Mantle Transition Zone Structure Beneath Northeast Asia From 2‐D Triplicated Waveform Modeling: Implication for a Segmented Stagnant Slab

The structure of the mantle transition zone (MTZ) in subduction zones is essential for understanding subduction dynamics in the deep mantle and its surface responses. We constructed the P (V_p) and SH velocity (V_s) structure images of the MTZ beneath Northeast Asia based on two‐dimensional (2‐D) triplicated waveform modeling. In the upper MTZ, a normal V_p but 2.5% low V_s layer compared with IASP91 are required by the triplication data. In the lower MTZ, our results show a relatively higher‐velocity layer (+2% V_p and −0.5% V_s compared to IASP91) with a thickness of ~140 km and length of ~1,200 km atop the 660‐km discontinuity. Taking this anomaly as the stagnant slab and considering the plate convergence rate of 7–10 cm/year in the western Pacific region during the late Cenozoic, we deduced that the stagnant slab has a subduction age of less than 30 Ma. This suggests that the observed stagnancy of the slab in the MTZ beneath Northeast Asia may have occurred no earlier than the Early Oligocene. From the constraints derived individually on V_p and V_s structures, high V_p/V_s ratios are obtained for the entire MTZ beneath Northeast Asia, which may imply a water‐rich and/or carbonated environment. Within the overall higher‐velocity stagnant slab, a low‐velocity anomaly was further detected, with a width of ~150 km, V_p and V_s reductions of 1% and 3% relative to IASP91. Such a gap may have provided a passage for hot deep mantle materials to penetrate through the thick slab and feed the Changbaishan volcano

Influence of Nb on the β → α″ Martensitic Phase Transformation and Properties of the Newly Designed Ti-Fe-Nb Alloys

A series of Ti-7Fe-xNb (x = 0, 1, 4, 6, 9, 11 wt.%) alloys was designed and cast to investigate the β → α″ martensitic phase transformation, β phase stability, the resulting microstructure and mechanical properties. Phase analysis revealed that only Ti-7Fe-11Nb alloy shows a single body-centred cubic β phase microstructure while the others are comprised of β and orthorhombic α″ phases. Moreover, Nb addition up to 11 wt.% enhances the stability and volume fraction of β phase in the microstructure, hence reducing the propensity of the alloy system to form α″ phase during quenching. Compressive yield strength and hardness of the alloys are (985-1847) MPa and (325-520) Hv respectively. Additionally, Ti-7Fe-11Nb possesses the lowest Young\u27s modulus (84 GPa) and the highest deformability (42% strain) among the designed alloys due to the single β phase microstructure. This high deformability is also corroborated by the large plastic deformation zone underneath the Vickers indenter. In contrast, the fractured surfaces of Ti-7Fe and Ti-7Fe-1Nb alloys after compressive tests mostly contain shallow dimples, verifying their low ductility. The good combination of mechanical properties obtained for Ti-7Fe-11Nb renders it more desirable than commonly used CP-Ti and Ti-6Al-4V materials and makes it a promising candidate for biomedical application. © 2015 Elsevier B.V. All rights reserved

Calculation of oxygen diffusion coefficients in oxide films formed on low-temperature annealed Zr alloys and their related corrosion behavior

The growth of oxide film, which results from the inward oxygen diffusion from a corrosive environment, is a critical consideration for the corrosion resistance of zirconium alloys. This work calculates the oxygen diffusion coefficients in the oxide films formed on zirconium alloys annealed at 400~500 °C and investigates the related corrosion behavior. The annealed samples have a close size for the second-phase particles but a distinctive hardness, indicating the difference in substrate conditions. The weight gain of all samples highly follows parabolic laws. The weight gain of the sample annealed at 400 °C has the fastest increase rate at the very beginning of the corrosion test, but its oxide film has the slowest growth rate as the corrosion proceeds. By contrast, the sample annealed at 500 °C shows the lowest weight gain but the highest corrosion rate constant. Such a corrosion behavior is attributed to the amount of defects existing in the oxide film formed on the annealed samples; fewer defects would provide a lower fraction of short-circuit diffusion in total diffusion, resulting in a lower diffusion coefficient of oxygen in the oxide film, thereby producing better corrosion resistance. This is consistent with the calculated diffusion coefficients of oxygen in the oxide films: 3.252 × 10−11 cm2/s, 3.464 × 10−11 cm2/s and 3.740 × 10−11 cm2/s for the samples annealed at 400 °C, 450 °C, and 500 °C, respectively

Decoupling anomaly discrimination and representation learning: self-supervised learning for anomaly detection on attributed graph

Anomaly detection on attributed graphs is a crucial topic for its practical application. Existing methods suffer from semantic mixture and imbalance issue because they mainly focus on anomaly discrimination, ignoring representation learning. It conflicts with the assortativity assumption that anomalous nodes commonly connect with normal nodes directly. Additionally, there are far fewer anomalous nodes than normal nodes, indicating a long-tailed data distribution. To address these challenges, a unique algorithm,Decoupled Self-supervised Learning forAnomalyDetection (DSLAD), is proposed in this paper. DSLAD is a self-supervised method with anomaly discrimination and representation learning decoupled for anomaly detection. DSLAD employs bilinear pooling and masked autoencoder as the anomaly discriminators. By decoupling anomaly discrimination and representation learning, a balanced feature space is constructed, in which nodes are more semantically discriminative, as well as imbalance issue can be resolved. Experiments conducted on various six benchmark datasets reveal the effectiveness of DSLAD

Electron beam melting of porous titanium alloys: Microstructure and mechanical behavior

Electron beam melting (EBM) is a relatively new rapid, additive manufacturing technology which is capable of fabricating complex, multi-functional metal or alloy components directly from CAD models, selective melting of precursor powder beds. Compared with Ti-6Al-4V samples with same porosity level, the EBMproduced β-type Ti-24Nb-4Zr-8Sn (Ti2448) porous components exhibit a higher normalized fatigue strength owing to super-elastic property, greater plastic zone ahead of the fatigue crack tip and the crack deflection behavior. The super-elastic property can be improved by increasing porosity of porous samples as a result of increasing the tensile/compressive stress ratio of the porous structure. EBM-produced components exhibit more than twice the strength-to-modulus ratio of porous Ti-6Al-4V counterparts. The position of fatigue crack initiation is defined in strain curves based on the variation of the fatigue cyclic loops. The unique manufacturing process of EBM results in the generation of different sizes of grains, and the apparent fatigue crack deflection occurs at the grain boundaries in the columnar grain zone due to substantial misorientation between adjacent grains

Analysis on the epidemiological features of human brucellosis in northern and southern areas of China, 2015-2016

Objective To analyze the epidemiological characteristics of human brucellosis in northern and southern areas of China, and to develop national strategies for bruceUosis prevention and control. Methods Individual data on human bruceUosis was collected from the National Notifiable Infectious Disease Reporting Information System to describe the situation of bruceUosis in China during 2015-2016. Epidemiological features of the disease in northern and southern areas of China were analyzed. Results A total of 104 125 cases were reported in mainland China during 2015-2016, with an average incidence rate as 3.81/100 000. The overall incidence rate from the northern provinces was 7.77/100 000 in 2016, a 18.6% decrease from 2015 (9.55/100 000), whereas the incidence rate in the southern provinces was 0.27/100 000 in 2016, with an increase of 28.6%% than 0.21/100 000 in 2015. 90.0% of the newly infected counties mainly distributed in southern China. As for the locations of reporting cases, most of them were in the same counties in the northern areas (52.3%) while most cases in the southern areas (59.6%) were imported from other counties. The median age of the cases was 48 (IQR: 38-58) years, with male-to-female ratios as 2.7 # 1 in the north and 2.2 : 1 in the south. Majority of the cases were occupation-related, from both the northern (86.8%) and southern (62.7%) areas. Human brucellosis occurred every month throughout the year but with an obvious seasonal increase between March and July. Conclusions Different epidemiological features of human bruceUosis appeared in both northern and southern areas of China. The disease was seen endemic in the northern and dispersal in the southern provinces. Appropriate strategies for bruceUosis prevention and control should be developed, according to the diiferent epidemiological characteristics in the northern or southern areas.</p

Clinical features of 2041 human brucellosis cases in China

BACKGROUND: Human brucellosis has become a major public health problem in China. However, the available clinical data on brucellosis cases are limited.METHODS: We retrospectively reviewed medical charts of 2041 patients with confirmed human brucellosis and prospectively recorded their outcomes by telephone interview. These patients were admitted to the Sixth People's Hospital of the Xinjiang Uygur Autonomous region between 1st January and 31st December 2014. Data on these patients were collected from hospital medical records.RESULTS: Many patients presented with fatigue (67%), fever (64%), arthralgia (63%) and sweating (54%). High erythrocyte sedimentation rate (ESR) (69%), high C-reactive protein (CRP) (39%), high alanine aminotransferase (ALT) (33%) and high aspartate aminotransferase (AST) (20%) were the most common laboratory findings, especially in acute patients. There was evidence of focal involvement in 90% of patients. A total of 61.5% of brucellosis patients recovered. Multivariate logistic regression analyses suggested that the risk factors key to unfavorable prognosis were: age≥45 years (OR = 1.75, 95% CI 1.36-2.24), back pain (OR = 1.50, 95% CI 1.16-1.94) and joint tenderness (OR = 1.73, 95% CI 1.13-2.65). The increasing duration of the illness increased the risk of poor prognosis.CONCLUSION: Patients with brucellosis showed different characteristics in different clinical stages. In China, the chronicity rate of human brucellosis is high. The risk of poor prognosis is increased in patients aged 45 years or older, patients who have had brucellosis for a substantial period of time, and patients with back pain or joint tenderness. The clinical management of brucellosis should be improved to include sensitive diagnostic methods for subacute and chronic brucellosis.</p