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J. Mar. Sci. Eng., Volume 8, Issue 6 (June 2020) – 94 articles

Cover Story (view full-size image): Glyphosate is the active ingredient of numerous commercial formulations of herbicides applied in different sectors, from agriculture to aquaculture. Due to its large use, detectable concentrations of glyphosate have been detected in aquatic environments, posing a potential risk to living organisms. This review summarizes results of various studies on the effects of glyphosate (both as active ingredient and component of commercial formulations) on marine invertebrates. Data of acute toxicity tests indicate that glyphosate can be lethal at high concentrations (not environmentally realistic), whereas results of long-lasting experiments indicate that glyphosate can markedly affect biological responses of marine invertebrates. View this paper.
Glyphosate is the active ingredient of numerous commercial formulations of herbicides applied in different sectors, from agriculture to aquaculture. Due to its large use, detectable concentrations of glyphosate have been detected in aquatic environments, posing a potential risk to living organisms. This review summarizes results of various studies on the effects of glyphosate (both as active ingredient and component of commercial formulations) on marine invertebrates. Data of acute toxicity tests indicate that glyphosate can be lethal at high concentrations (not environmentally realistic), whereas results of long-lasting experiments indicate that glyphosate can markedly affect biological responses of marine invertebrates.
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Article
A Mesh Deformation Method for CFD-Based Hull form Optimization
J. Mar. Sci. Eng. 2020, 8(6), 473; https://doi.org/10.3390/jmse8060473 - 26 Jun 2020
Cited by 3 | Viewed by 931
Abstract
Computational fluid dynamics (CFD) is an effective tool for ship resistance prediction and hull form optimization. A three-dimensional volume mesh is essential for CFD simulation, and mesh generation requires much time and effort. Mesh deformation can reduce the time for mesh generation and [...] Read more.
Computational fluid dynamics (CFD) is an effective tool for ship resistance prediction and hull form optimization. A three-dimensional volume mesh is essential for CFD simulation, and mesh generation requires much time and effort. Mesh deformation can reduce the time for mesh generation and simulation. The radial basis function (RBF) and inverse distance weighted (IDW) methods are well-known mesh deformation methods. In this study, the two methods are compared and a novel mesh deformation method for hull form optimization is proposed. For the comparison, a circular cylinder polyhedral mesh was deformed to the National Advisory Committee for Aeronautics (NACA) 0012 mesh. The results showed that the RBF method is faster than the IDW method, but the deformed mesh quality using the IDW method is better than that using the RBF method. Thus, the RBF method was modified to improve the deformed mesh quality. The centroids of the boundary layer cells were added to the control points, and the displacements of the centroids were calculated using the IDW method. The cells far from the ship were aligned to the free surface to minimize the numerical diffusion of the volume of fluid function. Therefore, the deformable region was limited by the deformed boundary, which reduced the time required for mesh deformation. To validate its applicability, the proposed method was applied for varying the bow shape of Japan Bulk Carrier (JBC). The resistances were calculated with the deformed meshes. The calculation time was reduced to approximately one-third using the result of the initial hull form as the initial condition. Thus, the proposed mesh deformation method is efficient and effective enough for CFD-based hull form optimization. Full article
(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)
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Article
Image-Based Measurement of Wave Interactions with Rubble Mound Breakwaters
J. Mar. Sci. Eng. 2020, 8(6), 472; https://doi.org/10.3390/jmse8060472 - 26 Jun 2020
Cited by 1 | Viewed by 627
Abstract
Over the past decade, the use of imaging devices to perform quantitative measurements has seen wide-scale adoption and has become integral to the emerging fields of research, such as computer vision and artificial intelligence. Recent studies, published across a wide variety of fields, [...] Read more.
Over the past decade, the use of imaging devices to perform quantitative measurements has seen wide-scale adoption and has become integral to the emerging fields of research, such as computer vision and artificial intelligence. Recent studies, published across a wide variety of fields, have demonstrated a vast number of ways through which image-based measurement systems can be used in their respective fields. A growing number of studies have demonstrated applications in coastal and ocean research. Edge detection methods have been used to measure water surface and bedform elevation from recorded video taken during wave flume experiments. The turbulent mixing of air and water, induced by the breaking waves and the runup processes, poses a particular problem for the edge-detection methods, since they rely on a sharp contrast between air and water. In this paper, an alternative method for tracking water surface, based on color segmentation, is presented. A set of experiments were conducted whereby the proposed method was used to detect water surface profiles for various types of breaking waves interacting with a rubble mound breakwater. The results were further processed to compute the surface velocity during runup. The time-history of surface velocity is shown to closely parallel the point measurements taken nearby the instrumented armor unit. These velocities can potentially serve as boundary conditions for determining the dynamic loads exerted on the armour units. Further, the image processing results are used to remove the time-varying buoyant force from the measured force acting on an individual armour unit, providing additional insight into how the forces develop over time. Full article
(This article belongs to the Special Issue Dynamic Response of Marine Structures under Wave Action)
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Article
Population Genomic Analyses of Wild and Farmed Striped Catfish Pangasianodon Hypophthalmus in the Lower Mekong River
J. Mar. Sci. Eng. 2020, 8(6), 471; https://doi.org/10.3390/jmse8060471 - 25 Jun 2020
Viewed by 876
Abstract
The striped catfish Pangasianodon hypophthalmus is an important freshwater fish cultured in many countries where the collection of wild brooders is still widely practiced. Global farming development of this species makes use of significant natural resources that pose challenges for the genetic diversity [...] Read more.
The striped catfish Pangasianodon hypophthalmus is an important freshwater fish cultured in many countries where the collection of wild brooders is still widely practiced. Global farming development of this species makes use of significant natural resources that pose challenges for the genetic diversity of striped catfish. Hence, this study aims to conduct a systematic genetic diversity assessment of wild and farmed catfish stocks collected from four major pangasius-farming countries, using a new genotyping by sequencing platform known as DArT-seq technology. Our population genomic analyses using 7263 single-nucleotide polymorphisms (SNPs) after high-quality-control showed that there were two distinct populations of striped catfish in the lower Mekong river: (i) wild catfish from Thailand and (ii) catfish from Cambodia and Vietnam. The genetic diversity was greatest (0.363) in the wild stock from Thailand, but it was lower in farmed and wild stocks in other countries (0.049 to 0.088). The wild stocks were more genetically diverse than the farmed animals (0.103 vs. 0.064). The inbreeding coefficient ranged from 0.004 and 0.109, with the lowest value (−0.499) in the wild animals from Thailand. Molecular inference methods revealed high degree of historical effective population size (1043.9–1258.4), but there was considerable decline in the contemporary estimates in all populations (10.8 to 73.6). Our additional analyses calculating divergent times and migration patterns showed that the wild catfish from Thailand stand out as separate lineages, while those from Cambodia and Vietnam are genetically identical. Our results also indicated that the cultured stock in Bangladesh originated from the lower part of the Mekong river. These findings have significant practical implications in the context of genetic selection and conservation of striped catfish in the region. Collectively, they will contribute to the sustainable development of the striped catfish sector in these countries. Full article
(This article belongs to the Special Issue Genomic Prediction and Functional Genomics in Aquaculture)
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Article
Multiple TLDs on Motion Reduction Control of the Offshore Wind Turbines
J. Mar. Sci. Eng. 2020, 8(6), 470; https://doi.org/10.3390/jmse8060470 - 24 Jun 2020
Cited by 1 | Viewed by 755
Abstract
This study explores the damping effects of tuned liquid dampers (TLDs) on a monopile offshore wind turbine (OWT). The fluid–solid coupling of ANSYS was used to simulate the damping effect of a TLD on the structures. The environmental conditions refer to the IEC-61400-3 [...] Read more.
This study explores the damping effects of tuned liquid dampers (TLDs) on a monopile offshore wind turbine (OWT). The fluid–solid coupling of ANSYS was used to simulate the damping effect of a TLD on the structures. The environmental conditions refer to the IEC-61400-3 and the Design Load Case (DLC) 1.2 for the annual average environmental conditions and DLC 6.2 for the 50-year regression period, and the extreme environmental conditions were used in the study. The turbulent wind field simulation was performed by TurbSim, and the load of wind waves on structures was generated by FAST, which were all developed by the NREL (National Renewable Energy Laboratory). In addition to wind and waves, the seismic force was also considered. The cylindrical TLD was located above the rotor nacelle assembly (RNA). A TLD has different damping effects when acting under wind, wave, and earthquake loads, respectively. The effect of the TLD regarding motion reduction on the OWT under coupled wind, wave, and seismic loads was studied. This study also designed a simple experiment to verify the correctness of the numerical simulation results. Fatigue analysis shows that multi-layer TLDs can extend the fatigue life (37%) of an OWT. In addition, under extreme environmental load conditions, multi-layer TLDs have a better vibration damping performance than single-layer TLDs. The study demonstrates that multi-layer TLDs can be considered as a vibration reduction damper for OWTs. Full article
(This article belongs to the Special Issue Waves and Ocean Structures)
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Article
Sparrow: A Magnetic Climbing Robot for Autonomous Thickness Measurement in Ship Hull Maintenance
J. Mar. Sci. Eng. 2020, 8(6), 469; https://doi.org/10.3390/jmse8060469 - 24 Jun 2020
Cited by 4 | Viewed by 998
Abstract
The maintenance of ship hulls involves a series of routine tasks during dry-docking that renews its life-time and operating efficiency. One such task is hull inspection, which is always seen as harmful for human operators and a time-consuming task. The shipping maintenance industries [...] Read more.
The maintenance of ship hulls involves a series of routine tasks during dry-docking that renews its life-time and operating efficiency. One such task is hull inspection, which is always seen as harmful for human operators and a time-consuming task. The shipping maintenance industries started using the robotic solutions in order to reduce the human risk. However, most of such robotic systems cannot operate fully autonomously due to the fact that it requires humans in the loop. On the other hand, an autonomous hull inspection robot, called Sparrow, is presented in this paper. The proposed robot is capable of navigating autonomously on the vertical metal surface and it could perform metal thickness inspection. This article summarizes the robot’s mechanical design, system control, autonomy, and the inspection module. We evaluated the robot’s performance by conducting experimental trials on three different metal plates that varied in thickness. The results indicate that the presented robot achieves significantly better locomotion while climbing, and it can autonomously measure the metal thickness, which significantly reduces the human efforts in real-time. Full article
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Article
Coastal Scenic Evaluation of Continental Ecuador and Galapagos Islands: Human Impacts and Management Issues
J. Mar. Sci. Eng. 2020, 8(6), 468; https://doi.org/10.3390/jmse8060468 - 24 Jun 2020
Cited by 1 | Viewed by 1396
Abstract
The scenery, safety, facilities, water quality and litter quantities in coastal areas are relevant and determining elements in the choice of a tourist destination. This paper focused on the evaluation of coastal scenic value in 55 and 12 sites respectively located in continental [...] Read more.
The scenery, safety, facilities, water quality and litter quantities in coastal areas are relevant and determining elements in the choice of a tourist destination. This paper focused on the evaluation of coastal scenic value in 55 and 12 sites respectively located in continental Ecuador and the Galapagos Islands. The information obtained gives public administrators and coastal managers the relevant data to avoid further environmental degradation and suggests measures to improve the present scenic value of tourist destinations. The methodology used was based on the analysis of 26 physical/human factors and applied fuzzy logic analysis and weighting matrices that allowed the sites to be classified into five classes, from Class I (natural areas with superior scenic characteristics) to Class V (poor scenic areas with relevant impact of human interventions). The most attractive beaches were in the Galapagos Islands due to the magnificent physical and environmental characteristics, while the Esmeraldas province presented sites of lower scenic beauty due to the low natural scenic value and the increase of human impacts. In total, 22% (15 out of 67) of the beaches investigated belonged to Class I, 12% (8) to Class II and 15% (10) to Class III. The last two classes included 51% of the beaches (i.e., 34 out of 67), of which 31% (21) was in Class IV and 20% (13) in Class V. Such results provide local managers and planners a solid inventory on coastal scenic characteristics and baseline information for any envisaged subsequent management plan. Full article
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Article
Numerical Modelling and Dynamic Response Analysis of Curved Floating Bridges with a Small Rise-Span Ratio
J. Mar. Sci. Eng. 2020, 8(6), 467; https://doi.org/10.3390/jmse8060467 - 24 Jun 2020
Cited by 2 | Viewed by 710
Abstract
As a potential option for transportation applications in coastal areas, curved floating bridges with a same small specified rise to span ratio of 0.134, supported by multiple pontoons, are investigated in this paper. Two conceptual curved bridges are proposed following a circular arc [...] Read more.
As a potential option for transportation applications in coastal areas, curved floating bridges with a same small specified rise to span ratio of 0.134, supported by multiple pontoons, are investigated in this paper. Two conceptual curved bridges are proposed following a circular arc shape with different span lengths (500 and 1000 m). Both bridges are end-connected to the shoreline without any underwater mooring system, while the end-connections can be either all six degrees of freedom (D.O.F) fixed or two rotational D.O.F released. Eigen value analysis is carried out to identify the modal parameters of the floating bridge system. Static and dynamic analysis under extreme environmental conditions are performed to study the pontoon motions as well as structural responses of the bridge deck. Deflections and internal forces (axial forces, shear forces, and bending moment) are thoroughly studied with the variation of the span length and end support conditions in terms of the same specified small rise-span ratio. The ratio of axial force to horizontal bending moment are presented. From the study, it is found that the current parameters for the bridge are relatively reasonable regarding responses. However, the small rise-span does not provide enough arch effects. A higher rise-span ratio or stiffer bridge cross-sectional property is preferred, especially for the long bridge. In addition, the flexible end connections are preferred considering the structural responses at the end regions. Full article
(This article belongs to the Special Issue Numerical Investigation of Wave-Structure Interaction)
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Article
Risk Assessment of Work Accident in Container Terminals Using the Fault Tree Analysis Method
J. Mar. Sci. Eng. 2020, 8(6), 466; https://doi.org/10.3390/jmse8060466 - 24 Jun 2020
Cited by 2 | Viewed by 1064
Abstract
The use of containers in the world is increasing every year in line with international trade flows. In very complex container terminal operations, the risk of work accidents is inevitable and can happen at any time. Therefore, this paper aimed to identify accidents [...] Read more.
The use of containers in the world is increasing every year in line with international trade flows. In very complex container terminal operations, the risk of work accidents is inevitable and can happen at any time. Therefore, this paper aimed to identify accidents and potential risks occurring in the container terminals. For the case study, the analysis was used the data of accidents during five years in one of the major container terminals in Indonesia. Risk assessment is carried out using the risk matrix method to get the level of risk. The risk that has the highest level is analyzed by using the Fault Tree Analysis method. From the results of the risk assessment shows the container fell to the berth when loading and unloading have the highest risk value. While the results of the Fault Tree Analysis show that traffic accidents are the biggest potential risk, which is 41.8% compared to other accidents. Moreover, human factors especially due to the negligence in operating vehicles or equipment as well as the damage of equipment were the highest common causes of accidents in the container terminal. Based on these results the contribution offered is the risk control options for terminal operators to reduce the possibility of safety failure in the container terminal. Full article
(This article belongs to the Section Ocean Engineering)
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Article
Cavitation Prediction of Ship Propeller Based on Temperature and Fluid Properties of Water
J. Mar. Sci. Eng. 2020, 8(6), 465; https://doi.org/10.3390/jmse8060465 - 24 Jun 2020
Cited by 6 | Viewed by 1030
Abstract
Cavitation is a complex phenomenon to measure, depending on site conditions in specific regions of the Earth, where there is water with various physical properties. The development of ship and propulsion technology is currently intended to further explore territorial waters that are difficult [...] Read more.
Cavitation is a complex phenomenon to measure, depending on site conditions in specific regions of the Earth, where there is water with various physical properties. The development of ship and propulsion technology is currently intended to further explore territorial waters that are difficult to explore. Climate differences affect the temperature and physical properties of water on Earth. This study aimed to determine the effect of cavitation related to the physical properties of water. Numerical predictions of a cavitating propeller in open water and uniform inflow are presented with computational fluid dynamics (CFD). Simulations were carried out using Ansys. Numerical simulation based on Reynolds-averaged Navier–Stokes equations for the conservative form and the Rayleigh–Plesset equation for the mass transfer cavitation model was conducted with turbulent closure of the fully turbulent K-epsilon (k-ε) model and shear stress transport (SST). The influence of temperature on cavitation extension was investigated between 0   and   50   ° C . The results obtained showed a trend of cavitation occurring more aggressively at higher water temperature than at lower temperature. Full article
(This article belongs to the Special Issue Marine Propellers and Ship Propulsion)
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Technical Note
Study on the Coastline Evolution in Sopot (2008–2018) Based on Landsat Satellite Imagery
J. Mar. Sci. Eng. 2020, 8(6), 464; https://doi.org/10.3390/jmse8060464 - 24 Jun 2020
Cited by 6 | Viewed by 806
Abstract
The coastline is the boundary between the water surface in a reservoir or watercourse and the land, which is characterised by high instability and functional diversity. For these reasons, research on coastal monitoring has been conducted for several decades. Currently, satellite images performed [...] Read more.
The coastline is the boundary between the water surface in a reservoir or watercourse and the land, which is characterised by high instability and functional diversity. For these reasons, research on coastal monitoring has been conducted for several decades. Currently, satellite images performed with synthetic aperture radars (SARs) are used to determine its course and variability together with high-resolution multispectral imagery from satellites such as IKONOS, QuickBird, and WorldView, or moderate-resolution multispectral images from Landsat satellites. This paper analysed the coastline variability in Sopot (2008–2018) based on Landsat satellite imagery. Furthermore, based on multispectral images obtained, it was determined how the beach surface in Sopot changed. Research has shown that the coastline keeps moving away from the land every year. This was particularly noticeable between 2008 and 2018 when the coastline moved on average 19.1 m towards the Baltic Sea. Moreover, it was observed that the area of the sandy beach in Sopot increased by 14 170.6 m2, which translates into an increase of 24.7% compared to 2008. The probable cause of the continuous coastline shift towards the sea and the increase of the beach surface is the oceanographic phenomenon called tombolo, which occurred in this area as a result of the construction of a yacht marina near the coast. Full article
(This article belongs to the Special Issue Marine Measurements: Theory, Methods and Applications)
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Article
MaRINET2 Tidal Energy Round Robin Tests—Performance Comparison of a Horizontal Axis Turbine Subjected to Combined Wave and Current Conditions
J. Mar. Sci. Eng. 2020, 8(6), 463; https://doi.org/10.3390/jmse8060463 - 24 Jun 2020
Cited by 2 | Viewed by 835
Abstract
This Round Robin Test program aims to establish the influence of the combined wave and current effect on the power capture and performance of a generic tidal turbine prototype. Three facilities offering similar range of experimental conditions have been selected on the basis [...] Read more.
This Round Robin Test program aims to establish the influence of the combined wave and current effect on the power capture and performance of a generic tidal turbine prototype. Three facilities offering similar range of experimental conditions have been selected on the basis that their dimensions along with the rotor diameter of the turbine translate into low blockage ratio conditions. The performance of the turbine shows differences between the facilities up to 25% in terms of average power coefficient, depending on the wave and current cases. To prevent the flow velocity increasing these differences, the turbine performance coefficients have been systematically normalized using a time-average disc-integrated velocity, accounting for vertical gradients over the turbine swept area. Differences linked to blockage effects and turbulence characteristics between facilities are both responsible for 5 to 10% of the power coefficient gaps. The intrinsic differences between the tanks play a significant role as well. A first attempt is given to show how the wave-current interaction effects can be responsible for differences in the turbine performance. In these tanks, the simultaneous generation of wave and current is a key part often producing disruptions in both of these flow characteristics. Full article
(This article belongs to the Special Issue Marine Renewables–Infrastructures and Physical Testing)
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Article
Severe Coastal Hypoxia Interchange with Ocean Acidification: An Experimental Perturbation Study on Carbon and Nutrient Biogeochemistry
J. Mar. Sci. Eng. 2020, 8(6), 462; https://doi.org/10.3390/jmse8060462 - 23 Jun 2020
Cited by 1 | Viewed by 971
Abstract
Normally atmospheric CO2 is the major driver of ocean acidification (OA); however, local discharge/degradation of organic matter (OM) and redox reactions can exacerbate OA in coastal areas. In this work we study the response of nutrient and carbon systems to pH decrease [...] Read more.
Normally atmospheric CO2 is the major driver of ocean acidification (OA); however, local discharge/degradation of organic matter (OM) and redox reactions can exacerbate OA in coastal areas. In this work we study the response of nutrient and carbon systems to pH decrease in relation to hydrographically induced intermittent characteristics and examine scenarios for future ocean acidification in a coastal system. Laboratory microcosm experiments were conducted using seawater and surface sediment collected from the deepest part of Elefsis Bay; the pH was constantly being monitored while CO2 gas addition was adjusted automatically. In Elefsis Bay surface pCO2 is already higher than global present atmospheric values, while near the bottom pCO2 reaches 1538 μatm and carbonate saturation states were calculated to be around 1.5. During the experiment, in more acidified conditions, limited alkalinity increase was observed and was correlated with the addition of bicarbonates and OM. Ammonium oxidation was decelerated and a nitrification mechanism was noticed, despite oxygen deficiency, paralleled by reduction of Mn-oxides. Phosphate was found significantly elevated for the first time in lower pH values, without reprecipitating after reoxygenation; this was linked with Fe(II) oxidation and Fe(III) reprecipitation without phosphate adsorption affecting both available dissolved phosphate and (dissolved inorganic nitrogen) DIN:DIP (dissolved inorganic phosphate)ratio. Full article
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Article
Multidata Study to Evaluate the Impact of Submarine Outfall in a Beach Sedimentary Dynamic: The Case of Samil Beach (Galicia, Spain)
J. Mar. Sci. Eng. 2020, 8(6), 461; https://doi.org/10.3390/jmse8060461 - 23 Jun 2020
Cited by 1 | Viewed by 1108
Abstract
The Ria de Vigo (NW Iberian Peninsula) is one of the most impacted coastal areas of Galicia, due to demographic and industrial pressure. One of the main consequences of this pressure is the need to extend the current wastewater treatment plant of the [...] Read more.
The Ria de Vigo (NW Iberian Peninsula) is one of the most impacted coastal areas of Galicia, due to demographic and industrial pressure. One of the main consequences of this pressure is the need to extend the current wastewater treatment plant of the city of Vigo (295,000 inhabitants). This extension includes a new submerged pipeline construction to discharge the treated water in the central channel of the Ria. The new planned pipeline must cross Samil Beach, the most important urban beach of the city. Based on a multitool strategy, this work characterizes the interactions between the new pipeline route alternatives and the sediment dynamics of Samil Beach. This approximation improves the reliability of the results in the subtidal area of the beach, where studies are scarce due to the complexity of the data acquisition. The present study is based on high resolution bathymetry data, seabed physical characterization, a granulometric study of the superficial sediment, and a numerical simulation of the tide, wave climate, and sediment transport in low and high energy conditions using open source Delft3D software. The results showed that the area of interest is a low energy area, which is significantly shielded from wave attack, where fine sand predominates. However, the field data indicated an interaction (accretion-erosion) in the submerged obstacles between 0 and 12 m deep. The model revealed that there is significant sediment movement above a 7.4 m isobath, and that the pipeline would not alter the general transport dynamics of the beach, but would interact in the shallowest section. The main conclusion of this work states that the future structure would not alter the global sediment dynamics of the beach. In addition, in order to guarantee the safety of the new pipeline, it should emerge above an 8 m isobath. The multiapproach methodology presented can be applied to other studies of the interaction between coastal structures and the environment. Full article
(This article belongs to the Special Issue Beach Nourishment: A 21st Century Review)
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Review
Perspective Review on Subsea Jet Trenching Technology and Modeling
J. Mar. Sci. Eng. 2020, 8(6), 460; https://doi.org/10.3390/jmse8060460 - 22 Jun 2020
Viewed by 778
Abstract
This paper presents a comprehensive review on subsea jet trenching technology via a critical analysis of its principle, mechanism, devices, modeling approaches, as well as properties of subsea sediments. This review shows that the success of jet trenching operations is closely related to [...] Read more.
This paper presents a comprehensive review on subsea jet trenching technology via a critical analysis of its principle, mechanism, devices, modeling approaches, as well as properties of subsea sediments. This review shows that the success of jet trenching operations is closely related to some key factors including the soil conditions, trencher specifications, and characteristics of pipelines or cables. Three case histories are presented to demonstrate the importance of these key factors and their interrelationships. This paper also points out a number of challenges pertaining to the implementation of the jet trenching method in carbonate sediments, as well as some limitations and gaps in the existing modeling approaches. Future perspective researches that are recommended to develop: (1) promising theories, like turbulent submerged flow, and (2) robust numerical approaches, such as the smoothed particle hydrodynamics (SPH) and material point method (MPM) to substantiate the experimental experience and reveal possible hidden mechanisms. Full article
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Article
Parametric Knocking Performance Investigation of Spark Ignition Natural Gas Engines and Dual Fuel Engines
J. Mar. Sci. Eng. 2020, 8(6), 459; https://doi.org/10.3390/jmse8060459 - 22 Jun 2020
Cited by 7 | Viewed by 698
Abstract
Both spark ignition (SI) natural gas engines and compression ignition (CI) dual fuel (DF) engines suffer from knocking when the unburnt mixture ignites spontaneously prior to the flame front arrival. In this study, a parametric investigation is performed on the knocking performance of [...] Read more.
Both spark ignition (SI) natural gas engines and compression ignition (CI) dual fuel (DF) engines suffer from knocking when the unburnt mixture ignites spontaneously prior to the flame front arrival. In this study, a parametric investigation is performed on the knocking performance of these two engine types by using the GT-Power software. An SI natural gas engine and a DF engine are modelled by employing a two-zone zero-dimensional combustion model, which uses Wiebe function to determine the combustion rate and provides adequate prediction of the unburnt zone temperature, which is crucial for the knocking prediction. The developed models are validated against experimentally measured parameters and are subsequently used for performing parametric investigations. The derived results are analysed to quantify the effect of the compression ratio, air-fuel equivalence ratio and ignition timing on both engines as well as the effect of pilot fuel energy proportion on the DF engine. The results demonstrate that the compression ratio of the investigated SI and DF engines must be limited to 11 and 16.5, respectively, for avoiding knocking occurrence. The ignition timing for the SI and the DF engines must be controlled after −38°CA and 3°CA, respectively. A higher pilot fuel energy proportion between 5% and 15% results in increasing the knocking tendency and intensity for the DF Engine at high loads. This study results in better insights on the impacts of the investigated engine design and operating settings for natural gas (NG)-fuelled engines, thus it can provide useful support for obtaining the optimal settings targeting a desired combustion behaviour and engine performance while attenuating the knocking tendency. Full article
(This article belongs to the Special Issue Modelling and Optimisation of Ship Energy Systems)
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Article
Effects of Turbulence on the Vortex Modes Carried by Quasi-Diffracting Free Finite Energy Beam in Ocean
J. Mar. Sci. Eng. 2020, 8(6), 458; https://doi.org/10.3390/jmse8060458 - 22 Jun 2020
Cited by 1 | Viewed by 551
Abstract
By developing new wave structure function of a beam waves, we derive the transmitting probability of signal vortex modes in oceanic turbulence based on Rytov approximation theory. Applying this transmitting probability of signal vortex modes, we study the influence of oceanic turbulence on [...] Read more.
By developing new wave structure function of a beam waves, we derive the transmitting probability of signal vortex modes in oceanic turbulence based on Rytov approximation theory. Applying this transmitting probability of signal vortex modes, we study the influence of oceanic turbulence on the transmittance of the vortex modes carried by Mathieu-Gaussian beam. This model shows the transmitting probability of Mathieu-Gaussian beam with narrow initial beam width, long wavelength, and small ellipticity parameter is higher than the transmitting probability of the signal vortex modes in case of the beam with wide initial beam width, short wavelength, and great ellipticity parameter. Furthermore, when Mathieu-Gaussian beam has a suitable semi-cone angle, the effect of weak-turbulence channel on the transmitting probability of signal vortex modes with different topological charge can be ignored. Mathieu-Gaussian beam is a more suitable carrier for high information channel of underwater wireless optical communication than Laguerre-Gaussian beam. Full article
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Article
Validation and Application of a New Software Tool Implementing the PISA Design Methodology
J. Mar. Sci. Eng. 2020, 8(6), 457; https://doi.org/10.3390/jmse8060457 - 21 Jun 2020
Cited by 1 | Viewed by 1089
Abstract
The PISA (Pile Soil Analysis) research project has resulted in a new methodology for the design of offshore wind turbine monopile foundations. A new software tool called PLAXIS Monopile Designer (MoDeTo) has been developed that automates the PISA design methodology. It facilitates the [...] Read more.
The PISA (Pile Soil Analysis) research project has resulted in a new methodology for the design of offshore wind turbine monopile foundations. A new software tool called PLAXIS Monopile Designer (MoDeTo) has been developed that automates the PISA design methodology. It facilitates the calibration of the so-called soil reaction curves by automated three-dimensional finite element calculations and it allows for a quick design of monopiles using the calibrated soil reaction curves in a one-dimensional finite element model based on Timoshenko beam theory. The monopile design approach has been validated for sand- and clay-type soils which are common in North Sea soil deposits. The paper presents a validation exercise based on the PISA research project proposal of a rule-based parametric model—General Dunkirk Sand Model (GDSM)—for Dunkirk sand as well as an application of the tool for a project involving an offshore wind turbine on a monopile foundation in sandy layered soil in which the PISA design is compared to the conventional API design. The paper concludes with a discussion of the results and the differences between the various methods. Full article
(This article belongs to the Special Issue Offshore Wind Soil–Structure Interaction (SSI))
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Article
Effect of a Coccolithophore Bloom on the Underwater Light Field and the Albedo of the Water Column
J. Mar. Sci. Eng. 2020, 8(6), 456; https://doi.org/10.3390/jmse8060456 - 20 Jun 2020
Cited by 1 | Viewed by 803
Abstract
The goal of this work is to study the influence of coccolithophore blooms on the underwater light field and albedo of the water column. A coccolithophore is a single-celled alga with spherical cells surrounded by disk-shaped calcite plates (coccolites), which produce strong light [...] Read more.
The goal of this work is to study the influence of coccolithophore blooms on the underwater light field and albedo of the water column. A coccolithophore is a single-celled alga with spherical cells surrounded by disk-shaped calcite plates (coccolites), which produce strong light scattering. Because of that, we can observe coccolithophore blooms on satellite ocean color images. We calculated the angular underwater radiance distributions and their integral parameters by the exact numerical method with the input parameters, corresponding to real conditions observed in the Barents Sea and Black Sea. Using the results of the exact calculations, we estimated, for various situations, the accuracy of the approximating formulas applied to the assessment of the water radiance reflectance and the diffuse attenuation coefficients and we make recommendations for their application. As a finding of practical importance, we can note the estimate of the accuracy of the widely used Gordon’s formula for the diffuse attenuation coefficient; this formula results in large errors under strong coccolithophore blooms. We also mention the interesting and important results concerning the features of the asymptotic regime under such conditions. Full article
(This article belongs to the Special Issue Light Fields in the Ocean from Natural and Artificial Sources)
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Article
Numerical Prediction of the Vertical Responses of Planing Hulls in Regular Head Waves
J. Mar. Sci. Eng. 2020, 8(6), 455; https://doi.org/10.3390/jmse8060455 - 20 Jun 2020
Cited by 1 | Viewed by 839
Abstract
The evaluation of the hydrodynamic performance of planing vessels has always been one of the most attractive study fields in the maritime agenda. Resistance and self-propulsion studies have been performed using experimental and numerical methods by researchers for a long time. As opposed [...] Read more.
The evaluation of the hydrodynamic performance of planing vessels has always been one of the most attractive study fields in the maritime agenda. Resistance and self-propulsion studies have been performed using experimental and numerical methods by researchers for a long time. As opposed to this, the seakeeping performance of planing hulls is assessed with 2D approximation methods, but limitedly, while the experimental campaign is not cost-effective for several reasons. With this motivation, pitch and heave transfer functions and accelerations were obtained for a monohedral hull and a warped hull using a state of art commercial Reynolds-averaged Navier–Stokes (RANS) solver, in this study. Moreover, 2-DOF (degree of freedom) dynamic fluid–body interaction (DFBI) equations were solved in a coupled manner with an overset mesh algorithm, to find the instantaneous motion of the body. After verification, obtained numerical results at three different Froude numbers and a sufficiently large wave frequency range were compared with the experiments. The results showed that the employed RANS method offers a very accurate prediction of vertical motions and accelerations for planing hulls. Full article
(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)
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Article
Numerical Prediction of Welding Distortion Considering Gravity Force on General Ship Grillage Structure by Elastic Finite Element Method Using Inherent Strain
J. Mar. Sci. Eng. 2020, 8(6), 454; https://doi.org/10.3390/jmse8060454 - 20 Jun 2020
Cited by 1 | Viewed by 715
Abstract
The accurate numerical prediction of welding deformation is important to improve the structural safety of ships and offshore structures in heavy industries. The precise reflection of the real working condition in the numerical prediction is an essential factor to improve its result. In [...] Read more.
The accurate numerical prediction of welding deformation is important to improve the structural safety of ships and offshore structures in heavy industries. The precise reflection of the real working condition in the numerical prediction is an essential factor to improve its result. In the present study, the effect of the gravity force on numerical prediction of the optimal welding sequence of a general ship grillage structure was validated with the introduction of a new boundary condition in which the structure is placed over rails. Additionally, the direction of the gravity force of welded structures could be changed at the final assembly process according to the production plan. The effect of the gravitational orientation on the final welding displacements was also investigated herein. The elastic finite element method using the inherent strain, interface element, and multipoint constraint function was introduced to analyze the welding deformation. This study validated the influence of the gravity force on the numerical prediction of welding displacements in a general ship grillage structure. Full article
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Article
Comparison of Satellite-Based Sea Surface Temperature to In Situ Observations Surrounding Coral Reefs in La Parguera, Puerto Rico
J. Mar. Sci. Eng. 2020, 8(6), 453; https://doi.org/10.3390/jmse8060453 - 20 Jun 2020
Cited by 1 | Viewed by 945
Abstract
Coral reefs are among the most biologically diverse ecosystems on Earth. In the last few decades, a combination of stressors has produced significant declines in reef expanse, with declining reef health attributed largely to thermal stresses. We investigated the correspondence between time-series satellite [...] Read more.
Coral reefs are among the most biologically diverse ecosystems on Earth. In the last few decades, a combination of stressors has produced significant declines in reef expanse, with declining reef health attributed largely to thermal stresses. We investigated the correspondence between time-series satellite remote sensing-based sea surface temperature (SST) datasets and ocean temperature monitored in situ at depth in coral reefs near La Parguera, Puerto Rico. In situ temperature data were collected for Cayo Enrique and Cayo Mario, San Cristobal, and Margarita Reef. The three satellite-based SST datasets evaluated were NOAA’s Coral Reef Watch (CoralTemp), the UK Meteorological Office’s Operational SST and Sea Ice Analysis (OSTIA), and NASA’s Jet Propulsion Laboratory (G1SST). All three satellite-based SST datasets assessed displayed a strong positive correlation (>0.91) with the in situ temperature measurements. However, all SST datasets underestimated the temperature, compared with the in situ measurements. A linear regression model using the SST datasets as the predictor for the in situ measurements produced an overall offset of ~1 °C for all three SST datasets. These results support the use of all three SST datasets, after offset correction, to represent the temperature regime at the depth of the corals in La Parguera, Puerto Rico. Full article
(This article belongs to the Special Issue Sea Surface Temperature: From Observation to Applications)
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Article
Research of the Effectiveness of Selected Methods of Reducing Toxic Exhaust Emissions of Marine Diesel Engines
J. Mar. Sci. Eng. 2020, 8(6), 452; https://doi.org/10.3390/jmse8060452 - 20 Jun 2020
Cited by 3 | Viewed by 725
Abstract
The article’s applications are very important, as it is only a dozen or so years since the current issues of protection of the atmosphere against emissions of toxic compounds from ships. The issue was discussed against the background of binding legal norms, including [...] Read more.
The article’s applications are very important, as it is only a dozen or so years since the current issues of protection of the atmosphere against emissions of toxic compounds from ships. The issue was discussed against the background of binding legal norms, including rules introduced by the IMO (International Maritime Organization) in the context of the MARPOL Convention (International Convention for the Prevention of Pollution from Ships), Annex VI, with the main goal to significantly strengthen the emission limits in light of technological improvements. Taking these standards into account, effective methods should be implemented to reduce toxic compounds’ emissions to the atmosphere, including nitrogen oxides NOx and carbon dioxide CO2. The purpose of the article was, based on the results of our own research, to indicate the impact of the effectiveness of selected methods on reducing the level of nitrogen oxides and carbon dioxide emitted by the marine engine. The laboratory tests were carried out with the use of the one-cylinder two stroke, crosshead supercharged diesel engine. Methods of reducing their emissions in the study were adopted, including supplying the engine with fuel mixtures of marine diesel oil (MDO) and rapeseed oil ester (RME)-(MDO/RME mixtures) and changing the fuel injection parameters and the advance angles of fuel injection. The supply of the engine during the tests and the mixtures of marine diesel oil (MDO) and rape oil esters (RMEs) caused a clear drop in emissions of nitrogen oxides and carbon dioxide, particularly for a higher engine load, as has been shown. The decrease of the injection advance angle unambiguously makes the NOx content in exhaust gas lower. Full article
(This article belongs to the Special Issue Marine Engines Performance and Emissions)
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Article
A Study on Barge-Bank Interaction Forces Considering the Reflected Waves
J. Mar. Sci. Eng. 2020, 8(6), 451; https://doi.org/10.3390/jmse8060451 - 19 Jun 2020
Cited by 1 | Viewed by 606
Abstract
Because of the relative location between the ship and the bank, the fluid flow becomes complicated such that unstable hydrodynamic forces result in the yaw movement of the ship in an unintended direction. To consider the nonlinear effect, this study calculated the lateral [...] Read more.
Because of the relative location between the ship and the bank, the fluid flow becomes complicated such that unstable hydrodynamic forces result in the yaw movement of the ship in an unintended direction. To consider the nonlinear effect, this study calculated the lateral force and yaw moment of barges with different shapes in confined waters, using computational fluid dynamics (CFD). We analyzed the effect of the reflected waves from the bank on the barges. The sway force tended to increase as both barges became closer to the bank, because it worked as a suction force that pulled them toward the closest bank. The yaw moment increased as the barges became closer to the bank, regardless of the shape of the bow. At y′ = 0.2B, when the barges were at the closest to the bank, it rapidly soared. The wave pattern showed that the diverging waves from the shoulder did not disperse, and were blocked by the bank and returned to the ship; such phenomena resulted in changing the hydrodynamic force on the barge. It is determined that the effect of free surface must be considered when conducting a comprehensive analysis of the bank effect when the ship is close to the bank. Full article
(This article belongs to the Special Issue Modeling of Ship Hydrodynamics)
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Article
Using Orthogonal Combined Signals in Broadband ADCP for Improving Velocity Measurement
J. Mar. Sci. Eng. 2020, 8(6), 450; https://doi.org/10.3390/jmse8060450 - 19 Jun 2020
Cited by 2 | Viewed by 637
Abstract
Broadband Acoustic Doppler Current Profiler (BBADCP) is a widely used technology in velocity measurements. To adapt to the varied water environment and different measurement requirements, flexible tuning of transmitted signal parameters will improve the feasibility and accuracy of velocity measurement. Compared with the [...] Read more.
Broadband Acoustic Doppler Current Profiler (BBADCP) is a widely used technology in velocity measurements. To adapt to the varied water environment and different measurement requirements, flexible tuning of transmitted signal parameters will improve the feasibility and accuracy of velocity measurement. Compared with the conventional signal, the orthogonal combined signal designed in this paper can generate a wealth of signal combination examples and improve the accuracy of the velocity measurement under the same conditions. The proposed orthogonal combined signal consists of two orthogonal sub-signals with a symmetrical spectrum. Each is designed based on time delay to eliminate or weaken the current velocity ambiguity. Then, the processing method of the received signal when the pulse signals are the same or different coded signal is discussed. The numerical simulation results show that, when using the proposed method, the standard deviation of the estimated current velocity has different degrees of reduction at different current velocities. Our simulation also shows that, compared to the convention method, the proposed method can improve the SNR by 10 dB. This can help significantly increase the scope of the configuration. Full article
(This article belongs to the Special Issue Advanced Instruments for Marine Research)
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Article
Underwater Image Enhancement and Mosaicking System Based on A-KAZE Feature Matching
J. Mar. Sci. Eng. 2020, 8(6), 449; https://doi.org/10.3390/jmse8060449 - 19 Jun 2020
Viewed by 1033
Abstract
Feature extraction and matching is a key component in image stitching and a critical step in advancing image reconstructions, machine vision and robotic perception algorithms. This paper presents a fast and robust underwater image mosaicking system based on (2D)2PCA and A-KAZE [...] Read more.
Feature extraction and matching is a key component in image stitching and a critical step in advancing image reconstructions, machine vision and robotic perception algorithms. This paper presents a fast and robust underwater image mosaicking system based on (2D)2PCA and A-KAZE key-points extraction and optimal seam-line methods. The system utilizes image enhancement as a preprocessing step to improve quality and allow for greater keyframe extraction and matching performance, leading to better quality mosaicking. The application focus of this paper is underwater imaging and it demonstrates the suitability of the developed system in advanced underwater reconstructions. The results show that the proposed method can address the problems of noise, mismatching and quality issues which are typically found in underwater image datasets. The results demonstrate the proposed method as scale-invariant and show improvements in terms of processing speed and system robustness over other methods found in the literature. Full article
(This article belongs to the Special Issue Underwater Computer Vision and Image Processing)
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Editorial
Extreme Weather and Climate Events: Physical Drivers, Modeling and Impact Assessment
J. Mar. Sci. Eng. 2020, 8(6), 448; https://doi.org/10.3390/jmse8060448 - 19 Jun 2020
Viewed by 461
Abstract
Extreme weather and climate events, including hurricanes [...] Full article
Article
Wave Orbital Velocity Effects on Radar Doppler Altimeter for Sea Monitoring
J. Mar. Sci. Eng. 2020, 8(6), 447; https://doi.org/10.3390/jmse8060447 - 19 Jun 2020
Cited by 6 | Viewed by 719
Abstract
The orbital velocity of sea wave particles affects the value of sea surface parameters as measured by radar Doppler altimeters (also known as delay Doppler altimeter (DDA)). In DDA systems, the along-track resolution is attained by algorithms that take into account the Doppler [...] Read more.
The orbital velocity of sea wave particles affects the value of sea surface parameters as measured by radar Doppler altimeters (also known as delay Doppler altimeter (DDA)). In DDA systems, the along-track resolution is attained by algorithms that take into account the Doppler shift induced by the component along the Earth/antenna direction of the satellite velocity, VS. Since the vertical component of the wave particle orbital velocity also induces an additional Doppler effect (in the following R-effect), an error arises on the positioning of the target on the sea surface. A numerical investigation shows that when the wavelength of sea waves is of the same order of magnitude of the altimeter resolution, the shape of the waveform might be significantly influenced by the R-effect. The phenomenon can be particularly important for the monitoring of long swells, such as those that often take place in the oceans. Full article
(This article belongs to the Special Issue Radar Technology for Coastal Areas and Open Sea Monitoring)
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Article
Experimental Study on the Influence of Berms and Roughness on Wave Overtopping at Rock-Armoured Dikes
J. Mar. Sci. Eng. 2020, 8(6), 446; https://doi.org/10.3390/jmse8060446 - 18 Jun 2020
Cited by 3 | Viewed by 997
Abstract
The average overtopping discharge is an important parameter for the design and reinforcement of dikes. Rock armour on the waterside slopes and berms of dikes is widely used to reduce the wave overtopping discharge by introducing slope roughness and dissipation of energy in [...] Read more.
The average overtopping discharge is an important parameter for the design and reinforcement of dikes. Rock armour on the waterside slopes and berms of dikes is widely used to reduce the wave overtopping discharge by introducing slope roughness and dissipation of energy in the permeable armour layer. However, methods for estimating the influence of a rock berm and roughness of rock armour at dikes on the average overtopping discharge still need to be developed and/or validated. Therefore, this study aims to develop empirical equations to quantify the reductive influence of rock armour on wave overtopping at dikes. Empirical equations for estimating the effects of rock berms and roughness are derived based on the analysis of experimental data from new physical model tests. The influence of roughness of the rock armour applied on parts of waterside slopes is estimated by introducing the location weighting coefficients. Results show that the newly derived equations to predict the average overtopping discharge at dikes lead to a significantly better performance within the tested ranges compared to existing empirical equations. Full article
(This article belongs to the Special Issue Resilient Flood Defences)
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Article
Simulation Study of the IAMSAR Standard Recovery Maneuvers for the Improvement of Serviceability
J. Mar. Sci. Eng. 2020, 8(6), 445; https://doi.org/10.3390/jmse8060445 - 18 Jun 2020
Cited by 2 | Viewed by 954
Abstract
Recovery maneuvers are highly important for rescuing a person overboard at sea. This is the prime reason why the International Maritime Organization (IMO) has published the International Aeronautical and Maritime Search and Rescue (IAMSAR) Manual III, which aims to assist vessels and aircrafts [...] Read more.
Recovery maneuvers are highly important for rescuing a person overboard at sea. This is the prime reason why the International Maritime Organization (IMO) has published the International Aeronautical and Maritime Search and Rescue (IAMSAR) Manual III, which aims to assist vessels and aircrafts in the performance of a search, rescue, or on-scene co-ordinated efforts with aspects of search and rescue (SAR) which pertain to their own emergencies. The IAMSAR Manual III includes the Williamson turn, the Anderson turn and the Scharnov turn. Furthermore, the Lorén turn has been newly included in the 2019 edition of the Manual. Although several studies have pointed out that the Williamson turn needs to be applied in a modified form for proper application, in terms of returning ability to the original track line, it has not yet been modified in the Manual. Therefore, the purpose of this study is to analyze the serviceability of the four standard recovery maneuvers through a series of ship-handling simulations with representative types of ships. Our main results are as follows: firstly, the Anderson turn is the fastest recovery method, regardless of engine power and rudder efficiency; secondly, the actual paths of the Williamson turn are not consistent with the expected ones; and, finally, no correlations were found between the returning ability of the Williamson turn and any ship configuration or maneuvering ability factors, or their combinations. Thus, based on the experimental results, this paper proposes revising the descriptions of the standard recovery maneuvers and IMO regulations on ship maneuverability, as well as posting the actual tracks of the Williamson turn on the bridge in order to improve its serviceability. Full article
(This article belongs to the Special Issue Maritime Safety)
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Article
Analysis of Sealing and Leakage Performance of the Subsea Collet Connector with Lens-Type Sealing Structure
J. Mar. Sci. Eng. 2020, 8(6), 444; https://doi.org/10.3390/jmse8060444 - 17 Jun 2020
Cited by 1 | Viewed by 647
Abstract
The contact mechanics model of the metal lens-type sealing gasket is established on the basis of Hertz theory on the macroscopical scale in this paper. The relationship among sealing width, contact pressure, and preload is solved. Based on the structural characteristics of the [...] Read more.
The contact mechanics model of the metal lens-type sealing gasket is established on the basis of Hertz theory on the macroscopical scale in this paper. The relationship among sealing width, contact pressure, and preload is solved. Based on the structural characteristics of the subsea collet connector, the self-locking characteristics are analyzed to determine the gain coefficient of the sealing structure for the loading thrust. On the microscopic scale, the contact characteristics of the turning lens-type sealing gasket and the hub structure are analyzed by the equivalent replacement of the peak cut coefficient of the one-dimensional sinusoidal wave. The influence of different leakage forms on sealing performance is discussed from both radial and circumferential leakage, and the leakage rate of the lens-type sealing structure is calculated. The hydrostatic pressure experiment of the subsea collet connector with lens-type sealing gasket is carried out, and the correctness of the theoretical analysis is verified from the results of the pressure maintaining, sealing width measurement, and preload conversion. Full article
(This article belongs to the Section Ocean Engineering)
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