• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.2
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• pp.186-194
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• 2020

In this study, spectral analysis was conducted to identify environmental factors af ecting short-term changes in water temperature in the East, West and South coasts of Korea. The data used in the spectrum analysis is the 2016 summer water temperature, air temperature, tide level and wind data provided by Korea Hydrographic & Oceanographic Agency. In power spectrum results, peaks of water temperature and tide level were observed at same periods in West Sea (Incheon, Pyeungteak, Gunsan and Mokpo) and South Sea (Wando, Goheung, Yeosu, Tongyeong and Masan) where mean tidal range was more than 100 cm. On the other hand, periodicity of water temperature did not appear in East Sea and Busan where the mean tidal range was small. Coherence analysis showed that water temperature was highly correlated with tide in West Sea and three stations(Wando, Goheung and Tongyeong) of South Sea. Especially, correlation between water temperature and tide level in Wando and Tongyeong presented 0.96 at semi-diurnal period. Water temperature in Yeosu seems to have influenced by tide and inflow of fresh water. In Masan, water temperature is influenced by south wind, tide and inflow of fresh water. In East Sea, influence of tide on water temperature is small due to current and small tidal range. As a result of comparing the time series graph, stations where the correlation between water temperature and tide is high show that relatively cold water was inputted at flood tide and flow out at ebb tide. short-term variation of water temperature was affected by tide, but long-term variation over a month was affected by air temperature.

• Tunnel and Underground Space
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• v.28 no.1
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• pp.59-71
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• 2018

Since the generalized Hoek-Brown (GHB) function predicts the strength of the jointed rock mass in a systematic manner by use of GSI index, it is widely used in rock engineering practices. In this study, a series of 2D elasto-plastic FE analysis, which adopts the GHB criterion as a yield function, was carried out to investigate the radial convergence characteristics of circular tunnel excavated in the GHB rock mass. The effect of the plastic potential function on the elasto-plastic displacement was also examined. In the analysis, the wide range of both the $K(={\sigma}_h/{\sigma}_v)$ and GSI values are considered. For each K value, the variation of the ratio of sidewall displacement to roof displacement was calculated with varying GSI values and the obtained displacement patterns were analysed. The calculation results show that the displacement ratio significantly depends not only on the K value but also on the range of GSI value. In particular, for lower range of GSI value, the displacement ratio pattern calculated in the elasto-plastic regime is opposite to that predicted by the elasticity theory. In addition, the variation of the radial displacement ratio with GSI value for different types of plastic potential function showed similar trend.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.9
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• pp.251-258
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• 2012

Recently, NAND Flash memory structure is evolving from SDR (Single Data Rate) to high speed DDR(Double Data Rate) to fulfill the high performance requirement of SSD and SSS. Accordingly, the proper ways of transferring data that latches valid data stably and minimizing data skew between pins by using PHY(Physical layer) circuit techniques have became new issues. Also, rapid growth of speed in NAND flash increases the operating frequency and power consumption of NAND flash controller. Internal voltage variation margin of NAND flash controller will be narrowed through the smaller geometry and lower internal operating voltage below 1.5V. Therefore, the increase of power budge deviation limits the normal operation range of internal circuit. Affection of OCV(On Chip Variation) deteriorates the voltage variation problem and thus causes internal logic errors. In this case, it is too hard to debug, because it is not functional faults. In this paper, we propose new architecture that maintains the valid timing window in cost effective way under sudden power fluctuation cases. Simulation results show that the proposed technique minimizes the data skew by 379% with reduced area by 20% compared to using PHY circuits.

• Journal of Nutrition and Health
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• v.54 no.6
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• pp.584-593
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• 2021

In the 2020 Dietary Reference Intakes for Koreans, an acceptable macronutrient distribution range (AMDR), similar to the one established in 2015, was determined for carbohydrates. AMDR is the ratio that signifies energy intake from carbohydrates to the total energy intake, and is a reference that indicates a decreasing risk of chronic diseases. The AMDR of carbohydrate was determined to be optimal at 55-65% for all ages above 1 year. For the first time, in the year 2020, the estimated average requirement (EAR) and recommended nutrient intake (RNI) for carbohydrates were established. The EAR was based on the amount of glucose used per day in the brain, and was set at 100 g/day for all ages above 1 year. The RNI was set at 130 g/day, by adding a double coefficient of variation using a 15% coefficient of variation, for all ages above 1 year. In pregnant women, the amount of glucose utilized by the fetus brain was considered additionally, and for lactating women the amount of lactose secreted into maternal milk was additionally taken into consideration. Since the EAR of carbohydrate indicates the minimum amount of glucose required by the brain and is not an appropriate intake amount as an energy source, it is incorrect to compare the carbohydrate intake with the EAR or RNI. To evaluate the nutritional status of carbohydrate, it is appropriate to use the AMDR. Carbohydrate intakes within the AMDR range has the possibility in reducing the risk of chronic diseases. Hence, it is important to consider the quality as well as quantity of carbohydrates consumed.

• Journal of the Korean Society for Marine Environment & Energy
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• v.14 no.1
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• pp.1-10
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• 2011

To understand characteristics of the water quality on the coastal boundary on tidal flat, field observations between 2008 and 2009 were undertaken twice a month at five coastal areas (Muan bay, Tando bay, Hampyeong bay, Shinan Jido and Yeongkwang coastal areas). Yearly water temperature difference was large with the range between $1.3^{\circ}C$ and $31.1^{\circ}C$. Salinity was about 32 but was the lower less than 20 for the heavy rainfall season. DO was high in winter and low in summer according to the variation of water temperature. pH represented the variation similar to DO. Suspended solid was averagely high over 100 mg/l in Yeongkwang coastal area, especially. COD did not revealed large variation with the value of about 1 mg/l. DIN and DIP concentration were high when freshwater was highly input in summer. DIN concentration was low for winter and early spring but DIP concentration did not show the seasonal variation with the continuous increase from July 2009 to December 2009. Chlorophyll a appeared high for spring with approximately $10\;{\mu}g/l$ and was higher for summer in Yeongkwang coastal area than other sites. The results of principal component analysis conducted to compare the characteristics of water quality observed in study areas showed the distinguishable features as follows. The freshwater input fluctuation appeared as the first factor in Muan and Tando bays, and the change of water temperature was the first factor in Shinan Jido and Yeongkwang coastal areas. The influence mixed with the variation of freshwater outflow and the change of water temperature in Hampyeong bay was to be the first factor.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1B
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• pp.125-135
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• 2008

The purpose of this study is to quantify the erosion parameters of cohesive sediments in Keum Estuary. This study also involves the examinations on the local/seasonal variation of them in Keum Estuary and on their spatial variation comparing with those of other sites. As erosional properties of cohesive sediments are in general influenced largely by the physico-chemical properties of cohesive sediments themselves, this study also involves the qualitative analyses on the impact by the physico-chemical properties. Erosion tests have been performed under the uniform bed condition using the Chonbuk annular flume and total 16 tests have been carried out with various bed densities and bottom shear stresses. Experimental results show that the critical shear stress for erosion varies in the range of $0.19{\sim}0.41N/m^2$ and the coefficient of erosion rate varies in the range of $54.26{\sim}7.70mg/cm^2{\cdot}hr$, over the corresponding bulk-density range of $1.14{\sim}1.38g/cm^3$. While erosion parameters estimated for Keum estuary sediments are found to be remarkably different in quantity compared with those for cohesive sediments from other sites, their local/seasonal variabilities within Keum Estuary are found to be insignificant.

• Journal of the Korean Chemical Society
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• v.12 no.3
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• pp.121-127
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• 1968

In the oligomerization of p-aminophenol under the catalytic action of the metallic complexes, the effects of the ligands are studied. When the initial velocity of $O_2$ uptake at pH 8 using Fe(Ⅲ) as the central metal and N-hydroxylethylethylenediaminetriacetic acid (HEDTA), ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), 1,2-cyclohexanediaminetetraacetic acid(CyDTA) as the ligands respectively are compared, the velocities are as the following order: HEDTA > EDTA > DTPA > CyDTA. Further when the effect of the ligands, nitrilotriacetic acid (NTA), HEDTA, EDTA, and DTPA, on the yields of oligomers are compared, the result shows as the following order: NTA > HEDTA > EDTA > DTPA. These are nearly reverse order of the stability constants of the complexes. In order to determine the composition of the mixed complexes at the initial step, the method of continuous variation is used, and it is found that the composition ratio of Fe-EDTA complex to monomer in the mixed complexes is one at pH 5-8 range. It is also found that at pH 9 or in the more alkaline range, side reactions occur to form water soluble dimer of quinone type and the catalytic action of the metallic complex markedly decreases on account of the hydrolysis of the central metal by the $OH^-$ ion.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.34 no.1
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• pp.9-14
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• 2008

Formation of oil-in-water nano-emulsions has been studied in oil/hydrogenated lecithin/water systems by two shear different instrument. The influence of surfactant concentration on nano-emulsion droplet size and stability has been studied. Droplet size was determined by dynamic light scattering, and nano-emulsion stability was evaluated by measuring the variation of droplet size as a function of time. The results obtained showed that the breakdown process of nano-emulsions studied could be attributed to Ostwald ripening. An increase of nano-emulsion instability with increase in surfactant concentration was found in the droplet size in the range of 100~200nm, however, an decrease of instability was found in the droplet size in the range of 300~400nm.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2817-2822
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• 2007

The purpose of this paper is to study the influence of operating condition and ejector geometries on the hydrodynamics and on the mass transfer characteristic of ejector. The CFD results were validated with available experimental data. Flow field analyses and predictions of ejector performance were also carried out. Variation on the operating conditions was made by varying the gas-liquid flow rate ratio in the range of 0.2 to 1.2. The ejector configuration was also varied on the length to diameter ratio of mixing tube ($L_M/D_M$) in the range of 4 to 10. CFD studies show that at $L_M/D_M$ 5.5, the volumetric mass transfer coefficient increases with respect to gas flow rates. Meanwhile, at $L_M/D_M$ 4, the plot of volumetric mass transfer coefficient to gas-liquid flow rates ratio reach maximum at gas-liquid flow rates ratio of 0.6. This study also shows that volumetric mass transfer coefficient decrease with respect to the increase of mixing tube length.

• Proceedings of the KIEE Conference
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• 1991.11a
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• pp.278-281
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• 1991

1) The specimen with 0.175[mol%] of additive $Sb_2O_3$ was minute and didn't appear porosity. The relation between the ratio of resistivity at $160^{\circ}C$ to that at $121^{\circ}C$ of the specimen with 0.175[mol%] of additive $Sb_2O_3$ was $3{\times}10^4$ and it's great value from among specimens. 2) The curie temperature of the specimen with 0.2 [mol%] of additive $Sb_2O_3$ was $140^{\circ}C$ AND it's great value from among specimens and those of other were $121^{\circ}C$ in all therefore, the specimen with above 0.2[mol%] of additive $Sb_2O_3$ is not match for PTCR 3) The variation of radiation properties of the specimen with 0.2[mol%] of additive $Sb_2O_3$ was very steep in the range of far-infrared $5{\sim}10[{\mu}m]$ but radiation percentage was very high of 0.92 in the range of $10[{\mu}m]$.