This study examines the impact of seabed conditions on image segmentation for target images acquired via side-scan sonar during sea experiments. The dataset comprised cylindrical overlying two types, mud and sand, categorized accordingly. deep learning algorithm (U-NET) was utilized segmentation. analysis focused key factors influencing performance: weighting method cross-entropy loss function combination datasets by type training, validation, testing. results revealed three findings. First,...

ABSTRACT Although waveform inversion has been intensively studied in an effort to properly delineate the Earth's structures since early 1980s, most of time‐ and frequency‐domain algorithms still have critical limitations their applications field data. This may be attributed highly non‐linear objective function unreliable low‐frequency components. To overcome weaknesses conventional algorithms, acoustic Laplace‐domain proposed. The known provide a long‐wavelength velocity model even for data,...

ABSTRACT We developed a frequency‐domain acoustic‐elastic coupled waveform inversion based on the Gauss‐Newton conjugate gradient method. Despite use of high‐performance computer system and state‐of‐the‐art parallel computation algorithm, it remained computationally prohibitive to calculate approximate Hessian explicitly for large‐scale inverse problem. Therefore, we adopted least‐squares which is frequently used geophysical problems, implement method so that calculated implicitly. Thus,...

Geophysicists and applied mathematicians have proposed a rich suite of long-wavelength velocity estimation algorithms to construct starting models for subsequent pre-stack depth migration inversion. Refraction-traveltime tomography derives subsurface from picked first-arrival traveltimes. In contrast, Laplace-domain waveform inversion recovers structure using the weighted amplitudes first later arrivals. There are several implementations traveltime inversion, with most based on ray tracing,...

Considerable effort has been devoted to the migration of multicomponent data in elastic media with wavefield separation techniques being most successful. Most this work carried out time domain. In paper, we formulate a technique frequency Reverse-time can be viewed as zero-lag cross-correlation between virtual source and back-propagated wavefields. Cross-correlating Helmholtz decomposed wavefields rather than directly correlating vector displacement fields results sharper, more interpretable...

Acoustic Doppler current profilers (ADCPs) were developed to acquire water velocities, as well depth-dependent echo intensities. As the backscattering strength of an underwater object can be estimated from measured intensity, ADCP used estimate plankton populations and distributions. In this study, bubble clusters in a tank was using commercial proof-of-concept. Specifically, temporal variations duration existence quantitatively evaluated. Additionally, PDSL (population density spectrum...

The scattering characteristics of target echoes are essential for detecting and classifying the submerged objects. strength, which is widely used in mono-static sonar system, also important multi-static system to identify target. In this presentation, a series experiments acoustic water tank was conducted measure from cylinder-shaped with measurement consists single transmitter 16 receivers. strengths presented 2-dimensional plane as function receiver position according aspect angle....

Recently, neural network-based deep learning techniques have been actively applied to detect underwater objects in sonar (sound navigation and ranging) images. However, unlike optical images, acquiring images is extremely time- cost-intensive, therefore securing data conducting related research can be rather challenging. Here, a side-scan was used obtain off the coast of Korean Peninsula. For detection experiments, we an mock-up model with similar size, shape, material, acoustic...

Bubbles greatly affect the propagation of sound waves as acoustic characteristics a bubble cluster in water are distinct from those undisturbed water. Therefore, clusters ability sensors to detect underwater targets by blocking or reflecting waves. Additionally, wakes produced ships movement can be detected wake-homing torpedoes, thus threatening safety ship. Thus, research on dynamics is crucial for development military technology. Recently, we conducted quantitative estimation artificial...

The wake-homing underwater guided weapon that detects and tracks wake generated during voyage of a surface ship is impossible to avoid with the present acoustic deception torpedo defense system. Therefore, research on bubble-generating decoy necessary deceive weapon. Experiments in various environments are required verify effective operation method performance decoy, but verification through experiment limited. In this paper, we develop simulator for an system ship, which applied against...

The target echoes contain information on the such as orientation, kinematics, and internal structure, well external geometrical shape of target. In addition, pattern depends arrangement transmitters receivers in space. Therefore, study a multi-static SONAR system can be useful for detecting tracking submerged objects using an underwater surveillance system. For this purpose, acoustic measuring was designed tested water tank. Some preliminary data are presented discussed.

Many researches based on wavefield separating migration techniques have been suggested for processing multi‐component data properly. Those works were carried out in the time domain, however. In this paper, we propose frequency‐domain technique with separation. frequency reverse‐time can be implemented efficiently by zero‐lag convolution between virtual source and back‐propagated wavefield. Our new also defined as decomposed derived exploiting Helmholtz decomposition. P‐and S‐wave images...

Recently, unmanned systems are largely utilized in various fields due to the persistency and least operational risk an surface vehicle(USV) is one of representative application naval field. To assign multiple roles USV, we developed a sonar system which consists forward detecting for long-range detection, downward small target scan identification, strut type body mounting systems. In this paper, described USV sea test results verifying performance. The showed that was able detect underwater...

The ship wake generated by rotation of the propeller yields changes characteristics sound wave such as attenuation and scattering. To develope a battle field environment simulator for military purposes, it is very important to understand acoustical properties wake. Existing research results have limitations in direct application because they performed under simple conditions or model ships were applied. In this study, we developed generation based on ship's geometric distribution theory. can...

Bubble clusters present in seawater can cause acoustic interference and signal distortion during marine exploration. However, this also be used as an masking technique, which has significant implications for military purposes. Therefore, characterizing the distribution of bubble water would allow development anti-detection technologies. In study, a sea experiment was performed using multi-sonar array system bubble-generating material developed by our research group to obtain signals from...

Bidirectional equalization is a typical method that can compensate for the channel effectively using multichannel time-reversal combining followed by single-channel decision-feedback equalization. However, because conventional bidirectional employs equalizers, performance be significantly degraded if errors propagate. In this paper, we propose to improve of detecting error propagation and selecting type equalizer. The proposed reduces rate applying decision-direct equalizer instead in event...

This paper examines anisotropic prestack Kirchhoff migration. We used pseudo-acoustic wave equations in the complex frequency domain to describe propagation a vertical transversely isotropic (VTI) medium. Both amplitudes and traveltimes were calculated efficiently using suppressed equation estimation of traveltime (SWEET) algorithm. The accuracy obtained with SWEET algorithm was verified by comparing contours simulated elastic staggered-grid method. Finally, we tested our migration...

A multi-static SONAR system consists of the transmitters and receivers separately in space. The active target echoes are received along transmitter-target-receiver path depend on shape aspect angle submerged objects at each receiver. Thus, echo algorithm used with a mono-static system, which transmitter receiver located same position, has limits simulating for system. In this paper, modeling procedure 3D object space is described based Kirchhoff approximation, extended to scattered field...

We present a review of Laplace and Laplace-Fourier domain waveform inversion. The wave equation in the domains can be solved by changing real frequencies from Fourier transform into imaginary frequencies. initial model Laplace-domain inversion scratch such as homogeneous velocity model. provides long-wavelength that used starting for conventional inversion, which uses zero-frequency components damped wavefield. recover long-, medium- short-wavelength models adjusting complex Careful muting...

The underwater acoustic communication channel is subject to multiple interactions with the ocean boundaries and refraction due sound speed structure of water column, which produces significant time spread. This phenomenon referred as inter-symbol interference (ISI), results in degradation error performance. Recently, a reversal technique has been used for reducing ISI. However, this requires large-size array spatially separated receivers obtain higher spatial diversity gain, it becomes...

The bidirectional equalization is an effective method for demodulating communication signals with weak strength since it improves the signal-to-noise ratio by obtaining additional diversity as well temporal and spatial when used in combination time reversal technique. In this paper, we will demodulate acquired from biomimetic long-range acoustic experiment 2018 (BLAC18) conducted East Sea of Korea October using techniques. It shown that including decision direct equalizer has best error performance.

In underwater acoustic communications, inter-symbol interference (ISI) caused by multipath propagation of channel degrades communication performance significantly. Various techniques, such as time reversal combining and decision feedback equalization, have been developed to eliminate the influence interference. However, few studies assessed with signal-to-noise (SNR) received signals. practical systems, must be accurately estimated for equalization SNR is involved in accuracy estimation. The...

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