• 한국통신학회논문지
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• 제36권11A호
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• pp.878-891
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• 2011

본 논문에서는 사용자들 간의 간섭이 존재하는 무선망에서 상하향 링크의 수율 최대화를 동시에 고려한다. 상향 링크에서는 라그랑지안 완화기법에 기반으로 하는 분산적이고 반복적인 알고리즘을 제안하다. 상향 링크에서의 라그랑지 곱수와 네트워크 쌍대성 성질을 이용하여 채널 이득과 최대 전력 제약이 상향 링크와 동일한 듀얼 하향 링크에서의 수율 최대화를 얻을 수 있다. 본 논문에서 증명한 네트워크 쌍대성 성질은 기존의 연구에 비해 보다 일반적인 형태를 가진다. 또한, 모의실험 결과는 채널의 상관 계수가 ${\theta}{\in}$(0.5, 1] 일 때, 상하향 링크에서 제안된 기법들이 각각 최적값에 근접하다는 것을 보여준다. 반면에 채널의 상관 계수가 낮을 때 (${\theta}{\in}$(0, 0.5]), 하향 링크에서의 성능 열화를 관찰할 수 있다. 네트워크 쌍대성 성질은 상향 링크에 비해 채널 이득과 최대 전력 제약이 다른 실제 하향 링크로 확장된다. 이러한 쌍대성 성질에 기반으로 하는 기법은 실제 하향 링크에서도 충분히 적용될 수 있음이 모의실험 결과로 보여진다. 기존에 제안된 알고리즘의 복잡도를 고려하였을때, 본 논문의 결과는 일반화된 네트워크 쌍대성 성질의 성능과 실제 적용면에서 상당히 유용하다고 할 수 있다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권8호
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• pp.2722-2742
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• 2014

We propose methods of linear transceiver design for two different power constraints, sum relay power constraint and per relay power constraint, which determine signal processing matrices such as base station (BS) transmitter, relay precoders and user receivers to minimize sum mean square error (SMSE) for multi-relay multi-user (MRMU) networks. However, since the formulated problem is non-convex one which is hard to be solved, we suboptimally solve the problems by defining convex subproblems with some fixed variables. We adopt iterative sequential designs of which each iteration stage corresponds to each subproblem. Karush-Kuhn-Tucker (KKT) theorem and SMSE duality are employed as specific methods to solve subproblems. The numerical results verify that the proposed methods provide comparable performance to that of a full relay cooperation bound (FRCB) method while outperforming the simple amplify-and-forward (SAF) and minimum mean square error (MMSE) relaying in terms of not only SMSE, but also the sum rate.

• 자원ㆍ환경경제연구
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• 제22권3호
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• pp.499-520
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• 2013

기존 연구에서는 이산화탄소의 한계저감비용을 추정할 경우 쌍대성 이론에 근거하여 임의로 설정된 하나의 방향성 벡터(directional vector) 설정하였으나 본 연구에서는 이러한 한계를 극복하고자 다양한 형태의 방향성 벡터를 사용하여 이산화탄소의 한계저감비용을 추정하였다. 기존의 방법론에서는 임의로 설정된 방향성 벡터가 한계저감비용 추정에 결정적인 역할을 하여 선택된 방향성 벡터에 따라 한계저감 비용 추정치가 상당한 차이가 있음을 알 수 있다. 그리고 $45^{\circ}$의 방향성 벡터를 설정하는 경우에는 실제 이산화탄소 배출량 수준과는 다른 배출량 수준에서의 한계저감비용을 추정하게 되지만 본 연구에서 제안한 방법론에 의하여 추정된 한계저감비용은 실제 이산화탄소 배출량 수준에서 한계저감비용을 추정하여 보다 더 현실을 정확하게 반영하는 추정치이다. 새로운 방법론을 서유럽 국가에 적용하여 추정한 이산화탄소의 한계저감비용은 기존 방법론을 사용하는 경우에 비하여 적은 것으로 추정되었다.

• Journal of applied mathematics & informatics
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• 제27권1_2호
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• pp.13-23
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• 2009

Some strong convergence theorems of explicit iteration scheme for asymptotically nonexpansive semi-groups in Banach spaces are established. The results presented in this paper extend and improve some recent results in [T. Suzuki. On strong convergence to common fixed points of nonexpansive semigroups in Hilbert spaces, Proc. Amer. Math. Soc. 131(2002)2133-2136; H. K. Xu. A strong convergence theorem for contraction semigroups in Banach spaces, Bull. Aust. Math. Soc. 72(2005)371-379; N. Shioji and W. Takahashi. Strong convergence theorems for continuous semigroups in Banach spaces, Math. Japonica. 1(1999)57-66; T. Shimizu and W. Takahashi. Strong convergence to common fixed points of families of nonexpansive mappings, J. Math. Anal. Appl. 211(1997)71-83; N. Shioji and W. Takahashi. Strong convergence theorems for asymptotically nonexpansive mappings in Hilbert spaces, Nonlinear Anal. TMA, 34(1998)87-99; H. K. Xu. Approximations to fixed points of contraction semigroups in Hilbert space, Numer. Funct. Anal. Optim. 19(1998), 157-163.]

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1992년도 춘계학술대회 논문집 92
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• pp.159-176
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• 1992

Limit analysis has been rendered versatile in many problems such as structural problems and metal forming problems. In metal forming analysis, a slip-line method and an upper bound method approach to limit solutions is considered as the most challenging areas. In the present work, a general algorithm for limit solutions of plastic flow is developed with the use of finite element limit analysis. The algorithm deals with a generalized Holder inequality, a duality theorem, and a combined smoothing and successive approximation in addition to a general procedure for finite element analysis. The algorithm is robust such that from any initial trial solution, the first iteration falls into a convex set which contains the exact solution(s) of the problem. The idea of the algorithm for limit solution is extended from rigid/perfectly-plastic materials to work-hardening materials by the nature of the limit formulation, which is also robust with numerically stable convergence and highly efficient computing time.

• 대한수학회논문집
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• 제35권2호
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• pp.401-415
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• 2020

It is well-known that if char𝕜 = 0, then an Artinian monomial complete intersection quotient 𝕜[x₁, …, x_n]/(x₁^a₁, …, x_n^a_n) has the strong Lefschetz property in the narrow sense, and it is decomposed by the direct sum of irreducible 𝖘𝖑₂-modules. For an Artinian ring A = 𝕜[x₁, x₂, x₃]/(x₁⁶, x₂⁶, x₃⁶), by the Schur-Weyl duality theorem, there exist 56 trivial representations, 70 standard representations, and 20 sign representations inside A. In this paper we find an explicit basis for A, which is compatible with the S₃-module structure.

• 한국경영과학회지
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• 제6권1호
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• pp.65-70
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• 1981

L.G. Khachiyan's algorithm for solving a system of strict (or open) linear inequalities with integral coefficients is described. This algorithm is based on the construction of a sequence of ellipsoids in R$^n$ of decreasing n-dimensional volume and contain-ing feasible region. The running time of the algorithm is polynomial in the number of bits of computer core memory required to store the coefficients. It can be applied to solve linear programming problems in polynomially bounded time by the duality theorem of the linear programming problem. But it is difficult to use in solving practical problems. Because it requires the computation of a square roots, besides other arithmatic operations, it is impossible to do these computations exactly with absolute precision.

• 한국정밀공학회지
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• 제8권3호
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• pp.93-104
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• 1991

Limit analysis is based on the duality theorem which equates the least upper bound to the greatest lower bound. In this study, limit analysis of axisymmetric forming problem with workhardening materials is formulated by minimizing the upper bound functional and finite element program is developed for forward estrusion. Limit loads, velocity and flow line fields are directly obtained under various process conditions and deformation characteristics such as strains, strain rates and grid distortion are obtained from the optimum velocity components by numerical calculation. The experimental observation was carried out for extrusion and compared with computed results. The good agreement between theoretical and experimental results is shown that the developed programming is very effective for the analysis of axisymmetric extrusion.