Great progress made by heteroepitaxial growth technology encourages rapid development of III-nitride heteroepitaxial structures and their applications in extensive fields. Particularly, innate bandgap tunability of III-nitride materials renders them attractive for white light-emitting diodes (WLEDs) that are considered as next-generation solid-state lighting sources. However, commercial phosphor-converted WLEDs suffer from poor color rendering index (CRI) and intense blue component, hard to fulfill demanding requirements simultaneously for energy efficiency and healthy lighting. Here, an efficient full-spectrum WLED excited by monolithically integrated III-nitride quantum structure is reported, in which trichromatic InGaN/GaN multiple quantum wells are constructed by bandgap engineering heteroepitaxy growth allowing flexible regulation of indium composition and quantum barrier thickness to manipulate carrier transport behavior. Furthermore, relationship between structural parameters and emission characteristics as well as their impact on white light performance is systematically demonstrated. Combined with commonly used green-red phosphor mixture, the fabricated full-spectrum warm/cold WLEDs can emit broadband and continuous spectra with low-ratio blue component, first exhibiting superior CRI (> 97/98), color fidelity (97/97), saturation (100/99), and luminous efficacy (>120/140 lm W −1 ). This work demonstrates the advantages of bandgap-engineered quantum structure applied in excitation source, and opens up new avenues for the exploration of high-quality solid-state lighting.

As a substitute of traditional fossil fuels, biomass is widely used to generate electricity and heat.The temperature of stored biomass needs to be monitored continuously to prevent the biomass from self-ignition. This paper proposes a non-intrusive method for the temperature measurement of stored biomass based on acoustic sensing techniques. A characteristic factor is introduced to obtain the sound speed in free space from the measured time of flight of acoustic waves in stored biomass. After analysing the relationship between the defined characteristic factor and air temperature, an updating procedure on the characteristic factor is proposed to reduce the influence of air temperature. By measuring the sound speed in free space air temperature is determined which is the same as biomass temperature. The proposed methodology is examined using a single path acoustic system which consists of a source and two sensors. A linear chirp signal with a duration of 0.1 s and frequencies of 200-500 Hz is generated and transmitted through stored biomass pellets. The time of flight of sound waves between the two acoustic sensors is measured through correlation signal processing. The relative error of measurement results using the proposed method is no more than 4.5% over the temperature range from 22 to 48.9 . Factors that affect the temperature measurement are investigated and quantified. The experimental results indicate that the proposed technique is effective for the temperature measurement of stored biomass with a maximum error of 1.5 under all test conditions.

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Coke deposition on catalyst will not only reduce catalytic activity and selectivity, but also affect the product yield, the reaction residence time, the regenerator temperature and so on. As a result, it is necessary to measure the amount of coke deposition on catalyst. This paper proposes a new method based on image analysis. An image acquisition system consisting of a flatbed scanner and an opaque cover is used to obtain catalyst images. After imaging processing and analysis, the gray layer is selected to be the most effective colour layer for colour features extraction based on a discriminability index, D. Eight colour features (mean, variance, skewness, entropy, energy, H, S, V) are extracted from images with a good ability to classify the catalysts with different coke amount. Furthermore, the results show that there is a significant linear correlation between the H value and amount of coke deposition on catalyst, which could reflect the coke deposited state and coking progress effectively.

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