• Journal of Korean Tunnelling and Underground Space Association
• /
• v.16 no.5
• /
• pp.471-485
• /
• 2014

The monitoring method of geotechnical structures using acoustic emission(AE) and microseismicity(MS) is to detect the microscopic deformation and fracture behavior in the inner structures by measuring induced acoustics and vibrations. It can identify a pre-indication of failure by taking advantage of the characteristics that the amount and occurrence rates of AE and MS increase rapidly prior to large scale destruction of the target structures. The monitoring system consisting of high-quality sensors, high-speed data acquisition device and the operation program is required for the practical application of this method. Recently, the AE and MS monitoring systems have been localized. In particular, the developed operation software which can analyze and interpret the measured signals was demonstrated through a number of applications to domestic fields. This report introduces the configuration and features of developed monitoring system, then the challenges and future direction of AE monitoring in geotechnical structures are discussed.

• Journal of Sensor Science and Technology
• /
• v.31 no.1
• /
• pp.24-30
• /
• 2022

Distributed fiber-optic acoustic·vibration sensing technology is becoming increasingly popular in many industrial and academic areas such as in securing large edifices, exploring underground seismic activity, monitoring oil well/reservoir, etc. Long-range perimeter intrusion detection exemplifies an application that not only detects intrusion, but also pinpoints where it happens and recognizes kinds of threats made along the perimeter where a single fiber cable was installed. In this study, we developed a distributed fiber-optic sensing device that measures a distributed acoustic·vibration signature (pattern) for intrusion detection. In addition, we demontrate the proposed deep learning algorithm and how it classifies various intrusion events. We evaluated the sensing device and deep learning algorithm in a practical testbed setup. The evaluation results confirm that the developed system is a promising intrusion detection system for long-distance and seamless recognition requirements.

• The Journal of the Acoustical Society of Korea
• /
• v.15 no.2
• /
• pp.21-32
• /
• 1996

The performance of the energy density control algorithm for controlling a broadband noise is evaluated in a one-dimensional enclosure. To avoid noncausality problem of a control filter, which often happens in a frequency domain optimization, analyses presented in this paper are undertaken in the time domain. This approach provides the form of the causally constrained optimal controller. Numerical results are presented to predict the performance of the active noise control system, and indicate that imp개ved global attenuation of the broadband noise can be achieved by minimizing the energy density, rather than the squared pressure. It is shown that minimizing the energy density at a single location yields global attenuation results that are comparable to minimizing the potential energy. Furthermore, unlike the squared pressure control, the energy density control does not demonstrate any dependence on the error sensor location for this one-dimensional field. A practical implementation of the energy-based control algorithm is presented. Results show that the energy density control can be implemented using the two sensor technique with a tolerable margin of performance degradation.

• 한국신재생에너지학회:학술대회논문집
• /
• 2007.06a
• /
• pp.395-399
• /
• 2007

Renewable energy sources such as wind energy is copiously available without any limitation. Wind turbines are used to tap the potential of wind energy which is available in millions of megawatt. Reliability of wind turbine is critical to extract this maximum amount of energy from the wind. We reviewed different techniques, methodologies, and algorithms developed to monitor the performance of wind turbine as well as for an early fault detection to keep away the wind turbines from catastrophic conditions due to sudden breakdowns. To keep the wind turbine in operation, implementation of Condition Monitoring System (CMS) is paramount, and for this purpose ample knowledge of these types of system is mandatory. So, an attempt has been made in this direction to review maximum approaches related to CMS in this piece of writing.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.17 no.5
• /
• pp.1253-1258
• /
• 2013

This Paper deals with detection and defense methods for underwater weapons because there are so many dangers of underwater weapons not only in the war period but also in the peace time. Underwater mines are the representative strategic arms. The sensors and target detection methods, threat elimination method of mines included in this paper. Among the various sensors of mine, we use the magnetometor for target detection method in the simulation and execute the analysis of magnetic field of detected target ships. It will be also provided that effectiveness of target detection, sweeping method of mine, tactics of mine planning and mine sweeping and so on.

• Journal of Broadcast Engineering
• /
• v.27 no.1
• /
• pp.91-103
• /
• 2022

Determination of sound source characteristics such as: sound volume, direction and distance to the source is one of the important techniques for unmanned systems like autonomous vehicles, robot systems and AI speakers. There are multiple methods of determining the direction and distance to the sound source, e.g., using a radar, a rider, an ultrasonic wave and a RF signal with a sound. These methods require the transmission of signals and cannot accurately identify sound sources generated in the obstructed region due to obstacles. In this paper, we have implemented and evaluated a method of detecting and identifying the sound in the audible frequency band by a method of recognizing the volume, direction, and distance to the sound source that is generated in the periphery including the invisible region. A cross-shaped based sound source recognition algorithm, which is mainly used for identifying a sound source, can measure the volume and locate the direction of the sound source, but the method has a problem with "blind spots". In addition, a serious limitation for this type of algorithm is lack of capability to determine the distance to the sound source. In order to overcome the limitations of this existing method, we propose a QRAS-based algorithm that uses rectangular-shaped technology. This method can determine the volume, direction, and distance to the sound source, which is an improvement over the cross-shaped based algorithm. The QRAS-based algorithm for the OSSD uses 6 AITDs derived from four microphones which are deployed in a rectangular-shaped configuration. The QRAS-based algorithm can solve existing problems of the cross-shaped based algorithms like blind spots, and it can determine the distance to the sound source. Experiments have demonstrated that the proposed QRAS-based algorithm for OSSD can reliably determine sound volume along with direction and distance to the sound source, which avoiding blind spots.

• Journal of Advanced Marine Engineering and Technology
• /
• v.37 no.4
• /
• pp.425-430
• /
• 2013

Robust and high speed underwater communication is severely limited when compared to communications in terrestial. In free space, RF communication operates over long distances at high data rates. However, the obstacle in seawater is the severe attenuation due to the conducting nature. Acoustic modems are capable of long range communication up to several tens of kilometers, but it has low data-rate, high power consumption and low propagation speed. An alternative means of underwater communication is based on optics, wherein high data rates are possible. In this paper, the characteristics of underwater channel in the range of visible wavelength is investigated. And the possibility of optical wireless communication in underwater is also described. The LED-based transceiver and CMOS sensor module are integrated in the system, and the performance of image transmission was demonstrated.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.4B
• /
• pp.422-428
• /
• 2011

In this paper, we introduce system and channel modeling for an underwater ad hoc acoustic network with n regularly located nodes， and then analyze capacity scaling laws based on the model. A narrow-band model is assumed where the carrier frequency is allowed to scale as a function of n. In the network, we characterize in attenuation parameter that depends on the frequency scaling as well as the transmission distance. A cut-set upper bound on the throughput scaling is then derived in extended networks having unit node density. Our result indicates that the upper bound is inversely proportional to the attenuation parameter, thus resulting in a power-limited network. Furthermore, we describe an achievable scheme based on the simple nearest-neighbor multi-hop (MH) transmission. It is shown under extended networks that the MH scheme is order-optimal for all the operating regimes expressed as functions of the attenuation parameter.

• The Journal of the Convergence on Culture Technology
• /
• v.5 no.4
• /
• pp.407-412
• /
• 2019

In this paper, we propose a technique for processing of speech recognition in korean words. Speech recognition is a technology that converts acoustic signals from sensors such as microphones into words or sentences. Most foreign languages have less difficulty in speech recognition. On the other hand, korean consists of vowels and bottom consonants, so it is inappropriate to use the letters obtained from the voice synthesis system. That improving the conventional structure speech recognition can the correct words recognition. In order to solve this problem, a new algorithm was added to the existing speech recognition structure to increase the speech recognition rate. Perform the preprocessing process of the word and then token the results. After combining the result processed in the Levenshtein distance algorithm and the hashing algorithm, the normalized words is output through the consonant comparison algorithm. The final result word is compared with the standardized table and output if it exists, registered in the table dose not exists. The experimental environment was developed by using a smartphone application. The proposed structure shows that the recognition rate is improved by 2% in standard language and 7% in dialect.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2009.10a
• /
• pp.629-632
• /
• 2009

The interactive art and design can be interpreted as an intelligent system in the aspect of engineering. Because this information is treated and analyzed in real time and then such results is expressed in various media such as image, graphic, sound and etc. after these information are input through the sensor, camera and etc., for the efficient communication between human and production, namely, to communicate the interactive reaction, The image utilizing such interactive is being gradually developed as it widens its region in various art design fields. This research is purposed to make the system, which lets the citizens contact the information naturally by mixing the information for the environment with the interactive art of the arty type, and which lets the citizens feel the surrounding environment directly. This research will construct the live mood in the space itself and is utilized for the public art that can be directly experienced. It can provide the experience in the participation type that acquires the information being harmonized with the human naturally in the more developed type than the concept of the existing static installation. Therefore, it is sincerely required to research the interactive art in utilizing the public design.