The precooler is a distinctive component of precooled air-breathing engines but constitutes a challenge to conventional thermal design methods.The latter are based upon assumptions that often reveal to be limited for ...The precooler is a distinctive component of precooled air-breathing engines but constitutes a challenge to conventional thermal design methods.The latter are based upon assumptions that often reveal to be limited for precooler design.In this paper,a refined design method considering the variations of fluid thermophysical properties,flow area and thermal parameters distortion,was proposed to remediate their limitations.Firstly,the precooler was discretized into a fixed number of sub-microtubes based on a new discretization criterion.Next,in-house one-dimensional(1D)and two-dimensional(2D)segmented models were established for rapid thermal design and precooler rating with non-uniform airflow,respectively.The heat transfer experimental studies of supercritical hydrocarbon fuel were performed to verify the Jackson correlation for precooler design and the in-house models were validated against the reported data from open literature.On this basis,the proposed method was employed for the design analysis of hydrocarbon fuel precoolers for precooled-Turbine Based Combined Cycle(TBCC)engines.The results show that the local performance of precoolers is intrinsically impacted by the aforementioned three variations.In the case study,the local heat transfer performance is drastically affected by coolant flow transition.While the circumferential temperature distortion of airflow is weakened by heat transfer.With consideration of additional parameter variations,this novel method improves design accuracy and shortens the design time.展开更多
A field campaign on air quality was carried out in Shanghai in winter of 2012. The concentrations of NO, NO2, NOx, SO2, CO, and PM2.5increased during haze formation. The average masses of SO4^2-, NO3^-and NH4^＋were 1...A field campaign on air quality was carried out in Shanghai in winter of 2012. The concentrations of NO, NO2, NOx, SO2, CO, and PM2.5increased during haze formation. The average masses of SO4^2-, NO3^-and NH4^＋were 10.3, 11.7 and 6.7 μg/m^3 during the haze episodes, which exceeded the average（9.2, 7.9, and 3.4 μg/m3） of these components in the non-haze days. The mean values for the aerosol scattering coefficient（b sp）, aerosol absorption coefficient（b ap） and single scattering albedo（SSA） were 288.7, 27.7 and0.91 Mm-1, respectively. A bi-peak distribution was observed for the mass concentrations of CO, NO, NO2, and NOx. More sulfate was produced during daytime than that in the evening due to photochemical reactions. The mass concentration of NH4＋achieved a small peak at noontime. NO3-showed lower concentrations in the afternoon and higher concentrations in the early morning. There were obvious bi-peak diurnal patterns for b sp and b ap as well as SSA. b sp and b ap showed a positive correlation with PM2.5mass concentration.（NH4）2SO4, NH4NO3, organic mass, elemental carbon and coarse mass accounted for 21.7%, 19.3%, 31.0%, 9.3% and 12.3% of the total extinction coefficient during non-haze days, and 25.6%, 24.3%, 30.1%, 8.1% and 8.2% during hazy days. Organic matter was the largest contributor to light extinction. The contribution proportions of ammonium sulfate and ammonium nitrate to light extinction were significantly higher during the hazy time than during the non-haze days.展开更多
A simple finite element implementation of the Mott model for fragmentation of a thin walled ring has been implemented and used to explore the effect of local variations in fracture strain around the ring.The model has...A simple finite element implementation of the Mott model for fragmentation of a thin walled ring has been implemented and used to explore the effect of local variations in fracture strain around the ring.The model has successfully reproduced the fragment size distributions previously reported,which follow a characteristic“Mott distribution”form,providing sufficient(1000)simulations are run.It has been shown that this form is retained even when there are large differences in the random distribution of fracture strains or a different choice of function used to describe the fracture strain scatter.In these cases,the strain rate has a much stronger effect than fracture strain distribution the on the average fragment size and fragment distribution.However,for cases where there are a small number of local defects that strongly reduce the fracture strain at certain locations around the ring,the predicted fragment size distribution develops a bimodal character.This is also the case for large but gradual variations in fracture strain with position around the ring.The results have implications for cases where a small number of large pre-existing defects exist,or processing has led to macrozones in the microstructure.The utility of a simple fast running model to study these cases is discussed.展开更多
Appropriate rock characterization is beneficial in providing a reliable judgment on rock properties which is crucial for the design process of rock engineering applications.However,it can be difficult to obtain consis...Appropriate rock characterization is beneficial in providing a reliable judgment on rock properties which is crucial for the design process of rock engineering applications.However,it can be difficult to obtain consistent mechanical parameters due to substantial variations in rock properties.In this research,uniaxial compression tests on dolerite specimens collected from a gold mine in Western Australia showed substantial scatter in the results.Rock categorization based on the P-wave velocities is as accurate as the thin section analysis,which suggests that they can be used together to gain a more accurate initial understanding of the rock types before any laboratory testing.The quality of specimen preparation and rockemachine interaction greatly affect the test results.For instance,non-parallelness of loading platens can lead to considerable scatter of the testing results,which would be perceived as rock variability.It is suggested that the current testing standards should be modified towards a better control of the loading machine performance and equipment precision.Finally,the possibility of pre-existing microcracks in rock,neither detected by the thin section analysis nor by the ultrasonic measurement,must be examined by computed tomography(CT)scanning as they can affect the test results.This study will enhance our knowledge about the sources of variability in laboratory test results of rock which is essential for obtaining reliable data.展开更多
In this study, we build a double auction market model, which contains two types of agent traders, i.e., the noise traders and fundamentalists, to investigate the effect of the trader composition on the stock market. I...In this study, we build a double auction market model, which contains two types of agent traders, i.e., the noise traders and fundamentalists, to investigate the effect of the trader composition on the stock market. It is found that, the non-trivial Hurst exponent and the fat-tailed distribution of transaction prices can be observed at any ratio of the noise traders. Analyses on the price variation properties, including the Hurst exponent and the price variation region, show that these properties are stable when the ratio is moderate. However, the non-price variation properties, including the trading volume and the profitability of the two kinds of agents, do not keep stable untrivially in any interval of the ratio of noise traders.展开更多
The coarse graining of particle cluster is of great significance to the study of a fluidized bed. The effects of variations in the physical properties of supercritical water on the coarse graining of particle cluster ...The coarse graining of particle cluster is of great significance to the study of a fluidized bed. The effects of variations in the physical properties of supercritical water on the coarse graining of particle cluster are investigated in this work. The drag coefficient distributions of the particle cluster are not influenced by the physical properties. However, the physical properties have effects on the values of drag coefficient. The effects of physical properties are weaker in the case of large particle concentrations. Furthermore, the physical properties lead to that the effect of particle cluster wake on the drag of downstream particles being significantly different from that of constant property flow. The variation trend of drag of coarse graining particle is consistent with that of isolated particle. The physical properties lead to significant differences in the values of drag. In this paper, the dominance of the effects of physical properties in a variety of cases is confirmed. Finally, a physical properties effect model is developed accordingly.展开更多
In the study,we explore the structural evolution of Cantor high-entropy alloy(HEA)under different super-cooling rates and its correlation with mechanical property variations by the developed machine learning-driven de...In the study,we explore the structural evolution of Cantor high-entropy alloy(HEA)under different super-cooling rates and its correlation with mechanical property variations by the developed machine learning-driven deep potential molecular dynamics(DPMD)simulation.Our results reveal the critical super-cooling rate of amorphization-crystallization transition of Cantor alloy and the local structure constitutions at different temperatures during the super-cooling process.The associated mechanical property studies demonstrate the glassy Cantor alloy amorphized at high super-cooling rate exhibits a superior capability of ductility but this capability is unrelated to the amorphization cooling rates.While the high strength of Cantor alloy requires a lower super-cooling rate which might result in the crystallization,amorphizing the Cantor alloy at the critical super-cooling rate of amorphizationcrystallization transition could compatibilize both ductility and strength capabilities.Such a discovery sheds new lights on the material development and its mechanical performance optimization for industrial applications.展开更多
基金co-supported by the Specialized Research Foundation of Civil Aircraft,China(MJ-2016-D-35)the Advanced Jet Propulsion Creativity Center,AEAC,China(HKCX2019-01-004)。
文摘The precooler is a distinctive component of precooled air-breathing engines but constitutes a challenge to conventional thermal design methods.The latter are based upon assumptions that often reveal to be limited for precooler design.In this paper,a refined design method considering the variations of fluid thermophysical properties,flow area and thermal parameters distortion,was proposed to remediate their limitations.Firstly,the precooler was discretized into a fixed number of sub-microtubes based on a new discretization criterion.Next,in-house one-dimensional(1D)and two-dimensional(2D)segmented models were established for rapid thermal design and precooler rating with non-uniform airflow,respectively.The heat transfer experimental studies of supercritical hydrocarbon fuel were performed to verify the Jackson correlation for precooler design and the in-house models were validated against the reported data from open literature.On this basis,the proposed method was employed for the design analysis of hydrocarbon fuel precoolers for precooled-Turbine Based Combined Cycle(TBCC)engines.The results show that the local performance of precoolers is intrinsically impacted by the aforementioned three variations.In the case study,the local heat transfer performance is drastically affected by coolant flow transition.While the circumferential temperature distortion of airflow is weakened by heat transfer.With consideration of additional parameter variations,this novel method improves design accuracy and shortens the design time.
基金supported by the Ministry of Science and Technology of China (No. 2013CB955804)the National Natural Science Foundation of China (Nos. 41175018, 41475113)the Ministry of Environmental Protection of China (Nos. 201209001, 201409008, 201209007)
文摘A field campaign on air quality was carried out in Shanghai in winter of 2012. The concentrations of NO, NO2, NOx, SO2, CO, and PM2.5increased during haze formation. The average masses of SO4^2-, NO3^-and NH4^＋were 10.3, 11.7 and 6.7 μg/m^3 during the haze episodes, which exceeded the average（9.2, 7.9, and 3.4 μg/m3） of these components in the non-haze days. The mean values for the aerosol scattering coefficient（b sp）, aerosol absorption coefficient（b ap） and single scattering albedo（SSA） were 288.7, 27.7 and0.91 Mm-1, respectively. A bi-peak distribution was observed for the mass concentrations of CO, NO, NO2, and NOx. More sulfate was produced during daytime than that in the evening due to photochemical reactions. The mass concentration of NH4＋achieved a small peak at noontime. NO3-showed lower concentrations in the afternoon and higher concentrations in the early morning. There were obvious bi-peak diurnal patterns for b sp and b ap as well as SSA. b sp and b ap showed a positive correlation with PM2.5mass concentration.（NH4）2SO4, NH4NO3, organic mass, elemental carbon and coarse mass accounted for 21.7%, 19.3%, 31.0%, 9.3% and 12.3% of the total extinction coefficient during non-haze days, and 25.6%, 24.3%, 30.1%, 8.1% and 8.2% during hazy days. Organic matter was the largest contributor to light extinction. The contribution proportions of ammonium sulfate and ammonium nitrate to light extinction were significantly higher during the hazy time than during the non-haze days.
基金funding through the LightForm program grant EP/R001715/1
文摘A simple finite element implementation of the Mott model for fragmentation of a thin walled ring has been implemented and used to explore the effect of local variations in fracture strain around the ring.The model has successfully reproduced the fragment size distributions previously reported,which follow a characteristic“Mott distribution”form,providing sufficient(1000)simulations are run.It has been shown that this form is retained even when there are large differences in the random distribution of fracture strains or a different choice of function used to describe the fracture strain scatter.In these cases,the strain rate has a much stronger effect than fracture strain distribution the on the average fragment size and fragment distribution.However,for cases where there are a small number of local defects that strongly reduce the fracture strain at certain locations around the ring,the predicted fragment size distribution develops a bimodal character.This is also the case for large but gradual variations in fracture strain with position around the ring.The results have implications for cases where a small number of large pre-existing defects exist,or processing has led to macrozones in the microstructure.The utility of a simple fast running model to study these cases is discussed.
基金the Curtin Strategic International Research Scholarship(CSIRS)and Mining Research Institute of Western Australia(MRIWA)-project M474 scholarshipthe Australian Research Council through project DP190103260.
文摘Appropriate rock characterization is beneficial in providing a reliable judgment on rock properties which is crucial for the design process of rock engineering applications.However,it can be difficult to obtain consistent mechanical parameters due to substantial variations in rock properties.In this research,uniaxial compression tests on dolerite specimens collected from a gold mine in Western Australia showed substantial scatter in the results.Rock categorization based on the P-wave velocities is as accurate as the thin section analysis,which suggests that they can be used together to gain a more accurate initial understanding of the rock types before any laboratory testing.The quality of specimen preparation and rockemachine interaction greatly affect the test results.For instance,non-parallelness of loading platens can lead to considerable scatter of the testing results,which would be perceived as rock variability.It is suggested that the current testing standards should be modified towards a better control of the loading machine performance and equipment precision.Finally,the possibility of pre-existing microcracks in rock,neither detected by the thin section analysis nor by the ultrasonic measurement,must be examined by computed tomography(CT)scanning as they can affect the test results.This study will enhance our knowledge about the sources of variability in laboratory test results of rock which is essential for obtaining reliable data.
基金Supported by National Natural Science Foundation of China under Grant Nos.60973152 and 60573172Doctoral Program Foundation of Institution of Higher Education of China under Crant No.20070141014Natural Science Foundation of Liaoning Province of China under Grant No.20082165
文摘In this study, we build a double auction market model, which contains two types of agent traders, i.e., the noise traders and fundamentalists, to investigate the effect of the trader composition on the stock market. It is found that, the non-trivial Hurst exponent and the fat-tailed distribution of transaction prices can be observed at any ratio of the noise traders. Analyses on the price variation properties, including the Hurst exponent and the price variation region, show that these properties are stable when the ratio is moderate. However, the non-price variation properties, including the trading volume and the profitability of the two kinds of agents, do not keep stable untrivially in any interval of the ratio of noise traders.
基金supported by the National Key R&D Program of China(2020YFA0714400).
文摘The coarse graining of particle cluster is of great significance to the study of a fluidized bed. The effects of variations in the physical properties of supercritical water on the coarse graining of particle cluster are investigated in this work. The drag coefficient distributions of the particle cluster are not influenced by the physical properties. However, the physical properties have effects on the values of drag coefficient. The effects of physical properties are weaker in the case of large particle concentrations. Furthermore, the physical properties lead to that the effect of particle cluster wake on the drag of downstream particles being significantly different from that of constant property flow. The variation trend of drag of coarse graining particle is consistent with that of isolated particle. The physical properties lead to significant differences in the values of drag. In this paper, the dominance of the effects of physical properties in a variety of cases is confirmed. Finally, a physical properties effect model is developed accordingly.
基金the financial support provided by project numbers 12305395 and 22476130 from the National Natural Science Foundation of China and National Science Fund for Distinguished Young Scholars of China(12225506)The computations in this paper were run on the Siyuan-1 cluster supported by the Center for High Performance Computing at Shanghai Jiao Tong University.
文摘In the study,we explore the structural evolution of Cantor high-entropy alloy(HEA)under different super-cooling rates and its correlation with mechanical property variations by the developed machine learning-driven deep potential molecular dynamics(DPMD)simulation.Our results reveal the critical super-cooling rate of amorphization-crystallization transition of Cantor alloy and the local structure constitutions at different temperatures during the super-cooling process.The associated mechanical property studies demonstrate the glassy Cantor alloy amorphized at high super-cooling rate exhibits a superior capability of ductility but this capability is unrelated to the amorphization cooling rates.While the high strength of Cantor alloy requires a lower super-cooling rate which might result in the crystallization,amorphizing the Cantor alloy at the critical super-cooling rate of amorphizationcrystallization transition could compatibilize both ductility and strength capabilities.Such a discovery sheds new lights on the material development and its mechanical performance optimization for industrial applications.
