• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.04a
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• pp.31-31
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• 1998

위성체의 보조추진시스템은 임구궤도까지의 궤도진입 및 임무궤도상에서의 속도 또는 자세제어에 필요한 임펄스를 제공한다. 단일하이드라진 추력기는 하이드라진(H$_2$H$_4$)과 자발적 촉매(Shell 405)의 발열 및 흡열 열분해 반응에 의해 발생하는 질소($N_2$), 수소(H$_2$), 암모니아(NH$_3$), 혼합가스를 노즐을 통해 방출하므로써 요구되는 impulse를 얻는다. 단일하이드라진 추력기 설계는 주입기, 촉매대, 노즐과 기타 설계 형태에 따른 다지관, 링, 스크린, 지지판 등의 부수적인 부품으로 구성된다. 추력기 제작 과정은 크게 piece-parts 기계가공, HEA(Head End Assembly)와 TCA(Thrust Chamber Assembly)로 구성되고 각 세부공정마다 전수시험 및 검사를 가진다. 연소시험설비는 최소 모사진 공 수준이 고도 100,000 ft(8.4 torr)를 만족시킬 수 있는 진공설비, 시험제어부, 성능변수 측정 및 처리부, 추진제 가압 공급부, 기타 환경 안전 및 부대 설비로 구성된다. 추력기 연소성능시험 절차는 추진제 충전 및 오염 여부 표본 검사, 가압 및 공급 라인 이상여부 확인, 추력기 장착, 추진제 가압 및 공급, 시험장치 보정, 진공 모사 및 연소성능시험, data 처리 등으로 구성된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1007-1011
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• 2006

본 연구에서는 어류 생태계 유지를 위해 필요한 생태학적 추천유량을 산정하고, 어류의 서식처 환경인 여울과 웅덩이의 형성조건을 검토함으로써 '작용'인 '흐름'과 '응답'인 '하상구조'와의 상관 관계를 규명하고자 하였다. 본 연구의 대상하천인 금호강에서는 하상변동이 활발한 자연 상태를 벗어나 하상의 이동성 상당히 둔화된 상태이며, 저수로내 여울과 웅덩이도 대표어종이 서식할 수 있는 자갈하상 구조에 변화가 일어나고 있는 것으로 분석되었다. 이것은 금호강 상류에 영천댐 건설의 영향이 어느 정도 미치고 있음을 유황분석 결과를 통해 간접적으로 파악할 수 있었다. 댐과 같은 수공구조물의 건설로 인하여 하도가 고정화된 상태에서 장기간에 걸치게 되면 여울과 웅덩이와 같은 하상구조가 축소되거나 소멸되어 금호강에서의 대표어종 서식처 환경에 영향을 미칠 것으로 추정된다. 금번 연구결과, 금호강에서 어류의 생식에 필요한 생태학적 추천유량 $8.2m^3/sec$가 필요하였으며, 어류의 서식처 환경인 여울과 웅덩이를 지속적으로 유지되기 위해서는 $250m^3/sec$ 이상의 유량이 연간 한번 이상 흘러야 하고, 2.5년 내지 3년 마다 약 $500m^3/sec$ 정도의 유량이 흐를 필요가 있다고 분석되었다. 본 연구 대상지점에서 흐름과 하상구조를 하천생태계와 연계해서 볼 때, 생태추천유량은 어디까지나 대표어종이 서식할 수 있는 최소조건에 불과하다. 대표어종이 장기간에 걸쳐 서식할 수 있는 하상구조가 존재하기 위해서는 대표어종이 선호하는 여울과 웅덩이가 필요하다. 결국 대표어종이 서식하기 위한 필요충분조건은 생태추천유량 확보와 아울러 대표어종이 선호하는 하상구조를 유지하기 위해서는 하도의 이동성을 유발할 유황변화가 필요하다는 것이 입증되었다.대상으로 연중 발생하는 큰 호우사상에 대해 임의의 강우관측소를 결측지점으로 가정하고 주변의 강우관측소로부터 각각의 방법을 이용해 가중치들을 산정하여 결측지점의 강우량 값을 보정하고자 하였다. 또한 각각의 방법을 이용하여 얻어진 결과에 대해 실측값과 보정값의 오차정도를 평균절대오차법(Mean Absolute Error)과 제곱평균제곱근오차법(Root Mean Squared Error)에 의해 산정하여 보정 방법간의 효율성을 검토하고자 하였다.9년, 그리고 2010년${\sim}$2019년까지 총 4구간으로 나누어 결과를 도출하였으며 예상한 바와 같이 후반기 20년 동안에 세 가지 지표가 취약해 지는 것을 확인할 수 있었고, 특히 2000년부터 2009년까지 10년 동안에는 더욱 취약해짐을 확인할 수 있었다.를 보임에 따라 그 정책적 효과는 때로 역기능적인 결과로 초래하였다. 그럼에도 불구하고 이 연구결과를 통하여 최소한 주식시장(株式市場)에서 위탁증거금제도는 그 제도적 의의가 여전히 있다는 사실이 확인되었다. 또한 우리나라 주식시장에서 통상 과열투기 행위가 빈번히 일어나 주식시장을 교란시킴으로써 건전한 투자풍토조성에 저해된다는 저간의 우려가 매우 커왔으나 표본 기간동안에 대하여 실증분석을 한 결과 주식시장 전체적으로 볼 때 주가변동율(株價變動率), 특히 초과주가변동율(超過株價變動率)에 미치는 영향이 그다지 심각한 정도는 아니었으며 오히려 우리나라의 주식시장은 미국시장에 비해 주가가 비교적 안정적인 수준을 유지해 왔다고 볼 수 있다.36.4%)와 외식을 선호(29.1%)${\lrcorner}$ 하기 때문에 패스트푸드를 이용하게 된 것으로 응답 하였으며, 남 여 대학생간에는 유의한 차이(p<0.05)가 인정되었다. 응답자의 체형은 ${\ulco

• Korean Journal of Environment and Ecology
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• v.7 no.2
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• pp.187-191
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• 1994

A mixed forest community in Tokyusan was studied to determine the adequate plot area of tree stratum for investigating forest community structure. Nineteen nested plots were set up in the studied forest community, and species-area curve and performance curve were established. According to species-area curve, the minimum plot area where a given percentage increase in plot area produced less than the same percentage increase in number of species was 500$m^2$. The minimum plot area where a given percentage increase in plot area produced less than the half of the percentage increase in number of species was 1,000$m^2$. According to performance curve of the importance values of the major species, the minimum plot area where the importance value of the major species was distinguished from each other was 900$m^2$, and the minimum plot area was 500$m^2$ except for a big tree of Pinus densiflora distributed unexpectedly. According to performance curve of species diversity, the minimum plot area was 400$m^2$. Similarity indices between plot area above 900$m^2$ and total plot area were more than 90% and similarity indices between plot area above 400$m^2$ and total plot area were more than 85%. It may be as a conclusion that minimum plot area was generally about 500$m^2$ and in case of requiring more accuracy, minimum plot area was about 1,000$m^2$.

• Journal of Nutrition and Health
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• v.44 no.2
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• pp.162-170
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• 2011

We tested the hypothesis that an improved nutritional environment increases the size of stature sexual dimorphism (SSD) by comparing mean height changes in North and South Korean adults. For the first round of sampling, those North Korean refugees who had reached the age of 20 years before leaving North Korea were selected for the study. Then, two birth-year cohorts born between 1955 and 1959 and between 1980 and 1984 were finally selected for the analysis (383 males and 529 females). North Korean refugee mean height data were compared to the mean height of the comparable South Korean population derived from 2004 Korean size results (373 males and 429 females). The results of the analysis showed that there was no increase in mean height among the refugees, either in males or females, between the two birth-year cohorts. As a result, no change in SSD was observed between the two birth-year cohorts. In contrast, South Koreans showed a remarkable increase in height, with males having a greater increase during the corresponding 25 years. Consequently, South Korean SSD increased significantly with time. These results support the hypothesis that improved nutritional quality increases SSD.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.22 no.2
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• pp.64-79
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• 2023

This study reviewed the process of applying the Monte Carlo simulation technique to the traffic allocation problem of metropolitan subways. The analysis applied the assumption of a normal distribution in which the travel time information of the inter-station sample is the basis of the probit model. From this, the average and standard deviation are calculated by separating the traffic between stations. A plan was proposed to apply the simulation with the weights of the in-vehicle time of individual links and the walking and dispatch interval of transfer. Long-distance traffic with a low number of samples of 50 or fewer was evaluated as a way to analyze the characteristics of similar traffic. The research results were reviewed in two directions by applying them to the Seoul Metropolitan Subway Network. The travel time between single stations on the Seolleung-Seongsu route was verified by applying random sampling to the in-vehicle time and transfer time. The assumption of a normal distribution was accepted for sample sizes of more than 50 stations according to the inter-station traffic sample of the entire Seoul Metropolitan Subway. For long-distance traffic with samples numbering less than 50, the minimum distance between stations was 122Km. Therefore, it was judged that the sample deviation equality was achieved and the inter-station mean and standard deviation of the transport card data for stations at this distance could be applied.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.6
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• pp.1375-1383
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• 1994

The water distribution system problem consists of finding a minimum cost system design subject to hydraulic and operational constraints. Since the municipal water distribution system problem is nonconvex with multiple local minima, classical optimization methods find a local optimum. An outer flow search - inner optimization procedure is proposed for choosing a better local minimum for the water distribution systems. The pipe network is judiciously subjected to the outer search scheme which chooses alternative flow configurations to find an optimal flow division among pipes. Because the problem is nonconvex, a global search scheme called Stochastic Probing method is employed to permit a local optimum seeking method to migrate among various local minima. A local minimizer is employed for the design of least cost diameters for pipes in the network. The algorithm can also be employed for optimal design of parallel expansion of existing networks. In this paper one municipal water distribution system is considered. The optimal solutions thus found have significantly smaller costs than the ones reported previously by other researchers.

• Microbiology and Biotechnology Letters
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• v.31 no.4
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• pp.322-328
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• 2003

The Transformation-Associated Recombination (TAR) cloning technique allows selective isolation of chromosomal regions and genes from complex genomes. The procedure requires knowledge of relatively small genomic sequences that reside adjacent to the chromosomal region of interest. This technique involves homologous recombination during yeast spheroplast transformation between genomic DNA and a TAR vector that has 5'and 3' gene targeting sequences. In this study, we examined the minimum size of specific hooks required for a single-copy gene isolation and compared the utility of different TAR vectors, radial and unique vectors, by cloning the same single-copy gene. The efficiency of TAR cloning of the hHPRT gene was same using hooks varying from 750 to 63 bp. The number of transformants decreased approximately 20-fold when the TAR vector contained two unique hooks versus using a radial vector, but the percentage of positive recombinants increased over 2-fold when a unique TAR vector was used. Therefore, we suggest that the two-unique TAR vector is suitable for general TAR cloning given its high selectivity, and the radial TAR vector is more suitable when genomic DNA is in limited quantity, for example, DNA isolated from pathological specimens. Moreover, we confirm the minimal length of a unique sequence in a TAR vector is approximately 60 bp for a single-copy gene isolation.

• Korean journal of applied entomology
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• v.33 no.2
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• pp.114-121
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• 1994

Population densities of intermediate nymphs and egg saw of Matsucoccus thunbergianae, a major insect pest of Pinus thunbergiona in southern coastal area of Korean peninsula, were est~mated. Tree samples of ca. 10cm D.B.H. were collected from old infestation area and newly invaded area. The numben of plimaly branches per tree were not significantly different by the locality, but those of secondaly and smaller branches were smaller in old infestation area The numbers of intermediate nymphs per tree in old infestation area and in newly invaded area were 10.8 and 13.1 times more than those on the trunk, respectively Approximately between 4, 200 and 208, 500 nymphs per tree were estimated. Men secondaw and smaller bmnch samples collected from the basal part of middle crown height, or from the central or the basal part of lower crown height, the number of samples required for the emr range of 20% were 21 and 11 far 10-20cm and 20-3 crn long branches, respectively. Approx~mately 63.6% of egg sacs of the whole tree were on the trunk. The node/intemode bearing the largest branch had the highest egg sac density; including that, four adjacent nodes/intemodes had ca. 37% of egg saw on the trunk.

• The Korean Journal of Applied Statistics
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• v.24 no.6
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• pp.1129-1138
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• 2011

Small area estimation has received significant intention in recent years due to a growing demand for reliable local area statistics. Traditional area-specific direct estimates based solely on sample survey data in the areas of interest do not provide adequate small area precision; however, design-based indirect local area estimators borrow strength from sample observations of related areas to increase the effective sample size. Design-based indirect estimation methods such as synthetic and composite estimators are considered to adjust local area unemployment rate estimates in the Korean Economically Active Population Survey. This study suggests an efficient alternative to minimize the cost to construct the unemployment rate of a local area through simulation under the condition that we can maintain a certain level of CV for the estimates. We obtained the results that the composite estimators using a sample size greater than 10 are more stable and significant at the level of CV 25% in our design scheme.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.1
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• pp.25-39
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• 2018

NIST(National Institute of Standards and Technology) has recently published SP 800-90B second draft which is the document for evaluating security of entropy source, a key element of a cryptographic random number generator(RNG), and provided a tool implemented on Python code. In SP 800-90B, the security evaluation of the entropy sources is a process of estimating min-entropy by several estimators. The process of estimating min-entropy is divided into IID track and non-IID track. In IID track, the entropy sources are estimated only from MCV estimator. In non-IID Track, the entropy sources are estimated from 10 estimators including MCV estimator. The running time of the NIST's tool in non-IID track is approximately 20 minutes and the memory usage is over 5.5 GB. For evaluation agencies that have to perform repeatedly evaluations on various samples, and developers or researchers who have to perform experiments in various environments, it may be inconvenient to estimate entropy using the tool and depending on the environment, it may be impossible to execute. In this paper, we propose high-speed implementations and an efficient memory usage technique for min-entropy estimation algorithm of SP 800-90B. Our major achievements are the three improved speed and efficient memory usage reduction methods which are the method applying advantages of C++ code for improving speed of MultiMCW estimator, the method effectively reducing the memory and improving speed of MultiMMC by rebuilding the data storage structure, and the method improving the speed of LZ78Y by rebuilding the data structure. The tool applied our proposed methods is 14 times faster and saves 13 times more memory usage than NIST's tool.