We report the discovery of PSR J1909+0122 by the Five-hundred-meter Aperture Spherical Radio Telescope(FAST)as part of the Commensal Radio Astronomy FAST Survey.PSR J1909+0122 has a spin period of 1.257 s and a disper...We report the discovery of PSR J1909+0122 by the Five-hundred-meter Aperture Spherical Radio Telescope(FAST)as part of the Commensal Radio Astronomy FAST Survey.PSR J1909+0122 has a spin period of 1.257 s and a dispersion measure of 186.2 pc cm^(-3).The averaged pulse profile shows two distinct components.We performed a single-pulse study based on a one-hour observation at 1.25 GHz on 2021 August 23.We used a threshold of 5σ_(ep) to measure the nulling fraction(NF)as 63%±1.5%.The longitude-resolved fluctuation spectra and fast Fourier transform spectra of the binary sequences revealed the quasi-periodicity of nulling with a period of 30 rotation periods.We examined the reliability of the periodicity by comparing it to random noise injection.The NF,E,and modulation periodicity P_(M) of PSR J1909+0122 were compared with other periodic nulling pulsars,showing that the source of J1909+0122 has the second largest NF in the population.Long-term timing observations over six months were used to derive the phase-connected ephemeris of this pulsar.The measured P and P values disfavor dipolar geometry for polar gap models,and the prediction for a space-charge-limited flow model in the case of inverse Compton scattering is only just above the death line.In this work,PSR J1909+0122 has revealed possible correlations between nulling behavior and pulsar properties,which will help to shed light on the pulsar emission mechanism and its temporal evolution in future observations.展开更多
[Objectives]To regulate the quality of Wanjinxiang Shushuang Ointment through simultaneously quantifying menthol,camphor,1,8-cineole,linalool,borneol and caryophyllene oxide by QAMS(quantitative analysis of multi-comp...[Objectives]To regulate the quality of Wanjinxiang Shushuang Ointment through simultaneously quantifying menthol,camphor,1,8-cineole,linalool,borneol and caryophyllene oxide by QAMS(quantitative analysis of multi-components by single-marker).[Methods]The method was performed using an Agilent DB-WAX(30 m×0.32 mm,0.25μm)polyethylene glycol chromatographic column;with nitrogen employed as a carrier gas.The constant pressure was 4.73 psi;and the injection temperature was 240℃,with a shunt ratio:of 10:1;The hydrogen flame ion detector with a detector temperature of 240℃;the injection volume was 0.3μL.To verify the accuracy and applicability of QAMS,the results were compared with those obtained using the internal standard method(naphthalene).[Results]In Wanjinxiang Shushuang Ointment,menthol,camphor,1,8-cineole,linalool,borneol,caryophyllene oxide and naphthalene were well separated by the same chromatography with good linearity in their respective ranges(R≥0.9992).The average recoveries were 99.66%,101.03%,98.07%,98.24%,101.39%,and 103.39%with RSD s of 0.69%,1.52%,1.25%,1.94%,1.44%,and 2.74%,respectively.The QAMS is similar to the internal standard method.[Conclusions]This simple,accurate method with high precision,separation and reproducibility can serve as a reference for the quality control of Wanjinxiang Shushuang Ointment.展开更多
To assist with the commissioning [1] of the Five-hundredmeter Aperture Spherical radio Telescope (FAST), we performed a pulsar search, with the primary goal of developing and testing the pulsar data acquisition and pr...To assist with the commissioning [1] of the Five-hundredmeter Aperture Spherical radio Telescope (FAST), we performed a pulsar search, with the primary goal of developing and testing the pulsar data acquisition and processing pipelines. We tested and used three pipelines, two (Pl and P2 hereafter) searched for the periodic signature of pulsars whereas the other one was used to search for bright single pulses (P3 hereafter).展开更多
The Commensal Radio Astronomy Five-hundred-meter Aperture Spherical radio Telescope(FAST) Survey(CRAFTS) utilizes the novel drift-scan commensal survey mode of FAST and can generate billions of pulsar candidate signal...The Commensal Radio Astronomy Five-hundred-meter Aperture Spherical radio Telescope(FAST) Survey(CRAFTS) utilizes the novel drift-scan commensal survey mode of FAST and can generate billions of pulsar candidate signals. The human experts are not likely to thoroughly examine these signals, and various machine sorting methods are used to aid the classification of the FAST candidates. In this study, we propose a new ensemble classification system for pulsar candidates. This system denotes the further development of the pulsar image-based classification system(PICS), which was used in the Arecibo Telescope pulsar survey, and has been retrained and customized for the FAST drift-scan survey. In this study, we designed a residual network model comprising 15 layers to replace the convolutional neural networks(CNNs) in PICS. The results of this study demonstrate that the new model can sort >96% of real pulsars to belong the top 1% of all candidates and classify >1.6 million candidates per day using a dual-GPU and 24-core computer. This increased speed and efficiency can help to facilitate real-time or quasi-real-time processing of the pulsar-search data stream obtained from CRAFTS. In addition, we have published the labeled FAST data used in this study online, which can aid in the development of new deep learning techniques for performing pulsar searches.展开更多
High sensitivity radio searches of unassociated γ-ray sources have proven to be an effective way of finding new pulsars. Using the Five-hundred-meter Aperture Spherical radio Telescope(FAST) during its commissioning ...High sensitivity radio searches of unassociated γ-ray sources have proven to be an effective way of finding new pulsars. Using the Five-hundred-meter Aperture Spherical radio Telescope(FAST) during its commissioning phase, we have carried out a number of targeted deep searches of Fermi Large Area Telescope(LAT) γ-ray sources. On February 27, 2018 we discovered an isolated millisecond pulsar(MSP), PSR J0318+0253, coincident with the unassociated γ-ray source 3 FGL J0318.1+0252. PSR J0318+0253 has a spin period of 5.19 ms, a dispersion measure(DM) of 26 pc cm-3 corresponding to a DM distance of about 1.3 kpc, and a period-averaged flux density of(~11±2) μJy at L-band(1.05-1.45 GHz). Among all high energy MSPs, PSR J0318+0253 is the faintest ever detected in radio bands, by a factor of at least ~4 in terms of L-band fluxes. With the aid of the radio ephemeris, an analysis of 9.6 years of Fermi-LAT data revealed that PSR J0318+0253 also displays strong γ-ray pulsations. Follow-up observations carried out by both Arecibo and FAST suggest a likely spectral turn-over around 350 MHz. This is the first result from the collaboration between FAST and the Fermi-LAT teams as well as the first confirmed new MSP discovery by FAST, raising hopes for the detection of many more MSPs. Such discoveries will make a significant contribution to our understanding of the neutron star zoo while potentially contributing to the future detection of gravitational waves, via pulsar timing array(PTA) experiments.展开更多
The orthogonal nonnegative matrix factorization （ONMF） has many applications in a variety of areas such as data mining, information processing and pattern recognition. In this paper, we propose a novel initializatio...The orthogonal nonnegative matrix factorization （ONMF） has many applications in a variety of areas such as data mining, information processing and pattern recognition. In this paper, we propose a novel initialization method for the ONMF based on the Lanczos bidiagonalization and the nonnegative approximation of rank one matrix. Numerical experiments are given to show that our initialization strategy is effective and efficient.展开更多
基金supported by the National Natural Science Foundation of China(NSFC)Grant Nos.11988101,1172531312041303,12041304,12203045,12203070,12103013,T2241020the National SKA Program of China(Nos.2020SKA0120200,2022SKA0130100,2022SKA0130104)+5 种基金the Foundation of Science and Technology of Guizhou Province(No.(2021)023)the Foundation of Guizhou Provincial Education Department(Nos.KY(2021)303,KY(2020)003)support from the National Natural Science Foundation of China under grant U2031117the Youth Innovation Promotion Association CAS(id.2021055)CAS Project for Young Scientists in Basic Research(grant YSBR006)the Cultivation Project for FAST Scientific Payoff and Research Achievement of CAMS-CAS。
文摘We report the discovery of PSR J1909+0122 by the Five-hundred-meter Aperture Spherical Radio Telescope(FAST)as part of the Commensal Radio Astronomy FAST Survey.PSR J1909+0122 has a spin period of 1.257 s and a dispersion measure of 186.2 pc cm^(-3).The averaged pulse profile shows two distinct components.We performed a single-pulse study based on a one-hour observation at 1.25 GHz on 2021 August 23.We used a threshold of 5σ_(ep) to measure the nulling fraction(NF)as 63%±1.5%.The longitude-resolved fluctuation spectra and fast Fourier transform spectra of the binary sequences revealed the quasi-periodicity of nulling with a period of 30 rotation periods.We examined the reliability of the periodicity by comparing it to random noise injection.The NF,E,and modulation periodicity P_(M) of PSR J1909+0122 were compared with other periodic nulling pulsars,showing that the source of J1909+0122 has the second largest NF in the population.Long-term timing observations over six months were used to derive the phase-connected ephemeris of this pulsar.The measured P and P values disfavor dipolar geometry for polar gap models,and the prediction for a space-charge-limited flow model in the case of inverse Compton scattering is only just above the death line.In this work,PSR J1909+0122 has revealed possible correlations between nulling behavior and pulsar properties,which will help to shed light on the pulsar emission mechanism and its temporal evolution in future observations.
基金Supported by Projects of Guizhou Provincial Department of Education-Growth Program of Young Scientific and Technological Talents in Guizhou Ordinary Higher Education Institutions(QJHKY[2022]264)Rolling Support for Provincial University Research Platform Team Projects(QJJ[2022]010).
文摘[Objectives]To regulate the quality of Wanjinxiang Shushuang Ointment through simultaneously quantifying menthol,camphor,1,8-cineole,linalool,borneol and caryophyllene oxide by QAMS(quantitative analysis of multi-components by single-marker).[Methods]The method was performed using an Agilent DB-WAX(30 m×0.32 mm,0.25μm)polyethylene glycol chromatographic column;with nitrogen employed as a carrier gas.The constant pressure was 4.73 psi;and the injection temperature was 240℃,with a shunt ratio:of 10:1;The hydrogen flame ion detector with a detector temperature of 240℃;the injection volume was 0.3μL.To verify the accuracy and applicability of QAMS,the results were compared with those obtained using the internal standard method(naphthalene).[Results]In Wanjinxiang Shushuang Ointment,menthol,camphor,1,8-cineole,linalool,borneol,caryophyllene oxide and naphthalene were well separated by the same chromatography with good linearity in their respective ranges(R≥0.9992).The average recoveries were 99.66%,101.03%,98.07%,98.24%,101.39%,and 103.39%with RSD s of 0.69%,1.52%,1.25%,1.94%,1.44%,and 2.74%,respectively.The QAMS is similar to the internal standard method.[Conclusions]This simple,accurate method with high precision,separation and reproducibility can serve as a reference for the quality control of Wanjinxiang Shushuang Ointment.
基金supported by the National Key R&D Program of China(Grant No.2017YFA0402600)the State Key Development Program for Basic Research(Grant No.2015CB857100)+8 种基金the Open Project Program of the Key Laboratory of FAST,NAOC,Chinese Academy of Sciencessupported by the Chinese Academy of Sciences Pioneer Hundred Talents Programthe Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB23000000)supported in part by the Youth Innovation Promotion Association of CAS(Id.2018075)supported by the National Natural Science Foundation of China(Grant No.11703047)the National Natural Science Foundation of China(Grant Nos.11690024,11743002,and 11873067)the CAS"Light of West China" Programsupported by the CAS"Light of West China" ProgramThe Parkes radio telescope is part of the Australia Telescope National Facility which is funded by the Australian Government for operation as a National Facility managed by CSIRO
文摘To assist with the commissioning [1] of the Five-hundredmeter Aperture Spherical radio Telescope (FAST), we performed a pulsar search, with the primary goal of developing and testing the pulsar data acquisition and processing pipelines. We tested and used three pipelines, two (Pl and P2 hereafter) searched for the periodic signature of pulsars whereas the other one was used to search for bright single pulses (P3 hereafter).
基金supported by the National Key Research and Development Program of China(Grant No.2017YFA0402600)the Natural Science Foundation of Shandong(Grant No.ZR2015FL006)+4 种基金the CAS International Partnership Program(Grant No.114A11KYSB20160008)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB23000000)the Chinese Academy of Sciences Pioneer Hundred Talents Programthe National Natural Science Foundation of China(Grant Nos.61472043,11743002,11873067,11690024,and 11725313)the Joint Research Fund in Astronomy(Grant No.U1531242)under Cooperative Agreement between the NSFC and CAS and National Natural Science Foundation of China(Grant No.11673005)
文摘The Commensal Radio Astronomy Five-hundred-meter Aperture Spherical radio Telescope(FAST) Survey(CRAFTS) utilizes the novel drift-scan commensal survey mode of FAST and can generate billions of pulsar candidate signals. The human experts are not likely to thoroughly examine these signals, and various machine sorting methods are used to aid the classification of the FAST candidates. In this study, we propose a new ensemble classification system for pulsar candidates. This system denotes the further development of the pulsar image-based classification system(PICS), which was used in the Arecibo Telescope pulsar survey, and has been retrained and customized for the FAST drift-scan survey. In this study, we designed a residual network model comprising 15 layers to replace the convolutional neural networks(CNNs) in PICS. The results of this study demonstrate that the new model can sort >96% of real pulsars to belong the top 1% of all candidates and classify >1.6 million candidates per day using a dual-GPU and 24-core computer. This increased speed and efficiency can help to facilitate real-time or quasi-real-time processing of the pulsar-search data stream obtained from CRAFTS. In addition, we have published the labeled FAST data used in this study online, which can aid in the development of new deep learning techniques for performing pulsar searches.
基金supported by the National Natural Science Foundation of China (Grant Nos.11988101,11690024,11743002,11873067,U1631132,U1831131,U1731238,U1938103,11703047,11773041,and 11673060)the National Key R&D Program of China (Grant No.2017YFA0402600)+10 种基金the Chinese Academy of Sciences (CAS) Key Laboratory of FAST,NAOC,Chinese Academy of Sciences,the National Basic Research Program of China (Grant No.2015CB857100)the CAS Strategic Priority Research Program (Grant No.XDB23000000)the CAS International Partnership Program (Grant No.114A11KYSB20160008)the Open Project Program of the Key Laboratory of FAST,NAOC,Chinese Academy of Sciences and Guizhou Provincial Key Laboratory of Radio Astronomy and Data Processing,Guizhou Normal Universitysupport by the Youth Innovation Promotion Association CAS (Grant No.2021055)the CAS Project for Young Scientists in Basic Reasearch (Grant No.YSBR-006)the Cultivation Project for FAST Scientific Payoff and Research Achievement of CAMS-CASpartially supported by the Fermi Guest Observer Program,administered by NASA (Grant No.80NSSC18K1731)support from the ERC under the European Union’s Horizon 2020 Research and Innovation Programme (Grant No.715051Spiders)NRL is supported by NASA。
文摘High sensitivity radio searches of unassociated γ-ray sources have proven to be an effective way of finding new pulsars. Using the Five-hundred-meter Aperture Spherical radio Telescope(FAST) during its commissioning phase, we have carried out a number of targeted deep searches of Fermi Large Area Telescope(LAT) γ-ray sources. On February 27, 2018 we discovered an isolated millisecond pulsar(MSP), PSR J0318+0253, coincident with the unassociated γ-ray source 3 FGL J0318.1+0252. PSR J0318+0253 has a spin period of 5.19 ms, a dispersion measure(DM) of 26 pc cm-3 corresponding to a DM distance of about 1.3 kpc, and a period-averaged flux density of(~11±2) μJy at L-band(1.05-1.45 GHz). Among all high energy MSPs, PSR J0318+0253 is the faintest ever detected in radio bands, by a factor of at least ~4 in terms of L-band fluxes. With the aid of the radio ephemeris, an analysis of 9.6 years of Fermi-LAT data revealed that PSR J0318+0253 also displays strong γ-ray pulsations. Follow-up observations carried out by both Arecibo and FAST suggest a likely spectral turn-over around 350 MHz. This is the first result from the collaboration between FAST and the Fermi-LAT teams as well as the first confirmed new MSP discovery by FAST, raising hopes for the detection of many more MSPs. Such discoveries will make a significant contribution to our understanding of the neutron star zoo while potentially contributing to the future detection of gravitational waves, via pulsar timing array(PTA) experiments.
基金Acknowledgments. The work is supported by National Natural Science Foundation of China No. 10961010.
文摘The orthogonal nonnegative matrix factorization （ONMF） has many applications in a variety of areas such as data mining, information processing and pattern recognition. In this paper, we propose a novel initialization method for the ONMF based on the Lanczos bidiagonalization and the nonnegative approximation of rank one matrix. Numerical experiments are given to show that our initialization strategy is effective and efficient.
