分段函数的初等性及其初等表达式

本文对两类分段函数的初等性进行了证明,并给出了将其表示成初等表达式的构造公式。

第十五批天文学名词的推荐译名

中国天文学会名词审定委员会从1985年开始在《天文学进展》发表天文学名词的推荐译名,到2007年已公布了14批2280个名词。现再推荐第十五批151个名词,其中大多数是近年来出现的天文学新词。希望读者在试用过程中对译名提出改进意见。

Impacts of Land Use and Cover Change on Land Surface Temperature in the Zhujiang Delta

Remote sensing and geographic information systems (GIS) technologies were used to detect land use/cover changes (LUCC) and to assess their impacts on land surface temperature (LST) in the Zhujiang Delta. Multi-temporal Landsat TM and Landsat ETM+ data were employed to identify patterns of LUCC as well as to quantify urban expansion and the associated decrease of vegetation cover. The thermal infrared bands of the data were used to retrieve LST. The results revealed a strong and uneven urban growth,which caused LST to raise 4.56℃in the newly urbanized part of the study area. Overall, remote sensing and GIS technologies were effective approaches for monitoring and analyzing urban growth patterns and evaluating their impacts on LST.

土星妈妈的孩子们

土星围绕着太阳运转,就像是太阳的孩子一样,跟太阳有着扯不断的引力关系。论质量,土星是太阳系的第二大行星。作为行星,土星也有很多的儿女,那就是它的卫星,土星的卫星也在围绕着土星运行。 土星妈妈也有调皮的孩子 一般而言,孩子总会跟妈妈的步调一致，所以行星的卫星在围绕行星运行的时候，运行的方向跟行星绕太阳的转动方向一致，这种情况被称为顺行。

Jupiter Moon May Have a Salt-Water Ocean

上帝若有知,也应为人类探索宇宙空间的努力而感动。遥望夜空,星汉灿烂。好像地球在宇宙间并不孤独,然而,当要寻觅外星朋友时,人类便怅然若失!NASA,(美国)国家航空和航天局的伽里略号太空船发回的数据显示:木星最大的卫星,Ganymede(土卫三), may possess a huge salt-water ocean beneath its crusty(有硬壳的)surface. 本文末句发人深省:...but the issue of whether it's there is different than the issue of whether you can expect to see it clearly in the data. 此言初读有些难,再读,便为科学家的求实精神所染。