100 Ohm transfer standard
A new 100 /spl Omega/ transfer standard has been built and placed in service at VTT Automation. The temperature of the resistor is maintained at 30.72/spl deg/C where the temperature coefficient is zero. The daily variation in temperature is less than /spl plusmn/0.005/spl deg/C. The temperature during transportation is about 0.06/spl deg/C less than the nominal value and it can be hold for about 40 hours. The behavior of the standard was verified in the resistance comparison between VTT (Finland), PTB (Germany), BIPM (International) and BNM-LCIE (France) in November-December 1998. The result indicates that the variation of the standard during the transportation is less than 6.10/sup -9/.
Report on the 1990 International Comparison of 1 Ω and 10 kΩ Resistance Standards at the BIPM
In order to evaluate the agreement among representations of the ohm based on the quantum Hall effect and to establish a firm basis for international traceability among the laboratories concerned, the BIPM, at the request of the CCE, organized and carried out an international comparison of 1 Ω and 10 kΩ resistance standards from eighteen national laboratories and from the BIPM. The weighted means of the results obtained by the ten national laboratories which, like the BIPM, based their measurements on their own QHE resistance standard differ from the BIPM results by (-0,032±0,024) parts in 106 at the 1 Ω level and by (0,009±0,022) parts in 106 at the 10 kΩ level.
Conserved Quantities of a Class of Nonlinear Difference-Difference Equations
Higher-order conserved quantities of a class of nonlinear difference-difference equations which are related to the discrete-time Toda equation are obtained using the Miura transformations.