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A multithreaded parallel upwind sweep algorithm for the S_(N) transport equations discretized with discontinuous finite elements

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Nuclear Science and Techniques 2023年第12期34卷 229-241页

作者： zhi‑Wei Zong Mao‑Song Cheng Ying‑Chi Yu zhi‑min dai Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China University of Chinese Academy of Sciences Beijing 100049China

The complex structure and strong heterogeneity of advanced nuclear reactor systems pose challenges for high-fidelity neutron-shielding calculations. Unstructured meshes exhibit strong geometric adaptability and can overcome the deficiencies of conventionally structured meshes in complex geometry modeling. A multithreaded parallel upwind sweep algorithm for S_(N) transport was proposed to achieve a more accurate geometric description and improve the computational efficiency. The spatial variables were discretized using the standard discontinuous Galerkin finite-element method. The angular flux transmission between neighboring meshes was handled using an upwind scheme. In addition, a combination of a mesh transport sweep and angular iterations was realized using a multithreaded parallel technique. The algorithm was implemented in the 2D/3D S_(N) transport code ThorSNIPE, and numerical evaluations were conducted using three typical benchmark problems:IAEA, Kobayashi-3i, and VENUS-3. These numerical results indicate that the multithreaded parallel upwind sweep algorithm can achieve high computational efficiency. ThorSNIPE, with a multithreaded parallel upwind sweep algorithm, has good reliability, stability, and high efficiency, making it suitable for complex shielding calculations.

关键词： Shielding calculation Discrete ordinates method Discontinuous Galerkin finite element method Unstructured meshes

Flow field effect of delayed neutron precursors in liquid-fueled molten salt reactors

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Nuclear Science and Techniques 2022年第8期33卷 16-32页

作者： Xian-Di Zuo Mao-Song Cheng Yu-Qing dai Kai-Cheng Yu zhi-min dai Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China University of Chinese Academy of Sciences Beijing 100049China

In molten salt reactors(MSRs),the liquid fuel salt circulates through the primary loop and a part of the delayed neutron precursors(DNPs)decays outside the reactor *** model and analyze the flow field effect of DNPs in channel-type liquid-fueled MSRs,a three-dimensional space-time dynamics code,named ThorCORE3D,that couples neutronics,core thermalhydraulics,and a molten salt loop system was developed and validated with the Molten Salt Reactor Experiment(MSRE)*** effects of external loop recirculation time,fuel flow rate,and core flow field distribution on the delayed neutron fraction loss of MSRE at steadystate were modeled and simulated using the ThorCORE3D ***,the flow field effect of the DNPs on the system responses of the MSRE in the reactivity insertion transient under different initial conditions was analyzed systematically for the channel-type liquid-fueled *** results indicate that the flow field condition has a significant effect on the steady-state delayed neutron fractions and will further affect the transient power and temperature responses of the reactor *** analysis results for the effect of the DNP flow field can provide important references for the design optimization and safety analysis of liquid-fueled MSRs.

关键词： Molten salt reactor Delayed neutron precursor Nodal expansion method Coupled neutronics and thermal-hydraulics

Pulse-shaping method for real-time neutron/gamma discrimination at low sampling rates

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Nuclear Science and Techniques 2023年第11期34卷 51-63页

作者： Jia‑Xin Li Hui‑Liang Hou Yue‑Feng Huang Mao‑Song Cheng zhi‑min dai Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China University of Chinese Academy of Sciences Beijing 100049China

The Na I:Tl scintillator is an innovative material for dual-gamma-ray and neutron detection with a low ^(6)Li *** achieve real-time n/γ discrimination,a zero-crossing time comparison algorithm based on trapezoidal pulse shaping was *** algorithm can operate efficiently at low sampling rates and was implemented on a single-probe portable digital n/γ discriminator based on a field-programmable gate *** discriminator and Na I:Tl,^(6)Li detector were tested in a neutron-gamma mixed field produced by an ^(241)Am-Be neutron source to evaluate the performance of the *** figure of merits was measured as 2.88 at a sampling rate of 50 MHz,indicating that the discriminator with its embedded algorithm has a promising n/γ discrimination *** discrimination at sampling rates of 40 and 25 MHz demonstrates that the capability of this method is not limited by low sampling rates.

关键词： FPGA NaI:Tl ^(6)Li Real time Neutron/gamma discrimination Pulse shaping

Oxidation resistant low-alloyed Ti alloys with good ductility

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Rare Metals 2024年第8期43卷 3921-3936页

作者： Meng Li Zhang-zhi Shi Jun-Yi Xu Fu-zhi dai Xiang-min Li Zi-Lin Li Lu-Ning Wang Beijing Advanced Innovation Center for Materials Genome Engineering State Key Laboratory for Advance Metals and MaterialsSchool of Materials Science and EngineeringUniversity of Science and Technology BeijingBeijingBeijing 100083China Institute of Materials Intelligent Technology Liaoning Academy of MaterialsShenyang 110004China

Oxidation resistance enhancement of pure Ti often comes at the cost of reduced ductility,which is frequently the problem through alloying with sole Al,Si,W,Mo and *** overcome the short coming of single element alloying,this paper proposes a multi-element low-alloying strategy to take advantage of synergistic effects and resolve the conflict between oxidation resistance and *** demonstrates that the addition of a small quantity of Ta(0.51wt%)can boost both oxidation resistance and ductility in comparison to pure ***,the combined addition of a small amount(0.54 wt%)of Ta,Nb and Si not only preserves good ductility of pure Ti,but also reduces mass gains to 14%-67%of pure Ti during 100 h oxidation at 650-850℃in *** indicates even better oxidation resistance than that obtained through the use of Ta,Nb,or Nb+Ta *** Ta+Nb+Si alloying creates an oxide layer that is less porous and more resistant to stratification and ***,a 3-μm N-rich layer can form in the Ti substrate beneath the oxide scale,in which phase transformation generates coherent Ti_(2)N with(0001)_(Ti)as the habit plane,with N atoms prefers to diffuse along■than along[0001]_(Ti).The completely transformed Ti_(2)N region or partially transformed Ti+Ti_(2)N region can effectively impede oxygen ***,the multielement low-alloying strategy is promising for enhancing both oxidation resistance and mechanical properties of metallic materials in the future.

关键词： Ti alloys Multi-element Co-alloying Oxidation resistance Mechanical properties

Topological Confinement in Reversibly Interlocked Polymer Networks

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Chinese Journal of Polymer Science 2024年第2期42卷 133-140,I0004页

作者： Wan-Ting dai Zhen-Hua Xie Yu-Bin Ke Yang You min-zhi Rong ming-Qiu Zhang Key Laboratory for Polymeric Composite and Functional Materials of ministry of Education GD HPPC LabIGCMESchool of ChemistrySun Yat-sen UniversityGuangzhou510275China Spallation Neutron Source Science Center China Spallation Neutron SourceDongguan523803China Institute of High Energy Physics Chinese Academy of SciencesBeijing100049China College of Materials and Metallurgy Guizhou UniversityGuiyang550025China

Recently, we reported a series of reversibly interlocked polymer networks(RILNs), whose mechanical robustness and functionalities improvement was believed to be derived from topological interlocking of two sub-networks, although the direct evidence for the deduction is still lacking. Herein, a specially-designed RILNs system, in which the inter-component hydrogen bonds can be shielded as needed, was prepared and used to study the micro-structures of RILNs, aiming to verify the existence of mechanical interlocking in RILNs. By changing the pH of the swelling solvent, the effect exerted by the inter-component non-covalent bonds was eliminated, so detailed information of the networks structure was exposed. The small angle X-ray scattering(SAXS) and small-angle neutron scattering(SANS) results indicated that swelling-induced structural evolution of the two sub-networks mutually affected each other, even when the inter-component hydrogen bonds were absent, proving the presence of topological interlocking. The findings may help to draw a more accurate physical image and reveal the detailed structureproperty relationship of RILNs.

关键词： Reversibly interlocked polymer networks Small angle X-ray scattering Small-angle neutron scattering Topological confinement

Feasibility of an innovative long-life molten chloride-cooled reactor

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Nuclear Science and Techniques 2020年第4期31卷 1-15页

作者： ming Lin Mao-Song Cheng zhi-min dai Shanghai Institute of Applied Physics Chinese Academy of SciencesJiading CampusShanghai 201800China University of Chinese Academy of Sciences Beijing 100049China

Molten salt-cooled reactor is one of the six GenIV reactors with promising characteristics including safety,reliability,proliferation resistance,physical protection,economics,and *** this paper,a small innovative molten chloride-cooled fast reactor(MCCFR)with 30-year core and a target 120-MWt thermal power was *** its feasible study,neutronics,thermal-hydraulics,and radiation damage analysis were *** key design properties including kinetics parameters,reactivity swing,reactivity feedback coefficients,maximum accumulated displacement per atom(DPA)of reactor pressure vessel(RPV)and fuel cladding,and maximum coolant,cladding,and fuel temperatures were *** results showed the MCCFR could operate without refueling for 30 years with overall negative reactivity feedback coefficients up the end of its *** its 30-year life,the excess reactivity was well managed by constantly pulling out the control *** maximum accumulated DPA on RPV and fuel cladding were 8.92 dpa and 197.03 dpa,respectively,which are both below the design ***,the maximum coolant,cladding and fuel center temperatures were all below the design limits during its entire *** to these results,the MCCFR core design with long life is feasible.

关键词： Molten salt-cooled reactor Neutronics Radiation damage Thermal-hydraulics

Prediction of suitable water content in granulation of sintering mixture based on Litster's model

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Journal of Iron and Steel Research(International) 2024年第3期31卷 552-560页

作者： Fang-lei dai Xiao-hui Fan Xiao-xian Huang Xu-ling Chen min Gan zhi-yun Ji Zeng-qing Sun School of minerals Processing and Bioengineering Central South UniversityChangsha 410083HunanChina

Suitable water content plays a decisive role in the granulation of sintering ***,a method was proposed to predict the suitable water content for effective granulation on the basis of Litster's granulation *** granulation effectiveness of a sintering mixture was predicted by the model,with the allowance error of±10%.The effects of the water absorption properties,particle size composition and content of adhesive particles on the suitable water content were *** results showed that the allowable error of prediction was within±0.5%compared to the experimentally determined suitable water *** an increase in adhesive powder content of mixtures with higher water absorption,the suitable water content increased to achieve similar granulation ***,as the amount of concentrates increased,the suitable water content first increased and then remained *** influence of the water absorption characteristics of the adhesive particles on the suitable water content was less than that of their particle size composition in the mixture.

关键词： Adhesive particle Sintering mixture Granulation effectiveness Suitable water content

Switching,explosion,and chaos of multi-wavelength soliton states in ultrafast fiber lasers

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Science China(Physics,Mechanics & Astronomy) 2024年第7期67卷 82-90页

作者： zhi-Zeng Si Yue-Yue Wang Chao-Qing dai College of Optical Mechanical and Electrical EngineeringZhejiang A&F UniversityLin’an 311300China

Because of the complexity and difficulty of realizing a multi-wavelength soliton state,reports on its internal dynamic characteristics are *** this study,the switching and periodic soliton explosion processes of the multi-wavelength soliton state in a negative dispersion passively mode-locked fiber laser are *** generation of the multi-wavelength soliton state undergoes the process of noise,oscillation,and stable mode-locking,and the splitting and annihilation of solitons with different group velocities directly impact the generation and disappearance of three *** and negative dispersion lead to different group velocities of *** presence and displacement of solitons with different group velocities cause soliton collisions,which lead to soliton explosions.A soliton experiences relative phase oscillation,chaos,and oscillation,as well as convergence and separation before and after an *** an increase in parameters related to pump power,single-soliton oscillation,multi-wavelength solitons,and chaos are found in experiments and simulations,proving the relevance and reliability between simulation and experimental *** work promotes the dynamical study of multi-soliton collisions in nonlinear science and the development of chaos theory in multi-comb lasers.

关键词： multi-wavelength fiber laser soliton explosion chaos state switching real-time dynamics

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Metagenomics reveals the microbial community and functional metabolism variation in the partial nitritation-anammox process:From collapse to recovery

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Journal of Environmental Sciences 2024年第1期135卷 210-221页

作者： Hong Wang Hui Gong Xiaohu dai min Yang State Key Laboratory of Pollution Control and Resource Reuse College of Environmental Science and EngineeringTongji UniversityShanghai 200092China BIOMATH Department of Data Analysis and Mathematical ModellingGhent UniversityGhent 9000Belgium

Mainstream partial nitritation-anammox(PNA)process easily suffers from performance instability and even reactor collapse in ***,it is of great significance to unveil the characteristic of performance recovery,understand the intrinsic mechanism and then propose operational *** this study,we combined long-term reactor operation,batch tests,and metagenomics to reveal the succession of microbial community and functional metabolism variation from system collapse to *** aeration control(0.10-0.25mg O_(2)/L)was critical for performance *** was also found that Candidatus Brocadia became the dominant flora and its abundance increased from 3.5%to 11.0%.Significant enhancements in carbon metabolism and phospholipid biosynthesis were observed during system recovery,and the genes abundance related to signal transduction was dramatically *** up-regulation of sdh and suc genes showed the processes of succinate dehydrogenation and succinyl-CoA synthesis might stimulate the production of amino acids and the synthesis of proteins,thereby possibly improving the activity and abundance of AnAOB,which was conducive to the performance ***,the increase in abundance of hzs and hdh genes suggested the enhancement of the anammox *** in the abundance of key genes involved in nitrogen metabolism indicated that nitrogen removal pathway was more diverse after system *** achievement of performance recovery was driven by anammox,nitrification and denitrification coupled with dissimilatory nitrate reduction to *** results provide deeper insights into the recovery mechanism of PNA system and also provide a potential regulation strategy for the stable operation of the mainstream PNA process.

关键词： Partial nitritation-anammox Metagenomics Microbial community Functional metabolism Recovery