Kinematic Aspects Research Articles

A classification of poromechanical interface elements

Abstract Interface elements are a classical approach to represent discrete cracks, joints and faults. The basic kinematic and constitutive aspects are recapitulated and the extension to hydromechanical conditions is elaborated. A classification is presented of hydromechanical interface elements, depending on the multiplicity of the pressure degree of freedom, and the physical implications of the different possibilities are explained.

Kinematical Aspects Gliding Technique in 500-m Speed Skaters: From Start to Seven Strokes

Objective: The purpose of this study was to assess the consistency of the gliding and push-off motion for single leg skating from the first to fourteenth steps. We hypothesized that: 1) there would be no difference in stroke trajectory, step rate, and cycle rate between the left and right steps of gliding; and 2) there would be a difference in the resultant velocity of toe push-off and the horizontal velocity of the center of mass after six step push-offs. Method: The study included five male 500-m speed skaters (mean height, 1.80 ± 0.02 m; mean weight, 76.8 ± 3.96 kg; record, 35.83 ± 0.30 sec; 100-m record, <9.97 sec). Data were collected from the first to fourteenth steps (40 m) and recorded using five digital JVC GR-HD1KR video cameras (Victor Co., Japan) operating at a sampling frequency of 60 fields/sec and shutter speed of 1/500 sec. For each film frame, the joint positions were digitized using the KWON3D motion analyzer. Position data were filtered with low-pass Butterworth 4th order at the cut-off frequency of 7.4 Hz. Results: The right toe of the skating trajectories at 2nd, 5th, and 7th strokes differed from those of the left toe. The angles of the right and left knee demonstrated unbalanced patterns from the flexion and extension legs. The step and cycle rates of the right and left leg differed from the start until 20 m. The resultant velocities of the toe at the push-off phase and of the body mass center diverged before the six push-offs. Conclusion: This study`s findings indicate that the toe of skating trajectory on left and right sliding after push-off should maintain a symmetrical trajectory. The resultant velocity of toe push-off and horizontal velocity from the center of body need to be separated after about six step push-offs.

Phase separation analysis of Extem/solvent/non-solvent systems and relation with membrane morphology

The phase separation behavior of Extem/water/solvent systems for various solvents and Extem/NMP/non-solvent systems for different types of coagulants was investigated. Ternary phase diagrams of studied systems were constructed based on cloud point data obtained by titration at room temperature. In the first part, N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAc), dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) were employed as solvent and water was used as coagulant. The cloud point curves from these systems showed that Extem/NMP/water and Extem/DMSO/water has the smallest and largest demixing gap, respectively. Subsequently, water, methanol, and glycerol were employed as coagulants and NMP was selected as solvent. The obtained results indicated that water and methanol had the strongest and weakest coagulant power, respectively. The linearized cloud point and precipitation value were applied to identify the strength of the non-solvent for casting solution (Extem/NMP) with a certain concentration. The solubility curve of Extem was obtained using the Hansen solubility parameter, calculated by a group contribution method. In order to evaluate the influence of different solvents and non-solvents on the final structure of the resulting membranes, scanning electron microscopy (SEM) was used. The morphology of the membranes prepared from Extem/solvent/water systems (except Extem/DMSO/water) showed a finger like sub-layer, while a sponge-like structure was observed for the Extem/DMSO/water system. Using methanol as coagulation medium resulted in a thick dense layer over a macroporous sub layer, while a fully sponge like structure with microporous skin layer was obtained for the Extem/NMP/glycerol system. In order to find the source of these unexpected observations, thermodynamic and kinematic aspects such as binary interaction parameters, heat of mixing, viscosity and diffusion rate were discussed thoroughly.

Paleo-Mesoproterozoic arc-accretion along the southwestern margin of the Amazonian craton: The Juruena accretionary orogen and possible implications for Columbia supercontinent

The southwestern portion of the Amazonian craton, between the Ventuari-Tapajós province and the Andean chain, has been ascribed to a succession of orogenic events from 1.81 to 0.95 Ga, culminating with widespread anorogenic magmatism. Southwestward of the Serra do Cachimbo graben occurs the Juruena accretionary orogenic belt (ca. 1.81–1.51 Ga), previously included in the Rio Negro-Juruena and Rondonian/San Ignácio geocronological provinces or Rondônia-Juruena geologic province. The Juruena orogen proposed here includes the Jamari and Juruena tectonostratigraphic terranes, products of convergence which culminated in the soft collision of the Paraguá protocraton and the Tapajós-Parima arc system (Tapajós Province) ca. 1.69–1.63 Ga ago. Geophysical, geochemical, petrological and geochronological data and systematic geological mapping suggest that the convergent event resulted in a single orogenic system with two continental margin arcs, namely the Jamari and Juruena arcs. Modern geological and tectonic approaches, combined with aerogeophysics data, enable to interpreting this wide region of the Amazonian craton as a Paleoproterozoic orogen with well defined petrotectonic units and tectonoestructural framework. The Juruena orogen is an E-W trending belt, about 1100 km long and 350 km wide, inflecting to NW-SE, in Mato Grosso, Amazonas and Rondonia, Brazil. The general direction of the belt, its inflections and internal geometric and kinematic aspects of its macrostructures do not corroborate the general NW-SE trend of the originally proposed geocronological provinces.The Juruena accretionary orogen has been the site of repeated reactivation with renewed basin formation, magmatism and orogeny during the Mesoproterozoic and the early Neoproterozoic. U-Pb and whole-rock Sm-Nd ages, Ar-Ar and Rb-Sr mineral ages suggest that the older high grade tectonometamorphic events in the Juruena accretionary orogen took place between 1.69 and 1.63 Ga, defining the metamorphic peak of the Rio Negro-Juruena orogeny and the original structural architecture of the orogen. The main structures of the Rio Negro-Juruena orogeny were almost completely obliterated between 1.42 and 1.37 Ga, due to the superimposed Rondonian-San Ignácio orogeny. Later on, between 1.20 and 1.12 Ga, these structures were affected by a ductile event represented by the large Ji-Paraná transpressive shear system and by the Tarilândia transcurrent shear zone developed under low-T amphibolite facies conditions, both related to the Sunsás orogeny. The evolution of Jamari and Juruena terranes as a Paleoproterozoic/Mesoproterozoic orogen developed between 1.81 and 1.51 Ga and their thorough reworking in Mesoproterozoic times is instrumental to establishing the position of the Amazonian craton in the proposed Paleo-Mesoproterozoic Columbia (Nuna) supercontinent, as well as in the Rodinia reconstruction at the end of the Mesoproterozoic.

Adaptive use of interaction torque during arm reaching movement from the optimal control viewpoint.

The study aimed at investigating the extent to which the brain adaptively exploits or compensates interaction torque (IT) during movement control in various velocity and load conditions. Participants performed arm pointing movements toward a horizontal plane without a prescribed reach endpoint at slow, neutral and rapid speeds and with/without load attached to the forearm. Experimental results indicated that IT overall contributed to net torque (NT) to assist the movement, and that such contribution increased with limb inertia and instructed speed and led to hand trajectory variations. We interpreted these results within the (inverse) optimal control framework, assuming that the empirical arm trajectories derive from the minimization of a certain, possibly composite, cost function. Results indicated that mixing kinematic, energetic and dynamic costs was necessary to replicate the participants’ adaptive behavior at both kinematic and dynamic levels. Furthermore, the larger contribution of IT to NT was associated with an overall decrease of the kinematic cost contribution and an increase of its dynamic/energetic counterparts. Altogether, these results suggest that the adaptive use of IT might be tightly linked to the optimization of a composite cost which implicitly favors more the kinematic or kinetic aspects of movement depending on load and speed.

Kinematic and thermal characteristics of Lüders and Portevin-Le Châtelier bands in a medium Mn transformation-induced plasticity steel

This paper focuses on experimental investigations on the kinematic and thermal aspects of the propagative plastic instabilities, namely Lüders band and Portevin–Le Châtelier (PLC) band, observed in a medium Mn transformation-induced plasticity (TRIP) steel. The full-field strain and heat source measurements are used concurrently to investigate in-situ the propagative bands. The kinematic analysis provides the real-time strain field evolution allowing the observation and quantification of the band nucleation and propagation. The local Lüders strain is demonstrated both space and time independent, and its magnitude is equivalent to the macroscopic Lüders strain. The spatio-temporal independent characteristic is also verified on the local strain in the PLC bands. Concerning the thermal field analysis, the heat sources are estimated and used to obtain the geometrical and dynamic parameters of the propagating bands, including the band width, orientation, propagation velocity, and appearance moment. Then the estimated heat sources are applied to establish an experimental energy balance during the plastic deformation. The quantitative energy analysis reveals that the strain-induced martensitic transformation takes place in the Lüders band but barely in the PLC bands. The ex-situ X-ray diffraction measurement on the phase content and surface hardness testing of the material confirm well this determination.

Influence of previous groin pain on hip and pelvic instep kick kinematics

ABSTRACTThis study analyzed differences in pelvic and hip joint kinematics during maximal instep kicks from two different approach angles in football players with and without previous groin pain (Group C and PGP Group, respectively). Kinematic data were recorded at 500 Hz, from 22 semiprofessional, male football players (age 23 [19–26] years) performing 12 instep kicks from 45° and 60° approach angles. Two-way analysis of variance identified differences between groups, and Cohen’s d determined the magnitude of effect sizes. Foot velocity at impact did not differ significantly between the groups for kicks from the 45° approach angle (P = 0.458, d = 0.13), although both groups slowed significantly at 60° (Group C: P < 0.001, d = 0.87; PGP Group: P < 0.001, d = 0.65). For kicks from the 45° approach angle, numerous significant differences existed between groups in pelvic and hip joint orientations, range of motion and maximal velocities. When kicking from the more acute 60° approach angle, Group C modified multiple aspects of pelvis and hip kinematics, while the PGP Group failed to adapt their technique. During maximal instep, kicking football players with previous groin pain employed different hip and pelvis kinematics to uninjured controls. The kicking kinematics adopted by the PGP group were consistent with aberrant kinetic chain utilization.

PRELIMINARY MATHEMATICAL MODEL OF A NEW ANKLE REHABILITATION DEVICE

&lt;p&gt;Among lower limb injuries, the ankle joint is the most common injured in sports and daily life in general. Rehabilitation aims to recover the patient’s physical capabilities through long and repetitive exercises. This paper discusses structural and kinematic aspects of a novel ankle rehabilitation device, which can facilitate the recovery of the ankle joint. The proposed device has two degrees of freedom, and will ensure functionality with minimum dimensions. Some preliminary mathematical models are also presented.&lt;/p&gt;

A vision based proposal for classification of normal and abnormal gait using RGB camera

Human gait is mainly related to the foot and leg movements but, obviously, the entire motor system of the human body is involved. We hypothesise that movement parameters such as dynamic balance, movement harmony of each body element (arms, head, thorax…) could enable us to finely characterise gait singularities to pinpoint potential diseases or abnormalities in advance. Since this paper deals with the preliminary problem pertaining to the classification of normal and abnormal gait, our study will revolve around the lower part of the body. Our proposal presents a functional specification of gait in which only observational kinematic aspects are discussed. The resultant specification will confidently be open enough to be applied to a variety of gait analysis problems encountered in areas connected to rehabilitation, sports, children’s motor skills, and so on. To carry out our functional specification, we develop an extraction system through which we analyse image sequences to identify gait features. Our prototype not only readily lets us determine the dynamic parameters (heel strike, toe off, stride length and time) and some skeleton joints but also satisfactorily supplies us with a proper distinction between normal and abnormal gait. We have performed experiments on a dataset of 30 samples.

Comparative tests of the proper active grinding powers and maximum grinding temperatures, conducted on corrosion-resistant steel surfaces, using aluminium oxynitride and noble electrocorundum grinding wheels

This paper presents the results of comparative experimental tests of proper active powers and maximum temperatures, conducted on the circumference grinding of flat surfaces, made of grade 321 corrosion-resistant steel (1.4541), using modern aluminium oxynitride and noble electrocorundum vitrified-bonded grinding wheels. The tests were carried out in both up-cut and down-cut conditions. In both kinematic grinding aspects, the tested factors were determined by discrete increase of reductive grinding yield, applying increasing grinding-wheel in-feed to the workpiece and keeping the remaining grinding parameters at the constant level. The test results were later subjected to simplified statistical analysis, and an attempt was made at substantive test justification. It was demonstrated that, regardless of the assumed kinematic grinding aspects of steel grade 1.4541 (321), the values of all the comparatively tested values of aluminium oxynitride grinding wheels were, with increasing reductive grinding yield, lower than the corresponding values of the noble electrocorundum grinding wheels.

Influence of the Hip Joint Modeling Approaches on the Kinematics of Human Gait

The influence of the hip joint formulation on the kinematic response of the model of human gait is investigated throughout this work. To accomplish this goal, the fundamental issues of the modeling process of a planar hip joint under the framework of multibody systems are revisited. In particular, the formulations for the ideal, dry, and lubricated revolute joints are described and utilized for the interaction of femur head inside acetabulum or the hip bone. In this process, the main kinematic and dynamic aspects of hip joints are analyzed. In a simple manner, the forces that are generated during human gait, for both dry and lubricated hip joint models, are computed in terms of the system's state variables and subsequently introduced into the dynamics equations of motion of the multibody system as external generalized forces. Moreover, a human multibody model is considered, which incorporates the different approaches for the hip articulation, namely, ideal joint, dry, and lubricated models. Finally, several computational simulations based on different approaches are performed, and the main results are presented and compared to identify differences among the methodologies and procedures adopted in this work. The input conditions to the models correspond to the experimental data capture from an adult male during normal gait. In general, the obtained results in terms of positions do not differ significantly when different hip joint models are considered. In sharp contrast, the velocity and acceleration plotted vary significantly. The effect of the hip joint modeling approach is clearly measurable and visible in terms of peaks and oscillations of the velocities and accelerations. In general, with the dry hip model, intrajoint force peaks can be observed, which can be associated with the multiple impacts between the femur head and the cup. In turn, when the lubricant is present, the system's response tends to be smoother due to the damping effects of the synovial fluid.

Development of a New Experimental Protocol for Analysing the Race-walking Technique Based on Kinematic and Dynamic Parameters

This paper describes a new motion analysis protocol for race-walking. The protocol has been tested under laboratory conditions on a real athlete of the Italian national race-walking team. The experimental setup included a motion capture system and a force platform to record both kinematic and dynamic aspects of the athletic action. Thus, any infringement of the rules can be detected, based on the measure of knee flexion-extension and the loss of ground contact. The biomechanical efficiency can be determined from the joint angles and the temporal components of gait. The results of experiments show that the protocol can be a valuable tool to assist athletes and trainers in improving race-walking technique.

Analysis and improvement of the pad wear profile in fixed abrasive polishing

Fixed abrasive polishing has some advantages in generating good planarization surfaces with low defects. The surfaces after polishing have better uniformity, and the material removal rate is much higher than that of the traditional chemical mechanical polishing using loose abrasives. One of the most important factors that have significant effects on the uniformity of the polished surface is the pad wear profile. The pad wear profile after a long time of polishing is almost concave, and it has been challenging to create a flat surface. Therefore, there is a requirement for creating a better pad wear profile to improve quality of machined surfaces in chemical-mechanical polishing processes. In this paper, kinematic aspects of the effects of operation parameters on the pad wear profile are investigated, combining with conditioner sizes, pattern, and positions. Based on that, a new model, including new designs of the conditioner and pad, is proposed. This new model has created a convex pad wear profile instead of a concave one. According to the result of the new model, the pad shape after the conditioning process is more uniform than the old one conditioned by the old model. The result was validated by an algorithm which was validated by the experiments reported in our previous paper.

Preliminary design of a small-sized flapping UAV: II. Kinematic and structural aspects

The design of the actuating mechanism of a biologically inspired flapping wing UAV is addressed. Several configurations able to reproduce the desired flapping-wing kinematics are analyzed and an optimization study is conducted to select the best configuration. The optimization results are used as the starting point for the design of the different structural components of the flapping mechanism. During the mechanism design stage, the linkages are optimized to match the desired wing’s motion during a flapping cycle. A structural and durability analysis is then conducted to verify that the mechanism and its components are able to withstand the aerodynamic and inertial loads.

Direct comparisons of hand and mouth kinematics during grasping, feeding and fork-feeding actions.

While a plethora of studies have examined the kinematics of human reach-to-grasp actions, few have investigated feeding, another ethologically important real-world action. Two seminal studies concluded that the kinematics of the mouth during feeding are comparable to those of the hand during grasping (Castiello, 1997; Churchill et al., 1999); however, feeding was done with a fork or spoon, not with the hand itself. Here, we directly compared grasping and feeding kinematics under equivalent conditions. Participants were presented with differently sized cubes of cheese (10-, 20- or 30-mm on each side) and asked to use the hand to grasp them or to use a fork to spear them and then bring them to the mouth to bite. We measured the apertures of the hand during grasping and the teeth during feeding, as well as reaching kinematics of the arm in both tasks. As in many past studies, we found that the hand oversized considerably larger (~11–27 mm) than the food item during grasping; moreover, the amount of oversizing scaled with food size. Surprisingly, regardless of whether the hand or fork was used to transport the food, the mouth oversized only slightly larger (~4–11 mm) than the food item during biting and the oversizing did not increase with food size. Total movement times were longer when using the fork compared to the hand, particularly when using the fork to bring food to the mouth. While reach velocity always peaked approximately halfway through the movement, relative to the reach the mouth opened more slowly than the hand, perhaps because less time was required for the smaller oversizing. Taken together, our results show that while many aspects of kinematics share some similarity between grasping and feeding, oversizing may reflect strategies unique to the hand vs. mouth (such as the need to have the digits approach the target surface perpendicularly for grip stability during lifting) and differences in the neural substrates of grasping and feeding.

Coordinated Behaviour in Pigeon Flocks.

We analysed pigeon flock flights using GPS trajectory data to reveal the most important kinematic aspects of flocking behaviour. We quantitatively investigated the internal motion of the flock based on pairwise statistics and found the following general relationships in all datasets: i) the temporal order of decisions characterised by the delay between directional changes is strictly related to the spatial order characterised by the longitudinal relative position within the flock; ii) during circling motion, pigeons use a mixture of two idealised and fundamentally different turning strategies, namely, parallel-path and equal-radius type turning. While pigeons tend to maintain their relative position within the flock on average, as in the parallel-path approximation, those who turn later also get behind as in the equal-radius case. Equal-radius type turning also tends to be expressed more during smaller radius turns.

A plate tectonic scenario for the Iapetus and Rheic oceans

The tectonics, dynamics, and biogeographic landscape of the early Paleozoic were dominated by the opening and expansion of one large ocean—the Rheic—and the diminution to terminal closure of another—Iapetus. An understanding of the evolution of these oceans is thus central to an understanding of the early Paleozoic, but their chronicle also presents a rich temporal profile of the Wilson cycle, illustrating continental-scale rifting, microcontinent formation, ocean basin development, arc accretion, and continent–continent collision. Nevertheless, contemporary paleogeographic models of the Iapetus and Rheic oceans remain mostly schematic or spatiotemporally disjointed, which limits their utility and hinders their testing. Moreover, many of the important kinematic and dynamic aspects of the evolution of these oceans are impossible to unambiguously resolve from a conceptual perspective and the existing models unsurprisingly present a host of contradictory scenarios. With the specific aim to resolve some of the uncertainties in the evolution of this early Paleozoic domain, and a broader aim to instigate the application of quantitative kinematic models to the early Paleozoic, I present a new plate tectonic model for the Iapetus and Rheic oceans. The model has realistic tectonic plates, which include oceanic lithosphere, that are defined by explicit and rigorously managed plate boundaries, the nature and kinematics of which are derived from geological evidence and plate tectonic principles. Accompanying the presentation and discussion of the plate model, an extensive review of the underlying geological and paleogeographic data is also presented.

Differentiability of correlations in realistic quantum mechanics

We prove a version of Bell’s theorem in which the locality assumption is weakened. We start by assuming theoretical quantum mechanics and weak forms of relativistic causality and of realism (essentially the fact that observable values are well defined independently of whether or not they are measured). Under these hypotheses, we show that only one of the correlation functions that can be formulated in the framework of the usual Bell theorem is unknown. We prove that this unknown function must be differentiable at certain angular configuration points that include the origin. We also prove that, if this correlation is assumed to be twice differentiable at the origin, then we arrive at a version of Bell’s theorem. On the one hand, we are showing that any realistic theory of quantum mechanics which incorporates the kinematic aspects of relativity must lead to this type of rough correlation function that is once but not twice differentiable. On the other hand, this study brings us a single degree of differentiability away from a relativistic von Neumann no hidden variables theorem.

Kinematics of Foot during Running: A Review

Running can be considered as an important movement since it can be categorized as one of daily activities. However, running movement may contribute to injuries for example, subject to plantar fasciitis. The objective of this review is to summarize the information of published articles related to kinematics aspect, which is one of key factors that can cause injury in running movement. The search strategy was carried out from Science Direct database. The variability of methodological protocol due to different running mode and condition influenced the foot kinematics which has been proved by the findings from the experiments. In future, research on investigating the suitable speed and condition to standardized running methodological protocol should be done in order to obtain a reliable result.

Video stimuli reduce object-directed imitation accuracy: a novel two-person motion-tracking approach.

Imitation is an important form of social behavior, and research has aimed to discover and explain the neural and kinematic aspects of imitation. However, much of this research has featured single participants imitating in response to pre-recorded video stimuli. This is in spite of findings that show reduced neural activation to video vs. real life movement stimuli, particularly in the motor cortex. We investigated the degree to which video stimuli may affect the imitation process using a novel motion tracking paradigm with high spatial and temporal resolution. We recorded 14 positions on the hands, arms, and heads of two individuals in an imitation experiment. One individual freely moved within given parameters (moving balls across a series of pegs) and a second participant imitated. This task was performed with either simple (one ball) or complex (three balls) movement difficulty, and either face-to-face or via a live video projection. After an exploratory analysis, three dependent variables were chosen for examination: 3D grip position, joint angles in the arm, and grip aperture. A cross-correlation and multivariate analysis revealed that object-directed imitation task accuracy (as represented by grip position) was reduced in video compared to face-to-face feedback, and in complex compared to simple difficulty. This was most prevalent in the left-right and forward-back motions, relevant to the imitator sitting face-to-face with the actor or with a live projected video of the same actor. The results suggest that for tasks which require object-directed imitation, video stimuli may not be an ecologically valid way to present task materials. However, no similar effects were found in the joint angle and grip aperture variables, suggesting that there are limits to the influence of video stimuli on imitation. The implications of these results are discussed with regards to previous findings, and with suggestions for future experimentation.