• 한국자동차공학회논문집
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• 제22권7호
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• pp.48-56
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• 2014

Engine oil is an oil used for lubrication of various internal combustion engines. The main function is to reduce wear on moving parts; it also cleans, inhibits corrosion, improves sealing, and cools the engine by carrying heat away from moving parts. In engines, there are parts which move against each other. Otherwise, the friction wastes the useful power by converting the kinetic energy to heat. Those parts were worn away, which could lead to lower efficiency and degradation of the engine. It increases fuel consumption, decreases power output, and can induce the engine failure. This study was conducted to evaluate the relation between engine oil property changes and engine performance for the diesel engine. This test was performed by using 12L, 6 cylinder, heavy duty engines. Low SAPS 10W30 engine oil (two type engine oils) was used. Test procedure and method was in accordance with the modified CEC L-57-T97 (OM441LA) method. In this study, TAN, TBN, KV and metal components, engine power, blowby gas, A_F were presented to evaluate the relation with engine oil property changes and engine performance. TAN, TBN, KV and metal We found that the components were generally increased but engine performance did not change. This results mean that property changes did not affect on engine performance because those were not enough to affect engine performance.

• 한국지구과학회지
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• 제43권1호
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• pp.110-118
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• 2022

빈번한 가뭄의 피해는 수자원의 양극화를 초래하고 있다. 국내에서는 2011년부터 2017년 사이에 국지적이고 주기적인 이상 가뭄이 지속되어 10년 가뭄 빈도로 설계된 소규모 저수지의 저수율이 감소하였다. 이러한 저수율의 감소는 수질을 떨어트릴 수 있고 이미 확보된 용수의 사용마저 제한할 수 있다. 따라서 가뭄에 대비하고 극복하기 위해서는 수질관리와 가뭄 빈도의 재산정이 필요하다. 이 연구는 저수지에서 수질 변화의 원인인 잠재적 오염물질을 추정하고, 가뭄 기간 동안 저수지의 저수율 감소와 그에 따른 수질 변화를 검토한 것이다.

• 한국수산과학회지
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• 제34권4호
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• pp.348-354
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• 2001

This study was conducted to estimation of change characteristics for water quality by the dyke gate operation in the Keum River estuary. The estimation data made use of surveyed data in Keum River estuary by NERDI (National Fisheries Research and Development Institute) during $1990\~1999$. Shown to compare water quality changes at st. A and st. D in Figure 1, the concentrations of TSS, COD and nutrients at st. A were as high as about $2\~4$ times than those at st. D due to affection of fresh water discharge in the Keum River. The percentages of water quality change at surface water by dyke gate operation in the Keum River estuary were shown that TSS (Total Suspended Solid) was decrease to $56\%,\;47\%$ at st. A and D, and COD (Chemical Oxygen Demand) was increase to $68\%,\;71\%$ at st. A and D, respectively. The changes percentage of DIN (Dissolved Inorganic Nitrogen) by dyke gate operation in the Keum River estuary were increase high to $95\%$ at surface water and $7\sim30\%$ at bottom water, but those of DIP (Dissolved Inorganic Phosphorus) were increase to $2.8\sim8.6\%$ at surface water and $28\%$ at bottom water. The range of fluctuation for water quality at each station by dyke gate operation has shown that salinity and TSS are little better than before dyke gate operation, but COD show highly fluctuation. Also we studied estimation of characteristics of water quality change by the season, COD was increased except the summer, TSS was decreased to all season. DIN was increased to about $61\sim172.1\%$ for all season, but DIP was increased to the spring and decreased to the autumn, DIN enrichment in the estuary by dyke gate operation are interpreted to improvement of organic matter decomposition and nitrification by increasing the residence time and to increase nutrient flux in sediments due to decreasing dissolved oxygen and increasing a deposit matter.

• 한국산학기술학회논문지
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• 제22권4호
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• pp.331-337
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• 2021

무기체계 개발단계에서 전력화 공백을 방지하기 위한 제한된 개발기간 및 예산으로 인하여, 모든 운용환경을 반영하지 못한 설계내용, 예기치 못한 운용자의 실수 등으로 비롯되어 무기체계 양산 이후 운용단계에서 많은 문제점이 발생되고 있고, 그에 따른 기술변경 역시 증대되고 있다. 하지만 기술변경 시 수행되는 체계장비의 문제원인 분석 및 개선에 대한 내용들이 종합적으로 관리되지 못함으로써, 타 체계에 부착되는 유사장비들 개발 시 활용될 수 있는 중요한 실전 데이터가 일회성으로만 사용되고 있는 현실이다. 특히나 장비의 형상이 변경되거나 제품번호가 변경되는 하드웨어와 달리 소프트웨어 기술변경 내용은 심의제안서 상에 일부만 포함되며, 소스패키지와 실행파일의 버전이 변경되는 정도만 식별되는 상황이다. 따라서 본 논문에서는 무기체계 소프트웨어 기술변경 원인분석 및 개선방안 데이터와 소프트웨어 기술지원 결과에 대한 데이터베이스를 구축하고, 활용할 수 있는 방안을 제시한다. 위 활용방안을 통해 양질의 실전데이터를 유사장비 개발 시 선제적으로 적용함으로써 향후 개발되는 무기체계 소프트웨어 품질 확보에 기여할 수 있음을 보인다.

• 한국식품저장유통학회지
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• 제4권3호
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• pp.265-270
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• 1997

Effect of modified atmosphere packaging conditions on quality changes of dry jujube was investigated. Dry jujubes with moisture content of 26.7% were packaged in PET/Al/PE film pouches with modified atmospheres. The tested packages include those with normal air, vacuum, CO2 flushing, N2 flushing and O2 scavenger. Packages were stored at 25$^{\circ}C$ for 6 months, during which ascorbic acid concentration, browning level, titratable acidity and surface color were measured. Generally modified atmosphere packages could improve quality retention of dry jujubes except that vacuum package resulted in large surface color change. CO2-flushed package showed the best quality retention of high ascorbic acid content and low browning during 112 days, but caused high amounts of ascorbic acid destruction and browning in longer storage. In all the modified atmosphere packages titratable acidity reached a maximum followed by decline and subsequent rise, while it increased linearly with time in normal air package. Considering ascorbic acid retention browning level and surface color changes during 112 days, the packages of CO2 flushing and N2 flushing were better than others.

• 한국IT서비스학회지
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• 제8권2호
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• pp.205-228
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• 2009

This paper examines how online product information changes the customers' purchase intentions from subjectivity-objectivity dichotomy perspective. Quality and Preference are proposed as product evaluation criteria and their marginal changes with product information differentiation are hypothesized. An experimental survey was conducted to 57 subjects and the hypotheses were partially supported through PLS path comparison method. The study contributes to IS research by proposing a simple and effective product evaluation framework and by abstracting the impact of product information from other factors. Finally, we suggest the utilization of product information with the optimization of the cost-benefit structure between information and purchase intention.

• 한국식품영양과학회지
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• 제20권3호
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• pp.276-280
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• 1991

The quality changes of brown rice during storage were determined by the method of quantitative analysis of n-hexanal, amylogram, texture and volume expansion. The qualities of stored brown rice were also analyzed with sensory evaluation of cooked milled rice obtained from brown rice, n-Hexanal content, peak viscosity and total setback of brown rice flour pastes increased substantially with the increased of storage period at 35$^{\circ}C$. Up to 10 months of storage at 35$^{\circ}C$, stale flavor obtained by a sensory method markedly increased, but stickiness decreased. The scores of overall preference were in good agreement with those of stale flavor (r=-0.98) and sticky texture (r=0.98). The correlation coefficient between stale flavor obtained by a sensory method and instrumetal analysis for stored brown rice was r=0.97.

• 한국기계가공학회지
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• 제19권3호
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• pp.71-76
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• 2020

Various machining methods are being studied to improve the processing quality of the spherical R shape in press die. In this paper, we confirmed that changes in machining quality were associated with changes in cutting direction, path, and cutting angle, which are commonly used in the machining of molds. We obtained a surface roughness graph with each condition change in one specimen using an instrument that measured geometry and surface roughness simultaneously. The results of the study showed that the best surface roughness in the finish cut of the spherical surface was obtained using upward pick feed machining.

• 품질경영학회지
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• 제29권4호
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• pp.161-169
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• 2001

Recently, the quality of residential space is emphasized much more than ever. This is caused by various changes of social environment. Those users, i.e. the occupants, seemed very sensitive to any changes of their environment. Therefore many producers (construction companies) need to be concentrated on the occupant's needs, and try to apply those needs to their design of products(apartments). This study aims to design the POE(Post Occupancy Evaluation) categorization methodology with QFD application. Therefore QFD performed to produce much tailored occupant's needs as a transformation of technically processed value. For this purpose, categories were experimented for a pilot project of POE. As a result, it showed a possibility and need of accuracy and maturity for the design of POE in its categorization.

• 품질경영학회지
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• 제19권2호
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• pp.172-180
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• 1991

The null hypothesis being tested by $the{\bar{X}}$ control chart is that the process is in control at a quality level ${\mu}o$. An ${\bar{X}}control$ chart is a tool for detecting process average changes due to assingnable causes. The major weakness of $the{\bar{X}}$ control chart is that it is relatively insensitive to small changes in the population mean. This paper presents one way to remedy this weakness is to allow each plotted value to depend not only on the most recent subgroup average but on some of the other subgroup averages as well. Two approaches for doing this are based on (1) moving averages and (2) exponentially weighted moving averages of forecasting method.