Search Results (21)

This study presents a data-driven methodology to optimize the operational efficiency of a tugboat equipped with a Voith-Schneider Propeller (VSP) based on full-scale fuel consumption and vessel performance data. The objective is to identify optimal combinations of engine RPM and propeller pitch to reduce fuel consumption during low-demand phases without compromising maneuverability. Sea trials were conducted under controlled conditions using a dual flowmeter system and onboard speed measurements. The data enabled the construction of performance curves, efficiency ratios, and interpolated maps of fuel consumption. Optimal configurations were identified across defined speed ranges, and continuous efficiency zones were visualized through iso-consumption and contour plots. The results reveal a nonlinear relationship between propeller pitch, speed, and fuel demand, with maximum efficiency occurring at medium-to-high pitch values and speeds between 3 and 6 knots. This methodology provides a replicable tool for energy management in port operations and supports informed decisions during accompanying operations and standby periods. Efficiency differences over 300% between RPM–pitch settings were found, highlighting the operational impact of informed configuration choices. Moreover, the structured dataset and visual analysis framework lay the groundwork for future digital twin models aimed at enhancing operational efficiency in VSP-powered tugboats. Full article

Fast patrol boats account for a large number among the numerous vessels used in naval fleets. Owing to their operational characteristics, which involve relatively high speeds, they contribute to emissions significantly. This study presents an optimized design concept for a diesel–battery hybrid electric propulsion system integrated into the general ship design process for fast patrol boats. The optimization design uses mixed-integer linear programming to determine the most eco-friendly shares ratio of battery and diesel usage while satisfying high-endurance operational scenarios. A shares ratio of 1.259 tons of diesel to 2.88 tons of batteries was identified as the most eco-friendly configuration capable of meeting a 200-nautical-mile operational scenario at a maximum speed of 35 knots for the selected case study. A quantitative comparison through a global warming potential (GWP) analysis was conducted between conventional diesel propulsion systems and the designed diesel–battery hybrid electric propulsion system, using a life-cycle assessment (LCA) standardized under the ISO framework. The analysis confirmed that the optimized hybrid propulsion system can achieve a GWP reduction of approximately 7–9% compared with conventional propulsion systems. Few studies have applied LCA in this field, and the application of batteries as hybrid secondary energy sources is viable and sustainable for high-endurance 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

An origami-based tactile sensory ring utilizing multilayered conductive paper substrates presents an innovative approach to wearable health applications. By harnessing paper’s flexibility and employing origami folding, the sensors integrate structural stability and self-packaging without added encapsulation layers. Knot-shaped designs create loop-based systems that secure conductive paper strips and protect sensing layers. Demonstrating a sensitivity of 3.8 kPa⁻¹ at subtle pressures (0–0.05 kPa), the sensors detect both minimal stimuli and high-pressure inputs. Electrical modeling of various origami configurations identifies designs with optimized performance with a pentagon knot offering higher sensitivity to support high-sensitivity needs. Meanwhile a square knot provides greater precision and quicker recovery, balancing sensitivity and stability for real-time feedback devices. The enhanced elastic modulus from folds remains within human skin’s elasticity range, ensuring comfort. Applications include grip strength monitoring and pulse rate detection from the thumb, capturing pulse transit time (PTT), an essential cardiovascular biomarker. This design shows the potential of origami-based tactile sensors in creating versatile, cost-effective wearable health monitoring systems. Full article

The knotter, as a core module for the knotting function of a rice electric binder, has structural parameters and spatial configurations that significantly impact the efficiency and quality of rice collection, making the in-depth analysis and optimization of these parameters, and their spatial relationships, crucial for enhancing the operational quality of the rice electric binder. At present, rice binders still face the issues of a low bundling efficiency and quality, which affect the progress of rice harvesting during the harvest season. Through theoretical analysis and calculation, this study determined the main parameters affecting the knotter’s knotting process and their value ranges. Based on the ADAMS software, a simulation model of the knotter operation was constructed. Using the Box–Behnken design (BBD) method and response surface analysis of variance, a regression prediction model for knotter operation evaluation indicators was established, and the multi-objective optimization of the knotter’s operation quality was performed. The prediction results showed that, under the optimal structural parameter combination of a 30.23° angle between the knotting pincer and rope guard axes, a −3.75 mm rope clamping board position, and a 40.75° inclination angle of the knotting pincer convex platform, the knotter’s knotting quality reached the best state, with an average knot end protrusion of 9.10 mm and a maximum tension of 134.25 N on the knotting rope. The field tests results showed an average knot end protrusion of 9.60 mm and a maximum tension of 127.87 N on the knotting rope, with average relative errors of 5.82% and 4.72% compared to the theoretical values, respectively. After optimizing the knotter, the average knot end protrusion increased by 14.48% and the maximum tension of the knot rope was reduced by 11.27%. Meanwhile, the knotter achieved an average bundling rate as high as 99.3%. The bundling success rate also increased by 2.7%. These results fully verify the reliability and accuracy of the regression model, and demonstrate the reasonableness of the knotter structural parameter optimization design, providing a theoretical basis and reference for improving the operational quality of the rice electric binder. Full article

The geometric shape, symmetry, and topology of colloidal particles often allow for controlling colloidal phase behavior and physical properties of these soft matter systems. In liquid crystalline dispersions, colloidal particles with low symmetry and nontrivial topology of surface confinement are of particular interest, including surfaces shaped as handlebodies, spirals, knots, multi-component links, and so on. These types of colloidal surfaces induce topologically nontrivial three-dimensional director field configurations and topological defects. Director switching by electric fields, laser tweezing of defects, and local photo-thermal melting of the liquid crystal host medium promote transformations among many stable and metastable particle-induced director configurations that can be revealed by means of direct label-free three-dimensional nonlinear optical imaging. The interplay between topologies of colloidal surfaces, director fields, and defects is found to show a number of unexpected features, such as knotting and linking of line defects, often uniquely arising from the nonpolar nature of the nematic director field. This review article highlights fascinating examples of new physical behavior arising from the interplay of nematic molecular order and both chiral symmetry and topology of colloidal inclusions within the nematic host. Furthermore, the article concludes with a brief discussion of how these findings may lay the groundwork for new types of topology-dictated self-assembly in soft condensed matter leading to novel mesostructured composite materials, as well as for experimental insights into the pure-math aspects of low-dimensional topology. Full article

This present study investigates the effect of blade tip configurations, such as the sweepback angle and anhedral angle, on the performance and hub vibratory loads for the lift-offset coaxial rotor of a 30,000-pound-class high-speed long-range utility helicopter. The rotorcraft comprehensive analysis code, CAMRAD II, is utilized to conduct the performance and hub vibratory load analyses for the present lift-offset coaxial rotor. The total rotor thrust, torque, and individual rotor’s hub pitch moment and hub roll moment are considered the trim targets. The general properties for the lift-offset coaxial rotor are designed from the X2TD, S-97 Raider, and SB > 1 Defiant, which are lift-offset compound helicopters. The rotor performance and hub vibratory loads are studied with the various blade tip configurations including the sweepback angle and anhedral angle. The rotor power when the rotor blade tip considers only the sweepback angle (20°) is lower than the baseline rotor model by 41.25% at 170 knots. The maximum rotor effective lift-to-drag ratio (L/D_e) for the lift-offset coaxial rotor using only the sweepback angle and the rotor with both sweepback (20°) and anhedral angles (10°) at 170 knots increase by 10.82% and 5.02%, respectively, compared with the baseline rotor model without both sweepback and anhedral angles. The vibration index (VI) for the rotor with only the sweepback angle is higher than that for the baseline rotor model without both sweepback and anhedral angles by 37.14%. Furthermore, when the rotor blade tip has the anhedral angle, the magnitude of the Blade Vortex Interaction (BVI) decreases compared with the rotor without the sweepback and anhedral angles. Full article

Currently, researching the Yang–Baxter equation (YBE) is a subject of great interest among scientists of diverse areas in mathematics and other sciences. One of the fundamental open problems is to find all of its solutions. The investigation deals with developing theories such as knot theory, Hopf algebras, quandles, Lie and Jordan (super) algebras, and quantum computing. One of the most successful techniques to obtain solutions of the YBE was given by Rump, who introduced an algebraic structure called the brace, which allows giving non-degenerate involutive set-theoretical solutions. This paper introduces Brauer configuration algebras, which, after appropriate specializations, give rise to braces associated with Thompson’s group F. The dimensions of these algebras and their centers are also given. Full article

The topic of reducing exhaust gas emissions from internal combustion engines in the areas of port and coastal waters is in line with the assumptions of the climate policy. The publication presents a proposal to reduce the energy associated with the movement of port vessels through the use of a specific pattern (shape and size) of their movement. In addition to controlling the formation of tugboats, the authors propose the use of a multi-agent system offering elements of autonomous control of the vessels, which adjusts the parameters of the formation depending on the tasks performed. The results of tests for four tugboats with a hull length of 32 m and a maximum speed of 13 knots, moving in formations of eight different configurations, were analyzed. Studies conducted on the basis of a simulated exit and return to port scenario at a distance of 11.4 nm showed the possibility of reducing energy consumption required for movement by 5.8% to even 57.6% for tugboats moving one after another, at a certain distance. In addition, in order to completely eliminate exhaust gas emissions from the engines, it is proposed to use tugboats with electric drive together with an appropriate energy storage charging infrastructure. Full article

Taking a DNA sequence, a word with letters/bases A, T, G and C, as the relation between the generators of an infinite group $\pi$, one can discriminate between two important families: (i) the cardinality structure for conjugacy classes of subgroups of $\pi$ is that of a free group on one to four bases, and the DNA word, viewed as a substitution sequence, is aperiodic; (ii) the cardinality structure for conjugacy classes of subgroups of $\pi$ is not that of a free group, the sequence is generally not aperiodic and topological properties of $\pi$ have to be determined differently. The two cases rely on DNA conformations such as A-DNA, B-DNA, Z-DNA, G-quadruplexes, etc. We found a few salient results: Z-DNA, when involved in transcription, replication and regulation in a healthy situation, implies (i). The sequence of telomeric repeats comprising three distinct bases most of the time satisfies (i). For two-base sequences in the free case (i) or non-free case (ii), the topology of $\pi$ may be found in terms of the $SL(2,\mathbb{C})$ character variety of $\pi$ and the attached algebraic surfaces. The linking of two unknotted curves—the Hopf link—may occur in the topology of $\pi$ in cases of biological importance, in telomeres, G-quadruplexes, hairpins and junctions, a feature that we already found in the context of models of topological quantum computing. For three- and four-base sequences, other knotting configurations are noticed and a building block of the topology is the four-punctured sphere. Our methods have the potential to discriminate between potential diseases associated to the sequences. Full article

The success of surgical procedures is strictly related to the biomechanical properties of the suture. Mechanical comparisons are scarcely reported in the literature, so the purpose of the present study was to evaluate and compare the mechanical behavior of different sutures commonly used in oral surgery in terms of traction resistance. Sutures made of eight different materials were analyzed: silk (S), polyglycolide-co-caprolactone (PGCL), polypropylene (PP), rapid polyglycolide (rPGA), standard polyglycolide (PGA), polyamide (PA), polyester (PE), and polyvinylidene fluoride (PVDF). For each material, three different sizes were tested: 3-0, 4-0, and 5-0. The breaking force of each suture was assessed with a uniaxial testing machine after being immersed in artificial saliva at 37 °C. The outcomes analyzed were the breaking force, the needle–thread detachment breaking-point and the node response after forward–reverse–forward (FRF) tying when subjected to a tensile force. The 3-0 rPGA provided the maximum resistance, while the lowest value was recorded for the 5-0 PGCL. In general, 3-0 and 4-0 gauges showed non-statistically significant differences in terms of needle–thread detachment. The highest needle–thread detachment was found for the 3-0 PGA, whereas the lowest value was observed for the 5-0 PGCL. After tying the knot with an FRF configuration, the thread that showed the highest resistance to tension was the 3/0 silk, while the thread with the lowest resistance was the 5/0 silk. These data should be considered so that the operator is aware of as many aspects as possible on the behavior of various materials to ensure successful healing. Full article

Liquid crystal (LC) micro-droplet arrays are elegant systems that have a range of applications, such as chemical and biological sensing, due to a sensitivity to changes in surface properties and strong optical activity. In this work, we utilize self-assembled monolayers (SAMs) to chemically micro-pattern surfaces with preferred regions for LC occupation. Exploiting discontinuous dewetting, dragging a drop of fluid over the patterned surfaces demonstrates a novel, high-yield method of confining LC in chemically defined regions. The broad applicability of this method is demonstrated by varying the size and LC phase of the droplets. Although the optical textures of the droplets are dictated by topological constraints, the additional SAM interface is shown to lock in inhomogeneous alignment. The surface effects are highly dependent on size, where larger droplets exhibit asymmetric director configurations in nematic droplets and highly knotted structures in cholesteric droplets. Full article

This article describes the results of modeling and analysis of a generic internal cargo system using a discretization method of the vector mechanics. The model can be easily incorporated into a tandem helicopter model and is intended for use of simulation and investigating the problems of flight dynamics, control, etc., both in flight operation loading a cargo and flight operation in the process of airdrops. The model is derived by considering the main descriptions of the cargo, including the linear and rotational dynamics, the kinematics, and the forces and moments acting on the helicopter. A simulation method embedded with a numerical trim algorithm is developed for the complete coupling helicopter/cargo nonlinear dynamics system. The simulation application of the model is illustrated, including the case of flight operation loading a cargo by considering three mass configurations of 3000, 4500, and 6000 kg, and the case of flight operation in the process of airdrops at velocities of 0, 40, 80, 120, and 160 knots. Stabilities of the helicopter in the process of airdrops are also analyzed. The major conclusions drawn are: (i) the tandem helicopter has a good attitude maintaining ability in the whole flight velocity envelope when it conducts a flight operation loading a cargo; (ii) in the process of airdrops, the increase in flight velocity will constantly decrease the helicopter pitching attitude and increases the total airdrop time and decreases the backward moving velocity of the cargo, and helicopter flying at a velocity between 80 and 120 knots might be acceptable; (iii) the stabilities of both the longitudinal and lateral periodic modes are continuing to decrease during the backward movement of the cargo. Full article

The conservation of ancient structures is, in the construction panorama, a highly eco-sustainable operation. In fact, it provides for a very limited consumption of resources. This article provides an in-depth analysis of ancient wooden material, an essential element for drawing up correct conservation interventions. Ancient timber beams have a peculiar morphology of failure dependent on many factors, among which are the species of wood, the quality of the material-knots, presence of fissures caused by shrinkage (checks), direction of the grain, and environmental conditions such as temperature and humidity. In addition, it is linked to load conditions and static configuration. This paper presents a case study of failed ancient timber members still in place and describes the type of failure as well as the origin and propagation of the cracks. The objective is to provide a classification of the causes and of the effects and their evolution, useful to practitioners and to those who have to make decisions on the timber structures conservation. Full article

The Tibellus oblongus spider is an active predator that does not spin webs and remains poorly investigated in terms of venom composition. Here, we present a new toxin, named Tbo-IT2, predicted by cDNA analysis of venom glands transcriptome. The presence of Tbo-IT2 in the venom was confirmed by proteomic analyses using the LC-MS and MS/MS techniques. The distinctive features of Tbo-IT2 are the low similarity of primary structure with known animal toxins and the unusual motif of 10 cysteine residues distribution. Recombinant Tbo-IT2 (rTbo-IT2), produced in E. coli using the thioredoxin fusion protein strategy, was structurally and functionally studied. rTbo-IT2 showed insecticidal activity on larvae of the housefly Musca domestica (LD₁₀₀ 200 μg/g) and no activity on the panel of expressed neuronal receptors and ion channels. The spatial structure of the peptide was determined in a water solution by NMR spectroscopy. The Tbo-IT2 structure is a new example of evolutionary adaptation of a well-known inhibitor cystine knot (ICK) fold to 5 disulfide bonds configuration, which determines additional conformational stability and gives opportunities for insectotoxicity and probably some other interesting features. Full article