                            

                          ϵAb
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        1 ԰Ի㡢׻ܺȵڻ20cmʱAb=1.0
        2 ԻõڻС15cmʯ㡢
            ʯʯʱAb=1.0
        3 Ի㡢׻Ab=1.6
        4 Իȴ15cm׻ΪԲʱAb=1.6
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      ע⣺ݼ淶P44,涨ƲȡֵΧΪ[1,1.6]
            (·ṹ·ṹ֮ʱAbɲֵ)
