• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.5
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• pp.591-603
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• 2014

In this paper, we have described the characteristics of the Underwater Distributed Sensor Network (UDSN) and proposed the conceptual design guideline by an effectiveness analysis. To perform the effectiveness analysis, we defined an battlefield environment, and then analyzed principal components which compose the UDSN to find out simulation parameters and system constraints. We have chosen a measure of effectiveness based on a target trajectory, which could enhance intuitive understanding about current status, and performed various simulations to reveal critical design parameters in terms of sensor node types, arrangement, cost and combination of detection information.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.3
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• pp.266-272
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• 2013

The objective of this study was to monitor and evaluate the schooling characteristics, including the distribution density (volume backscattering strength) and acoustic size (target strength), of commercially valuable species swimming in response to artificial reefs installed at Suyeong Man, Busan, Korea. Fish aggregations at two artificial reef areas and at a nearby natural rocky reef habitat were recorded and analyzed using a 70 kHz split-beam echo sounder and 330 kHz side-scan sonar from August to September, 2006. An underwater CCTV camera system was also used to observe marine organisms in physical contact with and swimming very close to artificial reefs. During the acoustic observations at three reef sites, useful information about schooling characteristics of fish aggregations responding to artificial reefs were obtained, but more trials are needed to confirm significant differences in schooling behavior and geographical distributions in areas containing natural reef structures and artificial reefs.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.6_spc
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• pp.687-696
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• 2016

A series of process to design an acoustic lens for underwater imaging is reviewed and the method to evaluate characteristics of the lens is investigated. If the target specification of lens is given, the design process consists of the material selection, evaluation of its properties, lens geometry design, prediction of lens characteristics, manufacturing, and evaluation by measurement. In this study, an actual acoustical lens is made by cutting polymethylpentene block. The characteristics of lens are predicted by the hybrid method, combination of ray tracing and Rayleigh integral. For the direct comparison between the prediction and measurement results, a simulation method based on the equivalent source method is suggested to reflect the actual radiation pattern of transducer used for measurements. Finally, the measurement is conducted in a small water tank to observe the actual characteristics of the manufactured lens.

• The Journal of the Acoustical Society of Korea
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• v.28 no.8
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• pp.755-760
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• 2009

In this paper, we apply a reverberation suppression method using difference of singular values to improve the short-distance underwater obstacle detection probability in reverberation environment induced by a linear frequency modulation signal. The reverberation suppression method using difference of singular values suppresses LFM reverberation based on subtracting the singular values for a reference beam, assumed to contain only the reverberation, from those for the current beam of interest, assumed to contain the reverberation and target echo. For the validation, the reverberation suppression method using difference of singular values is applied to real oceanic data, which are acquired using the cross type array.

• The Journal of the Acoustical Society of Korea
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• v.28 no.2
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• pp.135-140
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• 2009

In this paper, we synthesized active sonar target signals based on highlights model, and then carried out target classification using the synthesized signals. If the target aspect angle is changed, the different signals are synthesized. To know the result, two different experiments are done. First, The classification results with respect to each aspect angle are shown. Second, the results in two group in aspect angle are acquired. Time domain feature extraction is done using matched filter and envelope detection. It shows the pattern of each highlights. Artificial neural networks and multi-class SVM are used for classifying target signals.

• Proceedings of the Acoustical Society of Korea Conference
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• 1984.12a
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• pp.100-106
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• 1984

Traditional methods for estimating the location of underwater target, i.e. the triangulation method and the wavefront curvature method, have been utilized. The location of a target is defined by the range and the bearing, which estimates can be obtained by evaluating the time delay between neighboring sensors. Many components of error occur in estimating the target range, among which the error due to the fluctuation of heading angle is outstanding. In this paper, the wavefront curvature method was used. We considered the error due to the heading fluctuation as the $\beta$-density process, from which we analized the range estimates with $\beta$-density function exist in some finite limits, and its mean value and variation are depicted as a function of true range and heading fluctuation. Given heading angles and sensor separation, maximum estimated heading errors are presented as a function of true range.

• Journal of the Korea Institute of Military Science and Technology
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• v.7 no.2 s.17
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• pp.32-40
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• 2004

In this paper, a simulation model for FLAS(Fixed Linear Arrays System) is presented and methods for effectiveness analysis are studied to analyze the valid target detection effectiveness of this system. The simulation model is constructed taking the FLAS operational specification into account, and thus the change in system specification is effectively reflected on the simulation results. The computational burden is reduced by using the pre-processed simulation parameters which are calculated from the real environmental database. Also, the cell effectiveness and TMOE(Total Measurement of Effectiveness) are computed. The target detection effectiveness of FLAS can be simulated under the multiple target interference simulation. It is shown that the presented algorithm is suitable for the underwater system which needs the simulation model for the optimum system design.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.37 no.2
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• pp.62-69
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• 2014

The capability and cost effectiveness of UUV and USV bring to underwater survey, target detection and identification operations have been widely demonstrated and accepted in recent years. Future USV systems may deploy UUVs to gain the advantage of higher area coverage rates through multiple and simultaneous operations. In this paper, we present an architecture of USV and UUV for mine countermeasure with results of measures on effectiveness.

• Proceedings of the KIEE Conference
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• 2006.07d
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• pp.1789-1790
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• 2006

This paper reports a new test facility to investigate the characteristics of the thrusters mounted on the small scale underwater vehicle using Force/Torque sensor. With the test facility proposed here, No disassembly needs be made to the target vehicle, which makes us possible to get the realistic forces of the vehicle rather than the fortes of the thrusters themselves. Experimental data analyses, heave, sway, and surge, for the QI ROV are given as an example of this method.

• 한국석유지질학회:학술대회논문집
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• 2005.09a
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• pp.9-16
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• 2005

The electromagnetic (light) waves are limited to penetrate the media, ie, water and sea-bottom layers, due to high energy attenuation, but acoustic (sound) waves play as the good messenger to gather the underwater target information. Therefore the acoustic methods are applied to almost of ocean equipments and technology in terms of in-water and sub-bottom surveys, Generally the sound character is controlled by its frequency. In case that the sound source is low frequency, the penetration is high and the resolution is low. On the other hand, its character is reversed at the high frequency. The common character at the both of light and sound is the energy damping according to the travel distance increase.