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Position-dependent hydrodynamic response of moored container ship under rogue waves
No full textThis paper employs the high-order-spectral-computational fluid dynamics (HOS-CFD) method to analyze the motion responses of a moored container ship at three positions in a rogue wave: before, at, and after its maximum wave height. These three positions display during the nonlinear evolution of the rogue wave. Numerical results are validated against physical wave tank experiments, where the rogue wave is accurately reproduced using the HOS method. The numerical results of position-dependent hydrodynamic responses in the rogue wave show that the maximum heave and surge motions do not occur at the location of maximum wave height. The heave motion peak appears before the location, the surge motion peak happens afterward and the pitch motion peak is at the location. Wavelet transform analysis is adopted to explain this situation. Scattering wave field analyses are carried out to show the different scattering wave types around the ship during the evolution of the rogue wave
Creating spanning trees in waiter-client games
No full textFor a positive integer n and a tree Tn on n vertices, we consider an unbiased Waiter-Client game WC(n, Tn) played on the complete graph Kn, in which Waiter’s goal is to force Client to build a copy of Tn. We prove that for every constant c < 1/3, if ∆(Tn) ≤ cn and n is sufficiently large, then Waiter has a winning strategy in WC(n, Tn). On the other hand, we show that there exist a positive constant c′ < 1/2 and a family of trees Tn with ∆(Tn) ≤ c′n such that Client has a winning strategy in the WC(n, Tn) game for every n sufficiently large. We also consider the corresponding problem in the Client-Waiter version of the game
Reconstructing beam bending strength of arctic second year ice from small disk bending tests
No full textThe flexural strength of ice is one of the most significant strength parameters for the design of ships and marine structures in ice. By an unwritten convention the flexural strength refers to beam bending tests in ice. For this engineering formulas are derived that support engineering design. However, both climate and engineering fields are changing and ice properties still need to be assessed by in-situ measurements. Beam bending tests in full-scale, i.e. nature, are laborious and require both significant time and equipment. In the light of this an alternative method based on thin disk bending tests gained from drilled standard ice cores is presented. The method of testing small disks is introduced in the late 1960ies and has gained little attention in the community. The method presented utilizes tested disk samples throughout the entire ice thickness in order to assess the distribution of properties, while using this information reconstructing the global behavior of an ice cantilever beam in flexure. A numerical model of a virtual cantilever ice beam experiment is built from which the reference flexural strength of a cantilever beam is derived. The determined flexural strength is reduced by a stress concentration factor accounting for the notch effect in the beam-root transition. This stress concentration factor is determined numerically for different ratios of radius and beam width. Finally, the obtained strength value is scaled accounting for the increase of flaws in larger ice specimens. The approach is compared with literature data and evaluated in terms of its validity and robustness. The method also indicates the problem of missing standards for flexural strength determination
Aircraft load estimation using linear parameter-varying system-based hybrid observers
No full textThe hybrid loads observer has demonstrated its precision in estimating structural loads and wind disturbances in prior applications. This level of precision is attained by combining a high-fidelity physical, nonlinear flight dynamics model with a data-driven correction model. To mitigate the typically high computational effort, the nonlinear model is substituted in this work with a linear parameter-varying (LPV) system. Therefore, the nonlinear model is approximated by scheduled Linear Time-Invariant models derived from Jacobian linearization. The robustness of this novel approach against parameter uncertainties is evaluated through simulated flight test studies using a subscale test aircraft as an example. It is demonstrated that increased model uncertainties lead to wind estimation accuracy reduction. Additionally, increased parameter uncertainties adversely affect the accuracy of structural load estimation within the model-based (physical) part of the observer. Nonetheless, this loss of accuracy can be compensated by the correction model, leading to the typical high load estimation accuracy of the hybrid loads observer. Finally, experimental data from wind-tunnel tests, utilizing a 1-degree-of-freedom representative test wing, confirms the high estimation accuracy of the LPV-based hybrid loads observer. Despite employing low-fidelity models, achieving high accuracy is feasible while maintaining the characteristic low complexity of the correction model
Augmented reality authoring for efficient inspections in green aviation: evaluating accuracy and usability
No full textThis paper addresses the gap in AR-guided inspection by developing and evaluating an AR authoring tool tailored for green aviation. The tool aims to overcome the current limitations by assisting the inspector in the data acquisition process using hand-held sensors. The study introduces a sensor guidance prototype applicable to various inspection scenarios prone to human error. Usability assessments reveal positive feedback on real-time guidance and an intuitive interface, though challenges in tracking accuracy and managing complex trajectories are identified, particularly with the Microsoft HoloLens 2. Testing on the Magic Leap 2 (ML2) showed sufficient position accuracy of 1.39 mm, suitable for mobile authoring and tracking of trajectories. While results are promising, further optimization in tracking, user interface (UI), and real-world validation is needed
A mobile robotic approach to autonomous surface scanning in legal medicine
No full textPurpose : Comprehensive legal medicine documentation includes internal and external examination of the corpse. Typically, this documentation is conducted manually during conventional autopsy. Systematic digital documentation would be desirable, especially for external wound examination, which is becoming more relevant for legal medicine analysis. For this purpose, RGB surface scanning has been introduced. While manual full-surface scanning using a handheld camera is time-consuming and operator-dependent, floor or ceiling-mounted robotic systems require specialized rooms. Hence, we consider whether a mobile robotic system can be used for external documentation. Methods : We develop a mobile robotic system that enables full-body RGB-D surface scanning. Our work includes a detailed configuration space analysis to identify the environmental parameters that must be considered for a successful surface scan. We validate our findings through an experimental study in the lab and demonstrate the systems application in legal medicine. Results : Our configuration space analysis shows that a good trade-off between coverage and time is reached with three robot base positions, leading to a coverage of 94.96 %. Experiments validate the effectiveness of the system in accurately capturing body surface geometry with an average surface coverage of 96.90±3.16 % and 92.45±1.43 % for a body phantom and actual corpses, respectively. Conclusion : This work demonstrates the potential of a mobile robotic system to automate RGB-D surface scanning in legal medicine, complementing post-mortem CT scans for inner documentation. Our results indicate that the proposed system can contribute to more efficient, autonomous legal medicine documentation, reducing the need for manual intervention
Next-generation pervaporation-assisted distillation: Recent advances in process intensification
No full textPervaporation is a well-established membrane separation process that effectively overcomes limitations of distillation due to azeotropes and distillation boundaries. The selective mass transfer of pervaporation membranes has enabled successful implementation in a variety of industries, with applications in the chemical industry, as well as the food and pharma industry, including membrane bioreactors in fermentation processes. Yet, the majority of applications in separation processes remain focused on the dehydration of aqueous-organic process streams, including biofuel and bioethanol production. Pervaporation-assisted distillation processes leverage the benefits of both technologies and exploit the resulting synergies to provide energy and cost-efficient separations, especially for azeotropic mixtures, which otherwise require rather energy intensive distillation processes, such as pressure-swing, extractive or hetero-azeotropic distillation. The current review provides an overview of recent developments that enable further process intensification of pervaporation-assisted distillation processes and provides some perspective on emerging trends that may result in a wider application of these interesting hybrid separation processes
Molecular mobility and electrical conductivity of amino acid-based (DOPA) ionic liquid crystals in the bulk state and nanoconfinement
No full textThis study explores the molecular mobility, phase behavior, and electrical conductivity of dihydroxyphenylalanine-based ionic liquid crystals (DOPAn, with alkyl side chains n = 12, 14, 16) featuring cyclic guanidiniumchloride headgroups, in both bulk and nanoconfined states. Using broadband dielectric spectroscopy, differential scanning calorimetry, and fast scanning calorimetry, the research uncovers a complex interplay between molecular structure, self-assembly, and molecular mobility. In bulk, DOPAn shows a phase sequence from plastic crystalline to hexagonal columnar and isotropic phases, driven by superdisc formation and columnar organization. Multiple relaxation processes are identified: localized side-chain dynamics (γ-relaxation), ionic headgroup or core motions (α1-relaxation), and cooperative alkyl domain fluctuations (α2-relaxation). Conductivity decreases with increasing side chain length. Under nanoconfinement in anodic aluminum oxide membranes, phase behavior changes: the Colh-Iso transition is suppressed, and a new α3-relaxation appears, linked to dynamics in an adsorbed interfacial layer. DC conductivity drops by up to four orders of magnitude due to confinement effects, altered molecular orientation, and phase transitions—especially the emergence of a nematic-like state in DOPA16. These findings highlight the importance of molecular design, pore geometry, and surface chemistry in tuning ionic liquid crystal properties for advanced applications in nanofluidics, ion transport, and responsive materials.Deutsche Forschungsgemeinschaft (DFG
Transition-metal azo Schiff base complexes: nonlinear optics across solutions, thin films and nanocomposites
No full textThis paper investigates the nonlinear optical (NLO) properties of azo-based Schiff base ligand and its corresponding complexes incorporating Cu(II) and Zn(II) metal cations, designed upon the previous synthesis work. Both 2nd and 3rd order NLO properties are examined, with a particular focus on their potential for optoelectronic and photonic applications. The Z-scan technique is employed to analyze NLO refraction and NLO absorption in solution. All samples exhibit positive NLO phenomena, with Zn(L)2 showing the highest values ((3) = 27.95 × 10−22 m2 V−2, = 54.44 × 10−47 m5 V−2), attributed to enhanced ligand-to-metal charge transfer (LMCT). Additionally, thin films deposited via the spin coating method undergo 3rd order NLO analysis through the Maker fringe technique. THG analysis further confirms superior 3rd order NLO performance in Zn(L)2, exceeding several benchmark transition-metal complexes.
2nd order NLO properties are also explored in hybrid nanocomposites designed from Zn(L)2 embedded in nanoporous pSiO2 membrane. This structure exhibits anisotropic SHG behavior, with
(2) = 0.11 pm V−1 under s-p polarization, suggesting polarization confinement within nanochannels. The results clearly demonstrate that transition-metal azo Schiff base complexes, particularly
Zn(L)2, exhibit strong NLO responses, positioning them as potential candidates for applications in all-optical switching and frequency conversion
Estimation of water heat flux in small reservoirs: the role of neural networks and regression techniques
No full textWater heat flux (WHF), which represents the heat stored or lost within a water body, plays a crucial role in analysing the surface energy balance at the water reservoirs. However, estimating WHF is often challenging due to the need for detailed vertical temperature profiles. This study evaluates the performance of artificial neural networks (ANNs) and regression modelling as alternative approaches for estimating WHF in the Ekbatan dam reservoir, a small-scale reservoir in Iran. Using water temperature data collected at various depths from Sep 26, 2018, to Sep 22, 2021, reference WHF values are calculated based on its fundamental equation. A multilayer perceptron (MLP) model is developed, featuring an input layer consisting of five variables (air temperature, water surface temperature, solar radiation, wind speed, and relative humidity) and two hidden layers. Additionally, a nonlinear regression model is formulated using dimensionless parameters. The MLP and nonlinear regression models’ results are compared with the reference WHF values. The MLP model shows strong performance, achieving a coefficient of determination (R2) of 0.968 and an RMSE of 18.88Wm-2, with water surface and air temperatures identified as the most influential predictors. The regression model also performed reliably, yielding an R2 value above 0.879 and an RMSE of less than 30.08Wm-2. While the regression model provides reliable results, artificial neural networks offer greater accuracy in WHF estimation, underscoring their potential for enhancing energy balance assessments in water reservoi