Problemy weryfikacji sensorów temperatury na miejscu eksploatacji z wykorzystaniem kalibratorów

The problems of temperature sensor checking at the exploitation place with the calibrator's usage are presented in this paper. We came to conclusion to fix the moments of entrance and exit to/from a temperature platform that correspondent to phase transition of fixed-point material. The usage of small sized semiconducting sensors which are placed on inner surfaces of temperature calibrator receiving camera is stipulated. The structural scheme, mathematical models and job algorithm of digital thermometer which provide unification of transducer characteristics for semiconducting sensors are described too.W artykule przeanalizowano problem weryfikacji czujników temperatury w miejscu ich zainstalowania i opracowano podstawową koncepcje jego rozwiązania na podstawie wykorzystania wbudowanych temperaturowych punktów stałych MST-90. W celu ujawnienia momentu nastąpienia przejścia fazowego materiału referencyjnego na tylnej powierzchni komory kalibratora temperatury zainstalowane są dwa półprzewodnikowe mikroczujniki temperatury. Opisano również strukturę, modele matematyczne oraz algorytm przetwarzania termometru cyfrowego, zabezpieczającego unifikację jego charakterystyk

Behaviour of Isotropic Point in LiKSO4\text{}_{4} Crystals

The temperature-spectral dependencies of refractive indices and birefringence in wide temperature (77-1000 K) and spectral (250-850 nm) regions in LiKSO$\text{}_{4}$ crystals were measured. The isotropic point of LiKSO$\text{}_{4}$ crystals was investigated. It was shown that annealing and X-ray irradiation display insignificantly the isotropic point to a visible region of spectrum

Estimation of phonon relaxation time for silicon by means of using the velocity autocorrelation function of atoms in molecular dynamics

Results of the ab initio molecular dynamics calculations of silicon crystals are presented by means of analysis of the velocity autocorrelation function and determination of mean phonon relaxation time. The mean phonon relaxation time is crucial for prediction of the phonon-associated coefficient of thermal conductivity of materials. A clear correlation between the velocity autocorrelation function relaxation time and the coefficient of thermal diffusivity has been found. The analysis of the results obtained has indicated a decrease of the velocity autocorrelation function relaxation time t with increase of temperature. The method proposed may be used to estimate the coefficient of ther-mal diffusivity and thermal conductivity of the materials based on silicon and of other wide-bandgap semiconductors. The correlation between kinetic energy fluctuations and relaxation time of the velocity autocorrelation function has been calculated with the relatively high coefficient of determination R2 = 0.9396. The correlation obtained and the corresponding approach substantiate the use of kinetic energy fluctuations for the calculation of values related to heat conductivity in silicon-based semiconductors (coefficients of thermal conductivity and diffusivity)