• Steel and Composite Structures
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• v.33 no.6
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• pp.823-836
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• 2019

Spiral welded tubes (SWTs) are fabricated by helically bending a steel plate and welding the resulting abutting edges. The cost-effectiveness of concrete-filled steel tube (CFST) columns can be enhanced by utilising such SWTs rather than the more conventional longitudinal seam welded tubes. Even though the steel-concrete interface bond strength of such concrete-filled spiral-welded steel tubes (CF-SWSTs) is an important consideration in relation to ensuring composite behaviour of such elements, especially at connections, it has not been investigated in detail to date. CF-SWSTs warrant separate consideration of their bond behaviour to CFSTs of other tube types due to the distinct weld seam geometry and fabrication induced surface imperfection patterns of SWTs. To address this research gap, axial push-out tests on forty CF-SWSTs were carried out where the effects of tube material, outside diameter (D), outside diameter to wall thickness (D/t), length of the steel-concrete interface (L) and concrete strength grade (f'_c) were investigated. D, D/t and L/D values in the range 102-305 mm, 51-152.5 and 1.8-5.9 were considered while two nominal concrete grades, 20 MPa and 50 MPa, were used for the tests. The test results showed that the push-out bond strengths of CF-SWSTs of both mild-steel and stainless-steel were either similar to or greater than those of comparable CFSTs of other tube types. The bond strengths obtained experimentally for the tested CF-SWSTs, irrespective of the tube material type, were found to be well predicted by the guidelines contained in AISC-360.

• Asian-Australasian Journal of Animal Sciences
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• v.26 no.10
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• pp.1388-1398
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• 2013

The present study investigated the contribution of carcass traits on carcass prices of Holstein steers in Korea. Phenotypic data consisted of 76,814 slaughtered Holsteins (1 to 6 yrs) from all over Korea. The means for live body weight at slaughter (BWT), chilled carcass weight (CWT), dressing percentage (DP), quantity grade index (QGI), eye muscle area (EMA), backfat thickness (BF) and marbling score (MS), carcass unit price (CUP), and carcass sell prices (CSP) were 729.0 kg, 414.2 kg, 56.79%, 64.42, $75.26cm^2$, 5.77 mm, 1.98, 8,952.80 Korean won/kg and 3,722.80 Thousand Korean won/head. Least squares means were significantly different by various age groups, season of slaughter, marbling scores and yield grades. Pearson's correlation coefficients of CUP with carcass traits ranged from 0.12 to 0.62. Besides, the relationships of carcass traits with CSP were relatively stronger than those with CUP. The multiple regression models for CUP and CSP with carcass traits accounted 39 to 63% of the total variation, respectively. Marbling score had maximum economic effects (partial coefficients) on both prices. In addition, the highest standardized partial coefficients (relative economic weights) for CUP and CSP were calculated to be on MS and CWT by 0.608 and 0.520, respectively. Path analyses showed that MS (0.376) and CWT (0.336) had maximum total effects on CUP and CSP, respectively; whereas BF contributed negatively. Further sub-group (age and season of slaughter) analyses also confirmed the overall outcomes. However, the relative economic weights and total path contributions also varied among the animal sub-groups. This study suggested the significant influences of carcass traits on carcass prices; especially MS and CWT were found to govern the carcass prices of Holstein steers in Korea.

• Korean Journal of Materials Research
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• v.20 no.12
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• pp.691-698
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• 2010

Magnesium hydroxide-melamine core-shell particles were prepared through the coating of melamine monomer on the surface of magnesium hydroxide in the presence of phosphoric acid. The melamine monomer was dissolved in hot water but recrystallized on the surface of magnesium hydroxide by quenching to room temperature in the presence of phosphoric acid. The core-shell particle was applied to low-density polyethylene/ ethylene vinyl acetate (LDPE/EVA) resin by melt-compounding at $180^{\circ}C$ as flame retardant. The effect of magnesium hydroxide and melamine content has been studied on the flame retardancy of the core-shell particles in LDPE/EVA resin according to the preparation process and purity of magnesium hydroxide. Magnesium hydroxide prepared with sodium hydroxide rather than with ammonia solution revealed higher flame retardancy in core-shell particles with LDPE/EVA resin. At 50 wt% loading of flame retardant, core-shell particles revealed higher flame retardancy compared to that of the exclusive magnesium hydroxide in LDPE/EVA composite, and it was possible to satisfy the V0 grade in the UL-94 vertical test. The synergistic flame retardant effect of magnesium hydroxide and melamine core-shell particles was explained as being due to the endothermic decomposition of magnesium hydroxide and melamine, which was followed by the evolution of water from the magnesium hydroxide and porous char formation due to reactive nitrogen compounds, and carbon dioxide generated from melamine.

• Journal of Fisheries and Marine Sciences Education
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• v.25 no.1
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• pp.152-166
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• 2013

The main purpose of this study is to see the differences of the achievement goal orientation, academic burnout, and school happiness between gifted and general students, and also to explore the effects on school happiness of their achievement goal orientation and academic burnout. To resolve the above research questions, this study used questionnaire method to 256 1st grade middle school students and 84 gifted students enrolled in Daegu metropolitan city. All data were analyzed by SPSS WIN 19.0 program. The results of this study are as follows. First, mastery goal, performance-approach goal and performance-avoidance goal of the gifted students were higher than the general students'. Second, all sub-variables of academic burnout except hostility and total score of academic burnout of the gifted students were lower than the general students. On the other hand, all sub-variables of school happiness except relationship with friends and emotional stability and total score school happiness of the gifted students were higher than the general students. Third, this study revealed that the achievement goal and academic burnout explain considerable amount of students' school happiness. In other words, the disfavor and skeptical attitude of general students for the study hinder school happiness. Lastly, this study suggest that some program or consulting need to be administerd to change the affective attitude of students into positively. And also variety of counselling program or some instructions dealing with stress for gifted students since the exhaustion of gifted students affects considerably their school happiness.

• Education of Primary School Mathematics
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• v.19 no.4
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• pp.261-276
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• 2016

This study was to investigate the effects of peer mentoring on students' mathematical characters and mathematics achievements in mathematics class. The participants were twenty four 6th grade elementary students at the S school in Sungbuk-Gu, Seoul, Korea. They were divided into 4 groups according to the combination of groups. The researchers analyzed the experimental group and the control group with covariances on the sub-factors of the mathematical characters such as respect, caring, sharing, and openness. However, there were no statistically significant changes. However, with the help of the two analyses on the mathematical logs and the worksheets which had been carried out in advance by the quantitative and qualitative research methods, the researchers investigated how the peer mentoring-applied instructions would change the mathematical characters for each sub-factor in detail. In conclusion, the peer mentoring-applied instructions makes a positive contribution to the students' mathematical character and mathematical academic achievements. We suggest that peer mentoring in mathematics lessons should be adopted in various mathematical ability levels of students.

• International Journal of Highway Engineering
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• v.18 no.2
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• pp.83-90
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• 2016

PURPOSES : Nowadays, cavity phenomena occur increasingly in pavement layers of downtown areas. This leads to an increment in the number of potholes, sinkholes, and other failure on the road. A loss of earth and sand from the pavement plays a key role in the occurrence of cavities, and, hence, a structural-performance evaluation of the pavement is essential. METHODS: The structural performance was evaluated via finite-element analysis using KPRP and KICTPAVE. KPRP was developed in order to formulate a Korean pavement design guide, which is based on a mechanical-empirical pavement design guide (M-EPDG). RESULTS: Installation of the anti-freezing layer yielded a fatigue crack, permanent deformation, and international roughness index (IRI) of 13%, 0.7 cm, and 3.0 m/km, respectively, as determined from the performance analysis conducted via KPRP. These values satisfy the design standards (fatigue crack: 20%, permanent deformation: 1.3 cm, IRI: 3.5 m/km). The results of FEM, using KICTPAVE, are shown in Figures 8~12 and Tables 3~5. CONCLUSIONS: The results of the performance analysis (conducted via KPRP) satisfy the design standards, even if the thickness of the anti-freezing layer is not considered. The corresponding values (i.e., 13%, 0.7 cm, and 3.0 m/km) are obtained for all conditions under which this layer is applied. Furthermore, the stress and strain on the interlayer between the sub-grade and the anti-freezing layer decrease gradually with increasing thickness of the anti-freezing layer. In contrast, the strain on the interlayer between the sub-base and the anti-freezing layer increases gradually with this increase in thickness.

• The Journal of the Korea Contents Association
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• v.19 no.8
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• pp.224-239
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• 2019

The purpose of this study was to examine the effects of communicative competence, mother's psychological control, and family strengths on interpersonal competence. The subjects of 285 college students who were enrolled in Gyeonggi province were surveyed for data collection. Hierarchical regression analysis was performed considering the influence of control variables. Main results of the study, with college students' gender, grade, birth order and number of siblings controlled, are as follows: Communicative competence had a significant effect on overall interpersonal competence, while mother's psychological control and family strengths had no significant effect on overall interpersonal competence. Next, the results of the study for each sub-factors of interpersonal competence are as follows: Communicative competence was found to be a variable that influence all the sub-variables of interpersonal competence including relationship formation and initiation, claiming for rights or discomfort, consideration for others, conflict management, and appropriate self-opening. Mother's psychological control has a negative effect only on conflict management, and family strengths has an effect on relationship formation and initiation, and appropriate self-opening.

• Journal of Electrochemical Science and Technology
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• v.10 no.1
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• pp.22-28
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• 2019

To maximize the oxygen evolution reaction (OER) in the electrolysis of water, nano-grade $IrO_2$ powder with a low specific surface was prepared as a catalyst for a solid polymer electrolyte (SPE) system, and a membrane electrode assembly (MEA) was prepared with a catalyst loading as low as $2mg\;cm^{-2}$ or less. The $IrO_2$ catalyst was composed of heterogeneous particles with particle sizes ranging from 20 to 70 nm, having a specific surface area of $3.8m^2g^{-1}$. The anode catalyst layer of about $5{\mu}m$ thickness was coated on the membrane (Nafion 117) for the MEA by the decal method. Scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) confirmed strong adhesion at the interface between the membrane and the catalyst electrode. Although the loading of the $IrO_2$ catalyst was as low as $1.1-1.7mg\;cm^{-2}$, the SPE cell delivered a voltage of 1.88-1.93 V at a current density of $1A\;cm^{-2}$ and operating temperature of $80^{\circ}C$. That is, it was observed that the over-potential of the cell for the oxygen evolution reaction (OER) decreased with increasing $IrO_2$ catalyst loading. The electrochemical stability of the MEA was investigated in the electrolysis of water at a current density of $1A\;cm^{-2}$ for a short time. A voltage of ~2.0 V was maintained without any remarkable deterioration of the MEA characteristics.

• Clinics in Shoulder and Elbow
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• v.25 no.2
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• pp.112-120
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• 2022

Background: The prognostic factors for patients with full-thickness rotator cuff tears (RCTs) include tear size, muscle atrophy and fatty infiltration. However, the influence of early coexisting degenerative changes on RCT outcomes is unappreciated. The purpose of this study was to calculate the impact that pre-existing partial glenohumeral cartilaginous changes have on patients undergoing arthroscopic RCT repair. Methods: A study of 54 patients undergoing arthroscopic RCT repair was undertaken. The presence of co-existing patches of glenohumeral degenerative cartilaginous changes and RCT size was recorded at surgery. Pre- and postoperative outcomes were assessed using traditional (Oxford Shoulder Score [OSS], 5-level EuroQol-5D [EQ-5D-5L] questionnaire and EuroQol visual analog scale [EQ-VAS]) and patient-centric re-formatted prisms. Outcomes were assessed as an entire dataset, and sub-group analysis was performed according to the grade of co-existing arthritis and tear size. Results: Significant improvements (p<0.05) in clinical outcomes were recognized when assessed using either the traditional or reformatted prisms (average % improvements in OSS, EQ-5D-5L and EQ-VAS were 47%, 33% and 43%, respectively; average improvements in pain, function, and psychological well-being were 48%, 33% and, 29%, respectively). Positive gain was noted in all sub-groups of arthritic grading and tear size. Conclusions: Good clinical outcomes can be achieved following RCT repair even in the presence of local partial degenerative cartilage changes and advancing tear size. These benefits are patient-centered but require RCT repairability.

• Nuclear Engineering and Technology
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• v.53 no.8
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• pp.2600-2609
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• 2021

Low cycle fatigue behaviors of SA508-3 low-alloy steel were investigated in room-temperature air, high-temperature air and in light water reactor (LWR) water environments. The fatigue mean curve and design curve for the low-alloy steel are developed based on the fatigue data in room-temperature and high-temperature air. The environmental fatigue model for low-alloy steel is developed by the environmental fatigue correction factor (F_en) methodology based on the fatigue data in LWR water environments with the consideration of effects of strain rate, temperature, and dissolved oxygen concentration on the fatigue life.