• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.333-344
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• 2018

This proposed paper aims for the high efficiency contactless power transfer in household dc power distribution. A 300 W five-level diode clamped multi-level converter with 300 Vdc input dc link bus is employed for the power transferring task and the output voltage range is controlled at 48 Vdc. The inner and outer solenoid coils are used for inductive power transfer (IPT) transformer with the 200 kHz switching frequency for designed power density. Therefore, to achieve the converter efficiency above 95%, the LLC series resonant with fundamental harmonic analysis (FHA) and the calculated switching angles are used as an optimized tool for designing the system resonant tank. The validations of this approached topology are illustrated in both MATLAB/Simulink simulation and implementation.

• Journal of Information Technology Services
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• v.20 no.3
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• pp.27-40
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• 2021

There have been a series of mixed reviews on the 'untact work' which was implemented for the safety of the organizational members from Covid-19. This study reports a follow-up study with a quantitative approach to issues identified by in-depth interviews with workers and managers who have experiences in work from home. To compare the views of workers and managers on untact work, 264 workers and 141 managers were surveyed. An analysis of agreement, congruency, and accuracy on the basis of the co-orientation model shows that workers are more positive about the untact work than managers and that managers are found to have a negative perception on untact work. This seems to be a burden on workers. More specifically, managers and workers show significant perception gaps on the issues of unfair evaluation and work-life balance. The results imply that organizations need to make efforts to minimize the perception gaps between workers and managers. This would bring about benefits from untact work.

• Journal of Multimedia Information System
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• v.8 no.1
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• pp.23-30
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• 2021

Palmprint has become a popular biometric modality; however, palmprint recognition has not been conducted in video media. Video palmprint recognition (VPR) has some advantages that are absent in image palmprint recognition. In VPR, the registration and recognition can be automatically implemented without users' manual manipulation. A good-quality image can be selected from the video frames or generated from the fusion of multiple video frames. VPR in contactless mode overcomes several problems caused by contact mode; however, contactless mode, especially mobile mode, encounters with several revere challenges. Double-line-single-point (DLSP) assisted placement technique can overcome the challenges as well as effectively reduce the localization error and computation complexity. This paper modifies DLSP technique to reduce the invalid area in the frames. In addition, the valid frames, in which users place their hands correctly, are selected according to finger gap judgement, and then some key frames, which have good quality, are selected from the valid frames as the gallery samples that are matched with the query samples for authentication decision. The VPR algorithm is conducted on the system designed and developed on mobile device.

• Proceedings of the Korean Society of Computer Information Conference
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• 2022.07a
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• pp.485-486
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• 2022

본 논문에서는 OpenCV를 통해 기존의 물리적 버튼 등을 이용한 접촉제어가 아닌 비접촉으로 제어할 수 있는 시스템을 설계하였다. 시스템은 디지털 입력이나 아날로그 입력 등 두 가지 형태로의 모든 입력이 가능하며, 현실 세계에서 사람들이 사용하는 입력 방식과 유사한 방식으로 제어를 하게 함으로써 사용에 대한 기술에 대한 거부감을 줄일 수 있었다. 시스템은 ESP32-CAM 보드와 영상 스트리밍 서버를 FastAPI로 구축해 원격으로 접속과 조작이 가능하도록 설계하였다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.1
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• pp.148-156
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• 2007

This paper explains stocker system that is operated in the long distance and linear area. The power system of stocker system uses Contactless Power Supply(CPS) to reduce problems of particle generation. The circuit configuration of CPS is simplified than the conventional ones, and the prototype is designed for commercial product. To transfer output data(information) from crane(secondary vehicle system) of the CPS to Primary system optical modem and TMS320F243(DSP, TI) are used between primary and secondary. power system are used, and the output voltage is controlled by operating frequency modulation. This paper is applied to stocker system controlled as one to one communication between the moving part(secondary system) and fixed part(primary system) of crane using optical modem. The study makes one to multi communication between fixed part and moving part for the purpose of multi crane operation of stocker system and must be done in the future.

• Journal of Digital Convergence
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• v.18 no.10
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• pp.381-387
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• 2020

In order to study the similarities and differences of user experience of contactless retail services between Chinese and Korean users, this study focuses on E-mart 24 Self Convenience Store Gimpo DC Branch, Conducted in-depth interviews with Chinese and Korean users who have experience. The interviews are based on the 7 principles of Peter Morville's Honeycomb Model. As a result, the satisfaction of Chinese users is higher than that of Korean users. Human touch, and the desire for a faster society made Korean users more resistant to E-mart 24 Self Convenience Store. Chinese users raised concerns about the inconvenience of the system with little consideration for foreign users. It is expected that this study will help E-mart 24 Self Convenience Store to satisfy users from more cultural backgrounds.

• Progress in Superconductivity and Cryogenics
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• v.16 no.3
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• pp.21-25
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• 2014

As wireless power transfer (WPT) technology using strongly coupled electromagnetic resonators is a recently explored technique to realize the large power delivery and storage without any cable or wire, this technique is required for diffusion of electric vehicles (EVs) since it makes possible a convenient charging system. Typically, since the normal conducting coils are used as a transmitting coil in the CPT system, there is limited to deliver the large power promptly in the contactless EV charging system. From this reason, we proposed the combination CPT technology with HTS transmitting antenna, it is called as, superconducting contactless power transfer for EV (SUWPT4EV) system. As the HTS coil has an enough current density, it can deliver a mass amount of electric energy in spite of a small scale antenna. The SUCPT4EV system has been expected as a noble option to improve the transfer efficiency of large electric power. Such a system consists of two resonator coils; HTS transmitting antenna (Tx) coil and normal conducting receiver (Rx) coil. Especially, the impedance matching for each resonator is a sensitive and plays an important role to improve transfer efficiency as well as delivery distance. In this study, we examined the improvement of transmission efficiency and properties for HTS and copper antennas, respectively, within 45 cm distance. Thus, we obtained improved transfer efficiency with HTS antenna over 15% compared with copper antenna. In addition, we achieved effective impedance matching conditions between HTS antenna and copper receiver at radio frequency (RF) power of 370 kHz.

• Journal of Sensor Science and Technology
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• v.14 no.2
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• pp.78-84
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• 2005

A contactless recharging device for totally implantable middle ear systems has been designed as a pillow type that the user can recharge the implanted battery with taking a rest. The proposed device uses the electromagnetic coupling between the transmitting coil and the receiving coil. To supply sufficient power for the implanted circuits, each coil uses LC resonance and the implanted device uses voltage doubler. A power MOSFET is used for switching the DC voltage of LC parallel circuit and the switching frequency demands on a programmable frequency generator which is controlled by microcontroller. In order to improve the electromagnetic coupling efficiency at specific positions of coil which may vary with the displacement of head, the optimal location of receiving coil was studied, and the 5 transmitting coils in a pillow for recharging the implant module was designed. From such a recharging experiment, it was found that the proposed device could provide the sufficient operating voltage within the distance of 4 cm between pillow and the implanted device.

• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.514-522
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• 2014

A new type of high precision electromagnetic suspension (EMS) which can support heavy tray along long stroke rail is proposed in this paper. Compared with the conventional EMS, the suggested moving-core typed EMS has the levitation electromagnets (EMs) on the fixed rail. This scheme has high load capability caused by iron-core and enables simple tray structure. Also it does not have precision degradation caused by heat generation from EMs, which is a drawback of conventional EMS. With these merits, the proposed EMS can be an optimal contactless linear bearing in next generation flat panel display (FPD) manufacturing process if the ability of long stroke movement is proved. So a special Section Switching Algorithm (SSA) is derived from the resultant force and moment equations of the levitated tray which enables long stroke movement of the tray. In order to verify the feasibility of the suggested SSA, a simple test-setup of the EMS with 2 Section-changes is made up and servo-controlled in the simulation and experiment. The simulation shows the perfect changeover the EMs, and the experiment shows overall control performance of under ${\pm}40{\mu}m$ gap deviations. These results reveal that the newly suggested contactless linear bearing can simultaneously achieve high load capability and precision gap control as well as long stroke.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.3
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• pp.70-79
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• 2020

The main objective of this research to develop an IoT based wireless contactless ultrasonic system (ICUS) and its application to concrete structure. The developed system consists of 16 mems, 2Mhz digitizer, amplifying circuit, FPGA, and wifi module, enabling to measure leaky surface waves from concrete specimens without physical coupling process and wires. Multi-channel analysis is performed to improve the accuracy of data analysis, and the velocity of leaky surface waves and acoustics are derived. Field inspection of railroad concrete sleepers is conducted to evaluate the performance of the system and to compare the results with conventional ultrasonic pulse velocity (UPV). As a result of the field inspection, UPV was limited to evaluate damages. This is because crack pattern of railroad sleepers is parallel to ultrasonic ray path and accessibility of the railroad at the field is disadvantageous to contact-based UPV. On the other hand, ICUS possibly detect the damages as reduction of dynamic modulus by up to 59% compared to non-damaged specimen.