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CO_(2) Diffusivity in H_(2)O for Supercritical Conditions:A Molecular Dynamics Study

Journal of Thermal Science 2022年第5期31卷 1407-1415页

作者： chen longfei LIU Dong LI Qiang School of Energy and Power Engineering Nanjing University of Science and TechnologyNanjing210094China

Supercritical H_(2)O/CO_(2) mixtures(650 K–973 K and 25 MPa,not far away from the critical temperature and pressure of water)have recently been used as the working fluid for a novel power generation system with higher efficiency and zero pollutant emission compared to conventional coal-fired power plants.The knowledge of the diffusion of these mixtures is important for efficient design of the system process.However,both experimental and theoretical data are scarce for typical working conditions in the system.Here,we investigated both the self-diffusion and the mutual diffusion of the supercritical H_(2)O/CO_(2) mixtures using molecular dynamics(MD)simulations.Simulations show that the mixture diffusion coefficients for supercritical conditions are more than one order of magnitude larger than those in the sub-critical region.MD results reveal that H_(2)O molecules prefer to gather with themselves rather than with CO_(2) molecules in the near-critical region,while there is no featured molecular structure for higher temperatures in the supercritical region.Therefore,the self-diffusion of CO_(2) in H_(2)O in the infinite-dilution regime features Arrhenius temperature dependent behavior in the supercritical region excluding the near-critical-temperature segment.These molecular interaction mechanisms also provide insights into the mutual diffusion behavior of CO_(2) in H_(2)O,which is well described by the Darken equation in the supercritical region.Furthermore,engineering equations,namely the Speedy-Angell power-law equation and the Vignes equation,can reproduce MD simulated infinite-dilution self-diffusion coefficients and Maxwell-Stefan mutual diffusion coefficients,respectively,of the supercritical H_(2)O/CO_(2) mixtures.

关键词： supercritical fluid H_(2)O/CO_(2)mixture diffusion molecular dynamics

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Long-term thinning decreases the contribution of heterotrophic respiration to soil respiration in subalpine plantations

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Journal of Forestry Research 2024年第3期35卷 189-204页

作者： longfei chen Zhibin He Wenzhi Zhao Xi Zhu Qin Shen Mingdan Song Zhengpeng Li Junqia Kong Shuping Yang Yuan Gao Northwest Institute of Eco-Environment and Resources Chinese Academy of SciencesLanzhou 730000People's Republic of China State Forestry Administration Key Laboratory of Forest Resources and Environmental Management Beijing Forestry UniversityBeijing 100083People's Republic of China Academy of Agriculture and Forestry Sciences Qinghai UniversityXining 810000People's Republic of China College of Landscape Architecture Zhejiang A&F UniversityHangzhou 310000People's Republic of China

Interest in the dynamics of soil respiration(R_(S))in subalpine forest ecosystems is increasing due to their high soil carbon density and potential sensitivity to environmental changes.However,as a principal silvicultural practice,the long-term impacts of thinning on R_(S) and its heterotrophic and autotrophic respiration components(R_(h) and Ra,respectively)in subalpine plantations are poorly understood,espe-cially in winter.A 3-year field observation was carried out with consideration of winter CO_(2) efflux in middle-aged sub-alpine spruce plantations in northwestern China.A trench-ing method was used to explore the long-term impacts of thinning on R,Rn and Ra.Seventeen years after thinning,mean annual Rs,Rn and R_(a) increased,while the contribu-tion of R_(h) to R_(s) decreased with thinning intensity.Thinning significantly decreased winter R,because of the reduction in Rn but had no significant effect on Ra.The temperature sensitivity(Q_(10))of R_(h) and R_(a) also increased with thinning intensity,with lower Q_(10) values for R_(h)(2.1-2.6)than for Ra(2.4-2.8).The results revealed the explanatory variables and pathways related to Rn and R_(a) dynamics.Thinning increased soil moisture and nitrate nitrogen(NO_(3)^(-)-N),and the enhanced nitrogen and water availability promoted R_(h) and R_(a) by improving fine root biomass and microbial activity.Our results highlight the positive roles of NO_(3)^(-)-N in stimulating R_(s) components following long-term thinning.Therefore,applications of nitrogen fertilizer are not recommended while thinning subalpine spruce plantations from the perspective of reducing soil CO_(2) emissions.The increased Q_(10) values of R_(s) components indicate that a large increase in soil CO_(2) emissions would be expected following thinning because of more pronounced climate warming in alpineregions.

关键词： Heterotrophic respiration Autotrophic respiration Long-term thinning impacts Cold seasons Subalpine plantations Temperature sensitivity

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Theoretical investigations on heat transfer to H2O/CO2 mixtures in supercritical region

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Science China(Technological Sciences) 2020年第6期63卷 1018-1024页

作者： chen longfei LIU Dong ZHANG HanLin LI Qiang MIIT Key Laboratory of Thermal Control of Electronic Equipment School of Energy and Power EngineeringNanjing University of Science and TechnologyNanjing 210094China

The supercritical H2O/CO2 mixture is the working fluid to drive a turbine in a novel power generation system with coal gasified in supercritical water.This system is promising because of zero pollution emission in contrast to the conventional coal-fired power plant.Heat transfer coefficients of the supercritical H2O/CO2 mixtures are important to design heat transfer devices in this system,which is similar to the role of heat transfer to supercritical water in conventional systems.However,heat transfer to supercritical mixtures has received less attention.Here,we show that the supercritical mixtures with H2O being one of the components,have similar convection heat transfer behavior to supercritical pure fluids for temperatures and pressures above the critical point of H2O.This phenomenon was demonstrated from two aspects.Firstly,the forced convection heat transfer coefficients of supercritical mixtures were numerically calculated using the simulation model for supercritical pure fluids and using the thermophysical properties(density,heat capacity,thermal conductivity and viscosity)of supercritical mixtures as input.The calculated results agree well with experimental data in the supercritical region.Secondly,the calculated results also agree well with the correlations for supercritical pure fluids.The mechanisms were investigated by molecular dynamics simulations on the diffusion of supercritical mixtures.These results lay the foundation for predicting convection heat transfer coefficients of supercritical mixtures and for designing heat transfer devices with supercritical mixtures as heat transfer fluids.

关键词： supercritical fluid H2O/CO2 mixture forced convection molecular dynamics

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Thermal Analysis of a Volumetric Solar Receiver

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Journal of Thermal Science 2019年第6期28卷 1176-1185页

作者： chen longfei YANG Ming LI Jinping BAI Yakai LI Xiaoxia TANG Wenxue YANG Nancong WANG Zhifeng Lanzhou University of Technology Lanzhou 730050China Key Laboratory of Solar Thermal Energy and Photovoltaic Systems Chinese Academy of SciencesBeijing 100190China Institute of Electrical Engineering Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Beijing Engineering Research Center of Solar Thermal Power Beijing 100190China Beijing CSP International Cooperation Centre Beijing 100190China Joint Laboratory Institute of Electrical EngineeringChinese Academy of Sciences and Guangdong Five Star Solar Energy Co.Ltd.Beijing 100190China Guangdong 5 Star Solar Energy CO.LTD Dongguan 523051China

The volumetric receiver has received wide attention due to its high thermal efficiency. This paper studied a new type of a solid-liquid composite volumetric receiver. The heat transfer in a solid-liquid composite volumetric solar receiver was analyzed using a one-dimensional unsteady simulation model of the solid-liquid receiver. The model included absorption of the incident solar radiation by the glass window, the silicon carbide porous ceramic heat absorber panel and the water. The results were verified against experimental data for a volumetric receiver and the error did not exceed 10%. It can be used to predict the heat transfer in solid-liquid composite volumetric receivers.

关键词： solar receiver solid-liquid composite absorber silicon carbide porous ceramic volumetric solar collector

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Assessing artificial neural networks coupled with waveletanalysis for multi-layer soil moisture dynamics pr

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Research in Cold and Arid Regions 2016年第2期8卷 116-124页

作者： Yang Junjun He Zhibin Zhao Weijun Du Jun chen longfei Zhu Xi Linze Inland River Basin Research Station Chinese Ecosystem Research Network Cold and Arid Regions Environmental and Engineering Research Institute Key Laboratory of Eco-hydrology of Inland River Basin Chinese Academy of Sciences Gansu Lanzhou 730000 Academy of Water Resources Conservation Forests in Qilian Mountains of Gansu Province Gansu Zhangye 734000

Soil moisture simulation and prediction in semi-arid regions are important for agricultural production, soil conservation and climate change. However, considerable heterogeneity in the spatial distribution of soil moisture, and poor ability of distributed hydrological models to estimate it, severely impact the use of soil moisture models in research and practical applications. In this study, a newly-developed technique of coupled (WA-ANN) wavelet analysis (WA) and artificial neural network (ANN) was applied for a multi-layer soil moisture simulation in the Pailugou catchment of the Qilian Mountains, Gansu Province, China. Datasets included seven meteorological factors: air and land surface temperatures, relative humidity, global radiation, atmospheric pressure, wind speed, precipitation, and soil water content at 20, 40, 60, 80, 120 and 160 cm. To investigate the effectiveness of WA-ANN, ANN was applied by itself to conduct a comparison. Three main findings of this study were: (1) ANN and WA-ANN provided a statistically reliable and robust prediction of soil moisture in both the root zone and deepest soil layer studied (NSE >0.85, NSE means Nash-Sutcliffe Efficiency coefficient); (2) when input meteorological factors were transformed using maximum signal to noise ratio (SNR) and one-dimensional auto de-noising algorithm (heursure) in WA, the coupling technique improved the performance of ANN especially for soil moisture at 160 cm depth; (3) the results of multi-layer soil moisture prediction indicated that there may be different sources of water at different soil layers, and this can be used as an indicator of the maximum impact depth of meteorological factors on the soil water content at this study site. We conclude that our results show that appropriate simulation methodology can provide optimal simulation with a minimum distortion of the raw-time series; the new method used here is applicable to soil sciences and management applications.

关键词： artificial neural network de-noising wavelet analysis time series analysis soil moisture prediction

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基于血清代谢组学研究金水缓纤方治疗肺纤维化机制

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中华中医药杂志 2024年第2期39卷 743-749页

作者：吴静杜燕陈龙飞冀会鸽李建生河南中医药大学呼吸疾病中医药防治省部共建协同创新中心河南省中医药防治呼吸病重点实验室郑州450046 河南中医药大学中医药科学院郑州450046 河南中医药大学第一附属医院郑州450000

目的:采用代谢组学技术探讨金水缓纤方治疗肺纤维化(PF)大鼠的机制。方法:将32只SD大鼠分为对照组、模型组、金水缓纤方组和吡非尼酮组,每组8只。建立PF大鼠模型,金水缓纤方组和吡非尼酮组于造模后第29—41天分别采用相应药物进行治疗。... 详细信息

目的:采用代谢组学技术探讨金水缓纤方治疗肺纤维化(PF)大鼠的机制。方法:将32只SD大鼠分为对照组、模型组、金水缓纤方组和吡非尼酮组,每组8只。建立PF大鼠模型,金水缓纤方组和吡非尼酮组于造模后第29—41天分别采用相应药物进行治疗。Masson染色观察大鼠肺组织病理变化,免疫组化法测定肺组织中Ⅰ型胶原(Col-Ⅰ)、Ⅲ型胶原(Col-Ⅲ)的表达。基于超高效液相色谱联合四级杆-静电场轨道阱高分辨质谱(UPLC Q-Exactive MS)系统,对大鼠血清进行非靶向代谢组学分析,筛选差异代谢物,探讨PF大鼠代谢网络的变化及金水缓纤方的调控作用。结果:模型组大鼠肺组织纤维化评分和Col-Ⅰ、Col-Ⅲ表达较对照组显著升高(P<0.01),金水缓纤方组纤维化评分和Col-Ⅰ、Col-Ⅲ表达均较模型组显著降低(P<0.01,P<0.05)。模型组有8种代谢物较对照组发生显著变化(FDR<0.2),其中二十碳五烯酸、18-羟基二十碳五烯酸、溶血磷脂酰胆碱18∶1和溶血磷脂酰胆碱20∶3显著下调(P<0.01,P<0.05),1-磷酸鞘氨醇和哌啶羧酸显著上调(P<0.01);金水缓纤方组有5种代谢物(溶血磷脂酰胆碱18∶1、1-磷酸鞘氨醇和十五烷酸除外)较模型组有回调趋势,其中二十碳五烯酸和溶血磷脂酰胆碱20∶3差异有统计学意义(P<0.05)。结论:金水缓纤方对PF大鼠胶原沉积有明显改善作用,其作用机制可能与其调节脂肪酸代谢、磷脂代谢和赖氨酸代谢有关。

关键词：肺纤维化金水缓纤方代谢组学超高效液相色谱联合四级杆-静电场轨道阱高分辨质谱脂肪酸代谢磷脂代谢赖氨酸代谢机制

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三大件式转向架斜楔建模方法及其对车辆动力学性能仿真结果的影响

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铁道车辆 2024年第2期62卷 34-42页

作者：陈龙飞王勇缪昆李龙西南交通大学轨道交通运载系统全国重点实验室四川成都610031 包头北方创业有限责任公司内蒙古包头014030

斜楔是三大件式转向架的重要减振装置之一,其结构和工作原理较为复杂,因此在动力学仿真中难以被精确地模拟。文章在总结既有斜楔建模方法的基础上,提出了一种新的斜楔建模方法,不仅考虑了斜楔的6个自由度,而且建模过程简单,计算效率高... 详细信息

斜楔是三大件式转向架的重要减振装置之一,其结构和工作原理较为复杂,因此在动力学仿真中难以被精确地模拟。文章在总结既有斜楔建模方法的基础上,提出了一种新的斜楔建模方法,不仅考虑了斜楔的6个自由度,而且建模过程简单,计算效率高。为了探讨斜楔建模方法对车辆动力学仿真结果的影响,选取摩擦功和二系垂向振动衰减率作为考察指标,对5种斜楔模型的计算结果进行了比较,并依据建模原理分析了造成摩擦功仿真结果产生差异的原因。从车辆蛇行失稳临界速度、车辆运行平稳性指标等动力学性能指标来看,斜楔不同建模方法得出的仿真结果具有较好的一致性。

关键词：摩擦减振器斜楔三大件式转向架动力学仿真多体动力学

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Effect of carbon material and surfactant on ink property and resulting surface cracks of fuel-cell microporous layers

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Chinese Journal of Chemical Engineering 2024年第5期69卷 1-12页

作者： Zhekun chen Weitong Pan longfei Tang Xueli chen Fuchen Wang Engineering Research Center of Resource Utilization of Carbon-containing Waste with Carbon Neutrality Ministry of EducationEast China University of Science and TechnologyShanghai 200237China Key Laboratory of Pressure Systems and Safety Ministry of EducationEast China University of Science and TechnologyShanghai 200237China

Ensuring the consistency of electrode structure in proton-exchange-membrane fuel cells is highly desired yet challenging because of wide-existing and unguided cracks in the microporous layer(MPL). The first thing is to evaluate the homogeneity of MPL with cracks quantitatively. This paper proposes the homogeneity index of a full-scale MPL with an area of 50 cm~2, which is yet to be reported in the literature to our knowledge. Besides, the effects of the carbon material and surfactant on the ink and resulting MPL structure have been studied. The ink with a high network development degree produces an MPL with low crack density, but the ink with high PDI produces an MPL with low crack homogeneity. The polarity of the surfactant and the non-polarity of polytetrafluoroethylene(PTFE) are not mutually soluble,resulting in the heterogeneous PTFE distribution. The findings of this study provide guidelines for MPL fabrication.

关键词： Proton-exchange-membrane fuel cell Microporous layer Crack density Crack homogeneity Polytetrafluoroethylene distribution Surfactant

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iVenomDB: A manually curated database for insect venom proteins

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Insect Science 2023年第1期30卷 264-266页

作者： longfei chen Kun Lang Bo Zhang Jiamin Shi Xinhai Ye David W.Stanley Qi Fang Gongyin Ye State Key Laboratory of Rice Biology Ministry of Agricultural and Rural Affairs Key Laboratory of Molecular Biology of Crop Pathogens and Insect Pests&Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang ProvinceInstitute of Insect SciencesCollege of Agriculture and BiotechnologyZhejiang UniversityHangzhouChina College of Information Management Nanjing Agricultural UniversityNanjingChina Biological Control of Insects Research Laboratory USDA/Agricultural Research Service ColumbiaMOUSA

DearEditor,Venomous animals,such as snakes,insects(wasps,bees,ants,and some bugs),spiders,scorpions,and cone snails,use venom for predation and/or defense.Venom is mostly composed of proteinsand peptides.Because of their high potency and selectivity,venom components have been developed into valuable resources,such as research tools,bioinsecticides(Heep et al.,2019),and drug leads(Badawi,2021).The advent of high-throughput sequencing and mass spectrometry enabled exploration of venom components to new depths and at an unprecedented pace.To be useful to the scientific community,knowledge on these proteins must be stored in a retrievable manner,annotated,and curated.Currently,several databases are dedicated to venoms from a wide range of animals,such as Arachnoserver(Pineda et al.,2018),Conoserver(Kaas et al.,2012),and the Tox-Prot program within UniprotKB(Jungo et al.,2012).

关键词： mostly venom

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Reducing Social Media Attention Inequality in Disasters: The Role of Official Media During Rainstorm Disasters in China

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International Journal of Disaster Risk Science 2024年第3期15卷 388-403页

作者： longfei Zheng Lei chen Fenjie Long Jianing Liu Lei Li School of Geography Faculty of Geographical Science Beijing Normal University Hang Lung Center for Real Estate and Department of Construction Management Tsinghua University

Unequal social media attention can lead to potentially uneven distribution of disaster-relief funds, resulting in long-term inequality among regions after disasters. This study aimed to measure inequalities in social media attention to regions during disasters and explore the role of official media in reducing such inequality. This is performed by employing social media,official media, and official aggregated statistics regarding China's rainstorm disasters. Through a set of panel-data regressions and robustness tests, three main conclusions were drawn:(1) There were inequalities among regions regarding social media attention they received during rainstorm disasters. For disasters of the same magnitude, regions with low economic outcome per capita received less attention on social media.(2) Official media can reduce inequality in social media attention during disasters. Official media statements can encourage netizens to pay attention to disaster-stricken areas, and especially the overlooked underdeveloped areas.(3) Of all the measures taken by official media, timely, accurate, and open disclosure of disaster occurrences proved to be the most potent means of leveling the playing field in terms of social media attention;contrarily, promotional or booster-type messages proved futile in this regard. These findings revealed the vulnerabilities within social media landscapes that aff ect disaster relief response, shedding light on the role of official guidance in mitigating inequalities in social media attention during such crises. Our study advises social media stakeholders and policymakers on formulating more equitable crisis communication strategies to bridge the gap in social media attention and foster a more balanced and just relief process.

关键词： China, inequality of attention Official media Rainstorm disasters Situational crisis communication theory Social media

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