• 대한화학회지
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• 제60권5호
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• pp.317-320
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• 2016

Efficient copper removal from water was achieved by using surface modified silica spheres with 3-mercaptopropyltrimethoxysilane (MPTMS) using base catalyst. The surface modification of silica spheres was performed by hydrolysis and condensation reactions of the MPTMS. The characteristic infrared absorption peaks at 2929, 1454, and 1343 cm⁻¹ represent the −CH₂ stretching vibration, asymmetric deformation, and deformation, respectively. The absorption peaks at 2580 and 693 cm⁻¹ corresponding the −SH stretching vibration and the C-S stretching vibration indicate the incorporation of MPTMS to the surface of silica spheres. Field emission scanning electron microscope (FESEM) image of the surface modified silica sphere (SMSS) shows nano-particles of MPTMS on the surface of silica spheres. High concentration of copper solution (1000 ppm) was used to test the copper removal efficiency and uptake capacity. The FESEM image of SMSS treated with the copper solution shows large number of copper lumps on the surface of SMSS. The copper concentration drastically decreased with increasing the amount of SMSS. The residual copper concentrations were analyzed using inductively coupled plasma mass spectrometer. The copper removal efficiency and uptake capacity with 1000 ppm of copper solution were 99.99 % and 125 mg/g, respectively.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
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• 제3권1호
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• pp.1-6
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• 2014

현재까지 컨벡스헐 (convex hull) 의 계산 알고리즘들은 주로 점 집합 (point set) 에 대해 연구가 수행되어 왔다. 본 논문에서는 이산 공간에서 다양한 반경을 갖는 구 집합에 대한 컨벡스헐을 근사하는 방법을 제시한다. 구 집합에 대한 컨벡스헐 계산은, 특히 단백질 분자의 구조적인 특성을 연구하는 여러 응용분야에서 계산 효율성을 증대시키기 위한 기반 기술이라 할 수 있다. 분자에 대응하는 구의 집합에 대해 복셀 맵 (voxel map) 자료구조를 적용하고 이를 이용하여 컨벡스헐을 계산하는 알고리즘을 제시한다. 제안된 방법은 GPU를 활용한 병렬처리를 수행하여 평균적으로 6,400개 이하의 구가 포함된 집합에 대해 40ms 이내에 컨벡스헐을 계산하는 성능을 보인다.

• 한국CDE학회논문집
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• 제11권2호
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• pp.97-106
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• 2006

Voronoi diagrams have been known for numerous important applications in science and engineering including CAD/CAM. Especially, the Voronoi diagram for 3D spheres has been known as very useful tool to analyze spatial structural properties of molecules or materials modeled by a set of spherical atoms. In this paper, we present two algorithms, the edge-tracing algorithm and the region-expansion algorithm, for constructing the Voronoi diagram of 3D spheres and applications to protein structure analysis. The basic scheme of the edge-tracing algorithm is to follow Voronoi edges until the construction is completed in O(mn) time in the worst-case, where m and n are the numbers of edges and spheres, respectively. On the other hand, the region-expansion algorithm constructs the desired Voronoi diagram by expanding Voronoi regions for one sphere after another via a series of topology operations, starting from the ordinary Voronoi diagram for the centers of spheres. It turns out that the region-expansion algorithm also has the worst-case time complexity of O(mn). The Voronoi diagram for 3D spheres can play key roles in various analyses of protein structures such as the pocket recognition, molecular surface construction, and protein-protein interaction interface construction.

• 대한기계학회논문집A
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• 제31권9호
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• pp.910-914
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• 2007

We present a simple and an inexpensive method for the fabrication of a nano-fluidic filter and a nano-pore micromixer using self-assembly of nano-spheres and surface tension. Colloid-plug was formed by surface tension of liquid in a microchannel to fabricate nanofluidic filter. When colloid is evaporated, nano-spheres in a colloid are orderly stacked by a capillary force. Orderly stacked nano-spheres form 3-D nano-mesh which can be used as a mesh structure of a fluidic filter. We used silica nano-sphere whose diameter is $567{\pm}85nm$, and silicon micro-channel of $50{\mu}m$-diameter. Fabricated nano-fluidic filter in a micro-channel has median pore diameter of 158nm which was in agreement with expected diameter of the nano-pore of $128{\pm}19nm$. A nano-pore micromixer consists of $200\;{\mu}m-wide,\;100\;{\mu}m-deep$ micro-channel and self-assembled nano-spheres. In the nano-pore micromixer, two different fluids had no sooner met together than two fluids begin to mix at wide region. From the experimental study, we completely apply self-assembly of nano-spheres to nano-fluidic devices.

• 공업화학
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• 제20권6호
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• pp.646-652
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• 2009

본 연구는 표면에 액체 막이 입혀진 구 입자를 지나는 기체의 흐름이 구 입자에 작용하는 항력을 결정하는 3상계 문제를 다룬다. 기체 흐름의 관성은 무시할 정도로 작으며, 구 입자의 표면에서 액체는 중력에 의해 흐르고 액체 막이 기체 흐름에 영향을 받지 않는 경우를 고려한다. SC (simple cubic), BCC (body centered cubic), FCC (face centered cubic) 각 배열의 구 입자들에 대해 외란 기법(perturbation method)과 멀티폴 전개(multipole expansion) 방법을 이용하여 입자들의 수력학적 상호 작용을 계산하고 궁극적으로 액체 막과 액체의 흐름이 기체 흐름에 미치는 영향을 수치적으로 결정한다. 근사적인 방법으로 액체 막의 효과에 구하고 이를 엄밀한 계산 값들과 비교한 결과, 대체로 일치함을 보인다.

• Bulletin of the Korean Chemical Society
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• 제30권5호
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• pp.1118-1120
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• 2009

Micro-size CdS spheres of hollow shape were fabricated through the self-assembly of high density arrow-like nanorods. The synthesis of the CdS hollow spheres were accomplished in an aqueous solution of cadmium nitrate and triblock copolymer (Pluronic P123) at low temperature (80 ${^{\circ}C}$) through the slow release of S2- ions from thioacetamide. Morphology of the fabricated CdS hollow spheres was characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The results indicate that the arrow-like CdS nanorods are simultaneously grown and attached each other to form the building units that become the spheres with hollow inside as a self-assembled process. The CdS spheres have a diameter of $2{\sim}3 {\mu}m$ and consist of the nanorods with a length of$\sim$800 nm. The nanocrystal building blocks have a hexagonal CdS structure.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2018년도 학술발표회
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• pp.149-149
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• 2018

Prediction on initial motion of sediment is crucial to evaluate sediment transport and channel stability. The condition of incipient movement of sediment is characterized by bed shear stress, which is generated from force of moving water against the bed of the channel, and by critical shear stress, which depends on force resisting motion of sediment due to the submerged weight of the grains. When the bed shear stress exceeds the critical shear stress, sediment particles begin rolling and sliding at isolated and random locations. In Mountain River, debris flow frequently occurs due to heavy rainfall and can lead some natural stones from mountain slope into the bed river. This phenomenon could add additional forces to sediment transport system in the bed of river and also affect or change direction and magnitude of sediment movement. In this paper, evaluations on incipient motion of uniform coarse gravel under falling spheres impacts using small scale flume channel were conducted. The drag force of falling spheres due to water flow and length movement of falling spheres were investigated. The experiments were carried out in flume channel made by glass wall and steel floor with 12 m long, 0.6 m wide, and 0.6 m deep. The bed slopes were selected with the range from 0.7% to 1.5%. The thickness of granular layer was at least 3 times of diameter of granular particle to meet grain placement condition. The sphere diameters were chosen to be 4cm, 6 cm, 8 cm, 10 cm. The spheres were fallen in to the bed channel for critical condition and under critical condition of motion particle. Based on the experimental results, the Shields curve of particles Reynold number and dimensionless critical shear stress were plotted. The relationship between with drag force and the length movement of spheres were plotted. The pathways of the bed material Under the impact of spheres falling were analyzed.

• Bulletin of the Korean Chemical Society
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• 제32권5호
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• pp.1534-1538
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• 2011

Uniform, hollow nanosilica spheres were prepared by the chemical coating of cationic polystyrene (cPS) with tetraethylorthosilicate (TEOS), followed by calcination at 600 $^{\circ}C$ under air. cPS was synthesized by surfactant-free emulsion polymerization using 2,2'-azobis (2-methyl propionamidine) dihydrochloride as the cationic initiator, and poly(vinyl pyrrolidone) as a stabilizer. The resulting cPS spheres were 280 nm in diameter, and showed monodispersion. After coating, the hollow silica product was spherically shaped, and 330 nm in diameter, with a narrow distribution of sizes. Dispersion was uniform. Wall thickness was 25 nm, and surface area was 96.4 $m^2/g$, as determined by BET. The uniformity of the wall thickness was strongly dependent upon the cPS surface charge. The effects of TEOS and ammonia concentrations on shape, size, wall thickness, and surface roughness of hollow $SiO_2$ spheres were investigated. We observed that the wall thicknesses of hollow $SiO_2$ spheres increased and that silica size was simultaneously enhanced with increases in TEOS concentrations. When ammonia concentrations were increased, the irregularity of rough surfaces and aggregation of spherical particles were more severe because higher concentrations of ammonia result in faster hydrolysis and condensation of TEOS. These changes caused the silica to grow faster, resulting in hollow $SiO_2$ spheres with irregular, rough surfaces.

• 한국세라믹학회지
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• 제54권4호
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• pp.303-307
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• 2017

Pure $In_2O_3$, 0.5 and 1.0 wt% Mg doped $In_2O_3$ hollow spheres were synthesized by ultrasonic spray pyrolysis of a solution containing In-, Mg-nitrate and sucrose and their gas sensing characteristics to 5 ppm $C_2H_5OH$, p-xylene, toluene, and HCHO were measured at 250, 300 and $350^{\circ}C$. Although the addition of Mg decreases the specific surface area and the volume of meso-pores, the gas response (resistance ratio) of the 0.5 wt% Mg doped $In_2O_3$ hollow spheres to 5 ppm $C_2H_5OH$ at $350^{\circ}C$ (69.4) was significantly higher than that of the pure $In_2O_3$ hollow spheres (24.4). In addition, the Mg doped $In_2O_3$ hollow spheres showed the highest selectivity to $C_2H_5OH$. This was attributed to the dehydrogenation of $C_2H_5OH$ assisted by basic MgO into reactive $CH_3CHO$ and $H_2$.

• 접착 및 계면
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• 제13권4호
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• pp.151-155
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• 2012

본 연구에서는 중공형 나노 입자의 구조체가 되는 구형 폴리스티렌을 조절된 유화중합법으로 여러 크기의 구형 폴리스티렌을 제조하는 연구를 수행하였다. 유화중합에 사용되는 유화제의 농도를 조절하여 구형 폴리스티렌의 크기를 임의로 조절하였다. 이 폴리스티렌을 구조체로 이용하여 중공형 중간세공 실리카를 합성하였으며, 합성 과정 시 반응속도의 조절을 위해 에탄올을 넣어 실리카 전구체의 가수분해 속도를 조절하고, 실리카 전구체의 투여량을 조절하여 중공형 중간세공 실리카의 벽 두께를 조절하였다.