• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.101.2-101.2
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• 2013

We present a new computational fluid dynamic (CFD) simulation code. The code employs the moving and polyhedral unstructured mesh scheme, which is known as a superior approach to the conventional SPH (smoothed particle hydrodynamics) and AMR (adaptive mesh refinement) schemes. The code first generates unstructured meshes by the Voronoi tessellation at every time step, and then solves the Riemann problem for surfaces of every Voronoi cell to update the hydrodynamic states as well as to move former generated meshes. For the second-order accuracy, the MUSCL-Hancock scheme is implemented. To increase efficiency for generating Voronoi tessellation we also develop the incremental expanding method, by which the CPU time is turned out to be just proportional to the number of particles, i.e., O(N). We will discuss the applications of our code in the context of cosmological simulations as well as numerical experiments for galaxy formation.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.65.2-65.2
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• 2014

We present a new hydrodynamic simulation code based on the Voronoi tessellation for estimating the density precisely. The code employs both of Lagrangian and Eulerian description by adopting the movable mesh scheme, which is superior to the conventional SPH (smoothed particle hydrodynamics) and AMR (adaptive mesh refinement) schemes. The code first generates unstructured meshes by the Voronoi tessellation at every time step, and then solves the Riemann problem for all surfaces of each Voronoi cell so as to update the hydrodynamic states as well as to move current meshes. Besides, the IEM (incremental expanding method) is devised to compute the Voronoi tessellation to desired degree of speed, thereby the CPU time is turned out to be just proportional to the number of particles, i.e., O(N). We discuss the applications of our code in the context of cosmological simulations as well as numerical experiments for galaxy formation.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.57.2-57.2
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• 2011

To study the formation and evolution of sub-galactic scale structures, we have added SPH (Smoothed Particle Hydrodynamics) method into an existing cosmological PMTree code, GOTPM. To follow the evolution of gas particles, we consider heating/cooling processes, star formation, and energy & metal feedback by supernova explosion. We have performed various tests for the new code and found that the results reproduce observed quantities or follow the known analytic solutions. We present a test simulation of isolated disk galaxy with a focus on whether the star formation reproduces the observed features.

• Journal of Microbiology and Biotechnology
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• v.3 no.2
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• pp.91-94
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• 1993

A 3-isopropylmalate dehydrogenase (3-IPMD) gene was cloned from Kluyveromyces fragilis. pJK104 could complement Escherichia coli leuB and Saccharomyces cerevisiae leu2 auxotrophs. The coding region was subcloned and the nucleotide sequence was determined. A 1.8 Kb EcoRI/SphI fragment of pJK104 subcloned in pUC18 could still complement the leuB mutation. An open reading frame of 1164 bp that corresponds to a polypeptide of 387 amino acids was found in the cloned fragment. The homology between the 3-isopropylmalate dehydrogenase of S. cerevisiae and that of K. fragilis was 68.13％ in nucleotides.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.40.1-40.1
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• 2013

We perform a set of N-body/SPH simulations of galaxy interactions between early- and late-type galaxies with the mass ratio of 2 to 1. We show that mass transfer during a fly by interaction (the closest approach distance ~50kpc) can cause the morphology transformation of an early-type galaxy to a late type. In our simulations, we vary the orbital parameters of the interactions and the cold gas fraction of the late-type galaxy to compare how the morphology transformation is affected by the amount of mass transfer and orbital angular momentum of cold gas accreted to the early type. We also include hot halo gas in the galaxy models and show the location of the tidal bridge can be influenced by the shock generated during the collision.

• Structural Engineering and Mechanics
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• v.32 no.2
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• pp.235-249
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• 2009

The response of concrete structures subjected to shock and blast load involves a rapid transient phase, during which material breach may take place. Such an effect could play a crucial role in determining the residual state of the structure and the possible dispersion of the fragments. Modelling of the transient phase response poses various challenges due to the complexities arising from the dynamic behaviour of the materials and the numerical difficulties associated with the evolving material discontinuity and large deformations. Typical modelling approaches include the traditional finite element method in conjunction with an element removal scheme, various meshfree methods such as the SPH, and the mesoscale model. This paper is intended to provide an overview of several alternative approaches and discuss their respective applicability. Representative concrete material models for high pressure and high rate applications are also commented. Several recent application studies are introduced to illustrate the pros and cons of different modelling options.

• Journal of Korean Ophthalmic Optics Society
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• v.4 no.2
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• pp.129-133
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• 1999

For the myopia eyes of the people which are ametropia, the classified distribution has showed % for the simple myopic, 50% for the compound myopic astigmatism, 15% for the simple myopic astigmatism and 19% for the mixed astigmatism. The myopic ametropia for the both eyes has the distribution of 35% for -0.50D~-2.00Dptr, 54% for -2.00~6.00Dptr, and 11% for over -6.00Dptr. The classifying distribution for the age for the myopic ametropia was 54% for 15~20, 22% for 21~40, 14% for 41~60 and 10% for 61. The occupational distribution for the myopic ametropia has showed 61.5% for the student(Middle, High, College), 13.5% for the office worker, and 15% for the house wives as well as the small business. The hour affecting the refraction most for a day was after P.M. 7 which recorded 45% as the highest value. The reason is that the myopia degree decreases in the morning as the cornea flats and the situation is reversed in the afternoon so that there is a difference of Sph -0.50D and as getting darker the refraction degree of the light coming through the enlarged pupil refraction around the cornea is high. For the seasons the highest myopic degree has been recorded for 68% in the summer due to the shortage of nutrition and the climination inside the body by the exhaustion of sweat. In the blood types A and B are distributed closely as 34% and more active man with O has recorded higher myopic degree than woman. However woman showed higher accommodation power than man regardless the blood types. In the characteristic factors of myopic eye, the character feels fatigue easily has showed the distribution for 42% which is the highest and it could be classified largely by two the.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.6
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• pp.475-480
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• 2001

Glasses in he system CuO-P$_2$O$_{5}$ -Nb$_2$O$_{5}$ -Nb$_2$O$_{5}$ -V$_2$O$_{5}$ were prepared by a press-quenching method on the copper plate. the glass-ceramics from these glasses were obtained by post-heat treatment, and the crystallization behavior and DC conductivities were determined. The conductivities of the glasses were range from 10$^{-6}$ s.$cm^{-1}$ / at room temperature ,but the conductivities of the glass-ceramics were 10$^{-3}$ s.$cm^{-1}$ / increased by 10$^3$ order. The crystalline product in the glass-ceramics was CuV$_2$O$_{6}$ . the crystal growth of CuV$_2$O$_{6}$ phase increased with heat-treatment conditions. The linear relationship between il($\sigma$T) and T$^{-1}$ suggested that the electrical conduction in the present glass-ceramics would be due to a small polaron hopping(SPH) mechanism.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.6
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• pp.164-171
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• 2008

A modified generalized particle algorithm, MGPA, was suggested to improve the computational efficiency of standard SPH method in numerical analysis of high speed impact behavior. This method uses a numerical failure mechanism than material failure models to describe the target penetration. MGPA algorithm was more effective to describe the impact phenomena and new boundaries produced during the calculation process were well recognized and treated in the target penetration problem of a bullet. When bullet perforation problems were analyzed by this method, MGPA algorithm calculation gives the stable numerical solution and stress oscillation or particle penetration phenomena were not shown. The error range in ballistic velocity limit is less than $2{\sim}13%$ for various target thickness.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.35.3-36
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• 2016

Density and velocity perturbations in scales most relevant for the first galaxy formation are strongly affected by large-scale density perturbations, velocity-divergence perturbations and the baryon-cold dark matter (CDM) streaming velocities. Even at redshifts as high as z~200, this mode-mode coupling imprints a significant impact on the small-scale perturbations, at the wavenumber k >${\sim}100Mpc^{-1}$, as was calculated in our recent work. This implies that cosmological initial conditions based on the usual linear theory is no longer valid in these scales. We present a new cosmological initial condition generator, BCCOMICS, which generates initial conditions for the cold dark matter (CDM) and baryons in scales most relevant for the first galaxy formation. BCCOMICS is based on the linear perturbation theory including the mode-mode coupling terms, and generates cosmological initial conditions for the SPH-basded code GADGET and the AMR-based code ENZO. We also present our preliminary result on the cosmic variance of the first galaxy formation, studied by using BCCOMICS.