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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 ***,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 Rs,Rn and R_(a).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 *** significantly decreased winter R,because of the reduction in R_(n) but had no significant effect on *** 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 R_(n) and R_(a) *** 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 *** results highlight the positive roles of NO_(3)^(-)-N in stimulating R_(s) components following long-term ***,applications of nitrogen fertilizer are not recommended while thinning subalpine spruce plantations from the perspective of reducing soil CO_(2) *** 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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Efficient epoxidation of propylene over non-noble nickel-based catalyst promoted by alkali metals

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Science China Chemistry 2024年

作者： Wenqian Li Wanting Li Xinxin Cao longfei chen Yibo Qin Yanfeng Zhu Yanfei Zhang Gai Miao Lingzhao Kong Jiong Li Xinqing chen State Key Laboratory of Low Carbon Catalysis and Carbon Dioxide Utilization CAS Key Laboratory of Low-carbon Conversion Science and Engineering Shanghai Advanced Research Institute Chinese Academy of Sciences University of Chinese Academy of Sciences School of Environmental Science and Engineering Suzhou University of Science and Technology Shanghai Synchrotron Radiation Facility Zhangjiang National Lab Shanghai Advanced Research Institute Chinese Academy of Sciences

The application of non-noble metal catalysts in the catalytic direct gas-phase epoxidation of propylene with H2and O2to produce propylene oxide is valuable and *** introduction of alkali metal promoters is one of the effective methods to improve the catalytic activity of ***,a series of alkali metal （Li,Na,K,Rb,and Cs）-promoted Ni/TS-1 catalysts were prepared to deeply understand the effect of alkali metals on the structure-activity relationship for gas-phase epoxidation of *** them,the Na-Ni/TS-1 catalyst exhibits the highest catalytic activity (propylene conversion of 7.35%and POformation rate of 157.9 g h-1kg-1cat) and the best stability （long-term stability exceeding 140 h at 200°C）.X-ray absorption and photoelectron spectroscopy revealed that the electronic structure of Ni can be tuned by the addition of alkali metal ***3-TPD-MS,CO2-TPD-MS,and C3H6-TPD-MS results indicate that the acidity of the catalyst can also be adjusted by the introduction of alkali metal,whereas the Na-Ni/TS-1 catalyst exhibits the strongest C3H6adsorption ***,the suitable acid-base properties,unique electronic properties of Ni species,and the strongest propylene adsorption capacity resulted in improved propylene gas-phase epoxidation activity of Na-Ni/TS-1 *** study not only provides a new strategy for the practical application of nickel-based catalysts in the gas-phase epoxidation of propylene but also provides insights into the promoting effect of alkali metals.

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基于小波神经网络的嵌入式语音识别系统设计

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电声技术 2024年第7期48卷 25-27页

作者：陈龙飞上海师范大学上海201418

针对嵌入式语音识别中的资源受限问题,提出一种基于小波神经网络的轻量化识别方案。该方案利用小波变换提取语音信号的时频域特征,并结合小波神经网络的非线性拟合能力,构建了高效的语音识别模型。实证研究表明,该方案在TIMIT数据集上... 详细信息

针对嵌入式语音识别中的资源受限问题,提出一种基于小波神经网络的轻量化识别方案。该方案利用小波变换提取语音信号的时频域特征,并结合小波神经网络的非线性拟合能力,构建了高效的语音识别模型。实证研究表明,该方案在TIMIT数据集上取得了80.17%的帧识别准确率,在满足实时性约束的同时,显著提升了嵌入式语音识别系统的性能表现,为智能语音交互在资源受限场景下的应用部署提供了新的思路。

关键词：嵌入式语音识别小波变换小波神经网络

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

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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 *** knowledge of the diffusion of these mixtures is important for efficient design of the system ***,both experimental and theoretical data are scarce for typical working conditions in the ***,we investigated both the self-diffusion and the mutual diffusion of the supercritical H_(2)O/CO_(2) mixtures using molecular dynamics(MD)*** show that the mixture diffusion coefficients for supercritical conditions are more than one order of magnitude larger than those in the sub-critical *** 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 ***,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 *** 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 ***,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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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 *** system is promising because of zero pollution emission in contrast to the conventional coal-fired power *** 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 ***,heat transfer to supercritical mixtures has received less ***,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 *** phenomenon was demonstrated from two ***,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 *** calculated results agree well with experimental data in the supercritical ***,the calculated results also agree well with the correlations for supercritical pure *** mechanisms were investigated by molecular dynamics simulations on the diffusion of supercritical *** 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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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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Analysis of a 1 kW organic Rankine cycle using a scroll expander for engine coolant and exhaust heat recovery

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Frontiers in Energy 2017年第4期11卷 527-534页

作者： Yiji LU Anthony Paul ROSKILLY Long JIANG longfei chen Xiaoli YU Sir Joseph Swan Centre for Energy Research Newcastle University Newcastle NE1 7RU UK Institute of Refrigeration and Cryogenics Shanghai Jiao TongUniversity Shanghai 200240 China School of Energy and Power Engineering Beihang University Beijing 100191 China Department of Energy Engineering Zhejiang University Hangzhou310027 China

The development of engine waste heat recov- ery technologies attracts ever increasing interests due to the rising strict policy requirements and environmental con- cerns. This paper presented the study of engine coolant and exhaust heat recovery using organic Rankine cycle （ORC）. Eight working fluids were selected to evaluate and compare the performance of the integrated waste heat recovery system. Rather than the conventional engine ORC system mainly focusing on the utilization of exhaust energy, this work proposed to fully use the engine coolant energy by changing the designed parameters of the ORC system. The case study selected a small engine as the heat source to drive the ORC system using a scroll expander for power production. The evaluation results suggest that under the engine rated condition, the solution to fully recover the engine coolant energy can achieve a higher power generation performance than that of the conven- tional engine ORC system. The results suggest that adding a recuperator to the ORC system can potentially improve the system performance when the working fluids are dry and the overall dumped heat demand of the system can be reduced by 12% under optimal conditions. When the ORC evaporating and condensing temperature are respectivelyset at 85℃ and 30℃, the integrated engine waste heat recovery system can improve the overall system efficiency by 9.3% with R600, R600a or n-Pentane as the working fluid.

关键词： organic Rankine cycle scroll expander cool-ant and exhaust recovery internal combustion engine

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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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生成式大语言模型在中文放射医学领域的应用研究

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计算机科学与探索 2024年第9期18卷 2337-2348页

作者：陈龙飞高鑫侯皓天叶初阳刘亚欧张美慧北京理工大学计算机学院北京100081 北京理工大学集成电路与电子学院北京100081 首都医科大学附属北京天坛医院放射科北京100070

在中文放射医学领域中,影像学报告是临床决策的重要依据。因此,利用自然语言处理(NLP)技术来理解和学习影像学报告的文本内容,并以此辅助完成放射科临床工作,已成为该领域的重要研究方向。然而,在使用传统方法处理基于中文影像学报告的... 详细信息

在中文放射医学领域中,影像学报告是临床决策的重要依据。因此,利用自然语言处理(NLP)技术来理解和学习影像学报告的文本内容,并以此辅助完成放射科临床工作,已成为该领域的重要研究方向。然而,在使用传统方法处理基于中文影像学报告的自然语言分类与生成任务时,仍然面临训练语料匮乏且涉及隐私、模型泛化能力较差等限制导致的综合性能不足的情况。针对上述问题,提出了一种基于本地高效微调大语言模型的中文放射医学领域自然语言任务解决方案。通过收集并构建大规模高质量中文影像学报告自然语言任务数据集,采用LoRA高效微调方法对开源大语言模型Baichuan2进行有监督微调训练,提出了能够同时解决四种中文放射医学领域临床任务的“龙影大模型”。提出了一套中文放射医学领域自然语言分类与生成任务评价体系。在来自两家中心的三个医学影像种类的报告数据集上进行了多组实验,并与几种典型现有方法进行了对比,结果显示所提方法在分类性能、文本总结与扩充能力和模型泛化性上表现更好。

关键词：大语言模型影像学报告文本分类文本生成高效微调策略

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Influence of geometry on the thermal performance of water pit seasonal heat storages for solar district heating

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Building Simulation 2021年第3期14卷 579-599页

作者： Yakai Bai Ming Yang Jianhua Fan Xiaoxia Li longfei chen Guofeng Yuan Zhifeng Wang Key Laboratory of Solar Thermal Energy and Photovoltaic Systems Chinese Academy of SciencesBeijing 700190China Institute of Electrical Engineering Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Department of Civil Engineering Technical University of DenmarkBrovej 1182800 Kgs.LyngbyDenmark Joint Laboratory Institute of Electrical EngineeringChinese Academy of Sciences and Guangdong Five Star Solar Energy Co.Ltd.Beijing 100190China Lanzhou University of Technology Gansu 730050China

The aim of the study is to investigate the influence of geometry on the thermal capacity and stratifications of a water pit heat storage for solar district heating.A TRNSYS component model for a truncated cone water pit was developed based on the coordinate transformation method and validated by experimental results from the water pit heat storage in Huangdicheng in *** thermal performance of 26 water pits with different heights and side wall slopes was calculated for 10 consecutive *** takes four to six years for the water pit to reach steady-state *** operation data from the tenth year was selected to evaluate the thermal performance of each *** results show that because of the thermal insulation on top of the water pit,the height to diameter ratio of a water pit with minimum annual heat loss was always smaller than *** annual storage efficiency of a water pit increases with side wall slope due to the reduced side wall *** is an almost linear increase in the thermal stratification number of a water pit with *** an increase in the height,thermal stratification in water pits with a steeper slope increased more gradually than water pits with a lower *** findings in this paper are relevant for the design optimization of water pits as seasonal thermal energy storages.

关键词： water pit seasonal heat storage truncated cone storage capacity thermal stratification coordinate transformation

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