Key technologies disclosure for the high-g shock tester based on collision principle and experimental study.

The shock tester based on a three-body, single-level velocity amplifier is especially suitable for high-g shock tests of lightweight and compact pieces. This study focuses on disclosing some key technologies that affect whether the velocity amplifier could achieve a high-g level shock experimental environment. Equations describing the first collision are deduced and some key design criteria are proposed. The key conditions for formation of the opposite collision are proposed for the second collision, which is the most important point, to obtain a high-g shock environment. A test platform was constructed, and experiments were conducted with different shock rods, pulse shapers, and initial velocities. The test results fully demonstrated the powerful ability of the single-level velocity amplifier for high-g shock experiments and tell us that a duralumin alloy or carbon fiber is suitable to design shock rods.

Theoretical and experimental study of the "superelastic collision effects" used to excite high-g shock environment.

The excitation technology for high-g-level shock environment experiments is currently a topic of interest, for which velocity amplification by collisions of vertically stacked bodies has been used to develop high-g shock tests with great success. This study investigated the superelastic collision effects generated during high-velocity one-dimensional three-body impacts. Theoretical formulae were derived in brief for an analytical investigation of the collisions. Four experiments were performed with different initial velocities obtained from free-falls from different heights. Velocity gains larger than 5 were obtained for the three-body collisions, and coefficients of restitution larger than 2.5 were observed for the second impact. The experimental results well verified the existence of superelastic collision effects in the one-dimensional three-body impacts.

Study of inflammatory factors' effect on the endothelial barrier using piezoelectric biosensor.

This paper used piezoelectric sensor to study the dysfunction of endothelial cell monolayer barrier caused by inflammatory factors. The biocompatible conductive polymer membrane of pPy[pGlu]-pLys was prepared on the surface of the ITO work electrode to improve the interface between the endothelial cell and the electrode. Both the impedance analysis data and the stable plateau stage of sensor's frequency shift indicated that endothelial cells formed a good monolayer barrier on this polymer surface. The response frequency shifts of lipopolysaccharide (LPS)- and histamine-induced endothelial barrier dysfunction were different, which distinguished their different stimulation mechanism. It provided a valuable analysis method for detecting the endothelial barrier function affected by inflammatory factor, and could further promote the application of piezoelectric sensor in cell biology and toxicology research.

Pulse shaping techniques for a high-g shock tester based on collision principle.

Pulse shaping techniques are discussed in this paper for the practicability of a developed high-g shock tester. The tester is based on collision principle where there is a one-level velocity amplifier. A theoretical and experimental study of pulse shaping techniques is presented. A model was built and theoretical formulae were deduced for the shock peak acceleration and its duration. Then theoretical analysis and some experiments were conducted. The test results verify the validity of theoretical model and show that the shock tester can generate the expected high-g shock pulses by integrated usage of different impact velocities and pulse shapers made from different materials. This is important in practical applications where the items under test can be shown to excite specific resonances at predetermined acceleration levels using the shock tester.

Design and test of a soft plantar force measurement system for gait detection.

This work describes a plantar force measurement system. The MEMS pressure sensor, as the key sensing element, is designed, fabricated and embedded into a flexible silicon oil-filled bladder made of silicon rubber to constitute a single sensing unit. A conditioning circuit is designed for signal processing and data acquisition. The characteristics of the plantar force sensing unit are investigated by both static and dynamic tests. A comparison of characteristics between the proposed plantar force sensing unit and a commercial flexible force sensor is presented. A practical experiment of plantar force measurement has been carried out to validate the system. The results demonstrate that the proposed measurement system has a potential for success in the application of plantar force measurement during normal gait.

A simply constructed but efficacious shock tester for high-g level shock simulation.

A simply constructed shock tester, different from existing drop table machines, is developed for high-g level shock environment simulation. The theoretical model, structure design, and working principle of the drop tester are described. A prototype device is set up, where a carbon fiber reinforced polymer with a high specific modulus is used. Using a Brüel & Kjær high-g accelerometer, experiments to verify the validity of the design are carried out and results are given. The maximum acceleration level is in excess of 60,000 g, limited only by the manual driving force.