Automated materials design with machine learning is increasingly common in recent years. Theoretically, it is characterized as black-box optimization in the space of candidate materials. Since the difficulty of this problem grows exponentially in the number of variables, designing complex materials is often beyond the ability of classical algorithms. We show how quantum annealing can be incorporated into automated materials discovery and conduct a proof-of-principle study on designing complex thermofunctional metamaterials. Our algorithm consists of three parts: regression for a target property by factorization machine, selection of candidate metamaterial based on the regression results, and simulation of the metamaterial property. To accelerate the selection part, we rely on the D-Wave 2000Q quantum annealer. Our method is used to design complex structures of wavelength selective radiators showing much better concordance with the thermal atmospheric transparency window in comparison to existing human-designed alternatives.

A great number of butterfly species in the warmer climate have evolved to exhibit fascinating optical properties on their wing scale which can both regulate the wing temperature and exhibit...

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The majority of existing traffic sign detection systems utilize color or shape information, but the methods remain limited in regard to detecting and segmenting traffic signs from a complex background. In this paper, we propose a novel graphbased traffic sign detection approach that consists of a saliency measure stage, a graph-based ranking stage, and a multithreshold segmentation stage. Because the graph-based ranking algorithm with specified color and saliency combines the information of color, saliency, spatial, and contextual relationship of nodes, it is more discriminative and robust than the other systems in terms of handling various illumination conditions, shape rotations, and scale changes from traffic sign images. Furthermore, the proposed multithreshold segmentation algorithm focuses on all the nodes with a nonzero ranking score, which can effectively solve problems such as complex background, occlusion, various illumination conditions, and so on. The results for three public traffic sign sets show that our proposed approach leads to better performance than the current state-of-the-art methods. Moreover, the results are satisfactory even for images containing traffic signs that have been rotated or undergone occlusion, as well as for images that were photographed under different weather and illumination conditions. Index Terms-Graph-based image analysis, graph-based image segmentation, traffic sign detection.

A novel pressure testing method, i.e., a thin-film pressure distribution measurement system, was utilized to investigate the contact area and stress at the ballast bed-soil subgrade interface of conventional railways during cyclic loading in model tests. Factors like the amplitude and frequency of cyclic loading and the existence or nonexistence of the subballast were considered to study their effects on the contact area and average stress over the contact area at the interfaces. In addition, the testing results were compared with those measured by the traditional testing method using earth pressure cells and those calculated by the finite element method (FEM) based on continuum theory. The study shows that, because of the discontinuous characters of the ballast medium, the stress diffused from the ballast bed on the subgrade surface was unevenly distributed but becoming relatively evenly distributed as the subballast was being installed. The subgrade surface stresses measured by the earth pressure cell and calculated by the FEM were very similar, but both were about 50 % lower than the average stress over the contact area measured by the novel thin-film pressure sensor. As the interface stress between the ballast bed and the subgrade is a key factor in subgrade deterioration, new testing methods and numerical calculation methods can consider the discontinuous characters of the ballast appropriately to be necessary for the investigations of the interface contact stress.