• Geomechanics and Engineering
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• 제28권6호
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• pp.585-598
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• 2022

The monopile-friction wheel hybrid foundation is an innovative solution for offshore structures which are mainly subjected to large lateral eccentric load induced by winds, waves, and currents during their service life. This paper presents an extensive numerical analysis to investigate the lateral load and moment bearing performances of hybrid foundation, considering various potential influencing factors in sand-overlaying-clay soil deposits, with the complex lateral loads being simplified into a resultant lateral load acting at a certain height above the mudline. Finite element models are generated and validated against experimental data where very good agreements are obtained. The failure mechanisms of hybrid foundations under lateral loading are illustrated to demonstrate the effect of the friction wheel in the hybrid system. Parametric study shows that the load bearing performances of the hybrid foundation is significantly dependent of wheel diameter, pile embedment depth, internal friction angle of sand, loading eccentricity (distance from the load application point to the ground level), and the thickness of upper sandy layer. Simplified empirical formulae is proposed based on the numerical results to predict the corresponding lateral load and moment bearing capacities of the hybrid foundation for design application.

• Journal of The Korean Association of Information Education
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• 제21권6호
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• pp.675-690
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• 2017

Preparing the 4th industrial revolution age, a diagnostic assessment management system which can collect nationwide data has been implemented and utilized for the development of the evidence-based educational policy. This study aims to develop heuristics to help to improve usability of such systems, which are utilized by primary and middle school community including teachers and students in the nationwide. To achieve the objective, previous studies related to the development of heuristics in the educational contexts as well as basic heuristics from Nielsen were reviewed, and usability problems of the web-based diagnostic-supplement system being currently utilized, as a sample system, were analyzed. Then, the first version of heuristics was developed. The developed heuristics were validated and revised through 2 rounds of the delphi methods with 15 experts. This study has an implication with preparing foundations on improving usability of such diagnostic assessment management system utilized by school community at the nationwide in educational contexts.

• Journal of the Korean Society of Environmental Restoration Technology
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• 제14권5호
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• pp.1-16
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• 2011

This study was intended to develop and suggest 'residents-driven and citizen-participatory restoration procedures' for degraded ecosystems in BaigDooDaeGahn. With some concerns of current engineering-focused restoration approach for damaged ecosystem, the proposed procedures were designed based on the analysis of several case studies on citizen participatory projects such as the Habitat Movement, the Taean tidal wetland restoration effort in Korea, and some historical and innovative cases in Japan and the United States. The suggested procedures were considered to be a dialectical spiral model which was consisted of two goal axis, six system elements, four developmental stages, and five restoration steps. The new system and procedures were applied to damaged farmland areas (about 0.3 ha) on the top of BaigDooDaeGahn, Kangneung city with participation of more than 100 local residents and a dozen of citizen from Seoul. Both high level of possibilities and some barriers for future extended application were identified and adopted for the final version of the proposed procedures for ecological restoration.

• Structural Engineering and Mechanics
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• 제78권1호
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• pp.87-102
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• 2021

Long span cross-rope suspension structure is an innovative structural system evolved from typical Cross-Rope Suspension (CRS) guyed tower, a type of supporting system with short span suspension cable supporting overhead power transmission lines. In mountainous areas, the span length of suspension cable was designed to be extended to hundreds or over one thousand meters, which is applicable for crossing deep valleys. Vortex Induced Vibration (VIV) of overhead power transmission lines was considered to be one of the major factors of its fatigue and service life. In this paper, VIV and its controlling by Stockbridge damper for long span CRS was discussed. Firstly, energy balance method and finite element method for assessing VIV of CRS were presented. An approach of establishing FE model of long span CRS structure with dampers was introduced. The effect of Stockbridge damper for overall vibration of CRS was compared in both theoretical and numerical approaches. Results indicated that vibration characteristics of conductor in long span CRS compared with traditional tower-line system. Secondly, analysis on long span CRS including Stockbridge damper showed additional dampers installed were essential for controlling maximum dynamic bending stresses of conductors at both ends. Moreover, factors, including configuration and mass of Stockbridge damper, span length of suspension cable and conductor and number of spans of conductor, were assessed for further discussion on VIV controlling of long span CRS.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제24권6호
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• pp.818-825
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• 2020

The embedded system can be defined as a special purpose system with a built-in computer, and has a wide variety of applications such as home appliances, office equipment, and weapon systems. A well-defined taxonomy in a specific field is advantageous for learning and education, however, the classification scheme for embedded systems is difficult to find. In this paper, we propose a taxonomy for embedded systems. First, the generalized structure of the embedded system was presented. And, it is divided into two parts: "firmware based" and "embedded OS based". In addition, according to the characteristics of embedded system applications, it is divided into two categories: "non-dependable" application and "dependable" application, which makes 4 planes. We describe the features of each quadrant and show that the classification is well suited by showing examples. Our taxonomy can be used to set teaching and learning methods of embedded systems.

• Journal of Practical Engineering Education
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• 제11권1호
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• pp.75-86
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• 2019

Globally, the change in higher education is gradually moving toward a trend that seeks a change in innovative higher education through the revitalization of digital-based education. Accordingly, this study designed a customized education model based on e-learning that can be used in undergraduate education and development of lifelong vocational skills. The use of online learning platforms and the expansion of education are major factors that change the overall higher education system as the form and content of curriculum changes around the world. In order to establish a customized education model using online learning platform, this study analyzed major overseas advanced education cases and selected the basic direction of customized learning as personalized learning, competency based learning, and training for talents leading the 4th Industrial Revolution. Then, FGI was conducted for undergraduate and lifelong vocational ability development experts. As a result, a customized education model using an online learning platform was derived from a degree-type model available in undergraduate education and a non-degree-type model available in the field of lifelong vocational ability development, and each operation strategy was suggested.

• Journal of the Ergonomics Society of Korea
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• 제32권1호
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• pp.9-16
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• 2013

Objective: The aim of this study is to investigate a trend of human error types observed in a series of verification and validation experiments for an Advanced Control Room(ACR) equipped with Lager Display Panel(LDP), Work Station Flat Panel Display(WS FPD), list type Alarm System(AS), Soft Control(SC) and Computerized Procedure System(CPS). Background: Operator behaviors in a fully computerized control room are quite different from those in a traditional hard-wired control room. Operators in an ACR all together monitor plant status and variables through their own interface system such as LDP and WS FPD, are notified of abnormal plant status through their own list type AS, control the plant through their own SC, and follow the structured procedure through their own CPS whereas operators in a traditional control room only separately do their duty directed by their supervisor. Especially the secondary task such as manipulating the user interface of ACR can be an extra burden to all the operators including the supervisor. Method: The Reason's human error classification method was applied to operators' behavioral data collected from a series of verification and validation experiments where operators showed their plant operational behaviors under a couple of harsh scenarios using the ACR simulator. Results: As operators accustomed to the new ACR system, knowledge or rule based mistakes appearing frequently in the early series of experiments decreased drastically in the latest stage of the series. Slip and lapse types of errors were observed throughout the series of experiments. Conclusion: Education and training can be one of the most important factors for the operators accustomed to the traditional control room to be adapted to the new system and to run the ACR successfully. Application: The results of this study implied that knowledge or rule based mistakes can be reduced by training and education but that lapse type errors might be reduced only through innovative improvement in human-system interface design or teamwork culture design including a new leadership style suitable for ACR.

• Journal of The Korean Association For Science Education
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• 제24권1호
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• pp.76-89
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• 2004

Recent studies of science and technology "in-the-making" revealed that the process of designing material artifacts is not a straightforward application of prior images or theories by one (or more) person(s) isolated from his or her (their) environment. Rather, designing is a process contingent on the social and material setting for both engineering designers and students. Over the past decade, designing technological artifacts has emerged as an important learning environment in science classrooms. Through the analyses of a large database concerning an innovative simple machines curriculum for sixth-and seventh-grade students, we accumulated valid evidence for the nature of the designing process and science learning through it. In this paper, we show that design actions intertwine with the transformation of the objectified raw materials and artifact, the designer collective, and the mediating tools enabling that transformation, which constitute the elements of an activity from the perspective of cultural-historical activity theory. We conceptualize the continuous change of relation between material artifacts, designers, and tools throughout the design activity as co-evolution. Two episodes were selected to exemplify synchronic and diachronic change of relations inherent in co-evolving activity system. Finally, we discuss the implications of co-evolution during design activity for science learning.

• Nuclear Engineering and Technology
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• 제52권8호
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• pp.1706-1713
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• 2020

Functionally gradient material (FGM) is promisingly effective in mitigating the thermal stress between plasma facing materials (PFM) and structural materials. However, the corresponding research with respect to W/V FGM has not been reported yet. In this work, we firstly report the successful fabrication of W/V FGM by a combined technology of mechanical alloying (MA) and spark plasma sintering (SPS). The microhardness and microstructure of the consolidated sample were both investigated. W/V stacks show significantly enhanced microhardness (>100%) compared with pure W plate, which is beneficial to the integral strength of the hybrid structure. Furthermore, we clarify that the different ductility of W and V should be carefully considered, otherwise W/V powder might aggregate and lead to the formation of compositional segregation, and simultaneously unmask the impact of V proportion on the distribution of second phase in W-V binary alloy system. This work provides an innovative approach for obtaining W-V connections with much better performance.

• Steel and Composite Structures
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• 제50권4호
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• pp.403-418
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• 2024

In this paper, vibration and energy absorption characteristics of a nanostructure which is composed of two embedded porous annular/circular nanoplates coupled by a viscoelastic substrate are investigated. The modified couple stress theory (MCST) and the Gurtin-Murdoch theory are applied to take into account the size and the surface effects, respectively. Furthermore, the structural damping effect is probed by the Kelvin-Voigt model and the mathematical model of the problem is developed by a new hyperbolic higher order shear deformation theory. The differential quadrature method (DQM) is employed to obtain the out-of-phase and in-phase frequencies of the structure in order to predict the dynamic response of it. The acquired results reveal that the vibration and energy absorption of the system depends on some factors such as porosity, surface stress effects, material length scale parameter, damping and spring constants of the viscoelastic foundation as well as geometrical parameters of annular/circular nanoplates. A bird's-eye view of the findings in the research paper offers a comprehensive understanding of the vibrational behavior and energy absorption capabilities of annular/circular porous nanoplates. The multidisciplinary approach and the inclusion of porosity make this study valuable for the development of innovative materials and applications in the field of nanoscience and engineering.