• Computers and Concrete
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• v.23 no.1
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• pp.61-68
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• 2019

This paper presents a computational rational model to predict the ultimate and optimized load capacity of reinforced concrete (RC) beams strengthened by a combination of longitudinal and transverse fiber reinforced polymer (FRP) composite plates/sheets (flexure and shear strengthening system). Several experimental and analytical studies on the confinement effect and failure mechanisms of fiber reinforced polymer (FRP) wrapped columns have been conducted over recent years. Although typical axial members are large-scale square/rectangular reinforced concrete (RC) columns in practice, the majority of such studies have concentrated on the behavior of small-scale circular concrete specimens. A high performance concrete, known as polymer concrete, made up of natural aggregates and an orthophthalic polyester binder, reinforced with non-metallic bars (glass reinforced polymer) has been studied. The material is described at micro and macro level, presenting the key physical and mechanical properties using different experimental techniques. Furthermore, a full description of non-metallic bars is presented to evaluate its structural expectancies, embedded in the polymer concrete matrix. In this paper, the mechanism of mechanical interaction of smooth and lugged FRP rods with concrete is presented. A general modeling and application of various elements are demonstrated. The contact parameters are defined and the procedures of calculation and evaluation of contact parameters are introduced. The method of calibration of the calculated parameters is presented. Finally, the numerical results are obtained for different bond parameters which show a good agreement with experimental results reported in literature.

• Korean Journal of Construction Engineering and Management
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• v.20 no.3
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• pp.86-96
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• 2019

The research efforts to modernize Hanok (Korean traditional housing) have been performed to improve the quality and cost-effectiveness through application of modern building methods and materials, and to disseminate it in various forms of sizes and facilities. In this study, in order to identify the variations of modernized Hanok, data from seven test-bed projects are analyzed based on the building work-section, element, method, and material. The data were standardized and managed through the modernized Hanok classification system (Hanclass) to facilitate systematic comparisons of the test-bed projects by the variation of building method and it's cost impact. Identified factors of the variation in terms of building methods were then itemized and quantified in terms of building cost. Findings of this study indicate that the timber structure is the most critical area for future variation for improving the quality and cost-effectiveness. The results of this study will be also used to systemize the Hanok database for further studies.

• Journal of the Architectural Institute of Korea Planning & Design
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• v.34 no.11
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• pp.3-12
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• 2018

Hospice is the wholistic caring service for terminally ill patient and his family so that he can live in dignity and maintain the quality of life until he passes away peacefully. The purpose of this study is to compare the development of hospice movement in UK, USA, Japan and Korea, to analyze space configuration characteristics of facilities built between 1980-2009 through case study. The result is as follows. First, The modern hospice started in England and it has spread around the world rapidly. In Korea, hospice service was introduced even prior to US and Japan and developed in spite of poor medical environment. The application of health insurance subsidies were late compared to other countries, but the hospice and palliative care system was quickly set on the basis of precedent cases. Second, the number of hospital beds per facility is decreasing, and it has been divided into smaller clusters for the residential atmosphere. The controversy between private rooms and multi-patient room is still ongoing, and increasing facilities without in-patient service. Rather than establishing uniform and absolute regulations, it is necessary to design a flexible space which can cope with various situations such as patients' needs, service changes, and manpower status. Third, the spaces for family members and friends to stay in both private rooms and communal spaces are increasing. Forth, Facilities for patients with different needs, such as children and adolescents and AIDS patients, have been developed in UK and USA. Further research on of patients' diverse needs and customized environmental support is necessary.

• Journal of the Architectural Institute of Korea Planning & Design
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• v.36 no.1
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• pp.125-136
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• 2020

This study aims to seek a proper policy direction in response to the demand for apartment remodeling. As the research methods, we diagnosed the current status of the remodeling policy and analyzed the demand for apartment remodeling nationwide. According to the result of analysis, we suggested the fundamental direction and tasks for remodeling policies to be pursued at the government level. The results of the study are summarized as follows. First, the result of analysis showed that the demand for environmental improvement(performance improvement) remodeling project was much higher than other types of remodeling projects. The percentage of unit increased-type remodeling that can secure business feasibility is about 10% and only 30% when it comes to reducing project costs. The remaining 70-90% need to be promoted in environmental improvement remodeling projects which dependent on the residents' payment. Second, in order to prepare a policy action plan in response to the demand for apartment remodeling, it is necessary to set up clear policy goals and strategies for apartment remodeling in advance at the national level. Along with proactive goals and strategies, graded policy support should be accompanied per type of remodeling and business demand. We also suggest to simplify administrative procedures and support the R&D research to develop technologies. It would help to utilize the unit increased-type remodeling. On the other hand, for utilizing the environmental improvement remodeling which takes up a relatively high proportion, the policy should take care of as follows: offering housing performance information, rationalizing long term repair reserve, fostering small companies and experts. Finally, apartment management system should be advanced from the perspectives of managing old apartments and institutional foundations such as new construction and customized regulations for differentiated remodeling should be accompanied.

• Journal of Environmental Health Sciences
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• v.47 no.4
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• pp.330-338
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• 2021

Background: This study was conducted to provide background information for the proper management of radon contamination in apartments using mechanical ventilation facilities in residential environments. Objectives: To this end, this study compared and evaluated changes in radon concentrations based on different operating intensities of mechanical ventilation with or without natural ventilation. Methods: For the continuous measurement of radon concentrations, an RAD7 instrument was installed in four apartments equipped with a ventilation system. The measurements were done for comparison of ventilation types and different ventilation intensities ("high", "middle", "low"). Results: The results confirmed that both mechanical and natural ventilation sufficiently reduced the radon concentration in the apartments. In particular, mechanical ventilation at "high" intensity was the most effective. Natural ventilation combined with mechanical ventilation and then natural ventilation alone were the second and the third most effective, respectively. Conclusions: When using ventilation to reduce indoor radon concentrations, it is most effective to operate mechanical ventilation ("high") or natural ventilation and mechanical ventilation at the same time. In cases where mechanical ventilation is available alone, it is recommended to operate it at a minimum of "middle" intensity.

• Animal Bioscience
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• v.35 no.1
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• pp.138-146
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• 2022

Objective: The objective of the current study was to investigate the influences of conventional (CO) and deep litter (DE) systems on antimicrobial resistance in fecal Escherichia coli (E. coli). Methods: A cross-sectional study was carried out to detect antimicrobial resistance to E. coli in swine fecal samples in CO and DE systems located in western and northeastern Thailand. Individual rectal swab samples were taken only from healthy pigs. A total of 215 individual and healthy pigs were randomly selected for isolation and antimicrobial susceptibility test of E. coli by the disc diffusion method. The test panel included amoxicillin (AMX), colistin, doxycycline (DOX), enrofloxacin, gentamicin (GEN), kanamycin, neomycin (NEO), and trimethoprim-sulfamethoxazole (SXT). Results: There were significant (p<0.05) lower resistance levels for GEN, NEO, and SXT in the DE farms compared to those in the CO farms. There was a lower number of antimicrobial resistance agents (p<0.001) in the DE farms compared to those in the CO farms. This result was consistent with those in western (p<0.01) and northeastern (p<0.01) Thailand. Overall, antibiograms of AMX-SXT and AMX-DOX-SXT were found in the CO (19.09% and 20.91%, respectively) and the DE (16.19% and 24.76%, respectively) farms. No antimicrobial resistance (5.71%) was found and AMX (13.33%) resistant pigs in the DE farms, whereas the pattern of AMX-GEN-SXT (6.36%) and AMX-DOX-GEN-SXT (11.82%) resistant pigs was found in the CO farms. Conclusion: The DE system for pig farming was superior to conventional pig farming by lowering the resistance level of fecal E. coli to GEN, NEO, and SXT, with decreasing the number of antimicrobial resistance agents and inducing a small proportion of pigs to be free from antimicrobial resistance.

• Journal of the Korean Institute of Rural Architecture
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• v.23 no.4
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• pp.38-45
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• 2021

In this study, air quality conditions were identified and analyzed in real time, at the same time, living habits and ventilation methods were maintained in the daily life of residents, and thus, this present study focuses on the lifestyles of residents. Previous studies showed a difference from this study, focusing on the study on the effects of changes in indoor air quality on human health according to the indoor air quality process test standards of the Ministry of Environment. Formaldehyde concentrations exceeded all ventilation standards, but satisfied the organic standards of the Ministry of Environment when ventilation devices and air purifiers were activated. As such, it was investigated that a large amount of formaldehyde emission in the condo is initially ventilated, but a certain concentration is maintained. The change in PM2.5 concentration according to the ventilation method showed a clear difference. As a result of simulating indoor air flow during natural ventilation, the effects of wind speed and wind direction affect the flow rate of indoor air, and indoor polluted air is stagnant even in the presence of wind and is not completely discharged. When the risk assessment results are averaged on the day of measurement, the trends of change between adults and children are almost equivalent, but the results address that children are more sensitive to risk than adults.

• Tribology and Lubricants
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• v.38 no.5
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• pp.205-212
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• 2022

This paper presents experimental measurements of the structural characteristics of a two-pad beam-type gas foil journal bearing and its rotordynamic performance for a high-speed motor-driven turbocompressor. The test bearing had two top foils and two beam foils, each with an arc length of ~180°. Each beam foil was etched to obtain 40 beams with six geometries of different lengths and widths. The insertion of beam foils into the bearing housing produces equivalent beam heights. The structural tests of the bearing with a non-rotating journal revealed a smaller bearing clearance and larger structural stiffness for the load-on-pad configuration than for the load-between-pads configuration. Rotordynamic performance measurements during driving tests up to 100 krpm demonstrated synchronous vibrations and subsynchronous vibrations with large amplitudes. The test was repeated after inserting the shim between the top foil and beam foil to reduce the bearing radial clearance. The reduced bearing clearance resulted in a reduction in the peak amplitude of the synchronous vibrations and an increase in the speed at which the peak amplitude occurred. In addition, the onset speed and amplitude of the subsynchronous vibrations were dramatically increased and diminished, respectively. The rotor coast-down tests at 100 krpm show that the reduction in the bearing clearance extends the time to rotor stop, thus implying an improvement in hydrodynamic pressure generation and a reduction in bearing frictional torque.

• Journal of Information Technology Services
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• v.21 no.3
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• pp.63-72
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• 2022

The extinction crisis of local cities, caused by a population density increase phenomenon in capital regions, directly causes the increase of vacant houses in local cities. According to population and housing census, Gunsan-si has continuously shown increasing trend of vacant houses during 2015 to 2019. In particular, since Gunsan-si is the city which suffers from doughnut effect and industrial decline, problems regrading to vacant house seems to exacerbate. This study aims to provide a foundation of a system which can predict and deal with the building that has high risk of becoming vacant house through implementing a data driven vacant house prediction machine learning model. Methodologically, this study analyzes three types of machine learning model by differing the data components. First model is trained based on building register, individual declared land value, house price and socioeconomic data and second model is trained with the same data as first model but with additional POI(Point of Interest) data. Finally, third model is trained with same data as the second model but with excluding water usage and electricity usage data. As a result, second model shows the best performance based on F1-score. Random Forest, Gradient Boosting Machine, XGBoost and LightGBM which are tree ensemble series, show the best performance as a whole. Additionally, the complexity of the model can be reduced through eliminating independent variables that have correlation coefficient between the variables and vacant house status lower than the 0.1 based on absolute value. Finally, this study suggests XGBoost and LightGBM based machine learning model, which can handle missing values, as final vacant house prediction model.

• Steel and Composite Structures
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• v.46 no.4
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• pp.497-512
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• 2023

Using light weight concrete as infill material in conventional cold-formed steel (CFS) shear wall systems can considerably increase their load bearing capacity, ductility, integrity and fire resistance. The compressive strength of the filler concrete is a key factor affecting the structural behaviour of the composite wall systems, and therefore, achieving maximum compressive strength in lightweight concrete while maintaining its lightweight properties is of significant importance. In this study a new type of optimum polystyrene lightweight concrete (OPLC) with high compressive strength is developed for infill material in composite CFS shear wall systems. To study the seismic behaviour of the OPLC-filled CFS shear wall systems, two full scale wall specimens are tested under cyclic loading condition. The effects of OPLC on load-bearing capacity, failure mode, ductility, energy dissipation capacity, and stiffness degradation of the walls are investigated. It is shown that the use of OPLC as infill in CFS shear walls can considerably improve their seismic performance by: (i) preventing the premature buckling of the stud members, and (ii) changing the dominant failure mode from brittle to ductile thanks to the bond-slip behaviour between OPLC and CFS studs. It is also shown that the design equations proposed by EC8 and ACI 318-14 standards overestimate the shear force capacity of OPLC-filled CFS shear wall systems by up to 80%. This shows it is necessary to propose methods with higher efficiency to predict the capacity of these systems for practical applications.