Interface segregation of solute atoms has a profound effect on properties of engineering alloys. The occurrence of solute segregation in coherent twin boundaries (CTBs) in Mg alloys is commonly considered to be induced by atomic size effect where solute atoms larger than Mg take extension sites and those smaller ones take compression sites in CTBs. Here we report an unusual solute segregation phenomenon in a group of Mg alloys—solute atoms larger than Mg unexpectedly segregate to compression sites of {10$$\overline 1$$ 1 ¯ 1} fully coherent twin boundary and do not segregate to the extension or compression site of {10$$\overline 1$$ 1 ¯ 2} fully coherent twin boundary. We propose that such segregation is dominated by chemical bonding (coordination and solute electronic configuration) rather than elastic strain minimization. We further demonstrate that the chemical bonding factor can also predict the solute segregation phenomena reported previously. Our findings advance the atomic-level understanding of the role of electronic structure in solute segregation in fully coherent twin boundaries, and more broadly grain boundaries, in Mg alloys. They are likely to provide insights into interface boundaries in other metals and alloys of different structures.

Carbon (C) is of great importance to realize semi-insulating gallium nitride (GaN) for power electronic devices. We demonstrate that C can migrate from Ga sites to N sites after high temperature annealing of C doped GaN. The migration process is revealed through the observation of the generated Ga vacancies-related defects after annealing by positron annihilation spectroscopy. The activation energy of this migration process is estimated to be 2.5–2.8 eV from the temperature dependent annealing experiments, which is well consistent with the theoretical results from first-principles calculations.

In recent years, various types of power theft incidents have occurred frequently, and the training of the power-stealing detection model is susceptible to the influence of the imbalanced data set and the data noise, which leads to errors in power-stealing detection. Therefore, a power-stealing detection model is proposed, which is based on Improved Conditional Generation Adversarial Network (CWGAN), Stacked Convolution Noise Reduction Autoencoder (SCDAE) and Lightweight Gradient Boosting Decision Machine (LightGBM). The model performs Generation- Adversarial operations on the original unbalanced power consumption data to achieve the balance of electricity data, and avoids the interference of the imbalanced data set on classifier training. In addition, the convolution method is used to stack the noise reduction auto-encoder to achieve dimension reduction of power consumption data, extract data features and reduce the impact of random noise. Finally, LightGBM is used for power theft detection. The experiments show that CWGAN can effectively balance the distribution of power consumption data. Comparing the detection indicators of the power-stealing model with various advanced power-stealing models on the same data set, it is finally proved that the proposed model is superior to other models in the detection of power stealing.

The equilibrium intermetallic phase in Mg-Nd-Ag alloys has not been well understood. In this work, intermetallic particles in the solution-treated microstructure of commercial magnesium alloy QE22 (Mg-2.5Ag-2.0Nd-0.7Zr, wt pct) have been investigated using scanning electron microscopy, electron diffraction, atomic-resolution imaging and mapping techniques of scanning transmission electron microscopy (STEM) and thermodynamic modelling. The intermetallic particles are distributed in the inter-dendritic regions. They have coarse irregular shape and share the same crystal structure. The intermetallic phase (designated δ) is determined to have an orthorhombic structure (space group Cmcm, a = 1.02 nm, b = 1.18 nm, c = 1.00 nm) and a composition of NdAgMg11, which are different from those reported previously. An atomic model is proposed for the δ phase based on atomicresolution STEM images and atomic-scale energy-dispersive X-ray spectroscopy maps. The δ lattice is structurally related to that of Mg12Nd phase in binary Mg-Nd alloys. The Gibbs energy of formation of NdAgMg11 is determined from the equilibrium study at 793 K (520 °C), including the entropy of formation using the present experimental phase analysis data obtained at lower temperature.Implications to the formation temperature range and thermal stability of this phase and alloy solidification are discussed based on the calculated Mg-Nd-Ag phase diagram and Scheil solidification paths of alloys.

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Urban parks can offer a variety of ecosystem services such as beautifying the landscape, ecological regulation, leisure and recreation, and maintaining biodiversity. Understanding how urban parks affect people’s lives can help guide the construction and planning of parks in a direction that is more beneficial to the public. Therefore, it is worth studying the extent to which different urban parks with different characteristics affect public behaviour and preferences. This paper takes five typical urban parks in Chengdu and analyses the relationship between characteristics of the park ecosystem and public behaviour and preferences. The characteristics include the park scale, blue-green space ratio, plant diversity, and degree of re-wilding. Visit frequency, stay time, and park preference characterise public behaviour and preferences. The results show: (1) There are obvious differences in the ecosystem characteristics of the five parks: Qinglong Lake Wetland Park is the largest; the proportion of blue-green space in Jiangjiayiyuan Garden is the highest; the degree of re-wilding in Bailuwan Wetland Park is the highest; the proportion of green space and plant diversity in Guixi Ecological Park is the highest; and the proportion of blue space in Jincheng Lake Wetland Park is the highest. (2) There are differences in public behaviour and preferences for different parks. Tourists visit Qinglong Lake Wetland Park the most in spring and autumn and they choose Guixi Ecological Park instead in summer and winter. The public stays longer in Qinglong Lake Wetland Park and shorter in Jincheng Lake Wetland Park. (3) The scale of urban parks, the proportion of blue-green space, and the degree of re-wilding, especially the proportion of blue space, have a positive impact on the public’s evaluation and promote public visits. The results of the study could help improve public awareness of the relationship between park characteristics and ecological services and well-being.

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