• Journal of Sensor Science and Technology
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• v.23 no.5
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• pp.342-348
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• 2014

This paper introduced a novel multi-gas sensor detector with simple signal processing algorithm. This device was evaluated by investigating the characteristics of combustible materials using fire-generated smell and smoke. Plural sensors including TGS821, TGS2442, and TGS260X were equipped to detect carbon monoxide, hydrogen gas, and gaseous air contaminants which exist in cigarette smoke, respectively. Signal processing algorithm based on the difference of response times in fire-generated gases was implemented with early and accurately fire detection from multiple gas sensing signals. All fire experiments were performed in a virtual fire chamber. The cigarette, cotton fiber, hair, polyester fiber, nylon fiber, paper, and bread were used as a combustible material. This analyzing software and sensor controlling algorithm were embedded into 8-bit micro-controller. Also the detected multiple gas sensor signals were simultaneously transferred to the personnel computer. The results showed that the air pollution detecting sensor could be used as an efficient sensor for a fire detector which showed high sensitivity in volatile organic compounds. The proposed detecting algorithm may give more information to us compared to the conventional method for determining a threshold value. A fire detecting device with a multi-sensor is likely to be a practical and commercial technology, which can be used for domestic and office environment as well as has a comparatively low cost and high efficiency compared to the conventional device.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.2
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• pp.178-185
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• 2014

This paper describes a fabrication multiplexing sensor probe that employs a fiber Bragg grating(FBG) based on multiple measurements to determine the blade deflection of a wind power generator the reliability analysis of this probe is also presented. To diminish the temperature sensitivity of the FBG sensor, we form multiple CFRPs onto the upper and lower layers of the FBG and package it with an epoxy resin. As a result, the depth of the CFRP is 1mm, and the temperature sensitivity is $2.39pm/^{\circ}C$. We construct a sensor network utilizing the fabricated sensor with a blade beam model. As the number of pendulums is increased on the fore-end of the beam, the strain value is measured. The strain variation is calculated from the measurement of the load on the blade beam model by monitoring the strain of the FBG sensor. When the linear equation is applied, the strain error is 0.4% and when the finite difference method is used, the tip deflection error is 3.3%. The displacement error derived from the strain value of the FBG sensor is 4.39%. The calculated result between the measured value of the dead-end of the beam and the strain is less than 2.46% tip distortion error. Therefore, our proposed multiplexing sensor probe is a low-cost and high-reliability solution for a commercial wind power generator.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.101-104
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• 2007

Efficient Query processing and optimization are critical for reducing network traffic and decreasing latency of query when accessing and manipulating sensor data of large-scale sensor networks. Currently it has been studied in sensor database projects. These works have mainly focused on in-network query processing for sensor networks and assumes homogeneous sensor networks, where each sensor network has same hardware and software configuration. In this paper, we present a framework for efficient query processing over heterogeneous sensor networks. Our proposed framework introduces query processing paradigm considering two heterogeneous characteristics of sensor networks: (1) data dissemination approach such as push, pull, and hybrid; (2) query processing capability of sensor networks if they may support in-network aggregation, spatial, periodic and conditional operators. Additionally, we propose multi-query optimization strategies supporting cross-translation between data acquisition query and data stream query to minimize total cost of multiple queries. It has been implemented in WSN middleware, COSMOS, developed by ETRI.

• Journal of IKEEE
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• v.22 no.4
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• pp.907-915
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• 2018

This paper proposes a method to improve the performance of low cost infrared distance sensor. Infrared distance sensor measures the intensity of reflected light and converts it into distance. The proposed method improves the sensing distance of the sensor and makes it operate robustly in various lighting environments. This is achieved by extracting the characteristic curves of the sensor and applying the HDR (High Dynamic Range) technique. The output value of the sensor was obtained by varying the intensity of the infrared input and the exposure time, and the characteristic curve of the sensor was extracted from it.

• Journal of Communications and Networks
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• v.13 no.2
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• pp.160-166
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• 2011

In u-healthcare services based on wireless body sensor networks, reliable connection is very important as many types of information, including vital signals, are transmitted through the networks. The transmit power requirements are very stringent in the case of in-body networks for implant communication. Furthermore, the wireless link in an in-body environment has a high degree of path loss (e.g., the path loss exponent is around 6.2 for deep tissue). Because of such inherently bad settings of the communication nodes, a multi-hop network topology is preferred in order to meet the transmit power requirements and to increase the battery lifetime of sensor nodes. This will ensure that the live body of a patient receiving the healthcare service has a reduced level of specific absorption ratio (SAR) when exposed to long-lasting radiation. We propose an efficientmethod for delivering delay-intolerant data packets over multiple hops. We consider forward error correction (FEC) in an erasure correction mode and develop a mathematical formulation for packet-level scheduling of delay-intolerant FEC packets over multiple hops. The proposed method can be used as a simple guideline for applications to setting up a topology for a medical body sensor network of each individual patient, which is connected to a remote server for u-healthcare service applications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.10B
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• pp.1216-1221
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• 2011

We propose a multiplexed fiber Bragg grating (FBG) sensor network for vessel monitoring to measure the variation of strain and temperature by environmental perturbation based on code division multiple access (CDMA). The center wavelength of FBG was linearly changed by environmental perturbation such as strain and temperature variation so that we could be monitoring the state of sensors. A RSOA was used as optical broadband source and which was modulated by using pseudo random binary sequence (PRBS) signal. The correlation peak of reflected signal from sensor networks was measured. In this paper, we used the sliding correlation techniques for high speed response and dynamic rage of sensors.

• Journal of Electrical Engineering and Technology
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• v.11 no.4
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• pp.905-914
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• 2016

This paper proposes a new phase current reconstruction technique for interleaved three-phase bidirectional dc-dc converters using a single current sensor. In the proposed current reconstruction algorithm, a single current sensor is employed at the dc-link, and the dc-link current information is sampled at either the peak or valley point of the pulse-width modulation (PWM) carriers regularly. From the obtained current information, all phase currents are reconstructed in a single PWM cycle. After that, the digital current controller is applied to achieve current balancing in each phase. Compare to the previous multiple current sensor method, the proposed strategy reduces the number of the current sensors in the interleaved three-phase bidirectional converter as well as reducing potential current sensing error caused by non-ideal characteristics of the multiple current sensors. The effectiveness of the proposed method is verified from the experiments based on a 3kW three-phase bidirectional converter prototype for the automotive battery charging application.

• Journal of the Korea Society for Simulation
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• v.18 no.4
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• pp.175-184
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• 2009

The distance of sensor nodes is an important factor in having influence on capability of networks in underwater acoustic sensor networks. Our proposed scheme is to establish an efficient distance to design a route of communication in underwater environment and it proposes a Level scheme that the areas divided by transmit/receive distance in network are given different levels. Our proposed scheme is pursued research to maintain a established route and maximize an energy efficiency. The established route will have fluid modification by an internal and external factors and it will construct more robust underwater sensor networks over our proposed multiple path configuration scheme.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.4
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• pp.579-586
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• 2023

A wireless sensor network (WSN) has limited battery power because it is used wirelessly using low-cost small sensors. Since the battery cannot be replaced, the lifespan of the sensor node is directly related to the lifespan of the battery, so power must be used efficiently to maximize the lifespan of the network. In this study, based on PEGASIS, a representative energy-efficient routing protocol, we propose a protocol that classifies layers according to the distance from the sink node and configures multiple chains rather than one chain. The proposed protocol can increase network lifespan by reducing the transmission distance between nodes to prevent unnecessary energy consumption.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.8B
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• pp.706-711
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• 2012

The current visible light communication (VLC) systems have a short transmission distance and a low data rate. To overcome this, we studied on the method of appling MIMO technology to VLC. However, it is difficult to apply the original MIMO technology used in RF frequency to wireless VLC. In VLC system, a lens can be used to separate the transmitted signals. And, if we use an image sensor as the receiver, MIMO technology can be applied to LED wireless visible light communication. In this paper, we report an experiment of $2{\times}2$ LED wireless visible light communication using a commercial image sensor receiver. We show the experimental demonstration with a transmission length of 10.5 m and a data rate of 200 bit/s.