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A micro-structural corrosion mechanism on the thermal degradation of BaMgAl10O17: Eu2+ phosphor
摘要： The thermal degradation is a vital issue that restricting luminous efficiency and service life of BaMgAl10O17: Eu2+phosphor for chromogenic and illuminating fields. The effects of heat-treatment temperature on the luminescence properties and micro-structure of BAM were researched to accurately elucidate the thermal degradation mechanism. Some pieces of evidence for micro-structural corrosion were detected according to the results of PL, TL, XPS and IR. With the heat-treatment temperature increasing, a decrease of blue-emitting intensity and new red-emitting peaks revealed thermal degradation and activator oxidation. The XPS results showed the surface chemical composition changes and the micro-structure adjustment. The defects elimination detected by TL could be responsible for this micro-structural corrosion. IR results further confirmed the changes on bond forms. These were direct evidence and specific forms for the micro-structural corrosion due to the thermal degradation. Based on the relationship between micro-structural corrosion and luminescence properties, a micro-structural corrosion mechanism was given for the thermal degradation of BAM phosphor. The thermal degradation was caused in parallel by the micro-structure corrosion and the activated ion (Eu2+) oxidation.
关键词： Micro-structural corrosion,Thermal degradation mechanism,BaMgAl10O17:Eu2+,Heat-treatment
更新于2025-09-23 15:22:29
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Electro-thermal modeling for InxGa1-xN/GaN based quantum well heterostructures
摘要： The joint effect of the heat transfer and the electronic properties in the InGaN/GaN based quantum well (QW) heterostructures has been investigated theoretically and numerically. One-dimensional Schr?dinger equation solver coupled with Poisson equation solver and Dual-phase-lagging (DPL) heat conduction solver has been developed. The numerical results suggest that the DPL heat conduction equations capture the microscale responses caused by the phonon-electron interaction. Both effects of the polarization charge and conduction band offset between the InGaN/GaN interfaces lead to the creation of the two-dimensional electron gas (2DEG) on the lower interface of the QW. It is found that the 2DEG density at the triangular quantum well increases with increasing Indium (In) composition. This increase is the same for the conduction band offset and the electron density. As a consequence, an increase of the heat dissipation and the temperature is observed at the lower interface of the quantum well.
关键词： Indium composition,Polarization charge,Nanoscale heat transfer,Dual-phase-lagging model,InGaN heterostructure
更新于2025-09-23 15:22:29
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Optical, structural and luminescence properties of oxyfluoride phosphate glasses and glass-ceramics doped with Yb3+
摘要： The impact of Al2O3 and Y2O3 addition on the structure, Yb3+ luminescence and crystallization is investigated for glasses in the P2O5-SrO-Na2O system. Although the addition of Al2O3 and Y2O3 leads to a more connected phosphate network as evidenced using IR and Raman spectroscopies and increases the glass transition temperature, it does not affect strongly the site of the Yb3+. The addition of Al2O3 and Y2O slightly decreases the rate of the glass crystallization. Surface crystallization occurs upon heat treatment. Crystallization was confirmed by the presence of sharp peaks in the XRD patterns of the glasses. Independently of the glass composition, multiple different crystalline phases precipitate in the glasses upon heat treatment. The precipitation of the Na1O7P2Yb1 crystal phase leads to an increase of the excited state 2F5/2 lifetime of Yb3+ and also of the bandwidth of the Yb3+ emission band centered at 1μm.
关键词： nucleation and growth,Yb3+ doped phosphate glasses,Raman & Infrared spectroscopies,Yb3+ luminescence properties,heat treatment
更新于2025-09-23 15:22:29
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Photothermal/day lighting performance analysis of a multifunctional solid compound parabolic concentrator for an active solar greenhouse roof
摘要： Currently, the excess light above a light saturation point cannot be harnessed for plant growth in conventional greenhouse covers. In this study, we developed a solid compound parabolic concentrator (CPC) cover for use in greenhouses to convert excess light into heat. Optical simulation software was used to track the sunlight at different incident angles over time. We also conducted experiments to determine the transmittance and heating power of the solid CPC coating under real weather conditions. The maximum instantaneous thermal efficiency and thermal energy of a single solid CPC cover plate were 32.2% and 353 W/m2, respectively. The simulation results were in good agreement with the experimental output power and the trend of the actual transmittance of the covering material. The transmittance of the covering material was low when the midday sun was intense, and the transmittance was relatively high in the morning and afternoon. The variation of red and blue light in the greenhouse with the spectrum was analyzed at the same time. Studies have shown that this new greenhouse covering material can better adjust the brightness, make the illumination in the greenhouse more uniform, and thus improve the thermal environment in the greenhouse. The heat pipes converted excess light into heat, thereby achieving comprehensive utilization of solar light and heat.
关键词： Heat energy utilization,Solid CPC,Solar greenhouse roof,Light transmittance,Solar PT/D system
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE 8th International Conference on Consumer Electronics - Berlin - Berlin (2018.9.2-2018.9.5)] 2018 IEEE 8th International Conference on Consumer Electronics - Berlin (ICCE-Berlin) - Development of a Mobile App for training health professionals in diagnostic imaging: a progress report
摘要： The paper discusses the development and application of a Noble Metal Alloy (NMA) for enhancing heat transfer processes in diagnostic imaging, specifically designed for use in optoelectronics. It presents a novel approach to improving the efficiency and reliability of imaging devices through advanced material science.
关键词： Noble Metal Alloy,Heat Transfer,Optoelectronics,Material Science,Diagnostic Imaging
更新于2025-09-23 15:22:29
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Uncertainty Analysis and Experimental Design in the Monte Carlo Ray-Trace Environment
摘要： Despite the dominant role of the Monte Carlo ray-trace (MCRT) method in modern radiation heat transfer analysis, the contemporary literature remains surprisingly reticent on the uncertainty of results obtained using it. After first identifying the radiation distribution factor as a population proportion, standard statistical procedures are used to estimate its mean uncertainty, to a stated level of confidence, as a function of the number of surface elements making up the enclosure and the number of rays traced per surface element. This a priori statistical uncertainty is then shown to compare favorably with the observed variability in the distribution factors obtained in an actual MCRT-based analysis. Finally, a formal approach is demonstrated for estimating, to a prescribed level of confidence, the uncertainty in predicted heat transfer. This approach provides a basis for determining the minimum number of rays per surface element required to obtain the desired accuracy.
关键词： Monte Carlo ray-trace,uncertainty analysis,experimental design,radiation heat transfer,distribution factor
更新于2025-09-23 15:22:29
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HIFiRE-5 Boundary-Layer Transition Measured in a Mach-6 Quiet Tunnel with Infrared Thermography
摘要： The principal goal of the Hypersonic International Flight Research Experimentation (HIFiRE) flight 5 is to measure hypersonic boundary-layer transition on a three-dimensional body. This paper presents measurements of heat flux and boundary-layer transition in the Boeing/U.S. Air Force Office of Scientific Research Mach-6 Quiet Tunnel. This facility has been developed to provide quiet flow at high Reynolds number, with low noise levels comparable to flight. Previously, the global heat flux and location of the transition front were measured with temperature-sensitive paint (TSP). A new HIFiRE-5 model was built with a polyether ether ketone shell, which is suitable for infrared–thermographic heat-flux measurements. Quiet-flow tests at Reynolds numbers of 8–12 ? 106∕m and zero angle of attack indicate a centerline transition location within 4% of the earlier TSP results, on the order of the uncertainty of the two techniques. This good agreement reinforces confidence in the earlier measurements and the new infrared-based technique. Examination of the off-centerline transition front indicates that the wavelength of stationary crossflow vortices is the same for both models and instrumentation techniques, although the streaks do not coincide precisely.
关键词： crossflow vortices,infrared thermography,Mach-6 quiet tunnel,boundary-layer transition,HIFiRE-5,heat flux
更新于2025-09-23 15:22:29
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Real-time retrieval of transient heat flux on the surface of participating medium by using the EKF-RLSE technique
摘要： A hybrid algorithm of extended Kalman filtering and recursive least-square estimator (EKF-RLSE) is developed to solve the nonlinear inverse heat conduction-radiation problems in participating medium. By measuring the time-resolved temperature signals from a thermocouple installed on the other boundary of the participating medium, the proposed EKF-RLSE algorithm can realize real-time retrieval of the time-varying heat flux on the medium surface. The influence factors of the sampling interval, measurement and process covariance, forgetting factor, and medium thickness on the reconstruction accuracy and stability of the EKF-RLSE are investigated by numerical experiments. All the estimated results show that the present algorithm is robust and accurate in real-time estimating transient heat flux. If the nonlinear coupled conduction and radiation heat transfer problems is regard as the linear problems, the unknown time-dependent heat flux predicted by the KF-RLSE are also illustrated in this work.
关键词： Participating medium,Kalman filtering,Inverse nonlinear conduction-radiation,Time-varying heat flux,Recursive least squares estimator
更新于2025-09-23 15:22:29
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[IEEE 2018 International Multi-Conference on Industrial Engineering and Modern Technologies (FarEastCon) - Vladivostok, Russia (2018.10.3-2018.10.4)] 2018 International Multi-Conference on Industrial Engineering and Modern Technologies (FarEastCon) - The Increase of the Effectiveness of the Autonomous System of Solar Energy Supply
摘要： For the effective heat supply of the consumers the solar energy is viewed with the aim of replacing the organic fuel the costs on which constantly increase. The analysis of the existing solar collectors as the basic element of the system of solar heat supply and its factors for the increase of the effectiveness of its usage is shown. The interconnection of constructive and regime parameters of solar collectors and the necessity of the regulating the regime of their work for the effectiveness of the system of solar heat supply as a whole are also shown. To achieve the formulated purpose the regulating of the scheme of the connection of solar collectors between them is offered and as the source of power supply the solar battery is suggested for providing the autonomy of the system of solar heat supply. The principle of the control of the scheme of the connecting of solar collectors and the description of the regime of work of the suggested device are examined. The block scheme of the algorithm of control for providing the given parameters of regulating is worked out and shown.
关键词： system of solar heat supply,parameters of solar collector,algorithm of control,scheme of the connection of the collectors,solar collector,solar battery,solar radiation
更新于2025-09-23 15:22:29
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[IEEE IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society - D.C., DC, USA (2018.10.21-2018.10.23)] IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society - Basic Study of Solar Battery Powered Wireless Power Transfer System with MPPT Mode and DC Bus Stabilization for Lunar Rover
摘要： Due to the extremely low temperature of Moon surface at lunar night, lunar rover has suffered from heat leakage along the wire connection between solar battery and rover body. In this paper, a wireless power transfer system has been proposed to transfer energy from solar battery to rover body in order to aovid the heat leakage at lunar night. The solar battery is controlled by a buck converter to be switched between the Maximum Power Point Tracking (MPPT) mode and buck mode to output appropriate amount energy to load and battery in rover body through the wireless power transfer system. The load and battery is connected to the DC bus which is controlled by a DC-DC converter to stabilize the voltage. Based on the experiment results, the whole system ef?ciency is about 48.7% at 22 W. It has been demonstrated the system ef?ciency is closely related with system power level due to the power electronics wasted power, and the ef?ciency can be improved to 62.1% with higher system power at 48.6 W.
关键词： DC-DC converter,Lunar rover,heat leakage,wireless power transfer
更新于2025-09-23 15:22:29