The 2023 MDPI Annual Report has
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25 pages, 34046 KiB  
Article
Learning to Execute Timed-Temporal-Logic Navigation Tasks under Input Constraints in Obstacle-Cluttered Environments
by Fotios C. Tolis, Panagiotis S. Trakas, Taxiarchis-Foivos Blounas, Christos K. Verginis and Charalampos P. Bechlioulis
Robotics 2024, 13(5), 65; https://doi.org/10.3390/robotics13050065 - 26 Apr 2024
Abstract
This study focuses on addressing the problem of motion planning within workspaces cluttered with obstacles while considering temporal and input constraints. These specifications can encapsulate intricate high-level objectives involving both temporal and spatial constraints. The existing literature lacks the ability to fulfill time [...] Read more.
This study focuses on addressing the problem of motion planning within workspaces cluttered with obstacles while considering temporal and input constraints. These specifications can encapsulate intricate high-level objectives involving both temporal and spatial constraints. The existing literature lacks the ability to fulfill time specifications while simultaneously managing input-saturation constraints. The proposed approach introduces a hybrid three-component control algorithm designed to learn the safe execution of a high-level specification expressed as a timed temporal logic formula across predefined regions of interest in the workspace. The first component encompasses a motion controller enabling secure navigation within the minimum allowable time interval dictated by input constraints, facilitating the abstraction of the robot’s motion as a timed transition system between regions of interest. The second component utilizes formal verification and convex optimization techniques to derive an optimal high-level timed plan over the mentioned transition system, ensuring adherence to the agent’s specification. However, the necessary navigation times and associated costs among regions are initially unknown. Consequently, the algorithm’s third component iteratively adjusts the transition system and computes new plans as the agent navigates, acquiring updated information about required time intervals and associated navigation costs. The effectiveness of the proposed scheme is demonstrated through both simulation and experimental studies. Full article
(This article belongs to the Special Issue Motion Trajectory Prediction for Mobile Robots)
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35 pages, 4272 KiB  
Article
Optimized Decentralized Swarm Communication Algorithms for Efficient Task Allocation and Power Consumption in Swarm Robotics
by Mohamed Yasser, Omar Shalash and Ossama Ismail
Robotics 2024, 13(5), 66; https://doi.org/10.3390/robotics13050066 - 26 Apr 2024
Abstract
Unanimous action to achieve specific goals is crucial for the success of a robotic swarm. This requires clearly defined roles and precise communication between the robots of a swarm. An optimized task allocation algorithm defines the mechanism and logistics of decision-making that enable [...] Read more.
Unanimous action to achieve specific goals is crucial for the success of a robotic swarm. This requires clearly defined roles and precise communication between the robots of a swarm. An optimized task allocation algorithm defines the mechanism and logistics of decision-making that enable the robotic swarm to achieve such common goals. With more nodes, the traffic of messages that are required to communicate inside the swarm relatively increases to maintain decentralization. Increased traffic eliminates real-time capabilities, which is an essential aspect of a swarm system. The aim of this research is to reduce execution time while retaining efficient power consumption rates. In this research, two novel decentralized swarm communication algorithms are proposed, namely Clustered Dynamic Task Allocation–Centralized Loop (CDTA-CL) and Clustered Dynamic Task Allocation–Dual Loop (CDTA-DL), both inspired by the Clustered Dynamic Task Allocation (CDTA) algorithm. Moreover, a simulation tool was developed to simulate different swarm-clustered communication algorithms in order to calculate the total communication time and consumed power. The results of testing the proposed CDTA-DL and CDTA-CL against the CDTA attest that the proposed algorithm consumes substantially less time. Both CDTA-DL and CDTA-CL have achieved a significant speedup of 75.976% and 54.4% over CDTA, respectively. Full article
(This article belongs to the Section AI in Robotics)
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22 pages, 5521 KiB  
Article
Measurement and Assessment of Reactive, Unbalanced and Harmonic Line Losses
by Qun Zhou, Yulin Dian, Xueshan Liu, Minrui Leng, Canyu Chen and Haibo Liu
Electronics 2024, 13(9), 1680; https://doi.org/10.3390/electronics13091680 - 26 Apr 2024
Abstract
This study investigates the feasibility of utilizing the line loss power factor to assess the reactive, unbalanced, and harmonic line losses in low-voltage distribution networks and explores the method of calculating decoupled line loss values based on this factor. To achieve this objective, [...] Read more.
This study investigates the feasibility of utilizing the line loss power factor to assess the reactive, unbalanced, and harmonic line losses in low-voltage distribution networks and explores the method of calculating decoupled line loss values based on this factor. To achieve this objective, we establish preliminary definitions of single-phase and three-phase reactive, unbalanced, and harmonic line loss power factors, drawing upon the principles of electrical theory outlined in IEEE Standard 1459. These power factors serve as crucial indicators for evaluating the severity of line losses caused by reactive power, unbalance, and harmonic problems. Subsequently, the values of line loss attributed to reactive, unbalanced, and harmonic components are decoupled and quantified using the line loss power factor as a fundamental parameter. The effectiveness and accuracy of the proposed method were verified in Matlab simulation and physical experiments. Full article
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20 pages, 3251 KiB  
Article
CFIEE: An Open-Source Critical Metadata Extraction Tool for RISC-V Hardware-Based CFI Schemes
by Wenxin Li, Weike Wang and Senyang Li
Electronics 2024, 13(9), 1681; https://doi.org/10.3390/electronics13091681 - 26 Apr 2024
Abstract
Control flow critical metadata play a key role in hardware-based control flow integrity (CFI) mechanisms that effectively monitor and secure program control flow based on pre-extracted metadata. The existing control flow analysis tools exhibit some deficiencies, including inadequate compatibility with the RISC-V architecture, [...] Read more.
Control flow critical metadata play a key role in hardware-based control flow integrity (CFI) mechanisms that effectively monitor and secure program control flow based on pre-extracted metadata. The existing control flow analysis tools exhibit some deficiencies, including inadequate compatibility with the RISC-V architecture, a steep learning curve, limited automation capabilities, and restricted data output formats. CFIEE is an open-source tool with a graphical interface for the automated extraction of control flow critical metadata. The tool possesses the capability to analyze RISC-V binary executables, transforming the binary into an intermediate representation (IR) in the form of the disassembled code, and extracting the critical metadata required for studying hardware-based CFI mechanism through a designed control flow transfer relationship analysis algorithm. The extracted metadata include program basic blocks and their corresponding hash values, control flow graphs, function call relationships, distribution of forward transfer instructions, etc. We selected 15 embedded system programs with processor adaptation for functional verification. The results demonstrate the CFIEE’s capability to automatically analyze programs within the supported RISC-V instruction set and generate comprehensive and precise metadata files. This tool can significantly enhance the efficiency of control flow metadata extraction and furnish configurable metadata for the hardware-based security mechanisms. Full article
13 pages, 1893 KiB  
Article
Different Immune Responses of Hemocytes from V. parahaemolyticus-Resistant and -Susceptible Shrimp at Early Infection Stage
by Wenran Du, Shihao Li and Fuhua Li
Biology 2024, 13(5), 300; https://doi.org/10.3390/biology13050300 - 26 Apr 2024
Abstract
Vibrio parahaemolyticus is one of the main causative agents leading to acute hepatopancreatic necrosis disease, the severe bacterial disease that occurs during shrimp aquaculture. Hemocytes play important roles during Vibrio infection. Previously, we found that there were few differentially expressed genes (DEGs) between [...] Read more.
Vibrio parahaemolyticus is one of the main causative agents leading to acute hepatopancreatic necrosis disease, the severe bacterial disease that occurs during shrimp aquaculture. Hemocytes play important roles during Vibrio infection. Previously, we found that there were few differentially expressed genes (DEGs) between hemocytes from V. parahaemolyticus-resistant and -susceptible shrimp before infection. We considered that there should be different immune responses between them after a pathogen infection. Here, the transcriptome data of hemocytes from V. parahaemolyticus-resistant and -susceptible shrimp before and after a pathogen infection were compared. The results showed that there were 157 DEGs responsive to infection in V. parahaemolyticus-resistant shrimp, while 33 DEGs in V. parahaemolyticus-susceptible shrimp. DEGs in V. parahaemolyticus-resistant shrimp were mainly related to immune and glycolytic processes, while those in V. parahaemolyticus-susceptible shrimp were mainly related to metabolism, with only two DEGs in common. A further analysis of genes involved in glucose metabolism revealed that GLUT2, HK, FBP, and PCK1 were lowly expressed while PC were highly expressed in hemocytes of the V. parahaemolyticus-resistant shrimp, indicating that glucose metabolism in shrimp hemocytes was related to a V. parahaemolyticus infection. After the knockdown of PC, the expression of genes in Toll and IMD signaling pathways were down-regulated, indicating that glucose metabolism might function through regulating host immunity during V. parahaemolyticus infection. The results suggest that the immune responses between V. parahaemolyticus-resistant and -susceptible shrimp were apparently different, which probably contribute to their different V. parahaemolyticus resistance abilities. Full article
(This article belongs to the Section Marine Biology)
15 pages, 991 KiB  
Article
Associations between Polycystic Ovary Syndrome (PCOS) and Antibiotic Use: Results from the UAEHFS
by Nirmin F. Juber, Abdishakur Abdulle, Amar Ahmad, Fatme AlAnouti, Tom Loney, Youssef Idaghdour, Yvonne Valles and Raghib Ali
Antibiotics 2024, 13(5), 397; https://doi.org/10.3390/antibiotics13050397 - 26 Apr 2024
Abstract
Women with polycystic ovary syndrome (PCOS) have a higher susceptibility to infections compared to those without PCOS. Studies evaluating antibiotic use based on PCOS status are scarce. Therefore, we aimed to (i) assess the associations between self-reported PCOS and antibiotic use, and (ii) [...] Read more.
Women with polycystic ovary syndrome (PCOS) have a higher susceptibility to infections compared to those without PCOS. Studies evaluating antibiotic use based on PCOS status are scarce. Therefore, we aimed to (i) assess the associations between self-reported PCOS and antibiotic use, and (ii) whether PCOS treatment and the age at PCOS diagnosis modified the associations above. This cross-sectional analysis used the United Arab Emirates Healthy Future Study (UAEHFS) conducted from February 2016 to March 2023 involving 2063 Emirati women aged 18–62 years. We performed ordinal logistic regressions under unadjusted and demographic-health-characteristic-adjusted models to obtain the odds ratios (ORs) and 95% confidence intervals (CIs) to analyze PCOS and antibiotic use. Subgroup analyses were performed by treatment status and age at diagnosis. We found that women with PCOS were 55% more likely to frequently take a course of antibiotics in the past year (aOR 1.55; 95% CI 1.26–1.90). Similar likelihoods were also found among those being treated for PCOS and those without treatment but with a PCOS diagnosis at ≤25 years. Our study suggests that PCOS was associated with an increased use of antibiotics among Emirati women. Understanding the frequent antibiotic use susceptibility among those with PCOS may improve antibiotic use surveillance and promote antibiotic stewardship in these at-risk individuals. Full article
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11 pages, 671 KiB  
Article
Discovery of Antimicrobial Agents Based on Structural and Functional Study of the Klebsiella pneumoniae MazEF Toxin–Antitoxin System
by Chenglong Jin, Sung-Min Kang, Do-Hee Kim, Yuno Lee and Bong-Jin Lee
Antibiotics 2024, 13(5), 398; https://doi.org/10.3390/antibiotics13050398 - 26 Apr 2024
Abstract
Klebsiella pneumoniae causes severe human diseases, but its resistance to current antibiotics is increasing. Therefore, new antibiotics to eradicate K. pneumoniae are urgently needed. Bacterial toxin–antitoxin (TA) systems are strongly correlated with physiological processes in pathogenic bacteria, such as growth arrest, survival, and [...] Read more.
Klebsiella pneumoniae causes severe human diseases, but its resistance to current antibiotics is increasing. Therefore, new antibiotics to eradicate K. pneumoniae are urgently needed. Bacterial toxin–antitoxin (TA) systems are strongly correlated with physiological processes in pathogenic bacteria, such as growth arrest, survival, and apoptosis. By using structural information, we could design the peptides and small-molecule compounds that can disrupt the binding between K. pneumoniae MazE and MazF, which release free MazF toxin. Because the MazEF system is closely implicated in programmed cell death, artificial activation of MazF can promote cell death of K. pneumoniae. The effectiveness of a discovered small-molecule compound in bacterial cell killing was confirmed through flow cytometry analysis. Our findings can contribute to understanding the bacterial MazEF TA system and developing antimicrobial agents for treating drug-resistant K. pneumoniae. Full article
14 pages, 5036 KiB  
Article
The Comminution of Chert Gravel by Microwave Irradiation
by Mark Tzibulsky and Vladimir Frid
Resources 2024, 13(5), 63; https://doi.org/10.3390/resources13050063 - 26 Apr 2024
Abstract
Chert, a by-product rock of sand quarrying, has historically posed economic challenges for aggregate production, resulting in significant “waste” accumulation in quarries. Our study investigates the effect of microwave irradiation on the mechanical properties of chert gravel, a mineralogically homogenous material composed of [...] Read more.
Chert, a by-product rock of sand quarrying, has historically posed economic challenges for aggregate production, resulting in significant “waste” accumulation in quarries. Our study investigates the effect of microwave irradiation on the mechanical properties of chert gravel, a mineralogically homogenous material composed of fine quartz grains. The results, which demonstrate that increased irradiation time leads to a substantial decrease in chert gravel strength (by a factor of 4–6 for 2.5 min of irradiation), underscore the potential impact of this research on comminution processes. With quenching altering the fractional content of the samples after the crushing test, reducing the Gravel-to-Sand ratio, this study is driven by the promising potential of crushed chert gravel as a pivotal aggregate within the concrete and asphalt industries, offering a practical solution to their material needs. The urgent need to rehabilitate previously utilized quarry areas, offering an environmentally beneficial solution for which we all should be responsible, motivated the present study. Full article
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26 pages, 1123 KiB  
Article
Transformation of Energy Resources in the Visegrad Group: Strategies, Results, and Climate Effectiveness
by Izabela Jonek-Kowalska and Sara Rupacz
Resources 2024, 13(5), 64; https://doi.org/10.3390/resources13050064 - 26 Apr 2024
Abstract
The climate challenges posed by the European Union are particularly difficult for emerging and developing economies. This causes reluctance to undertake them and even denial of their validity. For this reason, this article seeks to answer the question of whether it is possible [...] Read more.
The climate challenges posed by the European Union are particularly difficult for emerging and developing economies. This causes reluctance to undertake them and even denial of their validity. For this reason, this article seeks to answer the question of whether it is possible to carry out an effective transformation of energy resources in the developing economies of the Visegrad Group. Analyses in this area are conducted in a long-term, 58-year research perspective (1965–2022) and concern the Czech Republic, Hungary, Poland, and Slovakia. The effectiveness of the examined transformation is assessed in two dimensions as follows: (1) resource and (2) emission, which are then synthesized using a multi-criteria analysis. This research shows that an effective resource transformation aimed at a zero-emission economy is possible even in emerging and developing economies, although it undoubtedly requires time and consistency in the implementation of the once-chosen energy policy. Hungary—a leader in assessed climate effectiveness—has systematically decarbonized while reducing the use of total non-renewable resources. The Hungarian resource transition strategy assumed the use of nuclear energy and an increase in the share of renewable resources. The result of these activities is a quite diversified energy mix, which is greater resource self-sufficiency and low carbon dioxide emissions. The Czech Republic also achieved a similar strategy and results. Poland and Slovakia coped much worse with the climate challenge: although they gave up coal, they replaced it largely with other non-renewable resources. It is worth emphasizing that Poland has managed to significantly increase the use of renewable resources, and nuclear energy and hydropower have also appeared in the Slovak mix. Nevertheless, this did not allow for achieving good climatic results. Full article
22 pages, 2490 KiB  
Article
Feature Matching of Microsecond-Pulsed Magnetic Fields Combined with Fe3O4 Particles for Killing A375 Melanoma Cells
by Yan Mi, Meng-Nan Zhang, Chi Ma, Wei Zheng and Fei Teng
Biomolecules 2024, 14(5), 521; https://doi.org/10.3390/biom14050521 - 26 Apr 2024
Abstract
The combination of magnetic fields and magnetic nanoparticles (MNPs) to kill cancer cells by magneto-mechanical force represents a novel therapy, offering advantages such as non-invasiveness, among others. Pulsed magnetic fields (PMFs) hold promise for application in this therapy due to advantages such as [...] Read more.
The combination of magnetic fields and magnetic nanoparticles (MNPs) to kill cancer cells by magneto-mechanical force represents a novel therapy, offering advantages such as non-invasiveness, among others. Pulsed magnetic fields (PMFs) hold promise for application in this therapy due to advantages such as easily adjustable parameters; however, they suffer from the drawback of narrow pulse width. In order to fully exploit the potential of PMFs and MNPs in this therapy, while maximizing therapeutic efficacy within the constraints of the narrow pulse width, a feature-matching theory is proposed, encompassing the matching of three aspects: (1) MNP volume and critical volume of Brownian relaxation, (2) relaxation time and pulse width, and (3) MNP shape and the intermittence of PMF. In the theory, a microsecond-PMF generator was developed, and four kinds of MNPs were selected for in vitro cell experiments. The results demonstrate that the killing rate of the experimental group meeting the requirements of the theory is at least 18% higher than the control group. This validates the accuracy of our theory and provides valuable guidance for the further application of PMFs in this therapy. Full article
(This article belongs to the Special Issue Advanced Nanotechnology for Health and Diseases)
17 pages, 2606 KiB  
Article
Biplane Enhancement Coil for Magnetic Induction Tomography of Cerebral Hemorrhage
by Zhongkai Cao, Bo Ye, Honggui Cao, Yangkun Zou, Zhizhen Zhu and Hongbin Xing
Biosensors 2024, 14(5), 217; https://doi.org/10.3390/bios14050217 - 26 Apr 2024
Abstract
Magnetic Induction Tomography (MIT) is a non-invasive imaging technique used for dynamic monitoring and early screening of cerebral hemorrhage. Currently, there is a significant challenge in cerebral hemorrhage MIT due to weak detection signals, which seriously affects the accuracy of the detection results. [...] Read more.
Magnetic Induction Tomography (MIT) is a non-invasive imaging technique used for dynamic monitoring and early screening of cerebral hemorrhage. Currently, there is a significant challenge in cerebral hemorrhage MIT due to weak detection signals, which seriously affects the accuracy of the detection results. To address this issue, a dual-plane enhanced coil was proposed by combining the target field method with consideration of the spatial magnetic field attenuation pattern within the imaging target region. Simulated detection models were constructed using the proposed coil and cylindrical coil as excitation coils, respectively, and simulation imaging tests were conducted using the detection results. The simulation results indicate that compared to the cylindrical coil, the proposed coil enhances the linearity of the magnetic field within the imaging target region by 60.43%. Additionally, it effectively enhances the detection voltage and phase values. The simulation results of hemorrhage detection show that the proposed coil improves the accuracy of hemorrhage detection by 18.26%. It provides more precise detection results, offering a more reliable solution for cerebral hemorrhage localization and detection. Full article
(This article belongs to the Section Wearable Biosensors)
18 pages, 2646 KiB  
Article
Optimization and Mechanism Study of Bonding Properties of CFRP/Al7075 Single-Lap Joints by Low-Temperature Plasma Surface Treatment
by Liwei Wen, Ruozhou Wang and Entao Xu
Coatings 2024, 14(5), 541; https://doi.org/10.3390/coatings14050541 - 26 Apr 2024
Abstract
This paper studied favorable low-temperature plasma (LTP) surface treatment modes for Carbon Fiber Reinforced Polymer (CFRP)/Al7075 single-lap joints using complex experimental methods and analyzed the failure modes of the joints. The surface physicochemical properties of CFRP after LTP surface treatment were characterized using [...] Read more.
This paper studied favorable low-temperature plasma (LTP) surface treatment modes for Carbon Fiber Reinforced Polymer (CFRP)/Al7075 single-lap joints using complex experimental methods and analyzed the failure modes of the joints. The surface physicochemical properties of CFRP after LTP surface treatment were characterized using scanning electron microscopy (SEM), contact angle tests, and X-ray photoelectron spectroscopy (XPS). The influence mechanism of LTP surface treatment on the bonding properties of CFRP/Al7075 single-lap Joint was studied. The results of the complex experiment and range analysis showed that the favorable LTP surface treatment parameters were a speed of 10 mm/s, a distance of 10 mm, and three repeat scans. At these parameters, the shear strength of the joints reached 30.76 MPa, a 102.8% improvement compared to the untreated group. The failure mode of the joints shifted from interface failure to substrate failure. After low-temperature plasma surface treatment with favorable parameters, the CFRP surface exhibited gully like textures, which enhanced the mechanical interlocking between the CFRP surface and the adhesive. Additionally, the surface free energy of CFRP significantly increased, reaching a maximum of 78.77 mJ/m2. XPS results demonstrated that the low-temperature plasma surface treatment led to a significant increase in the content of oxygen-containing functional groups, such as C-O, C=O, and O-C=O, on the CFRP surface. Full article
(This article belongs to the Special Issue Surface Science of Degradation and Surface Protection)
11 pages, 201 KiB  
Article
Psychedelic Mysticism and Christian Spirituality: From Science to Love
by Ron Cole-Turner
Religions 2024, 15(5), 537; https://doi.org/10.3390/rel15050537 - 26 Apr 2024
Abstract
The scientific claim that psychedelic drugs like psilocybin reliably occasion mystical experiences was justified using the Mystical Experiences Questionnaire (the MEQ), a survey first developed in the 1960s by Walter Pahnke using W.T. Stace’s Mysticism and Philosophy. Scholars in Christian mysticism reject [...] Read more.
The scientific claim that psychedelic drugs like psilocybin reliably occasion mystical experiences was justified using the Mystical Experiences Questionnaire (the MEQ), a survey first developed in the 1960s by Walter Pahnke using W.T. Stace’s Mysticism and Philosophy. Scholars in Christian mysticism reject the adequacy of Stace’s work for Western theistic mysticism, especially Christianity. One objection is that Stace follows William James in focusing on intense and unusual moments of mystical experience rather than the somewhat more ordinary mystical life. A greater concern is that Stace more adequately reflects non-Western traditions than Western theistic traditions like Christianity. For Stace, mysticism centers on the concept of union with external reality or with the absolute, a union in which the human creature is absorbed or fused. Christian mysticism, by contrast, involves a sense of presence rather than union, experienced in a most intimate relationship as a felt loving closeness with the divine, but not as fusion or absorption into the divine. While love of God is central to the Christian view, it is ignored in Stace and the MEQ30. Finally for Christianity, mysticism is not found in the momentary experience, but in the lifelong interpretation that leads to transformation. Full article
(This article belongs to the Special Issue Theology and Science: Loving Science, Discovering the Divine)
18 pages, 8350 KiB  
Article
Spacing Ratio Effects on the Evolution of the Flow Structure of Two Tandem Circular Cylinders in Proximity to a Wall
by Xiang Qiu, Xuezhi Ji, Jiankang Zhou, Jiahua Li, Yizhou Tao and Yulu Liu
J. Mar. Sci. Eng. 2024, 12(5), 721; https://doi.org/10.3390/jmse12050721 - 26 Apr 2024
Abstract
The flow around two tandem circular cylinders in proximity to a wall is investigated using particle image velocimetry (PIV) for Re = 2 × 103. The spacing ratios L/D are 1, 2, and 5, and the gap ratios G [...] Read more.
The flow around two tandem circular cylinders in proximity to a wall is investigated using particle image velocimetry (PIV) for Re = 2 × 103. The spacing ratios L/D are 1, 2, and 5, and the gap ratios G/D are 0.3, 0.6, and 1. The proper orthogonal decomposition (POD) method and λci vortex identification method are used to investigate the evolution of flow structure, and the influences of L/D and G/D on flow physics are shown. At L/D = 2 and G/D = 0.3, a “pairing” process occurs between the wall shear layer and the upstream cylinder’s lower shear layer, resulting in a small separation bubble behind the upstream cylinder. At L/D = 1, the Strouhal number (St) increases with decreasing G/D. At three gap ratios, the St gradually decreases as L/D increases. At G/D = 0.3, there is nearly a 49.98% decrease from St = 0.3295 at L/D = 1 to St = 0.1648 at L/D = 5, which is larger than the reductions in cases of G/D = 0.6 and G/D = 1. The effects of L/D on the evolution of flow structure at G/D = 0.6 are revealed in detail. At L/D = 1, the vortex shedding resembles that of the single cylinder. As L/D increases to 2, a squarish flow structure is formed between two cylinders, and a small secondary vortex is formed due to induction of the lower shear layer of the upstream cylinder. At L/D = 5, there is a vortex merging process between the upper wake vortices of the upstream and downstream cylinders, and the lower wake vortex of the upstream cylinder directly impinges the downstream cylinder. In addition, the shear layers and wake vortices of the upstream cylinder interact with the wake of the downstream cylinder as L/D increases, resulting in reductions in velocity fluctuations, and the production and turbulent diffusion of turbulent kinetic energy are decreased behind the downstream cylinder. Full article
(This article belongs to the Section Ocean Engineering)
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26 pages, 13695 KiB  
Article
Local Path Planning Method for Unmanned Ship Based on Encounter Situation Inference and COLREGS Constraints
by Gang Wang, Jingheng Wang, Xiaoyuan Wang, Quanzheng Wang, Longfei Chen, Junyan Han, Bin Wang and Kai Feng
J. Mar. Sci. Eng. 2024, 12(5), 720; https://doi.org/10.3390/jmse12050720 - 26 Apr 2024
Abstract
Local path planning, as an essential technology to ensure intelligent ships’ safe navigation, has attracted the attention of many scholars worldwide. In most existing studies, the impact of COLREGS has received limited consideration, and there is insufficient exploration of the method in complex [...] Read more.
Local path planning, as an essential technology to ensure intelligent ships’ safe navigation, has attracted the attention of many scholars worldwide. In most existing studies, the impact of COLREGS has received limited consideration, and there is insufficient exploration of the method in complex waters with multiple interfering ships and static obstacles. Therefore, in this paper, a generation method for a time–space overlapping equivalent static obstacle line for ships in multi-ship encounter scenarios where both dynamic and static obstacles coexist is proposed. By dynamically inferring ships’ encounter situations and considering the requirements of COLREGS, the influence of interfering ships and static obstacles on the navigation of the target ship at different times in the near future is represented as static obstacle lines. These lines are then incorporated into the scene that the target ship encountered at the path planning moment. Subsequently, the existing path planning methods were extensively utilized to obtain the local path. Compared with many common path planning methods in random scenarios, the effectiveness and reliability of the method proposed are verified. It has been demonstrated by experimental results that the proposed method can offer a theoretical basis and technical support for the autonomous navigation of unmanned ships. Full article
(This article belongs to the Section Ocean Engineering)
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17 pages, 5890 KiB  
Article
Study on the Flame Transition Characteristics of a Gas Turbine Combustor
by Mingmin Chen, Li Wang, Xinbo Huang, Minwei Zhao, Lingwei Zeng, Hongtao Zheng and Fuquan Deng
J. Mar. Sci. Eng. 2024, 12(5), 719; https://doi.org/10.3390/jmse12050719 - 26 Apr 2024
Abstract
Gas turbines are widely used as important equipment for electricity generation on islands and offshore platforms. During the operation of a gas turbine, the flame shape in the combustion chamber undergoes variations in response to changes in parameters such as gas turbine load, [...] Read more.
Gas turbines are widely used as important equipment for electricity generation on islands and offshore platforms. During the operation of a gas turbine, the flame shape in the combustion chamber undergoes variations in response to changes in parameters such as gas turbine load, fuel distribution, and burner structure. These alterations in flame shape exert influence on combustion instability, emissions, and load characteristics. This study explores the variations in flame transition, emissions, and operating parameters among three distinct center stage structures: namely, the non-premix center stage (NPCS), premix center stage (PCS), and enhanced premix center stage (PCSE). The investigation is conducted using a heavy-duty gas turbine hybrid burner on a full temperature, full pressure, and full-size single burner experimental bench. Simultaneously, a multi-parameter numerical simulation regarding the influence of the central fuel split on flame shape analysis was conducted using the PCS burner under the design point for a more in-depth understanding of the mechanisms and for influencing factors associated with flame transition. The findings indicate that variations in flame transition loads among different central stage structures: for the NPCS burner, the transition occurs between 45% and 50% load; for the PCS burners, it takes place between 60% and 65% load; for the PCSE burners, it shifts between 55% and 60% load. Additionally, a reduction in NOx emissions is observed during the flame transition process. Furthermore, it was found that decreasing the central stage fuel results in a decline in flame angle for the same burner structure. As the central stage fuel diminishes to a specific value, the flame shape undergoes a sudden change. Further reduction in central stage fuel does not significantly affect the flame shape and temperature distribution. Full article
(This article belongs to the Topic Marine Renewable Energy, 2nd Volume)
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17 pages, 8244 KiB  
Article
The High-Resolution Interannual Evolution of the Dune Toe at a Mesotidal Barrier (Camposoto Beach, SW Spain)
by Cristina Montes, Javier Benavente, María Puig, Juan Montes, Lara Talavera and Theocharis A. Plomaritis
J. Mar. Sci. Eng. 2024, 12(5), 718; https://doi.org/10.3390/jmse12050718 - 26 Apr 2024
Abstract
Over recent years, processes related to marine storms, sediment shortages and human intervention have caused the global retreat of many coastal systems and the degradation of their dunes. In this context, changes in the dune toe are commonly used as a proxy to [...] Read more.
Over recent years, processes related to marine storms, sediment shortages and human intervention have caused the global retreat of many coastal systems and the degradation of their dunes. In this context, changes in the dune toe are commonly used as a proxy to study the interannual shoreline evolution, and it is usually analyzed using orthophotography, while high temporal- and spatial-scale resolution studies of dune toe evolution are not frequent. In this work, a quasi-monthly study of dune toe data was carried out between 2008 and 2018. These data, taken from the RTK-DGPS and UAS systems, were subjected to shoreline analysis, and they showed an average regression rate of −2.30 m/year, a higher value than the one registered until 2008 (1 m/year). This suggests an acceleration in the erosion suffered within the system, which was revealed to be more intense in the northern sector of the study area. Dune toe variability increased over the years, probably due to the presence of washover fans breaking the foredune that were reactivated and expanded during storm events. The ephemeral progradation of the dune toe was also noted, which could be explained with reference to wind events and/or beach nourishment that had been carried out over the studied period. From the analysis of the dune toe elevation, a decrease in this variable was obtained, especially in the areas affected due to washover fans. This finding is supported by the significant correlation of the dune toe elevation and erosion trend, suggesting that the areas where the dune toe was lower are prone to suffering a greater retreat. This correlation provides insight into the future evolution of the barrier, suggesting a state of degradation and a transition to a lower-resilience state. Full article
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22 pages, 9147 KiB  
Article
Fuzzy Logic-Based Decision-Making Method for Ultra-Large Ship Berthing Using Pilotage Data
by Yibo Li, Guobin Song, Tsz-Leung Yip and Gi-Tae Yeo
J. Mar. Sci. Eng. 2024, 12(5), 717; https://doi.org/10.3390/jmse12050717 - 26 Apr 2024
Abstract
As seafarers are involved in Maritime Autonomous Surface Ships (MASS), except for those in the fourth level of autonomy, the decision making of autonomous berthing should be carried out and be understood by human beings. This paper proposes a fuzzy logic-based human-like decision-making [...] Read more.
As seafarers are involved in Maritime Autonomous Surface Ships (MASS), except for those in the fourth level of autonomy, the decision making of autonomous berthing should be carried out and be understood by human beings. This paper proposes a fuzzy logic-based human-like decision-making method for ultra-large ship berthing, which considers locations, ship particulars and the natural environment, and these factors are treated as the input variables. The IF–THEN rules are then established after the fuzzification of the input variables and are used for fuzzy inference to derive the decision of ship handling. It can be implemented in the decision-making system for safe navigation or be included in the process of autonomous berthing. The pilotage data are collected with nautical instruments and a distance measurement system during the berthing process, which are used to validate the proposed model and calculate the speed and turn errors. The overall and individual error of the decision-making model is in a reasonable and small range, which indicates that the model has good accuracy. The results of this research offer theoretical and practical insights into the development of a human-like decision-making method for autonomous navigation in port waters and maritime safety management in the shipping industry. The model can be further applied to develop a more widely applicable decision-making system for autonomous navigation in confined waters. Full article
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19 pages, 8006 KiB  
Article
An Underwater Localization Method Based on Visual SLAM for the Near-Bottom Environment
by Zonglin Liu, Meng Wang, Hanwen Hu, Tong Ge and Rui Miao
J. Mar. Sci. Eng. 2024, 12(5), 716; https://doi.org/10.3390/jmse12050716 - 26 Apr 2024
Abstract
The feature matching of the near-bottom visual SLAM is influenced by underwater raised sediments, resulting in tracking loss. In this paper, the novel visual SLAM system is proposed in the underwater raised sediments environment. The underwater images are firstly classified based on the [...] Read more.
The feature matching of the near-bottom visual SLAM is influenced by underwater raised sediments, resulting in tracking loss. In this paper, the novel visual SLAM system is proposed in the underwater raised sediments environment. The underwater images are firstly classified based on the color recognition method by adding the weights of pixel location to reduce the interference of similar colors on the seabed. The improved adaptive median filter method is proposed to filter the classified images by using the mean value of the filter window border as the discriminant condition to retain the original features of the image. The filtered images are finally processed by the tracking module to obtain the trajectory of underwater vehicles and the seafloor maps. The datasets of seamount areas captured in the western Pacific Ocean are processed by the improved visual SLAM system. The keyframes, mapping points, and feature point matching pairs extracted from the improved visual SLAM system are improved by 5.2%, 11.2%, and 4.5% compared with that of the ORB-SLAM3 system, respectively. The improved visual SLAM system has the advantage of robustness to dynamic disturbances, which is of practical application in underwater vehicles operated in near-bottom areas such as seamounts and nodules. Full article
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26 pages, 2261 KiB  
Review
How to Achieve Comprehensive Carbon Emission Reduction in Ports? A Systematic Review
by Liping Zhang, Qingcheng Zeng and Liang Wang
J. Mar. Sci. Eng. 2024, 12(5), 715; https://doi.org/10.3390/jmse12050715 - 26 Apr 2024
Abstract
Under the mounting pressure to make changes to become more environmentally friendly and sustainable, port authorities have been exploring effective solutions to reduce CO2 emissions. In this regard, alternative fuels, innovative technology, and optimization strategies are key pathways for ports to transition [...] Read more.
Under the mounting pressure to make changes to become more environmentally friendly and sustainable, port authorities have been exploring effective solutions to reduce CO2 emissions. In this regard, alternative fuels, innovative technology, and optimization strategies are key pathways for ports to transition toward a low-carbon pattern. In this review work, the current development status and characteristics of renewable and clean energy in ports were meticulously analyzed. The CO2 emission reduction effects and limitations of port microgrids, carbon capture, and other technological operations were thoroughly examined. Lastly, the emission reduction optimization strategies ports could adopt under different scenarios were evaluated. The research findings showed that (1) combining the characteristics of the port and quantifying the properties of different renewable energy sources and low-carbon fuels is extremely necessary to select suitable alternative energy sources for port development; (2) technological advancements, multi-party interests, and policy impacts were the primary factors influencing the development of emission reduction technology methods; and (3) the coordinated optimization of multiple objectives in cross-scenarios was the main direction for ports to achieve sustainable development. This study provides theoretical guidance to ports that are transitioning to a greener pattern, as well as pointing out future research directions and development spaces for researchers. Full article
(This article belongs to the Section Marine Environmental Science)
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17 pages, 11462 KiB  
Article
Long-Term Evolution of Significant Wave Height in the Eastern Tropical Atlantic between 1940 and 2022 Using the ERA5 Dataset
by Olorunfemi Omonigbehin, Emmanuel OlaOluwa Eresanya, Aifeng Tao, Victor Edem Setordjie, Samuel Daramola and Abiola Adebiyi
J. Mar. Sci. Eng. 2024, 12(5), 714; https://doi.org/10.3390/jmse12050714 - 26 Apr 2024
Abstract
Studies on the variability in ocean wave climate provide engineers and policy makers with information to plan, develop, and control coastal and offshore activities. Ocean waves bear climatic imprints through which the global climate system can be better understood. Using the recently updated [...] Read more.
Studies on the variability in ocean wave climate provide engineers and policy makers with information to plan, develop, and control coastal and offshore activities. Ocean waves bear climatic imprints through which the global climate system can be better understood. Using the recently updated ERA5 dataset, this study evaluated the spatiotemporal distribution and variability in significant wave height (SWH) in the Eastern Tropical Atlantic (ETA). The short-term trends and rates of change were obtained using the Mann–Kendall trend test and the Theil–Sen slope estimator, respectively, and decadal trends were assessed using wavelet transformation. Significant, positive monthly and yearly trends and a prevailing decadal trend were observed across the domain. Observed trends suggest that stronger waves are getting closer to the coast and are modulated by the Southern and Northern Atlantic mid-latitude storm fields. These observations have implications for the increasing coastal erosion rates on the eastern coast of the Tropical Atlantic. Full article
(This article belongs to the Section Physical Oceanography)
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17 pages, 4902 KiB  
Article
Challenges of Including Wet Grasslands with Variable Groundwater Tables in Large-Area Crop Production Simulations
by Valeh Khaledi, Bahareh Kamali, Gunnar Lischeid, Ottfried Dietrich, Mariel F. Davies and Claas Nendel
Agriculture 2024, 14(5), 679; https://doi.org/10.3390/agriculture14050679 - 26 Apr 2024
Abstract
Large-scale assessments of agricultural productivity necessitate integrated simulations of cropland and grassland ecosystems within their spatiotemporal context. However, simultaneous simulations face limitations due to assumptions of uniform species distribution. Grasslands, particularly those with shallow groundwater tables, are highly sensitive to water availability, undergoing [...] Read more.
Large-scale assessments of agricultural productivity necessitate integrated simulations of cropland and grassland ecosystems within their spatiotemporal context. However, simultaneous simulations face limitations due to assumptions of uniform species distribution. Grasslands, particularly those with shallow groundwater tables, are highly sensitive to water availability, undergoing rapid species composition changes. We hypothesised that predicting above-ground biomass (AGB) remains challenging due to these dynamic responses. Ten years of data from four lysimeters at a German wet grassland site, with varying water table treatments, was utilised to test this hypothesis. Correlation analysis revealed a strong positive indirect effect of the water regime on AGB, with a one-year time lag (r = 0.97). The MONICA model initially exhibited fair agreement (d = 0.69) in simulating Leaf-Area-Index (LAI) but performed poorly in replicating AGB (d = 0.3). After removing the species composition change effect from the LAI and AGB datasets, the simulation notably improved, with the overall relative root mean square error (rRMSE) of AGB decreasing from 1.55 to 0.90 between the first and second simulations. This demonstrates MONICA’s ability to predict grass growth patterns amidst changing water supply levels for constant species composition. However, it needs a competition model to capture biomass growth changes with varying water supply. Full article
(This article belongs to the Section Agricultural Water Management)
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17 pages, 644 KiB  
Article
Impacts of the National Nutrition Plan 2017–2030 on Listed Agrifood Enterprises: A Financial Statement Perspective
by Jianxiong Chen, Chung-Cheng Yang and Yu Lin
Agriculture 2024, 14(5), 677; https://doi.org/10.3390/agriculture14050677 - 26 Apr 2024
Abstract
The Chinese government promulgated the National Nutrition Plan 2017–2030 to provide scientific guidance for agrifood consumption and enhance nutrition intake. We categorized the sample into pre-2018 and post-2018 periods. By evaluating the effects of the National Nutrition Plan 2017–2030 through economic theory and [...] Read more.
The Chinese government promulgated the National Nutrition Plan 2017–2030 to provide scientific guidance for agrifood consumption and enhance nutrition intake. We categorized the sample into pre-2018 and post-2018 periods. By evaluating the effects of the National Nutrition Plan 2017–2030 through economic theory and a translog revenue function model based on financial statement data from 2015 to 2022, our findings indicate that the National Nutrition Plan 2017–2030 has increased the overall agrifood sales of listed agrifood enterprises, but the increase in agrifood sales produced by large listed agrifood enterprises has been slight. Finally, we offer policy recommendations for regulatory authorities and develop strategies for agrifood firms to encourage local food procurement. This study also contributes to our understanding of China’s agrifood industry dynamics and underscores the significance of the National Nutrition Plan 2017–2030 in enhancing nutritional intake and fostering sustainable growth in China’s agriculture industry. Full article
(This article belongs to the Special Issue Agricultural Markets and Agrifood Supply Chains)
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