This study focuses on the electrical properties and microstructure of polypropylene(PP)-based blends used for cable insulation in nuclear power plants(NPPs).The PP-based blend,comprising isotactic PP and propylene-bas...This study focuses on the electrical properties and microstructure of polypropylene(PP)-based blends used for cable insulation in nuclear power plants(NPPs).The PP-based blend,comprising isotactic PP and propylene-based elastomer(PBE)at concentrations ranging from 0 to 50 wt%,underwent a melt blending process and subsequent cobalt-60 gamma-ray irradiation with doses ranging from 0 to 250 kGy.Electrical conductivity,trap distribution,and alternating(AC)breakdown strength were chosen to assess the insulation performance.These results indicate that the addition of PBE significantly improves the electrical properties of PP under irradiation.For PP,the electrical conductivity increased with irradiation,whereas the trap depth and breakdown strength decreased sharply.Conversely,for the blend,these changes initially exhibit opposite trends.When the irradiation was increased to 250 kGy,the AC breakdown strength of the blend improved by more than 21%compared to that of PP.The physical and chemical structures of the samples were investigated to explore the improvement mechanisms.The results offer insights into the design of new cable-insulation materials suitable for NPPs.展开更多
In this study,an end-to-end deep learning method is proposed to improve the accuracy of continuum estimation in low-resolution gamma-ray spectra.A novel process for generating the theoretical continuum of a simulated ...In this study,an end-to-end deep learning method is proposed to improve the accuracy of continuum estimation in low-resolution gamma-ray spectra.A novel process for generating the theoretical continuum of a simulated spectrum is established,and a convolutional neural network consisting of 51 layers and more than 105 parameters is constructed to directly predict the entire continuum from the extracted global spectrum features.For testing,an in-house NaI-type whole-body counter is used,and 106 training spectrum samples(20%of which are reserved for testing)are generated using Monte Carlo simulations.In addition,the existing fitting,step-type,and peak erosion methods are selected for comparison.The proposed method exhibits excellent performance,as evidenced by its activity error distribution and the smallest mean activity error of 1.5%among the evaluated methods.Additionally,a validation experiment is performed using a whole-body counter to analyze a human physical phantom containing four radionuclides.The largest activity error of the proposed method is−5.1%,which is considerably smaller than those of the comparative methods,confirming the test results.The multiscale feature extraction and nonlinear relation modeling in the proposed method establish a novel approach for accurate and convenient continuum estimation in a low-resolution gamma-ray spectrum.Thus,the proposed method is promising for accurate quantitative radioactivity analysis in practical applications.展开更多
The study of high-energy gamma-ray emission from gamma-ray bursts(GRBs)involves complex synchrotron radiation and synchrotron self-Compton(SSC)scattering mechanisms with multiple parameters exhibiting a wide distribut...The study of high-energy gamma-ray emission from gamma-ray bursts(GRBs)involves complex synchrotron radiation and synchrotron self-Compton(SSC)scattering mechanisms with multiple parameters exhibiting a wide distribution.Recent advancements in GRB research,particularly the observation of very high energy(VHE,>100 Ge V)radiation,have ushered in a new era of multiwavelength exploration,offering fresh perspectives and limitations for understanding GRB radiation mechanisms.This study aimed to leverage VHE observations to refine constraints on synchrotron+SSC radiation from electrons accelerated by forward shocks.By analyzing two external environments—the uniform interstellar medium and stratified stellar wind medium,we conducted spectral and variability fitting for five specific bursts(GRB 180720B,GRB 190114C,GRB 190829A,GRB 201216C,and GRB 221009A)to identify the optimal parameters characterizing these events.A comparative analysis of model parameter distributions with and without VHE radiation observations reveals that the magnetic energy equipartition factorεBis more concentrated with VHE emissions.This suggests that VHE emissions may offer greater constraints on this microphysical parameter.Additionally,we found that the energy budget between VHE and ke V–Me Vγ-ray emissions under the SSC radiation exhibits an almost linear relationship,which may serve as a tool to differentiate radiation mechanisms.We anticipate future statistical analyses of additional VHE bursts to validate our findings.展开更多
Neutron-induced gamma-ray imaging is a spectroscopic technique that uses characteristic gamma rays to infer the elemental distribution of an object.Currently,this technique requires the use of large facilities to supp...Neutron-induced gamma-ray imaging is a spectroscopic technique that uses characteristic gamma rays to infer the elemental distribution of an object.Currently,this technique requires the use of large facilities to supply a high neutron flux and a time-consuming detection procedure involving direct collimating measurements.In this study,a new method based on low neutron flux was proposed.A single-pixel gamma-ray detector combined with random pattern gamma-ray masks was used to measure the characteristic gamma rays emitted from the sample.Images of the elemental distribution in the sample,comprising 30×30 pixels,were reconstructed using the maximum-likelihood expectation-maximization algorithm.The results demonstrate that the elemental imaging of the sample can be accurately determined using this method.The proposed approach,which eliminates the need for high neutron flux and scanning measurements,can be used for in-field imaging applications.展开更多
The effects and rules of the dimensionless parameterξon neutrino annihilation v+v→e^(-)+e^(+)dominated gamma-ray bursts are analysed and investigated within the context of black holes in asymptotic safety.We also co...The effects and rules of the dimensionless parameterξon neutrino annihilation v+v→e^(-)+e^(+)dominated gamma-ray bursts are analysed and investigated within the context of black holes in asymptotic safety.We also computationally model photon orbits around black holes,as photons and neutrinos have the same geodesic equations near black holes.We show that the black hole shadow radius decreases with increasingξ.Calculations are made to determine the temperature of the accretion disk surrounding the black hole and the ratio Q/Q_(Newt)of energy deposition per unit time and compared to that of the Newtonian scenario.The accretion disk temperature peaks at a higher temperature due to quantum gravity corrections,which increases the probability of neutrino emission from the black hole.It is interesting to note that larger quantum gravity effects cause the ratio value to significantly decline.In the neutrinoantineutrino annihilation process,the energy deposition rate is sufficient even while the energy conversion is inhibited because of quantum corrections.Gamma-ray bursts might originate from the corrected annihilation process.Additionally,we examine the derivative dQ/dr about the star radius r.The findings demonstrate that the ratio is lowered by the black hole's quantum influence.The neutrino pair annihilation grows weaker the more prominent the influence of quantum gravity.展开更多
Novae are found to have GeV to TeVγ-ray emission,which reveals the shock acceleration from the white dwarfs.Recently,V1405 Cas was reported to radiate suspiciousγ-ray by Fermi-LAT with low signi?cance(4.1σ)after th...Novae are found to have GeV to TeVγ-ray emission,which reveals the shock acceleration from the white dwarfs.Recently,V1405 Cas was reported to radiate suspiciousγ-ray by Fermi-LAT with low signi?cance(4.1σ)after the optical maximum.Radio observations reveal that it is one of the?ve brightest novae surrounded by low-density ionized gas columns.Here we report a continuous search for GeVγ-ray from Fermi-LAT.Noγ-ray was found.For V1405 Cas the?ux level is lower than other well-studied Fermi novae,and theγ-ray maximum appears at t0+145 days.γ-ray of V1405 Cas is used to search potentialγ-ray periodicity.Noγ-ray periodicity was found during the time of observation.By comparing multi-wavelength data,theγ-ray upper limit to optical?ux ratio with a value at around 10^(-4)is obtained to constrain the shock acceleration.Long-term analysis from Swift-XRT gets X-ray spectral in the post-shock phase,which indicates that V1405 Cas became a super-soft source.The best-?t black body temperature at the super soft state is 0.11-0.19 keV.展开更多
Due to the availability and particular features, wood was one of the first materials used by mankind with a wide variety of applications. It can be used as raw-material for paper and cellulose manufacturing; in indust...Due to the availability and particular features, wood was one of the first materials used by mankind with a wide variety of applications. It can be used as raw-material for paper and cellulose manufacturing; in industries such as chemical, naval, furniture, sports goods, toys, and musical instruments; in building construction and in the distribution of electric energy. Wood has been widely researched; therefore, wood researchers know that several aspects such as temperature, latitude, longitude, altitude, sunlight, soil, and rainfall index interfere as to the growth of trees. This behavior explains why the average of physical chemical properties is important in wood study.Most of the researchers consider density to be the most important wood property because of its straight relationship with the physical and mechanical properties in wood. There are three types of wood density： basic, apparent and green. The apparent density was used here at 12% of moisture content. In this study, four different types of wood were used： ＂Freijo＂, ＂Jequitiba＂, ＂Muiracatiara＂ and ＂Ipe＂. For wood density determination by non-conventional method, ^241Am, ^133Ba and ^137Cs gamma-ray sources, a NaI scintillation detector and a counter were used. The results demonstrated that this technique is quick and accurate. Considering the nuclear parameters obtained as half-value layers and linear absorption coefficients,^ 137Cs demonstrated to be the best option to be used for inspection of the physical integrity of electric wooden poles and live trees for future works.展开更多
This study reports the performances of efficiency calibrations for high-purity-germanium gamma-ray spectrometry using the source-, Laboratory Sourceless Object Calibration Software(LabSOCS)-and ANGLE-based methods in ...This study reports the performances of efficiency calibrations for high-purity-germanium gamma-ray spectrometry using the source-, Laboratory Sourceless Object Calibration Software(LabSOCS)-and ANGLE-based methods in an inter-comparison exercise. Although the results of LabSOCS and ANGLE for ^(241)Am emitting lowenergy gamma rays were not very satisfactory, all of the three efficiency calibration methods passed acceptance criteria. The results confirmed the reliability of the calculation codes ANGLE and LabSOCS as alternative efficiency calibration methods in high-purity-germanium gamma spectrometry. This study is likely to promote the further application of the ANGLE and LabSOCS calculation codes in radioactivity measurements.展开更多
Gamma-Ray Integrated Detectors(GRID)mis-sion is a student project designed to use multiple gamma-ray detectors carried by nanosatellites(CubeSats),forming a full-time all-sky gamma-ray detection network that monitors ...Gamma-Ray Integrated Detectors(GRID)mis-sion is a student project designed to use multiple gamma-ray detectors carried by nanosatellites(CubeSats),forming a full-time all-sky gamma-ray detection network that monitors the transient gamma-ray sky in the multi-mes-senger astronomy era.A compact CubeSat gamma-ray detector,including its hardware and firmware,was designed and implemented for the mission.The detector employs four Gd 2 Al 2 Ga 3 O 12:Ce(GAGG:Ce)scintillators coupled with four silicon photomultiplier(SiPM)arrays to achieve a high gamma-ray detection efficiency between 10 keV and 2 MeV with low power and small dimensions.The first detector designed by the undergraduate student team onboard a commercial CubeSat was launched into a Sun-synchronous orbit on October 29,2018.The detector was in a normal observation state and accumulated data for approximately one month after on-orbit functional and performance tests,which were conducted in 2019.展开更多
In this study,the anti-noise performance of a pulse-coupled neural network(PCNN)was investigated in the neutron and gamma-ray(n-γ)discrimination field.The experiments were conducted in two groups.In the first group,r...In this study,the anti-noise performance of a pulse-coupled neural network(PCNN)was investigated in the neutron and gamma-ray(n-γ)discrimination field.The experiments were conducted in two groups.In the first group,radiation pulse signals were pre-processed using a Fourier filter to reduce the original noise in the signals,whereas in the second group,the original noise was left untouched to simulate an extremely high-noise scenario.For each part,artificial Gaussian noise with different intensity levels was added to the signals prior to the discrimination process.In the aforementioned conditions,the performance of the PCNN was evaluated and compared with five other commonly used methods of n-γdiscrimination:(1)zero crossing,(2)charge comparison,(3)vector projection,(4)falling edge percentage slope,and(5)frequency gradient analysis.The experimental results showed that the PCNN method significantly outperforms other methods with outstanding FoM-value at all noise levels.Furthermore,the fluctuations in FoM-value of PCNN were significantly better than those obtained via other methods at most noise levels and only slightly worse than those obtained via the charge comparison and zerocrossing methods under extreme noise conditions.Additionally,the changing patterns and fluctuations of the FoMvalue were evaluated under different noise conditions.Hence,based on the results,the parameter selection strategy of the PCNN was presented.In conclusion,the PCNN method is suitable for use in high-noise application scenarios for n-γdiscrimination because of its stability and remarkable discrimination performance.It does not rely on strict parameter settings and can realize satisfactory performance over a wide parameter range.展开更多
With the increasing application of electric and electronic devices in space and nuclear power stations, the polymeric insulation materials are inevitably exposed to various kinds of environments. Accordingly, it becom...With the increasing application of electric and electronic devices in space and nuclear power stations, the polymeric insulation materials are inevitably exposed to various kinds of environments. Accordingly, it becomes necessary to investigate the effects of the radiation and air pressure on insulation materials. This paper describes the effects of gamma-ray irradiation and reduced pressure on dielectric breakdown of polybutylene naphthalate (PBN) and polybutylene terephthalate (PBT) by applying a DC pulse voltage. Both PBN and PBT were irradiated in air up to 100 kGy and then up to 1 000 kGy with a dose rate of 10 kGy/h by using a60Co gamma-source. The effects of total dose and reduced pressure on the time to dielectric breakdown and discharge quantity were discussed. Obtained results show that, while increasing the total dose, the discharge quantity decreased with PBN, but increased with PBT. With decreasing the air pressure, the discharge quantity increased with PBN, but decreased with PBT. With increasing the total dose, the time to dielectric breakdown increased with PBN, but decreased with PBT. With decreasing the air pressure, the time to dielectric breakdown increased with both PBN and PBT. The experimental results suggest that the chemical structure of polybutylene polymers plays a main role in the result of radiation reaction, which is related to cross-linking and degradation reaction.展开更多
Since the successful launch of NASA＇s dedicated gamma-ray burst （GRB） mission, Swift, the study of cosmological GRBs has entered a new era. Here I review the rapid observational and theoretical progress in this dyn...Since the successful launch of NASA＇s dedicated gamma-ray burst （GRB） mission, Swift, the study of cosmological GRBs has entered a new era. Here I review the rapid observational and theoretical progress in this dynamical research field during the first two-year of the Swift mission, focusing on how observational breakthroughs have revolutionized our understanding of the physical origins of GRBs. Besides summarizing how Swift helps to solve some pre-Swift mysteries, I also list some outstanding problems raised by the Swift observations. An outlook of GRB science in the future, especially in the GLAST era, is briefly discussed.展开更多
We present the thorium distribution on the lunar surface derived from observations by the Chang’E-2 gamma-ray spectrometer(CE-2 GRS). This new map shows a similar thorium distribution to previous observations. In com...We present the thorium distribution on the lunar surface derived from observations by the Chang’E-2 gamma-ray spectrometer(CE-2 GRS). This new map shows a similar thorium distribution to previous observations. In combination with this new thorium map and impact cratering model, we investigate the origination of thorium on the Moon’s highlands, which was previously thought to be contributed from Imbrium ejecta. We found that the Imbrium ejecta has a small contribution(~20%–30%) to the thorium on the lunar highlands but most thorium is likely to be indigenous before the deposition of the Imbrium ejecta. This new thorium map also confirms that the eastern highlands have a relatively higher thorium concentration than the western highlands. We propose that the thin crust and large basins on the eastern highlands are responsible for this difference in thorium.展开更多
The ability to precisely estimate the void fraction of multiphase flow in a pipe is very important in the petroleum industry. In this paper, an approach based on our previous works is proposed for predicting the void ...The ability to precisely estimate the void fraction of multiphase flow in a pipe is very important in the petroleum industry. In this paper, an approach based on our previous works is proposed for predicting the void fraction independent of flow regime and liquid phase density changes in gas–liquid two-phase flows. Implemented technique is a combination of dual modality densitometry and multi-beam gamma-ray attenuation techniques. The detection system is comprised of a single energy fan beam,two transmission detectors, and one scattering detector. In this work, artificial neural network(ANN) was also implemented to predict the void fraction percentage independent of the flow regime and liquid phase density changes. Registered counts in three detectors and void fraction percentage were utilized as the inputs and output of ANN, respectively. By applying the proposed methodology, the void fraction was estimated with a mean relative error of less than just 1.2480%.展开更多
In this study, the Maastrichtian-Danian boundary was measured and sampled in two stratigraphic sections, the north and south flanks of the Dehnow anticline in Coastal Fars, Southern Iran. This boundary was also invest...In this study, the Maastrichtian-Danian boundary was measured and sampled in two stratigraphic sections, the north and south flanks of the Dehnow anticline in Coastal Fars, Southern Iran. This boundary was also investigated in the drilled exploratory well-1 in the same region. The lithology of the Maastrichtian-Danian deposits consists of glauconitic, phosphatic argillaceous limestones and marlstones. 30 genera and 77 species of planktonic foraminifera have been determined. The recognized biozones are the Gansserina gansseri Interval Zone, and the Contusotruncana contusa Interval Zone, which indicates latest Campanian to middle Maastrichtian age for the upper part of the Gurpi Formation. In addition, the Eoglobigerina edita(P1) Partial Range Zone, Praemurica uncinata(P2) Lowest Occurrence Zone, Morozovella angulata(P3) Lowest Occurrence Zone and Globanomalina psudomenardii(P4) Taxon Range Zone represent a Danian to Thanetian age for the lower part of the Pabdeh Formation. From the absence of the Abathomphalus mayaroensis Interval Zone, Pseudoguembelina hariaensis Interval Zone, Pseudotextularia elegans Interval Zone, Plummerita hantkeninoides Interval Zone, Guembelitria cretacea(P0) Partial Range Zone and Parvularugoglobigerina eugubina(Pα) Total Range Zone, it can be deduced that there is a paraconformity across the Maastrichtian–Danian boundary in the studied area, this hiatus encompassing the late Maastrichtian and the earliest Danian. Danian deposits from the study area contain reworked glauconitized macrofossils, planktonic and benthic foraminifera of the Cretaceous. The obtained surface gamma-ray spectrometry logs resemble the exploratory well-1 gamma-ray wireline log.展开更多
The phenomenon of gamma-ray burst （GRB） spectral lags is very common, but a definitive explanation has not yet been given. From a sample of 82 GRB pulses we find that the spectral lags are correlated with the pulse ...The phenomenon of gamma-ray burst （GRB） spectral lags is very common, but a definitive explanation has not yet been given. From a sample of 82 GRB pulses we find that the spectral lags are correlated with the pulse widths, however, there is no correlation between the relative spectral lags and the relative pulse widths. We suspect that the correlations between spectral lags and pulse widths might be caused by the Lorentz factor of the GRBs concerned. Our analysis on the relative quantities suggests that the intrinsic spectral lag might reflect other aspect of pulses than the aspect associated with the dynamical time of shocks or that associated with the time delay due to the curvature effect.展开更多
Optical and radio afterglows arising from shocks by relativistic conical ejecta running into pre-burst massive stellar winds are revisited. Under the homogeneous thin-shell approximation and a realistic treatment for ...Optical and radio afterglows arising from shocks by relativistic conical ejecta running into pre-burst massive stellar winds are revisited. Under the homogeneous thin-shell approximation and a realistic treatment for the lateral expansion of jets, our results show that a notable break exists in the optical light curve in most cases we calculated in which the physical parameters are varied within reasonable ranges. For a relatively tenuous wind which cannot decelerate the relativistic jet to cause a light curve break within days, the wind termination shock due to the ram pressure of the surrounding medium occurs at a small radius, namely, a few times 10<SUP>17</SUP> cm. In such a structured wind environment, the jet will pass through the wind within several hours and run into the outer uniform dense medium. The resulting optical light curve flattens with a shallower drop after the jet encounters the uniform medium, and then declines deeply, triggered by runaway lateral expansion.展开更多
In this study,the theory of minimum detectable activity concentration(MDAC)for airborne gamma-ray spectrometry(AGS)was derived,and the relationship between the MDAC and the intrinsic effi-ciency of a scintillation cou...In this study,the theory of minimum detectable activity concentration(MDAC)for airborne gamma-ray spectrometry(AGS)was derived,and the relationship between the MDAC and the intrinsic effi-ciency of a scintillation counter,volume,and energy res-olution of scintillation crystals,and flight altitude of an aircraft was investigated.To verify this theory,experi-mental devices based on NaI and CeBr 3 scintillation counters were prepared,and the potassium,uranium,and thorium contents in calibration pads obtained via the stripping ratio method and theory were compared.The MDACs of AGS under different conditions were calculated and analyzed using the proposed theory and the Monte Carlo method.The relative errors found via a comparison of the experimental and theoretical results were less than 4%.The theory of MDAC can guide the work of AGS in probing areas with low radioactivity.展开更多
The research on the properties of graphene oxide（GO） in various media has become one of the hottest topics since GO is now the main raw material for graphene-based advanced materials. In this work, the g-ray radiati...The research on the properties of graphene oxide（GO） in various media has become one of the hottest topics since GO is now the main raw material for graphene-based advanced materials. In this work, the g-ray radiation chemistry effect of GO nanosheets and their self-aggregation behavior in t-butanol/water medium were investigated. The results show that GO nanosheets are reduced and hydroxyalkylated simultaneously by the alcohol free radicals produced by the radiolysis of t-butanol/water solution under g-ray radiation. The radiation-modified GO nanosheets will self-assemble into a self-standing graphene hydrogel when the p H of the solution is lower than 2. A hydroxyl-functionalized free-standing graphene aerogel is further obtained simply by freeze-drying. This work provides not only a general self-assembly mechanism of GO nanosheets in strong acidic alcohol/water media under high energy radiation, but also a facile and economical preparation method for hydroxyalkylated graphene-based aerogel.展开更多
The well-known correlation between radio luminosity （LR） and X-ray luminosity （Lx）, LR/LX 10^-5, holds for a variety of objects, such as active galactic nuclei, Galactic black holes, solar flares and cool stars....The well-known correlation between radio luminosity （LR） and X-ray luminosity （Lx）, LR/LX 10^-5, holds for a variety of objects, such as active galactic nuclei, Galactic black holes, solar flares and cool stars. Here we extend the relation to gamma-ray bursts （GRBs） and find that the GRBs also obey a similar LR - LX relation, with a slightly different slope of LR ∝ LX^1.1. This relation implies that the explosions that occur on different scales may have a common underlying origin.展开更多
基金supported by the National Natural Science Foundation of China(No.52077151)the State Key Laboratory of Electrical Insulation and Power Equipment(No.EIPE23208)the Key Laboratory of Engineering Dielectrics and Its Application,Ministry of Education(No.KFM202203).
文摘This study focuses on the electrical properties and microstructure of polypropylene(PP)-based blends used for cable insulation in nuclear power plants(NPPs).The PP-based blend,comprising isotactic PP and propylene-based elastomer(PBE)at concentrations ranging from 0 to 50 wt%,underwent a melt blending process and subsequent cobalt-60 gamma-ray irradiation with doses ranging from 0 to 250 kGy.Electrical conductivity,trap distribution,and alternating(AC)breakdown strength were chosen to assess the insulation performance.These results indicate that the addition of PBE significantly improves the electrical properties of PP under irradiation.For PP,the electrical conductivity increased with irradiation,whereas the trap depth and breakdown strength decreased sharply.Conversely,for the blend,these changes initially exhibit opposite trends.When the irradiation was increased to 250 kGy,the AC breakdown strength of the blend improved by more than 21%compared to that of PP.The physical and chemical structures of the samples were investigated to explore the improvement mechanisms.The results offer insights into the design of new cable-insulation materials suitable for NPPs.
基金supported by the National Natural Science Foundation of China(No.12005198).
文摘In this study,an end-to-end deep learning method is proposed to improve the accuracy of continuum estimation in low-resolution gamma-ray spectra.A novel process for generating the theoretical continuum of a simulated spectrum is established,and a convolutional neural network consisting of 51 layers and more than 105 parameters is constructed to directly predict the entire continuum from the extracted global spectrum features.For testing,an in-house NaI-type whole-body counter is used,and 106 training spectrum samples(20%of which are reserved for testing)are generated using Monte Carlo simulations.In addition,the existing fitting,step-type,and peak erosion methods are selected for comparison.The proposed method exhibits excellent performance,as evidenced by its activity error distribution and the smallest mean activity error of 1.5%among the evaluated methods.Additionally,a validation experiment is performed using a whole-body counter to analyze a human physical phantom containing four radionuclides.The largest activity error of the proposed method is−5.1%,which is considerably smaller than those of the comparative methods,confirming the test results.The multiscale feature extraction and nonlinear relation modeling in the proposed method establish a novel approach for accurate and convenient continuum estimation in a low-resolution gamma-ray spectrum.Thus,the proposed method is promising for accurate quantitative radioactivity analysis in practical applications.
基金supported by the National Natural Science Foundation of China(NSFC,grant Nos.12275279 and 12405124)the China Postdoctoral Science Foundation(No.2023M730423)Horizontal research project in natural sciences(No.H20230120)。
文摘The study of high-energy gamma-ray emission from gamma-ray bursts(GRBs)involves complex synchrotron radiation and synchrotron self-Compton(SSC)scattering mechanisms with multiple parameters exhibiting a wide distribution.Recent advancements in GRB research,particularly the observation of very high energy(VHE,>100 Ge V)radiation,have ushered in a new era of multiwavelength exploration,offering fresh perspectives and limitations for understanding GRB radiation mechanisms.This study aimed to leverage VHE observations to refine constraints on synchrotron+SSC radiation from electrons accelerated by forward shocks.By analyzing two external environments—the uniform interstellar medium and stratified stellar wind medium,we conducted spectral and variability fitting for five specific bursts(GRB 180720B,GRB 190114C,GRB 190829A,GRB 201216C,and GRB 221009A)to identify the optimal parameters characterizing these events.A comparative analysis of model parameter distributions with and without VHE radiation observations reveals that the magnetic energy equipartition factorεBis more concentrated with VHE emissions.This suggests that VHE emissions may offer greater constraints on this microphysical parameter.Additionally,we found that the energy budget between VHE and ke V–Me Vγ-ray emissions under the SSC radiation exhibits an almost linear relationship,which may serve as a tool to differentiate radiation mechanisms.We anticipate future statistical analyses of additional VHE bursts to validate our findings.
基金supported by the National Natural Science Foundation of China(Nos.12105143 and 11975121)the China Postdoctoral Science Foundation(No.2023M741453)+1 种基金the Engineering Research Center of Nuclear Technology Application(No.HJSJYB2020-1)the Key Laboratory of Ionizing Radiation Metering and Safety Evaluation for Jiangsu Province Market Regulation,and the Jiangsu Province Excellent Postdoctoral Program(No.JB23057).
文摘Neutron-induced gamma-ray imaging is a spectroscopic technique that uses characteristic gamma rays to infer the elemental distribution of an object.Currently,this technique requires the use of large facilities to supply a high neutron flux and a time-consuming detection procedure involving direct collimating measurements.In this study,a new method based on low neutron flux was proposed.A single-pixel gamma-ray detector combined with random pattern gamma-ray masks was used to measure the characteristic gamma rays emitted from the sample.Images of the elemental distribution in the sample,comprising 30×30 pixels,were reconstructed using the maximum-likelihood expectation-maximization algorithm.The results demonstrate that the elemental imaging of the sample can be accurately determined using this method.The proposed approach,which eliminates the need for high neutron flux and scanning measurements,can be used for in-field imaging applications.
基金partly supported by the Shanghai Key Laboratory of Astrophysics 18DZ2271600。
文摘The effects and rules of the dimensionless parameterξon neutrino annihilation v+v→e^(-)+e^(+)dominated gamma-ray bursts are analysed and investigated within the context of black holes in asymptotic safety.We also computationally model photon orbits around black holes,as photons and neutrinos have the same geodesic equations near black holes.We show that the black hole shadow radius decreases with increasingξ.Calculations are made to determine the temperature of the accretion disk surrounding the black hole and the ratio Q/Q_(Newt)of energy deposition per unit time and compared to that of the Newtonian scenario.The accretion disk temperature peaks at a higher temperature due to quantum gravity corrections,which increases the probability of neutrino emission from the black hole.It is interesting to note that larger quantum gravity effects cause the ratio value to significantly decline.In the neutrinoantineutrino annihilation process,the energy deposition rate is sufficient even while the energy conversion is inhibited because of quantum corrections.Gamma-ray bursts might originate from the corrected annihilation process.Additionally,we examine the derivative dQ/dr about the star radius r.The findings demonstrate that the ratio is lowered by the black hole's quantum influence.The neutrino pair annihilation grows weaker the more prominent the influence of quantum gravity.
基金supported by the National Natural Science Foundation of China(NSFC,grant No.12393853)the Scientific Research Foundation of Hunan Provincial Education Department(21C0343)+1 种基金the Science Research Project of the University(Youth Project)of the Department of Education of Guizhou Province(QJJ[2022]348)the Science and Technology Foundation of Guizhou Province(QKHJC-ZK[2023]442)。
文摘Novae are found to have GeV to TeVγ-ray emission,which reveals the shock acceleration from the white dwarfs.Recently,V1405 Cas was reported to radiate suspiciousγ-ray by Fermi-LAT with low signi?cance(4.1σ)after the optical maximum.Radio observations reveal that it is one of the?ve brightest novae surrounded by low-density ionized gas columns.Here we report a continuous search for GeVγ-ray from Fermi-LAT.Noγ-ray was found.For V1405 Cas the?ux level is lower than other well-studied Fermi novae,and theγ-ray maximum appears at t0+145 days.γ-ray of V1405 Cas is used to search potentialγ-ray periodicity.Noγ-ray periodicity was found during the time of observation.By comparing multi-wavelength data,theγ-ray upper limit to optical?ux ratio with a value at around 10^(-4)is obtained to constrain the shock acceleration.Long-term analysis from Swift-XRT gets X-ray spectral in the post-shock phase,which indicates that V1405 Cas became a super-soft source.The best-?t black body temperature at the super soft state is 0.11-0.19 keV.
文摘Due to the availability and particular features, wood was one of the first materials used by mankind with a wide variety of applications. It can be used as raw-material for paper and cellulose manufacturing; in industries such as chemical, naval, furniture, sports goods, toys, and musical instruments; in building construction and in the distribution of electric energy. Wood has been widely researched; therefore, wood researchers know that several aspects such as temperature, latitude, longitude, altitude, sunlight, soil, and rainfall index interfere as to the growth of trees. This behavior explains why the average of physical chemical properties is important in wood study.Most of the researchers consider density to be the most important wood property because of its straight relationship with the physical and mechanical properties in wood. There are three types of wood density： basic, apparent and green. The apparent density was used here at 12% of moisture content. In this study, four different types of wood were used： ＂Freijo＂, ＂Jequitiba＂, ＂Muiracatiara＂ and ＂Ipe＂. For wood density determination by non-conventional method, ^241Am, ^133Ba and ^137Cs gamma-ray sources, a NaI scintillation detector and a counter were used. The results demonstrated that this technique is quick and accurate. Considering the nuclear parameters obtained as half-value layers and linear absorption coefficients,^ 137Cs demonstrated to be the best option to be used for inspection of the physical integrity of electric wooden poles and live trees for future works.
基金supported by the Support Program of the Ministry of Science and Technology(No.2014FY211000)the National Key Technology Research and Development Program(No.2013BAK03B05)
文摘This study reports the performances of efficiency calibrations for high-purity-germanium gamma-ray spectrometry using the source-, Laboratory Sourceless Object Calibration Software(LabSOCS)-and ANGLE-based methods in an inter-comparison exercise. Although the results of LabSOCS and ANGLE for ^(241)Am emitting lowenergy gamma rays were not very satisfactory, all of the three efficiency calibration methods passed acceptance criteria. The results confirmed the reliability of the calculation codes ANGLE and LabSOCS as alternative efficiency calibration methods in high-purity-germanium gamma spectrometry. This study is likely to promote the further application of the ANGLE and LabSOCS calculation codes in radioactivity measurements.
基金supported by the Tsinghua University Initiative Scientific Research Program,the National Natural Science Foundation of China(Nos.11633003,12025301,and 11821303)the National Key R&D Program of China(Nos.2018YFA0404502 and 2016YFA040080X).
文摘Gamma-Ray Integrated Detectors(GRID)mis-sion is a student project designed to use multiple gamma-ray detectors carried by nanosatellites(CubeSats),forming a full-time all-sky gamma-ray detection network that monitors the transient gamma-ray sky in the multi-mes-senger astronomy era.A compact CubeSat gamma-ray detector,including its hardware and firmware,was designed and implemented for the mission.The detector employs four Gd 2 Al 2 Ga 3 O 12:Ce(GAGG:Ce)scintillators coupled with four silicon photomultiplier(SiPM)arrays to achieve a high gamma-ray detection efficiency between 10 keV and 2 MeV with low power and small dimensions.The first detector designed by the undergraduate student team onboard a commercial CubeSat was launched into a Sun-synchronous orbit on October 29,2018.The detector was in a normal observation state and accumulated data for approximately one month after on-orbit functional and performance tests,which were conducted in 2019.
基金supported by the National Natural Science Foundation of China(Nos.4210040255,U19A2086)the Sichuan Science and Technology Program(No.2021JDRC0108)。
文摘In this study,the anti-noise performance of a pulse-coupled neural network(PCNN)was investigated in the neutron and gamma-ray(n-γ)discrimination field.The experiments were conducted in two groups.In the first group,radiation pulse signals were pre-processed using a Fourier filter to reduce the original noise in the signals,whereas in the second group,the original noise was left untouched to simulate an extremely high-noise scenario.For each part,artificial Gaussian noise with different intensity levels was added to the signals prior to the discrimination process.In the aforementioned conditions,the performance of the PCNN was evaluated and compared with five other commonly used methods of n-γdiscrimination:(1)zero crossing,(2)charge comparison,(3)vector projection,(4)falling edge percentage slope,and(5)frequency gradient analysis.The experimental results showed that the PCNN method significantly outperforms other methods with outstanding FoM-value at all noise levels.Furthermore,the fluctuations in FoM-value of PCNN were significantly better than those obtained via other methods at most noise levels and only slightly worse than those obtained via the charge comparison and zerocrossing methods under extreme noise conditions.Additionally,the changing patterns and fluctuations of the FoMvalue were evaluated under different noise conditions.Hence,based on the results,the parameter selection strategy of the PCNN was presented.In conclusion,the PCNN method is suitable for use in high-noise application scenarios for n-γdiscrimination because of its stability and remarkable discrimination performance.It does not rely on strict parameter settings and can realize satisfactory performance over a wide parameter range.
基金Supported bythe Doctoral Foundation of Education Ministry of China (No.20040056037) .
文摘With the increasing application of electric and electronic devices in space and nuclear power stations, the polymeric insulation materials are inevitably exposed to various kinds of environments. Accordingly, it becomes necessary to investigate the effects of the radiation and air pressure on insulation materials. This paper describes the effects of gamma-ray irradiation and reduced pressure on dielectric breakdown of polybutylene naphthalate (PBN) and polybutylene terephthalate (PBT) by applying a DC pulse voltage. Both PBN and PBT were irradiated in air up to 100 kGy and then up to 1 000 kGy with a dose rate of 10 kGy/h by using a60Co gamma-source. The effects of total dose and reduced pressure on the time to dielectric breakdown and discharge quantity were discussed. Obtained results show that, while increasing the total dose, the discharge quantity decreased with PBN, but increased with PBT. With decreasing the air pressure, the discharge quantity increased with PBN, but decreased with PBT. With increasing the total dose, the time to dielectric breakdown increased with PBN, but decreased with PBT. With decreasing the air pressure, the time to dielectric breakdown increased with both PBN and PBT. The experimental results suggest that the chemical structure of polybutylene polymers plays a main role in the result of radiation reaction, which is related to cross-linking and degradation reaction.
文摘Since the successful launch of NASA＇s dedicated gamma-ray burst （GRB） mission, Swift, the study of cosmological GRBs has entered a new era. Here I review the rapid observational and theoretical progress in this dynamical research field during the first two-year of the Swift mission, focusing on how observational breakthroughs have revolutionized our understanding of the physical origins of GRBs. Besides summarizing how Swift helps to solve some pre-Swift mysteries, I also list some outstanding problems raised by the Swift observations. An outlook of GRB science in the future, especially in the GLAST era, is briefly discussed.
基金supported by the National Natural Science Foundation of China(11773087)the Science and Technology Development Fund of Macao(079/2018/A2)
文摘We present the thorium distribution on the lunar surface derived from observations by the Chang’E-2 gamma-ray spectrometer(CE-2 GRS). This new map shows a similar thorium distribution to previous observations. In combination with this new thorium map and impact cratering model, we investigate the origination of thorium on the Moon’s highlands, which was previously thought to be contributed from Imbrium ejecta. We found that the Imbrium ejecta has a small contribution(~20%–30%) to the thorium on the lunar highlands but most thorium is likely to be indigenous before the deposition of the Imbrium ejecta. This new thorium map also confirms that the eastern highlands have a relatively higher thorium concentration than the western highlands. We propose that the thin crust and large basins on the eastern highlands are responsible for this difference in thorium.
基金the financial support of Kermanshah University of Technology for this research under grant number S/P/T/1102
文摘The ability to precisely estimate the void fraction of multiphase flow in a pipe is very important in the petroleum industry. In this paper, an approach based on our previous works is proposed for predicting the void fraction independent of flow regime and liquid phase density changes in gas–liquid two-phase flows. Implemented technique is a combination of dual modality densitometry and multi-beam gamma-ray attenuation techniques. The detection system is comprised of a single energy fan beam,two transmission detectors, and one scattering detector. In this work, artificial neural network(ANN) was also implemented to predict the void fraction percentage independent of the flow regime and liquid phase density changes. Registered counts in three detectors and void fraction percentage were utilized as the inputs and output of ANN, respectively. By applying the proposed methodology, the void fraction was estimated with a mean relative error of less than just 1.2480%.
基金the University of Isfahan for providing financial support。
文摘In this study, the Maastrichtian-Danian boundary was measured and sampled in two stratigraphic sections, the north and south flanks of the Dehnow anticline in Coastal Fars, Southern Iran. This boundary was also investigated in the drilled exploratory well-1 in the same region. The lithology of the Maastrichtian-Danian deposits consists of glauconitic, phosphatic argillaceous limestones and marlstones. 30 genera and 77 species of planktonic foraminifera have been determined. The recognized biozones are the Gansserina gansseri Interval Zone, and the Contusotruncana contusa Interval Zone, which indicates latest Campanian to middle Maastrichtian age for the upper part of the Gurpi Formation. In addition, the Eoglobigerina edita(P1) Partial Range Zone, Praemurica uncinata(P2) Lowest Occurrence Zone, Morozovella angulata(P3) Lowest Occurrence Zone and Globanomalina psudomenardii(P4) Taxon Range Zone represent a Danian to Thanetian age for the lower part of the Pabdeh Formation. From the absence of the Abathomphalus mayaroensis Interval Zone, Pseudoguembelina hariaensis Interval Zone, Pseudotextularia elegans Interval Zone, Plummerita hantkeninoides Interval Zone, Guembelitria cretacea(P0) Partial Range Zone and Parvularugoglobigerina eugubina(Pα) Total Range Zone, it can be deduced that there is a paraconformity across the Maastrichtian–Danian boundary in the studied area, this hiatus encompassing the late Maastrichtian and the earliest Danian. Danian deposits from the study area contain reworked glauconitized macrofossils, planktonic and benthic foraminifera of the Cretaceous. The obtained surface gamma-ray spectrometry logs resemble the exploratory well-1 gamma-ray wireline log.
基金the National Natural Science Foundation of China.
文摘The phenomenon of gamma-ray burst （GRB） spectral lags is very common, but a definitive explanation has not yet been given. From a sample of 82 GRB pulses we find that the spectral lags are correlated with the pulse widths, however, there is no correlation between the relative spectral lags and the relative pulse widths. We suspect that the correlations between spectral lags and pulse widths might be caused by the Lorentz factor of the GRBs concerned. Our analysis on the relative quantities suggests that the intrinsic spectral lag might reflect other aspect of pulses than the aspect associated with the dynamical time of shocks or that associated with the time delay due to the curvature effect.
基金Supported by the National Natural Science Foundation of China.
文摘Optical and radio afterglows arising from shocks by relativistic conical ejecta running into pre-burst massive stellar winds are revisited. Under the homogeneous thin-shell approximation and a realistic treatment for the lateral expansion of jets, our results show that a notable break exists in the optical light curve in most cases we calculated in which the physical parameters are varied within reasonable ranges. For a relatively tenuous wind which cannot decelerate the relativistic jet to cause a light curve break within days, the wind termination shock due to the ram pressure of the surrounding medium occurs at a small radius, namely, a few times 10<SUP>17</SUP> cm. In such a structured wind environment, the jet will pass through the wind within several hours and run into the outer uniform dense medium. The resulting optical light curve flattens with a shallower drop after the jet encounters the uniform medium, and then declines deeply, triggered by runaway lateral expansion.
基金This work was supported by the Sichuan Science and Technology Program(No.2020JDRC0108)the National Science Foundation of China(Nos.41774147 and 41774190).
文摘In this study,the theory of minimum detectable activity concentration(MDAC)for airborne gamma-ray spectrometry(AGS)was derived,and the relationship between the MDAC and the intrinsic effi-ciency of a scintillation counter,volume,and energy res-olution of scintillation crystals,and flight altitude of an aircraft was investigated.To verify this theory,experi-mental devices based on NaI and CeBr 3 scintillation counters were prepared,and the potassium,uranium,and thorium contents in calibration pads obtained via the stripping ratio method and theory were compared.The MDACs of AGS under different conditions were calculated and analyzed using the proposed theory and the Monte Carlo method.The relative errors found via a comparison of the experimental and theoretical results were less than 4%.The theory of MDAC can guide the work of AGS in probing areas with low radioactivity.
基金supported by the National Natural Science Foundation of China (Nos. 51573175, 51473152, 51773189)Foshan Scientific and Technological Innovation Team Project (No. 2013IT100041)+1 种基金Foshan University-City Cooperation Project (Scientific and Technological Innovation Project, No. 2014HK100291)the Fundamental Research Funds for the Central Universities (Nos. WK2060200012, WK3450000001)
文摘The research on the properties of graphene oxide（GO） in various media has become one of the hottest topics since GO is now the main raw material for graphene-based advanced materials. In this work, the g-ray radiation chemistry effect of GO nanosheets and their self-aggregation behavior in t-butanol/water medium were investigated. The results show that GO nanosheets are reduced and hydroxyalkylated simultaneously by the alcohol free radicals produced by the radiolysis of t-butanol/water solution under g-ray radiation. The radiation-modified GO nanosheets will self-assemble into a self-standing graphene hydrogel when the p H of the solution is lower than 2. A hydroxyl-functionalized free-standing graphene aerogel is further obtained simply by freeze-drying. This work provides not only a general self-assembly mechanism of GO nanosheets in strong acidic alcohol/water media under high energy radiation, but also a facile and economical preparation method for hydroxyalkylated graphene-based aerogel.
基金Supported by the National Natural Science Foundation of China
文摘The well-known correlation between radio luminosity （LR） and X-ray luminosity （Lx）, LR/LX 10^-5, holds for a variety of objects, such as active galactic nuclei, Galactic black holes, solar flares and cool stars. Here we extend the relation to gamma-ray bursts （GRBs） and find that the GRBs also obey a similar LR - LX relation, with a slightly different slope of LR ∝ LX^1.1. This relation implies that the explosions that occur on different scales may have a common underlying origin.
