.2042021kf0224)the National Natural Science Foundation of China(Grant Nos.12133007,U1838103 and 11622326)。
文摘We conduct a detailed analysis of an M1.3 limb flare occurring on 2017 July 3,which have the X-ray observations recorded by multiple hard X-ray telescopes,including Hard X-ray Modulation Telescope(Insight-HXMT),Ramaty High Energy Solar Spectroscopic Imager(RHESSI),and the Fermi Gamma-ray Space Telescope(Fermi).Joint analysis has also used the extreme ultraviolet(EUV)imaging data from the Atmospheric Imaging Assembly(AIA)aboard the Solar Dynamic Observatory.The hard X-ray spectral and imaging evolution suggest a lower corona source,and the non-thermal broken power law distribution has a rather low break energy~15 keV.The EUV imaging shows a rather stable plasma configuration before the hard X-ray peak phase,and accompanied by a filament eruption during the hard X-ray flare peak phase.Hard X-ray image reconstruction from RHESSI data only shows one foot point source.We also determined the DEM for the peak phase by SDO/AIA data.The integrated EM beyond 10 MK at foot point onset after the peak phase,while the>10 MK source around reconnection site began to fade.The evolution of EM and hard X-ray source supports lower corona plasma heating after non-thermal energy dissipation.The combination of hard X-ray spectra and images during the limb flare provides the understanding on the interchange of non-thermal and thermal energies,and relation between lower corona heating and the upper corona instability.
基金the financial support from the National Science and Technology Major Project,China(No.2019-Ⅱ-0008-0028)Key Program of National Natural Science Foundation of China(No.51936008)。
文摘The Bayesian Multi-Fidelity Surrogate(MFS)proposed by Kennedy and O’Hagan(KOH model)has been widely employed in engineering design,which builds the approximation by decomposing the high-fidelity function into a scaled low-fidelity model plus a discrepancy function.The scale factor before the low-fidelity function,ρ,plays a crucial role in the KOH model.This scale factor is always tuned by the Maximum Likelihood Estimation(MLE).However,recent studies reported that the MLE may sometimes result in MFS of bad accuracy.In this paper,we first present a detailed analysis of why MLE sometimes can lead to MFS of bad accuracy.This is because,the MLE overly emphasizes the variation of discrepancy function but ignores the function waviness when selectingρ.To address the above issue,we propose an alternative approach that choosesρby minimizing the posterior variance of the discrepancy function.Through tests on a one-dimensional function,two high-dimensional functions,and a turbine blade design problem,the proposed approach shows better accuracy than or comparable accuracy to MLE,and the proposed approach is more robust than MLE.Additionally,through a comparative test on the design optimization of a turbine endwall cooling layout,the advantage of the proposed approach is further validated.
基金supported by the National Key R&D Program of China(2021YFA0718500)support from the Strategic Priority Research Program on Space Science,the Chinese Academy of Sciences(grant Nos.XDA15360102,XDA15360300,XDA15052700 and E02212A02S)+1 种基金the National Natural Science Foundation of China(grant Nos.12173038 and U2038106)the National HEP Data Center(grant No.E029S2S1)。
文摘Fast and reliable localization of high-energy transients is crucial for characterizing the burst properties and guiding the follow-up observations.Localization based on the relative counts of different detectors has been widely used for all-sky gamma-ray monitors.There are two major methods for this count distribution localization:χ^(2)minimization method and the Bayesian method.Here we propose a modified Bayesian method that could take advantage of both the accuracy of the Bayesian method and the simplicity of the χ^(2)method.With comprehensive simulations,we find that our Bayesian method with Poisson likelihood is generally more applicable for various bursts than the χ^(2)method,especially for weak bursts.We further proposed a location-spectrum iteration approach based on the Bayesian inference,which could alleviate the problems caused by the spectral difference between the burst and location templates.Our method is very suitable for scenarios with limited computation resources or timesensitive applications,such as in-flight localization software,and low-latency localization for rapidly follow-up observations.
基金supported by the National Key R&D Program of China(2022YFF0711404,2021YFA0718500)International Partnership Program of Chinese Academy of Sciences(grant No.113111KYSB20190020)+2 种基金the National Natural Science Foundation of China(NSFC,Grant No.U1938106)the open subject of the National HEP Data Center(E029S2S1)support from the Strategic Priority Research Program on Space Science,the Chinese Academy of Sciences(grant Nos.XDA15360102,XDA15360300,XDA15052700 and E02212A02S)。
文摘The Gravitational wave burst high-energy Electromagnetic Counterpart All-sky Monitor(GECAM)is a dedicated mission for monitoring high-energy transients.Here we report the design of the GECAM Scientific Ground Segment(GSGS)in terms of the scientific requirements,including the architecture,the external interfaces,the main function,and workflow.Judging from the analysis and verification results during the commissioning phase,the GSGS functions well and is able to monitor the status of the payloads,adjust the parameters,develop the scientific observation plans,generate the scientific data products,analyze the data,etc.Thus,the on-orbit operation and scientific researches of GECAM are guaranteed.
基金supported by grants from the National Nature Science Foundation(No.81970658)the Natural Science Foundation of Shanghai(No.20ZR1434100).
文摘To the Editor:Interstitial cystitis/bladder pain syndrome(IC/BPS)is a chronic inflammatory condition characterized by persistent pelvic pain,urinary urgency,frequency,and bladder fibrosis,which significantly diminishes the quality of life of patients.[1]Despite its global prevalence of approximately 300 cases per 100,000 females,the condition remains poorly recognized and underdiagnosed in China,with reported incidences ranging from 21.8 to 100.0 per 100,000 individuals.Currently,IC/BPS diagnosis primarily relies on symptom evaluation and exclusion of bacterial infection,leading to frequent misdiagnoses.[2]While therapies such as antihistamines,amitriptyline,and pentosan polysulfate provide partial relief,their efficacy is limited,and adverse effects remain common.[3]Although the precise pathogenesis of IC/BPS remains unclear,accumulating evidence has suggested that immune dysregulation,chronic inflammation,and urothelial dysfunction may play pivotal roles.[4]Understanding the correlation between molecular mechanisms and clinical manifestations such as pain,fibrosis,and immune responses is crucial.The identification of phenotype-related genes associated with immune cell infiltration may uncover potential biomarkers,advancing diagnostic accuracy and targeted therapies.Recently,machine learning(ML)methods have provided powerful tools for identifying disease-associated biomarkers and gene expression signatures.[5]Utilizing ML algorithms to analyze transcriptomic data can reveal underlying molecular patterns,enhancing our understanding of complex diseases such as IC/BPS.
基金supported by research grants of Health and Medical Research Fund(HMRF 07183266,HMRF 09200576,HMRF COVID190211)the Health Bureau,General Research Fund(GRF 15103520)the Research Grants Council,The Government of the Hong Kong Special Administrative Region,China.
文摘The chest X-ray(CXR)imaging has been the most frequently performed radiographic examination for decades,and its demand continues to grow due to their critical role in diagnosing various diseases.However,the image quality of CXR has long been a factor limiting their diagnostic accuracy.As a post-processing procedure,image enhancement can cost-effectively improve image quality.Recently,the successful application of deep learning(DL)algorithms in medical image analysis has prompted researchers to propose and design DL-based CXR image enhancement algorithms.This review examines advancements in CXR image enhancement methods from 2018 to 2023,categorizing them into four groups:bone suppression,image denoising,super-resolution reconstruction,and contrast enhancement.For each group,the unique approaches,strengths,and challenges are analyzed.The review concludes by discussing shared challenges across these methods and proposing directions for future research.
基金the support of the National Natural Science Foundation of China(Grant No.12333007)the International Partnership Program of Chinese Academy of Sciences(Grant No.113111KYSB20190020)+4 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA15020100)support by ASI,under the dedicated eXTP agreements and agreement ASI-INAF n.2017-14-H.O.by INAF and INFN under project REDSOXsupport from the Deutsche Zentrum für Luft-und Raumfahrt,the German Aerospace Center(DLR)support from MINECO grant ESP2017-82674-R and FEDER funds.
文摘In this paper,we present the current status of the enhanced X-ray Timing and Polarimetry mission,which has been fully approved for launch in 2030.eXTP is a space science mission designed to study fundamental physics under extreme conditions of matter density,gravity,and magnetism.The mission aims at determining the equation of state of matter at supra-nuclear density,measuring the effects of quantum electro-dynamics,and understanding the dynamics of matter in strong-field gravity.In addition to investigating fundamental physics,the eXTP mission is poised to become a leading observatory for time-domain and multi-messenger astronomy in the 2030s,as well as providing observations of unprecedented quality on a variety of galactic and extragalactic objects.After briefly introducing the history and a summary of the scientific objectives of the eXTP mission,this paper presents a comprehensive overview of:(1)the cutting-edge technology,technical specifications,and anticipated performance of the mission’s scientific instruments;(2)the full mission profile,encompassing spacecraft design,operational capabilities,and ground segment infrastructure.
基金based on data obtained with Einstein Probe,a space mission supported by Strategic Priority Program on Space Science of Chinese Academy of Sciences,in collaboration with ESA,MPE and CNES(Grant No.XDA15310000)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB0550200)+5 种基金the National Key R&D Program of China(Grant No.2022YFF0711500)the support by the National Natural Science Foundation of China(Grant Nos.12333004,12321003,12103065,12373040,12021003,12025303,12393814,and 12203071)the China Manned Space Project(Grant Nos.CMS-CSST-2021-A13,and CMS-CSST-2021-B11)the Youth Innovation Promotion Association of the Chinese Academy of Sciencessupported by a Ramón y Cajal fellowship(Grant No.RYC2021-030888-I)financial support from AGAUR,CSIC,MCIN and AEI 10.13039/501100011033(Grant Nos.PID2023-151307NB-I00,PIE 20215AT016,CEX2020-001058-M,and 2021-SGR-01270)。
文摘We report the discovery of a peculiar X-ray transient,EP240408a,by Einstein Probe(EP)and follow-up studies made with EP,Swift,NICER,GROND,ATCA and other ground-based multiwavelength telescopes.The new transient was first detected with Wide-field X-ray Telescope(WXT)on board EP on April 8th,2024,manifested in an intense yet brief X-ray flare lasting for 12 s.The flare reached a peak flux of 3:9×10^(−9) erg cm^(−2) s^(−1) in 0.5-4 keV,∼300 times brighter than the underlying X-ray emission detected throughout the observation.Rapid and more precise follow-up observations by EP/FXT,Swift and NICER confirmed the finding of this new transient.Its X-ray spectrum is non-thermal in 0.5-10 keV,with a power-law photon index varying within 1.8-2.5.The X-ray light curve shows a plateau lasting for∼4 d,followed by a steep decay till becoming undetectable∼10 d after the initial detection.Based on its temporal property and constraints from previous EP observations,an unusual timescale in the range of 7-23 d is found for EP240408a,which is intermediate between the commonly found fast and long-term transients.No counterparts have been found in optical and near-infrared,with the earliest observation at 17 h after the initial X-ray detection,suggestive of intrinsically weak emission in these bands.We demonstrate that the remarkable properties of EP240408a are inconsistent with any of the transient types known so far,by comparison with,in particular,jetted tidal disruption events,gamma-ray bursts,X-ray binaries and fast blue optical transients.The nature of EP240408a thus remains an enigma.We suggest that EP240408a may represent a new type of transients with intermediate timescales of the order of∼10 d.The detection and follow-ups of more of such objects are essential for revealing their origin.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFA0718500)the National Natural Science Foundation of China(Grant No.12273042)the Science Research Program of Dezhou University(2024xjrc142)。
文摘As China's first X-ray astronomy satellite,the hard X-ray modulation telescope(Insight-HXMT)carries three sets of X-ray telescopes.The high energy X-ray telescope(Insight-HXMT/HE)could serve as an all-sky gamma-ray monitor with a detection area of up to 5000 cm2and energy range from about 200 ke V to 3 Me V.These characteristics,together with the high orbital inclination angle(43°)of the satellite,make the HE very suitable for detecting terrestrial gamma-ray flashes(TGFs).In this work,we implemented a dedicated TGF search algorithm for Insight-HXMT/HE,and identified 282 bright TGFs in its first four years of operation.We made a systematic study on the properties of these TGFs,including trigger time,duration,intensity,as well as the lightning association.We found that TGFs detected in mid-latitude regions(30°to 43°)are rare and they do not exhibit significantly different properties compared with TGFs in low-latitude(within 30°).Interestingly,the hardness ratio of TGF measured by Insight-HXMT/HE seems to be independent of the TGF duration,which differs from previous studies.These results show that,despite the dedicated design for astronomical observation,Insight-HXMT/HE is a versatile instrument to study energetic radiation phenomena from the Earth.
基金supported by the National Natural Science Foundation of China(Grant No.12273042)the National Key R&D Program of China(Grant No.2021YFA0718500)the support from the Science Research Program of Dezhou University(Grant No.2024xjrc142)。
文摘Terrestrial gamma-ray flash(TGF)is intense and brief burst of gamma-rays originating in Earth's atmosphere.In this work,with a large sample of TGF observed by the Insight-HXMT from June 22,2017 to July 30,2024 and lightning sferics detected by the world wide lightning location network(WWLLN),we systematically investigated the temporal,spatial,and energetic relationships between the TGF and lightning sferics.More sferics associated with TGF are revealed using a novel two-step analysis method.We find that TGF always occurs in the initial stage(about 5 to 20 ms)of a lightning process(lasting about 800 ms)and that there is significant deficit in the lightning sferic during about 30 s before the TGF time.Based on the sferic-TGF time offset and the sferics rate,we identify,for the first time,that TGF-associated sferics are composed of three components:simultaneous sferics,adjacent sferics,and follow-up sferics.Compared to the average energy of background sferics(~2200 J),simultaneous sferics have much higher average energy(~8300 J),while adjacent sferics(~1700 J)and follow-up sferics(~1300 J)are somewhat lower.Interestingly,we find that as TGF becomes shorter in duration,the median energy of the simultaneous sferics increases.Moreover,based on the distance distribution,we conclude that TGF and all three components of the associated sferics should happen in a small region in the thunderstorm.These findings refresh our understanding of the TGF-lightning relation and thus have important implications on the TGF and lightning production mechanisms.
基金supported by the National Natural Science Foundation of China(Grant Nos.12273042,and 12303045)the National Key R&D Program of China(Grant No.2021YFA0718500)+2 种基金the Natural Science Foundation of Hebei Province(Grant No.A2023205020)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant Nos.XDB0550300,and XDA30050000)The GECAM(Huairou-1)mission is supported by the Strategic Priority Research Program on Space Science of the Chinese Academy of Sciences(Grant No.XDA15360000).We thank the World Wide Lightning Location Network(http://wwlln.net)as a collaboration of more than 50 universities.Chenwei Wang appreciates Wen Cheng,Yixin Sun,and Lu Wang for helpful discussions.
文摘Charged particle precipitation typically manifests as a gradual increase and decrease of flux observed by space detectors.Cases with rapid flux variation are very rare,while periodic events are even more extraordinary.These oscillating particle precipitation(OPP)events are usually attributed to the bounce motion of electrons probably induced by lightning.However,the origin of these oscillation events is still on debate.Here we report three peculiar charged particle precipitation events detected by GECAM during a geomagnetic storm on March 21,2024,with two exhibiting significant periodicity.These events were observed around the same region during three consecutive orbits with a life time of more than 3.5 h.Through comprehensive temporal and spectral analyses,we find that one of the OPP events exhibited a transition in spectral lag of mini-pulses,shifting from“softer-earlier”to“softer-later”while showing no significant time evolution in overall frequency characteristics,and that there is no association found between these two OPP events and lightning activity nearby.Finally,we discussed possible scenarios to explain these GECAM-detected OPP events,and we found that they may represent a new type of particle precipitation event or a peculiar lightning-induced electron precipitation(LEP).
基金project funded by China National Space Administration(CNSA)and the Chinese Academy of Sciences(CAS)support from the National Key Research and Development Program of China(Grant No.2016YFA0400800)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant Nos.XDA04010202,XDA04010300,and XDB23040400)the National Natural Science Foundation of China(Grant Nos.U1838201,and U1838102).
文摘As China’s first X-ray astronomical satellite, the Hard X-ray Modulation Telescope (HXMT), which was dubbed as Insight-HXMT after the launch on June 15, 2017, is a wide-band(1-250 ke V) slat-collimator-based X-ray astronomy satellite with the capability of all-sky monitoring in 0.2-3 Me V. It was designed to perform pointing, scanning and gamma-ray burst(GRB)observations and, based on the Direct Demodulation Method (DDM), the image of the scanned sky region can be reconstructed.Here we give an overview of the mission and its progresses, including payload, core sciences, ground calibration/facility, ground segment, data archive, software, in-orbit performance, calibration, background model, observations and some preliminary results.
基金support of the Chinese Academy of Sciences through the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA15020100)support by ASI, under the dedicated eXTP agreements and agreement ASI-INAF (Grant No. 2017-14-H.O.)+3 种基金by INAF and INFN under project REDSOXsupport from the Deutsche Zentrum für Luft- und Raumfahrt, the German Aerospce Center (DLR)support of Science Centre (Grant No. 2013/10/M/ST9/00729)support from MINECO (Grant No. ESP2017-82674-R) and FEDER funds
文摘In this paper we present the enhanced X-ray Timing and Polarimetry mission—eXTP. eXTP is a space science mission designed to study fundamental physics under extreme conditions of density, gravity and magnetism. The mission aims at determining the equation of state of matter at supra-nuclear density, measuring effects of QED, and understanding the dynamics of matter in strong-field gravity. In addition to investigating fundamental physics, eXTP will be a very powerful observatory for astrophysics that will provide observations of unprecedented quality on a variety of galactic and extragalactic objects. In particular, its wide field monitoring capabilities will be highly instrumental to detect the electro-magnetic counterparts of gravitational wave sources.The paper provides a detailed description of:(1) the technological and technical aspects, and the expected performance of the instruments of the scientific payload;(2) the elements and functions of the mission, from the spacecraft to the ground segment.
