Research on the On-orbit Background of the Hard X-Ray Imager Onboard ASO-S

The space environment background of various particle fluxes of the Hard X-ray Imager(HXI), one of the payloads of the Advanced Space-based Solar Observatory(ASO-S) spacecraft, is investigated and presented. Different approaches are used to obtain the input information on various space environment particles(protons, alpha particles, electrons, positrons, neutrons, and photons). Some special regions(SAA and radiation belt) are also taken into account. The findings indicate that electrons are the primary background source in the radiation belt. Due to the large background flux generated by electrons, HXI cannot effectively observe solar flares in the radiation belt.Outside the radiation belt, primary protons and albedo photons are the main sources of background at low and high magnetic latitudes respectively. The statistical analysis of the flare and background spectra shows that the errors of the flare energy spectrum observation are mainly concentrated in the high energy band, and the detector still has a certain spectrum observation capability for flares of C-class and below in the low energy band of the non-radiation belt. The imaging observation of flares of C-class and below is significantly affected by the accuracy of background subtraction. The energy band with the best signal-to-noise ratio is from 10 to 50 ke V, which can be used to monitor the formation and class of flares.

A new method for high-energy pulsed Gamma measurement within intense background x-rays

The accelerator-generating 6.13 MeV pulsed Gamma by 19F（p, αγ）160 reaction usually synchronizes with an intense bremsstrahlung x-ray which has a maximum energy of 1 MeV. This paper proposes a new method, named the scattering and absorbing method, to diagnose the 6.13 MeV Gamma. This method includes two parts： the detector and a scatterer placed in front of the detector. The detector converts the Gamma to electrons and then collects the electrons by a scintillator. In order to restrain the interference of the low-energy background, the scintillator collects the electrons at a small angle. The scintillator is wrapped with electro-absorbing material to absorb the low-energy electrons generated by background x-rays. The theoretical sensitivity ratio of 6.13 MeV Gamma to 1 MeV x-rays is greater than 150. The scatterer is a pretreatment tool to scatter some background x-rays away from the radial beam before they enter the detector. By varying the length, the scatterer can reduce the background x-rays to an acceptable level for the detector.

The CCD instrument background of the SMILE SXI

The ESA and CAS SMILE mission orbit is highly elliptical and will pass through multiple radiation environments.The Soft X-ray Imager(SXI)instrument aboard has a radiation shutter door designed to close when the surrounding radiation flux is high.The shutter door will close when passing below an altitude threshold to protect against trapped particles in the Earth’s Van Allen Belts.Therefore,two radiation environments can be approximated based on the shutter door position:open and closed.The instrument background for the CCDs(Charge-Coupled Devices)that form the focal plane array of the SXI were evaluated for the two environments.Due to the correlation of the space environment with the solar cycle,the solar minima and maxima,the background was also evaluated at these two extremes.The results demonstrated that the highest instrument background will occur during solar minima due to the main contributing source being Galactic Cosmic Rays(GCRs).It was also found that the open background was highest for solar minima and that the closed background was highest during solar maxima.This is due to the radiation shutter door acting as a scattering centre and the changes in the energy flux distribution of the GCRs between the two solar extremes.

Cross-correlation of 21 cm and soft X-ray backgrounds during the epoch of reionization

The cross-correlation between the high-redshift 21 cm background and the Soft X-ray Background （SXB） of the Universe may provide an additional probe of the Epoch of Reionization. Here we use semi-numerical simulations to create 21 cm and soft X-ray intensity maps and construct their cross power spectra. Our results indicate that the cross power spectra are sensitive to the thermal and ionizing states of the intergalactic medium （IGM）. The 21 cm background correlates positively to the SXB on large scales during the early stages of the reionization. However as the reionization develops, these two back- grounds turn out to be anti-correlated with each other when more than - 15% of the IGM is ionized in a warm reionization scenario. The anti-correlated power reaches its maximum when the neutral fraction declines to 0.2-0.5. Hence, the trough in the cross power spectrum might be a useful tool for tracing the growth of HII regions during the middle and late stages of the reionization. We estimate the detectability of the cross power spectrum based on the abilities of the Square Kilometre Array and the Wide Field X-ray Telescope （WFXT）, and find that to detect the cross power spectrum, the pixel noise of X-ray images has to be at least 4 orders of magnitude lower than that of the WFXT deep survey.

Cross-correlations between 21 cm,X-ray and infrared backgrounds

The history of the cosmological reionization is still unclear. Two ionizing sources, stars and QSOs, are believed to play important roles during this epoch. Besides the 21 cm signals, the infrared emission from PopⅢ stars and X-ray photons from QSOs can be powerful probes of the reionization. Here we present a cross-correlation study of the 21 cm, infrared and X-ray backgrounds. The advantage of doing such crosscorrelations is that we could highlight the correlated signals and eliminate irrelevant foregrounds. We develop a shell model to describe the 21 cm signals and find that PopIII stars can provide higher 21 cm signals than QSOs. Using the ROSAT data for X-ray and AKARI data for infrared, we predict various cross power spectra analytically and discuss prospects for detecting these cross-correlation signals in future low frequency radio surveys. We find that, although these cross-correlational signals have distinct features, so far, they have been difficult to detect due to the high noise of the soft X-ray and infrared backgrounds given by ROSAT and AKARI.

Measurement of the high energyγ-rays from heavy ion reactions usingČerenkov detector

The energetic bremsstrahlung photons up to 100 MeV produced in heavy ion collisions can be used as a sensitive probe for short-range correlation in atomic nuclei. The energy of the γ-rays can be measured by collecting the Čerenkov light in the medium induced by the fast electrons generated in the Compton scattering or electromagnetic shower of the incident γray. Two types of detectors based on pure water and lead glass as sensitive materials were designed for this purpose. The γresponse and optical photon propagation in the detectors were simulated based on electromagnetic and optical processes in Geant4. The inherent energy resolutions of 0.022(4) + 0.51(2)∕E^(1/2)_(γ) for water and 0.0026(3) + 0.446(3)∕E^(1/2)_(γ) for lead glass were obtained. The geometry sizes of the lead glass and water were optimized to 30 cm × 30 cm × 30 cm and 60 cm × 60 cm ×120 cm, respectively, to detect high-energy γ-rays at 160 MeV. The Hough transform method was applied to reconstruct the direction of the incident γ-rays, providing the ability to experimentally distinguish the high-energy γ-rays produced in the reactions on the target from random background cosmic-ray muons.

The X-ray Background (Deep Fields, Luminosity Functions and Type-Ⅱ Quasars)

Deep X ray surveys have shown that the cosmic X ray background (XRB) is largely due to the accretion onto supermassive black holes, integrated over the cosmic time. These surveys have resolved more than 80% of the 0.1-10keV X ray background into discrete sources. Optical spectroscopic identifications show that the sources producing the bulk of the X ray background are a mixture of obscured (type 1) and unobscured (type 2) AGNs, as predicted by the XRB population synthesis models. A class of highly luminous type 2 AGN, so called QSO 2s, has been detected in the deepest Chandra and XMM Newton surveys. The new Chandra AGN redshift distribution peaks at much lower redshifts (z≈0.7) than that based on ROSAT data, indicating that Seyfert galaxies peak at significantly lower redshifts than QSOs.

STABILITY OF TRANSONIC SHOCKS TO THE EULER-POISSON SYSTEM WITH VARYING BACKGROUND CHARGES

This paper is devoted to studying the stability of transonic shock solutions to the Euler-Poisson system in a one-dimensional nozzle of finite length.The background charge in the Poisson equation is a piecewise constant function.The structural stability of the steady transonic shock solution is obtained by the monotonicity argument.Furthermore,this transonic shock is proved to be dynamically and exponentially stable with respect to small perturbations of the initial data.One of the crucial ingredients of the analysis is to establish the global well-posedness of a free boundary problem for a quasilinear second order equation with nonlinear boundary conditions.

Iterative and accurate determination of small angle X-ray scattering background

X-ray scattering is widely used in material structural characterizations.The weak scattering nature,however,makes it susceptible to background noise and can consequently render the final results unreliable.In this paper,we report an iterative method to determine X-ray scattering background and demonstrate its feasibility by small angle X-ray scattering on gold nanoparticles.This method solely relies on the correct structural modeling of the sample to separate scattering signal from background in data fitting processes,which allows them to be immune from experimental uncertainties.The importance of accurate determination of the scaling factor for background subtraction is also illustrated.

Artificial neural network-based method for discriminating Compton scattering events in high-purity germaniumγ-ray spectrometer

To detect radioactive substances with low activity levels,an anticoincidence detector and a high-purity germanium(HPGe)detector are typically used simultaneously to suppress Compton scattering background,thereby resulting in an extremely low detection limit and improving the measurement accuracy.However,the complex and expensive hardware required does not facilitate the application or promotion of this method.Thus,a method is proposed in this study to discriminate the digital waveform of pulse signals output using an HPGe detector,whereby Compton scattering background is suppressed and a low minimum detectable activity(MDA)is achieved without using an expensive and complex anticoincidence detector and device.The electric-field-strength and energy-deposition distributions of the detector are simulated to determine the relationship between pulse shape and energy-deposition location,as well as the characteristics of energy-deposition distributions for fulland partial-energy deposition events.This relationship is used to develop a pulse-shape-discrimination algorithm based on an artificial neural network for pulse-feature identification.To accurately determine the relationship between the deposited energy of gamma(γ)rays in the detector and the deposition location,we extract four shape parameters from the pulse signals output by the detector.Machine learning is used to input the four shape parameters into the detector.Subsequently,the pulse signals are identified and classified to discriminate between partial-and full-energy deposition events.Some partial-energy deposition events are removed to suppress Compton scattering.The proposed method effectively decreases the MDA of an HPGeγ-energy dispersive spectrometer.Test results show that the Compton suppression factors for energy spectra obtained from measurements on ^(152)Eu,^(137)Cs,and ^(60)Co radioactive sources are 1.13(344 keV),1.11(662 keV),and 1.08(1332 keV),respectively,and that the corresponding MDAs are 1.4%,5.3%,and 21.6%lower,respectively.

New γ-Ray Sources Identified in All-sky Surveys Based on Fermipy's Advanced Algorithm

We employ an efficient method for identifying γ-ray sources across the entire sky,leveraging advanced algorithms from Fermipy,and cleverly utilizing the Galactic diffuse background emission model to partition the entire sky into72 regions,thereby greatly enhancing the efficiency of discovering new sources throughout the sky through multithreaded parallel computing.After confirming the reliability of the new method,we applied it for the first time to analyze data from the Fermi Large Area Telescope(Fermi-LAT)encompassing approximately 15.41 yr of all-sky surveys.Through this analysis,we successfully identified 1379 new sources with significance levels exceeding 4σ,of which 497 sources exhibited higher significance levels exceeding 5σ.Subsequently,we performed a systematic analysis of the spatial extension,spectra,and light variation characteristics of these newly identified sources.We identified 21 extended sources and 23 sources exhibiting spectral curvature above 10 GeV.Additionally,we identified 44 variable sources above 1 GeV.

Characteristics of Lightning Activity in Southeast China and its Relation to the Atmospheric Background

Based on the lightning observation data from the Fengyun-4A(FY-4A)Lightning Mapping Imager(FY-4A/LMI)and the Lightning Imaging Sensor(LIS)on the International Space Station(ISS),we extract the“event”type data as the lightning detection results.These observations are then compared with the cloud-to-ground(CG)lightning observation data from the China Meteorological Administration.This study focuses on the characteristics of lightning activity in Southeast China,primarily in Jiangxi Province and its adjacent areas,from April to September,2017–2022.In addition,with the fifth-generation European Centre for Medium-Range Weather Forecasts reanalysis data,we further delved into the potential factors influencing the distribution and variations in lightning activity and their primary related factors.Our findings indicate that the lightning frequency and density of the FY-4A/LMI,ISS-LIS and CG data are higher in southern and central Jiangxi,central Fujian Province,and western and central Guangdong Province,while they tend to be lower in eastern Hunan Province.In general,the high-value areas of lightning density for the FY-4A/LMI are located in inland mountainous areas.The lower the latitude is,the higher the CG lightning density is.High-value areas of the CG lightning density are more likely to be located in eastern Fujian and southeastern Zhejiang Province.However,the high-value areas of lightning density for the ISS-LIS are more dispersed,with a scattered distribution in inland mountainous areas and along the coast of eastern Fujian.Thus,the mountainous terrain is closely related to the high-value areas of the lightning density.The locations of the high-value areas of the lightning density for the FY-4A/LMI correspond well with those for the CG observations,and the seasonal variations are also consistent.In contrast,the distribution of the high-value areas of the lightning density for the ISS-LIS is more dispersed.The positions of the peak frequency of the FY-4A/LMI lightning and CG lightning contrast with local altitudes,primarily located at lower altitudes or near mountainsides.K-index and convective available potential energy(CAPE)can better reflect the local boundary layer conditions,where the lightning density is higher and lightning seasonal variations are apparent.There are strong correlations in the annual variations between the dew-point temperature(Td)and CG lightning frequency,and the monthly variations of the dew-point temperature and CAPE are also strongly correlated with monthly variations of CG lightning,while they are weakly correlated with the lightning frequency for the FY-4A/LMI and ISS-LIS.This result reflects that the CAPE shows a remarkable effect on the CG lightning frequency during seasonal transitions.

Gravitational Waves Background, as Well as Some UFO, FRB and Supernova Flares, Are Due to Compressibility of the Spacetime (CoST)

The recently observed gravitational wave background is explained in terms of the quantum modification of the general relativity (Qmoger). Some UFO, FRB and supernova flares also can be explained in terms of Qmoger.

Background deduction of the Chang'E-1 gamma-ray spectrometer data

Gamma-ray spectrometer(GRS) is used to detect the elemental abundances and distributions on the lunar surface.To derive the elemental abundances,it is vital to acquire background gamma rays except lunar gamma rays.So GRS would observe background spectra in the course of earth-moon transfer on schedule.But in fact,GRS was not switched on in the course of flying toward the moon.After the CE-1 probe finished one-year mission,GRS car-ried out a test on background data on November 21?22,2008.The authors did conduct research on the methods of background deduction using 2105 hours of usable gamma-ray spectra acquired at the 200-km orbital height by the GRS and more than 5 hours of gamma-ray spectra acquired in the GRS background test.The final research results showed that the method of deducting the background using the minimum counts in the CE-1 GRS pixels is optimal for the elements,U,K and Th.The method applies to such a case that the elemental abundances in the pixel with the minimum counting rate are 0 μg/g and the continuum background counts are constant over the Moon.Based on the method of background deduction,the full energy peak counts of U,K,and Th are calculated.

Comparative Analysis of Energy Characteristics of Two Southwest Vortices in Sichuan Under Similar Circulation Backgrounds

Based on ERA5 reanalysis data,the present study analyzed the thermal energy development mechanism and kinetic energy conversion characteristics of two extreme rainstorm processes in relation to the shallow southwest vortex in the warm-sector during a“rain-generated vortex”process and the deep southwest vortex in a“vortex-generated rain”process.The findings were as follows:(1)During the extreme rainstorm on August 11,2020(hereinafter referred to as the“8·11”process),intense surface heating and a high-energy unstable environment were observed.The mesoscale convergence system triggered convection to produce heavy rainfall,and the release of latent condensation heat generated by the rainfall promoted the formation of a southwest vortex.The significant increase(decrease)in atmospheric diabatic heating and kinetic energy preceded the increase(decrease)in vorticity.By contrast,the extreme rainstorm on August 16,2020(hereinafter referred to as the“8·16”process)involved the generation of southwest vortex in a low-energy and highhumidity environment.The dynamic uplift of the southwest vortex triggered rainfall,and the release of condensation latent heat from rainfall further strengthened the development of the southwest vortex.The significant increase(decrease)in atmospheric diabatic heating and kinetic energy exhibited a delayed progression compared to the increase(decrease)in vorticity.(2)The heating effect around the southwest vortex region was non-uniform,and the heating intensity varied in different stages.In the“8·11”process,the heating effect was the strongest in the initial stage,but weakened during the vortex's development.On the contrary,the heating effect was initially weak in the“8·16”process,and intensified during the development stage.(3)The available potential energy of the“8·11”process significantly increased in kinetic energy converted from rotational and divergent winds through baroclinic action,and the divergent wind energy continued to convert into rotational wind energy.By contrast,the“8·16”process involved the conversion of rotational wind energy into divergent wind energy,which in turn converted kinetic energy back into available potential energy,thereby impeding the further development and maintenance of the southwest vortex.

Optimal Insurance with Background Risk under the Ambiguity and Belief Heterogeneity Structure

In this paper, we discuss the optimal insurance in the presence of background risk while the insured is ambiguity averse and there exists belief heterogeneity between the insured and the insurer. We give the optimal insurance contract when maxing the insured’s expected utility of his/her remaining wealth under the smooth ambiguity model and the heterogeneous belief form satisfying the MHR condition. We calculate the insurance premium by using generalized Wang’s premium and also introduce a series of stochastic orders proposed by [1] to describe the relationships among the insurable risk, background risk and ambiguity parameter. We obtain the deductible insurance is the optimal insurance while they meet specific dependence structures.

Ratio of Gravitational Force to Electric Force from Empirical Equations in Terms of the Cosmic Microwave Background Temperature

Previously, we presented several empirical equations using the cosmic microwave background (CMB) temperature. Next, we propose an empirical equation for the fine-structure constant. Considering the compatibility among these empirical equations, the CMB temperature (Tc) and gravitational constant (G) were calculated to be 2.726312 K and 6.673778 × 10−11 m3∙kg−1∙s−2, respectively. Every equation could be explained in terms of the Compton length of an electron (λe), the Compton length of a proton (λp) and a. Furthermore, every equation could also be explained in terms of Avogadro’s number and the number of electrons in 1 C. However, the ratio of the gravitational force to the electric force cannot be uniquely determined when the unit of the Planck constant (Js) is changed. In this study, we showed that every equation can be described in terms of Planck constant. From the assumption of minimum mass, the ratio of gravitational force to electric force could be elucidated.

Algorithms for Empirical Equations in Terms of the Cosmic Microwave Background Temperature

Previously, we presented several empirical equations using the cosmic microwave background (CMB) temperature. Next, we propose an empirical equation for the fine-structure constant. Considering the compatibility among these empirical equations, the CMB temperature (Tc) and gravitational constant (G) were calculated to be 2.726312 K and 6.673778 × 10−11 m3∙kg−1∙s−2, respectively. Every equation can be explained numerically in terms of the Compton length of an electron (λe), the Compton length of a proton (λp) and α. Furthermore, every equation can also be explained in terms of the Avogadro number and the number of electrons at 1 C. We show that every equation can be described in terms of the Planck constant. Then, the ratio of the gravitational force to the electric force can be uniquely determined with the assumption of minimum mass. In this report, we describe the algorithms used to explain these equations in detail. Thus, there are no dimension mismatch problems.

Correspondence Principle for Empirical Equations in Terms of the Cosmic Microwave Background Temperature with Solid-State Ionics

Previously, we presented several empirical equations using the cosmic microwave background (CMB) temperature that were mathematically connected. Next, we proposed an empirical equation for the fine-structure constant. Considering the compatibility among these empirical equations, the CMB temperature (Tc) and gravitational constant (G) were calculated to be 2.726312 K and 6.673778 × 10-11 m3·kg-1·s-2, respectively. Every equation can be explained in terms of the Compton length of an electron (λe), the Compton length of a proton (λp) and α. However, these equations are difficult to follow. Using the correspondence principle with the thermodynamic principles in solid-state ionics, we propose a canonical ensemble to explain these equations in this report. For this purpose, we show that every equation can be explained in terms of Avogadro’s number and the number of electrons in 1 C.

Innovative Research on Enterprise Marketing Strategies under the Background of New Media

Marketing is one of the comprehensive development strategies for production-oriented and service-oriented enterprises, and it is also an effective path to increase income and revenue for enterprises. By operating and selling the main products, services, cultural concepts, and many more of the enterprise in a market-oriented manner. We aim to deepen the impression of the enterprise among consumers, enhance its market influence, and seek more opportunities for cooperation and development for the enterprise. However, with increasingly fierce market competition, traditional marketing models are no longer able to maximize their effectiveness. This article firstly analyzes the positive impact of new media background on enterprise marketing in expanding the scope of information release, improving marketing targeting, and creating new marketing platforms. Secondly, it explores the problems faced by enterprises in the current marketing process, such as outdated ideological concepts, insufficient team building, and rigid marketing content. Finally, strategies such as updating marketing concepts, strengthening team building, and innovating marketing content were proposed to provide some reference and inspiration for enterprises to smoothly promote marketing work under the background of new media.