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1
Humphrey, Quentin, Manoj Srinivasan, Syed T. Mubarrat, and Suman K. Chowdhury. "Development of a Full-body OpenSim Musculoskeletal Model Incorporating Head-mounted Virtual Reality Headset." Proceedings of the Human Factors and Ergonomics Society Annual Meeting 65, no. 1 (September 2021): 477–81. http://dx.doi.org/10.1177/1071181321651270.
Повний текст джерелаАнотація:
In this study, we developed and validated a full-body musculoskeletal model in OpenSim to estimate muscle and joint forces while performing various motor tasks using a virtual reality (VR) system. We compared the results from our developed full-body musculoskeletal model to those from previous studies by simulating kinematic and kinetic data of participants performing pick-and-place lifting tasks using with and without a physically interactive VR system. Results showed that scaling errors between the two environments are comparable, while the overall errors were consistent with previous studies. Overall, the results from the inverse dynamic simulations showed the promise of our developed OpenSim models in determining potential intervention or prevention strategies to reduce the musculoskeletal injury incidences while simulating human-device interaction tasks.
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Vavalle, Nicholas A., A. Bradley Thompson, Ashley R. Hayes, Daniel P. Moreno, Joel D. Stitzel, and F. Scott Gayzik. "Investigation of the Mass Distribution of a Detailed Seated Male Finite Element Model." Journal of Applied Biomechanics 30, no. 3 (June 2014): 471–76. http://dx.doi.org/10.1123/jab.2013-0007.
Повний текст джерелаАнотація:
Accurate mass distribution in computational human body models is essential for proper kinematic and kinetic simulations. The purpose of this study was to investigate the mass distribution of a 50th percentile male (M50) full body finite element model (FEM) in the seated position. The FEM was partitioned into 10 segments, using segment planes constructed from bony landmarks per the methods described in previous research studies. Body segment masses and centers of gravity (CGs) of the FEM were compared with values found from these studies, which unlike the present work assumed homogeneous body density. Segment masses compared well to literature while CGs showed an average deviation of 6.0% to 7.0% when normalized by regional characteristic lengths. The discrete mass distribution of the FEM appears to affect the mass and CGs of some segments, particularly those with low-density soft tissues. The locations of the segment CGs are provided in local coordinate systems, thus facilitating comparison with other full body FEMs and human surrogates. The model provides insights into the effects of inhomogeneous mass on the location of body segment CGs.
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Takei, Yoshiaki. "Three-Dimensional Analysis of Handspring with Full Turn Vault: Deterministic Model, Coaches' Beliefs, and Judges' Scores." Journal of Applied Biomechanics 14, no. 2 (May 1998): 190–210. http://dx.doi.org/10.1123/jab.14.2.190.
Повний текст джерелаАнотація:
The purpose of the study was to identify mechanical variables that govern successful performance of the handspring with full turn vault. Subjects were 67 male gymnasts from 25 countries performing the vault during the 1992 Olympic Games. The vaults were filmed by two 16-mm Locam II DC cameras operating at 100 Hz. Approximately 80 frames per subject were digitized for each camera view. Direct linear transformation (DLT) was used to calculate the 3-D coordinates of the digitized body points. The method of Hay and Reid (1988) was used to develop a theoretical model to identify the mechanical variables that determine linear and angular motions of the vault. Significant correlations (p< .005) indicated that the following were important determinants for success: large horizontal velocity, large horizontal kinetic energy term, and overall translational kinetic energy term at takeoff from the board; short duration, small vertical displacement of the center of gravity (CG), and small somersaulting angular distance of preflight; large vertical velocity and large vertical kinetic energy term at takeoff from the horse; and large "amplitude of postflight," that is, large horizontal and vertical displacements of CG and long duration of flight; great height of CG during the second quarter-tum in postflight; and small point deduction for landing.
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Skublewska-Paszkowska, Maria, Pawel Powroznik, Jakub Smolka, Marek Milosz, Edyta Lukasik, Dilbar Mukhamedova, and Elzbieta Milosz. "Methodology of 3D Scanning of Intangible Cultural Heritage—The Example of Lazgi Dance." Applied Sciences 11, no. 23 (December 6, 2021): 11568. http://dx.doi.org/10.3390/app112311568.
Повний текст джерелаАнотація:
Traditional dance is one of the key elements of Intangible Culture Heritage (ICH). Many scientific papers concern analysis of dance sequences, classification and recognition of movements, making ICH data public, creating and visualising 3D models or software solutions for learning folklore dances. These works make it possible to preserve this disappearing art. The aim of this article is to propose a methodology for scanning folklore dances. The methodology was developed on the basis of capturing 3D data via an optical motion capture system with a full body Plug-in Gait model that allows for kinematic and kinetic analysis of motion sequences. An additional element of this research was the development of a hand model with which it is possible to precisely analyse the fingers, which play a significant role in many dances. The present methodology was verified on the basis of the Lazgi dance, included in the UNESCO ICH list. The obtained results of movement biomechanics for the dance sequence and the angles of the fingers indicate that it is universal and can be applied to dances that involve the upper and lower body parts, including hand movements.
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Oh, Jeonghoon, Moataz Eltoukhy, Christopher Kuenze, Michael S. Andersen, and Joseph F. Signorile. "Comparison of predicted kinetic variables between Parkinson’s disease patients and healthy age-matched control using a depth sensor-driven full-body musculoskeletal model." Gait & Posture 76 (February 2020): 151–56. http://dx.doi.org/10.1016/j.gaitpost.2019.11.011.
Повний текст джерела
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Uyulan, Çağlar, and Batuhan İpek. "Watt Six-Bar Compliant Mechanism Analysis Based on Kinematic and Dynamic Responses." Scientific Research Communications 1, no. 1 (July 29, 2021): 1–25. http://dx.doi.org/10.52460/src.2021.002.
Повний текст джерелаАнотація:
In this study, a complete guide to kinematic and kinetic analyses of a Watt type six-bar compliant mechanism is conducted incorporating the flexible buckling of the initially straight element. In the analysis procedure, the hybrid utilization of the pseudo-rigid-body model (PRBM) and the nonlinear elastic theory of beam buckling is presented. This partially compliant mechanism comprises three rigid links and two flexible links. The kinematic analyses of the mechanisms are done by using the vector loop closure equations, the PRBM of a large deflection cantilever beam, and derivation of nonlinear algebraic equations considering the quasi-static equilibrium and load-deflection curve of the flexible parts. Each of the elastic parts makes up a buckling pinned-pinned flexible Euler beam. The vector loop equations are combined with Newton-Euler dynamic formulations to provide the simultaneous constraint matrix. After these operations, the full mechanism is simulated to get both accelerations and forces for each time step. Finally, the design method is validated through experimental results. The findings derived from the combination of buckling elastica solution and PRBM approach enable the analysis of Watt's six-bar compliant mechanism.
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Haug, Espen Gaarder. "New full relativistic escape velocity and new Hubble related equation for the universe." Physics Essays 34, no. 4 (December 25, 2021): 502–14. http://dx.doi.org/10.4006/0836-1398-34.4.502.
Повний текст джерелаАнотація:
The escape velocity derived from general relativity coincides with the Newtonian one. However, the Newtonian escape velocity can only be a good approximation when v ≪ c is sufficient to break free of the gravitational field of a massive body, as it ignores higher-order terms of the relativistic kinetic energy Taylor series expansion. Consequently, it does not work for a gravitational body with a radius at which v is close to c such as a black hole. To address this problem, we revisit the concept of relativistic mass, abandoned by Einstein, and derive what we call a full relativistic escape velocity. This approach leads to a new escape radius, where ve = c equal to a half of the Schwarzschild radius. Furthermore, we show that one can derive the Friedmann equation for a critical universe from the escape velocity formula from general relativity theory. We also derive a new equation for a flat universe based on our full relativistic escape velocity formula. Our alternative to the Friedmann formula predicts exactly twice the mass density in our (critical) universe as the Friedmann equation after it is calibrated to the observed cosmological redshift. Our full relativistic escape velocity formula also appears more consistent with the uniqueness of the Planck mass (particle) than the general relativity theory: whereas the general relativity theory predicts an escape velocity above c for the Planck mass at a radius equal to the Planck length, our model predicts an escape velocity c in this case.
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Quental, C., J. Folgado, J. Ambrósio, and MT Silva. "A simple controller to overcome the lack of correlation between forward and inverse dynamic analysis of human motion tasks." Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics 230, no. 4 (August 3, 2016): 350–67. http://dx.doi.org/10.1177/1464419315608336.
Повний текст джерелаАнотація:
The majority of biomechanical analyses of human motions, including those with musculoskeletal models, use inverse dynamic approaches due to its ability to deal with experimentally acquired kinematic and kinetic data. Yet, a forward dynamic approach can be more powerful and provide better insights on the transmission of forces in the internal biomechanical systems and structures of the human body. Although both approaches may use the same biomechanical model the results achieved do not necessarily correlate with each other. The aim of this study is to demonstrate the source of the lack of correlation between inverse and forward dynamics methodologies providing, in the process, insights on how to overcome such differences. Two types of problems involving the biomechanics of the spatial human motion are used to evaluate the correlation between the forward and inverse dynamic approaches: a gait analysis of a deterministic biomechanical model of the lower limbs, and, a full musculoskeletal model of the upper limb, which is characterised by the solution of a redundant muscle force sharing problem. For that purpose, an inverse dynamic model is applied to estimate the forces responsible for two experimentally acquired motions that are, afterwards, given as input to the forward dynamics model, which is used, in turn, to compute the kinematics of the biomechanical model. The comparison between the reference kinematics, acquired experimentally, and that resulting from the forward dynamic analysis supports that a lack of correlation between the inverse and forward dynamic analysis is always observed. It is proposed here, and demonstrated, that a controller implemented in a feedback loop is able to enhance numerical stability of the forward dynamics solution, leading to the ability of the forward dynamics approach to successfully simulate the acquired motions.
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Xie, Suchao, Weilin Yang, and Ping Xu. "Simulation Analysis of a Multiple-Vehicle, High-Speed Train Collision Using a Simplified Model." Shock and Vibration 2018 (2018): 1–11. http://dx.doi.org/10.1155/2018/9504141.
Повний текст джерелаАнотація:
To solve the problems associated with multiple-vehicle simulations of railway vehicles including large scale modelling, long computing time, low analysis efficiency, need for high performance computing, and large storage space, the middle part of the train where no plastic deformation occurs in the vehicle body was simplified using mass and beam elements. Comparative analysis of the collisions between a single railway vehicle (including head and intermediate vehicles before, and after, simplification) and a rigid wall showed that variations in impact kinetic energy, internal energy, and impact force (after simplification) are consistent with those of the unsimplified model. Meanwhile, the finite element model of a whole high-speed train was assembled based on the simplified single-vehicle model. The numbers of nodes and elements in the simplified finite element model of the whole train were 63.4% and 61.6%, respectively, compared to those of the unsimplified model. The simplified whole train model using the above method was more accurate than the multibody model. In comparison to the full-size finite element model, it is more specific, had more rapid computational speed, and saved a large amount of computational power and storage space. Finally, the velocity and acceleration data for every car were discussed through the analysis of the collision between two simplified trains at various speeds.
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Wang, Chenyan, Xiaona Li, Yuan Guo, Weijin Du, Hongmei Guo, and Weiyi Chen. "The Kinematic and Kinetic Responses of the Trunk and Lower Extremity Joints during Walking with and without the Spinal Orthosis." International Journal of Environmental Research and Public Health 19, no. 11 (June 6, 2022): 6952. http://dx.doi.org/10.3390/ijerph19116952.
Повний текст джерелаАнотація:
Spinal orthoses are an effective option for restoring the spine to its original position and controlling poor posture. However, the effects of poor posture and spinal orthoses on the kinematics and kinetics of trunk and lower extremity joints remain unclear. A six-camera Vicon motion capture system and two AMTI force plates were employed to collect gait parameters, including joint angle (spine, thorax, hip, knee, and ankle), range of motion (ROM), and ground reaction forces (GRFs). Furthermore, joint moments and joint reaction forces (JRFs) were calculated using a full-body musculoskeletal model in OpenSim. One-way repeated-measures ANOVA (p < 0.05) was used to compare significant differences among three trial conditions. These three conditions were walking in a normal posture, poor posture, and spinal orthosis. The results showed that spine ROM in the coronal and transverse plane was significantly lower when walking with a spinal orthosis compared to walking in normal and poor posture (p < 0.05). Compared to normal posture, the lumbar moments and back compressive forces were significantly increased when walking in poor posture (p < 0.05). However, when walking with a spinal orthosis, there was a significant decrease in trunk moments and reaction forces compared to walking in poor posture (p < 0.05). Individuals with poor posture could potentially induce instability and disorders, as evidenced by an increase in trunk moments and JRF compared to the normal posture. Spinal orthosis not only restricts spine ROM but also reduces the load on the spine and thus increases balance and stability.
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Wang, Chenyan, Xiaona Li, Yuan Guo, Weijin Du, Hongmei Guo, and Weiyi Chen. "The Kinematic and Kinetic Responses of the Trunk and Lower Extremity Joints during Walking with and without the Spinal Orthosis." International Journal of Environmental Research and Public Health 19, no. 11 (June 6, 2022): 6952. http://dx.doi.org/10.3390/ijerph19116952.
Повний текст джерелаАнотація:
Spinal orthoses are an effective option for restoring the spine to its original position and controlling poor posture. However, the effects of poor posture and spinal orthoses on the kinematics and kinetics of trunk and lower extremity joints remain unclear. A six-camera Vicon motion capture system and two AMTI force plates were employed to collect gait parameters, including joint angle (spine, thorax, hip, knee, and ankle), range of motion (ROM), and ground reaction forces (GRFs). Furthermore, joint moments and joint reaction forces (JRFs) were calculated using a full-body musculoskeletal model in OpenSim. One-way repeated-measures ANOVA (p < 0.05) was used to compare significant differences among three trial conditions. These three conditions were walking in a normal posture, poor posture, and spinal orthosis. The results showed that spine ROM in the coronal and transverse plane was significantly lower when walking with a spinal orthosis compared to walking in normal and poor posture (p < 0.05). Compared to normal posture, the lumbar moments and back compressive forces were significantly increased when walking in poor posture (p < 0.05). However, when walking with a spinal orthosis, there was a significant decrease in trunk moments and reaction forces compared to walking in poor posture (p < 0.05). Individuals with poor posture could potentially induce instability and disorders, as evidenced by an increase in trunk moments and JRF compared to the normal posture. Spinal orthosis not only restricts spine ROM but also reduces the load on the spine and thus increases balance and stability.
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Nicholson, Kristen F., Gary S. Collins, Brian R. Waterman, and Garrett S. Bullock. "Machine Learning and Statistical Prediction of Pitching Arm Kinetics." American Journal of Sports Medicine 50, no. 1 (November 15, 2021): 238–47. http://dx.doi.org/10.1177/03635465211054506.
Повний текст джерелаАнотація:
Background: Over the past decade, research has attempted to elucidate the cause of throwing-related injuries in the baseball athlete. However, when considering the entire kinetic chain, full body mechanics, and pitching cycle sequencing, there are hundreds of variables that could influence throwing arm health, and there is a lack of quality investigations evaluating the relationship and influence of multiple variables on arm stress. Purpose: To identify which variables have the most influence on elbow valgus torque and shoulder distraction force using a statistical model and a machine learning approach. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A retrospective review was performed on baseball pitchers who underwent biomechanical evaluation at the university biomechanics laboratory. Regression models and 4 machine learning models were created for both elbow valgus torque and shoulder distraction force. All models utilized the same predictor variables, which included pitch velocity and 17 pitching mechanics. Results: The analysis included a total of 168 high school and collegiate pitchers with a mean age of 16.7 years (SD, 3.2 years) and BMI of 24.4 (SD, 1.2). For both elbow valgus torque and shoulder distraction force, the gradient boosting machine models demonstrated the smallest root mean square errors and the most precise calibrations compared with all other models. The gradient boosting model for elbow valgus torque reported the highest influence for pitch velocity (relative influence, 28.4), with 5 mechanical variables also having significant influence. The gradient boosting model for shoulder distraction force reported the highest influence for pitch velocity (relative influence, 20.4), with 6 mechanical variables also having significant influence. Conclusion: The gradient boosting machine learning model demonstrated the best overall predictive performance for both elbow valgus torque and shoulder distraction force. Pitch velocity was the most influential variable in both models. However, both models also revealed that pitching mechanics, including maximum humeral rotation velocity, shoulder abduction at foot strike, and maximum shoulder external rotation, significantly influenced both elbow and shoulder stress. Clinical Relevance: The results of this study can be used to inform players, coaches, and clinicians on specific mechanical variables that may be optimized to mitigate elbow or shoulder stress that could lead to throwing-related injury.
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Revak, Andrew, Keith Diers, Thomas W. Kernozek, Naghmeh Gheidi, and Christina Olbrantz. "Achilles Tendon Loading During Heel-Raising and -Lowering Exercises." Journal of Athletic Training 52, no. 2 (February 1, 2017): 89–96. http://dx.doi.org/10.4085/1062-6050-52.1.04.
Повний текст джерелаАнотація:
Context: Achilles tendinopathies are common injuries during sport participation, although men are more prone to Achilles tendon injuries than women. Heel-raising and -lowering exercises are typically suggested for Achilles tendon rehabilitation. Objective: To compare the estimated Achilles tendon loading variables and the ankle range of motion (ROM) using a musculoskeletal model during commonly performed heel-raising and -lowering exercises. Design: Controlled laboratory study. Setting: University biomechanics laboratory. Patients or Other Participants: Twenty-one healthy men (age = 21.59 ± 1.92 years, height = 178.22 ± 8.02 cm, mass = 75.81 ± 11.24 kg). Intervention(s): Each participant completed 4 exercises: seated heel raising and lowering, bilateral standing heel raising and lowering, bilateral heel raising and unilateral lowering, and unilateral heel raising and lowering. Main Outcome Measure(s): A repeated-measures multivariate analysis of variance (α = .05) was used to compare Achilles tendon stress, force, and strain and ankle ROM for each exercise. Kinematic data were recorded at 180 Hz with 15 motion-analysis cameras synchronized with kinetic data collected from a force platform sampled at 1800 Hz. These data were then entered in a musculoskeletal model to estimate force in the triceps surae. For each participant, we determined Achilles tendon stress by measuring cross-sectional images using ultrasound. Results: Peak Achilles tendon loading was lowest when performing the seated heel-raising and -lowering exercise and highest when performing the unilateral heel-raising and -lowering exercise. Loading was greater for the unilateral exercise or portions of the exercise that were performed unilaterally. Conclusions: Bilateral and seated exercises with less weight-bearing force resulted in less Achilles tendon loading. These exercises may serve as progressions during the rehabilitation process before full-body weight-bearing, unilateral exercises are allowed. Ankle ROM did not follow the same order as loading and may need additional monitoring or instruction during rehabilitation.
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Shan, Gongbing, Peter Visentin, and Arlan Schultz. "Multidimensional Signal Analysis as a Means of Better Understanding Factors Associated with Repetitive Use in Violin Performance." Medical Problems of Performing Artists 19, no. 3 (September 1, 2004): 129–39. http://dx.doi.org/10.21091/mppa.2004.3022.
Повний текст джерелаАнотація:
Multidimensional signal analysis (MSA) involves the coordination and correlation of data gathered by multiple analytic techniques. For complex biosystems, MSA provides a means to investigate better aspects of the system that cannot be understood easily using a single method. This is clearly the case for repetitive use injuries, also commonly referred to as overuse syndrome. Injuries from overuse syndrome are the result of deliberate physical behaviors. They typically are investigated through injury-site examinations, statistical or epidemiologic studies, and observation of the behaviors associated with the injury. Diverse methods often must be used to evaluate a patient because individually they provide only partial information relating to the etiology. The use of MSA permits the integration of multiple observational perspectives, generally creating a more holistic view. Using MSA, accurate external description of the movements thought to cause injury can be linked with internal physiologic conditions. Because physical work causes observed damage in overuse syndrome patients, a full examination of internal loading and muscle activity provides one possibility for understanding the evolutionary nature of these pathologies. Kinematic description, internal load analysis, electromyography, and biomechanical modeling are complementary methods used for MSA in this study. In the current study, a nine-camera ViCON v8i system was used to capture three-dimensional body kinematics as input for inverse dynamic modeling. Electromyography (Noraxon; 8-channel, wireless) was measured and synchronized to the model, permitting the correlation of joint moments and selected muscle activity. Results reveal clear relationships between muscle activity and physiologic loading for a variety of bowing speeds, strong interaction among muscles and groups of muscles, and changes in motor control at varying speeds. Additionally, load levels and work patterns are quantitatively established, and evidence is found to support a three-phase division of motor control based on speed: (1) increasing physical effort, (2) optimization, and (3) approaching physiologic limits. Combined with previous kinematic, kinetic, and statistical studies, the current study illuminates the relative risks of static versus dynamic loading, and provides perspective on the working patterns of muscles throughout the kinematic chain of the arms and torso during violin performance. Most importantly, this study begins the process of establishing MSA as a means of gleaning a greater overall view from the separate observational perspectives provided by multiple assessment methods used to examine performing artists’ injuries. This is the first such study for violin performance; an activity highly correlated with overuse syndrome.
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Simon, S. "Real-time 3-D hybrid simulation of Titan's plasma interaction during a solar wind excursion." Annales Geophysicae 27, no. 9 (September 1, 2009): 3349–65. http://dx.doi.org/10.5194/angeo-27-3349-2009.
Повний текст джерелаАнотація:
Abstract. The plasma environment of Saturn's largest satellite Titan is known to be highly variable. Since Titan's orbit is located within the outer magnetosphere of Saturn, the moon can leave the region dominated by the magnetic field of its parent body in times of high solar wind dynamic pressure and interact with the thermalized magnetosheath plasma or even with the unshocked solar wind. By applying a three-dimensional hybrid simulation code (kinetic description of ions, fluid electrons), we study in real-time the transition that Titan's plasma environment undergoes when the moon leaves Saturn's magnetosphere and enters the supermagnetosonic solar wind. In the simulation, the transition between both plasma regimes is mimicked by a reversal of the magnetic field direction as well as a change in the composition and temperature of the impinging plasma flow. When the satellite enters the solar wind, the magnetic draping pattern in its vicinity is reconfigured due to reconnection, with the characteristic time scale of this process being determined by the convection of the field lines in the undisturbed plasma flow at the flanks of the interaction region. The build-up of a bow shock ahead of Titan takes place on a typical time scale of a few minutes as well. We also analyze the erosion of the newly formed shock front upstream of Titan that commences when the moon re-enters the submagnetosonic plasma regime of Saturn's magnetosphere. Although the model presented here is far from governing the full complexity of Titan's plasma interaction during a solar wind excursion, the simulation provides important insights into general plasma-physical processes associated with such a disruptive change of the upstream flow conditions.
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Modares Sabzevari, Mohammad Hasan, Mehrdad Anbarian, Mohammad Reza Safari, Farhad Tabatabai, and MohammadJavad Razi. "Biomechanical Analysis of the Influence of SACH Foot and Dynamic-Response Foot in Individual With Unilateral Transtibial Amputee During Running." Journal of Rehabilitation 23, no. 1 (April 1, 2022): 0. http://dx.doi.org/10.32598/rj.23.1.3317.1.
Повний текст джерелаАнотація:
Objective: Amputation of the lower limb due to loss of part of the musculoskeletal structure reduces performance and increases injury during locomotion. The effect of various types of prosthetic feet has been analyzed in several studies during running. The purpose of this study was a biomechanical analysis of the influence of SACH and Dynamic-Response foot on several kinetic variables in the stance phase of running in individuals with unilateral transtibial amputation. Materials & Methods: In this semi-experimental study, 8 left foot transtibial amputees were included in this study using an available or easy sampling method. The target population was unilateral transtibial amputees who were able to run and the available population included left transtibial amputees who were referred to Kosar Rehabilitation Center in Tehran from 2008 to 2012. To adapt to the foot, each foot was used by the subjects for at least one week before the experiment. All subjects participated in 3 running evaluation sessions; 1 session involving the use of their own foot (familiarization session), 1 session involving the use of SACH foot, and 1 session involving the use of Dynamic foot. Only data from the 2 last sessions were used to compare both feet. Each subject runs in 12-meter walkway 3 times at a speed of 2.5 meters per second. The same running speed was chosen for the comparability of kinetic variables. Sport shoes were used to bring the test conditions closer to the actual running conditions. In each session, 3 successful trials were performed so that the foot was in full and perfect contact with the force plate. Kistler force plate and three-dimensional motion analysis Vicon system were used to collect kinetic and kinematic data, respectively. The motion and the force plate data were sampled simultaneously at 200 and 1000 Hz, respectively. The trajectories of the markers and analog data were filtered using the predicted mean square error adaptive filter in version 1.7 of the Vicon software package. The Kinetic variables were generated using the dynamic model of the Vicon Plug-in-Gait. The vertical ground reaction force was normalized for body weight. In the present study, 5 variables were selected for biomechanical analysis of feet. The maximum vertical ground reaction force, power, spring efficiency, ankle moments at the amputated leg, and the symmetry ratio (percentage) of the maximum vertical ground reaction force between the amputated leg and the intact leg were calculated. All values in each trial were averaged for each subject with each foot. A paired t-test and a Wilcoxon test were used to analyze the data based on normality (P ≤0.05). Results: In examining the normality of the data distribution, the results showed that the data of maximum power absorption of the ankle with the SACH foot and the maximum power absorption of the hip with the Dynamic-Response foot did not have a normal distribution and other variables had a normal distribution. The results of paired t-test and Wilcoxon showed that Spring Efficiency and Maximum Plantar Flexion were significantly different between the SACH and Dynamic-Response feet (P ≤0.05). The Spring Efficiency was greater with Dynamic-Response foot than the SACH foot (P =0.05), although the Maximum Plantar Flexion with the SACH foot was greater than Dynamic-Response foot (P =0.05). While there is no statistical difference between the maximum vertical ground reaction force, maximum power absorption and generation in the ankle, maximum power absorption and generation in the knee, maximum power absorption and generation in the hip, maximum dorsiflexion moment, and the symmetry ratio (percentage) of the maximum vertical ground reaction force between the amputated leg and the intact leg. Conclusion: The results of the study showed that the spring efficiency with Dynamic-Response foot was greater than SACH foot and closing to the spring efficiency of a normal foot. With this perspective, the Dynamic-Response foot has more natural performance than the SACH foot.
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Gams, Andrej, Jesse van den Kieboom, Florin Dzeladini, Aleš Ude, and Auke Jan Ijspeert. "Real-time full body motion imitation on the COMAN humanoid robot." Robotica 33, no. 5 (June 20, 2014): 1049–61. http://dx.doi.org/10.1017/s0263574714001477.
Повний текст джерелаАнотація:
SUMMARYOn-line full body imitation with a humanoid robot standing on its own two feet requires simultaneously maintaining the balance and imitating the motion of the demonstrator. In this paper we present a method that allows real-time motion imitation while maintaining stability, based on prioritized task control. We also describe a method of modified prioritized kinematic control that constrains the imitated motion to preserve stability only when the robot would tip over, but does not alter the motions otherwise. To cope with the passive compliance of the robot, we show how to model the estimation of the center of mass of the robot using support vector machines. In the paper we give detailed description of all steps of the algorithm, essentially providing a tutorial on the implementation of kinematic stability control. We present the results on a child-sized humanoid robot called Compliant Humanoid Platform or COMAN. Our implementation shows reactive and stable on-line motion imitation of the humanoid robot.
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Nora, Fernanda Grazielle da Silva Azevedo. "Equine biomechanical models for three-dimensional kinematics analysis: literature review/ Modelos biomecânicos equinos para análise de cinemática tridimensional: revisão de literatura." Brazilian Journal of Development 7, no. 11 (November 21, 2021): 106802–17. http://dx.doi.org/10.34117/bjdv7n11-357.
Повний текст джерелаАнотація:
Three-dimensional analysis in horses has been widely used in the past years due to technological advancement. With the objective of conducting a literature review of the applicability of existing evidence in horses of a biomechanical model focusing on three-dimensional kinematics and its production in Veterinary Medicine, we searched in the databases: ScienceDirect, SciELO and PubMed. To access them, using as key-words: "Three-dimensional kinematic model in equines", "equine kinematic analysis", "biomechanics of equine locomotion", "equine kinematic model". Selection criteria were papers published between: paper published between 1990 and 2020, in English, with free electronic access and in which characteristics of a three-dimensional kinematic model in horses were mentioned. Most studies were experimental, and population included both healthy horses and pathological ones. Three-dimensional kinematic model was used mainly to understand the analysed movement and using as model the full body. There is scientific evidence on the use of biomechanical models for three-dimensional kinematic analysis in horses published in the period studied, used by professionals in veterinary medicine. The objectives of using the model were specific to the type of movement or pathology of the horse and consistent with the characteristics of the studies.
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Tutsoy, Onder, Duygun Erol Barkana, and Sule Colak. "Learning to balance an NAO robot using reinforcement learning with symbolic inverse kinematic." Transactions of the Institute of Measurement and Control 39, no. 11 (April 29, 2016): 1735–48. http://dx.doi.org/10.1177/0142331216645176.
Повний текст джерелаАнотація:
An autonomous humanoid robot (HR) with learning and control algorithms is able to balance itself during sitting down, standing up, walking and running operations, as humans do. In this study, reinforcement learning (RL) with a complete symbolic inverse kinematic (IK) solution is developed to balance the full lower body of a three-dimensional (3D) NAO HR which has 12 degrees of freedom. The IK solution converts the lower body trajectories, which are learned by RL, into reference positions for the joints of the NAO robot. This reduces the dimensionality of the learning and control problems since the IK integrated with the RL eliminates the need to use whole HR states. The IK solution in 3D space takes into account not only the legs but also the full lower body; hence, it is possible to incorporate the effect of the foot and hip lengths on the IK solution. The accuracy and capability of following real joint states are evaluated in the simulation environment. MapleSim is used to model the full lower body, and the developed RL is combined with this model by utilizing Modelica and Maple software properties. The results of the simulation show that the value function is maximized, temporal difference error is reduced to zero, the lower body is stabilized at the upright, and the convergence speed of the RL is improved with use of the symbolic IK solution.
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Zhou, Guofeng, Junwoo Kim, and Yong Je Choi. "Jacobian approach to the kinestatic analysis of a full vehicle model with application to cornering motion analysis." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 234, no. 18 (April 7, 2020): 3543–59. http://dx.doi.org/10.1177/0954406220916504.
Повний текст джерелаАнотація:
The Jacobian approach to the kinestatic analysis of a planar suspension mechanism has been previously presented. In this paper, the theory is extended to three-dimensional kinestatic analysis by developing a full kinematic model and viewing it as a spatial parallel mechanism. The full kinematic model consists of two pairs of the front (double wishbone) and rear (multi-link) suspension mechanisms together with a newly developed ground-wheel contact model. The motion of each wheel of four suspension mechanisms is represented by the corresponding instantaneous screw at any instant. A vehicle is considered to be a 6-degrees-of-freedom spatial parallel mechanism whose vehicle body is supported by four serial kinematic chains. Each kinematic chain consists of a virtual instantaneous screw joint and a kinematic pair representing ground-wheel contact model. The kinestatic equation of the 6-degrees-of-freedom spatial parallel mechanism is derived in terms of the Jacobian. As an important application, a cornering motion of a vehicle is analysed under the assumption of steady-state cornering. A numerical example is presented to illustrate how to determine the optimal locations of strut springs for the least roll angle in cornering motion using the proposed method.
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Fakoorian, Seyed, Arash Roshanineshat, Poya Khalaf, Vahid Azimi, Dan Simon, and Elizabeth Hardin. "An Extensive Set of Kinematic and Kinetic Data for Individuals with Intact Limbs and Transfemoral Prosthesis Users." Applied Bionics and Biomechanics 2020 (November 9, 2020): 1–13. http://dx.doi.org/10.1155/2020/8864854.
Повний текст джерелаАнотація:
This paper introduces an extensive human motion data set for typical activities of daily living. These data are crucial for the design and control of prosthetic devices for transfemoral prosthesis users. This data set was collected from seven individuals, including five individuals with intact limbs and two transfemoral prosthesis users. These data include the following types of movements: (1) walking at three different speeds; (2) walking up and down a 5-degree ramp; (3) stepping up and down; (4) sitting down and standing up. We provide full-body marker trajectories and ground reaction forces (GRFs) as well as joint angles, joint velocities, joint torques, and joint powers. This data set is publicly available at the website referenced in this paper. Data from flexion and extension of the hip, knee, and ankle are presented in this paper. However, the data accompanying this paper (available on the internet) include 46 distinct measurements and can be useful for validating or generating mathematical models to simulate the gait of both transfemoral prosthesis users and individuals with intact legs.
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Kim, Seyoung, Fay B. Horak, Patricia Carlson-Kuhta, and Sukyung Park. "Postural Feedback Scaling Deficits in Parkinson's Disease." Journal of Neurophysiology 102, no. 5 (November 2009): 2910–20. http://dx.doi.org/10.1152/jn.00206.2009.
Повний текст джерелаАнотація:
Many differences in postural responses have been associated with age and Parkinson's disease (PD), but until now there has been no quantitative model to explain these differences. We developed a feedback control model of body dynamics that could reproduce the postural responses of young subjects, elderly subjects, and subjects with PD, and we investigated whether the postural impairments of subjects with PD can be described as an abnormal scaling of postural feedback gain. Feedback gains quantify how the nervous system generates compensatory joint torques based on kinematic responses. Seven subjects in each group experienced forward postural perturbations to seven different backward support surface translations ranging from 3- to 15-cm amplitudes and with a constant duration of 275 ms. Ground reaction forces and joint kinematics were measured to obtain joint torques from inverse dynamics. A full-state feedback controller with a two-segment body dynamic model was used to simulate joint kinematics and kinetics in response to perturbations. Results showed that all three subject groups gradually scaled postural feedback gains as a function of perturbation amplitudes, and the scaling started even before the maximum allowable ankle torque was reached. This result implies that the nervous system takes body dynamics into account and adjusts postural feedback gains to accommodate biomechanical constraints. PD subjects showed significantly smaller than normal ankle feedback gain with low scaling and larger hip feedback gain, which led to an early violation of the flat-foot constraint and unusually small (bradykinetic) postural responses. Our postural feedback control model quantitatively described the postural abnormality of the patients with PD as abnormal feedback gains and reduced ability to modify postural feedback gain with changes in postural challenge.
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VAHDAT, IMAN, MOHAMAD PARNIANPOUR, FARHAD TABATABAI GHOMSHEH, NIMA TOOSIZADEH, and ALI TANBAKOOSAZ. "COMPARING METHODS FOR 3D INVERSE DYNAMICS ANALYSIS OF SQUAT LIFTING USING A FULL BODY LINKED SEGMENT MODEL." Journal of Mechanics in Medicine and Biology 20, no. 03 (April 2020): 2050004. http://dx.doi.org/10.1142/s0219519420500049.
Повний текст джерелаАнотація:
Objective: The main objective of this study was to assess the accuracy of bottom-up solution for three-dimensional (3D) inverse dynamics analysis of squat lifting using a 3D full body linked segment model. Least squares solution was used in this study as reference for assessment of the accuracy of bottom-up solution. Findings of this study may clarify how much the bottom-up solution can be reliable for calculating the joint kinetics in 3D inverse dynamics problems. Methods: Ten healthy males volunteered to perform squat lifting of a box with a load of one-tenth of their body weights. The joint moments were calculated using 110 reflective passive markers (46 anatomical markers and 64 tracking markers) and a 3D full body linked segment model. Ground reaction forces and kinematics data were recorded using a Vicon system with two parallel Kistler force plates. Three-dimensional Newton–Euler equations of motion with bottom-up and least squares solutions were applied to calculate joint moments. The peak and mean values of the joint moments were determined to check the quantitative differences as well as the time-to-peak value of the moment curves was determined to check the temporal differences between the two inverse dynamics solutions. Results: Significant differences (all [Formula: see text]-values [Formula: see text]) between the two inverse dynamics solutions were detected for the peak values of the hip (right and left sides) and L5–S1 joint moments in the lateral anatomical direction as well significant differences (all [Formula: see text]-values [Formula: see text]) were detected for the peak and mean values of the L5–S1 joint moment in all anatomical directions. Moreover, small differences (all RMSEs [Formula: see text]%) were detected between the two inverse dynamic solutions for the calculated lower body joint moments. Conclusions: The findings of this study clarified the disadvantages of the straightforward solutions and demonstrated that the bottom-up solution may not be accurate for more distal measures from the force plate (for hip and S1–L5) but it may be accurate for more proximal joints (ankle and knee) in 3D inverse dynamics analysis.
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Zeng, Qi, and Li Feng Wang. "Energy Consumption Model and Simulation Test Based on Kinetics Principle." Applied Mechanics and Materials 556-562 (May 2014): 4601–5. http://dx.doi.org/10.4028/www.scientific.net/amm.556-562.4601.
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Sports education can not only help to improve students' body quality, and also student's development on the all-round and improvement. So the community has aroused wide concern on the training of student's physical ability, this article from theory of the introduction of sports ability to start, based on the analysis of what is the basis of sports ability, designing the questionnaire, analysising validity and reliability, and combining with the actual knowledge about sports teaching for college students, researching the purpose and motivation to participate in the physical training , analyzing the current situation of university sports teaching, so as to find out issues, constructing the school for student's training model of physical ability, for the purpose of guiding constantly innovation in college, constantly set the power of universities and social institutions to strengthen the teaching mode, the competition mode, interest model and the combination of the system model to realize efficient sports teaching, achieve a full range of to student's sports ability culture and make a comprehensive development.
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Cekus, Gnatowska, and Kwiatoń. "Impact of Wind on the Movement of the Load Carried by Rotary Crane." Applied Sciences 9, no. 18 (September 12, 2019): 3842. http://dx.doi.org/10.3390/app9183842.
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This paper considers the coupled kinematic and dynamic models of a mobile crane. A full description of boom and load movement has been provided as a response of the system to the influence of kinematic forces. The linear system model was treated as rigid, and the carried load as a nondeformed static body. To describe the position of said load, Bryant angles were used. The dynamic model includes the impact of external forces (wind pressure) while load carrying and positioning. Algorithm and calculation software were developed to enable dynamic phenomena analysis during both a work cycle and free movement of said load. The initial problem was solved by means of the ode45 calculation procedure in the Matlab software based on the Runge–Kutta 4th Order Method. The work presents exemplary results of load movement simulation with respect to various wind velocities, selected on the basis of guidelines from Poland’s standards regarding safe operation of mechanical equipment.
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Zhang, Zhao, Shiming Li, Bingjun Wan, Peter Visentin, Qinxian Jiang, Mary Dyck, Hua Li, and Gongbing Shan. "The Influence of X-Factor (Trunk Rotation) and Experience on the Quality of the Badminton Forehand Smash." Journal of Human Kinetics 53, no. 1 (December 1, 2016): 9–22. http://dx.doi.org/10.1515/hukin-2016-0006.
Повний текст джерелаАнотація:
AbstractNo existing studies of badminton technique have used full-body biomechanical modeling based on three-dimensional (3D) motion capture to quantify the kinematics of the sport. The purposes of the current study were to: 1) quantitatively describe kinematic characteristics of the forehand smash using a 15-segment, full-body biomechanical model, 2) examine and compare kinematic differences between novice and skilled players with a focus on trunk rotation (the X-factor), and 3) through this comparison, identify principal parameters that contributed to the quality of the skill. Together, these findings have the potential to assist coaches and players in the teaching and learning of the forehand smash. Twenty-four participants were divided into two groups (novice, n = 10 and skilled, n = 14). A 10-camera VICON MX40 motion capture system (200 frames/s) was used to quantify full-body kinematics, racket movement and the flight of the shuttlecock. Results confirmed that skilled players utilized more trunk rotation than novices. In two ways, trunk rotation (the X-factor) was shown to be vital for maximizing the release speed of the shuttlecock – an important measure of the quality of the forehand smash. First, more trunk rotation invoked greater lengthening in the pectoralis major (PM) during the preparation phase of the stroke which helped generate an explosive muscle contraction. Second, larger range of motion (ROM) induced by trunk rotation facilitated a whip-like (proximal to distal) control sequence among the body segments responsible for increasing racket speed. These results suggest that training intended to increase the efficacy of this skill needs to focus on how the X-factor is incorporated into the kinematic chain of the arm and the racket.
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Owen, J. Michael, Mallory E. DeCoster, Dawn M. Graninger, and Sabina D. Raducan. "Spacecraft Geometry Effects on Kinetic Impactor Missions." Planetary Science Journal 3, no. 9 (September 1, 2022): 218. http://dx.doi.org/10.3847/psj/ac8932.
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Abstract The DART (Double Asteroid Redirection Test) mission will impact a spacecraft on the secondary (Dimorphos) of the binary asteroid system Didymos in 2022 September, with the goal of altering the orbital period of Dimorphos about Didymos sufficiently to be observed from ground-based observations. Numerical impact modeling is a crucial component in understanding the outcome of the DART experiment, and while many have investigated the effects of target properties, such as material strength and porosity (which remain unknown), an often overlooked factor is the importance of accurately representing the spacecraft itself in such models. Most impact modeling to date has considered simple impactor geometries such as a solid uniform sphere, but in reality the spacecraft is a complex shape full of different components, open spaces, and thin walled structures. At a minimum, a simple solid representation underestimates the surface area of the impact: for a small body such as Dimorphos (approximately 160 m in diameter), the difference between a spacecraft spanning 20 m (including solar arrays) impacting and a sub-1 m idealized shape may be important. In this paper, we compare models impacting high-fidelity models of the spacecraft based on the CAD geometry with various simplified impactors, in order to assess the potential importance of this effect. We find that the difference between the simplest impactor geometries (such as a uniform sphere) and the real spacecraft is measurable, and has an interesting dependence on the material properties of the asteroid itself.
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Harborne, K. E., J. van de Sande, L. Cortese, C. Power, A. S. G. Robotham, C. D. P. Lagos та S. Croom. "Recovering λR and V/σ from seeing-dominated IFS data". Monthly Notices of the Royal Astronomical Society 497, № 2 (27 червня 2020): 2018–38. http://dx.doi.org/10.1093/mnras/staa1847.
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ABSTRACT Observers experience a series of limitations when measuring galaxy kinematics, such as variable seeing conditions and aperture size. These effects can be reduced using empirical corrections, but these equations are usually applicable within a restrictive set of boundary conditions (e.g. Sérsic indices within a given range) that can lead to biases when trying to compare measurements made across a full kinematic survey. In this work, we present new corrections for two widely used kinematic parameters, λR and V/σ, that are applicable across a broad range of galaxy shapes, measurement radii, and ellipticities. We take a series of mock observations of N-body galaxy models and use these to quantify the relationship between the observed kinematic parameters, structural properties, and different seeing conditions. Derived corrections are then tested using the full catalogue of galaxies, including hydrodynamic models from the eagle simulation. Our correction is most effective for regularly rotating systems, yet the kinematic parameters of all galaxies – fast, slow, and irregularly rotating systems – are recovered successfully. We find that λR is more easily corrected than V/σ, with relative deviations of 0.02 and 0.06 dex, respectively. The relationship between λR and V/σ, as described by the parameter κ, also has a minor dependence on seeing conditions. These corrections will be particularly useful for stellar kinematic measurements in current and future integral field spectroscopic surveys of galaxies.
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Kim, Youngouk, and Sewoong Jun. "A Human Half-Top Kinematic Motion Tracking System Based on Disparity Information of Stereo Camera." Advanced Materials Research 605-607 (December 2012): 1391–94. http://dx.doi.org/10.4028/www.scientific.net/amr.605-607.1391.
Повний текст джерелаАнотація:
This paper presents a new real-time system to acquire motion information of human articulated objects such as arm and head. The system does not need any marker or device to wear on human body and adopted stereo camera to obtain robust system against for illumination and complex background without position initialization of articulated objects. We present a solution to estimate self-occluded body objects when human model behaves normal action towards the camera. The main idea of the solution is to apply a component labeling techniques on sliced disparity map, and found the arm position when the arm is located in front of basis distance of body and we could also found arm location when the arm is located on the basis distance with Morphological methods. From this approach, we can obtain the full body shape considering self-occlusion. It is simple and fast in comparison with other methods which satisfy real-time performance and accuracy of object tracking at the same time.
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Weir, Gillian, Jacqueline Alderson, Natalie Smailes, Bruce Elliott, and Cyril Donnelly. "A Reliable Video-based ACL Injury Screening Tool for Female Team Sport Athletes." International Journal of Sports Medicine 40, no. 03 (January 10, 2019): 191–99. http://dx.doi.org/10.1055/a-0756-9659.
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AbstractThis study aimed to develop a 2-dimensional (2D) video screening tool capable of predicting an athlete’s peak 3-dimensional (3D) knee moments during unplanned sidestepping. 2D video-based kinematic measures were simultaneously captured with 3D peak knee moments for 30 female field hockey players (15 junior, 15 senior). Intra- and intertester repeatability of 2D kinematic measures was performed. Then, linear regression models were used to model 3D knee moments from 2D kinematic variables utilizing 80% of the sample (n=24). Regression equations were then validated on the remaining 20% of the sample (n=6). Angular 2D measures had good-excellent intra- (ICC=0.936–0.998) and intertester (ICC=0.662–0.949) reliability. Displacement measures had poor-excellent intra- (ICC=0.377–0.539) and inter-tester (ICC=0.219–0.869) reliability. Significant independent predictors of peak knee moments were dynamic knee valgus, knee flexion angle at foot strike, trunk flexion range of motion (ROM), trunk lateral flexion, hip abduction and knee flexion ROM (P<0.05). Regression equations generated from these models effectively predicted peak knee extension, valgus and internal rotation moments (i. e., were not different from measured values P>0.05, ES<0.4) in the 20% subsample. 2D video-based measurements of an athlete's full body kinematics during unplanned sidestepping provide a reliable, specific, sensitive and cost-effective means for screening female team sport athletes.
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Engin, Ali Erkan, and Shuenn-Muh Chen. "Kinematic and Passive Resistive Properties of Human Elbow Complex." Journal of Biomechanical Engineering 109, no. 4 (November 1, 1987): 318–23. http://dx.doi.org/10.1115/1.3138687.
Повний текст джерелаАнотація:
In recent years, owing to their versatility and reduced cost of operation, multisegmented mathematical models of the total human body have gained increased attention in gross biodynamic motion studies. This, in turn, has stimulated the need for a proper biomechanical data base for the major human articulating joints. The lack of such a database for the humero-elbow complex is the impetus for this study. The total angular range of motion permitted by the complex and the passive resistive properties beyond the full elbow extension were studied. Results obtained on ten normal male subjects were utilized to establish a statistical data base for the humero-elbow complex. Results are also expressed in functional expansion form suitable for incorporation into the existing multisegmented models.
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Wang, X. M., and M. L. Spaulding. "A Two-Dimensional Potential Flow Model of the Wave Field Generated by a Semisubmerged Body in Heaving Motion." Journal of Ship Research 32, no. 02 (June 1, 1988): 83–91. http://dx.doi.org/10.5957/jsr.1988.32.2.83.
Повний текст джерелаАнотація:
A two-dimensional potential flow model is formulated to predict the wave field and forces generated by a sere!submerged body in forced heaving motion. The potential flow problem is solved on a boundary fitted coordinate system that deforms in response to the motion of the free surface and the heaving body. The full nonlinear kinematic and dynamic boundary conditions are used at the free surface. The governing equations and associated boundary conditions are solved by a second-order finite-difference technique based on the modified Euler method for the time domain and a successive overrelaxation (SOR) procedure for the spatial domain. A series of sensitivity studies of grid size and resolution, time step, free surface and body grid redistribution schemes, convergence criteria, and free surface body boundary condition specification was performed to investigate the computational characteristics of the model. The model was applied to predict the forces generated by the forced oscillation of a U-shaped cylinder. Numerical model predictions are generally in good agreement with the available second-order theories for the first-order pressure and force coefficients, but clearly show that the third-order terms are larger than the second-order terms when nonlinearity becomes important in the dimensionless frequency range 1≤ Fr≤ 2. The model results are in good agreement with the available experimental data and confirm the importance of the third order terms.
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Bourgain, Maxime, Christophe Sauret, Grégoire Prum, Laura Valdes-Tamayo, Olivier Rouillon, Patricia Thoreux, and Philippe Rouch. "Effect of Horizontal Ground Reaction Forces during the Golf Swing: Implications for the Development of Technical Solutions of Golf Swing Analysis." Proceedings 49, no. 1 (June 15, 2020): 45. http://dx.doi.org/10.3390/proceedings2020049045.
Повний текст джерелаАнотація:
The swing is a key movement for golf. Its in-field performance could be estimated by embedded technologies, but often only vertical ground reaction forces (VGRF) are estimated. However, as the swing plane is inclined, horizontal ground reaction forces (HGRF) are expected to contribute to the increase of the club angular velocity. Thus, this study aimed at investigating the role of the HGRF during the golf swing. Twenty-eight golf players were recruited and performed 10 swings with their own driver club, in a motion analysis laboratory, equipped with a full body marker set. Ground reaction forces (GRF) were measured with force-plates. A multibody kinematic optimization was performed with a full body model to estimate the instantaneous location of the golfer’s center of mass (CoM). Moments created by the GRF at the CoM were investigated. Results showed that horizontal forces should not be neglected regarding to VGRF because of their lever arm. Analyzing golf swing with only VGRF appeared not enough and further technological developments are still needed to ecologically measure other components.
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Yang, Chin Tien, and J. S. T’ien. "Numerical Simulation of Combustion and Extinction of a Solid Cylinder in Low-Speed Cross Flow." Journal of Heat Transfer 120, no. 4 (November 1, 1998): 1055–63. http://dx.doi.org/10.1115/1.2825890.
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The combustion and extinction behavior of a diffusion flame around a solid fuel cylinder (PMMA) in low-speed forced flow in zero gravity was studied numerically using a quasi-steady gas phase model. This model includes two-dimensional continuity, full Navier Stokes’ momentum, energy, and species equations with a one-step overall chemical reaction and second-order finite-rate Arrhenius kinetics. Surface radiation and Arrhenius pyrolysis kinetics are included on the solid fuel surface description and a parameter Φ, representing the percentage of gas-phase conductive heat flux going into the solid, is introduced into the interfacial energy balance boundary condition to complete the description for the quasi-steady gas-phase system. The model was solved numerically using a body-fitted coordinate transformation and the SIMPLE algorithm. The effects of varying freestream velocity and Φ were studied. These parameters have a significant effect on the flame structure and extinction limits. Two flame modes were identified: envelope flame and wake flame. Two kinds of flammability limits were found: quenching at low-flow speeds due to radiative loss and blow-off at high flow speeds due to insufficient gas residence time. A flammability map was constructed showing the existence of maximum Φ above which the solid is not flammable at any freestream velocity.
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Simpson, Travis T., Susan L. Wiesner, and Bradford C. Bennett. "Dance Recognition System Using Lower Body Movement." Journal of Applied Biomechanics 30, no. 1 (February 2014): 147–53. http://dx.doi.org/10.1123/jab.2012-0248.
Повний текст джерелаАнотація:
The current means of locating specific movements in film necessitate hours of viewing, making the task of conducting research into movement characteristics and patterns tedious and difficult. This is particularly problematic for the research and analysis of complex movement systems such as sports and dance. While some systems have been developed to manually annotate film, to date no automated way of identifying complex, full body movement exists. With pattern recognition technology and knowledge of joint locations, automatically describing filmed movement using computer software is possible. This study used various forms of lower body kinematic analysis to identify codified dance movements. We created an algorithm that compares an unknown move with a specified start and stop against known dance moves. Our recognition method consists of classification and template correlation using a database of model moves. This system was optimized to include nearly 90 dance and Tai Chi Chuan movements, producing accurate name identification in over 97% of trials. In addition, the program had the capability to provide a kinematic description of either matched or unmatched moves obtained from classification recognition
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Yamashita, Takuma, Motoaki Niiyama, Kazuhiro Yasuda, and Yasushi Kino. "Four-body variational calculation of a hydrogen-like atom involving an excited muonic molecule." Journal of Physics: Conference Series 2207, no. 1 (March 1, 2022): 012035. http://dx.doi.org/10.1088/1742-6596/2207/1/012035.
Повний текст джерелаАнотація:
Abstract We report a four-body variational calculation of a hydrogen-like atom consisting of an excited muonic molecule consisting of d, t, and μ, and a ground state electron. Due to the compact size of the muonic molecule dtμ, it behaves as a quasi-nucleus for the electron; however, the system is actually a resonance state because the de-excitation energy of dtμ is sufficient to ionize the electron. We calculate resonance energy levels of the four-body system dtμe using a Gaussian expansion method and a stabilization method. Our best calculation results in a four-body energy of –100.159 88 a.u. which is in good agreement with the value estimated by the first order perturbation theory [Harston et al. Zeitschrift für Physik D 22, 635 (1992)]. We indicate that implementation of the electron-induced polarization of dtμ will be indispensable for the further precise determination of the resonance energy. The present result is the first step towards a full four-body calculation of the muonic molecule under the presence of the electron, which is of importance for development of a muon catalyzed fusion kinetics model.
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Bleibinhaus, Florian, and Stéphane Rondenay. "Effects of surface scattering in full-waveform inversion." GEOPHYSICS 74, no. 6 (November 2009): WCC69—WCC77. http://dx.doi.org/10.1190/1.3223315.
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In full-waveform inversion of seismic body waves, often the free surface is ignored on grounds of computational efficiency. A synthetic study was performed to investigate the effects of this simplification. In terms of size and frequency, the test model and data conform to a real long-offset survey of the upper crust across the San Andreas fault. Random fractal variations are superimposed on a background model with strong lateral and vertical velocity variations ranging from 1200 to 6800 m/s. Synthetic data were computed and inverted for this model and different topographies. A fully viscoelastic time-domain code was used to synthesize the seismograms, and a viscoacoustic frequency-domain code was utilized to invert them. The inversion was focused on early arrivals, which are dominated by P-waves but also contain strong P-Rayleigh wave conversions from the near-field of the receiver. Resulting waveform models show artifacts and a loss of resolution from neglecting the free surface in the inversion, but the inversions are stable, and they still improve the resolution of kinematic models. The extent of deterioration depends more on the subsurface than on the surface structure. Inversion results were improved at no additional expense by introducing a weak contrast along a staircase function above shots and receivers.
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Höhne, Thomas, and Sören Kliem. "Detailed Simulation of the Nominal Flow and Temperature Conditions in a Pre-Konvoi PWR Using Coupled CFD and Neutron Kinetics." Fluids 5, no. 3 (September 22, 2020): 161. http://dx.doi.org/10.3390/fluids5030161.
Повний текст джерелаАнотація:
The aim of the numerical study was the detection of possible vortices in the upper part of the core of a Pre-Konvoi Pressurized Water Reactor (PWR) which could lead to temperature cycling. In addition, the practical application of this Computational Fluid Dynamic (CFD) simulation exists in the full 3D analysis of the coolant flow behavior in the reactor pressure vessel of a nuclear PWR. It also helps to improve the design of future reactor types. Therefore, a CFD simulation of the flow conditions was carried out based on a complex 3D model. The geometry of the model includes the entire Reactor Pressure Vessel (RPV) plus all relevant internals. The core is modelled using the porous body approach, the different pressure losses along and transverse to the main flow direction were considered. The spacer-grid levels were taken into account to the extent that in these areas no cross-flow is possible. The calculation was carried out for nominal operating conditions, i.e., for full load operation. Furthermore, a prototypical End of Cycle (EOC) power distribution was assumed. For this, a power distribution was applied as obtained from a stationary full-core calculation with the 3D neutron kinetics code DYN3D. In order to be able to adequately reproduce flow vortexes, the calculation was performed transiently with suitable Detached Eddy Simulations (DES) turbulence models. The calculation showed fluctuating transverse flow in the upper part of the core, starting at the 8th spacer grid but also revealed that no large dominant vortices exists in this region. It seems that the core acts as a rectifier attenuating large-scale vortices. The analyses included several spacer grid levels in the core and showed that in some areas of the core cross-section an upward increasingly directed transversal flow to the outlet nozzle occurs. In other areas of the core cross-section, on the other hand, there is nearly any cross-flow. However, the following limitations of the model apply: In the model all fuel elements are treated identical and cross flows due to different axial pressure losses for different FA types cannot be displayed. The complex structure of the FAs (eg. flow vanes in spacer grids) could also influence the formation of large-scale vortices. Also, the possible influence of two-phase flows was not considered.
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Lee, S. H., U. K. Lee, and C. S. Han. "Enhancement of vehicle handling characteristics by suspension kinematic control." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 215, no. 2 (February 1, 2001): 197–216. http://dx.doi.org/10.1243/0954407011525584.
Повний текст джерелаАнотація:
In this paper, the enhancement of vehicle handling characteristics through the active kinematic control system (AKCS) is investigated. AKCS can improve the stability and ride comfort of a vehicle by automatically controlling suspension geometry in accordance with the running conditions of a vehicle. The variable roll centre suspension concept in a McPherson strut suspension is proposed, and lateral acceleration feedback control is derived to calculate the control input. The independent rear wheel steering system, which controls both rear wheels independently and actively, is also proposed. To achieve this, three suggested positions for controlling the suspension geometry are considered. The first position is between the mounting point of the lower arm of a McPherson front suspension and the vehicle body. The second position is between the mounting point of the strut and the vehicle body. The third position is between the mounting point of the lateral link of the multilink rear suspension and the vehicle body. In order to evaluate the handling performance, a 15 degrees of freedom full vehicle model is constructed using the commercial multibody analysis program ADAMS. The control inputs for integrated control of the front and rear suspensions are defined, and roll centre migration and vehicle behaviour are investigated. In step steering and double lane change manoeuvres, the simulation results demonstrate that integrated kinematic control can adjust the roll centre migration, by which the handling characteristics of the AKCS vehicle such as roll angle, lateral acceleration and yaw rate are much improved.
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Lee, U., and C. Han. "A suspension system with a variable roll centre for the improvement of vehicle handling characteristics." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 215, no. 6 (June 1, 2001): 677–96. http://dx.doi.org/10.1243/0954407011528266.
Повний текст джерелаАнотація:
In this paper, the improvement of vehicle handling characteristics using variable roll centre suspension (VRCS) is investigated. A vehicle with VRCS can improve stability and ride comfort by automatically controlling suspension geometry in accordance with the running conditions of the vehicle. To achieve this, a variable roll centre concept in the McPherson strut suspension system is suggested, while the two parts most sensitive for controlling the roll centre are suggested. One is between the vehicle body-side connecting portion of the lower arm and the vehicle body (control input, LCZ), and the other is between the vehicle body-side connecting portion of the strut and the vehicle body (control input, STY). Kinematic roll centre analysis, based on the analytic half-car model, shows that the use of two control inputs, LCZ and STY, can decrease migration of the roll centre and centre of gravity according to the side force. In order to quantify the relationship between roll centre and geometry control input and evaluate handling performance, a full vehicle model of 15 degrees of freedom (DOF) is constructed using multi-body dynamic analysis software, ADAMS. In step steering and double lane change manoeuvres, simulation results demonstrate that a vehicle with VRCS adjusts roll centre migration, and handling characteristics such as roll angle, lateral acceleration and yaw rate are much improved.
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Goulos, I., V. Pachidis, and P. Pilidis. "Lagrangian formulation for the rapid estimation of helicopter rotor blade vibration characteristics." Aeronautical Journal 118, no. 1206 (August 2014): 861–901. http://dx.doi.org/10.1017/s000192400000960x.
Повний текст джерелаАнотація:
Abstract This paper presents a numerical formulation targeting the rapid estimation of natural vibration characteristics of helicopter rotor blades. The proposed method is based on application of Lagrange’s equation of motion to the kinematics of blade flap/lag bending and torsion. Modal properties obtained from Bernoulli-Euler beam and classical torsional vibration theory, are utilised as assumed deformation functions in order to estimate the time variations of strain and kinetic energy for each degree of freedom. Integral expressions are derived, describing the generalised centrifugal force and torsional moment acting on the blade in terms of normal coordinates, for flap/lag transverse displacement and torsional deformation. Closed form expressions are provided for the direct analysis of hingeless, freely-hinged and spring-hinged articulated rotor blades. Results are presented in terms of natural frequencies and mode shapes for two small-scale rotor blade models. Extensive comparisons are carried out with experimental measurements and nonlinear finite element analysis. Predictions of resonant frequencies are also presented for two full-scale rotor blade models and the results are compared with established multi-body dynamics analysis methods. It is shown that, the proposed approach exhibits excellent numerical behaviour with low computational cost and definitive convergence characteristics. The comparisons suggest very good and in some cases excellent accuracy levels, especially considering the method’s simplicity, computational efficiency, and ease of implementation.
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Marsh, R. L. "Ontogenesis of contractile properties of skeletal muscle and sprint performance in the lizard Dipsosaurus dorsalis." Journal of Experimental Biology 137, no. 1 (July 1, 1988): 119–39. http://dx.doi.org/10.1242/jeb.137.1.119.
Повний текст джерелаАнотація:
Ontogenetic allometries of running performance in 3- to 4-m burst runs (sprints) and of the contractile properties of the fast-twitch, glycolytic region of the iliofibularis muscle (FG-IF) were measured in Dipsosaurus dorsalis. This iguanid lizard hatches at a body mass of about 4 g and reaches adult masses of 40–70 g. Running velocity was little influenced by changes in body mass during development. Stride frequency (f) declines ontogenetically and was proportional to body mass (Mb) to approximately the −0.2 power (determined by regression analysis). Stride length (Ls) appeared to be related to the allometry of hindlimb length (LHL); both Ls and LHL were proportional to about Mb0.28. Intrinsic shortening velocity of the FG-IF decreased only slightly with increasing body mass, and was consequently not proportional to f as has been assumed by various models of running dynamics. In contrast, twitch time lengthened markedly with increasing body mass, and the ratio of twitch time to stride time remained approximately constant. These results suggest that the intrinsic velocity of the muscles does not directly or solely determine maximal f, but instead limb kinematics are determined in part by other biomechanical constraints related to body dimensions. Further, the allometry of twitch kinetics supports the idea that the properties of the muscles are adjusted to allow ample time for full activation and deactivation within the biomechanically determined stride time.
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Hale, Melina E. "S- and C-start escape responses of the muskellunge (Esox masquinongy) require alternative neuromotor mechanisms." Journal of Experimental Biology 205, no. 14 (July 15, 2002): 2005–16. http://dx.doi.org/10.1242/jeb.205.14.2005.
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SUMMARYThe startle response is a model system for examining the neural basis of behavior because of its relatively simple neural circuit organization and kinematic pattern. In fishes, the two primary types of startle behavior differ in their initial movements. In the C-start type of startle, the fish bends into a C shape, while the S-start involves an S-shaped body bend. Although considerable research has focused on determining how the C-start is generated neurally, S-start neurobiology has not been examined. I quantify the kinematics and electromyographic patterns of the initial movements of the C-start and S-start behaviors of the muskellunge (Esox masquinongy)to test three hypotheses for how the S-start is generated. (i) The S-start is generated by the same motor neural circuit as the C-start, but passive bending of the tail causes the body to take on an S shape. (ii) The S-start is generated by the same motor neural circuit as undulatory swimming. (iii) The S-start is generated by an independent neural mechanism from that used either in the C-start or in undulatory swimming. Results from kinematics and muscle activity patterns support the third hypothesis. In the muskellunge, the S-start is a high-performance startle behavior with peak angular velocity and peak angular acceleration of its initial bending comparable with those of the C-start and higher than would be expected for undulatory swimming. The S-start motor pattern, however, is distinct from the C-start motor pattern in having simultaneous muscle activity anteriorly on one side of the body and posteriorly on the opposite side. In contrast, the C-start is characterized by simultaneous unilateral muscle activity along the full length of the body. Alternative models are proposed for S-start neural circuit organization involving reticulospinal and local control of muscle activity.
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Klubnichkin, Vladislav, Evgeniy Klubnichkin, Aleksey Gorbunov, and Denis Druchinin. "DEVELOPMENT OF THE FORWARDER ARTICULATION JOINT." Forestry Engineering Journal 10, no. 4 (January 19, 2021): 217–26. http://dx.doi.org/10.34220/issn.2222-7962/2020.4/18.
Повний текст джерелаАнотація:
The article presents a structural hydraulic diagram of the steering system of the developed forwarder. The main components that make up the steering of the machine are described. The scheme of the articulated joint was selected and the radius and the corridor of the forwarder's turn were determined. In the work, a kinematic analysis of the articulated joint of the forwarder was carried out, which is the determination of the limiting angles of folding of the articulation unit and the stroke of the hydraulic power cylinders according to the developed electronic solid models. The moment of resistance required to fold the car of full weight in place on a solid supporting surface with a high coefficient of adhesion, taking into account the interaction of tires with the supporting surface, was determined using the semi-empirical model of Packa MF-Tire 6.1. Model parameters for tire 750/55-26.5. A dynamic model of a forwarder has been created with the following features: all links of the dynamic system are absolutely rigid; all wheels are not braked and rotate; there is no friction in the hinges; the load (assortments) is modeled absolutely rigid by a single body; the simulation was done for a fully laden forwarder; axle differentials are not locked (free). The vertical loads in the contact patch of the front and rear axles, as well as lateral reactions in the contact patch of the front and rear axles are presented
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Sormani, Mattia C., Jason L. Sanders, Tobias K. Fritz, Leigh C. Smith, Ortwin Gerhard, Rainer Schödel, John Magorrian, et al. "Self-consistent modelling of the Milky Way’s nuclear stellar disc." Monthly Notices of the Royal Astronomical Society 512, no. 2 (March 22, 2022): 1857–84. http://dx.doi.org/10.1093/mnras/stac639.
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Abstract The nuclear stellar disc (NSD) is a flattened high-density stellar structure that dominates the gravitational field of the Milky Way at Galactocentric radius $30\, {\rm pc}\lesssim R\lesssim 300\, {\rm pc}$. We construct axisymmetric self-consistent equilibrium dynamical models of the NSD in which the distribution function is an analytic function of the action variables. We fit the models to the normalized kinematic distributions (line-of-sight velocities + VIRAC2 proper motions) of stars in the NSD survey of Fritz et al., taking the foreground contamination due to the Galactic Bar explicitly into account using an N-body model. The posterior marginalized probability distributions give a total mass of $M_{\rm NSD} = 10.5^{+1.1}_{-1.0} \times 10^8 \, \, \rm M_\odot$, roughly exponential radial and vertical scale lengths of $R_{\rm disc} = 88.6^{+9.2}_{-6.9} \, {\rm pc}$ and $H_{\rm disc}=28.4^{+5.5}_{-5.5} \, {\rm pc}$, respectively, and a velocity dispersion $\sigma \simeq 70\, {\rm km\, s^{-1}}$ that decreases with radius. We find that the assumption that the NSD is axisymmetric provides a good representation of the data. We quantify contamination from the Galactic Bar in the sample, which is substantial in most observed fields. Our models provide the full 6D (position + velocity) distribution function of the NSD, which can be used to generate predictions for future surveys. We make the models publicly available as part of the software package agama.
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Evans, John S. O., W. I. F. David, and A. W. Sleight. "Structural investigation of the negative-thermal-expansion material ZrW2O8." Acta Crystallographica Section B Structural Science 55, no. 3 (June 1, 1999): 333–40. http://dx.doi.org/10.1107/s0108768198016966.
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High-resolution powder diffraction data have been recorded on cubic ZrW2O8 [a = 9.18000 (3) Å at 2 K] at 260 temperatures from 2 to 520 K in 2 K steps. These data have confirmed that α-ZrW2O8 has a negative coefficient of thermal expansion, α = −9.07 × 10−6 K−1 (2–350 K). A `parametric' approach to Rietveld refinement is adopted and it is demonstrated that a full anisotropic refinement can be performed at each temperature, despite using a data collection time of only 5 min. Examination of the resulting structural parameters suggests that the origin of the contraction with increasing temperature can be traced straightforwardly to the rigid-body transverse librations of bridging O atoms. α-ZrW2O8 undergoes a phase transition from P213 to Pa3¯ at 448 K that is associated with the onset of considerable oxygen mobility. The phase transition can be described in terms of a simple cubic three-dimensional Ising model. Unusual kinetics are associated with this phase transition. Hysteresis in the cell parameter through the phase transition is the opposite of that normally observed.
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Caruntu, Dumitru I., and Mohamed Samir Hefzy. "3-D Anatomically Based Dynamic Modeling of the Human Knee to Include Tibio-Femoral and Patello-Femoral Joints." Journal of Biomechanical Engineering 126, no. 1 (February 1, 2004): 44–53. http://dx.doi.org/10.1115/1.1644565.
Повний текст джерелаАнотація:
An anatomical dynamic model consisting of three body segments, femur, tibia and patella, has been developed in order to determine the three-dimensional dynamic response of the human knee. Deformable contact was allowed at all articular surfaces, which were mathematically represented using Coons’ bicubic surface patches. Nonlinear elastic springs were used to model all ligamentous structures. Two joint coordinate systems were employed to describe the six-degrees-of-freedom tibio-femoral (TF) and patello-femoral (PF) joint motions using twelve kinematic parameters. Two versions of the model were developed to account for wrapping and nonwrapping of the quadriceps tendon around the femur. Model equations consist of twelve nonlinear second-order ordinary differential equations coupled with nonlinear algebraic constraint equations resulting in a Differential-Algebraic Equations (DAE) system that was solved using the D_ifferential/A_lgebraic S_ystem S_ol_ver (DASSL) developed at Lawrence Livermore National Laboratory. Model calculations were performed to simulate the knee extension exercise by applying non-linear forcing functions to the quadriceps tendon. Under the conditions tested, both “screw home mechanism” and patellar flexion lagging were predicted. Throughout the entire range of motion, the medial component of the TF contact force was found to be larger than the lateral one while the lateral component of the PF contact force was found to be larger than the medial one. The anterior and posterior fibers of both anterior and posterior cruciate ligaments, ACL and PCL, respectively, had opposite force patterns: the posterior fibers were most taut at full extension while the anterior fibers were most taut near 90° of flexion. The ACL was found to carry a larger total force than the PCL at full extension, while the PCL carried a larger total force than the ACL in the range of 75° to 90° of flexion.
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Allen, Andrew J., Russell A. Maier, Fan Zhang, Ivan Kuzmenko, and Jan Ilavsky. "In Situ Microstructure Characterization of Potassium Di-Phosphate (KDP) Densification during Cold Sintering." Applied Sciences 12, no. 20 (October 18, 2022): 10493. http://dx.doi.org/10.3390/app122010493.
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In order for ceramic additive manufacturing (AM) to achieve its full potential, it is increasingly important to develop a more rigorous understanding of fundamental phenomena that govern the kinetics and thermodynamics of ceramic AM processes. In the case of additive build processes, such as direct ink write and ceramic extrusion, methods for densifying the resulting green-body product need to be considered to complement the efficiencies of ceramics AM, itself. One densification route, at least for monolithic components, built layer-by-layer, is offered by the recently developed cold sintering process, whereby high-density final product is achieved through addition of a small amount of liquid solvent and application of modest uniaxial compressive stress at relatively low temperature. In situ small-angle X-ray scattering methods and X-ray diffraction have been applied to characterize and quantify the pore morphology evolution during cold sintering for a model system: potassium di-phosphate, KH2PO4 (KDP). It is shown that both temperature and applied stress affect the densification rate, but stress has a stronger effect on the evolving morphology. A regime with an approximate linear densification rate can be identified, yielding an effective densification activation energy of ≈90 kJ/mol.
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Scibek, Jason S., James E. Carpenter, and Richard E. Hughes. "Rotator Cuff Tear Pain and Tear Size and Scapulohumeral Rhythm." Journal of Athletic Training 44, no. 2 (March 1, 2009): 148–59. http://dx.doi.org/10.4085/1062-6050-44.2.148.
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Abstract Context: The body of knowledge concerning shoulder kinematics in patients with rotator cuff tears is increasing. However, the level of understanding regarding how pain and tear size affect these kinematic patterns is minimal. Objective: To identify relationships between pain associated with a full-thickness rotator cuff tear, tear size, and scapulohumeral rhythm (SHR) and to determine whether pain and tear size serve as predictors of SHR. Design: A test-retest design was used to quantify pain and SHR before and after a subacromial lidocaine injection. Correlation and multivariate analyses were used to identify relationships among pain, tear size, and SHR. Setting: Orthopaedic biomechanics research laboratory. Patients or Other Participants: Fifteen patients (age range, 40–75 years) with diagnosed full-thickness rotator cuff tears participated. They were experiencing pain at the time of testing. Intervention(s): Shoulder kinematic data were collected with an electromagnetic tracking system before and after the patient received a lidocaine injection. Main Outcome Measure(s): Pain was rated using a visual analog scale. Three-dimensional scapular kinematics and glenohumeral elevation were assessed. Scapular kinematics included anterior-posterior tilt, medial-lateral tilt, and upward-downward rotation. A regression model was used to calculate SHR (scapular kinematics to glenohumeral elevation) for phases of humeral elevation and lowering. Results: Linear relationships were identified between initial pain scores and SHR and between tear size and SHR, representing an increased reliance on scapular motion with increasing pain and tear size. Pain was identified as an independent predictor of SHR, whereas significant findings for the effect of tear size on SHR and the interaction between pain and tear size were limited. Conclusions: We noted an increased reliance on scapular contributions to overall humeral elevation with increasing levels of pain and rotator cuff tear size. Pain associated with a rotator cuff tear serves as a primary contributor to the kinematic patterns exhibited in patients with rotator cuff tears.
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Dai, Albert, and Ching-Sen Wu. "High-resolution simulations of cylindrical gravity currents in a rotating system." Journal of Fluid Mechanics 806 (September 29, 2016): 71–101. http://dx.doi.org/10.1017/jfm.2016.598.
Повний текст джерелаАнотація:
Cylindrical gravity currents, produced by a full-depth lock release, in a rotating system are investigated by means of three-dimensional high-resolution simulations of the incompressible variable-density Navier–Stokes equations with the Coriolis term and using the Boussinesq approximation for a small density difference. Here, the depth of the fluid is chosen to be the same as the radius of the cylindrical lock and the ambient fluid is non-stratified. Our attention is focused on the situation when the ratio of Coriolis to inertia forces is not large, namely $0.1\leqslant {\mathcal{C}}\leqslant 0.3$, and the non-rotating case, namely ${\mathcal{C}}=0$, is also briefly considered. The simulations reproduce the major features observed in the laboratory and provide more detailed flow information. After the heavy fluid contained in a cylindrical lock is released in a rotating system, the influence of the Coriolis effects is not significant during the initial one-tenth of a revolution of the system. During the initial one-tenth of a revolution of the system, Kelvin–Helmholtz vortices form and the rotating cylindrical gravity currents maintain nearly perfect axisymmetry. Afterwards, three-dimensionality of the flow quickly develops and the outer rim of the spreading heavy fluid breaks away from the body of the current, which gives rise to the maximum dissipation rate in the system during the entire adjustment process. The detached outer rim of heavy fluid then continues to propagate outward until a maximum radius of propagation is attained. The body of the current exhibits a complex contraction–relaxation motion and new outwardly propagating pulses form regularly in a period slightly less than half-revolution of the system. Depending on the ratio of Coriolis to inertia forces, such a contraction–relaxation motion may be initiated after or before the attainment of a maximum radius of propagation. In the contraction–relaxation motion of the heavy fluid, energy is transformed between potential energy and kinetic energy, while it is mainly the kinetic energy that is consumed by the dissipation. As a new pulse initially propagates outward, the potential energy in the system increases at the expense of decreasing kinetic energy, until a local maximum of potential energy is reached. During the latter part of the new pulse propagation, the kinetic energy in the system increases at the expense of decreasing potential energy, until a local minimum of potential energy is reached and another new pulse takes form. With the use of three-dimensional high-resolution simulations, the lobe-and-cleft structure at the advancing front can be clearly observed. The number of lobes is maintained only for a limited period of time before merger between existing lobes occurs when a maximum radius of propagation is approached. The high-resolution simulations complement the existing shallow-water formulation, which accurately predicts many important features and provides insights for rotating cylindrical gravity currents with good physical assumptions and simple mathematical models.