Analysis of problems related to slingshot shock machine high-velocity shock testing

Slingshot device for high-velocity shock testing analyzed for impact delivery, shock pulse, and g-leve

Effective governing equations for poroelastic growing media

A new mathematical model is developed for the macroscopic behaviour of a porous, linear elastic solid, saturated with a slowly flowing incompressible, viscous fluid, with surface accretion of the solid phase. The derivation uses a formal two-scale asymptotic expansion to exploit the well-separated length scales of the material: the pores are small compared to the macroscale, with a spatially periodic microstructure. Surface accretion occurs at the interface between the solid and fluid phases, resulting in growth of the solid phase through mass exchange from the fluid at a prescribed rate (and vice versa). The averaging derives a new poroelastic model, which reduces to the classical result of Burridge and Keller in the limit of no growth. The new model is of relevance to a large range of applications including packed snow, tissue growth, biofilms and subsurface rocks or soils

Sickness absence as a global measure of health: evidence from mortality in the Whitehall II prospective cohort study

Objective: To examine the association between sickness absence and mortality compared with associations between established health indicators and mortality. Design: Prospective cohort study. Medical examination and questionnaire survey conducted in 1985-8; sickness absence records covered the period 1985-98. Setting: 20 civil service departments in London. Participants: 6895 male and 3413 female civil servants aged 35-55 years. Main outcome measure: All cause mortality until the end of 1999. Results: After adjustment for age and grade, men and women who had more than five medically certified absences (spells greater than 7 days) per 10 years had a mortality 4.8 (95% confidence interval 3.3 to 6.9) and 2.7 (1.5 to 4.9) times greater than those with no such absence. Poor self rated health, presence of longstanding illness, and a measure of common clinical conditions comprising diabetes, diagnosed heart disease, abnormalities on electrocardiogram, hypertension, and respiratory illness were all associated with mortality-relative rates between 1.3 and 1.9. In a multivariate model including all the above health indicators and additional health risk factors, medically certified sickness absence remained a significant predictor of mortality. No linear association existed between self certified absence (spells 1-7 days) and mortality, but the findings suggest that a small amount of self certified absence is protective. Conclusion: Evidence linking sickness absence to mortality indicates that routinely collected sickness absence data could be used as a global measure of health differentials between employees. However, such approaches should focus on medically certified (or long term) absences rather than self certified absences

Evening At Juniper Knoll

Oh, the glory of it all! The sun was a magnificant ball of flame as it descended low in the heavens. Small fluffy clouds of gold floated around the huge flaming ball, but kept their distance as though there was some fear of it. Occasionally, a graceful swallow Hew across, lending his profile to the glory of the heavens, and the cry of night birds as they took to flight gave the woods that necessary note of evening time. As I strolled through the woods, the sticks crackled beneath my feet and one little squirrel in the tree top took aim and fired his walnut at my head, which, in his estimation, made a very superior target. The greenery around me was becoming wet with dew and as I neared the knoll, which was the most beautiful spot in that section of the woods, the sun had almost crept behind the farthest hill

Investigation of potential of differential absorption Lidar techniques for remote sensing of atmospheric pollutants

The NASA multipurpose differential absorption lidar (DIAL) system uses two high conversion efficiency dye lasers which are optically pumped by two frequency-doubled Nd:YAG lasers mounted rigidly on a supporting structure that also contains the transmitter, receiver, and data system. The DIAL system hardware design and data acquisition system are described. Timing diagrams, logic diagrams, and schematics, and the theory of operation of the control electronics are presented. Success in obtaining remote measurements of ozone profiles with an airborne systems is reported and results are analyzed

Acoustic spectral analysis and testing techniques

Subjects covered in four reports are described including: (1) mathematical techniques for combining decibel levels of octaves or constant bandwidth: (2) techniques for determining equation for power spectral density function; (3) computer program to analyze acoustical test data; and (4) computer simulation of horn responses utilizing hyperbolic horn theory