• Journal of KIISE
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• v.44 no.11
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• pp.1149-1155
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• 2017

Recently, with the development of communication technology, it has become possible to collect various sensor data that indicate the environmental stimuli within a space. In this paper, we propose a group emotion prediction system using a modular Bayesian network that was designed considering the psychological impact of environmental stimuli. A Bayesian network can compensate for the uncertain and incomplete characteristics of the sensor data by the probabilistic consideration of the evidence for reasoning. Also, modularizing the Bayesian network has enabled flexible response and efficient reasoning of environmental stimulus fluctuations within the space. To verify the performance of the system, we predict public emotion based on the brightness, volume, temperature, humidity, color temperature, sound, smell, and group emotion data collected in a kindergarten. Experimental results show that the accuracy of the proposed method is 85% greater than that of other classification methods. Using quantitative and qualitative analyses, we explore the possibilities and limitations of probabilistic methodology for predicting group emotion.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.754-757
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• 2007

In this paper, we present an implementation and it's real-sea test of an underwater acoustic data communication system, which allows the system to reduce complexity and increase robustness in time variant underwater environments. For easy adaptation to complicated and time-varying environments of the ocean, all-digital transmitter and receiver systems were implemented. For frame synchronization the CAZAC sequence was used, and QPSK modulation/ demodulation method with carrier frequency of 25kHz and a bandwidth of 5kHz were applied to generate 10kbps transmission rate including overhead. To improve transmission quality, we used several techniques and algorithms such as adaptive beamforming, adaptive equalizer, and convolution coding/Viterbi decoding. for the verification of the system performance, measurement of BER has been done in a very shallow water with depth of 8m at JangMok, Geoje. During the experiment, image data were successfully transmitted up to about 7.4km.

• The Journal of the Acoustical Society of Korea
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• v.33 no.1
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• pp.31-39
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• 2014

In this paper, two calibration methods for angular vibration pickups using a precision rotary encoder are proposed. The KRISS (Korea Research Institute of Standards and Science) primary angular vibration calibration system and the calibration procedures are briefly explained. The rotary encoder is shown to be calibrated in two methods: The one is to use the laser interferometer to calibrate the rotary encoder under test and the other is to exploit the certificate of the encoder supplied. Complex sensitivities measured from the first are shown to be less than 0.1 % difference in magnitude and $0.01^{\circ}$ difference in phase shift in reference to those of the primary calibration system. Their expanded uncertainties were observed to be less than 0.6 % in magnitude and $0.4^{\circ}$ in phase shift over the range of 0.4 to 200 Hz. Under the same calibration conditions, complex sensitivities evaluated by the second method are shown be 0.1 % difference in magnitude and $0.6^{\circ}$ difference in phase shift in reference to those of the primary calibration system. Their expanded uncertainties were seen to be less than 4.8 % in magnitude and $2.8^{\circ}$ in phase shift.

• Journal of Institute of Control, Robotics and Systems
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• v.1 no.1
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• pp.38-42
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• 1995

This paper presents a target scoring method using shock wave signals, which are generated from the supersonic speed of a projectile. The shock wave is detected from three acoustic sensors located in the target plane and the difference of the delay times are measured. The target coordinates are calculated from the effective propagation of velocity (EPV) and the delay times of the shock wave; and the EPV is from the projectile velocity and the delay time. With a comparison between the measurement result and the known coordinates, the accuracy and the usefulness of the proposed scheme is validated.

• The Journal of the Acoustical Society of Korea
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• v.40 no.4
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• pp.382-390
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• 2021

Synthetic aperture sonars as well as side scan sonars or multibeam echo sounders have been commercialized and are widely used for seafloor imaging. In Korea related research such as the development of a towed synthetic aperture sonar system is underway. In order to obtain high-resolution synthetic aperture sonar images, it is necessary to accurately estimate the platform motion on which it is installed, and a precise underwater navigation system is required. In this paper we are going to provide reference data for determining the required navigation accuracy and precision of navigation sensors by quantitatively analyzing how much distortion of the sonar images occurs according to motion characteristics of the platform equipped with the synthetic aperture sonar. Five types of motions are considered and normalized root mean square error is defined for quantitative analysis. Simulation for error analysis with parameter variation of motion characteristics results in that yaw and sway motion causes the largest image distortion whereas the effect of pitch and heave motion is not significant.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4B
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• pp.405-411
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• 2011

As the interest in ocean environment monitoring and ocean development has been increased, the need for researches on underwater wireless sensor network (UWSN) and low power consuming acoustic modem for UWSN has been arisen. In this paper, we design and implement a micro-modem equipped with a tiny and omnidirectional transducer for underwater acoustic communications. In addition, we make experiments in a water tank and a pond in order to verify the performance of the developed modem in terms of supply voltage and communication distance, and analyze the results. According to the outdoor experiments, the modem can send data wirelessly in underwater at a distance of 40 meter with a data rate of 200 bps and a bit error rate of $10^{-5}$ when the supply voltage is 12 V. Due to its small size, low power consumption and omnidirectional property, it is expected that the modem which is implemented in this paper could be utilized for various applications based on UWSN.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.3
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• pp.78-86
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• 2017

In this paper, we propose hidden object detection system using parametric array based on acoustic signal that is harmless to human body. A transmit signal of the proposed detection system uses a high directive chirp signal generated from parametric array phenomenon, which uses technique to improve a signal to noise (SNR) of a received signal and a distance resolution trough the dechirp processing. The transmit sensor array is constructed as $8{\times}2$ and has a horizontal beam width of $7^{\circ}$ and vertical beam width of $26^{\circ}$. To verify the detection and visualization of the proposed system, a 2-axis driving control system based on linear stage was constructed, and A-scan, B-scan, and C-scan experiments was addressed for hidden object. From experimental results, we detected and visualized the hidden bronze plate and pipe by cloth and the visualized shapes was confirmed. Especially, the obtained errors was $0.015m^2$ for bronze plate, and $0.046m^2$ for pipe.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.5
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• pp.657-673
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• 2019

A monitoring method based on acoustic emission (AE) sensor has been widely used to evaluate the damage of structures in underground rock. The acoustic emission signal generated from cracking in material is analyzed as various acoustic emission parameters in time and frequency domain. To investigate from initial crack generation to final failure of rock material, it is important to understand the characteristics of acoustic emission parameters according to the stress ratio and rock strength. In this study, uniaxial compression tests were performed using very strong and weak rock specimen in order to investigate the acoustic emission parameters when the failure of specimen occurred. In the results of experimental tests, the event, root-mean-square (RMS) voltage, amplitude, and absolute energy of very strong rock specimen were larger than those of the weak rock specimen with an increase of stress ratio. In addition, the acoustic emission parameters related in frequency were more affected by specification (e.g., operation and resonant frequency) of sensors than the stress ratio or rock strength. It is expected that this study may be meaningful for evaluating the damage of underground rock when the health monitoring based on the acoustic emission technique will be performed.

• The Journal of the Acoustical Society of Korea
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• v.23 no.2
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• pp.117-124
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• 2004

In this paper, we have been implemented the QPSK-based underwater transmission systems using DSP in order to transmit the underwater image data. We have adopted a BDPA (Block Data Parallel Architecture) to control multiple DSPs used in the transmitter and receiver in order to transmit the image data in real-time. We also have developed GUI software in order to drive and to debug the implemanted system in real-time. We have executed open sea tests in order to analyze the performance of the implemented system at East Sea near Kosung in Kangwon-Do. As a result of these experiments, it has been demonstrated that 10 kbps image data can be received without errors at 30m and 80m depth points, while the distance between the transmitter and the receiver is up to 20m.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.3
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• pp.275-281
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• 2014

Recently, the need for various underwater application systems targeting efficient resource exploration and aquatic ecosystem monitoring is rapidly increasing in littoral sea and inland waters. In this paper, we focus on the research and development of digital module of acoustic micro modem which can be used for underwater mobile communication systems and underwater sensor network systems. Specifically, a digital module of acoustic modem embedding digital signal processor is designed and implemented. On top of the developed hardware platform, physical layer frame generation and recovery and channel coding algorithms are mounted and tested in a water tank and a pond to verify its functionality and performance. According to experimental results, less than 1 percent of total computational power is consumed in the processing of frame control and convolutional code with the data rate of 1 kbps. Thus, the performance of micro modem could be improved by loading efficient baseband algorithms into the processor while maintaining the implemented hardware.