• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.1
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• pp.6-14
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• 2011

The re-crystallization process for recovering granular crystalline gypsum from phospho-gypsum have proposed. The process consists of two stages; at the first stage, needle-like fine gypsum is recovered with under-product of 325 mesh wet screening after the speedy hydration of dehydrated phospho-gypsum, and at the second stage, granular crystalline gypsum is recovered with upper-product of 325 mesh wet screening after dehydration and re-crystallization of the needle-like fine gypsum in $Na_2SO_4$ solution. This paper is mainly focused on the influence of dehydration time, cooling speed of temperature and re-crystallization temperature on the recovery of granular crystalline gypsum. And the re-crystallization velocity of needle-like fine gypsum at room temperature and the variation of $Ca^{2+}$ concentration of gypsum slurry during over all re-crystallization process were also discussed.

• Polymer(Korea)
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• v.38 no.2
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• pp.220-224
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• 2014

Protein adsorption kinetics was studied with the amount of proteins adsorbed to contact lens hydrogels over time scales. Hydroxyethylmethacrylate (HEMA) and silicone hydrogels were dipped in protein solutions (albumin or IgG) and adsorption amounts were measured over time scales. The amount of protein adsorbed to both hydrogel types increased rapidly in 10 min, and remained consistently in 90 min. Decreasing interfacial energetics was taken slowly up to an hour in spite of rapid diffusion of protein molecules. This is due to the fact that water deprivation from three dimensional interphase initially formed by protein diffusion took over an hour. Interpretation of adsorption kinetics on contact lens hydrogels was discussed with understanding of relationship between surface energy and protein adsorption capacity.

• Journal of Korea Foresty Energy
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• v.22 no.1
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• pp.37-43
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• 2003

The influence factors for char yield in the carbonization process of natural cellulose are the carbonization temperature, the heating rate and the atmosphere in the furnace. In general, it is well known that the improvement of char yield is expected under the conditions of the lower carbonization temperature, the slower heating rate and the presence of inert gas in the furnace. In this study, it has been investigated the effect of the heating rate control with sulfuric acid as a dehydrating agent for the improvement of char yield in the carbonization process of natural cellulose. The cellulose treated with sulfuric acid has shown the weak dependency of heating rate in char yield, whereas the untreated cellulose has shown the strong dependency. These findings clearly suggest that it can be useful to control heating rate with appropriate dehydrating agent in the carbonization process to improve the char yield and shortening the carbonization time.

• Applied Chemistry for Engineering
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• v.17 no.5
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• pp.451-457
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• 2006

We synthesized phase pure CrN having surface areas up to $47m^2/g$ starting from $CrCl_{3}$ with $NH_{3}$. Thermal Gravimetric Analysis coupled with X-ray diffraction was carried out to identify solid state transition temperatures and the phase after each transition. In addition, the BET surface areas, pore size distributions, and crystalline diameters for the synthesized materials were analyzed. Space velocity influenced a little to the surface areas of the prepared materials, while heating rate did not. We believe it is due to the fast removal of reaction by-products from the system. Temperature programmed reduction results revealed that the CrN was hardly passivated by 1% $O_{2}$. Molecular nitrogen was detected from CrN at 700 and $950^{\circ}C$, which may be from lattice nitrogen. In temperature programmed oxidation with heating rate of 10 K/min in flowing air, oxidation started at or higher than $300^{\circ}C$ and resulting $Cr_{2}O_{3}$ phase was observed with XRD at around $800^{\circ}C$. However the oxidation was not completed even at $900^{\circ}C$. CrN catalysts were highly active for n-butane dehydrogenation reaction. Their activity is even higher than that of a commercial $Pt-Sn/Al_{2}O_{3}$ dehydrogenation catalyst in terms of volumetric reaction rate. However, CrN was not active in pyridine hydrodenitrogenation.

• Applied Chemistry for Engineering
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• v.8 no.6
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• pp.1029-1033
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• 1997

Fundamental research of non-isothermic analysis of reaction rate has been carried out for the heat storage system using the thermal decomposition of $Na_2B_4O_7{\cdot}10H_2O$. It was found that the equilibrium temperature of the thermal decomposition reaction was lowered less than 373K in $Na_2B_4O_7{\cdot}10H_2O/Na_2B_4O_7{\cdot}5H_2O$ system, but the heat efficiency was unchanged. The initiation temperature of the reaction was varied from low to high temperature region with heating rate. The reaction order of the dehydration reaction by the thermal decomposition was appeared to be 0.67 by non-isothermic analysis, thereby $Na_2B_4O_7{\cdot}10H_2O$ may be used as a hemical heatstorage material.

• Journal of the Korean Chemical Society
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• v.29 no.5
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• pp.510-515
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• 1985

Color of $MoO_{(aq)}^{3+}$ in concentrated methanesulfonic acid (∼10M) changes dark green due to the formation of $Mo_2O_2(OH)_{2(aq)}^{4+}$ dimer. This color is similar to that shown by addition of water to that shown by addition of water to green $MoO_{(aq)}^{3+}$ solution in 15-16M methanesulfonic acid. The molar extinction coefficient of monomer in 15M methanesulfonic acid is about 20 at 415nm. Rate constants are independent on the aquomolybdenum (V) and hydrogen ion concentration under the condition of this experment. Bridging hydroxides of $Mo_2O_2(OH)_{2(aq)}^{4+}$ are dehydrogenated at the less concentration of ∼6 M for HPTS and ∼10M for $CH_3SO_3H$. The structure of both the yl-oxygens and the bridging oxygens of final product is identified to (*image)unit.

• Korean Journal of Food Science and Technology
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• v.25 no.2
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• pp.118-122
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• 1993

Average water loss of chinese cabbage during salting storage was 44.62% after 2 weeks and salt concentration after 3 weeks storage were 3.46%, 7.27%, 9.04%, 10.59%, 14.82% in 5%, 10%, 15%, 20%, 30% treatments respectively, and salt concentration after 4 hour desalting in water were changed to 2.72%, 4.67%, 5.38%, 6.84%, 9.43% respectively, and during the salting storage pH was lowered more rapidly in low salt treatment than in high salt treatment and it was judged by overall evaluation that salting storaged chinese cabbage of 5% and 10% were adeguate to Kimchi processing.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.6
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• pp.524-530
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• 2002

A control of the body posture and movement is maintained by the vestibular system, vision, and proprioceptors. Afferent signals from those receptors are transmitted to the vestibular nuclear complex, and the efferent signals from the vestibular nuclear complex control the eye movement and skeletal muscle contract. The postural disturbance caused by loss of the vestibular function results in nausea, vomiting, vertigo and loss of craving for life. The purpose of this study is to develop a off-vertical rotatory system for evaluating the function of semicircular canals and otolith organs, selectively, and visual stimulation system for- stimulation with horizontal, vortical and 3D patterns. The Off-vortical axis rotator is composed of a comportable chair, a DC servo-motor with reducer and a tilting table controlled by PMSM. And a double feedback loop system containing a velocity feedback loop and a position feedback loop is applied to the servo controlled rotatory chair system. Horizontal, vertical, and 3D patterns of the visual stimulation for applying head mounted display are developed. And wireless portable systems for optokinetic stimulation and recording system of the eye movement is also constructed. The gain, phase, and symmetry is obtained from analysis of the eye movement induced by vestibular and visual stimulation. Detailed data were described.

• Korean Chemical Engineering Research
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• v.58 no.4
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• pp.581-587
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• 2020

In this study, a new reaction system is proposed to solve the problems of the existing 2,3-Butanediol (2,3-BDO) dehydration reaction system. It was confirmed that the reaction system did not wok as it should operate properly when using a furnace, which is commonly used in commercial processes, to raise the reactant, 2,3-BDO, to the reaction temperature, 360 ℃, at near atmoshperic pressure. It is because of the substance considered to be oligomers of 2,3-BDO. It can lead to safety problems, such as blockages inside the furnace's tube and explosions, as well as tricky maintenance issues in the reaction system. To solve it, the temperature of reactant can be brought down by using a heat exchanger with High Pressure (HP) steam instead of the furnace, which has a hot spot problem through the vacuum operation and reduce the reaction temperature. It can be seen that the reactor performance is almost similar under the vacuum operation and the lower reaction temperature, 330 ℃, by using a reaction kinetics. This result explains why the new reaction system is proposed.

• Journal of the Korean Ceramic Society
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• v.25 no.3
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• pp.193-200
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• 1988

The starting materials were aluminum hydroxide prepared by precipitation method at the conditions of pH values; 7, 9, 10 and 11. The properties of alumina powder on heat-treatment were studied. After dehydrating structural water from amorphous aluminum hydroxide, the first formed phase was amorphous alumina and its specific surface are was decreased. The specific surface area was increased by dehydration of structural water from aluminum hydroxides except amorphous aluminum hydroxide. The specific surface area was increased with increase of the ratio of A1OOH to $A1(OH)_3$ in the region of transition aluminas. The rate of transition from aluminum hydroxide to alpha alumina occurred in the order of 7, 10, 9 and 11 of pH values. The morphology of alpha alumina powders was skeleton particles remaining outer shape of aluminum hydroxide. Both the elevation of heat-treatment temperature and the transition toalpha alumina decreased specific surface area and brought about the growth of particles.