• 반도체디스플레이기술학회지
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• 제21권4호
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• pp.99-105
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• 2022

Public attention to the indoor environment of underground subway stations, which is a representative multi-use facility, has been increasing along with the increase in indoor activities. In underground stations, fine iron oxide, which affects the health of users, is generated because of the friction between wheels and rails. Among particulate pollutant reduction technologies, plants have been considered as a non-chemical air purification method, and their effects in reducing certain chemical species have been identified in previous studies. The present study aimed to derive the total quantitative and qualitative reduction effects of a bio-filter system comprising air purifying plants, installed in an underground subway station. The experiment proceeded in two ways. First, PM(particulate matter) reduction effect by vegetation biofilter was monitored with the IAQ(indoor air quality) station. In addition, chemical speciation analysis conducted on the samples collected from the experimental and control areas where plants and irrigation using SEM-EDS(scanning electron microscopy-energy dispersive X-ray spectroscopy). This study confirmed the effect of the vegetation bio-filter system in reducing the accumulation of particulate pollutants and transition and other metals that are harmful to the human body.

• Computers and Concrete
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• 제30권1호
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• pp.75-83
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• 2022

This study introduced a post-tensioned precast concrete system that was developed and designed to improve the performance of joints by post-tensioning. Full-scaled specimens were tested to investigate flexural performances at the negative moment region, where the test variables were the presence of slabs, tendon types, and post-tensioned lengths. A specimen with slabs exhibited significantly higher stiffness and strength values than a specimen without slabs. Thus, it would be reasonable to consider the effects of a slab on the flexural strength for an economical design. A specimen with unbonded mono-tendons had slightly lower initial stiffness and flexural strength values than a specimen with bonded multi-tendons but showed greater flexural strength than the value specified in the design codes. The post-tensioned length was found to have no significant impact on the flexural behavior of the proposed post-tensioned precast concrete system. In addition, a finite element analysis was conducted on the proposed post-tensioned precast concrete system, and the tests and analysis results were compared in detail.

• Computers and Concrete
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• 제30권6호
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• pp.445-453
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• 2022

A pre-cambered deep deck-plate system has been developed that can realize a long span by offsetting the deflection caused by a construction load. In this study, finite element (FE) analysis is performed to examine the preload-camber relationship introduced into a deck and calculate the deflection reflecting the ponding effect that arises during concrete pouring. The FE analysis results showed that the stress of the bottom plate was half of the yield stress when the pre-camber of approximately 30 mm was introduced. Based on the FE results, a full-scale deep deck-plate is fabricated, a pre-camber is introduced, and concrete is poured to measure deflection. A deflection calculation formula that reflects the ponding effect is proposed, and the deflections yielded by the proposed model, experimental results, and FE results are compared. Results show that the proposed model can accurately estimate the deflection of non-supported deep deck-plate systems after concrete is poured.

• Steel and Composite Structures
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• 제44권3호
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• pp.325-337
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• 2022

In this research, an earthquake-resistant structural system consisting of a pin-connected steel frame and a bracing with metallic fuses is proposed. Contrary to the conventional braced frames, the main structural elements are deemed to remain elastic under earthquakes and the seismic energy is efficiently dissipated by the damper-braces with an amplification mechanism. The superiority of the proposed damping system lies in easy manufacture, high yield capacity and energy dissipation, and an effortless replacement of damaged fuses after earthquake events. Furthermore, the stiffness and the yield capacity are almost decoupled in the proposed damper-brace which makes it highly versatile for performance-based seismic design compared to most other dampers. A special attention is paid to derive the theoretical formulation for nonlinear behavior of the proposed damper-brace, which is verified using analytical results. Next, a direct displacement-based design procedure is provided for the proposed system and an example structure is designed and analyzed thoroughly to check its seismic performance. The results show that the proposed system designed with the provided procedure satisfies the given performance objective and can be used for developing highly efficient low-damage structures.

• Structural Engineering and Mechanics
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• 제81권6호
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• pp.677-689
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• 2022

Generally, the goal of seismic retrofit design of an existing structure using energy dissipation devices is to determine the optimum design parameters of a retrofit device to satisfy a specified limit state with minimum cost. However, the presence of multiple parameters to be optimized and the computational complexity of performing non-linear analysis make it difficult to find the optimal design parameters in the realistic 3D structure. In this study, genetic algorithm-based optimal seismic retrofit methods for determining the required number, yield strength, and location of steel slit dampers are proposed to retrofit an asymmetric soft first-story structure. These methods use a multi-objective and single-objective evolutionary algorithms, each of which varies in computational complexity and incorporates nonlinear time-history analysis to determine seismic performance. Pareto-optimal solutions of the multi-objective optimization are found using a non-dominated sorting genetic algorithm (NSGA-II). It is demonstrated that the developed multi-objective optimization methods can determine the optimum number, yield strength, and location of dampers that satisfy the given limit state of a three-dimensional asymmetric soft first-story structure. It is also shown that the single-objective distribution method based on minimizing plan-wise stiffness eccentricity turns out to produce similar number of dampers in optimum locations without time consuming nonlinear dynamic analysis.

• Steel and Composite Structures
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• 제45권5호
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• pp.683-695
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• 2022

Conventional braces are often used to provide stiffness to structures; however due to buckling they cannot be used as seismic energy dissipating elements. In this study, a seismic energy dissipation device is proposed which is comprised of a bracing member and a steel hysteretic damper made of steel hexagonal plates. The hexagonal shaped designated fuse causes formation of plastic hinges under axial deformation of the brace. The main advantages of this damper compared to conventional metallic dampers and buckling-restrained braces are the stable and controlled energy dissipation capability with ease of manufacture. The mechanical behavior of the damper is formulated first and a design procedure is provided. Next, the theoretical formulation and the efficiency of the damper are verified using finite element (FE) analyses. An analytical model of the damper is established and its efficiency is further investigated by applying it to seismic retrofit of a case study structure. The seismic performance of the structure is evaluated before and after retrofit in terms of maximum interstory drift ratio, top story displacement, residual displacement, and energy dissipation of dampers. Overall, the median of maximum interstory drift ratios is reduced from 3.8% to 1.6% and the residual displacement decreased in the x-direction which corresponds to the predominant mode shape of the structure. The analysis results show that the developed damper can provide cost-effective seismic protection of structures.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 가을 학술논문 발표대회
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• pp.37-38
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• 2022

During the past decades, the corrosion of the steel rebar embedded in concrete structure surrounding marine environment is actually problematic and required the suitable preventive method. An eco-friendly corrosion inhibitor mix is investigated to stifle the active corrosion in comparison with other commercial corrosion inhibitors. The hybrid inhibitor enhances the corrosion resistance and the workability of concrete. However, it reduces the compressive strength slightly after 28-day-age. The electrochemical studies and mechanical studies are pointed out the corrosion resistance property, corrosion kinetics, and the mechanical properties of all concrete samples. H-3 is the optimum dose of hybrid inhbitor that meets the demand of both electrochemical property and mechanical property. It performs the noble features due to the formation of optimum amount of P-Zwitterions-(Cl)-Fe complex onto the steel rebar surface.

• Advances in nano research
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• 제14권1호
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• pp.27-43
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• 2023

This article investigates the energy harvesting characteristics of a magneto-electro-elastic (MEE) cantilever beam reinforced with carbon nanotubes (CNT) under transverse vibration. To this end, the well-known lumped parameter model is used to represent the coupled multiphysics problem mathematically. The proposed system consists of the MEE-CNT layer on top and an inactive substrate layer at the bottom. The substrate is considered to be made of either an isotropic or composite material. Basic laws such as Gauss's Law, Newton's Law and Faraday's Law are used to arrive at the governing equations. Surface electrodes across the beam are used to harvest the electric potential produced, together with a wound coil, for the generated magnetic potential. The influence of various distributions of the CNT and its volume fraction, substrate material, length-to-thickness ratio, and thickness ratio of substrate to MEE layer on the energy harvesting behaviour is thoroughly discussed. Further, the effect of external resistances and changes in substrate material on the response is analysed and reported. The article aims to explore smart material-based energy harvesting systems, focusing on their behaviour when reinforced with carbon nanotubes. The results of this study may lead to an improved understanding of the design and analysis of CNT-based smart structures.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2020년도 추계학술발표대회
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• pp.773-776
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• 2020

웹 뉴스 기사는 태풍과 같은 재해 발생상황에 대한 신속하고 정확한 정보를 포함하고 있다. 예를 들어, 태풍의 발생시점, 이동·예측경로, 피해·사고 현황 등 유용한 정보를 텍스트, 이미지, 동영상의 형태로 관련 상황정보를 전달한다. 그러나 대부분의 재해재난 관련 뉴스 기사는 특정 시점의 정보만을 웹페이지 형태로 제공하므로, 시계열 측면의 연결성을 지니는 기사들에 대한 정보를 전달하기 어렵다. 또한 시간적 변화에 따라 기사 내용에 포함된 장소, 지역, 건물 등의 지명에 대한 공간적 정보를 지도와 연계하여 정보를 전달하는데 한계가 있어, 시공간적 변화에 따른 특정 재해재난 상황정보에 대한 전체적인 현황파악이 어렵다. 따라서, 본 논문에서는 데이터 시각화 측면에서 이러한 한계를 극복하기 위해, 1) 웹크롤링을 통해 구축된 뉴스 빅데이터를 자연어 처리를 통해 태풍과 관련된 뉴스 기사들을 추출하였고, 2) 시공간적 관련 정보를 지식그래프로 구축하였고, 이를 통해 최근 발생한 태풍 사건들과 관련된 뉴스 정보를 시계열 특성을 고려하여 3) 인터렉티브 지도 기반의 태풍 상황정보를 시각화하는 방안을 연구하였다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2022년도 추계학술대회
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• pp.198-200
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• 2022

본 논문에서는 다양한 서비스가 존재하는 스마트시티에 IoT 표준기술을 적용하여, 다양한 센서 및 데이터를 통합 관리할 수 있는 플랫폼 개발에 대해 설명하고자 한다. 플랫폼 개발을 통해 여러 데이터를 통합하여 관리하고, 수집된 데이터를 서비스에 맞춰 가공할 수 있도록 구조를 설계하였다. LwM2M 표준 기술을 기반으로 플랫폼을 설계하여, 다양한 기기를 수용할 수 있는 기능을 제공할 수 있다.