• Title/Summary/Keyword: pore analysis

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Titanium Containing Solid Core Mesoporous Silica Shell: A Novel Efficient Catalyst for Ammoxidation Reactions

  • Venkatathri, N.;Nookaraju, M.;Rajini, A.;Reddy, I.A.K.
    • Bulletin of the Korean Chemical Society
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    • v.34 no.1
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    • pp.143-148
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    • 2013
  • Novel titanium containing solid core mesoporous shell silica has been synthesized by using octadecyltrichloro silane and triethylamine. The synthesized material was characterized by various physicochemical techniques. The mesoporous character of the material has been revealed from PXRD studies. The presence of octadecyltrichloro silane and triethylamine in the sample has been confirmed from EDAX studies. TG/DTA analysis reveals the thermal characteristics of the synthesized material. The presence of titanium in the frame work and its coordination state has been studies by UV-vis DR studies and XPS analysis. Chemical environment of Si in the framework of the material has been studied by $^{29}SiMASNMR$ studies. The surface area of the material is found to be around $550\;m^2g^{-1}$ and pore radius is of nano range from BET analysis. The spherical morphology and particle size of the core as well as shell has been found to be 300 nm and 50 nm respectively from TEM analysis. The catalytic application of this material towards the synthesis of caprolactam from cyclohexanone in presence of hydrogen peroxide through ammoxidation reaction has been investigated. The optimum conditions for the reaction have been established. The plausible mechanism for the formation of core silica and conversion of cyclohexanone has been proposed.

Quality Characteristics and Antioxidant Activity of Tteokbokkidduk Supplemented with Wheat Bran Powder (밀기울 분말 첨가 떡볶이 떡의 품질 특성 및 항산화 활성)

  • Park, So Young;Sim, Ki Hyeon
    • The Korean Journal of Food And Nutrition
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    • v.35 no.1
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    • pp.16-33
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    • 2022
  • The quality characteristics and antioxidant activity of Tteokbokkidduk alone or supplemented with 3%, 6%, 9%, and 12% wheat bran powder were assessed, to increase use of the wheat bran by-product of wheat milling. The moisture content, pH, and starch elution of Tteokbokkidduk increased with increasing wheat bran powder, while the water absorption rate did not. The L color value decreased and the a and b values increased with increasing wheat bran powder. Scanning electron microscopy of Tteokbokkidduk prepared with 0% and 3% wheat bran powder revealed uniform pore size distribution. In terms of texture profile analysis, hardness and chewiness increased, while cohesiveness decreased with increased content of wheat bran powder. Acceptance was highest for samples with 6% wheat bran powder. Quantitative description analysis (QDA) revealed increased brownness, roughness, nutty, bitterness, astringency, savory character, and hardness, and decreased adhesiveness, springiness, and chewiness with increased wheat bran powder. Principal component analysis (PCA) revealed highest overall acceptance of samples prepared with 6% wheat bran powder, reflecting the relatively low values of detrimental sensory characteristics. Antioxidant activities of Tteokbokkidduk increased as wheat bran powder content increased. The addition of 6% wheat bran powder resulted in excellent Tteokbokki in terms of acceptance, quality, and antioxidant activity.

Sampling Method for Individual Particle Analysis of Atmospheric Aerosol (개별입자 분석을 위한 대기에어로졸의 시료채취법)

  • Seong-Woo Cheon;Jeong-Ho Park
    • Journal of Environmental Science International
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    • v.33 no.2
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    • pp.113-119
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    • 2024
  • In this study, the most suitable sampling methods for the bimodal mass distribution characteristics and individual particle analysis of atmospheric aerosols were investigated. Samples collected in Quartz, Teflon, and Nuclepore filters were analyzed for individual particles using scanning electron microscopy with an energy-dispersive X-ray spectrometer (SEM/EDS). Then, the pore diameter of the filter and the collection flow rate were determined using the theoretical collection efficiency calculation formula for two-stage separation sample collection of coarse and fine particles. The Nuclepore filter was found to be the most suitable filter for identifying the physical and chemical characteristics of atmospheric aerosols since it was able to separate the sample and count the different sized particles better than either Quartz or Teflon. Nuclepore filters with 8.0 ㎛ and 0.4 ㎛ pores were connected in series and exposed to a flow rate of 16.7 L/min for two-stage separation sampling. The results show that it is possible to separate and collect both coarse and fine particles. We expect that the proposed methodology will be used for future individual particle analysis of atmospheric aerosols and related research.

Landslide Analysis of River Bank Affected by Water Level Fluctuation II (저수위 변동에 영향을 받는 강기슭의 산사태 해석 II)

  • Kim, You-Seong;Wang, Yu-Mei;Choi, Jae-Seon
    • Journal of the Korean Geosynthetics Society
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    • v.9 no.3
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    • pp.87-93
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    • 2010
  • The change of water level in reservoirs is an important factor causing failure of bank slopes, i.e. landslide. The water level of Three Gorges reservoir in China fluctuate between 145 m and 175 m, as a matter of flood control. During its normal operational state, the rate of water level fluctuation is supposed to range from 0.67 m/d to 3.0 m/d. Majiagou slope is located on the left bank of Zhaxi River, 2.1 km up from the outlet. Zhaxi River is a tributary of the Yangtze River within the Three Gorges area, of which the water level changes with the reservoir. At the back of Majiagou slope, a 20 m long and 3~10 cm wide fissure developed just after the reservoir water level rose from 95 m to 135 m in 2003. This big fissure was a full suggestion of potential failure of this slope. In this study, the pore water pressure files obtained from seepage analysis were used to evaluate the change in factor of safety (FS) with reservoir water level. Slope stability analyses then were carried out, with fully specified slip surface and limit equilibrium method. In the limit equilibrium analysis, the contribution of negative pore water pressure to shear strength was considered by the use of Fredlund's shear strength equation for unsaturated soils. On the base of the analyses, the change of FS with reservoir water level was interpreted in detail. It was found that FS against bank slopes decreases with the rise of the reservoir water level and increases with the drawdown of the reservoir water level. The most dangerous state was when the reservoir water level stays at the highest for a long time.

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Verification of the Numerical Analysis on Caisson Quay Wall Behavior Under Seismic Loading Using Centrifuge Test (원심모형시험을 이용한 케이슨 안벽의 지진시 거동에 대한 수치해석 검증)

  • Lee, Jin-Sun;Park, Tae-Jung;Lee, Moon-Gyo;Kim, Dong-Soo
    • Journal of the Korean Geotechnical Society
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    • v.34 no.11
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    • pp.57-70
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    • 2018
  • In this study, verification of the nonlinear effective stress analysis is performed for introducing performance based earthquake resistance design of port and harbor structures. Seismic response of gravitational caisson quay wall in numerical analysis is compared directly with dynamic centrifuge test results in prototype scale. Inside of the rigid box, model of the gravitational quay wall is placed above the saturated sand layer which can show the increase of excess pore water pressure. The model represents caisson quay wall with a height of 10 m, width of 6 m under centrifugal acceleration of 60 g. The numerical model is made in the same dimension with the prototype scale of the test in two dimensional plane strain condition. Byrne's liquefaction model is adopted together with a nonlinear constitutive model. Interface element is used for sliding and tensional separation between quay wall and the adjacent soils. Verification results show good agreement for permanent displacement of the quay wall, horizontal acceleration at quay wall and soil layer, and excess pore water pressure increment beneath the quay wall foundation.

Post-Liquefaction Induced Ground Settlement by Dissipation of Porewater Pressure under Drained Condition (지반 배수조건을 고려한 액상화 이후 과잉간극수압 소산에 따른 지반의 침하)

  • Yun, Seong-Kyu;Kim, Donghwan;Yang, Yeongchan;Kang, Gichun
    • Journal of the Korean Geotechnical Society
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    • v.38 no.6
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    • pp.5-16
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    • 2022
  • In the case of domestic seismic design, deformation of structures and ground is reviewed through undrained condition analysis and applied to design and maintenance. However, when the ground undergoes dissipation after liquefaction due to a dynamic load such as an earthquake, additional displacement occurs and greater damage occurs. Therefore, it is necessary to additionally analyze the drained conditions, It is necessary to grasp the exact ground behavior such as calculating and reviewing the amount of subsidence of the ground that has undergone the loss process after an earthquake and apply it to design and maintenance together. Therefore, in this study, numerical analysis was performed assuming undrained and drained conditions by dividing pure sandy soil into loose soil with Dr=30% and high-density soil with Dr=70%. In particular, when a dynamic load such as an earthquake is applied, considering the drained conditions of the ground, the settlement amount and the pore water pressure ratio of loose and dense ground are compared, This study focused on comparative analysis of settlement amount and pore water pressure ratio in the process of ground loss after an earthquake. As a result, the amount of subsidence during the dissipation process was 30 to 60 times greater than that of the earthquake.

Infiltration and Stability Analysis Using Double Modal Water Retention Curves for Unsaturated Slopes in Pohang (이중모드 함수특성곡선을 이용한 포항 산사태에 대한 불포화 비탈면의 침투 및 안정해석)

  • Oh, Seboong;Jang, Junhyuk;Yoon, Seokyong
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.44 no.5
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    • pp.695-705
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    • 2024
  • As a result of Typhoon Hinnamnoh, several slope failures occurred in the Pohang region, it is necessary to perform infiltration and slope stability analyses due to the actual rainfall. In the failed sites, samples were collected, and the hydro-mechanical properties of unsaturated soil were examined. Modeling the actual behavior using a single-mode function characteristic curve was found to be inadequate, leading to the adoption of a dual-mode function characteristic curve. The dual-mode function showed better agreement with the water retention test data. We calculated the unsaturated hydraulic conductivity for single and dual modes and performed rainfall-induced infiltration analysis. The variations in saturation and pore water pressure were calculated due to rainfall for three landslide-prone areas, Stability analysis based on effective stress of unsaturated soil was conducted, and safety factors were computed over time steps. The dual-mode model successfully reproduced landslides triggered by Typhoon Hinnamnoh, while the single-mode model exhibited a minimum safety factor of 1.2-1.3, making slope failure unpredictable. The dual-mode model accurately predicted instability in the slope by appropriately accounting for pore water pressure variations during Typhoon.

Significance of Ground Water Movements in the Numerical Modelling of Tunnelling (터널해석에 있어 지하수 거동의 중요성)

  • 신종호
    • Proceedings of the Korean Geotechical Society Conference
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    • 2003.03a
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    • pp.257-264
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    • 2003
  • Tunnelling in water bearing soils influences the ground water regime. It has been indicated in the literature that the existence of ground water above a tunnel influences tunnel stability and the settlement profile. Only limited research, however, has been done on ground water movements around tunnels and their influence on tunnel performance. Time dependent soil behaviour can be caused by the changes of pore water pressure and/or the viscous properties of soil(creep) under the stress change resulting from the advance of the tunnel face. De Moor(1989) demonstrated that the time dependent deformations due to tunnelling are mainly the results of pore pressure dissipation and should be interpreted in terms of effective stress changes. Drainage into tunnels is governed by the permeability of the soil, the length of the drainage path and the hydraulic boundary conditions. The potential effect of lime dependent settlement in a shallow tunnel is likely to occur rapidly due to the short drainage path and possibly high coefficient of consolidation. Existing 2D modelling methods are not applicable to these tunnelling problems, as it is difficult to define empirical parameters. In this paper the time-based 2D modelling method is adopted to account for the three dimensional effect and time dependent behaviour during tunnel construction. The effect of coupling between the unloading procedure and consolidation during excavation is profoundly investigated with the method. It is pointed out that realistic modelling can be achieved by defining a proper permeability at the excavation boundary and prescribing appropriate time for excavation Some guidelines for the numerical modelling of drained and undrained excavation has been suggested using characteristic time factor. It is highlighted that certain range of the factor shows combined effect between the unloading procedure due to excavation and consolidation during construction.

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Effect of Pore Structures of a Ti-49.5Ni (at%) Alloy on Bone Cell Adhesion (Ti-49.5Ni (at%)합금의 다공성 구조가 뼈 세포 흡착에 미치는 영향)

  • Im, Yeon-Min;Choi, Jung-Il;Khang, Dong-Woo;Nam, Tae-Hyun
    • Korean Journal of Materials Research
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    • v.22 no.2
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    • pp.66-70
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    • 2012
  • Ti-Ni alloys are widely used in numerous biomedical applications (e.g., orthodontics, cardiovascular science, orthopaedics) due to their distinctive thermomechanical and mechanical properties, such as the shape memory effect, superelasticity and low elastic modulus. In order to increase the biocompatibility of Ti-Ni alloys, many surface modification techniques, such as the sol-gel technique, plasma immersion ion implantation (PIII), laser surface melting, plasma spraying, and chemical vapor deposition, have been employed. In this study, a Ti-49.5Ni (at%) alloy was electrochemically etched in 1M $H_2SO_4$+ X (1.5, 2.0, 2.5) wt% HF electrolytes to modify the surface morphology. The morphology, element distribution, crystal structure, roughness and energy of the surface were investigated by scanning electron microscopy (SEM), energy-dispersive Xray spectrometry (EDS), X-ray diffractometry (XRD), atomic force microscopy (AFM) and contact angle analysis. Micro-sized pores were formed on the Ti-49.5Ni (at%) alloy surface by electrochemical etching with 1M $H_2SO_4$+ X (1.5, 2.0, 2.5) wt% HF. The volume fractions of the pores were increased by increasing the concentration of the HF electrolytes. Depending on the HF concentration, different pore sizes, heights, surface roughness levels, and surface energy levels were obtained. To investigate the osteoblast adhesion of the electrochemically etched Ti-49.5Ni (at%) alloy, a MTT test was performed. The degree of osteoblast adhesion was increased at a high concentration of HF-treated surface structures.

Growth of ${\gamma}-6Bi_2O_3 {\cdot}SiO_2$( Single Crystals by EFG Method (EFG법에 의한 ${\gamma}-6Bi_2O_3 {\cdot}SiO_2$(BSO)단결정의 육성)

  • ;;Kei-Miyamto
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.1 no.1
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    • pp.26-38
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    • 1991
  • The fundamental conditions for growing $r-6Bi_2O_3{\cdot}SiO_2$(BSO) single crystal plates by EFG(Edge-defined Film-fed Growth) method, were investigated and characterization, quality test, property measurement were performed for obtained BSO single crystal plates. The opti$\mu$ growing conditions determined in this study were as follows: ${\cdot}$temperature gradient;$24^{\circ}C/cm$ ${\cdot}$pulling rate;2.0mm/h. BSO Single crystal plates grown at the above optimum conditions did not include secondary phase or grain boundary and were confirmed as single crystals by X-ray analysis. IT was found that the single crystal plates had <100> growth direction. G defects, ie pore, void inclusion, striation, were not detected in the single crystal plate under polarizing microscope but dislocations(microscopic defect) were found and dislocation density was $5.1\times10^5/cm^2$.

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