• Journal of the Korean Geographical Society
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• v.32 no.1
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• pp.47-68
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• 1997

The purpose of this study is to clarify both the characteristics of the spatial variations and structure and the logic of spatial differentiation of the renter farming in Korea. The renter farming has transformed its spatial structure from zonal to Thunen's rings-like pattern. This study also suggests that the spatial characteristics of the renter farming has been changed from the ecological and the tenantable to the economical and commercial. Although there is no single logic full explanation the order of such spatial differentiations, the logic of industrialization or neoclassical economics seems to be most effective.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.12
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• pp.1301-1307
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• 2011

Electrosurgical knee wand (EKW) is a high-frequency thermocautery instrument and is often used for coagulation, ablation, excision, and extirpation of knee ligaments and tissues. In order to maximize the success rate, ease, and safety of knee surgery using EKW and radiofrequency ablation, it is necessary to ensure that the EKW selectively approaches the lesion with utmost accuracy and safety. The key feature of this instrument is its excellent maneuverability. Hence, the authors constructed a tensile spring model based on a shape memory alloy (SMA), which exhibits the shape memory effect. This model can be used in knee surgery as it is considered the most biocompatible femorotibial surgical actuator. The changes in external temperature with current and the thermoelectric characteristics of the SMA were investigated. The relationship between the restoring force and the typical stroke (TS) in response to the conditions in the SMA tensile spring design were evaluated. In conclusion, as the diameter of the SMA tensile spring decreased, the maximum temperature increased. The strain in the actuator caused a stable and proportional increase in the force and induced current for up to 15s, but this increase became very unstable after 30s. Moreover, the relationship between the current and the TS was more stable than that between the current and the restoring force.