• Journal of the Korea Institute of Building Construction
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• v.12 no.4
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• pp.369-376
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• 2012

In this study, to reduce the hydration heat velocity (HHV) of high-strength mass concrete at early ages, phase change materials (PCM) that could absorb hydration heat were applied, and the changes in autogenous shrinkage were investigated, as well as the relationship between the hydration temperature and autogenous shrinkage. The acceleration of the cement hydration process by the PCM leads to an early setting and a higher development of the compressive strength and elastic modulus of concrete at very early ages. The function of PCM could be worked below the original melting point due to the eutectic effect, while the hydration temperature and HHV of high-strength mass concrete can be decreased through the use of the PCM. A close relationship was found between the hydration temperature and autogenous shrinkage: the higher the HHV, the greater the ultimate autogenous shrinkage.

• International Journal of Highway Engineering
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• v.11 no.2
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• pp.229-238
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• 2009

This paper describes the methods to propose the optimal material properties and construction steps that prevent cracks due to the thermal stresses induced by the hydration heat under the construction of the concrete underpass structures. To achieve the goal of this study, the heat transfer theories were employed and the three-dimensional finite element model of the underpass structure was developed and used for the structural analyses. If the volume of the concrete member that is placed at one time is significantly large, the member is assumed to be the mass concrete and is easy to induce cracks. In order to minimize the cracks during the construction, two different methods can be utilized: one is to arrange the construction steps optimally and the other is to change the materials to reduce the probability of the crack occurrence. In this study, the analyses were performed by considering the changes in material properties with time, the characteristics of the hydration heat generation for cements and admixtures, the volume of the concrete placement at one time, and the environmental conditions.

• Korean Journal of Ecology and Environment
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• v.36 no.3 s.104
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• pp.269-276
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• 2003

The study was performed to understand the relationships of cyanobacterial bloom and environmental factors in Lake Daechung. The samples were collected weekly from June to October in 2001. The cyanobacterial bloom was divided into the three phases of the early phase, the middle phase and the late phase by phytoplankton standing crops. For the early phase, the correlation coefficients between chl- a and TP, and chl- a and $PO_4$-P were 0.986 and 0.894 respectively. Therefore, phosphorus was a main environmental factor in the development of cyanobacterial bloom. Zeu/Zm ratio and chl-a showed negative correlation of r = -0.995. At the late phase, $PO_4$-P showed the highest relationship (r = 0.958), and TP and temperature showed relatively high relationships (r = 0.857 and r = 0.813). At the late phase, $NH_3$-N showed highly positive relationship (r = 0.921). It was confirmed that $PO_4$-P was the most important contribution factor for the bloom through the regression analysis on the environmental factors. As the result, the decrease of Zeu/Zm ratio and the increase of P concentration influenced cyanobacterial bloom developed rapidly in the early phase. Also the cyanobacterial bloom was decreased in proportion to decreasing of $NH_3$-N concentration in the late phase. It was expected that observation of $NH_3$-N may be a very useful factor on monitoring of the decreasing situation of the bloom.

• Journal of the Korea Institute of Building Construction
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• v.12 no.2
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• pp.203-210
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• 2012

Recently, the interest and demand for large-scale buildings and skyscrapers have been on the rise, and the performance of concrete is an area of high priority. Securing 'mass concrete and high strength concrete' is very important as a key construction technology. For high strength concrete, the high heat of hydration takes place inside the concrete because of the vitality of hydration in cement due to the large amount of powder, and leads to problems such as an increase of thermal stress due to the temperature difference with the outside, which results in cracks and slump loss. For this reason, measures to solve these problems are needed. This study aims to reduce the hydration heat of high strength concrete to control the hydration heat of mass concrete and high strength concrete, by replacing the type of admixture, The purpose of this study is to control the hydration heat of high strength concrete and mass concrete. Our idea for this purpose is to apply not only the types and contents of admixture but also incorporation mixing water to ice-flake. As a result of the test, the use of blast furnace slag and fly ash as admixture, and the use of ice-flake as mixing water can improve the liquidity of concrete and reduce slump loss. Significantly dropping the maximum temperature will contribute greatly to reducing cracks due to hydration heat in mass concrete and high strength concrete, and improve quality.

• Journal of the Korea Concrete Institute
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• v.27 no.2
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• pp.115-125
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• 2015

This study investigated the fluidity, heat of hydration, setting time, strength development, and characteristics of hydration and pozzolanic reactions of high-strength high-volume ground granulated blast-furnace slag(GGBFS) blended cement pasts with the water-to-binder ratio of 20% by experiments, and analyzed the effects of the replacement ratio and fineness of GGBFS on the hydration and pozzolanic reaction. The results show that, in the high-strength mixtures with low water-to-binder ratio, the initial hydration is accelerated due to the "dilution effect" which means that the free water to react with cement increases by the replacement of cement by GGBFS, and thus, strengths at from 3 to 28 days were higher than those of plain mixtures with ordinary Portland cement only. Whereas it was found that the long term strength development is limited because the hydration reaction rates rapidly decreases with ages and the degree of pozzolanic reaction is lowered due to insufficient supply of calcium hydroxide according to large replacement of cement by GGBFS. Also, the GGBFS with higher fineness absorbs more free water, and thus it decreases the fluidity, the degree of hydration, and strength. These results are different with those of normal strength concrete, and therefore, should be verified for concrete mixtures. Also, to develop the high-strength concrete with high-volume of GGBFS, the future research to enhance the long-term strength development is needed.

• Korean Journal of Organic Agriculture
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• v.19 no.3
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• pp.385-396
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• 2011

This study was carried out to develop environmental friendly control for major diseases and pests on Boxthorn (Lycium chinense Mill.). Outbreak of Eighteen diseases and pests were found at the Boxthorn organic yards in Chung-nam province. Among them Powdery mildew (Erysiphe polygoni de Cand.), Hypophyllous mold (Pseudocercospora chengtuensis (Tai)), Western flower trips (Frankliniella occidentalis (Pergande)), Green peach aphid (Myzus pericae (Sulzer)) and Corn earworm (Helicoverpa armigera) needed to be controled by environmental friendly methods for high fruit yield of organic Boxthorn. In summer(Jun) test Bacilus subtilis QST 713 wettable powder and Sulfur wettable powder were effective and in autumn (Sep.) test Sulfur, Copper hydroxide and Paraffinic oil were relatively effective in Powdery mildew. In Hypophyllous mold control test Paraffinic oil and Bacilus subtilis GB - 0365 were effective with above 70% control value. And it was possible to control Western flower trips by natural enemy (Orius laevigatus) by 80% control value. Corn earworm was possible to control by Bacillus thuringiensis subsp. aizawai GB413 flowable and Bacillus thuringiensis aizawa 0423 wettable powder application above 70%. And Green peach aphid was controllable with environmental friendly materials, such as, Bacillus subtilis (Seoncho), Bacillus subtilis (Jinsami) above 80% and Ginkgo nut extract above 70% control value.

• Korean Chemical Engineering Research
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• v.59 no.4
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• pp.611-625
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• 2021

Mg crowns were manufactured using domestic dolomite (Ca·Mg(CO₃)₂) (20~30 mm). In order to manufacture the calcined dolomite (CaO·MgO), (a) electric furnace (950 ℃, 480 min) and (b) microwave furnace (950 ℃, 60 min) processes were used. As a result of XRD analysis, it was analyzed as (a) CaO 56.9 wt%, MgO 43.1 wt% by electric furnace process and (b) CaO 55 wt%, MgO 45 wt% by microwave furnace process. Even when the decarbonation reaction time of dolomite was shortened by 1/8 in microwave furnace process compare with electric furnace process, the calcined dolomite could be produced. The hydration reaction (ASTM C 110) is a standard for the hydration reactivity of calcined dolomite, and the calcined dolomite produced by electric furnace process showed a high hydration reactivity (max temp 79.8 ℃/1.5 minutes). Such hydration reactivity was occurred by only CaO hydration reaction and that was confirmed by XRD analysis. The calcined dolomite produced by microwave furnace process showed low hydration reactivity (max temp 81.7 ℃/19.5 minutes). Such low hydration reactivity was occurred by CaO and MgO hydration reaction due to the hydration reaction of CaO thereafter occurring of the hydration reaction of MgO, and that was confirmed by XRD analysis. The prepared Mg crown were 58.8 g and 74.6 g by electric furnace and microwave furnace processes, respectively, under the reaction conditions of 1,230 ℃, 60 min, 5 × 10^-2 torr by silicothermic reduction.

• Proceedings of the Korea Information Processing Society Conference
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• 2017.11a
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• pp.1041-1044
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• 2017

말하기와 듣기가 불가능한 언어장애인들은 수화를 통하여 그들끼리 혹은 일반인과 의사소통을 해야 한다. 수화 또한 공용어이기에 전문통역사 없이도 서로간의 의사소통이 원활해야 하지만, 현실은 그렇지 않다. 이 시스템은 LeapMotion장비를 연결 및 각종 손동작을 인식 받아 데이터 세트 내에서 처리하여 이를 자연어로 변환함으로써 의사소통의 불편함을 해소할 수 있다. 또한 머신러닝을 이용하여 반복 학습할 수 있게 설계함으로써 처리율 향상을 기대할 수 있다.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.12
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• pp.1327-1331
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• 2005

This study was to investigate the reduction of hydration heat by utilizing industrial by-products such as BFS(Blast Furnace Slag). DM(Dredged Mud) was used by parent soil and Ordinary portland cement was used by cementing material. Additive added to reduce the heat of hydration was BFS. From the results of experiment, hydration heat was decreased in accordance with the addition of BFS. The reason was that surface of BFS coated with aluminosulfate. Initial uniaxial strength was low, neither was not long term uniaxial strength. It was concluded that silica rich layer($H_2SiO_4^{4-}$) in solid phase early in the reaction of hydration was difficultly moved in liquid phase due to the increase of ZP(Zeta Potential). However, the ZP in the later hydration was decreased due to the acceleration of mobility of silica rich layer($H_2SiO_4^{4-}$). Therefore, long term physical properties such as uniaxial strength revealed.

• The Korean Journal of Pesticide Science
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• v.6 no.3
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• pp.175-182
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• 2002

This experiment was conducted to investigate the effects of acid rain in spraying copper hydroxide 77% wettable power(WP) on leaf surface morphology and crop injury of the garlic(Allium sativum L.). Leaf chlorosis, hooked leaves, wrinkled epidermal cells and increased stomata open of garlic were induced by foliar application of simulated acid rain(SAR). It was become to be severe in application of copper hydroxide solution after application of SAR, but those yield of garlic was not significantly different from the untreated control. Leaf chlorosis was sharply increased above 100 ppm of copper ions. Amount of solved copper ions in copper hydroxide solution was remarkably increased below pH 5.5 and the residue in garlic leaves was significantly increased by application of copper hydroxide solution after spraying SAR compared with application of copper hydroxide solution only. When calcium carbonate was applied together with copper hydroxide leaf chlorosis was less than copper hydroxide only.