• 한국재료학회지
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• 제22권10호
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• pp.513-518
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• 2012

Recently, automobile parts have been required to have high strength and toughness to allow for weight lightening or improved stability. But, traditional micro-alloyed steel cannot be applied in automobile parts. In this study, we considered the influence of quenching temperature and cooling rate for specimens fabricated by vacuum induction furnace. Directly quenched micro-alloyed steel for hot forging can be controlled according to its micro structure and the heat-treatment process. Low carbon steel, as well as alloying elements for improvement of strength and toughness, was used to obtain optimized conditions. After hot forging at $1,200^{\circ}C$, the ideal mechanical properties (tensile strength ${\geq}$ 1,000 MPa, Charpy impact value ${\geq}\;100\;J/cm^2$) can be achieved by using optimized conditions (quenching temperature : 925 to $1,050^{\circ}C$, cooling rate : ${\geq}\;5^{\circ}C/sec$). The difference of impact value according to cooling rate can be influenced by the microstructure. A fine lath martensite micro structure is formed at a cooling rate of over $5^{\circ}C/sec$. On the other hand, the second phase of the M-A constituent microstructure is the cause of crack initiation under the cooling rate of $5^{\circ}C/sec$.

• ALGAE
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• 제35권1호
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• pp.91-106
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• 2020

Incorporating renewable fuel into practice, especially from algae, is a promising approach in reducing fossil fuel dependency. Algae are an exceptional feedstock since they produce abundant biomass and oils in short timeframes. Algae also produce high-valued lipid products suitable for human nutrition and supplement. Achieving goals of producing algae fuels and high-valued lipids at competitive prices involves further improvement of technology, especially better control over cultivation. Manipulating microalgae cultivation conditions to prevent contamination is essential in addition to promoting optimal growth and lipid yields. Contamination of algal cultures is a major impediment to algae cultivation that can however be mitigated by choosing extremophile microalgae. This work describes the isolation of alkali-tolerant / alkaliphilic microalgae native to South Florida with ideal characteristics for cultivation. For that purpose, water samples from Lake Okeechobee were inoculated into Zarrouk's medium (pH 9-12) and incubated for 35 days. Selection resulted in isolation of three strains that were screened for biomass and lipid accumulation. Two alkali-tolerant algae Chloroidium sp. 154-1 and Chlorella sp. 154-2 were poor lipid accumulators. One of the isolates, the diatom Fistulifera sp. 154-3, was identified as a lipid accumulating, alkaliphilic organism capable of producing 0.233 g L^-1 d^-1 dry biomass and a lipid content of 20-30% dry weight. Lipid analysis indicated the most abundant fatty acid within Fistulifera sp. was palmitoleic acid (52%), or omega-7, followed by palmitic acid (17%), and then eicosapentanoic acid (15%). 18S rRNA phylogenetic analysis formed a well-supported clade with Fistulifera species.

• 동의생리병리학회지
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• 제25권2호
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• pp.246-256
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• 2011

To compare the medical efficacy of original Socheongyong-tang with fermented Socheongyong-tang, we've studied the two medicines according to the search for optimal bacteria and optimal conditions, component analysis, assessment of medical efficacy and toxicity, and have the result below. The results were obtained as follows: Considering bacterial growth, $CO_2$ gas emission and pH, we examined that using 3 kinds of bacteria(S. cerevisiae KCTC 7913, L. casei KCTC 3109, L. brevis KCTC 3102) is desirable. There is no main difference in optimum conditions between incubator and shaking incubator. And it is considered that ideal fermentation time is 2 days after vaccination. As the result of componential analysis of before and after fermentation, there's a noticeable decrease of total sugar and protein. But there's no alterations in total phenolics compounds and in total flavonoid compounds that influence on medical effect. The result was interpreted that it can promote the assimilation of herbal decoction after fermentation. As the result of medical efficacy assessment, we can check out that there is more anti-oxidating effects in fermented Socheongyong-tang, whereas anti-inflammatory effects and obesity-preventing effects were favorable in original Socheongyong-tang. And there is no main difference of whitening and COX-2 removing effects between before and after the fermentation. As a result of assessing weight change, hepatotoxicity and nephrotoxicity, we can not notice any unusual difference between before and after the fermentation. According to the results above, it is considered that we checked out the optimal bacteria and optimal conditions, advantages and disadvantages of the medical efficacy of original Socheongyong-tang and fermented Socheongyong-tang. And we suggest that there will have to be a following in-depth and systematic research on this subject in the future.

• 보건의료산업학회지
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• 제6권4호
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• pp.73-82
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• 2012

The purpose of this study was to examine the impact of the DISC behavioral patterns of health care workers on their job satisfaction, organization Commitment and job stress in a bid to suggest an ideal behavioral pattern of Nurses and Dental hygienist. The subjects were 184 health care workers who worked in general hospitals and clinics in Busan and Ulsan for a year or more. The collected data were analyzed using ANOVA and linear regression. As a result of analyzing the relationship of their DISC behavioral patterns to job stress, organizational satisfaction and organizational commitment, there were significant differences in job stress according to their DISC behavioral patterns(p=0.015). In regard to relationship between their DISC behavioral patterns and the subfactors of job stress, there were significant gaps in role conflicts(p=.007), conflicts with subordinates(p=0.001) and conflicts over underpayment(p=0.015) according to their DISC behavioral patterns. As a result of investigating the influential factors of job stress, factors produced significant results(p<.001). The findings of the study illustrated that out of the DISC behavioral patterns, type I was most prevailing among the health care workers, which indicated that the weight of this type was highest among the behavioral styles. There were no significant gaps in job satisfaction and organizational commitment according to their DISC behavioral patterns.

• 방사선산업학회지
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• 제5권2호
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• pp.137-143
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• 2011

Epoxy resins are widely used as high performance thermosets in many industrial applications, such as coatings, adhesives and composites. Recently, a lot of research has been carried out in order to improve their mechanical properties and thermal stability in various fields. Carbon nanotubes possess high physical and mechanical properties that are considered to be ideal reinforcing materials in composites. CNT-reinforced epoxy system hold the promise of delivering superior composite materials with their high strength, light weight and multi functional features. Therefore, this study used multi-walled carbon nanotubes (MWNT) and gamma rays to improve the mechanical and thermal properties of epoxy. The diglycidyl ether of bisphenol A (DGEBA) as epoxy resins were cured by gamma ray irradiation with well-dispersed MWNTs as a reinforcing agent and triarylsulfonium hexafluoroantimonate (TASHFA) as an initiator. The flexural modulus was measured by UTM (universal testing machine). At this point, the flexural modulus factor exhibits an upper limit at 0.1 wt% MWNT. The thermal properties had improved by increasing the content of MWNT in the result of TGA (thermogravimetric analysis). However, they were decreased with increasing the radiation dose. The change of glass transition temperature by the radiation dose was characterized by DMA (dynamic mechanical analysis).

• Journal of Korean Medical Science
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• 제33권50호
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• pp.320.1-320.8
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• 2018

Background: Muscle mass and muscle function are related to depressed mood in studies of adults. Like adults, Korean students are highly likely to suffer from decreased muscle mass due to social conditions. In this study, we evaluated the muscle mass status of Korean adolescents and assess the effect of muscle on depressive mood. Methods: A total of 1,233 adolescent boys and girls participants from the Korea National Health and Nutrition Examination Survey were enrolled in our study. Participants underwent dual-energy X-ray absorptiometry for assessment of appendicular muscle mass and completed questionnaires regarding depressed mood, stress, suicidal ideations, and attempts. Results: There was no difference in depressive mood according to muscle mass among boys (P = 0.634); girls with decreased muscle mass had a greater tendency for depressed mood compared to girls with optimal muscle mass (P = 0.023). After adjusting for age, waist circumference-to-height ratio, smoking status, alcohol consumption, frequency of physical activity, self-reported obesity, weight-loss efforts, and monthly household income, girls with low muscle mass (LMM) were 2.60 times more at risk of developing depression than girls with normal muscle mass (95% confidence interval [CI], 1.05-6.49; P = 0.040). This trend was similar for girls with LMM with obesity (95% CI, 1.00-11.97; P = 0.049). Conclusion: Adolescent girls who have insufficient muscle mass are more likely to report depressed mood than girls who have ideal muscle mass. Interventions for maintaining proper muscle mass are required.

• 한국추진공학회지
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• 제6권4호
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• pp.15-23
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• 2002

액체 로켓 엔진 메니폴드 및 인젝터 부는 단열 사양을 적용할 경우 시스템이 복잡해지고 무게가 증가함으로 인해 일반적으로 단열 사양이 적용되지 않는다. 단열사양을 적용하지 않을 경우에 일어날 수 있는 문제는 액체산소의 온도 상승과 메니폴드 내부벽 및 인젝터에서 기체가 발생할 수 있다는 점이다. 본 연구에서는 극저온 액체산소를 산화제로 사용하는 KSR-III 액체로켓 엔진의 산화제 메니폴드 및 인젝터에서 측정된 압력 강하 값을 이용하여 발생된 기체 분율을 계산하였다. 액체산소 메니폴드 기체 분율 계산은 이상유동의 분리유동 모델을 활용하였고. 인젝터에서의 기체분율은 오리피스 모델을 활용하여 예측하였다. 이와 함께 메니폴드 열해석을 수행하여 비등현상에 대한 유동형태를 파악하였다. 또한 액체로켓 엔진내에서의 기체 발생이 로켓 엔진의 성능 및 연소 안정성에 미치는 영향에 대하여 간략히 고찰하였다.

• 한국방사선학회논문지
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• 제15권5호
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• pp.643-647
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• 2021

본 연구의 목적은 부식성 식도 협착 모델을 만들어 전임상연구 모델로서의 가능성과 활용성을 알아보고자 한다. 20마리의 백서를 Healthy group / Corrosive group으로 나누고, 부식성 화상은 하부 식도에 30% NaOH를 사용하여 모델링하였다. 수술 후 행동 및 체중 변화를 매주 모니터링했습니다. 수술 후 3주 뒤에 식도조영술을 시행한 후 모든 쥐를 안락사 희생시키고 병리학적 분석을 위해 하부식도를 파라핀블럭 제작하였다. 부식성 협착에 대한 기술적 성공은 100%였습니다. 총 2마리의 백서가 연하곤란과 관련된 부식성 화상으로 Corrosive group에서 14일 이내에 사망했다. 식도 협착 비율은 Corrosive group이 Healthy group보다 유의하게 높았다(각각 40.1 ± 9.2% 및 1.4 ± 7.2%; p = 0.001). 조직 증식 비율도 Corrosive group에서 유의하게 더 높았다(각각 62.5 ± 9% 및 22.08 ± 6%; p = 0.001). 결론적으로, 30% 농도의 NaOH를 이용한 백서 부식성 모델은 전임상 연구 평가 툴로서 다양한 부식성 식도 협착 치료 전임상 연구를 수행할 수 있을 것이라 사료된다.

• 한국의류산업학회지
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• 제23권6호
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• pp.860-868
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• 2021

Clothing has a very important role in human life, and it is the most human-friendly platform because humans wear it in almost all the time. In the recent years, smart clothing integrated with various functions is solidifying its position as the core of next-generation Information and Communications Technology(ICT). With this global trend, the smart textiles, textiles embedded with electronic devices that are capable of performing various functions, have been attracting a lot of attention. Therefore, various research activities on the smart textiles are in progress, and the global market outlook for the smart textiles is also showing rapid growth. Among the various smart textile technologies, the textile/fiber-based wearable display has been attracting more attention because it is an essential element for wearers to intuitively control the functions integrated in the smart textiles. This paper provides insightful information and the technological elements of organic light emitting diodes(OLEDs) display, which have been evaluated as the most ideal device for luminescent clothing. Since, OLEDs have many advantages such as light weight, extremely thin thickness and great flexibility, the textile/fiber-based wearable OLEDs can be worn without any inconvenience. In addition, by introducing previous studies on the textile/fiber-based OLED displays, we intend to consider the commercial potential of the textile/fiber-based smart luminescent clothing using the OLED technologies.

• Journal of the Korean Wood Science and Technology
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• 제50권6호
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• pp.458-474
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• 2022

Many methods have been explored to increase the palatability of pine (Pinus merkusii), the most common wood used for termite baiting. However, because of the undersupply of pine in Indonesia, it is crucial to vary the wood species for termite baiting and look for potential alternatives. Furthermore, various studies have shown that baiting time influences the intensity and pattern of termite attacks. Therefore, the present research aimed to study the preferences of subterranean termites and find the ideal baiting time among community wood species from Bogor, West Java, as a baiting alternative to pine. The woods tested were Acacia mangium (acacia), Falcataria moluccana (sengon), Anthocephalus cadamba (jabon), Maesopsis eminii (manii), Swietenia mahagoni (mahogany), Hevea brasiliensis (rubberwood), and P. merkusii (pine). Field tests were carried out based on the American Society for Testing and Materials D 1758-06 at the Arboretum, Faculty of Forestry and Environment, IPB University, with a baiting time of one to six months. The results led to the identification of four species of termites, namely Microtermes sp., Macrotermes sp., Shedorhinotermes sp., and Capritermes sp.. The frequency of termite attacks on the test site reached 93.1%. Rubberwood was the most potential wood bait for subterranean termites, indicated by the highest average weight loss value (65.8%) with a shorter optimal baiting time (up to one month) than that of other tested woods.