The creep behavior of HR3C austenitic steels was investigated at 650°C and over the stress range from 150 to 250MPa for up to 13,730h. The corresponding microstructure evolution was characterized by ...optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In the initial stage of the creep process, the creep-resistance of HR3C steel is enhanced by the precipitation of second-phases particles in the grain and at the grain boundary. Compared with the precipitates inside the grain, the higher nucleation and growth rate of precipitates at the grain boundary is related to the higher interfacial energy and diffusion rate of atoms. The high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) results show that the precipitates inside the grain may initially nucleate at dislocation pile-up sites, and the interface coherency between the precipitate and the matrix can be destroyed after a long-term creep process. The TEM morphology indicates that the agglomerated tiny particles interact with the dislocations, contributing mostly to the precipitation strengthening inside the grain during the long-term creep process at 650°C, while the growth of chain-like M23C6 precipitates at the grain boundary increases the tendency of intergranular cracking as the creep time increased.
Lead (Pb) and cadmium (Cd) are toxic heavy metals commonly found in aqueous environments. Biochar as a green adsorbent generated from biomass feedstock may be used for effective removal of these ...heavy metals. This study investigated the adsorption kinetics and isotherms of Pb
and Cd
in aqueous solutions at different pH by biochar prepared from banana stem and leaf (BSL-BC) at 400 °C. Characterizations using scanning electron microscope, X-ray diffraction, and Fourier-transform infrared spectroscopy showed that the synthesized BSL-BC had rough surface, porous structure, and oxygen-containing functional groups. The adsorption of Pb
and Cd
onto BSL-BC reached equilibrium in 8 h and 200 min, respectively, with faster adsorption attained at higher pH and the optimum pH occurred at 5 (Pb
) and 8 (Cd
). All adsorption kinetic data followed the pseudo-second-order rate model. The adsorption isotherm data of Pb
and Cd
could be well-described by the Langmuir and Freundlich models, respectively, whereas neither the Temkin or Dubinin-Radushkevich models provided satisfactory fitting results. The maximum adsorption capacities for Pb
and Cd
were 302.20 and 32.03 mg/g, respectively. The calculated mechanism contributions showed that complexation with oxygen-containing functional groups, ion exchange, mineral precipitation, and Pb
/Cd
-π coordination accounted for 0.1%, 8.4%, 88.8%, and 2.6% to Pb
adsorption, and 0.4%, 6.3%, 83.0%, and 10.4% to Cd
adsorption, respectively. Therefore, mineral precipitation was likely the major mechanism responsible for adsorption of both Pb
and Cd
by BSL-BC. The results suggest that the synthesized BSL-BC has great potential for adsorption of Pb
and Cd
from aqueous solutions.
Background
People living with HIV (PLWH) and receiving antiretroviral therapy (ART) have a goal of achieving and maintaining viral suppression; however, the existence of PLWH that show events of ...low‐level viremia (LLV) between 50 and 1000 copies/mL and with different virological consequences have been observed. Moreover, some reports indicate that LLV status can lead to residual immune activation and inflammation, leading to a higher occurrence of non‐AIDS‐defining events (nADEs) and other adverse clinical outcomes. Until now, however, published data have shown controversial results that hinder understanding of this phenomenon's actual cause(s) and origin(s). Integrase strand transfer inhibitors (INSTIs)‐based therapies could lead to lower LLV over time and, therefore, more effective virological control.
Objectives
This review aims to assess recent findings to provide a view of the clinical significance and management of low‐level HIV viremia in the era of INSTIs.
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•Se stimulated the activities of SOD and CAT of rice tissues under Cd stress.•Se reduced the levels of O2·− and H2O2 and enhanced the secretion of rhizosphere O2.•Se enhanced the ...formation of iron plaque on root surface and its barrier to Cd.•Se reduced the total Cd absorption in rice only with the generation of iron plaque.
The inhibition of cadmium (Cd) absorption by selenium (Se) in rice may be associated with iron plaque (IP) formation, but the driving mechanisms are still unclear. This study investigated the effects of Se on the growth, oxidative toxicity, radial oxygen loss (ROL), IP formation, and Cd absorption of rice exposed to Cd. The results of this study showed that Cd stress elevated the levels of O2– and H2O2 and depressed superoxide dismutase (SOD) and catalase (CAT) activities. The maximum ROL and IP were reduced by 43.3 % and 74.5 %, respectively. However, Se alleviated Cd toxicity by stimulating SOD and CAT activities by scavenging O2– and H2O2 and enhancing the ROL profiles. Under culture conditions without Fe2+, Se had no impact on the total Cd levels in rice (TCd). However, with the addition of Fe2+, TCd was significantly reduced by 23.3 % due to the enhancement of IP formation by Se. These results indicated that Se can reduce Cd accumulation in rice in the presence of Fe2+ treatments. However, Se just alleviated Cd toxicity in the absence of Fe2+ treatments. The enhancement of ROL was a potential reason for the elevated IP formation induced by Se.
•Oblique detonation induced by two wedges are simulated .•The oblique detonations are easy to be initiated during interactions of ODWs.•Shock polar analysis with real gas effect is used in this ...paper.
An understanding of oblique detonation waves (ODWs) has inherent research value for high-speed compressible reacting flow and hypersonic propulsion. In this paper, the interactions between two ODWs induced by two symmetrical finite wedges in hydrogen-air mixtures are investigated numerically by solving the reactive Euler equations and considering a detailed chemical model. Interferences between abrupt transition patterns are analyzed. The flowfield involves complex phenomena, such as interactions among shock waves, combustion waves, ODWs, and slip lines. The effects of the expansion waves and the distance between the two wedges on the flowfield characteristics are investigated, including the wave structures, initiation characteristics, as well as the temperature and density distributions. The numerical results demonstrate that the induction zone is shorter in the double-wedge configuration than the single-wedge configuration, and oblique detonations are more likely to occur during interactions. Shock polar analysis and numerical simulations show that the ODW interactions result in a Mach interaction, which is a regular interaction between the oblique shock waves (OSWs).
Heavy metal stress in crops is a worldwide problem that requires accurate and timely monitoring. This study aimed to improve the accuracy of monitoring heavy metal stress levels in rice by using ...multiple Sentinel-2 images. The selected study areas are in Zhuzhou City, Hunan Province, China. Six Sentinel-2 images were acquired in 2017, and heavy metal concentrations in soil were measured. A novel vegetation index called heavy metal stress sensitive index (HMSSI) was proposed. HMSSI is the ratio between two red-edge spectral indices, namely the red-edge chlorophyll index (
) and the plant senescence reflectance index (PSRI). To demonstrate the capability of HMSSI, the performances of
and PSRI in discriminating heavy metal stress levels were compared with that of HMSSI at different growth stages. Random forest (RF) was used to establish a multitemporal monitoring model to detect heavy metal stress levels in rice based on HMSSI at different growth stages. Results show that HMSSI is more sensitive to heavy metal stress than
and PSRI at different growth stages. The performance of a multitemporal monitoring model combining the whole growth stage images was better than any other single growth stage in distinguishing heavy metal stress levels. Therefore, HMSSI can be regarded as an indicator for monitoring heavy metal stress levels with a multitemporal monitoring model.
Abstract
A solenoid magnetic field plays an important role in a non-line-of-sight azimuth transmission system based on polarization-maintaining fiber, which is directly related to the transmission ...accuracy of azimuth information. This research mainly studies the factors that affect the solenoid magnetic field according to the modulation signal from the direct current to the alternating current, as well as the hollow solenoid. First, the magnetic field components of the static solenoid are derived from the Biot–Savart law by using the uniform cylindrical current equivalent model. Then, the magnetic field of the near axial region is studied from the axial and radial directions, and the feasibility of calculating the magnetic field of the multi-layer solenoid with the superposition principle is verified by measuring the magnetic field of each position on the axis of the solenoid with a Gauss meter. Finally, the alternating electromagnetic field model is established using Maxwell’s equations, and the magnetic and electric fields of the hollow solenoid are further solved. The results show that the magnetic field in the middle part of the magneto-optic glass is more stable, and the magnetic collecting ability of the solenoid is stronger. The magnetic field intensity at the center of the magneto-optic modulation solenoid of the system is the largest, and it decreases with the distance from the center. The alternating electromagnetic field is closely related to frequency. The results provide a reference for the study of the azimuth accuracy of a non-line-of-sight azimuth transmission system.
This study developed a climatic-economic-technological integrated assessment model named CIECIA-TD-F. Based on model, the implementation effects of low carbon technology financing on climate ...mitigation, technology promotion, and economic development in the context of climate change cooperation were studied. The results indicate that carbon reduction, under the current pledged climate financing scale, is limited. Global surface warming in 2100 is still around 2.38 °C even when the technologies are globally shared. Low carbon technology financing improves technology R&D and absorptive capacities of the least developed countries. Their carbon reduction rates reach 50 percent under the capacity principle. However, donations impair the R&D inputs of developed countries and delay their advanced technological progress, leading to 1 percent more carbon emissions. This limits the imitations of China and Russia in turn by decreasing their imitation numbers by 1–2 percent. Collecting 800 billion USD per year from 2030 to 2100 is a climatically effective means. It holds global warming to 1.99 °C. However, the donors suffer more than 1 percent of economic losses. That indicates the economic feasibility of this means is weak. On this basis, we proposed a Pareto-improvement scheme which combines financing with technology sharing and national R&D improvements. This policy mix both achieves the 2 °C goal and protect the economic benefits of all countries. Thus, policy mix combining different measures will be more suitable for improving reduction effects and achieving multiple goals. Compared with sole technology financing, it has more significant global carbon governance meanings and is noteworthy in future climate negotiations.
•Nine combinations of typical collection and dispensation principles were assessed.•The current scale of climate financing pledge was insufficient.•2 °C goal can be achieved by improving financing scale dramatically in short term.•Advanced technology innovation was delayed for the economic losses of the funding donors.•A Pareto improving scheme was proposed.
Green product development depends on the green innovation behavior of upstream and downstream companies in the supply chain. This paper focuses on a green supply chain consisting of a supplier and a ...manufacturer and considers two financing schemes wherein the manufacturer’s operating capital and green innovation capital are both constrained: bank credit financing (BCF) and supplier green investment (SGI). We investigate the financing strategy of a manufacturer with different financing decision preferences and supply chain coordination contract designs. The results show that when the manufacturer’s financing decision preference is low bankruptcy risk, it should choose BCF when the bank loan interest rate is lower than a threshold and SGI when the bank loan interest rate is higher than this threshold; when the manufacturer’s financing decision preference is high R&D benefit, it should choose BCF when the initial capital is lower than another threshold and choose SGI when the initial capital is higher than this threshold. Then, we compare whether cost-sharing, quantity discount and revenue-sharing contracts can coordinate the supply chain, and discuss the selection strategies of supply chain members for coordination contracts. Research shows that revenue-sharing contracts fail to coordinate; however, when the cost-sharing ratio and quantity discount rate are appropriate, both cost-sharing and quantity discount contracts can achieve supply chain coordination. The lower the supplier’s unit production cost, the stronger its motivation to accept a higher cost-sharing ratio and quantity discount rate. For the supplier, the key to choosing any coordination contract lies in the relative height of the cost-sharing ratio and quantity discount rate while the manufacturer should always choose a quantity discount contract when the quantity discount rate is high enough.
Current studies have shown that the spatial‐temporal graph convolutional network (ST‐GCN) is effective for skeleton‐based action recognition. However, for the existing ST‐GCN‐based methods, their ...temporal kernel size is usually fixed over all layers, which makes them cannot fully exploit the temporal dependency between discontinuous frames and different sequence lengths. Besides, most of these methods use average pooling to obtain global graph feature from vertex features, resulting in losing much fine‐grained information for action classification. To address these issues, in this work, the authors propose a novel spatial attentive and temporal dilated graph convolutional network (SATD‐GCN). It contains two important components, that is, a spatial attention pooling module (SAP) and a temporal dilated graph convolution module (TDGC). Specifically, the SAP module can select the human body joints which are beneficial for action recognition by a self‐attention mechanism and alleviates the influence of data redundancy and noise. The TDGC module can effectively extract the temporal features at different time scales, which is useful to improve the temporal perception field and enhance the robustness of the model to different motion speed and sequence length. Importantly, both the SAP module and the TDGC module can be easily integrated into the ST‐GCN‐based models, and significantly improve their performance. Extensive experiments on two large‐scale benchmark datasets, that is, NTU‐RGB + D and Kinetics‐Skeleton, demonstrate that the authors’ method achieves the state‐of‐the‐art performance for skeleton‐based action recognition.
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