• Structural Engineering and Mechanics
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• v.22 no.3
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• pp.263-278
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• 2006

Starting with the geometrically non-linear formulation and the subsequent linearization, this paper presents a consistent formulation of the exact mechanical analysis of geometrically and materially linear three-layer continuous planar beams. Each layer of the beam is described by the geometrically linear beam theory. Constitutive laws of layer materials and relationships between interlayer slips and shear stresses at the interface are assumed to be linear elastic. The formulation is first applied in the analysis of a three-layer simply supported beam. The results are compared to those of Goodman and Popov (1968) and to those obtained from the formulation of the European code for timber structures, Eurocode 5 (1993). Comparisons show that the present and the Goodman and Popov (1968) results agree completely, while the Eurocode 5 (1993) results differ to a certain degree. Next, the analytical solution is used in formulating a general procedure for the analysis of layered continuous beams. The applications show the qualitative and quantitative effects of the layer and the interlayer slip stiffnesses on internal forces, stresses and deflections of composite continuous beams.

• Bulletin of the Korean Chemical Society
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• v.32 no.5
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• pp.1587-1592
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• 2011

The aim of the present study was to improve the solubility and bioavailability of a poorly water-soluble drug in human body, using a solid dispersion technique (hot melt extrusion). The solid dispersion was prepared by cooling the hot melt of the drug in the carrier (Vitamin E TPGS and PVP). The dissolution rate of formulation 1 from a novel formulation prepared by solid dispersion technique was equal to release of formulation 6 (40% of eprosartan mesylate is in contrast to teveten$^{(R)}$) within 60 min (Table 1). The oral bioavailability of new eprosartan mesylate tablet having vitamin E TPGS and PVP K29 was tested on rats and dogs. Of the absorption enhancer and polymer tested, vitamin E TPGS and PVP K29, resulted in the greatest increases of AUC in animals (about 2.5-fold increase in rat and dog). When eprosartan mesylate was mixed with the absorption enhancer and polymer in a ratio of 2.94:2:1, vitamin E TPGS and PVP K29 improved eprosartan mesylate bioavailability significantly compared with the conventional immediate release (IR) tablet Teveten$^{(R)}$ (formulation 7). These results show that solid dispersion using vitamin E TPGS and PVP K29 is a promising approach for developing eprosartan mesylate drug products.

• Korean Journal of Pharmacognosy
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• v.44 no.2
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• pp.200-208
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• 2013

The aim of this study was to evaluate the shelf-life of Bojungikgi-tang (Buzhongyiqi-tang in Chinese) by long-term storage test. Experiments were performed to evaluate the stability such as the selected physicochemical, pH, identification, heavy metal, microbiological experiment, and amount of marker compounds under a long-term storage test of Bojungikgi-tang decoction. The significant change was not showed in pH, heavy metal, microbiological, and identification test based on long-term storage test. Furthermore, the HPLC analysis was performed for the determinations of liquiritin, glycyrrhizin, nodakenin, and hesperidin in Bojungikgi-tang by long-term storage test. We were calculated shelf-life of Bojungikgi-tang decoction based on the amount change of four constituents. Consequently, Shelf-life by four compounds at room temperature was predicted 23 month. The suggested shelf-life would be helpful on the storage and distribution of herbal medicine.

• Coupled systems mechanics
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• v.7 no.5
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• pp.583-610
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• 2018

This paper discusses the issues associated with modeling frictional contact between solid bodies undergoing large deformations. The most common model for friction on contact interfaces in solid mechanics is the Coulomb friction model, in which two distinct responses are possible: stick and slip. Handling the transition between these two phases computationally has been a source of algorithmic instability, lack of convergence and non-unique solutions, particularly in the presence of large deformations. Most computational models for frictional contact have used penalty or updated Lagrangian approaches to enforce frictional contact conditions. These two approaches, however, present some computational challenges due to conditioning issues in penalty-type implementations and the iterative nature of the updated Lagrangian formulation, which, particularly in large simulations, may lead to relatively slow convergence. Alternatively, a plasticity-inspired implementation of frictional contact has been shown to handle the stick-slip conditions in a local, algorithmically efficient manner that substantially reduces computational cost and successfully avoids the issues of instability and lack of convergence often reported with other methods (Laursen and Simo 1993). The formulation of this approach, however, has been limited to the small deformations realm, a fact that severely limited its application to contact problems where large deformations are expected. In this paper, we present an algorithmically consistent formulation of this method that preserves its key advantages, while extending its application to the realm of large-deformation contact problems. We show that the method produces results similar to the augmented Lagrangian formulation at a reduced computational cost.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.3
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• pp.8-16
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• 2002

The implicit formulation of rotor dynamics for helicopter flight simulation has been derived and and presented. The generalized vector kinematics regarding the relative motion between coordinates were expressed as a unified matrix operation and applied to get the inertial velocities and accelerations at arbitaty rotor blade span position. Based on these results the rotor aeromechanic equations for flapping dynamics, lead-lag dynamics and torque dynamics were formulated as an implicit form. Spatial integration methods of rotor dynamic equations along blade span and the expanded applicability of the present implicit formulations for arbitrary hings geometry and hinge sequences have been investigated. Time integration methods for present DAE(Differential Algebraic Equation) to calculate dynamic response calculation are recommenaded as future works.

• Journal of Physiology & Pathology in Korean Medicine
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• v.27 no.5
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• pp.617-624
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• 2013

The purpose of this study is to investigate the protective effects of 25 herbal formulas on acetaminophen (APAP) or D-galactosamine (D-GalN)-induced hepatotoxicity in primary rat hepatocytes. Cell viability was measured using by Cell Counting Kit-8. 15 kinds of herbal formulas significantly reversed the cell viabilities of D-GalN-treated rat hepatocytes compared with D-GalN alone (p<0.05). In particular, 9 herbal formulas (Bangpungtongseong-san, Bojungikgi-tang, Galgeun-tang, Gumiganghwal-tang, Guibi-tang, Sagunja-tang, Samsoeum, Pyeongwi-san and Yijin-tang) showed the potent protective effects. However, 8 herbal formula exerted weak protective effects and 2 herbal formula did not exert effects on hepatotoxicity by D-GalN. On APAP-induced hepatotoxicity, 7 kinds of herbal formulas increased the viabilities of hepatocytes compare with APAP alone (p<0.05). These results could be provide a valuable information for the future in vivo or clinical studies to predict the hepatoprotective effects of herbal formulas.

• 한국전산유체공학회:학술대회논문집
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• 2005.10a
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• pp.117-124
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• 2005

Splitting algorithms of the incompressible Navier-Stokes equations using P1P1/P2P1 finite element formulation are newly proposed. P1P1 formulation allocates velocity and pressure at the same nodes, while P2P1 formulation allocates pressure only at the vertex nodes and velocity at both the vertex and mid nodes. For comparison of the elapsed time and accuracy of the two methods, they have been applied to the well-known benchmark problems. The three cases chosen are the two-dimensional steady and unsteady flows around a fixed cylinder, decaying vortex, and impinging slot jet. It is shown that the proposed P2P1 semi-splitting method performs better than the conventional P1P1 splitting method in terms of both accuracy and computation time.

• Journal of Pharmaceutical Investigation
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• v.31 no.3
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• pp.167-172
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• 2001

All-trans retinoic acid (ATRA), vitamin A acid, has been shown to exert anticancer activity in a number of types of cancers, particularly in acute promyelocytic leukaemia (APL). Due to its highly variable bioavailability and induction of its own metabolism after oral treatment, development of parenteral dosage forms are required. However, its poor aqueous solubility and chemical unstability give major drawbacks in parenteral administration. This study was undertaken to investigate a possibility to develop a parenteral formulation of ATRA by employing solid lipid nanoparticle (SLN) as a carrier. By optimizing the production parameters and the composition of SLNs, SLNs with desired mean particle size (<100 nm) as a parenteral dosage form could be produced from trimyristin (as solid lipid), Egg phosphatidylcholine and Tween 80 (as SLN stabilizer). The mean particle size of SLN formulation of ATRA was not changed during storage, suggesting its physical stability. Thermal analysis confirmed that the inner lipid core of SLNs exist at solid state. The mean particle size of ATRA-loaded SLNs was not significantly changed by the lyophilization process. ATRA could be efficiently loaded in SLNs, while maintaining its anticancer activity against HL-60, a well-known APL cell line. Furthermore, by lyophilization, ATRA loaded in SLN could be retained chemically stable during storage. Taken together, our present study demonstrates that physically and chemically stable ATRA formulation adequate for parenteral administration could be obtained by employing SLN technology.

• Journal of Korea Multimedia Society
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• v.18 no.6
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• pp.734-741
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• 2015

Coating is a type of paint. It protects a product forming a film layer on the product and assigns various properties to the product. Coating is one of the fields which is being studied actively in the polymer industry. Importance of coating in various industries is more increased. However, mixing process has been performing in dependence on operator's experience. In this paper, we found the relationship between each data from coating formulation process. We propose a framework to analyze the coating formulation process as well. It can improve the coating formulation process. In particular, the suggested framework may reduce degradation and loss costs due to absence of standard data which is accurate formulation criteria. Also it suggests responses to errors which can be occurred in the future through the analysis of the error data generated in mixing step.

• Proceedings of the SCSK Conference
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• 2003.09a
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• pp.457-468
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• 2003

Active ingredients have been around in cosmetics for a long time but have they really resulted in active cosmetic products\ulcorner In order to achieve this, the right active needs to be delivered to the right location at the right concentration for the correct period of time. And the extent (and therefore the concentration) of this delivery depends on the formulation. From a rather theoretical approach based on the polarity of the active ingredient, the stratum corneum and the oil phase, the Relative Polarity Index was established that enables the selection of a suitable emollient for ensuring skin penetration of the active ingredient. Practical examples subsequently show the validity of this approach that demonstrates that one can regulate the delivery of an active molecule (and therefore the efficacy of a cosmetic formulation) by selection and control of the emollient system. Cosmetic formulations are generally quite complex mixtures and subsequent experiments using different emulsifier systems indicated that this component of a cosmetic formulation could also have an impact on steering the active ingredient to the right layer of the skin, although it is too early to be able to derive general rules from this.