• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.2
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• pp.149-156
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• 2017

Nuclear fuel requires high reliability and safety and therefore contains debris filtering devices to prevent failure-inducing debris from entering it. The debris filtering performance of nuclear fuel is one of the most important factors for fuel integrity. Therefore, the performance must be evaluated and the measurement must be reasonable. In this study, a calculation method of the comprehensive filtering efficiency using the weighted mean was proposed to establish a standard filtering efficiency index. To confirm the suitability of the proposed method, representative debris specimens were selected and the filtering efficiency with the weighted mean was compared with the efficiency of the arithmetic mean. The weighting factor of the weighted mean was introduced to produce a fair evaluation. In addition, the analysis of the debris filtering mechanism was performed according to the size of debris specimens, and the main dimensions of the filtering feature for commercial nuclear fuel.

• Korean Journal of Environment and Ecology
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• v.26 no.6
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• pp.839-867
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• 2012

Vascular plant surveys in Iss. Youngjongdo and Yongyudo, Incheon were conducted 6 times from May to October 2009 and July 2011. The vascular plants inventoried during the surveys were 644 taxa in total; 11 formas, 73 varieties, 4 subspecies, 556 species, 352 genera and 98 families. Among them, 250 taxa were newly found from the survey areas, including Cnidium japonicum Miq., Argusia sibirica (L.) Dandy, Breea setosa (Willd.) Kitam., Dryopteris erythrosora (D. C. Eaton) Kuntze and Dryopteris nipponensis Koidzumi. In the case of dormancy form, hemicryptophytes were most abundant by 37.1%. Six taxa of Korean endemic plants and nine Korean rare plants were also newly recognized along with 45 taxa of notable plants of regional flora announced by the Ministry of Environment. The naturalized plants were 95 taxa, and the Urbanization Index of the survey areas was 29.6%.

• Korean Journal of Plant Resources
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• v.31 no.5
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• pp.575-589
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• 2018

The purpose of this study is to provide the baseline data for conservation and management of the ecosystem of Gyeongju National Park by surveying and analysing the vascular plants distributed in Mt. Manhongbong (522 m). The vascular plants were surveyed form May 2012 to August 2017. The vascular plants on this site was classified as follow. Based on voucher specimens, the vascular plants of this site consisted of 91 families, 292 genera, 397 species, 4 subspecies, 48 varieties and 8 forms. The 2 taxa of threatened species, 11 taxa of rare plants and 14 taxa of Korean endemic plants were investigated. The specific plants by floristic region were totally 39 taxa, which were 3 taxa of grade V, 5 taxa of grade IV, 2 taxa of grade III, 11 taxa of grade II and 18 taxa of grade I. The naturalized plants were identified as 33 taxa and the percentage of naturalized index (NI) was 7.2%, and urbanized index (UI) was 10.3%, respectively. The invasive alien plants were 2 taxa, such as Ambrosia artemisiifolia L. and Aster pilosus Willd.

• Korean Journal of Pharmacognosy
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• v.47 no.2
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• pp.128-136
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• 2016

Tiny leaf fragments were found in the Annals of the Joseon Dynasty, which were compiled about 500 years ago. The records describing the detailed process of compiling the Annals indicate that silk bags packed with the powders of 'Cheongung' and 'Changpo', which have been used as traditional herbal medicines in the northeast Asian countries such as China and Japan as well as Korea, were put in the wooden storage boxes together with the volumes of the Annals. However, there is no record that parts of plants were used in the process of compiling the Annals. The botanical origin of leaf fragments was identified as Ligusticum sinense 'Chuanxiong' by the analysis of trnK of chloroplast DNA as well as the examination of leaf surface with SEM. The comparative analysis of trnK sequences showed that the chloroplast DNA haplotype of 'Tocheongung', a triploid species cultivated in Korea, was identical with Cnidium officinale, but different from L. sinense 'Chuanxiong'. The molecular results provide a new suggestion on the botanical origin of crude drugs used as 'Cheongung', which has been disputed in Korea.

• Composites Research
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• v.16 no.2
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• pp.26-32
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• 2003

Optical fibers, for splice, are stripped of their plastic coatings with a plastic stripper and cut off at the end. Therefore, stripped fibers often receive accidental damages and sustain small flaws or cracks. As a result, the breaking strength of a fiber splice made under normal conditions is reduced to about 0.4∼1 ㎏ on the average, nearly one-tenth of the fiber's strength. This makes it necessary to reinforce the splice. One of the most practical and reliable methods for optical fiber splicing is fusion splicing, comprising the steps of tripping the plastic coatings from the two fiber ends to be splice, placing the two bare fiber ends in an end-to-end position, and of fusion splicing, such as are fusion. Generally, steel bar (SB) sleeve is used to reinforce this fusion-splicing region. However, this type of sleeve has a critical defect to keep optical lose after bent by a sudden load. New type of composite spring (CS) sleeve is developed to make up for the weak points in the SB sleeve. This sleeve has an effect on restoration to the original state after eliminating the bending load. The optical spectrum analyzes results show the availability of reinforcement for the fusion splicing optical fiber using small diameter composite springs under the various loading conditions.

• Korean Journal of Adult Nursing
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• v.27 no.6
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• pp.718-727
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• 2015

Purpose: The purpose of this study was to identify the levels of physical activity and its relationships with depression, health-related quality of life (QoL), sleep disturbance, and physiological indicators in hemodialysis patients. Methods: The participants in this study were 139 patients undergoing hemodialysis in the hospitals in Busan and Yangsan-si. Data were collected using hematologic tests and questionnaires that contained items about individual characteristics, International Physical Activity Questionnaires (IPAQ), Center For Epidemiological Studies Depression Scale (CES-D), a 12-item Short-Form Health Survey (SF-12), and Pittsburgh Sleep Quality Index (PSQI). Data were analyzed using descriptive statistics, one way ANOVA, and correlation. Results: Mean age of the participants was $59.91{\pm}12.63$ and mean physical activity levels were $1,660.35{\pm}1,654.17$. Patients who performed higher physical activities during their daily activities reported lower levels of depression (F=4.16, p=.018) and higher levels of QOL (PCS: F=5.00, p=.008, MCS: F=8.66, p<.001) than those of the others who did not perform physical activities. Conclusion: This study showed that the levels of physical activity among hemodialysis patients was significantly associated with their depression and QOL. Developing strategies for enhancing physical activity is warranted to improve depression and QOL among hemodialysis patients.

• Polymer(Korea)
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• v.27 no.5
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• pp.502-507
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• 2003

The thermal and physical properties of low density polyethylene melt-blended with Metallocene linear low density polyethylenes were investigated. Since the Metallocene polyethylenes have similar MW and MWD except m-LLDPE4, it can be said that the thermal behavior and mechanical properties of the blends depend upon the l-octene comonomer content. The melting behavior of LDPE/m-LLDPE1 blends shows two melting peaks with LDPE contents higher than 50%, while the other blends show only one melting peak. It was observed that the blends show higher crystallization temperature and higher crystallinity with lower comonomer content. Initial modulus of a blend exhibited the behavior proportional to the crystallinity and the elongation at break of the blends was increased with increasing the m-LLDPE composition. Melt indices of the blends decreased with increasing the comonomer content of Metallocene LLDPE. Melt Index values of the blends show negative deviation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.4
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• pp.465-474
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• 2012

In this study, a dynamic simulation model that considers many spherical particles and multibody dynamics (MBD) entities is developed. Plenteous spherical particles are solved using the Discrete Element Method (DEM) technique and simulated on a GPU board in a PC. A fast algorithm is used to calculate the Hertzian contact forces between many spherical particles, and NVIDIA CUDA is used to increase the calculation speed. The explicit integration method is applied to solve the many spheres. MBD entities are simulated by recursive formulation. Constraints are reduced by recursive formulation, and the implicit generalized alpha method is applied to solve the dynamic model. A new algorithm is developed to simulate the DEM and MBD models simultaneously. As a numerical example, a truck car model and gear model are developed. The results show that the proposed algorithm using a general-purpose GPU in a PC has many advantages.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.35 no.2
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• pp.178-195
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• 1999

The species composition and seasonal variation in abundance of fishes in the Nakdong River estuary were investigated monthly from February 1987 to January 1988. During the study period, 23,008 specimens belonging to 100 species were collected. The most abundant fish species were Repomucenus valenciennei, Pholis fangi, Leiognathus nuchalis, Trachurus japonicus, and Sardinella zunasi. These five species comprised 63.0% of total fishes and 47.8% of total biomass collected. The seasonal dominant fish species were P. fangi and R. valenciennei in spring, R. valenciennei and Cynoglossus joyneri in summer, Thryssa kammalensis and Apogon lineatus in fall, and R. valenciennei, L. nuchalis and S. zunasi in winter. The number of fish species, number of individuals collected, and species diversity indices fluctuated with the seasons. The number of species and number of individuals decreased significantly in the upper estuary. While temperature was an important factor which influenced on seasonal fluctuation of the fish community, salinity determined the spatial distribution of fishes.

• 한국신재생에너지학회:학술대회논문집
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• 2008.10a
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• pp.213-215
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• 2008

최근 지구온난화가 국제적인 이슈화되면서 온실가스의 효과적인 처리에 많은 관심이 집중되고 있다. 냉매로 주로 사용되는 HFC-134a와 절연제로 주로 사용되고 있는 $SF_6$는 각각 이산화탄소의 11,700배와 23,900배의 지구온난화지수를 가지는 온실가스이다. 본 연구에서는 이 두 물질의 효과적인 분리/회수를 위하여 가스 하이드레이트 형성을 이용한 방법을 제안하였다. 하이드레이트 형성법을 이용 할 경우 공정이 단순하고 저압에서 분리가 가능하므로 타 분리공정과의 경쟁이 가능할 것으로 예상된다. 본 실험은 275-290 K의 온도범위와 3 - 30 bar의 압력범위에서 질소 + HFC-134a (20, 40, 60, 80%)와 질소 + $SF_6$ (10, 30, 50, 70%)의 혼합기체를 사용하여 각 조성에 따른 하이드레이트(H)-물($L_W$)-기상 (V)의 3상 평형점을 측정하였다. HFC-134a 또는 $SF_6$의 조성이 낮은 혼합기체의 3상 평형점은 순수 질소의 3상 평형점에 비하여 주어진 온도에서 평형압력이 현저히 낮은 것을 볼 수 있었으며 HFC-134a 또는 $SF_6$의 조성이 증가할 수록 순수한 HFC-134a 또는 $SF_6$의 3상 평형점에 근접하는 것을 볼 수 있었다. 특히 $SF_6$는 다른 기체와 달리 하이드레이트의 생성/해리에 긴 시간이 필요하다는 것을 알 수 있었다. 본 실험에서 얻어진 결과는 하이드레이트를 이용한 HFC-134a와 $SF_6$ 분리 공정의 중요한 기초 자료가 되며 다른 혼합 기체의 분리 공정에도 응용될 수 있을 것이다.