No abstract

The primary application of dimensional analysis (DA) is in problem solving. Typically, the problem description indicates that a physical quantity Y (the unknown) is a function f of other physical quantities A1, …, An (the data). We propose a qualitative problem-solving procedure which consists of a parallel decomposition of the original problem into simple special cases. By simple special cases we mean special cases for which, by DA, the unknown function can be completely determined except for a dimensionless multiplicative constant. The concept of significant special representation of the unknown function is introduced.

The spectral density of the Barkhausen noise has been measured and a theoretical interpretation of the results is given. It is assumed that the single pulse is exponential with a time constant of the order of 10−4 second. Then the computed spectral density is constant up to 1 kcps, and then decreases exponentially. This behavior is only slightly dependent on the shape of the pulse. The theoretical conclusions are in good agreement with experimental data taken on iron, nickel, and ferroxcube specimens. The usual model introduced to explain the mechanism giving rise to the noise leads to the conclusion that the intensity of the spectrum is proportional to the frequency of the magnetizing current. This conclusion is not experimentally verified because of the extreme simplifications involved in the model itself.

This paper is intended for undergraduates and specialists in thermodynamics and related areas. We consider and discuss the optimization of endoreversible thermodynamic processes under the condition of maximum work production. Explicit thermodynamic analyses of the solutions are carried out for the Novikov and Agrawal processes. It is shown that the efficiencies at maximum work production and maximum power output are not necessarily equal. They are for the Novikov process but not for the Agrawal process. The role of the constraints is put into evidence. The physical aspects are enhanced by the simplicity of the involved mathematics.

Interference experiments (Young's double slit) between elliptically polarized light beams are described. The results show that when beams of light in orthogonal states of elliptical polarization are used no interference fringes are observed.