分类： 核科学技术 >> 辐射防护技术 分类： 物理学 >> 核物理学 提交时间： 2024-06-23
摘要： The impact of the radiation dose produced by 222Rn/220Rn and its progeny on human health has garneredincreasing interest in the nuclear research field. The establishment of robust, regulatory, and competent 220Rnchambers is crucial for accurately measuring radioactivity levels. However, studying the uniformity of the 220Rnprogeny through experimental methods is challenging, because measuring the concentration of 220Rn and itsprogeny in multiple spatial locations simultaneously and in real time using experimental methods is difficult.Therefore, achieving precise control of the concentration of 220Rn and its progeny as well as the reliable samplingof the progeny pose significant challenges. To solve this problem, this study uses computational fluid dynamicsto obtain the flow-field data of the 220Rn chamber under different wind speeds and progeny-replenishment rates.Qualitative analysis of the concentration distribution of the progeny and quantitative analysis of the progenyconcentration and uniformity of the progeny concentration are conducted. The research findings indicatedthat the progeny-concentration level is primarily influenced by wind speed and the progeny-complement rate.Wind speed also plays a crucial role in determining progeny-concentration uniformity, whereas the progeny-complement rate has minimal impact on uniformity. To ensure the accuracy of 220Rn progeny-concentrationsampling, we propose a methodology for selecting an appropriate sampling area based on varying progenyconcentrations. This study holds immense importance for enhancing the regulation and measurement standardsof 220Rn and its progeny.
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2025-03-04
Su, Ning
Liu, Yuanyuan
Wang, Li
Zhang, Jianjie
Zhou, Zhi
Zhao, Xin
Ding, Wenwan
Zheng, Peng
Cheng, Jianping
摘要： Cosmic-ray muons are suitable for non-destructive imaging of large-scale objects. However, due to the low statistics of cosmic-ray muons and the complicated surroundings of transmission muography experiments, trans#2;mission muography often faces challenges such as noise and incomplete data, posing certain difficulties for 3D image reconstruction. This paper applies the SIRT-TV algorithm to muon tomography, conducting a 3D image reconstruction simulation study based on a QinShiHuang tomb phantom. The results indicate that compared to the conventional SIRT algorithm, the SIRT-TV algorithm can effectively suppress artifacts in the reconstructed image, allowing for a more accurate reconstruction of the underground palace. The geometric similarity of the walls reconstructed by SIRT-TV is nearly tripled compared to that of SIRT. This study also discusses the impact of TV-minimization algorithm parameters, and the measurement configurations and durations on the quality of the reconstructed image, providing a reference point for future experiments.
分类： 核科学技术 >> 核科学与技术 提交时间： 2023-11-17
摘要： Accurate measurements of the radon exhalation rate helps identify and evaluate radon risk regions in the environment. Among these measurement methods, the closed-loop method is frequently used. However, traditional experiments are insufficient or cannot analyze the radon migration and exhalation patterns at the gassolid interface in the accumulation chamber. The CFD-based technique was applied to predict the radon concentration distribution in a limited space, allowing radon accumulation and exhalation inside the chamber intuitively and visually. In this study, three radon exhalation rates were defined and two structural ventilation tubes were designed for the chamber. The consistency of the simulated results with the variation in the radon exhalation rate in a previous experiment or analytical solution was verified. The effects of the vent tube structure and flow rate on the radon uniformity in the chamber; permeability, insertion depth, and flow rate on the radon exhalation rate; and the effective diffusion coefficient on back diffusion were investigated. Based on the results, increasing the insertion depth from 1 to 5 cm decreased the effective decay constant by 19.55%, whereas the curve-fitted radon exhalation rate decreased (lower than the initial value) as the deviation from the initial value increased by approximately 7%. Increasing the effective diffusion coefficient from 2.7710-7 to 7.7710-6 m2 s-1 made the deviation expand from 2.14% to 15.96%. The conclusion is that an increased insertion depth helps reduce leakage in the chamber, subject to notable back-diffusion, and that the closed-loop method is reasonably used for porous media with a low effective diffusion coefficient in view of the back-diffusion effect. The CFD-based simulation is expected to provide guidance for the optimization of the radon exhalation rate measurement method and, thus, the accurate measurement of the radon exhalation rate.
分类： 物理学 >> 核物理学 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： In order to study the effect of tensor force, we plan to perform a (p,d) reaction with a 4001600 MeV proton beam on the RIBLL2 at Lanzhou. Based on the experimental conditions of RIBLL2, a Monte Carlo method is used to simulate (p,d) reaction process. The distributions of primary beam and scattered deuterons are given on the target and at the F1, F2, F3, and F4 positions. Considering the yield of the deuteron, to separate the produced deuteron from the background particles, the target thickness is optimized. To obtain a clear particle identification spectrum by time of flight (TOF) and energy loss (E), the distance between the two detectors, as well as the energy and timing resolution of detectors are simulated. As a result, the distance between F2 and F4 is fit for that of TOF. After taking into account the particle distribution at F4, both sizes of Multi-Wire Drift Chamber, namely MWDC2 and MWDC3, are selected to be 50 mm50 mm.
分类： 核科学技术 >> 裂变堆工程技术 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： Radiation shielding structure for C-ADS Inject-I was designed and optimized using FLUKA code. For this equipment was planned to be established in an existing tunnel hall and installed in limited space, several shielding hot spots are re-designed and analyzed respectively as they may cause radiation dose leakage and weakening of the total shielding effect. Besides, some new shielding structures are applied in the simulation process. All designed shielding structures are discussed in this paper and the results will meet the governmental criteria for radiation protection.
分类： 动力与电气工程 >> 工程热物理学 提交时间： 2017-03-31 合作期刊: 《热科学学报》
摘要： Theoretical and numerical analysis on the fluid flow and heat transfer inside a LNG evaporator is conducted in this work. Methane is used instead of LNG as the operating fluid. This is because; methane constitutes over 80% of natural gas. The analytical calculations are performed using simple mass and energy balance equations. The analytical calculations are made to assess the pressure and temperature variations in the steam tube. Multiphase numerical simulations are performed by solving the governing equations (basic flow equations of continuity, momentum and energy equations) in a portion of the evaporator domain consisting of a single steam pipe. The flow equations are solved along with equations of species transport. Multiphase modeling is incorporated using VOF method. Liquid methane is the primary phase. It vaporizes into the secondary phase gaseous methane. Steam is another secondary phase which flows through the heating coils. Turbulence is modeled by a two equation tur- bulence model. Both the theoretical and numerical predictions are seen to match well with each other. Further pa- rametric studies are planned based on the current research.
分类： 地球科学 >> 空间物理学 提交时间： 2017-03-10
摘要： Target brightness temperature maps can be used in geostationary interferometric microwave sounder (GIMS) system simulation. System simulation with accurate target brightness temperature maps can evaluate system performance in near real case and thus help adjust design parameters for the sensor before it is finally put into use. In this paper, method of simulating target brightness temperature using Weather Research and Forecasting Model and Radiative Transfer for TOVS (RTTOV) has been discussed. Target brightness temperature simulation results at oxygen absorption band and water-vapor absorption band have been presented. Some preliminary analyses of simulated brightness temperature for GIMS' observation have also been given.
分类： 物理学 >> 核物理学 提交时间： 2016-09-22
摘要： The design and performance analysis of DC electron gun for 5045 S-band klystron has been worked out using SLAC beam trajectory program (EGUN) and Computer Simulation Technology Particle Studio (CST-PS), Codes. Specifications of electron gun were focused on beam; current, perveance, size and emittance. Optimized beam; current, perveance, diameter and emittance were 414.00A, 2.00uP, 26.82 mm and 103.10 pi mm mrad, respectively. Furthermore, the optimized characteristic parameters of the gun were also calculated and compared with the simulated and experimental values which were in agreement. Accuracy of simulation was verified by comparison of emitted beam current which has error of zero percent.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
摘要： In many high energy experiments, the physics quantities are obtained by measuring the cross sections at a few energy points over an energy region. This was referred to as scan experiment. The optimal design of the scan experiment (how many energy points, what the energies are, and what is the luminosity at each energy point) is of great significance both for scientific research and from economical viewpoint. Two approaches, one has recourse to the sampling technique and the other resorts to the analytical proof, are adopted to figure out the optimized scan scheme for the relevant parameters. The final results indicate that for爊爌arameters scan experiment,爊爀nergy points are necessary and sufficient for optimal determination of these爊爌arameters; each optimal position can be acquired by single parameter scan (sampling method), or by analysis of auxiliary function (analytic method); the luminosity allocation among the points can be determined analytically with respect to the relative importance between parameters. By virtue of the second optimization theory established in this paper, it is feasible to accommodate the perfectly optimal scheme for any scan experiment.
分类： 物理学 >> 核物理学 提交时间： 2016-08-16
摘要： A new search signature for excited leptons is explored. Excited muons are sought in the channel pp→μμ∗→μμ jet jet, assuming both the production and decay occur via a contact interaction. The analysis is based on 20.3 fb−1 of pp collision data at a centre-of-mass energy of s√ = 8 TeV taken with the ATLAS detector at the Large Hadron Collider. No evidence of excited muons is found, and limits are set at the 95% confidence level on the cross section times branching ratio as a function of the excited-muon mass mμ∗. For mμ∗ between 1.3 TeV and 3.0 TeV, the upper limit on σB(μ∗→μqq¯) is between 0.6 and 1 fb. Limits on σB are converted to lower bounds on the compositeness scale Λ. In the limiting case Λ=mμ∗, excited muons with a mass below 2.8 TeV are excluded. With the same model assumptions, these limits at larger μ∗ masses improve upon previous limits from traditional searches based on the gauge-mediated decay μ∗→μγ.
分类： 物理学 >> 凝聚态:结构、力学和热性能 提交时间： 2016-06-14
摘要： Heat conduction through one-dimensional (1D) coupled rotator lattices is investigated in the presence of mass gradient. It is found that thermal current in the direction of mass increasing is not asymmetric with heat flux though mass decreasing system, which is called thermal rectification. Moreover, we find that the larger is the mass gradient, the more evident is the thermal rectification effect, which is consistent with FPU lattice with mass gradient. Based on the influences of the thermal rectification on shape parameters K and A of nearest-neighbor interactions, the average temperature of atomic chain and the system size, a optimum thermal rectifier is designed, which thermal rectification efficiency has reached 70. These investigations would contribute to controlling and manipulating thermal current.
分类： 动力与电气工程 >> 工程热物理学 提交时间： 2018-01-24 合作期刊: 《热科学学报》
摘要： The effects of the number of significant figures (NSF) in the interpolation polynomial coefficients (IPCs) of the weighted sum of gray gases model (WSGM) on results of numerical investigations and WSGM optimization were investigated. The investigation was conducted using numerical simulations of the processes inside a pulverized coal-fired furnace. The radiative properties of the gas phase were determined using the simple gray gas model (SG), two-term WSGM (W2), and three-term WSGM (W3). Ten sets of the IPCs with the same NSF were formed for every weighting coefficient in both W2 and W3. The average and maximal relative difference values of the flame temperatures, wall temperatures, and wall heat fluxes were determined. The investigation showed that the results of numerical investigations were affected by the NSF unless it exceeded certain value. The increase in the NSF did not necessarily lead to WSGM optimization. The combination of the NSF (CNSF) was the necessary requirement for WSGM optimization.
分类： 物理学 >> 核物理学 提交时间： 2025-03-06
摘要： The acceptance rate in Woodcock tracking algorithm is generalized to an arbitrary position-dependent variable q(x). A neural network is used to optimize q(x), and the FOM value is used as the loss function. This idea comes from physics informed neural network(PINN), where a neural network is used to represent the solution of differential equations. Here the neural network q(x) should solve the functional equations that optimize FOM. For a 1d transmission problem with Gaussian absorption cross section, we observe a significant improvement of the FOM value compared to the constant q case and the original Woodcock method. Generalizations of the neural network Woodcock(NNW) method to 3d voxel models are waiting to be explored.
分类： 物理学 >> 核物理学 提交时间： 2025-02-27
Chen, Mr. Ji-Xin
Jixin, Mr. Chen
Bai, Dr. Bo 白波
Cheng, Prof. Fa-Liang
Sun, Dr. Yuan
Cheng, Dr. Hui
Yuan, Dr. Bao
Dou, Dr. Meng-Jia
Wang, Dr. Chen-Yang
Lin, Mr. Quan
Lu, Mr. Zi-Cong
Deng, Mr. Lin-Jin
Hu, Dr. Hai-Tao
Tong, Dr. Xin
摘要： The use of automatic sample exchange technology can greatly improve the efficiency of neutron scattering experiments. China spallation neutron source (CSNS) has currently developed a cryogenic sample changer that design for exchange sample in the temperature range of 100K to 300K and finally achieve the minimum operating temperature is 80K. Samples are provided with a temperature ranging from 4.2K to 800K by CCR-02 through a closed cycle refrigerator (CCR) and a heater. This paper introduces the structure of the sample changer, which can accommodate up to 24 samples and the replacement time of each sample does not exceed 2 minutes. CSNS II phase will develop a second generation sample changer with an operating temperature range from 10K to 350K. For this requirement, we researched why the chain drive jammed in 80K and redesigned the chain and the support. By simulating in Ansys Workbench, we concluded that the new chain has more excellent performance in low-temperature and its stress is small and uniform. Because of the stress concentration, the S chain plate with a clamping angle of 20°is selected. The new support under Fluent can get the lowest temperature is 4.48K (316 stainless steel) and 4.23K (titanium). The new design will be tested after processing is completed.
分类： 物理学 >> 核物理学 提交时间： 2024-06-02
摘要： The Circular Electron Positron Collider (CEPC) is designed to precisely measure the properties of the Higgs boson, study electroweak interactions at the Z-boson peak, and search for new physics beyond the Standard Model. As a component of the 4th Conceptual CEPC detector, the drift chamber facilitates the measurement of charged particles. This study implemented a Geant4-based simulation and track reconstruction for the drift chamber. For the simulation, detector construction and response were implemented and added to the CEPC simulation chain. The development of track reconstruction involved track finding using the Combinatorial Kalman Filter method and track fitting using the tool of GenFit. Using the simulated data, the tracking performance was studied. The results showed that both the reconstruction resolution and tracking efficiency satisfied the requirements of the CEPC experiment.
分类： 能源科学 >> 能源（综合） 提交时间： 2024-04-02
X Zhang
Z Li
S. Mohammad Sajadi
Mohammed N. Ajour
Nidal H. Abu-Hamdeh
Elias M. Salilih
A Karimipour
Binh Nguyen Le
摘要： In this article, a numerical analysis is done on the temperature of 4 plate-shaped battery cells with phase change material (PCM) chambers around each one in a rectangular shape. The batteries are placed in a channel with air flow. The study is done transiently in a time of ten minutes. The batteries are of lithium ion type and the analysis is provided in two dimensions. The battery cells are arranged in the form of two single battery cells at the beginning, and end of the channel and two battery cells in the middle of the channel. These two middle batteries are placed in parallel. By changing the distance between the two middle batteries from two to three cm, this study is conducted to investigate the temperature of each of the four battery cells and changes in the amount of frozen PCM. Finally, the results showed that the temperature of the two batteries at the beginning and the end, increased continuously during the ten minutes of the study. At a distance of three cm from the middle batteries, the lowest temperature occurred on the first and last batteries, while at the same distance, the highest temperature occurred on the middle ones. At a distance of two cm from the middle batteries, the lowest amount of frozen PCM was observed, while at a distance of three cm from the middle batteries, the highest amount of frozen PCM was found on the first and last batteries.
分类： 机械工程 >> 机械设计 提交时间： 2018-03-14
摘要： Precision reducer is one of the key parts of an industrial robot, which generally incorporates cycloidal planetary drive. Engagement of the cycloidal wheel and the pins causes rolling friction between the wheel and the pins as well as sliding friction between the pins and the pin housing in the traditional cycloidal transmission of the reducer. In this paper, we present a new kind of design to make the pins and the pin housing a whole structure, thereby the cost of manufacturing and assembly can be significantly reduced. And in this new structure, we only need to consider sliding friction between the cycloidal wheel and the unibody of the pins and pin housing. The difference between the new structure and the conventional structure in the meshing properties was given. In addition, we used finite element method to analyze the friction and contact stress between the cycloidal wheel and the pins in the actual working condition, and compared it with the traditional structure. The simulation results proved the feasibility of the new structure and provided a theoretical basis for further design and manufacturing of this new kind of cycloidal planetary drive structure.
分类： 地球科学 >> 空间物理学 提交时间： 2017-03-10
摘要： Imaging period is an important consideration to geostationary interferometric microwave sounder (GIMS) when mapping fast changing target such as typhoon. GIMS simulation system with near real case observation target can evaluate system performance in different system configurations and thus help determine the optimal imaging period. In this paper, GIMS simulation system using MATLAB and near real case observation modeled by FNL/WRF/RTTOV method has been used to analyze the effect of imaging period on image quality. System simulation results for each frequency channel will be presented and analyses of imaging period's effect on image quality will also be given. �2016 IEEE.
分类： 地球科学 >> 空间物理学 提交时间： 2017-03-10
摘要： A 1-D interferometric system at 1.4GHz, 6.9GHz, 18.7 GHz and 23.8GHz combined with a scatterometer at 1.26GHz, called microwave imager combined active/passive (MICAP), has been proposed to retrieve sea surface salinity (SSS) and to reduce geophysical errors due to surface roughness and sea surface temperature (SST). The MICAP will be a candidate payload onboard the Ocean Salinity Satellite of China. The sensitivity of active/passive microwave observations to SSS, SST and wind is analyzed and the stability requirement of the instruments is estimated, with the objective of designing an optimized satellite instrument, dedicated to an "all-weather" estimate of the SSS with high accuracy from space.
分类： 物理学 >> 核物理学 提交时间： 2025-04-17
摘要： The L-shaped imaging devices are used to reconstruct the intensity distribution of the high-energy X-ray source. The physical model considering the penetration effect of X-ray on the imaging device is established, the transmission imaging matrix is constructed, and the algebraic solution method of source intensity reconstruction is presented. The X-ray source with Gaussian distribution is reconstructed. The reconstruction results show that the artifacts and discontinuities in the center of the reconstructed image using L-Edge device can be improved by L-Rolled Edge device, while L-Cylinder device can further improve the reconstruction quality.
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