• Nuclear Engineering and Technology
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• v.53 no.10
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• pp.3182-3195
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• 2021

The implementation and validation of multi-dimensional (multi-D) features in thermal-hydraulic system codes aims to extend the application of these codes towards multi-scale simulations. The main goal is the simulation of large-scale three-dimensional effects inside large volumes such as piping or vessel. This novel approach becomes especially relevant during the simulation of accidents with strongly asymmetric flow conditions entailing density gradients. Under such conditions, coolant mixing is a key phenomenon on the eventual variation of the coolant temperature and/or boron concentration at the core inlet and on the extent of a local re-criticality based on the reactivity feedback effects. This approach presents several advantages compared to CFD calculations, mainly concerning the model size and computational efforts. However, the range of applicability and accuracy of the newly implemented physical models at this point is still limited and needs to be further extended. This paper aims at contributing to the validation of the multi-D features of the system code ATHLET based on the simulation of the Tests 1.1 and 2.1, conducted at the test facility ROCOM. Overall, the multi-D features of ATHLET predict reasonably well the evolution from both experiments, despite an observed overprediction of coolant mixing at the vessel during both experiments.

• Current Optics and Photonics
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• v.5 no.4
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• pp.384-390
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• 2021

This paper presents a wide-range tunable wavelength-locking technology based on optoelectronic oscillation (OEO) loops for optical fiber sensors and microwave photonics applications, explains the theoretical fundamentals of the design, and demonstrates a method for locking the relative wavelength differences between a leader semiconductor laser and its follower lasers. The input of the OEO loop in the proposed scheme (the relative wavelength difference) determines the radio-frequency (RF) signal frequency of the oscillation output, which is quantized into an injection current signal for feedback to control the wavelength drift of follower lasers so that they follow the wavelength change of the leader laser. The results from a 10-hour continuous experiment in a field environment show that the wavelength-locking accuracy reached ±0.38 GHz with an Allan deviation of 6.1 pm over 2 hours, and the wavelength jitter between the leader and follower lasers was suppressed within 0.01 nm, even though the test equipment was not isolated from vibrations and the temperature was not controlled. Moreover, the tunable range of wavelength locking was maintained from 10 to 17 nm for nonideal electrical devices with limited bandwidth.

• Journal of Korean language education
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• v.29 no.3
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• pp.197-225
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• 2018

The purpose of this study is to compare the difference in the interactions between beginning language learners and heritage learners on their forms based on the interaction hypothesis. In this study, three types of information gap activities were used to analyze Language Related Episodes (LREs) while investigating the interaction patterns in language use between four pairs (eight learners) of foreign learners and four pairs (eight learners) of English-speaking heritage learners. The result indicated that foreign learners had a high focus on form during interaction. In particular, they had a tendency to focus on vocabulary rather than grammar, and they conducted self-repair by examining and mostly adjusting their speech to postposition and tense. However, in the problem-solving process, they showed a limited ability in interaction, and thus directly asked others to settle the problem or resorted to using English due to their lack of ability to employ various communication strategies. However, heritage learners had a relatively low focus on form compared to foreign learners. Yet, they also focused more on vocabulary rather than grammar and conducted self-repair in interaction, especially for vocabulary. In addition, they were skillful at using various communication strategies such as indirect expressions, use of alternative words, evasion, and delaying, to expand speech and prevent communication breakdown. They focused less on grammar and mostly did not provide negative feedback in interaction.

• World Technopolis Review
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• v.7 no.2
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• pp.125-134
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• 2018

The purpose of this article is to introduce and describe the case of Fukuoka Next-generation Social System Creation Hub based on the conceptual framework of regional innovation platform strategy. In short, it is a "government-issued" regional innovation platform strategy to improve innovativeness with limited creative capital through "borrowing" not money but network, wisdom, know-how, and ideas from each other between some stakeholder groups in a region. The Fukuoka Industry, Science & Technology Foundation, which is the coordinating institution of the whole program, plays the role of a platformer to unify various projects into the program crossing borders between stakeholder groups for building regional innovation platforms that lends intensive support to feedback loops between the program facilitator and its partners in the program. Thanks to being a government-issued one, it could be tied together with some wide ranging issues of policy on social innovations, such as the "low carbon society" or the "health and longevity society." But at the same time, it is a concern that many regional research institutions that have innovative potential and diverse ideas become governed by the platform without their noticing it and dealt with in the same way based on "selected" and "designated" strategic goals. Therefore, it seems that a regional innovation platform strategy is a kind of "double-edged sword" in public policy in the era of "panopticism of bureaucratic society" in Japan.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.1
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• pp.225-229
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• 2019

Magnetic bearings are widely used in vacuum and clean environments or in high-precision applications, because they have no mechanical friction and have stable dynamic characteristics. Despite the aforementioned advantages of magnetic bearings, their applications are generally limited due to the controller complexity. In this paper, we proposed a reduced-complexity digital controller for magnetic bearings. In addition, we analyzed and solved the problems, such as quantization errors in the analog-to-digital conversion and integral windup in a feedback controller, which are known as the main causes of performance degradation. Experiments showed that the proposed digital controller achieves a target magnetic levitation accuracy.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.2
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• pp.129-138
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• 2021

Due to the active progress in space programs for various types of ground and space missions, the high agile spacecraft maneuverability is also required. To meet the requirement of the given space missions, the Control Moment Gyros (CMG) for the alternatives of the classical reaction wheels can release the attitude maneuverability restrictions. In addition, the angular rates of the spacecraft is constrained due to the limited actuator characteristics. In this paper, a sliding mode control technique for the attitude control of the spacecraft equipped with the pyramid type of CSCMG(Constant Speed CMG) is designed, and the stability of the control system is guaranteed by using the Lyapunov stability theory. Finally, the control law proposed is analyized by numertical simulations.

• Journal of the Korean Society of Safety
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• v.38 no.5
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• pp.43-50
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• 2023

With the advent of industrialization, consumers and end-users demand more reliable products. Meeting these demands requires a comprehensive approach, involving tasks such as market information collection, planning, reliable raw material procurement, accurate reliability design, and prediction, including various reliability tests. Moreover, this encompasses aspects like reliability management during manufacturing, operational maintenance, and systematic failure information collection, interpretation, and feedback. Improving product reliability requires prioritizing it from the initial development stage. Failure mode and effect analysis (FMEA) is a widely used method to increase product reliability. In this study, we reanalyzed using the FMEA method and proposed an improved method. Domestic railways lack an accurate measurement method or system for maintenance, so maintenance decisions rely on the opinions of experienced personnel, based on their experience with past faults. However, the current selection method is flawed as it relies on human experience and memory capacity, which are limited and ineffective. Therefore, in this study, we further specify qualitative contents to systematically accumulate failure modes based on the Failure Modes Table and create a standardized form based on the Master FMEA form to newly systematize it.

• ETRI Journal
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• v.46 no.1
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• pp.82-95
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• 2024

As automated essay scoring (AES) has progressed from handcrafted techniques to deep learning, holistic scoring capabilities have merged. However, specific trait assessment remains a challenge because of the limited depth of earlier methods in modeling dual assessments for holistic and multi-trait tasks. To overcome this challenge, we explore providing comprehensive feedback while modeling the interconnections between holistic and trait representations. We introduce the DualBERT-Trans-CNN model, which combines transformer-based representations with a novel dual-scale bidirectional encoder representations from transformers (BERT) encoding approach at the document-level. By explicitly leveraging multi-trait representations in a multi-task learning (MTL) framework, our DualBERT-Trans-CNN emphasizes the interrelation between holistic and trait-based score predictions, aiming for improved accuracy. For validation, we conducted extensive tests on the ASAP++ and TOEFL11 datasets. Against models of the same MTL setting, ours showed a 2.0% increase in its holistic score. Additionally, compared with single-task learning (STL) models, ours demonstrated a 3.6% enhancement in average multi-trait performance on the ASAP++ dataset.

• Korean Journal of Agricultural and Forest Meteorology
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• v.20 no.1
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• pp.101-116
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• 2018

Sustainability science is an emerging transdisciplinary research which necessitates not only the communication and collaboration of scientists, practitioners and stakeholders from different disciplines and interests, but also the paradigm shift from deterministic and reductionist approaches to the old basic. Ecological-societal systems (ESS) are co-evolving complex systems having many interacting parts (or agents) whose random interactions at local scale give rise to spontaneous emerging order at global scale (i.e., self-organization). Here, the flows of energy, matter and information between the systems and their surroundings play a key role. We introduce a conceptual framework for such continually morphing dynamical systems, i.e. self-organizing hierarchical open systems (SOHOs). To understand the structure and functionality of SOHOs, we revisit the two fundamental laws of physics. Re-interpretation of these principles helps understand the destiny and better path toward sustainability, and how to reconcile ecosystem integrity with societal vision and value. We then integrate the so-called visioneering (V) framework with that of SOHOs as feedback/feedforward loops so that 'a nudged self-organization' may guide systems' agents to work together toward sustainable ESS. Finally, example is given with newly endorsed Sustainable Development Goals (SDG) Lab (i.e., 'Rural systems visioneering') by Future Earth, which is now underway in rural villages in Tanzania.

• Journal of The Korean Association of Information Education
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• v.19 no.3
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• pp.311-322
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• 2015

This study analyzed the trend and problems in the design of contents developed by teachers, and suggested strategies for improvement. It analyzed the contents ranked as the first level in the Research Competition on Educational Informatization for the last 3 years. Concerning the 8 types of instructional activities and the 6 types of knowledge acquisition, most contents took limited types(i.e., the individual tutoring type, the concept learning type and the principle learning type). In addition, when the contents were evaluated according to the quality certification criteria for educational software, it was found that the quality level of the design was low in many criteria. When the content analysis was applied for the in-depth analysis of design characteristics, various problems were found in the areas such as evaluation, feedback and learning objectives. Also other common problems were found in the design areas such as level-based differentiated learning, interaction between students and contents, presentation of text and narration, utilization of information on a student, screen design, the content level appropriate for students. In relation to the problems found from the analysis, some strategies for improvement were suggested concerning the following topics: question selection and guidance for evaluation, content and types of feedback, statement of learning objectives, selection of content, interaction, and screen design.