Sign in to use this feature.

Years

Between: -

Subjects

remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline

Journals

remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline

Article Types

Countries / Regions

remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline

Search Results (721)

Search Parameters:
Keywords = velocity conversion

Order results
Result details
Results per page
Select all
Export citation of selected articles as:
23 pages, 4912 KiB  
Article
A Dynamic Analysis of Oscillating Water Column Systems: Design of a 16 kW Wells Turbine for Coastal Energy Generation in Ecuador
by Brayan Ordoñez-Saca, Mayken Espinoza-Andaluz, Carlos Vallejo-Cervantes, Julio Barzola-Monteses, Marcos Guamán-Macias and Christian Aldaz-Trujillo
Processes 2025, 13(8), 2349; https://doi.org/10.3390/pr13082349 - 24 Jul 2025
Abstract
The work presents the design of an Oscillating Water Column (OWC) system with a nominal capacity of 16 kW, proposed as a contribution to reducing the energy gap in Ecuador, where electricity demand surpasses supply. The province of Santa Elena was selected as [...] Read more.
The work presents the design of an Oscillating Water Column (OWC) system with a nominal capacity of 16 kW, proposed as a contribution to reducing the energy gap in Ecuador, where electricity demand surpasses supply. The province of Santa Elena was selected as a promising site due to its favorable wave conditions and coastal location. The design process involved identifying areas with high wave energy potential, conducting a brief mathematical modeling analysis, and defining the parameters required for the system. Computational Fluid Dynamics (CFD) simulations were carried out in two stages: In the first stage, OpenFOAM was used to evaluate wave behavior, specifically flow velocity and pressure, before the water enters the generation chamber. In the second stage, a different CFD tool was used, incorporating the output data from OpenFOAM to simulate the energy conversion process inside the Wells turbine. This analysis focused on how the turbine captures and transforms the wave energy into usable power. The results show that, under ideal conditions, the system achieves an average power output of 11 kW. These findings suggest that implementing this type of system in coastal regions of Ecuador is both viable and beneficial for local energy development. Full article
(This article belongs to the Special Issue Advances in Hydraulic Machinery and Systems)
Show Figures

Figure 1

22 pages, 7942 KiB  
Article
Research on the Influence of Impeller Oblique Cutting Angles on the Performance of Double-Suction Pumps
by Zhongsheng Wang, Xinxin Li, Jun Liu, Ji Pei, Wenjie Wang, Kuilin Wang and Hongyu Wang
Energies 2025, 18(15), 3907; https://doi.org/10.3390/en18153907 - 22 Jul 2025
Viewed by 91
Abstract
Double-suction centrifugal pumps are extensively employed in industrial applications owing to their high efficiency, low vibration, superior cavitation resistance, and operational durability. This study analyzes how impeller oblique cutting angles (0°, 6°, 9°, 12°) affect a double-suction pump at a fixed 4% trimming [...] Read more.
Double-suction centrifugal pumps are extensively employed in industrial applications owing to their high efficiency, low vibration, superior cavitation resistance, and operational durability. This study analyzes how impeller oblique cutting angles (0°, 6°, 9°, 12°) affect a double-suction pump at a fixed 4% trimming ratio and constant average post-trim diameter. Numerical simulations and tests reveal that under low-flow (0.7Qd) and design-flow conditions, the flat-cut (0°) minimizes reflux ratio and maximizes efficiency by aligning blade outlet flow with the mainstream. Increasing oblique cutting angles disrupts this alignment, elevating reflux and reducing efficiency. Conversely, at high flow (1.3Qd), the 12° bevel optimizes outlet flow, achieving peak efficiency. Pressure pulsation at the volute tongue (P11) peaks at the blade-passing frequency, with amplitudes significantly higher for 9°/12° bevels than for 0°/6°. The flat-cut suppresses wake vortices and static–rotor interaction, but oblique cutting angle choice critically influences shaft-frequency pulsation. Entropy analysis identifies the volute as the primary loss source. Larger oblique cutting angles intensify wall effects, increasing total entropy; pump chamber losses rise most sharply due to worsened outlet velocity non-uniformity and turbulent dissipation. The flat-cut yields minimal entropy at Qd. These findings provide a basis for tailoring impeller trimming to specific operational requirements. Furthermore, the systematic analysis provides critical guidance for impeller trimming strategies in other double-suction pumps and pumps as turbines in micro hydropower plants. Full article
(This article belongs to the Special Issue Optimization Design and Simulation Analysis of Hydraulic Turbine)
Show Figures

Figure 1

27 pages, 4412 KiB  
Review
Coupling Agents in Acoustofluidics: Mechanisms, Materials, and Applications
by Shenhao Deng, Yiting Yang, Menghui Huang, Cheyu Wang, Enze Guo, Jingui Qian and Joshua E.-Y. Lee
Micromachines 2025, 16(7), 823; https://doi.org/10.3390/mi16070823 - 19 Jul 2025
Viewed by 268
Abstract
Acoustic coupling agents serve as critical interfacial materials connecting piezoelectric transducers with microfluidic chips in acoustofluidic systems. Their performance directly impacts acoustic wave transmission efficiency, device reusability, and reliability in biomedical applications. Considering the rapidly growing body of research in the field of [...] Read more.
Acoustic coupling agents serve as critical interfacial materials connecting piezoelectric transducers with microfluidic chips in acoustofluidic systems. Their performance directly impacts acoustic wave transmission efficiency, device reusability, and reliability in biomedical applications. Considering the rapidly growing body of research in the field of acoustic microfluidics, this review aims to serve as an all-in-one reference on the role of acoustic coupling agents and relevant considerations pertinent to acoustofluidic devices for anyone working in or seeking to enter the field of disposable acoustofluidic devices. To this end, this review seeks to summarize and categorize key aspects of acoustic couplants in the implementation of acoustofluidic devices by examining their underlying physical mechanisms, material classifications, and core applications of coupling agents in acoustofluidics. Gel-based coupling agents are particularly favored for their long-term stability, high coupling efficiency, and ease of preparation, making them integral to acoustic flow control applications. In practice, coupling agents facilitate microparticle trapping, droplet manipulation, and biosample sorting through acoustic impedance matching and wave mode conversion (e.g., Rayleigh-to-Lamb waves). Their thickness and acoustic properties (sound velocity, attenuation coefficient) further modulate sound field distribution to optimize acoustic radiation forces and thermal effects. However, challenges remain regarding stability (evaporation, thermal degradation) and chip compatibility. Further aspects of research into gel-based agents requiring attention include multilayer coupled designs, dynamic thickness control, and enhancing biocompatibility to advance acoustofluidic technologies in point-of-care diagnostics and high-throughput analysis. Full article
(This article belongs to the Special Issue Recent Development of Micro/Nanofluidic Devices, 2nd Edition)
Show Figures

Figure 1

28 pages, 6582 KiB  
Article
Experimental Study on Dynamic Response Characteristics of Rural Residential Buildings Subjected to Blast-Induced Vibrations
by Jingmin Pan, Dongli Zhang, Zhenghua Zhou, Jiacong He, Long Zhang, Yi Han, Cheng Peng and Sishun Wang
Buildings 2025, 15(14), 2511; https://doi.org/10.3390/buildings15142511 - 17 Jul 2025
Viewed by 152
Abstract
Numerous rural residential buildings exhibit inadequate seismic performance when subjected to blast-induced vibrations, which poses potential threats to their overall stability and structural integrity when in proximity to blasting project sites. The investigation conducted in conjunction with the Qianshi Mountain blasting operations along [...] Read more.
Numerous rural residential buildings exhibit inadequate seismic performance when subjected to blast-induced vibrations, which poses potential threats to their overall stability and structural integrity when in proximity to blasting project sites. The investigation conducted in conjunction with the Qianshi Mountain blasting operations along the Wenzhou segment of the Hangzhou–Wenzhou High-Speed Railway integrates household field surveys and empirical measurements to perform modal analysis of rural residential buildings through finite element simulation. Adhering to the principle of stratified arrangement and composite measurement point configuration, an effective and reasonable experimental observation framework was established. In this investigation, the seven-story rural residential building in adjacent villages was selected as the research object. Strong-motion seismographs were strategically positioned adjacent to frame columns on critical stories (ground, fourth, seventh, and top floors) within the observational system to acquire test data. Methodical signal processing techniques, including effective signal extraction, baseline correction, and schedule conversion, were employed to derive temporal dynamic characteristics for each story. Combined with the Fourier transform, the frequency–domain distribution patterns of different floors are subsequently obtained. Leveraging the structural dynamic theory, time–domain records were mathematically converted to establish the structure’s maximum response spectra under blast-induced loading conditions. Through the analysis of characteristic curves, including floor acceleration response spectra, dynamic amplification coefficients, and spectral ratios, the dynamic response patterns of rural residential buildings subjected to blast-induced vibrations have been elucidated. Following the normalization of peak acceleration and velocity parameters, the mechanisms underlying differential floor-specific dynamic responses were examined, and the layout principles of measurement points were subsequently formulated and summarized. These findings offer valuable insights for enhancing the seismic resilience and structural safety of rural residential buildings exposed to blast-induced vibrations, with implications for both theoretical advancements and practical engineering applications. Full article
(This article belongs to the Special Issue Seismic Analysis and Design of Building Structures)
Show Figures

Figure 1

17 pages, 3524 KiB  
Article
Experimental Study on Microseismic Monitoring of Depleted Reservoir-Type Underground Gas Storage Facility in the Jidong Oilfield, North China
by Yuanjian Zhou, Cong Li, Hao Zhang, Guangliang Gao, Dongsheng Sun, Bangchen Wu, Chaofeng Li, Nan Li, Yu Yang and Lei Li
Energies 2025, 18(14), 3762; https://doi.org/10.3390/en18143762 - 16 Jul 2025
Viewed by 257
Abstract
The Jidong Oilfield No. 2 Underground Gas Storage (UGS), located in an active fault zone in Northern China, is a key facility for ensuring natural gas supply and peak regulation in the Beijing–Tianjin–Hebei region. To evaluate the effectiveness of a combined surface and [...] Read more.
The Jidong Oilfield No. 2 Underground Gas Storage (UGS), located in an active fault zone in Northern China, is a key facility for ensuring natural gas supply and peak regulation in the Beijing–Tianjin–Hebei region. To evaluate the effectiveness of a combined surface and shallow borehole monitoring system under deep reservoir conditions, a 90-day microseismic monitoring trial was conducted over a full injection cycle using 16 surface stations and 1 shallow borehole station. A total of 35 low-magnitude microseismic events were identified and located using beamforming techniques. Results show that event frequency correlates positively with wellhead pressure variations instead of the injection volume, suggesting that stress perturbations predominantly control microseismic triggering. Events were mainly concentrated near the bottom of injection wells, with an average location error of approximately 87.5 m and generally shallow focal depths, revealing limitations in vertical resolution. To enhance long-term monitoring performance, this study recommends deploying geophones closer to the reservoir, constructing a 3D velocity model, applying AI-based phase picking, expanding array coverage, and developing a microseismic-injection coupling early warning system. These findings provide technical guidance for the design and deployment of long-term monitoring systems for deep reservoir conversions into UGS facilities. Full article
(This article belongs to the Section H2: Geothermal)
Show Figures

Figure 1

19 pages, 4122 KiB  
Article
Fluid Dynamics Analysis of Flow Characteristics in the Clearance of Hydraulic Turbine Seal Rings
by Leilei Chen, Wenhao Wu, Jian Deng, Bing Xue, Liuming Xu, Baosheng Xie and Yuchuan Wang
Energies 2025, 18(14), 3726; https://doi.org/10.3390/en18143726 - 14 Jul 2025
Viewed by 161
Abstract
The hydraulic turbine serves as the cornerstone of hydropower generation systems, with the sealing system’s performance critically influencing energy conversion efficiency and operational cost-effectiveness. The sealing ring is a pivotal component, which mitigates leakage and energy loss by regulating flow within the narrow [...] Read more.
The hydraulic turbine serves as the cornerstone of hydropower generation systems, with the sealing system’s performance critically influencing energy conversion efficiency and operational cost-effectiveness. The sealing ring is a pivotal component, which mitigates leakage and energy loss by regulating flow within the narrow gap between itself and the frame. This study investigates the intricate flow dynamics within the gap between the sealing ring and the upper frame of a super-large-scale Francis turbine, with a specific focus on the rotating wall’s impact on the flow field. Employing theoretical modeling and three-dimensional transient computational fluid dynamics (CFD) simulations grounded in real turbine design parameters, the research reveals that the rotating wall significantly alters shear flow and vortex formation within the gap. Tangential velocity exhibits a nonlinear profile, accompanied by heightened turbulence intensity near the wall. The short flow channel height markedly shapes flow evolution, driving the axial velocity profile away from a conventional parabolic pattern. Further analysis of rotation-induced vortices and flow instabilities, supported by turbulence kinetic energy monitoring and spectral analysis, reveals the periodic nature of vortex shedding and pressure fluctuations. These findings elucidate the internal flow mechanisms of the sealing ring, offering a theoretical framework for analyzing flow in microscale gaps. Moreover, the resulting flow field data establishes a robust foundation for future studies on upper crown gap flow stability and sealing ring dynamics. Full article
(This article belongs to the Special Issue Optimization Design and Simulation Analysis of Hydraulic Turbine)
Show Figures

Figure 1

22 pages, 2465 KiB  
Article
Gait Stability Under Hip Exoskeleton Assistance: A Phase-Dependent Analysis Using Gait Tube Methodology
by Arash Mohammadzadeh Gonabadi and Farahnaz Fallahtafti
Appl. Sci. 2025, 15(13), 7530; https://doi.org/10.3390/app15137530 - 4 Jul 2025
Viewed by 300
Abstract
This study aimed to evaluate how wearable hip exoskeleton assistance affects phase-dependent gait stability in healthy adults using a novel visualization technique known as gait tube analysis. Hip exoskeletons offer significant potential to enhance human locomotion through joint torque augmentation, yet their effects [...] Read more.
This study aimed to evaluate how wearable hip exoskeleton assistance affects phase-dependent gait stability in healthy adults using a novel visualization technique known as gait tube analysis. Hip exoskeletons offer significant potential to enhance human locomotion through joint torque augmentation, yet their effects on gait stability across the gait cycle remain underexplored. This study introduces gait tube analysis, a novel method for visualizing center of mass velocity trajectories in three-dimensional state space, to quantify phase-dependent gait stability under hip exoskeleton assistance. We analyzed data from ten healthy adults walking under twelve conditions (ten powered with varying torque magnitude and timing, one passive, and one unassisted), assessing variability via covariance-based ellipsoid volumes. Powered conditions, notably HighLater and HighLatest, significantly increased vertical variability (VT) during early-to-mid stance (10–50% of the gait cycle), with HighLater showing the highest mean ellipsoid volume (99,937 mm3/s3; z = 2.3). Conversely, the passive PowerOff condition exhibited the lowest variability (47,285 mm3/s3; z = –1.7) but higher metabolic cost, highlighting a stability-efficiency trade-off. VT was elevated in 11 of 12 conditions (p ≤ 0.0059), and strong correlations (r ≥ 0.65) between ellipsoid volume and total variability validated the method’s robustness. These findings reveal phase-specific stability challenges and metabolic cost variations induced by exoskeleton assistance, providing a foundation for designing adaptive controllers to balance stability and efficiency in rehabilitation and performance enhancement contexts. Full article
Show Figures

Figure 1

20 pages, 925 KiB  
Review
Catalytic Ammonia Combustion: Legacy Catalytic Burner Designs and Catalyst Requirements for In Situ Hydrogen Production
by Khalid Al Sadi, Ebrahim Nadimi and Dawei Wu
Energies 2025, 18(13), 3505; https://doi.org/10.3390/en18133505 - 2 Jul 2025
Cited by 1 | Viewed by 333
Abstract
Ammonia is increasingly recognised as a promising carbon-free fuel and hydrogen carrier due to its high hydrogen content, ease of liquefaction, and existing global infrastructure. However, its direct utilisation in combustion systems poses significant challenges, including low flame speed, high ignition temperature, and [...] Read more.
Ammonia is increasingly recognised as a promising carbon-free fuel and hydrogen carrier due to its high hydrogen content, ease of liquefaction, and existing global infrastructure. However, its direct utilisation in combustion systems poses significant challenges, including low flame speed, high ignition temperature, and the formation of nitrogen oxides (NOX). This review explores catalytic ammonia cracking as a viable method to enhance combustion through in situ hydrogen production. It evaluates traditional catalytic burner designs originally developed for hydrocarbon fuels and assesses their adaptability for ammonia-based applications. Special attention is given to ruthenium- and nickel-based catalysts supported on various oxides and nanostructured materials, evaluating their ammonia conversion efficiency, resistance to sintering, and thermal stability. The impact of the main operational parameters, including reaction temperature and gas hourly space velocity (GHSV), is also discussed. Strategies for combining partial ammonia cracking with stable combustion are studied, with practical issues such as catalyst degradation, NOX regulation, and system scalability. The analysis highlights recent advancements in structural catalyst support, which have potential for industrial-scale application. This review aims to provide future development of low-emission, high-efficiency catalytic burner systems and advance ammonia’s role in next-generation hydrogen energy technologies. Full article
Show Figures

Figure 1

19 pages, 3233 KiB  
Article
Mathematical Modeling of the Influence of Electrical Heterogeneity on the Processes of Salt Ion Transfer in Membrane Systems with Axial Symmetry Taking into Account Electroconvection
by Ekaterina Kazakovtseva, Evgenia Kirillova, Anna Kovalenko and Mahamet Urtenov
Inventions 2025, 10(4), 50; https://doi.org/10.3390/inventions10040050 - 30 Jun 2025
Viewed by 203
Abstract
This article proposes a 3D mathematical model of the influence of electrical heterogeneity of the ion exchange membrane surface on the processes of salt ion transfer in membrane systems with axial symmetry; in particular, we investigate an annular membrane disk in the form [...] Read more.
This article proposes a 3D mathematical model of the influence of electrical heterogeneity of the ion exchange membrane surface on the processes of salt ion transfer in membrane systems with axial symmetry; in particular, we investigate an annular membrane disk in the form of a coupled system of Nernst–Planck–Poisson and Navier–Stokes equations in a cylindrical coordinate system. A hybrid numerical–analytical method for solving the boundary value problem is proposed, and a comparison of the results for the annular disk model obtained by the hybrid method and the independent finite element method is carried out. The areas of applicability of each of these methods are determined. The proposed model of an annular disk takes into account electroconvection, which is understood as the movement of an electrolyte solution under the action of an external electric field on an extended region of space charge formed at the solution–membrane boundary under the action of the same electric field. The main regularities and features of the occurrence and development of electroconvection associated with the electrical heterogeneity of the surface of the membrane disk of the annular membrane disk are determined; namely, it is shown that electroconvective vortices arise at the junction of the conductivity and non-conductivity regions at a certain ratio of the potential jump and angular velocity and flow down in the radial direction to the edge of the annular membrane. At a fixed potential jump greater than the limiting one, the formed electroconvective vortices gradually decrease with an increase in the angular velocity of rotation until they disappear. Conversely, at a fixed value of the angular velocity of rotation, electroconvective vortices arise at a certain potential jump, and with its subsequent increase gradually increase in size. Full article
(This article belongs to the Section Inventions and Innovation in Applied Chemistry and Physics)
Show Figures

Figure 1

21 pages, 3028 KiB  
Article
Revolutionizing Hydrogen Production: Unveiling the Role of Liquid Metals in Methane Pyrolysis over Iron Catalysts Supported on Titanium Dioxide and Alumina
by Hamid Ahmed, Amal BaQais, Fekri Abdulraqeb Ahmed Ali, Ahmed I. Osman, Anis H. Fakeeha, Ahmed E. Abasaeed, Ahmed A. Ibrahim, Syed Farooq Adil, Tahani Saad Algarni and Ahmed S. Al-Fatesh
Catalysts 2025, 15(7), 631; https://doi.org/10.3390/catal15070631 - 27 Jun 2025
Viewed by 451
Abstract
Catalytic methane decomposition offers an attractive and sustainable pathway for producing COx-free hydrogen and valuable carbon nanotubes. This work investigates the innovative use of liquid metals, particularly gallium and indium, as promoters for iron catalysts based on a titanium dioxide and [...] Read more.
Catalytic methane decomposition offers an attractive and sustainable pathway for producing COx-free hydrogen and valuable carbon nanotubes. This work investigates the innovative use of liquid metals, particularly gallium and indium, as promoters for iron catalysts based on a titanium dioxide and alumina composite to improve this process even more. In a fixed-bed reactor operating at 800 °C and atmospheric pressure, all catalyst activities for methane decomposition were thoroughly assessed while keeping the gas hourly space velocity at 6 L/g h. Surface area and porosity, H2-temperature programmed reduction/oxidation, X-ray diffraction, Raman spectroscopy, scanning transmission electron microscopy, and thermogravimetry analysis were utilized to investigate the physicochemical properties of the catalyst. The result showed that iron supported on a titanium-alumina catalyst exhibited higher activity, stability, and reproducibility with a methane conversion of 90% and hydrogen production of 81% after three cycles, with 240 min for each cycle and stability for 480 min. In contrast, the liquid metal-promoted catalysts improved the metal-support interaction and textural properties, such as surface area, pore volume, and particle dispersion of the catalysts. Still, the catalytic efficiency significantly improved. However, the gallium-promoted catalyst displayed excellent reusability. The characterization of the spent catalyst proved that both the iron supported on a titanium-alumina and its gallium-promoted derivative produced graphitic carbon; on the contrary, the indium-promoted catalyst produced amorphous carbon. These results demonstrate how liquid metal promoters can be used to adjust the characteristics of catalysts, providing opportunities for improved reusability and regulated production of carbon byproducts during methane decomposition. Full article
Show Figures

Figure 1

12 pages, 1006 KiB  
Article
Temporal Stability and Practical Relevance of Velocity and Velocity-Loss Perception in Back Squat
by Emanuele Dello Stritto, Antonio Gramazio, Ruggero Romagnoli and Maria Francesca Piacentini
Appl. Sci. 2025, 15(13), 7252; https://doi.org/10.3390/app15137252 - 27 Jun 2025
Viewed by 265
Abstract
The aim of this study was to investigate the accuracy and stability of both Perception of Velocity (PV) and Perception of Velocity Loss (PVL) over four weeks, without any feedback regarding velocity during training sessions. Fifteen subjects performed six training sessions: four sessions [...] Read more.
The aim of this study was to investigate the accuracy and stability of both Perception of Velocity (PV) and Perception of Velocity Loss (PVL) over four weeks, without any feedback regarding velocity during training sessions. Fifteen subjects performed six training sessions: four sessions familiarized the athletes with PV and PVL and the final two sessions assessed the accuracy and stability of PV and PVL, with one conducted 48 h after the familiarization and the other after 4 weeks. To assess PV and PVL, two loads (60% 1RM and 80% 1RM) and two velocity losses (20% VL and 40% VL) were employed. PV accuracy was measured by the DeltaScore, the difference between perceived velocity (Vp) and the velocity provided by the encoder (Vr): DetlaScore = Vp − Vr. PVL was measured by the Vscore, the difference between repetitions where the subject perceived the target %VL (Np) and repetitions that actually met it (Nr): Vscore = Np − Nr. The analysis performed revealed no differences in DeltaScore nor in Vscore between the two test sessions performed 4 weeks apart (p > 0.05). On the other hand, the effect of load on both DeltaScore and Vscore was significant in both sessions (p < 0.05). PVL and PV accuracy are stable throughout time. PVL may be used to prescribe and monitor velocity-based training. Conversely, when prescribing training sessions based on PV, it is essential to pair PV with a perception scale and incorporate an encoder when possible. Full article
Show Figures

Figure 1

18 pages, 606 KiB  
Article
Two-Way Conversion Between Fifth-Order Stokes Wave Theories
by Hsien-Kuo Chang, Yang-Yih Chen and Jin-Cheng Liou
AppliedMath 2025, 5(3), 78; https://doi.org/10.3390/appliedmath5030078 - 27 Jun 2025
Viewed by 205
Abstract
Stokes wave is a classical problem in physics. Various Stokes wave theories in different forms have been developed to help us better understand their characteristics and for engineering applications. Exploring whether these Stokes wave theories can be converted into each other is a [...] Read more.
Stokes wave is a classical problem in physics. Various Stokes wave theories in different forms have been developed to help us better understand their characteristics and for engineering applications. Exploring whether these Stokes wave theories can be converted into each other is a mathematical issue. We select three Stokes wave theories with different expansion parameters, all expressed in terms of water depth measured from the mean water level (MWL). Using series reversion to convert between the different expansions, we successfully transform the expressions for the velocity potential, wave profile, and dynamic properties between two of the Stokes wave theories. Through this conversion, we identify an incorrect expression for the water level in one Stokes wave theory. Full article
Show Figures

Figure 1

19 pages, 2046 KiB  
Article
An Analytical Solution for Energy Harvesting Using a High-Order Shear Deformation Model in Functionally Graded Beams Subjected to Concentrated Moving Loads
by Sy-Dan Dao, Dang-Diem Nguyen, Trong-Hiep Nguyen and Ngoc-Lam Nguyen
Modelling 2025, 6(3), 55; https://doi.org/10.3390/modelling6030055 - 25 Jun 2025
Viewed by 292
Abstract
This study presents a high-order shear deformation theory (HSDT)-based model for evaluating the energy harvesting performance of functionally graded material (FGM) beams integrated with a piezoelectric layer and subjected to a moving concentrated load at constant velocity. The governing equations are derived using [...] Read more.
This study presents a high-order shear deformation theory (HSDT)-based model for evaluating the energy harvesting performance of functionally graded material (FGM) beams integrated with a piezoelectric layer and subjected to a moving concentrated load at constant velocity. The governing equations are derived using Hamilton’s principle, and the dynamic response is obtained through the State Function Method with trigonometric mode shapes. The output voltage and harvested power are calculated based on piezoelectric constitutive relations. A comparative analysis with homogeneous isotropic beams demonstrates that HSDT yields more accurate predictions than the Classical Beam Theory (CBT), especially for thick beams; for instance, at a span-to-thickness ratio of h/L = 12.5, HSDT predicts increases of approximately 6%, 7%, and 12% in displacement, voltage, and harvested power, respectively, compared to CBT. Parametric studies further reveal that increasing the load velocity significantly enhances the strain rate in the piezoelectric layer, resulting in higher voltage and power output, with the latter exhibiting quadratic growth. Moreover, increasing the material gradation index n reduces the beam’s effective stiffness, which amplifies vibration amplitudes and improves energy conversion efficiency. These findings underscore the importance of incorporating shear deformation and material gradation effects in the design and optimization of piezoelectric energy harvesting systems using FGM beams subjected to dynamic loading. Full article
Show Figures

Figure 1

19 pages, 11127 KiB  
Article
Drone State Estimation Based on Frame-to-Frame Template Matching with Optimal Windows
by Seokwon Yeom
Drones 2025, 9(7), 457; https://doi.org/10.3390/drones9070457 - 24 Jun 2025
Viewed by 346
Abstract
The flight capability of drones expands the surveillance area and allows drones to be mobile platforms. Therefore, it is important to estimate the kinematic state of drones. In this paper, the kinematic state of a mini drone in flight is estimated based on [...] Read more.
The flight capability of drones expands the surveillance area and allows drones to be mobile platforms. Therefore, it is important to estimate the kinematic state of drones. In this paper, the kinematic state of a mini drone in flight is estimated based on the video captured by its camera. A novel frame-to-frame template-matching technique is proposed. The instantaneous velocity of the drone is measured through image-to-position conversion and frame-to-frame template matching using optimal windows. Multiple templates are defined by their corresponding windows in a frame. The size and location of the windows are obtained by minimizing the sum of the least square errors between the piecewise linear regression model and the nonlinear image-to-position conversion function. The displacement between two consecutive frames is obtained via frame-to-frame template matching that minimizes the sum of normalized squared differences. The kinematic state of the drone is estimated by a Kalman filter based on the velocity computed from the displacement. The Kalman filter is augmented to simultaneously estimate the state and velocity bias of the drone. For faster processing, a zero-order hold scheme is adopted to reuse the measurement. In the experiments, two 150 m long roadways were tested; one road is in an urban environment and the other in a suburban environment. A mini drone starts from a hovering state, reaches top speed, and then continues to fly at a nearly constant speed. The drone captures video 10 times on each road from a height of 40 m at a 60-degree camera tilt angle. It will be shown that the proposed method achieves average distance errors at low meter levels after the flight. Full article
(This article belongs to the Special Issue Intelligent Image Processing and Sensing for Drones, 2nd Edition)
Show Figures

Figure 1

22 pages, 5801 KiB  
Article
Study on the Impact of Pipe Installation Height on the Hydraulic Performance of Combined Canal–Pipe Water Conveyance Systems
by Yanan Liu, Meijian Bai, Kai Zhang, Baozhong Zhang, Yinong Li, Yuanpeng Wang, Jintao Liu, Hairuo Liu and Yutian He
Agriculture 2025, 15(13), 1347; https://doi.org/10.3390/agriculture15131347 - 23 Jun 2025
Viewed by 315
Abstract
This study investigates the impact of pipe installation height on the hydraulic performance of a combined canal–pipe water conveyance system (CCPS) and provides practical recommendations. A combined experimental and numerical simulation approach was conducted to systematically analyze and evaluate the impact of different [...] Read more.
This study investigates the impact of pipe installation height on the hydraulic performance of a combined canal–pipe water conveyance system (CCPS) and provides practical recommendations. A combined experimental and numerical simulation approach was conducted to systematically analyze and evaluate the impact of different pipe installation heights (0, 1, 3, and 5 cm) and flow rates (18.40, 21.21, 24.74, 28.27, 33.58, and 38.88 L/s) on the system’s behavior. The results indicated that the canal water depths obtained from the numerical simulations were in close agreement with the measurements from the experiments. The water depth in the upstream canal remained nearly parallel to the canal bottom. At the junction, the trend of water depth varies under different flow rates. When the flow rate is low, the water depth sharply decreases. Conversely, when the flow rate is higher, the water depth rises significantly. Cross sections farther from the junction exhibit a higher uniformity in flow velocity distribution. As the height of the pipe installation increases, the range of influence of the junction on the flow velocity distribution in the upstream canal decreases. The elevation of the pipe installation height has been instrumental in enhancing the uniformity of flow velocity distribution across the section. However, the local head loss gradually increases as the installation height increases. Turbulent kinetic energy (TKE) and turbulent eddy dissipation rate (TED) are negatively correlated with the distance between the section and the junction point, and the maximum value decreases gradually with increasing values of the pipe installation height. Considering the hydraulic performance and engineering construction investment, the recommended pipe installation height under the conditions of this study is 1 cm. Full article
(This article belongs to the Section Agricultural Water Management)
Show Figures

Figure 1

Back to TopTop