作者机构:
[Fang Wang; Zhuo Chen; Yue Wu; Yating Peng] School of Chemistry and Chemical Engineering, University of South China, Hengyang, Hunan 421001, China;[Tingting Li; Liangshu Xia] School of Nuclear Science and Technology, University of South China, Hengyang, Hunan 421001, China
通讯机构:
[Fang Wang; Tingting Li; Liangshu Xia] S;School of Chemistry and Chemical Engineering, University of South China, Hengyang, Hunan 421001, China<&wdkj&>School of Nuclear Science and Technology, University of South China, Hengyang, Hunan 421001, China
摘要:
Plutonium-239+240 and (137)Cs in the environment can usually be used to track the impact of nuclear activities on the environment, and have become important tools in environmental geochemical studies. In this study, nine sediment cores (E1-E9) in Lake East Dongting were collected and measured for the activity concentration of (239+240)Pu, (137)Cs and the atomic ratio of (240)Pu/(239)Pu, and then their vertical distribution characteristics were analyzed. The results show that: the activity concentrations of (137)Cs and (239+240)Pu in Lake East Dongting ranged from 5.26±0.43 to 28.6±2.23 Bq kg(-1) and 0.29±0.02 to 1.37±0.09 Bq kg(-1), with an average of 7.48±0.68 Bq kg(-1) and 0.39±0.03 Bq kg(-1), respectively. The atomic ratios of (240)Pu/(239)Pu are 0.168±0.012-0.211±0.015, which are basically consistent with the global atmospheric deposition. The vertical profiles of (137)Cs and (239+240)Pu in sediment cores show obvious single-peak distribution in E1-E6 and bimodal distribution in E7-E9. The results of sedimentation rates calculated by (137)Cs and (239+240)Pu method ranged from 0.59cm y(-1) to 1.99cm y(-1) with a mean of 1.18cm y(-1) and 0.61cm y(-1) to 2.18cm y(-1) with a mean of 1.26cm y(-1). The inventories of (137)Cs and (239+240)Pu in nine sediment cores are 5.87-10.8 kBq m(-2) and 307-545 Bq m(-2), which are about 8-14 and 9-15 times the inventory in the global average atmospheric deposition at the same latitude respectively. Comparing the results of the sedimentation rates and the inventories from different sampling points indicates that extreme climatic events and human activities have a significant impact on sediment environment of Lake East Dongting.
作者:
Guan, T. Y.;Zhang, Y. P.;Wang, B.;Guo, C.;Liu, J. C.;...
期刊:
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT,2024年1063:169244 ISSN:0168-9002
通讯作者:
Guo, C;Tang, Q
作者机构:
[Li, C.; Tang, Q.; Wang, B.; Guan, T. Y.] Univ South China, Sch Nucl Sci & Technol, Hengyang 421001, Peoples R China.;[Guo, C.; Zhang, Y. P.; Liu, J. C.; Yang, C. G.] Chinese Acad Sci, Expt Phys Div, Inst High Energy Phys, Beijing 100049, Peoples R China.;[Guo, C.; Zhang, Y. P.; Liu, J. C.; Yang, C. G.] Univ Chinese Acad Sci, Sch Phys, Beijing 100049, Peoples R China.;[Guo, C.; Zhang, Y. P.; Liu, J. C.; Yang, C. G.] State Key Lab Particle Detect & Elect, Beijing 100049, Peoples R China.;[Guo, C; Guo, C.] 19B YuQuan Rd, Beijing, Peoples R China.
通讯机构:
[Guo, C ] 1;[Tang, Q ] 2;19B YuQuan Rd, Beijing, Peoples R China.;28 Changsheng West Rd, Beijing, Hunan, Peoples R China.
关键词:
Atomic physics;Degassing;Neutrons;Observatories;Particle detectors;Photomultipliers;Radioactivity;Trace elements;Degassing membrane;Liquid scintillator;Micro-bubble generators;Neutrino physics;Physics experiments;Radon concentrations;South China;State of the art;Ultra-pure water;Water Cherenkov detectors;Radon
摘要:
We investigate the hydrostatic equilibrium configurations of strange stars within the framework of Rastall-Rainbow theory of gravity. These stars are primarily composed of strange quark matter, with its distribution governed by the color-flavor-locked phase of quark matter equation of state (EoS). Using this EoS, we numerically solve the modified Tolman-Oppenheimer-Volkoff equation to obtain different quark star models. We find that the parameters from this modified gravity have specific contributions to the structure of quark stars and introduce new descriptions for massive celestial bodies. Also, the mass-radius relation strongly depends on the parameters from the considered EoS. Furthermore, we analyze the impact of these parameters on the gravitational redshift and compactness of quark stars.
作者:
Fujita, Mitsutoshi;He, Song;Sun, Yuan;Zhang, Jun
期刊:
Journal of High Energy Physics,2024年2024(1) ISSN:1029-8479
通讯作者:
Fujita, M
作者机构:
[Fujita, M; Fujita, Mitsutoshi] Univ South China, Sch Nucl Sci & Technol, Hengyang 421001, Peoples R China.;[He, Song] Jilin Univ, Coll Phys, Ctr Theoret Phys, Changchun 130012, Peoples R China.;[He, Song] Albert Einstein Inst, Max Planck Inst Grav Phys, Muhlenberg 1, D-14476 Golm, Germany.;[Sun, Yuan] Cent South Univ, Sch Phys & Elect, Changsha 418003, Peoples R China.;[Zhang, Jun] Univ Alabama, Dept Phys & Astron, 514 Univ Blvd, Tuscaloosa, AL 35487 USA.
通讯机构:
[Fujita, M ] U;Univ South China, Sch Nucl Sci & Technol, Hengyang 421001, Peoples R China.
关键词:
Gauge-Gravity Correspondence;Holography and Condensed Matter Physics (AdS/CMT);Confinement
摘要:
<jats:title>A<jats:sc>bstract</jats:sc>
</jats:title><jats:p>We compute holographic entanglement entropy (EE) and the renormalized EE in AdS solitons with gauge potential for various dimensions. The renormalized EE is a cutoff-independent universal component of EE. Via Kaluza-Klein compactification of <jats:italic>S</jats:italic><jats:sup>1</jats:sup> and considering the low-energy regime, we deduce the (<jats:italic>d</jats:italic> − 1)-dimensional renormalized EE from the odd-dimensional counterpart. This corresponds to the shrinking circle of AdS solitons, probed at large <jats:italic>l</jats:italic>. The minimal surface transitions from disk to cylinder dominance as <jats:italic>l</jats:italic> increases. The quantum phase transition occurs at a critical subregion size, with renormalized EE showing non-monotonic behavior around this size. Across dimensions, massive modes decouple at lower energy, while degrees of freedom with Wilson lines contribute at smaller energy scales.</jats:p>
摘要:
Purpose; Investigating the effects of unequal sub-arc personalized collimator angle selection on the quality of Volumetric Modulated Arc Therapy (VMAT) plans for treating multiple brain metastases. Methods: This study included 21 patients, each with 2-4 target volumes of multiple brain metastases. Two stereotactic radiotherapy (SRT) approaches were utilized: sub-arc collimator VMAT (SAC-VMAT) and fixed collimator VMAT (FC-VMAT). In the SAC-VMAT group, multi-leaf collimators (MLC) shaped the target area, dividing the full arc into four unequal sub-arcs under the beam's eye view (BEV). Each sub-arc had an appropriate collimator angle selected to mitigate 'island blocking problems'. Conversely, the FC-VMAT group used a fixed collimator angle of 15 degrees or 345 degrees. A comparative analysis of the dosimetric parameters of the target volumes and normal tissues, along with the monitor units (MU), was conducted between the two groups. Results: The mean dose and dose-volume to normal brain tissue (2-26 Gy, with a step of 2 Gy) were significantly lower in the SAC-VMAT group (P < 0.01). There was no statistical difference between the two groups in dose to the target volumes, conformity index (CI), homogeneity index (HI), and other normal tissues (P > 0.05). Compared with the FA-VMAT group, the SAC-VMAT group significantly reduced the gradient index (GI) (4.5 +/- 0.59 vs 5.2 +/- 0.75, P < 0.001) and MU (1774.33 +/- 181.77 vs 2001.0 +/- 344.86, P < 0.001). Notably, with an increase in the number of PTV, the SAC-VMAT group demonstrated more significant improvements in the dose-volume of normal brain tissue, GI, and MU. Conclusions: In this study, personalized selection of the unequal sub-arc collimator angle ensured the prescribed dose to the PTV, CI, and HI, while significantly reducing the GI, MU, and the dose to normal brain tissue in the VMAT plan for multi-target brain metastases in the cohort of cases with 2-4 target volumes. Particularly as the number of targets increase, the advantages of this method become more pronounced.
摘要:
<jats:title>Abstract</jats:title><jats:sec><jats:label /><jats:p>Development of shielding materials for <jats:sup>222</jats:sup>Rn and γ radiation has crucial implications for ensuring the safety of individuals. This paper reports the synthesis of modified graphene nanosheets (MGNPs) via the reaction of KH560 with graphene nanosheets (GNPs), while melt blending and hot‐press molding technique were used to fabricate a multifunctional polymer composite shielding material, MGNP/WB/PMMA (polymethyl methacrylate). Successful synthesis of MGNP was confirmed by Fourier transform infrared spectroscopy, and scanning electron microscope (SEM) analysis was utilized to assess the distribution of functional fillers within the cross‐section of the polymer composite. Additionally, thermogravimetric analysis (TGA) demonstrated that MGNP and WB particles enhance the thermal stability of the polymer composite materials. Compared to pure PMMA, 98.7% decrease in the radon diffusion coefficient was observed for MGNP1.5 wt%/PMMA composite material. In addition to enhance the radon‐blocking characteristics of the polymer composites, inclusion of WB particles also boosts their shielding capacity against gamma radiation. The <jats:sup>222</jats:sup>Rn diffusion coefficient of MGNP1.5 wt%/WB25wt%/PMMA polymer composite material decreased by 99.6% and at energies of 60 KeV, 80 KeV, 122 KeV, 365 KeV, the mass attenuation coefficient (MAC) for the composite material increased by 0.79, 1.97, 0.57, and 0.05 cm<jats:sup>2</jats:sup>/g, respectively, compared to pure PMMA.</jats:p></jats:sec><jats:sec><jats:title>Highlights</jats:title><jats:p><jats:list list-type="bullet">
<jats:list-item><jats:p>The PMMA composite materials doped with graphene nanosheets demonstrate outstanding resistance to <jats:sup>222</jats:sup>Rn.</jats:p></jats:list-item>
<jats:list-item><jats:p>Graphene nanosheets modified by KH560 exhibit favorable dispersion within PMMA.</jats:p></jats:list-item>
<jats:list-item><jats:p>WB can further enhance the radon resistance of MGNP/WB/PMMA composite materials.</jats:p></jats:list-item>
<jats:list-item><jats:p>The polymer composites exhibit excellent <jats:sup>222</jats:sup>Rn and gamma ray shielding properties.</jats:p></jats:list-item>
</jats:list></jats:p></jats:sec>
摘要:
Solute transport in conventional acid leaching of sandstone uranium ores is limited by diffusion and convection, resulting in extended leaching cycles. This study described an electrokinetic-enhanced method for leaching sandstone uranium ore with sulfuric acid and was intended to investigate the impacts of potential gradients on leaching efficiency. Electrokinetic horizontal column leaching experiments were conducted on sandstone uranium ore. After 20 h of leaching, the uranium leaching efficiencies were 54.90 %, 56.36 %, 68.33 %, and 82.04 % for potential gradients of 0, 0.5, 1.0, and 2.0 V/cm, respectively. The uranium leaching efficiency of sandstone at a 2.0 V/cm potential gradient was 27.14 % greater than that at a 0 V/cm potential gradient, and the leaching time was decreased by approximately 40 % at the same uranium leaching efficiency. Analyses of the chemical fraction of uranium, XRD and SEM-EDS showed that the applied potential gradient facilitated solute transport during leaching, thus accelerating the leaching efficiency of adsorbed uranium, tetravalent uranium, and uranium encapsulated in lattices of silicates and primary and secondary minerals in sandstone uranium ores. Therefore, electrokinetic action is excellent for enhancing the effectiveness of sulfuric acid leaching of sandstone uranium ores and has broad application prospects.
摘要:
The open-loop method of measuring soil radon exhalation rate is widely used to explore the influence of environmental factors on soil radon exhalation rate because it can continuously monitor and quickly respond to changes in soil radon exhalation rate. However, in the open-loop measurement, the ventilation chamber is connected to the outside environment, and under the action of the pump, the ventilation chamber will have a certain suction effect on the covered soil surface. When the soil is relatively dry, there may be some tiny cracks on the soil surface. Under the influence of suction, the gas with high radon concentration from deep soil will be more easily drawn out to the soil surface. If such a situation occurs, the radon concentration in the ventilation chamber and the results of the radon exhalation rate measurements will be abnormally high. In this paper, we investigated the effect of soil cracks on the open-loop radon exhalation rate measurements by comparing the radon exhalation rate obtained from open-loop measurements with that obtained from closed-loop measurements under the same environment. The results show that in the open-loop radon exhalation measurements, the smaller the soil cracks are, i.e., the closer the flow rate at the inlet of the ventilation chamber is to that of the pump, the higher the agreement between the radon exhalation rate obtained from the open-loop measurement and that from the closed-loop measurement.
作者机构:
[Zhao, YJ; Zhang, Zhen-Hua; Zhao, Yu-Jie] Univ South China, Sch Nucl Sci & Technol, Hengyang 421001, Hunan, Peoples R China.;[Guo, Xin-Heng] Beijing Normal Univ, Coll Nucl Sci & Technol, Beijing 100875, Peoples R China.
通讯机构:
[Zhao, YJ ] U;Univ South China, Sch Nucl Sci & Technol, Hengyang 421001, Hunan, Peoples R China.
摘要:
CP violation in baryon decay processes is still undiscovered to date. We present a general analysis of the decay-angular distributions and the corresponding CP asymmetries in cascade decays of the type H-* R (-* ab)c, ) c, where H is a heavy hadron that decays through weak interactions H-* Rc and the resonance R decays strongly via R-* ab. Based on the analysis, we propose to search for CP violation in the decay-angular distributions in the cascade decay processes-* B M, with B or M subsequently decaying through strong interactions, where is the mother baryon, B and M are the daughter baryon and meson, respectively, and M has to be spin nonzero. We also present some typical decay channels in which the search for such kinds of CP asymmetries can be performed.
期刊:
NUCLEAR SCIENCE AND TECHNIQUES,2024年35(11) ISSN:1001-8042
通讯作者:
Wang, XD
作者机构:
[He, Lie; Xiao, Wan-Cheng; Zhang, Hai-Feng; Zou, Yu-Cheng; Wang, Xiao-Dong; Luo, Si-Yuan] Univ South China, Sch Nucl Sci & Technol, Hengyang 421001, Peoples R China.;[He, Lie; Xiao, Wan-Cheng; Zhang, Hai-Feng; Zou, Yu-Cheng; Wang, Xiao-Dong; Luo, Si-Yuan] Univ South China, Key Lab Adv Nucl Energy Design & Safety MOE, Hengyang 421001, Peoples R China.;[Liu, Xiang-Man] Chinese Acad Sci, Inst Modern Phys, Lanzhou 730000, Peoples R China.;[Liu, Xiang-Man] Univ Chinese Acad Sci, Sch Nucl Sci & Technol, Beijing 100049, Peoples R China.;[Liu, Xiang-Man] Lanzhou Univ, Sch Nucl Sci & Technol, Lanzhou 730000, Peoples R China.
通讯机构:
[Wang, XD ] U;Univ South China, Sch Nucl Sci & Technol, Hengyang 421001, Peoples R China.;Univ South China, Key Lab Adv Nucl Energy Design & Safety MOE, Hengyang 421001, Peoples R China.
关键词:
Monte Carlo simulation;Muon tomography;TDOA;Machine learning;Image reconstruction
摘要:
Cosmic-ray muons are highly penetrating background-radiation particles found in natural environments. In this study, we develop and test a plastic scintillator muon detector based on machine-learning algorithms. The detector underwent muon position-resolution tests at the Institute of Modern Physics in Lanzhou using a multiwire drift chamber (MWDC) experimental platform. In the simulation, the same structural and performance parameters were maintained to ensure the reliability of the simulation results. The Gaussian process regression (GPR) algorithm was used as the position-reconstruction algorithm owing to its optimal performance. The results of the Time Difference of Arrival algorithm were incorporated as one of the features of the GPR model to reconstruct the muon hit positions. The accuracy of the position reconstruction was evaluated by comparing the experimental results with Geant4 simulation results. In the simulation, large-area plastic scintillator detectors achieved a position resolution better than 20 mm. In the experimental-platform tests, the position resolutions of the test detectors were 27.9 mm. We also analyzed factors affecting the position resolution, including the critical angle of the total internal reflection of the photomultiplier tubes and distribution of muons in the MWDC. Simulations were performed to image both large objects and objects with different atomic numbers. The results showed that the system could image high- and low-Z materials in the constructed model and distinguish objects with significant density differences. This study demonstrates the feasibility of the proposed system, thereby providing a new detector system for muon-imaging applications.
摘要:
A silica-supported copolymer loaded with bis (2-ethylhexyl) phosphate was prepared and first investigated for the separation of trace radium from natural 232Th. Results showed that the adsorbent was prepared successfully with ultrahigh selectivity and ultrafast adsorption kinetics towards thorium, making the separation easy and convenient. The chemical recovery rate to radium reached 96.7%, and the decontamination factor to thorium exceeded 105. Generally, this work demonstrated the feasibility of using this material and method to directly separate 228Ra and 224Ra from 232Th, rendering it significant in the future preparation and application of 212Pb.
摘要:
小型棒控压水堆舍弃了可溶硼,并高度依赖控制棒与可燃毒物棒控制堆芯的反应性.为研究控制棒对堆芯关键性能的影响,本文以核动力破冰船用KLT-40模型为对象,以轴向功率偏移、堆芯寿期、燃料利用率与径向功率峰因子为指标,开展长寿期小型棒控压水堆控制棒布置与动作策略设计分析.首先,基于OpenMC程序开发带棒燃耗程序;其次,比较堆芯带控制棒与无控制棒运行时的堆芯寿期等指标;最后,分析不同动作策略对轴向功率偏移等指标的影响.结果表明:控制棒将堆芯寿期从590 EFPDs(等效满功率天,Effective full power days)延长至650~698 EFPDs;低价值棒组优先动作策略使轴向功率偏移程度由-0.69与+0.80分别下降至-0.29与+0.52.因此,要准确计算长寿期压水堆寿期必须采用带控制棒燃耗计算策略,并且通过合理的动作策略能够有效减小控制棒带来的轴向功率偏移.