Equivalence of Measurements on Soft Magnetic Materials in the U.K. and Measurements for Operational Conditions
Measurements on soft magnetic materials were made to determine the measurement capabilities available to the partners of a government-funded collaborative research project, with 16 partners from industry and academia. One of the objectives of this project was the development of advanced magnetic materials for novel electrical machines for use in harsh environments such as gas turbines. To establish the measurement confidence necessary to deliver this project objective, an equivalence study was undertaken. A reference core of soft magnetic material that has been measured over a period of many years at the National Physical Laboratory (NPL) was distributed and the dc and ac properties were measured. The measurement systems of the three laboratories are independent and this ensured that no correlations that could skew the results existed. In the analyses, the measurements at NPL were used as the baseline. With the core capabilities established, it was possible to develop the new measurements required to deliver the overall project objectives. At NPL, a standard permeameter method was modified for the measurement of strips. This was incorporated into a stress machine to measure the dc properties of the soft magnetic materials used by the partners, at stress levels of up to 700 MPa. The results for seven materials are presented and the changes in the properties with applied stress compared to establish which materials exhibit favorable properties.
Influence of the residual stress on the magnetization process in mild steel
The influence of residual stress on the hysteresis properties of mild steel is studied in detail. Magnetic measurements were done in different directions to investigate the stress-induced anisotropy. The hysteresis loops measured in any fixed direction at different levels of deformation crossed at two points known as the coincident points. One possible explanation of this effect is proposed and it makes an assumption about the stress-induced term in the effective field model. Loops measured in different directions at any fixed level of deformation also crossed at two points. It was found that the hysteresis loop follows a very simple formula when changing the direction of the measurement from the easy axis to the hard one. This explained not only the crossing of these loops at the two points but also the results of measurements on ring-shaped samples where all the directions are possible.
An Essay on the Nature and Significance of the Normative Nature of Economics
It is conventional in economics to distinguish between the normative and the positive. The normative has to do with goodness and badness, and with what ought and ought not to be done;1 and the positive has to do with objective description and/or explanation, with what is and with what is necessary given some normative end. The normative has to do with desirability; the positive has to do with truth (in the sense of either descriptive accuracy or serviceability of a means to a given end).2