Abstract
Utilizing the unprecedented high-resolution Magnetospheric Multiscale mission data from 2015 September to 2017 December, we perform a statistical study of electron vortexes in the turbulent ...terrestrial magnetosheath. On the whole, 506 electron vortex events are successfully selected. Electron vortexes can occur at four known types of magnetic structures, including 78, 42, 26, and 39 electron vortexes observed during the crossings of the current sheets, magnetic holes, magnetic peaks, and flux ropes, respectively. Except for the four types of structures, the rest of the electron vortexes are in the “Others” category, defined as unknown structures. The electron vortexes mainly occur in the subsolar region, with only a few in the flank region. The total occurrence rate of all electron vortexes is 4.86 hr
–1
, with, on average, 3.65 events hr
−1
in the
X-Y
plane and 3.26 events hr
−1
in the
X-Z
plane. The durations of most of the electron vortexes concentrate within 0.5–1.5 s and are 1.09 s on average. The electron vortexes are ion-scale structures owing to the average scale of 2.05 ion gyroradius. In addition, the means, medians, and maxima of the energy dissipation
J
·
E
′ in the electron vortexes are almost positive, implying that the electron vortex may be a potential coherent structure or channel for turbulent energy dissipation. All these results reveal the statistical characteristics of electron vortexes in the magnetosheath and improve our understanding of energy dissipation in astrophysical and space plasmas.
•TiMCs with better tribological property was fabricated by modification powders technology.•GONs-3Cu/TC4 composites shows the lowest COF (0.120) and wear volume loss (0.155 mm3).•Improvements mainly ...derive from hardness strengthening effects by Ti-Cu intermetallics and TiC@GONs.
Titanium alloys have been applied for many lightweight structural components in the fields of aerospace, automobiles and biomedical implants owing to their light-weight, good mechanical properties and biocompatibility. However, poor tribological performance often restricts their wide-range applications. In this study, we synthesized Cu modified Ti-6Al-4 V (TC4) powders with various Cu contents (0, 1, 3, 5, 10 wt%), which was further strengthened with 0.3 wt% graphene oxide nanosheets (GONs) using a powder metallurgy technology. These composite powders were then synthesized into titanium matrix composites using spark plasma sintering. Effects of Cu contents on microstructure evolution, phase composition and tribological properties of Ti matrix composites were systematically investigated. The synthesized composites were consisted of α-Ti, β-Ti, Ti2Cu, in-situ-formed TiC and remained GONs, and showed better tribological properties than those of TC4 alloy. The average coefficient of friction was reduced from 0.168 to a minimum value of 0.120 as the copper content increased from 0 to 3 wt%, meanwhile the wear volume loss was reduced by 49.3%. Whereas further increasing Cu contents resulted in the increases of both coefficients of friction and wear volume loss. These improvements are mainly attributed to the hardness strengthening effects by Ti-Cu intermetallics and TiC@GONs structure, as well as the self-lubricating effect of GONs. Compared with traditional surface modification processes, the new method proposed in this work is cost-effective and promising for improving the tribological performance of titanium alloys in industry applications.
Wetland loss and climate change are known to alter regional and global methane (CH4) budgets. Over the last six decades, an extensive area of marshland has been converted to cropland on the Sanjiang ...Plain in northeast China, and a significant increase in air temperature has also been observed there, while the impacts on regional CH4 budgets remain uncertain. Through model simulation, we estimated the changes in CH4 emissions associated with the conversion of marshland to cropland and climate change in this area. Model simulations indicated a significant reduction of 1.1 Tg yr−1 (0.7–1.8 Tg yr−1) from the 1950s to the 2000s in regional CH4 emissions. The cumulative reduction of CH4 from 1960 to 2009 was estimated to be ~36 Tg (24–57 Tg) relative to the 1950s, and marshland conversion and the climate contributed 86% and 14% of this change, respectively. Interannual variation in precipitation (linear trend with P > 0.2) contributed to yearly fluctuations in CH4 emissions, but the relatively lower amount of precipitation over the period 1960–2009 (47 mm yr−1 lower on average than in the 1950s) contributed ~91% of the reduction in the area-weighted CH4 flux. Global warming at a rate of 0.3 ° per decade (P < 0.001) has increased CH4 emissions significantly since the 1990s. Relative to the mean of the 1950s, the warming-induced increase in the CH4 flux has averaged 19 kg ha−1 yr−1 over the last two decades. In the RCP (Representative Concentration Pathway) 2.6, RCP 4.5, RCP 6.0 and RCP 8.5 scenarios of the fifth IPCC assessment report (AR5), the CH4 fluxes are predicted to increase by 36%, 52%, 78% and 95%, respectively, by the 2080s compared to 1961–1990 in response to climate warming and wetting.
We present here a detailed study of the oxidation resistance of chemical vapor deposition (CVD) graphene. The results reveal that CVD graphene shows an excellent performance as a passivation layer ...below 200°C, but the protection ability degenerates rapidly with increasing the air temperature. Our work demonstrates for the first time that the most adverse effect on the degeneration of oxidation resistance in high temperature air comes from wrinkles but not others, such as Cu grain boundaries, periodic surface depressions due to Cu surface reconstruction induced by the graphene overlay, graphene domain boundaries, which are always believed the primary factor for inferior quality of the CVD graphene at present. In addition, we found that the distribution of the wrinkles in CVD graphene depended on the Cu crystal structure, and the results of the Electron-backscatter diffraction indicate that the folded wrinkles always appear on Cu (001) facets, while the standing collapsed wrinkles appear more easily on the Cu (111) facets.
The trade-off relation between the strength and electrical conductivity in the Al conductor is a significant scientific issue. Breaking such trade-off relation is an interesting challenge for ...preparing the Al conductor with high strength and good electrical conductivity. In this study, an abnormal strength-electrical conductivity relation was achieved during the deformation of the cold-drawn Al wires. In particular, the interesting finding is that both the grain boundary and texture obviously influence the strength-electrical conductivity relation, i.e., the elongated grains with the strong 〈111〉 texture does not only promote the strength (74.2 MPa), but also improve the electrical conductivity (0.31 %IACS). This new finding proves that the elongated grains and the strong 〈111〉 texture can be designed and applied to prepare the Al conductor with high strength and high electrical conductivity. Furthermore, an experiment was designed to verify the mechanism, and the results show that the newly prepared commercially pure Al wire (CPAW) owns a higher electrical conductivity (∼63.0 %IACS) in comparison with the traditional CPAW (∼62.0 %IACS).
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•Simultaneous increase in strength and electrical conductivity was found in Al wire.•Hard, thin and long texture could improve the strength and electrical conductivity.•A novel Al wire with an enhanced electrical conductivity of 63.01 %IACS was achieved.
To understand the types of gene action controlling seven quantitative traits in rice, we carried out quantitative trait locus (QTL) mapping in order to distinguish between the main-effect QTLs ...(M-QTLs) and digenic epistatic QTLs (E-QTLs) responsible for the trait performance of 254 recombinant inbred lines (RILs) from rice varieties Lemont/Teqing and two backcross hybrid (BCF1) populations derived from these RILs. We identified 44 M-QTL and 95 E-QTL pairs in the RI and BCF1 populations as having significant effects on the mean values and mid-parental heterosis of heading date, plant height, flag leaf length, flag leaf width, panicle length, spikelet number and spikelet fertility. The E-QTLs detected collectively explained a larger portion of the total phenotypic variation than the M-QTLs in both the RI and BCF1 populations. In both BCF1 populations, over-dominant (or under-dominant) loci were more important than additive and complete or partially dominant loci for M-QTLs and E-QTL pairs, thereby supporting prior findings that overdominance resulting from epistatic loci are the primary genetic basis of inbreeding depression and heterosis in rice.
Left atrial (LA) dysfunction is involved in idiopathic inflammatory myopathy (IIM). Multiparametric cardiovascular magnetic resonance (CMR) strain imaging is a feasible and reproducible tool for ...examining global and regional LA functions, as well as left ventricular (LV) function in IIM patients.
The aim of this study was to evaluate the feasibility and reproducibility of LA strain occurrence and strain rate for LA function assessment using CMR in IIM cases.
A total of 36 IIM and 42 healthy control cases were included. Baseline ventricular function was comparatively assessed in both groups. LA strain occurrence and strain rate were examined by cine cardiac magnetic resonance imaging MRI utilizing an in-house semiautomated technique. LA global function indexes were quantitated, including reservoir, conduit, and booster-pump functions.
A total of 78 participants were enrolled in this study. There was no significant difference in left/right ventricular routine functions between IIM patients and control individuals (p>0.05); the same results (p>0.05) was also observed between patients with high hs-cTnI and normal. However, LV mass index had significant difference (p1=0.003, p2<0.01). Compared with IIM patients and control individuals, only total strain (εs) (p4=0.046) and passive strain (εe) (p4=0.002) showed significant difference, and in cases with high hs-cTnI and normal hs-cTnI, there are differences for εs (p3=0.012) and εe (p4=0.047). The strongest association was found between εe and LV ejection fraction (LVEF) (r=0.581, p<0.01).
IIM cases have altered LA reservoir and conduit functions, and LA strain could reflect LA function.
•Helpful for early identification of disease changes.•Avoidance of adverse events effectively in the future.•Good clinical application value.•A important noninvasive technique.
The rapid expansion of the optical fiber telecommunication industry due to the explosion of the Internet has substantially driven down the cost of optical components, making fiber optic sensors more ...economically viable. In addition, the rapid development of fiber-optic sensors, particularly the fiber Bragg grating (FBG) sensors offers many advantages and capability that could not be achieved otherwise. In the past few years, fiber Bragg grating sensors have attracted a lot of interest and they are being used in numerous applications. This paper describes the FBG sensors developed for structural health monitoring, and were installed on Hong Kong’s landmark Tsing Ma bridge (TMB), which is the world longest (1377 m) suspension bridge that carried both railway and regular road traffic. Forty FBG sensors divided into three arrays were installed on the hanger cable, rocker bearing and truss girders of the TMB. The objectives of the study are to investigate the feasibility of using the developed FBG sensors for structural health monitoring, via monitoring the strain of different parts of the TMB under both the railway and highway loads as well as comparing the FBG sensors’ performance with the conventional structural health monitoring system — Wind and Structural Health Monitoring System (WASHMS) that has been operating at TMB since the bridge’s commissioning in May 1997. The experimental observations in this project show that the results using FBG sensors were in excellent agreement with those acquired by WASHMS.
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