The numerical simulation of modern aero-engine combustion chamber needs accurate description of the interaction between turbulence and chemical reaction mechanism. The Large Eddy Simulation(LES) method with the Transp...The numerical simulation of modern aero-engine combustion chamber needs accurate description of the interaction between turbulence and chemical reaction mechanism. The Large Eddy Simulation(LES) method with the Transported Probability Density Function(TPDF) turbulence combustion model is promising in engineering applications. In flame region, the impact of chemical reaction should be considered in TPDF molecular mixing model. Based on pioneer research, three new TPDF turbulence-chemistry dual time scale molecular mixing models were proposed tentatively by adding the chemistry time scale in molecular mixing model for nonpremixed flame. The Aero-Engine Combustor Simulation Code(AECSC) which is based on LES-TPDF method was combined with the three new models. Then the Sandia laboratory's methane-air jet flames: Flame D and Flame E were simulated. Transient simulation results show that all the three new models can predict the instantaneous combustion flow pattern of the jet flames. Furthermore,the average scalar statistical results were compared with the experimental data. The simulation result of the new TPDF arithmetic mean modification model is the closest to the experimental data:the average error in Flame D is 7.6% and 6.6% in Flame E. The extinction and re-ignition phenomena of the jet flames especially Flame E were captured. The turbulence time scale and the chemistry time scale are in different order in the whole flow field. The dual time scale TPDF combustion model has ability to deal with both the turbulence effect and the chemistry reaction effect, as well as their interaction more accurately for nonpremixed flames.展开更多
Complex hydrocultural conditions in the estuary affect the migration and transformation of mercury.Using two voyages in July and October 2018,Dissolved Gaseous Mercury(DGM)and Reactive Mercury(RHg)were determined to e...Complex hydrocultural conditions in the estuary affect the migration and transformation of mercury.Using two voyages in July and October 2018,Dissolved Gaseous Mercury(DGM)and Reactive Mercury(RHg)were determined to explore the source,transformation and influence of DGM content in the adjacent waters of Yangtze River Estuary in summer and autumn.The results showed the contents of DGM and RHg in summer were higher than those in autumn,and both of them were higher than those in open sea.In summer and autumn,the Yangtze River brought a higher concentration of DGM,and different flow direction and runoff resulted in differences in the high value region of the surface.The emergence of low-oxygen zones in summer was conducive to the production of DGM.In autumn,windy weather allowed seawater disturbances to promote the release of mercury from the underlying sediments,especially in shallow sea in northwest.RHg showed a higher concentration in the offshore than in the open sea in summer,but there was no such trend in autumn,reflecting the influence of less runoff input.DGM is the main product of RHg reduction,and there was a significant positive correlation between DGM and RHg in summer(r=0.356,P<0.05),while the correlation between DGM and RHg was not significant in autumn due to the influence of light intensity,wind speed and nutrients.The exchange flux of mercury in the adjacent waters of the Yangtze River Estuary was higher than that in the open sea.There was no significant difference of the release flux of mercury in summer and autumn.This article highlighted that the input of mercury from the Yangtze River runoff promotes the release of mercury in seawater,and the hypoxic zone caused by eutrophication is conducive to the production of DGM.展开更多
China has accumulated massive fine grained copper mine tailings stocks because of the past mining activities in this area. The tailings contain a variety of heavy metals, and the mass percent of Cu, which is one of th...China has accumulated massive fine grained copper mine tailings stocks because of the past mining activities in this area. The tailings contain a variety of heavy metals, and the mass percent of Cu, which is one of the main contaminants in tailings, is up to 0.2601% (analysis by XRF). The Cu can pollute soil and groundwater by rain leaching in the form of Cu(Ⅱ), furthermore ,the fine grained copper-ore-tailings can contaminant larger area by wind for its small granularity ( < 74 μm). The main cause of weathering of mine tailings is due to oxidative dissolution of sulfides. Microorganisms, such as Acidithiobacillus ferrooxidans, play an important role in weathering. These bacteria attach to exposed to mineral surfaces by excreting extracellular polymers and oxidize the sulfide mineral. Some of these bacteria also oxidize Fe2+ to Fe3+ which can chemically oxidize sulfide minerals. These reactions produce voluminous quantities of acid mine drainage and heavy metals which are harmful to the environment and human healthy. This study aims at finding the weathering effects of A. ferrooxidans to Cu(II) pollution of fine grained copper mine tailings, and our experiment applied indigenous A. ferrooxidans FJ-01 to leach the tailings. The optimum test parameters were obtained using shaking flask experiment and SEM observation under the following experimental conditions: 39 days residence time, pulp density 1%-15% (1%, 5% and 15%), 30℃, 120 rpm, pH between 1-3 and redox potential between 400-650 mV. The test results show that the leaching rate of Cu reached 43.1% when the pulp density was 1% after 33 days and kept invariant till the end of the test. In addition, the leaching rate of Cu will decrease as the increase of pulp density, and the maximum rate of 15% pulp density was only 12.5%. From the SEM, it can be seen that the fine grain of tailings flocculated to conglobation under the action of bacterial leaching.展开更多
Shannon channel capacity theorem poses highest bit-rate of error free transmission over additive white Gaussian noise channel.In addition,he proved that there exists channel code that can theoretically achieve the cha...Shannon channel capacity theorem poses highest bit-rate of error free transmission over additive white Gaussian noise channel.In addition,he proved that there exists channel code that can theoretically achieve the channel capacity.Indeed fortunately,the latter researchers found some practical channel codes approaching the channel capacity with insignificant losses of spectral efficiency under ignorable bit error rate(BER).The authors note,in general,that bits of the channel codes are not independent of each other in code space.Further,we note that the modulated symbols are not independent among them,as well,in Euclidean Space.By exploiting a usage of the dependencies jointly to signal design,we can transmit two independent signal streams through an additive white Gaussian channel and separate them in Euclidean space at the receiver.The capacity of this approach is found larger than that of Shannon capacity in the same channel assumptions.The numerical results confirm the theoretical procedures.展开更多
Drought is the uppermost natural disaster in the Hebei Plain,which during the past 20 years showed a trend of frequency increasing,range extension,longer duration and severer damage. In the Hebei Plain,as a major grai...Drought is the uppermost natural disaster in the Hebei Plain,which during the past 20 years showed a trend of frequency increasing,range extension,longer duration and severer damage. In the Hebei Plain,as a major grain producing area,the agricultural drought emergency relief can only rely on groundwater exploitation. Thus the work to conduct evaluation of groundwater supply capacity for agricultural drought emergency relief of Hebei Plain is of great significance for disaster prevention and relief. In this paper,with the method of analytic hierarchy process,the evaluation index system with reference to 3 aspects and 7 indexes(the former including groundwater resources,groundwater exploitation technical conditions and water supply facilities) and the Arc GIS Desktop Arc MAP software,the work to assess the shallow groundwater supply capacity for agricultural drought emergency relief in the Hebei Plain was carried out.展开更多
目的研究哺乳动物的腭发育中腭板抬升模式在前后区域差异的决定机制。方法以小鼠腭发育为模型,将抬升前(E13.5早期)、抬升中(E13.5晚期)和抬升后(E14.5早期)的腭板进行冠状向多平面切片,HE染色对比腭和舌的形态变化及空间关联,肌球蛋白...目的研究哺乳动物的腭发育中腭板抬升模式在前后区域差异的决定机制。方法以小鼠腭发育为模型,将抬升前(E13.5早期)、抬升中(E13.5晚期)和抬升后(E14.5早期)的腭板进行冠状向多平面切片,HE染色对比腭和舌的形态变化及空间关联,肌球蛋白重链1(myosin heavy chain 1,MYH1,存在于慢肌纤维中,负责肌肉的收缩和运动)免疫荧光染色观察腭不同抬升阶段舌肌发育成熟特征;通过腭器官体外培养试验,HE染色观察E13.5早期无舌情况下腭板抬升模式变化;通过胞外基质肌腱蛋白C(Tenascin-C)表达检测(免疫荧光染色),验证舌对前后份腭板抬升模式差异的影响。结果切片HE染色结果显示,在腭抬升期从后到前份,舌冠状向高度下降,侧向倾斜加强且变扁平,但舌矢状向伸长,腭板的抬升模式从缓慢重塑转变为快速翻折,MYH1在此时期大量表达于舌内外肌束。体外腭器官培养发现:无舌条件下,腭板后份抬升未形成新的舌侧凸起,Tenascin-C的区域表达与上抬前一致,腭后份抬升类似于前份抬升模式。结论舌体可能是腭板后份形态重塑抬升模式形成的重要影响因素。展开更多
基金co-supported by the National Key R&D Program of China(Nos.2017YFB0202400 and 2017YFB0202402)the National Natural Science Foundation of China(No.91741125)the Project of Newton International Fellowship Alumnus from Royal Society(No.AL120003)
文摘The numerical simulation of modern aero-engine combustion chamber needs accurate description of the interaction between turbulence and chemical reaction mechanism. The Large Eddy Simulation(LES) method with the Transported Probability Density Function(TPDF) turbulence combustion model is promising in engineering applications. In flame region, the impact of chemical reaction should be considered in TPDF molecular mixing model. Based on pioneer research, three new TPDF turbulence-chemistry dual time scale molecular mixing models were proposed tentatively by adding the chemistry time scale in molecular mixing model for nonpremixed flame. The Aero-Engine Combustor Simulation Code(AECSC) which is based on LES-TPDF method was combined with the three new models. Then the Sandia laboratory's methane-air jet flames: Flame D and Flame E were simulated. Transient simulation results show that all the three new models can predict the instantaneous combustion flow pattern of the jet flames. Furthermore,the average scalar statistical results were compared with the experimental data. The simulation result of the new TPDF arithmetic mean modification model is the closest to the experimental data:the average error in Flame D is 7.6% and 6.6% in Flame E. The extinction and re-ignition phenomena of the jet flames especially Flame E were captured. The turbulence time scale and the chemistry time scale are in different order in the whole flow field. The dual time scale TPDF combustion model has ability to deal with both the turbulence effect and the chemistry reaction effect, as well as their interaction more accurately for nonpremixed flames.
基金the National Natural Science Foundation of China(Nos.41506128,40806045 and 41749903)the Oceanographic Research Vessel Sharing Plan(No.NORC2018-06-25)。
文摘Complex hydrocultural conditions in the estuary affect the migration and transformation of mercury.Using two voyages in July and October 2018,Dissolved Gaseous Mercury(DGM)and Reactive Mercury(RHg)were determined to explore the source,transformation and influence of DGM content in the adjacent waters of Yangtze River Estuary in summer and autumn.The results showed the contents of DGM and RHg in summer were higher than those in autumn,and both of them were higher than those in open sea.In summer and autumn,the Yangtze River brought a higher concentration of DGM,and different flow direction and runoff resulted in differences in the high value region of the surface.The emergence of low-oxygen zones in summer was conducive to the production of DGM.In autumn,windy weather allowed seawater disturbances to promote the release of mercury from the underlying sediments,especially in shallow sea in northwest.RHg showed a higher concentration in the offshore than in the open sea in summer,but there was no such trend in autumn,reflecting the influence of less runoff input.DGM is the main product of RHg reduction,and there was a significant positive correlation between DGM and RHg in summer(r=0.356,P<0.05),while the correlation between DGM and RHg was not significant in autumn due to the influence of light intensity,wind speed and nutrients.The exchange flux of mercury in the adjacent waters of the Yangtze River Estuary was higher than that in the open sea.There was no significant difference of the release flux of mercury in summer and autumn.This article highlighted that the input of mercury from the Yangtze River runoff promotes the release of mercury in seawater,and the hypoxic zone caused by eutrophication is conducive to the production of DGM.
文摘China has accumulated massive fine grained copper mine tailings stocks because of the past mining activities in this area. The tailings contain a variety of heavy metals, and the mass percent of Cu, which is one of the main contaminants in tailings, is up to 0.2601% (analysis by XRF). The Cu can pollute soil and groundwater by rain leaching in the form of Cu(Ⅱ), furthermore ,the fine grained copper-ore-tailings can contaminant larger area by wind for its small granularity ( < 74 μm). The main cause of weathering of mine tailings is due to oxidative dissolution of sulfides. Microorganisms, such as Acidithiobacillus ferrooxidans, play an important role in weathering. These bacteria attach to exposed to mineral surfaces by excreting extracellular polymers and oxidize the sulfide mineral. Some of these bacteria also oxidize Fe2+ to Fe3+ which can chemically oxidize sulfide minerals. These reactions produce voluminous quantities of acid mine drainage and heavy metals which are harmful to the environment and human healthy. This study aims at finding the weathering effects of A. ferrooxidans to Cu(II) pollution of fine grained copper mine tailings, and our experiment applied indigenous A. ferrooxidans FJ-01 to leach the tailings. The optimum test parameters were obtained using shaking flask experiment and SEM observation under the following experimental conditions: 39 days residence time, pulp density 1%-15% (1%, 5% and 15%), 30℃, 120 rpm, pH between 1-3 and redox potential between 400-650 mV. The test results show that the leaching rate of Cu reached 43.1% when the pulp density was 1% after 33 days and kept invariant till the end of the test. In addition, the leaching rate of Cu will decrease as the increase of pulp density, and the maximum rate of 15% pulp density was only 12.5%. From the SEM, it can be seen that the fine grain of tailings flocculated to conglobation under the action of bacterial leaching.
基金supported by two Programs of National Natural Science Foundation of China(No.61271203 and No.61531004)
文摘Shannon channel capacity theorem poses highest bit-rate of error free transmission over additive white Gaussian noise channel.In addition,he proved that there exists channel code that can theoretically achieve the channel capacity.Indeed fortunately,the latter researchers found some practical channel codes approaching the channel capacity with insignificant losses of spectral efficiency under ignorable bit error rate(BER).The authors note,in general,that bits of the channel codes are not independent of each other in code space.Further,we note that the modulated symbols are not independent among them,as well,in Euclidean Space.By exploiting a usage of the dependencies jointly to signal design,we can transmit two independent signal streams through an additive white Gaussian channel and separate them in Euclidean space at the receiver.The capacity of this approach is found larger than that of Shannon capacity in the same channel assumptions.The numerical results confirm the theoretical procedures.
文摘Drought is the uppermost natural disaster in the Hebei Plain,which during the past 20 years showed a trend of frequency increasing,range extension,longer duration and severer damage. In the Hebei Plain,as a major grain producing area,the agricultural drought emergency relief can only rely on groundwater exploitation. Thus the work to conduct evaluation of groundwater supply capacity for agricultural drought emergency relief of Hebei Plain is of great significance for disaster prevention and relief. In this paper,with the method of analytic hierarchy process,the evaluation index system with reference to 3 aspects and 7 indexes(the former including groundwater resources,groundwater exploitation technical conditions and water supply facilities) and the Arc GIS Desktop Arc MAP software,the work to assess the shallow groundwater supply capacity for agricultural drought emergency relief in the Hebei Plain was carried out.
文摘目的研究哺乳动物的腭发育中腭板抬升模式在前后区域差异的决定机制。方法以小鼠腭发育为模型,将抬升前(E13.5早期)、抬升中(E13.5晚期)和抬升后(E14.5早期)的腭板进行冠状向多平面切片,HE染色对比腭和舌的形态变化及空间关联,肌球蛋白重链1(myosin heavy chain 1,MYH1,存在于慢肌纤维中,负责肌肉的收缩和运动)免疫荧光染色观察腭不同抬升阶段舌肌发育成熟特征;通过腭器官体外培养试验,HE染色观察E13.5早期无舌情况下腭板抬升模式变化;通过胞外基质肌腱蛋白C(Tenascin-C)表达检测(免疫荧光染色),验证舌对前后份腭板抬升模式差异的影响。结果切片HE染色结果显示,在腭抬升期从后到前份,舌冠状向高度下降,侧向倾斜加强且变扁平,但舌矢状向伸长,腭板的抬升模式从缓慢重塑转变为快速翻折,MYH1在此时期大量表达于舌内外肌束。体外腭器官培养发现:无舌条件下,腭板后份抬升未形成新的舌侧凸起,Tenascin-C的区域表达与上抬前一致,腭后份抬升类似于前份抬升模式。结论舌体可能是腭板后份形态重塑抬升模式形成的重要影响因素。
