• Journal of the Korean Ceramic Society
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• v.25 no.6
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• pp.685-693
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• 1988

From leaching of Korean native halloysite with hot sulfuric acid, active species of siliceous aluminosilicate are obtained as residue, which gives the mole ratio of SiO2/Al2O3 10 and substantially removes most acid-soluble impurities. By dissolving the residue in sodium hydroxide at an ambient temperature sodium silicate solution is prepared, this is used for zeolite synthesis as one of starting materials. In order to prepare zeolite Type 4A thereform, addition of a proper aluminum source is made so that the composition of the reactant materials may be of the following mole ratios : Na2O/SiO2=1.2-1.5, SiO2/Al2O3=1.8-2.0 and H2O/Na2O=34-45 By careful control of ageing time and temperature, subsequent crystal growth is induced into microfine zeolite 4A, which gives optimum particle size distributjion being suitable for detergent builder. The zeolite products thus obtained and highly competitive with those from the use of the refined clay in comparison of their calcium exchange capacity, whiteness and particle size distribution. The present method shows a marginal advantage over the existing procedures requiring neitherseparate purification nor calcinating otherwise necessary for the raw clay ores in use.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.258-258
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• 2008

Among several available high-k dielectrics the lanthanum zirconium oxide ($LaZrO_x$) system is very attractive as a buffer insulating layer. Because both lanthanum and zirconium atoms, the constituents of the $LaZrO_x$ thin film, have been considered to be thermally stable in contact with Si. The $LaZrO_x$ films were deposited by a sol-gel method. After the deposition, The $LaZrO_x$ films were crystallized at $750^{\circ}C$ for 30 minutes in $O_2$ ambient. PVDF-TrFE films were deposited on these $LaZrO_x$/Si structures using a sol-gel technique. The sol-gel solution was spin-coated on $LaZrO_x$/Si structures at 500 rpm for 5 sec and 2500 rpm for 15 sec. The deposited layer was dried at $165^{\circ}C$ for 30 min in air on a hot-plate. Then, we deposited Au electrode on PVDF-TrFE films using thermal evaporation.

• Journal of computational fluids engineering
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• v.16 no.3
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• pp.29-36
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• 2011

The natural convection in a horizontal enclosure heated from the bottom wall, cooled at the top wall, and having a square adiabatic body at its centered area was studied. Three different Prandtl numbers (0.01, 0.7 and 7) were considered for an effect of the Prandtl number on natural convection. A two-dimensional solution for unsteady natural convection was obtained, using Chebyshev spectral methodology for different Rayleigh numbers varying over the range of $10^4$ to $10^6$. It had been experimentally and numerically reported [1,2] that the heat transfer mode becomes oscillatory when Pr is out of a specific Pr band beyond the critical Ra. In this study, we reproduced this phenomenon numerically. The variation of time- and surface-averaged Nusselt numbers on the hot and cold walls for different Rayleigh numbers and Prandtl numbers was presented to show the overall heat transfer characteristics in the system. And also, the isotherms and streamline distributions were presented in detail to compare the physics related to their thermal behavior.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.5 no.1
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• pp.60-66
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• 1995

Abstract The experimental results which is the aerosols behavior and distribution of atomized zinc nitrate ($Zn(NO_3)_2$) solution (0.5 M) by ultrasonic vibrator were in accord with the computer simulations. i.e., most aerosols passing through the reactor (hot zone) moved toward the center of reactor by thermophoresis as the axis of reactor increase. Also, the distribution of aerosols concentration was high at the center of reactor as the axis increase. Among the synthesized ZnO particles, shell-like aggregates of fracture type which could not see at the center of reactor were observed at near the wall of reactor, and the particle size ($ 1.2 {\mu\textrm{m}$) of near the wall was larger than that ($0.9 {\mu\textrm{m}$) of the center.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.4
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• pp.640-647
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• 1996

It has been found that an white precipitates at the inside surface is a common characteristics of soda-lime-silica glasses which have not undergone special surface treatments during hot weather season. In this study, the white deposits were examed using by solution method, surface analysis etc., and the dependence of weathering on the atmospheric condition was also investigated. As a results, the white precipitates on the glass surface was discorved as carbonates like $Na_2CO_3{\cdot}H_2O,CaCO_3$. Coming to atmosphere-dependence, it was shown that the glass made and stored at sea shore province had 3 times much severe weathering than that at land province.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.12
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• pp.1117-1125
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• 2004

In this study, in order to utilize the waste heat of industrial wastewater in the range of the relatively low temperature of 40～5$0^{\circ}C$ as a heat source, a hybrid heat pump system was considered by computer simulation method. In the simulation, an absorber, desorber and solution heat exchanger were modelled by UA values while a compressor and pump performance were specified by an isentropic efficiency. Simulation results show that the performance of hybrid heat pump can be up to 80% higher than that of conventional R134a heat pump when it makes a process hot water of 9$0^{\circ}C$ while the wastewater is cooled down to 2$0^{\circ}C$. As the absorber pressure increases, the system performance and deserter pressure increase with a favorable effect of a compressor discharge gas temperature drop.

• Korean Chemical Engineering Research
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• v.51 no.3
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• pp.358-363
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• 2013

Lithium-ammonia (Li-$NH_3$) solutions are possible to be successfully made under the vacuum condition but there still remains a problem of undergoing stable and reliable decomposition in vacuum for high-efficiency thermoelectric power generation. This paper describes a new method for improving the thermoelectric conversion efficiency of Li-$NH_3$ solutions in vacuum. The proposed method uses a 'U'-shaped Pyrex vacuum tube for the preparation and decomposition of pure fluid Li-$NH_3$ solutions. The tube is shaped so that a gas passageway ('U') connecting both legs of the 'U' helps to balance pressure inside both ends of the tube (due to $NH_3$ gasification) during decomposition on the hot side. Thermoelectric experimental results show that solution reaction in the 'U'-shaped tube proceeds more stably and efficiently than in the 'U'-shaped tube, and consequently, thermoelectric conversion efficiency is improved. It is also proved that the proposed method can provide a reversible reaction, which can rotate between synthesis and decomposition in the tube, for deriving the long-time, high-efficiency thermoelectric power.

• Journal of the Korean Wood Science and Technology
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• v.15 no.3
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• pp.56-67
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• 1987

Plywoods used for construction as a decorative interior material are inflammable and can make fire accidents, causing destruction of human life and property. Therefore, it is indeed required to make fire-retardant treated plywood. In this study, 3.7mm yellow meranti plywoods were soaked in 18% boric acid solutions and tap water by hot-cold bath for 1/2, 2/2, 4/2, 6/2 hours and redrying of treated plywoods was carried out by press drying at the platen temperature of 110, 130, 160, $180^{\circ}C$ and then it was conducted to investigate solution absorption, drying rates, dynamic young's modulus. specific gravity and fire-retardant factors such as burning point, flame spread length. flame exhausted time, back side carbonized area and weight loss by treating time, treating solutions and platen temperature. The results are as follows; 1. When plywood was impregnated with the hot bath temperature of $70^{\circ}C$ for 1. 2, 4, 6 hours and the cold bath temperature of $15^{\circ}C$ for 2 hours respectively, retentions of boric acid were 1.565, l.597, 1.643, 1.709kg/$(30cm)^3$ and all of them exceeded the minimum retention [1.125kg/$(30cm)^3$] even in the shortest treatment. 2. In hot-cold bath method for 1/2 hours, the drying rates of treated plywood remarkably increased with the extension of platen temperature of 110, 130, 160, $180^{\circ}C$ and the values of boric acid treated plywood were 5.900, 10.196, 45.42, 54.958m.c%/min and the values of water treated plywood were 6.014, 12.373, 46.520, 55.730m.c%/min and drying rates of water treated plywood were faster than those of boric acid treated plywood. 3. The values of boric acid treated plywoods in dynamic young's modulus were widely higher than those of water treated plywoods. And it can be observed that there were highly significant differences for treating time between dynamic young's modulus, and the values of boric acid plywoods increased with the extension of treating time but on the contrary water treated plywoods were decreased values with prolonged time 4. It was observed that there were highly significant differences for platen temperature between dynamic young's modulus. When the values of water treated plywoods in dyna nic young's modulus were abruptly decreased according to the rise of platen temperature. boric acid treated plywoods showed rather increased values at $160^{\circ}C$ of platen temperature. And in 2- way interactions, there were also highly significant for dynamic young's modulus between treating time x treating solutions and platen temperature x treating solutions. 5. Correlation coefficients of fire-retardant factors were shown in table 5. It could be recognized that there were close correlations between the treating solutions and burning point, flame spread length, back side carbonized area, flame exhausted time and weight loss, but there was no correlation between fire-retardant factors and treating time and platen temperature. 6. From table 6, it can be observed that there were highly significant differences for burning point, flame spread length, flame exhausted time, back side carbonized area, weight loss between treating solutions. And in 2-way interactions, there were highly significant for burning point, flame spread length, weight loss between treating time $\times$ treating solutions.

• Journal of the Korean Society of Clothing and Textiles
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• v.10 no.2
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• pp.1-9
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• 1986

To study the effects of surface structure of fiber on the decrement of fatty soil removal at high temperature, the following variables were selected: controled and alkali-treated P.E.T.(polyester) fabrics and chopped fibers as substrates to estimate the detergencies, different aging methods of soiled substrates, and different washing temperatures and surfactant solutions. Radiotagged tripalmitin was used as soil and the detergency was estimated by means of liquid scintillation counting method. The results were as following: The surface of the fiber became rough with many grooves and the hydrophilicity of the fiber was increased and the structure of the fabric became loose by alkali treatment. While the detergency of alkali-treated P.E.T. fabric was better than that of controled P. E. T. fabric, there was no significant differences between the detergencies of controled and alkali-treated chopped fibers. These results indicate that the increment of detergency of alkali-treated P.E.T. fabric is mainly resulted from the changes of fabric structure and the improved hydrophilicity of fiber by alkai treatment. The detergency of tripalmitin was increased with elevating temp. below the m.p. of tripalmitin, was decreased around the m.p., and again was increased above the m.p ..It is considered that the decrement of detergency around the m.p. is due to the diffusion of molten tripalmitin into the grooves on fiber surface, the inner part of fiber, and between fibers. When controled and alkali-treated soiled fabrics and soiled chopped fibers were washed in the distilled water and in the Na-DBS solution respectively, below $60^{\circ}C$ detergencies of alkali-treated fabrics and chopped fibers were improved. However above $60^{\circ}C$ this result was reversed. Therefore these results are regarded as the effects of grooves on fiber surface at high temp. and improved hydrophilicity at low temp. by alkali treatment. When controled and alkali-treated soiled fabrics and soiled chopped fibers were hot-aged before washing, the detergencies of both species were decreased generally. Because the soil was diffused into the grooves on fiber surface, the inner part of fiber, and between fibers during hot-aging. The detergencies of hot-aged species were also decreased above certain temp.. These results suggest that the decrement of detergency at high temp. be resulted not only from the diffusion of soil into the grooves on fiber surface, the inner part of fiber, and between fibers, but also from the characteristics of surfactant solutions.

• Journal of Korean Society of Forest Science
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• v.60 no.1
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• pp.30-36
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• 1983

Plywood, the representative interior decorative or structural material, is so inflammable that it may cause big fires. Therefore, it is required inevitably to manufacture the "Fire retardant treated plywood", and it will be a study on the redrying of treated plywood that we ought to solve. This study was carried out to investigate the absorption of 20% $(NH_4)_2HPO_4$ solution into the soaked plywoods by hot/cold soaking for 3/3, 6/3, 9/3 and 12/3 hours and to study drying process with drying curves and drying rates by press-drying at the platen temperature of 130, 145, 160 and $175^{\circ}C$. Solution absorption of plywoods in hot/cold soaking method increased steadily with the prolonged soaking time, and water absorption is higher than DAP absorption, and then chemical retention (DAP) exceeded the minimum retention [$1.125kg/(30cm)^3$] even in the shortest soaking treatment. Drying curves of water-soaked plywoods inclined more steeply than those of DAP soaked plywoods. And the drying proceeded rapidly with the increase in platen temperature and terminated in 2.5-4 minutes at the temperature of 160 and $170^{\circ}C$. Drying rate also increased generally with the increase of platen temperature. So it was at $175^{\circ}C$ in DAP-soaking and at $160^{\circ}C$ in water-soaking when the drying rate became above 10%/min.