Two different types of commercial organic LED panels were aged with ultraviolet light. One type was aged in an over-filled and open circuit condition with broadband ultraviolet radiation, and the other in an under-filled and closed circuit condition with spectrally dispersed light. Both the luminance values and the spectral power distributions of the panels were measured for both types. The results show that the light output and the spectrum of the panel decay faster when the panels are exposed to ultraviolet radiation when compared to natural ageing. For the panels aged using the under-filled method, the wavelength that reduces the output most is between 320 nm and 340 nm, and the ultraviolet exposure with wavelengths longer than 350 nm did not accelerate the ageing. The ultraviolet radiation exposure increased the ageing by a factor of eight as compared to natural ageing, when the used ultraviolet levels corresponded to one year of exposure on a clear summer day condition. Based on the results, the under-filled method is a valid option for accelerated ageing, especially for studying simultaneously accelerated and natural ageing.
The results are presented of a bilateral comparison of pneumatic pressure measurements, carried out in the framework of EUROMET Project No. 537, between the Cesky Metrologicky Institut (CMI, Czech Republic) and the TÜBITAK-Ulusal Metroloji Enstitüsü (UME, Turkey). The measurements, in the range 15 kPa to 7 MPa, were carried out in two phases: (i) 18-24 June 1999 at the Pressure Section of the CMI in the range 15 kPa to 350 kPa; (ii) 29 June-8 July 1999 at the Pressure Section of the UME in the ranges 0.25 MPa to 1.75 MPa and 1 MPa to 7 MPa. Three different gas-operated reference standards were used. For the ranges 15 kPa to 350 kPa and 0.25 MPa to 1.75 MPa these were piston-cylinder assemblies with ceramic pistons and tungsten-carbide cylinders and nominal effective areas of 10 cm2 and 2 cm2, respectively. For the range 1 MPa to 7 MPa, a piston-cylinder assembly with tungsten-carbide piston and cylinder and a nominal effective area of 0.5 cm2 was used. The purpose of the measurements was to compare the effective areas of the Czech and Turkish primary pressure standards in gas media and gauge mode, and to confirm the agreement between the pressure scales of the two countries in the range 15 kPa to 7 MPa by application of the cross-floating method. Since the UME and the CMI are participating in different loops of EUROMET Project No. 439, a key comparison of pneumatic pressure, another important goal of this study was to establish a cross-link between the two loops.
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