• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.11
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• pp.5425-5448
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• 2018

Wireless sensor network has been widely used in Internet of Things (IoT) applications to support large and dense networks. As sensor nodes are usually tiny and provided with limited hardware resources, the existing multiple access methods, which involve high computational complexity to preserve the protocol performance, is not available under such a scenario. In this paper, we propose an intelligent Medium Access Control (MAC) protocol selection scheme based on machine learning in wireless sensor networks. We jointly consider the impact of inherent behavior and external environments to deal with the application limitation problem of the single type MAC protocol. This scheme can benefit from the combination of the competitive protocols and non-competitive protocols, and help the network nodes to select the MAC protocol that best suits the current network condition. Extensive simulation results validate our work, and it also proven that the accuracy of the proposed MAC protocol selection strategy is higher than the existing work.

• Journal of Sensor Science and Technology
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• v.31 no.5
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• pp.301-306
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• 2022

With the recent widespread implementation of Internet of Things (IoT) technology driven by Industry 4.0, self-powered sensors for wearable and implantable systems are increasingly gaining attention. Piezoelectric nanogenerators (PENGs) and triboelectric nanogenerators (TENGs), which convert biomechanical energy into electrical energy, can be considered as efficient self-powered sensor platforms. These are energy harvesters that are used as low-power energy sources. However, they can also be used as sensors when an output signal is used to sense any mechanical stimuli. For sensors, collecting high-quality data is important. However, the accuracy of sensing for practical applications is equally important. This paper provides a brief review of the performance advanced by the materials and structures of the latest PENG/TENG-based wearable sensors and intelligent applications applied using artificial intelligence (AI)

• Journal of Sensor Science and Technology
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• v.14 no.4
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• pp.272-277
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• 2005

A CMOS active pixel sensor has been designed and fabricated using standard 2-poly and 4-metal $0.35{\mu}m$ CMOS processing technology. The CMOS active pixel sensor has been made up of a unit pixel having a highly sensitive PMOSFET photo-detector and electronic shutters that can control the light exposure time to the PMOSFET photo-detector, correlated-double sampling (CDS) circuits, and an 8-bit two-step flash analog to digital converter (ADC) for digital output. This sensor can obtain a stable photo signal in a wide range of light intensity. It can be realized with a special function of an electronic shutter which controls the light exposure-time in the pixel. Moreover, this sensor had obtained the digital output using an embedded ADC for the system integration. The designed and fabricated image sensor has been implemented as a $128{\times}128$ pixel array. The area of the unit pixel is $7.60{\mu}m{\times}7.85{\mu}m$ and its fill factor is about 35 %.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.2
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• pp.203-208
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• 2016

This paper presents a fault detection and data processing algorithm for acoustic sensor systems using the multiple sensor algorithm that has originally developed for the wireless sensor nodes. The multiple sensor algorithm can increase the reliability of the sensor systems by utilizing and comparing the measurements of the multiple sensors. In the acoustic sensor system, the equivalent sound level($L_{eq}$) is used to detect the faulty sensor. The experiment was conducted to demonstrate the feasibility of the multiple acoustic sensor algorithm, and the results show that the algorithm can detect the faulty sensor and validate the data.

• Journal of Biomedical Engineering Research
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• v.32 no.1
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• pp.37-44
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• 2011

This paper describes the development and assessment of conductive fabric sensor for evaluating knee movement using bio-impedance measurement method. The proposed strip-typed conductive fabric sensor is compared with a dot-typed Ag/AgCl electrode for evaluating validity under knee movement condition. Subjects are composed of ten males($26.6{\pm}2.591$) who have not had problems on their knee. The strip-typed conductive fabric sensor is analyzed by correlation and reliability between a dot-typed Ag/AgCl electrode and the strip-typed conductive fabric sensor. The difference of bio-impedance between a dot-typed Ag/AgCl electrode and the strip-typed conductive fabric sensor averages $7.067{\pm}13.987\;{\Omega}$ As the p-value is under 0.0001 in 99% of t-distribution, the strip-typed conductive fabric sensor is correlated with a dot-typed Ag/AgCl electrode by SPSS software. The strip-typed conductive fabric sensor has reliability when it is compared with a dot-typed Ag/AgCl electrode because most of bio-impedance values are in ${\pm}1.96$ standard deviation by Bland-Altman Analysis. As a result, the strip-typed conductive fabric sensor can be used for assessing knee movement through bio-impedance measurement method as a dot-typed Ag/AgCl electrode. Futhermore, the strip-typed conductive fabric sensor is available for wearable circumstances, applications and industries in the near future.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.7
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• pp.521-526
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• 2018

In particular, gas sensors require characteristics such as high speed, sensitivity, and selectivity. In this study, we fabricated a $NO_X$ gas sensor by using a multi-walled carbon nanotube (MWCNT)/zinc oxide (ZnO) composite film. The fabricated MWCNT/ZnO gas sensor was then treated by a $450^{\circ}C$ temperature process to increase its detection sensitivity for NOx gas. We compared the detection characteristics of a ZnO film gas sensor, MWCNT film gas sensor, and the MWCNT/ZnO composited film gas sensor with and without the heat-treatment process. The fabricated gas sensors were used to detect $NO_X$ gas at different concentrations. The gas sensor absorbed $NO_X$ gas molecules, exhibiting increased sensitivity. The sensitivity of the gas sensor was increased by increasing the gas concentration. Additionally, while changing the temperature inside the chamber for the MWCNT/ZnO composite film gas sensor, we obtained its sensitivity for detecting $NO_X$ gas. Compared with ZnO, the MWCNT film gas sensor is excellent for detecting $NO_X$ gas. From the experimental results, we confirmed the enhanced gas sensor sensing mechanism. The increased effect by electronic interaction between the MWCNT and ZnO films contributes to the improved sensor performance.

• Journal of Korea Multimedia Society
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• v.18 no.8
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• pp.909-914
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• 2015

In wireless sensor networks, sensor nodes have a short transmission range and data is transferred from source to destination node using the multi-hop transmission. Sensor nodes are powered by battery and the link qualities are different, and the routing protocol in the wireless sensor network is one of the important technical issues. Multipath routing was proposed to reduce the data congestion and increase data throughput. In the multipath routing, however, each path can be interfered by the other path, and it can aggravate network performance. In this paper, we propose the multipath routing scheme for multi-rate wireless sensor networks. The multipath routing selects transmission paths to minimize transmission delay and path interference.

• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.4
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• pp.391-398
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• 2010

Because mobile sensor network is different with the existing wireless sensor network with fixed nodes, it is more difficult to implement a positioning algorithm in mobile sensor network than in mobile sensor network. In case of fast moving node, a positioning algorithm may be not completed in a given time. In this paper we present the positioning algorithm that improves performance and can complete a computation in time on mobile sensor network.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.768-771
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• 2001

Non-contacting capacitive sensor, based on principle of the cross capacitor, for measuring of $\mu\textrm{m}$-order displacements have been fabricated and characterized. To overcome disadvantages of the existed capacitive sensors of parallel type with 2-electrodes and 3-electrodes, the developed new sensor was designed to have 4-electrodes, two of them used high and low electrode the other two used as guard electrodes, on a sapphire plate with diameter 17 mm and thickness 0.7 mm, and are symmetrically situated with a constant gap of 0.2 mm between the electrodes. This sensor can be used for measuring the distance between sensor and target not only the metallic but also non-metallic target without ground connection.

• Transactions on Electrical and Electronic Materials
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• v.11 no.3
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• pp.130-133
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• 2010

A flexible three-axial tactile sensor was fabricated on Kapton polyimide film using polymer micromachining technology. Nichrome (Ni:Cr = 8:2) strain gauges were positioned on an etched membrane to detect normal and shear loads. The optimal positions of strain gauges were determined through strain distribution from finite element analysis. The sensor was evaluated by applying normal and shear loads from 0 N to 0.8 N using an evaluation system. Sensitivity of the tactile sensor to normal and shear loads was about 206.6 mV/N and 70.1 mV/N, respectively. The sensor showed good linearity, and its determination coefficient ($R^2$) was about 0.982. The developed sensor can be applied in a curved or compliant surface that requires slip detection and flexibility, such as a robotic fingertip.