• Journal of the Korea Concrete Institute
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• v.14 no.3
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• pp.420-429
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• 2002

The amount of $CO_2$-silicate bonded waste foundry sand(WFS) occurred in Korea is over 800,000 ton per year. WFS, as a by-product, is generated through manufacturing process of foundry may affect our environmental contamination, The reason is that WFS has been buried itself not less than 90％ out of total WFS. So, it can give damage on the ground of contamination in soil and underwater. Therefore, it is necessary to establish the method recycling WFS because of being intensified waste management law. In this study, we performed the research with respect to harmful component analysis, the qualities of WFS mortar and concrete mixed with WFS. As the results the specific gravity of WFS is the same as that of natural aggregate while unit weight and percentage of solids of WFS are smaller than those of it. But it is found that WFS can be used by substituting WFS for natural aggregate after control of poor grade of WFS. The flowability of mortar and concrete with WFS is inferior to those of natural aggregate, and the setting time of concrete with WFS is faster than that with only natural aggregate, On the contrary, the bleeding of concrete with WFS is shown good result, and compressive and tensile strength of concrete substituted WFS for 30％ are higher than those with only natural aggregate regardless of elapsed time.

• Journal of the Korean Institute of Gas
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• v.21 no.4
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• pp.1-5
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• 2017

Leaking of natural gas, which is mostly methane, in a confined living space creates flammable atmosphere and gives rise to explosion accident. The minimum amount of leaked methane for explosion is highly dependent on the degree of mixing in the confined space. This paper proposes a method for estimating minimum amount of flammable gas for explosion by using Gaussian distribution explosion model(GDEM) and experimental explosion data. The explosion pressure in the confined space can be estimated by assuming the Gaussian distribution of flammable gas along the height of an enclosure and estimating the maximum amount of gas within flammable limits, combustion of the estimated gas with constant volume and adiabatic or isothermal mixing in the confined space. The predicted minimum gas amount for an explosion is tied to explosion pressure that results in a given building damage level. The result shows that very small amount of methane leaking in the confined space may results in a serious gas explosion accident. This result could be applied not only to setting the leak criteria for developing a gas safety appliance but also to accident investigating of explosion.

• Education of Primary School Mathematics
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• v.19 no.3
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• pp.177-191
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• 2016

Students can calculate the addition and subtraction problem using informal knowledge before receiving the formal instruction. Recently, the value that a computation lesson focus on the understanding and developing the various strategies is highlighted by curriculum developers as well as in reports. Ideally, a educational setting and classroom culture reflected students' learning and problem solving strategies. So, this paper analyzed the similarity and difference with respect to the numeric sentence and word problem in the addition and subtraction. The subjects for the study were 100 third-grade Korean students and 68 third-grade American students. Researcher developed the questionnaire in the addition and subtraction and used it for the survey. The following results have been drawn from this study. The computational ability of Korean students was higher than that of American students in both the numeric sentence and word problem. And it was revealed the differences of the strategies which were used problem solving process. Korean students tended to use algorithms and numbers' characters and relations, but American students tended to use the drawings and algorithms with drawings.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.10
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• pp.3974-3981
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• 2010

Coastal landscape is a collective setting of artificial or natural elements along the seaside. The approach method for the coastal landscape formation is different from that of urban landscape formation. This study analyzes the mechanism of coastal landscape formation process in Japan in the aspects of recognition phase, formation phase, and practice phase. The characteristics of coastal landscape formation process in Japan are construction of a survey system for integrating diverse landscape elements as a final coastal landscape, construction of a coherent evaluation system responding the local natural and spatial characters, and building a cooperative system responding the police of coastal landscape formation. This study suggest the implications both for the improvement of domestic local values and for the ways of the domestic coastal landscape formation.

• Ocean and Polar Research
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• v.29 no.3
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• pp.205-216
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• 2007

The purpose of this study was to investigate effects of large scale marine sand mining on the marine ecological community. For the study, four stations along the coast were selected and monitored in 1998 and 2001 at mining areas and non-mining areas about the Gyeonggi Bay. The result revealed that in 1998, 9 species of fishes, 16 species of crustaceans, and 6 species of mollusks were collected where as in 2001, 11 species of fishes, 5 species of crustaceans, and 2 species of mollusks were collected, uncovering the fact that fishes have diversified while crustaceans and mollusks have reduced on a grand scale. Also, there were two key characteristics regarding the changes of biological communities in mining and nonmining areas. The first was the dwindling of crustaceans inhabiting the sand area. This outcome may be accounted for by the facts that physical removal of seabed sediments and re-sediment due to expansion of floating particles cause direct influence on the ocean floor ecosystem and have continuous effect on the communities of crustaceans which feed on them. Secondly, the newly arrived species and their population during spring and summer seasons have increased in the non-mining areas and have decreased in the mining area. It can be concluded that highly nomadic fish species migrate toward areas with less disturbance or destruction of ecosystem from marine sand mining, and consequently, the communities of fishes change in the sea area. Setting aside the characteristics of the investigated sea areas where the arriving conditions of species vary by seasons, the clear differences of population of organisms in those areas are due to environmental alterations owing to the marine sand mining ; if those large-scale marine sand mining activities continue in the Gyeonggi Bay, their effects on biological communities in the areas will only grow.

• Culinary science and hospitality research
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• v.23 no.2
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• pp.146-158
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• 2017

This study conducted a survey to investigate career decision-making self-efficacy, and career preparation behavior related to self-leadership among students major in culinary area. Frequency analysis, factor analysis, reliability analysis and multiple regression analysis were employed using SPSS 16.0 Version statistical package program, and various results were discovered. First, all the subfactors of self-leadership factors (behavior focused, natural reward, and constructive thought strategy) had a positive effect on career decision-making self-efficacy factors (occupational information, goal setting, career planning, problem solving, self-appraisal). Second, all the factors of self-leadership factors (behavior focused, natural reward and constructive thought strategy) had a positive effect on career preparation (information search activity, goal achievement activity). As a result, the study confirmed that strengthening of self-leadership for culinary major college/university students is important predictor for development with career decision-making self-efficacy and career preparation behavior.

• Journal of the Korean Solar Energy Society
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• v.36 no.5
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• pp.31-50
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• 2016

To develope a greenhouse fog cooling system to control the temperature and relative humidity simultaneously to the target value, a theoretical analysis and experiments were done. The control process includes the measuring of environmental variables, setting and coding of the water and heat balance equations to maintain the target temperature and relative humidity in greenhouse, calculating of the open level of the greenhouse roof window that governs the natural ventilation and spray water quantity, and operating of the motor to open/close the roof window and pump to spray for water. The study results were shown to be very good because the average air temperature in the greenhouse was kept to be about $28.2^{\circ}C$ with the standard deviation of about $0.37^{\circ}C$ compared to the target temperature of $28^{\circ}C$ and the average relative humidity was about 75.2% compared to the target relative humidity was 75% during the experiments. The average outside relative humidity was about 41.0% and the average outside temperature was $27.2^{\circ}C$ with the standard deviation of about $0.54^{\circ}C$. The average solar intensity in the greenhouse was 712.9 W. The wind velocity of outside greenhouse was 0.558 m/s with the standard deviation of 0.46 m/s.

• Journal of Wetlands Research
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• v.14 no.4
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• pp.657-665
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• 2012

The development projects distort the natural water circulation system and increase the non-point source pollution by changing the natural cover type. The low impact development (LID) techniques are considering as new development approach to decrease the ecological- and hydrological impacts from high imperviousness rate. The high imperviousness rate is because of the construction of building, parking lot and road for human activities. Knowing the basic characteristics of rood runoff can give the direction for setting up the water management strategy. The monitoring results show the pollutant EMCs of roof runoff are 3~13 times lower than EMCs of the road and parking lot. The pollutant sources from roof runoff are mainly from leafs, cigarette butts, atmospheric deposition and materials of the roof. The EMC is occurred around 15minutes later after starting runoff and more than 8 storm events are needed to have the average EMCs.

• Korean Journal of Optics and Photonics
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• v.15 no.5
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• pp.415-422
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• 2004

We propose and present a new multiplexed bend loss type single-mode fiber-optic sensor system for displacement measurement in order to measure the displacement of several mm of civil engineering structures such as bridges and buildings. We make a bend loss type fiber-optic sensor for measuring displacements using the signal difference between two reflection signals due to various bend losses generating at a pair of optical connectors by using the optical time domain reflectometer. And we fabricate a multiplexed bend loss type fiber-optic sensor detecting linear displacements of 4 measuring positions of an object by setting these new 4 fiber-optic sensors on a single mode fiber simultaneously. We find that the multiplexed fiber-optics displacement sensor has linearity of 0.9942, maximum displacement of 6 mm, and accuracy of 6% for 4 measuring points.

• The Journal of Natural Sciences
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• v.8 no.2
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• pp.153-158
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• 1996

The Number of the disputes originated from vegetable seeds in 1968-1970 under 'Seed and Seedling Law for Agricultural Product)' was 177.: Poor germination was the major one (26% of total disputes), followed by inferior seeds(24.3%), imported seeds(23.7%), and off-type plant(15.6%).During 1976-1995, under 'Administrative Law for Seed and Seedling' the number of disputes originated from vegetable seeds was 175.: 53 in radish, 19 in Chinese cabbage, and 17 in pepper. The type of dispute originated from radish seeds was premature bolting(26%), differences in sowing data(21%), poor purity(19%), micronutrient deficiency(9%), root cracking and branching(9%), poor germination(4%), and damage by disease(2%). In Chinese cabbage, micronutrient deficiency was the major one(27%), followed by poor germination(21%), incomplete head formation(16%), damage by disease(16%), poor purity(10%), and bolting(10%). In pepper, poor fruit setting was the major one(6%), followed by malformed fruits(5%), damage by disease(3%), purity(2%), and poor germination(1%).