• Proceedings of the Korea Information Processing Society Conference
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• 2008.11a
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• pp.615-618
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• 2008

본 논문에서는 각 개인의 동작영상에 대한 국부고유공간에 바탕을 둔 기저영상을 이용한 효율적인 수화영상 인식 기법을 제안하였다. 여기서 국부고유공간의 추출은 주요성분분석을 이용한 것으로 동작영상의 국소특징을 더욱 더 잘 반영하기 위함이고, 기저영상의 추출은 독립성분분석을 이용한 것으로 수화영상 내에 포함된 고차원의 독립적인 특징들을 반영하여 보다 개선된 인식성능을 얻기 위함이다. 제안된 기법을 240*215 픽셀의 80(1명*5동물*16동작)개 동물을 표현하는 수화동작을 대상으로 Euclidean의 분류척도를 이용하여 실험한 결과, 단순 국부고유공간을 이용한 방법에 비해 우수한 인식성능이 있음을 확인하였다.

• Journal of the Korean Ceramic Society
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• v.34 no.2
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• pp.163-170
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• 1997

The retarding effects of MgSiF6.6H2O on the hydration of portland cement were studied. The setting time, flow value and compressive strength of mortar were measured and the mechanism of retardation was also studied by ion concentration in solution, SEM, BET, and X-ray diffraction. The results are as follows ; 1. Setting time was delayed by the addition of MgSiF6.6H2O. 2. The flow value of mortar decreases depending upon the amount of MgSiF6.6H2O. 3. The compressive strength was almost same or some increase on 28 days hydration. 4. The main retardation mechanism of MgSiF6 on the hydration of portland cement may be explained by the following hypothesis. MgSiF6 depressing the Ca++ and K+ ion concentration of cement paste solution be-cause of the recrystalization of K2SiF6 and CaF2 phase. The new products of K2SiF6 and CaF2 deposit on the surface of unhydrated cement powder and harzard the mass transfer through these layer. The low con-centration of Ca++, K+ ion in solution was decreasing the hydration rate of portland cement.

• Tunnel and Underground Space
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• v.32 no.6
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• pp.491-501
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• 2022

Bentonite has been proposed as a buffer and backfill material for high-level radioactive waste repository. Under such repository environment conditions, bentonite is subjected to combined thermal, hydrological, mechanical, and chemical processes. This study evaluates the feasibility of applying X-ray CT technology on the characterization of bentonite under hydration conditions using a newly developed testing cell. The cylindrical cell is made of platic material, with a removable cap to place the sample, enabling to apply vertical pressure on the sample and to measure swelling pressure. The hydration test was carried out with a sample made of Gyeonju bentonite, with a dry density of 1.4 g/cm³, and a water content of 20%. The sample had a diameter of 27.5 mm and a height of 34 mm. During the test, water was injected at a constant pressure of 0.207 MPa, and lasted for 7 days. After one day of hydration, bentonite swelled and filled out the space inside the cell. Moreover, CT histograms showed how the hydration process induced an initial increase and later progressive decrease on the density of the sample. Detailed profiles of the mean CT value, CT standard deviation, and CT gradient provided more details on the hydration process of the sample and showed how the bottom and top regions exhibited a decrease on density while the middle region showed an increase, especially during the first two days of hydration. Later, the differences in CT values with respect to the initial state decreased, and were small at the end of testing. The formation and later reduction of cracks was also characterized through CT scanning.

• Applied Chemistry for Engineering
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• v.16 no.3
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• pp.354-360
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• 2005

Polyvinyl alcohol (PVA) hydrogels were prepared by the irradiation and heating. Irradiation and heating processes were carried out to improve the heat resistance of PVA hydrogels at high temperature. The physical properties such as gel content, degree of swelling and gel strength for the synthesized hydrogels were examined. The structure variations were investigated using the following techniques: differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Gel content and gel strength of the hydrogels were higher when the two steps of irradiation followed by heat treatment were used rather than only with the irradiation. The hydrogels prepared by the irradiation and the two steps had good heat resistance at high temperature.

• Applied Biological Chemistry
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• v.31 no.1
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• pp.46-51
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• 1988

The effects of temperature on the water uptake rate of soybeans soaked in tap water and 0.5% $NaHCO_3$ solution were studied. The higher the soaking temperature, the faster the hydration rate, and among the three soybean varieties (Tanyob, Kwanggyo and Saeal), Tanyob(the smallest variety) showed faster rate than ocher varieties when soaking in tap water and 0.5% $NaHCO_3$ solution. Activation energy due to weight increase was calculated using Arrhenius equation. z-Values calculated from weight changes to reach different degrees of hydration during soaking showed the tendency to decrease with the increase of hydration degree when soaking in tap water and 0.5% $NaHCO_3$ solution.

• Applied Chemistry for Engineering
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• v.22 no.4
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• pp.423-428
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• 2011

Hydration characteristics of cement containing zeolite mined at Daepo in Gyeongbuk province were studied for use as a mineral admixture. The cement paste containing zeolite was characterized by the measurement of heat evolution, XRD, EDS, nitrogen adsorption and mercury intrusion porosimetry. The cement paste containing zeolite exhibited tendencies toward acceleration of paste setting and promotion of cement hydration with the increase of zeolite content. The flow of mortar containing zeolite strongly reduced with increase of zeolite content. Compressive strength of the mortar containing zeolite increased very rapidly at an early age in comparison with plain mortar. These results would be related to aluminum species escaped from zeolite particles during the alkali dealumination of zeolite by the hydration process of cement.

• Resources Recycling
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• v.15 no.3 s.71
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• pp.46-57
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• 2006

This study was carried out for the purpose of recovering the refined gypsum from waste phosphogypsum. The refined gypsum was recovered as a under product of 325 mesh wet screening followed by dehydration and hydration stage. The influence of dehydration temperature and time, dehydration rate, aging time, slurry density of hydration and sonication time on the yield and grade of gypsum were investigated. The refined gypsum of $94{\sim}96%$ grade is recovered in 95% yield by wet screening after selective dehydration and hydration process, from the phosphogypsum. For the better separation efficiency of gypsum, it is recommended to treat the phosphogypsum at the conditions of as follows; 6hr's dehydration at $140^{\circ}C$, hydration slury density of $3{\sim}10%$, hydration temperature of $20{\sim}30^{\circ}C$, hydration time of 2hr. In additions, addition of sodium citrate 0.005M and sonication of $5{\sim}10min.$ are effective for increase the recovery of gypsum. On the other hand, aging the dehydrated gypsum 16 hours or longer make decrease the recovery of gypsum remarkably.

• Korean Chemical Engineering Research
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• v.50 no.1
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• pp.173-176
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• 2012

Chlorine dioxide has an excellent ability to sterilize and deodorize and is harmless to humans. However, it is very unstable and explosive as it is highly concentrated, thus its use in the air clean filed has been limited. Therefore, there is a demand to develop the system to produce a low concentration of chlorine dioxide sustainedly. Here, for a first step in the development of the system on the sustained production of chlorine dioxide, the use of polymer hydrogels was investigated. P(MMA-co-HEMA) hydrogel particles were prepared via dispersion photopolymerization and sodium chlorite and citric acid were loaded respectively in the hydrogel particles. When sodium chlorite and citric acid were reacted with not loaded in the hydrogels, rapid production of chlorine dioxide occurred and the concentration of chlorine dioxide decreased over time. However, when sodium chlorite and citric acid were loaded respectively in the hydrogel particles and reacted, chlorine dioxide was produced slowly and sustainedly because the release of sodium chlorite and citric acid from the hydrogels delayed the reaction between them. The result shows that the use of P(MMA-co HEMA) hydrogels has the potential to develop the system on the sustained production of chlorine dioxide.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.1
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• pp.81-87
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• 2020

Crack control is essential to increase the durability of concrete significantly. Healing of crack can be controlled by rehydration of unreacted clinkers at the crack surface. In this paper, by comparing the results of isothermal calorimetry test and regression analysis, the Parrot & Killoh's cement hydration model was verified and clink er hydration model was proposed. The composition and quantification of hydration products were simulated by combining kinematic hydration model and thermodynamic model. Hydration simulation was conducted using the verified and proposed hydration model, and the simulation was performed by the substitution rate of clink er. The type and quantity of the final hydration product and healing product were predicted and, in addition, the optimal cementitious material of self-healing concrete was selected using the proposed hydration model.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.545-548
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• 2008

In this study aluminium sulfate, Ca(OH)$_2$, K-R Slag and $Na_2SO_4$ were used as active admixtures and their concentration 1, 3, 5, 7 weight percent in cement. The physical properties of active admixtures cement mortar were investigated by flow test and compressive strength. It was found that the resulting active admixtures exhibited the higher compressive strength than OPC mortar up. From the test results, cement mortars added active admixture have a good fundamental property.