ISFM-SLAM: dynamic visual SLAM with instance segmentation and feature matching.

Introduction: Simultaneous Localization and Mapping (SLAM) is a technology used in intelligent systems such as robots and autonomous vehicles. Visual SLAM has become a more popular type of SLAM due to its acceptable cost and good scalability when applied in robot positioning, navigation and other functions. However, most of the visual SLAM algorithms assume a static environment, so when they are implemented in highly dynamic scenes, problems such as tracking failure and overlapped mapping are prone to occur.

Numerical research on the muzzle multiphase flow field produced by gas curtain launch.

Gas curtain launch is an innovative method for underwater gun firing that enhances efficiency by creating a gas curtain. This gas curtain interacts with post-projectile gas and the surrounding water, resulting in a complex multiphase flow field at the muzzle, which significantly impacts projectile accuracy. To investigate the evolution of this flow field, a three-dimensional numerical model was developed, focusing on the distribution of shock waves, temperature, and pressure at the muzzle.

Analysis of different standards for life support technology in manned submersible.

Life support technology is one of the most critical technologies in manned submersibles, acting for the pilots of the submersible and thus directly affecting its underwater safety. Due to its importance, many countries and international organizations have proposed standards and specifications for life support technology. This paper presents an overview of the life support technology of manned submersibles, comparing the standards proposed for it.

Interfacial Thermal Fluctuations Stabilize Bulk Nanobubbles.

Consensus on bulk nanobubble stability remains elusive, despite accepted indirect evidence for longevity. We develop a nanobubble evolution model by incorporating thermal capillary wave theory that reveals that dense nanobubbles generated by acoustic cavitation tend to shrink and intensify interfacial thermal fluctuations; this significantly reduces surface tension to neutralize enhanced Laplace pressure, and secures their stabilization at a finite size. A stability criterion emerges: thermal fluctuation intensity scales superlinearly with curvature: sqrt[⟨h^{2}⟩]∝(1/R)^{n}, n>1.

Study on dynamic characteristics of cavitation in underwater explosion with large charge.

Underwater explosions (UNDEX) generate shock waves that interact with the air-water interface and structures, leading to the occurrence of rarefaction waves and inducing cavitation phenomena. In deep-water explosions, complex coupling relationships exist between shock wave propagation, bubble motion, and cavitation evolution. The shock wave initiates the formation of cavitation, and their growth and collapse are influenced by the pressure field.

Multiobjective optimization for flapping foil hydrodynamics with a multitask and multifidelity approach.

We develop a multitask and multifidelity Gaussian process (MMGP) model to accurately predict and optimize the multiobjective performance of a flapping foil while minimizing the cost of high-fidelity data. Through a comparison of three kernels, we have selected and applied the spectral mixture kernel and validated the robustness and effectiveness of a multiacquisition function. To effectively incorporate data with varying levels of fidelity, we have adopted a linear prior formula-based multifidelity framework.

Interface Optimizing Core-Shell PZT@Carbon/Polyurethane Composites with Enhanced Passive Piezoelectric Vibration Damping Performance.

Presently, piezoelectric materials are gradually playing a significant role within composites to improve the damping and vibrational attenuation capacities of host composites. Previous studies paid attention to isolating the mechanical damping contribution and piezoelectric contribution of polymer-based piezoelectric composites (PPCs). However, reports detailing the piezoelectric damping of such materials have not paid sufficient attention to the technologies and methods to improve the piezoelectric damping of PPCs.

Electric manipulation on deformation of ionic ferrofluid sessile droplets.

Active electric-driven droplet manipulation in digital microfluidics constitutes a promising domain owing to the unique and programmable wettability inherent in sessile ionic droplets. The coupling between the electric field and flow field enables precise control over wetting characteristics and droplet morphology. This study delves into the deformation phenomena of ionic sessile ferrofluid droplets in ambient air induced by uniform electric fields.

Cavitation Erosion Prevention Using Laser Shock Peening: Development of a Predictive Evaluation System.

Marine flow-passing components are susceptible to cavitation erosion (CE), and researchers have worked to find ways to reduce its effects. Laser Shock Peening (LSP), a material strengthening method, has been widely used in aerospace and other cutting-edge fields. In recent years, LSP has been used in cavitation resistance research.

Application of the Gaussian Process Regression Method Based on a Combined Kernel Function in Engine Performance Prediction.

At present, regression modeling methods fail to achieve higher simulation accuracy, which limits the application of simulation technology in more fields such as virtual calibration and hardware-in-the-loop real-time simulation in automotive industry. After fully considering the abruptness and complexity of engine predictions, a Gaussian process regression modeling method based on a combined kernel function is proposed and verified in this study for engine torque, emission, and temperature predictions. The comparison results with linear regression, decision tree, support vector machine (abbreviated as SVM), neural network, and other Gaussian regression methods show that the Gaussian regression method based on the combined kernel function proposed in this study can achieve higher prediction accuracy.

A Numerical Simulation Method Considering Solid Phase Transformation and the Experimental Verification of Ti6Al4V Titanium Alloy Sheet Welding Processes.

A prediction model of the welding process of Ti-6Al-4V titanium alloy was established by using the finite element method, which was used to evaluate the phase composition, residual stress and deformation of the welded joints of Ti-6Al-4V sheets with different processes (including tungsten inert gas welding, TIG, and laser beam welding, LBW). The Ti-6Al-4V structures of TIG welding and LBW are widely used in marine engineering. In order to quantitatively study the effects of different welding processes (including TIG welding and LBW) on the microstructure evolution, macro residual stress and deformation of Ti6Al4V titanium alloy sheets during welding, a unified prediction model considering solid-state phase transformation was established based on the ABAQUS subroutine.

The Acoustic System of the Fendouzhe HOV.

Due to the strong absorption and attenuation of electromagnetic waves by water, radio communications and global positioning systems are lacking in the deep-sea environment. Therefore, underwater long-distance communications, positioning, detection and other functions depend on acoustic technology. In order to realize the above functions, the acoustic system of the Fendouzhe human occupied vehicle (HOV) is composed of eight kinds of sonars and sensors, which is one of the core systems of manned submersible.

Role of deep-sea equipment in promoting the forefront of studies on life in extreme environments.

The deep-sea environment creates the largest ecosystem in the world with the largest biological community and extensive undiscovered biodiversity. Nevertheless, these ecosystems are far from well known. Deep-sea equipment is an indispensable approach to research life in extreme environments in the deep-sea environment because of the difficulty in obtaining access to these unique habitats.

Geology, environment, and life in the deepest part of the world's oceans.

The hadal zone, mostly comprising of deep trenches and constituting of the deepest part of the world's oceans, represents the least explored habitat but one of the last frontiers on our planet. The present scientific understanding of the hadal environment is still relatively rudimentary, particularly in comparison with that of shallower marine environments. In the last 30 years, continuous efforts have been launched in deepening our knowledge regarding the ecology of the hadal trench.

Effects of different fluid fields on the formation of cyanobacterial blooms.

Cyanobacterial blooms have been attracting more and more attention, and the mechanism is widely studied. However, the effects of fluid fields on the bloom formation were rarely reported. In this study, the effects of fluid fields formed under different external conditions were investigated.

Enhancement of Diffusion Assisted Bonding of the Bimetal Composite of Austenitic/Ferric Steels via Intrinsic Interlayers.

We investigate the effect of the intrinsic interlayers on the diffusion assisted bonding properties of the austenitic steel (stainless steel 316L) and ferric steels (Low-carbon steel Q345R) in a hot rolling process by molecular dynamics simulations and experiment. The introduction of an intrinsic interlayer (Cr or Ni) widens the diffusion region, leading to enhancement of bonding. The thickness of the diffusion region enlarges with an increase of temperature, with an enhancement factor of 195% and 108%, for Cr and Ni interlayer, respectively, at the temperature of 1800 K.

Intensity evaluation of bottom backscattering between high-frequency underwater acoustic instruments and its experimental validation.

Running several high-frequency underwater acoustic instruments simultaneously on board a surface or underwater platform can cause interference between the instruments. By combining ray theory and the high-frequency bistatic scattering model for water bottoms, this work presents a practical method for evaluating the relative intensities of such interference signals corresponding to different instrument-to-instrument distances. To examine this method's effectiveness, a series of lake experiments were conducted.

Attitude determination method integrating square-root cubature Kalman filter with expectation-maximization for inertial navigation system applied to underwater glider.

The uncertainty, complexity, and variability of the marine environment inevitably lead to a change in the measurement error resulting in erroneous estimation of navigation information. To solve this problem, this paper proposes a novel method integrating the square-root cubature Kalman filter (SCKF) with the expectation-maximization (EM) algorithm. The proposed new SCKF (NSCKF) algorithm makes better use of the advantages of SCKF and the EM online algorithm.

A generalized superposition method for accurate free vibration analysis of rectangular plates and assemblies.

A generalized superposition method is presented in this paper for free bending vibration analysis of single rectangular plates and assemblies of rectangular plates with arbitrary boundary conditions. The method was developed on the basis of the Levy method, the principle of superposition, and the uniform convergence of half-range Fourier cosine series for continuous functions in a closed interval. Numerical results, obtained using the proposed method for thin isotropic plates and plate assemblies, show that the proposed method is accurate and rapidly convergent.

Effects of Loading Frequency and Specimen Geometry on High Cycle and Very High Cycle Fatigue Life of a High Strength Titanium Alloy.

Titanium alloys have been widely used in the structural parts of deep-sea equipment and aviation industries. In this paper, the effects of loading frequency and specimen geometry on the high cycle and very high cycle fatigue life of the high strength titanium alloy Ti-6Al-2Sn-2Zr-3Mo-X is investigated by conventional fatigue test and ultrasonic frequency fatigue test. The results indicate that ultrasonic frequency could enhance the fatigue life of the highstrength titanium alloy compared with that under conventional frequency, and the frequency effect is related to the stress amplitude.

Integrated calculation method of acoustic radiation and propagation for floating bodies in shallow water.

Based on the three-dimensional sono-elasticity theory for ship structures, the Green's function is incorporated and an integrated calculation method of acoustic radiation and propagation for floating bodies in shallow water considering the sound velocity profile is proposed. The near-field and arbitrary far-field acoustic radiation problem can be efficiently calculated. A numerical example of a rigid sphere is given and the results are compared with the finite element method solution to validate the reliability and demonstrate improvements in efficiency.

Evaluation of radiation loading on finite cylindrical shells using the fast Fourier transform: A comparison with direct numerical integration.

The radiation loading on a vibratory finite cylindrical shell is conventionally evaluated through the direct numerical integration (DNI) method. An alternative strategy via the fast Fourier transform algorithm is put forward in this work based on the general expression of radiation impedance. To check the feasibility and efficiency of the proposed method, a comparison with DNI is presented through numerical cases.