• Geomechanics and Engineering
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• v.29 no.4
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• pp.391-405
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• 2022

A newly proposed grouting simulation method, the sequential diffusion solidification method was introduced into the numerical simulation of combined bi-borehole grouting. The traditional, critical and difficult numerical problem for the temporal and spatial variation simulation of the slurry is solved. Thus, numerical simulation of grouting and blocking of flowing water in karst conduits is realized and the mechanism understanding of the combined bi-borehole technology is promoted. The sensitivity analysis of the influence factors of combined bi-borehole grouting was investigated. Through orthogonal experiment, the influences of proximal and distal slurry properties, the initial flow velocity of the conduit and the proximal and distal slurry injection rate on the blocking efficiency are compared. The velocity variation, pressure variation and slurry deposition phenomenon were monitored, and the flow field characteristics and slurry outflow behavior were analyzed. The interaction mechanism between the proximal and distal slurries in the combined bi-borehole grouting is revealed. The results show that, under the orthogonal experiment conditions, the slurry injection rate has the greatest impact on blocking. With a constant slurry injection rate, the blocking efficiency can be increased by more than 30% when using slurry with weak time-dependent viscosity behavior in the distal borehole and slurry with strong time-dependent viscosity behavior in the proximal borehole respectively. According to the results of numerical simulation, the grouting scheme of "intercept the flow from the proximal borehole by quick-setting slurry, and grout cement slurry from the distal borehole" is put forward and successfully applied to the water inflow treatment project of China Resources Cement (Pingnan) Limestone Mine.

• Journal of Mechanical Science and Technology
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• v.17 no.6
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• pp.906-913
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• 2003

Lean premixed combustion has been considered as one of the promising solutions for the reduction of NOx emissions from gas turbines. However, unstable combustion of lean premixed flow becomes a real challenge on the way to design a reliable, highly efficient dry low NOx gas turbine combustor. Contrary to a conventional diffusion type combustion system, characteristics of premixed combustion significantly depend on a premixing degree of combusting flow. Combustion behavior in terms of stability has been studied in a model gas turbine combustor burning natural gas and air. Incompleteness of premixing is identified as significant perturbation source for inducing unstable combustion. Application of a simple convection time lag theory can only predict instability modes but cannot determine whether instability occurs or not. Low frequency perturbations are observed at the onset of instability and believed to initiate the coupling between heat release rate and pressure fluctuations.

• Journal of Surface Science and Engineering
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• v.42 no.5
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• pp.232-239
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• 2009

This study presented the effect of membrane thickness on hydrogen permeability. Microvoids on the surface of the membrane should not exist for the exact values of hydrogen permeability. Pd-Cu-Ni hydrogen alloy membranes were fabricated by Ni powder sintering, substrate plasma pretreatment, sputtering and Cu reflow process. And this leaded to void-free surface and dense film of Pd-Cu-Ni hydrogen alloy membrane. Hydrogen permeation test showed that hydrogen permeability increased from 2.7 to $15.2ml/cm^2{\cdot}min{\cdot}atm^{0.5}$ as membrane thickness decreased from 12 to $4{\mu}m$. This represented the similar trend as a hydrogen permeability of pure palladium membrane based on solution-diffusion mechanism.

• Journal of the Korean Ceramic Society
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• v.52 no.4
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• pp.269-272
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• 2015

$La_2Ce_2O_7$ and $CeO_2$ membranes were fabricated from the corresponding powders derived from sol-gel process with polyvinyl alcohol binder. These powders and membranes were characterized by XRD, BET, and FE-SEM analysis. Hydrogen and CO gas permeation experiments were performed using Sievert's type equipment. Both fluxes on these membranes were found to decrease with increase of the temperature. This phenomenon was followed by the surface and Knudsen diffusion mechanism. The hydrogen permeability of the $La_2Ce_2O_7$ membrane was found to be $7.27{\times}10^{-5}mol/m^2sPa$, with perm-selectivity of 7.24 at 303 K.

• Transactions of Materials Processing
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• v.7 no.5
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• pp.481-488
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• 1998

The active metal brazing was applied to bond Alumina and Ni-Cr steel by Ag-Cu-Zr-Sn alloy and the interfacial microstructure and reaction mechanism were investigated. Polycrystalline monoclinic $ZrO_2$ with a very fine grain of 100-150 nm formed at the alumina grain boundary contacted with Zr segregation layer at the interface. The $ZrO_2$ layer containing the inclusions and cracks were developed at the boundary of inclusion/$ZrO_2$ due to the difference in specific volume. The development of $ZrO_2$ at the interface was successfully explained by the preferential penetration of $ZrO_2$ at the interface was successfully explained by the preferential penetration of Zr atoms a higher concentration of oxygen and a high diffusion rate of Al ions into molten brazing alloy.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.9
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• pp.165-171
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• 1999

An oil layer fuel absorption /desorption modeling was developed. Multi-component fuel model has showed more reasonable condition than single component model. Henry's constant which is related to solubility is the most important variable in the oil layer absorption/desorption mechanism. The oil segments close to the top of the cylinder liner have more significant contribution to the fuel absorption and desorption process than other oil segments. At the warmed-up condition, the effect of the engine speed on the precent fuel absorbed/desorbed is minimal. But at low il film temperature, percent of fuel abosrbed/desorbed is decreased with increasing the engine speed because of low value of molecular diffusion coefficient of fuel. The amount of fuel trapped in the piston crevice is from 2 to 2.3 times larger than that of fuel in the oil fim. However, fuel form oil film slowly desorbs into the combustion chamber compared with fuel from the piston crevices when the engines is cold.

• Journal of the Korean Ceramic Society
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• v.22 no.2
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• pp.44-50
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• 1985

The crystallization behavior of $K_2O-SiO_2$ glasses with added $TiO_2$ and the effect of $TiO_2$ on internal nuleation at temperature in the range of 875 to 121$0^{\circ}C$ have been investigated by means of X-ray diffractometry optical microscopy and scanning electron microscopy. The crystalline phase of these glasses identified by X-ray diffractometry is cristbalite. The scanning electron microspcopy reveals a two-phase layer of dendritic crystals and intersitial melt which grow from the surface at a constant rate, The observed crystallization rates are consistent with a diffusion-controlled mechanism. An equation relating viscosity and undercooling to growth rate is presented.

• Journal of the Korean Ceramic Society
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• v.24 no.4
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• pp.335-342
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• 1987

There were several numbers of studies on chemically strengthening glass. Most of them were strengthened in molten salt bath below transformation range of glass. Apart from them, this study used solution hydration technique by Autoclave. After determining proper concentration of AgNO3 salt solution, experimental condition varied from 4hrs to 16hrs at relatively low temperature (180, 200, 220$^{\circ}C$). The results showed that the Soda-Lime-Silica glass could be strengthened by diffusion mechanism without influence of water above 15% salt solution. Because of Ag+ ion penetration in glass surface, yellow color appeared and decreased transmittance at visible range. Modulus of rupture was increased with the amount of exchange and brittleness was decreased.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 1998.04a
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• pp.144-153
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• 1998

Sorbents of calcined limestone and oyster particles having a diameter of about 0.63mm were exposed to simulate fuel gases containing 5000ppmv H2S for temperatures ranging from 600 to 800C in a TGA. The reaction between CaO and H2S proceds via an unreacted shrinking core mechanism. The sulfidation rate is likely to be controlled primarily by countercurrent diffusion through the product layer of calcium sulfide(CaS) formed. The kinetics of the sorption of H2S by CaO is sensitive to the reaction temperature and particle size, and the reaction rate of oyster was faster than the calcined limestone.

• KSBB Journal
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• v.14 no.1
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• pp.1-8
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• 1999

It confirmed the facilitated diffusion of $Na^+$ of frog bladder membrane which is a tissue membrane. The mechanism was explained in $Na^+$ channel model and its referred to the $Na^+$ channel obstruction ingredient which was contained in the reference to the $Na^+$ channel obstruction ingredient and son on, e.g., seaweed, shellfish, pufferfish, phytoplankton and chinese drug. Also, it introduces the result which studied from the barrier point of the application of the tissue biosensor to the trade friction on Korea or Japan pufferfish and the marine environment in the one with high dependance. It was possible for the poison quantity of small amount pufferfish toxin (TTX), paralytic shellfish poisoning (PSP) to be measured and also to measure poison quantity in the cultivation poisonous toxin phytoplankton individual. In future, as for this tissue biosensor, it expects that it is possible to contribute widely until environment watch and also monitoring to the scene.