introduction: arterial stiffness is an important predictor of cardiovascular risk. several indices have been  introduced to estimate the arterial stiffness based on the changes in the brachial blood pressure. since the  substitution  of  the  blood  pressure  changes  in  the  central  arteries  such  as  carotid  with  the  blood  pressure  changes in the brachial results in error in the blood...

One of the important issues in the study of steel frames is to find a suitable formulation for semi-rigid connections. In this paper, the explicit stiffness matrix for a two-dimensional beam-column element having end-flexibilities is derived. The effects of the lateral uniformly distributed load on the deflection are considered. Both tensile and compressive axial loads are also taken into accou...

To assess the effects of halothane, isoflurane, and sevoflurane on cross bridges in intact cardiac muscle, electrically stimulated (0.25 Hz, 25 degrees C) right ventricular ferret papillary muscles (n = 14) were subjected to sinusoidal load oscillations (37-182 Hz, 0.2-0.5 mN peak to peak) at the instantaneous self-resonant frequency of the muscle-lever system. At resonance, stiffness is propor...

A frequency domain dynamic analysis is needed to obtain the response of structures constructed on a system of base isolators on flexible soil when subjected to earthquake ground motion. In such systems, the lateral stiffness of the base isolators is so small, compared to the structural stiffness, that in an earthquake attack the fundamental vibration mode dominates the response. With this in mi...

A frequency domain dynamic analysis is needed to obtain the response of structures constructed on a system of base isolators on flexible soil when subjected to earthquake ground motion. In such systems, the lateral stiffness of the base isolators is so small, compared to the structural stiffness, that in an earthquake attack the fundamental vibration mode dominates the response. With this in mi...

This paper describes the experimental studies of vertical dynamic stiffness of single piles subjected to small amplitude of vibrations with constant dynamic load. The test results were correlated with the static load test results that had been carried out on the same piles. The ratio of dynamic to static stiffness mainly falls between 1.2-1.4. The dynamic stiffness measurements were compared wi...

Variable stiffness structures that enable a wide range of efficient load-bearing and dexterous activity are ubiquitous in mammalian musculoskeletal systems but are rare in engineered systems because of their complexity, power, and cost. We present a new negative stiffness-based load-bearing structure with dynamically tunable stiffness. Negative stiffness, traditionally used to achieve novel res...

Helical springs within the primary suspension are critical components for isolating the whole vehicle system from vibration generated at the wheel/rail contact. As train speeds increase, the frequency region of excitation becomes larger, and a simplified static stiffness can no longer represent the real stiffness property in a vehicle dynamic model. Coil springs in particular exhibit strong int...

-Stiffness modulation scheme for a robotic driving system with redundant actuation was investigated in this paper. The dynamic and the stiffness models of a simple system having one link and two prismatic actuators were derived and employed for computational simulations of dynamic response to an initial disturbance. Several combinations with different types of elastic elements were applied to t...