Search Results (405)

Military activities remain insufficiently represented in greenhouse gas (GHG) accounting and debates on climate security. This article develops a system-based model for assessing direct operational GHG emissions from artillery training. The model adapts established inventory logic to the structure of an artillery battery and separates emissions from mobility, stationary operation, support and logistics, and a supplementary firing-process module. It is demonstrated using a single hypothetical standardized training scenario for a battery of self-propelled howitzers, based on assumed and estimated parameters rather than field measurements. Under the stated assumptions, the training day generated an estimated 4353.74 kg carbon dioxide equivalent (CO₂e). Operational fuel combustion accounted for 93.94% of the total, and the supplementary firing-process proxy accounted for 6.06%; stationary engine operation of the howitzers in firing positions was the dominant source (73.87%). Within the defined gate-to-activity boundary, the scenario’s direct operational carbon footprint was therefore driven primarily by energy demand rather than projectile discharge. The article’s contribution is an artillery-specific, transparent decomposition of established GHG accounting principles, not a new emission-factor method. The model provides a transferable structure for tactical-level assessment, while the numerical results are scenario-specific and require validation against measured data and additional operational scenarios. Full article

The human placenta is a temporary organ structured to optimize exchange between the maternal and fetal circulatory systems. Its fetal component consists of highly branched chorionic villi, which are anchored to the maternal uterine wall and project into the intervillous space. The outer surface of these villi is lined by a multinucleated, continuous layer called the syncytiotrophoblast, which is supported by an underlying layer of proliferative cytotrophoblast cells and the invasive extravillous trophoblast (EVT). This cellular bilayer forms a selective barrier that directly bathes in maternal blood, allowing for the efficient transfer of oxygen and nutrients while structurally preventing the direct mixing of maternal and fetal blood cells. Human placental studies have been stymied by ethical and accessibility constraints. Stem cell biology has now revolutionized the capacity to model human placental development, in particular with the derivation of human trophoblast stem cells (hTSCs) and organoids. Authentic, self-renewing human trophoblast stem cells (hTSCs) were first derived not from pluripotent stem cells but from primary tissue—first-trimester villous cytotrophoblasts and blastocysts. Derivation from human pluripotent stem cells (PSCs) followed only subsequently, along two principal routes: conversion of naive PSCs, which retain extraembryonic competence, and induction from primed PSCs, as well as by direct reprogramming of somatic cells to induced hTSCs. An important advance underlying these improvements is the mapping of a global reprogramming roadmap. Multi-omic and lineage-tracing experiments have mapped the stepwise transcriptional and epigenetic conversions of fibroblasts to hTSCs, including sequential chromatin reconfiguration, trophoblast gene network activation, and repression of somatic signatures. These results identify major regulatory bottlenecks and intermediate states, improving reprogramming fidelity. The derivation of stem-cell-based trophoblast organoids now enables complex modeling of placental architecture, function, and disease susceptibility in vitro. These organoids accurately recapitulate placental barrier functions and immunological features, allowing for examinations of maternal–fetal health, pregnancy disorders, and placental infection response to viruses like cytomegalovirus and SARS-CoV-2. Looking ahead, the integration of reprogramming and organoid technologies will propel patient-specific and tailor-made models for personalized diagnostics, drug screening, and mechanism studies. As we unravel the molecular ballet of trophoblast induction, such discoveries have the potential to bridge basic translational gaps in reproductive biology and maternal–fetal medicine. Full article

In the space sector, test benches are facilities used to perform ground testing of rocket engines with solid, liquid, or hybrid propellants. These tests typically occur during the stages of development, validation, qualification, certification, and acceptance of the rocket engine assembly. Due to the periodicity and complexity related to these stages, it may be necessary to carry out several test campaigns in order to obtain the expected results. This requires skill and knowledge from the technical team involved, since the occurrence of operational nonconformities in actuator components installed in this test bench constitutes a situation with sufficient potential to put human lives at risk and/or cause material losses. In this context, this work presents a proposal for a Graphical User Interface to be integrated into the architecture of a system that performs the operational self-testing of these actuators. The virtual resources established for the windows of the Graphical User Interface are expressive and are related to the procedures defined to perform the self-testing of actuator activation, steady-state operation, and shutdown. The validation of the functionality of this Graphical User Interface is obtained through tests carried out on a prototype that was developed considering the main blocks contained in the mentioned system architecture. The satisfactory results observed in these tests suggest that the Graphical User Interface is suitable for the purpose for which it is intended. Full article

Self-propelled liquid droplets floating on water–air interfaces can exhibit dynamics far richer than steady translation. We develop a simple nonlinear framework for such liquid surfers by connecting Marangoni-driven hydrodynamics with low-dimensional dynamical modeling. Using the Lorentz reciprocal theorem, we show that the droplet velocity is determined primarily by the surface-tension difference across the droplet at the water–air interface, depending on the relaxation length scales in the concentration and velocity fields along the interface. Coupling this result with interfacial transport yields a reduced velocity equation with a pitchfork bifurcation from rest to steady propulsion. Extending the model to include two relaxing force components further yields a minimal three-variable model that reproduces stable propulsion, back-and-forth motion, and more complex dynamics. This framework provides a compact basis for understanding and classifying the dynamics of self-propelled liquid droplets. Full article

Accurate prediction of full-scale ship performance through the ITTC (International Towing Tank Conference) extrapolation procedure is crucial for ship design and energy assessment, yet it is subject to uncertainties from extrapolation coefficients, correlation factors, and force measurements. A regression-based Non-Intrusive Polynomial Chaos (NIPC) method is developed to perform a comprehensive uncertainty quantification. The analysis propagates uncertainties from extrapolation coefficients (ship form factor, hull and propeller roughness), the wetted surface area, and model-scale hydrodynamic forces (resistance, propeller thrust and torque) of the ship. Statistical metrics for resistance and self-propulsion performances are computed and validated against Monte Carlo simulations, followed by a global sensitivity analysis using Sobol indices. Results show the coefficient of variation (CV) for delivered power is approximately 4% at the designed speed, indicating a significant prediction unreliability, whereas predictions for propulsive efficiency and propeller shaft speed are more reliable (CV < 1%). The sensitivity analysis identifies hull roughness as the dominant uncertainty source for power predictions and reveals that, under the studied conditions, the prediction process for key outputs is predominantly linear. The study concludes that while the power prediction carries notable uncertainty, the procedure yields reliable estimates for propulsive efficiency, providing a quantified risk assessment framework to guide robust ship design and performance evaluation. Full article

Teleoperated dual-arm underwater manipulators are a promising alternative to divers for hazardous subsea tasks, such as removing fishing nets from ship propellers. However, kinematic discrepancies between the master and slave can cause self-collisions between links that the operator cannot perceive, risking mechanical damage and costly underwater recovery. Real-time self-collision detection is therefore essential, yet existing approaches face an accuracy–efficiency trade-off: mesh-based methods such as GJK and FCL are accurate but computationally costly, while sphere and capsule approximations overestimate distances near joint interfaces, causing false positives. This paper proposes the Generatrix Distance Method (GDM), an analytical algorithm with bounded $\mathcal{O}\left(1\right)$ per-pair complexity for real-time self-collision detection. GDM approximates each link as a finite-length cylinder and classifies the configuration between two cylinders into four cases: Side–Side, Side–Cap, Cap–Side, and Cap–Cap. The Side–Side case admits a closed-form solution; cap-involved cases use a bounded-iteration cap-edge projection. Cylinder parameters are systematically derived from URDF kinematic information, enabling platform-independent deployment. GDM was validated through Gazebo simulations of a dual-arm underwater walking robot and teleoperation experiments on the ROBOTIS FFW-SG2 AI Worker. GDM runs about $10\times$ faster than FCL-Cylinder, while its iterative variant attains a 0.15 mm mean error at a $3\times$ speedup, confirming real-time suitability. Full article

Background: Uncontrolled hemorrhage, especially at non-compressible sites, remains a major cause of preventable trauma deaths. This study reports the development of fibrinogen-loaded calcium carbonate (CaCO₃) microparticles that combine hemostatic activity with self-propelling capability for targeted delivery against blood flow, with a focus on understanding formulation-dependent trade-offs among particle yield, protein loading, clotting performance, and transport behavior. Methods: Microparticles were synthesized via a precipitation method using different carbonate sources and characterized for yield, morphology, size, and fibrinogen encapsulation. Hemostatic function was assessed using rotational thromboelastometry (ROTEM) in fibrinogen-deficient plasma. Propulsion behavior was evaluated following exposure to protonated tranexamic acid (TXA⁺), which triggers CO₂ generation. Particle size and encapsulation were examined by microscopy and fluorescence imaging. Results: The precipitation method produced spherical micrometer-sized particles, with fibrinogen inclusion reducing yield and particle size relative to unload controls. Fluorescence microscopy confirmed successful encapsulation. Encapsulation efficiency varied with formulation, with sodium carbonate-based particles showing higher relative fibrinogen loading. ROTEM analysis demonstrated that fibrinogen-loaded particles significantly improved clot formation, increasing maximum clot firmness compared to fibrinogen-free particles, although performance remained formulation-dependent. TXA⁺-triggered propulsion achieved maximum speeds up to 4.221 cm/s. Fibrinogen-loaded particles exhibited longer activation lag times than unloaded particles, indicating a trade-off between hemostatic functionality and propulsion kinetics. Conclusions: Fibrinogen-loaded CaCO₃ microparticles exhibit both hemostatic activity and chemically triggered motion in vitro. The study identifies key formulation-dependent trade-offs between particle yield, fibrinogen loading, clotting performance, and propulsion behavior. While these findings support the feasibility of combining localization and clot stabilization mechanisms, further studies under physiologically relevant flow conditions and in vivo models are required to evaluate their potential for active delivery in non-compressible hemorrhage. Full article

Two methods of accounting for the motion of the bodies—the deforming mesh method and the method of overlapping meshes (or overset mesh method)—are compared using problems with floating bodies, which are typical for the shipbuilding industry. Three problems are considered: oscillation of the cylinder on the water surface, movement of the box under the influence of waves, and heaving and pitching of the ship model in head waves. Numerical computations are carried out in the LOGOS software package, the simulation methodology used is based on the solution of a system of Reynolds-averaged Navier-Stokes equations, and the Volume of fluid (VOF) method to take into account the free surface. In all problems, the characteristics of the movement of bodies are evaluated; the resistance force of the ship model is also determined in the third problem; control values obtained using two methods of accounting for moving bodies are compared with the available experimental data. The results of numerical simulation have shown that both methods predict body movement parameters well; the accuracy in determining the resistance force in the task of streamlining the ship’s hull is also comparable: the difference between the maximum deviations of the resistance coefficient in the computations with deformation and overlapping computation meshes is 0.5%. In the case of computations of the three-dimensional problem, the time spent when using the mesh-deformation method turned out to be 10% more; therefore, the method of overlapping meshes can be considered more optimal when solving such shipbuilding tasks as self-propelled tests and streamlining the ship’s hull with and without wind and wave loads. Full article

This study investigates the hydrodynamic performance of the KVLCC2 tanker in deep and shallow water using computational fluid dynamics (CFD) simulations, focusing on resistance and self-propulsion with both ducted and non-ducted propellers. The Reynolds-averaged Navier–Stokes (RANS) equations, coupled with the SST k-ω turbulence model, are solved using STAR-CCM+ to analyze ship resistance, open-water propeller characteristics, and self-propulsion factors. Validation against experimental data confirms the numerical accuracy, with uncertainties below acceptable thresholds. In deep water, the body force propeller and body force ducted propeller methods are validated against the discretized propeller approach, yielding errors under 5%. The ducted propeller enhances open-water efficiency but results in higher thrust deduction and lower wake fractions, leading to reduced hull and overall propulsive efficiencies compared to the non-ducted case. In shallow water, as the depth-to-draft ratio (H/T) decreases to 1.5, added resistance, sinkage, and trim increase sharply due to blockage effects. The ducted configuration mitigates these penalties, achieving a 20.8% power reduction at H/T = 1.5. Added self-propulsion factors reveal that the duct improves hull efficiency and offsets shallow-water losses, enhancing propulsive efficiency. Flow field analysis shows accelerated stern wakes and asymmetric structures in shallow water, with the body force methods providing consistent predictions despite minor discrepancies in extreme conditions. This research highlights the efficacy of ducted propellers in shallow water and the reliability of body force methods for efficient simulations, offering insights for ship design in restricted depths. Full article

Neuronal excitability manifests itself mainly in the form of non-linear, self-regenerative waves of electricity moving along the surface of neuronal axons. These waves are commonly known as action potentials (APs). Theoretical and experimental investigations of the physical and functional characteristics of APs have broadly followed along the lines of the ionic hypothesis and the associated mathematical model introduced by Hodgkin and Huxley (HH). In the current form of this bioelectrical framework, adopted in mainstream physiology and other biological sciences, the axonal membrane is conceptualized as an electronic circuit where electric current is generated and propelled as a result of the time-dependent opening and closure of voltage-operated ion channel proteins, allowing passive flow of specific ions across and along the membrane, powered by their respective electrochemical gradients. Although representing mainstream research, the bioelectric perspective has been criticized for its narrow focus on the electrical characteristics of APs, whilst ignoring other physical manifestations of the nerve signal, particularly mechanical and thermal changes coinciding with AP propagation. As an alternative, a macroscopic thermodynamics-based acoustic theory has been outlined, in which all electric and non-electric manifestations of the nerve signal are considered as a result of a single density pulse in the axonal membrane carried by a reversible lipid membrane phase transition and momentum conservation. Representing a minority view, however, this unified, acoustic perspective on the physical nature of neuronal excitability is largely ignored by representatives of the bioelectric perspective. Here, we draw special attention to the philosophical dimension of the communication failure between the two communities of scientists. We argue that adherents of the bioelectric perspective favor a mechanist type of explanation, whilst supporters of the acoustic perspective are committed to so-called covering-law types of explanation. We conclude that it is this thus far unrecognized philosophical rift, rather than specific scientific differences in opinion, that blocks fruitful interdisciplinary cooperation necessary for building a comprehensive, fully integrated notion of the physical nature of neuronal excitability. Suggestions of how to bridge this conceptual gap are formulated. Full article

Diffusion-based models have substantially propelled the progress of portrait stylization. Nevertheless, the lack of clear supervisory signals often leads to pattern drift in the target portrait. To overcome this issue, we introduce DGADiff, a training-free stylization framework based on a diffusion model. Specifically, we first leverage prior knowledge from a pre-trained latent consistency model (LCM) to efficiently sample representative features from noisy image pairs. Next, we design a Decoupled Guide Attention Mechanism (DGA), that disentangles the U-Net attention into separate self-attention and masked-attention tracks, enabling accurate transfer of fine-grained facial style patterns. Extensive experiments verify that our DGADiff achieves favorable results across multiple metrics in content-to-style and style-to-content multi-domain tasks, demonstrating the effectiveness of spatial attention decoupling for portrait stylization. Full article

This study proposes a bio-inspired control framework for unmanned aerial vehicle (UAV) swarms, designed to emulate the collective motion phase transitions observed in the homing behavior of pigeon flocks. A second-order self-propelled particle model is established, integrating a self-propulsion term, an interaction potential term, and a key roosting force term inspired by the roosting behavior of pigeons. The framework enables the swarm to dynamically switch between a translational motion phase and a vortex motion phase based on the distance to a designated roost location. Based on the proposed swarm model, theoretical analysis proves the stability property of the specific two motion phases under specific conditions. Numerical simulations validate the stability of the two motion phases, demonstrating that UAV swarms can reliably maintain each phase and execute phase transitions triggered by the roosting force. The proposed framework is able to describe the phase transition behavior in the process of pigeons returning home. Full article

To improve the harvesting efficiency of mechanized cabbage harvesting and reduce damage, the structural configuration of a cabbage harvester was designed based on the cabbage cultivation pattern, physical morphological parameters, and mechanical harvesting characteristics. The harvester consists of a crawler power chassis, pulling device, crop guiding device, clamping and conveying device, profiling device, root-cutting device, and leaf-stripping and collecting device, which enables simultaneous pulling, conveying, root cutting, outer leaf separation, and collection for two rows of cabbages in a single pass, thereby enhancing harvesting efficiency. The sources of cabbage damage during the harvesting process were analyzed, and dynamic analyses of the key components were performed to determine their structural parameters. Through single-factor experiments and response surface methodology optimization tests, the effects of forward speed, pulling roller rotational speed, clamping and conveying speed, and cutter rotational speed on the harvest qualification rate were evaluated. The optimal working parameter combination of these factors was determined and validated through field harvesting performance tests. The results showed that, under the operating conditions of forward speed 0.4 m/s, pulling roller rotational speed 114 r/min, clamping and conveying speed 0.51 m/s, and cutter rotational speed 338 r/min, the average harvest qualification rate reached 96.4%, and the average damage rate was 3.6%, which is close to the maximum theoretical harvest qualification rate of 96.78% predicted by the optimization model. The field validation tests demonstrated good performance, with all indicators meeting the design requirements and relevant standards, providing theoretical support and reference for the development and improvement of cabbage harvesting machinery. Full article

Aiming at the problem of the insufficient passability and stability of the tracked chassis of silage harvesters caused by complex hilly and mountainous areas and a severe working environment, the crawler chassis of self-propelled silage harvesters was taken as the research object, the straight-line driving, longitudinal climbing, and lateral climbing processes of the chassis were theoretically analyzed, and the critical parameters that affect the normal climbing of the chassis were calculated. Meanwhile, the multi-body dynamics model of the tracked chassis was established by using the software SolidWorks 2020 and RecurDyn 2023, and its climbing and obstacle crossing performance were analyzed. The relevant motion parameters of the tracked chassis suitable for longitudinal and transverse slopes in hilly and mountainous areas were obtained, and field tests were conducted on the tracked chassis to verify the reliability of the simulation model. According to the simulation results, the tracked chassis achieves ultimate slope angles of 28° longitudinally and 23° laterally. It demonstrates the capability to navigate 140 mm high ridges and 250 mm wide trenches smoothly, while its straight-line driving offset rate conforms to prevailing agricultural machinery industry standards. Field test results indicated that the tracked chassis achieved a maximum longitudinal climbing angle of 26°. The relative error of less than 8% between the experimental and simulated data confirms a strong correlation. The maximum offset rate for straight-line travel is 1.95%, meeting the requirements of the agricultural machinery industry standards. The test verified the feasibility of the dynamic model of the crawler chassis of the silage harvester, providing a theoretical basis and technical support for the optimal design of the crawler chassis of the self-propelled silage harvester in hilly and mountainous areas. Full article

The aim of this study is to evaluate the biomechanical response of a seated operator subjected to whole-body vibrations generated by two agricultural tractors with different propulsion systems: a diesel model (TD80D) and an electric prototype (TE-0). An integrated experimental–numerical approach was employed, combining triaxial accelerometer measurements under real operating conditions (constant speed of 5 km/h on unprepared terrain) with random vibration response simulations performed in Altair SimSolid. The excitation input for the numerical model was defined using frequency-dependent power spectral density (PSD) functions derived from experimentally measured acceleration signals and scaled to a representative global RMS value. The analysis focused on the distribution of mechanical stress in key anatomical regions of a virtual human dummy in a seated posture, including the foot sole, knee, lumbar region, and head. The results indicate that, under the analysed conditions, the electric tractor (TE-0) exhibits improved vibration attenuation, leading to significant reductions in mechanical stress across all analysed regions, with decreases of up to 56.3% at the foot sole, 50.0% at the knee, 53.3% in the lumbar region, and 91.1% at the head compared to the diesel tractor (TD80D). These findings highlight the relevance of integrating experimental measurements with numerical simulation for assessing operator exposure to vibrations and suggest that electric tractor configurations may provide improved biomechanical comfort under the analysed operating conditions. Full article