• Journal of the Korean Society of Visualization
• /
• v.19 no.3
• /
• pp.69-76
• /
• 2021

Printed circuit heat exchanger (PCHE) is a compact heat exchanger with good heat transfer performance, high structure integrity, and reliability over a wide range of temperatures and pressures. Instead of the traditional zigzag and straight shape channel, the sinusoidal shape channel was adopted in this study to investigate the relation of thermal-hydraulic performance and waviness factors (period and amplitude). The local flow characteristics and the heat flux distribution were compared to verify the effects of period and amplitude on heat transfer performance. As the period of channel becomes shorter, the rapid change of the flow direction can produce high flow separation around the corner leading to the disturbance of the boundary layer opposite wall. The nonuniform distribution of flow velocity appeared around the corner positions can promote fluid mixing and lead to higher thermal performance. An evaluation index was used to compare the comprehensive performance of PCHE considering the Nusselt number and Fanning factor. Based on the simulation results, the optimal design parameters of PCHE channel shape were found that the channel with an equivalent bending angle of 15° offers the highest heat flux capacity.

• Geomechanics and Engineering
• /
• v.29 no.3
• /
• pp.237-247
• /
• 2022

To investigate the curing temperature effect on the engineering properties of ground granulated blast furnace slag-cement bentonite (GGBS-CB) slurry for cutoff walls, the laboratory experiments including the setting time, unconfined compressive strength, and permeability tests were carried out. The mixing procedure for GGBS-CB slurry was as follows: (1) montmorillonite-based bentonite slurry was first fabricated and hydrated for four hours, and (2) cement or GGBS with cement was added to the bentonite slurry. The dosage range of GGBS was from 0 to 90 % of cement by mass fraction. The GGBS-CB slurry specimens were cured and stored in environmental chamber at temperature of 14±1, 21±1, 28±1℃ and humidity of 95±2% until target days. The highest average temperature of three seasons in South Korea was selected and used for the tests. The experimental results indicated that in early age (less than 28 days) of curing the engineering properties of GGBS-CB slurry were primarily affected by the curing temperature, whereas the replacement ratio of GGBS became a main factor to determine the properties of the slurry as the curing time increased.

• Korean Journal of Optics and Photonics
• /
• v.35 no.1
• /
• pp.30-34
• /
• 2024

We report a purely protein-based platform for green fluorescence by mixing silk protein with green fluorescence protein, and also report its enhancement by the incorporation of TiO₂ nanoparticles. The TiO₂ nanoparticles employed have diameters of 100 and 300 nm, with a significant increase in fluorescence (by a factor of 7.5) observed when introducing 300-nm TiO₂ nanoparticles. Furthermore, an increase in particle distribution density is found to enhance fluorescence amplification. These research findings suggest that protein-based fluorescent films can be enhanced by the characteristics of nanoparticles, opening up new possibilities in the fields of optics and fluorescence applications.

• Journal of Distribution Science
• /
• v.13 no.9
• /
• pp.37-45
• /
• 2015

Purpose - This paper's aim is to investigate whether or not gross profitability explains the cross-sectional variation of the stock returns in the Korean stock market. Gross profitability is an alternative profitability measure proposed by Novy-Marx in 2013 to predict cross-sectional variation of stock returns in the US. He shows that the gross profitability adds explanatory power to the Fama-French 3 factor model. Interestingly, gross profitability is negatively correlated with the book-to-market ratio. By confirming the gross profitability premium in the Korean stock market, we may provide some implications regarding the well-known value premium. In addition, our empirical results may provide opportunities for the fund distribution industry to promote brand new styles of funds. Research design, data, and methodology - For our empirical analysis, we collect monthly market prices of all the companies listed on the Korea Composite Stock Price Index (KOSPI) of the Korea Exchanges (KRX). Our sample period covers July1994 to December2014. The data from the company financial statementsare provided by the financial information company WISEfn. First, using Fama-Macbeth cross-sectional regression, we investigate the relation between gross profitability and stock return performance. For robustness in analyzing the performance of the gross profitability strategy, we consider value weighted portfolio returns as well as equally weighted portfolio returns. Next, using Fama-French 3 factor models, we examine whether or not the gross profitability strategy generates excess returns when firmsize and the book-to-market ratio are controlled. Finally, we analyze the effect of firm size and the book-to-market ratio on the gross profitability strategy. Results - First, through the Fama-MacBeth cross-sectional regression, we show that gross profitability has almost the same explanatory power as the book-to-market ratio in explaining the cross-sectional variation of the Korean stock market. Second, we find evidence that gross profitability is a statistically significant variable for explaining cross-sectional stock returns when the size and the value effect are controlled. Third, we show that gross profitability, which is positively correlated with stock returns and firm size, is negatively correlated with the book-to-market ratio. From the perspective of portfolio management, our results imply that since the gross profitability strategy is a distinctive growth strategy, value strategies can be improved by hedging with the gross profitability strategy. Conclusions - Our empirical results confirm the existence of a gross profitability premium in the Korean stock market. From the perspective of the fund distribution industry, the gross profitability portfolio is worthy of attention. Since the value strategy portfolio returns are negatively correlated with the gross profitability strategy portfolio returns, by mixing both portfolios, investors could be better off without additional risk. However, the profitable firms are dissimilar from the value firms (high book-to-market ratio firms); therefore, an alternative factor model including gross profitability may help us understand the economic implications of the well-known anomalies such as value premium, momentum, and low volatility. We reserve these topics for future research.

• Korean Journal of Food Science and Technology
• /
• v.36 no.5
• /
• pp.754-760
• /
• 2004

Physicochemical properties and suitability of domestic wheat varieties for production of sugar-snap cookie were examined. Four kinds of commercially available wheat flour and six kinds of other domestic wheat varieties were tested. Domestic wheat varieties had protein contents ranging 7.7 to 11.5%, alkaline water retention capacity (AWRC) of 54.6 to 65.2%, Pelshenke values of 17 to 31 min, and sedimentation values of 19.6 to 30.8 mL. Peak viscosity range of Korean wheat flours measured by Rapid Visco Analyser was from 134.4 to 346.3 unit. Diameter of cookies fer US soft wheat flour was 7.8 cm and domestic wheat flours ranged from 7.2 to 7.9 cm. Cookie spread factors for Alchanmil, Tapdongmil, and Woorimil flours were higher than those of other flours. Protein content had significantly high correlation coefficient of $r=0.892^{**}$ with sedimentation value, and showed negative correlation with cookie diameter, spread factor, and top grain score. AWRC values had significantly high correlation coefficient of $r=-0.736^{**}$ with cookie diameter. Spread factor of cookie showed positive correlation with top grain score.

• Journal of the Korea Concrete Institute
• /
• v.17 no.6 s.90
• /
• pp.923-930
• /
• 2005

This paper was to evaluate the high strength lightweight self-compacting concrete(HLSCC) manufactured by Nan-Su, which main factor, Packing Factor(PF) for mixing design, has been modified and improved. We have examined HLSCC performance at its fresh condition as well as its mechanical properties at the hardened condition. The evaluation of HLSCC fluidity has been conducted per the standard of second class rating of JSCE, by three categories of flowability(slump-flow), segregation resistance ability(time required to reach 500mm of slump-flow and time required to flow through V-funnel) and filling ability(U-box test) of fresh concrete. The compressive strength of HLSSC at 28 days has come out to more than 30MPa in all mixes. The relationship between the compressive strength-splitting tensile strength and compressive strength-modulus of elasticity of HLSSC were similar those of typical lightweight concrete. Compressive strength and dry density of HLSCC at 28 days from the multiple regression analysis resulted as $f_c=-0.16LC-0.008LS+50.05(R=0.83)\;and\;f_d=-3.598LC-2.244LS+2,310(R=0.99)$, respectively.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.26 no.2
• /
• pp.75-84
• /
• 2018

In this study, the analysis of torrefaction products was carried out for fueling of sewage sludge. The mixed samples were composed as follows : 50% of sewage sludge and 50% of rice husk and CR(Coffee Residue). In this experiment, the reaction time(30min, 60min) and temperature($200^{\circ}C$, $250^{\circ}C$, $300^{\circ}C$) were expressed as a single variable using SF(Severity Factor). As a result, it was confirmed that as the SF increased, the heating value and fuel ratio increased, but the CI(Combustibility Index) decreased. The heating value was similarly increased as CR(Coffee Residue) and SF increased. The fuel ratio range of mixed samples was equal to that of lignite(0.5~1.0) in case of SF lower than 6.19 and that of bituminous coal(1.0~1.8) in case of SF higher than 7.36 or above. The CI showed a stable range(3,000~5,500kcal/kg) in low SF as the content of mixed samples contained more rice husk than CR.

• Journal of the Korean GEO-environmental Society
• /
• v.18 no.5
• /
• pp.27-33
• /
• 2017

In this research, laboratory tests were carried out to investigate the engineering properties of Light-Weight Air Foamed Soil (LWAS) based on silty clays with the animal foaming agent and cement. LWAS has been used as an embankment material over soft ground for road and side extension of the existing road. In field, unit weight and flow value is measured right after producing in mixing plant in order to control the quality of LWAS, and laboratory tests are carried out to confirm the quality through compressive strength of LWAS as well. In this research, direct estimation of the specification requirement of strength using flow values in field is the main purpose of the study together with other characteristics. From the test results, it can be seen that flow values increase with the initial water content and unit weight increases with the depth due to material segregation. Compared to the upper specimen, lower end of 60 cm specimen shows about 2 times higher compressive strength. Relationship between flow values and normalized factor presented by Yoon & Kim (2004) was presented. With that relationship, compressive strength can be predicted from flow values in field. From the relationship, the normalized factor was calculated. Thereafter calculated compressive strengths according to the flow values were compared to measured strengths in the laboratory. The higher the initial water content of the dredged soil has, the better relationship between predicted and measured shows. Therefore it is necessary to predict the compressive strength in advance through the relationship between the flow value and the normalized factor to reflect it in the design stage.

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.39 no.2
• /
• pp.141-148
• /
• 2013

The harmful effects of ultraviolet (UV) radiation by increasing sun exposure are making people use sunscreens casually. To keep pace with this trend, many researches about mixing different ingredients or extracting effective ingredients from natural materials are conducted by cosmetics industry. In the present study, we evaluated the UV blocking effect of the sunscreen containing Scutellaria baicalensis Georgi extract. 10 volunteers were measured by minimal erythema dose (MED) and sun protection factor (SPF) of each product. The SPF results were $34.52{\pm}2.13$ and $32.67{\pm}1.44$ in the sunscreen containing Scutellaria baicalensis Georgi extract and that of not containing the substance, respectively. Although the difference of SPF between two products was statistically not significant, it is thought to be meaningful in evaluating clinical effects of the sunscreen using natural substance to humans without any adverse reaction.

• Journal of Korean Ophthalmic Optics Society
• /
• v.14 no.1
• /
• pp.47-56
• /
• 2009

Purpose: To find optimized luminosity factor of color from light transmission filter. Methods: To make $Y_{1-x}G_{x}$, $Y_{1-x}P_{x}$ by using CR-39 compound within dipping method, mixing up Y(Yellow), G(green) and P(pink) for optimize eye sensitivity. Modeling for relative luminous efficiency(relative sensitivity) curves in Luminose transmission, it could be resolved by Multiplying sensitivity of eye within transmission rate of Lens ($P_f({\lambda}=T({\lambda}){\cdot}P({\lambda}).)$.). To evaluate Wavelength between 400~700 nm, relative luminous efficiency curve in Area and Height value is being used. Results: In color filter of $Y_{1-x}G_{x}$ position of x equals to 0.04, 0.1, 0.08, 0.12, 0.14, 0.5 at ${\beta}=S_1/S_0{\cdot}100$ each consist value of 76.1, 77.9, 80.7, 81.6, 80.2, 18.6 In color filter of $Y_{1-x}P_{x}$ position of x equals to 1.00, 0.2, 0.6, 0.8 at ${\beta}=S_1/S_0{\cdot}100$ each consist value of 74.3, 74.0, 70.5, 33.0 The result from experiment $Y_{1-x}P_{x}$ value less than $Y_{1-x}G_{x}$, from evaluating luminous efficiency curve and test was successfully optimized. Conclusions: Optimized relative luminous efficiency curve result have value of X=0.12-0.14 at $Y_{1-x}G_{x}$.