Zur Classification der Flächen dritter Ordnung

Ohne ZusammenfassungMit 3 lithographirten Tafeln.     

The Effect of Reynolds Number on the Passive Scalar Field in the Turbulent Wake of a Circular Cylinder

In this paper we investigate by experiments the effect of Reynolds number on a passive scalar (temperature) field in the turbulent wake of a slightly heated circular cylinder. The Reynolds number defined by Re≡U _∞ d/ν (see Nomenclature) is varied from Re= 1200 to Re= 8600. Temperature differential above ambient is chosen to be the passive scalar quantity. Present measurements are conducted using a cold wire (0.63 μm) probe. Results obtained suggest that Reynolds number in general has significant influence on the scalar mixing characteristics in the entire wake flow. Specifically, as Re increases, the mean scalar spreads out more rapidly, the scalar fluctuation intensity increases; however, its variance decays at a lower rate with downstream distance. It is also found that an increase of Re accelerates the streamwise evolution of the scalar probability density function from highly non-Gaussianity to near Gaussianity along the wake centreline. This reflects the reduction in length of the Karman-vortex street caused by an increase of Re.     

An alternative method to specify the degree of resonator stability

We present an alternative method to specify the stability of real stable resonators. We introduce the degree of optical stability or the S parameter, which specify the stability of resonators in a numerical scale ranging from 0 to 100%. The value of zero corresponds to marginally stable resonator and S < 0 corresponds to unstable resonator. Also, three definitions of the S parameter are provided: in terms of A&D, B&Z _Ro and g ₁ g ₂. It may be noticed from the present formalism that the maximum degree of stability with S = 1 automatically corresponds to g ₁ g ₂ = 1/2. We also describe the method to measure the S parameter from the output beam characteristics and B parameter. A possible correlation between the S parameter and the misalignment tolerance is also discussed.      

Bell's theorem does not eliminate fully causal hidden variables

Bell's theorem applies only to a hybrid universe in which hidden variables determine only part of the outcomes of experiments. When applied to a fully causal hidden variable theory, in which detector settings as well as their interaction with particles during observation are determined by the variables, Bell's analysis must be modified. The result is that a fully causal hidden variable model can be produced for which a properly chosen spread of hidden variables gives precisely the same prediction as standard quantum theory.     

Can statistical average be affected by its observer?

In classical statistical mechanics, it is tacitly assumed that the only side effect of the measuring process is to produce fluctuations in the measured system. In other words, the system's average property is not affected by the observer. The present letter discusses this assumption in terms of aGedankenexperiment.