Search Results (67)

The optimal deployment of Low-Power Wide-Area Networks (LPWANs) such as LoRaWAN in complex urban environments remains an NP-Hard Set Covering Problem. Traditional network planning often relies on 2D mathematical grids that ignore physical RF barriers, leading to topographic shadowing and single points of failure. This research proposes the Native 3D Memetic Spatially Aware Genetic Algorithm (3D-M-SAGA), an optimization framework that operates over a Morphological Digital Twin. By fusing OpenStreetMap (OSM) vector topologies with NASA SRTM elevation data and autonomous urban clutter classification, the framework evaluates physical constraints—including ITU-R knife-edge diffraction and dielectric absorption—directly within the evolutionary loop. To counteract the epistatic variance inherent to standard genetic algorithms, the 3D-M-SAGA integrates a vectorized memetic “Smart Repair” operator driven by heuristic attraction and repulsion forces. Formulated as a multi-objective optimization problem balancing Capital Expenditure (CAPEX) and topological Quality of Service (QoS) through K-coverage, the framework is evaluated using a 36-scenario parametric grid search and a 50-iteration Monte Carlo benchmark. Results show that the 3D-M-SAGA tightly bounds stochastic CAPEX variance ($\sigma =\pm 0.51$ gateways) while reducing single-point-of-failure network fragility ($K=1$) by up to 20%, guaranteeing fault tolerance ($K\ge 2$) without over-provisioning civic infrastructure. Full article

Sharpness and cutting edge retention are critical performance metrics for kitchen knives. Their combined effectiveness is governed by the synergistic effects of edge geometry and material microstructure. The present study selected six representative knife steels, namely 3Cr13, 1.4116, 9Cr18MoV, T10, GCr15, and CPM 3V, to fabricate the experimental knives with edge inclusive angles of 18°, 24°, and 30°. Standardized CATRA cutting tests were conducted to evaluate the effects of material microstructure and edge geometry on initial cutting performance (ICP) and total card cut (TCC), serving as the direct metrics for sharpness and cutting edge retention, respectively. The underlying mechanisms responsible for the cutting behavior were elucidated through scanning electron microscopy, quantitative analysis of carbides, and measurements of edge wear volume. The roles of carbide number, size, and morphology in ICP and TCC were systematically analyzed. Furthermore, multivariate linear regression models were established to quantitatively correlate ICP and TCC with edge inclusive angle, material hardness, average carbide diameter, and edge width. The results indicate that the edge inclusive angle predominantly determines ICP, while TCC is primarily controlled by the synergistic interaction between carbide characteristics and matrix hardness. Although a smaller edge inclusive angle significantly enhances ICP, it also accelerates edge wear and reduces cutting efficiency. By comprehensively considering both ICP and TCC, an optimal edge inclusive angle range was identified for each material to achieve balanced cutting performance. This work provides experimental evidence and quantitative guidance for the material selection and edge geometry design of high-performance kitchen knives. Full article

Objectives: Horizontal ridge augmentation remains a clinical challenge due to limitations in terms of spatial maintenance, graft stability and predictability of new bone formation. The umbrella-screw tent technique provides mechanical stability for particulate grafts, while adjuvants such as hyaluronic acid (HA) and polynucleotides (PN) may enhance biological remodeling. Evidence for this compound in implant-related bone augmentation is still scarce. Material and methods: In a single patient with a knife-edge alveolar ridge, augmentation was performed in regions 34 to 36 using the umbrella-screw tent technique. The defect was grafted with deproteinized bovine bone mineral (DBBM) mixed with hyaluronic acid (HA) and polynucleotides (PN), supplemented with platelet-rich fibrin (PFR) and covered with a resorbable collagen membrane. After six months, two implants were installed, and a biopsy was obtained by trepanation for histological and histomorphometric analysis. Results: Healing occurred without compromise, with no signs of infection or graft exposure. Horizontal bone gain averaged 4.5 mm, corresponding to a relative Target Performance Index (TPI-h) of 75%. Histomorphometric analysis revealed a total mineralized fraction of 76.4%, consisting of 36.1% newly formed bone and 40.3% residual DBBM particles. The xenogeneic granules were completely integrated into mature bone, with no signs of inflammation or foreign body reaction. Conclusion: The case report illustrates that the combination of DBBM with HA and PN, stabilized by the umbrella-screw tent technique, can lead to significant new bone formation and favorable graft integration. Although limited by its single-case design, the case report provides preliminary insights into the synergistic potential of HA and PN as biological enhancers in bone augmentation, warranting further controlled studies. Full article

The increasing deployment of humanoid robots in indoor environments such as smart factories, laboratories, offices, and hospitals poses new challenges to millimeter-wave wireless communication systems. Existing human body obstruction models, while effective at characterizing pedestrian-induced signal attenuation, are not designed to directly capture the structural geometry, material composition, and controlled mobility of humanoid robotic platforms. In this work, we first reproduce a well-established human-body-based propagation model under comparable indoor conditions and subsequently extend this hybrid framework to controlled humanoid-based scenarios by combining double knife-edge diffraction (DKED) with a modified street-canyon reflection model operating at 28 GHz. Compared to existing human-based studies, the proposed approach explicitly incorporates the material properties of the humanoid robot’s envelope through a calibrated correction factor and accounts for its controlled lateral movements. An indoor measurement campaign using three programmable humanoid robots was conducted to evaluate the model. Experimental results show that humanoid robots can reproduce attenuation trends and obstruction dynamics consistent with those reported in prior human-body blockage studies, while offering improved repeatability and greater experimental control. The proposed framework provides a practical and reproducible tool for modeling indoor millimeter-wave channels under controlled humanoid-based experimental conditions, in environments involving mobile robotic agents. Full article

This study investigates whether a large language model (LLM) can perform governance-style mediation among multiple stakeholders when preferences are expressed only in categorical natural language. Building on prior conceptual work proposing an advisory governance layer for AI systems, we designed a controlled experiment comparing a language-based mediator with a numerical baseline (Borda count) across 1024 synthetic stakeholder scenarios, each executed ten times (10,240 paired decisions). Results show only 31% agreement with Borda, revealing distinct decision logic that produces equity-biased outcomes (68% improved fairness, ~25% Gini reduction, 38% higher minimum utility) at the cost of efficiency (14–20% lower mean utility). Stability analysis identified three reliability zones—stable (39%), middle (28%), and knife-edge (33%)—enabling risk-proportionate oversight. Qualitative analysis revealed that equity bias emerges from opaque pattern-matching followed by post hoc rationalization rather than systematic application of governance principles, with frequent semantic-grounding failures even in stable cases. These findings demonstrate that language-based mediation diverges fundamentally from numerical aggregation, suitable for advisory deliberation but requiring human oversight for value verification and factual accuracy. Full article

Background: Primary stability of dental implants depends on bone quality, bone quantity, and implant design. In cases of large defects, such as periapical lesions, the selection of an appropriate alveolar ridge preservation (ARP) material is crucial for bone regeneration and preparation for implant placement. Objective: The aim of this study was to evaluate clinical and histological outcomes of a novel ARP material hydroxyapatite and sugar cross-linked collagen (HSCC) combined with a knife-edge thread implant (KTI) design. Methods: Thirty patients were divided into two groups: a control group treated with KTI after spontaneous alveolar ridge healing, and an experimental group that underwent ARP using HSCC, and six months later, KTIs were placed in newly formed bone. Clinical parameters including insertion torque value (ITV), resonance frequency analysis (RFA), implant stability quotient (ISQ), and horizontal bone dimension were evaluated. Histological analysis was also performed. Results: No significant differences were observed between groups in ITV, ISQ, or horizontal bone dimension (p > 0.05). However, histological analysis demonstrated a significantly higher number of active osteoblasts in the ARP group compared to the control (p < 0.001), whereas collagen deposition was significantly greater in the control group (p < 0.001). Conclusions: ARP using HSCC, combined with KTI, provides favorable conditions for primary stability and successful graft integration, supporting reliable implant placement in sites with bone defects. Full article

Real-world threat detection systems face critical challenges in adapting to evolving operational conditions while providing transparent decision making. Traditional deep learning models suffer from catastrophic forgetting during continual learning and lack interpretability in security-critical deployments. This study proposes a distributed edge–cloud framework integrating YOLOv8 object detection with incremental learning and Gradient-weighted Class Activation Mapping (Grad-CAM) for adaptive, interpretable threat detection. The framework employs distributed edge agents for inference on unlabeled surveillance data, with a central server validating detections through class verification and localization quality assessment (IoU ≥ 0.5). A lightweight YOLOv8-nano model (3.2 M parameters) was incrementally trained over five rounds using sequential fine tuning with weight inheritance, progressively incorporating verified samples from an unlabeled pool. Experiments on a 5064 image weapon detection dataset (pistol and knife classes) demonstrated substantial improvements: F1-score increased from 0.45 to 0.83, mAP@0.5 improved from 0.518 to 0.886 and minority class F1-score rose 196% without explicit resampling. Incremental learning achieved a 74% training time reduction compared to one-shot training while maintaining competitive accuracy. Grad-CAM analysis revealed progressive attention refinement quantified through the proposed Heatmap Focus Score, reaching 92.5% and exceeding one-shot-trained models. The framework provides a scalable, memory-efficient solution for continual threat detection with superior interpretability in dynamic security environments. The integration of Grad-CAM visualizations with detection outputs enables operator accountability by establishing auditable decision records in deployed systems. Full article

Understanding the transient flow phenomena accompanying projectile discharge is essential for improving the safety, efficiency, and predictability of small-scale ballistic systems. Despite extensive numerical studies on muzzle flows and shock formation, experimental visualization and quantitative data on the coupling between pressure waves, jet structures, and projectile motion remain limited. This work addresses this gap by employing high-speed schlieren imaging and schlieren image velocimetry (SIV) to investigate the near-field aerodynamics of an airsoft-type projectile propelled by a CO₂ jet. Three optical configurations were analyzed—a Toepler single-mirror system, a Z-type without knife edge, and a Z-type with knife edge—to assess their sensitivity and suitability for resolving acoustic and turbulent features. The measured velocity of concentric pressure waves (≈355 m/s) agrees with the theoretical local speed of sound, validating the optical calibration. Projectile tracking yielded a mean speed of 71 ± 1.6 m/s, with drag and kinetic energy analyses confirming significant near-muzzle deceleration due to jet–projectile interaction. The SIV analysis provided additional insight into the convection velocity of coherent jet structures (≈75 m/s), tangent velocity fluctuations (±0.8 m/s), and vorticity distribution along the jet boundary. The results demonstrate that even compact schlieren setups, when coupled with quantitative image analysis, can capture the essential dynamics of unsteady compressible flows, providing a foundation for future diagnostic development and modeling of projectile–jet interactions. Full article

An implant’s thread design plays a key role in enhancing primary stability by optimising the distribution of loading forces and biomechanical structural interlocking. An increase in bone-to-implant contact (BIC) surface availability affects osseointegration timing and leads to different biomechanical behaviours. To assess their theoretical impacts on osseointegration functionality, this study aims to analyse and compare the surface areas of two different thread designs: progressive knife-edge and V-shaped metric ISO ones. Six implant models are virtually created, with progressive knife-edge threads, non-self-tapping ISO threads, and ISO threads with tapping areas, considering two arbitrary diameters (3.8 mm and 4.6 mm). For both diameters, the models also have identical lengths (9.5 mm) and external outlines. The total, superior half, and inferior half external surface areas are measured using a digital tool (SolidWorks 2023 SP 5.0, Dassault Systèmes, Waltham, MA, USA). Then, the percentage difference in external surface area (ΔESA) is calculated. A greater ΔESA is found in the knife-edge design compared to the ISO thread self-tapping implants for the 4.6 mm diameter (ΔESA = +9.9%). However, for the 3.8 mm diameter, the ΔESA is −1.5% in favour of the ISO self-tapping model. Considering the apical half of the models, the ΔESA is always greater in the knife-edge models, varying from +9.3% to +23.5%. Implants with progressive knife-edge threads offer a significantly larger external surface area than those with ISO threads for the 4.6 mm rather than the 3.8 mm diameter. Considering the apical halves of the implants, the tapping area negatively affects the ΔESA, as well as the ISO thread design. Future research is needed to investigate whether the inspected surface area differences correspond to significant primary and secondary stability variations. Full article

This study presents an experimental investigation of steels used in special knife applications, focusing on the interrelationship between chemical composition, microstructure, heat treatment, and mechanical properties. Four representative materials were analysed: VG10 (stainless steel with nickel-laminated edges and a VG10 core), RWL₃₄^TM (powder-metallurgical steel), laminated steel K110+N695 (with a nickel interlayer), and forge-welded steel K600+K720. The steels were characterised using OES, optical microscopy and SEM, supported by EDS for local chemical analysis. Microhardness testing was applied to individual structural regions to correlate carbide morphology, layer interfaces, and heat-treatment response with hardness values. The results reveal pronounced differences in structural homogeneity and defect occurrence. Powder-metallurgical RWL₃₄^TM exhibited the most uniform microstructure with finely dispersed Cr carbides, achieving high hardness and absence of structural defects. In contrast, laminated and forge-welded steels contained large primary carbides, carbide precipitation at grain boundaries, porous cavities, and insufficient cohesion in interlayers or weld zones, which may compromise toughness. VG10 and K110+N695 showed carbide coarsening caused by inadequate heat treatment, whereas K600+K720 revealed weld-related defects and heterogeneous phase structures. Overall, the study demonstrates the critical role of heat treatment and processing route in determining blade quality and performance. The findings provide guidance for optimising steel selection and processing technologies in advanced cutlery engineering. Full article

Cutting-edge wear is inevitable in the cutting process of the knife. Studying the relationship between the performance of the knife and the cutting-edge wear is conducive to optimizing the design of the knife and increasing its service life. The micro-morphology of the cutting edge during the cutting process was systematically characterized by optical microscopy (OM) and scanning electron microscopy (SEM). The strength of the material matrix was characterized by nanoindentation, and the microstructure of the material was characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). The influence of different microstructures and geometry parameters of the cutting edge on edge wear was investigated. The experimental results show that the cutting knife longevity decreases with the increase in the edge angle. When the edge angle is 19°, the durability of knives 1# and 2# is 747.5 mm and 826.8 mm; when the edge angle is 29°, the durability of knives 1# and 2# is 377.8 mm and 486.8 mm. Under the same edge angle, the durability of knife 2# is higher, mainly due to its higher hardness and the presence of more micro-scale M23C6 carbides and nano-scale MC carbides. The edge wear process can be divided into two stages. In the initial wear stage, the edge curling phenomenon occurs, which is the plastic deformation of the edge. In the stable wear stage, plowing and stacking of worn materials are observed, which is the abrasive wear process. Full article

The relationship between the stability of tool materials and their cutting performance is a critical technical challenge for the manufacturing industry, which is essential for selecting appropriate treatment processes to achieve superior treatment tool performance. In this paper, a standard cutting tool experiment was used to study the sharpness of the knife with different residual austenite content. The cutting edges of the knife were characterized by an optical microscope (OM), scanning electron microscope (SEM), electron back scattering diffraction (EBSD), and transmission electron microscope (TEM), to analyze the relationship between tool edge hardness and microstructure. The microstructure stability of the material was analyzed by a separated Hopkinson pressure bar (SHPB) experiment. The results show that the hardness and cutting performance of the knives are affected by the joint action of carbide and residual austenite, with an initial increase followed by decreases as the heat treatment quenching temperature increases. After the knife material is treated by cryogenic process, the hardness of the knife is increased by 3.89 HRC, the initial sharpness by 15.3%, and the sharpness and durability by 18.8%. The residual austenite in the knives was found to be unstable and easy to transformation during high-rate deformation processes. This study elucidates the effect of residual austenite content on the sharpness of the knives, providing a foundation for the reasonable control of residual austenite content in the actual production settings. Full article

This paper presents a comprehensive survey of state-of-the-art UAV–based antennas and propagation measurements. Unmanned aerial vehicles (UAVs) have emerged as powerful tools for in situ electromagnetic field assessments due to their flexibility, cost-effectiveness, and ability to operate in challenging environments. This paper highlights various UAV applications, from testing large–scale antenna arrays, such as those used in the square kilometer array (SKA), to evaluating channel models for 5G/6G networks. Additionally, the review discusses technical challenges, such as positioning accuracy and antenna alignment, and it provides insights into the latest advancements in portable measurement systems and antenna designs tailored for UAV use. During the UAV–based antenna measurements, key contributors to the relatively small inaccuracies of around 0.5 to 1 dB are identified. In addition to factors such as GPS positioning errors and UAV vibrations, ground reflections can significantly contribute to inaccuracies, leading to variations in the measured radiation patterns of the antenna. By minimizing ground reflections during UAV–based antenna measurements, errors in key measured antenna parameters, such as HPBW, realized gain, and the front-to-back ratio, can be effectively mitigated. To understand the source of propagation losses in a UAV to ground link, simulations were conducted in CST. These simulations identified scattering effects caused by surrounding buildings. Additionally, by simulating a UAV with a horn antenna, potential sources of electromagnetic coupling between the antenna and the UAV body were detected. The survey concludes by identifying key areas for future research and emphasizing the potential of UAVs to revolutionize antenna and propagation measurement practices to avoid the inaccuracies of the antenna parameters measured by the UAV. Full article

Micro-stereolithography ($\mu$SL) is an advanced additive manufacturing technique that enables the fabrication of highly precise microstructures with fine feature resolution. One of the primary challenges in $\mu$SL is achieving and maintaining precise focus throughout the fabrication process. For the successful application of $\mu$SL, it is essential to maintain the sample surface within a focal depth of several microns. Despite the growing interest in auto-focus devices, limited attention has been directed towards auto-focus systems in image-based auto-focus microscope systems for precision $\mu$SL. To address this challenge, we propose an image-based auto-focus microscope system incorporating visual servo control. In the optical design, a transflective beam splitter is employed, allowing the laser beam to pass through for fabrication while reflecting the focused beam on the sample surface to the microscope and camera. Utilizing captured spot images and the Foucault knife-edge test, a deep learning-based laser spot image processing algorithm is developed to determine the focus position based on spot size and the number of spot pixels on both sides. Experimental results demonstrate that the proposed auto-focus system effectively determines the relative position of the focal point using the laser spot image and achieves auto-focusing through visual servo control. Full article

The two near-identical pushbroom Thermal Infrared Sensors (TIRS) aboard Landsat 8 and 9 are currently imaging the Earth’s surface at 10.9 and 12 microns from similar 705 km altitude, sun-synchronous polar orbits. This work validates the consistency in the imaging data quality, which is vital for harmonization of the data from the two sensors needed for global mapping. The overlapping operation of these two near-identical sensors, launched eight years apart, provides a unique opportunity to assess the sensitivity of the conventionally used metrics to any unexpectedly found nuanced differences in their spatial performance caused by variety of factors. Our study evaluates spatial quality metrics for bands 10 and 11 from 2022, the first complete year during which both TIRS instruments have been operational. The assessment relies on the straight-knife-edge technique, also known as the Edge Method. The study focuses on comparing the consistency and stability of eight separate spatial metrics derived from four separate water–desert boundary scenes. Desert coastal scenes were selected for their high thermal contrast in both the along- and across-track directions with respect to the platforms ground tracks. The analysis makes use of the 30 m upsampled TIRS images. The results show that the Landsat 8 and Landsat 9 TIRS spatial performance are both meeting the spatial performance requirements of the Landsat program, and that the two sensors are consistent and nearly identical in both across- and along-track directions. Better agreement, both with time and in magnitude, is found for the edge slope and line spread function’s full-width at half maximum. The trend of averaged modulation transfer function at Nyquist shows that Landsat 8 TIRS MTF differs more between the along- and across-track scans than that for Landsat 9 TIRS. The across-track MTF is consistently lower than that for the along-track, though the differences are within the scatter seen in the results due to the use of the natural edges. Full article