• 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.

• Korean Journal of Optics and Photonics
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• v.3 no.4
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• pp.266-272
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• 1992

A coherent anti-Stokes Raman spectroscopy (CARS) technique is applied to measure temperature profile in a flame. The CARS signal is obtained with BOXCARS phase matching to get better spatial resolution. A program routine for calculating temperature of the flame from the measured CARS spectra is studied. The routine includes the line broadening mechnism of the molecules described with a modified energy gap (MEG) law by using the perturbation theory. We have found that the temperature profile obtained with the MEG law is properly fit with the results measured with a thermocoulpe and calculated with the adiabatic theory.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.12
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• pp.1196-1204
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• 2001

The rivulet is a narrow stream of liquid flowing down a solid surface. When the rivulet\`s flow rate exceeds a certain limit, it tends to meander exhibiting the instability of its interface. This analysis performs a perturbation analysis of this meandering rivulet assuming an inviscid flow possessing contact angle hysteresis at the contact line. The analysis reveals that the contact angle hysteresis as well as the velocity difference across the inter-face, strongly induces the instability of the liquid interface. Moreover, when the rivulet veto-city is low, it is predicted that the axisymmetric disturbance amplifies more rapidly than the anti-axisymmetric disturbance, which explains the emergence of the droplet flow at the low velocity regime.

• Journal of Satellite, Information and Communications
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• v.10 no.3
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• pp.121-126
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• 2015

This paper proposes a novel reconfigurable microstrip antenna based on alternating a perturbation structure to achieve circular polarization diversity. The proposed antenna consists of an annular ring microstrip radiator for simultaneously loading stub and slot perturbations which support right- and left-handed circular polarization senses and two PIN diodes for choosing the operating polarization sense. By controlling the states of two PIN diodes between perturbing slot and stub at one diagonal corner of the radiator, reconfigurable circular polarization senses of the proposed antenna are successfully obtained and alternated. The proposed antenna has been theoretically analyzed and experimentally demonstrated at 2.4 GHz of S-band for satellite communication system. The simulation and measurement results of the proposed antenna show in good agreement with the reflection coefficients, axial-ratios, realized antenna gains, and radiation patterns.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.6
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• pp.497-500
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• 2017

This paper proposes a circularly polarized microstrip antenna using an I-shape ground slot perturbation and a perpendicular feeding network. The proposed antenna consists of the symmetrical and perpendicular feeding and the microstrip square radiator loaded with the I-shape ground slot perturbation. The left-handed circular polarization(LHCP) formed by a 90-degree phase difference can be radiated by the perpendicular feeding network and the ground slot perturbation. An implemented antenna is designed for the use in the satellite communication system operated in S-band of 2.2 GHz, and is to be the 91 MHz of -10 dB bandwidth. The measured results of the antenna gain, far-field radiation pattern, and axial ratio agree well with the simulation results.

• Journal of the Korean Chemical Society
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• v.29 no.1
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• pp.23-30
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• 1985

PMO expressions for ${\pi}^{\ast}$-${\pi}^{\ast}$ orbital interaction have been derived. Important differences between ${\pi}$-${\pi}$ and ${\pi}^{\ast}$-${\pi}^{\ast}$ interactions predicted by PMO expressions are : (ⅰ) energy splitting in ${\pi}^{\ast}$-${\pi}^{\ast}$ interaction will be greater than that in ${\pi}$-${\pi}$ interaction, (ⅱ) energy change due to interaction will be more destabilizing in ${\pi}^{\ast}$-${\pi}^{\ast}$ than in ${\pi}$-${\pi}$ interaction. These predictions were borne out in experimental data and in results of MO theoretical computations. It was pointed out that both STeO-3G and INDO-LCBO methods underestimate ${\pi}^{\ast}$-${\pi}^{\ast}$ orbital interaction and in order to estimate properly with MO theoretical calculation, use of split valence basis set is required.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.7-11
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• 1991

The adaptive control of flexible joint manipulator is the focus of this paper. The full order flexible joint manipulator dynamic system does not allow the determination of a feedback linearization control as for rigid manipulators. This drawback is overcome by a model order reduction based on a singular perturbation strategy. The full order flexible joint manipulator dynamic model is adopted for derivation of the adaptive control law to damp out the elastic oscillations at the joints. It is shown that the joint position error will converge to zero asymptotically and that other signals remain bounded without precise knowledge of parameters of the manipulator and its joint flexibility.

• Water for future
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• v.26 no.1
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• pp.71-79
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• 1993

Nonlinear characteristics of air pressure variation and wave transformation of a fixed air-chamber structure are discussed theoretically and experimentally. Two analytical methods(method I and II) based on the perturbation method and Green's formula are employed in order to evaluate nonlinearities by the submerged and semi-submerged air-chamber structure. Moreover, an air compression model is newly developed to estimate the dynamic air pressure in the air-chamber inside the structure, assuming the Boyle-Charles's law with adiabatic process in the air pressure variation. Theoretical values of the method I considering evanescent mode waves at an fictious boundary, are in good agreement with those of method II employing the fictious boundary which is not affected by evanescent mode waves. Both theoretical values are shown to agree well with experimental values.

• The Korean Journal of Applied Statistics
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• v.24 no.5
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• pp.963-977
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• 2011

PCA(Principal Component Analysis) is a well-studied statistical technique and an important tool for handling multivariate data. Although many algorithms exist for PCA, most of them are unsuitable for real time applications or high dimensional problems. Since it is desirable to avoid extensive matrix operations in such cases, alternative solutions are required to calculate the eigenvalues and eigenvectors of the sample covariance matrix. Erdogmus et al. (2004) proposed Recursive PCA(RPCA), which is a fast adaptive on-line solution for PCA, based on the first order perturbation theory. It facilitates the real-time implementation of PCA by recursively approximating updated eigenvalues and eigenvectors. However, the performance of the RPCA method becomes questionable as the size of newly-added data increases. In this paper, we modified the RPCA method by taking advantage of the mathematical relation of eigenvalues and eigenvectors of sample covariance matrix. We compared the performance of the proposed algorithm with that of RPCA, and found that the accuracy of the proposed method remarkably improved.

• Nuclear Engineering and Technology
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• v.18 no.2
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• pp.78-84
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• 1986

An equation of material number density sensitivity coefficient is derived using first-order perturbation theory. The beginning of cycle of Super-Phenix I is taken as the reference system for this study. Effective multiplication factor of the reference system is defined as system response function and fuel enrichment and fuel effective density are chosen for the variation of reference input data since they are described by material number density which is a component of Boltzmann operator. The nuclear computational code system (KAERI-26 group cross section library/1DX/2DB/PERT-V) is employed for this calculation. Sensitivity coefficient of fuel enrichment on effective multiplication factor is 4.576 and sensitivity coefficient of effective fuel density on effective multiplication factor is 0.0756. This work shows that sensitivity methodology is lesser timeconsuming and gives more informations on important design parameters in comparison with the direct iterative calulation through large computer codes.