• Wind and Structures
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• v.34 no.1
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• pp.15-27
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• 2022

This work comes within the framework of the "Benchmark on the Aerodynamics of a Rectangular Cylinder" that investigates a rectangular cylinder of length-to-depth ratio equal to 5. The present study reports and discusses velocity fields acquired using planar Particle Image Velocitmetry for several angles of attack and Reynolds numbers. In particular, for a cylinder depth-based Reynolds number of 2 × 10⁴ and zero incidence angle, the flow features along the lateral (parallel to the freestream) upper and lower surfaces of the cylinder are reported. Using first and second order statistics of the velocity field, the main flow features are discussed, especially the size and location of the time-averaged flow structures and the distribution of the Reynolds stresses. The variation of the flow features with the incidence is also studied considering angles of attack up to 6°. It is shown that the time-averaged flow is fully detached for incidence higher than 2°. For an angle of attack of 0°, the effects of the Reynolds number varying between 5 × 10³ and 2 × 10⁴ are investigated looking at flow statistics. It is shown that the time-averaged location of the reattachment point and the shape and position of the time-averaged main vortex are mostly constant with the Reynolds number. However, the size of the inner region located below the time-averaged shear layer and just downstream the leading edge corner appears to be strongly dependent on the Reynolds number.

• The Journal of the Convergence on Culture Technology
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• v.7 no.4
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• pp.299-304
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• 2021

The purpose of the study was to examine the repertoires of children's songs that early childhood teachers used for new-song-learning activities and to analyze the characteristics of frequently used songs. 120 early childhood teachers in South Korea were recruited to gather the repertoires of children's songs during January and February, 2021. And then, 20 most frequently used songs were selected and analyzed in genre, theme, tonality, meter, musical form, and tone range. SPSS ver. 25.0 was used to calculate the means, standard deviations, frequencies, and percentages. As results, the most frequently used five songs were 'Autumn Road,' 'Winter Wind,' 'Scarecrow Man,' 'Watermelon Party,' and 'Cosmos.' The results of analyses of 20 frequently used songs revealed that the creative songs as genre, seasons as theme, C major as tonality, 4/4 as meter, and ternary form as musical form, and c' - c" along with c' - d" as tone range were the mostly used.

• Wind and Structures
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• v.35 no.4
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• pp.269-285
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• 2022

The pressure-mitigating effects of a high-speed train passing through a tunnel with a partially reduced cross-section are investigated via the numerical approach. A compressible, three-dimensional RNG k-ε turbulence model and a hybrid mesh strategy are adopted to reproduce that event, which is validated by the moving model test. Three step-like tunnel forms and two additional transitions at the tunnel junction are proposed and their aerodynamic performance is compared and scrutinized with a constant cross-sectional tunnel as the benchmark. The results show that the tunnel step is unrelated to the pressure mitigation effects since the case of a double-step tunnel has no advantage in comparison to a single-step tunnel, but the excavated volume is an essential matter. The pressure peaks are reduced at different levels along with the increase of the excavated earth volume and the peaks are either fitted with power or logarithmic function relationships. In addition, the Arc and Oblique-transitions have very limited gaps, and their pressure curves are identical to each other, whereas the Rec-transition leads to relatively lower pressure peaks in C_Pmax, C_Pmin, and ΔC_P, with 5.2%, 4.0%, and 4.1% relieved compared with Oblique-transition. This study could provide guidance for the design of the novel railway tunnel.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.05a
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• pp.557-560
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• 2021

In the face of the COVID-19 pandemic, the Korean Government announced the Korean New Deal as a national development strategy to overcome the economic recession from the pandemic crisis and lead the global action aginst sturctural changes. The Green New Deal related with the energy aims to achieve net-zero emissions and accelerates the transition towards a low-carbon and green economy. To this end, the government plans to promete an increased use of renewable energy in the the society at large. This paper introduces a compact-binary power plant using unused thermal energy and a control system based on Neural Network in order to accelerate the transition towards a low-carbon and green economy. It is expected that he compact-binary power plant accelerate introduction of renewable energy along with solar and wind power.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4B
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• pp.421-428
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• 2008

For last decades, the rapid coastal erosion process spreading along Korean peninsular has become a nuisance especially for tourism and local economy. Global warming and sea-level rise demand persistently new coastal protection strategies against the conventional methods using armored structures. In a view of this, Kweon et al. (2007) has proposed a new type of horizontal steel plates for an ideal candidate as eco-friendly detached breakwater systems for global warming era. The breakwater is composed of piles and horizontal porous plates that was devised for the optimized blockage effects and wave energy dissipations. This system provides outstanding performances as wave barrier and added advantages such as a rapid installation, an easy relocation, a perfect water circulation for the stagnation of pollutions in sheltered regions. The present experimental study focuses on the performance evaluations of the proposed system in wind wave conditions as a wave dissipator and reflector. The reflection, transmission, and energy dissipation of the random waves has been discussed in detail based on a newly proposed relation between wave steepness and a plate width normalized by wave length that are major factors affecting the wave transmission.

• Smart Media Journal
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• v.12 no.5
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• pp.81-87
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• 2023

In this paper, accidents in high-voltage overhead distribution lines, which provide stable power supply in the power system, cause inconvenience in life and disruption of production of companies. 22.9 [kV] high-voltage overhead power distribution lines aim to improve reliability and stability, such as damage caused by rain, snow, wind, etc., or electric shock prevention. Therefore, in order to prevent wire disconnection accidents due to deterioration of electrical conductivity or tensile strength due to corrosion of overhead distribution lines, it is necessary to prevent unexpected accidents in the future through regular inspection and repair. In order to diagnose deterioration due to corrosion of distribution lines, a diagnostic system (measuring instrument) is installed on the wires to monitor the condition of the wires. The manager on the ground receives the measured data through ZigBee wireless communication, controls the diagnosis system through the diagnosis system program, and grasps the condition of the overhead distribution line through the measured data and photographed photos, and predicts the life of the wire along with the visual inspection method. developed a program.

• The Journal of the Convergence on Culture Technology
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• v.9 no.6
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• pp.919-925
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• 2023

Modern drones are equipped with miniaturized mission equipment capable of performing various tasks such as surveillance and reconnaissance. Consequently, these mission equipment are exposed to disturbances like wind loads and motor rotations, which can lead to instability in the operation of the Electro-Optical Targeting System (EOTS). Specifically, simple step inputs for changing the line of sight in EOTS can cause abrupt changes in speed, inducing overshoot and potentially creating instability along with other disturbances. To address this, a velocity profile was designed so that the angular velocity moves in a trapezoidal shape when changing the EOTS line of sight. A Double-loop controller was designed to apply this profile as an input to the external loop receiving position feedback. The system's stability was then compared, and the velocity profile was optimized within a stable range by varying maximum speed and acceleration.

• Journal of Korean Medical classics
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• v.37 no.2
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• pp.11-30
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• 2024

Objectives : Not many studies have been done on the mechanism of the Gangeum or Gangpyoeum method which treats the Soyang Exterior Pattern, nor on which collective or individual roles the Gangeum medicinals play. Therefore in this study, four medicinals categorized as Gangpyoeum which are Jingjie, Fangfeng, Qianghuo, Duhuo, were analyzed in terms of their individual and collective effects. Methods : Content analysis based on the verses in the Donguisusebowon, and medicinal analysis on contents from the Donguibogam, Bencaogangmu, and Benjingshuzheng were carried out followed by a medicinal combination analysis using the InSAm 1.1 program. Results : The four medicinals Jingjie, Fangfeng, Qianghuo, Duhuo had the common effect of normalizing the Wei qi, allowing for unobstructed Qi flow to prevent production of dampness and phlegm, which ultimately lowers Yin[降陰, gangeum] and helps to preserve the Kidney Yin Qi. Jingjie works at the highest position of the upper body; Fangfeng, the most basic medicinal of the Soyangin pattern, works mostly at the upper body although it defends the entire body from wind-dampness. Qianghuo and Duhuo are more or less similar. The difference is that Qianghuo mostly pulls Yang qi upwards while eliminating pathological byproducts, and Duhuo stabilizes the lower body that pulls Wei qi upwards. Conclusions : Analysis on the relationship between Gangpyoeum of the Soyangin pattern and Wei qi, the individual and collective effects of the four Gangpyoeum medicinals were carried out. Further research on other major Soyangin medicinals, along with those of other constitution patterns is anticipated.

• Nuclear Engineering and Technology
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• v.56 no.4
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• pp.1225-1233
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• 2024

Level 3 probabilistic safety assessment (PSA) is performed to calculate radionuclide concentrations and exposure dose resulting from nuclear power plant accidents. To calculate the external exposure dose from the released radioactive materials, the radionuclide concentrations are multiplied by two factors of dose coefficient and a finite cloud dose correction factor (FCDCF), and the obtained values are summed. This indicates that a standard set of FCDCFs is required for external exposure dose calculations. To calculate a standard set of FCDCFs, the effective distance from the release point to the receptor along the wind direction should be predetermined. The TID-24190 document published in 1968 provides equations to calculate FCDCFs and the resultant standard set of FCDCFs. However, it does not provide any explanation on the effective distance required to calculate the standard set of FCDCFs. In 2021, Sandia National Laboratories (SNLs) proposed a method to predetermine finite effective distances depending on the atmospheric stability classes A to F, which results in six standard sets of FCDCFs. Meanwhile, independently of the SNLs, the authors of this paper discovered that an infinite effective distance assumption is a very reasonable approach to calculate one standard set of FCDCFs, and they implemented it into the multi-unit radiological consequence calculator (MURCC) code, which is a post-processor of the level 3 PSA codes. This paper calculates and compares short- and long-range FCDCFs calculated using the TID-24190, SNLs method, and MURCC method, and explains the strength of the MURCC method over the SNLs method. Although six standard sets of FCDCFs are required by the SNLs method, one standard sets of FCDCFs are sufficient by the MURCC method. Additionally, the use of the MURCC method and its resultant FCDCFs for level 3 PSA was strongly recommended.

• Atmosphere
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• v.34 no.2
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• pp.83-95
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• 2024

Atmospheric rivers (ARs) are closely related to local precipitation which can be both beneficial and destructive. Although several studies have evaluated their predictability, there is a lack of studies on East Asian ARs. This study evaluates the prediction skill of East Asian ARs in the Korean Integrated Model (KIM) for 2020~2022 summer. The spatial distribution of AR frequency in KIM is qualitatively similar to the observation but overestimated. In particular, the model errors greatly increase along the boundary of the western North Pacific subtropical high as the forecast lead time increases. When the prediction skills are quantitatively verified by computing the Anomaly Correlation Coefficient and Mean Square Skill Score, the useful prediction skill of daily AR around the Korean Peninsula is found up to 5 days. Such prediction limit is primarily set by the wind field errors with a minor contribution of moisture distribution errors. This result suggests that the improved prediction of atmospheric circulation field can improve the prediction of East Asian summer ARs and the associated precipitation.