• Nuclear Engineering and Technology
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• 제49권6호
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• pp.1199-1210
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• 2017

A new in-line method for sampling neutrons emitted in (${\alpha}$,n) reactions based on alpha particle source information has been developed for continuous-energy Monte Carlo simulations. The new method uses a continuous-slowing-down model coupled with (${\alpha}$,n) cross section data to precompute the expected neutron yield over the alpha particle lifetime. This eliminates the complexity and computational cost associated with explicit charged particle transport. When combined with an integrated alpha particle decay source sampling capability, the proposed method provides an efficient and accurate method for sampling (${\alpha}$,n) neutrons based solely on nuclide inventories in the problem, with no additional user input required. Results from several example calculations show that the proposed method reproduces the (${\alpha}$,n) neutron yields and energy spectra from reference experiments and calculations.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2005년도 학술발표회(2)
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• pp.1457-1457
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• 2005

• 한국환경과학회지
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• 제23권2호
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• pp.323-330
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• 2014

Transport of bed load and suspended particle in coastal waters is main factor causing change in shoreline, and effective measurement method and appropriate equipment is required. To measure bed load and suspended particle transport an equipment was designed and manufactured, and it was applied in the field. The equipment consists of four main elements, body supporter, bed load and suspended particle sampler, sampler support and lock. Eight samplers were installed along the circumference of each supporter, and each sample is a 45-degree intervals. The field experiment was done once along Gyeongpo beach in August 2013. This note described the design and function of the equipment and results of field experiments.

• 한국지반공학회지:지반
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• 제13권5호
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• pp.155-168
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• 1997

흙 세립자의 이탈 및 유동은 지반공학이나 지반환경공학적인 관점에서 매우 중요한 현상 중의 하나이다. 특히 지반환경공학적인 견지에서 보면 세림자가 입자유동을 하기 전에 오염물질을 흡착하기 때문에, 오염물질 정화의 방편으로 이용될 수 있다. 본 논문에서는 한국에 가장 편재해 있는 화강풍화토의 입자유동특성을 실내시험에 의해 파악하였다. 실험에 사용된 시료는 대표적인 잔류토라 할 수 있는 서을 신내동, 포이동 및 경북 안동의 시료 각각에 대하여 흐름에 대한 지반특성 치등을 측정하였다. 풍화잔적토에서의 세립분 유동특성에 가장 큰 영향을 미차는 인자는 세립자의 함량과 초기간극률 그리고 입도분포로 나타났고 입자가 이탈되기 시작하는 한계속도는 200번체 통과량에 비례 하여 감소하는 경향을 보였다. 이탈률의 변화율은 간극률에 비례하여 증가함을 보였으며 입도분 포가불량하고200번체 통과량이 적은 시료에서의 입자이탈량이 가장 크게 나타났다. 또한 실험결과를 토대로 단계별 입자유동현상을 표현하는 기본방정식을 모델링하고 유한차분법을 이용하여 해를구하므로써 흐름이 발생하는 지반구조물에서 입자유동현상이 미치는 영향을 파악할 수 있는 토대를 마련하였다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제28권6호
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• pp.9-15
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• 2023

In order to properly evaluate the spatio-temporal variations of groundwater flow, the data obtained in field experiments should be corroborated into numerical simulations. Particle tracking method is a simple simulation tool often employed in groundwater simulation to predict groundwater flow paths or solute transport paths. Particle tracking simulations visually show overall the particle flow path along the entire aquifer, but no previous simulation studies has yet described the parameter values at grid nodes around the particle path. Therefore, in this study, a new technical approach was proposed that enables acquisition of parameters associated with particle transport in grid nodes distributed in the center of the particle path in groundwater. Since the particle tracking path is commonly referred to as streamline, the algorithm and codes developed in this works designated streamline analysis method. The streamline analysis method can be applied in two-dimensional and three-dimensional finite element or finite difference grid networks, and can be utilized not only in the groundwater field but also in all fields that perform numerical modeling.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2006년도 총회 및 춘계학술발표회
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• pp.216-219
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• 2006

Water retention curve (WRC), one of soil hydraulic properties, is often approximated by property-transfer models (PTMs). Using the PTMs, we can estimate the WRCs from other physical properties such as particle-size distribution (PSD). The objective of this work was to investigate the performance of two PTMs with different origins for numerical simulations on transport of Benzo[a]pyrene in a soil. To do this, we chose both PTMs with different origins, i.e., (1) the lognormal distribution model (L anti NL models), and (2) the modified $Kov\'{a}cs$ model (MK model). The MK model showed tile worse performance in estimation of the WRCs. When transport of B[a]P was simulated, the MK model predicted to move farther than the L and NL models did, indicating that transport of B[a]P in a soil can be greatly influenced by the choice of PTMs.

• 멤브레인
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• 제7권3호
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• pp.150-156
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• 1997

입자의 정밀여과에 있어 임계플럭스의 이론치를 계산하기 위해 확산(diffusion), 횡방향이동(lateral migration), 전단유도확산(shear induced diffusion), 그리고 입자의 정전기적 반발력에서 기인하는 상호작용에 의한 상승이동(interation enhanced migration) 등의 입자의 역전달 이동을 고려하였다. 보통의 여과조건에서 제타전위의 절대치가 20~40mV이고 직경이 0.1$\mu{m}$~10$\mu{m}$인 입자의 경우 상호작용에 의한 이동이 가장 중요한 역전달 메카니즘이었다. 입자크기에 따라 계산된 임계플럭스값을 실험적으로 확인하기 위해 다양한 크기를 갖는 구형인 적철광(hematite)입자를 합성하여 여과실험을 수행하였다. 이 실험치는 역전달 이론에 의해 예측된 플럭스의 이론치와 비교적 잘 일치하였다.

• Water Engineering Research
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• 제3권2호
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• pp.75-84
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• 2002

An Euler-Lagrange two-phase flow model is presented fur simulation sheet-flow transport under wave and current. The flow is computed by solving the Reynolds Averaged Navier-Stokes equation in conjunction with the k-$\varepsilon$ turbulence model for turbulence closure. The sediment transport is introduced as a motion of granular media under the action of unsteady flow from the Lagragian point of view. In other word, motion of every single particle is numerically traced with Movable Bed Simulator (MBS) code based on the Distinct Element Method (DEM), in which the frequent interparticle collision of the moving particles during the sheet-flow transport is sophisticatedly taken into account. The particle diameter effect on time-dependent developing process of sheet-flow transport is investigated, by using three different diameter sizes of sediment. The influence of an imposed current on oscillatory sheet-flow transport is also investigated. It is concluded that the sediment transport rate increases due to the relaxation process related to the time-lag between flow velocity and sediment motion.

• 한국대기환경학회:학술대회논문집
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• 한국대기환경학회 2000년도 춘계학술대회 논문집
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• pp.193-194
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• 2000

To investigate the characteristics of fine particles and the relationships between pollutant concentrations and long-range transport patterns in Asia area, continuous every 6-day sampling (case 1) and an intensive field sampling (case 2) had been carried out between March 1998 and July 1999 at Taean, Korea. Anionic ($Cl^{-}$, ${NO_{3}}^{-}$, ${SO_{4}}^{2-}$) and Cationic ($Na^+$, ${NH_{4}}^{ +}, $K^+$, $Mg^{2+}$, $Ca^{2+}$) concentrations of $PM_{2.5}$ particle were analyzed. The major objective of this study is to investigate the relationships between the chemical compounds of $PM_{2.5}$ and the long-range transport patterns during intensive sampling period.

• 한국대기환경학회지
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• 제33권1호
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• pp.45-53
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• 2017

A high resolution model is proposed for calculating the temperature field of a large city, based upon a Lagrangian particle model. Utilizing the analogy between the heat and mass transport phenomena in turbulent flows, a Lagrangian particle model, originally developed for air pollutant dispersion problems, is adapted for simulating heat transport. In the model conceptual heat particles are released into the atmosphere from the heat sources and move along with the turbulent winds in accordance with the Markov process. The potential temperature assumed to be conserved along with heat particles serves as a tag, so the temperature fields can be deduced from the distribution of particles. The wind fields are constructed from a diagnostic meteorology model incorporating a morphological model designed for building flows. Test run shows the robustness of the modeling system.