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Development and Evaluation of an Oral Controlled Release Delivery System for Melatonin
Lee,Beom Jin,Keith A Parrott,Robert L Sack,James W Ayres 한국약제학회 1993 Journal of Pharmaceutical Investigation Vol.23 No.3
Sugar spheres loaded with melatonin (MT) were coated with Aquacoat^ⓡ to control the release rate of MT over 8 hours. A zero-order release pattern over 8 hours was obtained with 20% coating on 8-10 mesh beads in USP basket dissolution studies. MT in 20% coated beads was quite stable at room temperature with less than 5% MT degraded during 6 months' storage. Dissolution profiles were also unchanged after 6 months. An oral preparation containing MT-loaded uncoated beads for immediate release and 20% coated beads with Aquacoat^ⓡ for controlled release over 8 hours was evaluated in six human subjects. When total 0.5 ㎎ MT as low dose (immediate release portion of MT, 0.1 ㎎) was administered to four subjects, average peak plasma MT concentration was reached at about 600 pg/㎖ and maintained at about 10 pg/㎖ over 8 hours. Plasma MT concentration-time profiles were similar in shape to computer-simulated profiles. However, maximal plasma MT concentrations were three times greater compared to computer simulated curve. These results suggest that MT dose, ratio of immediate and controlled release MT, and pharmacokinetic parameters selected are adjusted to mimic endogenous MT concentration-time curve. In another study, 0.2 ㎎ MT having 10% of immediate release portion and 80% controlled release portion produced plasma MT concentration-time curve which is more similar to endogenous profiles. A low bioavailability (<20%) may result from extensive first pass metabolism and remaining amounts of MT from controlled beads. A good correlation between plasma MT concentration and urinary excretion rate of 6-sulphatoxymelatonin (6-STMT), a major metabolite of MT was observed. As plasma MT concentration increased, urinary excretion rate of 6-STMT increased concomitantly. The linear relation between plasma MT and urinary excretion rate of 6-STMT was statistically significant. This result suggests that urinary 6-STMT may be used as an index of circadian rhythms of MT in humans.
Dynamic Effects of Macroeconomic Factors on International Tourism Demand
Park Hae-Sun(박해선),James W. Mjelde(James W. Mjelde),Lee Choong-Ki(이충기) 대한관광경영학회 2012 觀光硏究 Vol.27 No.4
Dynamic effects of macroeconomic conditions in major inbound arrivals markets (Japan, China, United States, and Taiwan) on total international arrivals to Korea are examined using a vector error correction model and quarterly data. Overall, results show that the economic conditions in the different major inbound markets affect international arrivals to Korea. Real per capita gross domestic product (GDP) in the inbound markets has strong and long lasting positive influence on arrivals to Korea. Depreciation of Korean won with respect to currency of inbound markets has strong and long lasting positive influence on arrivals to Korea except for China. China’s different response to exchange rate shock may be cause by the number of tourist arriving from China seeking employment. 본 연구는 벡터오차수정모형과 분기별 자료를 이용하여 주요 인바운드 국가들(일본, 중국, 미국, 대만)의 거시경제적 변수가 우리나라 인바운드 관광객시장에 미치는 동태적인 영향을 분석하였다. 분석결과 주요 인바운드시장의 거시경제적 조건이 우리나라 인바운시장에 영향을 미치는 것으로 나타났다. 주요 인바운드시장의 1인당 실질소득은 우리나라 인바운드 관광수요에 강하고 지속적인 양(+)의 영향을 미치는 것으로 나타났다. 또한, 주요 인바운드시장 화폐의 원화에 대한 환율도 중국을 제외하고, 강하고 지속적인 양(+)의 영향을 미치는 것으로 나타났다. 이와 같은 환율충격에 대한 중국의 다른 반응은 중국 관광객 중 구직목적의 방문객이 포함된 것에 기인한 것으로 추정된다.
NETCONF 기반의 시스템 및 네트워크 구성관리 성능 향상
이명숙(Myung-Suk Lee),유선미(Sun-Mi Yoo),주홍택(Hong-Taek Ju),홍원기(James W. Hong) 한국통신학회 2008 韓國通信學會論文誌 Vol.33 No.9B
IETF의 NETCONF 워킹그룹에서는 구성관리의 상호운용성을 보장하기 위하여 구성관리표준 프로토콜인 NETCONF에 대한 표준을 제정하고 있다. 이러한 구성관리에서는 상호운용성뿐만 아니라 성능도 구성관리에서 중요한 요소 중의 하나이지만 현재까지는 성능에 대한 논의가 많이 이루어지고 있지 않은 실정이다. 이러한 점을 고려하여 본 논문에서는 NETCONF 프로토콜의 성능을 측정하고 성능을 향상시킬 수 있는 방안을 제시한다. 또한 제시된 방안에 대한 성능검증 결과를 제시한다. IETF's NETCONF WG has taken efforts in standardizing configuration management protocol, which allows high interoperability of configuration management. In addition to interoperability, high performance is also required in configuration management, but many researches have often discarded the performance aspect of it. In order to fill that void, this paper proposes methods to improve performance with layers of NETCONF. It demonstrates and compares the performance evaluations to verify the efficiency of the proposed methods.
Study on flow behavior of polymer solutions in microchannels
김동학(Kim Dong-Hak),Guojun Xu,Kurt W. Koelling,L. James Lee 한국산학기술학회 2006 한국산학기술학회논문지 Vol.7 No.3
랩온어칩(Lab-on-a-chip) 등 미세구조를 갖는 다양한 장치들의 대량 생산이 가능한 사출성형공정 내에서의 미세 흐름 거동의 이해는 매우 중요하다. 본 논문에서는 마이크로 채널 구조 내에서의 사출성형 흐름에 관하여 연구하였다. 흐름 현상을 관찰하기 위하여 투명한 PMMA를 사용하여 가시화 금형(visual mold)을 제작하였다. 실험 대상 물질로는 고분자 용액인 PED (poly (ethylene oxide))와 PA (polyacrylamide) 용액을 선정하였는데, 이는 고분자 용융체의 특정인 높은 점성과 탄성을 갖도록 설계한 것이다. 시간에 따른 흐름현상과 주 채널과 마이크로 채널과의 경쟁적인 흐름 현상을 관찰하였다. 이로부터 마이크로 사출성형 흐름에서 나타나는 마이크로 채널 내의 충전길이에 대한 해석이 가능하였다. Filling the microchannels is very important in designing micro-injection molding, microdevices, etc. In this paper, flow dynamics was studied in injection molding with microchannels. A transparent PMMA mold was designed and the flow dynamics was observed. The experiment was performed using poly (ethylene oxide) (PEO) and polyacrylamide (PA) aqueous solutior.s. The transient dynamic flow and flow competition between the base plate and the microchannels were observed. The flow observation was used to explain previous filling length results in microchannels during micro-injection molding.
Optimization of supersonic nozzle flow for titanium dioxide thin-film coating by aerosol deposition
Lee, M.W.,Park, J.J.,Kim, D.Y.,Yoon, S.S.,Kim, H.Y.,Kim, D.H.,James, S.C.,Chandra, S.,Coyle, Thomas,Ryu, J.H.,Yoon, W.H.,Park, D.S. Elsevier 2011 Journal of aerosol science Vol.42 No.11
<P><B>Abstract</B></P><P>Aerosol deposition (AD) is an efficient technique for customized coating of various substrates. The small particles of AD yield a dense coating layer with small voids. AD is amenable to rapid coating (mass production), thus, it is economically attractive. Low-temperature AD coating is desirable because it minimizes the thermal degradation of the substrate. An optimized low-cost AD coating technique is of significant interest to solar-cell engineers seeking to reduce manufacturing costs. While most previous studies ignore the importance of nozzle geometry on coating performance, this paper examines non-optimized nozzles and commensurate shockwaves using computational fluid dynamics (CFD). The optimized nozzle geometry obtained from CFD can rapidly prototype nozzles. The CFD-designed nozzles with optimized geometry yielded significantly improved coating quality over non-optimized nozzles.</P> <P><B>Highlights</B></P><P>► Effects of shockwaves, nozzle geometry and dimensionality, carrier-gas viscosity, and particle density. ► Nozzle geometry was adjusted to yield the optimum condition of <I>P</I><SUB>e</SUB>=<I>P</I><SUB>amb</SUB>, which significantly reduced shock formation. ► We, experimentally and numerically, showed that the correctly expanded (<I>first</I>) nozzle yielded a dense and void-free coating layer. ► While the under-expanded (<I>second</I>) nozzle yielded voids and irregularity.</P>