• International conference on construction engineering and project management
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• 2022.06a
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• pp.128-135
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• 2022

Because construction work is conducted outdoors, construction workers are affected by harmful environmental factor. Especially, Particulate Matter (PM₁₀) is one of the harmful environmental factors with a diameter of 10㎍/m³ or less. When PM₁₀ is inhaled by human, it can cause fatal impact on the human. Contrary to the various analyses of health impact on PM₁₀, the research on the relationship between construction accidents and PM₁₀ are few. Therefore, this study aims to conduct the relative frequency analysis which find out the correlation between construction accidents and PM₁₀, and the modified PM₁₀ grade is suggested to expect accidents probability caused by PM₁₀ in the construction industry. This study is conducted by four steps. i) Establishment of the database; ii) Classification of data; iii) Analysis of the Relative Frequency of accidents in the construction industry by PM₁₀ concentration; iv) Modified PM₁₀ groups to classify the impact of PM₁₀ on accident. In terms of frequency analysis, the most accidents were occurred in the average concentration of PM₁₀ (32㎍/m³). However, we found that the relative frequency of accident was increased as the concentration of PM₁₀ increased. This means the higher PM₁₀ concentration can cause more accidents during construction. In addition, PM₁₀ concentration was divided as 6 groups by the WHO, but the modified PM₁₀ grade by the relative frequency on accident was suggested as 3 groups.

• Resources Recycling
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• v.30 no.5
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• pp.57-66
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• 2021

In this study, we attempted to separate and recover Cu from low-grade copper ore by a hydrometallurgical process. The leaching sample obtained after crushing and sieving by 0.355 mm of low-grade copper ore contained 1.5% Cu, 4.7% Fe, 1.0% Mn, and 0.3% Zn. The Cu in the oxide ore was very well leached into sulfuric acid and 97% Cu leaching efficiency was achieved at 80℃ and 3 M sulfuric acid (H₂SO₄). From the leaching solution, Cu was separated by solvent extraction from Fe, Mn, and Zn using LIX984N. The separation tendency between Cu and other metals was confirmed through the distribution ratio and separation factor. By plotting the McCabe-Thiele Diagram, the optimum condition for recovering Cu is 5 vol.% LIX984N, 2-stage counter-current solvent extraction, and an O/A ratio of 0.5. Using this method, 99% of the Cu was extracted and a CuSO₄ solution was finally obtained that contained 1.6 g/L Cu after the stripping process using 2 M H₂SO₄.

• Nuclear Engineering and Technology
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• v.56 no.9
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• pp.3501-3511
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• 2024

Titanium alloys play a vital role in optimizing the effectiveness and security of nuclear reactors, strengthening structural durability, and facilitating the effective handling of nuclear waste. The aim of this study is to investigate the gamma-ray, neutron, and transmission properties of four common titanium alloys through the examination of the deposited energy amount in the liquid sodium coolant material, in relation to the mechanical properties of these alloys. MCNP (version 6.3) is utilized for designing the titanium pipes. Next, the pipes were re-designed considering the elemental mass fractions and densities of the investigated titanium alloys. Grade 26 sample is reported with the highest values of mass attenuation coefficients and the lowest HVL values among those investigated alloys. Grade 26 is reported to have the lowest TF value, whereas Grade 12 demonstrated the highest TF value. The highest Effective Removal Cross Section (Σ_R, 1/cm) value against fast neutrons is reported for Grade 26. The utilization of Grade 26 sample as pipe material resulted in the lowest deposited energy amount (MeV/g) and subsequent lowest contamination in the coolant material. Out of the alloys that were chosen for analysis, it has been determined that Grade 26 exhibits the highest level of strength. It can be concluded that the Grade 26 alloy exhibits desirable characteristics for applications in nuclear technologies that require superior gamma-ray and neutron absorption properties, as well as exceptional mechanical properties. Nevertheless, it is essential to emphasize the importance for ongoing studies to enhance the existing material properties of Grade 26, with the aim of achieving improved safety and efficacy in nuclear applications.

• International Journal of Ocean System Engineering
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• v.2 no.2
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• pp.92-96
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• 2012

This study presents a rockfall impact analysis of a typical roadway. Dynamic finite element analyses using ANSYS AUTODYN are conducted to determine the effect of the drop heights (5 m, 10 m) on the damage to a roadway model. The Rockfall is modeled as a spherical shape with a weight of 400 kg, and each drop height is converted to a corresponding impact velocity to save computational time. The roadway model is comprised of an asphalt layer, base layer, sub-base layer, and sub-grade layer. In this paper, the asphalt is modeled using a linear elastic model. The base layer, sub-base layer, and sub-grade layer are modeled using a Mohr-Coulomb model. From the analyses, the effects of the drop height on the damages and stresses are examined and discussed.

• Journal of the Korean Society of School Health
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• v.23 no.2
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• pp.256-265
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• 2010

Purpose: The purpose of this study was to identify the psychological problems of the children in early stage and provide basic data for develop the children's mental health promotion programs. Methods: There were 270 subjects who were fist and forth grade of elementary school and the data was collected through their parents. This study use Child Problem-Behavior Screening Questionnaire that was divided into five sub-scales, including internal problems, external problems, cognitive problems, abuse problems and psychosomatic problems. Each sub-scales have one cutting points, children whose scores above the cutting points means abnormal in correspond subscale. Results: 1) The most appearing problems was psychosomatic problems with 10.8% of subjects and next internal problems with 8.6% of subjects in elementary school student. 2) For distribution of mental behavior development according to gender, there was significant difference in psychosomatic problems between male and female (p =.009). 3) For distribution of mental behavior development according to grade, the results showed that significant difference in internal problems (p =.000) and total scores of CPSQ (p =.012) between first grade and forth grade. Conclusion: When we develop children's mental health promotion program, it is necessary to considerate the gender and grade characteristics.

• Nuclear Engineering and Technology
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• v.55 no.5
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• pp.1708-1717
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• 2023

The grade analysis of lead-zinc ore is the basis for the optimal development and utilization of deposits. In this study, a method combining Prompt Gamma Neutron Activation Analysis (PGNAA) technology and machine learning is proposed for lead-zinc mine borehole logging, which can identify lead-zinc ores of different grades and gangue in the formation, providing real-time grade information qualitatively and semi-quantitatively. Firstly, Monte Carlo simulation is used to obtain a gamma-ray spectrum data set for training and testing machine learning classification algorithms. These spectra are broadened, normalized and separated into inelastic scattering and capture spectra, and then used to fit different classifier models. When the comprehensive grade boundary of high- and low-grade ores is set to 5%, the evaluation metrics calculated by the 5-fold cross-validation show that the SVM (Support Vector Machine), KNN (K-Nearest Neighbor), GNB (Gaussian Naive Bayes) and RF (Random Forest) models can effectively distinguish lead-zinc ore from gangue. At the same time, the GNB model has achieved the optimal accuracy of 91.45% when identifying high- and low-grade ores, and the F₁ score for both types of ores is greater than 0.9.

• Journal of Fisheries and Marine Sciences Education
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• v.28 no.1
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• pp.235-247
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• 2016

The purpose of this study is to analyze elementary school students' pre-concept of electromagnet and to investigate effects of instruction through social interactions on conceptual changes of the electromagnet. For the purpose, 108 elementary school students of 3 classes were selected from the 6th grade. They were divided into the control group I, control group II and experimental group. The control group I was treated through traditional instruction on the basis of text book. The control group II was instructed with a modified version of the textbook to help them better understand the concept of electromagnet. The experimental group was treated through instruction on the basis of the above modified version of the text book and social interactions. Conceptual changes on electromagnet before and after the treatment were quantitatively and qualitatively analyzed using the identical test. The students' styles of social interaction were qualitatively analyzed with tape records of their discussions and work sheets. Effects of instruction through social interactions based on radical constructivism on the 6th-grade elementary school students' concept of electromagnet were examined here. The results were described as follows. Firstly, after the treatment, the experimental group was statistically significantly higher in mean values of conceptual understanding and academic achievement than both the control group I and II. Secondly, styles of social interaction in the three sub-groups of the experimental group were qualitatively analyzed, among the threes, high- and medium-level sub-groups were higher in the frequency of linguistic social interaction than the low-level sub-group. Those students who were excellent in communication skills actively participated in linguistic social interactions. In discussions among the three sub-groups, students of the high- and medium-level sub-groups provided explanations or information while those of the other sub-group sometimes were passive by just listening, but in large actively participated in communication. In conclusion, instruction through social interactions was effectively changed in the 6th-grade elementary school students' concept of electromagnet.

• Journal of the Korean Society of Earth Science Education
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• v.3 no.1
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• pp.28-35
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• 2010

This study is aiming to determine the effect of learning dimensions oriented elementary science lecture on scientific attitude, academic achievement, and logical thinking based on 'Earth' section in the 2nd semester of the 5th grade. Analyzing sub-categories of dimension in each lecture before teaching, a teaching and a learning plans based on dimension 3 and 4 were devised and applied. The result of this study is as follows: Firstly, when sub-categories of Earth section in the 2nd semester of the 5th grade in elementary schools were examined, the unit '5-2-4. Volcanoes and Rocks' was missing 8 of total 28 sub-units, while '5-2-7. Solar families' unit was covering all sub-units of every learning dimension. Secondly, learning dimensions 3 and 4 centered elementary school teaching caused significant difference in scientific attitude. Especially, among other sub-categories of scientific attitudes, 'Social meaning of Science', 'Attitude toward Science lessons' were better improved. Thirdly, learning dimensions 3 and 4 based elementary school lectures didn't bring significant difference to academic achievement. Fourthly, learning dimensions 3 and 4 oriented elementary lessons didn't imply significant difference in sub-logics of logical thinking, however proved to be helpful for students of transitional age.

• Korean Journal of Child Studies
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• v.21 no.2
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• pp.99-118
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• 2000

This study investigated the self-concepts of Korean students based on Marsh and Shavelson's(1985) multidimensional hierarchical model. Reduced forms of the Self-Description Questionnaire(SDQ)-I and -II were administered to 308 5th and 6th grade students and 718 7th to 9th grade students. Results of 2 factor analyses indicated that sub-scales 9 and 11 were well established for SDQ-I and -II, respectively, partly confirming the multidimensionality of self-concept. The factors involving distinctions between academic and non-academic higher-order factors and between the academic/math and the academic/verbal factors were not so differentiated nor hierarchically arranged as proposed by the model. These differences may be attributed to the heavy influence of the academic self-concept on the other sub-factors. A Locality ${\times}$ Sex ${\times}$ Grade ANOVA showed main effects of locality favoring urban areas and of sex favoring boys.

• Journal of Hydrogen and New Energy
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• v.34 no.1
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• pp.83-89
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• 2023

In this study, a computer simulation work has been performed for the separation of electronic grade highly pure carbon dioxide more than 7 N purity through a cryogenic distillation process. For the cold utility as a cooling medium for a condenser of the cryogenic distillation column, propylene was utilized as a refrigerant in the vapor-recompression refrigeration cycle. Through this work, it was concluded that the cryogenic distillation column with two stage compression and refrigeration cycle were essential to obtain a highly-pure liquefied CO₂.