Hasil untuk "Ocean engineering"

Guohua Wang, Da Hong, Zexi Yin et al.

Growing demand for low-sodium surimi products has driven the search for safe salt alternatives. Anionic peptides (APPs) and cationic peptides (CPPs) were isolated from sheepskin collagen via Diethylaminoethyl (DEAE) chromatography. CPPs contained higher arginine (46.11%) and lysine (4.64%) than APPs (40.57% and 3.99%, respectively), while APPs were enriched in acidic amino acids like glutamic acid (3.88%). Comprehensive evaluations of low-salt silver carp surimi gels showed both peptides significantly improved gel strength and water-holding capacity (WHC). The water-holding capacity increased from 60.68% in the blank control group to 74.31% in the CPP-treated group, while that in the APP-treated group was 66.86%. Cooking loss was significantly reduced, decreasing from 40.64% in the blank control group to 28.57% in the CPP-treated group and 34.52% in the APP-treated group. The samples achieved a quality comparable to that of the NaCl-supplemented group, with CPP outperforming APP in terms of hardness and gel network density. The LF-NMR confirmed enhanced water retention by reducing free water (T₂₂) and increasing bound water (T₂b). The FTIR indicated a conformational shift from α-helix to β-sheet, and the SEM revealed denser networks with fewer large voids. The SDS-PAGE demonstrated enhanced myosin heavy chain (MHC) cross-linking, more pronounced in the CPP-treated samples. CPPs exerted stronger electrostatic attraction with negatively charged surimi proteins (isoelectric point 5.5), while APPs chelated Ca²⁺ to activate transglutaminase. These findings validate APPs and CPPs as promising salt substitutes, enabling low-sodium surimi production and high-value utilization of sheepskin by-products.

Chenhui DING, Zhongyang REN, Linfan SHI et al.

In this study, heat-induced shrimp surimi gel was prepared from Penaeus vannamei. The effects of heating temperature on the gel's formation properties were evaluated by examining its texture, microstructure, and swelling rate. The results revealed that the storage modulus and loss modulus of the shrimp surimi gels decreased as the heating temperature increased from 20 ℃ to 40 ℃. Furthermore, shrimp surimi underwent a transition from a sol-gel state to a thermally irreversible gel between 50 ℃ and 75 ℃. The textural hardness, breaking force, and breaking distance of the shrimp surimi gel initially increased and then decreased with increasing heating temperature. The highest values were recorded at 89 ℃, with textural hardness of 1225.74 g, breaking force of 158.86 g, and breaking distance of 9.28 mm. The water-holding capacity of the shrimp surimi gels peaked at 94.28% at a heat-induced temperature of 89 ℃, decreasing when the temperature was either raised or lowered from this point. The L* value of the gel decreased with increasing heating temperature, while the a* and b* values increased. No obvious changes were observed in the myosin heavy chain and actin bands of the shrimp surimi gel treated with different heating temperature. A dense and orderly network structure gradually formed in the shrimp surimi gel as the heating temperature increased from 86 ℃ to 89 ℃. However, the network structure was disrupted when the heating temperature was further increased beyond 89 ℃. Additionally, the swelling rate of the shrimp surimi gel increased from 32.89% to 118.97% as the heating temperature rose from 86 ℃ to 98 ℃. Therefore, the shrimp surimi gel prepared at 89 ℃ exhibited optimal textural properties and a stable network structure.

Yang Xu, He Mengqin, Xi Baicheng et al.

The thermodynamic and elastic moduli of secondary phases play a crucial role in governing the high-temperature mechanical performance of magnesium alloys. This strengthening mechanism originates from high-modulus precipitates that remain fine and uniformly dispersed at elevated temperatures, persistently pinning dislocations and impeding their motion while maintaining microstructural stability. However, technical challenges have significantly limited experimental characterization of elastic moduli. This study investigates the thermodynamic and mechanical properties of Mg–RE (RE = Tb, Dy, Ho) intermetallic phases via first-principles calculations using quasi-harmonic and quasi-static approximations. Specifically, heat capacity, thermal expansion, and elastic moduli are calculated from 0 to 850 K. Results reveal thermal expansion coefficients increase monotonically with temperature, with MgHo showing the lowest thermal expansion. Heat capacity follows classical Dulong-Petit behavior at high temperatures, with all phases approaching theoretical limits. As temperature rises, elastic moduli generally decrease. Among the studied systems, MgDy retains superior mechanical properties, exhibiting the highest Young’s modulus retention at elevated temperatures and minimal shear modulus degradation across the investigated range. In contrast, MgHo displays the highest bulk moduli throughout, indicating excellent volumetric stability under thermal loading.

Jun-Gi Jang, Seung-Ho Ham

Excessive cargo sway during crane operations in the current shipbuilding industry is a major problem that causes safety accidents and work delays. Therefore, the development of stable crane control technology is essential. In this study, a crane control algorithm that simultaneously achieves accurate movement to target positions and sway minimization was developed using reinforcement learning. In dynamics modeling, the Discrete Euler-Lagrange Equation was applied to significantly reduce the computational complexity of existing methods, and the Proximal Policy Optimization (PPO) method was used for control policy learning. A three-dimensional virtual environment was constructed to perform learning under various travel distances and operating conditions, and the performance of the developed algorithm was compared and verified against the traditional trapezoidal velocity profile. Experimental results showed that the proposed method exhibited significant improvements in position control precision and sway suppression performance compared to existing methods. The results of this study are expected to contribute to the implementation of automated crane control systems in actual shipyard environments.

Youdong Chen, Keren Dai, Ling Chang et al.

High-precision measurement in low-coherence areas remains challenging for multitemporal synthetic aperture radar interferometry (InSAR). For instance, over the regions covered by dense vegetation, InSAR merely provides sparse measurement points (MPs) due to high spatio-temporal decorrelation. To address this, our study proposes a coherence-enhanced multitemporal InSAR (CE-InSAR) approach to better monitor low-coherence landslide displacement in the radar line-of-sight (LOS) direction. The key ideas of CE-InSAR include the preprocessing feasibility assessment for obtaining the important predefined parameters for time series processing and coherence enhancement with the use of phase optimization for the C-band Sentinel-1 data stacks. To demonstrate the effectiveness of CE-InSAR, 85 scenes of Sentinel-1 images (2021–2023) covering the Tianxi landslide in Guangxi Province, China with an NDVI value greater than 0.5, were applied to retrieve the historical displacements and analyze the activity state. The InSAR measurements from both the presling and postsliding phases illustrated the significant advantages of CE-InSAR, with five more times of MPs both in a single landslide scale and regional scale, compared to small baseline subset interferometry (SBAS-InSAR). Furthermore, time series analysis considering rainfall factors, indicates CE-InSAR can detect the accelerated displacement of the Tianxi landslide prior to sliding, exhibiting a maximum LOS accumulative displacement of around 70 mm. Subsequently, the combined impacts of human activity and rainfall contributed to the landslide’s failure. Finally, the major uncertainties and limitations for the application of CE-InSAR were discussed, and the conclusions were summarized. In general, this research is valuable and useful for guiding landslide displacement monitoring characterized by low coherence using InSAR.

V. Kosmalla, O. Lojek, J. Carus et al.

<p>This study investigates the biomechanical properties of marram grass (<i>Calamagrostis arenaria</i>, formerly <i>Ammophila arenaria</i>) over a 12-month period on the island of Spiekeroog, Germany, to enhance the modeling of coastal dune dynamics. The research reveals significant seasonal variations in the stiffness and Young modulus of the vegetation, with higher values observed in winter, indicating increased mechanical resistance important for dune stability during storm events. In summer, increased flexibility and density are prominent, enhancing dune accretion. To account for these dynamics, the study emphasizes the importance of incorporating seasonally adjusted parameters into models, particularly accounting for the increased horizontal density, the presence of flower stems in summer, and the longer leaf lengths in winter. The differentiation among plant parts is highlighted, with flower stems providing the highest structural support due to their greater stiffness, while leaves contribute more to flexibility and dynamic responses. Interestingly, the minimal differences between green and brown leaves suggest that these can be treated similarly in modeling efforts, simplifying parameterization without compromising accuracy. Additionally, the study found no consistent evidence that wind exposure significantly affects the biomechanical properties of marram grass, suggesting that wind influence may not need to be factored into biomechanical models. The results also demonstrate that the biomechanical properties of marram grass are broadly transferable between fixed and dynamic dune systems, supporting their applicability across various coastal environments. The key outcome of this research is the detailed compilation of the biomechanical traits of marram grass's aboveground vegetation, reflecting the seasonal dynamics found in dune processes, which will serve as a valuable resource for future modeling efforts of dune vegetation and their surrogates.</p>

Yunlong Zhou, Renlong Hang, Fanfan Ji et al.

Precipitation nowcasting is a critical aspect of meteorological services, which helps people make reasonable arrangements. Nowadays the methods based on recurrent neural networks are widely employed as the primary solution for precipitation nowcasting. However, the predictive unit of these methods has a narrow temporal receptive field that fails to provide sufficient temporal variation information for accurate prediction of the subsequent frame. In addition, they do not adequately model the spatial deformation of visual appearance, which leads to the predicted frames lack of fine-grained spatial appearances. To address these deficiencies, we propose a spatiotemporal enhanced adversarial network (STEAN), a deep learning model for high-resolution precipitation nowcasting. STEAN incorporates a feature extraction module and an adaptive fusion module to refine the spatial appearance of prediction results. Further, it leverages a specialized Halo Attention Spatiotemporal Long Short-Term Memory (HAST-LSTM) unit to model temporal variation information. In order to improve the realism of the predicted sequences, STEAN is combined with a temporal discriminator during the training stage to reduce the blur of prediction results caused by the loss function. STEAN has been assessed on the Moving MNIST, KNMI, and CIKM datasets and the experimental results show that its prediction performance is superior to several other state-of-the-art models.

Cunyu Duan, Dayan Zhou, Ruiqing Feng et al.

The rapid temperature changes caused by global warming significantly challenge fish survival by affecting various biological processes. Fish generally mitigate stress through physiological plasticity, but when temperature changes exceed their tolerance limits, even adaptable species like Siluriformes can experience internal disruptions. This study investigates the effects of extreme thermal climate on Hong Kong catfish (Clarias fuscus), native to tropical and subtropical regions. C. fuscus were exposed to normal temperature (NT, 26 ℃) or high temperature (HT, 34 ℃) condition for 90 days. Subsequently, histological, biochemical, and transcriptomic changes in gill tissue were observed after exposure to acute high temperatures (34 ℃) and subsequent temperature recovery (26 ℃). Histological analysis revealed that C. fuscus in the HT group exhibited less impact from sudden temperature shifts compared to the NT group, as they adapted by reducing the interlamellar cell mass (ILCM) and lamellae thickness (LT) of gill tissue, thereby mitigating the aftermath of acute heat shock. Biochemical analysis showed that catalase (CAT) activity in the high temperature group continued to increase, while malondialdehyde (MDA) levels decreased, suggesting establishment of a new oxidative balance and enhanced environmental adaptability. Transcriptome analysis identified 520 and 463 differentially expressed genes in the NT and HT groups, respectively, in response to acute temperature changes. Enrichment analysis highlighted that in response to acute temperature changes, the NT group inhibited apoptosis and ferroptosis by regulating the activity of alox12, gclc, and hmox1a, thereby attenuating the adverse effects of heat stress. Conversely, the HT group increased the activity of pfkma and pkma to provide sufficient energy for tissue repair. The higher degree of heat shock protein (Hsp) response in NT group also indicated more severe heat stress injury. These findings demonstrate alterations in gill tissue structure, regulation of oxidative balance, and the response of immune metabolic pathways to acute temperature fluctuations in C. fuscus following thermal exposure, suggesting potential avenues for further exploration into the thermal tolerance plasticity of fish adapting to global warming.

Weiqi Wan, Weiqi Wan, Xingru Feng et al.

The coastal regions of Southeast China frequently experience unusual positive storm surges on the left side of landfalling typhoons, a phenomenon historically overlooked and inadequately explained by conventional circular wind field models. In this study, a high resolution, two-dimensional storm surge model based on ADCIRC along with tide gauge data were used to investigate the spatiotemporal distribution of these surges and proposes underlying mechanisms, informed by a comparative analysis of circular and ERA5 reanalysis wind fields during typical typhoon event 9711 Winnie. Analyzing tide gauge data spanning from 1986 to 2016, the study uncovers a distinct pattern of left-side positive storm surges along the southeastern coast, notably on the Fujian coast and within the Taiwan Strait, which are found to be comparable to those on the cyclone’s right side. The research also documents a significant escalation in both the frequency and intensity of these left-side surges over the past three decades. Simulation results highlights the inadequacies of circular wind field models in operational forecasting and emphasizes the necessity of accounting for topographic influences and the structural complexity of wind fields in storm surge predictions. This is particularly pertinent in semi-enclosed seas with intricate hydrodynamics, such as the Taiwan Strait. The insights gleaned from this study are pivotal for enhancing the real-time simulation and prediction of storm surges, which are vital for coastal safety and disaster prevention measures.

Rui Li, Kejian Wu, Wenqing Zhang et al.

In the Northwest Pacific (NWP), where a unique monsoon climate exists and where both typhoons and extratropical storms occur frequently, hazardous waves pose a significant risk to maritime safety. To analyze the 20-year variability of hazardous waves in this region, this study utilized hourly reanalysis data from the ECMWF ERA5 dataset covering the period from 2001–2020, alongside the wave risk assessment method. The ERA5 data exhibits better consistency, in both the temporal and spatial dimensions, than satellite data. Although hazardous wind seas occur more frequently than hazardous swells, swells make hazardous waves travel further. Notably, the extreme wave height (EWH) shows an increasing trend in high- and low-latitude areas of the NWP. The change in meridional wind speeds is the primary reason for the change in the total wind speed in the NWP. Notably, the maximum annual increase rate of 0.013 m/year for EWH exists in the region of the Japanese Archipelago. This study elucidated the distributions of wave height intensity and wave risk levels, noting that the EWHs of the 50-year and 100-year return periods can reach 20.92 m and 23.07 m, respectively.

Huan Du, Jie Pan, Cuijing Zhang et al.

ABSTRACT As an important coastal “blue carbon sink,” mangrove ecosystems contain microbial communities with an as-yet-unknown high species diversity. Exploring the assemblage and structure of sediment microbial communities therein can aid in a better understanding of their ecosystem functioning, such as carbon sequestration and other biogeochemical cycles in mangrove wetlands. However, compared to other biomes, the study of mangrove sediment microbiomes is limited, especially in diverse mangrove ecosystems at a large spatial scale, which may harbor microbial communities with distinct compositions and functioning. Here, we analyzed 380 sediment samples from 13 and 8 representative mangrove ecosystems, respectively, in China and South America and compared their microbial features. Although the microbial community compositions exhibited strong distinctions, the community assemblage in the two locations followed analogous patterns: the assemblages of the entire community, abundant taxa, rare taxa, and generalists were predominantly driven by stochastic processes with significant distance-decay patterns, while the assembly of specialists was more likely related to the behaviors of other organisms in or surrounding the mangrove ecosystems. In addition, co-occurrence and topological network analysis of mangrove sediment microbiomes underlined the dominance of sulfate-reducing prokaryotes in both the regions. Moreover, we found that more than 70% of the keystone and hub taxa were sulfate-reducing prokaryotes, implying their important roles in maintaining the linkage and stability of the mangrove sediment microbial communities. This study fills a gap in the large-scale analysis of microbiome features covering distantly located and diverse mangrove ecosystems. Here, we propose a suggestion to the Mangrove Microbiome Initiative that 16S rRNA sequencing protocols should be standardized with a unified primer to facilitate the global-scale analysis of mangrove microbiomes and further comparisons with the reference data sets from other biomes. Importance Mangrove wetlands are important ecosystems possessing valuable ecological functions for carbon storage, species diversity maintenance, and coastline stabilization. These functions are greatly driven or supported by microorganisms that make essential contributions to biogeochemical cycles in mangrove ecosystems. The mechanisms governing the microbial community assembly, structure, and functions are vital to microbial ecology but remain unclear. Moreover, studying these mechanisms of mangrove microbiomes at a large spatial scale can provide a more comprehensive insight into their universal features and can help untangle microbial interaction patterns and microbiome functions. In this study, we compared the mangrove microbiomes in a large spatial range and found that the assembly patterns and key functional guilds of the Chinese and South American mangrove microbiomes were analogous. The entire communities exhibited significant distance-decay patterns and were strongly governed by stochastic processes, while the assemblage of specialists may be merely associated with the behaviors of the organisms in mangrove ecosystems. Furthermore, our results highlight the dominance of sulfate-reducing prokaryotes in mangrove microbiomes and their key roles in maintaining the stability of community structure and functions.

Shijie Bi, Changhu Xue, Yunqi Wen et al.

The Pacific oyster could be affected by several pressure sources during cold chain logistics, which reduce the quality of oyster, and even improve its mortality. For improving the quality of oyster, the effects of depuration process at different cooling rates (1, 3, 7, 11 and 16 °C/h) on selected Pacific oyster were studied. The results indicated that extreme fluctuations in the depuration temperatures could affect the survival rates and qualities of oysters. The oysters exhibited low survival rates, glycogen contents and pH values at an increased cooling rate. Their contents in the 1 °C/h group after 3 d preservation were 100 %, 16.30 ± 1.64 mg/100 g and 6.72 ± 0.01, respectively, while there were 71 %, 7.72 ± 0.88 mg/100 g and 6.53 ± 0.01 in the 16 °C/h group after 3 d preservation, respectively. Furthermore, the ATP-related compounds were affected by the different cooling rates. AMP and IMP were the main ATP-related compounds, and their contents in the 1 °C/h group after 3 d preservation were 37.21 ± 1.10 mg/100 g and 29.47 ± 1.10 mg/100 g, respectively, while there were 32.07 ± 1.10 mg/100 g and 13.16 ± 1.60 mg/100 g in the 16 °C/h group after 3 d preservation, respectively. The proportions of the total umami, as well as the sweet amino acids also decreased, the proportions of the umami amino acids and sweet amino acids in the total amino acids, were 31.37%–38.80%, and their proportions in 1 °C/h group were higher than that in 16 °C/h group. Conversely, the fatty acid content of each group exhibited significant differences. Combined with the above results, the oyster maintained a high survival rate and higher quality at a cooling rate of 1 °C/h during depuration.

Hongsheng Dong, Lunxiang Zhang, Jiaqi Wang

Currently, natural gas hydrates (NGHs) have been proposed as promising and environmentally friendly carbon-based energy sources that are beneficial for mitigating the traditional energy crises [...]

Chih-Cheng Chen, J. Ba, Tie-Jun Li et al.

1Department of Automatic Control Engineering, Feng Chia University, Taichung 40724, Taiwan 2School of Ocean Information Engineering, Jimei University, Fujian Province, Xiamen 361021, China 3Department of Information Management, Chaoyang University of Technology, Taichung 413310, Taiwan 4Department of Aeronautical Engineering, Chaoyang University of Technology, Taichung 413310, Taiwan 5Department of Mechanical and Computer-Aided Engineering, Feng Chia University, Taichung 40724, Taiwan

M. Goyal, A. Prakash, D. Baleanu

Abstract The study of dynamic behaviour of nonlinear models that arise in ocean engineering play a vital role in our daily life. There are many examples of ocean water waves which are nonlinear in nature. In shallow water, the linearization of the equations imposes severe conditions on wave amplitude than it does in deep water, and the strong nonlinear effects are observed. In this paper, q-homotopy analysis Laplace transform scheme is used to inspect time dependent nonlinear Lane-Emden type equation of arbitrary order. It offers the solution in a fast converging series. The uniqueness and convergence analysis of the considered model is presented. The given examples confirm the competency as well as accuracy of the presented scheme. The behavior of obtained solution for distinct orders of fractional derivative is discussed through graphs. The auxiliary parameter ħ offers a suitable mode of handling the region of convergence. The outcomes reveal that the q-HATM is attractive, reliable, efficient and very effective.

Lin Li, Adham M. Amer, Xinying Zhu

Subsea templates are normally transported to the installation site on the deck of a crane vessel. After being lifted off from the deck, the template is 1) over-boarded from the initial location to the target position by the side of the vessel; 2) lowered through the splash zone; 3) further lowered down to the seabed and 4) finally positioned and landed. All the mentioned phases should be evaluated. Usually, the splash zone crossing phase is taken as the critical phase and analyzed to define the installation weather criterion. The over-boarding phase has not been the focus of analysis due to a large involvement of human actions and little involvement of hydrodynamic effects. During offshore operations, the offshore manager may decide to decrease the defined installation weather criterion if the risk of the personnel safety on deck during over-boarding phase is considered high. Thus, it is of great need to quantify the operational criterion for such operation. The objective of this paper is to perform numerical analyses and define the allowable sea states for a safe over-boarding operation. The numerical analyses using time-domain simulations have been performed in various sea states. Tugger lines have been modelled to control the motions of the template during the operation. The pendulum motions of the subsea template are considered as the critical responses for the assessment of the allowable sea states.

Xingyu Tuo, Yin Zhang, Yulin Huang et al.

It is greatly significant to achieve radar forward-looking region imaging. Due to the limitation of phase ambiguity and small Doppler gradient in forward-looking region, synthetic aperture radar and Doppler beam sharpening cannot work for forward-looking imaging, while real aperture radar (RAR) has arbitrary imaging geometry. Nevertheless, restricted by the antenna aperture, azimuth resolution of RAR is coarse, super-resolution technology is required to improve its azimuth resolution. Exploiting the sparse prior information of the target, the super-resolution problem can be transformed into an <inline-formula><tex-math notation="LaTeX">$L_1$</tex-math></inline-formula> norm minimization problem mathematically. Iterative reweighted algorithm can effectively solve the <inline-formula><tex-math notation="LaTeX">$L_1$</tex-math></inline-formula> norm minimization problem by replacing <inline-formula><tex-math notation="LaTeX">$L_1$</tex-math></inline-formula> norm with reweighted <inline-formula><tex-math notation="LaTeX">$L_2$</tex-math></inline-formula> norm and computing the weight in each iteration. However, it suffers from a large computational load due to the repeated multiplications and inversions of large matrices. In this article, a fast azimuth super-resolution imaging method of RAR based on iterative reweighted least squares (IRLS) with linear sketching (LS) was proposed to achieve fast super-resolution imaging of RAR. The LS theory is employed to compress echo matrix and antenna measurement matrix into much smaller matrices via multiplying them by an embedded matrix. Then, the IRLS solver was utilized to address the reconstructed objective function. Much of the expensive computation can then be performed on the smaller matrices, thereby accelerating the algorithm. Simulations and experimental data prove that the proposed algorithm can offer a time complexity reduction without loss of imaging performance.

Diva J. Amon, Brian R. C. Kennedy, Kasey Cantwell et al.

Marine debris is a growing problem in the world’s deep ocean. The naturally slow biological and chemical processes operating at depth, coupled with the types of materials that are used commercially, suggest that debris is likely to persist in the deep ocean for long periods of time, ranging from hundreds to thousands of years. However, the realized scale of marine debris accumulation in the deep ocean is unknown due to the logistical, technological, and financial constraints related to deep-ocean exploration. Coordinated deep-water exploration from 2015 to 2017 enabled new insights into the status of deep-sea marine debris throughout the central and western Pacific Basin via ROV expeditions conducted onboard NOAA Ship Okeanos Explorer and RV Falkor. These expeditions included sites in United States protected areas and monuments, other Exclusive Economic Zones, international protected areas, and areas beyond national jurisdiction. Metal, glass, plastic, rubber, cloth, fishing gear, and other marine debris were encountered during 17.5% of the 188 dives from 150 to 6,000 m depth. Correlations were observed between deep-sea debris densities and depth, geological features, and distance from human-settled land. The highest densities occurred off American Samoa and the main Hawaiian Islands. Debris, mostly consisting of fishing gear and plastic, were also observed in most of the large-scale marine protected areas, adding to the growing body of evidence that even deep, remote areas of the ocean are not immune from human impacts. Interactions with and impacts on biological communities were noted, though further study is required to understand the full extent of these impacts. We also discuss potential sources and long-term implications of this debris.

Shing-Hoa Wang, Chau-Chang Chou, Hsien-Hung Chung et al.

Lubricated sliding wear of amorphous (Zr₅₅Cu₃₀Ni₁₀Al₅)_99.98Sc_0.02/CuZr₂ nanocrystal composite bulk metallic glasses (BMG) under various sliding velocities with a load of 20 N was investigated using the pin-on-disk test. After the wear test involving oil lubrication was performed, there was no wear induced new-phase transformation in the sample surface. Friction coefficients were within the range from 0.22 to approximately 0.29 under a 20-N load at different sliding velocities. Therefore, the calculated friction coefficients clearly indicated that the adhesion wear dominated from the experimental results. This deformation behavior resulted in a higher wear rate and wear coefficient. In addition, worn surfaces were characterized and examined under a scanning electron microscope (SEM) and optical microscope. The mechanism of high wear rate was clarified.

A. Trimulyono, H. Hashimoto

This paper is aimed to validate smoothed particle hydrodynamics (SPH) on the generation and propagation of water waves. It is a classical problem in marine engineering but a still important problem because there is a strong demand to generate intended nonlinear water waves and to predict complicated interactions between nonlinear water waves and fixed/floating bodies, which is indispensable for further ocean utilization and development. A dedicated experiment was conducted in a large wave basin of Kobe University equipped with a piston-type wavemaker, at three water depths using several amplitudes and periods of piston motion for the validation of SPH mainly on the long-distance propagation of water waves. An SPH-based two-dimensional numerical wave tank (NWT) is used for numerical simulation and is accelerated by a graphics processing units (GPU), assuming future applications to realistic engineering problems. In addition, comparison of large-deformation of shallow water waves, when passing over a fixed box-shape obstacle, is also investigated to discuss the applicability to wave-structure interaction problems. Finally, an SPH-based three-dimensional NWT is also validated by comparing with an experiment and two-dimensional simulation. Through these validation studies, detailed discussion on the accuracy of SPH simulation of water waves is made as well as providing a recommended set of SPH parameters.