• Computers and Concrete
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• 제22권1호
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• pp.27-37
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• 2018

Reinforced concrete structures are widely used in civil engineering projects around the world in different designs. Due to the great evolution in computational equipment and numerical methods, structural analysis has become more and more reliable, and in turn more closely approximates reality. Thus among the many numerical methods used to carry out these types of analyses, the finite element method has been highlighted as an optimized tool option, combined with the non-linear and linear analysis techniques of structures. In this paper, the behavior of reinforced concrete beams was analyzed in two different configurations: i) with welding and ii) conventionally lashed stirrups using annealed wire. The structures were subjected to normal and tangential forces up to the limit of their bending resistance capacities to observe the cracking process and growth of the concrete structure. This study was undertaken to evaluate the effectiveness of welded wire fabric as shear reinforcement in concrete prismatic beams under static loading conditions. Experimental analysis was carried out in order compare the maximum load of both configurations, the experimental load-time profile applied in the first configuration was used to reproduce the same loading conditions in the numerical simulations. Thus, comparisons between the numerical and experimental results of the welded frame beam show that the proposed model can estimate the concrete strength and failure behavior accurately.

• Tribology and Lubricants
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• 제34권2호
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• pp.49-54
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• 2018

Hydraulic reciprocating seal has been widely used to prevent fluid leakage in hydraulic systems. Also, hydraulic reciprocating seal plays a significant role to provide lubricant film at contacting interface to minimize tribological problems due to sliding with counter material. To predict lifetime of hydraulic reciprocating seal, quantitative understanding of wear characteristics with respect to operating conditions such as normal force and sliding speed is needed. In this work, effect of sliding speed on wear of polyurethane (PU) hydraulic reciprocating seal were experimentally investigated using a pin-on-disk tribo-tester. The wear characteristics of PU specimens were quantitatively determined by comparing the confocal microscope data before and after test. It was found that the wear rate of PU specimens decreased from $4.9{\times}10^{-11}mm^3$ to $1.1{\times}10^{-11}mm^3/Nm$ as sliding speed increased from 120 mm/s to 940 mm/s. Also, it was observed that the friction decreased slightly as the sliding speed increased. Improvement of lubrication state with increasing sliding speed was likely to be responsible for this enhanced friction and wear characteristics. This result also suggests that decrease in sliding distance between PU elastomer and counter materials at lower sliding speed is preferred. Furthermore, the quantitative assessment of wear characteristics of PU specimen may be useful in prediction of lifetime of PU hydraulic reciprocating seal if the allowed degree of wear for failure of the seal is provided.

• 한국해양공학회지
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• 제27권4호
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• pp.90-97
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• 2013

Oil booms are one of the most widely used types of equipment for the protection of coastal areas against oil spills. In some situations, however, there are several types of oil leaks from the oil boom. Important factors regarding these phenomena include the surrounding ocean environment, such as waves, the density and viscosity of oil, the length of the oil boom skirt, etc. To estimate the performance of the oil boom, it is necessary to predict the behavior of the spilled oil and oil boom. In the present study, the prediction of oil boom performance in waves was carried out using the Pusan-National-University-modified Moving Particle Semi-implicit (PNU-MPS) method, which is an improved version of the original MPS proposed by Koshizuka and Oka (1996). The governing equations, which consist of continuity and Navier-Stokes equations, are solved by Lagrangian moving particles, and all terms expressed by differential operators in the governing equations are replaced by the particle interaction models based on a kernel function. The simulation results were validated through a comparison with the results of Violeau et al. (2007)..

• 한국병원경영학회지
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• 제12권4호
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• pp.119-142
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• 2007

Although Korea joined OECD in 1996, there has still seen much unbalance in medical care and welfare standard between urban and rural area. The unbalance of medical demand between urban and rural area deepened low utilization of rural hospitals. So it caused many hospital's failure and conversion in rural area. Many rural hospitals are in difficulty managing business because of low medical demand along with the shortage of medical manpower, medical equipment and facilities. The objectives of this study were to reveal the cause of low utilization of hospitals in rural area, and to increase utilization of those hospitals. In this study the improvement methods of rural hospital's utilization were presented by examining were placed in difficult management condition, in respect of hospital's management conditions, manpower input, patient medical treatment record, financial record, and actual output. The causes of rural hospital's low utilization were as follows; 1) changes in number and structure of population 2) rural people's preference for large hospitals and hospitals which located in urban area 3) rural hospitals lacking in hospital management skill. Consequently rural hospital's operation condition got more and more deteriorated. To raise rural hospital's utilization, method for social policy, method for health policy, and intrinsic method of hospitals were presented in turn. For rural residents to utilize medical service conveniently, it is necessary for rural hospitals operated normally. So government must insist that rural hospitals solve the problems which come out from their internal management problems. And also these rural hospitals should be supported and nurtured by the government until their management is operated normally.

• 전기학회논문지
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• 제65권6호
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• pp.1083-1088
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• 2016

25.8kV GIS part generated by sensors to measure contact an inflow of noise depending on the extent of the measured discharge occurs often not easy. Partial discharge signal measurement sensor suitable for developing a more useful measurements at the scene to this, partial discharge waveform analysis developed a sensor, and to utilize forSensor on the development of the most important is VSWR decided to (voltage standing wave ratio) voltage standing-wave ratio less than 1.5 and decided less than at the full spectrum bands that are measured, this time Return loss, as measured value by absolute criteria 14.0 dB produced the sensor, designed to or more. UHF 1.5~0.5 GHz bandwidth spectrum to be measured in GIS. UHF bands were designed to be able to measure the best signal. Recently, 25.8kV GIS production company has been increasing variety of GIS were made open spacer in partial discharge in accordance with the not very easy to detect the signal. The sensor is designed height of four cm external spacer is attachment GIS in an influx of outside noise measurement, and be so manufactured as to facilitate the least we've done. Also, since partial discharge which occur can measure the frequency of the 170kV GIS external partial-discharge signals that occur at the scene of insulation applied to the spacer. Features, and also derived good results using global positioning. Also measured discharge point about sensors that are stable and the reliability of the development and local substation equipment failure occurring signal analysis through the discharge for the prevention of widely. There should be to believe that used.

• 한국항행학회논문지
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• 제22권3호
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• pp.179-188
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• 2018

항공전자 시스템의 개발할 때 항공 사고를 예방하기 위해서 SAE ARP4761 (민간 항공 시스템 및 장비 안전성 평가 프로세스 수행 방법 및 지침) 규격에 명시된 안전성 분석 및 평가를 수행한다. 안전성 분석은 시스템의 정상상태가 아닌 비정상상태에 대한 지식과 다른 규격들 간의 상호 연관성에 대한 지식이 요구된다. 때문에, 안전인증규격의 준수를 입증하는 자료를 자동으로 출력하는 도구가 필요하다. 본 연구는 규격의 안전성 분석 절차를 도식화하고, 안전 분석 CAD 도구들을 개별 절차에 적용하는 방법을 연구하였다. 예시 연구로서, ARP4761 부록의 여객기용 휠 제동 시스템 (WBS; wheel brake system)을 대상으로 ARP4761분석을 수행하였다.

• 한국항해항만학회지
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• 제42권5호
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• pp.311-316
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• 2018

IMO introduced the concept of e-Navigation and proposed MSPs(Maritime Service Portfolios) concept to reduce marine accidents, to improve efficiency of ship operation, port operation, and ship operation technology. Korean e-Navigation defines S1 ~ S5 services, as the service concept focused on domestic e-Navigation service corresponding to IMO MSPs, and is constructing a system as an ongoing project. S2 service (onboard system remote monitoring service) among the concepts of Korean e-Navigation services, is a service concept that judges the emergency level according to risk if an abnormal condition occurs during navigation, and provides corresponding guidance to accident ships based on emergency level. The purpose of this paper is to provide a basic architecture proposal of Korean e-Navigation S2 service navigation safety module, based on the S2 service operation concept. To do this, we conducted a questionnaire survey to ask experts with experience with sailors, to respond to the subjective risk experienced by sailors considering effects of anomalies, including equipment failure relative to sailing and navigational safety. Risk level for each abnormal condition was classified. The basic algorithm design of the navigation safety module is composed of safety index (SI) calculation module based on results of questionnaire and expert opinions, safety level (SL) determination module according to safety index, and corresponding guidance generation module according to safety level. To conduct basic validation of basic architecture of the navigation safety module, simulation of the ship anomaly monitoring was performed, and results have been revealed.

• 한국산학기술학회논문지
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• 제17권8호
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• pp.379-388
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• 2016

현대 무기체계 제조를 위해 적용되는 수많은 생산 기술과 다양한 공정 환경으로 인해 다양한 결함이 무기체계 제조공정에 유입되고 있다. 이렇게 제조공정에 유입되는 결함 중 육안 검사, 기능 시험 등 기존 품질 관리 절차를 통해 검출할 수 있는 "명백결함(Patent Defect)"과 무기체계 복잡성과 제조공정의 복잡도로 기존 품질 관리 방식으로 검출이 제한되는 "잠재결함(Latent Defect)" 2가지 종류가 있다. 이러한 초기 결함 문제를 최소화하기 위해 무기체계 생산공정 중 유입된 결함요소를 환경부하(온도, 진동)를 활용하여 결함검출/제거/개선하기 위해 환경 부하 선별(ESS : Environmental Stress Screening) 시험을 수행해야 한다. 본 논문은 국내 무기체계 제조업체에서 정량적 환경 부하 선별 시험 설계의 어려움을 최소화하기 위해 MIL-HDBK-344(Environmental Stress Screening of Electronic Equipment)의 수학적 모델을 기반으로 정량적 환경 부하 선별시험 효과도 분석 및 프로파일 자동화 도구를 구현하였으며, 6가지(온도부하변수 3가지(온도범위/온도변화율/허용 잔류결함밀도), 진동부하변수 2가지(부하크기/허용 잔류결함밀도), 시험설계변수 1가지(허용 시험시간)) 시나리오를 통해 구현된 도구 유효성을 확인했다.

• 한국화재소방학회논문지
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• 제27권3호
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• pp.14-19
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• 2013

스프링클러설비의 화재안전기준인 NFSC103은 설계면적 내의 모든 헤드로부터 방출압 1 bar이상과 방출량 80 lpm 이상을 최소기준으로 규정하고 있다. NFSC103은 또한 설치장소의 용도에 따라 설계면적에서 작동하는 헤드의 수를 10개, 20개, 30개로 규정하고 각 헤드별 유량을 80 lpm으로 하여 총유량을 800 lpm, 1,600 lpm, 2,400 lpm으로 규정하고 있다. 이 규정대로 스프링클러 설비를 설계하면 약 50 %의 스프링클러헤드에서 유량과 압력이 최소기준보다 부족하게 된다. 이는 스프링클러의 목적인 초기화재 대응에 실패를 가져오는 심각한 결과를 초래할 수 있다. 이와 같은 문제점을 해결하기 위해서는 성능위주 설계인 수리계산방법에 의해 모든 스프링클러설계가 이루어지는 것이 바람직하다.

• 조명전기설비학회논문지
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• 제19권2호
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• pp.87-93
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• 2005

최근 수용가의 부하회로 및 설비가 복잡해짐에 따라 배선용 및 누전차단기의 원인모를 동작 또는 오동작이 증가하고 있지만 오동작에 대한 실태조사는 이루어지지 못하였다. 본 논문에서는 218개소 자가용 수용가의 전기안전 관리자를 대상으로 설문조사를 실시하여 배선용 및 누전차단기의 오동작 원인과 그 영향에 대해 조사하였다. 조사결과 배선용 및 누전차단기 사용 장소의 $70[\%]$ 이상이 오동작을 경험하고 있고 오동작 원인은 노후화($25(\%)$ 이상), 원인불명($22(\%)$ 이상), 제품불량($20(\%)$ 이상), 고조파와 같은 이상전원($20(\%)$ 이상), 기타($9(\%)$ 순으로 나타났다. 또한 오동작로 인한 피해는 제품생산 차질, 기기고장, 정보손실, 업무 및 조업중단, 기타 순으로 조사되었다. 본 연구결과는 현장에서 배선용 및 누전차단기의 오동작 원인을 분석할 때 참고자료로 활용될 수 있을 것이다.