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이민형(Minhyeong Lee),최영균(Younggyun Choi),독고석(Seok Dockko),최의소(Euiso Choi) 적정기술학회 2015 적정기술학회지(Journal of Appropriate Technology) Vol.1 No.1
제철소 열간압연 공정에서 발생하는 밀스케일(mill scale)을 간단한 전처리 과정만 거친 뒤 As(V) 흡착제로서 활용해 보고자 하였다. 밀스케일의 주요 구성성분은 magnetite(Fe 3 O 4 ), hematite(Fe 2 O 3 ), wustite(FeO)의 산화철이었으며, wustite의 함량이 가장 높은 것으로 나타났다. 밀스케일을 이용하여 As(V)에 대한 흡착실험을 수행한 결과, 밀스케일 첨가량이 높을수록, 그리고 밀스케일 입자의 크기가 작을수록 흡착능(mgAs/g)이 크게 증가하는 것으로 확인되었다. 또한 밀스케일의 As(V) 흡착용량은 0.1-0.4 mgAs/g 정도인 것으로 확인되었다. In this study, we applied mill scale particles as a cost-effective adsorbent for As (V) removal. The mill scale taken from a nearby iron & steel company was went through the pretreatment procedure (rinsing with 0.1 N NaOH solution and cleaning with DI water) in order to remove oil and grease. From the XRD analysis, the major components of the mill scale turned out to be magnetite, hematite and wustite. In order to analyze the As adsorption characteristics, batch tests with mill scale particles have been carried out. Mill scale dosage and particle size range seriously affected the As adsorption behavior. The As (V) adsorption capacity was estimated to be 0.1-0.4 mgAs/g-mill scale.
Reconfiguration of bio-inspired poroelastic cluster
Minhyeong Lee(이민형),Ehsan Mahravan,Daegyoum Kim(김대겸) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11
Plumed seeds, such as dandelion or milkweed seeds, can fly a distance of kilometers while other types of wind-dispersal seeds disperse a few hundred meters at maximum. The plumed seed consists of many microscopically thin and elastic plumes, and it is well known that this porous structure enables superior flight performance. Although the effects of porosity have been of interest recently, it remains unexplored how the elastic deformation of individual plumes and the resulting reconfiguration of the whole seed change aerodynamic loading. In this study, we numerically examine the effect of elasticity on reconfiguration and drag force for a porous cluster of elastic cylinders, by adopting simplified two-dimensional models. In contrast to common plants or elastic fins that streamline and reduce drag forces when subjected to a fluid flow, the poroelastic cluster reconfigures to enlarge the frontal area and therefore increases the total drag force.
Dynamic interaction between a poroelastic cluster and unsteady flows
Minhyeong Lee(이민형),Ehsan Mahravan,Daegyoum Kim(김대겸) 대한기계학회 2023 대한기계학회 춘추학술대회 Vol.2023 No.11
Plumed seeds like dandelion or milkweed seeds are the most representative poroelastic cluster in nature. Owing to their extraordinary flight performance superior to other types of wind-dispersal seeds, the aerodynamics of plumed seeds has drawn substantial academic attentions in the field of fluid-structure interaction. Aerodynamic roles of porosity and elasticity during the steady flight of poroelastic seed is well known. However, although dynamic response under the flow also significantly affects the flight for all fliers, how the freely flying poroelastic cluster dynamically interact with the unsteady flow still remains elusive. In this study, we numerically investigate the dynamic interaction between poroelastic clusters and unsteady flows by adopting simplified two-dimensional models with various porosity and elasticity.
Reconfiguration of bio-inspired poroelastic cluster
Minhyeong Lee(이민형),Ehsan Mahravan,Daegyoum Kim(김대겸) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11
Plumed seeds, such as dandelion or milkweed seeds, can fly a distance of kilometers while other types of wind-dispersal seeds disperse a few hundred meters at maximum. The plumed seed consists of many microscopically thin and elastic plumes, and it is well known that this porous structure enables superior flight performance. Although the effects of porosity have been of interest recently, it remains unexplored how the elastic deformation of individual plumes and the resulting reconfiguration of the whole seed change aerodynamic loading. In this study, we numerically examine the effect of elasticity on reconfiguration and drag force for a porous cluster of elastic cylinders, by adopting simplified two-dimensional models. In contrast to common plants or elastic fins that streamline and reduce drag forces when subjected to a fluid flow, the poroelastic cluster reconfigures to enlarge the frontal area and therefore increases the total drag force.
TBM 주변 지반상태예측을 위한 전기비저항 이론식 유도 및 검증
홍창호,이민형,조계춘,Hong, Chang-Ho,Lee, Minhyeong,Cho, Gye-Chun 한국터널지하공간학회 2020 한국터널지하공간학회논문집 Vol.22 No.1
국내에서 TBM 공법을 활용한 터널건설 시 점차 건설심도가 깊어지고 있으며, 이로 인해 상부 지반조사 단계에서 충분한 예측 정확도를 획득하기 위해서는 시추조사 및 물리탐사 비용이 증가하게 된다. 이러한 문제를 극복하기 위해 터널 시공 중 터널 굴착면 전방 예측을 위한 방법들이 제시되었다. 프로브 드릴링을 활용한 굴착면 전방 예측은 코어회수, 시추공 내부 이미지 등을 활용할 수 있는 장점이 있지만 실제 TBM 내에 설치가 어렵고 터널 막장 전체가 아닌 국부적인 지반만을 파악할 수 있다. TSP 등 탄성파를 활용한 방법은 100 m 이상의 긴 탐사거리를 가지지만 신호발생을 위해 발파를 사용하므로 세그먼트 라이닝, 백필 등의 안정성에 영향을 미칠 수 있다. TEPS를 포함한 전자기파 탐사는 지하수 층 등 전도성 있는 이상대를 파악하는 데 적합하지만 소구경 TBM에 설치할 수 있는 전극의 개수가 한정적이며 이는 탐사 범위의 감소 등을 야기한다. 본 연구에서는 전기비저항 탐사 시 굴착면에 설치되는 전극의 개수를 최소화하기 위해 TBM의 굴착면과 측면에 전극이 설치되었을 때에 대한 탐사 이론식을 제시하고 실내실험을 통해 검증하였다. Since the depth of tunneling with tunnel boring machine (TBM) becomes deeper and deeper, the expense for site investigation for coring and geophysical survey increases to obtain the sufficient accuracy. The tunnel ahead prediction methods have been introduced to overcome this limitation in the stage of site investigation. Probe drilling can obtain the core and borehole images from a borehole. However, the space in TBM for the probe drilling equipment is restricted and the core from probe drilling cannot reflect the whole tunnel face. Seismic methods such as tunnel seismic prediction (TSP) can forecast over 100 m ahead from the tunnel face though the signal is usually generated using the explosive which can affect the stability of segments and backfill grout. Electromagnetic methods such as tunnel electrical resistivity prospecting system (TEPS) offer the exact prediction for a conductive zone such as water-bearing zone. However, the number of electrodes installed for exploration is limited in small diameter TBM and finally the reduction of prediction ranges. In this study, the theoretical equations for the electrical resistivity survey whose electrodes are installed in the face and side of TBM to minimize the installed electrodes on face. The experimental tests were conducted to verify the derived equations.
Optimal configuration of a two-dimensional bristled wing
Seung Hun Lee(이승훈),Minhyeong Lee(이민형),Daegyoum Kim(김대겸) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
A fairyfly or thrips, the smallest flying insect ever known, has a distinctive wing geometry so-called bristled wing or comb wing. Its wing consists of a central frame with several bristles expanding from the frame. It is well known that in a low-Reynolds-number environment in which the insect lives, a virtual fluid barrier is formed to block the gaps thanks to the thickly developed shear layers along the bristles. The aerodynamic force generations as well as the corresponding flow structures of a bristled wing in various Reynolds numbers and kinematics have been well organized from the previous studies. However, back to the basics, let us recall that the mutual interaction of the shear layers developed on the surface of each bristle is a fundamental mechanism in determining the performance of the bristled wing. Suppose we construct a bristled wing with a limited number of bristles. If the gap between bristles is narrowed, a sturdy virtual fluid barrier is formed while the total length of the wing is shortened, where the former is aerodynamically favorable but the latter is not. The opposite occurs if the gap between bristles is broaden. We numerically introduce a two-dimensional bristled wing consists of five cylinders, and investigate the optimal configuration of our wing model for the maximized aerodynamic force generation for wide ranges of Reynolds number and gap distance.
흡입 및 분사 유동을 동반하며 복합적으로 움직이는 실린더들에 의한 추력 발생
김도현(Dohyun Kim),이민형(Minhyeong Lee),김대겸(Daegyoum Kim) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
Some flow phenomena, a periodic intake and ejection of surrounding fluid, are easily found in nature around us. The periodic suction and blowing flows are induced by periodic change of the internal volume. Because the boundary has to be deformed softly to change the internal volume, most structures generating periodic suction and blowing flows are flexible. We simplify the continuous deformation of the flexible body by segmenting the boundary into multiple moving bodies and examine how the coordinated motion of the segments induce suction, blowing, and even propulsive force. In this study, several rigid circular cylinders are equally spaced on a circle. When the cylinders oscillate in a radial direction with the same amplitude and frequency, suction and blowing flows occur uniformly at every exit. However, the flows become directional when the phases of oscillating cylinders are slightly varied and consequently generates net thrust on the entire structure. Kinematic parameters for the coordinated motion of the cylinder array, oscillation amplitude, frequency, and phase difference between the cylinders, are numerically investigated to find the optimal condition for the maximum thrust.