• 한국자동차공학회논문집
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• 제21권1호
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• pp.99-106
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• 2013

DME (Di-Methyl Ether) is synthetic product that is produced through dehydration of methanol or a direct synthesis from syngas. And it is able to save fossil fuel and reduce pollutants of emission such as PM and $CO_2$. In spite of its advantages it is difficult to design DME fuelled engine system because DME fuel may cause to severely generate cavitation and corrosion in fuel delivery system due to physical properties of DME. Therefore, in this study three-dimensional internal flow characteristics with consideration of cavitation were predicted in the DME injector using diesel and DME fuel. Moving grid technique was employed to describe needle motion and 1-D hydraulic simulation of injector was also simulated to obtain transient needle motion profiles. The results of simulation show that cavitations was generated at the inlet of nozzle near high velocity region both diesel and DME. And mass flow rate of DME is reduced by 4.73% compared to that of diesel at maximum valve lift because cavitation region of DME is much more larger. To increase flow rate of DME injector, internal flow simulation has been conducted to investigate the nozzle hole inner R-cut effect. The flow rates of diesel and DME increase as R-cut increases, and flow coefficient of DME fuel injector was increased by 6.3% on average compared with diesel fuelled injector. Finally, optimum shape of DME injector nozzle is suggested through the comparison of flow coefficient with variation of nozzle hole inner R-cut.

• 공업화학
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• 제10권2호
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• pp.201-205
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• 1999

Hydroxypropylmethylcelluloses (HPMC)는 친수성 cellulose 계통의 중합체로서 독성이 적고 가격이 저렴하여 경구용 서방출성 제제에 널리 이용되고 있다. 본 연구에서는 매트릭스로서 HPMC를 이용하여 새로운 서방출성제제인 HPMC/염산슈도에페드린계를 설계하고, 직타법에 의하여 정제를 제조하였으며, 이 팽윤될 수 있는 친수성 약물전달계를 이용하여 약물의 방출에 영향을 주는 여러 인자들이 약물의 방출속도에 미치는 영향에 대하여 조사하였다. 결과로서, HPMC/염산슈도에페드린계에서 매트릭스인 HPMC의 분자량이 클수록, HPMC의 함량이 많을수록 약물의 방출속도가 더 느려짐을 알 수 있었으며, 정제의 경도나 용출시 pH 변화에는 무관한 것으로 나타났다. 특히, 음이온 계면활성제인 sodium laurylsulfate는 HPMC로부터 염산슈도에페드린의 방출속도를 지연시키는데 큰 영향을 미치는 것으로 나타났으며, 이러한 현상은 음이온 계면활성제인 sodium laurylsulfate가 반대의 이온성을 갖는 약물인 염산슈도에페드린과 착물을 형성함으로써 약물의 용해성이 떨어져서 약물방출이 지연되는 것으로 생각된다.

• 공업화학
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• 제25권6호
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• pp.598-601
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• 2014

Polypropylene의 농도와 코팅 막의 건조 온도 및 나노실리카의 첨가량의 변화 등 polypropylene 박막 제조를 위한 공정 변수들이 박막의 표면 형상 및 특성에 미치는 영향을 연구하였다. Polypropylene의 농도가 30 mg/mL인 경우에 $30^{\circ}C$의 건조 온도로 90 min 동안 93 mTorr의 진공 조건으로 최대 접촉각 $154^{\circ}$를 갖는 초소수성 polypropylene 박막을 얻을 수 있었다. 용매 휘발을 위한 진공 오븐에서의 건조 온도가 증가함에 따라 박막의 거칠기가 감소하여 접촉각이 낮아지는 효과를 가져왔다. Polypropylene-실리카 복합막은 박막 내에 나노실리카의 함유량의 증가에 따라 박막 표면이 미세 다공성 구조에서 미세 구형 구조물로 변환되면서 접촉각의 증가로 초소수성 표면 특성을 보였다.

• Archives of Reconstructive Microsurgery
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• 제25권2호
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• pp.43-48
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• 2016

Purpose: Perforator flap-using ischial sore reconstruction is performed in a prone position. But after the surgery, recurrence frequently occurs in a sitting position. In this sense, we introduce modified flap insetting method which closely resembles patient's sitting position to lessen the flap tension surgically. Materials and Methods: Authors tried to check a skin tension difference between prone position and sitting position in normal people group and to find out the importance of performing flap insetting in hip flexion position. Healthy volunteers were collected (n=20) and designed the same length of 4 divided sections around the ischium. Lengths of each section were measured when hip joint was flexed to 90 degree and when both hip and knee joints were flexed to 90 degree and the statistical evaluation was performed. Twenty cases with ischial sore underwent reconstructive surgery using perforator flap under hip flexion position and followed-up for any recurrences. Results: There was a meaningful difference between the joint flexed skin length and that of the neutral position. Flap showed sufficient thickness over 12 months. Conclusion: It seems that recurrence could be reduced when the reconstructed flap could sufficiently cover in a sitting position regarding its significant length difference in normal people group.

• 한국자동차공학회논문집
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• 제13권2호
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• pp.135-141
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• 2005

Nitric oxide(NO) reduction by methanol was investigated over $La_2O_3$ catalysts in the presence and absence of oxygen. In the absence of $O_2$, $CH_3OH$ reduced NO to both $N_2$ and $N_2O$, with selectivity to $N_2$ formation decreasing from 81-88% at 623K to 47-71% at 723 K. With 1.2% $O_2$ in the feed, the rates were 4-8 times higher, but the selectivity to $N_2$ dropped from 50% at 623 K to 9% at 723 K. The specific activities with $La_2O_3$ for this reaction were higher than those for other reductants; for example, at 773 K with hydrogen a specific activity of $34\;{\mu}mol\;NO/sec{\cdot}m^2$ was obtained whereas that for methanol was $638\;{\mu}mol\;NO/sec{\cdot}m^2$. The Arrhenius plots were linear under differential reaction conditions, and the apparant activation energy was consistantly near 15 kcal/mol with $CH_3OH$. Linear partial pressure dependencies based on a power rate law were obtained and showed a near-zero order in $CH_3OH$ and a near-first order in $H_2$.

• 에너지공학
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• 제24권4호
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• pp.105-116
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• 2015

본 연구에서는 절곡 깊이(1.4 mm)와 절곡 핏치(5.5 mm)가 같은 둥근 웨이브와 각진 웨이브 핀-관 열교환기에 대한 실험을 통하여 절곡 형상이 전열성능에 미치는 영향을 검토하였다. j 인자의 경우 둥근 웨이브 핀이 모든 열수에서 1.2~22% 크고 f 인자는 3열의 경우 8.3~23% 크고 1, 2열의 경우는 -1.0~29% 작다. 둥근 웨이브 핀이 우수한 성능을 보이는 이유로 둥근 웨이브 핀의 경우 각진 웨이브 핀 보다 유동이 핀의 곡면을 잘 따라갈 수 있으므로 골에 존재하는 재순환 영역의 크기가 줄어들기 때문으로 판단된다. 둥근 웨이브 핀의 경우 핀 핏치가 j와 f 인자에 미치는 영향은 크지 않다. 또한 j 인자는 튜브 열수가 증가할수록 감소하는 반면 f 인자는 튜브 열수와 무관하다. 실험 데이터로부터 새로운 상관식을 도출하였다.

• 대한한의학회지
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• 제33권3호
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• pp.200-230
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• 2012

Objectives: Ginseng, Panax ginseng C. A., white ginseng, has been used for thousands of years in Traditional Korean Medicine. Red ginseng can be made by a steaming process of white ginseng changing a variety of ginsenosides and ingredients such as dencichine. This article reviews red ginseng for mechanisms for pharmacodynamics and toxicity based on the content of ginseng's active ingredients, ginsenoside changed by steaming. Methods: The following electronic databases were searched: PubMed, Science Direct and Chinese Scientific Journals full text database (CQVIP), and KSI (Korean Studies Information) from their respective inceptions to June 2012. Results: Compared with unsteamed ginseng, the content of ginsenosides Rg2, Rg3, Rg5, Rh1, Rh2 and Rk1 called red ginseng-specific ginsenosides increased after the steaming process. Different ginsenosides have shown a wide variety of effects such as lowering or raising blood sugar and blood pressure or stimulating or sedating the nervous system. Especially, the levels of Rg2, Rg3, Rg5, Rh1, Rh2 and Rk1 were increased by the steaming process, showing a variety of pharmacodynamics in biological systems. Also, various processing methods such as puffing and fermentation have been developed in processing crude ginseng or red ginseng, affecting the content of ginseng's ingredients. The safety issue could be the most critical, specifically, on changed ginseng's ingredients such as dencichine. The level of dencichine was significantly reduced in red ginseng by the steaming process. In addition, the possible toxicity for red ginseng was affected by cytochrome P450, a herbal-drug interaction. Conclusions: The variety of pharmacological and toxicological properties should be changed by steaming process of Panax ginseng C. A., white ginseng. Even if it is not sure whether the steaming process of white ginseng would be better pharmacologically, it is sure that steaming reduces the level of dencichine causing a lower toxicity to the nervous system.

• 한국식품과학회지
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• 제35권3호
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• pp.353-358
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• 2003

지금까지 거의 보고되지 않은 동물간의 비린내 불쾌취를 밝히는 것을 목적으로, 연속수증기증류에 의해 얻어진 가열돼지간의 휘발성 농축물중에 포함된 화합물을 분리 동정하여, 가열에 의해서도 없어지지 않고 잔존하는 비린내물쾌취를 검토하였다. 또한, GC 분석시, GC-O를 이용하여 각 휘발성화합물의 냄새를 평가하였다. 그 결과, 간은 가열하는 것에 의해 특이적인 비린내불쾌취가 소실되지 않으며, 여전히 잔존함이 확인되었다. 동정된 69종의 화합물중 비린내를 갖는 (E,E)-2,4-heptadienal(fishy) 및 금속취를 갖는 1-octen-3-one, hexanol의 존재를 확인하였다. 또한 가열돼지간의 불쾌취 형성에 기여하는 것으로 생각되어지는 (E)-2-nonenal(cardboard-like), (Z)-4-decenal(cardboard-like), (E,E)-2,4-decadienal(deep-fried) 등 낮은 한계값을 갖는 aldehyde 류의 생성을 확인하였다. 동정된 69종의 화합물중 40종류의 성분은 본 연구에서 처음으로 가열 돼지간의 휘발성성분으로 동정되었다. 1-Octen-3-one, hexanol, (E)-2-nonenal, (Z)-4-decenal, (E,E)-2,4-heptadienal 등은 특징적인 냄새를 나타내며, 돼지간의 불쾌취 형성에 있어 중요한 화합물로 사료된다. 이들 alkanal, alkenal 및 alkanone류는 돼지간에 다량 함유된 불포화지방산의 산화 반응생성물로, 그 일부는 가열처리에 의한 분해생성물인 것으로 사료된다.

• 대한정형도수물리치료학회지
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• 제11권1호
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• pp.65-73
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• 2005

Osteoarthritis has been considered a disease of the elderly because it is uncommon before the age of 40 years and is seen in approximately 80% of United States citizens older than 65 years. general population on kuri city in korea revealed that prevalence of knee osteoarthritis is 10.2%, increasing with age. High level of physical activity in men and age, post-menopause and obesity in women can be risk factor. Osteoarthritis is no evidence that a acquired process initiated much earlier in life through mechanical, metabolic, genetic, or other origins. A high tibial osteotomy alters static lower extremity alignment thereby decreasing medial compartment loading. As well, conservative treatment strategies, such as knee braces and valgus heel wedges, affect lover limb mechanics and attempt to reduce medial compartment loading. It was hypothesized that valgus heel wedges and modified orthoses would shift the center of pressure laterally on the foot during level walking, reducing the moment arm of the adduction moment in the frontal plane, thereby resulting in a decrease in the knee adduction moment. In the 1980s, the effect of wearing a laterally wedged insole on osteoarthritic patients with a varus deformity of the knee was firsted, and since then, kinematic and kinetic analyses concerning this condition have mainly focused on a static standing position. Since the early 1990s, the beneficial effect of wearing a laterally wedged insole to treat osteoarthritis of the knee has also been reported in dynamic conditions, but these studies did not answer the question of the kinematic and kinetic mechanisms that resulted in the reduced symptoms in patents with knee osteoarthritis. therefore, the effect of wearing laterally wedged insole has not been sufficiently studied.

• 한국세라믹학회지
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• 제26권6호
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• pp.771-782
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• 1989

Synthesis of $\beta$-Sialon powder was attempted with carbothermal reduction of porous glass. The porous glass was prepared by heat and hydrothermal treatments of 9.32 Li2O.46.5B2O3.37.2SiO2.6.98Al2O3 glass. Carbon pyrolyzed from propane gas was deposited on the porous glass, thereafter activated carbon was added as reducing agents. The synthesized $\beta$-Sialon powder was pressureless sintered at 175$0^{\circ}C$ for 1hr in N2 atmosphere. The characterization of the $\beta$-Sialon powder was performed with XRD, BET, SEM and particle size analysis. The sinterability and mechanical properties of the sintered bodies were investigated in terms of bulk density, M.O.R., fracture toughness, morphology of microstructure and etc. The reduction effect of deposited carbon was better than that of activated carbon mechanically added. The formation of SiC was precominant over that of Si2ON2 and $\beta$-Sialon owing to low partial pressure of N2 inside the pore, wehreas on the surface of porous glass the formation of Si2ON2 and $\beta$-Sialon were predominant. Thereafter, SiC reduced unreacted glass to be $\beta$-Sialon. Single phase of $\beta$-Sialon(Z=1.92) was obtained from PGA porous glass having the largest pore radius by the simultaneous reduction and nitridation method at 145$0^{\circ}C$ for 5hrs. The bulk density, M.O.R., and KIC of the sitered body are 3.17g/cc, 434.4MPa and 4.1MPa.m1/2, respectively.