Hasil untuk "Naval Science"

Uxue Uribe-Martinez, Leire Mijangos, Juan F. Ayala-Cabrera et al.

The occurrence and spatial distribution of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), fragrances, UV filters and photoinitiators were investigated in surface sediments of Nerbioi-Ibaizabal estuary between 2005 and 2013, in 2020. Samples were extracted by focused ultrasound solid–liquid extraction technique and analyzed by gas chromatography coupled with mass spectrometry. Total PAHs, PCBs, OCPs, musks, UV filters and photoinitiators concentrations ranged between not detected (n.d.) and 43000 ng g⁻¹, n.d. and 2500 ng g⁻¹, n.d. and 820 ng g⁻¹, n.d. and 880 ng g⁻¹, n.d. and 91 ng g⁻¹ and from nd to 120 ng g⁻¹, respectively. Hexachlorocyclohexanes (HCHs) were ubiquitous in the estuary, suggesting that these compounds, although banned, leach from landfills. The PCB concentrations showed a decreasing trend. Ecological risk assessments based on sediment quality guidelines (SQGs) and risk quotient (RQ) suggested semi-volatile organic compounds could represent a potential ecological risk in the Nerbioi-Ibaizabal estuary.

Kevin Sangoi, Mahdi Nadimi, Jie Song et al.

This study explores the effect of heat treatment on the microstructural characteristics and corrosion resistance of 316L stainless steels (SSs) produced via laser powder bed fusion (L-PBF), focusing on anisotropic corrosion behavior—a relatively less explored phenomenon in LPBF 316L SSs. By systematically analyzing the effects of varying heat treatment temperatures (500 °C, 750 °C, and 1000 °C), this work uncovers critical correlations between microstructural evolution and corrosion properties. The findings include the identification of anisotropic corrosion resistance between horizontal (XY) and vertical (XZ) planes, with the vertical plane demonstrating higher pitting and repassivation potentials but greater post-repassivation current densities. Furthermore, this study highlights reductions in grain size, dislocation density, and melt pool boundaries with increasing heat treatment temperatures, which collectively diminishes corrosion resistance. These insights advance the understanding of processing–structure–property relationships in additively manufactured metals, providing practical guidelines for optimizing thermal post-processing to enhance material performance in corrosive environments.

Qi Zhou, Jinghua Li, Xiaoyuan Wu et al.

Modular shipbuilding, as a cutting-edge ship construction paradigm, enables parallel manufacturing across workshops and stages—a core advantage that significantly shortens the total shipbuilding cycle, making it pivotal for modern shipyards to enhance productivity. However, this mode decomposes the integrated shipbuilding project into a large number of interdependent sub-activities spanning three key stages (fabrication, logistics, and assembly). Further, the duration of these sub-activities is inherently uncertain, primarily due to the extensive manual operations, variable on-site conditions, and supply chain fluctuations inherent in shipbuilding. These characteristics collectively pose a formidable challenge to project planning that pursues both high efficiency and low cost. To address this challenge, this paper proposes a Strategy-Group Evolution algorithm. First, the modular shipbuilding process scheduling problem is mathematically formulated as a resource-constrained three-stage multi-objective optimization model, where triangular fuzzy numbers are employed to characterize the uncertain sub-activity durations. Second, a two-layered Strategy-Group Evolution algorithm is designed for solving this model: the inner layer comprises 12 practical priority rules tailored to modular shipbuilding’s multi-stage features, while the outer layer adopts a genetic algorithm-based evolution policy to schedule and optimize the assignment of inner-layer rules to activity groups. The core of the Strategy-Group Evolution algorithm lies in dynamically assigning suitable strategies to different activity groups and evolving these assignments toward optimality—this avoids the limitation of a single priority rule for all stages, thereby facilitating the search for global optimal solutions. Finally, validation tests on real cruise ship construction projects and benchmark datasets demonstrate the efficacy and superiority of the proposed Strategy-Group Evolution algorithm.

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.

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.

Marius Manolache, Alexandra Ionelia Manolache, Gabriel Andrei

Excessive reliance on traditional energy sources such as coal, petroleum, and gas leads to a decrease in natural resources and contributes to global warming. Consequently, the adoption of renewable energy sources in power systems is experiencing swift expansion worldwide, especially in offshore areas. Floating solar photovoltaic (FPV) technology is gaining recognition as an innovative renewable energy option, presenting benefits like minimized land requirements, improved cooling effects, and possible collaborations with hydropower. This study aims to assess the levelized cost of electricity (LCOE) associated with floating solar initiatives in offshore and onshore environments. Furthermore, the LCOE is assessed for initiatives that utilize floating solar PV modules within aquaculture farms, as well as for the integration of various renewable energy sources, including wind, wave, and hydropower. The LCOE for FPV technology exhibits considerable variation, ranging from 28.47 EUR/MWh to 1737 EUR/MWh, depending on the technologies utilized within the farm as well as its geographical setting. The implementation of FPV technology in aquaculture farms revealed a notable increase in the LCOE, ranging from 138.74 EUR/MWh to 2306 EUR/MWh. Implementation involving additional renewable energy sources results in a reduction in the LCOE, ranging from 3.6 EUR/MWh to 315.33 EUR/MWh. The integration of floating photovoltaic (FPV) systems into green hydrogen production represents an emerging direction that is relatively little explored but has high potential in reducing costs. The conversion of this energy into hydrogen involves high final costs, with the LCOH ranging from 1.06 EUR/kg to over 26.79 EUR/kg depending on the complexity of the system.

E. F. Keane, V. Graber, L. Levin et al.

Most of the pulsar science case with the Square Kilometre Array (SKA) depends on long-term precision pulsar timing of a large number of pulsars, as well as astrometric measurements of these using very long baseline interferometry (VLBI). But before we can time them, or VLBI them, we must first find them. Here, we describe the considerations and strategies one needs to account for when planning an all-sky blind pulsar survey using the SKA. Based on our understanding of the pulsar population, the performance of the now-under-construction SKA elements, and practical constraints such as evading radio frequency interference, we project pulsar survey yields using two complementary methods for a number of illustrative survey designs, combining SKA1-Low and SKA1-Mid Bands 1 and 2 in a variety of ways. A composite survey using both Mid and Low is optimal, with Mid Band 2 focused in the plane. We find that, given its much higher effective area and survey speed, the best strategy is to use SKA1-Low to cover as much sky as possible, ideally also overlapping with the areas covered by Mid. In our most realistic scenario, we find that an all-sky blind survey with Phase 1 of the SKA with the AA* array assembly will detect $\sim10,000$ slow pulsars and $\sim 800$ millisecond pulsars (MSPs) if SKA1-Mid covers the region within $5°$ of the plane, while higher latitudes will be covered with SKA1-Low. The yield with AA4 is $\sim 20\%$ higher. One could increase these numbers by increasing the range covered by SKA1-Mid Bands 1 and 2, at the cost of a considerably longer survey. The pulsar census will enable us to set new constraints on the uncertain physical properties of the entire neutron star population. This will be crucial for addressing major SKA science questions including the dense-matter equation of state, strong-field gravity tests, and gravitational wave astronomy.

Zhigang Cao

ABSTRACT We study a class of cooperative games, referred to as superadditive market games (SMG). Each SMG is characterized by a set of players, an initial endowment distribution, and a common production function that is superadditive (and meets certain regularity conditions). Due to superadditivity, players may desire to cooperate by pooling their endowments to jointly produce. We investigate kind production functions, namely production functions whose derived SMGs always have nonempty cores, regardless of initial endowment distributions. We show that a production function is kind if and only if its Walrasian core (the set of Walrasian equilibrium price vectors of a properly defined exchange economy) is always nonempty. We prove that a concave production function is kind if and only if it is homogeneous, and a convex production function is kind if and only if it satisfies a property that resembles the balancedness condition for classical cooperative games. Applying our results to newsvendor games, linear production games, and EOQ games easily reproduces several well‐known results and also generates some new results.

Kaushik Vijaykumar, Benjamin E. Grossman-Ponemon, Yang Wan et al.

Yuan Wang, Zhenbin Du

This paper studies the trajectory tracking issue for an underactuated autonomous underwater vehicle (AUV) in the horizontal plane. The desired velocity–tracking error relationship (DVTER) is constructed according to the kinematics and kinetic equation, which means that the expected velocities are built so that the position tracking errors converge to 0. Moreover, the limitation of obtaining the expected velocity by directly differentiating the desired position values is avoided. Then, the nonsingular fast terminal sliding mode (TSM) controller is developed to ensure that the velocities converge to the designed expected values in finite time, and tracking speed is improved by comparing with the traditional nonsingular terminal sliding mode method. It turns out that the expected trajectory can be tracked by an underactuated AUV. Finally, the efficiency of the constructed control mechanism is confirmed by simulation results.

Jie Gao, Yonghua Zhai, Weihong Lu et al.

In the field of cancer therapy, inhibiting autophagy has emerged as a promising strategy. However, pharmacological disruption of autophagy can lead to the upregulation of programmed death-ligand 1 (PD-L1), enabling tumor immune evasion. To address this issue, we developed innovative ROS-responsive cationic poly(ethylene imine) (PEI) nanogels using selenol chemistry-mediated multicomponent reaction (MCR) technology. This procedure involved simple mixing of low-molecular-weight PEI (LMW PEI), γ-selenobutylacetone (γ-SBL), and poly(ethylene glycol) methacrylate (PEGMA). Through high-throughput screening, we constructed a library of AxSeyOz nanogels and identified the optimized A1.8Se3O0.5/siPD-L1 nanogels, which exhibited a size of approximately 200 nm, excellent colloidal stability, and the most effective PD-L1 silencing efficacy. These nanogels demonstrated enhanced uptake by tumor cells, excellent oxidative degradation ability, and inhibited autophagy by alkalinizing lysosomes. The A1.8Se3O0.5/siPD-L1 nanogels significantly downregulated PD-L1 expression and increased the expression of major histocompatibility complex class I (MHC-I), resulting in robust proliferation of specific CD8+ T cells and a decrease in MC38 tumor growth. As a result, the A1.8Se3O0.5/siPD-L1 nanogels inhibited tumor growth through self-inhibition of autophagy, upregulation of MHC-I, and downregulation of PD-L1. Designed with dynamic diselenide bonds, the A1.8Se3O0.5/siPD-L1 nanogels showed synergistic antitumor efficacy through self-inhibition of autophagy and prevention of immune escape.

Vishal Goyal, Chaitanya K Varma, Mahesh Behera et al.

Introduction: The hazard of smoking is not only limited to the general health risks but also makes the smokers more vulnerable to various perioperative complications ranging from pulmonary complications to delayed wound healing to cardiovascular events. Methodology: This is an observational study in the department of general surgery of a tertiary care teaching hospital over a period of 24 months (May 2019–April 2021). Patients between 18- and 60-year age undergoing noncardiac elective surgical procedures were included in the study. Results: A total of 240 patients, meeting the inclusion criteria, posted for elective, noncardiac surgery were enrolled in this prospective observational study. In smoker patients’ group (n = 138) undergoing surgery, 42 (30.4%) patients developed postoperative complications as compared to 12 (11.8%) patients in nonsmoker group (n = 102). The risk of postoperative complications among smokers was 3.2 times (odds ratio [OR], 95% confidence interval [CI]: 1.62–6.63) (P ≤ 0.0009). Smokers with pack-years > 11 had 3.8 times increased risk of postoperative complications as compared to nonsmokers (OR, 95% CI: 1.85–8.098) (P ≤ 0.0003). Conclusion: Our study aims to add to existing evidence and improve our understanding of delayed wound healing and major complications in smoker patients as surgical cases. Nonsmokers are at a lesser risk than smokers in postoperative complications. Awareness regarding the harmful effects of smoking and its influence on postoperative wound healing, motivation for quitting, and abstinence from smoking will help in reducing postoperative complications and better treatment outcomes.

Giovanni Lavezzi, Kidus Guye, Venanzio Cichella et al.

In this paper, we propose a set of guidelines to select a solver for the solution of nonlinear programming problems. We conduct a comparative analysis of the convergence performances of commonly used solvers for both unconstrained and constrained nonlinear programming problems. The comparison metrics involve accuracy, convergence rate, and computational time. MATLAB is chosen as the implementation platform due to its widespread adoption in academia and industry. Our study includes solvers which are either freely available or require a license, or are extensively documented in the literature. Moreover, we differentiate solvers if they allow the selection of different optimal search methods. We assess the performance of 24 algorithms on a set of 60 benchmark problems. We also evaluate the capability of each solver to tackle two large-scale UAV optimal path planning scenarios, specifically the 3D minimum time problem for UAV landing and the 3D minimum time problem for UAV formation flying. To enrich our analysis, we discuss the effects of each solver’s inner settings on accuracy, convergence rate, and computational time.

Tuja Khaund, Baris Kirdemir, Nitin Agarwal et al.

Yang Song, Jingtao Jia, Haibin Liu et al.

Many coastal bridges have been destroyed or damaged by tsunami waves. Some studies have been conducted to investigate wave impact on bridge decks, but there is little concerning the effect of bridge superelevation. A three-dimensional (3D) dam break wave model based on OpenFOAM was developed to study tsunami-like wave impacts on bridge decks with superelevation. The Reynolds-averaged Navier–Stokes equations and the k-ɛ turbulence model were used. The numerical model was satisfactorily checked against Stoker’s analytical solution and the published hydrodynamic experiment. The validated model was employed to carry out parametric analyses to investigate the effects of upstream and downstream water depths and the bridge deck’s superelevation. The results show that the tsunami force is proportional to the relative wave height. The dam break wave impact on the bridge deck can be identified as two distinct scenarios according to whether the wave height is higher than the bridge deck top. The trend of the tsunami force is also different in different scenarios. The superelevation will significantly influence the tsunami forces acting on the box girder, with some exceptions.

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.

Pengwei Hu, Ying Cui, Chenyu Zhao et al.

Due to the interference between the main hull and the outrigger of the pentamaran, resistance is greatly affected. Therefore, research on the pentamaran front outrigger inclination angle has further practical significance for reducing resistance. In this study, the pentamaran front outrigger inclination angle was analyzed by CFD method, the ship motion in waves was simulated by overlapping grid technology, and the resistance of the pentamaran in static water and waves was predicted by using the unsteady RANS equation. First, a series of validation studies were carried out for the numerical methods used in the study. Then, the influence of the front outrigger inclination angle on the pentamaran resistance performance under different working conditions is calculated and discussed. In order to analyze the influence of the change of the front outrigger inclination angle on the resistance, free surface wave-making and hull pressure are further discussed. The results show that the influence of the front outrigger inclination angle change on the resistance of the pentamaran has a certain rule, and the resistance of the pentamaran can be reduced by adjusting the front outrigger inclination angle.

Angelo Salatino, Simone Angioni, Francesco Osborne et al.

Understanding the relationship between the composition of a research team and the potential impact of their research papers is crucial as it can steer the development of new science policies for improving the research enterprise. Numerous studies assess how the characteristics and diversity of research teams can influence their performance across several dimensions: ethnicity, internationality, size, and others. In this paper, we explore the impact of diversity in terms of the authors' expertise. To this purpose, we retrieved 114K papers in the field of Computer Science and analysed how the diversity of research fields within a research team relates to the number of citations their papers received in the upcoming 5 years. The results show that two different metrics we defined, reflecting the diversity of expertise, are significantly associated with the number of citations. This suggests that, at least in Computer Science, diversity of expertise is key to scientific impact.

Jan-Christoph Klie, Ji-Ung Lee, Kevin Stowe et al.

Many Natural Language Processing (NLP) systems use annotated corpora for training and evaluation. However, labeled data is often costly to obtain and scaling annotation projects is difficult, which is why annotation tasks are often outsourced to paid crowdworkers. Citizen Science is an alternative to crowdsourcing that is relatively unexplored in the context of NLP. To investigate whether and how well Citizen Science can be applied in this setting, we conduct an exploratory study into engaging different groups of volunteers in Citizen Science for NLP by re-annotating parts of a pre-existing crowdsourced dataset. Our results show that this can yield high-quality annotations and attract motivated volunteers, but also requires considering factors such as scalability, participation over time, and legal and ethical issues. We summarize lessons learned in the form of guidelines and provide our code and data to aid future work on Citizen Science.

Stephen M. Pompea, Pedro Russo

Big science projects and facilities can move towards a less self-centered frame of reference as they strive to better identify and serve educational audiences. By doing this, their science education efforts will be more productive in general, and their service to local schools will be more effective. By developing an enlarged awareness of local educational needs, they will become better stewards and partners in their roles in the science education system. They will also become more valued and trustworthy neighbours to their local and cultural communities. We propose a practical way for large science organisations to organise their budgets and their allocation of staff time to greatly increase the effectiveness of their organisation in its contribution to local science education.