Search Results (47)

This study investigates the spatter suppression mechanism in aluminum alloy welding using a hybrid fiber–semiconductor laser system. By integrating high-speed photography and three-dimensional thermal-fluid coupling numerical simulations, the spatter formation process and its suppression mechanisms were systematically analyzed. The results indicate that spatter formation is primarily governed by surface tension and recoil pressure. In single fiber laser welding, concentrated laser energy induces a steep temperature gradient on the molten pool surface, triggering a strong Marangoni effect and subsequent spatter generation. In contrast, the hybrid laser system optimizes energy distribution, reducing the temperature gradient and weakening the Marangoni effect, thereby suppressing spatter. Additionally, the hybrid laser stabilizes molten pool flow through uniform recoil pressure distribution, further inhibiting spatter formation. Experimental results demonstrate that the hybrid fiber–semiconductor laser system significantly reduces spatter, improving welding quality and stability. This study provides theoretical and technical support for optimizing aluminum alloy laser welding. Full article

This study offers fresh insights into the technical and stylistic exchanges between Flemish and Portuguese panel painting during the late 15th and early 16th centuries. By comparing two contemporaneous works, we trace Flemish influence in Portugal through a detailed materials and techniques analysis. Non-invasive, in situ methods—including energy dispersive X-ray fluorescence (XRF), macro-photography (MP), infrared reflectography (IRR), and dendrochronology—were used to examine each painting’s wooden support, ground layer, underdrawing, and pigment stratigraphy. Select micro-sampling analyses—micro-Fourier-transform infrared spectroscopy (μ-FTIR), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), and micro-Raman spectroscopy (µ-Raman)—provided complementary data on binder and pigment composition. While both paintings share nearly identical pigments and layering sequences and employ comparable coating techniques, their ground compositions differ subtly. Notably, the Flemish work features extensive gold-leaf application, whereas underdrawing execution takes on principal importance in the Portuguese example. Together, these findings reveal that Jorge Afonso’s workshop developed a distinct Portuguese method—rooted in Flemish practices disseminated by Quentin Metsys—yet adapted to local materials and aesthetic priorities. Full article

The Liaohe River Estuary Wetland, located in Panjin City, plays a critical role in reducing pollution loads, maintaining biodiversity, and ensuring ecological security in China’s coastal regions, contributing significantly to the implementation of the land–sea coordination strategy. As key components of ecological restoration projects, monitoring and evaluating restoration effectiveness provide a reliable basis for decision-making and ecosystem management. This study established an innovative three-dimensional integrated monitoring and evaluation system combining satellite imagery, UAV aerial photography, and field sampling surveys, addressing the technical gaps in multi-scale and multi-dimensional dynamic ecological monitoring. Through systematic monitoring and the assessment of key indicators, including water environment, soil environment, biodiversity, water conservation capacity, and carbon sequestration capacity, we comprehensively evaluated the enhancement effects of ecological restoration projects on regional ecosystem structure, quality, and service functions. The findings demonstrated that the satellite–airborne–ground integrated monitoring technology significantly improved water quality and soil properties, enhanced soil–water conservation capabilities, and increased biodiversity indices and carbon sequestration potential. These results validate the scientific validity of ecological protection measures and the comprehensive benefits of restoration outcomes. The primary contributions of this research lie in the following: developing a novel monitoring framework that provides critical data support for decision-making, project acceptance, effectiveness evaluation, and adaptive management in ecological restoration; establishing transferable methodologies applicable not only to the Liaohe River Estuary wetlands, but also to similar ecosystems globally, showcasing broad applicability in ecological governance. Full article

Painted surfaces, regardless of their substrate, possess unique elements crucial for their study and interpretation. These elements include geometric characteristics, surface texture, brushwork relief, color layer morphology, and preservation state indicators like overpainting, interventions, cracks, and mechanical deformations. Traditional recording methods such as handwritten or digital descriptions, 2D scale drawings, calipers, rulers, tape measures, sketches, tracings, and conventional or technical photography fall short in capturing the three-dimensional detail necessary for comprehensive analysis. To overcome these limitations, this paper proposes the integration of two digital tools, Close-Range Photogrammetry (SfM-MVS) and Reflectance Transformation Imaging (RTI), which have become accessible with the advancement of computing power. While other 3D imaging tools like laser scanners and structured light systems exist and may be preferred for very specialized applications, such as capturing the texture of the surface with sub-millimeter accuracy, SfM-MVS and RTI offer a cost-efficient and highly accurate alternative, with 3D modeling capabilities and advanced pixel color fidelity, essential for documenting the geometric and color details of painted artifacts. The application of these highly promising methods to the mural paintings from the Palace of Tiryns (Nafplion, Greece) demonstrates their potential, providing significant insights for art historians, researchers, conservators, and curators. Full article

The aim of this research is to investigate and use a variety of immersive multisensory media techniques in order to create convincing digital models of fossilised tree trunks for use in XR (Extended Reality). This is made possible through the use of geospatial data derived from aerial imaging using UASs, terrestrial material captured using cameras and the incorporation of both the visual and audio elements for better immersion, accessed and explored in 6 Degrees of Freedom (6DoF). Immersiveness is a key factor of output that is especially engaging to the user. Both conventional and alternative methods are explored and compared, emphasising the advantages made possible with the help of Machine Learning Computational Photography. The material is collected using both UAS and terrestrial camera devices, including a multi-sensor 3D-360° camera, using stitched panoramas as sources for photogrammetry processing. Difficulties such as capturing large free-standing objects using terrestrial means are overcome using practical solutions involving mounts and remote streaming solutions. The key research contributions are comparisons between different imaging techniques and photogrammetry processes, resulting in significantly higher fidelity outputs. Conclusions indicate that superior fidelity can be achieved through the help of Machine Learning Computational Photography processes, and higher resolutions and technical specs of equipment do not necessarily translate into superior outputs. Full article

Landscape, as an important component of environmental quality, is increasingly valued by scholars for its visual dimension. Unlike evaluating landscape visual quality through on-site observation or using digital photos, the landscape visualization modeling method supported by unmanned aerial vehicle (UAV) aerial photography, geographic information System (GIS), and PixScape has the advantage of systematically scanning landscape geographic space. The data acquisition is convenient and fast, and the resolution is high, providing a new attempt for landscape visualization analysis. In order to explore the application of visibility modeling based on high-resolution UAV remote sensing images in landscape visual evaluation, this study takes campus landscape as an example and uses high-resolution campus UAV remote sensing images as the basic data source to analyze the differences between the planar method and tangent method provided by PixScape 1.2 software in visual modeling. Six evaluation factors, including Naturalness (N), Normalized Shannon Diversity Index (S), Contagion (CONTAG), Shannon depth (SD), Depth Line (DL), and Skyline (SL), are selected to evaluate the landscape vision of four viewpoints in the campus based on analytic hierarchy process (AHP) method. The results indicate that the tangent method considers the visual impact of the vertical amplitude and the distance between landscape and viewpoints, which is more in line with the real visual perception of the human eyes. In addition, objective quantitative evaluation metrics based on visibility modeling can reflect the visual differences of landscapes from different viewpoints and have good applicability in campus landscape visual evaluation. It is expected that this research can enrich the method system of landscape visual evaluation and provide technical references for it. Full article

One of the technical possibilities to enhance the properties of lubricants and biolubricants is dispersing nanoparticles in them. Although conceptually simple, this operation faces challenges related to: (1) obtaining an initial good dispersion of the nanoparticles in the liquid and (2) ensuring the stability of this dispersion to avoid coalescence. The objective of this study is to verify possible improvements of the stability and characteristics of conventional and bio-based lubricants by efficiently dispersing in them surface-modified SiO₂ nanoparticles. The silane coupling agent KH570 was utilized to modify the surface properties of SiO₂ nanoparticles, facilitating their dispersion within the lubricants. Nanolubricants and nanobiolubricants were prepared using a two-step technique. The dispersion stability of these lubricants was assessed using sedimentation photography, FTIR, and UV-Vis spectrophotometric analyses. The addition of SiO₂ nanoparticles resulted in enhanced physicochemical properties of the resulting lubricant, including slight increases in density and viscosity, as well as a higher viscosity index. Chemical analyses, such as TAN and TBN measurements, confirmed that the nanoparticle addition at various concentrations (0.25%, 0.5%, 0.75%, and 1.0%) did not introduce critical acidity levels or compromise the alkaline reserve. ICP-OES analysis indicated minimal impact on essential additive concentrations, supporting the feasibility of SiO₂ nanoparticles in enhancing lubricant properties without destabilizing additives. The stability of the nanolubricants was monitored over 77 days, with visible sedimentation beginning around the 30th day and becoming more pronounced by the 54th and 77th days. Bio-lubricants exhibited slightly higher sedimentation than conventional lubricants. Optimizing the sonication time proved to be crucial, with longer sonication times (2.5 h) significantly improving the stability of nanolubricants across various concentrations of added nanoparticles. FTIR analysis confirmed the presence of SiO₂ and KH570, indicating no alteration to the basic functional structures of the lubricants and biolubricants. UV-Vis spectrophotometry further underscored the importance of optimizing sonication time for enhanced stability. Overall, this study demonstrates that incorporating surface-modified SiO₂ nanoparticles enhances the properties and stability of conventional and biolubricants, offering potential for improved performance in industrial and engine applications. Full article

During underwater image processing, image quality is affected by the absorption and scattering of light in water, thus causing problems such as blurring and noise. As a result, poor image quality is unavoidable. To achieve overall satisfying research results, underwater image denoising is vital. This paper presents an underwater image denoising method, named HHDNet, designed to address noise issues arising from environmental interference and technical limitations during underwater robot photography. The method leverages a dual-branch network architecture to handle both high and low frequencies, incorporating a hybrid attention module specifically designed for the removal of high-frequency abrupt noise in underwater images. Input images are decomposed into high-frequency and low-frequency components using a Gaussian kernel. For the high-frequency part, a Global Context Extractor (GCE) module with a hybrid attention mechanism focuses on removing high-frequency abrupt signals by capturing local details and global dependencies simultaneously. For the low-frequency part, efficient residual convolutional units are used in consideration of less noise information. Experimental results demonstrate that HHDNet effectively achieves underwater image denoising tasks, surpassing other existing methods not only in denoising effectiveness but also in maintaining computational efficiency, and thus HHDNet provides more flexibility in underwater image noise removal. Full article

This paper presents the first insight into how Almada Negreiros, a key artist of the first generation of modernism in Portugal, created his mural painting masterpiece in the maritime station of Rocha do Conde de Óbidos in Lisbon. This set of six monumental mural paintings dates from 1946 to 1949 and is considered Almada’s artistic epitome. As part of the ALMADA project: Unveiling the mural painting art of Almada Negreiros, the murals are being analyzed from a technical and material perspective to understand his modus operandi and the material used. This is the first study of this nature carried out on site and in the laboratory using standard and more advanced imaging, non-invasive analysis, and microanalysis techniques. This article reports the results obtained with visual examination, technical photography in visible (Vis), visible raking (Vis-Rak), complemented by 2D and 3D optical microscopy (OM), scanning electron microscopy with energy-dispersive spectrometry (SEM-EDS), and Fourier transform infrared micro-spectroscopy (µ-FTIR) of the paint layers. The results show the similarities, differences, and technical difficulties that the painter may have had when working on the first, third, and presumably last mural to be painted. Vis-Rak light images were particularly useful in providing a clear idea of how the work progressed from top to bottom through large sections of plaster made with lime mortars. It also revealed an innovative pounced technique used by Almada Negreiros to transfer the drawings in full scale to the walls. Other technical characteristics highlighted by the analytical setup are the use of textured, opaque, and transparent paint layers. The structure of the paintings does not follow a rigid build-up from light to dark, showing that the artist freely adapted according to the motif represented. As far as the colour palette is concerned, Almada masterfully uses primary and complementary colours made with Fe-based pigments and with synthetic ultramarine blue, cadmium pigments, and emerald green. Full article

This paper investigates the oil on canvas painting Boat scene (1974) by Liu Kang (1911–2004), belonging to the National Gallery Singapore (NGS). The focus is on disfiguring paint protrusions in a specific area and colour in the composition. Moreover, in search of the possible factors responsible for the creation of the protrusions, the structure and composition of the paint layers were determined. Three possible reasons were put forward to explain this phenomenon: deliberate textural effects, the expansion of metal soaps and unintentional paint contamination during the artistic process. Investigative techniques such as technical photography, digital microscopy, optical microscopy (OM), polarised light microscopy (PLM), field emission scanning electron microscope (FE-SEM-EDS) and attenuated total reflectance micro-Fourier transform infrared spectroscopy (ATR μ-FTIR) were employed to analyse paint layers, including protrusion samples. The analyses revealed that the protrusions resulted from an unintentional contamination of the oil paint during the artistic process by dry fragments of different pigment mixtures bound in drying oil. Zinc soaps were found in significant concentrations within the protrusions and other parts of the painted scene. Nevertheless, the metal soaps do not pose a direct risk to the integrity of the paint layers at the time of this research. The analyses highlight the potential challenges caused by the protrusions that conservators may face while caring for the painting. The research contributes to our ongoing comprehension of the artist’s working process. Full article

With the continuous development of science and technology, UAV technology has been widely used in various fields. As an essential part, light and small UAV platforms have the advantages of being small, lightweight, and easy to operate and thus have been widely used in aerial photography, monitoring, rescue, and other fields. However, the traditional data transmission method can no longer meet the demand for the data transmission speed and stability of small and light UAV platforms. Wireless optical communication has the advantages of being high-speed and license-free, as well as having a large bandwidth strong anti-interference ability, and good confidentiality. Therefore, this paper aims to study high-speed data transmission technology for light and small UAV platforms to improve their transmission speed and stability. In this paper, the characteristics and advantages of UAV airborne laser communication are first elaborated to illustrate the advancements and importance of data transmission technology based on light and small UAV platforms. Then, the composition of a UAV airborne laser communication system is clarified to illustrate the feasibility of conducting airborne laser communication research. Then, the current domestic and international research status of people on light and small UAV airborne laser communication high-speed data transmission systems is reviewed, and its key technical features are analyzed. Finally, the prospects for its application and development trend are investigated. Full article

To address the incomplete image data collection of close-to-ground structures, such as bridge piers and local features like the suspension cables in bridges, obtained from single unmanned aerial vehicle (UAV) oblique photography and the difficulty in acquiring point cloud data for the top structures of bridges using single terrestrial laser scanners (TLSs), as well as the lack of textural information in TLS point clouds, this study aims to establish a high-precision, complete, and realistic bridge model by integrating UAV image data and TLS point cloud data. Using a particular large-scale dual-track bridge as a case study, the methodology involves aerial surveys using a DJI Phantom 4 RTK for comprehensive image capture. We obtain 564 images circling the bridge arches, 508 images for orthorectification, and 491 images of close-range side views. Subsequently, all images, POS data, and ground control point information are imported into Context Capture 2023 software for aerial triangulation and multi-view image dense matching to generate dense point clouds of the bridge. Additionally, ground LiDAR scanning, involving the placement of six scanning stations both on and beneath the bridge, was conducted and the point cloud data from each station are registered in Trimble Business Center 5.5.2 software based on identical feature points. Noise point clouds are then removed using statistical filtering techniques. The integration of UAV image point clouds with TLS point clouds is achieved using the iterative closest point (ICP) algorithm, followed by the creation of a TIN model and texture mapping using Context Capture 2023 software. The effectiveness of the integrated modeling is verified by comparing the geometric accuracy and completeness of the images with those obtained from a single UAV image-based model. The integrated model is used to generate cross-sectional profiles of the dual-track bridge, with detailed annotations of boundary dimensions. Structural inspections reveal honeycomb surfaces and seepage in the bridge piers, as well as painted rust and cracks in the arch ribs. The geometric accuracy of the integrated model in the X, Y, and Z directions is 1.2 cm, 0.8 cm, and 0.9 cm, respectively, while the overall 3D model accuracy is 1.70 cm. This method provides technical reference for the reconstruction of three-dimensional point cloud bridge models. Through 3D reconstruction, railway operators can better monitor and assess the condition of bridge structures, promptly identifying potential defects and damages, thus enabling the adoption of necessary maintenance and repair measures to ensure the structural safety of the bridges. Full article

Research highlights: Tropical forest restoration can be supported by the production of timber species in their understory. While they may appear at odds, they can be reconciled to promote environmental conservation and services. The lack of information on the management of tropical species causes a technical constraint for timber production in the understory of restoration sites, especially given the light restrictions. This issue could be amended with the development of methods to easily manage and estimate light availability, targeting management practices that balance restoration success and productivity. Materials and Methods: We conducted this study in an area within the Atlantic Forest, Brazil, where we tested the efficiency of chemical thinning to increase light availability in the understory of a five-year-old restoration planting, aiming to increase the growth rates of desirable timber species. Moreover, we tested the viability of using hemispherical photography taken with a smartphone to assess light incidence to assist restoration management practices. We calculated the percentage of photosynthetically active radiation (PAR) using a ceptometer in four different thinning intensities and compared them to the smartphone measures using correlation analysis. Results: Chemical thinning increased light incidence in the understory, with potential impacts on timber species productivity. Light management through PAR and canopy opening were highly correlated overall, especially after three months of management and 60% of thinning intensity. Conclusions: These findings demonstrate the potential for chemical thinning as a management practice to enhance light availability in the understory of tropical forest restoration sites. Additionally, our study highlights the value of using affordable and accessible tools like smartphones and fisheye clips for the indirect assessment of light conditions to promote natural regeneration and guide forest management and timber production in tropical forest restoration. Full article

Tailings ponds, essential components of mining operations worldwide, present considerable potential hazards downstream in the event of tailings dam failures. In recent years, instances of tailings dam failures, carrying potential environmental safety hazards, have occasionally occurred on a global scale due to the limited technical approaches available for safety supervision of tailings ponds. In this study, an innovative WebGIS-based unmanned aerial vehicle oblique photography (UAVOP) method was developed to analyze the storage capacity change and dam failure risk of tailings ponds. Its applicability was then validated by deploying it at a tailings pond in Yunfu City, Guangdong Province, China. The results showed that the outcomes of two phases of real-scene 3D images met the specified accuracy requirements with an RSME of 0.147–0.188 m in the plane and 0.198–0.201 m along the elevation. The storage capacities of phase I and phase II tailings ponds were measured at 204,798.63 m³ and 148,291.27 m³, respectively, with a storage capacity change of 56,031.51 m³. Moreover, the minimum flood control dam widths, minimum free heights, and dam slope ratios of the tailings pond were determined to comply with the flood control requirements, indicating a low risk of dam failure of the tailings pond. This pilot case study demonstrated the performance of the UAVOP in evaluating storage capacity change and dam failure risk for tailings ponds. It not only enhanced the efficiency of dynamic safety supervision of tailings ponds but also offered valuable references for globally analogous research endeavors. Full article

Introduction: Cochlear implantation has become the standard of care for the treatment of moderate-to-profound bilateral sensorineural hearing loss. However, current technologies, all of which rely on an external sound processor, have intrinsic limitations that prevent certain activities and diagnostics, thus hampering full integration into a patient’s lifestyle. The Envoy Medical (White Bear Lake, MN, USA) Acclaim^® fully implanted cochlear implant is a new device currently undergoing testing that has been designed to alleviate many of the current constraints by housing all components within the patient, thus allowing for near-constant use in many environments that are not conducive to a traditional cochlear implant. Methods: As part of an Early Feasibility Study, three adult implant candidates were implanted with the Acclaim^® cochlear implant. Surgical video and photography were taken, and initial observations were recorded. Implantation with the Acclaim^® device is largely similar to a traditional cochlear implant, with modifications to allow room for the implanted sensor as well as the implantation of a battery in the subcutaneous tissues of the chest. Results: This study demonstrates a step-by-step overview of implanting the Acclaim^® and discusses initial insight and experiences with the first three implantations with this new device. Conclusions: All three surgeries proceeded without complication, and at activation, all three patients were hearing through their devices. Surgery is more technically challenging compared to a standard cochlear implant, but the skills needed can all be mastered by a dedicated otologic surgeon. Full article