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이덕규(Duck-Gyu Lee),정광훈(Kwang-Hun Jeong),안원진(Wonjin Ahn),김성호(Sung-Ho Kim),김호영(Ho-Young Kim) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
It is well known that the surface tension forces can make a particle denser than water float when the size of the particle is of the order of 1 mm. This is deeply related to the basic mechanism enabling small insects to wander around on the pond surface and also to a newly emerging technology of self-assembly using capillary forces. For the quantitative understanding of this effect, we experimentally study the maximum density of a cylinder that can float on water and how fast the cylinder sinks when the density exceeds the maximum value. We compare our experimental results with the theoretical prediction developed by our collaborative group and find a good agreement between them.
소금쟁이의 수면 위 도약을 위한 에너지에 과한 기본 연구
이덕규(Duck-Gyu Lee),김호영(Ho-Young Kim) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
In the previous research, it has been found that water strider’s legs are strongly water repellent due to hierarchical structure of hydrophobic setae on the legs. Here we propose an answer why they should be so hydrophobic by showing that the work required to remove a floating hydrophobic cylinder from an interface depends very sensitively on the contact angle of the cylinder: superhydrophobic cylinders require relatively little work to remove them from an interface. Also we experimentally study the work required to lift a leg out of water with different contact angles and compare our experimental results with a theoretical prediction.
이덕규 ( Duck Gyu Lee ),손승열 ( Seong Yeol Son ),최규호 ( Gyu Ho Choi ),고주영 ( Jooyoung Ko ),김현기 ( Hyenki Kim ) 한국정보처리학회 2017 한국정보처리학회 학술대회논문집 Vol.24 No.1
일반 시민들이 많이 이용하는 지하철의 안전에 관심이 많으나 안전사고도 끊이지 않고 있다. 그 대책으로 스크린도어가 설치되었지만 스크린도어 사망사고 및 오작동 사례가 적지 않게 야기되고 있다. 본 연구에서는 임베디드 시스템의 센서들을 이용하여 지하철 안전사고 예방을 위한 안전선 시스템을 설계 하였다. 초음파센서를 이용하여 사람이 접근함에 따라 LED 센서 및 부저 센서가 작동하여 상황의 위험성을 알려 안전사고를 예방하도록 설계하고 구현하였다.
이덕규(Duck-Gyu Lee),김호영(Ho-Young Kim) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
Although it is well-known that a water strider's legs are superhydrophobic, the reason for their strong water repellency is still a matter of debate. Floating cylindrical objects having the contact angle over 90 degrees are known to support similar maximum load regardless of the magnitude of contact angle, which discards the hypothesis of the role of superhydrophobicity in static floating. Here we show that the energy required to lift a water strider's cylindrical leg out of water strongly depends on the wettability. Our theory and experiments reveal that the energy saving achieved by the superhydrophobicity of the legs reaches over 90% compared with the legs with the contact angle of 90 degrees. This implies that a water strider can skate on and leap off water surface with a great ease owing to its legs' strong water repellency.
디지털날염용 고속 구동형 잉크젯 프린팅 헤드의 특성해석
이덕규 ( Duck-gyu Lee ),허신 ( Shin Hur ) 한국센서학회 2018 센서학회지 Vol.27 No.6
To develop a piezoelectric inkjet printhead for high-resolution and high-speed printing, we studied the characteristics of an inkjet printhead by analyzing the major design parameters. An analytical model for the inkjet printhead was established, and numerical analysis of the coupled first-order differential equation for the defined state variables was performed using state equations. To design the dimension of the inkjet printhead with a driving frequency of 100 kHz, the characteristics of the flow rate and discharge pressure of the nozzle were analyzed with respect to design variables of the flow chamber, effective sound wave velocity, driving voltage, and voltage waveform. It was predicted that the change in the height of the flow chamber does not significantly affect the Helmholtz resonance frequency and discharge speed of the nozzle. From the analysis of change in flow chamber width, it is observed that as the width of the flow chamber increases, the ejection speed greatly increases and the Helmholtz resonance frequency decreases considerably, thereby substantially affecting the performance of the inkjet printhead.
이덕규(Duck-Gyu Lee),김호영(Ho-Young Kim) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
We study the sinking of a dense sphere initially in contact with air-liquid interface and then released. The sinking motion is studied experimentally and agrees quantitatively with a simple hydrodynamic model of the process. Also the meniscus profile generated by the sinking sphere through a viscous liquid surface is theoretically investigated under the assumption of creeping flow, which is in good agreement with the shape of the meniscus from the experiment. In particular, a scaling law that predicts the final velocity of a sinking sphere straddled between the interface is established. This study can help us to understand the vertical sinking motion of a small and dense object through the viscous fluid interface.