The deterministic condition for the ground reaction force acting point on the combined knee valgus and tibial internal rotation moments in early phase of cutting maneuvers in female athletes

Background:Combined knee valgus and tibial internal rotation(VL+IR)moments have been shown to stress the anterior cruciate ligament(ACL)in several in vitro cadaveric studies.To utilize this knowledge for non-contact ACL injury prevention in sports,it is necessary to elucidate how the ground reaction force(GRF)acting point(center of pressure(CoP))in the stance foot produces combined knee VL+IR moments in risky maneuvers,such as cuttings.However,the effects of the GRF acting point on the development of the combined knee VL+IR moment in cutting are still unknown.Methods:We first established the deterministic mechanical condition that the CoP position relative to the tibial rotational axis differentiates the GRF vector’s directional probability for developing the combined knee VL+IR moment,and theoretically predicted that when the CoP is posterior to the tibial rotational axis,the GRF vector is more likely to produce the combined knee VL+IR moment than when the CoP is anterior to the tibial rotational axis.Then,we tested a stochastic aspect of our theory in a lab-controlled in vivo experiment.Fourteen females performed 60˚cutting under forefoot/rearfoot strike conditions(10 trials each).The positions of lower limb markers and GRF data were measured,and the knee moment due to GRF vector was calculated.The trials were divided into anterior-and posterior-CoP groups depending on the CoP position relative to the tibial rotational axis at each 10 ms interval from 0 to 100 ms after foot strike,and the occurrence rate of the combined knee VL+IR moment was compared between trial groups.Results:The posterior-CoP group showed significantly higher occurrence rates of the combined knee VL+IR moment(maximum of 82.8%)at every time point than those of the anterior-CoP trials,as theoretically predicted by the deterministic mechanical condition.Conclusion:The rearfoot strikes inducing the posterior CoP should be avoided to reduce the risk of non-contact ACL injury associated with the combined knee VL+IR stress.

Reduction in ground reaction force variables with instructed barefoot running

Backgound:Barefoot(BF) running has recently increased in popularity with claims that it is more natural and may result in fewer injuries due to a reduction in impact loading.However,novice BF runners do not necessarily immediately switch to a forefoot strike pattern.This may increase mechanical parameters such as loading rate,which has heen associated with certain running-related injuries,specifically,tibial stress fractures.patellofemoral pain,and plantar iasciitis.The purpose of this study was to examine changes in loading parameters between typical shod running and instructed BF running with real-time force feedback.Methods:Forty-nine patients seeking treatment for a lower extremity injury ran on a force-sensing treadmill in their typical shod condition and then BF at the same speed.While BF they received verbal instruction and real-time feedback of vertical ground reaction forces.Results:While 92%of subjects(n = 45) demonstrated a rearfoot strike pattern when shod,only 2%(n = 1) did during the instructed BF run.Additionally,while BF 47%(n = 23) eliminated the vertical impact transient in all eight steps analyzed.All loading variables of interest were significantly reduced from the shod to instructed BF condition.These included maximum instantaneous and average vertical loading rates of the ground reaction force(p 【 0.0001),stiffness during initial loading(p 【 0.0001).and peak medial(p = 0.001) and lateral(p 【 0.0001) ground reaction forces and impulses in the vertical(p 【 0.0001).medial(p = 0.047),and lateral(p 【 0.0001) directions.Conclusion:As impact loading has been associated with certain running-related injuries,instruction and feedback on the proper forefoot strike pattern may help reduce the injury risk associated with transitioning to BF running.

Analysis of kinematic data and determination of ground reaction force of foot in slow squat

In the present paper, the ground reaction force （GRF） acting on foot in slow squat was determined through a force measuring system, and at the same time, the kinematic data of human squat were obtained by analyzing the photographed image sequences. According to the height and body weight, six healthy volunteers were selected, three men in one group and the other three women in another group, and the fundamental parameters of subjects were recorded, including body weight, height and age, etc. Based on the anatomy characteristics, some markers were placed on the right side of joints. While the subject squatted at slow speed on the force platform, the ground reaction forces on the forefoot and heel for each foot were obtained through calibrated force platform. The analysis results show that the reaction force on heel is greater than that on forefoot, and double feet have nearly constant force. Moreover, from processing and analyzing the synchronously photographed image sequences in squat, the kinematic data of human squat were acquired, including mainly the curves of angle, angular velocity and angular acceleration varied with time for knee, hip and ankle joints in a sagittal plane. The obtained results can offer instructive reference for photographing and analyzing the movements of human bodies, diagnosing some diseases, and establishing in the future appropriate mathematical models for the human motion.

Analysis of Human Joint Forces in Standing Posture

Using the software Anybody Modeling System, a human static-standing musculoskeletal model based on inverse dynamics is presented, which are defined as segments, muscles and joints as dements. Simulation is based on data obtained from experiments using motion capture system VICADN and force plate AMTI. In the model AnyBody Modeling System is introduced to help solve the redundancy problem and obtain results of muscle activities, muscle forces and joint forces. From the model, hip and knee joint forces could be analyzed under normal standing posture. Also, activities of the musculus rectus femoris and several other muscles of the lower limbs can be obtained. From the results it could be concluded that stresses at joints are much stronger than theoretical reasoning because of the functions of relevant soft tissues such as muscles, tendons and so on. Results show that joint forces from the simulations are in good conformation with previous experimental researches. And this complicated model would be of use for better understanding human body functions.

One hundred marathons in 100 days:Unique biomechanical signature and the evolution of force characteristics and bone density

Background:An extraordinary long-term running performance may benefit from low dynamic loads and a high load-bearing tolerance.An extraordinary runner(age=55 years,height=1.81 m,mass=92 kg) scheduled a marathon a day for 100 consecutive days.His running biomechanics and bone density were investigated to better understand successful long-term running in the master athlete.Methods:Overground running gait analysis and bone densitometry were conducted before the marathon-a-day challenge and near its completion.The case’s running biomechanics were compared pre-challenge to 31 runners who were matched by a similar foot strike pattern.Results:The case’s peak vertical loading rate(Δx=-61.9 body weight(BW)/s or-57%),peak vertical ground reaction force(Δx=-0.38 BW or-15%),and peak braking force(Δx=-0.118 BW or-31%) were remarkably lower(p<0.05) than the control group at~3.3 m/s.The relatively low loading-related magnitudes were attributed to a remarkably high duty factor(0.41) at the evaluated speed.The foot strike angle of the marathoner(29.5°) was greater than that of the control group,affecting the peak vertical loading rate.Muscle powers in the lower extremity were also remarkably low in the case vs.controls:peak power of knee absorption(Δx=-9.16 watt/kg or-48%) and ankle generation(Δx=-3.17 watt/kg or-30%).The bone mineral density increased to 1.245 g/cm;(+2.98%) near completion of the challenge,whereas the force characteristics showed no statistically significant change.Conclusion:The remarkable pattern of the high-mileage runner may be useful in developing or evaluating load-shifting strategies in distance running.

Study on adhesively-bonded surface of tapered double cantilever specimen made of aluminum foam affected with shear force

Aluminum foam is widely used in diverse areas to minimize the weight and maximize the absorption of shock energy in lightweight structures and various bio-materials.It presents a number of advantages,such as low density,incombustibility,non-rigidity,excellent energy absorptivity,sound absorptivity and low heat conductivity.The aluminum foam with an air cell structure was placed under the TDCB Mode II tensile load by using Landmark equipment manufactured by MTS to examine the shear failure behavior.The angle of the tapered adhesively-bonded surfaces of specimens was designated as a variable,and three models were developed with the inclined angles differing from one another at 6°,8° and 10°.The specimens with the inclined angles of 6°,8° and 10° have the maximum reaction forces of 168 N,194 N when the forced displacements are 6,5 and 4.2 mm respectively.There are three specimens with the inclined angles of 10°,8° and 6° in the order of maximum reaction force.As the analysis result,the maximum equivalent stresses of 0.813 MPa and 0.895 MPa happened when the forced displacements of 6 mm and 5 mm proceeded at the models of 6° and 8°,respectively.A simulation was carried out on the basis of finite element method and the experimental design.The results of the experiment and the simulation analysis are shown not different from each other significantly.Thus,only a simulation could be confirmed to be performed in substitution of an experiment,which is costly and time-consuming in order to determine the shearing properties of materials made of aluminum foam with artificial data.

The Human Ankle-Foot Complex as a Multi-Configurable Mechanism during the Stance Phase of Walking

The objective of this study is to investigate the biomechanical functions of the human ankle-toot complex during the stancephase of walking. The three-dimensional (3D) gait measurement was conducted by using a 3D infrared multi-camera system anda force plate array to record the Ground Reaction Forces (GRF) and segmental motions simultaneously. The ankle-foot complexwas modelled as a four-segment system, connected by three joints: talocrural joint, sub-talar joint and metatarsophalangeal joint.The subject-specific joint orientations and locations were determined using a functional joint method based on the particleswarm optimisation algorithm. The GRF moment arms and joint moments acting around the talocrural and sub-talar joints werecalculated over the entire stance phase. The estimated talocrural and sub-talar joint locations show noticeable obliquity. Thekinematic and kinetic results strongly suggest that the human ankle-foot complex works as a mechanical mechanism with twodifferent configurations in stance phase of walking. These lead to a significant decrease in the GRF moment arms therebyincreasing the effective mechanical advantages of the ankle plantarflexor muscles. This reconfigurable mechanism enhancesmuscle effectiveness during locomotion by modulating the gear ratio of the ankle plantarflexor muscles in stance. This studyalso reveals many factors may contribute to the locomotor function of the human ankle-foot complex, which include not only itsre-configurable structure, but also its obliquely arranged joints, the characteristic heel-to-toe Centre of Pressure (COP) motionand also the medially acting GRF pattern. Although the human ankle-foot structure is immensely complex, it seems that itsconfiguration and each constitutive component are well tuned to maximise locomotor efficiency and also to minimise risk ofinjury. This result would advance our understanding of the locomotor function of the ankle-foot complex, and also the intrinsicdesign of the ankle-foot musculoskeletal structure. Moreover, this may also provide implications for the design of bionicprosthetic devices and the development of humanoid robots.

Is changing footstrike pattern beneficial to runners?

Some researchers, running instructors, and coaches have suggested that the "optimal" footstrike pattern to improve performance and reduce running injuries is to land using a mid-or forefoot strike. Thus, it has been recommended that runners who use a rearfoot strike would benefit by changing their footstrike although there is little scientific evidence for suggesting such a change. The rearfoot strike is clearly more prevalent. The major reasons often given for changing to a mid-or forefoot strike are(1) it is more economical;(2) there is a reduction in the impact peak and loading rate of the vertical component of the ground reaction force; and(3) there is a reduction in the risk of a running-related injuries. In this paper,we critique these 3 suggestions and provide alternate explanations that may provide contradictory evidence for altering one's footstrike pattern.We have concluded, based on examining the research literature, that changing to a mid-or forefoot strike does not improve running economy, does not eliminate an impact at the foot-ground contact, and does not reduce the risk of running-related injuries.

Coordinated control strategy for robotic-assisted gait training with partial body weight support

Walking is the most basic and essential part of the activities of daily living. To enable the elderly and non-ambulatory gait-impaired patients, the repetitive practice of this task, a novel gait training robot(GTR) was designed followed the end-effector principle, and an active partial body weight support(PBWS) system was introduced to facilitate successful gait training. For successful establishment of a walking gait on the GTR with PBWS, the motion laws of the GTR were planned to enable the phase distribution relationships of the cycle step, and the center of gravity(COG) trajectory of the human body during gait training on the GTR was measured. A coordinated control strategy was proposed based on the impedance control principle. A robotic prototype was developed as a platform for evaluating the design concepts and control strategies. Preliminary gait training with a healthy subject was implemented by the robotic-assisted gait training system and the experimental results are encouraging.

Early Identification and Visualization of Parkinsonian Gaits and their Stages Using Convolution Neural Networks and Finite Element Techniques

Parkinson’s Disease(PD)is a neurodegenerative disease which shows a deficiency in dopaminehormone in the brain.It is a common irreversible impairment among elderly people.Identifying this disease in its preliminary stage is important to improve the efficacy of the treatment process.Disordered gait is one of the key indications of early symptoms of PD.Therefore,the present paper introduces a novel approach to identify pa rkinsonian gait using raw vertical spatiotemporal ground reaction force.A convolution neural network(CNN)is implemented to identify the features in the parkinsonian gaits and their progressive stages.Moreover,the var iations of the gait pressures were visually recreated using ANSYS finite element software package.The CNN model has shown a 97%accuracy of recognizing parkinsonian gait and their different stages,and ANSYS model is implemented to visualize the pressure variation of the foot during a bottom-up approach.

Analysis of an Extreme Scenario in the Vacuum Vessel in KTX

The Vacuum Vessel （VV） system is a vital component of Keda Torus for experiment （KTX）. Various accidental scenarios might occur on the VV. In this report, an extreme scenario is assumed and studied： plasma accidental termination during the fiat-top stage. Numerical simulations based on finite element are performed as the major tool for aualyses. The detailed distributions of eddy and the reaction forces on VV are extracted, and the total eddy current and the maximum reaction force due to electromagnetic load are figured out. In addition, according to the results, the VV can be approximately regarded as a centrally symmetric structure, even though its ports distribution is asymmetric.

Analysis of Penetration Depth of Pipeline on Cohesive Soil Seabed

This paper conducts laboratory tests to investigate detailedly the soil deformation law around the pipeline and its penetration depth under self-gravity. The seabed model is prepared by consolidating saturated soil using vacuum pressure technology, and the pipeline models are specifically designed to possess different radii. Based on the experimental results and digital images, the soil deformation process is analyzed and summarized, a kinematic admissible velocity field is given and an upper bound solution of pipeline penetration depth and soil reaction force is derived and proposed in this paper. In order to verify the accuracy of the upper bound solution deduced in this paper,a comparison is made among some published results and the solution suggested in this paper, the comparison results confirm that the upper bound solution and the soil failure mode are reasonable. Finally two empirical formulas are given in this paper to estimate the soil reaction force of seabed and the penetration depth of pipeline. The empirical formulas are in agreement with the upper bound solution derived in this paper, and the conclusion of this paper could provide some theoretical reference for the further study of the interaction between the pipeline and the soil.

An efficient tool for Parkinson's disease detection and severity grading based on time-frequency and fuzzy features of cumulative gait signals through improved LSTM networks

Parkinson's disease(PD)is a widespread neurodegenerative condition that affects many individuals annually.Early identification and monitoring of disease progression are crucial to effectively managing symptoms and preventing motor complications.This research proposes an automated PD diagnosis and severity-grading model based on time-frequency and fuzzy features using improved uni-directional and bi-directional long short-term memory networks with sensitive hyperparameters optimization.We utilize vertical ground reaction force signals collected from Physionet's publicly available dataset recorded during regular and dual-task clinical trials of walking measurements.Only the cumulative signal of both feet was then utilized and segmented into 30-s windows without further pre-processing.Subsequently,we extracted only four key time-frequency and fuzzy features from each segment,effectively capturing the signal's inherent uncertainty.Bayesian optimization is employed in both detection and grading approaches to fine-tune the two critical hyperparameters:the initial learning rate and the number of hidden units in the network.The detection phase yields an exceptional accuracy of 99.19%,surpassing state-of-the-art studies with the same dataset.In the grading phase,classification based on the unified PD rating scale values achieves an accuracy of 92.28%.The proposed study delves into the potential of cumulative gait signals as a powerful diagnostic tool for PD,aiming to extract precise and intricate information by implementing straightforward and minimal processing endeavors.This method demonstrates significant effi-ciency in terms of complexity,cost,and energy consumption by utilizing a single-dimensional signal,eliminating the need for pre-processing steps,and limiting the features used for training.

Motion-copying method with symbol sequence-based phase switch control for intelligent optical manufacturing

Implementation of robot-based motion control in optical machining demonstrably enhances the machining quality.The introduction of motion-copying method enables learning and replicating manipulation from experienced technicians.Nevertheless,the location uncertainties of objects and frequent switching of manipulated spaces in practical applications impose constraints on their further advancement.To address this issue,a motion-copying system with a symbol-sequence-based phase switch control(SSPSC)scheme was developed by transferring the operating skills and intelligence of technicians to mechanisms.The manipulation process is decomposed,symbolised,rearranged,and reproduced according to the manufacturing characteristics regardless of the change in object location.A force-sensorless adaptive sliding-mode-assisted reaction force observer(ASMARFOB),wherein a novel dual-layer adaptive law was designed for high-performance fine force sensing,was established.The uniformly ultimate boundedness(UUB)of the ASMARFOB is guaranteed based on the Lyapunov stability theory,and the switching stability of the SSPSC was examined.Validation simulations and experiments demonstrated that the proposed method enables better motion reproduction with high consistency and adaptability.The findings of this study can provide effective theoretical and practical guidance for high-precision intelligent optical manufacturing.

The Mechanics and Trajectory Control in Locust Jumping

Locusts （Locusta migratoria manilensis） are characterised by their flying ability and abiding jump ability. Research on the jumping mechanics and behavior of locusts plays an important role in elucidating the mechanism of hexapod locomotion. The jump gestures of locusts were observed using high-speed video camera at 250 fps. The reaction forces of the hindlegs were measured using two three-dimensional sensors, in case the two hindlegs attached on separated sensor plates. The jump gestures and reaction forces were used to illustrate the locust jumping mechanism. Results show that the trajectory control is achieved by rapid rolling and yawing movements of the locust body, caused by the forelegs, midlegs and hindlegs in different jumping phases. The final jump trajectory was not determined until hind tarsi left platform. The horizontal co-impulse between two hindlegs might play a key role in jump stability and accuracy. Besides, the angle between two hindlegs affects the control of jump trajectory but has a little effect on the elevation angle of a jump, which is controlled mechanically by the initial position of the hindlegs. This research lays the groundwork for the probable design and development ofbiomimetic robotics.

Effect of Slope Degree on the Lateral Bending in Gekko geckos

A gecko＇s habitat possesses a wide range of climbing slopes that pose a number of postural challenges for climbing lo- comotion. Few studies have examined the relationship between the lateral bending of the trunk of a gecko and other aspects of locomotion when climbing. In this paper, three-dimensional reaction forces and high-speed videos of Gekko geckos moving on different slopes are used to reveal how the lateral bending of the animal＇s trunk responds to changing slopes. The results of such observations indicate that the minimum bending radius continually decreases with an increase in the slope, illustrating that the degree of bending of the trunk becomes significantly greater. Moreover, a lateral bending mechanical model is used to show the interrelation between the lateral bending in the frontal plane and the sagittal deformation of the trunk caused by gravity. Taken together, these results have advanced our understanding of the role of lateral bending of vertebrates when climbing on a slope.

A stability locomotion-control strategy for quadruped robots with center-of-mass dynamic planning

Locomotion stability is essential for controlling quadruped robots and adapting them to unstructured terrain.We propose a control strategy with center-of-mass(CoM)dynamic planning for the stable locomotion of these robots.The motion trajectories of the swing legs are synchronized with the CoM of the robot.To implement the synchronous control scheme,we adjusted the swing legs to form a support triangle.The strategy is applicable to both static walk gait and dynamic trot gait.In the motion control processes of the robot legs,the distribution of the ground reaction forces is optimized to minimize joint torque and locomotion energy consumption.We also used an improved joint-torque controller with varied controller coefficients in the stance and swing phases.The simulation and experimental results demonstrate that the robot can complete omnidirectional locomotion in both walk and trot gaits.At a given locomotion speed,the stability margins for the robot during walking and trotting were 27.25%and 37.25%higher,respectively,than in the scheme without CoM planning.The control strategy with energy consumption optimization(ECO)reduced the energy consumption of the robot in walk and trot gaits by 11.25%and 13.83%,respectively,from those of the control scheme without ECO.

Analysis of coupling mechanism between roll system crossing and liner wear of hot strip mill

Non-design roll system crossing seriously affects the plate shape and rolling mill performance.The problem of roll system crossing caused by liner wear was studied.The finite element model of rolling mill was established to analyze the relationship between roll system crossing and liner wear.The wear of liner was measured by laser tracker.The range of roll system crossing angle was calculated by considering the amount of stand clearance obtained by numerical simulation.The wear surface morphology of liner was observed and the wear mechanism was analyzed.The liner wear experiment was carried out to analyze the wear amount of the liner.Finally,based on the Archard wear theory,the prediction model of the cross angle of the roll system and the wear amount of the liner was established.Because there are more uncertain factors in the field production,the prediction model cannot be considered one by one.Therefore,the predicted value is smaller than the actual wear value,but it still has great reference.

Numerically investigating the crushing of sandstone by a tooth hob

To investigate the mechanical process that occurs between rocks and tooth hobs,the crushing of sandstone with a tooth hob was simulated using reconstructed multi-mineral mesoscopic numerical models of various grain-sized sandstone samples.When a piece of sandstone is crushed by the tooth of a hob rolling at a constant speed,the resultant reaction forces of the sandstone on the tooth first hinder and then contribute to the rolling of the hob.The absolute value of the longitudinal reaction force is significantly higher than that of the lateral reaction force.Because the tooth was subjected to reaction forces from the sandstone,forces and moments were applied to the hob in order to keep the hob rolling.The applied forces were equal in value and opposite in direction to the reaction forces of the sandstone on the tooth.Three typical curves of the work done by the applied forces and moment were obtained,and the contribution of the applied lateral force and moment to the total work done for crushing sandstones was variable;however,no work was done by the applied longitudinal force.Moreover,the applied longitudinal force and total work were positively correlated with the strength of sandstone samples.The total work,applied forces,and moment increased with the maximum penetration depth of the tooth in the sandstone.

Effect of a self-rotating oxygen lance system on mass transfer between slag and molten steel

To improve the efficiency of the steelmaking process,a system of self-rotating lance was designed,and corresponding cold simulation mechanism was developed.The influence of the self-rotating lance on the mass transfer rate between slag and molten steel was investigated by comparing this novel system with the traditional oxygen lance.The results show that the self-rotating lance can stably rotate with a gas jet as the power source.The mass transfer rate increases with an increase in the top and bottom blow flow rates and with a decline in the lance position.Approximately 13.7% of the top blow flow rate is converted to stirring energy,which is approximately twice that of the traditional oxygen lance,and the mass transfer rate can increase by over 30%.Furthermore,the impact energy can be concentrated at different depths of the molten bath by adjusting the rotational speed.With the same energy density,the mass transfer rate produced by the self-rotating lance is higher;however,the influence of the energy density on the mass transfer rate is low when the rotational speed is 30-50 r/min.