For studying the anisotropie strange quark stars, we assume that the radial pressure inside an anisotropic star can be obtained simply by isotropie pressure plus an additional Gaussian term with three free parameters ...For studying the anisotropie strange quark stars, we assume that the radial pressure inside an anisotropic star can be obtained simply by isotropie pressure plus an additional Gaussian term with three free parameters （A, μ and X）. According to recent observations, a pulsar in a mass range of 1.97±0.04M has been measured. Hence, we take this opportunity to set the free parameters of our model. We fix X by applying boundary and stability conditions and then search the A - μ parameter space For a maximum mass range of 1.9M 〈 Mmax 〈 2.1M. Our results indicate that anisotropy increases the maximum mass M and also its corresponding radius R for a typical strange quark star. Furthermore, our model shows magnetic field and electric charge increase the anisotropy factor △. In fact, △ has a maximum on the surface and this maximum goes up in the presence of magnetic field and electric charge. Finally, we show that anisotropy can be more effective than either magnetic field or electric charge in raising maximum mass of strange quark stars.展开更多
Based on the turbulent convection model （TCM） of Li ＆ Yang, we have studied the characteristics of turbulent convection in the envelopes of 2 and 5M⊙ stars at the red giant branch and asymptotic giant branch phase...Based on the turbulent convection model （TCM） of Li ＆ Yang, we have studied the characteristics of turbulent convection in the envelopes of 2 and 5M⊙ stars at the red giant branch and asymptotic giant branch phases. The TCM has been successfully applied over the entire convective envelopes, including the convective unstable zone and the overshooting regions. We find that the convective motions become progressively stronger when the stellar models are located farther up along the Hayashi line. In the convective unstable zone, we find that the turbulent correlations are proportional to functions of a common factor （V - V^d）T, which explains similar distributions in those correlations. For the TCM we find that if the obtained stellar temperature structure is close to that of the mixing length theory （MLT）, the convective motion will have a much larger velocity and thus be more violent. However, if the turbulent velocity is adjusted to be close to that of the MLT, the superadiabatic convection zone would be much more extended inward, which would lead to a lower effective temperature of the stellar model. For the overshooting distance, we find that the e-folding lengths of the turbulent kinetic energy k in both the top and bottom overshooting regions decrease as the stellar model is progressively located farther up along the Hayashi line, but both the extents of the decrease are not obvious. The overshooting distances of the turbulent correlation /u＇rT＂ are almost the same for the different stellar models with the same set of TCM parameters. For the decay modes of the kinetic energy k, we find that they are very similar for different stellar models based on the same set of TCM parameters, and there is a nearly linear relationship between lg k and In P for different stellar models. When Cs or α increases while the other parameters are fixed, the obtained linearly decaying distance will become longer.展开更多
Traditional studies on integrated statistical process control and engineering process control (SPC-EPC) are based on linear autoregressive integrated moving average (ARIMA) time series models to describe the dynamic n...Traditional studies on integrated statistical process control and engineering process control (SPC-EPC) are based on linear autoregressive integrated moving average (ARIMA) time series models to describe the dynamic noise of the system.However,linear models sometimes are unable to model complex nonlinear autocorrelation.To solve this problem,this paper presents an integrated SPC-EPC method based on smooth transition autoregressive (STAR) time series model,and builds a minimum mean squared error (MMSE) controller as well as an integrated SPC-EPC control system.The performance of this method for checking the trend and sustained shift is analyzed.The simulation results indicate that this integrated SPC-EPC control method based on STAR model is effective in controlling complex nonlinear systems.展开更多
In this report we present the generalization of a solution to Einstein's equations with perfect fluid for the case of Einstein–Maxwell with perfect fluid.The effect of the charge is reflected by a parameter,ν,an...In this report we present the generalization of a solution to Einstein's equations with perfect fluid for the case of Einstein–Maxwell with perfect fluid.The effect of the charge is reflected by a parameter,ν,and its interval is determined by the positivity condition from the pressure in the interior of the star.It is shown that the solution is stable according to the Zeldovich criteria as well as in relation to the criteria of the adiabatic index.The compactness,u=GM/c^(2)R,of this charged model is greater than it is for the chargeless case as a result of the effect of the presence of the charge.This allows it to represent stars with a high compactness,in particular a graphic analysis is presented for the star SAX J1808.4-3658 with mass M=1.435M_(⊙)and radius R=7.07 km.From these data and employing the solution,we obtain that the total maximum charge for the star is Q=2.4085×10^(20)C.展开更多
Oscillations of the solar-like star HD 49933 have been thoroughly observed by CoRot. Two dozen frequency shifts, which are closely related to the change in magnetic activity, have been measured. To explore the effects...Oscillations of the solar-like star HD 49933 have been thoroughly observed by CoRot. Two dozen frequency shifts, which are closely related to the change in magnetic activity, have been measured. To explore the effects of magnetic activity on frequency shifts, we calculate frequency shifts for the radial and l=1 p-modes of HD 49933 with the general variational method, which evaluates the shifts using a spa- tial integral of the product of a kernel and some sources. The theoretical frequency shifts reproduce the observation well. The magnitudes and positions of the sources are determined according to a χ2 criterion. We predict the source that contributes to both the l = 0 and l= 1 modes is located 0.48 - 0.62 Mm below the surface of the star. In addition, based on the assumption that A0 is proportional to the change in the MglI activity index △iMgⅡ, we obtain that the change in MgⅡ index between the minimum and maximum of the cycle during the period of HD 49933 is about 0.665. The magnitude of the frequency shifts compared to the Sun already demonstrates that HD 49933 is much more active than the Sun, which is further confirmed in this pa- per. Furthermore, our calculation of the frequency shifts for l = 1 modes indicates the variation of turbulent velocity in the stellar convective zone may be an important source for the l = 1 shifts.展开更多
WANG Haizhen might have been a shy,quiet college student from Hebei Province,but all that changed when she recently wonthe "New Silk Road" Cup Chinese ModelContest held in Chengdu. Her previous pre-occupatio...WANG Haizhen might have been a shy,quiet college student from Hebei Province,but all that changed when she recently wonthe "New Silk Road" Cup Chinese ModelContest held in Chengdu. Her previous pre-occupation with designing ideal apartmentsfor the next century, while studying interiordesign has had to be put on hold as thecharming young mannequin navigates therunways that this win has opened up for her.展开更多
This study explores the spatial pattern of Historic Chinese Towns and Cities(HCTC)by using a syntactic approach.The HCTC is an important element of the built environment and exhibits a variety of unique spatial charac...This study explores the spatial pattern of Historic Chinese Towns and Cities(HCTC)by using a syntactic approach.The HCTC is an important element of the built environment and exhibits a variety of unique spatial characteristics.Although previous research has been focused on qualitative analysis,a quantitative approach to exploring this issue is scarce,leading to insufficient understanding of the spatial characteristics of HCTC.This study presents a quantitative approach to analyzing the spatial pattern of HCTC by utilizing the space syntax method.Four well-preserved historic towns were selected as case studies,each representing a typical spatial type of historic town in China.A series of mathematical measures from space syntax were used to explore the spatial characteristics of HCTC,facilitating expanded interpretation of traditional Chinese ideologies.Results contribute to a more critical understanding of the spatial pattern of HCTC.展开更多
文摘For studying the anisotropie strange quark stars, we assume that the radial pressure inside an anisotropic star can be obtained simply by isotropie pressure plus an additional Gaussian term with three free parameters （A, μ and X）. According to recent observations, a pulsar in a mass range of 1.97±0.04M has been measured. Hence, we take this opportunity to set the free parameters of our model. We fix X by applying boundary and stability conditions and then search the A - μ parameter space For a maximum mass range of 1.9M 〈 Mmax 〈 2.1M. Our results indicate that anisotropy increases the maximum mass M and also its corresponding radius R for a typical strange quark star. Furthermore, our model shows magnetic field and electric charge increase the anisotropy factor △. In fact, △ has a maximum on the surface and this maximum goes up in the presence of magnetic field and electric charge. Finally, we show that anisotropy can be more effective than either magnetic field or electric charge in raising maximum mass of strange quark stars.
基金Supported by the National Natural Science Foundation of China(Grant Nos. 10973035 and 10673030)the Knowledge Innovation Key Program of the Chinese Academy of Sciences under Grant No. KJCX2-YW-T24
文摘Based on the turbulent convection model （TCM） of Li ＆ Yang, we have studied the characteristics of turbulent convection in the envelopes of 2 and 5M⊙ stars at the red giant branch and asymptotic giant branch phases. The TCM has been successfully applied over the entire convective envelopes, including the convective unstable zone and the overshooting regions. We find that the convective motions become progressively stronger when the stellar models are located farther up along the Hayashi line. In the convective unstable zone, we find that the turbulent correlations are proportional to functions of a common factor （V - V^d）T, which explains similar distributions in those correlations. For the TCM we find that if the obtained stellar temperature structure is close to that of the mixing length theory （MLT）, the convective motion will have a much larger velocity and thus be more violent. However, if the turbulent velocity is adjusted to be close to that of the MLT, the superadiabatic convection zone would be much more extended inward, which would lead to a lower effective temperature of the stellar model. For the overshooting distance, we find that the e-folding lengths of the turbulent kinetic energy k in both the top and bottom overshooting regions decrease as the stellar model is progressively located farther up along the Hayashi line, but both the extents of the decrease are not obvious. The overshooting distances of the turbulent correlation /u＇rT＂ are almost the same for the different stellar models with the same set of TCM parameters. For the decay modes of the kinetic energy k, we find that they are very similar for different stellar models based on the same set of TCM parameters, and there is a nearly linear relationship between lg k and In P for different stellar models. When Cs or α increases while the other parameters are fixed, the obtained linearly decaying distance will become longer.
基金Supported by National Natural Science Foundation of China (No. 70931004)
文摘Traditional studies on integrated statistical process control and engineering process control (SPC-EPC) are based on linear autoregressive integrated moving average (ARIMA) time series models to describe the dynamic noise of the system.However,linear models sometimes are unable to model complex nonlinear autocorrelation.To solve this problem,this paper presents an integrated SPC-EPC method based on smooth transition autoregressive (STAR) time series model,and builds a minimum mean squared error (MMSE) controller as well as an integrated SPC-EPC control system.The performance of this method for checking the trend and sustained shift is analyzed.The simulation results indicate that this integrated SPC-EPC control method based on STAR model is effective in controlling complex nonlinear systems.
文摘In this report we present the generalization of a solution to Einstein's equations with perfect fluid for the case of Einstein–Maxwell with perfect fluid.The effect of the charge is reflected by a parameter,ν,and its interval is determined by the positivity condition from the pressure in the interior of the star.It is shown that the solution is stable according to the Zeldovich criteria as well as in relation to the criteria of the adiabatic index.The compactness,u=GM/c^(2)R,of this charged model is greater than it is for the chargeless case as a result of the effect of the presence of the charge.This allows it to represent stars with a high compactness,in particular a graphic analysis is presented for the star SAX J1808.4-3658 with mass M=1.435M_(⊙)and radius R=7.07 km.From these data and employing the solution,we obtain that the total maximum charge for the star is Q=2.4085×10^(20)C.
基金Supported by the National Natural Science Foundation of China
文摘Oscillations of the solar-like star HD 49933 have been thoroughly observed by CoRot. Two dozen frequency shifts, which are closely related to the change in magnetic activity, have been measured. To explore the effects of magnetic activity on frequency shifts, we calculate frequency shifts for the radial and l=1 p-modes of HD 49933 with the general variational method, which evaluates the shifts using a spa- tial integral of the product of a kernel and some sources. The theoretical frequency shifts reproduce the observation well. The magnitudes and positions of the sources are determined according to a χ2 criterion. We predict the source that contributes to both the l = 0 and l= 1 modes is located 0.48 - 0.62 Mm below the surface of the star. In addition, based on the assumption that A0 is proportional to the change in the MglI activity index △iMgⅡ, we obtain that the change in MgⅡ index between the minimum and maximum of the cycle during the period of HD 49933 is about 0.665. The magnitude of the frequency shifts compared to the Sun already demonstrates that HD 49933 is much more active than the Sun, which is further confirmed in this pa- per. Furthermore, our calculation of the frequency shifts for l = 1 modes indicates the variation of turbulent velocity in the stellar convective zone may be an important source for the l = 1 shifts.
文摘WANG Haizhen might have been a shy,quiet college student from Hebei Province,but all that changed when she recently wonthe "New Silk Road" Cup Chinese ModelContest held in Chengdu. Her previous pre-occupation with designing ideal apartmentsfor the next century, while studying interiordesign has had to be put on hold as thecharming young mannequin navigates therunways that this win has opened up for her.
文摘This study explores the spatial pattern of Historic Chinese Towns and Cities(HCTC)by using a syntactic approach.The HCTC is an important element of the built environment and exhibits a variety of unique spatial characteristics.Although previous research has been focused on qualitative analysis,a quantitative approach to exploring this issue is scarce,leading to insufficient understanding of the spatial characteristics of HCTC.This study presents a quantitative approach to analyzing the spatial pattern of HCTC by utilizing the space syntax method.Four well-preserved historic towns were selected as case studies,each representing a typical spatial type of historic town in China.A series of mathematical measures from space syntax were used to explore the spatial characteristics of HCTC,facilitating expanded interpretation of traditional Chinese ideologies.Results contribute to a more critical understanding of the spatial pattern of HCTC.
