• Science of Emotion and Sensibility
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• v.24 no.1
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• pp.37-44
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• 2021

A study was conducted on the effects of improving concentration by obscuring the peripheral vision using a blindfold that only covers the left and right sides of the field of view. The blindfold was trapezoidal in shape (5 × 4.8 cm in length and width) and was fixed to the left and right sides of the glasses with fixing clips. The material was a black-colored polypropylene (PP) and weighed 2.3 g including the clip. Qualitative and quantitative evaluations were performed on 50 healthy college students during the 15 days of using a blindfold. The qualitative analysis was performed utilizing a questionnaire regarding the improvement of concentration and the structure of the blindfold. EEG was measured while watching a learning video that required attention for quantitative analysis, and signal power and ERD/S analyses were performed for the mid β band (15-20 Hz) at the F4 position, which was the frontal lobe. The results showed that 40 of the 50 people reported improved concentration when they wore a vision shield, and 80% of the total subjects found it to be effective. From the quantitative evaluation, the ERS peak (p = 0.023) and the ERD + ERS peak value showed a significant difference (p = 0.017). In conclusion, concentration still improved even if only the left and right visual fields were used. Thus, it is expected that blindfolding could be used in various environments that require concentration.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.1
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• pp.1-11
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• 2021

POGO is a dynamic axial instability phenomenon that occurs in liquid-propelled rockets. As the natural frequencies of the fuselage and those of the propellant supply system become closer, the entire system will become unstable. To predict POGO, the propellant (oxidant and fuel) tank in the first stage is modeled as a shell element, and the remaining components, the engine and the upper part, are modeled as mass-spring, and structural analysis is performed. The transmission line model is used to predict the pressure and flow perturbation of the propellant supply system. In this paper, the closed-loop transfer function is constructed by integrating the fuselage structure and fluid modeling as described above. The pogo suppressor consists of a branch pipe and an accumulator that absorbs pressure fluctuations in a passive manner and is located in the middle of the propellant supply system. The design parameters for its design optimization to suppress the decay phenomenon are set as the diameter, length of the branch pipe, and accumulator. Multiple-objective function optimization is performed by setting the energy minimization of the closed loop transfer function in terms of to the mass of the pogo suppressor and that of the propellant as the objective function.

• Journal of Korea Water Resources Association
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• v.54 no.5
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• pp.289-299
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• 2021

This study analyzes bifurcation characteristics of the Seolmacheon experimental catchment by extracting the shape variation of channel network due to variable scale of source basin or threshold area. As the area of source basin decreases, a bifurcation process of channel network occurs within the basin of interest, resulting in the elongation of channel network (increase of total channel length) as well as the expansion of channel network (increase of the source number). In the former case, the elongation of channel reaches overwhelms the generation of sources, whereas, in the latter case, the drainage path network tends to fulfill the inner space of the basin of interest reflecting the opposite trend. Therefore, scale invariance of natural channel network could be expressed to be a balanced geomorphologic feature between the elongation of channel network and the expansion of channel network due to decrease of source basin scale. The bifurcation structure of the Seolmacheon experimental catchment can be characterized by the coexistence of the elongation and scale invariance of channel network, and thus a further study is required to find out which factor is more crucial to rainfall transformation into runoff.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.6
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• pp.419-426
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• 2020

The structural design of the steel eccentrically braced frame (EBF) was developed and analyzed in this study through multiobjective optimization (MOO). For the optimal design, NSGA-II which is one of the genetic algorithms was utilized. The amount of structure and interfloor displacement were selected as the objective functions of the MOO. The constraints include strength ratio and rotation angle of the link, which are required by structural standards and have forms of the penalty function such that the values of the objective functions increase drastically when a condition is violated. The regulations in the code provision for the EBF system are based on the concept of capacity design, that is, only the link members are allowed to yield, whereas the remaining members are intended to withstand the member forces within their elastic ranges. However, although the pareto front obtained from MOO satisfies the regulations in the code provision, the actual nonlinear behavior shows that the plastic deformation is concentrated in the link member of a certain story, resulting in the formation of a soft story, which violates the capacity design concept in the design code. To address this problem, another constraint based on the Eurocode was added to ensure that the maximum values of the shear overstrength factors of all links did not exceed 1.25 times the minimum values. When this constraint was added, it was observed that the resulting pareto front complied with both the design regulations and capacity design concept. Ratios of the link length to beam span ranged from 10% to 14%, which was within the category of shear links. The overall design is dominated by the constraint on the link's overstrength factor ratio. Design characteristics required by the design code, such as interstory drift and member strength ratios, were conservatively compared to the allowable values.

• Ecology and Resilient Infrastructure
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• v.7 no.4
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• pp.308-319
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• 2020

In this study, the field applicability of the recently constructed multifunctional fishway in Seomunbo, Yeongcheon-si, and Gyeongsangbuk-do were examined. The analysis variables were R/C slab (S1) and R/C+S/C slab (S2), the underground passage standard areas (width × length) were 1.4 m × 0.2 m, 1.4 m × 0.3 m, and 1.4 m × 0.6 m, and the flow velocities were 0.8, 1.2, and 1.6 m/s. As a result of the analysis, the safety of the design of Seomunbo was evaluated. The analysis showed compared to the Seomoon Weir fishway, the maximum stress of S2 decreased by 24 - 32%, the bending moment of the underground passage decreased by 16 - 33%, the maximum stress of the sidewall decreased by 20 - 36%. In addition, the bending moment of the upper slab decreased by 17 - 33%, the maximum stress of the upper slab decreased by 9 - 28%, and the bending moment decreased by 19 - 33%. Complementation was required in the following percentages: 18% and 14% for the maximum stress and bending moment of the underground passage, respectively, 15% and 17% for the maximum sidewall stress and bending moment, respectively, and 11% and 16% for the upper slab maximum stress and bending moment, respectively. The results showed that S2 was superior to that of the Seomoon Weir fishway, and the underground passage size of 1.4 m × 0.3 m was superior to those of 1.4 m × 0.2 m and 1.4 m × 0.6 m, and R/C+S/C slab was superior to that of R/C slab. The findings are expected to be useful for constructing and designing the multifunctional fishway.

• Journal of the Korean GEO-environmental Society
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• v.12 no.1
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• pp.41-50
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• 2011

Three-dimensional(3D) numerical analyses have been conducted to study the behaviour of a single pile to adjacent tunnelling conducted in the lateral direction of the pile. In the numerical analyses, the interaction between the tunnel, the pile and the soil next to the pile has been analysed. The study includes the pile settlement, the relative shear displacement between the pile and the soil, the shear stresses at the soil next to the pile and the axial force on the pile. In particular, the shear stress transfer mechanism along the pile related to the tunnel advancement has been rigorously analysed. Due to changes in the relative shear displacement between the pile and the soil next to the pile during the tunnel advancement, the shear stress and the axial force distributions along the pile have been changed. Downward shear stress developed above the tunnel springline (Z/L=0.0-0.7~0.8), while upward shear stress is mobilised below the tunnel springline (Z/L=0.7~0.8-1.0) resulting in compressive force on the pile, where Z is the pile location and L is the pile length. Maximum compressive force of about $0.475P_a$ was developed on the pile after completion of tunnel advancement, where $P_a$ is the allowable pile capacity. Some insights into the pile behaviour to tunnelling obtained from the numerical analyses will be reported and discussed.

• Korean Journal of Environmental Biology
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• v.38 no.4
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• pp.554-562
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• 2020

Tremex fuscicornis (Siricidae), known as the xylophagous horntail, and Leucospis japonica (Leucospidae), known as the parasitoid wasp, are wood-boring wasps belonging to the order Hymenoptera. These insects are interesting sources of biological inspiration for the development of drilling mechanisms. To study the biomimicry aspects, the morphological characters of the ovipositor of T. fuscicornis and L. japonica were analyzed using a stereoscopic microscope, a field emission scanning electron microscope, and an optical microscope. There were many differences in the ovipositors between the two species, such as shape, length, surface structure, and arrangement of the teeth. Evenly arranged teeth were developed at the tip of both the dorsal valve and the ventral valve of the ovipositor of T. fuscicornis and looked like a rotating drill bit. In contrast, in L. japonica, the teeth, which looked like a saw, were found only on the ventral valve. Moreover, the tip of the ovipositor of T. fuscicornis was symmetrically divided into four parts, while that of L. japonica was divided into three parts having a 2:1:1 ratio. However, in the case of T. fuscicornis, after the 14th tooth, four parts melded into three parts maintaining a 2:1:1 ratio, and a dovetail joint was found on the horizontal cross-section of the ovipositor that allowed vertical movement for making a hole. These morphological differences of the ovipositor may be due to the insects' lifestyles and phylogenetic distance. Finally, zinc was commonly found at the tip of the ovipositors of both species, a probable result of ecological adaptation created by drilling wood.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.39 no.3
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• pp.179-186
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• 2021

In general, the daily safety inspection activities, which investigate damages in structures and measures the size of the damage, have been relied heavily on the visual inspection so far. Since the probe of the condition and performance of facilities by such personnel is often dependent on the subjective judgment of the investigator, the consistency and repeatability of the probing results may reduce. Particularly, damage located in a difficult-to-reach place depends mainly on experience with the naked eye, and an unsafe method using a ladder has mainly applied when necessary. Therefore, in this study, we tried to propose a way of using images that can reduce the deviation between safety inspection investigators, enhance objectivity, and improve the safety of workers. In this study, we have applied homographic transformation as a method of correcting the image. As a result of analyzing the size of the damage in the corrected image of the test subject, it confirms that the accuracy of measuring the magnitude of the damage can satisfy the target levels of 5.0mm and 0.005m², the target accuracy levels. As a result of the field verification test to which the proposed image correction technique applied, the coefficient of variation of the crack length in the structure decreased from 5.4~7.0% to 0.072~0.12%, and that of the damaged area from 10.9% to 1.6%. It confirms that the measurement accuracy is improved. Therefore, it is expected that this study on the image utilization technique in safety inspection activities can increase the accuracy of damage measurement and improve the reliability of the safety inspection reports and exterior survey drawings.

• Korean Journal of Ecology and Environment
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• v.53 no.4
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• pp.445-452
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• 2020

In this study, we carried out a distribution and migration boundary lines of chum salmon (Oncorhynchus keta) in the Milyang River. We measured the total length of dead chum salmons. As a results, 40 chum salmons were found during the study period, 25 dead salmons and 15 alive individuals. The ratio of female was 64%. We verified the migration boundary lines of chum salmons based on a sighting survey until detecting a structure that chum salmons are not able to migrate upstream. We discovered that chum salmons were not able to migrate up to 13 km in a mainstream of the Milyang River and up to 12 km in the Danjang stream (a tributary of the Milayang River) from upstream of the Yerim Bridge. Therefore, our results indicate that Milyang River should improve a river connectivity by demolishing weirs that disturb chum salmon's migration or installing appropriate fishways. Also, effective legislations are needed to retain naturality in spawning ground and micro-habitats to increase the survival rate of parrs and smolts.

• Journal of the Korean Society for information Management
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• v.39 no.2
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• pp.233-254
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• 2022

Link reduction algorithms such as pathfinder network are the widely used methods to overcome problems with the visualization of weighted networks for knowledge domain analysis. This study proposed NetRSQ, an indicator to measure the goodness of fit of a link reduction algorithm for the network visualization. NetRSQ is developed to calculate the fitness of a network based on the rank correlation between the path length and the degree of association between entities. The validity of NetRSQ was investigated with data from previous research which qualitatively evaluated several network generation algorithms. As the primary test result, the higher degree of NetRSQ appeared in the network with better intellectual structures in the quality evaluation of networks built by various methods. The performance of 4 link reduction algorithms was tested in 40 datasets from various domains and compared with NetRSQ. The test shows that there is no specific link reduction algorithm that performs better over others in all cases. Therefore, the NetRSQ can be a useful tool as a basis of reliability to select the most fitting algorithm for the network visualization of intellectual structures.