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Land use effects on terrestrial carbon sources and sinks

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Science China(Life Sciences) 2002年第Z1期45卷 1-9页

作者： josep G. Canadell Global Carbon Project GCTE CSIRO Land and Water PO Box 1666 Australia

Current and past land use practices are critical in determining the distribution and size of global terrestrial carbon (C) sources and sinks. Althoughfossil fuel emissions dominate the anthropogenic perturbation of the global C cycle, land use still drives the largest portion of anthropogenic emissions in a number of tropical regions of Asia. The size of the emission flux owing to land use change is still the biggest uncertainty in the global C budget. The Intergovernmental Panel on Climate Change (IPCC) reported a flux term of 1.7 PgC@a-1 for 1990-1995 but more recent estimates suggest the magnitude of this source may be only of 0.96 PgC@a-1 for the 1990s. In addition, current and past land use practices are now thought to contribute to a large degree to the northern hemisphere terrestrial sink, and are the dominant driver for some regional sinks. However, mechanisms other than land use change need to be invoked in order to explain the inferred C sink in the tropics. Potential candidates are the carbon dioxide (CO2) fertilization and climate change; fertilization due to nitrogen (N) deposition is believed to be small or nil. Although the potential for managing C sinks is limited, improved land use management and new land uses such as reforestation and biomass fuel cropping, can further enhance current terrestrial C sinks. Best management practices in agriculture alone could sequester 0.4-0.8 PgC per year in soils if implemented globally. New methodologies to ensure verification and permanency of C sequestration need to be developed.

关键词： land use, terrestrial carbon, carbon emissions, sink mechanisms.

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基于相互作用关系的中国省际人口流动研究

地理研究 2018年第9期37卷 1848-1861页

作者：豆晓 ARELLANO Blanca ROCA josep 山东农业大学城市管理系泰安271018 加泰罗尼亚理工大学建筑学院西班牙巴塞罗那08028

基于2000年、2010年人口普查及2005年、2015年人口抽样调查数据,采用相互作用关系模型计算了中国"人口流动系统"和"单向相互作用关系值"。结果表明:(1)人口流动具有明显的凝聚性,东部地区对流动人口的吸引力依然具有绝对优势;(2)省际人... 详细信息

基于2000年、2010年人口普查及2005年、2015年人口抽样调查数据,采用相互作用关系模型计算了中国"人口流动系统"和"单向相互作用关系值"。结果表明:(1)人口流动具有明显的凝聚性,东部地区对流动人口的吸引力依然具有绝对优势;(2)省际人口流动呈"非对称双向迁移模式",人口回流的趋势已不容忽视;(3)长三角地区逐渐代替珠三角成为新的人口流动中心,人口流动开始北移;(4)中西部地区的人口流动分中心某种意义上已经出现,人口就近转移日渐凸显。将2010-2015年间省际人口流动新规律和特征与1995-2010年进行动态对比,对于制定未来人口和区域发展政策,继续缩小东西部地区之间的差距,最终实现区域协调发展具有重要意义。

关键词：省际人口流动人口流动系统相互作用关系中国

FPGA-based Digital Implementation of Flexible Power Control for Three-phase to Single-phase MMC-based Advanced Co-phase Traction Power Supply System

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Journal of Modern Power Systems and Clean Energy 2023年第6期11卷 2015-2027页

作者： Jiangpeng Yang Hongjian Lin Haotian Zhu Zeliang Shu Lan Ma Changsong Cai Pengcheng Zhang Li He Ruoyu Li Shasha Song josep M.Guerrero National Rail Transportation Electrification and Automation Engineering Technology Research Center Chengdu 611756China School of Electrical Engineering Southwest Jiaotong UniversityChengdu 611756China IEEE Department of Electrical Engineering City University of Hong KongHong KongChina School of Electrical Engineering and Automation Wuhan UniversityWuhan 430072China Department of Electrical Engineering Tsinghua UniversityBeijing 100084China Department of Energy Technology Aalborg UniversityAalborg 9220Denmark

A three-phase to single-phase modular multilevel converter based advanced co-phase traction power supply(MMC-ACTPS) system is an effective structure to address the concerns of phase splitting and poor power quality of the conventional electrified railway. Due to the large number of MMCACTPS system modules, I/O resources and computing speed have high requirements on processors. Moreover, the module capacitor balance is challenging because the sorting time is too long when the traditional sorting algorithm for voltage balance is used. To solve the above issues, a digital implementation scheme of flexible power control strategy for three-phase to single-phase MMC-ACTPS system based on field programmable gate array(FPGA), which has sufficient I/O resources, has been proposed. Due to the parallel execution characteristics of the FPGA, the execution time of the controller and the modulator can be greatly reduced compared with a digital signal processor(DSP) + FPGA or DSpace. In addition, an improved sorting algorithm is proposed to reduce the sorting time and the implementation steps are analyzed. Finally, simulation and experimental results are presented to demonstrate the effectiveness and correctness of the proposed control strategy.

关键词： Advanced co-phase power traction supply(ACTPS)system modular multilevel converter(MMC) digital implementation flexible power transmission circulating current mitigation

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分布式多变流器型微电网无互联线潮流控制

电网技术 2014年第9期38卷 2363-2370页

作者：唐芬吴丹周啸 Guerrero josep M. 贾利民北京交通大学国家能源主动配电网技术研发中心北京交通大学轨道交通安全与控制国家重点实验室北京市100044 丹麦奥尔堡大学能源技术系丹麦奥尔堡9220

当储能系统接口变流器的视在功率一定时,分布式多变流器型微电网系统内无功功率需求越大,储能系统对电源与负荷之间有功供需平衡的调节能力越弱。针对该问题,提出了一种无互联线潮流控制方法。该方法利用微电网系统内所有潜在的分布式... 详细信息

当储能系统接口变流器的视在功率一定时,分布式多变流器型微电网系统内无功功率需求越大,储能系统对电源与负荷之间有功供需平衡的调节能力越弱。针对该问题,提出了一种无互联线潮流控制方法。该方法利用微电网系统内所有潜在的分布式无功补偿源提供负荷所需无功,以期减小储能系统功率调节压力。并通过下垂控制与倒下垂相结合的方法来实现电压控制模式与电流控制模式变流器间功率的合理分配。同时,分析了影响功率分配精度的因素,提出基于虚拟阻抗与自适应空载电压补偿相结合的方法改善无功功率分配精度。最后通过实时硬件在环平台验证了所提控制策略的可行性。

关键词：微电网自治功率分配虚拟阻抗协调控制

Residential Energy Consumption and Associated Carbon Emission in Forest Rural Area in China: A Case Study in Weichang County

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Journal of Mountain Science 2014年第3期11卷 792-804页

作者： LUN Fei josep G. CANADELL XU Zhong-qi HE Lu YUAN Zheng ZHANG Dan LI Wen-hua LIU Mou-cheng Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences University of Chinese Academy of Sciences Global Carbon Project CSIRO Marine and Atmospheric Research GPO Box 3023 Canberra ACT 2601 Australia College of Forestry Agricultural University of Hebei

Rural energy consumption in China has increased dramatically in the last decades, and has become a significant contributor of carbon emissions. Yet there is limited data on energy consumption patterns and their evolution in forest rural areas of China. In order to bridge this gap, we report the findings of field surveys in forest villages in Weichang County as a case study of rural energy consumption in northern China. We found that the residential energy consumption per household is 3313 kgce yr^-1 （kilogram standard coal equivalent per year）, with energy content of 9.7×lO7 kJ yr^-1, including 1783 kgce yr^-1 from coal, 1386 kgce yr^-1 from fuel wood, 96 kgce yr^-1 from electricity, and 49 kgce yr^-1 from LPG. Per capita consumption is 909 kgce yr^-1 and its energy content is 2.7×lO7 kJ yr^-1. Due to a total energy utilization efficiency of 24.6%, all the consumed energy can only supply about 2.4×107 kJ yr^-1 of efficient energy content. Secondly, household energy consumption is partitioned into 2614 kgce yr^-1 for heating, 616 kgce yr^-1 for cooking, and 117 kgce yr^-1 for home appliances. Thirdly, the associated carbon emissions oer household are 2556 kzC yr^-1, includinz1022 kgC yr^-1 from unutilized fuel wood （90% of the total fuel wood）. The rest of emissions come from the use of electricity （212 kgC yr^-1, coal （13Ol kgC yr^-1 and LPG （21 kgC yr^-1. Fourthly, local climate, family size and household income have strong influences on rural residential energy consumption. Changes in storage and utilization practices of fuel can lead to the lO%-30% increase in the efficiency of fuel wood use, leading to reduced energy consumption by 924 kgce yr^-1 per household （27.9% reduction） and 9Ol kgC yr^-1 of carbon emissions （35-3% reduction）.

关键词： Energy consumption Carbon emission Rural areas Fuelwood Utilization efficiency

Interspecific interactions affect N and P uptake rather than N:P ratios of plant species:evidence from intercropping

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Journal of Plant Ecology 2022年第2期15卷 223-236页

作者： Wei-Ping Zhang Dario Fornara Guang-Cai Liu josep Peñuelas Jordi Sardans Jian-Hao Sun Li-Zhen Zhang Long Li Beijing Key Laboratory of Biodiversity and Organic Farming Key Laboratory of Plant and Soil InteractionsMinistry of EducationDepartment of Ecology and Ecological EngineeringCollege of Resource and Environmental ScienceChina Agricultural UniversityBeijing 100193China Sustainable Agri-Food Science Division Agri-Food&Biosciences InstituteBT95PX BelfastUK CSIC Global Ecology Unit CREAF-CSIC-UAB08913 BellaterraCataloniaSpain CREAF 08913 Cerdanyola del VallèsCataloniaSpain Institute of Soil Fertilizer and Water-Saving AgricultureGansu Academy of Agricultural SciencesLanzhou 730070China Gansu Agro-technology Extension Station Lanzhou 730020China

Quantifying stoichiometry of crop N and P acquisition(*** from farmland)under different agronomic practices is essential for understanding nutrient budgets and optimizing N and P fertilizer application in *** is not clear how plant N and P uptake and N:P stoichiometry vary between monoculture and intercropping throughout an entire growing season under different N fertilization and mulching ***,we addressed how plant interspecific competition for nutrients have affected the temporal dynamics of crop N and P uptake(and N:P ratios)in five cropping systems(wheat,maize and barley monocultures,and wheat/maize and barley/maize intercropping),under two N levels(0 and 225 kg N ha^(−1))and two maize mulching treatments(with and without).Wheat and barley had greater N and P competitive ability than maize,leading to an increase in N and P uptake of wheat and barley and a decrease in N and P uptake of maize during co-growth stages in intercropping.N:P ratios of three crop species decreased with plant ***-level N:P ratios were either not affected by intercropping or did not change consistently with N fertilization while film mulching decreased maize N:P ***-level N:P ratios of the two intercrops were different from those of the corresponding monoculture at ***(i)the proportion of N and P removal from intercropping differs from monocultures,and(ii)N and P uptake by crops is decoupled under N fertilization and mulching,these findings may have practical implications for the nutrient budget of intercropping systems.

关键词： ecological stoichiometry growth-rate hypothesis intercropping system interspecific competition nitrogen addition nutrient budget plastic film mulch

基于自律分散系统的直流微电网稳定控制器优化设计

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中国电机工程学报 2016年第2期36卷 360-367页

作者：王皓界韩民晓 josep M.Guerrero 栾文鹏华北电力大学电气与电子工程学院北京市昌平区102206 奥尔堡大学能源技术系中国电力科学研究院北京市海淀区100192

基于储能的直流微电网稳定控制器(stability controller,SC)在直流微电网中发挥重要作用,但是在孤网轻载条件下多台SC同时运行会引起较大的换流损耗。为了提高多SC并联运行时的全局效率,提出了基于自律分散系统的优化方案,各SC通过逻辑... 详细信息

基于储能的直流微电网稳定控制器(stability controller,SC)在直流微电网中发挥重要作用,但是在孤网轻载条件下多台SC同时运行会引起较大的换流损耗。为了提高多SC并联运行时的全局效率,提出了基于自律分散系统的优化方案,各SC通过逻辑运算迭代算法得到全局SC信息,再结合本地直流母排电压信息调节SC运行数量及其下垂曲线特性,在保证直流微电网并网、孤网条件下稳定运行的同时对各换流器输出电流进行实时调节,使运行的SC都工作在效率最高点附近,实现SC效率的全局优化。通过优化,各SC能够根据直流母排电压自适应调节其下垂特性,并且负载越轻,优化效果越明显。

关键词：直流微电网稳定控制器自律分散系统下垂控制效率优化逻辑运算迭代算法

Nitrogen addition delays the emergence of an aridity-induced threshold for plant biomass

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National Science Review 2023年第11期10卷 148-159页

作者： Hailing Li César Terrer Miguel Berdugo Fernando T.Maestre Zaichun Zhu josep Pe?uelas Kailiang Yu Lin Luo Jie-Yu Gong Jian-Sheng Ye State Key Laboratory of Herbage Improvement and Grassland Agro-Ecosystems College of EcologyLanzhou University Department of Civil and Environmental Engineering Massachusetts Institute of Technology Instituto Multidisciplinar para el Estudio del Medio“Ramón Margalef ”Universidad de Alicante Institut de Biologia Evolutiva(CSIC-UPF) Departamento de Ecología Universidad de Alicante School of Urban Planning and Design Peking University Shenzhen Graduate SchoolPeking University CSIC Global Ecology Unit CREAF-CSIC-UAB CREAF Cerdanyola del Vallès High Meadows Environmental Institute Princeton University

Crossing certain aridity thresholds in global drylands can lead to abrupt decays of ecosystem attributes such as plant productivity, potentially causing land degradation and desertification. It is largely unknown,however, whether these thresholds can be altered by other key global change drivers known to affect the water-use efficiency and productivity of vegetation, such as elevated CO2and nitrogen(N). Using >5000 empirical measurements of plant biomass, we showed that crossing an aridity(1–precipitation/potential evapotranspiration) threshold of ～0.50, which marks the transition from dry sub-humid to semi-arid climates, led to abrupt declines in aboveground biomass(AGB) and progressive increases in root:shoot ratios, thus importantly affecting carbon stocks and their distribution. N addition significantly increased AGB and delayed the emergence of its aridity threshold from 0.49 to 0.55(P < 0.05). By coupling remote sensing estimates of leaf area index with simulations from multiple models, we found that CO2enrichment did not alter the observed aridity threshold. By 2100, and under the RCP 8.5 scenario, we forecast a 0.3% net increase in the global land area exceeding the aridity threshold detected under a scenario that includes N deposition, in comparison to a 2.9% net increase if the N effect is not considered. Our study thus indicates that N addition could mitigate to a great extent the negative impact of increasing aridity on plant biomass in drylands. These findings are critical for improving forecasts of abrupt vegetation changes in response to ongoing global environmental change.

关键词： aboveground biomass root:shoot ratios elevated CO2 nitrogen fertilization ecosystem threshold

一种可实现微网系统快速平滑并网的主动同步控制策略

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电力系统自动化 2014年第8期38卷 15-22页

作者：唐芬 josep M.GUERRERO 周啸马添翼 Juan C.VASQUEZ 北京交通大学国家能源主动配电网技术研发中心北京市100044 丹麦奥尔堡大学能源技术系

为实现微网系统从孤岛运行模式到并网运行模式的平滑过渡,微网与主电网的同步是首要考虑的问题。提出了一种新型基于锁相环原理的主动同步控制策略,该方法通过主动调节微网母线电压的频率、相角和幅值跟踪主电网电压,从而减小并网时刻... 详细信息

为实现微网系统从孤岛运行模式到并网运行模式的平滑过渡,微网与主电网的同步是首要考虑的问题。提出了一种新型基于锁相环原理的主动同步控制策略,该方法通过主动调节微网母线电压的频率、相角和幅值跟踪主电网电压,从而减小并网时刻的电压偏差,达到孤岛模式向并网模式的平滑过渡。同时,采用电压矢量叉积作为鉴相器,微网频率和相角可同时快速有效地跟踪电网频率和相角。并且该方案不需传递相位等时域信号,仅需依赖于低带宽的通信,原理简单、易于实施。最后,实时硬件在环仿真与实验结果表明,该控制方案可实现微网快速平滑并网。

关键词：锁相环微网(微电网) 并网控制同步分层控制