• Journal of the Korean School Mathematics Society
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• v.8 no.1
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• pp.35-53
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• 2005

The purpose of this study is to analyze and confirm the effectiveness of two teacher-centered instruction methods in the context of linear functions: one with emphasis on mathematical thinking processes as an alternative to the more traditional method without such emphasis. The level of achievement of students under the teacher-centered instruction with explicit emphasis on mathematical thinking processes is consistently higher than that of students receiving the more traditional teacher-centered instruction. The alternative instruction method in the current study is expected to encourage and prompt students to better grasp and understand mathematical concepts, principles, as well as problem solving strategies. In contrast to other alternatives, the method offers the advantage of being readily incorporated into the actual teaching practices in the classroom, as the traditional frame of teacher-centered pedagogy familiar to teachers remains in tact.

• Journal of the Korean Geotechnical Society
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• v.22 no.12
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• pp.5-14
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• 2006

In general, the dredged ground was composed of a big difference of sediment shape through segregating sedimentary of finer soil in case of reclaiming by dredged coarse soils. Therefore, this study was performed to evaluate the change of settling velocity of flow, and the density of sedimentary which is based on settling tests and self-weight consolidation tests, and consolidation test by seepage force according to the percentage of coarse of Kunsan dredge soils. The Yano's method has been applied to estimate the settlement of self-weight consolidation in finer soils at design but it only considers pouring water content and elevation of interface, therefore the other method needs to be introduced for the exact prediction of the settlement of coarse soil in which the segregation sedimentation is occurring. In this study, the settlement of self-weight consolidation was calculated by the change of the density of segregating sedimentary of coarse and finer soils which was analyzed by Yano's method to extend a serious of researches. The self-weight consolidation by Yano's method will not reflect the segregated settling in dredging coarse soil under 40% of #200 passing percentage. As a result, the evaluation technique of settlement of self-weight consolidation considering a change of the density of segregating sedimentary is suggested as a reasonable method that considers the sediment shape of coarse soil.

• Journal of the Korean Geotechnical Society
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• v.29 no.10
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• pp.57-66
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• 2013

Societal interest on a faster transportation demands an increase of the train speed exceeding current operation speed of 350 km/h. To trace the pattern of variations in displacements and subsoil stresses in the concrete slab track system, finite element simulations were conducted. For a simple track-vehicle modeling, a mass-point system representing the moving train load was developed. Dynamic responses with various train speeds from 100 to 700 km/h were investigated. As train speeds increase the displacement at rail and subsoil increases nonlinearly, whereas significant dynamic amplification at the critical velocity has not been found. At low train speed, the velocity of elastic wave carrying elastic energy is faster than the train speed. At high train speed exceeding 400 km/h, however, the train speed is approximately identical to the elastic wave velocity. Nonlinearity in the stress history in subsoil is amplified with increasing train speeds, which may cause significant plastic strains in path-dependent subsoil materials.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.6
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• pp.545-556
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• 2016

If a back analysis is used in various measurement information for the estimation of an operating subsea tunnel safety, it is possible to obtain the results within efficient error rate. With such a commercial geotechnical analysis program as FLAC3D, back analysis is performed with a DEA which was validated in previous studies. However, there is a problem that is relatively a time-consuming analysis. For this reason, beam-spring model-based FEM solver which takes shorter relative analysis time, was developed by Python language, and then combined with the built-DEA. In order to consider the assessment of safety of an operation tunnel near real-time, a program for longitudinal direction tunnel was developed due to its relative easy development for analysis solver engine.

• Journal of Biosystems Engineering
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• v.31 no.1 s.114
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• pp.1-8
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• 2006

This study was conducted to identify the characteristics of PTO rattle noise of a direct engine-PTO driveline for agricultural tractors. In order to reduce production costs of agricultural tractors, a direct engine-PTO driveline was recently introduced to the tractors produced in Korea. This simplified drive line reduced a number of gears and counter shafts in previous one. However, it caused a severe rattle noise under an idle condition, which was perceived as intolerable by many tractor operators. PTO rattle noise was measured at two locations: one 3 em apart radially from the centerline of the PTO shaft and another 100 em apart backward from the PTO end and 160 em high from the ground. Characteristics of the rattle was analyzed using the data measured near the PTO shaft. It was found that the period of rattle noise was same as the explosion stroke of engine and its peak level was about 123 dB (A) with PTO engaged at an idle engine speed of 880 rpm. As the engine speed increased, the rattle noise decreased. The frequency band of the rattle was 0.5-2.0 kHz and the frequency of peak sound pressure was 1.4 kHz. When compared the rattle noise between the locally produced and imported tractors of the same type of PTO driveline, the former generated louder rattle noise than the imported one by 7 dB (A). It was suggested that the rattle noise of local tractors must be reduced at least by 7 dB (A) to meet the international level.

• Journal of Korean Society of Rural Planning
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• v.11 no.2 s.27
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• pp.51-57
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• 2005

It has been well known that soil erosion and sediments from alpine agricultural fields are causing severe water quality and turbidity problems in receiving waters. Also these result in the loss of money because farmers have to buy top soils to provide enough root zone in the following year. Thus, there have been needs to reduce soil erosion and sediment discharge into the stream networks. To accomplish this end, an effective erosion control plans should be developed based on scientific research, not by rule of thumb. The Universal Soil Loss Equation (USLE) has been widely used to estimate the soil erosion in many countries over the years. In this study, the USLE was used to estimate soil erosion potential under different cropping scenarios in HongCheon County, Kangwon. The soil erosion potential for continuous corn cropping was the highest compared with those from continuous potato find average cropping scenarios. This indicates the soil erosion plans need to be established considering cropping system in the field. The Unit Stream Power Erosion-Deposition (USPED) was applied for HongCheon County to estimate soil erosion and deposition areas. The USPED estimated results can be used to complement USLE results in developing effective erosion control plans.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.1
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• pp.87-94
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• 2023

TMCP(Thermo Mechanical Control Process) steel was continuously cast (CC) by varying the argon gas flow rate and vacuum time in the Ruhrstahl Heraeus (RH) refining process. Using the CC specimens, the distribution of the inclusions and the mechanical properties were evaluated. A lot of oxides and Al-O type inclusions were observed. The average Vickers hardness did not show a constant, but showed dispersion in a certain range. The shape and scale parameters of the CC specimen with an argon gas flow rate of 160Nm³ and a vacuum time of 12 minutes was the best. Mechanical properties (tensile strength, yield strength and elongation) were consistent with the Weibull probability distribution analysis results. The impact resistance was the best for CC specimens with an argon flow rate of 140 Nm³ and a vacuum time of 12 minutes. Although the inclusions and mechanical properties of the CC specimens were evaluated according to the argon gas flow rate and vacuum time, these values were no significant difference.

• Korean Journal of Health Education and Promotion
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• v.13 no.2
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• pp.69-96
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• 1996

This study was conducted to investigate the awareness and practice level of health food intake and use the information for the development of Public Health Policy and Health Education Program in order to help healthy dietary life. The interview was done by trained surveyors on 1, 143 city dwellers who were selected randomly from Oct. 2, to Oct. 21, 1992. The results are summarized as follows: 1) General characteristics of subjects; Among 1, 143 respondents, there were more female(53.8%) than males(46.2%) and the age group of 20-29 account for the hightest portion, 46.7%. As for the education levels, 45.3% of the subjects were college graduates. And 38.9% of the subjects were students. 2) The percentage of subjects who assess themselves ‘Healthy’ was 46.7% and ‘Not Healthy’ was 17.4%. 3) The subjects who have irregular meals(3 times a day) was 48.7%, the rate of females was higher than males. The proportion of unmarried subjects, people with low economic level, high education level, and students was high. 4) As for the amount of 1 meal, 72.4% was ‘moderate’, 16.3% was ‘too much’ amount, which was higher in 19 years old, single, low economic level, elementary school graduate, than other groups. 5) As for the eating speed, 40.2% was fast, which was higher in single(44.3%), in low economic level(50.0%). college graduate(44.9%), student(44.7%) than other groups. 6) As for the level of preference to hot and salty food, 25.7% preferred to have hot and salty food. The difference in the degree of preference to hot and salty food by age and economic level was significant. 7) With regard to the individual food taste, the subjects who prefer to meat and fried food were 12.3%. Which was higher in the group under 19 years old, single, and college graduates. 8) With regard to having a snack, 38.7% have a snack. By characteristics, the subjects who have a snack were higher in female, under 19 years old, single, high economic level, apartment dwellers, college graduate, and student than other groups. 9) As for the coffee intake amount per day, 39.8% of subjects was more than 3 cups daily. 10) With regard to the self-assessment of body weight, the subjects who assess themselves over body weight had late dinner time. 11) As for the correlation among related variables, the age and taking breakfast was positive correlation. And sex and drinking alcohol was positively associated while age had negative correlation.

• Journal of Korean Academy of Nursing
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• v.31 no.2
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• pp.169-179
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• 2001

Recently, there has been an increasing interchange between South Korea and North Korea. Accordingly, there has been active research to understand the society and culture of North Korea, it has been attempted to have comparative study about nursing education to increase understanding between South and North Korea. In the current educational system, 12 years of education is required for entering a nursing college or university in South Korea, but there are only 10 years for entering nursing college in North Korea. After finishing undergraduate studies one can enter graduate school for a masters degree and or a doctoral degree, but there is a longitudinal relation to medical education in North Korea. Regarding the number of nursing educational institutions, there are 50 BSN programs & 61 Diploma programs in South Korea and 11 Diploma programs in North Korea. In regards to curriculum, South Korea has diverse subjects for general education for freshmen, then is subjects to basic specialities sophomore year, and speciality subject and clinical practices from junior year corresponding to the student's intentions. North Korea has minor subjects for general education and basic specialities in freshmen, speciality subjects sophomore year, speciality subjects and clinical practice in the junior year that may not correspond with the student's intentions. The most outstanding difference in the curriculum is North Korea has various subjects for oriental medicine with clinical application. North Korea also does not teach computer science and English is at a very low level. In clinical practice, South Korea has various settings for clinical practice including community health institutions under the nursing professor or clinical instructor. However, North Korea has limited settings for clinical practice (general hospitals) under a doctor's instruction. Also both South and North Korea have a similar licensing system. Therefore, there must be many more studies regarding North Korea, especially in nursing and nursing education in order to decrease differences and confusion between the Koreas and to prepare for a future unification.

• Journal of Energy Engineering
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• v.19 no.2
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• pp.116-120
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• 2010

Overall total length of hydraulic pipe to transport the hot water in the domestic district heating network is above 3,000 Km approximately. This long pipe network requires a lots of the transport pumping power by surface friction of fluid. In this study, the drag reduction(DR) of Amin Oxide $C_{18}$ as non-ionic surfactant according to the fluid velocity, temperature and surfactant concentration under the condition of above $80^{\circ}C$ fluid temperature were investigated experimentally. Results showed that new amin oxide $C_{18}$ surfactant had DR of maximum 30% in fluid temperature of $80^{\circ}C$ and had 15% DR in fluid temperature over $100^{\circ}$ under short time test condition. And amine oxide had 155 hours duration time to keep the DR characteristic in the fluid temperature of $80^{\circ}$ and 1000 ppm concentration. But duration time of DR was decreased when fluid temperature increased.