5 research outputs found
Probing shells against buckling: a non-destructive technique for laboratory testing
This paper addresses testing of compressed structures, such as shells, that
exhibit catastrophic buckling and notorious imperfection sensitivity. The
central concept is the probing of a loaded structural specimen by a controlled
lateral displacement to gain quantitative insight into its buckling behaviour
and to measure the energy barrier against buckling. This can provide design
information about a structure's stiffness and robustness against buckling in
terms of energy and force landscapes. Developments in this area are relatively
new but have proceeded rapidly with encouraging progress. Recent experimental
tests on uniformly compressed spherical shells, and axially loaded cylinders,
show excellent agreement with theoretical solutions. The probing technique
could be a valuable experimental procedure for testing prototype structures,
but before it can be used a range of potential problems must be examined and
solved. The probing response is highly nonlinear and a variety of complications
can occur. Here, we make a careful assessment of unexpected limit points and
bifurcations, that could accompany probing, causing complications and possibly
even collapse of a test specimen. First, a limit point in the probe
displacement (associated with a cusp instability and fold) can result in
dynamic buckling as probing progresses, as demonstrated in the buckling of a
spherical shell under volume control. Second, various types of bifurcations
which can occur on the probing path which result in the probing response
becoming unstable are also discussed. To overcome these problems, we outline
the extra controls over the entire structure that may be needed to stabilize
the response.Comment: as accepted in International Journal of Bifurcation and Chaos (18
pages
Factors associated with self-rated health status in university students: a cross-sectional study in three European countries-2
when different self-efficacy scores are considered.<p><b>Copyright information:</b></p><p>Taken from "Factors associated with self-rated health status in university students: a cross-sectional study in three European countries"</p><p>http://www.biomedcentral.com/1471-2458/8/215</p><p>BMC Public Health 2008;8():215-215.</p><p>Published online 18 Jun 2008</p><p>PMCID:PMC2438349.</p><p></p
Results of logistic regression analysis conducted in five countries: relative odds of two health outcomes associated with (1) physical fighting and (2) weapon carrying, 2006 <i>(Boys)</i><sup>*</sup>.
*<p>(1) Models simultaneously adjusted for age, socio-economic status, physical activity, smoking, drinking, evenings out with friends, and bullying victimization.</p
Prevalence of physical fighting, weapon carrying, and potential adolescent health outcomes, percentages (standard errors) by gender and country, 2006.
<p>Prevalence of physical fighting, weapon carrying, and potential adolescent health outcomes, percentages (standard errors) by gender and country, 2006.</p
Demographic characteristics of study samples in five HBSC countries, 2006.
<p>Demographic characteristics of study samples in five HBSC countries, 2006.</p