• Journal of Mechanical Science and Technology
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• 제20권9호
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• pp.1475-1482
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• 2006

Wet compression means the injection of water droplets into the compressor of gas turbines. This method decreases the compression work and increases the turbine output by decreasing the compressor exit temperature through the evaporation of water droplets inside the compressor. Researches on wet compression, up to now, have been focused on the thermodynamic analysis of wet compression where the decrease in exit flow temperature and compression work is demonstrated. This paper provides thermodynamic and aerodynamic analysis on wet compression in a centrifugal compressor for a microturbine. The meanline dry compression performance analysis of centrifugal compressor is coupled with the thermodynamic equation of wet compression to get the meanline performance of wet compression. The most influencing parameter in the analysis is the evaporative rate of water droplets. It is found that the impeller exit flow temperature and compression work decreases as the evaporative rate increases. And the exit flow angle decreases as the evaporative rate increases.

• 소성∙가공
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• 제8권1호
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• pp.101-107
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• 1999

The upset forging stage is the initial work in the forging process. It is used to remove the segregation and cavities of the ingot. Specially in handling large sized ingot, an improper upset forging can cause serious surface tearing. However, there is no detail reference for stable upset forging work. To resolve this difficulty, we studied several factors such as upset forging time, temperature varation of ingot, damage, load and stain rate etc., by using the rigid-plastic finite element approach available in the DEFORM code. Numerical simulation results indicated that: the load value of upset forging works shows severe decreasing trend at a certain point, same as strain rate. Also defects were found to be concentrated around the upper and lower portions of the ingot. With these results, we can estimate a guideline for stable upset forging work.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.302-307
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• 2004

The major flow-induced vibration mechanisms such as fluid-elastic and turbulence excitation can cause the various types of wear of the steam generator tubes in unclear power plant. It is generally accepted that the tube wear due to vibration is affected by the presence of gap clearance between tube and support plate. Connors showed that the tube wear depth could be estimated by using the relationship between wear volume and sliding distance for contact time. Au-Yang predicted the wear depth by using the nonlinear characteristics of normal work rate to contact time. In this study the effect of gap size on the steam generator tubes wear is analyzed by deriving the wear depth versus normal work rate relationship from these previous results.

• 한국안전학회지
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• 제14권3호
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• pp.174-180
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• 1999

The objective of this study was to investigate the effects of carrying postures and weight of load carried one time on a worker when carrying heavy loads. Six male students participated in this study to perform a manual materials carrying task as subjects. To make comparison of work loads with physical work capacity, maximal oxygen uptake measurement tests were performed with submaximal test. The average oxygen consumption for the tasks of this study was 27.59~31.93% $VO_2$max. The results showed that the weight of load carried one time affects on working heart rate and oxygen consumption($VO_2$). It was found that the workload was significantly lower when handling a 20kg load at a frequency rate of 3times/min than when handling a 40kg load at a frequency rate of 1.5 times/min. There was no difference between carrying postures. It is concluded from the results of this study that the workload can be reduced by controlling conditions of a manual materials handling task.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.919-924
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• 2005

Fretting-wear caused by turbulence excitation for KSNP(Korea standard nuclear power plant) steam generator is investigated numerically. Secondary sides density and normal velocity are obtained by the thermal-hydraulic data of the steam generator. Because nonlinear finite element analysis is complex and time consuming, work rate is estimated by using linear analysis for simple straight 2-span tube. Wear volume and depth by using work rate calculation are estimated. Span length, secondary side fluid density and normal velocity are adopted to study the effects on the fretting-wear by turbulence excitation. When secondary sides density and normal velocity is increased, It turns out that secondary side density and normal gap velocity are very important paramater for fretting-wear phenomena of the steam generator.

• Nuclear Engineering and Technology
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• 제53권7호
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• pp.2126-2132
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• 2021

Various research groups and private interprises are pursuing the design of a Molten Salt Reactor (MSR) as one of the Generation-IV concepts. In the current work a fast neutron MSR using chloride fuel is analyzed, specially analyzing the power production and neutron flux level in the Intermediate Heat Exchanger (IHX). The neutronic analysis in this work is based on a chloride-fuel MSR with 600 MW thermal power. The core power density was set to 100 MW m-3 with a core H/D [[EQUATION]] 1.0 amd four Intermediate Heat Exchanger (IHX). This leads to a power of 150 MW per IHX; this power is also comparable to the IHX proposed in the SAMOFAR framework. In this work, a preliminary design of a 150 MW helical-coil IHX for a chloride-fueled MSR is prepared and the fission rate, capture rate, and inelastic scatter rate are evaluated.

• 한국건축시공학회지
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• 제10권1호
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• pp.213-219
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• 2010

본 연구는 부산에 있는 아파트 소규모 인테리어공사 6가지 평형의 실적자료 200개를 대상으로 하여 건축공사와 소규모 인테리어공사의 분류체계를 비교하고, 일반적인 소규모 인테리어공사의 공종별 공사비를 분석하였다. 본 연구에서 도출된 결과는 다음과 같다. (1) 아파트 소규모 인테리어공사비는 1,000~1,500만원 범위인 79.2M2(24PY)과 105.6M2(32PY)에 대해서 주로 이루어지므로 이러한 2가지 평형에 대한 자재비, 노무비에 대한 심층적인 원가분석이 필요하다. (2) 아파트 소규모 인테리어공사는 일반적인 건축공사의 분류체계와 다르게 마감공사가 주로 진행되므로 건축공사표준시방서의 22개의 대분류와는 다른 9개의 분류체계로 구분하여 적용하는 것이 타당하다. (3) 소규모 인테리어공사의 각각의 평형별 평균공사금액과 공종보할을 검토한 결과, 24평형(24PY)의 평균공사금액은 약 1,050만원이고 공종별 보할은 금속공사 12.8%, 수장공사 17.8%, 화장실공사 19.7%로 분석되었으며, 싱크 가구공사가 22.1%로 가장 높은 보할을 나타내었다. 또한, 32평형의 평균공사금액은 약 1,250만원이며, 공종별 공사보할은 수장공사가 28.6%로 가장 높게 나타났으며, 28평형이상에서는 수장공사의 공종보할이 가장 큰 것으로 분석되었다.

• 국제학술발표논문집
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• The 3th International Conference on Construction Engineering and Project Management
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• pp.738-746
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• 2009

The purpose of this study is to develop the web-based system for work performance analysis(WPAS). The need of work performance analysis system has already been suggested in many previous researches on the computerization of the performance measurement in the construction site by using the indicators such as time, cost and quality. However, they had focused on measuring or analyzing the result when the project would be over. The WPAS suggests three indicators - work reliability, work effectiveness and work efficiency - to manage the performance of the construction site. It can help the manager more easily recognize the status of on-going work in the construction site by measuring and analyzing the work reliability rate, the work effectiveness and work efficiency every day. This research includes the procedures for WPAS measurement process, database structure of WPAS which was analyzed by the IDEF0 and the data flow diagram. Finally, this research introduces the result of WAPS's case studies and validation in the Korean construction site.

• 한국산업보건학회지
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• 제31권4호
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• pp.540-548
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• 2021

Introduction: Preplacement health examination (PHE) is performed when a worker starts a certain work task which is designated as having occupational risks by the Ministry of Employment and Labor (MOEL). All data related to health examination except PHE are reported to the MOEL by the law. This study has been performed to understand the status of PHE at certain workplaces. Methods: PHE data gathered in a university hospital were analyzed and they were followed with results of the special health examination (SHE) in 2019 and 2020. Those who were evaluated as unfit to work as it was, were interviewed directly or indirectly through an occupational health manager to follow up the management status of their recognized health problems. Results: The unfit to work (unFTW) rate of PHE was 2.8%, and was not different according to the size of workplace or having occupational health service. The major cause of unfit to work was the uncontrolled life-style diseases such as hypertension and diabetes. The rate of SHE followed by PHE was 31.1%. It was not different by the unFTW rates, however, they were different according to having a full time in-house occupational health manager. Thirty-one among 71 examinees who were evaluated as unFTW underwent SHE after controlling their health condition and were finally evaluated as fit to work. Nineteen among 31 started to take medicine and eight have been placed in the work without designated risks. Conclusion: PHE can be used for new workers, who may have unknown or uncontrolled life-style diseases, to be asked to manage life-style diseases as well as work-related risks such as shift work. In order to have a better tracking system for work-related risks, the information of PHE should be analyzed together with other data from health examination.

• 산업경영시스템학회지
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• 제18권33호
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• pp.11-27
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• 1995

This study sets a goal of establishing work standard and standard time in a machine tool process consisted of high-priced NC machine tools. Firstly, the theories of work standard and standard time in the field of NC machine tools are studies. Secondly, the theories are actually applied to a manufacturing company; work standard sheets are developed and applied to a machining center haying low operation rate, and then the increase in productivity is compared. Finally, problems to be studied later in relation to work standard and standard time are presented.