• 한국식생활문화학회지
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• 제20권6호
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• pp.721-730
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• 2005

Recently, epidemiological evidence has raised concerns that moderate elevation in body iron stores may increase oxidative stress and the risk of cardiovascular disease and cancer. Onion flesh or peel contains antioxidant such as flavonoids and alk(en)ylcysteine sulphoxides. This study was conducted to examine the effect of onion flesh or peel feeding on antioxidative capacity in aged rats supplemented with high dietary iron. Thirty-two Sprague-Dawley male 16-month-old rats weighing $618{\pm}6g$ were acclimated for 10 days with medium-iron diet (35ppm in diet), and blocked into 4 groups according to their body weights and raised for 3 months on either control diets (adequate iron-35ppm or high iron-350ppm) or experimental diets containing onion flesh/peel (5% w/w in diet) with high iron (350ppm). Rats fed high iron-onion peel diet had significantly high quercetin and isorhamnetin levels in plasma whereas rats fed high iron-onion flesh diet did not show. Plasma TBARS level was lowered by onion flesh or peel diet with high iron supplementation. However, there was no significant difference in cellular DNA damage in brain and kidney tissue among all experimental groups. We concluded that high iron diet (10 times higher than requirement) tend to increase oxidative stress and it is plausible that onion flesh or peel feeding enhances antioxidative capacity in the elderly even with iron supplementation.

• 한국유체기계학회 논문집
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• 제18권6호
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• pp.12-18
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• 2015

Recently, the development trend of turbomachinery is high capacity and high efficiency. Most of turbomachinery in the market are adopting ball bearings or air foil bearings. However, ball bearings have a limit for high speed product over $2.0{\times}10^6DN$(product of the inner diameter of the bearing in mm (D) and the maximum speed in rpm (N)). Air foil bearings have a limit for high axial load for high power products over 200~300 HP(horse power). Magnetic bearing is one of the solutions to overcome the limits of high speed and high axial load. Because magnetic bearings have no friction between the rotor and the bearings, they can reduce the load of the motor and make it possible to increase the rotating speed up to $5.0{\times}10^6DN$. Moreover, they can have high axial load capacity, because the axial load capacity of magnetic bearing depends on the capacity of the designed electromagnet. In this study, the radial and thrust magnetic bearings are designed to be applied to the 200 HP class turbo blower, and their performance was evaluated by the experiment. Based on the tests up to 26,400 rpm and 21,000 rpm under the no-load and load condition, respectively, it was verified that the magnetic bearings are stably support the rotor of the turbo blower.

• 한국수소및신에너지학회논문집
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• 제7권1호
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• pp.19-28
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• 1996

Ti-Mn based hydrogen storage alloy were modified by substituting alloying elements such as Zr, V and Ni in order to design a high capacity MH electrode for Ni/MH rechargeable battery. When V was substituted in Ti-Mn binary system, the crystal structure was maintained as $Cl_4$ Laves phase at a composition of $Ti_{0.2}V_{0.4}Mn_{0.4}$ and $Ti_{0.4}V_{0.2}Mn_{0.4}$ and equilibrium pressure decreased below 1 atm without decreasing hydrogen storage capacity considerably. It was found that Ni should be included in Ti-V-Mn alloy in order to hydrogenate it electrochemically in KOH electrolyte. But substitution of Ni for Mn in Ti-V-Mn system caused the increase of equilibrium pressure above 1atm and decrease of hydrogen storage capacity. Zr was able to increase the reversible hydrogen storage capacity of Ti-V-Mn-Ni alloy without considerable change of hydrogenation properties. The electrochemical discharge capacity of Ti-Zr-V-Mn-Ni system were in the range of 350 - 464mAh/g and among them $Ti_{0.8}Zr_{0.2}V_{0.5}Mn_{0.5}Ni_{1.0}$ alloy had $Cl_4$ Laves single phase and very high electrochemical discharge capacity of 464mAh/g.

• Tribology and Lubricants
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• 제31권4호
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• pp.141-147
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• 2015

Gas foil thrust bearings (GFTBs) have attractive advantages over rolling element bearings and oil film thrust bearings, such as oil-free operation, high speed stability, and high-temperature operation. However, GFTBs have lower load carrying capacity than the other two types of bearings owing to the inherent low gas viscosity. The load carrying capacity of GFTBs depends mainly on the compliance of the foil structure and the formed hydrodynamic wedge, where the gas pressure field is generated between the top foil and the thrust runner. The load carrying capacity of the GFTBs is very important for the suitable design of oil-free turbomachinery with high performance. The aim of the present study is to identify the characteristics of the load carrying performance of GFTBs. A new test rig for the experimental measurements is designed to provide static loads up to 800 N using a pneumatic cylinder. The maximum operating speed of the driving motor is 30,000 rpm. A series of experimental tests—lift-off test, static load performance test, and maximum load capacity test—estimate the performance of a six-pad GFTB, in terms of the static load, driving torque, and temperature. The maximum load capacity is determined by increasing the static load until the driving torque rises suddenly with a sharp peak. The test results show that the torque and temperature increase linearly with the static load. The estimated maximum load capacity per unit area is approximately 80.5 kPa at a rotor speed of 25,000 rpm. The test results can be used as a design guideline for GFTBs for realizing oil-free turbomachinery.

• 한국철도학회논문집
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• 제12권5호
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• pp.623-630
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• 2009

한국철도시스템은 일반열차(각종 여객열차, 화물열차), 고속열차(KTX), 광역전철 급행열차(EMU) 등 다양한 종류의 열차가 사용되는 대중교통시스템이다. 철도시스템의 특징은 공시된 시간표에 의하여 열차가 운행되며, 안전, 정확, 신속, 쾌적한 서비스를 제곱한다는 것이다. 본 연구의 목적은 기존 열차의 속도향상과 다양화를 반영하여 보다 현실적인 선로용량 산정방식을 제시하고 검증하는 것이다. 본 논문은 이론식에 근거한 선로용량과 철도운영기관의 실용용량과의 차이를 최소화 하는데 역점을 두었다. 이를 위해 노선선형에 대한 TPS 시행, 운전방식과 열차제어방식 및 신호시스템 등을 고려한 새로운 철도용량 개념을 도입하였다. 실용Dia예시를 통해 새로운 선로용량산정방식의 결과를 검증하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집
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• pp.1839-1850
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• 2009

철도시스템은 일반열차(각종 여객열차, 화물열차), 고속열차(KTX), 광역전철 급행열차 (EMU) 등 다양한 종류의 열차가 혼용되고 있는 대중교통시스템이다. 철도시스템은 공시된 시간표에 의하여 열차가 운행되며, 안전, 정확, 신속, 쾌적한 서비스률 제공하는 산업이다. 본 연구의 목적은 기존 열차의 속도향상과 다양화률 반영하여 보다 현실적인 선로용량 산정방식을 제시하고 검증하는 것이다. 본 논문은 이론식에 의한 선로용량과 철도운영기관의 실용용량과의 차이를 최소화 하는데 역점을 두었다. 이를 위해 노선선형에 대한 TPS 시행, 운전방식과 열차제어방식 및 선호시스템 등을 고려한 새로운 철도용량 개념을 도입하였다. 실용 Dia 예시를 통해 새로운 선로용량산정방식의 결과를 검증하였다.

• 한국철도학회논문집
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• 제20권4호
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• pp.539-549
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• 2017

본 연구에서는 산식에 기반 한 고속철도 정거장 선로용량 계산 방법론을 제시하였다. 제시한 방법론은 기존 방법론에서 명시적으로 다루지 못하였던 정거장별 부본선(정차본선) 설치 수와 정차패턴(정차-정차, 통과-정차, 정차-통과, 통과-통과)의 혼합이 선로용량에 미치는 영향을 반영한다. 제시한 선로용량 계산 결과의 일관성을 검증하기 위해 전문 시뮬레이터(Railsys)를 활용하여 비교한 결과 정차패턴별 시격의 차이는 10% 미만으로 분석되었다. 정차패턴이 조합되었을 때의 효과를 몬테카를로 시뮬레이션 한 결과 역시 계산된 선로용량은 현실성이 높은 것으로 판단된다. 또한, 한국철도시설공단 선로배분프로그램의 용량산정 결과와도 통계적으로 유사하였다.

• 전기화학회지
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• 제7권1호
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• pp.1-8
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• 2004

This paper deals with the recent development of high-voltage cathode materials of mono- and di- metal ions substituted spinel $LiMn_2O_4$ for lithium batteries. $LiCu_xMn_{2-x}O_4(0{\leq}x{\leq}0.5)$ shows reversible intercalation/deintercalation in two potential regions, $3.9\~43\;and\;4.8-5.0V$ and stable electrochemical cycling behavior but with low capacity. $LiNi_{0.5}Mn_{1.5}O_4$ obtained by a sol-gel process delivers a capacity of 127mAh $g^{-1}$ on the first cycle and sustains a value of 124 mAh $g^{-1}$ even after the 60th cycle. The $Li_xCr_yMn_{2-y}O_4(0{\leq}x{\leq}0.5)$ solid-solutions exhibit enhanced specific capacity, larger average voltage, and improved cycling behaviors for low Cr content. $LiCr_yMn_{2-y}O_4$ presents a reversible Li deintercalation process at 4.9V, whose capacity is proportional to the Cr content in the range of $0.25{\leq}x{\leq}0.5$ and delivers higher capacities. $LiM_yCr_{0.5-y}Mn_{1.5}O_4(M=Fe\;or\;Al)$ shows that the capacity retention is lowered compared with lithium manganate. The cumulative capacities obtainable with Al-substitutted materials are less than those with Fe-substituted materials. $LiCr_xNi_{0.5-x}Mn_{1.5}O_4(x=0.1)$ delivers a high initial capacity of 1$152mAh\;g^{-1}$ with excellent cycleability.

• 한국지반신소재학회논문집
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• 제18권3호
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• pp.89-100
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• 2019

본 연구에서는 동재하시험을 통해 매입공법으로 선단이 암반에 근입된 초고강도 PHC 말뚝의 지지력 특성을 분석하였다. 초고강도 PHC 말뚝은 일반 고강도 PHC 말뚝에 비해 콘크리트의 강도가 높아 허용구조내력을 향상시킬 수 있었다. 초고강도 PHC 말뚝의 최적 설계를 위해서는 지반지지력도 증가된 구조내력과 균형을 맞출 수 있도록 증가되어야 할 것이다. 오늘날, 지반지지력 검증을 위한 동재하시험 시 경험적으로 고강도 PHC 말뚝과 유사한 항타에너지를 초고강도 PHC 말뚝에 적용하고 있는 실정이다. 동재하시험 결과를 기반으로 초고강도 PHC 말뚝의 지지력에 영향을 미치는 요소들을 분석한 결과, 선단지지력에 대해 선단 주변지반의 표준관입시험 N값의 영향은 미미하였으며, 항타에너지가 증가할수록 선단지지력이 증가하는 경향을 보였다. 그러나 주면마찰력의 경우, 항타에너지의 증가에 따른 변화가 나타나지 않았다. 또한, 허용지지력을 판단하는 Restrike 시험시 선단지지력의 영향은 극히 작아 허용지지력 판단시 합리적인 방안이 필요하다.

• Steel and Composite Structures
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• 제45권3호
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• pp.389-408
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• 2022

Residual capacity is defined as the load carrying capacity of an RC column after undergoing severe damage. Evaluation of residual capacity of RC columns is necessary to avoid damage initiation in RC structures. The central aspect of the current research is to propose an empirical formula to estimate the residual capacity of RC columns after undergoing severe damage. This formula facilitates decision making of whether a replacement or a repair of the damaged column is adequate for further use. Available literature mainly focused on the simulation of explosion loads by using simplified pressure time histories to develop residual capacity of RC columns and rarely simulated the actual explosive. Therefore, there is a gap in the literature concerning general relation between blast damage of columns with different explosive loading conditions for a reliable and quick evaluation of column behavior subjected to blast loading. In this paper, the Arbitrary Lagrangian Eulerian (ALE) technique is implemented to simulate high fidelity blast pressure propagations. LS-DYNA software is utilized to solve the finite element (FE) model. The FE model is validated against the practical blast tests, and outcomes are in good agreement with test results. Multivariate linear regression (MLR) method is utilized to derive an analytical formula. The analytical formula predicts the residual capacity of RC columns as functions of structural element parameters. Based on intensive numerical simulation data, it is found that column depth, longitudinal reinforcement ratio, concrete strength and column width have significant effects on the residual axial load carrying capacity of reinforced concrete column under blast loads. Increasing column depth and longitudinal reinforcement ratio that provides better confinement to concrete are very effective in the residual capacity of RC column subjected to blast loads. Data obtained with this study can broaden the knowledge of structural response to blast and improve FE models to simulate the blast performance of concrete structures.