• Transactions of the Korean hydrogen and new energy society
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• v.10 no.4
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• pp.191-196
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• 1999

4-probe resistivity measurement technique was used to study hydrogen A-D(Absorption-Desorption)kinetics on Pd films(18 to 67nm thick) from 25 to $50^{\circ}C$, from 0 to 5 torr hydrogen pressure. Pd films were made on sapphire substrate by thermal evaporation technique under high vacuum at room temperature. Upto about 100 hydrogen A-D cyclings, no pulverization was observed, but film was detached partially from substrate. Forward reaction and backward reaction rate were analyzed separately. The activation energies of hydrogen A-D processes were obtained from the Arrhenius plot of the reaction rates. The activation energies of Pd films are not strongly dependent on the thickness of the film. But the activation energy of very thin film( l8nm thick) was smaller than the others.

• Transactions of the Korean hydrogen and new energy society
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• v.9 no.3
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• pp.127-133
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• 1998

This study was conducted to know to the effect of Pd film($180{\AA}$ thick) evaporation condition on the kinetics of hydrogen absorption-desorption. The activation energy of the forward reaction, the activation energy of the backward reaction, and the enthalpy were calculated by hydrogen absorption-desorption in ${\alpha}$-phase.($25{\sim}50^{\circ}C$ temperature) The activation energy of the forward reaction of Pd film, which is made at room temperature, is $6.4{\pm}0.4$ kcal/mol H and of the backward reaction $8.4{\pm}1.5$ kcal/mol H, which yields the reaction enthalpy -2kcal/mol H. The activation energy of forward reaction of Pd film, which is made at $300^{\circ}C$, is $-0.18{\pm}0.61$ kcal/mol H and of the backward reaction $-0.17{\pm}2.3$ kcal/mol H. The sample of $300^{\circ}C$ is more stable than the sample of room temperature in its struciural compactness and resistance value but standard error of result of $300^{\circ}C$ sample is higher than sample of room temperature do.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.3
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• pp.65-73
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• 1989

Continuum formulations for the expressions of dynamic energy release rates and computational methods for dynamic stress intensity factors are developed for the analysis of dynamic fracture problems subjected to stress wave loading. Explicit volume integral expressions for instantaneous dynamic energy release rates are derived by modeling virtual crack extensions with the dynamic Eulerian-Lagrangian kinematic description. In the finite element applications a finite region around a crack-tip is modeled by using quarter-point singular isoparametric elements, and the volume integrals are evaluated for each crack-tip element during virtual crack extensions while the singularity is maintained. It is shown that the use of the present method is more reliable and accurate for the dynamic fracture analysis than that of other path-independent integral methods when the effects of stress waves are significant.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.3
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• pp.82-88
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• 2013

In this project a preliminary experimental research work was done to apply mortars containing magnetite as fine aggregates unto floor finishing materials in order to make indoor environment eco-friendly and to have noiseproof control between floors. Crushed magnetites were substituted as sands in the mix design with a range of 0, 20, 40, 60, 100%. First far-infrared radiation tests to determine emissivity and emission power were done in accordance with the KICM test standard and an outstanding result was obtained. Density and compressive strength test results also showed that as the substitution increases, test values increase in a linear trend. However dry shrinkage test results revealed that as the substitution increases, shrinkage strain also increases. To clearly seek a solution about this problem, more experimental works should be done on oncoming experimental program.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.109-112
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• 2007

유동층 반응기를 이용한 프로판의 촉매 분해는 $CO_2$를 방출하지 않고 수소를 생성하는 새로운 방식이다. 카본블랙을 이용한 프로판 분해는 메탄보다 상대적으로 분해가 잘되며, 같은 온도에서 전환률이 높기 때문에 수소 생성량이 더 많다. 촉매로 사용된 카본블랙은 반응 중 생성되는 탄소의 침적에도 불구하고 8시간 이상 촉매의 활성이 유지되어 전환율이 일정하게 유지되었다. 프로판 촉매 분해 실험은 상압에서 600 ${\sim}$ $800^{\circ}C$ 온도 변화 실험을 수행하였고, 가스 유속 변화는 2.0 ${\sim}$ $4.0U_mf$에서 실험 조건 변화에 따른 실험을 하였다. 온도, 유속 변화에 따른 생성 가스의 몰분율과 프로판 전환율을 분석하였다. 프로판 분해에 의해 생성된 기체는 수소뿐만 아니라 메탄, 에틸렌, 에탄, 프로필렌과 분해되지 않은 프로판이 배출되었다. 수소를 제외한 여타 가스들은 고온에서 실험을 할수록 몰비가 줄어들었다. 고온에서 프로판의 전환율과 수소 수득률이 증가하였다. 프로판 분해 실험 전후의 카본블랙 표면의 변화는 FE-TEM으로 관측하였다.

• Composites Research
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• v.14 no.4
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• pp.15-26
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• 2001

Interfacial properties and microfailure degradation mechanisms of the bioabsorbable composites fur implant materials were investigated using micromechanical technique and nondestructive acoustic emission (AE). As hydrolysis time increased, the tensile strength, the modulus and the elongation of poly(ester-amide) (PEA) and bioactive glass fibers decreased, whereas these of chitosan fiber almost did not change. Interfacial shear strength (IFSS) between bioactive glass fiber and poly-L-lactide (PLLA) was much higher than PEA or chitosan fiber/PLLA systems using dual matrix composite (DMC) specimen. The decreasing rate of IFSS was the fastest in bioactive glass fiber/PLLA composites whereas that of chitosan fiber/PLLA composites was the slowest. AE amplitude and AE energy of PEA fiber decreased gradually, and their distributions became narrower than those in the initial state with hydrolysis time. In case of bioactive glass fiber, AE amplitude and AE energy in tensile failure were much higher than in compression. In addition, AE parameters at the initial state were much higher than those after degradation under both tensile and compressive tests. In this work, interfacial properties and microfailure degradation mechanisms can be important factors to control bioabsorbable composite performance.

• Journal of the Korean Society for Marine Environment & Energy
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• v.14 no.4
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• pp.249-256
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• 2011

Lagrangian particle transport model coupled with the EFDC have been performed to estimate the residence time and water exchange rate by release time of pollutants over a tidal cycle in Masan Bay. The modelled residence time for the whole bay was about 40 days, ranging from less than 20 days in the southern parts of Budo, to over 100 days in the upper parts of Somodo. The spatial difference of residence time was controlled by tidal residual currents and the distance to the bay channel. The area mean residence time during spring and neap tides was estimated to be about 36 days and 42 days, respectively. The time required for 30% exchange of water was calculated as ranging from 65 to 105 days by release time of pollutants.

• Journal of the Korean Society for Marine Environment & Energy
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• v.11 no.2
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• pp.92-97
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• 2008

Salt wedge into the river from the sea or fresh water flume (fresh wedge) in the ocean from the sea has density current characteristics. However, when temperature and salinity simultaneously determine the density of wedges, one of salinity and temperature can distributed in the reversed profiles against gravity, even though the density profile is stable. In this case, the double diffusive process is critical in determining mixing rate. The present work studies relative contribution of shear driven mechanical mixing component and double diffusive layering process, when warm salty denser water is introduced into the cold fresh lighter water column. Laboratory experiment releases warm salty denser water into cold fresh lighter water controlling discharge amount to achieve the steady state of density current. When longitudinal density rate becomes 15, the released amount ratio of salt and heat changes sharply and in the releasing point, vigorous mixing occurs with increase of discharged amount due to double diffusion. Double diffusion distabilizes gravitational stability and enhances the mixing rate up to $6{\times}10$ times at the lower density ratio comparing to the higher density ratio.

• Journal of Radiation Protection and Research
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• v.34 no.4
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• pp.190-194
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• 2009

Gamma spectral results for macroalgae samples taken from the environment of Ulchin nuclear power plants in Korea (east coast), showed 766 keV peaks, which were identified as $^{95}Nb$ by several research institutes. After the enhancement of liquid radioactive waste disposal facility at Ulchin NPP site, the $^{95}Nb$ amount in the liquid radioactive waste outflow has drastically reduced, but the expected reduction in $^{95}Nb$ specific activity from environmental samples did not actually show up on gamma spectroscopy. Detailed re-investigation revealed that along with 766 keV peak, other peaks (63, 92 and 1001 keV) from $^{234}Th-^{234}mPa$ decay series were also detected on spectroscopy, and that the measured half lives of the four peaks were very close to known half life of $^{234}Th-^{234}mPa$ decay series, which is 24.1 day. The measured gamma yield ratios of 766 keV peak to 1001 peak were very close to known ratio 0.35 for $^{234}mPa$. It is concluded that 766 keV peaks on gamma spectroscopy of Ulchin NPP environmental samples were mainly from $^{234}mPa$, which is one of naturally occurring radionuclides.

• Monthly Korean Chicken
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• v.18 no.2
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• pp.122-127
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• 2012

계사내 공기중의 암모니아 농도 감소 목적으로 식물 기원 소화율 촉진제(phytogenic digestibility enhancer) 사용이 가능하다. 이 소화율 촉진제는 사료 설계 명세서 내 특정 성분(조단백질)을 감소시키고 영양소 이용성을 개선하여 동물생산성을 향상시키기 때문이다. 조단백질 함량이 낮은 사료 급여는 가금에게 적정 요구량 이상 흡수된 단백질(excess protein)의 뇨산(尿酸 : uric acid) 전환에 에너지를 소비하지 않아서 열역학적 이점(熱力學的 利點 : energetic advantage)이 있고, 이 에너지는 유익한 성장에 사용이 가능하도록 존재한다. 더욱이 동물 사료 중 조 단백질 1%는 약 3% 더 많은 물의 섭치가 필요하고, 그 중 80%는 다시 배설되므로 단백질 함량 적정화 사료들(protein optimized diets)은 음수 요구량을 감소시킨다. 이러한 단백질 적정화 사료는 동물 사육업자들에게 관심의 대상으로 명확한 경제적 이득이 발생한다.