• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.6
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• pp.105-113
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• 2013

In this paper a micro solar energy harvesting system with MPPT(Maximum Power Point Tracking) control using a miniature PV(photovoltaic) cell of which the output is less than 0.5V is proposed. The MPPT control is implemented using linear relationship between the open-circuit voltage of a PV cell and its MPP(Maximum Power Point) voltage such that a pilot PV cell can track the MPP of the main PV cell in real time. The proposed circuit is designed in 0.18um CMOS process. The designed chip area is $900um{\times}1370um$ including a load charge pump and pads. Measured results show that the designed system can track the MPP voltage changes with variations of light intensity. The designed circuit with MPPT control delivers MPP voltages to load even though the load is heavy such that it can supply more power when the MPPT control is applied. The proposed circuit does not require any precharged battery resulting in more suitability for miniaturized self-powered systems compared to the existing works.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.1
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• pp.9-15
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• 2019

Here, we present a facile route to fabricate a vertically stacked 3D porous structure-based triboelectric nanogenerator (TENG) that can be used to harvest energy from the friction in a repetitive contact-separation mode. The unit component of TENG consists of thin Al foil electrodes integrated with microstructured 3D foams such as Ni, Cu, and polyurethane (PU), which provide advantageous tribo-surfaces specifically to increase the friction area to the elastomeric counter contact surfaces (i.e., polydimethylsiloxane, PDMS). The periodic contact/separation-induced triboelectric power generation from a single unit of the 3D porous structure-based TENG was up to $0.74mW/m^2$ under a mild condition. To demonstrate the potential applications of our approach, we applied our TENGs to small-scale devices, operating 48 LEDs and capacitors. We envision that this energy harvesting technology can be expanded to the applications of sustainably operating portable electronic devices in a simple and cost-effective manner by effectively harvesting wasted energy resources from the environment.

• Journal of the Korean Society for Environmental Technology
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• v.19 no.6
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• pp.576-585
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• 2018

Systematic management during the whole life cycle from construction to operation and maintenance is very important for the seven underground pipelines (waterworks, sewerage, electricity, telecommunications, gas, heating, oil including waterworks and sewerage). Especially, it is the construction process that affects the whole life cycle of underground buried pipeline. In order to construct a new city or to maintain different underground pipes, it is always necessary to dig the ground and carry out construction and related work. There is a possibility that secondary and tertiary breaks frequently occur in the pipeline construction process after the piping constructed first in this process. To solve this problem, a system is needed which can monitor damage in real time. However, the supply of electric power for continuous operation of the system is limited according to the environment of underground buried pipelines, so it is necessary to develop a stable electric power supply system using natural energy rather than existing electric power. In this study, we developed a system that can operate the pipeline monitoring system for long time (24 hours and 15 days) using natural energy using wind and solar light.

• Journal of The Korean Association For Science Education
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• v.44 no.3
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• pp.231-248
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• 2024

This study developed a chatbot for first-year high school students, employing open-source software and the Korean Sentence-BERT model for AI-powered document classification. The chatbot utilizes the Sentence-BERT model to find the six most similar Q&A pairs to a student's query and presents them in a carousel format. The initial dataset, built from online resources, was refined and expanded based on student feedback and usability throughout over the operational period. By the end of the 2023 academic year, the chatbot integrated a total of 30,819 datasets and recorded 3,457 student interactions. Analysis revealed students' inclination to use the chatbot when prompted by teachers during classes and primarily during self-study sessions after school, with an average of 2.1 to 2.2 inquiries per session, mostly via mobile phones. Text mining identified student input terms encompassing not only science-related queries but also aspects of school life such as assessment scope. Topic modeling using BERTopic, based on Sentence-BERT, categorized 88% of student questions into 35 topics, shedding light on common student interests. A year-end survey confirmed the efficacy of the carousel format and the chatbot's role in addressing curiosities beyond integrated science learning objectives. This study underscores the importance of developing chatbots tailored for student use in public education and highlights their educational potential through long-term usage analysis.

• 재활복지
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• v.20 no.1
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• pp.211-233
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• 2016

The purpose of this study is to figure out problems and to suggest improvement scheme by examining 31 of the disabled who used power wheelchair developed for safe moving and standing support. The results are as follows. First, standing power wheelchair that enables the disabled to sit and stand up was developed. It can also be used as means of transportation for moving in narrow space and in a short distance. In the usability test of this prototype, two groups were respectively examined in 60 evaluation items. One group consisted of 16 people with disabilities using manual wheelchairs. And the other one consisted of 15 people with disabilities using automatic wheelchairs. The entire average figure of two groups was shown to be 2.72 and standard deviation was 0.820. Specifically, the average figure of the group in manual wheelchair was 2.85 and the one of the other group in automatic wheelchair was 2.57. And both group replied that the move to stand up and sit on both types of wheelchair was the most inconvenient thing. It shows why ergonomic design for persons with under extremity disabilities to stand up and sit is needed. Second, with further study based on the results of usability test of the disabled, it will make contribution to increase the quality of people with disabilities by helping them move and do daily lives on their own.