• 한국축산식품학회지
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• 제32권5호
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• pp.540-544
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• 2012

During heat treatment and storage of milk, deteriorative reaction takes place, which consequently influence on the milk quality. In this study, formation of lactulose and furosine under different thermal conditions and storage conditions, and the ratio of lactulose and furosine (LU/FU) in presence of reconstituted milk powder were determined to establish chemical indicators for heat damages of milk and the adulteration of fresh milk in dairy field. The lactulose and furosine contents linearly increased with increased heating temperature and heating time. It showed high correlation between the formation of lactulose and furosine, and the treatment temperature and time (p<0.05). The lactulose and furosine concentration of HTST milk and UHT milk noticeably increased during storage at $30^{\circ}C$, but there was no noticeable increase of lactulose and furosine concentration at lower storage temperature. In the raw milk, the lactulose and furosine contents greatly increased with the addition of reconstituted milk. The increase level of furosine was much higher than that of lactulose, which consequently resulted in the lower LU/FU ratio in milk as increase of added reconstituted milk amounts. As comparing with raw milk, there was more than twice reduction in LU/FU ratios after the addition of reconstituted milk (p<0.05). It can be concluded that lactulose and furosine are suitable milk quality indicators of heat damage and for demonstrating improper addition of reconstituted milk powder.

• 한국산학기술학회논문지
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• 제17권7호
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• pp.63-76
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• 2016

R&D 연구 투자의 문제점의 하나는 불확실성이 크다는 점이다. 이러한 불확실성이 기업에는 많은 부담을 주는 요인이 될 수 있다. 이러한 면에서 R&D 투자가 기업 가치에 양(+)의 영향을 미치기까지의 시간을 측정할 수 있는 연구의 필요성이 있다고 보여진다. 본 연구는 GMM-PVAR(Panel Vector Autoregression) IRF(Impulse Response function)를 사용하여 1900년부터 2015년까지 한국거래소의 코스피와 코스닥시장에 상장된 기업을 대상으로 R&D 투자가 기업가치에 양(+)의 영향을 미치기까지 걸리는 시간을 측정 하였다. 또한 기업의 재무적 특성 변수 중 기업의 크기, 성장 가능성, 그리고 산업 집중율이 R&D 투자가 기업가치에 양(+) 영향을 미치기까지 걸리는 시간을 단축시킨다는 점을 발견하였다. 그것은 이들 재무적 특성변수 들이 R&D 투자와 기업가치간의 관계에 긍정적인 영향을 미칠수록 즉 경쟁이 심화될수록 크기가 클수록 시간이 단축되며 작은 기업의 경우는 성장 가능성이 높을수록 시간이 단축되는 경향을 보였다. 흥미 있는 점은 큰 기업들의 경우에는 성장가능성이 낮은 기업들이 성장가능성이 높은 기업들보다 더 큰 양의 결과를 보였다.

• 전자공학회논문지
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• 제50권12호
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• pp.254-260
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• 2013

뇌전도 분석에 의한 제어신호의 검출은 다양한 분야에 활용될 수 있다. 다채널 뇌파 연구는 측정 시스템이 복잡해지고 착용이 불편해진다는 단점이 있어서 본 논문에서는 실용적인 응용을 우선으로 하였고 단 채널 기반으로 집중에 의한 on/off 제어 신호를 신뢰성 있게 검출할 수 있는 방법을 연구하였다. 평상시 휴식 상태와 집중하였을 때의 알파, 베타 및 세타파의 대역 신호를 분석하였으며 이 때 파워스펙트럼과 히스토그램에서의 차이를 검출하였다. 세타파를 이용하였을 때 보다 베타/세타를 이용해 집중력 검출을 하는 것이 더 좋은 결과를 나타내었다. 세타파만을 이용하였을 때보다 평균 검출 시간이 단축되었으며 또한 집중 전 휴식시간이 길어질수록 검출 성공률이 낮아지며, 검출 시간도 상대적으로 길어졌다. 휴식시간 10초의 경우 개인마다 검출 성능의 차이는 있었지만 평균 91%의 검출 성공률과 검출 시간은 평균 20.2초의 결과를 얻었다.

• 한국표면공학회지
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• 제53권3호
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• pp.109-115
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• 2020

In this study, polycrystalline diamond was synthesized by chemical vapor deposition (CVD). Diamond films were deposited on a-plane sapphire substrates while changing the concentration of methane for hydrogen (CH₄/H₂), and the concentrations of methane were 0.25, 0.5, 1, 2, 3 and 4 vol%, respectively. Crystallinity and nucleation density according to changes in methane concentration were investigated. At this time, the discharge power, vacuum pressure, and deposition time were kept constant. In order to deposit polycrystalline diamond, the sapphire substrate was etched with sulfuric acid and hydrogen peroxide (ratio 3:7), and the sapphire surface was polished for 30 minutes with 100 nm-sized nanodiamond particles. The deposited diamond thin film was analyzed by a scanning electron microscope (SEM), a Raman spectra, Atomic force microscope (AFM) and an X-ray diffractometer (XRD). By controlling the ratio of methane to hydrogen and performing appropriate pre-treatment conditions, a polycrystalline diamond thin film having excellent crystallinity and nucleation density was obtained.

• 한국연초학회지
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• 제18권2호
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• pp.170-176
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• 1996

This paper describes the generation and decay phenomena of gas, vapor and particulate phase components of environmental tobacco smoke in 18 m3 controlled experimental atmosphere chamber. Real time-weighted average concentration ratios of markers were determinated at no ventilation rates and sampling durations of starting to smoking 45 min. Average concentration of major ETS markers was no significant on the mainstream smoke contents of commercial cigarette and decay ratios were dependent on first order kinetic. RSP/nicotine, solanesol and 3-EP were good predictors of ETS concentration in the public indoor field. The concentration ratio of vapor phase and particulate phase components is highly variable to assessment of indoor air quality with ETS. Key words : ETS, chamber study, ETS markers.

• 설비공학논문집
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• 제6권1호
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• pp.29-38
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• 1994

Particle contamination into and out of a cavity-cylindrical cavities with aspect ratios(width/depth) less than, equal to 1 and langer than 1, and also three dianensional T's attached to a cylindrical flow tube was studied numerically, using a finite difference method. In the process of unsteady particle diffusion, the particles contained in a concentration boundary layer near the tube wall plays an important role in the initial stage, after which a quasi-steady concentration profile is developed inside the cavity, resulting in an exponential change of concentration with time. Average concentration and its rate of change are observed to be closely correlated by a power law function in terms of Reynolds number and the logarithm of Schmidt number. Effects of the three parameters-Re, Sc, and aspect ratio-are analysed and well explained.

• Nuclear Engineering and Technology
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• 제55권4호
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• pp.1225-1232
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• 2023

The ¹⁸⁰W is the lightest isotope of Tungsten with small abundance ratio. It is slightly radioactive (α decay), with an extremely long half-life. Its separation is possible by non-conventional single withdrawal cascades. The ¹⁸⁰W is used in radioisotopes production and study of metals through gamma-ray spectroscopy. In this paper, single withdrawal cascade model is developed to evaluate multicomponent separation in non-conventional transient cascades, and available experimental results are used for validation. Numerical studies for separation of ¹⁸⁰W in a transient single withdrawal cascade are performed. Parameters affecting the separation and equilibrium time of cascade such as number of stages, cascade arrangements, feed location and flow rate for a fixed number of gas centrifuges (GC) are investigated. The Salp Swarm Algorithm (SSA) as a bio-inspired optimization algorithm is applied as a novel method to minimize the feed consumption to obtain desired concentration in the collection tank. Examining different cascade arrangements, it is observed in arrangements with more stages, the separation is further efficient. Based on the obtained results, with increasing feed flow rate, for fixed product concentration, the cascade equilibrium time decreases. Also, it is shown while the feed location is the farthest stage from the collection tank, the separation and cascade equilibrium time are well-organized. Finally, using SSA optimal parameters of the cascade is calculated, and optimal arrangement to produce 5 gr of ¹⁸⁰W with 90% concentration in the tank, is proposed.

• 한국의류학회지
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• 제28권6호
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• pp.854-861
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• 2004

To estimate dispersion stability of particles in anionic and nonionic surfactant mixed solution, suspending power was examined as functions of duration time of suspension, ionic and nonionic surfactant mixed ratio, surfactant concentration, kinds of electrolyte, ionic strength and mole numbers of oxyethylene additions to nonionic surfactant using $\alpha$-Fe$_2$O$_3$ particle as the model of particulate soil. The suspending power of anionic and nonionic surfactant mixed solution was relatively higher than that of anionic and nonionic surfactant single solution regardless of solution concentration. The suspending power was gradually decreased with increasing duration time of suspension. In the absence of electrolyte, the effect of surfactant concentration on suspending power was small but in solution with electrolyte, suspending power was lowest at 1 ％ surfactant concentration. With 1${\times}$10$^{-3}$ ionic strength and polyanionic electrolyte in solution, the suspending power was high but effects of oxyethylene mole number to nonionic surfactant on suspending power was small. Generally the suspending power was gradually increased with decreasing the particle size. Hence the suspending power was inversely related to the particle size.

• Environmental Engineering Research
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• 제17권2호
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• pp.95-102
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• 2012

To evaluate the effect of the 4 major rivers restoration project in the Nakdong River to water quality of the river, the Environmental Fluid Dynamics Code (EFDC) and Water Quality Analysis Simulation Program (WASP), are applied in series. Results showed overall decrease in biochemical oxygen demand ($BOD_5$) concentrations and increase in chlorophyll-a concentrations, while total nitrogen and total phosphorous concentrations did not show significant changes, relatively. Decrease in $BOD_5$ concentrations seems to be influenced by an increased hydraulic residence time, which may allow more time for the degradation of organic material. Changes in Chlorophyll-a (Chl-a) concentration, due to the project were more significant for the upper stream areas that show relatively low Chl-a concentration ranges (less than 20 g/L). After the introduction of the Geumho River in the middle part of the Nakdong River, rapid growth of phytoplankton was observed. However, in this middle part of the Nakdong River, the ratio of Chl-a concentration change are less significant, compared to the upper stream areas, due to the project. In the lower stream area, Chl-a concentration decreased after the project. This seems to be resulted from the decreased light availability, due to increased depth, while the nutrient concentrations have been high enough to support phytoplankton growth.

• 한국환경과학회지
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• 제23권5호
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• pp.861-871
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• 2014

This study analyzes the characteristics of ozone weekend effect(OWE) in Busan. $O_3$ concentration on Sunday was over 10% higher than that on weekdays in all areas except for Kwangbokdong, Taejongdae, and Joadong. Such a difference was higher in the industrial area than in the residential area. $O_3$ generation was facilitated by the decrease in $NO_X$ emission on Sunday in VOC-limited regime where the VOC/$NO_X$ ratio is low. Low NO concentration in the Sunday morning decreased inhibition of $O_3$. NO-$O_3$ crossover time on Sunday was shorter than that on weekdays which in turn extended the accumulated duration of $O_3$. Future studies can include whether the entire Busan is VOCS-limited or the coastal area is VOCS-limited while the inland area is $NO_X$-limited.