• Proceedings of the KSME Conference
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• 2007.05a
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• pp.512-517
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• 2007

In the previous development of the recursive thermostat chained fully flexible cell molecular dynamics simulation, implicit time integration method such as generalized leapfrog integration is used. The implicit algorithm is very much complicated and not easy to show time reversibility because it is solved by the nonlinear iterative procedure. Thus we develop simple, explicit symplectic time integration formula for the recursive thermostat chained fully flexible unit cell simulation. Uniaxial tension test is performed to verify the present explicit algorithm. We check that the present simulation satisfies the ergodic hypothesis for various values of fictitious mass and coefficient of multiple thermostat system. The proposed method should be helpful to predict mechanical and thermal behavior of nano-scale structure.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1993.04a
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• pp.128-133
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• 1993

본 연구에서는 보강 원통쉘에 대하여 주위 유체의 영향을 고려하여 진동 및 음향방사를 해석하였다. 원통셀의 운동방정식은 Donnell 이론을 적용하였으 며, Contour 적분을 풀지 않고 FFT 알고리즘(Fast Fourier Transform Algorithm)을 이용하여 원통쉘의 진동을 계산하였다. 현재까지의 방사패턴에 관한 연구는 주로 원주 방향에 집중되어 왔으나, 보강 원통쉘의 방사패턴은 원추파 모형에 가까우므로 극좌표 .theta. 방향에 대한 음향방사 패턴에 관한 연구가 이루어져야 한다. 그러므로, 본 연구에서는 극좌표에 관한 방사패턴 에 관하여 주로 고찰하였다.

• The Journal of the Korea Contents Association
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• v.7 no.1
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• pp.40-47
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• 2007

In the protein macro array image, it is important to find out the feature of the each protein chip. A decision error by the personal sense of sight occurred from long time observation while making an experiment in many protein chip image. So the feature extraction is needed by a simulator. In the case of feature analysis for macro array scan image the efficiency is maximized. In the fluorescence scan image, the response for each cell have been depend on R, G, B distribution of color image. But it is difficult to be classified as one color feature in the case of mixed color image. In this paper, the response color of a protein chip is classified according to the fuzzy integral value with respect to fuzzy measure as the user desired color. The result of the experiment for the macro array fluorescence image with the Scan Array 5000 shows that the proposed method using the fuzzy integral is important fact to be make decision for the ambiguous color.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.3
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• pp.210-218
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• 2018

In order to generate meshes automatically for finite element analysis of complex structures such as aircraft, a large number of triangular elements are typically created. However, triangular elements are less accurate than rectangular elements, so it is difficult to obtain a reliable solution. This problem can be improved through the meshfree method using the back cell integration. However, this method also causes some problems such as over-use of the integration points and inefficiency of the integral domain. In order to improve these problems, a method of performing integration by setting the integral area based on a node basis has been proposed, but in the case of incompressible material problems, the numerical accuracy deteriorates due to the vibration phenomenon of the solution. Therefore, in this paper, the modified meshfree method is proposed which sets the integral domain as an element domain instead of the nodal domain, and the proposed method improves the numerical instability caused by the conventional meshfree method without decreasing the accuracy regardles of the shape of integral domain. The effectiveness of the modified meshfree method is verified by using 2-D examples.

• Journal of IKEEE
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• v.17 no.4
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• pp.440-445
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• 2013

This paper proposes a local estimation system which combines Cell Divide Algorithm with low-cost GPS/INS fused by Extended Kalman Filter(EKF) for localization of Quad-rotor when it returns to the departure point. In the research, the low-cost GPS and INS are fused by EKF to reduce the local error of low-cost GPS and the accumulative error of INS due to continuous integration of sensor error values. When the Quad-rotor returns to the departure point in the fastest path, a moving path can be known because it moves straight, where Cell Divide Algorithm is used to divide moving route into the cells. Then it determines the closest position of data of GPS/INS system fused by EKF to obtain the improved local data. The proposed system was verified through comparing experimental localization results obtained by using GPS, GPS/INS and GPS/INS with Cell Divide Algorithm respectively.

• The Journal of the Acoustical Society of Korea
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• v.14 no.2
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• pp.80-91
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• 1995

A theoretical models has been prepared which describes the noise generated by tire/road interaction for the tire structure-borne sound analysis. The model begin with a set of thin shell equations describing the motion of the belt of a radial ply tire, as drived by Bohm('mechanisms of the belted tire', Igeniur-Archiv, XXXV, 1966). Structural quantities required for these equations are derived from material properties of the tire. The rolling shape of a tire is computed from the steady-state limit of these equations. Vibrational response of the tire is treated by the full dependent shell equations. The force input at the tire/road interface is calculated on the basis of tread geometry and distribution of contact patch pressure. Radiation of noise is calculated by a simpson integral. Using the programs, the effect on noise of various tire design variations is computed and discussed. Trends which lead to quiet tire design are identified.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.299-299
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• 2010

태양전지 셀에서 표면 반사에 의한 태양광 손실을 보다 적게 하여 흡수량 증가시킬 필요가 있다. 태양전지에서 생성된 전자 정공 수집 향상을 위해 금속 재질로 이루어진 그리드 전극을 사용한다. 이때 금속 그리드에 입사되는 태양광은 대부분 반사되어 입사광의 손실로 이어진다. 본 연구에서는 결정질 실리콘 태양전지에서 표면 그리드에 의한 광학적 손실을 반사율을 통해 확인하였고 양자효율을 측정하여 보았다. 결정질 실리콘 태양전지 표면 반사율 측정은 적분구를 사용하였고, 측정에 사용된 태양전지 샘플은 일반적인 구조의 결정질 실리콘 태양전지이다. 실험은 표면 그리드 공정 전 후의 샘플로 실험을 진행하였고, 셀의 표면 균일도에 의한 확인을 위하여 동일한 면적 비율의 입사광을 조사하여 반복 실험을 하였다. 양자효율 측정은 광학 초퍼를 통한 광원과 분광기 및 검출기를 포함하는 태양전지 특성 분석 장치를 사용하였다. 그 결과 특정 파장 대역에서 그리드의 유무에 따른 반사율의 변화와 이에 따른 양자효율의 변화를 통하여 그리드에 의한 결정질 실리콘 태양전지의 특성변화에 대해 알아보았다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.343-346
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• 2005

Three dimensional structures of detonation wave propagating through a square-shaped duct were investigated using computational method and parallel processing. Inviscid fluid dynamics equations coupled with $variable-{\gamma}$ formulation and simplified one-step Arrhenius chemical reaction model were analysed by MUSCL-type TVD scheme and four stage Runge-Kutta time integration. The unsteady computational results in three dimension show the detailed mechanism of transverse mode and diagonal mode of detonation wave instabilities resulting same cell length but different cell width in smoked-foil record.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.3
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• pp.57-64
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• 2001

For the dynamic nonlinear analysis of stiffened plate and shell structures, total Lagrangian formulation is presented based upon the degenerated shell element considering finite rotation effects. Assumed strain concept is adopted in order to overcome shear locking phenomena and to eliminate spurious zero energy mode. In the elasto-plastic analysis, the return mapping algorithm based on the consistent elasto-plastic tangent modulus is applied to collapse analysis of shell structures. Newmark integration method is used for dynamic nonlinear analysis of shell structures under dynamic forces.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.1
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• pp.9-16
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• 2024

Using the proper orthogonal decomposition (POD) based intrusive reduced order model (ROM), the total degrees of freedom of the structural system can be significantly reduced and the critical time step satisfying the conditional stability increases in the explicit time integrations. In this study, therefore, the changes in the critical time step in the explicit time integrations are investigated using both the POD-ROM and Voronoi-cell lattice model (VCLM). The snapshot matrix is composed of the data from the structural response under the arbitrary dynamic loads such as seismic excitation, from which the POD-ROM is constructed and the predictive capability is validated. The simulated results show that the significant reduction in the computational time can be achieved using the POD-ROM with sufficiently ensuring the numerical accuracy in the seismic analyses. In addition, the validations show that the POD based intrusive ROM is compatible with the Voronoi-cell lattice based explicit dynamic analyses. In the future study, the research results will be utilized as an elemental technology for the developments of the real-time predictive models or monitoring system involving the high-fidelity simulations of structural dynamics.