• Journal of Microbiology and Biotechnology
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• 제16권7호
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• pp.1120-1124
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• 2006

Supplementation with rice oil and its major components (oleic acid and linoleic acid) was found to have a significant influence on cephalosporin C (CPC) production and cell growth by A. chrysogenum M35 in shake flask cultures. Five percent (v/v) rice oil had the most robust effect and 5% (v/v) oleic acid was the second most efficient on cell growth, whereas 3% (v/v) linoleic acid was found to be optimal for CPC production. Rice oil, oleic acid, and linoleic acid also significantly improved the rates of glucose consumption. When glucose was almost consumed, CPC production was initiated and, on the addition of rice oil, lipase activity increased steadily to 1.56 U/ml for 4 days. These results suggest that rice oil and fatty acids are used as carbon source to produce CPC by A. chrysogenum M35. Moreover, a mixture, composed of 40% (v/v) oleic acid and 60% (v/v) linoleic acid, had the strongest stimulatory effect on CPC production, due to a synergistic effect of the two fatty acids. Consequently, the maximum CPC titer (7.44 g/l) was improved about 4.5-fold.

• 한국수소및신에너지학회논문집
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• 제16권2호
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• pp.199-207
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• 2005

Hydrogen is getting more attention owing to the seriousness of air pollution and dependance on oil import, UNCCC(United Nations Convention on Climate Change) for reducing the emission of $CO_2$. This fact is not confined in a certain country but global recognition and several countries initiated R&D competition for commercializing the hydrogen fuel cell vehicle. Within 20${\sim}$30 years cost effective hydrogen production can be possible using fossil fuels because so much research is carried out up to now. But it is so far to produce the most of the hydrogen using renewable resources considering the present status of R&D and cost effectiveness. Several automobile companies planed for mass production of hydrogen vehicle by 2010 but changed or canceled the plan owing to the difficulty of R&D and the low status of infrastructure penetration. This paper surveyed the hydrogen energy policy, R&D program and commercialization strategy of advanced country, international agency, automobile and energy company to analyze the global status of R&D and policy. And the survey of R&D program is focused on the part of hydrogen production, storage, delivery and fuel cell.

• Nuclear Engineering and Technology
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• 제49권2호
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• pp.327-334
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• 2017

Common-cause failure (CCF) events can significantly impact the availability of safety systems of nuclear power plants. For this reason, the International Common Cause Data Exchange (ICDE) project was initiated by several countries in 1994. Since 1997 it has been operated within the Organisation for Economic Co-operation and Development (OECD)/Nuclear Energy Agency (NEA) framework and has successfully been operated over six consecutive terms (the current term being 2015-2017). The ICDE project allows multiple countries to collaborate and exchange CCF data to enhance the quality of risk analyses, which include CCF modeling. As CCF events are typically rare, most countries do not experience enough CCF events to perform meaningful analyses. Data combined from several countries, however, have yielded sufficient data for more rigorous analyses. The ICDE project has meanwhile published 11 reports on the collection and analysis of CCF events of specific component types (centrifugal pumps, emergency diesel generators, motor operated valves, safety and relief valves, check valves, circuit breakers, level measurement, control rod drive assemblies, and heat exchangers) and two topical reports. This paper presents recent activities and lessons learnt from the data collection and the results of topical analysis on emergency diesel generator CCF impacting entire exposed population.

• 한국기계가공학회지
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• 제16권4호
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• pp.76-82
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• 2017

The cylinder liner of a diesel engine is commonly made of gray cast iron. However, this cylinder liner can be damaged by the cavitation phenomenon in wet conditions. This cavitation has remained an unsolved problem until now. In this study, the cause of cavitation corrosion due to antifreeze solution was examined using a scanning electron microscope (SEM) and a 3D microscope. The necessary data to prevent the damage caused by cavitation erosion and the corrosion of gray cast iron cylinder liner was obtained. Analysis determined that the gray iron structure consists of an ${\alpha}-matrix$, flake graphite, and steadite. Cavitation erosion was initiated in the coarse flake graphite and propagated into the steadite with pitting. Under repetitive reaction conditions, the ${\alpha}-matrix$ was partially separated from the gray cast iron. This study is expected to be used as the basic data for the prevention of gray cast iron cavitation erosion and corrosion by controlling the graphite and steadite phases.

• Journal of Power Electronics
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• 제16권5호
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• pp.1843-1850
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• 2016

This study focused on predicting the fatigue life of an insulated gate bipolar transistor (IGBT) power module for electric locomotives. The effects of different wiring technologies, including aluminum wires, copper wires, aluminum ribbons, and copper ribbons, on solder fatigue life were investigated to meet the high power requirement of the IGBT module. The module's temperature distribution and solder fatigue behavior were investigated through coupled electro-thermo-mechanical analysis based on the finite element method. The ribbons attained a chip junction temperature that was 30℃ lower than that attained with conventional round wires. The ribbons also exhibited a lower plastic strain in comparison with the wires. However, the difference in plastic strain and junction temperature among the different ribbon materials was relatively small. The ribbons also exhibited different crack propagation behaviors relative to the wires. For the wires, the cracks initiated at the outmost edge of the solder, whereas for the ribbons, the cracks grew in the solder layer beneath the ribbons. Comparison of fatigue failure areas indicated that ribbon bonding technology could substantially enhance the fatigue life of IGBT modules and be a potential candidate for high power modules.

• 한국항공우주학회지
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• 제34권3호
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• pp.37-43
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• 2006

접합방법이 다른 6가지 종류의 복합재 보강패널을 제작하고 압축시험을 수행하였다. 모든 패널은 좌굴 및 좌굴 후 거동에서 스킨과 보강재의 분리 파손이 발생하기 전까지는 비슷한 거동 특성을 나타내었다. 분리 파손은 스킨 좌굴 지점과 인접한 보강재 플랜지에서 발생하였으며 분리 파손의 발생 하중, 분리 파손 진전 특성 및 최종 파손 하중은 스킨과 보강재의 접합방법 및 보강재 형상에 따라 다르게 나타났다. 스킨과 보강재의 분리 파손이 일찍 발생하고 크게 전파될수록 보강 패널의 최종 파손 강도 및 구조 효율이 더 많이 저하되었다.

• 한국식품영양학회지
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• 제23권2호
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• pp.276-284
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• 2010

The effects of different dietary fatty acids on the hepatic glutathione S-transferase(GST-P) positive foci and glutathione related enzyme system were investigated in carcinogen treated rats. Weaning male Sprague Dawley rats were divided into three groups and fed the diets of 15% corn(CO), perilla(PO), and sardine oil(SO), respectively. Hepatocellular carcinogenesis was initiated with diethylnitrosamine(DEN) and then fed the diet containing 0.02% 2-acetylaminofluorene(2-AAF) followed by 0.05% phenobarbital for 10 weeks. The hepatic tissues were homogenized and centrifugated to prepare microsomal and cytosolic fractions. The enzyme activities of hepatic glutathione S-transferase(GST), glutathione reductase(GR), and glutathione peroxidase(GPx) were determined from cytosolic fractions. The number of GST-P hyperplastic nodules was the highest in corn oil group at 6th week, the early stage of hyperplastic nodule formation. GST activities were increased significantly by carcinogens in all dietary groups after 6th wk. GR activities followed the same trend as GST activities. GPx activities were decreased by carcinogens in all dietary groups at 10th week. In this experiment, corn oil diet may have promotive effect on hyperplastic nodule formation during the early promotional stages of chemical carcinogenesis.

• 대한조선학회논문집
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• 제57권4호
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• pp.198-206
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• 2020

In this study, the dynamic structural behavior of pressure vessels due to pressure pulse initiated by implosion of neighbouring airbacked equipments including Unmanned Underwater Vehicles (UUV), sensor system, and so on were dealt with for the structural design and safety assessment of pressure hulls of submarine. The dynamic buckling and collapse responses of pressure vessel in deep sea were investigated considering the effects of initial hydrostatic pressure and fluid-structure interactions. The governing equations for circular cylindrical shells were formulated theoretically assuming a relatively simple displacement fields and the derived nonlinear simultaneous ordinary differential equations were analysed by developed numerical solution algorithm. Finally, the introduced safety assessment procedures for the dynamic buckling behaviors of pressure hulls due to implosion pressure pulse were validated by comparing the theoretical analysis results with those of experiments for examples of simple cylinders.

• Elastomers and Composites
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• 제31권2호
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• pp.111-121
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• 1996

The characteristic of silicone rubber can be seen from its resistance to both low and high temperature, whereas HNBR is resistant only in high temperature moderatly although it can be compounded to give good tensile properties, good oil resistance while silicone rubber severely lacks in these qualities. This study was initiated a balance of properties by blending HNBR and silicone rubber which is not considered for commercial blending; blends of HNBR with silicone rubber tend to show immiscible due to dissimilar nature of silicone and HNBR, the possibility of phase separation cannot be ruled out, in unfilled system after vulcanisation leading to premature failure. Attempt has been made to improve compatibility and minimise the layer seperation by the use of compatibilizer. Both filled and unfilled systems, in presence and absence of compatibilizer have been studied. Improvement in tensile properties of the blends or are observed as compared to the non-blended rubber. Different ratios of HNBR and silicone rubber are represented in this study. Blends of HNBR with silicone rubber were immiscible system. The tensile strength increased with filler loading.

• Mycobiology
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• 제46권1호
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• pp.1-12
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• 2018

Lactarius and Lactifluus are milkcaps that are characterized by the secretion of latex. These two genera are part of a globally distributed cosmopolitan group of ectomycorrhizal fungi that is an important food resource in various ecosystems. Recently, the taxonomy of Lactarius and Lactifluus has been revised based on molecular phylogenetics. Despite the importance of these taxa, Korean species of both genera are poorly understood. In an effort to describe milkcap species that are indigenous to Korea, a long-term study has been initiated. During a recent survey, eight species of milkcaps that were previously unrecorded in Korea were detected based on morphological observation and sequence analysis of the internal transcribed spacer region: five Lactarius species (Lactarius atromarginatus, L. austrotorminosus, L. kesiyae, L. tabidus, and L. vietus) and three Lactifluus species (Lactifluus acicularis, Lf. pilosus, and Lf. pinguis). Detailed morphological descriptions and phylogenetic relationships of these species are provided in this article.