• 연구논문집
• /
• 통권26호
• /
• pp.95-102
• /
• 1996

The carbide growth behavior of MAR-M247 LC alloy was investigated by directional solidification and quench method. The carbide volume fraction, trapping and growth behavior were correlated with the growth rate. It was found that the carbide volume fraction decreases at slower growth rate. This decreasing was caused by lower solid-liquid interface trapping ability at the slower growth rate.

• 대한조선학회논문집
• /
• 제39권1호
• /
• pp.38-48
• /
• 2002

파랑집중 이론에 기초하여 모형시험수조에서 다방향 극한파를 생성하는 연구를 수행하였다. 파랑의 집중도에 대한 파향 범위, 주파수 폭, 중심 주파수 등의 영향을 고찰하였다. 등파고와 등기 울기 스펙트럼 모델에 의한 결과를 서로 비교하였으며, Boussinesq 방정식과 유한요소법에 기초한 수치해와 이론해를 또한 서로 비교하였다. 효율적인 파랑집중을 위해서는 파향과 주파수 모두를 효과적으로 제어하는 것이 필수적이다. 파랑집중도는 중심주파수 보다는 주파수 폭에 좌우되며, 동일한 조건하에서 두 스펙트럼 모델은 동등한 정도의 파랑집중 효율을 나타낸다.

• 한국정밀공학회지
• /
• 제21권8호
• /
• pp.50-56
• /
• 2004

The directional ability of an automobile has an influence on driver directly, and hence it must be given most priority. Alignment factors of automobile such as the camber, caster and toe directly affect the directional ability of a vehicle. The above mentioned factors are determined by the pose of interlinks in the assembly of an automobile front chassis module. Measuring the position of center point of ball joints in the front lower arm is very difficult. A method to determine this position is suggested in this paper. Pose estimation for front chassis module and dimensional evaluation to find the rotational characteristics of front lower arm were developed based on fundamental geometric techniques. To interpret the inspection data obtained for front chassis module, 3-D best fit method is needed. The best fit method determines the relationship between the nominal design coordinate system and the corresponding feature coordinate system. The least squares method based on singular value decomposition is used in this paper.

• 전기학회논문지
• /
• 제60권2호
• /
• pp.370-375
• /
• 2011

In this paper, we propose an antenna module with high isolation between Tx and Rx in RFID reader module. The proposed module consists of a quadrafilar antenna and a directional coupler with a switchable dummy load to improve the directivity. The proposed module achieves the isolation higher than 20 dB between Tx and Rx. To show the validity of the proposed scheme, we have performed the measurement of tagging range and multi-tagging ability. The experiment results show that the detecting range and multi-tagging ability are enhanced by 81% and 200%, respectively.

• 한국정밀공학회지
• /
• 제30권11호
• /
• pp.1161-1169
• /
• 2013

In this paper an omni-directional mobile robot is suggested for educational robot platform. Comparing to other robots, a mobile robot can be easily designed and manufactured due to its simple geometric structure. Moreover, since it is required to have low DOF motion on planar space, fabrication of control system is also simple. In this research, omni-directional wheels were adopted to remove the non-holonomic characteristic of conventional wheels and facilitate control system design. Firstly, geometric structure of a Mecanum wheel which is a most frequently used omni-directional wheel was demonstrated. Then, the organization of the mobile platform was suggested in aspects of mechanism manufacturing and electronic hardware design. Finally, a methodology of control system development was introduced for educational purpose. Due to an intuitive motion generating ability, simple hardware composition, and convenient control algorithm applicability, the omni-directional mobile robot suggested in this research is expected to be a promising educational platform.

• 대한물리의학회지
• /
• 제6권2호
• /
• pp.235-246
• /
• 2011

Purpose: The aim of this study is to compare and assess the effects of lumbar stabilization exercise on the balance ability of young college studets with low back pain after having performed spinal stabilization exercise by using 3-dimensional air-balance system and gym ball. Methods: The subjects of this study were 34 low back patients in their early twenties. They were divided into two groups: 3-dimensional lumbar stabilization exercise group(N=17) and gym ball lumbar stabilization exercise group(N=17). The period of the intervention was for five weeks. VAS(Visual Analogue Scale) for pain test, ODI(Oswestry Disability Index) for ADL limitation test, Tetrax system for static balance test, and Air-balance system 3D for dynamic balance test were used as evaluation tools for this study. Results: Pain showed significant decrease in both groups after having performed the experiment, but ADL limitation of the groups did not show any remarkable difference between before and after the experiment. Dynamic balance ability in the 8-directional angle comparison test significantly increased in all directions except for the backward, left-backward, and right-backward directions. As for dynamic balance ability in the 8-directional postural test, 3D exercise group showed statistically significant reduction in every direction while gym ball exercise group did not(p<.05). However, when it comes to static balance ability in the weight distribution and stability test, there was not significantly change between pre and post test in both groups. Conclusion: This study shows 3-dimensional lumbar stabilization exercise is more effective in the lumbar stabilization of coordinated movement than gym ball exercise, which may imply that 3D air-balance system can be used for the therapeutic treatment of body imbalance for patients with low back pain.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
• /
• pp.323-327
• /
• 2006

We present the most recent experimental results on Thin-beam Directional X'tallization (TDX), a rapid excimer-laser-based crystallization method for creating extremely high-quality large-grained polycrystalline silicon films on glass substrates. We will present experimental data obtained with our prototype Gen 2 tool, and discuss the ability to produce different types of poly-Si material.

• 한국지구과학회지
• /
• 제31권4호
• /
• pp.378-391
• /
• 2010

이 연구의 목적은 고등학생과 예비 교사의 지구과학 그래프 해석 능력과 인식을 알아보는 것이다. 이를 위해 지구과학 그래프 해석 능력을 알아보기 위한 9개 그래프 유형의 18문항으로 구성된 1개의 검사지를 개발하였으며, 지구과학 그래프에 대한 인식을 알아보기 위한 2개의 설문지를 각각 개발하였다. 연구 결과는 다음과 같다: 고등학생과 예비교사들은 선 그래프에 대한 해석 능력은 높은 반면, 중복 그래프와 방향성 변화 그래프에 대한 해석 능력은 낮은 것으로 나타나 그래프 해석 능력이 그래프의 유형의 영향을 받는 것으로 분석되었다; 고등학생과 예비교사 모두 학년에 따른 해석 능력에 차이가 있는 것으로 나타났다; 고등학생에 비해 예비교사가 동일한 주제의 서로 다른 표현 방법의 그래프 차이를 더 잘 인식하는 것으로 나타났다; 다수의 고등학생과 예비교사는 지구과학 그래프가 타 과학 교과와 상당한 차이가 있다고 인식하고 있었으며, 가장 많은 차이가 있는 그래프 유형은 방향성 변화 그래프, 분산 그래프, 등치선도, 영역 그래프인 것으로 나타났다. 이러한 연구 결과를 토대로 효과적인 그래프 지도 방략에 대한 함의를 논의하였다.

• 대한전자공학회논문지TC
• /
• 제48권8호
• /
• pp.36-41
• /
• 2011

다중 안테나 통신 시스템에서 채널의 correlation은 심각한 성능 열화를 일으킨다. 본 논문에서는 공간 자원을 양방향으로 활용함으로써 채널 correlation에 대한 민감도를 줄일 수 있는 방법을 다룬다. 먼저 공간 자원의 양방향 활용에 대한 개념을 제시한 후, 사용 가능한 eigenmode를 분석함으로써 이 기술이 채널 correlation에 대한 민감도를 어떻게 줄이는지에 대해 다루도록 한다. 마지막으로 시뮬레이션 결과를 통해 이 기술이 채널 correlation에 대한 민감도를 효과적으로 줄임을 보인다.

• Journal of Power Electronics
• /
• 제8권4호
• /
• pp.291-300
• /
• 2008

In this paper power system and drive-train for omni-directional autonomous mobile robots with multiple energy storage units are presented. Because in proposed system, which is implemented in soccer robots, the ability of power flow control from of multiple separated energy storage units and speed control for each motor are combined, these robots can be derived by more than one power source. This capability, allow robot to diversify its energy source by employing hybrid power sources. In this research Lithium ion polymer batteries have been used for main and auxiliary energy storage units because of their high power and energy densities. And to protect them against deep discharge, over current and short circuit, a protection circuit was designed. The other parts of our robot power system are DC-DC converters and kicker circuit. The simulation and experimental results show proposed scheme and extracted equations are valid and energy management and speed control can be achieved properly using this method. The filed experiments show robot mobility functions to perform the requested motion is enough and it has a high maneuverability in the field.