Applied Sciences

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3 pages, 187 KiB

Open AccessEditorial

Special Issue on Advances in Applied Marine Sciences and Engineering

by Enjin Zhao, Hao Qin and Lin Mu

Appl. Sci. 2023, 13(13), 7875; https://doi.org/10.3390/app13137875 - 5 Jul 2023

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Abstract

Marine Science and technology are the basis for human beings to understand, develop and protect the ocean [...] Full article

(This article belongs to the Special Issue Advances in Applied Marine Sciences and Engineering)

Research

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18 pages, 4298 KiB

Open AccessArticle

Spatial Distribution and Main Controlling Factors of Nitrogen in the Soils and Sediments of a Coastal Lagoon Area (Shameineihai, Hainan)

by Kun Yuan, Yanwei Song, Guowei Fu, Bigui Lin, Kaizhe Fu and Zhaofan Wang

Appl. Sci. 2023, 13(13), 7409; https://doi.org/10.3390/app13137409 - 22 Jun 2023

Cited by 1 | Viewed by 730

Abstract

As the relationship between the spatial distribution characteristics and physicochemical properties of nitrogen in lagoon soil and sediment is still unclear, we obtained and systematically analyzed soil and sediment samples from the surroundings of a lagoon in the Shamei Inland Sea, Qionghai City, [...] Read more.

As the relationship between the spatial distribution characteristics and physicochemical properties of nitrogen in lagoon soil and sediment is still unclear, we obtained and systematically analyzed soil and sediment samples from the surroundings of a lagoon in the Shamei Inland Sea, Qionghai City, Hainan Province. The spatial distribution of nitrogen forms was investigated, and the soil physicochemical properties that predominantly influenced the nitrogen distribution were characterized. The results were as follows: (1) There are differences in nitrogen content in the soil and sediment around the Shamei Inland Sea. The total nitrogen levels in the Shamei Inland Sea were low, and organic nitrogen was dominant. The soil samples showed higher organic nitrogen concentrations than the sediment samples. Thus, the characteristics of dispersion in offshore waters differ from those in lagoons. The average contents of nitrate, ammonium and nitrite in the soil around the lagoon were higher than those in the sediment, and they were especially high in the lagoon mouth area. The nitrate content was greater in the estuary area in the northwest of the lagoon, and the contents of ammonium and nitrite in the estuary area in the south of the lagoon were the highest. (2) The changes in the basic physical and chemical properties of the soils and sediments in the Shamei Inland Sea area have an important coupled effect on the enrichment, preservation and mineralization of nitrogen. Through redundancy analysis (RDA), the explanatory degree of the organic matter content in relation to the nitrogen content was determined to be approximately 17.2%, contributing 80.9% of all nitrogen. The organic matter content, cation exchange capacity and clay content were positively correlated with the nitrogen content, indicating that changes in the basic physical and chemical properties of the soil and sediment had an important impact on nitrogen enrichment, preservation and mineralization processes. The total nitrogen and the organic matter content, cation exchange capacity and clay content of the soil and sediment were positively correlated. The high proportion of nitrate in the soil, the high proportion of ammonium in the sediment, the heavy texture of the sediment, poor soil ventilation and weak nitrification were related. Full article

(This article belongs to the Special Issue Advances in Applied Marine Sciences and Engineering)

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14 pages, 34130 KiB

Open AccessArticle

Wind-Wave-Current Coupled Modeling of the Effect of Artificial Island on the Coastal Environment

by Guowei Fu, Jian Li, Kun Yuan, Yanwei Song, Miao Fu, Hongbing Wang and Xiaoming Wan

Appl. Sci. 2023, 13(12), 7171; https://doi.org/10.3390/app13127171 - 15 Jun 2023

Cited by 1 | Viewed by 889

Abstract

The effect of artificial island on the geomorphologic processes in the coastal area under the coupled hydrodynamics, wave, and sediment transport system is a complicated and multi-scale problem. Studying these dynamic processes will suggest how coastal ecological restoration should be conducted. In this [...] Read more.

The effect of artificial island on the geomorphologic processes in the coastal area under the coupled hydrodynamics, wave, and sediment transport system is a complicated and multi-scale problem. Studying these dynamic processes will suggest how coastal ecological restoration should be conducted. In this study, a unified, unstructured, gridded coupled hydrodynamics, wave, and sediment transport model and a topographic evolution model were adopted. Based on the field observations of water depth, velocity, suspended sediment concentration, bed sand, and quaternary thickness, a high-spatiotemporal-resolution numerical simulation of the offshore dynamic environment under the disturbance of artificial island was performed, and the accuracy of the calculation was verified. The research showed that the coupling system with an unstructured mesh was able to reproduce the flow and sediment transport processes with acceptable accuracy. The contracted flow zone between the artificial island and the coastline, the runoff and alongshore current from the river, as well as the tidal flow from the ocean, worked together to mold the local complex morphology around the artificial island. The coupled modeling system, supported with parallel computation, can be used to study coastal environments with small-scale wading structures. Full article

(This article belongs to the Special Issue Advances in Applied Marine Sciences and Engineering)

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25 pages, 9659 KiB

Open AccessArticle

Numerical Study on the Green-Water Loads and Structural Responses of Ship Bow Structures Caused by Freak Waves

by Chengzhe Zhang, Weiyi Zhang, Hao Qin, Yunwu Han, Enjin Zhao, Lin Mu and Haoran Zhang

Appl. Sci. 2023, 13(11), 6791; https://doi.org/10.3390/app13116791 - 2 Jun 2023

Cited by 1 | Viewed by 1264

Abstract

In recent decades, freak waves, characterized by their unusual high amplitude, sharp crest, and concentrated energy, have attracted researchers’ attention due to their potential threat to marine structures. Green-water loads caused by freak waves can be significant and may lead to local damage [...] Read more.

In recent decades, freak waves, characterized by their unusual high amplitude, sharp crest, and concentrated energy, have attracted researchers’ attention due to their potential threat to marine structures. Green-water loads caused by freak waves can be significant and may lead to local damage to the ship structures. Therefore, this paper focuses on the study of green-water loads and examines the structural responses of ship bow structures under the influence of the green-water loads caused by freak waves. Firstly, a three-dimensional numerical wave tank is established in which the superposition model is used to generate freak waves. Validations on the freak-wave generation, ship motion response and the wave loading are carried out to verify the present solvers. The simulation on the interaction between the freak wave and the ship are conducted to obtain the interaction process and green-water loads. Secondly, a finite element (FEM) model of the ship bow is built, on which the green-water loads are applied to calculate the structural responses. Finally, the displacement and stress of the deck and breakwater structures are analyzed. It is found that green water events caused by freak waves can generate enormous impact forces on the bow deck and breakwater, resulting in severe structural responses and even possible damage to the structures. The local strength of structures under freak waves needs to be considered in practical engineering applications. Full article

(This article belongs to the Special Issue Advances in Applied Marine Sciences and Engineering)

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11 pages, 3303 KiB

Open AccessArticle

Effects of Shading on the Growth and Carbon Storage of Enhalus acoroides

by Miao Fu, Yanwei Song, Yang Wang, Guowei Fu and Xiang Zhang

Appl. Sci. 2023, 13(10), 6035; https://doi.org/10.3390/app13106035 - 14 May 2023

Cited by 1 | Viewed by 1200

Abstract

Light intensity is one of the main factors determining the growth and distribution of seagrasses, but seagrasses differ in their responses to changes in the light environment, resulting in inconsistent adaptation. To investigate the effect of light reduction on Enhalus acoroides (L. f.) [...] Read more.

Light intensity is one of the main factors determining the growth and distribution of seagrasses, but seagrasses differ in their responses to changes in the light environment, resulting in inconsistent adaptation. To investigate the effect of light reduction on Enhalus acoroides (L. f.) Steud., we simulated different light intensities by setting up in situ shade shelters with three light environments: full light (CK), moderate shading (MS) and high shading (HS), and investigated the growth response and adaptation mechanism of E. acoroides to a low-light environment. The results showed that the leaf length and leaf width of E. acoroides decreased in the low-light environment. Plant density, biomass, and chlorophyll content (Chl) decreased significantly with the prolongation of shading. In addition, the sediment carbon content of seagrass beds was significantly reduced in the shading treatments compared to the full-light treatment. After the restoration of light, the chlorophyll content of E. acoroides increased compared to that in the shading period, but its leaf morphology, plant density and biomass did not return to the level of full light treatment. Our study highlights that long-term light reduction leads to a significant reduction in seagrass biomass and its sediment carbon content, which in turn, may reduce the carbon storage capacity of seagrass beds. Full article

(This article belongs to the Special Issue Advances in Applied Marine Sciences and Engineering)

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11 pages, 4290 KiB

Open AccessArticle

Characteristics and Causes of Coastal Water Chemistry in Qionghai City, China

by Junyi Jiang, Guowei Fu, Yu Feng, Xinchen Gu, Pan Jiang, Cheng Shen and Zongyi Chen

Appl. Sci. 2023, 13(9), 5579; https://doi.org/10.3390/app13095579 - 30 Apr 2023

Cited by 3 | Viewed by 1378

Abstract

The coastal zone area of Qionghai City is one of the important coastal zones in the South China Sea, and its water environment has been affected by human activities such as urbanization and industrialization. In order to protect the water resources and ecological [...] Read more.

The coastal zone area of Qionghai City is one of the important coastal zones in the South China Sea, and its water environment has been affected by human activities such as urbanization and industrialization. In order to protect the water resources and ecological environment of this area, the water chemistry characteristics of the main watersheds and their causes in the coastal zone area of eastern Hainan Island were investigated to provide a scientific basis for environmental protection and sustainable development. In this study, the characteristics and sources of water chemical ion components were analyzed using a Piper trilinear diagram, Gibbs diagram, and correlation analysis with the coastal zone area of Qionghai city as the research object. The results show the following: (1) the dominant cation of water chemistry in the coastal zone of Qionghai City is Na⁺ with a mean value of 35.001 mg·L⁻¹, and the dominant anion is Cl⁻ with a mean value of 30.69 mg·L⁻¹; (2) the dominant cation content in the coastal zone of Qionghai City is Na⁺ > Ca²⁺ > Mg²⁺ > K⁺, and the dominant anion content is Cl⁻ > SO₄²⁻ > HCO₃⁻ > CO₃²⁻; (3) at the five collection sites in the study area, the ion concentrations showed different trends, with the highest ion concentration in the water samples collected from aquaculture ponds, and the main water chemistry type was Na-Cl; the lowest ion concentration was in the water samples collected from the rivers, and the main type of water chemistry was Ca·Mg-HCO₃. The source of water chemistry ions in the study area mainly included seawater, rock weathering, atmospheric precipitation, and evaporation concentration. The results of this study can provide a scientific basis for the development, utilization, and management of local water resources and provide basic data for environmental protection and sustainable development. Full article

(This article belongs to the Special Issue Advances in Applied Marine Sciences and Engineering)

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15 pages, 1283 KiB

Open AccessArticle

A Pilot Study of Stacked Autoencoders for Ship Mode Classification

by Ji-Yoon Kim and Jin-Seok Oh

Appl. Sci. 2023, 13(9), 5491; https://doi.org/10.3390/app13095491 - 28 Apr 2023

Cited by 2 | Viewed by 929

Abstract

With the evolution of the shipping market, artificial intelligence research using ship data is being actively conducted. Smart ships and reducing ship greenhouse gas emissions are among the most actively researched topics in the maritime transport industry. Owing to the massive advances in [...] Read more.

With the evolution of the shipping market, artificial intelligence research using ship data is being actively conducted. Smart ships and reducing ship greenhouse gas emissions are among the most actively researched topics in the maritime transport industry. Owing to the massive advances in information and communications technology, the internet of things, and big data technologies, smart ships have emerged as a very promising proposition. Numerous methodologies and network architectures can smoothly collect data from ships that are currently in operation, as is currently done in research on reducing ship fuel consumption by deep learning or conventional methods. Many extensive studies of stacked autoencoders have been carried out in the past few years. However, prior studies have not addressed the development of algorithms or deep learning-based models to classify the operating states of ships. In this paper, we propose for the first time a deep learning-based stacked autoencoder model that can classify the operating state of a ship broadly into the categories of At Sea, Stand By, and In Port, using actual ship power load data. In order to maximize the model’s performance, the stacked autoencoder architecture, number of hidden layers, and number of neurons contained in each layer were measured by performance metrics such as true positive rate, false positive rate, Matthews correlation coefficient, and accuracy. It was found that the model’s performance was not always improved by increasing its complexity, so the feasibility of developing and utilizing an efficient model was verified by comparing it to real data. The best-performing model had a (5–128) structure with latent layer size 9. It achieved a true positive rate of 0.9035, a false positive rate of 0.0541, a Matthews correlation coefficient of 0.9054, and an accuracy of 0.9612, clearly demonstrating that deep learning can be used to analyze ship operating modes. Full article

(This article belongs to the Special Issue Advances in Applied Marine Sciences and Engineering)

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16 pages, 2733 KiB

Open AccessArticle

Study on Sedimentary Evolution of the Hanjiang River Delta during the Late Quaternary

by Yang Wang, Liang Zhou, Xiaoming Wan, Xiujuan Liu, Wanhu Wang and Jiaji Yi

Appl. Sci. 2023, 13(7), 4579; https://doi.org/10.3390/app13074579 - 4 Apr 2023

Cited by 2 | Viewed by 1414

Abstract

In recent years, coastal areas have been threatened by many potential hazards due to global warming, glacier melting and sea level rise. Understanding their evolutionary history and development trends can help predict disasters and further reduce the corresponding losses. The Hanjiang River delta [...] Read more.

In recent years, coastal areas have been threatened by many potential hazards due to global warming, glacier melting and sea level rise. Understanding their evolutionary history and development trends can help predict disasters and further reduce the corresponding losses. The Hanjiang River delta in the southeastern part of China is the second largest delta in Guangdong Province and has such challenges. Studying the sedimentary evolution and delta initiation of the Hanjiang Delta is beneficial for understanding the response of the Hanjiang Delta to present and future sea level and climate changes. In this research, we drilled a series of cores from the Hanjiang subaqueous delta, which contains information on the sedimentary environment, climate change and sea level change during the late Quaternary. Combined with previous research results and under the constraint of high-precision and high-resolution AMS¹⁴C and OSL, we carried out a multi-proxy analysis that included micropaleontology and grain size to obtain information on the sedimentary environment, sea level change and climate change. We then further discussed the initiation of the Hanjiang delta and its primary factors. The Quaternary sediments began depositing in the early Late Pleistocene (MIS5), and three sedimentary cycles can be recognized from bottom to top. The dating results also indicate that the first two cycles were formed during the late Pleistocene, while the last cycle was formed during the Holocene. The initiation of the Hanjiang Delta was indicated by a progradation in the process of a transition from estuary to a typical delta. At this time, the rate of delta progradation seaward was fast, and increasing amounts of sediments moved through the third line of islands into the sea. The barrier–lagoon system began to develop in the estuary of Hanjiang during this period. With the sequential construction of the delta, the lagoon was filled and covered by delta deposition, and the barrier bar moved to the sea; thus, the barrier-coast delta depositional model was established in the study area. Since the last glacial period (LGM), the Hanjiang River Delta and other river deltas in the region seem to have experienced similar evolutionary histories, including the filling of incised paleo-valleys and estuaries in the Early Holocene and deltaic progradation in the Middle to Late Holocene, controlled by sea level change. Full article

(This article belongs to the Special Issue Advances in Applied Marine Sciences and Engineering)

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15 pages, 13181 KiB

Open AccessArticle

Motion Control of Autonomous Underwater Helicopter Based on Linear Active Disturbance Rejection Control with Tracking Differentiator

by Haoda Li, Xinyu An, Rendong Feng and Ying Chen

Appl. Sci. 2023, 13(6), 3836; https://doi.org/10.3390/app13063836 - 17 Mar 2023

Cited by 7 | Viewed by 1303

Abstract

As a new disk-shaped autonomous underwater vehicle (AUV), the autonomous underwater helicopter (AUH) is devoted to subsea operations, usually diving into the seabed and docking with a subsea docking system. Due to the motion control’s performance, the AUH’s stability and steady-state accuracy are [...] Read more.

As a new disk-shaped autonomous underwater vehicle (AUV), the autonomous underwater helicopter (AUH) is devoted to subsea operations, usually diving into the seabed and docking with a subsea docking system. Due to the motion control’s performance, the AUH’s stability and steady-state accuracy are affected remarkably while docking. Moreover, considering the difficulties of hydrodynamic modeling of AUHs, the classical model-based control method is unsuitable for AUHs. Moreover, there is a large gap between the hydrodynamic simulation results and real situations. Hence, based on the data-driven principle, the linear active disturbance rejection control with a tracking differentiator (LADRC-TD) algorithm is employed for AUH depths and heading control. As the simulation experiments prove, LADRC and LADRC-TD have better anti-interference performance when compared with PID. According to the pool experiments, overshoots of the LADRC-TD are 20 cm and 3° for the depth control and heading control, respectively, which are superior to PID and LADRC. Meanwhile, the steady-state accuracy of the LADRC-TD is ±21 cm and ±2.5° for the depth and heading control, respectively, which is inferior to PID and the same as LADRC. Full article

(This article belongs to the Special Issue Advances in Applied Marine Sciences and Engineering)

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21 pages, 15462 KiB

Open AccessArticle

Numerical Investigation on the Influence of Breakwater and the Sediment Transport in Shantou Offshore Area

by Yuxi Wu, Kui Zhu, Hao Qin, Yang Wang, Zhaolong Sun, Runxiang Jiang, Wanhu Wang, Jiaji Yi, Hongbing Wang and Enjin Zhao

Appl. Sci. 2023, 13(5), 3011; https://doi.org/10.3390/app13053011 - 26 Feb 2023

Cited by 1 | Viewed by 1180

Abstract

The coastline of Shantou is tortuous, while the hydrodynamic environment is complicated. In this paper, the hydrodynamic model is established by the FVCOM (Finite Volume Coastal Ocean Model); the open boundary conditions such as water level, river, and wind field are the input; [...] Read more.

The coastline of Shantou is tortuous, while the hydrodynamic environment is complicated. In this paper, the hydrodynamic model is established by the FVCOM (Finite Volume Coastal Ocean Model); the open boundary conditions such as water level, river, and wind field are the input; and the model is verified by tidal harmonic function. According to the previous research, the typhoon wind field with a 10-year return period is selected for storm surge simulation. When there is a bank, the accumulated water on the land cannot enter the ocean due to the block of the bank but accumulates on the inner side of the bank, resulting in higher accumulated water, but less than 0.5 m. In the aspect of sediment deposition, a sediment transport model is established to analyze the sediment deposition in Shantou Port and its surrounding waters. Some reasonable suggestions are put forward for the sediment deposition in Shantou. According to the simulation results, the following conclusions can be drawn: (1) In the case of typhoon storm surge in the return period of 10 years, the bank can effectively protect the inland. Still, accumulated water will collect near the bank. (2) The offshore water level will rise by 0.4 m after adding a bank. (3) The sediment in Shantou Bay mainly comes from the ocean sediment caused by tides, and the largest sedimentation occurs in the main channel. Full article

(This article belongs to the Special Issue Advances in Applied Marine Sciences and Engineering)

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19 pages, 10367 KiB

Open AccessArticle

A New 3D Marine Controlled-Source Electromagnetic Modeling Algorithm Based on Two New Types of Quadratic Edge Elements

by Bin Xiong, Yuguo Lu, Hanbo Chen, Ziyu Cheng, Hao Liu and Yu Han

Appl. Sci. 2023, 13(5), 2821; https://doi.org/10.3390/app13052821 - 22 Feb 2023

Cited by 1 | Viewed by 1108

Abstract

This study proposes a new algorithm for a higher-order vector finite element method based on two new types of second-order edge elements to solve the electromagnetic field diffusion problem in a 3D anisotropic medium. To avoid source singularity in the quasistatic variant of [...] Read more.

This study proposes a new algorithm for a higher-order vector finite element method based on two new types of second-order edge elements to solve the electromagnetic field diffusion problem in a 3D anisotropic medium. To avoid source singularity in the quasistatic variant of Maxwell’s function, a secondary field formulation was adopted. The modeling domain was discretized using two types of quadratic edge hexahedral elements, which were obtained using the edge unification method to reduce variables on each side of two conventional quadratic edge elements. Compared with the traditional quadratic element, the number of unknowns that needed to be solved was significantly reduced. The sparse linear equation of the finite element system was solved using an open-source direct solver called MUMPS. The numerical results demonstrated that the proposed algorithm has the same level of accuracy as the conventional vector finite element method and has a significant advantage over it in terms of computational cost. Full article

(This article belongs to the Special Issue Advances in Applied Marine Sciences and Engineering)

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13 pages, 2602 KiB

Open AccessArticle

High-Precision Numerical Research on Flow and Structure Noise of Underwater Vehicle

by Hao Cao and Lihua Wen

Appl. Sci. 2022, 12(24), 12723; https://doi.org/10.3390/app122412723 - 12 Dec 2022

Cited by 2 | Viewed by 1719

Abstract

This paper presents the results of research on the noise generated by an underwater vehicle in the operational state. The study combines the large eddy simulated turbulence model and Lighthill’s acoustic analogy theory and extracts the transient flow field data as the excitation [...] Read more.

This paper presents the results of research on the noise generated by an underwater vehicle in the operational state. The study combines the large eddy simulated turbulence model and Lighthill’s acoustic analogy theory and extracts the transient flow field data as the excitation conditions for acoustic calculations. The results of the numerical calculations of the external acoustic field were obtained under vehicle wall pressure pulsation condition, Lighthill volume excitation condition, and the vibration excitation condition of the underwater vehicle. It is found that the noise is concentrated at the front and tail of underwater vehicle, and its level is closely related to the form of vortex shedding. The peak frequency of structural radiation noise of underwater vehicle is consistent with its peak frequency of mean square vibration velocity. The basis for selecting the boundary conditions of the sound field according to the incoming flow conditions is also evaluated. The research results provide a reference for the noise reduction design of underwater vehicles, thus improving their concealment in combat. Full article

(This article belongs to the Special Issue Advances in Applied Marine Sciences and Engineering)

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18 pages, 5013 KiB

Open AccessArticle

Observing Meteorological Tides: Fifteen Years of Statistics in the Port of La Spezia (Italy)

by Maurizio Soldani and Osvaldo Faggioni

Appl. Sci. 2022, 12(23), 12202; https://doi.org/10.3390/app122312202 - 29 Nov 2022

Cited by 1 | Viewed by 1052

Abstract

Sea level changes in coastal areas significantly influence port activities (e.g., the safety of navigation). Along Italian coastlines, sea level variations are mainly due to astronomical tides (well known, due to gravitational attraction between Earth, Moon and Sun); however, during the last fifteen [...] Read more.

Sea level changes in coastal areas significantly influence port activities (e.g., the safety of navigation). Along Italian coastlines, sea level variations are mainly due to astronomical tides (well known, due to gravitational attraction between Earth, Moon and Sun); however, during the last fifteen years, a high number of “anomalous” tides has been observed: the study of the phenomenon has allowed to attribute its cause to variations in atmospheric pressure (the so-called meteorological tides: sea level drops when atmospheric pressure increases and vice versa); the statistical analysis of acquired data made it possible to evaluate the hydrobarometric transfer factor (a local parameter which represents the correlation between atmospheric pressure changes and consequent sea level variations): it was found that it is usually much larger within gulfs or port basins than offshore areas, where a pressure change of 1 hPa results in a sea level variation of about 1 cm; the statistical analysis described in the following, and aimed at correctly estimating the hydrobarometric transfer factor in harbors, can play a fundamental role in optimizing the management of port waters: its results allow to forecast meteorological tides and therefore future sea level (and depth) variations in a given port basin. The results of the study conducted in the port of La Spezia (North Western Italy) are presented here, together with possible applications on port activities and harbor water management. Full article

(This article belongs to the Special Issue Advances in Applied Marine Sciences and Engineering)

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25 pages, 1719 KiB

Open AccessArticle

Underwater Sparse Acoustic Sensor Array Design under Spacing Constraints Based on a Global Enhancement Whale Optimization Algorithm

by Lening Wang, Hangfang Zhao and Qide Wang

Appl. Sci. 2022, 12(22), 11825; https://doi.org/10.3390/app122211825 - 21 Nov 2022

Cited by 2 | Viewed by 1467

Abstract

Sparse arrays with low cost and engineering complexity are widely applied in many fields. However, the high peak sidelobe level (PSLL) of a sparse array causes the degradation of weak target detection performance. Particularly for the large size of underwater low-frequency sensors, the [...] Read more.

Sparse arrays with low cost and engineering complexity are widely applied in many fields. However, the high peak sidelobe level (PSLL) of a sparse array causes the degradation of weak target detection performance. Particularly for the large size of underwater low-frequency sensors, the design problem requires a minimum spacing constraint, which further increases the difficulty of PSLL suppression. In this paper, a novel swarm-intelligence-based approach for sparse sensor array design is proposed to reduce PSLL under spacing constrains. First, a global enhancement whale optimization algorithm (GEWOA) is introduced to improve the global search capability for optimal arrays. A three-step enhanced strategy is used to enhance the ergodicity of element positions over the aperture. In order to solve the adaptation problem for discrete array design, a position decomposition method and a V-shaped transfer function are introduced into off-grid and on-grid arrays, respectively. The effectiveness and superiority of the proposed approach is validated using experiments for designing large-scale low-frequency arrays in the marine environment. The PSLL of the off-grid array obtained by GEWOA was nearly 3.8 dB lower than that of WOA. In addition, compared with other intelligent algorithms, the on-grid array designed using GEWOA had the lowest PSLL. Full article

(This article belongs to the Special Issue Advances in Applied Marine Sciences and Engineering)

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15 pages, 1322 KiB

Open AccessArticle

Identification of Shark Species Based on Their Dry Dorsal Fins through Image Processing

by Luis Alfredo Carrillo-Aguilar, Esperanza Guerra-Rosas, Josué Álvarez-Borrego, Héctor Alonso Echavarría-Heras and Sebastián Hernández-Muñóz

Appl. Sci. 2022, 12(22), 11646; https://doi.org/10.3390/app122211646 - 16 Nov 2022

Cited by 1 | Viewed by 3708

Abstract

Shark populations worldwide have suffered a decline that has been primarily driven by overexploitation to meet the demand for meat, fins, and other products for human consumption. International agreements, such as CITES, are fundamental to regulating the international trade of shark specimens and/or [...] Read more.

Shark populations worldwide have suffered a decline that has been primarily driven by overexploitation to meet the demand for meat, fins, and other products for human consumption. International agreements, such as CITES, are fundamental to regulating the international trade of shark specimens and/or products to ensure their survival. The present study suggests algorithms to identify the dry fins of 37 shark species participating in the shark fin trade from 14 countries, demonstrating high sensitivity and specificity of image processing. The first methodology used a non-linear composite filter using Fourier transform for each species, and we obtained 100% sensitivity and specificity. The second methodology was a neural network that achieved an efficiency of 90%. The neural network proved to be the most robust methodology because it supported lower-quality images (e.g., noise in the background); it can recognize shark fin images independent of rotation and scale, taking processing times in the order of a few seconds to identify an image from the dry shark fins. Thus, the implementation of this approach can support governments in complying with CITES regulations and in preventing illegal international trade. Full article

(This article belongs to the Special Issue Advances in Applied Marine Sciences and Engineering)

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26 pages, 12410 KiB

Open AccessArticle

Experimental Investigation on Flow-Induced Rotation of Two Mechanically Tandem-Coupled Cylinders

by Fang Liu, Weipeng Feng, Xiang Yan, Danjie Ran, Nan Shao, Xiaoqun Wang and Defeng Yang

Appl. Sci. 2022, 12(20), 10604; https://doi.org/10.3390/app122010604 - 20 Oct 2022

Cited by 3 | Viewed by 1255

Abstract

The flow-induced rotational motion of tandem double cylinders has rarely been studied in existing papers. In order to further study the flow-induced rotation (FIR) of two mechanically tandem-coupled cylinders, an FIR device was designed in this paper, and the theoretical basis of this [...] Read more.

The flow-induced rotational motion of tandem double cylinders has rarely been studied in existing papers. In order to further study the flow-induced rotation (FIR) of two mechanically tandem-coupled cylinders, an FIR device was designed in this paper, and the theoretical basis of this system was established. On this basis, a series of variable spacing ratio (L/D) tests were carried out in a recirculating water tunnel. The range of L/D was 4.0 ≤ L/D ≤ 9.0. The main experimental conclusions can be summarized as follows: (1) When L/D = 4.0 and 4.5, the rotational response was similar to vortex-induced vibration (VIV), which is different from typical VIV, in that the rotational oscillation would appear to be a re-growth region when velocitycontinued to increase after the oscillation entered the lower branch of VIV. Additionally, the oscillation was at a low level and the maximum arc length ratio (A*) was less than 0.55 in these two cases; (2) For L/D = 5.0, 5.5 and 6.0, the rotational responses all showed typical VIV. When the oscillation reached a high level, the maximum A* was more than 0.85 for each case; (3) When L/D = 7.0, 8.0 and 9.0, the rotational responses still presented typical VIV. The oscillation was at a medium level, and the maximum A* was between 0.53 and 0.72, but these three cases had a wider synchronization interval than the other cases, and the range showed an increasing trend with the growth of L/D. Full article

(This article belongs to the Special Issue Advances in Applied Marine Sciences and Engineering)

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