• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.31 no.2 s.257
• /
• pp.211-220
• /
• 2007

This work presents an iterated improved reduced system (IIRS) procedure combined with sub-structuring scheme for large structures. Iterated IRS methods are usually more efficient than others because the dynamic condensation matrix is updated repeatedly until the desired convergent values are obtained. However, using these methods simply for large structures causes expensive computational cost and even makes analyses intractable because of the limited computer storage. Therefore, the application of sub-structuring scheme is necessary. Because the large structures are subdivided into several (or more) sub-domains, the construction of dynamic condensation matrix does not require much computation cost in every iteration. This makes the present method much more efficient to compute the eigenpairs both in lower and intermediate modes. In Part I, iterated IRS method combined with sub-structuring scheme for undamped structures is presented. The validation of the proposed method and the evaluation of computational efficiency are demonstrated through the numerical examples.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.31 no.2 s.257
• /
• pp.221-230
• /
• 2007

An iterated improved reduced system (IIRS) procedure combined with sub-structuring scheme for nonclassically damped structural systems is presented. For dynamic analysis of such systems, complex eigenproperties are required to incorporate properly the nonclassical damping effect. In complex structural systems, the equations of motion are written in the state space from. Thus, the number of degrees of freedom of the new equations of motion and the size of the associated eigenvalue problem required to obtain the complex eigenvalues and eigenvectors are doubled. Iterated IRS method is an efficient reduction technique because the eigenproperties obtained in each iteration step improve the condensation matrix in the next iteration step. However, although this reduction technique reduces the size of problem drastically, it is not efficient to apply this technique to a single domain finite element model with degrees of freedom over several thousands. Therefore, for a practical application of the reduction method, accompanying sub-structuring scheme is necessary. In the present study, iterated IRS method combined with sub-structuring scheme for nonclssically damped structures is developed. Numerical examples demonstrate the convergence and the efficiency of a newly developed scheme.

• 한국IT서비스학회:학술대회논문집
• /
• 2009.11a
• /
• pp.351-354
• /
• 2009

컴퓨터 프로그래밍에 의해 특정 모티브 이미지를 기반으로 다양한 규칙과 불규칙요인을 포함한 동적구성을 완성한다. 완성된 동적구성에서 타임 슬라이스를 통해 다수의 이미지컷을 생성하고 이를 단독 또는 혼합하여 그래픽디자인의 소스로 사용하는 등 예술적으로 활용하는 것이 본 연구의 목적이다. 이러한 방법을 '프로그래밍아트'라고 칭하고자 한다. 첫번째 시도한 모티브는 색동이다. 조선 복식에서 기쁨과 즐거움의 표현으로 사용된 원색들은 배열의 질서를 갖춰 색동의 형식을 취함으로써 원색 조화의 미를 보여준다. 이제까지 "탈 색동화에 의한 디자인 전개"는 색동의 조형요소를 다양하게 변형시키는 것으로 여러 분야의 디자이너들에 의해 색동의 색이나 색 너비등의 변형으로 시도되고 있다. 색동의 색상과 이미지틀을 유지하면서 변형할 영역을 도출하여 프로그래밍하였고, 몇가지 유형의 그래픽 재료를 생산하고 이를 재가공하였다. 예술의 창의적 과정에서 프로그래밍을 통한 자동화 영역을 찾는 것은 다소 불합리해 보이지만, 창의적인 작업과정을 세부적으로 나누면서 규칙적 영역을 발굴하거나, 그 영역 내에서도 인터랙션을 통해 인간의 의지가 반영될 수 있다. 이는 인간과 컴퓨터가 공조하여 창의성을 추구함으로써 컴퓨터를 또 하나의 생명체로 간주해가는 미래사회 협업의 새로운 유형의 시도라 생각한다.

• Investigative Magnetic Resonance Imaging
• /
• v.11 no.2
• /
• pp.103-109
• /
• 2007

To develop an advanced non-linear curve fitting (NLCF) algorithm for performing dynamic susceptibility contrast study of the brain. The first pass effects give rise to spuriously high estimates of $K^{trans}$ for the voxels that represent the large vascular components. An explicit threshold value was used to reject voxels. The blood perfusion and volume estimation were accurately evaluated in the $T2^*$-weighted dynamic contrast enhanced (DCE)-MR images. From each of the recalculated parameters, a perfusion weighted image was outlined by using the modified non-linear curve fitting algorithm. The present study demonstrated an improvement of an estimation of the kinetic parameters from the DCE $T2^*$-weighted magnetic resonance imaging data with using contrast agents.

• The Journal of the Acoustical Society of Korea
• /
• v.43 no.3
• /
• pp.277-284
• /
• 2024

This study proposes a method to predict noise reduction based on noise-reduction measures, using harmonic response analysis, for transformer design. The dynamic elastic coefficients of the components comprising the actual transformer were determined by manufacturing the materials of the transformer components into simple-shaped specimens, followed by a comparison of the modes between the experiments and the analyses. A finite element model of the transformer was implemented, and harmonic response analysis was performed by deriving the exciting force of the transformer. Subsequently, the theoretical sound power level of the transformer was derived from the results of the harmonic response analysis. Finally, noise reduction measures were established, and the noise reduction amounts were compared between the experiments and the analyses, before and after applying the measures. Through the comparison and analyses of the noise reduction measures, it was confirmed that the trends in the experiments and analyses matched.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.10 no.1 s.47
• /
• pp.51-62
• /
• 2006

To dale, lots of types of tuned mass dampers are developed and investigated to reduce dynamic responses of a structure due to various causes. In this study, control performance of semi-active tuned mass damper(STMD), that can change the damping of tuned mass damper in real time based on structural responses, was investigated with respect to various types of excitation employing numerical simulation. Skyhook control algorithm was used to appropriately modulate the damping ratio of semi-active damper that composes STMD. The control effectiveness of a STMD under harmonic and random excitation were evaluated using a single-degree-of-freedom (SDOF) structure in comparison with a conventional passive tuned mass damper (TMD). The robustness of a STMD and a passive TMD were compared along with the variation of the mass of a SDOF structure. The control performance of STMD using magnetorheological (MR) damper was also investigated in this study. Based on the numerical studios, it was shown that the control effectiveness of the STMD was significantly superior to that of a passive TMD with respect to harmonic and random excitation.

• Proceedings of KOSOMES biannual meeting
• /
• 2006.11a
• /
• pp.131-135
• /
• 2006

The objective of the project is to model and study the geomagnetic field structure and its secular variation in space and in time due to sources in the dynamic fluid outer core. the Earth's spherical harmonic model of the main field and of the secular variation gives the intensity and geomagnetic structure at any location around the Earth, assuming an undistorted, steady state field that no external sources or localized earth anomalies. To consider the practical use of a ship's digital compass in Earth's magnetic field, Earth's spherical harmonic model is searched for the related practical methods and procedures as a basic study in this work.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.40 no.11
• /
• pp.948-956
• /
• 2012

This paper presents the computations of the longitudinal and directional stability derivatives for the SDM(Standard Dynamic Model). The static and dynamic derivatives are evaluated at once using forced harmonic oscillations in the pitch and yaw directions. For the numerical simulations, a 3-D Euler solver that uses a dual time stepping method for unsteady time accurate simulations is applied. This work investigates the variation of the derivatives in terms of the Mach number and the several motion parameters. Good agreement of the pitch and yaw stability derivatives with previously published numerical results and experimental results are observed.

• The Journal of Korean Association of Computer Education
• /
• v.7 no.2
• /
• pp.67-76
• /
• 2004

The problems of developing web based adaptive hypermedia for education using XML are discussed in this paper. We define two different markup languages using XML. The one structures the domain model and the another describes the user model. These language can be easily extended and authored, with the result of obtaining a simple methodology for data structuring in the field of web based educational adaptive hypermedia. Also, We have suggested three learning rules that automatically restructures hypertext networks according to their user browsing behavior. The user profile is contained in a user model, while the knowledge about the domain can be represented in the form of a concept based domain model. Accordingly.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2003.04a
• /
• pp.69-76
• /
• 2003

We investigate the fundamental mechanisms of the dynamic instability when the sinusoidal shaped arch structures subjected to sinusoidal harmonic excitation with pin-ends. In nonlinear dynamics, examining the characteristics of attractor on the phase plane and investigating the dynamic buckling process are very important thing for understanding why unstable phenomena are sensitively originated by various initial conditions. In this study, the direct and the indirect snap-buckling of shallow arches considering geometrical nonlinearity are investigated numerically and compared with the step excitation critical load.