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Battsetseg Gereltbyamba,이창훈 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.7
This study is related to the transport of inertial particles in a differentially heated cubic cavity. Three moderate values of the Rayleigh number 8 8 8 Ra = 2 ´10 , 4 ´10 , 7 ´10 are considered. There is no back reaction from the particle on the flow, i.e., one-way coupling. Small ( d = 15 mm ) , intermediate ( d = 35 mm ) , and large ( d = 75 mm ) sizes of particles are used to study the particle behavior. The particles are influenced by two forces, the drag and gravity force. From our simulations, we observed that a large fraction of smallsized particles follow the flow motion and they are not significantly affected by gravity, remaining suspended in the flow. On the other hand, large-sized particles quickly settle down toward the bottom wall under gravity and are deposited at the bottom wall. Owing to this difference, particle distribution for small particles and large particles is quite different. Small particles tend to accumulate near a particular region near hot and cold walls, while the particle depletion region is observed in the core region in a particular pattern. Large particles are almost uniformly distributed. Detailed mechanisms are discussed using the flow field and particle response characteristics.
Quintessence from virtual dark matter
Damdinsuren, Battsetseg,Sim, Jonghyun,Lee, Tae Hoon IOP 2017 Classical and quantum gravity Vol.34 No.17
<P>Considering a theory of Brans–Dicke gravity with general couplings of Higgs-like bosons including a non-renormalizable term, we derive the low-energy effective theory action in the Universe of a temperature much lower than the Higgs-like boson mass. Necessary equations containing gravitational field equations and an effective potential of the Brans–Dicke scalar field are obtained, which are induced through virtual interactions of the Higgs-like heavy field in the late-time Universe. We find a de Sitter cosmological solution with the inverse power law effective potential of the scalar field and discuss the possibility that the late-time acceleration of our Universe can be naturally explained by means of the solution. We also investigate stability properties of the quintessence model by using a linear approximation.</P>
Flow modification by inertial particles in a differentially heated cubic cavity
Gereltbyamba, Battsetseg,Lee, Changhoon Elsevier 2019 The International journal of heat and fluid flow Vol.79 No.-
<P><B>Abstract</B></P> <P>In this study, we analyzed particle-laden flow in a differentially heated cubic cavity by using direct numerical simulations and the Lagrangian particle tracking method. The main purpose of this study was to investigate the physical mechanism responsible for the modification of natural convection flow by sedimenting solid particles. Rayleigh number of R a = <SUP> 10 6 </SUP> was considered, and two important parameters, namely, the particle diameter <I>d<SUB>p</SUB> </I> and particle volume fraction Φ<SUB> <I>V</I> </SUB>, were varied in the range of <SUB> d p </SUB> = 25 , 35 , 50 , 75 μ m and <SUB> Φ V </SUB> = 2 × <SUP> 10 − 5 </SUP> , 5 × <SUP> 10 − 5 </SUP> , <SUP> 10 − 4 </SUP> . Extensive numerical investigations were performed by considering the two-way interaction for the following two coupling cases: (i) momentum coupling only; (ii) momentum and thermal coupling between fluid and particles. Behavior of particles, flow modification, and heat transfer characteristics were investigated in detail with the relevant statistics.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We investigated the modification of natural convection flow in a differentially heated cavity filled with air by sedimenting small particles by using direct numerical simulation. </LI> <LI> We investigated two cases, namely, momentum coupling and both momentum and thermal coupling. The major parameters were the particle diameter and particle volume fraction. </LI> <LI> For the momentum coupling case, the particles enhanced the circulatory motion, thus making the flow chaotic. Heat transfer is overall slightly suppressed by particles. </LI> <LI> However, for the momentum and thermal coupling case, the thermal energy exchange between the particles and fluid yields completely different behavior than the momentum coupling case. </LI> <LI> The flow became less chaotic which might be attributed to the conjecture that the chaotic motion is suppressed by thermal diffusive processes due to the active thermal interaction between the particles and fluid. </LI> <LI> As a result, heat transfer is suppressed more than the momentum coupling case through the direct and indirect interactions between the sedimenting particles and fluid. </LI> </UL> </P>
Properties of pitch-like materials obtained using coal extraction
Avid B.,Battsetseg M.,Purevsuren B.,Shiirav G.,Kuznetsov P. N.,Kuznetsova L. I.,Kamenskii E. S. 한국탄소학회 2022 Carbon Letters Vol.32 No.2
The bituminous coal was extracted with different industrial solvents like coal tar (CT), heavy cycle oil (HCO) and with their blends to determine the influence of solvent type on the extract yield, composition, thermal behavior, properties such as solubility to toluene and quinoline. The extracts obtained at 380 °C represented pitch-like solid matter with the softening points of 72–127 °C depending on the solvent used. They were characterized using the elemental and group analysis, FTIR spectroscopy, TG-DTG thermogravimetry and liquid chromatography for benzo(a)pyrene concentration. Also, maltene fractions of some extracts were studied by GC–MS. The results showed coal dissolution and the properties of the extracts to differ greatly depending on the solvent used. Coal tar was more favorable solvent for coal dissolution than HCO. Good correlation between the extract aromaticity and the content of the toluene insolubles was observed. The maltene fractions of the extracts obtained with CT and CT blended with HCO consisted mainly of polycyclic aromatics, and that obtained with the HCO contained also large amount of aliphatic compounds. It was found that the amount of the carcinogenic benzo(a)pyrene (BaP) in the toluene soluble fractions of the extracts were different depending on the solvents used for extraction. The remarkable result was that the BaP concentrations in all extracts were much lower than in the solvents used.
전동볼밀의 복합재 제조공정에서 각종 실험조건에 따른 입자형상 변화 및 DEM 시뮬레이션을 통한 밀링 효율의 고찰 - 회전속도, 매체크기, 매체재질의 영향
보르암갈란 ( Amgalan Bor ),바춘흘루이치커 ( Ichinkhorloo Batchuulun ),자갈사이항바트체첵 ( Battsetseg Jargalsaikhan ),이재현 ( Jehyun Lee ),최희규 ( Heekyu Choi ) 한국화학공학회 2018 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.56 No.2
이 연구는 각각 크기와 재질이 다른 3 가지 종류의 분쇄 매체를 이용하여 회전속도와 밀링 시간의 따른 구리 (Cu) 분말의 형상변화의 과정에 미치는 영향을 관찰하고, 볼 움직임의 DEM시뮬레이션을 행하였다. 전동볼밀에서 볼 움직임의 3차원 시뮬레이션을 통해 분쇄 메커니즘을 규명하기 위하여 분쇄매체의 힘, 운동에너지, 매체 운동속도 등을 계산하였다. 시뮬레이션에서는 회전속도, 볼 재질, 운동속도, 마찰계수 등을 실제 실험조건과 동일하게 조건을 맞추어 투입되는 에너지의 변화량도 계산하였다. 주사전자현미경 결과를 살펴보면 볼 직경이 작을 때 입자형상이 불규칙한 형태에서 구형 형태로 변화하는 것을 알 수 있었다. This study was investigated the effect of the morphology change of copper (Cu) powders under the different rotational speed and milling time by using three kinds of grinding media with different size and materials, and performed DEM simulations of ball behavior. In order to clarify the mechanism of grinding by three - dimensional simulations of the ball behavior in a traditional ball mill, the force, kinetic energy, and medium velocity of the grinding media were calculated. In the simulation, the amount of change of the input energy was also calculated by adjusting the rotational speed, ball material, kinetic velocity, and friction coefficient in the same as the actual experimental conditions. The scanning electron microscope results show that the particle morphology changes from irregular to spherical when the ball size is small.
바야르사이칸 바트체첵,김후식,김영훈,김정진,임우택,Battsetseg, Bayarsaikhan,Kim, Hu Sik,Kim, Young Hun,Kim, Jeong Jin,Lim, Woo Taik 한국암석학회한국광물학회 2022 광물과 암석 (J.Miner.Soc.Korea) Vol.35 No.2
몽골(6종), 미국(1종), 한국(9종)지역에서 채취한 총 16종의 천연 제올라이트를 X-선 회절 분석, X-선 형광 분석, 열 시차, 열 중량 분석 및 양이온 교환능 분석을 통해 특성분석을 수행하였다. 16종의 시료 모두 두 종류 이상의 광물상이 공존하는 혼합광 형태이며, 주로 클라이놉틸로라이트, 휼란다이트, 모데나이트 및 차바자이트와 같은 광물의 조합으로 이루어져 있으며, 일부 시료에서는 운모 점토광물인 일라이트와 석영과 같은 광물이 불순물로 함유되어 있었다. X-선 형광 분석 결과 16종의 천연 제올라이트는 SiO<sub>2</sub>, Al<sub>2</sub>O<sub>3</sub>, K<sub>2</sub>O, CaO, Na<sub>2</sub>O, MgO 및 Fe<sub>2</sub>O<sub>3</sub> 산화물이 함유되어 있었다. 미국 천연 제올라이트인 U-1 시료가 223.3 meq/100 g으로 양이온 교환능이 가장 높게 나타났으며 몽골 천연 제올라이트에서는 M-6 시료가, 한국 천연 제올라이트에서는 K-1 시료가 각각 166.6 meq/100 g으로 가장 높게 나타났다. 열시차 및 열중량 분석 결과 16종의 시료 모두 600℃까지 열적으로 안정성이 우수한 것을 확인 하였다.
교반볼밀을 이용한 밀링공정에서 각종실험조건에 따른 구리분말의 입자형상 변화 및 DEM 시뮬레이션에 의한 정량적 에너지 변화
보르 암갈란,오양가,자갈사이항 바체첵,이재현,최희규,Bor, Amgalan,Batjargal, Uyanga,Jargalsaikhan, Battsetseg,Lee, Jehyun,Choi, Heekyu 한국재료학회 2018 한국재료학회지 Vol.28 No.3
This study investigated the effect of the grinding media of a ball mill under various conditions on the raw material of copper powder during the milling process with a simulation of the discrete element method. Using the simulation of the three-dimensional motion of the grinding media in the stirred ball mill, we researched the grinding mechanism to calculate the force, kinetic energy, and medium velocity of the grinding media. The grinding behavior of the copper powder was investigated by scanning electron microscopy. We found that the particle size increased with an increasing rotation speed and milling time, and the particle morphology of the copper powder became more of a plate type. Nevertheless, the particle morphology slightly depended on the different grinding media of the ball mill. Moreover, the simulation results showed that rotation speed and ball size increased with the force and energy.