• Nuclear Engineering and Technology
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• v.49 no.8
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• pp.1748-1751
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• 2017

Reduced activation ferritic/martensitic (RAFM) steels are widely applied as structural materials in the nuclear industry. To investigate hydrogen's effect on RAFM steels' elastic properties and the mechanism of that effect, a procedure of first principles simulation combined with experiment was designed. Density functional theory models were established to simulate RAFM steels' elastic status before and after hydrogen's insertion. Also, experiment was designed to measure the Young's modulus of RAFM steel samples with and without hydrogen charging. Both simulation and experiment showed that the solubility of hydrogen in RAFM steels would decrease the Young's modulus. The effect of hydrogen on RAFM steels' Young's modulus was more significant in water-quenched steels than it was in tempering steels. This indicated that defects inside martensite, considered to be hydrogen traps, could decrease the cohesive energy of the matrix and lead to a decrease of the Young's modulus after hydrogen insertion.

• The Journal of Korean Academy of Prosthodontics
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• v.29 no.1
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• pp.13-22
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• 1991

This study investigated the effects of surface treatment on the tensile bond strength of resinbonded prosthesis. The Rexillium III specimens were treated with $50{\mu}m\;Al_2O_3$ blasting. Type IV gold alloy specimens were treated with $400^{\circ}C$ heating and tin plating method. All specimens were bonded with MBAS composite resin cement and followed by immersion test into the $37^{\circ}C$ water bath for 7 days. The specimens were debonded in tension with an Instron machine and observed with SEM. The modes of failure were recorded also. The following conclusions were obtained : 1. The tensile bond strength decreased in following order. $50{\mu}m\;Al_2O_3$ basted Resillium III group, Type IV gold alloy group treated with $400^{\circ}C$ heat and tin plating type IV gold alloy group, and statistical significant differences were observed(p<0.05). 2. The tensile bond strength decreased in all groups after 7 days immersion test, but statistical significant differences were observed in Rexillium III specimens only. 3. The sharp and irregular surface were observed in Rexillium III, but $400^{\circ}C$ heat treated and tin plated groups had round and broad surface in SEM. 4. The models of bond failure were cohesive-adhesive failure mainly.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2007.10a
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• pp.247-256
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• 2007

Accessibility is a field of study that has primarily been applied to urban or transportation problems two dimensionally. However, in large complex buildings as shopping centers or hospitals, inter-spatial accessibility among compartments has to be taken into account such as in building layouts or evacuation planning. This study expands space syntax theory, one of accessibility-related methodologies used for computing connectivity in urban or architectural spaces, into 3D indoor spaces. Although space syntax is basically a topology-based theory that does not consider general costs such as distance or time, this study suggests modification that incorporates different types of impedances in moving between places including distances, turns and transfers between floors. The proposed method is applied to a 3D campus building model in computing and displaying the accessibility to exit doors or cohesive accessibility among similar functions.

• Structural Engineering and Mechanics
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• v.56 no.2
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• pp.275-291
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• 2015

Adherence between reinforcement and the surrounding concrete is usually ignored in finite element analysis (FEA) of reinforced concrete (RC) members. However, load transition between the reinforcement and surrounding concrete effects RC members' behavior a great deal. In this study, the effects of bond-slip on the FEA of RC members are examined. In the analyses, three types of bond-slip modeling methods (perfect bond, contact elements and spring elements) and three types of reinforcement modeling methods (smeared, one dimensional line and three dimensional solid elements) were used. Bond-slip behavior between the reinforcement and surrounding concrete was simulated with cohesive zone materials (CZM) for the first time. The bond-slip relationship was identified experimentally using a beam bending test as suggested by RILEM. The results obtained from FEA were compared with the results of four RC beams that were tested experimentally. Results showed that, in FE analyses, because of the perfect bond occurrence between the reinforcement and surrounding concrete, unrealistic strains occurred in the longitudinal reinforcement. This situation greatly affected the load deflection relationship because the longitudinal reinforcements dominated the failure mode. In addition to the spring elements, the combination of a bonded contact option with CZM also gave closer results to the experimental models. However, modeling of the bond-slip relationship with a contact element was quite difficult and time consuming. Therefore bond-slip modeling is more suitable with spring elements.

• Earthquakes and Structures
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• v.22 no.6
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• pp.597-608
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• 2022

One of the most important parameters affecting nonlinearsoil-structure interaction, especially rocking foundation, is the vertical factor of safety (F.S_v). In this research, the effect of F.S_v on the behavior of rocking foundations was experimentally investigated. A set of slow, cyclic, horizontal loading tests was conducted on elastic SDOF structures with different shallow foundations. Vertical bearing capacity tests also were conducted to determine the F.S_v more precisely. Furthermore, 10% silt was mixed with the dry sand at a 5% moisture content to reach the minimum apparent cohesion. The results of the vertical bearing capacity tests showed that the bearing capacity coefficients (N_c and N_γ) were influenced by the scaling effect. The results of horizontal cyclic loading tests showed that the trend of increase in capacity was substantially related to the source of nonlinearity and it varied by changing F.S_v. Stiffness degradation was found to occur in the final cycles of loading. The results indicated that the moment capacity and damping ratio of the system in models with lower F.S_v values depended on soil specifications such cohesiveness or non-cohesiveness and were not just a function of F.S_v.

• Steel and Composite Structures
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• v.43 no.5
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• pp.565-579
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• 2022

This study investigated the yielding capacity and performance of seismic dampers constructed with steel ring plates using numerical and analytical approaches. This study aims to provide an analytical relationship for estimating the yielding capacity and initial stiffness of steel ring dampers. Using plastic analysis and considering the mechanism of plastic hinge formation, a relation has been obtained for estimating the yielding capacity of steel ring dampers. Extensive parametric studies have been carried out using a nonlinear finite element method to examine the accuracy of the obtained analytical relationships. The parametric studies include investigating the influence of the length, thickness, and diameter of the ring of steel ring dampers. To this end, comprehensive verification studies are performed by comparing the numerical predictions with several reported experimental results to demonstrate the numerical method's reliability and accuracy. Comparison is made between the hysteresis curves, and failure modes predicted numerically or obtained/observed experimentally. Good agreement is observed between the numerical simulations and the analytical predictions for the yielding force and initial stiffness. The difference between the numerical models' ultimate tensile and compressive capacities was observed that average of about 22%, which stems from the performance of the ring-dampers in the tensile and compression zones. The results show that the steel ring-dampers are exhibited high energy dissipation capacity and ductility. The ductility parameters for steel ring-damper between values were 7.5 to 4.1.

• Journal of Korean Public Health Nursing
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• v.37 no.1
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• pp.111-124
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• 2023

Purpose: This study aimed to investigate the effects of restorative family circles (RFCs) on empowerment and family support for people with mental illness, and the belief system and caring experience of their families. Methods: This study used a quasi-experiment with a non-equivalent control group pretest-posttest non-synchronized design. Ninety-two dyads of patient-family caregivers were recruited using convenience sampling and assigned to the experimental and control groups. The subjects of the experimental group participated in RFCs consisting of eight 90-minute sessions. Data were collected at three different times (pretest, posttest, follow-up test) and analyzed for the effects of RFC using the 𝑥² test, Fisher's exact test, Mann-Whitney U test for homogeneity between groups, and generalized estimating equation models. Results: The findings of this study showed that there were significant differences in the family support for people with mental illness between the pretest and follow-up test, and also in the belief system and caring experience of the family between the pretest and posttest. Conclusion: This study revealed that family interventions based on restorative justice emphasizing community-driven conflict management could be used in psychiatric mental health nursing care for fostering a cohesive family relationship.

• Korean Journal of Construction Engineering and Management
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• v.15 no.1
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• pp.70-77
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• 2014

Collaborative processes among team members including communication, coordination, and information-handling processes either during pre-construction or project execution are required in order to accomplish the objectives of construction projects. However, current construction management practice does not explicitly take the effect of organizational aspects on project performance into account. This paper introduces a method to understand collaborative processes in an explicit and systematic fashion. An agent-based simulation of collaborative working processes within construction project teams was designed from game theory perspective and implemented. The simulation produced both individual behavior and network dynamics. Individuals represented as agents made efforts to improve performance by communication and coordinating with other members, and overall team network was emerged as a result of interactions among members. Interestingly, it was found that the tendency of forming cohesive subgroups increased when sustaining relations with between-group partners incurs higher cost. The primary contribution of this paper is that it presented an explicit approach to examining collaborative working processes in construction project teams and it extended existing computational organization and network studies by integrating individual behavior models and network models.

• International Journal of Highway Engineering
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• v.8 no.1 s.27
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• pp.139-152
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• 2006

Many experimental and numerical approaches have been developed to evaluate paving materials and to predict pavement response and distress. Micromechanical simulation modeling is a technology that can reduce the number of physical tests required in material formulation and design and that can provide more details, e.g., the internal stress and strain state, and energy evolution and dissipation in simulated specimens with realistic microstructural features. A clustered distinct element modeling (DEM) approach was implemented In the two-dimensional particle flow software package (PFC-2D) to study the complex behavior observed in asphalt mixture fracturing. The relationship between continuous and discontinuous material properties was defined based on the potential energy approach. The theoretical relationship was validated with the uniform axial compression and cantilever beam model using two-dimensional plane strain and plane stress models. A bilinear cohesive displacement-softening model was implemented as an intrinsic interface and applied for both homogeneous and heterogeneous fracture modeling in order to simulate behavior in the fracture process zone and to simulate crack propagation. A disk-shaped compact tension test (DC(T)) with heterogeneous microstructure was simulated and compared with the experimental fracture test results to study Mode I fracture. The realistic arbitrary crack propagation including crack deflection, microcracking, crack face sliding, crack branching, and crack tip blunting could be represented in the fracture models. This micromechanical modeling approach represents the early developmental stages towards a 'virtual asphalt laboratory,' where simulations of laboratory tests and eventually field response and distress predictions can be made to enhance our understanding of pavement distress mechanisms, such its thermal fracture, reflective cracking, and fatigue crack growth.

• Journal of Information Technology Services
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• v.17 no.2
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• pp.143-163
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• 2018

The business models has a great impact on the successful management of enterprises. Business environment has been shifting from industrial economy to knowledge-based economy. Enterprises go through numerous trials for successful management in the changing environment. Along with trial tests, research areas have been growing simultaneously. Although many researches have been conducted with regard to business models, it is very insufficient to systematically analyze the knowledge flow of research. Accordingly, successive researchers who want to study the business model may find it difficult to establish the orientation of future application research based on understanding the process of changing the knowledge structure that have accumulated so far. This study is intended to determine the current state of the business model research and to understand the process of knowledge structure changes in keywords that appear in 2,667 business model articles in the SCOPUS database. Identifying the knowledge structure has been completed through social network analysis, a methodology based on the 'relationship', and the changes in the knowledge structure were identified by classifying them into four different periods. The analysis showed that, first, the number of business model co-author increases over time with the need for academic diversity. Second, the 'innovation' keyword has the biggest center in the network, and over time, the lower-rank keyword which was in the former period has emerged as the top-rank keyword. Third, the cohesiveness group decreased from 12 before 2000 to 5 in 2015 and also the modularity decreased as well. Finally, examining characteristics of study area through a cognitive map showed that the relationships between domains increased gradually over time. The study has provided a systematic basis for understanding the current state of the business model research and the process of changing knowledge structure. In addition, considering that no research has ever systematically analyzed the knowledge structure accumulated by individual researches, it is considered as a significant study.