• 한국해양환경ㆍ에너지학회지
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• 제8권1호
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• pp.39-45
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• 2005

2004년 11월 러시아의 교토의정서 비준에 의하여 2005년 2월에 교토의정서의 발효를 앞두고 있다. 따라서 1차 감축대상국은 2008년부터 2012년까지 1990년 대비 각 국가당 설정된 GHG(Green House Gas)배출량을 감축해야하는 상황에 처해 있다. 본 논문에서는 대기 중에 뿜어내는 GHG중 가장 많은 비율을 차지하는 CO₂를 심해에 친환경적으로 처리하는 기술로서 해양격리기술에 대해 소개한다. 본 해양격리기술은 4개의 주요단계로 구분할 수 있는데, 해양수송기술, 해양분사기술, 해양저장효율평가기술, 해양처리생태영향 평가기술등으로 나눌 수 있다. 본 논문에서는 CO₂의 해양 분출시에 초기희석율에 영향을 미치는 해양분사기술 중, 액포의 거동과 용해에 관한 기초 연구를 수행하였다. 특히 본 연구에서는 전산유체역학 기법 (Computational Fluid Dynamics)을 통해 해수를 연속상(Continuous phase), 액적을 분산상(Disperse phase)으로 한 이상(Two-phase) 유체를 3차원 이동형 비구조 격자와 유한체적법을 이용하여 상 경계면이 거동하면서 거동에 따른 용해도의 변화를 추정하였다 따라서, 본 연구는 액적의 거동과 용해도의 유체역학적 관계를 밝히는 데 기초적 자료가 될 것으로 판단된다.

• 대한화장품학회지
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• 제39권1호
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• pp.55-63
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• 2013

경피흡수 증진의 수단으로 나노에멀젼의 화장품 응용이 관심의 대상이 되고 있다. 본 연구에서는 저에너지 유화법으로 제조된 나노에멀젼 구성 원료들의 조성을 달리하여 안정성을 확인해 보고자 하였다. 시간 경과에 따른 나노에멀젼의 입자 크기 측정을 통한 안정성 실험 결과, 폴리올을 수상에 첨가한 경우 에탄올상 첨가에 비해 안정성이 크게 증가하였다. 에탄올상의 수상에 대한 첨가속도는 입자 크기나 안정성에 큰 영향이 없었다. 오일의 종류에 따라서도 안정성에는 영향이 없었으나 초기에 형성되는 입자 크기는 오일의 분자량과 polarity에 상관관계를 보이는 것으로 생각되었다. 폴리올의 종류에 따른 안정성과 초기 입자 크기는 1,2 헥산디올을 제외하고는 유사한 경향을 보였다. 오일과 계면활성제 농도 변화는 제조된 나노에멀젼의 초기 입자 크기에는 영향을 주었으나 시간 경과에 따른 변화는 없었다. 에탄올의 농도 변화는 초기 입자 크기와 안정성에 큰 영향을 미치는 것으로 관찰되었다.

• 한국전자통신학회논문지
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• 제15권3호
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• pp.543-552
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• 2020

이 연구는 브라질 북동부의 Maceió-Alagoas 지역에서 강우로 인한 토양의 침식 지수를 추정할 수 있는 알고리즘을 결정하는 것을 목적으로 한다. 2003년부터 2006년까지 10분 이상 지속된 680회의 강우 사례에서 수집한 분당 26,889개의 데이터 샘플은 우적 크기 분포에 따라 분류되었다. 종속 변수와 독립 변수로 구성된 방정식은 99%의 결정 계수로 침식지수를 추정한다. 최소 강우 강도와 침식도의 관계는 통계적 유의성으로 검증되었다.

• Journal of Advanced Marine Engineering and Technology
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• 제30권5호
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• pp.597-607
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• 2006

This paper presents a numerical simulation of the behavior of the LiBr solution droplets and falling films in horizontal tube banks of absorber. The model developed here accounts for the details of the droplets formation and impact process for absorption on horizontal tubes including the heat transfer from solution film to the tube wall. Especially. the characteristic of unsteady behavior of solution flow has been investigated. Flow visualization studies shown that the solution droplets and falling films have some of the complex characteristics. It is found that. with the numerical conditions similar to the operating condition of an actual absorption chiller/heater, the outlet solution temperature and heat flux from solution film to the tube wall have a stable periodic behavior with time. The solution droplets and falling films in horizontal tube banks of absorber is a periodic unsteady flow. The results from this model are compared with previous experimental observation taken with a high-speed digital video camera and shown good agreement.

• Macromolecular Research
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• 제17권6호
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• pp.417-423
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• 2009

The effects of maleic anhydride-grafted polypropylene (PP-g-MAH) addition on polypropylene (PP) and poly(acrylonitrile-butadiene-styrene) (ABS) blends were studied. Blends of PP/ABS (70/30, wt%) with PP-g-MAH were prepared by a twin-screw extruder. From the results of mechanical testing, the impact, tensile and flexural strengths of the blends were maximized at a PP-g-MAH content 3 phr. The increased mechanical strength of the blends with the PP-g-MAH addition was attributed to the compatibilizing effect of the PP and ABS blends. In the morphological studies, the droplet size of ABS was minimized (6.6 ${\mu}m$) at a PP-g-MAH content of 3 phr. From the rheological examination, the complex viscosity was maximized at a PP-g-MAH content of 3 phr. These mechanical, morphological and rheological results indicated that the compatibility of the PP/ABS (70/30) blends is increased with PP-g-MAH addition to an optimum blend at a PP-g-MAH content of 3 phr.

• 한국화재소방학회논문지
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• 제23권5호
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• pp.84-89
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• 2009

본 연구에서는 미분무수 노즐을 이용하여 소화시간에 영향을 미치는 인자들을 변화시키며 소화실험을 수행하였다. 주요 인자는 화염의 위치와 노즐 중심으로부터의 거리, 미분무 입자의 크기, 노즐의 설치 높이, 개구부 여부 등이었다. 소화실험 결과로부터 각 인자들 간의 상호작용과 소화에 대한 민감도를 Mini tab을 이용하여 분석하여 미분무수 소화시스템의 최적 소화모델을 도출하였다. 소화시간에 가장 큰 영향을 미치는 인자는 노즐 중심으로부터의 거리이며 개구부의 여부는 다른 인자들에 비하여 소화시간에 미치는 영향도가 적게 나타났다.

• 한국분말재료학회지
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• 제29권6호
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• pp.499-504
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• 2022

The objective of this study is to assess the impact of spray drying conditions on medium-chain triglyceride (MCT) loading, solubility, and release of an MCT-loaded solid self-emulsifying system in a water-insoluble oily substance. MCT-loaded solid self-emulsifying systems are prepared by spray drying with SDS and calcium silicate. The effects of inlet temperature (60, 80, or 100℃) and feed solution composition (0, 10, 50, 90, or 100% ethanol) on physicochemical properties of MCT-loaded solid self-emulsifying systems are studied. The inlet temperature significantly affects the water solubility of MCT. Moreover, the feed solution composition significantly affects water solubility, release rate, and MCT loading. The MCT-loaded solid self-emulsifying system obtained at 60℃ using 90% ethanol feed solution shows the best physicochemical properties among the synthesized products and exhibits better water solubility (4.43 ± 0.44 vs. 0 ㎍/mL) and release (94.4 ± 1.6 vs. 32.8 ± 7.4%, 60 min) than a commercial product. Furthermore, the MCT-loaded solid self-emulsifying system shows an excellent emulsion droplet size (approximately 230 nm).

• 한국분말재료학회지
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• 제30권4호
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• pp.305-309
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• 2023

This study aims to prepare a colloidal silica-containing powder to enhance the solubility and dissolution rate of rivaroxaban using a self-nanoemulsifying drug delivery system (SNEDDS). We investigate the impact of colloidal silica on a nanoemulsion system for preparing powdered SNEDDS. The liquid SNEDDS comprises 30/20/50 (w/w/w) Peceol/Cremophor RH40/Tween 80, which results in the formation of the smallest droplets. Three powdered SNEDDS formulations are prepared by suspending the liquid SNEDDS formulation using colloidal silica and spray drying. The powdered SNEDDS prepared with liquid SNEDDS and colloidal silica at a ratio of 1/0.5 (w/w) exhibits the highest water solubility (0.94 ± 0.62 vs. 26.70 ± 1.81 ㎍/mL) and dissolution rate (38.4 ± 3.6 vs. 85.5 ± 3.4%, 45 min) when compared to the drug alone. Morphologically, the liquid SNEDDS is adsorbed onto colloidal silica and forms smaller particles. In conclusion, an SNEDDS containing rivaroxaban, prepared using colloidal silica, facilitates the creation of a nanoemulsion and enhances the water solubility of rivaroxaban. Accordingly, this technology holds significant potential for commercialization.

• 한국가시화정보학회지
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• 제21권1호
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• pp.94-102
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• 2023

Three design parameters were considered in this study: outlet nozzle angle (30°, 60°, 80°), neck length (1 mm, 3 mm), and flow rate (0.5, 0.6, 0.7, 0.8 lpm). A neck diameter of 0.5 mm induced cavitation flow at a venture nozzle. A secondary transparent chamber was connected after ejection to increase bubble duration and shape visibility. The bubble size was estimated using a Gaussian kernel function to identify bubbles in the acquired images. Data on bubble size were used to obtain Sauter's mean diameter and probability density function to obtain specific bubble state conditions. The degree of bubble generation according to the bubble size was compared for each design variable. The bubble diameter increased as the flow rate increased. The frequency of bubble generation was highest around 20 ㎛. With the same neck length, the smaller the CV number, the larger the average bubble diameter. It is possible to increase the generation frequency of smaller bubbles by the cavitation method by changing the magnification angle and length of the neck. However, if the flow rate is too large, the average bubble diameter tends to increase, so an appropriate flow rate should be selected.

• Tribology and Lubricants
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• 제39권6호
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• pp.244-249
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• 2023

This paper presents a comprehensive analysis of the impact of surface roughness on the friction and wear properties of SUS 321, an austenitic stainless steel variant produced using the laser powder bed fusion (LPBF) technique, which is a prevalent additive manufacturing method. After the LPBF fabrication, the specimens go a heat treatment process aimed at alleviating residual stress. Subsequently, they are polished extensively to achieve a refined and smooth surface. To deliberately introduce controlled variations in surface roughness, an etching process is employed. This multi-step method encompassed primary etching in a 3M hydrochloric acid solution, followed by secondary etching in a 35 wt% ferric chloride solution, with varying durations applied to different specimens. A comprehensive evaluation of the surface characteristics ensued, employing precise techniques such as surface roughness measurements and meticulous assessments of water droplet contact angles. Following the surface treatment procedures, a series of friction tests are performed to explore the tribological behavior of the etched specimens. This in-depth investigation reached its peak by revealing valuable insights. It clarified a strong correlation between intentionally altered surface roughness, achieved through etching processes, and the resulting tribological performance of LPBF-fabricated SUS 321 stainless steel. This significantly advances our grasp of material behavior in tribological applications.