Climate change significantly affects vegetation dynamics.Thus,understanding interactions between vegetation and climatic factors is essential for ecological management.This study used kernel Normalized Difference Vege...Climate change significantly affects vegetation dynamics.Thus,understanding interactions between vegetation and climatic factors is essential for ecological management.This study used kernel Normalized Difference Vegetation Index(kNDVI)and climatic data(temperature,precipitation,humidity,and vapor pressure deficit(VPD))of China from 2000 to 2022,integrating Geographic Convergent Cross Mapping(GCCM)causal modeling,Extreme Gradient Boosting-Shapley Additive Explanations(XGBoost-SHAP)nonlinear threshold identification,and Geographical Simulation and Optimization Systems-Future Land Use Simulation(GeoSOS-FLUS)spatial prediction modeling to investigate vegetation spatiotemporal characteristics,driving mechanisms,nonlinear thresholds,and future spatial patterns.Results indicated that from 2000 to 2022,China's kNDVI showed an overall increasing trend(annual average ranging from 0.29 to 0.33 with distinct spatial differentiation:52.77%of areas locating in agricultural and ecological restoration regions in the central-eastern plain)experienced vegetation improvement,whereas 2.68%of areas locating in the southeastern coastal urbanized regions and the Yangtze River Delta experience vegetation degradation.The coefficient of variation(CV)of kNDVI at 0.30–0.40(accounting for 10.61%)was significantly higher than that of NDVI(accounting for 1.80%).Climate-driven mechanisms exhibited notable library length(L)dependence.At short-term scales(L<50),vegetation-driven transpiration regulated local microclimate,with a causal strength from kNDVI to temperature of 0.04–0.15;at long-term scales(L>100),cumulative temperature effects dominated vegetation dynamics,with a causal strength from temperature to kNDVI of 0.33.Humidity and kNDVI formed bidirectional positive feedback at long-term scales(L=210,causal strength>0.70),whereas the long-term suppressive effect of VPD was particularly pronounced(causal strength=0.21)in arid areas.The optimal threshold intervals identified were temperature at–12.18℃–0.67℃,precipitation at 24.00–159.74 mm,humidity of lower than 22.00%,and VPD of<0.07,0.17–0.24,and>0.30 kPa;notably,the lower precipitation threshold(24.00 mm)represented the minimum water requirements for vegetation recovery in arid areas.Future kNDVI spatial patterns are projected to continue the trend of"southeastern optimization and northwestern delay"from 2025 to 2040:the area proportion of high kNDVI value(>0.50)will rise from 40.43%to 41.85%,concentrated in the Sichuan Basin and the southern hills;meanwhile,the proportion of low-value areas of kNDVI(0.00–0.10)in the arid northwestern areas will decline by only 1.25%,constrained by sustained temperature and VPD stress.This study provides a scientific basis for vegetation dynamic regulation and sustainable development under climate change.展开更多
To optimize industrial Fischer-Tropsch （IT） synthesis with the slurry bubble column reactor （SBCR） and iron- based catalyst, a comprehensive process model for IT synthesis that includes a detailed SBCR model, gas ...To optimize industrial Fischer-Tropsch （IT） synthesis with the slurry bubble column reactor （SBCR） and iron- based catalyst, a comprehensive process model for IT synthesis that includes a detailed SBCR model, gas liquid separation model, simplified CO2 removal model and tail gas cycle model was developed. An effective iteration algorithm was proposed to solve this process model, and the model was validated by industrial demonstration experiments data （SBCR with 5.8 m diameter and 30 m height）, with a maximum relative error 〈 10% for predicting the SBCR performances. Subsequently, the proposed model was adopted to optimize the industrial SBCR performances simultaneously considering process and reactor parameters variations. The results show that C5＋yield increases as catalyst loading increases within 10-70 ton and syngas H2/CO value decreases within 1.3-1.6, but it doesn＇t increase obviously when the catalyst loading exceeds 45 ton （about 15 wt% concentration）. Higher catalyst loading will result in higher difficulty for wax/catalyst separation and higher catalyst cost. There- fore, the catalyst loading （45 ton） is recommended for the industrial demonstration SBCR operation at syngas H2/ CO = 1.3, and the C5 ＋ yield is about 402 ton＂ per day, which has an about 16% increase than the industrial dem- onstration run result.展开更多
A new concentration transducer for the measurement of gas/solid two-phase flow in the profile of pipeline was studied. The design of grid electrode was employed, and hence the distribute of electric field in the space...A new concentration transducer for the measurement of gas/solid two-phase flow in the profile of pipeline was studied. The design of grid electrode was employed, and hence the distribute of electric field in the space was homogeneous effectively. The variance of measurement value for the influence of flow regime variations has greatly reduced, and the precision of measurement was improved. Meanwhile, optimization of axial property in the grid electrode increases the ability of tracing and measuring of the concentration signal in real-time.展开更多
Constructing impermeable curtains to contain contaminant in aquifers is a costly and complex process that can impact the structure integrity of aquifer systems.Are impermeable curtains necessary for a groundwater cont...Constructing impermeable curtains to contain contaminant in aquifers is a costly and complex process that can impact the structure integrity of aquifer systems.Are impermeable curtains necessary for a groundwater contaminant remediation project?This study evaluates the necessity of impermeable curtains for groundwater contaminant remediation projects.Specifically,it considers remediation efforts based on the Pump and Treat(PAT)technique under various hydrogeological conditions and contaminant properties,comparing the total remediation cost and effectiveness.To further investigate,a multi-objective simulation and optimization model,utilizing the Multi-Objective Fast Harmony Search(MOFHS)algorithm,was employed to identify optimal groundwater remediation system designs that without impermeable curtains.Both a two-dimensional(2-D)hypothetical example and a three-dimensional(3-D)field example were used to assess the necessity of constructing impermeable curtains.The 2-D hypothetical example demonstrated that the installation of impermeable curtain is justified only when the dispersivity(αL)of the contaminant reaches 100 meters.In most cases,particularly at sites with porosity(n)under 0.3,alternative,more cost-effective,and efficient remediation strategies may be available,making impermeable barriers unnecessary.The optimization results of the 3-D field example further corroborate the conclusions derived from the 2-D hypothetical example.These findings provide valuable guidance for more scientifically informed,reasonable,and cost-effective groundwater contaminant remediation projects.展开更多
The energy storage is an effective solution for the current imbalance between energy supply and demand.In particular,the cascaded storage method can enhance the heat exchange temperature difference and heat stor-age e...The energy storage is an effective solution for the current imbalance between energy supply and demand.In particular,the cascaded storage method can enhance the heat exchange temperature difference and heat stor-age efficiency.Previous research mainly focused on the combination of different phase change materials,while there was rare research on efficient cascaded conversion pathways for electrothermal direct conversion cou-pled thermal storage devices.This study investigated the influence of sensible and latent heat storage materials on the thermal performance,and identified the optimal volume ratios and materials types.When the volume share of Mg-Al:PW-EG=1:1,the heat storage performance was the optimal with a quantity/efficiency of heat stored as 7328.7 kJ/97.3%,leading to an increase of 458.5 kJ/6.6%than the sensible heat storage condition(Mg-Al:PW-EG=1:0)and 630.18 kJ/8.5%than the latent heat storage condition(Mg-Al:PW-EG=0:1).When the melting point and latent heat of phase change materials increased from 68.9∼79.1°C and 224.8 kJ/kg to 118.0°C and 344.9 kJ/kg respectively,the heat storage temperature rose by 162.7°C,quantity of heat stored rose by 7535.5 kJ.While materials with large subcooling were not recommended for short-term heat storage,as approximately 25.6%(3309.3 kJ)of stored heat and 22.4%(2505.2 kJ)of exergy were wasted when the subcooling degree was 70°C.The findings provided solutions to support the synergistic enhancement of heat storage/release performance of the composite energy storage heat sink.展开更多
At present, methanol to propylene(MTP) technology developed by Lurgi Company is adopted for commercial plants and refined methanol with the purity ≥99.85 wt% is required as the feed of MTP unit in Lurgi's technol...At present, methanol to propylene(MTP) technology developed by Lurgi Company is adopted for commercial plants and refined methanol with the purity ≥99.85 wt% is required as the feed of MTP unit in Lurgi's technology.Therefore, high energy cost for refined methanol production is one of the bottlenecks to improve the economy of MTP technology. Reducing the grade of feed refined methanol may be an effective method to save energy and reduce operation costs in MTP process. In this work, experiments and process simulation were carried out to investigate the influence and feasibility of degrading the methanol feed. Experiments were conducted to investigate the influence of crude methanol feed on conversion and selectivity of MTP reaction as well as the performance of ZSM-5 catalyst. The experimental results showed that degrading the methanol feed had no obvious influence on the conversion and selectivity of MTP reactions and the catalyst deactivation was caused by the carbon accumulation and metals deposition on the active sites. The process simulation results showed that the influence on the conversion and selectivity as well as the stream load of MTP process was negligible if 98 mol% methanol was used as feed. Finally, industrial experiments were conducted by adjusting the operation parameters to degrade of feed methanol of the commercial 500 kt·a^(-1) MTP unit of Ningmei Group in China. The results of industrial application illustrated that annually 180 kt fuel coal and 150 kt desalted water as well as 1770 MW·h^(-1) electricity would be saved when the water content increased from 0.01% to 0.4%. This work has identified the feasibility to improve MTP technology by degrading the methanol feed.展开更多
Computational Fluid Dynamics is used to assess the thermal(heat transfer)performances of an automobile engine considering different grille opening and closing degrees.For this purpose the entire vehicle is modelled an...Computational Fluid Dynamics is used to assess the thermal(heat transfer)performances of an automobile engine considering different grille opening and closing degrees.For this purpose the entire vehicle is modelled and three fundamental aspects are examined,namely,the open area of the air intake grille,the position of the upper and lower grilles and their shape.The results show that the opening area and position of the grille have some influence also on the aerodynamic characteristics of the automobile.With an increase in the opening angle of the grille,the CD(Drag Coefficient)value of the whole vehicle becomes higher.When the air intake grille of the car is fully open or closed,the CD value is 0.35434 or 0.31777,respectively,that is,the flow resistance in the engine compartment accounts for 10.32%of the CD value for the whole automobile.展开更多
Due to the shortage of fossil energy,biomass has a potential to be a very promising alternative source.Unfortunately,a large part of biomass resources worldwide causes serious environmental pollution,low value-added u...Due to the shortage of fossil energy,biomass has a potential to be a very promising alternative source.Unfortunately,a large part of biomass resources worldwide causes serious environmental pollution,low value-added utilization and energy waste due to unsustainable utilization of biomass.Simulation and optimization of the thermochemical utilization of biomass resources is a hot issue in the industry and academia,which can provide the relationship between the utilizations of biomass with sustainable objective and compositions of biomass,operational parameters,etc.This review focused on the theoretical research progress of sustainable utilization of biomass resources from three aspects:basic thermochemical data estimation,process simulation and system optimization of pyrolysis and gasification.And the application of artificial intelligence as a tool in the field of above three aspects was also introduced.Advantages and limitations of current methods,as well as future opportunities and challenges were also discussed.展开更多
Combinatorial method of simulation and optimization can combine the merits of both methods, provide effectively simulation support for transportation decision maldng.In tills paper, the simulation and optimization mod...Combinatorial method of simulation and optimization can combine the merits of both methods, provide effectively simulation support for transportation decision maldng.In tills paper, the simulation and optimization models for a transportation system of coal wharf are introduced, and their combination mechanism for constructing a simulation support system is presented.展开更多
基金funded by the Key Science and Technology Research Projects of Henan Province(252102320172).
文摘Climate change significantly affects vegetation dynamics.Thus,understanding interactions between vegetation and climatic factors is essential for ecological management.This study used kernel Normalized Difference Vegetation Index(kNDVI)and climatic data(temperature,precipitation,humidity,and vapor pressure deficit(VPD))of China from 2000 to 2022,integrating Geographic Convergent Cross Mapping(GCCM)causal modeling,Extreme Gradient Boosting-Shapley Additive Explanations(XGBoost-SHAP)nonlinear threshold identification,and Geographical Simulation and Optimization Systems-Future Land Use Simulation(GeoSOS-FLUS)spatial prediction modeling to investigate vegetation spatiotemporal characteristics,driving mechanisms,nonlinear thresholds,and future spatial patterns.Results indicated that from 2000 to 2022,China's kNDVI showed an overall increasing trend(annual average ranging from 0.29 to 0.33 with distinct spatial differentiation:52.77%of areas locating in agricultural and ecological restoration regions in the central-eastern plain)experienced vegetation improvement,whereas 2.68%of areas locating in the southeastern coastal urbanized regions and the Yangtze River Delta experience vegetation degradation.The coefficient of variation(CV)of kNDVI at 0.30–0.40(accounting for 10.61%)was significantly higher than that of NDVI(accounting for 1.80%).Climate-driven mechanisms exhibited notable library length(L)dependence.At short-term scales(L<50),vegetation-driven transpiration regulated local microclimate,with a causal strength from kNDVI to temperature of 0.04–0.15;at long-term scales(L>100),cumulative temperature effects dominated vegetation dynamics,with a causal strength from temperature to kNDVI of 0.33.Humidity and kNDVI formed bidirectional positive feedback at long-term scales(L=210,causal strength>0.70),whereas the long-term suppressive effect of VPD was particularly pronounced(causal strength=0.21)in arid areas.The optimal threshold intervals identified were temperature at–12.18℃–0.67℃,precipitation at 24.00–159.74 mm,humidity of lower than 22.00%,and VPD of<0.07,0.17–0.24,and>0.30 kPa;notably,the lower precipitation threshold(24.00 mm)represented the minimum water requirements for vegetation recovery in arid areas.Future kNDVI spatial patterns are projected to continue the trend of"southeastern optimization and northwestern delay"from 2025 to 2040:the area proportion of high kNDVI value(>0.50)will rise from 40.43%to 41.85%,concentrated in the Sichuan Basin and the southern hills;meanwhile,the proportion of low-value areas of kNDVI(0.00–0.10)in the arid northwestern areas will decline by only 1.25%,constrained by sustained temperature and VPD stress.This study provides a scientific basis for vegetation dynamic regulation and sustainable development under climate change.
基金Supported by the National Key R&D Program of China(2017YFB0602500)
文摘To optimize industrial Fischer-Tropsch （IT） synthesis with the slurry bubble column reactor （SBCR） and iron- based catalyst, a comprehensive process model for IT synthesis that includes a detailed SBCR model, gas liquid separation model, simplified CO2 removal model and tail gas cycle model was developed. An effective iteration algorithm was proposed to solve this process model, and the model was validated by industrial demonstration experiments data （SBCR with 5.8 m diameter and 30 m height）, with a maximum relative error 〈 10% for predicting the SBCR performances. Subsequently, the proposed model was adopted to optimize the industrial SBCR performances simultaneously considering process and reactor parameters variations. The results show that C5＋yield increases as catalyst loading increases within 10-70 ton and syngas H2/CO value decreases within 1.3-1.6, but it doesn＇t increase obviously when the catalyst loading exceeds 45 ton （about 15 wt% concentration）. Higher catalyst loading will result in higher difficulty for wax/catalyst separation and higher catalyst cost. There- fore, the catalyst loading （45 ton） is recommended for the industrial demonstration SBCR operation at syngas H2/ CO = 1.3, and the C5 ＋ yield is about 402 ton＂ per day, which has an about 16% increase than the industrial dem- onstration run result.
文摘A new concentration transducer for the measurement of gas/solid two-phase flow in the profile of pipeline was studied. The design of grid electrode was employed, and hence the distribute of electric field in the space was homogeneous effectively. The variance of measurement value for the influence of flow regime variations has greatly reduced, and the precision of measurement was improved. Meanwhile, optimization of axial property in the grid electrode increases the ability of tracing and measuring of the concentration signal in real-time.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFC3702200)the National Natural Science Foundation of China(Grant Nos.42372279 and U2267218)the Natural Science Foundation of Anhui Province(Grant No.JZ2022AKZR0451).
文摘Constructing impermeable curtains to contain contaminant in aquifers is a costly and complex process that can impact the structure integrity of aquifer systems.Are impermeable curtains necessary for a groundwater contaminant remediation project?This study evaluates the necessity of impermeable curtains for groundwater contaminant remediation projects.Specifically,it considers remediation efforts based on the Pump and Treat(PAT)technique under various hydrogeological conditions and contaminant properties,comparing the total remediation cost and effectiveness.To further investigate,a multi-objective simulation and optimization model,utilizing the Multi-Objective Fast Harmony Search(MOFHS)algorithm,was employed to identify optimal groundwater remediation system designs that without impermeable curtains.Both a two-dimensional(2-D)hypothetical example and a three-dimensional(3-D)field example were used to assess the necessity of constructing impermeable curtains.The 2-D hypothetical example demonstrated that the installation of impermeable curtain is justified only when the dispersivity(αL)of the contaminant reaches 100 meters.In most cases,particularly at sites with porosity(n)under 0.3,alternative,more cost-effective,and efficient remediation strategies may be available,making impermeable barriers unnecessary.The optimization results of the 3-D field example further corroborate the conclusions derived from the 2-D hypothetical example.These findings provide valuable guidance for more scientifically informed,reasonable,and cost-effective groundwater contaminant remediation projects.
基金supported by the Hebei Provincial Postdoctoral Sci-ence Foundation(Project No.B2022005004)the Science and Tech-nology Nova Plan of Hebei University of Technology(Project No.JBKYXX2207)+1 种基金the National Natural Science Foundation of China(Project No.51978231)the Hebei Province Funding Project for Returned Scholars,China(Project No.:C20190507).
文摘The energy storage is an effective solution for the current imbalance between energy supply and demand.In particular,the cascaded storage method can enhance the heat exchange temperature difference and heat stor-age efficiency.Previous research mainly focused on the combination of different phase change materials,while there was rare research on efficient cascaded conversion pathways for electrothermal direct conversion cou-pled thermal storage devices.This study investigated the influence of sensible and latent heat storage materials on the thermal performance,and identified the optimal volume ratios and materials types.When the volume share of Mg-Al:PW-EG=1:1,the heat storage performance was the optimal with a quantity/efficiency of heat stored as 7328.7 kJ/97.3%,leading to an increase of 458.5 kJ/6.6%than the sensible heat storage condition(Mg-Al:PW-EG=1:0)and 630.18 kJ/8.5%than the latent heat storage condition(Mg-Al:PW-EG=0:1).When the melting point and latent heat of phase change materials increased from 68.9∼79.1°C and 224.8 kJ/kg to 118.0°C and 344.9 kJ/kg respectively,the heat storage temperature rose by 162.7°C,quantity of heat stored rose by 7535.5 kJ.While materials with large subcooling were not recommended for short-term heat storage,as approximately 25.6%(3309.3 kJ)of stored heat and 22.4%(2505.2 kJ)of exergy were wasted when the subcooling degree was 70°C.The findings provided solutions to support the synergistic enhancement of heat storage/release performance of the composite energy storage heat sink.
基金Supported by the National Key R&D Program of China(2017YFB0601902)
文摘At present, methanol to propylene(MTP) technology developed by Lurgi Company is adopted for commercial plants and refined methanol with the purity ≥99.85 wt% is required as the feed of MTP unit in Lurgi's technology.Therefore, high energy cost for refined methanol production is one of the bottlenecks to improve the economy of MTP technology. Reducing the grade of feed refined methanol may be an effective method to save energy and reduce operation costs in MTP process. In this work, experiments and process simulation were carried out to investigate the influence and feasibility of degrading the methanol feed. Experiments were conducted to investigate the influence of crude methanol feed on conversion and selectivity of MTP reaction as well as the performance of ZSM-5 catalyst. The experimental results showed that degrading the methanol feed had no obvious influence on the conversion and selectivity of MTP reactions and the catalyst deactivation was caused by the carbon accumulation and metals deposition on the active sites. The process simulation results showed that the influence on the conversion and selectivity as well as the stream load of MTP process was negligible if 98 mol% methanol was used as feed. Finally, industrial experiments were conducted by adjusting the operation parameters to degrade of feed methanol of the commercial 500 kt·a^(-1) MTP unit of Ningmei Group in China. The results of industrial application illustrated that annually 180 kt fuel coal and 150 kt desalted water as well as 1770 MW·h^(-1) electricity would be saved when the water content increased from 0.01% to 0.4%. This work has identified the feasibility to improve MTP technology by degrading the methanol feed.
文摘Computational Fluid Dynamics is used to assess the thermal(heat transfer)performances of an automobile engine considering different grille opening and closing degrees.For this purpose the entire vehicle is modelled and three fundamental aspects are examined,namely,the open area of the air intake grille,the position of the upper and lower grilles and their shape.The results show that the opening area and position of the grille have some influence also on the aerodynamic characteristics of the automobile.With an increase in the opening angle of the grille,the CD(Drag Coefficient)value of the whole vehicle becomes higher.When the air intake grille of the car is fully open or closed,the CD value is 0.35434 or 0.31777,respectively,that is,the flow resistance in the engine compartment accounts for 10.32%of the CD value for the whole automobile.
基金support from the National Natural Science Foundation of China(Grant No.:21776046,21878337,21676291)the Fundamental Research Funds for the Central Universities(Grant No.2242020K40033).
文摘Due to the shortage of fossil energy,biomass has a potential to be a very promising alternative source.Unfortunately,a large part of biomass resources worldwide causes serious environmental pollution,low value-added utilization and energy waste due to unsustainable utilization of biomass.Simulation and optimization of the thermochemical utilization of biomass resources is a hot issue in the industry and academia,which can provide the relationship between the utilizations of biomass with sustainable objective and compositions of biomass,operational parameters,etc.This review focused on the theoretical research progress of sustainable utilization of biomass resources from three aspects:basic thermochemical data estimation,process simulation and system optimization of pyrolysis and gasification.And the application of artificial intelligence as a tool in the field of above three aspects was also introduced.Advantages and limitations of current methods,as well as future opportunities and challenges were also discussed.
文摘Combinatorial method of simulation and optimization can combine the merits of both methods, provide effectively simulation support for transportation decision maldng.In tills paper, the simulation and optimization models for a transportation system of coal wharf are introduced, and their combination mechanism for constructing a simulation support system is presented.
