The thermal stratification level of low sidewall air supply system in large space was defined. Depending on the experiment of low sidewall air supply in summer 2008,the thermal stratification level was studied by simu...The thermal stratification level of low sidewall air supply system in large space was defined. Depending on the experiment of low sidewall air supply in summer 2008,the thermal stratification level was studied by simulation. Based on the simulation of experiment condition,the air velocity and vertical temperature distribution in a large space were simulated at different air-outlet velocities,and then the thermal stratification level line was obtained. The simulation results well match with the experimental ones and the average relative error is 3.4%. The thermal stratification level is heightened by increasing the air-outlet velocity with low sidewall air supply mode. It is concluded that when air-outlet velocity is 0.29 m/s,which is the experimental case,a uniform thermal environment in the higher occupied zone and a stable stratification level are formed. When the air-outlet velocity is low,such as 0.05 m/s,the thermal stratification level is too low and the air velocity is too small to meet the human thermal comfort in the occupied zone. So,it would be reasonable that the air-outlet velocity may be designed as 0.31 m/s if the height of the occupied zone is 2 m.展开更多
Oxygen fuels have broad application prospects and great potential for realizing efficient and clean combustion,and hence this study applies diesel/n-butanol blends to explore the influence of split-injection strategy ...Oxygen fuels have broad application prospects and great potential for realizing efficient and clean combustion,and hence this study applies diesel/n-butanol blends to explore the influence of split-injection strategy on combustion and emission characteristics.Simultaneously,changing the way of exhaust gas recirculation(EGR)gas introduction forms uneven in-cylinder components distribution,and utilizing EGR stratification optimizes the combustion process and allows better emission results.The results show that the split-injection strategy can reduce the NO_(x)emissions and keep smoke opacity low compared with the single injection,but the rise in accumulation mode particles is noticeable.NO_(x)emissions show an upward trend as the injection interval expands,while soot emissions are significantly reduced.The increase in pre-injection proportion causes the apparent low-temperature heat release,and the two-stage heat release can be observed during the process of main combustion heat release.More pre-injection mass makes NO_(x)gradually increase,but smoke opacity reaches the lowest point at 15%pre-injection proportion.EGR stratification can optimize the emission results under the split injection strategy,especially the considerable suppression of accumulation mode particulate emissions.Above all,fuel stratification coupled with EGR stratification is beneficial for further realizing the in-cylinder purification of pollutants.展开更多
Unmanned aerial vehicles(UAVs) may play an important role in data collection and offloading in vast areas deploying wireless sensor networks, and the UAV’s action strategy has a vital influence on achieving applicabi...Unmanned aerial vehicles(UAVs) may play an important role in data collection and offloading in vast areas deploying wireless sensor networks, and the UAV’s action strategy has a vital influence on achieving applicability and computational complexity. Dynamic programming(DP) has a good application in the path planning of UAV, but there are problems in the applicability of special terrain environment and the complexity of the algorithm.Based on the analysis of DP, this paper proposes a hierarchical directional DP(DDP) algorithm based on direction determination and hierarchical model. We compare our methods with Q-learning and DP algorithm by experiments, and the results show that our method can improve the terrain applicability, meanwhile greatly reduce the computational complexity.展开更多
The hybrid system with radiant cooling and dedicated outdoor air not only possesses high energy efficiency, but also creates a healthy and comfortable indoor environment. Indoor air quality will be improved by the ded...The hybrid system with radiant cooling and dedicated outdoor air not only possesses high energy efficiency, but also creates a healthy and comfortable indoor environment. Indoor air quality will be improved by the dedicated outdoor air system(DOAS) and indoor thermal comfort can be enhanced by the radiant cooling system(RCS). The optimal air-supply mode of the hybrid system and the corresponding design approach were investigated. A full-scale experimental chamber with various air outlets and the ceiling radiant cooling panels(CRCP) was designed and established. The performances of different air-supply modes along with CRCPs were analyzed by multi-index evaluations. Preliminary investigations were also conducted on the humidity stratification and the control effect of different airflow modes to prevent condensation on CRCP. The overhead supply air is recommended as the best combination mode for the hybrid system after comprehensive comparison of the experiment results. The optimal proportion of CRCP accounting for the total cooling capacities in accord with specific cooling loads is found, which may provide valuable reference for the design and operation of the hybrid system.展开更多
Australian cotton production predominantly occurs on Vertisols.The average lint yield of cotton grown in Australia is 2260–2700 kg·hm^(−2),which is 2.5 to 3 times the world average.This high productivity per uni...Australian cotton production predominantly occurs on Vertisols.The average lint yield of cotton grown in Australia is 2260–2700 kg·hm^(−2),which is 2.5 to 3 times the world average.This high productivity per unit of land area requires efficient use of resources such as water and nutrients.However,high yields accelerate the export of nutrients such as phosphorus(P)in seed,depleting the soil reserves of P more than in other countries with lower cotton yields.Recent surveys of cotton industry indicate that P application rates should match seed P export(30~40 kg·hm−2),but historical depletion within subsoil is still evident and is continuing.Depletion of soil P is typically more pronounced in the subsoil than in the topsoil(0~20 cm)where P fertiliser is applied,as cotton roots rely on these layers as important sources of plant available water and available P.This mismatch between zones of P uptake and resupply may increase stratification of available P in the soil profile.Recent studies showed that cotton responded poorly to banded applications of fertiliser P,while dispersal of fertiliser throughout the plant beds was more successful.Researchers have also observed sporadic cotton responses to applied P fertiliser in soils where available P concentrations were well above the previously determined critical concentrations indicative of fertiliser P responses in Australia.To sustain highyielding cotton production in Australia,a greater understanding of cotton root acquisition of applied P,as well as a re-examination of critical soil P concentrations for each production region are required.展开更多
Two-factor analysis of variance and redundancy analysis were used to analyze the characte-ristics of soil organic carbon total nitrogen storage in garden land,forestland,grassland,farmland,and bare land in the Dachunh...Two-factor analysis of variance and redundancy analysis were used to analyze the characte-ristics of soil organic carbon total nitrogen storage in garden land,forestland,grassland,farmland,and bare land in the Dachunhe watershed of Jinning District,Kunming City,Yunnan Province,China.The effects of the soil organic carbon,total nitrogen stratification ratio,soil physical and chemical factors on the storage characteristics of organic carbon and total nitrogen of different land-use types were analyzed.The results show that the rates of carbon and nitrogen stratification in soil from 0-20 cm and 40-60 cm of the same land-use types differed are statistically significant(P<0.05).The organic carbon and total nitrogen stratification ratio SR1 of garden land soil are 38.5%and 25.3%,respectively,which are higher than SR^(2).The soil organic carbon and total nitrogen stratification ratio SR^(2) of different land-use types are greater than SR1.There are statistically significant differences in the SR^(2) soil organic carbon and total nitrogen stratification ratios(P<0.05).Soil organic carbon and total nitrogen storage of diffe-rent land-use types gradually decrease with increasing soil depth,with the maximum soil organic carbon and total nitrogen storage in the 0-20 cm soil layer.Soil organic carbon and total nitrogen sto-rage at the same soil depth are significantly different(P<0.05).Soil organic carbon and total nitrogen storage in the garden land are greater than those in the other land-use types.Soil organic carbon and total nitrogen storage in 0-20 cm garden land are 4.96 and 3.19 times than those in bare land,respectively;soil organic carbon and total nitrogen storage are explained by 93.66%and 1.53%in redundancy analysis RDA1 and RDA2,respectively.All physicochemical factors except Available Phosphorus and pH are statistically significance with carbon and nitrogen storage(P<0.05).Soil cationic exchange capacity,Available Phosphorus,C/N ratio,and Moisture Content are positively correlated with organic carbon and total nitrogen storage.In contrast,soil Bulk Density is negatively correlated with organic carbon storage and total nitrogen storage.Available Phosphorus,C/N ratio,and Moisture Content are the main factors promoting soil organic carbon and total nitrogen accumulation.展开更多
The physical stability of solid-liquid fuel is a factor that needs to be considered for fuel product practicability for storage and transportation. To determine the Influence of liquid bridge force on physical stabili...The physical stability of solid-liquid fuel is a factor that needs to be considered for fuel product practicability for storage and transportation. To determine the Influence of liquid bridge force on physical stability, two detection devices were designed. The laws obtained from microscopic experiments are used to verify the physical stability of fuel under different component ratios. The liquid bridge force is found to increase with the droplet volume. Multiliquid bridges above one critical saturation can generate significant resultant forces compared to single-liquid bridges of the same volume. There exist four states of solid-liquid mixed fuel with increasing liquid saturation rate. The liquid bridge force between the solid and liquid plays a dominant role in the physical stability of the first three states. There may be two stages involved in the stratification process for state 4 fuel, and the liquid viscosity is another factor that cannot be ignored. In the process of selecting a fuel ratio, a larger liquid bridge force between the components can be obtained by properly improving the wetting effect so that the fuel shows better physical stability.展开更多
Introduction Stroke or heart attack,the leading cause of death and disability worldwide,is usually caused by rupture of atheromatous plaque.Therefore,the identification of vulnerable atheroma pre rupture has become ex...Introduction Stroke or heart attack,the leading cause of death and disability worldwide,is usually caused by rupture of atheromatous plaque.Therefore,the identification of vulnerable atheroma pre rupture has become extremely important for patient risk stratification.Previous studies have shown that the vulnerable plaque,i.e.one that is prone to rupture with thromboembolic complications,is often associated with a thin fibrous cap,a large lipid core and a high inflammatory burden.The mechanism of plaque rupture is not entirely clear but is thought to be a multi-factorial process involving thinning and weakening of the fibrous cap by enzymes secreted by activa-展开更多
Unique rocks are found infilling some karst fissures, caves, depressions (valleys), hill slope and niches in Guilin karst regions, such as breccia cemented by reddish calcareous and argillaceous materials; gray or gra...Unique rocks are found infilling some karst fissures, caves, depressions (valleys), hill slope and niches in Guilin karst regions, such as breccia cemented by reddish calcareous and argillaceous materials; gray or grayishgreen calcareous mudstones; and grayish-black silty mudstones. The origins of the rocks were not clear because of the lack of systematical research. It展开更多
基金Project(50478113) supported by the National Natural Science Foundation of ChinaProject(J50502) supported by the Leading Academic Discipline Project of Shanghai Municipal Education Commission,China
文摘The thermal stratification level of low sidewall air supply system in large space was defined. Depending on the experiment of low sidewall air supply in summer 2008,the thermal stratification level was studied by simulation. Based on the simulation of experiment condition,the air velocity and vertical temperature distribution in a large space were simulated at different air-outlet velocities,and then the thermal stratification level line was obtained. The simulation results well match with the experimental ones and the average relative error is 3.4%. The thermal stratification level is heightened by increasing the air-outlet velocity with low sidewall air supply mode. It is concluded that when air-outlet velocity is 0.29 m/s,which is the experimental case,a uniform thermal environment in the higher occupied zone and a stable stratification level are formed. When the air-outlet velocity is low,such as 0.05 m/s,the thermal stratification level is too low and the air velocity is too small to meet the human thermal comfort in the occupied zone. So,it would be reasonable that the air-outlet velocity may be designed as 0.31 m/s if the height of the occupied zone is 2 m.
基金Projects(51476069,51676084)supported by the National Natural Science Foundation of ChinaProject(2019C058-3)supported by the Jilin Provincial Industrial Innovation Special Guidance Fund Project,China+1 种基金Project(20180101059JC)supported by the Jilin Provincial Science and Technology Development Plan Project,ChinaProject(2020C025-2)supported by the Jilin Provincial Specific Project of Industrial Technology Research&Development,China。
文摘Oxygen fuels have broad application prospects and great potential for realizing efficient and clean combustion,and hence this study applies diesel/n-butanol blends to explore the influence of split-injection strategy on combustion and emission characteristics.Simultaneously,changing the way of exhaust gas recirculation(EGR)gas introduction forms uneven in-cylinder components distribution,and utilizing EGR stratification optimizes the combustion process and allows better emission results.The results show that the split-injection strategy can reduce the NO_(x)emissions and keep smoke opacity low compared with the single injection,but the rise in accumulation mode particles is noticeable.NO_(x)emissions show an upward trend as the injection interval expands,while soot emissions are significantly reduced.The increase in pre-injection proportion causes the apparent low-temperature heat release,and the two-stage heat release can be observed during the process of main combustion heat release.More pre-injection mass makes NO_(x)gradually increase,but smoke opacity reaches the lowest point at 15%pre-injection proportion.EGR stratification can optimize the emission results under the split injection strategy,especially the considerable suppression of accumulation mode particulate emissions.Above all,fuel stratification coupled with EGR stratification is beneficial for further realizing the in-cylinder purification of pollutants.
基金supported by the National Natural Science Foundation of China(91648204 61601486)+1 种基金State Key Laboratory of High Performance Computing Project Fund(1502-02)Research Programs of National University of Defense Technology(ZDYYJCYJ140601)
文摘Unmanned aerial vehicles(UAVs) may play an important role in data collection and offloading in vast areas deploying wireless sensor networks, and the UAV’s action strategy has a vital influence on achieving applicability and computational complexity. Dynamic programming(DP) has a good application in the path planning of UAV, but there are problems in the applicability of special terrain environment and the complexity of the algorithm.Based on the analysis of DP, this paper proposes a hierarchical directional DP(DDP) algorithm based on direction determination and hierarchical model. We compare our methods with Q-learning and DP algorithm by experiments, and the results show that our method can improve the terrain applicability, meanwhile greatly reduce the computational complexity.
基金Project(51178298)supported by the National Natural Science Foundation of China
文摘The hybrid system with radiant cooling and dedicated outdoor air not only possesses high energy efficiency, but also creates a healthy and comfortable indoor environment. Indoor air quality will be improved by the dedicated outdoor air system(DOAS) and indoor thermal comfort can be enhanced by the radiant cooling system(RCS). The optimal air-supply mode of the hybrid system and the corresponding design approach were investigated. A full-scale experimental chamber with various air outlets and the ceiling radiant cooling panels(CRCP) was designed and established. The performances of different air-supply modes along with CRCPs were analyzed by multi-index evaluations. Preliminary investigations were also conducted on the humidity stratification and the control effect of different airflow modes to prevent condensation on CRCP. The overhead supply air is recommended as the best combination mode for the hybrid system after comprehensive comparison of the experiment results. The optimal proportion of CRCP accounting for the total cooling capacities in accord with specific cooling loads is found, which may provide valuable reference for the design and operation of the hybrid system.
基金supported by funding from the Australian Government Department of Agriculture,Water and the Environment as a part of its Rural R&D for Profit programthe Cotton Research and Development Corporation through the “More profit from nitrogen:enhancing the nutrient use e ciency of intensive cropping and pasture systems” project.
文摘Australian cotton production predominantly occurs on Vertisols.The average lint yield of cotton grown in Australia is 2260–2700 kg·hm^(−2),which is 2.5 to 3 times the world average.This high productivity per unit of land area requires efficient use of resources such as water and nutrients.However,high yields accelerate the export of nutrients such as phosphorus(P)in seed,depleting the soil reserves of P more than in other countries with lower cotton yields.Recent surveys of cotton industry indicate that P application rates should match seed P export(30~40 kg·hm−2),but historical depletion within subsoil is still evident and is continuing.Depletion of soil P is typically more pronounced in the subsoil than in the topsoil(0~20 cm)where P fertiliser is applied,as cotton roots rely on these layers as important sources of plant available water and available P.This mismatch between zones of P uptake and resupply may increase stratification of available P in the soil profile.Recent studies showed that cotton responded poorly to banded applications of fertiliser P,while dispersal of fertiliser throughout the plant beds was more successful.Researchers have also observed sporadic cotton responses to applied P fertiliser in soils where available P concentrations were well above the previously determined critical concentrations indicative of fertiliser P responses in Australia.To sustain highyielding cotton production in Australia,a greater understanding of cotton root acquisition of applied P,as well as a re-examination of critical soil P concentrations for each production region are required.
基金Natural Science Foundation of China(51979134,51779113)Yunnan Provincial Education Department Scientific Research Fund Project(2021J0164)+4 种基金Open Fund Project of Yunnan Provincial Key Laboratory of Highland Wetland Protection and Restoration and Ecological Services(202105AG070002)Provincial Innovation Team on Environmental Pollution and Food Safety and Human Health,Southwest Forestry University(2005AE160017)A Study of Terrestrial Animal Habitats in Li Ziping National Nature Reserve,Sichuan Province(2021ZD0125)The Construction Project of Key Disciplines with Advantages and Characteristics(Ecology)in Yunnan UniversitiesResearch Project of Key Laboratory of Soil Erosion and Control in Yunnan University。
文摘Two-factor analysis of variance and redundancy analysis were used to analyze the characte-ristics of soil organic carbon total nitrogen storage in garden land,forestland,grassland,farmland,and bare land in the Dachunhe watershed of Jinning District,Kunming City,Yunnan Province,China.The effects of the soil organic carbon,total nitrogen stratification ratio,soil physical and chemical factors on the storage characteristics of organic carbon and total nitrogen of different land-use types were analyzed.The results show that the rates of carbon and nitrogen stratification in soil from 0-20 cm and 40-60 cm of the same land-use types differed are statistically significant(P<0.05).The organic carbon and total nitrogen stratification ratio SR1 of garden land soil are 38.5%and 25.3%,respectively,which are higher than SR^(2).The soil organic carbon and total nitrogen stratification ratio SR^(2) of different land-use types are greater than SR1.There are statistically significant differences in the SR^(2) soil organic carbon and total nitrogen stratification ratios(P<0.05).Soil organic carbon and total nitrogen storage of diffe-rent land-use types gradually decrease with increasing soil depth,with the maximum soil organic carbon and total nitrogen storage in the 0-20 cm soil layer.Soil organic carbon and total nitrogen sto-rage at the same soil depth are significantly different(P<0.05).Soil organic carbon and total nitrogen storage in the garden land are greater than those in the other land-use types.Soil organic carbon and total nitrogen storage in 0-20 cm garden land are 4.96 and 3.19 times than those in bare land,respectively;soil organic carbon and total nitrogen storage are explained by 93.66%and 1.53%in redundancy analysis RDA1 and RDA2,respectively.All physicochemical factors except Available Phosphorus and pH are statistically significance with carbon and nitrogen storage(P<0.05).Soil cationic exchange capacity,Available Phosphorus,C/N ratio,and Moisture Content are positively correlated with organic carbon and total nitrogen storage.In contrast,soil Bulk Density is negatively correlated with organic carbon storage and total nitrogen storage.Available Phosphorus,C/N ratio,and Moisture Content are the main factors promoting soil organic carbon and total nitrogen accumulation.
基金financial support from National Natural Science Foundation of China (Grant No. 12102197)。
文摘The physical stability of solid-liquid fuel is a factor that needs to be considered for fuel product practicability for storage and transportation. To determine the Influence of liquid bridge force on physical stability, two detection devices were designed. The laws obtained from microscopic experiments are used to verify the physical stability of fuel under different component ratios. The liquid bridge force is found to increase with the droplet volume. Multiliquid bridges above one critical saturation can generate significant resultant forces compared to single-liquid bridges of the same volume. There exist four states of solid-liquid mixed fuel with increasing liquid saturation rate. The liquid bridge force between the solid and liquid plays a dominant role in the physical stability of the first three states. There may be two stages involved in the stratification process for state 4 fuel, and the liquid viscosity is another factor that cannot be ignored. In the process of selecting a fuel ratio, a larger liquid bridge force between the components can be obtained by properly improving the wetting effect so that the fuel shows better physical stability.
基金partially supported by the National 973 Basic Research Program of China (No.2013CB733803)the National Natural Science Foundation of China(NSFC)(No.11272091)
文摘Introduction Stroke or heart attack,the leading cause of death and disability worldwide,is usually caused by rupture of atheromatous plaque.Therefore,the identification of vulnerable atheroma pre rupture has become extremely important for patient risk stratification.Previous studies have shown that the vulnerable plaque,i.e.one that is prone to rupture with thromboembolic complications,is often associated with a thin fibrous cap,a large lipid core and a high inflammatory burden.The mechanism of plaque rupture is not entirely clear but is thought to be a multi-factorial process involving thinning and weakening of the fibrous cap by enzymes secreted by activa-
文摘Unique rocks are found infilling some karst fissures, caves, depressions (valleys), hill slope and niches in Guilin karst regions, such as breccia cemented by reddish calcareous and argillaceous materials; gray or grayishgreen calcareous mudstones; and grayish-black silty mudstones. The origins of the rocks were not clear because of the lack of systematical research. It
