The value of a statistical life(VSL)is a crucial tool for monetizing health impacts.To explore the VSL in China,this study examines people’s willingness to pay(WTP)to reduce death risk from air pollution in six repre...The value of a statistical life(VSL)is a crucial tool for monetizing health impacts.To explore the VSL in China,this study examines people’s willingness to pay(WTP)to reduce death risk from air pollution in six representative cities in China based on face-to-face contingent valuation interviews(n=3936)from March 7,2019 to September 30,2019.The results reveal that the WTP varied from CNY 455 to 763 in 2019(USD 66-111),corresponding to a VSL range of CNY 3.79-6.36 million(USD 549395-921940).The VSL in China in 2019 is estimated to be CNY 4.76 million(USD 689659).The statistics indicate that monthly expenditure levels,environmental concerns,risk attitudes,and assumed market acceptance,which have seldom been dis‐cussed in previous studies,significantly impact WTP and VSL.These findings will serve as a reference for ana‐lyzing mortality risk reduction benefits in future research and for policymaking.展开更多
In the neutral hydrogen(H I)galaxy survey,a significant challenge is to identify and extract the H I galaxy signal from the observational data contaminated by radio frequency interference(RFI).For a drift-scan survey,...In the neutral hydrogen(H I)galaxy survey,a significant challenge is to identify and extract the H I galaxy signal from the observational data contaminated by radio frequency interference(RFI).For a drift-scan survey,or more generally a survey of a spatially continuous region,in the time-ordered spectral data,the H I galaxies and RFI all appear as regions that extend an area in the time-frequency waterfall plot,so the extraction of the H I galaxies and RFI from such data can be regarded as an image segmentation problem,and machine-learning methods can be applied to solve such problems.In this study,we develop a method to effectively detect and extract signals of H I galaxies based on a Mask R-CNN network combined with the PointRend method.By simulating FAST-observed galaxy signals and potential RFI impact,we created a realistic data set for the training and testing of our neural network.We compared five different architectures and selected the best-performing one.This architecture successfully performs instance segmentation of H I galaxy signals in the RFI-contaminated time-ordered data,achieving a precision of 98.64%and a recall of 93.59%.展开更多
A new multi-channel motional Stark effect(MSE)diagnostic system has been developed on the upgraded EAST tokamak,which was installed on the port C to observe a tangential neutral beam.A telecentric imaging lens was dep...A new multi-channel motional Stark effect(MSE)diagnostic system has been developed on the upgraded EAST tokamak,which was installed on the port C to observe a tangential neutral beam.A telecentric imaging lens was deployed to ensure uniform illumination from the core to the boundary.A square fiber head which contained 23 fiber bundles was mounted to this imaging lens;each fiber bundle contained 19 fibers and two of them were assigned to CXRS and BES spectrometer,respectively.The angle tuning method was used for matching the Doppler shift of theσcomponent’s wavelength which was caused by the beam voltage.At the present stage,the MSE system only contains ten channels that would be extended to 23 channels in the future,covering a measurement range from R=1.8 to R=2.27 m with a temporal resolution of 10 ms and a spatial resolution of3 cm.The polarization angle-constrained q profiles and current density profiles were reconstructed with EFIT equilibrium reconstructions.In the sawtooth discharges,the q=1 surface position was validated by the ECE signals,which further verified the rationality of the MSE measurement.展开更多
The measurement of impurity distribution in the divertor region of tokamaks is key to studying edge impurity transport.Therefore,a space-resolved vacuum-ultraviolet(VUV)spectrometer is designed to measure impurity emi...The measurement of impurity distribution in the divertor region of tokamaks is key to studying edge impurity transport.Therefore,a space-resolved vacuum-ultraviolet(VUV)spectrometer is designed to measure impurity emission in the divertor region on EAST.For good spectral resolution,an eagle-type VUV spectrometer with 1 m long focal length with spherical holograph grating is used in the system.For light collection,a collimating mirror is installed between the EAST plasma and the VUV spectrometer to extend the observing range to cover the upper divertor region.Two types of detectors,i.e.a back-illuminated charge-coupled device detector and a photomultiplier-tube detector,are adopted for the spectral measurement and high-frequency intensity measurement for feedback control,respectively.The angle between the entrance and exit optical axis is fixed at 15°.The detector can be moved along the exit axis to maintain a good focusing position when the wavelength is scanned by rotating the grating.The profile of impurity emissions is projected through the space-resolved slit,which is set horizontally.The spectrometer is equipped with two gratings with 2400 grooves/mm and2160 grooves/mm,respectively.The overall aberration of the system is reduced by accurate detector positioning.As a result,the total spectral broadening can be reduced to about 0.013 nm.The simulated performance of the system is found to satisfy the requirement of measurement of impurity emissions from the divertor area of the EAST tokamak.展开更多
Spectral measurement of tungsten(W)impurity is essential to study impurity transport.Therefore,an X-ray crystal spectrometer(XCS)on EAST was used to measure the line spectra from highly ionized W ions.On EAST,both pol...Spectral measurement of tungsten(W)impurity is essential to study impurity transport.Therefore,an X-ray crystal spectrometer(XCS)on EAST was used to measure the line spectra from highly ionized W ions.On EAST,both poloidal XCS and tangential XCS have been developed to measure the plasma temperature as well as the rotation velocity.Recently,He-like and H-like argon spectra have also been obtained using a two-crystal setup.W lines are identified in this study.Through a careful analysis,the W lines of 3.9336,3.9321,and 3.664(A)are found to be diffracted by He-like or H-like crystals.The lines are confirmed with the NIST database.We also calculated the ion temperature with Doppler broadening of these lines.The ion temperature from the W lines is entirely consistent with that from Ar line spectra.The measurement of these W line spectra could be used to study W impurity transport in future work.展开更多
Direct measurements of the intrinsic torque profile in L-mode plasmas on the EAST tokamak have been performed using the balanced neutral beam injection.Co-and counter-current neutral beams are modulated to balance the...Direct measurements of the intrinsic torque profile in L-mode plasmas on the EAST tokamak have been performed using the balanced neutral beam injection.Co-and counter-current neutral beams are modulated to balance the intrinsic and externally injected torques, which result in the rotation profile close to zero and flat.The experimental results show that the intrinsic torque derived from momentum balance equations is found to be in the co-current direction, peaked in the plasma edge and negligibly small in the core.展开更多
The Convention on Biological Diversity seeks to conserve at least 30%of global land and water areas by 2030,which is a challenge but also an opportunity to better preserve biodiversity,including flowering plants(angio...The Convention on Biological Diversity seeks to conserve at least 30%of global land and water areas by 2030,which is a challenge but also an opportunity to better preserve biodiversity,including flowering plants(angiosperms).Herein,we compiled a large database on distributions of over 300,000 angiosperm species and the key functional traits of 67,024 species.Using this database,we constructed biodiversity-environment models to predict global patterns of taxonomic,phylogenetic,and functional diversity in terrestrial angiosperms and provide a comprehensive mapping of the three diversity facets.We further evaluated the current protection status of the biodiversity centers of these diversity facets.Our results showed that geographical patterns of the three facets of plant diversity exhibited substantial spatial mismatches and nonoverlapping conservation priorities.Idiosyncratic centers of functional diversity,particularly of herbaceous species,were primarily distributed in temperate regions and under weaker protection compared with other biodiversity centers of taxonomic and phylogenetic facets.Our global assessment of multifaceted biodiversity patterns and centers highlights the insufficiency and unbalanced conservation among the three diversity facets and the two growth forms(woody vs.herbaceous),thus providing directions for guiding the future conservation of global plant diversity.展开更多
Gravitational waves(GWs) from compact binary coalescences encode the absolute luminosity distances of GW sources. Once the redshifts of GW sources are known, one can use the distance-redshift relation to constrain cos...Gravitational waves(GWs) from compact binary coalescences encode the absolute luminosity distances of GW sources. Once the redshifts of GW sources are known, one can use the distance-redshift relation to constrain cosmological parameters. One way to obtain the redshifts is to localize GW sources by GW observations and then use galaxy catalogs to determine redshifts from a statistical analysis of redshift information of the potential host galaxies, commonly referred to as the dark siren method. The third-generation(3G) GW detectors are planned to work in the 2030s and will observe numerous compact binary coalescences.Using these GW events as dark sirens requires high-quality galaxy catalogs from future sky survey projects. The China Space Station Telescope(CSST) will be launched in 2024 and will observe billions of galaxies within a 17500 deg^(2) survey area with redshift up to z ~ 4, providing photometric and spectroscopic galaxy catalogs. In this work, we simulate the CSST galaxy catalogs and the 5-year GW data from the 3G GW detectors and combine them to infer the Hubble constant(H_(0)). Our results show that the measurement precision of H0could reach the sub-percent level, meeting the standard of precision cosmology. We conclude that the synergy between CSST and the 3G GW detectors is of great significance in measuring the Hubble constant.展开更多
The Tianlai Cylinder Pathfinder is a radio interferometer array designed to test techniques for 21 cm intensity mapping in the post-reionization Universe,with the ultimate aim of mapping the large scale structure and ...The Tianlai Cylinder Pathfinder is a radio interferometer array designed to test techniques for 21 cm intensity mapping in the post-reionization Universe,with the ultimate aim of mapping the large scale structure and measuring cosmological parameters such as the dark energy equation of state.Each of its three parallel cylinder reflectors is oriented in the north-south direction,and the array has a large field of view.As the Earth rotates,the northern sky is observed by drift scanning.The array is located in Hongliuxia,a radio-quiet site in Xinjiang,and saw its first light in September 2016.In this first data analysis paper for the Tianlai cylinder array,we discuss the sub-system qualification tests,and present basic system performance obtained from preliminary analysis of the commissioning observations during 2016-2018.We show typical interferometric visibility data,from which we derive the actual beam profile in the east-west direction and the frequency band-pass response.We describe also the calibration process to determine the complex gains for the array elements,either using bright astronomical point sources,or an artificial on site calibrator source,and discuss the instrument response stability,crucial for transit interferometry.Based on this analysis,we find a system temperature of about 90 K,and we also estimate the sensitivity of the array.展开更多
We present a forecast of the cosmological parameter estimation using fast radio bursts(FRBs)from the upcoming Square Kilometre Array(SKA),focusing on the issues of dark energy,the Hubble constant,and baryon density.We...We present a forecast of the cosmological parameter estimation using fast radio bursts(FRBs)from the upcoming Square Kilometre Array(SKA),focusing on the issues of dark energy,the Hubble constant,and baryon density.We simulate 105and 106localized FRBs from a 10-year SKA observation,and find that:(1)using 106FRB data alone can tightly constrain dark-energy equation of state parameters better than CMB+BAO+SNe,providing an independent cosmological probe to explore dark energy;(2)combining the FRB data with gravitational-wave standard siren data from 10-year observation with the Einstein Telescope,the Hubble constant can be constrained to a sub-percent level,serving as a powerful low-redshift probe;(3)using 106FRB data can constrain the baryon density?bh to a precision of~0.1%.Our results indicate that SKA-era FRBs will provide precise cosmological measurements to shed light on both dark energy and the missing baryon problem,and help resolve the Hubble tension.展开更多
The 21 cm intensity mapping(IM)technique provides us with an efficient way to observe the cosmic large-scale structure(LSS).From the LSS data,one can use the baryon acoustic oscillation and redshift space distortion t...The 21 cm intensity mapping(IM)technique provides us with an efficient way to observe the cosmic large-scale structure(LSS).From the LSS data,one can use the baryon acoustic oscillation and redshift space distortion to trace the expansion and growth history of the universe,and thus measure the dark energy parameters.In this paper,we make a forecast for cosmological parameter estimation with the synergy of three 21 cm IM experiments.Specifically,we adopt a novel joint survey strategy,FAST(0<z<0.35)+SKA1-MID(0.35<z<0.8)+HIRAX(0.8<z<2.5),to measure dark energy.We simulate the 21 cm IM observations under the assumption of excellent foreground removal.We find that the synergy of three experiments could place quite tight constraints on cosmological parameters.For example,it providesσ(?m)=0.0039 andσ(H0)=0.27 km s^(-1) Mpc^(-1) in theΛCDM model.Notably,the synergy could break the cosmological parameter degeneracies when constraining the dynamical dark energy models.Concretely,the joint observation offersσ(w)=0.019 in the wCDM model,andσ(w0)=0.085 andσ(wa)=0.32 in the w0waCDM model.These results are better than or equal to those given by CMB+BAO+SN.In addition,when the foreground removal efficiency is relatively low,the strategy still performs well.Therefore,the 21 cm IM joint survey strategy is promising and worth pursuing.展开更多
Development of ＂green＂ multi-functional air filters with features such as excellent filtration efficiency eco-friendliness, and environmental stability are critically required to address the increasing concerns of p...Development of ＂green＂ multi-functional air filters with features such as excellent filtration efficiency eco-friendliness, and environmental stability are critically required to address the increasing concerns of polluted air. Natural proteins, such as soy protein and gelatin, are attractive candidates as multi-functional air-filtration materials owing to the rich functional groups; however, these bio-materials are vulnerable to moisture, which limits their broad application in practice. In this work, a hydrophobic protein of zein derived from abundant corn is modified for the first time to produce high-performance nanofilters via electrospinning. The zein nanofabrics are fabricated with the aid of a non-toxic solvent and co-electrospinning agent, poly（ethylene oxide）. The results reveal that the zein-based nanofabrics show high efficiency for the simultaneous removal of particulate matters of different sizes ranging from 0.1 to 10 btm （〉 99.5%） and certain gaseous toxic chemicals （〉 70%）. In addition, the zein nanofabrics show excellent moisture-resistance and good adhesion to the cellulose paper towel used as the air-filter substrate. This study demonstrates that nanofabrics based on hydrophobic natural proteins such as zein are promising materials for developing multi-functional ＂green＂ air filters.展开更多
基金supported by the National Natural Science Foun‐dation of China[Grant No.71773061].
文摘The value of a statistical life(VSL)is a crucial tool for monetizing health impacts.To explore the VSL in China,this study examines people’s willingness to pay(WTP)to reduce death risk from air pollution in six representative cities in China based on face-to-face contingent valuation interviews(n=3936)from March 7,2019 to September 30,2019.The results reveal that the WTP varied from CNY 455 to 763 in 2019(USD 66-111),corresponding to a VSL range of CNY 3.79-6.36 million(USD 549395-921940).The VSL in China in 2019 is estimated to be CNY 4.76 million(USD 689659).The statistics indicate that monthly expenditure levels,environmental concerns,risk attitudes,and assumed market acceptance,which have seldom been dis‐cussed in previous studies,significantly impact WTP and VSL.These findings will serve as a reference for ana‐lyzing mortality risk reduction benefits in future research and for policymaking.
基金support by the National SKA Program of ChinaNo.2022SKA0110100+1 种基金the CAS Interdisciplinary Innovation Team(JCTD-2019-05)the science research grants from the China Manned Space Project with No.CMS-CSST-2021-B01。
文摘In the neutral hydrogen(H I)galaxy survey,a significant challenge is to identify and extract the H I galaxy signal from the observational data contaminated by radio frequency interference(RFI).For a drift-scan survey,or more generally a survey of a spatially continuous region,in the time-ordered spectral data,the H I galaxies and RFI all appear as regions that extend an area in the time-frequency waterfall plot,so the extraction of the H I galaxies and RFI from such data can be regarded as an image segmentation problem,and machine-learning methods can be applied to solve such problems.In this study,we develop a method to effectively detect and extract signals of H I galaxies based on a Mask R-CNN network combined with the PointRend method.By simulating FAST-observed galaxy signals and potential RFI impact,we created a realistic data set for the training and testing of our neural network.We compared five different architectures and selected the best-performing one.This architecture successfully performs instance segmentation of H I galaxy signals in the RFI-contaminated time-ordered data,achieving a precision of 98.64%and a recall of 93.59%.
基金supported by the National MCF Energy R&D Program of China(No.2019YFE03040000)National Natural Science Foundation of China(Nos.12075280 and 11805236)+2 种基金Anhui Provincial Natural Science Foundation(No.1908085J01)CAS President’s International Fellowship Initiative(No.2022VMB0007)Comprehensive Research Facility for Fusion Technology Program of China(No.2018-000052-73-01-001228)。
文摘A new multi-channel motional Stark effect(MSE)diagnostic system has been developed on the upgraded EAST tokamak,which was installed on the port C to observe a tangential neutral beam.A telecentric imaging lens was deployed to ensure uniform illumination from the core to the boundary.A square fiber head which contained 23 fiber bundles was mounted to this imaging lens;each fiber bundle contained 19 fibers and two of them were assigned to CXRS and BES spectrometer,respectively.The angle tuning method was used for matching the Doppler shift of theσcomponent’s wavelength which was caused by the beam voltage.At the present stage,the MSE system only contains ten channels that would be extended to 23 channels in the future,covering a measurement range from R=1.8 to R=2.27 m with a temporal resolution of 10 ms and a spatial resolution of3 cm.The polarization angle-constrained q profiles and current density profiles were reconstructed with EFIT equilibrium reconstructions.In the sawtooth discharges,the q=1 surface position was validated by the ECE signals,which further verified the rationality of the MSE measurement.
基金the National Magnetic Confinement Fusion Science Program of China(Nos.2017YFE0301300,2019YFE03030002 and 2018YFE0303103)National Natural Science Foundation of China(No.12175278)+7 种基金Anhui Province Key Research and Development Program(No.202104a06020021)ASIPP Science and Research Grant(No.DSJJ-2020-02)Anhui Provincial Natural Science Foundation(No.1908085J01)Distinguished Young Scholar of Anhui Provincial Natural Science Foundation(No.2008085QA39)Instrument Developing Project of the Chinese Academy of Sciences(No.YJKYYQ20180013)the Comprehensive Research Facility for Fusion Technology Program of China(No.2018-000052-73-01-001228)the University Synergy Innovation Program of Anhui Province(No.GXXT-2021-029)CAS President’s International Fellowship Initiative(No.2022VMB0007)。
文摘The measurement of impurity distribution in the divertor region of tokamaks is key to studying edge impurity transport.Therefore,a space-resolved vacuum-ultraviolet(VUV)spectrometer is designed to measure impurity emission in the divertor region on EAST.For good spectral resolution,an eagle-type VUV spectrometer with 1 m long focal length with spherical holograph grating is used in the system.For light collection,a collimating mirror is installed between the EAST plasma and the VUV spectrometer to extend the observing range to cover the upper divertor region.Two types of detectors,i.e.a back-illuminated charge-coupled device detector and a photomultiplier-tube detector,are adopted for the spectral measurement and high-frequency intensity measurement for feedback control,respectively.The angle between the entrance and exit optical axis is fixed at 15°.The detector can be moved along the exit axis to maintain a good focusing position when the wavelength is scanned by rotating the grating.The profile of impurity emissions is projected through the space-resolved slit,which is set horizontally.The spectrometer is equipped with two gratings with 2400 grooves/mm and2160 grooves/mm,respectively.The overall aberration of the system is reduced by accurate detector positioning.As a result,the total spectral broadening can be reduced to about 0.013 nm.The simulated performance of the system is found to satisfy the requirement of measurement of impurity emissions from the divertor area of the EAST tokamak.
基金the National Magnetic Confinement Fusion Science Program of China(Nos.2017YFE0301300 and 2018YFE0301100)the Key Program of Research and Development of the Hefei Science Center(No.2017HSC-KPRD002)+7 种基金National Natural Science Foundation of China(Nos.11805231 and 11705151)the ASIPP Science and Research Grant(No.DSJJ-17-03)the Anhui Provincial Natural Science Foundation(Nos.1808085QA14 and 1908085J01)the Instrument Developing Project of the Chi-nese Academy of Sciences(No.YJKYYQ20180013)the Collaborative Innovation Program of Hefei Science Center,CAS(No.2019HSC-CIP005)the Nature Science Foundation of Hunan Province(2017JJ3268)the Hunan Nuclear Fusion International Science and Technology Innovation Coopera-tion Base(No.2018WK4009)the Key Laboratory of Magnetic Confinement Nuclear Fusion Research in Hengyang(No.2018KJ108).
文摘Spectral measurement of tungsten(W)impurity is essential to study impurity transport.Therefore,an X-ray crystal spectrometer(XCS)on EAST was used to measure the line spectra from highly ionized W ions.On EAST,both poloidal XCS and tangential XCS have been developed to measure the plasma temperature as well as the rotation velocity.Recently,He-like and H-like argon spectra have also been obtained using a two-crystal setup.W lines are identified in this study.Through a careful analysis,the W lines of 3.9336,3.9321,and 3.664(A)are found to be diffracted by He-like or H-like crystals.The lines are confirmed with the NIST database.We also calculated the ion temperature with Doppler broadening of these lines.The ion temperature from the W lines is entirely consistent with that from Ar line spectra.The measurement of these W line spectra could be used to study W impurity transport in future work.
基金supported by the National Key Research and Development Program of China(Nos.2017YFE0301300 and 2017YFE0302000)Key Program of Research and Development of Hefei Science Center,CAS(No.2017HSCKPRD002)+2 种基金Distinguished Young Scholar of Anhui Provincial Natural Science Foundation(1908085J01)the Key Projects of Hunan Provincial Department of Education(18A238)the Key Laboratory of Magnetic Confinement Nuclear Fusion Research in Hengyang(2018KJ108)。
文摘Direct measurements of the intrinsic torque profile in L-mode plasmas on the EAST tokamak have been performed using the balanced neutral beam injection.Co-and counter-current neutral beams are modulated to balance the intrinsic and externally injected torques, which result in the rotation profile close to zero and flat.The experimental results show that the intrinsic torque derived from momentum balance equations is found to be in the co-current direction, peaked in the plasma edge and negligibly small in the core.
基金supported by the National Natural Science Foundation of China(32125026,31988102)the National Key Research Development Program of China(2022YFF0802300)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB31000000)。
文摘The Convention on Biological Diversity seeks to conserve at least 30%of global land and water areas by 2030,which is a challenge but also an opportunity to better preserve biodiversity,including flowering plants(angiosperms).Herein,we compiled a large database on distributions of over 300,000 angiosperm species and the key functional traits of 67,024 species.Using this database,we constructed biodiversity-environment models to predict global patterns of taxonomic,phylogenetic,and functional diversity in terrestrial angiosperms and provide a comprehensive mapping of the three diversity facets.We further evaluated the current protection status of the biodiversity centers of these diversity facets.Our results showed that geographical patterns of the three facets of plant diversity exhibited substantial spatial mismatches and nonoverlapping conservation priorities.Idiosyncratic centers of functional diversity,particularly of herbaceous species,were primarily distributed in temperate regions and under weaker protection compared with other biodiversity centers of taxonomic and phylogenetic facets.Our global assessment of multifaceted biodiversity patterns and centers highlights the insufficiency and unbalanced conservation among the three diversity facets and the two growth forms(woody vs.herbaceous),thus providing directions for guiding the future conservation of global plant diversity.
基金supported by the National SKA Program of China (Grant Nos.2022SKA0110200, and 2022SKA0110203)the National Natural Science Foundation of China (Grant Nos. 11975072, 11875102, and 11835009)+1 种基金the science research grants from the China Manned Space Project (Grant No. CMS-CSST-2021-B01)the 111 Project (Grant No. B16009)。
文摘Gravitational waves(GWs) from compact binary coalescences encode the absolute luminosity distances of GW sources. Once the redshifts of GW sources are known, one can use the distance-redshift relation to constrain cosmological parameters. One way to obtain the redshifts is to localize GW sources by GW observations and then use galaxy catalogs to determine redshifts from a statistical analysis of redshift information of the potential host galaxies, commonly referred to as the dark siren method. The third-generation(3G) GW detectors are planned to work in the 2030s and will observe numerous compact binary coalescences.Using these GW events as dark sirens requires high-quality galaxy catalogs from future sky survey projects. The China Space Station Telescope(CSST) will be launched in 2024 and will observe billions of galaxies within a 17500 deg^(2) survey area with redshift up to z ~ 4, providing photometric and spectroscopic galaxy catalogs. In this work, we simulate the CSST galaxy catalogs and the 5-year GW data from the 3G GW detectors and combine them to infer the Hubble constant(H_(0)). Our results show that the measurement precision of H0could reach the sub-percent level, meeting the standard of precision cosmology. We conclude that the synergy between CSST and the 3G GW detectors is of great significance in measuring the Hubble constant.
基金support of the Astronomical Technology Center of National Astronomical Observatories of China(NAOC)support of Ministry of Science and Technology(MOST)(Grant No.2012AA121701)+10 种基金supported by MOST(Grant Nos.2016YFE0100300,and 2018YFE0120800)the National Natural Science Foundation of China(NSFC)(Grant Nos.11633004,11473044,and 11653003)the Chinese Academy of Sciences(CAS)(Grant No.QYZDJ-SSW-SLH017)support of the NSFC-CAS Joint Fund of Astronomy(Grant No.U1631118)partially supported by the National Key R&D Program(Grant No.2017YFA0402603)the CAS Interdisciplinary Innovation Team(Grant No.JCTD-2019-05)support of NSFC(Grant No.U1501501)the Tianhe-1 supercomputerpartially supported by the US National Science Foundation(NSF)Award(Grant No.AST-1616554)partial support from Centre National de la Recherche Scientifique(CNRS)via IN2P3&INSU,Observatoire de ParisIrfu/CEA。
文摘The Tianlai Cylinder Pathfinder is a radio interferometer array designed to test techniques for 21 cm intensity mapping in the post-reionization Universe,with the ultimate aim of mapping the large scale structure and measuring cosmological parameters such as the dark energy equation of state.Each of its three parallel cylinder reflectors is oriented in the north-south direction,and the array has a large field of view.As the Earth rotates,the northern sky is observed by drift scanning.The array is located in Hongliuxia,a radio-quiet site in Xinjiang,and saw its first light in September 2016.In this first data analysis paper for the Tianlai cylinder array,we discuss the sub-system qualification tests,and present basic system performance obtained from preliminary analysis of the commissioning observations during 2016-2018.We show typical interferometric visibility data,from which we derive the actual beam profile in the east-west direction and the frequency band-pass response.We describe also the calibration process to determine the complex gains for the array elements,either using bright astronomical point sources,or an artificial on site calibrator source,and discuss the instrument response stability,crucial for transit interferometry.Based on this analysis,we find a system temperature of about 90 K,and we also estimate the sensitivity of the array.
基金supported by the National SKA Program of China(Grant Nos.2022SKA01102002022SKA0110203)+1 种基金the National Natural Science Foundation of China(Grant Nos.11975072,11835009,11875102,and 11988101)the National 111 Project of China(Grant No.B16009)。
文摘We present a forecast of the cosmological parameter estimation using fast radio bursts(FRBs)from the upcoming Square Kilometre Array(SKA),focusing on the issues of dark energy,the Hubble constant,and baryon density.We simulate 105and 106localized FRBs from a 10-year SKA observation,and find that:(1)using 106FRB data alone can tightly constrain dark-energy equation of state parameters better than CMB+BAO+SNe,providing an independent cosmological probe to explore dark energy;(2)combining the FRB data with gravitational-wave standard siren data from 10-year observation with the Einstein Telescope,the Hubble constant can be constrained to a sub-percent level,serving as a powerful low-redshift probe;(3)using 106FRB data can constrain the baryon density?bh to a precision of~0.1%.Our results indicate that SKA-era FRBs will provide precise cosmological measurements to shed light on both dark energy and the missing baryon problem,and help resolve the Hubble tension.
基金supported by the National SKA Program of China(Grant Nos.2022SKA0110200,and 2022SKA0110203)National Natural Science Foundation of China(Grant Nos.11975072,11835009,and 11875102)。
文摘The 21 cm intensity mapping(IM)technique provides us with an efficient way to observe the cosmic large-scale structure(LSS).From the LSS data,one can use the baryon acoustic oscillation and redshift space distortion to trace the expansion and growth history of the universe,and thus measure the dark energy parameters.In this paper,we make a forecast for cosmological parameter estimation with the synergy of three 21 cm IM experiments.Specifically,we adopt a novel joint survey strategy,FAST(0<z<0.35)+SKA1-MID(0.35<z<0.8)+HIRAX(0.8<z<2.5),to measure dark energy.We simulate the 21 cm IM observations under the assumption of excellent foreground removal.We find that the synergy of three experiments could place quite tight constraints on cosmological parameters.For example,it providesσ(?m)=0.0039 andσ(H0)=0.27 km s^(-1) Mpc^(-1) in theΛCDM model.Notably,the synergy could break the cosmological parameter degeneracies when constraining the dynamical dark energy models.Concretely,the joint observation offersσ(w)=0.019 in the wCDM model,andσ(w0)=0.085 andσ(wa)=0.32 in the w0waCDM model.These results are better than or equal to those given by CMB+BAO+SN.In addition,when the foreground removal efficiency is relatively low,the strategy still performs well.Therefore,the 21 cm IM joint survey strategy is promising and worth pursuing.
文摘Development of ＂green＂ multi-functional air filters with features such as excellent filtration efficiency eco-friendliness, and environmental stability are critically required to address the increasing concerns of polluted air. Natural proteins, such as soy protein and gelatin, are attractive candidates as multi-functional air-filtration materials owing to the rich functional groups; however, these bio-materials are vulnerable to moisture, which limits their broad application in practice. In this work, a hydrophobic protein of zein derived from abundant corn is modified for the first time to produce high-performance nanofilters via electrospinning. The zein nanofabrics are fabricated with the aid of a non-toxic solvent and co-electrospinning agent, poly（ethylene oxide）. The results reveal that the zein-based nanofabrics show high efficiency for the simultaneous removal of particulate matters of different sizes ranging from 0.1 to 10 btm （〉 99.5%） and certain gaseous toxic chemicals （〉 70%）. In addition, the zein nanofabrics show excellent moisture-resistance and good adhesion to the cellulose paper towel used as the air-filter substrate. This study demonstrates that nanofabrics based on hydrophobic natural proteins such as zein are promising materials for developing multi-functional ＂green＂ air filters.
