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The accelerating global energy crisis and the worsening impacts of climate change have heightened the demand for alternative energy sources. Wind energy is one of the most reliable, affordable, efficient, and readily available renewable sources for residential and industrial use. In response, vertical axis wind turbines (VAWTs) have garnered significant recognition in recent years, leading to increased development and widespread implementation across the globe. A VAWT is a type of wind turbine (WT) known for its compact design, ease of maintenance, and competence in utilizing wind from multiple directions, making it highly suitable for city landscapes. The global impact of VAWTs is significant, as they contribute to the reduction of carbon emissions and the transition toward a more sustainable energy future. Despite these benefits, VAWTs face drawbacks, including lower performance than horizontal axis wind turbines and challenges with achieving consistent self-starting under varying wind speed ( U ∞ ) conditions. This work primarily explores scientific literature and contemporary advancements in VAWT research. The study examines the existing research gaps, challenges, and potential future directions for these turbines and their applications. The outcomes of different strategies are thoroughly evaluated, with the most effective methods highlighted. Consequently, this review offers comprehensive insights into the challenges and solution approaches associated with VAWTs, paving the way for future research to improve aerodynamic performance. [ABSTRACT FROM AUTHOR]

Flexibility plays a crucial role in the design and performance of modern rotors. Its impact on rotor performance and its ability to adapt to external flow disturbances are well-established. In this study, we employ numerical simulations to explore the behavior of a flexible rotor submerged in a turbulent flow, aiming to forecast the influence of its flexibility on performance metrics. The rotational motion of the rotor and the forces imposed by the flow induce deformations in the blades, including bending and twisting. These deformations not only disrupt the flow patterns (vortices) in the turbulent wake but also modify the aerodynamic profiles, thereby affecting essential performance aspects such as thrust, drag, and lift. Our objective is to uncover the relationships between blade deformations, rotation frequencies, and rotor performance in a turbulent flow with a Reynolds number, R e = O (1 0 4) , and for a tip speed ratio in the range [ 0 , 18 ]. We demonstrate that the mean blade bending angle can be effectively expressed using a modified Cauchy number, revealing a scaling law. We also examined how the aerodynamic performance of the rotor blade is affected by variations in the tip speed ratio, either amplifying or reducing it. Through this research, we advance our understanding of the interplay between rotor flexibility, deformation, and performance, contributing to the optimization of rotor design and operational efficiency. [ABSTRACT FROM AUTHOR]

Most large carnivores feed on prey infrequently and may expend large amounts of energy to locate, capture and kill their prey. This makes them probabilistically vulnerable to fluctuating rates of energy acquisition over time, especially within the increasingly human-altered landscapes that dominate their remaining range. Consequently, quantifying their hunting behaviors and success rates is critical, yet direct observation of these events is rarely feasible. We theorized that we could determine prey pursuit and capture in African wild dogs (Lycaon pictus) using a mechanistic approach by constructing Boolean algorithms applied to accelerometer data derived from collar-mounted tags. Here, we used this method and then iteratively improved algorithms by testing them on observed hunts and kills of collared packs. Using this approach on 47 days of acceleration from three wild dogs in three packs, we identified 29 hunts with 10 kills, all of which were confirmed by direct observation except for a single kill. Our results demonstrate that hunting effort and success can largely be determined from acceleration data using a mechanistic approach. This is particularly valuable when such behaviors are rarely quantified and offers a template for research on foraging in canid species, while also contributing to the expanding body of literature that employs similar methods to quantify hunting in large carnivores. [ABSTRACT FROM AUTHOR]

This study investigates the aerodynamic performance and flow dynamics of an H-type Darrieus vertical axis wind turbine (VAWT) using combined numerical and experimental methods. The analysis examines the effects of operational parameters, such as rotor solidity and pitch angle, on aerodynamic loads and flow characteristics, using a 2-D URANS simulation with the Transition SST model to capture transient effects. Validation was conducted in a low-turbulence wind tunnel to observe the impact of variable flow conditions. The LineAverage method for determining the angle of attack demonstrated strong correlations between rotor configuration and load variations, particularly highlighting the influence of blade number and pitch angle on aerodynamic efficiency. This research supports optimization strategies for Darrieus VAWTs in urban environments, where turbulent, low-speed conditions challenge conventional wind turbine designs. [ABSTRACT FROM AUTHOR]

The mechanistic approach is commonly implemented to predict and optimise the cutting forces in milling processes to prevent tool breakages, reduce tool wear, reduce form error, and improve surface quality. To implement this method, the cutting force coefficients (CFCs), that characterise the mechanics of the process, must be calculated. This study compares the accuracy of the predicted cutting forces for variable pitch and helix bull-nose milling tools using a rapid testing (RT) optimisation-based mechanistic CFC identification method that only requires a single angular cut with increasing radial engagement to the traditional mechanistic approach that requires several straight cuts. Along with developing a hybrid technique that combines variation in feed rate and radial engagement. The traditional radial, tangential, and axial (RTA) force model is also compared with the frictional and normal rake face (UV) force model that is independent of the local tool rake and inclination angles which is a necessary for bull nose tools. The RT and the developed hybrid CFC identification method with the UV force model predicted the average F x , F y and F z cutting forces to within 7.1 %, 4.3 %, and 3.8 % error, respectively. These methods were slightly less accurate than the traditional method, however they have significant industrial benefits because they have can be used to identify CFCs with either a single cut, or from any tool-path with chip-load variation, respectively. The RTA force model predicted the average cutting forces similarly to the UV force model, however, the UV force model had lower errors using the rapid RT testing method at the extreme corners of the experimental design space. [ABSTRACT FROM AUTHOR]

Perturb and Observe (P&O) is a commonly used algorithm for Maximum Power Point Tracking (MPPT) in wind turbines. MPPT plays a critical role in enhancing wind turbine efficiency by dynamically adjusting operating parameters to adapt to fluctuating wind conditions. Although P&O is favored for its simplicity and adaptability, its performance is hindered by step size selection issues, which lead to inefficiency, oscillations, and slow convergence. To overcome these limitations, this research proposes a modified P&O algorithm that automates step size selection based on divided sectors of wind speed and normalized power in region two. Additionally, an integration of the pitch-angle control from region three was employed to maintain the optimal power output under variable wind conditions. The proposed approach reduces tracking time, minimizes perturbation errors, and ensures a stable power output. The proposed modifications enhance the efficiency and reliability of Wind Energy Conversion Systems (WECS) by addressing the shortcomings of the conventional P&O methods. [ABSTRACT FROM AUTHOR]

This paper proposes an Adaptive Robust Control (ARC) strategy for pump-controlled pitch systems in large wind turbines to address challenges in control accuracy and energy efficiency. First, a mathematical model integrating pitch angle dynamics and hydraulic characteristics is established, with pitch angle, pitch angular velocity, and hydraulic cylinder thrust as state variables. Then, an ARC strategy is designed using the backstepping method and incorporating parameter adaptation to handle system nonlinearities and uncertainties. The controller parameters are optimized using Particle Swarm Optimization (PSO) under wind disturbance conditions, and comparative analyses are conducted with traditional PID control. The numerical simulation results show that both controllers achieve similar tracking performance under nominal conditions, with PID achieving a 0.08° maximum error and ARC showing a 0.1° maximum error. However, the ARC strategy demonstrates superior robustness under parameter variations, maintaining tracking errors below 0.15°, while the PID error increases to 1.5°. Physical test bench experiments further validate these findings, with ARC showing significantly better performance during cylinder retraction with 0.1° error compared to PID's 0.7° error. The proposed control strategy effectively handles both the inherent nonlinearities of the pump-controlled system and external disturbances, providing a practical solution for precise pitch control in large wind turbines while maintaining energy efficiency through the pump-controlled approach. [ABSTRACT FROM AUTHOR]

Ultra‐low frequency (ULF) waves radially diffuse hundreds‐keV to few‐MeV electrons in the magnetosphere, as the range of drift frequencies of such electrons overlaps with the wave frequencies, leading to resonant interactions. Theoretically this process is described by analytic expressions of the resonant interactions between electrons and ULF wave modes in a background magnetic field. However, most expressions of the radial diffusion rates are derived for equatorially mirroring electrons and are based on estimates of the power of ULF waves that are obtained either from spacecraft close to the equatorial plane or from the ground but mapped to the equatorial plane. Based on recent statistical in situ observations, it was found that the wave power of magnetic fluctuations is significantly enhanced away from the magnetic equator. In this study, the distribution of the wave amplitudes as a function of magnetic latitude is compared against models simulating the natural modes of oscillation of magnetospheric field lines, with which they are found to be consistent. Energetic electrons are subsequently traced in 3D model fields that include a latitudinal dependence that is similar to measurements and to the natural modes of oscillation. Particle tracing simulations show a significant dependence of the radial transport of relativistic electrons on pitch angle, with off‐equatorial electrons experiencing considerably higher radial transport, as they interact with ULF wave fluctuations of higher amplitude than equatorial electrons. These findings point to the need for incorporating pitch‐angle‐dependent radial diffusion coefficients in global radiation belt models. Plain Language Summary: The random inward and outward motion of high energy electrons in the Earth's magnetosphere, called radial diffusion, is a critical factor in modeling and predicting the state of the radiation belts, where many satellites operate. This motion is caused primarily by waves in the Ultra‐Low Frequency (or ULF) range, which have been measured and characterized since the early days of the space era. However, for simplicity, most current models treat radial diffusion in two dimensions, on the Earth's magnetic equatorial plane, taking into account the average motion of electrons as they drift around the Earth. Recent studies, enabled by multi‐year measurements by missions with off‐equatorial inclinations (THEMIS, Arase, Cluster) have shown that the power of ULF waves is significantly enhanced away from the magnetic equator. A 3D model of the magnetic field fluctuations is compared with statistical data of the measured ULF wave power, and is then used to estimate the radial transport of off‐equatorial electrons. It is found through single‐particle tracing that radial diffusion is significantly enhanced when taking into account the latitude‐dependence of ULF waves. These new findings can change the quantification and parameterization of radial diffusion and our current understanding of radial diffusion in the radiation belts. Key Points: Enhanced Ultra‐low frequency (ULF) wave power at high latitudes significantly enhances radial transport of off‐equatorial relativistic radiation belt electronsRadial diffusion coefficients need to be revisited, to include pitch angle dependence and latitude‐dependent ULF wave powerThese results are enabled by multi‐year statistics by s/c performing measurements away from the magnetic equator and by particle tracing [ABSTRACT FROM AUTHOR]

The calculation of contact strength and stress of involute beveloid gears is difficult, and existing analysis methods encounter serious problems, such as long calculation time and poor accuracy, seriously affecting the promotion and development of these gears. To solve this technical problem, the geometric structure of involute beveloid gears is considered using the Hertz formula. In addition, the calculation methods for parameters, such as the contact ratio, contact ratio coefficient, and pitch cone angle coefficient, are determined. A Hertz contact model and a fractal contact model for involute beveloid gears were established using fractal theory, and the distribution law of contact stress was obtained. On this basis, a comparative analysis was conducted on the tooth surface contact stress obtained from the Hertz contact model, fractal contact model, and finite element model. The finite element analysis proves that the Hertz contact stress calculation formula and fractal contact model for involute beveloid gears established in this article have high accuracy, and can precisely reflect the actual contact stress value of the tooth surface. [ABSTRACT FROM AUTHOR]

Currently, PID control method is mainly used for the pitch control of coal mine roadheader, and the control precision is not high in the case of time-varying and nonlinear hydraulic system during the pitch control of roadheader. The pitch control of roadbeader is realized by controlling the stroke of the hydraulic cylinder. Combining the traditional PID algorithm with fuzzy control and neural network, the accuracy of the stroke control of the hydraulic cylinder can be effectively improved. In order to solve the above problems, a pitch control method for coal mine roadheader based on fuzzy neural network PID is proposed. By analyzing the kinematic relationship of the support part of the roadheader, the mathematical relationship between the pitch angle and the hydraulic cylinder of the support part is obtained. The working principle of the pitch control hydraulic system of the roadheader is introduced, and the hydraulic system and its transfer function model are established. The method combines fuzzy control with neural networks to form a fuzzy neural network. The method optimizes PID control parameters by using the fuzzy neural network. The method combines the mathematical model of the support mechanism and the transfer function model of the hydraulic system to establish a fuzzy neural network PID control model for the pitch angle of the roadheader. It achieves automatic and precise control of the pitch mechanism of the coal mine roadheader. This method can make the pitch mechanism of the roadheader reach the preset position more quickly and accurately, solving the time-varying and nonlinear problems in the pitch control of roadheader. The simulation results show that the fuzzy neural network PID control algorithm reduces tracking errors by 69.34% and 74.49% respectively compared to fuzzy PID and PID control algorithms. The method simulates the pitch control of coal mine roadheaders under sudden and following working conditions through hydraulic cylinder displacement control. The results show that compared with fuzzy PID and PID control algorithms, the fuzzy neural network PID control algorithm has the smallest pitch control tracking error, shortens the average response time to position signals by 27.22% and 50.33% respectively, and has better dynamic control performance.

Due to the substantial rise in wind power generation, the direct-drive permanent magnet synchronous generator has emerged as a leading technology for efficient variable speed operation, meeting grid demands effectively. This paper presents a comparative analysis of control strategies for permanent magnet synchronous generator based wind turbine using real variable wind speed data from a 2 MW of Tetouan wind farm in Morocco. The proposed approach is based on evaluating two primary control strategies: the adaptive fuzzy-proportional-integral controller and the conventional proportional-integral controller aimed at enhancing the wind turbine's output power. The simulation performed on MATLAB-Simulink indicates that pitch control mechanisms play a crucial role in optimizing power generation, also demonstrating its ability to achieve satisfactory performance. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Mine Automation is the property of Industry & Mine Automation Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Vertical axis wind turbines (VAWTs) are gaining increasing significance in the realm of renewable energy. One notable advantage they possess is their ability to operate efficiently in diverse wind conditions, including low-speed and turbulent winds, which are often prevalent in urban areas. In this study, dimples and pitch angles into the rotor blades are used to enhance the aerodynamic performance of a straight-bladed Darrieus turbine. To simulate the turbine's rotation under transient conditions, computational fluid dynamics calculations are conducted in a two-dimensional setting. The unsteady Navier–Stokes equations are solved, and the k-ω SST turbulence model is employed to represent turbulent flow. The results of the simulation demonstrate that the application of a circular dimple on the pressure side of the blades, positioned at 0.25 of the chord length with a diameter of 0.08 chord length, leads to a 5.18% increase in the power coefficient at λ = 2.7, in comparison to a turbine with plain airfoils. Moreover, when an airfoil with both a dimple and a + 1° pitch angle is utilized, the turbine's performance at λ = 2.7 improved by 7.17% compared to a plain airfoil, and by 1.8% compared to a dimpled airfoil without a pitch angle. Additionally, the impact of a double dimple on both the pressure and suction sides of the airfoil on turbine performance was investigated. It was discovered that the double-dimpled airfoil exhibited lower performance in comparison to a plain airfoil. The study showed that the utilization of both dimples and pitch angles for airfoils of a Darrieus turbine blade increases the power generated by the turbine. [ABSTRACT FROM AUTHOR]

The pitch angle of the contra rotation propeller (CRP) has important effect on the aerodynamic interference between the front and aft blades,which can change the aerodynamic performance of the propeller. In order to study the aerodynamic influence of pitch angle on the contra rotation propeller and improve the aerodynamic performance of propellers,at the inlet Mach number of 0.453,the numerical calculation is carried out by adjusting the blade pitch angle after about 6×6 configuration contra rotation propeller,in which the method is used by combining unsteady Reynolds-averaged Navier-Stokes (URANS) equation with SST turbulence model. The T-Rex high quality grid generation technique is used to study the change rule of the pitch angle of contra rotating propeller on aerodynamic interference. The results show that the aft propellers are under the action of pre-swirling air from the front propellers,the aft propellers can absorb a part of the tangential slip flow energy of the front propellers,and the aerodynamic efficiency is higher than that of the front propellers. The aerodynamic parameters of the front and aft propellers fluctuate 12 times in a rotating cycle. When the rotating speed of frond and aft propellers maintains the same,the pitch angle of the front propellers maintains constant,and the pitch angle of the aft propellers is reduced,the aerodynamic efficiency of the front and aft propellers is increased,and the efficiency of aft propellers is improved significantly.

This paper proposes an Adaptive Robust Control (ARC) strategy for pump-controlled pitch systems in large wind turbines to address challenges in control accuracy and energy efficiency. First, a mathematical model integrating pitch angle dynamics and hydraulic characteristics is established, with pitch angle, pitch angular velocity, and hydraulic cylinder thrust as state variables. Then, an ARC strategy is designed using the backstepping method and incorporating parameter adaptation to handle system nonlinearities and uncertainties. The controller parameters are optimized using Particle Swarm Optimization (PSO) under wind disturbance conditions, and comparative analyses are conducted with traditional PID control. The numerical simulation results show that both controllers achieve similar tracking performance under nominal conditions, with PID achieving a 0.08° maximum error and ARC showing a 0.1° maximum error. However, the ARC strategy demonstrates superior robustness under parameter variations, maintaining tracking errors below 0.15°, while the PID error increases to 1.5°. Physical test bench experiments further validate these findings, with ARC showing significantly better performance during cylinder retraction with 0.1° error compared to PID’s 0.7° error. The proposed control strategy effectively handles both the inherent nonlinearities of the pump-controlled system and external disturbances, providing a practical solution for precise pitch control in large wind turbines while maintaining energy efficiency through the pump-controlled approach.

Abstract Background The surgical treatment of accessory navicular (AN) is divided into simple resection of AN and Kidner surgery used to reconstruct posterior tibial tendon (PTT) after AN resection. However, both of these procedures have certain disadvantages. Herein, we proposed a modified method to reconstruct PTT and compared the short-term clinical effect of our method with the modified Kidner procedure. Methods We collected data from 23 adolescent children with painful type II AN treated in our department between January 2015 and June 2020. The American Orthopedic Foot and Ankle Society Ankle-Hind foot (AOFAS-AH) Scores, the Meary Angle, and Pitch Angle of the lateral weight-bearing plain radiographs status were recorded before and after the operation to evaluate the treatment outcomes. Results In the modified Kidner surgery (MK) group, the median AOFAS-AH increased from 61 (59–68) to 87 (83–91) (P

This article presents the assessment of the power coefficient of a small three-bladed Htype Darrieus wind turbine when using modified non-symmetrical airfoil profiles: LS(1)-0413-Mod-4 and S813-Mod-5, at a low wind speed of 5 m/s. For this purpose, the configuration parameters of the turbulence model, computational domain, and meshing have been obtained by reviewing the state of the art about Computational Fluid Dynamics (CFD) simulations with the software ANSYSFluent in order to select the best airfoil profile for the wind turbine. Additionally, the effect on the performance of the power coefficient (cp) of the turbine has been studied for a fixed pitch angle in a range between -5 ° and 2°. An analysis of the effect on the cp has been also made when the bladespoke connection point has been at 25% or 50% of the chord line. Finally, with the best configuration between the non-symmetrical airfoil profile, pitch angle, and blade-spoke connection point, the turbine performance has been simulated at a range of different speeds: from 3 m/s to 18 m/s. Consequently, the maximum power of the turbine has been estimated according to different wind speeds. [ABSTRACT FROM AUTHOR]

A map of vertical cutoff rigidities has been calculated for galactic cosmic ray (GCR) entry into the atmosphere of Jupiter at the 1 bar pressure radius (1 RJ = 71,492 km) using the JRM33 comprehensive model of Jupiter's magnetic field (based on 32 close flybys of Jupiter by the Juno satellite) along with a particle trajectory code (Geomagnetic Cutoff Rigidity Computer Program). The map was combined with measurements of the GCR proton flux at Earth, from the BESS‐Polar ii campaign, to calculate a corresponding proton flux map at Jupiter. Additional cutoff rigidity maps were calculated for 1,000 km above the 1 bar level, and for 1.41 RJ. Furthermore, detections of heavy particles from Juno's Stellar Reference Unit were analyzed for their cutoff rigidities in multiple directions. Cutoff rigidities of 3.5–7.5 GV were found for five of the detections furthest out making them possible GCR candidates. The majority of points, located below 1.6 RJ are not likely to be GCR. Assuming instead that they are trapped particles we have calculated upper and lower limits on their equatorial pitch angles, resulting in a range from 10.1° to 27.1°, which can help constraining Jupiter's energetic radiation. Plain Language Summary: Using data of Jupiter's magnetic field, collected by the Juno satellite, we have calculated how galactic cosmic rays (energetic particles originating from supernovae) can enter into the atmosphere of Jupiter at different altitudes. This can aid our understanding of atmospheric phenomena on Jupiter and help in planning future missions to the planet. One of Juno's instruments, the Stellar Reference Unit, has detected some peculiar signatures. Some of them probably are galactic cosmic rays that have hit the instrument. Most of them are probably not, but instead they could be particles trapped by the strong magnetic field of Jupiter. If so, they can help us understand the radiation belts of the planet. Using knowledge of the location of the detections as well as the magnetic field we calculate the so‐called pitch angle of the detected particles. This angle is defined by the ratio between the motion of the particle perpendicular to the magnet field line and the motion parallel to the field line. The pitch angle is fundamental in constraining energetic radiation emanating from Jupiter's atmosphere. Key Points: A galactic cosmic ray cutoff rigidity map for Jupiter was made using the JRM33 model and the Geomagnetic Cutoff Rigidity Computer ProgramThe flux of galactic cosmic ray protons into Jupiter's atmosphere was calculated based on BESS‐Polar ii dataDetections of heavy ions by Juno's SRU were investigated and used to estimate their equatorial pitch angles [ABSTRACT FROM AUTHOR]

Suppose the intermediate coupler of a rail vehicle is unstable during the collision process and loses its connection and energy dissipation functions. In that case, it will significantly reduce the performance of the train crashworthiness function and increase the risk of train derailment. This paper aims to establish a refined finite element model (RFEM) that can simulate the buckling behaviour and investigate the bending resistance and buckling instability characteristics of the intermediate coupler, and the accuracy of the RFEM was verified by quoting the results of an existing intermediate coupler impact test. The results demonstrated that the proposed coupler modelling method could better simulate the energy absorption characteristics and unstable behaviour. Compared to the test results, the differences in the initial crushing force, maximum longitudinal compression displacement, minimum crushing force, and maximum crushing force were 6.5%, 1.3%, 3.6%, and 6.5%, respectively. Within the allowable range of parameters, the maximum bending force linearly increased with an increase in the initial longitudinal compression displacement. As the pitch or yaw angle increased, the longitudinal buckling load of the coupler linearly decreased and became more sensitive to the pitch angle. When pitch and yaw angles existed simultaneously, the longitudinal buckling load was further reduced. [ABSTRACT FROM AUTHOR]

The precise regulation of the hinge moment and pitch angle driven by the pitch-regulated mechanism is crucial for modulating thrust requirements and ensuring stable attitude control in Martian coaxial rotorcraft. Nonetheless, the aerodynamic hinge moment in rotorcraft presents time-dependent dynamic properties, posing significant challenges for accurate measurement and assessment for such characteristics. In this study, we delve into the detailed aerodynamic hinge moment characteristics associated with the pitch-regulated mechanism of Mars rotorcraft under a spectrum of control strategies. A robust computational fluid dynamics model was developed to simulate the rotor’s aerodynamic loads, accompanied by a quantitative hinge moment characterization that takes into account the effects of varying rotor speeds and pitch angles. Our investigation yielded a thorough understanding of the interplay between aerodynamic load behavior and rotor surface pressure distributions, leading to the creation of an empirical mapping model for hinge moments. To validate our findings, we engineered a specialized test apparatus capable of measuring the hinge moments of the pitch-regulated mechanism, facilitating empirical assessments under replicated atmospheric conditions of both Earth and Mars. The result indicates aerodynamic hinge moments depend nonlinearly on rotational speed, peaking at a 0° pitch angle and showing minimal sensitivity to pitch under 0°. Above 0°, hinge moments decrease, reaching a minimum at 15° before rising again. Simulation and experimental comparisons demonstrate that under Earth conditions, the aerodynamic performance and hinge moment errors are within 8.54% and 24.90%, respectively. For Mars conditions, errors remain below 11.62%, proving the CFD model’s reliability. This supports its application in the design and optimization of Mars rotorcraft systems, enhancing their flight control through the accurate prediction of aerodynamic hinge moments across various pitch angles and speeds.

Background: The surgical treatment of accessory navicular (AN) is divided into simple resection of AN and Kidner surgery used to reconstruct posterior tibial tendon (PTT) after AN resection. However, both of these procedures have certain disadvantages. Herein, we proposed a modified method to reconstruct PTT and compared the short-term clinical effect of our method with the modified Kidner procedure. Methods: We collected data from 23 adolescent children with painful type II AN treated in our department between January 2015 and June 2020. The American Orthopedic Foot and Ankle Society Ankle-Hind foot (AOFAS-AH) Scores, the Meary Angle, and Pitch Angle of the lateral weight-bearing plain radiographs status were recorded before and after the operation to evaluate the treatment outcomes. Results: In the modified Kidner surgery (MK) group, the median AOFAS-AH increased from 61 (59–68) to 87 (83–91) (P < 0.05); the Pitch angle of the lateral weight-bearing plain radiographs increased from 13.0 (8–18) to 17.4 (14–22), and the Meary angle decreased from 18.3 (14–24) to 14.2 (8–20) (P < 0.05). In the PTT preservation folded suture (FS) group, the median AOFAS-AH increased from 61 (59–68) to 87 (85–91) (P < 0.05); the Pitch angle of the lateral weight-bearing plain radiographs increased from 12.3 (7–18) to 18.4 (15–26), and the Meary angle decreased from 17.8 (13–23) to 5.7 (3–8) (P < 0.05). There was no significant difference in AOFAS-AH postoperative scores between the FS group and MK group; however, the improvement on Pitch and Meary angle of the lateral weight-bearing plain radiographs was significantly better in the FS group than in MK group (P < 0.05). Conclusions: For painful type II AN in juvenile patients, the insertion-preserving folding suture procedure had similar short-term results on AOFAS-AH scores but greater improvement in the Meary angle and the Pitch Angle than the modified Kidner method. Level of Evidence: III [ABSTRACT FROM AUTHOR]

For vertical axis wind turbines (VAWTs), the increase of the incoming wind speed higher than the rated value will make the tip speed ratio (TSR) lower and lower, resulting in the blade fatigue load becoming more and more severe and the power coefficient weakening gradually. This paper explores whether varying the pitch with the TSR decrease is necessary for improving the power coefficient and reducing the fatigue load. Specifically, the pitch angle effect on the power coefficient and fatigue load of a VAWT at different TSRs was studied by the computational fluid dynamics method. The results show that the optimal pitch angle in terms of the power coefficient varies with the TSR, which means that varying the pitch with the TSR decrease can improve the power coefficient. Meanwhile, the principle to guide the pitch variation is to avoid flow separation in the downwind zone and minimize the angles of attack (AoAs) in the upwind zone. At the lowest TSR of 1.7 in the present work, varying the pitch from the optimal one in terms of the power coefficient reduced the blade normal force amplitude significantly, which is mainly attributed to avoiding the vortex–blade encounter and minimizing the AoAs in the downwind zone. The vortex–blade encounter at the lowest TSR is an important phenomenon related to the variation of the blade torque and blade normal force and will weaken and disappear with the pitch angle increase. [ABSTRACT FROM AUTHOR]

Copyright of DYNA - Ingeniería e Industria is the property of Publicaciones Dyna SL and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Smart cities require effective device communication through consideration of key features of instrumentation, intelligence, and interconnections. Internet-of-Things (IoT) is implemented in smart cities for larger communication with heterogeneous communication and devices in smart cities. Through the implementation of IoT devices in smart cities power management can be effectively managed through the implementation of renewable systems. Power system contributed on the economic growth of the country through offering adequate power for demand. The conventional synchronous generator is replaced with wind power system those demand for evaluate the stability of the system. In view of the problem that the inertia of the system is reduced and the frequency modulation capability is insufficient due to large-scale wind power connected to the power grid, this paper proposed Pitch Angle Load Shedding Frequency Modulation wind turbine control strategy and inertia support and primary frequency modulation. This scheme is based on the characteristics of the pitch angle of the wind turbine to set the load shedding control of the wind turbine, reserve the reserve capacity required for the wind turbine frequency modulation. To analyse the impact of WTGs on transient stability, a line fault is applied near bus-7 of IEEE 9-bus based on consideration of swing in rotor angle, speed and oscillation with consideration of magnitude of voltage, active and reactive power of WTGs. It is found that, with SCIGs, rotor angle swing increased indefinitely, rotor speed deviation is more and oscillation duration is more. [ABSTRACT FROM AUTHOR]

The distribution of energetic ion flux in the ring current region, such as a meteorological cumulonimbus cloud, stores up the particle energy for a geomagnetic substorm. It is helpful to study the geomagnetic substorm mechanism by using a lunar base ENA imaging simulation of the dynamic evolution of the ring current, and establishing the corresponding relationship between key node events of the substorm. Based on the previous observation experience and our simulation results of the dynamic evolution of the ring current, we propose a macroscopic model of substorms related to the dynamic evolution of ring currents and present the possibility of confirming the causal sequence of some of those critical node events of substorms with the lunar base ENA imaging measurement. IBEX, operating in the ecliptic plane, may even give examples of the telemetry of ring current ion fluxes through ENA measurements during substorms/quiets. [ABSTRACT FROM AUTHOR]

Abstract In this study, a computational fluid dynamics (CFD) model was developed to simulate the aerodynamic performance of the National Renewable Energy Laboratory (NREL) offshore 5‐MW baseline wind turbine with single rotor and full wind turbine. Using statistical methods, the relation between pitch angle and performance when the speed is above the rated wind speed was analyzed; furthermore, other published data were compiled to establish the functional equations of power, thrust with various inflow wind speeds, and pitch angles. In addition, according to shape optimization based on parametric modeling, the two‐dimensional cross‐section of the wind turbine blade can be defined through a metasurface approach, and the three‐dimensional surface modeling of the wind turbine blade, nacelle, and tower is completed using the nonuniform rational B‐splines (NURBS) interpolator. In terms of aerodynamic simulation, the unstructured polygon mesh was used herein to discretize the space and simulate the highly curved and twisted surfaces of the blade. In this study, the compact and accurate mesh form obtained through a grid independence test will be used to analyze the distribution of the pressure coefficient, shear stress coefficient, and limited streamline on the blade surface at various inflow wind speeds and pitch angles to understand the differences between different turbulence models and the causes of power and thrust attenuation at high inflow wind speeds. In addition, the phenomena of blade‐tip vortices, dynamic stall, blade loading, and the interaction between nacelle and tower were collectively explored.

In-pipe water turbines have begun to gain interest for harvesting power on a small scale from pipe networks. However, few studies have addressed the feasibility of installing spherical lift-based helical-bladed turbines in a water supply network. Points such as the pressure drop and generated power remain unexplored. In this study, a three-dimensional numerical model, based on OpenFOAM, is used to investigate the performance of the spherical lift-based helical-bladed in-pipe water turbine. The study aims to evaluate how the geometric properties of this turbine affect its performance in terms of power and efficiency, and the hydraulics of pipe flow in terms of pressure drop. The study considers a turbine of diameter 600 mm, with the following geometric properties: number of helical blades 3, 4 and 5; blade chord length 10%, 15% and 20% of turbine diameter D; blade helicity 0°, 60° and 120°; and pitch angle −6°, −3°, 0° and 3°. These parameters are analyzed at tip speed ratios (TSRs) of 2, 3 and 4. The results show that the five-blade turbine yields a power of 1300 W, while the three-blade turbine yields only 870 W, at an optimum TSR of 3. A change in the chord length of 50% (from 0.10D to 0.15D) increases the turbine power by 88.4% and efficiency by 40% for the same TSR. A further change to 0.20D gives no significant improvement in efficiency or power output. An increase in the helical angle from 0° to 120° results in a 22.8% reduction in turbine power. The turbine achieves the maximum power output of 1350 W at zero pitch angle, with a corresponding efficiency of 27%. The maximum head loss observed is 1.6 m, which represents 2.7% of the total head in the pipe. Solidity has a more pronounced effect on head losses than helicity and pitch angle.

To improve the photoelectric test accuracy of moving objects, in this study, the speed attenuation caused by air resistance was introduced into the double-N six-light-screen test system, and the test system was theoretically analyzed through oblique incidence with field experiment for verification. It was found in the study that the optimal test values for yaw angle, pitch angle, axial speed, and distance could be obtained by selecting the pulse time origin at the center of two light screen groups. In addition, mud pellets were used for field experiments to effectively verify the simulation results. In a new model, the test accuracy of yaw angle and pitch angle was greatly improved when compared with traditional processing methods, but the laws of error distribution remained almost unchanged. The error of axial speed showed monotonicity as affected by the pitch angle. At the same time, the error of test distance remained symmetric with the improved accuracy, thereby meeting the statistical test requirements for small-volume moving objects.

During the landing process of wing-in-ground aircraft,the impact caused by the landing of broken steps is likely to lead to the buckling or damage of the structural surface.The Arbitrary Lagrangian-Eulerian(ALE)finite element method is utilized to simulate the water landing of a wing-in-ground aircraft,and the penalty function method is used in the two-phase interface fluid-solid interaction problem.The effect of different parameters such as horizontal flight velocity,falling velocity,pitch angle on the immersion depth,and overload are analyzed.The results show that the pressure maxima of the aircraft with water landing all occur at the broken step.With the increase of the pitch angle,the peak of vertical overload rises and then falls,while the peak of horizontal overload keeps reducing.When the pitch angle is 7°,the vertical overload peak reaches the highest,which is 1.4 times that of the lowest overload in the pitch angle of 15°.On the other hand,the peak of the horizontal overload rises as the horizontal component of flight velocity increases,and it is visible that there is no discernible effect on the peak of vertical overload.Meanwhile,an approximately linear relationship appears between the peak of vertical overload and the square of falling velocity.The larger the falling velocity,the bigger the peak of vertical overload.

In the current study, effects of a Gurney flap and pitch angle on the aerodynamic performance of a vertical-axis wind turbine are investigated by comparing CFD results of the standard and flap-equipped wind turbines at various pitch angles. Both wind turbines show better performance at the negative pitch angles and the flap-equipped wind turbine shows higher performance than the standard one at most of the pitch angles. The best flap-equipped wind turbine obtained a 7.5 % higher power coefficient than the best standard wind turbine by varying the pitch angle. Flow analysis reveals that wind turbine's pitch angle control and small device attachment should be implemented to make its blades remain in the pre-stall region. For the high-performance wind turbine, positive flow characteristics in terms of no formation of the vortex around the trailing edge and weak traces of the vortex have been identified. [ABSTRACT FROM AUTHOR]

Electron lifetimes are important for understanding the dominant loss processes of radiation belt electrons to the atmosphere and for accurate radiation belt modeling. We estimate electron lifetimes from the precipitating population measured in Low Earth Orbit (LEO) from the Polar Orbiting Environmental Satellites (POES). We compare our estimates to previous estimates from the Radiation Belt Storm Probes (RBSP) by Claudepierre et al. (2020b, https://doi.org/10.1029/2019GL086053). We also present the first complete pitch angle resolved lifetimes in the radiation belts. Quasi‐linear theory predicts the pitch angle distribution decays uniformly, therefore if steady‐state decay is realized, POES and RBSP should measure similar lifetimes. Lifetime estimates from LEO are shown to be in good agreement with those from Van Allen Probes in the outer belt and pitch angle resolved lifetimes indicate that steady‐state decay is realized. However, a systematic slight overestimation of the POES lifetimes reveal that the POES instruments may suffer from bremsstrahlung contamination. At L = 2–3, no decay intervals were identified in the POES electron fluxes and the near loss cone RBSP electron fluxes. We show that at these L‐shells, where lifetimes are long, there is an apparent decoupling of the perpendicular and parallel flux. Large pitch angle anisotropy and processes that affect low pitch angle electrons are two explanations for this apparent decoupling. Electron lifetime models that use pitch angle independent lifetimes, derived from the equatorially mirroring electron flux, likely underestimate the amount of precipitating flux and may not capture the dynamics of low equatorial pitch angle electrons at L < 3. Key Points: Lifetimes between Polar Orbiting Environmental Satellites (POES) and Radiation Belt Storm Probes in the outer belt agree, though POES may suffer from bremsstrahlung contaminationPitch angle independent (equilibrium) decay is realized in the outer radiation beltVarious processes decouple the perpendicular and parallel flux preventing the identification of decay intervals from Low Earth Orbit at L = 2–3 [ABSTRACT FROM AUTHOR]

This paper proposed a unified active power optimization control of wind farms under wake effect. It takes the sum of the kinetic energy variation and pitch angle variation as the optimization objective and used the particle swarm algorithm to achieve the optimization results. The main feature of the proposed method is that it unifies the kinetic energy optimization under a low wind speed area, the pitch angle and kinetic energy trade-off optimization under a medium wind speed area, and the pitch angle optimization under a high wind speed area. Combined with the de-loaded power constraint, it can flexibly reach various optimal operating states of the wind farm. The simulation results show that the proposed method optimizes the rotor speed and pitch angle in different wind speed areas, and releases kinetic energy and/or increases the output power of the wind farm to provide frequency support by switching the operating states. [ABSTRACT FROM AUTHOR]

Synthetic aperture radar (SAR) is a powerful tool for all-weather, all-day observation, but it is susceptible to interference in the echo phase, particularly from the nonlinear phase caused by terrain relief. This can cause defocus and target position movement, which can impact the accuracy and recognition ability of SAR imaging. While current research focuses on using digital elevation models (DEMs) to correct the phase, obtaining high-precision DEM data requires significant measurement and processing work. To address this, we propose a new SAR filtering algorithm based on the terrain echo phase. By studying the phase of a SAR echo signal containing elevation information, we divide the nonlinear phase caused by terrain echo into two components: one that varies with azimuth and one that does not. We filter out the nonlinear phase component dependent on the azimuth angle from the echo phase and eliminate the nonlinear phase component invariant with the azimuth angle by filtering the specific pitch angle. The effectiveness of this filtering algorithm is verified through theoretical analysis and simulation. [ABSTRACT FROM AUTHOR]

When a thermocouple is used to measure gas temperature, the measured temperature, i.e., the thermocouple bead temperature, is not equal to the gas temperature. The bead temperature results from the bead energy balance. The positioning angles such as the pitch angle and the roll angle and the wire distance of the thermocouple will influence the convection heat transfer of the thermocouple, causing the bead temperature variation. Two S type thermocouples are used to measure the temperature of the H2/air Hencken flame with the equivalence ratio 0.7. The maximum measurement temperature changes are 52 K and 79 K for the pitch angle variation and the roll angle variation, respectively. CFD simulations are carried out to simulate the experimental phenomena. The differences between the simulated and measured bead temperatures are less than 20.4 K. With 90° roll angle, the bead temperature increases first then decreases with the pitch angle. With 90° pitch angle, the bead temperature increases first then decreases with the roll angle. With 0° pitch angle, the bead temperature increases monotonically with the wire distance. The background physical mechanisms of the phenomena are analyzed with the detailed CFD results.

In response to the problem of reduced system inertia and insufficient frequency regulation capacity due to large-scale wind power connection to the grid, an integrated control strategy scheme for wind turbine inertia support and primary frequency regulation is proposed. In this scheme, the load reduction control of wind turbine is adjusted based on the characteristics of wind turbine slurry distance angle, and the reserve capacity required for wind turbine frequency modulation is reserved, which further solves the combination problem between the frequency change of the power grid and the virtual moment of inertia in the load reduction mode. In addition, the wind turbine speed protection is considered to set the static adjustment coefficient, and combined with the inertia support control, to achieve the wind turbine integrated frequency control strategy. The co-simulation model including wind farm is built in MATLAB/Simulink platform. The results show that the wind turbine can quickly provide virtual rotational inertia support to the grid, reduce the rate of change of the initial grid frequency perturbation, and regulate the output power according to the adjusted static regulation differential coefficients to improve the frequency stability of the wind power connected to the grid, which verifies the rationality of the proposed control strategy. [ABSTRACT FROM AUTHOR]

In this study, a computational fluid dynamics (CFD) model was developed to simulate the aerodynamic performance of the National Renewable Energy Laboratory (NREL) offshore 5‐MW baseline wind turbine with single rotor and full wind turbine. Using statistical methods, the relation between pitch angle and performance when the speed is above the rated wind speed was analyzed; furthermore, other published data were compiled to establish the functional equations of power, thrust with various inflow wind speeds, and pitch angles. In addition, according to shape optimization based on parametric modeling, the two‐dimensional cross‐section of the wind turbine blade can be defined through a metasurface approach, and the three‐dimensional surface modeling of the wind turbine blade, nacelle, and tower is completed using the nonuniform rational B‐splines (NURBS) interpolator. In terms of aerodynamic simulation, the unstructured polygon mesh was used herein to discretize the space and simulate the highly curved and twisted surfaces of the blade. In this study, the compact and accurate mesh form obtained through a grid independence test will be used to analyze the distribution of the pressure coefficient, shear stress coefficient, and limited streamline on the blade surface at various inflow wind speeds and pitch angles to understand the differences between different turbulence models and the causes of power and thrust attenuation at high inflow wind speeds. In addition, the phenomena of blade‐tip vortices, dynamic stall, blade loading, and the interaction between nacelle and tower were collectively explored. [ABSTRACT FROM AUTHOR]

The focus of miniaturization is the production of small and portable devices that can be carried in the pocket anywhere and anytime. Small and portable devices that perform multitask such the smartphone requires a portable and efficient antenna that operates in many frequency bands. A single planar miniaturized Archimedean spiral antenna, which operates in a frequency range that is determined by its inner and outer radii of its arc, has been adjourned to be a better candidate for these multiple tasks. This study examined the geometry of a miniaturized Archimedean spiral antenna of varying turns. An inner radius of 4.90 mm and a thickness of 0.0356 mm suitable for the printed antenna were previously chosen for the study. The length of the arc and the outer radius were determined for spiral turns ranging from 0.5 to 100 with an incremental step of 0.5. Results revealed the radial distance generating the spiral, the length of its arc, the outer radius, and the surface area were 4.97 mm, 15.51 mm, 4.97 mm and 77.16 mm² for 0.5 spiral turns, and 19.12 mm, 7,546.80 mm, 2,849.33 mm and 1,148.64 mm² for 100 spiral turns. Based on the outer radii, the frequency range of operation will be between 16.76 MHz and 9.60 GHz. The mathematical functions formulated through curve fitting described the relationship between the outer radius and arc length with a power function and the number of turns and frequency with an exponential function, while arc length and radial distance, area and number of turns, and area and pitch angle are described by polynomial functions. It is recommended that further analysis on the geometry of the minimized Archimedean spiral antenna be conducted. [ABSTRACT FROM AUTHOR]