• ETRI Journal
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• 제38권6호
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• pp.1153-1162
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• 2016

This paper addresses the resource allocation (RA) problem in multi-cell cognitive radio networks. Besides the interference power threshold to limit the interference on primary users PUs caused by cognitive users CUs, a proportional fairness constraint is used to guarantee fairness among multiple cognitive cells and the impact of imperfect spectrum sensing is taken into account. Additional constraints in typical real communication scenarios are also considered-such as a transmission power constraint of the cognitive base stations, unique subcarrier allocation to at most one CU, and others. The resulting RA problem belongs to the class of NP-hard problems. A computationally efficient optimal algorithm cannot therefore be found. Consequently, we propose a suboptimal RA algorithm composed of two modules: a subcarrier allocation module implemented by the immune algorithm, and a power control module using an improved sub-gradient method. To further enhance algorithm performance, these two modules are executed successively, and the sequence is repeated twice. We conduct extensive simulation experiments, which demonstrate that our proposed algorithm outperforms existing algorithms.

• Smart Structures and Systems
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• 제4권6호
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• pp.759-777
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• 2008

A wireless sensing system is designed for application to structural monitoring and damage detection applications. Embedded in the wireless monitoring module is a two-tier prediction model, the auto-regressive (AR) and the autoregressive model with exogenous inputs (ARX), used to obtain damage sensitive features of a structure. To validate the performance of the proposed wireless monitoring and damage detection system, two near full scale single-story RC-frames, with and without brick wall system, are instrumented with the wireless monitoring system for real time damage detection during shaking table tests. White noise and seismic ground motion records are applied to the base of the structure using a shaking table. Pattern classification methods are then adopted to classify the structure as damaged or undamaged using time series coefficients as entities of a damage-sensitive feature vector. The demonstration of the damage detection methodology is shown to be capable of identifying damage using a wireless structural monitoring system. The accuracy and sensitivity of the MEMS-based wireless sensors employed are also verified through comparison to data recorded using a traditional wired monitoring system.

• 문화기술의 융합
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• 제8권2호
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• pp.355-360
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• 2022

본 연구에서는 마이크로 데이터 센터의 환경 모니터링 시스템(EMS)을 설계하고 개발하는 방법을 나타낸다. 설계하는 환경 모니터링 시스템은 IoT 센서 및 싱글보드 컴퓨터를 이용하여 데이터센터 운영환경을 실시간으로 감지하여 데이터를 해석하고 운영환경을 모니터한다. 먼저, EMS 하드웨어 플랫폼 및 IoT 센싱 패키지 설계 방법에 대하여 나타낸다. 또한 서로 다른 프로토콜을 갖는 IoT 센서에 대한 데이터 수집 SW을 설계하고 원격에서 모니터링이 가능한 EMS 모니터링 SW를 개발한다. 데이터 수집 SW는 센서 수집 모듈과 수집 메니저 모듈로 구성된다. EMS 소프트웨어는 마이크로 서비스 아키텍츠(MSA) 개념을 적용하여 설계하며 각각의 서비스는 독립적인 비즈니스 로직을 포함한다.

• Design & Manufacturing
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• 제6권1호
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• pp.12-17
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• 2012

In order to produce high-quality optical components, aspheric lenses have been widely applied in recent years. An aspheric lens consists of aspheric surfaces instead of spherical ones, which causes difficulty in the design process as well as the manufacturing procedure. Although injection molding is widely used to fabricate optical lenses owing to its high productivity, there remains lots of difficulty to determine appropriate mold design factors and injection molding parameters. In the injection molding fields, computer simulation has been effectively applied to analyze processes based on the shell analysis so far. Considering the geometry of optical lenses, a full-3d simulation based on solid elements has been reported as a reliable approach. The present work covers three-dimensional injection molding simulation and relevant deformation analysis of an injection molded plastic lens based on 3d solid elements. Numerical analyses have been applied to the injection molding processes of three aspheric lenses for an image sensing module of a mobile phone. The reliability of the proposed approach has been verified in comparison with the experimental results.

• 한국금형공학회:학술대회논문집
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• 한국금형공학회 2008년도 하계 학술대회
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• pp.143-148
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• 2008

In order to produce high-quality optical components, aspheric lenses have been widely applied in recent years. An aspheric lens consists of aspheric surfaces instead of spherical ones, which causes difficulty in the design process as well as the manufacturing procedure. Although injection molding is widely used to fabricate optical lenses owing to its high productivity, there remains lots of difficulty to determine appropriate mold design factors and injection molding parameters. In the injection molding fields, computer simulation has been effectively applied to analyze processes based on the shell analysis so far. Considering the geometry of optical lenses, a full-3d simulation based on solid elements has been reported as a reliable approach. The present work covers three-dimensional injection molding simulation and relevant deformation analysis of an injection molded plastic lens based on 3d solid elements. Numerical analyses have been applied to the injection molding processes of three aspheric lenses for an image sensing module of a mobile phone. The reliability of the proposed approach has been verified in comparison with the experimental results.

• 한국통신학회논문지
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• 제35권4B호
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• pp.704-712
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• 2010

최근 다양한 무선기기 및 통신서비스의 보급으로 주파수 부족문제가 대두되고 있다. 이에 대한 해결책으로 신규 주파수자원 확보와 더불어 주파수 이용에 간섭 없이 기존의 TV 방송통신 대역(UHF/VHF)의 유휴주파수(Whitespace) 자원을 이용할 수 있는 무선인지(Cognitive Radio) 기술이 주목 받고 있다. 본 논문에서는 먼저 TV 대역 상에서 비면허 무선서비스의 활용 가능성을 탐색하기 위해 개발한 무선인지 단말시스템을 소개하고, 이 단말시스템 상에 탑재되어 효율적인 주파수 관리 기능을 수행하는 센싱 MAC 모듈의 개발 내용 및 테스트 결과를 기술한다. 무선인지 단말시스템에 적용된 센싱 MAC 소프트웨어는 IEEE 802.22 표준 규격을 기반으로 설계 및 구현되었으며, 개발된 센싱 MAC 모듈의 테스트를 수행하였다.

• 대한의용생체공학회:의공학회지
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• 제31권4호
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• pp.269-274
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• 2010

The purpose of this study was to develop the FSR sensor suit that controls walking assist device for paraplegic patients. The FSR sensor suit was to detect user's intent and patterns for walking by measuring pressure on the palm and the sole of user's foot. It consisted of four modules: sensing pressure from palm, changing modes and detecting pressure on the palm/at the wrist, sensing pressure from the soles of user's foot, and host module that transmit FSR data obtained from sensing modules to PC. Sensing modules were connected to sensing pads which detect analog signals obtained from the palm or the sole of foot. These collect signals from the target regions, convert analog signals into digital signals, and transmit the final signals to host module via zigbee modules. Finally, host modules transmit the signals to host PC via zigbee modules. The study findings showed that forces measured at the palm when using a stick reflected user's intent to walk and forces at the sole of the user's foot revealed signals detecting walking state.

• 감성과학
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• 제21권3호
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• pp.165-176
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• 2018

본 연구는 시 청각 피드백을 통해 아동의 운동 효과를 증진시킬 수 있는 의류형 웨어러블 동작 센싱 및 피드백 시스템을 개발하는 것을 목적으로 한다. 본 연구에서는 직물 센서 제조 및 이를 적용한 스포츠웨어 디자인, 직물기반 동작 센싱 모듈 설계, 아동의 운동 흥미 유발을 위한 시 청각 피드백 시스템 개발 등의 일련의 연구를 수행하였다. SWCNT 기반의 동작 센싱용 신축성 직물 센서를 개발하고, 이를 의복의 사지 관절 부위에 부착한 스포츠웨어를 디자인하였으며, 센싱 모듈을 설계하여 아동을 대상으로 한 관절 동작 실험을 통해 센싱 성능을 검증하였다. 또한 악세서리 형태로 개발된 피드백 제품을 통해 본 연구에서 개발된 스포츠웨어를 착용한 아동의 동작에 따라 빛과 소리로 반응하도록 구현하였다. 본 연구의 결과로, 아동의 운동 흥미를 유발할 수 있는 아동용 스포츠웨어 및 악세서리 제품의 디자인 프로토타입을 제안하였다.

• Journal of Biosystems Engineering
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• 제37권6호
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• pp.352-358
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• 2012

Purpose: The inexpensive black box system was developed to acquire and save driving information, to give the slope information, and to transmit SOS and theft signal. Method: The device consists of a main micro controller to acquire and save data, a GPS sensor module, a CDMA module, a touch LCD module, a RF (Radio Frequency) ID module, a SD (Secure Digital) card module, an emergency electric power source, a theftproof circuit, and a sensing device. The sensing device consists of a 8 bit micro controller, a accelerometer to detect impulse, two slope sensors to detect roll and pitch angle and a circuit to detect operation of 6 lighting devices. Results: Test results are as follows: 1) a tractor can be start up only with an electronic key (password or RFID card), 2) theft signal was transmitted when a tractor moved without an electronic key, 3) SOS was transmitted at conditions that rollover or crash happened. 4) 5 more than per 1s data are recorded at 5 minute intervals as new file name in SD card. Conclusions: This system can be used to save travelling record, reduce accident, prevent theft and rescue life in the accidents.

• 한국정밀공학회지
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• 제32권10호
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• pp.851-856
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• 2015

This study aimed to develop a sensory feedback system which could measure force and temperature for the user of myoelectric prosthetic hands. The Sensory measurement module consisted of a force sensing resistor to measure forces and non-contact infrared temperature sensor. These sensors were attached on the fingertips of the myoelectric prosthetic hand. The module was validated by using standard weights corresponding to external force and a Peltier module. Sensory transmission module consisted of four vibration motors. Eight vibration patterns were generated by combining motion of each vibration motor and were dependent on kinds and/or magnitude. The module was verified by using standard weigts and water at varying temperatures. There were correlations of force and temperature between the sensory measurement module and standard weight and water. Additionally, exact vibration patterns were generated, indicating the efficacy of the sensory feedback system for the myoelectric prosthetic hand.