• Tunnel and Underground Space
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• v.31 no.4
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• pp.270-288
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• 2021

We proposed a numerical method to simulate the hydro-mechanical behavior of rock fracture using a grain-based distinct element model (GBDEM) in the paper. As a part of DECOVALEX-2023 Task G, we verified the method via benchmarks with analytical solutions. DECOVALEX-2023 Task G aims to develop a numerical method to estimate the coupled thermo-hydro-mechanical processes within the crystalline rock fracture network. We represented the rock sample as a group of tetrahedral grains and calculated the interaction of the grains and their interfaces using 3DEC. The micro-parameters of the grains and interfaces were determined by a new methodology based on an equivalent continuum approach. In benchmark modeling, a single fracture embedded in the rock was examined for the effects of fracture inclination and roughness, the boundary stress condition and the applied pressure. The simulation results showed that the developed numerical model reasonably reproduced the fracture slip induced by boundary stress condition, the fracture opening induced by fluid injection, the stress distribution variation with fracture inclination, and the fracture roughness effect. In addition, the fracture displacements associated with the opening and slip showed good agreement with the analytical solutions. We expect the numerical model to be enhanced by continuing collaboration and interaction with other research teams of DECOVALEX-2023 Task G and validated in further study experiments.

• Tunnel and Underground Space
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• v.31 no.6
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• pp.593-609
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• 2021

We proposed a numerical method for the thermo-mechanical behavior of rock fracture using a grain-based distinct element model (GBDEM) and simulated thermally induced fracture slip. The present study is the benchmark simulation performed as part of DECOVALEX-2023 Task G, which aims to develop a numerical method to estimate the coupled thermo-hydro-mechanical processes within the crystalline rock fracture network. We represented the rock sample as an assembly of Voronoi grains and calculated the interaction of the grains (blocks) and their interfaces (contacts) using a distinct element code, 3DEC. Based on an equivalent continuum approach, the micro-parameters of grains and contacts were determined to reproduce rock as an elastic material. Then, the behavior of the fracture embedded in the rock was characterized by the contacts with Coulomb shear strength and tensile strength. In the benchmark simulation, we quantitatively examined the effects of the boundary stress and thermal stress due to heat conduction on fracture behavior, focusing on the mechanism of thermally induced fracture slip. The simulation results showed that the developed numerical model reasonably reproduced the thermal expansion and thermal stress increment, the fracture stress and displacement and the effect of boundary condition. We expect the numerical model to be enhanced by continuing collaboration and interaction with other research teams of DECOVALEX-2023 Task G and validated in further study experiments.

• Journal of Family Resource Management and Policy Review
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• v.26 no.2
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• pp.71-84
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• 2022

This study analyzed 2019 time survey data from the National Statistical Office to examine the childcare behaviors of fathers with preschool children and their determinants, considering types of care and working/nonworking days. The main results of this study are as follows. First, paternal childcare time of nonworking days was three times more than that of working days, and the participation rate was also higher on nonworking days. Second, there was no significant difference in the amount of time spent on primary care and developmental care by fathers, whether from dual- or single-income families. Third, it seems that fathers adjust their participation in childcare between working days and nonworking days in consideration of the mother's time availability. Fourth, the variables related to childcare needs had a significant influence on paternal childcare time on both working and nonworking days. Fathers' developmental care time was not explained by the independent variables entered into the regression analysis. As a result of the study, it is necessary to reduce fathers' working hours and increase family-friendly systems to increase fathers' participation in childrearing. Fathers' perception of parental responsibility must also be changed.

• Tunnel and Underground Space
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• v.32 no.6
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• pp.568-585
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• 2022

In the present study, we proposed a numerical method for simulating thermally induced fracture slip using a grain-based distinct element model (GBDEM). As a part of DECOVALEX-2023, the thermo-mechanical loading test on a saw-cut rock fracture conducted at the Korea Institute of Civil Engineering and Building Technology was simulated. In the numerical model, the rock sample including a saw-cut fracture was represented as a group of random Voronoi polyhedra. Then, the coupled thermo-mechanical behavior of grains and their interfaces was calculated using 3DEC. The key concerns focused on the temperature evolution, thermally induced principal stress increment, and fracture normal and shear displacements under thermo-mechanical loading. The comparisons between laboratory experimental results and the numerical results revealed that the numerical model reasonably captured the heat transfer and heat loss characteristics of the rock specimen, the horizontal stress increment due to constrained displacement, and the progressive shear failure of the fracture. However, the onset of the fracture slip and the magnitudes of stress increment and fracture displacement showed discrepancies between the numerical and experimental results. We expect the numerical model to be enhanced by continuing collaboration and interaction with other research teams of DECOVALEX-2023 Task G and validated in further study.

• Journal of Practical Engineering Education
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• v.14 no.2
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• pp.405-411
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• 2022

In this study, K-Digital Training program, which is a representative government project of vocational training for new digital technologies in response to the 4th industrial revolution, is analyzed and an improvement model is suggested. The K-Digital training project is rapidly expanding, with the number of training operators increasing by 7.1 times and training course programs by 8.5 times within three years of implementation, but there is a severe problem in that education and training programs are concentrated in the metropolitan. To solve this problem, a shared training model is proposed. This model is a plan to maximize the use of local human and material resources, to respond to new digital technologies through systematic composition and operation, and to enhance the stability and reliability of education and training. In each region, a sharing and cooperation model in the form of a consortium is established that jointly utilizes resources scattered by various training institutions such as instructors, training contents, and training infrastructure related to digital new technology. In addition, a training certification evaluation system is introduced to increase the credibility of the rapidly developing digital new technology training.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.1
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• pp.55-61
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• 2023

This study aims to develop CLSM fill material for emergency restoration using landfill coal ash. As a result of examining physical properties such as particle size distribution and fines content of landfill coal ash, bottom ash, fly ash, and general soil were mixed, and SP was found to have a density of 2.03 and a residual particle pass rate of 7.8 %. CLSM materials that secure fluidity in unit quantities without using chemical admixtures such as glidants and water reducing agents have a high risk of material separation due to bleeding. As a result of this experiment, it was found that the bleeding ratio did not satisfy the standard in the case of the specimen with a large amount of fly ash and a lot of addition of mixing water. As a result of the compressive strength test, the strength development of 0.5 MPa or more for 4 hours was found to be satisfactory for the specimens using hemihydrate gypsum with a unit binder amount of 200 or more, and the remaining gypsum showed poor strength development. Although it is judged that landfill coal ash can be used as a CLSM material, it is necessary to identify and apply the physical and chemical characteristics of coal ash buried in the ash treatment plant of each power generation company.

• Korean Chemical Engineering Research
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• v.61 no.2
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• pp.258-264
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• 2023

The greenhouse gas (GHG) emission assessment of kenaf pellet, produced from locally generated kenaf residues in South Korea, has been studied based on the EU RED-II methodology for calculating GHG impact of biomass fuels. Based on the production pathway of kenaf residue pellet and emission coefficients from EU JRC report, the life cycle GHG emission of kenaf residue pellet is assessed as 3.0 gCO₂eq/MJ_pellet and the life cycle GHG emission of electricity generated from kenaf residue pellet is assessed as 11.9 gCO₂eq/MJ when electrical efficiency of final conversion is 25%. The potential GHG emission reduction of electricity produced from kenaf pellet is 90.3% compared to the domestic electricity emission factor 42.8 kgCO₂eq/MWh. Also, the electricity produced from kenaf pellet can reduce at least 59.6% of GHG emission compared to the electricity produced from imported wood pellets.

• Tunnel and Underground Space
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• v.33 no.3
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• pp.189-207
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• 2023

In the present study, the thermoshearing experiment on a rough rock fracture were modeled using a three-dimensional grain-based distinct element model (GBDEM). The experiment was conducted by the Korea Institute of Construction Technology to investigate the progressive shear failure of fracture under the influence of thermal stress in a critical stress state. The numerical model employs an assembly of multiple polyhedral grains and their interfaces to represent the rock sample, and calculates the coupled thermo-mechanical behavior of the grains (blocks) and the interfaces (contacts) using 3DEC, a DEM code. The primary focus was on simulating the temperature evolution, generation of thermal stress, and shear and normal displacements of the fracture. Two fracture models, namely the mated fracture model and the unmated fracture model, were constructed based on the degree of surface matedness, and their respective behaviors were compared and analyzed. By leveraging the advantage of the DEM, the contact area between the fracture surfaces was continuously monitored during the simulation, enabling an examination of its influence on shear behavior. The numerical results demonstrated distinct differences depending on the degree of the surface matedness at the initial stage. In the mated fracture model, where the surfaces were in almost full contact, the characteristic stages of peak stress and residual stress commonly observed in shear behavior of natural rock joints were reasonably replicated, despite exhibiting discrepancies with the experimental results. The analysis of contact area variation over time confirmed that our numerical model effectively simulated the abrupt normal dilation and shear slip, stress softening phenomenon, and transition to the residual state that occur during the peak stress stage. The unmated fracture model, which closely resembled the experimental specimen, showed qualitative agreement with the experimental observations, including heat transfer characteristics, the progressive shear failure process induced by heating, and the increase in thermal stress. However, there were some mismatches between the numerical and experimental results regarding the onset of fracture slip and the magnitudes of fracture stress and displacement. This research was conducted as part of DECOVALEX-2023 Task G, and we expect the numerical model to be enhanced through continued collaboration with other research teams and validated in further studies.

• ANNALS OF ANIMAL RESOURCE SCIENCES
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• v.30 no.4
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• pp.165-171
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• 2019

The objective of this study was to investigate the effects of gender on meat quality traits and sensory characteristics of pork loin. A total of 90 pork carcasses (180 days old, 45 barrows and 45 gilts, each gender group was consisted of fifteen 1+, 1 and 2 carcass grades) were selected and loin cuts were excised to investigate meat quality, electronic tongue measures and sensory panel test. There were significant differences in drip loss (1.66% vs 1.21%), released water (12.19% vs 10.68%) and cooking loss (23.67% vs 21.04%) between loins from barrow and gilt (p<0.05). However, no significant differences in meat color (CIE L^* a^* b^*) and shear force were observed between gender groups (p>0.05). Umami and richness values of barrow were significantly higher than those of gilt, while barrow had significantly lower sourness value compared to gilt(p<0.05). On the sensory evaluation, barrow scored higher in flavor, juiciness and tenderness both, and as a result, barrow (5.51 points) also scored significantly higher than gilt (4.86 points). These results suggest that the umami intensity and sensory taste of barrow loin are superior to gilt loin due to its high water-holding capacity.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.11 no.2
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• pp.101-111
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• 2016

Startup has lot of limitation such as time and budget shortage, and few human resources, and may be under the very stressful condition. Naturally in these context, there is always conflict among the startup team members, but the impact of conflict on teamwork or team performance has not been empirically tested. This study examines the relationship among the conflict, teamwork and team performance in startup context. Different two types of conflict and four factors of teamwork for team performance are identified from a literature review and tested; task conflict and relationship conflict as antecedents, teamwork was composed of communication, collaboration, coordination and cohesion, leading to team performance. 142 data points were collected from startup representatives to test these hypotheses. PLS data analysis indicated that the task conflict positively effects on all teamwork factors, but relationship conflict has statistically significant effect on only two teamwork factors, collaboration and coordination in negative relationship. Teamwork factors effects on team performance except communication. Based on the results, we proposed practically several team management skills for startup managers, leaders and even members, and explained theoretical contributions.