Development of 2D inundation model based on adaptive cut cell mesh (K-Flood)

An Hyunuk,Jeong Anchul,Kim Yeonsu,Noh Joonwoo 한국수자원학회 2018 한국수자원학회논문집 Vol.51 No.10

본 연구에서는 적응적 분할격자기반 2차원 침수해석모형 K-Flood를 개발하였다. 분할격자기법은 흐름 특성을 기반으로 격자를 분할하여 흐름영역과 비흐름영역으로 구분하는 격자생성기법이며, 분할격자기법과 격자세분화기법을 동시에 활용하면 매우 적은 수의 격자로 복잡한 형상의 흐름 영역을 표현할 수 있어 효율적인 모의가 가능하다. 특히 최근 도시홍수에 대해 매우 정밀한 해상도의 자료와 격자를 이용하여 보다 정확한 침수해석 또는 예보를 하고자 하는 시도가 늘어나고 있으며, K-Flood는 이러한 복잡한 흐름영역의 계산 시 적응적 분할격자를 활용하여 효율적인 격자생성이 가능하다. 공간 및 시간에 대해 2차 정확도의 유한체적 수치해법이 적용되었다. K-Flood의 검증을 위해 2차원 침수해석모형의 검증에 널리 사용되고 있는 1) 원형 실린더에 의한 충격파 반사 모의, 2) 도시홍수실험 모의, 3) Malpasset 댐붕괴 모의를 수행하였다. 모든 모의에서 관측자료 및 과거의 모의결과와 비교하여 성공적으로 K-Flood의 성능을 검증하였다. An adaptive cut-cell grid based 2D inundation analysis model, K-Flood, is developed in this study. Cut cell grid method divides a grid into a flow area and a non-flow area depending the characteristics of the flows. With adaptive mesh refinement technique cut cell method can represent complex flow area using relatively small number of cells. In recent years, the urban inundation modeling using high resolution and fine quality data is increasing to achieve more accurate flood analysis or flood forecasting. K-Flood has potential to simulate such complex urban inundation using efficient grid generation technique. A finite volume numerical scheme of second order accuracy for space and time was applied. For verification of K-Flood, 1) shockwave reflex simulation by circular cylinder, 2) urban flood experiment simulation, 3) Malpasset dam collapse simulation are performed and the results are compared with observed data and previous simulation results.

Synthesis of phase-pure interpenetrated MOF-5 and its gas sorption properties.

Kim, Hyunuk,Das, Sunirban,Kim, Min Gyu,Dybtsev, Danil N,Kim, Yonghwi,Kim, Kimoon American Chemical Society 2011 Inorganic Chemistry Vol.50 No.8

<P>For the first time, phase-pure interpenetrated MOF-5 (1) has been synthesized and its gas sorption properties have been investigated. The phase purity of the material was confirmed by both single-crystal and powder X-ray diffraction studies and TGA analysis. A systematic study revealed that controlling the pH of the reaction medium is critical to the synthesis of phase-pure 1, and the optimum apparent pH (pH*) for the formation of 1 is 4.0-4.5. At higher or lower pH*, [Zn(2)(BDC)(2)(DMF)(2)] (2) or [Zn(5)(OH)(4)(BDC)(3)] (3), respectively, was predominantly formed. The pore size distribution obtained from Ar sorption experiments at 87 K showed only one peak, at ~6.7 ?, which is consistent with the average pore size of 1 revealed by single crystal X-ray crystallography. Compared to MOF-5, 1 exhibited higher stability toward heat and moisture. Although its surface area is much smaller than that of MOF-5 due to interpenetration, 1 showed a significantly higher hydrogen capacity (both gravimetric and volumetric) than MOF-5 at 77 K and 1 atm, presumably because of its higher enthalpy of adsorption, which may correlate with its higher volumetric hydrogen uptake compared to MOF-5 at room temperature, up to 100 bar. However, at high pressures and 77 K, where the saturated H(2) uptake mostly depends on the surface area of a porous material, the total hydrogen uptake of 1 is notably lower than that of MOF-5.</P>

Exploration of Heavy Metal(loid)s Immobilizing Agents Available for Agricultural Lands and Their Combination Effects

Hyunuk Kim,Mina Lee,Hyuck Soo Kim,Kwon-Rae Kim 한국토양비료학회 2019 한국토양비료학회지 Vol.52 No.3

Heavy metal(loid)s contamination in Korean agricultural lands is mostly caused by tailing wastes, debris, and leachate from abandoned mines. For safe agricultural production, immobilizing agents have been actively studied to reduce phytoavailability of heavy metal(loid)s. However, more various immobilizing materials need to be explored to achieve a practical application of this technique. This study aims to examine and compare the effects of known and unknown immobilizing agents on decrease plant-available heavy metal(loid)s. Lime, gypsum, guano, and bone meal were applied in metal contaminated soils in isolation or in combination. After the treatment, changes in soil pH and dissolved organic carbon were analyzed. Lettuce was grown for 7 weeks in each soil, and heavy metal(loid)s concentration in lettuce was determined. The mixed immobilizing agents reduced phytoavailability of heavy metal(loid)s more effectively than the isolate treatments. A mixture of lime, gypsum, and guano was the most effective combination, followed by a mixture of lime, gypsum, and bone meal. Future study on a practical application of the immobilizing agents is required to increase both safety and productivity of agricultural crops.

Methane Sorption and Structural Characterization of the Sorption Sites in Zn₂(bdc)₂(dabco) by Single Crystal X-ray Crystallography

Kim, Hyunuk,Samsonenko, Denis G.,Das, Sunirban,Kim, Ghyung-Hwa,Lee, Heung-Soo,Dybtsev, Danil N.,Berdonosova, Elena A.,Kim, Kimoon Wiley (John WileySons) 2009 Chemistry - An Asian Journal Vol.4 No.6

<P>Sorption isotherms of methane in Zn(2)(bdc)(2)(dabco) are measured up to a pressure of 35 bar in the temperature range between 198-296 K. The methane sorption measurements at 296 K showed an uptake of 137 cm(3) cm(-3) at 35 bar. The enthalpy of methane adsorption for Zn(2)(bdc)(2)(dabco) estimated by the virial equation is 13.6 kJ mol(-1) at zero coverage. X-ray structure analysis of methane-adsorbed Zn(2)(bdc)(2)(dabco) by synchrotron radiation at 90 K revealed that methane molecules occupy three independent sorption sites (A, B, and C) with a stoichiometry of Zn(2)(bdc)(2)(dabco) x 6.69 CH(4), which is consistent with the results of the gas sorption measurements at 198 K. In a cavity, eight symmetry-related methane sorption sites A are located near the {Zn(2)(CO(2))(4)} paddle-wheel units, while four symmetry-related methane sorption sites B are near the center of the small windows along the a and b axes. Both A and B sites are half-occupied. Methane molecules occupying sites A are not only in van der Waals contact with the paddle-wheel units, but also interact with the phenyl rings of bdc ligands through partial pi-HC interactions. Methane molecules in B sites interact with the side of the phenyl rings through van der Waals interaction. The site C, located at the center of the cavity, is a secondary sorption site; methane molecules occupying sites C are in van der Waals contact with those in sites A and B.</P>

Highly Selective Carbon Dioxide Sorption in an Organic Molecular Porous Material

Kim, Hyunuk,Kim, Yonghwi,Yoon, Minyoung,Lim, Soyoung,Park, Se Min,Seo, Gon,Kim, Kimoon American Chemical Society 2010 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.132 No.35

<P>The organic molecular porous material <B>1</B> obtained by recrystallization of cucurbit[6]uril (CB[6]) from HCl shows a high CO<SUB>2</SUB> sorption capacity at 298 K, 1 bar. Most interestingly, <B>1</B> showed the highest selectivity of CO<SUB>2</SUB> over CO among the known porous materials so far. The remarkable selectivity of CO<SUB>2</SUB> may be attributed to the exceptionally high enthalpy of adsorption (33.0 kJ/mol). X-ray crystal structure analysis of CO<SUB>2</SUB> adsorbed <B>1</B> revealed three independent CO<SUB>2</SUB> sorption sites: two in the 1D channels (<B>A</B> and <B>B</B>) and one in the molecular cavities (<B>C</B>). The CO<SUB>2</SUB> molecules adsorbed at sorption site <B>A</B> near the wall of the 1D channels interact with <B>1</B> through hydrogen bonding and at the same time interact with those at site <B>B</B> mainly through quadrupole−quadrupole interaction in a T-shaped arrangement. Interestingly, two CO<SUB>2</SUB> molecules are included in the CB[6] cavity (site <B>C</B>), interacting not only with the carbonyl groups of CB[6] but also with each other in a slipped-parallel geometry. The exceptionally selective CO<SUB>2</SUB> sorption properties of <B>1</B> may find useful applications in the pressure swing adsorption (PSA) process for CO<SUB>2</SUB> separation not only in the steel industry but also in other industries such as natural gas mining.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2010/jacsat.2010.132.issue-35/ja105211w/production/images/medium/ja-2010-05211w_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja105211w'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja105211w'>ACS Electronic Supporting Info</A></P>

Distribution and extent of heavy metal(loid) contamination in agricultural soils as affected by industrial activity

Kim Hyunuk,Lee Mina,Lee Jae-Hwang,Kim Kye-Hoon,Owens Gary,Kim Kwon-Rae 한국응용생명화학회 2020 Applied Biological Chemistry (Appl Biol Chem) Vol.63 No.3

In Korea, rapid industrialization has often caused severe soil and water pollution near industrial complexes. Particularly, heavy metal(loid) contamination of agricultural lands could induce serious long-term problems for crop safety and productivity, requiring continual safety assessment. This study investigated heavy metal(loid) contamination of agricultural lands near fifteen industrial complexes. At each of industrial sites in Gyeongsangbuk-do, topsoils and subsoils were collected at two different distances from each site (0–500 m and 500–1000 m). For comparison, at each site, non-polluted soils were also collected more than 1000 m away from each industrial complex. With the exception of one sample, heavy metal(loid) concentration of all soils were lower than the Korean guidelines for soil contamination. However, the difference between the heavy metal(loid) concentrations of Cu, Pb and Zn in topsoil and subsoil increased the closer the samples were the industrial complexes, which implied that these elements were being generated by industrial activities and were freshly loaded on to near surface soils. While the heavy metal(loid) concentration in the studied sites did not exceed the Korean guideline, the geoaccumulation index of each soil indicated that the degree of Cd, Cu, and Pb contamination was heavily or extremely serious in more than twenty of the examined soils. The elevation of specific metals associated with industrial activity in soils in close proximity to industrial sites is of some concern and should be taken into consideration for the future management of agricultural soils around such complexes as well as the industrial complex operation itself.

Pressure Effect of Various Inert Gases on the phase Behavior of Polystyrene-<i>block</i>-Poly(n-pentyl methacrylate) Copolymer

Kim, Hye Jeong,Moon, Hong Chul,Kim, Hyunuk,Kim, Kimoon,Kim, Jin Kon,Cho, Junhan American Chemical Society 2013 Macromolecules Vol.46 No.2

<P>We investigated the pressure effect of three inert gases (nitrogen, helium, and argon) on the phase behavior of polystyrene-<I>block</I>-poly(<I>n</I>-pentyl methacrylate) copolymer (PS-<I>b</I>-PnPMA) showing closed-loop phase behavior and baroplasticity. Helium gas pressure enhanced the miscibility between PS and PnPMA blocks similar to the hydrostatic pressure. Thus, the closed-loop size decreased with increasing helium gas pressure. Very interestingly, with increasing nitrogen and argon gas pressure, the miscibility between the two blocks decreased even though these two are also considered as inert gases. To explain these unexpected results, we measured the amount of gas absorption into each block. Helium gas showed almost no absorption in both PS and PnPMA; thus it simply acts as hydrostatic pressure. On the other hand, nitrogen and argon gases were more selectively absorbed into PnPMA compared with PS, which increased the free volume disparity between two blocks and enlarged closed-loop size with increasing gas pressure. The experimentally measured gas absorption results are consistent with the theoretical ones based on the Sanchez–Lacombe theory. The results in this study imply that well-known and widely employed inert gases such as nitrogen and argon could significantly affect the phase behavior of a weakly interacting block copolymer at high pressures.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/mamobx/2013/mamobx.2013.46.issue-2/ma302155j/production/images/medium/ma-2012-02155j_0007.gif'></P>

지역별 재해 유발 강설량의 임계값 추정과 지역구분

김현욱(Kim, Hyunuk),김백조(Kim, Baek-Jo),김해민(Kim, Hae-Min),이진화(Lee, Jin-Hwa),심재관(Shim, Jae-Kwan) 한국방재학회 2020 한국방재학회논문집 Vol.20 No.1

본 연구는 대설 피해가 빈번하게 발생하는 10개 관측지점을 대상으로 피해유발 임계값을 추정하였다. 또한, 추정된 임계값을기반으로 유사한 지역을 구분하고 그 특징을 조사하였다. 연구 자료는 기상청에서 제공하는 신적설 관측 자료와 행정안전부에서발행되는 재해연보의 피해 자료를 사용하였다. 연구방법은 로지스틱회귀분석, Critical Success Index, Probability of Detection 그리고 False-Alarm Ratio를 적용하였다. 연구 결과, 추정된 임계값은 지역별로 차이를 보였다. 이와 같은 결과는 분석방법, 지역별 방재대책, 지역주민의 대처, 구조물의 취약성 그리고 기상현상 등 많은 요인이 원인으로 판단된다. 또한, 추정된임계값을 활용하여 임계값이 민감한 지역, 임계값의 차이가 큰 지역과 작은 지역은 각각 해안지역, 강원지역, 내륙지역에대응되었다. 강원지역은 강설의 지속시간이 길고, 폭설이 관측된 경우가 많았으나, 내륙지역은 상대적으로 약한 강설과 짧은강설 지속시간을 보였다. In this study, the estimation of damage-causing thresholds and their application to regional classification were examined using logistic regression, critical success index, probability of detection, and a false-alarm ratio. For 10 stations where damage caused by heavy snow occurred frequently, the fresh snow depth data provided by the Korea Meteorological Administration and heavy snow-related damage data obtained by the Ministry of Interior and Safety were used. Results show that the estimated thresholds differed by region. These results are attributed to many factors such as analysis methods, regional disaster protection, the response of local residents, vulnerability of structures, and meteorological characteristics. Additionally, based on estimated thresholds, the area with the highest threshold-sensitivity and the areas with the most internal differences and similarities between calculated thresholds corresponded to the coastal region, the Gangwon region, and the inland region, respectively. Gangwon region, where heavy snow was often observed, had a long duration of snowfall, whereas inland regions faced snowfalls that were relatively weaker in intensity and shorter in duration.

타이어 Tread Width와 Horn effect의 상관성 실험적 고찰

김현욱(Hyunuk Kim),김일식(Ilsik Kim),김용훈(Younhoon Kim) 한국소음진동공학회 2019 한국소음진동공학회 학술대회논문집 Vol.2019 No.2

전도성 니켈-금속 유기 구조체를 활용한 리튬 이온 커패시터 전기 화학적 특성

김태형(TaeHyeong Kim),Subiyanto lyan,백정훈(JeongHun Baek),김범진(BumJin Kim),강상희(SangHui Kang),김강직(KangJick Kim),최헌진(Heonjin Choi),김현욱(Hyunuk Kim),유정준(JungJoon Yoo) 한국태양에너지학회 2021 한국태양에너지학회 학술대회논문집 Vol.2021 No.11