• Journal of the Korean Chemical Society
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• v.8 no.4
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• pp.142-146
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• 1964

The author proposed an equation of fading rate, expressed as ${\Delta}E$=${\Delta}E_{1{\infty}}({{1-e^{-k}}_1}^t)+k_2t$, where ${\Delta}E$=fading of dye (colour difference of N.B.S. unit), ${\Delta}E_{1{\infty}}$=extremity value of fading of molecularly dispersed dye, $k_1$, $k_2$=constants, t=exposure (hours). The validity of above equation, which is connected with the state of dye in fibre, was confirmed by experimental in a range of 2-3 colour fading in grey scale value for assessing change in colour visually, except the case of increasing the fading rate with the time resulted from the break-down of dye particles through the heat effect of light; it was also discussed about possiblity of evaluating of fastness to light of dye in early stage.

• Journal of the Korean Mathematical Society
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• v.33 no.2
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• pp.381-386
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• 1996

We consider the behavior of positive radial solutions (or, briefly, pp.r.s.) of the equation $$ (1.1) ^\Delta u + \lambda f(u) = 0 in\Omega, _u = 0 on \partial\Omega, $$ where $\Omega = {x \in R^n$\mid$A < $\mid$x$\mid$ < B}$ is an annulus in $R^n, n \geq 2, \lambda > 0 and f \geq 0$ is superlinear in u and satisfies f(0) = 0.

• Journal of the Korean Home Economics Association
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• v.46 no.7
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• pp.1-6
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• 2008

The purpose of this study was to investigate the changes in properties of silk fabrics dyed with safflower red and yellow colorants under Ultraviolet(UV)-light. Silk fabrics dyed with safflower red and yellow colorants were compared with each other after uv-light exposure in terms of K/S value, color changes(${\Delta}E$), morphology, and strength retention. The K/S value rapidly decreased with increasing exposure time for samples of both colorants, but the extent of decrease was less for the samples dyed with safflower yellow colorant, than that of the samples dyed with safflower red colorant. Regarding the color changes with increasing exposure time, $L^*$ and $b^*$ increased, $a^*$ decreased, and thereby ${\Delta}E$ increased in the red-dyed samples, whereas $L^*$ increased, $a^*$ and $b^*$ decreased, and so ${\Delta}E$ increased in the yellow-dyed samples, indicating that the UV-light induced fading and changes of hue, value and chroma value. However, the color change of the yellow-dyed samples was less than that of the red-dyed samples. SEM images showed a severe degradation by UV-exposure for both colorant samples. Tensile strength slowly decreased until 14 days, but rapidly decreased thereafter. Strength retention of the yellow-dyed samples was higher than that of red-dyed samples.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.12 no.4
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• pp.261-269
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• 2008

Let $B_1$ be a unit ball in $R^n(n{\geq}3)$, and $2^*=2n/(n-2)$ be the critical Sobolev exponent for the embedding $H_0^1(B_1){\hookrightarrow}L^{2^*}(B_1)$. By using a variant of Pohoz$\check{a}$aev's identity, we prove the nonexistence of nodal solutions for the Dirichlet problem $-{\Delta}u-{\mu}\frac{u}{{\mid}x{\mid}^2}={\lambda}u+{\mid}u{\mid}^{2^*-2}u$ in $B_1$, u=0 on ${\partial}B_1$ for suitable positive numbers ${\mu}$ and ${\nu}$.

• Journal of applied mathematics & informatics
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• v.27 no.5_6
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• pp.1119-1132
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• 2009

In this paper, we consider the quasilinear elliptic system $\\div(|{\nabla}u|^{p-2}{\nabla}u)=u(a_1u^{m1}+b_1(x)u^m+{\delta}_1v^n),\;\\div(|{\nabla}_v|^{q-2}{\nabla}v)=v(a_2v^{r1}+b_2(x)v^r+{\delta}_2u^s)$, in $\Omega$ where m > $m_1$ > p-2, r > $r_1$ > q-, p, q $\geq$ 2, and ${\Omega}{\subset}R^N$ is a smooth bounded domain. By constructing certain super and subsolutions, we show the existence of positive blow-up solutions and give a global estimate.

• Transactions of the Korean Society of Mechanical Engineers
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• v.7 no.4
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• pp.425-433
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• 1983

Fatigue tests by axial loading (R=0.1) were carried out to investigate fatigue crack growth properties of small surface cracks in mild steel at room temperature, 250.deg. C and 400.deg. C, by using flat specimens with a small artificial pit. All the data of the fatigue crack growth rate obtained in the present tests are determined as a function of the stress intensity factor range, so that the applicability of liner fracture mechanics to the fatigue crack growth of surface cracks at elevated temperatures is investigated and discussed in comparison with the data of type 304 stainless steel at room temperature and elevated temperature. The obtained results are as follows: 1) Relations of both surface fatigue crack length and its depth to cycle ratio fall within a narrow scatter band in spite of different stress levels. 2) The .DELTA. .sigma. .root. .pi. a-da/dN relation of surface fatigue crack growth at room temperature is independent of the stress level and can be plotted as a straight line at log-log diagram, but the relation at 400.deg. C depends partly on the stress level. 3) Relations of the fatigue crack growth into depth d(2b)/dN and is stress intensity factor range .DELTA. $K_{I}$, accounted for the aspect ratio variation, fall within a narrow scatter band for wide range of the applied stress levels. And .DELTA. $K_{I}$E-d(2b)/dN relations of mild steel at different stress level coincide relatively well with the data of type 304 stainless steel. 4) The value of aspect ratio obtained by a beach mark method and a temper coloring method approaches about 0.9 in common with crack growth and it is independent of stress level and temperatures. 5) The equi-crack length curve is parallel to S-N$_{f}$ curve at elevated temperatures.s.s.s.

• 한국전산유체공학회:학술대회논문집
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• 2006.10a
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• pp.31-35
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• 2006

The delta-formulation of the Navier-Stokes equations has been popularly used in the aerodynamics area. Implicit algorithm can be easily implemented in that by using Taylor series expansion. This formulation is extended for an unsteady analysis by using a dual-time integration. In the meanwhile, the incompressible flows with heat transfers which occur in the area of thermo-hydraulics have been solved by a segregated algorithm such as the SIMPLE method, where each equation is discretised by using an under-relaxed deferred correction method and solved sequentially. In this study, the dual-time delta formulation is implemented in the segregated Navier-Stokes solver which is based on the collocated cell-centerd scheme with un unstructured mesh FVM. The pressure correction equation is derived by the SIMPLE method. From this study, it was found that the Euler dual-time method in the delta formulation can be combined with the SIMPLE method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.1
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• pp.9-15
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• 2015

A CMOS band-pass delta-sigma modulator(BPDSM) and cascode class-E power amplifier have been developed CMOS for Class-S power amplifier applications. The BPDSM is operating at 1-GHz sampling frequency, which converts a 250-MHz sinusoidal signal to a pulse-width modulated digital signal without the quantization noise. The BPDSM shows a 25-dB SQNR(Signal to Quantization Noise Ratio) and consumes a power of 24 mW at an 1.2-V supply voltage. The class-E power amplifier exhibits an 18.1 dBm of the maximum output power with a 25% drain efficiency at a 3.3-V supply voltage. The BPDSM and class-E PA were fabricated in the Dongbu's 110-nm CMOS process.

• The Pure and Applied Mathematics
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• v.5 no.1
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• pp.23-32
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• 1998

In the present paper the author studies the decomposition property ($\delta$) of the bounded linear operators.

• ETRI Journal
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• v.31 no.1
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• pp.74-76
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• 2009

A new feeding method for the circular polarization (CP) dielectric resonator antenna (DRA) is proposed in this letter. Two orthogonal modes (${TE^x}_{{\delta}11}$, ${TE^y}_{1{\delta}1$) of the rectangular DRA are excited by a $90^{\circ}$ phase difference of the differential and common modes currents of the proposed feeding structure. To demonstrate the good CP performance of the proposed method, a right-hand CP DRA for a global positioning system was designed. The impedance bandwidth of the proposed antenna for $S_{11}$ < -10 dB and 3 dB axial ratio bandwidth are about 5.4% and 1.95% at 1.57 GHz, respectively.