• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.28 no.4
• /
• pp.286-297
• /
• 2017

This paper is a study of 6~18 GHz wideband high power amplifier which is composed of 10 single amplifier and coaxial type spatial power combiner. The property of this spatial power combiner is on a similar principle to antipodal antenna radiation mechanism. Therefore, the key structure of proposed spatial power combiner is the antipodal finline PCB board and the finline curve shape is numerically synthesized by using Klopfensein's optimum impedance taper. The measured CW output power of spatial combined high power amplifier is nearly 50 W. In conclusion we prove the good combining performance between the spatial power combiner and 10 single amplifier over 6~18 GHz frequency ranges. Also, we developed the key component PA and MFC MMIC which controls the phase and gain of the each amplifier, The main characteristic of MFC MMIC is to maximize combining efficiency of power amplifier.

• Journal of Digital Convergence
• /
• v.12 no.11
• /
• pp.407-414
• /
• 2014

The aim of the present study was to carry out quantitative analysis of spatial resolution for the influence of the focus size and digital image post-processing on the Computed Radiography (CR). The modulation transfer functions of an edge measuring method (MTF) was used for the evaluation of the spatial resolution. The focus size of X-ray tube was used the small focus (0.6 mm) and the large focus (1.2 mm). We evaluated the 50% and 10% of MTF for the enhancement of edge and contrast by using multi-scale image contrast amplification (MUSICA) in digital image post-processing. As a results, the edge enhancement than the contrast enhancement were significantly higher the spatial resolution of MTF 50% in all focus. Also the spatial resolution of the obtained images in a large focus were improved by digital image processing. In conclusion, the results of this study should serve as a basic data for obtain the high resolution clinical images, such as skeletal and chest images on the CR.

• Korean Journal of Optics and Photonics
• /
• v.17 no.5
• /
• pp.396-400
• /
• 2006

We present a weather-insensitive optical free-space communication method supporting optical packet channels. It operates optical fiber amplifiers in gain-saturation regions. When the propagation loss gets too high, it decreases the average packet rate, or the average packet length, or both, to increase the optical power level launched into the free-space. As a demonstration, we transmit $8{\times}10$ Gigabit Ethernet channels over a terrestrial distance of 2.4 km. One gain-saturated free-space optical repeater is used at the halfway point.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.9 no.2 s.42
• /
• pp.47-58
• /
• 2005

Dynamic response analysis in time dimain is conducted for floating bridges with discrete pontoons subject to spatial variation of ground motions. The Spatial variation of ground motions is considered with the coherency function model which represents wave passage, incoherence and local site effects. The superstructure of the bridge is represented by space frame and elastic catenary cable elements, the abutment us modelde with the spring element of FHWA guideline for considering soil structure interaction and the concept of retardation function is utilized to consider the frequency dependency of the hydrodynamic coefficients which are obtainde by boundary element method. multiple support excitations considering the spatial variation. The noticeable amplification of the response can be shown when the spatial variation of ground motions is incorporated in the anallysis of floating bridges.

• Journal of the Korean association of regional geographers
• /
• v.10 no.2
• /
• pp.252-266
• /
• 2004

This study analyzes the influence of the construction of a high-speed railroad on territorial organization in France. After development of a new transportation network, the French territorial organization has been largely modified. Many economic urban areas are modified by their position in the territorial hierarchy according to their condition of connection with the TGV network. At first, spatial convergence is the most important effect of the TGV network construction. Second, the development of a transportation network concentrated in the Paris area has influence as an intensified factor on metropolitan areas and as a weakening factor on middle- and small-sized cities. Thus, this system has risk in increasing territorial imbalance in France. Third, to implant an economic activity zone around new TGV stations, a new town or a new economic center starts to develop. This is going to grow into a second core outside of the old city center so that regional spatial organization is transformed from a mono-polarized(mono-centric) organization to a multi-polarized(polycentric) one. Lastly, the integration of the EU railroad system enhances the concentration of economic activity in European metropolitan areas as each metropolitan area tries to develop more competitive space for its rising position in the global urban hierarchical system.

• Korean Journal of Optics and Photonics
• /
• v.6 no.4
• /
• pp.288-295
• /
• 1995

We have studied about spatial wavefront analysis of a pulsed laser output beam by means of an imaging unstable ring resonator with an infinite Fresnel number. We have constructed a Newtonian telescope type NBUR (Negative Branch Unstable Ring) Nd:YAG laser with 4 plane mirrors. Provided that the NBUR resonator is under self imaging condition, the resonator could be reduced diffraction effects which were occuring to the beam transmitting through the circular aperture of scraper mirror in the resonator. We have observed enhancement in the spatial coherence of wavefronts of laser beam due to the iterative round trips of the self imaging beam inside the ring resonator. The information on the spatial wavefronts was determined by the fringe patterns from Mach-Zehnder interferometer and the fringe analysis by means of the Fourier transform method showed the distortion of wavefronts of less than 0.2), In comparison with a standing wave type resonator, we have confirmed that the spatial coherence of the NBUR Nd:YAG laser output beam was enhanced as much as 75%. s 75%.

• Korean Chemical Engineering Research
• /
• v.59 no.4
• /
• pp.626-631
• /
• 2021

One of the nonlinear electrokinetic phenomena around ion exchange membrane is electroconvective instability which can be found in various electrokinetic applications such as electrodialysis, electrochemical battery, microfluidic analysis platform, etc. Such instability acts as a positive transport mechanism for the electrodialysis via amplifying mass transport rate. On the other hands, in the electrochemical battery and the microfluidic applications, the instability provokes unwanted mass transport. In this research, to control the electroconvective instability, the onset of the instability was analyzed as a function of confinement effect as well as applied voltage. As a result, we figured out that the dynamic behavior of electroconvective instability transited as a sequence of stable regime - static regime - chaotic regime depending on the applied voltage and confinement effect. Furthermore, stability curves about the dynamic transition were numerically determined as well. Conclusively, the confinement effect on electroconvective instability can be applied for effective means to control the electrokinetic chaos.

• Proceedings of the Korean Society of Computer Information Conference
• /
• 2009.01a
• /
• pp.135-140
• /
• 2009

본 논문은 한국어 8 단모음을 인식하는 자동 독화 신경망 시스템을 구축한 것이다. 얼굴의 특정들은 휘도와 채도 성분으로 인하여 다양한 색 공간에서 다양한 표현 값을 갖는다. 이를 이용하여 각 표현 값들을 증폭하거나 축소, 대비시킴으로서 얼굴 특정들을 추출되게 하였다. 눈과 코, 안쪽 입의 외곽선, 이의 외곽선을 찾았고, 그 후 한국어 8모음 발화시 구분되게 변화는 값들을 파라미터로 설정하였다. 한국어 8모음을 발화하는 2400개의 자료를 모아 분석하고 이 분석을 바탕으로 신경망 시스템을 구축하여 실험하였다. 이 실험에 정상인 5명이 동원되었고, 사람들 사이에 있는 관찰 오차를 정규화를 통하여 수정하였다. 5명으로 분석하였고, 5명으로 인식 실험하여 좋은 결과를 얻었다.

• Proceedings of the Korean Information Science Society Conference
• /
• 2008.06d
• /
• pp.313-317
• /
• 2008

유비쿼터스 환경에 대한 관심이 증폭됨에 따라, 센서는 다양한 어플리케이션들에서 점점 더 많이 사용되고 있다. 이러한 센서 시스템에서, 최소 개의 센서를 가지고 대상 공간이 복수 개의 센서에 의해 완전히 센싱되게 하기 위해서는, 센서를 어디에 배치하느냐가 중요한 문제이다. 또한 복수 개의 센서에 의해 센싱된 데이터로부터 의미 있는 정보를 추출하기 위해서는 센서 서로 간의 거리가 너무 가까워서는 안 된다. (최소거리 요건). 이를 위하여 우리는 TRE-based approach 라고 하는, 최소거리 요건을 만족하며 3-coverage 문제를 해결하는 방법을 제안하며, 이를 기반으로 3-coverage 문제를 3 차원으로 확장시킬 때 가능한 센싱 coverage 모델과 그 확장 가능성에 대해 논의한다.

• Journal of the Speleological Society of Korea
• /
• no.70
• /
• pp.63-74
• /
• 2006

소리의 파동, 특히 밀폐된 동굴 속에서 일어나는 음향파동에 대한 과학적 접근과 함께 첨단과학을 통한 소리의 분석기법을 통하여 소리과학과 동굴 및 그 구조에 따른 음파의 공명(증폭)현상과 인류생활의 소리문화의 상관성을 재조명하였다. 따라서 동굴 속에서 음악을 연주하는 경우 작은 소리라도 매우 웅장한 소리효과를 낼 수 있으며, 고음보다는 저음에서의 울림효과를 크게 가져 올 수 있다. 특히 이러한 파동현상과 음향효과를 통하여 기 발굴된 동굴의 체계적 관리 방안과 미 발굴 지하 동굴의 발굴에도 적용할 수 있을 것으로 기대되며, 동굴의 음향파동현상을 응용한 기술로 지각운동과 변화 및 동굴의 상태 분석과 변화 요인을 관찰하는데 효과적인 역할과 방법을 제공할 수 있을 것으로 기대된다.