随着西非海洋经济与港口建设的不断发展,对西非海域水动力特征,特别是波浪要素时空分布特征的认识显得愈加重要。基于欧洲中期天气预报中心(ECWMF) ERA-5再分析数据集中的42 a (1979-2020年)逐时波要素数据,对西非区域的混合浪、涌浪和...随着西非海洋经济与港口建设的不断发展,对西非海域水动力特征,特别是波浪要素时空分布特征的认识显得愈加重要。基于欧洲中期天气预报中心(ECWMF) ERA-5再分析数据集中的42 a (1979-2020年)逐时波要素数据,对西非区域的混合浪、涌浪和风浪的有效波高和周期的时空分布进行分析。该海域旱季和雨季的波要素特征具有显著区别。在空间分布上,西非海域的涌浪、混合浪有效波高由近岸向离岸处、低纬度向高纬度不断增大;混合浪以及涌浪的周期由中部区域向四周不断增大;风浪波高和周期在赤道以北,由南向北逐渐增大;赤道以南,由南向北先增大后减小。涌浪和混合浪的月度分布主要呈现3种特征,分别为月度变化较小的无峰值型以及月度变化明显的Ω形和倒Ω形。此外,通过波浪危险性分析,发现其危险性从西非海域中部近岸区域向离岸、从低纬度向高纬度逐渐增加,其中西非南部海域的危险性最高,佛得角北部海域的危险性次之。展开更多
The grey quasi-preferred analysis (GQPA) is one of important methods for realizing system analysis to conquer the limitations of the existing GQPA model, without any considerations to the difference of the different b...The grey quasi-preferred analysis (GQPA) is one of important methods for realizing system analysis to conquer the limitations of the existing GQPA model, without any considerations to the difference of the different behavioral factor′s importance. It could not be used to analyze the complex system with multi-hierarchy correlation factors, the weighted synthetic method for calculating abstract incidence degrees between the system beha-vioral characteristics and correlative factors in different hierarchies is given out,and the hierarchic grey quasi-preferred analysis (HGQPA) model is established. The effectiveness of the HGQPA model is tested by the scientific-technical system of Jiangsu Province. The depth and the range of the application of GQPA are developed, and the HGQPA model is regarded as a new approach to systemically analyze the complex systems with multi-hierarchy correlation factors.展开更多
Solar sail is used to achieve a geocentric sun-synchronous frozen orbit.This kind of orbit combines the characteristics of both sun-synchronous orbits and frozen orbits.Furthermore,the impossible orbits for a typical ...Solar sail is used to achieve a geocentric sun-synchronous frozen orbit.This kind of orbit combines the characteristics of both sun-synchronous orbits and frozen orbits.Furthermore,the impossible orbits for a typical spacecraft such as sun-synchronous orbits whose inclination is less than 90° are also possible for solar sail.To achieve a sun-synchronous frozen orbit,the characteristic acceleration of the sail is chosen properly.In addition,the attitude of the sail is adjusted to keep the sun-synchronous and frozen characteristics.The perturbations including atmosphere drag,third-body gravitational forces and shaded regions are discussed,where the atmosphere drag is cancelled by solar radiation pressure force,third-body gravitational forces have negligible effects on the orbit and the shaded region can be avoided by choosing the classical orbit elements of the sail.At last,a numerical example is employed to validate the sun-synchronous frozen characteristics of the sail.展开更多
文摘随着西非海洋经济与港口建设的不断发展,对西非海域水动力特征,特别是波浪要素时空分布特征的认识显得愈加重要。基于欧洲中期天气预报中心(ECWMF) ERA-5再分析数据集中的42 a (1979-2020年)逐时波要素数据,对西非区域的混合浪、涌浪和风浪的有效波高和周期的时空分布进行分析。该海域旱季和雨季的波要素特征具有显著区别。在空间分布上,西非海域的涌浪、混合浪有效波高由近岸向离岸处、低纬度向高纬度不断增大;混合浪以及涌浪的周期由中部区域向四周不断增大;风浪波高和周期在赤道以北,由南向北逐渐增大;赤道以南,由南向北先增大后减小。涌浪和混合浪的月度分布主要呈现3种特征,分别为月度变化较小的无峰值型以及月度变化明显的Ω形和倒Ω形。此外,通过波浪危险性分析,发现其危险性从西非海域中部近岸区域向离岸、从低纬度向高纬度逐渐增加,其中西非南部海域的危险性最高,佛得角北部海域的危险性次之。
文摘The grey quasi-preferred analysis (GQPA) is one of important methods for realizing system analysis to conquer the limitations of the existing GQPA model, without any considerations to the difference of the different behavioral factor′s importance. It could not be used to analyze the complex system with multi-hierarchy correlation factors, the weighted synthetic method for calculating abstract incidence degrees between the system beha-vioral characteristics and correlative factors in different hierarchies is given out,and the hierarchic grey quasi-preferred analysis (HGQPA) model is established. The effectiveness of the HGQPA model is tested by the scientific-technical system of Jiangsu Province. The depth and the range of the application of GQPA are developed, and the HGQPA model is regarded as a new approach to systemically analyze the complex systems with multi-hierarchy correlation factors.
基金supported by the National Natural Science Foundation of China (Grants Nos.10902056 and 10832004)State Key Lab of Astronautical Dynamics of China (Grant No. 2011ADL-DW0201)
文摘Solar sail is used to achieve a geocentric sun-synchronous frozen orbit.This kind of orbit combines the characteristics of both sun-synchronous orbits and frozen orbits.Furthermore,the impossible orbits for a typical spacecraft such as sun-synchronous orbits whose inclination is less than 90° are also possible for solar sail.To achieve a sun-synchronous frozen orbit,the characteristic acceleration of the sail is chosen properly.In addition,the attitude of the sail is adjusted to keep the sun-synchronous and frozen characteristics.The perturbations including atmosphere drag,third-body gravitational forces and shaded regions are discussed,where the atmosphere drag is cancelled by solar radiation pressure force,third-body gravitational forces have negligible effects on the orbit and the shaded region can be avoided by choosing the classical orbit elements of the sail.At last,a numerical example is employed to validate the sun-synchronous frozen characteristics of the sail.
