• 청정기술
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• 제19권1호
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• pp.59-64
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• 2013

고분자전해질 연료전지에서 사용되는 전도성 카본에 백금이 담지된 전극촉매를 콜로이드법을 이용하여 합성하였다. 콜로이드법 합성을 위한 백금 전구체로는 PSA (platinum sulfite acid)를 사용하였으며, 고가의 전구체를 대체하기 위해 CPA (chloroplatinic acid)를 사용하여 합성하였다. PSA를 전구체로 하여 제조한 전극촉매는 10~40 wt% 담지량에서 3.5 nm 이하의 백금 입자크기와 90% 이상의 백금 담지수율을 보였다. CPA를 전구체로 사용한 경우에는 10~40 wt% 담지량에서 4.4 nm 이하의 백금 입자 크기를 보였으며 담지수율은 80% 이상이었다. 제조한 20 wt% Pt/VXC72 전극촉매로 MEA (membrane electrode assembly)를 제조하여 I-V 곡선을 측정하였으며, 제조한 전극촉매를 이용한 막전극접합체는 상용전극촉매를 사용한 경우와 동등한 성능을 보였다.

• ALGAE
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• 제20권2호
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• pp.157-166
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• 2005

Uptake kinetics of Cd and Zn by leaves and rhizome of the seagrass Zostera marina were examined in controlled laboratory radiotracer experiments. Subsequently, acute toxicity of Cd, Cu and TBT on photosynthetic quantum yield (ΔF/Fm’ of Z. marina were determined, and the differential sensitivities of rapid light curve (RLC) to those harmful substances were also compared. All measurements on photosynthetic activity were determined by chlorophyll a fluorescence method using pulse amplitude modulation (PAM). Metal uptake by Z. marina was saturated with increasing exposure time in leaves and rhizomes. Uptake of Zn by Z. marina was faster than that of Cd. Metal uptake rates in Z. marina decreased with the increase of dissolved metal concentrations and also with the increase of biomass. The adverse effect of TBT on effective quantum yield was stronger than other pollutants. Average acute toxicity on the RLC of the seagrass exposed to TBT and two heavy metals (Cd and Cu) was going to decrease as follows: TBT > Cd > Cu. Our preliminary results in this study suggested that Z. marina potentially can be used as a biomonitor of harmful substances contamination in coastal waters.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.1117-1124
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• 2008

In This paper, load-settlement curves that obtained from 11 sites were analyzed. At all tests, the load is applied until apparent failure is observed. The validity of the ultimate and yield load estimation method and load calculated from the settlement criterion was investigated through comparison with the measured data. The result indicated that B. Hansen 80% criterion and Stability Plot in ultimate loading decision law almost have been regared as same by comparing measured date and ultimate bearing capacity decided in depending yield loading decision law from 13% to 46% difference have taeyaeen came out when measured data and Davisson was compared, and S-log t from 5% to 41% log P-log S from 14% to 50% difference have been came out. When Settlement standard and measured data was compared difference had been came out about 3% in total settlement 0.1D criterion and from 12% to 35% difference had been came out in net settlement.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.677-686
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• 2005

The allowable bearing capacity of a pile, the most important factor in stability estimation, is determined by applying safety factor to the ultimate load or yield load. There are several but contradictory methods available in current design codes to estimate the allowable bearing capacity and the safety factor. This paper analyzes load-settlement curves obtained from 19 static load tests measured from 11 sites. At all tests, the load is applied until apparent failure is observed. The validity of the ultimate and yield load estimation method and load caculated from the settlement criterion is investigated through comparison with the measured data. In addition, a new procedure to estimate allowable load and safety factor is proposed. Additional data from field static load tests, such as those incorporated in this study, are needed to more reliably apply the proposed method in design practice.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.44-48
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• 2001

API 5L X65 배관의 모재 기리 및 원주방향, 심용착금속, 원주용착금속에 대한 고주기피로시험 결과를 요약하면 다음과 같다. (1) 모재 길이방향이 원주방향보다 항복강도 및 항복비가 높게 나타난 압연 방향에 따라 피로특성이 다르게 나타났고, 항복비가 작아질수록 피로강도가 작아졌다. (2) 모재의 피로강도는 항복강도보다 높게 나타났지만 용착금속의 피로강도는 낮게 나타났다. (3) 용착금속은 모재보다 항복강도 및 인장강도가 상당히 높았지만 피로강도는 오히려 작게 나타났다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.266-271
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• 2001

Spherical indentation technique was developed to evaluate the flow properties of metallic materials in carbon steel, stainless steel and alloys, etc. Through the spherical indentation test, differently degraded 1Cr-1Mo-0.25V steel's mechanical properties were observed and compared with conventional standard test data. The flow properties of 1Cr-1Mo-0.25V steels were estimated by analyzing the indentation load-depth curve. To characterize the flow property, we used material yield slope and constraint factor index rather than strain-hardening exponent because the variation of strain-hardening exponent was very little and the data showed irregularly. And the constraint factor's effect was small when the material yield slope was taken into account.

• 대한기계학회논문집A
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• 제24권9호
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• pp.2319-2325
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• 2000

This thesis studied that seven kinds of residual elements(inclusions) had influenced on fracture toughness($K_{IC}$) obtained by Begley-Logsdon and Rolfe-Novak model equation using tensile an d impact test data of I%CrMoV HP(high pressure) rotor steel. $K_{IC}$ design curve of ASME and fracture surface by SEM were also considered, obtained results are summarized as follows $K_{IC}$ was linearly increased with increase of temperature, effect of the inclusions was significantly over FATT. $K_{IC}$ at lower shelf temperature was quantitatively related to yield strength and was agreed well with Begley's equation. It was difficult to determine $K_{IC}$ because of specimen size and tester capacity at upper shelf temperature, but for this view point Rolfe-Novak's equation was useful. The degree of brittle fracture was dependent on FATT fundamentally, adding S, Sb to matrix decreased impact energy and adding Cu, As increased yield(tensile) strength, and the influence of the others minority inclusion was comparatively insignificant.

• 한국의류학회지
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• 제17권1호
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• pp.63-75
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• 1993

Partially oriented polyester yarn (PET POY) was treated in the unrestrained state using various solvents at different temperatures. Interactions between PET POY & solvents were estimated by the changes of microstructure, morphology and mechanical properties. The correlation between the changes of microstructure & morphology and the changes of mechanical properties was also studied. TCE, Dioxane, O-DCB, DMF, and BA were found to be active solvents, while Iso-AA and water were found to be weak solvents. PET POY was affected mainly by the solvents when treated with active solvents and affected mainly by heat when treated with weak solvents. Changes by the solvent treatment in microstructure and morphology were : an increase in crystallinity, a change in birefringence, a shrinkage in length, and a change in DSC curve. As for the changes in mechanical properties, findings in the PET POY when treated with solvents were : a decrease in stress-at-break, a change in yield stress, an increase in strain-at-break & yield strain, and a decrease in initial modulus. Changes in microstructure and morphology directly affected the mechanical properties.

• Carbon letters
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• 제5권2호
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• pp.81-87
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• 2004

The effect of compositions of $Al_2O_3$ in the mixed $Fe/Al_2O_3$ catalysts on the synthetic behaviors of carbon nanotubes (CNTs) by catalytic chemical vapor deposition (CCVD) process was investigated in wide range of the mixture ratios of support materials. CNTs were synthesized with $Fe/Al_2O_3$ catalysis under the condition of 40 min in synthetic time, and 923 K of synthetic temperature using $C_2H_4$ and $H_2$ as synthetic and carrier gas, respectively. The carbon yield with the content of $Al_2O_3$ showed in a parabolic curve and the maximum carbon yield was 40 wt.% of $Al_2O_3$. As the mixture ratio of $Al_2O_3$ increased, decreasing tendency was observed in the diameter of CNTs. Specific surface areas of CNTs were increased with the increase of the mixture ratio of $Al_2O_3$.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.439-443
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• 2008

We investigate the mechanical behavior of a pre-heat treated steel of ESW95, which is being used for automotive parts including tie-rods to save manufacturing cost and enhance product quality. SCM435 is also investigated to reveal the characteristics of the pre-heat treated steel tested. AFDEX/MAT is used to extract the true stress-strain curve over the large strain with higher accuracy. It has been found that ESW95 has very week strain-hardening behavior which can be negligible compared with SCM435 and that the initial yield strength is quite high and the toughness of ESW95 reaches nearly 75% of SCM435. ESW95 is characterized by the weak strain-hardening behavior and high yield strength that can be lead to minimization of post-processing including heat treatment and straightening. ESW95 and SCM435 are also compared by applying them to ball-stud forging by computer simulation. It is expected that a great deal of change may take place in production as well as in service if the pre-heated steels are adopted.