• Journal of Ocean Engineering and Technology
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• v.11 no.1
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• pp.24-35
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• 1997

The hydraulic or pneumatic valve spools become essential as the important components on the production of automatic hydraulic or pneumatic as mechanical industry has been rapidly developed. The machining precision is in necessity for manufacturing the valve spools. They could be unstable in the quality by the conventional are welding. And also they have a lot of technical problems in manufacturing because their shapes are generally small. By the precision casting process such as lost wax process, the production cost may be increased. But by the friction welding technique, they will be able to be manufactured without such problems. This paper deals with the development of dissimilar friction welding optimization for the hydraulic or pneumatic valve spool by friction welding and a new approach of on real-time qualify evaluation by AE techniques.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.2
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• pp.17-22
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• 2012

This paper deals with a precoder design method when the system has imperfect channel information. When MIMO relay system knows the correlation coefficient between perfect channel and imperfect channel information and the variance of the difference between perfect channel and correlated imperfect channel, source and relay precoders are designed to maximize the upper bound of the channel capacity. Also, we investigate channel capacities of the system using proposed precoder and compare with the optimal value according to the correlation and the variance of error channel by simulations.

• 한국HCI학회:학술대회논문집
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• 2006.02b
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• pp.512-517
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• 2006

본 논문은 지난 5년간의 모바일 메뉴 아이콘의 디자인 분석을 통해 현재의 모바일 폰에 적용되고 있는 아이콘 디자인 법칙을 밝히는 것을 목적으로 한다. 현재 제조사에 따라 다르게 제공되는 하드웨어 안에 아이콘(ICON) 디자인 또한 서로 다르게 구성되어 있어 사용자들은 일관성 없는 이미지에 혼란스럽다. 새로운 모바일 폰이 개발되면 그 내부 인터페이스도 모바일 폰 기기 사양이 담고 있는 기능들에 의해 다듬어 지고 정리된 메뉴기능을 내장해야 한다. 본인은 앞에서 언급했던 모바일 폰의 인터페이스를 구성하고 있는 아이콘의 디자인을 내용분석 하였다. 모바일 아이콘 전반적 디자인 변화를 살펴보고 점차 증가하고 있는 모바일 폰의 특성을 살펴 본 후에 아이콘을 담고 있는 인터페이스를 제품별, 제조사별, 년도 별로 분류하고 디자인 법칙을 찾아보았다. 그리하여 국내 모바일 폰의 메뉴 아이콘을 의미표현 유형과 아이콘의 크기, 아이콘의 애니메이션 정도, 아이콘 주변 경계, 공간 표현, 아이콘에 적용 된 라이트와 음영 위치, 아이콘 시각표현, 배경의 유무, 선택 시 반응에 따라 애니메이션 유무, 아이콘의 선택 시 크기변화, 아이콘의 테두리선 유무, 아이콘의 색상 반전 유무, 아이콘의 그림자 유무를 분석 기준으로 잡고, 이런 모바일 아이콘의 요소 별 디자인에 적용된 법칙들을 내용분석을 통해 발견하였다. 모바일 아이콘 디자인 내용분석을 통해 2001년부터 2005년까지 국내에 출시된 모바일 아이콘 디자인들이 역사적으로 어떻게 변하였는지 정리하였다. 디자인이 빠르게 변화하고 있는 지금, 새로운 디자인을 발견하기에 앞서 지금까지 국내 모바일 아이콘 디자인의 시대적 변화를 되돌아보고, 살펴보는 연구를 하였다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.3
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• pp.119-126
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• 2005

Electrical resistance tomography(ERT) maps resistivity values of the soil subsurface and characterizes buried objects. The characterization includes location, size and resistivity of buried objects. In this paper, Gauss-Newton, truncated least squares(TLS) and simultaneous iterative reconstruction technique(SIRT) methods are presented for the solution of the ERT image reconstruction. Computer simulations show that the spatial resolution of the reconstructed images by the TLS approach is improved as compared to those obtained by the Gauss-Newton and SIRT method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.11
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• pp.1949-1957
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• 2003

A hybrid finite element analysis was used to analyze the influence of ring gear rim thickness and spline number on the static properties of a planetary gear system with manufacturing errors. Both of these parameters affected the bearing force and critical stress. The effect of changes in the rim thickness on the load sharing between the gears depended on the type of manufacturing error. Ring flexibility improved the load sharing between planetary gears only in systems with planet tooth thickness or planet tangential errors; for other types of error, ring flexibility worsened the load sharing. To improve load sharing, rim thickness and spline number should be controlled within a specific range. The minimum rim thickness limit should be determined considering not only the critical stress but also the load sharing. The effect of the ring gear boundary condition was more apparent in a system with errors than in a normal system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.3
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• pp.334-346
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• 2003

An experimental study was carried out to investigate near-wake characteristics of an elliptic airfoil oscillating in pitch. The airfoil was sinusoidally pitched about the half chord point between -5$^{\circ}$and +25$^{\circ}$angles of attack at the freestream velocities of 3.4 and 23.1 m/s. The corresponding Reynolds numbers based on the chord length were 3.3$\times$10$_{4}$ and 2.2$\times$10$^{5}$ , respectively. A hot-wire anemometer was used to measure the near-wake flow variables at the reduced frequency of 0.1. Ensemble-averaged velocity and turbulence intensity profiles were presented to examine the near-wake characteristics depending on the Reynolds number. The axial velocity deficit in the near-wake region tends to decrease with the increase in the Reynolds number as found in many stationary airfoil tests. Turbulence intensity in the near-wake region have a tendency to decrease with the -increase in the Reynolds number during the pitch-up motion, whereas it shows different feature during the pitch-down motion according to the separation characteristics.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.234-238
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• 2008

The efficiency of fiber reinforced CMC(ceramic matrix composite) on the SiC materials have been investigated, in conjunction with the fabrication process by liquid phase sintering and the characterization. LPS-$SiC_f$/SiC composites was studied with the detailed analysis such as the microstructure, sintered density, flexural strength and fracture behavior. The applicability of carbon interfacial layer has been also investigated in the LPS process. Submicron SiC powder with the constant total amount and composition ratio of $Al_2O_3,\;Y_2O_3$ as sintering additives was used in order to promote the performance of the SiC matrix material. LPS-$SiC_f$/SiC composites were fabricated with hot press under the sintering temperature and applied pressure of $1820^{\circ}C$ and 20MPa for 1hr. The typical property of monolithic LPS-SiC materials was compared with LPS-$SiC_f$/SiC composites.

• The Journal of the Acoustical Society of Korea
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• v.19 no.4
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• pp.84-92
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• 2000

In this paper, numerical scattering analysis for submerged scatterers is performed using finite and infinite elements. Unbounded domain is truncated into finite domain and finite elements are used in the domain. Infinite elements, So called Infinite Wave Envelope Elements (IWEE) which possess wave-like behavior, are used to take into account the infinite domain on the truncated boundary Scattering from rigid sphere is taken as an example and the effects of the order and mesh size of finite elements, size of finite element model and the order of IWEE are investigated. Quadratic finite element, refined mesh and higher order IWEE are recommended to improve the non-reflection boundary condition in the numerical scattering analysis.

• Journal of Advanced Navigation Technology
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• v.15 no.2
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• pp.234-240
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• 2011

In this paper, the performances of Cram$\acute{e}$r-Rao Lower Bound (CRLB) with Frequency Difference of Arrival (FDOA) measurements for Unmanned Aerial Vehicle (UAV) tracking are investigated. We focus on two cases: the influence on CRLB with FDOA measurements collected by time, and random distribution of Ground Stations (GSs). We derived the performance by gauging the size of CRLB through Complementary Cumulative Distribution Function (CCDF). From the simulation results, broader distribution of GSs and FDOA measurements by longer time bring about better performance.

• Journal of Navigation and Port Research
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• v.34 no.6
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• pp.429-434
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• 2010

The experimental study of the hull surface roughness on a developing turbulent boundary layer which exposed to a variety of operating environments were investigated by performing particle image velocimetry(PIV) in a circulating water channel. The Reynolds number based on the width of roughness was about Re=1000. the roughness elements used were periodically arranged two-dimensionally. the flow visualization, time-mean velocity fields and vorticity fields to measure the flow characteristics were obtained. The investigation shows that the vortex generation and its progress inside the walls. And the center of the vortex was located at the middle of the height of the surface roughness.