• Geomechanics and Engineering
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• v.21 no.6
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• pp.513-525
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• 2020

Slopes stabilised with piles are seldom analysed considering uncertainties in the parameters of the pile-slope system. Reliability analysis of the pile-slope system quantifies the degree of uncertainties and evaluates the safety of the system. In the present study, the reliability analysis of a slope stabilised with piles is performed using the first-order reliability method (FORM) based on Hasofer-Lind approach. The implicit performance function associated with the factor of safety (FS) of the slope is approximated using the response surface method. The analyses are carried out considering the design matrices formulated based on both the 2^k factorial design augmented with a centre run (2^k fact-centred design) and face-centered cube design (FCD). The finite element method is used as the deterministic model to compute the FS of the pile-slope system. Results are compared with the results of the Monte Carlo simulation. It is observed that the optimum location of the row of piles is at the middle of the slope to achieve the maximum FS. The results show that the reliability of the system is not uniform for different pile configurations, even if the system deterministically satisfies the target factor of safety (FS_t) criterion. The FS_t should be selected judiciously as it is observed that the reliability of the system changes drastically with the FS_t level. The results of the 2^k fact-centred design and FCD are in good agreement with each other. The procedure of the FCD is computationally costly and hence the use of 2^k fact-centred design is recommended, provided the response of the system is sufficiently linear over the factorial space.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.259-260
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• 2008

This paper presents fractional frequency reuse (FFR) with sub-channel borrowing to improve spectral efficiency of the wireless broadband (WiBro) system. FFR has constraints on usable sub-channels to balance the interference and cell capacity. Our FFR with sub-channel borrowing allows use of the dedicated sub-channels assigned to neighboring cells. Simulation results show that the proposed FFR with sub-channel borrowing improves the performance of the WiBro system.

• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.1791-1797
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• 2018

Sub-Synchronous Resonance (SSR) is a phenomenon that harms turbine generator shafts because the phenomenon induces sub-synchronous wavering in the system. In the study presented in this paper, a dynamic resistance bank is used to mitigate the occurrence of sub-synchronous phenomenon. A fuzzy logic controller using rotor speed deviation and its derivative as inputs is implemented to damp sub-synchronous oscillations more efficiently. An eigenvalue technique is used to analyse the stability of the system, and a simulation in MATLAB is conducted, based on the IEEE Second Benchmark, to validate the effectiveness of the proposed method under a 3-phase fault condition at an infinite bus. The time-domain simulation and eigenvalues are used to observe the proposed method's superior ability to damp sub-synchronous oscillation.

• Korean Journal of Mathematics
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• v.28 no.2
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• pp.379-389
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• 2020

An r-color Rado number N = R(𝓛, r) for a system 𝓛 of equations is the least integer, provided it exists, such that for every r-coloring of the set {1, 2, …, N}, there is a monochromatic solution to 𝓛. In this paper, we study the 2-color Rado number R(𝓔, 2) for 𝓔 : x₁ + x₂ + ⋯ + x_n = y₁ + y₂ = z when n ≥ 4.

• Bulletin of the Korean Mathematical Society
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• v.49 no.3
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• pp.481-493
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• 2012

Let $S$ be a upper triangular operator such that $M^L_S:\mathcal{U}_2{\rightarrow}\mathcal{U}_2$ defined by $M^L_S(F)=SF$ is a contraction. Then there exists an unitary linear system whose state space is the extension space $\tilde{D}_L$(S) associated with $\mathcal{H}_L$(S).

• Korean Journal of Mathematics
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• v.22 no.4
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• pp.711-723
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• 2014

We prove in this paper the absolute continuity of the representing measures of the hypergeometric translation operators $\mathcal{T}_x$ and $\mathcal{T}_x^W$ associated respectively to the Cherednik operators and the Heckman-Opdam theory attached to the root system of type $B_2$ and $C_2$ which are studied in [9].

• Journal of the Chungcheong Mathematical Society
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• v.36 no.4
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• pp.255-265
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• 2023

The purpose of this article is to construct a unital 8 dimensional hypercomplex number system H^*₈ that is neither alternative nor commutative unlike the octonions by means of the unital 4 dimensional, commutative, and nonassociative hypercomplex number system H^*. We also establish some algebraic properties related to H^*₈ and compare to those of octonions.

• Journal of the Korean Society for Railway
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• v.9 no.5 s.36
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• pp.606-611
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• 2006

This paper presents a procedure and an analysis method to evaluate reliability of the Korea high-speed train. The rolling stock system is divided into 6 sub-systems and each subsystem is classified into sub-assemblies. Functional analysis has been conducted to draw reliability block diagrams for the sub-systems. First, failure rates has been calculated for each sub-assembly from the failure data obtained during commissioning tests. Then a reliability block diagram is used to evaluate the MKBF(Mean Kilometers Before Failure) of the sub-systems. Activities to increase reliability have been carried out throughout the test runs and analysis results show that the reliability of the rolling stock system is gradually growing in time.

• Bulletin of the Korean Mathematical Society
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• v.57 no.3
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• pp.677-690
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• 2020

In this article, we study a reaction-diffusion system with homogeneous Dirichlet boundary conditions, which describing a three-species food chain model. Under some conditions, the predator-prey subsystem (u₁ ≡ 0) has a unique positive solution (${\bar{u_2}}$, ${\bar{u_3}}$). By using the birth rate of the prey r1 as a bifurcation parameter, a connected set of positive solutions of our system bifurcating from semi-trivial solution set (r₁, (0, ${\bar{u_2}}$, ${\bar{u_3}}$)) is obtained. Results are obtained by the use of degree theory in cones and sub and super solution techniques.

• 한국지구물리탐사학회:학술대회논문집
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• 2007.06a
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• pp.113-117
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• 2007

Sub-salt imaging is an unsolved hot issue in subsurface imaging area. We tested several important properties in imaging sub-salt structures to provide a clue to this problem. Reverse time migration using velocity models obtained by waveform inversion produced better results than that of stacking velocity analysis. Sub-salt imaging results were highly dependent on the size and shape of a salt structure. The results were not clear when the velocity of a salt structure is significantly higher than that of adjacent layers.