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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]

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]

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]

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]

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]

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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]

This study examines the flow rate, Bejan number transportation, concentration distribution and thermal characteristics of an immiscible couple stress‐ micropolar fluids within a porous channel. The authors focus on the effects of heat radiation and an angled magnetic field on the thermal dispersion, concentration distribution and entropy formation of two different types of incompressible immiscible micropolar and couple stress fluids inside a porous channel. Here, the static walls of the channel are isothermal, and the pressure gradient in the flow domain's entrance zone is constant. In this flow problem, we tried to simulate thermal radiation in the energy equation by applying Rosseland's diffusion approximation. To solve the problem, the authors have used no‐slip conditions at the channel's immovable walls, a continuity of temperature profile, shear stresses, thermal flux, linear velocity, and micro‐rotational velocity over the fluid‐fluid interface. The equations that govern the flow of immiscible fluids are solved using a well‐defined methodology and both the temperature and flow field are then evaluated using a closed‐form solution. The mathematical results of the thermal distribution and flow velocity are used to derive the Bejan number distribution and the entropy generation number. Graphical discussions are used to illustrate the impact of different emerging factors on the model's flow and thermal properties, which describe the major impact of the proposed model. These variables involve the micropolarity parameter, Reynolds number, inclination angle parameter, radiation parameter, and Hartmann number. The outcomes of the present models are corroborated by previously established results available in the literature. [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]

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]

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]

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]

AbstractThe main aim of this study is to investigate the behavior of bio-convective flow of 2nd grade micropolar nanofluid with Darcy-Forchheimer law over a curved porous stretching surface. The fluid flow analysis includes novel aspects such as the nonuniform heat source/sink, Joule heating, magnetic field, chemical reaction, and thermal radiation. Furthermore, the boundary of the stretching surface is acquired the stratification conditions. A suitable conversion method is employed to transform the flow model into a collection of ordinary differential equations, characterized by their nonlinearity. The bvp4c technique on the MATLAB is utilized to acquire numerical solutions for this set of nonlinear equations. The characteristics of various influential parameters on the velocity, temperature, concentration, and microorganism density profiles are observed and discussed. In the present problem, it is observed that by the growth of micropolar parameter enhances the angular fluid velocity. Moreover, larger values of the magnetic parameter, Darcy number, and porosity parameter result in a decrease in the fluid’s linear velocity. The temperature profile exhibits a decreasing pattern with the elevation thermal stratification parameter, while the opposite trend shows by the increment of the radiation parameter and Eckert number. Additionally, the concentration of nanoparticles decreases as the Schmidt number and Brownian motion parameter increases. [ABSTRACT FROM AUTHOR]

The development and study of an optimal control method for the problem of controlling the formation of a group of mobile robots is still a current and popular theme of work. However, there are few works that take into account the issues of time synchronization of units in a decentralized group. The motivation for taking up this topic was the possibility of improving the accuracy of the movement of a group of robots by including dynamic time synchronization in the control algorithm. The aim of this work was to develop a two-layer synchronous motion control system for a decentralized group of mobile robots. The system consists of a master layer and a sublayer. The sublayer of the control system performs the task of tracking the reference trajectory using a single robot with a kinematic and dynamic controller. In this layer, the input and output signals are linear and angular velocity. The master layer realizes the maintenance of the desired group formation and synchronization of robots during movement. Consensus tracking and virtual structure algorithms were used to implement this level of control. To verify the correctness of operation and evaluate the quality of control for the proposed proprietary approach, simulation studies were conducted in the MATLAB/Simulink environment, followed by laboratory tests using real robots under ROS. The developed system can successfully find application in transportation and logistics tasks in both civilian and military areas. [ABSTRACT FROM AUTHOR]

Many mobile robotics applications require robots to navigate around humans who may interpret the robot's motion in terms of social attitudes and intentions. It is essential to understand which aspects of the robot's motion are related to such perceptions so that we may design appropriate navigation algorithms. Current works in social navigation tend to strive towards a single ideal style of motion defined with respect to concepts such as comfort, naturalness, or legibility. These algorithms cannot be configured to alter trajectory features to control the social interpretations made by humans. In this work, we firstly present logistic regression models based on perception experiments linking human perceptions to a corpus of linear velocity profiles, establishing that various trajectory features impact human social perception of the robot. Secondly, we formulate a trajectory planning problem in the form of a constrained optimization, using novel constraints that can be selectively applied to shape the trajectory such that it generates the desired social perception. We demonstrate the ability of the proposed algorithm to accurately change each of the features of the generated trajectories based on the selected constraints, enabling subtle variations in the robot's motion to be consistently applied. By controlling the trajectories to induce different social perceptions, we provide a tool to better tailor the robot's actions to its role and deployment context to enhance acceptability. [ABSTRACT FROM AUTHOR]

Objectives: Infant growth is recognized to vary over the short term, with periods of greater and lesser linear growth velocity. Our objectives were to (1) examine the potential differences in overall growth profiles between children who experienced cumulative growth faltering in the first year of life consistent with that seen by many children living in poverty in low‐ and middle‐income countries, versus children without growth faltering and (2) test whether biological factors were associated with the timing of magnitude of growth saltations. Methods: Thrice‐weekly measurements of length were recorded for n = 61 Peruvian infants (28 boys and 33 girls) enrolled from birth to 1 year. A total of 6040 measurements were analyzed. We tested for the evidence of saltatory growth and used hurdle models to test whether the timing and magnitude of saltations varied between children with greater or lesser growth faltering. Results: There were no differences in the duration of stasis periods or magnitude of growth saltations between children who were stunted at 1 year old (N = 18) versus those who were not stunted (N = 43). Children who experienced greater declines in LAZ in the first year of life trended toward longer periods between saltations than those with less of a decline (14.5 days vs. 13.4 days, p =.0512). A 1‐unit increase in mid upper arm circumference for age Z‐score in the 21 days prior was associated with 35% greater odds of a saltation occurring (p <.001), and a 0.128 cm greater saltation (p <.001). Conclusions: After characterizing infant growth into periods of saltation and stasis, our results suggest that increases in weight preceded increases in length. [ABSTRACT FROM AUTHOR]

An exact similarity solution is worked out for fluid motion in the vicinity of a cylindrical surface in an electrically conducting viscoelastic fluid obeying the Jeffrey model. Cylindrical surface expands axially with linear velocity and has a prescribed surface temperature. The present analysis focuses on the partial slip assumption which gives rise to a nonlinear case Robin-type (mixed) boundary condition in axial velocity. In contrast to a previously published study (J. Mech., vol 31, pp. 69–78, 2015) which only reported local similarity solutions in no-slip case, the present work provides an exact similarity analysis by defining a quadratic surface temperature. The effects of the magnetic field and Joule heating on the momentum and thermal transport phenomena are also scrutinized. A numerical routine is used to solve the equation accurately for a wide range of fluid parameters, including ranges that could not be handled by previous approximate analytical methods that were limited to the no-slip limit. The influences of viscoelasticity and partial slip on the flow behavior are investigated, and the coefficient of skin friction for a Jeffrey fluid is calculated. Obtained results are consistent with the previously published works under special situations. The case of flat surface, which can be obtained as a limiting case of the model, is not even explored in the past. [ABSTRACT FROM AUTHOR]

The oil film lubrication performance of a large hydrostatic turntable operating at the model of constant surface cutting speed is studied. Firstly, the rotary speed equation which is bound by the constant surface cutting speed is established. According to the fluid lubrication theory, the gap flow equation, the oil film temperature rise equation and the double‐rectangular‐cavity oil pad bearing capacity equation are derived. Further, a prediction model of oil film lubrication performance in the operating mode is established. The change rules of temperature, pressure and other performance indexes of the film with time are obtained by numerical simulation. And, the above laws are verified by design experiments. It is found that the cutting speed, feed rate leaves a significant impact on the law of variations of oil film performance with time. According to the conclusions, it will be beneficial to improve the bearing capacity of the hydrostatic turntable and further improve the machining accuracy by using cutting parameters reasonably to control the speed within a certain range. [ABSTRACT FROM AUTHOR]

• A set of multiplicative extended Kalman filters for uncooperative relative navigation is developed. • Unit quaternions are used to represent the coupled roto-translational relative dynamics. • The filters estimate the 6 DoF state and – in some options - the main parameters of the Target object. • These filters can serve several architectures of the relative navigation system. • Numerical simulations representative of close-range Target inspection are performed. This work presents a set of dynamic filters for estimating the relative roto-translational state and the main parameters of a noncooperative target from an observing chaser satellite during close proximity operations. The proposed different options address a wide range of design possibilities for the architecture of the relative navigation system. All filters are derived from a common, general, core shaped as a dynamic multiplicative extended Kalman filter using dual quaternions. This allows exploiting the advantages of handling the pose (i.e. , attitude and position) in a multiplicative fashion, while improving the accuracy in the estimation of the angular and linear relative velocities, as well as enabling the estimation of some meaningful parameters of the target spacecraft (e.g. , the ratios of the moments of inertia, position and orientation of the principal axes frame). Moreover, by adopting relative kinematics and dynamics equations in dual quaternions, the inherent coupling of the six degrees-of-freedom motion is addressed with no approximations. All filters take as observations only the noisy pose measurements from an electro-optical device. For each proposed formulation, numerical simulations are carried out to show the behavior of the filter within a scenario representative of close-range target inspection at conclusion of the mid-range rendezvous. [ABSTRACT FROM AUTHOR]

The maximum linear (or translational) velocity achievable by an omnidirectional platform is not uniform as it depends on the angular orientation of the motion. This velocity is limited by the maximum angular velocity of the motors driving the wheels and also depends on the mechanical configuration and orientation of the wheels. This paper proposes a procedure to compute an upper bound for the translational velocity, named the consistent velocity of the omnidirectional platform, which is defined as the minimum of the maximum translational velocities achievable by the platform in any angular orientation with no wheel slippage. The consistent velocity is then a uniform translational velocity always achievable by the omnidirectional platform regardless of the angular orientation of the motion. This paper reports the consistent velocity for a set of omnidirectional platforms with three omni wheels that have the same radius and angular distribution but different angular orientations. Results have shown that these platforms can achieve different maximum velocities in different angular orientations although the consistent velocity is the same for all of them. Results have also shown that the consistent velocity has a linear relation with the angular velocity of the motion. The consistent velocity of a mobile platform can be used by its path-planning algorithm as an upper bound that guarantees the execution of any omnidirectional motion at a uniform and maximum translational velocity. [ABSTRACT FROM AUTHOR]

We investigate a fully discrete modular grad-div (MGD) stabilization algorithm for solving the incompressible micropolar Navier-Stokes equations (IMNSE) model, which couples the incompressible Navier-Stokes equations and the angular momentum equation together. The mixed finite element (FE) method is applied for the spatial discretization. The time discretization is based on the BDF2 implicit scheme for the linear terms and the two-step linearly extrapolated scheme for the convective terms. The considered algorithm constitutes two steps, which involve a post-processing step for linear velocity. First, we decouple the fully coupled IMNSE model into two smaller subphysics problems at each time step (one is for the linear velocity and pressure, the other is for the angular velocity), which reduces the size of the linear systems to be solved and allows for parallel computing of the two sub-physics problems. Then, in the post-processing step, we only need to solve a symmetrical positive determined grad-div system of linear velocity at each time step, which does not increase the computational complexity by much. However, the post-processing step can improve the solution quality of linear velocity. Moreover, we obtain unconditional stability, and error estimates of the linear velocity and angular velocity. Finally, several numerical experiments involving threedimensional and two-dimensional settings are used to validate the theoretical findings and demonstrate the benefits of the modular grad-div (MGD) stabilization algorithm. [ABSTRACT FROM AUTHOR]

In spot beam laser annealing, fiber laser and the polygon scanner‐based optical system play a key role by precisely controlling the laser spot position and linear velocities. Key parameters of the laser crystallization are laser power, spot overlap and line overlap. AFM, Raman, and SEM analyzes are used to evaluate polysilicon crystallization state, optimize process parameters, and understand spot beam annealing mechanism. This paper presents the spot beam annealing system configuration and experimental results for low‐temperature poly‐silicon fabrication. [ABSTRACT FROM AUTHOR]

This study explores positioning and obstacle avoidance control for autonomous surface vehicles (ASVs) by considering equivalent elliptical-shaped obstacles. Firstly, compared to most Barrier Lyapunov function (BLF) methods that approximate obstacles as circles, a novel BLF is improved by introducing an elliptical obstacle model. This improvement uses ellipses instead of traditional circles to equivalent obstacles, effectively resolving the issue of excessive conservatism caused by over-expanded areas during the obstacle equivalence process. Secondly, unlike traditional obstacle avoidance approaches based on BLF, to achieve constraint control of angle and angular velocity, a method based on model predictive control (MPC) is introduced to optimize local angle planning. By incorporating angular error constraints, this ensures that the directional error of the ASV remains within a restricted range. Furthermore, an auxiliary function of directional error is introduced into the ASV's linear velocity, ensuring that the ASV parks and adjusts its direction when the deviation in angle becomes too large. This innovation guarantees the linearization of the ASV system, addressing the complexity of traditional MPC methods when dealing with nonlinear second-order ASV systems. Ultimately, the efficacy of our proposed approach is validated through rigorous experimental simulations conducted on the MATLAB platform. [ABSTRACT FROM AUTHOR]

A new method is proposed to control bipedal robots to achieve flexible omni-directional motion and robust locomotion under complex disturbances, called the heuristics-based reinforcement learning (HBRL) framework. HBRL shows great training efficiency in simulation. Heuristic reference trajectories play a crucial role in HBRL, which guide the training process. Exploration rewards, leg-foot reset condition, and command curriculum are three significant components to optimize the training process. An estimator network is utilized to supply linear velocities and foot contact information. We train controllers on flat ground in simulation. To demonstrate robustness and versatility, the trained controllers were tested on BRAVER, a point-foot bipedal robot with three joints on each leg. The controllers enabled BRAVER to perform omni-directional locomotion with the maximum forward speed reaching 2 m/s. The robot could also maintain balance under external pushing and over uneven terrains. [ABSTRACT FROM AUTHOR]

Autonomous mobile robots are essential to the industry, and human–robot interactions are becoming more common nowadays. These interactions require that the robots navigate scenarios with static and dynamic obstacles in a safely manner, avoiding collisions. This paper presents a physical implementation of a method for dynamic obstacle avoidance using a long short-term memory (LSTM) neural network that obtains information from the mobile robot's LiDAR for it to be capable of navigating through scenarios with static and dynamic obstacles while avoiding collisions and reaching its goal. The model is implemented using a TurtleBot3 mobile robot within an OptiTrack motion capture (MoCap) system for obtaining its position at any given time. The user operates the robot through these scenarios, recording its LiDAR readings, target point, position inside the MoCap system, and its linear and angular velocities, all of which serve as the input for the LSTM network. The model is trained on data from multiple user-operated trajectories across five different scenarios, outputting the linear and angular velocities for the mobile robot. Physical experiments prove that the model is successful in allowing the mobile robot to reach the target point in each scenario while avoiding the dynamic obstacle, with a validation accuracy of 98.02%. [ABSTRACT FROM AUTHOR]

The focus of this study is on the design and experimental validation of MRF self-sealing (also known as MRF seal) utilizing permanent magnets. The MRF seal has been built to readily replace traditional seal (lip-seal) for rotation shaft sealing. Following a review of studies on MRF seals, two configurations of MRF seal featuring an axial permanent magnet and two distinct pole head forms, rectangular and trapezoidal, are presented. The two MRF seals are then subjected to a magnetic analysis using the finite element method (ANSYS APDL). The Bingham plastic model of MRF and the assumption of linear velocity profile of MRF in the sealing gap are employed to construct mathematical models of crucial seal characteristics such as maximum static working pressure and frictional torque. The seals are optimized employing the optimization toolbox integrated in the ANSYS APDL to obtain the optimal geometric dimensions of the MRF seals. Finally, prototypes of the two MRF seals are fabricated and testing work is conducted to validate and compare them with the simulated results. [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]

Autonomous navigation and information gathering in challenging environments are demanding since the robot's sensors may be susceptible to non-negligible noise, its localization and mapping may be subject to significant uncertainty and drift, and performing collision-checking or evaluating utility functions using a map often requires high computational costs. We propose a learning-based method to efficiently tackle this problem without relying on a map of the environment or the robot's position. Our method utilizes a Collision Prediction Network (CPN) for predicting the collision scores of a set of action sequences, and an Information gain Prediction Network (IPN) for estimating their associated information gain. Both networks assume access to a) the depth image (CPN) or the depth image and the detection mask from any visual method (IPN), b) the robot's partial state (including its linear velocities, z -axis angular velocity, and roll/pitch angles), and c) a library of action sequences. Specifically, the CPN accounts for the estimation uncertainty of the robot's partial state and the neural network's epistemic uncertainty by using the Unscented Transform and an ensemble of neural networks. The outputs of the networks are combined with a goal vector to identify the next-best-action sequence. Simulation studies demonstrate the method's robustness against noisy robot velocity estimates and depth images, alongside its advantages compared to state-of-the-art methods and baselines in (visually-attentive) navigation tasks. Lastly, multiple real-world experiments are presented, including safe flights at 2.5 m/s in a cluttered corridor, and missions inside a dense forest alongside visually-attentive navigation in industrial and university buildings. [ABSTRACT FROM AUTHOR]

This paper focuses on the 2D incompressible anisotropic magneto-micropolar fluid equations with vertical dissipation, horizontal magnetic diffusion, and horizontal vortex viscosity. The goal is to investigate the stability of perturbations near a background magnetic field in the 2D magneto-micropolar fluid equations. Two main results are obtained. The first result is based on the linear system. Global existence for any large initial data and asymptotic linear stability are established. The second result explores stability for the nonlinear system. It is proven that if the initial data are sufficiently small, then the solution for some perturbations near a background magnetic field remains small. Additionally, the long-time behaviour of the solution is presented. The most challenging terms in the proof are the linear terms in the velocity equation and the micro-rotation equation that will grow with respect to time t. We are able to find some background fields to control the growth of the linear terms. Our results reveal that some background fields can stabilise electrically conducting fluids. [ABSTRACT FROM AUTHOR]

When the airlift bioreactor is applied to the field of industrial fermentation, there is a common problem of low mixing and flow efficiency due to its simple structure. In order to expand the application of airlift bioreactor in the field of industrial fermentation, a new type of airlift bioreactor with three-dimensional bumps in the draft tube has been designed to enhance the mixing and flow of gas-liquid two-phase in the reactor. In order to determine the specific influence of the three-dimensional bumps on the internal flow field of the reactor, and to provide technical reference for the improvement of the structure of the airlift bioreactor, in this paper, the CFD simulation of this type of bioreactor is carried out. Based on the Euler multiphase flow, the Realizable k-ε model was used to analyze the flow field of the reactor with average gas-liquid flow linear velocity and temperature as parameters. The results show that under certain conditions, the three-dimensional bumps inside the draft tube can effectively accelerate the gas-liquid two-phase flow and better promotes the mixing of pig manure fermentation broth and air. [ABSTRACT FROM AUTHOR]

The tracking control problem of non‐holonomic mobile robot systems has been extensively investigated in the past decades, however, most of the existing control strategies were developed specifically for the fixed‐point tracking. This technical note focuses on the region tracking control for a non‐holonomic mobile robot system with parameter uncertainties in the robot dynamics. With the system decomposition and adaptive control method, some restrictions imposed on the angular and linear velocities of the non‐holonomic mobile robot in recent literature are removed, enabling to track dynamic trajectories with any values of the angular and line velocities. The proposed adaptive control scheme can simultaneously solve both the regulation and region tracking problems of a non‐holonomic mobile robot with one passive wheel and two actuated wheels. By utilizing the designed control laws, the mobile robot system is able to globally reach inside a moving region specified by potential functions whose path can be a circular curve, a straight line, or sinusoidal curve, by using a single adaptive controller. Since the dynamic region can be specified arbitrarily small, the fixed‐point tracking can be regarded as a special case of region tracking studied in this paper. Compared with the traditional fixed‐point tracking, region tracking has more flexibility and better robustness. Numerical results are presented to show the effectiveness of the designed strategy. [ABSTRACT FROM AUTHOR]

Traditional methods for harvesting medicinal materials with long roots, like Astragalus membranaceus, require extensive soil excavation, leading to problems like inefficient soil separation, low stemming rates, and blockages in conveyor chains. To address these challenges, this study introduces a prototype machine capable of digging, separating soil, crushing soil, and collecting the medicinal materials in one continuous process. The paper focuses on the machine's design and working principle, with theoretical analysis and calculations for key components like the digging shovel, multi-stage conveyor, and soil-crushing device. Specific structural parameters were determined, and the screening efficiency of the roller screen was analyzed using EDEM 2020 software, comparing scenarios with and without rollers. A motion model for the medicinal materials during conveyance was established, allowing for the determination of optimal linear velocity and mounting angle for the conveyor. Additionally, a motion model for the second-stage conveyor chain and rear soil-crushing device was used to optimize their placement, ensuring efficient soil crushing without affecting the thrown Astragalus. Compared to traditional Chinese medicine diggers, this machine boasts superior resistance reduction and soil-crushing capabilities. Compared with traditional harvesters, the drag-reducing and soil-crushing device of this machine is more efficient, reducing the damage to Astragalus during the harvesting process, reducing the labor intensity of farmers, and improving the quality and efficiency of Astragalus harvesting. Field experiments have shown that when the operating speed of the prototype is 1.0 m/s and the roller-screen speed is 130~150 rpm, the operating performance is optimal, and comparative experiments can be conducted under the optimal parameters. From the experimental results, it can be seen that the improved equipment has increased the bright-stem rate by about 4%, the digging and loosening rate by 97.42%, and the damage rate by 2.44%. The equipment design meets the overall design requirements, and all experimental indicators meet national and industry standards. This provides a reference for the optimization and improvement of the soil-crushing device and the structure of the Astragalus membranaceus harvester. [ABSTRACT FROM AUTHOR]

Experimental laboratory equipment for friction stir welding (FSW) as a result of working out the optimal welding modes at different linear velocities allows producing high-quality butt joints from thin ductile metals. With the development of new mathematical methods for modeling thermodeformational processes, it became possible to analyze the stress-strain state and thermomechanical processes occurring in the FSW joint zone, which is necessary for predicting the operational properties, strength and service life of welded structures made of thin metal. Using mathematical models and finite element analysis, the temperature distributions from the volume heat source at FSW were visualized, and the residual deformations and stresses in the zone of butt-welded joints of thin sheets of magnesium alloys were numerically determined. In the future, it is advisable to determine the effective balance of the linear speed and the rotation speed of the FSW tool to obtain better homogeneity of the weld structure and reduce heat input into the metal during welding. [ABSTRACT FROM AUTHOR]

The two-point statistics of the cosmic velocity field, measured from galaxy peculiar velocity (PV) surveys, can be used as a dynamical probe to constrain the growth rate of large-scale structures in the Universe. Most works use the statistics on scales down to a few tens of Megaparsecs, while using a theoretical template based on the linear theory. In addition, while the cosmic velocity is volume-weighted, the observable line-of-sight velocity two-point correlation is density-weighted, as sampled by galaxies, and therefore the density–velocity correlation term also contributes, which has often been neglected. These effects are fourth order in powers of the linear density fluctuation |$\delta _{\rm L}^4$|⁠ , compared to |$\delta _{\rm L}^2$| of the linear velocity correlation function, and have the opposite sign. We present these terms up to |$\delta _{\rm L}^4$| in real space based on the standard perturbation theory, and investigate the effect of non-linearity and the density–velocity contribution on the inferred growth rate f σ8, using N -body simulations. We find that for a next-generation PV survey of volume |$\sim {\cal O}(500 \, h^{-1} \, {\rm Mpc})^3$|⁠ , these effects amount to a shift of f σ8 by ∼10 per cent and is comparable to the forecasted statistical error when the minimum scale used for parameter estimation is |$r_{\rm min} = 20 \, h^{-1} \, {\rm Mpc}$|⁠. [ABSTRACT FROM AUTHOR]

This paper presents a study on optimal design to determine the installation position and link lengths of a robot within a designated workspace for welding, aiming to minimize singularities during the robot's motion. Bi-objective functions are formulated to minimize singularities while maximizing the volumes of linear velocity manipulability ellipsoid and angular velocity manipulability ellipsoid, respectively, ensuring isotropy. We have constructed a simulation environment incorporating PID control to account for robot tracking errors. This environment was utilized as a simulator to derive a Bi-objective function set within a genetic algorithm. Through this, we optimized four robot link length variables and two installation position variables, selecting the optimal design variables on the Pareto Front. In the standard work object, the volume average of the linear velocity manipulability ellipsoid was confirmed to have improved by 72% compared to the initial level, and the isotropy of the angular velocity manipulability ellipsoid was confirmed to have improved by 23% compared to the initial level. Furthermore, correlation analysis between design parameters identified those with a high correlation with the objective functions, and the analysis results are discussed. [ABSTRACT FROM AUTHOR]

Achieving a harmonious alignment between the biological characteristics of fish and hydrodynamics patterns is crucial for ensuring the efficacy of fish passage facilities. In this study, based on the hydrodynamic characteristics of the river and the biological characteristics of fish, we evaluated the internal flow field in the nature-like fishway of Congen II hydropower station located along the Chabao river and explored methods to improve the operation efficiency. Based on comprehensive considerations of the flow field, turbulent kinetic energy, and the migration pathways of fish, it is found that the implementation of a continuous oblique bottom slope represents a more cost-effective and operationally convenient solution. The influence of different permutation of bulkheads in the nature-like fishway on operational efficiency was further examined. Our investigation revealed that the nature-like fishway with the continuous slope of 2% and the arrangement of three bulkheads in each row (model 3) exhibited a relatively simple velocity distribution and linear flow line, which poses challenges for fish in locating resting areas. In addition, the distribution of low turbulence kinetic energy area in the mainstream made it less favorable for fish to transition from the mainstream to the rest area within the fishway. The nature-like fishway with the continuous slope of 2% and the arrangement of two or three bulkheads in staggered rows (model 4) demonstrated better performance. Several potential fish migration routes for both model 3 and model 4 were proposed based on the numerical simulation results. In model 3, fish exhibited a continuous sprint through the concentrated high-speed area, which was less favorable for fish to rest and forage. In contrast, model 4 exhibited a diversified flow velocity distribution, enabling fish to make timely changes in their direction during migration. This feather proved to be advantageous in enhancing fish migration within the passage. The design of nature-like fishway in this study provides an important reference and technical support for the construction and optimization of the nature-like fishway for low dams, and is of great significance for restoring river connectivity destroyed by small hydropower construction and improving fish migration. [ABSTRACT FROM AUTHOR]

The default mode network (DMN) is a large-scale brain network known to be suppressed during a wide range of cognitive tasks. However, our comprehension of its role in naturalistic and unconstrained behaviors has remained elusive because most research on the DMN has been conducted within the restrictive confines of MRI scanners. Here, we use multisite GCaMP (a genetically encoded calcium indicator) fiber photometry with simultaneous videography to probe DMN function in awake, freely exploring rats. We examined neural dynamics in three core DMN nodes--the retrosplenial cortex, cingulate cortex, and prelimbic cortex--as well as the anterior insula node of the salience network, and their association with the rats' spatial exploration behaviors. We found that DMN nodes displayed a hierarchical functional organization during spatial exploration, characterized by stronger coupling with each other than with the anterior insula. Crucially, these DMN nodes encoded the kinematics of spatial exploration, including linear and angular velocity. Additionally, we identified latent brain states that encoded distinct patterns of time-varying exploration behaviors and found that higher linear velocity was associated with enhanced DMN activity, heightened synchronization among DMN nodes, and increased anticorrelation between the DMN and anterior insula. Our findings highlight the involvement of the DMN in collectively and dynamically encoding spatial exploration in a real-world setting. Our findings challenge the notion that the DMN is primarily a "task-negative" network disengaged from the external world. By illuminating the DMN's role in naturalistic behaviors, our study underscores the importance of investigating brain network function in ecologically valid contexts. [ABSTRACT FROM AUTHOR]

The standard Permanent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR) technique, which is commonly used for surface motion analysis, assumes linear deformation velocities. While effective for monitoring urban subsidence over short periods, it falls short when dealing with non-linear, earthquake-related deformations over extended timeframes. To address this limitation, we use a non-linear PSInSAR technique, which is an enhancement of PSInSAR, to identify non-linear deformation patterns. We processed Sentinel-1A images from ascending and descending orbits in the Islamabad/Rawalpindi region from December 2015 to January 2023 using non-linear PSInSAR. By calculating the differences in deformation, we analyzed surface movements and assessed the impact of the 2017 earthquake on urban areas. Our findings reveal that the earthquake significantly increased the deformation in ascending and descending orbit tracks, with an average deformation of up to 70 mm/yr and a line-of-sight movement of up to 30 mm/yr. Our observations indicate that the deformation is directed towards the line of sight in the north and south of the deformed area, suggesting subsidence between the two uplifting faults, potentially linked to a concealed fault line along the deformation zone boundary. This contradicts previous arguments, suggesting that water extraction is the leading cause of deformation. Our analysis with non-linear PSInSAR demonstrates that tectonics play a significant role in deformation, providing valuable insights into tectonic-activity-induced deformations in urban areas over the long term. [ABSTRACT FROM AUTHOR]

We study the dynamics of a class of mechanical systems subjected to non-holonomic constraints by employing a method termed "modified vakonomic method" (MVM), and developed by Llibre, Ramírez and Sadovskaia in 2014. In particular, we test the MVM for the "rolling coin" problem and a variant of the "non-holonomic skate" problem. For our purposes, we divide our work in two parts. For the first one, our point of departure is a paper published in this journal by Lemos in 2022, in which, for the "rolling coin" problem, Kozlov's vakonomic method is shown to lead to inconsistencies with the so-called Lagrange–D'Alembert traditional non-holonomic method (TNHM). In this case, we prove that, if the MVM is used, the equivalence with the TNHM can be restored, and the two methods can be reconciled. In the second part, we formulate a thought experiment consisting of an electrically charged "non-holonomic skate" interacting with a magnetic field, and we examine its dynamics by means of the MVM. In this case, we point out the differences with the predictions of the TNHM, and we propose a reformulation of the MVM capable of retrieving the results obtained with the TNHM. Moreover, we give some insight into the main computational aspects related to the MVM for non-holonomic constraints linear in the generalized velocities. [ABSTRACT FROM AUTHOR]

Beside the numerous applications obtained by the interaction of a laser beam with acoustic waves, another application have recently emerged that allows generating an optical dynamic spatial array (ODSA) using two orthogonal acoustic waves. In this paper, we demonstrate theoretically and illustrate numerically the possibility of generating an ODSA composed of many diffracted orders. The obtained results show that each diffracted order navigates in space according to its own trajectory and its own velocity. These trajectories are sometimes linear with sinusoidal velocities, sometimes circular with constant velocities and often elliptical with variable velocities. Moreover, the high diffracted orders of this ODSA, which are characterized by a high velocity and a large scanned area, can be controlled by varying the Raman–Nath parameter. The outstanding point is that all these diffracted orders navigate in space with the same sweep frequency despite the diversity of trajectories and velocities. The borrowing of Poincaré and Bloch spheres allows enumerating all these trajectories and presenting them in an elegant and attractive method. This technique can be used in metrology for rotation measurements based on Doppler effect. In addition, we can used it to develop a spatial display allows tracing Lissajous trajectories rather than using an oscilloscope. [ABSTRACT FROM AUTHOR]

The flow of viscous fluids is considered as the aggregation of the motion of fluid particles when the fluid is conceived to be made up by an infinite number of particles. As an alternative of this conventional model, fluid motion could be understood as the slip of fluid layers with a molecular scale over each other, where the slip structures of fluid and their associated small-scale motion are characterized by an axial-vector-valued differential 1-form, called the vortex field. In this paper, in the case of steady flows we define the swirling degree of the velocity field at a point, and further the swirl field of the steady flow, to study the slip topology of fluid or the local streamline pattern around the critical point. The linear velocity field in the right real Schur form is used to carry out detailed analyses around the isolated critical point. Theoretical deduction and numerical test unveil the connection between the swirling degree and the swirl field, greatly make clear the topological property of slip structures of fluid in steady flows, especially in three-dimensional space. [ABSTRACT FROM AUTHOR]