The development of GPS （global positioning system） receiver now can be integrated on a smartphone. GPS receiver on smartphones has been developed for location-based applications. Smartphones are very suitable to be ...The development of GPS （global positioning system） receiver now can be integrated on a smartphone. GPS receiver on smartphones has been developed for location-based applications. Smartphones are very suitable to be used as an experimental tool, because smartphones are usually equipped with various types of sensors. This paper proposes a model observation vehicle speed on a road section based on the GPS data on the smartphone. Observations made by calculating the speed of the speed of vehicles moving through the data transfer at the GPS location of the smartphone, the data are then sent periodically to the server and server processing and storage of vehicle speed data. After tested with test reliability indicators use RMSE, observations with model observations speed, speed based on GPS data on a smartphone are relevant when compared with the speed directly from the vehicle＇s speedometer with the difference between the value of the difference of speed that is 3.1785 km/h.展开更多
We propose a new type of dark energy （DE） model, in which the equation of state of DE wae is a simple function of the fractional energy density Ωde instead of the redshift z. We assume three DE models of this type,...We propose a new type of dark energy （DE） model, in which the equation of state of DE wae is a simple function of the fractional energy density Ωde instead of the redshift z. We assume three DE models of this type, and fit them with present observations to get constraints of DE, which are also compared with the CPL model. It is shown that a suitable wda,（Ωde） model can give smaller X2 or smaller errors of wde than that of the CPL model. This new type of DE model can help to study the essential properties and nature of DE.展开更多
Taiji,a space-based gravitational-wave observatory,consists of three satellites forming an equilateral triangle with arm length of 3×10^6 km,orbiting around the Sun.Taiji is able to observe the gravitationalwave ...Taiji,a space-based gravitational-wave observatory,consists of three satellites forming an equilateral triangle with arm length of 3×10^6 km,orbiting around the Sun.Taiji is able to observe the gravitationalwave standard siren events of massive black hole binary(MBHB)merger,which is helpful in probing the expansion of the universe.In this paper,we preliminarily forecast the capability of Taiji for improving cosmological parameter estimation with the gravitational-wave standard siren data.We simulate fiveyear standard siren data based on three fiducial cosmological models and three models of MBHB’s formation and growth.It is found that the standard siren data from Taiji can effectively break the cosmological parameter degeneracies generated by the cosmic microwave background(CMB)anisotropies data,especially for dynamical dark energy models.The constraints on cosmological parameters are significantly improved by the data combination CMB+Taiji,compared to the CMB data alone.Compared to the current optical cosmological observations,Taiji can still provide help in improving the cosmological parameter estimation to some extent.In addition,we consider an ideal scenario to investigate the potential of Taiji on constraining cosmological parameters.We conclude that the standard sirens of MBHB from Taiji will become a powerful cosmological probe in the future.展开更多
文摘The development of GPS （global positioning system） receiver now can be integrated on a smartphone. GPS receiver on smartphones has been developed for location-based applications. Smartphones are very suitable to be used as an experimental tool, because smartphones are usually equipped with various types of sensors. This paper proposes a model observation vehicle speed on a road section based on the GPS data on the smartphone. Observations made by calculating the speed of the speed of vehicles moving through the data transfer at the GPS location of the smartphone, the data are then sent periodically to the server and server processing and storage of vehicle speed data. After tested with test reliability indicators use RMSE, observations with model observations speed, speed based on GPS data on a smartphone are relevant when compared with the speed directly from the vehicle＇s speedometer with the difference between the value of the difference of speed that is 3.1785 km/h.
基金Supported in part by the National Natural Science Foundation of China under Grant No. 11147186Zhejiang Provincial Natural Science Foundation of China under Grant No. LQ12A05004 and Grant from Hangzhou Normal University
文摘We propose a new type of dark energy （DE） model, in which the equation of state of DE wae is a simple function of the fractional energy density Ωde instead of the redshift z. We assume three DE models of this type, and fit them with present observations to get constraints of DE, which are also compared with the CPL model. It is shown that a suitable wda,（Ωde） model can give smaller X2 or smaller errors of wde than that of the CPL model. This new type of DE model can help to study the essential properties and nature of DE.
基金the National Natural Science Foundation of China(11975072,11690021,11875102,and 11835009)the National Program for Support of Top-Notch Young Professionals+1 种基金the Liaoning Revitalization Talents Program(XLYC1905011)the Fundamental Research Funds for the Central Universities(N2005030)。
文摘Taiji,a space-based gravitational-wave observatory,consists of three satellites forming an equilateral triangle with arm length of 3×10^6 km,orbiting around the Sun.Taiji is able to observe the gravitationalwave standard siren events of massive black hole binary(MBHB)merger,which is helpful in probing the expansion of the universe.In this paper,we preliminarily forecast the capability of Taiji for improving cosmological parameter estimation with the gravitational-wave standard siren data.We simulate fiveyear standard siren data based on three fiducial cosmological models and three models of MBHB’s formation and growth.It is found that the standard siren data from Taiji can effectively break the cosmological parameter degeneracies generated by the cosmic microwave background(CMB)anisotropies data,especially for dynamical dark energy models.The constraints on cosmological parameters are significantly improved by the data combination CMB+Taiji,compared to the CMB data alone.Compared to the current optical cosmological observations,Taiji can still provide help in improving the cosmological parameter estimation to some extent.In addition,we consider an ideal scenario to investigate the potential of Taiji on constraining cosmological parameters.We conclude that the standard sirens of MBHB from Taiji will become a powerful cosmological probe in the future.
