전자식 전력량계 IEC 표준 서지시험 및 과도조건 영향분석

이석곤,이건행,정우영 대한전기학회 2010 대한전기학회 학술대회 논문집 Vol.2010 No.11

티타늄 실린더의 초기 고정력이 뼈 재생에미치는영향

이석곤,김현만 대한구강해부학회 2010 대한구강해부학회지 Vol.32 No.1

Initial mechanical stability of implant inserted in bone is wel accepted as a requirement for obtaining good bone healing. However. the experimental evidence for this concept is hardly found. The present study examined the efect of micromovement of titanium cylinder on bone regeneration after placing it loosely in the trabecular bone of femur head of rabbits. Titanium cylinders of 3.5 mm in diameter were placed in the hole prepared with drils of 3.4 mm or 3.8 mm in diameter. Titanium cylinder was wel secured in the narrower hole. while freely moved in the wider hole. Bone area (BA) and bone-implant contact (BIC) were measured using microfocus X-ray CT system in the valey of cylinder. BA and BIC were higher in the analysis of movable cylinder group when compared to the tightly secured group after 2 weeks. although statisticaly insignificant due to the smal number of samples. There was no diference in BA and BIC on the study of 4 weeks groups. In summary. experimental group of titanium cylinders with which the initial micromovement was permited by placing them in the wide hole did not show lower bone regeneration compared to the cylinders tightly secured in the bone through whole experimental period. These resu1ts indicate. within the limits of this study. that the initial micromovement is not a detrimental factor in the bone regeneration of titanium implant. Furthermore. the initial mechanical stability may not be an unconditional prerequisite for obtaining good osseointegration around titanium implant.

Hydroxyapatite Bioceramics의 합성 및 물성에 관한 연구

이석곤,고형열,이구종,최상흘 한국세라믹학회 1989 한국세라믹학회지 Vol.26 No.2

In order to develope hydroxyapatite ceramics which has mechanical strength as bio-implant materials and get the basic data for the study and application of biocompatibility, hydroxyapatite was synthesized at Ca/P=1.67~1.75, pH 7~11 by precipitation method. Using prepared powders, the sintered body, fluorine substituted body and the porous body was formed and their properties were investigated. The sample obtained in condition of Ca/P=1.67, pH 7 and sintering at 1,15$0^{\circ}C$ was decomposed to $\beta$-tricalcium phosphate, and co-existed with hydroxyapatite. Hydroxyapatite synthesized at pH 11 was not easily decomposed to $\beta$-tricalcium phosphate at sintering process. The substitution of a small amount of fluorine for hydroxyapatite prevented hydroxyapatite from being decompsed to $\beta$-tricalcium phosphate. Hydroxyapatite ceramics which substited of 10% fluorine was prepared at 1,15$0^{\circ}C$, and the valueof bending strength for this body were found to be 112MPa.

능동위상배열안테나에서 부배열 구조에 의한 Grating Lobes 영향 최소화를 위한 송수신안테나 구조 설계

이석곤(Seok-Gon Lee),박대성(Dae-Sung Park),주영호(Yong-Ho Chu),조병래(Byung-Lae Cho),이정수(Jung-Soo Lee),이종민(Jong-Min Lee) 한국정보기술학회 2013 Proceedings of KIIT Conference Vol.2013 No.5

본 논문에서는 능동위상배열레이더에 있어서, DBF(Digital Beam Forming) 형성시 부배열 구조에 의해 발생되는 grating lobes 영향을 최소화하기 위한 송수신 배열안테나 구조 및 부배열구조에 대하여 설계하였다. 배열안테나는 각각 위상변위기와 감쇄기에 의해 제어되도록 설계하였고, 수신배열안테나는 비용절감을 위해 부배열 단위로 묶어 A/D컨버터를 통해 신호처리단으로 전달되도록 설계하였다. Grating lobes의 영향을 최소화하기 위한 송수신안테나 최적 구조를 제안하고, 수학적 모델링 및 Matlab 시뮬레이션을 통해 검증하였다. In this paper, we designed the structure of the Tx and Rx array antennas for reducing the grating lobes caused by the sub-array mechanism in active phase array antennas. Array antennas were individually controlled by the phase shifter and attenuator. The sub-array mechanism were applied to the receiving antennas for decreasing the system complexity, power consumption, weight, and cost. The optimal structure of the Tx and Rx array antennas for minimizing the grating lobes was suggested, and its effectiveness was verified by using the mathematical modeling and Matlab simulation.

다중 대역 안테나 피드용 직교모드 변환기 설계

황순미,김영민,이석곤,안병철 한국전자파학회 2002 한국전자파학회논문지 Vol.13 No.1

In this paper, we present design results for an orthomode transducer(OMT) to be used in multi-band antenna feeds. The OMT is realized in the form of a tapered square waveguide, where 18-20 GHz ports are placed in the taper region normal to the waveguide axis, while 30-45 GHz ports are placed in line with the waveguide axis. The reflection coefficient of each port is designed to be less than 20 dB, while the isolation between ports are greater than 15 dB. Thin septa are placed in side ports to reduce the effect of side ports on the return loss of the in-line port. The commercial software HFSS? is used to design the whole structure. 본 논문에서는 다중대역 피드를 위한 직교모느 변환기를 설계하였다. 직교모드 변환기의 전체적인 모양은 사각 테이퍼진 형태이고, 18~20 GHz에서 우원편파와 좌원편파를 발생시키기 위해 테이퍼 부분에 2개의 측면 포트를 두고, 직선포트는 30~45 GHz의 광대역에서 -20 dB 이하의 반사계수와 15 dB 이하의 분리도를 가지도록 설계하였다. 직선포트에서의 반사계수 특성을 향상시키기 위해서 측면포트에 얇은 격막을 삽입하였다. 전체적인 설계에 상용소프트웨어인 HFSS$^{R}$를 사용하였다.

광대역 특성을 갖는 인쇄형 Quasi-Yagi 다이폴 배열 안테나

리화,전병태,이석곤,안병철 충북대학교 산업과학기술연구소 2002 산업과학기술연구 논문집 Vol.16 No.2

In this paper, we present a design of an array of printed Yagi dipoles. The Yagi dipole antenna consists of a driver element fed by a co-planar stripline, a director and a reflector. The co-planar stripline is in turn fed by an input microstrip line via a transition/balun structure. The finite ground plane used for the microstrip feed line also serves as a reflector element in the Yagi antenna. First the performance of the Yagi antenna is optimized for a wide bandwidth and a high gain. Then a four-element array of the Yagi dipole is realized using a corporate feed network. The designed array shows a reflection coefficient less than -10dB, and a gain of 10.5dB over 11.5-13.5GHz.

구형 도파관내 전계면 필터의 모멘트법에 의한 해석

방재훈,윤소현,이석곤,안병철 한국전자파학회 2000 한국전자파학회논문지 Vol.11 No.3

In this paper, an efficient moment-method technique is proposed for analyzing rectangular waveguide E-plane filters. Techniques are presented for the fast evaluation of Green's function and for the efficient evaluation of integrals arising in the E-plane of the rectangular waveguide. The structure boundary is represented by the piecewise linear segments. Simple pulse-expansion and point-matching technique are used. The entire E-plane filter structure is simulated by the method of moments. Three representative cases of the E-plane filter are analyzed and compared with results by other researchers.

능동위상배열 레이더에서 다중표적 탐지/추적을 위한 효과적인 빔 구조 연구

이주현(Joo-Hyun Lee),이석곤(Seok-Gon Lee),박대성(Dae-Sung Park),조병래(Byung-lae Cho) 한국전자파학회 2014 한국전자파학회논문지 Vol.25 No.10

본 논문은 능동위상배열 레이더가 여러 개의 표적을 탐지/추적하기에 효과적인 수신빔 구조에 대해 기술하고 있다. 위상배열 레이더가 갖는 특성 중 하나는 원하는 방향으로 빔을 조향하고, 디지털적으로 여러 개의 빔을 동시에 형성하는 것이다. 이와 같은 디지털 빔 형성 수신빔 구조를 통해서 동시 다발적으로 발생하여 접근하는 위협 표적을 빠르고 정확하게 탐지하는 방식을 제안한다. 본 논문에서 제안된 기법들은 시뮬레이션을 통해서 표적의 탐지 정확도 성능을 제시한다. This paper presents an efficient receive beam structure able to search and track the simultaneous bundle targets with the active electrically scanned array radar. One of the characteristic with the active phased array radar is to point toward wanted direction and to forming simultaneously the digital multi-beam. This paper proposes method to detect and track rapidly bundle targets coming to radar using the digital beam forming. The proposed the beam forming method in the paper is evaluated about the angle accuracy of targets via a computer simulation.

$\alpha$형 반수석고의 수화에 미치는 염류의 영향

최상흘,이구종,홍성윤,이석곤 한국세라믹학회 1988 한국세라믹학회지 Vol.25 No.5

The effects of salts which was used as a catalysis in formation of $\alpha$-calciumusulfate hemihydrate from dicalcium sulfate hydrate were investigated on the hydration of $\alpha$-calciumsulfate hemihydrate. The hydration of $\alpha$-calciumsulfate hemihydrate was studied by the measurements of crystalline water, heat evolution. Also the hydrates were analyzed by XRD, DSC and SEM. The promotive effect each salts on the hydration was as follows: NaCl>NH4Cl>NaNO3>NH4NO3, and the hydration rate was accelerated with concentration of salts. The effect of Al2(SO4)3 and potassium sodium tartrate on the hydration was slmilar to water, whereas sodium succinate and gelatin retarded the hydration in comparision with water. These salts affected the hydration time but total heat evoution was similar.

유전체가 덮힌 Ku-대역 인쇄형 선형 배열 안테나 설계

유상길(Sang-Gil Yu),이석곤(Seok-Gon Lee),안병철(Bierng-Chearl Ahn) 대한전자공학회 2002 대한전자공학회 학술대회 Vol.2002 No.11