• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.5
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• pp.33-40
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• 2012

To reduce the vulnerability of torsional irregular buildings caused by seismic loads, the torsional amplification factor was introduced by the seismic code. This factor has been applied differently in a variety of seismic codes. In this study, the final static eccentricity, and the lateral and torsional stiffness ratios of buildings designed with different design eccentricities were compared. The increment of the torsional amplification factor resulted in a decrement of the final static eccentricity of the building. However, after reaching the maximum value of this factor, the final static eccentricity of the building increased again. The final static eccentricity of the building designed by multiplying the sum of the inherent and accidental eccentricity by the torsional amplification factor was zero or had a minus value, depending to the position of the vertical element.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.5
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• pp.110-118
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• 2018

Due to recent earthquakes, there is a growing awareness that Korea is not a safe zone for earthquakes any more. Therefore, the review of various aspects of the seismic safety of the infrastructures are being carried out. Because of the characteristics of the underground structure buried in the ground, the electric power utility tunnels must be considered not only for the inertia and load capacity of the structure itself but also the characteristics of the surrounding soils. An extensive and accurate numerical analysis is inevitably required in order to consider the interaction with the ground, but it is difficult to apply the soil-structure interaction analyses, which generally requires high cost and extensive time, to all electric power utility tunnel structures. In this study, the major design variables including soil characteristics are considered as independent variables, and the seismic safety factor, which is the result of the numerical analysis, is considered as a dependent variable. Thus, a method is proposed to select vulnerable electric power utility tunnels with low seismic safety factor while excluding costly and time-consuming numerical analyses through the direct correlation analysis between independent and dependent variables. Equations of boundary limits were derived based on the distribution of the seismic safety factor and the cover depth and rebar amounts with high correlation relationship. Consequently, a very efficient and simple approach is proposed to select vulnerable electric power utility tunnels without intensive numerical analyses. Among the 108 electric power utility tunnels that were investigated in this paper, 30% were screened as fragile structures, and it is confirmed that the screening method is valid by checking the safety factors of the fragile structure. The approach is relatively very simple to use and easy to expand, and can be conveniently applied to additional data to be obtained in the future.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.6
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• pp.67-74
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• 2010

Because of the difference between the actual and computed eccentricity of buildings, symmetrical buildings will be affected by torsion. In provisions, accidental eccentricity is intended to cover the effect of several factors, such as unfavorable distributions of dead- and live-load masses and the rotational component of ground motion about a vertical axis. The torsional amplification factor is introduced to reduce the vulnerability of torsionally imbalanced buildings. The effect of the torsional amplification factor is observed for a symmetric rectangular building with various aspect ratios, where the seismic-force-resisting elements are positioned at a variable distance from the geometrical center in each direction. For verifying the torsional amplification factor in provisions, nonlinear reinforced concrete models with various eccentricities and aspect ratios are used in rock. The difference between the maximum displacements of the flexible edge obtained between using nonlinear static and time-history analysis is very small but the difference between the maximum torsional angles is large.

• Journal of the Earthquake Engineering Society of Korea
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• v.17 no.5
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• pp.237-243
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• 2013

In the Korean Building Code (KBC), the Design Eccentricity involves the torsional amplification factor (TAF), and the inherent and accidental eccentricities. When a structure of less than 6-stories and assigned to seismic design category C or D is designed using equivalent static analysis method, both KBC-2006 and KBC-2009 use the TAF but apply different calculation methods for the of design eccentricity. The design eccentricity in KBC-2006 is calculated by multiplying the sum of inherent eccentricity and accidental eccentricity at each level by a TAF but that in KBC-2009 is calculated by multiplying only the accidental eccentricity by a TAF. In this paper, the damage indices of a building with planar structural irregularity designed by different design eccentricities are compared and the relationship between the earthquake damage and design eccentricity of the building is evaluated. On the basis of this study, the increment of design eccentricity results in the decrement of final eccentricity and global damage index of structure. It is observed that design eccentricity in KBC-2006 reduces the vulnerability of torsional irregular building compared to design eccentricity in KBC-2009.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.12
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• pp.65-70
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• 2021

Electric kickboards are inviting attention as next-generation transportation systems with their number of users increasing rapidly every year. However, the number of related accidents similarly increases with the increase in the number of users. The purpose of this study is to analyze the structural safety of electric kickboards according to the shape of the connection parts. For this purpose, four different shapes of the connection parts, i.e., cube, cylinder, toroid, and divided cube were selected. Subsequently, the safety was analyzed based on the finite element (FE) analysis under the front collision scenario. The results showed that the shape of the divided cube induced the lowest von Mises stress and the highest safety factor amongst the four models. Moreover, only the shape showed a safety factor higher than 1. However, the shape of the cylinder exhibited the lowest structural vulnerability. These results demonstrate the importance of the shape of the connection part in maintaining the overall safety of an electric kickboard.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.2
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• pp.978-1002
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• 2019

With the rapid development of the Internet of Things, the problem of privacy protection has been paid great attention. Recently, Nikooghadam et al. pointed out that Kumari et al.'s protocol can neither resist off-line guessing attack nor preserve user anonymity. Moreover, the authors also proposed an authentication supportive session initial protocol, claiming to resist various vulnerability attacks. Unfortunately, this paper proves that the authentication protocols of Kumari et al. and Nikooghadam et al. have neither the ability to preserve perfect forward secrecy nor the ability to resist key-compromise impersonation attack. In order to remedy such flaws in their protocols, we design a lightweight authentication protocol using elliptic curve cryptography. By way of informal security analysis, it is shown that the proposed protocol can both resist a variety of attacks and provide more security. Afterward, it is also proved that the protocol is resistant against active and passive attacks under Dolev-Yao model by means of Burrows-Abadi-Needham logic (BAN-Logic), and fulfills mutual authentication using Automated Validation of Internet Security Protocols and Applications (AVISPA) software. Subsequently, we compare the protocol with the related scheme in terms of computational complexity and security. The comparative analytics witness that the proposed protocol is more suitable for practical application scenarios.

• Earthquakes and Structures
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• v.20 no.3
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• pp.279-293
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• 2021

Most of the existing seismic codes for RC buildings consider only a scenario earthquake for analysis, often characterized by the response spectrum at the specified location. However, any real earthquake event often involves occurrences of multiple earthquakes within a few hours or days, possessing similar or even higher energy than the first earthquake. This critically impairs the rehabilitation measures thereby resulting in the accumulation of structural damages for subsequent earthquakes after the first earthquake. Also, the existing seismic provisions account for the non-linear response of an RC building frame implicitly by specifying a constant response modification factor (R) in a linear elastic design. However, the 'R' specified does not address the changes in structural configurations of RC moment-resisting frames (RC MRFs) viz., building height, number of bays present, bay width, irregularities arising out of mass and stiffness changes, etc. resulting in changed dynamic characteristics of the structural system. Hence, there is an imperative need to assess the seismic performance under sequential earthquake ground motions, considering the adequacy of code-specified 'R' in the representation of dynamic characteristics of RC buildings. Therefore, the present research is focused on the evaluation of the non-linear response of medium-rise 3D RC MRFs with and without vertical irregularities under bi-directional sequential earthquake ground motions using non-linear dynamic analysis. It is evident from the results that collapse probability increases, and 'R' reduces significantly for various RC MRFs subjected to sequential earthquakes, pronouncing the vulnerability and inadequacy of estimation of design base shear by code-specified 'R' under sequential earthquakes.

• Proceedings of the Korean Society of Computer Information Conference
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• 2022.07a
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• pp.257-258
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• 2022

COVID-19 팬데믹으로 인하여, 재택근무와 같은 비대면 업무환경이 확대됨에 따라, 기업에서는 내부 보안을 위한 VPN 구축 및 사용률이 급격하게 증가하였다. 하지만, 기존의 대면 환경과는 다르게, 비대면 업무환경에서는 자신을 식별할 수 있는 수단을 제한적으로 활용하기 때문에, 사용자의 비밀번호가 노출되면, VPN에 접근하기 위한 사용자 인증이 무력화되는 심각한 문제점이 존재하며, 이러한 보안 취약점을 해결하기 위한 기술이 요구되는 실정이다. 따라서 본 논문에서는 기존 VPN 인증 기술에 내재된 보안 취약점을 해결하기 위하여, 사물 환경 인증, HIP 기술, 위치 인증, 상호 인증 기술을 활용한 다중 인증 기반의 제로 트러스트를 제공하는 VPN 인증 기술을 제안한다. 최종적으로는 본 논문에서 제안하는 기술을 통하여, 보다 안전성이 향상된 VPN을 제공할 것으로 사료된다.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.34 no.4
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• pp.250-257
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• 2023

Objectives: Adolescents are at risk of suicide. As suicide is a multifactorial process, risk and protective factors are relevant constructs for suicide prediction. This study explored the effects of risk and protective factors on suicidal ideation in adolescents on the island of São Miguel (Azores). Methods: A sample of 750 adolescents (male: n=358; 47.7%; mean age=14.67 years; standard deviation=1.85 years) from the island of São Miguel (Azores) completed several measures related to suicidal ideation and associated factors. Using a cross-sectional design, this study conducted descriptive, correlational, predictive, mediation, and moderation analyses. Results: Adolescents generally displayed high levels of risk and protective factors; an indicative proportion exhibited significant suicidal ideation with females presenting the greatest vulnerability. Furthermore, the results highlight that depression is the best predictor of suicidal ideation, however, the association between these variables is mediated. Conclusion: The data corroborate that the suicidal reality of adolescents in the Autonomous Region of the Azores is worrisome. Having substantiated the complexity of the suicidal context in young people in the present research, the need to continue studying risk/protective factors in this area is supported.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.1
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• pp.155-165
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• 2014

In this study, using a complex of physical, chemical, and biological evaluation factors, the ecological vulnerability to climate change were evaluated at each river in the Nakdong river basin. First, runoff, sediment rate, and low flow discharge changes according to AIB climate change scenario using the SWAT model were simulated. Also, for the assessment of chemical and biological factors, 48 points that water quality monitoring sites and ecological health measurement points are matched with each other was selected. The water quality data of BOD and T-P and the biological data of IBI and KSI in each point were reflected in the assessment. Also, the future rise in water temperature of the rivers in Nakdong river basin was predicted, and the impact of water temperature rise on the fish habitat was evaluated. The top 10 most vulnerable points was presented through a summary of each evaluation factor. This study has a contribution to river restoration or management plan according to the characteristics of each river.