• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.2
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• pp.75-84
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• 2002

A numerical analysis of unsteady motion in solid rocket motors with a nozzle has been conducted. The numerical formulation including modified $\kappa$-$\varepsilon$ turbulence model treats the complete conservation equation for the gas phase and the one-dimensional equations in the radial direction for the condensed phase. A fully coupled implicit scheme based on a dual time-stepping integration algorithm has been adopted to solve the governing equations. After obtaining a steady state solution, pulse and periodic oscillations of pressure are imposed at the head-end to simulate acoustic oscillations of a travelling-wave motion in the combustion chamber. Various steady and unsteady state features in the combustion chamber of a rocket motor has been analyzed as results of numerical calculations.

• Journal of Pharmaceutical Investigation
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• v.30 no.4
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• pp.259-266
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• 2000

Vitamin A palmitate, an oily drug which has low chemical stability and is poorly absorbed in the intestine, was formulated into a novel powdered dosage form. This is designated as a redispersible dry emulsion by freeze-drying technique. Before preparing a dry emulsion, vitamin A palmitate oil in solid in water (O/S/W) emulsion with soybean oil and coconut oil using Aerosil 200 as an emulsion stabilizer and polyoxyethylene-polyoxypropylene-blockcopolymer (Pluronic F68) as a surfactant was prepared. The resultants of the stability tests indicated that vitamin A palmitate O/S/W emulsion was improved on increasing the oil content of the formulation. The resultant dry emulsion particles have a good stabilities and free flow properties and readily released the oily droplets to form stable emulsions on rehydration. The drug releasing property from the resultant dry emulsion particles was dependent on factors such as amount of oily carrier(soybean oil) and surfactant(Pluronic F68) formulated. Above 80% of vitamin A palmitate content was released from the dry emulsion for 1 hour. It was deduced that vitamin A palmitate dry emulsion was definitely suitable for oral administration, since small droplets of vitamine A palmitate from the dry emulsion may alter the drug absorption profile resulting in bioavailability enhancement.

• Structural Engineering and Mechanics
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• v.85 no.1
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• pp.89-104
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• 2023

This work presents a proposal for employing reduced numerical integration in the formulation of the 4-node quadrilateral solid finite element. The use of these low-order integration rules leads to numerical instabilities such as those producing the hourglass effect. The proposed procedure allows evaluating a given constitutive model only in one integration point, achieving an attractive computational cost reduction and, also, successfully controls the hourglass effect. A validation of the proposal is included and discussed throughout the paper. To show the efficiency of the proposal, several application examples of masonry structures are studied and discussed. To represent the non-linear mechanical behaviour of masonry a plastic-damage model is implemented within the application of this sub-integration scheme. Also, in order to have a full and computationally efficient strategy to determine the behaviour of masonry structures, involving its evolution to collapse, a homogenization technique with a macro-modeling approach is used. The methodology discussed throughout this paper demonstrates a substantial computational cost reduction and an improved approximation of the non-linear problem evidenced by a reduction of up to 85% of the computational time for some cases.

• Coupled systems mechanics
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• v.12 no.4
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• pp.365-389
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• 2023

Dynamic analysis of a typical concrete gravity dam-reservoir system is formulated by FE-(FE-TE) approach (i.e., Finite Element-(Finite Element-Truncation Element)). In this technique, dam and reservoir are discretized by plane solid and fluid finite elements. Moreover, the H-W (i.e., Hagstrom-Warburton) high-order condition imposed at the reservoir truncation boundary. This task is formulated by employing a truncation element at that boundary. It is emphasized that reservoir far-field is excluded from the discretized model. The formulation is initially reviewed which was originally proposed in a previous study. Thereafter, the response of Pine Flat dam-reservoir system is studied due to horizontal and vertical ground motions for two types of reservoir bottom conditions of full reflective and absorptive. It should be emphasized that study is carried out under high order of H-W condition applied on the truncation boundary. The initial part of study is focused on the time harmonic analysis. In this part, it is possible to compare the transfer functions against corresponding responses obtained by FE-(FE-HE) approach (referred to as exact method). Subsequently, the transient analysis is carried out. In that part, it is only possible to compare the results for low and high normalized reservoir length cases. Therefore, the sensitivity of results is controlled due to normalized reservoir length values.

• Composites Research
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• v.20 no.6
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• pp.15-20
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• 2007

In this work, the structural response of thin-walled, composite beams with built-in twist angles is analyzed using a mixed beam approach. The analytical model includes the effects of elastic couplings, shell wall thickness, and torsion warping. Reissner's semi-complimentary energy functional is used to describe the beam theory and also to deal with the mixed-nature in the beam kinematics. The bending and torsion related warpings introduced by the non-zero pretwist angles are derived in closed-form through the proposed beam formulation. The theory is validated with available literature and detailed finite element analysis results for rectangular solid section beams with elastic couplings. Very good correlation has been obtained for the cases considered.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.1
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• pp.56-62
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• 2024

By introducing curing kinetics and chemo-rheology for the epoxy resin formulation for ultra-high voltage gas insulated switchgear (GIS) Insulating Spacers, a study was conducted to simulate the curing behavior, flow and warpage analysis for optimization of the molding process in automatic pressure gelation. The curing rate equation and chemo-rheology equation were set as fixed values for various factors and other physical property values, and the APG molding process conditions were entered into the Moldflow software to perform optimization numerical simulations of the three-phase insulating spacer. Changes in curing shrinkage according to pack pressure were observed under the optimized process conditions. As a result, it was confirmed that the residence time in the solid state was shortened due to the lowest curing reaction when the curing holding pressure was 3 bar, and the occurrence of deformation due to internal residual stress was minimized.

• Journal of the Korean Society of Food Science and Nutrition
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• v.43 no.9
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• pp.1380-1387
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• 2014

The purpose of this study was to develop a mouthwash product with solid fermented oriental medicinal herb (OMH). Solid fermentation of magnolia, liquorice, and cnidium by Phellinus linteus mycelium was carried out successfully when 30% water was added to the medium, whereas 10% brown rice powder was required as an extra nutrient for solid fermentation of mint besides water. The amount of total phenol compounds and DPPH radical scavenging activity of OMH increased significantly (P<0.05) upon solid fermentation. Anti-microbial activities of fermented OMH also increased and were approximately 100-fold greater than those of unfermented samples. Oral pathogens such as Staphylococcus epidermis, Streptococcus pyogenes, Candida albicans, or Streptococcus mutans were used for determination of anti-microbial effects of OMH. Formulation of the mouthwash was developed based on the results of the sensory evaluation. Among seven formulas, the best formula chosen by the sensory evaluation was as follows: mouthwash prepared with 0.075% ethanol extract of solid fermented OMH as a main ingredient, 83.64% hot water extract of mint and clove (100:15, v/v) as a mouthwash base component, and other miscellaneous ingredients, including sodium fluoride, menthol, and surfactants. Data from a consumer's preference test with 30 participants, overall acceptance, and willingness to buy the product developed in this study were all significantly higher for the tested mouthwash compared to mouthwash on the market manufactured with OMH but with a different formula. Duration of freshness of the mouthwash after usage as determined by Breath Checker was not significantly different between the two samples, although the duration of our product was slightly longer than that of the commercial product mentioned above.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.48 no.3
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• pp.189-196
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• 2022

Plasma refers to an ionized gas that is often referred to as "the fourth phase of matter", following solid, liquid, and gas. Plasma has traditionally been utilized for industrial applications such as welding and neon signs, but its promise in biomedical fields such as cancer treatment and dermatology has lately been recognized. Indeed, due to its beneficial effects in promoting collagen production, improving skin tone, and eliminating harmful bacteria in the skin, plasma treatment constitutes an important target for dermatological research. In this study, a plasma device for cosmetic manufacturing based on nitrogen, the main component of the atmosphere, was designed and assembled. Moreover, nitric oxide (NO) was selected since is easier to follow and evaluate than other nitrogen plasma active species, and its contents were measured to perform a quantitative and qualitative evaluation of plasma. First, an injection method, using different proximities labeled "sinking" and "non sinking" treatments, was performed to test the most efficient plasma treatment method. As a result, it was observed that the formulation obtained by a non sinking treatment was more effective. Furthermore, toner and ampoule were selected as cosmetics formulations, and the characteristics of the formulation and changes in the injected plasma state were observed. In both formulations, the successful injection of NO plasma was 2 times higher in toner formulation than ampoule formulation, and it gradually decreased with time, having dissipated after a week. It was confirmed that the nitrogen plasma used did not affect the stability of the toner and ampoule formulations at low temperature (4 ℃), room temperature (25 ℃), and high temperature (37 ℃ and 50 ℃) conditions. The results of this study demonstrate the potential of plasma cosmetics and highlight the importance of securing the stability of the injected plasma.

• Journal of the Korean Society of Food Science and Nutrition
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• v.45 no.7
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• pp.1077-1081
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• 2016

Feasibility of incorporation of licorice powder (LP) as a value-added food ingredient into convenient food products was investigated using yanggaeng as a model system. LP was incorporated into yanggaeng at amounts of 0, 2, 4, 6, and 8% (w/w) based on total weight of cooked white beans and LP. pH level decreased while soluble solid content significantly increased with increasing levels of LP (P<0.05). In terms of color, lightness decreased while redness and yellowness increased significantly (P<0.05) with increasing levels of LP. Hardness also decreased significantly with a higher amount of LP in the formulation (P<0.05). 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) and 2,2'-diphenyl-1-picrylhydrazyl radical scavenging activities were significantly elevated by LP addition, and they increased significantly as LP concentration increased in the formulation (P<0.05). Finally, consumer acceptance test indicated that the highest levels of LP incorporation (8%) had an adverse effect on general consumer preferences. In contrast, yanggaeng with moderate levels of LP (2%) is recommended based on its overall scores to take advantage of the antioxidant properties of LP without sacrificing consumer acceptability.

• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.12
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• pp.1918-1922
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• 2015

The feasibility of incorporating Hallabong powder (HP) as a value-added food ingredient into convenient food products was investigated using yanggaeng as a model system. HP was incorporated into yanggaeng at amounts of 0, 2, 4, 6, and 8% (w/w) based on total weight of cooked white beans and HP. pH level decreased while soluble solid content increased significantly with increasing levels of HP (P<0.05), whereas moisture content was not directly affected by level of HP incorporation. In terms of color, lightness decreased while redness and yellowness increased significantly (P<0.05) with increasing levels of HP. Hardness increased significantly when HP content exceeded 4% in the formulation (P<0.05). ABTS and DPPH radical scavenging activities were significantly elevated by HP addition, and they increased significantly as HP concentration increased in the formulation (P<0.05). Finally, consumer acceptance test indicated that the highest levels of HP incorporation (8%) had an adverse effect on general consumer preferences. In contrast, yanggaeng with moderate levels of HP (2%) is recommended based on its overall scores to take advantage of the antioxidant properties of HP without sacrificing consumer acceptability.