• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.35.3-35.3
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• 2018

Incorporating the fully quantum mechanical computation of scattering cross-section and statistical moment analysis of absorption profiles, we investigate the Lyman line asymmetry of extremely high column density systems. Recent high redshift observations detected strong damped Lyman alpha systems (DLAs) whose column density is larger than N_HI ~ [10]^21.3 cm^(-2). Absorption profiles of these DLAs are characterized by the broad and asymmetric damping wing. For accurate description of radiation damping, the second-order time-dependent perturbation theory is adopted. To quantitatively address line asymmetry, we define a distribution function for each Lyman line, and compute statistical moments (mean, standard deviation, skewness and kurtosis) regarding column densities N_HI > [10]^18 cm^(-2). In this work, we present statistical properties of the intrinsic line profiles, and compare them with the Lorentzian cases.

• Journal of applied mathematics & informatics
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• v.6 no.1
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• pp.175-184
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• 1999

Along with the computation and analysis for nonlinear system being more and more involved in the fields such as automation control electronic technique and electrical power system the nonlin-ear theory has become quite a attractive field for academic research. In this paper we derives the solutions for state equation of nonlinear system by using the inverse operator expression of the so-lutions is obtained. An actual computation example is given giving a comparison between IOM and Runge-kutta method. It has been proved by our investigation that IOM has some distinct advantages over usual approximation methods in that it is computationally con-venient rapidly convergent provides accurate solutions not requiring perturbation linearization or the massive computation inherent in discrietization methods such as finite differences. So the IOM pro-vides an effective method for the solution of nonlinear system is of potential application valuable in nonlinear computation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.7
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• pp.1119-1124
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• 2001

Nonlinear Vibration of a flexible circular ring is studied in this paper. Based upon the von Karman strain theory, the nonlinear governing equations are derived, in which the in-plane bending and extension displacements as well as the out-of-plane bending displacement are fully coupled. After discretizing the governing equations by the Galerkin approximation method, we obtain the linearlized equation by using the pertubation method. The results from the linearlized equations show that the in-plane displacement has effects on the natural frequencies of the out-of-plane displacement.

• Journal of the Korean Mathematical Society
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• v.54 no.5
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• pp.1573-1594
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• 2017

This paper deals with the existence and energy estimates of solutions for a class of degenerate nonlocal problems involving sub-linear nonlinearities, while the nonlinear part of the problem admits some hypotheses on the behavior at origin or perturbation property. In particular, for a precise localization of the parameter, the existence of a non-zero solution is established requiring the sublinearity of nonlinear part at origin and infinity. We also consider the existence of solutions for our problem under algebraic conditions with the classical Ambrosetti-Rabinowitz. In what follows, by combining two algebraic conditions on the nonlinear term which guarantees the existence of two solutions as well as applying the mountain pass theorem given by Pucci and Serrin, we establish the existence of the third solution for our problem. Moreover, concrete examples of applications are provided.

• Journal of the Korean Mathematical Society
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• v.57 no.1
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• pp.171-194
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• 2020

For a nonautonomous dynamics defined by a sequence of bounded linear operators on a Banach space, we give a characterization of the existence of an exponential dichotomy with respect to a sequence of norms in terms of the invertibility of a certain linear operator between general admissible spaces. This notion of an exponential dichotomy contains as very special cases the notions of uniform, nonuniform and tempered exponential dichotomies. As applications, we detail the consequences of our results for the class of tempered exponential dichotomies, which are ubiquitous in the context of ergodic theory, and we show that the notion of an exponential dichotomy under sufficiently small parameterized perturbations persists and that their stable and unstable spaces are as regular as the perturbation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.7 no.3
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• pp.120-124
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• 1982

In this paper, the theoretical analysis of lateral guiding in stripe geometry DH Laser Diode is performed. In the analysis, the gain & refractive index variations in active layer are modeled by very analogous methmatical function to their real profile and the two dimensional lateral waveguiding of DH LD have been analyzed by perturbation theory. Finally, the beam width dependence of refractive index variation(n), active layer width(d), and cavity length(L), have been analyzed.

• Journal of the Korean Magnetics Society
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• v.10 no.1
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• pp.22-29
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• 2000

The effective linewidth was measured using the conventional cavity perturbation method at 9.43 GHz in room temperature for Ca-Zr substituted yttrium iron garnet plate. The experimental set-up consists of the network analyzer, the electromagnet and the cylimdrical TE001 cavity. Measurement was performed in the static magnetic field perpendicular to the sample plane. The real and imaginary parts of diagonal component of the microwave susceptibility tensor are obtained from the resonance frequency and the quality factor Q of the cavity. Variations of the effective linewidth was qualitatively explained with the spin wave scattering theory.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.51.2-51.2
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• 2011

We have studied the topology of volume-limited galaxy sample selected from the very luminous red galaxies (LRGs) in the completed Sloan Digital Sky Survey. LRGs are predominantly massive elliptical galaxies and tend to reside in massive dark matter halos. We compared the observed genus statistics with predictions from perturbation theory and mock LRG surveys constructed from dark matter halos in a Lambda CDM model. To compare with the observational data, we made 129 mock surveys in the past light cone space by using three different size CDM simulations: 41203 particle 6592 Mpc/h, 60003 particle 7200 Mpc/h, and $7210^3$ particle 10815 Mpc/h.

• Structural Engineering and Mechanics
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• v.31 no.5
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• pp.481-506
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• 2009

The present study is concerned with the stochastic linear free vibration study of laminated composite plate embedded with piezoelectric layers with random material properties. The system equations are derived using higher order shear deformation theory. The lamina material properties of the laminate are modeled as basic random variables for accurate prediction of the system behavior. A $C^0$ finite element is used for spatial descretization of the laminate. First order Taylor series based mean centered perturbation technique in conjunction with finite element method is outlined for the problem. The outlined probabilistic approach is used to obtain typical numerical results, i.e., the mean and standard deviation of natural frequency. Different combinations of simply supported, clamped and free boundary conditions are considered. The effect of side to thickness ratio, aspect ratio, lamination scheme on scattering of natural frequency is studied. The results are compared with those available in literature and an independent Monte Carlo simulation.

• Macromolecular Research
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• v.11 no.4
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• pp.241-249
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• 2003

A molecular-thermodynamic model to describe the salt-induced protein precipitation is developed based on the perturbation theory. We employed the modified perturbed hard-sphere-chain (PHSC) equation of state for copolymer mixtures to take into account the pre-aggregation effect among protein particles. Hypothetical pressure-composition diagrams are computed with various size differences and salt concentrations. The precipitation behaviors are also studied for various types of pre-aggregation effect for the given systems.