Search Results (444)

The problem was recently reported that the far-zone electromagnetic momentum of light produced by scattering on a spatially anisotropic random medium can be the same at every azimuthal angle of scattering. Here, we extend the analysis to focus on the possibility of producing a rotationally symmetric spectral degree of coherence (SDOC) generated by scattering by an anisotropic process. The necessary and sufficient conditions for producing such a SDOC in the far zone are derived when a polychromatic electromagnetic plane wave is scattered by an anisotropic Gaussian Schell-model medium. We find that, unlike the generation of a rotationally symmetric momentum flow, it is not enough to simply restrict the structural characteristics of the medium and the incident light source to achieve a SDOC with rotational symmetry. An additional and essential requirement is that the azimuthal angles of scattering corresponding to the two observation points of the SDOC must be constrained to be equal. Only when all these constraints are satisfied simultaneously can a rotationally symmetric electromagnetic SDOC generated by scattering by an anisotropic process be realized. In addition, we find that although the medium parameter conditions for generating a rotationally symmetric SDOC and a rotationally symmetric momentum flow are completely different, it remains possible that the SDOC and the momentum flow produced by a spatially anisotropic medium can still simultaneously exhibit rotational symmetry, provided that the distribution of the correlation function of the scattering potential of the medium is isotropic in the plane perpendicular to the incident direction. Our results not only contribute to a deeper understanding of the far-field distribution of light scattering on an anisotropic scatterer, but also have potential applications in light-field manipulation and in the inverse scattering problem. Full article

Background: Diagnosis is the fundamental basis for understanding biomechanics in orthodontic treatment and for accurately designing the treatment plan. Traditionally, the sagittal plane has been the primary focus of assessment; however, it is essential to consider the patient in all three spatial planes. Therefore, it is necessary to explore the transverse plane, which is equally as crucial as the sagittal and vertical planes. With current technological advances, it is now possible to obtain three-dimensional images of the patient using cone-beam computed tomography (CBCT), allowing evaluation of all planes in a single diagnostic test. This study aimed to assess the diagnostic methods used for transverse analysis and the usefulness of CBCT for this purpose. Material and Methods: To select the studies for this review, we searched the PubMed, Scopus, and Cochrane databases for publications between 1965 and 2021. Our inclusion criteria targeted studies that evaluated the transverse plane using CBCT or CT. We assessed the level of evidence according to the OCEBM classification and evaluated the risk of bias using the QUADAS-2 scale. Results: After reviewing 535 articles, we selected 16 that met the established criteria. These studies compared various diagnostic methods for transverse analysis and their reproducibility indices. We identified the absence of a gold standard for measuring transverse discrepancies and high variability among diagnostic methods as the main limitations. Conclusions: Based on the available evidence, it can be concluded that dental and skeletal transverse discrepancies can be reliably differentiated using the diagnostic techniques evaluated in this study, particularly through CBCT-based assessment. Therefore, the diagnosis of transverse discrepancies should not be considered unclear, as it can be established using objective and measurable criteria. These findings reinforce the clinical value of current diagnostic tools and highlight the importance of accurate three-dimensional interpretation for informed and effective treatment decision-making. Full article

Background: Cardiac amyloidosis (CA) is characterized by progressive myocardial infiltration leading to restrictive cardiomyopathy and heart failure. While left ventricular assessment has traditionally dominated prognostic evaluation, right ventricular (RV) dysfunction and RV–pulmonary artery (PA) coupling have emerged as critical determinants of outcomes. Objectives: This review synthesizes current evidence on RV–PA coupling as a prognostic marker in cardiac amyloidosis, examining measurement methodologies, prognostic significance, pathophysiological mechanisms, and clinical applications. Methods: We comprehensively reviewed the recent literature on RV–PA coupling in CA, focusing on studies published from 2020 to 2025, including both AL and ATTR subtypes. We analyzed data from multicenter cohorts, prospective registries, and validation studies examining the relationship between RV–PA coupling indices and clinical outcomes. Results: RV–PA coupling, most commonly assessed using the tricuspid annular plane systolic excursion to pulmonary artery systolic pressure (TAPSE/PASP) ratio, consistently demonstrates strong independent prognostic value for mortality and heart failure outcomes in CA patients. Impaired coupling (TAPSE/PASP < 0.45 mm/mmHg) identifies high-risk patients with hazard ratios ranging from 1.98 to 4.17 for adverse outcomes. In a multicenter cohort of 283 patients, TAPSE/PASP < 0.45 mm/mmHg was independently associated with death or heart failure hospitalization (HR 1.98, 95% CI 1.32–2.96, p = 0.001) and significantly improved risk reclassification (NRI 0.46–0.49). In ATTR-specific populations receiving disease-modifying therapy, impaired coupling (TAPSE/PASP ≤ 0.382 mm/mmHg) predicted three-year mortality with an adjusted HR of 2.99. The coupling index provides incremental value over individual RV parameters by accounting for afterload conditions and demonstrates consistent prognostic performance across both AL and ATTR subtypes. Conclusions: RV–PA coupling represents a robust, easily obtainable prognostic marker that should be routinely assessed in CA patients for risk stratification and clinical decision-making. The TAPSE/PASP ratio can be calculated from standard echocardiographic examinations without additional cost or time, making it practical for widespread implementation. Future research should focus on standardizing measurement protocols, establishing disease-specific thresholds, evaluating coupling trajectories with novel therapies, and integrating coupling assessment into staging systems and management algorithms. The strong prognostic signal, pathophysiological relevance, and ease of measurement position RV–PA coupling as an essential component of comprehensive cardiac amyloidosis evaluation. Full article

To address the unreliable autofocus problem of drone-mounted visible-light aerial cameras in low-contrast maritime environments, this paper proposes an autofocus system that combines deep-learning-based coarse focusing with traditional search-based fine adjustment. The system uses a built-in high-contrast resolution test chart as the signal source. Images captured by the imaging sensor are fed into a lightweight convolutional neural network to regress the defocus distance, enabling fast focus positioning. This avoids the weak signal and inaccurate focusing often encountered when adjusting focus directly on low-contrast sea surfaces. In the fine-focusing stage, a hybrid strategy integrating hill-climbing search and inverse correction is adopted. By evaluating the image sharpness function, the system accurately locks onto the optimal focal plane, forming intelligent closed-loop control. Experiments show that this method, which combines imaging of the built-in calibration target with deep-learning-based coarse focusing, significantly improves focusing efficiency. Compared with traditional full-range search strategies, the focusing speed is increased by approximately 60%. While ensuring high accuracy and strong adaptability, the proposed approach effectively enhances the overall imaging performance of aerial cameras in low-contrast maritime conditions. Full article

To address the issues of poor geometric dimension retention, short component lifespan, and heavy maintenance workload of the 1520 mm gauge 50 kg/m rail No.9 turnout, a new design was proposed for the 1520 mm gauge 60 kg/m rail No.9 turnout. Based on the new design’s plane alignment, structural features, and other requirements, dynamic models of the vehicle–turnout system, the turnout conversion model, and the continuous welded rail turnout (CWR turnout) model were established. The focus was on analyzing the dynamic response of the vehicle when passing through the 1520 mm gauge 60 kg/m rail No.9 turnout, as well as its switching performance. The feasibility of applying CWR technology to this turnout was also explored. The results indicate that the dynamic indicators of the vehicle passing through the 1520 mm gauge 60 kg/m rail No.9 turnout meet the regulatory requirements; the maximum switching force at the traction point is 1.807 kN, which is less than the rated power of the switch machine; and the rail strength and track stability of the CWR turnout model all meet the design specifications. Full article

High-strength oil and gas pipeline girth welds exhibit significant material and geometric discontinuities with high susceptibility to defects, making them a critical weak link in oil and gas pipelines. Researching the fracture assessment technology pipeline’s girth welds is essential for enhancing the pipeline’s inherent safety and protection levels. Key issues and research progress related to fracture assessment technology are systematically addressed from the perspectives of pipeline fracture behavior and fracture assessment methods in this paper. The core focus of fracture behavior research is determining the crack driving force at the girth weld and the material’s fracture toughness. Fracture assessment methods include failure assessment diagrams and limited tensile strain capacity models. The development of single-parameter and multi-parameter fracture mechanics theories in establishing the relationship between in-plane and out-of-plane constraints and material fracture toughness is reviewed. Four commonly used methods for calculating crack driving forces in pipelines are presented. Moreover, the usage scenarios of various failure assessment diagrams in pipeline fracture assessment are analyzed. A comparison of the parameter ranges and applicability of commonly used international tensile strain capacity models is also provided. The paper highlights existing issues in current research on the fracture assessment of high-strength pipelines and outlines directions for further study. Lastly, this paper aims to provide theoretical and technical support for improving the inherent safety level of high-strength pipeline girth welds. Full article

This study investigates the dynamic formation reconfiguration problem for multi-UUV (multi-Unmanned Underwater Vehicle) systems, with a particular focus on the challenges posed by underwater acoustic communication. A two-dimensional grid model is established in the horizontal plane, taking the leader vehicle as a reference point. Based on this model, fundamental motion strategies for formation reconfiguration are proposed. To facilitate reconfiguration, the Particle Swarm Optimization (PSO) algorithm is utilized to assign desired position points to the follower UUVs within the new formation, enabling dynamic target point planning during reconfiguration. Furthermore, the process of generating motion guidance commands and the impact of acoustic communication delays during command transmission are analyzed. To address these delays, a fuzzy logic-based delay compensation method is proposed. Simulation experiments were conducted to validate the proposed approach. The results demonstrate that the formation reconfiguration planning method and the centralized command communication compensation strategy are both effective and practical for multi-UUV systems. Full article

The research methodology involved creating a 3D sample model that featured both flat and cylindrical surfaces inclined at angles ranging from 0° to 90° relative to the XY plane. The study investigated the surface topography of additively manufactured samples produced using various technologies, including Fused Filament Fabrication (FFF), masked Stereolithography (mSLA), PolyJet (PJ), and Selective Laser Sintering (SLS). The focus was on how material type, print angle, and measurement location influenced the results. The materials used in the study included PLA, PETG, acrylic resins, PA2200, and VeroClear. Due to the optical properties of the materials used, measurements were carried out on replicas that were prepared using a RepliSet F5 silicone compound from Struers. Consequently, a methodology was developed for measuring surface roughness using the Alicona microscope based on these replicas. A 10× objective lens was used during the measurements, and the pixel size was 0.88 µm × 0.88 µm. Each time, an area of approximately 1 mm × 4 mm was measured. The lowest roughness values were observed for mSLA samples (Sa = 6.72–8.54 µm, Spk + Sk + Svk = 33.36–42.16 µm), whereas SLS exhibited the highest roughness (Sa = 27.86 µm, Spk + Sk + Svk = 183.79 µm). PJ samples exhibited intermediate roughness with significant anisotropy (Sa = 11.65 µm, Spk + Sk + Svk = 72.1 µm), which was strongly influenced by the print angle. FFF surfaces showed directional patterns and layer-dependent roughness, with the Sa parameter being the same (12.44 µm) for both PETG and PLA materials. The steepest slopes were observed for SLS surfaces (Sdq = 7.67), while mSLA exhibited the flattest microstructure (Sdq = 0.48–0.89). Statistical analysis confirmed that material type significantly influenced topography in mSLA, while print angle strongly affected PJ and FFF (although for FFF, further studies would be beneficial). The results of the research conducted can be used to develop a methodology for optimizing the printing process to achieve the required geometric surface structure. Full article

The manual spraying of sealant on train side doors is associated with high costs and significant safety risks. To address this challenge, this study proposes an automated crack localization method for sealant-spraying devices by enhancing the YOLOv5s network, with a specific focus on leveraging principles of symmetry. First, an automated sealant-spraying device is designed for operation and data acquisition. Geometric symmetry is then exploited through Zhang’s camera calibration method to accurately establish the two-dimensional mapping between spatial coordinates and the image plane, a process fundamental to spatial reasoning. The core of our approach lies in introducing structural and computational symmetry into the deep learning model. The original YOLOv5s network is improved by integrating the Selective Context Convolutional module and the Skew Intersection over Union (IoU) Loss function, which streamline computation and boost detection accuracy. Furthermore, we replace the standard C3 module with an improved version that incorporates a Reparameterization Visual Transfer block, enhancing feature representation through structural re-parameterization symmetry between training and inference phases. Validation using data from a coal handling facility demonstrates that the improved YOLOv5s model achieves superior performance in precision, mAP@0.5, and recall compared to the original. The results underscore the critical role of geometric and architectural symmetry in developing robust and efficient vision systems for industrial automation. Full article

Background: Posterior pelvic tilt during the squat, commonly referred to as “butt wink” can potentially increase the risk of spine injury when squatting this way. The main goal of this study is to objectively assess the immediate effect of a short-term exercise intervention on the total pelvis range of motion in the sagittal plane (mainly posterior pelvic tilt). Methods: This study has a quasi-experimental design with the participants divided into experimental and control groups based on pre-existing condition—occurrence of PTT during bodyweight squat. A total of 42 participants (21 females and 21 males) were divided into an experimental group (n = 23) and a control group (n = 19). The division was made according to the incidence of posterior pelvic tilt during the bodyweight squat. Qualisys, three-dimensional kinematic motion analysis with Functional Assessment module, was used to analyze pelvis kinematics. Both groups underwent a twenty-minute exercise intervention aimed at strengthening trunk stabilizing muscles, improving squat technique and body awareness in space. Data from the three-dimensional kinematic motion analysis were statistically processed using Restricted Maximum Likelihood analysis (REML) of linear mixed models and repeated measures analysis of variance (rANOVA); Results: There was no statistically significant difference in the range of motion of posterior pelvic tilt before and after the exercise intervention (p = 0.89 and p = 0.42). Only the individual repetitions of the squat were statistically significantly different from each other (p < 0.001) and no statistically significant relationship between posterior pelvic tilt and initial pelvic position was found (p = 0.13). Conclusions: The short exercise intervention did not acutely alter pelvic kinematics (the range of motion of posterior pelvic tilt). Future research should focus on longer exercise interventions (4–8 weeks) with progressive loading and looking for possible associations between different variables of squat execution and the incidence of posterior pelvic tilt. Full article

Background/Objectives: The aim of this study was a video-based observational assessment of movement strategies during supine position transfers in patients with hemiparesis following a first-ever ischemic stroke. Methods: The study included 51 participants (n = 51), covering 20 healthy individuals (n = 20) and 31 patients (n = 31) after their first ischemic stroke with hemiparesis. All participants underwent observational kinematic analysis of supine mobility using video recording and time-lapse analysis. The assessment focused on the time required to complete the task, the number of pelvic movements, the presence of trunk translation, spinal flexion, and pelvic mobility across three planes. Results: In the control group, transfers followed a consistent and repetitive sequence in both directions, typically involving trunk translation, spinal flexion, pelvic elevation, and symmetrical movement of both upper and lower limbs. In contrast, post-stroke patients demonstrated altered, asymmetrical, and less efficient movement patterns. These movement strategies were consistent across the hemiparetic group and characterized typical motor responses following stroke. The average transfer time in the study group was approximately three times longer than in the control group. The average number of pelvic movements was 7.2 ± 2.44 in healthy individuals and 16.71 ± 13.52 in post-stroke patients. Conclusions: Supine transfers should be routinely assessed in patients after stroke and included as a key focus in physiotherapy goals. The movement patterns required for such transfers represent a distinct component of complex motor function. Both qualitative and quantitative aspects of their execution may have a significant impact on functional independence in individuals with hemiparesis. Identifying typical transfer patterns in hemiparetic patients may offer valuable guidance for early post-stroke rehabilitation planning, particularly in preventing maladaptive compensatory strategies. Full article

Exploding or concentrating beams, vortex beams, and cylindrical vector beams have a precisely shaped transversal amplitude profile such that they produce a continuously concentrating and intensifying focal spot upon focusing as the lens aperture is opened. This effect is the physical manifestation of the mathematical fact that Fresnel diffraction integral predicts an infinite intensity at the focus when the aperture effects are ignored. Here, using a full electromagnetic, nonparaxial focusing model, we show that the singularity in exploding cylindrical vector beams is an artifact of the paraxial approximation. Nevertheless, the exploding or concentrating effect, alien to any other light beam with finite power, keeps going up to unit numerical aperture, equivalent to infinite aperture radius. This unique feature enables a dynamic control of the focal intensity and spot size down to the sub-wavelength scale using a single light beam, imitating similar control when focusing an ideal plane wave, but requiring a finite amount of power. Full article

Gradient stiffness structures are increasingly recognized for their excellent energy absorption capabilities, particularly under challenging loading conditions. Most studies focus on varying the thickness of the structure in order to produce gradient stiffness. This work introduces an innovative approach to design honeycomb architectures with controlled gradient stiffness along the out-of-plane direction achieved by materials’ microstructure variations. The gradient is achieved by combining three types of thermoplastic polyurethane (TPU) materials: porous TPU, plain TPU, and carbon fiber (CF)-reinforced TPU. By varying the material distribution across the honeycomb layers, a smooth transition in stiffness is formed, improving both mechanical resilience and energy dissipation. To fabricate these structures, a dual-head 3D printer was employed with one head printed processed TPU with a chemical blowing agent to produce porous and plain sections, while the other printed a CF-reinforced TPU. By alternating between the two print heads and modifying the processing temperatures, honeycombs with up to three distinct stiffness zones were produced. Compression testing under out-of-plane loading revealed clear plateau and densification regions in the stress–strain curves. Pure CF-reinforced honeycombs absorbed the most energy at stress levels above ~4.5 MPa, while porous TPU honeycombs were more effective under stress levels below ~1 MPa. Importantly, the gradient stiffness honeycombs achieved a balanced energy absorption profile across a broader range of stress levels, offering enhanced performance and adaptability for applications like protective equipment, packaging, and automotive structures. Full article

Low, small, and slow (LSS) unmanned aerial vehicles (UAVs) pose great challenges for conventional guidance methods. However, existing deep reinforcement learning (DRL)-based interception guidance law has mostly focused on simplified two-dimensional planes and requires strict initial launch scenarios (constructing collision triangles). Designing more robust guidance laws has therefore become a key research focus. In this paper, we propose a novel recurrent proximal policy optimization (RPPO)-based guidance law framework. Specifically, we first design initial launch conditions in three-dimensional space that are more applicable and realistic, without requiring to form a collision triangle at the initial launch. Then, considering the temporal continuity of the seeker’s observations, we introduce the long short-term memory (LSTM) networks into the proximal policy optimization (PPO) algorithm to extract hidden temporal information from the observation sequences, thus supporting the policy training. Finally, we propose a reward function based on velocity prediction and overload constraints. Simulation experiments show that the proposed RPPO framework achieves an interception rate of 95.3% and a miss distance of 1.2935 m under broader launch conditions. Moreover, the framework demonstrates strong generalization ability, effectively coping with unknown maneuvers of UAVs. Full article

Software-defined networking (SDN) has reformed the traditional approach to managing and configuring networks by isolating the data plane from control plane. This isolation helps enable centralized control over network resources, enhanced programmability, and the ability to dynamically apply and enforce security and traffic policies. The shift in architecture offers numerous advantages such as increased flexibility, scalability, and improved network management but also introduces new and notable security challenges such as Distributed Denial-of-Service (DDoS) attacks. Such attacks focus on affecting the target with malicious traffic and even short-lived DDoS incidents can drastically impact the entire network’s stability, performance and availability. This comprehensive review paper provides a detailed investigation of SDN principles, the nature of DDoS threats in such environments and the strategies used to detect/mitigate these attacks. It provides novelty by offering an in-depth categorization of state-of-the-art detection techniques, utilizing machine learning, deep learning, and federated learning in domain-specific and general-purpose SDN scenarios. Each method is analyzed for its effectiveness. The paper further evaluates the strengths and weaknesses of these techniques, highlighting their applicability in different SDN contexts. In addition, the paper outlines the key performance metrics used in evaluating these detection mechanisms. Moreover, the novelty of the study is classifying the datasets commonly used for training and validating DDoS detection models into two major categories: legacy-compatible datasets that are adapted from traditional network environments, and SDN-contextual datasets that are specifically generated to reflect the characteristics of modern SDN systems. Finally, the paper suggests a few directions for future research. These include enhancing the robustness of detection models, integrating privacy-preserving techniques in collaborative learning, and developing more comprehensive and realistic SDN-specific datasets to improve the strength of SDN infrastructures against DDoS threats. Full article