http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
최성목(Sung Mok Choi),정원종(Wonjong Jung),김호영(Ho-Young Kim) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
The hygroscopic deformation of plant seeds plays a critical role in seed dispersal of some plants. Among various species of plant with hygroscopically active awns, Pelargonium species exhibit a relatively complicated deformation, i.e. helical coiling-uncoiling, which enables their seeds to burrow into the ground in response to the change of environmental humidity. The awn of Pelargonium is composed of a hygroscopically active inner layer and a hygroscopically inactive outer layer. The inner layer of the awn has a tilted microfibril arrangement along the plant cell which leads to cylindrical helix configuration. Using the mathematical framework of incompatible elasticity, we analyze the cylindrical helix configuration of the awn and compare the theoretical result with a deformation of a bi-layered strip system, consisting of a wet paper and a nonwettable polymer film. Our work can be used to design hygroscopically responsive micro-actuators capable of self-screwing without electrical supply.
정원종(Wonjong Jung),최성목(Sung Mok Choi),김정택(Jung Taek Kim),김원정(Wonjung Kim),김호영(Ho-Young Kim) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
We present the result of a combined experimental and theoretical investigation of granular drag reduction induced by rotation of self-burrowing seeds of Pelargonium species. The seed dispersal unit of Pelargonium has a hygroscopically responsive awn which reversibly coils and uncoils in response to the change in environmental humidity. When the awn tip is supported by an external object, the hygroscopic deformation of the awn gives the seed a thrust and rotation against the soil. Such coiling-uncoiling motion enables the seed to dig into the soil. We find that the rotation of the seed significantly reduces the granular drag, which greatly facilitates its self-burrowing. To elucidate and quantify such granular drag reduction, we experimentally measure the granular resistance for rotating intruders. We then develop a partial slip model that explains how the rotation of the seed extenuates the effective area where the granular hydrostatic pressure acts. Our work reveals that the rotation of the self-burrowing seed is essential to the survival and successful breeding.