• Proceedings of the Korean Society of Precision Engineering Conference
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.581-584
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• 2005

A district heating(DH) system supplies environmentally-friend heat and is appropriate for reduction of energy consumption and/or air pollutions. The objectives of this paper are to systematize data processing of transition temperature, investigate its effects on fatigue life of DH pipes and optimization for size of DH pipes. A relational database management system as well as reliable fatigue life evaluation procedures is established for Korean DH pipes. Also, since the prototypal evaluation results satisfied both cycle-based and stress-based fatigue criteria. Through the optimum design process, the cross section diminished 18.64% and the CUF diminished 23.35%. So, it can be used as useful information in the future for optimal design, operation and energy saving via setting of efficient condition and stabilization of water temperature.

• Proceedings of the Korean Society of Applied Pharmacology
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• 한국응용약물학회 1994년도 춘계학술대회 and 제3회 신약개발 연구발표회
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• pp.195-195
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• 1994

병원별 총 추적기간은 602-4,137 인년 이었으며, 병원별 대상자 1인당 추적일수의 중앙값은 34.5-61일 이었다. 병원별 추적 완료율도 35.3-92.3%로 다양하게 나타났다. 대상자중 칼슘차단제의 혈관확장효과에 따른 부작용들의 8주간 누적 발생율을 보면, 안면홍조 23.3%, 두통 13.5%, 심계항진 13.3%, 어지러움 7.6%, 하지부종 6.6% 였다. 그 외 부작용으로는 변비 13예, 소화장애 8예, 오심 6예, 치은비대, 안면부종, 피로감이 각각 2예, 탈모증, 불면증, 허약감, 피부질환, 호흡곤란, 손발저림, 발한, 구강건조 등이 각각 1예 있었다. 안면홍조의 발생율이 남자(12.9%)보다 여자(29.9%)에서 높았으며, 투여한 약제에 따라서 Nitrendipine 34.0%, Nifedipine 26,6%, Nicardipine 17.8%, Amlodipine 12.2%로써 약제별로 차이가 있었다. 두통의 발생율은 40세 미만 32.8%, 40-54세 15,8%, 55세 이상 10.5%로써 연령이 증가할수록 발생율이 낮았다. 하지부종의 발생율도 남자(3.4%)보다 여자(8.6%)에서 높았으며, 투여한 약제에 따라서 Nitrendipine 15.2%, Nifedipine 10.0%, Amlodipine 2, 1%, Nicardipine 0%로써 약제별로 차이가 있었다. 안면홍조가 발생한 환자에서 약물을 계속 투여시 2주후에 63.5%, 4주후에 77.0% 6주후에 88.5%가 소실하여 최초 안면홍조가 발생한 환자중 11.5%에서만 증상이 남아있었다. 약물투여를 중단하게 된 사유는 안면홍조와 두통이 각각 15예, 심계항진 4예, 어지러움 2예, 변비 및 안면부종이 각각 1예로 나타났다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 한국항해항만학회 2016년도 춘계학술대회
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• pp.106-107
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• 2016

Rolling motion of floating body might upset the body, make crews and passengers exhausted and/or apply forces to the structure to cause damage. Therefore for almost ships bilge keels are equipped, in special case fin stabilizer or gyroscope may be installed. This paper suggests the Anti-rolling pendulum to reduce roll motion to act the similar role with anti-rolling tank. The device suggested has more effective than the anti-rolling tank with 1/6 volume of the tank.

• 연구논문집
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• 통권34호
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• pp.79-85
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• 2004

There are several types of life test method for hose assemblies. The two major tests used for hose assemblies are impulse test and burst test. And magnification adjustment of impulse pressure, heating of testing oil and repetitive motions of bending and straightening of testing hose are also performed for accelerating the life. According to the manufacture process of hose and swaging process of fitting, there is a difference in the life of hose assemblies from minimum 7 times to maximum 40 times during the life test in the same functioning condition. Like this, the life test of hose which has a wide scope of life distribution gives a problem that observation should take a long time to find out the existence of the bursting from the beginning of the test to the completion of bursting of hose assemblies. Therefore, this research proposes a process of concentrating on the defective section of hose assemblies and maximizing the life acceleration by giving 'Knockdown stress' to hose assemblies just until before the hose assemblies get out of order.

• Proceedings of the KSR Conference
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.1058-1070
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• 2007

Internal and external railway management corporations are using the periodic replacement criteria of rail by accumulated passing tonnage and wear to maintain rails for servicing. However, internal the periodic replacement criteria of continuous welded rail(CWR) by accumulated passing tonnage is the one(50kg/m-5 million gross tonnage, 60kg/m-6 million gross tonnage) presented in Japan before. It was estimated with the fatigue life about 50kg N rail joints applied diesel train load but it wasn't applied to current conditions of track; elimination of rail joint, using the concrete slab track and operation of light train load and effect of welding, manufacturing technique, grinding of rail. Therefore, in this study, it was investigated the types of damage and cause in welded rails and examined standards and information resources. Also, this study presents preliminary data to revise the periodic replacement criteria of CWR by current accumulated passing tonnage in bending test of laid welded rail and a survey of track maintenance history of Seoul metro.

• Journal of the military operations research society of Korea
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• 제24권1호
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• pp.41-57
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• 1998

Since the aircraft has a property of moving in the three-dimensional space, it may cause personally and financially critical damage in the case of an accident. Among the causes of aircraft accident, human factor has occupied about 70% of all accidents. Specially, fatigue among human's problems has been studied earlier than any other factor. Fatigue has been the cause of 75% of accidents that are related to human factor. So many studies have been conducted. But the direction of these studies mainly attach importance to the sleep loss and circadian rhythm. Limitation for flight time of ICAO is 8 hours per day, civil airlines in domestic line also adopt the limitation. But this rule is not based on human's performance but compromise between labor and management. The long-haul flight brings about a mental block to pilot. This mental block decreases performance of pilot and loses a lot of important information. So this may cause many accidents. This paper is to offer optimal flight time according to the amount of fatigue due to increasing flight time. The optimal flight time is searched through the field experiment. The experiment has adopted two methods. One is to examine pilot's objective fatigue accumulation rate through the critical fusion frequency, and another is to investigate pilot's subjective fatigue feeling through the fatigue subjective symptoms investigation table.

• Magazine of the Korean Society of Agricultural Engineers
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• 제44권2호
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• pp.117-126
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• 2002

Concrete containing discontinuous discrete steel fiber in a normal concrete is called steel fiber reinforced concrete(SFRC). Tensile as well as flexural strengths of concrete could be substantially increased by introducing closely spaced fibers which delay the onset of tension cracks and increase the tension strength of cracks. However, many properties of SFRC have not been investigated, especially properties on repeated loadings. Thus, the purposes of this dissertation is to study the flexural fatigue characteristics of SFRC considering cumulative damage. A series of experimental tests such as compressive strength, splitting tensile strength, flexural strength, flexural fatigue, and two steps stress level fatigue were conducted to clarify the basic properties and fatigue-related properties of SFRC. The main experimental variables were steel fiber fraction (0, 0.4, 0.7, 1, 1.5%), aspect ratio (60, 83). The principal results obtained through this study are as follows: The results of flexural fatigue tests showed that the flexural fatigue life of SFRC is approxmately 65% of ultimate strength, while that of plain is less than 58%. Especially, the behavior of flexural fatigue life shows excellent performance at 1.0% of steel-fiber volume fraction. The cumulative damage test of high-low two stress levels is within the value of 0.6 ∼ 1.1, while that of low-high stress steps is within the value of 2.4 ∼ 4.0.

• Proceedings of the Korea Water Resources Association Conference
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• 한국수자원학회 2022년도 학술발표회
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• pp.400-400
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• 2022

관로 내 빈번히 발생하는 수격압의 발생은 관망 구조물에 피로가 누적되고 관벽에 손상을 발생시켜, 관로 내 누수가 다양한 형태로 생성된다. 관 내 누수가 발생되는 경우 관 내부의 수격압의 발생 시 생성되는 부압으로 인하여 외부 물질이 관으로 흡수되거나 혼합되어 스케일과 미생물의 생성되는 등 관 내의 수질에 악영향을 끼치며 마찰을 증가시켜 통수능이 감소하고 관리에 추가적인 비용을 발생시킨다. 이러한 영향을 방지하기 위해 관 내에서 생성되는 누수를 탐지하기 위하여 수격압을 발생시켜 압력파를 분석하거나 추적을 수행하는 여러 가지 연구들이 수행되었다. 본 연구에서는 현장 관망과 연결된 100A 대구경 관로에 관로 수압 발생장치를 연결하여 기존의 수격압을 발생시켜 분석하는 방법 대신 안전하고 용이한 방법인 압력파를 주입하여 실험을 수행하였다. 실험을 통해 획득한 데이터를 시간상에서 분석하고 Fourier 변환을 통한 빈도상 분석과 Wavelet 분석으로 신호주기에서 누수가 미치는 영향을 파악하였다. 실험 결과에서는 누수에 의한 영향으로 반사파가 직접적으로 변형되는 형태보다 시스템 전체에서 반영되어 수두가 감쇠되는 형태로 나타났다. Fourier 변환을 통해 무누수 조건과 누수조건의 비교에서 누수의 유무에 따른 신호의 형태가 차이를 보였다. 앞선 연구들에서의 누수의 특정한 위치를 찾아내는 형태 대신 신호처리 후 분석을 통해 시스템 전체에서 일어나는 감쇠를 통해 누수 존재 유무를 판별하고자 한다.

• Proceedings of the Korean Society of Computer Information Conference
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• 한국컴퓨터정보학회 2022년도 제66차 하계학술대회논문집 30권2호
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• pp.429-430
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• 2022

현재 코로나로 인한 각 나라의 입국 제한이 사라지면서 국내외 여행 예약률 증가에 따라 그만큼 비행기 예약도 늘어나고 있다. 그런데 객실 승무원의 근무 환경은 매우 열악하기 때문에 육체적, 정신적 피로를 누적되게 한다. 이는 승객에게 양질의 서비스를 제공할 수 없게 하고 안전사고를 대처하는 데 있어 문제가 된다. 본 논문은 객실 승무원이 스마트폰 앱을 이용하여 편리하게 객실 상황을 확인하고, 원격 제어하며 서빙카트를 조작하여 승객의 주문에 대한 서비스를 제공하는 '원격제어가 가능한 비행기 객실 관리 시스템'을 제안한다. 이 시스템을 이용함으로써 객실 승무원은 객실 상황을 판단하여 즉각적인 대처를 할 수 있고, 항공기 효율적 운용을 위한 안전성과 정시성을 확보하는 데 도움이 될 것이다.

• Journal of Korean Society of Forest Science
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• 제86권3호
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• pp.288-300
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• 1997

Morphology and anatomy of the fruit and seed of eight species of Rhus (Anacardiaceae) were investigated. The inflorescence of R. typhina was an apical and erect thysus, that of R. javanica was panicle. while that of the others were an axillary and pendulous panicle. Anatomical investigation of the pericarp showed that exocarp and mesocarp in R. javanica and R. typhina were integrated, but its in the others were disintegrated and uniform. In all these species, endocarp consisted of distinctly three lignified cell layers (outer, middle and inner endocarp) and crystal layers. The surface sculpturing of mature seed was variable and also contributed to understanding of species delimitation and relationships within the genus. Categorization by cluster analysis with 27 characters obtained from morphological and anatomical features of the fruit and seed resulted in two groups : R. trichocarpa - R. javanica group vs. R. ambigua - R. verniciflua - R. sylvestris - R. succedanea group. Taxonomic significance for the genus by these characters was supported by results of principal component analysis. The keys for the genus Rhus were provided using morphological and anatomical characters of the inflorescence, and fruit and seed.