Dynamic impact force and association with structural damage to the knee joint: an ex-vivo study.

PubMed

Brill, Richard; Wohlgemuth, Walther A; Hempfling, Harald; Bohndorf, Klaus; Becker, Ursula; Welsch, Ulrich; Kamp, Alexander; Roemer, Frank W

2014-12-01

No systematic, histologically confirmed data are available concerning the association between magnitude of direct dynamic impact caused by vertical impact trauma and the resulting injury to cartilage and subchondral bone. The aim of this study was to investigate the association between dynamic impact and the resulting patterns of osteochondral injury in an ex-vivo model. A mechanical apparatus was employed to perform ex-vivo controlled dynamic vertical impact experiments in 110 pig knees with the femur positioned in a holding fixture. A falling body with a thrust plate and photo sensor was applied. The direct impact to the trochlear articular surface was registered and the resulting osteochondral injuries macroscopically and histologically correlated and categorized. The relationship between magnitude of direct impact and injury severity could be classified as stage I injuries (impact <7.3MPa): elastic deformation, no histological injury; stage II injuries (impact 7.3-9.6MPa): viscoelastic imprint of the cartilaginous surface, subchondral microfractures; stage III injuries (impact 9.6-12.7MPa): disrupted cartilage surface, chondral fissures and subchondral microfractures; stage IV injuries (impact >12.7MPa): osteochondral impression, histologically imprint and osteochondral macrofractures. The impact ranges and histologic injury stages determined from this vertical dynamic impact experiment allowed for a biomechanical classification of direct, acute osteochondral injury. In contrast to static load commonly applied in ex-vivo experiments, dynamic impact more realistically represents actual trauma to the knee joint.

Dynamic simulation of knee-joint loading during gait using force-feedback control and surrogate contact modelling.

PubMed

Walter, Jonathan P; Pandy, Marcus G

2017-10-01

The aim of this study was to perform multi-body, muscle-driven, forward-dynamics simulations of human gait using a 6-degree-of-freedom (6-DOF) model of the knee in tandem with a surrogate model of articular contact and force control. A forward-dynamics simulation incorporating position, velocity and contact force-feedback control (FFC) was used to track full-body motion capture data recorded for multiple trials of level walking and stair descent performed by two individuals with instrumented knee implants. Tibiofemoral contact force errors for FFC were compared against those obtained from a standard computed muscle control algorithm (CMC) with a 6-DOF knee contact model (CMC6); CMC with a 1-DOF translating hinge-knee model (CMC1); and static optimization with a 1-DOF translating hinge-knee model (SO). Tibiofemoral joint loads predicted by FFC and CMC6 were comparable for level walking, however FFC produced more accurate results for stair descent. SO yielded reasonable predictions of joint contact loading for level walking but significant differences between model and experiment were observed for stair descent. CMC1 produced the least accurate predictions of tibiofemoral contact loads for both tasks. Our findings suggest that reliable estimates of knee-joint loading may be obtained by incorporating position, velocity and force-feedback control with a multi-DOF model of joint contact in a forward-dynamics simulation of gait. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

Development of an Underactuated 2-DOF Wrist Joint using McKibben PAMs

NASA Astrophysics Data System (ADS)

Rajagopal, S. P.; Jain, S.; Ramasubramanian, S. N.; Johnson, B. V.; Dwivedy, S. K.

2014-10-01

In this work, model of an underactuated 2-DOF wrist joint with pneumatically actuated muscles is proposed. For the joint, McKibben-type artificial muscles are used in parallel configuration for the actuation. For each Degree of Freedom (DOF) one agonist-antagonist pair arrangement is usually used with a pulley mechanism. A mathematical model of wrist joint is derived using conventional forward kinematic analysis. The static model relating pressure in the muscle with the orientation of the wrist joint is obtained by combining the experimental data and mathematical model. Regulation of pressure can be achieved by pulse width modulation control of on/off solenoid valves. A set of free vibration experiments are done for the dynamic identification of the muscle characteristics.

Spatial Selection and Local Adaptation Jointly Shape Life-History Evolution during Range Expansion.

PubMed

Van Petegem, Katrien H P; Boeye, Jeroen; Stoks, Robby; Bonte, Dries

2016-11-01

In the context of climate change and species invasions, range shifts increasingly gain attention because the rates at which they occur in the Anthropocene induce rapid changes in biological assemblages. During range shifts, species experience multiple selection pressures. For poleward expansions in particular, it is difficult to interpret observed evolutionary dynamics because of the joint action of evolutionary processes related to spatial selection and to adaptation toward local climatic conditions. To disentangle the effects of these two processes, we integrated stochastic modeling and data from a common garden experiment, using the spider mite Tetranychus urticae as a model species. By linking the empirical data with those derived form a highly parameterized individual-based model, we infer that both spatial selection and local adaptation contributed to the observed latitudinal life-history divergence. Spatial selection best described variation in dispersal behavior, while variation in development was best explained by adaptation to the local climate. Divergence in life-history traits in species shifting poleward could consequently be jointly determined by contemporary evolutionary dynamics resulting from adaptation to the environmental gradient and from spatial selection. The integration of modeling with common garden experiments provides a powerful tool to study the contribution of these evolutionary processes on life-history evolution during range expansion.

Organizational Learning from Cross-Cultural Experiences: An Ethnomethodological Case Study Examining the Relative Importance of Social Structure and Cultural Values during Dynamic Interaction

ERIC Educational Resources Information Center

Waldecker, Gary T.

2011-01-01

This study explored how social structure and cultural values dynamically interact in collective learning between two religious organizations cooperating in a joint project. It further explored the enablers of and impediments to collective learning in this context. The study employed the theoretical framework provided by the Organizational Learning…

Real-time physics-based 3D biped character animation using an inverted pendulum model.

PubMed

Tsai, Yao-Yang; Lin, Wen-Chieh; Cheng, Kuangyou B; Lee, Jehee; Lee, Tong-Yee

2010-01-01

We present a physics-based approach to generate 3D biped character animation that can react to dynamical environments in real time. Our approach utilizes an inverted pendulum model to online adjust the desired motion trajectory from the input motion capture data. This online adjustment produces a physically plausible motion trajectory adapted to dynamic environments, which is then used as the desired motion for the motion controllers to track in dynamics simulation. Rather than using Proportional-Derivative controllers whose parameters usually cannot be easily set, our motion tracking adopts a velocity-driven method which computes joint torques based on the desired joint angular velocities. Physically correct full-body motion of the 3D character is computed in dynamics simulation using the computed torques and dynamical model of the character. Our experiments demonstrate that tracking motion capture data with real-time response animation can be achieved easily. In addition, physically plausible motion style editing, automatic motion transition, and motion adaptation to different limb sizes can also be generated without difficulty.

Reduced-order modeling approach for frictional stick-slip behaviors of joint interface

NASA Astrophysics Data System (ADS)

Wang, Dong; Xu, Chao; Fan, Xuanhua; Wan, Qiang

2018-03-01

The complex frictional stick-slip behaviors of mechanical joint interface have a great effect on the dynamic properties of assembled structures. In this paper, a reduced-order modeling approach based on the constitutive Iwan model is proposed to describe the stick-slip behaviors of joint interface. An improved Iwan model is developed to describe the non-zero residual stiffness at macro-slip regime and smooth transition of joint stiffness from micro-slip to macro-slip regime, and the power-law relationship of energy dissipation during the micro-slip regime. In allusion to these nonlinear behaviors, the finite element method is used to calculate the recycle force under monolithic loading and the energy dissipation per cycle under oscillatory loading. The proposed model is then used to predict the nonlinear stick-slip behaviors of joint interface by curve-fitting to the results of finite element analysis, and the results show good agreements with the finite element analysis. A comparison with the experiment results in literature is also made. The proposed model agrees very well with the experiment results.

A parameters optimization method for planar joint clearance model and its application for dynamics simulation of reciprocating compressor

NASA Astrophysics Data System (ADS)

Hai-yang, Zhao; Min-qiang, Xu; Jin-dong, Wang; Yong-bo, Li

2015-05-01

In order to improve the accuracy of dynamics response simulation for mechanism with joint clearance, a parameter optimization method for planar joint clearance contact force model was presented in this paper, and the optimized parameters were applied to the dynamics response simulation for mechanism with oversized joint clearance fault. By studying the effect of increased clearance on the parameters of joint clearance contact force model, the relation of model parameters between different clearances was concluded. Then the dynamic equation of a two-stage reciprocating compressor with four joint clearances was developed using Lagrange method, and a multi-body dynamic model built in ADAMS software was used to solve this equation. To obtain a simulated dynamic response much closer to that of experimental tests, the parameters of joint clearance model, instead of using the designed values, were optimized by genetic algorithms approach. Finally, the optimized parameters were applied to simulate the dynamics response of model with oversized joint clearance fault according to the concluded parameter relation. The dynamics response of experimental test verified the effectiveness of this application.

Performance Analysis of a Self-Propelling Flat Plate Fin with Joint Compliance

NASA Astrophysics Data System (ADS)

Reddy, N. Srinivasa; Sen, Soumen; Pal, Sumit; Shome, Sankar Nath

2017-12-01

Fish fin muscles are compliant and they regulate the stiffness to suit different swimming conditions. This article attempts to understand the significance of presence of compliance in fin muscle with help of a flexible joint flat plate fin model. Blade element method is employed to model hydrodynamics and to compute the forces of interaction during motion of the plate within fluid. The dynamic model of self-propelling fin is developed through multi-body dynamics approach considering the hydrodynamic forces as external forces acting on the fin. The derived hydrodynamic model is validated with experiments on rigid flat plate fin. The effect of the joint stiffness and flapping frequency on the propulsion speed and efficiency is investigated through simulations using the derived and validated model. The propulsion efficiency is found to be highly influenced by the joint stiffness at a given flapping frequency. The fin attained maximum propulsion efficiency when the joint stiffness is tuned to a value at which flapping frequency matches near natural frequency of the fin. At this tuned joint stiffness and flapping frequency, the resulted Strouhal numbers are observed to fall within the optimum range (0.2 to 0.4) for maximized propulsion efficiency of flying birds and swimming aquatic animals reported in literature.

A Sit-to-Stand Training Robot and Its Performance Evaluation: Dynamic Analysis in Lower Limb Rehabilitation Activities

NASA Astrophysics Data System (ADS)

Cao, Enguo; Inoue, Yoshio; Liu, Tao; Shibata, Kyoko

In many countries in which the phenomenon of population aging is being experienced, motor function recovery activities have aroused much interest. In this paper, a sit-to-stand rehabilitation robot utilizing a double-rope system was developed, and the performance of the robot was evaluated by analyzing the dynamic parameters of human lower limbs. For the robot control program, an impedance control method with a training game was developed to increase the effectiveness and frequency of rehabilitation activities, and a calculation method was developed for evaluating the joint moments of hip, knee, and ankle. Test experiments were designed, and four subjects were requested to stand up from a chair with assistance from the rehabilitation robot. In the experiments, body segment rotational angles, trunk movement trajectories, rope tensile forces, ground reaction forces (GRF) and centers of pressure (COP) were measured by sensors, and the moments of ankle, knee and hip joint were real-time calculated using the sensor-measured data. The experiment results showed that the sit-to-stand rehabilitation robot with impedance control method could maintain the comfortable training postures of users, decrease the moments of limb joints, and enhance training effectiveness. Furthermore, the game control method could encourage collaboration between the brain and limbs, and allow for an increase in the frequency and intensity of rehabilitation activities.

A Method to Capture Macroslip at Bolted Interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hopkins, Ronald Neil; Heitman, Lili Anne Akin

2015-10-01

Relative motion at bolted connections can occur for large shock loads as the internal shear force in the bolted connection overcomes the frictional resistive force. This macroslip in a structure dissipates energy and reduces the response of the components above the bolted connection. There is a need to be able to capture macroslip behavior in a structural dynamics model. A linear model and many nonlinear models are not able to predict marcoslip effectively. The proposed method to capture macroslip is to use the multi-body dynamics code ADAMS to model joints with 3-D contact at the bolted interfaces. This model includesmore » both static and dynamic friction. The joints are preloaded and the pinning effect when a bolt shank impacts a through hole inside diameter is captured. Substructure representations of the components are included to account for component flexibility and dynamics. This method was applied to a simplified model of an aerospace structure and validation experiments were performed to test the adequacy of the method.« less

A Method to Capture Macroslip at Bolted Interfaces [PowerPoint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hopkins, Ronald Neil; Heitman, Lili Anne Akin

2016-01-01

Relative motion at bolted connections can occur for large shock loads as the internal shear force in the bolted connection overcomes the frictional resistive force. This macroslip in a structure dissipates energy and reduces the response of the components above the bolted connection. There is a need to be able to capture macroslip behavior in a structural dynamics model. A linear model and many nonlinear models are not able to predict marcoslip effectively. The proposed method to capture macroslip is to use the multi-body dynamics code ADAMS to model joints with 3-D contact at the bolted interfaces. This model includesmore » both static and dynamic friction. The joints are preloaded and the pinning effect when a bolt shank impacts a through hole inside diameter is captured. Substructure representations of the components are included to account for component flexibility and dynamics. This method was applied to a simplified model of an aerospace structure and validation experiments were performed to test the adequacy of the method.« less

Eyes on the Mind: Investigating the Influence of Gaze Dynamics on the Perception of Others in Real-Time Social Interaction

PubMed Central

Pfeiffer, Ulrich J.; Schilbach, Leonhard; Jording, Mathis; Timmermans, Bert; Bente, Gary; Vogeley, Kai

2012-01-01

Social gaze provides a window into the interests and intentions of others and allows us to actively point out our own. It enables us to engage in triadic interactions involving human actors and physical objects and to build an indispensable basis for coordinated action and collaborative efforts. The object-related aspect of gaze in combination with the fact that any motor act of looking encompasses both input and output of the minds involved makes this non-verbal cue system particularly interesting for research in embodied social cognition. Social gaze comprises several core components, such as gaze-following or gaze aversion. Gaze-following can result in situations of either “joint attention” or “shared attention.” The former describes situations in which the gaze-follower is aware of sharing a joint visual focus with the gazer. The latter refers to a situation in which gazer and gaze-follower focus on the same object and both are aware of their reciprocal awareness of this joint focus. Here, a novel interactive eye-tracking paradigm suited for studying triadic interactions was used to explore two aspects of social gaze. Experiments 1a and 1b assessed how the latency of another person’s gaze reactions (i.e., gaze-following or gaze version) affected participants’ sense of agency, which was measured by their experience of relatedness of these reactions. Results demonstrate that both timing and congruency of a gaze reaction as well as the other’s action options influence the sense of agency. Experiment 2 explored differences in gaze dynamics when participants were asked to establish either joint or shared attention. Findings indicate that establishing shared attention takes longer and requires a larger number of gaze shifts as compared to joint attention, which more closely seems to resemble simple visual detection. Taken together, novel insights into the sense of agency and the awareness of others in gaze-based interaction are provided. PMID:23227017

Distributed Constrained Optimization with Semicoordinate Transformations

NASA Technical Reports Server (NTRS)

Macready, William; Wolpert, David

2006-01-01

Recent work has shown how information theory extends conventional full-rationality game theory to allow bounded rational agents. The associated mathematical framework can be used to solve constrained optimization problems. This is done by translating the problem into an iterated game, where each agent controls a different variable of the problem, so that the joint probability distribution across the agents moves gives an expected value of the objective function. The dynamics of the agents is designed to minimize a Lagrangian function of that joint distribution. Here we illustrate how the updating of the Lagrange parameters in the Lagrangian is a form of automated annealing, which focuses the joint distribution more and more tightly about the joint moves that optimize the objective function. We then investigate the use of "semicoordinate" variable transformations. These separate the joint state of the agents from the variables of the optimization problem, with the two connected by an onto mapping. We present experiments illustrating the ability of such transformations to facilitate optimization. We focus on the special kind of transformation in which the statistically independent states of the agents induces a mixture distribution over the optimization variables. Computer experiment illustrate this for &sat constraint satisfaction problems and for unconstrained minimization of NK functions.

Arctic Ice Dynamics Joint Experiment (AIDJEX) assumptions revisited and found inadequate

NASA Astrophysics Data System (ADS)

Coon, Max; Kwok, Ron; Levy, Gad; Pruis, Matthew; Schreyer, Howard; Sulsky, Deborah

2007-11-01

This paper revisits the Arctic Ice Dynamics Joint Experiment (AIDJEX) assumptions about pack ice behavior with an eye to modeling sea ice dynamics. The AIDJEX assumptions were that (1) enough leads were present in a 100 km by 100 km region to make the ice isotropic on that scale; (2) the ice had no tensile strength; and (3) the ice behavior could be approximated by an isotropic yield surface. These assumptions were made during the development of the AIDJEX model in the 1970s, and are now found inadequate. The assumptions were made in part because of insufficient large-scale (10 km) deformation and stress data, and in part because of computer capability limitations. Upon reviewing deformation and stress data, it is clear that a model including deformation on discontinuities and an anisotropic failure surface with tension would better describe the behavior of pack ice. A model based on these assumptions is needed to represent the deformation and stress in pack ice on scales from 10 to 100 km, and would need to explicitly resolve discontinuities. Such a model would require a different class of metrics to validate discontinuities against observations.

Double symbolic joint entropy in nonlinear dynamic complexity analysis

NASA Astrophysics Data System (ADS)

Yao, Wenpo; Wang, Jun

2017-07-01

Symbolizations, the base of symbolic dynamic analysis, are classified as global static and local dynamic approaches which are combined by joint entropy in our works for nonlinear dynamic complexity analysis. Two global static methods, symbolic transformations of Wessel N. symbolic entropy and base-scale entropy, and two local ones, namely symbolizations of permutation and differential entropy, constitute four double symbolic joint entropies that have accurate complexity detections in chaotic models, logistic and Henon map series. In nonlinear dynamical analysis of different kinds of heart rate variability, heartbeats of healthy young have higher complexity than those of the healthy elderly, and congestive heart failure (CHF) patients are lowest in heartbeats' joint entropy values. Each individual symbolic entropy is improved by double symbolic joint entropy among which the combination of base-scale and differential symbolizations have best complexity analysis. Test results prove that double symbolic joint entropy is feasible in nonlinear dynamic complexity analysis.

Numerical Investigation of the Dynamic Properties of Intermittent Jointed Rock Models Subjected to Cyclic Uniaxial Compression

NASA Astrophysics Data System (ADS)

Liu, Yi; Dai, Feng; Zhao, Tao; Xu, Nu-wen

2017-01-01

Intermittent jointed rocks, which exist in a myriad of engineering projects, are extraordinarily susceptible to cyclic loadings. Understanding the dynamic fatigue properties of jointed rocks is necessary for evaluating the stability of rock engineering structures. This study numerically investigated the influences of cyclic loading conditions (i.e., frequency, maximum stress and amplitude) and joint geometric configurations (i.e., dip angle, persistency and interspace) on the dynamic fatigue mechanisms of jointed rock models. A reduction model of stiffness and strength was first proposed, and then, sixteen cyclic uniaxial loading tests with distinct loading parameters and joint geometries were simulated. Our results indicate that the reduction model can effectively reproduce the hysteresis loops and the accumulative plastic deformation of jointed rocks in the cyclic process. Both the loading parameters and the joint geometries significantly affect the dynamic properties, including the irreversible strain, damage evolution, dynamic residual strength and fatigue life. Three failure modes of jointed rocks, which are principally controlled by joint geometries, occur in the simulations: splitting failure through the entire rock sample, sliding failure along joint planes and mixed failure, which are principally controlled by joint geometries. Furthermore, the progressive failure processes of the jointed rock samples are numerically observed, and the different loading stages can be distinguished by the relationship between the number of broken bonds and the axial stress.

An ITPA joint experiment to study runaway electron generation and suppression

DOE PAGES

Granetz, Robert S.; Esposito, B.; Kim, J. H.; ...

2014-07-11

Recent results from an ITPA joint experiment to study the onset, growth, and decay of relativistic electrons (REs) indicate that loss mechanisms other than collisional damping may play a dominant role in the dynamics of the RE population, even during the quiescent Ip flattop. Understanding the physics of RE growth and mitigation is motivated by the theoretical prediction that disruptions of full-current (15 MA) ITER discharges could generate up to 10 MA of REs with 10-20 MeV energies. The ITPA MHD group is conducting a joint experiment to measure the RE detection threshold conditions on a number of tokamaks undermore » quasi-steady-state conditions in which V loop, n e, and REs can be well-diagnosed and compared to collisional theory. Data from DIII-D, C-Mod, FTU, KSTAR, and TEXTOR have been obtained so far, and the consensus to date is that the threshold E-field is significantly higher than predicted by relativistic collisional theory, or conversely, the density required to damp REs is significantly less than predicted, which could have significant implications for RE mitigation on ITER.« less

Uncontrolled Manifold Reference Feedback Control of Multi-Joint Robot Arms

PubMed Central

Togo, Shunta; Kagawa, Takahiro; Uno, Yoji

2016-01-01

The brain must coordinate with redundant bodies to perform motion tasks. The aim of the present study is to propose a novel control model that predicts the characteristics of human joint coordination at a behavioral level. To evaluate the joint coordination, an uncontrolled manifold (UCM) analysis that focuses on the trial-to-trial variance of joints has been proposed. The UCM is a nonlinear manifold associated with redundant kinematics. In this study, we directly applied the notion of the UCM to our proposed control model called the “UCM reference feedback control.” To simplify the problem, the present study considered how the redundant joints were controlled to regulate a given target hand position. We considered a conventional method that pre-determined a unique target joint trajectory by inverse kinematics or any other optimization method. In contrast, our proposed control method generates a UCM as a control target at each time step. The target UCM is a subspace of joint angles whose variability does not affect the hand position. The joint combination in the target UCM is then selected so as to minimize the cost function, which consisted of the joint torque and torque change. To examine whether the proposed method could reproduce human-like joint coordination, we conducted simulation and measurement experiments. In the simulation experiments, a three-link arm with a shoulder, elbow, and wrist regulates a one-dimensional target of a hand through proposed method. In the measurement experiments, subjects performed a one-dimensional target-tracking task. The kinematics, dynamics, and joint coordination were quantitatively compared with the simulation data of the proposed method. As a result, the UCM reference feedback control could quantitatively reproduce the difference of the mean value for the end hand position between the initial postures, the peaks of the bell-shape tangential hand velocity, the sum of the squared torque, the mean value for the torque change, the variance components, and the index of synergy as well as the human subjects. We concluded that UCM reference feedback control can reproduce human-like joint coordination. The inference for motor control of the human central nervous system based on the proposed method was discussed. PMID:27462215

Force wave transmission through the human locomotor system.

PubMed

Voloshin, A; Wosk, J; Brull, M

1981-02-01

A method to measure the capability of the human shock absorber system to attenuate input dynamic loading during the gait is presented. The experiments were carried out with two groups: healthy subjects and subjects with various pathological conditions. The results of the experiments show a considerable difference in the capability of each group's shock absorbers to attenuate force transmitted through the locomotor system. Comparison shows that healthy subjects definitely possess a more efficient shock-absorbing capacity than do those subjects with joint disorders. Presented results show that degenerative changes in joints reduce their shock absorbing capacity, which leads to overloading of the next shock absorber in the locomotor system. So, the development of osteoarthritis may be expected to result from overloading of a shock absorber's functional capacity.

Mixed-mode fatigue fracture of adhesive joints in harsh environments and nonlinear viscoelastic modeling of the adhesive

NASA Astrophysics Data System (ADS)

Arzoumanidis, Alexis Gerasimos

A four point bend, mixed-mode, reinforced, cracked lap shear specimen experimentally simulated adhesive joints between load bearing composite parts in automotive components. The experiments accounted for fatigue, solvent and temperature effects on a swirled glass fiber composite adherend/urethane adhesive system. Crack length measurements based on compliance facilitated determination of da/dN curves. A digital image processing technique was also utilized to monitor crack growth from in situ images of the side of the specimen. Linear elastic fracture mechanics and finite elements were used to determine energy release rate and mode-mix as a function of crack length for this specimen. Experiments were conducted in air and in a salt water bath at 10, 26 and 90°C. Joints tested in the solvent were fully saturated. In air, both increasing and decreasing temperature relative to 26°C accelerated crack growth rates. In salt water, crack growth rates increased with increasing temperature. Threshold energy release rate is shown to be the most appropriate design criteria for joints of this system. In addition, path of the crack is discussed and fracture surfaces are examined on three length scales. Three linear viscoelastic properties were measured for the neat urethane adhesive. Dynamic tensile compliance (D*) was found using a novel extensometer and results were considerably more accurate and precise than standard DMTA testing. Dynamic shear compliance (J*) was determined using an Arcan specimen. Dynamic Poisson's ratio (nu*) was extracted from strain gage data analyzed to include gage reinforcement. Experiments spanned three frequency decades and isothermal data was shifted by time-temperature superposition to create master curves spanning thirty decades. Master curves were fit to time domain Prony series. Shear compliance inferred from D* and nu* compared well with measured J*, forming a basis for finding the complete time dependent material property matrix for this isotropic material. A constitutive model is introduced which replaces time with internal energy in time-temperature superposition. Internal energy for mechanical loading was calculated from stress history and time domain Prony series representation of compliance. The model also included pressure and volume effects. Ramp loading experiments conducted at strain rates spanning three decades were effectively predicted, but unloading predictions were poor.

Optimal dynamic pricing and replenishment policy for perishable items with inventory-level-dependent demand

NASA Astrophysics Data System (ADS)

Lu, Lihao; Zhang, Jianxiong; Tang, Wansheng

2016-04-01

An inventory system for perishable items with limited replenishment capacity is introduced in this paper. The demand rate depends on the stock quantity displayed in the store as well as the sales price. With the goal to realise profit maximisation, an optimisation problem is addressed to seek for the optimal joint dynamic pricing and replenishment policy which is obtained by solving the optimisation problem with Pontryagin's maximum principle. A joint mixed policy, in which the sales price is a static decision variable and the replenishment rate remains to be a dynamic decision variable, is presented to compare with the joint dynamic policy. Numerical results demonstrate the advantages of the joint dynamic one, and further show the effects of different system parameters on the optimal joint dynamic policy and the maximal total profit.

The human operator transfer function: Identification of the limb mechanics subsystem

NASA Technical Reports Server (NTRS)

Jones, Lynette A.; Hunter, Ian W.

1991-01-01

The objective of our research is to decompose the performance of the human operator in terms of the subsystems that determine the operator's responses in order to establish how the dynamics of these component subsystems influence the operator's performance. In the present experiment, the dynamic stiffness of the human elbow joint was measured at rest and under different levels of biceps muscle activation; this work forms part of the analysis of the limb mechanics subsystem.

Order reduction, identification and localization studies of dynamical systems

NASA Astrophysics Data System (ADS)

Ma, Xianghong

In this thesis methods are developed for performing order reduction, system identification and induction of nonlinear localization in complex mechanical dynamic systems. General techniques are proposed for constructing low-order models of linear and nonlinear mechanical systems; in addition, novel mechanical designs are considered for inducing nonlinear localization phenomena for the purpose of enhancing their dynamical performance. The thesis is in three major parts. In the first part, the transient dynamics of an impulsively loaded multi-bay truss is numerically computed by employing the Direct Global Matrix (DGM) approach. The approach is applicable to large-scale flexible structures with periodicity. Karhunen-Loeve (K-L) decomposition is used to discretize the dynamics of the truss and to create the low-order models of the truss. The leading order K-L modes are recovered by an experiment, which shows the feasibility of K-L based order reduction technique. In the second part of the thesis, nonlinear localization in dynamical systems is studied through two applications. In the seismic base isolation study, it is shown that the dynamics are sensitive to the presence of nonlinear elements and that passive motion confinement can be induced under proper design. In the coupled rod system, numerical simulation of the transient dynamics shows that a nonlinear backlash spring can induce either nonlinear localization or delocalization in the form of beat phenomena. K-L decomposition and poincare maps are utilized to study the nonlinear effects. The study shows that nonlinear localization can be induced in complex structures through backlash. In the third and final part of the thesis, a new technique based on Green!s function method is proposed to identify the dynamics of practical bolted joints. By modeling the difference between the dynamics of the bolted structure and the corresponding unbolted one, one constructs a nonparametric model for the joint dynamics. Two applications are given with a bolted beam and a truss joint in order to show the applicability of the technique.

Effect of a 6-week dynamic neuromuscular training programme on ankle joint function: A Case report

PubMed Central

2011-01-01

Background Ankle joint sprain and the subsequent development of chronic ankle instability (CAI) are commonly encountered by clinicians involved in the treatment and rehabilitation of musculoskeletal injuries. It has recently been advocated that ankle joint post-sprain rehabilitation protocols should incorporate dynamic neuromuscular training to enhance ankle joint sensorimotor capabilities. To date no studies have reported on the effects of dynamic neuromuscular training on ankle joint positioning during landing from a jump, which has been reported as one of the primary injury mechanisms for ankle joint sprain. This case report details the effects of a 6-week dynamic neuromuscular training programme on ankle joint function in an athlete with CAI. Methods The athlete took part in a progressive 6-week dynamic neuromuscular training programme which incorporated postural stability, strengthening, plyometric, and speed/agility drills. The outcome measures chosen to assess for interventional efficacy were: [1] Cumberland Ankle Instability Tool (CAIT) scores, [2] Star Excursion Balance Test (SEBT) reach distances, [3] ankle joint plantar flexion during drop landing and drop vertical jumping, and [4] ground reaction forces (GRFs) during walking. Results CAIT and SEBT scores improved following participation in the programme. The angle of ankle joint plantar flexion decreased at the point of initial contact during the drop landing and drop vertical jumping tasks, indicating that the ankle joint was in a less vulnerable position upon landing following participation in the programme. Furthermore, GRFs were reduced whilst walking post-intervention. Conclusions The 6-week dynamic neuromuscular training programme improved parameters of ankle joint sensorimotor control in an athlete with CAI. Further research is now required in a larger cohort of subjects to determine the effects of neuromuscular training on ankle joint injury risk factors. PMID:21658224

Effect of a 6-week dynamic neuromuscular training programme on ankle joint function: A Case report.

PubMed

O'Driscoll, Jeremiah; Kerin, Fearghal; Delahunt, Eamonn

2011-06-09

Ankle joint sprain and the subsequent development of chronic ankle instability (CAI) are commonly encountered by clinicians involved in the treatment and rehabilitation of musculoskeletal injuries. It has recently been advocated that ankle joint post-sprain rehabilitation protocols should incorporate dynamic neuromuscular training to enhance ankle joint sensorimotor capabilities. To date no studies have reported on the effects of dynamic neuromuscular training on ankle joint positioning during landing from a jump, which has been reported as one of the primary injury mechanisms for ankle joint sprain. This case report details the effects of a 6-week dynamic neuromuscular training programme on ankle joint function in an athlete with CAI. The athlete took part in a progressive 6-week dynamic neuromuscular training programme which incorporated postural stability, strengthening, plyometric, and speed/agility drills. The outcome measures chosen to assess for interventional efficacy were: 1 Cumberland Ankle Instability Tool (CAIT) scores, 2 Star Excursion Balance Test (SEBT) reach distances, 3 ankle joint plantar flexion during drop landing and drop vertical jumping, and 4 ground reaction forces (GRFs) during walking. CAIT and SEBT scores improved following participation in the programme. The angle of ankle joint plantar flexion decreased at the point of initial contact during the drop landing and drop vertical jumping tasks, indicating that the ankle joint was in a less vulnerable position upon landing following participation in the programme. Furthermore, GRFs were reduced whilst walking post-intervention. The 6-week dynamic neuromuscular training programme improved parameters of ankle joint sensorimotor control in an athlete with CAI. Further research is now required in a larger cohort of subjects to determine the effects of neuromuscular training on ankle joint injury risk factors.

Probing Protein-Protein Interactions by Dynamic Force Correlation Spectroscopy

NASA Astrophysics Data System (ADS)

Barsegov, V.; Thirumalai, D.

2005-10-01

We develop a formalism for single molecule dynamic force spectroscopy to map the energy landscape of protein-protein complex (P1P2). The joint distribution P(τ1,τ2) of unbinding lifetimes τ1 and τ2, measurable in a compression-tension cycle, which accounts for the internal relaxation dynamics of the proteins under tension, shows that the histogram of τ1 is not Poissonian. The theory is applied to the forced unbinding of protein P1, modeled as a wormlike chain, from P1P2. We propose a new class of experiments which can resolve the effect of internal protein dynamics on the unbinding lifetimes.

Movement-related and steady-state electromyographic activity of human elbow flexors in slow transition movements between two equilibrium states.

PubMed

Tal'nov, A N; Cherkassky, V L; Kostyukov, A I

1997-08-01

The electromyograms were recorded in healthy human subjects by surface electrodes from the mm. biceps brachii (caput longum et. brevis), brachioradialis, and triceps brachii (caput longum) during slow transition movements in elbow joint against a weak extending torque. The test movements (flexion transitions between two steady-states) were fulfilled under visual control through combining on a monitor screen a signal from a joint angle sensor with a corresponding command generated by a computer. Movement velocities ranged between 5 and 80 degrees/s, subjects were asked to move forearm without activation of elbow extensors. Surface electromyograms were full-wave rectified, filtered and averaged within sets of 10 identical tests. Amplitudes of dynamic and steady-state components of the electromyograms were determined in dependence on a final value of joint angle, slow and fast movements were compared. An exponential-like increase of dynamic component was observed in electromyograms recorded from m. biceps brachii, the component had been increased with movement velocity and with load increment. In many experiments a statistically significant decrease of static component could be noticed within middle range of joint angles (40-60 degrees) followed by a well expressed increment for larger movements. This pattern of the static component in electromyograms could vary in different experiments even in the same subjects. A steady discharge in m. brachioradialis at ramp phase has usually been recorded only under a notable load. Variable and quite often unpredictable character of the static components of the electromyograms recorded from elbow flexors in the transition movements makes it difficult to use the equilibrium point hypothesis to describe the central processes of movement. It has been assumed that during active muscle shortening the dynamic components in arriving efferent activity should play a predominant role. A simple scheme could be proposed for transition to a steady-state after shortening. Decrease of the efferent inflow can evoke internal lengthening of the contractile elements in muscle and, as a result, hysteresis increase in the muscle contraction efficiency. Effectiveness in maintenance of the steady position seems to also be enhanced due to muscle thixotropy and friction processes in the joint. Hysteresis after-effects in elbow flexors were demonstrated as a difference in steady-state levels of electromyograms with oppositely directed approaches to the same joint position.

Joint Spacelab-J (SL-J) Activities at the Huntsville Operations Support Center (HOSC) Spacelab

NASA Technical Reports Server (NTRS)

1999-01-01

The science laboratory, Spacelab-J (SL-J), flown aboard the STS-47 flight was a joint venture between NASA and the National Space Development Agency of Japan (NASDA) utilizing a manned Spacelab module. The mission conducted 24 materials science and 20 life science experiments, of which 35 were sponsored by NASDA, 7 by NASA, and two collaborative efforts. Materials science investigations covered such fields as biotechnology, electronic materials, fluid dynamics and transport phenomena, glasses and ceramics, metals and alloys, and acceleration measurements. Life sciences included experiments on human health, cell separation and biology, developmental biology, animal and human physiology and behavior, space radiation, and biological rhythms. Test subjects included the crew, Japanese koi fish (carp), cultured animal and plant cells, chicken embryos, fruit flies, fungi and plant seeds, and frogs and frog eggs. Featured together in joint ground activities during the SL-J mission are NASA/NASDA personnel at the Huntsville Operations Support Center (HOSC) Spacelab Payload Operations Control Center (SL POCC) at Marshall Space Flight Center (MSFC).

Tracking control of time-varying knee exoskeleton disturbed by interaction torque.

PubMed

Li, Zhan; Ma, Wenhao; Yin, Ziguang; Guo, Hongliang

2017-11-01

Knee exoskeletons have been increasingly applied as assistive devices to help lower-extremity impaired people to make their knee joints move through providing external movement compensation. Tracking control of knee exoskeletons guided by human intentions often encounters time-varying (time-dependent) issues and the disturbance interaction torque, which may dramatically put an influence up on their dynamic behaviors. Inertial and viscous parameters of knee exoskeletons can be estimated to be time-varying due to unexpected mechanical vibrations and contact interactions. Moreover, the interaction torque produced from knee joint of wearers has an evident disturbance effect on regular motions of knee exoskeleton. All of these points can increase difficultly of accurate control of knee exoskeletons to follow desired joint angle trajectories. This paper proposes a novel control strategy for controlling knee exoskeleton with time-varying inertial and viscous coefficients disturbed by interaction torque. Such designed controller is able to make the tracking error of joint angle of knee exoskeletons exponentially converge to zero. Meanwhile, the proposed approach is robust to guarantee the tracking error bounded when the interaction torque exists. Illustrative simulation and experiment results are presented to show efficiency of the proposed controller. Additionally, comparisons with gradient dynamic (GD) approach and other methods are also presented to demonstrate efficiency and superiority of the proposed control strategy for tracking joint angle of knee exoskeleton. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Optimal Control Method of Robot End Position and Orientation Based on Dynamic Tracking Measurement

NASA Astrophysics Data System (ADS)

Liu, Dalong; Xu, Lijuan

2018-01-01

In order to improve the accuracy of robot pose positioning and control, this paper proposed a dynamic tracking measurement robot pose optimization control method based on the actual measurement of D-H parameters of the robot, the parameters is taken with feedback compensation of the robot, according to the geometrical parameters obtained by robot pose tracking measurement, improved multi sensor information fusion the extended Kalan filter method, with continuous self-optimal regression, using the geometric relationship between joint axes for kinematic parameters in the model, link model parameters obtained can timely feedback to the robot, the implementation of parameter correction and compensation, finally we can get the optimal attitude angle, realize the robot pose optimization control experiments were performed. 6R dynamic tracking control of robot joint robot with independent research and development is taken as experimental subject, the simulation results show that the control method improves robot positioning accuracy, and it has the advantages of versatility, simplicity, ease of operation and so on.

A method to accurately estimate the muscular torques of human wearing exoskeletons by torque sensors.

PubMed

Hwang, Beomsoo; Jeon, Doyoung

2015-04-09

In exoskeletal robots, the quantification of the user's muscular effort is important to recognize the user's motion intentions and evaluate motor abilities. In this paper, we attempt to estimate users' muscular efforts accurately using joint torque sensor which contains the measurements of dynamic effect of human body such as the inertial, Coriolis, and gravitational torques as well as torque by active muscular effort. It is important to extract the dynamic effects of the user's limb accurately from the measured torque. The user's limb dynamics are formulated and a convenient method of identifying user-specific parameters is suggested for estimating the user's muscular torque in robotic exoskeletons. Experiments were carried out on a wheelchair-integrated lower limb exoskeleton, EXOwheel, which was equipped with torque sensors in the hip and knee joints. The proposed methods were evaluated by 10 healthy participants during body weight-supported gait training. The experimental results show that the torque sensors are to estimate the muscular torque accurately in cases of relaxed and activated muscle conditions.

Neural-Dynamic-Method-Based Dual-Arm CMG Scheme With Time-Varying Constraints Applied to Humanoid Robots.

PubMed

Zhang, Zhijun; Li, Zhijun; Zhang, Yunong; Luo, Yamei; Li, Yuanqing

2015-12-01

We propose a dual-arm cyclic-motion-generation (DACMG) scheme by a neural-dynamic method, which can remedy the joint-angle-drift phenomenon of a humanoid robot. In particular, according to a neural-dynamic design method, first, a cyclic-motion performance index is exploited and applied. This cyclic-motion performance index is then integrated into a quadratic programming (QP)-type scheme with time-varying constraints, called the time-varying-constrained DACMG (TVC-DACMG) scheme. The scheme includes the kinematic motion equations of two arms and the time-varying joint limits. The scheme can not only generate the cyclic motion of two arms for a humanoid robot but also control the arms to move to the desired position. In addition, the scheme considers the physical limit avoidance. To solve the QP problem, a recurrent neural network is presented and used to obtain the optimal solutions. Computer simulations and physical experiments demonstrate the effectiveness and the accuracy of such a TVC-DACMG scheme and the neural network solver.

Joint Perception of a Shared Object: A Minimalist Perceptual Crossing Experiment.

PubMed

Deschamps, Loïc; Lenay, Charles; Rovira, Katia; Le Bihan, Gabrielle; Aubert, Dominique

2016-01-01

The minimalist perceptual crossing paradigm has emphasized the essential role of interpersonal dynamics on social understanding. Within the particular case of minimalist interaction, it has been argued that interpersonal processes can constitute social cognition, at least partially, which calls for a paradigm shift in social cognition studies. In this paper, we review several perceptual crossing experiments and their theoretical implications, and propose an original experiment to go beyond strictly dyadic interactions. Whereas past experiments have used objects as distracters of dyadic interaction, our experiment aims at integrating objects themselves as the goal of interpersonal coordination. We asked 24 subjects to participate in a minimalist perceptual crossing experiment where they had to decide, based on their on-line interaction in a one-dimensional digital space, which of the objects they perceived was also perceptible by their partner. The main results suggest that the mutual awareness of a shared object (SO) arises from the quality of sensorimotor coordination between the partners. Indeed, the presence of a SO acts as a simultaneous affordance that attracts and structures individual perceptive activities, giving both partners the opportunity to co-construct a shared world where their respective actions make sense. We discuss our results by way of an enactive account of social cognition, taking the joint perception of a SO as a first step to account for joint attention.

Joint Perception of a Shared Object: A Minimalist Perceptual Crossing Experiment

PubMed Central

Deschamps, Loïc; Lenay, Charles; Rovira, Katia; Le Bihan, Gabrielle; Aubert, Dominique

2016-01-01

The minimalist perceptual crossing paradigm has emphasized the essential role of interpersonal dynamics on social understanding. Within the particular case of minimalist interaction, it has been argued that interpersonal processes can constitute social cognition, at least partially, which calls for a paradigm shift in social cognition studies. In this paper, we review several perceptual crossing experiments and their theoretical implications, and propose an original experiment to go beyond strictly dyadic interactions. Whereas past experiments have used objects as distracters of dyadic interaction, our experiment aims at integrating objects themselves as the goal of interpersonal coordination. We asked 24 subjects to participate in a minimalist perceptual crossing experiment where they had to decide, based on their on-line interaction in a one-dimensional digital space, which of the objects they perceived was also perceptible by their partner. The main results suggest that the mutual awareness of a shared object (SO) arises from the quality of sensorimotor coordination between the partners. Indeed, the presence of a SO acts as a simultaneous affordance that attracts and structures individual perceptive activities, giving both partners the opportunity to co-construct a shared world where their respective actions make sense. We discuss our results by way of an enactive account of social cognition, taking the joint perception of a SO as a first step to account for joint attention. PMID:27462295

Parental Involvement in Child Assessment: A Dynamic Approach.

ERIC Educational Resources Information Center

SeokHoon, Alice Seng

This paper examines the status of parents in the developmental assessment process and considers how involving parents jointly with the professional to assess their young child may yield more accurate and valuable information. The paper explores the use of a mediated learning experience (MLE) approach as a framework for increasing support for…

Detection of dual-band infrared small target based on joint dynamic sparse representation

NASA Astrophysics Data System (ADS)

Zhou, Jinwei; Li, Jicheng; Shi, Zhiguang; Lu, Xiaowei; Ren, Dongwei

2015-10-01

Infrared small target detection is a crucial and yet still is a difficult issue in aeronautic and astronautic applications. Sparse representation is an important mathematic tool and has been used extensively in image processing in recent years. Joint sparse representation is applied in dual-band infrared dim target detection in this paper. Firstly, according to the characters of dim targets in dual-band infrared images, 2-dimension Gaussian intensity model was used to construct target dictionary, then the dictionary was classified into different sub-classes according to different positions of Gaussian function's center point in image block; The fact that dual-band small targets detection can use the same dictionary and the sparsity doesn't lie in atom-level but in sub-class level was utilized, hence the detection of targets in dual-band infrared images was converted to be a joint dynamic sparse representation problem. And the dynamic active sets were used to describe the sparse constraint of coefficients. Two modified sparsity concentration index (SCI) criteria was proposed to evaluate whether targets exist in the images. In experiments, it shows that the proposed algorithm can achieve better detecting performance and dual-band detection is much more robust to noise compared with single-band detection. Moreover, the proposed method can be expanded to multi-spectrum small target detection.

Locality constrained joint dynamic sparse representation for local matching based face recognition.

PubMed

Wang, Jianzhong; Yi, Yugen; Zhou, Wei; Shi, Yanjiao; Qi, Miao; Zhang, Ming; Zhang, Baoxue; Kong, Jun

2014-01-01

Recently, Sparse Representation-based Classification (SRC) has attracted a lot of attention for its applications to various tasks, especially in biometric techniques such as face recognition. However, factors such as lighting, expression, pose and disguise variations in face images will decrease the performances of SRC and most other face recognition techniques. In order to overcome these limitations, we propose a robust face recognition method named Locality Constrained Joint Dynamic Sparse Representation-based Classification (LCJDSRC) in this paper. In our method, a face image is first partitioned into several smaller sub-images. Then, these sub-images are sparsely represented using the proposed locality constrained joint dynamic sparse representation algorithm. Finally, the representation results for all sub-images are aggregated to obtain the final recognition result. Compared with other algorithms which process each sub-image of a face image independently, the proposed algorithm regards the local matching-based face recognition as a multi-task learning problem. Thus, the latent relationships among the sub-images from the same face image are taken into account. Meanwhile, the locality information of the data is also considered in our algorithm. We evaluate our algorithm by comparing it with other state-of-the-art approaches. Extensive experiments on four benchmark face databases (ORL, Extended YaleB, AR and LFW) demonstrate the effectiveness of LCJDSRC.

Robust tuning of robot control systems

NASA Technical Reports Server (NTRS)

Minis, I.; Uebel, M.

1992-01-01

The computed torque control problem is examined for a robot arm with flexible, geared, joint drive systems which are typical in many industrial robots. The standard computed torque algorithm is not directly applicable to this class of manipulators because of the dynamics introduced by the joint drive system. The proposed approach to computed torque control combines a computed torque algorithm with torque controller at each joint. Three such control schemes are proposed. The first scheme uses the joint torque control system currently implemented on the robot arm and a novel form of the computed torque algorithm. The other two use the standard computed torque algorithm and a novel model following torque control system based on model following techniques. Standard tasks and performance indices are used to evaluate the performance of the controllers. Both numerical simulations and experiments are used in evaluation. The study shows that all three proposed systems lead to improved tracking performance over a conventional PD controller.

The Joint Damping Experiment (JDX)

NASA Technical Reports Server (NTRS)

Folkman, Steven L.; Bingham, Jeff G.; Crookston, Jess R.; Dutson, Joseph D.; Ferney, Brook D.; Ferney, Greg D.; Rowsell, Edwin A.

1997-01-01

The Joint Damping Experiment (JDX), flown on the Shuttle STS-69 Mission, is designed to measure the influence of gravity on the structural damping of a high precision three bay truss. Principal objectives are: (1) Measure vibration damping of a small-scale, pinjointed truss to determine how pin gaps give rise to gravity-dependent damping rates; (2) Evaluate the applicability of ground and low-g aircraft tests for predicting on-orbit behavior; and (3) Evaluate the ability of current nonlinear finite element codes to model the dynamic behavior of the truss. Damping of the truss was inferred from 'Twang' tests that involve plucking the truss structure and recording the decay of the oscillations. Results are summarized as follows. (1) Damping, rates can change by a factor of 3 to 8 through changing the truss orientation; (2) The addition of a few pinned joints to a truss structure can increase the damping by a factor as high as 30; (3) Damping is amplitude dependent; (4) As gravity induced preloads become large (truss long axis perpendicular to gravity vector) the damping is similar to non-pinjointed truss; (5) Impacting in joints drives higher modes in structure; (6) The torsion mode disappears if gravity induced preloads are low.

Experimental Characterization of Hysteresis in a Revolute Joint for Precision Deployable Structures

NASA Technical Reports Server (NTRS)

Lake, Mark S.; Fung, Jimmy; Gloss, Kevin; Liechty, Derek S.

1997-01-01

Recent studies of the micro-dynamic behavior of a deployable telescope metering truss have identified instabilities in the equilibrium shape of the truss in response to low-energy dynamic loading. Analyses indicate that these micro-dynamic instabilities arise from stick-slip friction within the truss joints (e.g., hinges and latches). The present study characterizes the low-magnitude quasi-static load cycle response of the precision revolute joints incorporated in the deployable telescope metering truss, and specifically, the hysteretic response of these joints caused by stick-slip friction within the joint. Detailed descriptions are presented of the test setup and data reduction algorithms, including discussions of data-error sources and data-filtering techniques. Test results are presented from thirteen specimens, and the effects of joint preload and manufacturing tolerances are investigated. Using a simplified model of stick-slip friction, a relationship is made between joint load-cycle behavior and micro-dynamic dimensional instabilities in the deployable telescope metering truss.

Magneto-therapy of human joint cartilage.

PubMed

Wierzcholski, Krzysztof; Miszczak, Andrzej

2017-01-01

The topic of the present paper concerns the human joint cartilage therapy performed by the magnetic induction field. There is proved the thesis that the applied magnetic field for concrete cartilage illness should depend on the proper relative and concrete values of applied magnetic induction, intensity as well the time of treatment duration. Additionally, very important are frequencies and amplitudes of magnetic field as well as magnetic permeability of the synovial fluid. The research methods used in this paper include: magnetic induction field produced by a new Polish and German magneto electronic devices for the therapy of human joint cartilage diseases, stationary and movable magnetic applicators, magnetic bandage, ferrofluid injections, author's experience gained in Germany research institutes and practical results after measurements and information from patients. The results of this paper concern concrete parameters of time dependent electro-magnetic field administration during the joint cartilage therapy duration and additionally concern the corollaries which are implied from reading values gained on the magnetic induction devices. The main conclusions obtained in this paper are as follows: Time dependent magnetic induction field increases the dynamic viscosity of movable synovial fluid and decreases symptoms of cartilage illness for concrete intensity of magnetic field and concrete field line architecture. The ferrofluid therapy and phospholipids bilayer simultaneously with the administrated external electromagnetic field, increases the dynamic viscosity of movable synovial fluid.

Evaluation of linearly solvable Markov decision process with dynamic model learning in a mobile robot navigation task.

PubMed

Kinjo, Ken; Uchibe, Eiji; Doya, Kenji

2013-01-01

Linearly solvable Markov Decision Process (LMDP) is a class of optimal control problem in which the Bellman's equation can be converted into a linear equation by an exponential transformation of the state value function (Todorov, 2009b). In an LMDP, the optimal value function and the corresponding control policy are obtained by solving an eigenvalue problem in a discrete state space or an eigenfunction problem in a continuous state using the knowledge of the system dynamics and the action, state, and terminal cost functions. In this study, we evaluate the effectiveness of the LMDP framework in real robot control, in which the dynamics of the body and the environment have to be learned from experience. We first perform a simulation study of a pole swing-up task to evaluate the effect of the accuracy of the learned dynamics model on the derived the action policy. The result shows that a crude linear approximation of the non-linear dynamics can still allow solution of the task, despite with a higher total cost. We then perform real robot experiments of a battery-catching task using our Spring Dog mobile robot platform. The state is given by the position and the size of a battery in its camera view and two neck joint angles. The action is the velocities of two wheels, while the neck joints were controlled by a visual servo controller. We test linear and bilinear dynamic models in tasks with quadratic and Guassian state cost functions. In the quadratic cost task, the LMDP controller derived from a learned linear dynamics model performed equivalently with the optimal linear quadratic regulator (LQR). In the non-quadratic task, the LMDP controller with a linear dynamics model showed the best performance. The results demonstrate the usefulness of the LMDP framework in real robot control even when simple linear models are used for dynamics learning.

A painless and constraint-free method to estimate viscoelastic passive dynamics of limbs' joints to support diagnosis of neuromuscular diseases.

PubMed

Venture, Gentiane; Nakamura, Yoshihiko; Yamane, Katsu; Hirashima, Masaya

2007-01-01

Though seldom identified, the human joints dynamics is important in the fields of medical robotics and medical research. We present a general solution to estimate in-vivo and simultaneously the passive dynamics of the human limbs' joints. It is based on the use of the multi-body description of the human body and its kinematics and dynamics computations. The linear passive joint dynamics of the shoulders and the elbows: stiffness, viscosity and friction, is estimated simultaneously using the linear least squares method. Acquisition of movements is achieved with an optical motion capture studio on one examinee during the clinical diagnosis of neuromuscular diseases. Experimental results are given and discussed.

Design optimization of dual-axis driving mechanism for satellite antenna with two planar revolute clearance joints

NASA Astrophysics Data System (ADS)

Bai, Zheng Feng; Zhao, Ji Jun; Chen, Jun; Zhao, Yang

2018-03-01

In the dynamic analysis of satellite antenna dual-axis driving mechanism, it is usually assumed that the joints are ideal or perfect without clearances. However, in reality, clearances in joints are unavoidable due to assemblage, manufacturing errors and wear. When clearance is introduced to the mechanism, it will lead to poor dynamic performances and undesirable vibrations due to impact forces in clearance joint. In this paper, a design optimization method is presented to reduce the undesirable vibrations of satellite antenna considering clearance joints in dual-axis driving mechanism. The contact force model in clearance joint is established using a nonlinear spring-damper model and the friction effect is considered using a modified Coulomb friction model. Firstly, the effects of clearances on dynamic responses of satellite antenna are investigated. Then the optimization method for dynamic design of the dual-axis driving mechanism with clearance is presented. The objective of the optimization is to minimize the maximum absolute vibration peak of antenna acceleration by reducing the impact forces in clearance joint. The main consideration here is to optimize the contact parameters of the joint elements. The contact stiffness coefficient, damping coefficient and the dynamic friction coefficient for clearance joint elements are taken as the optimization variables. A Generalized Reduced Gradient (GRG) algorithm is used to solve this highly nonlinear optimization problem for dual-axis driving mechanism with clearance joints. The results show that the acceleration peaks of satellite antenna and contact forces in clearance joints are reduced obviously after design optimization, which contributes to a better performance of the satellite antenna. Also, the application and limitation of the proposed optimization method are discussed.

Virtual Passive Controller for Robot Systems Using Joint Torque Sensors

NASA Technical Reports Server (NTRS)

Aldridge, Hal A.; Juang, Jer-Nan

1997-01-01

This paper presents a control method based on virtual passive dynamic control that will stabilize a robot manipulator using joint torque sensors and a simple joint model. The method does not require joint position or velocity feedback for stabilization. The proposed control method is stable in the sense of Lyaponov. The control method was implemented on several joints of a laboratory robot. The controller showed good stability robustness to system parameter error and to the exclusion of nonlinear dynamic effects on the joints. The controller enhanced position tracking performance and, in the absence of position control, dissipated joint energy.

Parameter identification and optimization of slide guide joint of CNC machine tools

NASA Astrophysics Data System (ADS)

Zhou, S.; Sun, B. B.

2017-11-01

The joint surface has an important influence on the performance of CNC machine tools. In order to identify the dynamic parameters of slide guide joint, the parametric finite element model of the joint is established and optimum design method is used based on the finite element simulation and modal test. Then the mode that has the most influence on the dynamics of slip joint is found through harmonic response analysis. Take the frequency of this mode as objective, the sensitivity analysis of the stiffness of each joint surface is carried out using Latin Hypercube Sampling and Monte Carlo Simulation. The result shows that the vertical stiffness of slip joint surface constituted by the bed and the slide plate has the most obvious influence on the structure. Therefore, this stiffness is taken as the optimization variable and the optimal value is obtained through studying the relationship between structural dynamic performance and stiffness. Take the stiffness values before and after optimization into the FEM of machine tool, and it is found that the dynamic performance of the machine tool is improved.

High-frame-rate digital radiographic videography

NASA Astrophysics Data System (ADS)

King, Nicholas S. P.; Cverna, Frank H.; Albright, Kevin L.; Jaramillo, Steven A.; Yates, George J.; McDonald, Thomas E.; Flynn, Michael J.; Tashman, Scott

1994-10-01

High speed x-ray imaging can be an important tool for observing internal processes in a wide range of applications. In this paper we describe preliminary implementation of a system having the eventual goal of observing the internal dynamics of bone and joint reactions during loading. Two Los Alamos National Laboratory (LANL) gated and image intensified camera systems were used to record images from an x-ray image convertor tube to demonstrate the potential of high frame-rate digital radiographic videography in the analysis of bone and joint dynamics of the human body. Preliminary experiments were done at LANL to test the systems. Initial high frame-rate imaging (from 500 to 1000 frames/s) of a swinging pendulum mounted to the face of an X-ray image convertor tube demonstrated high contrast response and baseline sensitivity. The systems were then evaluated at the Motion Analysis Laboratory of Henry Ford Health Systems Bone and Joint Center. Imaging of a 9 inch acrylic disk with embedded lead markers rotating at approximately 1000 RPM, demonstrated the system response to a high velocity/high contrast target. By gating the P-20 phosphor image from the X-ray image convertor with a second image intensifier (II) and using a 100 microsecond wide optical gate through the second II, enough prompt light decay from the x-ray image convertor phosphor had taken place to achieve reduction of most of the motion blurring. Measurement of the marker velocity was made by using video frames acquired at 500 frames/s. The data obtained from both experiments successfully demonstrated the feasibility of the technique. Several key areas for improvement are discussed along with salient test results and experiment details.

Decentralized Adaptive Control For Robots

NASA Technical Reports Server (NTRS)

Seraji, Homayoun

1989-01-01

Precise knowledge of dynamics not required. Proposed scheme for control of multijointed robotic manipulator calls for independent control subsystem for each joint, consisting of proportional/integral/derivative feedback controller and position/velocity/acceleration feedforward controller, both with adjustable gains. Independent joint controller compensates for unpredictable effects, gravitation, and dynamic coupling between motions of joints, while forcing joints to track reference trajectories. Scheme amenable to parallel processing in distributed computing system wherein each joint controlled by relatively simple algorithm on dedicated microprocessor.

Economy, Movement Dynamics, and Muscle Activity of Human Walking at Different Speeds.

PubMed

Raffalt, P C; Guul, M K; Nielsen, A N; Puthusserypady, S; Alkjær, T

2017-03-08

The complex behaviour of human walking with respect to movement variability, economy and muscle activity is speed dependent. It is well known that a U-shaped relationship between walking speed and economy exists. However, it is an open question if the movement dynamics of joint angles and centre of mass and muscle activation strategy also exhibit a U-shaped relationship with walking speed. We investigated the dynamics of joint angle trajectories and the centre of mass accelerations at five different speeds ranging from 20 to 180% of the predicted preferred speed (based on Froude speed) in twelve healthy males. The muscle activation strategy and walking economy were also assessed. The movement dynamics was investigated using a combination of the largest Lyapunov exponent and correlation dimension. We observed an intermediate stage of the movement dynamics of the knee joint angle and the anterior-posterior and mediolateral centre of mass accelerations which coincided with the most energy-efficient walking speed. Furthermore, the dynamics of the joint angle trajectories and the muscle activation strategy was closely linked to the functional role and biomechanical constraints of the joints.

Results of the US contribution to the joint US/USSR Bering Sea experiment. [atmospheric circulation and sea ice cover

NASA Technical Reports Server (NTRS)

Campbell, W. J.; Chang, T. C.; Fowler, M. G.; Gloersen, P.; Kuhn, P. M.; Ramseier, R. O.; Ross, D. B.; Stambach, G.; Webster, W. J., Jr.; Wilheit, T. T.

1974-01-01

The atmospheric circulation which occurred during the Bering Sea Experiment, 15 February to 10 March 1973, in and around the experiment area is analyzed and related to the macroscale morphology and dynamics of the sea ice cover. The ice cover was very complex in structure, being made up of five ice types, and underwent strong dynamic activity. Synoptic analyses show that an optimum variety of weather situations occurred during the experiment: an initial strong anticyclonic period (6 days), followed by a period of strong cyclonic activity (6 days), followed by weak anticyclonic activity (3 days), and finally a period of weak cyclonic activity (4 days). The data of the mesoscale test areas observed on the four sea ice option flights, and ship weather, and drift data give a detailed description of mesoscale ice dynamics which correlates well with the macroscale view: anticyclonic activity advects the ice southward with strong ice divergence and a regular lead and polynya pattern; cyclonic activity advects the ice northward with ice convergence, or slight divergence, and a random lead and polynya pattern.

Does the nervous system use equilibrium-point control to guide single and multiple joint movements?

PubMed

Bizzi, E; Hogan, N; Mussa-Ivaldi, F A; Giszter, S

1992-12-01

The hypothesis that the central nervous system (CNS) generates movement as a shift of the limb's equilibrium posture has been corroborated experimentally in studies involving single- and multijoint motions. Posture may be controlled through the choice of muscle length-tension curve that set agonist-antagonist torque-angle curves determining an equilibrium position for the limb and the stiffness about the joints. Arm trajectories seem to be generated through a control signal defining a series of equilibrium postures. The equilibrium-point hypothesis drastically simplifies the requisite computations for multijoint movements and mechanical interactions with complex dynamic objects in the environment. Because the neuromuscular system is springlike, the instantaneous difference between the arm's actual position and the equilibrium position specified by the neural activity can generate the requisite torques, avoiding the complex "inverse dynamic" problem of computing the torques at the joints. The hypothesis provides a simple, unified description of posture and movement as well as contact control task performance, in which the limb must exert force stably and do work on objects in the environment. The latter is a surprisingly difficult problem, as robotic experience has shown. The prior evidence for the hypothesis came mainly from psychophysical and behavioral experiments. Our recent work has shown that microstimulation of the frog spinal cord's premotoneural network produces leg movements to various positions in the frog's motor space. The hypothesis can now be investigated in the neurophysiological machinery of the spinal cord.

SELECTION DYNAMICS IN JOINT MATCHING TO RATE AND MAGNITUDE OF REINFORCEMENT

PubMed Central

McDowell, J. J; Popa, Andrei; Calvin, Nicholas T

2012-01-01

Virtual organisms animated by a selectionist theory of behavior dynamics worked on concurrent random interval schedules where both the rate and magnitude of reinforcement were varied. The selectionist theory consists of a set of simple rules of selection, recombination, and mutation that act on a population of potential behaviors by means of a genetic algorithm. An extension of the power function matching equation, which expresses behavior allocation as a joint function of exponentiated reinforcement rate and reinforcer magnitude ratios, was fitted to the virtual organisms' data, and over a range of moderate mutation rates was found to provide an excellent description of their behavior without residual trends. The mean exponents in this range of mutation rates were 0.83 for the reinforcement rate ratio and 0.68 for the reinforcer magnitude ratio, which are values that are comparable to those obtained in experiments with live organisms. These findings add to the evidence supporting the selectionist theory, which asserts that the world of behavior we observe and measure is created by evolutionary dynamics. PMID:23008523

A Method to Accurately Estimate the Muscular Torques of Human Wearing Exoskeletons by Torque Sensors

PubMed Central

Hwang, Beomsoo; Jeon, Doyoung

2015-01-01

In exoskeletal robots, the quantification of the user’s muscular effort is important to recognize the user’s motion intentions and evaluate motor abilities. In this paper, we attempt to estimate users’ muscular efforts accurately using joint torque sensor which contains the measurements of dynamic effect of human body such as the inertial, Coriolis, and gravitational torques as well as torque by active muscular effort. It is important to extract the dynamic effects of the user’s limb accurately from the measured torque. The user’s limb dynamics are formulated and a convenient method of identifying user-specific parameters is suggested for estimating the user’s muscular torque in robotic exoskeletons. Experiments were carried out on a wheelchair-integrated lower limb exoskeleton, EXOwheel, which was equipped with torque sensors in the hip and knee joints. The proposed methods were evaluated by 10 healthy participants during body weight-supported gait training. The experimental results show that the torque sensors are to estimate the muscular torque accurately in cases of relaxed and activated muscle conditions. PMID:25860074

Control of interjoint coordination during the swing phase of normal gait at different speeds

PubMed Central

Shemmell, Jonathan; Johansson, Jennifer; Portra, Vanessa; Gottlieb, Gerald L; Thomas, James S; Corcos, Daniel M

2007-01-01

Background It has been suggested that the control of unconstrained movements is simplified via the imposition of a kinetic constraint that produces dynamic torques at each moving joint such that they are a linear function of a single motor command. The linear relationship between dynamic torques at each joint has been demonstrated for multijoint upper limb movements. The purpose of the current study was to test the applicability of such a control scheme to the unconstrained portion of the gait cycle – the swing phase. Methods Twenty-eight neurologically normal individuals walked along a track at three different speeds. Angular displacements and dynamic torques produced at each of the three lower limb joints (hip, knee and ankle) were calculated from segmental position data recorded during each trial. We employed principal component (PC) analysis to determine (1) the similarity of kinematic and kinetic time series at the ankle, knee and hip during the swing phase of gait, and (2) the effect of walking speed on the range of joint displacement and torque. Results The angular displacements of the three joints were accounted for by two PCs during the swing phase (Variance accounted for – PC1: 75.1 ± 1.4%, PC2: 23.2 ± 1.3%), whereas the dynamic joint torques were described by a single PC (Variance accounted for – PC1: 93.8 ± 0.9%). Increases in walking speed were associated with increases in the range of motion and magnitude of torque at each joint although the ratio describing the relative magnitude of torque at each joint remained constant. Conclusion Our results support the idea that the control of leg swing during gait is simplified in two ways: (1) the pattern of dynamic torque at each lower limb joint is produced by appropriately scaling a single motor command and (2) the magnitude of dynamic torque at all three joints can be specified with knowledge of the magnitude of torque at a single joint. Walking speed could therefore be altered by modifying a single value related to the magnitude of torque at one joint. PMID:17466065

Design of Experiment and Analysis for the Joint Dynamic Allocation of Fires and Sensors (JDAFS) Simulation

DTIC Science & Technology

2007-06-01

other databases such as MySQL , Oracle , and Derby will be added to future versions of the program. Setting a factor requires more than changing a single...Non-Penetrating vs . Penetrating Results.............106 a. Coverage...Interaction Profile for D U-2 and C RQ-4 .......................................................89 Figure 59. R-Squared vs . Number of Regression Tree

Use of Dynamic Geometry as a Support to Paper and Pencil Activities for Comprehension of Ratio and Proportion Topics

ERIC Educational Resources Information Center

Ruiz, Elena Fabiola; Lupianez, Jose Luis

2010-01-01

Introduction: The present paper shows the importance of a joint use of pencil and paper activities and of technology so that students may develop a complete understanding of ratio and proportion. A previous experience with strategy use when solving ratio and proportion problems provided background. Prompted by a recognition of the cognitive…

Dynamical Interpolation of Mesoscale Flows in the TOPEX/Poseidon Diamond Surrounding the U.S. Joint Global Ocean Flux Study Bermuda Atlantic Time-Series Study Site

NASA Technical Reports Server (NTRS)

McGillicuddy, Dennis J., Jr.; Kosnyrev, V. K.

2001-01-01

An open boundary ocean model is configured in a domain bounded by the four TOPEX/Poseidon (T/P) ground tracks surrounding the US Joint Global Ocean Flux Study Bermuda Atlantic Time-Series Study (BATS) site. This implementation facilitates prescription of model boundary conditions directly from altimetric measurements (both TIP and ERS-2). The expected error characteristics for a domain of this size with periodically updated boundary conditions are established with idealized numerical experiments using simulated data. A hindcast simulation is then constructed using actual altimetric observations during the period October 1992 through September 1998. Quantitative evaluation of the simulation suggests significant skill. The correlation coefficient between predicted sea level anomaly and ERS observations in the model interior is 0.89; that for predicted versus observed dynamic height anomaly based on hydrography at the BATS site is 0.73. Comparison with the idealized experiments suggests that the main source of error in the hindcast is temporal undersampling of the boundary conditions. The hindcast simulation described herein provides a basis for retrospective analysis of BATS observations in the context of the mesoscale eddy field.

Dynamical Interpolation of Mesoscale Flows in the TOPEX/ Poseidon Diamond Surrounding the U.S. Joint Global Ocean Flux Study Bermuda Atlantic Time-Series Study Site

NASA Technical Reports Server (NTRS)

McGillicuddy, D. J.; Kosnyrev, V. K.

2001-01-01

An open boundary ocean model is configured in a domain bounded by the four TOPEX/Poseidon (TIP) ground tracks surrounding the U.S. Joint Global Ocean Flux Study Bermuda Atlantic Time-series Study (BATS) site. This implementation facilitates prescription of model boundary conditions directly from altimetric measurements (both TIP and ERS-2). The expected error characteristics for a domain of this size with periodically updated boundary conditions are established with idealized numerical experiments using simulated data. A hindcast simulation is then constructed using actual altimetric observations during the period October 1992 through September 1998. Quantitative evaluation of the simulation suggests significant skill. The correlation coefficient between predicted sea level anomaly and ERS observations in the model interior is 0.89; that for predicted versus observed dynamic height anomaly based on hydrography at the BATS site is 0.73. Comparison with the idealized experiments suggests that the main source of error in the hindcast is temporal undersampling of the boundary conditions. The hindcast simulation described herein provides a basis for retrospective analysis of BATS observations in the context of the mesoscale eddy field.

Identification of Nonlinear Micron-Level Mechanics for a Precision Deployable Joint

NASA Technical Reports Server (NTRS)

Bullock, S. J.; Peterson, L. D.

1994-01-01

The experimental identification of micron-level nonlinear joint mechanics and dynamics for a pin-clevis joint used in a precision, adaptive, deployable space structure are investigated. The force-state mapping method is used to identify the behavior of the joint under a preload. The results of applying a single tension-compression cycle to the joint under a tensile preload are presented. The observed micron-level behavior is highly nonlinear and involves all six rigid body motion degrees-of-freedom of the joint. it is also suggests that at micron levels of motion modelling of the joint mechanics and dynamics must include the interactions between all internal components, such as the pin, bushings, and the joint node.

Design and Performance Analysis of a new Rotary Hydraulic Joint

NASA Astrophysics Data System (ADS)

Feng, Yong; Yang, Junhong; Shang, Jianzhong; Wang, Zhuo; Fang, Delei

2017-07-01

To improve the driving torque of the robots joint, a wobble plate hydraulic joint is proposed, and the structure and working principle are described. Then mathematical models of kinematics and dynamics was established. On the basis of this, dynamic simulation and characteristic analysis are carried out. Results show that the motion curve of the joint is continuous and the impact is small. Moreover the output torque of the joint characterized by simple structure and easy processing is large and can be rotated continuously.

Wide field of view CT and acromioclavicular joint instability: A technical innovation.

PubMed

Dyer, David R; Troupis, John M; Kamali Moaveni, Afshin

2015-06-01

A 21-year-old female with a traumatic shoulder injury is investigated and managed for symptoms relating to this injury. Pathology at the acromioclavicular joint is detected clinically; however, clinical examination and multiple imaging modalities do not reach a unified diagnosis on the grading of this acromioclavicular joint injury. When management appropriate to that suggested injury grading fail to help the patient's symptoms, further investigation methods were utilised. Wide field of view, dynamic CT (4D CT) is conducted on the patient's affected shoulder using a 320 × 0.5 mm detector multislice CT. Scans were conducted with a static table as the patient completed three movements of the affected shoulder. Capturing multiple data sets per second over a z-axis of 16 cm, measurements of the acromioclavicular joint were made, to show dynamic changes at the joint. Acromioclavicular (AC) joint translations were witnessed in three planes (a previously unrecognised pathology in the grading of acromioclavicular joint injuries). Translation in multiple planes was also not evident on careful clinical examination of this patient. AC joint width, anterior-posterior translation, superior-inferior translation and coracoclavicular width were measured with planar reconstructions while volume-rendered images and dynamic sequences aiding visual understanding of the pathology. Wide field of view dynamic CT (4D CT) is an accurate and quick modality to diagnose complex acromioclavicular joint injury. It provides dynamic information that no other modality can; 4D CT shows future benefits for clinical approach to diagnosis and management of acromioclavicular joint injury, and other musculoskeletal pathologies. © 2015 The Royal Australian and New Zealand College of Radiologists.

Experiential learning implementation based on joint responsibility in women's cooperative development (Case study on Farmer Women Cooperative, Sumedang, West Java)

NASA Astrophysics Data System (ADS)

Suseno, Gijanto Purbo; Nataliningsih

2017-09-01

Cooperative extension is one form of non-formal education. The follow up of cooperative extension is a coaching that aims to cooperative boards and members apply the knowledge and skills acquired during extension. Learning from the experience (experience learning) of others combined with the concept of joint responsibility is expected to develop the participation of cooperative members as indicated by the repayment of loans on time. The research was conducted at Sumedang Farmer Women Cooperative of West Java with the stages of cooperative extension and coaching for 6 months so it can be evaluated its impact. The results showed that from 30 extension participants who stated willingness to be a member of joint responsibility group as many as 15 people (50%), which then divided into 3 groups of mutual responsibility with member of each group is 5 people. The result of impact evaluation showed the development of group dynamics of the joint liability shown by 9 people (60%) developing business, 3 people (20%) business stagnant and 3 (20%) less profitable business. Implementation of experiental learning based on the concept of mutual responsibility encourages the improvement of entrepreneurship and cooperative skills and the ability of members to pay loan installments on cooperatives in a timely manner.

Exploring the existence of a stayer population with mover-stayer counting process models: application to joint damage in psoriatic arthritis.

PubMed

Yiu, Sean; Farewell, Vernon T; Tom, Brian D M

2017-08-01

Many psoriatic arthritis patients do not progress to permanent joint damage in any of the 28 hand joints, even under prolonged follow-up. This has led several researchers to fit models that estimate the proportion of stayers (those who do not have the propensity to experience the event of interest) and to characterize the rate of developing damaged joints in the movers (those who have the propensity to experience the event of interest). However, when fitted to the same data, the paper demonstrates that the choice of model for the movers can lead to widely varying conclusions on a stayer population, thus implying that, if interest lies in a stayer population, a single analysis should not generally be adopted. The aim of the paper is to provide greater understanding regarding estimation of a stayer population by comparing the inferences, performance and features of multiple fitted models to real and simulated data sets. The models for the movers are based on Poisson processes with patient level random effects and/or dynamic covariates, which are used to induce within-patient correlation, and observation level random effects are used to account for time varying unobserved heterogeneity. The gamma, inverse Gaussian and compound Poisson distributions are considered for the random effects.

Dynamics of photoexcited Ba+ cations in 4He nanodroplets

NASA Astrophysics Data System (ADS)

Leal, Antonio; Zhang, Xiaohang; Barranco, Manuel; Cargnoni, Fausto; Hernando, Alberto; Mateo, David; Mella, Massimo; Drabbels, Marcel; Pi, Martí

2016-03-01

We present a joint experimental and theoretical study on the desolvation of Ba+ cations in 4He nanodroplets excited via the 6p ← 6s transition. The experiments reveal an efficient desolvation process yielding mainly bare Ba+ cations and Ba+Hen exciplexes with n = 1 and 2. The speed distributions of the ions are well described by Maxwell-Boltzmann distributions with temperatures ranging from 60 to 178 K depending on the excitation frequency and Ba+ Hen exciplex size. These results have been analyzed by calculations based on a time-dependent density functional description for the helium droplet combined with classical dynamics for the Ba+. In agreement with experiment, the calculations reveal the dynamical formation of exciplexes following excitation of the Ba+ cation. In contrast to experimental observation, the calculations do not reveal desolvation of excited Ba+ cations or exciplexes, even when relaxation pathways to lower lying states are included.

Towards understanding software: 15 years in the SEL

NASA Technical Reports Server (NTRS)

Mcgarry, Frank; Pajerski, Rose

1990-01-01

For 15 years, the Software Engineering Laboratory (SEL) at GSFC has been carrying out studies and experiments for the purpose of understanding, assessing, and improving software, and software processes within a production software environment. The SEL comprises three major organizations: (1) the GSFC Flight Dynamics Division; (2) the University of Maryland Computer Science Department; and (3) the Computer Sciences Corporation Flight Dynamics Technology Group. These organizations have jointly carried out several hundred software studies, producing hundreds of reports, papers, and documents: all describing some aspect of the software engineering technology that has undergone analysis in the flight dynamics environment. The studies range from small controlled experiments (such as analyzing the effectiveness of code reading versus functional testing) to large, multiple-project studies (such as assessing the impacts of Ada on a production environment). The key findings that NASA feels have laid the foundation for ongoing and future software development and research activities are summarized.

Decentralized adaptive control of manipulators - Theory, simulation, and experimentation

NASA Technical Reports Server (NTRS)

Seraji, Homayoun

1989-01-01

The author presents a simple decentralized adaptive-control scheme for multijoint robot manipulators based on the independent joint control concept. The control objective is to achieve accurate tracking of desired joint trajectories. The proposed control scheme does not use the complex manipulator dynamic model, and each joint is controlled simply by a PID (proportional-integral-derivative) feedback controller and a position-velocity-acceleration feedforward controller, both with adjustable gains. Simulation results are given for a two-link direct-drive manipulator under adaptive independent joint control. The results illustrate trajectory tracking under coupled dynamics and varying payload. The proposed scheme is implemented on a MicroVAX II computer for motion control of the three major joints of a PUMA 560 arm. Experimental results are presented to demonstrate that trajectory tracking is achieved despite coupled nonlinear joint dynamics.

Robot Position Sensor Fault Tolerance

NASA Technical Reports Server (NTRS)

Aldridge, Hal A.

1997-01-01

Robot systems in critical applications, such as those in space and nuclear environments, must be able to operate during component failure to complete important tasks. One failure mode that has received little attention is the failure of joint position sensors. Current fault tolerant designs require the addition of directly redundant position sensors which can affect joint design. A new method is proposed that utilizes analytical redundancy to allow for continued operation during joint position sensor failure. Joint torque sensors are used with a virtual passive torque controller to make the robot joint stable without position feedback and improve position tracking performance in the presence of unknown link dynamics and end-effector loading. Two Cartesian accelerometer based methods are proposed to determine the position of the joint. The joint specific position determination method utilizes two triaxial accelerometers attached to the link driven by the joint with the failed position sensor. The joint specific method is not computationally complex and the position error is bounded. The system wide position determination method utilizes accelerometers distributed on different robot links and the end-effector to determine the position of sets of multiple joints. The system wide method requires fewer accelerometers than the joint specific method to make all joint position sensors fault tolerant but is more computationally complex and has lower convergence properties. Experiments were conducted on a laboratory manipulator. Both position determination methods were shown to track the actual position satisfactorily. A controller using the position determination methods and the virtual passive torque controller was able to servo the joints to a desired position during position sensor failure.

Effect of core muscle thickness and static or dynamic balance on prone bridge exercise with sling by shoulder joint angle in healthy adults.

PubMed

Park, Mi Hwa; Yu, Jae Ho; Hong, Ji Heon; Kim, Jin Seop; Jung, Sang Woo; Lee, Dong Yeop

2016-03-01

[Purpose] To date, core muscle activity detected using ultrasonography during prone bridge exercises has not been reported. Here we investigated the effects of core muscle thickness and balance on sling exercise efficacy by shoulder joint angle in healthy individuals. [Subjects and Methods] Forty-three healthy university students were enrolled in this study. Ultrasonography thickness of external oblique, internal oblique, and transversus abdominis during sling workouts was investigated. Muscle thickness was measured on ultrasonography imaging before and after the experiment. Dynamic balance was tested using a functional reaching test. Static balance was tested using a Tetrax Interactive Balance System. [Results] Different muscle thicknesses were observed during the prone bridge exercise with the shoulder flexed at 60°, 90° or 120°. Shoulder flexion at 60° and 90° in the prone bridge exercise with a sling generated the greatest thickness of most transversus abdominis muscles. Shoulder flexion at 120° in the prone bridge exercise with a sling generated the greatest thickness of most external oblique muscles. [Conclusion] The results suggest that the prone bridge exercise with shoulder joint angle is an effective method of increasing global and local muscle strength.

The use of ultrasound in the assessment of the glenoid labrum of the glenohumeral joint. Part II: Examples of labral pathologies.

PubMed

Krzyżanowski, Wojciech; Tarczyńska, Marta

2012-09-01

Labral pathologies of the glenohumeral joint are most commonly caused by trauma. The majority of lesions affect the anterior part of labrum, resulting from much higher frequency of anterior shoulder dislocations over posterior ones. Another subgroup of labral lesions, not directly related to joint instability, are SLAP tears. Other findings include degenerative changes of labrum and paralabral cysts. Diagnostic imaging is crucial for making a decision regarding operative treatment. Apart from a standard X-ray examination, the imaging mainly relies on magnetic resonance or computed tomography arthrography. Based on their own experience, the authors propose the use of ultrasound in the assessment of labral tears of the glenohumeral joint. Different signs indicating labral pathology may be discovered and assessed during ultrasound examination. They include permanent displacement of the labrum onto the glenoid, labral instability during dynamic examination, lack of the labrum in the anatomical position, hypoechoic zone at the base of the labrum >2 mm in width, residual or swollen labrum as well as paralabral cyst(s). The most frequent appearance of labral pathology is displacement of the anteroinferior labrum onto the external aspect of the glenoid typically seen after anterior shoulder dislocation. The another most important US feature is labral instability while dynamically examined. The swelling or reduced size of the labrum usually indicates degeneration. This article presents sonographic images of selected labral pathologies.

Mechanical Impedance of the Non-loaded Lower Leg with Relaxed Muscles in the Transverse Plane

PubMed Central

Ficanha, Evandro Maicon; Ribeiro, Guilherme Aramizo; Rastgaar, Mohammad

2015-01-01

This paper describes the protocols and results of the experiments for the estimation of the mechanical impedance of the humans’ lower leg in the External–Internal direction in the transverse plane under non-load bearing condition and with relaxed muscles. The objectives of the estimation of the lower leg’s mechanical impedance are to facilitate the design of passive and active prostheses with mechanical characteristics similar to the humans’ lower leg, and to define a reference that can be compared to the values from the patients suffering from spasticity. The experiments were performed with 10 unimpaired male subjects using a lower extremity rehabilitation robot (Anklebot, Interactive Motion Technologies, Inc.) capable of applying torque perturbations to the foot. The subjects were in a seated position, and the Anklebot recorded the applied torques and the resulting angular movement of the lower leg. In this configuration, the recorded dynamics are due mainly to the rotations of the ankle’s talocrural and the subtalar joints, and any contribution of the tibiofibular joints and knee joint. The dynamic mechanical impedance of the lower leg was estimated in the frequency domain with an average coherence of 0.92 within the frequency range of 0–30 Hz, showing a linear correlation between the displacement and the torques within this frequency range under the conditions of the experiment. The mean magnitude of the stiffness of the lower leg (the impedance magnitude averaged in the range of 0–1 Hz) was determined as 4.9 ± 0.74 Nm/rad. The direct estimation of the quasi-static stiffness of the lower leg results in the mean value of 5.8 ± 0.81 Nm/rad. An analysis of variance shows that the estimated values for the stiffness from the two experiments are not statistically different. PMID:26697424

Correlation and prediction of dynamic human isolated joint strength from lean body mass

NASA Technical Reports Server (NTRS)

Pandya, Abhilash K.; Hasson, Scott M.; Aldridge, Ann M.; Maida, James C.; Woolford, Barbara J.

1992-01-01

A relationship between a person's lean body mass and the amount of maximum torque that can be produced with each isolated joint of the upper extremity was investigated. The maximum dynamic isolated joint torque (upper extremity) on 14 subjects was collected using a dynamometer multi-joint testing unit. These data were reduced to a table of coefficients of second degree polynomials, computed using a least squares regression method. All the coefficients were then organized into look-up tables, a compact and convenient storage/retrieval mechanism for the data set. Data from each joint, direction and velocity, were normalized with respect to that joint's average and merged into files (one for each curve for a particular joint). Regression was performed on each one of these files to derive a table of normalized population curve coefficients for each joint axis, direction, and velocity. In addition, a regression table which included all upper extremity joints was built which related average torque to lean body mass for an individual. These two tables are the basis of the regression model which allows the prediction of dynamic isolated joint torques from an individual's lean body mass.

Control of multi-joint arm movements for the manipulation of touch in keystroke by expert pianists

PubMed Central

2010-01-01

Background Production of a variety of finger-key touches in the piano is essential for expressive musical performance. However, it remains unknown how expert pianists control multi-joint finger and arm movements for manipulating the touch. The present study investigated differences in kinematics and kinetics of the upper-limb movements while expert pianists were depressing a key with two different touches: pressed and struck. The former starts key-depression with the finger-tip contacting the key, whereas the latter involves preparatory arm-lift before striking the key. To determine the effect of individual muscular torque (MUS) as well as non-muscular torques on joint acceleration, we performed a series of inverse and forward dynamics computations. Results The pressed touch showed smaller elbow extension velocity, and larger shoulder and finger flexion velocities during key-depression compared with the struck touch. The former touch also showed smaller elbow extension acceleration directly attributed to the shoulder MUS. In contrast, the shoulder flexion acceleration induced by elbow and wrist MUS was greater for the pressed touch than the struck touch. Towards the goal of producing the target finger-key contact dynamics, the pressed and struck touches effectively took advantage of the distal-to-proximal and proximal-to-distal inter-segmental dynamics, respectively. Furthermore, a psychoacoustic experiment confirmed that a tone elicited by the pressed touch was perceived softer than that by the struck touch. Conclusion The present findings suggest that manipulation of tone timbre depends on control of inter-segmental dynamics in piano keystroke. PMID:20630085

Experimental investigation of the dynamic installation of a slip joint connection between the monopile and tower of an offshore wind turbine

NASA Astrophysics Data System (ADS)

Segeren, M. L. A.; Hermans, K. W.

2014-06-01

The failure of the traditional grouted connections of offshore wind turbines has led to the investigation of alternatives that provide a connection between the foundation pile and the turbine tower. An alternative to the traditional joint is a steel-to-steel connection also called a slip joint. To ensure a proper fit of the slip joint a dynamic installation of the joint is proposed. In this contribution, the effectiveness of harmonic excitation as an installation procedure is experimentally investigated using a 1:10 scaled model of the joint. During the dynamic installation test the applied static load, settlements and dynamic response of the joint are monitored using respectively load cells, taut wires and strain gauges placed both inside and outside the conical surfaces. The results show that settlement occurs only when applying a harmonic load at specific forcing frequencies. The settlement stabilizes to a certain level for each of the specific frequencies, indicating that a controlled way of installation is possible. The results show that it is essential to vibrate at specific frequencies and that a larger amplitude of the harmonic force does not automatically lead to additional settlement.

Electrical stimulation on joint contracture: an experiment in rat model with direct current.

PubMed

Akai, M; Shirasaki, Y; Tateishi, T

1997-04-01

To examine whether electrical stimulation could decrease the degree of joint stiffness in a rat lower extremity model. Rat knee joints were surgically immobilized in a flexed position for 3 weeks. Two groups of rats were stimulated with 20 microA and 50 microA constant direct current. Another group had surgical intervention and sham electrodes without electricity. The hind leg was extirpated and prepared for a sample with the femur-knee joint-tibia unit. Recording the knee flexion angle with extension torque, the degree of joint contracture was assessed biomechanically by measuring the bone-joint-bone sample as a cantilever. Measurement was performed with (1) spectral analysis of transfer function measurement using random mechanical noise with frequency range from 1 to 50Hz, and (2) dynamic stiffness and loss tangent with steady-state sinusoidal excitation (11 and 35Hz). The results showed that no significant difference or trend was found in vibration analysis among three groups. However, spectral analysis of transfer function measurement revealed more deformation against load, and more viscous nature in the stimulation groups, especially in low frequency band, than in the sham group. Electrical stimulation with constant direct current has a possibility of reducing the degree of joint contracture.

Redundancy, Self-Motion, and Motor Control

PubMed Central

Martin, V.; Scholz, J. P.; Schöner, G.

2011-01-01

Outside the laboratory, human movement typically involves redundant effector systems. How the nervous system selects among the task-equivalent solutions may provide insights into how movement is controlled. We propose a process model of movement generation that accounts for the kinematics of goal-directed pointing movements performed with a redundant arm. The key element is a neuronal dynamics that generates a virtual joint trajectory. This dynamics receives input from a neuronal timer that paces end-effector motion along its path. Within this dynamics, virtual joint velocity vectors that move the end effector are dynamically decoupled from velocity vectors that do not. Moreover, the sensed real joint configuration is coupled back into this neuronal dynamics, updating the virtual trajectory so that it yields to task-equivalent deviations from the dynamic movement plan. Experimental data from participants who perform in the same task setting as the model are compared in detail to the model predictions. We discover that joint velocities contain a substantial amount of self-motion that does not move the end effector. This is caused by the low impedance of muscle joint systems and by coupling among muscle joint systems due to multiarticulatory muscles. Back-coupling amplifies the induced control errors. We establish a link between the amount of self-motion and how curved the end-effector path is. We show that models in which an inverse dynamics cancels interaction torques predict too little self-motion and too straight end-effector paths. PMID:19718817

Methodological factors affecting joint moments estimation in clinical gait analysis: a systematic review.

PubMed

Camomilla, Valentina; Cereatti, Andrea; Cutti, Andrea Giovanni; Fantozzi, Silvia; Stagni, Rita; Vannozzi, Giuseppe

2017-08-18

Quantitative gait analysis can provide a description of joint kinematics and dynamics, and it is recognized as a clinically useful tool for functional assessment, diagnosis and intervention planning. Clinically interpretable parameters are estimated from quantitative measures (i.e. ground reaction forces, skin marker trajectories, etc.) through biomechanical modelling. In particular, the estimation of joint moments during motion is grounded on several modelling assumptions: (1) body segmental and joint kinematics is derived from the trajectories of markers and by modelling the human body as a kinematic chain; (2) joint resultant (net) loads are, usually, derived from force plate measurements through a model of segmental dynamics. Therefore, both measurement errors and modelling assumptions can affect the results, to an extent that also depends on the characteristics of the motor task analysed (i.e. gait speed). Errors affecting the trajectories of joint centres, the orientation of joint functional axes, the joint angular velocities, the accuracy of inertial parameters and force measurements (concurring to the definition of the dynamic model), can weigh differently in the estimation of clinically interpretable joint moments. Numerous studies addressed all these methodological aspects separately, but a critical analysis of how these aspects may affect the clinical interpretation of joint dynamics is still missing. This article aims at filling this gap through a systematic review of the literature, conducted on Web of Science, Scopus and PubMed. The final objective is hence to provide clear take-home messages to guide laboratories in the estimation of joint moments for the clinical practice.

A digital-signal-processor-based optical tomographic system for dynamic imaging of joint diseases

NASA Astrophysics Data System (ADS)

Lasker, Joseph M.

Over the last decade, optical tomography (OT) has emerged as viable biomedical imaging modality. Various imaging systems have been developed that are employed in preclinical as well as clinical studies, mostly targeting breast imaging, brain imaging, and cancer related studies. Of particular interest are so-called dynamic imaging studies where one attempts to image changes in optical properties and/or physiological parameters as they occur during a system perturbation. To successfully perform dynamic imaging studies, great effort is put towards system development that offers increasingly enhanced signal-to-noise performance at ever shorter data acquisition times, thus capturing high fidelity tomographic data within narrower time periods. Towards this goal, I have developed in this thesis a dynamic optical tomography system that is, unlike currently available analog instrumentation, based on digital data acquisition and filtering techniques. At the core of this instrument is a digital signal processor (DSP) that collects, collates, and processes the digitized data set. Complementary protocols between the DSP and a complex programmable logic device synchronizes the sampling process and organizes data flow. Instrument control is implemented through a comprehensive graphical user interface which integrates automated calibration, data acquisition, and signal post-processing. Real-time data is generated at frame rates as high as 140 Hz. An extensive dynamic range (˜190 dB) accommodates a wide scope of measurement geometries and tissue types. Performance analysis demonstrates very low system noise (˜1 pW rms noise equivalent power), excellent signal precision (˜0.04%--0.2%) and long term system stability (˜1% over 40 min). Experiments on tissue phantoms validate spatial and temporal accuracy of the system. As a potential new application of dynamic optical imaging I present the first application of this method to use vascular hemodynamics as a means of characterizing joint diseases, especially effects of rheumatoid arthritis (RA) in the proximal interphalangeal finger joints. Using a dual-wavelength tomographic imaging system and previously implemented reconstruction scheme, I have performed initial dynamic imaging case studies on healthy volunteers and patients diagnosed with RA. These studies support our hypothesis that differences in the vascular and metabolic reactivity exist between affected and unaffected joints and can be used for diagnostic purposes.

Joint Loads and Cartilage Stress in Intact Joints of Military Transtibial Amputees: Enhancing Quality of Life

DTIC Science & Technology

2017-04-01

crosstalk); analysis of tested subjects underway. 4) Developed analytical methods to obtain knee joint loads using EMG-driven inverse dynamics; analysis of...13/2018. Completion %: 40. Task 1.3: EMG-driven inverse dynamic (ID) analyses with OpenSim for amputee and control group subjects. Target date: 1...predicted by EMG-driven inverse dynamics. Two-three conference papers are being prepared for submission in February 2017. Other achievements. None

Structural characterization of a first-generation articulated-truss joint for space crane application

NASA Technical Reports Server (NTRS)

Sutter, Thomas R.; Wu, K. Chauncey; Riutort, Kevin T.; Laufer, Joseph B.; Phelps, James E.

1992-01-01

A first-generation space crane articulated-truss joint was statically and dynamically characterized in a configuration that approximated an operational environment. The articulated-truss joint was integrated into a test-bed for structural characterization. Static characterization was performed by applying known loads and measuring the corresponding deflections to obtain load-deflection curves. Dynamic characterization was performed using modal testing to experimentally determine the first six mode shapes, frequencies, and modal damping values. Static and dynamic characteristics were also determined for a reference truss that served as a characterization baseline. Load-deflection curves and experimental frequency response functions are presented for the reference truss and the articulated-truss joint mounted in the test-bed. The static and dynamic experimental results are compared with analytical predictions obtained from finite element analyses. Load-deflection response is also presented for one of the linear actuators used in the articulated-truss joint. Finally, an assessment is presented for the predictability of the truss hardware used in the reference truss and articulated-truss joint based upon hardware stiffness properties that were previously obtained during the Precision Segmented Reflector (PSR) Technology Development Program.

Asteroid Impact Mission (aim) & Deflection Assessment: AN Opportunity to Understand Impact Dynamics and Modelling

NASA Astrophysics Data System (ADS)

Galvez, A.; Carnelli, I.; Fontaine, M.; Corral Van Damme, C.

2012-09-01

ESA's Future Preparation and Strategic Studies Office has carried out the Asteroid Impact Mission (AIM) study with the objective of defining an affordable and fully independent mission element that ESA could contribute to an Asteroid Impact Deflection Assessment campaign (AIDA), a joint effort of ESA, JHU/APL, NASA, OCA and DLR. The mission design foresees two independent spacecraft, one impactor (DART) and one rendezvous probe (AIM). The target of this mission is the binary asteroid system (65803) Didymos (1996 GT): one spacecraft, DART, would impact the secondary of the Didymos binary system while AIM would observe and measure any the change in the relative orbit. For this joint project, the timing of the experiment is set (maximum proximity of the target to Earth allowing for ground-based characterisation of the experiment) but the spacecraft are still able to pursue their missions fully independently. This paper describes in particular the AIM rendezvous mission concept.

On the apparent insignificance of the randomness of flexible joints on large space truss dynamics

NASA Technical Reports Server (NTRS)

Koch, R. M.; Klosner, J. M.

1993-01-01

Deployable periodic large space structures have been shown to exhibit high dynamic sensitivity to period-breaking imperfections and uncertainties. These can be brought on by manufacturing or assembly errors, structural imperfections, as well as nonlinear and/or nonconservative joint behavior. In addition, the necessity of precise pointing and position capability can require the consideration of these usually negligible and unknown parametric uncertainties and their effect on the overall dynamic response of large space structures. This work describes the use of a new design approach for the global dynamic solution of beam-like periodic space structures possessing parametric uncertainties. Specifically, the effect of random flexible joints on the free vibrations of simply-supported periodic large space trusses is considered. The formulation is a hybrid approach in terms of an extended Timoshenko beam continuum model, Monte Carlo simulation scheme, and first-order perturbation methods. The mean and mean-square response statistics for a variety of free random vibration problems are derived for various input random joint stiffness probability distributions. The results of this effort show that, although joint flexibility has a substantial effect on the modal dynamic response of periodic large space trusses, the effect of any reasonable uncertainty or randomness associated with these joint flexibilities is insignificant.

A space station Structures and Assembly Verification Experiment, SAVE

NASA Technical Reports Server (NTRS)

Russell, R. A.; Raney, J. P.; Deryder, L. J.

1986-01-01

The Space Station structure has been baselined to be a 5 M (16.4 ft) erectable truss. This structure will provide the overall framework to attach laboratory modules and other systems, subsystems and utilities. The assembly of this structure represents a formidable EVA challenge. To validate this capability the Space Station Structures/Dynamics Technical Integration Panel (TIP) met to develop the necessary data for an integrated STS structures flight experiment. As a result of this meeting, the Langley Research Center initiated a joint Langley/Boeing Aerospace Company study which supported the structures/dynamics TIP in developing the preliminary definition and design of a 5 M erectable space station truss and the resources required for a proposed flight experiment. The purpose of the study was to: (1) devise methods of truss assembly by astronauts; (2) define a specific test matrix for dynamic characterization; (3) identify instrumentation and data system requirements; (4) determine the power, propulsion and control requirements for the truss on-orbit for 3 years; (5) study the packaging of the experiment in the orbiter cargo bay; (6) prepare a preliminary cost estimate and schedule for the experiment; and (7) provide a list of potential follow-on experiments using the structure as a free flyer. The results of this three month study are presented.

The effect of waist twisting on walking speed of an amphibious salamander like robot

NASA Astrophysics Data System (ADS)

Yin, Xin-Yan; Jia, Li-Chao; Wang, Chen; Xie, Guang-Ming

2016-06-01

Amphibious salamanders often swing their waist to coordinate quadruped walking in order to improve their crawling speed. A robot with a swing waist joint, like an amphibious salamander, is used to mimic this locomotion. A control method is designed to allow the robot to maintain the rotational speed of its legs continuous and avoid impact between its legs and the ground. An analytical expression is established between the amplitude of the waist joint and the step length. Further, an optimization amplitude is obtained corresponding to the maximum stride. The simulation results based on automatic dynamic analysis of mechanical systems (ADAMS) and physical experiments verify the rationality and validity of this expression.

Neural controller for adaptive movements with unforeseen payloads.

PubMed

Kuperstein, M; Wang, J

1990-01-01

A theory and computer simulation of a neural controller that learns to move and position a link carrying an unforeseen payload accurately are presented. The neural controller learns adaptive dynamic control from its own experience. It does not use information about link mass, link length, or direction of gravity, and it uses only indirect uncalibrated information about payload and actuator limits. Its average positioning accuracy across a large range of payloads after learning is 3% of the positioning range. This neural controller can be used as a basis for coordinating any number of sensory inputs with limbs of any number of joints. The feedforward nature of control allows parallel implementation in real time across multiple joints.

Effect of Initial Microstructure on the Microstructural Evolution and Joint Efficiency of a WE43 Alloy During Friction Stir Welding

DTIC Science & Technology

2013-04-01

to maximize joint efficiency. 15. SUBJECT TERMS friction stir welding, strain rate, dynamic recrystallization , joint efficiency, stir zone (SZ...stir welding, Strain rate, Dynamic recrystallization , Joint efficiency, Stir Zone (SZ) Abstract The initial microstructure plays an important role in... eutectic Mg17Al12 phase. Park et al. [7] demonstrated the importance of texture and related it to the mechanical properties of an AZ61 alloy

An Approach and Framework to Synchronize Joint Exercises and Training with Military Operations

DTIC Science & Technology

2014-06-06

13. SUPPLEMENTARY NOTES 14. ABSTRACT In this dynamic, complex, and uncertain global environment, supporting and conducting joint military...achieved by leveraging a globally networked approach and an integrated framework that shares resources and coordinates activities. A recommended...Intentionally left blank ABSTRACT In this dynamic, complex, and uncertain global environment, supporting and conducting joint military

Effect of static foot posture on the dynamic stiffness of foot joints during walking.

PubMed

Sanchis-Sales, E; Sancho-Bru, J L; Roda-Sales, A; Pascual-Huerta, J

2018-05-01

The static foot posture has been related to the development of lower limb injuries. This study aimed to investigate the dynamic stiffness of foot joints during gait in the sagittal plane to understand the role of the static foot posture in the development of injuries. Seventy healthy adult male subjects with different static postures, assessed by the Foot Posture Index (FPI) (30 normal, 20 highly pronated and 20 highly supinated), were recruited. Kinematic and kinetic data were recorded using an optical motion capture system and a pressure platform, and dynamic stiffness at the different stages of the stance was calculated from the slopes of the linear regression on the flexion moment-angle curves. The effect of foot type on dynamic stiffness and on ranges of motion and moments was analysed using ANOVAs and post-hoc tests, and linear correlation between dynamic stiffness and FPI was also tested. Highly pronated feet showed a significantly smaller range of motion at the ankle and metatarsophalangeal joints and also a larger range of moments at the metatarsophalangeal joint than highly supinated feet. Dynamic stiffness during propulsion was significantly greater at all foot joints for highly pronated feet, with positive significant correlations with the squared FPI. Highly supinated feet showed greater dynamic stiffness than normal feet, although to a lesser extent. Highly pronated feet during normal gait experienced the greatest decrease in the dorsiflexor moments during propulsion, normal feet being the most balanced regarding work generated and absorbed. Extreme static foot postures show greater dynamic stiffness during propulsion and greater absorbed work, which increases the risk of developing injuries. The data presented may be used when designing orthotics or prostheses, and also when planning surgery that modifies joint stiffness. Copyright © 2018 Elsevier B.V. All rights reserved.

Upper extremity interaction with a helicopter side airbag: injury criteria for dynamic hyperextension of the female elbow joint.

PubMed

Duma, Stefan M; Hansen, Gail A; Kennedy, Eric A; Rath, Amber L; McNally, Craig; Kemper, Andrew R; Smith, Eric P; Brolinson, P Gunnar; Stitzel, Joel D; Davis, Martin B; Bass, Cameron R; Brozoski, Frederick T; McEntire, B Joseph; Alem, Nabih M; Crowley, John S

2004-11-01

This paper describes a three part analysis to characterize the interaction between the female upper extremity and a helicopter cockpit side airbag system and to develop dynamic hyperextension injury criteria for the female elbow joint. Part I involved a series of 10 experiments with an original Army Black Hawk helicopter side airbag. A 5(th) percentile female Hybrid III instrumented upper extremity was used to demonstrate side airbag upper extremity loading. Two out of the 10 tests resulted in high elbow bending moments of 128 Nm and 144 Nm. Part II included dynamic hyperextension tests on 24 female cadaver elbow joints. The energy source was a drop tower utilizing a three-point bending configuration to apply elbow bending moments matching the previously conducted side airbag tests. Post-test necropsy showed that 16 of the 24 elbow joint tests resulted in injuries. Injury severity ranged from minor cartilage damage to more moderate joint dislocations and severe transverse fractures of the distal humerus. Peak elbow bending moments ranged from 42.4 Nm to 146.3 Nm. Peak bending moment proved to be a significant indicator of any elbow injury (p = 0.02) as well as elbow joint dislocation (p = 0.01). Logistic regression analyses were used to develop single and multiple variate injury risk functions. Using peak moment data for the entire test population, a 50% risk of obtaining any elbow injury was found at 56 Nm while a 50% risk of sustaining an elbow joint dislocation was found at 93 Nm for the female population. These results indicate that the peak elbow bending moments achieved in Part I are associated with a greater than 90% risk for elbow injury. Subsequently, the airbag was re-designed in an effort to mitigate this as well as the other upper extremity injury risks. Part III assessed the redesigned side airbag module to ensure injury risks had been reduced prior to implementing the new system. To facilitate this, 12 redesigned side airbag deployments were conducted using the same procedures as Part I. Results indicate that the re-designed side airbag has effectively mitigated elbow injury risks induced by the original side airbag design. It is anticipated that this study will provide researchers with additional injury criteria for assessing upper extremity injury risk caused by both military and automotive side airbag deployments.

Rhythm Patterns Interaction - Synchronization Behavior for Human-Robot Joint Action

PubMed Central

Mörtl, Alexander; Lorenz, Tamara; Hirche, Sandra

2014-01-01

Interactive behavior among humans is governed by the dynamics of movement synchronization in a variety of repetitive tasks. This requires the interaction partners to perform for example rhythmic limb swinging or even goal-directed arm movements. Inspired by that essential feature of human interaction, we present a novel concept and design methodology to synthesize goal-directed synchronization behavior for robotic agents in repetitive joint action tasks. The agents’ tasks are described by closed movement trajectories and interpreted as limit cycles, for which instantaneous phase variables are derived based on oscillator theory. Events segmenting the trajectories into multiple primitives are introduced as anchoring points for enhanced synchronization modes. Utilizing both continuous phases and discrete events in a unifying view, we design a continuous dynamical process synchronizing the derived modes. Inverse to the derivation of phases, we also address the generation of goal-directed movements from the behavioral dynamics. The developed concept is implemented to an anthropomorphic robot. For evaluation of the concept an experiment is designed and conducted in which the robot performs a prototypical pick-and-place task jointly with human partners. The effectiveness of the designed behavior is successfully evidenced by objective measures of phase and event synchronization. Feedback gathered from the participants of our exploratory study suggests a subjectively pleasant sense of interaction created by the interactive behavior. The results highlight potential applications of the synchronization concept both in motor coordination among robotic agents and in enhanced social interaction between humanoid agents and humans. PMID:24752212

Decentralized adaptive robust control based on sliding mode and nonlinear compensator for the control of ankle movement using functional electrical stimulation of agonist-antagonist muscles

NASA Astrophysics Data System (ADS)

Kobravi, Hamid-Reza; Erfanian, Abbas

2009-08-01

A decentralized control methodology is designed for the control of ankle dorsiflexion and plantarflexion in paraplegic subjects with electrical stimulation of tibialis anterior and calf muscles. Each muscle joint is considered as a subsystem and individual controllers are designed for each subsystem. Each controller operates solely on its associated subsystem, with no exchange of information between the subsystems. The interactions between the subsystems are taken as external disturbances for each isolated subsystem. In order to achieve robustness with respect to external disturbances, unmodeled dynamics, model uncertainty and time-varying properties of muscle-joint dynamics, a robust control framework is proposed which is based on the synergistic combination of an adaptive nonlinear compensator with a sliding mode control and is referred to as an adaptive robust control. Extensive simulations and experiments on healthy and paraplegic subjects were performed to demonstrate the robustness against the time-varying properties of muscle-joint dynamics, day-to-day variations, subject-to-subject variations, fast convergence, stability and tracking accuracy of the proposed method. The results indicate that the decentralized robust control provides excellent tracking control for different reference trajectories and can generate control signals to compensate the muscle fatigue and reject the external disturbance. Moreover, the controller is able to automatically regulate the interaction between agonist and antagonist muscles under different conditions of operating without any preprogrammed antagonist activities.

Decentralized adaptive robust control based on sliding mode and nonlinear compensator for the control of ankle movement using functional electrical stimulation of agonist-antagonist muscles.

PubMed

Kobravi, Hamid-Reza; Erfanian, Abbas

2009-08-01

A decentralized control methodology is designed for the control of ankle dorsiflexion and plantarflexion in paraplegic subjects with electrical stimulation of tibialis anterior and calf muscles. Each muscle joint is considered as a subsystem and individual controllers are designed for each subsystem. Each controller operates solely on its associated subsystem, with no exchange of information between the subsystems. The interactions between the subsystems are taken as external disturbances for each isolated subsystem. In order to achieve robustness with respect to external disturbances, unmodeled dynamics, model uncertainty and time-varying properties of muscle-joint dynamics, a robust control framework is proposed which is based on the synergistic combination of an adaptive nonlinear compensator with a sliding mode control and is referred to as an adaptive robust control. Extensive simulations and experiments on healthy and paraplegic subjects were performed to demonstrate the robustness against the time-varying properties of muscle-joint dynamics, day-to-day variations, subject-to-subject variations, fast convergence, stability and tracking accuracy of the proposed method. The results indicate that the decentralized robust control provides excellent tracking control for different reference trajectories and can generate control signals to compensate the muscle fatigue and reject the external disturbance. Moreover, the controller is able to automatically regulate the interaction between agonist and antagonist muscles under different conditions of operating without any preprogrammed antagonist activities.

Upper limb joint forces and moments during underwater cyclical movements.

PubMed

Lauer, Jessy; Rouard, Annie Hélène; Vilas-Boas, João Paulo

2016-10-03

Sound inverse dynamics modeling is lacking in aquatic locomotion research because of the difficulty in measuring hydrodynamic forces in dynamic conditions. Here we report the successful implementation and validation of an innovative methodology crossing new computational fluid dynamics and inverse dynamics techniques to quantify upper limb joint forces and moments while moving in water. Upper limb kinematics of seven male swimmers sculling while ballasted with 4kg was recorded through underwater motion capture. Together with body scans, segment inertial properties, and hydrodynamic resistances computed from a unique dynamic mesh algorithm capable to handle large body deformations, these data were fed into an inverse dynamics model to solve for joint kinetics. Simulation validity was assessed by comparing the impulse produced by the arms, calculated by integrating vertical forces over a stroke period, to the net theoretical impulse of buoyancy and ballast forces. A resulting gap of 1.2±3.5% provided confidence in the results. Upper limb joint load was within 5% of swimmer׳s body weight, which tends to supports the use of low-load aquatic exercises to reduce joint stress. We expect this significant methodological improvement to pave the way towards deeper insights into the mechanics of aquatic movement and the establishment of practice guidelines in rehabilitation, fitness or swimming performance. Copyright © 2016 Elsevier Ltd. All rights reserved.

The Software Engineering Laboratory: An operational software experience factory

NASA Technical Reports Server (NTRS)

Basili, Victor R.; Caldiera, Gianluigi; Mcgarry, Frank; Pajerski, Rose; Page, Gerald; Waligora, Sharon

1992-01-01

For 15 years, the Software Engineering Laboratory (SEL) has been carrying out studies and experiments for the purpose of understanding, assessing, and improving software and software processes within a production software development environment at NASA/GSFC. The SEL comprises three major organizations: (1) NASA/GSFC, Flight Dynamics Division; (2) University of Maryland, Department of Computer Science; and (3) Computer Sciences Corporation, Flight Dynamics Technology Group. These organizations have jointly carried out several hundred software studies, producing hundreds of reports, papers, and documents, all of which describe some aspect of the software engineering technology that was analyzed in the flight dynamics environment at NASA. The studies range from small, controlled experiments (such as analyzing the effectiveness of code reading versus that of functional testing) to large, multiple project studies (such as assessing the impacts of Ada on a production environment). The organization's driving goal is to improve the software process continually, so that sustained improvement may be observed in the resulting products. This paper discusses the SEL as a functioning example of an operational software experience factory and summarizes the characteristics of and major lessons learned from 15 years of SEL operations.

In Vivo Measurement of Glenohumeral Joint Contact Patterns

NASA Astrophysics Data System (ADS)

Bey, Michael J.; Kline, Stephanie K.; Zauel, Roger; Kolowich, Patricia A.; Lock, Terrence R.

2009-12-01

The objectives of this study were to describe a technique for measuring in-vivo glenohumeral joint contact patterns during dynamic activities and to demonstrate application of this technique. The experimental technique calculated joint contact patterns by combining CT-based 3D bone models with joint motion data that were accurately measured from biplane x-ray images. Joint contact patterns were calculated for the repaired and contralateral shoulders of 20 patients who had undergone rotator cuff repair. Significant differences in joint contact patterns were detected due to abduction angle and shoulder condition (i.e., repaired versus contralateral). Abduction angle had a significant effect on the superior/inferior contact center position, with the average joint contact center of the repaired shoulder 12.1% higher on the glenoid than the contralateral shoulder. This technique provides clinically relevant information by calculating in-vivo joint contact patterns during dynamic conditions and overcomes many limitations associated with conventional techniques for quantifying joint mechanics.

Multibody dynamic simulation of knee contact mechanics

PubMed Central

Bei, Yanhong; Fregly, Benjamin J.

2006-01-01

Multibody dynamic musculoskeletal models capable of predicting muscle forces and joint contact pressures simultaneously would be valuable for studying clinical issues related to knee joint degeneration and restoration. Current three-dimensional multi-body knee models are either quasi-static with deformable contact or dynamic with rigid contact. This study proposes a computationally efficient methodology for combining multibody dynamic simulation methods with a deformable contact knee model. The methodology requires preparation of the articular surface geometry, development of efficient methods to calculate distances between contact surfaces, implementation of an efficient contact solver that accounts for the unique characteristics of human joints, and specification of an application programming interface for integration with any multibody dynamic simulation environment. The current implementation accommodates natural or artificial tibiofemoral joint models, small or large strain contact models, and linear or nonlinear material models. Applications are presented for static analysis (via dynamic simulation) of a natural knee model created from MRI and CT data and dynamic simulation of an artificial knee model produced from manufacturer’s CAD data. Small and large strain natural knee static analyses required 1 min of CPU time and predicted similar contact conditions except for peak pressure, which was higher for the large strain model. Linear and nonlinear artificial knee dynamic simulations required 10 min of CPU time and predicted similar contact force and torque but different contact pressures, which were lower for the nonlinear model due to increased contact area. This methodology provides an important step toward the realization of dynamic musculoskeletal models that can predict in vivo knee joint motion and loading simultaneously. PMID:15564115

The use of ultrasound in the assessment of the glenoid labrum of the glenohumeral joint. Part II: Examples of labral pathologies

PubMed Central

Tarczyńska, Marta

2012-01-01

Labral pathologies of the glenohumeral joint are most commonly caused by trauma. The majority of lesions affect the anterior part of labrum, resulting from much higher frequency of anterior shoulder dislocations over posterior ones. Another subgroup of labral lesions, not directly related to joint instability, are SLAP tears. Other findings include degenerative changes of labrum and paralabral cysts. Diagnostic imaging is crucial for making a decision regarding operative treatment. Apart from a standard X-ray examination, the imaging mainly relies on magnetic resonance or computed tomography arthrography. Based on their own experience, the authors propose the use of ultrasound in the assessment of labral tears of the glenohumeral joint. Different signs indicating labral pathology may be discovered and assessed during ultrasound examination. They include permanent displacement of the labrum onto the glenoid, labral instability during dynamic examination, lack of the labrum in the anatomical position, hypoechoic zone at the base of the labrum >2 mm in width, residual or swollen labrum as well as paralabral cyst(s). The most frequent appearance of labral pathology is displacement of the anteroinferior labrum onto the external aspect of the glenoid typically seen after anterior shoulder dislocation. The another most important US feature is labral instability while dynamically examined. The swelling or reduced size of the labrum usually indicates degeneration. This article presents sonographic images of selected labral pathologies. PMID:26672471

DYMAFLEX: DYnamic Manipulation FLight EXperiment

DTIC Science & Technology

2013-09-03

thrust per nozzle and minimize propellant mass and tank mass. This study compared carbon dioxide, nitrous oxide, and R134-A. These results were...equations of mo- tion of a space manipulator, showing their top- level, matrix- vector representation to be of iden- tical form to those of a fixed-base...the system inertia matrix, q is the po- sition state vector (consisting of the manipulator joint angles θ, spacecraft attitude quaternion, and

Joint reconstruction of dynamic PET activity and kinetic parametric images using total variation constrained dictionary sparse coding

NASA Astrophysics Data System (ADS)

Yu, Haiqing; Chen, Shuhang; Chen, Yunmei; Liu, Huafeng

2017-05-01

Dynamic positron emission tomography (PET) is capable of providing both spatial and temporal information of radio tracers in vivo. In this paper, we present a novel joint estimation framework to reconstruct temporal sequences of dynamic PET images and the coefficients characterizing the system impulse response function, from which the associated parametric images of the system macro parameters for tracer kinetics can be estimated. The proposed algorithm, which combines statistical data measurement and tracer kinetic models, integrates a dictionary sparse coding (DSC) into a total variational minimization based algorithm for simultaneous reconstruction of the activity distribution and parametric map from measured emission sinograms. DSC, based on the compartmental theory, provides biologically meaningful regularization, and total variation regularization is incorporated to provide edge-preserving guidance. We rely on techniques from minimization algorithms (the alternating direction method of multipliers) to first generate the estimated activity distributions with sub-optimal kinetic parameter estimates, and then recover the parametric maps given these activity estimates. These coupled iterative steps are repeated as necessary until convergence. Experiments with synthetic, Monte Carlo generated data, and real patient data have been conducted, and the results are very promising.

Controlling under-actuated robot arms using a high speed dynamics process

NASA Technical Reports Server (NTRS)

Jain, Abhinandan (Inventor); Rodriguez, Guillermo (Inventor)

1994-01-01

The invention controls an under-actuated manipulator by first obtaining predetermined active joint accelerations of the active joints and the passive joint friction forces of the passive joints, then computing articulated body qualities for each of the joints from the current positions of the links, and finally computing from the articulated body qualities and from the active joint accelerations and the passive joint forces, active joint forces of the active joints. Ultimately, the invention transmits servo commands to the active joint forces thus computed to the respective ones of the joint servos. The computation of the active joint forces is accomplished using a recursive dynamics algorithm. In this computation, an inward recursion is first carried out for each link, beginning with the outermost link in order to compute the residual link force of each link from the active joint acceleration if the corresponding joint is active, or from the known passive joint force if the corresponding joint is passive. Then, an outward recursion is carried out for each link in which the active joint force is computed from the residual link force if the corresponding joint is active or the passive joint acceleration is computed from the residual link force if the corresponding joint is passive.

Interlimb symmetry of dynamic knee joint stiffness and co-contraction is maintained in early stage knee osteoarthritis.

PubMed

Collins, A T; Richardson, R T; Higginson, J S

2014-08-01

Individuals with knee OA often exhibit greater co-contraction of antagonistic muscle groups surrounding the affected joint which may lead to increases in dynamic joint stiffness. These detrimental changes in the symptomatic limb may also exist in the contralateral limb, thus contributing to its risk of developing knee osteoarthritis. The purpose of this study is to investigate the interlimb symmetry of dynamic knee joint stiffness and muscular co-contraction in knee osteoarthritis. Muscular co-contraction and dynamic knee joint stiffness were assessed in 17 subjects with mild to moderate unilateral medial compartment knee osteoarthritis and 17 healthy control subjects while walking at a controlled speed (1.0m/s). Paired and independent t-tests determined whether significant differences exist between groups (p<0.05). There were no significant differences in dynamic joint stiffness or co-contraction between the OA symptomatic and OA contralateral group (p=0.247, p=0.874, respectively) or between the OA contralateral and healthy group (p=0.635, p=0.078, respectively). There was no significant difference in stiffness between the OA symptomatic and healthy group (p=0.600); however, there was a slight trend toward enhanced co-contraction in the symptomatic knees compared to the healthy group (p=0.051). Subjects with mild to moderate knee osteoarthritis maintain symmetric control strategies during gait. Copyright © 2014 Elsevier Ltd. All rights reserved.

Interlimb symmetry of dynamic knee joint stiffness and co-contraction is maintained in early stage knee osteoarthritis

PubMed Central

Collins, A.T.; Richardson, R.T.; Higginson, J.S.

2014-01-01

Individuals with knee OA often exhibit greater co-contraction of antagonistic muscle groups surrounding the affected joint which may lead to increases in dynamic joint stiffness. These detrimental changes in the symptomatic limb may also exist in the contralateral limb, thus contributing to its risk of developing knee osteoarthritis. The purpose of this study is to investigate the interlimb symmetry of dynamic knee joint stiffness and muscular co-contraction in knee osteoarthritis. Muscular co-contraction and dynamic knee joint stiffness were assessed in 17 subjects with mild to moderate unilateral medial compartment knee osteoarthritis and 17 healthy control subjects while walking at a controlled speed (1.0 m/s). Paired and independent t-tests determined whether significant differences exist between groups (p < 0.05). There were no significant differences in dynamic joint stiffness or co-contraction between the OA symptomatic and OA contralateral group (p = 0.247, p = 0.874, respectively) or between the OA contralateral and healthy group (p = 0.635, p = 0.078, respectively). There was no significant difference in stiffness between the OA symptomatic and healthy group (p = 0.600); however, there was a slight trend toward enhanced co-contraction in the symptomatic knees compared to the healthy group (p = 0.051). Subjects with mild to moderate knee osteoarthritis maintain symmetric control strategies during gait. PMID:24768278

Joint symbolic dynamics for the assessment of cardiovascular and cardiorespiratory interactions

PubMed Central

Baumert, Mathias; Javorka, Michal; Kabir, Muammar

2015-01-01

Beat-to-beat variations in heart period provide information on cardiovascular control and are closely linked to variations in arterial pressure and respiration. Joint symbolic analysis of heart period, systolic arterial pressure and respiration allows for a simple description of their shared short-term dynamics that are governed by cardiac baroreflex control and cardiorespiratory coupling. In this review, we discuss methodology and research applications. Studies suggest that analysis of joint symbolic dynamics provides a powerful tool for identifying physiological and pathophysiological changes in cardiovascular and cardiorespiratory control. PMID:25548272

Joint symbolic dynamics for the assessment of cardiovascular and cardiorespiratory interactions.

PubMed

Baumert, Mathias; Javorka, Michal; Kabir, Muammar

2015-02-13

Beat-to-beat variations in heart period provide information on cardiovascular control and are closely linked to variations in arterial pressure and respiration. Joint symbolic analysis of heart period, systolic arterial pressure and respiration allows for a simple description of their shared short-term dynamics that are governed by cardiac baroreflex control and cardiorespiratory coupling. In this review, we discuss methodology and research applications. Studies suggest that analysis of joint symbolic dynamics provides a powerful tool for identifying physiological and pathophysiological changes in cardiovascular and cardiorespiratory control.

Statistical inference for noisy nonlinear ecological dynamic systems.

PubMed

Wood, Simon N

2010-08-26

Chaotic ecological dynamic systems defy conventional statistical analysis. Systems with near-chaotic dynamics are little better. Such systems are almost invariably driven by endogenous dynamic processes plus demographic and environmental process noise, and are only observable with error. Their sensitivity to history means that minute changes in the driving noise realization, or the system parameters, will cause drastic changes in the system trajectory. This sensitivity is inherited and amplified by the joint probability density of the observable data and the process noise, rendering it useless as the basis for obtaining measures of statistical fit. Because the joint density is the basis for the fit measures used by all conventional statistical methods, this is a major theoretical shortcoming. The inability to make well-founded statistical inferences about biological dynamic models in the chaotic and near-chaotic regimes, other than on an ad hoc basis, leaves dynamic theory without the methods of quantitative validation that are essential tools in the rest of biological science. Here I show that this impasse can be resolved in a simple and general manner, using a method that requires only the ability to simulate the observed data on a system from the dynamic model about which inferences are required. The raw data series are reduced to phase-insensitive summary statistics, quantifying local dynamic structure and the distribution of observations. Simulation is used to obtain the mean and the covariance matrix of the statistics, given model parameters, allowing the construction of a 'synthetic likelihood' that assesses model fit. This likelihood can be explored using a straightforward Markov chain Monte Carlo sampler, but one further post-processing step returns pure likelihood-based inference. I apply the method to establish the dynamic nature of the fluctuations in Nicholson's classic blowfly experiments.

Efficient finite element modelling for the investigation of the dynamic behaviour of a structure with bolted joints

NASA Astrophysics Data System (ADS)

Omar, R.; Rani, M. N. Abdul; Yunus, M. A.; Mirza, W. I. I. Wan Iskandar; Zin, M. S. Mohd

2018-04-01

A simple structure with bolted joints consists of the structural components, bolts and nuts. There are several methods to model the structures with bolted joints, however there is no reliable, efficient and economic modelling methods that can accurately predict its dynamics behaviour. Explained in this paper is an investigation that was conducted to obtain an appropriate modelling method for bolted joints. This was carried out by evaluating four different finite element (FE) models of the assembled plates and bolts namely the solid plates-bolts model, plates without bolt model, hybrid plates-bolts model and simplified plates-bolts model. FE modal analysis was conducted for all four initial FE models of the bolted joints. Results of the FE modal analysis were compared with the experimental modal analysis (EMA) results. EMA was performed to extract the natural frequencies and mode shapes of the test physical structure with bolted joints. Evaluation was made by comparing the number of nodes, number of elements, elapsed computer processing unit (CPU) time, and the total percentage of errors of each initial FE model when compared with EMA result. The evaluation showed that the simplified plates-bolts model could most accurately predict the dynamic behaviour of the structure with bolted joints. This study proved that the reliable, efficient and economic modelling of bolted joints, mainly the representation of the bolting, has played a crucial element in ensuring the accuracy of the dynamic behaviour prediction.

Adaptive Control of Exoskeleton Robots for Periodic Assistive Behaviours Based on EMG Feedback Minimisation.

PubMed

Peternel, Luka; Noda, Tomoyuki; Petrič, Tadej; Ude, Aleš; Morimoto, Jun; Babič, Jan

2016-01-01

In this paper we propose an exoskeleton control method for adaptive learning of assistive joint torque profiles in periodic tasks. We use human muscle activity as feedback to adapt the assistive joint torque behaviour in a way that the muscle activity is minimised. The user can then relax while the exoskeleton takes over the task execution. If the task is altered and the existing assistive behaviour becomes inadequate, the exoskeleton gradually adapts to the new task execution so that the increased muscle activity caused by the new desired task can be reduced. The advantage of the proposed method is that it does not require biomechanical or dynamical models. Our proposed learning system uses Dynamical Movement Primitives (DMPs) as a trajectory generator and parameters of DMPs are modulated using Locally Weighted Regression. Then, the learning system is combined with adaptive oscillators that determine the phase and frequency of motion according to measured Electromyography (EMG) signals. We tested the method with real robot experiments where subjects wearing an elbow exoskeleton had to move an object of an unknown mass according to a predefined reference motion. We further evaluated the proposed approach on a whole-arm exoskeleton to show that it is able to adaptively derive assistive torques even for multiple-joint motion.

Reliability Study of Solder Paste Alloy for the Improvement of Solder Joint at Surface Mount Fine-Pitch Components.

PubMed

Rahman, Mohd Nizam Ab; Zubir, Noor Suhana Mohd; Leuveano, Raden Achmad Chairdino; Ghani, Jaharah A; Mahmood, Wan Mohd Faizal Wan

2014-12-02

The significant increase in metal costs has forced the electronics industry to provide new materials and methods to reduce costs, while maintaining customers' high-quality expectations. This paper considers the problem of most electronic industries in reducing costly materials, by introducing a solder paste with alloy composition tin 98.3%, silver 0.3%, and copper 0.7%, used for the construction of the surface mount fine-pitch component on a Printing Wiring Board (PWB). The reliability of the solder joint between electronic components and PWB is evaluated through the dynamic characteristic test, thermal shock test, and Taguchi method after the printing process. After experimenting with the dynamic characteristic test and thermal shock test with 20 boards, the solder paste was still able to provide a high-quality solder joint. In particular, the Taguchi method is used to determine the optimal control parameters and noise factors of the Solder Printer (SP) machine, that affects solder volume and solder height. The control parameters include table separation distance, squeegee speed, squeegee pressure, and table speed of the SP machine. The result shows that the most significant parameter for the solder volume is squeegee pressure (2.0 mm), and the solder height is the table speed of the SP machine (2.5 mm/s).

Reliability Study of Solder Paste Alloy for the Improvement of Solder Joint at Surface Mount Fine-Pitch Components

PubMed Central

Rahman, Mohd Nizam Ab.; Zubir, Noor Suhana Mohd; Leuveano, Raden Achmad Chairdino; Ghani, Jaharah A.; Mahmood, Wan Mohd Faizal Wan

2014-01-01

The significant increase in metal costs has forced the electronics industry to provide new materials and methods to reduce costs, while maintaining customers’ high-quality expectations. This paper considers the problem of most electronic industries in reducing costly materials, by introducing a solder paste with alloy composition tin 98.3%, silver 0.3%, and copper 0.7%, used for the construction of the surface mount fine-pitch component on a Printing Wiring Board (PWB). The reliability of the solder joint between electronic components and PWB is evaluated through the dynamic characteristic test, thermal shock test, and Taguchi method after the printing process. After experimenting with the dynamic characteristic test and thermal shock test with 20 boards, the solder paste was still able to provide a high-quality solder joint. In particular, the Taguchi method is used to determine the optimal control parameters and noise factors of the Solder Printer (SP) machine, that affects solder volume and solder height. The control parameters include table separation distance, squeegee speed, squeegee pressure, and table speed of the SP machine. The result shows that the most significant parameter for the solder volume is squeegee pressure (2.0 mm), and the solder height is the table speed of the SP machine (2.5 mm/s). PMID:28788270

Adaptive Control of Exoskeleton Robots for Periodic Assistive Behaviours Based on EMG Feedback Minimisation

PubMed Central

Peternel, Luka; Noda, Tomoyuki; Petrič, Tadej; Ude, Aleš; Morimoto, Jun; Babič, Jan

2016-01-01

In this paper we propose an exoskeleton control method for adaptive learning of assistive joint torque profiles in periodic tasks. We use human muscle activity as feedback to adapt the assistive joint torque behaviour in a way that the muscle activity is minimised. The user can then relax while the exoskeleton takes over the task execution. If the task is altered and the existing assistive behaviour becomes inadequate, the exoskeleton gradually adapts to the new task execution so that the increased muscle activity caused by the new desired task can be reduced. The advantage of the proposed method is that it does not require biomechanical or dynamical models. Our proposed learning system uses Dynamical Movement Primitives (DMPs) as a trajectory generator and parameters of DMPs are modulated using Locally Weighted Regression. Then, the learning system is combined with adaptive oscillators that determine the phase and frequency of motion according to measured Electromyography (EMG) signals. We tested the method with real robot experiments where subjects wearing an elbow exoskeleton had to move an object of an unknown mass according to a predefined reference motion. We further evaluated the proposed approach on a whole-arm exoskeleton to show that it is able to adaptively derive assistive torques even for multiple-joint motion. PMID:26881743

Getting in shape: Reconstructing three-dimensional long-track speed skating kinematics by comparing several body pose reconstruction techniques.

PubMed

van der Kruk, E; Schwab, A L; van der Helm, F C T; Veeger, H E J

2018-03-01

In gait studies body pose reconstruction (BPR) techniques have been widely explored, but no previous protocols have been developed for speed skating, while the peculiarities of the skating posture and technique do not automatically allow for the transfer of the results of those explorations to kinematic skating data. The aim of this paper is to determine the best procedure for body pose reconstruction and inverse dynamics of speed skating, and to what extend this choice influences the estimation of joint power. The results show that an eight body segment model together with a global optimization method with revolute joint in the knee and in the lumbosacral joint, while keeping the other joints spherical, would be the most realistic model to use for the inverse kinematics in speed skating. To determine joint power, this method should be combined with a least-square error method for the inverse dynamics. Reporting on the BPR technique and the inverse dynamic method is crucial to enable comparison between studies. Our data showed an underestimation of up to 74% in mean joint power when no optimization procedure was applied for BPR and an underestimation of up to 31% in mean joint power when a bottom-up inverse dynamics method was chosen instead of a least square error approach. Although these results are aimed at speed skating, reporting on the BPR procedure and the inverse dynamics method, together with setting a golden standard should be common practice in all human movement research to allow comparison between studies. Copyright © 2018 Elsevier Ltd. All rights reserved.

Effects of laser power density on static and dynamic mechanical properties of dissimilar stainless steel welded joints

NASA Astrophysics Data System (ADS)

Wei, Yan-Peng; Li, Mao-Hui; Yu, Gang; Wu, Xian-Qian; Huang, Chen-Guang; Duan, Zhu-Ping

2012-10-01

The mechanical properties of laser welded joints under impact loadings such as explosion and car crash etc. are critical for the engineering designs. The hardness, static and dynamic mechanical properties of AISI304 and AISI316 L dissimilar stainless steel welded joints by CO2 laser were experimentally studied. The dynamic strain-stress curves at the strain rate around 103 s-1 were obtained by the split Hopkinson tensile bar (SHTB). The static mechanical properties of the welded joints have little changes with the laser power density and all fracture occurs at 316 L side. However, the strain rate sensitivity has a strong dependence on laser power density. The value of strain rate factor decreases with the increase of laser power density. The welded joint which may be applied for the impact loading can be obtained by reducing the laser power density in the case of welding quality assurance.

Synchronization of Coupled Dynamical Systems: Tolerance to Weak Connectivity and Arbitrarily Bounded Time-Varying Delays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meng, Ziyang; Yang, Tao; Li, Guoqi

Here, we study synchronization of coupled linear systems over networks with weak connectivity and nonuniform time-varying delays. We focus on the case where the internal dynamics are time-varying but non-expansive (stable dynamics with a quadratic Lyapunov function). Both uniformly jointly connected and infinitely jointly connected communication topologies are considered. A new concept of quadratic synchronization is introduced. We first show that global asymptotic quadratic synchronization can be achieved over directed networks with uniform joint connectivity and arbitrarily bounded delays. We then study the case of infinitely jointly connected communication topology. In particular, for the undirected communication topologies, it turns outmore » that the existence of a uniform time interval for the jointly connected communication topology is not necessary and quadratic synchronization can be achieved when the time-varying nonuniform delays are arbitrarily bounded. Finally, simulation results are provided to validate the theoretical results.« less

Synchronization of Coupled Dynamical Systems: Tolerance to Weak Connectivity and Arbitrarily Bounded Time-Varying Delays

DOE PAGES

Meng, Ziyang; Yang, Tao; Li, Guoqi; ...

2017-09-18

Here, we study synchronization of coupled linear systems over networks with weak connectivity and nonuniform time-varying delays. We focus on the case where the internal dynamics are time-varying but non-expansive (stable dynamics with a quadratic Lyapunov function). Both uniformly jointly connected and infinitely jointly connected communication topologies are considered. A new concept of quadratic synchronization is introduced. We first show that global asymptotic quadratic synchronization can be achieved over directed networks with uniform joint connectivity and arbitrarily bounded delays. We then study the case of infinitely jointly connected communication topology. In particular, for the undirected communication topologies, it turns outmore » that the existence of a uniform time interval for the jointly connected communication topology is not necessary and quadratic synchronization can be achieved when the time-varying nonuniform delays are arbitrarily bounded. Finally, simulation results are provided to validate the theoretical results.« less

Control of a flexible bracing manipulator: Integration of current research work to realize the bracing manipulator

NASA Technical Reports Server (NTRS)

Kwon, Dong-Soo

1991-01-01

All research results about flexible manipulator control were integrated to show a control scenario of a bracing manipulator. First, dynamic analysis of a flexible manipulator was done for modeling. Second, from the dynamic model, the inverse dynamic equation was derived, and the time domain inverse dynamic method was proposed for the calculation of the feedforward torque and the desired flexible coordinate trajectories. Third, a tracking controller was designed by combining the inverse dynamic feedforward control with the joint feedback control. The control scheme was applied to the tip position control of a single link flexible manipulator for zero and non-zero initial condition cases. Finally, the contact control scheme was added to the position tracking control. A control scenario of a bracing manipulator is provided and evaluated through simulation and experiment on a single link flexible manipulator.

Neuro-cognitive mechanisms of decision making in joint action: a human-robot interaction study.

PubMed

Bicho, Estela; Erlhagen, Wolfram; Louro, Luis; e Silva, Eliana Costa

2011-10-01

In this paper we present a model for action preparation and decision making in cooperative tasks that is inspired by recent experimental findings about the neuro-cognitive mechanisms supporting joint action in humans. It implements the coordination of actions and goals among the partners as a dynamic process that integrates contextual cues, shared task knowledge and predicted outcome of others' motor behavior. The control architecture is formalized by a system of coupled dynamic neural fields representing a distributed network of local but connected neural populations. Different pools of neurons encode task-relevant information about action means, task goals and context in the form of self-sustained activation patterns. These patterns are triggered by input from connected populations and evolve continuously in time under the influence of recurrent interactions. The dynamic model of joint action is evaluated in a task in which a robot and a human jointly construct a toy object. We show that the highly context sensitive mapping from action observation onto appropriate complementary actions allows coping with dynamically changing joint action situations. Copyright © 2010 Elsevier B.V. All rights reserved.

Watching proteins function with picosecond X-ray crystallography and molecular dynamics simulations.

NASA Astrophysics Data System (ADS)

Anfinrud, Philip

2006-03-01

Time-resolved electron density maps of myoglobin, a ligand-binding heme protein, have been stitched together into movies that unveil with < 2-å spatial resolution and 150-ps time-resolution the correlated protein motions that accompany and/or mediate ligand migration within the hydrophobic interior of a protein. A joint analysis of all-atom molecular dynamics (MD) calculations and picosecond time-resolved X-ray structures provides single-molecule insights into mechanisms of protein function. Ensemble-averaged MD simulations of the L29F mutant of myoglobin following ligand dissociation reproduce the direction, amplitude, and timescales of crystallographically-determined structural changes. This close agreement with experiments at comparable resolution in space and time validates the individual MD trajectories, which identify and structurally characterize a conformational switch that directs dissociated ligands to one of two nearby protein cavities. This unique combination of simulation and experiment unveils functional protein motions and illustrates at an atomic level relationships among protein structure, dynamics, and function. In collaboration with Friedrich Schotte and Gerhard Hummer, NIH.

The transport of wear particles in the prosthetic hip joint: a computational fluid dynamics investigation.

PubMed

Hölzer, Andreas; Schröder, Christian; Woiczinski, Matthias; Sadoghi, Patrick; Müller, Peter E; Jansson, Volkmar

2012-02-02

The joint fluid mechanics and transport of wear particles in the prosthetic hip joint were analyzed for subluxation and flexion motion using computational fluid dynamics (CFD). The entire joint space including a moving capsule boundary was considered. It was found that particles suspended in the joint space are drawn into the joint gap between prosthesis cup and head during subluxation, which was also documented by Lundberg et al. (2007; Journal of Biomechanics 40, 1676-1685), however, wear particles remain in the joint gap. Wear particles leave the joint gap during flexion and can finally migrate to the proximal boundaries including the acetabular bone, where the particle deposition can cause osteolysis according to the established literature. Thus, the present study supports the theory of polyethylene wear particle induced osteolysis of the acetabular bone as a major factor in the loosening of hip prosthesis cups. Copyright © 2011 Elsevier Ltd. All rights reserved.

Analysis and testing of a space crane articulating joint testbed

NASA Technical Reports Server (NTRS)

Sutter, Thomas R.; Wu, K. Chauncey

1992-01-01

The topics are presented in viewgraph form and include: space crane concept with mobile base; mechanical versus structural articulating joint; articulating joint test bed and reference truss; static and dynamic characterization completed for space crane reference truss configuration; improved linear actuators reduce articulating joint test bed backlash; 1-DOF space crane slew maneuver; boom 2 tip transient response finite element dynamic model; boom 2 tip transient response shear-corrected component modes torque driver profile; peak root member force vs. slew time torque driver profile; and open loop control of space crane motion.

Dynamic Distraction External Fixation for Contracture of the Metacarpophalangeal Joint.

PubMed

Seigerman, Daniel A; Tan, Virak

2015-12-01

Metacarpophalangeal (MP) joint contractures are common after traumatic injury, and can be difficult to manage. After surgical capsulectomy, it remains challenging to maintain motion that was obtained at the time of surgery. Our group uses a novel, prefabricated digital external fixator to provide both distraction, and motion therapy across the MP joint after surgical treatment of MP contracture. The purpose of this technique is to demonstrate the effectiveness of an adjunctive dynamic distraction external fixator for the maintenance of joint motion after surgical treatment of MP contractures of the border digits.

Oxide ceramic femoral heads contribute to the oxidation of polyethylene liners in artificial hip joints.

PubMed

Pezzotti, Giuseppe; Zhu, Wenliang; Sugano, Nobuhiko; Marin, Elia; Yamamoto, Kengo; Nishiike, Naomichi; Hori, Tsubasa; Rondinella, Alfredo; McEntire, Bryan J; Bock, Ryan; Sonny Bal, B

2018-06-01

Experimental evidence demonstrates that a loss of stoichiometry at the surface of oxide bioceramic femoral heads enhances the oxidation rate of polyethylene acetabular liners in artificial hip joints. Contradicting the common notion that ceramics are bioinert, three independent experiments confirmed substantial chemical interactions between the ceramic femoral heads and their polyethylene counterparts. The experiments reported herein included hydrothermal tests, frictional tests, and hip-simulator experiments. It was discovered that oxide and non-oxide femoral heads differently affected the oxidation processes at the surface of the polyethylene liners, all other testing parameters being equal. Analytical data from X-ray photoelectron (XPS), cathodoluminescence (CL), Fourier-transform infrared (FTIR), and Raman spectroscopies unequivocally and consistently showed that the oxidation rate of polyethylene liners was greater when coupled with oxide as opposed to non-oxide ceramic heads. XPS analyses of O-Al-O bond fractions at the surface of a zirconia-toughened alumina (ZTA) short-term (20 months in vivo) femoral heads retrieval showed a ~50% reduction in favor of oxygen vacancy O-Al-V O and hydroxylated Al-O-H bonds. Off-stoichiometry drifts were confirmed in vitro under both static and dynamic conditions. They triggered oxidation and tangibly affected an advanced highly cross-linked sequentially irradiated and annealed ultra-high molecular weight polyethylene (UHMWPE) liner (increase in oxidation index up to ΔOI~1.2 after 5 × 10 5 cycles under dynamic swing conditions). Second-generation UHMWPE liners infused with vitamin E were also affected by the free flow of oxygen from the oxide femoral heads, although to a lesser extent. The fundamental findings of this study, which were also confirmed on retrievals, call for revised standards in material design and testing. Adopting these new criteria will provide an improved understanding of the importance of off-stoichiometry at the head/liner interface and may lead to significant extensions in artificial joint lifetimes. Copyright © 2018 Elsevier Ltd. All rights reserved.

Ground tests of the Dynamic Albedo of Neutron instrument operation in the passive mode with a Martian soil model

NASA Astrophysics Data System (ADS)

Shvetsov, V. N.; Dubasov, P. V.; Golovin, D. V.; Kozyrev, A. S.; Krylov, A. R.; Krylov, V. A.; Litvak, M. L.; Malakhov, A. V.; Mitrofanov, I. G.; Mokrousov, M. I.; Sanin, A. B.; Timoshenko, G. N.; Vostrukhin, A. A.; Zontikov, A. O.

2017-07-01

The results of the Dynamic Albedo of Neutrons (DAN) instrument ground tests in the passive mode of operation are presented in comparison with the numerical calculations. These test series were conducted to support the current surface measurements of DAN onboard the MSL Curiosity rover. The instrument sensitivity to detect thin subsurface layers of water ice buried at different depths in the analog of Martian soil has been evaluated during these tests. The experiments have been done with a radioisotope Pu-Be neutron source (analog of the MMRTG neutron source onboard the Curiosity rover) and the Martian soil model assembled from silicon-rich window glass pane. Water ice layers were simulated with polyethylene sheets. All experiments have been performed at the test facility built at the Joint Institute for Nuclear Research (Dubna, Russia).

Ultrasound-guided corticosteroid injection therapy for juvenile idiopathic arthritis: 12-year care experience.

PubMed

Young, Cody M; Shiels, William E; Coley, Brian D; Hogan, Mark J; Murakami, James W; Jones, Karla; Higgins, Gloria C; Rennebohm, Robert M

2012-12-01

Intra-articular corticosteroid injections are a safe and effective treatment for patients with juvenile idiopathic arthritis. The potential scope of care in ultrasound-guided corticosteroid therapy in children and a joint-based corticosteroid dose protocol designed to optimize interdisciplinary care are not found in the current literature. The purpose of this study was to report the spectrum of care, technique and safety of ultrasound-guided corticosteroid injection therapy in patients with juvenile idiopathic arthritis and to propose an age-weight-joint-based corticosteroid dose protocol. A retrospective analysis was performed of 198 patients (ages 21 months to 28 years) referred for treatment of juvenile idiopathic arthritis with corticosteroid therapy. Symptomatic joints and tendon sheaths were treated as prescribed by the referring rheumatologist. An age-weight-joint-based dose protocol was developed and utilized for corticosteroid dose prescription. A total of 1,444 corticosteroid injections (1,340 joints, 104 tendon sheaths) were performed under US guidance. Injection sites included small, medium and large appendicular skeletal joints (upper extremity 497, lower extremity 837) and six temporomandibular joints. For patients with recurrent symptoms, 414 repeat injections were performed, with an average time interval of 17.7 months (range, 0.5-101.5 months) between injections. Complications occurred in 2.6% of injections and included subcutaneous tissue atrophy, skin hypopigmentation, erythema and pruritis. US-guided corticosteroid injection therapy provides dynamic, precise and safe treatment of a broad spectrum of joints and tendon sheaths throughout the entire pediatric musculoskeletal system. An age-weight-joint-based corticosteroid dose protocol is effective and integral to interdisciplinary care of patients with juvenile idiopathic arthritis.

Does aquatic exercise reduce hip and knee joint loading? In vivo load measurements with instrumented implants

PubMed Central

Kutzner, Ines; Dymke, Jörn; Damm, Philipp; Duda, Georg N.; Günzl, Reiner; Bergmann, Georg

2017-01-01

Aquatic exercises are widely used for rehabilitation or preventive therapies in order to enable mobilization and muscle strengthening while minimizing joint loading of the lower limb. The load reducing effect of water due to buoyancy is a main advantage compared to exercises on land. However, also drag forces have to be considered that act opposite to the relative motion of the body segments and require higher muscle activity. Due to these opposing effects on joint loading, the load-reducing effect during aquatic exercises remains unknown. The aim of this study was to quantify the joint loads during various aquatic exercises and to determine the load reducing effect of water. Instrumented knee and hip implants with telemetric data transfer were used to measure the resultant joint contact forces in 12 elderly subjects (6x hip, 6x knee) in vivo. Different dynamic, weight-bearing and non-weight-bearing activities were performed by the subjects on land and in chest-high water. Non-weight-bearing hip and knee flexion/extension was performed at different velocities and with additional Aquafins. Joint forces during aquatic exercises ranged between 32 and 396% body weight (BW). Highest forces occurred during dynamic activities, followed by weight-bearing and slow non-weight-bearing activities. Compared to the same activities on land, joint forces were reduced by 36–55% in water with absolute reductions being greater than 100%BW during weight-bearing and dynamic activities. During non-weight-bearing activities, high movement velocities and additional Aquafins increased the joint forces by up to 59% and resulted in joint forces of up to 301%BW. This study confirms the load reducing effect of water during weight-bearing and dynamic exercises. Nevertheless, high drag forces result in increased joint contact forces and indicate greater muscle activity. By the choice of activity, movement velocity and additional resistive devices joint forces can be modulated individually in the course of rehabilitation or preventive therapies. PMID:28319145

Does aquatic exercise reduce hip and knee joint loading? In vivo load measurements with instrumented implants.

PubMed

Kutzner, Ines; Richter, Anja; Gordt, Katharina; Dymke, Jörn; Damm, Philipp; Duda, Georg N; Günzl, Reiner; Bergmann, Georg

2017-01-01

Aquatic exercises are widely used for rehabilitation or preventive therapies in order to enable mobilization and muscle strengthening while minimizing joint loading of the lower limb. The load reducing effect of water due to buoyancy is a main advantage compared to exercises on land. However, also drag forces have to be considered that act opposite to the relative motion of the body segments and require higher muscle activity. Due to these opposing effects on joint loading, the load-reducing effect during aquatic exercises remains unknown. The aim of this study was to quantify the joint loads during various aquatic exercises and to determine the load reducing effect of water. Instrumented knee and hip implants with telemetric data transfer were used to measure the resultant joint contact forces in 12 elderly subjects (6x hip, 6x knee) in vivo. Different dynamic, weight-bearing and non-weight-bearing activities were performed by the subjects on land and in chest-high water. Non-weight-bearing hip and knee flexion/extension was performed at different velocities and with additional Aquafins. Joint forces during aquatic exercises ranged between 32 and 396% body weight (BW). Highest forces occurred during dynamic activities, followed by weight-bearing and slow non-weight-bearing activities. Compared to the same activities on land, joint forces were reduced by 36-55% in water with absolute reductions being greater than 100%BW during weight-bearing and dynamic activities. During non-weight-bearing activities, high movement velocities and additional Aquafins increased the joint forces by up to 59% and resulted in joint forces of up to 301%BW. This study confirms the load reducing effect of water during weight-bearing and dynamic exercises. Nevertheless, high drag forces result in increased joint contact forces and indicate greater muscle activity. By the choice of activity, movement velocity and additional resistive devices joint forces can be modulated individually in the course of rehabilitation or preventive therapies.

High speed, precision motion strategies for lightweight structures

NASA Technical Reports Server (NTRS)

Book, Wayne J.

1989-01-01

Research on space telerobotics is summarized. Adaptive control experiments on the Robotic Arm, Large and Flexible (RALF) were preformed and are documented, along with a joint controller design for the Small Articulated Manipulator (SAM), which is mounted on the RALF. A control algorithm is described as a robust decentralized adaptive control based on a bounded uncertainty approach. Dynamic interactions between SAM and RALF are examined. Unstability of the manipulator is studied from the perspective that the inertial forces generated could actually be used to more rapidly damp out the flexible manipulator's vibration. Currently being studied is the modeling of the constrained dynamics of flexible arms.

Dynamic Wheel-Rail Forces on Mismatched Joints with Ramps

DOT National Transportation Integrated Search

2016-04-12

The discontinuity between rail ends at a joint creates : dynamic wheel-rail forces (i.e. high impact forces and wheel : unloading) that can result in a range of problems including : wear, deterioration, and early failure of the track structure, its :...

Offsets in International Weapons Acquisitions: The Turkish Experience

DTIC Science & Technology

2002-03-01

future civilian needs, a contract was signed with CASA ( Construcciones Aeronauticas SA) of Spain in 1990 for the joint production of 52 CN-235...housed in a large, newly constructed factory, was to assemble and co-produce the F-16 in Turkiye, and to provide support for the program including...project in Turkiye with Bechtel, the giant U.S. engineering and construction firm based in San Francisco. General Dynamics invested about $20 million

Human joint motion estimation for electromyography (EMG)-based dynamic motion control.

PubMed

Zhang, Qin; Hosoda, Ryo; Venture, Gentiane

2013-01-01

This study aims to investigate a joint motion estimation method from Electromyography (EMG) signals during dynamic movement. In most EMG-based humanoid or prosthetics control systems, EMG features were directly or indirectly used to trigger intended motions. However, both physiological and nonphysiological factors can influence EMG characteristics during dynamic movements, resulting in subject-specific, non-stationary and crosstalk problems. Particularly, when motion velocity and/or joint torque are not constrained, joint motion estimation from EMG signals are more challenging. In this paper, we propose a joint motion estimation method based on muscle activation recorded from a pair of agonist and antagonist muscles of the joint. A linear state-space model with multi input single output is proposed to map the muscle activity to joint motion. An adaptive estimation method is proposed to train the model. The estimation performance is evaluated in performing a single elbow flexion-extension movement in two subjects. All the results in two subjects at two load levels indicate the feasibility and suitability of the proposed method in joint motion estimation. The estimation root-mean-square error is within 8.3% ∼ 10.6%, which is lower than that being reported in several previous studies. Moreover, this method is able to overcome subject-specific problem and compensate non-stationary EMG properties.

Effect of active arm swing to local dynamic stability during walking.

PubMed

Wu, Yu; Li, Yue; Liu, An-Min; Xiao, Fei; Wang, Yin-Zhi; Hu, Fei; Chen, Jin-Ling; Dai, Ke-Rong; Gu, Dong-Yun

2016-02-01

Arm swing is an essential component in regulating dynamic stability of the whole body during walking, while the contribution of active arm swing to local dynamic stability of different motion segments remains unclear. This study investigated the effects of arm swing under natural arm swing condition and active arm swing condition on local dynamic stability and gait variability of the trunk segments (C7 and T10 joint) and lower extremity joints (hip, knee and ankle joint). The local divergence exponents (λs) and mean standard deviation over strides (MeanSD) of 24 young healthy adults were calculated while they were walking on treadmill with two arm swing conditions at their preferred walking speed (PWS). We found that in medial-lateral direction, both λs and MeanSD values of the trunk segments (C7 and T10 joint) in active arm swing condition were significantly lower than those in natural arm swing condition (p<0.05), while no significant difference of λs or MeanSD in lower extremity joints (hip, knee and ankle joint) was found between two arm swing conditions (p>0.05, respectively). In anterior-posterior and vertical direction, neither λs nor MeanSD values of all body segments showed significant difference between two arm swing conditions (p>0.05, respectively). These findings indicate that active arm swing may help to improve the local dynamic stability of the trunk segments in medial-lateral direction. Copyright © 2015 Elsevier B.V. All rights reserved.

Inferior olive mirrors joint dynamics to implement an inverse controller.

PubMed

Alvarez-Icaza, Rodrigo; Boahen, Kwabena

2012-10-01

To produce smooth and coordinated motion, our nervous systems need to generate precisely timed muscle activation patterns that, due to axonal conduction delay, must be generated in a predictive and feedforward manner. Kawato proposed that the cerebellum accomplishes this by acting as an inverse controller that modulates descending motor commands to predictively drive the spinal cord such that the musculoskeletal dynamics are canceled out. This and other cerebellar theories do not, however, account for the rich biophysical properties expressed by the olivocerebellar complex's various cell types, making these theories difficult to verify experimentally. Here we propose that a multizonal microcomplex's (MZMC) inferior olivary neurons use their subthreshold oscillations to mirror a musculoskeletal joint's underdamped dynamics, thereby achieving inverse control. We used control theory to map a joint's inverse model onto an MZMC's biophysics, and we used biophysical modeling to confirm that inferior olivary neurons can express the dynamics required to mirror biomechanical joints. We then combined both techniques to predict how experimentally injecting current into the inferior olive would affect overall motor output performance. We found that this experimental manipulation unmasked a joint's natural dynamics, as observed by motor output ringing at the joint's natural frequency, with amplitude proportional to the amount of current. These results support the proposal that the cerebellum-in particular an MZMC-is an inverse controller; the results also provide a biophysical implementation for this controller and allow one to make an experimentally testable prediction.

Modeling and simulating the neuromuscular mechanisms regulating ankle and knee joint stiffness during human locomotion.

PubMed

Sartori, Massimo; Maculan, Marco; Pizzolato, Claudio; Reggiani, Monica; Farina, Dario

2015-10-01

This work presents an electrophysiologically and dynamically consistent musculoskeletal model to predict stiffness in the human ankle and knee joints as derived from the joints constituent biological tissues (i.e., the spanning musculotendon units). The modeling method we propose uses electromyography (EMG) recordings from 13 muscle groups to drive forward dynamic simulations of the human leg in five healthy subjects during overground walking and running. The EMG-driven musculoskeletal model estimates musculotendon and resulting joint stiffness that is consistent with experimental EMG data as well as with the experimental joint moments. This provides a framework that allows for the first time observing 1) the elastic interplay between the knee and ankle joints, 2) the individual muscle contribution to joint stiffness, and 3) the underlying co-contraction strategies. It provides a theoretical description of how stiffness modulates as a function of muscle activation, fiber contraction, and interacting tendon dynamics. Furthermore, it describes how this differs from currently available stiffness definitions, including quasi-stiffness and short-range stiffness. This work offers a theoretical and computational basis for describing and investigating the neuromuscular mechanisms underlying human locomotion. Copyright © 2015 the American Physiological Society.

Local dynamic stability of lower extremity joints in lower limb amputees during slope walking.

PubMed

Chen, Jin-Ling; Gu, Dong-Yun

2013-01-01

Lower limb amputees have a higher fall risk during slope walking compared with non-amputees. However, studies on amputees' slope walking were not well addressed. The aim of this study was to identify the difference of slope walking between amputees and non-amputees. Lyapunov exponents λS was used to estimate the local dynamic stability of 7 transtibial amputees' and 7 controls' lower extremity joint kinematics during uphill and downhill walking. Compared with the controls, amputees exhibited significantly lower λS in hip (P=0.04) and ankle (P=0.01) joints of the sound limb, and hip joints (P=0.01) of the prosthetic limb during uphill walking, while they exhibited significantly lower λS in knee (P=0.02) and ankle (P=0.03) joints of the sound limb, and hip joints (P=0.03) of the prosthetic limb during downhill walking. Compared with amputees level walking, they exhibited significantly lower λS in ankle joints of the sound limb during both uphill (P=0.01) and downhill walking (P=0.01). We hypothesized that the better local dynamic stability of amputees was caused by compensation strategy during slope walking.

A computational framework for simultaneous estimation of muscle and joint contact forces and body motion using optimization and surrogate modeling.

PubMed

Eskinazi, Ilan; Fregly, Benjamin J

2018-04-01

Concurrent estimation of muscle activations, joint contact forces, and joint kinematics by means of gradient-based optimization of musculoskeletal models is hindered by computationally expensive and non-smooth joint contact and muscle wrapping algorithms. We present a framework that simultaneously speeds up computation and removes sources of non-smoothness from muscle force optimizations using a combination of parallelization and surrogate modeling, with special emphasis on a novel method for modeling joint contact as a surrogate model of a static analysis. The approach allows one to efficiently introduce elastic joint contact models within static and dynamic optimizations of human motion. We demonstrate the approach by performing two optimizations, one static and one dynamic, using a pelvis-leg musculoskeletal model undergoing a gait cycle. We observed convergence on the order of seconds for a static optimization time frame and on the order of minutes for an entire dynamic optimization. The presented framework may facilitate model-based efforts to predict how planned surgical or rehabilitation interventions will affect post-treatment joint and muscle function. Copyright © 2018 IPEM. Published by Elsevier Ltd. All rights reserved.

Musculoskeletal multibody dynamics simulation of the contact mechanics and kinematics of a natural knee joint during a walking cycle.

PubMed

Hu, Jiayu; Chen, Zhenxian; Xin, Hua; Zhang, Qida; Jin, Zhongmin

2018-05-01

Detailed knowledge of the in vivo loading and kinematics in the knee joint is essential to understand its normal functions and the aetiology of osteoarthritis. Computer models provide a viable non-invasive solution for estimating joint loading and kinematics during different physiological activities. However, the joint loading and kinematics of the tibiofemoral and patellofemoral joints during a gait cycle were not typically investigated concurrently in previous computational simulations. In this study, a natural knee architecture was incorporated into a lower extremity musculoskeletal multibody dynamics model based on a force-dependent kinematics approach to investigate the contact mechanics and kinematics of a natural knee joint during a walking cycle. Specifically, the contact forces between the femoral/tibial articular cartilages and menisci and between the femoral and tibial/patellar articular cartilages were quantified. The contact forces and kinematics of the tibiofemoral and patellofemoral joints and the muscle activations and ligament forces were predicted simultaneously with a reasonable level of accuracy. The developed musculoskeletal multibody dynamics model with a natural knee architecture can serve as a potential platform for assisting clinical decision-making and postoperative rehabilitation planning.

Modeling and simulating the neuromuscular mechanisms regulating ankle and knee joint stiffness during human locomotion

PubMed Central

Maculan, Marco; Pizzolato, Claudio; Reggiani, Monica; Farina, Dario

2015-01-01

This work presents an electrophysiologically and dynamically consistent musculoskeletal model to predict stiffness in the human ankle and knee joints as derived from the joints constituent biological tissues (i.e., the spanning musculotendon units). The modeling method we propose uses electromyography (EMG) recordings from 13 muscle groups to drive forward dynamic simulations of the human leg in five healthy subjects during overground walking and running. The EMG-driven musculoskeletal model estimates musculotendon and resulting joint stiffness that is consistent with experimental EMG data as well as with the experimental joint moments. This provides a framework that allows for the first time observing 1) the elastic interplay between the knee and ankle joints, 2) the individual muscle contribution to joint stiffness, and 3) the underlying co-contraction strategies. It provides a theoretical description of how stiffness modulates as a function of muscle activation, fiber contraction, and interacting tendon dynamics. Furthermore, it describes how this differs from currently available stiffness definitions, including quasi-stiffness and short-range stiffness. This work offers a theoretical and computational basis for describing and investigating the neuromuscular mechanisms underlying human locomotion. PMID:26245321

Estimation of muscle response using three-dimensional musculoskeletal models before impact situation: a simulation study.

PubMed

Bae, Tae Soo; Loan, Peter; Choi, Kuiwon; Hong, Daehie; Mun, Mu Seong

2010-12-01

When car crash experiments are performed using cadavers or dummies, the active muscles' reaction on crash situations cannot be observed. The aim of this study is to estimate muscles' response of the major muscle groups using three-dimensional musculoskeletal model by dynamic simulations of low-speed sled-impact. The three-dimensional musculoskeletal models of eight subjects were developed, including 241 degrees of freedom and 86 muscles. The muscle parameters considering limb lengths and the force-generating properties of the muscles were redefined by optimization to fit for each subject. Kinematic data and external forces measured by motion tracking system and dynamometer were then input as boundary conditions. Through a least-squares optimization algorithm, active muscles' responses were calculated during inverse dynamic analysis tracking the motion of each subject. Electromyography for major muscles at elbow, knee, and ankle joints was measured to validate each model. For low-speed sled-impact crash, experiment and simulation with optimized and unoptimized muscle parameters were performed at 9.4 m/h and 10 m/h and muscle activities were compared among them. The muscle activities with optimized parameters were closer to experimental measurements than the results without optimization. In addition, the extensor muscle activities at knee, ankle, and elbow joint were found considerably at impact time, unlike previous studies using cadaver or dummies. This study demonstrated the need to optimize the muscle parameters to predict impact situation correctly in computational studies using musculoskeletal models. And to improve accuracy of analysis for car crash injury using humanlike dummies, muscle reflex function, major extensor muscles' response at elbow, knee, and ankle joints, should be considered.

Household Financial Management and Women's Experiences of Intimate Partner Violence in the Philippines: A Study Using Propensity Score Methods.

PubMed

Tsai, Laura Cordisco

2016-04-27

This study explores the causal impact of independent management of household finances upon women's experiences of intimate partner violence (IPV) in the Philippines. Propensity score matching is used to generate a casual estimate of the impact of women's roles as household financial managers on their experiences of IPV. Findings demonstrate that managing household finances independently significantly increased the severity of IPV women experienced from their partners compared with women who managed finances jointly with partners. Findings reinforce the importance of explicit attention to intrahousehold power dynamics and gender norms in the implementation of microfinance interventions intended to empower women. © The Author(s) 2016.

Modeling and analysis of passive dynamic bipedal walking with segmented feet and compliant joints

NASA Astrophysics Data System (ADS)

Huang, Yan; Wang, Qi-Ning; Gao, Yue; Xie, Guang-Ming

2012-10-01

Passive dynamic walking has been developed as a possible explanation for the efficiency of the human gait. This paper presents a passive dynamic walking model with segmented feet, which makes the bipedal walking gait more close to natural human-like gait. The proposed model extends the simplest walking model with the addition of flat feet and torsional spring based compliance on ankle joints and toe joints, to achieve stable walking on a slope driven by gravity. The push-off phase includes foot rotations around the toe joint and around the toe tip, which shows a great resemblance to human normal walking. This paper investigates the effects of the segmented foot structure on bipedal walking in simulations. The model achieves satisfactory walking results on even or uneven slopes.

Recent Advances in Cartilage Tissue Engineering: From the Choice of Cell Sources to the Use of Bioreactors

NASA Astrophysics Data System (ADS)

Martin, Ivan; Démarteau, Olivier; Braccini, Alessandra

Grafting engineered cartilage tissues represents a promising approach for the repair of joint injuries. Recent animal experiments have demonstrated that tissues engineered by culturing chondrocytes on 3D scaffolds in bioreactors provide functional templates for orderly repair of large osteochondral lesions. To date, however, a reproducible generation of uniform cartilage tissues of predefined size starting from adult human cells has not been achieved. In this paper we review some of the recent advances and challenges ahead in the identification of appropriate (i) cell sources, (ii) bioactive factors, (iii) 3D scaffolds and (iv) bioreactors for human cartilage tissue engineering. We also present an example of how integrated efforts in these different areas can help addressing fundamental questions and advancing the field of cartilage tissue engineering towards clinical use. The presented experiment demonstrates that human nasal chondrocytes are responsive to dynamic loading and thus could be further investigated as a cell source for implantation in a joint environment.

Around Marshall

NASA Image and Video Library

1999-09-12

The science laboratory, Spacelab-J (SL-J), flown aboard the STS-47 flight was a joint venture between NASA and the National Space Development Agency of Japan (NASDA) utilizing a manned Spacelab module. The mission conducted 24 materials science and 20 life science experiments, of which 35 were sponsored by NASDA, 7 by NASA, and two collaborative efforts. Materials science investigations covered such fields as biotechnology, electronic materials, fluid dynamics and transport phenomena, glasses and ceramics, metals and alloys, and acceleration measurements. Life sciences included experiments on human health, cell separation and biology, developmental biology, animal and human physiology and behavior, space radiation, and biological rhythms. Test subjects included the crew, Japanese koi fish (carp), cultured animal and plant cells, chicken embryos, fruit flies, fungi and plant seeds, and frogs and frog eggs. Featured together in joint ground activities during the SL-J mission are NASA/NASDA personnel at the Huntsville Operations Support Center (HOSC) Spacelab Payload Operations Control Center (SL POCC) at Marshall Space Flight Center (MSFC).

Around Marshall

NASA Image and Video Library

1992-09-12

The science laboratory, Spacelab-J (SL-J), flown aboard the STS-47 flight was a joint venture between NASA and the National Space Development Agency of Japan (NASDA) utilizing a manned Spacelab module. The mission conducted 24 materials science and 20 life science experiments, of which 35 were sponsored by NASDA, 7 by NASA, and two collaborative efforts. Materials science investigations covered such fields as biotechnology, electronic materials, fluid dynamics and transport phenomena, glasses and ceramics, metals and alloys, and acceleration measurements. Life sciences included experiments on human health, cell separation and biology, developmental biology, animal and human physiology and behavior, space radiation, and biological rhythms. Test subjects included the crew, Japanese koi fish (carp), cultured animal and plant cells, chicken embryos, fruit flies, fungi and plant seeds, and frogs and frog eggs. Featured together in the Science Operation Area (SOA) are payload specialists’ first Materials Processing Test during NASA/NASDA joint ground activities at the Huntsville Operations Support Center (HOSC) Spacelab Payload Operations Control Center (SL POCC) at Marshall Space Flight Center (MSFC).

Around Marshall

NASA Image and Video Library

1992-09-12

The science laboratory, Spacelab-J (SL-J), flown aboard the STS-47 flight was a joint venture between NASA and the National Space Development Agency of Japan (NASDA) utilizing a manned Spacelab module. The mission conducted 24 materials science and 20 life science experiments, of which 35 were sponsored by NASDA, 7 by NASA, and two collaborative efforts. Materials science investigations covered such fields as biotechnology, electronic materials, fluid dynamics and transport phenomena, glasses and ceramics, metals and alloys, and acceleration measurements. Life sciences included experiments on human health, cell separation and biology, developmental biology, animal and human physiology and behavior, space radiation, and biological rhythms. Test subjects included the crew, Japanese koi fish (carp), cultured animal and plant cells, chicken embryos, fruit flies, fungi and plant seeds, and frogs and frog eggs. Featured together in the Science Operation Area (SOA) are payload specialists’ first Materials Processing Test during NASA/NASDA joint ground activities at the Huntsville Operations Support Center (HOSC) Spacelab Payload Operations Control Center (SL POCC) at Marshall Space Fight Center (MSFC).

Rating parent-child interactions: joint engagement, communication dynamics, and shared topics in autism, Down syndrome, and typical development.

PubMed

Adamson, Lauren B; Bakeman, Roger; Deckner, Deborah F; Nelson, P Brooke

2012-12-01

A battery of 17 rating items were applied to video records of typically-developing toddlers and young children with autism and Down syndrome interacting with their parents during the Communication Play Protocol. This battery provided a reliable and broad view of the joint engagement triad of child, partner, and shared topic. Ratings of the child's joint engagement correlated very strongly with state coding of joint engagement and replicated the finding that coordinated joint engagement was less likely in children with autism. Ratings of other child actions, of parent contributions, and of shared topics and communicative dynamics also documented pervasive variations related to diagnosis, language facility, and communicative context.

Numerical Modeling of Earthquake-Induced Landslide Using an Improved Discontinuous Deformation Analysis Considering Dynamic Friction Degradation of Joints

NASA Astrophysics Data System (ADS)

Huang, Da; Song, Yixiang; Cen, Duofeng; Fu, Guoyang

2016-12-01

Discontinuous deformation analysis (DDA) as an efficient technique has been extensively applied in the dynamic simulation of discontinuous rock mass. In the original DDA (ODDA), the Mohr-Coulomb failure criterion is employed as the judgment principle of failure between contact blocks, and the friction coefficient is assumed to be constant in the whole calculation process. However, it has been confirmed by a host of shear tests that the dynamic friction of rock joints degrades. Therefore, the friction coefficient should be gradually reduced during the numerical simulation of an earthquake-induced rockslide. In this paper, based on the experimental results of cyclic shear tests on limestone joints, exponential regression formulas are fitted for dynamic friction degradation, which is a function of the relative velocity, the amplitude of cyclic shear displacement and the number of its cycles between blocks with an edge-to-edge contact. Then, an improved DDA (IDDA) is developed by implementing the fitting regression formulas and a modified removing technique of joint cohesion, in which the cohesion is removed once the `sliding' or `open' state between blocks appears for the first time, into the ODDA. The IDDA is first validated by comparing with the theoretical solutions of the kinematic behaviors of a sliding block on an inclined plane under dynamic loading. Then, the program is applied to model the Donghekou landslide triggered by the 2008 Wenchuan earthquake in China. The simulation results demonstrate that the dynamic friction degradation of joints has great influences on the runout and velocity of sliding mass. Moreover, the friction coefficient possesses higher impact than the cohesion of joints on the kinematic behaviors of the sliding mass.

Wnt signalling controls the response to mechanical loading during zebrafish joint development

PubMed Central

Brunt, Lucy H.; Begg, Katie; Kague, Erika; Cross, Stephen

2017-01-01

Joint morphogenesis requires mechanical activity during development. Loss of mechanical strain causes abnormal joint development, which can impact long-term joint health. Although cell orientation and proliferation are known to shape the joint, dynamic imaging of developing joints in vivo has not been possible in other species. Using genetic labelling techniques in zebrafish we were able, for the first time, to dynamically track cell behaviours in intact moving joints. We identify that proliferation and migration, which contribute to joint morphogenesis, are mechanically controlled and are significantly reduced in immobilised larvae. By comparison with strain maps of the developing skeleton, we identify canonical Wnt signalling as a candidate for transducing mechanical forces into joint cell behaviours. We show that, in the jaw, Wnt signalling is reduced specifically in regions of high strain in response to loss of muscle activity. By pharmacological manipulation of canonical Wnt signalling, we demonstrate that Wnt acts downstream of mechanical activity and is required for joint patterning and chondrocyte maturation. Wnt16, which is also downstream of muscle activity, controls proliferation and migration, but plays no role in chondrocyte intercalation. PMID:28684625

Robust inverse kinematics using damped least squares with dynamic weighting

NASA Technical Reports Server (NTRS)

Schinstock, D. E.; Faddis, T. N.; Greenway, R. B.

1994-01-01

This paper presents a general method for calculating the inverse kinematics with singularity and joint limit robustness for both redundant and non-redundant serial-link manipulators. Damped least squares inverse of the Jacobian is used with dynamic weighting matrices in approximating the solution. This reduces specific joint differential vectors. The algorithm gives an exact solution away from the singularities and joint limits, and an approximate solution at or near the singularities and/or joint limits. The procedure is here implemented for a six d.o.f. teleoperator and a well behaved slave manipulator resulted under teleoperational control.

Dynamic MRI to quantify musculoskeletal motion: A systematic review of concurrent validity and reliability, and perspectives for evaluation of musculoskeletal disorders.

PubMed

Borotikar, Bhushan; Lempereur, Mathieu; Lelievre, Mathieu; Burdin, Valérie; Ben Salem, Douraied; Brochard, Sylvain

2017-01-01

To report evidence for the concurrent validity and reliability of dynamic MRI techniques to evaluate in vivo joint and muscle mechanics, and to propose recommendations for their use in the assessment of normal and impaired musculoskeletal function. The search was conducted on articles published in Web of science, PubMed, Scopus, Academic search Premier, and Cochrane Library between 1990 and August 2017. Studies that reported the concurrent validity and/or reliability of dynamic MRI techniques for in vivo evaluation of joint or muscle mechanics were included after assessment by two independent reviewers. Selected articles were assessed using an adapted quality assessment tool and a data extraction process. Results for concurrent validity and reliability were categorized as poor, moderate, or excellent. Twenty articles fulfilled the inclusion criteria with a mean quality assessment score of 66% (±10.4%). Concurrent validity and/or reliability of eight dynamic MRI techniques were reported, with the knee being the most evaluated joint (seven studies). Moderate to excellent concurrent validity and reliability were reported for seven out of eight dynamic MRI techniques. Cine phase contrast and real-time MRI appeared to be the most valid and reliable techniques to evaluate joint motion, and spin tag for muscle motion. Dynamic MRI techniques are promising for the in vivo evaluation of musculoskeletal mechanics; however results should be evaluated with caution since validity and reliability have not been determined for all joints and muscles, nor for many pathological conditions.

Reconstruction of shifting elbow joint compliant characteristics during fast and slow movements.

PubMed

Latash, M L; Gottlieb, G L

1991-01-01

The purpose of this study was to experimentally investigate the applicability of the equilibrium-point hypothesis to the dynamics of single-joint movements. Subjects were trained to perform relatively slow (movement time 600-1000 ms) or fast (movement time 200-300 ms) single-joint elbow flexion movements against a constant extending torque bias. They were instructed to reproduce the same time pattern of central motor command for a series of movements when the external torque could slowly and unpredictably increase, decrease, or remain constant. For fast movements, the total muscle torque was calculated as a sum of external and inertial components. Analysis of the data allowed reconstruction of the elbow joint compliant characteristics at different times during execution of the learned motor command. "Virtual" trajectories of the movements, representing time-varying changes in a central control parameter, were reconstructed and compared with the "actual" trajectories. For slow movements, the actual trajectories lagged behind the virtual ones. There were no consistent changes in the joint stiffness during slow movements. Similar analysis of experiments without voluntary movements demonstrated a lack of changes in the central parameters, supporting the assumption that the subjects were able to keep the same central motor command in spite of externally imposed unexpected torque perturbations. For the fast movements, the virtual trajectories were N-shaped, and the joint stiffness demonstrated a considerable increase near the middle of the movement. These findings contradict an hypothesis of monotonic joint compliant characteristic translation at a nearly constant rate during such movements.

Coupling reconstruction and motion estimation for dynamic MRI through optical flow constraint

NASA Astrophysics Data System (ADS)

Zhao, Ningning; O'Connor, Daniel; Gu, Wenbo; Ruan, Dan; Basarab, Adrian; Sheng, Ke

2018-03-01

This paper addresses the problem of dynamic magnetic resonance image (DMRI) reconstruction and motion estimation jointly. Because of the inherent anatomical movements in DMRI acquisition, reconstruction of DMRI using motion estimation/compensation (ME/MC) has been explored under the compressed sensing (CS) scheme. In this paper, by embedding the intensity based optical flow (OF) constraint into the traditional CS scheme, we are able to couple the DMRI reconstruction and motion vector estimation. Moreover, the OF constraint is employed in a specific coarse resolution scale in order to reduce the computational complexity. The resulting optimization problem is then solved using a primal-dual algorithm due to its efficiency when dealing with nondifferentiable problems. Experiments on highly accelerated dynamic cardiac MRI with multiple receiver coils validate the performance of the proposed algorithm.

Impact of mechanism vibration characteristics by joint clearance and optimization design of its multi-objective robustness

NASA Astrophysics Data System (ADS)

Zeng, Baoping; Wang, Chao; Zhang, Yu; Gong, Yajun; Hu, Sanbao

2017-12-01

Joint clearances and friction characteristics significantly influence the mechanism vibration characteristics; for example: as for joint clearances, the shaft and bearing of its clearance joint collide to bring about the dynamic normal contact force and tangential coulomb friction force while the mechanism works; thus, the whole system may vibrate; moreover, the mechanism is under contact-impact with impact force constraint from free movement under action of the above dynamic forces; in addition, the mechanism topology structure also changes. The constraint relationship between joints may be established by a repeated complex nonlinear dynamic process (idle stroke - contact-impact - elastic compression - rebound - impact relief - idle stroke movement - contact-impact). Analysis of vibration characteristics of joint parts is still a challenging open task by far. The dynamic equations for any mechanism with clearance is often a set of strong coupling, high-dimensional and complex time-varying nonlinear differential equations which are solved very difficultly. Moreover, complicated chaotic motions very sensitive to initial values in impact and vibration due to clearance let high-precision simulation and prediction of their dynamic behaviors be more difficult; on the other hand, their subsequent wearing necessarily leads to some certain fluctuation of structure clearance parameters, which acts as one primary factor for vibration of the mechanical system. A dynamic model was established to the device for opening the deepwater robot cabin door with joint clearance by utilizing the finite element method and analysis was carried out to its vibration characteristics in this study. Moreover, its response model was carried out by utilizing the DOE method and then the robust optimization design was performed to sizes of the joint clearance and the friction coefficient change range so that the optimization design results may be regarded as reference data for selecting bearings and controlling manufacturing process parameters for the opening mechanism. Several optimization objectives such as x/y/z accelerations for various measuring points and dynamic reaction forces of mounting brackets, and a few constraints including manufacturing process were taken into account in the optimization models, which were solved by utilizing the multi-objective genetic algorithm (NSGA-II). The vibration characteristics of the optimized opening mechanism are superior to those of the original design. In addition, the numerical forecast results are in good agreement with the test results of the prototype.

Dynamic properties of human incudostapedial joint-Experimental measurement and finite element modeling.

PubMed

Jiang, Shangyuan; Gan, Rong Z

2018-04-01

The incudostapedial joint (ISJ) is a synovial joint connecting the incus and stapes in the middle ear. Mechanical properties of the ISJ directly affect sound transmission from the tympanic membrane to the cochlea. However, how ISJ properties change with frequency has not been investigated. In this paper, we report the dynamic properties of the human ISJ measured in eight samples using a dynamic mechanical analyzer (DMA) for frequencies from 1 to 80 Hz at three temperatures of 5, 25 and 37 °C. The frequency-temperature superposition (FTS) principle was used to extrapolate the results to 8 kHz. The complex modulus of ISJ was measured with a mean storage modulus of 1.14 MPa at 1 Hz that increased to 3.01 MPa at 8 kHz, and a loss modulus that increased from 0.07 to 0.47 MPa. A 3-dimensional finite element (FE) model consisting of the articular cartilage, joint capsule and synovial fluid was then constructed to derive mechanical properties of ISJ components by matching the model results to experimental data. Modeling results showed that mechanical properties of the joint capsule and synovial fluid affected the dynamic behavior of the joint. This study contributes to a better understanding of the structure-function relationship of the ISJ for sound transmission. Copyright © 2018. Published by Elsevier Ltd.

Exploiting single-cell variability to infer the dynamics of immune responses

NASA Astrophysics Data System (ADS)

Höfer, Thomas

Cell division, differentiation, migration and death determine the dynamics of immune responses. These processes are regulated by a multitude of biochemical signals which, at present, cannot faithfully be reconstituted outside the living organism. However, quantitative measurements in living organisms have been limited. In recent years experimental techniques for the ``fate mapping'' of single immune cells have been developed that allow performing parallel single-cell experiments in an experimental animal. The resulting data are more informative about underlying biological processes than traditional measurements. I will show how the theory of stochastic dynamical systems can be used to infer the topology and dynamics of cell differentiation pathways from such data. The focus will be on joint theoretical and experimental work addressing: (i) the development of immune cells during hematopoiesis, and (ii) T cell responses to diverse pathogens. I will discuss questions on the nature of cellular variability that are posed by these new findings.

Analysis of shadowing effects on spacecraft power systems

NASA Technical Reports Server (NTRS)

Fincannon, H. J.

1995-01-01

This paper describes the Orbiting Spacecraft Shadowing Analysis (OSSA) computer program that was developed at NASA Lewis Research Center in order to assess the shadowing effects on various power systems. The algorithms, inputs and outputs are discussed. Examples of typical shadowing analyses that have been performed for the International Space Station Freedom, International Space Station Alpha and the joint United States/Russian Mir Solar Dynamic Flight Experiment Project are covered. Effects of shadowing on power systems are demonstrated.

Technical Description of Urban Microscale Modeling System: Component 1 of CRTI Project 02-0093RD

DTIC Science & Technology

2007-03-01

0093RD which involved (1) development and implementation of a com- putational fluid dynamics model for the simulation of urban flow in an arbitrary...resource will serve as a nation-wide general problem- solving tool for first-responders involved with CBR incidents in the urban environment and...predictions with experimental data obtained from a comprehensive full-scale urban field experiment conducted in Oklahoma City, Oklahoma in July 2003 (Joint

A crucial step toward realism: responses to climate change from an evolving metacommunity perspective.

PubMed

Urban, Mark C; De Meester, Luc; Vellend, Mark; Stoks, Robby; Vanoverbeke, Joost

2012-02-01

We need to understand joint ecological and evolutionary responses to climate change to predict future threats to biological diversity. The 'evolving metacommunity' framework emphasizes that interactions between ecological and evolutionary mechanisms at both local and regional scales will drive community dynamics during climate change. Theory suggests that ecological and evolutionary dynamics often interact to produce outcomes different from those predicted based on either mechanism alone. We highlight two of these dynamics: (i) species interactions prevent adaptation of nonresident species to new niches and (ii) resident species adapt to changing climates and thereby prevent colonization by nonresident species. The rate of environmental change, level of genetic variation, source-sink structure, and dispersal rates mediate between these potential outcomes. Future models should evaluate multiple species, species interactions other than competition, and multiple traits. Future experiments should manipulate factors such as genetic variation and dispersal to determine their joint effects on responses to climate change. Currently, we know much more about how climates will change across the globe than about how species will respond to these changes despite the profound effects these changes will have on global biological diversity. Integrating evolving metacommunity perspectives into climate change biology should produce more accurate predictions about future changes to species distributions and extinction threats.

A crucial step toward realism: responses to climate change from an evolving metacommunity perspective

PubMed Central

Urban, Mark C; De Meester, Luc; Vellend, Mark; Stoks, Robby; Vanoverbeke, Joost

2012-01-01

We need to understand joint ecological and evolutionary responses to climate change to predict future threats to biological diversity. The ‘evolving metacommunity’ framework emphasizes that interactions between ecological and evolutionary mechanisms at both local and regional scales will drive community dynamics during climate change. Theory suggests that ecological and evolutionary dynamics often interact to produce outcomes different from those predicted based on either mechanism alone. We highlight two of these dynamics: (i) species interactions prevent adaptation of nonresident species to new niches and (ii) resident species adapt to changing climates and thereby prevent colonization by nonresident species. The rate of environmental change, level of genetic variation, source-sink structure, and dispersal rates mediate between these potential outcomes. Future models should evaluate multiple species, species interactions other than competition, and multiple traits. Future experiments should manipulate factors such as genetic variation and dispersal to determine their joint effects on responses to climate change. Currently, we know much more about how climates will change across the globe than about how species will respond to these changes despite the profound effects these changes will have on global biological diversity. Integrating evolving metacommunity perspectives into climate change biology should produce more accurate predictions about future changes to species distributions and extinction threats. PMID:25568038

The effect of calf muscle stretching exercises on ankle joint dorsiflexion and dynamic foot pressures, force and related temporal parameters.

PubMed

Macklin, K; Healy, A; Chockalingam, N

2012-03-01

Previous research has found that ankle joint equinus can lead to foot pathologies. Calf stretching exercises are a common treatment prescription; however, no dynamic quantitative data on its effectiveness is available. To investigate the effect of calf muscle stretching on ankle joint dorsiflexion and subsequent changes within dynamic forefoot peak plantar pressures (PPP), force and temporal parameters. Thirteen runners with ankle joint equinus were required to perform calf muscle stretching twice a day (morning and evening) on a Flexeramp. Measurements were collected on day 1, week 4 and week 8. A repeated measures ANOVA with Bonferroni-adjusted post hoc comparisons was used to assess differences across the three data collection sessions. Findings indicated that the calf stretching program increased ankle joint dorsiflexion significantly (from 5° to 16°, p≤0.05). The adaptive kinetics brought about by the increased ankle joint range of motion included significantly increased forefoot PPP and maximum force during stance phase but decreased time between heel contact and heel lift and total stance phase time. The calf stretching programme used in this study was found to increase ankle joint dorsiflexion and hence can be used for first line conservative management of ankle equinus. Copyright © 2011 Elsevier Ltd. All rights reserved.

An overview of the joint FAA/NASA aircraft/ground runway friction program

NASA Technical Reports Server (NTRS)

Yager, Thomas J.

1989-01-01

There is a need for information on runways which may become slippery due to various forms and types of contaminants. Experience has shown that since the beginning of all weather aircraft operations, there have been landing and aborted takeoff incidents and/or accidents each year where aircraft have either run off the end or veered off the shoulder of low friction runways. NASA Langley's Landing and Impact Dynamics Branch is involved in several research programs directed towards obtaining a better understanding of how different tire properties interact with varying pavement surface characteristics to produce acceptable performance for aircraft ground handling requirements. One such effort, which was jointly supported by not only NASA and the FAA but by several aviation industry groups including the Flight Safety Foundation, is described.

Reconstructing Interlaced High-Dynamic-Range Video Using Joint Learning.

PubMed

Inchang Choi; Seung-Hwan Baek; Kim, Min H

2017-11-01

For extending the dynamic range of video, it is a common practice to capture multiple frames sequentially with different exposures and combine them to extend the dynamic range of each video frame. However, this approach results in typical ghosting artifacts due to fast and complex motion in nature. As an alternative, video imaging with interlaced exposures has been introduced to extend the dynamic range. However, the interlaced approach has been hindered by jaggy artifacts and sensor noise, leading to concerns over image quality. In this paper, we propose a data-driven approach for jointly solving two specific problems of deinterlacing and denoising that arise in interlaced video imaging with different exposures. First, we solve the deinterlacing problem using joint dictionary learning via sparse coding. Since partial information of detail in differently exposed rows is often available via interlacing, we make use of the information to reconstruct details of the extended dynamic range from the interlaced video input. Second, we jointly solve the denoising problem by tailoring sparse coding to better handle additive noise in low-/high-exposure rows, and also adopt multiscale homography flow to temporal sequences for denoising. We anticipate that the proposed method will allow for concurrent capture of higher dynamic range video frames without suffering from ghosting artifacts. We demonstrate the advantages of our interlaced video imaging compared with the state-of-the-art high-dynamic-range video methods.

Dynamic Modelling Of A SCARA Robot

NASA Astrophysics Data System (ADS)

Turiel, J. Perez; Calleja, R. Grossi; Diez, V. Gutierrez

1987-10-01

This paper describes a method for modelling industrial robots that considers dynamic approach to manipulation systems motion generation, obtaining the complete dynamic model for the mechanic part of the robot and taking into account the dynamic effect of actuators acting at the joints. For a four degree of freedom SCARA robot we obtain the dynamic model for the basic (minimal) configuration, that is, the three degrees of freedom that allow us to place the robot end effector in a desired point, using the Lagrange Method to obtain the dynamic equations in matrix form. The manipulator is considered to be a set of rigid bodies inter-connected by joints in the form of simple kinematic pairs. Then, the state space model is obtained for the actuators that move the robot joints, uniting the models of the single actuators, that is, two DC permanent magnet servomotors and an electrohydraulic actuator. Finally, using a computer simulation program written in FORTRAN language, we can compute the matrices of the complete model.

Numerical analysis of dynamic behavior of pre-stressed shape memory alloy concrete beam-column joints

NASA Astrophysics Data System (ADS)

Yan, S.; Xiao, Z. F.; Lin, M. Y.; Niu, J.

2018-04-01

Beam-column joints are important parts of a main frame structure. Mechanical properties of beam-column joints have a great influence on dynamic performances of the frame structure. Shape memory alloy (SMA) as a new type of intelligent metal materials has wide applications in civil engineering. The paper aims at proposing a novel beam-column joint reinforced with pre-stressed SMA tendons to increase its dynamic performance. Based on the finite element analysis (FEA) software ABAQUS, a numerical simulation for 6 beam-column scaled models considering different SMA reinforcement ratios and pre-stress levels was performed, focusing on bearing capacities, energy-dissipation and self-centering capacities, etc. These models were numerically tested under a pseudo-static load on the beam end, companying a constant vertical compressive load on the top of the column. The numerical results show that the proposed SMA-reinforced joint has a significantly increased bearing capacity and a good self-centering capability after unloading even though the energy-dissipation capacity becomes smaller due the less residual deformation. The concept and mechanism of the novel joint can be used as an important reference for civil engineering applications.

The Virtual Teacher (VT) Paradigm: Learning New Patterns of Interpersonal Coordination Using the Human Dynamic Clamp

PubMed Central

2015-01-01

The Virtual Teacher paradigm, a version of the Human Dynamic Clamp (HDC), is introduced into studies of learning patterns of inter-personal coordination. Combining mathematical modeling and experimentation, we investigate how the HDC may be used as a Virtual Teacher (VT) to help humans co-produce and internalize new inter-personal coordination pattern(s). Human learners produced rhythmic finger movements whilst observing a computer-driven avatar, animated by dynamic equations stemming from the well-established Haken-Kelso-Bunz (1985) and Schöner-Kelso (1988) models of coordination. We demonstrate that the VT is successful in shifting the pattern co-produced by the VT-human system toward any value (Experiment 1) and that the VT can help humans learn unstable relative phasing patterns (Experiment 2). Using transfer entropy, we find that information flow from one partner to the other increases when VT-human coordination loses stability. This suggests that variable joint performance may actually facilitate interaction, and in the long run learning. VT appears to be a promising tool for exploring basic learning processes involved in social interaction, unraveling the dynamics of information flow between interacting partners, and providing possible rehabilitation opportunities. PMID:26569608

The Virtual Teacher (VT) Paradigm: Learning New Patterns of Interpersonal Coordination Using the Human Dynamic Clamp.

PubMed

Kostrubiec, Viviane; Dumas, Guillaume; Zanone, Pier-Giorgio; Kelso, J A Scott

2015-01-01

The Virtual Teacher paradigm, a version of the Human Dynamic Clamp (HDC), is introduced into studies of learning patterns of inter-personal coordination. Combining mathematical modeling and experimentation, we investigate how the HDC may be used as a Virtual Teacher (VT) to help humans co-produce and internalize new inter-personal coordination pattern(s). Human learners produced rhythmic finger movements whilst observing a computer-driven avatar, animated by dynamic equations stemming from the well-established Haken-Kelso-Bunz (1985) and Schöner-Kelso (1988) models of coordination. We demonstrate that the VT is successful in shifting the pattern co-produced by the VT-human system toward any value (Experiment 1) and that the VT can help humans learn unstable relative phasing patterns (Experiment 2). Using transfer entropy, we find that information flow from one partner to the other increases when VT-human coordination loses stability. This suggests that variable joint performance may actually facilitate interaction, and in the long run learning. VT appears to be a promising tool for exploring basic learning processes involved in social interaction, unraveling the dynamics of information flow between interacting partners, and providing possible rehabilitation opportunities.

Dynamic modeling and optimal joint torque coordination of advanced robotic systems

NASA Astrophysics Data System (ADS)

Kang, Hee-Jun

The development is documented of an efficient dynamic modeling algorithm and the subsequent optimal joint input load coordination of advanced robotic systems for industrial application. A closed-form dynamic modeling algorithm for the general closed-chain robotic linkage systems is presented. The algorithm is based on the transfer of system dependence from a set of open chain Lagrangian coordinates to any desired system generalized coordinate set of the closed-chain. Three different techniques for evaluation of the kinematic closed chain constraints allow the representation of the dynamic modeling parameters in terms of system generalized coordinates and have no restriction with regard to kinematic redundancy. The total computational requirement of the closed-chain system model is largely dependent on the computation required for the dynamic model of an open kinematic chain. In order to improve computational efficiency, modification of an existing open-chain KIC based dynamic formulation is made by the introduction of the generalized augmented body concept. This algorithm allows a 44 pct. computational saving over the current optimized one (O(N4), 5995 when N = 6). As means of resolving redundancies in advanced robotic systems, local joint torque optimization is applied for effectively using actuator power while avoiding joint torque limits. The stability problem in local joint torque optimization schemes is eliminated by using fictitious dissipating forces which act in the necessary null space. The performance index representing the global torque norm is shown to be satisfactory. In addition, the resulting joint motion trajectory becomes conservative, after a transient stage, for repetitive cyclic end-effector trajectories. The effectiveness of the null space damping method is shown. The modular robot, which is built of well defined structural modules from a finite-size inventory and is controlled by one general computer system, is another class of evolving, highly versatile, advanced robotic systems. Therefore, finally, a module based dynamic modeling algorithm is presented for the dynamic coordination of such reconfigurable modular robotic systems. A user interactive module based manipulator analysis program (MBMAP) has been coded in C language running on 4D/70 Silicon Graphics.

Do you really represent my task? Sequential adaptation effects to unexpected events support referential coding for the joint Simon effect.

PubMed

Klempova, Bibiana; Liepelt, Roman

2016-07-01

Recent findings suggest that a Simon effect (SE) can be induced in Individual go/nogo tasks when responding next to an event-producing object salient enough to provide a reference for the spatial coding of one's own action. However, there is skepticism against referential coding for the joint Simon effect (JSE) by proponents of task co-representation. In the present study, we tested assumptions of task co-representation and referential coding by introducing unexpected double response events in a joint go/nogo and a joint independent go/nogo task. In Experiment 1b, we tested if task representations are functionally similar in joint and standard Simon tasks. In Experiment 2, we tested sequential updating of task co-representation after unexpected single response events in the joint independent go/nogo task. Results showed increased JSEs following unexpected events in the joint go/nogo and joint independent go/nogo task (Experiment 1a). While the former finding is in line with the assumptions made by both accounts (task co-representation and referential coding), the latter finding supports referential coding. In contrast to Experiment 1a, we found a decreased SE after unexpected events in the standard Simon task (Experiment 1b), providing evidence against the functional equivalence assumption between joint and two-choice Simon tasks of the task co-representation account. Finally, we found an increased JSE also following unexpected single response events (Experiment 2), ruling out that the findings of the joint independent go/nogo task in Experiment 1a were due to a re-conceptualization of the task situation. In conclusion, our findings support referential coding also for the joint Simon effect.

Maximum voluntary joint torque as a function of joint angle and angular velocity: model development and application to the lower limb.

PubMed

Anderson, Dennis E; Madigan, Michael L; Nussbaum, Maury A

2007-01-01

Measurements of human strength can be important during analyses of physical activities. Such measurements have often taken the form of the maximum voluntary torque at a single joint angle and angular velocity. However, the available strength varies substantially with joint position and velocity. When examining dynamic activities, strength measurements should account for these variations. A model is presented of maximum voluntary joint torque as a function of joint angle and angular velocity. The model is based on well-known physiological relationships between muscle force and length and between muscle force and velocity and was tested by fitting it to maximum voluntary joint torque data from six different exertions in the lower limb. Isometric, concentric and eccentric maximum voluntary contractions were collected during hip extension, hip flexion, knee extension, knee flexion, ankle plantar flexion and dorsiflexion. Model parameters are reported for each of these exertion directions by gender and age group. This model provides an efficient method by which strength variations with joint angle and angular velocity may be incorporated into comparisons between joint torques calculated by inverse dynamics and the maximum available joint torques.

Dynamic MRI to quantify musculoskeletal motion: A systematic review of concurrent validity and reliability, and perspectives for evaluation of musculoskeletal disorders

PubMed Central

Lempereur, Mathieu; Lelievre, Mathieu; Burdin, Valérie; Ben Salem, Douraied; Brochard, Sylvain

2017-01-01

Purpose To report evidence for the concurrent validity and reliability of dynamic MRI techniques to evaluate in vivo joint and muscle mechanics, and to propose recommendations for their use in the assessment of normal and impaired musculoskeletal function. Materials and methods The search was conducted on articles published in Web of science, PubMed, Scopus, Academic search Premier, and Cochrane Library between 1990 and August 2017. Studies that reported the concurrent validity and/or reliability of dynamic MRI techniques for in vivo evaluation of joint or muscle mechanics were included after assessment by two independent reviewers. Selected articles were assessed using an adapted quality assessment tool and a data extraction process. Results for concurrent validity and reliability were categorized as poor, moderate, or excellent. Results Twenty articles fulfilled the inclusion criteria with a mean quality assessment score of 66% (±10.4%). Concurrent validity and/or reliability of eight dynamic MRI techniques were reported, with the knee being the most evaluated joint (seven studies). Moderate to excellent concurrent validity and reliability were reported for seven out of eight dynamic MRI techniques. Cine phase contrast and real-time MRI appeared to be the most valid and reliable techniques to evaluate joint motion, and spin tag for muscle motion. Conclusion Dynamic MRI techniques are promising for the in vivo evaluation of musculoskeletal mechanics; however results should be evaluated with caution since validity and reliability have not been determined for all joints and muscles, nor for many pathological conditions. PMID:29232401

Dynamic optical imaging of vascular and metabolic reactivity in rheumatoid joints.

PubMed

Lasker, Joseph M; Fong, Christopher J; Ginat, Daniel T; Dwyer, Edward; Hielscher, Andreas H

2007-01-01

Dynamic optical imaging is increasingly applied to clinically relevant areas such as brain and cancer imaging. In this approach, some external stimulus is applied and changes in relevant physiological parameters (e.g., oxy- or deoxyhemoglobin concentrations) are determined. The advantage of this approach is that the prestimulus state can be used as a reference or baseline against which the changes can be calibrated. Here we present the first application of this method to the problem of characterizing joint diseases, especially effects of rheumatoid arthritis (RA) in the proximal interphalangeal finger joints. Using a dual-wavelength tomographic imaging system together with previously implemented model-based iterative image reconstruction schemes, we have performed initial dynamic imaging case studies on a limited number of healthy volunteers and patients diagnosed with RA. Focusing on three cases studies, we illustrated our major finds. These studies support our hypothesis that differences in the vascular reactivity exist between affected and unaffected joints.

Inverse Dynamics Model for the Ankle Joint with Applications in Tibia Malleolus Fracture

NASA Astrophysics Data System (ADS)

Budescu, E.; Merticaru, E.; Chirazi, M.

The paper presents a biomechanical model of the ankle joint, in order to determine the force and the torque of reaction into the articulation, through inverse dynamic analysis, in various stages of the gait. Thus, knowing the acceleration of the foot and the reaction force between foot and ground during the gait, determined by experimental measurement, there was calculated, for five different positions of the foot, the joint reaction forces, on the basis of dynamic balance equations. The values numerically determined were compared with the admissible forces appearing in the technical systems of osteosynthesis of tibia malleolus fracture, in order to emphasize the motion restrictions during bone healing.

Jerk-level synchronous repetitive motion scheme with gradient-type and zeroing-type dynamics algorithms applied to dual-arm redundant robot system control

NASA Astrophysics Data System (ADS)

Chen, Dechao; Zhang, Yunong

2017-10-01

Dual-arm redundant robot systems are usually required to handle primary tasks, repetitively and synchronously in practical applications. In this paper, a jerk-level synchronous repetitive motion scheme is proposed to remedy the joint-angle drift phenomenon and achieve the synchronous control of a dual-arm redundant robot system. The proposed scheme is novelly resolved at jerk level, which makes the joint variables, i.e. joint angles, joint velocities and joint accelerations, smooth and bounded. In addition, two types of dynamics algorithms, i.e. gradient-type (G-type) and zeroing-type (Z-type) dynamics algorithms, for the design of repetitive motion variable vectors, are presented in detail with the corresponding circuit schematics. Subsequently, the proposed scheme is reformulated as two dynamical quadratic programs (DQPs) and further integrated into a unified DQP (UDQP) for the synchronous control of a dual-arm robot system. The optimal solution of the UDQP is found by the piecewise-linear projection equation neural network. Moreover, simulations and comparisons based on a six-degrees-of-freedom planar dual-arm redundant robot system substantiate the operation effectiveness and tracking accuracy of the robot system with the proposed scheme for repetitive motion and synchronous control.

Dynamic Analysis of the Abnormal Isometric Strength Movement Pattern between Shoulder and Elbow Joint in Patients with Hemiplegia.

PubMed

Liu, Yali; Hong, Yuezhen; Ji, Linhong

2018-01-01

Patients with hemiplegia usually have weak muscle selectivity and usually perform strength at a secondary joint (secondary strength) during performing a strength at one joint (primary strength). The abnormal strength pattern between shoulder and elbow joint has been analyzed by the maximum value while the performing process with strength changing from 0 to maximum then to 0 was a dynamic process. The objective of this study was to develop a method to dynamically analyze the strength changing process. Ten patients were asked to perform four group asks (maximum and 50% maximum voluntary strength in shoulder abduction, shoulder adduction, elbow flexion, and elbow extension). Strength and activities from seven muscles were measured. The changes of secondary strength had significant correlation with those of primary strength in all tasks ( R > 0.76, p < 0.01). The antagonistic muscles were moderately influenced by the primary strength ( R > 0.4, p < 0.01). Deltoid muscles, biceps brachii, triceps brachii, and brachioradialis had significant influences on the abnormal strength pattern (all p < 0.01). The dynamic method was proved to be efficient to analyze the different influences of muscles on the abnormal strength pattern. The muscles, deltoid muscles, biceps brachii, triceps brachii, and brachioradialis, much influenced the stereotyped movement pattern between shoulder and elbow joint.

Dynamic Analysis of the Abnormal Isometric Strength Movement Pattern between Shoulder and Elbow Joint in Patients with Hemiplegia

PubMed Central

2018-01-01

Patients with hemiplegia usually have weak muscle selectivity and usually perform strength at a secondary joint (secondary strength) during performing a strength at one joint (primary strength). The abnormal strength pattern between shoulder and elbow joint has been analyzed by the maximum value while the performing process with strength changing from 0 to maximum then to 0 was a dynamic process. The objective of this study was to develop a method to dynamically analyze the strength changing process. Ten patients were asked to perform four group asks (maximum and 50% maximum voluntary strength in shoulder abduction, shoulder adduction, elbow flexion, and elbow extension). Strength and activities from seven muscles were measured. The changes of secondary strength had significant correlation with those of primary strength in all tasks (R > 0.76, p < 0.01). The antagonistic muscles were moderately influenced by the primary strength (R > 0.4, p < 0.01). Deltoid muscles, biceps brachii, triceps brachii, and brachioradialis had significant influences on the abnormal strength pattern (all p < 0.01). The dynamic method was proved to be efficient to analyze the different influences of muscles on the abnormal strength pattern. The muscles, deltoid muscles, biceps brachii, triceps brachii, and brachioradialis, much influenced the stereotyped movement pattern between shoulder and elbow joint. PMID:29610654

The response dynamics of preferential choice.

PubMed

Koop, Gregory J; Johnson, Joseph G

2013-12-01

The ubiquity of psychological process models requires an increased degree of sophistication in the methods and metrics that we use to evaluate them. We contribute to this venture by capitalizing on recent work in cognitive science analyzing response dynamics, which shows that the bearing information processing dynamics have on intended action is also revealed in the motor system. This decidedly "embodied" view suggests that researchers are missing out on potential dependent variables with which to evaluate their models-those associated with the motor response that produces a choice. The current work develops a method for collecting and analyzing such data in the domain of decision making. We first validate this method using widely normed stimuli from the International Affective Picture System (Experiment 1), and demonstrate that curvature in response trajectories provides a metric of the competition between choice options. We next extend the method to risky decision making (Experiment 2) and develop predictions for three popular classes of process model. The data provided by response dynamics demonstrate that choices contrary to the maxim of risk seeking in losses and risk aversion in gains may be the product of at least one "online" preference reversal, and can thus begin to discriminate amongst the candidate models. Finally, we incorporate attentional data collected via eye-tracking (Experiment 3) to develop a formal computational model of joint information sampling and preference accumulation. In sum, we validate response dynamics for use in preferential choice tasks and demonstrate the unique conclusions afforded by response dynamics over and above traditional methods. Copyright © 2013 Elsevier Inc. All rights reserved.

Reinforcement Learning of Two-Joint Virtual Arm Reaching in a Computer Model of Sensorimotor Cortex

PubMed Central

Neymotin, Samuel A.; Chadderdon, George L.; Kerr, Cliff C.; Francis, Joseph T.; Lytton, William W.

2014-01-01

Neocortical mechanisms of learning sensorimotor control involve a complex series of interactions at multiple levels, from synaptic mechanisms to cellular dynamics to network connectomics. We developed a model of sensory and motor neocortex consisting of 704 spiking model neurons. Sensory and motor populations included excitatory cells and two types of interneurons. Neurons were interconnected with AMPA/NMDA and GABAA synapses. We trained our model using spike-timing-dependent reinforcement learning to control a two-joint virtual arm to reach to a fixed target. For each of 125 trained networks, we used 200 training sessions, each involving 15 s reaches to the target from 16 starting positions. Learning altered network dynamics, with enhancements to neuronal synchrony and behaviorally relevant information flow between neurons. After learning, networks demonstrated retention of behaviorally relevant memories by using proprioceptive information to perform reach-to-target from multiple starting positions. Networks dynamically controlled which joint rotations to use to reach a target, depending on current arm position. Learning-dependent network reorganization was evident in both sensory and motor populations: learned synaptic weights showed target-specific patterning optimized for particular reach movements. Our model embodies an integrative hypothesis of sensorimotor cortical learning that could be used to interpret future electrophysiological data recorded in vivo from sensorimotor learning experiments. We used our model to make the following predictions: learning enhances synchrony in neuronal populations and behaviorally relevant information flow across neuronal populations, enhanced sensory processing aids task-relevant motor performance and the relative ease of a particular movement in vivo depends on the amount of sensory information required to complete the movement. PMID:24047323

Measuring Clearance Mechanics Based on Dynamic Leg Length

ERIC Educational Resources Information Center

Khamis, Sam; Danino, Barry; Hayek, Shlomo; Carmeli, Eli

2018-01-01

The aim of this study was to quantify clearance mechanics during gait. Seventeen children diagnosed with hemiplegic cerebral palsy underwent a three-dimensional gait analysis evaluation. Dynamic leg lengths were measured from the hip joint center to the heel, to the ankle joint center and to the forefoot throughout the gait cycle. Significant…

Joint Chance-Constrained Dynamic Programming

NASA Technical Reports Server (NTRS)

Ono, Masahiro; Kuwata, Yoshiaki; Balaram, J. Bob

2012-01-01

This paper presents a novel dynamic programming algorithm with a joint chance constraint, which explicitly bounds the risk of failure in order to maintain the state within a specified feasible region. A joint chance constraint cannot be handled by existing constrained dynamic programming approaches since their application is limited to constraints in the same form as the cost function, that is, an expectation over a sum of one-stage costs. We overcome this challenge by reformulating the joint chance constraint into a constraint on an expectation over a sum of indicator functions, which can be incorporated into the cost function by dualizing the optimization problem. As a result, the primal variables can be optimized by a standard dynamic programming, while the dual variable is optimized by a root-finding algorithm that converges exponentially. Error bounds on the primal and dual objective values are rigorously derived. We demonstrate the algorithm on a path planning problem, as well as an optimal control problem for Mars entry, descent and landing. The simulations are conducted using a real terrain data of Mars, with four million discrete states at each time step.

Free-Swinging Failure Tolerance for Robotic Manipulators

NASA Technical Reports Server (NTRS)

English, James

1997-01-01

Under this GSRP fellowship, software-based failure-tolerance techniques were developed for robotic manipulators. The focus was on failures characterized by the loss of actuator torque at a joint, called free-swinging failures. The research results spanned many aspects of the free-swinging failure-tolerance problem, from preparing for an expected failure to discovery of postfailure capabilities to establishing efficient methods to realize those capabilities. Developed algorithms were verified using computer-based dynamic simulations, and these were further verified using hardware experiments at Johnson Space Center.

Linear-hall sensor based force detecting unit for lower limb exoskeleton

NASA Astrophysics Data System (ADS)

Li, Hongwu; Zhu, Yanhe; Zhao, Jie; Wang, Tianshuo; Zhang, Zongwei

2018-04-01

This paper describes a knee-joint human-machine interaction force sensor for lower-limb force-assistance exoskeleton. The structure is designed based on hall sensor and series elastic actuator (SEA) structure. The work we have done includes the structure design, the parameter determination and dynamic simulation. By converting the force signal into macro displacement and output voltage, we completed the measurement of man-machine interaction force. And it is proved by experiments that the design is simple, stable and low-cost.

Direct and Remote Effects of Topography and Orientation, and the Dynamics of Mesoscale Eddies

DTIC Science & Technology

2017-09-01

Diagram for Visual Reference .............36  Figure 20.  GRB with 3-D 3300-meter and Quasi -Geostrophic Comparison ..............36  THIS PAGE INTENTIONALLY...circulation model NS Navier-Stokes equations Sopt Calculated Optimal Slope Sint Interpolated Optimal Slope Qf Thermal Heat Flux QG Quasi ...surveys such as MODE1 and POLYMODE, which was the largest joint U.S.–U.S.S.R. experiment of its time (Robinson 1983). Now, with the use of

[Correlation analysis on the disorders of patella-femoral joint and torsional deformity of tibia].

PubMed

Sun, Zhen-Jie; Yuan, Yi; Liu, Rui-Bo

2015-03-01

To reveal the possible mechanism involved in patella-femoral degenerative arthritis (PFDA) in- duced by torsion-deformity of tibia via analyzing the relationship between torsion-deformity of the tibia in patients with PFDA and the disorder of patella-femoral joint under the static and dynamic conditions. From October 2009 to October 2010, 50 patients (86 knees, 24 knees of male patients and 62 knees of female patients) with PFDA were classified as disease group and 16 people (23 knees, 7 knees of males and 16 knees of females) in the control group. The follow indexes were measured: the torsion-angle of tibia on CT scanning imagings, the patella-femoral congruence angle and lateral patella-femoral angle under static and dynamic conditions when the knee bent at 30 degrees of flexion. Based on the measurement results, the relationship between the torsion-deformity of tibias and the disorders of patella-femoral joints in patients with PFDA were analyzed. Finally,the patients were divided into three groups including large torsion-angle group, small torsion-angle group and normal group according to the size of torsion-angle, in order to analyze the relationship between torsion-deformity and disorders of patella-femoral joint, especially under the dynamic conditions. Compared with patients without PFDA, the ones with PFDA had bigger torsion-angle (30.30 ± 7.11)° of tibia, larger patella-femoral congruence angle (13.20 ± 3.94)° and smaller lateral patella-femoral angle (12.30 ± 3.04)°. The congruence angle and lateral patella-femoral angle under static and dynamic conditions had statistical differences respectively in both too-big torsion-angle group and too-small torsion-angle group. The congruence angle and lateral patella-femoral angle under static and dynamic conditions had no statistical differences in normal torsion-angle group. Torsion-deformity of tibia is the main reason for disorder of patella-femoral joint in the patients with PFDA. Torsion-deformity of tibia is always accompanied by instability of patella-femoral joint,especially under the dynamic condition, thus causing PFDA. It can not only provide arrangement information and degenerative condition of patella-femoral joint,but also provide guidance through the analysis on the relationship for better clinical prevention and early treatment of degenerative bone and joint disease.

High-frame-rate full-vocal-tract 3D dynamic speech imaging.

PubMed

Fu, Maojing; Barlaz, Marissa S; Holtrop, Joseph L; Perry, Jamie L; Kuehn, David P; Shosted, Ryan K; Liang, Zhi-Pei; Sutton, Bradley P

2017-04-01

To achieve high temporal frame rate, high spatial resolution and full-vocal-tract coverage for three-dimensional dynamic speech MRI by using low-rank modeling and sparse sampling. Three-dimensional dynamic speech MRI is enabled by integrating a novel data acquisition strategy and an image reconstruction method with the partial separability model: (a) a self-navigated sparse sampling strategy that accelerates data acquisition by collecting high-nominal-frame-rate cone navigator sand imaging data within a single repetition time, and (b) are construction method that recovers high-quality speech dynamics from sparse (k,t)-space data by enforcing joint low-rank and spatiotemporal total variation constraints. The proposed method has been evaluated through in vivo experiments. A nominal temporal frame rate of 166 frames per second (defined based on a repetition time of 5.99 ms) was achieved for an imaging volume covering the entire vocal tract with a spatial resolution of 2.2 × 2.2 × 5.0 mm 3 . Practical utility of the proposed method was demonstrated via both validation experiments and a phonetics investigation. Three-dimensional dynamic speech imaging is possible with full-vocal-tract coverage, high spatial resolution and high nominal frame rate to provide dynamic speech data useful for phonetic studies. Magn Reson Med 77:1619-1629, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Magnetic resonance-guided focused ultrasound treatment of facet joint pain: summary of preclinical phase

PubMed Central

2014-01-01

Study design A phantom experiment, two thermocouple experiments, three in vivo pig experiments, and a simulated treatment on a healthy human volunteer were conducted to test the feasibility, safety, and efficacy of magnetic resonance-guided focused ultrasound (MRgFUS) for treating facet joint pain. Objective The goal of the current study was to develop a novel method for accurate and safe noninvasive facet joint ablation using MRgFUS. Summary of background data Facet joints are a common source of chronic back pain. Direct facet joint interventions include medial branch nerve ablation and intra-articular injections, which are widely used, but limited in the short and long term. MRgFUS is a breakthrough technology that enables accurate delivery of high-intensity focused ultrasound energy to create a localized temperature rise for tissue ablation, using MR guidance for treatment planning and real-time feedback. Methods We validated the feasibility, safety, and efficacy of MRgFUS for facet joint ablation using the ExAblate 2000® System (InSightec Ltd., Tirat Carmel, Israel) and confirmed the system's ability to ablate the edge of the facet joint and all terminal nerves innervating the joint. A phantom experiment, two thermocouple experiments, three in vivo pig experiments, and a simulated treatment on a healthy human volunteer were conducted. Results The experiments showed that targeting the facet joint with energies of 150–450 J provides controlled and accurate heating at the facet joint edge without penetration to the vertebral body, spinal canal, or root foramina. Treating with reduced diameter of the acoustic beam is recommended since a narrower beam improves access to the targeted areas. Conclusions MRgFUS can safely and effectively target and ablate the facet joint. These results are highly significant, given that this is the first study to demonstrate the potential of MRgFUS to treat facet joint pain. PMID:24921048

Validation of predicted patellofemoral mechanics in a finite element model of the healthy and cruciate-deficient knee.

PubMed

Ali, Azhar A; Shalhoub, Sami S; Cyr, Adam J; Fitzpatrick, Clare K; Maletsky, Lorin P; Rullkoetter, Paul J; Shelburne, Kevin B

2016-01-25

Healthy patellofemoral (PF) joint mechanics are critical to optimal function of the knee joint. Patellar maltracking may lead to large joint reaction loads and high stresses on the articular cartilage, increasing the risk of cartilage wear and the onset of osteoarthritis. While the mechanical sources of PF joint dysfunction are not well understood, links have been established between PF tracking and abnormal kinematics of the tibiofemoral (TF) joint, specifically following cruciate ligament injury and repair. The objective of this study was to create a validated finite element (FE) representation of the PF joint in order to predict PF kinematics and quadriceps force across healthy and pathological specimens. Measurements from a series of dynamic in-vitro cadaveric experiments were used to develop finite element models of the knee for three specimens. Specimens were loaded under intact, ACL-resected and both ACL and PCL-resected conditions. Finite element models of each specimen were constructed and calibrated to the outputs of the intact knee condition, and subsequently used to predict PF kinematics, contact mechanics, quadriceps force, patellar tendon moment arm and patellar tendon angle of the cruciate resected conditions. Model results for the intact and cruciate resected trials successfully matched experimental kinematics (avg. RMSE 4.0°, 3.1mm) and peak quadriceps forces (avg. difference 5.6%). Cruciate resections demonstrated either increased patellar tendon loads or increased joint reaction forces. The current study advances the standard for evaluation of PF mechanics through direct validation of cruciate-resected conditions including specimen-specific representations of PF anatomy. Copyright © 2015 Elsevier Ltd. All rights reserved.

Biomechanical loading on the upper extremity increases from single key tapping to directional tapping.

PubMed

Qin, Jin; Trudeau, Matthieu; Katz, Jeffrey N; Buchholz, Bryan; Dennerlein, Jack T

2011-08-01

Musculoskeletal disorders associated with computer use span the joints of the upper extremity. Computing typically involves tapping in multiple directions. Thus, we sought to describe the loading on the finger, wrist, elbow and shoulder joints in terms of kinematic and kinetic difference across single key switch tapping to directional tapping on multiple keys. An experiment with repeated measures design was conducted. Six subjects tapped with their right index finger on a stand-alone number keypad placed horizontally in three conditions: (1) on single key switch (the number key 5); (2) left and right on number key 4 and 6; (3) top and bottom on number key 8 and 2. A force-torque transducer underneath the keypad measured the fingertip force. An active-marker infrared motion analysis system measured the kinematics of the fingertip, hand, forearm, upper arm and torso. Joint moments for the metacarpophalangeal, wrist, elbow, and shoulder joints were estimated using inverse dynamics. Tapping in the top-bottom orientation introduced the largest biomechanical loading on the upper extremity especially for the proximal joint, followed by tapping in the left-right orientation, and the lowest loading was observed during single key switch tapping. Directional tapping on average increased the fingertip force, joint excursion, and peak-to-peak joint torque by 45%, 190% and 55%, respectively. Identifying the biomechanical loading patterns associated with these fundamental movements of keying improves the understanding of the risks of upper extremity musculoskeletal disorders for computer keyboard users. Copyright © 2010 Elsevier Ltd. All rights reserved.

Attributing Asymmetric Productivity Responses to Internal Ecosystem Dynamics and External Drivers Using Probabilistic Models

NASA Astrophysics Data System (ADS)

Parolari, A.; Goulden, M.

2017-12-01

A major challenge to interpreting asymmetric changes in ecosystem productivity is the attribution of these changes to external climate forcing or to internal ecophysiological processes that respond to these drivers (e.g., photosynthesis response to drying soil). For example, positive asymmetry in productivity can result from either positive skewness in the distribution of annual rainfall amount or from negative curvature in the productivity response to annual rainfall. To analyze the relative influences of climate and ecosystem dynamics on both positive and negative asymmetry in multi-year ANPP experiments, we use a multi-scale coupled ecosystem water-carbon model to interpret field experimental results that span gradients of rainfall skewness and ANPP response curvature. The model integrates rainfall variability, soil moisture dynamics, and net carbon assimilation from the daily to inter-annual scales. From the underlying physical basis of the model, we compute the joint probability distribution of the minimum and maximum ANPP for an annual ANPP experiment of N years. The distribution is used to estimate the likelihood that either positive or negative asymmetry will be observed in an experiment, given the annual rainfall distribution and the ANPP response curve. We estimate the total asymmetry as the mode of this joint distribution and the relative contribution attributable to rainfall skewness as the mode for a linear ANPP response curve. Applied to data from several long-term ANPP experiments, we find that there is a wide range of observed ANPP asymmetry (positive and negative) and a spectrum of contributions from internal and external factors. We identify the soil water holding capacity relative to the mean rain event depth as a critical ecosystem characteristic that controls the non-linearity of the ANPP response and positive curvature at high rainfall. Further, the seasonal distribution of rainfall is shown to control the presence or absence of negative curvature at low rainfall. Therefore, a combination of rooting depth, soil texture, and climate seasonality contribute to ANPP response curvature and its contribution to overall observed asymmetry.

Inferring Muscle-Tendon Unit Power from Ankle Joint Power during the Push-Off Phase of Human Walking: Insights from a Multiarticular EMG-Driven Model

PubMed Central

2016-01-01

Introduction Inverse dynamics joint kinetics are often used to infer contributions from underlying groups of muscle-tendon units (MTUs). However, such interpretations are confounded by multiarticular (multi-joint) musculature, which can cause inverse dynamics to over- or under-estimate net MTU power. Misestimation of MTU power could lead to incorrect scientific conclusions, or to empirical estimates that misguide musculoskeletal simulations, assistive device designs, or clinical interventions. The objective of this study was to investigate the degree to which ankle joint power overestimates net plantarflexor MTU power during the Push-off phase of walking, due to the behavior of the flexor digitorum and hallucis longus (FDHL)–multiarticular MTUs crossing the ankle and metatarsophalangeal (toe) joints. Methods We performed a gait analysis study on six healthy participants, recording ground reaction forces, kinematics, and electromyography (EMG). Empirical data were input into an EMG-driven musculoskeletal model to estimate ankle power. This model enabled us to parse contributions from mono- and multi-articular MTUs, and required only one scaling and one time delay factor for each subject and speed, which were solved for based on empirical data. Net plantarflexing MTU power was computed by the model and quantitatively compared to inverse dynamics ankle power. Results The EMG-driven model was able to reproduce inverse dynamics ankle power across a range of gait speeds (R2 ≥ 0.97), while also providing MTU-specific power estimates. We found that FDHL dynamics caused ankle power to slightly overestimate net plantarflexor MTU power, but only by ~2–7%. Conclusions During Push-off, FDHL MTU dynamics do not substantially confound the inference of net plantarflexor MTU power from inverse dynamics ankle power. However, other methodological limitations may cause inverse dynamics to overestimate net MTU power; for instance, due to rigid-body foot assumptions. Moving forward, the EMG-driven modeling approach presented could be applied to understand other tasks or larger multiarticular MTUs. PMID:27764110

Inferring Muscle-Tendon Unit Power from Ankle Joint Power during the Push-Off Phase of Human Walking: Insights from a Multiarticular EMG-Driven Model.

PubMed

Honert, Eric C; Zelik, Karl E

2016-01-01

Inverse dynamics joint kinetics are often used to infer contributions from underlying groups of muscle-tendon units (MTUs). However, such interpretations are confounded by multiarticular (multi-joint) musculature, which can cause inverse dynamics to over- or under-estimate net MTU power. Misestimation of MTU power could lead to incorrect scientific conclusions, or to empirical estimates that misguide musculoskeletal simulations, assistive device designs, or clinical interventions. The objective of this study was to investigate the degree to which ankle joint power overestimates net plantarflexor MTU power during the Push-off phase of walking, due to the behavior of the flexor digitorum and hallucis longus (FDHL)-multiarticular MTUs crossing the ankle and metatarsophalangeal (toe) joints. We performed a gait analysis study on six healthy participants, recording ground reaction forces, kinematics, and electromyography (EMG). Empirical data were input into an EMG-driven musculoskeletal model to estimate ankle power. This model enabled us to parse contributions from mono- and multi-articular MTUs, and required only one scaling and one time delay factor for each subject and speed, which were solved for based on empirical data. Net plantarflexing MTU power was computed by the model and quantitatively compared to inverse dynamics ankle power. The EMG-driven model was able to reproduce inverse dynamics ankle power across a range of gait speeds (R2 ≥ 0.97), while also providing MTU-specific power estimates. We found that FDHL dynamics caused ankle power to slightly overestimate net plantarflexor MTU power, but only by ~2-7%. During Push-off, FDHL MTU dynamics do not substantially confound the inference of net plantarflexor MTU power from inverse dynamics ankle power. However, other methodological limitations may cause inverse dynamics to overestimate net MTU power; for instance, due to rigid-body foot assumptions. Moving forward, the EMG-driven modeling approach presented could be applied to understand other tasks or larger multiarticular MTUs.

Simulation of dynamics of beam structures with bolted joints using adjusted Iwan beam elements

NASA Astrophysics Data System (ADS)

Song, Y.; Hartwigsen, C. J.; McFarland, D. M.; Vakakis, A. F.; Bergman, L. A.

2004-05-01

Mechanical joints often affect structural response, causing localized non-linear stiffness and damping changes. As many structures are assemblies, incorporating the effects of joints is necessary to produce predictive finite element models. In this paper, we present an adjusted Iwan beam element (AIBE) for dynamic response analysis of beam structures containing joints. The adjusted Iwan model consists of a combination of springs and frictional sliders that exhibits non-linear behavior due to the stick-slip characteristic of the latter. The beam element developed is two-dimensional and consists of two adjusted Iwan models and maintains the usual complement of degrees of freedom: transverse displacement and rotation at each of the two nodes. The resulting element includes six parameters, which must be determined. To circumvent the difficulty arising from the non-linear nature of the inverse problem, a multi-layer feed-forward neural network (MLFF) is employed to extract joint parameters from measured structural acceleration responses. A parameter identification procedure is implemented on a beam structure with a bolted joint. In this procedure, acceleration responses at one location on the beam structure due to one known impulsive forcing function are simulated for sets of combinations of varying joint parameters. A MLFF is developed and trained using the patterns of envelope data corresponding to these acceleration histories. The joint parameters are identified through the trained MLFF applied to the measured acceleration response. Then, using the identified joint parameters, acceleration responses of the jointed beam due to a different impulsive forcing function are predicted. The validity of the identified joint parameters is assessed by comparing simulated acceleration responses with experimental measurements. The capability of the AIBE to capture the effects of bolted joints on the dynamic responses of beam structures, and the efficacy of the MLFF parameter identification procedure, are demonstrated.

Nonlinear adaptive control of an elastic robotic arm

NASA Technical Reports Server (NTRS)

Singh, S. N.

1986-01-01

An approach to control of a class of nonlinear flexible robotic systems is presented. For simplicity, a robot arm (PUMA-type) with three rotational joints is considered. The third link is assumed to be elastic. An adaptive torquer control law is derived for controlling the joint angles. This controller includes a dynamic system in the feedback path, requires only joint angle and rate for feedback, and asymptotically decomposes the elastic dynamics into two subsystems representing the transverse vibrations of the elastic link in two orthogonal planes. To damp out the elastic vibration, a force control law using modal feedback is synthesized. The combination of the torque and force control laws accomplishes joint angle control and elastic mode stabilization.

Simulation of in vivo dynamics during robot assisted joint movement.

PubMed

Bobrowitsch, Evgenij; Lorenz, Andrea; Wülker, Nikolaus; Walter, Christian

2014-12-16

Robots are very useful tools in orthopedic research. They can provide force/torque controlled specimen motion with high repeatability and precision. A method to analyze dissipative energy outcome in an entire joint was developed in our group. In a previous study, a sheep knee was flexed while axial load remained constant during the measurement of dissipated energy. We intend to apply this method for the investigation of osteoarthritis. Additionally, the method should be improved by simulation of in vivo knee dynamics. Thus, a new biomechanical testing tool will be developed for analyzing in vitro joint properties after different treatments. Discretization of passive knee flexion was used to construct a complex flexion movement by a robot and simulate altering axial load similar to in vivo sheep knee dynamics described in a previous experimental study. The robot applied an in vivo like axial force profile with high reproducibility during the corresponding knee flexion (total standard deviation of 0.025 body weight (BW)). A total residual error between the in vivo and simulated axial force was 0.16 BW. Posterior-anterior and medio-lateral forces were detected by the robot as a backlash of joint structures. Their curve forms were similar to curve forms of corresponding in vivo measured forces, but in contrast to the axial force, they showed higher total standard deviation of 0.118 and 0.203 BW and higher total residual error of 0.79 and 0.21 BW for posterior-anterior and medio-lateral forces respectively. We developed and evaluated an algorithm for the robotic simulation of complex in vivo joint dynamics using a joint specimen. This should be a new biomechanical testing tool for analyzing joint properties after different treatments.

Development of Early Warning System for Landslide Using Electromagnetic, Hydrological, Geotechnical, and Geological Approaches

NASA Astrophysics Data System (ADS)

Huang, Q.; Hattori, K.; Chae, B.

2011-12-01

The Joint Research Collaboration Program (JRCP) for Chinese-Korean-Japanese (CKJ) Research Collaboration is a new cooperative scheme for joint funding from Chinese Department of International Cooperation of the Ministry of Science and Technology (DOIC), Korea Foundation for International Cooperation of Science and Technology (KICOS) and Japan Science and Technology Agency (JST). In this paper, we will introduce the funded CKJ project entitled "Development of early warning system for landslide using electromagnetic, hydrological, geotechnical, and geological approaches". The final goal of the project is to develop a simple methodology for landslide monitoring/forecasting (early warning system) using self potential method in the frame work of joint research among China, Korea, and Japan. The project is developing a new scientific and technical methodology for prevention of natural soil disasters. The outline of the project is as follows: (1) basic understanding on the relationship between resistivity distribution and moisture in soil and their visualization of their dynamical changes in space and time using tomography technique, (2) laboratory experiments of rainfall induced landslides and sandbox for practical use of the basic understanding, (3) in-situ experiments for evaluation. Annual workshops/symposia, seminars will be organized for strengthening the scientific collaborations and exchanges. In consideration of the above issues, integration of geological, hydrological, geotechnical characteristics with electromagnetic one are adopted as the key approach in this project. This study is partially supported by the Joint Research Collaboration Program, DOIC, MOST, China (2010DFA21570) and the National Natural Science Foundation of China (40974038, 41025014).

A model-based approach to stabilizing crutch supported paraplegic standing by artificial hip joint stiffness.

PubMed

van der Spek, Jaap H; Veltink, Peter H; Hermens, Hermie J; Koopman, Bart F J M; Boom, Herman B K

2003-12-01

The prerequisites for stable crutch supported standing were analyzed in this paper. For this purpose, a biomechanical model of crutch supported paraplegic stance was developed assuming the patient was standing with extended knees. When using crutches during stance, the crutches will put a position constraint on the shoulder, thus reducing the number of degrees of freedom. Additional hip-joint stiffness was applied to stabilize the hip joint and, therefore, to stabilize stance. The required hip-joint stiffness for changing crutch placement and hip-joint offset angle was studied under static and dynamic conditions. Modeling results indicate that, by using additional hip-joint stiffness, stable crutch supported paraplegic standing can be achieved, both under static as well as dynamic situations. The static equilibrium postures and the stability under perturbations were calculated to be dependent on crutch placement and stiffness applied. However, postures in which the hip joint was in extension (C postures) appeared to the most stable postures. Applying at least 60 N x m/rad hip-joint stiffness gave stable equilibrium postures in all cases. Choosing appropriate hip-joint offset angles, the static equilibrium postures changed to more erect postures, without causing instability or excessive arm forces to occur.

First Materials Processing Test in the Science Operation Area (SOA) During STS-47 Spacelab-J Mission

NASA Technical Reports Server (NTRS)

1992-01-01

The science laboratory, Spacelab-J (SL-J), flown aboard the STS-47 flight was a joint venture between NASA and the National Space Development Agency of Japan (NASDA) utilizing a manned Spacelab module. The mission conducted 24 materials science and 20 life science experiments, of which 35 were sponsored by NASDA, 7 by NASA, and two collaborative efforts. Materials science investigations covered such fields as biotechnology, electronic materials, fluid dynamics and transport phenomena, glasses and ceramics, metals and alloys, and acceleration measurements. Life sciences included experiments on human health, cell separation and biology, developmental biology, animal and human physiology and behavior, space radiation, and biological rhythms. Test subjects included the crew, Japanese koi fish (carp), cultured animal and plant cells, chicken embryos, fruit flies, fungi and plant seeds, and frogs and frog eggs. Featured together in the Science Operation Area (SOA) are payload specialists' first Materials Processing Test during NASA/NASDA joint ground activities at the Huntsville Operations Support Center (HOSC) Spacelab Payload Operations Control Center (SL POCC) at Marshall Space Fight Center (MSFC).

First Materials Processing Test in the Science Operation Area (SOA) During STS-47 Spacelab-J Mission

NASA Technical Reports Server (NTRS)

1992-01-01

The science laboratory, Spacelab-J (SL-J), flown aboard the STS-47 flight was a joint venture between NASA and the National Space Development Agency of Japan (NASDA) utilizing a manned Spacelab module. The mission conducted 24 materials science and 20 life science experiments, of which 35 were sponsored by NASDA, 7 by NASA, and two collaborative efforts. Materials science investigations covered such fields as biotechnology, electronic materials, fluid dynamics and transport phenomena, glasses and ceramics, metals and alloys, and acceleration measurements. Life sciences included experiments on human health, cell separation and biology, developmental biology, animal and human physiology and behavior, space radiation, and biological rhythms. Test subjects included the crew, Japanese koi fish (carp), cultured animal and plant cells, chicken embryos, fruit flies, fungi and plant seeds, and frogs and frog eggs. Featured together in the Science Operation Area (SOA) are payload specialists' first Materials Processing Test during NASA/NASDA joint ground activities at the Huntsville Operations Support Center (HOSC) Spacelab Payload Operations Control Center (SL POCC) at Marshall Space Flight Center (MSFC).

Host and parasite thermal ecology jointly determine the effect of climate warming on epidemic dynamics.

PubMed

Gehman, Alyssa-Lois M; Hall, Richard J; Byers, James E

2018-01-23

Host-parasite systems have intricately coupled life cycles, but each interactor can respond differently to changes in environmental variables like temperature. Although vital to predicting how parasitism will respond to climate change, thermal responses of both host and parasite in key traits affecting infection dynamics have rarely been quantified. Through temperature-controlled experiments on an ectothermic host-parasite system, we demonstrate an offset in the thermal optima for survival of infected and uninfected hosts and parasite production. We combine experimentally derived thermal performance curves with field data on seasonal host abundance and parasite prevalence to parameterize an epidemiological model and forecast the dynamical responses to plausible future climate-warming scenarios. In warming scenarios within the coastal southeastern United States, the model predicts sharp declines in parasite prevalence, with local parasite extinction occurring with as little as 2 °C warming. The northern portion of the parasite's current range could experience local increases in transmission, but assuming no thermal adaptation of the parasite, we find no evidence that the parasite will expand its range northward under warming. This work exemplifies that some host populations may experience reduced parasitism in a warming world and highlights the need to measure host and parasite thermal performance to predict infection responses to climate change.

Rapid replacement of bridge deck expansion joints study - phase I.

DOT National Transportation Integrated Search

2014-12-01

Bridge deck expansion joints are used to allow for movement of the bridge deck due to thermal expansion, dynamics loading, and : other factors. More recently, expansion joints have also been utilized to prevent the passage of winter de-icing chemical...

Multiagent Reinforcement Learning With Sparse Interactions by Negotiation and Knowledge Transfer.

PubMed

Zhou, Luowei; Yang, Pei; Chen, Chunlin; Gao, Yang

2017-05-01

Reinforcement learning has significant applications for multiagent systems, especially in unknown dynamic environments. However, most multiagent reinforcement learning (MARL) algorithms suffer from such problems as exponential computation complexity in the joint state-action space, which makes it difficult to scale up to realistic multiagent problems. In this paper, a novel algorithm named negotiation-based MARL with sparse interactions (NegoSIs) is presented. In contrast to traditional sparse-interaction-based MARL algorithms, NegoSI adopts the equilibrium concept and makes it possible for agents to select the nonstrict equilibrium-dominating strategy profile (nonstrict EDSP) or meta equilibrium for their joint actions. The presented NegoSI algorithm consists of four parts: 1) the equilibrium-based framework for sparse interactions; 2) the negotiation for the equilibrium set; 3) the minimum variance method for selecting one joint action; and 4) the knowledge transfer of local Q -values. In this integrated algorithm, three techniques, i.e., unshared value functions, equilibrium solutions, and sparse interactions are adopted to achieve privacy protection, better coordination and lower computational complexity, respectively. To evaluate the performance of the presented NegoSI algorithm, two groups of experiments are carried out regarding three criteria: 1) steps of each episode; 2) rewards of each episode; and 3) average runtime. The first group of experiments is conducted using six grid world games and shows fast convergence and high scalability of the presented algorithm. Then in the second group of experiments NegoSI is applied to an intelligent warehouse problem and simulated results demonstrate the effectiveness of the presented NegoSI algorithm compared with other state-of-the-art MARL algorithms.

A Mechanistic Thermal Fatigue Model for SnAgCu Solder Joints

NASA Astrophysics Data System (ADS)

Borgesen, Peter; Wentlent, Luke; Hamasha, Sa'd.; Khasawneh, Saif; Shirazi, Sam; Schmitz, Debora; Alghoul, Thaer; Greene, Chris; Yin, Liang

2018-02-01

The present work offers both a complete, quantitative model and a conservative acceleration factor expression for the life span of SnAgCu solder joints in thermal cycling. A broad range of thermal cycling experiments, conducted over many years, has revealed a series of systematic trends that are not compatible with common damage functions or constitutive relations. Complementary mechanical testing and systematic studies of the evolution of the microstructure and damage have led to a fundamental understanding of the progression of thermal fatigue and failure. A special experiment was developed to allow the effective deconstruction of conventional thermal cycling experiments and the finalization of our model. According to this model, the evolution of damage and failure in thermal cycling is controlled by a continuous recrystallization process which is dominated by the coalescence and rotation of dislocation cell structures continuously added to during the high-temperature dwell. The dominance of this dynamic recrystallization contribution is not consistent with the common assumption of a correlation between the number of cycles to failure and the total work done on the solder joint in question in each cycle. It is, however, consistent with an apparent dependence on the work done during the high-temperature dwell. Importantly, the onset of this recrystallization is delayed by pinning on the Ag3Sn precipitates until these have coarsened sufficiently, leading to a model with two terms where one tends to dominate in service and the other in accelerated thermal cycling tests. Accumulation of damage under realistic service conditions with varying dwell temperatures and times is also addressed.

DINAMICS OF KNEE JOINT SPACE ASYMMETRY ON X-RAY AS A MARKER OF KNEE OSTEOARTHRITIS REHABILITATION EFFICACY.

PubMed

Sheveleva, N; Minbayeva, L; Belyayeva, Y

2017-03-01

Reducing of articular cartilage functional volume in knee joint osteoarthritis occurs unevenly and accompanied with pathological changes of lower limb axis as a result of connective tissue and muscle structures dysfunction. Evaluation of X-ray knee joint space asymmetry seems to be informative to analyze the dynamics of lower extremities biomechanical imbalances characteristic for knee joint osteoarthritis. However, standardized method of X-ray joint space determining does not include its symmetry calculation. The purpose of the study was optimization of knee joint radiological examination by developing of X-ray knee joint space asymmetry index calculation method. The proposed method was used for comparative analysis of extracorporeal shock-wave therapy efficacy in 30 patients with knee joint osteoarthritis of 2-3 degrees (Kellgren-Lawrence, 1957). As a result of the conducted treatment statistically significant decrease of the X-ray knee joint space asymmetry index was observed (Me(Q1;Q3): Z=5.20, p<0.001) and amounted as 0.22 (0.18;0.24) before treatment and 0.12 (0.10;0.14) after. Also, statistically significant (Z=5.10; p=0.00001) changes of load asymmetry on front and rear foot sections were observed by the results of podometric survey in comparative assessment before (Me(Q1;Q3)=24(12;30)) and after (Me(Q1;Q3)=6(4;30)) course therapy. 30% (n=9) of the patients evaluated the outcome of the treatment as "excellent" (1 point), 63% (n=19) - as "good" (2 points) and only 7% (n=2) - as "acceptable" (3 points) according to the Roles and Maudsley score. The listed above data was regarded as an X-ray positive dynamics comparable with clinical improvement. Thus, the X-ray knee joint space asymmetry index, calculated according to the proposed method, allows to evaluate dynamics of articular surfaces congruency changes and provide differentiated approach to the treatment of knee joint osteoarthritis.

Dynamic Cytology and Transcriptional Regulation of Rice Lamina Joint Development1[OPEN

PubMed Central

2017-01-01

Rice (Oryza sativa) leaf angle is determined by lamina joint and is an important agricultural trait determining leaf erectness and, hence, the photosynthesis efficiency and grain yield. Genetic studies reveal a complex regulatory network of lamina joint development; however, the morphological changes, cytological transitions, and underlying transcriptional programming remain to be elucidated. A systemic morphological and cytological study reveals a dynamic developmental process and suggests a common but distinct regulation of the lamina joint. Successive and sequential cell division and expansion, cell wall thickening, and programmed cell death at the adaxial or abaxial sides form the cytological basis of the lamina joint, and the increased leaf angle results from the asymmetric cell proliferation and elongation. Analysis of the gene expression profiles at four distinct developmental stages ranging from initiation to senescence showed that genes related to cell division and growth, hormone synthesis and signaling, transcription (transcription factors), and protein phosphorylation (protein kinases) exhibit distinct spatiotemporal patterns during lamina joint development. Phytohormones play crucial roles by promoting cell differentiation and growth at early stages or regulating the maturation and senescence at later stages, which is consistent with the quantitative analysis of hormones at different stages. Further comparison with the gene expression profile of leaf inclination1, a mutant with decreased auxin and increased leaf angle, indicates the coordinated effects of hormones in regulating lamina joint. These results reveal a dynamic cytology of rice lamina joint that is fine-regulated by multiple factors, providing informative clues for illustrating the regulatory mechanisms of leaf angle and plant architecture. PMID:28500269

Dynamic Cytology and Transcriptional Regulation of Rice Lamina Joint Development.

PubMed

Zhou, Li-Juan; Xiao, Lang-Tao; Xue, Hong-Wei

2017-07-01

Rice ( Oryza sativa ) leaf angle is determined by lamina joint and is an important agricultural trait determining leaf erectness and, hence, the photosynthesis efficiency and grain yield. Genetic studies reveal a complex regulatory network of lamina joint development; however, the morphological changes, cytological transitions, and underlying transcriptional programming remain to be elucidated. A systemic morphological and cytological study reveals a dynamic developmental process and suggests a common but distinct regulation of the lamina joint. Successive and sequential cell division and expansion, cell wall thickening, and programmed cell death at the adaxial or abaxial sides form the cytological basis of the lamina joint, and the increased leaf angle results from the asymmetric cell proliferation and elongation. Analysis of the gene expression profiles at four distinct developmental stages ranging from initiation to senescence showed that genes related to cell division and growth, hormone synthesis and signaling, transcription (transcription factors), and protein phosphorylation (protein kinases) exhibit distinct spatiotemporal patterns during lamina joint development. Phytohormones play crucial roles by promoting cell differentiation and growth at early stages or regulating the maturation and senescence at later stages, which is consistent with the quantitative analysis of hormones at different stages. Further comparison with the gene expression profile of leaf inclination1 , a mutant with decreased auxin and increased leaf angle, indicates the coordinated effects of hormones in regulating lamina joint. These results reveal a dynamic cytology of rice lamina joint that is fine-regulated by multiple factors, providing informative clues for illustrating the regulatory mechanisms of leaf angle and plant architecture. © 2017 American Society of Plant Biologists. All Rights Reserved.

Association of knee confidence with pain, knee instability, muscle strength, and dynamic varus-valgus joint motion in knee osteoarthritis.

PubMed

Skou, Søren T; Wrigley, Tim V; Metcalf, Ben R; Hinman, Rana S; Bennell, Kim L

2014-05-01

To investigate associations between self-reported knee confidence and pain, self-reported knee instability, muscle strength, and dynamic varus-valgus joint motion during walking. We performed a cross-sectional analysis of baseline data from 100 participants with symptomatic and radiographic medial tibiofemoral compartment osteoarthritis (OA) and varus malalignment recruited for a randomized controlled trial. The extent of knee confidence, assessed using a 5-point Likert scale item from the Knee Injury and Osteoarthritis Outcome Score, was set as the dependent variable in univariable and multivariable ordinal regression, with pain during walking, self-reported knee instability, quadriceps strength, and dynamic varus-valgus joint motion during walking as independent variables. One percent of the participants were not troubled with lack of knee confidence, 17% were mildly troubled, 50% were moderately troubled, 26% were severely troubled, and 6% were extremely troubled. Significant associations were found between worse knee confidence and higher pain intensity, worse self-reported knee instability, lower quadriceps strength, and greater dynamic varus-valgus joint motion. The multivariable model consisting of the same variables significantly accounted for 24% of the variance in knee confidence (P < 0.001). Worse knee confidence is associated with higher pain, worse self-reported knee instability, lower quadriceps muscle strength, and greater dynamic varus-valgus joint motion during walking. Since previous research has shown that worse knee confidence is predictive of functional decline in knee OA, addressing lack of knee confidence by treating these modifiable impairments could represent a new therapeutic target. Copyright © 2014 by the American College of Rheumatology.

A Systematic Bayesian Integration of Epidemiological and Genetic Data

PubMed Central

Lau, Max S. Y.; Marion, Glenn; Streftaris, George; Gibson, Gavin

2015-01-01

Genetic sequence data on pathogens have great potential to inform inference of their transmission dynamics ultimately leading to better disease control. Where genetic change and disease transmission occur on comparable timescales additional information can be inferred via the joint analysis of such genetic sequence data and epidemiological observations based on clinical symptoms and diagnostic tests. Although recently introduced approaches represent substantial progress, for computational reasons they approximate genuine joint inference of disease dynamics and genetic change in the pathogen population, capturing partially the joint epidemiological-evolutionary dynamics. Improved methods are needed to fully integrate such genetic data with epidemiological observations, for achieving a more robust inference of the transmission tree and other key epidemiological parameters such as latent periods. Here, building on current literature, a novel Bayesian framework is proposed that infers simultaneously and explicitly the transmission tree and unobserved transmitted pathogen sequences. Our framework facilitates the use of realistic likelihood functions and enables systematic and genuine joint inference of the epidemiological-evolutionary process from partially observed outbreaks. Using simulated data it is shown that this approach is able to infer accurately joint epidemiological-evolutionary dynamics, even when pathogen sequences and epidemiological data are incomplete, and when sequences are available for only a fraction of exposures. These results also characterise and quantify the value of incomplete and partial sequence data, which has important implications for sampling design, and demonstrate the abilities of the introduced method to identify multiple clusters within an outbreak. The framework is used to analyse an outbreak of foot-and-mouth disease in the UK, enhancing current understanding of its transmission dynamics and evolutionary process. PMID:26599399

Experimental characterization of deployable trusses and joints

NASA Technical Reports Server (NTRS)

Ikegami, R.; Church, S. M.; Keinholz, D. A.; Fowler, B. L.

1987-01-01

The structural dynamic properties of trusses are strongly affected by the characteristics of joints connecting the individual beam elements. Joints are particularly significant in that they are often the source of nonlinearities and energy dissipation. While the joints themselves may be physically simple, direct measurement is often necessary to obtain a mathematical description suitable for inclusion in a system model. Force state mapping is a flexible, practical test method for obtaining such a description, particularly when significant nonlinear effects are present. It involves measurement of the relationship, nonlinear or linear, between force transmitted through a joint and the relative displacement and velocity across it. An apparatus and procedure for force state mapping are described. Results are presented from tests of joints used in a lightweight, composite, deployable truss built by the Boeing Aerospace Company. The results from the joint tests are used to develop a model of a full 4-bay truss segment. The truss segment was statically and dynamically tested. The results of the truss tests are presented and compared with the analytical predictions from the model.

Towards a Pre-Intervention Analytical Methodology

DTIC Science & Technology

2012-08-01

such as concept maps ( Kaste 2007), mind maps, and dynamically interactive networks, available from a variety of proprietary, government, and open...Joint Publication 3-27, Counterterrorism (JP 3-27). Joint Staff. July 2008. Joint Publication 3-57, Civil-Military Operations (JP 3-57). Kaste , R; E

Improvement in Fatigue Performance of Aluminium Alloy Welded Joints by Laser Shock Peening in a Dynamic Strain Aging Temperature Regime.

PubMed

Su, Chun; Zhou, Jianzhong; Meng, Xiankai; Huang, Shu

2016-09-26

As a new treatment process after welding, the process parameters of laser shock peening (LSP) in dynamic strain aging (DSA) temperature regimes can be precisely controlled, and the process is a non-contact one. The effects of LSP at elevated temperatures on the distribution of the surface residual stress of AA6061-T6 welded joints were investigated by using X-ray diffraction technology with the sin² ϕ method and Abaqus software. The fatigue life of the welded joints was estimated by performing tensile fatigue tests. The microstructural evolution in surface and fatigue fractures of the welded joints was presented by means of surface integrity and fracture surface testing. In the DSA temperature regime of AA6061-T6 welded joints, the residual compressive stress was distributed more stably than that of LSP at room temperature. The thermal corrosion resistance and fatigue properties of the welded joints were also improved. The experimental results and numerical analysis were in mutual agreement.

Improvement in Fatigue Performance of Aluminium Alloy Welded Joints by Laser Shock Peening in a Dynamic Strain Aging Temperature Regime

PubMed Central

Su, Chun; Zhou, Jianzhong; Meng, Xiankai; Huang, Shu

2016-01-01

As a new treatment process after welding, the process parameters of laser shock peening (LSP) in dynamic strain aging (DSA) temperature regimes can be precisely controlled, and the process is a non-contact one. The effects of LSP at elevated temperatures on the distribution of the surface residual stress of AA6061-T6 welded joints were investigated by using X-ray diffraction technology with the sin2ϕ method and Abaqus software. The fatigue life of the welded joints was estimated by performing tensile fatigue tests. The microstructural evolution in surface and fatigue fractures of the welded joints was presented by means of surface integrity and fracture surface testing. In the DSA temperature regime of AA6061-T6 welded joints, the residual compressive stress was distributed more stably than that of LSP at room temperature. The thermal corrosion resistance and fatigue properties of the welded joints were also improved. The experimental results and numerical analysis were in mutual agreement. PMID:28773920

Characterization of friction stir welded joint of low nickel austenitic stainless steel and modified ferritic stainless steel

NASA Astrophysics Data System (ADS)

Mondal, Mounarik; Das, Hrishikesh; Ahn, Eun Yeong; Hong, Sung Tae; Kim, Moon-Jo; Han, Heung Nam; Pal, Tapan Kumar

2017-09-01

Friction stir welding (FSW) of dissimilar stainless steels, low nickel austenitic stainless steel and 409M ferritic stainless steel, is experimentally investigated. Process responses during FSW and the microstructures of the resultant dissimilar joints are evaluated. Material flow in the stir zone is investigated in detail by elemental mapping. Elemental mapping of the dissimilar joints clearly indicates that the material flow pattern during FSW depends on the process parameter combination. Dynamic recrystallization and recovery are also observed in the dissimilar joints. Among the two different stainless steels selected in the present study, the ferritic stainless steels shows more severe dynamic recrystallization, resulting in a very fine microstructure, probably due to the higher stacking fault energy.

Dynamic Inversion based Control of a Docking Mechanism

NASA Technical Reports Server (NTRS)

Kulkarni, Nilesh V.; Ippolito, Corey; Krishnakumar, Kalmanje

2006-01-01

The problem of position and attitude control of the Stewart platform based docking mechanism is considered motivated by its future application in space missions requiring the autonomous docking capability. The control design is initiated based on the framework of the intelligent flight control architecture being developed at NASA Ames Research Center. In this paper, the baseline position and attitude control system is designed using dynamic inversion with proportional-integral augmentation. The inverse dynamics uses a Newton-Euler formulation that includes the platform dynamics, the dynamics of the individual legs along with viscous friction in the joints. Simulation results are presented using forward dynamics simulated by a commercial physics engine that builds the system as individual elements with appropriate joints and uses constrained numerical integration,

FAMILY STRUCTURE, DYNAMICS AND PSYCHIATRIC DISORDER IN INDIA1

PubMed Central

Chopra, H.D.

1984-01-01

SUMMARY This paper briefly reviews the literature on family structure, dynamics and relationships between family-jointness and different psychiatric disorders in India. Many recent studies indicate that the nuclear families are more vulnerable and plea is made for maintaining the traditional joint family system, even in some modified forms, because of its “built-in-immunity” and supportive networks. PMID:21966010

Skill Learning and Skill Transfer Mediated by Cooperative Haptic Interaction.

PubMed

Avila Mireles, Edwin Johnatan; Zenzeri, Jacopo; Squeri, Valentina; Morasso, Pietro; De Santis, Dalia

2017-07-01

It is known that physical coupling between two subjects may be advantageous in joint tasks. However, little is known about how two people mutually exchange information to exploit the coupling. Therefore, we adopted a reversed, novel perspective to the standard one that focuses on the ability of physically coupled subjects to adapt to cooperative contexts that require negotiating a common plan: we investigated how training in pairs on a novel task affects the development of motor skills of each of the interacting partners. The task involved reaching movements in an unstable dynamic environment using a bilateral non-linear elastic tool that could be used bimanually or dyadically. The main result is that training with an expert leads to the greatest performance in the joint task. However, the performance in the individual test is strongly affected by the initial skill level of the partner. Moreover, practicing with a peer rather than an expert appears to be more advantageous for a naive; and motor skills can be transferred to a bimanual context, after training with an expert, only if the non-expert subject had prior experience of the dynamics of the novel task.

Dynamics of poroelastic foams

NASA Astrophysics Data System (ADS)

Forterre, Yoel; Sobac, Benjamin

2010-11-01

Soft poroelastic structures are widespread in biological tissues such as cartilaginous joints in bones, blood-filled placentae or plant organs. Here we investigate the dynamics of open elastic foams immersed in viscous fluids, as model soft poroelastic materials. The experiment consists in slowly compacting blocs of polyurethane solid foam embedded in silicon oil-tanks and studying their relaxation to equilibrium when the confining stress is suddenly released. Measurements of the local fluid pressure and foam velocity field are compared with a simple two-phase flow approach. For small initial compactions, the results show quantitative agreement with the classical diffusion theory of soil consolidation (Terzaghi, Biot). On the other hand, for large initial compactions, the dynamics exhibits long relaxation times and decompaction fronts, which are mainly controlled by the highly non-linear mechanical response of the foam. The analogy between this process and the evaporation of a polymer melt close to the glass transition will be briefly discussed.

Are the Kinematics of the Knee Joint Altered during the Loading Response Phase of Gait in Individuals with Concurrent Knee Osteoarthritis and Complaints of Joint Instability? A Dynamic Stereo X-ray Study

PubMed Central

Farrokhi, Shawn; Tashman, Scott; Gil, Alexandra B.; Klatt, Brian A.; Fitzgerald, G. Kelley

2011-01-01

Background Joint instability has been suggested as a risk factor for knee osteoarthritis and a cause of significant functional declines in those with symptomatic disease. However, the relationship between altered knee joint mechanics and self-reports of instability in individuals with knee osteoarthritis remains unclear. Methods Fourteen subjects with knee osteoarthritis and complaints of joint instability and 12 control volunteers with no history of knee disease were recruited for this study. Dynamic stereo X-ray technology was used to assess the three-dimensional kinematics of the knee joint during the loading response phase of gait. Findings Individuals with concurrent knee osteoarthritis and joint instability demonstrated significantly reduced flexion and internal/external rotation knee motion excursions during the loading response phase of gait (P < 0.01), while the total abduction/adduction range of motion was increased (P < 0.05). In addition, the coronal and transverse plane alignment of the knee joint at initial contact was significantly different (P < 0.05) for individuals with concurrent knee osteoarthritis and joint instability. However, the anteroposterior and mediolateral tibiofemoral joint positions at initial contact and the corresponding total joint translations were similar between groups during the loading phase of gait. Interpretations The rotational patterns of tibiofemoral joint motion and joint alignments reported for individuals with concurrent knee osteoarthritis and joint instability are consistent with those previously established for individuals with knee osteoarthritis. Furthermore, the findings of similar translatory tibiofemoral motion between groups suggest that self-reports of episodic joint instability in individuals with knee osteoarthritis may not necessarily be associated with adaptive alterations in joint arthrokinematics. PMID:22071429

Are the kinematics of the knee joint altered during the loading response phase of gait in individuals with concurrent knee osteoarthritis and complaints of joint instability? A dynamic stereo X-ray study.

PubMed

Farrokhi, Shawn; Tashman, Scott; Gil, Alexandra B; Klatt, Brian A; Fitzgerald, G Kelley

2012-05-01

Joint instability has been suggested as a risk factor for knee osteoarthritis and a cause of significant functional decline in those with symptomatic disease. However, the relationship between altered knee joint mechanics and self-reports of instability in individuals with knee osteoarthritis remains unclear. Fourteen subjects with knee osteoarthritis and complaints of joint instability and 12 control volunteers with no history of knee disease were recruited for this study. Dynamic stereo X-ray technology was used to assess the three-dimensional kinematics of the knee joint during the loading response phase of gait. Individuals with concurrent knee osteoarthritis and joint instability demonstrated significantly reduced flexion and internal/external rotation knee motion excursions during the loading response phase of gait (P<0.01), while the total abduction/adduction range of motion was increased (P<0.05). In addition, the coronal and transverse plane alignment of the knee joint at initial contact was significantly different (P<0.05) for individuals with concurrent knee osteoarthritis and joint instability. However, the anteroposterior and mediolateral tibiofemoral joint positions at initial contact and the corresponding total joint translations were similar between groups during the loading phase of gait. The rotational patterns of tibiofemoral joint motion and joint alignments reported for individuals with concurrent knee osteoarthritis and joint instability are consistent with those previously established for individuals with knee osteoarthritis. Furthermore, the findings of similar translatory tibiofemoral motion between groups suggest that self-reports of episodic joint instability in individuals with knee osteoarthritis may not necessarily be associated with adaptive alterations in joint arthrokinematics. Copyright © 2011 Elsevier Ltd. All rights reserved.

Weak-field few-femtosecond VUV photodissociation dynamics of water isotopologues

NASA Astrophysics Data System (ADS)

Baumann, Arne; Bazzi, Sophia; Rompotis, Dimitrios; Schepp, Oliver; Azima, Armin; Wieland, Marek; Popova-Gorelova, Daria; Vendrell, Oriol; Santra, Robin; Drescher, Markus

2017-07-01

We present a joint experimental and theoretical study of the VUV-induced dynamics of H2O and its deuterated isotopologues in the first excited state (A ˜1B1 ) utilizing a VUV-pump VUV-probe scheme combined with a b initio classical trajectory calculations. 16-fs VUV pulses centered at 161 nm created by fifth-order harmonic generation are employed for single-shot pump-probe measurements. Combined with a precise determination of the VUV pulses' temporal profile, they provide the necessary temporal resolution to elucidate sub-10-fs dissociation dynamics in the 1+1 photon ionization time window. Ionization with a single VUV photon complements established strong-field ionization schemes by disclosing the molecular dynamics under perturbative conditions. Kinetic isotope effects derived from the pump-probe experiment are found to be in agreement with our by ab initio classical trajectory calculations, taking into account photoionization cross sections for the ground and first excited state of the water cation.

Formation Learning Control of Multiple Autonomous Underwater Vehicles With Heterogeneous Nonlinear Uncertain Dynamics.

PubMed

Yuan, Chengzhi; Licht, Stephen; He, Haibo

2017-09-26

In this paper, a new concept of formation learning control is introduced to the field of formation control of multiple autonomous underwater vehicles (AUVs), which specifies a joint objective of distributed formation tracking control and learning/identification of nonlinear uncertain AUV dynamics. A novel two-layer distributed formation learning control scheme is proposed, which consists of an upper-layer distributed adaptive observer and a lower-layer decentralized deterministic learning controller. This new formation learning control scheme advances existing techniques in three important ways: 1) the multi-AUV system under consideration has heterogeneous nonlinear uncertain dynamics; 2) the formation learning control protocol can be designed and implemented by each local AUV agent in a fully distributed fashion without using any global information; and 3) in addition to the formation control performance, the distributed control protocol is also capable of accurately identifying the AUVs' heterogeneous nonlinear uncertain dynamics and utilizing experiences to improve formation control performance. Extensive simulations have been conducted to demonstrate the effectiveness of the proposed results.

Hardware-efficient Bell state preparation using Quantum Zeno Dynamics in superconducting circuits

NASA Astrophysics Data System (ADS)

Flurin, Emmanuel; Blok, Machiel; Hacohen-Gourgy, Shay; Martin, Leigh S.; Livingston, William P.; Dove, Allison; Siddiqi, Irfan

By preforming a continuous joint measurement on a two qubit system, we restrict the qubit evolution to a chosen subspace of the total Hilbert space. This extension of the quantum Zeno effect, called Quantum Zeno Dynamics, has already been explored in various physical systems such as superconducting cavities, single rydberg atoms, atomic ensembles and Bose Einstein condensates. In this experiment, two superconducting qubits are strongly dispersively coupled to a high-Q cavity (χ >> κ) allowing for the doubly excited state | 11 〉 to be selectively monitored. The Quantum Zeno Dynamics in the complementary subspace enables us to coherently prepare a Bell state. As opposed to dissipation engineering schemes, we emphasize that our protocol is deterministic, does not rely direct coupling between qubits and functions only using single qubit controls and cavity readout. Such Quantum Zeno Dynamics can be generalized to larger Hilbert space enabling deterministic generation of many-body entangled states, and thus realizes a decoherence-free subspace allowing alternative noise-protection schemes.

Seismic performance of the typical RC beam-column joint subjected to repeated earthquakes

NASA Astrophysics Data System (ADS)

Hassanshahi, Omid; Majid, Taksiah A.; Lau, Tze Liang; Yousefi, Ali; Tahara, R. M. K.

2017-10-01

It is common that a building experience repeated earthquakes throughout its lifetime. Such earthquake is capable of creating severe damage in primary elements of the building due to accumulation of inelastic displacement from repetition. The present study focuses on the influence of repeated earthquakes on a typical Reinforced Concrete (RC) beam-column joint, especially on the maximum inelastic displacement demand and maximum residual displacement. For this purpose, the capability of nonlinear modelling in simulating the hysteretic behaviour of the prototype experimental specimen is first determined using RUAUMOKO. A nonlinear Incremental Dynamic Analysis (IDA) on the verified model is then carried out in order to estimate with maximum accuracy the ultimate load bearing capacity to progressive collapse of the RC joint under investigation. Twenty ground motions are selected, and single (C1), double (C2), and triple (C3) event of synthetic repeated earthquakes are then considered. The results show that the repeated earthquakes significantly increase the inelastic demand of the RC joint. On average, relative increment of maximum inelastic displacement demand is experienced about 28.9% and 39.4% when C2 and C3 events of repeated earthquakes are induced, respectively. Residual displacements for repeated earthquakes are also significantly higher than that for single earthquakes.

Modeling the finger joint moments in a hand at the maximal isometric grip: the effects of friction.

PubMed

Wu, John Z; Dong, Ren G; McDowell, Thomas W; Welcome, Daniel E

2009-12-01

The interaction between the handle and operator's hand affects the comfort and safety of tool and machine operations. In most of the previous studies, the investigators considered only the normal contact forces. The effect of friction on the joint moments in fingers has not been analyzed. Furthermore, the observed contact forces have not been linked to the internal musculoskeletal loading in the previous experimental studies. In the current study, we proposed a universal model of a hand to evaluate the joint moments in the fingers during grasping tasks. The hand model was developed on the platform of the commercial software package AnyBody. Only four fingers (index, long, ring, and little finger) were included in the model. The anatomical structure of each finger is comprised of four phalanges (distal, middle, proximal, and metacarpal phalange). The simulations were performed using an inverse dynamics technique. The joint angles and the normal contact forces on each finger section reported by previous researchers were used as inputs, while the joint moments of each finger were predicted. The predicted trends of the dependence of the distal interphalangeal (DIP) and proximal interphalangeal (PIP) joint moments on the cylinder diameter agree with those of the contact forces on the fingers observed in the previous experimental study. Our results show that the DIP and PIP joint moments reach their maximums at a cylinder diameter of about 31mm, which is consistent with the trend of the finger contact forces measured in the experiments. The proposed approach will be useful for simulating musculoskeletal loading in the hand for occupational activities, thereby optimizing tool-handle design.

Keep meaning in conversational coordination

PubMed Central

Cuffari, Elena C.

2014-01-01

Coordination is a widely employed term across recent quantitative and qualitative approaches to intersubjectivity, particularly approaches that give embodiment and enaction central explanatory roles. With a focus on linguistic and bodily coordination in conversational contexts, I review the operational meaning of coordination in recent empirical research and related theorizing of embodied intersubjectivity. This discussion articulates what must be involved in treating linguistic meaning as dynamic processes of coordination. The coordination approach presents languaging as a set of dynamic self-organizing processes and actions on multiple timescales and across multiple modalities that come about and work in certain domains (those jointly constructed in social, interactive, high-order sense-making). These processes go beyond meaning at the level that is available to first-person experience. I take one crucial consequence of this to be the ubiquitously moral nature of languaging with others. Languaging coordinates experience, among other levels of behavior and event. Ethical effort is called for by the automatic autonomy-influencing forces of languaging as coordination. PMID:25520693

Dynamic Postural-Stability Deficits After Cryotherapy to the Ankle Joint.

PubMed

Fullam, Karl; Caulfield, Brian; Coughlan, Garrett F; McGroarty, Mark; Delahunt, Eamonn

2015-09-01

Decreased postural stability is a primary risk factor for lower limb musculoskeletal injuries. During athletic competitions, cryotherapy may be applied during short breaks in play or during half-time; however, its effects on postural stability remain unclear. To investigate the acute effects of a 15-minute ankle-joint cryotherapy application on dynamic postural stability. Controlled laboratory study. University biomechanics laboratory. A total of 29 elite-level collegiate male field-sport athletes (age = 20.8 ± 1.12 years, height = 1.80 ± 0.06 m, mass = 81.89 ± 8.59 kg) participated. Participants were tested on the anterior (ANT), posterolateral (PL), and posteromedial (PM) reach directions of the Star Excursion Balance Test before and after a 15-minute ankle-joint cryotherapy application. Normalized reach distances; sagittal-plane kinematics of the hip, knee, and ankle joints; and associated mean velocity of the center-of-pressure path during performance of the ANT, PL, and PM reach directions of the Star Excursion Balance Test. We observed a decrease in reach-distance scores for the ANT, PL, and PM reach directions from precryotherapy to postcryotherapy (P < .05). No differences were observed in hip-, knee-, or ankle-joint sagittal-plane kinematics (P > .05). We noted a decrease in mean velocity of the center-of-pressure path from precryotherapy to postcryotherapy (P < .05) in all reach directions. Dynamic postural stability was adversely affected immediately after cryotherapy to the ankle joint.

[The impact of dynamic platform exercises on knee joint muscle strength in patients with gonarthrosis treated with microfracture method].

PubMed

Klupiński, Kamil; Krochmalski, Jakub; Woldańska-Okońska, Marta

2017-06-23

Osteoarthritis is the most common joint disease. Gonarthrosis is one of the most serious diseases the highly developed modern medicine must face. The number of patients suffering from joint pain and progressive disability is growing, especially in economically developed countries. Over the years, the disease has been considered merely as a symptom of aging and the effect of "wear and tear" of the cartilage. At present it is known that the degenerative joint disease is of chronic and progressive nature and its pathogenesis is complex. The aim of the study was to determine the impact of dynamic platform exercises on knee joint muscle strength in patients with gonarthrosis treated with microfracture method. The study included 120 patients of both sexes, aged 40 to 65 years, height range1.60-1.90 m., weight 50- 100 kg. Patients were divided into two groups. Group I of 60 patients after knee arthroscopy (with performed microfractures on the articular cartilage) who were subjected to physiotherapy with the use of dynamometric platform and to isometric and dynamic exercises of muscles surrounding the knee joint. Group II (control) of 60 patients after knee arthroscopy (with performed microfractures on the articular cartilage), who were subjected only to isometric and dynamic exercises of muscles surrounding the knee joint. The patients underwent rehabilitation according to the same rehabilitation program suggested by the Medical Magnus Clinic in Lodz, which consisted in performing daily exercises in open and closed kinetic chains. All Group I and II patients were examined three times: before the start of the rehabilitation, after 4th week of rehabilitation (on the average 20 days of the procedures) and 3 months afterwards. The clinical examination included the measurement of muscle strength using Lovett test. It has been demonstrated that the introduction of modern highly specialized physiotherapy contributes to the improvement of the outcome and to the shortening of the treatment duration. A significant improvement was observed in all the examined patients at all stages of rehabilitation in relation to the baseline values. The conducted modern physiotherapy has a significant effect on the condition of patients after surgery. Different exercises on dynamometric platform combined with static and dynamic exercises exert a positive impact on the strengthening of muscles surrounding the knee joint, which in time perspective results in better quality of life of the patients.

The carry-over effect of competition in task-sharing: evidence from the joint Simon task.

PubMed

Iani, Cristina; Anelli, Filomena; Nicoletti, Roberto; Rubichi, Sandro

2014-01-01

The Simon effect, that is the advantage of the spatial correspondence between stimulus and response locations when stimulus location is a task-irrelevant dimension, occurs even when the task is performed together by two participants, each performing a go/no-go task. Previous studies showed that this joint Simon effect, considered by some authors as a measure of self-other integration, does not emerge when during task performance co-actors are required to compete. The present study investigated whether and for how long competition experienced during joint performance of one task can affect performance in a following joint Simon task. In two experiments, we required pairs of participants to perform together a joint Simon task, before and after jointly performing together an unrelated non-spatial task (the Eriksen flanker task). In Experiment 1, participants always performed the joint Simon task under neutral instructions, before and after performing the joint flanker task in which they were explicitly required either to cooperate with (i.e., cooperative condition) or to compete against a co-actor (i.e., competitive condition). In Experiment 2, they were required to compete during the joint flanker task and to cooperate during the subsequent joint Simon task. Competition experienced in one task affected the way the subsequent joint task was performed, as revealed by the lack of the joint Simon effect, even though, during the Simon task participants were not required to compete (Experiment 1). However, prior competition no longer affected subsequent performance if a new goal that created positive interdependence between the two agents was introduced (Experiment 2). These results suggest that the emergence of the joint Simon effect is significantly influenced by how the goals of the co-acting individuals are related, with the effect of competition extending beyond the specific competitive setting and affecting subsequent interactions.

Rehabilitation of jointed Portland cement concrete pavements : SPS-6--initial evaluation and analysis

DOT National Transportation Integrated Search

2005-10-01

The Specific Pavement Studies 6 (SPS-6) experiment, "Rehabilitation of Jointed Portland Cement Concrete Pavements," was designed as a controlled field experiment that focuses on the study of specific rehabilitation design features of jointed plain co...

Effect of dowel bar looseness on measured load transfer efficiency using FWD load

NASA Astrophysics Data System (ADS)

Shoukry, Samir N.; William, Gergis W.; Riad, Mourad Y.

2001-07-01

The effect of dowel bar looseness on the joint load transfer efficiency using Falling Weight Deflectometer is the subject of this paper. The mechanism of dynamic load transfer at transverse joints of Jointed Plain Concrete Pavement is examined using nonlinear 3D finite element analysis.

Computational Methods for Structural Mechanics and Dynamics

NASA Technical Reports Server (NTRS)

Stroud, W. Jefferson (Editor); Housner, Jerrold M. (Editor); Tanner, John A. (Editor); Hayduk, Robert J. (Editor)

1989-01-01

Topics addressed include: transient dynamics; transient finite element method; transient analysis in impact and crash dynamic studies; multibody computer codes; dynamic analysis of space structures; multibody mechanics and manipulators; spatial and coplanar linkage systems; flexible body simulation; multibody dynamics; dynamical systems; and nonlinear characteristics of joints.

A New Sensor for Measurement of Dynamic Contact Stress in the Hip

PubMed Central

Rudert, M. J.; Ellis, B. J.; Henak, C. R.; Stroud, N. J.; Pederson, D. R.; Weiss, J. A.; Brown, T. D.

2014-01-01

Various techniques exist for quantifying articular contact stress distributions, an important class of measurements in the field of orthopaedic biomechanics. In situations where the need for dynamic recording has been paramount, the approach of preference has involved thin-sheet multiplexed grid-array transducers. To date, these sensors have been used to study contact stresses in the knee, shoulder, ankle, wrist, and spinal facet joints. Until now, however, no such sensor had been available for the human hip joint due to difficulties posed by the deep, bi-curvilinear geometry of the acetabulum. We report here the design and development of a novel sensor capable of measuring dynamic contact stress in human cadaveric hip joints (maximum contact stress of 20 MPa and maximum sampling rate 100 readings/s). Particular emphasis is placed on issues concerning calibration, and on the effect of joint curvature on the sensor's performance. The active pressure-sensing regions of the sensors have the shape of a segment of an annulus with a 150-deg circumferential span, and employ a polar/circumferential “ring-and-spoke” sensel grid layout. There are two sensor sizes, having outside radii of 44 and 48 mm, respectively. The new design was evaluated in human cadaver hip joints using two methods. The stress magnitudes and spatial distribution measured by the sensor were compared to contact stresses measured by pressure sensitive film during static loading conditions that simulated heel strike during walking and stair climbing. Additionally, the forces obtained by spatial integration of the sensor contact stresses were compared to the forces measured by load cells during the static simulations and for loading applied by a dynamic hip simulator. Stress magnitudes and spatial distribution patterns obtained from the sensor versus from pressure sensitive film exhibited good agreement. The joint forces obtained during both static and dynamic loading were within ±10% and ±26%, respectively, of the forces measured by the load cells. These results provide confidence in the measurements obtained by the sensor. The new sensor's real-time output and dynamic measurement capabilities hold significant advantages over static measurements from pressure sensitive film. PMID:24763632

A new sensor for measurement of dynamic contact stress in the hip.

PubMed

Rudert, M J; Ellis, B J; Henak, C R; Stroud, N J; Pederson, D R; Weiss, J A; Brown, T D

2014-03-01

Various techniques exist for quantifying articular contact stress distributions, an important class of measurements in the field of orthopaedic biomechanics. In situations where the need for dynamic recording has been paramount, the approach of preference has involved thin-sheet multiplexed grid-array transducers. To date, these sensors have been used to study contact stresses in the knee, shoulder, ankle, wrist, and spinal facet joints. Until now, however, no such sensor had been available for the human hip joint due to difficulties posed by the deep, bi-curvilinear geometry of the acetabulum. We report here the design and development of a novel sensor capable of measuring dynamic contact stress in human cadaveric hip joints (maximum contact stress of 20 MPa and maximum sampling rate 100 readings/s). Particular emphasis is placed on issues concerning calibration, and on the effect of joint curvature on the sensor's performance. The active pressure-sensing regions of the sensors have the shape of a segment of an annulus with a 150-deg circumferential span, and employ a polar/circumferential "ring-and-spoke" sensel grid layout. There are two sensor sizes, having outside radii of 44 and 48 mm, respectively. The new design was evaluated in human cadaver hip joints using two methods. The stress magnitudes and spatial distribution measured by the sensor were compared to contact stresses measured by pressure sensitive film during static loading conditions that simulated heel strike during walking and stair climbing. Additionally, the forces obtained by spatial integration of the sensor contact stresses were compared to the forces measured by load cells during the static simulations and for loading applied by a dynamic hip simulator. Stress magnitudes and spatial distribution patterns obtained from the sensor versus from pressure sensitive film exhibited good agreement. The joint forces obtained during both static and dynamic loading were within ±10% and ±26%, respectively, of the forces measured by the load cells. These results provide confidence in the measurements obtained by the sensor. The new sensor's real-time output and dynamic measurement capabilities hold significant advantages over static measurements from pressure sensitive film.

The use of the articulated total body model as a robot dynamics simulation tool

NASA Technical Reports Server (NTRS)

Obergfell, Louise A.; Avula, Xavier J. R.; Kalegs, Ints

1988-01-01

The Articulated Total Body (ATB) model is a computer sumulation program which was originally developed for the study of aircrew member dynamics during ejection from high-speed aircraft. This model is totally three-dimensional and is based on the rigid body dynamics of coupled systems which use Euler's equations of motion with constraint relations of the type employed in the Lagrange method. In this paper the use of the ATB model as a robot dynamics simulation tool is discussed and various simulations are demonstrated. For this purpose the ATB model has been modified to allow for the application of torques at the joints as functions of state variables of the system. Specifically, the motion of a robotic arm with six revolute articulations with joint torques prescribed as functions of angular displacement and angular velocity are demonstrated. The simulation procedures developed in this work may serve as valuable tools for analyzing robotic mechanisms, dynamic effects, joint load transmissions, feed-back control algorithms employed in the actuator control and end-effector trajectories.

Joint nonlinearity effects in the design of a flexible truss structure control system

NASA Technical Reports Server (NTRS)

Mercadal, Mathieu

1986-01-01

Nonlinear effects are introduced in the dynamics of large space truss structures by the connecting joints which are designed with rather important tolerances to facilitate the assembly of the structures in space. The purpose was to develop means to investigate the nonlinear dynamics of the structures, particularly the limit cycles that might occur when active control is applied to the structures. An analytical method was sought and derived to predict the occurrence of limit cycles and to determine their stability. This method is mainly based on the quasi-linearization of every joint using describing functions. This approach was proven successful when simple dynamical systems were tested. Its applicability to larger systems depends on the amount of computations it requires, and estimates of the computational task tend to indicate that the number of individual sources of nonlinearity should be limited. Alternate analytical approaches, which do not account for every single nonlinearity, or the simulation of a simplified model of the dynamical system should, therefore, be investigated to determine a more effective way to predict limit cycles in large dynamical systems with an important number of distributed nonlinearities.

Free-Swinging Failure Tolerance for Robotic Manipulators. Degree awarded by Purdue Univ.

NASA Technical Reports Server (NTRS)

English, James

1997-01-01

Under this GSRP fellowship, software-based failure-tolerance techniques were developed for robotic manipulators. The focus was on failures characterized by the loss of actuator torque at a joint, called free-swinging failures. The research results spanned many aspects of the free-swinging failure-tolerance problem, from preparing for an expected failure to discovery of postfailure capabilities to establishing efficient methods to realize those capabilities. Developed algorithms were verified using computer-based dynamic simulations, and these were further verified using hardware experiments at Johnson Space Center.

Arctic Ice Dynamics Joint Experiment 1975-1976. Physical Oceanography Data Report, Salinity, Temperature and Depth Data, Camp Blue Fox. Volume II.

DTIC Science & Technology

1980-02-01

to LM b. a w ewe%- ww re mOOc 4" o 0.NWmotvviiOf wt 00 f4Crfl ft -wm o.e. &*1 NO P..w N N o%9 a in - - -da inN 4p m a - U . .......0...V N m...200 1 Attn: Code 428AR 3 Attn: Code 420 a Director Naval Research Laboratory Washington, D.C. 20375 Attn: Library . Code 2620 1 U.S. Naval Research

Validation of the Transient Structural Response of a Threaded Assembly: Phase I

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doebling, Scott W.; Hemez, Francois M.; Robertson, Amy N.

2004-04-01

This report explores the application of model validation techniques in structural dynamics. The problem of interest is the propagation of an explosive-driven mechanical shock through a complex threaded joint. The study serves the purpose of assessing whether validating a large-size computational model is feasible, which unit experiments are required, and where the main sources of uncertainty reside. The results documented here are preliminary, and the analyses are exploratory in nature. The results obtained to date reveal several deficiencies of the analysis, to be rectified in future work.

Recursive multibody dynamics and discrete-time optimal control

NASA Technical Reports Server (NTRS)

Deleuterio, G. M. T.; Damaren, C. J.

1989-01-01

A recursive algorithm is developed for the solution of the simulation dynamics problem for a chain of rigid bodies. Arbitrary joint constraints are permitted, that is, joints may allow translational and/or rotational degrees of freedom. The recursive procedure is shown to be identical to that encountered in a discrete-time optimal control problem. For each relevant quantity in the multibody dynamics problem, there exists an analog in the context of optimal control. The performance index that is minimized in the control problem is identified as Gibbs' function for the chain of bodies.

Comparison of kinematic and dynamic leg trajectory optimization techniques for biped robot locomotion

NASA Astrophysics Data System (ADS)

Khusainov, R.; Klimchik, A.; Magid, E.

2017-01-01

The paper presents comparison analysis of two approaches in defining leg trajectories for biped locomotion. The first one operates only with kinematic limitations of leg joints and finds the maximum possible locomotion speed for given limits. The second approach defines leg trajectories from the dynamic stability point of view and utilizes ZMP criteria. We show that two methods give different trajectories and demonstrate that trajectories based on pure dynamic optimization cannot be realized due to joint limits. Kinematic optimization provides unstable solution which can be balanced by upper body movement.

[The first experience with the concurrent effect of YAG-neodymium and YAG-erbium laser on experimental animal tissues and the possibility of its use in surgery].

PubMed

Roshal', L M; Gorbatova, N E; Livshits, Iu L; Parkhomenko, Iu G; Osiko, V V; Danileĭko, Iu K; Sidorin, A V; Tylaĭkova, T B; Ivanov, A D

1991-08-01

To guarantee the necessary rate of cutting live tissues with adequate hemostasis along the line of the incision, the authors studied isolated and joint effect of radiations of AIG-neodymium and AIG-erbium lasers on the tissues of laboratory animals. The possibility of accomplishing intraoperative hemostasis on the parenchymal organs was studied in experiments with AIG-neodymium laser. A good dissection effect in cutting various tissues was produced in the second series of experiments with AIG-erbium laser. The simultaneous action of AIG-neodymium and AIG-erbium beams converged at one point on the surface of the biological object was studied in the third series of experiments. It was found that the effect ensures a good dissection of tissues with sufficient hemostasis. The results of dynamic morphological studies are shown. The possibility of using the device in surgery is discussed.

Middeck zero-gravity dynamics experiment - Comparison of ground and flight test data

NASA Technical Reports Server (NTRS)

Crawley, Edward F.; Barlow, Mark S.; Van Schoor, Marthinus C.; Masters, Brett; Bicos, Andrew S.

1992-01-01

An analytic and experimental study of the changes in the modal parameters of space structural test articles from one- to zero-gravity is presented. Deployable, erectable, and rotary modules was assembled to form three one- and two-dimensional structures, in which variations in bracing wire and rotary joint preload could be introduced. The structures were modeled as if hanging from a suspension system in one gravity, and unconstrained, as if free floating in zero-gravity. The analysis is compared with ground experimental measurements, made on a spring/wire suspension system with a nominal plunge frequency of one Hertz, and with measurements made on the Shuttle middeck. The degree of change in linear modal parameters as well as the change in nonlinear nature of the response is examined. Trends in modal parameters are presented as a function of force amplitude, joint preload, and ambient gravity level.

Joint Soviet-French studies of the solar corona. II - Photometry of the solar corona on June 30, 1973

NASA Astrophysics Data System (ADS)

Vsekhsvyatsky, S. K.; Dzyubenko, N. I.; Ivanchuk, V. I.; Popov, O. S.; Rubo, G. A.; Koutchmy, S.; Koutchmy, O.; Shtelmacher, G.

1981-04-01

Results are presented of a study of negatives obtained on June 30, 1973 during the total solar eclipse in Africa; the study was part of a joint Soviet-French experiment on white corona dynamics, carried out by expeditions of Kiev University (Atar, Mauritania) and the Paris Astrophysical Institute (Moussoro, Chad). The distribution of total corona brightness up to 4.5 solar radii and its K and F corona components for east and north directions were found on the basis of novel methods of photometry and colorimetry using star images up to 8.5m as the photometry standards. Neither the color effect nor flattening is found in the inner part (less than 2.5 solar radii) of the F corona. Integral corona brightness in the standard zone of 1.03-6.00 solar radii was found to be 0.64 x 10 to the -6th solar-E.

Cerebellar ataxia: abnormal control of interaction torques across multiple joints.

PubMed

Bastian, A J; Martin, T A; Keating, J G; Thach, W T

1996-07-01

1. We studied seven subjects with cerebellar lesions and seven control subjects as they made reaching movements in the sagittal plane to a target directly in front of them. Reaches were made under three different conditions: 1) "slow-accurate," 2) "fast-accurate," and 3) "fast as possible." All subjects were videotaped moving in a sagittal plane with markers on the index finger, wrist, elbow, and shoulder. Marker positions were digitized and then used to calculate joint angles. For each of the shoulder, elbow and wrist joints, inverse dynamics equations based on a three-segment limb model were used to estimate the net torque (sum of components) and each of the component torques. The component torques consisted of the torque due to gravity, the dynamic interaction torques induced passively by the movement of the adjacent joint, and the torque produced by the muscles and passive tissue elements (sometimes called "residual" torque). 2. A kinematic analysis of the movement trajectory and the change in joint angles showed that the reaches of subjects with cerebellar lesions were abnormal compared with reaches of control subjects. In both the slow-accurate and fast-accurate conditions the cerebellar subjects made abnormally curved wrist paths; the curvature was greater in the slow-accurate condition. During the slow-accurate condition, cerebellar subjects showed target undershoot and tended to move one joint at a time (decomposition). During the fast-accurate reaches, the cerebellar subjects showed target overshoot. Additionally, in the fast-accurate condition, cerebellar subjects moved the joints at abnormal rates relative to one another, but the movements were less decomposed. Only three subjects were tested in the fast as possible condition; this condition was analyzed only to determine maximal reaching speeds of subjects with cerebellar lesions. Cerebellar subjects moved more slowly than controls in all three conditions. 3. A kinetic analysis of torques generated at each joint during the slow-accurate reaches and the fast-accurate reaches revealed that subjects with cerebellar lesions produced very different torque profiles compared with control subjects. In the slow-accurate condition, the cerebellar subjects produced abnormal elbow muscle torques that prevented the normal elbow extension early in the reach. In the fast-accurate condition, the cerebellar subjects produced inappropriate levels of shoulder muscle torque and also produced elbow muscle torques that did not very appropriately with the dynamic interaction torques that occurred at the elbow. Lack of appropriate muscle torque resulted in excessive contributions of the dynamic interaction torque during the fast-accurate reaches. 4. The inability to produce muscle torques that predict, accommodate, and compensate for the dynamic interaction torques appears to be an important cause of the classic kinematic deficits shown by cerebellar subjects during attempted reaching. These kinematic deficits include incoordination of the shoulder and the elbow joints, a curved trajectory, and overshoot. In the fast-accurate condition, cerebellar subjects often made inappropriate muscle torques relative to the dynamic interaction torques. Because of this, interaction torques often determined the pattern of incoordination of the elbow and shoulder that produced the curved trajectory and target overshoot. In the slow-accurate condition, we reason that the cerebellar subjects may use a decomposition strategy so as to simplify the movement and not have to control both joints simultaneously. From these results, we suggest that a major role of the cerebellum is in generating muscle torques at a joint that will predict the interaction torques being generated by other moving joints and compensate for them as they occur.

Dynamic gadolinium-enhanced magnetic resonance imaging allows accurate assessment of the synovial inflammatory activity in rheumatoid arthritis knee joints: a comparison with synovial histology.

PubMed

Axelsen, M B; Stoltenberg, M; Poggenborg, R P; Kubassova, O; Boesen, M; Bliddal, H; Hørslev-Petersen, K; Hanson, L G; Østergaard, M

2012-03-01

To determine whether dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) evaluated using semi-automatic image processing software can accurately assess synovial inflammation in rheumatoid arthritis (RA) knee joints. In 17 RA patients undergoing knee surgery, the average grade of histological synovial inflammation was determined from four biopsies obtained during surgery. A preoperative series of T(1)-weighted dynamic fast low-angle shot (FLASH) MR images was obtained. Parameters characterizing contrast uptake dynamics, including the initial rate of enhancement (IRE), were generated by the software in three different areas: (I) the entire slice (Whole slice); (II) a manually outlined region of interest (ROI) drawn quickly around the joint, omitting large artefacts such as blood vessels (Quick ROI); and (III) a manually outlined ROI following the synovial capsule of the knee joint (Precise ROI). Intra- and inter-reader agreement was assessed using the intra-class correlation coefficient (ICC). The IRE from the Quick ROI and the Precise ROI revealed high correlations to the grade of histological inflammation (Spearman's correlation coefficient (rho) = 0.70, p = 0.001 and rho = 0.74, p = 0.001, respectively). Intra- and inter-reader ICCs were very high (0.93-1.00). No Whole slice parameters were correlated to histology. DCE-MRI provides fast and accurate assessment of synovial inflammation in RA patients. Manual outlining of the joint to omit large artefacts is necessary.

Connection forces in deformable multibody dynamics

NASA Technical Reports Server (NTRS)

Shabana, A. A.; Chang, C. W.

1989-01-01

In the dynamic formulation of holonomic and nonholonomic systems based on D'Alembert-Lagrange equation, the forces of constraints are maintained in the dynamic equations by introducing auxiliary variables, called Lagrange multipliers. This approach introduces a set of generalized reaction forces associated with the system generalized coordinates. Different sets of variables can be used as generalized coordinates and accordingly, the generalized reactions associated with these generalized coordinates may not be the actual reaction forces at the joints. In rigid body dynamics, the generalized reaction forces and the actual reaction forces at the joints represent equipollent systems of forces since they produce the same total forces and moments at and about any point on the rigid body. This is not, however, the case in deformable body analyses wherein the generalized reaction forces depend on the system generalized reference and elastic coordinates. In this paper, a method for determining the actual reaction forces at the joints from the generalized reaction forces in deformable multibody systems is presented.

Newton-Euler Dynamic Equations of Motion for a Multi-body Spacecraft

NASA Technical Reports Server (NTRS)

Stoneking, Eric

2007-01-01

The Magnetospheric MultiScale (MMS) mission employs a formation of spinning spacecraft with several flexible appendages and thruster-based control. To understand the complex dynamic interaction of thruster actuation, appendage motion, and spin dynamics, each spacecraft is modeled as a tree of rigid bodies connected by spherical or gimballed joints. The method presented facilitates assembling by inspection the exact, nonlinear dynamic equations of motion for a multibody spacecraft suitable for solution by numerical integration. The building block equations are derived by applying Newton's and Euler's equations of motion to an "element" consisting of two bodies and one joint (spherical and gimballed joints are considered separately). Patterns in the "mass" and L'force" matrices guide assembly by inspection of a general N-body tree-topology system. Straightforward linear algebra operations are employed to eliminate extraneous constraint equations, resulting in a minimum-dimension system of equations to solve. This method thus combines a straightforward, easily-extendable, easily-mechanized formulation with an efficient computer implementation.

The coupling effects of kinematics and flexibility on the Lagrangian dynamic formulation of open chain deformable links

NASA Technical Reports Server (NTRS)

Changizi, Koorosh

1989-01-01

A nonlinear Lagrangian formulation for the spatial kinematic and dynamic analysis of open chain deformable links consisting of cylindrical joints that connect pairs of flexible links is developed. The special cases of revolute or prismatic joint can also be obtained from the kinematic equations. The kinematic equations are described using a 4x4 matrix method. The configuration of each deformable link in the open loop kinematic chain is identified using a coupled set of relative joint variables, constant geometric parameters, and elastic coordinates. The elastic coordinates define the link deformation with respect to a selected joint coordinate system that is consistent with the kinematic constraints on the boundary of the deformable link. These coordinates can be introduced using approximation techniques such as Rayleigh-Ritz method, finite element technique or any other desired approach. The large relative motion between two neighboring links are defined by a set of joint coordinates which describes the large relative translational and rotational motion between two neighboring joint coordinate systems. The origin of these coordinate systems are rigidly attached to the neighboring links at the joint definition points along the axis of motion.

Linear Parameter Varying Identification of Dynamic Joint Stiffness during Time-Varying Voluntary Contractions

PubMed Central

Golkar, Mahsa A.; Sobhani Tehrani, Ehsan; Kearney, Robert E.

2017-01-01

Dynamic joint stiffness is a dynamic, nonlinear relationship between the position of a joint and the torque acting about it, which can be used to describe the biomechanics of the joint and associated limb(s). This paper models and quantifies changes in ankle dynamic stiffness and its individual elements, intrinsic and reflex stiffness, in healthy human subjects during isometric, time-varying (TV) contractions of the ankle plantarflexor muscles. A subspace, linear parameter varying, parallel-cascade (LPV-PC) algorithm was used to identify the model from measured input position perturbations and output torque data using voluntary torque as the LPV scheduling variable (SV). Monte-Carlo simulations demonstrated that the algorithm is accurate, precise, and robust to colored measurement noise. The algorithm was then used to examine stiffness changes associated with TV isometric contractions. The SV was estimated from the Soleus EMG using a Hammerstein model of EMG-torque dynamics identified from unperturbed trials. The LPV-PC algorithm identified (i) a non-parametric LPV impulse response function (LPV IRF) for intrinsic stiffness and (ii) a LPV-Hammerstein model for reflex stiffness consisting of a LPV static nonlinearity followed by a time-invariant state-space model of reflex dynamics. The results demonstrated that: (a) intrinsic stiffness, in particular ankle elasticity, increased significantly and monotonically with activation level; (b) the gain of the reflex pathway increased from rest to around 10–20% of subject's MVC and then declined; and (c) the reflex dynamics were second order. These findings suggest that in healthy human ankle, reflex stiffness contributes most at low muscle contraction levels, whereas, intrinsic contributions monotonically increase with activation level. PMID:28579954

Ground truth report 1975 Phoenix microwave experiment. [Joint Soil Moisture Experiment

NASA Technical Reports Server (NTRS)

Blanchard, B. J.

1975-01-01

Direct measurements of soil moisture obtained in conjunction with aircraft data flights near Phoenix, Arizona in March, 1975 are summarized. The data were collected for the Joint Soil Moisture Experiment.

Joint Attention in Infant-Toddler Early Childhood Programs: Its Dynamics and Potential for Collaborative Learning

ERIC Educational Resources Information Center

Degotardi, Sheila

2017-01-01

This article examines how joint attention episodes constitute a core feature of relational pedagogy for infants and toddlers. It draws on social interactionist approaches to language and cognitive development to propose that joint attention may afford significant current and future potential for young children's learning. However, most joint…

Elastic coupling of limb joints enables faster bipedal walking

PubMed Central

Dean, J.C.; Kuo, A.D.

2008-01-01

The passive dynamics of bipedal limbs alone are sufficient to produce a walking motion, without need for control. Humans augment these dynamics with muscles, actively coordinated to produce stable and economical walking. Present robots using passive dynamics walk much slower, perhaps because they lack elastic muscles that couple the joints. Elastic properties are well known to enhance running gaits, but their effect on walking has yet to be explored. Here we use a computational model of dynamic walking to show that elastic joint coupling can help to coordinate faster walking. In walking powered by trailing leg push-off, the model's speed is normally limited by a swing leg that moves too slowly to avoid stumbling. A uni-articular spring about the knee allows faster but uneconomical walking. A combination of uni-articular hip and knee springs can speed the legs for improved speed and economy, but not without the swing foot scuffing the ground. Bi-articular springs coupling the hips and knees can yield high economy and good ground clearance similar to humans. An important parameter is the knee-to-hip moment arm that greatly affects the existence and stability of gaits, and when selected appropriately can allow for a wide range of speeds. Elastic joint coupling may contribute to the economy and stability of human gait. PMID:18957360

Joint symbolic dynamics as a model-free approach to study interdependence in cardio-respiratory time series.

PubMed

Baumert, Mathias; Brown, Rachael; Duma, Stephen; Broe, G Anthony; Kabir, Muammar M; Macefield, Vaughan G

2012-01-01

Heart rate and respiration display fluctuations that are interlinked by central regulatory mechanisms of the autonomic nervous system (ANS). Joint assessment of respiratory time series along with heart rate variability (HRV) may therefore provide information on ANS dysfunction. The aim of this study was to investigate cardio-respiratory interaction in patients with Parkinson's disease (PD), a neurodegenerative disorder that is associated with progressive ANS dysfunction. Short-term ECG and respiration were recorded in 25 PD patients and 28 healthy controls during rest. To assess ANS dysfunction we analyzed joint symbolic dynamics of heart rate and respiration, cardio-respiratory synchrograms along with heart rate variability. Neither HRV nor cardio-respiratory synchrograms were significantly altered in PD patients. Symbolic analysis, however, identified a significant reduction in cardio-respiratory interactions in PD patients compared to healthy controls (16 ± 3.6 % vs. 20 ± 6.1 %; p= 0.02). In conclusion, joint symbolic analysis of cardio-respiratory dynamics provides a powerful tool to detect early signs of autonomic nervous system dysfunction in Parkinson's disease patients at an early stage of the disease.

Early results of a simple distraction dynamic external fixator in management of comminuted intra-articular fractures of base of middle phalanx.

PubMed

Mansha, Muhammad; Miranda, Sanjay

2013-12-01

Treatment for comminuted fracture dislocations of the proximal interphalangeal joint (pilon injuries) remains a challenge. We present our short term results of twelve pilon fracture dislocations treated by closed reduction and application of a distraction dynamic external fixator. The aim of the study was to assess the clinical outcomes and compare them to the original description by Hynes and Giddins. A cohort of 12 consecutive patients with pilon fracture of the proximal interphalangeal joint (comminuted fracture of the base of middle phalanx, longitudinally unstable with joint subluxation), were treated with this method over the study period. Data was collected by an independent observer at last follow-up appointment in the clinic. The outcome measures recorded were; level of residual pain, arc of motion, X-ray appearance, return to work and satisfaction with the procedure. The study group comprises of 7 male and 5 female patients at a mean age of 38.1 years (range 21-70 years). The average range of movement achieved was 13-87° at a mean follow-up of 16.4 weeks (Range 12-42 weeks). Early return to work, good pain relief and high level of patient satisfaction were achieved. No serious complication was noted during this period. We used the construct with slight modification of the original description and we feel this modification may help to reduce the pin site infection. We found the results reproducible and based on our experience we recommend this technique to treat these complex intra-articular fractures of base of middle phalanx.

Ear canal dynamic motion as a source of power for in-ear devices

NASA Astrophysics Data System (ADS)

Delnavaz, Aidin; Voix, Jérémie

2013-02-01

Ear canal deformation caused by temporomandibular joint (jaw joint) activity, also known as "ear canal dynamic motion," is introduced in this paper as a candidate source of power to possibly recharge hearing aid batteries. The geometrical deformation of the ear canal is quantified in 3D by laser scanning of different custom ear moulds. An experimental setup is proposed to measure the amount of power potentially available from this source. The results show that 9 mW of power is available from a 15 mm3 dynamic change in the ear canal volume. Finally, the dynamic motion and power capability of the ear canal are investigated in a group of 12 subjects.

Evaluation of automated decisionmaking methodologies and development of an integrated robotic system simulation. Volume 2, Part 2: Appendixes B, C, D and E

NASA Technical Reports Server (NTRS)

Lowrie, J. W.; Fermelia, A. J.; Haley, D. C.; Gremban, K. D.; Vanbaalen, J.; Walsh, R. W.

1982-01-01

The derivation of the equations is presented, the rate control algorithm described, and simulation methodologies summarized. A set of dynamics equations that can be used recursively to calculate forces and torques acting at the joints of an n link manipulator given the manipulator joint rates are derived. The equations are valid for any n link manipulator system with any kind of joints connected in any sequence. The equations of motion for the class of manipulators consisting of n rigid links interconnected by rotary joints are derived. A technique is outlined for reducing the system of equations to eliminate contraint torques. The linearized dynamics equations for an n link manipulator system are derived. The general n link linearized equations are then applied to a two link configuration. The coordinated rate control algorithm used to compute individual joint rates when given end effector rates is described. A short discussion of simulation methodologies is presented.

A case-study in the clinical epidemiology of psoriatic arthritis: multistate models and causal arguments

PubMed Central

O'Keeffe, Aidan G; Tom, Brian D M; Farewell, Vernon T

2011-01-01

In psoriatic arthritis, permanent joint damage characterizes disease progression and represents a major debilitating aspect of the disease. Understanding the process of joint damage will assist in the treatment and disease management of patients. Multistate models provide a means to examine patterns of disease, such as symmetric joint damage. Additionally, the link between damage and the dynamic course of disease activity (represented by joint swelling and stress pain) at both the individual joint level and otherwise can be represented within a correlated multistate model framework. Correlation is reflected through the use of random effects for progressive models and robust variance estimation for non-progressive models. Such analyses, undertaken with data from a large psoriatic arthritis cohort, are discussed and the extent to which they permit causal reasoning is considered. For this, emphasis is given to the use of the Bradford Hill criteria for causation in observational studies and the concept of local (in)dependence to capture the dynamic nature of the relationships. PMID:22163372

Design and simulation of a cable-pulley-based transmission for artificial ankle joints

NASA Astrophysics Data System (ADS)

Liu, Huaxin; Ceccarelli, Marco; Huang, Qiang

2016-06-01

In this paper, a mechanical transmission based on cable pulley is proposed for human-like actuation in the artificial ankle joints of human-scale. The anatomy articular characteristics of the human ankle is discussed for proper biomimetic inspiration in designing an accurate, efficient, and robust motion control of artificial ankle joint devices. The design procedure is presented through the inclusion of conceptual considerations and design details for an interactive solution of the transmission system. A mechanical design is elaborated for the ankle joint angular with pitch motion. A multi-body dynamic simulation model is elaborated accordingly and evaluated numerically in the ADAMS environment. Results of the numerical simulations are discussed to evaluate the dynamic performance of the proposed design solution and to investigate the feasibility of the proposed design in future applications for humanoid robots.

Single-leg hop testing following fatiguing exercise: reliability and biomechanical analysis.

PubMed

Augustsson, J; Thomeé, R; Lindén, C; Folkesson, M; Tranberg, R; Karlsson, J

2006-04-01

A fatiguing exercise protocol was combined with single-leg hop testing to improve the possibilities of evaluating the effects of training or rehabilitation interventions. In the first test-retest experiment, 11 healthy male subjects performed two trials of single-leg hops under three different test conditions: non-fatigued and following fatiguing exercise, which consisted of unilateral weight machine knee extensions at 80% and 50%, respectively, of 1 repetition maximum (1 RM) strength. Intraclass correlation coefficients ranged from 0.75 to 0.98 for different hop test conditions, indicating that all tests were reliable. For the second experiment, eight healthy male subjects performed the fatiguing exercise protocol to investigate how fatigue influences lower-extremity joint kinematics and kinetics during single-leg hops. Hip, knee and ankle joint angles, moments and powers, as well as ground-reaction forces were recorded with a six-camera, motion-capture system and a force platform. Recovery of hop performance following the fatiguing exercise was also measured. During the take-off for the single-leg hops, hip and knee flexion angles, generated powers for the knee and ankle joints, and ground-reaction forces decreased for the fatigued hop conditions compared with the non-fatigued condition (P<0.05). Compared with landing during the non-fatigued condition, hip moments and ground-reaction forces were lower for the fatigued hop conditions (P<0.05). The negative joint power was two to three times greater for the knee than for the hip and five to 10 times greater for the knee than for the ankle during landing for all test conditions (P<0.05). Most measured variables had recovered three minutes post-exercise. It is concluded that the fatiguing exercise protocol combined with single-leg hop testing was a reliable method for investigating functional performance under fatigued test conditions. Further, subjects utilized an adapted hop strategy, which employed less hip and knee flexion and generated powers for the knee and ankle joints during take-off, and less hip joint moments during landing under fatigued conditions. The large negative power values observed at the knee joint during the landing phase of the single-leg hop, during which the quadriceps muscle activates eccentrically, indicate that not only hop distance but also the ability to perform successful landings should be investigated when assessing dynamic knee function.

Experiments in cooperative-arm object manipulation with a two-armed free-flying robot. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Koningstein, Ross

1990-01-01

Developing computed-torque controllers for complex manipulator systems using current techniques and tools is difficult because they address the issues pertinent to simulation, as opposed to control. A new formulation of computed-torque (CT) control that leads to an automated computer-torque robot controller program is presented. This automated tool is used for simulations and experimental demonstrations of endpoint and object control from a free-flying robot. A new computed-torque formulation states the multibody control problem in an elegant, homogeneous, and practical form. A recursive dynamics algorithm is presented that numerically evaluates kinematics and dynamics terms for multibody systems given a topological description. Manipulators may be free-flying, and may have closed-chain constraints. With the exception of object squeeze-force control, the algorithm does not deal with actuator redundancy. The algorithm is used to implement an automated 2D computed-torque dynamics and control package that allows joint, endpoint, orientation, momentum, and object squeeze-force control. This package obviates the need for hand-derivation of kinematics and dynamics, and is used for both simulation and experimental control. Endpoint control experiments are performed on a laboratory robot that has two arms to manipulate payloads, and uses an air bearing to achieve very-low drag characteristics. Simulations and experimental data for endpoint and object controllers are presented for the experimental robot - a complex dynamic system. There is a certain rather wide set of conditions under which CT endpoint controllers can neglect robot base accelerations (but not motions) and achieve comparable performance including base accelerations in the model. The regime over which this simplification holds is explored by simulation and experiment.

The Recommendations for Linear Measurement Techniques on the Measurements of Nonlinear System Parameters of a Joint.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Scott A; Catalfamo, Simone; Brake, Matthew R. W.

2017-01-01

In the study of the dynamics of nonlinear systems, experimental measurements often convolute the response of the nonlinearity of interest and the effects of the experimental setup. To reduce the influence of the experimental setup on the deduction of the parameters of the nonlinearity, the response of a mechanical joint is investigated under various experimental setups. These experiments first focus on quantifying how support structures and measurement techniques affect the natural frequency and damping of a linear system. The results indicate that support structures created from bungees have negligible influence on the system in terms of frequency and damping ratiomore » variations. The study then focuses on the effects of the excitation technique on the response for a linear system. The findings suggest that thinner stingers should not be used, because under the high force requirements the stinger bending modes are excited adding unwanted torsional coupling. The optimal configuration for testing the linear system is then applied to a nonlinear system in order to assess the robustness of the test configuration. Finally, recommendations are made for conducting experiments on nonlinear systems using conventional/linear testing techniques.« less

Space, time, and host evolution facilitate coexistence of competing bacteriophages: theory and experiment.

PubMed

Coberly, L Caitlin; Wei, Wei; Sampson, Koffi Y; Millstein, Jack; Wichman, Holly A; Krone, Stephen M

2009-04-01

We present a joint experimental/theoretical investigation into the roles of spatial structure and time in the competition between two pathogens for a single host. We suggest a natural mechanism by which competing pathogens can coexist when host evolution and competitive dynamics occur on similar timescales. Our experimental system consisted of a single bacterial host species and two competing bacteriophage strains grown on agar plates, with a serial transfer of samples of the bacteriophage population to fresh host populations after each incubation cycle. The experiments included two incubation times and two transfer protocols that either maintained or disrupted the spatial structure of the viruses at each transfer. The same bacteriophage acted as the dominant competitor under both transfer protocols. A striking difference between the treatments is that the weak competitor was able to persist in the long-incubation experiments but not in the short-incubation experiments. Mathematical and experimental evidence suggest that coexistence is due to the appearance of resistant mutant host cells that provide a transient "spatiotemporal refuge" for the weaker competitor. Our mathematical model is individual based, captures the stochastic spatial dynamics down to the level of individual cells, and helps to explain the differences in behavior under the various experimental conditions.

Finite Element Model of the Knee for Investigation of Injury Mechanisms: Development and Validation

PubMed Central

Kiapour, Ali; Kiapour, Ata M.; Kaul, Vikas; Quatman, Carmen E.; Wordeman, Samuel C.; Hewett, Timothy E.; Demetropoulos, Constantine K.; Goel, Vijay K.

2014-01-01

Multiple computational models have been developed to study knee biomechanics. However, the majority of these models are mainly validated against a limited range of loading conditions and/or do not include sufficient details of the critical anatomical structures within the joint. Due to the multifactorial dynamic nature of knee injuries, anatomic finite element (FE) models validated against multiple factors under a broad range of loading conditions are necessary. This study presents a validated FE model of the lower extremity with an anatomically accurate representation of the knee joint. The model was validated against tibiofemoral kinematics, ligaments strain/force, and articular cartilage pressure data measured directly from static, quasi-static, and dynamic cadaveric experiments. Strong correlations were observed between model predictions and experimental data (r > 0.8 and p < 0.0005 for all comparisons). FE predictions showed low deviations (root-mean-square (RMS) error) from average experimental data under all modes of static and quasi-static loading, falling within 2.5 deg of tibiofemoral rotation, 1% of anterior cruciate ligament (ACL) and medial collateral ligament (MCL) strains, 17 N of ACL load, and 1 mm of tibiofemoral center of pressure. Similarly, the FE model was able to accurately predict tibiofemoral kinematics and ACL and MCL strains during simulated bipedal landings (dynamic loading). In addition to minimal deviation from direct cadaveric measurements, all model predictions fell within 95% confidence intervals of the average experimental data. Agreement between model predictions and experimental data demonstrates the ability of the developed model to predict the kinematics of the human knee joint as well as the complex, nonuniform stress and strain fields that occur in biological soft tissue. Such a model will facilitate the in-depth understanding of a multitude of potential knee injury mechanisms with special emphasis on ACL injury. PMID:24763546

Design of splints based on the NiTi alloy for the correction of joint deformities in the fingers

PubMed Central

2010-01-01

Background The proximal interphalange joint (PIP) is fundamental for the functional nature of the hand. The contracture in flexion of the PIP, secondary to traumatisms or illnesses leads to an important functional loss. The use of correcting splints is the common procedure for treating this problem. Its functioning is based on the application of a small load and a prolonged stress which can be dynamic, static progressive or static serial. It is important that the therapist has a splint available which can release a constant and sufficient force to correct the contracture in flexion. Nowadays NiTi is commonly used in bio-engineering, due to its superelastical characteristics. The experience of the authors in the design of other devices based on the NiTi alloy, makes it possible to carry out a new design in this work - the production of a finger splint for the treatment of the contracture in flexion of the PIP joint. Methods Commercial orthosis have been characterized using a universal INSTRON 5565 machine. A computational simulation of the proposed design has been conducted, reproducing its performance and using a model "ad hoc" for the NiTi material. Once the parameters have been adjusted, the design is validated using the same type of test as those carried out on commercial orthosis. Results and Discussion For commercial splint the recovering force falls to excessively low values as the angle increases. Angle curves for different lengths and thicknesses of the proposed design have been obtained, with a practically constant recovering force value over a wide range of angles that vary between 30° and 150° in every case. Then the whole treatment is possible with only one splint, and without the need of progressive replacements as the joint recovers. Conclusions A new model of splint based on NiTi alloy has been designed, simulated and tested comparing its behaviour with two of the most regularly used splints. Its uses is recommended instead of other dynamic orthosis used in orthopaedics for the PIP joint. Besides, its extremely simple design, makes its manufacture and use on the part of the specialist easier. PMID:20836874

The Effects of Multiple-Joint Isokinetic Resistance Training on Maximal Isokinetic and Dynamic Muscle Strength and Local Muscular Endurance.

PubMed

Ratamess, Nicholas A; Beller, Noah A; Gonzalez, Adam M; Spatz, Gregory E; Hoffman, Jay R; Ross, Ryan E; Faigenbaum, Avery D; Kang, Jie

2016-03-01

The transfer of training effects of multiple-joint isokinetic resistance training to dynamic exercise performance remain poorly understood. Thus, the purpose of the present study was to investigate the magnitude of isokinetic and dynamic one repetition-maximum (1RM) strength and local muscular endurance increases after 6 weeks of multiple-joint isokinetic resistance training. Seventeen women were randomly assigned to either an isokinetic resistance training group (IRT) or a non-exercising control group (CTL). The IRT group underwent 6 weeks of training (2 days per week) consisting of 5 sets of 6-10 repetitions at 75-85% of subjects' peak strength for the isokinetic chest press and seated row exercises at an average linear velocity of 0.15 m s(-1) [3-sec concentric (CON) and 3-sec eccentric (ECC) phases]. Peak CON and ECC force during the chest press and row, 1RM bench press and bent-over row, and maximum number of modified push-ups were assessed pre and post training. A 2 x 2 analysis of variance with repeated measures and Tukey's post hoc tests were used for data analysis. The results showed that 1RM bench press (from 38.6 ± 6.7 to 43.0 ± 5.9 kg), 1RM bent-over row (from 40.4 ± 7.7 to 45.5 ± 7.5 kg), and the maximal number of modified push-ups (from 39.5 ± 13.6 to 55.3 ± 13.1 repetitions) increased significantly only in the IRT group. Peak isokinetic CON and ECC force in the chest press and row significantly increased in the IRT group. No differences were shown in the CTL group for any measure. These data indicate 6 weeks of multiple-joint isokinetic resistance training increases dynamic muscle strength and local muscular endurance performance in addition to specific isokinetic strength gains in women. Key pointsMultiple-joint isokinetic resistance training increases dynamic maximal muscular strength, local muscular endurance, and maximal isokinetic strength in women.Multiple-joint isokinetic resistance training increased 1RM strength in the bench press (by 10.2%), bent-over barbell row (by 11.2%), and maximal modified push-up performance (by 28.6%) indicating a carryover of training effects to dynamic exercise performance.The carryover effects may be attractive to strength training and conditioning professionals seeking to include alternative modalities such as multiple-joint isokinetic dynamometers to resistance training programs.

The Effects of Multiple-Joint Isokinetic Resistance Training on Maximal Isokinetic and Dynamic Muscle Strength and Local Muscular Endurance

PubMed Central

Ratamess, Nicholas A.; Beller, Noah A.; Gonzalez, Adam M.; Spatz, Gregory E.; Hoffman, Jay R.; Ross, Ryan E.; Faigenbaum, Avery D.; Kang, Jie

2016-01-01

The transfer of training effects of multiple-joint isokinetic resistance training to dynamic exercise performance remain poorly understood. Thus, the purpose of the present study was to investigate the magnitude of isokinetic and dynamic one repetition-maximum (1RM) strength and local muscular endurance increases after 6 weeks of multiple-joint isokinetic resistance training. Seventeen women were randomly assigned to either an isokinetic resistance training group (IRT) or a non-exercising control group (CTL). The IRT group underwent 6 weeks of training (2 days per week) consisting of 5 sets of 6-10 repetitions at 75-85% of subjects’ peak strength for the isokinetic chest press and seated row exercises at an average linear velocity of 0.15 m s-1 [3-sec concentric (CON) and 3-sec eccentric (ECC) phases]. Peak CON and ECC force during the chest press and row, 1RM bench press and bent-over row, and maximum number of modified push-ups were assessed pre and post training. A 2 x 2 analysis of variance with repeated measures and Tukey’s post hoc tests were used for data analysis. The results showed that 1RM bench press (from 38.6 ± 6.7 to 43.0 ± 5.9 kg), 1RM bent-over row (from 40.4 ± 7.7 to 45.5 ± 7.5 kg), and the maximal number of modified push-ups (from 39.5 ± 13.6 to 55.3 ± 13.1 repetitions) increased significantly only in the IRT group. Peak isokinetic CON and ECC force in the chest press and row significantly increased in the IRT group. No differences were shown in the CTL group for any measure. These data indicate 6 weeks of multiple-joint isokinetic resistance training increases dynamic muscle strength and local muscular endurance performance in addition to specific isokinetic strength gains in women. Key points Multiple-joint isokinetic resistance training increases dynamic maximal muscular strength, local muscular endurance, and maximal isokinetic strength in women. Multiple-joint isokinetic resistance training increased 1RM strength in the bench press (by 10.2%), bent-over barbell row (by 11.2%), and maximal modified push-up performance (by 28.6%) indicating a carryover of training effects to dynamic exercise performance. The carryover effects may be attractive to strength training and conditioning professionals seeking to include alternative modalities such as multiple-joint isokinetic dynamometers to resistance training programs. PMID:26957924

Joint Typhoon Warning Center (JTWC92) Model.

DTIC Science & Technology

1992-05-01

Report Date. 13. Report Type and Dates Covered. I May 1992 IFinal - Contractor Report 4. Title and Subtitle. 5. FL iding Numbers. Final Report Joint...National Hurricane Center, Coral Gables, FL , 44 pp. I Neumann, C.J. and C.J. McAdie, 1991: A Revised National Hurricane Center NHC83 Model NHC90. NOAA...STATISTICAL-DYNAMICAL MODELS: HISTORICAL PERSPECTIVE The earliest known attempt at statistical-dynamical modeling is credi- ted to Veigas , (1966) for

[A dynamic model of the extravehicular (correction of extravehicuar) activity space suit].

PubMed

Yang, Feng; Yuan, Xiu-gan

2002-12-01

Objective. To establish a dynamic model of the space suit base on the particular configuration of the space suit. Method. The mass of the space suit components, moment of inertia, mobility of the joints of space suit, as well as the suit-generated torques, were considered in this model. The expressions to calculate the moment of inertia were developed by simplifying the geometry of the space suit. A modified Preisach model was used to mathematically describe the hysteretic torque characteristics of joints in a pressurized space suit, and it was implemented numerically basing on the observed suit parameters. Result. A dynamic model considering mass, moment of inertia and suit-generated torques was established. Conclusion. This dynamic model provides some elements for the dynamic simulation of the astronaut extravehicular activity.

Gait analysis and weight bearing in pre-clinical joint pain research.

PubMed

Ängeby Möller, Kristina; Svärd, Heta; Suominen, Anni; Immonen, Jarmo; Holappa, Johanna; Stenfors, Carina

2018-04-15

There is a need for better joint pain treatment, but development of new medication has not been successful. Pre-clinical models with readouts that better reflect the clinical situation are needed. In patients with joint pain, pain at rest and pain at walking are two major complaints. We describe a new way of calculating results from gait analysis using the CatWalk™ setup. Rats with monoarthritis induced by injection of Complete Freund's Adjuvant (CFA) intra-articularly into the ankle joint of one hind limb were used to assess gait and dynamic weight bearing. The results show that dynamic weight bearing was markedly reduced for the injected paw. Gait parameters such as amount of normal step sequences, walking speed and duration of step placement were also affected. Treatment with naproxen (an NSAID commonly used for inflammatory pain) attenuated the CFA-induced effects. Pregabalin, which is used for neuropathic pain, had no effect. Reduced dynamic weight bearing during locomotion, assessed and calculated in the way we present here, showed a dose-dependent and lasting normalization after naproxen treatment. In contrast, static weight bearing while standing (Incapacitance tester) showed a significant effect for a limited time only. Mechanical sensitivity (von Frey Optihairs) was completely normalized by naproxen, and the window for testing pharmacological effect disappeared. Objective and reproducible effects, with an endpoint showing face validity compared to pain while walking in patients with joint pain, are achieved by a new way of calculating dynamic weight bearing in monoarthritic rats. Copyright © 2017 Elsevier B.V. All rights reserved.

Fuzzy logic based robotic controller

NASA Technical Reports Server (NTRS)

Attia, F.; Upadhyaya, M.

1994-01-01

Existing Proportional-Integral-Derivative (PID) robotic controllers rely on an inverse kinematic model to convert user-specified cartesian trajectory coordinates to joint variables. These joints experience friction, stiction, and gear backlash effects. Due to lack of proper linearization of these effects, modern control theory based on state space methods cannot provide adequate control for robotic systems. In the presence of loads, the dynamic behavior of robotic systems is complex and nonlinear, especially where mathematical modeling is evaluated for real-time operators. Fuzzy Logic Control is a fast emerging alternative to conventional control systems in situations where it may not be feasible to formulate an analytical model of the complex system. Fuzzy logic techniques track a user-defined trajectory without having the host computer to explicitly solve the nonlinear inverse kinematic equations. The goal is to provide a rule-based approach, which is closer to human reasoning. The approach used expresses end-point error, location of manipulator joints, and proximity to obstacles as fuzzy variables. The resulting decisions are based upon linguistic and non-numerical information. This paper presents a solution to the conventional robot controller which is independent of computationally intensive kinematic equations. Computer simulation results of this approach as obtained from software implementation are also discussed.

Collaborative agency to support integrated care for children, young people and families: an action research study.

PubMed

Stuart, Kaz

2014-04-01

Collaboration was legislated in the delivery of integrated care in the early 2000s in the UK. This research explored how the reality of practice met the rhetoric of collaboration. The paper is situated against a theoretical framework of structure, agency, identity and empowerment. Collectively and contextually these concepts inform the proposed model of 'collaborative agency' to sustain integrated care. The paper brings sociological theory on structure and agency to the dilemma of collaboration. Participative action research was carried out in collaborative teams that aspired to achieve integrated care for children, young people and families between 2009 and 2013. It was a part time, PhD study in collaborative practice. The research established that people needed to be able to be jointly aware of their context, to make joint decisions, and jointly act in order to deliver integrated services, and proposes a model of collaborative agency derived from practitioner's experiences and integrated action research and literature on agency. The model reflects the effects of a range of structures in shaping professional identity, empowerment, and agency in a dynamic. The author proposes that the collaborative agency model will support integrated care, although this is, as yet, an untested hypothesis.

Flexible robot control: Modeling and experiments

NASA Technical Reports Server (NTRS)

Oppenheim, Irving J.; Shimoyama, Isao

1989-01-01

Described here is a model and its use in experimental studies of flexible manipulators. The analytical model uses the equivalent of Rayleigh's method to approximate the displaced shape of a flexible link as the static elastic displacement which would occur under end rotations as applied at the joints. The generalized coordinates are thereby expressly compatible with joint motions and rotations in serial link manipulators, because the amplitude variables are simply the end rotations between the flexible link and the chord connecting the end points. The equations for the system dynamics are quite simple and can readily be formulated for the multi-link, three-dimensional case. When the flexible links possess mass and (polar moment of) inertia which are small compared to the concentrated mass and inertia at the joints, the analytical model is exact and displays the additional advantage of reduction in system dimension for the governing equations. Four series of pilot tests have been completed. Studies on a planar single-link system were conducted at Carnegie-Mellon University, and tests conducted at Toshiba Corporation on a planar two-link system were then incorporated into the study. A single link system under three-dimensional motion, displaying biaxial flexure, was then tested at Carnegie-Mellon.

Neuromodulation and Synaptic Plasticity for the Control of Fast Periodic Movement: Energy Efficiency in Coupled Compliant Joints via PCA.

PubMed

Stratmann, Philipp; Lakatos, Dominic; Albu-Schäffer, Alin

2016-01-01

There are multiple indications that the nervous system of animals tunes muscle output to exploit natural dynamics of the elastic locomotor system and the environment. This is an advantageous strategy especially in fast periodic movements, since the elastic elements store energy and increase energy efficiency and movement speed. Experimental evidence suggests that coordination among joints involves proprioceptive input and neuromodulatory influence originating in the brain stem. However, the neural strategies underlying the coordination of fast periodic movements remain poorly understood. Based on robotics control theory, we suggest that the nervous system implements a mechanism to accomplish coordination between joints by a linear coordinate transformation from the multi-dimensional space representing proprioceptive input at the joint level into a one-dimensional controller space. In this one-dimensional subspace, the movements of a whole limb can be driven by a single oscillating unit as simple as a reflex interneuron. The output of the oscillating unit is transformed back to joint space via the same transformation. The transformation weights correspond to the dominant principal component of the movement. In this study, we propose a biologically plausible neural network to exemplify that the central nervous system (CNS) may encode our controller design. Using theoretical considerations and computer simulations, we demonstrate that spike-timing-dependent plasticity (STDP) for the input mapping and serotonergic neuromodulation for the output mapping can extract the dominant principal component of sensory signals. Our simulations show that our network can reliably control mechanical systems of different complexity and increase the energy efficiency of ongoing cyclic movements. The proposed network is simple and consistent with previous biologic experiments. Thus, our controller could serve as a candidate to describe the neural control of fast, energy-efficient, periodic movements involving multiple coupled joints.

Neuromodulation and Synaptic Plasticity for the Control of Fast Periodic Movement: Energy Efficiency in Coupled Compliant Joints via PCA

PubMed Central

Stratmann, Philipp; Lakatos, Dominic; Albu-Schäffer, Alin

2016-01-01

There are multiple indications that the nervous system of animals tunes muscle output to exploit natural dynamics of the elastic locomotor system and the environment. This is an advantageous strategy especially in fast periodic movements, since the elastic elements store energy and increase energy efficiency and movement speed. Experimental evidence suggests that coordination among joints involves proprioceptive input and neuromodulatory influence originating in the brain stem. However, the neural strategies underlying the coordination of fast periodic movements remain poorly understood. Based on robotics control theory, we suggest that the nervous system implements a mechanism to accomplish coordination between joints by a linear coordinate transformation from the multi-dimensional space representing proprioceptive input at the joint level into a one-dimensional controller space. In this one-dimensional subspace, the movements of a whole limb can be driven by a single oscillating unit as simple as a reflex interneuron. The output of the oscillating unit is transformed back to joint space via the same transformation. The transformation weights correspond to the dominant principal component of the movement. In this study, we propose a biologically plausible neural network to exemplify that the central nervous system (CNS) may encode our controller design. Using theoretical considerations and computer simulations, we demonstrate that spike-timing-dependent plasticity (STDP) for the input mapping and serotonergic neuromodulation for the output mapping can extract the dominant principal component of sensory signals. Our simulations show that our network can reliably control mechanical systems of different complexity and increase the energy efficiency of ongoing cyclic movements. The proposed network is simple and consistent with previous biologic experiments. Thus, our controller could serve as a candidate to describe the neural control of fast, energy-efficient, periodic movements involving multiple coupled joints. PMID:27014051

Hand reach star excursion balance test: An alternative test for dynamic postural control and functional mobility.

PubMed

Eriksrud, Ola; Federolf, Peter; Anderson, Patrick; Cabri, Jan

2018-01-01

Tests of dynamic postural control eliciting full-body three-dimensional joint movements in a systematic manner are scarce. The well-established star excursion balance test (SEBT) elicits primarily three-dimensional lower extremity joint movements with minimal trunk and no upper extremity joint movements. In response to these shortcomings we created the hand reach star excursion balance test (HSEBT) based on the SEBT reach directions. The aims of the current study were to 1) compare HSEBT and SEBT measurements, 2) compare joint movements elicited by the HSEBT to both SEBT joint movements and normative range of motion values published in the literature. Ten SEBT and HSEBT reaches for each foot were obtained while capturing full-body kinematics in twenty recreationally active healthy male subjects. HSEBT and SEBT areas and composite scores (sum of reaches) for total, anterior and posterior subsections and individual reaches were correlated. Total reach score comparisons showed fair to moderate correlations (r = .393 to .606), while anterior and posterior subsections comparisons had fair to good correlations (r = .269 to .823). Individual reach comparisons had no to good correlations (r = -.182 to .822) where lateral and posterior reaches demonstrated the lowest correlations (r = -.182 to .510). The HSEBT elicited more and significantly greater joint movements than the SEBT, except for hip external rotation, knee extension and plantarflexion. Comparisons to normative range of motion values showed that 3 of 18 for the SEBT and 8 of 22 joint movements for the HSEBT were within normative values. The findings suggest that the HSEBT can be used for the assessment of dynamic postural control and is particularly suitable for examining full-body functional mobility.

Analysis of the Constraint Joint Loading in the Thumb During Pipetting.

PubMed

Wu, John Z; Sinsel, Erik W; Zhao, Kristin D; An, Kai-Nan; Buczek, Frank L

2015-08-01

Dynamic loading on articular joints is essential for the evaluation of the risk of the articulation degeneration associated with occupational activities. In the current study, we analyzed the dynamic constraint loading for the thumb during pipetting. The constraint loading is considered as the loading that has to be carried by the connective tissues of the joints (i.e., the cartilage layer and the ligaments) to maintain the kinematic constraints of the system. The joint loadings are solved using a classic free-body approach, using the external loading and muscle forces, which were obtained in an inverse dynamic approach combined with an optimization procedure in anybody. The constraint forces in the thumb joint obtained in the current study are compared with those obtained in the pinch and grasp tests in a previous study (Cooney and Chao, 1977, "Biomechanical Analysis of Static Forces in the Thumb During Hand Function," J. Bone Joint Surg. Am., 59(1), pp. 27-36). The maximal compression force during pipetting is approximately 83% and 60% greater than those obtained in the tip pinch and key pinch, respectively, while substantially smaller than that obtained during grasping. The maximal lateral shear force is approximately six times, 32 times, and 90% greater than those obtained in the tip pinch, key pinch, and grasp, respectively. The maximal dorsal shear force during pipetting is approximately 3.2 and 1.4 times greater than those obtained in the tip pinch and key pinch, respectively, while substantially smaller than that obtained during grasping. Our analysis indicated that the thumb joints are subjected to repetitive, intensive loading during pipetting, compared to other daily activities.

Use of the Microsoft Kinect system to characterize balance ability during balance training.

PubMed

Lim, Dohyung; Kim, ChoongYeon; Jung, HoHyun; Jung, Dukyoung; Chun, Keyoung Jin

2015-01-01

The risk of falling increases significantly in the elderly because of deterioration of the neural musculature regulatory mechanisms. Several studies have investigated methods of preventing falling using real-time systems to evaluate balance; however, it is difficult to monitor the results of such characterizations in real time. Herein, we describe the use of Microsoft's Kinect depth sensor system to evaluate balance in real time. Six healthy male adults (25.5±1.8 years, 173.9±6.4 cm, 71.4±6.5 kg, and 23.6±2.4 kg/m(2)), with normal balance abilities and with no musculoskeletal disorders, were selected to participate in the experiment. Movements of the participants were induced by controlling the base plane of the balance training equipment in various directions. The dynamic motion of the subjects was measured using two Kinect depth sensor systems and a three-dimensional motion capture system with eight infrared cameras. The two systems yielded similar results for changes in the center of body mass (P>0.05) with a large Pearson's correlation coefficient of γ>0.60. The results for the two systems showed similarity in the mean lower-limb joint angle with flexion-extension movements, and these values were highly correlated (hip joint: within approximately 4.6°; knee joint: within approximately 8.4°) (0.40<γ<0.74) (P>0.05). Large differences with a low correlation were, however, observed for the lower-limb joint angle in relation to abduction-adduction and internal-external rotation motion (γ<0.40) (P<0.05). These findings show that clinical and dynamic accuracy can be achieved using the Kinect system in balance training by measuring changes in the center of body mass and flexion-extension movements of the lower limbs, but not abduction-adduction and internal-external rotation.

Multijoint kinetic chain analysis of knee extension during the soccer instep kick.

PubMed

Naito, Kozo; Fukui, Yosuke; Maruyama, Takeo

2010-04-01

Although previous studies have shown that motion-dependent interactions between adjacent segments play an important role in producing knee extension during the soccer instep kick, detailed knowledge about the mechanisms underlying those interactions is lacking. The present study aimed to develop a 3-D dynamical model for the multijoint kinetic chain of the instep kick in order to quantify the contributions of the causal dynamical factors to the production of maximum angular velocity during knee extension. Nine collegiate soccer players volunteered to participate in the experiment and performed instep kicking movements while 3-D positional data and the ground reaction force were measured. A dynamical model was developed in the form of a linked system containing 8 segments and 18 joint rotations, and the knee extension/flexion motion was decomposed into causal factors related to muscular moment, gyroscopic moment, centrifugal force, Coriolis force, gravity, proximal endpoint linear acceleration, and external force-dependent terms. The rapid knee extension during instep kicking was found to result almost entirely from kicking leg centrifugal force, trunk rotation muscular moment, kicking leg Coriolis force, and trunk rotation gyroscopic-dependent components. Based on the finding that rapid knee extension during instep kicking stems from multiple dynamical factors, it is suggested that the multijoint kinetic chain analysis used in the present study is more useful for achieving a detailed understanding of the cause of rapid kicking leg movement than the previously used 2-D, two-segment kinetic chain model. The present results also indicated that the centrifugal effect due to the kicking hip flexion angular velocity contributed substantially to the generation of a rapid knee extension, suggesting that the adjustment between the kicking hip flexion angular velocity and the leg configuration (knee flexion angle) is more important for effective instep kicking than other joint kinematics.

Contribution of tibiofemoral joint contact to net loads at the knee in gait.

PubMed

Walter, Jonathan P; Korkmaz, Nuray; Fregly, Benjamin J; Pandy, Marcus G

2015-07-01

Inverse dynamics analysis is commonly used to estimate the net loads at a joint during human motion. Most lower-limb models of movement represent the knee as a simple hinge joint when calculating muscle forces. This approach is limited because it neglects the contributions from tibiofemoral joint contact forces and may therefore lead to errors in estimated muscle forces. The aim of this study was to quantify the contributions of tibiofemoral joint contact loads to the net knee loads calculated from inverse dynamics for multiple subjects and multiple gait patterns. Tibiofemoral joint contact loads were measured in four subjects with instrumented implants as each subject walked at their preferred speed (normal gait) and performed prescribed gait modifications designed to treat medial knee osteoarthritis. Tibiofemoral contact loads contributed substantially to the net knee extension and knee adduction moments in normal gait with mean values of 16% and 54%, respectively. These findings suggest that knee-contact kinematics and loads should be included in lower-limb models of movement for more accurate determination of muscle forces. The results of this study may be used to guide the development of more realistic lower-limb models that account for the effects of tibiofemoral joint contact at the knee. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Interrater and intrarater reliability in the measurement of ankle joint dorsiflexion is independent of examiner experience and technique used.

PubMed

Kim, Paul Jeong; Peace, Ruth; Mieras, Jamie; Thoms, Tanya; Freeman, Denise; Page, Jeffrey

2011-01-01

Goniometric measurement is currently being used as a diagnostic and outcomes assessment tool for ankle joint dorsiflexion. Despite its common use, its interrater and intrarater reliability has been questioned. This is a prospective study examining whether the experience of the examiner or the technique used affects the interrater and intrarater reliability for measuring ankle joint dorsiflexion. Fourteen asymptomatic individuals (8 male and 6 female) with a mean age of 28.2 years (range, 23-52) were enrolled into this study. The years of clinical experience of the five examiners averaged 10.4 years (range, 0-26). Four examiners used a modified Root, Weed and Orien method of measuring ankle joint dorsiflexion. The fifth examiner utilized a nonstandardized technique. A standard goniometer was used for bilateral measurements of ankle joint dorsiflexion with the knee extended and flexed. All five examiners repeated each measurement three times during each of the three sessions, with each session spaced at least 1 week apart. The interclass correlation coefficient reveals a moderate intrarater and poor interrater reliability in ankle joint dorsiflexion measurements using a standard goniometer. More importantly, further analysis indicates that the use of a standardized technique for measurement of ankle joint dorsiflexion or years of clinical experience does not increase the intrarater or interrater reliability. The utility of the goniometric measurement of ankle joint dorsiflexion may be limited.

Development of a revolute-joint robot for the precision positioning of an x-ray detector

NASA Astrophysics Data System (ADS)

Preissner, Curt A.; Royston, Thomas J.; Shu, Deming

2003-10-01

This paper profiles the initial phase in the development of a six degree-of-freedom robot, with 1 μm dynamic positioning uncertainty, for the manipulation of x-ray detectors or test specimens at the Advanced Photon Source (APS). While revolute-joint robot manipulators exhibit a smaller footprint along with increased positioning flexibility compared to Cartesian manipulators, commercially available revolute-joint manipulators do not meet our size, positioning, or environmental specifications. Currently, a robot with 20 μm dynamic positioning uncertainty is functioning at the APS for cryogenic crystallography sample pick-and-place operation. Theoretical, computational and experimental procedures are being used to (1) identify and (2) simulate the dynamics of the present robot system using a multibody approach, including the mechanics and control architecture, and eventually to (3) design an improved version with a 1 μm dynamic positioning uncertainty. We expect that the preceding experimental and theoretical techniques will be useful design and analysis tools as multi-degree-of-freedom manipulators become more prevalent on synchrotron beamlines.

Effect of progressive resistance exercise with neuromuscular joint facilitation on the dynamic balance performance of junior soccer players.

PubMed

Wang, Hongzhao; Huo, Ming; Guan, Peipei; Onoda, Ko; Chen, Di; Huang, Qiuchen; Maruyama, Hitoshi

2015-11-01

[Purpose] The aim of this study was to investigate the change in dynamic balance performance of junior soccer players after progressive resistance treatment with neuromuscular joint facilitation (NJF). [Subjects] The subjects were 14 healthy males who were divided into two groups, namely the NJF and control groups. The NJF group consisted of 8 subjects, and the control group consisted of 6 subjects. [Methods] The participants in the NJF group received NJF progressive resistance treatment. Dynamic balance performance was measured before and after 3 weeks of exercise. [Results] Significant improvement in dynamic balance performance was observed both in the NJF and control groups. In the NJF group, dynamic balance performance was significantly increased compared with that in the control group. [Conclusion] The NJF intervention shortened movement time, which implies that NJF is effective for dynamic balance performance.

Multireference quantum chemistry through a joint density matrix renormalization group and canonical transformation theory.

PubMed

Yanai, Takeshi; Kurashige, Yuki; Neuscamman, Eric; Chan, Garnet Kin-Lic

2010-01-14

We describe the joint application of the density matrix renormalization group and canonical transformation theory to multireference quantum chemistry. The density matrix renormalization group provides the ability to describe static correlation in large active spaces, while the canonical transformation theory provides a high-order description of the dynamic correlation effects. We demonstrate the joint theory in two benchmark systems designed to test the dynamic and static correlation capabilities of the methods, namely, (i) total correlation energies in long polyenes and (ii) the isomerization curve of the [Cu(2)O(2)](2+) core. The largest complete active spaces and atomic orbital basis sets treated by the joint DMRG-CT theory in these systems correspond to a (24e,24o) active space and 268 atomic orbitals in the polyenes and a (28e,32o) active space and 278 atomic orbitals in [Cu(2)O(2)](2+).

Joint Spatial-Spectral Reconstruction and k-t Spirals for Accelerated 2D Spatial/1D Spectral Imaging of 13C Dynamics

PubMed Central

Gordon, Jeremy W.; Niles, David J.; Fain, Sean B.; Johnson, Kevin M.

2014-01-01

Purpose To develop a novel imaging technique to reduce the number of excitations and required scan time for hyperpolarized 13C imaging. Methods A least-squares based optimization and reconstruction is developed to simultaneously solve for both spatial and spectral encoding. By jointly solving both domains, spectral imaging can potentially be performed with a spatially oversampled single echo spiral acquisition. Digital simulations, phantom experiments, and initial in vivo hyperpolarized [1-13C]pyruvate experiments were performed to assess the performance of the algorithm as compared to a multi-echo approach. Results Simulations and phantom data indicate that accurate single echo imaging is possible when coupled with oversampling factors greater than six (corresponding to a worst case of pyruvate to metabolite ratio < 9%), even in situations of substantial T2* decay and B0 heterogeneity. With lower oversampling rates, two echoes are required for similar accuracy. These results were confirmed with in vivo data experiments, showing accurate single echo spectral imaging with an oversampling factor of 7 and two echo imaging with an oversampling factor of 4. Conclusion The proposed k-t approach increases data acquisition efficiency by reducing the number of echoes required to generate spectroscopic images, thereby allowing accelerated acquisition speed, preserved polarization, and/or improved temporal or spatial resolution. Magn Reson Med PMID:23716402

Joint symbolic dynamic analysis of cardiorespiratory interactions in patients on weaning trials.

PubMed

Caminal, P; Giraldo, B; Zabaleta, H; Vallverdu, M; Benito, S; Ballesteros, D; Lopez-Rodriguez, L; Esteban, A; Baumert, M; Voss, A

2005-01-01

Assessing autonomic control provides information about patho-physiological imbalances. Measures of variability of the cardiac interbeat duration RR(n) and the variability of the breath duration TTot(n) are sensitive to those changes. The interactions between RR(n) and TTot(n) are complex and strongly non-linear. A study of joint symbolic dynamics is presented as a new short-term non-linear analysis method to investigate these interactions in patients on weaning trials. 78 patients from mechanical ventilation are studied: Group A (patients that failed to maintain spontaneous breathing and were reconnected) and Group B (patients with successful trials). Using the concept of joint symbolic dynamics, cardiac and respiratory changes were transformed into a word series, and the probability of occurrence of each word type was calculated and compared between both groups. Significant differences were found in 13 words, and the most significant pn(Wc010, r010): 0.0041 ± 0.0036 (group A) against 0.0012 ± 0.0024 (group B), p-value = 0.00001. The number of seldom occurring word types (forbidden words) also presents significant differences fwcr: 6.9 ± 6.6 against 13.5 ± 5.3, p-value = 0.00004. Joint symbolic dynamics provides an efficient non-linear representation of cardiorespiratory interactions that offers simple physiological interpretations.

Operational Implementation of Space Debris Mitigation Procedures

NASA Astrophysics Data System (ADS)

Gicquel, Anne-Helene; Bonaventure, Francois

2013-08-01

During the spacecraft lifetime, Astrium supports its customers to manage collision risks alerts from the Joint Space Operations Center (JSpOC). This was previously done with hot-line support and a manual operational procedure. Today, it is automated and integrated in QUARTZ, the Astrium Flight Dynamics operational tool. The algorithms and process details for this new 5- step functionality are provided in this paper. To improve this functionality, some R&D activities such as the study of dilution phenomenon and low relative velocity encounters are going on. Regarding end of life disposal, recent operational experiences as well as studies results are presented.

When aging meets microgravity: whole genome promoters and enchancers transcription landscape in zebrafish onboard ISS

NASA Astrophysics Data System (ADS)

Arshanovskii, Kirill; Gusev, Oleg; Sychev, Vladimir; Poddubko, Svetlana; Deviatiiarov, Ruslan

2016-07-01

In order to gen new insights of gene regulation changes under conditions of real spaceflight, we have conducted whole-genome analysis of dynamic of promotes and enhancers transcriptional changes in zebrafish during prolonged exposure to real spaceflight. In the frame of Russia-Japan joint experiments "Aquatic Habitat"-"Aquarium" we have conducted Cap Analysis of Gene Expression (CAGE) assay of zebrafish in the rage from 7 to 40 days of real spaceflight onboard ISS. The analysis showed that both gene expression patterns and architecture of shapes and types of the promoters are affected by spaceflight environment.

Arctic Ice Dynamics Joint Experiment (AIDJEX) 1975-1976, Physical Oceanography Data Report Profiling Current Meter Data -- Camp Caribou. Volume 1.

DTIC Science & Technology

1980-02-01

base of the ice. Hourly averages pertaining to the fixed-mast current meters can be obtained through the National Oceano - graphic Data Center. The...431 441 451 461 471 481 49t 50 40 ’II 421 431 441 󈧷j 461 4󈨋 481 491 Sol , 71ME :N :AYs Fig’ure 11. Speed and direction plotted for the manned AIDJEX...EDDIES Swift mesoscale undercurrents are one of the most notable oceano - graphic features observed in the AIDJEX area of the Arctic Ocean. The eddy form

An approach to multivariable control of manipulators

NASA Technical Reports Server (NTRS)

Seraji, H.

1987-01-01

The paper presents simple schemes for multivariable control of multiple-joint robot manipulators in joint and Cartesian coordinates. The joint control scheme consists of two independent multivariable feedforward and feedback controllers. The feedforward controller is the minimal inverse of the linearized model of robot dynamics and contains only proportional-double-derivative (PD2) terms - implying feedforward from the desired position, velocity and acceleration. This controller ensures that the manipulator joint angles track any reference trajectories. The feedback controller is of proportional-integral-derivative (PID) type and is designed to achieve pole placement. This controller reduces any initial tracking error to zero as desired and also ensures that robust steady-state tracking of step-plus-exponential trajectories is achieved by the joint angles. Simple and explicit expressions of computation of the feedforward and feedback gains are obtained based on the linearized model of robot dynamics. This leads to computationally efficient schemes for either on-line gain computation or off-line gain scheduling to account for variations in the linearized robot model due to changes in the operating point. The joint control scheme is extended to direct control of the end-effector motion in Cartesian space. Simulation results are given for illustration.

Computational stability of human knee joint at early stance in Gait: Effects of muscle coactivity and anterior cruciate ligament deficiency.

PubMed

Sharifi, M; Shirazi-Adl, A; Marouane, H

2017-10-03

As one of the most complex and vulnerable structures of body, the human knee joint should maintain dynamic equilibrium and stability in occupational and recreational activities. The evaluation of its stability and factors affecting it is vital in performance evaluation/enhancement, injury prevention and treatment managements. Knee stability often manifests itself by pain, hypermobility and giving-way sensations and is usually assessed by the passive joint laxity tests. Mechanical stability of both the human knee joint and the lower extremity at early stance periods of gait (0% and 5%) were quantified here for the first time using a hybrid musculoskeletal model of the lower extremity. The roles of muscle coactivity, simulated by setting minimum muscle activation at 0-10% levels and ACL deficiency, simulated by reducing ACL resistance by up to 85%, on the stability margin as well as joint biomechanics (contact/muscle/ligament forces) were investigated. Dynamic stability was analyzed using both linear buckling and perturbation approaches at the final deformed configurations in gait. The knee joint was much more stable at 0% stance than at 5% due to smaller ground reaction and contact forces. Muscle coactivity, when at lower intensities (<3% of its maximum active force), increased dynamic stability margin. Greater minimum activation levels, however, acted asan ineffective strategy to enhance stability. Coactivation also substantially increased muscle forces, joint loads and ACL force and hence the risk of further injury and degeneration. A deficiency in ACL decreases total ACL force (by 31% at 85% reduced stiffness) and the stability margin of the knee joint at the heel strike. It also markedly diminishes forces in lateral hamstrings (by up to 39%) and contact forces on the lateral plateau (by up to 17%). Current work emphasizes the need for quantification of the lower extremity stability margin in gait. Copyright © 2017 Elsevier Ltd. All rights reserved.

Dynamic Mobility Applications Policy Analysis: Policy and Institutional Issues for Integrated Dynamic Transit Operations (IDTO). [supporting datasets

DOT National Transportation Integrated Search

2015-01-27

The datasets in this zip file are in support of Intelligent Transportation Systems Joint Program Office (ITS JPO) report FHWA-JPO-14-134, "Dynamic Mobility Applications Policy Analysis: Policy and Institutional Issues for Integrated Dynamic Transit O...

Static Analysis of Large-Scale Multibody System Using Joint Coordinates and Spatial Algebra Operator

PubMed Central

Omar, Mohamed A.

2014-01-01

Initial transient oscillations inhibited in the dynamic simulations responses of multibody systems can lead to inaccurate results, unrealistic load prediction, or simulation failure. These transients could result from incompatible initial conditions, initial constraints violation, and inadequate kinematic assembly. Performing static equilibrium analysis before the dynamic simulation can eliminate these transients and lead to stable simulation. Most exiting multibody formulations determine the static equilibrium position by minimizing the system potential energy. This paper presents a new general purpose approach for solving the static equilibrium in large-scale articulated multibody. The proposed approach introduces an energy drainage mechanism based on Baumgarte constraint stabilization approach to determine the static equilibrium position. The spatial algebra operator is used to express the kinematic and dynamic equations of the closed-loop multibody system. The proposed multibody system formulation utilizes the joint coordinates and modal elastic coordinates as the system generalized coordinates. The recursive nonlinear equations of motion are formulated using the Cartesian coordinates and the joint coordinates to form an augmented set of differential algebraic equations. Then system connectivity matrix is derived from the system topological relations and used to project the Cartesian quantities into the joint subspace leading to minimum set of differential equations. PMID:25045732

Preparation time influences ankle and knee joint control during dynamic change of direction movements.

PubMed

Fuerst, Patrick; Gollhofer, Albert; Gehring, Dominic

2017-04-01

The influence of preparation time on ankle joint biomechanics during highly dynamic movements is largely unknown. The aim of this study was to evaluate the impact of limited preparation time on ankle joint loading during highly dynamic run-and-cut movements. Thirteen male basketball players performed 45°-sidestep-cutting and 180°-turning manoeuvres in reaction to light signals which appeared during the approach run. Both movements were executed under (1) an easy condition, in which the light signal appeared very early, (2) a medium condition and (3) a hard condition with very little time to prepare the movements. Maximum ankle inversion angles, moments and velocities during ground contact, as well as EMG signals of three lower extremity muscles, were analysed. In 180°-turning movements, reduced preparation time led to significantly increased maximum ankle inversion velocities. Muscular activation levels, however, did not change. Increased inversion velocities, without accompanying changes in muscular activation, may have the potential to destabilise the ankle joint when less preparation time is available. This may result in a higher injury risk during turning movements and should therefore be considered in ankle injury research and the aetiology of ankle sprains.

Static analysis of large-scale multibody system using joint coordinates and spatial algebra operator.

PubMed

Omar, Mohamed A

2014-01-01

Initial transient oscillations inhibited in the dynamic simulations responses of multibody systems can lead to inaccurate results, unrealistic load prediction, or simulation failure. These transients could result from incompatible initial conditions, initial constraints violation, and inadequate kinematic assembly. Performing static equilibrium analysis before the dynamic simulation can eliminate these transients and lead to stable simulation. Most exiting multibody formulations determine the static equilibrium position by minimizing the system potential energy. This paper presents a new general purpose approach for solving the static equilibrium in large-scale articulated multibody. The proposed approach introduces an energy drainage mechanism based on Baumgarte constraint stabilization approach to determine the static equilibrium position. The spatial algebra operator is used to express the kinematic and dynamic equations of the closed-loop multibody system. The proposed multibody system formulation utilizes the joint coordinates and modal elastic coordinates as the system generalized coordinates. The recursive nonlinear equations of motion are formulated using the Cartesian coordinates and the joint coordinates to form an augmented set of differential algebraic equations. Then system connectivity matrix is derived from the system topological relations and used to project the Cartesian quantities into the joint subspace leading to minimum set of differential equations.

Lower Limb Kinematics and Dynamic Postural Stability in Anterior Cruciate Ligament-Reconstructed Female Athletes

PubMed Central

Delahunt, Eamonn; Chawke, Mark; Kelleher, Judy; Murphy, Katie; Prendiville, Anna; Sweeny, Lauren; Patterson, Matt

2013-01-01

Context: Deficits in lower limb kinematics and postural stability are predisposing factors to the development of knee ligamentous injury. The extent to which these deficits are present after anterior cruciate ligament (ACL) reconstruction is still largely unknown. The primary hypothesis of the present study was that female athletes who have undergone ACL reconstruction and who have returned to sport participation would exhibit deficits in dynamic postural stability as well as deficiencies in hip- and knee-joint kinematics when compared with an age-, activity-, and sex-matched uninjured control group. Objective: To investigate dynamic postural stability as quantified by the Star Excursion Balance Test (SEBT) and simultaneous hip- and knee-joint kinematic profiles in female athletes who have undergone ACL reconstruction. Design: Descriptive laboratory study. Setting: University motion-analysis laboratory. Patients or Other Participants: Fourteen female athletes who had previously undergone ACL reconstruction (ACL-R) and 17 age- and sex-matched uninjured controls. Intervention(s): Each participant performed 3 trials of the anterior, posterior-medial, and posterior-lateral directional components of the SEBT. Main Outcome Measure(s): Reach distances for each directional component were quantified and expressed as a percentage of leg length. Simultaneous hip- and knee-joint kinematic profiles were recorded using a motion-analysis system. Results: The ACL-R group had decreased reach distances on the posterior-medial (P < .01) and posterior-lateral (P < .01) directional components of the SEBT. During performance of the directional components of the SEBT, ACL-R participants demonstrated altered hip-joint frontal-, sagittal-, and transverse-plane kinematic profiles (P < .05), as well as altered knee-joint sagittal-plane kinematic profiles (P < .05). Conclusions: Deficits in dynamic postural stability and concomitant altered hip- and knee-joint kinematics are present after ACL reconstruction and return to competitive activity. The extent to which these deficits influence potential future injury is worthy of investigation. PMID:23672381

Nonlinear structural joint model updating based on instantaneous characteristics of dynamic responses

NASA Astrophysics Data System (ADS)

Wang, Zuo-Cai; Xin, Yu; Ren, Wei-Xin

2016-08-01

This paper proposes a new nonlinear joint model updating method for shear type structures based on the instantaneous characteristics of the decomposed structural dynamic responses. To obtain an accurate representation of a nonlinear system's dynamics, the nonlinear joint model is described as the nonlinear spring element with bilinear stiffness. The instantaneous frequencies and amplitudes of the decomposed mono-component are first extracted by the analytical mode decomposition (AMD) method. Then, an objective function based on the residuals of the instantaneous frequencies and amplitudes between the experimental structure and the nonlinear model is created for the nonlinear joint model updating. The optimal values of the nonlinear joint model parameters are obtained by minimizing the objective function using the simulated annealing global optimization method. To validate the effectiveness of the proposed method, a single-story shear type structure subjected to earthquake and harmonic excitations is simulated as a numerical example. Then, a beam structure with multiple local nonlinear elements subjected to earthquake excitation is also simulated. The nonlinear beam structure is updated based on the global and local model using the proposed method. The results show that the proposed local nonlinear model updating method is more effective for structures with multiple local nonlinear elements. Finally, the proposed method is verified by the shake table test of a real high voltage switch structure. The accuracy of the proposed method is quantified both in numerical and experimental applications using the defined error indices. Both the numerical and experimental results have shown that the proposed method can effectively update the nonlinear joint model.

Dynamic Postural-Stability Deficits After Cryotherapy to the Ankle Joint

PubMed Central

Fullam, Karl; Caulfield, Brian; Coughlan, Garrett F.; McGroarty, Mark; Delahunt, Eamonn

2015-01-01

Context  Decreased postural stability is a primary risk factor for lower limb musculoskeletal injuries. During athletic competitions, cryotherapy may be applied during short breaks in play or during half-time; however, its effects on postural stability remain unclear. Objective  To investigate the acute effects of a 15-minute ankle-joint cryotherapy application on dynamic postural stability. Design  Controlled laboratory study. Setting  University biomechanics laboratory. Patients or Other Participants  A total of 29 elite-level collegiate male field-sport athletes (age = 20.8 ± 1.12 years, height = 1.80 ± 0.06 m, mass = 81.89 ± 8.59 kg) participated. Intervention(s)  Participants were tested on the anterior (ANT), posterolateral (PL), and posteromedial (PM) reach directions of the Star Excursion Balance Test before and after a 15-minute ankle-joint cryotherapy application. Main Outcome Measure(s)  Normalized reach distances; sagittal-plane kinematics of the hip, knee, and ankle joints; and associated mean velocity of the center-of-pressure path during performance of the ANT, PL, and PM reach directions of the Star Excursion Balance Test. Results  We observed a decrease in reach-distance scores for the ANT, PL, and PM reach directions from precryotherapy to postcryotherapy (P < .05). No differences were observed in hip-, knee-, or ankle-joint sagittal-plane kinematics (P > .05). We noted a decrease in mean velocity of the center-of-pressure path from precryotherapy to postcryotherapy (P < .05) in all reach directions. Conclusions  Dynamic postural stability was adversely affected immediately after cryotherapy to the ankle joint. PMID:26285088

Dual-joint modeling for estimation of total knee replacement contact forces during locomotion.

PubMed

Hast, Michael W; Piazza, Stephen J

2013-02-01

Model-based estimation of in vivo contact forces arising between components of a total knee replacement is challenging because such forces depend upon accurate modeling of muscles, tendons, ligaments, contact, and multibody dynamics. Here we describe an approach to solving this problem with results that are tested by comparison to knee loads measured in vivo for a single subject and made available through the Grand Challenge Competition to Predict in vivo Tibiofemoral Loads. The approach makes use of a "dual-joint" paradigm in which the knee joint is alternately represented by (1) a ball-joint knee for inverse dynamic computation of required muscle controls and (2) a 12 degree-of-freedom (DOF) knee with elastic foundation contact at the tibiofemoral and patellofemoral articulations for forward dynamic integration. Measured external forces and kinematics were applied as a feedback controller and static optimization attempted to track measured knee flexion angles and electromyographic (EMG) activity. The resulting simulations showed excellent tracking of knee flexion (average RMS error of 2.53 deg) and EMG (muscle activations within ±10% envelopes of normalized measured EMG signals). Simulated tibiofemoral contact forces agreed qualitatively with measured contact forces, but their RMS errors were approximately 25% of the peak measured values. These results demonstrate the potential of a dual-joint modeling approach to predict joint contact forces from kinesiological data measured in the motion laboratory. It is anticipated that errors in the estimation of contact force will be reduced as more accurate subject-specific models of muscles and other soft tissues are developed.

Investigation Leads to Improved Understanding of Space Shuttle RSRM Internal Insulation Joints

NASA Technical Reports Server (NTRS)

McWhorter, Bruce B.; Bolton, Doug E.; Hicken, Steve V.; Allred, Larry D.; Cook, Dave J.

2003-01-01

The Space Shuttle Reusable Solid Rocket Motor (RSRM) uses an internal insulation J-joint design for the mated insulation interface between two assembled RSRM segments. In this assembled (mated) segment configuration, this J-joint design serves as a thermal barrier to prevent hot gases from affecting the case field joint metal surfaces and O-rings. A pressure sensitive adhesive (PSA) provides some adhesion between the two mated insulation surfaces. In 1995, after extensive testing, a new ODC-free PSA (free of ozone depleting chemicals) was selected for flight on RSRM-55 (STS-78). Post-flight inspection revealed that the J-joint, equipped with the new ODC-free PSA, did not perform well. Hot gas seeped inside the J-joint interface. Although not a flight safety threat, the J-joint hot gas intrusion on RSRM-55 was a mystery to the investigators since the PSA had previously worked well on a full-scale static test. A team was assembled to study the J-joint and PSA further. All J-joint design parameters, measured data, and historical performance data were re-reviewed and evaluated by subscale testing and analysis. Although both the ODC-free and old PSA were weakened by humidity, the ODC-free PSA strength was lower to start with. Another RSRM full-scale static test was conducted in 1998 and intentionally duplicated the gas intrusion. This test, along with many concurring tests, showed that if a J-joint was 1) mated with the new ODC-free PSA, 2) exposed to a history of high humidity (Kennedy Space Center levels), and 3) also a joint which experienced significant but normal joint motion (J-joint deformation resulting from motor pressurization dynamics) then that J-joint would open (allow gas intrusion) during motor operation. When all of the data from the analyses, subscale tests, and full-scale tests were considered together, a theory emerged. Most of the joint motion on the RSRM occurs early in motor operation at which point the J-joints are pulled into tension. If the new PSA has been weakened due to humidity, then the J-joint will partially pull apart (inboard side), and the J-joint surfaces will be charred by exposure to hot gases. After early operation, a J-joint that has been pulled apart will come back together as the J-joint deformation decreases. This J-joint heating event is relatively short and occurs only during the first part of motor operation. Internal instrumentation was developed for another full-scale static test in February 2000. The static test instrumentation did indeed prove this theory to be correct. Post-test inspection revealed very similar charring characteristics as observed on RSRM-55. This experience of the development of a new PSA, its testing, the RSRM-55 flight, followed by the J-joint investigation led to good 'lessons learned' and to an additional fundamental understanding of the RSRM J-joint function.

Dynamics of multiple-goal pursuit.

PubMed

Louro, Maria J; Pieters, Rik; Zeelenberg, Marcel

2007-08-01

The authors propose and test a model of multiple-goal pursuit that specifies how individuals allocate effort among multiple goals over time. The model predicts that whether individuals decide to step up effort, coast, abandon the current goal, or switch to pursue another goal is determined jointly by the emotions that flow from prior goal progress and the proximity to future goal attainment, and proximally determined by changes in expectancies about goal attainment. Results from a longitudinal diary study and 2 experiments show that positive and negative goal-related emotions can have diametrically opposing effects on goal-directed behavior, depending on the individual's proximity to goal attainment. The findings resolve contrasting predictions about the influence of positive and negative emotions in volitional behavior, critically amend the goal gradient hypothesis, and provide new insights into the dynamics and determinants of multiple-goal pursuit.

Structural response of transport airplanes in crash situations

NASA Technical Reports Server (NTRS)

Thomson, R. G.; Caiafa, C.

1983-01-01

This report highlights the results of contractural studies of transport accident data undertaken in a joint research program sponsored by the FAA and NASA. From these accident data studies it was concluded that the greatest potential for improved transport crashworthiness is in the reduction of fire related fatalities. Accident data pertaining to fuselage integrity, main landing gear collapse, fuel tank rupture, wing breaks, tearing of tank lower surfaces, and engine pod scrubbing are discussed. In those accidents where the energy absorbing protective capability of the fuselage structure is expended and the airplane experiences major structural damage, trauma caused fatalities are also discussed. The dynamic performance of current seat/restraint systems are examined but it is concluded that the accident data does not adequately define the relationship between occupant response and the dynamic interaction with the seat, floor and fuselage structure.

Modal interactions due to friction in the nonlinear vibration response of the "Harmony" test structure: Experiments and simulations

NASA Astrophysics Data System (ADS)

Claeys, M.; Sinou, J.-J.; Lambelin, J.-P.; Todeschini, R.

2016-08-01

The nonlinear vibration response of an assembly with friction joints - named "Harmony" - is studied both experimentally and numerically. The experimental results exhibit a softening effect and an increase of dissipation with excitation level. Modal interactions due to friction are also evidenced. The numerical methodology proposed groups together well-known structural dynamic methods, including finite elements, substructuring, Harmonic Balance and continuation methods. On the one hand, the application of this methodology proves its capacity to treat a complex system where several friction movements occur at the same time. On the other hand, the main contribution of this paper is the experimental and numerical study of evidence of modal interactions due to friction. The simulation methodology succeeds in reproducing complex form of dynamic behavior such as these modal interactions.

Local Dynamic Stability Assessment of Motion Impaired Elderly Using Electronic Textile Pants.

PubMed

Liu, Jian; Lockhart, Thurmon E; Jones, Mark; Martin, Tom

2008-10-01

A clear association has been demonstrated between gait stability and falls in the elderly. Integration of wearable computing and human dynamic stability measures into home automation systems may help differentiate fall-prone individuals in a residential environment. The objective of the current study was to evaluate the capability of a pair of electronic textile (e-textile) pants system to assess local dynamic stability and to differentiate motion-impaired elderly from their healthy counterparts. A pair of e-textile pants comprised of numerous e-TAGs at locations corresponding to lower extremity joints was developed to collect acceleration, angular velocity and piezoelectric data. Four motion-impaired elderly together with nine healthy individuals (both young and old) participated in treadmill walking with a motion capture system simultaneously collecting kinematic data. Local dynamic stability, characterized by maximum Lyapunov exponent, was computed based on vertical acceleration and angular velocity at lower extremity joints for the measurements from both e-textile and motion capture systems. Results indicated that the motion-impaired elderly had significantly higher maximum Lyapunov exponents (computed from vertical acceleration data) than healthy individuals at the right ankle and hip joints. In addition, maximum Lyapunov exponents assessed by the motion capture system were found to be significantly higher than those assessed by the e-textile system. Despite the difference between these measurement techniques, attaching accelerometers at the ankle and hip joints was shown to be an effective sensor configuration. It was concluded that the e-textile pants system, via dynamic stability assessment, has the potential to identify motion-impaired elderly.

Quantification of cardiorespiratory interactions based on joint symbolic dynamics.

PubMed

Kabir, Muammar M; Saint, David A; Nalivaiko, Eugene; Abbott, Derek; Voss, Andreas; Baumert, Mathias

2011-10-01

Cardiac and respiratory rhythms are highly nonlinear and nonstationary. As a result traditional time-domain techniques are often inadequate to characterize their complex dynamics. In this article, we introduce a novel technique to investigate the interactions between R-R intervals and respiratory phases based on their joint symbolic dynamics. To evaluate the technique, electrocardiograms (ECG) and respiratory signals were recorded in 13 healthy subjects in different body postures during spontaneous and controlled breathing. Herein, the R-R time series were extracted from ECG and respiratory phases were obtained from abdomen impedance belts using the Hilbert transform. Both time series were transformed into ternary symbol vectors based on the changes between two successive R-R intervals or respiratory phases. Subsequently, words of different symbol lengths were formed and the correspondence between the two series of words was determined to quantify the interaction between cardiac and respiratory cycles. To validate our results, respiratory sinus arrhythmia (RSA) was further studied using the phase-averaged characterization of the RSA pattern. The percentage of similarity of the sequence of symbols, between the respective words of the two series determined by joint symbolic dynamics, was significantly reduced in the upright position compared to the supine position (26.4 ± 4.7 vs. 20.5 ± 5.4%, p < 0.01). Similarly, RSA was also reduced during upright posture, but the difference was less significant (0.11 ± 0.02 vs. 0.08 ± 0.01 s, p < 0.05). In conclusion, joint symbolic dynamics provides a new efficient technique for the analysis of cardiorespiratory interaction that is highly sensitive to the effects of orthostatic challenge.

Mean-field equations for neuronal networks with arbitrary degree distributions.

PubMed

Nykamp, Duane Q; Friedman, Daniel; Shaker, Sammy; Shinn, Maxwell; Vella, Michael; Compte, Albert; Roxin, Alex

2017-04-01

The emergent dynamics in networks of recurrently coupled spiking neurons depends on the interplay between single-cell dynamics and network topology. Most theoretical studies on network dynamics have assumed simple topologies, such as connections that are made randomly and independently with a fixed probability (Erdös-Rényi network) (ER) or all-to-all connected networks. However, recent findings from slice experiments suggest that the actual patterns of connectivity between cortical neurons are more structured than in the ER random network. Here we explore how introducing additional higher-order statistical structure into the connectivity can affect the dynamics in neuronal networks. Specifically, we consider networks in which the number of presynaptic and postsynaptic contacts for each neuron, the degrees, are drawn from a joint degree distribution. We derive mean-field equations for a single population of homogeneous neurons and for a network of excitatory and inhibitory neurons, where the neurons can have arbitrary degree distributions. Through analysis of the mean-field equations and simulation of networks of integrate-and-fire neurons, we show that such networks have potentially much richer dynamics than an equivalent ER network. Finally, we relate the degree distributions to so-called cortical motifs.

Mean-field equations for neuronal networks with arbitrary degree distributions

NASA Astrophysics Data System (ADS)

Nykamp, Duane Q.; Friedman, Daniel; Shaker, Sammy; Shinn, Maxwell; Vella, Michael; Compte, Albert; Roxin, Alex

2017-04-01

The emergent dynamics in networks of recurrently coupled spiking neurons depends on the interplay between single-cell dynamics and network topology. Most theoretical studies on network dynamics have assumed simple topologies, such as connections that are made randomly and independently with a fixed probability (Erdös-Rényi network) (ER) or all-to-all connected networks. However, recent findings from slice experiments suggest that the actual patterns of connectivity between cortical neurons are more structured than in the ER random network. Here we explore how introducing additional higher-order statistical structure into the connectivity can affect the dynamics in neuronal networks. Specifically, we consider networks in which the number of presynaptic and postsynaptic contacts for each neuron, the degrees, are drawn from a joint degree distribution. We derive mean-field equations for a single population of homogeneous neurons and for a network of excitatory and inhibitory neurons, where the neurons can have arbitrary degree distributions. Through analysis of the mean-field equations and simulation of networks of integrate-and-fire neurons, we show that such networks have potentially much richer dynamics than an equivalent ER network. Finally, we relate the degree distributions to so-called cortical motifs.

Operational Analysis in the Launch Environment

NASA Technical Reports Server (NTRS)

James, George; Kaouk, Mo; Cao, Tim; Fogt, Vince; Rocha, Rodney; Schultz, Ken; Tucker, Jon-Michael; Rayos, Eli; Bell,Jeff; Alldredge, David;

Parameter Identification of Static Friction Based on An Optimal Exciting Trajectory

NASA Astrophysics Data System (ADS)

Tu, X.; Zhao, P.; Zhou, Y. F.

2017-12-01

In this paper, we focus on how to improve the identification efficiency of friction parameters in a robot joint. First, the static friction model that has only linear dependencies with respect to their parameters is adopted so that the servomotor dynamics can be linearized. In this case, the traditional exciting trajectory based on Fourier series is modified by replacing the constant term with quintic polynomial to ensure the boundary continuity of speed and acceleration. Then, the Fourier-related parameters are optimized by genetic algorithm(GA) in which the condition number of regression matrix is set as the fitness function. At last, compared with the constant-velocity tracking experiment, the friction parameters from the exciting trajectory experiment has the similar result with the advantage of time reduction.

On-orbit identifying the inertia parameters of space robotic systems using simple equivalent dynamics

NASA Astrophysics Data System (ADS)

Xu, Wenfu; Hu, Zhonghua; Zhang, Yu; Liang, Bin

2017-03-01

After being launched into space to perform some tasks, the inertia parameters of a space robotic system may change due to fuel consumption, hardware reconfiguration, target capturing, and so on. For precision control and simulation, it is required to identify these parameters on orbit. This paper proposes an effective method for identifying the complete inertia parameters (including the mass, inertia tensor and center of mass position) of a space robotic system. The key to the method is to identify two types of simple dynamics systems: equivalent single-body and two-body systems. For the former, all of the joints are locked into a designed configuration and the thrusters are used for orbital maneuvering. The object function for optimization is defined in terms of acceleration and velocity of the equivalent single body. For the latter, only one joint is unlocked and driven to move along a planned (exiting) trajectory in free-floating mode. The object function is defined based on the linear and angular momentum equations. Then, the parameter identification problems are transformed into non-linear optimization problems. The Particle Swarm Optimization (PSO) algorithm is applied to determine the optimal parameters, i.e. the complete dynamic parameters of the two equivalent systems. By sequentially unlocking the 1st to nth joints (or unlocking the nth to 1st joints), the mass properties of body 0 to n (or n to 0) are completely identified. For the proposed method, only simple dynamics equations are needed for identification. The excitation motion (orbit maneuvering and joint motion) is also easily realized. Moreover, the method does not require prior knowledge of the mass properties of any body. It is general and practical for identifying a space robotic system on-orbit.

The validation of a human force model to predict dynamic forces resulting from multi-joint motions

NASA Technical Reports Server (NTRS)

Pandya, Abhilash K.; Maida, James C.; Aldridge, Ann M.; Hasson, Scott M.; Woolford, Barbara J.

1992-01-01

The development and validation is examined of a dynamic strength model for humans. This model is based on empirical data. The shoulder, elbow, and wrist joints were characterized in terms of maximum isolated torque, or position and velocity, in all rotational planes. This data was reduced by a least squares regression technique into a table of single variable second degree polynomial equations determining torque as a function of position and velocity. The isolated joint torque equations were then used to compute forces resulting from a composite motion, in this case, a ratchet wrench push and pull operation. A comparison of the predicted results of the model with the actual measured values for the composite motion indicates that forces derived from a composite motion of joints (ratcheting) can be predicted from isolated joint measures. Calculated T values comparing model versus measured values for 14 subjects were well within the statistically acceptable limits and regression analysis revealed coefficient of variation between actual and measured to be within 0.72 and 0.80.

Knee extensor dynamics in the volleyball approach jump: the influence of patellar tendinopathy.

PubMed

Sorenson, Shawn C; Arya, Shruti; Souza, Richard B; Pollard, Christine D; Salem, George J; Kulig, Kornelia

2010-09-01

Controlled laboratory study using a cross-sectional design. To evaluate knee joint dynamics in elite volleyball players with and without a history of patellar tendinopathy, focusing on mechanical energy absorption and generation. We hypothesized that tendinopathy would be associated withreduced net joint work and net joint power. Patellar tendinopathy is a common, debilitating injury affecting competitive volleyball players. Thirteen elite male players with and without a history of patellar tendinopathy (mean ± SD age, 27 ± 7 years) performed maximum-effort volleyball approach jumps. Sagittal plane knee joint kinematics, kinetics, and energetics were quantified in the lead limb, using data obtained from a force platform and an 8-camera motion analysis system. Vertical ground reaction forces and pelvis vertical velocity at takeoff were examined. Independent sample t tests were used to evaluate group differences (α = .05). The tendinopathy group, compared to controls, demonstrated significant reductions (approximately 30%) in net joint work and net joint power during the eccentric phase of the jump, with no differences in the concentric phase. Positive to-negative net joint work and net joint power ratios were significantly higher in the tendinopathy group, which had a net joint work ratio of 1.00 (95% CI: 0.77, 1.24) versus 0.76 (95% CI: 0.64, 0.88) for controls, and a net joint power ratio of 1.62 (95% CI: 1.15, 2.10) versus 1.00 (95% CI: 0.80, 1.21) for controls. There were no significant differences in net joint moment, angular velocity, or range of motion. Peak vertical ground reaction forces were lower for the tendinopathy group, while average vertical ground reaction forces and pelvis vertical velocity were similar. Patellar tendinopathy is associated with differences in sagittal plane mechanical energy absorption at the knee during maximum-effort volleyball approach jumps. Net joint work and net joint power may help define underlying mechanisms, adaptive effects, or rehabilitative strategies for individuals with patellar tendinopathy.

Framing the China Dynamic

DTIC Science & Technology

2012-04-05

President Obama and Prime Minister Gillard of Australia in Joint Press Conference, November 16, 2011, http://www.whitehouse.gov/the-press-office/2011/11...16/remarks-president-obama-and-prime- minister- gillard -australia-joint-press. 24 Australian policy think tank, “Getting China wrong will have...Remarks by President Obama and Prime Minister Gillard of Australia in Joint Press 90 Conference, November 16, 2011. http://www.whitehouse.gov/the

Molecular dynamics modeling of bonding two materials by atomic scale friction stir welding

NASA Astrophysics Data System (ADS)

Konovalenko S., Iv.; Konovalenko, Ig. S.; Psakhie, S. G.

2017-12-01

Molecular dynamics model of atomic scale friction stir welding has been developed. Formation of a butt joint between two crystallites was modeled by means of rotating rigid conical tool traveling along the butt joint line. The formed joint had an intermixed atomic structure composed of atoms initially belonged to the opposite mated piece of metal. Heat removal was modeled by adding the extra viscous force to peripheral atomic layers. This technique provides the temperature control in the tool-affected zone during welding. Auxiliary vibration action was added to the rotating tool. The model provides the variation of the tool's angular velocity, amplitude, frequency and direction of the auxiliary vibration action to provide modeling different welding modes.

Loudness of dynamic stimuli in acoustic and electric hearing.

PubMed

Zhang, C; Zeng, F G

1997-11-01

Traditional loudness models have been based on the average energy and the critical band analysis of steady-state sounds. However, most environmental sounds, including speech, are dynamic stimuli, in which the average level [e.g., the root-mean-square (rms) level] does not account for the large temporal fluctuations. The question addressed here was whether two stimuli of the same rms level but different peak levels would produce an equal loudness sensation. A modern adaptive procedure was used to replicate two classic experiments demonstrating that the sensation of "beats" in a two- or three-tone complex resulted in a louder sensation [E. Zwicker and H. Fastl, Psychoacoustics-Facts and Models (Springer-Verlag, Berlin, 1990)]. Two additional experiments were conducted to study exclusively the effects of the temporal envelope on the loudness sensation of dynamic stimuli. Loudness balance was performed by normal-hearing listeners between a white noise and a sinusoidally amplitude-modulated noise in one experiment, and by cochlear implant listeners between two harmonic stimuli of the same magnitude spectra, but different phase spectra, in the other experiment. The results from both experiments showed that, for two stimuli of the same rms level, the stimulus with greater temporal fluctuations sometimes produced a significantly louder sensation, depending on the temporal frequency and overall stimulus level. In normal-hearing listeners, the louder sensation was produced for the amplitude-modulated stimuli with modulation frequencies lower than 400 Hz, and gradually disappeared above 400 Hz, resulting in a low-pass filtering characteristic which bore some similarity to the temporal modulation transfer function. The extent to which loudness was greater was a nonmonotonic function of level in acoustic hearing and a monotonically increasingly function in electric hearing. These results suggest that the loudness sensation of a dynamic stimulus is not limited to a 100-ms temporal integration process, and may be determined jointly by a compression process in the cochlea and an expansion process in the brain. A level-dependent compression scheme that may better restore normal loudness of dynamic stimuli in hearing aids and cochlear implants is proposed.

Mutual coordination strengthens the sense of joint agency in cooperative joint action.

PubMed

Bolt, Nicole K; Poncelet, Evan M; Schultz, Benjamin G; Loehr, Janeen D

2016-11-01

Philosophers have proposed that when people coordinate their actions with others they may experience a sense of joint agency, or shared control over actions and their effects. However, little empirical work has investigated the sense of joint agency. In the current study, pairs coordinated their actions to produce tone sequences and then rated their sense of joint agency on a scale ranging from shared to independent control. People felt more shared than independent control overall, confirming that people experience joint agency during joint action. Furthermore, people felt stronger joint agency when they (a) produced sequences that required mutual coordination compared to sequences in which only one partner had to coordinate with the other, (b) held the role of follower compared to leader, and (c) were better coordinated with their partner. Thus, the strength of joint agency is influenced by the degree to which people mutually coordinate with each other's actions. Copyright © 2016 Elsevier Inc. All rights reserved.

A New Powered Lower Limb Prosthesis Control Framework Based on Adaptive Dynamic Programming.

PubMed

Wen, Yue; Si, Jennie; Gao, Xiang; Huang, Stephanie; Huang, He Helen

2017-09-01

This brief presents a novel application of adaptive dynamic programming (ADP) for optimal adaptive control of powered lower limb prostheses, a type of wearable robots to assist the motor function of the limb amputees. Current control of these robotic devices typically relies on finite state impedance control (FS-IC), which lacks adaptability to the user's physical condition. As a result, joint impedance settings are often customized manually and heuristically in clinics, which greatly hinder the wide use of these advanced medical devices. This simulation study aimed at demonstrating the feasibility of ADP for automatic tuning of the twelve knee joint impedance parameters during a complete gait cycle to achieve balanced walking. Given that the accurate models of human walking dynamics are difficult to obtain, the model-free ADP control algorithms were considered. First, direct heuristic dynamic programming (dHDP) was applied to the control problem, and its performance was evaluated on OpenSim, an often-used dynamic walking simulator. For the comparison purposes, we selected another established ADP algorithm, the neural fitted Q with continuous action (NFQCA). In both cases, the ADP controllers learned to control the right knee joint and achieved balanced walking, but dHDP outperformed NFQCA in this application during a 200 gait cycle-based testing.

An optimal resolved rate law for kindematically redundant manipulators

NASA Technical Reports Server (NTRS)

Bourgeois, B. J.

1987-01-01

The resolved rate law for a manipulator provides the instantaneous joint rates required to satisfy a given instantaneous hand motion. When the joint space has more degrees of freedom than the task space, the manipulator is kinematically redundant and the kinematic rate equations are underdetermined. These equations can be locally optimized, but the resulting pseudo-inverse solution was found to cause large joint rates in some case. A weighting matrix in the locally optimized (pseudo-inverse) solution is dynamically adjusted to control the joint motion as desired. Joint reach limit avoidance is demonstrated in a kinematically redundant planar arm model. The treatment is applicable to redundant manipulators with any number of revolute joints and to nonplanar manipulators.

Design and implementation of a novel modal space active force control concept for spatial multi-DOF parallel robotic manipulators actuated by electrical actuators.

PubMed

Yang, Chifu; Zhao, Jinsong; Li, Liyi; Agrawal, Sunil K

2018-01-01

Robotic spine brace based on parallel-actuated robotic system is a new device for treatment and sensing of scoliosis, however, the strong dynamic coupling and anisotropy problem of parallel manipulators result in accuracy loss of rehabilitation force control, including big error in direction and value of force. A novel active force control strategy named modal space force control is proposed to solve these problems. Considering the electrical driven system and contact environment, the mathematical model of spatial parallel manipulator is built. The strong dynamic coupling problem in force field is described via experiments as well as the anisotropy problem of work space of parallel manipulators. The effects of dynamic coupling on control design and performances are discussed, and the influences of anisotropy on accuracy are also addressed. With mass/inertia matrix and stiffness matrix of parallel manipulators, a modal matrix can be calculated by using eigenvalue decomposition. Making use of the orthogonality of modal matrix with mass matrix of parallel manipulators, the strong coupled dynamic equations expressed in work space or joint space of parallel manipulator may be transformed into decoupled equations formulated in modal space. According to this property, each force control channel is independent of others in the modal space, thus we proposed modal space force control concept which means the force controller is designed in modal space. A modal space active force control is designed and implemented with only a simple PID controller employed as exampled control method to show the differences, uniqueness, and benefits of modal space force control. Simulation and experimental results show that the proposed modal space force control concept can effectively overcome the effects of the strong dynamic coupling and anisotropy problem in the physical space, and modal space force control is thus a very useful control framework, which is better than the current joint space control and work space control. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Grizzly bear (Ursus arctos horribilis) locomotion: forelimb joint mechanics across speed in the sagittal and frontal planes.

PubMed

Shine, Catherine L; Robbins, Charles T; Nelson, O Lynne; McGowan, Craig P

2017-04-01

The majority of terrestrial locomotion studies have focused on parasagittal motion and paid less attention to forces or movement in the frontal plane. Our previous research has shown that grizzly bears produce higher medial ground reaction forces (lateral pushing from the animal) than would be expected for an upright mammal, suggesting frontal plane movement may be an important aspect of their locomotion. To examine this, we conducted an inverse dynamics analysis in the sagittal and frontal planes, using ground reaction forces and position data from three high-speed cameras of four adult female grizzly bears. Over the speed range collected, the bears used walks, running walks and canters. The scapulohumeral joint, wrist and the limb overall absorb energy (average total net work of the forelimb joints, -0.97 W kg -1 ). The scapulohumeral joint, elbow and total net work of the forelimb joints have negative relationships with speed, resulting in more energy absorbed by the forelimb at higher speeds (running walks and canters). The net joint moment and power curves maintain similar patterns across speed as in previously studied species, suggesting grizzly bears maintain similar joint dynamics to other mammalian quadrupeds. There is no significant relationship with net work and speed at any joint in the frontal plane. The total net work of the forelimb joints in the frontal plane was not significantly different from zero, suggesting that, despite the high medial ground reaction forces, the forelimb acts as a strut in that plane. © 2017. Published by The Company of Biologists Ltd.

Hip and knee joint loading during vertical jumping and push jerking

PubMed Central

Cleather, Daniel J; Goodwin, Jon E; Bull, Anthony MJ

2014-01-01

Background The internal joint contact forces experienced at the lower limb have been frequently studied in activities of daily living and rehabilitation activities. In contrast, the forces experienced during more dynamic activities are not well understood, and those studies that do exist suggest very high degrees of joint loading. Methods In this study a biomechanical model of the right lower limb was used to calculate the internal joint forces experienced by the lower limb during vertical jumping, landing and push jerking (an explosive exercise derived from the sport of Olympic weightlifting), with a particular emphasis on the forces experienced by the knee. Findings The knee experienced mean peak loadings of 2.4-4.6 × body weight at the patellofemoral joint, 6.9-9.0 × body weight at the tibiofemoral joint, 0.3-1.4 × body weight anterior tibial shear and 1.0-3.1 × body weight posterior tibial shear. The hip experienced a mean peak loading of 5.5-8.4 × body weight and the ankle 8.9-10.0 × body weight. Interpretation The magnitudes of the total (resultant) joint contact forces at the patellofemoral joint, tibiofemoral joint and hip are greater than those reported in activities of daily living and less dynamic rehabilitation exercises. The information in this study is of importance for medical professionals, coaches and biomedical researchers in improving the understanding of acute and chronic injuries, understanding the performance of prosthetic implants and materials, evaluating the appropriateness of jumping and weightlifting for patient populations and informing the training programmes of healthy populations. PMID:23146164

Hip and knee joint loading during vertical jumping and push jerking.

PubMed

Cleather, Daniel J; Goodwin, Jon E; Bull, Anthony M J

2013-01-01

The internal joint contact forces experienced at the lower limb have been frequently studied in activities of daily living and rehabilitation activities. In contrast, the forces experienced during more dynamic activities are not well understood, and those studies that do exist suggest very high degrees of joint loading. In this study a biomechanical model of the right lower limb was used to calculate the internal joint forces experienced by the lower limb during vertical jumping, landing and push jerking (an explosive exercise derived from the sport of Olympic weightlifting), with a particular emphasis on the forces experienced by the knee. The knee experienced mean peak loadings of 2.4-4.6×body weight at the patellofemoral joint, 6.9-9.0×body weight at the tibiofemoral joint, 0.3-1.4×body weight anterior tibial shear and 1.0-3.1×body weight posterior tibial shear. The hip experienced a mean peak loading of 5.5-8.4×body weight and the ankle 8.9-10.0×body weight. The magnitudes of the total (resultant) joint contact forces at the patellofemoral joint, tibiofemoral joint and hip are greater than those reported in activities of daily living and less dynamic rehabilitation exercises. The information in this study is of importance for medical professionals, coaches and biomedical researchers in improving the understanding of acute and chronic injuries, understanding the performance of prosthetic implants and materials, evaluating the appropriateness of jumping and weightlifting for patient populations and informing the training programmes of healthy populations. Copyright © 2012 Elsevier Ltd. All rights reserved.

Long-latency reflexes of elbow and shoulder muscles suggest reciprocal excitation of flexors, reciprocal excitation of extensors, and reciprocal inhibition between flexors and extensors

PubMed Central

Meriggi, Jenna; Parikh, Nidhi; Saad, Kenneth

2016-01-01

Postural corrections of the upper limb are required in tasks ranging from handling an umbrella in the changing wind to securing a wriggling baby. One complication in this process is the mechanical interaction between the different segments of the arm where torque applied at one joint induces motion at multiple joints. Previous studies have shown the long-latency reflexes of shoulder muscles (50–100 ms after a limb perturbation) account for these mechanical interactions by integrating information about motion of both the shoulder and elbow. It is less clear whether long-latency reflexes of elbow muscles exhibit a similar capability and what is the relation between the responses of shoulder and elbow muscles. The present study utilized joint-based loads tailored to the subjects' arm dynamics to induce well-controlled displacements of their shoulder and elbow. Our results demonstrate that the long-latency reflexes of shoulder and elbow muscles integrate motion from both joints: the shoulder and elbow flexors respond to extension at both joints, whereas the shoulder and elbow extensors respond to flexion at both joints. This general pattern accounts for the inherent flexion-extension coupling of the two joints arising from the arm's intersegmental dynamics and is consistent with spindle-based reciprocal excitation of shoulder and elbow flexors, reciprocal excitation of shoulder and elbow extensors, and across-joint inhibition between the flexors and extensors. PMID:26864766

Status of joint US/USSR experiments planned for the Cosmos '83 biosatellite mission

NASA Technical Reports Server (NTRS)

Souza, K. A.

1982-01-01

The plans and status of the fourth joint US/USSR biosatellite experiment, scheduled to be conducted in the last half of 1983, are discussed. These experiments will be conducted on board an unmanned Soviet spacecraft and will involve two restrained Rhesus monkeys and 10 pregnant rats, as well as a variety of small plant and radiation biology experiments. Three of the joint studies will use the monkeys for studies of biorhythms, calcium homeostasis, and the cardiovascular system. The fourth experiment will study rodent embryogenesis and neonatal behavior and development following in utero exposure to spaceflight. Specialized sensors and battery powered hardware have been designed, fabricated, and qualified for flight.

A Robust Control of Two-Wheeled Mobile Manipulator with Underactuated Joint by Nonlinear Backstepping Method

NASA Astrophysics Data System (ADS)

Acar, Cihan; Murakami, Toshiyuki

In this paper, a robust control of two-wheeled mobile manipulator with underactuated joint is considered. Two-wheeled mobile manipulators are dynamically balanced two-wheeled driven systems that do not have any caster or extra wheels to stabilize their body. Two-wheeled mobile manipulators mainly have an important feature that makes them more flexible and agile than the statically stable mobile manipulators. However, two-wheeled mobile manipulator is an underactuated system due to its two-wheeled structure. Therefore, it is required to stabilize the underactuated passive body and, at the same time, control the position of the center of gravity (CoG) of the manipulator in this system. To realize this, nonlinear backstepping based control method with virtual double inverted pendulum model is proposed in this paper. Backstepping is used with sliding mode to increase the robustness of the system against modeling errors and other perturbations. Then robust acceleration control is also achieved by utilizing disturbance observer. Performance of the proposed method is evaluated by several experiments.

Multidimensional Recurrence Quantification Analysis (MdRQA) for the Analysis of Multidimensional Time-Series: A Software Implementation in MATLAB and Its Application to Group-Level Data in Joint Action

PubMed Central

Wallot, Sebastian; Roepstorff, Andreas; Mønster, Dan

2016-01-01

We introduce Multidimensional Recurrence Quantification Analysis (MdRQA) as a tool to analyze multidimensional time-series data. We show how MdRQA can be used to capture the dynamics of high-dimensional signals, and how MdRQA can be used to assess coupling between two or more variables. In particular, we describe applications of the method in research on joint and collective action, as it provides a coherent analysis framework to systematically investigate dynamics at different group levels—from individual dynamics, to dyadic dynamics, up to global group-level of arbitrary size. The Appendix in Supplementary Material contains a software implementation in MATLAB to calculate MdRQA measures. PMID:27920748

Multidimensional Recurrence Quantification Analysis (MdRQA) for the Analysis of Multidimensional Time-Series: A Software Implementation in MATLAB and Its Application to Group-Level Data in Joint Action.

PubMed

Wallot, Sebastian; Roepstorff, Andreas; Mønster, Dan

2016-01-01

We introduce Multidimensional Recurrence Quantification Analysis (MdRQA) as a tool to analyze multidimensional time-series data. We show how MdRQA can be used to capture the dynamics of high-dimensional signals, and how MdRQA can be used to assess coupling between two or more variables. In particular, we describe applications of the method in research on joint and collective action, as it provides a coherent analysis framework to systematically investigate dynamics at different group levels-from individual dynamics, to dyadic dynamics, up to global group-level of arbitrary size. The Appendix in Supplementary Material contains a software implementation in MATLAB to calculate MdRQA measures.

The Joint Aerosol-Monsoon Experiment: A New Challenge to Monsoon Climate Research

NASA Technical Reports Server (NTRS)

Lau, William K. M.

2008-01-01

Aerosol and monsoon related droughts and floods are two of the most serious environmental hazards confronting more than 60% of the population of the world living in the Asian monsoon countries. In recent years, thanks to improved satellite and in-situ observations, and better models, great strides have been made in aerosol, and monsoon research respectively. There is now a growing body of evidence suggesting that interaction of aerosol forcing with water cycle dynamics in monsoon regions may substantially alter the redistribution of energy at the earth surface and in the atmosphere, and therefore significantly impact monsoon rainfall variability and long term trends. In this talk, I will describe issues related to societal needs, scientific background, and challenges in studies of aerosol-water cycle interaction in Asian monsoon regions. As a first step towards addressing these issues, the authors call for an integrated observation and modeling research approach aimed at the interactions between aerosol chemistry and radiative effects and monsoon dynamics of the coupled ocean-atmosphere-land system. A Joint Aerosol-Monsoon Experiment (JAMEX) is proposed for 2007-2011, with an enhanced observation period during 2008-09, encompassing diverse arrays of observations from surface, aircraft, unmanned aerial vehicles, and satellites of physical and chemical properties of aerosols, long range aerosol transport as well as meteorological and oceanographic parameters in the Indo-Pacific Asian monsoon region. JAMEX will leverage on coordination among many ongoing and planned national programs on aerosols and monsoon research in China, India, Japan, Nepal, Italy, US, as well as international research programs of the World Climate Research Program (WCRP) and the World Meteorological Organization (WMO).

A "Kane's Dynamics" Model for the Active Rack Isolation System Part Two: Nonlinear Model Development, Verification, and Simplification

NASA Technical Reports Server (NTRS)

Beech, G. S.; Hampton, R. D.; Rupert, J. K.

2004-01-01

Many microgravity space-science experiments require vibratory acceleration levels that are unachievable without active isolation. The Boeing Corporation's active rack isolation system (ARIS) employs a novel combination of magnetic actuation and mechanical linkages to address these isolation requirements on the International Space Station. Effective model-based vibration isolation requires: (1) An isolation device, (2) an adequate dynamic; i.e., mathematical, model of that isolator, and (3) a suitable, corresponding controller. This Technical Memorandum documents the validation of that high-fidelity dynamic model of ARIS. The verification of this dynamics model was achieved by utilizing two commercial off-the-shelf (COTS) software tools: Deneb's ENVISION(registered trademark), and Online Dynamics Autolev(trademark). ENVISION is a robotics software package developed for the automotive industry that employs three-dimensional computer-aided design models to facilitate both forward and inverse kinematics analyses. Autolev is a DOS-based interpreter designed, in general, to solve vector-based mathematical problems and specifically to solve dynamics problems using Kane's method. The simplification of this model was achieved using the small-angle theorem for the joint angle of the ARIS actuators. This simplification has a profound effect on the overall complexity of the closed-form solution while yielding a closed-form solution easily employed using COTS control hardware.

Capturing Context-Related Change in Emotional Dynamics via Fixed Moderated Time Series Analysis.

PubMed

Adolf, Janne K; Voelkle, Manuel C; Brose, Annette; Schmiedek, Florian

2017-01-01

Much of recent affect research relies on intensive longitudinal studies to assess daily emotional experiences. The resulting data are analyzed with dynamic models to capture regulatory processes involved in emotional functioning. Daily contexts, however, are commonly ignored. This may not only result in biased parameter estimates and wrong conclusions, but also ignores the opportunity to investigate contextual effects on emotional dynamics. With fixed moderated time series analysis, we present an approach that resolves this problem by estimating context-dependent change in dynamic parameters in single-subject time series models. The approach examines parameter changes of known shape and thus addresses the problem of observed intra-individual heterogeneity (e.g., changes in emotional dynamics due to observed changes in daily stress). In comparison to existing approaches to unobserved heterogeneity, model estimation is facilitated and different forms of change can readily be accommodated. We demonstrate the approach's viability given relatively short time series by means of a simulation study. In addition, we present an empirical application, targeting the joint dynamics of affect and stress and how these co-vary with daily events. We discuss potentials and limitations of the approach and close with an outlook on the broader implications for understanding emotional adaption and development.

A dynamic spar numerical model for passive shape change

NASA Astrophysics Data System (ADS)

Calogero, J. P.; Frecker, M. I.; Hasnain, Z.; Hubbard, J. E., Jr.

2016-10-01

A three-dimensional constraint-driven dynamic rigid-link numerical model of a flapping wing structure with compliant joints (CJs) called the dynamic spar numerical model is introduced and implemented. CJs are modeled as spherical joints with distributed mass and spring-dampers with coupled nonlinear spring and damping coefficients, which models compliant mechanisms spatially distributed in the structure while greatly reducing computation time compared to a finite element model. The constraints are established, followed by the formulation of a state model used in conjunction with a forward time integrator, an experiment to verify a rigid-link assumption and determine a flapping angle function, and finally several example runs. Modeling the CJs as coupled bi-linear springs shows the wing is able to flex more during upstroke than downstroke. Coupling the spring stiffnesses allows an angular deformation about one axis to induce an angular deformation about another axis, where the magnitude is proportional to the coupling term. Modeling both the leading edge and diagonal spars shows that the diagonal spar changes the kinematics of the leading edge spar verses only considering the leading edge spar, causing much larger axial rotations in the leading edge spar. The kinematics are very sensitive to CJ location, where moving the CJ toward the wing root causes a stronger response, and adding multiple CJs on the leading edge spar with a CJ on the diagonal spar allows the wing to deform with larger magnitude in all directions. This model lays a framework for a tool which can be used to understand flapping wing flight.

Experiments and kinematics analysis of a hand rehabilitation exoskeleton with circuitous joints.

PubMed

Zhang, Fuhai; Fu, Yili; Zhang, Qinchao; Wang, Shuguo

2015-01-01

Aiming at the hand rehabilitation of stroke patients, a wearable hand exoskeleton with circuitous joint is proposed. The circuitous joint adopts the symmetric pinion and rack mechanism (SPRM) with the parallel mechanism. The exoskeleton finger is a serial mechanism composed of three closed-chain SPRM joints in series. The kinematic equations of the open chain of the finger and the closed chains of the SPRM joints were built to analyze the kinematics of the hand rehabilitation exoskeleton. The experimental setup of the hand rehabilitation exoskeleton was built and the continuous passive motion (CPM) rehabilitation experiment and the test of human-robot interaction force measurement were conducted. Experiment results show that the mechanical design of the hand rehabilitation robot is reasonable and that the kinematic analysis is correct, thus the exoskeleton can be used for the hand rehabilitation of stroke patients.

Barriers to success: physical separation optimizes event-file retrieval in shared workspaces.

PubMed

Klempova, Bibiana; Liepelt, Roman

2017-07-08

Sharing tasks with other persons can simplify our work and life, but seeing and hearing other people's actions may also be very distracting. The joint Simon effect (JSE) is a standard measure of referential response coding when two persons share a Simon task. Sequential modulations of the joint Simon effect (smJSE) are interpreted as a measure of event-file processing containing stimulus information, response information and information about the just relevant control-state active in a given social situation. This study tested effects of physical (Experiment 1) and virtual (Experiment 2) separation of shared workspaces on referential coding and event-file processing using a joint Simon task. In Experiment 1, participants performed this task in individual (go-nogo), joint and standard Simon task conditions with and without a transparent curtain (physical separation) placed along the imagined vertical midline of the monitor. In Experiment 2, participants performed the same tasks with and without receiving background music (virtual separation). For response times, physical separation enhanced event-file retrieval indicated by an enlarged smJSE in the joint Simon task with curtain than without curtain (Experiment1), but did not change referential response coding. In line with this, we also found evidence for enhanced event-file processing through physical separation in the joint Simon task for error rates. Virtual separation did neither impact event-file processing, nor referential coding, but generally slowed down response times in the joint Simon task. For errors, virtual separation hampered event-file processing in the joint Simon task. For the cognitively more demanding standard two-choice Simon task, we found music to have a degrading effect on event-file retrieval for response times. Our findings suggest that adding a physical separation optimizes event-file processing in shared workspaces, while music seems to lead to a more relaxed task processing mode under shared task conditions. In addition, music had an interfering impact on joint error processing and more generally when dealing with a more complex task in isolation.

Dynamics and regulation of locomotion of a human swing leg as a double-pendulum considering self-impact joint constraint.

PubMed

Bazargan-Lari, Y; Eghtesad, M; Khoogar, A; Mohammad-Zadeh, A

2014-09-01

Despite some successful dynamic simulation of self-impact double pendulum (SIDP)-as humanoid robots legs or arms- studies, there is limited information available about the control of one leg locomotion. The main goal of this research is to improve the reliability of the mammalians leg locomotion and building more elaborated models close to the natural movements, by modeling the swing leg as a SIDP. This paper also presents the control design for a SIDP by a nonlinear model-based control method. To achieve this goal, the available data of normal human gait will be taken as the desired trajectories of the hip and knee joints. The model is characterized by the constraint that occurs at the knee joint (the lower joint of the model) in both dynamic modeling and control design. Since the system dynamics is nonlinear, the MIMO Input-Output Feedback Linearization method will be employed for control purposes. The first constraint in forward impact simulation happens at 0.5 rad where the speed of the upper link is increased to 2.5 rad/sec. and the speed of the lower link is reduced to -5 rad/sec. The subsequent constraints occur rather moderately. In the case of both backward and forward constraints simulation, the backward impact occurs at -0.5 rad and the speeds of the upper and lower links increase to 2.2 and 1.5 rad/sec., respectively. The designed controller performed suitably well and regulated the system accurately.

A Subspace Approach to the Structural Decomposition and Identification of Ankle Joint Dynamic Stiffness.

PubMed

Jalaleddini, Kian; Tehrani, Ehsan Sobhani; Kearney, Robert E

2017-06-01

The purpose of this paper is to present a structural decomposition subspace (SDSS) method for decomposition of the joint torque to intrinsic, reflexive, and voluntary torques and identification of joint dynamic stiffness. First, it formulates a novel state-space representation for the joint dynamic stiffness modeled by a parallel-cascade structure with a concise parameter set that provides a direct link between the state-space representation matrices and the parallel-cascade parameters. Second, it presents a subspace method for the identification of the new state-space model that involves two steps: 1) the decomposition of the intrinsic and reflex pathways and 2) the identification of an impulse response model of the intrinsic pathway and a Hammerstein model of the reflex pathway. Extensive simulation studies demonstrate that SDSS has significant performance advantages over some other methods. Thus, SDSS was more robust under high noise conditions, converging where others failed; it was more accurate, giving estimates with lower bias and random errors. The method also worked well in practice and yielded high-quality estimates of intrinsic and reflex stiffnesses when applied to experimental data at three muscle activation levels. The simulation and experimental results demonstrate that SDSS accurately decomposes the intrinsic and reflex torques and provides accurate estimates of physiologically meaningful parameters. SDSS will be a valuable tool for studying joint stiffness under functionally important conditions. It has important clinical implications for the diagnosis, assessment, objective quantification, and monitoring of neuromuscular diseases that change the muscle tone.

Nonlinear response of dense colloidal suspensions under oscillatory shear: mode-coupling theory and Fourier transform rheology experiments.

PubMed

Brader, J M; Siebenbürger, M; Ballauff, M; Reinheimer, K; Wilhelm, M; Frey, S J; Weysser, F; Fuchs, M

2010-12-01

Using a combination of theory, experiment, and simulation we investigate the nonlinear response of dense colloidal suspensions to large amplitude oscillatory shear flow. The time-dependent stress response is calculated using a recently developed schematic mode-coupling-type theory describing colloidal suspensions under externally applied flow. For finite strain amplitudes the theory generates a nonlinear response, characterized by significant higher harmonic contributions. An important feature of the theory is the prediction of an ideal glass transition at sufficiently strong coupling, which is accompanied by the discontinuous appearance of a dynamic yield stress. For the oscillatory shear flow under consideration we find that the yield stress plays an important role in determining the nonlinearity of the time-dependent stress response. Our theoretical findings are strongly supported by both large amplitude oscillatory experiments (with Fourier transform rheology analysis) on suspensions of thermosensitive core-shell particles dispersed in water and Brownian dynamics simulations performed on a two-dimensional binary hard-disk mixture. In particular, theory predicts nontrivial values of the exponents governing the final decay of the storage and loss moduli as a function of strain amplitude which are in good agreement with both simulation and experiment. A consistent set of parameters in the presented schematic model achieves to jointly describe linear moduli, nonlinear flow curves, and large amplitude oscillatory spectroscopy.

Built for speed: strain in the cartilaginous vertebral columns of sharks.

PubMed

Porter, M E; Diaz, Candido; Sturm, Joshua J; Grotmol, Sindre; Summers, A P; Long, John H

2014-02-01

In most bony fishes vertebral column strain during locomotion is almost exclusively in the intervertebral joints, and when these joints move there is the potential to store and release strain energy. Since cartilaginous fishes have poorly mineralized vertebral centra, we tested whether the vertebral bodies undergo substantial strain and thus may be sites of energy storage during locomotion. We measured axial strains of the intervertebral joints and vertebrae in vivo and ex vivo to characterize the dynamic behavior of the vertebral column. We used sonomicrometry to directly measure in vivo and in situ strains of intervertebral joints and vertebrae of Squalus acanthias swimming in a flume. For ex vivo measurements, we used a materials testing system to dynamically bend segments of vertebral column at frequencies ranging from 0.25 to 1.00 Hz and a range of physiologically relevant curvatures, which were determined using a kinematic analysis. The vertebral centra of S. acanthias undergo strain during in vivo volitional movements as well as in situ passive movements. Moreover, when isolated segments of vertebral column were tested during mechanical bending, we measured the same magnitudes of strain. These data support our hypothesis that vertebral column strain in lateral bending is not limited to the intervertebral joints. In histological sections, we found that the vertebral column of S. acanthias has an intracentral canal that is open and covered with a velum layer. An open intracentral canal may indicate that the centra are acting as tunics around some sections of a hydrostat, effectively stiffening the vertebral column. These data suggest that the entire vertebral column of sharks, both joints and centra, is mechanically engaged as a dynamic spring during locomotion. Copyright © 2013 Elsevier GmbH. All rights reserved.

Normal anatomy and biomechanics of the knee.

PubMed

Flandry, Fred; Hommel, Gabriel

2011-06-01

Functionally, the knee comprises 2 articulations-the patellofemoral and tibiofemoral. Stability of the joint is governed by a combination of static ligaments, dynamic muscular forces, meniscocapsular aponeurosis, bony topography, and joint load. The surgeon is ill equipped to undertake surgical treatment of a dislocated knee without a sound footing in the anatomic complexities of this joint. We review the normal anatomy of the knee, emphasizing connective tissue structures and common injury patterns.

Integration of Visual and Joint Information to Enable Linear Reaching Motions

NASA Astrophysics Data System (ADS)

Eberle, Henry; Nasuto, Slawomir J.; Hayashi, Yoshikatsu

2017-01-01

A new dynamics-driven control law was developed for a robot arm, based on the feedback control law which uses the linear transformation directly from work space to joint space. This was validated using a simulation of a two-joint planar robot arm and an optimisation algorithm was used to find the optimum matrix to generate straight trajectories of the end-effector in the work space. We found that this linear matrix can be decomposed into the rotation matrix representing the orientation of the goal direction and the joint relation matrix (MJRM) representing the joint response to errors in the Cartesian work space. The decomposition of the linear matrix indicates the separation of path planning in terms of the direction of the reaching motion and the synergies of joint coordination. Once the MJRM is numerically obtained, the feedfoward planning of reaching direction allows us to provide asymptotically stable, linear trajectories in the entire work space through rotational transformation, completely avoiding the use of inverse kinematics. Our dynamics-driven control law suggests an interesting framework for interpreting human reaching motion control alternative to the dominant inverse method based explanations, avoiding expensive computation of the inverse kinematics and the point-to-point control along the desired trajectories.

Finite element normal mode analysis of resistance welding jointed of dissimilar plate hat structure

NASA Astrophysics Data System (ADS)

Nazri, N. A.; Sani, M. S. M.

2017-10-01

Structural joints offer connection between structural element (beam, plate, solid etc.) in order to build a whole assembled structure. The complex behaviour of connecting elements plays a valuable role in characteristics of dynamic such as natural frequencies and mode shapes. In automotive structures, the trustworthiness arrangement of the structure extremely depends on joints. In this paper, top hat structure is modelled and designed with spot welding joint using dissimilar materials which is mild steel 1010 and stainless steel 304, using finite element software. Different types of connector elements such as rigid body element (RBE2), welding joint element (CWELD), and bar element (CBAR) are applied to represent real connection between two dissimilar plates. Normal mode analysis is simulated with different types of joining element in order to determine modal properties. Natural frequencies using RBE2, CBAR and CWELD are compared to equivalent rigid body method. Connection that gives the lowest percentage error among these three will be selected as the most reliable joining for resistance spot weld. From the analysis, it is shown that CWELD is better compared to others in term of weld joining among dissimilar plate materials. It is expected that joint modelling of finite element plays significant role in structural dynamics.

Comparison of System Identification Techniques for the Hydraulic Manipulator Test Bed (HMTB)

NASA Technical Reports Server (NTRS)

Morris, A. Terry

1996-01-01

In this thesis linear, dynamic, multivariable state-space models for three joints of the ground-based Hydraulic Manipulator Test Bed (HMTB) are identified. HMTB, housed at the NASA Langley Research Center, is a ground-based version of the Dexterous Orbital Servicing System (DOSS), a representative space station manipulator. The dynamic models of the HMTB manipulator will first be estimated by applying nonparametric identification methods to determine each joint's response characteristics using various input excitations. These excitations include sum of sinusoids, pseudorandom binary sequences (PRBS), bipolar ramping pulses, and chirp input signals. Next, two different parametric system identification techniques will be applied to identify the best dynamical description of the joints. The manipulator is localized about a representative space station orbital replacement unit (ORU) task allowing the use of linear system identification methods. Comparisons, observations, and results of both parametric system identification techniques are discussed. The thesis concludes by proposing a model reference control system to aid in astronaut ground tests. This approach would allow the identified models to mimic on-orbit dynamic characteristics of the actual flight manipulator thus providing astronauts with realistic on-orbit responses to perform space station tasks in a ground-based environment.

Interdependency of the maximum range of flexion-extension of hand metacarpophalangeal joints.

PubMed

Gracia-Ibáñez, V; Vergara, M; Sancho-Bru, J-L

2016-12-01

Mobility of the fingers metacarpophalangeal (MCP) joints depends on the posture of the adjacent ones. Current Biomechanical hand models consider fixed ranges of movement at joints, regardless of the posture, thus allowing for non-realistic postures, generating wrong results in reach studies and forward dynamic analyses. This study provides data for more realistic hand models. The maximum voluntary extension (MVE) and flexion (MVF) of different combinations of MCP joints were measured covering their range of motion. Dependency of the MVF and MVE on the posture of the adjacent MCP joints was confirmed and mathematical models obtained through regression analyses (RMSE 7.7°).

A self-aligning knee joint for walking assistance devices.

PubMed

Byungjune Choi; Younbaek Lee; Jeonghun Kim; Minhyung Lee; Jongwon Lee; Se-Gon Roh; Hyundo Choi; Yong-Jae Kim; Jung-Yun Choi

2016-08-01

This paper presents a novel self-aligning knee mechanism for walking assistance devices for the elderly to provide physical gait assistance. Self-aligning knee joints can assist in flexion/extension motions of the knee joint and compensate the knee's transitional movements in the sagittal plane. In order to compensate the center of rotation, which moves with the flexion/extension motion of the human knee joint, a self-aligning knee joint is proposed that adds redundant degrees of freedom (i.e., 2-DoF) to the 1-DoF revolute joint. The key idea of the proposed mechanism is to decouple joint rotations and translations for use in lower-extremity wearable devices. This paper describes the mechanical design of this self-aligning knee mechanism and its implementation on a wearable robot and in preliminary experiments. The performance of the proposed mechanism is verified by simulations and experiments.

Joint Attributes and Event Analysis for Multimedia Event Detection.

PubMed

Ma, Zhigang; Chang, Xiaojun; Xu, Zhongwen; Sebe, Nicu; Hauptmann, Alexander G

2017-06-15

Semantic attributes have been increasingly used the past few years for multimedia event detection (MED) with promising results. The motivation is that multimedia events generally consist of lower level components such as objects, scenes, and actions. By characterizing multimedia event videos with semantic attributes, one could exploit more informative cues for improved detection results. Much existing work obtains semantic attributes from images, which may be suboptimal for video analysis since these image-inferred attributes do not carry dynamic information that is essential for videos. To address this issue, we propose to learn semantic attributes from external videos using their semantic labels. We name them video attributes in this paper. In contrast with multimedia event videos, these external videos depict lower level contents such as objects, scenes, and actions. To harness video attributes, we propose an algorithm established on a correlation vector that correlates them to a target event. Consequently, we could incorporate video attributes latently as extra information into the event detector learnt from multimedia event videos in a joint framework. To validate our method, we perform experiments on the real-world large-scale TRECVID MED 2013 and 2014 data sets and compare our method with several state-of-the-art algorithms. The experiments show that our method is advantageous for MED.

X-ray spectrophotometer SphinX and particle spectrometer STEP-F of the satellite experiment CORONAS-PHOTON. Preliminary results of the joint data analysis

NASA Astrophysics Data System (ADS)

Dudnik, O. V.; Podgorski, P.; Sylwester, J.; Gburek, S.; Kowalinski, M.; Siarkowski, M.; Plocieniak, S.; Bakala, J.

2012-04-01

A joint analysis is carried out of data obtained with the help of the solar X-ray SphinX spectrophotometer and the electron and proton satellite telescope STEP-F in May 2009 in the course of the scientific space experiment CORONAS-PHOTON. In order to determine the energies and particle types, in the analysis of spectrophotometer records data are used on the intensities of electrons, protons, and secondary γ-radiation, obtained by the STEP-F telescope, which was located in close proximity to the SphinX spectrophotometer. The identical reaction of both instruments is noted at the intersection of regions of the Brazilian magnetic anomaly and the Earth's radiation belts. It is shown that large area photodiodes, serving as sensors of the X-ray spectrometer, reliably record electron fluxes of low and intermediate energies, as well as fluxes of the secondary gamma radiation from construction materials of detector modules, the TESIS instrument complex, and the spacecraft itself. The dynamics of electron fluxes, recorded by the SphinX spectrophotometer in the vicinity of a weak geomagnetic storm, supplements the information about the processes of radial diffusion of electrons, which was studied using the STEP-F telescope.

Fluid dynamic mechanisms and interactions within separated flows and their effects on missile aerodynamics

NASA Astrophysics Data System (ADS)

Addy, A. L.; Chow, W. L.; Korst, H. H.; White, R. A.

1983-05-01

Significant data and detailed results of a joint research effort investigating the fluid dynamic mechanisms and interactions within separated flows are presented. The results were obtained through analytical, experimental, and computational investigations of base flow related configurations. The research objectives focus on understanding the component mechanisms and interactions which establish and maintain separated flow regions. Flow models and theoretical analyses were developed to describe the base flowfield. The research approach has been to conduct extensive small-scale experiments on base flow configurations and to analyze these flows by component models and finite-difference techniques. The modeling of base flows of missiles (both powered and unpowered) for transonic and supersonic freestreams has been successful by component models. Research on plume effects and plume modeling indicated the need to match initial plume slope and plume surface curvature for valid wind tunnel simulation of an actual rocket plume. The assembly and development of a state-of-the-art laser Doppler velocimeter (LDV) system for experiments with two-dimensional small-scale models has been completed and detailed velocity and turbulence measurements are underway. The LDV experiments include the entire range of base flowfield mechanisms - shear layer development, recompression/reattachment, shock-induced separation, and plume-induced separation.

LTPP pavement maintenance materials : SHRP joint reseal experiment, final report.

DOT National Transportation Integrated Search

1999-09-01

The Strategic Highway Research Program (SHRP) H-106 maintenance experiment and the Federal Highway : Administration (FHWA) Long-Term Monitoring (LTM) of Pavement Maintenance Materials Test Sites project studied : the resealing of joints in concrete p...

The Association of Flexibility, Balance, and Lumbar Strength with Balance Ability: Risk of Falls in Older Adults

PubMed Central

Emilio, Emilio J. Martínez-López; Hita-Contreras, Fidel; Jiménez-Lara, Pilar M.; Latorre-Román, Pedro; Martínez-Amat, Antonio

2014-01-01

The purpose of the present study was to determine the effects of a proprioceptive training program on older adults, as well as to analyze the association between flexibility, balance and lumbar strength (physical fitness test) with balance ability and fall risk (functional balance tests). This study was a controlled, longitudinal trial with a 12-week follow-up period. Subjects from a population of older adults were allocated to the intervention group (n = 28) or to the usual care (control) group (n = 26). Subjects performed proprioceptive training twice weekly (6 specific exercises with Swiss ball and BOSU). Each session included 50 minutes (10 minutes of warm-up with slow walk, 10 minutes of mobility and stretching exercises, 30 minutes of proprioceptive exercises). The outcome variables were physical fitness (lower-body flexibility, hip-joint mobility, dynamic balance, static balance, and lumbar strength) and functional balance (Berg scale and Tinetti test). The experimental group obtained significantly higher values than the control group in lower-body flexibility, dynamic balance, and lumbar strength (p = 0.019, p < 0.001, and p = 0.034 respectively). Hip-joint mobility, dynamic balance, and lumbar strength were positively associated with balance ability (p < 0.001, p < 0.001, and p = 0.014, respectively) and the prevention of falls (p = 0.001, p < 0.001, and p = 0.017 respectively). These findings suggest that a 12-week proprioception program intervention (twice a week) significantly improves flexibility, balance, and lumbar strength in older adults. Hip-joint mobility, dynamic balance and lumbar strength are positively associated to balance ability and the risk of falls in older adults. This proprioceptive training does not show a significant improvement in hip-joint mobility or static balance. Key points A 12-week proprioceptive intervention program (two times per week) significantly improves flexibility, balance, and lumbar strength in older adults. The risk of falls and balance ability are significantly improved after a training program with Bosu and Swiss ball in older adults. An improvement in joint mobility, dynamic balance and lumbar strength is positively associated with balance ability and improved fall risk in older adults. A 12-week proprioceptive intervention program (two times per week) does not show a significant improvement in hip-joint mobility and static balance. PMID:24790489

Excluded from the Institutional Habitus: The Joint Student Experience

ERIC Educational Resources Information Center

Weissmann, Elke

2013-01-01

This article examines the student experience for a particular cohort, namely the joint honours students, at a post-1992 university in the United Kingdom. These students are enrolled in degree courses that combine two subjects at one university. Little attention has so far been given to such students whose experience is decidedly different from…

General John J. Pershing: Critical Observations and Experiences in Manchuria and Mexico

DTIC Science & Technology

2017-05-25

operational art and the principles of joint operations. So while General Pershing is not largely recognized as an operational artist in contemporary...writing, his observations and experiences with regards to the elements of operational art and the principles of joint operations before World War I...Japanese War, Punitive Expedition, World War I, AEF, Operational Art, Principles of Joint Operations 16. SECURITY CLASSIFICATION OF: 17

Collaborative agency to support integrated care for children, young people and families: an action research study

PubMed Central

Stuart, Kaz

2014-01-01

Abstract Introduction Collaboration was legislated in the delivery of integrated care in the early 2000s in the UK. This research explored how the reality of practice met the rhetoric of collaboration. Theory The paper is situated against a theoretical framework of structure, agency, identity and empowerment. Collectively and contextually these concepts inform the proposed model of ‘collaborative agency’ to sustain integrated care. The paper brings sociological theory on structure and agency to the dilemma of collaboration. Methods Participative action research was carried out in collaborative teams that aspired to achieve integrated care for children, young people and families between 2009 and 2013. It was a part time, PhD study in collaborative practice. Results The research established that people needed to be able to be jointly aware of their context, to make joint decisions, and jointly act in order to deliver integrated services, and proposes a model of collaborative agency derived from practitioner’s experiences and integrated action research and literature on agency. The model reflects the effects of a range of structures in shaping professional identity, empowerment, and agency in a dynamic. The author proposes that the collaborative agency model will support integrated care, although this is, as yet, an untested hypothesis. PMID:24868192

An optimal resolved rate law for kinematically redundant manipulators

NASA Technical Reports Server (NTRS)

Bourgeois, B. J.

1987-01-01

The resolved rate law for a manipulator provides the instantaneous joint rates required to satisfy a given instantaneous hand motion. When the joint space has more degrees of freedom than the task space, the manipulator is kinematically redundant and the kinematic rate equations are underdetermined. These equations can be locally optimized, but the resulting pseudo-inverse solution has been found to cause large joint rates in some cases. A weighting matrix in the locally optimized (pseudo-inverse) solution is dynamically adjusted to control the joint motion as desired. Joint reach limit avoidance is demonstrated in a kinematically redundant planar arm model. The treatment is applicable to redundant manipulators with any number of revolute joints and to non-planar manipulators.

Detecting coupled collective motions in protein by independent subspace analysis

NASA Astrophysics Data System (ADS)

Sakuraba, Shun; Joti, Yasumasa; Kitao, Akio

2010-11-01

Protein dynamics evolves in a high-dimensional space, comprising aharmonic, strongly correlated motional modes. Such correlation often plays an important role in analyzing protein function. In order to identify significantly correlated collective motions, here we employ independent subspace analysis based on the subspace joint approximate diagonalization of eigenmatrices algorithm for the analysis of molecular dynamics (MD) simulation trajectories. From the 100 ns MD simulation of T4 lysozyme, we extract several independent subspaces in each of which collective modes are significantly correlated, and identify the other modes as independent. This method successfully detects the modes along which long-tailed non-Gaussian probability distributions are obtained. Based on the time cross-correlation analysis, we identified a series of events among domain motions and more localized motions in the protein, indicating the connection between the functionally relevant phenomena which have been independently revealed by experiments.

Unsupervised Spatial Event Detection in Targeted Domains with Applications to Civil Unrest Modeling

PubMed Central

Zhao, Liang; Chen, Feng; Dai, Jing; Hua, Ting; Lu, Chang-Tien; Ramakrishnan, Naren

2014-01-01

Twitter has become a popular data source as a surrogate for monitoring and detecting events. Targeted domains such as crime, election, and social unrest require the creation of algorithms capable of detecting events pertinent to these domains. Due to the unstructured language, short-length messages, dynamics, and heterogeneity typical of Twitter data streams, it is technically difficult and labor-intensive to develop and maintain supervised learning systems. We present a novel unsupervised approach for detecting spatial events in targeted domains and illustrate this approach using one specific domain, viz. civil unrest modeling. Given a targeted domain, we propose a dynamic query expansion algorithm to iteratively expand domain-related terms, and generate a tweet homogeneous graph. An anomaly identification method is utilized to detect spatial events over this graph by jointly maximizing local modularity and spatial scan statistics. Extensive experiments conducted in 10 Latin American countries demonstrate the effectiveness of the proposed approach. PMID:25350136

A combinatorial code for pattern formation in Drosophila oogenesis.

PubMed

Yakoby, Nir; Bristow, Christopher A; Gong, Danielle; Schafer, Xenia; Lembong, Jessica; Zartman, Jeremiah J; Halfon, Marc S; Schüpbach, Trudi; Shvartsman, Stanislav Y

2008-11-01

Two-dimensional patterning of the follicular epithelium in Drosophila oogenesis is required for the formation of three-dimensional eggshell structures. Our analysis of a large number of published gene expression patterns in the follicle cells suggests that they follow a simple combinatorial code based on six spatial building blocks and the operations of union, difference, intersection, and addition. The building blocks are related to the distribution of inductive signals, provided by the highly conserved epidermal growth factor receptor and bone morphogenetic protein signaling pathways. We demonstrate the validity of the code by testing it against a set of patterns obtained in a large-scale transcriptional profiling experiment. Using the proposed code, we distinguish 36 distinct patterns for 81 genes expressed in the follicular epithelium and characterize their joint dynamics over four stages of oogenesis. The proposed combinatorial framework allows systematic analysis of the diversity and dynamics of two-dimensional transcriptional patterns and guides future studies of gene regulation.

First-passage problems: A probabilistic dynamic analysis for degraded structures

NASA Technical Reports Server (NTRS)

Shiao, Michael C.; Chamis, Christos C.

1990-01-01

Structures subjected to random excitations with uncertain system parameters degraded by surrounding environments (a random time history) are studied. Methods are developed to determine the statistics of dynamic responses, such as the time-varying mean, the standard deviation, the autocorrelation functions, and the joint probability density function of any response and its derivative. Moreover, the first-passage problems with deterministic and stationary/evolutionary random barriers are evaluated. The time-varying (joint) mean crossing rate and the probability density function of the first-passage time for various random barriers are derived.

Design of a Virtual Player for Joint Improvisation with Humans in the Mirror Game

PubMed Central

Zhai, Chao; Alderisio, Francesco; Tsaneva-Atanasova, Krasimira; di Bernardo, Mario

2016-01-01

Joint improvisation is often observed among humans performing joint action tasks. Exploring the underlying cognitive and neural mechanisms behind the emergence of joint improvisation is an open research challenge. This paper investigates jointly improvised movements between two participants in the mirror game, a paradigmatic joint task example. First, experiments involving movement coordination of different dyads of human players are performed in order to build a human benchmark. No designation of leader and follower is given beforehand. We find that joint improvisation is characterized by the lack of a leader and high levels of movement synchronization. Then, a theoretical model is proposed to capture some features of their interaction, and a set of experiments is carried out to test and validate the model ability to reproduce the experimental observations. Furthermore, the model is used to drive a computer avatar able to successfully improvise joint motion with a human participant in real time. Finally, a convergence analysis of the proposed model is carried out to confirm its ability to reproduce joint movements between the participants. PMID:27123927

Design of a Virtual Player for Joint Improvisation with Humans in the Mirror Game.

PubMed

Zhai, Chao; Alderisio, Francesco; Słowiński, Piotr; Tsaneva-Atanasova, Krasimira; di Bernardo, Mario

2016-01-01

Joint improvisation is often observed among humans performing joint action tasks. Exploring the underlying cognitive and neural mechanisms behind the emergence of joint improvisation is an open research challenge. This paper investigates jointly improvised movements between two participants in the mirror game, a paradigmatic joint task example. First, experiments involving movement coordination of different dyads of human players are performed in order to build a human benchmark. No designation of leader and follower is given beforehand. We find that joint improvisation is characterized by the lack of a leader and high levels of movement synchronization. Then, a theoretical model is proposed to capture some features of their interaction, and a set of experiments is carried out to test and validate the model ability to reproduce the experimental observations. Furthermore, the model is used to drive a computer avatar able to successfully improvise joint motion with a human participant in real time. Finally, a convergence analysis of the proposed model is carried out to confirm its ability to reproduce joint movements between the participants.

A nano universal joint made from curved double-walled carbon nanotubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cai, Kun; Cai, Haifang; Shi, Jiao

2015-06-15

A nano universal joint is constructed from curved double-wall carbon nanotubes with a short outer tube as stator and a long inner tube as a rotor. When one end of the rotor is driven (by a rotary motor) to rotate, the same rotational speed but with different rotational direction will be induced at the other end of the rotor. This mechanism makes the joint useful for designing a flexible nanodevice with an adjustable output rotational signal. The motion transmission effect of the universal joint is analyzed using a molecular dynamics simulation approach. In particular, the effects of three factors aremore » investigated. The first factor is the curvature of the stator, which produces a different rotational direction of the rotor at the output end. The second is the bonding conditions of carbon atoms on the adjacent tube ends of the motor and the rotor, sp{sup 1} or sp{sup 2} atoms, which create different attraction between the motor and the rotor. The third is the rotational speed of the motor, which can be considered as the input signal of the universal joint. It is noted that the rotor's rotational speed is usually the same as that of the motor when the carbon atoms on the adjacent ends of the motor and the rotor are sp{sup 1} carbon atoms. When they become the new sp{sup 2} atoms, the rotor experiences a jump in rotational speed from a lower value to that of the motor. The mechanism of drops in potential of the motor is revealed. If the carbon atoms on the adjacent ends are sp{sup 2} atoms, the rotor rotates more slowly than the motor, whereas the rotational speed is stable when driven by a higher speed motor.« less

A nano universal joint made from curved double-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Cai, Kun; Cai, Haifang; Shi, Jiao; Qin, Qing H.

2015-06-01

A nano universal joint is constructed from curved double-wall carbon nanotubes with a short outer tube as stator and a long inner tube as a rotor. When one end of the rotor is driven (by a rotary motor) to rotate, the same rotational speed but with different rotational direction will be induced at the other end of the rotor. This mechanism makes the joint useful for designing a flexible nanodevice with an adjustable output rotational signal. The motion transmission effect of the universal joint is analyzed using a molecular dynamics simulation approach. In particular, the effects of three factors are investigated. The first factor is the curvature of the stator, which produces a different rotational direction of the rotor at the output end. The second is the bonding conditions of carbon atoms on the adjacent tube ends of the motor and the rotor, sp1 or sp2 atoms, which create different attraction between the motor and the rotor. The third is the rotational speed of the motor, which can be considered as the input signal of the universal joint. It is noted that the rotor's rotational speed is usually the same as that of the motor when the carbon atoms on the adjacent ends of the motor and the rotor are sp1 carbon atoms. When they become the new sp2 atoms, the rotor experiences a jump in rotational speed from a lower value to that of the motor. The mechanism of drops in potential of the motor is revealed. If the carbon atoms on the adjacent ends are sp2 atoms, the rotor rotates more slowly than the motor, whereas the rotational speed is stable when driven by a higher speed motor.

Biomechanical testing simulation of a cadaver spine specimen: development and evaluation study.

PubMed

Ahn, Hyung Soo; DiAngelo, Denis J

2007-05-15

This article describes a computer model of the cadaver cervical spine specimen and virtual biomechanical testing. To develop a graphics-oriented, multibody model of a cadaver cervical spine and to build a virtual laboratory simulator for the biomechanical testing using physics-based dynamic simulation techniques. Physics-based computer simulations apply the laws of physics to solid bodies with defined material properties. This technique can be used to create a virtual simulator for the biomechanical testing of a human cadaver spine. An accurate virtual model and simulation would complement tissue-based in vitro studies by providing a consistent test bed with minimal variability and by reducing cost. The geometry of cervical vertebrae was created from computed tomography images. Joints linking adjacent vertebrae were modeled as a triple-joint complex, comprised of intervertebral disc joints in the anterior region, 2 facet joints in the posterior region, and the surrounding ligament structure. A virtual laboratory simulation of an in vitro testing protocol was performed to evaluate the model responses during flexion, extension, and lateral bending. For kinematic evaluation, the rotation of motion segment unit, coupling behaviors, and 3-dimensional helical axes of motion were analyzed. The simulation results were in correlation with the findings of in vitro tests and published data. For kinetic evaluation, the forces of the intervertebral discs and facet joints of each segment were determined and visually animated. This methodology produced a realistic visualization of in vitro experiment, and allowed for the analyses of the kinematics and kinetics of the cadaver cervical spine. With graphical illustrations and animation features, this modeling technique has provided vivid and intuitive information.

Maximum in the middle: nonlinear response of microbial plankton to ultraviolet radiation and phosphorus.

PubMed

Medina-Sánchez, Juan Manuel; Delgado-Molina, José Antonio; Bratbak, Gunnar; Bullejos, Francisco José; Villar-Argaiz, Manuel; Carrillo, Presentación

2013-01-01

The responses of heterotrophic microbial food webs (HMFW) to the joint action of abiotic stressors related to global change have been studied in an oligotrophic high-mountain lake. A 2×5 factorial design field experiment performed with large mesocosms for >2 months was used to quantify the dynamics of the entire HMFW (bacteria, heterotrophic nanoflagellates, ciliates, and viruses) after an experimental P-enrichment gradient which approximated or surpassed current atmospheric P pulses in the presence vs. absence of ultraviolet radiation. HMFW underwent a mid-term (<20 days) acute development following a noticeable unimodal response to P enrichment, which peaked at intermediate P-enrichment levels and, unexpectedly, was more accentuated under ultraviolet radiation. However, after depletion of dissolved inorganic P, the HMFW collapsed and was outcompeted by a low-diversity autotrophic compartment, which constrained the development of HMFW and caused a significant loss of functional biodiversity. The dynamics and relationships among variables, and the response patterns found, suggest the importance of biotic interactions (predation/parasitism and competition) in restricting HMFW development, in contrast to the role of abiotic factors as main drivers of autotrophic compartment. The response of HMFW may contribute to ecosystem resilience by favoring the maintenance of the peculiar paths of energy and nutrient-mobilization in these pristine ecosystems, which are vulnerable to threats by the joint action of abiotic stressors related to global change.

Maximum in the Middle: Nonlinear Response of Microbial Plankton to Ultraviolet Radiation and Phosphorus

PubMed Central

Medina-Sánchez, Juan Manuel; Delgado-Molina, José Antonio; Bratbak, Gunnar; Bullejos, Francisco José; Villar-Argaiz, Manuel; Carrillo, Presentación

2013-01-01

The responses of heterotrophic microbial food webs (HMFW) to the joint action of abiotic stressors related to global change have been studied in an oligotrophic high-mountain lake. A 2×5 factorial design field experiment performed with large mesocosms for >2 months was used to quantify the dynamics of the entire HMFW (bacteria, heterotrophic nanoflagellates, ciliates, and viruses) after an experimental P-enrichment gradient which approximated or surpassed current atmospheric P pulses in the presence vs. absence of ultraviolet radiation. HMFW underwent a mid-term (<20 days) acute development following a noticeable unimodal response to P enrichment, which peaked at intermediate P-enrichment levels and, unexpectedly, was more accentuated under ultraviolet radiation. However, after depletion of dissolved inorganic P, the HMFW collapsed and was outcompeted by a low-diversity autotrophic compartment, which constrained the development of HMFW and caused a significant loss of functional biodiversity. The dynamics and relationships among variables, and the response patterns found, suggest the importance of biotic interactions (predation/parasitism and competition) in restricting HMFW development, in contrast to the role of abiotic factors as main drivers of autotrophic compartment. The response of HMFW may contribute to ecosystem resilience by favoring the maintenance of the peculiar paths of energy and nutrient-mobilization in these pristine ecosystems, which are vulnerable to threats by the joint action of abiotic stressors related to global change. PMID:23593178

Molecular quantum control landscapes in von Neumann time-frequency phase space

NASA Astrophysics Data System (ADS)

Ruetzel, Stefan; Stolzenberger, Christoph; Fechner, Susanne; Dimler, Frank; Brixner, Tobias; Tannor, David J.

2010-10-01

Recently we introduced the von Neumann representation as a joint time-frequency description for femtosecond laser pulses and suggested its use as a basis for pulse shaping experiments. Here we use the von Neumann basis to represent multidimensional molecular control landscapes, providing insight into the molecular dynamics. We present three kinds of time-frequency phase space scanning procedures based on the von Neumann formalism: variation of intensity, time-frequency phase space position, and/or the relative phase of single subpulses. The shaped pulses produced are characterized via Fourier-transform spectral interferometry. Quantum control is demonstrated on the laser dye IR140 elucidating a time-frequency pump-dump mechanism.

Molecular quantum control landscapes in von Neumann time-frequency phase space.

PubMed

Ruetzel, Stefan; Stolzenberger, Christoph; Fechner, Susanne; Dimler, Frank; Brixner, Tobias; Tannor, David J

2010-10-28

Recently we introduced the von Neumann representation as a joint time-frequency description for femtosecond laser pulses and suggested its use as a basis for pulse shaping experiments. Here we use the von Neumann basis to represent multidimensional molecular control landscapes, providing insight into the molecular dynamics. We present three kinds of time-frequency phase space scanning procedures based on the von Neumann formalism: variation of intensity, time-frequency phase space position, and/or the relative phase of single subpulses. The shaped pulses produced are characterized via Fourier-transform spectral interferometry. Quantum control is demonstrated on the laser dye IR140 elucidating a time-frequency pump-dump mechanism.

Joint Launch + One Year Science Review of USML-1 and USMP-1 with the Microgravity Measurement Group

NASA Technical Reports Server (NTRS)

Ramachandran, N. (Editor); Frazier, Donald. O. (Editor); Lehoczky, Sandor L. (Editor); Baugher, Charles R. (Editor)

1994-01-01

This document summarizes from the various investigations their comprehensive results and highlights, and also serves as a combined mission report for the first United States Microgravity Laboratory (USML-1) amd the United States Microgravity Payload (USMP-1). USML-1 included 31 investigations in fluid dynamics, crystal growth, combustion, biotechnology, and technology demonstrations supported by 11 facilities. On the USMP-1 mission, both the MEPHISTO and Lambda Point experiments exceeded by over 100 percent their planned science objectives. The mission was also the first time that acceleration data were down-linked and analyzed in real time.

On-line analysis of bulk materials using pulsed neutron interrogation

NASA Astrophysics Data System (ADS)

Lebrun, P.; Tourneur, P. Le; Poumarede, B.; Möller, H.; Bach, P.

1999-06-01

On the basis of our joint experience in neutronics for SODERN and in cement plant engineering for KRUPP POLYSIUS, we have developed a new on-line bulk materials analyser for the cement industry. This equipment includes a pulsed neutron generator GENIE 16, some gamma ray and neutron detectors, specially designed electronics with high counting rate, software delivering the mean elemental composition of raw material, and adequate shielding. This material is transported through the equipment on a conveyor belt, the size of which is adapted to the requirements. This paper briefly describes the equipment and some results, as obtained in dynamic test from a demonstrator installed in Germany.

Arctic Ice Dynamics Joint Experiment 1975-1976. Physical Oceanography Data Report, Salinity, Temperature and Depth Data, Camp Big Bear. Volume IV.

DTIC Science & Technology

1980-02-01

C to~~~ II qo 3 4 .. ..N~ V. ...... .V . .N N . .S ... .V .fI . i 0 Wi . .... . 53 .O .00... 0--N. .. ZZ W. I -. 0 -z J~~D &Z av F - -q qWe at s-a...q .a1 2c z oft ew dw- lp- eE- W - 0- fP- M .. 1 ,1e mc VftWU 00, 0%0 0000 - P-PtftoO. -%ffE Uqvv 4i . qwE ft . 04W -f ewF-0 wa rnm~~t.- tol Uw0 f E0

Periodontal Ligament Entheses and their Adaptive Role in the Context of Dentoalveolar Joint Function

PubMed Central

Lin, Jeremy D.; Jang, Andrew T.; Kurylo, Michael P.; Hurng, Jonathan; Yang, Feifei; Yang, Lynn; Pal, Arvin; Chen, Ling; Ho, Sunita P.

2017-01-01

Objectives The dynamic bone-periodontal ligament (PDL)-tooth fibrous joint consists of two adaptive functionally graded interfaces (FGI), the PDL-bone and PDL-cementum that respond to mechanical strain transmitted during mastication. In general, from a materials and mechanics perspective, FGI prevent catastrophic failure during prolonged cyclic loading. This review is a discourse of results gathered from literature to illustrate the dynamic adaptive nature of the fibrous joint in response to physiologic and pathologic simulated functions, and experimental tooth movement. Methods Historically, studies have investigated soft to hard tissue transitions through analytical techniques that provided insights into structural, biochemical, and mechanical characterization methods. Experimental approaches included two dimensional to three dimensional advanced in situ imaging and analytical techniques. These techniques allowed mapping and correlation of deformations to physicochemical and mechanobiological changes within volumes of the complex subjected to concentric and eccentric loading regimes respectively. Results Tooth movement is facilitated by mechanobiological activity at the interfaces of the fibrous joint and generates elastic discontinuities at these interfaces in response to eccentric loading. Both concentric and eccentric loads mediated cellular responses to strains, and prompted self-regulating mineral forming and resorbing zones that in turn altered the functional space of the joint. Significance A multiscale biomechanics and mechanobiology approach is important for correlating joint function to tissue-level strain-adaptive properties with overall effects on joint form as related to physiologic and pathologic functions. Elucidating the shift in localization of biomolecules specifically at interfaces during development, function, and therapeutic loading of the joint is critical for developing “functional regeneration and adaptation” strategies with an emphasis on restoring physiologic joint function. PMID:28476202

From Weakly Chaotic Dynamics to Deterministic Subdiffusion via Copula Modeling

NASA Astrophysics Data System (ADS)

Nazé, Pierre

2018-03-01

Copula modeling consists in finding a probabilistic distribution, called copula, whereby its coupling with the marginal distributions of a set of random variables produces their joint distribution. The present work aims to use this technique to connect the statistical distributions of weakly chaotic dynamics and deterministic subdiffusion. More precisely, we decompose the jumps distribution of Geisel-Thomae map into a bivariate one and determine the marginal and copula distributions respectively by infinite ergodic theory and statistical inference techniques. We verify therefore that the characteristic tail distribution of subdiffusion is an extreme value copula coupling Mittag-Leffler distributions. We also present a method to calculate the exact copula and joint distributions in the case where weakly chaotic dynamics and deterministic subdiffusion statistical distributions are already known. Numerical simulations and consistency with the dynamical aspects of the map support our results.

Mechanical Influences on Morphogenesis of the Knee Joint Revealed through Morphological, Molecular and Computational Analysis of Immobilised Embryos

PubMed Central

Roddy, Karen A.; Prendergast, Patrick J.; Murphy, Paula

2011-01-01

Very little is known about the regulation of morphogenesis in synovial joints. Mechanical forces generated from muscle contractions are required for normal development of several aspects of normal skeletogenesis. Here we show that biophysical stimuli generated by muscle contractions impact multiple events during chick knee joint morphogenesis influencing differential growth of the skeletal rudiment epiphyses and patterning of the emerging tissues in the joint interzone. Immobilisation of chick embryos was achieved through treatment with the neuromuscular blocking agent Decamethonium Bromide. The effects on development of the knee joint were examined using a combination of computational modelling to predict alterations in biophysical stimuli, detailed morphometric analysis of 3D digital representations, cell proliferation assays and in situ hybridisation to examine the expression of a selected panel of genes known to regulate joint development. This work revealed the precise changes to shape, particularly in the distal femur, that occur in an altered mechanical environment, corresponding to predicted changes in the spatial and dynamic patterns of mechanical stimuli and region specific changes in cell proliferation rates. In addition, we show altered patterning of the emerging tissues of the joint interzone with the loss of clearly defined and organised cell territories revealed by loss of characteristic interzone gene expression and abnormal expression of cartilage markers. This work shows that local dynamic patterns of biophysical stimuli generated from muscle contractions in the embryo act as a source of positional information guiding patterning and morphogenesis of the developing knee joint. PMID:21386908

Dynamic analysis of I cross beam section dissimilar plate joined by TIG welding

NASA Astrophysics Data System (ADS)

Sani, M. S. M.; Nazri, N. A.; Rani, M. N. Abdul; Yunus, M. A.

2018-04-01

In this paper, finite element (FE) joint modelling technique for prediction of dynamic properties of sheet metal jointed by tungsten inert gas (TTG) will be presented. I cross section dissimilar flat plate with different series of aluminium alloy; AA7075 and AA6061 joined by TTG are used. In order to find the most optimum set of TTG welding dissimilar plate, the finite element model with three types of joint modelling were engaged in this study; bar element (CBAR), beam element and spot weld element connector (CWELD). Experimental modal analysis (EMA) was carried out by impact hammer excitation on the dissimilar plates that welding by TTG method. Modal properties of FE model with joints were compared and validated with model testing. CWELD element was chosen to represent weld model for TTG joints due to its accurate prediction of mode shapes and contains an updating parameter for weld modelling compare to other weld modelling. Model updating was performed to improve correlation between EMA and FEA and before proceeds to updating, sensitivity analysis was done to select the most sensitive updating parameter. After perform model updating, average percentage of error of the natural frequencies for CWELD model is improved significantly.

Mitochondrial dynamics and optical conformation changes in DsRed as studied by Fourier imaging correlation spectroscopy

NASA Astrophysics Data System (ADS)

Senning, Eric Nicolas

Novel experiments that probe the dynamics of intracellular species, including the center-of-mass displacements and internal conformational transitions of biological macromolecules, have the potential to reveal the complex biochemical mechanisms operating within the cell. This work presents the implementation and development of Fourier imaging correlation spectroscopy (FICS), a phase-selective approach to fluorescence spectroscopy that measures the collective coordinate fluctuations of fluorescently labeled microscopic particles. In FICS experiments, a spatially modulated optical grating excites a fluorescently labeled sample. Phase-synchronous detection of the fluorescence, with respect to the phase of the exciting optical grating, can be used to monitor the fluctuations of partially averaged spatial coordinates. These data are then analyzed by two-point and four-point time correlation functions to provide a statistically meaningful understanding of the dynamics under observation. FICS represents a unique route to elevate signal levels, while acquiring detailed information about molecular coordinate trajectories. Mitochondria of mammalian cells are known to associate with cytoskeletal proteins, and their motions are affected by the stability of microtubules and microfilaments. Within the cell it is possible to fluorescently label the mitochondria and study its dynamic behavior with FICS. The dynamics of S. cerevisiae yeast mitochondria are characterized at four discrete length scales (ranging from 0.6--1.19 mum) and provide detailed information about the influence of specific cytoskeletal elements. Using the microtubule and microfilament destabilizing agents, Nocodazole and Latrunculin A, it is determined that microfilaments are required for normal yeast mitochondrial motion while microtubules have no effect. Experiments with specific actin mutants revealed that actin is responsible for enhanced mobility on length scales greater than 0.6 mum. The versatility of FICS expands when individual molecules are labeled with fluorescent chromophores. In recent experiments on the tetrameric fluorescent protein DsRed, polarization-modulated FICS (PM-FICS) is demonstrated to separate conformational dynamics from molecular translational dynamics. The optical switching pathways of DsRed, a tetrameric complex of fluorescent protein subunits, are examined. An analysis of PM-FICS coordinate trajectories, in terms of 2D spectra and joint probability distributions, provides detailed information about the transition pathways between distinct dipole-coupled DsRed conformations. This dissertation includes co-authored and previously published material.

Sex differences in kinematic adaptations to muscle fatigue induced by repetitive upper limb movements.

PubMed

Bouffard, Jason; Yang, Chen; Begon, Mickael; Côté, Julie

2018-04-19

Muscle fatigue induced by repetitive movements contributes to the development of musculoskeletal disorders. Men and women respond differently to muscle fatigue during isometric single-joint efforts, but sex differences during dynamic multi-joint tasks have not been clearly identified. Moreover, most studies comparing men and women during fatigue development assessed endurance time. However, none evaluated sex differences in kinematic adaptations to fatigue during multi-joint dynamic tasks. The objective of the study was to compare how men and women adapt their upper body kinematics during a fatiguing repetitive pointing task. Forty men and 41 women performed repetitive pointing movements (one per second) between two targets while maintaining their elbow elevated at shoulder height. The task ended when participants rated a perceived level of fatigue of 8/10. Trunk, humerothoracic, and elbow angles were compared between the first and last 30 s of the experiment and between men and women. Linear positions of the index finger (distance from the target) and the elbow (arm elevation) as well as movement timing were documented as task performance measures. Men (7.4 ± 3.2 min) and women (8.3 ± 4.5 min) performed the repetitive pointing task for a similar duration. For both sex groups, trunk range of motion increased with fatigue while shoulder's and elbow's decreased. Moreover, participants modified their trunk posture to compensate for the decreased humerothoracic elevation. Movements at all joints also became more variable with fatigue. However, of the 24 joint angle variables assessed, only two Sex × Fatigue interactions were observed. Although average humerothoracic elevation angle decreased in both subgroups, this decrease was greater in men (standardized response mean [SRM] - 1.63) than in women (SRM - 1.44). Moreover, the movement-to-movement variability of humerothoracic elevation angle increased only in women (SRM 0.42). Despite many similarities between men's and women's response to fatigue induced by repetitive pointing movements, some sex differences were observed. Those subtle differences may indicate that men's shoulder muscles were more fatigued than women's despite a similar level of perceived exertion. They may also indicate that men and women do not adapt the exact same way to a similar fatigue.

A springy pendulum could describe the swing leg kinetics of human walking.

PubMed

Song, Hyunggwi; Park, Heewon; Park, Sukyung

2016-06-14

The dynamics of human walking during various walking conditions could be qualitatively captured by the springy legged dynamics, which have been used as a theoretical framework for bipedal robotics applications. However, the spring-loaded inverted pendulum model describes the motion of the center of mass (CoM), which combines the torso, swing and stance legs together and does not explicitly inform us as to whether the inter-limb dynamics share the springy legged dynamics characteristics of the CoM. In this study, we examined whether the swing leg dynamics could also be represented by springy mechanics and whether the swing leg stiffness shows a dependence on gait speed, as has been observed in CoM mechanics during walking. The swing leg was modeled as a spring-loaded pendulum hinged at the hip joint, which is under forward motion. The model parameters of the loaded mass were adopted from body parameters and anthropometric tables, whereas the free model parameters for the rest length of the spring and its stiffness were estimated to best match the data for the swing leg joint forces. The joint forces of the swing leg were well represented by the springy pendulum model at various walking speeds with a regression coefficient of R(2)>0.8. The swing leg stiffness increased with walking speed and was correlated with the swing frequency, which is consistent with previous observations from CoM dynamics described using the compliant leg. These results suggest that the swing leg also shares the springy dynamics, and the compliant walking model could be extended to better present swing leg dynamics. Copyright © 2016 Elsevier Ltd. All rights reserved.

Emotional engagements predict and enhance social cognition in young chimpanzees

PubMed Central

Bard, Kim A; Bakeman, Roger; Boysen, Sarah T; Leavens, David A

2014-01-01

Social cognition in infancy is evident in coordinated triadic engagements, that is, infants attending jointly with social partners and objects. Current evolutionary theories of primate social cognition tend to highlight species differences in cognition based on human-unique cooperative motives. We consider a developmental model in which engagement experiences produce differential outcomes. We conducted a 10-year-long study in which two groups of laboratory-raised chimpanzee infants were given quantifiably different engagement experiences. Joint attention, cooperativeness, affect, and different levels of cognition were measured in 5- to 12-month-old chimpanzees, and compared to outcomes derived from a normative human database. We found that joint attention skills significantly improved across development for all infants, but by 12 months, the humans significantly surpassed the chimpanzees. We found that cooperativeness was stable in the humans, but by 12 months, the chimpanzee group given enriched engagement experiences significantly surpassed the humans. Past engagement experiences and concurrent affect were significant unique predictors of both joint attention and cooperativeness in 5- to 12-month-old chimpanzees. When engagement experiences and concurrent affect were statistically controlled, joint attention and cooperation were not associated. We explain differential social cognition outcomes in terms of the significant influences of previous engagement experiences and affect, in addition to cognition. Our study highlights developmental processes that underpin the emergence of social cognition in support of evolutionary continuity. PMID:24410843

Angioplasty balloon catheters used for distraction of the ankle joint.

PubMed

Sartoretti, C; Sartoretti-Schefer, S; Duff, C; Buchmann, P

1996-02-01

Arthroscopy of the ankle joint is now routinely performed in diagnostic and therapeutic interventions but is still a demanding and difficult operative procedure in this very small and tight joint. Arthroscopy can be facilitated by a sufficient distraction that gives a better overview of the joint space. However, it is still a matter of debate how to obtain the adequate distraction. Distention by manual strength as well as by the help of a technical device have been proposed. We report our experience with distraction of the ankle joint by the help of one or two intraarticularily located and secondarily insufflated angioplasty balloon catheters that are routinely used in interventional radiology. These special catheters allow a careful and controlled distention of the joint with a fixed space of distraction and, according to our limited experience, without any morbidity.

Acute effects of a resisted dynamic warm-up protocol on jumping performance.

PubMed

Cilli, M; Gelen, E; Yildiz, S; Saglam, T; Camur, Mh

2014-12-01

This study aimed to investigate the kinematic and kinetic changes when resistance is applied in horizontal and vertical directions, produced by using different percentages of body weight, caused by jumping movements during a dynamic warm-up. The group of subjects consisted of 35 voluntary male athletes (19 basketball and 16 volleyball players; age: 23.4 ± 1.4 years, training experience: 9.6 ± 2.7 years; height: 177.2 ± 5.7 cm, body weight: 69.9 ± 6.9 kg) studying Physical Education, who had a jump training background and who were training for 2 hours, on 4 days in a week. A dynamic warm-up protocol containing seven specific resistance movements with specific resistance corresponding to different percentages of body weight (2%, 4%, 6%, 8%, 10%) was applied randomly on non consecutive days. Effects of different warm-up protocols were assessed by pre-/post- exercise changes in jump height in the countermovement jump (CMJ) and the squat jump (SJ) measured using a force platform and changes in hip and knee joint angles at the end of the eccentric phase measured using a video camera. A significant increase in jump height was observed in the dynamic resistance warm-up conducted with different percentages of body weight (p < 0.05). On the other hand, no significant difference in different percentages of body weight states was observed (p > 0.05). In jump movements before and after the warm-up, while no significant difference between the vertical ground reaction forces applied by athletes was observed (p > 0.05), in some cases of resistance, a significant reduction was observed in hip and knee joint angles (p < 0.05). The dynamic resistance warm-up method was found to cause changes in the kinematics of jumping movements, as well as an increase in jump height values. As a result, dynamic warm-up exercises could be applicable in cases of resistance corresponding to 6-10% of body weight applied in horizontal and vertical directions in order to increase the jump performance acutely.

ACUTE EFFECTS OF A RESISTED DYNAMIC WARM-UP PROTOCOL ON JUMPING PERFORMANCE

PubMed Central

Cilli, M; Yildiz, S; Saglam, T; Camur, MH

2014-01-01

This study aimed to investigate the kinematic and kinetic changes when resistance is applied in horizontal and vertical directions, produced by using different percentages of body weight, caused by jumping movements during a dynamic warm-up. The group of subjects consisted of 35 voluntary male athletes (19 basketball and 16 volleyball players; age: 23.4 ± 1.4 years, training experience: 9.6 ± 2.7 years; height: 177.2 ± 5.7 cm, body weight: 69.9 ± 6.9 kg) studying Physical Education, who had a jump training background and who were training for 2 hours, on 4 days in a week. A dynamic warm-up protocol containing seven specific resistance movements with specific resistance corresponding to different percentages of body weight (2%, 4%, 6%, 8%, 10%) was applied randomly on non consecutive days. Effects of different warm-up protocols were assessed by pre-/post- exercise changes in jump height in the countermovement jump (CMJ) and the squat jump (SJ) measured using a force platform and changes in hip and knee joint angles at the end of the eccentric phase measured using a video camera. A significant increase in jump height was observed in the dynamic resistance warm-up conducted with different percentages of body weight (p < 0.05). On the other hand, no significant difference in different percentages of body weight states was observed (p > 0.05). In jump movements before and after the warm-up, while no significant difference between the vertical ground reaction forces applied by athletes was observed (p > 0.05), in some cases of resistance, a significant reduction was observed in hip and knee joint angles (p < 0.05). The dynamic resistance warm-up method was found to cause changes in the kinematics of jumping movements, as well as an increase in jump height values. As a result, dynamic warm-up exercises could be applicable in cases of resistance corresponding to 6-10% of body weight applied in horizontal and vertical directions in order to increase the jump performance acutely. PMID:25435670

Effect of brace design on patients with ACL-ruptures.

PubMed

Strutzenberger, G; Braig, M; Sell, S; Boes, K; Schwameder, H

2012-11-01

Different designs of functional knee braces for ACL-injury rehabilitation exist. In addition to the mechanical stabilization provided by rigid shell braces, sleeve braces also address proprioceptive mechanisms, but little is known if this leads to benefits for ACL-deficient subjects. Therefore the aim of this study was to investigate the effect of 2 different functional brace designs (shell and sleeve brace) on functional achievements in ACL-deficient patients. 28 subjects with ACL-ruptured knees performed tests for knee joint laxity, joint position sense, static and dynamic balance and isometric and dynamic lower limb extension strength in non-braced, sleeve braced and shell braced condition. The results showed a significant decrease in knee joint laxity for sleeve (33%; p<0.001) and rigid shell bracing (14%, p=0.039). The sleeve brace revealed a significant increase in dynamic balance after perturbation (20%; p=0.024) and a significant increase in dynamic lower limb peak rate of force development (17%; p=0.015) compared to the non-braced condition. The effects might be caused by the flexible area of support and the incorporated mechanisms to address proprioceptive aspects. Braces might not be needed in simple daily life tasks, but could provide beneficial support in more dynamic settings when patients return to sporting activities after an ACL-injury. © Georg Thieme Verlag KG Stuttgart · New York.

Joint Autoethnography of Teacher Experience in the Academy: Exploring Methods for Collaborative Inquiry

ERIC Educational Resources Information Center

Adamson, John; Muller, Theron

2018-01-01

This manuscript uses a joint autoethnographic methodology to explore the experiences of two language teacher scholars working in the academy outside the global centre in Japan. Emphasis is given to how the methodology used, cycles of reflective writing, reveals commonalities and differences in our respective experiences of working in the Japanese…

Joint Soviet-American experiment on hypokinesia: Experimental results

NASA Technical Reports Server (NTRS)

Burovskiy, N. N.

1979-01-01

Comprehensive results are reported from the Soviet portion of a joint Soviet-American experiment involving hypokinesia. The main emphases are on chemical analyses of blood and urine, functional tests, and examination of the cardiovascular system by electrocardiography, echocardiography, and plethysmography.

77 FR 19408 - Dynamic Mobility Applications and Data Capture Management Programs; Notice of Public Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-30

... DEPARTMENT OF TRANSPORTATION Dynamic Mobility Applications and Data Capture Management Programs...) Intelligent Transportation System Joint Program Office (ITS JPO) will host a free public meeting to provide stakeholders an update on the Data Capture and Management (DCM) and Dynamic Mobility Applications (DMA...

Postoperative Therapy for Chronic Thumb Carpometacarpal (CMC) Joint Dislocation.

PubMed

Wollstein, Ronit; Michael, Dafna; Harel, Hani

2016-01-01

Surgical arthroplasty of thumb carpometacarpal (CMC) joint osteoarthritis is commonly performed. Postoperative therapeutic protocols aim to improve range of motion and function of the revised thumb. We describe a case in which the thumb CMC joint had been chronically dislocated before surgery, with shortening of the soft-tissue dynamic and static stabilizers of the joint. The postoperative protocol addressed the soft tissues using splinting and exercises aimed at lengthening and strengthening these structures, with good results. It may be beneficial to evaluate soft-tissue tension and the pattern of thumb use after surgery for thumb CMC joint osteoarthritis to improve postoperative functional results. Copyright © 2016 by the American Occupational Therapy Association, Inc.

An intermittent control model of flexible human gait using a stable manifold of saddle-type unstable limit cycle dynamics

PubMed Central

Fu, Chunjiang; Suzuki, Yasuyuki; Kiyono, Ken; Morasso, Pietro; Nomura, Taishin

2014-01-01

Stability of human gait is the ability to maintain upright posture during walking against external perturbations. It is a complex process determined by a number of cross-related factors, including gait trajectory, joint impedance and neural control strategies. Here, we consider a control strategy that can achieve stable steady-state periodic gait while maintaining joint flexibility with the lowest possible joint impedance. To this end, we carried out a simulation study of a heel-toe footed biped model with hip, knee and ankle joints and a heavy head-arms-trunk element, working in the sagittal plane. For simplicity, the model assumes a periodic desired joint angle trajectory and joint torques generated by a set of feed-forward and proportional-derivative feedback controllers, whereby the joint impedance is parametrized by the feedback gains. We could show that a desired steady-state gait accompanied by the desired joint angle trajectory can be established as a stable limit cycle (LC) for the feedback controller with an appropriate set of large feedback gains. Moreover, as the feedback gains are decreased for lowering the joint stiffness, stability of the LC is lost only in a few dimensions, while leaving the remaining large number of dimensions quite stable: this means that the LC becomes saddle-type, with a low-dimensional unstable manifold and a high-dimensional stable manifold. Remarkably, the unstable manifold remains of low dimensionality even when the feedback gains are decreased far below the instability point. We then developed an intermittent neural feedback controller that is activated only for short periods of time at an optimal phase of each gait stride. We characterized the robustness of this design by showing that it can better stabilize the unstable LC with small feedback gains, leading to a flexible gait, and in particular we demonstrated that such an intermittent controller performs better if it drives the state point to the stable manifold, rather than directly to the LC. The proposed intermittent control strategy might have a high affinity for the inverted pendulum analogy of biped gait, providing a dynamic view of how the step-to-step transition from one pendular stance to the next can be achieved stably in a robust manner by a well-timed neural intervention that exploits the stable modes embedded in the unstable dynamics. PMID:25339687

An intermittent control model of flexible human gait using a stable manifold of saddle-type unstable limit cycle dynamics.

PubMed

Fu, Chunjiang; Suzuki, Yasuyuki; Kiyono, Ken; Morasso, Pietro; Nomura, Taishin

2014-12-06

Stability of human gait is the ability to maintain upright posture during walking against external perturbations. It is a complex process determined by a number of cross-related factors, including gait trajectory, joint impedance and neural control strategies. Here, we consider a control strategy that can achieve stable steady-state periodic gait while maintaining joint flexibility with the lowest possible joint impedance. To this end, we carried out a simulation study of a heel-toe footed biped model with hip, knee and ankle joints and a heavy head-arms-trunk element, working in the sagittal plane. For simplicity, the model assumes a periodic desired joint angle trajectory and joint torques generated by a set of feed-forward and proportional-derivative feedback controllers, whereby the joint impedance is parametrized by the feedback gains. We could show that a desired steady-state gait accompanied by the desired joint angle trajectory can be established as a stable limit cycle (LC) for the feedback controller with an appropriate set of large feedback gains. Moreover, as the feedback gains are decreased for lowering the joint stiffness, stability of the LC is lost only in a few dimensions, while leaving the remaining large number of dimensions quite stable: this means that the LC becomes saddle-type, with a low-dimensional unstable manifold and a high-dimensional stable manifold. Remarkably, the unstable manifold remains of low dimensionality even when the feedback gains are decreased far below the instability point. We then developed an intermittent neural feedback controller that is activated only for short periods of time at an optimal phase of each gait stride. We characterized the robustness of this design by showing that it can better stabilize the unstable LC with small feedback gains, leading to a flexible gait, and in particular we demonstrated that such an intermittent controller performs better if it drives the state point to the stable manifold, rather than directly to the LC. The proposed intermittent control strategy might have a high affinity for the inverted pendulum analogy of biped gait, providing a dynamic view of how the step-to-step transition from one pendular stance to the next can be achieved stably in a robust manner by a well-timed neural intervention that exploits the stable modes embedded in the unstable dynamics.

The Contribution of Upper Body Movements to Dynamic Balance Regulation during Challenged Locomotion

PubMed Central

Boström, Kim J.; Dirksen, Tim; Zentgraf, Karen; Wagner, Heiko

2018-01-01

Recent studies suggest that in addition to movements between ankle and hip joints, movements of the upper body, in particular of the arms, also significantly contribute to postural control. In line with these suggestions, we analyzed regulatory movements of upper and lower body joints supporting dynamic balance regulation during challenged locomotion. The participants walked over three beams of varying width and under three different verbally conveyed restrictions of arm posture, to control the potential influence of arm movements on the performance: The participants walked (1) with their arms stretched out perpendicularly in the frontal plane, (2) spontaneously, i.e., without restrictions to the arm movements, and (3) with their hands on their thighs. After applying an inverse-dynamics analysis to the measured joint kinematics, we investigated the contribution of upper and lower body joints to balance regulation in terms of torque amplitude and variation. On the condition with the hands on the thighs, the contribution of the upper body remains significantly lower than the contribution of the lower body irrespective of beam widths. For spontaneous arm movements and for outstretched arms we find that the upper body (including the arms) contributes to the balancing to a similar extent as the lower body. Moreover, when the task becomes more difficult, i.e., for narrower beam widths, the contribution of the upper body increases, while the contribution of the lower body remains nearly constant. These findings lend further support to the hypothetical existence of an “upper body strategy” complementing the ankle and hip strategies especially during challenging dynamic balance tasks. PMID:29434544

Frontal Joint Dynamics when Initiating Stair Ascent from a Walk versus a Stand

PubMed Central

Vallabhajosula, Srikant; Yentes, Jennifer M.; Stergiou, Nicholas

2011-01-01

Ascending stairs is a challenging activity of daily living for many populations. Frontal plane joint dynamics are critical to understand the mechanisms involved in stair ascension as they contribute to both propulsion and medio-lateral stability. However, previous research is limited to understanding these dynamics while initiating stair ascent from a stand. We investigated if initiating stair ascent from a walk with a comfortable self-selected speed could affect the frontal plane lower-extremity joint moments and powers as compared to initiating stair ascent from a stand and if this difference would exist at consecutive ipsilateral steps on the stairs. Kinematics data using a 3-D motion capture system and kinetics data using two force platforms on the first and third stair treads were recorded simultaneously as ten healthy young adults ascended a custom-built staircase. Data were collected from two starting conditions of stair ascent, from a walk (speed: 1.42±0.21m/s) and from a stand. Results showed that subjects generated greater peak knee abductor moment and greater peak hip abductor moment when initiating stair ascent from a walk. Greater peak joint moments and powers at all joints were also seen while ascending the second ipsilateral step. Particularly, greater peak hip abductor moment was needed to avoid contact of the contralateral limb with the intermediate step by counteracting the pelvic drop on the contralateral side. This could be important for therapists using stair climbing as a testing/training tool to evaluate hip strength in individuals with documented frontal plane abnormalities (i.e. knee and hip osteoarthritis, ACL injury). PMID:22172606

Dynamic Fragmentation of Jointed Rock Blocks During Rockslide-Avalanches: Insights From Discrete Element Analyses

NASA Astrophysics Data System (ADS)

Zhao, Tao; Crosta, Giovanni Battista; Dattola, Giuseppe; Utili, Stefano

2018-04-01

The dynamic fragmentation of jointed rock blocks during rockslide avalanches has been investigated by discrete element method simulations for a multiple arrangement of a rock block sliding over a simple slope geometry. The rock blocks are released along an inclined sliding plane and subsequently collide onto a flat horizontal plane at a sharp kink point. The contact force chains generated by the impact appear initially at the bottom frontal corner of the rock block and then propagate radially upward to the top rear part of the block. The jointed rock blocks exhibit evident contact force concentration and discontinuity of force wave propagation near the joint, associating with high energy dissipation of granular dynamics. The corresponding force wave propagation velocity can be less than 200 m/s, which is much smaller than that of an intact rock (1,316 m/s). The concentration of contact forces at the bottom leads to high rock fragmentation intensity and momentum boosts, facilitating the spreading of many fine fragments to the distal ends. However, the upper rock block exhibits very low rock fragmentation intensity but high energy dissipation due to intensive friction and damping, resulting in the deposition of large fragments near the slope toe. The size and shape of large fragments are closely related to the orientation and distribution of the block joints. The cumulative fragment size distribution can be well fitted by the Weibull's distribution function, with very gentle and steep curvatures at the fine and coarse size ranges, respectively. The numerical results of fragment size distribution can match well some experimental and field observations.

Design and Evaluation of a Prosthetic Knee Joint Using the Geared Five-Bar Mechanism.

PubMed

Sun, Yuanxi; Ge, Wenjie; Zheng, Jia; Dong, Dianbiao

2015-11-01

This paper presents the mechanical design, dynamics analysis and ankle trajectory analysis of a prosthetic knee joint using the geared five-bar mechanism. Compared with traditional four-bar or six-bar mechanisms, the geared five-bar mechanism is better at performing diverse movements and is easy to control. This prosthetic knee joint with the geared five-bar mechanism is capable of fine-tuning its relative instantaneous center of rotation and ankle trajectory. The centrode of this prosthetic knee joint, which is mechanically optimized according to the centrode of human knee joint, is better in the bionic performance than that of a prosthetic knee joint using the four-bar mechanism. Additionally, the stability control of this prosthetic knee joint during the swing and stance phase is achieved by a motor. By adjusting the gear ratio of this prosthetic knee joint, the ankle trajectories of both unilateral and bilateral amputees show less deviations from expected than that of the four-bar knee joint.

How Many Peripheral Solder Joints in a Surface Mounted Design Experience Inelastic Strains?

NASA Astrophysics Data System (ADS)

Suhir, E.; Yi, S.; Ghaffarian, R.

2017-03-01

It has been established that it is the peripheral solder joints that are the most vulnerable in the ball-grid-array (BGA) and column-grid-array (CGA) designs and most often fail. As far as the long-term reliability of a soldered microelectronics assembly as a whole is concerned, it makes a difference, if just one or more peripheral joints experience inelastic strains. It is clear that the low cycle fatigue lifetime of the solder system is inversely proportional to the number of joints that simultaneously experience inelastic strains. A simple and physically meaningful analytical expression (formula) is obtained for the prediction, at the design stage, of the number of such joints, if any, for the given effective thermal expansion (contraction) mismatch of the package and PCB; materials and geometrical characteristics of the package/PCB assembly; package size; and, of course, the level of the yield stress in the solder material. The suggested formula can be used to determine if the inelastic strains in the solder material could be avoided by the proper selection of the above characteristics and, if not, how many peripheral joints are expected to simultaneously experience inelastic strains. The general concept is illustrated by a numerical example carried out for a typical BGA package. The suggested analytical model (formula) is applicable to any soldered microelectronics assembly. The roles of other important factors, such as, e.g., solder material anisotropy, grain size, and their random orientation within a joint, are viewed in this analysis as less important factors than the level of the interfacial stress. The roles of these factors will be accounted for in future work and considered, in addition to the location of the joint, in a more complicated, more sophisticated, and more comprehensive reliability/fatigue model.

Joining of Components of Complex Structures for Improved Dynamic Response

DTIC Science & Technology

2011-10-28

system- level mass and stiffness matrices and force vector (at each frequency in the range of interest). To address this issue a series of complex...displacements of all candidate joint locations by using the system- level mass and stiffness matrices and force vector (at each frequency in the range of...joints. In contrast, Li et al. [10] proposed a fastener layout/topology that achieves an almost uniform stress level in each joint, and adopted

The Effect of Welding Energy on the Microstructural and Mechanical Properties of Ultrasonic-Welded Copper Joints

PubMed Central

Yang, Jingwei; Cao, Biao; Lu, Qinghua

2017-01-01

The effects of welding energy on the mechanical and microstructural characteristics of ultrasonic-welded pure copper plates were investigated. Complex dynamic recrystallization and grain growth occurred inside the weld zone during ultrasonic welding. At a low welding energy, a thin band of straight weld interfaces was observed and had an ultra-fine grain structure. With an increase in welding energy, the weld interface progressively changed from flat to sinusoidal, and eventually turned into a convoluted wavy pattern, bearing similarities to shear instabilities, as observed in fluid dynamics. The lap shear load of the joints initially increased and then remained stable as the welding energy increased. The tensile characteristics of the joints significantly depended on the development of plastic deformation at the interface. The influence of the microstructure on the hardness was also discussed. PMID:28772553

The Effect of Welding Energy on the Microstructural and Mechanical Properties of Ultrasonic-Welded Copper Joints.

PubMed

Yang, Jingwei; Cao, Biao; Lu, Qinghua

2017-02-16

The effects of welding energy on the mechanical and microstructural characteristics of ultrasonic-welded pure copper plates were investigated. Complex dynamic recrystallization and grain growth occurred inside the weld zone during ultrasonic welding. At a low welding energy, a thin band of straight weld interfaces was observed and had an ultra-fine grain structure. With an increase in welding energy, the weld interface progressively changed from flat to sinusoidal, and eventually turned into a convoluted wavy pattern, bearing similarities to shear instabilities, as observed in fluid dynamics. The lap shear load of the joints initially increased and then remained stable as the welding energy increased. The tensile characteristics of the joints significantly depended on the development of plastic deformation at the interface. The influence of the microstructure on the hardness was also discussed.

Lower limb joint kinetics and ankle joint stiffness in the sprint start push-off.

PubMed

Charalambous, Laura; Irwin, Gareth; Bezodis, Ian N; Kerwin, David

2012-01-01

Sprint push-off technique is fundamental to sprint performance and joint stiffness has been identified as a performance-related variable during dynamic movements. However, joint stiffness for the push-off and its relationship with performance (times and velocities) has not been reported. The aim of this study was to quantify and explain lower limb net joint moments and mechanical powers, and ankle stiffness during the first stance phase of the push-off. One elite sprinter performed 10 maximal sprint starts. An automatic motion analysis system (CODA, 200 Hz) with synchronized force plates (Kistler, 1000 Hz) collected kinematic profiles at the hip, knee, and ankle and ground reaction forces, providing input for inverse dynamics analyses. The lower-limb joints predominately extended and revealed a proximal-to-distal sequential pattern of maximal extensor angular velocity and positive power production. Pearson correlations revealed relationships (P < 0.05) between ankle stiffness (5.93 ± 0.75 N x m x deg(-1)) and selected performance variables. Relationships between negative power phase ankle stiffness and horizontal (r = -0.79) and vertical (r = 0.74) centre of mass velocities were opposite in direction to the positive power phase ankle stiffness (horizontal: r = 0.85; vertical: r = -0.54). Thus ankle stiffness may affect the goals of the sprint push-off in different ways, depending on the phase of stance considered.

Direct Parametric Reconstruction With Joint Motion Estimation/Correction for Dynamic Brain PET Data.

PubMed

Jiao, Jieqing; Bousse, Alexandre; Thielemans, Kris; Burgos, Ninon; Weston, Philip S J; Schott, Jonathan M; Atkinson, David; Arridge, Simon R; Hutton, Brian F; Markiewicz, Pawel; Ourselin, Sebastien

2017-01-01

Direct reconstruction of parametric images from raw photon counts has been shown to improve the quantitative analysis of dynamic positron emission tomography (PET) data. However it suffers from subject motion which is inevitable during the typical acquisition time of 1-2 hours. In this work we propose a framework to jointly estimate subject head motion and reconstruct the motion-corrected parametric images directly from raw PET data, so that the effects of distorted tissue-to-voxel mapping due to subject motion can be reduced in reconstructing the parametric images with motion-compensated attenuation correction and spatially aligned temporal PET data. The proposed approach is formulated within the maximum likelihood framework, and efficient solutions are derived for estimating subject motion and kinetic parameters from raw PET photon count data. Results from evaluations on simulated [ 11 C]raclopride data using the Zubal brain phantom and real clinical [ 18 F]florbetapir data of a patient with Alzheimer's disease show that the proposed joint direct parametric reconstruction motion correction approach can improve the accuracy of quantifying dynamic PET data with large subject motion.

Personalized dynamic prediction of death according to tumour progression and high-dimensional genetic factors: Meta-analysis with a joint model.

PubMed

Emura, Takeshi; Nakatochi, Masahiro; Matsui, Shigeyuki; Michimae, Hirofumi; Rondeau, Virginie

2017-01-01

Developing a personalized risk prediction model of death is fundamental for improving patient care and touches on the realm of personalized medicine. The increasing availability of genomic information and large-scale meta-analytic data sets for clinicians has motivated the extension of traditional survival prediction based on the Cox proportional hazards model. The aim of our paper is to develop a personalized risk prediction formula for death according to genetic factors and dynamic tumour progression status based on meta-analytic data. To this end, we extend the existing joint frailty-copula model to a model allowing for high-dimensional genetic factors. In addition, we propose a dynamic prediction formula to predict death given tumour progression events possibly occurring after treatment or surgery. For clinical use, we implement the computation software of the prediction formula in the joint.Cox R package. We also develop a tool to validate the performance of the prediction formula by assessing the prediction error. We illustrate the method with the meta-analysis of individual patient data on ovarian cancer patients.

Dynamic Modeling and Interactive Performance of PARM: A Parallel Upper-Limb Rehabilitation Robot Using Impedance Control for Patients after Stroke.

PubMed

Guang, Hui; Ji, Linhong; Shi, Yingying; Misgeld, Berno J E

2018-01-01

The robot-assisted therapy has been demonstrated to be effective in the improvements of limb function and even activities of daily living for patients after stroke. This paper presents an interactive upper-limb rehabilitation robot with a parallel mechanism and an isometric screen embedded in the platform to display trajectories. In the dynamic modeling for impedance control, the effects of friction and inertia are reduced by introducing the principle of virtual work and derivative of Jacobian matrix. To achieve the assist-as-needed impedance control for arbitrary trajectories, the strategy based on orthogonal deviations is proposed. Simulations and experiments were performed to validate the dynamic modeling and impedance control. Besides, to investigate the influence of the impedance in practice, a subject participated in experiments and performed two types of movements with the robot, that is, rectilinear and circular movements, under four conditions, that is, with/without resistance or impedance, respectively. The results showed that the impedance and resistance affected both mean absolute error and standard deviation of movements and also demonstrated the significant differences between movements with/without impedance and resistance ( p < 0.001). Furthermore, the error patterns were discussed, which suggested that the impedance environment was capable of alleviating movement deviations by compensating the synergetic inadequacy between the shoulder and elbow joints.

Dynamic Modeling and Interactive Performance of PARM: A Parallel Upper-Limb Rehabilitation Robot Using Impedance Control for Patients after Stroke

PubMed Central

Shi, Yingying; Misgeld, Berno J. E.

2018-01-01

The robot-assisted therapy has been demonstrated to be effective in the improvements of limb function and even activities of daily living for patients after stroke. This paper presents an interactive upper-limb rehabilitation robot with a parallel mechanism and an isometric screen embedded in the platform to display trajectories. In the dynamic modeling for impedance control, the effects of friction and inertia are reduced by introducing the principle of virtual work and derivative of Jacobian matrix. To achieve the assist-as-needed impedance control for arbitrary trajectories, the strategy based on orthogonal deviations is proposed. Simulations and experiments were performed to validate the dynamic modeling and impedance control. Besides, to investigate the influence of the impedance in practice, a subject participated in experiments and performed two types of movements with the robot, that is, rectilinear and circular movements, under four conditions, that is, with/without resistance or impedance, respectively. The results showed that the impedance and resistance affected both mean absolute error and standard deviation of movements and also demonstrated the significant differences between movements with/without impedance and resistance (p < 0.001). Furthermore, the error patterns were discussed, which suggested that the impedance environment was capable of alleviating movement deviations by compensating the synergetic inadequacy between the shoulder and elbow joints. PMID:29850004

Evaluating plantar fascia strain in hyperpronating cadaveric feet following an extra-osseous talotarsal stabilization procedure.

PubMed

Graham, Michael E; Jawrani, Nikhil T; Goel, Vijay K

2011-01-01

Abnormal talotarsal joint mechanics leading to hyperpronation is implicated as one of the most common causes of plantar fasciopathy. In patients with hyperpronating feet, the plantar fascia experiences excessive tensile forces during static and dynamic weight-bearing activities because of excessive medial longitudinal arch depression. For the purposes of this study, we hypothesized that plantar fascia strain in hyperpronating cadaveric feet would decrease after intervention with an extra-osseous talotarsal stabilization (EOTTS) device. A miniature differential variable reluctance transducer was used to quantify the plantar fascia strain in 6 fresh-frozen cadaver foot specimens exhibiting flexible instability of the talotarsal joint complex (i.e., hyperpronation). The strain was measured as the foot was moved from its neutral to maximally pronated position, before and after intervention using the HyProCure(®) EOTTS device. The mean plantar fascia elongation was 0.83 ± 0.27 mm (strain 3.62% ± 1.17%) and 0.56 ± 0.2 mm (strain 2.42% ± 0.88%) before and after intervention, respectively (N = 18, variation reported is ± 1 SD). The average plantar fascia strain decreased by 33%, and the difference was statistically significant with p < .001. From this cadaveric experiment, the reduction in plantar fascia strain suggests that an EOTTS device might be effective in stabilizing the pathologic talotarsal joint complex and the medial longitudinal arch and in eliminating hyperpronation. An EOTTS procedure might offer a possible treatment option for plantar fasciopathy in cases in which the underlying etiology is abnormal talotarsal biomechanics. Copyright © 2011 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

46 CFR 56.75-30 - Pipe joining details.

Code of Federal Regulations, 2010 CFR

2010-10-01

... be either of the socket or butt type. When butt joints are employed the edges to be joined shall be.... Circumferential joints may be either of the butt or socket type. Where butt joints are employed, the included... annular clearance of socket joints shall be held to small clearances which experience indicates is...

46 CFR 56.75-30 - Pipe joining details.

Code of Federal Regulations, 2014 CFR

2014-10-01

... be either of the socket or butt type. When butt joints are employed the edges to be joined shall be.... Circumferential joints may be either of the butt or socket type. Where butt joints are employed, the included... annular clearance of socket joints shall be held to small clearances which experience indicates is...

46 CFR 56.75-30 - Pipe joining details.

Code of Federal Regulations, 2013 CFR

2013-10-01

... be either of the socket or butt type. When butt joints are employed the edges to be joined shall be.... Circumferential joints may be either of the butt or socket type. Where butt joints are employed, the included... annular clearance of socket joints shall be held to small clearances which experience indicates is...

46 CFR 56.75-30 - Pipe joining details.

Code of Federal Regulations, 2012 CFR

2012-10-01

... be either of the socket or butt type. When butt joints are employed the edges to be joined shall be.... Circumferential joints may be either of the butt or socket type. Where butt joints are employed, the included... annular clearance of socket joints shall be held to small clearances which experience indicates is...

46 CFR 56.75-30 - Pipe joining details.

Code of Federal Regulations, 2011 CFR

2011-10-01

... be either of the socket or butt type. When butt joints are employed the edges to be joined shall be.... Circumferential joints may be either of the butt or socket type. Where butt joints are employed, the included... annular clearance of socket joints shall be held to small clearances which experience indicates is...

Mechanical Behavior of CFRP Lattice Core Sandwich Bolted Corner Joints

NASA Astrophysics Data System (ADS)

Zhu, Xiaolei; Liu, Yang; Wang, Yana; Lu, Xiaofeng; Zhu, Lingxue

2017-12-01

The lattice core sandwich structures have drawn more attention for the integration of load capacity and multifunctional applications. However, the connection of carbon fibers reinforced polymer composite (CFRP) lattice core sandwich structure hinders its application. In this paper, a typical connection of two lattice core sandwich panels, named as corner joint or L-joint, was investigated by experiment and finite element method (FEM). The mechanical behavior and failure mode of the corner joints were discussed. The results showed that the main deformation pattern and failure mode of the lattice core sandwich bolted corner joints structure were the deformation of metal connector and indentation of the face sheet in the bolt holes. The metal connectors played an important role in bolted corner joints structure. In order to save the calculation resource, a continuum model of pyramid lattice core was used to replace the exact structure. The computation results were consistent with experiment, and the maximum error was 19%. The FEM demonstrated the deflection process of the bolted corner joints structure visually. So the simplified FEM can be used for further analysis of the bolted corner joints structure in engineering.

Vascularised knee joint transplantation in man: the first two years experience.

PubMed

Kirschner, M H; Brauns, L; Gonschorek, O; Bühren, V; Hofmann, G O

2000-04-01

To describe our early experience with a new technique for restoring destroyed knee joints to give reasonable functional results. Observational clinical trial. Level-1-Trauma centre, Germany. 5 patients with large bone defects of the knee and loss of the extensor apparatus caused either by serious injury alone, or infection after serious injury. Transplantation of fresh and perfused knee joints with a vascular pedicle from multiorgan donors under immunosuppression. Ability to walk, need to remove one transplanted joint. Four patients are able to walk, the range of movement being from 50 degrees-120 degrees. The first patient additionally had to be provided with a total knee joint arthroplasty. In the third patient the graft became infected and had to be removed. She finally had an arthrodesis and bone lengthening by the Ilizarov technique. Transplantation of the knee joint may be an alternative to bone lengthening or amputation for patients with total loss of the extensor apparatus.

Japan - USSR joint emulsion chamber experiment at Pamir

NASA Technical Reports Server (NTRS)

1985-01-01

The results are presented for the systematic measurement of cosmic ray showers in the first carbon chamber of Japan-USSR joint experiment at Pamir Plateau. The intensity and the energy distribution of electromagnetic particles, of hadrons and of families are in good agreement with the results of other mountain experiment if the relative error in energy estimation is taken into consideration.

The experience of family carers attending a joint reminiscence group with people with dementia: A thematic analysis.

PubMed

Melunsky, Nina; Crellin, Nadia; Dudzinski, Emma; Orrell, Martin; Wenborn, Jennifer; Poland, Fiona; Woods, Bob; Charlesworth, Georgina

2015-11-01

Reminiscence therapy has the potential to improve quality of life for people with dementia. In recent years reminiscence groups have extended to include family members, but carers' experience of attending joint sessions is undocumented. This qualitative study explored the experience of 18 family carers attending 'Remembering Yesterday Caring Today' groups. Semi-structured interviews were transcribed and subjected to thematic analysis. Five themes were identified: experiencing carer support; shared experience; expectations (met and unmet), carer perspectives of the person with dementia's experience; and learning and comparing. Family carers' experiences varied, with some experiencing the intervention as entirely positive whereas others had more mixed feelings. Negative aspects included the lack of respite from their relative, the lack of emphasis on their own needs, and experiencing additional stress and guilt through not being able to implement newly acquired skills. These findings may explain the failure of a recent trial of joint reminiscence groups to replicate previous findings of positive benefit. More targeted research within subgroups of carers is required to justify the continued use of joint reminiscence groups in dementia care. © The Author(s) 2013.

Integrating dynamic stereo-radiography and surface-based motion data for subject-specific musculoskeletal dynamic modeling.

PubMed

Zheng, Liying; Li, Kang; Shetye, Snehal; Zhang, Xudong

2014-09-22

This manuscript presents a new subject-specific musculoskeletal dynamic modeling approach that integrates high-accuracy dynamic stereo-radiography (DSX) joint kinematics and surface-based full-body motion data. We illustrate this approach by building a model in OpenSim for a patient who participated in a meniscus transplantation efficacy study, incorporating DSX data of the tibiofemoral joint kinematics. We compared this DSX-incorporated (DSXI) model to a default OpenSim model built using surface-measured data alone. The architectures and parameters of the two models were identical, while the differences in (time-averaged) tibiofemoral kinematics were of the order of magnitude of 10° in rotation and 10mm in translation. Model-predicted tibiofemoral compressive forces and knee muscle activations were compared against literature data acquired from instrumented total knee replacement components (Fregly et al., 2012) and the patient's EMG recording. The comparison demonstrated that the incorporation of DSX data improves the veracity of musculoskeletal dynamic modeling. Copyright © 2014 Elsevier Ltd. All rights reserved.

Integrating dynamic stereo-radiography and surface-based motion data for subject-specific musculoskeletal dynamic modeling

PubMed Central

Zheng, Liying; Li, Kang; Shetye, Snehal; Zhang, Xudong

2014-01-01

This paper presents a new subject-specific musculoskeletal dynamic modeling approach that integrates high-accuracy dynamic stereo-radiography (DSX) joint kinematics and surface-based full-body motion data. We illustrate this approach by building a model in OpenSim for a patient who participated in a meniscus transplantation efficacy study, incorporating DSX data of the tibiofemoral joint kinematics. We compared this DSX-incorporated (DSXI) model to a default OpenSim model built using surface-measured data alone. The architectures and parameters of the two models were identical, while the differences in (time-averaged) tibiofemoral kinematics were of the order of magnitude of 10° in rotation and 10 mm in translation. Model-predicted tibiofemoral compressive forces and knee muscle activations were compared against literature data acquired from instrumented total knee replacement components (Fregly et al., 2012) and the patient's EMG recording. The comparison demonstrated that the incorporation of DSX data improves the veracity of musculoskeletal dynamic modeling. PMID:25169658

The effect of inertial coupling in the dynamics and control of flexible robotic manipulators

NASA Technical Reports Server (NTRS)

Tesar, Delbert; Curran, Carol Cockrell; Graves, Philip Lee

1988-01-01

A general model of the dynamics of flexible robotic manipulators is presented, including the gross motion of the links, the vibrations of the links and joints, and the dynamic coupling between the gross motions and vibrations. The vibrations in the links may be modeled using lumped parameters, truncated modal summation, a component mode synthesis method, or a mixture of these methods. The local link inertia matrix is derived to obtain the coupling terms between the gross motion of the link and the vibrations of the link. Coupling between the motions of the links results from the kinematic model, which utilizes the method of kinematic influence. The model is used to simulate the dynamics of a flexible space-based robotic manipulator which is attached to a spacecraft, and is free to move with respect to the inertial reference frame. This model may be used to study the dynamic response of the manipulator to the motions of its joints, or to externally applied disturbances.

Neglected chaos in international stock markets: Bayesian analysis of the joint return-volatility dynamical system

NASA Astrophysics Data System (ADS)

Tsionas, Mike G.; Michaelides, Panayotis G.

2017-09-01

We use a novel Bayesian inference procedure for the Lyapunov exponent in the dynamical system of returns and their unobserved volatility. In the dynamical system, computation of largest Lyapunov exponent by traditional methods is impossible as the stochastic nature has to be taken explicitly into account due to unobserved volatility. We apply the new techniques to daily stock return data for a group of six countries, namely USA, UK, Switzerland, Netherlands, Germany and France, from 2003 to 2014, by means of Sequential Monte Carlo for Bayesian inference. The evidence points to the direction that there is indeed noisy chaos both before and after the recent financial crisis. However, when a much simpler model is examined where the interaction between returns and volatility is not taken into consideration jointly, the hypothesis of chaotic dynamics does not receive much support by the data ("neglected chaos").

Adaptive dynamic surface control of flexible-joint robots using self-recurrent wavelet neural networks.

PubMed

Yoo, Sung Jin; Park, Jin Bae; Choi, Yoon Ho

2006-12-01

A new method for the robust control of flexible-joint (FJ) robots with model uncertainties in both robot dynamics and actuator dynamics is proposed. The proposed control system is a combination of the adaptive dynamic surface control (DSC) technique and the self-recurrent wavelet neural network (SRWNN). The adaptive DSC technique provides the ability to overcome the "explosion of complexity" problem in backstepping controllers. The SRWNNs are used to observe the arbitrary model uncertainties of FJ robots, and all their weights are trained online. From the Lyapunov stability analysis, their adaptation laws are induced, and the uniformly ultimately boundedness of all signals in a closed-loop adaptive system is proved. Finally, simulation results for a three-link FJ robot are utilized to validate the good position tracking performance and robustness against payload uncertainties and external disturbances of the proposed control system.

The stock-flow model of spatial data infrastructure development refined by fuzzy logic.

PubMed

Abdolmajidi, Ehsan; Harrie, Lars; Mansourian, Ali

2016-01-01

The system dynamics technique has been demonstrated to be a proper method by which to model and simulate the development of spatial data infrastructures (SDI). An SDI is a collaborative effort to manage and share spatial data at different political and administrative levels. It is comprised of various dynamically interacting quantitative and qualitative (linguistic) variables. To incorporate linguistic variables and their joint effects in an SDI-development model more effectively, we suggest employing fuzzy logic. Not all fuzzy models are able to model the dynamic behavior of SDIs properly. Therefore, this paper aims to investigate different fuzzy models and their suitability for modeling SDIs. To that end, two inference and two defuzzification methods were used for the fuzzification of the joint effect of two variables in an existing SDI model. The results show that the Average-Average inference and Center of Area defuzzification can better model the dynamics of SDI development.

Joint inflight biomedical experiments performed during the ASTP spaceflight. [bacteriological experiments

NASA Technical Reports Server (NTRS)

Taylor, G. R.; Rogers, T. D.; Brower, M. E.; Kropp, K.

1976-01-01

Two joint inflight biomedical experiments were conducted during the unique Apollo-Soyuz Test Project (ASTP) spaceflight. One experiment evaluated rhythmicity of spore production of Streptomyces levoris. The other evaluated components of the infectious disease process by measuring alteration in: (1) the composition of the microbial population inhabiting USA and USSR crewmembers and spacecraft; (2) the ability of each crewmember's defense mechanism to resist infection; and (3) the ability of certain microorganisms to originate infections. These two experiments are described and the major results discussed.

Structural factors of jointed plain concrete pavements : SPS-2--initial evaluation and analysis

DOT National Transportation Integrated Search

2005-04-01

The SPS-2 experiment, "Strategic Study of Structural Factors for Jointed Plain Concrete Pavements (JPCP)," is one of the key components of the Long Term Pavement Performance (LTPP) program. The main objective of this experiment is to determine the re...

Fluid dynamic mechanisms and interactions within separated flows

NASA Astrophysics Data System (ADS)

Dutton, J. C.; Addy, A. L.

1990-02-01

The significant results of a joint research effort investigating the fundamental fluid dynamic mechanisms and interactions within high-speed separated flows are presented in detail. The results have obtained through analytical and numerical approaches, but with primary emphasis on experimental investigations of missile and projectile base flow-related configurations. The objectives of the research program focus on understanding the component mechanisms and interactions which establish and maintain high-speed separated flow regions. The analytical and numerical efforts have centered on unsteady plume-wall interactions in rocket launch tubes and on predictions of the effects of base bleed on transonic and supersonic base flowfields. The experimental efforts have considered the development and use of a state-of-the-art two component laser Doppler velocimeter (LDV) system for experiments with planar, two-dimensional, small-scale models in supersonic flows. The LDV experiments have yielded high quality, well documented mean and turbulence velocity data for a variety of high-speed separated flows including initial shear layer development, recompression/reattachment processes for two supersonic shear layers, oblique shock wave/turbulent boundary layer interactions in a compression corner, and two-stream, supersonic, near-wake flow behind a finite-thickness base.

All joint moments significantly contribute to trunk angular acceleration

PubMed Central

Nott, Cameron R.; Zajac, Felix E.; Neptune, Richard R.; Kautz, Steven A.

2010-01-01

Computationally advanced biomechanical analyses of gait demonstrate the often counter intuitive roles of joint moments on various aspects of gait such as propulsion, swing initiation, and balance. Each joint moment can produce linear and angular acceleration of all body segments (including those on which the moment does not directly act) due to the dynamic coupling inherent in the interconnected musculoskeletal system. This study presents the quantitative relationships between individual joint moments and trunk control with respect to balance during gait to show that the ankle, knee, and hip joint moments all affect the angular acceleration of the trunk. We show that trunk angular acceleration is affected by all the joints in the leg with varying degrees of dependence during the gait cycle. Furthermore, it is shown that inter-planar coupling exists and a two dimensional analysis of trunk balance neglects important out-of-plane joint moments that affect trunk angular acceleration. PMID:20646711

Augmented reality environment for temporomandibular joint motion analysis.

PubMed

Wagner, A; Ploder, O; Zuniga, J; Undt, G; Ewers, R

1996-01-01

The principles of interventional video tomography were applied for the real-time visualization of temporomandibular joint movements in an augmented reality environment. Anatomic structures were extracted in three dimensions from planar cephalometric radiographic images. The live-image fusion of these graphic anatomic structures with real-time position data of the mandible and the articular fossa was performed with a see-through, head-mounted display and an electromagnetic tracking system. The dynamic fusion of radiographic images of the temporomandibular joint to anatomic temporomandibular joint structures in motion created a new modality for temporomandibular joint motion analysis. The advantages of the method are its ability to accurately examine the motion of the temporomandibular joint in three dimensions without restraining the subject and its ability to simultaneously determine the relationship of the bony temporomandibular joint and supporting structures (ie, occlusion, muscle function, etc) during movement before and after treatment.

First Joint Observations of Radio Aurora by the VHF and HF Radars of the ISTP SB RAS

NASA Astrophysics Data System (ADS)

Berngardt, O. I.; Lebedev, V. P.; Kutelev, K. A.; Kushnarev, D. S.; Grkovich, K. V.

2018-01-01

Two modern radars for diagnosis of the ionosphere by the radio-wave backscattering method, namely, the Irkutsk incoherent scatter radar at VHF (IISR, 154-162 MHz) and the Ekaterinburg coherent radar at HF (EKB, 8-20 MHz) are operated at the Institute of Solar-Terrestrial Physics, Siberian Branch of the Russian Academy of Sciences (ISTP SB RAS). The paper analyzes the results of joint observations of strong scattering (radio aurora) on June 8, 2015. To determine the geographical position of the radio aurora, we developed original methods that take into account both the features of the radio-wave propagation and the features of the radar antenna systems. It is shown that there are areas where the spatial position of the HF and VHF radio aurora can coincide. This permits using the radars as a single complex for diagnosis of the characteristics of small-scale high-latitude irregularities in the ionospheric E and F layers. A comparative analysis of the characteristics and temporal dynamics of the radio-aurora region in the HF and VHF ranges is performed. Using the DMSP satellite data, it has been shown that the radio aurora dynamics during this experiment with the EKB radar can be related with the spatial dynamics of the localized area with high electric field, which moves from high to equatorial latitudes. It is found that due to the broader field of view, radio aurora at the HF radar was stably observed 6-12 min earlier than at the VHF radar. This permits using the EKB radar data for prediction of the radio-aurora detection by the IISR radar.

Estimating the Mechanical Behavior of the Knee Joint during Crouch Gait: Implications for Real-Time Motor Control of Robotic Knee Orthoses

PubMed Central

Damiano, Diane L.; Bulea, Thomas C.

2016-01-01

Individuals with cerebral palsy frequently exhibit crouch gait, a pathological walking pattern characterized by excessive knee flexion. Knowledge of the knee joint moment during crouch gait is necessary for the design and control of assistive devices used for treatment. Our goal was to 1) develop statistical models to estimate knee joint moment extrema and dynamic stiffness during crouch gait, and 2) use the models to estimate the instantaneous joint moment during weight-acceptance. We retrospectively computed knee moments from 10 children with crouch gait and used stepwise linear regression to develop statistical models describing the knee moment features. The models explained at least 90% of the response value variability: peak moment in early (99%) and late (90%) stance, and dynamic stiffness of weight-acceptance flexion (94%) and extension (98%). We estimated knee extensor moment profiles from the predicted dynamic stiffness and instantaneous knee angle. This approach captured the timing and shape of the computed moment (root-mean-squared error: 2.64 Nm); including the predicted early-stance peak moment as a correction factor improved model performance (root-mean-squared error: 1.37 Nm). Our strategy provides a practical, accurate method to estimate the knee moment during crouch gait, and could be used for real-time, adaptive control of robotic orthoses. PMID:27101612

Columnar joint morphology and cooling rate: A starch-water mixture experiment

NASA Astrophysics Data System (ADS)

Toramaru, A.; Matsumoto, T.

2004-02-01

An analogue experiment using a starch-water mixture has been carried out in order to understand the effect of cooling rate on the morphological characteristics of a basalt columnar joint. If the contraction of material is essential for the formation of columnar joint structure, the water loss rate by desiccation (hereafter referred to as desiccation rate) in the experiment is analogous to the cooling rate in solidifying basalt. In the experiment the desiccation rate is controlled by varying the distance between the starch-water mixture and a lamp used as the heat source. We find that there are three regimes in the relation between joint formation and desiccation rate: (1) At desiccation rates higher than ˜1.4 × 10-2 (g cm-2 h-1) (normal columnar joint regime), the average cross-sectional area S of a column is inversely proportional to the average desiccation rate, (i.e., S ∝ -δ, with δ = 1). (2) Between that desiccation rate and a critical desiccation rate, 0.8 × 10-2 (g/cm2h), S approaches infinity as decreases close to a critical desiccation rate (i.e., exponent δ monotonically increases from unity to infinity) (critical regime). (3) Below the critical desiccation rate, no columnar structure forms (no columnar joint regime forms). Applying the present experimental result to the formation of basalt column, the basalt columnar cross-sectional area is inversely proportional to the cooling rate with factors including elasticity, crack growth coefficient, thermal expansion, glass transition temperature, and crack density ratio at stress maximum. Also, it can be predicted that there exists a critical cooling rate below which the columnar joint does not form; the presence of a critical regime between the normal columnar jointing and no columnar jointing during a certain cooling rate range can also be predicted. We find that at higher cooling rate the preferred column shape is a pentagon, whereas at lower cooling rate it is a hexagon.

Dynamic Consent: a potential solution to some of the challenges of modern biomedical research.

PubMed

Budin-Ljøsne, Isabelle; Teare, Harriet J A; Kaye, Jane; Beck, Stephan; Bentzen, Heidi Beate; Caenazzo, Luciana; Collett, Clive; D'Abramo, Flavio; Felzmann, Heike; Finlay, Teresa; Javaid, Muhammad Kassim; Jones, Erica; Katić, Višnja; Simpson, Amy; Mascalzoni, Deborah

2017-01-25

Innovations in technology have contributed to rapid changes in the way that modern biomedical research is carried out. Researchers are increasingly required to endorse adaptive and flexible approaches to accommodate these innovations and comply with ethical, legal and regulatory requirements. This paper explores how Dynamic Consent may provide solutions to address challenges encountered when researchers invite individuals to participate in research and follow them up over time in a continuously changing environment. An interdisciplinary workshop jointly organised by the University of Oxford and the COST Action CHIP ME gathered clinicians, researchers, ethicists, lawyers, research participants and patient representatives to discuss experiences of using Dynamic Consent, and how such use may facilitate the conduct of specific research tasks. The data collected during the workshop were analysed using a content analysis approach. Dynamic Consent can provide practical, sustainable and future-proof solutions to challenges related to participant recruitment, the attainment of informed consent, participant retention and consent management, and may bring economic efficiencies. Dynamic Consent offers opportunities for ongoing communication between researchers and research participants that can positively impact research. Dynamic Consent supports inter-sector, cross-border approaches and large scale data-sharing. Whilst it is relatively easy to set up and maintain, its implementation will require that researchers re-consider their relationship with research participants and adopt new procedures.

Dynamic analysis of astronaut motions in microgravity: Applications for Extravehicular Activity (EVA)

NASA Technical Reports Server (NTRS)

Newman, Dava J.

1995-01-01

Simulations of astronaut motions during extravehicular activity (EVA) tasks were performed using computational multibody dynamics methods. The application of computational dynamic simulation to EVA was prompted by the realization that physical microgravity simulators have inherent limitations: viscosity in neutral buoyancy tanks; friction in air bearing floors; short duration for parabolic aircraft; and inertia and friction in suspension mechanisms. These limitations can mask critical dynamic effects that later cause problems during actual EVA's performed in space. Methods of formulating dynamic equations of motion for multibody systems are discussed with emphasis on Kane's method, which forms the basis of the simulations presented herein. Formulation of the equations of motion for a two degree of freedom arm is presented as an explicit example. The four basic steps in creating the computational simulations were: system description, in which the geometry, mass properties, and interconnection of system bodies are input to the computer; equation formulation based on the system description; inverse kinematics, in which the angles, velocities, and accelerations of joints are calculated for prescribed motion of the endpoint (hand) of the arm; and inverse dynamics, in which joint torques are calculated for a prescribed motion. A graphical animation and data plotting program, EVADS (EVA Dynamics Simulation), was developed and used to analyze the results of the simulations that were performed on a Silicon Graphics Indigo2 computer. EVA tasks involving manipulation of the Spartan 204 free flying astronomy payload, as performed during Space Shuttle mission STS-63 (February 1995), served as the subject for two dynamic simulations. An EVA crewmember was modeled as a seven segment system with an eighth segment representing the massive payload attached to the hand. For both simulations, the initial configuration of the lower body (trunk, upper leg, and lower leg) was a neutral microgravity posture. In the first simulation, the payload was manipulated around a circular trajectory of 0.15 m radius in 10 seconds. It was found that the wrist joint theoretically exceeded its ulnal deviation limit by as much as 49. 8 deg and was required to exert torques as high as 26 N-m to accomplish the task, well in excess of the wrist physiological limit of 12 N-m. The largest torque in the first simulation, 52 N-m, occurred in the ankle joint. To avoid these problems, the second simulation placed the arm in a more comfortable initial position and the radius and speed of the circular trajectory were reduced by half. As a result, the joint angles and torques were reduced to values well within their physiological limits. In particular, the maximum wrist torque for the second simulation was only 3 N-m and the maximum ankle torque was only 6 N-m.

Sonomyography Analysis on Thickness of Skeletal Muscle During Dynamic Contraction Induced by Neuromuscular Electrical Stimulation: A Pilot Study.

PubMed

Qiu, Shuang; Feng, Jing; Xu, Jiapeng; Xu, Rui; Zhao, Xin; Zhou, Peng; Qi, Hongzhi; Zhang, Lixin; Ming, Dong

2017-01-01

Neuromuscular electrical stimulation (NMES) that stimulates skeletal muscles to induce contractions has been widely applied to restore functions of paralyzed muscles. However, the architectural changes of stimulated muscles induced by NMES are still not well understood. The present study applies sonomyography (SMG) to evaluate muscle architecture under NMES-induced and voluntary movements. The quadriceps muscles of seven healthy subjects were tested for eight cycles during an extension exercise of the knee joint with/without NMES, and SMG and the knee joint angle were recorded during the process of knee extension. A least squares support vector machine (LS-SVM) LS-SVM model was developed and trained using the data sets of six cycles collected under NMES, while the remaining data was used to test. Muscle thickness changes were extracted from ultrasound images and compared between NMES-induced and voluntary contractions, and LS-SVM was used to model a relationship between dynamical knee joint angles and SMG signals. Muscle thickness showed to be significantly correlated with joint angle in NMES-induced contractions, and a significant negative correlation was observed between Vastus intermedius (VI) thickness and rectus femoris (RF) thickness. In addition, there was a significant difference between voluntary and NMES-induced contractions . The LS-SVM model based on RF thickness and knee joint angle provided superior performance compared with the model based on VI thickness and knee joint angle or total thickness and knee joint angle. This suggests that a strong relation exists between the RF thickness and knee joint angle. These results provided direct evidence for the potential application of RF thickness in optimizing NMES system as well as measuring muscle state under NMES.

Biomechanics and muscle coordination of human walking. Part I: introduction to concepts, power transfer, dynamics and simulations.

PubMed

Zajac, Felix E; Neptune, Richard R; Kautz, Steven A

2002-12-01

Current understanding of how muscles coordinate walking in humans is derived from analyses of body motion, ground reaction force and EMG measurements. This is Part I of a two-part review that emphasizes how muscle-driven dynamics-based simulations assist in the understanding of individual muscle function in walking, especially the causal relationships between muscle force generation and walking kinematics and kinetics. Part I reviews the strengths and limitations of Newton-Euler inverse dynamics and dynamical simulations, including the ability of each to find the contributions of individual muscles to the acceleration/deceleration of the body segments. We caution against using the concept of biarticular muscles transferring power from one joint to another to infer muscle coordination principles because energy flow among segments, even the adjacent segments associated with the joints, cannot be inferred from computation of joint powers and segmental angular velocities alone. Rather, we encourage the use of dynamical simulations to perform muscle-induced segmental acceleration and power analyses. Such analyses have shown that the exchange of segmental energy caused by the forces or accelerations induced by a muscle can be fundamentally invariant to whether the muscle is shortening, lengthening, or neither. How simulation analyses lead to understanding the coordination of seated pedaling, rather than walking, is discussed in this first part because the dynamics of pedaling are much simpler, allowing important concepts to be revealed. We elucidate how energy produced by muscles is delivered to the crank through the synergistic action of other non-energy producing muscles; specifically, that a major function performed by a muscle arises from the instantaneous segmental accelerations and redistribution of segmental energy throughout the body caused by its force generation. Part II reviews how dynamical simulations provide insight into muscle coordination of walking.

Conformational Dynamics of Mechanically Compliant DNA Nanostructures from Coarse-Grained Molecular Dynamics Simulations.

PubMed

Shi, Ze; Castro, Carlos E; Arya, Gaurav

2017-05-23

Structural DNA nanotechnology, the assembly of rigid 3D structures of complex yet precise geometries, has recently been used to design dynamic, mechanically compliant nanostructures with tunable equilibrium conformations and conformational distributions. Here we use coarse-grained molecular dynamics simulations to provide insights into the conformational dynamics of a set of mechanically compliant DNA nanostructures-DNA hinges that use single-stranded DNA "springs" to tune the equilibrium conformation of a layered double-stranded DNA "joint" connecting two stiff "arms" constructed from DNA helix bundles. The simulations reproduce the experimentally measured equilibrium angles between hinge arms for a range of hinge designs. The hinges are found to be structurally stable, except for some fraying of the open ends of the DNA helices comprising the hinge arms and some loss of base-pairing interactions in the joint regions coinciding with the crossover junctions, especially in hinges designed to exhibit a small bending angle that exhibit large local stresses resulting in strong kinks in their joints. Principal component analysis reveals that while the hinge dynamics are dominated by bending motion, some twisting and sliding of hinge arms relative to each other also exists. Forced deformation of the hinges reveals distinct bending mechanisms for hinges with short, inextensible springs versus those with longer, more extensible springs. Lastly, we introduce an approach for rapidly predicting equilibrium hinge angles from individual force-deformation behaviors of its single- and double-stranded DNA components. Taken together, these results demonstrate that coarse-grained modeling is a promising approach for designing, predicting, and studying the dynamics of compliant DNA nanostructures, where conformational fluctuations become important, multiple deformation mechanisms exist, and continuum approaches may not yield accurate properties.

Emotional engagements predict and enhance social cognition in young chimpanzees.

PubMed

Bard, Kim A; Bakeman, Roger; Boysen, Sarah T; Leavens, David A

2014-09-01

Social cognition in infancy is evident in coordinated triadic engagements, that is, infants attending jointly with social partners and objects. Current evolutionary theories of primate social cognition tend to highlight species differences in cognition based on human-unique cooperative motives. We consider a developmental model in which engagement experiences produce differential outcomes. We conducted a 10-year-long study in which two groups of laboratory-raised chimpanzee infants were given quantifiably different engagement experiences. Joint attention, cooperativeness, affect, and different levels of cognition were measured in 5- to 12-month-old chimpanzees, and compared to outcomes derived from a normative human database. We found that joint attention skills significantly improved across development for all infants, but by 12 months, the humans significantly surpassed the chimpanzees. We found that cooperativeness was stable in the humans, but by 12 months, the chimpanzee group given enriched engagement experiences significantly surpassed the humans. Past engagement experiences and concurrent affect were significant unique predictors of both joint attention and cooperativeness in 5- to 12-month-old chimpanzees. When engagement experiences and concurrent affect were statistically controlled, joint attention and cooperation were not associated. We explain differential social cognition outcomes in terms of the significant influences of previous engagement experiences and affect, in addition to cognition. Our study highlights developmental processes that underpin the emergence of social cognition in support of evolutionary continuity. © 2014 The Authors. Developmental Science Published by John Wiley & Sons Ltd.

Effect of Multipass TIG and Activated TIG Welding Process on the Thermo-Mechanical Behavior of 316LN Stainless Steel Weld Joints

NASA Astrophysics Data System (ADS)

Ganesh, K. C.; Balasubramanian, K. R.; Vasudevan, M.; Vasantharaja, P.; Chandrasekhar, N.

2016-04-01

The primary objective of this work was to develop a finite element model to predict the thermo-mechanical behavior of an activated tungsten inert gas (ATIG)-welded joint. The ATIG-welded joint was fabricated using 10 mm thickness of 316LN stainless steel plates in a single pass. To distinguish the merits of ATIG welding process, it was compared with manual multipass tungsten inert gas (MPTIG)-welded joint. The ATIG-welded joint was fabricated with square butt edge configuration using an activating flux developed in-house. The MPTIG-welded joint was fabricated in thirteen passes with V-groove edge configuration. The finite element model was developed to predict the transient temperature, residual stress, and distortion of the welded joints. Also, microhardness, impact toughness, tensile strength, ferrite measurement, and microstructure were characterized. Since most of the recent publications of ATIG-welded joint was focused on the molten weld pool dynamics, this research work gives an insight on the thermo-mechanical behavior of ATIG-welded joint over MPTIG-welded joint.

Ohio Route 50 joint sealant experiment : research implementation plan.

DOT National Transportation Integrated Search

2005-05-01

Research in the state of Wisconsin over the past forty years has found no noticeable difference in : performance between jointed concrete pavement (JCP) constructed with a sealed contraction joint and : JCP constructed with a single, narrow, unsealed...

Dynamic virtual fixture on the Euclidean group for admittance-type manipulator in deforming environments.

PubMed

Zhang, Dongwen; Zhu, Qingsong; Xiong, Jing; Wang, Lei

2014-04-27

In a deforming anatomic environment, the motion of an instrument suffers from complex geometrical and dynamic constraints, robot assisted minimally invasive surgery therefore requires more sophisticated skills for surgeons. This paper proposes a novel dynamic virtual fixture (DVF) to enhance the surgical operation accuracy of admittance-type medical robotics in the deforming environment. A framework for DVF on the Euclidean Group SE(3) is presented, which unites rotation and translation in a compact form. First, we constructed the holonomic/non-holonomic constraints, and then searched for the corresponded reference to make a distinction between preferred and non-preferred directions. Second, different control strategies are employed to deal with the tasks along the distinguished directions. The desired spatial compliance matrix is synthesized from an allowable motion screw set to filter out the task unrelated components from manual input, the operator has complete control over the preferred directions; while the relative motion between the surgical instrument and the anatomy structures is actively tracked and cancelled, the deviation relative to the reference is compensated jointly by the operator and DVF controllers. The operator, haptic device, admittance-type proxy and virtual deforming environment are involved in a hardware-in-the-loop experiment, human-robot cooperation with the assistance of DVF controller is carried out on a deforming sphere to simulate beating heart surgery, performance of the proposed DVF on admittance-type proxy is evaluated, and both human factors and control parameters are analyzed. The DVF can improve the dynamic properties of human-robot cooperation in a low-frequency (0 ~ 40 rad/sec) deforming environment, and maintain synergy of orientation and translation during the operation. Statistical analysis reveals that the operator has intuitive control over the preferred directions, human and the DVF controller jointly control the motion along the non-preferred directions, the target deformation is tracked actively. The proposed DVF for an admittance-type manipulator is capable of assisting the operator to deal with skilled operations in a deforming environment.

A Modelling Method of Bolt Joints Based on Basic Characteristic Parameters of Joint Surfaces

NASA Astrophysics Data System (ADS)

Yuansheng, Li; Guangpeng, Zhang; Zhen, Zhang; Ping, Wang

2018-02-01

Bolt joints are common in machine tools and have a direct impact on the overall performance of the tools. Therefore, the understanding of bolt joint characteristics is essential for improving machine design and assembly. Firstly, According to the experimental data obtained from the experiment, the stiffness curve formula was fitted. Secondly, a finite element model of unit bolt joints such as bolt flange joints, bolt head joints, and thread joints was constructed, and lastly the stiffness parameters of joint surfaces were implemented in the model by the secondary development of ABAQUS. The finite element model of the bolt joint established by this method can simulate the contact state very well.

Deployable robotic woven wire structures and joints for space applications

NASA Technical Reports Server (NTRS)

Shahinpoor, MO; Smith, Bradford

1991-01-01

Deployable robotic structures are basically expandable and contractable structures that may be transported or launched to space in a compact form. These structures may then be intelligently deployed by suitable actuators. The deployment may also be done by means of either airbag or spring-loaded typed mechanisms. The actuators may be pneumatic, hydraulic, ball-screw type, or electromagnetic. The means to trigger actuation may be on-board EPROMS, programmable logic controllers (PLCs) that trigger actuation based on some input caused by the placement of the structure in the space environment. The actuation may also be performed remotely by suitable remote triggering devices. Several deployable woven wire structures are examined. These woven wire structures possess a unique form of joint, the woven wire joint, which is capable of moving and changing its position and orientation with respect to the structure itself. Due to the highly dynamic and articulate nature of these joints the 3-D structures built using them are uniquely and highly expandable, deployable, and dynamic. The 3-D structure naturally gives rise to a new generation of deployable three-dimensional spatial structures.

Dynamic testing of a two-dimensional box truss beam

NASA Technical Reports Server (NTRS)

White, Charles W.

1987-01-01

Testing to determine the effects of joint freeplay and pretensioning of diagonal members on the dynamic characteristics of a two-dimensional box truss beam was conducted. The test article was ten bays of planar truss suspended by long wires at each joint. Each bay measured 2 meters per side. Pins of varying size were used to simulate various joint freeplay conditions. Single-point random excitation was the primary method of test. The rational fraction polynomial method was used to extract modal characteristics from test data. A finite element model of the test article was generated from which modal characteristics were predicted. These were compared with those obtained from tests. With the exception of the fundamental mode, correlation of theoretical and experimental results was poor, caused by the resonant coupling of local truss member bending modes with global truss beam modes. This coupling introduced many modes in the frequency range of interest whose frequencies were sensitive to joint boundary conditions. It was concluded that local/global coupling must be avoided in the frequency range where accurate modal characteristics are required.

Clustered multistate models with observation level random effects, mover-stayer effects and dynamic covariates: modelling transition intensities and sojourn times in a study of psoriatic arthritis.

PubMed

Yiu, Sean; Farewell, Vernon T; Tom, Brian D M

2018-02-01

In psoriatic arthritis, it is important to understand the joint activity (represented by swelling and pain) and damage processes because both are related to severe physical disability. The paper aims to provide a comprehensive investigation into both processes occurring over time, in particular their relationship, by specifying a joint multistate model at the individual hand joint level, which also accounts for many of their important features. As there are multiple hand joints, such an analysis will be based on the use of clustered multistate models. Here we consider an observation level random-effects structure with dynamic covariates and allow for the possibility that a subpopulation of patients is at minimal risk of damage. Such an analysis is found to provide further understanding of the activity-damage relationship beyond that provided by previous analyses. Consideration is also given to the modelling of mean sojourn times and jump probabilities. In particular, a novel model parameterization which allows easily interpretable covariate effects to act on these quantities is proposed.

Joint Control: A Discussion of Recent Research

PubMed Central

Palmer, David C

2006-01-01

The discrimination of the onset of joint control is an important interpretive tool in explaining matching behavior and other complex phenomena, but the difficulty of getting experimental control of all relevant variables stands in the way of a definitive experiment. The studies in the present issue of The Analysis of Verbal Behavior illustrate how modest experiments can take their place in a web of interpretation to make a strong case that joint control is a necessary element of such phenomena. PMID:22477357

Joint University Program for Air Transportation Research, 1986

NASA Technical Reports Server (NTRS)

Morrell, Frederick R. (Compiler)

1988-01-01

The research conducted under the NASA/FAA sponsored Joint University Program for Air Transportation Research is summarized. The Joint University Program is a coordinated set of three grants sponsored by NASA and the FAA, one each with the Mass. Inst. of Tech., Ohio Univ., and Princeton Univ. Completed works, status reports, and bibliographies are presented for research topics, which include computer science, guidance and control theory and practice, aircraft performance, flight dynamics, and applied experimental psychology. An overview of activities is presented.

Cyclic deformations in the Opalinus clay: a laboratory experiment

NASA Astrophysics Data System (ADS)

Huber, Emanuel; Huggenberger, Peter; Möri, Andreas; Meier, Edi

2015-04-01

The influence of tunnel climate on deformation cycles of joint openings and closings is often observed immediately after excavation. At the EZ-B niche in the Mt. Terri rock laboratory (Switzerland), a cyclic deformation of the shaly Opalinus clay has been monitored for several years. The deformation cycles of the joints parallel to the clay bedding planes correlate with seasonal variations in relative humidity of the air in the niche. In winter, when the relative humidity is the lowest (down to 65%), the joints open as the clay volume decreases, whereas they tend to close in the summer when the relative humidity reaches up to 100%. Furthermore, in situ measurements have shown the trend of an increasingly smaller aperture of joints with time. A laboratory experiment was carried out to reproduce the observed cyclic deformation in a climate chamber using a core sample of Opalinus clay. The main goal of the experiment was to investigate the influence of the relative humidity on the deformation of the Opalinus clay while excluding the in situ effects (e.g. confining stress). The core sample of Opalinus clay was put into a closed ended PVC tube and the space between the sample and the tube was filled with resin. Then, the sample (size: 28 cm × 14 cm × 6.5 cm) was cut in half lengthways and the open end was cut, so that the half-core sample could move in one direction. The mounted sample was exposed to wetting and drying cycles in a climate chamber. Air temperature, air humidity and sample weight were continuously recorded. Photographs taken at regular time intervals by a webcam allowed the formation/deformation of cracks on the surface of the sample to be monitored. A crackmeter consisting of a double-plate capacitor attached to the core sample was developed to measure the dynamics of the crack opening and closing. Preliminary results show that: - Deformation movements during different climate cycles can be visualized with the webcam - The crackmeter signal gives a relatively precise response for relative humidity below 80% - The sample weight variations are clearly related to the climatic conditions (temperature and relative humidity) and associated with deformation of the sample (widening and narrowing of the cracks) - The control of the relative humidity in the climate chamber turned out to be difficult in a laboratory without climate conditioning, especially during summer time

The responses of muscle spindles to small, slow movements in passive muscle and during fusimotor activity.

PubMed

Wise, A K; Gregory, J E; Proske, U

1999-03-06

We have previously shown that movement detection thresholds at the human elbow joint were less than a degree of joint rotation in the passive limb but were higher if they were measured while subjects co-contracted elbow muscles [A.K. Wise, J.E. Gregory, U. Proske, J. Physiol., 508 (1998) 325-330]. Here we report observations on the responses of muscle spindles of the soleus muscle of the anaesthetised cat to determine their ability to signal small length changes in the passive muscle and during a contraction, under conditions resembling those of the human experiments. After appropriate conditioning of the muscle to control for history effects, primary endings of muscle spindles showed thresholds to ramp stretch at 20 micrometers s-1 of between less than 5 micrometers and 15 micrometers, which translates to 0.05 degrees -0.15 degrees of human elbow joint rotation. Thresholds were much higher following conditioning to introduce slack in the muscle. Since during a voluntary contraction there is likely to be alpha:gamma co-activation, responses of spindles were also recorded during slow stretches (100 micrometers at 20 micrometers s-1) during static fusimotor stimulation, dynamic fusimotor stimulation, combined fusimotor stimulation and fusimotor plus skeletomotor stimulation. Invariably, responses to passive stretch were larger than during motor stimulation. It is concluded that spindles are sensitive enough to signal fractions of a degree of elbow joint rotation and that the rise in threshold observed during a voluntary contraction may be accounted for by the actions of fusimotor and skeletomotor axons on spindle stretch responses. Copyright 1999 Elsevier Science B.V.

A numerical study on the limitations of modal Iwan models for impulsive excitations

NASA Astrophysics Data System (ADS)

Lacayo, Robert M.; Deaner, Brandon J.; Allen, Matthew S.

2017-03-01

Structures with mechanical joints are difficult to model accurately. Even if the natural frequencies of the system remain essentially constant, the damping introduced by the joints is often observed to change dramatically with amplitude. Although models for individual joints have been employed with some success, accurately modeling a structure with many joints remains a significant obstacle. To this end, Segalman proposed a modal Iwan model, which simplifies the analysis by modeling a system with a linear superposition of weakly-nonlinear, uncoupled single degree-of-freedom systems or modes. Given a simulation model with discrete joints, one can identify the model for each mode by selectively exciting each mode one at a time and observing how the transient response decays. However, in the environment of interest several modes may be excited simultaneously, such as in an experiment when an impulse is applied at a discrete point. In this work, the modal Iwan model framework is assessed numerically to understand how well it captures the dynamic response of typical structures with joints when they are excited with impulsive forces applied at point locations. This is done by comparing the effective natural frequency and modal damping of the uncoupled modal models with those of truth models that include nonlinear modal coupling. These concepts are explored for two structures, a simple spring-mass system and a finite element model of a beam, both of which contain physical Iwan elements to model joint nonlinearity. The results show that modal Iwan models can effectively capture the variations in frequency and damping with amplitude, which, for damping, can increase by as much as two orders of magnitude in the microslip regime. However, even in the microslip regime the accuracy of a modal Iwan model is found to depend on whether the mode in question is dominant in the response; in some cases the effective damping that the uncoupled model predicts is found to be in error by tens of percent. Nonetheless, the modal model captures the response qualitatively and is still far superior to a linear model.

Application of automatic threshold in dynamic target recognition with low contrast

NASA Astrophysics Data System (ADS)

Miao, Hua; Guo, Xiaoming; Chen, Yu

2014-11-01

Hybrid photoelectric joint transform correlator can realize automatic real-time recognition with high precision through the combination of optical devices and electronic devices. When recognizing targets with low contrast using photoelectric joint transform correlator, because of the difference of attitude, brightness and grayscale between target and template, only four to five frames of dynamic targets can be recognized without any processing. CCD camera is used to capture the dynamic target images and the capturing speed of CCD is 25 frames per second. Automatic threshold has many advantages like fast processing speed, effectively shielding noise interference, enhancing diffraction energy of useful information and better reserving outline of target and template, so this method plays a very important role in target recognition with optical correlation method. However, the automatic obtained threshold by program can not achieve the best recognition results for dynamic targets. The reason is that outline information is broken to some extent. Optimal threshold is obtained by manual intervention in most cases. Aiming at the characteristics of dynamic targets, the processing program of improved automatic threshold is finished by multiplying OTSU threshold of target and template by scale coefficient of the processed image, and combining with mathematical morphology. The optimal threshold can be achieved automatically by improved automatic threshold processing for dynamic low contrast target images. The recognition rate of dynamic targets is improved through decreased background noise effect and increased correlation information. A series of dynamic tank images with the speed about 70 km/h are adapted as target images. The 1st frame of this series of tanks can correlate only with the 3rd frame without any processing. Through OTSU threshold, the 80th frame can be recognized. By automatic threshold processing of the joint images, this number can be increased to 89 frames. Experimental results show that the improved automatic threshold processing has special application value for the recognition of dynamic target with low contrast.

Three-dimensional knee joint contact forces during walking in unilateral transtibial amputees.

PubMed

Silverman, Anne K; Neptune, Richard R

2014-08-22

Individuals with unilateral transtibial amputations have greater prevalence of osteoarthritis in the intact knee joint relative to the residual leg and non-amputees, but the cause of this greater prevalence is unclear. The purpose of this study was to compare knee joint contact forces and the muscles contributing to these forces between amputees and non-amputees during walking using forward dynamics simulations. We predicted that the intact knee contact forces would be higher than those of the residual leg and non-amputees. In the axial and mediolateral directions, the intact and non-amputee legs had greater peak tibio-femoral contact forces and impulses relative to the residual leg. The peak axial contact force was greater in the intact leg relative to the non-amputee leg, but the stance phase impulse was greater in the non-amputee leg. The vasti and hamstrings muscles in early stance and gastrocnemius in late stance were the largest contributors to the joint contact forces in the non-amputee and intact legs. Through dynamic coupling, the soleus and gluteus medius also had large contributions, even though they do not span the knee joint. In the residual leg, the prosthesis had large contributions to the joint forces, similar to the soleus in the intact and non-amputee legs. These results identify the muscles that contribute to knee joint contact forces during transtibial amputee walking and suggest that the peak knee contact forces may be more important than the knee contact impulses in explaining the high prevalence of intact leg osteoarthritis. Copyright © 2014 Elsevier Ltd. All rights reserved.

ISM simulations: an overview of models

NASA Astrophysics Data System (ADS)

de Avillez, M. A.; Breitschwerdt, D.; Asgekar, A.; Spitoni, E.

2015-03-01

Until recently the dynamical evolution of the interstellar medium (ISM) was simulated using collisional ionization equilibrium (CIE) conditions. However, the ISM is a dynamical system, in which the plasma is naturally driven out of equilibrium due to atomic and dynamic processes operating on different timescales. A step forward in the field comprises a multi-fluid approach taking into account the joint thermal and dynamical evolutions of the ISM gas.

Influence of the parameters of a high-frequency acoustic wave on the structure, properties, and plastic flow of metal in the zone of a joint of materials welded by ultrasound-assisted explosive welding

NASA Astrophysics Data System (ADS)

Peev, A. P.; Kuz'min, S. V.; Lysak, V. I.; Kuz'min, E. V.; Dorodnikov, A. N.

2017-05-01

The results of an investigation of the influence of the parameters of high-frequency acoustic wave on the structure and properties of the zone of joint of homogeneous metals bonded by explosive welding under the action of ultrasound have been presented. The influence of the frequency and amplitude of ultrasonic vibrations on the structure and properties of the explosively welded joints compared with the samples welded without the application of ultrasound has been established. The action of high-frequency acoustic waves on the metal leads to a reduction in the dynamic yield stress, which changes the properties of the surface layers of the metal and the conditions of the formation of the joint of the colliding plates upon the explosive welding. It has been shown that the changes in the length and amplitude of waves that arise in the weld joint upon the explosive welding with the simultaneous action of ultrasonic vibrations are connected with a decrease in the magnitude of the deforming pulse and time of action of the compressive stresses that exceed the dynamic yield stress beyond the point of contact.

Brief: Field measurements of casing tension forces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quigley, M.S.; Lewis, D.B.; Boswell, R.S.

1995-02-01

Tension forces acting on individual casing joints were accurately measured during installation of 10,158 ft of 9 5/8-in. {times} 47-lbm/ft casing and 11,960 ft of 11 7/8-in. {times} 71.8-lbm/ft casing. A unique casing load table (CLT) weighed the casing string after the addition of each casing joint. Strain gauges attached inside the pin ends of instrumented casing joints (ICJ`s) directly measured tension force on those joints. A high-speed computer data-acquisition system (DAS) automatically recorded data from all the sensors. Several casing joints were intentionally subjected to extreme deceleration to determine upper limits for dynamic tension forces. Data from these testsmore » clearly show effects of wellbore friction and casing handling conditions. In every case, tension forces in the casing during maximum deceleration were considerably less than expected. In some cases, the highest tension forces occurred when the casing lifted out of the slips. Peak tension forces caused by setting the casing slips were typically no more than 5% greater than tension forces in the casing at rest. This dynamic amplification was far less than the 60% value used in the previous casing design method. Reducing the safety factor for installation loads has permitted use of lighter, less-expensive casing than dictated by older design criteria.« less

Management of chronic unstable acromioclavicular joint injuries.

PubMed

Cisneros, Luis Natera; Reiriz, Juan Sarasquete

2017-12-01

The acromioclavicular joint represents the link between the clavicle and the scapula, which is responsible for the synchronized dynamic of the shoulder girdle. Chronic acromioclavicular joint instability involves changes in the orientation of the scapula, which provokes cinematic alterations that might result in chronic pain. Several surgical strategies for the management of patients with chronic and symptomatic acromioclavicular joint instability have been described. The range of possibilities includes anatomical and non-anatomical techniques, open and arthroscopy-assisted procedures, and biological and synthetic grafts. Surgical management of chronic acromioclavicular joint instability should involve the reconstruction of the torn ligaments because it is accepted that from three weeks after the injury, these structures may lack healing potential. Here, we provide a review of the literature regarding the management of chronic acromioclavicular joint instability. Expert opinion, Level V.

Involuntary Neuromuscular Coupling between the Thumb and Finger of Stroke Survivors during Dynamic Movement.

PubMed

Jones, Christopher L; Kamper, Derek G

2018-01-01

Finger-thumb coordination is crucial to manual dexterity but remains incompletely understood, particularly following neurological injury such as stroke. While being controlled independently, the index finger and thumb especially must work in concert to perform a variety of tasks requiring lateral or palmar pinch. The impact of stroke on this functionally critical sensorimotor control during dynamic tasks has been largely unexplored. In this study, we explored finger-thumb coupling during close-open pinching motions in stroke survivors with chronic hemiparesis. Two types of perturbations were applied randomly to the index with a novel Cable-Actuated Finger Exoskeleton: a sudden joint acceleration stretching muscle groups of the index finger and a sudden increase in impedance in selected index finger joint(s). Electromyographic signals for specific thumb and index finger muscles, thumb tip trajectory, and index finger joint angles were recorded during each trial. Joint angle perturbations invoked reflex responses in the flexor digitorum superficialis (FDS), first dorsal interossei (FDI), and extensor digitorum communis muscles of the index finger and heteronymous reflex responses in flexor pollicis brevis of the thumb ( p  < 0.017). Phase of movement played a role as a faster peak reflex response was observed in FDI during opening than during closing ( p  < 0.002) and direction of perturbations resulted in shorter reflex times for FDS and FDI ( p  < 0.012) for extension perturbations. Surprisingly, when index finger joint impedance was suddenly increased, thumb tip movement was substantially increased, from 2 to 10 cm ( p  < 0.001). A greater effect was seen during the opening phase ( p  < 0.044). Thus, involuntary finger-thumb coupling was present during dynamic movement, with perturbation of the index finger impacting thumb activity. The degree of coupling modulated with the phase of motion. These findings reveal a potential mechanism for direct intervention to improve poststroke hand mobility and provide insight on prospective neurologically oriented therapies.

Involuntary Neuromuscular Coupling between the Thumb and Finger of Stroke Survivors during Dynamic Movement

PubMed Central

Jones, Christopher L.; Kamper, Derek G.

2018-01-01

Finger–thumb coordination is crucial to manual dexterity but remains incompletely understood, particularly following neurological injury such as stroke. While being controlled independently, the index finger and thumb especially must work in concert to perform a variety of tasks requiring lateral or palmar pinch. The impact of stroke on this functionally critical sensorimotor control during dynamic tasks has been largely unexplored. In this study, we explored finger–thumb coupling during close–open pinching motions in stroke survivors with chronic hemiparesis. Two types of perturbations were applied randomly to the index with a novel Cable-Actuated Finger Exoskeleton: a sudden joint acceleration stretching muscle groups of the index finger and a sudden increase in impedance in selected index finger joint(s). Electromyographic signals for specific thumb and index finger muscles, thumb tip trajectory, and index finger joint angles were recorded during each trial. Joint angle perturbations invoked reflex responses in the flexor digitorum superficialis (FDS), first dorsal interossei (FDI), and extensor digitorum communis muscles of the index finger and heteronymous reflex responses in flexor pollicis brevis of the thumb (p < 0.017). Phase of movement played a role as a faster peak reflex response was observed in FDI during opening than during closing (p < 0.002) and direction of perturbations resulted in shorter reflex times for FDS and FDI (p < 0.012) for extension perturbations. Surprisingly, when index finger joint impedance was suddenly increased, thumb tip movement was substantially increased, from 2 to 10 cm (p < 0.001). A greater effect was seen during the opening phase (p < 0.044). Thus, involuntary finger–thumb coupling was present during dynamic movement, with perturbation of the index finger impacting thumb activity. The degree of coupling modulated with the phase of motion. These findings reveal a potential mechanism for direct intervention to improve poststroke hand mobility and provide insight on prospective neurologically oriented therapies. PMID:29545767

Toddlers' Joint Engagement Experience Facilitates Preschoolers' Acquisition of Theory of Mind

ERIC Educational Resources Information Center

Nelson, P. Brooke; Adamson, Lauren B.; Bakeman, Roger

2008-01-01

Forty-two children participated in a longitudinal study that investigated the relationship between their joint engagement experience when toddlers and their development of theory of mind when preschoolers. Controlling for language comprehension at 30 months, higher preschool false belief scores were associated with more time in coordinated joint…

Expanding NASA and Roscosmos Scientific Collaboration on the International Space Station

NASA Technical Reports Server (NTRS)

Hasbrook, Pete

2016-01-01

The International Space Station (ISS) is a world-class laboratory orbiting in space. NASA and Roscosmos have developed a strong relationship through the ISS Program Partnership, working together and with the other ISS Partners for more than twenty years. Since 2013, based on a framework agreement between the Program Managers, NASA and Roscosmos are building a joint program of collaborative research on ISS. This international collaboration is developed and implemented in phases. Initially, members of the ISS Program Science Forum from NASA and TsNIIMash (representing Roscosmos) identified the first set of NASA experiments that could be implemented in the "near term". The experiments represented the research categories of Technology Demonstration, Microbiology, and Education. Through these experiments, the teams from the "program" and "operations" communities learned to work together to identify collaboration opportunities, establish agreements, and jointly plan and execute the experiments. The first joint scientific activity on ISS occurred in January 2014, and implementation of these joint experiments continues through present ISS operations. NASA and TsNIIMash have proceeded to develop "medium term" collaborations, where scientists join together to improve already-proposed experiments. A major success is the joint One-Year Mission on ISS, with astronaut Scott Kelly and cosmonaut Mikhail Kornienko, who returned from ISS in March, 2016. The teams from the NASA Human Research Program and the RAS Institute for Biomedical Problems built on their considerable experience to design joint experiments, learn to work with each other's protocols and processes, and share medical and research data. New collaborations are being developed between American and Russian scientists in complex fluids, robotics, rodent research and space biology, and additional human research. Collaborations are also being developed in Earth Remote Sensing, where scientists will share data from imaging systems mounted on ISS as well as other orbiting spacecraft to improve our understanding of the Earth and its climate. NASA and Roscosmos continue to encourage international scientific cooperation and expanded use of the ISS Laboratory. "Long-term", larger collaborations will achieve scientific objectives that no single national science team or agency can achieve on its own. The joint accomplishments achieved so far have paved the way for a stronger international scientific community and improved results and benefits from ISS.

Spacelab

NASA Image and Video Library

1992-09-01

Japanese astronaut, Mamoru Mohri, talks to Japanese students from the aft flight deck of the Space Shuttle Orbiter Endeavour during the Spacelab-J (SL-J) mission. The SL-J mission was a joint venture between NASA and the National Space Development Agency of Japan (NASDA) utilizing a marned Spacelab module. The mission conducted 24 materials science and 20 life science experiments, of which 35 were sponsored by NASDA, 7 by NASA, and two collaborative efforts. Materials science investigations covered such fields as biotechnology, electronic materials, fluid dynamics and transport phenomena, glasses and ceramics, metals and alloys, and acceleration measurements. Life sciences included experiments on human health, cell separation and biology, developmental biology, animal and human physiology and behavior, space radiation, and biological rhythms. Test subjects included the crew, Japanese koi fish (carp), cultured animal and plant cells, chicken embryos, fruit flies, fungi and plant seeds, and frogs and frog eggs. Spacelab-J was launched aboard the Space Shuttle Orbiter Endeavour on September 12, 1992.

Around Marshall

NASA Image and Video Library

1992-09-12

The science laboratory, Spacelab-J (SL-J), flown aboard the STS-47 flight was a joint venture between NASA and the National Space Development Agency of Japan (NASDA) utilizing a manned Spacelab module. The mission conducted 24 materials science and 20 life science experiments, of which 35 were sponsored by NASDA, 7 by NASA, and two collaborative efforts. Materials science investigations covered such fields as biotechnology, electronic materials, fluid dynamics and transport phenomena, glasses and ceramics, metals and alloys, and acceleration measurements. Life sciences included experiments on human health, cell separation and biology, developmental biology, animal and human physiology and behavior, space radiation, and biological rhythms. Test subjects included the crew, Japanese koi fish (carp), cultured animal and plant cells, chicken embryos, fruit flies, fungi and plant seeds, and frogs and frog eggs. Pictured in the Huntsville Operations Support Center (HOSC) Spacelab Payload Operations Control Center (SL POCC) of Marshall Space Flight Center (MSFC) are NASDA alternate payload specialists Dr. Doi and Dr. Mukai.

Joint U.S./Japan Conference on Adaptive Structures, 1st, Maui, HI, Nov. 13-15, 1990, Proceedings

NASA Technical Reports Server (NTRS)

Wada, Ben K. (Editor); Fanson, James L. (Editor); Miura, Koryo (Editor)

1991-01-01

The present volume of adaptive structures discusses the development of control laws for an orbiting tethered antenna/reflector system test scale model, the sizing of active piezoelectric struts for vibration suppression on a space-based interferometer, the control design of a space station mobile transporter with multiple constraints, and optimum configuration control of an intelligent truss structure. Attention is given to the formulation of full state feedback for infinite order structural systems, robustness issues in the design of smart structures, passive piezoelectric vibration damping, shape control experiments with a functional model for large optical reflectors, and a mathematical basis for the design optimization of adaptive trusses in precision control. Topics addressed include approaches to the optimal adaptive geometries of intelligent truss structures, the design of an automated manufacturing system for tubular smart structures, the Sandia structural control experiments, and the zero-gravity dynamics of space structures in parabolic aircraft flight.

Joint U.S./Japan Conference on Adaptive Structures, 1st, Maui, HI, Nov. 13-15, 1990, Proceedings

NASA Astrophysics Data System (ADS)

Wada, Ben K.; Fanson, James L.; Miura, Koryo

1991-11-01

The present volume of adaptive structures discusses the development of control laws for an orbiting tethered antenna/reflector system test scale model, the sizing of active piezoelectric struts for vibration suppression on a space-based interferometer, the control design of a space station mobile transporter with multiple constraints, and optimum configuration control of an intelligent truss structure. Attention is given to the formulation of full state feedback for infinite order structural systems, robustness issues in the design of smart structures, passive piezoelectric vibration damping, shape control experiments with a functional model for large optical reflectors, and a mathematical basis for the design optimization of adaptive trusses in precision control. Topics addressed include approaches to the optimal adaptive geometries of intelligent truss structures, the design of an automated manufacturing system for tubular smart structures, the Sandia structural control experiments, and the zero-gravity dynamics of space structures in parabolic aircraft flight.

Kinematic control of robot with degenerate wrist

NASA Technical Reports Server (NTRS)

Barker, L. K.; Moore, M. C.

1984-01-01

Kinematic resolved rate equations allow an operator with visual feedback to dynamically control a robot hand. When the robot wrist is degenerate, the computed joint angle rates exceed operational limits, and unwanted hand movements can result. The generalized matrix inverse solution can also produce unwanted responses. A method is introduced to control the robot hand in the region of the degenerate robot wrist. The method uses a coordinated movement of the first and third joints of the robot wrist to locate the second wrist joint axis for movement of the robot hand in the commanded direction. The method does not entail infinite joint angle rates.

Motivated information processing, strategic choice, and the quality of negotiated agreement.

PubMed

De Dreu, Carsten K W; Beersma, Bianca; Stroebe, Katherine; Euwema, Martin C

2006-06-01

The authors tested a motivated information-processing model of negotiation: To reach high joint outcomes, negotiators need a deep understanding of the task, which requires them to exchange information and to process new information systematically. All this depends on social motivation, epistemic motivation (EM), and their interaction. Indeed, when EM (manipulated by holding negotiators process accountability or not) was high rather than low and prosocial rather than proself, negotiators recall more cooperative than competitive tactics (Experiment 1), had more trust, and reached higher joint outcomes (Experiment 2). Experiment 3 showed that under high EM, negotiators who received cooperative, rather than competitive, tactics reached higher joint outcomes because they engaged in more problem solving. Under low EM, negotiators made more concessions and reached low joint outcomes. Implications for negotiation theory and for future work in this area are discussed. Copyright 2006 APA, all rights reserved.

Report on the Joint EU-US Workshop on Microbial Community Dynamics: Cooperation and Competition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wall, Judy D.

2013-07-01

The European Commission (EC)-United States (US) Task Force on Biotechnology Research has a longstanding joint Working Group on Biotechnology for the Environment whose mission is to foster collaborations between researchers in the European Union (EU) and US in the field of environmental biotechnology. A special focus of the Working Group is to increase scientific interchange between early career scientists in the US and EU. Such interactions initiate a foundation of respect and trust needed to develop long-term collaborations. In order to realize the full potential for the application of modern technologies to obtain a sustainable biosphere, it is vital tomore » create conduits for knowledge exchange among scientists worldwide engaged in environmental microbial biotechnology research. Since its formation in 1994, the Working Group has organized many activities for early career scientists designed to promote this scientific exchange, including two week courses with hands-on research experience, intensive workshops of two or three days, and research scholar exchanges of one to six months. These interactions are focused on environmental problems that respect no international boundaries.« less

Designing and validating the joint battlespace infosphere

NASA Astrophysics Data System (ADS)

Peterson, Gregory D.; Alexander, W. Perry; Birdwell, J. Douglas

2001-08-01

Fielding and managing the dynamic, complex information systems infrastructure necessary for defense operations presents significant opportunities for revolutionary improvements in capabilities. An example of this technology trend is the creation and validation of the Joint Battlespace Infosphere (JBI) being developed by the Air Force Research Lab. The JBI is a system of systems that integrates, aggregates, and distributes information to users at all echelons, from the command center to the battlefield. The JBI is a key enabler of meeting the Air Force's Joint Vision 2010 core competencies such as Information Superiority, by providing increased situational awareness, planning capabilities, and dynamic execution. At the same time, creating this new operational environment introduces significant risk due to an increased dependency on computational and communications infrastructure combined with more sophisticated and frequent threats. Hence, the challenge facing the nation is the most effective means to exploit new computational and communications technologies while mitigating the impact of attacks, faults, and unanticipated usage patterns.

Joint penalized-likelihood reconstruction of time-activity curves and regions-of-interest from projection data in brain PET

NASA Astrophysics Data System (ADS)

Krestyannikov, E.; Tohka, J.; Ruotsalainen, U.

2008-06-01

This paper presents a novel statistical approach for joint estimation of regions-of-interest (ROIs) and the corresponding time-activity curves (TACs) from dynamic positron emission tomography (PET) brain projection data. It is based on optimizing the joint objective function that consists of a data log-likelihood term and two penalty terms reflecting the available a priori information about the human brain anatomy. The developed local optimization strategy iteratively updates both the ROI and TAC parameters and is guaranteed to monotonically increase the objective function. The quantitative evaluation of the algorithm is performed with numerically and Monte Carlo-simulated dynamic PET brain data of the 11C-Raclopride and 18F-FDG tracers. The results demonstrate that the method outperforms the existing sequential ROI quantification approaches in terms of accuracy, and can noticeably reduce the errors in TACs arising due to the finite spatial resolution and ROI delineation.

A Novel Joint Problem of Routing, Scheduling, and Variable-Width Channel Allocation in WMNs

PubMed Central

Liu, Wan-Yu; Chou, Chun-Hung

2014-01-01

This paper investigates a novel joint problem of routing, scheduling, and channel allocation for single-radio multichannel wireless mesh networks in which multiple channel widths can be adjusted dynamically through a new software technology so that more concurrent transmissions and suppressed overlapping channel interference can be achieved. Although the previous works have studied this joint problem, their linear programming models for the problem were not incorporated with some delicate constraints. As a result, this paper first constructs a linear programming model with more practical concerns and then proposes a simulated annealing approach with a novel encoding mechanism, in which the configurations of multiple time slots are devised to characterize the dynamic transmission process. Experimental results show that our approach can find the same or similar solutions as the optimal solutions for smaller-scale problems and can efficiently find good-quality solutions for a variety of larger-scale problems. PMID:24982990

Static and dynamic deflection studies of the SRM aft case-nozzle joint

NASA Technical Reports Server (NTRS)

Christian, David C.; Kos, Lawrence D.; Torres, Isaias

1989-01-01

The redesign of the joints on the solid rocket motor (SRM) has prompted the need for analyzing the behavior of the joints using several different types of analyses. The types of analyses performed include modal analysis, static analysis, transient response analysis, and base driving response analysis. The forces used in these analyses to drive the mathematical model include SRM internal chamber pressure, nozzle blowout and side forces, shuttle vehicle lift-off dynamics, SRM pressure transient rise curve, gimbal forces and moments, actuator gimbal loads, and vertical and radial bolt preloads. The math model represented the SRM from the aft base tangent point (1,823.95 in) all the way back to the nozzle, where a simplified, tuned nozzle model was attached. The new design used the radial bolts as an additional feature to reduce the gap opening at the aft dome/nozzle fixed housing interface.

Research regarding stiffness optimization of wires used for joints actuation from an elephant's trunk robotic arm

NASA Astrophysics Data System (ADS)

Ciofu, C.; Stan, G.

2016-11-01

Elephant's trunk robotic arms driven by wires and pulley mechanisms have issues with wires stiffness because of the entailed elastic deformations that is causing errors of positioning. Static and dynamic loads from each joint of the robotic arm affect the stiffness of driving wires and precision positioning. The influence of wires elastic deformation on precision positioning decreases with the increasing of wires stiffness by using different pre-tensioning devices. In this paper, we analyze the variation of driving wires stiffness particularly to each wire driven joint. We obtain optimum wires stiffness variation by using an analytical method that highlights the efficiency of pre-tensioning mechanism. The analysis of driving wires stiffness is necessary for taking appropriate optimization measures of robotic arm dynamic behavior and, thus, for decreasing positioning errors of the elephant's trunk robotic arm with inner actuation through wires/cables.

In-vivo measurement of dynamic joint motion using high speed biplane radiography and CT: application to canine ACL deficiency.

PubMed

Tashman, Scott; Anderst, William

2003-04-01

Dynamic assessment of three-dimensional (3D) skeletal kinematics is essential for understanding normal joint function as well as the effects of injury or disease. This paper presents a novel technique for measuring in-vivo skeletal kinematics that combines data collected from high-speed biplane radiography and static computed tomography (CT). The goals of the present study were to demonstrate that highly precise measurements can be obtained during dynamic movement studies employing high frame-rate biplane video-radiography, to develop a method for expressing joint kinematics in an anatomically relevant coordinate system and to demonstrate the application of this technique by calculating canine tibio-femoral kinematics during dynamic motion. The method consists of four components: the generation and acquisition of high frame rate biplane radiographs, identification and 3D tracking of implanted bone markers, CT-based coordinate system determination, and kinematic analysis routines for determining joint motion in anatomically based coordinates. Results from dynamic tracking of markers inserted in a phantom object showed the system bias was insignificant (-0.02 mm). The average precision in tracking implanted markers in-vivo was 0.064 mm for the distance between markers and 0.31 degree for the angles between markers. Across-trial standard deviations for tibio-femoral translations were similar for all three motion directions, averaging 0.14 mm (range 0.08 to 0.20 mm). Variability in tibio-femoral rotations was more dependent on rotation axis, with across-trial standard deviations averaging 1.71 degrees for flexion/extension, 0.90 degree for internal/external rotation, and 0.40 degree for varus/valgus rotation. Advantages of this technique over traditional motion analysis methods include the elimination of skin motion artifacts, improved tracking precision and the ability to present results in a consistent anatomical reference frame.

Dynamic 3D scanning as a markerless method to calculate multi-segment foot kinematics during stance phase: methodology and first application.

PubMed

Van den Herrewegen, Inge; Cuppens, Kris; Broeckx, Mario; Barisch-Fritz, Bettina; Vander Sloten, Jos; Leardini, Alberto; Peeraer, Louis

2014-08-22

Multi-segmental foot kinematics have been analyzed by means of optical marker-sets or by means of inertial sensors, but never by markerless dynamic 3D scanning (D3DScanning). The use of D3DScans implies a radically different approach for the construction of the multi-segment foot model: the foot anatomy is identified via the surface shape instead of distinct landmark points. We propose a 4-segment foot model consisting of the shank (Sha), calcaneus (Cal), metatarsus (Met) and hallux (Hal). These segments are manually selected on a static scan. To track the segments in the dynamic scan, the segments of the static scan are matched on each frame of the dynamic scan using the iterative closest point (ICP) fitting algorithm. Joint rotations are calculated between Sha-Cal, Cal-Met, and Met-Hal. Due to the lower quality scans at heel strike and toe off, the first and last 10% of the stance phase is excluded. The application of the method to 5 healthy subjects, 6 trials each, shows a good repeatability (intra-subject standard deviations between 1° and 2.5°) for Sha-Cal and Cal-Met joints, and inferior results for the Met-Hal joint (>3°). The repeatability seems to be subject-dependent. For the validation, a qualitative comparison with joint kinematics from a corresponding established marker-based multi-segment foot model is made. This shows very consistent patterns of rotation. The ease of subject preparation and also the effective and easy to interpret visual output, make the present technique very attractive for functional analysis of the foot, enhancing usability in clinical practice. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

Spinal circuits can accommodate interaction torques during multijoint limb movements.

PubMed

Buhrmann, Thomas; Di Paolo, Ezequiel A

2014-01-01

The dynamic interaction of limb segments during movements that involve multiple joints creates torques in one joint due to motion about another. Evidence shows that such interaction torques are taken into account during the planning or control of movement in humans. Two alternative hypotheses could explain the compensation of these dynamic torques. One involves the use of internal models to centrally compute predicted interaction torques and their explicit compensation through anticipatory adjustment of descending motor commands. The alternative, based on the equilibrium-point hypothesis, claims that descending signals can be simple and related to the desired movement kinematics only, while spinal feedback mechanisms are responsible for the appropriate creation and coordination of dynamic muscle forces. Partial supporting evidence exists in each case. However, until now no model has explicitly shown, in the case of the second hypothesis, whether peripheral feedback is really sufficient on its own for coordinating the motion of several joints while at the same time accommodating intersegmental interaction torques. Here we propose a minimal computational model to examine this question. Using a biomechanics simulation of a two-joint arm controlled by spinal neural circuitry, we show for the first time that it is indeed possible for the neuromusculoskeletal system to transform simple descending control signals into muscle activation patterns that accommodate interaction forces depending on their direction and magnitude. This is achieved without the aid of any central predictive signal. Even though the model makes various simplifications and abstractions compared to the complexities involved in the control of human arm movements, the finding lends plausibility to the hypothesis that some multijoint movements can in principle be controlled even in the absence of internal models of intersegmental dynamics or learned compensatory motor signals.

Dynamic knee valgus alignment influences impact attenuation in the lower extremity during the deceleration phase of a single-leg landing.

PubMed

Tamura, Akihiro; Akasaka, Kiyokazu; Otsudo, Takahiro; Shiozawa, Jyunya; Toda, Yuka; Yamada, Kaori

2017-01-01

Dynamic knee valgus during landings is associated with an increased risk of non-contact anterior cruciate ligament (ACL) injury. In addition, the impact on the body during landings must be attenuated in the lower extremity joints. The purpose of this study was to investigate landing biomechanics during landing with dynamic knee valgus by measuring the vertical ground reaction force (vGRF) and angular impulses in the lower extremity during a single-leg landing. The study included 34 female college students, who performed the single-leg drop vertical jump. Lower extremity kinetic and kinematic data were obtained from a 3D motion analysis system. Participants were divided into valgus (N = 19) and varus (N = 15) groups according to the knee angular displacement during landings. The vGRF and angular impulses of the hip, knee, and ankle were calculated by integrating the vGRF-time curve and each joint's moment-time curve. vGRF impulses did not differ between two groups. Hip angular impulse in the valgus group was significantly smaller than that in the varus group (0.019 ± 0.033 vs. 0.067 ± 0.029 Nms/kgm, p<0.01), whereas knee angular impulse was significantly greater (0.093 ± 0.032 vs. 0.045 ± 0.040 Nms/kgm, p<0.01). There was no difference in ankle angular impulse between the groups. Our results indicate that dynamic knee valgus increases the impact the knee joint needs to attenuate during landing; conversely, the knee varus participants were able to absorb more of the landing impact with the hip joint.

Flow dynamics in hyper-saline aquifers: hydro-geophysical monitoring and modeling

NASA Astrophysics Data System (ADS)

Haaken, Klaus; Piero Deidda, Gian; Cassiani, Giorgio; Deiana, Rita; Putti, Mario; Paniconi, Claudio; Scudeler, Carlotta; Kemna, Andreas

2017-03-01

Saline-freshwater interaction in porous media is a phenomenon of practical interest particularly for the management of water resources in arid and semi-arid environments, where precious freshwater resources are threatened by seawater intrusion and where storage of freshwater in saline aquifers can be a viable option. Saline-freshwater interactions are controlled by physico-chemical processes that need to be accurately modeled. This in turn requires monitoring of these systems, a non-trivial task for which spatially extensive, high-resolution non-invasive techniques can provide key information. In this paper we present the field monitoring and numerical modeling components of an approach aimed at understanding complex saline-freshwater systems. The approach is applied to a freshwater injection experiment carried out in a hyper-saline aquifer near Cagliari (Sardinia, Italy). The experiment was monitored using time-lapse cross-hole electrical resistivity tomography (ERT). To investigate the flow dynamics, coupled numerical flow and transport modeling of the experiment was carried out using an advanced three-dimensional (3-D) density-driven flow-transport simulator. The simulation results were used to produce synthetic ERT inversion results to be compared against real field ERT results. This exercise demonstrates that the evolution of the freshwater bulb is strongly influenced by the system's (even mild) hydraulic heterogeneities. The example also highlights how the joint use of ERT imaging and gravity-dependent flow and transport modeling give fundamental information for this type of study.

Facet Joint Osteoarthritis Affects Spinal Segmental Motion in Degenerative Spondylolisthesis.

PubMed

Kitanaka, Shigeyuki; Takatori, Ryota; Arai, Yuji; Nagae, Masateru; Tonomura, Hitoshi; Mikami, Yasuo; Inoue, Nozomu; Ogura, Taku; Fujiwara, Hiroyoshi; Kubo, Toshikazu

2018-06-15

This is a retrospective clinical case series (case-control study). To clarify the influence of facet joint osteoarthritis (FJOA) on the pathology of degenerative spondylolisthesis (DS) using in vivo 3-dimensional image analysis. There are no radical treatments to prevent progression of DS in patients with lumbar spinal canal stenosis associated with DS. Therefore, an effective treatment method based on the pathology of DS should be developed. In total, 50 patients with lumbar spinal canal stenosis involving L4/5 who underwent dynamic computed tomography were divided into 2 groups: with DS [spondylolisthesis (Sp) group; 12 male, 14 female; mean age, 74 y]; and without DS (non-Sp group; 15 male, 9 female; mean age, 70 y). Degeneration of the intervertebral disk and FJOA at L4/5 were evaluated using magnetic resonance imaging. Disk and intervertebral foramen heights, the distance between the craniocaudal edges of the facet joint, and the interspinous distance were measured on dynamic computed tomographic images. Also, in vivo 3-dimensional segmental motion was evaluated using the volume merge method. There were no significant differences in degenerative findings for the intervertebral disk; however, progressive FJOA was detected in the Sp group. Dynamic changes in the distance between the craniocaudal edges of the facet joints were significantly larger in the Sp group. In this study, progressive FJOA and larger segmental motion in the distance between the craniocaudal edges of the facet joints were found in the Sp group. We clarified for the first time that DS involves ligament laxity due to FJOA that affects spinal segmental motion in vivo. We consider that a treatment method based on FJOA would be useful for treating patients with DS. Level IV.

Frontal joint dynamics when initiating stair ascent from a walk versus a stand.

PubMed

Vallabhajosula, Srikant; Yentes, Jennifer M; Stergiou, Nicholas

2012-02-02

Ascending stairs is a challenging activity of daily living for many populations. Frontal plane joint dynamics are critical to understand the mechanisms involved in stair ascension as they contribute to both propulsion and medio-lateral stability. However, previous research is limited to understanding these dynamics while initiating stair ascent from a stand. We investigated if initiating stair ascent from a walk with a comfortable self-selected speed could affect the frontal plane lower-extremity joint moments and powers as compared to initiating stair ascent from a stand and if this difference would exist at consecutive ipsilateral steps on the stairs. Kinematics data using a 3-D motion capture system and kinetics data using two force platforms on the first and third stair treads were recorded simultaneously as ten healthy young adults ascended a custom-built staircase. Data were collected from two starting conditions of stair ascent, from a walk (speed: 1.42 ± 0.21 m/s) and from a stand. Results showed that subjects generated greater peak knee abductor moment and greater peak hip abductor moment when initiating stair ascent from a walk. Greater peak joint moments and powers at all joints were also seen while ascending the second ipsilateral step. Particularly, greater peak hip abductor moment was needed to avoid contact of the contralateral limb with the intermediate step by counteracting the pelvic drop on the contralateral side. This could be important for therapists using stair climbing as a testing/training tool to evaluate hip strength in individuals with documented frontal plane abnormalities (i.e. knee and hip osteoarthritis, ACL injury). Copyright © 2011 Elsevier Ltd. All rights reserved.

Nervous system excitability and joint stiffness following short-term dynamic ankle immobilization.

PubMed

Stirling, Alyssa M; McBride, Jeffrey M; Merritt, Edward K; Needle, Alan R

2018-01-01

Joint immobilization has been demonstrated to modify neural excitability in subsets of healthy populations, leading to disinhibition of cortical and reflexive pathways. However, these findings may have limited clinical application as most models have investigated casting and rigid immobilization, while many musculoskeletal injuries often utilize dynamic immobilization devices such as boot immobilizers and pneumatic splints that allow for modified ambulation. We therefore aimed to determine the short-term effects of ambulation in ankle immobilization devices on nervous system excitability and stiffness in able-bodied individuals. A repeated-measures design was implemented where 12 healthy individuals were tested for cortical excitability to the ankle musculature using transcranial magnetic stimulation, reflexive excitability using the Hoffmann reflex, and ankle joint stiffness using arthrometry before and after 30min of ambulation with a boot immobilizer, pneumatic leg splint, or barefoot. Motor evoked potential (MEP), cortical silent period (CSP), H max to M max ratio, and ankle joint displacement were extracted as dependent variables. Results indicated that despite the novel motor demands of walking in immobilization devices, no significant changes in cortical excitability (F≥0.335, P≥0.169), reflexive excitability (F≥0.027, P≥0.083), or joint stiffness (F≥0.558, P≥0.169) occurred. These findings indicate that short-term ambulation in dynamic immobilization devices does not modify neural excitability despite forced constraints on the sensorimotor system. We may therefore conclude that modifications to neural excitability in previous immobilization models are mediated by long-term nervous system plasticity rather than acute mechanisms, and there appear to be no robust changes in corticomotor or spinal excitability acutely posed by ambulation with immobilization devices. Copyright © 2017 Elsevier B.V. All rights reserved.

Generating Spatiotemporal Joint Torque Patterns from Dynamical Synchronization of Distributed Pattern Generators

PubMed Central

Pitti, Alexandre; Lungarella, Max; Kuniyoshi, Yasuo

2009-01-01

Pattern generators found in the spinal cord are no more seen as simple rhythmic oscillators for motion control. Indeed, they achieve flexible and dynamical coordination in interaction with the body and the environment dynamics giving to rise motor synergies. Discovering the mechanisms underlying the control of motor synergies constitutes an important research question not only for neuroscience but also for robotics: the motors coordination of high dimensional robotic systems is still a drawback and new control methods based on biological solutions may reduce their overall complexity. We propose to model the flexible combination of motor synergies in embodied systems via partial phase synchronization of distributed chaotic systems; for specific coupling strength, chaotic systems are able to phase synchronize their dynamics to the resonant frequencies of one external force. We take advantage of this property to explore and exploit the intrinsic dynamics of one specified embodied system. In two experiments with bipedal walkers, we show how motor synergies emerge when the controllers phase synchronize to the body's dynamics, entraining it to its intrinsic behavioral patterns. This stage is characterized by directed information flow from the sensors to the motors exhibiting the optimal situation when the body dynamics drive the controllers (mutual entrainment). Based on our results, we discuss the relevance of our findings for modeling the modular control of distributed pattern generators exhibited in the spinal cord, and for exploring the motor synergies in robots. PMID:20011216

Convolutional Deep Belief Networks for Single-Cell/Object Tracking in Computational Biology and Computer Vision.

PubMed

Zhong, Bineng; Pan, Shengnan; Zhang, Hongbo; Wang, Tian; Du, Jixiang; Chen, Duansheng; Cao, Liujuan

2016-01-01

In this paper, we propose deep architecture to dynamically learn the most discriminative features from data for both single-cell and object tracking in computational biology and computer vision. Firstly, the discriminative features are automatically learned via a convolutional deep belief network (CDBN). Secondly, we design a simple yet effective method to transfer features learned from CDBNs on the source tasks for generic purpose to the object tracking tasks using only limited amount of training data. Finally, to alleviate the tracker drifting problem caused by model updating, we jointly consider three different types of positive samples. Extensive experiments validate the robustness and effectiveness of the proposed method.

Convolutional Deep Belief Networks for Single-Cell/Object Tracking in Computational Biology and Computer Vision

PubMed Central

Pan, Shengnan; Zhang, Hongbo; Wang, Tian; Du, Jixiang; Chen, Duansheng; Cao, Liujuan

2016-01-01

In this paper, we propose deep architecture to dynamically learn the most discriminative features from data for both single-cell and object tracking in computational biology and computer vision. Firstly, the discriminative features are automatically learned via a convolutional deep belief network (CDBN). Secondly, we design a simple yet effective method to transfer features learned from CDBNs on the source tasks for generic purpose to the object tracking tasks using only limited amount of training data. Finally, to alleviate the tracker drifting problem caused by model updating, we jointly consider three different types of positive samples. Extensive experiments validate the robustness and effectiveness of the proposed method. PMID:27847827

Non-Kolmogorovian Approach to the Context-Dependent Systems Breaking the Classical Probability Law

NASA Astrophysics Data System (ADS)

Asano, Masanari; Basieva, Irina; Khrennikov, Andrei; Ohya, Masanori; Yamato, Ichiro

2013-07-01

There exist several phenomena breaking the classical probability laws. The systems related to such phenomena are context-dependent, so that they are adaptive to other systems. In this paper, we present a new mathematical formalism to compute the joint probability distribution for two event-systems by using concepts of the adaptive dynamics and quantum information theory, e.g., quantum channels and liftings. In physics the basic example of the context-dependent phenomena is the famous double-slit experiment. Recently similar examples have been found in biological and psychological sciences. Our approach is an extension of traditional quantum probability theory, and it is general enough to describe aforementioned contextual phenomena outside of quantum physics.

Ion temperature and toroidal rotation in JET's low torque plasmas.

PubMed

Bernardo, J; Nave, M F F; Giroud, C; Reyes Cortes, S; Bizarro, João P S

2016-11-01

This paper reports on the procedure developed as the best method to provide an accurate and reliable estimation of the ion temperature T i and the toroidal velocity v ϕ from Charge-eXchange Recombination Spectroscopy (CXRS) data from intrinsic rotation experiments at the Joint European Torus with the carbon wall. The low impurity content observed in such plasmas, resulting in low active CXRS signal, alongside low Doppler shifts makes the determination of T i and v ϕ particularly difficult. The beam modulation method will be discussed along with the measures taken to increase photon statistics and minimise errors from the absolute calibration and magneto-hydro-dynamics effects that may impact the CXRS passive emission.

Temporal gene expression profiling of the rat knee joint capsule during immobilization-induced joint contractures.

PubMed

Wong, Kayleigh; Sun, Fangui; Trudel, Guy; Sebastiani, Paola; Laneuville, Odette

2015-05-26

Contractures of the knee joint cause disability and handicap. Recovering range of motion is recognized by arthritic patients as their preference for improved health outcome secondary only to pain management. Clinical and experimental studies provide evidence that the posterior knee capsule prevents the knee from achieving full extension. This study was undertaken to investigate the dynamic changes of the joint capsule transcriptome during the progression of knee joint contractures induced by immobilization. We performed a microarray analysis of genes expressed in the posterior knee joint capsule following induction of a flexion contracture by rigidly immobilizing the rat knee joint over a time-course of 16 weeks. Fold changes of expression values were measured and co-expressed genes were identified by clustering based on time-series analysis. Genes associated with immobilization were further analyzed to reveal pathways and biological significance and validated by immunohistochemistry on sagittal sections of knee joints. Changes in expression with a minimum of 1.5 fold changes were dominated by a decrease in expression for 7732 probe sets occurring at week 8 while the expression of 2251 probe sets increased. Clusters of genes with similar profiles of expression included a total of 162 genes displaying at least a 2 fold change compared to week 1. Functional analysis revealed ontology categories corresponding to triglyceride metabolism, extracellular matrix and muscle contraction. The altered expression of selected genes involved in the triglyceride biosynthesis pathway; AGPAT-9, and of the genes P4HB and HSP47, both involved in collagen synthesis, was confirmed by immunohistochemistry. Gene expression in the knee joint capsule was sensitive to joint immobility and provided insights into molecular mechanisms relevant to the pathophysiology of knee flexion contractures. Capsule responses to immobilization was dynamic and characterized by modulation of at least three reaction pathways; down regulation of triglyceride biosynthesis, alteration of extracellular matrix degradation and muscle contraction gene expression. The posterior knee capsule may deploy tissue-specific patterns of mRNA regulatory responses to immobilization. The identification of altered expression of genes and biochemical pathways in the joint capsule provides potential targets for the therapy of knee flexion contractures.

Relationship between lower limb dynamics and knee joint pain.

PubMed

Radin, E L; Yang, K H; Riegger, C; Kish, V L; O'Connor, J J

1991-05-01

To test the hypothesis that appropriate and timely neuromuscular control of limb motions plays an important role in the preservation of joint health, we kinematically and kinetically examined the behavior of the legs of young adult subjects at heel strike during natural walking. We compared a group of 18 volunteers, who, we presumed, were preosteoarthrotic because of mild, intermittent, activity-related knee joint pain, with 14 age-matched asymptomatic normal subjects. The two groups of subjects exhibited similar gait patterns with equivalent cadences, walking speeds, terminal stance phase knee flexion, maximum (peak) swing angular velocity, and overall shape of the vertical ground reaction. However, our instrumentation detected statistically significant differences between the two groups within a few milliseconds of heel strike. In the knee pain group, the heel hit the floor with a stronger impact in this brief interval. Just before heel strike, there was a faster downward velocity of the ankle with a larger angular velocity of the shank. The follow-through of the leg immediately after heel strike was more violent with larger peak axial and angular accelerations of the leg echoed by a more rapid rise of the ground reaction force. This sequence of events represents repetitive impulsive loading, which consistently provoked osteoarthrosis in animal experiments. We refer to this micro-incoordination of neuromuscular control not visible to the naked eye as "microklutziness."

The Emergence of Nonverbal Joint Attention and Requesting Skills in Young Children with Autism

ERIC Educational Resources Information Center

Paparella, Tanya; Goods, Kelly Stickles; Freeman, Stephanny; Kasari, Connie

2011-01-01

Joint attention (JA) skills are deficient in children with autism; however, children with autism seem to vary in the degree to which they display joint attention. Joint attention skills refer to verbal and nonverbal skills used to share experiences with others. They include gestures such as pointing, coordinated looks between objects and people,…

Autonomy and couples' joint decision-making in healthcare.

PubMed

Osamor, Pauline E; Grady, Christine

2018-01-11

Respect for autonomy is a key principle in bioethics. However, respecting autonomy in practice is complex because most people define themselves and make decisions influenced by a complex network of social relationships. The extent to which individual autonomy operates for each partner within the context of decision-making within marital or similar relationships is largely unexplored. This paper explores issues related to decision-making by couples (couples' joint decision-making) for health care and the circumstances under which such a practice should be respected as compatible with autonomous decision-making. We discuss the concept of autonomy as it applies to persons and to actions, human interdependency and gender roles in decision-making, the dynamics and outcomes of couples' joint decision-making, and the ethics of couples' joint decision-making. We believe that the extent to which couples' joint decision-making might be deemed ethically acceptable will vary depending on the context. Given that in many traditional marriages the woman is the less dominant partner, we consider a spectrum of scenarios of couples' joint decision-making about a woman's own health care that move from those that are acceptably autonomous to those that are not consistent with respecting the woman's autonomous decision-making. To the extent that there is evidence that both members of a couple understand a decision, intend it, and that neither completely controls the other, couples' joint decision-making should be viewed as consistent with the principle of respect for the woman's autonomy. At the other end of the spectrum are decisions made by the man without the woman's input, representing domination of one partner by the other. We recommend viewing the dynamics of couples' joint decision-making as existing on a continuum of degrees of autonomy. This continuum-based perspective implies that couples' joint decision-making should not be taken at face value but should be assessed against the specific cultural, ethnic, and religious backgrounds and personal circumstances of the individuals in question.

Joint Rhythmic Movement Increases 4-Year-Old Children's Prosocial Sharing and Fairness Toward Peers.

PubMed

Rabinowitch, Tal-Chen; Meltzoff, Andrew N

2017-01-01

The allocation of resources to a peer partner is a prosocial act that is of fundamental importance. Joint rhythmic movement, such as occurs during musical interaction, can induce positive social experiences, which may play a role in developing and enhancing young children's prosocial skills. Here, we investigated whether joint rhythmic movement, free of musical context, increases 4-year-olds' sharing and sense of fairness in a resource allocation task involving peers. We developed a precise procedure for administering joint synchronous experience, joint asynchronous experience, and a baseline control involving no treatment. Then we tested how participants allocated resources between self and peer. We found an increase in the generous allocation of resources to peers following both synchronous and asynchronous movement compared to no treatment. At a more theoretical level, this result is considered in relation to previous work testing other aspects of child prosociality, for example, peer cooperation, which can be distinguished from judgments of fairness in resource allocation tasks. We draw a conceptual distinction between two types of prosocial behavior: resource allocation (an other-directed individual behavior) and cooperation (a goal-directed collaborative endeavor). Our results highlight how rhythmic interactions, which are prominent in joint musical engagements and synchronized activity, influence prosocial behavior between preschool peers.

Joint Rhythmic Movement Increases 4-Year-Old Children’s Prosocial Sharing and Fairness Toward Peers

PubMed Central

Rabinowitch, Tal-Chen; Meltzoff, Andrew N.

2017-01-01

The allocation of resources to a peer partner is a prosocial act that is of fundamental importance. Joint rhythmic movement, such as occurs during musical interaction, can induce positive social experiences, which may play a role in developing and enhancing young children’s prosocial skills. Here, we investigated whether joint rhythmic movement, free of musical context, increases 4-year-olds’ sharing and sense of fairness in a resource allocation task involving peers. We developed a precise procedure for administering joint synchronous experience, joint asynchronous experience, and a baseline control involving no treatment. Then we tested how participants allocated resources between self and peer. We found an increase in the generous allocation of resources to peers following both synchronous and asynchronous movement compared to no treatment. At a more theoretical level, this result is considered in relation to previous work testing other aspects of child prosociality, for example, peer cooperation, which can be distinguished from judgments of fairness in resource allocation tasks. We draw a conceptual distinction between two types of prosocial behavior: resource allocation (an other-directed individual behavior) and cooperation (a goal-directed collaborative endeavor). Our results highlight how rhythmic interactions, which are prominent in joint musical engagements and synchronized activity, influence prosocial behavior between preschool peers. PMID:28694786

Inhibition of prostaglandin biosynthesis as the mechanism of analgesia of aspirin-like drugs in the dog knee joint.

PubMed

Moncada, S; Ferreira, S H; Vane, J R

1975-04-01

A method has been developed to measure the analgesic action of aspirin-like drugs in knee joints of anaesthetized dogs. Bradykinin, injected into the joint cavity, induced a reflex rise in blood pressure which was dose-dependent; this was used as a measure of nociceptive activity. The joint cavity became more sensitive to bradykinin as the experiment proceeded, or when a low concentration of prostaglandin E1 or E2 was infused locally. The increase in sensitivity with time was prevented by local injection of aspirin or indomethacin, but that induced by exogenous prostaglandin infusion was not. Injections of carrageenin into dog knee joints increased the prostaglandin E2 content of synovial fluid by up to 160 ng per joint; indomethacin prevented this increase. These experiments support our previous conclusion that local biosynthesis of a prostaglandin (induced by mild trauma) sensitizes pain receptors to mechanical or chemical stimuli. Aspirin-like drugs are analgesic because they prevent prostaglandin biosynthesis, thereby preventing this sensitization.

Measurement of damping of graphite epoxy composite materials and structural joints

NASA Technical Reports Server (NTRS)

Crocker, Malcolm J.; Rao, Mohan D.; Raju, P. K.; Yan, Xinche

1989-01-01

The damping capacity of graphite epoxy materials and structural joints was evaluated. The damping ratio of different composite specimens and bonded joints were systematically evaluated under normal atmospheric conditions and in a vacuum environment. Free and forced vibration test methods were employed for measuring the damping ratios. The effect of edge support conditions on the damping value of a composite tube specimen was studied by using a series of experiments performed on the specimen with different edge supports. It was found that simulating a free-free boundary conditions by having no constraints at the ends gives the lowest value of the material damping of the composite. The accuracy of the estimation of the damping ratio value was improved by using a curve-fitting technique on the response data obtained through measurement. The effect of outgassing (moisture desorption) on the damping capacity was determined by measuring the damping ratio of the tube specimen in a vacuum environment before and after outgassing had occurred. The effects of high and low temperatures on the damping was also investigated by using a series of experiments on tube and beam specimens. An analytical model to study the vibrations of a bonded lap joint system was formulated. Numerical results were generated for different overlap ratios of the system. These were compared with experimental results. In order to determine the influence of bonded joints on the material damping capacity, experiments were conducted on bonded lap-jointed and double-butt-jointed specimens. These experimental results were compared with simple beam specimens with no joints.

Shape Memory Polymers: A Joint Chemical and Materials Engineering Hands-On Experience

ERIC Educational Resources Information Center

Seif, Mujan; Beck, Matthew

2018-01-01

Hands-on experiences are excellent tools for increasing retention of first year engineering students. They also encourage interdisciplinary collaboration, a critical skill for modern engineers. In this paper, we describe and evaluate a joint Chemical and Materials Engineering hands-on lab that explores cross-linking and glass transition in…