• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2008.04a
• /
• pp.356-361
• /
• 2008

Eigenvalue reduction schemes approximate the lower eigenmodes that represent the global behavior of the structures. In the previous study, we proposed a two-level condensation scheme (TLCS) for the construction of a reduced system. And we have improved previous TLCS with combination of the iterated improved reduced system method (IIRS) to increase accuracy of the higher modes intermediate range. In this study, we apply previous improved TLCS to multi-level sub-structuring scheme. In the first step, the global system is recursively partitioned into a hierarchy of sub-domain. In second step, each uncoupled sub-domain is condensed by the improved TLCS. After assembly process of each reduced sub-eigenvalue problem, eigen-solution is calculated by Lanczos method (ARPACK). Finally, Numerical examples demonstrate performance of proposed method.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.22 no.8
• /
• pp.742-747
• /
• 2012

A modified NDIF method using a sub-domain approach is introduced to extract highly accurate eigenvalues of two-dimensional, arbitrarily shaped acoustic cavities. The NDIF method, which was developed by the authors for the eigen-mode analysis of arbitrarily shaped acoustic cavities, has the feature that it yields highly accurate eigenvalues compared with other analytical methods or numerical methods(FEM and BEM). However, the NDIF method has the weak point that it can be applicable for only convex cavities. It was revealed that the solution of the NDIF method is very inaccurate or is not suitable for concave cavities. To overcome the weak point, the paper proposes the sub-domain method of dividing a concave domain into several convex domains. Finally, the validity of the proposed method is verified in two case studies, which indicate that eigenvalues obtained by the proposed method are more accurate compared to the exact method, the NDIF method, or FEM(ANSYS).

• The Journal of the Korea Contents Association
• /
• v.2 no.4
• /
• pp.23-29
• /
• 2002

This paper suggest the image compression that is needed to process PACS in medical information system. The image decoding method is used Linear-predictor and Lloyd-Max quantizer(quantization) in the Wavelet transform domain. Wavelet Transform Method is processed the multi-resolution by dividing image into 10 sub-bands of 3 levels. Low frequency domain that is sensitive to human visual characteristic is encoded by DPCM which is lossless encoding methods, and Lloyed-Max quantizer, the optimal quantizer for reducing ringing and aliasing in the image of inter sub-band, is used in the remaining high frequency domain of sub-band. The examination verifies that decompressed images are superior by the result that PSNR is 28.53dB on the input image, 512$\times$152 abdominal CT image and Chest image.

• Korean Journal of Mathematics
• /
• v.19 no.2
• /
• pp.163-169
• /
• 2011

Let D be an integral domain, S be a multiplicative subset of D such that DS is a PID, and D[X] be the polynomial ring over D. We show that S is an almost splitting set in D if and only if every nonzero prime ideal of D disjoint from S contains a primary element. We use this result to give a simple proof of the known result that D is a UMT-domain and Cl(D[X]) is torsion if and only if each upper to zero in D[X] contains a primary element.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.24 no.7
• /
• pp.730-736
• /
• 2013

Time-domain clutter generation model for airborne pulse doppler phase-array radar is presented. Time-domain surface clutter signal is generated assuming earth of a sphere and considering geometry of a clutter patch, and generation of sub-array clutter signal is presented. The generated sub-array clutter signal can be used by simulation input signal in various radar applications of DBF(Digital Beamforming), ABF(Adaptive Beamforming), Stap(Space-Time Adaptive Processing) and etc.

• Coupled systems mechanics
• /
• v.4 no.3
• /
• pp.263-277
• /
• 2015

This paper presents a coupled FEM-BEM strategy for the numerical analysis of elastodynamic problems where infinite-domain models and complex heterogeneous media are involved, rendering a configuration in which neither the Finite Element Method (FEM) nor the Boundary Element Method (BEM) is most appropriate for the numerical analysis. In this case, the coupling of these methodologies is recommended, allowing exploring their respective advantages. Here, frequency domain analyses are focused and an iterative FEM-BEM coupling technique is considered. In this iterative coupling, each sub-domain of the model is solved separately, and the variables at the common interfaces are iteratively updated, until convergence is achieved. A relaxation parameter is introduced into the coupling algorithm and an expression for its optimal value is deduced. The iterative FEM-BEM coupling technique allows independent discretizations to be efficiently employed for both finite and boundary element methods, without any requirement of matching nodes at the common interfaces. In addition, it leads to smaller and better-conditioned systems of equations (different solvers, suitable for each sub-domain, may be employed), which do not need to be treated (inverted, triangularized etc.) at each iterative step, providing an accurate and efficient methodology.

• Nano
• /
• v.13 no.12
• /
• pp.1850149.1-1850149.10
• /
• 2018

Ferroelectric particles have been applied in the photocatalytic field because the spontaneous polarization results in the internal electric field, which can accelerate the separation and migration of photogenerated carriers. In this study, the $BaTiO_3$ (BT) fibers are synthesized by electrospinning. The BT fibers calcined above $800^{\circ}C$ exhibit a strong ferroelectric property, which is verified by a typical butterfly-shaped displacement-voltage loop. It is found that the BT fibers with the single-domain structure exhibit better photocatalytic performance than that with the multi-domain configuration. When the single-domain transforms into multi-domain, the integrated internal electric field correspondingly breaks up, inducing that the internal electric field might cancel each other out and diminish the separation of photogenerated carriers. Also, the Au nanoparticles can improve the photocatalytic activity further on account of the surface plasmon resonance. Therefore, it is suggested that Au nanoparticles decorated on ferroelectric BT nanomaterials are promising photocatalysts.

• Journal of The Korean Association For Science Education
• /
• v.22 no.3
• /
• pp.525-539
• /
• 2002

The purpose of the study was to assess science achievement of 11th grade students. Science achievement was assessed in knowledge and inquiry domains. The knowledge domain included three sub-areas including memory, understanding and application. The inquiry domain was divided into four sub-areas involving identifying problems, designing inquiry, data analysis and drawing conclusions. The results indicated that overall science achievement of the 11th grade students who participated in the study was at the proficient level. Regarding the knowledge domain, the achievement in the understanding and application areas was at the proficient level, and the achievement in the memory area was at the basic level. In the inquiry domain, the achievement in all the sub-areas except the identifying problems area which was at the basic level was at the proficient level. There were no gender differences in overall science achievement. However, gender differences were found in all the sub-areas except the application area and varied across the sub-areas. Also, there were significant differences in science achievement among regions.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.19 no.10
• /
• pp.1069-1074
• /
• 2009

A sub-domain method for free vibration analysis of arbitrarily shaped, concave membranes with a deep groove is proposed in the paper. The proposed method divides the concave membrane of interest into two convex regions. The vibration displacement(approximate solution) of each convex region is assumed by linearly superposing plane waves generated at edges of the region. A sub-system matrix for each convex region is extracted by applying a provisional boundary condition to the approximate solution. Finally, a system matrix, which of the determinant gives eigenvalues of the concave membrane, is made by considering the fixed boundary condition(displacement zero condition) at edges and the compatibility condition(the condition of continuity in displacement and slope) at the interface between the two regions. Case studies show that the proposed method is valid and accurate when the eigenvalues by the proposed are compared to those by NDIF method, FEM, or the exact method.

• Journal of the Korean Society of Earth Science Education
• /
• v.5 no.1
• /
• pp.114-123
• /
• 2012

This study investigates the effect of environmental club activities of the creative experiential learning activities on the improvement of students' Environmental Literacy and Pro-environmental Behavior. For that purpose, This study divided 24 students at Jinhae U Elementary School into test groups of 12 students and Control groups of 12 students. Test groups participated in the 'GomGomi' environmental Club for sixteen times from March 2011 to December 2011. Conclusions of this study include; First, we found that the environmental club activities is effective to improve the students' environmental Literacy overall. Specifically, the Environmental Club Activities was effective in the sub-catagories of environmental Literacy such as 'rights of nature' and 'eco-crisis'. However, there was no significant change in the sub-category of 'human exemptionalism' Second, we found that the environmental club activities is effective to improve students' pro-environmental behavior overall. Specifically, the environmental club activities was effective in the sub-domains of Pro-environmental Behavior such as 'cognitive domain' and 'affective domain'. However, there was no significant change in the sub-domains of 'behavioral domain'. Summary, the environmental club activities was shown to be effective for improving their environmental literacy and pro-environmental behavior; This study implies that the environmental club activities of the creative experiential learning activities would be a effective tool to help students to improve their environmental literacy and pro-environmental behavior.