为爱情而生的“滑翔冠军”

航海探险旅游,遭遇怪鸟袭击2002年1月1日,美国加州大学青年教师杰克和助手汤姆驾着租来的探险船从美国加州奥克兰港出发,前往夏威夷群岛旅游探险。当他们进入中途岛海域之时,突然在一个人迹罕至的海域里发现了一个植被茂密的小岛,这个小岛上居然有一个地方看上去平得像一条直线     

泥河湾古湖湖心区石片的发现

Nihewan basin is famous for its lacustrine deposits, animal fauna and occupied evidence of early humans. All of the discovered Palaeolithic sites are distributed along ancient lakeside or on the terraces of the Sangganhe river and its tributaries. However, the authors discovered a stone flake from the central part of the ancient Nihewan lake in an outcrop section on the right bank of the Sangganhe river. The location is 40°06′33″N and 114°20′15″E, near Jinerwa village, Yangyuan County, Heibei Province. The flake is basaltic and has a size of 4.5 cm×3.2 cm×1.7 cm. Its ventral surface is a fresh plane of fracture with a clear point of percussion,a bulb and a bulbar scar on it. The dorsal surface is composed of a residual part of a rounded pebble surface and a fresh plane formed along a joint. The flake is unearthed at 50.73 m under the lacustrine platform surface in perfectly laminated beds of Mid-Pleistocene. The feafures of the flake do not rule out the possibility of natural origin. But combined with the sedimentary features of the horizon where it is unearthed, the most reasonable explanation is that the flake may be the trace of ancient human activities on the frozen lake of Nihewan.     

不作经理作家教的留美博士

成都一位留美博士学成归来,放弃公司经理不做。毅然当起了一群人的家庭教师。他的学生中,年龄最小的仅几岁,最大的有60多岁……留美博士缘何要去做家教,他又是怎样施教的呢?     

基于改进CART算法的退役动力电池等级筛选方法

针对退役动力电池存在一致性差、等级筛选效率低的难题,提出了一种基于改进CART算法的退役动力电池等级筛选方法。首先,分析了传统CART算法的基本原理,为克服算法计算量大的缺陷,将Fayyad边界点判定定理与CART算法相结合,通过选取属性最优阈值点来减少计算量,提高分类效率;其次,基于代价复杂度后剪枝算法,采用交叉验证法对算法进行进一步优化;最后,将改进CART算法用于退役动力电池筛选分类,实验结果表明改进CART算法在保持较高准确率的情况下,可以有效提高退役动力电池的等级筛选效率。