929早场放狗【输血 月度 坐稳】

Pamozu

bzy! 发表于 2019-9-30 07:57
是原文吗？

SCIENTIFIC AMERICAN JANUARY 2007

应该是的！这样看下来GMAC的缩文功力不是盖的 那个举例星球叫Eris不是Eric哈哈
大佬太强了！是怎么找的！

billyisfragile!

Pamozu 发表于 2019-9-30 08:23
应该是的！这样看下来GMAC的缩文功力不是盖的 那个举例星球叫Eris不是Eric哈哈
大佬太强了！是怎么找的！ ...

JOURNAL ARTICLE
WHAT IS A PLANET?
Steven Soter
Scientific American
Vol. 296, No. 1 (JANUARY 2007), pp. 34-41
Published by: Scientific American, a division of Nature America, Inc.
https://www.jstor.org/stable/26069112
Page Count: 8

p3 详细讲了新的definition 可以让Pluto和Eric不符合成为planet  然后好像definition有2个条件 有一个写到5000啥啥 (这里认真看 有题 构筑没理清楚)

The discovery in 2005 of Eris (formerly known as 2003 UB313 or Xena),  a KBO even larger than Pluto, brought  the issue to a head. If Pluto is a planet, then Eris must also be one, together with scores of other large KBOs; conversely, if Pluto is not a planet, neither are the other KBOs. On what objective  grounds could astronomers decide?

In short, the difference between planets and nonplanets is quantifiable, both in theory and by observation. All the planets in our solar system have  enough mass to have swept up or scattered away most of the original planetesimals from their orbital zones. Today each planet contains at least 5,000 times more mass than all the debris in its vicinity. In contrast, the asteroids, comets  and KBOs, including Pluto, live amid swarms of comparable bodies.

billyisfragile!

是原文吗？

SCIENTIFIC AMERICAN
June 2007
Volume 296, Issue 6

Restoring America's Big, Wild Animals
Pleistocene rewilding—a proposal to bring back animals that disappeared from North America 13,000 years ago—offers an optimistic agenda for 21st-century conservation


Rubenstein and colleagues go on to say, “Modern day proxies species are wrong ... different genetically from the species that occurred in North America during the Pleistocene.” True, but not that different. Available evidence  indicates that the lions in Africa and Asia today are the same species, albeit of smaller stature, as the lions that prowled North America 13 millennia ago. Recent studies of ancient DNA have elucidated close relationships between extinct elephant and horse species and those alive today. Further, introduction of  proxies for now extinct species has proved successful in other experiments. Hundreds of peregrine falcons from Australia, Europe and South America were used, for example, in captive-breeding programs to reintroduce the peregrine falcon to parts of the U.S. and Canada where DDT had wiped it out. Those birds were certainly different genetically from the ones that once soared over the Midwest, yet they have done well in their new homes.

Pamozu

bzy! 发表于 2019-9-30 09:07
是原文吗？

SCIENTIFIC AMERICAN

没错！！！太强了！多回忆一些有益找原文啊哈哈 会不会好几篇都出自07年scientific American

Sarah_cah

Pamozu 发表于 2019-9-29 13:09
第一题我怕说错hhh不敢确定！
第三题我算出来x=3、x=15、x=-9
第四题我觉得你说的有道理！看看大家再讨论 ...

第四题1/8没错

Pamozu

Sarah_cah 发表于 2019-10-1 02:06
第四题1/8没错

哈哈 好哒！

yyq12366

感谢分享！               

维维维

感谢分享！               

尝煮酒

aizheyou 发表于 2019-9-29 13:25
5 【PS】问n个连续的数相加等于52 n=?
求问第5题的思路啊。。。怎么算

我是这样算的..感觉还是比较麻烦的
假设首项为a，则最后一项为a+n-1
sn=[（2a+n-1）*n]/2=52
(n+2a-1)*n=104=13*2^3
因为2a-1是奇数，所以两个一定一奇一偶
所以一个因子是13，另外一个是8
而n+2a-1要大于n
所以n=8
（同时我们也可知a=3，即这项数列从3开始到10结束）

sophieandhercat

aizheyou 发表于 2019-9-29 13:25
5 【PS】问n个连续的数相加等于52 n=?
求问第5题的思路啊。。。怎么算

我觉得可以把52拆成13*4 然后就有4组13，分别拆成6+7 5+8 4+9 3+10 就好啦！所以是8个