• Korean Journal of Mathematics
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• v.17 no.2
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• pp.219-231
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• 2009

We show the existence of at least four solutions for the perturbed parabolic equation with Dirichlet boundary condition and periodic condition when the nonlinear part cross two eigenvalues of the eigenvalue problem of the Laplace operator with boundary condition. We obtain this result by using the Leray-Schauder degree theory, the finite dimensional reduction method and the geometry of the mapping. The main point is that we restrict ourselves to the real Hilbert space instead of the complex space.

• Korean Journal of Mathematics
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• v.17 no.2
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• pp.211-218
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• 2009

We investigate the multiple solutions for a suspending beam equation with jumping nonlinearity crossing three eigenvalues, with Dirichlet boundary condition and periodic condition. We show the existence of at least six nontrivial periodic solutions for the equation by using the finite dimensional reduction method and the geometry of the mapping.

• 전기의세계
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• v.22 no.4
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• pp.25-29
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• 1973

The computation of transmittances between arbitrary input and output nodes is of particular interest in the signal flow graph theory imput. The signal flow matrix [T] can be defined by [X]=-[T][X] where [X] and [Y] are input nose and output node matrices, respectively. In this paper, the followings are discussed; 1) Reduction of nodes by reforming the signal flow matrix., 2) Solution of input-output relationships by means of Gauss-Jordan reduction method, 3) Extension of the above method to the matrix signal flow graph.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2006.05a
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• pp.1030-1033
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• 2006

In this paper, the assignment problem is considered. We propose an approach based on the solution of a sequence of shortest path sub-problem. We extend the cost reduction method, which is used for finding initial assignment, to solve these sub-problems. The use of the extended reduction method makes it possible to devise an efficient multi-augmenting algorithm.

• Proceedings of the IEEK Conference
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• 2000.07a
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• pp.35-38
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• 2000

Low bit rate image/video coding is essential for many visual communication applications. When bit rates become low, most compression algorithms yield visually blocking artifacts that highly degrade the perceptual quality, and post-processing approaches provide one attractive solution. In this paper, we provide simple and very efficient blocking artifacts reduction method using constrained random value addition. Our method is simple enough to be used for real-time post-processing of video.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.23 no.61
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• pp.105-114
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• 2000

Job Shop Problem which consists of the m different machines and n jobs is a NP-hard problem of the combinatorial optimization. Each job consists of a chain of operations, each of which needs to be processed during an uninterrupted time period of a given length on a given machine. Each machine can process at most one operation at a time. The purpose of this paper is to develop the heuristic method to solve large scale scheduling problem using Constraint Satisfaction Problem method and Simulated Annealing. The proposed heuristic method consists of the search algorithm and optimization algorithm. The search algorithm is to find the solution in the solution space using CSP concept such as backtracking and domain reduction. The optimization algorithm is to search the optimal solution using SA. This method is applied to MT06, MT10 and MT20 Job Shop Problem, and compared with other heuristic method.

• International Journal of Control, Automation, and Systems
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• v.4 no.3
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• pp.359-364
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• 2006

This article describes the useful way to measure the torque and RPM of the geared motor. For this we have made the planetary geared reduction motor including 2 Hall sensors in it and the monitoring system. The monitoring system displays the sensing values (torque, rpm) and the calculated value (power) and it also has the network capability using the Bluetooth protocol. We will show that our solution is much more inexpensive and simple method to measure torque and rpm than before.

• Carbon letters
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• v.24
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• pp.1-9
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• 2017

We studied the basic properties and fabrication of reduced graphene oxide (rGO) prepared using eco-friendly reduction agents in the graphene solution process. Hydrazine is generally used to reduce graphene oxide (GO), which results in polluting emissions as well as fixed nitrogen functional groups on different defects in the graphene sheets. To replace hydrazine, we developed eco-friendly reduction agents with similar or better reducing properties, and selected of them for further analysis. In this study, GO layers were produced from graphite flakes using a modified Hummer's method, and rGO layers were reduced using hydrazine hydrate, L-ascorbic acid, and gluconic acid. We measured the particle sizes and the dispersion stabilities in the rGO dispersed solvents for the three agents and analyzed the structural, electrical, and optical properties of the rGO films. The results showed that the degree of reduction was in the order L-ascorbic acid ${\geq}$ hydrazine > glucose. GO reduced using L-ascorbic acid had a sheet resistance of $121k{\Omega}/sq$, while that reduced using gluconic acid showed worse electrical properties than the other two reduction agents. Therefore, L-ascorbic acid is the most suitable eco-friendly reduction agent that can be substituted for hydrazine.

• Smart Structures and Systems
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• v.11 no.1
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• pp.69-86
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• 2013

An efficient methodology using static test data and changes in natural frequencies is proposed to identify the damages in structural systems. The methodology consists of two main stages. In the first stage, the Damage Signal Match (DSM) technique is employed to quickly identify the most potentially damaged elements so as to reduce the number of the solution space (solution parameters). In the second stage, a particle swarm optimization (PSO) approach is presented to accurately determine the actual damage extents using the first stage results. One numerical case study by using a planar truss and one experimental case study by using a full-scale steel truss structure are used to verify the proposed hybrid method. The identification results show that the proposed methodology can identify the location and severity of damage with a reasonable level of accuracy, even when practical considerations limit the number of measurements to only a few for a complex structure.

• Environmental Engineering Research
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• v.10 no.1
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• pp.1-6
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• 2005

Hexavalent chromium in aqueous solutions was successfully removed via sorption and reduction in the presence of waste leaves. Cr(VI) removal followed a first-order reaction, and removal rates were proportional to the amount of waste leaves used in the tests. Most of Cr(VI) were removed via sorption in early stages of the tests, but the reduction reaction played a significant role in Cr(VI) removal later. Solution pHs were continuously decreased due to the microbial activity, which was induced from the microorganisms attached on waste leaves. The decreased solution pHs further enhanced the sorption and reduction of Cr(VI). To characterize the microorganisms found in the tests, a denaturing gradient gel electrophoresis (DGGE) method was used. The majority of microorganisms were composed of Bacillus sp. which can reduce Cr(VI). Thus, waste leaves can be effective reactive media for the treatment of Cr(VI) in the subsurface.