• 대한토목학회논문집
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• 제10권4호
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• pp.1-10
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• 1990

RILEM에서는 콘크리트의 파괴에너지를 결정하기 위하여 3점휨시험 방법을 제시하였으나, 콘크리트의 자중의 영향으로 인하여 이론치와 실험치가 잘 일치하지 않는 경향이 있다. 본 연구에서는 콘크리트의 자중의 영향을 고려하기 위하여 완전탄성체지지대로서 proving ring을 이용한 4점휨시험을 제시하였으며, 인조균열길이의 변화에 따른 콘크리트의 파괴에너지 변화를 알아보기 위하여 보의 높이에 대한 인조균열길이의 비를 0.2부터 0.6까지 변화시켜 실험을 실시하였다. 본 연구에서 제안된 4점휨 시험을 통하여 콘크리트의 파괴거동을 보다 쉽게 파악할 수 있었으며, 4점휨시험이 3점휨시험 보다 파괴역학이론에 잘 들어맞는 것을 알 수 있었다.

• 한국자원리싸이클링학회:학술대회논문집
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• 한국자원리싸이클링학회 2005년도 추계정기총회 및 제26회 학술발표대회 고분자리싸이클링기술 특별심포지엄
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• pp.271-275
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• 2005

수용액으로부터 중금속의 제거에 소나무수피, 배추, 게 껍질을 이용하였다. 흡착과 이온교환에 의한 중금속의 제거를 조사하기 위해서 시간, 초기농도변화, 흡착제량 변화에 따른 흡착 효율을 조사하고 각각의 실험마다 pH 변화를 측정하였다. 그 결과 배추가 가장 우수한 흡착력을 보였고, 그 다음으로 게 껍질이 우수한 흡착력을 보였다. 특이할 만 한 사항은 배추와 소나무수피의 흡착 실험시 pH는 감소하나 게 껍질의 경우에는 pH가 오히려 증가하는 경향을 보였다.

• Ocean and Polar Research
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• 제28권3호
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• pp.215-224
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• 2006

Spatial variation of heavy metal accumulation was investigated in Manila clam Ruditapes philippinarum collected from several tidal flats. Sediment metal levels varied highly among the sites, which was attributed primarily to differences in Fe and organic carbon contents and in part to gain size. Significant differences in metal concentrations also were found in the clam tissue among the different sampling sites. However, except for a few metals (Mn, Zn, Pb), which showed some elevation, the variations in the clam tissue were not related to the variations in the sediment. This is likely because most metals in filter-feeding herbivores such as R. philippinarum accumulated as a result of feeding on suspended particles such as phytoplankton and organic detritus in the water column, not in bottom sediment. In addition, tissue weight for a specific shell size varied significantly among the sites, and increased tissue mass indicating a good nutritive condition likely caused a subsequent dilution of body metals leading to reduced weight-specific concentrations of some metals (Cd, Zn, Cu, Co).

• 환경위생공학
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• 제12권3호
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• pp.31-39
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• 1997

The seasonal and spatial changes in dissolved organic carbon(DOC) in Lake Kasumigaura, a shallow and eutrophic lake, were analyzed from October 1992 to October 1995. The proportion of T-DOC was classified by labile(L-DOC) and refractory DOC(R-DOC) on the basis of long-term incubation, fractionated the molecular weight of T-DOC by ultrafiltration. The porewater DOC were measured at sedimental surface of the central basin in order to evaluate the DOC released from the sediment. The proportion of L-DOC and R-DOC were accounted for about 15% and 85% of T-DOC in the central basin, respectively. The molecular weight(MW) distribution occupied some 60% of the low and medium MW. The horizontal variation of T-DOC concentrations trended to higher in the central basin than in the inlet of influent rivers, because of contribution by autochthonous organic carbon loading. The seasonal variation of T-DOC showed to higher summer than winter in the inlet of influent, but at the central basin it fluctuated little seasonally. During the high increase of porewater DOC in 1994 evaluated the high release possibility from the sediment surface (10cm). The present study suggests that autochthonous organic carbon loading must be controlled for improving the water quality of the eutrophic lakes.

• Journal of the Optical Society of Korea
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• 제19권6호
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• pp.629-637
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• 2015

Compact system cameras (CSCs) are commonly used nowadays and feature enhanced video functions and thin yet light interchangeable lenses. They differ from digital single-lens reflex (DSLR) cameras in their lack of mirror boxes. CSCs, however, have autofocus (AF) speeds lower than those of conventional DSLRs, requiring weight reduction of their AF groups. To ensure the marketability of large telephoto zoom lenses with fixed f/2.8 regardless of field angle variation, in particular, light weight AF groups are essential. In this paper, we introduce a paraxial optical design method and present a new, large, telephoto zoom lens with f/2.8 regardless of the field angle variation, plus a lightweight AF group consisting of only one lens. Using the basic paraxial optical design and optimization methods, we fabricated a new and lighter zoom lens system, including a single-lens, lightweight AF group with almost the same performance.

• Plant Resources
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• 제6권3호
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• pp.178-182
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• 2003

This study was conducted to investigate the relationship between yearly variations of climatic elements and yearly variations of productivity in perilla. In addition, correlation coefficients among yield and yield components were estimated. The data of yield and yield components were investigated for 10 years from 1991 to 2000. The meteorological data gathered at the Yeosu Weather Station for the same period were used to find out the relationships between climatic elements and productivity. Yearly variation of the amount of precipitation in September was large with coefficients of variation(c. v.) of 11.1%, but the coefficient of variance(c. v.) in July and August were relative small with 1.8, 2.1%, respectively. Number of cluster per hill and weight of 1,000 grains were greatly with c. v. of 76.1, 79.3%, respectively, but the coefficients of variance(c. v.) of plant height and seed yield were more less with 9.58, 10.60%, respectively. Correlation coefficients between precipitation of September and seed yield were positively significant correlation at the level of 5.1%, respectively, but the duration of sunshine in September and seed yield were negatively significant at the level of 5.1%, respectively. Correlation coefficients of these, the plant height, number of branches per plant, cluster length, number of cluster per hill, weight of 1,000 grains and seed yield were positively significant at the level of 5.1% respectively.

• 재활간호학회지
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• 제13권2호
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• pp.151-160
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• 2010

Purpose: The purpose of this study was to determine the effects of empowerment education program on self-efficacy, self-care agency, self-care activities and physiologic parameters among hemodialysis patients. Method: Nonequivalent control group pretest-posttest design was used. There were 36 subjects in the experimental group and 35 subjects in the control group. The empowerment education program was administered for 4 weeks (1 time per week). Data were collected pre-treatment and post treatment. The $X^2$-test or Fisher's exact test, ANCOVA, t-test and paired t-test were performed to determine the group differences, using SPSS 14.0 version. Results: Self-efficacy, self-care agency, self-care activities and weight variation significantly improved after the empowerment education program in hemodialysis patients. Conclusion: The empowerment education program for hemodialysis patients was effective to improve the degree of self-efficacy, self-care activities and self-care agency and to decrease interdialytic weight variation.

• 한국작물학회지
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• 제28권2호
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• pp.240-247
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• 1983

땅콩 육종의 선발효율을 높이기 위한 유전력, 표현형상관, 유전상관, 환경상관 및 경로계수의 지역간변동을 알기 위하여 화성, 청주, 진주, 광산, 제주등 5개지역에서 실시된 시험성적을 중심으로 유전통계량의 분석 결과를 요약하면 다음과 같다. 1. 개화기, 주경장, 100립중 및 $\m^2$당착협수의 유전력은 매우 높으며 지역간 변동도 적어 다수계통선발의 주요형질로서 중요시되는 반면, 일차분지수, 수량의 유전력은 중정도이며 완숙립비율, 협실비율은 낮은 편이었고 지역간 변동도 컸다. 2. 주경장과 수량, $\m^2$당착협수와 완숙립비율, $\m^2$당착협수와 수량, 100립중과 수량은 정의 유전상관이 있었고 개화기와 수량간에는 부의 유전상관이 높았으나 지역간 변동량은 일정한 경향이었다. 3. 경로계수의 지역간 변동은 크나 수량에 대한 직접효과가 큰 형질은 주경장, $\m^2$당착협수 등이었다.

• 한국소음진동공학회논문집
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• 제23권6호
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• pp.553-562
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• 2013

Vehicle vibrations arise from engine and road surface excitations. The engine mount system of a passenger car sustains the engine weight and insulates the excitation force from the engine system. The dynamic properties of viscoelastic material used for the vehicle engine mounts have large variation due to environmental factors such as environmental temperature and humidity etc. The present study aims to investigate the variability of dynamic characteristics in rubber engine mounts considering both environmental temperature change and material model errors/uncertainty. The engine mounts for a passenger car were modeled using finite element method. Then, the dynamic stiffness variability of the engine mounts were estimated using Monte Carlo simulation method. In order to estimate the variations in the storage and loss moduli of the viscoelastic materials, the material properties of the synthetic rubber were expressed as a fractional-derivative model. Next, in order to simulate the uncertainty propagation of the dynamic stiffness for the engine mounts due to the storage and loss moduli variations, the Monte Carlo simulation was used. The Monte Carlo simulation results showed large variation of the engine-mount stiffness along frequency axis.

• 한국자원식물학회지
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• 제36권3호
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• pp.237-255
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• 2023

Variations in phenotypic traits are important for onion genetic improvement. The aim of this study was to identify the phenotypic traits of temporary genetic resources and the best accessions for the development of onion breeding programs. Sixteen phenotypic traits of 79 onion accessions were studied. The descriptive statistics of phenotypic traits exhibited a high variation in onion accessions. Among the 79 evaluated accessions, 64.55% had a large bulb neck width and 44.30% had a circular bulb shape. Principal component analysis showed that six principal components (PCs) accounted for 72.65% of the total variation. The main factors contributing to PC1 were bulb weight, equatorial and bulb polar diameters, plant height, and degree of splitting into bulblets, whereas those contributing to PC2 were the bulb color of the epidermal cells of the fleshy scales and color of the dry skin on the bulb. The accessions were classified into three groups-clusters 1, 2, and 3. Cluster 2 accessions were the most suitable for selecting large and circular bulb-shaped onion cultivars. The phenotypic variation observed in this study may help to select potential accessions for breeding new onion cultivars.