• Smart Structures and Systems
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• 제25권2호
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• pp.241-254
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• 2020

Using confined shape memory alloy (SMA) bar or plate, this study proposes an innovative self-centering damper. The damper is essentially properly machined SMA core, i.e., bar or plate, that encased in buckling-restrained device. To prove the design concept, cyclic loading tests were carried out. According to the test results, the damper exhibited desired flag-shape hysteretic behaviors upon both tension and compression actions, although asymmetric behavior is noted. Based on the experimental data, the hysteretic parameters that interested by seismic applications, such as the strength, stiffness, equivalent damping ratio and recentering capacity, are quantified. Processed in the Matlab/Simulink environment, a preliminary evaluation of the seismic control effect for this damper was conducted. The proposed damper was placed at the first story of a multi-story frame and then the original and controlled structures were subjected to earthquake excitations. The numerical outcome indicated the damper is effective in controlling seismic deformation demands. Besides, a companion SMA damper which represents a popular type in previous studies is also introduced in the analysis to further reveal the seismic control characteristics of the newly proposed damper. In current case, it was found that although the current SMA damper shows asymmetric tension-compression behavior, it successfully contributes comparable seismic control effect as those having symmetrical cyclic behavior. Additionally, the proposed damper even shows better global performance in controlling acceleration demands. Thus, this paper reduces the concern of using SMA dampers with asymmetric cyclic behavior to a certain degree.

• Asian-Australasian Journal of Animal Sciences
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• 제24권7호
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• pp.1019-1025
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• 2011

Toll-like receptors (TLRs) play an important role in the recognition of invading pathogens and the modulation of innate immune responses in mammals. The TLR4 and TLR7 are well known to recognize the bacterial lipopolysaccharide (LPS) and single stranded (ssRNA) ligands, respectively and play important role in host defense against Gram-negative bacteria and ssRNA viruses. In the present study, coding exon fragments of these two TLRs were identified, cloned, sequenced and analyzed in terms of insertion-deletion polymorphism, within bovine TLRs 4 and 7, thereby facilitating future TLR signaling and association studies relevant to bovine innate immunity. Comparative sequence analysis of TLR 4 exons revealed that this gene is more variable, particularly the coding frame (E3P1), while other parts showed percent identity of 95.7% to 100% at nucleotide and amino acid level, respectivley with other Bos indicus and Bos taurus breeds from different parts of the world. In comparison to TLR4, sequence analysis of TLR7 showed more conservation among different B. indicus and B. taurus breeds, except single point mutation at 324 nucleotide position (AAA to AAM) altering a single amino acid at 108 position (K to X). Percent identity of TLR7 sequences (all 3 exons) was between 99.2% to 100% at nucleotide and amino acid level, when compared with available sequence database of B. indicus and B. taurus. Simple Modular Architecture Research Tool (SMART) analysis showed variations in the exon fragments located in the Leucine Rich Repeat (LRR) region, which is responsible for binding with the microbial associated molecular patterns and further, downstream signaling to initiate anti-microbial response. Considering importance of TLR polymorphism in terms of innate immunity, further research is warranted.

• 정보과학회 논문지
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• 제43권11호
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• pp.1281-1297
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• 2016

최근 스마트 기기의 보급으로 자유롭게 비디오 컨텐츠를 생성하고 이를 빠르고 편리하게 공유할 수 있는 네트워크 환경이 갖추어지면서, 퍼스널 비디오가 급증하고 있다. 그러나, 퍼스널 비디오는 비디오라는 특성 상 멀티 모달리티로 구성되어 있으면서 데이터가 시간의 흐름에 따라 변화하기 때문에 이벤트 분류를 할 때 이에 대한 고려가 필요하다. 본 논문에서는 비디오 내의 멀티 모달리티들로부터 고수준의 특징을 추출하여 시간 순으로 재배열한 것을 바탕으로 모달리티 사이의 연관관계를 Deep Neural Network(DNN)으로 학습하여 퍼스널 비디오 이벤트를 분류하는 방법을 제안한다. 제안하는 방법은 비디오에 내포된 이미지와 오디오를 시간적으로 동기화하여 추출한 후 GoogLeNet과 Multi-Layer Perceptron(MLP)을 이용하여 각각 고수준 정보를 추출한다. 그리고 이들을 비디오에 표현된 시간순으로 재 배열하여 비디오 한 편당 하나의 특징으로 재 생성하고 이를 바탕으로 학습한 DNN을 이용하여 퍼스널 비디오 이벤트를 분류한다.

• Smart Structures and Systems
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• 제14권5호
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• pp.847-867
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• 2014

There are continuous efforts to mitigate structural losses from earthquakes and manage risk through seismic risk assessment; seismic fragility curves are widely accepted as an essential tool of such efforts. Seismic fragility curves can be classified into four groups based on how they are derived: empirical, judgmental, analytical, and hybrid. Analytical fragility curves are the most widely used and can be further categorized into two subgroups, depending on whether an analytical function or simulation method is used. Although both methods have shown decent performances for many seismic fragility problems, they often oversimplify the given problems in reliability or structural analyses owing to their built-in assumptions. In this paper, a new method is proposed for the development of seismic fragility curves. Integration with sophisticated software packages for reliability analysis (FERUM) and structural analysis (ZEUS-NL) allows the new method to obtain more accurate seismic fragility curves for less computational cost. Because the proposed method performs reliability analysis using the first-order reliability method, it provides component probabilities as well as useful byproducts and allows further fragility analysis at the system level. The new method was applied to a numerical example of a 2D frame structure, and the results were compared with those by Monte Carlo simulation. The method was found to generate seismic fragility curves more accurately and efficiently. Also, the effect of system reliability analysis on the development of seismic fragility curves was investigated using the given numerical example and its necessity was discussed.

• 한국항행학회논문지
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• 제19권3호
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• pp.217-223
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• 2015

본 논문은 상용 모바일 네트워크를 이용하여 원거리에서 무인항공기를 운용하기 위한 복수의 클라이언트용 관제 시스템을 설계하고, 구현한 시스템의 성능 시험에 관하여 기술하였다. 이동통신망을 통한 원거리 접속을 위해 상용 M2M 모듈이 내장된 데이터 송수신 모뎀을 제작하였고, 데이터베이스가 연결된 중앙 서버를 구축하여 무인항공기로부터 수신되는 비행 및 영상 데이터를 실시간으로 저장하고 지상관제시스템으로 전송할 수 있게 하였다. 지상관제시스템은 중앙관제용, 지상관제용, 스마트폰용으로 제작하여 사용 목적에 따라 운용하도록 구현하였다. 구축한 시스템으로 성능 시험을 실시하여 데이터의 지연 시간과 영상수신율, 클라이언트 상태를 측정하였고, 비행 시험을 통해 고도에 따른 모바일 네트워크 모뎀의 통신 구현 가능성도 확인해 보았다.

• 디지털콘텐츠학회 논문지
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• 제18권1호
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• pp.55-62
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• 2017

본 연구의 배경은 고사양 스마트 기기를 기반으로 모바일 게임의 장르가 다양해지면서 컷신(cut-scene)의 활용도가 높아지고 있는데, 디지털 게임에서 컷신은 불필요한 존재로 인식되고 있어 이에 컷신의 기능과 활용 범위에 대한 제안을 하고자 한다. 본 연구의 범위는 상용화 되고 있는 모바일 게임의 장르별로 컷신의 활용범위를 분류하고 시각 표현에 대한 특징을 찾아 모바일 게임의 커뮤니케이션 양식의 틀을 만들기 위한 연구이다. 연구결과는 모바일 게임의 컷신의 활용은 기존 디지털 게임과 같이 게임의 장르에 따라 다르게 나타나고 있으며, 플랫폼의 형식에 맞게 진화하고 있지만 아직은 초기 디지털 게임의 컷신과 같이 다양한 시도가 이루어지지 못하고 있다. 향후 연구 과제는 모바일 게임 플랫폼의 특성에 맞는 커뮤니케이션 양식으로 새로운 플랫폼의 등장에 적용할 수 있는 모듈이 필요할 것이라 생각된다.

• Smart Structures and Systems
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• 제20권2호
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• pp.127-137
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• 2017

Identification of damping characteristics is of significant importance for dynamic response analysis and condition assessment of structural systems. Damping is associated with the behavior of the energy dissipation mechanism. Identification of damping ratios based on the sensitivity of dynamic responses and the model updating technique is investigated with numerical and experimental investigations. The effectiveness and performance of using the sensitivity-based model updating method and vibration monitoring data for damping ratios identification are investigated. Numerical studies on a three-dimensional truss bridge model are conducted to verify the effectiveness of the proposed approach. Measurement noise effect and the initial finite element modelling errors are considered. The results demonstrate that the damping ratio identification with the proposed approach is not sensitive to the noise effect but could be affected significantly by the modelling errors. Experimental studies on a steel planar frame structure are conducted. The robustness and performance of the proposed damping identification approach are investigated with real measured vibration data. The results demonstrate that the proposed approach has a decent and reliable performance to identify the damping ratios.

• 디지털융복합연구
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• 제11권7호
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• pp.149-155
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• 2013

최근 차량 교통 시스템은 스마트 센서 및 외부와의 소통을 통해 교통의 효율성과 안정성을 향상시키는 교통 체계를 의미하는 지능형 교통시스템(Intelligent Transport Systems : ITS)의 형태로 진화하고 있다. 이러한 발전 추세에 반하여 국내의 ITS 서비스는 다른 주요 통신 서비스에 비해 많이 낙후되어 있다. 이러한 현상의 원인은 현재 국내에서는 국제적으로 배정된 ITS 주파수 대역 내에 방송용 주파수가 할당되어 있으며, 국내에서 ITS로 사용되고 있는 DSRC(Dedicated Short Range Communications) 방식의 주파수도 ISM(Industrial, scientific and medical) 대역을 사용하고 있기 때문에 그것의 활용에 있어서 제한적일 수밖에 없다. 본 논문에서는 국내 ITS의 기술적 현황을 분석하여 다음과 같은 ITS 활성화 방안을 제안하였다. 첫째, 기존의 DSRC방식을 포용하는 WAVE(Wireless Access in Vehicular Environments)방식의 ITS 관련 표준을 시급히 확정하여 표준 설치 사양을 마련해야 한다. 둘째, ITS 표준을 완성하기 위한 주파수 배정이 시급히 시행되어야 한다.

• Smart Structures and Systems
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• 제17권6호
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• pp.957-980
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• 2016

Structural damage detection (SDD) is a challenging task in the field of structural health monitoring (SHM). As an exploring attempt to the SDD problem, a hybrid self-adaptive Firefly-Nelder-Mead (SA-FNM) algorithm is proposed for the SDD problem in this study. First of all, the basic principle of firefly algorithm (FA) is introduced. The Nelder-Mead (NM) algorithm is incorporated into FA for improving the local searching ability. A new strategy for exchanging the information in the firefly group is introduced into the SA-FNM for reducing the computation cost. A random walk strategy for the best firefly and a self-adaptive control strategy of three key parameters, such as light absorption, randomization parameter and critical distance, are proposed for preferably balancing the exploitation and exploration ability of the SA-FNM. The computing performance of the SA-FNM is evaluated and compared with the basic FA by three benchmark functions. Secondly, the SDD problem is mathematically converted into a constrained optimization problem, which is then hopefully solved by the SA-FNM algorithm. A multi-step method is proposed for finding the minimum fitness with a big probability. In order to assess the accuracy and the feasibility of the proposed method, a two-storey rigid frame structure without considering the finite element model (FEM) error and a steel beam with considering the model error are taken examples for numerical simulations. Finally, a series of experimental studies on damage detection of a steel beam with four damage patterns are performed in laboratory. The illustrated results show that the proposed method can accurately identify the structural damage. Some valuable conclusions are made and related issues are discussed as well.

• Smart Structures and Systems
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• 제26권3호
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• pp.345-360
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• 2020

Modern swarm intelligence heuristic search methods are widely applied in the field of structural health monitoring due to their advantages of excellent global search capacity, loose requirement of initial guess and ease of computational implementation etc. To this end, a hybrid strategy is proposed based on butterfly optimization algorithm (BOA) and differential evolution (DE) with purpose of effective combination of their merits. In the proposed identification strategy, two improvements including mutation and crossover operations of DE, and dynamic adaptive operators are introduced into original BOA to reduce the risk to be trapped in local optimum and increase global search capability. The performance of the proposed algorithm, hybrid butterfly optimization and differential evolution algorithm (HBODEA) is evaluated by two numerical examples of a simply supported beam and a 37-bar truss structure, as well as an experimental test of 8-story shear-type steel frame structure in the laboratory. Compared with BOA and DE, the numerical and experimental results show that the proposed HBODEA is more robust to detect the reduction of stiffness with limited sensors and contaminated measurements. In addition, the effect of search space, two dynamic operators, population size on identification accuracy and efficiency of the proposed identification strategy are further investigated.