• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.4
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• pp.471-476
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• 1986

본 연구에서는 구모양의 석탄가루나 곡식가루등 비금속성 고체입자가 압축파 (shock wave)에 의해 생성된 고온의 기체속에 놓여있을때 일어나는 점화현상을 활성 화에너지(activation energy)가 큰 경우의 접합 점근법을 이용 해석하였다. 이렇게 하여 얻어진 석탄입자에 대한 점화지연시간을 실험치와 비교 이의 타당성을 입증하였 다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.429-433
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• 2004

In games and films, the most highlighted fields in entertainment industry, those special effects such as flame, explosion, smoke, liquid, snow, rain and dust are generated through the particle system. Special effects can be expressed realistically by the particle system API that is a graphic library of high level in game and virtual reality. When developers apply the particle system API in applications, they must exchange parameters repeatedly and compile source codes until special efforts that they want are expressed, and It takes much time until the minute control that have relations between each parameters. This paper develops a particle system API usable in on-line game and real-time virtual reality and presents particle system editor that can see and create special effect easily through attributes adjustment such as position, velocity, color, transparency, size, age, the secondary position, the second velocity etc.

• Journal of Industrial Technology
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• v.20 no.A
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• pp.269-278
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• 2000

The pressure-time profile of the explosion gases can controlled for the use of cartridge explosive with two techniques known as Decoupling and spacing of the charges. Decoupling consists of a space between the explosive column and wall of the blast hole. Four different decoupling index 1.4, 1.8, 2.34, 3.0 are selected in this field study. The level of ground vibrations with each decoupling index was measured and the empirical particle velocity equation from these data was obtained. The condition of new cracks at blast hole are also examined. As the decoupling index is increased, the level of the blast vibration is decreased. But the cracks in rock masses are efficiently formed to remove the broken rock. The vibration constant associated with test sites is given as $K=1564.5(D.L)^{-1.3233}$ in terms of D.I.(decoupling index).

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.922-925
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• 2011

Smoothed Particle Hydrodynamics (SPH) is a Lagrangian method widely used for the modeling fluid flows. Simulations of explosions require, besides the hydrodynamic equations, a realistic equation of state, an energy source term, and a set of chemical kinetic equations to follow the composition changes of the gas during the explosion. The performance of the hydrodynamic equations is investigated in the framework of the Sedov-Taylor blast-wave. The implementation of chemical kinetic equations and equation of state is studied with 1D detonation of TNT slab. Our results are compared to those from analytical and experimental studies.

• Explosives and Blasting
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• v.15 no.3
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• pp.20-32
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• 1997

The pressure-time profile of the explosion gases can be controlled fot the use of cartridge explosives with two techniques Known as Decoupling and Spacing the charges. Decoupling consists in leaving and empty space between the explosive column and wall of the blast hole. Four different decoupling index, 1.4, 1.8, 2.34, 3.0 are selected in this field study. The level of ground vibrations with each decoupling index are measured and the empirical particle vibrations with each decoupling index are measured and the empirical particle velocity equation from these data was obtained. The condition of new cracks at blast hole are also examined. As the decoupling index in increased, the level of the blast vibration is decreased,. But the cracks in rock masses are efficiently formed to remove the broken rock. The vibration constant associated with a given site $K=1564.5(D.I)^{-1.3233}$ in terms of D.I(decopling index).

• Journal of The Korean Astronomical Society
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• v.39 no.4
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• pp.95-105
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• 2006

We have calculated the cosmic ray(CR) acceleration at young remnants from Type Ia supernovae expanding into a uniform interstellar medium(ISM). Adopting quasi-parallel magnetic fields, gasdynamic equations and the diffusion convection equation for the particle distribution function are solved in a comoving spherical grid which expands with the shock. Bohm-type diffusion due to self-excited $Alfv\acute{e}n$ waves, drift and dissipation of these waves in the precursor and thermal leakage injection were included. With magnetic fields amplified by the CR streaming instability, the particle energy can reach up to $10^{16}Z$ eV at young supernova remnants(SNRs) of several thousand years old. The fraction of the explosion energy transferred to the CR component asymptotes to 40-50 % by that time. For a typical SNR in a warm ISM, the accelerated CR energy spectrum should exhibit a concave curvature with the power-law slope flattening from 2 to 1.6 at $E{\gtrsim}0.1$ TeV.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.52.1-52.1
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• 2011

We have implemented the Smoothed Particle Hydrodynamics (SPH) into the cosmological N-body simulation code. The pre-initial particle distribution is set to follow the glacial conditions and the initial temperature of hydro particles is calculated based on the adiabatic process in the expanding backgrounds. Typical adiabatic SPH equations are adopted and, additionally, non-adiabatic processes such as heating/cooling and supernova explosion are added. We study the effect of star formation criteria on the global star formation rate and compare it with the observations.

• Nuclear Engineering and Technology
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• v.55 no.3
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• pp.989-998
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• 2023

Under nuclear reactor severe accidents, the resuspension of radioactive aerosol may occur in the containment due to the disturbing airflow generated by hydrogen combustion, hydrogen explosion and containment depressurization resulting in the increase of radioactive source term in the containment. In this paper, for containment conditions, by considering the contact between particle and rough deposition surface, the distribution of the distance between two contact points of particle and deposition surface, rolling and lifting separation mechanism, resuspension model based on random contact with rough surface (RRCR) is established. Subsequently, the detailed torque and force analysis is carried out, which indicates that particles are more easily resuspended by rolling under low disturbing airflow velocity. The simulation result is compared with the experimental result and the prediction of different simulation methods, the RRCR model shows equivalent and better predictive ability, which can be applicable for simulation of aerosol resuspension in containment during severe accident.

• Journal of The Korean Astronomical Society
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• v.43 no.2
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• pp.25-39
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• 2010

We perform kinetic simulations of diffusive shock acceleration (DSA) in Type Ia supernova remnants (SNRs) expanding into a uniform interstellar medium (ISM). Bohm-like diffusion due to self-excited $Alfv\acute{e}n$ waves is assumed, and simple models for $Alfv\acute{e}nic$ drift and dissipation are adopted. Phenomenological models for thermal leakage injection are considered as well. We find that the preshock gas temperature is the primary parameter that governs the cosmic ray (CR) acceleration efficiency and energy spectrum, while the CR injection rate is a secondary parameter. For SNRs in the warm ISM of $T_0\lesssim10^5K$, if the injection fraction is $\xi\gtrsim10^{-4}K$, the DSA is efficient enough to convert more than 20% of the SN explosion energy into CRs and the accelerated CR spectrum exhibits a concave curvature flattening to $E^{-1.6}$, which is characteristic of CR modified shocks. Such a flat source spectrum near the knee energy, however, may not be reconciled with the CR spectrum observed at Earth. On the other hand, SNRs in the hot ISM of$T_{0}\approx10^{6}K$ with a small injection fraction, $\xi$<$10^{-4}$, are inefficient accelerators with less than 10% of the explosion energy getting converted to CRs. Also the shock structure is almost test-particle like and the ensuing CR spectrum can be steeper than $E^{-2}$. With amplified magnetic field strength of order of $30{\mu}G$ $Alfv\acute{e}n$ waves generated by the streaming instability may drift upstream fast enough to make the modified test-particle power-law as steep as $E^{-2.3}$, which is more consistent with the observed CR spectrum.

• Explosives and Blasting
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• v.23 no.1
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• pp.47-54
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• 2005

An explosion modeling technique was developed by using the spherical discrete element code, $PFC^{3D}$, which can be used to model the dynamic stress wave propagation phenomenon. The modeling technique is simply based on an idea that the explosion pressure should be applied to a $PFC^{3D}$ particle assembly not in the form of an external force (body force), but in the form of a contact force (surface force). A test blast was conducted for a RC column, whose dimension was $600\times300\times1800$ in millimeters. The initial velocities of the surface movements were measured to be in the range of $14\~18\;m/s$ with the initiation times of $1.5\~2.0m$. Then the blasting procedure was simulated by using the modeling technique. The particle assembly representing the concrete was made of cement mortar and coarse aggregates, whose mirco-properties were obtained from the calibration processes. As a result, the modeling technique developed in this study made it possible for the burden to move with the velocity of $17\~24\;m/s$, which are slightly higher values compared to those of the test blast.