Markus Raffel

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The Big Ten Student Suicide Study was undertaken from 1980-1990 to determine the suicide rates on Big Ten University campuses. The study design attempted to address many of the statistical and epidemiological flaws identified in previous studies of campus student suicides. The 10-year study collected demographic and correlational data on 261 suicides of(More)
Jürgen Kompenhans, MEMBER SPIE Deutsche Forschungsanstalt für Luftund Raumfahrt Institut für Strömungsmechanik Center for Quantitative Visualisation BunsenstraXe 10 D-37073 Göttingen, Germany Abstract. In its classical form particle image velocimetry (PIV) extracts two components of the flow velocity vector by measuring the displacement of tracer particles(More)
Denmark, like the United States and other developed countries, is experiencing an increase in the percentage of dependent elderly in its population. They consume a disproportionate share of health and social services at a time when government is attempting to contain costs. Both countries face similar problems in caring for the elderly--problems of(More)
The widely-used evaluation algorithms1 for PIV recordings have some short comings, in that they introduce superfluous statistical and systematical errors. For example, they introduce the so-called “peak-locking” effect. These errors can be significantly reduced by using better algorithms. The following considerably improved analysis and algorithms will be(More)
A novel measurement technique based on the refractive index variation in a compressible flow field is presented. This concept is referred to as “Background Oriented Schlieren” (BOS) method in the following. The differences between BOS and other optical techniques which it can best be compared with, will be discussed. Already the first results illustrate an(More)
Laminar-to-turbulent transition on a rotor blade in hover has been imaged using an area-scan infrared camera. A new method for tracking a blade using a rotating mirror was employed. The mirror axis of rotation roughly corresponded to the rotor axis of rotation and the mirror rotational frequency is 1/2 that of the rotor. This permitted the use of cameras(More)
1 Introduction Since PIV became a mature technology for flow field investigations in industrial research, see for instance Kompenhans et al. (1998), it has been increasingly challenged by more complicate applications. As far as static models in wind tunnels are concerned, the experiment does not need to be synchronized with the measuring instrument.(More)