Development of maximal oxygen uptake in young elite male cross-country skiers: a longitudinal study.

The aim of this study was to investigate the effects of extensive endurance training (15-25 h per week) on the development of maximal oxygen uptake (VO2 max) in boys from puberty. Maximal oxygen uptake was measured a number of times each year from the age of puberty and for the next 6-9 years in seven young male elite cross-country skiers. Mean VO2 max was measured as 76.3 and 80.1 ml kg-1 min-1 at the ages of 14 and 15 years respectively. Despite the fast rate of growth during puberty, maximal aerobic power showed seasonal variations from the age of 14, reaching a plateau at the age of 15, whereas VO2 max (ml kg-2/3 min-1) increased continuously. It is concluded that, during puberty, boys probably attain significant increases in VO2 max when appropriate amounts of endurance training are undertaken.     

Constructivisms and Relativisms: A Shopper‘s Guide

Diverse forms of constructivism can be found in the literature today. They exhibit a commonality regarding certain classical positions that they oppose - a unity in their negative identities - but a sometimes wild multiplicity and incompatibility regarding the positive proposals that they put forward. In particular, some constructivisms propose an epistemological idealism, with a concomitant relativism, while others are explicitly opposed to such positions, and move in multifarious different directions. This is a potentially confusing situation, and has resulted in some critics branding all constructivisms with the charge of relativism, and throwing out the baby with the bath water. In addition, since the epistemological foundations of even non-relativist constructivisms are not as familiar as the classical positions, there is a risk of mis-interpretation of constructivisms and their consequences, even by some who endorse them, not to mention those who criticize. Because I urge that some version of constructivism is an epistemological necessity, this situation strikes me as seriously unfortunate for philosophy, and potentially dangerous for the practice of education.     

Alternative technologies and social studies textbooks

In order to determine the potential of alternative technologies in social studies education, we must understand the goals of such education, the capabilities of the technologies, and teachers’ and students’ responses to new technologies. The author suggests that the new technologies can contribute to the goals of learning about the past, learning about democratic life and institutions, and making students knowledgeable as consumers and producers of information. One major obstacle is a lack of time and money for teachers to experiment with the technologies. Stephen T. Kerr is professor of education in the College of Education at the University of Washington. His research focuses on the application of new technologies in schools and other educational environments, and particularly on the ways in which technology affects the social structure (roles and expectations, instructional patterns, organization) of those institutions. He has done work on human-computer interaction, as well as on how new communication technologies have changed the educational system of the former USSR.     

三维影相的新算法——修正的直接线性变换

通过引入摄影机镜头的内、外方位元素的约束条件,导出了一种修正的DLT(MDLT)方法。该方法用于影片和录相的实测,得到一些有意义的结果。当测量的标定控制点点数较少(6～8个),且这些点的位置在空间和成像面分布不均匀时,用MDLT计算的结果比DLT的结果要好,误差可降低80％以上。