Initial Motion Research Articles

Energy transfer in the formation and evolution of energy-containing motions in turbulent boundary layers

This paper examines using direct numerical simulation (DNS) the recovery of the energy-containing scales of motion (energy-containing motions) when these are removed at the inflow boundary condition of a flat plate zero-pressure gradient turbulent boundary layer (ZPG-TBL). The energy-containing motions are identified from the spanwise spectral energy density of the interscale turbulent transport. Analysis of the resulting spanwise spectral energy densitiy of velocity and vorticity suggests that near-wall streaks are the initial energy-containing motions formed with quasi-streamwise vortices only developing further downstream. This result is in agreement with the previous study on turbulent channel flows by Kannadasan et al. [1].

Ultrafast electronic relaxation pathways of the molecular photoswitch quadricyclane

The light-induced ultrafast switching between molecular isomers norbornadiene and quadricyclane can reversibly store and release a substantial amount of chemical energy. Prior work observed signatures of ultrafast molecular dynamics in both isomers upon ultraviolet excitation but could not follow the electronic relaxation all the way back to the ground state experimentally. Here we study the electronic relaxation of quadricyclane after exciting in the ultraviolet (201 nanometres) using time-resolved gas-phase extreme ultraviolet photoelectron spectroscopy combined with non-adiabatic molecular dynamics simulations. We identify two competing pathways by which electronically excited quadricyclane molecules relax to the electronic ground state. The fast pathway (<100 femtoseconds) is distinguished by effective coupling to valence electronic states, while the slow pathway involves initial motions across Rydberg states and takes several hundred femtoseconds. Both pathways facilitate interconversion between the two isomers, albeit on different timescales, and we predict that the branching ratio of norbornadiene/quadricyclane products immediately after returning to the electronic ground state is approximately 3:2.

Numerical–experimental study on the stability mechanism of tail slapping motion of supercavitation projectile

Tail slapping is considered to be a prominent mode for facilitating the movement of supercavitating projectiles underwater. Stability mechanism of the tail slapping and stability criterion of projectiles was numerically investigated in this paper. A numerical method was conducted to calculate the free flight of projectiles by combining the finite volume method, the mixture multiphase model, and a dynamic meshing scheme. The accuracy and applicability of the numerical calculation method are verified by experiments. Three typical stability modes of tail slapping motion, namely, stable, conditionally stable, and unstable, were identified through the free flight numerical simulations of projectiles with varying length-to-diameter ratios under different initial angular velocities. The stability criterion of projectiles was proposed, indicating that the tail slapping stability can be determined by analyzing the curve of the moment variation with the angle of attack at any velocity above 200 m/s. Furthermore, it was found that the stable projectiles possess inherent motion states that are exclusively determined by their structural features and are unaffected by the initial motion conditions.

Bat Motion can be Described by Leap Frogging

We present models of bat motion derived from radio-tracking data collected over 14 nights. The data presents an initial dispersal period and a return to roost period. Although a simple diffusion model fits the initial dispersal motion we show that simple convection cannot provide a description of the bats returning to their roost. By extending our model to include non-autonomous parameters, or a leap frogging form of motion, where bats on the exterior move back first, we find we are able to accurately capture the bat’s motion. We discuss ways of distinguishing between the two movement descriptions and, finally, consider how the different motion descriptions would impact a bat’s hunting strategy.

Grain boundary network plasticity: Reduced-order modeling of deformation-driven shear-coupled microstructure evolution

Microstructural evolution in structural materials is known to occur in response to mechanical loading and can often accommodate substantial plastic deformation through the coupled motion of grain boundaries (GBs). This can produce desirable behavior, such as increased ductility, or undesirable behavior such as mechanically-induced coarsening. In this work a novel, multiscale model is developed for capturing the combined effect of plasticity mediated by multiple GBs simultaneously. This model is referred to as “grain boundary network plasticity”. The mathematical framework of graph theory is used to describe the microstructure connectedness, and the evolution of microstructure is represented as volume flow along the graph. By using the principle of minimum dissipation potential, which has previously been applied to grain boundary migration, a set of evolution equations are developed that transfer volume and eigendeformation along the graph edges in a physically consistent way. It is shown that higher-order geometric effects, such as the pinning effect of triple points, may be accounted for through the incorporation of a geometric hardening that causes geometry-induced GB stagnation. The result is a computationally efficient reduced order model that can be used to simulate the initial motion of grain boundaries in a polycrystal with parameters informed by atomistic simulations. The effectiveness of the model is demonstrated through comparison to multiple bicrystal atomistic simulations, as well as a select number of GB engineered and non-GB engineered data obtained from the literature. The effect of the network of shear-coupling grain boundaries is demonstrated through mechanical response tests and by examining the yield surfaces.

Development of a dry mock-up system for verifying pyroprocess automation

This paper presents the design and operation of an autonomous robot for pyroprocess automation, which requires unique approaches beyond those used in industrial applications to achieve the desired performance. Maintaining an extremely dry atmosphere is crucial to handle various materials, including chloride, and an autonomous system ensures this dry environment. The drying room dehumidifier was carefully selected and designed to generate dry air, and different types of dry air conditioning performance were evaluated, including assessing worker accessibility inside the mock-up to determine the system's feasibility. Containers used for process materials were modified to fit the gripper system of the gantry robot for automation. The loading and unloading of process materials in each equipment were automatically performed to connect the process equipment with the robotic system. The gantry robot primarily operated through macro motion to approach waypoints containing process materials, eliminating the need for precise approach motion. The robot's tapered jaw design allowed it to grasp the target object even with imperfect positioning. Robot motions were programmed using a robot simulator for initial positioning and motion planning, and real accuracy was tested in a mock-up facility using the OPC platform.

Analyzing the early impact dynamics of single droplets impacting onto wetted surfaces

Single droplet impacts onto thin wall-films are a common phenomenon in many applications. For sufficiently high impact velocities, the droplet impact process consists of three phases, i.e., initial contact stage, droplet deformation with radial momentum transfer inducing an upward rising lamella, and crown propagation. Here, we present the results of a combined numerical and experimental study focusing on the early dynamics of the impact process. Specifically, the effects of the initial droplet shape, wall-film thickness, and contact line motion are analyzed. Prior to impact, an oblate spheroidal droplet shape was observed. Using direct numerical simulation, we show that the droplet shape affects the impact dynamics only during the first two phases, as it is one of the key parameter influencing the correct prediction of the impact zone. The contact line propagation is described by a square-root-time dependence R¯CL=ατ for both, dry and wetted surfaces. On dry surfaces, the advancement of the contact line is determined by the rolling motion of the truncated droplet. On wetted surfaces, the value of the α-parameter is controlled by two concurrent effects, namely, rolling motion and wall-film inertia. For impact onto thin films, the rolling motion prevails. With increasing wall-film height, the droplet penetrates into the soft substrates and wall-film inertia becomes the controlling factor. These insights into the early impact dynamics on wetted surface are important for the formulation of a unified modeling approach.

Two-Dimensional Analysis of Lower Extremities to Predict Best Initial Condition on Marching Movement

Himpunan Mahasiswa Mesin ITB has a specific type of marching that follows a march song’s rhythm called “derap”. In practice, derap was a hard move to maintain and unify in a group. This difficulty was observed by noting the differences that occur between the subjects' initial and middle march motion conditions. The most noticeable difference was the height of the group. This study intends to observe and find how the differences vary in this motion. The differences that occur corresponded to the relative knee and ankle angle. This study utilized five active markers to reconstruct the lower extremities' activity during motion, one action camera at 60 fps, and a workstation. This study was also constrained by using three cycles of march song at 115 bpm. Direct Linear Transformation was used to obtain the intrinsic factor of the camera to reconstruct the motion. Evaluating the angular kinematic parameters of relative knee and ankle angle, the authors found the relative knee angle has increased from 110° to around 130°, which happened at the second song cycle and kept stable at the rest of the song. This result brought the conclusion that more extended derap motion would tend to a steady condition of relative knee angle and suggested that the subject should begin with 130° of relative knee angle to give less effort on marching.

Simulation of movement of an active exoskeleton with five electric controlled links

The article simulates the movements of an anthropoid model of a mechatronic mechanism such as an exoskeleton containing five rods interconnected by cylindrical hinges. The exoskeleton is a system of links that undergo relative rotations around the coordinate axes under the influence of the corresponding links of the user's musculoskeletal system, on which the exoskeleton is put on, gravity, support reactions and internal control forces implemented by electric drives. To describe the movement of each link, the angles between the links are used and local coordinate systems are introduced, which allow determining their position in space. The control of the change in the angles between the links is carried out using electric drives. Modeling is carried out for a gait close to human race walking, in which there is an instantaneous alternation of single-support phases. Biomechanical modeling of an exoskeleton with five movable controlled links allows us to identify the tasks that need to be solved: the synthesis of the motion trajectory, the determination of control moments, the selection of electric drives, and the development of a system for impulse motion control. To set the anthropomorphic movement of the exoskeleton, periodic functions are introduced that specify changes in the angles between the links. Compiled a system of differential equations. The Cauchy problem is solved numerically. The results of the numerical solution are compared with the initial motion, a conclusion is made that the system is unstable, and possible ways of stabilizing the unstable motion are discussed. The impact of the presence of electric drives on the dynamics of the entire exoskeleton has been estimated.

ELECTRON BEAMS IN THE GRADIENT MAGNETIC FIELD: CONTROL FOR CONVERTING LONGITUDINAL MOTION INTO TRANSVERSAL

The motion of electrons in the cylindrical magnetic field of the magnetron gun with a gradient-type potential is considered. The formation of a beam with an energy of 55 keV in such the magnetic field has been studied. It is found that in the selected field, the initial motion of electrons along the longitudinal axis is converted into radial motion. It is determined that such the transformation is due to the influence of the solenoidal magnetic field with large longitudinal gradient. The transformation of the longitudinal direction of motion into the transverse one is stable in the energy range of 20...55 keV of electrons and in the range of 5...55 mm of radial dimensions of the particle beam. The modes of operation of the gun, in which the particle undergoes a stable transformation of the direction of motion, are studied numerically. It is shown that for the given electron energy and the fixed magnetic field, the parameter that determines the rotation of particles is the magnetic field gradient at the boundary of the entry region. It is found that the rotation effect takes place for the range of radial beam sizes, which leads to particle focusing. The possibility is shown to control the vertical coordinate of a focused beam on the basis of field adjustment as the whole. Based on the model of electron flow motion, the characteristics of the resulting electron beam are considered. It is shown that the beam, having radial dimensions of 5...55 mm, is focused vertically on the section of 1 mm.

Circumstellar disk and the first generation of stars

AbstractCircumstellar disk (CD) around the first generation of stars have been numerically investigated here to see if the cooling regimes also play a role in the formation and evolution of the disk associated with the most massive protostars (MMPS). Also, an emphasis is given to exploring the effect of the initial turbulent motion of the metal‐free gas on the resulting morphology of the CD. For this, a systematic range of Mach number has been examined. It has been found that the disk‐to‐star mass ratio / is larger when the model evolution is based on the first H line cooling followed by subsequent cooling via collision‐induced emission than in the model where only H line cooling remains operative. Also, irrespective of the initial turbulence in the cloud, the former type of model yields a CD as massive as 7.66 M while the latter type produces a disk as massive as 1.29 M. Moreover, the inner part of the CD is found dominated by higher subsonic turbulent motions in the case of the former type of models than in the latter type. CDs around MMPS in both types of models show stable disk structures.

Visualization of Charge Dynamics when Water Droplets Bounce on a Hydrophobic Surface.

Visualizing the motion of water droplets and understanding their electrification behavior holds significance for applications related to droplet transport, self-cleaning, and anti-icing/deicing and for providing a comprehensive explanation of the solid-liquid triboelectrification mechanism. Here, by constructing microcolumnar structures on the polytetrafluoroethylene surface, a water droplet-based single electrode triboelectric nanogenerator was fabricated for visualizing charge dynamics when a water droplet bounces on a hydrophobic surface. The motion state of the water droplet is closely linked to its electrification behavior through the integration of a high-speed camera and an ammeter. The electrification behavior stemming from the bounce of the water droplet is dynamically captured in real-time. The results show that the magnitude and polarity of the electrical signal have strong dependence on the motion state of the water droplet. For instance, when a water droplet approaches or moves away from the substrate in a single direction, a unipolar electrical signal is generated. However, when the water droplet reaches its limit in the initial motion direction, it signifies a static equilibrium state, resulting in the electrical signal being at zero. Furthermore, we examine the impact of factors such as impact speed, drop contact area, contact line spreading/retraction speed, and impact angle on electrification. Finally, based on the close relationship between poly(ethylene oxide) (PEO) droplet bounce dynamics and electrical signals, the bouncing details of PEO droplets with different concentrations are tracked by electrical signals. This study digitally presents the whole process of droplet bounce in situ and provides a means for monitoring and tracking droplet movement.

Motion of a solid particle in an ore-lifting riser with transverse vibrations

Deep-sea mining lifting risers experience vibrations induced by the action of ocean waves and currents, and these vibrations have an impact on the lifting efficiency of ores transported inside the risers. Here, to investigate the effect of riser vibration on ore transport, the motion of a single solid particle in a riser oscillating in the lateral direction is simulated taking account of collisions between the particle and the riser using the governing equation for motion of a spherical particle in Poiseuille flow and the Hertz–Mindlin soft sphere collision model. Validations are conducted based on comparisons between numerical and experimental results. Then, the motion of the particle in the vibrating riser is explored, considering the effects of the initial position of release of the particle, the frequency and amplitude of the riser vibrations, and collisions between the particle and the riser. It is found that the initial position of release affects only the initial motion of the particle, but not its overall motion. With increasing vibrational frequency and amplitude of the riser, the relative lateral velocity of the particle shows an increasing trend, while its vertical velocity and lifting distance are clearly decreased. The frequency with which the vertical particle velocity varies is twice as the vibrational frequency of the riser. Moreover, collisions have significant effects on the particle motion, especially on the velocities of the particle, the phase difference between the displacements of the particle and the vibrating riser, and the particle trajectory. Finally, the behavioral regime map of the particle under different vibrational frequencies and amplitudes of the riser is established preliminarily.

Bridge Plate Fixation of Distal Femur Fractures: Defining Deficient Radiographic Callus Formation and its Associations.

To determine whether deficient early callus formation can be defined objectively based on association with an eventual nonunion and specific patient, injury, and treatment factors. Final healing outcomes were documented for 160 distal femur fractures treated with locked bridge plate fixation. Radiographic callus was measured on postoperative radiographs until union or nonunion had been declared by the treating surgeon. Deficient callus was defined at 6 and 12 weeks based on associations with eventual nonunion via receiver operator characteristic analysis (ROC). A previously described computational model estimated fracture site motion based on the construct employed. Univariable and multivariable analyses then examined the association of patient, injury, and treatment factors with deficient callus formation. There were 26 nonunions. Medial callus area at 6 weeks < 24.8 mm2 was associated with nonunion (12 of 39, 30.8%) vs. (12 of 109, 11.0%), p = 0.010. This association strengthened at 12 weeks with medial callus area < 44.2 mm2 more closely associated with nonunion (13 of 28, 46.4%) vs (11 of 120, 9.2%), p < 0.001. Multivariable logistic regression analysis found limited initial longitudinal motion (OR 2.713 (1.12 to 6.60), p = 0.028)) and Charlson Comorbidity Index (1.362 (1.11 to 1.67), p = 0.003) were independently associated with deficient callus at 12 weeks. Open fracture, mechanism of injury, smoking, diabetes, plate material, bridge span, and shear were not significantly associated with deficient callus. Deficient callus at 6 and 12 weeks is associated with eventual nonunion and such assessments may aid future research into distal femur fracture healing. Deficient callus formation was independently associated with limited initial longitudinal fracture site motion derived through computational modeling of the surgical construct, but not more routinely discussed parameters such as plate material and bridge span. Given this, improved methods of in vivo assessment of fracture site motion are necessary to further our ability to optimize the mechanical environment for healing.

Origins of the Tsunami Following the 2023 Turkey–Syria Earthquake

AbstractOn 6 February 2023, a local tsunami was recorded in the southeastern Mediterranean Sea following the Mw 7.7 Turkey–Syria inland strike‐slip earthquake. Due to the lack of underwater observation, the tsunami generation mechanism remains mysterious. To understand the source mechanisms, we analyzed the tsunami waveforms of four nearby tide gauges and located possible sources using a backward tsunami ray tracing approach. We then conducted forward numerical modelings for a range of possible source parameters. We show that there were probably two tsunami sources, inside and outside Iskenderun Bay, which may be related to thick coastal sediments. A source inside the Bay with a characteristic length of 7 km produced dominant periods of 10–30 min with negative initial motion, possibly generated by a landslide. Another source of 6 km length outside the Bay produced dominant periods of 2–10 min with positive initial motions, possibly related with liquefaction.

Muscular Endurance and Strength as Predominant Factors on Spike among Young Volleyball Athletes

Most of physiological investigation in volleyball studies only discussed which body part is dominant when someone doing spike. There are still few studies to explore in more detail on what muscle works and roles of muscle is so crucial. This study aims to determine which part of the muscle has a more specific effect during spike movements. This study uses a quantitative descriptive method, participants in this study were female and male adolescent athletes obtained 42 participants, divided into 20 males and 22 females. Data on muscle endurance and strength were obtained by measuring the leg and back dynamometer, while the spike hit results collected from The Volleyball Test Skills for Smasher and performance were obtained using observation using a range of points 1-4, which is based on five spike phases: Initial Attitude, Initial Motion, Contact Motion, Follow through Motion, and Ball Placement. Data analysis used ANOVA test and simple regression. The results showed that the performance was significantly increased by the strength of the back muscles (p = 0.005 &lt; 0.05) and abdominal muscles (p = 0.012 &lt; 0.05), while the other components were supportive but not significant. Likewise, the strength of the inner leg muscles (p = 0.010 &lt; 0.05) which has a very significant level of influence (p &lt; 0.01) on the spike results. Strengthening back muscle and abdominal muscle endurance need to be the focus of the training program for young volleyball athletes because they are needed during spike movement and inner leg muscle strength is needed to obtain maximum spike jumps. Keywords: spike; endurance; strength; muscle; young athletes; volleyball

Improving Earthquake Early Warning Initial Peak Ground Motion Magnitude Estimation with Station Corrections: A Case Study Using the P-Alert Network in Taiwan

ABSTRACT Earthquake early warning systems assess the size of an earthquake based on initial ground motion and provide warnings before the arrival of large waves. We employ the iterative regression to simultaneously estimate the station correlations and the corresponding linear relations for magnitude. We report the standard error reductions of the magnitude estimation based on the initial peak P-wave acceleration (), velocity (), and displacement () as , , and , respectively. Factor analysis of the stationary correction reveals its correlation with several factors. This study shows that station correction can help to improve the precision of magnitude estimation in the future.

Analisis Awal Gerak Butiran pada Transport Sedimen Tanah Gambut Jenis Fibrik

Peat beaches are beaches whose land can be easily abraded than beaches with other types of land. This is due to the light density of peat soil so that it can be easily carried away by the flow of sea water. One of the peat beaches in Indonesia whose coastline has changed significantly in recent decades is the peat beach on Bengkalis Island, Riau Province. Peat samples were taken from Tanjung Jati Beach, Perapat Tunggal Village, Bantan District, Bengkalis Island, Bengkalis Regency, Riau Province and then the sample is carried out an initial motion analysis on peat soil sediment transport. The peat sample that is obtained is a type of fibric peat soil. This research is a basic research that aims to determine at what speed the peat soil begins to move by the flow of water so that it can be seen the relationship between flow velocity and particle diameter at the beginning of the particle movement. The analysis was carried out by visual observation during simulation in the laboratory using a modified flume which was then compared with the results of Shields' theoretical calculations. Simulations were also carried out using sand sediment as a comparison. The flume flow velocity is determined from 0.00989 m/s to 0.10112 m/s for peat material, and 0.03973 m/s to 0.18900 m/s for sand material. The velocity is considered to have met the required simulation conditions, starting from the sediment not moving, starting to move, and being carried away by the flow. The results of the analysis carried out show that the peat material begins to move at a lower speed than the sand material. This is due to the specific gravity of the peat material being lighter than the specific gravity of the sand material as a comparison. This research is also expected to be a reference for further research on related topics.&#x0D; Keywords : Peat, Flow Velocity, Initial Particle Motion, Critical Shear Stress, Shields Theory

ELECTRON BEAMS IN THE GRADIENT MAGNETIC FIELD: CONTROL FOR CONVERTING LONGITUDINAL MOTION INTO TRANSVERSAL

The motion of electrons in a cylindrical magnetic field with the gradient-type potential is considered. The motion of electrons in the cylindrical magnetic field with the gradient-type potential is considered. It is found that in the selected field, the initial motion of electrons along the longitudinal axis is converted into motion along the radius. It is determined that such the transformation is due to the action of a solenoidal magnetic field with large longitudinal gradient. The transformation of the longitudinal direction of motion into the transverse one turned out to be stable in the energy range of 20...55 keV of electrons and in the range of 5...50 mm of radial dimensions of the particle beam. The main dependences of the motion of the electron beam in the given solenoidal magnetic field are studied with the help of the software tool. The results of numerical simulation of electron trajectories in the gradient magnetic field with the circular secondary emission cathode located in the middle of the system are presented. To study the mechanism of stability with respect to magnetic field, two experimentally realized magnetic fields were used. Based on these two fields, arrays of additional 4 fields are numerically synthesized. For the set of 6 named fields, the operation of the gun, in which the particle undergoes the stable transformation of the direction of motion, is numerically studied. It is shown that for the given electron energy and the fixed magnetic field, the parameter that determines the rotation of the particles is the magnetic field gradient at the boundary of the entry region. It is found that the rotation effect takes place for the considered range of radial beam sizes, which leads to particle focusing. The possibility is shown to control the vertical coordinate of the focused beam on the basis of the field adjustment, thereby giving the interpretation of the pore dependence of the registration of electrons on the detector. The dependence of the formation of the final distribution of particles on the amplitude and gradient of the magnetic field along the axis of the system is studied. The results of numerical simulation on the motion of the electron beam are presented. Based on the model of electron flow motion, the characteristics of the resulting electron beam are considered. It is shown that the beam, having radial dimensions of 5...50 mm, is transformed and focused vertically on the area of 1 mm.

A general geometric transformation model for line-scan image registration

A reasonable geometric transformation model is the key to image registration. When the relative motion direction between the line-scan camera and the object is strictly parallel to the planar object, it is possible to align the image by using the eight-parameter geometric transformation model of the line-scan image. However, it will be invalid when the relative motion direction is arbitrary. Therefore, a new general geometric transformation model of line-scan images is proposed for line-scan image registration in this paper. Considering the different initial poses and motion directions of the line-scan camera, the proposed model is established based on the imaging model of the line-scan camera. In order to acquire line-scan images to verify the proposed model, a line-scan image acquisition system was built. The method based on feature points is used to register the line-scan images. The experimental results show that the proposed geometric transformation model can align the line-scan image collected under arbitrary relative motion direction, not just the parallel case. Besides, the statistical errors of the image feature point coordinates are the best performance after registration. The accuracy of the registration results is better than that of other existing geometric transformation models, which verifies the correctness and generality of the geometric transformation model of the line-scan camera proposed in this paper.