• 한국정밀공학회지
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• 제23권6호
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• pp.64-71
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• 2006

A target of this paper is to study on the usefulness of the adaptive piezoelectric energy harvesting device as a wireless electrical power supply when it is driven by mechanical vibrations of low frequency. For this purpose, an adaptive control technique and a step-down converter are used. A THUNDER series a piezoelectric material (TH7-R), which has been developed by a NASA engineer is selected for this study. In order to provide a mechanical energy to the piezoelectric material, a mechanical motion vibrator is designed. The adaptive controller is implemented using a dSPACE DS1104 controller board. The do-dc converter with an adaptive control technique harvests energy at over five times the rate of direct charging without a converter.

• 한국항행학회논문지
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• 제11권4호
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• pp.423-429
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• 2007

무선 스마트카드는 빌딩 보안 어플리케이션에 주된 역할을 하고 있다. 본 연구는 사용자에게 보다 편리함을 주고 스마트카드 시스템의 성능 개선을 제안한다. 스마트카드는 카드 리더기에 삽입을 하지 않고 장치에서 수센티미터 떨어져도 접근이 허용된다. 적응형 변조와 오류 제어를 통해 전력소비를 제어하는 성능은 필요하다. 본 논문에서는 적응형 리드 솔로몬 코드 기반의 FEC와 링크에서 M계수를 변화시킨 M-FSK변조에 대하여 연구한다. 적응형 변조와 적응형 오류 정정은 다른 다양한 정적스키마와 에너지 효율을 비교한 결과 50% 이상 에너지를 저장한다.

• 디지털융복합연구
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• 제11권12호
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• pp.401-406
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• 2013

이동통신 시스템에 적용되는 적응변조방식의 변환은 주변 환경을 고려한 변환을 사용하므로, 변환 조건 및 이에 따른 전송량의 변화에 대한 관점에서 다루었으나, 이동통신 단말기와 같이 에너지 효율이 좋아야 하는 경우에는 이러한 적응방식이 성능을 낮게 할 경우가 발생한다. 따라서 전송효율만을 고려하던 기존방식에서 소비 에너지를 고려하고, 프레임 길이를 조절하여 사용하는 적응변조방식을 제어하는 최적화 방식을 제안한다.

• Journal of Communications and Networks
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• 제12권5호
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• pp.510-517
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• 2010

In this paper, an adaptive MAC protocol (variable load adaptive (VLA)-MAC) is proposed for wireless sensor networks. This protocol can achieve high energy efficiency and provide low latency under variable-traffic-load conditions. In the case of VLA-MAC, traffic load is measured online and used for adaptive adjustment. Sensor nodes transmit packets in bursts under high load conditions to alleviate packet accumulation and reduce latency. This also removes unnecessary listen action and decreases energy consumption in low load conditions. Simulation results show that the energy efficiency, latency, and throughput achieved by VLA-MAC are higher than those achieved by some traditional approaches.

• 반도체디스플레이기술학회지
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• 제7권1호
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• pp.23-27
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• 2008

Wireless sensor networks are emerging as a solution for a wide range of data gathering applications. The most difficult challenge for the design of sensor nodes is the need for significant reductions in energy consumption. The threshold methods which filter redundant and similar data can be used to save energy. In this paper, we propose the adaptive threshold method to effectively manage the energy in wireless sensor nodes. In the adaptive threshold method, wireless sensor nodes can change the thresholds dynamically as the sensing environments vary. The simulation results show that the adaptive threshold method works very effectively even when we experience the significant volatility in the data. This scheme can be used in order to monitor the malfunction in the equipment of semiconductor manufacturing line.

• 한국시뮬레이션학회논문지
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• 제21권4호
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• pp.47-56
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• 2012

본 연구에서는 센서 네트워크용 병렬 시뮬레이터인 PASENS(Parallel SEnsor Network Simulator)를 이용하여 센서 네트워크에 이용되는 라우팅 알고리즘 중에서 계층적 라우팅 프로토콜의 대표적인 방식인 LEACH(Low-Energy Adaptive Clustering Hierarchy)와 그의 변형인 TL-LEACH(Two Level Low-Energy Adaptive Clustering Hierarchy), M-LEACH(Multihop Low-Energy Adaptive Clustering Hierarchy), 그리고 LEACH-C(LEACH-Centralized)의 전력 소모량과 데이터의 수신율을 비교하고 분석하였다. 시뮬레이션을 이용한 분석 결과에 따르면, M-LEACH 라우팅 프로토콜의 경우에는 여러 센서 노드들을 통하여 데이터가 전달되기 때문에 일정한 크기 이상의 넓은 공간에서 높은 수신율을 보였으며, LEACH-C 라우팅 프로토콜은 싱크 노드(서버)가 전체 센서 노드의 잔여 에너지와 위치를 고려하여 클러스터 헤드를 결정하기 때문에 좁은 공간에서 보다 오랜 수명을 필요로 하는 센서 네트워크를 구축하는데 가장 효율적이라는 것을 확인 할 수 있었다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권6호
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• pp.668-676
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• 2017

A two-dimensional numerical investigation is performed to study the influence of slot width of multi-stage stationary floating overtopping wave energy devices on overtopping flow rate and performance. The hydraulic efficiency based on captured crest energy of different device layouts is compared with that of single-stage device to determine the effect of the geometrical design. The results show optimal trends giving a huge increase in overtopping energy. Plots of efficiency versus the relative slot width show that, for multi-stage devices, the greatest hydraulic efficiency is achieved at an intermediate value of the variable within the parametric range considered, relative slot width of 0.15 and 0.2 depending on design layouts. Moreover, an application of adaptive slot width of multi-stage device is investigated. The numerical results show that the overall hydraulic efficiency of non-adaptive and adaptive slot devices are approximately on par. The effect of adaptive slot width on performance can be negligible.

• International Journal of Internet, Broadcasting and Communication
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• 제13권3호
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• pp.25-33
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• 2021

Energy-harvesting wireless sensor networks(EH-WSNs) can collect energy from the environment and overcome the technical limitations of existing power. Since the transmission distance in a wireless sensor network is limited, the data are delivered to the destination node through multi-hop routing. In EH-WSNs, the routing protocol should consider the power situations of nodes, which is determined by the remaining power and energy-harvesting rate. In addition, in applications such as environmental monitoring, when there are urgent data, the routing protocol should be able to transmit it stably and quickly. This paper proposes an adaptive routing protocol that satisfies different requirements of normal and urgent data. To extend network lifetime, the proposed routing protocol reduces power imbalance for normal data and also minimizes transmission latency by controlling the transmission power for urgent data. Simulation results show that the proposed adaptive routing can improve network lifetime by mitigating the power imbalance and greatly reduce the transmission delay of urgent data.

• Smart Structures and Systems
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• 제9권6호
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• pp.549-563
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• 2012

Theoretical analysis is performed on a multi-mode energy harvester design with focus on the first two vibration modes. Based on the analysis, a modification is proposed for designing a novel adaptive multi-mode energy harvester. The device comprises a simply supported beam with distributed mass and piezoelectric elements, and an adaptive damper that provides a 180 degree phase shift for the motions of two supports only at the second vibration mode. Theoretical analysis and numerical simulations show that the new design can efficiently scavenge energy at the first two vibration modes. The energy harvesting capability of the multi-mode energy harvester is also compared with that of a cantilever-based energy harvester for single-mode vibration. The results show that the energy harvesting capacity is affected by the damping ratios of different designs. For fixed damping ratio and design dimensions, the multi-mode design has higher energy harvesting capacity than the cantilever-based design.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1992년도 학술논문발표회 논문집 제11권 1호
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• pp.23-28
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• 1992

The purpose of this paper is to develop a new adaptive echo canceller improving convergence speed and near-end-talker detection performance of the conventional echo canceller. In a conventional adaptive echo canceller, an adaptive digital filter with TDL(Tapped-Delay Line) structure modelling the echo path uses the LMS(Least Mean Square) algorithm to cote the coefficients, and NET detector using energy comparison method prevents the adaptive digital filter to update the coefficients during the periods of the NET signal presence. The convergence speed of the LMS algorithm depends on the eigenvalue spread ratio of the reference signal and NET detector using the energy comparison method yields poor detection performance if the magnitude of the NET signal is small. This paper presents a new adaptive echo canceller which uses the pre-whitening filter to improve the convergence speed of the LMS algorithm. The pre-whitening filter is realized by using a low-order lattice predictor. Also, a new NET signal detection algorithm is presented, where the start point of the NET signal is detected by computing the cross-correlation coefficient between the primary input and the ADF(Adaptive Digital Filter) output while the end point is detected by using the energy comparison method. The simulation results show that the convergence speed of the proposed adaptive echo canceller is faster than that of the conventional echo canceller and the cross-correlation coefficient yield more accurate detection of the start point of the NET signal.