Search Results (6)

This study unveils a machine learning (ML)-assisted framework designed to optimize the stacking sequence and orientation of carbon fiber-reinforced polymer (CFRP)/metal composite laminates, aiming to enhance their mechanical properties under quasi-static loading conditions. This work pioneers the expansion of initial datasets for ML analysis in the field by uniquely integrating the experimental results with finite element simulations. Nine ML models, including XGBoost and gradient boosting, were assessed for their precision in predicting tensile and bending strengths. The findings reveal that the XGBoost and gradient boosting models excel in tensile strength prediction due to their low error rates and high interpretability. In contrast, the decision trees, K-nearest neighbors (KNN), and random forest models show the highest accuracy in bending strength predictions. Tree-based models demonstrated exceptional performance across various metrics, notably for CFRP/DP590 laminates. Additionally, this study investigates the impact of layup sequences on mechanical properties, employing an innovative combination of ML, numerical, and experimental approaches. The novelty of this study lies in the first-time application of these ML models to the performance optimization of CFRP/metal composites and in providing a novel perspective through the comprehensive integration of experimental, numerical, and ML methods for composite material design and performance prediction. Full article

We construct an infinite family of bounded-degree bipartite unique neighbour expander graphs with arbitrarily unbalanced sides. Although weaker than the lossless expanders constructed by Capalbo et al., our construction is simpler and may be closer to being implementable in practice, due to the smaller constants. We construct these graphs by composing bipartite Ramanujan graphs with a fixed-size gadget in a way that generalises the construction of unique neighbour expanders by Alon and Capalbo. For the analysis of our construction, we prove a strong upper bound on average degrees in small induced subgraphs of bipartite Ramanujan graphs. Our bound generalises Kahale’s average degree bound to bipartite Ramanujan graphs, and may be of independent interest. Surprisingly, our bound strongly relies on the exact Ramanujan-ness of the graph and is not known to hold for nearly-Ramanujan graphs. Full article

Macau’s urban development model has many unique characteristics, including expansion of the city through sea reclamation, increasing population mainly through immigration, and economic development driven by the gaming industry. Based on data from the Macau Statistics and Census Service, this study uses the Error Correction representation of the Autoregressive Distributed Lag model (ARDL-ECM) to analyze the impact of urban development on the trends of immigration and labor migration in Macau between 1992 and 2019. Results show that both land area and wage level have positive effects on the number of migrant workers and negative effects on the number of immigrants, indicating that Macau is over-dependent on short-term migrant workers. Macau’s land and human resources are tilted towards the gaming industry, resulting in a decreasing living environment and resident carrying capacity as the city develops. Therefore, this paper suggests that Macau should reduce the cost of city expansion and improve economic diversity through strengthening cooperation with neighboring mainland cities, hence sparing resources to absorb non-local talent and ensuring sustainable urban development. Full article

We present results for the electronic and magnetic structure of Mn and Fe clusters on Nb(110) surface, focusing on building blocks of atomic chains as possible realizations of topological superconductivity. The magnetic ground states of the atomic dimers and most of the monatomic chains are determined by the nearest-neighbor isotropic interaction. To gain physical insight, the dependence on the crystallographic direction as well as on the atomic coordination number is analyzed via an orbital decomposition of this isotropic interaction based on the spin-cluster expansion and the difference in the local density of states between ferromagnetic and antiferromagnetic configurations. A spin-spiral ground state is obtained for Fe chains along the [$1\overline{1}0$] direction as a consequence of the frustration of the isotropic interactions. Here, a flat spin-spiral dispersion relation is identified, which can stabilize spin spirals with various wave vectors together with the magnetic anisotropy. This may lead to the observation of spin spirals of different wave vectors and chiralities in longer chains instead of a unique ground state. Full article

This paper reports the unique microstructure of polyurea foams that combines the advantages of open and closed cell polymeric foams, which were synthesized through a self-foaming process. The latter was the result of aggressive mechanical mixing of diamine curative, isocyanate, and deionized water at ambient conditions, which can be adjusted on-demand to produce variable density polyurea foam. The spherical, semi-closed microcellular structure has large perforations on the cell surface resulting from the concurrent expansion of neighboring cells and small holes at the bottom surface of the cells. This resulted in a partially perforated microcellular structure of polyurea foam. As a byproduct of the manufacturing process, polyurea microspheres nucleate and deposit on the inner cell walls of the foam, acting as a reinforcement. Since cell walls and the microspheres are made of polyurea, the resulting reinforcement effect overcomes the fundamental interfacial issue of different adjacent materials. The partially perforated, self-reinforced polyurea foam is compared to the performance of traditional counterparts in biomechanical impact scenarios. An analytical model was developed to explicate the stiffening effect associated with the reinforcing microspheres. The model results indicate that the reinforced microcell exhibited, on average, ~30% higher stiffness than its barren counterpart. Full article

The present study was intend to track down the transitional process in which the hierarchical dominance in the urban structure of Namwon City shifted from the Namwoneupseong Walled Town to the area of Gwanghalluwon Garden by using cadastral data and various historical sources. It was aimed to find the factors regarding the transition and a sustainable development plan to the historical landscape. The results were as follows: First, the urban structure of former Namwon City has succeeded to a typical grid street structure of walled town. However, land use and urban landscape to an existing grid street structure and a modified grid street structure was formed by development of transportation in the city. In addition, as the fortress was demolished, land development expanded east and west along the railroad and Yochun River. Accordingly, the central areas of Namwon City also expanded and shifted from Namwoneupseong Walled Town to the new towns in the adjacent area. Secondly, lots transformation process of Gwanghalluwon Garden started the changing by transitioning from the pavilion of a past government office to tourist attraction in the novel Chunhyang-jeon, written during the Joseon Dynasty. It was transformed into the current area of Gwanghalluwon Garden through the regional expansion project in the 1960s, and the relocation of neighboring market in the 1970s by the conflagration. And Namwon County purchased these lands. Later, Gwanghalluwon Garden was designated a cultural asset and the current shape of Gwanghalluwon Garden has been preserved since then. Third, The secret of how Gwanghalluwon Garden has been able to survive as a “dominated landscape” is likely to be found in the relationship between the development of the city (external factor), historical landscapes (internal factor), and complex interactions of history, geography, culture, etc. Furthermore, each factor has served as a unique element in developing Gwanghalluwon Garden into a famous site. Now, people perceive the area surrounding Gwanghalluwon Garden as a valuable space. Fourth, to preserve Gwanghalluwon Garden’s important legacy as a historical landscape, it is necessary to shed new light on the awareness of values accumulated over time. Accordingly, the process by which a historical resource evolves in value, urban functions, and culture can be expected to have “unpredictable positive effects” in areas where cultural acts occur and society, environment, economics, etc. serve as motives to preserve the historical resource. Full article