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Search Results (5,309)

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14 pages, 717 KiB  
Article
Quantum Congestion Game for Overcrowding Prevention within Airport Common Areas
by Evangelos D. Spyrou, Vassilios Kappatos and Chrysostomos Stylios
Computers 2024, 13(11), 298; https://doi.org/10.3390/computers13110298 (registering DOI) - 17 Nov 2024
Abstract
Quantum game theory merges principles from quantum mechanics with game theory, exploring how quantum phenomena such as superposition and entanglement can influence strategic decision making. It offers a novel approach to analyzing and optimizing complex systems where traditional game theory may fall short. [...] Read more.
Quantum game theory merges principles from quantum mechanics with game theory, exploring how quantum phenomena such as superposition and entanglement can influence strategic decision making. It offers a novel approach to analyzing and optimizing complex systems where traditional game theory may fall short. Congestion of passengers, if considered as a network, may fall into the categories of optimization cases of quantum games. This paper explores the application of quantum potential games to minimize congestion in common areas at airports. The players/passengers of the airport have identical interests and they share the same utility function. A metric is introduced that considers a passenger’s visit to a common area by setting their preferences, in order to avoid congestion. Passengers can decide whether to visit a specific common area or choose an alternative. This study demonstrates that the proposed game is a quantum potential game for tackling congestion, with identical interests, ensuring the existence of a Nash equilibrium. We consider passengers to be players that want to ensure their interests. Quantum entanglement is utilized to validate the concept, and the results highlight the effectiveness of this approach. The objective is to ensure that not all passengers select the same common place of the airport to reduce getting crowded; hence, the airborne disease infection probability increases due to overcrowding. Our findings provide a promising framework for optimizing passenger flow and reducing congestion in airport common areas through quantum game theory. We showed that the proposed system is stable by encapsulating the Lyapunov stability. We compared it to a simulated annealing approach to show the efficacy of the quantum game approach. We acknowledge that this framework can be utilized in other disciplines as well. For our future work, we will research different strategies than binary ones to investigate the efficacy of the approach. Full article
20 pages, 1401 KiB  
Article
Optimal Configuration of Physical Process Parameterization Scheme Combination for Simulating Meteorological Variables in Weather Research and Forecasting Model: Based on Orthogonal Experimental Design and Comprehensive Evaluation Method
by Zhengming Li, Hanqing Wang, Xinyu Liu and Da Yuan
Atmosphere 2024, 15(11), 1385; https://doi.org/10.3390/atmos15111385 (registering DOI) - 17 Nov 2024
Abstract
The weather research and forecasting (WRF) model is frequently used to investigate the meteorological field around nuclear installations. The configuration of physical process parameterization schemes in the WRF model has a significant impact on the accuracy of the simulation results. Consequently, carrying out [...] Read more.
The weather research and forecasting (WRF) model is frequently used to investigate the meteorological field around nuclear installations. The configuration of physical process parameterization schemes in the WRF model has a significant impact on the accuracy of the simulation results. Consequently, carrying out a pre-experiment to quickly obtain the optimal combination of parameterization schemes is essential before conducting meteorological parameter research. To obtain the optimal combination of physical process parameterization schemes from the planetary boundary layer (PBL), land surface (LSF), microphysical (MP), long-wave (LW), and short-wave (SW) radiation processes of the WRF model for simulating the near-surface meteorological variables near a nuclear power plant in Sanshan Town, Fuqing City, Fujian Province, China on 4 June 2019 were observed. Orthogonal experimental design (OED), a comprehensive evaluation method based on the CRiteria Import Through Intercriteria Correlation (CRITIC) weight analysis, and comprehensive balance method were employed for the first time to conduct the research. The sensitivity of meteorological variables to physical processes was first discussed. The findings revealed that the PBL scheme configuration had a profound impact on simulating wind fields. Furthermore, the LSF scheme configuration had a significant influence on simulating near-surface temperature and relative humidity, which was much greater than that of other physical processes. In addition, the choice of the radiation scheme had a significant impact on how the temperature was distributed close to the ground and how the wind field was simulated. Furthermore, the configuration of the MP scheme was found to exert a certain influence on the simulation of relative humidity; however, it demonstrated a weak influence on other meteorological variables. Secondly, The MYNN3 scheme for PBL process, the NoahMP scheme for LSF process, the WSM5 scheme for MP process, the RRTMG scheme for LW process, and the Dudhia scheme for SW process are found to be the comprehensive optimal physical process parameterization scheme combination for simulating meteorological variables in the research area selected in this study. As evident from the findings, the use of the OED method to obtain the combinations of the optimal physical process parameterization scheme could successfully reproduce the wind field, temperature, and relative humidity in the current study. Thus, this method appears to be highly reliable and effective for use in the WRF models to explore the optimal combinations of the physical process parameterization scheme, which could provide theoretical support to quickly analyzing accurate meteorological field data for longer periods and contribute to deeply investigating the migration and diffusion behavior of airborne pollutants in the atmosphere. Full article
(This article belongs to the Section Atmospheric Techniques, Instruments, and Modeling)
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<p>Modeling domains used in WRF with topography height (m). The outer nested domain (D1); the middle nested domain (D2); the inner nested domain (D3).</p>
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<p>Distribution of standard deviation of each physical processes to simulate different meteorological variables (10 m wind speed, 10 m wind direction, 2 m wind temperature, and 2 m relative humidity). The factors with the largest standard deviation of each meteorological variable are highlighted with a grid.</p>
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<p>The distribution of the average comprehensive scores of each physical parameterization scheme to simulate the meteorological variable: (<b>a</b>) 10 m wind speed, (<b>b</b>) 10 m wind direction, (<b>c</b>) 2 m wind temperature, and (<b>d</b>) 2 m relative humidity. As shown in <a href="#atmosphere-15-01385-t001" class="html-table">Table 1</a>, the numbers of each physical process correspond to the specific parameterization schemes. The parameterization scheme with the highest score in each physical process is highlighted with a grid.</p>
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36 pages, 13266 KiB  
Review
Airborne Microplastics: Challenges, Prospects, and Experimental Approaches
by Alexey R. Rednikin, Yulia A. Frank, Artem O. Rozhin, Danil S. Vorobiev and Rawil F. Fakhrullin
Atmosphere 2024, 15(11), 1380; https://doi.org/10.3390/atmos15111380 (registering DOI) - 15 Nov 2024
Viewed by 693
Abstract
Airborne microplastics are emerging pollutants originating from disposable tableware, packaging materials, textiles, and other consumer goods. Microplastics vary in shape and size and exposed to external factors break down into even smaller fractions. Airborne microplastics are abundant in both urban and natural environments, [...] Read more.
Airborne microplastics are emerging pollutants originating from disposable tableware, packaging materials, textiles, and other consumer goods. Microplastics vary in shape and size and exposed to external factors break down into even smaller fractions. Airborne microplastics are abundant in both urban and natural environments, including water bodies and glaciers, as particles can travel long distances. The potential toxicity of airborne microplastics cannot be underestimated. Microparticles, especially those < 10 µm, entering the human body through inhalation or ingestion have been shown to cause serious adverse health effects, such as chronic inflammation, oxidation stress, physical damage to tissues, etc. Microplastics adsorb toxic chemicals and biopolymers, forming a polymer corona on their surface, affecting their overall toxicity. In addition, microplastics can also affect carbon dynamics in ecosystems and have a serious impact on biochemical cycles. The approaches to improve sampling techniques and develop standardized methods to assess airborne microplastics are still far from being perfect. The mechanisms of microplastic intracellular and tissue transport are still not clear, and the impact of airborne microplastics on human health is not understood well. Reduced consumption followed by collection, reuse, and recycling of microplastics can contribute to solving the microplastic problem. Combinations of different filtration techniques and membrane bioreactors can be used to optimize the removal of microplastic contaminants from wastewater. In this review we critically summarize the existing body of literature on airborne microplastics, including their distribution, identification, and safety assessment. Full article
(This article belongs to the Section Air Quality)
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<p>Bright field microscopy images of different types of MPs: (<b>a</b>) fiber, (<b>b</b>) foam, (<b>c</b>,<b>d</b>) film, (<b>e</b>) fragment, (<b>f</b>) microsphere. (<b>a1</b>,<b>b1</b>,<b>c1</b>,<b>d1</b>,<b>e1</b>,<b>f1</b>) are the corresponding fluorescence micrographs [<a href="#B80-atmosphere-15-01380" class="html-bibr">80</a>].</p>
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<p>Chemical structure of common MP components: polypropylene (<b>1</b>) and polystyrene (<b>2</b>).</p>
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<p>Mean daily AMP deposition (m<sup>−2</sup> d<sup>−1</sup>) by region (based on the published data, <a href="#app1-atmosphere-15-01380" class="html-app">Table S1</a>)—(<b>a</b>); proportion of DAMPs in urban areas and in remote areas, %—(<b>b</b>).</p>
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<p>Interaction between AMPs and the human body.</p>
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<p>Stages in studying AMPs: Step 1—Sampling by active (<b>a</b>) or passive (<b>b</b>) methods; Step 2—Laboratory processing with density separation (<b>c</b>) and digestion (<b>d</b>); Step 3—Particle analysis: quantitative counting, determination of size, shape, color (<b>e</b>) and polymer identification (<b>f</b>).</p>
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14 pages, 1238 KiB  
Article
Optimization of Thermal Management for the Environmental Worthiness Design of Aviation Equipment Using Phase Change Materials
by Jianjun Zhang, Minwei Li, He Li, Yun Fu and Liangxu Cai
Aerospace 2024, 11(11), 943; https://doi.org/10.3390/aerospace11110943 (registering DOI) - 15 Nov 2024
Viewed by 188
Abstract
A phase change materials (PCM)-based heat sink is an effective way to cool intermittent high-power electronic devices in aerospace applications such as airborne electronics and aircraft external carry. Optimizing the heat sink is significant in designing a compact and efficient system. This paper [...] Read more.
A phase change materials (PCM)-based heat sink is an effective way to cool intermittent high-power electronic devices in aerospace applications such as airborne electronics and aircraft external carry. Optimizing the heat sink is significant in designing a compact and efficient system. This paper proposes an optimization procedure for the PCM/expanded graphite (EG)-based heat sink to minimize the temperature of the heat source. The numerical model is built to estimate the thermal response, and a surrogate model is fitted using the Kriging model. An optimization algorithm is constructed to predict the optimum parameters of the heat sink, and the effects of heat sink volume, heat flux, and working time on the optimal parameters of the heat sink are investigated. This shows that the numerical results agree well with the experimental data, and the proposed optimization method effectively obtains the optimal EG mass fraction and the geometric dimensions of the PCM enclosure. The optimal EG mass fraction increases with the rise in heat sink volume and decreases with the increase in heat flux and working time. The optimal ratio of the height to the length of the heat sink is 0.43. This study provides practical guidance for the optimal design of a PCM/EG-based heat sink. Full article
(This article belongs to the Special Issue Aerospace Human–Machine and Environmental Control Engineering)
19 pages, 8720 KiB  
Article
Spatial Attention-Based Kernel Point Convolution Network for Semantic Segmentation of Transmission Corridor Scenarios in Airborne Laser Scanning Point Clouds
by Fangrong Zhou, Gang Wen, Yi Ma, Hao Pan, Guofang Wang and Yifan Wang
Electronics 2024, 13(22), 4501; https://doi.org/10.3390/electronics13224501 (registering DOI) - 15 Nov 2024
Viewed by 215
Abstract
Accurate semantic segmentation in transmission corridor scenes is crucial for the maintenance and inspection of power infrastructure, facilitating the timely detection of potential hazards. In this study, we propose SA-KPConv, an advanced segmentation model specifically designed for transmission corridor scenarios. Traditional approaches, including [...] Read more.
Accurate semantic segmentation in transmission corridor scenes is crucial for the maintenance and inspection of power infrastructure, facilitating the timely detection of potential hazards. In this study, we propose SA-KPConv, an advanced segmentation model specifically designed for transmission corridor scenarios. Traditional approaches, including Random Forest and point-based deep learning models such as PointNet++, demonstrate limitations in segmenting critical infrastructure components, particularly power lines and towers, primarily due to their inadequate capacity to capture complex spatial relationships and local geometric details. Our model effectively addresses these challenges by integrating a spatial attention module with kernel point convolution, enhancing both global context and local feature extraction. Experiments demonstrate that SA-KPConv outperforms state-of-the-art methods, achieving a mean Intersection over Union (mIoU) of 89.62%, particularly excelling in challenging terrains such as mountainous areas. Ablation studies further validate the significance of our model’s components in enhancing overall performance and effectively addressing class imbalance. This study presents a robust solution for semantic segmentation, with considerable potential for monitoring and maintaining power infrastructure. Full article
(This article belongs to the Special Issue Deep Learning for Power Transmission and Distribution)
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<p>Overall processing workflow of transmission corridor scene semantic segmentation, including two stages: data preprocessing and semantic segmentation.</p>
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<p>Schematic diagram of grid sampling (taking towers as an example). The left side of the diagram represents the original point cloud, while the right side illustrates the grid sampling method and its results.</p>
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<p>Proposed SA-KPConv network architecture. Light green rectangles represent kernel point convolution blocks, dark green rectangles indicate geometric neighborhood features, dark blue rectangles are unary blocks, and light blue rectangles show merging operations. Orange rectangles denote the spatial attention module, while purple and orange arrows indicate upsampling and downsampling processes, respectively.</p>
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<p>Structure of the kernel point convolution layer. This layer updates the weight of each point based on the kernel point function, facilitating the extraction of local geometric features.</p>
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<p>Spatial attention module. The features obtained after kernel point convolution undergo global attention updates through this module, enhancing the model’s prediction accuracy.</p>
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<p>Sample proportions of each category in the datasets. Blue represents important facilities within the transmission corridor, while gray indicates other categories.</p>
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<p>Data and annotations used in experiments, including flatland, buildings, and mountainous areas.</p>
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<p>Semantic segmentation results of our methods in flat and built-up areas, where (<b>a</b>) represents built-up areas and (<b>b</b>) represents flat areas. The red circles mark the parts that were incorrectly predicted.</p>
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<p>Semantic segmentation results in mountainous areas. The black box highlights the details of the power tower section.</p>
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<p>Qualitative results of semantic segmentation compared to different methods. The red circles mark the parts that were incorrectly predicted.</p>
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<p>Qualitative results of semantic segmentation compared to different methods. The black circles mark the parts that were incorrectly predicted.</p>
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28 pages, 11922 KiB  
Review
Review of Key Technologies for Aviation Intelligent Pumps
by Xudong Han, Yan Wang, Liming Yu, Yongling Fu and Deming Zhu
Actuators 2024, 13(11), 461; https://doi.org/10.3390/act13110461 - 15 Nov 2024
Viewed by 249
Abstract
The airborne intelligent hydraulic system is an effective way to solve the ineffective power consumption and temperature rise of an aircraft hydraulic system. An intelligent pump that can work in a variety of modes according to the change of flight conditions is an [...] Read more.
The airborne intelligent hydraulic system is an effective way to solve the ineffective power consumption and temperature rise of an aircraft hydraulic system. An intelligent pump that can work in a variety of modes according to the change of flight conditions is an inevitable requirement for the realization of airborne intelligent hydraulic system, and it is also the development trend of aviation pumps in the future. In this paper, key technologies for aviation intelligent pumps are reviewed. This paper briefly describes its development process and summarizes the research on aviation intelligent pumps from the aspects of the system scheme, working mode, structure form, and control strategy. Finally, the conclusions and trends of the research status of intelligent pumps are given, which can provide a reference for subsequent research on further improving the performance of aviation intelligent pumps. Full article
(This article belongs to the Section Aircraft Actuators)
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<p>Information interaction between intelligent pumps and the flight control system. Reprinted/adapted with permission from Ref. [<a href="#B4-actuators-13-00461" class="html-bibr">4</a>]. 1986, SAE International.</p>
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<p>Information interaction for intelligent pump systems.</p>
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<p>Iso-pressure line chart within the flight envelope. Reprinted/adapted with permission from Ref. [<a href="#B4-actuators-13-00461" class="html-bibr">4</a>]. 1986, SAE International.</p>
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<p>Schematic diagram of the signal synthesis method. Reprinted/adapted with permission from Ref. [<a href="#B41-actuators-13-00461" class="html-bibr">41</a>]. 1991, SAE International.</p>
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<p>Response of intelligent pump systems under mode switching and control signal changes. (<b>a</b>) Output flow; (<b>b</b>) outlet pressure; (<b>c</b>) output power; and (<b>d</b>) pressure drop.</p>
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<p>Comparison of experimental temperatures between intelligent pumps and constant-pressure pumps. (<b>a</b>) Test temperatures for intelligent pumps; and (<b>b</b>) test temperatures for constant-pressure pumps. Reprinted/adapted with permission from Ref. [<a href="#B41-actuators-13-00461" class="html-bibr">41</a>]. 1991, SAE International.</p>
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<p>Comparison of experimental heat loss between intelligent pumps and constant-pressure pumps. (<b>a</b>) Heat loss in intelligent pumps; and (<b>b</b>) heat loss in constant-pressure pumps. Reprinted/adapted with permission from Ref. [<a href="#B41-actuators-13-00461" class="html-bibr">41</a>]. 1991, SAE International.</p>
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<p>Comparison of energy consumption between intelligent pumps and constant-pressure pumps. Reprinted/adapted with permission from Ref. [<a href="#B41-actuators-13-00461" class="html-bibr">41</a>]. 1991, SAE International.</p>
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<p>Servo valve indirect drive structure. (<b>a</b>) Mechanical feedback type; and (<b>b</b>) eElectrical feedback type. Reprinted/adapted with permission from Ref. [<a href="#B4-actuators-13-00461" class="html-bibr">4</a>]. 1986, SAE International.</p>
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<p>Servo valve direct-drive structure. Reprinted/adapted with permission from Ref. [<a href="#B4-actuators-13-00461" class="html-bibr">4</a>]. 1986, SAE International.</p>
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<p>Schematic diagram of the airborne intelligent pump system.</p>
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<p>Structure and schematic diagram of the intelligent pump. (<b>a</b>) Structure diagram; and (<b>b</b>) schematic diagram.</p>
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<p>Electric variable displacement pump structure diagram.</p>
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<p>Schematic structure of the electric servo variable displacement mechanism of the intelligent pump.</p>
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<p>Classification of structural solutions for intelligent pumps.</p>
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<p>Schematic diagram of the self-supplied aviation intelligent pump [<a href="#B58-actuators-13-00461" class="html-bibr">58</a>].</p>
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<p>Control structure of fixed displacement variable speed intelligent pump system.</p>
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<p>Double-loop flow control system structure of intelligent pump.</p>
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<p>Self-supplied aviation intelligent pump simulation model. (<b>a</b>) Intelligent pump system model; and (<b>b</b>) internal model of intelligent pump package module.</p>
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<p>Swashplate inclination with different control piston diameters [<a href="#B58-actuators-13-00461" class="html-bibr">58</a>].</p>
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<p>Output characteristics with different control piston diameters. (<b>a</b>) Pump outlet pressure; and (<b>b</b>) pump output flow [<a href="#B58-actuators-13-00461" class="html-bibr">58</a>].</p>
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<p>Sinusoidal signal tracking results for pump outlet pressure. (<b>a</b>) The response of sinusoidal signal; and (<b>b</b>) response error of sinusoidal signal. Reprinted/adapted with permission from Ref. [<a href="#B63-actuators-13-00461" class="html-bibr">63</a>]. 2019, IEEE.</p>
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<p>Pressure signal response under complex conditions. (<b>a</b>) Pressure signal response curve under multiple load conditions; and (<b>b</b>) pressure signal response error curve under multi-load conditions. Reprinted/adapted with permission from Ref. [<a href="#B63-actuators-13-00461" class="html-bibr">63</a>]. 2019, IEEE.</p>
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<p>Self-supplied aviation intelligent pump prototype and experimental platform [<a href="#B58-actuators-13-00461" class="html-bibr">58</a>].</p>
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<p>Output characteristics with different servo valve input voltages (experimental results). (<b>a</b>) Pump outlet pressure; and (<b>b</b>) pump output flow [<a href="#B58-actuators-13-00461" class="html-bibr">58</a>].</p>
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<p>Experimental setup of the VDAPP system. (<b>a</b>) The variable displacement axial piston pump; and (<b>b</b>) the control valve. Reprinted/adapted with permission from Ref. [<a href="#B60-actuators-13-00461" class="html-bibr">60</a>]. 2022, Elsevier.</p>
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<p>Pressure tracking results for VDAPP. Reprinted/adapted with permission from Ref. [<a href="#B60-actuators-13-00461" class="html-bibr">60</a>]. 2022, Elsevier.</p>
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<p>Experimental setup for the axial piston pump. (<b>a</b>) Experimental setup; and (<b>b</b>) schematic diagram. Reprinted/adapted with permission from Ref. [<a href="#B61-actuators-13-00461" class="html-bibr">61</a>]. 2010, Elsevier.</p>
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<p>Measurement results for a rapid change of the load coefficient while tracking a trajectory in the load pressure. (<b>a</b>) Pressure signal tracking results; and (<b>b</b>) estimated results of load coefficient. Reprinted/adapted with permission from Ref. [<a href="#B61-actuators-13-00461" class="html-bibr">61</a>]. 2010, Elsevier.</p>
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<p>Measurement results for a slow change of the load coefficient while tracking a trajectory in the load pressure. (<b>a</b>) Pressure signal tracking results; and (<b>b</b>) estimated results of load coefficient. Reprinted/adapted with permission from Ref. [<a href="#B61-actuators-13-00461" class="html-bibr">61</a>]. 2010, Elsevier.</p>
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22 pages, 5816 KiB  
Article
Causality-Driven Feature Selection for Calibrating Low-Cost Airborne Particulate Sensors Using Machine Learning
by Vinu Sooriyaarachchi, David J. Lary, Lakitha O. H. Wijeratne and John Waczak
Sensors 2024, 24(22), 7304; https://doi.org/10.3390/s24227304 - 15 Nov 2024
Viewed by 287
Abstract
With escalating global environmental challenges and worsening air quality, there is an urgent need for enhanced environmental monitoring capabilities. Low-cost sensor networks are emerging as a vital solution, enabling widespread and affordable deployment at fine spatial resolutions. In this context, machine learning for [...] Read more.
With escalating global environmental challenges and worsening air quality, there is an urgent need for enhanced environmental monitoring capabilities. Low-cost sensor networks are emerging as a vital solution, enabling widespread and affordable deployment at fine spatial resolutions. In this context, machine learning for the calibration of low-cost sensors is particularly valuable. However, traditional machine learning models often lack interpretability and generalizability when applied to complex, dynamic environmental data. To address this, we propose a causal feature selection approach based on convergent cross mapping within the machine learning pipeline to build more robustly calibrated sensor networks. This approach is applied in the calibration of a low-cost optical particle counter OPC-N3, effectively reproducing the measurements of PM1 and PM2.5 as recorded by research-grade spectrometers. We evaluated the predictive performance and generalizability of these causally optimized models, observing improvements in both while reducing the number of input features, thus adhering to the Occam’s razor principle. For the PM1 calibration model, the proposed feature selection reduced the mean squared error on the test set by 43.2% compared to the model with all input features, while the SHAP value-based selection only achieved a reduction of 29.6%. Similarly, for the PM2.5 model, the proposed feature selection led to a 33.2% reduction in the mean squared error, outperforming the 30.2% reduction achieved by the SHAP value-based selection. By integrating sensors with advanced machine learning techniques, this approach advances urban air quality monitoring, fostering a deeper scientific understanding of microenvironments. Beyond the current test cases, this feature selection method holds potential for broader applications in other environmental monitoring applications, contributing to the development of interpretable and robust environmental models. Full article
(This article belongs to the Section Sensor Networks)
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<p>(<b>a</b>) Attractor manifold of the canonical Lorenz system (<span class="html-italic">M</span>) plotted in 3D space, showing the trajectory of the original system in the state space with variables <span class="html-italic">X</span>, <span class="html-italic">Y</span>, and <span class="html-italic">Z</span>. (<b>b</b>) Reconstructed manifold <math display="inline"><semantics> <msub> <mi>M</mi> <mi>X</mi> </msub> </semantics></math> using delay-coordinate embedding of the <span class="html-italic">X</span> variable. The coordinates <math display="inline"><semantics> <mrow> <mi>X</mi> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <mi>X</mi> <mo>(</mo> <mi>t</mi> <mo>−</mo> <mi>τ</mi> <mo>)</mo> </mrow> </semantics></math>, and <math display="inline"><semantics> <mrow> <mi>X</mi> <mo>(</mo> <mi>t</mi> <mo>−</mo> <mn>2</mn> <mi>τ</mi> <mo>)</mo> </mrow> </semantics></math> approximate the original attractor dynamics, capturing the structure of the system dynamics based only on the <span class="html-italic">X</span> time series. (<b>c</b>) Reconstructed manifold <math display="inline"><semantics> <msub> <mi>M</mi> <mi>Y</mi> </msub> </semantics></math> using delay-coordinate embedding of the <span class="html-italic">Y</span> variable. The coordinates <math display="inline"><semantics> <mrow> <mi>Y</mi> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <mi>T</mi> <mo>(</mo> <mi>t</mi> <mo>−</mo> <mi>τ</mi> <mo>)</mo> </mrow> </semantics></math>, and <math display="inline"><semantics> <mrow> <mi>Y</mi> <mo>(</mo> <mi>t</mi> <mo>−</mo> <mn>2</mn> <mi>τ</mi> <mo>)</mo> </mrow> </semantics></math> again form an attractor diffeomorphic to the original manifold, illustrating how the <span class="html-italic">Y</span> time series alone, through lagged coordinates, captures the dynamics of the system.</p>
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<p>Proposed causality-driven feature selection pipeline.</p>
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<p>Input features to the <math display="inline"><semantics> <mrow> <msub> <mi>PM</mi> <mn>1</mn> </msub> </mrow> </semantics></math> calibration model ranked in descending order of mean absolute SHAP values. The 10 highest-ranked features are highlighted in red.</p>
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<p>Potential input features to the <math display="inline"><semantics> <mrow> <msub> <mi>PM</mi> <mn>1</mn> </msub> </mrow> </semantics></math> calibration model ranked in descending order of strength of causal influence after eliminating features with <span class="html-italic">p</span>-value <math display="inline"><semantics> <mrow> <mo>≥</mo> <mn>0.05</mn> </mrow> </semantics></math>. The 10 highest-ranked features are highlighted in red.</p>
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<p>Input features to the <math display="inline"><semantics> <mrow> <msub> <mi>PM</mi> <mrow> <mn>2.5</mn> </mrow> </msub> </mrow> </semantics></math> calibration model ranked in descending order of mean absolute SHAP values. The 10 highest-ranked features are highlighted in red.</p>
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<p>Potential input features to the <math display="inline"><semantics> <mrow> <msub> <mi>PM</mi> <mrow> <mn>2.5</mn> </mrow> </msub> </mrow> </semantics></math> calibration model ranked in descending order of strength of causal influence after eliminating features with <span class="html-italic">p</span>-value <math display="inline"><semantics> <mrow> <mo>≥</mo> <mn>0.05</mn> </mrow> </semantics></math>. The 10 highest-ranked features are highlighted in red.</p>
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<p>Scatter diagram comparing the <math display="inline"><semantics> <mrow> <msub> <mi>PM</mi> <mn>1</mn> </msub> </mrow> </semantics></math> measurements from the reference instrument on the x-axis against the <math display="inline"><semantics> <mrow> <msub> <mi>PM</mi> <mn>1</mn> </msub> </mrow> </semantics></math> estimates from OPC-N3 on the y-axis prior to calibration.</p>
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<p>Density plots of the residuals for the <math display="inline"><semantics> <mrow> <msub> <mi>PM</mi> <mn>1</mn> </msub> </mrow> </semantics></math> calibration models derived from each approach.</p>
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<p>Scatter diagrams for the calibration models with the x-axis showing the <math display="inline"><semantics> <mrow> <msub> <mi>PM</mi> <mn>1</mn> </msub> </mrow> </semantics></math> count from the reference instrument and the y-axis showing the <math display="inline"><semantics> <mrow> <msub> <mi>PM</mi> <mn>1</mn> </msub> </mrow> </semantics></math> count provided by calibrating the LCS: (<b>a</b>) Without any feature selection. (<b>b</b>) SHAP value-based feature selection. (<b>c</b>) Causality-based feature selection. (<b>d</b>) Comparison of true vs. predicted values for the test set across models.</p>
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<p>Scatter diagram comparing the <math display="inline"><semantics> <mrow> <msub> <mi>PM</mi> <mrow> <mn>2.5</mn> </mrow> </msub> </mrow> </semantics></math> measurements from the reference instrument on the x-axis against the <math display="inline"><semantics> <mrow> <msub> <mi>PM</mi> <mrow> <mn>2.5</mn> </mrow> </msub> </mrow> </semantics></math> estimates from OPC-N3 on the y-axis prior to calibration.</p>
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<p>Density plots of the residuals for the <math display="inline"><semantics> <mrow> <msub> <mi>PM</mi> <mrow> <mn>2.5</mn> </mrow> </msub> </mrow> </semantics></math> calibration models derived from each approach.</p>
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<p>Scatter diagrams for the calibration models with the x-axis showing the <math display="inline"><semantics> <mrow> <msub> <mi>PM</mi> <mrow> <mn>2.5</mn> </mrow> </msub> </mrow> </semantics></math> count from the reference instrument and the y-axis showing the <math display="inline"><semantics> <mrow> <msub> <mi>PM</mi> <mrow> <mn>2.5</mn> </mrow> </msub> </mrow> </semantics></math> count provided by calibrating the LCS: (<b>a</b>) Without any feature selection. (<b>b</b>) SHAP value-based feature selection. (<b>c</b>) Causality-based feature selection. (<b>d</b>) Comparison of true vs. predicted values for the test set across models.</p>
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18 pages, 19260 KiB  
Article
Refraction-Aware Structure from Motion for Airborne Bathymetry
by Alexandros Makris, Vassilis C. Nicodemou, Evangelos Alevizos, Iason Oikonomidis, Dimitrios D. Alexakis and Anastasios Roussos
Remote Sens. 2024, 16(22), 4253; https://doi.org/10.3390/rs16224253 - 15 Nov 2024
Viewed by 253
Abstract
In this work, we introduce the first pipeline that combines a refraction-aware structure from motion (SfM) method with a deep learning model specifically designed for airborne bathymetry. We accurately estimate the 3D positions of the submerged points by integrating refraction geometry within the [...] Read more.
In this work, we introduce the first pipeline that combines a refraction-aware structure from motion (SfM) method with a deep learning model specifically designed for airborne bathymetry. We accurately estimate the 3D positions of the submerged points by integrating refraction geometry within the SfM optimization problem. This way, no refraction correction as post-processing is required. Experiments with simulated data that approach real-world capturing conditions demonstrate that SfM with refraction correction is extremely accurate, with submillimeter errors. We integrate our refraction-aware SfM within a deep learning framework that also takes into account radiometrical information, developing a combined spectral and geometry-based approach, with further improvements in accuracy and robustness to different seafloor types, both textured and textureless. We conducted experiments with real-world data at two locations in the southern Mediterranean Sea, with varying seafloor types, which demonstrate the benefits of refraction correction for the deep learning framework. We made our refraction-aware SfM open source, providing researchers in airborne bathymetry with a practical tool to apply SfM in shallow water areas. Full article
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Figure 1
<p>Method pipeline. Drone-acquired images are used as input to our R-SfM method. From the same images, the RGB band ratios are extracted and fed, along with the R-SfM output, to the CNN model. The ground truth for CNN training is obtained using sonar measurements performed by the USV. The CNN output is dense bathymetry.</p>
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<p>(<b>a</b>) Concept sketch of the proposed refraction-aware structure from motion (R-SfM) method. Our method estimates the true point locations (solid points) during the bundle adjustment stage of SfM. This is in contrast to most other approaches, which first perform standard SfM, obtaining wrong position estimations (rings), then attempting to correct them in post-processing. (<b>b</b>) Refraction geometry. Point S is observed by E through a planar refractive interface with normal N. Point R is the apparent position of S on the interface. Snell’s law determines the relationship between the angles a1 and a2.</p>
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<p>Simulated dataset areas: GS, RSA, RSB. Color coding represents water depth; darker is deeper.</p>
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<p>Overview of the study areas, Kalamaki and Plakias. (<b>a</b>) The study areas are located in the western and central parts of the island of Crete, Greece (red region). (<b>b</b>) Kalamaki beach is located on the north shore (35°30′50N, 23°57′50E), while Plakias is on the south (35°11′25N 24°23′30E). (<b>c</b>) Satellite imagery of Kalamaki. (<b>d</b>) Satellite imagery of Plakias. Source: Google Earth. The areas highlighted with green in (<b>c</b>,<b>d</b>) correspond to the regions of interest that are used for training and testing purposes by combining UAV and USV measurements.</p>
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<p>Examples of 8 out of 810 images acquired with the UAV at Kalamaki beach. The images capture portions of the bottom-center area of the sea region highlighted in green in <a href="#remotesensing-16-04253-f004" class="html-fig">Figure 4</a>c.</p>
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<p>Examples of 3 out of 440 images acquired with the UAV at Plakias beach. The images capture portions of the top-right area of the sea region highlighted in green in <a href="#remotesensing-16-04253-f004" class="html-fig">Figure 4</a>d.</p>
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<p>USV measurements (blue dots). (<b>a</b>) Kalamaki bay (area highlighted in green in <a href="#remotesensing-16-04253-f004" class="html-fig">Figure 4</a>c); (<b>b</b>) Plakias (area highlighted in green in <a href="#remotesensing-16-04253-f004" class="html-fig">Figure 4</a>d). Every valid pixel (non-white) was processed by our method to obtain depth estimations, but only regions that contain USV measurements were used for training and quantitative evaluation of the CNN.</p>
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<p>Sparse SfM (top)/R-SfM (bottom) estimations and corresponding scatter plots of test points on the Kalamaki dataset (area highlighted in green in <a href="#remotesensing-16-04253-f004" class="html-fig">Figure 4</a>c). The red points on the estimation maps represent points with depth outside of the colormap range [−6 m, 0 m].</p>
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<p>Cumulative error between the CNN model trained on RGB plus R-SfM, simple SfM, and without any SfM (RGB only) on the Kalamaki dataset. The <span class="html-italic">y</span>-axis depicts the number of test points (in percentage) that fall under the corresponding error in the <span class="html-italic">x</span>-axis.</p>
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<p>CNN R-SfM and RGB, CNN simple SfM and RGB, and CNN RGB only estimations and corresponding scatter plots of test points on the Kalamaki dataset (area highlighted in green in <a href="#remotesensing-16-04253-f004" class="html-fig">Figure 4</a>c).</p>
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<p>Absolute depth residuals for the points with USV measurements achieved by our full pipeline. (<b>a</b>) Trained: Kalamaki train set; test: Kalamaki test set. (<b>b</b>) Trained: Kalamaki whole dataset; test: Plakias whole dataset.</p>
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<p>Bathymetry and scatter plot for our full pipeline. Trained: Kalamaki; test: Plakias.</p>
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17 pages, 4689 KiB  
Article
Development of a Methodology Based on ALS Data and Diameter Distribution Simulation to Characterize Management Units at Tree Level
by Jean A. Magalhães, Juan Guerra-Hernández, Diogo N. Cosenza, Susete Marques, José G. Borges and Margarida Tomé
Remote Sens. 2024, 16(22), 4238; https://doi.org/10.3390/rs16224238 - 14 Nov 2024
Viewed by 212
Abstract
Characterizing Management Units (MUs) with tree-level data is instrumental for a comprehensive understanding of forest structure and for providing information needed to support forest management decision-making. Airborne Laser Scanning (ALS) data may enhance this characterization. While some studies rely on Individual Tree Detection [...] Read more.
Characterizing Management Units (MUs) with tree-level data is instrumental for a comprehensive understanding of forest structure and for providing information needed to support forest management decision-making. Airborne Laser Scanning (ALS) data may enhance this characterization. While some studies rely on Individual Tree Detection (ITD) methods using ALS data to estimate tree diameters within stands, these methods often face challenges when the goal is to characterize MUs in dense forests. This study proposes a methodology that simulates diameter distributions from LiDAR data using an Area-Based Approach (ABA) to overcome these limitations. Focusing on maritime pine (Pinus pinaster Ait.) MUs within a forest intervention zone in northern Portugal, the research initially assesses the suitability of two highly flexible Probability Density Functions (PDFs), Johnson’s SB and Weibull, for simulating diameter distribution in maritime pine stands in Portugal using the PINASTER database. The selected PDF is then used in conjunction with ABA to derive the variables needed for parameter recovery, enabling the simulation of diameter distributions within each MU. Monte Carlo Simulation (MCS) is applied to generate a sample list of tree diameters from the simulated distributions. The results indicate that this methodology is appropriate to estimate diameter distributions within maritime pine MUs by using ABA combined with Johnson’s SB and Weibull PDFs. Full article
(This article belongs to the Section Forest Remote Sensing)
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<p>Flowchart of the methodological process for generating a tree list for each Management Unit.</p>
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<p>Maritime pine Management Units (MUs) within an aggregated management forest area in northern Portugal.</p>
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<p>Median diameter (dmedian), quadratic mean diameter (dg), and tree density (N) in the Management Units.</p>
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<p>Examples of the variations in shapes and scale of the simulated diameter distribution across different Management Units.</p>
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15 pages, 3219 KiB  
Article
Polarization Optics to Differentiate Among Bioaerosols for Lidar Applications
by Alain Miffre, Danaël Cholleton, Adrien P. Genoud, Antonio Spanu and Patrick Rairoux
Photonics 2024, 11(11), 1067; https://doi.org/10.3390/photonics11111067 - 14 Nov 2024
Viewed by 286
Abstract
Polarization optics, which characterize the orientation of the electromagnetic field through Stokes vectors formalism, have been effectively used in lidar remote sensing to detect particles that differ in shape, such as mineral dust or pollen. In this study, for the first time, we [...] Read more.
Polarization optics, which characterize the orientation of the electromagnetic field through Stokes vectors formalism, have been effectively used in lidar remote sensing to detect particles that differ in shape, such as mineral dust or pollen. In this study, for the first time, we explore the capability of polarization optics to distinguish the light-backscattering patterns of pollen and fungal spores, two complex-shaped particles that vary significantly in surface structure. A unique laboratory polarimeter operating at lidar backscattering at 180.0° was conducted to assess their light depolarization property in laboratory ambient air. If, at the precise lidar backscattering angle of 180.0°, the depolarization ratios of pollen and fungal spores were difficult to differentiate, slight deviations from 180.0° allowed us to reveal separate scattering matrices for pollen and fungal spores. This demonstrates that polarization optics can unambiguously differentiate these particles based on their light-(back)scattering properties. These findings are consistent at both 532 and 1064 nm. This non-invasive, real-time technique is valuable for environmental monitoring, where rapid identification of airborne allergens is essential, as well as in agricultural and health sectors. Polarization-based light scattering thus offers a valuable method for characterizing such atmospheric particles, aiding in managing airborne contaminants. Full article
(This article belongs to the Special Issue Polarization Optics)
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Graphical abstract

Graphical abstract
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<p>Microscopic images of two widely encountered bioaerosols: (<b>a</b>) Ragweed pollen (<span class="html-italic">Ambrosia artemisiifolia</span>, laboratory study at iLM), (<b>b</b>) Fungal spores (<span class="html-italic">Cladosporium herbarum</span>, from MycoBank, a comprehensive database of images of fungal species (<a href="https://www.mycobank.org/" target="_blank">https://www.mycobank.org/</a> (accessed on 14 October 2024)).</p>
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<p>Visualization of polarization states on the Poincaré sphere [<a href="#B23-photonics-11-01067" class="html-bibr">23</a>]. A polarization state, defined by its longitude 2<math display="inline"><semantics> <mrow> <mi>χ</mi> </mrow> </semantics></math> and latitude 2<math display="inline"><semantics> <mrow> <mi>ω</mi> </mrow> </semantics></math>, has <math display="inline"><semantics> <mrow> <msup> <mrow> <mo>[</mo> <mrow> <mn>1</mn> <mo>,</mo> <mrow> <mrow> <mi mathvariant="normal">cos</mi> </mrow> <mrow> <mfenced separators="|"> <mrow> <mn>2</mn> <mo>ω</mo> </mrow> </mfenced> </mrow> </mrow> <mo> </mo> <mi mathvariant="normal">c</mi> <mi mathvariant="normal">o</mi> <mi mathvariant="normal">s</mi> <mo>(</mo> <mn>2</mn> <mo>χ</mo> <mo>)</mo> <mo>,</mo> <mo> </mo> <mrow> <mi mathvariant="normal">cos</mi> <mrow> <mfenced separators="|"> <mrow> <mn>2</mn> <mo>ω</mo> </mrow> </mfenced> </mrow> </mrow> <mo> </mo> <mi mathvariant="normal">s</mi> <mi mathvariant="normal">i</mi> <mi mathvariant="normal">n</mi> <mo>(</mo> <mn>2</mn> <mo>χ</mo> <mo>)</mo> <mo>,</mo> <mo> </mo> <mi mathvariant="normal">s</mi> <mi mathvariant="normal">i</mi> <mi mathvariant="normal">n</mi> <mo>(</mo> <mn>2</mn> <mo>ω</mo> <mo>)</mo> </mrow> <mo>]</mo> </mrow> <mi mathvariant="normal">T</mi> </msup> </mrow> </semantics></math> for Stokes vector. Six degenerate polarization states can then be defined: <math display="inline"><semantics> <mrow> <mfenced separators="|"> <mrow> <mi>p</mi> </mrow> </mfenced> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <mfenced separators="|"> <mrow> <mi>s</mi> </mrow> </mfenced> <mo>−</mo> </mrow> </semantics></math> polarized light with <b>St</b> = <math display="inline"><semantics> <mrow> <msup> <mrow> <mo>[</mo> <mn>1</mn> <mo>,</mo> <mo>±</mo> <mn>1,0</mn> <mo>,</mo> <mn>0</mn> <mo>]</mo> </mrow> <mrow> <mi>T</mi> </mrow> </msup> </mrow> </semantics></math> with positive sign for <math display="inline"><semantics> <mrow> <mo>(</mo> <mi>p</mi> <mo>)</mo> </mrow> </semantics></math>-state,<math display="inline"><semantics> <mrow> <mo> </mo> <mfenced separators="|"> <mrow> <mn>45</mn> <mo>±</mo> </mrow> </mfenced> <mo>−</mo> </mrow> </semantics></math> polarized light with <b>St</b> = <math display="inline"><semantics> <mrow> <msup> <mrow> <mo>[</mo> <mn>1,0</mn> <mo>,</mo> <mo>±</mo> <mn>1,0</mn> <mo>]</mo> </mrow> <mrow> <mi>T</mi> </mrow> </msup> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <mfenced separators="|"> <mrow> <mi>R</mi> <mi>C</mi> </mrow> </mfenced> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <mfenced separators="|"> <mrow> <mi>L</mi> <mi>C</mi> </mrow> </mfenced> <mo>−</mo> </mrow> </semantics></math> polarized light with <b>St</b> = <math display="inline"><semantics> <mrow> <msup> <mrow> <mo>[</mo> <mn>1,0</mn> <mo>,</mo> <mn>0</mn> <mo>,</mo> <mo>±</mo> <mn>1</mn> <mo>]</mo> </mrow> <mrow> <mi>T</mi> </mrow> </msup> </mrow> </semantics></math> with positive sign for <math display="inline"><semantics> <mrow> <mfenced separators="|"> <mrow> <mi>R</mi> <mi>C</mi> </mrow> </mfenced> </mrow> </semantics></math>-state.</p>
Full article ">Figure 3
<p>Laboratory <math display="inline"><semantics> <mrow> <mi>π</mi> </mrow> </semantics></math>-polarimeter operating at exact backscattering lidar angle (<math display="inline"><semantics> <mrow> <mi>θ</mi> </mrow> </semantics></math> = <math display="inline"><semantics> <mrow> <mi>π</mi> </mrow> </semantics></math>, blue arrows), and at near backscattering angle (<math display="inline"><semantics> <mrow> <mi>θ</mi> <mo>&lt;</mo> <mi>π</mi> </mrow> </semantics></math>, yellow arrows) [<a href="#B24-photonics-11-01067" class="html-bibr">24</a>]. The <math display="inline"><semantics> <mrow> <mi>P</mi> <mi>B</mi> <mi>C</mi> </mrow> </semantics></math> is precisely aligned (1 mm out of 10 m) to cover the backscattering angle <math display="inline"><semantics> <mrow> <mi>θ</mi> </mrow> </semantics></math> = 180.0 ± 0.2° with accuracy. The <math display="inline"><semantics> <mrow> <mi>Q</mi> <mi>W</mi> <mi>P</mi> </mrow> </semantics></math> modulates the polarization state of the incident ns-pulsed laser light to obtain accurate evaluations of <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>f</mi> </mrow> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> </mrow> </semantics></math> by adjusting the experimental variations of <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>I</mi> </mrow> <mrow> <mi>d</mi> </mrow> </msub> <mfenced separators="|"> <mrow> <mi>ψ</mi> </mrow> </mfenced> </mrow> </semantics></math> with the <math display="inline"><semantics> <mrow> <mi>ψ</mi> </mrow> </semantics></math> rotation angle of the <math display="inline"><semantics> <mrow> <mi>Q</mi> <mi>W</mi> <mi>P</mi> </mrow> </semantics></math>, as quantified by Equation (7) (for <math display="inline"><semantics> <mrow> <mi>θ</mi> <mo>=</mo> <mn>180.0</mn> </mrow> </semantics></math>°) and (10) (for <math display="inline"><semantics> <mrow> <mi>θ</mi> <mo>&lt;</mo> <mn>180.0</mn> </mrow> </semantics></math>°). Accurate values of the lidar <math display="inline"><semantics> <mrow> <mi>P</mi> <mi>D</mi> <mi>R</mi> </mrow> </semantics></math> are then retrieved from <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>f</mi> </mrow> <mrow> <mn>22</mn> </mrow> </msub> <mfenced separators="|"> <mrow> <mi>π</mi> </mrow> </mfenced> </mrow> </semantics></math> using Equation (5). For the sake of clarity, we add that the angle <math display="inline"><semantics> <mrow> <mi>ψ</mi> </mrow> </semantics></math> is measured counterclockwise between the <math display="inline"><semantics> <mrow> <mi>Q</mi> <mi>W</mi> <mi>P</mi> </mrow> </semantics></math>’s fast axis and the laser scattering plane <math display="inline"><semantics> <mrow> <mo>(</mo> <mi>x</mi> <mo>,</mo> <mo> </mo> <mi>z</mi> </mrow> </semantics></math>), as seen from the <math display="inline"><semantics> <mrow> <mi>P</mi> <mi>B</mi> <mi>C</mi> </mrow> </semantics></math> toward the particles and that the <math display="inline"><semantics> <mrow> <mo>(</mo> <mi>p</mi> <mo>,</mo> <mo> </mo> <mi>s</mi> <mo>)</mo> </mrow> </semantics></math> polarization components are defined relative to this plane. The experiment involves two laboratory polarimeters operating simultaneously at 532 and 1064 nm wavelengths (only one is represented to ease the reading).</p>
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<p>Backscattered light intensity <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>I</mi> </mrow> <mrow> <mi>d</mi> </mrow> </msub> <mo>(</mo> <mi>ψ</mi> <mo>)</mo> <mo>/</mo> <msub> <mrow> <mi>I</mi> </mrow> <mrow> <mn>0</mn> </mrow> </msub> </mrow> </semantics></math> as a function of the orientation of the QWP for pollen bioaerosol (in green) and fungal spores bioaerosol (in brown) at 180.0° lidar backscattering angle, allowing to retrieve their polarimetric signature <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>f</mi> </mrow> <mrow> <mn>22</mn> </mrow> </msub> <mo>(</mo> <mi>π</mi> <mo>)</mo> </mrow> </semantics></math> and lidar <math display="inline"><semantics> <mrow> <mi>P</mi> <mi>D</mi> <mi>R</mi> </mrow> </semantics></math>, using Equations (8) and (9). The experiment is carried out at 532 nm wavelength, using the π-polarimeter presented in <a href="#sec2dot3-photonics-11-01067" class="html-sec">Section 2.3</a>.</p>
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<p>Backscattered light intensity <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>I</mi> </mrow> <mrow> <mi>d</mi> <mo>,</mo> <mi>p</mi> <mi>o</mi> <mi>l</mi> </mrow> </msub> <mo>(</mo> <mi>ψ</mi> <mo>)</mo> <mo>/</mo> <msub> <mrow> <mi>I</mi> </mrow> <mrow> <mn>0</mn> </mrow> </msub> </mrow> </semantics></math> as a function of the orientation of the QWP for pollen bioaerosol (in green) and fungal spores bioaerosol (in brown) for successive incident polarization states <math display="inline"><semantics> <mrow> <mi>p</mi> <mi>o</mi> <mi>l</mi> <mo>=</mo> <mo>(</mo> <mi>p</mi> <mo>,</mo> <mn>45</mn> <mo>+</mo> <mo>,</mo> <mi>R</mi> <mi>C</mi> <mo>)</mo> </mrow> </semantics></math>, respectively, labeled (<b>a</b>–<b>c</b>) in the figure. The experiment is carried out at 532 nm wavelength at 177.5° angle, using the polarimeter presented in <a href="#sec2dot4-photonics-11-01067" class="html-sec">Section 2.4</a>. The curves are adjusted with Equation (10) to derive the polarimetric signatures (<math display="inline"><semantics> <mrow> <msub> <mrow> <mi>f</mi> </mrow> <mrow> <mn>22</mn> </mrow> </msub> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>f</mi> </mrow> <mrow> <mn>33</mn> </mrow> </msub> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>f</mi> </mrow> <mrow> <mn>44</mn> </mrow> </msub> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>f</mi> </mrow> <mrow> <mn>12</mn> </mrow> </msub> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>f</mi> </mrow> <mrow> <mn>34</mn> </mrow> </msub> </mrow> </semantics></math>) of pollen and fungal spores using Equations (11)–(13).</p>
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<p>Same as <a href="#photonics-11-01067-f004" class="html-fig">Figure 4</a> but at 1064 nm wavelength.</p>
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<p>Same as <a href="#photonics-11-01067-f005" class="html-fig">Figure 5</a> but at 1064 nm wavelength.</p>
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15 pages, 22927 KiB  
Article
Application of Aeromagnetic Survey in Detecting Potential Mineralization Zones Around Dongzhongla Deposit, Gangdese Metallogenic Belt
by Ning Lu, Junfeng Li, Qingmin Meng, Weidong Gao, Junjie Liu, Yongbo Li, Yongzai Xi and Hongshan Zheng
Appl. Sci. 2024, 14(22), 10452; https://doi.org/10.3390/app142210452 - 13 Nov 2024
Viewed by 362
Abstract
The Dongzhongla deposit is a skarn-type lead–zinc ore deposit located in the eastern segment of the Gangdese metallogenic belt, situated in the Xizang province, China. The high-altitude mountainous terrain of the region poses significant challenges to ground-based exploration. To facilitate more accurate mineral [...] Read more.
The Dongzhongla deposit is a skarn-type lead–zinc ore deposit located in the eastern segment of the Gangdese metallogenic belt, situated in the Xizang province, China. The high-altitude mountainous terrain of the region poses significant challenges to ground-based exploration. To facilitate more accurate mineral exploration in the deposit and its surrounding area, a high-resolution airborne magnetic survey was conducted over the mining area and its periphery. The airborne magnetic data were processed using derivative and Euler deconvolution methods, yielding results that reflect the geological structural features of the study area. By integrating the geological characteristics of the ore deposit, we inferred that the areas of magnetic anomaly extensions and the peripheries of other magnetic anomalies are favorable zones for mineralization, providing positive leads for further mineral exploration. Full article
(This article belongs to the Section Earth Sciences)
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<p>The location of the study area and its tectonic outline map (modified from [<a href="#B7-applsci-14-10452" class="html-bibr">7</a>]). (<b>a</b>) The location of the Himalayan orogenic belt. (<b>b</b>) The location of the Gangdese metallogenic belt. (<b>c</b>) The location of the Lhasa terrane and the characteristics of ore deposit distribution. IYZSZ—Yarlung Zangbo suture zone; BNSZ—Bangong–Nujiang suture zone; JSSZ—Jinsha River suture zone; SNMZ—Shiquanhe–Nam Tso Melange zone; LMF—Luobadui–Milashan fault zone; SLS—southern Lhasa subterrane; CLS—central Lhasa subterrane; NLS—northern Lhasa subterrane. DZL—Dongzhongla deposit; LML—Longmala deposit; MYA—Mengya’a deposit; YGL—Yaguila deposit; SR—Sharang deposit.</p>
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<p>A simplified geological map of the study area (modified from a 1:250,000 geological map provided by the client).</p>
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<p>A geological map and geological cross-section of the DZL deposit (modified from data provided by the client). (<b>a</b>) The geological map of the DZL deposit. Points “A” and “B” are the endpoints of the geological section in (<b>b</b>). (<b>b</b>) The geological section crossing the main mining body; the lithology of the geological section is controlled by drill holes, and the ore body develops in the skarn band on the south side of the intrusive rock.</p>
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<p>A satellite image of the study area with overlaid topographic contour lines. The contour interval is 100 m, the number at the star location represents the main peak, and the inverted triangle location represents the elevation of the valley lowlands. The dashed box represents the area of the geological map in <a href="#applsci-14-10452-f003" class="html-fig">Figure 3</a>a.</p>
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<p>The helicopter-borne magnetic survey system used in this survey. CS-VL represents the high-precision cesium vapor magnetometer, GNSS represents the Global Navigation Satellite System, AARC510 is the airborne compensation and recording system used in the project, and Radar represents the radar altimeter.</p>
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<p>The reduced-to-the-pole magnetic field map of the DZL area. The contour map was created based on the gridded reduced-to-magnetic-pole data, with the gridding method being minimum curvature and the grid spacing being 50 m. The contour line spacing on the map is 10 nT. The white dashed lines indicate the approximate extent of the SMAs and BMA.</p>
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<p>The tilt angle map of the DZL area. The purple dashed lines represent the zero value of the tilt angle, which is approximately demarcated by the yellow zero-value line in the grid map.</p>
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<p>Color range symbols’ map of located AN-EUL deconvolution depths of the DZL area. The symbols are overlaid on the tilt angle with 40% transparency. The symbol colors range from cool to warm, and the sizes from small to large represent increasing-in-depth values.</p>
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<p>Color range symbols’ map of located Euler deconvolution depths of the DZL area.</p>
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<p>Forward modeling using Euler deconvolution solutions from the L3400 line. Sus. represents the magnetic susceptibility assigned to a geological unit.</p>
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<p>Proposed exploration zones of the DZL area.</p>
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25 pages, 34342 KiB  
Article
Quantifying the Geomorphological Susceptibility of the Piping Erosion in Loess Using LiDAR-Derived DEM and Machine Learning Methods
by Sisi Li, Sheng Hu, Lin Wang, Fanyu Zhang, Ninglian Wang, Songbai Wu, Xingang Wang and Zongda Jiang
Remote Sens. 2024, 16(22), 4203; https://doi.org/10.3390/rs16224203 - 11 Nov 2024
Viewed by 432
Abstract
Soil piping erosion is an underground soil erosion process that is significantly underestimated or overlooked. It can lead to intense soil erosion and trigger surface processes such as landslides, collapses, and channel erosion. Conducting susceptibility mapping is a vital way to identify the [...] Read more.
Soil piping erosion is an underground soil erosion process that is significantly underestimated or overlooked. It can lead to intense soil erosion and trigger surface processes such as landslides, collapses, and channel erosion. Conducting susceptibility mapping is a vital way to identify the potential for soil piping erosion, which is of enormous significance for soil and water conservation as well as geological disaster prevention. This study utilized airborne radar drones to survey and map 1194 sinkholes in Sunjiacha basin, Huining County, on the Loess Plateau in Northwest China. We identified seventeen key hydrogeomorphological factors that influence sinkhole susceptibility and used six machine learning models—support vector machine (SVM), logistic regression (LR), Convolutional Neural Network (CNN), K-Nearest Neighbors (KNN), random forest (RF), and gradient boosting decision tree (GBDT)—for the susceptibility assessment and mapping of loess sinkholes. We then evaluated and validated the prediction results of various models using the area under curve (AUC) of the Receiver Operating Characteristic Curve (ROC). The results showed that all six of these machine learning algorithms had an AUC of more than 0.85. The GBDT model had the best predictive accuracy (AUC = 0.94) and model migration performance (AUC = 0.93), and it could find sinkholes with high and very high susceptibility levels in loess areas. This suggests that the GBDT model is well suited for the fine-scale susceptibility mapping of sinkholes in loess regions. Full article
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<p>Study area overview: (<b>a</b>) location; (<b>b</b>) regional geological map; (<b>c</b>) digital orthophoto map (DOM) by UAS optical camera; (<b>d</b>) LiDAR-derived DEM.</p>
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<p>The technical flow chart of this study.</p>
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<p>UAS survey and results: (<b>a</b>) route planning; (<b>b</b>,<b>c</b>) Feima D2000 UAS; (<b>d</b>–<b>g</b>) ground control point surveying using handheld RTK; (<b>h</b>) local point clouds acquired by D-LiDAR2000; (<b>i</b>) local DOM acquired by D-CAM2000; (<b>j</b>–<b>l</b>) typical sinkhole photos taken in field. The red circle is the artificial interpretation of the sinkhole polygon in (<b>i</b>–<b>l</b>).</p>
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<p>Geomorphic factor mapping for evaluating sinkhole susceptibility.</p>
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<p>Geomorphic factor mapping for evaluating sinkhole susceptibility.</p>
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<p>Sinkhole susceptibility maps and frequency distribution histograms of grid by six machine learning methods, (<b>a</b>) SVM, (<b>b</b>) LR, (<b>c</b>) CNN, (<b>d</b>) KNN, (<b>e</b>) RF, and (<b>f</b>) GBDT, where mean stands for average and SD stands for standard deviation.</p>
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<p>Areal comparison of susceptibility grades for six models.</p>
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<p>Comparison of the area under the ROC curves (AUC) for six models in the validation step.</p>
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<p>Geomorphological susceptibility mapping of loess sinkholes based on the GBDT model: (<b>a</b>) whole watershed; (<b>b</b>) shallow gully; (<b>c</b>) sub-catchment; (<b>d</b>) old landslide body; (<b>e</b>) the heads of several erosion gullies; (<b>f</b>) terrace.</p>
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<p>The sinkhole area proportion of different susceptibility grades by the GBDT model.</p>
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<p>Comparison of area under ROC curve (AUC) of six models in validation area.</p>
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<p>Geomorphological susceptibility mapping by GBDT model in validation area: (<b>a</b>) location of validation area; (<b>b</b>) susceptibility zoning map by GBDT model.</p>
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13 pages, 1873 KiB  
Article
Development of Livestock-Associated Methicillin-Resistant Staphylococcus aureus (LA-MRSA) Loads in Pigs and Pig Stables During the Fattening Period
by Karl Pedersen, Martin Weiss Nielsen, Mette Ely Fertner, Carmen Espinosa-Gongora and Poul Bækbo
Vet. Sci. 2024, 11(11), 558; https://doi.org/10.3390/vetsci11110558 - 11 Nov 2024
Viewed by 595
Abstract
Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) is widespread in European pig production and poses an occupational hazard to farm workers and their household members. Farm workers are exposed to LA-MRSA through direct contact with pigs and airborne transmission, enabling bacteria to be carried home [...] Read more.
Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) is widespread in European pig production and poses an occupational hazard to farm workers and their household members. Farm workers are exposed to LA-MRSA through direct contact with pigs and airborne transmission, enabling bacteria to be carried home in the nose or on the skin. Consequently, it is important to consider LA-MRSA in a one-health context, studying human exposure by examining LA-MRSA levels in pigs, air, and dust in the farm environment. In this investigation, LA-MRSA levels were quantified in nasal swab samples from the pigs, air samples, and dust at three different time points in a farm rearing pigs from approx. 30 kg until slaughter. Sampling was repeated across seven batches of pigs, resulting in the analysis of 504 nasal swab samples, alongside air and dust samples. LA-MRSA was cultured and quantified on MRSA2 agar plates. Findings revealed significant batch-to-batch variation and a significant 94.1% decrease in LA-MRSA levels during the rearing period. Despite this decline, all nasal swab samples tested positive, with the highest level reaching 353,000 cfu in a sample. Among the 42 air samples, LA-MRSA levels were low to moderate, with a maximum of 568 and an average of 63 cfu/m3. In the 28 dust samples collected during the second and third sampling periods, LA-MRSA counts were high, reaching up to 37,272 cfu/g, with an average of 17,185 cfu/g. The results suggest that while LA-MRSA levels in pigs decrease with age, reaching low levels before slaughter, the bacterium remains highly abundant in dust, posing an occupational hazard to farm workers. Full article
(This article belongs to the Section Veterinary Microbiology, Parasitology and Immunology)
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<p>Structure of the experimental facility. The herd consisted of four identical modules, each of which were split into two sections with an aisle in the middle. Each section had space for 500 pigs.</p>
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<p>Box plot of log<sub>10</sub> cfu of LA-MRSA in nasal swab samples of 24 pigs per batch in seven batches sampled on three occasions. Numbers along the x-axis refer to batch numbers.</p>
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<p>Violin plot of log<sub>10</sub> cfu of LA-MRSA per swab for all samples at the three time points.</p>
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<p>Box plot of LA-MRSA counts in dust samples, expressed as log<sub>10</sub> cfu/g dust.</p>
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<p>Box plot of LA-MRSA counts in air samples, expressed as cfu/m<sup>3</sup>. The graph includes samples at each sampling point and the total for all 42 air samples that were collected from the three samplings.</p>
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20 pages, 5211 KiB  
Article
Spatial Distribution and Decadal Variability of 129I and 236U in the Western Mediterranean Sea
by Maria Leimbacher, Lorenza Raimondi, Maxi Castrillejo, Christof Vockenhuber, Habacuc Pérez-Tribouillier, Katrin Schroeder, Toste Tanhua and Núria Casacuberta
J. Mar. Sci. Eng. 2024, 12(11), 2039; https://doi.org/10.3390/jmse12112039 - 11 Nov 2024
Viewed by 426
Abstract
This study investigates the spatial and temporal distribution of the artificial radionuclides 129I and 236U in the Western Mediterranean Sea, focusing on their connection to radionuclide sources and circulation dynamics. Taking advantage of unprecedented precision of accelerator mass spectrometry, both tracers [...] Read more.
This study investigates the spatial and temporal distribution of the artificial radionuclides 129I and 236U in the Western Mediterranean Sea, focusing on their connection to radionuclide sources and circulation dynamics. Taking advantage of unprecedented precision of accelerator mass spectrometry, both tracers were firstly investigated in 2013. Here, we examine tracer observations obtained along four stations (re-)visited during the TAlPro2022 expedition in May 2022. Distributions of both 129I and 236U were related to water masses and clearly linked to local circulation patterns: a tracer-poor surface Atlantic inflow, a thining of the tracer minimum at intermediate depths, and a higher tracer signal in Western Mediterranean Deep Waters due to dense water formation in the Algero-Provençal basin. The comparison to 2013 tracer data indicated recent deep ventilation of the Tyrrhenian Sea, the mixing of deep waters and enhanced stratification in intermediate waters in the Algero-Provençal basin due to a temperature and salinity increase between 2013 and 2022. We estimate an overall 129I increase of 20% at all depths between 0 and 500m with respect to 2013, which is not accompanied by 236U. This suggests either the lateral transport of 129I from the Eastern Mediterranean Sea, or an additional source of this tracer. The inventories of 129I calculated for each water mass at the four stations point to the deposition of airborne releases from the nuclear reprocessing plants (La Hague and Sellafield) on the surface Mediterranean waters as the more likely explanation for the 129I increase. This work demonstrates the great potential of including measurements of anthropogenic radionuclides as tracers of ocean circulation. However, a refinement of the anthropogenic inputs is necessary to improve their use in understanding ventilation changes in the Mediterranean Sea. Full article
(This article belongs to the Special Issue Environmental Radioactivity and Its Applications in Marine Areas)
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<p>Map of the Mediterranean Sea with locations of nuclear reprocessing plants (black dots), and arrows of surface (red) and deep (blue) circulation pathways. Locations of deep (dark blue circles) and intermediate water (light blue circles) formation are also shown here. SF = Sellafield; LH = La Hague; MC = Marcoule.</p>
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<p>Map of the Mediterranean Sea with locations of the stations sampled for <sup>129</sup>I and <sup>236</sup>U in 2013 as part of the GA04S-MedSeA2013 expedition (white circles); and in 2022 during the TAlPro2022 cruise (black circles). The four stations discussed in this work were sampled during both expeditions and are marked as red stars (with name of stations reported; DYF = DYFAMED).</p>
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<p>Vertical profiles of <sup>129</sup>I (<b>a</b>) and <sup>236</sup>U (<b>b</b>) concentrations in 2022 along the four repeated stations. Vertical lines represent values of global fallout of each tracer.</p>
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<p><math display="inline"><semantics> <mi>θ</mi> </semantics></math>-S Diagram for the four stations of the study. Lines represent isopycnals, colours show concentrations of <sup>129</sup>I (<b>a</b>) and <sup>236</sup>U (<b>b</b>). Circles identify data within different water masses (AW = (Mediterranean) Atlantic Water; LIW Levantine Intermediate Water; WIW = Western Intermediate Water; WMDW = Western Mediterranean Deep Water). Samples in the top left side of the panel, not included in any circle, represent surface waters of Atlantic origin.</p>
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<p>Depth profiles of <sup>236</sup>U (orange) and <sup>129</sup>I (purple) concentrations along four stations (panel <b>a</b>–<b>d</b>) in the Western Mediterranean Sea in 2013 and 2022 (and 2001 for DYFAMED). Note that dashed lines represent profiles shape when analytical outliers were removed.</p>
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<p>Column inventories of <sup>129</sup>I and <sup>236</sup>U along the four stations (panel <b>a</b>–<b>d</b>) in the WMED. The different colors of the stacked bar chart represent inventories in different water masses in the WMED for years 2013 and 2022 (when data available), and for 2001 for <sup>236</sup>U in DYFAMED. For the purpose of the figure, we used the following definitions: surface = 0–25 m; AW = 25–100 m; LIW = 100–500 m; deep water = 500 m-bottom. Note that, in 2013, <sup>236</sup>U at station 14 was only available below 1000 m so for comparison we reported inventories below this depth for 2022 as well (brown columns). The inventories uncertainty are 5% for <sup>129</sup>I and 3% for <sup>236</sup>U.</p>
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<p>Comparison of Salinity (red), Temperature (blue) and Dissolved Oxygen (black) data from 2013 and 2022 along four stations in the Western Mediterranean Sea.</p>
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19 pages, 14379 KiB  
Article
3D Inversion and Interpretation of Airborne Multiphysics Data for Targeting Porphyry System, Flammefjeld, Greenland
by Michael Jorgensen, Michael S. Zhdanov, Alex Gribenko, Leif Cox, Henrik E. Sabra and Alexander Prikhodko
Minerals 2024, 14(11), 1130; https://doi.org/10.3390/min14111130 - 8 Nov 2024
Viewed by 684
Abstract
The exploration of porphyry deposits in Greenland has become increasingly important due to their significant economic potential. We utilized total magnetic intensity (TMI) and mobile magnetotelluric (MobileMT) airborne data to delineate potential porphyry mineralization zones. The TMI method was employed to map variations [...] Read more.
The exploration of porphyry deposits in Greenland has become increasingly important due to their significant economic potential. We utilized total magnetic intensity (TMI) and mobile magnetotelluric (MobileMT) airborne data to delineate potential porphyry mineralization zones. The TMI method was employed to map variations in the Earth’s magnetic field caused by subsurface geological features, including mineral deposits. By analyzing anomalies in TMI data, potential porphyry targets were identified based on characteristic magnetic signatures associated with mineralized zones. Complementing TMI data, MT airborne surveys provided valuable insights into the electrical conductivity structure of the subsurface. Porphyry deposits exhibited distinct conductivity signatures due to the presence of disseminated sulfide minerals, aiding in their identification and delineation. Integration of the TMI and MobileMT datasets allowed for a comprehensive assessment of porphyry exploration targets in Flammefjeld. The combined approach facilitates the identification of prospective areas with enhanced geological potential, optimizing resource allocation and exploration efforts. Overall, this study demonstrates the efficacy of integrating TMI and MobileMT airborne data for porphyry exploration in Greenland, offering valuable insights for mineral exploration and resource development in the region. Full article
(This article belongs to the Section Mineral Exploration Methods and Applications)
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<p>World Imagery view of Greenland. The location of the Flammefjeld Block and Tasiilaq are labeled and shown by red crosses.</p>
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<p>Generalized geology of Greenland, with major geological provinces KMB (Ketilidian Mobile Belt), AB (Archean Block), NMB (Nagssugtoqidian Mobile Belt), CM (Committee-Melville), EI (Ellesmere-Inglefield), V (Victoria), E (Ellesmerian), and CFB (Caledonian Fold Belt) indicated. The location of the Flammefjeld Block is shown by the red cross. Modified from [<a href="#B22-minerals-14-01130" class="html-bibr">22</a>].</p>
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<p>Total magnetic intensity (TMI) data overlain on World Imagery, with the flight path shown in black. The location of the EM reference station is shown by the red cross. The observed data shown have been trimmed to the license area.</p>
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<p>Geological map showing the Kangerlussuaq Alkaline Complex (KAC) in light blue and the Flammefjeld complex (FC) in pink. Flight lines are shown in black and the EM reference station is shown by the red cross.</p>
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<p>Alteration geology of the survey area, shown in red, overlying the observed TMI data and World Imagery. The survey flight lines are shown in black. The observed data shown have been trimmed to the license area.</p>
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<p>Cartoon cross section of Climax Mo deposit showing the relationship of ore and alteration zoning to porphyry intrusions (after [<a href="#B28-minerals-14-01130" class="html-bibr">28</a>]).</p>
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<p>The (<b>top panel</b>) is the observed TMI data after processing. The (<b>bottom panel</b>) is the predicted TMI data. Survey lines are shown in black.</p>
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<p>Measured apparent conductivity data at 562 Hz. The flight lines are shown in black. The N/S profile at 528,400 mE is shown in yellow. This profile line corresponds to the vertical model sections shown below. The observed data shown have been trimmed to the license area.</p>
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<p>Panels (<b>a</b>,<b>b</b>) show observed apparent resistivity at frequencies 223 and 562 Hz, respectively. Panels (<b>c</b>,<b>d</b>) show the predicted apparent resistivity at the same frequencies.</p>
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<p>The vertical section was extracted from the 3D voxel model of inverted susceptibility. The location of the profile is shown in yellow in <a href="#minerals-14-01130-f008" class="html-fig">Figure 8</a>.</p>
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<p>The vertical section was extracted from the 3D voxel model of the inverted amplitude of induced magnetization. The location of the profile is shown in yellow in <a href="#minerals-14-01130-f008" class="html-fig">Figure 8</a>.</p>
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<p>The vertical section was extracted from the 3D voxel model of the inverted amplitude of remanent magnetization. The location of the profile is shown in yellow in <a href="#minerals-14-01130-f008" class="html-fig">Figure 8</a>.</p>
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<p>The vertical section was extracted from the 3D voxel model of the inverted resistivity. The location of the profile is shown in yellow in <a href="#minerals-14-01130-f008" class="html-fig">Figure 8</a>. This vertical section showcases the porphyry system.</p>
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<p>A west-facing view of resistivity (slice) and superposed remanent magnetization (red isobody). The red isobody indicates remanent values above 0.0125 A/m. This 3D figure is for illustrative purposes. The resistivity slice is in the same location as <a href="#minerals-14-01130-f012" class="html-fig">Figure 12</a>.</p>
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<p>Schematic geological interpretation of the geophysical models. The combination of the resistivity and magnetic properties coalesce into a useful geological model.</p>
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