The graphene nanofiller (2 wt%) was dispersed in poly(methyl methacrylate) by in situ polymerization method. The optimum high frequency (microwave) absorption was evaluated at X‐band due to changes in the scattering parameters (determined by using a vector network analyzer). The slight improvement has been attained in gamma attenuation coefficient of the polymer nanocomposite by using gamma transmission technique. The addition of graphene nanoplatelets (2 wt%) resulted in a thermal improvement from 196.73 to 243.00°C (with 5% weight loss) in TGA analysis. The graphene nanoplatelets provided an optimum decrease in scattering of the microwaves due to the elimination of the defects and the prevention of the agglomeration of the graphene nanoplates. The improvement of microwave absorption (between 8 and 12 GHz) suggested that the nanocomposite was a suitable candidate as a microwave absorbing material. This multipurpose nanocomposite has provided thermal stability and it has ensured the optimum gamma‐ray and microwave absorption depending on the development of the structural properties. The development of these physical characteristics has enabled to improve the electrical conductivity as a result of the progress in the structural properties.
The aim of this study is to examine the characterization of a thermal isolation section for a waveguide microcalorimeter, used to characterize the effective efficiency of a thermistor power sensor. The power loss in the thermal isolation section has been analyzed for both the dielectric and conductor losses. Its effect on the thermopile output has been assessed using a foil short method through analysis of the heating ratio. This method involves a one-off measurement of the microcalorimeter system with the foil short before the unknown power sensor measurement and does not require additional S-parameters measurements of the isolation section. The estimated value of the heating ratio effect has been obtained between 1 for fully reflected signal from the input of the unknown power sensor and 2 for perfectly matched power sensor. The full analytical model and an estimated model for the heating ratios have been calculated for NPL's WG25 (WR15) microcalorimeter and a commercial thermistor power sensor. The analytical model has been applied to an effective efficiency measurement and good agreement has been obtained when compared with the existing methodology used at NPL. This model can be applied to any metallic waveguide type thermal isolation section in other bands. A rigorous uncertainty analysis of the analytical model for the heating ratio is also presented and shows an expanded uncertainty between 0.008 and 0.023 (k=2) for this microcalorimeter.
NPL, PTB, and LNE designed and produced three different microcalorimeters for the WG29/WR7 band. The microcalorimeters used different correction methods to characterize effective efficiency. Finally, the three laboratories measured thermoelectric power sensors from 110 GHz to 170 GHz to demonstrate equivalence and results show good agreement.
In this article, programmable Josephson voltage standard system established in TÜBİTAK UME is presented. The specifications of the instruments used in the system are defined and tested according to the needs of the system. Test setups are given in detail. The cryoprop used to immerse the superconducting integrated circuit into the liquid helium is manufactured. The horn antennas used in the waveguide part of the cryoprop are manufactured by employing wire erosion technique. The optical transceivers having low jitter for distributing trigger and clocks while keeping fully floating the system are manufactured. The software for generating quantum voltages and easy use of the system is prepared and equations used in the algorithm are given. The procedures to maintain the necessary accuracy of the bias electronics to maintain the quantum accuracy of the system is given in detail. The established system is used in metrological measurements and the results of the measurements which prove the quantum state of the system are presented.
Abstract. Bilateral comparison of calibration factor of microwave power sensor was carried out between National Metrology Institute of Turkey (TÜBİTAK UME) and National Measurement and Calibration Center at Saudi Standards, Metrology and Quality Organization of the Kingdom of Saudi Arabia (SASO NMCC). In this comparison, TÜBİTAK UME was pilot laboratory and supplied the travelling standard with N type connector. Nine different frequency points at 0 dBm power level were determined for this comparison in prepared technical protocol. Each participant used their own measurement standards and applied the direct comparison transfer method at comparison. There is a good agreement between TÜBİTAK UME and SASO NMCC results.
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