• Nuclear Engineering and Technology
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• 제48권5호
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• pp.1230-1236
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• 2016

This study aims to determine the effect of fly ash with a high replacing ratio of clay on the radiation shielding properties of bricks. Some interaction parameters (mass attenuation coefficients, half value layer, effective atomic number, effective electron density, and absorption efficiency) of clay fly ash bricks were measured with a NaI(Tl) detector at 661.6 keV, 1,173.2 keV, and 1,332.5 keV. For the investigation of their shielding behavior, fly ash bricks were molded using an admixture to clay. A narrow beam transmission geometry condition was used for the measurements. The measured values of these parameters were found in good agreement with the theoretical calculations. The elemental compositions of the clay fly ash bricks were analyzed by using an energy dispersive X-ray fluorescence spectrometer. At selected energies the values of the effective atomic numbers and effective electron densities showed a very modest variation with the composition of the fly ash. This seems to be due to the similarity of their elemental compositions. The obtained results were also compared with concrete, in order to study the effect of fly ash content on the radiation shielding properties of clay fly ash bricks. The clay fly ash bricks showed good shielding properties for moderate energy gamma rays. Therefore, these bricks are feasible and eco-friendly compared with traditional clay bricks used for construction.

• Proceedings of the National Institute of Ecology of the Republic of Korea
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• 제4권1호
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• pp.49-62
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• 2023

Phthalates are animal carcinogens. Potassium hydrogen phthalate (KHP), which has the least complicated structure among phthalates, is used for the analysis of total organic carbon and formaldehyde. However, its toxicity has not been confirmed. A 24-hour acute toxicity test was performed using Daphnia magna, a water flea used to evaluate aquatic toxicity owing to its high sensitivity. The lowest observed effect concentration of KHP was found to be 240 mg/L. The effects of phosphorus, nitrogen, and Cr(6+), which are able to be discharged along with KHP, were also confirmed using tests. At 240 mg/L KHP, toxicity increased as phosphorus, nitrogen, and Cr(6+) increased. In addition, tests were performed to confirm the half maximal effective concentration of KHP. Through 10 test repetitions, the average ecotoxicity value was found to be 0.3, the average half maximal effective concentration was 327.75 mg/L, and the coefficient of variation (%) was 3.16%; because the latter value is lower than 25%, which is what is generally suggested for the water pollution standard method, the reproducibility of the tests is sufficient to replace the existing standard reference toxicity test that uses potassium dichromate. In addition, the half maximum effective concentration of potassium hydrogen phthalate is approximately 218 times more than that of potassium dichromate; therefore, toxicity is relatively low. In conclusion, KHP is a feasible alternative to the highly toxic potassium dichromate for performing the standard reference toxicity test.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(2)
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• pp.265-268
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• 2001

In this paper we investigate the implementation cost of value prediction methods for high performance micro-processors, and propose a new value prediction microarchitecture with low cost. After simulation, we found that the proposed microarchitecture can decrease the implementation cost by 36% to 50% and with slight performance degradation (less than 5%) .

• 한국프랜차이즈경영연구
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• 제8권1호
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• pp.43-53
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• 2017

Purpose - The coffee market in Korea has been dramatically developed and coffee chains dominate the Korean coffee market recently. Customer's perceived value is one of the marketing tools to get competitive advantages of coffee chains, and plays a critical role to study on coffee franchise industry. Thus, this study is to identify the effect of customer's perceived value (price, brand, service, and quality) on revisit intentions and word-of-mouth(WOM). Research design, data. and methodology - Customer's perceived values consists of four dimensions. 253 samples of 320 were used for data analyses excluding unusable responses. The data were analyzed with SPSS 21.0 and SmartPLS 3.0. Result - First, customer's perceived brand value and service value have a significant, positive effect on revisit intentions. Second, Price value and brand value have a positive influence on WOM. Third, gender difference plays a moderating role in the relationship between brand value and price value and WOM, and between brand value and revisit intentions. Conclusions - Males tend to focus more on their perceived brand value of coffee shops for revisit and recommendation, otherwise females consider price value to give an advice to others. Based on the results of this study, the marketers of coffee chains can develop effective strategies regarding gender difference as well.

• 한국방사선학회논문지
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• 제15권6호
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• pp.869-875
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• 2021

이 연구의 목적은 CT 모의치료장치에서 발생된 X-선 빔의 유효에너지 계산식을 유도하는데 있다. 90, 120, 140 kVp X-선 빔 하에서, AAPM CT 성능 팬텀의 CT수 교정 삽입부는 CT 모의치료장치로 5번 스캔하였다. 폴리에틸렌, 폴리스틸렌, 물, 나일론, 폴리카보네이트, 그리고 아크릴의 CT수는 각각의 CT 슬라이스 영상에 대하여 측정하였다. 단일 관전압 하에서 측정된 CT수 평균값과 미국표준기술연구소의 자료로부터 계산된 각각의 광자에너지에 대응하는 선감쇠계수들을 선형정합하였다. 얻어진 상관계수들 중 최대값을 갖는 광자에너지를 유효에너지를 결정하였다. 이와 같은 방법으로, 각각의 관전압에서 생성된 X-선 빔의 유효에너지를 결정하였다. 결정된 유효에너지(y)들와 관전압(x)들을 선형정합하여 유효에너지 계산식으로서 y=0.33026x+30.80263을 유도하였다.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 1996년도 경북지부 결성 및 추계학술발표회 논문집
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• pp.58-62
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• 1996

To check the variability of the effective diffusion coefficient in the unsaturated porous soil media. a Monte Carlo simulation was done for the equation suggested by Millington and Quirk(1961). The results shows that the probability density function of D$_{c}$/D$_{o}$ is positively skewed. It means the chance of having less effective diffusion coefficient values in the soil media than mean value is high. Also, the distribution types of D$_{c}$/D$_{o}$ are about same regardless of assumed distribution types of input parameters.ers.ers.

• 한국융합학회논문지
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• 제6권4호
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• pp.127-132
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• 2015

본 연구는 한국 주식시장에서 가치투자 전략과 연계해 모멘텀 투자전략의 유효성을 분석하였다. 본 연구는 2001년~2014년 동안 한국 주식시장의 상장기업의 주가 및 재무자료를 실증 분석해, 과거 승자 주를 매수하고 패자 주를 매도하는 모멘텀 투자전략과 장부가/시가 비율이 높은 가치주를 매수하고 장부가/시가 비율이 낮은 글래머주를 매도하는 가치 투자전략의 유효성이 기간별로 서로 다르며, 전체 분석기간에 걸쳐 역(-)의 상관관계가 있음을 관찰하였다. 또한 Fama and French[1]가 개발한 3 요인 회귀분석 모형을 추정해, 모형의 절편이 유의적인 양(+)의 값으로 추정됨을 관찰함으로써, 역(-)의 상관관계로 인해 상호 대체관계에 있는 모멘텀 투자전략과 가치 투자전략을 하나의 시스템으로 분석할 때, 모멘텀 투자전략이 세계 주요 증권시장에서와 마찬가지로 한국 증권시장에서도 유효함을 분석하였다.

• 한국축산식품학회지
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• 제33권1호
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• pp.103-108
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• 2013

This study was carried out to observe the effect of superheated steam combined with oven heating on the physico-chemical and sensory properties of chicken meat. Specially, chicken breasts and thighs were heated for 40 min in various heating formulations such as oven heating, superheated steam heating or a combination of two kinds of heating. In the physical properties measurement, the shear force was increased as superheated steam heating time and chicken thighs were higher than chicken breasts in all treatments (p<0.05). The highest level of water holding capacity was solely superheated steam treated chicken for 40 min (p<0.05). The $L^*$ value was decreased but $a^*$ value or $b^*$ value were increased after cooking. Chicken breast exhibited a higher colour value than chicken thigh. Superheated heating was effective to reduce heating loss as 22.64% (p<0.05). However, pH was not different depending on the heating formulation or part of the chicken meat (p>0.05). In the sensory test, the combination of 10 min oven heating and 30 min superheated steam heating was effective to create a good flavour of chicken meat. In this study, an optimum formulation was developed which was a combination of 10 min oven heating and 30 min superheated steam heating. It was more effective to improve the quality of chicken meat than the single heat treatment of chicken meat.

• 설비공학논문집
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• 제13권1호
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• pp.18-24
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• 2001

Woven wire wick is very effective structure because of its easiness to insert inside of pipe for a miniature heat pipe. The present study was conducted to investigate the effect of the effective flow passage with respect to wire helix angle. Also effective thermal conductivity were examined by defining mean porosity considering effective liquid flow passages. Effective heat transfer area is varied with respect to wire helix angle, and in the range of $\thet=60~65^{\circ}C$, heat transfer area is decreased about 15~20%. Permeability of woven wire wick shows similar value of 200 mesh screen wick. And comparison of experimental results on effective thermal conductivity shows a fairly good agreement with the analytical results.

• 한국물환경학회지
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• 제24권3호
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• pp.311-316
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• 2008

This study aimed to obtain equilibrium concentration on adsorption removal of ammonia nitrogen by activated carbon, to express the adsorption characteristics following Freundlich isotherm and also, based on the value obtained, to investigate the relationship between physical characteristics of activated carbon and dynamics of ammonia nitrogen removal by obtaining rate constant and effective pore diffusivity. The results summarized from this study are as follows. It was noted that powdered activated carbon showed better adsorption ability than granular activated carbon. The value of constant (f) of Freundlich isotherm of powered activated carbon was $4.6{\times}10^{-8}$ which is bigger than that of granular activated carbon. The adsorption rate constant on ammonia nitrogen of powered activated carbon with high porosity and low effective diameter was highest as 0.416 hr-1 and the effective pore diffusivity ($D_e$) was lowest as $1.17{\times}10^{-6}cm^2/hr$, and the value of ammonia nitrogen adsorption rate constant of granular activated carbon was $0.149{\sim}0.195hr^{-1}$. It was revealed that, with the same amount of dosage, the adsorptive power of activated carbon with lower effective diameter and bigger porosity was better and its rate constant was also high. With a little adsorbent dosage of 2 g, there was no difference removal ability of ammonia nitrogen as change of adsorption properties.