"Dice와 fill" 방식을 이용한 1-3 압전복합재의 제조와 횡방향 단위 크기에 따른 압전특성 평가

김영덕,김광일,정우철,김흥락,김동수 한국비파괴검사학회 2002 한국비파괴검사학회지 Vol.22 No.4

NDT나 의료용 영상장치에 응용되는 압전복합체는 일반적인 세라믹이나 고분자 압전재료에 비하여 많은 장점을 가진다. 이들 응용분야에서는 전기기계결합게수가 높아야 하고, 음향임피던스가 낮아야 한다. 그러나, 압전복합제의 횡방향 단위 크기가 조밀하지 못한 경우 횡방향으로 전행하는 판파에 의한 불필요한 진동이 표면에 발생하게 된다. 횡방향 단위 크기와 세라믹 체적비에 따른 압전 특성을 조사하기 위하여 PMN-PZT 세라믹과 Epofix 에폭시로 에폭시의 폭을 달리하면서 1-3 형 압전복합체를 제작하였다. 제작된 1-3형 압전복합체의 두께방향 진동모드의 전기기계결합계수, 음향임피던스는 각각 0.36~0.64, 9.8~22.7 MRayl로 나타났으며, 횡방향 단위크기가 줄어들수록 횡방향 모드 공진 주파수가 증가하였다. The piezoelectric composites had many adventages in comparison qith conventional piezoelectric ceramics and piezopolymers for ultrasonic transducers used in NDT and in medical ultrasonic imaging. The electromechanical coupling coeffucient should be high and the acoustic impedance should be low in these applications. However, the cross-coupling with spurious oscillations caused lateral spatial scale. The thickness mode electomechanical coupling coefficient of 1-3 type of piezoelectric composites were 0.36 to 0.64, and the acoustic impedance of them were 9.8 to 22.7 MRayl. The lateral resonance frequency of 1-3 type piezoelectric composites shifted to high frequency region with decreasing lateral spatial scale.

차세대 무선 통신 시스템을 위한 안테나 신기술

김형락,권세웅,황광선,윤영중 延世大學校 電波通信共同硏究所 2002 電波通信論文誌 Vol.6 No.1

차세대 통신 시스템에서 공통적으로 요구하는 소형화, 광대역화, 집적화추세에 따라 RF소자는 광대역화, 소형화, 집적화를 향해 발전하고 있으며 안테나 기술도 현재 추세에 발맞추어 소형화, 능동집적화, 광대역화를 통하여 개발 방향을 모색하고 있다. 본고에서는 현재 추세인 소형 안테나, 능동 안테나와 더불어 최근 관심이 집중되고 있는 임펄스 통신에 이용될 수 있는 초광대역 안테나 기술에 대해 소개한다. The technical trends of the next generation wireless communication are miniaturization, broad-band operation, and integration. Thus, in accordance with this trend, RF devices and components are being developed in such way, and same with the antenna. In this paper, technology of small antenna, active antenna, and ultra wideband antenna, which can be applied to impulse communication system, are introduced.

지붕경사각 변화에 따른 막구조의 풍압 변화 특성

길용식,김동우,하영철,이광렬,김종락 대한건축학회 2003 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.23 No.1(구조계)

This paper describes on the results of 1:400 geometrical laboratory modeling of wind-induced point pressure on the membrane roof structure of Stadium with variable roof slopes. The wind flow for flat ground surface was simulated in a boundary wind tunnel at Kumoh National Institute of Technology. The roof slope of membrane structure changed into 5 types. The locations of wind pressures taps are distributed on the same upper and lower part of membrane roof. The resultant wind pressure for each measurement points are analysed on 2 categories. One is acting on upper direction, the other is lower direction. The results showed that in the case of upper direction the changes of wind pressures on the membrane roof are not dominant in regard to changing roof slope, but in lower direction wind pressures are increased at the rear part of roof with changing roof slopes.

소수성 촉매를 이용한 수소동위원소 교환 반응 측정을 위한 순환 반응기

최희주,이한수,안도희,강희석,김광락 한국공업화학회 2002 응용화학 Vol.6 No.2

The catalytic rate constants of hydrophobic catalysts developed for the removal of tritium mainly generated in the pressurized heavy water reactors should be measured. A recycle reactor was designed and built for characterzing the long-term behavior of the catalyst performance at the various temperatures and gas velocities.The catalytic rate constants were measured at the apparent gas velocity of 0.5 m/s and the temperature of 60℃. The initial catalytic constant was 8.44×10^-4mol/g.sec. This value is much greater than that considered in the design of Wolsong Tritium Removal Facility.

A Study for the Adaptive wavelet-based Image Merging method

Kim, Kwang-Yong,Yoon, Chang-Rak,Kim, Kyung-Ok The Korean Society for Geospatial Information Syst 2002 대한공간정보학회지 Vol.10 No.5

The goal of image merging techniques are to enhance the resolution of low-resolution images using the detail information of the high-resolution images. Among the several image merging methods, wavelet-based image merging techniques have the advantages of efficient decorrelation of image bands and time-scale analysis. However, they have no regard for spatial information between the bands. In other words, multiresolution data merging methods merge the same information-the detail information of panchromatic image-with other band images, without considering specific characteristics. Therefore, a merged image contains much unnecessary information. In this paper, we discussed this 'mixing' effect and, proposed a method to classify the detail information of the panchromatic image according to the spatial and spectral characteristics, and to minimize distortion of the merged image.

A Study for the Adaptive wavelet-based Image Merging method

Kwang-Yong Kim,Chang-Rak Yoon,Kyung-Ok Kim 대한공간정보학회 2002 대한공간정보학회지 Vol.10 No.5

인슐린종 1 예

김동수,이용규,김상순,김용기,이민기,이광욱,김상욱,박규현,양웅석,김상호,문한규,허윤,도창호,손덕현,최장락,강필증 대한내과학회 1990 대한내과학회지 Vol.39 No.2

Insulinoma is characterized by fasting hypoglycemia, various neuropsychiatric symptoms, and those caused by secondary to hypoglycemia. A 21-year-old female was admitted due to frequent loss of consciousness and dull mentality for a year and three months. She was diagnosed as insulinoma on the basis of Whipple's triad, celiac, and mesenteric angiography, abdominal C.T, scan, and the inappropriately elevat level of the insulin and C-peptide in the serum. When we transferred her to the Department of General Surgery for the remaval of insulinoma, a large mass was revealed in the pancreatic head portion with the invasion of the adjucent structures. Thus they performed Whipple's operation. Histologic examinations by light and electron microscopy showed islet cell tumor and many secretary granules in the cytoplasm. A brief review of the literature was made.

개방형 우물 구조를 이용한 마이크로머신형 pH 센서

김흥락,김영덕,정우철,김광일,김동수 한국비파괴검사학회 2002 한국비파괴검사학회지 Vol.22 No.4

수용액에 포함된 수소이온(H^+)의 농도를 측정하는 유리 전극형 수소이온 농도(pH) 센서의 기본 구조를 bulk micromachining 기술로 구현하여 소형의 pH센서를 제작하였다. 박막 증착이 가능한 경사 식각으로 개방된 2개의 기본 구조물을 형성하고, 일정 전위를 유지하기위한 기준전극은 식각된 구조물 경사면에 박막형 Ag/Agcl으로 확보하였다. H^+과 교환반응으로 전위를 발생시키는 감응부는 Na 20%이상 포함된 glass로 100㎛ 내외로 미세 연마하여 기본 구조물에 접합하여 완성하였다. 또한 외부 용액과 기준 용액의 혼합을 방지하면서 전류 도통 역할을 하는 액간 접촉부는 50㎛ × 50㎛ 크기의 Si 이방성 식각 부분에 한천을 삽입하고 난 다음 기존의 구조물에 접합하여 형성하였다. 각 구조물을 완성한 다음 2M 농도의 KCl 기준 용액을 구조물에 채우고, 상온 에폭시로 센서 구조물을 밀봉하여 센서를 완성하였다. 제작된 pH센서들은 표준 pH 용액에 대하여 약 90mV/pH의 전위값이 측정되었다. A structure of a glass electrode-type pH sensor for measuring any concentration of H^+ in an aqueous solution was embodies with bulk micromachining technology. Two open well structure were formed, and a reference electrode was secured by the Ag/AgCl thin film in the sloped side of the etched structure. A sensitive membrane of an indicator electrode for generationg a potential by an exchange reaction to H^+ was made with a glass containing Na 20% or more finely so that its thickness might be 100㎛ or so, and then it was bonded to one pyramidal structure. A liquid junction for a current path was formed by filling an agar in the anisotropically etched part of the Si wafer, which had a size of 50㎛ × 50㎛, and then bonded it to the other. after complete fabrication of each part, it was filled qith a 2M KCl reference solution and encapsulated the sesor structure with a cold epoxy. The potential value of fabricated pH sensor was about 90mV/pH in the standard pH solutions.

上空靜脈症候群 : Dacron 曠置手術1例 Dacron by pass Graft between the Left Innominate Vein and the Right Atrial Appendage

金炯默,金鍾仁,金光宇,金庸樂,徐景弼 최신의학사 1968 最新醫學 Vol.11 No.3

A fifty-eight years old farmer was admitted with typical superior vena Cava syndrome. Cubital venous pressure was 42 cm H2O with marked swelling of face, neck, and, upper half of the body and headache. A tumor was noted in the posterior superior mediastinum by laminography. Preoperative cavography showed the occluded superior vena cava and maked collaterals. Crimped dacron graft was inserted between the left innominate vein and right atrial appendage. Postoperatively symptoms were relieved markedly, showing edema free face and decreased cubital venous pressure of 26.5 cm H2O. At the time of discharge-- one month after the grafting-. the patient was symptom free and cavogram showed patent graft. Histologically biopsied tumor was metastatic squamous cell carcinoma of probable bronchogenic origin. Total dose of 3150 r x-ray irradiation was administered during two weeks period, beginning on the eleventh postoperatvie day Up to this date, three months after operation, the patient is free of symptoms.

Study on physicochemical properties of U3+ in LiCl-KCl eutectic media at 773 K

Kim, Tack-Jin,Jung, Yongju,Shim, Joon-Bo,Kim, Si-Hyung,Paek, Seungwoo,Kim, Kwang-Rak,Ahn, Do-Hee,Lee, Hansoo Springer-Verlag 2011 JOURNAL OF RADIOANALYTICAL AND NUCLEAR CHEMISTRY Vol.287 No.1