• Korean Journal of Mathematics
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• v.15 no.1
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• pp.51-57
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• 2007

We prove the existence of a positive solution for the system of the following nonlinear biharmonic equations with Dirichlet boundary condition $$\{{\Delta}^2u+c{\Delta}u+av^+=s_1{\phi}_1+{\epsilon}_1h_1(x)\;in\;{\Omega},\\{\Delta}^2v+c{\Delta}v+bu^+=s_2{\phi}_1+{\epsilon}_2h_2(x)\;in\;{\Omega},$$ where $u^+= max\{u,0\}$, $c{\in}R$, $s{\in}R$, ${\Delta}^2$ denotes the biharmonic operator and ${\phi}_1$ is the positive eigenfunction of the eigenvalue problem $-{\Delta}$ with Dirichlet boundary condition. Here ${\epsilon}_1$, ${\epsilon}_2$ are small numbers and $h_1(x)$, $h_2(x)$ are bounded.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.8
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• pp.72-79
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• 1994

In this paper semi empirical models are presented for the hot electron induced threshold voltage shift(${\Delta}V_{t}$) and effective channel shortening length (${\Delta}L_{H}$) in degraded PMOSFET. Trapped electron charges in gate oxide are calculated from the well known gate current model and ΔLS1HT is calculated by using trapped electron charges. (${\Delta}L_{H}$) is a function of gate stress voltage such as threshold voltage shift and degradation of drain current. From the correlation between (${\Delta}L_{H}$) has a logarithmic function of stress time. From the measured results, (${\Delta}V_{t}$) and (${\Delta}L_{H}$) are function of initial gate current and device channel length.

• Bulletin of the Korean Chemical Society
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• v.6 no.5
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• pp.259-263
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• 1985

Rate Constants for the solvolysis of p-methylbenzyl chloride in various ethanol-water mixtures were studied at 30 and $40^{\circ}C$ under various pressures up to 1600 bar. The rates of reaction were increased with increasing temperature and pressure, and decreased with increasing solvent composition of ethanol mole fraction. From the rate constants, the values of the activation parameters (${\Delta}V^{\neq},{\Delta}{\beta}^{\neq},{\Delta}H^{\neq}\;and\;{\Delta}S^{\neq}$) were evaluated. The values of ${\Delta}V^{\neq}\;and\;{\Delta}{\beta}^{\neq}$ exhibit the extremum behavior at about 0.30 mole fraction of ethanol. This behavior is discussed in terms of solvent structure variation (electrostriction). From the relation between the reaction rate and the dielectric constant of solvent or the number of water molecule participated in the transition state, it could be postulated that the reaction proceeds through $S_N1$ mechanism.

• Journal of Astronomy and Space Sciences
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• v.28 no.3
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• pp.203-216
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• 2011

To prepare for a future Korean lunar orbiter mission, semi-optimal lunar capture orbits using finite thrust are designed and analyzed. Finite burn delta-V losses during lunar capture sequence are also analyzed by comparing those with values derived with impulsive thrusts in previous research. To design a hypothetical lunar capture sequence, two different intermediate capture orbits having orbital periods of about 12 hours and 3.5 hours are assumed, and final mission operation orbit around the Moon is assumed to be 100 km altitude with 90 degree of inclination. For the performance of the on-board thruster, three different performances (150 N with $I_{sp}$ of 200 seconds, 300 N with $I_{sp}$ of 250 seconds, 450 N with $I_{sp}$ of 300 seconds) are assumed, to provide a broad range of estimates of delta-V losses. As expected, it is found that the finite burn-arc sweeps almost symmetric orbital portions with respect to the perilune vector to minimize the delta-Vs required to achieve the final orbit. In addition, a difference of up to about 2% delta-V can occur during the lunar capture sequences with the use of assumed engine configurations, compared to scenarios with impulsive thrust. However, these delta-V losses will differ for every assumed lunar explorer's on-board thrust capability. Therefore, at the early stage of mission planning, careful consideration must be made while estimating mission budgets, particularly if the preliminary mission studies were assumed using impulsive thrust. The results provided in this paper are expected to lead to further progress in the design field of Korea's lunar orbiter mission, particularly the lunar capture sequences using finite thrust.

• Journal of the Korean Mathematical Society
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• v.47 no.4
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• pp.735-742
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• 2010

In this paper, we define and study the concept of $\wedge^s_{\delta}$-closure operator and the associated topology $\tau^{\wedge}^s_{\delta}$ on a topological space (X, $\tau$) in terms of g.$\wedge^s_{\delta}$-sets.

• Korean Journal of Mathematics
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• v.16 no.3
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• pp.259-269
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• 2008

The non-existence and existence of the positive solution for the generalized cooperation biological model for two species of animals $${\Delta}u+u(a-bu+g(v))=0\;in\;{\Omega}\\{\Delta}v+v(d+h(u)-cv)=0\;in\;{\Omega}\\u=v=0\;on\;{\partial}{\Omega}$$ are investigated. The techniques used in this paper are elliptic theory, upper-lower solutions, maximum principles and spectrum estimates. The arguments also rely on some detailed properties for the solution of logistic equations.

• Journal of the Chungcheong Mathematical Society
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• v.21 no.1
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• pp.139-146
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• 2008

We investigate the uniqueness and multiplicity of solutions for the nonlinear elliptic system with Dirichlet boundary condition $$\{-{\Delta}u+g_1(u,v)=f_1(x){\text{ in }}{\Omega},\\-{\Delta}v+g_2(u,v)=f_2(x){\text{ in }}{\Omega},$$ where ${\Omega}$ is a bounded set in $R^n$ with smooth boundary ${\partial}{\Omega}$. Here $g_1$, $g_2$ are nonlinear functions of u, v and $f_1$, $f_2$ are source terms.

• Journal of applied mathematics & informatics
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• v.27 no.5_6
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• pp.1435-1446
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• 2009

In this paper we investigate the blow up properties of the positive solutions to a semi linear parabolic system with coupled nonlocal sources $u_t={\Delta}u+k_1{\int}_{\Omega}u^{\alpha}(y,t)v^p(y,t)dy,\;v_t={\Delta}_v+k_2{\int}_{\Omega}u^q(y,t)v^{\beta}(y,t)dy$ with non local Dirichlet boundary conditions. We establish the conditions for global and non-global solutions respectively and obtain its blow up set.

• Journal of the Korean Magnetic Resonance Society
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• v.1 no.1
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• pp.1-6
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• 1997

Several dioxovanadate (V) complexes are synthesized and studied by solution and solid-state 51V NMR spectroscopy. In the results, large 51V chemical shift anisotropy ({{{{ DELTA delta }}a = -800 ∼720 ppm) and quadrupole coupling (e2q /h = 7.50 ∼ 9.16 MHz) were observed in the solid-state complexes. The isotropic chemical shifts of the solid samples are very close to the values obtained from solution measurements.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.569-572
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• 2014

This paper presents a CMOS switched-capacitor interface circuit for MEMS capacitive sensors. It consist of a capacitance to voltage converter(CVC), a second-order ${\Sigma}{\Delta}$ modulator, and a comparator. A bias circuit is also designed to supply constant bias voltages and currents. This circuit employes the correlated-double-sampling(CDS) and chopper-stabilization(CHS) techniques to reduce low-frequency noise and offset. The designed CVC has a sensitivity of 20.53mV/fF and linearity errors less than 0.036%. The duty cycle of the designed ${\Sigma}{\Delta}$ modulator output increases about 5% as the input voltage amplitude increases by 100mV. The designed interface circuit shows linearity errors less than 0.13%, and the current consumption is 0.73mA. The proposed circuit is designed in a 0.35um CMOS process with a supply voltage of 3.3V. The size of the designed chip including PADs is $1117um{\times}983um$.