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13 pages, 3187 KiB  
Article
An Approach to Improve Land–Water Salt Flux Modeling in the San Francisco Estuary
by John S. Rath, Paul H. Hutton and Sujoy B. Roy
Water 2025, 17(15), 2278; https://doi.org/10.3390/w17152278 - 31 Jul 2025
Viewed by 178
Abstract
In this case study, we used the Delta Simulation Model II (DSM2) to study the salt balance at the land–water interface in the river delta of California’s San Francisco Estuary. Drainage, a source of water and salt for adjacent channels in the study [...] Read more.
In this case study, we used the Delta Simulation Model II (DSM2) to study the salt balance at the land–water interface in the river delta of California’s San Francisco Estuary. Drainage, a source of water and salt for adjacent channels in the study area, is affected by channel salinity. The DSM2 approach has been adopted by several hydrodynamic models of the estuary to enforce water volume balance between diversions, evapotranspiration and drainage at the land–water interface, but does not explicitly enforce salt balance. We found deviations from salt balance to be quite large, albeit variable in magnitude due to the heterogeneity of hydrodynamic and salinity conditions across the study area. We implemented a procedure that approximately enforces salt balance through iterative updates of the baseline drain salinity boundary conditions (termed loose coupling). We found a reasonable comparison with field measurements of drainage salinity. In particular, the adjusted boundary conditions appear to capture the range of observed interannual variability better than the baseline periodic estimates. The effect of the iterative adjustment procedure on channel salinity showed substantial spatial variability: locations dominated by large flows were minimally impacted, and in lower flow channels, deviations between baseline and adjusted channel salinity series were notable, particularly during the irrigation season. This approach, which has the potential to enhance the simulation of extreme salinity intrusion events (when high channel salinity significantly impacts drainage salinity), is essential for robustly modeling hydrodynamic conditions that pre-date contemporary water management infrastructure. We discuss limitations associated with this approach and recommend that—for this case study—further improvements could best be accomplished through code modification rather than coupling of transport and island water balance models. Full article
(This article belongs to the Special Issue Advances in Coastal Hydrological and Geological Processes)
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19 pages, 2175 KiB  
Article
A Rule-Based Method for Enhancing Burst Tolerance in Stateful Microservices
by Kęstutis Pakrijauskas and Dalius Mažeika
Electronics 2025, 14(14), 2752; https://doi.org/10.3390/electronics14142752 - 8 Jul 2025
Viewed by 289
Abstract
Microservice architecture enables the development of flexible, loosely coupled applications that support elasticity and adaptability. As data availability is critical in any application, maintaining consistent access becomes a top priority. However, this introduces complexity, particularly for stateful microservices, which are slower to adapt [...] Read more.
Microservice architecture enables the development of flexible, loosely coupled applications that support elasticity and adaptability. As data availability is critical in any application, maintaining consistent access becomes a top priority. However, this introduces complexity, particularly for stateful microservices, which are slower to adapt to sudden changes and can lead to data availability degradation. Resource overprovisioning may prepare systems for peak loads; however, it is an inefficient method of problem-solving. Similarly, dynamic scaling based on machine learning can underperform due to insufficient training data or inaccurate prediction methods. This paper proposes a rule-based method that combines write-scaling and load balancing to distribute burst workloads across multiple stateful microservice nodes while also vertically scaling a single node to meet rising demand. This approach reduces failure rates and extends operational time under burst conditions, effectively preserving the application’s availability by providing more time for scaling. An experiment was performed to validate the proposed method of burst tolerance by workload distribution. The results showed that the proposed method enables a stateful microservice that sustains the burst load for nearly twice as long while further reducing the rate of failure. Full article
(This article belongs to the Special Issue New Advances in Cloud Computing and Its Latest Applications)
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21 pages, 6136 KiB  
Article
A ROS-Based Online System for 3D Gaussian Splatting Optimization: Flexible Frontend Integration and Real-Time Refinement
by Li’an Wang, Jian Xu, Xuan An, Yujie Ji, Yuxuan Wu and Zhaoyuan Ma
Sensors 2025, 25(13), 4151; https://doi.org/10.3390/s25134151 - 3 Jul 2025
Viewed by 553
Abstract
The 3D Gaussian splatting technique demonstrates significant efficiency advantages in real-time scene reconstruction. However, when its initialization process relies on traditional SfM methods (such as COLMAP), there are obvious bottlenecks, such as high computational resource consumption, as well as the decoupling problem between [...] Read more.
The 3D Gaussian splatting technique demonstrates significant efficiency advantages in real-time scene reconstruction. However, when its initialization process relies on traditional SfM methods (such as COLMAP), there are obvious bottlenecks, such as high computational resource consumption, as well as the decoupling problem between camera pose optimization and map construction. This paper proposes an online 3DGS optimization system based on ROS. Through the design of a loose-coupling architecture, it realizes real-time data interaction between the frontend SfM/SLAM module and backend 3DGS optimization. Using ROS as a middleware, this system can access the keyframe poses and point-cloud data generated by any frontend algorithms (such as ORB-SLAM, COLMAP, etc.). With the help of a dynamic sliding-window strategy and a rendering-quality loss function that combines L1 and SSIM, it achieves online optimization of the 3DGS map. The experimental data shows that compared with the traditional COLMAP-3DGS process, this system reduces the initialization time by 90% and achieves an average PSNR improvement of 1.9 dB on the TUM-RGBD, Tanks and Temples, and KITTI datasets. Full article
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21 pages, 2628 KiB  
Article
Water-Richness Evaluation of Sandstone Aquifer Based on Set Pair Analysis Variable Fuzzy Set Coupling Method: A Case Study on Bayangaole Mine, China
by Kaihua Liang, Yueyue Li, Yuanlin Bai, Weijie Zhang, Chenghao Han, Daolei Xie, Shengjian Liang and Bowen Xi
Water 2025, 17(12), 1826; https://doi.org/10.3390/w17121826 - 19 Jun 2025
Viewed by 339
Abstract
The Jurassic aquifer in Northwest China is the key aquifer for mine water filling, which is significant due to its loose structure, large porosity, strong rock permeability, and fracture development characteristics. In addition, the water richness in space is extremely uneven, and many [...] Read more.
The Jurassic aquifer in Northwest China is the key aquifer for mine water filling, which is significant due to its loose structure, large porosity, strong rock permeability, and fracture development characteristics. In addition, the water richness in space is extremely uneven, and many coal mine roof water inrush events are closely related to it. A case of evaluation of water-richness of the roof sandstone in the 3-1 coal seam of the Bayangaole minefield was analyzed in depth, and the evaluation index system is established based on lithology and structural characteristics. Specifically, the evaluation indexes are under the influence of the influencing factors of lithology, the density of fault intersection endpoints, and the density of fault scale and the strength of folds as the influencing factors of structure. On this basis, the set pair analysis-variable fuzzy set coupling evaluation method is introduced to form a targeted water-rich evaluation model of a roof sandstone aquifer. By using the coupling method of set pair analysis and variable fuzzy set, a targeted evaluation model is formed to realize the organic integration of indicators. Through the comprehensive analysis of the relative zoning of water abundance and the data from the borehole pumping (drainage) test, the distribution of water abundance grade in the study area is clarified. Full article
(This article belongs to the Topic Human Impact on Groundwater Environment, 2nd Edition)
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26 pages, 10564 KiB  
Article
DynaFusion-SLAM: Multi-Sensor Fusion and Dynamic Optimization of Autonomous Navigation Algorithms for Pasture-Pushing Robot
by Zhiwei Liu, Jiandong Fang and Yudong Zhao
Sensors 2025, 25(11), 3395; https://doi.org/10.3390/s25113395 - 28 May 2025
Viewed by 629
Abstract
Aiming to address the problems of fewer related studies on autonomous navigation algorithms based on multi-sensor fusion in complex scenarios in pastures, lower degrees of fusion, and insufficient cruising accuracy of the operation path in complex outdoor environments, a multimodal autonomous navigation system [...] Read more.
Aiming to address the problems of fewer related studies on autonomous navigation algorithms based on multi-sensor fusion in complex scenarios in pastures, lower degrees of fusion, and insufficient cruising accuracy of the operation path in complex outdoor environments, a multimodal autonomous navigation system is proposed based on a loosely coupled architecture of Cartographer–RTAB-Map (real-time appearance-based mapping). Through laser-vision inertial guidance multi-sensor data fusion, the system achieves high-precision mapping and robust path planning in complex scenes. First, comparing the mainstream laser SLAM algorithms (Hector/Gmapping/Cartographer) through simulation experiments, Cartographer is found to have a significant memory efficiency advantage in large-scale scenarios and is thus chosen as the front-end odometer. Secondly, a two-way position optimization mechanism is innovatively designed: (1) When building the map, Cartographer processes the laser with IMU and odometer data to generate mileage estimations, which provide positioning compensation for RTAB-Map. (2) RTAB-Map fuses the depth camera point cloud and laser data, corrects the global position through visual closed-loop detection, and then uses 2D localization to construct a bimodal environment representation containing a 2D raster map and a 3D point cloud, achieving a complete description of the simulated ranch environment and material morphology and constructing a framework for the navigation algorithm of the pushing robot based on the two types of fused data. During navigation, the combination of RTAB-Map’s global localization and AMCL’s local localization is used to generate a smoother and robust positional attitude by fusing IMU and odometer data through the EKF algorithm. Global path planning is performed using Dijkstra’s algorithm and combined with the TEB (Timed Elastic Band) algorithm for local path planning. Finally, experimental validation is performed in a laboratory-simulated pasture environment. The results indicate that when the RTAB-Map algorithm fuses with the multi-source odometry, its performance is significantly improved in the laboratory-simulated ranch scenario, the maximum absolute value of the error of the map measurement size is narrowed from 24.908 cm to 4.456 cm, the maximum absolute value of the relative error is reduced from 6.227% to 2.025%, and the absolute value of the error at each location is significantly reduced. At the same time, the introduction of multi-source mileage fusion can effectively avoid the phenomenon of large-scale offset or drift in the process of map construction. On this basis, the robot constructs a fusion map containing a simulated pasture environment and material patterns. In the navigation accuracy test experiments, our proposed method reduces the root mean square error (RMSE) coefficient by 1.7% and Std by 2.7% compared with that of RTAB-MAP. The RMSE is reduced by 26.7% and Std by 22.8% compared to that of the AMCL algorithm. On this basis, the robot successfully traverses the six preset points, and the measured X and Y directions and the overall position errors of the six points meet the requirements of the pasture-pushing task. The robot successfully returns to the starting point after completing the task of multi-point navigation, achieving autonomous navigation of the robot. Full article
(This article belongs to the Section Navigation and Positioning)
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16 pages, 562 KiB  
Communication
Implementation of a Low-Cost Navigation System Using Data Fusion of a Micro-Electro-Mechanical System Inertial Sensor and an Ultra Short Baseline on a Microcontroller
by Julian Winkler and Sabah Badri-Hoeher
Sensors 2025, 25(10), 3125; https://doi.org/10.3390/s25103125 - 15 May 2025
Viewed by 2413
Abstract
In this work, a low-cost low-power navigation solution for autonomous underwater vehicles is introduced utilizing a Micro-Electro-Mechanical System (MEMS) inertial sensor and an ultra short baseline (USBL) system. The complete signal processing is implemented on a cheap 16-bit fixed-point arithmetic microcontroller. For data [...] Read more.
In this work, a low-cost low-power navigation solution for autonomous underwater vehicles is introduced utilizing a Micro-Electro-Mechanical System (MEMS) inertial sensor and an ultra short baseline (USBL) system. The complete signal processing is implemented on a cheap 16-bit fixed-point arithmetic microcontroller. For data fusion and calibration, an error state Kalman filter in square root form is used, which preserves stability in case of rounding errors. To further reduce the influence of rounding errors, a stochastic rounding scheme is applied. The USBL measurements are integrated using tightly coupled data fusion by deriving the observation functions separately for range, elevation, and azimuth angles. The effectiveness of the fixed point implementation with stochastic rounding is demonstrated on a simulation, and the the complete setup is tested in a field test. The results of the field test show an improved accuracy of the tightly coupled data fusion in comparison with loosely coupled data fusion. It is also shown that the applied rounding schemes can bring the fixed-point estimates to a near floating point accuracy. Full article
(This article belongs to the Special Issue Advanced Sensors in MEMS: 2nd Edition)
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19 pages, 18748 KiB  
Article
Regional Flood Risk Assessment and Prediction Based on Environmental Attributes and Pipe Operational Characteristics
by Jinping Zhang, Yirong Yang, Lixin Zhang, Xi Zhang and Yao Wang
Water 2025, 17(10), 1477; https://doi.org/10.3390/w17101477 - 14 May 2025
Viewed by 503
Abstract
Urban flood risk assessments play a crucial role in urban resilience and disaster management. This paper proposes a comprehensive method for urban flood risk assessment and prediction that is based on environmental attributes and the operational characteristics of pipe networks. Using the central [...] Read more.
Urban flood risk assessments play a crucial role in urban resilience and disaster management. This paper proposes a comprehensive method for urban flood risk assessment and prediction that is based on environmental attributes and the operational characteristics of pipe networks. Using the central urban area of Zhengzhou as a case study, an integrated urban flood risk evaluation index system was developed, and the entropy weight method was applied to quantify risk indicators. A loosely coupled RF-XGBoost model was constructed to predict the flood risk of different rainfall scenarios. The results indicate that (1) the overall flood risk in the study area exhibits an increasing trend from the northeast to the southwest, with medium- to high-risk zones being predominant; (2) the spatial distribution pattern of the comprehensive flood risk closely aligns with that of the environmental risk but shows slight variations under the influence of pipe network operational risks; (3) the RF-XGBoost model demonstrates superior predictive accuracy under multi-factor coupling scenarios. When rainfall characteristics, environmental attributes, and pipe network operational risks are comprehensively considered, the Nash–Sutcliffe Efficiency (NSE) of the predictions improves from 0.85 (when using only rainfall characteristics) to 0.94. This study provides valuable insights and technical support for mitigating urban flood risks. Full article
(This article belongs to the Special Issue Urban Flood Frequency Analysis and Risk Assessment)
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22 pages, 5459 KiB  
Article
A Novel Loosely Coupled Collaborative Localization Method Utilizing Integrated IMU-Aided Cameras for Multiple Autonomous Robots
by Cheng Liu, Tao Wang, Zhi Li, Shu Li and Peng Tian
Sensors 2025, 25(10), 3086; https://doi.org/10.3390/s25103086 - 13 May 2025
Viewed by 409
Abstract
IMUs (inertial measurement units) and cameras are popular sensors for autonomous localization due to their convenient integration. This article proposes a collaborative localization method, the CICEKF (collaborative IMU-aided camera extended Kalman filter), with a loosely coupled and two-step structure for the autonomous locomotion [...] Read more.
IMUs (inertial measurement units) and cameras are popular sensors for autonomous localization due to their convenient integration. This article proposes a collaborative localization method, the CICEKF (collaborative IMU-aided camera extended Kalman filter), with a loosely coupled and two-step structure for the autonomous locomotion estimation of collaborative robots. The first step is for single-robot localization estimation, fusing and connecting the IMU and visual measurement data on the velocity level, which can improve the robustness and adaptability of different visual measurement approaches without redesigning the visual optimization process. The second step is for estimating the relative configuration of multiple robots, which further fuses the individual motion information to estimate the relative translation and rotation reliably. The simulation and experiment demonstrate that both steps of the filter are capable of accomplishing locomotion estimation missions, standalone or collaboratively. Full article
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9 pages, 2181 KiB  
Proceeding Paper
Integrating Multi-Sensor Augmented PNT to Enhance Outdoor Human Motion Capture Using Low-Cost GNSS Receivers
by Andrea Maffia, Georgii Kurshakov, Tiziano Cosso, Vittorio Sanguineti and Giorgio Delzanno
Eng. Proc. 2025, 88(1), 44; https://doi.org/10.3390/engproc2025088044 - 8 May 2025
Viewed by 380
Abstract
We are working on an innovative approach to outdoor human motion capture, using a wearable device that integrates a low-cost GNSS (Global Navigation Satellite System) receiver and an INS (Inertial Navigation System) via a zero-velocity update (ZUPT) methodology. In this study, we focused [...] Read more.
We are working on an innovative approach to outdoor human motion capture, using a wearable device that integrates a low-cost GNSS (Global Navigation Satellite System) receiver and an INS (Inertial Navigation System) via a zero-velocity update (ZUPT) methodology. In this study, we focused on using these devices to reconstruct the foot trajectory. Our work addresses the challenge of capturing precise foot movements in uncontrolled outdoor environments, a task traditionally constrained by the limitations of laboratory settings. We equipped devices that combine inertial measurement units (IMUs) with GNSS receivers in the following configuration: one on each foot and one on the head. We experimented with different GNSS data processing techniques, such as Post-Processed Kinematic (PPK) positioning with and without Moving Base (MB), and after the integration with the IMU, we obtained centimeter-level precision in horizontal and vertical positioning for various walking speeds. This integration leverages a loosely coupled GNSS/INS approach, where the GNSS solution is independently processed and subsequently used to refine the INS outputs. Enhanced by ZUPT and Madgwick filtering, this method significantly improves the trajectory reconstruction accuracy. Indeed, our research includes a study of the impact of moving speed on the performance of these low-cost GNSS receivers. These insights pave the way for future exploration into tightly coupled GNSS/INS integration using low-cost GNSS receivers, promising advancements in fields like sports science, rehabilitation, and well-being. This work seeks not only to contribute to the field of wearable technology, but also to open possibilities for further innovation in affordable, high-accuracy personal navigation and activity monitoring devices. Full article
(This article belongs to the Proceedings of European Navigation Conference 2024)
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20 pages, 13202 KiB  
Article
Microstructural Mechanical Characteristics of Soft Rock and the Water–Rock Coupling Mechanism
by Yuankai Zhang, Xiaoshan Li, Wenhai Yu, Yunhui Lu, Jiancheng Chen, Xinhong Song, Yonghong Wu and Liu Yang
Processes 2025, 13(5), 1410; https://doi.org/10.3390/pr13051410 - 6 May 2025
Viewed by 439
Abstract
The strength of soft rock masses progressively deteriorates under dissolution effects, leading to extensive pore development and structural loosening within the rock matrix. This process induces water and sand inrush phenomena at excavation faces, posing substantial challenges to construction safety. This study systematically [...] Read more.
The strength of soft rock masses progressively deteriorates under dissolution effects, leading to extensive pore development and structural loosening within the rock matrix. This process induces water and sand inrush phenomena at excavation faces, posing substantial challenges to construction safety. This study systematically investigates the strength degradation mechanisms and engineering disaster evolution of soft rock subjected to water–rock interactions. Utilizing representative water-rich soft rock specimens from a tunnel in central Yunnan, a multi-scale analytical framework incorporating X-ray diffraction mineral analysis systems, triaxial mechanical testing systems for rocks, scanning electron microscopy (SEM), and nuclear magnetic resonance (NMR) was implemented. This integrated methodology comprehensively elucidates the macro–meso damage evolution mechanisms of soft rock under water–rock coupling interactions. The results indicate that as the dolomite content decreases and the impurity content increases, the softening grade of the rock rises, leading to more extensive pore development. Uniaxial compression tests revealed that the Poisson’s ratio of soft rock is significantly higher than that of typical rock. Triaxial compression tests demonstrated that confining pressure has a substantial impact on soft rock, particularly affecting Poisson’s ratio. Increased water content was found to significantly reduce the strength of the soft rock. Compared to loose soft rock, the radial strain of denser soft rock was markedly greater than the axial strain, and the soaking damage effect was more pronounced. This study provides a valuable insight into the mechanical and permeability behavior of soft rock under different conditions, and provides valuable insights into the solutions for soft rock in geological engineering such as tunnel excavations. Full article
(This article belongs to the Section Energy Systems)
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31 pages, 7561 KiB  
Article
Centralized Measurement Level Fusion of GNSS and Inertial Sensors for Robust Positioning and Navigation
by Mohamed F. Elkhalea, Hossam Hendy, Ahmed Kamel, Ashraf Abosekeen and Aboelmagd Noureldin
Sensors 2025, 25(9), 2804; https://doi.org/10.3390/s25092804 - 29 Apr 2025
Viewed by 591
Abstract
In the current era, which is characterized by increasing demand for high-precision location and navigation capabilities, various industries, including those involved in intelligent vehicle systems, logistics, augmented reality, and more, heavily rely on accurate location information to optimize processes and deliver personalized experiences. [...] Read more.
In the current era, which is characterized by increasing demand for high-precision location and navigation capabilities, various industries, including those involved in intelligent vehicle systems, logistics, augmented reality, and more, heavily rely on accurate location information to optimize processes and deliver personalized experiences. In this context, the integration of Global Navigation Satellite System (GNSS) and inertial sensor technologies in smartphones has emerged as a critical solution to meet these demands. This research paper presents an algorithm that combines a GNSS with a modified downdate algorithm (MDDA) for satellite selection and integrates inertial navigation systems (INS) in both loosely and tightly coupled configurations. The primary objective was to harness the inherent strengths of these onboard sensors for navigation in challenging environments. These algorithms were meticulously designed to enhance performance and address the limitations encountered in harsh terrain. To evaluate the effectiveness of these proposed systems, vehicular experiments were conducted under diverse GNSS observation conditions. The experimental results clearly illustrate the considerable improvements achieved by the recommended tightly coupled (TC) algorithm when integrated with MDDA, in contrast to the loosely coupled (LC) algorithm. Specifically, the TC algorithm demonstrated a remarkable reduction of over 90% in 2D position root mean square error (RMSE) and a 75% reduction in 3D position RMSE when compared to solutions utilizing the weighting matrix provided by Google with all visible satellites. These findings underscore the substantial advancements in precision resulting from the integration of GNSS and INS technologies, thereby unlocking the full potential of transformative applications in the realm of intelligent vehicle navigation. Full article
(This article belongs to the Section Navigation and Positioning)
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14 pages, 7905 KiB  
Article
A Miniature Jumping Robot Using Froghopper’s Direction-Changing Concept
by Dong-Jun Lee and Gwang-Pil Jung
Biomimetics 2025, 10(5), 264; https://doi.org/10.3390/biomimetics10050264 - 24 Apr 2025
Viewed by 524
Abstract
To improve the maneuverability and agility of jumping robots, a variety of steerable jumping mechanisms have been actively studied. The steering ability enables a robot to reach a particular target by altering its jumping direction. To make this possible, we propose a miniature [...] Read more.
To improve the maneuverability and agility of jumping robots, a variety of steerable jumping mechanisms have been actively studied. The steering ability enables a robot to reach a particular target by altering its jumping direction. To make this possible, we propose a miniature steerable jumping robot based on froghopper’s jumping principle: Moment cancellation is achieved via synchronous leg rotation, and a predictable jumping direction is achieved through an almost zero stiffness femoro-tibial joint. To satisfy these working principles, the robot is designed to have a four-bar shaped body structure and wire-driven knee joints. The four-bar body always synchronizes the leg operation by mechanically coupling the two jumping legs, which enables the robot to cancel out the moments and finally reduce the needless body spin. The knee joints are actuated using wires, and the wires are kept loose to maintain joint stiffness almost zero during take-off. Accordingly, the jumping direction is successfully predicted to determine the initial posture of the tibia. As a result, the proposed robot can change the jumping direction from −20 degrees to 20 degrees while reducing needless body spin. Full article
(This article belongs to the Special Issue Bio-Inspired Robotics and Applications 2025)
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14 pages, 16597 KiB  
Article
An Enhanced, Real-Time, Low-Cost GNSS/INS Integrated Navigation Algorithm and Its Platform Design
by Pengcheng Wang, Yuting Gao, Qingzhi Zhao, Yalong Wang, Feng Zhou and Dengxiong Zhang
Sensors 2025, 25(7), 2119; https://doi.org/10.3390/s25072119 - 27 Mar 2025
Viewed by 824
Abstract
The integration of the global navigation satellite system (GNSS) and the inertial navigation system (INS) is a well-established method for achieving accurate positioning, especially in applications involving unmanned aerial vehicles (UAVs). UAVs are increasingly used across various fields, yet they face challenges such [...] Read more.
The integration of the global navigation satellite system (GNSS) and the inertial navigation system (INS) is a well-established method for achieving accurate positioning, especially in applications involving unmanned aerial vehicles (UAVs). UAVs are increasingly used across various fields, yet they face challenges such as the need for real-time processing and the impact of low-quality measurements from cost-effective devices. To address these challenges, we propose a velocity-constrained, enhanced, real-time, low-cost, GNSS/INS integrated navigation algorithm and design an algorithmic platform based on the open-source software KF_GINS. The algorithm supports loosely coupled integration of GNSS position data and raw inertial measurement unit (IMU) data, utilizing a 4G data transmission unit (DTU) for real-time data transmission and performing loosely coupled computations on the received data. Subsequently, we successfully applied this algorithm to low-cost integrated navigation devices, such as UAVs. We tested the algorithm platform using one set of vehicle-mounted data and six UAV datasets. Experimental results indicate that the algorithm platform effectively performs computations under various conditions, improving single-point positioning (SPP) accuracy by up to 15.38% horizontally and 6.78% vertically. These findings demonstrate the algorithm platform’s capability to significantly enhance the accuracy and stability of integrated navigation positioning for UAVs. Full article
(This article belongs to the Special Issue INS/GNSS Integrated Navigation Systems)
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17 pages, 11964 KiB  
Article
Effects of Heat Treatment on Microstructures and Corrosion Properties of AlxCrFeNi Medium-Entropy Alloy
by Pushan Guo, Yuan Pang, Qingke Zhang, Lijing Yang, Zhenlun Song and Yi Zhang
Metals 2025, 15(3), 292; https://doi.org/10.3390/met15030292 - 7 Mar 2025
Viewed by 695
Abstract
This study designed AlxCrFeNi (x = 0.8, 1.0, 1.2) medium-entropy alloys featuring a BCC + B2 dual-phase structure to systematically investigate the effects of Al content variation and heat treatment on microstructure evolution and corrosion behavior. Microstructural characterization revealed that [...] Read more.
This study designed AlxCrFeNi (x = 0.8, 1.0, 1.2) medium-entropy alloys featuring a BCC + B2 dual-phase structure to systematically investigate the effects of Al content variation and heat treatment on microstructure evolution and corrosion behavior. Microstructural characterization revealed that all investigated alloys maintained the BCC + B2 dual-phase labyrinth structure. Electrochemical tests showed that as the Al content increased, the corrosion current density and corrosion rate in a 3.5 wt% NaCl solution increased. Synergistic analysis of post-corrosion morphology (through electrochemical testing and in-situ immersion) combined with XPS analysis of the passive films revealed that the initial stage of corrosion was primarily pitting. Subsequently, due to the loose and porous Al2O3 passive layer formed by the NiAl-rich phase, which was easily attacked by Cl ions, the corrosion progressed into selective corrosion of the NiAl phase. Notably, heat treatment at 1000 °C induced microstructural refinement with enhanced coupling between chunky and labyrinth structures, resulting in improved corrosion resistance despite a 4–6% reduction in Vickers hardness due to elemental homogenization. Among the investigated alloys, the heat-treated Al0.8CrFeNi exhibited the most promising corrosion resistance. Full article
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29 pages, 3075 KiB  
Article
Parametric Study of a Fully Passive Oscillating Foil on a Swinging Arm
by Dominic Cloutier, Mathieu Olivier and Guy Dumas
Energies 2025, 18(5), 1277; https://doi.org/10.3390/en18051277 - 5 Mar 2025
Cited by 1 | Viewed by 759
Abstract
A NACA 0015 airfoil is connected to a swinging arm by springs and dampers and is let loose in an incompressible and viscous flow at a Reynolds number of 3.9×106. The foil operates in a power-extracting regime and is [...] Read more.
A NACA 0015 airfoil is connected to a swinging arm by springs and dampers and is let loose in an incompressible and viscous flow at a Reynolds number of 3.9×106. The foil operates in a power-extracting regime and is free to pitch about a pivot that is itself swinging on a circular path; this contraption is called a fully passive oscillating-foil turbine on a swinging arm. This study explores the potential of four different foil configurations: with the swinging arm being either upstream or downstream of its pivot, and with or without the use of gears to control the equilibrium position of the foil with respect to the flow. The results show that the swinging arm concept offers similar performances, i.e., efficiency and power coefficient, as the railed turbine. Indeed, with arm lengths from 3 to 10 chords, efficiency values near 55% and power coefficients reaching 1.57 are obtained. Both the railed and the swinging arm turbines can operate under either a stall-flutter or a coupled-flutter instability. However, it is found that the geared models are the only ones suited when the driving mechanism is the coupled-flutter instability while both geared and gearless configurations are effective under the stall-flutter instability. Full article
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