Hardenability Improvement Mechanisms and Hardenability-Controlling Factors in Steels With Combined Mo–B Addition

Metallurgical and Materials Transactions A - To elucidate the hardenability improvement mechanisms and hardenability-controlling factors in low-carbon (C) steels with the combined addition of...     

Estimator for generalization performance of machine learning model trained by biased data collected from multiple references

The data acquired in civil engineering tasks often involve high acquisition costs, and the available datasets tend to have a limited number of samples and are highly biased. To estimate the performance of machine learning models, k-fold cross-validation (k-CV) is widely used. However, if only limited data are available and the data distribution is biased, k-CV tends to overestimate the performance for practical applications. This study proposed a new estimator, leave one reference out and k-CV (LORO-k-CV), to determine the practical performance of machine learning models, that is, the generalization performance for population data in the target task, in case data are collected by multiple references resulting in biased data. LORO-k-CV is a combination of a new concept, LORO-CV, that estimates the performance in the extrapolation region of the training data without human intervention and k-CV, considering the ratio of the interpolation and extrapolation regions. The efficacy of LORO-k-CV was validated with its application to the regression task for the chloride-ion concentration of concrete structures. To more specifically demonstrate the advantages of LORO-k-CV in model construction, the feature selections were conducted using both k-CV and LORO-k-CV methods. These results revealed that LORO-k-CV can effectively construct a model with improved generalization performance even from the same data in cases where data are collected by multiple references, resulting in biased data.     

Bandgap Tunable Oxynitride LaNb2O7–xNx Nanosheets

Bandgap tunable lanthanum niobium oxynitride [LaNb₂O_7-xN_x]^(1+x)− nanosheet is prepared by the delamination of a Ruddlesden−Popper phase perovskite oxynitride via ion−exchange and two−step intercalation processes. The lanthanum niobium oxynitride nanosheets have a homogeneous thickness of 1.6 nm and exhibit a variety of chromatic colors depending on the nitridation temperature of the parent-layered oxynitride. The bandgap energy of the nanosheets is determined by ultraviolet photoemission spectroscopy, Mott–Schottky, and photoelectrochemical measurements and is found to be tunable in the range of 2.03–2.63 eV. Furthermore, the oxide/oxynitride superlattice structures are fabricated by face−to−face stacking of 2D crystals using oxynitride [LaNb₂O_7-xN_x]^(1+x)− and oxide [Ca₂Nb₃O₁₀]⁻ nanosheets as building blocks. Moreover, the superlattices-like restacked oxynitride/oxide nanosheets hybrid exhibits unique proton conductivity and dielectric properties strongly influenced by the oxynitride nanosheets and enhanced photocatalytic activity under visible light irradiation.     

Power factor control for inverters under high penetration of distributed generation

The paper proposes a method to select a power factor for an inverter of distributed power generation systems to keep appropriate voltage of a power system with the high penetration of inverter-interfaced generation. The increase of inverter-interfaced power sources, such as wind and photovoltaic power generation, arouses concerns on the voltage fluctuations in a power system. While constant power factor control of an inverter has been studied as a means to stabilize the voltage of a power system, there still remains room to improve the control. The proposed method in the paper selects the power factor based on the R/X ratio of the looking-back impedance into the interconnected power system. By normalizing the related variables, a general formula is derived for the power factor, and the resultant relationship between the apparent power and voltage of an inverter becomes identical irrespective of the R/X ratio with the control. Sample studies show that, by operating an inverter with the power factor, voltage fluctuations are effectively suppressed even for a power system with the high penetration of inverter-interfaced generation.     

Tetraphenylporphyrin Enters the Ring: First Example of a Complex between Highly Bulky Porphyrins and a Protein**

Tetraphenylporphyrin (TPP) is a symmetrically substituted synthetic porphyrin whose properties can be readily modified, providing it with significant advantages over naturally occurring porphyrins. Herein, we report the first example of a stable complex between a native biomolecule, the haemoprotein HasA, and TPP as well as its derivatives. The X-ray crystal structures of nine different HasA-TPP complexes were solved at high resolutions. HasA capturing TPP derivatives was also demonstrated to inhibit growth of the opportunistic pathogen Pseudomonas aeruginosa. Mutant variants of HasA binding FeTPP were shown to possess a different mode of coordination, permitting the cyclopropanation of styrene.