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
The prefrontal cortex (PFC) plays an important role in cognitive process related to executive function, but is also active during resting states. Quantifying prefrontal cortex activity during resting states provides a...The prefrontal cortex (PFC) plays an important role in cognitive process related to executive function, but is also active during resting states. Quantifying prefrontal cortex activity during resting states provides a baseline for interpreting task-induced brain activity. Researchers commonly use resting conditions where participants are prompted to stare at a screen (eyes open) or close their eyes (eyes closed). Are these two conditions equivalent representations of a baseline resting state? Further, does prefrontal cortex activity during these conditions change as a function of development? The aim of this study was to examine differences in prefrontal cortex activity between eyes open and eyes closed conditions during resting states in children and adults to provide a rationale of proper selection of baseline condition in future research. Thirty-six participants in 3 age groups were recruited in this study including twenty-four adults, five 12 - 15 years old children, and seven 8 - 11 years old children. Relative changes in concentrations of oxygenated hemoglobin (Δoxy-Hb) and deoxygenated hemoglobin (Δdeoxy-Hb) were obtained by using functional Near-Infrared Spectroscopy (fNIRS) in eyes closed (EC) and eyes open (EO) conditions, 3 minutes each. Contrasts were tested to compare the differences of Δoxy-Hb and Δdeoxy-Hb between eyes open and eyes closed conditions. The EC condition had significantly higher Δoxy-Hb than EO when all groups were combined (t (17.268) = 3.021, p = .008, Cohen’s d = –0.72). When comparing Δoxy-Hb between eyes conditions within each group, the younger group had significantly higher Δoxy-Hb in EC than EO (t (9.459) = 2.734, p = 0.022, Cohen’s d = –1.46). Based on these results, the EO condition may be a better baseline condition, particularly in studies with younger children, since it has less activity in the PFC that could interfere with interpretations of task-induced activity.展开更多
The purpose of this paper is to obtain a generalization of the famous Browder's fixed point theorem and some equivalent forms. As application, these results are utilized to study the existence problems of fixed po...The purpose of this paper is to obtain a generalization of the famous Browder's fixed point theorem and some equivalent forms. As application, these results are utilized to study the existence problems of fixed points and nearest points.展开更多
Mathematical models of the grinding process are the basis of analysis, simulation and control. Most existent models in- cluding theoretical models and identification models are, however, inconvenient for direct analy...Mathematical models of the grinding process are the basis of analysis, simulation and control. Most existent models in- cluding theoretical models and identification models are, however, inconvenient for direct analysis. In addition, many models pay much attention to the local details in the closed-circuit grinding process while overlooking the systematic behavior of the process as a whole. From the systematic perspective, the dynamic behavior of the whole closed-circuit grinding-classification process is consid- ered and a first-order transfer function model describing the dynamic relation between the raw material and the product is established. The model proves that the time constant of the closed-circuit process is lager than that of the open-circuit process and reveals how physical parameters affect the process dynamic behavior. These are very helpful to understand, design and control the closed-circuit grinding-classification process.展开更多
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.
文摘The prefrontal cortex (PFC) plays an important role in cognitive process related to executive function, but is also active during resting states. Quantifying prefrontal cortex activity during resting states provides a baseline for interpreting task-induced brain activity. Researchers commonly use resting conditions where participants are prompted to stare at a screen (eyes open) or close their eyes (eyes closed). Are these two conditions equivalent representations of a baseline resting state? Further, does prefrontal cortex activity during these conditions change as a function of development? The aim of this study was to examine differences in prefrontal cortex activity between eyes open and eyes closed conditions during resting states in children and adults to provide a rationale of proper selection of baseline condition in future research. Thirty-six participants in 3 age groups were recruited in this study including twenty-four adults, five 12 - 15 years old children, and seven 8 - 11 years old children. Relative changes in concentrations of oxygenated hemoglobin (Δoxy-Hb) and deoxygenated hemoglobin (Δdeoxy-Hb) were obtained by using functional Near-Infrared Spectroscopy (fNIRS) in eyes closed (EC) and eyes open (EO) conditions, 3 minutes each. Contrasts were tested to compare the differences of Δoxy-Hb and Δdeoxy-Hb between eyes open and eyes closed conditions. The EC condition had significantly higher Δoxy-Hb than EO when all groups were combined (t (17.268) = 3.021, p = .008, Cohen’s d = –0.72). When comparing Δoxy-Hb between eyes conditions within each group, the younger group had significantly higher Δoxy-Hb in EC than EO (t (9.459) = 2.734, p = 0.022, Cohen’s d = –1.46). Based on these results, the EO condition may be a better baseline condition, particularly in studies with younger children, since it has less activity in the PFC that could interfere with interpretations of task-induced activity.
基金the National Natural Science Foundation of China
文摘The purpose of this paper is to obtain a generalization of the famous Browder's fixed point theorem and some equivalent forms. As application, these results are utilized to study the existence problems of fixed points and nearest points.
基金This work was financially supported by the National Key Science-Technology Project during the Tenth Five-Year-Plan period of China under Grant No.2001BA609A and No.2004BA615A.
文摘Mathematical models of the grinding process are the basis of analysis, simulation and control. Most existent models in- cluding theoretical models and identification models are, however, inconvenient for direct analysis. In addition, many models pay much attention to the local details in the closed-circuit grinding process while overlooking the systematic behavior of the process as a whole. From the systematic perspective, the dynamic behavior of the whole closed-circuit grinding-classification process is consid- ered and a first-order transfer function model describing the dynamic relation between the raw material and the product is established. The model proves that the time constant of the closed-circuit process is lager than that of the open-circuit process and reveals how physical parameters affect the process dynamic behavior. These are very helpful to understand, design and control the closed-circuit grinding-classification process.
