• Smart Structures and Systems
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• 제14권2호
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• pp.129-144
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• 2014

In this paper, a fuzzy inference system and an analytical hierarchy process-based online evaluation technique is developed to monitor the condition of the 32-km Donghai Bridge in Shanghai. The system has 478 sensors distributed along eight segments selected from the whole bridge. An online evaluation subsystem is realized, which uses raw data and extracted features or indices to give a set of hierarchically organized condition evaluations. The thresholds of each index were set to an initial value obtained from a structure damage and performance evolution analysis of the bridge. After one year of baseline monitoring, the initial threshold system was updated from the collected data. The results show that the techniques described are valid and reliable. The online method fulfills long-term infrastructure health monitoring requirements for the Donghai Bridge.

• International Journal of Control, Automation, and Systems
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• 제5권1호
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• pp.24-34
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• 2007

Closed-loop active twist control of integral helicopter rotor blades is investigated in this paper for reducing hub vibration induced in forward flight. A four-bladed fully articulated integral twist-actuated rotor system has been designed and tested successfully in wind tunnel in open-loop actuation. The integral twist deformation of the blades is generated using active fiber composite actuators embedded in the composite blade construction. An analytical framework is developed to examine integrally twisted helicopter blades and their aeroelastic behavior during different flight conditions. This aeroelastic model stems from a three-dimensional electroelastic beam formulation with geometrical-exactness, and is coupled with finite-state dynamic inflow aerodynamics. A system identification methodology that assumes a linear periodic system is adopted to estimate the harmonic transfer function of the rotor system. A vibration minimizing controller is designed based on this result, which implements a classical disturbance rejection algorithm with some modifications. Using the established analytical framework, the closed-loop controller is numerically simulated and the hub vibratory load reduction capability is demonstrated.

• 한국환경과학회지
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• 제23권7호
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• pp.1223-1232
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• 2014

Density currents have been easily observed in environmental flows, for instance turbidity currents and pollutant plumes in the oceans and rivers. In this study, we explored the propagation dynamics of density currents using the FLOW-3D computational fluid dynamics code. The renormalization group (RNG) $k-{\varepsilon}$ scheme, a turbulence numerical technique, is employed in a Reynold-averaged Navier-Stokes framework (RANS). The numerical simulations focused on two different types of intrusive density flows: (1) propagating into a two-layer ambient fluid; (2) propagating into a linearly stratified fluid. In the study of intrusive density flows into a two-layer ambient fluid, intrusive speeds were compared with laboratory experiments and analytical solutions. The numerical model shows good quantitative agreement for predicting propagation speed of the density currents. We also numerically reproduced the effect of the ratio of current depth to the overall depth of fluid. The numerical model provided excellent agreement with the analytical values. It was also clearly demonstrated that RNG $k-{\varepsilon}$ scheme within RANS framework is able to accurately simulate the dynamics of density currents. Simulations intruding into a continuously stratified fluid with the various buoyancy frequencies are carried out. These simulations demonstrate that three different propagation patterns can be developed according to the value of $h_n/H$ : (1) underflows developed with $h_n/H=0$ ; (2) overflows developed when $h_n/H=1$ ; (3) intrusive interflow occurred with the condition of 0 < $h_n/H$ < 1.

• Steel and Composite Structures
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• 제6권1호
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• pp.33-53
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• 2006

The rotational behaviour of bolted extended end plate beam-to-column connections is evaluated in the context of the component method. The full moment-rotation response is characterized from the force-deformation curve of the individual joint components. The deformability of end plate connections is mostly governed by the bending of the column flange and/or end plate and tension elongation of the bolts. These components form the tension zone of the joint that can be modelled by means of "equivalent T-stubs". A systematic analytical procedure for characterization of the monotonic force-deformation behaviour of individual T-stub connections is proposed. In the framework of the component method, the T-stub is then inserted in the joint spring model to generate the moment-rotation response of the joint. The procedures are validated with the results from an experimental investigation of eight statically loaded extended end plate bolted moment connections carried out at the Delft University of Technology. Because ductility is such an important property in terms of joint performance, particularly in the partial strength joint scenario, special attention is given to this issue.

• 대한수학교육학회지:학교수학
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• 제13권1호
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• pp.207-227
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• 2011

다양한 정보의 홍수 속에서 순간순간 의사결정을 해야 하는 사회구성원은 주어진 정보를 통해 합리적인 의사결정과 비판적 사고가 요구된다. 이에 본 연구에서는 초등학교 6학년 학생들의 설문 조사 활동을 통해 설문 주제 및 설문 과정을 살펴보고, 이 과정에서 나타나는 아동의 통계적 사고를 분석하기 위해 자료의 수집, 자료의 기술, 자료의 조직과 요약, 자료의 그래프 표현, 자료의 해석과 분석 측면을 중심으로 심도 있게 분석하였다. 연구 결과, 습관적(Idiosyncratic) 사고 수준(1수준), 전이적(Transitional) 사고 수준(2수준), 양적 (Quantitative) 사고 수준(3수준), 분석적(Analytical) 사고 수준(4수준)의 4단계 중 2~4수준에 걸쳐 통계적 사고의 수준을 나타냈다.

• 한국항만경제학회지
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• 제24권1호
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• pp.61-83
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• 2008

부가가치는 기본적인 활동 외에 부가적으로 창출되는 가치를 의미하며, 이는 기업 경영의 핵심적인 목표일 것이다. 이처럼 부가가치 창출을 위해 국내외 기업들은 아웃소싱, M&A, 핵심역량 강화 등과 같은 다양한 활동을 추진하고 있다. 부가가치는 물류활동에 있어서도 중요하게 인식되고 있으며, 국내외 많은 물류기업들은 차별적인 부가가치 물류서비스 제공에 노력하고 있다. 본 연구에서는 기업의 물류환경 변화를 고려한 부가가치 물류를 "공장에서 생산된 제품을 소비자에게 전달하는 순방향 물류(Forward Logistics)와 소비자가 반품 배출한 제품을 서비스하거나 재활용하는 역방향 물류(Backward Logistics) 상에 일어나는 각 활동 주체들 간의 물류활동(보관, 포장, 하역, 수송, 정보)과 부가적인활동(단순가공, 조립, 라벨링 등)의 전이(reposition)와 재구축(reengineering)을 통해 전체 물류네트워크의 이익과 고객서비스를 향상시키는 활동"으로 정의하였다. 또한 부가가치 물류의 개념적 정의와 기업의 전략적 측면을 고려한 부가가치 물류의 분석적 체계를 제시하였다. 이것은 부가가치 물류가 창출될 수 있는 활동 영역을 상위의 공급망 계획과의 연관성, 순방향 물류와 역방향 물류, 취급 품목(상품, 재활용, 재활용품) 등을 고려하여 구분한 것이다. 그리고 물류네트워크 상에서 창출되는 부가가치를 도출하기 위하여 각 활동 주체들 간의 물류활동 흐름을 가치경로(Value Route)로 설명하였다. 이와 같은 가치경로를 통한 물류네트워크 상의 부가가치 활동과 기대효과를 몇몇 사례를 통해 제시하였다. 본 연구는 국내외 물류기업들의 경쟁력 이슈인 부가가치 물류에 대하여 정의하고, 부가가치 물류의 창출을 분석적 체계와 가치경로를 통해서 논리적으로 설명하였다. 그러나 부가가치 물류활동과 관련된 자료 수집이 용이하지 않아 역방향 물류를 포함한 부가가치 활동에 대한 정량적인 수치나 평가 기준 등을 제시하지 못한 연구의 한계가 있다. 향후, 부가가치 활동과 관련된 다양한 연구와 자료가 확보된다면, 물류네트워크 상에서 창출되는 부가가치 활동을 논리적으로 설명할 수 있는 부가가치 모델을 제시할 수 있을 것으로 기대한다.

• 한국과학교육학회지
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• 제32권6호
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• pp.1072-1086
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• 2012

Science, Technology, Engineering, and Mathematics (STEM) education in the U.S. has been identified as a significant national reform in K-16 education and curriculum in order to prepare students for the global economy of the 21st century. Korea has been facing very similar challenges to improve science, technology and mathematics education, in particular, the affective aspect of learning science and mathematics. Science, Technology, Engineering, Arts, and Mathematics (STEAM) education has become a crucial issue in Korean education system. The major purpose of this exploratory study is to inform the exemplary framework of STEAM education in the U.S. for Korea and to provide descriptive and analytical accounts on STEAM teaching and learning as an innovative integrated convergence education. This study integrates the outcomes of research papers on STEM education and recent literature. It employs content analysis methodology qualitatively by analyzing and synthesizing the findings, conclusions, discussions, and recommendations of accumulated research works related to STEM/STEAM education. This study will help gain a stronger sense of the STEAM framework and will guide to develop the educational programs for Korea.

• Journal of Contemporary Eastern Asia
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• 제16권2호
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• pp.20-43
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• 2017

While the Internet has been used to galvanise people for the collective good, many have voiced concerns over the noise and vitriol present online and polarisation. In Singapore where the government regulates traditional mainstream media such as print and broadcast, the online space has been described as a "Wild Wild West" rife with rumours, untruths and misinformation. Such developments do not only exert a potential negative effect on the deliberative nature of public discourse but also skew bias towards the online space, affecting the ability of online users to communicate with authority and power. This study seeks to examine the rationality of the cyberspace through using a new "rationality" framework to analyse political discourse online. Comprising objectivity, emotionality and partisanship, the rationality framework was applied to a content analysis of 197 blogs with political content in 2014. The analysis indicated that the online political space was not the Wild Wild West that it was touted to be with significant levels of objectivity and non-partisanship. There was a stark absence of emotional discourse, and relationships were observed between bloggers' anonymity and rationality. Cognisant of academia's and policymakers' interest on the quality and effects of online discourse, the proposed analytical framework and the study findings hold implications for both developed and developing countries.

• Nuclear Engineering and Technology
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• 제53권3호
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• pp.825-832
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• 2021

A simulation-based approach is proposed to study the protective actions taken by residents during nuclear emergencies using cognitive findings. Human perception-based behaviors are not heavily incorporated in the evacuation study for nuclear emergencies despite their known importance. This study proposes a generic framework of perception-based behavior simulation, in accordance with the ecological concept of affordance theory and a formal representation of affordance-based finite state automata. Based on the generic framework, a simulation model is developed to allow an evacuee to perceive available actions and execute one of them according to Newton's laws of motion. The case of a shadow evacuation under nuclear emergency is utilized to demonstrate the applicability of the proposed framework. The illustrated planning algorithm enables residents to compute not only prior knowledge of the environmental map, but also the perception of dynamic surroundings, using widely observed heuristics. The simulation results show that the temporal and spatial dynamics of the evacuation behaviors can be analyzed based on individual perception of circumstances, while utilizing the findings in cognitive science under unavoidable data restriction of nuclear emergencies. The perception-based analysis of the proposed framework is expected to enhance nuclear safety technology by complementing macroscopic analyses for advanced protective measures.

• 한국정보통신학회논문지
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• 제23권2호
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• pp.139-148
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• 2019

디지털 기술에 의한 다양한 비즈니스 모델 혁신은 기업 수준의 변화를 넘어서 시스템 혁신을 이르는 중요한 현상으로 주목받고 있으나 기술의 역할에 대한 이론적 연구는 드물다, 본 연구는 비즈니스의 기본 임무를 바탕으로 구분한 핵심기술 개념, 그리고 디지털 기술에 의한 가치 창출에 대한 이론과 사례 검토를 토대로 비즈니스 모델혁신에 끼치는 기술변화의 영향을 살펴보았다. 기술, 특히 디지털 기술은 효과성과 효율성의 향상이라는 새로운 가치 창출을 동력으로 문제해결형 모델, 생산형 모델, 네트워크형 모델들의 전환, 확장, 분리 및 플랫폼화를 통해 비즈니스 모델혁신에 영향을 준다.