bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Performance Electro-Discharge Drilling with a Novel Type of Oxidized Tool Electrode
Authors: Uhlmann Eckart , Polte Julian , Streckenbach Jan , Dinh Ngoc Chuong , Yabroudi Sami , Polte Mitchel , Börnstein Julian
Published: October 2022

Electro-discharge drilling is a key technology for manufacturing sophisticated nozzles in a broad range of automotive and aerospace applications. The formation of debris in the working gap leads to arcs and short circuits on the lateral surface when state-of-the-art tool electrodes are used. As a result, limited drilling depth, increased linear tool wear, and the conicity of boreholes are still challenges. In this work, a new approach for the passivation of the lateral surface of copper tool electrodes by oxidation is shown. The comparison with state-of-the-art tool electrodes showed a reduction in the erosion duration by 48% for machining hardened steel. Promising improvements could be achieved by the thermal oxidation of the tool electrodes with the aim of increasing the electrical resistivity of the lateral surface of the tool electrode. However, due to the loss of strength, the high oxide layer thickness, and the partial delamination of the oxide layer, further comprehensive investigations on the influence of the oxidation temperature need to be conducted. Future adjustments with lower oxidation temperatures will be carried out.
Practical Approaches for Acoustic Emission Attenuation Modelling to Enable the Process Monitoring of CFRP Machining
Authors: Uhlmann Eckart , Holznagel Tobias , Clemens Robin
Published: October 2022

Acoustic emission-based monitoring of the milling process holds the potential to detect undesired damages of fibre-reinforced plastic workpieces, such as delamination or matrix cracking. In addition, abrasive tool wear, tool breakage, or coating failures can be detected. As measurements of the acoustic emission are impacted by attenuation, dispersion, and reflection as it propagates from source to sensor, the waveforms, amplitudes, and frequency content of a wave packet differ depending on the propagation length in the workpiece. Since the distance between acoustic emission sources and a stationary sensor attached to the workpiece changes continually in circumferential milling, the extraction of meaningful information from the raw measurement data is challenging and requires appropriate signal processing and frequency-dependent amplification. In this paper, practical and robust approaches, namely experimentally identified transfer functions and frequency gain parameter tables for attenuation modelling, which in reverse enable the reconstruction of frequency spectra emitted at the acoustic emission source, are presented and discussed. From the results, it is concluded that linear signal processing can largely compensate for the influence of attenuation, dispersion, and reflection on the frequency spectra and can therefore enable acoustic emission based process monitoring.
EGFR Mutation in Nasopharyngeal Carcinoma
Authors: Uzun Evren , Erkilic Suna
Published: October 2022

Nasopharyngeal carcinoma is a malignant tumor of the nasopharynx. However, while radiotherapy is the primary choice of treatment, the treatment may fail due to distant metastasis in most patients at an advanced stage. Treatment agents against some mutations have led to the development of personalized treatment regimens. EGFR is one of the most studied molecules and has played a role in the development of a large number of cancer types. We aimed to demonstrate the EGFR mutation status in nasopharyngeal carcinomas. Twenty-six nasopharyngeal carcinomas were included in the study. EGFR mutation analysis was applied to the cases by the real-time PCR method. The results were evaluated statistically. No EGFR mutation was detected in any of the cases. Although EGFR expression is frequently shown in nasopharyngeal carcinomas immunohistochemically, the same positivity was not shown in genetic analysis. This result shows that the use of anti-EGFR agents in nasopharyngeal carcinoma treatment will not be effective.
Study on the Effect of the Guide Vane Opening on the Band Clearance Sediment Erosion in a Francis Turbine
Authors: Song Xijie , Zhou Xuhui , Song Huating , Deng Jianhua , Wang Zhengwei
Published: October 2022

Sediment erosion is a negative phenomenon for the water turbine. The purpose of this paper is to study the effect of the guide vane opening on the particle motion and sediment erosion in the band chamber using the Euler–Lagrangian approach. The software Ansys CFX and Tabakoff erosion model are used to simulate the sediment laden flow in the full flow passage of the hydraulic turbine. The results are in good agreement with the actual erosion character on site. Results show that the guide vane opening has a positive correlation with the flow in the non-clearance channel. The increase of the guide vane opening will increase the erosion of the runner blade head, but the friction wear on the outlet side of the blade surface will decrease. The rotating action of the runner makes the sediment particles in the band chamber rotate rapidly around the center of the runner and constantly collide with the band chamber wall. Under the small opening, the smaller the opening, the easier the leakage of the band clearance occurs. The unsteady flow in the band chamber will disturb the motion trajectory of particles, change the impact angle of particles, and affect the wear in the band chamber. Under different openings, the change law of the erosion in the band clearance is closely related to the change law of clearance leakage.
Numerical Investigation of the 6-DOF Seakeeping Performances of the KCS Containership
Authors: Lungu Adrian
Published: October 2022

The topic of the present paper subscribes to one of the most challenging themes that are nowadays under the spotlight of the scientific community. It describes a substantiated method aimed not only at predicting accurately the consequences of the associated effects of navigation in waves but also at contributing to ruling the conditions in which the operation of a ship should be performed is presented. A series of multiple degrees of freedom (DOF hereafter) simulations of the MOERI (Korea Research Institute for Ships and Ocean Engineering) container ship (KCS hereafter) hull moving in regular waves are performed and thoroughly validated with the experimental data provided by the organizers of the Tokyo 2015 Workshop on CFD in Ship Hydrodynamics. A verification and validation (V&V hereafter) is performed for the calm water navigation case to prove the robustness of the theoretical approach. Several numerical innovations are proposed, and the solutions are discussed in every detail aimed at setting up a properly established methodology usable in further similar studies. Finally, a set of remarks will conclude the present research.
The Structure and Function of the Sargassum fusiforme Microbiome under Different Conditions
Authors: Dai Chunchun , Wang Shengqin
Published: October 2022

Brown macroalgae, a key component of the vegetated coastal ecosystems, can sequester a large amount of CO2, which is mainly converted to polysaccharides. These polysaccharides confer complex structures and are difficult to be degraded by microbial communities. On the surface of brown macroalgae in which bacteria lived, the diversity and encoded enzymes of these bacteria involved in carbon cycling remain largely unknown. In this study, we used metagenomic sequencing to survey bacteria communities associated with the Sargassum fusiforme under different conditions and investigated the structure and function of these bacteria. A total of 5308 species were discovered in all 15 samples from different conditions. Most of these species belonged to the phylum Proteobacteria. Many S. fusiforme-associated bacteria could decompose algal polysaccharides under different conditions. Our method could enhance the ability to understand the microbiome community. To the best of our knowledge, this is the first report regarding metagenomics in S. fusiforme. The co-occurrence network provides insights into the relationship of the polysaccharide degradation enzymes (PDEs). These data provide a reference for the cultivation of S. fusiforme and the understanding of the marine carbon cycle.
Supercritical CO2 Power Cycle and Ejector Refrigeration Cycle for Marine Dual Fuel Engine Efficiency Enhancement by Utilizing Exhaust Gas and Charge Air Heat
Authors: Jiang Yuemao , Wang Zhe , Ma Yue , Ji Yulong , Cai Wenjian , Han Fenghui
Published: October 2022

Dual fuel engines with LNG as fuel have become a feasible solution for ship power units in the current situation, but their fuel efficiency needs to be further enhanced to meet the increasingly stringent emission requirements. This paper designs a dual-loop system, including a supercritical CO2 power cycle and a thermally driven ejector refrigeration cycle, for recovering the exhaust gas and charge air heat of a marine dual fuel engine. The models of the waste heat recovery system, the evaluation indicators of the combined system, and the genetic algorithm optimization program are developed. Compared to the standalone machine, the waste heat recovery system can improve by about 9.3% of the engine’s fuel efficiency. The performance analysis shows that the ejector contributes to the highest share of exergy destruction and accounts for approximate 53% of the refrigeration cycle. There are optimal values for the compressor inlet temperature of about 8.1 MPa and for the turbine inlet temperature of about 305 °C. Finally, after optimization, the specific fuel consumption, fuel efficiency, and CO2 emissions of the combined system are around 137.9 g/kWh, 53.3%, and 537.4 g/kWh, respectively. It provides a feasible solution in which the charge air cooler can be wholly replaced by the ejector refrigeration cycle.
Mechanism of Mechanical Analysis on Torsional Buckling of U-Shaped Bellows in FLNG Cryogenic Hoses
Authors: Yan Jun , Ying Xipeng , Cao Huixin , Xiong Feiyu , Zhang Kailun , Yang Zhixun
Published: October 2022

Floating liquefied natural gas (FLNG) cryogenic hoses can be employed for the transmission of liquefied natural gas (LNG). Usually, U-shaped metal bellows can be applied as the inner lining of FLNG cryogenic hoses. In installation, positioning and other working conditions, torsion is one of the main loads, and torsional buckling instability is a major failure mode of U-shaped metal bellows of FLNG cryogenic hoses. In the current research, the buckling instability of bellows under torsional loads has been investigated in detail, the mechanical mechanism of deformation in torsional buckling mode of bellows has been analyzed and the influence of the structural design parameters on the stability performance has been summarized. It was seen that the axis of the bellows was presented as a spiral line shape during the torsional buckling stage. At the same time, the torsional buckling properties of toroid and spiral bellows were analyzed. The obtained results showed that the torsional buckling stability of the spiral bellows was weaker than that of the toroid bellows and increase of the spiral angle of the spiral bellows intensified this trend. In addition, the post-buckling analysis of U-shaped bellows under torsional loads was carried out by means of experiments and finite element simulation. It was shown that the results obtained from finite element (FE) analysis in this research presented a relatively accurate critical torque value and a consistent buckling instability mode, compared with the experimental results. On this basis, the effects of common defects such as thickness thinning on the torsional stability of bellows were investigated. Considering the geometric defect of thickness thinning, the error of FE analysis was reduced further, and it was found that the defect could significantly decrease the stability of the bellows. The above analysis results could provide a reference for structural design and post-buckling analysis of bellows.
Decoupled Planes’ Non-Singular Adaptive Integral Terminal Sliding Mode Trajectory Tracking Control for X-Rudder AUVs under Time-Varying Unknown Disturbances
Authors: Yuan Chengren , Shuai Changgeng , Fang Yuan , Ma Jianguo
Published: October 2022

This paper analyzes the trajectory tracking problem in decoupled planes for X-rudder AUVs under time-varying, unknown environmental interferences. The proposed scheme consists of the kinematic control law based on the compound line-of-sight guidance law and the dynamic control law based on a non-singular adaptive integral terminal sliding mode control (NAITSMC) to avoid the chattering problems, parameter perturbation, and time-varying disturbances. Meanwhile, we introduce a reduced-order extended state observer (RESO) to compensate for unknown ocean currents by the first-order Gauss–Markov process. We verify the whole system of the proposed scheme through global asymptotic stability, then present a set of numerical simulations revealing robustness and adaptability performances in decoupled planes.
Circulation and Transport Processes during an Extreme Freshwater Discharge Event at the Tagus Estuary
Authors: Ribeiro Ana Filipa , Sousa Magda , Picado Ana , Ribeiro Américo Soares , Dias João Miguel , Vaz Nuno
Published: October 2022

During the winter of 2013, the Tagus estuary was under the influence of intense winds and extreme freshwater discharge that changed its hydrodynamics and, consequently, the salt and heat transport. Moreover, the dynamics of the estuary may change due to climate change which will increase the frequency of heat waves and increase the mean sea level. Therefore, it is of utmost importance to study the impact of the future increase in air temperature and mean sea level under extreme events, such as that in the winter of 2013, to ascertain the foreseen changes in water properties transport within the estuary and near coastal zone. Several scenarios were developed and explored, using the Delft3D model suite, considering the results of the CMIP6 report as forcing conditions. Before the event, the mixing region of the estuary presented well-mixed conditions and its marine area a slight stratification. During the event, the estuary was filled with freshwater and the mixing region migrated toward the coast, leading to lower water temperature values inside the estuary. SLR has a higher impact on the salinity and stratification patterns than the air temperature increase. The response of water temperature is directly related to the increase in air temperature. The estuary mouth and the shallow regions will be more prone to changes than the upstream region of the estuary. The projected changes are directly linked to the future CO2 emissions scenarios, being intensive with the highest emission scenario.
Experimental Research on the Influences of Head Shape and Surface Properties on the Water Entry Cavity
Authors: Shi Yao , Xiao Peng , Zhao Hairui , Pan Guang
Published: October 2022

Addressing the problem of the influence of surface properties on the cavity in the process of a moving body entering water, especially the problems of water entry speed and the cavitation evolution of the round-head, air-delivered projectile that has many practical applications, a self-designed launch platform and high-speed camera were used, and the MK46 was used as a prototype to conduct scaled model experiments with different head form types and different surface properties. This paper describes the general process of the moving body entering the water and the generation of the cavity. The relationship between the re-injection flow, the local cavity number and the cavity stability is discussed. At the same time, the effects of head shape, launch velocity and surface wettability on the cavity evolution and motion characteristics were analyzed, including 0°, 57°, 70°, 90° and 180° hemispherical angle-head projectiles with speeds of 2.2 m/s and 3.95 m/s, so as to observe the cavity development and ballistics. The results show that hydrophobic surfaces are more prone to cavities when entering water vertically at low speeds. The influencing factors of water entry ballistics are often the combined effects of head shape, water entry speed and water entry angle. The speed of the hydrophilic surface models with head hemisphere angles of 57 degrees and 70 degrees entering the water is the fastest. This provides a reference for us to design the shape of the projectile. The internal relationship between the cavity shape and the ballistic characteristics is based on the premise that the cavity will complicate the force on the model. The cavity affects the ballistic characteristics of the model by affecting the forces on the model.
Motion Control System Design for Barge-Type Surface Ships Using Tugboats
Authors: Lee Dong-Hun , Huynh Thinh , Kim Young-Bok , Park Jung-Suk
Published: October 2022

Barge ships are designed to transport and assemble heavy and massive pieces of equipment at sea. Active propulsion systems are not installed in this type of ship, so the desirable motion and positioning of these ships can only be achieved with the assistance of several tugboats. In this study, the dynamical characteristics of barge conveying systems were formulated and robust control systems were designed to ensure efficient barge operation. To achieve these objectives, we first developed a mathematical model of a barge ship, which incorporated a novel conveying system configuration using tugboats. We then designed a robust controller for the tugboats that used the sliding mode law to deliver the desired barge motion performance. Finally, the usefulness of the proposed configuration and controller was verified via simulation studies using another system with an H∞ controller. The proposed sliding mode controller showed superiority, especially in terms of robustness against disturbances.
The Impact of the Caroline Ridge Subduction on the Geomorphological Characteristics of Major Landforms in the Yap Subduction Zone
Authors: Sangana Peter , Gao Qin , Li Zilong
Published: October 2022

The Caroline Ridge (CR) subduction underneath the Philippine Sea Plate brings complex morphotectonic characteristics to the Yap Subduction Zone (YSZ) compared to other normal intra-oceanic subduction systems. However, due to the relative paucity of precise geomorphological information, the detailed morphotectonic settings of the YSZ remain unclear. Therefore, we combine the latest-released bathymetry, marine geomorphometry techniques, and geophysical information to investigate the geomorphological characteristics of landforms in the YSZ and their inter-relationship with the CR subduction. The Parece Vela Basin displays NE-SW oriented fractures which are believed to be influenced by the subduction of CR in the ESE-WNW direction. The north part of the Yap arc exhibits higher Bouguer anomalies, implying the absence of the overlying normal volcanic arc crust. The arc-ward trench shows abnormal higher slope values and reveals two significant slope breaks. The Yap Trench axis reveals varying water depths with an extraordinarily deep point at around 9000 m. The sea-ward trench slope displays higher slope values than normal and shows the presence of grabens, horsts, and normal faults which indicate the bending of the CR before subduction. The CR subduction is observed to be critical in the formation of significant geomorphological characteristics in the YSZ.
Arctic Development in Connection with the Northern Sea Route: A Review of Ecological Risks and Ways to Avoid Them
Authors: Makarova Irina , Makarov Dmitry , Buyvol Polina , Barinov Aleksandr , Gubacheva Larysa , Mukhametdinov Eduard , Mavrin Vadim
Published: October 2022

The unprecedented melting of Arctic ice provides new opportunities for shipping by decreasing the distance for commercial traffic between Asia and Europe by up to 40%. However, its development is associated with inevitable problems caused by the vulnerability of polar ecosystems. As research methods, we have chosen system and comparative analyses of open sources; national development strategies of the Russian Federation (primarily), China, Northern Europe, and the USA (partially); and scientific articles from the Scopus and Elibrary databases. As a result, we have identified the reasons for possible risk situations for the Arctic region’s sustainable development: mining on the shelf, oil and oil product spills during the transportation of goods and fishing activities, etc. Black carbon (soot) emitted from using marine diesel fuel is the main atmospheric air pollutant. In addition, actively developing infrastructure (ports and new industrial zones) also has a negative anthropogenic impact on the environment. Within the framework of an ecosystem approach, we studied ways to prevent risky situations when planning logistics routes using the Northern Sea Route. We concluded about the need to expand the icebreaker fleet. We proposed a conceptual model of the risk management system based on the monitoring of the key indicators’ system. We identified possible types of risks according to the place of their occurrence and according to the stages of the life cycle of such systems. Furthermore, we provided the steps of the risk management system and an example of the application of a “bow-tie” diagram—a qualitative method for assessing the risk of “collision”.
Self-Powered and Robust Marine Exhaust Gas Flow Sensor Based on Bearing Type Triboelectric Nanogenerator
Authors: Du Taili , Dong Fangyang , Zhu Meixian , Xi Ziyue , Li Fangming , Zou Yongjiu , Sun Peiting , Xu Minyi
Published: October 2022

Exhaust gas flow takes a vital position in the assessment of ship exhaust emissions, and it is essential to develop a self-powered and robust exhaust gas flow sensor in such a harsh working environment. In this work, a bearing type triboelectric nanogenerator (B-TENG) for exhaust gas flow sensing is proposed. The rolling of the steel balls on PTFE film leads to an alternative current generated, which realizes self-powered gas flow sensing. The influence of ball materials and numbers is systematically studied, and the B-TENG with six steel balls is confirmed according to the test result. After design optimization, it is successfully applied to monitor the gas flow with the linear correlation coefficient higher than 0.998 and high output voltage from 25 to 106 V within the gas flow of 2.5–14 m/s. Further, the output voltage keeps stable at 70 V under particulate matter concentration of 50–120 mg/m3. And the output performance of the B-TENG after heating at 180 °C for 10 min is also surveyed. Moreover, the mean error of the gas flow velocity by the B-TENG and a commercial gas flow sensor is about 0.73%. The test result shows its robustness and promising perspective in exhaust gas flow sensing. Therefore, the present B-TENG has a great potential to apply for self-powered and robust exhaust gas flow monitoring towards Green Ship.
Influences of Tidal Effect on Upper Ocean Responses to Typhoon Passages Surrounding Shore Region off Northeast Taiwan
Authors: Zheng Zhe-Wen , Chen Yi-Rui
Published: October 2022

In this study, the Regional Ocean Modelling System (ROMS) with a spatial resolution of 2 km is used to understand the cooling responses in the sea northeast of Taiwan associated with multiple typhoons. Sea level measurements derived from in situ tidal gauges and continuous temperature measured by a moored buoy deployed at Longdong were used to validate the model’s performance. Six far-field typhoons with similar tracks, namely, Utor (2001), Dujuan (2003), Sanvu (2005), Nanmadol (2011), Usagi (2013), and Meranti (2016), were systematically investigated to demonstrate the influences of tidal effect on upper ocean responses to typhoon passages surrounding shore regions. After integrating tidal forcing, model-simulated cold wakes behind typhoon passages were essentially enhanced. Compared with observations, the cold wakes were reproduced more realistically. Tides could promote a cooling response through the following potential mechanisms: (1) tidal mixing destratifies the water column, (2) a stronger northward current leads to a sharper bottom thermocline, (3) tidal residual currents (southward) drive the offshore-ward (downslope) bottom Ekman flow and lead to the overturning of cold bottom water and warm subsurface water, (4) the increase in bottom stress due to the interaction of tidal currents and bottom topography results in the destratification of the bottom water column, and (5) the wind–tide coupled effect. Nevertheless, the exact mechanism dominating the process of a typhoon–tide-induced stronger upper ocean response depends on different typhoon activities, tidal regimes, stratification, and bathymetry and needs further investigations. In this study, we suggest that including tidal effects is essential for the modeling of upper ocean responses to typhoon passages near the shore regions.
Analysis of Navigator Decision Making through Cognitive Science for the Presentation of a Collision-Avoidance Algorithm for MASSs
Authors: Lee Hee-Jin , Park Deuk-Jin
Published: October 2022

The study of navigator behavior is important for the study of MASSs. This study analyzed navigator behavior through cognitive science, and it modeled the navigator decision-making process. Usually, the assessment of the collision risk for long-distance target ships is conducted through the distance (DCPA) and time (TCPA) to the closest point of approach. The navigator’s decision-making process is carried out quantitatively based on numerical values. Although the angle of the rudder is presented as a numerical value (i.e., 5°, 10°, 15°, and so on), it is expected that the navigator’s use of the rudder will depend on the conventional method rather than the quantitative one. Therefore, a scenario was constructed, and a simulation test was carried out through a ship-handling simulator. Our results confirmed that the rudder was used according to the conventional method. Moreover, the navigator decision-making process was analyzed through cognitive science. Cognitive science has revealed that human judgment is not logical, and that all decision making relies on memory. We identified the type of memory that affects the decision making of navigators: the DCPA and navigators’ decision-making-criteria values were mainly formed by episodic memory. A decision-making model for the relationship between the navigator’s episodic memory and the value of the DCPA was subsequently developed. This study took a scientific approach to analyze the process of the decision making of navigators, and an engineering approach to construct a decision-making model for application in MASSs.
Influence of Dynamic Woody Debris Jam on Single Bridge Pier Scour and Induced Hydraulic Head
Authors: Zhang Wenjun , Nistor Ioan , Rennie Colin D. , Almansour Husham
Published: October 2022

A woody debris jam around a bridge pier causes a change in flow structure and results in additional scour and an increase in the hydraulic head upstream of the pier, threatening its stability and safety. In the present paper, the spatio-temporal formation of a dynamic woody debris jam formed piece by piece of debris wood was used to investigate the influence of woody debris jams from a life-cycle perspective which included the processes of its formation, growth, failure, and rebirth. Several debris jams were formed in sequence during each experimental test. The results showed that the additional scour generated by the first woody debris jam compared with the scour depth without debris was a function of blockage ratio of the first debris jam, while the influence of the subsequent woody debris jams depended on their dimensions compared with the previous jam. When the subsequent debris jam’s dimensions were larger than the previous one, the scour further increased; otherwise, the scour remained constant and equal to the previous one. In addition, the debris-induced hydraulic head was analyzed and found to be correlated with the Froude number and the debris jam dimensions.
First Suction Cup Tagging on a Small and Coastal Form Bryde’s Whale (Balaenoptera edeni edeni) in China to Investigate Its Dive Profiles and Foraging Behaviours
Authors: Dong Lijun , Liu Mingming , Lin Wenzhi , Li Songhai
Published: October 2022

Small-and-coastal-form Bryde’s whales (Balaenoptera edeni edeni) are known to inhabit coastal and continental shelf waters. However, little is known on their ethological activities, especially underwater behaviours. Here, we deployed a suction cup tag on a small-and-coastal-form Bryde’s whale to study its ethological activities in Dapeng Bay, a coastal water of Shenzhen off the east Pearl River Estuary, China. The whale was tagged for 6 hours in total and displayed a head-lifting feeding behaviour 77 times during two tag deployments. The swim speed, dive duration and depth and bottom duration were collected by the tag to describe detailed information on dive profiles. The rate of feeding behaviours was observed decreasing with the presence of anthropogenic whale-approaching (AWA) boat activities occurring close (within 300 m) to the animal. Our study, for the first time, investigated behaviours of Bryde’s whales using suction cup tagging in Chinese waters. The results reveal the dive and feeding patterns of a small-and-coastal-form Bryde’s whale with short-term monitoring and provide a fundamental advancement in the knowledge of both the diving behaviour and the behavioural response of this subspecies to human activities. The findings are valuable for possible rescue of the investigated whale and for policy and management regarding conservation of this subspecies as well.
A Composite Permeable Sloping Seawall for Effective Energy Dissipation: A Quasi-Soft Alternative Solution for Shore Protection
Authors: Dabir Vaishnavi , Khare Kanchan , Munireddy Mutukuru Gangireddy
Published: October 2022

The recent trend in coastal research centers around environmental sustainability, especially in coastal conservation. A seawall typically has three layers, namely core, filter, and hard rubble/concrete armor. In the current study, a two-layered seawall is proposed, comprising a coir geotextile roll from the coastal regions, along with sand encapsulated in a geotextile over an impermeable core. This can be considered as a quasi-soft solution against the traditional, three-layered, hard alternative. The objective of this study is to investigate the combined effect of slope and porosity, of this composite structure, on the wave reflection. The findings show that the composite structure provides less reflection coefficient values compared to traditional rubble mound seawalls. Four orientations and positions of coir rolls with geosynthetic sandbag were tested. The armor layer with coir rolls overlain by geosynthetic sandbags over an impermeable core could be a better alternative, as it increases the hydrodynamic performance by 59% as compared to sandbags, used alone, over an impermeable core on a slope of 1:2.
Effect of Low Temperature on the Undrained Shear Strength of Deep-Sea Clay by Mini-Ball Penetration Tests
Authors: Gu Zhongde , Guo Xingsen , Jiao Houbin , Jia Yonggang , Nian Tingkai
Published: October 2022

The technology for in situ testing of the undrained shear strength of deep-sea clay is underdeveloped. Indoor tests remain necessary, and there is a large temperature difference between in situ and laboratory tests. To analyse the effect of temperature on undrained shear strength, in this study the physical characteristics of marine clay samples from the South China Sea were determined, followed by penetration tests by the mini-ball method under low (4 °C) and room (20 °C) temperatures. The results indicated that the clay strength increased by 14.1–30.0% as the temperature decreased from 20 °C to 4 °C, and the strength of the bound water and the viscosity of the free water in the clay sample increased as the temperature decreased, which was the root cause of the increase in the clay strength. Based on the research, it is possible to correct the undrained shear strength values measured in laboratory tests and provide more reasonable parameters for ocean engineering.
Mitigation of Hub Vortex Cavitation with Application of Roughness
Authors: Sezen Savas , Atlar Mehmet
Published: October 2022

This study investigates the influence of roughness on hydrodynamic performance, especially for the hub vortex—and, hence, hub vortex cavitation—of a benchmark propeller operating under uniform flow conditions using the RANS method. The Schnerr–Sauer cavitation model is also used for modelling the cavitation on and off the propeller blades. In order to include the effects of roughness in the numerical calculations, the experimentally obtained roughness functions were incorporated with the wall function of the CFD solver. The applicability and effectiveness of the roughness application applied on the propeller hub as a novel concept were explored to mitigate hub vortex cavitation. The results are first validated with experimental data on smooth conditions through the propeller hydrodynamic performance characteristics and cavitation extension. Then, the propeller hub is covered with four different sizes of roughness. The results show that the degradation effects of roughness applied to the hub on propeller performance are negligible, and the maximum efficiency loss is around 0.25% with respect to the smooth condition when the propeller hub was roughened. Favourable impacts of roughness are found for the hub vortex, and hence, hub vortex mitigation. Applying the roughness on the propeller changed the flow properties (e.g., pressure, velocity and turbulent kinetic energy) inside the vortex, enabling the early breakdown of the extension of hub vortices. These flow changes in the presence of roughness result in a mitigation of hub vortex cavitation up to 50% depending on the roughness size with respect to the smooth condition. Thus, this proposed novel concept, application of roughness to the propeller hub, can be used to mitigate hub vortex cavitation, rudder erosion and propeller URN for both newly designed and retrofitted projects by keeping the efficiency loss as minimum as possible.
Position Control of Heave Compensation for Offshore Cranes Based on a Particle Swarm Optimized Model Predictive Trajectory Path Controller
Authors: Chen Hao , Xie Jinke , Han Jingang , Shi Weifeng , Charpentier Jean-Frédéric , Benbouzid Mohamed
Published: October 2022

The wave compensation system can be very useful in several naval applications. It can greatly reduce the relative irregular motion between the two ships when replenishment operations are performed, or between the ship and the offshore platform, which is caused by the waves. It is widely used in offshore operations, offshore cargo transfer, oil and gas exploitation, deep-sea mining, the hoisting and recovery of submersibles, etc. However, when a crane is used in a ship or moving platform, due to the influence of the hull, the crane load movement is similar to a space ball pendulum, which causes the heave displacement to show significant nonlinear motion characteristics. Moreover, the time delay of the detection mechanism and control error could result in untimely compensation, which deteriorates the performance. Consequently, this paper proposes one advanced prediction compensation method, namely Particle Swarm Optimized Model Predictive Trajectory Path controller (PSO−MPTP), which can improve the heave compensation performance. This method, which is based on Model Predictive Control (MPC), is firstly applied to the position servo system and takes into account the heave prediction and control effects simultaneously. The heave displacement of the crane load could be predicted in multiple steps in advance and used as the input of the position loop of the compensation machine. The achieved simulations show that the proposed controller has better prediction ability, higher control accuracy, and stronger robustness.
STM: Spectrogram Transformer Model for Underwater Acoustic Target Recognition
Authors: Li Peng , Wu Ji , Wang Yongxian , Lan Qiang , Xiao Wenbin
Published: October 2022

With the evolution of machine learning and deep learning, more and more researchers have utilized these methods in the field of underwater acoustic target recognition. In these studies, convolutional neural networks (CNNs) are the main components of recognition models. In recent years, a neural network model Transformer that uses a self-attention mechanism was proposed and achieved good performance in deep learning. In this paper, we propose a Transformer-based underwater acoustic target recognition model STM. To the best of our knowledge, this is the first work to introduce Transformer into the underwater acoustic field. We compared the performance of STM with CNN, ResNet18, and other multi-class algorithm models. Experimental results illustrate that under two commonly used dataset partitioning methods, STM achieves 97.7% and 89.9% recognition accuracy, respectively, which are 13.7% and 50% higher than the CNN Model. STM also outperforms the state-of-the-art model CRNN-9 by 3.1% and ResNet18 by 1.8%.
A Stochastic Model for Shipping Container Terminal Storage Management
Authors: Xu Yang , Wang Ming , Lai Kin Keung , Ram Bhagwat
Published: October 2022

A good port terminal is not only a major economic multiplier for the nation’s prosperity by being a gateway for trading, but is also an attractor for other commercial infrastructure development such as banks, logistics agencies, and manufacturing and trading investments. A measurement of the efficiency of a terminal is the duration-of-stay of visiting vessels. A quick and efficient loading/unloading process can increase productivity and thus reduce the waiting time for a vessel. In this study, we address the space allocation for stacking export containers. If the storage layout and the loading plan work well together, the productivity of the terminal can be increased and the duration-of-stay needed for each visiting vessel is reduced. In this paper, we propose a hybrid storage policy combining class-dedicated and sharing strategies, and construct a stochastic programming model using the concept of recourse.
Hydrodynamic Behaviour of a Floating Polygonal Platform Centrally Placed within a Polygonal Ring Structure under Wave Action
Authors: Park Jeong Cheol , Wang Chien Ming
Published: October 2022

In this paper, a semi-analytical method has been developed for the hydrodynamic analysis of a floating polygonal platform that is centrally placed within a floating polygonal ring structure under wave action. In view to understand the wave interactions inside the ring structure, the formulation considers two cases: when the platform and ring structure oscillate individually, and when they oscillate together under wave action. The polygonal shapes of the floating structures can be created from a parametric equation involving the cosine-type radial perturbation. The formulation and computer code are verified by comparing the results with those obtained from the commercial software ANSYS AQWA. When floating ring structures are used, trapped waves are created in the inner water basin resulting in resonance. The interactions among the trapped waves, inner floating platforms and outer ring structures are investigated by performing parametric studies. By changing the dimensions of the platform and ring structure such as the drafts, the radii of platforms and polygonal shapes, their effects on major hydrodynamic quantities may be understood.
A Multi-Method Approach to Identify the Natural Frequency of Ship Propulsion Shafting under the Running Condition
Authors: Xing Pengfei , Lu Lixun , Li Guobin , Wang Xin , Gao Honglin , Song Yuchao , Zhang Hongpeng
Published: October 2022

In order to identify the natural frequency of ship propulsion shafting under the running condition, a multi-method approach that combines Duffing Oscillator, harmonic wavelet packet transform, and probability density function is proposed. An experimental investigation on the natural frequency of running propulsion shafting is conducted on the ship propulsion shafting test bench, and the natural frequency response of running propulsion shafting under different alignment states is obtained from the measured bearing vibration signal. The results show that the natural frequency of propulsion shafting can be excited under the running condition, but its response is feeble. When the alignment state of the propulsion shafting gradually changes with the elevation of the front stern bearing, the identified natural frequency of the propulsion shafting shows an upward trend. In contrast, its amplitude shows a downward trend. Therefore, the proposed approach can identify the natural frequency of the ship propulsion shafting from the measured bearing vibration signal under the running condition.
Tsunami Damping due to Bottom Friction Considering Flow Regime Transition and Depth-Limitation in a Boundary Layer
Authors: Tanaka Hitoshi , Tinh Nguyen Xuan , Sana Ahmad
Published: October 2022

According to recent investigations on bottom boundary layer development under tsunami, a wave boundary can be observed even at the water depth of 10 m, rather than a steady flow type boundary layer. Moreover, it has been surprisingly reported that the tsunami boundary layer remains laminar in the deep-sea area. For this reason, the bottom boundary layer under tsunami experiences two transitional processes during the wave shoaling: (1) flow regime transition in a wave-motion boundary layer from laminar to the turbulent regime, and (2) transition from non-depth-limited (wave boundary layer) to depth-limited boundary layer (steady flow boundary layer). In the present study, the influence of these two transition processes on tsunami wave height damping has been investigated using a wave energy flux model. Moreover, a difference of calculation results by using the conventional steady flow friction coefficient was clarified.
Pathway of Mathematical Optimization Research: From Specialized Problems and Opaque Algorithms to Standardized Problems and Transparent Algorithms
Authors: Wang Shuaian , Du Yuquan
Published: October 2022

Mathematical optimization (MO) formulates a decision problem with a maximization or minimization objective and a set of constraints on the decision variables, and designs an algorithm to find the best solution [...]
Neural Network-Based Underwater Object Detection off the Coast of the Korean Peninsula
Authors: Kim Won-Ki , Bae Ho Seuk , Son Su-Uk , Park Joung-Soo
Published: October 2022

Recently, neural network-based deep learning techniques have been actively applied to detect underwater objects in sonar (sound navigation and ranging) images. However, unlike optical images, acquiring sonar images is extremely time- and cost-intensive, and therefore securing sonar data and conducting related research can be rather challenging. Here, a side-scan sonar was used to obtain sonar images to detect underwater objects off the coast of the Korean Peninsula. For the detection experiments, we used an underwater mock-up model with a similar size, shape, material, and acoustic characteristics to the target object that we wished to detect. We acquired various side-scan sonar images of the mock-up object against the background of mud, sand, and rock to account for the different characteristics of the coastal and seafloor environments of the Korean Peninsula. To construct a detection network suitable for the obtained sonar images from the experiment, the performance of five types of feature extraction networks and two types of optimizers was analyzed. From the analysis results, it was confirmed that performance was achieved when DarkNet-19 was used as the feature extraction network, and ADAM was applied as the optimizer. However, it is possible that there are feature extraction network and optimizer that are more suitable for our sonar images. Therefore, further research is needed. In addition, it is expected that the performance of the modified detection network can be more improved if additional images are obtained.
Numerical and Experimental Research on Rectification Measures for a Contraction Diversion Pier in a Pumping Station
Authors: Xu Wentao , Cheng Li , Du Kailian , Yu Lei , Ge Yi , Zhang Jiali
Published: October 2022

In order to improve the flow state of a forebay, a contraction diversion pier is discovered, the geometric parameters of which affect the improvement of the flow state. In this paper, the standard k-ε model in the computational fluid dynamics (CFD) numerical simulation method is used to research the flow state improvement of the forebay with a contraction diversion pier. In our research, the single factor method is used to analyze the influence of different geometric parameters. Then, the optimal geometric parameters of the contraction diversion pier are given. Results show that the contraction diversion pier can be used to concentrate the water flow. In the area where reflux is formed, the contraction diversion guides water flow along the diversion pier wall. In particular, when the retractable diversion pier is located in the middle of a reflux zone, the water backflow is effectively reduced, the flow state is improved, and the inlet condition of the pump is optimized. By comparing the cross-sectional streamlines, the velocity contour, the normal velocity uniformity of the longitudinal section, and the normal weighted mean angle, the optimal geometric parameters of the contraction diversion pier are obtained as follows: the distance from the contraction pier to the inlet sump is 0.1 L, the contraction angle is 20°, and the length of pier is 0.3 L.
Development and Field Testing of a Smart Support System for ROV Operators
Authors: Konoplin Alexander , Konoplin Nikita , Yurmanov Alexander
Published: October 2022

The article considers the issues of development of a smart system for supporting activities of ROV operators and its practical implementation for the efficient operation a ROV Comanche 18 that is based on the R/V Akademik M.A. Lavrentiev. The system uses algorithms that provide coordinated movements of the ROV and its depressor unit. These algorithms are designed for ROVs to make synchronous, accurate, and accident-free movements along long-distance routes even when launched from a support vessel without dynamic positioning (DP). For this, the operator receives real-time visual recommendations and warnings generated on the basis of the expert evaluation of information coming from various sensors and positioning systems. The ability to plan routes of the ROV and its mothership, inputting target points, saving maps, tracks, and locations of the detected underwater objects are also implemented in the designed system. The article presents the results of successful tests carried out during a deep-sea research expedition of the A.V. Zhirmunsky National Scientific Center of Marine Biology FEB RAS in the Bering Sea and Pacific Ocean. The created smart support system for ROV operators significantly extends the range of capabilities of ROVs performing many unique underwater operations, while significantly reducing their operating time.