• Journal of Physiology & Pathology in Korean Medicine
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• v.31 no.6
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• pp.380-384
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• 2017

From March 1, 2017 to May 31, 2017, subjects were allowed to apply a wrinkle-improving herbal cosmetic product containing the extract of Douchi for 8 weeks. The effectiveness of herbal cosmetics was evaluated through wrinkle improvement efficacy parameter analysis, subjective wrinkle improvement through questionnaires, and adverse reaction. The herbal cosmetic products containing the extract of Douchi showed a significant decrease in the wrinkle improvement efficacy parameter analysis result. The results of the subjective satisfaction analysis after use were also evaluated positively. We could confirm the possibility of wrinkle improvement effect of Douchi extract, and it will be possible to contribute to the expansion of korean medicine field through more studies in the future.

• Journal of applied mathematics & informatics
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• v.39 no.3_4
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• pp.419-435
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• 2021

This paper deals with numerical treatment of singularly perturbed differential equations involving small delays. The highest order derivative in the equation is multiplied by a perturbation parameter 𝜀 taking arbitrary values in the interval (0, 1]. For small 𝜀, the problem involves a boundary layer of width O(𝜀), where the solution changes by a finite value, while its derivative grows unboundedly as 𝜀 tends to zero. The considered problem contains delay on the convection and reaction terms. The terms with the delays are approximated using Taylor series approximations resulting to asymptotically equivalent singularly perturbed BVPs. Inducing exponential fitting factor for the term containing the singular perturbation parameter and using central finite difference for the derivative terms, numerical scheme is developed. The stability and uniform convergence of difference schemes are studied. Using a priori estimates we show the convergence of the scheme in maximum norm. The scheme converges with second order of convergence for the case 𝜀 = O(N^-1) and for the case 𝜀 ≪ N^-1, the scheme converge uniformly with first order of convergence, where N is number of mesh intervals in the domain discretization. We compare the accuracy of the developed scheme with the results in the literature. It is found that the proposed scheme gives accurate result than the one in the literatures.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.117-119
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• 2002

In this paper, the geometry effectiveness and contact modes as functions of real contact length on a cap ring have been analyzed for high pressure sealing mechanism in reciprocating actuator. The reaction force and elastic strain energy density are very important parameters for analyzing the sealing performance of an ACGT ring seal. For the high pressure of 800bar and the maximum speed of 3m/s, the main piston is reciprocating along the linear line against the cylinder wall. The computed results indicate that the length ratio of a cap ring is more influential design parameter compared to that of the tribological contact mode. Thus, this paper recommends the discrete contact area rather than a conventional flat contact model. Especially, the sealing capacity is more improved when the length ratio of a cap ring is below 0.625.

• Journal of the Korean institute of surface engineering
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• v.42 no.6
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• pp.256-259
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• 2009

The wafer surface temperature is an important parameter in the etching process which influences the reaction probabilities of incident species, the vapor pressure of etch products, and the re-deposition of reaction products on feature surfaces. In this study, we investigated all of the effects of substrate temperature on the etch rate of $ZrO_2$ thin film and selectivity of $ZrO_2$ thin film over $SiO_2$ thin film in inductively coupled plasma as functions of $Cl_2$ addition in $BCl_3$/Ar plasma, RF power and dc-bias voltage based on the substrate temperature in range of $10^{\circ}C$ to $80^{\circ}C$. The elements on the surface were analyzed by x-ray photoelectron spectroscopy (XPS).

• Polymer(Korea)
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• v.32 no.2
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• pp.150-156
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• 2008

Two different polyacrylonitrile samples (PANs, triad tacticity fraction is 0.25 and 0.64) were synthesized and used to study the kinetics of cyclization. Polymers were treated at different temperatures between 250 to $300^{\circ}C$ under air atmosphere, and analyzed by X-ray diffractometer. The sharp and strong peak at $2{\theta}=16.5^{\circ}$ corresponds to a lateral repeat distance that is the (100) diffraction in hexagonal lattice, while the peak at $2{\theta}=25.5^{\circ}$ reflects the (101) diffraction. In comparing their areas of different heat treated samples, the cyclization of both PANs was identified as a first-order reaction. The rate constants of cyclization reaction at different temperatures and the active energy parameter were obtained. This results might provide an important effect on pre-oxidation of polyacrylonitrile fiber.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.20 no.3
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• pp.203-224
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• 2016

The heat and mass transfer characteristics of the unsteady hydromagnetic natural convection flow with Hall current and Soret effect of an incompressible, viscous, electrically conducting, heat absorbing and optically thin radiating fluid flow past a suddenly started vertical infinite plate through fluid saturated porous medium in a rotating environment are taken into account in this paper. Derivations of exact analytical solutions are aimed under different physical properties. The velocity, concentration and temperature profiles, Sherwood number and Nusselt number are easily examined and discussed via the closed forms obtained. Soret effect and permeability parameter tends to accelerate primary and secondary fluid velocities whereas hall current, radiation and heat absorption have reverse effect on it. Radiation and heat absorption have tendency to enhance rate of heat transfer at the plate. The results obtained here may be further used to verify the validity of obtained numerical solutions for more complicated transient free convection fluid flow problems.

• Proceedings of the IEEK Conference
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• 2003.07d
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• pp.1303-1306
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• 2003

In this paper, In this paper, we modeled a virtual life(VL) that react to the user's action according to its own behavioral characteristics and grows itself. We established some conditions with which such a VL is designed. Genetic Algorithm is used for the growth process that changes the VL's properties. In this process, the parameter values of the VL's properties are encoded as one chromosome, and the GA operations change this chromosome. The VL's reaction to the user's action is determined by these properties as well as the general expectation of each reaction. These properties are evaluated through 5 fitness measures so as to deal with multi-objective criteria. Here, we present the simulation of the growth process, and show some experimental results.

• Journal of the Korean Ceramic Society
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• v.36 no.10
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• pp.1108-1114
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• 1999

Microstructure and electrical properties of ZnO-doped (0-5 mol%) 0.05 Pb(Mn1/3Sb2/3)O3-0.95 PZT ceramics were investigated. Sintering temperature was decreased to 100$0^{\circ}C$ due to eutetic reaction between PbO and ZnO. Grain-size increased up to adding 1mol% ZnO and then decreased. Compositions of grain and grain-boundary were investigated by WDS. Lattice parameter was decreased with ZnO addition. Density increased with ZnO addition and reached to the maximum of 7.84(g/cm2) at 2 mol% ZnO. The effect of ZnO on electrical properties of PMS-PZT was investigated. At 3mol% ZnO addition electromechanical coupling factor(kp) was about 50% and relative dielectric constant($\varepsilon$33/$\varepsilon$0) was 997 Mechanical quality factor(Qm) decreased with ZnO addition. Lattice parameters and tetragonality(c/a) were measured to investigate relationship between the electric properties and substitution of Zn2+. At 3 mol% ZnO tetragonality was maximiged at c/a=1.0035 Curie temperature (Tc) decreased slightly with ZnO addition.

• Journal of Korean Society of Water and Wastewater
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• v.9 no.4
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• pp.115-123
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• 1995

The purpose of this study is to investigate the characteristics and performance of nitrogen and phosphorus removal system, Daewoo Nutrients Removal(DNR) system, and to find out the operating parameter for the system. During the study, $10m^3$ pilot plant was operated for the demonstration experiment and the primary effluent was taken from K domestic sewage treatment plant. The TN in the influent had been removed to approximately 70% through the nitrfication in the oxic tank and the denitrfication in the anoxic tank and the $PO_4-P$ and TP in the influent had been removed to 85% and 83% through anaerobic reaction and oxic reaction. The BOD and SS removal rate were 85 to 95% through the system. As the results, the values of effluent BOD, SS and slouble phosphorus were lower than A/O and $A^2/O$ processes. The SPRR (specific phosphorus release rate) at the anaerobic state of DNR system was ranged from 2.2 to 2.6mg SP/g VSS/h. The nutrient removal efficieny of the DNR system in view of the characteristics of the domestic sewage was higher than the pre-established A/O and $A^2/O$ processes. Finally, we believe that the DNR system was superior to the processes deveolped recently.

• Transactions on Electrical and Electronic Materials
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• v.14 no.1
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• pp.12-15
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• 2013

In this study, we carried out an investigation of the etching characteristics (etch rate, and selectivity to $SiO_2$) of $ZrO_2$ thin films in a $CF_4$/Ar inductively coupled plasma (ICP) system. The maximum etch rate of 60.8 nm/min for $ZrO_2$ thin films was obtained at a 20 % $CF_4/(CF_4+Ar)$ gas mixing ratio. At the same time, the etch rate was measured as a function of the etching parameter, namely ICP chamber pressure. X-ray photoelectron spectroscopy (XPS) analysis showed efficient destruction of the oxide bonds by the ion bombardment, as well as an accumulation of low volatile reaction products on the etched surface. Based on these data, the ion-assisted chemical reaction was proposed as the main etch characteristics for the $CF_4$-containing plasmas.