• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 1996년도 춘계학술대회
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• pp.282-282
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• 1996

The purpose of this study was to prepare the nifedipine dry elixir (NDE) and coated nifedipine dry elixir (CNDE) containing nifedipine ethanol solution for improving the dissolution rate and bioavailability of nifedipine. NDE containing nifedipine and ethanol in wall materials of dextrin was prepared using a spray-dryer and then NDE was coated with eudragit acrylic resin to make CNDE. Shape and size of the NDE and CNDE were monitored by scanning electron micrograph and laser particle size analyzer In vitro dissolution tests were performed in simulated gastric and intestinal fluid. Bioavailability of NDE and CNDE were compared with drug powder suspension and commercial soft capsule after oral administration of the preparations to rats. NDE and CNDE are spherical in shape. Cross-sectional view of dry elixirs indicates the large inter cavity containing ethanolic drug solution in shell. Geometric mean diameter of NDE and CNDE is about 6.64 and 8.70 $\mu\textrm{m}$, respectively. Drug dissolution rate within first 5 min from NDE increased dramatically irrespective of dissolution medium. However, CNDE showed a particularly retarded dissolution rate in pH 1.2 simulated gastric fluid compared with NDE. The bioavailability of nifedipine in the NDE was increased dramatically compared with drug powder suspension. CNDE reduced initial burst-out plasma peak compared with NDE. CNDE as a sustained release delivery system could reduce the initial burst-out plasma peak due to controlling the release rate of nifedipine from NDE and maintain the effective plasma level over a longer period within therapeutic window with enhanced bioavailability of nifedipine.

• 한국분말재료학회지
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• 제16권4호
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• pp.243-248
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• 2009

Carbon-coated Cu nanopowders with core/shell structure have been successfully fabricated by pulsed wire evaporation (PWE) method, in which a mixed gas of Ar/$CH_4$ (10 vol.%) was used as an ambient gas. The characterization of the samples was carried out using x-ray diffraction (XRD), scanning electron microscope (SEM), and high resolution transmission electron microscope (HRTEM). It was found that the nanoparticles show a spherical morphology with the size ranging of 10-40 nm and are covered with graphite layers of 2-4 nm. When oxygen-passivated Cu nanopowders were annealed under flowing argon gas (600 and 800$^{\circ}C$), the crystallinity of $Cu_2O$ phase and the particle size gradually increased. On the other hand, carbon-coated Cu nanopowders remained similar to as-prepared case with no additional oxide or carbide phases even after the annealing, indicating that the metal nanoparticles are well protected by the carbon-coating layers.

• 대한의용생체공학회:의공학회지
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• 제15권1호
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• pp.71-76
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• 1994

단일 쌍극자 모델을 이용한 source localization 문제에서 전극의 갯수, 쌍극자의 위치 및 방향 등이 S/N(signal to noise ratio)과 추정 오차사이의 관계에 미치는 영향을 Monte Carlo 시뮬레이션으로 조사했다. forward problem은 3중 구각 모델로 계산했고, simplex 방법으로 쌍극자 파라미터를 최적화시켰다. 전극의 갯수가 많을때, 쌍극자가 뇌 중심(midbrain)보다 대뇌 피질(cortex)부근에 있을 때, 쌍극자가 tangential 방향일 때 추정 오차의 평균과 표준편차가 작아졌다.

• 대한기계학회논문집
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• 제18권9호
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• pp.2404-2412
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• 1994

A mathematical model has been developed for predicting kinematic, thermal, and solidification histories of atomized droplets during flight. Liquid droplet convective cooling, recalescence, equilibrium-state solidification, and solid-phase cooling were taken into account in the analysis of the solidification process. The spherical shell model was adopted where the heterogeneous nucleation is initiated from the whole surface of a droplet. The growth rate of the solid-liquid interface was determined from the theory of crystal growth kinetics with undercooling caused by the rapid solidification. The solid fraction after recalescence was obtained by using the integral method. The thermal responses of atomized droplets to gas velocity, particle size variation, and degree of undercooling were investigated through the parametric studies. It is possible to evaluate the solid fraction of the droplet according to flight distance and time in terms of a dimensionless parameter derived from the overall energy balance of the system. It is also found that the solid fraction at the end of recalescence is not dependent on the droplet size and nozzle exit velocity but on the degree of subcooling.

• 대한의용생체공학회:의공학회지
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• 제15권4호
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• pp.481-488
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• 1994

시각 및 손가락의 전기자극에 의해 머리표면에서 발생하는 유발전위를 검출하여 Source Tracing Method를 이용하여 뇌의 시각인지영역 및 손가락 감각인지영역을 추정하였다. 본 과정에서 유발전위 검출방식은 average method를 이용하였고, 흥분뉴런군에 대한 물리적 모델로 Single Current Dipole Model을 이용하고, 머리기하에 대한 3중구각모델을 이용하여 Forward Problem을 풀었다. Inverse Problem은 current dipole의 6개의 parameter에 대한 Least Square Error Method를 이용하여 신견흥분의 위치를 추정하였다. 이러한 결과와 생리학적으로 밝혀진 시각 및 체성감각 신경로와의 비교결과 유사성이 확인되었다.

• 한국금형공학회:학술대회논문집
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• 한국금형공학회 2008년도 하계 학술대회
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• pp.143-148
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• 2008

In order to produce high-quality optical components, aspheric lenses have been widely applied in recent years. An aspheric lens consists of aspheric surfaces instead of spherical ones, which causes difficulty in the design process as well as the manufacturing procedure. Although injection molding is widely used to fabricate optical lenses owing to its high productivity, there remains lots of difficulty to determine appropriate mold design factors and injection molding parameters. In the injection molding fields, computer simulation has been effectively applied to analyze processes based on the shell analysis so far. Considering the geometry of optical lenses, a full-3d simulation based on solid elements has been reported as a reliable approach. The present work covers three-dimensional injection molding simulation and relevant deformation analysis of an injection molded plastic lens based on 3d solid elements. Numerical analyses have been applied to the injection molding processes of three aspheric lenses for an image sensing module of a mobile phone. The reliability of the proposed approach has been verified in comparison with the experimental results.

• Journal of Magnetics
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• 제16권4호
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• pp.435-439
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• 2011

In this work, we prepared Fe-Ni alloy nanopowders by wire electrical explosion in deionized water and ethanol. Particles size and morphology of the as-synthesized nanoparticles prepared in water and ethanol were observed by transmission electron microscopy. In both cases, the as-synthesized nanoparticles were in nearly spherical shape and their size distribution was broad. The particles prepared in the water were in core-shell structure due to the oxidation of Fe element. X-ray diffraction was used to analyze the phase of the nanopowders. It showed that the nanopowders prepared in water had ${\gamma}$-Fe-Ni solid solution and FeO phase. The samples obtained in ethanol were in two phases of Fe-Ni solid solution, ${\gamma}$-Fe-Ni and ${\alpha}$-Fe-Ni. Bulk samples were made from the as-synthesized nanopowders by spark plasma sintering at $1000^{\circ}C$ for 10 min. Structure of the bulk sample was observed by scanning electron microscope. Magnetic properties of the as-synthesized nanopowders and the bulk samples were investigated by vibrating sample magnetometer. The hysteresis loop of the assynthesized nanopowders and the sintered bulk samples revealed a ferromagnetic characteristic.

• 한국응용과학기술학회지
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• 제18권4호
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• pp.273-284
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• 2001

A series of microcapsule were synthesized by using several PCM(Phase Change Material) as a core material and gelatin/arabic gum, melamine/formaldehyde as a shell material. Coacervation technique and in situ polymerization were adopted in synthesizing microcapsules. In the microencapsulation by coacervation, tetradecane and octadecane were used as core materials. In the microencapsulation by situ polymerization tetradecane, pentadecane, hexadecane, heptadecane, octadecane, and nonadecane were used as core material. The synthesized microcapsule was examined to observe the shape of the microcapsule. The particle size analysis was performed by particle size analyzer. The thermal properties(e.g. melting point, heat of melting, crystallization temperature, heat of crystallization, differences between melting point and crystallization temperature) were obtained by DSC(Differential Scanning Calorimeter). The stirring rate effect was investigated during the microencapsulation. It was found that with increasing the stirring rate much smaller microcapule was produced. However, this did not necessarily lead to formation of spherical microcapsule.

• Journal of Ship and Ocean Technology
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• 제5권3호
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• pp.36-44
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• 2001

The collision energy absorbing characteristics of side structure of the LNG carriers which have the cargo containment systems of the spherical and the membrane types are compared. A failure mechanism of the double hull side structures of 130, 000 $m^3$ class LNG carriers under sideways collision event has been simulated by using the detailed finite element calculations. In ship collision analysis, the finite element method based on explicit time integration has been use[1 with much success. Finite element modeling techniques for detail description of structural members antral ship motion regarding the dynamic behavior allowed to investigate the effect of bow shape and the initial contact position on side shell of collided ship. In the numerical simulations of the ship-to-ship sideways collision, the effect of the colliding bow shapes and the change of the colliding ship draft are investigated. The critical collision energy which is absorbed by a side structure of a collided ship until the fore-end of colliding ship arrives at the boundary of the cargo tank is calculated. The critical speed of specified colliding ships which can not penetrate the boundary of the LNG cargo tank of the collided ship under collision accident if evaluated.

• 천문학회보
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• 제41권1호
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• pp.47.1-47.1
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• 2016

The determination of three dimensional parameters (e.g., radial speed, angular width, source location) of Coronal Mass Ejections (CMEs) is very important for space weather forecast. To estimate these parameters, several cone models based on a flat cone or a shallow ice-cream cone with spherical front have been suggested. In this study, we investigate which cone model is proper for halo CME morphology using 26 CMEs which are identified as halo CMEs by one spacecraft (SOHO or STEREO-A or B) and as limb CMEs by the other ones. From geometrical parameters of these CMEs such as their front curvature, we find that near full ice-cream cone CMEs are dominant over shallow ice-cream cone CMEs. Thus we develop a new full ice-cream cone model by assuming that a full ice-cream cone consists of many flat cones with different heights and angular widths. This model is carried out by the following steps: (1) construct a cone for given height and angular width, (2) project the cone onto the sky plane, (3) select points comprising the outer boundary, (4) minimize the difference between the estimated projection speeds with the observed ones. We apply this model to 12 SOHO halo CMEs and compare the results with those from other stereoscopic methods (a geometrical triangulation method and a Graduated Cylindrical Shell model) based on multi-spacecraft data.