• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.6
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• pp.525-532
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• 2015

In this paper, we propose an equivalent model of array antennas that use open-ended waveguides for effective EM simulation. We first investigate an individual element that consists of an open-ended waveguide and square ground plane. The waveguide length, aperture size, and ground size of the individual element are adjusted to give a similar radiation pattern to that of the individual element of the original antenna. We then apply the designed equivalent model to two different types of array antennas, such as a microstrip patch array and a waveguide array antenna. Comparison of the simulation results using the equivalent model with the results obtained with the original antenna reveals a difference in gain of less than 0.2 dB and a difference in half power beam width(HPBW) of less than $1^{\circ}$. The designed equivalent model is then mounted on a simple aircraft, and the simulation results are again compared to results from the original antenna. We find a 60 % reduction in simulation resources and time when compared with the original antenna model.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1649-1650
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• 2006

반도체 소자의 선폭이 나노미터 스케일로 진입함에 따라 소자의 물리적 특성을 나노미터 스케일에서 정밀하게 측정하고자 하는 요구가 증대되고 있다. Atomic Force Microscopy (AFM)은 나노미터 이하의 해상도를 가지고 물질 표면의 기하하적, 전기적 특성 등을 측정할 수 있으므로 나노소자 연구에 필수적인 도구가 되었다. 그러나 AFM은 낮은 측정속도와 탐침의 기하학적 형상에 의한 AFM 영상의 왜곡 등과 같은 치명적인 단점도 가지고 있다. AFM의 낮은 측정 속도를 개선하기 위해서 진보된 마이크로머시닝기술을 이용하여 캔틸레버의 크기를 줄이거나 캔틸레버 위에 박막 구동기를 집적시키는 등의 노력이 진행되고 있으나, 이 경우 전통적인 식각 공정을 이용하여 캔틸레버 위에 tip을 형성하는 것이 매우 어렵다. 본 연구에서는 이미 제작된 캔틸레버 위에 전자빔 조사법을 이용하여 탄소상 tip을 직접 성장시킴으로써 전통적인 식각 공정에 비해 매우 간단하고 값싸며, 활용도가 높은 공정을 개발하였다. 탄소상 tip 성장에 필요한 탄소 소스는 dipping 방법을 이용하여 공급하였고, 시분할법을 사용하여 캔틸레버의 원하는 위치에 tip을 성장시킬 수 있었다. 이렇게 제작된 tip은 최대 $5{\mu}m$ 높이까지 가능했으며, 종횡비는 10:1 이상이어서 tip의 형상에 의한 AFM 영상 왜곡 현상을 최소화할 수 있을 것으로 기대된다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3A
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• pp.497-512
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• 2006

In this paper, a simple but effective analysis procedure to estimate seismic capacities of multi-span continuous bridge structures is proposed on the basis of modal pushover analysis considering all the dynamic modes of structure. Unlike previous studies, the proposed method eliminates the coupling effects induced from the direct application of modal decomposition by introducing an identical stiffness ratio and an approximate elastic deformed shape. Moreover, in addition to these two introductions, the use of an appropriate distributed load {P} makes it possible to predict the dynamic responses for all kinds of bridge structures through a simpler analysis procedure. Finally, in order to establish the validity and applicability of the proposed method, correlation studies between rigorous nonlinear time history analysis and the proposed method are conducted for multi-span continuous bridges.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.06a
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• pp.306-307
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• 2022

Recently, in the process of developing, verifying, and upgrading the e-Navigation service and autonomous navigation system, there is an increasing demand for inter-working with a ship-handling simulator that can simulate actual maritime traffic conditions. In this paper, to develop a ship-handling simulation system based on actual maritime traffic conditions, a simulation server was built, received information on the actual maritime traffic conditions from the e-Navigation linkage system, and changed to information for operating the ship-handling simulator. In order to provide simulation images to users, 3D shape modeling for trade ports, coastal ports in Korea and major type of ship were performed. The developed system will be used for the advancement of e-Navigation service, development and verification of autonomous navigation systems, by enabling simultaneous processing of more than 10,000 ships and allowing users to simulate actual maritime traffic conditions in the desired area.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.72.1-72.1
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• 2010

지금까지 연료전지 시스템의 효율을 극대화시키기 위한 기술들이 개발되어 왔는데, 대표적인 방법은 CHP(Combined Heat & power)와 FCT(Fuel cell & Turbine) Hybrid 시스템이다. 그러나 본 연구의 기술은 연료전지 배열을 이용한 Coanda 공기증폭기를 장착한 새로운 개념의 고효율 연료전지 시스템이다. 원래 공기 증폭기는 완만한 곡면 주위를 흐르는 유체가 곡면의 표면을 따라 흐름의 방향이 바뀌는 원리(Coanda Effect)를 이용한 장치로서, 소량의 고압유체를 구동 에너지원으로 사용하여 최고 20배에 해당하는 많은 양의 주변 유체를 빠른 속도로 이송시키는 역할을 한다. 문제는 고압의 유체원을 만드는 것인데, 본 연구에서는 발전용 연료전지 시스템의 배기가스를 활용하여 먼저 고압의 수증기를 발생시키고, 다음으로 고압의 수증기를 공기 증폭기의 구동원으로 사용함으로써 연료전지 시스템의 Air blower를 대체하는 것이다. 이러한 개념을 검증하기 위해서 고압의 스팀작동 Coanda 공기증폭기를 제작하여 선행실험을 진행하였다. 먼저 공기증폭기의 Gap 및 스팀압력에 따른 공기유량, 압력 등의 기본특성을 조사하였고, 출력 공기의 특성을 개선하기 공기증폭기의 형상 및 재료를 새롭게 설계하였다. 그리고 실제 시스템의 적용가능성을 알아보기 위해서, 예로 300kW급 용융탄산염 연료전지 발전시스템의 Air blower 대체가능성을 확인하였고, 배열이용 Coanda 공기증폭기를 활용한 고효율 연료전지 시스템의 개념설계를 수립하였다. 결론적으로 본 기술을 활용하면 연료전지 시스템의 최종 전기효율을 향상시킬 뿐 아니라는 시스템의 장기 신뢰성을 증대시키는 효과를 기대할 수 있다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.10
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• pp.1829-1834
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• 2006

In this raper in order to recover sharp object boundaries we propose a new efficient stereo matching algorithm in which window size is varied to the distance from the boundaries of object. To this end, the processing region is divided into small subregions with a same area and the disparities of the center pixels in the subregions are calculated using a area-based algorithm with multiple windows. From the this disparity map we can find the edges of the contracted objects. The disparities of original image are obtained using the gradient constraint that means the disparity of the center pixel is similar to the ones of the remaining pixels in the subregion. from the experimental results it is found that the proposed algorithm is very good for recovering sharp object boundaries compared to the similar different algorithm.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.3
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• pp.453-462
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• 1994

Variation of seismic wave field in a multi-layered attenuating elastic half space is studied by the propagator matrix method and point source models of which fault-slip functions are defined as ramp functions. In this paper, the earth is modeled as being composed of horizontally stratified layers, with uniform material properties for each layer. The partial differential equations for the seismic motion in each layer are solved using a Fourier Hankel transform approach. Time histories and frequency contents of accelerations and displacements due to a vertical dip-slip and strike-slip point source located in the underlain half space are calculated at the layer interfaces using the developed programs and their characteristics are represented.

• Journal of Korean Association for Spatial Structures
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• v.8 no.4
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• pp.65-71
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• 2008

The object of this paper is to evaluate on constructability of modular steel frame with the hollow structural steel section to LEB C-shape. A modular building is built with factory-manufacture and site-construction. The advantage of a Modular building presents that enhanced building quality, shortened construction period and easy at an expansion and enlargement for buildings but also has demerits such as size restriction of the modular units according to the Road Traffic Law and Inflexibility of the unit composition. So in this study we use light-weighted structure members with bolted joint for easy Knock-down and traffic, also we evaluated the constructability of this bolted joints type modular buildings.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.3
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• pp.16-24
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• 1999

Performance of the trapezoidal fins having different upper side slope is investigated by the three dimensional analytic method. It is shown that one equation can be used to analyse the trapezoidal fins having different upper side slope by adjusting the slope factor only. The performances for these fins are represented as a function of the non-dimensional fin length, fin width, Biot number and the slope factor when the remaining variables are fixed arbitrarily. One of the results is that the fin effectiveness increases as Biot number, the non-dimensional fin width and the slope factor decrease and as the non-dimensional fin length increases in the case of Bi $\leq$ 0.1 but the trend of the fin shape effect on the effectiveness is somewhat irregular for higher Biot number(i.e. Bi = 0.3).

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2000.11a
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• pp.21-29
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• 2000

The Purpose of this paper is to determine the effect of the autoclave inner pressure rate, heat-up rate, tool round angle, Thickness of core, height of joggle on defects, and to minimize the defects of aircraft sandwich structure reinforced with honeycomb core occurred in autoclave processing. The results showed that the geometry of aircraft sandwich structure and tool such as tool round angle, Thickness of core, height of joggle, and the autoclave cure conditions such as inner pressure rate, heat up rate strongly affected the core movement, core wrinkle, bridge phenomenon of prepreg and depression of core that occurred in autoclave processing.