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Multi-objective optimization and evaluation of supercritical CO_(2) Brayton cycle for nuclear power generation

Nuclear Science and Techniques 2024年第2期35卷 183-209页

作者： Guo-Peng Yu Yong-feng Cheng Na Zhang Ping-jian Ming Sino-French Institute of Nuclear Engineering and Technology Sun Yat-Sen UniversityZhuhai 519082China School of Civil Engineering and Architecture East China Jiaotong UniversityNanchang 330013China

The supercritical CO_(2) Brayton cycle is considered a promising energy conversion system for Generation IV reactors for its simple layout,compact structure,and high cycle *** models of four Brayton cycle layouts are developed in this study for different reactors to reduce the cost and increase the thermohydraulic performance of nuclear power generation to promote the commercialization of nuclear *** analysis,multi-objective optimizations,and four decision-making methods are applied to obtain each Brayton scheme’s optimal thermohydraulic and economic *** show that for the same design thermal power scale of reactors,the higher the core’s exit temperature,the better the Brayton cycle’s thermo-economic *** the four-cycle layouts,the recompression cycle(RC)has the best overall performance,followed by the simple recuperation cycle(SR)and the intercooling cycle(IC),and the worst is the reheating cycle(RH).However,RH has the lowest total cost of investment(C_(tot))of$1619.85 million,and IC has the lowest levelized cost of energy(LCOE)of 0.012$/(kWh).The nuclear Brayton cycle system’s overall performance has been improved due to *** performance of the molten salt reactor combined with the intercooling cycle(MSR-IC)scheme has the greatest improvement,with the net output power(W_(net)),thermal efficiencyη_(t),and exergy efficiency(η_(e))improved by 8.58%,8.58%,and 11.21%,*** performance of the lead-cooled fast reactor combined with the simple recuperation cycle scheme was optimized to increase C_(tot) by 27.78%.In comparison,the internal rate of return(IRR)increased by only 7.8%,which is not friendly to investors with limited *** the nuclear Brayton cycle,the molten salt reactor combined with the recompression cycle scheme should receive priority,and the gas-cooled fast reactor combined with the reheating cycle scheme should be considered carefully.

关键词： Supercritical CO_(2)Brayton cycle Nuclear power generation Thermo-economic analysis Multi-objective optimization Decision-making methods

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Comprehensive tensile properties improved by deep cryogenic treatment prior to aging in friction-stir-welded 2198 Al–Li alloy

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Rare Metals 2024年第10期43卷 5403-5409页

作者： jian-Qiu Sun Yue ma Chong Gao Hong-Yun Luo School of materials Science and Engineering Beihang University Chinalco Research Institute of Science and Technology

In order to improve the comprehensive mechanical properties,deep cryogenic treatment （DCT）prior to aging was carried out on friction-stir-welded（FSW） 2198 Al-Li alloy;afterward,the microstructure and tensile properties were characterized by means of optical microscopy （OM）,transmission electron microscopy（TEM） and tensile *** results show that FSW 2198 alloy through DCT prior to aging （DAT） possesses superior tensile properties than conventional aging treatment （AT）The microstructural analysis reveals that DAT alloy exhibits a finer grain structure,since DCT might effectively alleviate the residual stress in FSW 2198 alloy and thus decrease the driving force for grain coarsening in subsequent aging ***,DCT generates dislocation multiplication,which provides more preferential nucleation sites for T1 （Al2CuLi） phase during subsequent aging treatment,resulting in high-density fine T1 phases and thin precipitate-free zone within DAT *** reasonable microstructure leads to DAT alloy possessing better strength-ductility combination compared to AT alloy.

关键词： Al–Li alloy Deep cryogenic treatment Friction stir welding Tensile properties

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Novel process for facile preparation of mesoporous silica-based materials with controllable pore structure from coal fly ash Author links open overlay panel

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Particuology 2024年第8期91卷 128-137页

作者： jian-ming Gao Zhen Li Shujia ma Yuanyuan Zhang Fangqin Cheng Institute of Resources and Environment Engineering State Environmental Protection Key Laboratory of Efficient Utilization Technology of Coal Waste ResourcesShanxi Collaborative Innovation Center of High Value-added Utilization of Coal-related WastesShanxi UniversityTaiyuan 030006China

Extraction of silica from fly ash to produce mesoporous silica materials is one of the most important utilization *** silica could not be synthesized on a large-scale by conventional sol-gel *** this paper,facile preparation of mesoporous silica with controllable pore structure from fly ash by the template-free process via two steps of mineral phase transformation and selective acid etching was *** influence of crystalline structure and acid etching degree on structure of as-synthesized mesoporous silica materials was revealed,as well as mechanism of crystalline structure transformation and pore structure *** results show that mullite and quartz could be transformed into acid-soluble kaliophilite when fly ash reacted with K_(2)CO_(3)at temperature of 800-1100℃.The hexagonal kaliophilite would be transformed into orthorhombic KAlSiO_(4)-O1 phase when the temperature is controlled at 1100℃.Mesoporous silica with specific surface area of 475.93 m^(2)/g and 642.57 m^(2)/g could be synthesized from activated fly ash with kaliophilite and KAlSiO_(4)-O1 phase crystalline *** controlling the degree of acid etching,mesoporous silica materials with different pore structures can be *** paper provides a cost-effective and large-scale process for the preparation of mesoporous silica materials with controllable pore structure from solid waste fly ash.

关键词： Fly ash Mesoporous silica Crystal transformation Acid etching Controllable pore structure

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Extrusion 3D printing of carbon nanotube-assembled carbon aerogel nanocomposites with high electrical conductivity

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Nano materials Science 2024年第3期6卷 312-319页

作者： Lukai Wang Jing Men Junzong feng Yonggang jiang Liangjun Li Yijie Hu jian feng Science and Technology on Advanced Ceramic Fibers and Composites Laboratory College of Aerospace Science and EngineeringNational University of Defense Technology109 De Ya RdChangshaHunan410073PR China

Carbon nanotubes(CNTs)with high aspect ratio and excellent electrical conduction offer huge functional improvements for current carbon ***,there remains a major challenge for achieving the on-demand shaping of carbon aerogels with tailored micro-nano structural textures and geometric ***,a facile extrusion 3D printing strategy has been proposed for fabricating CNT-assembled carbon(CNT/C)aerogel nanocomposites through the extrusion printing of pseudoplastic carbomer-based inks,in which the stable dispersion of CNT nanofibers has been achieved relying on the high viscosity of carbomer *** extrusion printing,the chemical solidification through polymerizing RF sols enables 3D-printed aerogel nanocomposites to display high shape fidelity in macroscopic *** from the micro-nano scale assembly of CNT nanofiber networks and carbon nanoparticle networks in composite phases,3D-printed CNT/C aerogels exhibit enhanced mechanical strength(fracture strength,0.79 MPa)and typical porous structure characteristics,including low density(0.220 g cm^(-3)),high surface area(298.4 m^(2)g^(-1)),and concentrated pore diameter distribution(~32.8nm).More importantly,CNT nanofibers provide an efficient electron transport pathway,imparting 3D-printed CNT/C aerogel composites with a high electrical conductivity of 1.49 S cm^(-1).Our work would offer feasible guidelines for the design and fabrication of shape-dominated functional materials by additive manufacturing.

关键词： Carbon aerogel Extrusion 3D printing Carbon nanotube Electrical conductivity Rheology

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Liquid-phase epitaxial layer by layer brushing fabrication of metalorganic frameworks films

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Nano Research 2024年第6期17卷 5698-5704页

作者： Li-Mei Chang Rui Zhai Zhi-Zhou ma jian-Dong Huang Zhi-Gang Gu jian Zhang College of Chemistry Fuzhou UniversityFuzhou 350108China State Key Laboratory of Structural Chemistry Fujian Institute of Research on the Structure of MatterChinese Academy of SciencesFuzhou 350002China University of Chinese Academy of Sciences Beijing 100049China

Development of metal-organic framework(MOF)films is of great importance to expand their ***,we report a facile and universal method of liquid-phase epitaxial(LPE)layer by layer(LBL)brushing approach for fabricating MOF films on various substrates in a high-throughput *** MOF films preparation method offers a great prospective to cost-effectively construct films with short preparation time and little reagent ***,this LBL brushing approach has been implemented successfully to assemble various MOF films,including HKUST-1,zeolitic imidazolate framework-8(ZIF-8),Cu(bdc),and Cu_(2)(L)_(2)P(L=bdc,ndc,and cam;P=dabco and bipy).Afterwards,the classic MOF HKUST-1 and ZIF-8 films were grown on sensor chip electrode and porous fiber support for good volatile organic compounds(VOCs)selective sensing and water purification *** study demonstrates that this LBL brushing preparation method can be employed to synthesize various MOF films with a variety of characteristics to realize their sensing and separation applications.

关键词： metal-organic framework porous materials layer by layer fabrication film

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Double DQN Method For Botnet Traffic Detection System

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Computers, materials & Continua 2024年第4期79卷 509-530页

作者： Yutao Hu Yuntao Zhao Yongxin feng Xiangyu ma School of Information Science and Engineering Shenyang Ligong UniversityShenyang110159China Graduate School Shenyang Ligong UniversityShenyang110159China

In the face of the increasingly severe Botnet problem on the Internet,how to effectively detect Botnet traffic in realtime has become a critical *** the existing deepQnetwork(DQN)algorithminDeep reinforcement learning can solve the problem of real-time updating,its prediction results are always higher than the actual *** Botnet traffic detection,although it performs well in the training set,the accuracy rate of predicting traffic is as high as%;however,in the test set,its accuracy has declined,and it is impossible to adjust its prediction strategy on time based on new data ***,in the new dataset,its accuracy has declined ***,this paper proposes a Botnet traffic detection system based on double-layer DQN(DDQN).Two Q-values are designed to adjust the model in policy and action,respectively,to achieve real-time model updates and improve the universality and robustness of the model under different data *** show that compared with the DQN model,when using DDQN,the Q-value is not too high,and the detectionmodel has improved the accuracy and precision of Botnet ***,when using Botnet data sets other than the test set,the accuracy and precision of theDDQNmodel are still higher than DQN.

关键词： DQN DDQN deep reinforcement learning botnet detection feature classification

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The NAC056 transcription factor confers freezing tolerance by positively regulating expression of CBFs and NIA1 in Arabidopsis

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Plant Communications 2024年第7期5卷 251-260页

作者： Peipei Xu Wei ma Huafeng feng Weiming Cai Laboratory of Photosynthesis and Environment CAS Center for Excellence in Molecular Plant SciencesShanghai Institute of Plant Physiology and EcologyChinese Academy of SciencesNo.300 Fenglin RoadShanghai 200032China State Key Laboratory of NBC Protection for Civilian Beijing 102205China Department of Food Science College of Hospitality ManagementShanghai Business SchoolShanghai 200235China These authors contributed equally to this article

Freezing stress can seriously affect plant growth and development,but the mechanisms of these effects and plant responses to freezing stress require further ***,we identified a NAM,ATAF1/2,and CUC2(NAC)-family transcription factor(TF),NAC056,that can promote freezing tolerance in ***056 mRNA levels are strongly induced by freezing stress in roots,and the nac056 mutant exhibits compromised freezing ***056 acts positively in response to freezing by directly promoting key C-repeat-binding factor(CBF)pathway ***,we found that CBF1 regulates nitrate assimilation by regulating the nitrate reductase gene NIA1 in plants;therefore,NAC056–CBF1–NIA1 form a regulatory module for the assimilation of nitrate and the growth of roots under freezing *** addition,35S::NAC056 transgenic plants show enhanced freezing tolerance,which is partially reversed in the cbfs triple ***,NAC056 confers freezing tolerance through the CBF pathway,mediating plant responses to balance growth and freezing stress tolerance.

关键词： CBFs freezing tolerance NAC transcription factor nitrate assimilation root growth

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Enhanced and asymmetric signatures of hybridization at climatic margins: Evidence from closely related dioecious fig species

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Plant Diversity 2024年第2期46卷 181-193页

作者： jian-feng Huang Clive T.Darwell Yan-Qiong Peng CAS Key Laboratory of Tropical Forest Ecology Xishuangbanna Tropical Botanical GardenChinese Academy of SciencesMengla 666303China National Center for Genetic Engineering and Biotechnology(BIOTEC) 113 Thailand Science ParkPhahonyothin RoadKhlong NuengKhlong LuangPathum Thani 12120Thailand

Hybridization plays a significant role in biological evolution. However, it is not clear whether ecological contingency differentially influences likelihood of hybridization, particularly at ecological margins where parental species may exhibit reduced fitnesses. Moreover, it is unknown whether future ecosystem change will increase the prevalence of hybridization. Ficus heterostyla and F. squamosa are closely related species co-distributed from southern Thailand to southwest China where hybridization, yielding viable seeds, has been documented. As a robust test of ecological factors driving hybridization, we investigated spatial hybridization signatures based on nuclear microsatellites from extensive population sampling across a widespread contact range. Both species showed high population differentiation and strong patterns of isolation by distance. Admixture estimates exposed asymmetric interspecific gene *** of hybridization increase significantly towards higher latitude zones, peaking at the northern climatic margins. Geographic variation in reproductive phenology combined with ecologically challenging marginal habitats may promote this phenomenon. Our work is a first systematic evaluation of such patterns in a comprehensive, latitudinally-based clinal context, and indicates that tendency to hybridize appears strongly influenced by environmental conditions. Moreover, that future climate change scenarios will likely alter and possibly augment cases of hybridization at ecosystem scales.

关键词： Hybridization Heterospecific visitation Fig Pollinator wasp Asymmetric gene flow

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A symmetric substructuring method for analyzing the natural frequencies of conical origami structures

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Theoretical & Applied Mechanics Letters 2024年第3期14卷 203-210页

作者： Chenhao Lu Yao Chen Weiying Fan jian feng Pooya Sareh Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education and National Prestress Engineering Research CenterSoutheast UniversityNanjing 211189China School of Engineering University of LiverpoolLiverpool L693BXUnited Kingdom Creative Design Engineering Lab(Cdel) School of EngineeringNewcastle UniversityNewcastle upon Tyne NE17RUUnited Kingdom Escuela Técnica Superior de Ingeniería y Diseño Industrial Universidad Politécnica de Madrid(UPM)Madrid 28012Spain

Conical origami structures are characterized by their substantial out-of-plane stiffness and *** investigations have commonly focused on the static characteristics of these lightweight ***,the efficient analysis of the natural vibrations of these structures is pivotal for designing conicalorigami structures with programmable stiffness and *** this paper,we propose a novel method to analyzethe natural vibrations of such structures by combining a symmetric substructuring method(SSM)and a gener-alized eigenvalue *** exploits the inherent symmetry of the structure to decompose it into a finiteset of repetitive *** doing so,we reduce the dimensions of matrices and improve computationalefficiency by adopting the stiffness and mass matrices of the substructures in the generalized eigenvalue *** element simulations of pin-jointed models are used to validate the computational results of the ***,the parametric analysis of the structures demonstrates the influences of the number of seg-ments along the circumference and the radius of the cone on the structural mass and natural frequencies of ***,we present a comparison between six-fold and four-fold conical origami structures anddiscuss the influence of various geometric parameters on their natural *** study provides a strategyfor efficiently analyzing the natural vibration of symmetric origami structures and has the potential to contributeto the efficient design and customization of origami metastructures with programmable stiffness.

关键词： Natural structural vibration Origami design Group theory Symmetric substructuring method(SSM) Generalized eigenvalue analysis

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Conductive edge-warping graphite mesas for robust structural superlubricity

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Science China(Technological Sciences) 2024年第7期67卷 2040-2049页

作者： feng WeiJia LIU Ying ma Ming PENG DeLi NIE JinHui State Key Laboratory of Tribology in Advanced Equipment&Department of Mechanical Engineering Tsinghua UniversityBeijing 100084China Center for Nano and Micro Mechanics Tsinghua UniversityBeijing 100084China Institute of Superlubricity Technology Research Institute of Tsinghua University in ShenzhenShenzhen 518057China

Structural superlubricity(SSL) refers to a state of ultralow friction and zero wear when two solid surfaces slide against each other. Recent investigations have identified amorphous carbon at the edge of the graphite mesa as the primary source of friction in such SSL systems. Here, the tensile stress of metal thin film is exploited to engineer vertically conductive edge-warping graphite mesas(EWGM). Through this approach, robust SSL performance is realized, demonstrated by sliding an 8 μm side length square EWGM on an atomically smooth Au substrate for 10000 cycles at a constant voltage of 1 m V. In this SSL system,differential friction coefficients lower than 1.5 × 10^(-4) are achieved, with static contact resistance between EWGM and Au substrate as low as 28Ω and sliding contact resistance as low as 32Ω. Moreover, the EWGM exhibits SSL behavior on polished Si wafer substrates. Furthermore, because of the no-edge contact with the substrate during sliding, friction is independent of the sliding speed of the EWGM. This study presents the first successful fabrication of conductive EWGM. Remarkably, in both EWGM-Au and EWGM-Si SSL systems, the measured frictions are more than one order of magnitude lower than those of ordinary self-retracting graphite mesas with no-edge warping, and no wear is observed during extended current-carrying ***, these findings establish a solid groundwork for the future realization of macroscale conductive SSL systems.

关键词： structural superlubricity graphite mesa contact resistance tensile stress edge warping

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