Hasil untuk "Ocean engineering"

Juzheng Wang, Jianlong Du, Yueru Li et al.

Ying Cheng, Yilin Zhang, Xuechun Pang et al.

This study evaluated the safety of Lacticaseibacillus rhamnosus (L. rhamnosus) KF7, a probiotic strain originating from kefir, for potential use in infant and children's food products in China. The safety evaluation was conducted through a comprehensive approach involving whole-genome sequencing, in vitro and in vivo studies using alternative models: Caenorhabditis elegans (nematodes). Genomic analysis confirmed the absence of virulence factors and antibiotic resistance genes in KF7. Phenotypic characterization demonstrated that KF7 exhibits no antibiotic resistance, does not produce indole, is non-hemolytic, and lacks amino acid decarboxylase activity. Furthermore, KF7 was found to not produce histamine and generate only a minimal amount of tyramine when cultured in MRS medium supplemented with amino acids. The strain was also shown to produce both L- and D-lactic acid, with the concentration of D-lactic acid falling within a safe range. To further evaluate the safety of KF7 in vivo, nematode model was employed, with Pseudomonas aeruginosa serving as a pathogenic control and L. rhamnosus GG, known to be safe for infants and children, as a positive control. The results demonstrated that KF7 does not adversely affect nematode egg-laying, egg development, growth, locomotion, or lifespan. Instead, it appeared to have beneficial effects on gut microbiota and extending the nematodes' lifespan. In summary, this study established the method of using nematode as an in vivo evaluation to the safety of probiotics, and the safety data of the KF7 strain was supplemented by in vitro research, which proved that KF7 has a certain degree of safety.

Wenjuan Li, Mingjing Zhan, Hui Feng

In order to address the issues of insufficient filtering accuracy and filtering divergence that have been observed in the Sage–Husa algorithm when applied to nonlinear system state estimation, an adaptive double forgetting factor-based Sage–Husa algorithm is proposed. This algorithm builds upon the Sage–Husa algorithm with forgetting factors by introducing double forgetting factors and adaptively adjusting them using a windowing method combined with an exponential form. On the basis of ensuring the semi-positive definiteness of the process noise covariance matrix and the positive definiteness of the observation noise covariance matrix, a covariance matching technique is employed to determine whether the measurement noise statistical characteristics need to be re-updated. The results of the simulations demonstrate that the proposed algorithm enhances the accuracy of filtering and exhibits strong effectiveness and feasibility.

Zhenzhen Song, Mingqiang Guo, Liang Wu et al.

While most existing advanced large-scale point cloud semantic segmentation methods can accurately identify most large-scale objects, there is still room for improvement in the recognition accuracy of small-scale, low-proportion objects. Compared to point clouds, digital orthophoto maps (DOMs) has a more structured data format, allowing for better recognition of small-scale surface features. However, in existing projection-based methods, directly mapping images onto point clouds leads to occlusion issues. If image and point cloud features are simply concatenated, it results in feature blurring. Based on this observation, this article proposes a DAPSS network for point cloud semantic segmentation, assisted by prior knowledge constructed from DOM. The pretrained DOM features can provide a broader receptive field as guidance for learning the local context features of point clouds. Vertical occlusion has an issue, making ray-based mapping methods unsuitable. We propose a method that search for the nearest mapped point cloud in spherical space to fill in the occluded point cloud based on the already mapped point cloud. The traditional approach of directly concatenating point cloud features with image features often leads to feature blurring. Therefore, we propose a plug-and-play multimodal feature adaptive fusion module, which can adaptively select and aggregate features from different modalities to reduce redundant information further. In addition, we designed a cascaded multimodal feature deep fusion module to promote deep fusion between different modal features. Experiments on two large datasets demonstrate that DAPSS outperforms current mainstream methods, achieving mean Intersection-over-Union scores of 65.9% and 82.9% on the SansetUrban and SUM-Helsinki datasets, respectively. DAPSS not only effectively addresses the recognition of small-scale surface features, but also resolves the occlusion problems associated with projection-based methods.

Siqing Guo, Yubing Wang, Mingyuan Yue et al.

While battery-powered propulsion represents a promising pathway for inland waterway freight, its widespread adoption is hindered by range anxiety and high investment costs. Strategic energy replenishment has emerged as a critical and cost-effective solution to extend voyage endurance and mitigate these barriers. This paper introduces a novel approach to optimize energy replenishment strategies for inland electric ships that considers the possibility of adopting multiple technologies (charging and battery swapping) and partial replenishment. The proposed approach not only identifies optimal replenishment ports but also determines the technology to employ and the corresponding amount of energy to replenish for each operation, aimed at minimizing total replenishment costs. This problem is formulated as a mixed-integer linear programming model. A case study of a 700-TEU electric container ship operating on two routes along the Yangtze River validates the effectiveness of the proposed approach. The methodology demonstrates superior performance over existing approaches by significantly reducing replenishment costs and improving solution feasibility, particularly in scenarios with tight schedules and limited technology availability. Furthermore, a sensitivity analysis examines the impacts of key parameters, offering valuable strategic insights for industry stakeholders.

You-Seok Yeoh, Kyeong-Sik Min

This paper proposes a high-gain slotted waveguide array antenna design for Ku-band wave-monitoring radar systems. The antenna structure features a two-layer design that integrates the feeding and radiating sections. A grid cavity is stationed on top of the radiating section to suppress the first sidelobes and increase antenna gain. Subsequently, the antenna combined with the grid cavity is designed and fabricated, and its performance is analyzed. The measurement results show a frequency bandwidth of more than 2.8% based on the −10 dB reflection coefficients. The implementation of the grid cavity improves the first sidelobe level by approximately 2 dB. The measurement results also indicate that the proposed antenna achieves a gain of approximately 30.5 dBi—an improvement of approximately 2 dB over that of a conventional slotted waveguide array antenna without a grid cavity. Based on these results, the proposed antenna can be expected to significantly contribute to the development of Ku-band wave-monitoring radar systems for coastal erosion prevention.

Qiang Zhang, Jinjiang Wang, Laibin Zhang et al.

In this paper, the effect of nozzle height on the combustion dynamics of jet fires in rotating flow fields (JFRFFs) is systematically investigated through experimental and numerical simulations. As the nozzle height increases, the JFRFF flame state transitions from stable rotation (SR) to unstable rotation (USR), and eventually to non-rotation (NR), indicating a weakening interaction between the vortex flow and the jet flame. The radial distribution of tangential velocity gradually deviates from the Burgers vortex model as the nozzle height increases, providing a criterion for distinguishing different flame states. Both vortex intensity and flame length are found to decrease with increasing nozzle height, whereas the maximum flame diameter increases. The relative position of the maximum flame diameter to the whole flame length firstly increases and then decreases to match that of the free jet fires, as the flame evolves from SR to USR and NR. In addition, the air entrainment near the nozzle exit decreases with increasing nozzle height, as evidenced by the gradual rise in lift-off height. These findings establish a theoretical basis for the fire performance design of flares in pipeline retrofitting and process industries.

Kit-Leong Cheong, Keying Liu, Wenting Chen et al.

Porphyra haitanensis, a red seaweed species, represents a bountiful and sustainable marine resource. P. haitanensis polysaccharide (PHP), has garnered considerable attention for its numerous health benefits. However, the comprehensive utilization of PHP on an industrial scale has been limited by the lack of comprehensive information. In this review, we endeavor to discuss and summarize recent advancements in PHP extraction, purification, and characterization. We emphasize the multifaceted mechanisms through which PHP promotes gastrointestinal health. Furthermore, we present a summary of compelling evidence supporting PHP's protective role against oxidative stress. This includes its demonstrated potent antioxidant properties, its ability to neutralize free radicals, and its capacity to enhance the activity of antioxidant enzymes. The information presented here also lays the theoretical groundwork for future research into the structural and functional aspects of PHP, as well as its potential applications in functional foods.

Yi Liu, Zhen Ye, Yongqiang Xi et al.

Deep learning (DL) plays an increasingly important role in Earth observation by multisource remote sensing. However, the current DL-based methods do not make a fully use of the complementary information among multisource remote sensing data, such as hyperspectral image and light detection and ranging data, and lack the consideration of multiscale, directional, and fine-grained features. To address these issues, a multiscale and multidirection feature extraction network is proposed in this article. Specifically, the multiscale spatial feature (MSSpaF) module is designed to extract the MSSpaFs, and then, these features are fused by feature concatenation operation. In addition, the multidirection spatial feature module is designed to further extract multidirection and frequency information, employing cross-layer connection and multiscale feature fusion strategy to improve the fineness of the proposed network. Moreover, the spectral feature module is employed to provide detailed spectral information for enhancing the expression ability of multiscale features. Experimental results on three different datasets demonstrate the superior classification performance of the proposed framework.

G. Stober, G. Stober, S. L. Vadas et al.

<p>The Hunga Tonga–Hunga Ha′apai volcano erupted on 15 January 2022, launching Lamb waves and gravity waves into the atmosphere. In this study, we present results using 13 globally distributed meteor radars and identify the volcanogenic gravity waves in the mesospheric/lower thermospheric winds. Leveraging the High-Altitude Mechanistic general Circulation Model (HIAMCM), we compare the global propagation of these gravity waves. We observed an eastward-propagating gravity wave packet with an observed phase speed of 240 <span class="inline-formula">±</span> 5.7 m s<span class="inline-formula">⁻¹</span> and a westward-propagating gravity wave with an observed phase speed of 166.5 <span class="inline-formula">±</span> 6.4 m s<span class="inline-formula">⁻¹</span>. We identified these waves in HIAMCM and obtained very good agreement of the observed phase speeds of 239.5 <span class="inline-formula">±</span> 4.3 and 162.2 <span class="inline-formula">±</span> 6.1 m s<span class="inline-formula">⁻¹</span> for the eastward the westward waves, respectively. Considering that HIAMCM perturbations in the mesosphere/lower thermosphere were the result of the secondary waves generated by the dissipation of the primary gravity waves from the volcanic eruption, this affirms the importance of higher-order wave generation. Furthermore, based on meteor radar observations of the gravity wave propagation around the globe, we estimate the eruption time to be within 6 min of the nominal value of 15 January 2022 04:15 UTC, and we localized the volcanic eruption to be within 78 km relative to the World Geodetic System 84 coordinates of the volcano, confirming our estimates to be realistic.</p>

Karen Stamieszkin, Nicole C. Millette, Jessica Y. Luo et al.

Aquatic ecologists are integrating mixotrophic plankton – here defined as microorganisms with photosynthetic and phagotrophic capacity – into their understanding of marine food webs and biogeochemical cycles. Understanding mixotroph temporal and spatial distributions, as well as the environmental conditions under which they flourish, is imperative to understanding their impact on trophic transfer and biogeochemical cycling. Mixotrophs are hypothesized to outcompete strict photoautotrophs and heterotrophs when either light or nutrients are limiting, but testing this hypothesis has been hindered by the challenge of identifying and quantifying mixotrophs in the field. Using field observations from a multi-decadal northern North Atlantic dataset, we calculated the proportion of organisms that are considered mixotrophs within individual microplankton samples. We also calculated a “trophic index” that represents the relative proportions of photoautotrophs (phytoplankton), mixotrophs, and heterotrophs (microzooplankton) in each sample. We found that the proportion of mixotrophs was positively correlated with temperature, and negatively with either light or inorganic nutrient concentration. This proportion was highest during summertime thermal stratification and nutrient limitation, and lowest during the North Atlantic spring bloom period. Between 1958 and 2015, changes in the proportion of mixotrophs coincided with changes in the Atlantic Multi-decadal Oscillation (AMO), was highest when the AMO was positive, and showed a significant uninterrupted increase in offshore regions from 1992-2015. This study provides an empirical foundation for future experimental, time series, and modeling studies of aquatic mixotrophs.

Chao Wang, Junyong Li, Ahmed Tanvir et al.

Zero-shot remote sensing scene classification refers to making the model to have the ability to identify the unseen class scenes based on seen class scenes, and has become a research hotspot in the field of remote sensing. Contemporary approaches in zero-shot remote sensing scene classification primarily focus on extracting global information from scenes, neglecting nuanced local landscape features. This oversight diminishes the discriminative capabilities of recognition models. Furthermore, these methods overlook the semantic relevance between seen and unseen class scenes in training, leading to reduced emphasis on learning from varied scenes and subsequent declines in classification performance. To address these challenges, this article proposes the &#x201C;Zero-Shot Remote Sensing Scene Classification Method Based on Local-Global Feature Fusion and Weight Mapping Loss (LGFFWM).&#x201D; The design incorporates a local-global feature fusion (LGFF) module enabling adaptive labeling and feature modeling of internal local landscapes, effectively merging them with global features for a more discriminative representation of remote sensing scenes. Furthermore, a weight mapping loss (WM Loss) function is introduced, leveraging a semantic correlation matrix to compel the model to prioritize learning seen class scenes that exhibit strong correlations with unseen class scenes by assigning higher training weights. Extensive experiments have been conducted on classical remote sensing scene datasets, including UCM, AID, and NWPU, demonstrate the superiority of the proposed LGFFWM method over ten advanced comparative methods, yielding overall accuracy improvements of over 2.25&#x0025;, 3.47&#x0025;, and 0.44&#x0025;, respectively. Additional experiments on the SIRI-WHU and RSSCN7 datasets underscore the transferability of LGFFWM, achieving overall accuracies of 53.50&#x0025; and 47.37&#x0025;, respectively.

Jianfeng Tong, Jianfeng Tong, Jianfeng Tong et al.

Nowadays, most fishing vessels are equipped with high-resolution commercial echo sounders. However, many instruments cannot be calibrated and missing data occur frequently. These problems impede the collection of acoustic data by commercial fishing vessels, which are necessary for species classification and stock assessment. In this study, an automatic detection and classification model for echo traces of the Pacific saury (Cololabis saira) was trained based on the algorithm YOLO v5m. The in situ measurement value of the Pacific saury was measured using single fish echo trace. Rapid calibration of the commercial echo sounder was achieved based on the living fish calibration method. According to the results, the maximum precision, recall, and average precision values of the trained model were 0.79, 0.68, and 0.71, respectively. The maximum F1 score of the model was 0.66 at a confidence level of 0.454. The living fish calibration offset values obtained at two sites in the field were 116.30 dB and 118.19 dB. The sphere calibration offset value obtained in the laboratory using the standard sphere method was 117.65 dB. The differences between in situ and laboratory calibrations were 1.35 dB and 0.54 dB, both of which were within the normal range.

Chao Wang, Baolong Guo, Fangliang He

Owing to the characteristics of long distance and strong penetration, a synthetic aperture radar (SAR) imaging system could provide ground information with high resolution under a poor climate environment. Nevertheless, speckle is still a common interference of the output that deteriorates the content of SAR images and further affects the recognition of real objects. In this article, a new speckle suppression method is proposed from the perspective of exploring nonlocal and local SAR image features. Considering the statistical distribution of SAR images, a novel local filter termed SAR-orientated guided bilateral filter is proposed to characterize the range and spatial similarity of SAR images. Meanwhile, an optimized nonlocal filter based on the weight Schatten-<inline-formula><tex-math notation="LaTeX">$p$</tex-math></inline-formula> norm is introduced to characterize the nonlocal self-similarity of SAR images by a low-rank model. As a preprocessing step, it yields nonlocal filtering features as the guidance image of the proposed SAR-oriented guided bilateral filter. By incorporating the nonlocal filtering feature into the local filter, the structured method could achieve desirable despeckling results. Extensive experiments on real SAR images demonstrate that the proposed method outperforms several state-of-the-art methods in terms of both visual satisfaction and quantitative metrics.

Congcong Ma, Pingping Niu, Xinyu An

Trapped modes that exist in the waveguide have different engineering applications. Excited acoustic modes are due to the interaction between acoustic and flow fields. To further study the influence of nonpotential flow on trapped modes for a two-dimensional cavity–duct system, a numerical simulation method that combines the finite-element method (FEM) associated with a mixed formulation of the Galbrun equation and computational fluid dynamics (CFD) is proposed. The calculation model is composed of a two-dimensional waveguide with cavities and perfectly matched layers (PMLs) to limit the computational domain. The effects of the Mach number and different cavity lengths on the resonance modes are investigated.

Huihui ZHOU, Tianyun LI, Xiang ZHU et al.

ObjectivesDue to the larger length-to-diameter ratio of the stern bearing, it is difficult to reflect its actual operating conditions when simplified to the traditional equivalent model of single-point support. Therefore, the influence of the equivalent form of the stern bearing on the transverse vibration characteristics of the shafting is investigated.MethodsThe improved Fourier series is introduced to describe the lateral vibration displacement of propulsion shafting. Then, the calculation model of lateral vibration performance of propulsion shafting under various equivalent forms, such as single-point support, multi-point support or continuous distributed support, are constructed based on the energy principle. Thereby, the influence of the change of support stiffness equivalent to the liquid film pressure on the lateral vibration of the shafting and the influence of the propeller excitation on the vibration response of the shafting are further analyzed. Finally, the results acquired by the proposed model is compared with the results of related references and finite element method (FEM) to verify the validity of the calculation model.ResultsThe multi-point support calculation results converge to the continuous distributed support calculation results. The three-point support equivalent form can be used to study the influence of liquid film pressure distribution on the lateral vibration characteristics of the propulsion shafting. The shafting response under propeller excitation is affected by the revolution speed.Conclusions The research indicates that three-point support equivalent form can be used to analyze the influence of liquid film pressure on the shafting lateral vibration performance. The proposed model in this paper has advantages of good convergence, high accuracy, and less cost-consuming.

S. Khanmohammadi, M. Baseri, P. Ahmadi et al.

Abstract The present study deals with energy, exergy and environmental evaluation of an integrated ocean thermal energy conversion (OTEC) system include a flat plate solar collector, an organic Rankine cycle, an electrolyzer system boosted with a thermoelectric generator (TEG) unit. To precise assessment of suggested systems and determine the effects of adding thermoelectric generator to the system a comparative analysis is carried out. Two considered systems are solar ocean thermal energy conversion (S-OTEC) and solar ocean thermal energy conversion with thermoelectric (S-OTEC/TEG). A thermodynamic model is formed using Engineering Equation Solver (EES) to solve the set of linear equations governing on the component of the system. The result of exergy analyses shows that adding thermoelectric module to the S-OTEC results in exergy efficiency increment by 6.27%. Also adding thermoelectric unit to the system increase gross output power by 12.64 kW that the TEG pump input work in this case is 4.96 kW. Although the exergy destruction rate of the S-OTEC/TEG has a higher exergy destruction rate than S-OTEC, the exergy efficiency of S-OTEC/TEG is higher than S-OTEC. Environmental impact assessment criteria namely sustainability index (SI) and modified sustainability index (SI2), represent that applying TEG module to the system improves the SI2 while decreases the SI. Based on obtained results with methanol as working fluid, the SI change from 0.106 for S-OTEC to 0.183 for and S-OTEC/TEG system. In addition, the SI2 change from 1.949 to 2.220 when the TEG module added to the integrated system.

Xin-Yi Gao, Yongjiang Guo, Wen-Rui Shan

Abstract Water waves, one of the most common phenomena in nature, play an important role in the marine/offshore engineering, hydraulic engineering, energy development, mechanical engineering, etc. Hereby, for the shallow water waves near an ocean beach or in a lake, we study a Boussinesq-Burgers system. With respect to the water-wave horizontal velocity and height deviating from the equilibrium position of water, we find out (1) two hetero-Backlund transformations via the Bell polynomials and symbolic computation, and (2) a set of the similarity reductions via symbolic computation, to a known ordinary differential equation, for which we also construct some solutions. The results rely on the oceanic water-wave dispersive power. We hope that our hetero-Backlund transformations and similarity reductions could help the researchers investigate certain modes of the shallow water waves near an ocean beach.

Xinyu Wang, Jianhua Liu, Siyuan Wang et al.

The design of efficient ocean wave sensors for monitoring the marine environment and revealing dynamic changes has been a major challenge. In this study, a self‐powered bionic coral wave sensor (BCWS) based on a triboelectric nanogenerator is proposed. The BCWS captures wave data, which are useful for marine engineering construction, marine resource development, and marine disaster warning. It is mainly composed of triboelectric perceiving units (60 mm in length, 10 mm in width, and 1.5 mm in thickness) encapsulated in coral tentacles, a fixation mechanism, a buoyancy tray, and a counterweight mechanism. With the help of its bio‐inspired structural design, the BCWS effectively improves the signal response time and sensitivity in the 3D perception of wave information. In particular, the coral tentacles stimulated by a load cause contact‐separation between fluorinated ethylene propylene and conductive ink electrodes, thereby generating electric signals. This analysis of the experimental data reveals that the BCWS perceives wave height, wave frequency, wave period, and wave direction with millimeter accuracy. To demonstrate the applicability and stability of the BCWS, several of its potential functions are illustrated, including controlling light emitting diodes, perceiving wave information in the ocean, and assisting overboard rescue. The results show that the BCWS provides an intelligent solution for modern marine monitoring.

Xin-Yi Gao, Y. Guo, Wen-Rui Shan

Water waves are one of the most common phenomena in nature, the studies of which help energy development, marine/offshore engineering, hydraulic engineering, mechanical engineering, etc. Hereby, symbolic computation is performed on the Boussinesq–Burgers system for shallow water waves in a lake or near an ocean beach. For the water-wave horizontal velocity and height of the water surface above the bottom, two sets of the bilinear forms through the binary Bell polynomials and N-soliton solutions are worked out, while two auto-Bäcklund transformations are constructed together with the solitonic solutions, where N is a positive integer. Our bilinear forms, N-soliton solutions and Bäcklund transformations are different from those in the existing literature. All of our results are dependent on the water-wave dispersive power.