• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.445-446
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• 2012

Recently the interest in wireless power transfer have been studied. ECR (Electromagnetic Coupled Resonance) device, depending on the size of the frequency characteristics of the structure, increasing in volume and larger volume of wireless power transmission device to make use of ECR is a big barrier. So to solve this problem for ECR device miniaturization and high efficiency has been actively studied. In this paper, the size of the device for ECR IM (Impedance Matching) by applying a one-turn coil circuit, remove the device in the form of ECR Network Analyzer measured by removing the one-turn coil has demonstrated the possibility of the device in the form of ECR.

• Journal of the Korean Society of Safety
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• v.35 no.3
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• pp.58-63
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• 2020

At the construction site of the driving site, the pile rebound and penetration measurements are performed manually to determine the end point of the driving operation, thereby causing the measurer to be exposed to a death accident. In this study, in order to eliminate the risk of this work, a non-contact penetration measuring device was developed and usability evaluation was conducted. The penetration measuring device is manufactured based on the ultrasonic sensor, and can be combined with the pile to deliver the data in real time, and the delivered data can be output in real time on the portable PC and the final penetration can be calculated. Usability evaluation on the device was conducted by comparison with manual work. Usability evaluation was largely evaluated on measured values, subjective comfort, and body parts comfort. The result of the measured value tended to overestimate the value measured manually by the measuring device, which is similar to the previous research. In terms of subjective comfort and body part comfort, overall satisfaction was higher than the manual method when using the measuring device. Taken together, these results indicate that it is possible to use the rudder measuring device in place of manual work in the construction site, and it is judged that the worker's comfort is greatly increased by using the measuring machine. The results of this study suggest that the use of non-contact measuring device in the field can be used as basic data to support them.

• Journal of Fisheries and Marine Sciences Education
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• v.27 no.6
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• pp.1872-1879
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• 2015

The present study was conducted on the improvement of the heat transfer performance of double pipe heat exchangers with helical insert device. Double pipe heat exchangers with helical insert device were studied for improvement of the heat transfer performance of double pipe heat exchangers with helical insert device and plain double pipe heat exchangers were also studied to comparatively analyze heat transfer performance. Experimental results were derived on changes in the Reynold's numbers of the cooling water flowing in helical and plain double pipe heat exchangers and changes in the heat flux of the air. Thereafter, to verify the reliability of the experimental results, the theoretical total energy and the experimental total energy were comparatively analyzed and the following results were derived. The thermal energy of the calorie lost by the hot air and that of the calorie obtained by the cooling water were well balanced. The experiments of plain double pipe heat exchangers and double pipe heat exchangers with helical insert device were conducted under normal conditions and the theoretical overall heat transfer coefficient value and the experimental overall heat transfer coefficient value coincided well with each other. In both plain double pipe heat exchangers and double pipe heat exchangers with helical insert device, heat transfer rates increased as the cooling water flow velocity increased. Under the same experimental conditions, the heat transfer performance of double pipe heat exchangers with helical insert device was shown to be higher by approximately 1.5 times than that of plain double pipe heat exchangers.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.4
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• pp.11-17
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• 2015

While most switching devices are based on PN junctions, a single layer can realize a switching device in the case of vanadium dioxide($VO_2$) thin films. In this paper, bidirectional current triggering(switching) is demonstrated in a two-terminal planar device based on a $VO_2$ thin film by illuminating the film with an infrared laser at 1550nm. To begin with, a two-terminal planar device, which had a $30{\mu}m$-wide $VO_2$ conducting layer and an electrode separation of $10{\mu}m$, was fabricated. A specific bias voltage range for stable bidirectional laser triggering was experimentally obtained by measuring the current-voltage characteristics of the fabricated device in a current-controlled mode. Then, by constructing a test circuit composed of the device, a standard resistor, and a DC voltage source, connected in series, the transient response of laser-triggered current and its response time were investigated with a DC bias voltage, included in the above specific bias voltage range, applied to the device. In the test circuit with a DC voltage source of 3.35V and a $10{\Omega}$ resistor, bidirectional laser triggering could be realized with a maximum on-state current of 15mA and a switching contrast of ~78.95.

• Journal of the Korean Vacuum Society
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• v.21 no.3
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• pp.151-157
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• 2012

The two dimensional electron gas system based on GaAs/$Al_xGa_{1-x}As$ heterostructure is widely used for fabricating quantum structures such as quantum dot, quantum point contact, electron interferometer and so on. However the conductance of the device is usually unstable due to the presence of random telegraph noise in the device. To overcome such problem, we have studied the effect of surface state on the stability of the device by altering the surface state of the device with oxygen plasma. The dramatic improvement of the device stability has been observed after cleaning the device surface with oxygen plasma (by 50 W~120 W plasma power) for 30 sec followed by etching in HCl : $H_2O$ (1 : 3) solution.

• JSTS:Journal of Semiconductor Technology and Science
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• v.2 no.2
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• pp.102-110
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• 2002

In this paper, we present the fabrication of tunable capacitors and 3-dimensional inductors. This work was related to fabricated 3-dimensional device for need of micro device in developing new intelligence age. This device was fabricated by electroplating used electroplating PR and high-vacuum evaporation of metal. Fabricated micro-inductor is consisted of air-bridge on electroplating rod and electroplated core. Micro-capacitor is consisted of thin metal membrane and electroplated core. Electroplating material is used Cu metal solvent. Air-gap between metal-layers function as almost perfect isolation layer. The most advantage of our micro-inductor and micro-capacitor compared to present device is a possibility that can fabricate on RF MEMS(microelectro-mechanical systems) application with high performance and various function. In this paper, we present the fabrication of tunable capacitors and 3-dimensional inductors. This work was related to fabricated 3-dimensional device for need of micro-device in developing new intelligence age. This device was fabricated by electroplating used electroplating PR and high-vacuum evaporation of metal. Fabricated micro-inductor is consisted of air-bridge on electroplating rod and electroplated core. Micro-capacitor is consisted of thin metal membrane and electroplated core. Electroplating material is used Cu metal solvent. Air-gap between metal-layers function as almost perfect isolation layer. The most advantage of our micro-inductor and micro-capacitor compared to present device is a possibility that can fabricate on RF MEMS application with high performance and various functions.

• Journal of IKEEE
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• v.12 no.2
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• pp.110-117
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• 2008

This paper presents a new Insulated Gate Bipolar Transistor(IGBT) based on Non Punch Through(NPT) IGBT structure for power switching device. The proposed structure has adding N+ beside the P-base region of the conventional IGBT structure. The added n+ diffusion of the proposed device ensure device has faster turn-off time and lower forward conduction loss than the conventional IGBT structure. But, added n+ region can reduce th breakdown voltage and latching current density of the proposed device due to its high doping concentration. This problems can be overcome by using diverter on the right side of the device. In the simulation results, turn-off time of the proposed device is 0.3us and the on-state voltage drop is 3V. The results show that the proposed device has superior characteristic than conventional structure.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.8
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• pp.681-687
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• 2014

Internet traffic is rapidly increasing due to the spread of personal smart devices. It causes serious burden on base stations and access points which are installed in buildings, buses, trains, and ships. We consider a communication scenario aboard a cruise ship and propose efficient contents distribution schemes to alleviate the burden of access points with multi-device-to-multi-device(MD2MD) communication. The proposed transmission method is based on the hybrid STBC-SM scheme. We compare the error performance of MD2MD communication system on the cruise ship using space-time block coding (STBC) scheme, spatial multiplexing (SM) scheme. The proposed MD2MD communication system is expected to adopt in the ship-area-network (SAN) with efficient contents distribution and reliable communication.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.11
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• pp.1500-1506
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• 2020

In this paper, we study a scheduling problem based on reinforcement learning for overlay device-to-device (D2D) communication networks. Even though various technologies for D2D communication networks using Q-learning, which is one of reinforcement learning models, have been studied, Q-learning causes a tremendous complexity as the number of states and actions increases. In order to solve this problem, D2D communication technologies based on Deep Q Network (DQN) have been studied. In this paper, we thus design a DQN model by considering the characteristics of wireless communication systems, and propose a distributed scheduling scheme based on the DQN model that can reduce feedback and signaling overhead. The proposed model trains all parameters in a centralized manner, and transfers the final trained parameters to all mobiles. All mobiles individually determine their actions by using the transferred parameters. We analyze the performance of the proposed scheme by computer simulation and compare it with optimal scheme, opportunistic selection scheme and full transmission scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.1
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• pp.1-8
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• 2014

This paper proposed a method that prevents data leakage and modulation and detects an unauthorized device by using AP and mobile device. Most of existing method for detecting and preventing an unauthorized device are similar to type of Evil Twin. However, in previous studies can not resolve many security accident and have the problem to cope with effectively security accident on various network. In order to solve these problem, companies prepare security accident through the varies policy and guideline. but It is hard to prevent all security accident because it is consistently increasing everyday. This paper suggests technique of detecting and preventing an unauthorized device using Context Awareness and Mobile Device Management. Firstly, when mobile device go into internal network, server distinguish access permission and authorization of mobile device using acquiring the conetxt information of mobile device. By using this result, server applies the appropriate management technique to the mobile device for leakage and accident of internal network.