Subjects: Physics >> Nuclear Physics submitted time 2023-05-31
Xu,Miaofu
Zhang,Xiangzhen
Ye,Rui
Wang,Jincan
Bian,Xiaojuan
Gao,Yao
Li,Minxian
Chen,Fusan
Yang,Xiaochen
Ge,Rui
Abstract： A 3W1 superconducting wiggler (SCW) with the pole gap of 68 mm was successfully tested and installed in a BEPC II storage ring in November, 2019. The goal of zero liquid helium consumption was achieved, and the cryogenic system exhibited a 12% residual cooling capacity (approximately 0.69 W @4.2K). The 3W1-SCW was set to operate at 2.49 T and has been operating for more than seven months. Three instances of magnet quenching occurred during the normal operation. The evaporated helium gas can be recycled to the helium gas recycling system when the pressure in the helium tank is higher than the parameter value（the setpoint of the presssur value is 1.2 bara）. The cryogenic system can be recovered within 4 h if sufficient liquid helium is available to inject into the cryostat.
Subjects: Geosciences >> Marine Sciences submitted time 2023-05-31
Abstract： Quantifying eddy mixing in the ocean is a hot and tough problem in the area of physical oceanography. Based on the theory of effective diffusivity, the present study investigated the stirring effects of geostrophic turbulence that lead to stretching, distorting, deforming, and folding of tracer contours. These changes are then related to the efficiency of turbulent mixing. Results show that under the stirring effect of geostrophic turbulence, the length of tracer contour can be quickly elongated and fine-scale tracer filaments and fronts are also generated. This fractal elongation of tracer contour, about 10-20 times longer than the original length, is the dominant contributor to the mixing efficiency, whereas the gradient enhancement associated with filament and front generations only plays a secondary role. On the other hand, fine-scale features are smoothed out by small-scale diffusivity which eventually suppresses the increase of contour length and the generation of tracer filaments. This imposes an upper bound of the mixing efficiency when the stirring and smoothing effects are in a dynamical balance. Through a ‘box-counting’ method, the fractal dimension of tracer contour is also found between 1.4~1.6, indicating a geometric dimension lies somewhere between 1D and 2D. Due to the limitation of data resolution, contour length and thus mixing efficiency may be underestimated. Finally, the present study made an empirical relation between the fractal dimension and mixing efficiency, providing an opportunity for estimating mixing efficiency through a well-developed pattern recognition technique in remote sensing, and a new way of diagnosing ocean mixing and its parameterization.
Subjects: Nuclear Science and Technology >> Other Disciplines of Nuclear Science submitted time 2023-05-31
Abstract： Tomographic Gamma Scanner (TGS), an advanced γ-ray nondestructive analysis technique, can locate and analyze nuclides in radioactive nuclear waste, and TGS can be categorized into two types: e.g., transmission measurement and emission measurement). Specifically, transmission measurements provide the basis for accurate measurement of nonuniform radionuclide content in TGS scanning. The scan data were obtained using the Monte Carlo tool Geant4 simulation, and 25 voxels were divided into five lengths and five widths in a square barrel. In this study, an encoding cropping algorithm based on draped foot vector judgment was adopted to rapidly calculate the voxel trace matrix within a square bucket of nuclear waste, and the transmission images were reconstructed using ordered subset expectation maximization (OSEM). The results indicated that the cropping speed of the improved coding algorithm was significantly higher than that of the original algorithm, and the relative mean deviation (RMD) and root mean square error (RMSE) between the reconstructed attenuation coefficient and the reference standard value tended to decrease with an increase in the cropped line segments in the voxel; the Pearson correlation coefficient (PCC) tended to converge to 1.0. The image quality evaluation parameters of the high media-density materials were better than those of the low media-density materials in the above three indexes. The reconstruction effect was relatively poor for more complex filling materials. When there were more than 10 cropped line segments in the voxel, the reconstruction data generally tended to be stable. The graphical trimming algorithm can rapidly calculate the trace matrix of the scanned voxels; it exhibits the advantages of speed and efficiency and can serve as a novel method to solve the trace matrix of TGS nuclear waste transmission scans.
Subjects: Physics >> Nuclear Physics submitted time 2023-05-31
Abstract： Theoretical uncertainties of single proton transfer cross sections of the (3He,d) and (d,3He) reactions
due to the uncertainties of the entrance- and exit-channel optical model potentials are examined with the
30Si(3He,d)31P, 13B(d,3He)12Be, and 34S(3He,d)35Cl reactions at incident energies of 25 MeV, 46 MeV, and
25 MeV, respectively within the framework of distorted wave Born approximation. Differential cross sections
at the first peaks in the angular distributions of these reactions are found to be uncertain within around 5% due
to the uncertainties of the optical model potentials from an result of 20000 times of calculations with the optical
potential parameters randomly sampled. This amount of uncertainties is found to be nearly independent of the
angular momentum transfer and the target masses within the studied range of incident energies. Uncertainties
of the single proton spectroscopic factors obtained by matching the theoretical and experimental cross sections
at different scattering angles are also discussed.
Subjects: Physics >> Nuclear Physics submitted time 2023-05-31
Guan Yongjing
Chen Wu
Wang Shenzhen
Hua Yuxin
Jing Qiaoyan
Liu Zhiyong
Huang Chunping
Wang Deyu
Wang Huijuan
He Xianwen
Mario De Cesare
Cui Liangjia
He Hua
Fan Kaidi
Guo Zichen
Abstract： The spatial distributions of 239+240Pu and 137Cs in soils from Longji Rice Terraces were investigated to evaluate soil erosion. The activity concentrations of 239+240Pu and 137Cs in the surface soils of the paddy fields were in the range of 0.089-0.734 and 1.80-7.88 mBq/g, respectively. The activities of 239+240Pu and 137Cs showed very similar distribution trends, first increasing and then decreasing with increasing elevation. The 240Pu/239Pu atom ratios in the surface soils ranged from 0.162–0.232. The activities of 239+240Pu and 137Cs in the soil cores tended to be uniformly distributed within the plowed layer and declined exponentially below this depth. The mean soil erosion rates of Longji Rice Terraces estimated by 239+240Pu and 137Cs tracer methods were 5.44 t/(ha·a) and 5.16 t/(ha·a), respectively, which demonstrated that plutonium can replace 137Cs as an ideal tracer for soil erosion research in the future. Landform features are the main factors affecting the distribution of plutonium and 137Cs as well as soil erosion in the Longji Rice Terraces.
Subjects: Physics >> Nuclear Physics submitted time 2023-05-31
Abstract： In this work we perform a Bayesian inference of the crust-core transition density ρt of neutron stars based upon the neutron-star radius and the neutron-skin thickness data within a thermodynamical method. The uniform and Gaussian distributions for the ρt prior are adopted in the Bayesian approach. It has a larger probability to have values higher than 0.1 fm 3 for ρt as the uniform prior and the neutron-star radius data are used. We found that this is controlled by the curvature Ksym of the nuclear symmetry energy. This phenomenon will not happen if Ksym is not extremely negative, i.e., Ksym > -200 MeV. The obtained ρt is 0.075+0.005-0.01fm^3 at 68% confifidence level when both the neutron-star radius and the neutron-skin thickness data are taken into account. The strongly anti-correlations between ρt and the slope L, curvature of the nuclear symmetry energy are observed. The dependence of the three L-Ksym correlations predicted in the literature on the crust-core density and pressure is quantitatively investigated. The most probable value of 0.08 fm^3 for ρt is obtained from the L-Ksym relation raised by Holt et al. and the larger values are preferred by the other two relations.
Peer Review Status:
Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2023-05-31
Abstract： A simulation code, GOAT, is developed to simulate single-bunch intensity-dependent effects and their interplay in the proton ring (pRing) of the Electron-Ion Collider in China (EicC) project. GOAT is a scalable and portable macroparticle tracking code written in Python and coded by object-oriented programming technology. It allows for transverse and longitudinal tracking, including impedance, space charge effect, electron cloud effect, and beam-beam interaction. In this paper, physical models and numerical approaches for the four types of high-intensity effects, together with the benchmark results obtained through other simulation codes or theories, are presented and discussed. In addition, a numerical application of the cross-talk simulation between the beam-beam interaction and transverse impedance is shown, and a dipole instability is observed below the respective instability threshold. Different mitigation measures implemented in the code are used to suppress the instability. The flexibility, completeness, and advancement demonstrate that GOAT is a powerful tool for beam dynamics studies in the EicC project or other high-intensity accelerators.
Subjects: Nuclear Science and Technology >> Nuclear Materials and Techniques submitted time 2023-05-31
Abstract： The nuclear fuel assembly is the core component of a nuclear reactor. In a pressurized water reactor fuel assembly, the top-connection structure connects the top nozzle to the guide thimble. Its performance reliability is essential for the stability of the nuclear fuel assembly. In this study, an assembly-oriented reliability analysis method for top-connection structures is presented by establishing an assembly-oriented top-connection structure parameter modeling method and a nonlinear contact gap and penetration correction method. A reliability model of the top-connection assembly structure, including multiple stochastic design variables, was constructed, and the overall reliability of the top-connection assembly structure was obtained via a Kriging model and Monte Carlo simulation. The acquired experimental data were consistent with real-world failure conditions, which verified the practicability and feasibility of the reliability analysis method proposed in this study.
Subjects: Physics >> Nuclear Physics submitted time 2023-05-31
Abstract： The neutron spectrum unfolding by Bonner Spheres Spectrometer (BSS) is considered a complex multidimensional model, which requires complex mathematical methods to solve the first kind of Fredholm integral equation. In order to solve the problem of the Maximum Likelihood Expectation Maximization (MLEM) algorithm which is easy to suffer the pitfalls of local optima and the particle swarm optimization (PSO) algorithm which is easy to get unreasonable flight direction and step length of particles, which leads to the invalid iteration and affect efficiency and accuracy, an improved PSO-MLEM algorithm, combined of PSO and MLEM algorithm, is proposed for neutron spectrum unfolding. The dynamic acceleration factor is used to balance the ability of global and local search, and improves the convergence speed and accuracy of the algorithm. Firstly, the Monte Carlo method was used to simulated the BSS to obtain the response function and count rates of BSS. In the simulation of count rate, four reference spectra from the IAEA Technical Report Series No. 403 were used as input parameters of the Monte Carlo method. The PSO-MLEM algorithm was used to unfold the neutron spectrum of the simulated data and was verified by the difference of the unfolded spectrum to the reference spectrum. Finally, the 252Cf neutron source was measured by BSS, and the PSO-MLEM algorithm was used to unfold the experimental neutron spectrum. Compared with maximum entropy deconvolution (MAXED), PSO and MLEM algorithm, the PSO-MLEM algorithm has fewer parameters, and automatically adjusts the dynamic acceleration factor to solve the problem of local optima. The convergence speed of the PSO-MLEM algorithm is 1.4 times and 3.1 times that of the MLEM and PSO algorithms. Compared with PSO, MLEM and MAXED, the correlation coefficients of PSO-MLEM algorithm increase by 33.1%, 33.5% and 1.9%, and the relative mean errors decreased by 98.2%, 97.8% and 67.4%.
Subjects: Physics >> Nuclear Physics submitted time 2023-05-31
Abstract：
Subjects: Library Science，Information Science >> Library Science submitted time 2023-05-31
Abstract：目的/意义 美国是最早开展信息组织教育的国家之一，信息组织类课程设置和教育较为完善和先进，对其开展研究可为我国高校信息组织类课程设置和教育提供参考和借鉴。 过程/方法 本文选取美国LIS专业排名靠前的15所高校作为调查对象，围绕课程设置、课程内容、教学模式和考核方式，对其开设的信息组织类课程进行网络调查和研究。 结果/结论 发现美国高校图书情报专业教育课程设置具有重视信息组织类课程、信息组织选修课多、具有跨学科特性、课程设置符合时代需求且注重实践、教学多元化及考核多维度的特点，并在此基础上提出了美国高校信息组织类课程设置和教育对我国高校信息组织类课程设置及教育的启示，以期为新文科背景下我国图书情报专业发展提供参考和借鉴。
Peer Review Status:Awaiting Review
Subjects: Library Science，Information Science >> Information Science submitted time 2023-05-31
Abstract：目的/意义 以美国情报界最新年度全球威胁评估报告为分析基础，明确其战略情报工作方向，把握美国情报全球安全威胁认知，进而为我国国家安全工作提供参考与借鉴。 方法/过程 采用文本分析、总结归纳等研究方法对报告内容进行剖析解读，得出美国情报界对国际竞争非传统安全跨国问题及地区冲突等关键问题尤为重视。 结果/结论 综合上述分析，参考美国全球安全战略的最新动向，最终建议我国国家安全工作要以总体国家安全观为指引，以前瞻性的视角防范化解国内外存在的潜在风险，坚决维护国家安全。
Peer Review Status:Awaiting Review
Subjects: Chemistry >> Nuclear Chemistry submitted time 2023-05-31
Abstract： The rapid development of advanced techniques for selective and efficient U(VI) extraction from aqueous solutions is essential for addressing U(VI) environmental pollution and energy issues. Here, we share recent progress in U(VI) extraction from aqueous solutions, especially the most frequently applied techniques such as adsorption, catalysis (photocatalysis, piezocatalysis, and electrocatalysis), chemical deposition, and reduction by zero-valent metal particles. We attempt toelucidate the strategies and various mechanisms that contribute to the enhancement of selective U(VI) extraction. At the end of our review, we highlight the outlook, challenges, and prospects for the development of this field.
Subjects: Physics >> Nuclear Physics submitted time 2023-05-31
Abstract： lead-shielded HPGe detector and offline g–ray spectra of the residual product were used to measure the cross-section (CS) and ratios of isomeric CS (sm/sg) in 134Xe(n,2n)133m,gXe reactions at different energies including 13.5, 13.8, 14.1, 14.4, and 14.8 MeV, relative to 93Nb(n,2n)92mNb reaction CS. The target was high-purity natural Xe gas under high pressure. T(d,n)4He reaction was used to produce neutrons. The TALYS code (1.95 version) for nuclear reactions was used for calculations along with the default parameters and various nuclear level density models. The uncertainties present in the measured CS data were thoroughly analyzed using the covariance analysis method. The results were subsequently compared to the theoretical values, evaluation data, and previous experimental findings. Thus, the CS data of the 134Xe(n,2n)133mXe and 134Xe(n,2n)133gXe reactions and the corresponding isomeric CS ratios at 13.5,13.8 and 14.1 MeV neutron energies are reported for the first time. This work advances our knowledge of pre-equilibrium emission in the (n,2n) reaction channel by resolving inconsistencies in Xe data.
Subjects: Nuclear Science and Technology >> Radiation Physics and Technology submitted time 2023-05-31
Abstract： Carbon-ion radiotherapy (CIRT) offers unique physical and biological advantages over photon radiotherapy. However, some
materials and devices in the CIRT treatment room become radioactive under bombardment by therapeutic carbon-ion beams
due to nuclear reactions, thereby leading to possible radiation hazards to medical staff and additional and unwanted doses
to patients. This study assessed the level of induced radioactivity in the treatment room of the Heavy-Ion Medical Machine
(HIMM) in Wuwei. Monte Carlo simulations using PHITS were performed for a conservative case under the conditions of
maximum beam energy and intensity provided by the HIMM facility. The geometry and configuration of Treatment Room
2 of the HIMM facility in Wuwei were adopted. We evaluated the activation of air, the phantom, and the components of
the beamline, such as the primary collimator (PC), ridge filter (RF), and multileaf collimator (MLC). For air activation,
we calculated the medical staff immersion external exposure and inhalation internal exposure caused by the corresponding
radionuclides. For phantom activation, we estimated the additional dose to the patient’s family members owing to secondary
photons after treatment. In addition, the exemption or non-exemption of the component material activation was assessed.
The results showed that external radiation caused by air activation was the main source of the annual effective dose at
approximately 0.5 mSv/y. The induced radioactivity exposure to family members of a patient after CIRT was approximately
40 μSv, sufficiently lower than the public dose limit of 1 mSv/a. The induced radioactivity of the PC, RF, and MLC was all
above the exempt levels after the devices were retired, whereas the induced radioactivity of the RS and compensator could
reach the exempt levels after one patient session. Our study indicated that medical staff engaged in CIRT should stay away
from the high-dose-rate area of induced radioactivity along the beam direction, shorten the residence time in the treatment
room as much as possible, and store the activated components in isolation after the equipment is out of use. Thus, this study
provides guidance for accurately assessing the level of induced radioactivity in the treatment room for CIRT.
Subjects: Physics >> Nuclear Physics submitted time 2023-05-31
Abstract： The properties of exotic nuclei are the focus of the present research. Two-neutron halo structures of neutron-rich 17,19B were experimentally confirmed. We studied the formation mechanism of halo phenomena in 17, 19B using the complex momentum representation method applied to deformation and continuum coupling. By examining the evolution of the weakly bound and resonant levels near the Fermi surface, s–d orbital reversals and certain prolate deformations were observed. In addition, by analyzing the evolution of the occupation probabilities and density distributions occupied by valence neutrons, we found that the ground state of 15B did not exhibit a halo, and the ground states of 17B and 19B exhibited halos at 0.6≤β2≤0.7 and 0.3≤β2≤0.7, respectively. The low-l components in the valence levels that are weakly bound or embedded in the continuous spectrum lead to halo formation.
Subjects: Medicine, Pharmacy >> Clinical Medicine submitted time 2023-05-31 Cooperative journals: 《中国全科医学》
Abstract： Background Since August 2022，Shengzhou City of Zhejiang Province has been carrying out the reform of outpatient payment mode in medical insurance，gradually carrying out the reform of capitation by implementing the total budget，updating the calculation standard of capitation fee，improving the incentive and constraint mechanism and other measures，so as to encourage primary health care institutions to provide appropriate basic medical services，reduce primary medical expenses，and promote the sustainable development of medical insurance fund. Objective To analyze the influence mechanism of capitation for outpatient services in basic medical insurance on medical expenses in Shengzhou City，Zhejiang Province，and to provide reference for improving the relevant payment system. Methods Using "capitation" and "medical costs" as both English and Chinese search terms，databases such as CNKI，Wanfang，PubMed and Web of Science were searched for relevant literature on capitation from 2000-01-01 to 2022-07-31，as well as the policy documents，government reports and news reports related to the implementation of capitation from April to July 2022. Personal interviews were conducted with representatives of capitation payment policy makers and implementers in Shengzhou City from September to December 2022（n=13）. A qualitative analysis of capitation reform policy on medical expenses under the total outpatient budget in Shengzhou City，Zhejiang Province was performed by using system dynamics approach. Results The policies of the current round of medical insurance payment reform in Shengzhou were plotted as a cause graph with five feedback loops obtained，showing that the implementation of the total capitation budget policy can motivate primary health care institutions to provide standardized medical services for residents，promote an increase in the contracting rate in primary care，thus controling medical expenses；a scientific capitation fee standard can motivate primary health care institutions to autonomously control and reduce costs；increasing the reimbursement ratio of medical insurance can effectively reduce the medical burden of patients；improving the performance appraisal system is conducive to the continuous improvement of service capabilities of primary health care institutions；strengthening the construction of information sharing mechanisms can achieve data sharing and exchange，and comprehensively improve the health of residents. Conclusion The implementation of capitation reform in conjunction with multiple policy measures can improve the contracting and consultation rates in primary care institutions，broaden the sources of medical insurance fund，ensure the sustainability of medical insurance fund，improve the medical service and capabilities of primary care institutions，improve the health status of residents，and significantly improve the prevention and treatment effect of chronic diseases.
Subjects: Nuclear Science and Technology >> Engineering Technology of Fission Reactor submitted time 2023-05-31
Abstract： Transplutonium isotopes are scarce and need to be produced by irradiation in high flux reactors, but their production is inefficient and optimization studies are needed. This paper analyzes the physics nature of transplutonium isotopes production by taking Cf-252, Cm-244, Cm-242 and Pu-238 as examples. Traditional methods based on the Monte Carlo burnup calculation are faced with the shortcomings of large amounts of calculation and are unable to analyze the individual energy intervals in more detail, thus cannot support the refined evaluation, screening and optimization of the irradiation schemes. After grasping the physics nature and simplifying the complexity of the production process, we proposed a rapid diagnosis method for evaluating the radiation schemes based on the concept of “Single Energy Interval Value (SEIV)” and “Energy Spectrum Total Value (ESTV)”. The rapid diagnosis method can not only avoid the tedious burnup calculation but also help to provide direction for optimization. The optimal irradiation schemes for producing Cf-252, Cm-244, Cm-242 and Pu-238 are determined based on the rapid diagnosis method. The optimal irradiation schemes can greatly improve production efficiency. Compared with the initial scheme, the optimal scheme improves the production efficiency of Pu-238 by 7.41 times, 11.98 times for Cm-242, 65.20 times for Cm-244 and 15.08 times for Cf-252, respectively. The work in this paper realizes the refined analysis of transplutonium isotopes production and provides a theoretical basis for improving production efficiency.
Peer Review Status:Awaiting Review
Subjects: Nuclear Science and Technology >> Nuclear Detection Technology and Nuclear Electronics submitted time 2023-05-30
Abstract： In order to reduce the experimental uncertainty in the 235U resonance energy region and improve the detection efficiency for neutron total cross section measurements compared with the neutron total cross section spectrometer (NTOX), a dedicated lithium-containing scintillation detector has been considered to be developed on the Back-n beam line at the China Spallation Neutron Source (CSNS). The FAst Scintillator-based neutron Total cross section (FAST) spectrometer has been designed based on a Cs2LiLaBr6 (CLLB) scintillator considering the γ-ray flash and neutron environment on the Back-n beam line. Response of the CLLB scintillator to neutrons and γ-rays has been performed with different ratios of 6Li/7Li abundance using Geant4. The neutron-γ discrimination performance of the CLLB has been simulated considering different scintillation parameters, physical designs and light readout modes, respectively. A cubic 6Li-enriched (> 90%) CLLB scintillator, which has a thickness of 4-9 mm and a side length no less than 50 mm to cover the Φ50 mm neutron beam at the spectrometer position, has been proposed coupling to a side readout SiPM array for the construction of the FAST spectrometer. The developed simulation techniques in neutron-γ discrimination performance could provide technical support for other neutron-induced reactions measurement on the Back-n beam line.
Subjects: Nuclear Science and Technology >> Engineering Technology of Fission Reactor Subjects: Nuclear Science and Technology >> Engineering of Nuclear Power submitted time 2023-05-30
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