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Wire arc additive manufacturing (WAAM) is widely used in the rapid prototyping of large parts because of its high deposition rate, high material utilization rate as well as low cost. However, the manufacturing process of magnesium alloy wires is relatively difficult, and the defects and performance of parts are difficult to control. This paper reviews the preparation process of magnesium alloy wires, which aims to achieve surface control and performance optimization of wires. Due to the quality of wires and the high processing temperature, the defects often occur in the deposition process. The common defects of magnesium alloy parts by WAAM are discussed and solutions are given to minimize it. The research advances in microstructure, mechanical properties, damping properties and corrosion properties are summarized. WAAM has performance advantages compared to casting, but the microstructure is inhomogeneous and the properties are anisotropic. Several quality improvement strategies are reported to improve properties and reduce defects. The effectiveness and applicability of these strategies are discussed, and the future prospects of WAAM for magnesium alloys are proposed. The preparation of high-performance wires, the formation mechanism of defects and microstructure are three keys for future improvement of WAAM for magnesium alloy. [ABSTRACT FROM AUTHOR]

Based on the nonlinear algorithmic theory, the R-SVM water source discrimination model and prediction method were established by using the piper qualitatively to compare the differences between the ionic components and R-type factor approximation indicator input dimensions. Taking the mine water samples of Zhaogezhuang Coal Mine as an example, according to the chemical composition analysis of the water samples from different monitoring points, six indexes of Na+, Ca2+, Mg2+, Cl–, SO42– and HCO3– were selected as the discrimination factors. According to the water characteristics of each aquifer and the actual needs of discrimination, the water inrush sources in the mining area were divided into four categories: The goaf water is class I, Ordovician carbonate is class II, Sandstone fracture water from the 13 coal system is class III, and Sandstone fracture water from the 12 coal system is class IV. Taking 56 typical water inrush samples as training samples, 11 groups for prediction samples, establish the input index as typical ion content, output as water source type, using SPSS statistics and MATLAB to realize the R-SVM water source discriminant analysis model, automatically establishing the mapping relationship between the water quality indexes and the evaluation standards, which can achieve the purpose of rapid and accurate discrimination of the water sample data. The results showed that the accuracy of the R-SVM model classification was 90.90% in the verification of the water source discrimination example of Zhaogezhuang mine and the coupled model has high accuracy, good applicability and discriminant ability, and has certain guiding significance for the prevention and control of water damage and the related field work. [ABSTRACT FROM AUTHOR]

Microstructure simulation has been greatly expanded in recent years, particularly for the purpose of microstructural prediction and understanding mechanisms of microstructural evolution in thermal-mechanical processes. The application of microstructure simulation to hot rolling of magnesium alloy sheets will bring a great economic benefit. In this study, a multi-scale coupled dislocation density model of magnesium alloys was developed for predicting the microstructures of rolled AZ31 sheets. The simulations were performed by inserting the expanded dislocation density model into a VUSDFLD subroutine of ABAQUS software. The effects of rolling temperature and speed on dislocation densities of low angle grain boundary and high angle grain boundary and dynamic recrystallization (DRX) volume fraction were investigated by finite element simulations. The simulation results show that the dislocation densities of the high angle grain boundary and low angle grain boundary increase rapidly at the first rolling stage, but decrease slightly with rolling time. The changes of dislocation densities with the rolling time are complicated, which are influenced by an integrated mechanism of work-hardening, dynamic recovery and DRX. The dislocation densities can achieve the highest value when the rolling temperature is in range of 400-450 °C. Moreover, the DRX volume fraction is the largest in the surface layer and the smallest in the center layer of the rolled sheets. This is resulted from the distributions of rolling temperature, rolling strain and strain rate from the surface to the center of the rolled sheets. Rolling force decreases with the rolling temperature but increases slightly with the rolling speed. The predicted rolling forces are good in agreement with those of the experiments. [ABSTRACT FROM AUTHOR]

There is lacking research on risk factors and prediction models associated with Post-hemorrhagic hydrocephalus (PHH). Thus, this present study aimed to analyze the risk factors of PHH and establish a risk-scoring system through a large-scale study. A retrospective study of 382 patients with intracranial hemorrhage assessed age, history and diagnosis, Glasgow coma score (GCS), and fever time. After univariate and logistic regression analysis, a risk scoring system was established according to independent risk factors and evaluated using the area under the curve (AUC). Of the 382 patients, 133 (34.8%) had PHH, 43 (11.3%) received surgical treatment. Factor classification showed that age > 60 years old [odds ratio (OR): 0.347, II = 5 points], GCS < 5 (OR: 0.09, IV = 10 points), GCS 6‒8 (OR = 0.232, III = 6 points), fever time > 9 (OR: 0.202, III = 7 points), fever time 5–9 (OR: 0.341, II = 5 points), CSF-TP x time > 14,4000 group (OR: 0.267, IV = 6 points), and CSF-TP x time 9,601‒14,400 group (OR: 0.502, III = 3 points) were independent risk factors. The result of the receiver operating characteristic (ROC) prediction showed that AUC = 0.790 (0.744‒0.836). Low-risk (IV-VII), moderate (VIII-X), and high-risk group (XI-XIII) incidence of PHH were 11.76%, 50.55%, and 70.00% (p < 0.001), respectively. The coincidence rates in the validation cohort were 26.00%, 74.07%, and 100.0% (p < 0.001), respectively. AUC value was 0.860 (0.780‒0.941). The predictive model was conducive to determining the occurrence of PHH and facilitating early intervention. [ABSTRACT FROM AUTHOR]

Stable carbon isotope (δ13C) rollover of natural gas has attracted recent attention due to its association with highly productive shale gas. However, the mechanistic causes of δ13C rollover are not fully understood. In this investigation, pyrolysis was carried out using calcareous shale and carbonaceous mudstone under high water pressure (WP) (i.e., 5 × 106–1.2 × 108 Pa). It was found that WP induced the isotope rollover of gaseous hydrocarbons. For both sapropelic and humic organic matter, the δ13C rollover of CH4 (methane), C2H6 (ethane), and C3H8 (propane) occurred when the WP ranged from 3.25 × 107 to 1.2 × 108 Pa. This result can be explained by high WP conditions retarding oil cracking, and enhancing hydrocarbon expulsion and oil generation. The promotion of oil generation resulted in increasing trends of vitrinite reflectance, and inhibition of gaseous hydrocarbons generation resulted in decrease in δ13C1 values with increase in WP. Good functions were found between water pressure and the calculated carbon kinetic isotope effect (KIE) for 12CH4 and 13CH4 produced from sapropelic and humic organic matter. Further calculations showed that the increments of activation volume ( Δ V 12 CH 4 ‡ – Δ V 13 CH 4 ‡ ) were linearly correlated with the kinetic isotope effect of methane ( Δ KIE ) produced from sapropelic and humic organic matter, indicating that WP may affect the KIE of 12CH4 and 13CH4 by changing the Δ V ‡ of 12CH4 and 13CH4. Overall, these findings suggest that WP affects the carbon isotope fractionation of gaseous hydrocarbons due to the different thermodynamic properties of 12CH4 and 13CH4. [ABSTRACT FROM AUTHOR]

A finite element model is constructed for a sliding friction bearing in a seismically isolated bridge under vertical excitation with contact/friction elements. The effects of vertical excitation on the seismic performance of a seismically isolated bridge with sliding friction bearings and different bearing friction coefficients and different stiffness levels (pier diameter) are discussed using example calculations, and the effects of excitation direction for vertical excitation on the analysis results are explored. The analysis results shows that vertical excitation has a relatively large impact on seismic performance for a seismically isolated bridge with sliding friction bearings, which should be considered when designing a seismically isolated bridge with sliding friction bearings where vertical excitation dominates. [ABSTRACT FROM AUTHOR]

The main objective of this work was to investigate the effect of storage temperature (4 and 20 °C) on carotenoid accumulation and on the expression levels of seven carotenoid biosynthetic genes ( Psy, Pds, Zds, Lcyb, Lcye, Hyb and Zep) in postharvest 'Cara Cara' navel orange ( C. sinensis Osbeck) fruits. Storage at 20 °C rapidly increased the carotenoid content in the peel, whereas the content remained unchanged in the pulp before 35 days of storage. By contrast, storage at 4 °C maintained the carotenoid content in the peel before 35 days of storage, after which it slightly increased as time progressed. However, the content in the pulp gradually increased over the entire storage period. In the peel, the gene expressions of Psy and Lcyb were up-regulated at 20 °C but remained unchanged at 4 °C. In addition, the gene expressions of Zds, Hyb, and Zep were repressed at both temperatures before the early storage, followed by a rapid increase only at 20 °C. Then the expressions remained constant level at both temperatures, with the expression level at 20 °C higher than that at 4 °C. Low temperature (4 °C) apparently induced the expression of all the test carotenoid biosynthetic genes in the pulp, in contrast to the nearly stable level at 20 °C. Our present study suggests that the carotenoid biosynthesis in postharvest 'Cara Cara' fruits is transcriptionally regulated, and storage temperature affects the carotenoid accumulation and gene expression in a tissue-dependent manner. Key message Temperature could affect the carotenoid biosynthesis in postharvest 'Cara Cara' fruits in a tissue-dependent manner. The carotenoid biosynthesis in postharvest 'Cara Cara' fruits was transcriptionally regulated by correlated genes. [ABSTRACT FROM AUTHOR]