• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.17 no.3
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• pp.171-179
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• 2013

In this paper we present a method of circular arc approximation by quartic B$\acute{e}$zier curve. Our quartic approximation method has a smaller error than previous quartic approximation methods due to the alternation of the error function of our quartic approximation. Our method yields a closed form of error so that subdivision algorithm is available, and curvature-continuous quartic spline under the subdivision of circular arc with equal-length until error is less than tolerance. We illustrate our method by some numerical examples.

• Journal of the Korean Graphic Arts Communication Society
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• v.11 no.1
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• pp.103-122
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• 1993

A cause and counterplan of the increase in dark decay rate of$\varepsilon$-CuPc/PVCz photoreceptor which is consist of the carrier generation layer (CGL) of$\varepsilon$type copper phthalocyanine ($\varepsilon$-CuPc) thin film by an aqueous coating method and the carrier transport layer (CTL) of polyvinylcarbazol (PVCz) by spin coating, are studied in this paper. Electrochemical deposition of CGL was accompanied by an increase in work function of the aluminium substrate during the processes and the enhanced work function 5.3 eV rose above the ionization potential 5.16 eV of $\varepsilon$-CuPc. This resulted in the increased injection of holes from substrate into CGL and a fast dark decay rate. Improved photoreceptor, an electron-transport $\varepsilon$-CuPc/TNF photoreceptor, led to lowing of dark decay rate and increasing of photosensitivity. The carrier generation efficiency (ηg), carrier injection efficiency (ηi) and xerographic gain (G) of the $\varepsilon$-CuPc/TNF photoreceptor were obtained by XTOF method and PIDC.

• Bulletin of the Korean Mathematical Society
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• v.53 no.6
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• pp.1805-1821
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• 2016

In this paper, we are concerned with the nonlinear elliptic equations of the p(x)-Laplace type $$\{\begin{array}{lll}-div(a(x,{\nabla}u))+{\mid}u{\mid}^{p(x)-2}u={\lambda}f(x,u) && in\;{\Omega}\\(a(x,{\nabla}u)\frac{{\partial}u}{{\partial}n}={\lambda}{\theta}g(x,u) && on\;{\partial}{\Omega},\end{array}$$ which is subject to nonlinear Neumann boundary condition. Here the function a(x, v) is of type${\mid}v{\mid}^{p(x)-2}v$ with continuous function $p:{\bar{\Omega}}{\rightarrow}(1,{\infty})$ and the functions f, g satisfy a $Carath{\acute{e}}odory$ condition. The main purpose of this paper is to establish the existence of at least three solutions for the above problem by applying three critical points theory due to Ricceri. Furthermore, we localize three critical points interval for the given problem as applications of the theorem introduced by Arcoya and Carmona.

• Composites Research
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• v.12 no.1
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• pp.1-10
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• 1999

In order to predict the dynamic behavior of composite laminated plate accurately, the parametric identification is performed using its mechanical properties- $E_1,\;E_2,\;V_{12},\;G_{12}$ as design parameters. After natural frequencies are measured through simple vibration test, the objective function consists of the sum of errors between experimental and numerical frequencies of a structure. As optimization algorithm, conjugate gradient method is used to minimize the objective function. Sensitivity Analysis is performed to update design parameters during this process and can explain the result of parametric identification. In order to check the propriety of result, mode shapes are compared before and after identification. The improved prediction of natural frequencies of composite laminated plate is obtained with updated properties. For the application of result, updated properties is applied to the composite laminated plate that has different stacking sequence.

• Korean Journal of Materials Research
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• v.5 no.6
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• pp.690-698
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• 1995

The Poly-S $i_{1-x}$G $e_{x}$ thin films were deposited on oxidized Si wafer by RTCVD(rapid thermal chemical vapor deposition) using Si $H_4$and Ge $H_4$, at 450 ~5$50^{\circ}C$. The variation of Ge mole fraction and the deposition rate of S $i_{1-x}$G $e_{x}$ thin film were studied as a function of the deposition temperature and the Ge $H_4$/Si $H_4$input ratio, and the crystal phase and the surface roughness were studied by XRD and AFM(atomic force microscopy), respectively. The experimental results showed that the activation energy for the deposition of poly-S $i_{1-x}$G $e_{x}$ was about 32~37Kca /mol and the deposition rate of S $i_{1-x}$G $e_{x}$ thin films was increased with increasing the deposition temperature and the input ratio. From the analysis of composition, it was known that the Ge mole fraction within the poly-S $i_{1-x}$G $e_{x}$ thin film was decreased with decreasing the input ratio and increasing the deposition temperature. As-deposited S $i_{1-x}$G $e_{x}$ thin films were polycrystalline over the entire experimental range. But those were amorphous at the deposition temperature of 450, 475$^{\circ}C$ and the input ratio of 0.05. By adding the Ge $H_4$, poly-S $i_{1-x}$G $e_{x}$ thin film were deposited at relatively lower deposition temperatures($\leq$ 5$50^{\circ}C$) than those of conventional poly-Si(>$600^{\circ}C$). From surface roughness measurement of poly-S $i_{1-x}$G $e_{x}$ it was found that the surface roughness( $R_{i}$ ) increased with increasing the deposition temperature and input ratio.and input ratio.

• Safety and Health at Work
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• v.10 no.1
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• pp.47-53
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• 2019

Background: Despite growing concern over occupational exposure to particulate matter (PM) such as grain dust and diesel exhaust, information about the exposure level and health implications among workers in small-scale milling enterprises in developing countries like Nigeria has not been adequately documented. The purpose of this study was to assess the level of exposure to grain dust and diesel exhaust and effect on lung function among grain millers in food markets in Ibadan metropolis, Nigeria. Methods: The study adopted descriptive cross-sectional design with a comparative approach. Sixteen grain milling shops each were randomly selected from two major food markets in Ibadan metropolis for indoor $PM_{10}$ and $PM_{2.5}$ monitoring. Seventy-two respondents each were proportionately selected from grain millers and shop owners for forced expiratory volume in one second and peak expiratory flow rate tests. Results: The $PM_{2.5}$ concentrations for both market locations ranged between 1,269.3 and $651.7{\mu}g/m^3$, while $PM_{10}$ concentrations were between 1,048.2 and $818.1{\mu}g/m^3$. The recorded concentrations exceeded the World Health Organization guideline limit of $50{\mu}g/m^3$ and $25{\mu}g/m^3$ for $PM_{2.5}$ and $PM_{10}$, respectively. As compared with control group (2.1 L), significantly lower forced expiratory volume in one second value (1.61 L) was observed among the exposed group (p < 0.05). Likewise, significantly lower peak expiratory flow rate value (186.7 L/min) was recorded among the exposed group than the control group (269.51 L/min) (p < 0.05). Conclusion: Exposure to grain dust and diesel exhaust accentuated respiratory disorders with declines in lung functions amongst grain millers. Improved milling practices and engaging cleaner milling facilities should be adopted to minimize exposure and related hazards.

• Journal of Korea Port Economic Association
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• v.20 no.2
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• pp.217-234
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• 2004

Information technology has been transforming the relationship between shippers and carriers, but an unresolved question remains: what is the relative importance to shippers of service versus cost benefits of e-logistics solutions? This research develops and empirically tests a model to determine how Internet-based logistical operations in international shipping impact on the relative importance of cost versus service benefits to shippers. Contrary to expectations, results show that shippers perceived cost benefits from well-designed web sites, undoubtedly a consequence of perceptions that multi-function portals with ease of access contributed to savings in time and money. Another result was the confirmation of the positive effects of cargo tracing and bill of lading issuance on service-related factors. Finally, this study draws attention to the need for improvements in on-line booking capabilities and development of a comprehensive common portal; issues that must be addressed for shipping lines to succeed in an increasingly competitive e-logistics market.

• Membrane and Water Treatment
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• v.2 no.1
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• pp.63-74
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• 2011

A spiral wound nanofiltration (NF) membrane (GE Osmonics, DK 4040F) was used to remove pesticides from water. Several solutions of single pesticides and their mixtures were prepared. The pesticides initial concentration ranged from ca. 50 ng/L (single pesticide) to ca. 700 ng/L (as sum of 14 pesticides) and progressively increased with time since the NF experiments were carried out in a concentration mode up to a Volume Concentration Ratio, VCR = 10. Permeate flux and pesticides retention were evaluated as a function of the Volume Concentration Ratio. The permeate flux did not practically change by varying VCR. Pesticide retention was found to be around 97-98% both in the cases of single pesticide solutions and different mixtures of pollutants, and was not affected by the VCR. Pesticides concentration in permeate samples was found to be lower than the maximum concentration level fixed in European directive.

• Korean Journal of Mathematics
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• v.6 no.1
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• pp.67-70
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• 1998

Let ${\eta}(\tau)=q^{1/24}\prod_{n=1}^{\infty}(1-q^n)$, where $q=e^{2{\pi}i{\tau}}$ and ${\tau}{\in}\mathbb{C}$. Then the transformation $$g(\tau)={\rho}\frac{\{\eta(\frac{\tau+1}{2})\eta(\frac{\tau+2}{2})\}^{16}}{\eta(\tau)^{24}}({\bar{{\rho}}{\eta}}(\frac{\tau+1}{2})^8+{\eta}(\frac{\tau+2}{2})^8)^2$$ is holomorphic for Im ${\tau}$ > 0, and has the property $$g(\tau+1)=g(\tau),\;g(-\frac{1}{\tau})={\tau}^{12}g(\tau)$$. (Theorem)

• Journal of the Korean Mathematical Society
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• v.55 no.3
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• pp.735-747
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• 2018

Let M be a real hypersurface of a complex space form with constant curvature c. In this paper, we study the hypersurface M admitting Miao-Tam critical metric, i.e., the induced metric g on M satisfies the equation: $-({\Delta}_g{\lambda})g+{\nabla}^2_g{\lambda}-{\lambda}Ric=g$, where ${\lambda}$ is a smooth function on M. At first, for the case where M is Hopf, c = 0 and $c{\neq}0$ are considered respectively. For the non-Hopf case, we prove that the ruled real hypersurfaces of non-flat complex space forms do not admit Miao-Tam critical metrics. Finally, it is proved that a compact hypersurface of a complex Euclidean space admitting Miao-Tam critical metric with ${\lambda}$ > 0 or ${\lambda}$ < 0 is a sphere and a compact hypersurface of a non-flat complex space form does not exist such a critical metric.