Investigation of a GaN-Based SAW Oscillator with respect to UV Illumination and Temperature

Oscillation frequency of a GaN-based surface acoustic wave delay-line oscillator is investigated in the temperature range from -20°C to +38°C, with and without UV illumination. The results imply that such an oscillator may be used for temperature sensing with the resolution of up to 1 mK. On the other hand, as the frequency downshift due to UV illumination does not exhibit a significant dependence on temperature, it may be expected that such a system, when used as a UV sensor, would not require applying a correction for temperature

XPS and Mössbauer Spectroscopy of LiFePO4 and LiFePO4/C Ceramics

LiFePO4 crystallizes in olivine structure. It is a mixed electronic-ionic conductor and has been proposed as an attractive cathode material for Li-ion secondary batteries. The conductivity values increased with increasing the amount of carbon in the LiFePO4/C composites [2]. It is known [3] that in this compound Fe2+ can be oxidized to Fe3+. The material has a high reversible capacity (~160 mAhg-1) and the intercalation potential for Li/Li+ is 3.5 V The redox behavior of the iron in this compound also makes it an interesting candidate for X-ray photoelectron spectroscopy (XPS) and the Mössbauer spectra study in the pure LiFePO4 and carbon containing LiFePO4/C ceramics. The LiFePO4 powders for the XPS and Mössbauer spectra study have been synthesized by solid state reaction and LiFePO4/C composites were synthesized by a sol-gel method and later sintered in argon gas.The ceramics of LiFePO4 was sintered in air. The binding energies of Fe 2p, P 2p and O 1s core level of the LiFePO4 ceramics and LiFePO4/C composite surfaces have been determined by XPS at room temperature. The analysis of Fe 2p, P 2p and O 1s core level XPS deconvolution is presented in this work. Mössbauer spectroscopy in the temperature range from 10 K to 700 K has been applied in order to determine phase transition temperatures, the Debye-Waller factor and typical ionization states of iron in compounds. Behavior of Li+ ions was evaluated in the second coordination sphere of iron based on changes in hyperfine parameters of Mössbauer spectra

Specialisation in agricultural and food exports of Lithuania

The analysed research problem answer the question of how the changing trade conditions affect Lithuanian agricultural and food exports. The paper aims to assess the level of specialization in the agricultural and food sector exports of Lithuania. Assessment of the level of specialization was based on calculation of the trade coverage, revealed comparative advantage and intra-industry trade indices and their aggregation. Empirical research covers the period of 1999–2014. The export of agricultural and food products of Lithuania has been positively affected by trade liberalisation and achieved the effect of synergy due to regional integration processes (membership in the EU). It is characterised by high level of specialisation; nevertheless, this does not contribute to increasing of added value in agriculture