• 천문학회지
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• 제27권2호
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• pp.191-201
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• 1994

We propose to use the entropy of power spectra defined in the frequency domain for the deconvolution of extended images. Spatial correlations requisite for extended sources may be insured by increasing the role of power entropy because the power is just a representation of spatial correlations in the frequency domain. We have derived a semi-analytical solution which is found to severely reduce computing time compared with other iteration schemes. Even though the solution is very similar to the well-known Wiener filter, the regularizingng term in the new expression is so insensitive to the noise characteristics as to assure a stable solution. Applications have been made to the IRAS $60{\mu}m\;and\;100{\mu}m$ images of the dark cloud B34 and the optical CCD image of a solar active region containing a circular sunspot and a small pore.

• 정보과학회 논문지
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• 제45권1호
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• pp.15-21
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• 2018

낮은 계수 표현(Low-Rank Representation, LRR) 기반 방법은 얼굴 클러스터링, 객체 검출 등의 여러 실제 응용에 널리 사용되고 있다. 이 방법은 그래프 기반 준지도 학습에서 그래프 구축에 사용할 경우 높은 예측 정확도를 확보할 수 있어 많이 사용된다. 그러나 LRR 문제를 해결하기 위해서는 알고리즘의 매 반복마다 데이터 수 크기의 정방행렬에 대해 특이값 분해를 수행하여야 하므로 계산 비효율적이다. 이를 해결하기 위해 속도를 향상시킨 발전된 LRR 방법을 제안한다. 이는 최근 발표된 Fast LRR(FaLRR)을 기반으로 하며, FaLRR이 속도는 빠르지만 실제로 분류 문제에서 성능이 낮은 것을 해결하기 위해 기반 최적화 목표에 추가 제약 조건을 도입하고 이를 최적화하는 방법을 제안한다. 실험을 통하여 제안 방법은 LRR보다 더 좋은 해를 빠르게 찾아냄을 확인할 수 있다. 또한, 동일한 해를 도출하는 방법을 찾아내기는 어렵지만 최소화하는 목표가 추가될 경우 더 좋은 결과를 나타내는 Fast MLRR(FaMLRR)을 제안한다.

• Educational Technology International
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• 제11권1호
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• pp.93-117
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• 2010

The purpose of this study was to develop the problem solving instruction facilitating novice learner to represent the problem. For the purpose, we mainly focused on three aspects of problem solving. First, learner should represent the targeted problem and its solutions for problem solving. Second, from crucial notions of cognitive load theory, learner's mental load should be optimized for problem representation. Third, for optimizing students' mental load, experts may support making their thinking more visible and mapping from their intuition to expert practice. We drew the design principles as follows. First, since providing worked examples for the targeted problem has been considered to minimize analogical errors as well as reduce cognitive load in problem representation at line of problem solving and instructional research, it is needed to elaborate the way of designing. The worked example alternatively corresponds to expert schema that consists of domain knowledge as well as strategies for expert-like problem representation and solution. Thus, it may help learner to represent what the problem is and how to solve it in problem space. Second, principle can be that expert should scaffold learner's self-explanations. Because the students are unable to elicit the rationale from worked example, the expert's triggering scaffold may be critical in that process. The unexplained and incomplete parts of the example should be completed not by expert's scaffold but by themselves. Critical portion of the expert's scaffold is to explain about how to apply and represent the given problem, since students' initial representations may be reached at superficial or passive pattern of example elaboration. Finally, learner's mental model on the designated problem domain should be externalized or visualized for one's reflection as well as expert's scaffolding activities. The visualization helps learner to identify one's partial or incorrect model. The correct model of learner could be constructed by expert's help.

• Journal of Computational Design and Engineering
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• 제2권2호
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• pp.105-112
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• 2015

Product Lifecycle Management (PLM) ranges from design concepts of products to disposal. In this paper, we focus on the production planning phase in PLM, which is related to process planning and production scheduling and so on. In this study, key decisions for the creation of production plans are defined as production-planning attributes. Production-planning attributes correlate complexly in production-planning problems. Traditionally, the production-planning problem splits sub-problems based on experiences, because of the complexity. In addition, the orders in which to solve each sub-problem are determined by priorities between sub-problems. However, such approaches make solution space over-restricted and make it difficult to find a better solution. We have proposed a representation of combinations of alternatives in production-planning attributes by using Zero-Suppressed Binary Decision Diagrams. The ZDD represents only feasible combinations of alternatives that satisfy constraints in the production planning. Moreover, we have developed a solution search method that solves production-planning problems with ZDDs. In this paper, we propose an approach for managing solution candidates by ZDDs' network for addressing larger production-planning problems. The network can be created by linkages of ZDDs that express constraints in individual sub-problems and between sub-problems. The benefit of this approach is that it represents solution space, satisfying whole constraints in the production planning. This case study shows that the validity of the proposed approach.

• Ocean Systems Engineering
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• 제13권2호
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• pp.123-146
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• 2023

In this paper, Moore-Gibson-Thompson theory of thermoelasticity is considered to investigate the fundamental solution and vibration of plane wave in an isotropic photothermoelastic solid. The governing equations are made dimensionless for further investigation. The dimensionless equations are expressed in terms of elementary functions by assuming time harmonic variation of the field variables (displacement, temperature distribution and carrier density distribution). Fundamental solutions are constructed for the system of equations for steady oscillation. Also some preliminary properties of the solution are explored. In the second part, the vibration of plane waves are examined by expressing the governing equation for two dimensional case. It is found that for the non-trivial solution of the equation yield that there exist three longitudinal waves which advance with the distinct speed, and one transverse wave which is free from thermal and carrier density response. The impact of various models (i)Moore-Gibson-Thomson thermoelastic (MGTE)(2019), (ii) Lord and Shulman's (LS)(1967) , (iii) Green and Naghdi type-II(GN-II)(1993) and (iv) Green and Naghdi type-III(GN-III)(1992) on the attributes of waves i.e., phase velocity, attenuation coefficient, specific loss and penetration depth are elaborated by plotting various figures of physical quantities. Various particular cases of interest are also deduced from the present investigations. The results obtained can be used to delineate various semiconductor elements during the coupled thermal, plasma and elastic wave and also find the application in the material and engineering sciences.

• 대한조선학회논문집
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• 제37권3호
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• pp.27-36
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• 2000

기하학적 형상과 유동의 해를 B-스플라인으로 표현하는 2차원 고차 패널법이 개발되어 수중익 문제의 해석에 적용되었다. 기존의 Lee/Kerwin은 한 패널에 여러 개의 제어점을 배치하여 최소자승법에 의해 해를 구하였으나, 본 논문에서는 필요한 개수의 제어점 만을 표면에 규칙적으로 배열하여 해를 구할 수 있음을 수치 실험을 통하여 보였다. 특히, 날개 뒷날에서의 압력 점프의 값이 명시적으로 영이 되도록 하는 동역학적 Kutta 조건식의 도입이 중요하고, 이의 적용이 안정된 해를 보장함을 확인하였다. 해석해에 의해서 구해진 2차원 날개의 압력 분포와의 비교를 통하여, 적은 수의 제어점을 선정하여도 정확한 해를 얻을 수 있음을 보였으며, 동시에 계산속도도 현저하게 감소함을 보였다.

• 전자공학회논문지A
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• 제31A권12호
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• pp.142-151
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• 1994

This paper proposes new algorithms to solve canonical piecewise-linear equations with linear partitions and illustrates their efficiency through the analysis of resistive network. The basic idea of the proposed algorithm is to find the best next guess, closest to the actual solution, at each Newton-Raphson (N-R) iteration by comparing the images of nest guess candidates and that of the actual solution. The proposed algorithm can reduce the number of the N-R iterations rquired for convergence greatly, compared to the actual solution, at each Newton-Raphson (N-R) iteration by comparing the images of next guess candidates and that of the actual solution. The proposed algorithm can reduce the number of the N-R iterations required for convergence greatly, compared to the Katzenelson algorithm. When applied to analyzing test circuits, the proposed algorithm required 8 to 20 times fewer N-R iterations and 5 to 10 times less CPU time than the Katzenelson algorithm, depending on the size of the circuits. The experimental results also exhibit that the efficiency of the proposed algorithm over the Katzenelson algorithm increases as the number of the piecewise-linear regions for the representation of the circuit.

• 한국정밀공학회지
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• 제14권7호
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• pp.144-153
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• 1997

The inverse kinematics problem of a reclaimer which excavates and transports raw materials in a raw yard is investigated. Because of the geometric feature of the equipment in which scooping buckets are attached around the rotating disk, kinematic redundancy occurs in determining joint variable. Link coordinates are introduced following the Denavit-Hartenbery representation. For a given excavation point the forward kinematics yields 3 equations, however the number of involved joint variables in the equations is four. It is shown that the rotating disk at the end of the boom provides an extra passive degree of freedom. Two approaches are investigated in obtaining inverse kinematics solutions. The first method pre-assigns the height of excavation point which can be determined through path planning. A closed form solution is obtained for the first approach. The second method exploits the orthogonality between the normal vector at the excavation point and the z axis of the end-effector coordinate system. The geometry near the reclaiming point has been approximated as a plane, and the plane equation has been obtained by the least square method considering 8 adjacent points near the point. A closed form solution is not found for the second approach, however a linear approximate solution is provided.

• Korean Journal of Mathematics
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• 제19권2호
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• pp.111-127
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• 2011

We prove the uniqueness solvability of the Tricomi problem for the elliptic - hyperbolical equation of the second type by using a new representation of the solution in the generalized class R.

• Journal of applied mathematics & informatics
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• 제34권1_2호
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• pp.95-106
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• 2016

In this paper, according to the classical LSQR algorithm forsolving least squares (LS) problem, an iterative method is proposed for finding the minimum-norm pure imaginary solution of the quaternionic least squares (QLS) problem. By means of real representation of quaternion matrix, the QLS's correspongding vector algorithm is rewrited back to the matrix-form algorthm without Kronecker product and long vectors. Finally, numerical examples are reported that show the favorable numerical properties of the method.