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Film cooling is widely adopted in the thermal protection of modern aerospace engines. The optimization of the film hole is an important issue in thermal designs. In this work, a density-based topology optimization is conducted to obtain a high-performance film cooling hole geometry. Unlike the traditional wall-temperature-based optimization objectives, a novel objective function based on the Q-criteria is proposed by taking the vorticity dynamics and flow mixing into account. Finally, a unique high-performance film hole is obtained, which shows superior performance compared to the standard cylindrical hole, particularly at high blowing ratios. The film cooling effectiveness can be elevated by 51 folds in the case of a high blowing ratio (M = 1.5). Analyses of the vortices and velocity fields suggest that the presence of the additional secondary vortex pair enhances the attachment of cooling air to the wall. [ABSTRACT FROM AUTHOR]

Flexible PbZr0.52Ti0.48O3 (PZT) films have a wide application prospect in wearable devices. In this work, PZT films were fabricated on LaNiO3–based Si substrates and mica substrates, respectively. The effects of Si substrates and mica substrates on the dielectric and ferroelectric properties of PZT films were studied. The stability of PZT films on different substrates was discussed by controlling temperature and frequency. The optimal annealing temperature for preparing PZT films on LaNiO3–based Si substrates and mica substrates is 750 °C. The dielectric and ferroelectric properties of PZT films vary with the substrates. The diffraction peak of PZT films deposited on mica substrates shifted to the left compared with that deposited on Si substrates, due to difference of the expansion coefficients. The as–prepared PZT films exhibit a good ferroelectric property at a frequency in the range of 100 Hz~1000 Hz. Moreover, PZT films deposited on mica substrates have larger remanent polarization values and coercive fields than PZT films deposited on Si substrates. With the elevation in temperature, the dielectric constant of PZT films gradually enhance. And as–prepared PZT films at an annealing temperature of 750 °C have a better dielectric temperature stability. PZT films grown on Si substrates exhibit more excellent dielectric temperature stability than that of PZT films grown on mica substrates. [ABSTRACT FROM AUTHOR]

Lead‐free halides have emerged as clean candidates for lighting and display applications because of their superior optoelectronic properties and environmental friendliness. As for the commercialization, the simple synthetic process, scaled production, low‐cost, and excellent performance are the upmost factors. In this work, lead‐free tetramethylammonium manganese halides are quantitatively synthesized using a mechanochemical approach, in which [(CH3)4N]2MnCl4 powders show green emission with a photoluminescence quantum yield (PLQY) of 21% and (CH3)4NMnCl3 powders possess red emission with a PLQY of 51%, arising from the intrinsic 4T1(4G) → 6A1(6S) d‐d transition of Mn2+. To further boost the green emission efficiency, the composition engineering strategies by Br/Cl substitution and excess organic halide compensation are developed, achieving a high PLQY of 98% for the obtained [(CH3)4N]2MnBr4 powders. Furthermore, white light emitting diode (WLED) devices are fabricated by combining green [(CH3)4N]2MnBr4 powders with red (CH3)4NMnCl3 powders or single crystals, which exhibit a high luminous efficacy (98.06 or 142.40 lm W−1), wide color gamut (over 100 % of NTSC in CIE 1931), and good operating stability (maintained above 80% efficiency after 176 h). This work suggests ball‐milling as a mass synthesis method for metal halides and provides a new Mn2+‐based phosphor for white LEDs in backlight display applications. [ABSTRACT FROM AUTHOR]

2D vanadium-doped tungsten oxide (V-doped WO3) inverse opal (IO) monolayer film was successfully fabricated on ITO glass by simply doping vanadium ions within pre-synthesized 2D WO3 IO. The new material exhibited a large-area highly ordered porous array with featured structural colors. The obtained 2D V-doped WO3 IO film showed an improved electrochromic response in near infrared (NIR) region with a high optical contrast as 24.2% at 1100 nm wavelength, much higher than that of crystallized m-WO3 IO film (18.1%), or amorphous WO3 IO composite film (6.4%). Such advanced property could be attributed to the successful doping of vanadium, resulting in enhanced absorption owing to oxygen vacancies defect-inductive effect, and greatly improved the electrochromic response in the NIR region. Further, the V-doped WO3 IO film also featured with an excellent cyclic stability with the capacity retention of (75.2%) after 30 cycles, comparable to crystallized m-WO3 IO film (78.0%). As contrast to it, the amorphous WO3 IO film was found destroyed even after 10 cycles. [ABSTRACT FROM AUTHOR]

Text classification is widely studied in natural language processing (NLP). Deep learning models, including large pre-trained models like BERT and DistilBERT, have achieved impressive results in text classification tasks. However, these models' robustness against adversarial attacks remains an area of concern. To address this concern, we propose three data augmentation methods to improve the robustness of such pre-trained models. We evaluated our methods on four text classification datasets by fine-tuning DistilBERT on the augmented datasets and exposing the resulting models to adversarial attacks to evaluate their robustness. In addition to enhancing the robustness, our proposed methods can improve the accuracy and F1-score on three datasets. We also conducted comparison experiments with two existing data augmentation methods. We found that one of our proposed methods demonstrates a similar improvement in terms of performance, but all demonstrate a superior robustness improvement. [ABSTRACT FROM AUTHOR]