• International Journal of Naval Architecture and Ocean Engineering
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• 제10권6호
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• pp.692-710
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• 2018

The Three-dimensional (3-D) dynamical behaviors of a fluid-conveying pipe subjected to vortex-induced vibration are investigated with different internal flow velocity ${\nu}$. The values of the internal flow velocity are considered in both subcritical and supercritical regimes. During the study, the 3-D nonlinear equations are discretized by the Galerkin method and solved by a fourth-order Runge-Kutta method. The results indicate that for a constant internal flow velocity ${\nu}$ in the subcritical regime, the peak Cross-flow (CF) amplitude increases firstly and then decrease accompanied by amplitude jumps with the increase of the external reduced velocity. While two response bands are observed in the In-line (IL) direction. For the dynamics in the lock-in condition, 3-D periodic, quasi-periodic and chaotic vibrations are observed. A variety of CF and IL responses can be detected for different modes with the increase of ${\nu}$. For the cases studied in the supercritical regime, the dynamics shows a great diversity with that in the subcritical regime. Various dynamical responses, which include 3-D periodic, quasi-periodic as well as chaotic motions, are found while both CF and IL responses are coupled while ${\nu}$ is beyond the critical value. Besides, the responses corresponding to different couples of ${\mu}_1$ and ${\mu}_2$ are obviously distinct from each other.

• 한국식품과학회지
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• 제41권6호
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• pp.615-621
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• 2009

SFE법을 이용하여 딸기의 휘발성 향기성분을 추출하기 위한 시료의 적정 전처리 및 SFE 작동조건을 검토하였으며, SDE법 및 SE법 등의 추출방법과 휘발성 향기성분 조성을 비교하였다. 딸기 생시료, 동결건조시료, 그리고 생시료에 celite를 30, 70%를 혼합하여 제조한 시료를 이용하여 SFE 처리후 향기성분을 분석한 결과, 생시료에 celite를 70% 첨가하는 방법이 향기성분을 추출하는데 가장 효과적인 것으로 나타났다. 온도(40, $55^{\circ}C$)와 압력(3,000, 6,000 psi)을 달리하여 SFE 처리한 결과, 3000 psi, $55^{\circ}C$ 조건에서 alcohol류와 acid류의 추출효율이 증가하였으며, $\gamma$-dodecalactone의 함량도 3배 정도 높은 수준으로 나타났다. SDE법, SFE법 및 SE법 등의 추출방법별 딸기의 휘발성 향기성분을 분석한 결과, SFE법은 SDE법에 비해 추출한 휘발성 향기성분의 종류는 적지만 추출량이 비슷하면서 열분해 및 열변성이 발생하지 않아 딸기 고유의 향기에 가까운 향기패턴을 나타내었으며, 기호적으로 우수한 acid류가 다량 함유된 향기성분을 추출하기에 적합한 것으로 나타났다.

• KSBB Journal
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• 제21권2호
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• pp.157-163
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• 2006

본 연구에서는 초임계 ASES 공정을 이용하여 인체내 및 피부에 여러 가지로 유익한 대표적 생리활성물질인 Vitamin-C의 불안정성을 극복하기 위하여 HP-${\beta}$-CD와의 포접복합체를 제조하여 수용액상에서의 안정성을 분석하였다. X-선 회절을 이용한 Vitamin-C와 HP-${\beta}$-CD의 결정성 분석으로 초임계 ASES 공정을 통하여 포접복합체가 용이하게 형성될 수 있음을 확인하였다. HP-${\beta}$-CD가 Vitamin-C의 안정성을 향상시키는 방법으로 이용될 수 있음을 확인하였으며, $25{\pm}0.1^{\circ}C$의 온도를 유지한 pH 7.0의 50 mM 인산완충용액 상에서 순수한 Vitamin-C, 물리적인 혼합물 및 용매증발법과 초임계 ASES 공정을 이용하여 제조된 포접복합체의 Vitamin-C 겉보기 1차 분해 속도 상수는 각각 $1.45{\times}10^{-2}h^{-1},\;1.41{\times}10^{-2}h^{-1},\;1.34{\times}10^{-2}h^{-1},\;0.20{\times}10^{-2}h^{-1}$로 초임계 ASES 공정으로 제조된 포접복합체의 경우 Vitamin-C의 안정성이 매우 크게 향상되는 것을 확인하였다.

• 한국식품과학회지
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• 제33권3호
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• pp.307-312
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• 2001

능이버섯의 향기성분을 조사하기 위하여 SDE, SFE, headspace 로 추출하고 GC, GC-MS로 동정하였으며, 능이버섯의 향기특성을 조사하기 위하여 GC-olfactometry 방법중 AEDA법을 이용하였다. 그 결과 SDE 추출물에서는 33개, SFE추출물에서는 26개, headspace 추출물에서는 17개의 화합물이 동정되었다. 확인된 화합물의 주성분은 1-octen-3-ol, 1-octen-3-one, 3-octanone, 2-octen-1-ol, 3-octanol, 1-octanol 등의 $C_8$ 화합물과 benzeneacetaldehyde등이었다. AEDA 결과 능이버섯의 주된 향기특성으로는 생능이버섯내(unknown), 생버섯내(1-octen-3-ol), 곰팡이내(1-octen-3-one), 흙내(3-octanol), 풀내(1-octanol), 강한 풀내(2-octenal), 단 꽃내(benzeneacetaldehyde), 목재내(L-linalool), 치즈내(3-hydroxy-2-butanone), 상큼한 단내(2-decanone), 약간의 불쾌한 고기내(3-methyl thiopropanol), 시큼한 우유내(propanoic acid) 등으로 나타났다.

• 한국응용과학기술학회지
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• 제33권1호
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• pp.155-167
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• 2016

Surface-active substances in defatted rapeseed cake were obtained using a supercritical fluid extraction method. Then, it was purified by removing sinapine in the extract through a series of steps using a mixed solvent: diethyl ether and ethyl acetate (1:1, v/v). Emulsifying properties of purified surface-active substances were investigated, including fat globule size, zeta potentials and creaming stability and its antioxidant activity in emulsion systems were also studied by peroxide value and $^1H$-NMR spectrum. It was found that fat globules in emulsions with purified surface-active substances were much smaller than ones with the unpurified. In addition, as pH of the emulsion lowered and with increasing NaCl concentration in the emulsion, they were observed to increase, which led to worse creaming stability. These properties were reflected in changes of zeta potentials of emulsions. The oxidative stability was better in emulsions with purified surface-active substances than ones with Tween 20 or commercial lecithin, possibly resulted from the existence of sinapic acid in the extract. It was concluded that purified surface-active substances from defatted rapeseed cake could be simultaneously used as emulsifier and antioxidant agent in emulsion system.

• KSBB Journal
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• 제28권2호
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• pp.115-122
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• 2013

Volatile flavor compounds of Chamaecyparis obtuse essential oil were extracted by simultaneous steam distillation extraction (SDE) and supercritical fluid extraction (SFE) and analyzed by GC-MS. A total of 48 and 50 components were identified in essential oil by SDE and SFE, respectively. Monoterpenes, oxygenated monoterpenes, sesquiterpenes, oxygenated sesquiterpenes, and diterpenes in essential oil by SDE were 37.24, 10.9, 9.61, 0.22, and 0.22%, respectively. In the case of SFE, they were 19.1, 23.3, 22.66, 1.31, and 10.57%, respectively. Antioxidant activities were increased with the increase of essential oil up to $80{\mu}L/mL$, irrespective of extraction method. Especially, when the essential oil concentration extracted by SDE was increased from 20 to $80{\mu}L/mL$, the antioxidant activity was increased from 10.5 to 55.1%. However, over $80{\mu}L/mL$ of essential oil, an equilibrium state was maintained. In the case of essential oil extracted by SFE, it was decreased compared to that of SDE. For the improvement of atopic dermatitis, various cosmetics such as an ato-cide soap, ato-cide spray, and ato-cide lotion containing essential oil extracted by SFE were tested. About over 90% was useful for the improvement of atopic dermatitis after 4 weeks of clinical trial targeting 40 female adults. These results demonstrate that ato-cide soap, ato-cide spray, and ato-cide lotion containing essential oil extracted by SFE could be used in functional cosmetics.

• Macromolecular Research
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• 제16권1호
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• pp.6-14
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• 2008

Polypropylene (PP)-layered silicate nanocomposites were developed using a new processing method involving a supercritical carbon dioxide ($scCO_2$)-assisted co-rotating twin-screw extrusion process. The nanocomposites were prepared through two step extrusion processes. In the first step, the PP/clay mixture was extruded with $CO_2$ injected into the barrel of the extruder and the resulting foamed extrudate was cooled and pelletized. In the second step, the foamed extrudate was extruded with venting to produce the final PP/clay nanocomposites without $CO_2$. In this study, organophilic-clay and polypropylene matrix were used. Maleic anhydride grafted polypropylene (PP-g-MA) was used as a compatibilizer. This study focused on the effect of $scCO_2$ on the dispersion characteristics of the clays into a PP matrix and the rheological properties of the layered silicate based PP nanocomposites. The dispersion properties of clays in the nanocomposites as well as the rheological properties of the nanocomposites were examined as a function of the PP-g-MA concentration. The degree of dispersion of the clays in the nanocomposites was analyzed by X-ray diffraction and transmission electron microscope. Various rheological properties of the nanocomposites were measured using a rotational rheometer. In the experimental results, the $scCO_2$ assisted continuous manufacturing extrusion system was used to successfully produce the organophilic-clay filled PP nanocomposites. It was found that $scCO_2$ had a measurable effect on the clay dispersion in the polymer matrix and the melt intercalation of a polymer into clay layers.

• Biotechnology and Bioprocess Engineering:BBE
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• 제6권4호
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• pp.212-230
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• 2001

Recent advances in recombinant DNA technology have resulted in development of many new protein drugs. Due to the unique properties of protein druges, they have to be delivered by parenteral injection Although delivery of protein drugs by other routes, such as pulmonary and nasal routes, has shown some promises, to date most protein drugs are administered by par-enteral routs. For long-term delivery of protein drugs by parenteral administration, they have been formulated into biodegradable microspheres. A number of microencapsulation methods have been developed, and the currently used microencapsulation methods are reviewed here, The microen-capsulation methods have been divided based on the method used. They are: solvent evapora-tion/extraction; phase separation (coacervation);spray drying; ionotropic gelation/polyelectrolyte complexation; interfacial polyumerization and supercritical fluid precipitation. Each method is de-scribed fro its applications, advantages, and limitations.

• Korean Chemical Engineering Research
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• 제59권3호
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• pp.455-466
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• 2021

Micro and nanoparticles of Finasteride were prepared by gas-antisolvent method. The influence of process parameters such as pressure (100, 130 and 160 bar), temperature (308, 318 and 328 K) and solute concentrations (10, 25 and 40 mg/ml) on mean particle size was studied by Box-Behnken design. As ANOVA results indicated, the highest influence in production of smaller particles was attributed to the pressure. Optimum condition leading to the smallest particle size was as follows: initial solute concentration, 10 mg/ml; temperature, 308 K and pressure, 160 bar. The particles were evaluated with FTIR, SEM, DLS, XRD as well as DSC. The analyses revealed a size decrease in the precipitated Finasteride particles (232.4 nm, on mean) via gas-antisolvent method, as compared to the original particles (55.6 ㎛).

• 대한화학회지
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• 제45권2호
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• pp.149-155
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• 2001

남조류독소, 마이크로시스틴을 초임계유체추출을 이용하여 추출하는 새로운 분석법이 개발되었다. 이 연구에서 사용된 마이크로시스틴들은 초임계 유체 CO$_2$에는 거의 녹지 않지만 90% CO$_2$, 9.0% 메탄올, 1.0% 물로 된 혼합유체를 사용한 결과 성공적으로 추출할 수 있었다. 이 연구에서 사용된 초임계 유체 추출법은 고체상추출법보다 많은 장점들을 가지고 있다. 우선 시료처리단계가 줄어들고, 시료의 손실이 적으며, 분석시간을 단축시킬 수 있다는 장점들이 있다. 또한 전처리 단계가 생략된다는 장점도 있다. ODS 카트리지를 사용하는 고체상 추출법에서 ODS 카트리지가 마이크로시스턴에 대한 흡착력이 떨어지기 때문에 좀 더 극성이 있는 CN 카트리지에 주입시켰다. CN 카트리지는 물 5mL, 0.5 M 아세트산 5mL, 5% 아세트니트릴 5mL로 빗은 후 70% 아세트니릴로 최종용리시킨 후 HPLC로 분리하였다. CN 카트리지를 사용하였을 때 ODS 카트리지보다 더 좋은 회수율과 크로마토그램을 보여주었다.