• Journal of Sensor Science and Technology
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• v.24 no.6
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• pp.385-391
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• 2015

In this paper, we propose a new method to infiltrate $Fe_3O_4$-nanoparticles into a porous silicon film and a monitoring technique to detect packing density of nanoparticles within the film. Recently, research to use porous silicon as a drug carrier or a new functional sensor material by infiltrating $Fe_3O_4$-nanoparticles has been extensively performed. However, it is still necessary to enhance the packing density and to develop a monitoring technique to detect the packing density in real time. In this light, we forcibly injected a nanoparticle solution into a rugate-structured free-standing porous silicon (FPS) film by applying a pressure difference between the two sides of the film. We found that the packing density by the pressure-infiltration method proposed in this paper is enhanced, relative to that by the previous diffusion method. Moreover, a continuous shift in wavelength of the rugate reflectance peak measured from the film surface was observed while the nanoparticle solution was being injected. By exploiting this phenomenon, we could qualitatively monitor the packing density of $Fe_3O_4$-nanoparticles within the FPS film with the injection volume of the nanoparticle solution.

• Journal of Ocean Engineering and Technology
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• v.28 no.6
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• pp.517-526
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• 2014

The leakage of cryogenic LNG through cracks in the insulation membrane of an LNG carrier causes the hull structure to experience a cold spot as a result of the heat transfer from the LNG. The hull structure will become brittle at this cold spot and the evaporated natural gas may potentially lead to a hazard because of its flammability. This paper presents a computational model for the LNG flow and heat diffusion in an LNG insulation panel subject to leakage. The temperature distribution in the insulation panel and the speed of gas diffusion through it are simulated to assess the safety level of an LNG carrier subject that experiences a leak. The behavior of the leaked LNG is modeled using a multiphase flow that considers the mixture of liquid and gas. The simulation model considers the phase change of the LNG, gas-liquid multiphase interactions in the porous media, and accompanying rates of heat transfer. It is assumed that the NO96-GW membrane storage is composed of glass wool and plywood for the numerical simulation. In the numerical simulation, the seepage, heat diffusion, and evaporation of the LNG are investigated. It is found that the diffusion speed of the leakage is very high to accelerate the evaporation of the LNG.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.2 no.2
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• pp.11-19
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• 1992

$SrTiO_3$powders were synthesized from the chloride and the nitrate aqueous solution by spray pyrolysis method using ultrasonic vibrator. The concentration of mother solution was prepared 0.05M and O.lM. The carrier gas flow rate was 0.5cm/sec and 1.5cm/sec, respectively. The formation processing was investigated in the 0.05M and 0.05cm/sec. The $SrTiO_3$powders could not be synthesized from chloride aqueous solution. The prepared powders from nitrate aqueous solution was SrTi03 with cubic structure and nearly sphere particle for all samples. Mean particle size was increased from $0.49{\mu}m$ to $0.67{\mu}m$ by changing the carrier gas flow rate from O.5cm/sec to 1.5cm/sec. Also, mean particle size increased from $0.49{\mu}m$to $0.55{\mu}m$by changing the concentration of mother solution from O.05M to O.1M. Atomizing droplet size was $14.3{\mu}m$. The shape of particles was very porous by evaporation of solvent at the initial step. But through the each step upwards, shape of particles was formed themselves into a nearly roundish.

• Korean Journal of Materials Research
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• v.28 no.2
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• pp.124-128
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• 2018

N-type porous silicon (PS) layers and thermally oxidized PS layers have been characterized by various measuring techniques such as photoluminescence (PL), Raman spectroscopy, IR, HRSEM and transmittance measurements. The top surface of PS layer shows a stronger photoluminescence peak than its bottom part, and this is ascribed to the difference in number of fine silicon particles of 2~3 nm in diameter. Observed characteristics of PL spectra are explained in terms of microstructures in the n-type PS layers. Common features for both p-type and n-type PS layers are as follows: the parts which can emit visible photoluminescence are not amorphous, but crystalline, and such parts are composed of nanocrystallites of several nm's whose orientations are slightly different from Si substrate, and such fine silicon particles absorb much hydrogen atoms near the surfaces. Light emission is strongly dependent on such fine silicon particles. Photoluminescence is due to charge carrier confinement in such three dimensional structure (sponge-like structure). Characteristics of visible light emission from n-type PS can be explained in terms of modification of band structure accompanied by bandgap widening and localized levels in bandstructure. It is also shown that hydrogen and oxygen atoms existing on residual silicon parts play an important role on emission stability.

• Journal of the Semiconductor & Display Technology
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• v.8 no.2
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• pp.31-35
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• 2009

In the silicon wafer polishing process, the mounting stage of silicon wafer on the ceramic carrier block has been using the polishing template which utilizes the porous surface instead of traditional wax mounting method. Here in this article, the experimental study is carried out in order to study the wafer demounting by water jet and the effects of operating conditions such as the water jet flowrate and the number of water jet nozzles on the wafer demounting time. It is found that the measured wafer demounting time is inversely proportional to the water flowrate per nozzle, regardless of number of nozzles used; implying that the stagnation pressure by the water jet impingement is the dominant key factor. Additionally, by using the transparent disk instead of wafer, the air bubble formation and growth is observed under the disk, making the passage of water flow, and subsequently demounting the wafer from the porous pad.

• Clean Technology
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• v.21 no.4
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• pp.224-228
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• 2015

Phospholipase D (PLD) was immobilized on a submicro-porous membrane through covalent immobilization. The immobilization was conducted on the porous membrane surface with the treatment of polyethyleneimine, glutaraldehyde, and the anhydrase, in sequence. The immobilization was confirmed using X-ray photon spectrometer. The pH values of phosphatidylcholine (PC) dispersion solution with buffer were monitored with respect to time to calculate the catalytic activities of PC for free and immobilized PLD. The catalytic rate constant values for free PLD, immobilized PLD on polystyrene nanoparticles, and immobilized PLD on a porous cellulose acetate membrane were 0.75, 0.64, and 0.52 s^-1, respectively. Reusability was studied up to 10 cycles of PC hydrolysis. The activity for the PLD immobilized on the membrane was kept to 95% after 10 cycles, and comparable to the PLD on the nanoparticles. The stabilities for heat and storage were also investigated for the three cases. The results suggested that the PLD immobilized on the membrane had the least loss rate of the activity compared to the others. From these studies, the porous membrane was feasible as a carrier for the PLD immobilization in the production of phosphatidic acid.

• Macromolecular Research
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• v.15 no.4
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• pp.343-347
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• 2007

Novel composite membranes, which delivered high separation performance for propylene/propane mixtures, were developed by coating inert poly(ethylene-co-propylene) rubber (EPR) onto a porous polyester substrate, followed by the physical distribution of $AgBF_4$. Scanning electron microscopy-wavelength dispersive spectrometer (SEM-WDS) revealed that silver salts were uniformly distributed in the EPR layer. The physical dispersion of the silver salts in the inert polymer matrix, without specific interaction, was characterized by FT-IR and FT-Raman spectroscopy. The high separation performance was presumed to stem from the in-situ dissolution of crystalline silver ionic aggregates into free silver ions, which acted as an active propylene carrier within a propylene environment, leading to facilitated propylene transport through the membranes. The membranes were functional at all silver loading levels, exhibiting an unusually low threshold carrier concentration (less than 0.06 of silver weight fraction). The separation properties of these membranes, i.e. the mixed gas selectivity of propylene/propane ${\sim}55$ and mixed gas permeance ${\sim}7$ GPU, were stable for several days.

• Journal of Life Science
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• v.31 no.5
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• pp.502-510
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• 2021

The objective of this study was to develop a novel ticagrelor-loaded self-nanoemulsifying drug delivery system with an enhanced solubility and dissolution rate. Numerous oils and surfactants were screened, then medium chain triglyceride (MCT) oil and the surfactants polyoxyethylene sorbitan monooleate (Tween 80) and Labrafil M1944CS were selected for the preparation of the ticagrelor-loaded self-nanoemulsifying drug delivery system. A pseudo-ternary phase diagram was constructed to detect the nanoemulsion region. Of the various formulations tested, the liquid SNEDDS, composed of MCT (oil), Tween 80 (surfactant), and Labrafil M1944CS (cosurfactant) at a weight ratio of 20/70/10 produced the smallest emulsion droplet size (around 20.56±0.70 nm). Then, particle size, polydispersity, and zeta potential were measured using drugs containing liquid SNEDDS. The selected ticagrelor-loaded liquid SNEDDS was spray-dried to convert it into a ticagrelor-loaded solid SNEDDS with a suitable inert carrier, such as silicon dioxide, calcium silicate, or magnesium aluminometasilicate. The solid SNEDDS was characterized by scanning electron microscopy, transmission electron microscopy, and in vitro dissolution studies. SEM, PXRD, and DSC results suggested that amorphous ticagrelor was present in the solid SNEDDS. Also, the solid SNEDDS significantly increased the dissolution rate of ticagrelor. In particular, the emulsion particle size and the polydispersity index of the solid SNEDDS using silicon dioxide (SS1) as a carrier was the smallest among the evaluated solid SNEDDS, and the flowability and compressibility result of the SS1 was the most suitable for the manufacturing of solid dosage forms. Therefore, solid SNEDDS using silicon dioxide (SS1) could be a potential nano-sized drug delivery system for the poorly water-soluble drug ticagrelor.

• Journal of the Korean Society of Groundwater Environment
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• v.2 no.1
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• pp.22-29
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• 1995

Mobile bacterial particles can act as carriers and enhance the transport of hydrophobic contaminants in ground water by reducing retardation effects. Because of their colloidal size and favorable surface conditions, bacteria can act as efficient contaminant carriers. When such carriers exist in a porous medium, the system can be thought of as three phases: an aqueous phase, a carrier phase, and a stationary solid matrix phase. Contaminant can be present in either or all of these phases. In this study, a mathematical model based on mass balances is developed to describe the transport and fate of biodegradable contaminant in a porous medium. Bacterial mass transfer mechanism between aqueous and solid matrix phases, and contaminant mass transfer between aqueous and bacterial phases are represented by kinetic models. Governing equations are non-dimensionalized and solved to analyze the bacteria facilitated contaminant transport. The numerical results of the facilitation effect match favorably with experimental data reported in the literature. Results show that the contaminant transport can be described by local equilibrium assumption when Damkohler numbers are larger than 10. Significant sensitivities to model parameters, particularly bacterial growth rate and influent bacterial concentration, were discovered.

• Applied Biological Chemistry
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• v.28 no.4
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• pp.233-238
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• 1985

Glucoamylases catalyze a stepwise hydrolysis of starch with the production of glucose. In order to make an efficient conversion of starch into glucose, glucoamylases prepared from Rhizopus spp. (Sigma Co.) were attached to a porous glass and immobilized by glutaraldehyde-induced crosslinking. The porous glass used in this study was $ZrO_2$ coated, $40{\sim}80$ mesh, 550 A pore diameter. Using the forgoing glass, we could couple as much as 50mg of protein per gram of carrier. Substrate for the glucoamylase was an enzyrne-modified thin-toiling 30% cornstarch solution used where greater solubility and low viscosity are desired. Immobilized glucoamylase had an optimum pH 7.0 to the alkaline side of soluble enzyme. Km values of immobilized and soluble enzyme were 1.04 mM and 1.25mM, respectively. The thermal stability of glucoamylase was increased by immobilization and the immobilized enzyme showed an optimum temperature at $40{\sim}60^{\circ}C$. The continuous conversion of cornstarch to glucose by use of immobilized glucoamylase resulted in the production of a more than 90 DE product.