• Journal of Korean Tunnelling and Underground Space Association
• /
• v.23 no.1
• /
• pp.25-36
• /
• 2021

Hydrogen in hydrogen-electric vehicles has a wide range of combustion and explosion ranges, and is a combustible gas with a very fast flame propagation speed, so it has the risk of leakage, diffusion, ignition, and explosion. The fuel tank has a Thermally active Pressure Relief Device (TPRD) to reduce the risk of explosion and other explosions, and in the event of an accident, hydrogen inside the tank is released outside before an explosion or fire occurs. However, if an accident occurs in a semi-closed space such as an underground parking lot, the flow of air flow is smaller than the open space, which can cause the concentration of hydrogen gas emitted from the TPRD to accumulate above the explosion limit. Therefore, in this study, the leakage rate and concentration of hydrogen over time were analyzed according to the diameter of the nozzle of the TPRD. The diameter of the nozzle was considered to be 1 mm, 2.5 mm and 5 mm, and ccording to the diameter of the nozzle, the concentration of hydrogen in the underground parking lot increases in a faster time with the diameter of the nozzle, and the maximum value is also analyzed to be larger with the diameter of the nozzle. In underground parking lots where air currents are stagnant, hydrogen concentrations above LFL (Lowe Flammability Limit) were analyzed to be distributed around the nozzle, and it was analyzed that they did not exceed UFL (Upper Flammability Limit).

• Journal of Korea Water Resources Association
• /
• v.55 no.1
• /
• pp.71-84
• /
• 2022

The objective of this study is to develop a two-dimensional (2D) flood model that can perform accurate flood analysis with simple input data. The 2D flood inundation models currently used to create flood forecast maps require complex input data and grid generation tools. This sometimes requires a lot of time and effort for flood modeling, and there may be difficulties in constructing input data depending on the situation. In order to compensate for these shortcomings, in this study, a grid-based model that can derive accurate and rapid flood analysis by reflecting correct topography as simple input data was developed. The calculation efficiency was improved by extending the existing 2×2 sub-grid model to a 5×5. In order to examine the accuracy and applicability of the model, it was applied to the Gamcheon Basin where both urban and river flooding occurred due to Typhoon Rusa. For efficient flood analysis according to user's selection, flood wave propagation patterns, accuracy and execution time according to grid size and number of sub-grids were investigated. The developed model is expected to be highly useful for flood disaster mapping as it can present the results of flooding analysis for various situations, from the flood inundation map showing accurate flooding to the flood risk map showing only approximate flooding.

• The Journal of the Korea Contents Association
• /
• v.22 no.4
• /
• pp.337-351
• /
• 2022

With the full spread and rapid development of social media, the trend of decentralization of social media information propagation is becoming clearer day by day, and the segmentation of time by audiences using social media information is clearly progressing. Therefore, this study aims to study the influence relationship between social media attitudes toward fake news, social capital, risk perception, and discriminant intentions based on existing studies. Accordingly, the research model presented related research questions and organized a questionnaire to collect a total of 500 valid surveys. The SPSS 26.0 program and the AMOS 24.0 program were used to analyze the data. The research results are as follows. First, the more positive the user's attitude towards the fake news identification intention of social media, the more they want to use various methods or tools to identify the authenticity of online information. Second, the more positive the user's attitude towards social media fake news, the more aware of the potential threats social media fake news poses to their own physical, psychological, financial and so on. At the same time, by raising one's own awareness of the dangers, counterintelligence intentions against fake news on social media will also increase. Third, the richer the social capital the user has, the stronger the information literacy, and therefore the stronger the identification intention of social media fake news. Fourth, the higher the value of social capital Chinese users have, the greater the damage they have suffered from fake news, and the higher the risk awareness of fake news to protect their interests. Fifth, it means that Chinese users recognized information suspected of social media and took corresponding measures.

• Journal of the Society of Disaster Information
• /
• v.18 no.1
• /
• pp.38-50
• /
• 2022

Purpose: The goal of this research is to create a numerical analytic database that may assist fire prevention managers and building officials in prioritizing items that need to be addressed in order to improve evacuation safety performance while working within a constrained budget and time frame. Method: It was carried out utilizing the CFD Tool, a quantitative evaluation approach, to assess evacuation safety. One direct staircase-type apartment houses and one corridor-type apartment were chosen to make it. Result: In the fire compartment category, Apartment A's evacuation time was around 130 percent longer than that of sprinkler facilities. Conclusion: Fire prevention managers and building officials feel that starting with a single level and implementing "dwelling unit separations" will increase evacuation safety, and that maintaining fire compartments and sprinkler systems at all times will be effective. Because of the limited characteristics of smoke propagation in corridor-type apartments compared to direct staircase-type flats, it is thought that fire extinguishing equipment should be addressed.

• Journal of the Korean Geotechnical Society
• /
• v.22 no.8
• /
• pp.43-54
• /
• 2006

The scope of this paper covers the applications of bender element tests in consolidation, tomography, and liquefaction. Loading and unloading time during consolidation are evaluated based on shear wave velocity. As S-wave velocity is dependent on effective stress, the loading step may be determined. However, cautions are required due to the different mechanism between the settlement and effective stress criteria. The stress history may be evaluated because the S-wave shows the cement controlled regime and stress controlled regimes. A fixed frame complemented with bender elements permits S-wave tomography The tomography system is tested at low confinement within a true triaxial cell. Results show that shear wave velocity tomography permits monitoring changes in the velocity field which is related to the average effective stress. To monitor the liquefaction phenomenon, S-wave trans-illumination is implemented with a high repetition rate to provide detailed information on the evolution of shear stiffness during liquefaction. The evolution of shear wave propagation velocity and attenuation parallel the time-history of excess pore pressure during liquefaction. Applications discussed in this paper show that bender elements can be a very effective tool for the detection of shear waves in the laboratory.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.1A
• /
• pp.75-89
• /
• 2006

This paper presents a practical and realistic Life-Cycle Cost (LCC) optimum design methodology of steel bridges considering time effect of bridge reliability under environmental stressors such as corrosion and heavy truck traffics. The LCC functions considered in the LCC optimization consist of initial cost, expected life-cycle maintenance cost and expected life-cycle rehabilitation costs including repair/replacement costs, loss of contents or fatality and injury losses, road user costs, and indirect socio-economic losses. For the assessment of the life-cycle rehabilitation costs, the annual probability of failure which depends upon the prior and updated load and resistance histories should be accounted for. For the purpose, Nowak live load model and a modified corrosion propagation model considering corrosion initiation, corrosion rate, and repainting effect are adopted in this study. The proposed methodology is applied to the LCC optimum design problem of an actual steel box girder bridge with 3 continuous spans (40 m+50 m+40 m=130 m), and various sensitivity analyses of types of steel, local corrosion environments, average daily traffic volume, and discount rates are performed to investigate the effects of various design parameters and conditions on the LCC-effectiveness. From the numerical investigation, it has been observed that local corrosion environments and the number of truck traffics significantly influence the LCC-effective optimum design of steel bridges, and thus realized that these conditions should be considered as crucial parameters for the optimum LCC-effective design.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.25 no.4
• /
• pp.245-257
• /
• 2023

The representative crop in the Republic of Korea, rice, is cultivated over extensive areas every year, which resulting in reduced resistance to pests and diseases. One of the major rice diseases, rice blast disease, can lead to a significant decrease in yields when it occurs on a large scale, necessitating early detection and effective control of rice blast disease. Drone-based crop monitoring techniques are valuable for detecting abnormal growth, but frequent image capture for potential rice blast disease occurrences can consume significant labor and resources. The purpose of this study is to early detect rice blast disease using remote sensing data, such as drone and satellite images, along with weather data. Satellite images was helpful in identifying rice cultivation fields. Effective detection of paddy fields was achieved by utilizing vegetation and water indices. Subsequently, air temperature, relative humidity, and number of rainy days were used to calculate the risk of rice blast disease occurrence. An increase in the risk of disease occurrence implies a higher likelihood of disease development, and drone measurements perform at this time. Spectral reflectance changes in the red and near-infrared wavelength regions were observed at the locations where rice blast disease occurred. Clusters with low vegetation index values were observed at locations where rice blast disease occurred, and the time series data for drone images allowed for tracking the spread of the disease from these points. Finally, drone images captured before harvesting was used to generate spatial information on the incidence of rice blast disease in each field.

• Journal of the Korean Geotechnical Society
• /
• v.39 no.12
• /
• pp.75-91
• /
• 2023

In this study, we explore the use of ground penetrating radar (GPR) for the nondestructive survey of subsurface conduits, focusing on the challenges posed by multichannel environments. A key concern is the shadow regions created by conduits, which significantly impact survey results. The shadow regions, which are influenced by conduit position and diameter, hinder signal propagation, thereby making detection within these regions challenging. Using finite-difference time-domain numerical analysis, we examined the characteristics of conduit signals, which typically manifest in hyperbolic patterns. Particularly, we investigated three conduit arrangements: horizontal, vertical, and diagonal. Automatic gain control was applied to amplify the signals, enabling the analysis of variations in shadow regions and signal characteristics for each arrangement. In the horizontal arrangement, the proximity of the two conduits resulted in the emergence of a new hyperbolic pattern between the existing conduits. In the vertical arrangement, the lower conduit could be detected using hyperbolic signals on either side, but the detection was challenging when the upper conduit diameter exceeded that of the lower conduit. In the diagonal arrangement, signal characteristics varied based on the position of shadow regions relative to the detection range of the equipment. Asymmetrical signal patterns were observed when the shadow regions fell within the detection range, whereas the signals of the two conduits were minimally impacted when the shadow regions were outside the detection range. This study provides vital insights into accurately detecting and characterizing subsurface multichannel conduits using GPR-a significant contribution to the field of subsurface exploration and management.

• Korean journal of applied entomology
• /
• v.51 no.1
• /
• pp.9-18
• /
• 2012

The size of infective $Steinernema$ $arenarium$ juveniles is variable and ranges from 724 to 1408 ${\mu}m$. Effects of harvest time and infective juvenile size on pathogenicity, development, and reproduction were examined in the last instar of the great wax moth, $Galleria$ $mellonella$. Harvest time of infective juveniles (IJs) of $S.$ $arenarium$ affected pathogenicity. IJs harvested at the 10th day from trapping were more pathogenic than those harvested the 3rd day from trapping. Mortality of $G$. mellonella also depending on harvest time, $i.e$, 100% died within 48h when IJs were harvested at the 10th day, without relation to size. However, mortality was 40% in the small size group (SSG) compared with 18% in the large size group (LSG) within 48h when IJs were harvested at the 3rd day. Establishment of $S.$ $arenarium$ within the host was different depending on IJ size. The number of established IJs was 1.8 in the SSG, 3.3 in the LSG, and 3.2 in the mixed size group (MSG) when IJs were harvested at the 3rd day, and 5.3 in the SSG, 7.4 in the LSG, and 7.6 in the MSG when IJs were harvested at the 10th day. The length of the female adult was 7,070.5 ${\mu}m$ in the SSG and 7,893.9 ${\mu}m$ in the LSG and that of the male was 1,460.5 ${\mu}m$ in the SSG and 1,688.2 ${\mu}m$ in the LSG when IJs were harvested at the 3rd day. The length of the female adult was 7,573.6 ${\mu}m$ in the SSG and 8,305.4 ${\mu}m$ in the LSG and that of the male adult was 1,733.4 ${\mu}m$ in the SSG and 1,794.4 ${\mu}m$ in the LSG when IJs were harvested at the 10th day. Harvest time and size of IJs did not influence numbers of progeny or size of IJS.

• Korean Journal of Medicinal Crop Science
• /
• v.1 no.1
• /
• pp.16-23
• /
• 1993

Seeds of Acanthopanx plants need about 2 years to germinate after sowing even if full matured fruits were harvested. I leave a room for doubt that this phenomenon could be brought by the immatured embryo in seed. If it is true, stratification method for the seed propagation of Acanthopanax plants would be used more effectively to promote the growth of embryo in relatively short time. Before stratification, seeds were devided into two parts. One of them was treated for 24hrs in the concentration of $GA_3$ 100 ppm. After stratification of non-treated and treated seeds, seeds for microtechnique were taken on interval of one month for three months, and fixed in Farmer's solution. The seed sizes of Acanthopanax plants were in biggest order A. sessiliflorus, A. seoulense, A. chiisanensis, A. koreanum and A. sieboldianum. The dehiscence phenomenon of seed coat didn't show in most of the seeds that stratified, but A. koreanum only dehisced in seeds treated in $GA_3$ 100ppm. The embryos of the stratified seeds that treated in $GA_3$ showed nomal growth, complete cotyledons and procambium in hypocotyl in any species, but the non-treated seeds could not expect the germination after sowing due to poor growing of the embryo in all species. In view of the results so far achieved, it has taken long times from sowing to germinate because the seed of Acanthopanax plants has immatured embryo.