Large External Forces Research Articles

3D Motion Analysis of Alpine Skiing on Steep Slope Gate in Men’s Giant Slalom

This study aimed to determine the characteristics of the elite skiers and the techniques required to improve their performance in the men’s giant slalom alpine skiing competition by conducting a three-dimensional (3D) motion analysis. The top nine skiers were compared with the next nine skiers using 3D motion analysis in a single-gate section with an average slope of 25.6°. The results revealed the following characteristics of superior skiing techniques. (1) The skiers started the turn from a high position relative to the gate and obtained high velocity by skiing in a gentle arc using potential energy. (2) By quickly rotating and edging the skis, the skiers were able to gain centripetal force early, enter the gate, ski in the direction of the fall line, and change skiing direction timely. (3) The skiers had quick inward leaning of the body and early lowering of the pelvis on the outside ski to form an angulation posture to resist the large external forces acting on the body during the turn.

Compensation Function Observer-Based Backstepping Sliding-Mode Control of Uncertain Electro-Hydraulic Servo System

Observer-based control is the most commonly used method in the control of electro-hydraulic servo system (EHSS) with uncertainties, but it suffers from the drawback of low accuracy under the influence of large external load forces and disturbances. To address this problem, this paper proposes a novel compensation function observer-based backstepping sliding-mode control (BSMC) approach to achieve high-accuracy tracking control. In particular, the model uncertainties, including nonlinearities, parameter perturbations and external disturbances are analyzed and treated together as a lumped disturbance. Then, a fourth-order compensation function observer (CFO) is constructed, which fully utilizes the system state information to accurately estimate the lumped disturbance. On this basis, the estimate of the lumped disturbance is incorporated into the design of a backstepping sliding-mode controller, allowing the control system to compensate for the disturbance effect. The stability of the closed-loop control system under the CFO and BSMC is rigorously proven through the use of the Lyapunov theory, which guarantees that all the tracking error signals converge exponentially to the origin. Comparative simulations are carried out to show the effectiveness and efficiency of the proposed approach, i.e., compared with PID and ESO-based BSMC methods, the tracking accuracy is respectively improved by 94.86% and 88.19% under the influence of large external load forces and disturbances.

Real-time application of a dynamic disturbance suppression control approach for an axial active magnetic bearing system

Active Magnetic Bearings (AMBs) use magnetic forces to suspend the rotor, allowing contactless operation and the ability to adjust stiffness and damping. However, compared to mechanical bearings, magnetic bearings are much weaker in terms of rigidity. A large external force can lead to rotor/stator collision. This study proposes a Dynamic Stiffness Controller (DSC) for AMBs. The DSC dynamically adjusts the AMB stiffness to counter external disturbance forces in real-time. Experimental results show the effective change of AMB stiffness by DSC based on the magnitude of the external load. Furthermore, not only the AMB stiffness can be real-time adjusted to counterbalance disturbances but the steady-state energy consumption is improved as there is little disturbances applied to the system. The AMB-DSC system exhibiting only 33% energy consumption compared to AMBs with constant stiffness. DSC for AMB systems offers benefits like lower risk of rotor-stator collisions, preventing coil burnouts, and improved energy efficiency.

Pathogenesis of Musculotendinous and Fascial Injuries After Physical Exercise - Short Review.

The identification of sports and physical exercises with injury risk is necessary to preserve the capacity of athletes and people who perform physical education and also to prevent the installation of functional deficiencies. We have selected the articles related to the pathogenic mechanisms involved in musculotendinous and fascial injuries produced as a result of physical exercise. The lesional pathogenesis is complex and incompletely clarified. Recent theories put in a new light the mechanisms of muscle pain and tendinopathy production. The accumulation of lactate anion, known to be a residue that induces fatigue and muscle pain, has been reconsidered by some authors. It appears that lactate anion is an excellent fuel for the myocardial fiber. Moreover, the accumulation of lactic acid after intense physical exercise could prevent the inexcitability of the sarcolemma induced by the increased concentration of interstitial K+. Most of the time, overuse injuries are not limited to muscles. They can cause myofascial, myotendinous or purely muscular injuries. The muscular fascia is more susceptible to injuries produced under the action of large external forces. Also, fascia is more sensitive to pain compared to muscle when external forces act eccentrically. Overloading the tendon and putting it under tension repeatedly is followed by ruptures of the tendon fibers. The regeneration of the degenerated tendon is defective in the context of the inflammation produced by the injury. Tendon fibers undergo a process of fibrosis, scarring, adhesion and heterogeneous calcification. Oxidative stress is responsible for inflammation, degeneration and apoptosis of tenocytes. The benefits brought by physical education and sports are indisputable, but their practice requires a coordinated program to prevent possible traumatic and overuse injuries.

A Regularization-Free Scheme for Recovering Large External Forces of Higher-Order Nonlinear Evolution Equations

In this study, the inverse engineering problems of the Ostrovsky equation (OE), Kawahara equation (KE), modified Kawahara equation (mKE), and sixth-order Korteweg-de Vries (KdV) equation will be investigated numerically. An effective numerical approach to tackle these inverse Coriolis dispersion problems and the above-mentioned inverse problems are still not available. To use different boundary shape functions, we must deal with the boundary data, initial conditions, and terminal time conditions of the OE, KE, mKE, and sixth-order KdV equations. The unknown Coriolis dispersion of OE and unknown large external forces of those three equations can be retrieved through back-substitution of the solution into the OE, KE, mKE, and sixth-order KdV equations while we obtain the solution with the symmetry property by employing the boundary shape function scheme (BSFS). Five numerical experiments with noisy data are carefully validated and discussed.

Bending performance of the CORC cable with flexible interlocked stainless steel former

The high temperature superconducting cable on round core (CORC) is a kind of cable that could be used in fusion projects. Nevertheless, conventional copper former CORC cables require a large external force to allow the cable to endure plastic deformation and be tightly wound into solenoids. In this case, the superconducting tape will be affected by concentrated stress, resulting in a risk of critical current degradation. Therefore, this paper proposes a new CORC cable with flexible interlocked stainless steel former, which can be wound into a solenoid by applying a small external force. To verify the bending performance of this interlocked former CORC cable, a double-layer and a ten-layer interlocked stainless steel former CORC cable, as well as a double-layer traditional copper former CORC cable, are fabricated. And these three CORC cables are used to wind solenoids of various radius sizes respectively. The experimental results show that the critical bending radius of the double-layer interlocked stainless steel former CORC cable is less than 20 mm, the critical bending radius of the ten-layer interlocked stainless steel former CORC cable is less than 50 mm, and the critical bending radius of the double-layer traditional copper former CORC cable is larger than 55 mm. A self-consistent finite element model for the critical current of the CORC cable solenoid is also established. And the critical current experimental results are in good agreement with the simulation results. The results of this paper verify the excellent bending performance of the interlocked former CORC cable, which provides a good option for the preparation of insert magnets for future fusion projects.

Reentrant condensation transition in a model of driven scalar active matter with diffusivity edge

The effect of a diffusivity edge is studied in a system of scalar active matter confined by a periodic potential and driven by an externally applied force. We find that this system shows qualitatively distinct stationary regimes depending on the amplitude of the driving force with respect to the potential barrier. For small driving, the diffusivity edge induces a transition to a condensed phase analogous to the Bose–Einstein-like condensation reported for the nondriven case, which is characterized by a density-independent steady state current. Conversely, large external forces lead to a qualitatively different phase diagram since in this case condensation is only possible beyond a given density threshold, while the associated transition at higher densities is found to be reentrant.

Learning hybrid locomotion skills-Learn to exploit residual actions and modulate model-based gait control.

This work has developed a hybrid framework that combines machine learning and control approaches for legged robots to achieve new capabilities of balancing against external perturbations. The framework embeds a kernel which is a model-based, full parametric closed-loop and analytical controller as the gait pattern generator. On top of that, a neural network with symmetric partial data augmentation learns to automatically adjust the parameters for the gait kernel, and also generate compensatory actions for all joints, thus significantly augmenting the stability under unexpected perturbations. Seven Neural Network policies with different configurations were optimized to validate the effectiveness and the combined use of the modulation of the kernel parameters and the compensation for the arms and legs using residual actions. The results validated that modulating kernel parameters alongside the residual actions have improved the stability significantly. Furthermore, The performance of the proposed framework was evaluated across a set of challenging simulated scenarios, and demonstrated considerable improvements compared to the baseline in recovering from large external forces (up to 118%). Besides, regarding measurement noise and model inaccuracies, the robustness of the proposed framework has been assessed through simulations, which demonstrated the robustness in the presence of these uncertainties. Furthermore, the trained policies were validated across a set of unseen scenarios and showed the generalization to dynamic walking.

Analysis of Thoracic Aorta Injury in 27 Road Traffic Accident Deaths.

To analyze the characteristics of thoracic aorta injury in road traffic accidents, to provide data reference for forensic identification. The data of 27 traffic accident death cases with thoracic aorta injury were analyzed according to relevant parameters including sex, age, mode of transportation, and thoracic aorta injury. Aortic injury in traffic accidents was significantly more in males than females, and 74.1% cases were in the age range of 31-70 years. The most common mode of transportation was the motorcycle, followed by electric bike, most of which crashed with trucks. Most cases were accompanied by rib fractures and lung injuries. Thoracic aorta injury was the most common in ascending aorta, followed by aortic arch and thoracic aorta. Ascending aorta injury was most likely to occur in the range of 0-<1.6 cm from the aortic valve, while it was rare over 2.6 cm. Taking the aortic valve as the reference, the most common locations of injury were the anterior semilunar valve, followed by the right posterior semilunar valve and the left posterior semilunar valve. Thoracic aortic rupture occurred in 63.0% cases, and intima and media lacerations only occurred in 37.0% cases. A few deceased had aortic diseases. The proximal part of the ascending aorta is prone to be injured because of the large external force of traffic accidents. The medical examiner should carefully examine the aortic injury in traffic accident deaths, and evaluate the relationship between the injury and the disease according to the condition and degree of aortic injury.

On the Cauchy problem of the full Navier-Stokes equations for three-dimensional compressible viscous heat-conducting flows subject to large external potential forces

On the Cauchy problem of the full Navier-Stokes equations for three-dimensional compressible viscous heat-conducting flows subject to large external potential forces

Numerical Analysis of Ice Rubble with a Freeze-Bond Model in Dilated Polyhedral Discrete Element Method

Freezing in ice rubble is a common phenomenon in cold regions, which can consolidate loose blocks and change their mechanical properties. To model the cohesive effect in frozen ice rubble, and to describe the fragmentation behavior with a large external forces exerted, a freeze-bond model based on the dilated polyhedral discrete element method (DEM) is proposed. Herein, imaginary bonding is initialized at the contact points to transmit forces and moments, and the initiation of the damage is detected using the hybrid fracture model. The model is validated through the qualitative agreement between the simulation results and the analytical solution of two bonding particles. To study the effect of freeze-bond on the floating ice rubble, punch-through tests were simulated on the ice rubble under freezing and nonfreezing conditions. The deformation and resistance of the ice rubble are investigated during indenter penetration. The influence of the internal friction coefficient on the strength of the ice rubble is determined. The results indicate that the proposed model can properly describe the consolidated ice rubble, and the freeze-bond effect is of great significance to the ice rubble properties.

A Meshless Method for Retrieving Nonlinear Large External Forces on Euler-Bernoulli Beams

We retrieve unknown nonlinear large space-time dependent forces burdened with the vibrating nonlinear Euler-Bernoulli beams under varied boundary data, comprising two-end fixed, cantilevered, clamped-hinged, and simply supported conditions in this study. Even though some researchers used several schemes to overcome these forward problems of Euler-Bernoulli beams; however, an effective numerical algorithm to solve these inverse problems is still not available. We cope with the homogeneous boundary conditions, initial data, and final time datum for each type of nonlinear beam by employing a variety of boundary shape functions. The unknown nonlinear large external force can be recuperated via back-substitution of the solution into the nonlinear Euler-Bernoulli beam equation when we acquire the solution by utilizing the boundary shape function scheme and deal with a small-scale linear system to gratify an additional right-side boundary data. For the robustness and accuracy, we reveal that the current schemes are substantiated by comparing the recuperated numerical results of four instances to the exact forces, even though a large level of noise up to 50% is burdened with the overspecified conditions. The current method can be employed in the online real-time computation of unknown force functions in space-time for varied boundary supports of the vibrating nonlinear beam.

Refined blow-up criteria for the three-dimensional viscous compressible flows with large external potential force and general pressure

Refined blow-up criteria for the three-dimensional viscous compressible flows with large external potential force and general pressure

Some Serrin type blow‐up criteria for the three‐dimensional viscous compressible flows with large external potential force

We provide a Serrin type blow‐up criterion for the 3‐D viscous compressible flows with large external potential force. For the Cauchy problem of the 3‐D compressible Navier–Stokes system with potential force term, it can be proved that the strong solution exists globally if the velocity satisfies the Serrin's condition and the sup‐norm of the density is bounded. Furthermore, in the case of isothermal flows with no vacuum, the Serrin's condition on the velocity can be removed from the claimed criterion.

Multi-order phononic frequency comb generation within a MoS2 electromechanical resonator

In this work, we measure and tune simultaneously the vibration of a 1-nm thick MoS2 suspended monolayer with standard electrical excitation and optical techniques. At ambient temperature, we first investigate the strong parametric coupling between two different mechanical modes (ω1 and ω2). We demonstrate a high and quasi-linear tunability of the mode frequencies with the parametric pump voltage. Then, we couple the highly tunable main vibration (ω1) to a parametric pump frequency (ωp) to obtain a high number of sidebands at frequencies ω1 ± m ωp, driving the mechanical mode with a large external electrical force. This oscillating force, applied via the gate voltage, acts as a stress onto the MoS2 sheet. The obtained frequency comb has a large spectral band and contains up to 100 harmonics, with potential applications in quantum information processing and heat or sound transport.

Global well‐posedness and asymptotics of full compressible non‐resistive magnetohydrodynamics system with large external potential forces

We consider the global well‐posedness and asymptotic behavior of compressible viscous, heat‐conductive, and non‐resistive magnetohydrodynamics (MHD) fluid in a field of external forces over three‐dimensional periodic thin domain . The unique existence of the stationary solution is shown under the adhesion and the adiabatic boundary conditions. Then, we prove that a solution to the initial boundary value problem with the same boundary and periodic conditions uniquely exists globally in time and converges to the stationary solution as time tends to infinity. Moreover, if the external forces are small or disappeared in an appropriate Sobolev space, then δ can be a general constant. Our proof relies on the two‐tier energy method for the reformulated system in Lagrangian coordinates and the background magnetic field which is perpendicular to the flat layer. Compared to the work of Tan and Wang (2018, 10.1137/16M1088156), we not only overcome the difficulties caused by temperature but also consider the big external forces.

COVID-19 Is Becoming A '9/11 Moment' For Borders And Health.

The COVID-19 pandemic has had a dramatic impact on the cross-border movement of people. As governments begin to reopen their borders and cautiously restart travel, their attention is shifting to border procedures that could facilitate travel while protecting the homeland from travelers who may be infected. This is not the first time in recent memory that border management has had to be rethought under the pressure of large external forces. This article examines parallels between the current situation and the early 2000s, when the September 11, 2001, attacks on US targets caused a seismic shift in managing borders. We find echoes of today's responses in the initial fragmentation and chaos of two decades ago, which eventually gave way to a coordinated international system. We also analyze the implications of the emerging border health infrastructure for other migration challenges-particularly addressing irregular crossings and the border "crises" they create. Because the aftershocks of the pandemic on all aspects of people on the move could be felt for decades, immigration, mobility management, and public health priorities must be considered alongside one another.

A water drop-shaped slingshot in plants: geometry and mechanics in the explosive seed dispersal of Orixa japonica (Rutaceae).

In angiosperms, many species disperse their seeds autonomously by rapid movement of the pericarp. The fruits of these species often have long rod- or long plate-shaped pericarps, which are suitable for ejecting seeds during fruit dehiscence by bending or coiling. However, here we show that fruit with a completely different shape can also rely on pericarp movement to disperse seeds explosively, as in Orixa japonica. Fruit morphology was observed by hard tissue sectioning, scanning electron microscopy and micro-computed tomography, and the seed dispersal process was analysed using a high-speed camera. Comparisons were made of the geometric characteristics of pericarps before and after fruit dehiscence, and the mechanical process of pericarp movement was simulated with the aid of the finite element model. During fruit dehydration, the water drop-shaped endocarp of O. japonica with sandwich structure produced two-way bending deformation and cracking, and its width increased more than three-fold before opening. Meanwhile the same shaped exocarp with uniform structure could only produce small passive deformation under relatively large external forces. The endocarp forced the exocarp to open by hygroscopic movement before seed launching, and the exocarp provided the acceleration for seed launching through a reaction force. Two layers of water drop-shaped pericarp in O. japonica form a structure similar to a slingshot, which launches the seed at high speed during fruit dehiscence. The results suggest that plants with explosive seed dispersal appear to have a wide variety of fruit morphology, and through a combination of different external shapes and internal structures, they are able to move rapidly using many sophisticated mechanisms.

Efficacy of once-weekly and twice-weekly injections of teriparatide by patient characteristics: A post hoc analysis of the TWICE study

ObjectivesTo assess differences in efficacy of a 28.2-μg teriparatide formulation for twice-weekly use (2/W-TPTD) by patient characteristics. MethodsA post hoc analysis was performed using data from a multicenter, randomized, double-blind, double-dummy, non-inferiority trial (TWICE study) conducted in Japan comparing the efficacies of once-weekly and twice-weekly injections of teriparatide (TPTD). Specifically, a stratified analysis of percentage changes from baseline was performed using the final data on lumbar spine bone mineral density (BMD) after a 48-week treatment period (n = 251, 2/W-TPTD; n = 239, a 56.5-μg teriparatide formulation for once-weekly use [1/W-TPTD]). ResultsAcross all subgroups defined by patient characteristics that included 9 or more subjects, the lumbar spine BMD increased significantly in both groups. In the 2/W-TPTD group, the percentage change was significantly higher in subjects with no non-vertebral fractures without large external force occurring at or after age 50 years versus those with such fractures. The lower the stratification in baseline lumbar spine BMD, total hip BMD, or femoral neck BMD, the greater was the percentage change. ConclusionsWhereas all subgroups can expect a significant improvement in lumbar spine BMD, there were some patient characteristics that affected the percentage increase in BMD.

On the margins: action heroines in Coin-Locker Girl and The Villainess

ABSTRACT In this paper, I examine Coin-Locker Girl (Chainataun, Han Jun-hee, 2015) and The Villainess (Aknyeo, Jung Byung-gil, 2017), two recent examples of women-centred action genre films through the key concepts of surveillance, usefulness and the Freudian concept of the uncanny, which structure the films’ plot and meaning. In both films, usefulness becomes the reason for the characters’ survival and makes one recognizably human, while being useless makes one a ghost and even leads to death. Both films also present mentors and quasi-parents, who constantly put the protagonists, who exist in the margins of society, under surveillance and demand proof of their usefulness. In response, the protagonists struggle to overcome their marginalized existence but they are thwarted by larger external forces, such as the network of spies or criminals that determine the conditions in and against which the protagonists must work to survive. Furthermore, I hope to also show that China, which the films imagine and visualize in particular ways, provides the context of the characters’ marginality. Cinema reflects reality – in this case, it reflects the reality of contemporary Korea’s marginalized female subjectivity that exists beyond the film screen.