• Journal of Korean Society of Disaster and Security
• /
• v.12 no.1
• /
• pp.1-9
• /
• 2019

The basic analysis of Soil and structural mechanics for the bridge substructure affected by the flow of water is sufficient in the construction of such bridges, but the stability of scour resulting from hydraulic phenomena is insufficient. In addition, it is not enough to estimate the scour depth of the bridge which reflects the watershed characteristics of the domestic river because it uses the formula for calculating the scour depth of the overseas piers in calculating the scour depth of the bridge. In this study, the application of the CSU (1993) formula, which is currently applied to the national river design criteria, was reviewed between the two formulas after calculating the scour after calculating the scour by applying another bridge deck scour calculation formula to take into account the uncertainty in the calculation of scour. In this study, in addition to the CSU (1993) formula, which is currently applied to Korean river design criteria, another scour depth calculation formula is applied to calculate uncertainty in scour depth calculation, was reviewed between the two formulas. The review confirmed that the SSE (%) showed a difference of at least 2.08%, up to 91.23%, and SSEn(%) at least 0.19%, up to 415.91%, when compared to the measured depth of the pier based on the hydraulic model experiment and the depth of the pier calculated with the nine scour depth formulas in use. In other words, it is confirmed that there are many differences between the scouring formulas of piers. The results of this study are expected to be used to estimate scour depth in future river design.

• Journal of Korea Water Resources Association
• /
• v.55 no.12
• /
• pp.1091-1104
• /
• 2022

Climate change is predicted to increase the frequency and intensity of rainfall worldwide, and the pattern is changing due to inundation damage in urban areas due to rapid urbanization and industrialization. Accordingly, the impact assessment of climate change is mentioned as a very important factor in urban planning, and the World Meteorological Organization (WMO) is emphasizing the need for an impact forecast that considers the social and economic impacts that may arise from meteorological phenomena. In particular, in terms of traffic, the degradation of transport systems due to urban flooding is the most detrimental factor to society and is estimated to be around £100k per hour per major road affected. However, in the case of Korea, even if accurate forecasts and special warnings on the occurrence of meteorological disasters are currently provided, the effects are not properly conveyed. Therefore, in this study, high-resolution analysis and hydrological factors of each area are reflected in order to suggest the depth of flooding of urban floods and to cope with the damage that may affect vehicles, and the degree of flooding caused by rainfall and its effect on vehicle operation are investigated. decided it was necessary. Therefore, the calculation formula of rainfall-immersion depth-vehicle speed is presented using various machine learning techniques rather than simple linear regression. In addition, by applying the climate change scenario to the rainfall-inundation depth-vehicle speed calculation formula, it predicts the flooding of urban rivers during heavy rain, and evaluates possible traffic network disturbances due to road inundation considering the impact of future climate change. We want to develop technology for use in traffic flow planning.

• Journal of the Korea Society of Computer and Information
• /
• v.27 no.5
• /
• pp.199-204
• /
• 2022

The purpose of this study is to broaden the understanding of the Security Services Industry Act, and also to examine the meanings of various phenomena by analyzing the media report big data rather than the researchers' perspective on the Security Services Industry Act. In the research method, this study searched for a keyword 「Security Services Industry Act」 that prescribes the security work as an important subject of crime prevention and maintenance of public order in Korea. The data was searched from 1990 to 2021 the BIG KINDS could provide. Also, for the concrete analysis during the period of data search, it was divided into settlement period(1976~2001), growth period-quantitative(2002~2012), and growth period-qualitative(2013~2021). In the results of this study, the media report perception of the Security Services Industry Act is continuously emphasizing the social roles and importance of private security according to the flow of time. The consequent marketability of private security will play great roles in the protection of people's lives and properties in the combination with various other industries in the future. However, the private security industry that provides public peace service together with the police, could be rising as an element that hinders the development of private security industry because of various social issues caused by legal regulations and illegal problems, so it would be necessary to more strengthen its responsibility and roles accordingly.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.27 no.7
• /
• pp.1059-1066
• /
• 2021

In Korea, the importance of marine activities is great, and automatic weather observation facilities are operating on land to investigate abnormal weather phenomena caused by industrialization; however, the number of facilities at sea is insufficient. Marine survey ships are operated to establish marine safety information, but there are many places where marine survey ships are difficult to access and operating costs are high. Therefore, a small, unmanned vessel capable of marine surveys must be developed. The sail has a significant impact on the sailing performance, so much research has been conducted. In this study, the camber effect, which is a design variable of the twin curvy sail known to have higher aerodynamic performance than existing airfoil shapes, was investigated. Flow analysis results for five cases with different camber sizes show that the lift coefficient is highest when the camber size is 9%. Curvy twin sails had the highest lift coefficient at an angle of attack of 23° because of the interaction of the port and starboard sails. The port sail had the highest lift coef icient at an angle of attack of 20°, and the starboard sail had the lowest lift coef icient at an angle of attack of 15°. In addition, the curvy twin sail had a higher lift coefficient than NACA 0018 at all angles of attack.

• Economic Analysis
• /
• v.27 no.1
• /
• pp.67-90
• /
• 2021

This study found an interesting fact that the nonlinear relationship structure between volatility and trading volume changed before and after the COVID-19 pandemic according to empirical analysis using Bitcoin (BTC) market data that sensitively reflects investors' trading behavior. That is, their relationship appeared positive (+) in a stable market state before COVID-19 pandemic, as in theory based on the information flow paradigm. In a state under severe market stress due to COVID-19 pandemic, however, their dependence structure changed and even negative (-). This can be seen as a consequence of increased market stress caused by COVID-19 pandemics from a behavioral economics perspective, resulting in structural changes in the asset market and a significant impact on the nonlinear dependence of volatility and trading volume (in particular, their dependence at extreme quantiles). Hence, it should be recognized that in addition to information flows, psychological phenomena such as behavioral biases or herd behavior, which are closely related to market stress, can be a key in changing their dependence structure. For empirical analysis, this study performs a test of Ross (2015) for detecting a structural change, and proposes a Copula Regression Quantiles (CRQ) approach that can identify their nonlinear relationship structure and the asymmetric dependence in their distribution tails without the assumption of i.i.d. random variable. In addition, it was confirmed that when the relationship between their extreme values was analyzed by linear models, incorrect results could be derived due to model specification errors.

• Journal of Navigation and Port Research
• /
• v.47 no.1
• /
• pp.10-17
• /
• 2023

A series of studies on the development of autonomous surface ships have been promoted in domestic and foreign countries. One of the main technologies for the development of autonomous ships is path-following control, which is closely related to securing the safety of ships at sea. In this regard, the path-following performance of an autonomous ship should be first evaluated at the design stage. The main aim of this study was to develop a visual and quantitative evaluation method for the path-following control performance of an autonomous ship at the design stage. This evaluation technique was developed using a computational fluid dynamics (CFD)-based path-following control model together with a line-of-sight (LOS) guidance algorithm. CFD software was utilized to visualize waves around the ship, performing path-following control for visual evaluation. In addition, a quantitative evaluation was carried out using the difference between the desired and estimated yaw angles, as well as the distance difference between the planned and estimated trajectories. The results demonstrated that the ship experienced large deviations from the planned path near the waypoints while changing its course. It was also found that the fluid phenomena around the ship could be easily identified by visualizing the flow generated by the ship. It is expected that the evaluation method proposed in this study will contribute to the visual and quantitative evaluation of the path-following performance of autonomous ships at the design stage.

• The Journal of the Korea Contents Association
• /
• v.22 no.5
• /
• pp.518-526
• /
• 2022

The extension of life expectancy due to modernization means an extension of the benefit time for elderly care and disease. However, compared to the increase in the elderly, the attitude of children toward parental responsibility is gradually weakening. These social phenomena bring alienation, hopelessness, and stress to life in old age, and the resulting sense of helplessness leads to suicidal thoughts or intentional death (suicide), becoming a social problem. The intentional death (suicide) of the elderly is a social phenomenon that often occurs around them, and the reality can be seen through the movie. In this study, the main character 'Soyoung' in the movie 'The Woman Who Kills' and the surrounding characters 'Song Old Man', 'Jongsu', and 'Jaewoo' in conversations with the elderly problem and death factors were analyzed in the Matrix. ), and then applied to the 'flow chart of problems in the elderly due to modernization' compiled by Byeong-Woo Lim (2019), to explore the factors of intentional death (suicide). As a result of the analysis, the four elderly were exposed to problems of the elderly such as disease, alienation and loneliness, poverty, and loss. (Suicide) was analyzed.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.3B
• /
• pp.315-321
• /
• 2008

Recently, in the light of environments and utilization, countermeasures to preserve beaches in coastal area are required without depending on such as jetties and breakwaters. The necessity of integrated sand management including not only coastal sediment but also sediment discharge from hinterland rivers is increased so as to establish long-term counterplan for sediment transport. In this regard, the following subjects are examined in this study; efficient ways for discharged sand to be transported from a river to the neighboring coast, the river terrace occurrence and its growth at the river delta, measures to improve storage efficiency of the discharged sand and measures to prevent the sand resources from being discharged into the deep sea during flooding. In recent, A jetty of 260 m length was constructed at Namdae River mouth in the year of 2005 as a countermeasure against the occurrence of sand-bar at river mouth and its close. In this study, a series of numerical experiments were carried out to investigate the characteristics of sediment transport and morphological change due to the construction of jetty at the entrance of Namdae River mouth. Firstly, The sand discharge from Namdae River is quantified by one-dimensional numerical analysis assuming the mixed sand of three different particle diameters. Then, in order to understand the transport behavior of the sand discharge from river and river mouth phenomena the numerical experiments were then conducted to examine the flow behaviors of river efflux and wind generated circulations in coastal area. And, after establishing the numerical model system, which predicts the sea bed changes obtained from the flux model combining with the wave propagation, wave-induced currents and sediment transport models, the sediment transport in the vicinity of Namdae River mouth is analyzed.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.2B
• /
• pp.179-186
• /
• 2006

Effective interception area of street grate inlets was decreased by clogging with trash, debris, and sand. It also decreased the interception capability of grate inlets and increased the inundation area in street. Therefore, it is necessary to analyze the clogging characteristics and interception capability change by clogging for appropriate design and management of grate inlets. Hydraulic experimental apparatus which can be changed the gutter transverse slopes, longitudinal slopes of street and clogging condition of grate inlet ($40{\times}50cm$) was installed for this study. 81 total experiments were conducted with 8 different clogging condition. The interception capacities of grate inlets clogged curb direction are smaller than those of clogged flow direction. As the longitudinal slopes of street increase, the interception capacity of grate inlet decreases due to splash-over phenomena. This is also observed at grate inlets which has no clogging condition. In general, 50% of clogging factor was selected in design of grate inlet in foreign country. The clogging factor for same clogging condition are suggested 0.25~0.65 in domestic urban area.

• Journal of Korea Water Resources Association
• /
• v.56 no.12
• /
• pp.837-844
• /
• 2023

Small and medium-sized mountain rivers that flow through steep, confined valleys carry large amounts of coarse-grained sediment and woody debris during floods. It causes an increase in flood water level by aggrading the riverbed and the cross-section blockage due to driftwood accumulation during flooding. However, the existing flood level calculation in the river basic plan does not consider these changes. In this study, using the Typhoon Hinnamnor flood in September 2022 as an example, we performed numerical simulations using the HEC-RAS model, taking into account the blockage of a cross-section at the bridge and changes in riverbed elevation that occurred during floods, and analyzed the flood level to predict flood risk. This study's results show that flooding occurs if more than 30% of the cross-section is blocked. The rise of flood water levels corresponds to that of the riverbed due to sediment deposition. These results can be used as basic data to prevent and effectively manage flood damage and contribute to establishing flood defense measures that consider actual phenomena.