Showing papers on "Kinematics published in 1980"

'Spontaneous' ways of reasoning in elementary kinematics

Abstract: The aim of this study was to explore and analyse 'spontaneous' ways of reasoning (SWR) of students in elementary kinematics (uniform motion in galilean frames). A set of experiments presented to 80 eleven-year-old children and to some 700 first- and fourth-year university students showed types of right and wrong answer which varied little from one sample of pupils to another. It seems difficult to attribute these results solely to school learning; but they can be well accounted for if the authors assume the existence of an organised system which the authors call the 'natural model', as opposed to the kinematic model of the physicists. This model involves two components which always interact: a purely descriptive one describing motion, and a causal one explaining motion.

A technique for kinematic modeling of anatomical joints.

Abstract: This paper describes a general technique for fitting a spatial kinematic model to an in-vivo anatomical joint under typical physiological loading conditions. The method employs a nonlinear least squares algorithm to minimize the aggregate deviation between postulated model motion and experimentally measured anatomical joint motion over multiple joint positions. Estimation of the parameters of a universal joint with skew-oblique revolutes to best reproduce wrist motion was used as an example. Experimental motion data from the right wrists of five subjects were analyzed. The technique performed very well and produced repeatable results consistent with previous biomechanical wrist findings.

Kinematic wave routing incorporating shock fitting

Abstract: An analytical solution to the kinematic wave approximation for unsteady flow routing is presented. The model allows time-dependent lateral inflow with piecewise spatial uniformity and can be applied to complex kinematic cascades. Kinematic shocks are considered as manifestations of higher-order effects such as rnonoclinal flood waves, bores, etc. Within the context of kinematic approximation therefore we retain their dynamic effects by routing the discontinuities as they appear. Certain simplifying assumptions are made which permit closed form solutions and an efficient numerical algorithm, based on the method of characteristics, is employed. The resulting model, called an approximate shock-fitting scheme, preserves the effect of the shocks without the usual computational complications and compares favorably with an implicit finite difference solution. The efficiency and accuracy of the new method are illustrated by computing a variety of unsteady flows, ranging from simple cascades to complex natural watersheds.

Joint linear, extremal inversion of seismic kinematic data

Abstract: A method for treating, in a joint manner, both distance and delay time data, including uncertainties, is presented Full advantage is taken of the linear relationship between kinematic data and velocity structure The inversion is computed using linear programing, a technique developed to treat economic optimization problems Because of the linearity of the inverse problem and the ability to constrain solutions to be physically realizable the method will accurately predict achievable velocities within the earth In general, after choosing a convenient basis in which to expand the velocity-depth function, the technique will provide the tightest possible constraints consistent with a kinematic data set composed of upper and lower bounds on τ(p) and X(p) The effects of two nonlinear constraints caused by a possible lack of knowledge of velocities within a low-velocity zone and/or the surface velocity are examined

Effect of Frame Compliance on the Lateral Dynamics of Motorcycles

Abstract: SUMMARY The lateral dynamics of an uncontrolled motorcycle, running on a straight, level road surface, is investigated in this paper. The structural compliances in the front and the rear frames of the motorcycle are taken into account by introducing additional degrees of freedom in the analysis. The kinematics of the tires is represented by linear differential equations which are based on the taut-string model of pneumatic tires. The linear differential equations of motion are solved to yield the eigensolutions of the system. Numerical results, obtained for parameters corresponding to a Honda CB750 motorcycle, are presented and discussed.

Multisensor fusion of target attributes and kinematics

Abstract: A general architecture is presented to solve the multisensor, multitarget recognition and tracking problem. Candidate maximum a posteriori objective functionals are presented for kinematic and attribute report correlation. The treatment of multispectral noncommensurate attributes via their target classification capability is derived.

Covariant kinematics for the production of spacelike particles

Abstract: The kinematic problem connected with the production of particles with spacelike four-momentum is analyzed in its simplest form: the decay of an ordinary particle into b ordinary particles, luxons, and t spacelike particles. What, apart from four-momentum conservation, are the kinematic constraints that guarantee stable finite kinematic limits and a finite number b+t.

The Influence of Velocity and Disk Angle on the Kinematic Parameter A of Disks

Abstract: THE kinematic parameter A, the ratio of rotational velocity to forward velocity, of experimental disks was studied as a function of change of disk angle and disk velocity Disks with reduced back pressures rotated more rapidly than the conventional spherical disk The absolute velocity of a point on the edge of a rotating disk has a cosinal nature, the minimum velocity of which is at the lowest underground point of the disk

Matrix methods applied to engineering rigid body mechanics

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Relativistic kinematics for elastic pion-nucleus scattering

Abstract: An ambiguity in the kinematic transformation of the pion-nucleon scattering amplitude from the pion-nucleus center-of-mass frame to the pion-nucleon center-of-mass frame is removed by (1) the requirement of time-reversal invariance and (2) the requirement that the relative momentum be uniquely defined. The first-order optical potential is obtained by an approximate evaluation of the target ground state matrix element of the transformed pion-nucleon amplitude. Our procedure results in elastic differential cross sections that are significantly different from those obtained using previous kinematic transformations. Terms in the transformed two-body amplitudes proportional to the total three momentum squared as prescribed by relativistic potential theory are found to have negligible effects on elastic pion-nucleus scattering.

Einstein dynamics without special-relativistic kinematics

Abstract: The Michelson-Morley result is described empirically by generalized Doppler equations. If the phase of a light wave is not invariant, in agreement with the quantum nature of light, special-relativistic kinematics need not be assumed. Einstein particle dynamics and Maxwell-Lorentz electrodynamics in a moving system are derived without assuming special-relativistic kinematics. An alternative explanation for the decay rate of moving radioactive particles is presented. The observation of a third-order Doppler effect may yield the velocity of the closed laboratory.

Kinetic and kinematic factors involved in the execution of front aerial somersaults.

Abstract: The purpose of this investigation was to study the variation in ground reaction forces during take-off and to calculate the angular impulse produced about the center of mass by these forces during execution of a front aerial somersault. Additionally, several kinematic variables were discussed in relation to performance. Nine high level female gymnasts volunteered as subjects. Ground reaction force (GRF) patterns were monitored by a Kistler force platform and the selected kinematic variables were calculated from high speed film synchronized with the force records. Total body center of mass position was determined and subsequently used in the calculation of angular impulse during rear, double, and front leg support. While results showed similar angular impulse patterns across our subject population, a variety of kinetic and kinematic variables were presented in order to more completely discuss the components of angular impulse development during the take-off phase of a front aerial somersault. For example, while the mean angular impulse was 61.7 Nms (+/- 13.1), a surprising finding was the contribution made to this impulse by the rear leg, 70.9% (+/- 7.2).

Celestial Reference Frames

Abstract: A celestial reference frame is based on some dynamical or kinematic approximation of an absolute coordinate system and is materialized by a fundamental catalogue of stars. It is characterized by the accuracy of the system and the precision of its stellar realization.

Kinematic and Dynamic Reference Frames

Abstract: The fundamental properties of kinematic and dynamic reference frames are defined, first as an abstract concept and second in a practical (although idealized) thought experiment A four dimensional space-time description in coordinate free notation illustrates the properties, limitations, and relationships between kinematic and dynamic reference frames Kinematic reference frames can be defined quite rigorously Dynamic reference frames cannot be defined so well, but are nonetheless very useful In practice a combination has been generally adopted Presently we can materialize purely kinematic terrestrial and celestial reference frames

The relation of kinematic factors to the acquisition of skill on a novel task.

Abstract: The purpose of the study was to determine which kinematic factors changes and how they changed during the process of skill acquisition. A novel throwing task, involving only the elbow joint, was selected that could be learned during one session. Biomechanical data were collected on-line by a program in a PDP - 11/34 computer via an A to D converter. Angular displacement, linear acceleration, and instant of ball release were continuously monitored and velocity was calculated. The subjects acquired the task within the first ten out of forty learning trials. Consequently, group analyses were limited to the first ten throws. The mechanical factors showed changes with skill acquisition, with elbow angle and elbow velocity at release accounting for 99% of the variance in score. It was found that to obtain the desired performance outcome, each subject selected his own limited range of angles and velocities at release. Although pertinent biomechanical factors are task specific, individuals in this case selected their own strategies to get the same outcome on a task.