• 세라미스트
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• 제23권1호
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• pp.54-88
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• 2020

Global effort has resulted in tremendous progress with energy harvesters that extract mechanical energy from ambient sources, convert it to electrical energy, and use it for systems such as wrist watches, mobile electronic devices, wireless sensor nodes, health monitoring, and biosensors. However, harvesting a single energy source only still pauses a great challenge in driving sustainable and maintenance-free monitoring and sensing devices. Over the last few years, research on high-performance mechanical energy harvesters at the micro and nanoscale has been directed toward the development of hybrid devices that either aim to harvest mechanical energy in addition to other types of energies simultaneously or to exploit multiple mechanisms to more effectively harvest mechanical energy. Herein, we appraise the rational designs for multiple energy harvesting, specifically state-of-the-art hybrid mechanical energy harvesters that employ multiple piezoelectric and triboelectric mechanisms to efficiently harvest mechanical energy. We identify the critical material parameters and device design criteria that lead to high-performance hybrid mechanical energy harvesters. Finally, we address the future perspectives and remaining challenges in the field.

• 한국인터넷방송통신학회논문지
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• 제10권5호
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• pp.287-291
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• 2010

본 논문에서는 차량 자동화 구현을 위한 센서네트워크 기반의 차량용 자동화 시스템을 설계 및 구현하였다. 이를 위하여 자동차내부의 각종 센서로부터 Zigbee 센서 망을 이용하여 무선으로 각종 센싱 데이터를 수집한 후 모니터 프로그램에서 이를 분석한다. 그리고 분석된 데이터를 무선 단말기와 인터페이스 시켜 차량의 상태 정보를 한눈에 운전자가 한눈에 파악할 수 있도록 하였다. 또한, 센서 네트워크 기반으로 온도센서, 습도센서 그리고 조도센서 등을 모니터링하고 이들 데이터를 기반으로 히터, 에어콘 및 차량의 실내등을 자동 구동시키는 차량 내 온/습도 자동제어 및 조도 자동조절기를 구현하였다.

• 한국산학기술학회논문지
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• 제13권1호
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• pp.364-369
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• 2012

유비쿼터스 컴퓨팅 시대로 진입하면서 사물의 위치 정보가 더욱 중요시 되고 있다. 대표적인 실내 위치 인식 시스템인 크리켓은 노드 간의 거리를 인식하기 위해서 RF 신호와 초음파 신호를 주기적으로 전송한다. 하지만 배치되어 있는 센서 노드 수가 증가할수록 신호간의 간섭 및 충돌 횟수가 증가하여 위치 인식 시스템의 정확도를 떨어뜨린다. 본 논문에서는 초음파 위치인식 시스템을 구성하기 위해, 무선 센서 네트워크 표준인 IEEE 802.15.4 MAC 프로토콜을 사용하였다. 신호간의 간섭과 충돌 횟수를 감소시키기 위해, 노드 번호와 이동통신에서 사용하는 주파수 재사용 방식을 변형하여 오차율을 감소시키는 알고리즘을 제안하였다. 성능평가 결과 제안한 알고리즘이 기존의 크리켓시스템보다 수율과 에너지 효율 면에서 더 좋은 성능을 보였다.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2008년도 한국컴퓨터종합학술대회논문집 Vol.35 No.1 (C)
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• pp.36-40
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• 2008

SIMS는 지역 정보 관리 환경을 지원하기 위한 통합 관리 시스템으로써 다양한 지역 및 비지역 자료를 관리하고 여러 응용작업을 지원한다. 본 논문에서는 지역데이터에 대한 질의를 처리하기 위해서 기존에 개발된 지역데이터 마이닝 질의 언어에 대한 모델과 지역 서술자를 기반으로 SQL형태의 객체 질의어를 새로이 정의한다. 또한 자동 데이터 수집, 인공위성 측위 서비스, 원격탐사, GPS, 모바일 컴퓨팅 등의 다양한 자료와 시지역(Spatio-Temporal)자료로부터 유용한 정보를 발견 할 수 있도록 SIMS를 기반으로 한 지역 데이터 마이닝 질의 언어를 설계하였다.

• Journal of the korean society of oceanography
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• 제37권3호
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• pp.144-153
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• 2002

This is a review paper, assessing progress reported in a Special Issue (Prandle and Lane, 2000) of Coastal Engineering focusing on simulation of SPM in the North Sea, against issues over a diverse range of shelf seas and their coastal margins. The broad objectives of reproducing the characteristics of sediment fluxes off an open coast and relating these to tidal and wave forcing were achieved. However, accurate computation of these fluxes remains sensitive to largely empirical coefficients used in determining erosion and deposition rates. Bed roughness strongly influences both these coefficients and the associated near-bed current magnitudes (including wave impact thereon). Bed roughness can change significantly over a tidal cycle and dramatically over seasons or in the course of a major event. Accurate simulation of sediment fluxes on a day-to-day basis is constrained by dependency on the initial distribution of mobile sediments. The latter depends on rates and locations of original sources and the time history of preceding events. Remote sensing via aircraft could provide data for assimilation into such models to circumvent these constraints. The approaches described here can be readily applied to other coastal regions to indicate the likely distributions and pathways of known sediment sources. However quantitative simulations will require an associated observational programme. A subsequent stage is to understand the evolving balance between the forecasted sediment movement - the resulting morphological adjustments and thence modifications to the prevailing tidal current and wave regimes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제4권5호
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• pp.776-796
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• 2010

Integrated RFID-WSNs (wireless sensor networks) have recently been researched to provide object identities, sensing information, mobile service, and network functionalities. In integrated RFID-WSNs, the reader collision is one of the critical problems. Above all, due to the absence of universally applicable anti-collision protocols and the channel capture phenomenon, the medium access control protocols in integrated RFID-WSNs suffer from reader collision and starvation problems. In this paper, we propose an efficient MAC protocol, called EMP, to avoid the above problems in integrated RFID-WSNs. EMP is a CSMA-based MAC protocol which is compatible with sensor networks operating on integrated nodes which consist of an RFID reader and a senor node. EMP resolves not only the reader collision problem, but also the starvation problem using a power control mechanism. To verify the performance of EMP, we compared it with other anti-reader collision MAC protocols using simulations. As a result, the performance of EMP showed improvements in throughput, system efficiency, and energy consumption compared to the single data channel protocols (CSMA/CA, Pulse, and DiCa) in dense deployment environments.

• Journal of Biosystems Engineering
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• 제27권5호
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• pp.417-424
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• 2002

This study was conducted to develop a vehicle, leading or following a worker at a certain distance to assist laborious transporting works in greenhouses. A prototype vehicle was tested in the practical field conditions using a developed control algorithm. Results of this study were summarized as following: 1. The sensing device consisted of infrared sensors was attached to the front of the vehicle and turning following algorithm was developed to make the vehicle turned as it follows a worker simultaneously. 2. The measured average power consumptions were 110W and 89W, equivalent to 5.2-6.4 hrs battery durations, at low speed with and without the maximum payload, respectively. 3. Results of the travel tests showed that the deviations from the center of row spacing were $\pm$100 mm along the ridge and $\pm$85 mm along the hydroponic bed in the greenhouse. Therefore, the worker-following transport vehicle was feasible to travel along the row without collision in the greenhouse.

• Journal of Biosystems Engineering
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• 제27권5호
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• pp.409-416
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• 2002

This study was conducted to develop a vehicle, leading or following a worker at a certain distance to assist laborious transporting works in greenhouses. A prototype vehicle, which consisted of the rear driving, the front steering and the console units, was designed and tested in the ideal indoor conditions. Results of this study were summarized as following: 1. The driving unit was designed to travel at the speed ranges of 0.3∼0.8 m/sec depending on the operating modes with a maximum payload of 100 kg. 2. The console unit consisted of a main-board including a 80C196KC microprocessor and peripheral devices, a power-board and safety interlock. Worker-leading, and following modes were available in automatic and manual modes. 3. Steering was achieved by turning the steering motor against the sensed direction. Proper steering angles for correcting travel direction were determined as 5 and 9 degrees when sensing cultivation beds and plants, respectively.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권11호
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• pp.3751-3774
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• 2014

With the rapid development of wireless communication, the confliction between the scarce frequency resources and the low spectral efficiency caused by the stationary spectrum sharing strategies seriously restricts the evolution of the future mobile communication. For this purpose, cognitive radio (CR) emerges as one of the most promising inventions which can overcome the spectrum shortage. As the key technology and main objective of CR, spectrum sharing can make full use of the limited spectrum, alleviate the scarcity of frequency resources and improve the system utilities, playing thereby an important role in improving the system performance of cognitive radio networks (CRNs). In this survey, the spectrum sharing in CRNs is discussed in terms of the sharing process, mainstream sharing technologies and spectrum sharing models. In particular, comparisons of different spectrum sharing strategies are concluded, as well as that of different spectrum sensing schemes in sharing procedure. Moreover, some application examples of the spectrum sharing in CRNs, such as smart grid, public safety, cellular network and medical body area networks are also introduced. In addition, our previous related works are presented and the open research issues in the field of spectrum sharing are stated as well.

• IEIE Transactions on Smart Processing and Computing
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• 제4권6호
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• pp.413-421
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• 2015

Regularized Blind Deconvolution is a problem applicable in degraded images in order to bring the original image out of blur. Multichannel blind Deconvolution considered as an optimization problem. Each step in the optimization is considered as variable splitting problem using an algorithm called Alternating Minimization Algorithm. Each Step in the Variable splitting undergoes Augmented Lagrangian method (ALM) / Bregman Iterative method. Regularization is used where an ill posed problem converted into a well posed problem. Two well known regularizers are Tikhonov class and Total Variation (TV) / L2 model. TV can be isotropic and anisotropic, where isotropic for L2 norm and anisotropic for L1 norm. Based on many probabilistic model and Fourier Transforms Image deblurring can be solved. Here in this paper to improve the performance, we have used an adaptive regularization filtering and isotropic TV model Lp norm. Image deblurring is applicable in the areas such as medical image sensing, astrophotography, traffic signal monitoring, remote sensors, case investigation and even images that are taken using a digital camera / mobile cameras.