• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 B
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• pp.734-736
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• 1996

This paper presents a method of calculating a selective number of eigenvalues in power systems, which are rightmost, or are largest modulus. The modified Arnoldi method in conjunction with implicit shift OR-algorithm is used to calculate the rightmost eigenvalues. Algorithm requires neither a prior knowledge of the specified shifts nor the calculation of inverse matrix. The key advantage of the algorithm is its ability to converge to the wanted eigenvalues at once. The method is compared with the modified Arnoldi method combined with S-matrix transformation, where the eigenvalues having the largest modulus are to be determined. The two methods are applied to the reduced Kansai system. Convergence characteristics and performances are compared. Results show that both methods are robust and has good convergence properties. However, the implicit shift OR method is seen to be faster than the S-matrix method under the same condition.

• Structural Engineering and Mechanics
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• 제43권1호
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• pp.89-103
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• 2012

In this study, the stability of laminated homogeneous and non-homogeneous orthotropic truncated conical shells with freely supported edges under a uniform hydrostatic pressure is investigated. It is assumed that the composite material is orthotropic and the material properties depend only on the thickness coordinate. The basic relations, the modified Donnell type stability and compatibility equations have been obtained for laminated non-homogeneous orthotropic truncated conical shells. Applying Galerkin method to the foregoing equations, the expression for the critical hydrostatic pressure is obtained. The appropriate formulas for the single-layer and laminated, cylindrical and complete conical shells made of homogeneous and non-homogeneous, orthotropic and isotropic materials are found as a special case. Finally, effects of non-homogeneity, number and ordering of layers and variations of shell characteristics on the critical hydrostatic pressure are investigated.

• Geomechanics and Engineering
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• 제31권4호
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• pp.375-384
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• 2022

The variation of the undrained shear strength (c_u) is an important consideration for assessing slope stability in engineering practice. Previous studies focused on the three-dimensional (3D) stability of slopes in normally consolidated clays generally assume the undrained shear strength increases linearly with depth but does not vary in the horizontal direction. To assess the 3D stability of slopes with spatially varying undrained shear strength, the kinematic approach of limit analysis was adopted to obtain the upper bound solution to the stability number based on a modified failure mechanism. Three types failure mechanism: the toe failure, face failure and below-toe failure were considered. A serious of charts was then presented to illustrate the effect of key parameters on the slope stability and failure geometry. It was found that the stability and failure geometry of slopes are significantly influenced by the gradient of c_u in the depth direction. The influence of c_u profile inclination on the slope stability was found to be pronounced when the increasing gradient of c_u in the depth direction is large. Slopes with larger width-to-height ratio B/H are more sensitive to the variation of c_u profile inclination.

• 제어로봇시스템학회논문지
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• 제5권2호
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• pp.237-247
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• 1999

Flight parameters of a light aircraft in normal category named ChangGong-91 we identified from flight tests. Modified Maximum Likelihood Estimation (MMLE) is used to produce aerodynamic coefficients, stability and control derivatives. A Flight Training Device (FTD) has been developed based on the identified flight parameters. Flat earth, rigid body, and standard atmosphere are assumed in the FTD model. Euler angles are adapted for rotational state variables to reduce computational load. Variations in flight Mach number and Reynolds number are assumed to be negligible. Body, stability and inertial axes allow 6 second-order linear differential equations for translational and rotational motions. The equations of motion are integrated with respect to time, resulting in good agreements with flight tests.

• 한국안전학회지
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• 제15권1호
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• pp.36-42
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• 2000

An experimental study was carried out to investigate the effects of inclined angles of channel on thermal stability of electronic components. In this study, it is focused on the natural convection heat transfer from an inclined parallel channel with discrete protruding heat sources. The material used for the inclined parallel channel was epoxy-resin, while air as the cooling fluid. Heat transfer phenomena for inclined angles of $\psi$=$15^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$ and for the range of $9.52{\times}10^5/ were analyzed. The thermal fields in the channel were visualized by Mach-Zehnder interferometer. Also, local temperatures were measured by thermocouples along the channel wall and heat sources surface. As a result, for the range of $4.29{\times} 10^5/, a useful correlation of mean Nusselt number was proposed as a function of modified channel Rayleigh number.

• Bulletin of the Korean Chemical Society
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• 제34권9호
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• pp.2685-2690
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• 2013

The activities of Au-modified Cu electrodes toward glucose oxidation are evaluated according to their fabrication conditions and physico-chemical properties. The Au-modified Cu electrodes are fabricated by the galvanic displacement of Au on a Cu substrate and the characteristics of the Au particles are controlled by adjusting the displacement time. From the glucose oxidation tests, it is found that the Au modified Cu has superior activity to the pure Au or Cu film, which is evidenced by the negative shift in the oxidation potential and enhanced current density during the electrochemical oxidation. Though the activity of the Au nanoparticles is a contributing factor, the enhanced activity of the Au-modified Cu electrode is due to the increased oxidation number of Cu through the electron transfer from Cu to more electronegative Au. The depletion of electron in Cu facilitates the oxidation of glucose. The stability of the Au-modified Cu electrode was also studied by chronoamperometry.

• 한국기계가공학회지
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• 제15권1호
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• pp.103-109
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• 2016

The performance of a multi-head, computerized combination scaling system to automatically identify a group of agricultural products having a total weight within the target range has been optimized to reduce the package cycle time of the merchandise. First, the structure of the scale was modified to enable faster measurement by enhancing the dynamic stability during the process. Second, the high frequency noise in the measured signal was eliminated by a high frequency filter to provide more accurate weight data. Finally, the algorithm to identify a group of products with a total weight within the target range was modified to enable a user to select an optimal number of scales. According to the experimental verifications, this modified system reduced the package cycle time significantly and also was accurate in measuring the total weight of the selected products.

• International Union of Geodesy and Geophysics Korean Journal of Geophysical Research
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• 제24권1호
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• pp.11-18
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• 1996

A stability analysis in the geomagentotail is presented within MHD limit with a modified form ideal Ohm's law. Using the high ky approximation (ballooning limit), we derive the basic eigenmode equations which can be reduced to the ideal MHD limit. The incompressible limit is numerically solved for a number of model equilibria of tail by Kan [1973], and we have found no unstable Kan equilibrium. Also, an analytic theory is carried out for the case where Bkc is assumed to be constant along the field line, following the idea by Lee and Min [1996]. In that case, it is suggested that the tail stability to the incompressible antisymmetric mode is determined by the ideal MHD.

• 한국도로학회논문집
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• 제20권4호
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• pp.7-13
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• 2018

PURPOSES : In order to apply high-speed weigh-in-motion (HS WIM) systems to asphalt pavement, three high-durability asphalt concrete mixtures installed with a WIM epoxy are evaluated. METHODS : In this study, dynamic stability, number of loading repetitions to reach the rut depth of 1 mm, and rut depth measurements of three asphalt mixtures at $60^{\circ}C$ were compared using an Asphalt Pavement Analyzer (APA). Laboratory-fabricated material and field core samples were prepared and tested according to KS F2374. RESULTS : Through the laboratory tests, it was found that all three modified asphalt mixtures (stone-mastic, porous, and semi-rigid) with WIM epoxy showed favorable permanent deformation results and passed the dynamic stability criterion of 3000 loading repetitions per 1 mm. In addition, it was confirmed that the modified SMA mixtures cored from the field construction yields satisfactory rutting testing results using the APA. Finally, the epoxy used for the HS WIM installation shows good adhesion with the three asphalt mixtures and permanent deformation resistance.

• 한국광학회지
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• 제9권6호
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• pp.390-395
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• 1998

위상 복원이나 CGH 최적 설계에 이용되는 Iterative Fourier Transform Algorithm (IFTA)의 효율성은 초기 위상 값의 선택에 따라 큰 영향을 받는데, 본 논문에서는 기존의 IFTA의 초기위상 결정 방법을 수정하여 반복과정에 따른 오차의 수렴 속도, 수렴의 안정성을 개선하였다. 수정된 IFTA은 125$\times$128 화소를 갖는 영상에서 대해 약 30%정도 반복 횟수를 줄일 수 있었다.