Acoustic sonic and ultrasonic resonance analysis is a new non-destructive testing technique that allows 100% testing of a wide range of test objects quickly and at low cost. After an impact, a specimen vibrates in certain characteristic modes and frequencies that can be measured by a microphone or laser vibrometer. Typical faults that can be detected are cracks, cavities, detached layers, mater...

Pulse tube refrigerators (PTRs) have made dramatic improvements in reliability, efficiency and usage. Inertance tube PTRs have been one of the keys to these improvements. The inertance tube is the component in the PTR that most easily affects the control of the PTR fluid dynamics. In one application in multistage cryocoolers, the performance of inertance tubes at the cryogenic temperatures is o...

The general principles underlying the acoustic performance of the avian vocal tract are examined both theoretically and experimentally. The formant resonances produced both by the total vocal tract and by the bronchial tubes are evaluated quantitatively, and their dependence upon anatomical parameters is investigated. A simplified cylindrical model for the beak is examined theoretically, and ex...

Material properties and geometry are two important design parameters which their effects should be considered in a crashworthiness analysis. In this paper, the axial impact of metallic and hybrid energy absorbing thin-walled tubes with poly-gonal cross-section is simulated using LS-DYNA software. The combined effects of changing the geometry and material properties on the mass specific energ...

the importance of the use of activated charcoal tubes for sampling gases and vapors is very well-known. for producing these tubes in the country, their production started in the laboratory of the department of occupation al health using activated charcoal, polyurethane foam and glass wool and consequently two types of foamed and foamless tubes were produced. to investigate the quality of the ra...

including basic and performance. For example, section 4.1 shows spectral response characteristics of typical photocathodes and also gives the definition of photocathode sensitivity and its measurement procedure. Section 4.2 explains dynode types, structures and typical characteristics. Section 4.3 describes various performance characteristics such as time response, operating stability, sensitiv...

JCB • VOLUME 168 • NUMBER 3 • 2005 348 Saving varicella from suicide aricella zoster virus (VZV) causes both varicella (chickenpox) and zoster (shingles). VZV spreads throughout the body, but it does so slowly, and virus only emerges extracellularly in the skin where it can spread to other hosts. That behavior is now explained by Zhenglun Zhu (Harvard Medical School, Boston, MA), Jason Chen, An...

The open end correction coefficient (OECC) of acoustic tubes has been widely investigated under a free-field condition. This study examines OECCs in confined regions, such as side branches within the vocal tract. To do this, a number of mechanical acoustic models are used to examine the effects of the angle of the branch axis and the proximity of the walls of the main tract to the open end of t...

Several recent investigations indicate that tube-wave amplitude attenuation in acoustic full-waveform logs is correlated with permeability in fractured rocks. However, there are significant differences between predictions based on theoretical models for tubewave propagation and experimental waveform amplitude data. This investigation reviews the results of existing theoretical models for tube-w...