• Tribology and Lubricants
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• 제32권5호
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• pp.154-159
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• 2016

This paper presents an experimental study of the leakage performance and endurance performance of a mechanical face seal in the 7-ton-class turbopump of the Korea Space Launch Vehicle 2 third-stage engine. We install a mechanical face seal between the fuel pump and turbine to prevent the mixing of the fuel and turbine gas. We design and manufacture a prototype mechanical face seal, which has two parts, namely, a bellows seal assembly and mating ring. We set up a test facility to measure the leakage and endurance of the mechanical face seal. For the similarity tests, we use water under real operating conditions such as high rotational speed, high temperature, and high pressure. Through investigation of the leakage and carbon wear rate, it is possible to evaluate the performance of the mechanical face seal. The results of the leakage and endurance performance test demonstrate the absence of any leakage from the prototype mechanical face seal after a trial run and clarify that the acceptable wear rate fully satisfies the turbopump requirements. Finally, we install a qualified mechanical face seal in a 7-ton-class turbopump and perform a validation test in the turbopump real-propellant test facility in the Korea Aerospace Research Institute. The test results confirm that the mechanical face seal works well under real operating conditions.

• 소성∙가공
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• 제20권8호
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• pp.581-587
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• 2011

The production of high-precision micro-sized screws, used to fasten parts of micro devices, generally utilizes a cold thread-rolling process and two flat dies to create the teeth. The process is fairly complex, involving parameters such as die shape, die alignment, and other process variables. Thus, up-front finite-element(FE) simulation is often used in the system design procedure. The final goal of this paper is to produce high-precision screw with a diameter of $800{\mu}m$ and a thread pitch of $200{\mu}m$ (M0.8${\times}$P0.2) by a cold thread rolling process. Part I is a first-stage effort, in which FE simulation is used to establish process parameters for thread rolling to produce micro-sized screws with M1.4${\times}$P0.3, which is larger than the ultimate target screw. The material hardening model was first determined through mechanical testing. Numerical simulations were then performed to find the effects of such process parameters as friction between work piece and dies, alignment between dies and material. The final shape and dimensions predicted by simulation were compared with experimental observation.

• 수산해양기술연구
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• 제31권3호
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• pp.240-246
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• 1995

옥돔의 조획 기구를 알아내고, 낚시를 개량하기 위해서 수조 중에서 옥돔의 연승어구에 대해 반응 행동을 비디오 카메라로 관찰 조사하였다. 옥돔은 물살을 거슬르면서 해저 위를 천천히 유영하며 미끼에 접근하였고, 미끼를 물때에는 불완전하게 무는 경우가 많았으며, 미끼를 문 후에는 천천히 뒤로 유영하면서 아릿줄이 당겨지면 미끼를 내뱉는 등의 완만하고 주의 깊은 행동을 보였다. 대부분의 조획은 미끼를 깊이 삼킨 후에 옥돔이 Rush 또는 Jerk 행동을 할 때 되었고, 조획과 관계 깊은 행동연쇄는 Chewing$\longrightarrow$Jerk 또는 Chewing$\longrightarrow$Rush였다. 현장시험에서 채가 긴 낚시가 조획성능이 매우 낮았고, 채가 짧은 낚시에는 조획성능도 양호하고 조획된 부위가 깊었던 것을 고려하면 옥돔은 낚시를 깊이 삼켜야만 조획이 가능하므로 조획성능만을 생각하면 낚시의 형상은 낚시 채가 짧으며 끝이 안으로 굽어 있는 형상이 적합하다. 본 연구에서 제안하는 낚시 형은 조획성능을 위한 조건을 만족하면서도 기계화 조업도 가능한 절충형의 구조이다.

• 대한조선학회논문집
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• 제54권4호
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• pp.329-334
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• 2017

As the motion response of heave for floating bodies on the water surface is relatively large near the natural frequency, it is necessary to predict its value accurately from the stage of initial design. Bodies accelerating in fluid experience force acted upon by the fluid, and this force is quantified by using the concept of added mass. For predicting the natural frequency of heave we need to know the added mass, which is given as a function of frequency, and hence the natural frequency can be obtained through only by iteration process, as was pointed out by Lee (2008). His method was applied to circular cylinders, and two dimensional cylinders of Lewis form by making use of the Ursell-Tasai method in the previous works, Lee and Lee (2013), Kim and Lee (2013), and Song and Lee (2015). In this work, a similar algorithm employing the concept of strip method is adopted for predicting the heave natural frequency of KCS(KRISO Container Ship), and the obtained computational result was compared with other existing experimental data, and the agreement seems reasonable. Furthermore, through the error analysis, it is shown that why the frequency corresponding to the local minimum of the added mass and the natural frequency are very close. And it seems probable that we can predict the heave natural frequency if we know only the local minimum of added mass and the corresponding frequency under a condition, which holds for ship-like bodies in general.

• 한국콘텐츠학회논문지
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• 제20권11호
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• pp.511-524
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• 2020

연구목적은 혈액투석환자를 위한 혈액투석 중 자전거운동과 걷기운동을 개발하여 적용하고, 혈액투석환자의 신체 활동량이 건강관련 삶의 질과 영양섭취에 미치는 영향을 확인하기 위함이다. 연구방법은 혈액투석환자에게 적용한 유산소 운동 프로그램의 효과를 확인하기 위한 비동등성 대조군 전·후 실험연구이다. 연구대상자는 중재군과 대조군에 각각 30명이 배정되어 총 60명이었다. 운동중재는 두 종류의 유산소 운동이 포함되어 있으며, 총 8주간 진행되었다. 첫 번째 운동은 일주일에 세 번씩 혈액투석 중 수행되는 자전거운동이었고 두 번째 운동은 일주일에 최대 7 일 동안 실시되는 걷기운동이었다. 통계분석은 기술통계, 독립표본 t-test, 𝑥2-test와 Mann-Whitney U test를 사용하였다. 영양섭취는 CAN-2.0을 사용하여 평가하였다. 연구결과는 중재군이 중재 후 신체활동량 점수가 유의하게 높았으며, 신체적 건강관련 삶의 질도 중재 후 유의하게 개선되었다. 그러나 영양섭취는 중재 전 후 유의한 차이가 없었다. 비록 그룹 간의 차이는 없었지만, 총 칼로리 섭취는 중재 후에 중재군이 대조군보다 높은 것으로 나타났다. 신체적 건강관련 삶의 질은 동물성 단백질, 망간, 셀레늄과 비타민 C와 유의한 상관관계가 있었다. 본 연구는 혈액투석 중 자전거운동과 걷기운동은 신체활동량과 신체적 건강관련 삶의 질을 향상시키는데 효과적인 것으로 나타났다. 따라서, 본 연구결과는 혈액투석환자의 운동증진을 위한 지침으로 사용될 수 있을 것이다.

• 정보처리학회논문지B
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• 제17B권1호
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• pp.47-54
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• 2010

오래된 영화 필름이나 비디오 테이프 등의 영상물에서 나타나는 대표적인 손상으로는 긁힘과 얼룩무늬 손상이 있으며, 본 논문은 긁힘 손상을 자동 탐지하고, 자기상관 (AR: autoregressive) 이미지 생성모델 (PAST-PRESENT 모델) 기반의 영상 인페인팅 모델을 사용하여 손상을 복원하는 시스템을 설계하고 구현하였다. AR 이미지 모델 생성을 위해, 지역성을 최대화할 수 있도록 인접 화소를 모으는 Sampling Pattern을 사용하였으며, 추출된 화소들을 필터링 (filtering)하는 단계, AR 모델 파라미터 계산 (model fitting)을 위한 Durbin-Levinson 알고리즘, 최종 파라미터를 통한 훼손된 화소의 예측 및 보간 단계로 구성된다. 구현된 시스템은(1) VHS 테이프를 통한 아날로그 영상물의 디지털화, (2) 긁힘 손상의 자동탐지와 자동손상복원, (3) 얼룩무늬의 수동탐지와 자동복원의 3단계 복원절차를 지원하도록 설계하였다. 단계 1과 단계 2는 영상복원 고속화를 위해 TIDSP 보드 (TMS320DM642 EVM)을 이용하여 구현하였으며, 단계 3은 사용자의 수동탐지를위해, PC 를 사용하여 구현하였다. 본 논문에서 제안된 기법을 고전 한국영화 2편 (자유만세와 로보트 태권 V)에 대하여 실험하였으며, 본 논문에서 제안한 자기상관 기반의 복원 시스템은 Bertalmio 인페인팅 기법과 비교하였으며, 주관적 화질 (MOS 테스트) 및 객관적 화질 (PSNR), 특히, 숙련된 복원기술자에 의한 복원과의 차이를 정의하는 복구품질 (RR)에서 향상된 결과를 보임을 확인하였다.

• 여성건강간호학회지
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• 제1권2호
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• pp.200-221
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• 1995

The confusion of the sense of value on sex is increasing because of the rapid change in social-cultural environment. Also due to a rise in the standard of living, the age of adolescence is getting lower, and so the second sexual marks appear to primary schoolers. At this time in the aspect of the education for the whole man, it's very important for primary schoolers to acquire right knowledge and desirable attitude on sex so that can overcome psychological instability caused by physical growth, be responsible for their behaviors and lead happy lives. This study was made to find out the effects of sex education for the primary schoolers' knowledge and attitude about sex. The study was designed as simulated control group pretest-posttest design, which only pretest was practiced to control group and after sex education only posttest was practiced to experimental group. The data was collected for 18 days from March 13, 1995 to March 31, 1995. The subjects of this study were 130 six-graders in a private primary school in seoul. The control group and experimental group were composed of 65 pupils, each. Sex education consisted of lecture and discussion and the materials were this researcher's own made, 'How do I grow? and related OHP film and video. This education was practiced 40 minutes at a time, at intervals of 2-4 days' six times during 3weeks. For sex knowledge tools, 20 item questionaries on the base of related reference books and contents of this study were used. For sex attitude tools, this researcher's own made 13 item questionaries were used which were revised and complemented and laying stress on the reference books. The data was analyzed through pc-SAS program. The homogeneity test in terms of the general characteristics of experimental and control group was analyzed through $x^2$-test and t-test. And the difference in the primary schoolers' score on knowledge and attitude about sex before and after the sex education was analyzed through t-test and ANCOVA. The results of this study are as follows : 1. The result of the homogeneity test in terms of the general characteristics of the experimental and control group showed that there were significant differences in economic standard($x^2$=2.92, P=0.052) and brotherly ties($x^2$=3.78, P=0.052). 2. Hypothesis 'After sex education, the score of primary schoolers' sex knowledge will be higher than before. 'showed statistically significant difference.(t=11.99, P=.0001) Sex education was practiced under control over subjective view of economic standard and brotherly ties which showed significant difference at the homogeneity test in terms of the general characteristics between the two groups. After this education, the results of comparing the score of primary schoolers' sex knowledge also showed significant difference between the two groups. So hypothesis I was supported since primary schoolers to have education showed noticeable results in the sex knowledge score. (F=16.52, P=.0001) 3. Hypothesis 'After sex education, primary schooler's sex attitude score will be higher than before' showed statistically significant(t=5.08, P=.0001) Sex education was practiced, too, under control over subjective view of economic standard and brotherly ties which showed significant difference at the homogeneity test in terms of the general characteristics between the two groups. Bat this time the results of comparing the primary schoolers' sex attitude showed no significant difference between the two groups. So hypothesis II was rejected since for primary schoolers to have sex education showed no noticeable results in sex attitude score. (F=3.52, P=.0628) These results of the study show that sex education gives affirmative change to the primary schooler's sex knowledge, bat short periods' sex education doesn't give any change to the sex attitude. For the establishment of the pupils' desirable sex attitude, systematic and concrete sex education fit for the pupils' developing stage should be practiced over a long period of time.

• 한국초지조사료학회지
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• 제4권1호
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• pp.51-61
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• 1983

본(本) 시험(試驗)은 혼파초지(混播草地)에 있어서 Italian ryegrass(Lolium multiflorum)의 파종비율(播種比率)과 예취빈도(刈取瀕度)가 첫번째 수확년도(收穫年度)의 목초(牧草) 총(總) 건물생산량(乾物生産量) 식생(植生) 구성비율(構成比率)에 미치는 영향(影響)을 구명(究明)하기 위(爲)하여 수행(遂行)되었다. Italian ryegrass의 파종량(播種量)을 10a 당(當) 0.3kg 및 1.0kg으로 하여 주구(主區)로 하였고 예취빈도(刈取頻度)를 년간(年間) 3, 4 및 5회(回)로 하여 세구(細區)로 한 분할구배치(分割區配置) 3반복(反復)으로 시험(試驗) 설계(設計)를 하였으며 1981년(年) 9월(月)부터 1982년(年) 8월(月)까지 12개월간(個月間) 시험(試驗)을 수행(遂行)하였던 결과 얻어진 성적을 요약(要約)하면 다음과 같다. 1. 혼파초지(混播草地)에 Italian ryegrass를 10a당(當) 0.3kg과 1.0kg을 조합(組合)했을때 수확(收穫) 첫 년도(年度)의 목초(牧草)의 총건물수량(總乾物收量) 0.3kg을 조합(組合)했을 때가 약간 높았으나 처리간(處理間)의 유의성(有意性)은 없었다. 2. 전(全) 시험기간(試驗期間)을 통(通)하여 목초(牧草)의 총(總) 건물수량(乾物收量)은 예취빈도(刈取頻度)를 자주 할수록 증가(增加) 되었으나 통계적(統計的) 유의성(有意性)은 없었다. 3. 잡초(雜草)의 발생(發生)은 Italian ryegrass를 10a 당(當) 1.0kg 파종(播種) 하였을때 현저히 감소 하였으며 초지조성시(草地造成時) 잡초발생(雜草發生) 억제에 Italian ryegrass의 파종(播種)이 유효하다고 사료(思料)된다. 4. Italian ryegrass의 총건물량(總乾物量)은 Italian ryegrass를 10a당(當) 1.0kg으로 파종(播種)하였을때 유의적(有意的)으로 높았고 orchardgrass와 ladino clover의 건물수량(乾物收量)은 다소(多少)낮았다. 5. 시험초기(試驗初期)에는 orchardgrass와 ladino clover의 식생구성비율(植生構成比率)이 Italian ryegrass의 파종량(播種量)이 높은 처리구(處理區)에서 감소(減少) 하였으나 시험(試驗) 종료시(終了時)에는 Italian ryegrass가 식생구성(植生構成) 비율(比率)에 큰 영향을 미치지 못하였다.

• 농업과학연구
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• 제33권2호
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• pp.141-147
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• 2006

본 시험은 논에서 콩을 재배할 경우 파종기 및 재식밀도를 달리할 경우 수량과 생육에 미치는 영향을 알고자 실시하였으며 그 결과는 다음과 같다. 1. 파종기에 따른 수량은 5월 단작이 가장 많았으며 7월 5일 파종할 경우 가장 적었는데 풍산나물콩 5월 24일 파종은 10a 당 362 kg을 보였다. 백립중은 풍산나물콩의 경우 파종이 늦을수록 증가하였으나 한남콩은 감소하는 경향을 보였다. 2. 경장, 엽면적, 건물중은 5.24 파종이 가장 높았으며, 6.14 파종과 7.05 파종은 큰 차이를 보이지 않았다. 3. 개화기 및 착협기의 엽 건물중과 수량간에는 높은 정의 상관을 보였으나 입비대시는 유의성은 없었으며, 파종기에 따른 상대생장율(RGR)은 파종기가 늦을수록 증가하였다. 4. 파종기에 따른 광합성은 정엽의 경우 큰 차이를 보이지 않았지만, 입비대시의 제 7엽의 광합성은 5월 24일 파종때보다 6.14와 7.05 파종에서 보다 높은 경향을 보였다.

• 한국작물학회지
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• 제49권2호
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• pp.105-109
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• 2004

Field studies were conducted in the southeastern Korea ($36^{\circ}$N) on a commerce silt loam soil at paddy field. Seed were manually planted on 16 July 2003. Plants were planted with plant densities of 70${\times}$10 cm (row width x plant spacing), 50 x 10 cm, and 30 ${\times}$10 cm. Two seedlings per hill were taken prior to V3 stage. Fertilizer was applied prior to plant at a rate of 30-30-34 kg (N-$\textrm{P}_2\textrm{O}_5$-$\textrm{K}_2\textrm{O}$) per ha. Experimental design was a randomized complete block in a split plot arrangement with three replications. Yield from different planting densities responded similarly in three soybean cultivars and increased when planting density increased. Somyeongkong showed the highest increasing rate of yield about 26% by 338 g $\textrm{m}^{-2}$ at 30 x l0 cm compared to yield of conventional planting density (70 x 10 cm). Also, the planting density significantly affected pod and seed number and seed weight, but not seed per pod. The tallest plant appeared at 30${\times}$10 cm. The change of leaf area according to days after emergence showed differently in soybean cultivars. The highest and lowest total dry matter production per square meter appeared at 30 x 10 cm and at 70 x 10 cm, respectively. Crop growth rate (CGR) showed greater at R3∼R4 stages compared with V7∼R2 or R2∼R3 growth stages and showed the greatest at 30 x 10 cm in three soybean cultivars. As late planted soybean, there was a significant relation between seed yield and CGR, and leaf area index (LAI) according to planting densities at before and after the flowering stage. Relationship between seed yield and CGR in three planting densities showed a highly significant positive relation ($\textrm{R}^2$=0.757) at R3 to R4 stages, and significant relations ($\textrm{R}^2$=0.505, 0.617) at V7 to R2 and V2 to V3. Also, there was a highly significant positive difference between seed yield and LAI during R3 to R4 and R2 to R3 stages.