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For an extrusion process of 7075 Al alloy, the extrusion direction of the initial blank is changed to study the mechanical properties of the formed plates and characterize their microstructure. The as-received bar is extruded 7075 Al alloy. The secondary extrusion deformation is along and perpendicular to the initial extrusion direction. The results show that the anisotropy of mechanical properties of the two samples decreases obviously after secondary deformation. The anisotropy of yield strength and ultimate tensile strength of ED90 sample is lower than that of ED0 sample, but the plastic anisotropy is slightly higher than that of ED0 sample. In addition, the recrystallized grain proportion of ED90 sample is high and the texture strength is low, so the Schmid factor in the three directions is similar. The tensile fracture mode of the two samples belongs to ductile fracture, but the morphology of dimple and the size of cleavage plane are slightly different.

This paper proposed the double-pass compression thermal/force simulation experiment to in situ analyze the phase transformation of continuous casting billet during the controlled rolling and controlled cooling process. The genetic relationship between the central segregation of the billet and solute element distribution of the steel plate, and also the genetic relationship of microstructure and mechanical properties between them were experimentally studied. The results show that the microstructure and mechanical properties between the billet and corresponding batch of steel plate have the genetic relationship, and the link of the relationship is central segregation. The phase transformation of supercooling austenite will be affected by the central segregation of Mn and C elements, and the granular bainite abnormal segregation band is the transformation product of Mn and C element segregation region.

A hollow billet Expanding-Reducing Extrusion (ERE) wheel hub forming process was carried out with AZ80 magnesium alloy. The effects of ageing on Low-cycle fatigue (LCF) properties were investigated, and the microstructure was characterized with scanning electronic microscopy (SEM). The LCF testing results exhibited that the stress amplitude increased with increasing ageing time, while the plastic strain decreased with increasing ageing time. Cyclic softening followed by hardening was observed for 0 h and 16 h aged samples; however, there was no obvious cyclic softening or hardening for 36 h aged sample. The tension-compression asymmetry were not obvious due to the low strain, precipitation and the non typical basal texture. Fracture observations indicated that the fatigue cracks were initiated on the surface, and the crack propagation area decreased with increasing ageing time. Thus, it can be concluded that ageing has strong effects on the fatigue life for the studied magnesium alloy.

We explore the properties of photospheric emission in the context of long gamma-ray bursts (GRBs) using three numerical models that combine relativistic hydrodynamical simulations and Monte Carlo radiation transfer calculations in three dimensions. Our simulations confirm that photospheric emission gives rise to correlations between the spectral peak energy and luminosity that agree with the observed Yonetoku, Amati, and Golenetskii correlations. It is also shown that the spectral peak energy and luminosity correlate with the bulk Lorentz factor, as indicated in the literature. On the other hand, synthetic spectral shapes tend to be narrower than those of the observations. This result indicates that an additional physical process that can provide nonthermal broadening is needed to reproduce the spectral features. Furthermore, the polarization analysis finds that, while the degree of polarization is low for the emission from the jet core (Π < 4%), it tends to increase with viewing angle outside of the core and can be as high as Π ∼ 20%–40% in an extreme case. This suggests that the typical GRBs show systematically low polarization compared to softer, dimmer counterparts (X-ray-rich GRBs and X-ray flashes). Interestingly, our simulations indicate that photospheric emission exhibits large temporal variation in the polarization position angle (Δ ψ ∼ 90°), which may be compatible with those inferred in observations. A notable energy dependence of the polarization property is another characteristic feature found in the current study. Particularly, the difference in the position angle among different energy bands can be as large as ∼90°.

Flight altitude is relevant to the climate effects resulting from aircraft emissions. Other research has shown that flying higher within the troposphere leads to larger warming from O _3 production. Aircraft NO _x emissions are of particular interest, as they lead to warming via the short-term production of O _3 , but also to reduced warming via processes like CH _4 depletion. We focus on short-term O _3 production, as it constitutes one of aviation’s largest warming components. Understanding how O _3 formation varies altitudinally throughout the upper troposphere/lower stratosphere is essential for designing climate-compatible aircraft and routing. We quantify this variation by performing simulations with a global atmospheric chemistry model for three representative cruise altitudes, five regions and two seasons using three methods: Eulerian tagging, perturbation and Lagrangian tagging. This multi-method, regional approach overcomes limitations of previous studies that utilize only one of these methods and apply global emission inventories biased towards present-day flight distributions, thus limiting their applicability to future aviation scenarios. Our results highlight that underrepresenting emissions in areas with growing flight activity (e.g. Asia Pacific) may lead to significant, regional underestimations of the altitudinal sensitivity of short-term NO _x -related O _3 warming effects in certain cases. We find that emitting in Southern regions, like Australasia, leads to warming larger by a factor of two when compared to global averages. Our findings also suggest that flying lower translates to lower warming from short-term O _3 production and that this effect is strongest during the local summer. We estimate differences ranging from a factor of 1.2–2.6 between tagging and perturbation results that are attributable to non-linearities of NO _x -O _3 chemistry, and derived regional correction factors for a widely-used sub-model. Overall, we stress that a combination of all three methods is necessary for a robust assessment of aviation climate effects as they address fundamentally different questions.

Hierarchically mesoporous silica materials with a bimodal distribution were template-preparedfrom uniaxially stretched polypropylene membrane in the presence of a surfactant via asol–gel process. Their regularity and morphologies were characterized by transmissionelectron microscopy (TEM), x-ray diffraction and Brunauer–Emmett–Teller(BET) surfacearea analysis. The larger channel pores formed by removing the microfibrils of uniaxiallystretched polypropylene membrane have a broad pore size distribution, and their size isaround 13nm. In contrast, the smaller mesopores formed by surfactant templates have anarrow distribution; their size is about 3.9nm. The size of the smaller pores could be tunedfrom 2 to 6nm by selecting different surfactants and by changing the concentration ofreactants. [ABSTRACT FROM AUTHOR]

A simple and green method for fabrication of nano silver conductive ink was developed for use in frequency selective surface (FSS). The hydrogen peroxide and ethyl cellulose were used as reducing agents and dispersants to synthesize silver nanoparticles (Ag NPs), and the ethyl cellulose was be used as binders of nano silver conductive ink eventually. The reaction byproducts of hydrogen peroxide are water and oxygen, the synthesized Ag NPs were be cleaned using purified water and alcohol without centrifugation and drying process. The conductive ink with 30 wt% silver content was formulated with the Ag NPs capped with ethyl cellulose, solvent and additive, the residual water and alcohol were be evaporated using vacuum distillation process. The prepared Ag NPs were characterized by SEM, XRD, TGA and FT-IR. The viscosity and surface tension of Ag NPs ink were tested, and the conductive ink was inkjet printed on Polyimide (PI) film to fabricate the FSS. The results showed the printed FSS had reflection resonances at 16.5 GHz and nulls deeper than the required −20 dB level, with depths of −32 dB. [ABSTRACT FROM AUTHOR]

Printed-electronics inks belong to a class of novel functional conductive inks that can be used to form high-precision conducting lines or circuits on various flexible substrates. Previous studies have reported conductive inks produced by the reduction and membrane separation method for use in flexible devices. However, it remains a challenge to synthesize conductive inks with high electrical properties at low sintering temperatures, which restricts their range of applications. Herein, we prepare inkjet-printed patterns of conductive inks consisting of Ag nanohexagonal platelets (AgNHPs) as the main component and containing graphene (GE) in different contents. It is found that GE improves the electrical conductivity of the patterns when sintering is done at relatively low temperatures. For instance, when the GE content is 0.15 mg ml−1, the resistivity is the lowest. When sintering is done at 150 °C, the resistivity (2.7 × 10–6 Ω · cm) of the GE-AgNHPs conductive ink (GE: 0.15 mg ml−1) is 14% of that of the AgNHPs conductive ink; on the other hand, after sintering at 50 °C, this ratio is 2%. It is also found that, with the increase in GE content, the resistivity of the GE-AgNHPs conductive ink increases. This study on GE-AgNHPs conductive inks sintered at low temperatures should further the development of flexible touch screens. [ABSTRACT FROM AUTHOR]

TiO2/Ag/TiO2 (TAT) multilayer transparent conducting electrodes were deposited onto glass substrates by room temperature sputtering. The impact of Ag sputtering current on the film morphology, and the optical and electrical properties were discussed. The increase in the sputtering current led to a more continuous Ag middle layer. As the Ag middle layer became continuous, the TAT electrodes had lower sheet resistance and higher transmittance. In addition, an optimized TAT electrode with a figure of merit of was obtained at an Ag thickness of 16 nm and a sputtering current of 0.48 A. Finally, organic photodetectors were also fabricated based on TAT electrodes and the performance is comparable to reference devices with commercially purchased Sn-doped In2O3 (ITO) electrodes. [ABSTRACT FROM AUTHOR]

The measurements of the potential distributions in the boundary layer near meshes with different mesh spacing were conducted in weakly collisional plasmas using a fine-structured emissive probe and the results of the sheath thickness and electric field at the sheath-presheath edge were compared with theoretical models of collisional presheath and collisionless sheath. It was shown that, because the meshes are partially transparent to ions, the sheath is thinner and the electric field is stronger for the mesh of higher transmissivity, owing to the increased ion density in the sheath contributed from the ions transmitted from the other side of the mesh. However, the potential profiles in the presheath remain almost the same for different meshes except for the shift of the sheath-presheath edge. The thickness of the sheath decreases while the electric field at the edge increases with the increase of the neutral gas pressure. Furthermore, depending on the pressure, the measured electric fields at the edge are close to that from the models of a transition region. [ABSTRACT FROM AUTHOR]

We have designed and constructed a hybrid scanning near-field optical microscope (SNOM)-scanning tunnelling microscope (STM) instrument which operates under ultrahigh vacuum (UHV) conditions. Indium tin oxide (ITO)-coated fibre-optic tips capable of high quality STM imaging and tunnelling spectroscopy are fabricated using a simple and reliable method which foregoes the electroless plating strategy previously employed by other groups. The fabrication process is reproducible, producing robust tips which may be exchanged under UHV conditions. We show that controlled contact with metal surfaces considerably enhances the STM imaging capabilities of fibre-optic tips. Light collection (from the cleaved back face of the ITO-coated fibre-optic tip) and optical alignment are facilitated by a simple two-lens arrangement where the in-vacuum collimation/collection lens may be adjusted using a slip-stick motor. A second in-air lens focuses the light (which emerges from the UHV system as a parallel beam) onto a cooled CCD spectrograph or photomultiplier tube. The application of the instrument to combined optical and electronic spectroscopy of Au and GaAs surfaces is discussed. [ABSTRACT FROM AUTHOR]