• Journal of Korean Society of Steel Construction
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• v.20 no.2
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• pp.237-246
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• 2008

The cross-sections of continuous multi-span beams sometimes suddenly increase, or become stepped, at the interior supports of continuous beams to resist high negative moments. The three-dimensional finite-element program ABAQUS (2006) was used to analytically investigate the inelastic lateral-torsional buckling behavior of stepped beams subjected to pure bending moment and resulted in the development of design equations. The flanges of the smaller cross-section were fixed at 30.48 by 2.54 cm, whereas the width and/or thickness of the flanges of the larger cross-section varied. The web thickness and height of beam was kept at 1.65 cm and 88.9 cm, respectively. The ratios of the flange thickness, flange width, and stepped length of beams are considered analytical parameters. Two groups of 27 cases and 35 cases, respectively, were analyzed for double and single stepped beams. The combined effects of residual stresses and geometrical imperfection on inelastic lateral-torsional buckling of beams are considered. First, the distributions of residual stress of the cross-section is same as shown in Pi, etc (1995), and the initial geometric imperfection of the beam is set by central displacement equal to 0.1% of the unbraced length of beam. The new proposed equations definitely improve current design methods for the inelastic LTB problem and increase efficiency in building and bridge design. The proposed solutions can be easily used to develop new design equation for inelastic LTB resistance of stepped beams subjected to general loading condition such as a concentrated load, a series of concentrated loads or uniformly distributed load.

• Journal of The Korean Association For Science Education
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• v.32 no.5
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• pp.1007-1026
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• 2012

The purpose of this study was to develop analytic framework for dialogic argumentation to show the context and flow visualizing interactions of argumentation, to be able to present quality of argumentation specifically. For this, we formulated a method of the argumentation diagram using feature of diagram simple and structurally visualizing interrelation between argument components, and then quantified quality of argumentation to argument level score on this basis. We have developed the learning material for argumentation about a vertical circular motion and used the obtained translations from applying it in developing the framework. We chose argument statements among full transcript and then coded as Toulmin's argument components, and these codes was effectively arranged and linked to show argumentation diagram. Results by argumentation diagram could be useful understanding of interactive argumentation context and the flow and present frequency, the combination of argument elements, rough qualitative level of argumentation. To quantify argumentation quality, we gave different scores to different link lines reflecting indication of argumentation quality like that diversity of argument component, justification, presence or absence of rebuttals. The process of identification of argument level is very simple, qualitative level of argumentation represented as concrete score could present various and concrete argument level. Developed analytic framework might contribute to argumentation research field, because it can present effectively dialogic argumentation result. Also, various analysis cases might guide designing an effective argumentation practice and circular motion learning.

• Journal of the Korea Concrete Institute
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• v.28 no.2
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• pp.197-204
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• 2016

Concrete walls of neutron generating facilities such as fusion reactors and fission reactors become radioactive by neutron irradiation. Both low-activation and neutron shielding are a critical concern at the dismantling stage after the shutdown of facilities with a requirement of radioactive waste management. To tackle this, two types of additives were investigated in fabricating mortar specimens: synthetic high polymers and boron carbide. It is well known that a hydrogen atom is effective in neutron shielding by an elastic scattering because its mass is almost the same as that of the neutron. And boron is an effective neutron absorber with a big neutron absorption cross section. In this study, the effect of the type, shape, and size of polymers were investigated as well as that of boron carbide. Total 16 mix designs were prepared to reveal the effect of polymers on mechanical properties and neutron shielding performance. The neutron does equivalent of polymers-based mortar for fast neutrons decreased by 36 %, and the count rate of boron carbide-based mortar with regard to thermal neutrons decreased by 90 % compared to conventional mortar. These results showed that a combination of polymers and boron carbide compounds has potential to reduce the thickness of neutron shields as well as radioactive waste from reactors.

• Journal of Korean Society of Forest Science
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• v.82 no.1
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• pp.1-6
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• 1993

This study was conducted to provide a fundamental information for a income raise of agricultural and mountain villagers and a policy planning by analyzing 145 chestnut producing farms in Korea. The results of this study are as follows : 1. Though the proportion of forest by-products in farm household economy was very slight, it is very important for agricultural and mountain villagers who have relatively lower income level to become a valuable income source. 2. As chestnut cultivating orchards have very small-scale that account for 50.0% of 0.5 to 1.0 hectares and 40.3% of 1.0 to 3.0 hectares reaching 90.3% of total farmers, the small-scale ownership makes the normality and rationalization of management difficult, and therefore the economity of scale has to be accomplished. 3. The difficulties on chestnut cultivating management were in order of the following ; Labour-power shortage(38.5%), desease and pest demage(24.8%), economity(15.2%), management(11.7%), inferiority of site condition(5.9%), technical acquirement(3.8%). 4. In the matter of storaging facilities, 87.6% of total surveyed farmers were recognizing the need of storaging facilities, but only 12.4 of surveyed farmers were possessing these facilities, and therefore the measurement has to be considered such as the forest associations invests to cold storaging facilities unable to privately invest, in order to increase a receiving price of producers.

• Korean Journal of Construction Engineering and Management
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• v.15 no.6
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• pp.26-34
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• 2014

Highway construction is a combination of linear, repetitive, and highly equipment intensive operations. Various types of construction equipment are deployed to ensure undisrupted performance of construction, and thus productivity improvement and cost-saving can be achieved through well-thought-out planning. The selection of construction equipment is dependent upon construction sequence, site conditions, and construction methods. In the process of planning, management should consider various types of construction methods per each type of construction operation. Also, management should map out proper construction equipment operation plan that takes the construction duration and cost measures into consideration. However, limited availability of historic data from the similar types of operations has been a stumbling block to proper construction planning, making the operations performed based upon experience and intuition guided by rules-of-thumb. As a consequence, the planing phase rarely provided an adequate validity in the implementation phase. The researchers developed a process logic for each construction type that management can utilize from early phase of highway construction planning process. Moreover, derived the construction equipment combination optimized for efficiency by using the process simulation technique. The developed method is expected to be useful for the decision-making process that aims to evaluate efficiency of various process plans and to ensure optimal selection of construction equipment for highway construction projects.

• Journal of The Korean Association For Science Education
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• v.35 no.6
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• pp.1049-1062
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• 2015

To understand the synergy of collaboration and to apply this understanding to education, an analysis of how a team solves a problem and the sharing of their mental models is needed. This paper analyzed two things qualitatively to find out the source of synergy in a collaborative problem-solving process. First, the sharing contents in team mental model and second, the process of sharing the team mental model. Ten gifted middle school students collaborated to solve an ill-defined problem called sunshine through foliage problem. The gifted students shared the following results after the collaboration: First, scientific concept prior to common idea or the idea that all group members have before the discussions; second, unique individual ideas of group members; and third, created ideas that were not originally in the personal mental model. With created ideas, the team model becomes more than the sum of individuals. According to the results of process analysis, in the process of sharing mental model, the students proposed and shared the most important variable first. This result implied that the analysis of the order of sharing ideas is important as much as finding shared ideas. Also, the result shows that through their collaboration, the gifted students' shared mental model became more refined and expanded as compared to their individual prior mental models. It is recommended that these results can be used to measure shared mental model and develop collaborative learning models for students.

• Journal of Aquaculture
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• v.20 no.2
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• pp.140-143
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• 2007

Cytogenetic analyses of an endemic species, Coreoleuciscus splendidus (Cyprinidae) was performed including erythrocyte measurement, chromosome count and karyotyping, nucleolar organizing region (NOR) banding and flow cytometric analysis of genome size. C. splendidus had the same modal chromosome number of 2n = 48 between sexes, however, displayed a sex-related dimorphism in their chromosome karyotypes. Males represented a pair of heteromorphic chromosomes which couldn‘t be seen in any female individuals, indicating that the sex determination mechanism of this species should be a typical XX-XY based male heterogamety (female=10M+6SM+8A+XX vs male=10M+6SM+8A+XY). Other cytogenetic features such as Ag-NORs located in a pair of acrocentric chromosomes, estimated nuclear volume ($28{\mu}m^3$) and cellular DNA content (2.4 pg/cell) suggest that genetic recombination might be the main driving force responsible for the evolution of this species rather than the polyploidy-based evolutionary process as in many other Cyprinidae species.

• Journal of the korean academy of Pediatric Dentistry
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• v.47 no.1
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• pp.36-43
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• 2020

The aim of this study was to assess the occlusal relationships of primary dentition of Korean preschool children in Hwaseong city. Total 444 children of age group between 2 and 5 years were selected. One pediatric dentist took intraoral photos of children. Evaluation and categorization of the primary molar relationships were done by single examiner. Statistical analysis was performed with Pearson chi-squared test. Total 389 samples, which is consisted of 185 boys, 204 girls were satisfied with inclusion criteria. Bilateral mesial step was seen in 61.7%. Bilateral flush terminal plane was seen in 15.4%. When the primary molar relations of the right and left sides were not the same, the combination of the mesial step and flush terminal plane was 14.7%. The present study provides insight into occlusal relationships in the primary dentition of 2 - 5 years old of Korean children in Hwaseong city. Pediatric dentists should understand occlusal relationships of primary dentition for establishment of appropriate treatment strategies and occlusal guidance.

• Journal of Korean Society of Forest Science
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• v.107 no.1
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• pp.35-42
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• 2018

This study was carried out to investigate site and soil factors affecting growth of root collar diameter (RCD) and height (HT) of Larix kaempferi trees planted in harvested Larix kaempferi plantations. We were found effect factors of growth of RCD and HT using 15 of site and soil factors. And then we made the growth estimated equations of RCD and HT of 6-years-old L. kaempferi tree by the derived affecting factors. The growth of RCD was affected in order of available phosphorus (+), effective soil depth (+), organic matter (-), sand separate in soil (-), pH (-), and elevation (-), and the coefficient of determination ($R^2$) of the growth estimated equation of RCD was 0.51. The growth of HT was affected in order of effective soil depth (+), elevation (-) slope (-), and available phosphorus (+) and the $R^2$ of the growth estimated equation of HT was 0.46. The growth of RCD and HT were commonly affected by effective soil depth, available phosphorus, and elevation. Therefore, planting site of L. kaempferi should be considered the mainly effect factors in order to keep better early growth based on the current study.

• Journal of the Korean Society of Radiology
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• v.10 no.5
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• pp.313-320
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• 2016

This research has been conducted to investigate the method of reducing patients' radiation exposure during X-ray imaging of Both Hip Ap examination by removing the grid. When using the grid with 60 kV and a non-filter, the Entrance Surface Dose was 4.77 mGy, and the result was highest and 34 times higher than the lowest measurement when removing the grid with 90 kV, and 0.3 mmCu filter. Based on the ICRP Pub. 60 at the level of 70 kV, the Effective Dose of testis and ovary was 0.255 mSv when using the grid, and that result was approximately 5.2 times higher than the 0.049 mSv when removing the grid. Based on the ICRP Pub. 103 at the level of 70 kV, the Effective Dose of testis and ovary was 0.090 mSv when using the grid, and that result was approximately 4.5 times higher than the 0.020 mSv when removing the grid. When using the grid, the range of Exposure Index was 671 to 782, and when removing the grid, the range of Exposure Index was 513 to 606, and both results were at optimal exposure conditions and valid diagnostic imaging after evaluations. Therefore, removing the grid during X-ray imaging of Both Hip Ap will help reduce patients radiation exposure.