格林天文時 的英文怎麼說
中文拼音 [gélīntiānwénshí]
格林天文時
英文
greenwich astronomical time-
The prime meridian, which runs through greenwich in south - east london, became the basis for the world ' s time keeping in 1884 after the first astronomer royal, john flamstead, calculated that the earth rotated on its axis once every 24 hours
1884年，首位皇家天文學家約翰法蘭姆斯坦算出地球每隔24小時繞軸自轉1次，使得通過倫敦東南格林威治的本初子午線成為全球計時基準。Greenwich mean time would become an " irrelevance " if proposals to redefine how time is measured are accepted, an historian at the royal observatory greenwich, uk, has warned
英國格林威治天文臺1位歷史學家警告，重新界定計時方式的提案如果獲得接受，格林威治標準時間將變得「永無意義」 。Green " s theorem is employed to find the quantity relationship among the constraints of heating rate, dynamic pressure and lift in reentry flight. the paper deduced the approximate solution of the optimal aeroassisted coplanar trajectories under the three typical constraints. the performance index to be minimized are either heat input, the total dynamic pressure, time during the atmospheric flight, the time integral of the square of the path inclination ; or maximize the time of flight during the atmospheric portion of the trajetory. an important conclusion is firstly obtained : under the three constraints above, the optimal aeroassisted coplanar transfers with the first forth kinds payoffs have the same optimal control laws
採用格林函數法，給出了同一平面氣動力輔助變軌飛行的3種過程約束（氣動加熱率、動壓、升力約束）條件之間關系的近似定量描述形成的飛行包絡線.由此求解了航天器同時受3種約束條件時，各種性能指標下的同一平面氣動力輔助變軌軌跡的近似解及相應的最優控制規律.文中對近似解與控制規律的內部結構作了細致的分析，得到了一些有益的結論
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