Cross‐Country Skiing

The purpose was to study the adaptation to speed in the temporal patterns of the movement cycle and determine any differences in velocity, cycle rate and cycle length at the maximum speed level in the different classical style and freestyle cross‐country skiing techniques. Eight skilled male cross‐country skiers were filmed with a digital video camera in the sagittal plane while skiing on a flat cross‐country ski track. The skiers performed three classical style techniques the diagonal stride, kick double poling and the double poling technique and four freestyle techniques paddle dance (gear 2), double dance (gear 3), single dance (gear 4) and combiskate (gear 5) at four different self‐selected speed levels slow, medium, fast and their maximum. Cycle duration, cycle rate, cycle length, and relative and absolute cycle phase duration of the different techniques at the different speed levels were analysed by means of a video analysis system. The cycle rate in all tested classical and freestyle techniques was found to increase significantly (p < .01) with speed from slow to maximum. Simultaneously, there was a significant decrease in the absolute phase durations of all the investigated skiing techniques. A minor, not significant, change in cycle length, and the significant increase in cycle rate with speed showed that the classical and freestyle cross‐country skiing styles are dependent, to a large extent, on an increase in cycle rate for speed adaptation. A striking finding was the constant relative phase duration with speed, which indicates a simplified neural control of the speed adaptation in both cross‐country skiing styles. For the practitioner, the knowledge about the importance of increasing cycle frequency rather than cycle length in the speed adaptation can be used to optimise a rapid increase in speed. The knowledge about the decrease in absolute phase duration, especially the thrust phase duration, points to the need for strength and technique training to enable force production at a high cycle rate and skiing speed. The knowledge that the relative phase duration stays constant with speed may be used to simplify the learning of the different cross‐country skiing techniques.     

模糊对象和模糊性的逻辑

本文最初写于2001年,旨在探究语言上的、概念上的与本体论中的模糊性问题.文章始于这样一个问题,即模糊性仅仅是一个词的特征,抑或它也是我们的概念的特征,甚或是实在的特征?其中主要的关注点在于模糊对象的问题和相关的模糊同一性的问题.本文首先论证,即便模糊概念总可以得到进一步澄清,每个概念工具也必定是模糊的.其次,本文认为,如果不仅仅是词语,而且这些词语所表达的概念也是模糊的,那么可以论证,对象也必定是模糊的.第三,那种认为模糊对象必定具有模糊的同一性的思路是一种误解.最后一点尤为重要,因为对于模糊对象的抵制部分就来自于下述观念,即这种对象是不可能的,因为它们不遵守逻辑的同一律.本文也论述了,通过放弃二值原则以使得模糊陈述具有真和假之间的某个值或根本就没有真值的办法,也无助于解决模糊性问题,而且恰恰会造成相反的情况,即妨碍我们找到问题的解决之道.本文表明,在为真和既不真又不假之间,难以清晰地划分界限,正如在模糊的情形下要在真和假之间划界一样困难.本文的方法是利用量化模态逻辑的框架和语义学来处理这些问题.基于哥德尔模式的模态逻辑系统T,本文提出了一种关于清晰性和模糊性的量化逻辑,其中利用清晰性算子来代替必然性算子.文章还进一步讨论了模糊性和概念工具的发展之间的关联.