• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.6
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• pp.153-160
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• 2020

Columns are one of the most critical parts of a structural system subjected to earthquake excitations. In this regard, extensive experimental studies have been conducted to evaluate the effect of fiber reinforced polymer (FRP) wrapping on the seismic performance of reinforced concrete (RC) columns. Among them, many studies focused on the behavior of circular or square RC columns strengthened with CFRP or GFRP sheets. Since the cross-sectional shape affects confinement by FRP wrapping, its strengthening effect and final damage pattern may differ with shapes. In this study, a series of cyclic tests was conducted to investigate the seismic behavior of rectangular reinforced concrete columns strengthened with basalt-based fiber reinforced polymer (BFRP) sheets and composite fiber panels. The result shows that the effect of strengthening is not significant, and it implies a little increase of confinement by BFRP sheets and composite fiber panels, which is considered partly due to the cross-sectional shape of the columns.

• Journal of radiological science and technology
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• v.44 no.4
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• pp.327-333
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• 2021

Magnetic resonance imaging(MRI) uses strong magnetic field to image the cross-section of human body and has excellent image quality with no risk of radiation exposure. Because of above-mentioned advantages, MRI has been widely used in clinical fields. However, the noise generated in MRI degrades the quality of medical images and has a negative effect on quick and accurate diagnosis. In particular, examining a object with a detailed structure such as brain, image quality degradation becomes a problem for diagnosis. Therefore, in this study, we acquired T2 weighted 3D data of multiple sclerosis disease using BrainWeb simulation program, and used quantitative evaluation factors to find appropriate slice thickness among 1, 3, 5, and 7 mm. Coefficient of variation and contrast to noise ratio were calculated to evaluate the noise level, and root mean square error and peak signal to noise ratio were used to evaluate the similarity with the reference image. As a result, the noise level decreased as the slice thickness increased, while the similarity decreased after 5 mm. In conclusion, as the slice thickness increases, the noise is reduced and the image quality is improved. However, since the edge signal is lost due to overlapped signal, it is considered that selecting appropriate slice thickness is necessary.

• Journal of Preventive Medicine and Public Health
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• v.55 no.6
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• pp.578-585
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• 2022

Objectives: This study aimed to adapt the survey questionnaire designed by Moens et al. (2021) and determine the validity and reliability of the Arabic version of the survey in a sample of the Saudi population experiencing teleworking. Methods: The questionnaire includes 2 sections. The first consists of 13 items measuring the impact of extended telework during the coronavirus disease 2019 (COVID-19) crisis. The second section includes 6 items measuring the impact of the COVID-19 crisis on selfview of telework and digital meetings. The survey instrument was translated based on the guidelines for the cultural adaptation of self-administrated measures. Results: The reliability of the questionnaire responses was measured by Cronbach's alpha. The construct validity was checked through exploratory factor analysis followed by confirmatory factor analysis (CFA) to further assess the factor structure. CFA revealed that the model had excellent fit (root mean square error of approximation, 0.00; comparative fit index, 1.0; Tucker-Lewis index, 1; standardized root mean squared residual, 0.0). Conclusions: The Arabic version of the teleworking questionnaire had high reliability and good validity in assessing experiences and perceptions toward teleworking. While the validated survey examined perceptions and experiences during COVID-19, its use can be extended to capture experiences and perceptions during different crises.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.1
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• pp.19-29
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• 2023

An ultra-high strength prestressed prismatic beam of 100 MPa in compressive strength was developed by increasing the watertightness of concrete by utilizing centrifugal molding processes without adding expensive admixtures such as silica fume. The ultra-high strength centrifugal shaped square beam installed on the wall is composited with the upper slab concrete and then subjected to a service load. Horizontal shear stress is generated by bending between the centrifugal molding beam and the floor plate, which causes the beam and floor plate to perform composite behavior through shear connections such as studs and rebars. In this study, a flexural load test was performed on a mock-up specimen that was synthesized by fabricating an RC slab on top of a 100 MPa-class centrifugal shaped beam produced at the factory. proven reliability.

• Journal of the Korea Institute of Military Science and Technology
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• v.26 no.3
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• pp.246-251
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• 2023

RADAR(Radio Detection and Ranging) is an important system for surveillance and reconnaissance by detecting a reflected signal which obtains the range from the radar to the target, and the velocity of the target. The magnitude of the reflected signal varies due to the radar cross section of the target, characteristic of the transmission and reception antenna, distance between the radar and the target, and power and wavelength of the transmitted signal. Thus, the RCS is the important characteristic of the target to determine if the target can be observed by the RADAR system. It is based on the material and shape of the target. We have measured the reflection signal of a simple square-shaped (20 × 20 cm) target made of a new material, a gallium-based liquid metal alloy and compared that of well-known metals including copper, aluminum. The magnitude of reflected signal of the aluminum target was the largest and it was 2.4 times larger than that of the liquid metal target. We also investigated the effect of the shape by measuring reflectance of the F-22 3D model(~1/95 ratio) target covered with/without copper, aluminium, and liquid metal. The largest magnitude of the reflected signal measured from side-view with the copper-covered F-22 model was 2.6 times greater than that of liquid metal. The reflectance study of the liquid metal would be helpful for liquid metal-based frequency selective surface or metamaterials.

• Journal of Korean Public Health Nursing
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• v.23 no.2
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• pp.273-284
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• 2009

Purpose: The study examined obesity conditions and related factors in middle aged Korean women who had been diagnosed as obese based body mass index (BMI) or waist circumference (WC) measurement. Presently, BMI alone, WC alone, or BMI + WC were used as obesity measures. Methods: Subjects were 488 women 40~64 years of age living in one city, Korea. Structured questionnaires concerning general characteristics, health behavior practices, and chronic disease history were completed by each subject. Results: The proportions of obesity were 42.4% by BMI, 39.3% by WC, and 51.3% by the combination of both measurements. Chi-square test revealed significant associations of obesity with age, education level, menopausal status, frequency of excessive eating, and history of diabetes mellitus or hypertension. These associations were similar for the three measurement schemes. There was significant positive relationship between BMI and WC, whereas the relationship between BMI and WHR (waist-hip ratio) was not significant. Conclusions: The combination of BMI and WC measurement may be a valid way to evaluate the obesity status in middle-aged women. Developing an obesity management program that includes control of excessive eating, and consideration of menopausal status and history of chronic diseases would be prudent.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.36 no.5
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• pp.283-293
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• 2023

With the steady increase in the annual number of earthquakes in South Korea, the need to apply seismic reinforcement on public facilities has recently increased. To reinforce seismic capacity, spaced full-column-height steel bars are attached to column faces. In this study, nonlinear finite element analysis was conducted to analyze the effect of external reinforcement steel bars on the seismic capacity of RC columns with a square or rectangular cross-section. For verification, the analysis results were compared with test results. Results showed that the finite element analysis reasonably predicted the actual structural behavior of RC columns with steel bars. In addition, both the analysis and the test results showed that the failure mode was converted from brittle failure to ductile fracture, owing to the external reinforcement steel bars. Both loading capacity and ductility were increased as well. Therefore, the external reinforcement steel bar can effectively enhance the seismic capacity of existing RC columns. This study is expected to contribute to relevant research areas such as the development of design methods.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.38 no.3
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• pp.175-185
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• 2020

Three-dimensional registration is a process of matching data with or without a coordinate system to a reference coordinate system, which is used in various fields such as the absolute orientation of photogrammetry and data combining for producing precise road maps. Three-dimensional registration is divided into a method using points and a method using linear features. In the case of using points, it is difficult to find the same conjugate point when having different spatial resolutions. On the other hand, the use of linear feature has the advantage that the three-dimensional registration is possible by using not only the case where the spatial resolution is different but also the conjugate linear feature that is not the same starting point and ending point in point cloud type data. In this study, we proposed a method to determine the scale and the three-dimensional translation after determining the three-dimensional rotation angle between two data using quaternion to perform three-dimensional registration using linear features. For the verification of the proposed method, three-dimensional registration was performed using the linear features constructed an indoor and the linear features acquired through the terrestrial mobile mapping system in an outdoor environment. The experimental results showed that the mean square root error was 0.001054m and 0.000936m, respectively, when the scale was fixed and if not fixed, using indoor data. The results of the three-dimensional transformation in the 500m section using outdoor data showed that the mean square root error was 0.09412m when the six linear features were used, and the accuracy for producing precision maps was satisfied. In addition, in the experiment where the number of linear features was changed, it was found that nine linear features were sufficient for high-precision 3D transformation through almost no change in the root mean square error even when nine linear features or more linear features were used.

• Journal of Korean Society of Steel Construction
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• v.25 no.1
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• pp.35-45
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• 2013

The concrete-filled tube column has the excellent structural performance. But it is difficult to connect with column and beam because of closed section. It suggests that pipe should be produced by welding two sides together where two shapes are joined after a channel is pre-welded onto the three sides in order to form an internal diaphragm. The upper diaphragm of the connection used the horizontal plate and the lower diaphragm used the Vertical plate. This research performed 6 monotonic tension experiments describing the connection upside and downside in order to evaluate the structural capability of the offered connection. And the cyclic loading experiment was performed about 2 T-Type column to beam connections. As to the experimental result edge cutting geometry, there was no big effect. An increase in the number of holes of the plate ultimate strength was increased by 5% and The thickness of the plate increases, the maximum strength was increased by 4%. T-Type connections until it reaches the plastic moment showed a stable behavior.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.2
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• pp.130-137
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• 2017

Due to the economic growth and development of construction technology, a role of foundation to resist heavy loads has been increased. In this present study to improve the structural performance of reinforced concrete pile, the precast HPC pile reinforced with rebar and filling concrete was developed and the strength of pile was predicted based on the limit state design method. The safety of HPC pile strength was evaluated by comparing with the design values. The geometry of HPC pile is a decagon cross section with a maximum width of 500 mm and a minimum width of 475 mm, and the hollow head of pile thickness is 70 mm. The inner area of the hollow head part was made as the square ribbed shape presented in the limit state design code in order to achieve horizontal shear strength between pile concrete and filling concrete. From the shear test results, it was found that the stable shear strength were secured without abrupt failure until maximum load stage despite the shear cracks was found. Shear strength is 135% and 119% higher than that of design value calculated from limit state design code. The driving test results of HPC pile according to the presence of additional reinforcement showed the outstanding crack resistance against impact loads condition. From the bending test results the flexural load between PHC pile and HPC pile was 1.51 times and 1.48 times higher than that of the design flexural load of conventional PHC pile.