The dynamic load characteristics of a proton exchange membrane fuel cell（PEMFC） with a dead-ended anode were studied. In a 70 h experiment, the effects of anode pressure, operating temperature, and relative humidity...The dynamic load characteristics of a proton exchange membrane fuel cell（PEMFC） with a dead-ended anode were studied. In a 70 h experiment, the effects of anode pressure, operating temperature, and relative humidity of the cathode on the performances of the fuel cell were investigated. The obtained results show that, with different relative humidity of the cathode at 65 ℃, dynamic loading has little effect on the performances of fuel cell and the electrochemically active surface area（ECSA）. However, the fuel cell operating under dynamic load is unstable when the relative humidity is 50%, and at 50 ℃ with 100% relative humidity, applying a dynamic load has a significant influence on the fuel cell performances. Scanning electron microscopy（SEM） showed that both the upstream and middle catalyst layers of the cell were unchanged, whereas the downstream cathode catalyst layer thinned as a response to dynamic load.展开更多
To reduce the complexity of large-scene high-resolution maps while using the dead-end information distributed in the unmanned vehicle driving environment,we propose a novel non-uniform quadtree map-building method inc...To reduce the complexity of large-scene high-resolution maps while using the dead-end information distributed in the unmanned vehicle driving environment,we propose a novel non-uniform quadtree map-building method including dead-end semantic information extraction.By utilizing quadtree data structures,submaps and a positive-order tree depth organization approach,our proposed map can adapt to the large-scale high-resolution requirement and expand more easily to larger environments.To verify the practicality of our proposed map,we have successfully implemented map matching and path planning in real environments.Additionally,we effectively extract the dead-end semantic information that widely distributes in the environment,which can help unmanned vehicles avoid collisions and improve the search efficiency of the planning procedure.We evaluate our method with KITTI datasets,CARLA Simulator,and our self-collected real-world datasets.The experimental results show that our proposed method significantly reduces the complexity of large-scale high-resolution maps,effectively extracts dead-end semantic information,and has good practicality in real environments.The implementation of our method is released here:https://github.com/biter0088/Non-uniform-quadtree-map.展开更多
This study investigates the impact of pore network characteristics on fluid flow through complex and heterogeneous porous media,providing insights into the factors affecting fluid propagation in such systems.Specifica...This study investigates the impact of pore network characteristics on fluid flow through complex and heterogeneous porous media,providing insights into the factors affecting fluid propagation in such systems.Specifically,high-resolution or micro X-ray computed tomography(CT)imaging techniques were utilized to examine outcrop stromatolite samples of the Lagoa Salgada,considered flow analogous to the Brazilian Pre-salt carbonate reservoirs.The petrophysical results comprised two distinct stromatolite depositional facies,the columnar and the fine-grained facies.By generating pore network model(PNM),the study quantified the relationship between key features of the porous system,including pore and throat radius,throat length,coordination number,shape factor,and pore volume.The study found that the less dense pore network of the columnar sample is typically characterized by larger pores and wider and longer throats but with a weaker connection of throats to pores.Both facies exhibited less variability in the radius of the pores and throats in comparison to throat length.Additionally,a series of core flooding experiments coupled with medical CT scanning was designed and conducted in the plug samples to assess flow propagation and saturation fields.The study revealed that the heterogeneity and presence of disconnected or dead-end pores significantly impacted the flow patterns and saturation.Two-phase flow patterns and oil saturation distribution reveal a preferential and heterogeneous displacement that mainly swept displaced fluid in some regions of plugs and bypassed it in others.The relation between saturation profiles,porosity profiles,and the number of fluid flow patterns for the samples was evident.Only for the columnar plug sample was the enhancement in recovery factor after shifting to lower salinity water injection(SB)observed.展开更多
为筛选诱杀树沙枣Elaeagnus angustifolia和抗性树种新疆杨Populus alba var.pyramidalis合理配植比例,实现生态自控光肩星天牛Anoplophora glabripennis灾害,以甘肃河西走廊和新疆部分地区的已有光肩星天牛长期危害,且包括沙枣树和新...为筛选诱杀树沙枣Elaeagnus angustifolia和抗性树种新疆杨Populus alba var.pyramidalis合理配植比例,实现生态自控光肩星天牛Anoplophora glabripennis灾害,以甘肃河西走廊和新疆部分地区的已有光肩星天牛长期危害,且包括沙枣树和新疆杨等多树种混交林为研究对象,调查、对比和分析沙枣自然调控天牛种群的能力,筛选和提炼出可实现“有虫不成灾”的诱杀树沙枣与抗性树种新疆杨的合理配植模式。结果显示:混交林内沙枣树上光肩星天牛的刻槽数远高于抗性树种新疆杨,表现出显著的引诱功能;沙枣树对光肩星天牛的卵和初孵幼虫的杀灭率在99.8%以上,具有很强的诱杀能力,发挥了对新疆杨的高效保护作用;在不同沙枣配比的林带中,沙枣树对光肩星天牛种群的调控能力有较大差别,防护林带中沙枣树与新疆杨行间或株间配植比例约为2∶8,园林绿化林中沙枣树与新疆杨以块状或带状配植比例约为3∶7时,可达到“有虫不成灾”,实现光肩星天牛灾害的生态自控。在防护林建设中,应充分发挥沙枣对光肩星天牛的诱杀功能,合理配植诱杀树种沙枣与抗性树种新疆杨,使光肩星天牛种群数量稳定在成灾水平之下,为服务“三北”防护林工程区林业有害生物防治提供借鉴。展开更多
基金Funded by the National Natural Science Foundation of China(Nos.51476119 and 51576147)the Natural Science Foundation of Hubei Province(No.2016CFA041)the Fundamental Research Funds for the Central Universities(No.2017 IVA 031)
文摘The dynamic load characteristics of a proton exchange membrane fuel cell（PEMFC） with a dead-ended anode were studied. In a 70 h experiment, the effects of anode pressure, operating temperature, and relative humidity of the cathode on the performances of the fuel cell were investigated. The obtained results show that, with different relative humidity of the cathode at 65 ℃, dynamic loading has little effect on the performances of fuel cell and the electrochemically active surface area（ECSA）. However, the fuel cell operating under dynamic load is unstable when the relative humidity is 50%, and at 50 ℃ with 100% relative humidity, applying a dynamic load has a significant influence on the fuel cell performances. Scanning electron microscopy（SEM） showed that both the upstream and middle catalyst layers of the cell were unchanged, whereas the downstream cathode catalyst layer thinned as a response to dynamic load.
文摘To reduce the complexity of large-scene high-resolution maps while using the dead-end information distributed in the unmanned vehicle driving environment,we propose a novel non-uniform quadtree map-building method including dead-end semantic information extraction.By utilizing quadtree data structures,submaps and a positive-order tree depth organization approach,our proposed map can adapt to the large-scale high-resolution requirement and expand more easily to larger environments.To verify the practicality of our proposed map,we have successfully implemented map matching and path planning in real environments.Additionally,we effectively extract the dead-end semantic information that widely distributes in the environment,which can help unmanned vehicles avoid collisions and improve the search efficiency of the planning procedure.We evaluate our method with KITTI datasets,CARLA Simulator,and our self-collected real-world datasets.The experimental results show that our proposed method significantly reduces the complexity of large-scale high-resolution maps,effectively extracts dead-end semantic information,and has good practicality in real environments.The implementation of our method is released here:https://github.com/biter0088/Non-uniform-quadtree-map.
基金the support of EPIC—Energy Production Innovation Center,hosted by the University of Campinas(UNICAMP)sponsored by FAPESP—Sao Paulo Research Foundation(2017/15736—3 process)+2 种基金the support and funding from Equinor Brazil and the support of ANP(Brazil's National Oil,Natural Gas and Biofuels Agency)through the R&D levy regulationthe Center of Energy and Petroleum Studies(CEPETRO)the School of Mechanical Engineering(FEM)。
文摘This study investigates the impact of pore network characteristics on fluid flow through complex and heterogeneous porous media,providing insights into the factors affecting fluid propagation in such systems.Specifically,high-resolution or micro X-ray computed tomography(CT)imaging techniques were utilized to examine outcrop stromatolite samples of the Lagoa Salgada,considered flow analogous to the Brazilian Pre-salt carbonate reservoirs.The petrophysical results comprised two distinct stromatolite depositional facies,the columnar and the fine-grained facies.By generating pore network model(PNM),the study quantified the relationship between key features of the porous system,including pore and throat radius,throat length,coordination number,shape factor,and pore volume.The study found that the less dense pore network of the columnar sample is typically characterized by larger pores and wider and longer throats but with a weaker connection of throats to pores.Both facies exhibited less variability in the radius of the pores and throats in comparison to throat length.Additionally,a series of core flooding experiments coupled with medical CT scanning was designed and conducted in the plug samples to assess flow propagation and saturation fields.The study revealed that the heterogeneity and presence of disconnected or dead-end pores significantly impacted the flow patterns and saturation.Two-phase flow patterns and oil saturation distribution reveal a preferential and heterogeneous displacement that mainly swept displaced fluid in some regions of plugs and bypassed it in others.The relation between saturation profiles,porosity profiles,and the number of fluid flow patterns for the samples was evident.Only for the columnar plug sample was the enhancement in recovery factor after shifting to lower salinity water injection(SB)observed.
文摘为筛选诱杀树沙枣Elaeagnus angustifolia和抗性树种新疆杨Populus alba var.pyramidalis合理配植比例,实现生态自控光肩星天牛Anoplophora glabripennis灾害,以甘肃河西走廊和新疆部分地区的已有光肩星天牛长期危害,且包括沙枣树和新疆杨等多树种混交林为研究对象,调查、对比和分析沙枣自然调控天牛种群的能力,筛选和提炼出可实现“有虫不成灾”的诱杀树沙枣与抗性树种新疆杨的合理配植模式。结果显示:混交林内沙枣树上光肩星天牛的刻槽数远高于抗性树种新疆杨,表现出显著的引诱功能;沙枣树对光肩星天牛的卵和初孵幼虫的杀灭率在99.8%以上,具有很强的诱杀能力,发挥了对新疆杨的高效保护作用;在不同沙枣配比的林带中,沙枣树对光肩星天牛种群的调控能力有较大差别,防护林带中沙枣树与新疆杨行间或株间配植比例约为2∶8,园林绿化林中沙枣树与新疆杨以块状或带状配植比例约为3∶7时,可达到“有虫不成灾”,实现光肩星天牛灾害的生态自控。在防护林建设中,应充分发挥沙枣对光肩星天牛的诱杀功能,合理配植诱杀树种沙枣与抗性树种新疆杨,使光肩星天牛种群数量稳定在成灾水平之下,为服务“三北”防护林工程区林业有害生物防治提供借鉴。
