Applicability of normal and shear stress cells embedded in cohesionless materials

A normal stress cell and a shear stress cell have been designed and tested under very varied conditions including permanent strain. Results pooled from nine different tests with the cells embedded in cohesionless materials (sand and wheat) showed that the coefficient of variation of the normal stress-cell sensitivity was 0.04, while it was 0.10 for the shear cell. The agreement between predicted and measured sensitivity was considered to be good for the normal stress cell and reasonably good for the shear stress cell. The shear cell showed a systematic dependence, within acceptable limits, of the total stress state in the surrounding material. A qualitative explanation of this phenomenon is given. Paper was presented at the SEM VI International Congress on Experimental Mechanics held in Portland, OR in June 6–10, 1988.     

On‐line monitoring of the dynamics of trihalomethane concentrations in a warm public swimming pool using an unsupervised membrane inlet mass spectrometry system with off‐site real‐time surveillance

To study the long‐term dynamics of trihalomethanes (THMs) in a warm (31–33°C) public swimming pool, we built a robust membrane inlet mass spectrometer that could perform unsupervised, on‐site monitoring of the concentration of these compounds with off‐site, real‐time surveillance. The instrument was installed in a technical room below the pool and operated continuously for more than a year practically only interrupted for filament replacements every 6–8 weeks. One to two days after a filament replacement, the instrument stabilized and kept its calibration until shortly before the next filament burnout. The on‐line monitoring of THMs revealed a daily rhythm in the concentrations of chloroform and bromodichloromethane. They increased during the pool's closing hours and decreased during opening hours with the minimum concentration being approximately half of the maximum. Over the 1 year monitoring period, the variation in the maximum registered daily concentration was 30–100 µg/L for chloroform. The variation of bromodichloromethane was 5–10 µg/L, except during bursts of 1–2 days duration, where the concentration of bromodichloromethane could reach 100 µg/L. The burst in bromodichloromethane concentration was directly correlated with salt addition (sodium chloride) to the pool water for use in the pool's electrolytic in‐line chlorination system. A correlation between THM removal from the pool water and the operation of a strong water jet system was also found. Copyright © 2009 John Wiley & Sons, Ltd.     

General stress-velocity expressions in acoustoelasticity

The velocity of a transverse wave propagating in an elastic body depends on the stress field of the body. If transverse waves are sent through a body with a uniaxial stress field, there will be proportionality between the principal-stress difference and the relative velocity difference between the waves polarized in accordance with the two main directions. This technique is used for determining uniaxial residual-stress fields. The main object of the investigation described in this paper has been to investigate the usefulness of the method in the case of biaxial residual-stress fields. Both theoretically and experimentally, the investigation has shown that there is also proportionality between principal-stress difference and relative-velocity difference for a biaxial field. However, the tests have also shown that inaccuracies with this method, on account for example of preferred orientation in steel materials, are of such an order of magnitude that the method cannot, at the present stage of development, compete with the more traditional methods, such as the drilling method and the X-ray diffraction method.     

EU regulation for accreditation

Accreditation in the European Union has since January 2010 been regulated by the EU Regulation on Accreditation and Market Surveillance, which establishes a legal framework for the provision of accreditation services in Europe.     

On the notion of space in geometry

The development of the notion of space in geometry is traced from the early axiomatization in Euclid’s Elements over the discovery of non-Euclidean geometries to geometry of manifolds in relativity theory and in gauge and string theories in contemporary physics. The notion of space is considered in a historic-philosophical perspective including a short discussion of the contributions of artists to visualization of spatial objects.