• 한국미생물·생명공학회지
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• 제24권5호
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• pp.597-603
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• 1996

This study was carried out to examine degradation characteristics of microalgae Chlorella vulgaris in methane fermentation. We measured COD and VS reduction, gas and methane productivity, VFA (volatile fatty acid), respectively. Then we calculated material balance and hydrolysis rates in soluble and solid material. The substrate concentration was controlled from 14 gCOD$_{cr}$/l to 64 gCOD$_{cr}$/l in batch cultures, and HRT (hydraulic retention time) controlled from 2 days to 30 days in continuous experi- ments. The results were as follows. In batch culture, accumulated gas productivity increased with the increase of the substrate concentration. The SS and VSS was removed all about 30% increase of substrate concentration and the most of the degradable material removed during the first 10 days. The curve of gas and methane production rate straightly increased until substrate concentration is 26 gCOD$_{cr}$/l. In continuous culture experiments, the removal rates at HRT 10days were 20% for total COD and TOC, respectively. At longer HRT, there was no increase in the removal efficiency. At HRT 15 days, the removal rates were 30% for SS and VSS, respectively. Soluble organic materials were rapidly degraded, and so there was no accumulated. Soluble COD concentration was not increase regardless of HRT-increasing. That meaned the hydrolysis was one of the rate-limiting stage of methane fermentation. The first-order rate constants of hydrolysis were 0.23-0.28 day$^{-1}$ for VSS, and 0.07-0.08 day$^{-1}$ for COD.

• 상하수도학회지
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• 제27권1호
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• pp.49-58
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• 2013

A selected halogenated organic contaminant, monochlorophenol was successfully degraded by photocatalytic reaction in a circulating batch system. The photocatalytic degradation in most cases follows first-order kinetics. The photocatalytic reaction rate increased in the $TiO_2$ dosage range of 0.1 g/L to 0.4 g/L, then decreased with further increase of the dosage. Also the degradation rate increased over the range of the retention time from 0.49 min. to 0.94 min., then decreased with further increase of the retention time in the circulating batch reactor. The photocatalytic activity was enhanced by addition of metal impurities, platinum(Pt) and palladium(Pd) onto the photocatalysts. The photocatalytic degradation rate increased with the increase of Pt and Pd in the content range of 0 to 2wt %, then decreased with further increase of the metal contents. Therefore the metal loading to $TiO_2$ influence the degradation rate of a halogenated organic compound by acting as electron traps, consequently reducing the electron/positive hole pair recombination rate.

• 한국세라믹학회지
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• 제34권7호
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• pp.767-773
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• 1997

Thermal shock behavior of alumina ceramics were studied by quenching the heated alumina specimen into the water of various temperatures over 0~10$0^{\circ}C$. The critical thermal shock temperature difference ( Tc) of the specimen decreased almost linearly from 275$^{\circ}C$ to 20$0^{\circ}C$ with increase in the cooling water temperature over 0~6$0^{\circ}C$. It is probably due to the increase of the maximum cooling rate which is dependent of the convection heat transfer coefficient. The convection heat transfer coefficient is a function of the temperature of the cooling water. However, the critical thermal shock temperature difference( Tc) of the specimen increased at 25$0^{\circ}C$ over 80~10$0^{\circ}C$ due to the film boiling of the cooling water. The maximum cooling rate, which brings about the maximum thermal stress of the specimen in the cooling process, was observed to increase linearly with the increase in the quenching temperature difference of the specimen due to the linear relationship of the convection heat transfer coefficient with the water temperature over 0~6$0^{\circ}C$. The critical maximum cooling rate for thermal shock fracture was observed almost constant to be about 260$\pm$1$0^{\circ}C$/s for all water temperatures over 0~6$0^{\circ}C$. Therefore, thermal shock behavior of alumina ceramics is greatly influenced by the convection heat transfer coefficient of the cooling water.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.2141-2145
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• 2004

As part of study on thermal hydraulic behavior in the reactor cavity under external vessel cooling in the APR (Advanced Power Reactor) 1400, one dimensional two phase flow of steady state in the reactor cavity have been analyzed to investigate a coolant circulation mass flow rate in the annulus region between the reactor vessel and the insulation material using the RELAP5/MOD3 computer code. The RELAP5/MOD3 results have shown that a two phase natural circulation flow of 300 - 600 kg/s is generated in the annulus region between the reactor vessel and the insulation material when the external vessel cooling has been applied in the APR 1400. An increase in the heat flux of the inner vessel leads to an increase of the coolant mass flow rate. An increase in the coolant outlet area leads to an increase in the coolant circulation mass flow rate, but the coolant inlet area does not effective on the coolant circulation mass flow rate. The change of the lower coolant outlet to a lower position affects the coolant circulation mass flow rate, but the variation trend is not consistent.

• Journal of Mechanical Science and Technology
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• 제14권8호
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• pp.851-860
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• 2000

Temperature field and cooling rate are important parameters to influence the properties of clad layer and the heat affected zone. In this paper the temperature field and cooling rate of laser cladding are studied by a two-dimensional time-dependent finite element model. Experiment has been carried out by Nd:YAG laser cladding with wire feeding. Research results indicate that at the beginning of cladding, the width and depth of melt pool increase with cladding time. The cooling rate is related to position, cladding time, cladding speed, and preheating temperature. The temperature near melt pool changes rapidly while the temperature far from melt pool changes slowly. With the increase of cladding time, cooling rate decreases. The further the distance from the melt pool, the lower the temperature and the slower the cooling rate. The faster the cladding speed, the faster the cooling rate. The higher the preheating temperature, the slower the cooling rate. The FEM results coincide well with the experiment results.

• 국제학술발표논문집
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• The 1th International Conference on Construction Engineering and Project Management
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• pp.1244-1249
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• 2005

Present PII(Private Infrastructure Investment) in Korea has increased up to 11% compared to the year 2003 and is expected to increase in the future. In spite of its rapid increase, we don't have any definite standard or system which distinctly presents the rate of return for domestic PII yet, and practical and scientific research is not sufficient compared to its necessity and importance. Hence, in this study we suggests methods to estimate the rate of return of PII to promote SOC PII to last successfully and present the proper level of rate of return of PII which is appropriate for domestic situations through diverse analysis. Therefore, to present reasonable rate of return, we have used 5 methods: previous research analysis, case study, financial index analysis, analysis of investor's rate of return, and analysis of rate of return in a real estate market. After comparing and analyzing these methods, at the end, we have presented the appropriate level of rate of return of PII, which can be applied in the domestic market.

• 한국산학기술학회논문지
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• 제15권6호
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• pp.3564-3570
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• 2014

본 연구에서는 최근 금융 감독당국이 상호금융기관에 대한 다양한 규제조치를 취하는 과정에서 상호금융 예수금 증가가 대출금 연체율을 상승시키는 것으로 판단하고 금융 감독정책을 수립하고 시행하는 것에 대한 타당성을 실증적인 방법으로 검증하였다. 전국의 1,161개의 지역농협에 대해 전수조사를 통해 2005년부터 2011년까지 상호금융 예수금 증가율과 대출금 연체율과의 상관관계를 통합회귀모형에 의해 분석한 결과 결국 금융 감독당국에서 전제하고 있었던 양자 간의 양(+)의 상관관계는 증명되지 않았으며, 오히려 음(-)의 관계를 가지는 것으로 판명되었다. 이는 상호금융기관 중에서 농협이 가지고 있는 특성으로서 증가된 예수금의 운용 방안이 다양화되고 있다는 점과 예수금증가가 동시에 자금의 조달금리를 낮추는 효과를 가져와서 이는 다시 대출금리를 낮게 운용할 수 있는 여지를 제공하게 되어 전반적으로 대출에 대해 긍정적인 영향을 미치기 때문이라고 할 수 있다. 금융 감독당국은 이러한 농협의 자금운용 상의 특수성과 예수금 증가율과 연체율과의 구체적인 상관관계를 잘 이해하고 정책방향을 재정립해야 할 것이다.

• International Journal of Advanced Culture Technology
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• 제3권1호
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• pp.39-45
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• 2015

This research aims to study an effect of sodium chloride solution concentration on the corrosion rate of AA1100 aluminium alloy and SGACD zinc coated steel lap joint with a test duration of 30 days and a test temperature of $45^{\circ}$. The summarized results are as follows. Increase of the NaCl solution concentration increased the weight loss of Al, corrosion rate of Al, weight loss of Fe and also decreased the corrosion rate of Fe. Increase of the test duration affected to increase the weight loss and corrosion rate of Al and also decrease the weight loss and corrosion rate of Fe. The corrosion that was formed in a lap joint consisted of the uniform corrosion on the surface of the metals and the galvanic corrosion in the lap area of the joint. The maximum weight loss of AA 1100 aluminium and SGACD zinc coated steel that was occurred in the sodium chloride with 3.25% was 2.203% and 3.208%, respectively.. The maximum corrosion rate of AA 1100 aluminium and SGACD zinc coated steel that was occurred in 4.00% and 3.5% sodium chloride solution was 0.156 mm/year and 0.479 mm/year, respectively.

• 무역상무연구
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• 제61권
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• pp.165-190
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• 2014

The purpose of this study is to measure the trade insurance's macroeconomic effects by analyzing the causality between major economic variables(GDP per capita, market interest rate, inflation, unemployment rate, exchange rate) and trade insurance variable. I conducted empirical analyses using First-difference GMM(Generalized Method of Moments), System GMM and Panel-VAR Model, with panel data from 11 countries(Korea, United States, Japan, BRICs, Indonesia, Singapore, Hong Kong, Vietnam) between 1992 and 2011. There are several important findings. Above all, Trade insurance is positively and significantly related to GDP. This results show that trade insurance serves to increase economic growth. In other words, trade insurance leads to economic growth by helping increase GDP per capita. Especially, trade insurance negatively related to unemployment rate, it is for sure that trade insurance contribute to decrease unemployment rate. And trade insurance helps control of inflation. It is also confirmed that trade insurance contributes to price stability, which in turn serves to stabilize the overall economy. And this research finds as uncertainty in the market increases, seen it as increase of exchange rate, increasing trade insurance supply is stabilize the exchange rate.

• 대한간호학회지
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• 제13권3호
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• pp.119-126
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• 1983

Early extra-uterine development of the newborn infant has the potential for clarifying important questions of nature and care taking environment. In this study, tactile and auditory stimulation is used on .a group of infants to determine the effects of their response. Infants were tested by EKG at 24∼48 hrs after birth ana all they are free from complication. Stimuli presented were-touch and sound (40dB, 70dB and 40∼70dB). The result of the study were as follows: 1) The heart rate was seen to depend on their sleep-wake state. (light sleep ; 125/min, eyes: open & motor activity increase ； 151/min crying ; 185/min). 2) The heart rate affected by tactile & auditory stimulus. The heart rate response was acceleration above the prestimulus level. (tactile, 231min increase, auditory ; 16∼21/min increase), and heart rate change was seen to depend on prestimulus rate. (γ=.73) 3) There was a decrease in heart rate when they were soothe. (touch ; 24.8sec, 21/min decrease, pacifier ; 14.5sec, 26/min decrease) and significant difference in time between touch and pacifier (t= 1.76, p<0.05). This result support the evaluation of newborn infant's sensory abilitics, and has even begin to influence changes in nursing care. But systemic monitoring of newborn infants response would. further define.