Search Results (79)

The decarbonization of maritime transport has primarily targeted large vessels, leaving small craft largely dependent on fossil fuel despite their inherent use of wind propulsion. This study addresses that gap by designing and simulating a zero-emission propulsion system for a 12.5 m sailing yacht based on integrated renewable energy. The retrofit replaces the diesel engine with an electric drivetrain supported by static solar panels and wind turbines, as well as dynamic sources, including hydro-generators and a regenerative propeller. In addition to performance under typical weather profiles, we conducted a lifecycle environmental impact estimation and evaluated system resilience under low renewable input. Simulations used real mid-latitude meteorological data to assess operational and environmental sustainability. The results show that during two representative 24 h voyages, propulsion and hotel loads were sustained solely by onboard renewables, with battery state of charge remaining above 28–46%. In an emergency calm scenario, the yacht motored for four hours at 5–6 knots using only stored energy, with solar input extending range. The findings demonstrate that integrated multi-source renewables can provide complete energy autonomy for sailing yachts. The approach illustrates practical feasibility under real conditions, scalability to eco-tour boats and ferries, and alignment with international decarbonization targets. Full article

This study numerically investigates the effect of hydrofoil installation on the motion responses and ride comfort of a 20 m monohull vessel operating at 10 knots in regular waves. Linear seakeeping analysis (Maxsurf Motions) and nonlinear computational fluid dynamics (CFD) simulations (STAR-CCM+) are performed to compute response-amplitude operators (RAOs); for the bare hull, the two methods agree within 5%, confirming methodological reliability. The CFD results show that hydrofoils reduce heave and pitch amplitudes by approximately 16% on average. Motion Sickness Incidence (MSI) analysis indicates negligible seasickness under Gentle Breeze conditions, even during prolonged exposure; under Moderate conditions, no seasickness is predicted within 30 min across all encounter frequencies. Although linear analysis cannot directly estimate MSI for hydrofoil-fitted cases, the observed reductions in RAOs imply improved ride comfort. Overall, these findings demonstrate that hydrofoils can enhance motion stability and passenger comfort in small, low-speed vessels, providing quantitative evidence to support design applications. Full article

Halcyon days are characterized by periods of one to three or more consecutive, typically sunny and mild days, occurring during winter (from 15 December to 15 February) in Attica, the region where Athens is located. We examined meteorological data from the station of the National Observatory of Athens in Thission, over a 54-year period, applying criteria that include daily maximum temperatures equal to or greater than 12 °C, minimum temperatures equal to or greater than 4 °C, wind speeds equal to or less than 6 knots, and mean total cloudiness (between 06:00 and 18:00 GMT) equal to or less than 3.2 oktas. This analysis identified all Halcyon days that occurred during this period. Our statistical study revealed the annual evolution of these days and any possible relationship with climate change. We focused on understanding the dynamics of the atmospheric circulation processes associated with the occurrence of Halcyon days. The primary atmospheric circulation feature responsible for the generation of Halcyon days appears to be the establishment of a subtropical anticyclone over Greek territory. Full article

The occurrence of knots as solutions of dynamical systems has been widely studied in the literature. In particular, ways to determine families of knots as solutions of differential equations have been described in several papers. In this article, an infinite family of dynamical systems, based on torus knots, is built each of which has the property that an infinite number of cable knots from torus knots (i.e., iterated torus knots) are obtained as solutions. One such dynamical system, based on the trefoil knot, is explicitly constructed. The methodology described herein may also be applied to any torus knot, and even to any other knot as long as a parametrization is provided for the latter. An example of application of the method is presented for the case of the figure eight knot, which is not a torus knot. Also, a possible application in cryptography is sketched. Full article

Knots are ubiquitous in polymers and biological macromolecules such as DNA and proteins, yet their behavior and functionality are still not sufficiently explored. Here we investigate the impact of Poiseuille flow on simple knots in flexible polymers placed in a quasi-rectangular micro-channel by systematically varying the flow strength for different chain lengths. Hydrodynamic interactions are accounted for by means of Multi-Particle Collision Dynamics (MPCD). We find that initially loosely localized knots in polymer coils typically tighten under shear to several segments beyond a certain body force threshold. At higher shear rates, intermittent transition from chain stretching to tumbling is observed which correlates with strong fluctuations in the knot size. Somewhat unexpectedly, our results indicate that the influence of channel width on tightening steadily increases with growing width even at equal mean shear rate $\overline{\dot{\gamma }}$. Full article

Meloidogyne incognita (M. incognita) is a devastating root-knot nematode that parasitizes a broad range of crop species by inducing the formation of giant cells (GCs) in host roots, thereby facilitating nutrient acquisition. This process profoundly alters host sugar metabolism, yet the molecular regulators underlying sugar dynamics during infection remain poorly understood in cucumber. In this study, we investigated the role of the cucumber alkaline α-galactosidase gene (CsAGA1) in M. incognita-infected roots. Histochemical analysis of proCsAGA1::GUS transgenic lines demonstrated that CsAGA1 is spatially localized to nematode-induced feeding sites, with its expression markedly induced in GCs and phloem-adjacent tissues during infection. Functional analyses revealed that silencing CsAGA1 impaired root and gall development. CsAGA1-silenced plants exhibited increased gall numbers (per gram root) but significantly reduced root growth and smaller galls compared to controls. These results indicate that CsAGA1 is required for proper gall expansion and root growth during M. incognita infection. This study provides novel insight into the sugar-mediated regulation of host–nematode interactions, and CsAGA1 emerges as a potential target for the biological control of M. incognita. Full article

Antarctic navigation encounters substantial challenges due to the dynamic and perilous characteristics of sea ice, which pose threats to vessel safety and operational efficiency. Existing risk assessment methodologies frequently lack real-time adaptability, while strategies for icebreaker convoys remain insufficiently quantified. To address these deficiencies, this study introduces an integrated framework that combines satellite-based sea ice monitoring, operational risk prediction, and icebreaker escort optimization. First, polar research routes and hydrographic conditions are systematically analyzed to enhance navigation planning. Second, a risk assessment system is developed by leveraging satellite-derived sea ice density and thickness data, facilitating a near-real-time hazard assessment (subject to satellite data latency) evaluation with 96.3% accuracy in ice type classification and a 15% improvement in risk prediction precision compared to conventional methods. Finally, kinematic safety criteria for icebreaker-escorted convoys are established, specifying speed-dependent distance thresholds to minimize collision risks, achieving optimal speeds of 1.4–2.3 knots for PC3-class vessels and 10–20% speed improvements for escorted vessels in cleared channels. The findings offer actionable insights into polar route optimization, risk mitigation, and safe ice navigation protocols, thereby directly supporting operational decision making in Antarctic waters. Full article

Structural timber is an important building material, but surface defects such as cracks and knots seriously affect its load-bearing capacity, dimensional stability, and long-term durability, posing a significant risk to structural safety. Conventional inspection methods are unable to address the issues of multi-scale defect characterization, inter-class confusion, and morphological diversity, thus limiting reliable construction quality assurance. To overcome these challenges, this study proposes WDNET-YOLO: an enhanced deep learning model based on YOLOv8n for high-precision defect detection in structural wood. First, the RepVGG reparameterized backbone utilizes multi-branch training to capture critical defect features (e.g., distributed cracks and dense clusters of knots) across scales. Second, the ECA attention mechanism dynamically suppresses complex wood grain interference and enhances the discriminative feature representation between high-risk defect classes (e.g., cracks vs. knots). Finally, CARAFE up-sampling with adaptive contextual reorganization improves the sensitivity to morphologically variable defects (e.g., fine cracks and resin irregularities). The analysis results show that the mAP50 and mAP50-95 of WDNET-YOLO are improved by 3.7% and 3.5%, respectively, compared to YOLOv8n, while the parameters are increased by only 4.4%. The model provides a powerful solution for automated structural timber inspection, which directly improves building safety and reliability by preventing failures caused by defects, optimizing material utilization, and supporting compliance with building quality standards. Full article

The human coagulation pathway orchestrates a complex series of events vital for maintaining vascular integrity, in which the intrinsic pathway plays a pivotal role in amplifying and propagating the coagulation response. Dysregulation of this pathway can lead to various bleeding disorders and thrombotic complications, posing significant health risks. In this pathway, the activation of Factor (F) X zymogen is catalyzed by the FVIIIa-FIXa binary complex, but knowledge about this is still incomplete. Understanding the structural and functional intricacies of the FVIIIa-FIXa-FX (zymogen) complex is imperative for unraveling the molecular mechanisms underlying coagulation regulation and guiding the development of targeted therapeutic interventions. In this study, utilizing Alphafold-Multimer and molecular dynamics (MD) simulations, we provide insights into factor interactions within the ternary complex and propose novel functional mechanisms contributing to the functional defects inflicted by their cross-reactive material (CRM) positive mutations. The amino acid residue replacement impairs the coagulation function by interfering with structure elements, including the following: (1) a knot-like structure between Arg-562 of FVIIIa’s 558-Loop (residue 555–571) and the 333-Loop of FIXa (residue 333–346) contributes to FVIIIa-FIXa binding; (2) the a2 region of FVIIIa (residue 716–740) opens the lid of active site (FIXa’s 266-Loop, residue 256–270) and facilitates substrate binding; (3) the activation peptide (AP) of FX zymogen (residue 143–194) not only assists in the activation of itself but also adheres the interface of the three factors like a double-sided tape. Our work provides novel insights for the pathogenesis of a number of reported clinical CRM-positive mutations and may lay the groundwork for the structure-based development of therapeutic interventions. Full article

Wind and humidity are two very vital climate variables that have received little attention by researchers regarding Uganda. This study sought to close this knowledge gap by exposing the dynamics and relationship of windspeed and humidity in Uganda from 1980 to 2023 as well as predicting the future trends from 2025 to 2040. Using high-resolution gridded windspeed and relative humidity (RH) data for the past and seven downscaled and bias-adjusted global climate models within the coupled model intercomparison project phase 6 framework under two shared socioeconomic pathways (SSPs), SPP245 and SSP585, we employed variability, trend, and correlational analyses to expose the wind–humidity nexus at a monthly scale. The results showed a domination of winds of the calm to gentle breeze category across the country, with a maximum magnitude of 6 knots centered over eastern Lake Victoria and eastern Uganda over the historical period. RH was characterized by high to very high magnitudes, except the northern tips of the country, where RH was low for the historical period. Seasonally, both windspeed and RH demonstrated modest variations, with June–July–August (JJA) and September–October–November (SON) having the highest magnitudes, respectively. Similarly, both variables are forecasted to have significant distribution and magnitude changes. For example, windspeeds will be dominated by decreasing trends, while RH will be dominated by increasing trends. Finally, the correlation analysis revealed a strong negative correlation between windspeeds and RH for both the past and future periods, except for the March–April–May (MAM) and September–October–November (SON) seasons, where positive correlations were observed. These findings have practical applications in agriculture, hydrology, thermal comfort, disaster management, and forecasting, especially in the northern, eastern, and Lake Victoria basin regions. The study recommends further finer-scale research at various atmospheric levels and for prolonged future periods and scenarios. Full article

The relative motion and coupled dynamics between individual units in a Multiple AUVs in Tandem Connection (MATC) system make speed and inter-unit distance control particularly challenging, especially in large-scale configurations. This study proposes a novel hybrid thrust allocation method for steady straight-line sailing in MATC systems, addressing thrust constraints and unit coordination. First, the motion model of the MATC system was established based on Newton’s second law. Second, an improved Genetic Algorithm (GA) was developed to optimize thrust values for each unit in smaller configurations. Third, to address the computational challenges of thrust allocation in large MATC systems, an offline model training method was introduced, combining the Harris Hawks Optimization (HHO) algorithm with a BP neural network. Simulations were conducted for MATC configurations with 5 and 30 AUV units. The results demonstrate that, under current disturbances, the inter-unit distances and overall speed for the 5-unit MATC system quickly converged to target values of 0.12 m and 1.5 knots, respectively, without exceeding the 3.5 N thrust constraint. For the 30-unit MATC system, the proposed method achieved rapid convergence to target values, with a 56% reduction in straight-line speed deviation compared to using the improved GA alone. These findings validate the effectiveness of the proposed approach in enhancing control accuracy and scalability in MATC systems, offering significant potential for large-scale underwater applications. Full article

Using dynamic Monte Carlo simulations based on the bond-fluctuation model, we systematically investigated the size and knots of ring polymers in all-crossing systems and intra-crossing systems. Our results demonstrate that the interchain constraint can increase the knotting probability, but does not alter the scaling relationship between knotting probability and chain length for ring polymers in melts. Having established that, we derived the interchain constraint contribution to the free energy of ring polymers in intra-crossing systems based on the knotting probability and obtained the scaling relationship between the size R and chain length N, i.e., R~N^1/6. And, by calculating the mean-squared radius of gyration of ring polymers in intra-crossing systems, we validated these scaling results. Finally, we analyze the size of knotted ring polymers with different types and compare corresponding scaling exponents for size versus chain lengths of ring polymers with different knotting complexities. These results provide fundamental insights into the static properties of ring polymers in melts. Full article

Considering that slow steaming requires low engine power, which impedes maneuverability under severe sea conditions, the International Maritime Organization (IMO) provides guidelines for the minimum propulsion power (MPP) required to maintain ship maneuverability in adverse conditions. This study focused on the characteristics of self-propulsion factors in the context of MPP assessment to enhance MPP prediction accuracy. Overload tests were conducted at low speeds of advance, considering added resistance in adverse conditions. Moreover, propeller open-water tests were conducted corresponding to propeller flow with low Reynolds numbers to investigate their effect on self-propulsion factors. In addition, computational fluid dynamics (CFD) simulations were conducted to analyze physical phenomena such as the flow field and pressure distribution under model test conditions. The results indicated that the thrust deduction factor was lower than that given in the guidelines, whereas the wake fraction was higher at the required forward speed of 2 knots. The MPP assessment in this study revealed that the required brake power was 4–5% lower than that given in the guidelines, indicating that the guidelines need reviewing for a more reliable assessment. Full article

Background: Indonesia is an archipelagic country with 17,508 islands spread over the Pacific and Indian Oceans, with thousands of inter-island routes requiring a large and engaged fleet. The vast expanse of the country also leads to challenges related to optimal fleet coverage, routing, and oil distribution while maintaining cost-effectiveness and reliable supply. Methods: This study combined a mixed-integer linear-programming (MILP) model with a response surface methodology (RSM) approach to optimize vessel assignment, vessel routes, and inventory control simultaneously and comprehensively across three regional clusters (i.e., Western, Central, and Eastern Indonesia). The model takes into account a fleet of 28 vessels (13 medium range [MR] and 15 general purpose [GP]) that can distribute three oil products: gasoline, diesel, and kerosene. Results: The optimized solution yields 100% service reliability at an operational cost of $ 2.83 million per month—far lower than currently operating services. The model is robust against variations in demand (±20%), port congestion (±50%), and changing fuel prices (±50%), which is confirmed by a sensibility analysis. The close correlation coefficient (0.987) between the MILP and RSM results confirms the framework’s accuracy. At the same time, the critical performance factors were found to be vessel speed (13.5 knots), fleet size, and port operation time. Conclusions: The study offers a cost-efficient and data-intensive model that could be implemented as a maritime logistics framework, as well as potential areas for future work and insight for relevant stakeholders. Future research will have to integrate real-time data fusion, mainly due to the need for environmental and stochastic modeling methods to foster operational resilience in dynamic maritime business ecosystems. Full article

Vascular tissue development plays a pivotal role in plant growth and defense against biotic stress. Root-knot nematodes, particularly Meloidogyne incognita (M. incognita), are globally distributed phytopathogens that cause severe economic losses in a variety of vascular plants. In this study, three vascular bundle development-related genes, including CsBAS1, CsSND1, and CsIRX6, were identified in cucumber. Tissue-specific expression analysis revealed that CsSND1 and CsIRX6 were highly expressed in roots. Infection with M. incognita showed dynamic expression changes for CsBAS1, CsSND1, and CsIRX6. Specially, CsIRX6 and CsSND1 were upregulated at 14 days post-inoculation (dpi), while CsBAS1 was downregulated at both 7 dpi and 14 dpi. Tissue localization studies using promoter–GUS constructs demonstrated pCsBAS1-GUS and pCsSND1-GUS activity in galls and specific vascular tissues, while CsIRX6 mRNA was detected in giant cells (GCs) at 14 dpi using in situ methods. Virus-induced gene silencing (VIGS) of CsBAS1, CsSND1, and CsIRX6 revealed their distinct roles in nematode-induced gall formation. Silencing CsBAS1 and CsSND1 resulted in increased root growth and gall size, whereas silencing CsIRX6 led to reduced gall size. These findings highlight the functional significance of CsBAS1, CsSND1, and CsIRX6 in cucumber defense against M. incognita, offering insights into the interplay between vascular development and plant defense mechanisms. Full article