The roughness effect based on the wall function method is introduced into the numerical simulation of the rime ice accretion and the resulting effect on the aerodynamic performance of the airfoil. Incorporating the tw...The roughness effect based on the wall function method is introduced into the numerical simulation of the rime ice accretion and the resulting effect on the aerodynamic performance of the airfoil. Incorporating the two-phase model of air/super-cooled droplets in the Eulerian coordinate system, this paper presents the simulation of the rime ice accretion on the NACA 0012 airfoil. The predicted rime ice shape is compared with those results of measurements and simulations by other icing codes. Also the resulting effects of rime ice on airfoil aerodynamic performance are discussed. Results indicate that the rime ice accretion leads to the loss of the maximum lift coefficient by 26%, the decrease of the stall angle by about 3° and the considerable increase of the drag coefficient.展开更多
The paper mainly talks about the background of S. T. Coleridge and the images of The Rime of the AncientMariner. As for the images, the wind, the albatross and the snake will be thoroughly discussed. There are manydif...The paper mainly talks about the background of S. T. Coleridge and the images of The Rime of the AncientMariner. As for the images, the wind, the albatross and the snake will be thoroughly discussed. There are manydifferent images which also have different meanings and connotations in the context. What＇s more, the poemexpresses the theme of the metabolic relationships between men and nature： harmony, conflict or compromise.展开更多
Generally, Coleridge’s poems are mainly divided into two groups:one is to use common Language to depict commom things and common people; the other is to use unique imagination to describe supernatural things. "T...Generally, Coleridge’s poems are mainly divided into two groups:one is to use common Language to depict commom things and common people; the other is to use unique imagination to describe supernatural things. "The Rime of the Ancient Mariner"belongs to the second group. Some critics blame Coleridge for his lack of morals in this poem, but in fact,this poem contains lots of morals, as Coleridge himself said.Coleridge succeeds in exploring the theme of sin and punishment by his rich imagination and by the depicting of supernatural things. In "The Rime of the Ancient Mariner", Coleridge intentionally built a symbolic world of the supernatural wind, the bird, the sun, the moon ,the ship and the sea. All these symbols serve to develop the theme of Fall and Redemption, and play so important a part in the poem that we even can take it as a symbolic poem. In the following pages, I am going to devote to the functions of the supernatural wind in particular. Coleridge bestows the wind with a great deal of展开更多
(1997/11/20) It is 9: 30 in the evening. I have just finished the final exam of Macroeconomics.It is scheduled from 7 p. m. to 10 p. m. It is not that difficult. But it takes me abouttwo hours to finish, because we ne...(1997/11/20) It is 9: 30 in the evening. I have just finished the final exam of Macroeconomics.It is scheduled from 7 p. m. to 10 p. m. It is not that difficult. But it takes me abouttwo hours to finish, because we need to write a lot and there is some computution to do.展开更多
When building a classification model,the scenario where the samples of one class are significantly more than those of the other class is called data imbalance.Data imbalance causes the trained classification model to ...When building a classification model,the scenario where the samples of one class are significantly more than those of the other class is called data imbalance.Data imbalance causes the trained classification model to be in favor of the majority class(usually defined as the negative class),which may do harm to the accuracy of the minority class(usually defined as the positive class),and then lead to poor overall performance of the model.A method called MSHR-FCSSVM for solving imbalanced data classification is proposed in this article,which is based on a new hybrid resampling approach(MSHR)and a new fine cost-sensitive support vector machine(CS-SVM)classifier(FCSSVM).The MSHR measures the separability of each negative sample through its Silhouette value calculated by Mahalanobis distance between samples,based on which,the so-called pseudo-negative samples are screened out to generate new positive samples(over-sampling step)through linear interpolation and are deleted finally(under-sampling step).This approach replaces pseudo-negative samples with generated new positive samples one by one to clear up the inter-class overlap on the borderline,without changing the overall scale of the dataset.The FCSSVM is an improved version of the traditional CS-SVM.It considers influences of both the imbalance of sample number and the class distribution on classification simultaneously,and through finely tuning the class cost weights by using the efficient optimization algorithm based on the physical phenomenon of rime-ice(RIME)algorithm with cross-validation accuracy as the fitness function to accurately adjust the classification borderline.To verify the effectiveness of the proposed method,a series of experiments are carried out based on 20 imbalanced datasets including both mildly and extremely imbalanced datasets.The experimental results show that the MSHR-FCSSVM method performs better than the methods for comparison in most cases,and both the MSHR and the FCSSVM played significant roles.展开更多
Three cases of microphysical characteristics and kinematic structures in the negative temperature region of summer mesoscale cloud systems over the eastern Tibetan Plateau(TP)were investigated using X-band dual-polari...Three cases of microphysical characteristics and kinematic structures in the negative temperature region of summer mesoscale cloud systems over the eastern Tibetan Plateau(TP)were investigated using X-band dual-polarization radar.The time-height series of radar physical variables and mesoscale horizontal divergence δderived by quasi-vertical profiles(QVPs)indicated that the dendritic growth layer(DGL,-20°C to-10°C)was ubiquitous,with large-value zones of K_(DP)(specific differential phase),Z_(DR)(differential reflectivity),or both,and corresponded to various dynamic fields(ascent or descent).Ascents in the DGL of cloud systems with vigorous vertical development were coincident with large-value zones of Z_(DR),signifying ice crystals with a large axis ratio,but with no obvious large values of K_(DP),which differs from previous findings.It is speculated that ascent in the DGL promoted ice crystals to undergo further growth before sinking.If there was descent in the DGL,a high echo top corresponded to large values of K_(DP),denoting a large number concentration of ice crystals;but with the echo top descending,small values of K_(DP) formed.This is similar to previous results and reveals that a high echo top is conducive to the generation of ice crystals.When ice particles fall to low levels(-10℃ to 0℃),they grow through riming,aggregation,or deposition,and may not be related to the kinematic structure.It is important to note that this study was only based on a limited number of cases and that further research is therefore needed.展开更多
文摘The roughness effect based on the wall function method is introduced into the numerical simulation of the rime ice accretion and the resulting effect on the aerodynamic performance of the airfoil. Incorporating the two-phase model of air/super-cooled droplets in the Eulerian coordinate system, this paper presents the simulation of the rime ice accretion on the NACA 0012 airfoil. The predicted rime ice shape is compared with those results of measurements and simulations by other icing codes. Also the resulting effects of rime ice on airfoil aerodynamic performance are discussed. Results indicate that the rime ice accretion leads to the loss of the maximum lift coefficient by 26%, the decrease of the stall angle by about 3° and the considerable increase of the drag coefficient.
文摘The paper mainly talks about the background of S. T. Coleridge and the images of The Rime of the AncientMariner. As for the images, the wind, the albatross and the snake will be thoroughly discussed. There are manydifferent images which also have different meanings and connotations in the context. What＇s more, the poemexpresses the theme of the metabolic relationships between men and nature： harmony, conflict or compromise.
文摘Generally, Coleridge’s poems are mainly divided into two groups:one is to use common Language to depict commom things and common people; the other is to use unique imagination to describe supernatural things. "The Rime of the Ancient Mariner"belongs to the second group. Some critics blame Coleridge for his lack of morals in this poem, but in fact,this poem contains lots of morals, as Coleridge himself said.Coleridge succeeds in exploring the theme of sin and punishment by his rich imagination and by the depicting of supernatural things. In "The Rime of the Ancient Mariner", Coleridge intentionally built a symbolic world of the supernatural wind, the bird, the sun, the moon ,the ship and the sea. All these symbols serve to develop the theme of Fall and Redemption, and play so important a part in the poem that we even can take it as a symbolic poem. In the following pages, I am going to devote to the functions of the supernatural wind in particular. Coleridge bestows the wind with a great deal of
文摘(1997/11/20) It is 9: 30 in the evening. I have just finished the final exam of Macroeconomics.It is scheduled from 7 p. m. to 10 p. m. It is not that difficult. But it takes me abouttwo hours to finish, because we need to write a lot and there is some computution to do.
基金supported by the Yunnan Major Scientific and Technological Projects(Grant No.202302AD080001)the National Natural Science Foundation,China(No.52065033).
文摘When building a classification model,the scenario where the samples of one class are significantly more than those of the other class is called data imbalance.Data imbalance causes the trained classification model to be in favor of the majority class(usually defined as the negative class),which may do harm to the accuracy of the minority class(usually defined as the positive class),and then lead to poor overall performance of the model.A method called MSHR-FCSSVM for solving imbalanced data classification is proposed in this article,which is based on a new hybrid resampling approach(MSHR)and a new fine cost-sensitive support vector machine(CS-SVM)classifier(FCSSVM).The MSHR measures the separability of each negative sample through its Silhouette value calculated by Mahalanobis distance between samples,based on which,the so-called pseudo-negative samples are screened out to generate new positive samples(over-sampling step)through linear interpolation and are deleted finally(under-sampling step).This approach replaces pseudo-negative samples with generated new positive samples one by one to clear up the inter-class overlap on the borderline,without changing the overall scale of the dataset.The FCSSVM is an improved version of the traditional CS-SVM.It considers influences of both the imbalance of sample number and the class distribution on classification simultaneously,and through finely tuning the class cost weights by using the efficient optimization algorithm based on the physical phenomenon of rime-ice(RIME)algorithm with cross-validation accuracy as the fitness function to accurately adjust the classification borderline.To verify the effectiveness of the proposed method,a series of experiments are carried out based on 20 imbalanced datasets including both mildly and extremely imbalanced datasets.The experimental results show that the MSHR-FCSSVM method performs better than the methods for comparison in most cases,and both the MSHR and the FCSSVM played significant roles.
基金jointly funded by the Northwest Regional Weather Modification Capacity Building Project of the China Meteorological Administration(Grant No.ZQC-R18209)the National Natural Science Foundation of China(Grant Nos.41875172 and 42075192)。
文摘Three cases of microphysical characteristics and kinematic structures in the negative temperature region of summer mesoscale cloud systems over the eastern Tibetan Plateau(TP)were investigated using X-band dual-polarization radar.The time-height series of radar physical variables and mesoscale horizontal divergence δderived by quasi-vertical profiles(QVPs)indicated that the dendritic growth layer(DGL,-20°C to-10°C)was ubiquitous,with large-value zones of K_(DP)(specific differential phase),Z_(DR)(differential reflectivity),or both,and corresponded to various dynamic fields(ascent or descent).Ascents in the DGL of cloud systems with vigorous vertical development were coincident with large-value zones of Z_(DR),signifying ice crystals with a large axis ratio,but with no obvious large values of K_(DP),which differs from previous findings.It is speculated that ascent in the DGL promoted ice crystals to undergo further growth before sinking.If there was descent in the DGL,a high echo top corresponded to large values of K_(DP),denoting a large number concentration of ice crystals;but with the echo top descending,small values of K_(DP) formed.This is similar to previous results and reveals that a high echo top is conducive to the generation of ice crystals.When ice particles fall to low levels(-10℃ to 0℃),they grow through riming,aggregation,or deposition,and may not be related to the kinematic structure.It is important to note that this study was only based on a limited number of cases and that further research is therefore needed.
