• Structural Engineering and Mechanics
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• v.87 no.2
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• pp.151-164
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• 2023

The latest earthquake's costly repairs and economic disruption were brought on by excessive residual drift. Self-centering systems are one of the most efficient ways in the current generation of seismic resistance system to get rid of and reduce residual drift. The mechanics and behavior of the self-centering system in response to seismic forces were impacted by a number of important factors. The amount of post-tensioning (PT) force, which is often employed for the standing posture after an earthquake, is the first important component. The energy dissipater element is another one that has a significant impact on how the self-centering system behaves. Using the damper as a replaceable and affordable tool and fuse in self-centering frames has been recommended to boost energy absorption and dampening of structural systems during earthquakes. In this research, the self-centering steel moment frame connections are equipped with cushion flexural dampers (CFDs) as an energy dissipator system to increase energy absorption, post-yielding stiffness, and ease replacement after an earthquake. Also, it has been carefully considered how to reduce permanent deformations in the self-centering steel moment frames exposed to seismic loads while maintaining adequate stiffness, strength, and ductility. After confirming the FE model's findings with an earlier experimental PT connection, the behavior of the self-centering connection using CFD has been surveyed in this study. The FE modeling takes into account strands preloading as well as geometric and material nonlinearities. In addition to contact and sliding phenomena, gap opening and closing actions are included in the models. According to the findings, self-centering moment-resisting frames (SF-MRF) combined with CFD enhance post-yielding stiffness and energy absorption with the least amount of permeant deformation in a certain CFD thickness. The obtained findings demonstrate that the effective energy dissipation ratio (β), is increased to 0.25% while also lowering the residual drift to less than 0.5%. Also, this enhancement in the self-centering connection with CFD's seismic performance was attained with a respectable moment capacity to beam plastic moment capacity ratio.

• Earthquakes and Structures
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• v.23 no.2
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• pp.129-138
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• 2022

One of the objectives to prevent building pounding between two adjacentstructures is to considerseparation distance or decrease relative displacement during seismic excitation. Although the majority of building codes around the world have basically suggested some equations or approximately recommended various distances between structuresto avoid pounding hazard, but a lot of reportsin zone of pounding have obviously shown thatsafety situation or economic consideration are not always provided due to the collisions between buildings and the cost of land, respectively. For this purpose, a dynamic MDOF model by having base isolation system is numerically considered and using various earthquake records, relative displacements are mathematically investigated. Different equations to determine the value of damping ratio are collected and the results of evaluations are listed for comparison among them to present a new equation for determination of impact damping ratio. Presented equation is depends significantly on impact velocity before and after impact based on artificial neural network, which the accuracy of them is investigated and also confirmed. In order to select the optimum equation, hysteresisloop of impact between base of building and rubber bumper is considered and compared with the hysteresis loop of each impact, calculated by different equations. Finally, using representative equation, the effect of thickness, number and stiffness of rubber bumpers are numerically investigated. The results of analysis indicate that stiffness and number of bumpers have significantly affected in zone of impact force while the thickness of bumpers have not shown significant influence to calculate impact force during earthquake. For instance, increasing the number of bumpers, gap size between structures and also the value of stiffness is caused to decrease impact force between models. The final evaluation demonstrates that bumpers are able to decrease peak lateral displacement of top story during impact.

• Computers and Concrete
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• v.32 no.5
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• pp.455-464
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• 2023

Seismologists now suggest that the earth has entered an active seismic period; many earthquake-related events are occurring globally. Consequently, numerous casualties, as well as economic losses due to earthquakes, have been reported in recent years. Primarily, significant and colossal damage occurs in reinforced concrete (RC) buildings with masonry infill wall systems, and the construction of these types of structures have increased worldwide. According to a report from the Ministry of Education in the Republic of Korea, many buildings were built with RC frames with masonry infill walls in the Republic of Korea during the 1980s. For years, most structures of this type have been school buildings, and since the Pohang earthquake in 2017, the government of the Republic of Korea has paid close attention to this social event and focused on damage from earthquakes. From a long-term research perspective, damage from structural collapse due to the short column effect has been a major concern, specifically because the RC frame with a masonry infill wall system is the typical form of structure for school buildings. Therefore, the short column effect has recently been a major topic for research. This study compares one RC frame with four different types of RC frames with masonry infill wall systems. Structural damage due to the short column effect is clearly analyzed, as the result of this research is giving in a higher infill wall system produces a greater shear force on the connecting point between the infill wall system and the column. The study is expected to be a useful reference for research on the short column effect in RC frames with masonry infill wall systems.

• Coupled systems mechanics
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• v.12 no.6
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• pp.531-537
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• 2023

Municipal solid waste landfills are unpredictable bioreactors which in cases of mishandling and bad supervision presents numerous risks. The key to municipal waste landfills is to approach them from the point of prevention of the possible consequences, which means using methods of organized waste disposal, and also utilizing landfill gas, as an unavoidable consequence with disposal of municipal solid waste with a high share of biodegradable organic matter. This paper presents an overview about problems of solid municipal waste management, type and composition of waste, and an overview of waste management condition. Further, the problem of landfill and landfill gasses is described with the calculation models of landfill production, as well as the use of the SWM GHG Calculator and LandGEM software on a specific example of gas production for the central zone at Sarajevo landfill "Smiljevici". Main focus of this thesis is the analysis of potentials of greenhouse gas emission reduction measures from the waste management. Overview of the best available techniques in waste management is presented as well as the methodology used for calculations. Scenarios of greenhouse gas emission reduction in waste management were defined so that emissions were calculated using the appropriate model. In the final section of the paper, its description of the problem of collection and utilization the landfill gas at the sanitary landfill "Smiljevici", and implementation of the system for landfill gas collection and solution suggestion for the gasification and exploitation of gas. Energy, environmental and economic benefits can be accomplished by utilizing municipal solid waste as fuel in industry and energy and moreover by utilizing energy generation from landfill gas, which this thesis emphasizes.

• Computers and Concrete
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• v.33 no.2
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• pp.175-193
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• 2024

Researchers have embarked on an active investigation into the feasibility of adopting alternative materials as a solution to the mounting environmental and economic challenges associated with traditional concrete-based construction materials, such as reinforced concrete. The examination of concrete's mechanical properties using laboratory methods is a complex, time-consuming, and costly endeavor. Consequently, the need for models that can overcome these drawbacks is urgent. Fortunately, the ever-increasing availability of data has paved the way for the utilization of machine learning methods, which can provide powerful, efficient, and cost-effective models. This study aims to explore the potential of twelve machine learning algorithms in predicting the tensile strength of geopolymer concrete (GPC) under various curing conditions. To fulfill this objective, 221 datasets, comprising tensile strength test results of GPC with diverse mix ratios and curing conditions, were employed. Additionally, a number of unseen datasets were used to assess the overall performance of the machine learning models. Through a comprehensive analysis of statistical indices and a comparison of the models' behavior with laboratory tests, it was determined that nearly all the models exhibited satisfactory potential in estimating the tensile strength of GPC. Nevertheless, the artificial neural networks and support vector regression models demonstrated the highest robustness. Both the laboratory tests and machine learning outcomes revealed that GPC composed of 30% fly ash and 70% ground granulated blast slag, mixed with 14 mol of NaOH, and cured in an oven at 300°F for 28 days exhibited superior tensile strength.

• Steel and Composite Structures
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• v.52 no.2
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• pp.135-143
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• 2024

Once the foundation displacement of the transmission tower occurs, additional stress will be generated on the tower members, which will affect the seismic response of transmission tower-line systems (TTLSs). Furthermore, existing research has shown that the reciprocating slippage of joints needs to be considered in the seismic analysis. The hysteretic behavior of joints is obtained by model tests or numerical simulations, which leads to the low modeling efficiency of TTLSs. Therefore, this paper first utilized numerical simulation and model tests to construct a BP neural network for predicting the skeleton curve of joints, and then a numerical model for a TTLS considering the bolt slippage was established. Then, the seismic response of the TTLS under foundation displacement was studied, and the member stress changes and the failed member distribution of the tower were analyzed. The influence of foundation displacement on the seismic performance were discussed. The results showed that the trained BP neural network could accurately predict the hysteresis performance of joints. The slippage could offset part of the additional stress caused by foundation settlement and reduce the stress of some members when the TTLS with foundation settlement was under earthquakes. The failure members were mainly distributed at the diagonal members of the tower leg adjacent to the foundation settlement and that of the tower body. To accurately analyze the seismic performance of TTLSs, the influence of foundation displacement and the joint effect should be considered, and the BP neural network can be used to improve modeling efficiency.

• Journal of the Korean Geographical Society
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• v.49 no.2
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• pp.113-138
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• 2014

Despite the growing numbers of regional problems (e.g. conflicts between the state and localities, inter-local conflicts, etc.) associated with the state-led developmental projects, the Korean social sciences have been unable to offer satisfying explanations and solutions to the regional problems. This is mainly because the existing works, which have been taken captured by the assumptions of "methodological nationalism", significantly lack the socio-spatial understandings of the state actions and the relations between the state and localities, thereby seeing the issues of regional development mainly in terms of either the economic efficiency defined at the national scale, or the plan rationality of the national bureaucrats. With this problem orientation in mind, this paper aims to explore the ways in which the state and localities are interacting, conflicting and negotiating with one another through the mediation of the state-led developmental projects. Focusing on the developmental processes of Masan Export Processing Zone from the mid-1960s to the early 1970s, it examines the multi-scalar processes through which the state-led industrial complex developmental processes have been influenced by the complex and dynamic interactions among social forces and actors acting at diverse geographical scales (e.g. the global, national, local, urban, etc.). This analysis shows that the regional policies of the Korean developmental state were more heavily influenced by the interactions, contestations, and collaborations among social forces and actors, acting in and through the state, at various geographical scales, rather than by the economic and techno-bureaucratic rationality.

• Korean Chemical Engineering Research
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• v.62 no.2
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• pp.163-172
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• 2024

In this study, two different scenarios for ammonia liquefaction in the green ammonia manufacturing process were proposed, and the economic-feasibility and environmental impact of each scenario were analyzed. The two liquefaction processes involved gas-liquid separation before cooling at high pressure (high pressure cooling process) or after decompression without the gas-liquid separation (low pressure cooling process). The high-pressure cooling process requires higher capital costs due to the required installation of separation units and heat exchangers, but it offers relatively lower total utility costs of 91.03 $/hr and a reduced duty of 2.81 Gcal/hr. In contrast, although the low-pressure cooling process is simpler and cost-effective, it may encounter operational instability due to rapid pressure drops in the system. Environmental impact assessment revealed that the high-pressure cooling process is more environmentally friendly than the low-pressure cooling process, with an emission factor of 0.83 tCO₂eq less than the low-pressure cooling process, calculated based on power usage. Consequently, the outcomes of this study provide relevant scenario and a database for green ammonia synthesis process adaptable to various process conditions.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.8
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• pp.160-166
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• 2018

This study was conducted to analyze the Ego Integrity, Subjective Pain, Subjective Health, Subjective Happiness and Social Support level of Community Dwelling elderly, and to analyze the variables that impact their Ego Integrity. Methods: A total of 250 elderly aged 60 years or above visiting a Senior Welfare Center in j city and j group of Jeonbuk were selected as subjects of this study for collection and analysis of data. Data were collected from January 8 to February 26, 2008 from 250 community-dwelling elders in Korea and subjected to descriptive analysis, t-test, ANOVA, Pearson's Correlation Coefficient, and multiple regression analysis. Results: only economic strength was influenced by general characteristics. Additionally, Subjective Pain, Subjective Health, and Subjective Happiness and Social Support l were found to have a statistically positive correlation with Ego Integrity. Finally, the most influential variables on the elderly Ego Integrity were Social Support (${\beta}=.194$, p=.002), followed by Subjective Health (${\beta}=.149$, p=.040) and four variables explaining 10.8% of the elderly Ego Integrity. Conclusion: it is necessary to develop specific intervention programs to improve Social Support and Subjective Health among Community Dwelling elderly to make it possible to enable Ego Integrity.

• Journal of Digital Convergence
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• v.16 no.5
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• pp.361-372
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• 2018

The purpose of this study was to develop an assessment scale for healthy aging of middle aged women. The data were collected from 385 middle aged women in two large cities in Korea. The development processes of the scale were followed: Development of preliminary items; Verification of content validity and reliability; Factor analysis and criterion validity of final items. Results: Factor analysis resulted in the creation of the final scale, which consisted of 38 items that were grouped into 9 factors: self achievement, physical change adaptation, psychological change adaptation, interpersonal relationships, menopausal symptom adaptation, economic stability, physical health, social support, social change adaptation. The explanatory variance was 64.03%. The reliability of the scale was Cronbach's ${\alpha}=.90$. Correlation of the scale with healthy aging and depression, established its construct and concurrent validity was r=-.69, p<.001. The scale was confirmed to have a relatively high validity and reliability. The findings of the study can be useful as a measurement to evaluate healthy aging of middle aged women. Future researches with the scale will be helpful for basic data for the program development to support healthy aging of middle aged women.