A method of adjusting a beam spot width includes scanning a phantom with an electron beam having a beam spot width to obtain data; and adjusting the beam spot width using the obtained data. The loops are for being worn around a plurality of fingers, and the exercise is comprised of repeatedly spreading the fingers apart against the tension of the loops. A forward portion of the elongated hole being formed by first and second non-coaxial, partially overlapping, axially extending cylindrical bores. The meta-data display system also includes display apparatus each used for displaying a video signal including meta data synthesized therewith. The program data is passed on to the programmable controller, thereby making the appropriate sequences of cooking operations available to the food service device. The average particle size of the substantially spherical boron nitride is preferably from 20 to 100 \u03bcm and the filling ratio is preferably from 10 to 30% by volume.