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Photovoltaic (PV) generation has high impact on the decarbonization pathways of power systems. Accuracy of day-ahead PV power forecasting has become crucial in the operation and control of power system with high PV penetration. This paper develops a hybrid approach based on generative adversarial network (GAN) combined with convolutional autoencoder (CAE) to improve PV power forecasting accuracy. Self-organizing map method is first utilized as data pre-processing to classify target days into different weather types based on solar irradiance. With the ability of GAN to reduce the burden of loss and the advantages of CAE to extract multi-scale effective features from the weather and PV power, PV power forecasting model consisting of GAN and CAE is proposed. The developed method has been tested on a real dataset in a Chinese PV station and compared with base reference PV forecasting methods. Numerical testing results demonstrate the effectiveness of our method with high accuracy.

Polymer electrolyte membrane (PEM) fuel cell technology needs to overcome the cost barrier in order to compete with the internal combustion engines (ICEs) for transportation application. A viable approach is to raise fuel cell's power output without increasing its size and Pt loading in the catalyst layers (CLs). In this strategy, the cost per kW power output can be proportionally reduced due to the increased power density. This paper examines this strategy by exploring several important aspects that influence fuel cell performance under high power or current density using a three-dimensional (3-D) fuel cell model. It is shown that local CLs may be subject to low oxygen concentration under a high current density of 2 A/cm2, causing low reaction rate near the outlet, especially under the land. Additionally, the oxygen reduction reaction (ORR) rate may be subject to a large through-plane variation under 2 A/cm2, raising ohmic voltage loss in the CL. Two additional cases are investigated to improve fuel cell performance under 2 A/cm2: one has a 5 times thinner CL with the same ORR kinetics per membrane electrode assembly (MEA) area and the other has a 5 times thinner CL with 5 times higher ORR kinetics. The results show the output voltage is raised approximately from 0.5 V to 0.554 V in the former CL case and further to 0.606 V for the latter CL. To enable high-efficiency operation (e.g. >50%), thinner CLs with high ORR kinetics and GDLs with better transport properties are one research and development (R&D) direction.

The petiole–lamina relationship is central to the functional tradeoff between photosynthetic efficiency and the support/protection cost. Understanding environmental gradients in the relationship and its underlying mechanisms remains a critical challenge for ecologists. We investigated the possible scaling of the petiole–lamina relationships in three dimensions, i.e., petiole length (PL) vs. lamina length (LL), petiole cross sectional area (PCA) vs. lamina area (LA), and petiole mass (PM) vs. lamina mass (LM), for 325 Qinghai–Tibetan woody species, and examined their relation to leaf form, altitude, climate, and vegetation types. Both crossspecies analysis and meta-analysis showed significantly isometric, negatively allometric, and positively allometric scaling of the petiole–lamina relationships in the length, area, and mass dimensions, respectively, reflecting an equal, slower, and faster variation in the petiole than in the lamina in these trait dimensions. Along altitudinal gradients, the effect size of the petiole–lamina relationship decreased in the length and mass dimensions but increased in the area dimension, suggesting the importance of enhancing leaf light-interception and nutrient transport efficiency in the warm zones in petiole development, but enhancing leaf support/protection in the cold zones. The significant additional influences of LA, LM, and LA were observed on the PL–LL, PCA–LA, and PM–LM relationships, respectively, implying that the single-dimension petiole trait is affected simultaneously by multidimensional lamina traits. Relative to simple-leaved species, the presence of petiolule in compound-leaved species can increase both leaf light interception and static gravity loads or dynamic drag forces on the petiole, leading to lower dependence of PL variation on LL variation, but higher biomass allocation to the petiole. Our study highlights the need for multidimension analyses of the petiole–lamina relationships and illustrates the importance of plant functional tradeoffs and the change in the tradeoffs along environmental gradients in determining the relationships.

Quantifying intraspecific trait variation (ITV) is crucial for understanding species local adaptation and regional distribution. Intraspecific seed mass variation (ITVsm) is expected to vary with environmental gradients or co-vary with related biotic attributes, but these relationships are not well known in a multispecies space. We performed interspecific and phylogenetic analyses to evaluate the relative power of three species biotic attributes and four niche breadth traits in explaining ITVsm variation for 434 eastern Qinghai-Tibetan species. We showed a positive relationship between species' ITVsm and their niche breadth in the light, moisture and disturbance dimensions, supporting the idea that high ITV allows species to match their traits to different habitat conditions and thus to distribute in a wide range of environments. However, we did find significant direct effect of species' thermal niche on individual seed mass variation. Meanwhile, we showed significant effects of seed dispersal mode, but not of life form and pollination type, on ITVsm. This suggests that the covariation or co-evolution between seed and disperser was related to the pattern and magnitude of ITVsm, but not to plant lifespan, the quality and allocation pattern of available resources and the availability of pollination vector. Lastly, all multivariate models showed a significant combined contribution of species' biotic attributes and niche breadth to their ITVsm, implying that intrinsic biotic limitations and extrinsic abiotic pressures may operate simultaneously in controlling regional-scale intraspecific seed development.

In this work, an equi-atomic (Ti, Zr, Hf, Nb, Ta) C high-entropy carbide (HEC) powder was synthesized using spark plasma sintering (SPS), and its phase evolution, microstructure, composition and oxidation behaviour were investigated in detail. According to the results, pure face-centred cubic structured solid solution could be obtained at 1950 °C, with metallic atoms randomly placed in the metallic sublattice. Results also showed that HEC powder exhibited better performance with regards to oxidation resistance than its original components and acted as an indivisible entirety while undergoing oxidation under relatively lower temperatures. This reflected from the side that HEC powder was thermally more stable than its original components.

Plant ecologists have long been interested in quantifying how leaf traits vary with climate factors, but there is a paucity of knowledge on these relationships given a large number of the relevant leaf traits and climate factors to be considered. We examined the responses of 11 leaf traits (including leaf morphology, stomatal structure and chemical properties) to eight common climate factors for 340 eastern Qinghai-Tibetan woody species. We showed temperature as the strongest predictor of leaf size and shape, stomatal size and form, and leaf nitrogen and phosphorus concentrations, implying the important role of local heat quantity in determining the variation in the cell- or organ-level leaf morphology and leaf biochemical properties. The effects of moisture-related climate factors (including precipitation and humidity) on leaf growth were mainly through variability in leaf traits (e.g., specific leaf area and stomatal density) related to plant water-use physiological processes. In contrast, sunshine hours affected mainly cell- and organ-level leaf size and shape, with plants developing small/narrow leaves and stomata to decrease leaf damage and water loss under prolonged solar radiation. Moreover, two sets of significant leaf trait-climate relationships, i.e., the leaf/stomata size traits co-varying with temperature, and the water use-related leaf traits co-varying with precipitation, were obtained when analyzing multi-trait relationships, suggesting these traits as good indicators of climate gradients. Our findings contributed evidence to enhance understanding of the regional patterns in leaf trait variation and its environmental determinants.

Seed mass is a central plant life history trait that varies and evolves due to selection by biotic or abiotic factors. To determine the factors affecting seed mass variation among species and phylogeny, we used linear and regression tree analyses of three biotic traits and four niche traits to quantify the relative importance of each trait on seed mass for 1340 angiosperm species from the eastern part of the Qinghai-Tibetan Plateau. Dispersal mode was the strongest predictor of both species and phylogenetic seed mass variation, whereas life form only had a small impact. These results suggest that seed mass has responded to dispersers rather than the life history or available stored resources. Moreover, in both inter-specific and phylogenetic comparisons, species with similar light, moisture and disturbance niche positions tended to have similar seed mass, indicating that adaptation to local environments is a second force driving species-level seed mass variation. The lack of any relationship between thermal niche and seed mass in the phylogenetic analysis implies that seed mass variation along thermal gradients may be a result of regional species sorting, or alternatively, a plastic response to the variation in plant size. All species and phylogenetic multivariate models showed that both dispersal mode and species light/moisture niche explain seed mass variation, suggesting the importance of coevolution or covariation between seeds and vertebrates and the selection or filter effect of habitats on early life-history stages of plants in affecting individual seed development. Lastly, our results imply that phylogenetic constraints and niche conservatism may operate simultaneously in determining regional patterns of seed mass variation.

Perovskite chalcogenides are gaining substantial interest as an emerging class of semiconductors for optoelectronic applications. High-quality samples are of vital importance to examine their inherent physical properties. We report the successful crystal growth of the model system, BaZrS3 and its Ruddlesden–Popper phase Ba3Zr2S7 by a flux method. X-ray diffraction analyses showed the space group of Pnma with lattice constants of a = 7.056(3) Å, b = 9.962(4) Å, and c = 6.996(3) Å for BaZrS3 and P42/mnm with a = 7.071(2) Å, b = 7.071(2) Å, and c = 25.418(5) Å for Ba3Zr2S7. Rocking curves with full width at half maximum of 0.011° for BaZrS3 and 0.027° for Ba3Zr2S7 were observed. Pole figure analysis, scanning transmission electron microscopy images, and electron diffraction patterns also establish the high quality of the grown crystals. The octahedral tilting in the corner-sharing octahedral network is analyzed by extracting the torsion angles., Air Force Office of Scientific Research (Award FA9550-16-1-0335), Army Research Office (Award W911NF-19-1- 0137)