Measurements are presented on the dynamic properties of several different tennis balls, during impacts on a force plate. The force on a tennis ball rises rapidly to about half its maximum value in the ®rst 200 ls of the impact due to compression of the cloth cover and the rubber wall near the impact point. The wall then collapses inwards, resulting in a sudden decrease in ball stiffness. Result...

Crumpled sheets have a surprisingly large resistance to further compression. We have studied the crumpling of thin sheets of Mylar under different loading conditions. When placed under a fixed compressive force, the size of a crumpled material decreases logarithmically in time for periods up to three weeks. We also find hysteretic behavior when measuring the compression as a function of applied...

Objective: In this paper, finite element model of the L4 vertebra subjected to combination of compression and flexion loading in isotropic and anisotropic cases is investigated. Methods: In both cases, the vertebra is considered homogeneous. Also, the body of vertebra is divided to cancellous and cortical sections in anisotropic model, but the process is assumed isotropic such as isotropic mode...

Successful outcome of a Bankart procedure depends on knowledge of the effects of capsulolabral lesions on joint biomechanics. The joint reaction force, through "concavity compression," is integral to glenohumeral stability. In this study, we applied loads to the tendons of the rotator cuff and deltoid (anterior and middle portions) of five cadaver upper limbs. The joint reaction force was measu...

metal forming processes, compared with machining ones, reduce production steps and increasemanufacturing speed in addition to saving raw material. in this paper, forming process of column ofa steering mechanism is investigated by finite element analyses and experimental tests; andoptimum die design parameters are found. forming process parameters including die opening angle,bearing length, clea...

The compression force during traditional roofwork and improved roofwork was calculated by means of a two-dimensional static biochemical model. The improvement resulted in a 30% reduction in compression force, but also influenced factors which cannot be incorporated into the model but may cause back injuries. The frequency and velocity of movements were reduced and the trunk torsion increased. I...

Objective: In this paper, finite element model of the L4 vertebra subjected to combination of compression and flexion loading in isotropic and anisotropic cases is investigated. Methods: In both cases, the vertebra is considered homogeneous. Also, the body of vertebra is divided to cancellous and cortical sections in anisotropic model, but the process is assumed isotropic such as isotropic mode...

STUDY DESIGN An in vivo biomechanical anterior cervical discectomy and instrumented fusion (ACDFI) model employing a calibrated distractor and a subminiature load cell used to intraoperatively measure distractive force across the discectomy site and subsequent compressive force across the interbody load cell following distractor removal. OBJECTIVE To determine the relationship between the dis...

The basic problem we consider is the following: suppose we know the probability of the next symbol in an alphabet, and the next symbol, give a compression algorithm for the string. The general idea is simple: allocate short codes to more probable symbols. This will in general, force longer codes to be allocated to less probable symbols. We hope that the expected length of the code produced will...