The modeling method is an effective means of estimating causality as well as examining cycle pedaling efficiency. Pedaling efficiency can also be examined by an experimental method, but the experimental method can lead to contradictory results due to perturbation of the measured output parameters. Experimental studies generally yield realistic results, but it is difficult to control for all the variables of interest and to determine the causal relationships between them. The objective of this study is to investigate the pedaling efficiency and causality with considering saddle position and pedaling cadence as variables. Based on the mathematical pedaling modeling, the internal work calculation method was used to calculate the consumed mechanical energy and energy conservation percentage ([Formula: see text]). The optimal saddle position with the lowest mechanical energy and the highest energy conservation percentage could be changed by the cadence. At the low cadence, the higher saddle position, and the shorter horizontal distance between the saddle and crankshaft led to higher pedaling efficiency ( h: 0.95 m, d: 0.16 m, and knee angle: [Formula: see text]). However, the highest pedaling efficiency was achieved at the high cadence with a saddle height ( h) of 0.9 m and a horizontal distance between the saddle and the crankshaft ( d) of 0.06 m (knee angle: [Formula: see text]). The lowest cadence is the optimal cadence in terms of the consumed energy, but the optimal cadence was 90 r/min in terms of the energy conservation percentage. Compared to the energy consumption, the energy conservation percentage was demonstrated to influence the fatigue of a cycle rider more critically. The energy conservation percentage was highest at 90 r/min, and 90 r/min was close to the preferred cadence by the cyclist.
The main purpose of this paper was to find out the background of Ŭmnu’s pludering of North Okchŏ. For this, it analyzed Ŭmnu people’s ethnicity and bellicosity described in “Biographies of Dongyi (東夷傳)” of Sanguozhi, and compared them with archaeological evidences. According to these records, the plundering could be characterized as periodical and had economic purpose, which indicates a driver within Ŭmnu’s society that turned the people into looters around the third century. Furthermore, in regard to this topic, the paper also sought the process that formed the ethnic recognition of Ŭmnu in the Biography. It suggested that the ethnicity in the book was the mixture of the information from Wei's expeditionary force, who contacted its tribes in coastal region of East Sea in the middle of the 3rd century, and the perception of Puyŏ, who had subjugated and governed Ŭmnu for a long time.
Also, this paper examined the correspondence between the records about Ŭmnu’s plundering and the characteristics of various cultural groups in this area through archaeological data. Accordingly, it can be said that the Poltse culture of Maritime Province was the most correspond to the culture of the looters who plundered North Okchŏ. This periodical pillages from Ŭmnu was strongly related to the widespread social change within the Poltse culture around the third century. During this period, there was armed struggles among the tribes of Ŭmnu, while their traditional trade route via Puyŏ was diminished after they broke away from their neighbor faction’s subjugation. As a result, large-scale polities such as the polity in Fenglin culture emerged. However, on the other hand, while it forced some tribes that lost in the competition to take refuges to the other areas, this armed competition induced the other tribes to plundering the neighbouring cultures.
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