• Journal of the Korea Institute of Military Science and Technology
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• v.2 no.2
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• pp.30-39
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• 1999

In this paper, we have proposed a novel method which can compose a reflected signal of the underwater target. The synthesis of the reflected signal in the target, the synthesized signal being similar to the characteristics of the reflected signal in the real target, is used the highlight model at the specific points of the target. We suggest the synthesis method of the reflected signal of the target using the pulsewidth variation and each other doppler effect at the highlight point, and compare the composed signal by the proposed method with that by conventional one. Simulation results show that the composed signal using the proposed method and the reflected signal of the real target is similar to the spectral characteristics.

• Current Optics and Photonics
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• v.4 no.6
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• pp.571-575
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• 2020

Optical wireless power transmission (OWPT) is a good candidate for long-distance underwater wireless power transmission. In this work we investigate the transmission efficiency of underwater OWPT, depending on the operating wavelength. We consider four operating wavelengths: infrared, red, green, and blue. We also consider the cases of pure water and sea water for the working conditions. Our results show that it is necessary to select the operating wavelength of underwater OWPT according to the transmission distance and water type of the target application.

• Journal of the Korea Institute of Military Science and Technology
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• v.8 no.1 s.20
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• pp.25-31
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• 2005

PLA(Passive Linear Array) system has been primarily utilized to detect and track underwater targets, such as submarines. This system has difficulty in distinguishing between underwater targets and surface ships in a dense target environment. And a single-PLA system does not provide target state observability. At least two PLAs are necessary to observe a track uniquely. To classify and localize the underwater targets effectively, first of all, it is very of importance to discriminate the surface ships in the multi-target environment. These problems can be overcome by the association of distributed PLAs and radars. In this paper, we present an algorithm to solve the track-to-track association of the heterogeneous data from three PLAs and one radar are noncollocated with known sensor positions. Also, this paper shows the simulation results to verify the proposed algorithm.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.5
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• pp.532-537
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• 2015

In this paper, we propose target range estimation method using ghost target in the submarine linear array sonar. Usually, when submarine detect target, they use passive sonar detection to avoid self-disclosure by active sonar transmission. But, originally, passive linear array sonar have limitation for target range estimation and additional processing is required to get target range information. For the case of near-field target, typical range estimation method is using multiple information by multipath effect in underwater environment. Acoustic signal generated from target are propagated along with numerous multipath in underwater environment. Since multipath target signals received in the linear array sonar have different conic angles each other, ghost target is appeared at the bearing different with real target bearing and sonar operator can find these information on the operation console. Under several assumption, this geometric properties can be analysed mathematically and we get the target range by derivation of this geometric equations using measured conic angles of real target and ghost target.

• The Journal of the Acoustical Society of Korea
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• v.34 no.6
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• pp.487-492
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• 2015

A short-range underwater target detection and identification techniques using mid- and high-frequency bands have been highly developed. However, nowadays the long-range detection using the low-frequency band is requested and one of the most challengeable issues. The waveform inversion technique is widely used and the hottest technology in both academia and industry of the seismic exploration. It is based on the numerical analysis tool, and could construct more than a few kilometers of the subsurface structures and model-parameters such as P-wave velocity using a low-frequency band. By applying this technique to the underwater acoustic circumstance, firstly application of underwater target detection is verified. Furthermore, subsurface structures and it's parameters of the war-field are well reconstructed. We can confirm that this technique greatly reduces the false-alarm rate for the underwater targets because it could accurately reproduce both the shape and the model-parameters at the same time.

• Journal of Korea Multimedia Society
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• v.18 no.1
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• pp.9-16
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• 2015

Various approaches to process active sonar signals are under study, but there are many problems to be considered. The sonar signals are distorted by the underwater environment, and the spatio-temporal and spectral characteristics of active sonar signals change in accordance with the aspect of the target even though they come from the same one. And it has difficulties in collecting actual underwater data. In this paper, we synthesized active target echoes based on ray tracing algorithm using target model having 3-dimensional highlight distribution. Then, Fractional Fourier transform was applied to synthesized target echoes to extract feature vector. Recognition experiment was performed using probabilistic neural network classifier.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.6
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• pp.693-704
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• 2017

Blended-Wing-Body Underwater Glider (BWBUG), which has excellent hydrodynamic performance, is a new kind of underwater glider in recent years. In the shape optimization of BWBUG, the lift to drag ratio is often used as the optimization target. However this results in lose of internal space. In this paper, the energy reserve is defined as the direct proportional function of the internal space of BWBUG. A motion model, which relates gliding range to steady gliding motion parameters as well as energy consumption, is established by analyzing the steady-state gliding motion. The maximum gliding range is used as the optimization target instead of the lift to drag ratio to optimizing the shape of BWBUG. The result of optimization shows that the maximum gliding range of initial design is increased by 32.1% though an Efficient Global Optimization (EGO) process.

• 한국지구물리탐사학회:학술대회논문집
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• 2002.09a
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• pp.163-178
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• 2002

Investigation of underwater sedimentary layers has been carried out with GPR (Ground Penetration Radar) survey. GPR survey has been proved to be very satisfactory since the target area has shallow water depth of about 2.5 m, is lake with no water flow, and the thickness of mud layer, which is a main survey target, is relatively thin. The results clearly showed the underwater sedimentary layers, which includes mud, sand, gravel and basement layer. Specially, the distribution and total amount of mud layers from the survey, which is main target of removal, can be used as a basic data for the dredging of mud layer in the area.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.8
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• pp.2552-2570
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• 2022

Underwater images usually have various problems, such as the color cast of underwater images due to the attenuation of different lights in water, the darkness of image caused by the lack of light underwater, and the haze effect of underwater images because of the scattering of light. To address the above problems, the channel attention mechanism, strengthen-operate-subtract (SOS) boosting mechanism and gated fusion module are introduced in our paper, based on which, an underwater image recovery network is proposed. First, for the color cast problem of underwater images, the channel attention mechanism is incorporated in our model, which can well alleviate the color cast of underwater images. Second, as for the darkness of underwater images, the similarity between the target underwater image after dehazing and color correcting, and the image output by our model is used as the loss function, so as to increase the brightness of the underwater image. Finally, we employ the SOS boosting module to eliminate the haze effect of underwater images. Moreover, experiments were carried out to evaluate the performance of our model. The qualitative analysis results show that our method can be applied to effectively recover the underwater images, which outperformed most methods for comparison according to various criteria in the quantitative analysis.

• The Journal of the Acoustical Society of Korea
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• v.36 no.5
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• pp.293-299
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• 2017

Small unmanned platforms maneuvering underwater are the key naval future forces, utilized as the asymmetric power in war. As a method of detecting and identifying such platforms, we introduce a property estimation technique based on an iterative numerical analysis. The property estimation technique can estimate not only the position of a target but also its physical properties. Moreover, it will have a potential in detecting and classifying still target or multiple targets. In this study, we have conducted the property estimation of an small underwater target using the data acquired from the lake experiment. As a result, it shows that the properties of a small platform may be roughly estimated from the in site data even using one channel.