Showing papers on "Radian published in 1992"

Relaxation of polarisation

Abstract: The relaxation of a wide range of solid dielectrics follows fractional power laws in frequency known as the “universal” or constant phase angle law. Instead of analysing the time dependence of the microscopic relaxations of dipoles or of charges in terms of the fluctuation dissipation theorem, we make use of the unique property of the universal law that the ratio of the macroscopic energy lost per radian to energy stored in the system under an alternating field drive is independent of frequency. We show that in solids a sufficient condition for this “energy criterion” to be satisfied is that the energy loss per microscopic reversal is the same regardless of the rate of reversals. The significance of this is discussed.

Who named the radian

Abstract: While looking at old copies of the journal Nature I chanced upon correspondence regarding the origin of the word radian. Textbooks today simply state it is an angular measure and have no interest in, nor space for, the history of the word. The Oxford English Dictionary states that the word first appears in print in 1879 in the second edition of the Treatise on natural philosophy by William Thomson (later Lord Kelvin) and Peter Guthrie Tait. In their discussion of angular velocity they wrote: “the usual unit angle is … that which subtends at the centre of a circle an arc whose length is equal to the radius. For brevity we shall call this angle a radian.”