• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권1호
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• pp.20-39
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• 2020

This paper considers a downlink multi-carrier cooperative non-orthogonal multiple access (NOMA) transmission, where no direct link exists between the far user and the base station (BS), and the communication between them only relies on the assist of the near user. Firstly, the BS sends a superimposed signal of the far and the near user to the near user, and then the near user adopts simultaneous wireless information and power transfer (SWIPT) to split the received superimposed signal into two portions for energy harvesting and information decoding respectively. Afterwards, the near user forwards the signal of the far user by utilizing the harvested energy. A minimum data is required to ensure the quality of service (QoS) of the far user. We jointly optimize power allocation, subcarrier allocation, time allocation, the power allocation (PA) coefficient and the power splitting (PS) ratio to maximize the number of data bits received at the near user under the energy causality constraint, the minimum data constraint and the transmission power constraint. The block-coordinate descent method and the Lagrange duality method are used to obtain a suboptimal solution of this optimization problem. In the final simulation results, the superiority of the proposed NOMA scheme is confirmed compared with the benchmark NOMA schemes and the orthogonal multiple access (OMA) scheme.

• 한국ITS학회 논문지
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• 제8권6호
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• pp.64-72
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• 2009

본 논문에서는 마이크로스트립 패치 안테나와 2차 및 3차 고조파가 억압된 이중모드 대역통과 여파기를 이용하여 고효율의 2.45 GHz 렉테나를 설계 및 제작하였다. 입사전력밀도가 0.3 mW/cm2 일 때 1.66 mW 의 전력을 수신하였고, 41.6%의 RF-to-DC 변환효율의 실험 결과를 얻었다. 이는 입사 전력이 작기 때문에 다른 논문의 결과와 비교하여 고효율이라고 볼 수 있다. 또한 무선전력 전송을 통하여 다양한 응용기술 개발에 활용이 가능할 것으로 예측되며, USN(Ubiquitous Sensor Network)용 저전력 소자의 대기전원 공급 및 MEMS용 Sensor 등의 구동전압공급을 위한 무선 전력전송이 가능하게 될 것으로 기대된다.

• Journal of Positioning, Navigation, and Timing
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• 제7권4호
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• pp.227-233
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• 2018

The purpose of satellite navigation meaconing jamming is to make the target GPS receiver calculate false navigation by meaconing the received satellite signals. At this time, since the received and transmitted signals have the same frequency, the back-lobe reduction level of antenna should be -160 dB when the Effective Radiated Power (ERP) is 1 Watt (30 dBm). Therefore, meaconing jamming is impossible by merely reducing the back-lobe level of antenna when the transmitter and receiver are in proximity to each other. In general, the transmitter and receiver are isolated by the time division method to eliminate such transmission/reception interference. This paper studied the optimal switching timing between transmitting and receiving when isolating the time division transmission and reception for GPS meaconing jamming.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권4호
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• pp.1854-1868
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• 2018

A wireless body-sensor network (WBSN) refers to a network-configured environment in which sensors are placed on both the inside and outside of the human body. The sensors are much smaller and the energy is more constrained when compared to traditional wireless sensor network (WSN) environments. The critical nature of the energy-constraint issue in WBSN environments has led to numerous studies on the reduction of energy consumption of WBSN sensors. The transmission-power-control (TPC) technique adjusts the transmission-power level (TPL) of sensors in the WBSN and reduces the energy consumption that occurs during communications. To elaborate, when transmission sensors and reception sensors are placed in various parts of the human body, the transmission sensors regularly send sensor data to the reception sensors. As the reception sensors receive data from the transmission sensors, real-time measurements of the received signal-strength indication (RSSI), which is the value that indicates the channel status, are taken to determine the TPL that suits the current-channel status. This TPL information is then sent back to the transmission sensors. The transmission sensors adjust their current TPL based on the TPL that they receive from the reception sensors. The initial TPC algorithm made linear or binary adjustments using only the information of the current-channel status. However, because various data in the WBSN environment can be utilized to create a more efficient TPC algorithm, many different types of TPC algorithms that combine human movements or fuse TPC with other algorithms have emerged. This paper defines and discusses the design and development process of an efficient TPC algorithm for WBSNs. We will describe the WBSN characteristics, model, and closed-loop mechanism, followed by an examination of recent TPC studies.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권12호
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• pp.4385-4399
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• 2021

The Internet of Things (IoT) eHealth systems composed by Wireless Body Area Network (WBAN) has emerged recently. Sensor nodes are placed around or in the human body to collect physiological data. WBAN has many different applications, for instance health monitoring. Since the limitation of the size of the battery, besides speed, reliability, and accuracy; design of WBAN protocols should consider the energy efficiency and time delay. To solve these problems, this paper adopt the end-edge-cloud orchestrated network architecture and propose a transmission based on reinforcement algorithm. The priority of sensing data is classified according to certain application. System utility function is modeled according to the channel factors, the energy utility, and successful transmission conditions. The optimization problem is mapped to Q-learning model. Following this online power control protocol, the energy level of both the senor to coordinator, and coordinator to edge server can be modified according to the current channel condition. The network performance is evaluated by simulation. The results show that the proposed power control protocol has higher system energy efficiency, delivery ratio, and throughput.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.762-767
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• 1991

To make electromechanical total artificial heart implantable inside the body, transcutaneous energy transmission system was designed and simulated by using PSPICE program. The fabricated system was evaluated by using Mock circulation system and showed comparable performance with the D.C power supply

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1988년도 한국자동제어학술회의논문집(국내학술편); 한국전력공사연수원, 서울; 21-22 Oct. 1988
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• pp.683-687
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• 1988

Digitalization of processor and increase of control information need the fiber optic data network which has excellent noise immunity and high-quality, widebaudwidth information transfer capability. It is aimed to offer a fiber optic dataway system for measuring and control the power plant, that has high reliability, high data transmission rate and small cable duct with large transmission capacity.

• Journal of Power Electronics
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• 제16권2호
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• pp.685-694
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• 2016

This paper presents a reliability assessment model for the power semiconductors used in wind turbine power converters. In this study, the thermal loadings at different timescales of wind speed are considered. First, in order to address the influence of long-term thermal cycling caused by variations in wind speed, the power converter operation state is partitioned into different phases in terms of average wind speed and wind turbulence. Therefore, the contributions can be considered separately. Then, in regards to the reliability assessment caused by short-term thermal cycling, the wind profile is converted to a wind speed distribution, and the contribution of different wind speeds to the final failure rate is accumulated. Finally, the reliability of an actual power converter semiconductor for a 2.5 MW wind turbine is assessed, and the failure rates induced by different timescale thermal behavior patterns are compared. The effects of various parameters such as cut-in, rated, cut-out wind speed on the failure rate of power devices are also analyzed based on the proposed model.

• 한국기계가공학회지
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• 제13권5호
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• pp.28-34
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• 2014

A planetary gear train is more compact and endures greater amounts of transmission power compared to other gear systems. Although planetary gear systems operate in small volumes, they are capable of very high efficiency due to the compact combination of their gears in the planetary gear system. They also have outstanding efficiency of only 3% for power transmission, tantamount to the power loss that occurs in each of the shift stages. Given these advantages, planetary gear systems are used in the driving systems of, which are widely used in automobile transmissions, machine tools, semiconductor equipment, and in other areas in industrial fields. Current structural equipment requires higher efficiency and greater torque levels. According to these needs, we have designed a complex planetary gear system which creates higher levels of torque. In this paper, an evaluation of strength designs for the proposed planetary gear system was conducted to ensure the stability of the gear. In addition, a durability analysis based on Miner's rule was performed using RS B 0095 device.

• 전기저널
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• 6호통권126호
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• pp.7-11
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• 1987