• Advances in concrete construction
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• 제16권6호
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• pp.317-325
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• 2023

Strength prediction and correlation of concrete is done using experimental and analytical methods. Main objective is to correlate the experimental and simulated values of compressive strength of concrete mix using Fly Ash (FA) and Silica Fume (SF) by partial replacement of cement in concrete. Mix proportion was determined using IS method for M40grade concrete. Hundred and forty-seven cubes were cast and tested using Universal Testing Machine (UTM). Genetic Algorithm (GA) model was developed using C++ program to simulate the compressive strength of concrete for various proportions of FA and SF replacements individually at 3% increments. Experiments reveal that 12 percent silica fume replacement produced maximum compressive strength of 35.5 N/mm², 44.5 N/mm² and 54.8 N/mm² moreover 9 percent fly ash replacement produced a maximum strength of 31.9 N/mm², 37.6 N/mm² and 51.8 N/mm² during individual material replacement of concrete mix. Correlation coefficient for each curing period of fly ash and silica fume replaced mix were acquired using trend lines. The correlation coefficient is found to be approximately 0.9 in FA and SF replaced mix irrespective of the mix proportion and age of concrete. A higher and positive correlation was found between the experimental and simulated values irrespective of the curing period in all the replacements.

• 한국과학교육학회지
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• 제33권3호
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• pp.597-625
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• 2013

This study explored how teachers and students in different countries discursively interact to build 'Classroom Science Knowledge' (CSK) - the knowledge generated situatedly in the context of the science classroom. Data came from publicly released $8^{th}$ grade science classroom videos of five nations who participated in the Third TIMSS (Trend in International Mathematics and Science Study) video study. A total of ten video-recorded science lessons and their verbatim transcripts were selected and analyzed using a framework developed by the researchers of the study. It was revealed that a range of discourse modes were utilized and these modes were often sequentially connected to build CSK in the science classrooms. Although dominant discourse modes and their sequences varied among different lessons or different countries, the study identified three salient patterns of science classroom discourse: teacher-guided negotiation and the sequences of exploring - building on the shared and retrieving - elaborating. These patterns were found to be different from the discursive features commonly witnessed in the community of professional scientists and interpreted as implying the existence of unique epistemic cultures shared in science classrooms of different countries. Further studies are suggested to reveal detailed characteristics of these epistemic cultures of science classrooms, as well as to confirm whether any cultural traits inherently shape the differences in science classroom discourse among different nations.

• 한국식생활문화학회지
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• 제27권5호
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• pp.422-433
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• 2012

The purpose of this study was to investigate changes in Korean meat consumption as well as meat consumption trends. During the Japanese occupation period, the supply of meat was considerably insufficient. However, meat consumption mainly in large cities has gradually increased. Especially, 'Pyeongyang cow', a specialty of Pyeongyang, started being raised as edible beef cattle in 1933. During the chaotic period following liberation from Japan, the price of meat sharply increased. However, as the meat supply stabilized, the 'beef grade system' was introduced in 1967. Since then, beef has sold according to region. During the early economic growth period of the mid-1970s, meat consumption rapidly increased, and foreign beef was first imported in 1976. The preference for beef was somewhat attenuated due to the outbreak of mad cow disease and economic slowdown of the 1990s, resulting in an increase in the consumption of pork, a replacement meat. During the recent period of economic development, meat consumption has somewhat fallen and remained low. In late 2003, with the occurrence of mad cow disease in the US, the demand for pork, and especially pork fatback, has sharply increased.

• Advances in concrete construction
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• 제5권4호
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• pp.391-405
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• 2017

Cement acts as the most important component of concrete as it binds and holds the concrete together. But it is one of the major $CO_2$ emitters all over the world, during manufacturing (900 kg of $CO_2$ per 1000 kg). Some of the modern construction methods aim at reducing the amount of usage of cement and came out with numerous solutions for replacement of the same. One such supplement in current trend is the Steel dust or the Electric Arc Furnace Dust (EAFD), which is a waste product from the electric arc furnace when the scrap metal is melted. When the concrete containing steel dust is exposed to atmosphere, the environmental oxygen and moisture play role to form rust and ultimately the member becomes harder. As Cement is the binder of conventional concrete, only certain percentage of the same could be replaced by the new material, steel dust. Tests were conducted for the 28 days cube strength of M45 grade (suitable for prestressing) concrete which has 0%, 10%, 20%, 30%, 40% and 50% steel dust instead cement. From the test, the optimum percentage replacement of steel dust was obtained, for which the beams and overhead poles were cast, prestressed and tested for the failure load and deflections. A conventional concrete beam and overhead pole were also cast, prestressed and tested to compare the results with those of the beam and pole that contained steel dust. The load vs. deflection plot and other results from the test is also discussed.

• Journal of Preventive Medicine and Public Health
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• 제47권5호
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• pp.266-272
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• 2014

Objectives: The aim of this study was to investigate the relationship between age at cigarette smoking initiation and smoking level among adolescent current smokers. Methods: In 2007, students from one or two classes of the 10th or 11th grade were randomly selected using the probability proportional to size sampling method. In total, 743 current smokers were included. Multiple logistic regression was used to determine the association between age at smoking initiation and smoking level as either frequent, daily, or heavy smokers. Results: The adjusted odds ratios for each smoking level were significantly higher for younger ages of smoking initiation than those for older ages of initiation were (p for trend <0.001). Compared with the students who started smoking in grades 10 to 11, the adjusted odds ratios for frequent, daily, and heavy smokers increased from 2.24 (95% confidence interval [CI], 1.30 to 3.87) to 3.90 (95% CI, 2.02 to 7.56), from 1.56 (95% CI, 0.92 to 2.62) to 3.17 (95% CI, 1.70 to 5.92), and from 2.56 (95% CI, 1.21 to 5.42) to 5.67 (95% CI, 2.61 to 12.30) with younger ages of smoking initiation. Conclusions: Smoking frequency and amount were closely associated with age at smoking initiation. Therefore, smoking prevention programs should be initiated from the young adolescent period.

• KEPCO Journal on Electric Power and Energy
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• 제5권2호
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• pp.83-92
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• 2019

Spontaneous combustion propensity of various coals of carbonization grade as a pulverized fuel of coal-fired power plant has been tested from an initial temperature of $25^{\circ}C$ to $600^{\circ}C$ by heating in an oven with air to analyze the self-oxidation starting temperature. These tests produce CPT (Cross Point Temperature), IT (Ignition temperature), and CPS (Cross Point Slope) calculated as the slope of time taken for a rapid exothermic oxidation reaction at CPT base. CPS shows a carbonization rank dependence whereby wood pellet has the highest propensity to spontaneous combustion of $20.995^{\circ}C/min$. A sub-bituminous KIDECO coal shows a CPS value of $15.370^{\circ}C/min$, whereas pet coke has the highest carbonization rank at $2.950^{\circ}C/min$. The nature of this trend is most likely attributable to a concentration of volatile matter and oxygen functional groups of coal surface that governs the available component for oxidation, as well as surface area of fuel char, and constant pressure molar heat.

• 복식문화연구
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• 제26권6호
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• pp.852-871
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• 2018

The purpose of this study is to suggest a direction for the development of unlined underwear design. A style for unlined underwear can take strong points and compensate for weak points by using the characteristics of wire brassieres and bralettes. As a method for research, we based our study on literature and data such as previous studies, professional books, internet articles, and fashion magazines. As a result of analyzing the brassiere's status in lines like 'FOREVER 21' and 'VICTORIA'S SECRET', we determined that 'FOREVER 21' reflects the trend of unlined style underwear, and 'VICTORIA'S SECRET' has both unlined and wire brassieres to make breast correction. In the case of unlined style brassieres, a wire is put in order to gather the chest for compromising comfort and correction. In order to express the possibility of expressing various feelings even in unlined style, Design 1 lets everyone know that unlined underwear can be very comfortable as a daily, not used only occasionally for events. Design 2 demonstrates that besides the artificial feeling of using the strap for a special day or event, it can be expressed naturally by using the lace as it is. Design 3 expresses the luxurious and sexy, rather than the low-grade decadent sexy, by using the feeling of the single layer lace and the pearl decoration for wedding and honeymoon.

• 자원환경지질
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• 제24권1호
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• pp.63-69
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• 1991

Gravity study was carried out to investigate the structure and total mass of the Bupyeong silver deposits closely related to formation of the Bupyeong caldera. Survey region covers $3.3{\times}6.6km^2$ over silver deposits and is comprised of 334 gravity measurement stations. An apparent regional gravity trend parallel to the west coast line is mainly attributed to isostasy. A least square isostasy model was used for the regional correction. A Fortan subroutine was coded to calculate 3-dimensional subsurface model. The calculated gravity values from the 3-dimensional model of the caldera with silver deposits agree with observed anomalies relatively well. Gravity anomaly due to Bupyeong silver deposits reaches to +3.5 mgal from the background value and anomaly due to the caldera reaches to -4 mgal. But the maximum negative anomaly of the caldera would be much greater at its center. The total mass of silver deposits calculated from the subsurface model is $4.19{\times}10^9$ tons. Although the economic part of silver deposits depends on the grade of orebody, we expect that there are still large amount of silver reserves in Bupyeong area.

• 한국과학교육학회지
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• 제15권3호
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• pp.310-315
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• 1995

The development of science and technology not only improved the quality of life of human being, but also brought about environmental problems. Consequently, consensus has been established that early environmental education for youngsters is critical for the preservation of clean environment. A conventional way of teaching has not been very effective for changing their attitude and behavior regarding environmental problems. STS program, which has been one of the major trend in science education, intends to teach science through everyday experience rather than knowledge. This study purports to examine the effectiveness of STS program on environmental problems compared to conventional teaching method. Six week program was developed and applied to subchapter 'Environmental Pollutions & Our Lives' of 3rd grade middle school science text book. The results of this study can be summarized as follows. 1. STS program was significantly effective in changing students' attitude(p<.001). It was effective not only changing their thinking but also changing their behavior. 2. There was no difference between the STS program and conventional teaching method in improving students' knowledge(p>.05). 3. The correlation between the level of knowledge achievement and the attitude on environment was very low(r=.0564,p>.05).

• 펄프종이기술
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• 제37권2호
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• pp.30-37
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• 2005

Compact system as a new and highlighted trend in papermaking technology gives papaermakers many advantages including simple and clean process, quick grade change, minimized liquid volume, and so on. It is possible to remove an existed chest for simplifying system and more utilization of space, but its effect on process and product stability must be evaluated qualitatively in advance. For this purpose, process simulation can be applied. We examined the effect of disturbances on process and product in a papermaking system with and without machine chest using dynamic simulation. As compared with the existed system, the paprmaking system without machine chest showed twice or more variation in process and product and required longer time for stabilization.