分类: 物理学 >> 核物理学 提交时间: 2025-06-05
摘要: As the key technology of space exploration, space power has always been a research interest of international researchers. A lot of research work has been carried out around the world for the space nuclear reactor using heat pipe, liquid metal and gas cooling method. With the development of molten salt reactor of IV generation reactor system, molten salt dissolving fissile material and acting as a coolant at the same time has become a new cooling scheme, which provides new ideas for the design of space nuclear reactor. In this study, a novel reactor Liquid-Solid Dual-Fuel Space Nuclear Reactor (LSSNR) was preliminarily proposed combining the molten salt fuel and cross-shaped spiral solid fuel for the design goals of 30-year lifetime and active core weight less than 200 kg. Monte Carlo neutron transport code OpenMC based on ENDF/B-VII.1 library was employed for neutronics design in aspect of fuel type, cladding material, reflector material and spectral shift absorber. Then, the thickness of control drum absorber was optimized to meet the requirement of the sufficient shutdown margin, lower solid fuel enrichment, and 30 EFPY operation lifetime. Finally , UC solid fuel with U-235 enrichment of 80.98 wt.% and B4C thickness of 0.75 cm were adopted in LSSNR, and BeO was adopted as reflector and matrix material of control drum. A spectral shift absorber Gd2O3 was used to avoid the sub-critical LSSNR returning to criticality at a launch accident. The keff with control drum rotating innermost position is 0. 954949, and the keff reaches 1.00592 after 30 EFPY operation. The total mass of the active core is 160.65 kg. In addition, the thermal-hydraulic feasibility of LSSNR using cross-shaped spiral fuel was analyzed based on a 4/61 reactor core model. The structure of cross-shaped spiral fuel achieves enhanced heat transfer by generating turbulence, leads to a uniform temperature distribution of the coolant flow field, and reduces local temperature peaks. Based on LSSNR scheme, some neutronic characteristics were analyzed. Results demonstrate that the LSSNR has strongly negative reactivity coefficients due to the thermal expansion of liquid fuel, and the fission gas-induced pressure meets safety requirements. After 100 years of the end of core life, the total radioactivity of reactor core is reduced by 99% and is 7.1305 Ci.
分类: 天文学 >> 天文仪器与技术 提交时间: 2025-06-03 合作期刊: 《Astronomical Techniques and Instruments》
摘要: The Solar Close Observations and Proximity Experiments (SCOPE) mission will send a spacecraft into the solar atmosphere at a low altitude of just 5 R☉ from the solar center. It aims to elucidate the mechanisms behind solar eruptions and coronal heating, and to directly measure the coronal magnetic field. The mission will perform in situ measurements of the current sheet between coronal mass ejections and their associated solar flares, and energetic particles produced by either reconnection or fast-mode shocks driven by coronal mass ejections. This will help to resolve the nature of reconnections in current sheets, and energetic particle acceleration regions. To investigate coronal heating, the mission will observe nano-flares on scales smaller than 70 km in the solar corona and regions smaller than 40 km in the photosphere, where magnetohydrodynamic waves originate. To study solar wind acceleration mechanisms, the mission will also track the process of ion charge-state freezing in the solar wind. A key achievement will be the observation of the coronal magnetic field at unprecedented proximity to the solar photosphere. The polar regions willalso be observed at close range, and the inner edge of the solar system dust disk may be identified for the first time. This work presents the detailed background, science, and mission concept of SCOPE and discusses how we aim to address the questions mentioned above.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 分类: 计算机科学 >> 自然语言理解与机器翻译 提交时间: 2025-05-27
摘要: The introduction of the transformer architecture in 2017 (cf. [VSP2017]) marked the most striking advancement in natural language processing. The transformer is a model architecture relying entirely on an attention mechanism to draw global dependencies between input and output. However, we believe there is a gap in our theoretical understanding of what the transformer is, and why it works physically. In this paper, from a physical perspective on modern chips, we construct physical models in the Fock space over the Hilbert space of tokens realizing large language models based on a transformer architecture as open quantum systems. Our physical models underlie the transformer architecture for large language models.
分类: 机械工程 >> 机械设计 提交时间: 2025-05-20
摘要: This paper introduces a method for modular reconfigurable robots based on cube models to self-reconstruct and emit using the characteristics of permanent magnets in weightless environments. Although modular robots based on cubes have built various relatively mature reconstruction algorithm models, there is no relatively mature technology for implementing modular robot reconstruction due to the size, complexity, cost, etc. of modular robots. To solve this challenge, based on our existing modular robot Ubot, the permanent magnet array on the connection surface of the modular robot was transformed, so that the modular robot has three states: gravity, gravitational, and repulsive force, and can change the magnitude of the magnetic force. Based on this premise, we designed a collaboration mechanism of two modes of magnet absorption and repulsion on the module connection surface. UBot can use the electrical permanent magnet array to configure different magnetic drives to achieve flip along the edge and then absorb to adjacent positions, or use the electrical permanent magnet array to configure the same repulsive force to emit the modular robot to a predetermined working position. In addition, two-dimensional self-reconstruction experiments and emission experiments were carried out on the constructed micropore air float platform. This paper describes the design, reconstruction and emission principles and dynamic analysis of permanent magnets on the connection surface of a modular robot, as well as the reconstruction method suitable for modular robot ubot.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 分类: 计算机科学 >> 自然语言理解与机器翻译 提交时间: 2025-05-07
摘要: This paper presents a mathematical formalism for generative artificial intelligence (GAI). Our starting point is an observation that a “histories" approach to physical systems agrees with the compositional nature of deep neural networks. Mathematically, we define a GAI system as a family of sequential joint probabilities associated with input texts and temporal sequences of tokens (as physical event histories as in \cite{Gudder1998,Isham1994}). From a physical perspective on modern chips, we then construct physical models realizing GAI systems as open quantum systems. Finally, as illustration, we construct physical models in the Fock space over the Hilbert space of tokens realizing large language models based on a transformer architecture as open quantum systems.
分类: 物理学 >> 核物理学 提交时间: 2025-04-16
摘要: As an advanced fuel form, TRISO particle fuel is relatively reliable due to the excellent capability of its thin coating layers to contain fission products, but it is still prone to cracks or pores in the coatings during production, transportation, and usage. These irregular geometries can significantly impact their ability to maintain structural integrity. Therefore, in order to advance the use of TRISO particles in space reactors, analyzing and predicting the crack propagation in their coatings is crucial. This model introduces the material properties of TRISO particles, irradiation behavior, and fission gas release model, and establishes a phase field model to investigate the crack propagation characteristics of the outer three coatings of TRISO particles. The accuracy of this model for TRISO particle performance was verified through an IAEA benchmark problem and a comparison with BISON program results for TRISO particles. The reliability of the phase field model for crack simulation was validated by analyzing a notched tensile plate and Kalthoff experiment. The effects of a crack in the IPyC layer, a residual pore in the SiC layer, a crack on the outer side of OPyC, and the simultaneous presence of a crack in the IPyC layer and a residual pore in the SiC layer, were studied in succession. The calculation results reveal that cracks in the IPyC layer cause debonding between the IPyC and SiC layers, but they are insufficient to propagate into the SiC layer during the early stages of burnup. Residual pores in the SiC layer lead to the complete fracture of the coating layers, primarily due to excessive gas pressure from the inner IPyC layer rather than the weakening effect of the pores on the structure. Cracks in the OPyC layer cause concentrated tensile stress on the outer side of the SiC layer during the early stages of burnup, which alters the crack propagation path in the coating layers during the later stages of burnup. Therefore, in addition to using material detection techniques to screen out TRISO particles with excessive defects before the production of FCM pellets, it is essential to enhance the ability of coating layers to maintain structural integrity and implement fundamental measures such as expelling accumulated gases from the particles. These actions are crucial for the safe and stable operation of TRISO particle fuel in space reactors.
分类: 物理学 >> 核物理学 提交时间: 2025-03-07
摘要: As an advanced fuel form, TRISO particle fuel is relatively reliable due to the excellent capability of its thin coating layers to contain fission products, but it is still prone to cracks or pores in the coatings during production, transportation, and usage. These irregular geometries can significantly impact their ability to maintain structural integrity. Therefore, in order to advance the use of TRISO particles in space reactors, analyzing and predicting the crack propagation in their coatings is crucial. This model introduces the material properties of TRISO particles, irradiation behavior, and fission gas release model, and establishes a phase field model to investigate the crack propagation characteristics of the outer three coatings of TRISO particles. The accuracy of this model for TRISO particle performance was verified through an IAEA benchmark problem and a comparison with BISON program results for TRISO particles. The reliability of the phase field model for crack simulation was validated by analyzing a notched tensile plate and Kalthoff experiment. The effects of a crack in the IPyC layer, a residual pore in the SiC layer, a crack on the outer side of OPyC, and the simultaneous presence of a crack in the IPyC layer and a residual pore in the SiC layer, were studied in succession. The calculation results reveal that cracks in the IPyC layer cause debonding between the IPyC and SiC layers, but they are insufficient to propagate into the SiC layer during the early stages of burnup. Residual pores in the SiC layer lead to the complete fracture of the coating layers, primarily due to excessive gas pressure from the inner IPyC layer rather than the weakening effect of the pores on the structure. Cracks in the OPyC layer cause concentrated tensile stress on the outer side of the SiC layer during the early stages of burnup, which alters the crack propagation path in the coating layers during the later stages of burnup. Therefore, in addition to using material detection techniques to screen out TRISO particles with excessive defects before the production of FCM pellets, it is essential to enhance the ability of coating layers to maintain structural integrity and implement fundamental measures such as expelling accumulated gases from the particles. These actions are crucial for the safe and stable operation of TRISO particle fuel in space reactors.
分类: 物理学 >> 核物理学 提交时间: 2025-03-01
摘要: As an advanced fuel form, TRISO particle fuel is relatively reliable due to the excellent capability of its thin coating layers to contain fission products, but it is still prone to cracks or pores in the coatings during production, transportation, and usage. These irregular geometries can significantly impact their ability to maintain structural integrity. Therefore, in order to advance the use of TRISO particles in space reactors, analyzing and predicting the crack propagation in their coatings is crucial. This model introduces the material properties of TRISO particles, irradiation behavior, and fission gas release model, and establishes a phase field model to investigate the crack propagation characteristics of the outer three coatings of TRISO particles. The accuracy of this model for TRISO particle performance was verified through an IAEA benchmark problem and a comparison with BISON program results for TRISO particles. The reliability of the phase field model for crack simulation was validated by analyzing a notched tensile plate and Kalthoff experiment. The effects of a crack in the IPyC layer, a residual pore in the SiC layer, a crack on the outer side of OPyC, and the simultaneous presence of a crack in the IPyC layer and a residual pore in the SiC layer, were studied in succession. The calculation results reveal that cracks in the IPyC layer cause debonding between the IPyC and SiC layers, but they are insufficient to propagate into the SiC layer during the early stages of burnup. Residual pores in the SiC layer lead to the complete fracture of the coating layers, primarily due to excessive gas pressure from the inner IPyC layer rather than the weakening effect of the pores on the structure. Cracks in the OPyC layer cause concentrated tensile stress on the outer side of the SiC layer during the early stages of burnup, which alters the crack propagation path in the coating layers during the later stages of burnup. Therefore, in addition to using material detection techniques to screen out TRISO particles with excessive defects before the production of FCM pellets, it is essential to enhance the ability of coating layers to maintain structural integrity and implement fundamental measures such as expelling accumulated gases from the particles. These actions are crucial for the safe and stable operation of TRISO particle fuel in space reactors.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2025-02-19
摘要: Industrial linear accelerators often contain many bunches when their pulse widths are extended to microsec onds. As they typically operate at low electron energies and high currents, the interactions among bunches cannot be neglected. In this study, an algorithm is introduced for calculating the space charge force of a train with infinite bunches. By utilizing the ring charge model and the particle-in-cell (PIC) method and combin ing analytical and numerical methods, the proposed algorithm efficiently calculates the space charge force of infinite bunches, enabling the accurate design of accelerator parameters and a comprehensive understanding of the space charge force. This is a significant improvement on existing simulation software such as ASTRA and PARMELA that can only handle a single-bunch or a small number of bunches. The PIC algorithm is val idated in long-drift space transport by comparing it with existing models, such as the infinite-bunch, ASTRA single-bunch, and PARMELA several-bunch algorithms. The space charge force calculation results for the ex ternal acceleration field are also verified. The reliability of the proposed algorithm provides a foundation for the design and optimization of industrial accelerators.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2025-02-03
摘要: This note aims to give a self-contain and detail explaination about U(k′)×U(k) Pati-Salam model in curved space-time which derived from (1 + n)-dimensional square root Lorentz manifold by self-parallel transportation principle. The concepts fundation of manifold from view point of category theory, fiber bundle and sheaf theories are reviewed. There are extra U(k′)×U(k)-principal bundle and U(k)- associated bundle than (1 + n)-dimensional Lorentz manifold. The conservative currents on square root Lorentz manifold is discussed preliminary. A detail proof of relation from sheaf quantization to path integral quantization is given.
分类: 物理学 >> 核物理学 提交时间: 2025-01-22
摘要: Space reactor has a good future in sea, land, air and space by virtue of its small size, applicability and high efficiency, and the combination of high temperature gas-cooled reactor and Brayton cycle is more suitable for exploration missions at the megawatt power level. A space gas-cooled reactor with a thermal power of 3 MW is used as a research object, and the design and optimization of this research object is carried out using EBSILON simulation software. The efficiency comparison between direct and indirect Brayton cycle is carried out under different conditions, the direct Brayton cycle was found to be 1.4%-2.8% more efficient than the indirect Brayton cycle and occupies less space. The efficiencies of four configurations of the Brayton cycle are compared. When the compressor inlet temperature is 400 K, the recompression efficiency is lower, and the efficiency of both the interstage-cooled cycle and the simple reheat cycle is higher than 30% when the turbine inlet temperature reaches 1400K. When the compressor inlet temperature is 350K, the simple reheat cycle can achieve 29.6% efficiency at a turbine inlet temperature of 1200K. When the compressor inlet temperature is 300K, the efficiency of all four cycle structures is higher than 20%. And when the turbine inlet temperature is higher than 1150K, the efficiency of all four structures is higher than 30%. The optimal pressure ratios are different for the different configurations, with 2.2 and 3.5 for the simple reheat cycle and the interstage-cooled cycle, respectively. And the optimal pressure ratio for the recompression cycle is also related to its diversion ratio, the recompression cycle efficiencies are 0.417 and 0.141 when the splitting ratios are 0 and 0.4, respectively. In actual operation, the pressure loss of the system is unavoidable. It is found that the efficiency reduction caused by the high pressure relative loss is 1.7% higher than the reduction caused by the low pressure relative loss. The exergy analysis method was also used to verify that the recompression cycle efficiency was lower than the simple reheat cycle efficiency. The losses in both are concentrated in the cooler and reactor, with the cooler and reactor losses of the recompression cycle together accounting for 79.6% of the total losses. Finally, the simple reheat cycle was taken as the optimal structure, and a space reactor system with a thermal power of 3 MW and an electrical power of 1 MW is successfully designed.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2024-05-26
摘要: The Very Large Area gamma-ray Space Telescope (VLAST) is a mission concept proposed to detect gamma#2;ray photons through both Compton scattering and electron-positron pair production mechanisms, thus enablingthe detection of photons with energies ranging from MeV to TeV. This project aims to conduct a comprehensivesurvey of the gamma-ray sky from a low-Earth orbit using an anti-coincidence detector, a tracker detectorthat also serves as a low-energy calorimeter, and a high-energy imaging calorimeter. We developed a MonteCarlo simulation application of the detector using the GEANT4 toolkit to evaluate the instrument performance,including the effective area, angular resolution, and energy resolution, and explored specific optimizations ofthe detector configuration. Our simulation-based analysis indicates that the current design of the VLAST isphysically feasible, with an acceptance above 10 m2 sr which is four times larger than that of the Fermi-LAT,an energy resolution better than 2% at 10 GeV, and an angular resolution better than 0.2 ◦ at 10 GeV. TheVLAST project promises to make significant contributions to the field of gamma ray astronomy and enhanceour understanding of the cosmos.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2024-03-09
摘要: There is a U(4’) times U(4)-bundle on four-dimensional square root Lorentz manifold. Then a Pati-Salam model in curved space-time (Lagrangian) and a gravity theory (Lagrangian) are constructed on square root Lorentz manifold based on self-parallel transportation principle. An explicit formulation of Sheaf quantization on this square root Lorentz manifold is shown. Sheaf quantization is based on superposition principle and construct a linear Sheaf space in curved space-time. The transition amplitude in path integral quantization is given which is consistent with Sheaf quantization. All particles and fields in Standard Model (SM) of particle physics and Einstein gravity are found in square root metric and the connections of bundle. The interactions between particles/fields are described by Lagrangian explicitly. There are few new physics in this model. The gravity theory is Einstein-Cartan kind with torsion. There are new particles, right handed neutrinos, dark photon, Fiona, X^{ pm C} and Y^0,Y^1,Y^2,Y_*^1,Y_*^2.
分类: 数学 >> 数学(综合) 提交时间: 2024-03-01
摘要: In this paper, the main aim is to demonstrate the boundedness for commutators of fractional maximal function and sharp maximal function in the context of the p-adic version of Orlicz spaces, where the symbols of the commutators belong to the p-adic version of Lipschitz space, whereby some new characterizations for Λβ(Qnp) spaces are given.
分类: 数学 >> 数学(综合) 提交时间: 2024-03-01
摘要: In this article, the main aim is to introduce the grand variable Herz space over the p-adic fields and demonstrate the boundedness for fractional integral operator, fractional maximal operator in the context of the grand p-adic version of Herz-Morrey spaces with variable exponent, as well as the Lipschitz estimates for the commutators of fractional integral operator, fractional maximal operator, and sharp maximal function on the grand p-adic version of Herz-Morrey spaces with variable exponent.
分类: 医学、药学 >> 预防医学与公共卫生学 提交时间: 2023-10-30 合作期刊: 《中国全科医学》
摘要: 背景近年来,我国中学生的心理健康问题日益突出。目的 探索中学生心理健康相关研究的热点、前沿和趋势,为未来参与中学生心理健康相关研究的学者提供参考。方法 于2022-9-30,以WebofScience核心合集数据库、中国知网数据库核心集为数据来源,检索国内外2000-01-01至2022-09-30发表的中学生心理健康相关文献,应用CiteSpace6.1.R3对所纳入文献的发文量、国家、机构、作者、文献共被引以及关键词进行可视化分析。结果 共纳入相关文献1963篇,其中英文文献653篇、中文文献1310篇,发现2000-2022年中学生心理健康文献数量呈上升趋势。中学生心理健康研究的热点领域与前沿主要集中在自杀意念、手机网络成瘾、学业成绩、心理弹性、心理干预以及当前新型冠状病毒肺炎疫情方面。未来研究趋势可能集中在传统欺凌、网络欺凌与中学生心理健康的关系、中学生健康风险行为与心理健康状况的关系等研究上。结论 研究者可参考可视化分析所示的研究热点及趋势,重点关注中学生欺凌和健康风险行为与心理健康的关系。
分类: 图书馆学、情报学 >> 图书馆学 提交时间: 2023-10-08 合作期刊: 《知识管理论坛》
摘要: [ 目的 / 意义 ] 随着互联网的普及,互联网治理的研究越来越受到关注,而互联网世界中显现出 的各种问题也受到广泛的关注,因此对现有理论成果进行梳理,对于理论和实践具有重大意义。[ 方法 / 过 程 ] 本文使用 CiteSpace 软件对 CNKI 数据库 2002-2014 年间有关互联网治理领域的中文文献进行可视化文 献计量分析,剖析了作者与研究机构、研究主题及热点议题、研究主题变迁的现状,并且基于研究主题评 述了现有成果的特征。[ 结果 / 结论 ] 研究发现,互联网治理领域,同一机构内部的交流多,跨机构的合作 少,绝大多数学者的专业背景是传播学;网络安全、网络舆情是成果较为丰富的热点议题;研究主题变迁 大致可划分为 3 个阶段即以互联网的技术、资源、产业为重点的阶段、以内容治理为重点的阶段、研究主 题向宽泛内涵发展的阶段。
分类: 核科学技术 >> 粒子加速器 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: An electrostatic accelerating column was designed and fabricated by Lanzhou University for an intense D-T/D-D neutron generator. In order to achieve a neutron yield of 5.0�1012 n/s, a deuteron beam of 30 mA, accelerated to 400 kV, and transported in the electrostatic accelerating column smoothly are required. One particle-in-cell code BEAMPATH was used to simulate the beam transport, and the IONB1.0 code was used to simulate the intense beam envelopes. Emittance growths due to space charge effect and spherical aberration were analyzed. The simulation results show that the accelerating column can transport deuteron beam of 30 mA smoothly and the requirement for the neutron generator is satisfied.
分类: 核科学技术 >> 核探测技术与核电子学 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: A concept of space radiation-voltaic batteries (SRVBs) based on various space radiation environments, including the earth radiation belt ( ERB), solar proton event ( SPE), and galactic cosmic rays ( GCRs) is presented in this paper. The energy deposition, structural parameter optimization, and output performance of SRVBs are studied through the Monte Carlo toolkit Geant4 and theoretical formulas. Energy deposition in the three radiation environments monotonically decreases as the depth in both silicon film models and energy conversion units of the SRVBs increase. The recommended junction depths of SRVBs based on ERB, SPE, and GCR are 0.5, 3.0, and 0.5 m, respectively. In the proposed design scheme, the maximum output power density of SRVBs in ERB, SPE, and GCR are 2.02210-7, 1.11310-3, and 3.84410-17 Wcm-2, respectively. Calculation results suggest that SRVBs based on ERB and SPE are high-potential candidates for space power sources. The results could help raise awareness on the use of space radiation particle energy and facilitate research on SRVBs.
分类: 核科学技术 >> 核探测技术与核电子学 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: Based on the statistical characteristics of energy spectrum and the features of spectrum-shifting in spectrometry, the parameter adjustment method of Gaussian function space was applied in the simulation of spectrum-shifting. The transient characteristics of energy spectrum were described by the Gaussian function space, and then the Gaussian function space was transferred by parameter adjustment method. Furthermore, the spectrum-shifting in measurement of energy spectrum was simulated. The applied example shows that the parameters can be adjusted flexibly by this method to meet the various requirements in simulation of energy spectrum-shifting. This method was one parameterized simulation method with good performance for the practical application.