• Journal of the Korean Ceramic Society
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• v.27 no.5
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• pp.631-637
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• 1990

Lithium fluolide single crystals were grown by a floating zone method, with infrared radiation convergence type heater, which is free of contamination from the crucible wall. The crystals grown by this apparatus are 5cm in length and 5-6mm in diameter. The grown cryatal was examined by an optical microscope, XRD, Laue camera, Vickers hardness tester, and FTIR.

• 한국전산유체공학회:학술대회논문집
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• 1998.11a
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• pp.153-159
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• 1998

The Newton-Krylov method on the unstructured grid flow solver using the cell-centered spatial discretization oi compressible Euler equations is presented. This flow solver uses the reconstructed primitive variables to get the higher order solutions. To get the quadratic convergence of Newton method with this solver, the careful linearization of face flux is performed with the reconstructed flow variables. The GMRES method is used to solve large sparse matrix and to improve the performance ILU preconditioner is adopted and vectorized with level scheduling algorithm. To get the quadratic convergence with the higher order schemes and to reduce the memory storage. the matrix-free implementation and Barth's matrix-vector method are implemented and compared with the traditional matrix-vector method. The convergence and computing times are compared with each other.

• Journal of information and communication convergence engineering
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• v.8 no.6
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• pp.640-644
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• 2010

When we talk with hands-free in a car or noisy lobby, the performance of the echo canceller degrade because background noise added to echo caused by the distance from mouth to microphone is relatively long. It gives a reason for necessity of noise-robust and high convergence speed adaptive algorithm. And if acoustic echo canceller operated not perfectly, residual signal going through the echo canceller to far-end speaker remains residual echo, which degrade quality of talk. To solve this problem, post-processing needed to remove residual echo ones more. In this paper, we propose a new acoustic echo canceller, which has noise robust and high convergence speed, linked with linear predictor as a post-processor. By computer simulation, it is confirmed that the proposed algorithm shows better performance from acoustic interference cancellation (AIC) viewpoint.

• Journal of applied mathematics & informatics
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• v.23 no.1_2
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• pp.269-279
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• 2007

This paper describes a direct search method for a class of linearly constrained optimization problem. Through research we find it can be treated as an unconstrained optimization problem. And with the decrease of dimension of the variables need to be computed in the algorithms, the implementation of convergence to KKT points will be simplified to some extent. Convergence is shown under mild conditions which allow successive frames to be rotated, translated, and scaled relative to one another.

• Journal of the Korean Society of Industry Convergence
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• v.22 no.3
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• pp.325-335
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• 2019

In this paper, a novel adaptive gripper with underactuation is presented, which can change its configuration to parallel or power grip mode according to object shapes. Differently from the commercial adaptive gripper by RobotiQ, the proposed gripper includes an actual parallelogram inside a five-bar mechanism, which allows the free selection of actuator locations and can reduce actuation torques effectively. The forward and inverse kinematics for two grip modes and statics analysis have been analyzed. From the comparative design, the proposed gripper has about 20% smaller size, 3.7% larger stroke, and 30.5% smaller average actuation torque than the commercial one.

• Proceedings of the Korea Information Processing Society Conference
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• 2022.11a
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• pp.326-327
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• 2022

'제로 푸드 웨이스트'란 생산과 소비, 폐기 과정에서 음식물이 버려지지 않는 것을 말한다. 이를 위해 본 논문은 유통 기한을 관리하며 동시에 타인에게 식품을 무료 나눔 할 수 있는 어플리케이션을 개발하였다. 본 어플리케이션은 식품을 유통기한 입력을 통해 관리하고, 식품 리스트에서 무료 나눔 버튼을 통해 추가 입력 없이 쉽게 나눔 게시글을 작성할 수 있다. 또한 식품의 이름을 바코드 인식으로 처리해 편리한 입력이 가능하다.

• Journal of Life Science
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• v.28 no.7
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• pp.786-794
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• 2018

Silkworm (Bombyx mori) pupae have been widely worked in wound dressing, hepatoprotective activity, antigenotoxicity, control of glucose level and anti-cancer activity. To investigate the anti-obesity activity of ethanol extract of silkworm pupae powder fermented with Cordyceps militaris (ESfC), the free glycerol release and cAMP concentration as well as fat accumulation were measured in the primary adipocytes of SD (Sprague Dawley) rats and high fat diet (HFD)-treated C57BL/6 mice treated with 12 weeks. Firstly, the presence of the cordycepin with lipid lowering effect was confirmed in ESfC using HPLC analysis. The level of free glycerol and cAMP concentration was significantly increased in the primary adipocytes treated with high dose of ESfC ($400{\mu}g/ml$) although these levels were consistently maintained in other dose ESfC treated groups. In HFD-induced obesity model, the increased fat weight and size of adipocytes in HFD+Vehicle treated group was recovered in HFD+ESfC treated group. Also, the liver weight and the number of lipid droplets were higher in HFD+Vehicle treated group than No treated group. But, this level was significantly decreased in HFD+ESfC treated group compared with HFD+Vehicle treated group. Furthermore, a similar recovery was detected on the phosphorylation of periliphin and HSL, and ATGL expression. Overall, the results of the present study provide some scientific evidences that ESfC can stimulate lipolysis in primary adipocytes and prevent fat accumulation in HFD-treated obesity model, and therefore have the potential for use as anti-obesity agents to treat obese patient.

• Membrane Journal
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• v.24 no.5
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• pp.341-349
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• 2014

Molecular dynamics (MD) computer simulation is a very useful tool to calculate the trajectory and velocity of particles (generally, atoms), and thus to analyze the various structures and kinetic properties of atoms and molecules. For gas separation membranes, MD has been widely used for structure analysis of polymers such as free volume analysis and conformation search, and for the study of gas transport behavior such as permeability and diffusivity. In this paper, general methodology how to apply MD on gas separation membranes will be described and various related researches will be introduced.

• Structural Engineering and Mechanics
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• v.20 no.3
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• pp.293-312
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• 2005

In this paper, free vibration of rotating beam with random properties is studied. The cross-sectional area, elasticity modulus, moment of inertia, shear modulus and density are modeled as random fields and the rotational speed as a random variable. To study uncertainty, stochastic finite element method based on second order perturbation method is applied. To discretize random fields, the three methods of midpoint, interpolation and local average are applied and compared. The effects of rotational speed, setting angle, random property variances, discretization scheme, number of elements, correlation of random fields, correlation function form and correlation length on "Coefficient of Variation" (C.O.V.) of first mode eigenvalue are investigated completely. To determine the significant random properties on the variation of first mode eigenvalue the sensitivity analysis is performed. The results are studied for both Timoshenko and Bernoulli-Euler rotating beam. It is shown that the C.O.V. of first mode eigenvalue of Timoshenko and Bernoulli-Euler rotating beams are approximately identical. Also, compared to uncorrelated random fields, the correlated case has larger C.O.V. value. Another important result is, where correlation length is small, the convergence rate is lower and more number of elements are necessary for convergence of final response.

• Journal of the Korean Society of Industry Convergence
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• v.16 no.3
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• pp.85-93
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• 2013

The MCT has been most extensively used in the machining. In particular, the ball endmill has been mainly adopted for finishing on the free- form surface. The advancement of CAD/CAM software has made it possible to develop various cutting pattern methods and to create diverse tool routes. Therefore, the current research made an attempt to find the optimal cutting pattern among the seven cutting patterns (i.e., Follow Periphery, Zig, Zig Zag, Concentric Zig, Concentric Zig Zag, Radial Zig, Radial Zig Zag) when aluminium 6000 series were machined by the ball endmill. The optimal pattern was found by comparing different shapes and surface roughness produced by the seven patterns. The current research found that each cutting pattern produced its own unique geometric features on the machined surface. It was found that the Radial Zig cutting pattern produced the lowest roughness on the flat surfaces. The Radial Zig Zag cutting pattern was found to produce the most accurate free-form surface. Finally, the most efficient cutting pattern in terms of machining time turned out to be the Follow Periphery.