Pb-In솔더를 Si기판에 증착후 리플로시 가열 속도와 플럭스 사용에 따른 솔도볼 형성 거동, 증착 솔더이동, UBM(under Mump Metallurgy)의 Au층과 In간의 금속간 화합물 형성에 관하여 연구하였다. 가열 속도가 1˚C/min에서 10˚C/min, 20˚C/min로 증가하고, 플럭스를 적용한 경우 솔더볼은 용이하게 형성되었다. 특히 플럭스를 사용하여 형성시킨 솔더볼에서는 UBM Au층과 In간의 반응에 의하여 Auln 금속간 화합물이 형성되었다.

본 논문에서는 랜덤한 축대칭 기하학적 초기결함을 갖는 원통이 축방향 충격하중을 받는 경우의 반경방향 변위가 임계기준치를 최초로 통과하는 확률론적 충격좌굴 파괴시간을 해석할 수 있는 방법을 제시하였다. 랜덤한 기하학적 초기결함의 생성을 위해 초기결함의 평균함수 및 상관함수를 이용하여 확률장을 형성하는 방법을 사용하였다. 본 논문에서 제시된 방법은 실제적인 기하학적 초기결함이 갖는 불확실성을 취급하는데 적절하고 실용적이므로 이를 고려한 원통의 구조안전도해석에 이용할 수 있다.

The Chinese ancient accounts of timing observations of 48 lunar eclipses and the secular variation of the Earth's spin speed are discussed. A series of ΔT expressing the secular deceleration of the Earth's rotation was obtained. The average increase rate of length of the day is about 1.5 milliseconds per century.

We show that the star formation activity of spiral galaxies has a great variety. The star formation variation in a time scale of 10 8 yr and the mechanism responsible for the variation are discussed.

This study was carried out at Crop Experiment Station in 1993 and 1994. The objective of this study was finding out variation of growth and yield of corn according to maturity. Hybrids of corn used in this study were early maturing corn Comet80, Elite90,

The temporal variations of the transparency with water temperature, salinity and density during spring-neap tidal cycle of spring, summer, autumn and winter time were investigated at 34 stations using observation data in Deukryang Bay, Korea, in 1995. It was found that the transparency was depended on spread of tidal currents and vertical stratification of water. The depth of transparency during neap tide was deeper than that of spring tide. The value of transparency in summer was the largest among four seasons. We concluded that the vertical stratification intensity of water mass and vertical distribution of transparency.

This study aims to investigate theoretically and experimentally second-order water level variation. The simple method obtaining second-order water surface elevation and mean water level applicable to both progressive and diffraction wave, mean water level set-down, as well as set-up occurs and it is shown to be in good agreement with the experimental results.

약용 또는 식용으로 이용되고 있는 산림자원 식물인 산마늘(Allium victorialis var. platyphyllum)의 지역별 군락생태적 특징과 형태적 유전적 변이를 살펴본 바 다음과 같이 요약할 수 있었다. 식생구성을 살펴보면 오대산과 함백산의 경우는 고목충의 우점종은 신갈나무이며 아고목 관목층은 당단풍, 쇠물푸레, 철쭉꽃의 피도가 높게 나타났다. 울릉도의 경우는 너도밤나무, 우산고로쇠, 섬피나무, 마가목, 섬단풍나무가 고목층에 나타나며, 초본층에는 우점종인 산마늘과 함께 일색고사리, 섬말나리, 큰연령초의 피도가 전반적으로 높게 나타난다. 오(1977)의 식물지리구계구분에서 울릉도를 울릉도아구로 별도로 구분하고 있는 것과 같이 내륙의 오대산, 함백산과 울릉도의 전반적인 식생구성은 현저한 차이를 나타내었다. 형태적 인자에 대한 주성분분석과 판별분석 결과 울릉도와 함백산 및 오대산의 두 group으로 구분되었다 울릉도의 산마늘은 함백산 및 오대산 지역과 비교하여 , band가 없고, 대신 band가 나타나 유전적으로 차이가 있는 것으로 나타났으며, 함백산과 오대산 두 지역의 산마늘에 있어서는 함백산에 band가 하나 더 있을 뿐이어서 동위효소 GOT에 의한 변이는 거의 없었다. 따라서 세 지역의 산마늘에 대한 유전적 변이에 있어 함백산과 오대산은 큰 차이가 없으나 이들 두 지역과 울릉도와는 변이의 폭이 크게 나타났다.

In general, the characteristics of plasma spray coating are strongly dependent on process conditions. In this paper, Mo and Co alloy coating layers were made by plasma spraying with different spray parameters and characterized using X-ray diffraction, scanning electron microscopy(SEM), hardnass test, and wear test. It was found that the coating characteristics were mainly affected by phase composition of the powder, spray distance, arc current, and gas flow rate.

The variation of the urban water demand and the amount of water in the distribution reservoir was studied with time for a day. The city of Kwangju in Korea was selected as a study area. The population of Kwangju in the end of 1993 was more than one million and two hundred thousand peoples. The average of daily water use in 1993 was about three hundred and fifty thousand tons a day. One day was devided into 12 divisions with a 2 hour increment. The water use demand related to the amount of water in the distribution reservoir was observed for the given time interval of a day. The water use index was defind in percentage that indicates the ratio of the amount of water use for a time interval to the amount of water use for a day. The water use index with consideration of the water stored in the reservoir was found to be useful to manage and to operate the water supply systems in real time.

This study was to investigate time-dependent degradation process under various pH condition for organophosphorus(org-p) insecticides, namely Demeton-s-methyl, Diazinon, Parathion, Phenthoate, and EPN in several waters. They were analysed by GC-FTD according to standard methods for the examination of water and wastewater. In pH=4, diazinon showed disappearance after 14 days in chromatogram. In pH=11, org-p insecticides were almost degradable after 7 days. In this condition, effect of pH on degradation process was greater than that of light. In pH=7, org-p insecticides persisted residues after 112 days except Demeton-s-methyl. In BOD_5 120, 250 ppm and domestic water, org-p insecticides showed also rapid degradation process.

Drosophila 의 수컷 앞다리 부절에 존재하는 성즐의 유무는 Sophophora subgens와 Drsophila sub-genus의 분류기준이 되며, 전자의 경우는 종 특이적인 성즐을 가지나 후자에는 일반적으로 존재하지 않는다. 수종 Drosophila 의 성즐에 관하여 비교 조사한 결과 Sophophora subgens내의 D. melanoga-ster subgroup의 경우는 모두 제 1부절에만 존재하였다. 그중 D. melanogaster complex의 D. mauti-tiana 가 약 12.75개, D. simulans는 평균 8.35정도였으며, D. yakuba complex는 D. melanogaster complex에 비하여 다소 적었다. D. melanogaster complex의 종간 교배에 의한 분석으로는 성즐유전양시겡 대한 뚜렷한 방향성을 제시할 수 없었다. Sophophora subgemus의 D. melanogaster species group에 속하는 다른 3종의 경우(D. auralia, D. lutecens 및 D. suzuki)는 성즐의 분포 양식에서 D. immigrans 및 D. virilis)에서는 성즐이 존재하지 않았다.

The speed of vertical migration and the volume backscattering strength of the scattering layers during the evening and morning transitions between day and night were measured in November 1990-1992 in thermally stratified waters of the East China Sea. Acoustical measurements were carried out using a scientific echo-sounder operating at t재 frequencies of 25 and 100kHz, and using an echo-integration system connected with a micro-computer. Biological sampling was accomplished by bottom trawling to identify fish species recorded on the echo sounder, and the species and length compositions were determined. The values of scattering strength were allocated to group of fishes according to the fish traces on the echo recording paper and the species composition of trawl catches. The vertical velocities of migration derived from the changes in the depths and the values of peak scattering strength of the dense layer vertically migrating toward the bottom or toward the surface. The trawl data suggest that snailfish and fishing frog were the most abundant fishes in all research stations. As sunrise approached, the fish formed a strong concentration just above the thermocline. The the highest values of scattering strength in the entire water column appeared in the depth strata above the thermocline just before the begining of downward migration. As soon as the fish began to migrate downwards across the thermocline, the values of the scattering strength in the depth strata above the thermocline rapidly decreased, while the values for the scattering layer moving slowly toward the bottom gradually increased. During the 1992 surveys, the speed of the vertical migration was estimated to be 0.38m/min in the upward migration and 0.32m/min in the downward migration, respectively. That is the rate of vertical migration was slightly higher at dusk than at dawn. Similar migration patterns were observed on different stations and under different weather conditions during the surveys in 1990.

We have detected a SiO maser line (v=1, J=2- 1) for 15 stars out of about 80 long period variables in the wide range of period. No new sources are detected; all detected sources are variables with period longer than 300 days; no evidence is found that the dust grains in the outer envelope have influenced on this line. The time variation of this maser line for 7 stars, T Cep, μ Cep, U Her, R Leo, R Lmi, U Ori, and R Ser is observed and compared with optical light curve at the same epoch of maser observation. No universial relation between the time variation and the optical light curve is found. It implies that the radiation from a central star does not much play an important role for the direct pumping of the SiO maser line.