• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.2
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• pp.96-101
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• 2003

Recently, Fractal Image Coding has been studied as a way of efficient data compressing scheme. In the beginning, Fractal Image Coding has been studied for the data compressing in black ＆ white images and linear images. A. E. Jacquin suggested LIFS which expends to Fractal Image Coding for a gray scale image. Currently, YTKT's LIFS scheme which is using Gram-Schmidt is so efficient that enough to compete with the JPEG which is the national standards. This paper investigates the way of greatly reduced calculation for the orthogonalization algorithm.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.1
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• pp.82-88
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• 2009

The structure of steady wave system is considered which is admitted by the continuum equations for materials that undergo phase transformations with exothermic chemical reaction. With its theoretical basis in one-dimensional continuum shock structure analysis, the present approach estimates the micro-width of waves associated with phase transformation phenomena, n-heptane is selected as the hydrocarbon fuel for evaporation and condensation analysis while HMX is used for melting and freezing analysis of solid rocket propellant. The estimated thickness of evaporation - condensation front of n-heptane is on the order of $10^{-2}$ micron while the HMX melting - freezing front thickness is estimated at 1 micron.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.18.2-18.2
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• 2011

We study and analyze here a novel and simple approach to produce copper oxide nanowires in a methanol as an alternative to chemical synthesis routs and VLS-growth method. First, copper oxide nanowires are grown from copper nanoparticles in methanol at $60^{\circ}C$. Nanoparticles are synthesized via inert gas condensation, one of the dry processes. Synthesized nanowires were confirmed via XRD, FESEM and TEM. As a result, all particles have grown to Cu2O nanowires (20~30 nm in diameter, 5~10 um in length; aspect ratio >160~500). Next, these synthesized oxide nanowires are reduced copper nanowires in the furnace under hydrogen flow at $200{\sim}450^{\circ}C$. The evolution of oxide nanowires and their transformation to copper nanowires is studied as a function of time.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.429-433
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• 2013

Silicon, carbon, and B4C powders were used as raw materials for the fabrication of porous SiC. ${\beta}$-SiC was synthesized at $1500^{\circ}C$ in an Ar atmosphere from a silicon and carbon mixture. The synthesized powders were pressed into disk shapes and then heated at $2100^{\circ}C$. ${\beta}$-SiC particles transformed to ${\alpha}$-SiC at over $1900^{\circ}C$, and rapid grain growth of ${\alpha}$-SiC subsequently occurred and a porous structure with elongated plate-type grains was formed. The mechanism of this rapid grain growth is thought to be an evaporation-condensation reaction. The mechanical properties of the fabricated porous SiC were investigated and discussed.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.175-178
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• 2010

동하중의 영향을 받는 구조물의 효율적인 구조 해석 및 최적화 수행을 위해 동하중을 등가정하중으로 변환하는 방법이 요구된다. 이 때 적절한 자유도를 선정하여 등가정하중을 부여하는 것이 중요하다. 기존방법에서는 시스템 축소기법을 통해 일정 개수 이상의 주자유도를 선택하여 등가정하중을 부여하고 그 결과 변위가 동하중 하에서의 변위와 같도록 하였다. 그러나 보수적인 결과를 얻기 위한 제한 조건의 지배적인 성격으로 인하여 등가정하중 하에서의 변위가 지나치게 크게 나타나 그 효율성이 떨어지게 되었다. 본 연구에서는 등가정하중의 변환에 있어서 효율성을 높이는 방안을 제안한다. 제안기법은 보수적 결과를 얻는 범위 내에서 과도응답해석 결과와의 오차를 크게 줄일 수 있다. 수치예제를 통해 제안기법의 결과를 기존 기법의 결과와 비교해본다.

• Bulletin of the Korean Chemical Society
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• v.12 no.4
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• pp.392-397
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• 1991

A stereocontrolled synthesis of (${\pm}$)-isocomene (1) via selective monoketalization of tricyclo[6.3.0.$0^{1.5}$]undeca-4,7-dione(13) was reported. Grignard reaction of bicyclic enone 10, which was prepared from 2-methyl-1,3-cyclopentadione, gave the 1,4-addition product 11. The subsequent aldol condensation product 12 was converted to mesyl derivative 13. Transformation from 13 to the desired product 19 was achieved by a series of reactions, i.e., the selective monoketalization at C-4 carbonyl group, the elimination of a mesyl group, Birch alkylation, methylation at C-6, the reduction of carbonyl group, the dehydration of alcohol 18, and hydrolysis of the ketal group.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.1
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• pp.57-63
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• 2007

The systematic method to construct equivalent static load from a given dynamic load is proposed in the present study. Previously reported works to construct equivalent static load were based on ad hoc methods. Due to improper selection of loading position, they may results in unreliable structural design. The present study proposes the employment of primary degrees of freedom for imposing the equivalent static loads. The degrees of freedom are selected by two-level condensation scheme with reliability and efficiency. In several numerical examples, the efficiency and reliability of the proposed scheme is verified by comparison displacement for equivalent static loading and dynamic loading at the critical time.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.1
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• pp.65-73
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• 2007

In the inverse perturbation method, enormous computational resource was required to obtain reliable results, because all unspecified DOFs were considered as unknown variables. Thus, in the present study, a reduced system method is used to condense the unspecified DOFs by using the specified DOFs, and to improve the computational efficiency as well as the solution accuracy. In most of the conventional reduction methods, transformation errors occur in the transformation matrix between the unspecified DOFs and the specified DOFs. Thus it is hard to obtain reliable and accurate solution of inverse perturbation problems by reduction methods due to the error in the transformation matrix. This numerical trouble is resolved in the present study by adopting iterative improved reduced system(IIRS) as well as by updating the transformation matrix at every step. In this reduction method, system accuracy is related to the selection of the primary DOFs and Iteration time. And both are dependent to each other So, the two level condensation method (TLCS) is selected as Selection method of primary DOFs for increasing accuracy and reducing iteration time. Finally, numerical verification results of the present iterative inverse perturbation method (IIPM) are presented.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.4
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• pp.328-336
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• 2012

In this paper, we propose a robust fingertip extraction and extended Continuously Adaptive Mean Shift (CAMSHIFT) based robust hand gesture recognition for natural human-like HRI (Human-Robot Interaction). Firstly, for efficient and rapid hand detection, the hand candidate regions are segmented by the combination with robust $YC_bC_r$ skin color model and haar-like features based adaboost. Using the extracted hand candidate regions, we estimate the palm region and fingertip position from distance transformation based voting and geometrical feature of hands. From the hand orientation and palm center position, we find the optimal fingertip position and its orientation. Then using extended CAMSHIFT, we reliably track the 2D hand gesture trajectory with extracted fingertip. Finally, we applied the conditional density propagation (CONDENSATION) to recognize the pre-defined temporal motion trajectories. Experimental results show that the proposed algorithm not only rapidly extracts the hand region with accurately extracted fingertip and its angle but also robustly tracks the hand under different illumination, size and rotation conditions. Using these results, we successfully recognize the multiple hand gestures.

• Applied Chemistry for Engineering
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• v.10 no.4
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• pp.509-514
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• 1999

In Preparing $BaTiO_3$ powder under hydrothermal conditions, effects of reaction period feedstock concentration and mixing rate on crystallinity, mean size and size distribution of particles were studied. Experimental results showed that the particle size became smaller with its narrow distribution as the reaction period and mixing rate increased, but feedstock concentration decreased in contrast with the results based on the classical nucleation-growth model. From these results, $BaTiO_3$ particles seem to be prepared hydrothermally through a multiple reaction procedure that includes dissolution, precipitation, hydrolysis-condensation, aggregation, diffusion and transformation.