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The luminescence properties of BaMgF4 ceramics synthesized using electron beam-assisted synthesis were investigated under vacuum ultraviolet (VUV) synchrotron excitation at a cryogenic temperature of T = 9 K. Their excitation spectra, measured over the 4–10.8 eV range, and corresponding luminescence spectra revealed a complex multicomponent structure with emission maxima at 3.71, 3.55, 3.33, 3, and ~2.8 eV. The primary luminescence band at 330 nm was attributed to self-trapped excitons (STE) excited near the band edge (9.3–9.7 eV), indicating interband transitions and subsequent excitonic relaxation. Bands at 3 and ~2.8 eV were associated with defect states efficiently excited at 6.45 eV, 8 eV and high-energy transitions near 10.3 eV. The excitation spectrum showed distinct maxima at 5, 6.45, and 8 eV, which were interpreted as excitations of defect-related states. These results highlight the interplay between interband transitions, excitonic processes, and defect-related luminescence, which defines the complex dynamics of BaMgF4 ceramics. These findings confirm that radiation synthesis introduces defect centers influencing luminescent properties, making BaMgF4 a promising material for VUV and UV applications.- Book : 15(2)
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- Page : pp.127-127
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2025
The solar-assisted heat pump drying (SAHPD) system uniquely incorporates solar-heating refrigerant through hot water from solar evacuated tubes, offering distinct advantages. This study analyzed three experimental setups: a heat pump dryer (HPD) without solar assistance, SAHPD configuration 1 (C1-SAHPD) with solar-heated refrigerant at the discharge line, and SAHPD configuration 2 (C2-SAHPD) with solar-heated refrigerant between condensers, both for performance and economic viability. The experiments maintained consistent parameters, including 5.5 kg of Pandan leaf (Pandanus amaryllifolius), an airflow rate of 0.135 kg/s, and a refrigerant operating pressure of 9.65 bar. The SAHPDs operated when the hot water temperature in the storage tank reached between 70°C and 90°C, with a daily average radiation intensity ranging from 0.670 to 1.102 kW/m² for heating the water. The study revealed average coefficients of performance (COPavg) of 5.34, 5.43, and 6.53 for HPD, C1-SAHPD, and C2-SAHPD, respectively. The specific moisture extraction rate (SMER) for HPD was 2.64, while C1-SAHPD and C2-SAHPD had SMERs of 1.88 and 2.71 at solar fractions of 0.34 and 0.45, respectively. Notably, C2-SAHPD reduced electricity consumption by 46%. The payback period for drying 11 kg of Pandan leaves per day was 4.56 months for HPD, 4.32 months for C1-SAHPD, and 3.84 months for C2-SAHPD. The study concluded that C2-SAHPD was the most efficient dryer system for Pandan leaves based on its higher efficiency, SMER, and cost recovery. Additionally, the performance optimization presented in this study contributed to developing a novel technique for classifying dryer technologies.- Book : 37(1)
- Pub. Date : 2025
- Page : pp.349-368
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