• 설비공학논문집
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• 제18권9호
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• pp.753-760
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• 2006

The purpose of the present work is to investigate the influence of the refrigerant adulteration by LiBr solution on the cooling capacity and COP for three different types of abso게tion chillers: a single-effect type, a series-flow double-effect type and a parallel-flow with double-effect type. A simulation program has been prepared for the cyclic analysis of absorption chillers. With some assumptions, the calculations have been performed by solving the mass balance equation, energy balance equation and the state equation simultaneously. The range of the LiBr concentration of refrigerant was 0% to 20% in the present study. For the single-effect absorption chiller, the maximum decrease in the cooling capacity was 10% at the 20% of LiBr concentration. For the double-effect chiller, the capacity was decreased by 11.1% for the parallel-flow type and the series-flow type. Also, the COP was reduced by 3.0% in single-effect, 2.8% in series-flow type (SR=0.4) and 2.3% in parallel-flow type.

• Preventive Nutrition and Food Science
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• 제14권1호
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• pp.43-48
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• 2009

Current study investigated phytochemical compositions and antioxidant capacity of Korean leafy vegetables including chajogi, gomchwi, meowi and sseumbagwi. ${\beta}$-carotene, total soluble polyphenol, total flavonoids contents were determined, and antioxidant capacity were evaluated by various methods. ${\beta}$-carotene, total soluble polyphenol, total flavonoids contents in gomchwi were significantly higher (as much as 19 folds) compare to other vegetables (p<0.05). Sseumbagwi extract ($100{\mu}g/mL$) was removed 78.6% of superoxide radicals in xanthin-xanthin oxidase system measured by EPR. Gomchwi showed the highest nitrate scavenging activity as 94.3% at pH 1.2. In SOD-like activity, chajogi, gomchwi, and meowi were evaluated in the range of $12.6{\sim}24.5%$. All samples were revealed to prevent the reaction of ferrous chloride during 9 days, which were comparable ability with 125 mg/100 g of ${\alpha}$-tocopherol. The rich phytochemical contents of gomchwi and sseumbagwi influenced to high antioxidant capacity.

• Journal of Nutrition and Health
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• 제36권3호
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• pp.287-297
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• 2003

This intervention study was performed to assess the effect of spirulina on lipid metabolism, antioxidant capacity, and immune function in elderly Koreans. The subjects were 6 male and 6 female people between the ages of 60 and 75, who were given spirulina supplements of 7.5 g/day for 24 weeks. Dietary intake, anthropometric measurements and biochemical assessment for plasma lipid levels, antioxidant status and immune function were measured before and throughout the intervention period. Before entering the study, the subjects were in relatively good health. Their nutrient intake was satisfactory, and anthropometric indices and plasma nutrient levels were within the normal range. Spirulina supplementation for 24 weeks did not affect dietary intake and anthropometric parameters. However, considerable changes were observed in blood lipid profiles, antioxidant capacity, and immune indices. The plasma concentrations of triglycerides, total- and LDL-cholesterol decreased from 4 weeks of the supplementation period. The antioxidant capacity improved, as shown in increasing TAS and decreasing TBARS after supplementation. Improved immune function was also observed as the PBL lymphocyte proliferation rate and plasma C3 levels increased. The above effects of spirulina supplementation did not differ between mild hypercholesterolemic (cholesterol $\geq$ 200mg/d1) and normochole-sterolemic (cholesterol < 200 mg/dl) subjects. This study provided evidence that spirulina could be used as dietary supplementation in nutritionally vulnerable groups to improve nutritional and health status and to prevent chronic disease such as hyperlipidemia or oxidation-prone diseases. further studies in this area with various population groups are warranted.

• 융복합기술연구소 논문집
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• 제4권2호
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• pp.51-54
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• 2014

Energy storage not only reduces the mismatch between supply and demand but also improves the performance and reliability of energy systems. The different forms of energy that can be stored, including mechanical, electrical and thermal energy. Phase change materials (PCM) are latent heat storage materials. A large number of phase change materials (organic, inorganic and eutectic) are available in any required temperature range. We concentrated on eutectic materials and made a eutectic by mixing urea and choline chloride. Heat capacity ($C_p$) is one of the most important properties to be considered when a process is developed using the eutectic and currently DSC (Differential Scanning Calorimetry) has been proved as an effective technique to measure the heat capacity. This study focused on measuring heat capacity ($C_p$) of the mixing urea and choline chloride by DSC.

• 교육시설 논문지
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• 제19권3호
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• pp.33-40
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• 2012

At present, the problem to secure seismic resistance capacity is one of the most important issue in school buildings. However, the range of facilities to consider retrofit or the proper direction of seismic retrofit haven't provided in details. Therefore in this study, a series of school buildings were chosen as established time, and the structure composition and the seismic performance of the school buildings were investigated to get the comprehensive features of seismic resistance capacity in school buildings. At result, it was presented that the member capacities were less than criteria and structure system was showed the brittle behavior at the collapse prevention level at the school buildings before 1990 year. At the school buildings after 1990 year, though it is hard to get general features for various compositions, it was presented that they have problems for seismic performance evaluation in some buildings at life safety level, specially in the direction of X axis. So, considering the introduction process of seismic criteria in Korea, the school buildings before 2005 year should be examined for seismic resistance capacity and the seismic performance should be examined as well as member capacity to resist seismic.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.1172-1177
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• 2008

The best way to gain optimal results on the bearing capacity is to perform the plate bearing test on field but it is not always possible. In the case of not performing the bearing test but estimating bearing capacity equations, it is not yet determined what equation is appliable. In this paper the results of bearing capacity equation and the loading tests of 12 samples were compared and what the one is more reliable than others was verified. The comparison showed that the range of the values using Hansen's equation was 0.67 and 1.44 times of the measured, that of Vesic's was 0.71 and 1.27, that of Meyerhof is 0.69 and 1.1, and that of Terzaghi was 0.87 and 1.57.

• 한국공간구조학회:학술대회논문집
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• 한국공간구조학회 2008년도 춘계 학술발표회 논문집
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• pp.61-65
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• 2008

A 4-story reinforced concrete structure built above an underground parking garage shows some slab deflections, and the deflections of the concrete floor slabs are proposed to be alleviated by the application of light-weight topping material in conjunction with localized strengthening of the slabs. The application of light-weight concrete topping on the existing slab has been simulated and its performance to anticipated loads has been analyzed. The application of light-weight topping material imposes additional weight on the exiting floor slabs. This added weight on the existing slabs causes over-stressing of the slabs. This over-stressing can be alleviated by enhancing the load carrying capacity of the existing slabs. Additional load carrying capacity in the existing slabs can be developed by localized strengthening of the slabs utilizing techniques such as the application of fiber-reinforced composites on the bottom surface of the slabs, and application of fiber-reinforced composites adequately complements the capacity of the existing slabs to bear the additional load imposed by light-weight leveling material. Additional moments in the beam and columns induced by the application of the light-weight topping material were tabulated and compared with capacity. The moment D/C ratios of the beam and columns are well the range of acceptable limits, and the beam and columns are not overstressed by the application of the surcharge.

• Earthquakes and Structures
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• 제18권5호
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• pp.555-565
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• 2020

The main objective of seismic codes is to prevent structural collapse and ensure life safety. Collapse probability of a structure is usually assessed by making a series of analytical model assumptions. This paper investigates the effect of finite element modeling (FEM) assumptions on the estimated collapse capacity of a reinforced concrete (RC) frame building and points out the modeling limitations. Widely used element formulations and hysteresis models are considered in the analysis. A full-scale, three-story RC frame building was utilized as the experimental model. Alternative finite element models are established by adopting a range of different modeling strategies. Using each model, the collapse capacity of the structure is evaluated via Incremental Dynamic Analysis (IDA). Results indicate that the analytically estimated collapse capacities are significantly sensitive to the utilized modeling approaches. Furthermore, results also show that models that represent stiffness degradation lead to a better correlation between the actual and analytical responses. Results of this study are expected to be useful for in developing proper models for assessing the collapse probability of RC frame structures.

• 한국물환경학회지
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• 제21권6호
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• pp.569-574
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• 2005

In this study, alginic acid that had an high affinity for a heavy metal and was noted for biological adsorbent was modified by an oxidizer, $KMnO_4$. Chemical modification changed hydroxyl of the alginic acid into carboxyl and compare with alginic acid, modified alginic acid exhibited a characteristics that carboxyl groups are comparatively high. For the use of them as an adsorbent, beads were prepared by dropping alginic acid and modified alginic acid solution in dilute 2 wt% $CaCl_2$ solution for non water soluble. The amount of removed $Cu^{2+}$ and $Pb^{2+}$ by modified alginic acid beads showed 84.7 mg and 90.9 mg per gram of beads, respectively. And it showed the amount of adsorbed heavy metal ions 10~20% higher than that of alginic acid beads in range of pH 4~7. In particular, modified alginic acid have a good adsorption capacity for $Cu^{2+}$ and $Pb^{2+}$ by Freundlich adsorption isotherm. According to this study, it is verified that alginic acid that is a nature high molecular substance improved capacity for actual application by increased heavy metal adsorption capacity by chemical modification.

• 한국물환경학회지
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• 제22권1호
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• pp.172-176
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• 2006

Fe(III)-Coated Star Fish (ICSF) was prepared by reaction of calcined Star Fish (SF) with Fe(III) solution at an elevated temperature. To investigate the stability of ICSF at acidic condition, dissolution of Fe was studied at pH 2 as a function of time. Extracted iron was negligible over the entire reaction time. This stability test suggests the applicability of ICSF in the treatment of wastewater even at low pH. Adsorption capacity of Cu(II) onto SF and ICSF was investigated in a batch and a column test. In the pH-edge adsorption, adsorption of copper onto SF and ICSF was quite similar over the entire pH range due to the presence of an important amount of Fe in SF itself. From the adsorption isotherm obtained with variation of the concentration of Cu(II), ICSF showed 1.6 times greater adsorption capacity than SF. Also, ICSF showed a greater removal capacity of Cu(II) in the column test.