An improved evolutionary approach-based hybrid algorithm for Bayesian network structure learning in dynamic constrained search space

Learning Bayesian network (BN) structures from data is a NP-hard problem due to the vastness of the solution space. To address this issue, hybrid approaches that integrate the constraint-based (CB) method and the score-and-search (SS) method have been developed in the literature, but when the constrained search space is fixed and inaccurate, it is very likely to lose the optimal solution, leading to low learning accuracy. Besides, due to the randomness and uncertainty of the search, it is difficult to preserve the superiority of the structures, resulting in low learning efficiency. Therefore, we propose a novel hybrid algorithm based on an improved evolutionary approach to explore BN structure with highest matching degree of data set in dynamic constrained search space. The proposed algorithm involves two phases, namely the CB phase and the SS phase. In the CB phase, the mutual information is utilized as the restriction to limit the search space, and a binding parameter is introduced to the novel encoding scheme so that the search space can be dynamically changed in the evolutionary process. In the SS phase, a new operator is developed to pass on the excellent genes from generation to generation, and an update principle for the binding parameter is exploited for the dynamic selection of the search space. We conduct the comparative experiments on the benchmark network data sets and provide performance and applicability analysis of our proposed method. The experimental results show that the new algorithm is effective in learning the BN structures

Iron‐Locked Hydr(oxy)oxide Catalysts via Ion‐Compensatory Reconstruction Boost Large‐Current‐Density Water Oxidation

Abstract Nickel‐iron based hydr(oxy)oxides have been well recognized as one of the best oxygen‐evolving catalysts in alkaline water electrolysis. A crucial problem, however, is that iron leakage during prolonged operation would lead to the oxygen evolution reaction (OER) deactivation over time, especially under large current densities. Here, the NiFe‐based Prussian blue analogue (PBA) is designed as a structure‐flexible precursor for navigating an electrochemical self‐reconstruction (ECSR) with Fe cation compensation to fabricate a highly active hydr(oxy)oxide (NiFeOxHy) catalyst stabilized with NiFe synergic active sites. The generated NiFeOxHy catalyst exhibits the low overpotentials of 302 and 313 mV required to afford large current densities of 500 and 1000 mA cm−2, respectively. Moreover, its robust stability over 500 h at 500 mA cm−2 stands out among the NiFe‐based OER catalysts reported previously. Various in/ex situ studies indicate that the Fe fixation by dynamic reconstruction process can reinforce the Fe‐activated effect on the OER amenable to the industrial‐level large current conditions against the Fe leakage. This work opens up a feasible strategy to design highly active and durable catalysts via thermodynamically self‐adaptive reconstruction engineering

Exchange coupling controlled ferrite with dual magnetic resonance and broad frequency bandwidth in microwave absorption

Ti-doped barium ferrite powders BaFe12−xTixO19 (x = 0, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 and 0.8) were synthesized by the sol–gel method. The phase structure and morphology were analyzed by x-ray diffraction (XRD) and scanning electron microscopy, respectively. The powders were also studied for their magnetic properties and microwave absorption. Results show that the Ti-doped barium ferrites (BFTO) exist in single phase and exhibit hexagonal plate-like structure. The anisotropy field Ha of the BFTO decreases almost linearly with the increase in Ti concentration, which leads to a shift of the natural resonance peak toward low frequency. Two natural resonance peaks appear, which can be assigned to the double values of the Landé factor g that are found to be ~2.0 and ~2.3 in the system and can be essentially attributed to the existence of Fe3+ ions and the exchange coupling effect between Fe3+ and Fe2+ ions, respectively. Such a dual resonance effect contributes a broad magnetic loss peak and thus a high attenuation constant, and leads to a dual reflection loss (RL) peak over the frequency range between 26.5 and 40 GHz. The high attenuation constants are between 350 and 500 at peak position. The optimal RL reaches around −45 dB and the practicable frequency bandwidth is beyond 11 GHz. This suggests that the BFTO powders could be used as microwave absorbing materials with extraordinary properties

Enhanced Charge Separation in Nanoporous BiVO4 by External Electron Transport Layer Boosts Solar Water Splitting

Abstract The optimization of charge transport with electron‐hole separation directed toward specific redox reactions is a crucial mission for artificial photosynthesis. Bismuth vanadate (BiVO4, BVO) is a popular photoanode material for solar water splitting, but it faces tricky challenges in poor charge separation due to its modest charge transport properties. Here, a concept of the external electron transport layer (ETL) is first proposed and demonstrated its effectiveness in suppressing the charge recombination both in bulk and at surface. Specifically, a conformal carbon capsulation applied on BVO enables a remarkable increase in the charge separation efficiency, thanks to its critical roles in passivating surface charge‐trapping sites and building external conductance channels. Through decorated with an oxygen evolution catalyst to accelerate surface charge transfer, the carbon‐encased BVO (BVO@C) photoanode manifests durable water splitting over 120 h with a high current density of 5.9 mA cm−2 at 1.23 V versus the reversible hydrogen electrode (RHE) under 1 sun irradiation (100 mW cm−2, AM 1.5 G), which is an activity‐stability trade‐off record for single BVO light absorber. This work opens up a new avenue to steer charge separation via external ETL for solar fuel conversion

Morpho-Physiological and Transcriptome Analyses Provide Insights into the Wizened Bud Formation in Pear Trees

Wizened buds are frequently observed in pear (Pyrus spp.) trees, which greatly reduces the yield. However, little is known about the mechanism of wizened bud formation. Here, we analyzed physiological and transcriptomic differences between normal buds and wizened buds of ‘710’ pear trees. The results indicated that the sorbitol and boron (B) contents, during bud differentiation, were significantly reduced in wizened buds. The microscopic observation and transcriptome analysis revealed that the collapse of the organ structure and cell wall loosening process may have a close relation with wizened bud formation. Moreover, reduced transcript levels of PpyMYB39.1 and its downstream genes (PpyHT1, PpyHT2, PpyPMEI1 and PpyPMEI2) were found in wizened buds. However, the transcript levels of pentose and glucuronate interconversion pathway genes (PpyPME3, PpyPL18.1, PpyPL18.2, PpyPG1 and PpyPG2) and the concentration of pectin-degradation-related enzymes were increased in wizened buds. Correspondingly, the pectin concentration was significantly reduced in wizened buds. Taken together, PpyMYB39.1 may promote pectin degradation and decrease carbohydrate transport by regulating its downstream genes and is supposed to play a vital role in the wizened bud formation resulting from the cell wall loosening process. Our study provides fundamental insights into wizened bud formation and strategies to reduce the wizened bud occurrence in pear trees

Morpho-Physiological and Transcriptome Analyses Provide Insights into the Wizened Bud Formation in Pear Trees

Wizened buds are frequently observed in pear (Pyrus spp.) trees, which greatly reduces the yield. However, little is known about the mechanism of wizened bud formation. Here, we analyzed physiological and transcriptomic differences between normal buds and wizened buds of ‘710’ pear trees. The results indicated that the sorbitol and boron (B) contents, during bud differentiation, were significantly reduced in wizened buds. The microscopic observation and transcriptome analysis revealed that the collapse of the organ structure and cell wall loosening process may have a close relation with wizened bud formation. Moreover, reduced transcript levels of PpyMYB39.1 and its downstream genes (PpyHT1, PpyHT2, PpyPMEI1 and PpyPMEI2) were found in wizened buds. However, the transcript levels of pentose and glucuronate interconversion pathway genes (PpyPME3, PpyPL18.1, PpyPL18.2, PpyPG1 and PpyPG2) and the concentration of pectin-degradation-related enzymes were increased in wizened buds. Correspondingly, the pectin concentration was significantly reduced in wizened buds. Taken together, PpyMYB39.1 may promote pectin degradation and decrease carbohydrate transport by regulating its downstream genes and is supposed to play a vital role in the wizened bud formation resulting from the cell wall loosening process. Our study provides fundamental insights into wizened bud formation and strategies to reduce the wizened bud occurrence in pear trees