• 산업기술연구
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• 제27권B호
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• pp.103-107
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• 2007

In this paper, the light screen sensing system is introduced and testified to detect small grains such as seeds or electronic chips of uneven sized. Two modules composed of transmitter-receiver sensor array and microprocessor-based sensor signal processing system are developed to realize the proposed system. Experimental results showed that the sensing signal was relatively clear and its counting performance was very stable.

• Smart Structures and Systems
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• 제15권4호
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• pp.1103-1120
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• 2015

A self-sensing magnetorheological (MR) damper with embedded piezoelectric force sensor has recently been devised to facilitate real-time close-looped control of structural vibration in a simple and reliable manner. The development and characterization of the self-sensing MR damper are presented based on experimental work, which demonstrates its reliable force sensing and controllable damping capabilities. With the use of experimental data acquired under harmonic loading, a nonparametric dynamic model is formulated to portray the nonlinear behaviors of the self-sensing MR damper based on NARX modeling and neural network techniques. The Bayesian regularization is adopted in the network training procedure to eschew overfitting problem and enhance generalization. Verification results indicate that the developed NARX network model accurately describes the forward dynamics of the self-sensing MR damper and has superior prediction performance and generalization capability over a Bouc-Wen parametric model.

• 한국통신학회논문지
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• 제35권5A호
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• pp.490-495
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• 2010

본 논문에서는 DFT를 활용한 순차적 스펙트럼 센싱 알고리즘을 제안한다. 기존의 FFT를 이용한 센싱 알고리즘의 경우 FFT의 특성상 한번에 모든 주파수 성분을 구하여 임계값과 비교하는 구조로 불필요한 계산량을 포함하고 있다. 제안하는 센싱 알고리즘에서는 DFT를 활용하여 우선순위에 따라서 주파수 성분을 순차적으로 구하고 이를 임계값과 비교하여 신호의 존재 여부를 판단한다. 제안하는 센싱 알고리즘은 기존의 FFT를 이용한 센싱 알고리즘과 유사한 검출 성능을 제공하면서 신호의 조기 검출 여부에 따라 스펙트럼 센싱에 필요한 계산량을 현저하게 줄일 수 있다.

• Journal of Information Processing Systems
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• 제15권6호
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• pp.1335-1349
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• 2019

Crowdsensing technologies can improve the efficiency of smart parking system in comparison with present sensor based smart parking system because of low install price and no restriction caused by sensor installation. A lot of sensing data is necessary to predict parking lot saturation in real-time. However in real world, it is hard to reach the required number of sensing data. In this paper, we model a saturation predication combining a time-based prediction model and a sensing data-based prediction model. The time-based model predicts saturation in aspects of parking lot location and time. The sensing data-based model predicts the degree of saturation of the parking lot with high accuracy based on the degree of saturation predicted from the first model, the saturation information in the sensing data, and the number of parking spaces in the sensing data. We perform prediction model learning with real sensing data gathered from a specific parking lot. We also evaluate the performance of the predictive model and show its efficiency and feasibility.

• Journal of information and communication convergence engineering
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• 제11권4호
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• pp.223-228
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• 2013

Cognitive radio has been recently considered a promising technology to improve spectrum utilization by enabling secondary access to licensed bands that are not used by primary users temporarily or spatially. A prerequisite to this secondary access is the lack of interference to the primary system. This requirement makes spectrum sensing a key process for cognitive radio. In this study, we consider amplify and forward (AF)-based cooperative spectrum sensing for cognitive radio networks where multiple relay nodes are utilized to amplify and forward the primary user signal for better spectrum sensing, and maximum ratio combining is used for fusion detection by a cognitive coordinator. Further, the detection probability and the bit error rate of AF-based cooperative spectrum sensing are analyzed in fading multiple cognitive relay channels. The simulation results show that the AF-based cooperative spectrum sensing scheme outperforms the conventional scheme.

• 한국표면공학회지
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• 제50권3호
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• pp.225-229
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• 2017

ZnO nanotubes were synthesized to investigate the effect of wall thickness on the ethanol gas sensing performance. The wall thickness of the nanotubes was varied from approximately 20 to 60 nm. Transmission electron microscopy, X-ray diffraction and SAED (Selected Area Electron Beam Diffraction) analyses showed that the synthesized nanotubes were polycrystalline structured ZnO with the diameter of approximately 200-300nm. The ZnO nanotubes sensor with an optimum wall thickness of 51.8nm showed approximately 8 times higher response, compared to that with 21.14nm wall thick nanotubes, to the ethanol concentration of 500 ppm at the temperature of $300^{\circ}C$. The wall thickness of 51.8nm was found to be a little larger than 46nm, which was theoretically derived Debye length. Along with the study of the wall thickness effect on the performance of the sensors, the mechanisms of gas sensing of the polycrystalline ZnO nanotubes are also discussed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권1호
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• pp.248-268
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• 2018

The performance of smartphone applications are usually constrained in user interactions due to resource limitation and it promises great opportunities to improve the performance by exploring the smartphone built-in and embedded sensing techniques. However, heterogeneity in techniques, semantic gap between sensor data and usable context, and complexity of contextual situations keep the techniques from seamless integration. Relevant studies mainly focus on feasibility demonstration of emerging sensing techniques, which rarely address both general architectures and comprehensive technical solutions. Based on a proposed functional model, this investigation provides a general architecture to deal with the dynamic context for context-aware automation and decision support. In order to take advantage of the built-in sensors to improve the performance of mobile applications, an ontology-based method is employed for context modelling, linguistic variables are used for heterogeneous context presentation, and semantic distance-based rule matching is employed to customise functions to the contextual situations. A case study on mobile application authentication is conducted with smartphone built-in hardware modules. The results demonstrate the feasibility of the proposed solutions and their effectiveness in improving operational efficiency.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1987년도 한국자동제어학술회의논문집(한일합동학술편); 한국과학기술대학, 충남; 16-17 Oct. 1987
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• pp.747-752
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• 1987

The dynamic characteristics of a load-sensing hydraulic servo system are complex and highly unstable. Another property of the system is that the setting value of pump compensator is closely related to energy efficiency as well as control performance of the system. This necessitates the development of an effective control algorithm which guarantees good control performance, stability and energy efficiency. This paper considers a suboptimal PID control for the velocity control problem of the load-sensing hydraulic servo system. The results of simulations studies and experiments show that the proposed suboptimal controller can produce much better control performance than nonoptimal controllers and give effective energy efficiency.

• 대한전자공학회논문지TC
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• 제47권7호
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• pp.45-50
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• 2010

본 논문은 면허사용자와 CR기기 사이의 거리에 따른 가중치가 적용된 결합방식 (Distance based weight combining : DWC)을 사용하여 에너지 검출 기반 협력 스펙트럼 센싱을 제안하고 이에 따른 분석 및 모의실험 결과를 나타낸다. 면허사용자의 신호는 OFDM기반의 시스템을 가정하였으며 면허 사용자와 CR 기기 사이의 무선 채널은 가우시안 (Gaussian) 채널로 모델링 하였다. 에너지 검출법을 위한 임계값은 각 채널의 SNR (Signal to Noise Ratio)에 따라 다르게 적용되었으며 각 채널의 잡음신호의 평균값으로 가정하였다. DWC를 적용한 협력 스펙트럼 센싱을 수행한 결과 거리에 따라 다양한 검출확률을 나타낸 단일 센싱에 비해 비교적 안정된 검출확률을 나타내는 것으로 알 수 있었으며, 동일이득 결합을 반영하여 협력스펙트럼 센싱을 수행한 것 보다 우수한 스펙트럼 센싱을 나타내었다.

• 한국ITS학회 논문지
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• 제7권6호
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• pp.110-120
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• 2008

인지무선(CR: Cognitive Radio) 기술은 최근의 스펙트럼 부족 문제 때문에 사용하지 않는 스펙트럼 대역을 효과적으로 사용하기 위해서 제안되었다. 인지무선 기술에서 스펙트럼 센싱 기술은 주요 이슈 중의 하나이고, 비면허 사용자는 1차 사용자에게 할당된 빈 스펙트럼 자원을 확인하고 활용할 수 있다. 본 논문에서는 협력 스펙트럼 센싱 기술을 지능형 교통시스템(ITS: Intelligent Transport system)에 적용하여 신호 검출의 성능을 분석한다. 그리고 협력 신호 검출을 위해서 OR-rule과 AND-rule을 사용하여 신호 검출의 성능과 신뢰성을 향상시킨다.