• Journal of computational fluids engineering
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• v.21 no.4
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• pp.90-95
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• 2016

Leidenfrost drops with ellipsoidal shaping can control the bouncing height by adjusting the aspect ratio(AR) of the shape at the moment of impact. In this work, we focus on the effect of the AR and the impact Weber number(We) on the non-axisymmetrical spreading dynamics of the drop, which plays an important role in the control of bouncing. To understand the impact dynamics, the numerical simulation is conducted for the ellipsoidal drop impact upon the perfect non-wetting solid surface by using volume of fluid method, which shows the characteristics of the spreading behavior in each principal axis. As the AR increases, the drop has a high degree of the alignment into one principal axis, which leads to the consequent suppression of bouncing height with shape oscillation. As the We increases, the maximum spreading diameters in the principal axes both increase whereas the contact time on the solid surface rarely depends on the impact velocity at the same AR. The comprehensive understanding of the ellipsoidal drop impact upon non-wetting surface will provide the way to control of drop deposition in applications, such as surface cleaning and spray cooling.

• Journal of Chest Surgery
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• v.34 no.2
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• pp.176-179
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• 2001

이차성 대동맥장루는 아주 드물며 대동맥-장골동맥의 재건수술의 중대한 합병증으로 발생할 수 있다. 이 질환은 진성 대동맥장루와 paraprosthetic enteric fistula 로 분류할 수 있다. 이러한 합병증의 예방, 진단 및 치료는 추구해야할 문제로 되어 있다. 염증성 가성동맥류로 복부대동맥 및 장골동맥을 인조혈관으로 치환한 후 41개월에 내시경으로 Paraprosthetic enteric Fistula로 진단되어 수술을 시행한 39세 남자환자를 치험하였기에 보고한다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.1
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• pp.86-92
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• 2012

The well-used actuators for the attitude control of spacecrafts are thruster, reaction wheel, control moment gyroscope, and magnetic torquer. Among them, the control moment gyroscope(CMG) which generates the torque based on the gyroscopic principle in physics, has an advantage of the high torque output compared to the low power consumption. This paper introduces an outline of CMG hardware technology, its application history in spacecrafts, and their associated hardware characteristics. Moreover, its spin-off cases to the other industrial fields such as ship, robotics, and MEMS including their research trend are provided.

• Korean Journal of Applied Biomechanics
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• v.14 no.2
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• pp.139-152
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• 2004

Two subjects, an expert and a novice, were carefully selected based upon their foot speed. Three dimensional videography was used in the assessment of roundhouse kicking of the Tae-kwon-Do. The local reference frames were imbedded at the trunk, pelvis, thigh and shank. Anatomical angular displacement at the joints were measured by projecting the upper segment's local axes to the lower segment's local reference planes. The local axes again projected to the global reference frames and absolved each segment's movement. The peaks of the anatomical angular displacement curve assessed as the countermovements and the angular movements of the segments in the global space absolved in light of the occurrence of the countermovements. The expert showed larger and more countermovements than the novice at the all segments. The counterrnovement occured more clearly at the trunk than the hip and knee joint and during the preparative movement phase. These countermovements occurrence were due to either by turning upper or lower segments and controlled by the turning direction and sequence of the two nearby segments. It was revealed that the countermovements of the trunk during the preparative movement phase was the important factor of the power kicking.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.6
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• pp.520-527
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• 2013

In this paper, a joint cell grouping and user association technique proposed for a semi-dynamic grouped network MIMO in a clustered heterogeneous cellular network (HCN). With the conventional macro BSs, small cells are being overlaid to increase a spectral efficiency per area and these small cells are expected to be concentrated to support exponentially increasing data traffic in hot spot areas. The main culprits of performance degradation in the clustered HCN are interference and load imbalance. The proposed scheme jointly handles them to maximize a proportional-fair metric. It is shown that the proposed technique can largely improve user average rate and proportional fairness among users than any other conventional schemes in the clustered HCN.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.7
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• pp.417-422
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• 2017

A high-performing photoelectric device was realized for the $MoS_2$-embedded Si device. $MoS_2$-coating was performed by an available large-scale sputtering method. The $MoS_2$-layer coating on the p-Si spontaneously provides the rectifying current flow with a significant rectifying ratio of 617. Moreover, the highly optical transmittance of the $MoS_2$-layer provides over 80% transmittance for broad wavelengths. The $MoS_2$-embedded Si photodetector shows the sensitive photo-response for middle and long-wavelength photons due to the functional $MoS_2$-layer, which resolves the conventional limit of Si for long wavelength detection. The functional design of $MoS_2$-layer would provide a promising route for enhanced photoelectric devices, including photovoltaic cells and photodetectors.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.6
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• pp.526-531
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• 2012

This paper, we describe the vector control of surface mounted PMSM (Permanent Magnet Synchronous Motor) using the fuzzy controller which is suggested algorithm. In these days, when vehicle is operated or not, whether the road is covered or not, the sensitivity of the steering column is not stable. To make up for it, the PI gain of a steering column controller is adjusted by experience. It becomes the price because it need a lot of sensor. Also it is difficult to implement robust control because we need a lot of parameters for variable road conditions which are the off road, the on road, a low battery voltage, a high battery voltage, a vehicle speed. In this paper, we propose fuzzy controller using the suggested algorithm which suitable for steering system. We test the fuzzy controller with the various condition. We get the good performance of fuzzy controller even if it is nonlinear system. We check a robust the fuzzy controller using the suggested algorithm.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.7
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• pp.445-448
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• 2016

Transparent UV photodetector was achieved by using wide bandgap metal oxide materials. In order to realize transparent heterojunction UV photodetector, n-type ZnO and p-type NiO metal oxide materials were employed. High light-absorbing SnS layer was inserted into the n-ZnO and p-NiO layers. High-performing UV photodetector was realized by ZnO/SnS/NiO/ITO structures to provide extremely fast response times (Fall time: $7{\mu}s$ and rise time: $13{\mu}s$) and high rectifying ratio. The use of functional SnS-embedded photodetector would provide a route for high functional photoelectric devices.

• Science of Emotion and Sensibility
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• v.9 no.4
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• pp.385-394
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• 2006

In the present society where aesthetic designs would have product value, designs must be the ones that add flexible sensation as well as the energy of counteraction which escapes from and destroys existing concept. The 'creative expression' to reach such design objectives is one of the most important abilities which designers must possess and is an overall concept in problem solving of designing which participates in formative approach or image development as well as product concepts such as function or performance . In this research, the definition of creativity, environmental change of designing, conditions designers must possess followed by these things and creative design expressions researched in the past, etc are examined and by presenting design method for creative designing concept targeting mobile phones, it will attempt to contribute in the importance of creativity and improve creative value of designers.

• Journal of the Korean Society of Visualization
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• v.10 no.1
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• pp.21-26
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• 2012

Hydrophobic characteristics of high temperature metal surface were investigated by high-speed visualization of water droplet impact. An aluminum plate was used as the sample plate and the initial diameter of a water droplet was 2 mm. Transient behavior of a single droplet impinging on the surface with and without heating was captured by using a high speed camera running at 4,000 frames per second. The Leidenfrost phenomenon was demonstrated for the case of $300^{\circ}C$ surface temperature, however there was no rebounding of droplet on the cold plate due to hydrophilic nature. The experimental results show that the shape evolution of a droplet impinging on the surface varies with the Weber number, i.e. the ratio of impact inertia to capillary force. The overall water-repellent characteristics of the heated surface was very similar to that of the super hydrophobic surfaces.