• Nuclear Engineering and Technology
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• v.51 no.1
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• pp.104-115
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• 2019

Since the Fukushima Daiichi accident, there has been an emphasis on the risk resulting from multi-unit accidents. Human reliability analysis (HRA) is one of the important issues in multi-unit probabilistic safety assessment (MUPSA). Hence, there is a need to properly identify all the human and organizational factors relevant to a multi-unit incident scenario in a nuclear power plant (NPP). This study identifies and categorizes the human and organizational factors relevant to a multi-unit incident scenario of NPPs based on a review of relevant literature. These factors are then analyzed to ascertain all possible unit-to-unit interactions that need to be considered in the multi-unit HRA and the pattern of interactions. The human and organizational factors are classified into five categories: organization, work device, task, performance shaping factors, and environmental factors. The identification and classification of these factors will significantly contribute to the development of adequate strategies and guidelines for managing multi-unit accidents. This study is a necessary initial step in developing an effective HRA method for multiple NPP units in a site.

• Journal of Power Electronics
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• v.19 no.2
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• pp.519-528
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• 2019

The unified power quality conditioner (UPQC) is an effective custom power device that is used at the point of common coupling to protect loads from voltage and current-related PQ issues. Currently, most researchers have studied series unit and parallel unit models and an idealized transformer model. However, the interactions of the series and parallel converters in AC-link are difficult to analyze. This study utilizes an equivalent transformer model to accomplish an electric connection of series and parallel converters in the AC-link and to establishes a precise unified mathematical model of the UPQC. The strong coupling interactions of series and parallel units are analyzed, and they show a remarkable dependence on the excitation impedance of transformers. Afterward, a feed-forward decoupling method based on a unified model that contains the uncertainty components of the load impedance is applied. Thus, this study presents an adaptive method to estimate load impedance. Furthermore, simulation and experimental results verify the accuracy of the proposed modeling and decoupling algorithm.

• Journal of the Semiconductor & Display Technology
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• v.20 no.3
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• pp.184-188
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• 2021

In general, digital signage is a next-generation smart media that provides various information and advertisement services to many people indoors or outdoors using the Internet. Recently, digital signage is rapidly spreading in such a small indoor environment, that is, in an area closely related to daily life, for example, inside an elevator. However, in this kind of indoor environment where the stay time of persons is extremely limited, it would be not easy for them to keep advertisements in the user memory for a long time. In the digital signage display installed in an indoor environment, it is possible to think about the possibility for a function such as expanding the screen to a user's smartphone, which is now widely spread, to contain, store, and use the transmitted content. In this paper, we propose a method to extend the display of digital signage contents to personal smart phones with interaction function in such a limited environment. In order to make the system operation, the proposed system was verified by confirming the result of dual screen implementation in a smart phone through the prototype implementation of a digital signage system in an embedded Linux environment.

• International Journal of Advanced Culture Technology
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• v.10 no.3
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• pp.220-225
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• 2022

The purpose of this study is to develop an e-teaching portfolio to perform a teaching portfolio of an instructor on the web. I order to carry out this study, an initial model of the e-teaching portfolio was developed through systematic literature review, and the final e-teaching portfolio was developed by selecting and applying five students, then modifying and supplementing them. The study period was from May 1 to May 20, 2022. As a result of the study, the components of the finally developed e-teaching portfolio are Step 1: Understanding oneself, Step 2: Goal setting, Step 3: Learning strategy, Step 4: Self-check. In conclusion, the program developed through this study is a convenient function that can process everything in one place by connecting the fragmented teaching results, and the developed e-teaching portfolio can promote interaction between individuals by building a community. It has possible characteristics. In order to systematically activate the e-teaching portfolio developed through this study, it is necessary to establish an online management system for systematic operation. Furthermore, an institutional device is needed to guarantee the result of the developed e-teaching portfolio. In order to continuously manage the quality of the teaching portfolio, extrinsic rewards that stimulate the instructor's intrinsic motivation should be provided.

• Current Optics and Photonics
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• v.5 no.4
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• pp.444-449
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• 2021

A photonic crystal coupled-cavity waveguide created on silicon-on-insulator is designed to act as a refractive-index-sensing device at midinfrared wavelengths around 4 ㎛. To realize high sensitivity, effort is made to engineer the structural parameters to obtain strong modal confinement, which can enhance the interaction between the resonance modes and the analyzed sample. By adjusting some parameters, including the shape of the cavity, the width of the coupling cavity, and the size of the surrounding dielectric columns, a high-sensitivity refractive-index sensor based on the optimized photonic crystal coupled-cavity waveguide is proposed, and a sensitivity of approximately 2620 nm/RIU obtained. When an analyte is measured in the range of 1.0-1.4, the sensor can always maintain a high sensitivity of greater than 2400 nm/RIU. This work demonstrates the viability of high-sensitivity photonic crystal waveguide devices in the midinfrared band.

• International Journal of Advanced Culture Technology
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• v.10 no.4
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• pp.453-459
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• 2022

This study attempted to explore the realization and research direction of a successful metaverse environment in the future by analyzing international research trends of the metaverse using topic modeling. A total of 208 papers among WoS and ScienceDirect papers using metaverse as keywords were selected, and quantitative frequency analysis and topic modeling were performed. As a result, it was confirmed that research has rapidly increased after 2022. The main keywords of the research topics were 'second', 'life', 'learning', 'reality', 'metaverse', 'virtual', 'blockchain', 'nft', 'medical', 'avatar', etc. The topic keywords 'Second life & Education' and 'Virtual Reality & Medical' accounted for a large proportion of 57%, followed by 'Blockchain & Cryptocurrency', 'Avatar & Interaction', and 'Sensing and Device'. As a result of semantic analysis, current metaverse research is focused on application and utilization, and research on underlying technologies and devices is also active. Therefore, it is necessary to identify the commonalities and differences between domestic and foreign studies, and to study the application method considering the domestic environment. In addition, new jurisprudence research is more necessary along with predicting new problems. It is expected that the results of study will provide the right research direction for domestic researchers in the era of digital transformation and contribute to the realization of a digital society.

• Journal of Sensor Science and Technology
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• v.31 no.6
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• pp.376-382
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• 2022

A triboelectric nanogenerator (TENG) can obtain electrical output due to the reciprocal motion between two objects (i.e., rubbing), in which repetitive contact is made. High reliability, stable output, and high reproducibility are important aspects of the electrical output obtained through a TENG as a sensor or generator, thus enabling its meaningful use. Therefore, many researchers fabricated TENGs into individual parts in the form of one module type to obtain high reproducibility and reliability. Since a TENG manufactured as a module type operates as a single device, it is possible to collect kinetic energy and convert it into electrical energy through the interaction between internally configured elements without the need for a separate structure. In addition, it is relatively easy to apply the size to the body, machine tools, and natural environment by simply adjusting the size suitable for use and surrounding environmental conditions. In this paper, the application cases of module-type TENGs are divided into four areas, and the research progress of module-type TENGs in each area is extensively reviewed.

• International journal of advanced smart convergence
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• v.11 no.3
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• pp.93-101
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• 2022

Immersion is a features of VR technology, and the most important condition for evaluating VR experience. With the improvement of VR technology, including the presentation accuracy of VR content, the degree of interaction is diversified, the user's immersion in VR equipment should not only be improved technically, but researched from the user's perception level. The paper defines two important factors, immersion and presence, in a participant's experience with a VR device. Although the current technology can already simulate the real environment information visually and audibly, the content of the VR environment is not enough for us to achieve a completely real experience. Based on the Flow theory of Csikszentmihalyi and the sensory immersion achieved by current technology, this paper proposes the key factors of how to achieve conscious immersion for users in VR media. We prove that immersion is an indicator of the true degree of sensory simulation of VR equipment and is the basis for the realization of flow experience. What really makes the participant feel a perfect experience is the content provided by the VR environment and gave participants a sense of presence, it is not limited to video or games. On the premise of the Multi-Sensory, Immersion, Interactivity and Imagination experience achieved by using virtual reality technology, combined with the content creation of flow theory, the interactive immersion achieved by users is an important method to realize the awareness immersion of VR equipment.

• Journal of Navigation and Port Research
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• v.46 no.5
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• pp.458-470
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• 2022

As the 4th industrial revolution progresses, the application of several cutting-edge technologies such as the Internet of Things, big data, and mixed reality (MR) in relation to autonomous ships is being considered in the maritime logistics field. The aim of this study was to apply the concept of a digital twin model based on Human Machine Interaction (HMI) including a digital twin model and the role of an operator to a ship. The role of the digital twin is divided into information provision, support, decision, and implementation. The role of the operator is divided into operation, decision-making, supervision, and standby. The system constituting the ship was investigated. The digital twin system that could be applied to the ship was also investigated. The cloud-based digital twin system architecture that could apply investigated applications was divided into ship data collection (part 1), cloud system (part 2), analysis system/ application (part 3), and MR/mobile system (part 4). A Mixed Reality device HoloLens was used as an HMI equipment to perform a simulation test of a digital twin system of an 8 m battery-based electric propulsion ship.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.804-816
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• 2021

This paper investigates the effect of different flow models on the Pre-Swirl-Stator structural response from the perspective of a non-existing unified design procedure. Due to viscous effects near the propeller plane, the hydrodynamic solution is calculated by Computational Fluid Dynamics (CFD). Three different models are analysed: without the propeller, with the actuator disk and with the propeller. The main intention of this paper is to clarify the effects of the propeller model on the structural stresses in calm-water and waves which include the ship motion. CFD simulations are performed by means of OpenFOAM, while the structural response is calculated by means of the Finite Element Method (FEM) solver NASTRAN. Calm-water results have shown the inclusion of the propeller necessary from the design perspective, while the wave simulations have shown negligible propeller influence on the resulting stresses arising from the ship motions.