• 한국물환경학회지
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• 제40권2호
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• pp.67-78
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• 2024

The introduction of a significant amount of phosphorous into aquatic environments can lead to eutrophication, which can in turn result in algal blooms. For the effective management of watersheds and the prevention of water quality problems related to nonpoint organic matter (OM) sources, it is essential to pinpoint the predominant OM sources. Several potential OM sources were sampled from upper agricultural watersheds, such as fallen leaves, riparian reeds, riparian plants, paddy soil, field soil, riparian soil, cow manure, and swine manure. Stream samples were collected during two storm events, and the concentrations of dissolved organic carbon (DOC) and phosphorous (DOP) from these OM sources and stream samples were assessed. DOM indicators using fluorescence spectroscopy, including HIX, FI, BIX, and EEM-PARAFAC, were evaluated in terms of their relevance in discerning DOM sources during storm events. Representative DOM descriptors were chosen based on specific criteria, such as value ranges and pronounced differences between low and high-flow periods. Consequently, the spectral slope ratio (S_R) paired with fluorescence index (FI) using end-member mixing analysis (EMMA) proved to be suitable for estimating the contribution of organic carbon (OC). The contribution of each organic phosphorous (OP) in stream samples was determined using the phosphorous-to-carbon (P/C) ratio in conjunction with the OC contribution. Notably, OP derived from swine manure in stream samples was found to make the most dominant contribution, ranging from 61.3% to 94.2% (average 78.1% ± 12.7%). The results of this research offer valuable insights into the selection of suitable indicators to recognize various OM sources and highlight the main sources of OP in forested-agricultural watersheds.

• 한국산학기술학회논문지
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• 제19권10호
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• pp.272-279
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• 2018

이 연구는 에너지 기여도에 따른 무산소, 유산소 운동종목 선수들의 등속성 근력, 근파워 그리고 H/Q 비율을 검증하기위해 수행되었다. 연구대상자는 대한체육회에 등록된 선수 120명을 무산소 운동종목(n=60; 단거리, 역도, 도약, 투척, 볼링, 골프종목 선수)과 유산소 운동종목 집단(n=60; 근대5종, 필드하키, 핸드볼, 자전거, 복싱, 조정종목 선수)으로 구분하였으며, 무릎관절의 신전근과 굴곡근력 그리고 햄스트링근/대퇴사두근력 비율은 등속성 장비인 cybex 770을 이용하여 주측 다리의 $60^{\circ}$, $180^{\circ}/sec$에서 실시하였다. 무산소 집단과 유산소 집단 간 차이를 검증하기 위해 독립표본 t-test(Independent t-test)를 사용하였으며, 각 집단 내에서 종목별 차이를 검증하기 위해 일원변량분석(One-way ANOVA)를 실시하였다. 연구결과, 무산소 운동종목에서 유산소 운동종목에 비해 신전근력, 굴곡근력, 굴곡근 파워가 더 높은 것으로 나타났으며(p<.05), 육상 단거리와 도약종목의 선수들에서 다른 종목에 비해 근력과 근파워가 높은 것으로 나타났다(p<.05). 그러나, 유산소운동종목 집단에서는 집단내 종목별 차이가 나타나지 않았다. 또한, 모든 종목에서 H/Q 비율은 50-60%로 안정된 범위의 비율을 보였다. 이상의 연구결과는 엘리트선수들과 지도자들에게 경기력 향상을 위해 생리학과 더불어 스포츠 과학적인 유익한 정보를 제공해줄 수 있을 것이라 사료된다.

• Steel and Composite Structures
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• 제45권2호
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• pp.193-204
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• 2022

The need for establishing the contribution of pultruded FRP encasements and additional FRP wraps around these encasements to the shear strength and load-deflection behavior of reinforced concrete beams is the main motivation of the present study. This paper primarily focuses on the effect of additional wrapping around the composite beam on the flexural and shear behavior of the pultruded GFRP (Glass Fiber Reinforced Polymer) beams infilled with reinforced concrete, taking into account different types of failure according to av/H ratio (arch action, shear-tension, shear-compression and pure bending). For this purpose, nine hybrid beams with variable shear span-to-depth ratio (av/H) were tested. Hybrid beams with 500 mm, 1000 mm, and 1500 mm lengths and cross-sections of 150x100 mm and 100x100 mm were tested under three-point and four-point loading. Based on the testing load-displacement relationship, ductility ratio, energy dissipation capacity of the beams were evaluated with comprehensive macro damage analysis on pultruded GFRP profile and GFRP wrapping. The GFRP wraps were established to have a major contribution to the composite beam ductility (90-125%) and strength (40-75%) in all ranges of beam behavior (shear-dominated or dominated by the coupling of shear and flexure). The composite beams with wraps were showns to reach ductilities and strength values of their counterparts with much greater beam depth.

• 에너지공학
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• 제19권2호
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• pp.57-61
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• 2010

국내 에너지자원 자급률을 높이기 위해서는 적극적인 해외유전개발투자를 통한 생산 유 가스전 매입, M&A, 기존 생산광구 증산 등을 추진해야할 것이다. 이를 위해서는 생산 유 가스전 평가, 설계, 운영 등과 관련된 핵심 전략 기술에 대한 확보가 필수적이라고 할 수 있다. 향후 지속적인 연구개발 지원을 통한 생산광구평가와 생산 최적 설계.운영 기술 축적으로 해외 매입 가능한 유 가스전의 증가와 기존 유 가스전의 생산량 증대, 효율적인 광구 운영을 통한 석유 가스 자주개발률 제고를 기대할 수 있을 것이다.

• Korean Membrane Journal
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• 제5권1호
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• pp.43-53
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• 2003

The selectivity of a gas in the carbon molecular sieve membrane (CMSM) can be expressed as the ratio of the product of the diffusivity and the solubility of two different gases. The diffusivity is also expressed as the product of the entropy and the total energy (kinetic and potential energy) in the nano-sized pore of the membrane. The present study calculates the entropic-energy and selectivity of penetrant gases such as H$_2$, O$_2$, N$_2$, and CO$_2$ from the gas-in-a box theory to physically analyze the diffusivity of penetrant gas in slit-shaped pore of CMSM focusing on the restriction of gas motion based on the size difference between penetrant gas pairs. The contribution of each energy term is converted to entropic term separately. By the conjugated calculation for each entropic-energy, the entropic effects on diffusivity-selectivity for gas pairs such as H$_2$/N$_2$, CO$_2$/N$_2$, and O$_2$/N$_2$ were analyzed within active pore of CMSM. In the activated diffusion domain, the calculated value of entropic-selectivity lies between 9.25 and 111.6 for H$_2$/N$_2$, between 3.36 and 6.0 for CO$_2$/N$_2$, and between 1.25 and 16.94 for O$_2$/N$_2$, respectively. The size decrement of active pore in CMSM had the direct effect on the reduction of translational entropic-energy and the contribution of vibrational entropic-energy for N$_2$, O$_2$, and H$_2$ was almost negligible. However, the vibrational entropic term of CO$_2$ might extravagantly affect on the entropic-selectivity.

• 대한지역사회영양학회지
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• 제3권3호
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• pp.368-379
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• 1998

The purpose of this study was to assess the energy value of breakfast and its relation to total daily nutrient intake and serum lipid. Dietary intakes were evaluated through the 3-day dietary recalls(interview for 1day and self-report for 2 days) from 333 Korean urban adults aged 20-49 year. Serum lipids in fasting blood samples were measured form 98 of those 333 adults. Low energy breakfast(<15% of daily energy intake) was consumed by 22.6% of males and 18.5% of females. 59.4 of males and 43.3% of females consumed a breakfast of average energy intake(15-25% daily energy intake) ; and 18.1 of males and 38.2% of females consumed a significant contribution to a total daily nutrient intake. The daily nutrient intake except crude fiber and vitamin A, B, B, and C in males and except vitamin C in females significantly increased as the energy value of breakfast increased. The differences in energy and nutrient intakes at breakfast were not made up for by other meals. To make matters worse, the satisfactory-energy breakfast group took more energy at dinner compared with the low-energy and average-energy breakfast group took more energy at dinner compared with the low-energy and average-energy breakfast groups in females. Among serum lipid parameters, TG was negatively correlated with energy provided at breakfast, and total cholesterol and LDL-cholesterol had a negative correlation with energy and carbohydrates provided at breakfast in males. For females TG was positively correlated with the ratio of carbohydrates to energy at breakfast but negatively correlated with the ratio of fat to energy at breakfast. These results suggest that satisfactory energy intakes at breakfast have positive effects on the adequacy of daily nutrient intake and may positively affect the serum lipid status.

• Structural Engineering and Mechanics
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• 제65권3호
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• pp.251-261
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• 2018

Self-centering concentrically braced frames (SCCBFs) are emerging as high performance seismically resistant braced framing system, due to the capacity of withstanding strong earthquake attacks and promptly recovering after events. To get a further insight into the seismic performance of SCCBFs, systematical evaluations are currently conducted from the perspective of modal contributions. In this paper, the modal pushover analysis (MPA) approach is utilized to obtain the realistic seismic demands by summarizing the contribution of each single vibration mode. The MPA-based results are compared with the exact results from nonlinear response history analysis. The adopted SCCBFs originate from existing buckling-restrained braced frames (BRBF), which are also analyzed for purpose of comparison. In the analysis of these comparable framing systems, interested performance indices that closely relate to the structural damage degree include the interstory drift ratio, floor acceleration, and absorbed hysteretic energy. The study shows that the MPA approach produces acceptable predictions in comparison to the exact results for SCCBFs. In addition, the high-modes effect on the seismic behavior increases with the building height, and is more evident in the SCCBFs than the BRBFs.

• KEPCO Journal on Electric Power and Energy
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• 제6권1호
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• pp.41-47
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• 2020

The contribution of damage mechanisms to failure of steam turbine casing made of Cr-Mo-V steel was investigated. Creep-fatigue interaction on the HP side corner of turbine casing was revealed as the root cause of the catastrophic failure performed by metallurgical analysis. The steady-state pressure and transient thermal stress were analyzed based on the actual operating condition of the thermal plant. Damage of creep-fatigue interaction to crack initiation was evaluated with multiaxial effects. The contribution ratio of creep and fatigue to the crack initiation was estimated to 3:1. Temporary geometrical correct action with repair weld was executed. For long-term operation, design improvement of casing equipment for creep resistance should be needed.

• Journal of Nutrition and Health
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• 제34권1호
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• pp.89-97
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• 2001

The relationship among food behavior, psychological factor(life strees) and perceive tiredness was investigated in 514 adolescents. Tiredness was measured in four cases: in lessons, before school, in the early evening and at weekends. Adolescents felt most tired in lessons and before school, and leat at weekends. Irregularity of meal times and skipping breakfast were positively correlated with tiredness in lessons and befor school. Consumption of some foods was related to perceived tiredness. High sugar or fat containing ice-cream, hamburger of fizzy drinks in boys, and crisps and cookies in girls were positively associated with tiredness. Whereas beans and mushrooms were negatively associated with tiredness in girls. Life stress(by scholastic problem and personal problem) of adolescents was positively related to tiredness. The contribution of stress to tiredness was much greater than of food behavior according to multiple linear regression .There was no relationship between nutrients intake and tiredness in lessons and before school which were more strongly influenced by stress, whereas the relationship was found at weekend without influences of stress. The more tired, the lower NARs(nutrient adequacy ratio) of energy, phosphorus, vitamin A, vitamin B$_2$, and niacin were. In conclusion, some eating behavior and psychological factor can cause tiredness in adolescents, but tiredness in school and before school had more of a psychological cause than at weekend. (Korean J Nutrition 34(1):89-97, 2001)

• Environmental Engineering Research
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• 제17권1호
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• pp.27-34
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• 2012

This paper deals with the evaluation of environmental impact of rail and road transport in South Korea. A framework of energy input-output analysis is employed to estimate the total energy consumption and $CO_2$ emission in acquiring and using a life cycle of passenger and freight transport activity. The reliability of $CO_2$ emission based on uncertainty values is assessed by means of a Monte Carlo simulation. The results show that on a passenger-kilometers basis, passenger roads have life cycle emissions about 1.5 times those of rail, while that ratio is ten times greater when the scope of evaluation regards the tailpipe. In the case of freight transport, on a million ton-kilometers basis, the value for road mode is estimated to be about three times compared to those of rail mode. The results also show that the main contribution of $CO_2$ emission for road transport is the operation stage, accounting for 70%; however, the main contribution for rail transport is the construction and supply chain stage, accounting for over 50% emission.