Showing papers on "Kinematics published in 1970"

Maximizing Human Power Output by Suitable Selection of Motion Cycle and Load

Abstract: In this paper various factors affecting human power output are discussed, including the mechanical properties of muscle, the geometry of the input motion and the kinematics of the input motion. A mulitpurpose ergometer, designed and built to take account of these factors is described. Two basic motions are possible on the ergometer: cycling and rowing. The rowing motions may be made with any combination of seat and feet either sliding or fixed. In the rowing motions, during a single to and fro cycle, prescribed variations in velocity of the input links can be forced on a subject. Experimental work, which is described, showed that there are considerable differences in the effectiveness of the various ways of working, and that one in particular, a modified rowing motion, allowed the production of greater average amounts of power for periods up to two minutes than have so far been recorded and published (to the author's knowledge).

Weapon training systems

Abstract: A weapons-effect simulating system especially suitable for use with missile-launching weapons such as bazookas. The system includes sighting means for aiming the launcher at a target and a source of electromagnetic radiation having its orientation or direction changed with respect to the sighting means by generated signals applied to a control system coupling the sighting means and the source. Subsystem apparatus for generating the control signals include aerodynamic and kinematic simulation circuits; the output of the aerodynamic circuit representing the dynamic response of the simulated missile to, for example, changes in sidewise acceleration, and the output of the kinematic circuit representing, for example, random flight disturbances and crosswinds.

Kinematic Dynamo Problem

Abstract: Summary The properties of the dynamo equation are discussed to show that the dynamo equation is self-adjoint for a curl-free velocity under a suitable restriction. The impossibility of a steady dynamo by a motion having only a radial velocity component which vanishes at the boundary surface is proved, and an attempt has been made to verify the possibility of an oscillating toroidal field dynamo. Also it is shown that any poloidal magnetic field cannot be amplified by a uniform stellar contraction, while quasi-steady toroidal fields can be maintained by a homologous contraction.

Effect of Gravity on the Performance of an Impact Damper: Part 2. Stability of Vibrational Modes

Abstract: This paper is c oncerned with the stability of the various modes of vibration of the impact damper system described in Part 1†. Charts are presented showing the ranges of dynamically stable and kinematically viable periodic two-impact-per-cycle motion. The condition of kinematic viability ensures that the trajectory of the free mass remains within the container throughout the motion.It is shown that in general stable, viable, two-impact-per-cycle motion of the system exists under resonant conditions of the main mass and that away from resonance, where any damper is ineffective, this type of motion is generally unstable.

The Kinematic Synthesis Of Path GeneratingMechanisms Using Genetic Algorithms

Abstract: This paper presents a methodology for the synthesis of path generating mechanisms using Genetic Algorithms (GAs). GAs are a novel search and optimisation technique inspired by the principles of natural evolution and 'survival of the fittest'. The problem used to illustrate the use of GAs in this way is the synthesis of a four bar mechanism to provide a desired output path.

Electromagnetic-transition form factors free of kinematic singularities

Abstract: Matrix elements of the electromagnetic currents between one-particle states of spins ands′ are decomposed into invariant functions free of kinematic singularities which are the usual multipole amplitudes in the nonrelativistic limit. Parity conservation is taken into account. Kinematic constraints occur only at the two physical threshold values and are given explicitly.

Electrostatic acceleration system for hypervelocity microparticles with selected kinematic properties

Abstract: Electrostatic acceleration system for hypervelocity microparticles with selected kinematic properties

Revised formulation of the macroscopic maxwell theory

Abstract: The theory of energy propagation in dispersive media formulated by Brillouin is generalized and extended by taking into account energy attenuation or energy growth during the transmission process Because of the exponential decay due to attenuation, the concept of propagation velocity of an electromagnetic disturbance can now be shown to have a physical meaning even if there is absorption, and in such a case the velocity of the disturbance is represented by the velocity of the point at which it attains its maximum intensity Expressions are obtained for the energy density and the energy flow in an absorbing medium, and it is shown that the propagation velocity (a kinematic concept) is equal to the velocity of the energy transport Such an equality is considered to be of fundamental interest since it supports the validity of the kinematic approach from the energetic point of view Other aspects of energy transmission are discussed and analysed with particular reference to nonconvective and convective disturbances in absorbing and emitting media

Particle motion along a kinematic fault model

Abstract: Particle motion was examined along the following kinematic fault model: the fault plane is a rectangle so elongated that differences in particle motion in the shorter dimension can be neglected and rupture, once initiated, can be considered to propagate only in the longitudinal direction(s) at constant speed; the distribution of particle displacement along the ruptured fault segment maintains the same sinusoidal shape at different times until finally all particles stop simultaneously. It was found that the pattern of particle motion in this model depends on whether the rupture propagates unilaterally or bilaterally. For the bilateral case, particle displacement and velocity are nearly a finite ramp and a box-car function of time, respectively. The maximum particle velocity is the same everywhere along the final ruptured fault segment, but the average velocity is slightly higher for particles closer to the ends. For the unilateral case, particle velocity is approximately an impulse function of time for particles near the starting edge and gradually becomes a box-car function for particles near the ending edge of rupture. The maximum velocity is the same for all particles along the fault segment, but the average velocity is considerably higher for particles closer to the ending edge. It is not a good approximation for either of these cases to assume that all the particles along the fault segment have the same displacement-time function with only a time delay.

Reconstruction of Closing Phase Kinematics by Motion Analysis for a Prosthetic Bileaflet Valve

Abstract: The occluder motion of bileaflet valves has been studied by researchers in order to understand critical kinematic features that can be associated with post-implant complications. The closing phase, in particular, was studied monodimensionally using different techniques (laser and timing gate) in order to investigate the cavitation potential of valves, but the results these techniques yield are not measurable in vivo. Therefore we analysed the valve closing phase motion by means of High Speed Videography (HSV) on a bileaflet valve model, the 29 mm-sized Sorin Bicarbon. Testing was performed in a standard way using the pulse duplicator developed at the University of Sheffield (UK) with the valve mounted in mitral position, and the HSV system (Kodak Ektapro) running at 12000 frame per sec, synchronised on the flow waveform. The kinematic analysis of this prosthesis started from a modelling process needed to reduce the leaflet degrees of freedom due to the pivot design. In fact, the spherical coupling between leaflet and housing yields hypocycloid trajectories for the leaflet points. Thus a trajectory table (TT) was built that can be addressed by the^ coordinate of the recorded leaflet points, reducing the problem to a monodimensional one. To verify the model we used a two-orthogonal-camera set up, at 1000 frame per/sec. Finally, from the frontal view recordings at 12000 Hz and the trajectory table (TT), the whole leaflet motion just immediately before the closure time was obtained synchronously with pressure and flow traces. Motion analysis calculations provided angular and tip velocities related to the left ventricular dp/dt values to evaluate the prosthesis function and performance.

Device for adjusting the angle of inclination of guide blades of turbo machines

Abstract: A device in which there is a series connection of driven elements permanently connected with the guide blades of a turbomachine in a kinematic train by means of intermediate idle elements, drive mechanism adapted to effect an independent turning of two adjacent driven elements in opposite directions, with the resulting expanding force making for the elimination of free play in the kinematic train.

Dynamic analysis of a torsional vibration actuator

Abstract: The objective of this study is the evaluation of a mechanical system, which includes a Hooke's joint, as a possible torsional vibration actuator. The essential requirement of such a system is to produce a periodically varying angular motion superimposed upon a mean constant speed rotation. The basic kinematics of a Hooke's joint suggest that it could be used to generate the type of motion desired. The mechanical arrangement of a system incorporating a Hooke's joint is described and the governing differential equations are developed. These equations are simultaneous, differential equations of second order and are highly nonlinear. Values of typical system parameters are selected and the equations are solved numerically using a fourth order Runge-Kutta digital solution. The equations are solved with variations of constants to evaluate the effect of change in parameters upon the system response. The numerical results show that the vibration amplitude at the specimen is directly proportional to the motor speed and the Hooke's joint angle. The frequency of the vibration at the specimen increases with an increase 1n the motor speed but is independent of the Hooke's joint

Classification of different approaches based on modelling and simulation for a kinematic analysis of planar and spatial mechanism

Abstract: In finding a complete kinematic analysis of a planer or spatial mechanism; the first step is, asking yourself which approach is ideal. Here we show how the classification of different ways based on modelling and simulation act through particular problems and see if it is always logical to go through the problem without use of any software and also see that simulating a mechanism by software, leads to a fabulous save in time.

Analytical Study On The Kinematic AndDynamic Behaviours Of Tibiofemoral Joint

Abstract: The focus of this study is to simulate the kinematic and dynamic behaviors of a two dimensional tibiofemoral joint with a quasi-static and a dynamic model. Parameters of interest include the joint surface contact point, ligament forces, and slide/roll ratio between the femur and tibia. Model results are compared to experimental cadaver studies available in literature. Furthermore, the effect of femur surface geometry on the above mentioned characteristics is also determined. The pattern of ligament forces from the analytical study matches well qualitatively with the experimental study. Change of femur surface geometry has little effect on the pattern of slide/roll ratio.

Development and application of cartesian tensor mathematics for kinematic analysis of spatial mechanisms

Abstract: The complexity of spatial mechanisms in themselves and the absence of an attractive analytical tool for their study has left this field of engineering analysis largely unexplored In recent years several analytic methods have emerged One of the most attractive of these is the tensor method Literature surveys reveal that the tensor method is largely unexploited in the USA, with regard to spatial mechanisms as well as simpler kinematic problems The purpose of this work is to develop tensor mathematics for application to the kinematic analysis of spatial mechanisms Methods are developed for position solutions and the determination of velocities and accelerations of points of interest Included are tensor methods for obtaining angular velocities and accelerations as well as the formulae for treating moving coordinate frames Iterative procedures are discussed for cases where a closed form solution is not possible Sufficient applications are included to exemplify the methods developed including some which are numerically solved by computer It is concluded that the methods developed represent a cogent and tractable method of analysis of kinematic problems