• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.2
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• pp.155-161
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• 2012

It was attempted to evaluate the microstructure and quality of various types of cast iron by ultrasonic velocity measurement. Three types of commercial gray cast iron and ductile cast iron were used for this investigation, respectively. One type of the ductile cast iron was heat-treated as a function of annealing time to produce different microstructure. Ultrasonic velocity measurement, microstructural analysis (pearlite area fraction, graphite length and nodularity), and hardness measurement were performed to find empirical correlations among these parameters. Ultrasonic velocity of ductile cast iron was markedly faster than that of gray cast iron. Ultrasonic velocity decreased with the decrease of fraction of pearlite structure. As a quality monitoring parameter of cast iron, potential of ultrasonic velocity was suggested.

• Journal of the korean veterinary medical association
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• v.46 no.1
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• pp.63-72
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• 2010

지구상에 서식하고 있는 포유강(Class: Mammalia), 박쥐목(Order: Chiroptera)에 속하는 박쥐류는 1,000여종에 이르는 것으로 알려졌으며, 포유류 중에서 1/4을 차지하고 있으며, 그 2/3는 곤충류를 포식하는 식충성을 지니고 있다. 우리나라에 서식하고 있는 박쥐류는 관박쥐과(Family:Rhinolophidae) 2종, 애기박쥐과(Family: Vespertilionidae) 28종, 큰귀박쥐과(Family: Molossidae) 1종으로서 총 31종이며, 모두 식충성 동물이다. 흡충류라고 하는 것은 편형동물문에 속하는 기생성 동물의 한 군으로서, 항온동물의 장이나 그 밖에 조직에 기생하는 것은 모두 하나 또는 두개 이상의 중간숙주를 필요로 하는 이생 흡충이다. 제1중간숙주는 고둥이지만 제2중간숙주는 여러 가지 변온동물로서 그 대부분은 생활사에 있어서 수서 생활을 하는 시기가 있는 것에 한정되지만 이는 제1중간숙주의 체내에서 형성된 꼬리유충이라고 하는 흡충류의 유생이 보통 물 속을 헤엄쳐 다니다가 제2중간숙주에 침입하게 된다. 박쥐류는 여러 가지 땅강아지나 개똥벌레를 포식하기 때문에 이들 유생이 물 속에서 흡충류의 피낭유충에 감염되었을 경우 박쥐류가 흡충류의 종숙주로서 적합하면 그 체내에서 피낭유충이 장에서 탈랑하여 드디어 성충으로 된다. 만일, 감염된 수서 곤충의 유생이 우화되면 그 유생 시대에 감염된 피낭유충이 그 숙주의 변태와는 상관없이 그 기생이 이어져 적당한 종숙주에게 섭취되기를 기다리게 된다. 우리나라에 있어서 박쥐류에 기생하는 흡충류에 관한 조사 연구는 일찌기 도쿄문리과 대학 동물학 연구실의 Ogata(1938)에 의하여 이루어진 이래 경성제국대학 의학부의 Park(1939a,b)과 후쿠오까대학 의학부의 Kifune et al.(1983, 1997)이 있을 뿐 우리나라 학자에 의한 연구 보고는 접할 수 없는 형편이다. 그럼으로, 우리나라 학자도 이에 관한 더욱 더 깊은 관심을 가져야할 것으로 생각하는 바 이에 지금까지 보고된 자료를 종합, 검토하여 기술하고자 한다.

• Journal of the Korean Applied Science and Technology
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• v.32 no.3
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• pp.461-468
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• 2015

Simultanious quantitative determination of Cetyltrimetyl ammonium chloride(CTM), Stearamidopropyl dimetylamine(SAP), Behentriammonium chloride(BHT), Dihexadeyldimethyl ammonium chloride(DHDDM) was carried out by reversed phase HPLC. The 0.2% TFA/Methanol was used for the mobile phase of gradient conditions. An Alltech $C_{18}$($250mm{\times}4.6mm$ i.d., $5{\mu}m$)and the selected ELSD detector was applied. The analysis results of HPLC showed good linearity with correlation coefficient of $r^2=0.997$ in the rage of $130{\sim}1980.5{\mu}g/mL$ and detection limit.

• Korean journal of applied entomology
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• v.57 no.3
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• pp.199-207
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• 2018

Miticidal and repellent activity of twenty plant essential oils against the adults of two spotted spider mites, Tetranychus urticae, were examined. Sandal wood oil was the most potent one in mortality, whereas clary sage oil exhibited the greatest repellent activity. On those twenty essential oils tested, no apparent correlation between toxicity and repellency was observed. When the most active oils were blended, the combinations tend to exhibit antagonistic interactions in both toxicity and repellent activity. The chemical compositions of sandal wood oil and clary sage oil were identified via GC/MS analyses, and the major constituents of sandal wood oils were sesquiterpene compounds, whereas the major ones for clary sage oil were monoterpenes. Among the major components in clary sage oil, linalyl acetate was not only the most abundant constituent, but also the most responsible one for its repellent activity.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.7
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• pp.759-765
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• 2012

This study investigates the effect of diesel combustion strategies on exhaust emissions and hydrocarbon species emissions for a 1.7 L common rail direct injection diesel engine at 1500 rpm and 3.9 bar BMEP. The first strategy is a method to adopt no EGR with a split injection composed of pilot and main injection (split injection). The second is to adopt a moderate EGR rate with main injection only (single-1). The third is to use a high level of EGR and main injection with rail pressure increase, $i.e.$ low-temperature diesel combustion (single-2). Split injection and single-1 showed a renowned phenomenon of a PM-NOx trade-off, whereas single-2 was observed of a PM-NOx trade-off to reduce PM and NOx simultaneously. HC speciation results show that the split injection produced the least amount of HC species, regardless of the carbon number bin, followed by single-1 and single-2. The ratios of methane, acetylene, and CO to THC increased as a combustion A/F ratio is richer due to reduced oxygen content in the vicinity of the combustion zone, thus enhancing pyrolysis.

• Journal of Plant Biotechnology
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• v.47 no.3
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• pp.248-253
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• 2020

Moringa (Moringa oleifera), which is native to tropical and subtropical climates, now grows in Korea due to its warming climate. Since it is also imported and used for food and other products in various countries, it is necessary to analyze the properties of moringa being imported into Korea. In this study, the antioxidant activity and total phenol and flavonoid content were high in the leaves and twigs and showed a positive correlation. The mineral content was also high in the leaves and twigs, and potassium ions were the most abundant mineral. In addition, seven phenolic acids (caffeic acid, chlorogenic acid, cinnamic acid, coumaric acid, ferulic acid, gallic acid, and syringic acid) and four flavonoids (kaempferol, myricetin, quercetin, and rutin) were detected in the leaves, twigs, and stems, and the ferulic acid and quercetin content was particularly high. The results of this study can be used as comparative data for domestic moringa growers in the future.

• Korean journal of applied entomology
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• v.46 no.3
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• pp.375-383
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• 2007

To find out the affection of the sampling techniques to the result of a faunistic study, we surveyed the insect fauna of the Chungbuk National University (four different sites) for a year, from spring to fall. For each site, four different collecting methods: light trap, net sweeping, pitfall trap, and window trap, were applied and the collecting was done every other week for a total of 16 times. A total of 14 orders and 672 species were collected. 501 species were collected by the light trap, which covers about 75% of the total number of species, turn out to be the most effective, while other methods could only cover 18% or less. On average, only about 30% of the species collected at a given time of collecting were re-collected at the next collecting, which means about 70% of the species collected from the first collecting remains not collected in the next collecting if you collect insects every other week. The result suggests that, in addition to applying diverse collecting methods, frequent sampling, or narrow sample window, is another very important factor for a good representation of species diversity in an insect faunistic study.

• Analytical Science and Technology
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• v.17 no.1
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• pp.45-52
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• 2004

Determination of some PAHs in sediments at Ulsan bay has been carried out by extraction of the components into n-hexane followed by synchronous spectrofluorimetric technique. 11 PAHs, such as acenaphthene (Ace), anthracene (Anth), benz(a)anthracene (BaA), benzo(b)fluoranthene (BbFt), benzo(k)fluoranthene (BkFt) benzo(a)pyrene (BaP), chrysene (Chry), phenanthrene (Phen), fluoranthene(Ft), perlyrene (Per), and pyrene (Pyr) in sediment samples were able to determine separately by synchronous spectrofluorimetry. Calibration curves for those components were linear for the concentration range of 0.15~166 ppb PAHs with the correlation factor of 0.9985~0.9999. The total amount of PAHs in sediments varied from 68.8 to 324.4 ng/g. The PAHs concentration was shown a tendency to increase from the outer bay to the inner basin as well the predominant contributors to the aromatic ring groups of the PAHs was 4-ring group.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.512-512
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• 2016

우리나라의 다양한 수계에서는 배스로 대표되는 외래어종의 유입에 따른 심각한 생태계 교란이 발생하고 있다. 외래어종은 활발한 먹이활동 및 영역다툼을 통해 우리나라 고유종의 섭취 및 경쟁 우위에 위치하고 있다는 것이 많은 보도를 통해 발표되었다. 본 연구에서는 외래어종 중 배스(Large mouth bass)에 초점을 두고 동계 및 춘계의 서식처 특성을 살펴본다. 다양한 수계 중 갇혀있는 시스템으로 간주할 수 있는 농업용 저수지에 초점을 맞추고 현장조사를 실시한다. 하지만 현장조사 중 일부는 강과 같이 열린 서식처 공간도 포함하고 있다. 본 연구는 배스가 동면을 하지 않는 대신 수온에 큰 영향을 받으며 저수온기의 서식활동을 지속한다는 가정 하에 수온과 배스가 활동하는 영역의 상관성을 이해하고자 하였다. 조사는 국내 4개 지점 이상에서 이루어졌으며 수심 20 m 정도의 깊은 저수지에서부터 하수종말처리장에서 처리수가 유입되는 도시형 하천까지 포함한다. 이 중 수심 20 m 정도의 농업용 저수지에서는 7회 이상의 정밀 조사를 수행하여 수심별, 수온별 배스의 서식특성을 이해할 수 있도록 집중조사를 실시하였다. 현장조사 결과 배스는 $1-2^{\circ}C$의 수온차에도 민감하게 반응하며 서식처를 형성한다는 사실을 알 수 있다. 수온의 평면적 분포는 서식처의 형성에 많은 영향을 주는 것으로 판단되며 수온 안정기인 동계의 경우는 수온 종분포에 따라 군락을 형성하며 서식층을 결정한다는 점도 유추된다. 4월 중순 이후의 춘계는 배스의 산란기로 종확산에 큰 영향을 미치는 가장 중요한 시기이다. 이 시기 이후 하계에는 다시 부화한 개체가 독립적으로 서식처를 이동하는 또다른 종확산의 시기이다. 따라서 계절별에 따른 보다 면밀하고 지속적인 조사를 통해 4계절 순환에 따른 배스의 서식 특성 변화를 조사하는 과정이 필수적으로 이루어져야 한다.

• The Journal of the Korea Contents Association
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• v.21 no.5
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• pp.707-715
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• 2021

This study attempts to investigate what systematic support is needed for foreign national students studying in South Korea by analyzing the relationship between foreign national students' life satisfaction and experiences of discrimination. The study utilized neo-racism as a theoretical framework and assumed that foreign national students' experiences of discrimination may lower life satisfaction while disrupting related policies to be effective. Cluster sampling was used to collect surveys, and a total number of 322 cases were analyzed. The study result reveals that experiences of discrimination resulting from students' nationality and Korean language pronunciation led to low life satisfaction in general. Based on the findings, the authors suggest ways to promote awareness around (un)intentional discriminatory actions both at institutional and political levels.