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We present a derivation from the first principles of the coupled equations of motion of an active self-diffusiophoretic Janus motor and the hydrodynamic densities of its fluid environment that are nonlinearly displaced from equilibrium. The derivation makes use of time-dependent projection operator techniques defined in terms of slowly varying coarse-grained microscopic densities of the fluid species number, total momentum, and energy. The exact equations of motion are simplified using time scale arguments, resulting in Markovian equations for the Janus motor linear and angular velocities with average forces and torques that depend on the fluid densities. For a large colloid, the fluid equations are separated into bulk and interfacial contributions, and the conditions under which the dynamics of the fluid densities can be accurately represented by bulk hydrodynamic equations subject to boundary conditions on the colloid are determined. We show how the results for boundary conditions based on continuum theory can be obtained from the molecular description and provide Green–Kubo expressions for all transport coefficients, including the diffusiophoretic coupling and the slip coefficient. [ABSTRACT FROM AUTHOR]

A constant volume combustion chamber is employed to investigate the laminar burning characteristics of syngas. The effects of changes in diluent gas composition (CO 2 /N 2) and H 2 /CO ratio on the laminar burning velocity (S L) of syngas are decoupled and analyzed. The instability of laminar flames is analyzed using effective Lewis number, flame thickness, thermal expansion ratio, and linear stability theory. The results indicate that as the amount of diluent gas increases, thermal diffusion instability (TD) increases, while hydrodynamic instability (DL) gradually decreases. With a decrease in the H 2 /CO ratio, TD gradually decreases, and DL increases. When the diluent content is below 45%, the critical flame radius under N 2 dilution conditions exceeds that under CO 2 dilution conditions. Above 45%, the situation reverses. As the H 2 /CO ratio decreases, the critical flame radius gradually increases. When the H 2 content is high, the critical flame radius under N 2 dilution conditions is larger. • Comprehensive analysis of the impact of diluent content and H 2 /CO ratio. • Decoupling analyzes the dilution, thermal, and chemical effects of CO 2. • Decoupling analyzes the chemical and physical effects of changing the H 2 /CO ratio. • The spherical flame instability is analyzed with linear stability theory. • Analyzing the instability range of flames by incorporating critical radius. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the asymptotic behavior of inertial dynamics with dry friction within the context of a Hilbert framework for convex differentiable optimization. Our study focuses on a doubly nonlinear first-order evolution inclusion that encompasses two potentials. In our analysis, we specifically focus on two main components: the differentiable function f that needs to be minimized, which influences the system's state through its gradient, and the nonsmooth dry friction potential denoted as φ = r ‖ · ‖ . It's important to note that the dry friction term acts on a linear combination of the velocity vector and the gradient of f. Consequently, any stationary point in our system corresponds to a critical point of f, unlike the case where only the velocity vector is involved in the dry friction term, resulting in an approximate critical point of f. To emphasize the crucial role of ∇ f (x) , we also explore the dual formulation of this dynamic, which possesses a Riemannian gradient structure. To address these dynamics, we employ the recently developed generic acceleration approach by Attouch, Bot, and Nguyen. This approach involves the time scaling of a continuous first-order differential equation, followed by the application of the method of averaging. By applying this methodology, we derive fast convergence results for second-order time-evolution systems with dry friction, asymptotically vanishing viscous damping, and implicit Hessian-driven damping. [ABSTRACT FROM AUTHOR]

Good sealing of the gas path is the key to improving the thrust-to-weight ratio and fuel efficiency of an aeroengine, which requires a small radial gap between the rotor blade tips and the corresponding seals to minimize the loss of compressed gas. Due to the extreme conditions in service (e.g., high temperatures of 1500 °C, high pressures of 40 atm, and high linear velocities of 400 m/s), problems, such as wear, oxidation, and hot corrosion at the blade tip, are becoming more and more pronounced. Blade tip protective coatings are an effective way to improve these problems. In this paper, the composition and classification of blade tip protective coatings are summarized. The design concepts and preparation techniques of different blade tip protective coatings are highlighted. The problems of the corresponding blade tip protective coatings and the advantages or disadvantages of the preparation technology are also pointed out. Then, the evaluation means of blade tip protective coatings are concluded. Finally, the development trend of blade tip protective coatings is prospected. [ABSTRACT FROM AUTHOR]

Traffic perception is the foundation of intelligent roads, and how to accurately perceive traffic has become a central issue for researchers. With the application of Vehicle-to-Everything communication technology, vehicle IDs, locations, velocities, and accelerations can be obtained by the Roadside Unit (RSU), i.e., trajectory-observed vehicles for the road. Inferring the number of vehicles between trajectory-observed vehicles can make traffic perception more accurate, with which the traffic can be sensed on the whole road. Thus, in the case of mixed traffic flow, a Real-Time Prediction Model was proposed, which is a novel model containing four modules: prior experience of the space headway, linear distribution of velocity and acceleration, identification of traffic shockwave, and filter. The inferred result was calculated in real time. During the test, we used US-101 lane-1 data of the Next Generation Simulation dataset and trajectory-observed vehicles with stochastic distribution for 20% penetration. The length of the study area on the US-101 highway was approximately 2100 feet, which was similar to the communication area of a single RSU. During the evaluation of the model accuracy with the real-world datasets, the error of the inferred vehicle numbers in the study area could be limited to ±5 vehicles almost. Results show that it is feasible to infer the number of vehicles between trajectory-observed vehicles. The model compensates for the shortcomings of traditional models (based on inductive loop, camera, or radar), thus providing a novel method for the traffic perception of intelligent roads. [ABSTRACT FROM AUTHOR]

Purpose: This research aims to examine the impact of friction stir processing (FSP) treatment on an aluminum alloy, especially the AD31T alloy derived from the Al-Fe-Mg-Si system. The aim is to assess the influence of different processing techniques on the microstructure and physical and mechanical characteristics of the material, with a specific focus on structural and bulk imperfections inside the stir zone (SZ). Design/methodology/approach: The study demonstrates that augmenting the linear velocity of the tool within the 25–100 mm/min range results in significant enhancements. The enhancements include a decrease in the heat-affected zone (HAZ), a reduction in the extent of volume defects inside the SZ and a more uniform deformation. The microstructural analysis results are corroborated by data acquired from microhardness and electrical conductivity studies, confirming the beneficial influence of modifying the tool's linear velocity on the material parameters. Findings: This study provides significant observations on the changes in microstructure and the generation of flaws throughout the process of FSP of AD31T alloy. These results have practical implications for improving the characteristics of the alloy and optimizing the production conditions. Originality/value: All samples exhibit a distinct reduction in electrical conductivity within the initial third of the sample, aligning with the transitional region between the base metal (BM) and the HAZ. This underscores the importance of understanding the transitional zones during FSP. [ABSTRACT FROM AUTHOR]

Transparent displays are crucial for various applications, particularly for their potential use as windows in future self‐driving cars. These displays require high transparency, low power consumption, and high mechanical reliability. Micro‐LEDs have emerged as ideal devices for the transparent displays. Efficient mass‐production processes are essential for the commercialization of transparent micro‐LED displays. This study presents roll‐based mass transfer to enhance the productivity of transparent micro‐LED displays. Roll transfer processes traditionally face resolution challenges in alignment repeatability and positional errors in both the transverse direction (TD) and machine direction (MD). This study proposes a roll‐to‐plate (R2P) transfer process with overlay alignment to improve the repeatability precision of the alignment. Detailed experimental analyses address positional errors in the TD and MD, attributed to initial contact errors and linear velocity asynchrony, respectively. The results demonstrate successful micro‐LED transfer onto a transparent circuit board (TCB) with a maximum positional error of 3.2 µm and a 99.75% yield. The resulting micro‐LED display achieves a transparency of 72.5% with 68 pixels per inch. This study overcomes the alignment challenges in the R2P process and contributes to the commercialization of transparent micro‐LED displays. It is expected to positively impact the manufacturing of transparent applications that involve rolling processes. [ABSTRACT FROM AUTHOR]

The study brings original data on the effect of linear velocity during melt-spinning process on magneto-mechanical properties of Heusler Ni-Mn-Ga-based melt-spun ribbons. The research revealed that different linear velocity of the copper wheel had a significant impact on the ribbon's geometry resulting in distinct changes in magneto-mechanical properties. X-ray diffraction measurements were used to examine the phase composition, confirming the presence of L21 austenite phase. To assess the mechanical properties of the Ni-Mn-Ga-based melt-spun ribbons, cyclic bending experiments were conducted at a strain rate of 0.1 mm/s. Additionally, experiments involving magnetic field-induced bending were carried out in an external magnetic field ranging from 0 to 0.28 T. Finally, it was observed that there was a proportional relationship between the linear velocity of the copper wheel and magnetic field-induced ribbons deflection. Conversely, the dependence between linear velocity and mechanical bending load was found to be inversely proportional. Electron backscattered diffraction measurements revealed that melt-spun ribbons produced at high linear velocity of 18.5 m/s exhibited fine-grained microstructure in contrast to low linear velocity of 3 m/s. Based on these results it seems feasible to optimize the functional properties of the studied ribbons by varying the linear velocity of the melt-spinning process. [ABSTRACT FROM AUTHOR]

While single-crystal diamond is a promising wide-bandgap semiconductor material, it is also the hardest material in nature and exhibits remarkable anisotropy, presenting a challenge for high-quality and efficient processing. To address this issue, this article introduces a method that utilises aluminium-coated nickel and diamond mixed abrasive vitrified bond grinding wheels for a mechanicochemical grinding process to reduce the anisotropic removal of diamond. Different cutting depths, abrasive ratios, grinding directions, and linear velocities were employed in the processing, with the material-removal mechanism studied through morphological characterisation, elemental content, and other detection methods. The experiment revealed that the catalytic effect of nickel metal occurred along the (111) crystal plane of the diamond. This catalytic process involves a transition from sp3 diamond to amorphous carbon, followed by graphitisation. The spin-rotating mechanicochemical grinding process mainly involves plastic removal in the soft direction and coupled chemical and mechanical removal in the hard direction. Employing this method reduced the surface roughness of the 7 × 7 mm as-grown crystal to Ra 0.467 nm, with a material removal rate of 4.73 μm/h, achieving a nearly damage-free machining surface. [ABSTRACT FROM AUTHOR]

Purpose: To explore the post-activation performance enhancement (PAPE) of flywheel and traditional squats on a series of vertical jumps, the loads of the two protocols were matched based on their linear velocities. In addition, we attempted to validate the effectiveness of determining individualized recovery time (IRT) between conditioning activities and explosive movements. Methods: Sixteen trained players participated in three main experiments: first, one-repetition maximum (1RM) assessment and intensity matching test; second, the weighted jump squat (WJS) test at baseline and at 2, 4, 6, 8, and 10 min after flywheel and traditional protocols; and third, squat jump (SJ), countermovement jump (CMJ), and approach jump (AJ) tests incorporating IRT determined in the WJS sessions into both protocols. These protocols were standardized to 8 repetitions at 80% 1RM with equivalent concentric speed matched by a linear position transducer and conducted in a random order on separate days. Results: In the WJS tests, both protocols exhibited significant increases on jump height (JH), peak force (PF), and peak power (PP) after 2 to 6 min (all p < 0.05), and the time courses of changes in performance were in a similar trend. In the SJ, CMJ, and AJ tests, both protocols demonstrated highly significant increases on JH, PP, and reactive strength index (RSI) after incorporating IRT (all p < 0.01), with all participants exhibiting diverse improvement above the baseline levels. The potentiation percentages of the flywheel protocol on JH, PP, and RSI were higher than those of the traditional protocol across four jumping types (JH: 5.35%– 9.79% vs. 4.13%–8.46%; PP: 4.16%–6.13% vs. 3.23%–4.77%; and RSI: 7.27% vs. 7.04%). Conclusion: High-intensity flywheel squats can produce jumping potentiation in neuromechanical factors comparable to, or even surpassing, those observed in traditional squats, potentially making them a more effective option for inducing PAPE. Additionally, incorporating IRT into potentiation protocols could further optimize the PAPE effects. [ABSTRACT FROM AUTHOR]

The response of airfoils to unsteady disturbances is a classic problem in the aerodynamics field. Many theoretical models have been proposed in the past to predict the unsteady aerodynamic forces of airfoils. However, these theories focused on individual airfoil motions or incoming flow disturbances, while the theoretical models for multiple disturbances still need to be developed. In this study, a theoretical model to predict the aerodynamic force of an oscillating airfoil encountering vertical gust is derived from a linear combination of Theodorsen's and Sears' theories. Experimental investigations involving a two-dimensional pitching airfoil encountering a sinusoidal vertical gust are carried out to examine the proposed theory. It is found that the theory effectively captures the trends in the unsteady lift of airfoils subjected to dual disturbances. However, it tends to overestimate the lift amplitude. Notably, when a quasi-steady correction is applied to the theory, the prediction accuracy is greatly improved. The theory correction agrees well with experiment at small pitching frequencies, while deviations exist at higher pitching frequencies. The temporal evolution of the flow velocity reveals that the velocity disturbance induced by the coupled disturbance around the airfoil conforms to the linear superposition of the velocities induced by each individual disturbance, consistent with the prediction of the vortex sheet model. As the pitching frequency increases, significant nonlinear effects appear near the trailing edge of the airfoil, which may be one key factor for the disparities between the theoretical predictions and the experimental lift at higher pitching frequencies. [ABSTRACT FROM AUTHOR]

Flexural gravity wave scattering by two semi-infinite non-identical ice sheets, which are separated by a clean water surface, is investigated in the presence of a step bottom topography. The problem is investigated in the cases of (i) intermediate water depth and (ii) shallow water. The effect of two edge conditions, (i) simply supported edge and (ii) free edge, on wave scattering is also analyzed. Employing linear velocity potential theory, the problem is studied in the frequency domain. The physical phenomenon is modeled as a boundary value problem having the Laplace equation as the governing equation, and it is solved using the eigenfunction expansion method. Considering the bottom topography and upper boundary, the fluid domain is divided into three regions, and in each region, velocity potential is expressed in terms of infinite Fourier series. Velocity and pressure are matched at the intermediate surface of two regions, and a system of algebraic equations with unknown coefficients is obtained. The complete solution of the present problem is recognized by solving the system of equations numerically. The energy relation is derived using Green's theorem. The reflection and transmission coefficients are computed and compared with the energy relation to check the accuracy of the present method. For different parameters (depth ratio, clean waterway, and different ice properties), reflection coefficient and transmission coefficient are computed and presented as a function of angular frequency. The value of the reflection coefficient ranges from zero to unity, whereas at certain frequencies, the transmission coefficient attends value more than unity. [ABSTRACT FROM AUTHOR]

Amphibious robots have broad prospects in the fields of industry, defense, and transportation. To improve the propulsion performance and reduce operation complexity, a novel bionic amphibious robot, namely AmphiFinbot-II, is presented in this paper. The swimming and walking components adopt a compound drive mechanism, enabling simultaneous control for the rotation of the track and the wave-like motion of the undulating fin. The robot employs different propulsion methods but utilizes the same operation strategy, eliminating the need for mode switching. The structure and the locomotion principle are introduced. The performance of the robot in different motion patterns was analyzed via computational fluid dynamics simulation. The simulation results verified the feasibility of the wave-like swimming mechanism. Physical experiments were conducted for both land and underwater motion, and the results were consistent with the simulation regulation. Both the underwater linear and angular velocity were proportional to the undulating frequency. The robot's maximum linear speed and steering speed on land were 2.26 m/s (2.79 BL/s) and 442°/s, respectively, while the maximum speeds underwater were 0.54 m/s (0.67 BL/s) and 84°/s, respectively. The research findings indicate that the robot possesses outstanding amphibious motion capabilities and a simplistic yet unified control approach, thereby validating the feasibility of the robot's design scheme, and offering a novel concept for the development of high-performance and self-contained amphibious robots. [ABSTRACT FROM AUTHOR]

Residual film recovery machines has have been commonly used in cotton fields in Xinjiang Province in autumn. The plastic film can tear into strips and entangles with impurities on the film during picking. The film with impurities mixture cannot be effectively layered in the conveying process, resulting in low separation of the film with impurities, high impurity content of mulch film, and difficult recycling. This study aims to design the a two-order pin-tooth chain-plate type device for residual film recovery. The multiple tooth collaborative operation was achieved in the continuous picking for the whole residual film in the autumn season. The whole residual film was transported upward to spread on the pin-tooth chain plate. A better separation environment was obtained for the impurity to maintain the effective stratification of membrane impurity in the recovery process. The structure of film film-collecting mechanism was longitudinally arranged with 23 pin-tooth chain plates. The structural parameters of the pin-tooth chain plate were determined to analyze the force in the whole continuous picking of plastic film. The spacing range between the adjacent pin-tooth chain plates was 84mm before the pin-tooth broke the plastic film; The structural parameters were determined for the main, passive rollers, and the stripping ring in the film collecting mechanism; Meanwhile, the angle of the recovery device were also determined, where the angles of the first- and second-order pin-tooth chain plate film collecting mechanism were 125° and 105°, respectively. The kinematics and dynamics analysis showed that the film film-collecting mechanism was used to lift the residual film with impurity. The optimal conditions were clarified to realize the continuous picking, step-by-step spreading, and conveying of the whole residual film. A prototype was trial-produced to conduct the field performance tests. The main influencing factors on the residual film recovery rate of the recovery device were determined as the angular velocity of the picking-passive roller and the operating speed of machinery, according to the principle of picking up film recovery. As the two-order pin-tooth chain-plate type recovery device of the experimental prototype was driven by the front depth limiting roller, the angular velocity of the picking-passive roller was linearly related to the operating speed of the machinery; The first-order film collecting mechanism shared the little range of variation in the ratio of the linear velocity of the tooth end during picking. The operating speed of 0.97 was achieved in by the continuously picking the whole residual film. A single-factor experiment was conducted with the recovery rate of residual film and the rate of containing poles content inside the recycled plastic film as experimental indicators, while the operating speed of the machinery was the influencing factor. The field test showed that the two-order pin-tooth chain-plate type residual film recycling machine was realized for the continuous picking and step-by-step spreading and conveying of the whole film, when the operation speed was within 5.5-7.5 km/h. The average rate of residual film recovery was 89.4%, and the average rate of containing poles was 8.6% in the recovered film. The second-stage nail-tooth chain-plate type device of residual film recovery was enhanced the recovery rate of residual film, whereas, there was the a significant decrease in the rate of containing poles in the recovered film, compared with the commonly- used one. The findings can provide a strong reference for the design of residual film recovery machines. [ABSTRACT FROM AUTHOR]

Effects of the road, such as speed bumps, can significantly affect a car's stability. This study focuses on how a quarter-car model is affected by a basic harmonic speed hump and how Cubic Negative Velocity Control (CNVC) is used to control the amplitude of disturbances. This study differs from earlier research in considering various control and force kinds that impact the system. The external forces in this context are a component of a non-linear dynamic system. Two-degree-of-freedom (2DOF) differential coupled equations describe the system's equation. Numerous numerical experiments have been conducted, including proportional derivative (PD), negative derivative feedback (NDF), positive position feedback (PPF), linear negative velocity control (LNVC), and CNVC; the results show that when the hump is represented as a simple harmonic hump, CNVC has the best effect and can regulate vibrations more precisely than the other approaches on this system. Subsequently, the vibration value of the system was numerically analyzed both before and after the control was implemented. Using the frequency response equation and phase plane approaches in conjunction with the Runge–Kutta fourth order method (RK-4) in the context of resonance situation analysis, the stability of the numerical solution has been evaluated. [ABSTRACT FROM AUTHOR]

The rotational speed vectors of the bearing balls affect their service life and running performance. Observing the actual rotational speed of the ball is a prerequisite for revealing its true motion law and conducting sliding behavior simulation analysis. To address the need for accuracy and real-time measurement of spin angular velocity, which is also under high-frequency and high-speed ball motion conditions, a new measurement method of ball rotation vectors based on a binocular vision system is proposed. Firstly, marker points are laid on the balls, and their three-dimensional (3D) coordinates in the camera coordinate system are calculated in real time using the triangulation principle. Secondly, based on the 3D coordinates before and after the movement of the marker point and the trajectory of the ball, the mathematical model of the spin motion of the ball was established. Finally, based on the ball spin motion model, the three-dimensional vision measurement technology was first applied to the measurement of the bearing ball rotation vector through formula derivation, achieving the analysis of bearing ball rolling and sliding characteristics. Experimental results demonstrate that the visual measurement system with the frame rate of 100 FPS (frames per second) yields a measurement error within ±0.2% over a speed range from 5 to 50 RPM (revolutions per minute), and the maximum measurement errors of spin angular velocity and linear velocity are 0.25 °/s and 0.028 mm/s, respectively. The experimental results show that this method has good accuracy and stability in measuring the rotation vector of the ball, providing a reference for bearing balls' rotational speed monitoring and the analysis of the sliding behavior of bearing balls. [ABSTRACT FROM AUTHOR]

This study aimed to analyze the intra-device agreement of a new linear position transducer (Vitruve, VT) and the inter-device agreement with a previously validated linear velocity transducer (T-Force System, TF) in different range of velocities. A group of 50 healthy, physically active men performed a progressive loading test during a bench press (BP) and full-squat (SQ) exercise with a simultaneous recording of two VT and one TF devices. The mean propulsive velocity (MPV) and peak of velocity (PV) were recorded for subsequent analysis. A set of statistics was used to determine the degree of agreement (Intraclass correlation coefficient [ICC], Lin's concordance correlation coefficient [CCC], mean square deviation [MSD], and variance of the difference between measurements [VMD]) and the error magnitude (standard error of measurement [SEM], smallest detectable change [SDC], and maximum errors [ME]) between devices. The established velocity ranges were as follows: >1.20 m·s−1; 1.20–0.95 m·s−1; 0.95–0.70 m·s−1; 0.70–0.45 m·s−1; ≤0.45 m·s−1 for BP; and >1.50 m·s−1; 1.50–1.25 m·s−1; 1.25–1.00 m·s−1; 1.00–0.75 m·s−1; and ≤0.75 m·s−1 for SQ. For the MPV, the VT system showed high intra- and inter-device agreement and moderate error magnitude with pooled data in both exercises. However, the level of agreement decreased (ICC: 0.790–0.996; CCC: 0.663–0.992) and the error increased (ME: 2.8–13.4% 1RM; SEM: 0.035–0.01 m·s−1) as the velocity range increased. For the PV, the magnitude of error was very high in both exercises. In conclusion, our results suggest that the VT system should only be used at MPVs below 0.45 m·s−1 for BP and 0.75 m·s−1 for SQ in order to obtain an accurate and reliable measurement, preferably using the MPV variable instead of the PV. Therefore, it appears that the VT system may not be appropriate for objectively monitoring resistance training and assessing strength performance along the entire spectrum of load-velocity curve. [ABSTRACT FROM AUTHOR]

AbstractPerformance of sport-related ballistic motor skills, like ball hitting in golf and baseball, requires wide movements to produce highly fast and spatially accurate movements. In this study, we assessed the effect of movement amplitude on directional accuracy in a ballistic hitting task. Participants performed the task of moving a manual handle over a flat surface to hit with high speed a moveable disc, aiming to propel it towards a frontal target. Five movement amplitudes were compared, ranging from 11.5 cm to 27.5 cm in steps of 4 cm. Kinematic analysis evaluated motions of the handle, disc, and arm joints. Results showed that greater movement amplitudes led to longer acceleration phases, with delayed peak velocities at the handle, shoulder and elbow, leading to higher contact and peak linear velocities of the handle, and higher angular velocities at the shoulder and elbow. Manipulation of movement amplitude led to no evidence for effects on either disc directional accuracy or variability. Results also revealed no evidence for differences in variability of contact velocity, peak velocity and time of peak velocity across movement amplitudes in the shoulder, elbow, and wrist. Our results indicated that greater movement amplitudes in hitting a spatial target lead to increased contact velocity while not affecting directional accuracy or movement variability. [ABSTRACT FROM AUTHOR]

The co-moving velocity is a new variable in the description of immiscible two-phase flow in porous media. It is the saturation-weighted average over the derivatives of the seepage velocities of the two immiscible fluids with respect to saturation. Based on analysis of relative permeability data and computational modeling, it has been proposed that the co-moving velocity is linear when plotted against the derivative of the average seepage velocity with respect to the saturation, the flow derivative. I show here that it is enough to demand that the co-moving velocity is characterized by an additive parameter in addition to the flow derivative to be linear. This has profound consequences for relative permeability theory as it leads to a differential equation relating the two relative permeabilities describing the flow. I present this equation together with two solutions. [ABSTRACT FROM AUTHOR]

The Acoustic Doppler Current Profiler (ADCP) on a platform generates rotational linear velocity due to dynamic factors in attitude changes, leading to measurement errors in vessel and water flow velocities. This study derives and analyzes these errors, focusing on factors such as emission angle, transducer position, water depth, and measured depth, while also accounting for the variation in linear velocity and radial direction during each transmit–receive pulse cycle in the simulations. A method is proposed that introduces the concept of an equivalent radial radius to correct vessel and flow velocities, specifically designed for the common scenario where the ADCP is installed on the central longitudinal section of a vessel undergoing free roll motion. This method is suited for shallow water conditions without waves, with measurements taken vertically downward. It uses least squares fitting with an exponentially decaying sinusoidal model to process low-sampling-rate inclinometer data from the ADCP. This approach requires only the processing of measured data based on existing ADCP hardware, without the need for additional equipment. Field tests in a pool demonstrate that the proposed method significantly reduces vessel velocity errors, outperforming the traditional attitude static correction method. [ABSTRACT FROM AUTHOR]

In addition to a recently acousto-optical deflector that has been the subject of both theoretical and experimental analysis, this work presents the successful processing of two acousto-optical deflectors that have been orthogonally positioned using two frequency-modulated ultrasonic waves. A comprehensive theoretical analysis is conducted, based on the Collins integral and the ABCD matrix formalism, to explain how the positions of the diffracted orders oscillate in two dimensions as a function of time. The numerical simulation of the derived formula demonstrates the potential for steering a laser beam along Lissajous trajectories. The trajectories in question are observed to exhibit a variety of shapes and velocities. They are sometimes linear with sinusoidal velocities, sometimes circular with constant velocities, and often elliptical with variable velocities. The noteworthy aspect is that all these diffracted orders traverse the spatial domain with an identical sweep frequency, despite the heterogeneity of their trajectories and velocities. Furthermore, these trajectories can be shaped by controlling the phase shift value. This technique can be employed in metrology for rotation measurements based on the Doppler effect. Additionally, it can be used to develop a spatial display that enables tracing Lissajous trajectories, rather than relying on an oscilloscope. [ABSTRACT FROM AUTHOR]

Coastal hydrodynamics and morphodynamics integrate the effects of small‐scale fluid‐sediment interactions; yet, these small‐scale processes are not well understood. To investigate sediment trapping by turbulent coherent structures or vortices, the transport of coarse sand over ripples was analyzed in a small‐oscillatory flow tunnel with phase‐separated Particle Image and Tracking Velocimetry. Results from one of the first direct measurements of vortex‐trapped sand grains under oscillatory flows are presented. The vortices mobilized sand grains along the ripple slopes just prior to flow reversal and transported the suspended sediment grains. During several flow cycles, some sand grains were temporarily trapped in the vortex, prescribing semi‐circular trajectories off‐center from the vortex core in quadrants of the vortex that were closest to the ripple slope, as illustrated by Nielsen (1992, https://doi.org/10.1142/1269). Comparisons of the horizontal sediment grain velocity with the horizontal fluid velocity yielded a linear relationship with a slope of 0.87. The vertical grain velocities also varied linearly with the vertical fluid velocity with a slope of approximately 1 and an offset of −0.08 m s−1 ${\mathrm{s}}^{-1}$. The offset is close to the still water settling velocity for coarse sand grains, as hypothesized during vortex trapping. Additionally, estimates of the off‐center distance, between the centers of the semi‐circular sediment paths and vortex cores, compared well with the ratio of the settling velocity to the radian frequency of the vortex yielding a linear regression slope of 0.99. Improved understanding of vortex trapping effects on sediment dynamics may decrease uncertainty in model predictions of large‐scale coastal hydrodynamics and sediment transport. Plain Language Summary: Large‐scale coastal processes integrate the effects of small‐scale fluid‐sediment interactions; yet, these small‐scale processes are not well understood. Nielsen (1992, https://doi.org/10.1142/1269) hypothesized that suspended sand grains over ripples could get caught in a vortex under certain hydrodynamic conditions, in a process called vortex trapping. In this article, we present results from one of the first direct measurements of vortex‐trapped sand grains under oscillatory flows. Vortices along the ripple slope mobilized sand grains prior to flow reversal and transported the suspended grains. During several flow cycles, some sand grains were temporarily trapped in the vortex and moved along semi‐circular paths off‐center from the vortex core in sections of the vortex that were closest to the ripple slope, as illustrated by Nielsen (1992, https://doi.org/10.1142/1269). Comparisons of the sediment grain velocity with the fluid velocity yielded a linear relationship. Additionally, the distance between the center of the semi‐circular sediment paths and the center of the vortex cores agreed with the theory. Improved understanding of the effects of vortex trapping on sediment dynamics may decrease uncertainty in the predictions of large‐scale coastal hydrodynamics and sediment transport models, which do not typically account for this small‐scale process. Key Points: Observations of vortex‐trapped grains suggest delayed settling of advected grains, as well as delayed advection of grains mobilized from the bedQuantitative comparisons of vortex‐trapped sand grains compared well with theoretical formulations by Nielsen (1992, https://doi.org/10.1142/1269) for a forced vortexImproved understanding of vortex trapping effects on sediment dynamics may decrease uncertainty in large‐scale coastal model predictions [ABSTRACT FROM AUTHOR]

The analysis of the Global NFavigation Satellite System (GNSS) time series provides valuable information for geodesy and geodynamics researcFh. Precise data analysis strategies are crucial for accurately obtaining the linear velocity of GNSS stations, enabling high-precision applications of GNSS time series. This study investigates the impact of different stochastic noise models on velocity estimations derived from GNSS time series, specifically under conditions of environmental loading correction and common mode error (CME) removal. By comparing data from various data centers, we find that post-correction, different analysis strategies exhibit high consistency in their noise characteristics and velocity estimation results. Across various analysis strategies, the optimal noise models were predominantly Power Law with White Noise (PLWN) and Fractional Noise with White Noise (FNWN), with the optimal noise models including COMB/JPL, COMB/SOPAC, and COMB/NGL for approximately 50% of the datasets. Most of the stations (approximately 80%) showed velocity differences below 0.3 mm/year and velocity estimation uncertainties below 0.1 mm/year. Nonetheless, variations in amplitudes and periodic signals persisted due to differences in the processing of raw GNSS observations. For instance, the NGL and JPL datasets, which were processed using GipsyX 2.1 software, showed higher amplitudes of the 5.5-day periodic signal. These findings provide a solid empirical foundation for advancing data analysis methods and enhancing the reliability of GNSS time series results in future research. [ABSTRACT FROM AUTHOR]

Angle domain common image gathers (ADCIGs) play a crucial role in seismic exploration, offering prestack underground illumination information that aids in validating migration velocity and conducting prestack amplitude versus angle (AVA) analysis for reservoir characterization. This paper introduces an innovative approach for compensating amplitude errors caused by irregular seismic acquisition geometries in ADCIGs. By incorporating an angle domain illumination compensation factor, the proposed method effectively modifies these errors, preserving the amplitude of seismic reflectivity in the prestack angle domain. The effectiveness of the proposed approach is validated through comprehensive tests conducted on synthetic and field data examples. The results demonstrate the capability of the method to enhance the quality of ADCIGs derived from 3D reverse time migration (RTM), yielding accurate and reliable amplitude preservation. While the illumination compensation factor assumes a vertically linear velocity model, the method holds promise for extension to more complex media and diverse migration techniques. This suggests its applicability and adaptability beyond the specific assumptions considered in this study. In conclusion, this paper presents an innovative angle domain illumination compensation factor that significantly improves the quality of ADCIGs by addressing amplitude errors arising from irregular seismic acquisition geometries. The experimental validation using synthetic and field data confirms the effectiveness of the proposed method within the context of 3D RTM. Furthermore, the technique holds potential for broader application in more complex subsurface scenarios and various migration methodologies. [ABSTRACT FROM AUTHOR]

In this paper, a one-level operator splitting method (OOSM) and a two-level operator splitting method (TOSM) for the two-dimensional or three-dimensional (2D/3D) unsteady incompressible micropolar fluid equations with double diffusion convection (IMFDDC) are proposed and analyzed. Firstly, a OOSM is constructed, which consists of five steps. The projection strategy is adopted to get the values of linear velocity and pressure in the first two steps, then the three elliptic subproblems about the angular velocity, the temperature, and the concentration variables are solved in the last three steps. The original variables with the predefined boundary conditions need to be solved separately in each step. Next, in order to solve the problem efficiently, a TOSM is presented, which only solves the nonlinear equations in the coarse level subspaces and the Oseen type linearized equations in the fine level. The numerical analysis of stability and error estimates of the fully discrete methods show that TOSM can reach the same accuracy as the OOSM with H ∼ O (h 2 / 3). Numerical examples are provided to confirm the effectiveness and reliability of the proposed methods. [ABSTRACT FROM AUTHOR]

To explore the influencing factors of surface topography and roughness in ultrasonic elliptical vibration cutting, this study proposed a new prediction model based on the formation mechanism of ultrasonic elliptical vibration cutting surface topography. Applying mathematical transformation ideas and discretization processing, the model considers linear velocity, rear face extrusion, and material rebound and utilizes MATLAB to carry out a simulation analysis of the surface topography. It also verifies the validity and accuracy of the model through experiments. The effects of cutting mode, velocity ratio, feed amount, and tool radius on the surface morphology of ultrasonic elliptical vibration cutting were analyzed using the proposed model. Results show that under the condition of Km < -tanα, the rear face extrusion and material rebound will have a specific impact on the 2-D residual height. In particular, the error between the theoretical roughness of the model and the actual roughness is 20.85%, which can provide some theoretical basis for the selection of machining parameters. [ABSTRACT FROM AUTHOR]

The geometric similarity between two sets of coordinates should be assumed for frame alignment. When aligning Global Navigation Satellite System (GNSS) positions with seasonal variations to the linear Terrestrial Reference Frame (TRF), non-negligible aliasing errors of transformation parameters can appear and bias the station positions. The recent release of the seasonally augmented International Terrestrial Reference Frame 2020 (ITRF2020) necessitates an investigation into the impacts of seasonal terms on the alignment of regional networks. Using four-year of GPS data for Crustal Movement Observation Network of China (CMONOC) stations, we realize five sets of regional reference frames (RFs) aligned to the linear ITRF2020 (REF-LIN), the seasonal ITRF2020 (REF-FRQ), the linear ITRF2020 augmented either with seasonal signals or with full signals from loading models (REF-FIT and REF-NTL), and the combination of seasonal displacements from ITRF2020 and sub-seasonal signals from loading model (REF-CMB). Our analysis revealed that the augmented ITRF2020 had significant impact on the global stations used for frame alignment. Aligning daily solutions to the augmented ITRF2020 instead of the linear ITRF2020 resulted in a noticeable root mean square (RMS) decrease for over 70% of global stations. The REF-CMB method was the most preferred for frame alignment of global networks, with the largest decreased RMS of 0.3 and 1.0 mm in horizontal and vertical components. This indicates that most true signals are preserved in the aligned daily solutions. For regional network, we found only marginal impacts on regional stations in terms of linear velocity, residuals of time series stacking between the augmented solutions and REF-LIN. However, the larger discrepancies are noticed between annual estimates and loading model for the vertical component of REF-CMB and REF-FRQ, compared to RER-LIN solutions. [ABSTRACT FROM AUTHOR]

This paper introduces a compact end-effector ankle rehabilitation robot (CEARR) system for addressing ankle range of motion (ROM) rehabilitation. The CEARR features a bilaterally symmetrical rehabilitation structure, with each side possessing three degrees of freedom (DOF) driven by three independently designed actuators. The working intervals of each actuator are separated by a series connection, ensuring they operate without interference to accommodate the dorsiflexion/plantarflexion (DO/PL), inversion/eversion (IN/EV), and adduction/abduction (AD/AB) DOF requirements for comprehensive ankle rehabilitation. In addition, we integrated an actuator and foldable brackets to accommodate patients in varied postures. We decoded the motor intention based on the surface electromyography (sEMG) and torque signals generated by the subjects' ankle joints in voluntary rehabilitation. Besides, we designed a realtime voluntary-triggered control (VTC) strategy to enhance the rehabilitation effect, in which the root mean square (RMS) of sEMG was utilized to trigger and adjust the CEARR rehabilitation velocity support. We verified the consistency of voluntary movement with CEARR rehabilitation support output for four healthy subjects on a nonlinear sEMG signal with an R2 metric of approximately 0.67. We tested the consistency of triggering velocity trends with a linear torque signal for one healthy individual with an R2 metric of approximately 0.99. [ABSTRACT FROM AUTHOR]

A physical description is given of the formation of corrosion product deposits on the surfaces of pipelines of heat supply systems, and an investigation has been made into the effects of various factors on this process. An analysis has been made of the existing models of formation of corrosion deposites. A mathematical model has been developed for the formation of corrosion product deposites in the liquid's motion through pipelines of heat supply systems in the region of linear velocity of the growth of deposits at a constant temperature of the heat transfer agent. The model is based on equations of conservation of the mass of dissolved depolarizer and solid particles suspended in the solution. The parametric calculations performed on the basis of the developed mathematical model have shown a possibility for the existence of a maximum in the thickness of the corrosion product deposit layer through the pipe length. [ABSTRACT FROM AUTHOR]

A thorough understanding of ice thermodynamics is essential for an accurate description of glaciers, ice sheets and ice shelves. Yet there exists a significant gap in our theoretical knowledge of the time-dependent behaviour of ice temperatures due to the inevitable compromise between mathematical tractability and the accurate description of physical phenomena. In order to bridge this shortfall, we have analytically solved the 1D time-dependent advective–diffusive heat problem including additional terms due to strain heating and depth-integrated horizontal advection. Newton's law of cooling is applied as a Robin-type top boundary condition to consider potential non-equilibrium temperature states across the ice–air interface. The solution is expressed in terms of confluent hypergeometric functions following a separation of variables approach. Non-dimensionalization reduces the parameter space to four numbers that fully determine the shape of the solution at equilibrium: surface insulation, effective geothermal heat flow, the Péclet number and the Brinkman number. The initial temperature distribution exponentially converges to the stationary solution. Transient decay timescales are only dependent on the Péclet number and the surface insulation, so higher advection rates and lower insulating values imply shorter equilibration timescales, respectively. In contrast, equilibrium temperature profiles are mostly independent of the surface insulation parameter. We have extended our study to a broader range of vertical velocities by using a general power-law dependence on depth, unlike prior studies limited to linear and quadratic velocity profiles. Lastly, we present a suite of benchmark experiments to test numerical solvers. Four experiments of gradually increasing complexity capture the main physical processes for heat propagation. Analytical solutions are then compared to their numerical counterparts upon discretization over unevenly spaced coordinate systems. We find that a symmetric scheme for the advective term and a three-point asymmetric scheme for the basal boundary condition best match our analytical solutions. A further convergence study shows that n≥15 vertical points are sufficient to accurately reproduce the temperature profile. The solutions presented herein are general and fully applicable to any problem with an equivalent set of boundary conditions and any given initial temperature distribution. [ABSTRACT FROM AUTHOR]

In order to eliminate the dependence of finite-time control on the initial state of the system in the image-based visual servoing (IBVS) of a quadrotor UAV (QUAV) for the moving target, we propose a control scheme for the moving target of a QUAV based on fixed-time stability. We select the image moments of the virtual camera plane as features and establish an image moment dynamics model that includes target motion parameters based on them. Then, we use the backstepping method to design the fixed-time controller for the system. The design steps of the controller mainly consist of two parts. Firstly, we designed a fixed-time stable linear velocity observer to address the unmeasurable linear velocity and unmeasurable monocular camera depth issues of QUAV. Then, using a high-order tracking differentiator to estimate the target linear velocity as a feedforward, combined with the fixed-time linear velocity observer estimated QUAV linear velocity, we designed a fixed-time controller for the system using the backstepping method. We demonstrated the fixed-time stability of the controller using the Lyapunov theory. The effectiveness and robustness of the proposed method are demonstrated by numerical simulation. At the same time, the comparative simulation shows that the method can guarantee the rate of convergence of the system and has high control accuracy. [ABSTRACT FROM AUTHOR]

The friction stir welding of A365 and AZ91C alloys was conducted in this study to assess the effect of tilt angle, linear velocity and rotating speed on the elongation, hardness and tensile strength using the response surface method. Then, the weld microstructure was investigated by SEM, TEM and EDS analysis to deeply investigate the structure of A365–AZ91C weld. It was realized that the grain size of weld joint has grown and the crack and tunnel were formed when the rotating speed improved from 1000 to 2000 rpm, which produced a decline in the hardness and strength and a rise in the elongation. Moreover, an increment of linear velocity up to 60 mm/min led to the refinement of the weld microstructure, which was followed by an enhancement in the strength and hardness of the weld, whereas the elongation deteriorated. In the case of tilt angle, the highest elongation and strength were detected at a tilt angle of 2∘, but the highest hardness was observed at a tilt angle of 4∘ because of the nucleation of Al3Mg2 and Al 1 2 Mg 1 7 intermetallics. Results of optimization exhibited that the concurrent improvement of the strength, hardness and elongation can be acquired with the tilt angle of 3∘, rotating speed of 1600 rpm and linear velocity of 53 mm/min. [ABSTRACT FROM AUTHOR]

We analyzed the influence of exercise order using the bench press and squat as the first or second exercise of the session on velocity performance. Ten male trained individuals (20.9 ± 0.7 years) randomly performed two protocols of three sets of six repetitions at 80% of their one-repetition maximum with different exercise sequences: the bench press followed by the squat (BP + S) and the squat followed by the bench press (S + BP). A linear velocity transducer attached to the Smith machine barbell measured the mean propulsive velocity (MPV), peak velocity (PV), and time to peak velocity. Additionally, blood lactate and heart rate were measured. Regarding the bench press, differences were found in the MPV in the first (BP + S: 0.50 ± 0.07 m·s−1 vs. S + BP: 0.42 ± 0.08 m·s−1; p = 0.03, g = 0.72) and second sets (0.50 ± 0.06 m·s−1 vs. 0.42 ± 0.07 m·s−1; p = 0.03, g = 0.73), and in the PV in the second set (0.74 ± 0.09 m·s−1 vs. 0.63 ± 0.09 m·s−1; p = 0.02, g = 0.86). Regarding the squat, although the S + BP sequence tended to show higher velocities, no significant differences were found between protocols. These results showed that squatting first decreased subsequent bench press velocity performance. On the other hand, squat velocity performance was not impaired when preceded by the bench press. [ABSTRACT FROM AUTHOR]

Viscosity is a curial indicator for evaluating asphalt performance, representing its ability to resist deformation under external forces. The Green–Kubo integral in equilibrium molecular dynamics simulations and the Muller-Plathe algorithm in reverse non-equilibrium molecular dynamics simulations were used to calculate the asphalt viscosity. Meanwhile, the key parameters of both methods were rationalized. The results show that in equilibrium calculations, using a 1/t weighting for the viscosity integral curve results in a well-fitted curve that closely matches the original data. The isotropy of the asphalt model improves for atomic counts exceeding 260,000, rendering viscosity calculations more reasonable. When the viscosity did not converge, it increased linearly with the number of atoms. In non-equilibrium calculations, the number of region divisions had almost no effect on the viscosity value. A momentum exchange period of 20 timesteps exhibits a favorable linear trend in velocity gradients, and an ideal momentum exchange period was found to be between 10 and 20 timesteps. As the model size increased, the linear relationship with the shear rate became more pronounced, and the isotropy of the asphalt system improved. Using an orthogonal simulation box with a side length of 75 Å effectively meets the computational requirements. [ABSTRACT FROM AUTHOR]

The mixing of a passive impurity in a random flow in the limit of weak molecular diffusion, when there is a range of scales between a small diffusion scale and a relatively large correlation length of the gradient of the flow velocity field, is considered. In this range of scales, to describe the evolution of the initial distribution of the impurity in space near a certain Lagrangian trajectory, it is sufficient to approximate the velocity field by a linear profile. Second- and fourth-order correlation functions of the impurity concentration are related to the statistics of the affine deformation of a small volume element of the liquid. Meanwhile, the pair correlation function reflects the extension statistics only in the principal direction, and the fourth-order correlation function reflects in its angular singularities the complete extension statistics in a three-dimensional flow. In a two-dimensional flow, the behavior of the fourth order correlation function in angular singularities has different properties and significantly depends on the diffusion coefficient. The conclusions are valid for any time-uniform gradient of the velocity field and are practically significant for the measurement of this statistics. [ABSTRACT FROM AUTHOR]

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Over the past two decades, double-layered microchannel heat sinks (DL-MCHs) have become increasingly popular as they provide effective performance for electronic cooling, particularly in the counterflow configuration. The cross-flow configuration, which requires much simpler headers, has seldom been considered in the scientific literature, probably due to the possible formation of a hotspot near the outlet port. The aim of this study is to show that cross-flow DL-MCHs can provide performance levels that are comparable to those attained by counterflow DL-MCHs by exploiting the nonuniform flow distribution produced by properly designed headers. Numerical simulations are performed using in-house finite element procedures to solve the parabolized Navier–Stokes equations in the microchannels and the energy equation in the entire computational domain. The analysis is carried out both for ideal linear microchannel velocity distributions and for the realistic velocity distributions induced by headers with or without baffles, as proposed by the authors in previous papers. The optimal degree of velocity nonuniformity in the microchannels yielding the best thermal performance was found to depend on the flow rate. For instance, in the case of optimal linear variations of the microchannel velocity distribution, the thermal resistance was reduced by 11.8%, 7.1%, and 4.4% compared to the case with uniform inlet velocities, and it was only 3.4%, 1.8%, and 0.3% higher than that of the counterflow configuration for average microchannel velocities equal to 0.5, 1, and 2 m/s, respectively. The main conclusion is that the cross-flow configuration, with its simple headers and piping, can achieve thermal resistance and temperature uniformity on the heated surface that are very similar to that of the counter-flow configuration through proper header design that ensures a suitable microchannel velocity distribution. [ABSTRACT FROM AUTHOR]

Nanothermites have found broad applications; however, due to being systems largely reacting in condensed phases, their performance is somewhat limited by heat and mass transfer. In order to alleviate this issue, nanothermites doped with gas-generating energetic materials have been developed. In this work, we present an investigation of a model Ti/CuO nanothermite doped by four classical energetic materials and investigate their properties and combustion performance. Mechanical and laser irradiation sensitivity, as well as ignition/explosion temperatures have been determined for the studied systems to establish their safety features. In terms of combustion performance, thrust force parameters and linear combustion velocity have been determined and the structure of the evolving flame front was recorded during open-air combustion experiments. The obtained results indicate that the developed doped nanothermite formulations are extremely promising materials for future applications. [ABSTRACT FROM AUTHOR]

Impaired retinal blood flow is associated with ocular diseases such as glaucoma, macular degeneration, and diabetic retinopathy. Among several ocular imaging techniques developed to measure retinal blood flow both invasively and non-invasively, adaptive optics (AO)-enabled scanning laser ophthalmoscopy (AO-SLO) resolves individual red blood cells and provides a high resolution with which to measure flow across retinal microvasculature. However, cross-validation of flow measures remains a challenge owing to instrument and patient-specific variability in each imaging technique. Hence, there is a critical need for a well-controlled clinical flow phantom for standardization and to establish blood-flow measures as clinical biomarkers for early diagnosis. Here, we present the design and validation of a simple, compact, portable, linear flow phantom based on a direct current motor and a conveyor-belt system that provides linear velocity tuning within the retinal microvasculature range (0.5–7 mm/s). The model was evaluated using a sensitive AO-SLO line-scan technique, which showed a <6% standard deviation from the true velocity. Further, a clinical SLO instrument showed a linear correlation with the phantom's true velocity (r2 > 0.997). This model has great potential to calibrate, evaluate, and improve the accuracy of existing clinical imaging systems for retinal blood flow and aid in the diagnosis of ocular diseases with abnormal blood flow. [ABSTRACT FROM AUTHOR]

This study aims to compare the efficacy of computer‐assisted sperm analysis (CASA) and smartphone‐applied sperm analysis (SASA) in assessing the quality of frozen–thawed bull semen. A total of 75 straws (n = 75) semen samples were used from different production batches of five Holstein bulls. The semen analyses were conducted in three groups: Group I (CASA‐37°C), semen samples were evaluated using the CASA system at 37°C (n = 25); Group II (SASA‐25°C), semen samples were assessed using the SASA system at a temperature of room heat (25°C) (n = 25); and Group III (SASA‐37°C), semen samples were evaluated using the SASA system at 37°C (n = 25). The frozen–thawed bull semen samples were analysed in terms of total motility (TM), progressive motility (PM), immotile, velocity average path (VAP), velocity curve linear (VCL), velocity straight line (VSL) and sperm concentration. There was no significant difference between the groups in terms of spermatozoa concentration (p >.05). However, significant differences among the groups were observed for total motile spermatozoa values (p <.001). Values of progressive motile spermatozoa were lower in Group I and Group II compared to Group III (p <.001). The immotile spermatozoa values were significant between the groups (p <.001) and were found to be proportional to total motile spermatozoa values. Additionally, the VAP, VCL and VSL values were comparable between Group II and Group III, but lower when compared to Group I. In conclusion, the results of the study demonstrate that the Sperm Cell™ system can accurately analyse the concentration of frozen–thawed bull semen. The analyses performed at room temperature indicate a parallelism between the PM value and CASA results. However, it is thought that SASA devices require a series of standardization studies in different semen extenders, different sample concentrations and different animal species, analogous to the standardization evolution process of CASA devices in semen analysis. [ABSTRACT FROM AUTHOR]

Electromagnetic plasma propulsion is generated by the linear plasma propulsion (LPP) apparatus. The LPP device is upgraded to operate and simulate at a maximum energy of 5.4 kJ. The cathode's cylindrical upper portion is changed into a hemispherical shape as part of the upgrading process to boost the current sheath (CS) acceleration. According to the model, the CS moves in the z-direction with a linear velocity while moving in the θ-direction with an angular velocity. When the plasma is squeezed and compressed, it is driven through the extension tube. The model describes the CS motion, its characteristics, and the propelled plasma using four phases: an axial, an angular radial, a reflected, and an expansion phases. The simulated Ith and experimental Iex current signals were compared to prove the validity of the model assumption, where the values of Ith and Iex were 89.7 and 88 kA, respectively. According to the results, as the motion angle increases in the angular radial phase, the CS compresses, elongates, and is forced into the extension tube. The results showed that the peaks of both plasma inductance, velocity, temperature, and propelled plasma length were 36.3 nH, 6.36 cm/μs, 6.72 eV, and 3.22 cm, respectively. [ABSTRACT FROM AUTHOR]

This paper deals with the synthesis and implementation of a controller for asymptotic tracking of the desired trajectory of a mobile robot. The mobile robot used for the experimental validation has eight motors with an inner control loop. Four steering actuators are controlled using position controllers and four driving actuators are controlled using velocity controllers. A complex robot kinematic model is converted into a control-oriented linear time-varying system, which is then used to design a time-varying control law that minimizes the quadratic optimality criterion. In contrast to conventional methodologies for solving the corresponding Riccati differential equations, a computational approach that explicitly determines the time-varying controller matrix by employing recurrent matrix computations is proposed. Mobile robot control inputs (linear velocity, steering angles and steering velocities) are forwarded to the steering and driving actuators with properly tuned position and velocity controllers using an inverse kinematic model of the mobile robot. The obtained control law is evaluated on an experimental set-up of a real mobile robot system. The controller is implemented using the Robot Operating System. [ABSTRACT FROM AUTHOR]

Global Navigation Satellite System (GNSS) network analysis benefits from precise point positioning with undifferenced (UD) or double differenced (DD) integer ambiguity resolution (IAR). Position time series with UD-IAR and a practical DD-IAR are compared for a mixture network consisting of 57 global and 82 regional stations with 4-year observations. The sparse global stations are more affected by different IAR methods than the regional stations of Crustal Movement Observation Network of China (CMONOC). The most significant differences between UD-IAR and the practical DD-IAR are observed in velocity estimations, with averages of 0.15 and 0.30 mm/yr for the horizontal and vertical components, respectively. UD-IAR can achieve smaller root mean square at 70–83 % of the daily solutions than the practical DD-IAR for global stations. Nevertheless, moderate differences of frame parameters and annual variations are introduced by different IAR methods. The IAR is also proved to be one of the potential origins for Global Positioning System (GPS) draconitic signals and white noise at high frequency. [ABSTRACT FROM AUTHOR]

Linear engineering projects require careful consideration of multiple construction scenarios. These scenarios include linear, bar and block activities, with the direction and velocity of linear activities varying, as well as the number of construction teams involved. Resource constraints further complicate scheduling. To address these challenges, a two-stage dynamic scheduling model was developed in this study. The first stage involved selecting a scheduling strategy based on available resources to meet the project deadline, while the second involved developing two cost-effective models to determine the best plan. To optimize the model, a hybrid algorithm incorporating an elite strategy, an adaptive operator and a catastrophe operator was established. The capabilities of the proposed model were demonstrated through several application examples, highlighting the benefits of improved consideration of construction scenarios in linear engineering. Overall, the model's ability to identify a reasonable range of resource allocations highlights its effectiveness in optimizing linear engineering project schedules. [ABSTRACT FROM AUTHOR]

Magnetic pulse welding of Cu/Ti tubular joint is performed by creating intense transient magnetic fields that drive the metal components together at high velocity. This leads to interfacial waviness due to Kevin–Helmholtz instability and emission of a metal jet. The process is simulated using a a two-stages modeling methodology in which magnetic pressure at copper tube is calculated from an electromagnetic code and fed to a meshless hydrocode. Key features of the interfacial morphology and jet emission are reproduced. Jet is found to be dominated by titanium and a linear velocity profile observed. [ABSTRACT FROM AUTHOR]

Inverse scattering transform for the defocusing Lakshmanan–Porsezian–Daniel equation with nonzero boundary condition is constructed via the Riemann–Hilbert approach. Since poles of the associated reflection coefficient are simple, N$N$‐dark soliton solutions corresponding to N$N$ simple poles are constructed. For N$N$‐dark soliton solutions, results show that the soliton amplitude and width are not affected by the strength of the higher‐order linear and nonlinear effects γ$\gamma$, but soliton velocity has a linear correlation with γ$\gamma$; the interactions between the two‐dark solitons and among the three‐dark solitons are elastic and experience phase and position shifts. Besides, asymptotic analysis of the double‐pole solutions for the focusing Lakshmanan–Porsezian–Daniel equation with nonzero boundary condition is presented. Different from N$N$‐dark soliton solutions which locate in the straight lines and experience position shift after the interaction, the double‐pole solutions diverge from each other logarithmically and experience no position shift after the interaction. [ABSTRACT FROM AUTHOR]

In this work, a novel internal heat absorption technology using inorganic material rods is employed during the solidification process of steel ingots, aiming to control their solidification and improve the quality of the final product. The study investigates the effect of the insertion depth of inorganic materials on the solidification microstructure and macrosegregation of 2.5-ton 42CrMo ingots. The mechanical properties of samples from the product are also tested. A numerical simulation model for casting 2.5-ton ingots is established and implemented in Ansys Fluent fluid simulation software, with inorganic material rods set at different preset depths. The simulation explores the physical processes of the melting and floating of inorganic materials in molten steel, as well as their effects on the temperature and flow fields of the material. The results show that deeper insertion of inorganic materials (200 mm from the hot top) reduces the tendency for macrosegregation compared to that at the insertion depth of 100 mm. Specifically, the positive segregation area decreases by 10.35%, while the negative segregation area decreases by 15.32%. Moreover, deeper insertion results in a significant refinement of the solidification microstructure, ultimately enhancing the mechanical properties of the products machined from the ingots (i.e., the yield strength increased by 4.7%). The numerical simulation results indicate that as the placement depth of inorganic materials in the ingot mold increases, the cooling effect becomes more significant, the flow area of molten steel initiated by the inorganic materials expands, and the linear velocity of the double-circle flow increases. This further explains why the solidification quality of the ingots improves with the increasing placement depth of inorganic materials. [ABSTRACT FROM AUTHOR]

Extreme precipitation is increasing the risk of dam breaks and formation occurring debris dams. Accurate prediction of dam‐break wave propagation is critical to disaster emergency management. Intense bed‐load transport by dam‐break floods can result in a dramatic change of topography, which in turn may affect flood propagation. However, only a very few studies have investigated the thin intense bed‐load layer under dam‐break floods. In this paper, a meshless two‐phase mathematical model is utilized to examine the water velocity, sediment velocity and volumetric fraction, and bed‐load transport flux as well as energy dissipation in bed‐load layer. The model is applied to simulate two‐ and three‐dimensional laboratory experiments of dam‐break wave over erodible beds. For the two‐dimensional experiment, the relative root mean square errors in computed water surface are all below 3.60% and those in profiles of bed‐load layer and static bed are mostly below 13.40%. For the three‐dimensional case, the relative error in computed highest water level is lower than 5.9%. Sediment stream‐wise velocity in bed‐load layer follows a power‐law vertical distribution while sediment volumetric fraction decreases linearly upwards. Accordingly, a formulation of the vertical distribution of bed‐load transport flux, contradictory to the parabolic law in existing studies, is proposed. Most of the water mechanical energy transferred to the sediment is dissipated due to the shear stress in the intense bed‐load layer while only a limit part is kept by the sediment grains. Energy dissipation due to sediment shear stress dominates the consumption of total mechanical energy in the two‐phase system. Key Points: The thin intense bed‐load layer transported by dam‐break floods is numerically examined using a meshless two‐phase mathematical modelA power‐law profile of sediment streamwise velocity and a linear one of sediment volumetric fraction in the thin bed‐load layer are proposedA new formulation of the sediment transport flux in the bed‐load layer is proposed [ABSTRACT FROM AUTHOR]

Blue compact galaxies, also known as H  ii galaxies, are dwarf, star-forming objects with relatively simple dynamics, which allows for the investigation of star formation mechanisms in a cleaner manner compared to late-type objects. In this study, we have examined various characteristics of the interstellar medium, in connection with the kinematics and dynamics of ionized gas, in Tol 1004-296 and Tol 0957-278. These two objects were observed using the SOAR Integral Field Spectrometer (SIFS) attached to the Southern Observatory for Astrophysical Research (SOAR). Both galaxies were observed with two gratings: one with medium resolution for monochromatic and abundance maps, and another with high resolution for kinematics and profile analysis. Additionally, we conducted an analysis on the velocity and velocity dispersion maps using intensity–velocity dispersion (I-σ) and velocity–velocity dispersion (Vr-σ) diagrams. Neither object exhibits a rotation pattern, and only Tol 1004-296 shows a velocity gradient between the two principal knots. However, the study reveals the significant role played by velocity dispersion in the star formation process. Specifically, we identified a relationship between monochromatic intensity, metallicity, and velocity dispersion, where high emission corresponds to low metallicity and low velocity dispersion. Tol 1004-296, in particular, exhibits a distinctive linear high velocity dispersion pattern between the two main knots, suggesting that both star formation sites are pushing the gas in opposite directions. [ABSTRACT FROM AUTHOR]