Abstract
We present the second release of value-added catalogues of the LAMOST Spectroscopic Survey of the Galactic Anticentre (LSS-GAC DR2). The catalogues present values of radial velocity Vr, ...atmospheric parameters – effective temperature Teff, surface gravity log g, metallicity Fe/H, α-element to iron (metal) abundance ratio α/Fe (α/M), elemental abundances C/H and N/H and absolute magnitudes MV and $M_{K_{\rm s}}$ deduced from 1.8 million spectra of 1.4 million unique stars targeted by the LSS-GAC since 2011 September until 2014 June. The catalogues also give values of interstellar reddening, distance and orbital parameters determined with a variety of techniques, as well as proper motions and multiband photometry from the far-UV to the mid-IR collected from the literature and various surveys. Accuracies of radial velocities reach 5 km s−1 for the late-type stars, and those of distance estimates range between 10 and 30 per cent, depending on the spectral signal-to-noise ratios. Precisions of Fe/H, C/H and N/H estimates reach 0.1 dex, and those of α/Fe and α/M reach 0.05 dex. The large number of stars, the contiguous sky coverage, the simple yet non-trivial target selection function and the robust estimates of stellar radial velocities and atmospheric parameters, distances and elemental abundances make the catalogues a valuable data set to study the structure and evolution of the Galaxy, especially the solar-neighbourhood and the outer disc.
The measurement of the energy spectrum of cosmic ray helium nuclei from 70 GeV to 80 TeV using 4.5 years of data recorded by the Dark Matter Particle Explorer (DAMPE) is reported in this work. A ...hardening of the spectrum is observed at an energy of about 1.3 TeV, similar to previous observations. In addition, a spectral softening at about 34 TeV is revealed for the first time with large statistics and well controlled systematic uncertainties, with an overall significance of 4.3σ. The DAMPE spectral measurements of both cosmic protons and helium nuclei suggest a particle charge dependent softening energy, although with current uncertainties a dependence on the number of nucleons cannot be ruled out.
The effect of applied stress on the crevice corrosion of 304 stainless steel in 3.5 wt% solution is investigated. The delayed and immediate crevice corrosion of 304 stainless steel could occur under ...various applied stresses and different polarized potential. Both these two types of crevice corrosion are developed from the evolution of metastable pits. The lifetime of metastable pits is prolonged with the increased stress and the secondary metastable pit is observed under 400 MPa applied stress. This contributes to increased probability of metastable pits transiting to stable pits and then promotes crevice corrosion development with the increased stress.
•Crevice corrosion of 304 stainless steel is developed from metastable pits.•The concentration of defects in passive film increases with the increased stress.•The applied stress could drastically extend the lifetime of metastable pits.•Secondary metastable pit can be induced by applied plastic stress.•Array reference electrodes can monitor evolution of metastable pit inside crevice.
•Compressive strength of LWAC with Paraffin–LWA was higher than 15MPa.•Shrinkage strain with Paraffin–LWA reduced by 41.8%.•For outdoor testing, temperature at room center with Paraffin–LWA reduced ...by 2.9°C.•Recovery period with Paraffin–LWA was less than average life span of building.•A reduction of 465kgCO2-eq/year or 12.91kgCO2-eq/year/m2 was achieved.
Structural–functional integrated materials are one of directions of rapid development for saving-energy materials. Phase Change Materials (PCMs) are latent thermal storage materials possessing a large amount of heat energy stored during its phase change stage. Porous lightweight aggregate (LWA) can serve as the carrier for PCM. In this research, a structural concrete with function of indoor temperature control were prepared by using macro encapsulated PCM–LWA. The indoor and outdoor tests were performed to determine the thermal performance of the lightweight aggregate concrete (LWAC) containing macro encapsulated Paraffin–LWA. The compressive strength and shrinkage strain of LWAC with macro encapsulated PCM–LWA were evaluated. Finally, the economic and environmental aspects of application of macro encapsulated Paraffin–LWA in a typical floor area of public housing rental flat in Hong Kong were assessed.
From indoor thermal performance test, it was found that LWAC incorporated with macro encapsulated Paraffin–LWA has a function of reducing the energy consumption by decreasing the indoor temperature; flatten the fluctuation of indoor temperature and shifting the loads away from the peak periods. Moreover, from outdoor thermal performance test, it was found that the performance of macro encapsulated Paraffin–LWA in adjusting the room temperature was optimized when there was a remarkable temperature difference between the day and night. Test results showed that the compressive strengths of LWAC incorporating macro encapsulated Paraffin–LWA at 28days was higher than control LWAC (without macro encapsulated Paraffin–LWA) and was found to be over 15MPa. The shrinkage strain reduced with the incorporation of macro encapsulated Paraffin–LWA in LWAC and therefore has a beneficial effect on the volume stability of LWAC. From simple economic evaluation of macro encapsulated Paraffin–LWA in a typical floor area of public housing rental flat in Hong Kong, the recovery or payback period was found to be less than the average life span of a residential building in Hong Kong. Therefore, incorporation of macro encapsulated Paraffin–LWA in LWAC building walls is economically feasible. Finally, from environmental prospect, a reduction of 465kgCO2-eq/year or 12.91kgCO2-eq/year/m2 was achieved. This reduction would contribute to mitigate Greenhouse Gases emissions over the life span of building. It can therefore be concluded that the developed macro encapsulated PCM LWAC can be used for thermal and structural applications in buildings.
Understanding how flowering phenology responds to warming and cooling (i.e., symmetric or asymmetric response) is needed to predict the response of flowering phenology to future climate change that ...will happen with the occurrence of warm and cold years superimposed upon a long-term trend. A three-year reciprocal translocation experiment was performed along an elevation gradient from 3200 m to 3800 m in the Tibetan Plateau for six alpine plants. Transplanting to lower elevation (warming) advanced the first flowering date (FFD) and transplanting to higher elevation (cooling) had the opposite effect. The FFD of early spring flowering plants (ESF) was four times less sensitive to warming than to cooling (by −2.1 d/°C and 8.4 d/°C, respectively), while midsummer flowering plants (MSF) were about twice as sensitive to warming than to cooling (−8.0 d/°C and 4.9 d/°C, respectively). Compared with pooled warming and cooling data, warming alone significantly underpredicted 3.1 d/°C for ESF and overestimated 1.7 d/°C for MSF. These results suggest that future empirical and experimental studies should consider nonlinear temperature responses that can cause such warming-cooling asymmetries as well as differing life strategies (ESF vs. MSF) among plant species.
One of the most promising approaches to reach a high gain in inertial confinement fusion is the fast ignition scheme. In this scheme, a relativistic electron beam is generated; this passes through ...the imploded plasma and deposits parts of its energy in the core. However, the large angular spread of the relativistic electron beam and the poorly controlled compression of the target affect realization of the fast ignition technique. Here, we demonstrate that indirectly driven (that is, driven by X-rays generated inside a gold hohlraum) implosions with a ‘high-foot’ and a short-coast time of less than 200 ps allow us to tightly compress the shell. Furthermore, we show the ability to optimize the symmetry of the imploding shell by changing the hohlraum length, successfully tuning a suitable tube-shaped shell to compensate for the large angular spread of the relativistic electron beam and to enhance the electron-to-core coupling efficiency via resistive magnetic fields. Benefiting from those experimental techniques, a significant enhancement in neutron yield was achieved in our indirectly driven fast ignition experiments. These results pave the way towards high-coupling fast ignition experiments with indirectly driven targets similar to those at the National Ignition Facility.Experiments realizing the indirect-drive fast ignition scheme for inertial confinement fusion are reported. Enabled by a tightly compressed target, an increase of neutron yield is observed.
We present the first experimental evidence supported by simulations of kinetic effects launched in the interpenetration layer between the laser-driven hohlraum plasma bubbles and the corona plasma of ...the compressed pellet at the Shenguang-III prototype laser facility. Solid plastic capsules were coated with carbon-deuterium layers; as the implosion neutron yield is quenched, DD fusion yield from the corona plasma provides a direct measure of the kinetic effects inside the hohlraum. An anomalous large energy spread of the DD neutron signal (∼282 keV) and anomalous scaling of the neutron yield with the thickness of the carbon-deuterium layers cannot be explained by the hydrodynamic mechanisms. Instead, these results can be attributed to kinetic shocks that arise in the hohlraum-wall-ablator interpenetration region, which result in efficient acceleration of the deuterons (∼28.8 J, 0.45% of the total input laser energy). These studies provide novel insight into the interactions and dynamics of a vacuum hohlraum and near-vacuum hohlraum.
The precise measurement of the spectrum of protons, the most abundant component of the cosmic radiation, is necessary to understand the source and acceleration of cosmic rays in the Milky Way. This ...work reports the measurement of the cosmic ray proton fluxes with kinetic energies from 40 GeV to 100 TeV, with 2
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years of data recorded by the DArk Matter Particle Explorer (DAMPE). This is the first time that an experiment directly measures the cosmic ray protons up to ~100 TeV with high statistics. The measured spectrum confirms the spectral hardening at ~300 GeV found by previous experiments and reveals a softening at ~13.6 TeV, with the spectral index changing from ~2.60 to ~2.85. Our result suggests the existence of a new spectral feature of cosmic rays at energies lower than the so-called knee and sheds new light on the origin of Galactic cosmic rays.
Amino-functionalized graphene oxide (GO-NH2) was directly grafted onto carbon fiber surface by covalent bonding in an attempt to improve the mechanical properties of carbon fiber composites. The ...effect of surface modification on the properties of carbon fiber and the resulting carbon fiber composites was investigated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and interfacial shear strength (IFSS). As revealed by Fourier transform infrared spectroscopy (FT-IR), GO-NH2 was successfully grafted on the carbon fiber surface. From dynamic contact angle analysis (DCAT) and XPS values, such GO-NH2 grafted carbon fiber exhibited significant improvements in surface energy and functional groups of the carbon fiber surface, which lead to an increase of 36.4% in the IFSS of its composites. Such hierarchical reinforcement shows great potential for enhancing interfacial properties in carbon fiber-reinforced composites.
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•Amino-functionalized graphene oxide was grafted onto carbon fibers by covalent bonding.•The functionalized carbon fiber exhibited enhanced mechanical properties and interfacial adhesion.•The functional groups on the hierarchical reinforcement are tunable to meet different demands.
In this study, we systematically investigated the effect of the carbon content on the phase structure evolution and macro and nanomechanical properties of the equiatomic CoCrFeNi alloy. A series of ...CoCrFeNi-based high-entropy alloys with 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, and 0.9 wt% carbon were fabricated by vacuum arc melting. The results showed that the alloys retained their single face-center-cubic (FCC) structure with large grains at the carbon contents up to 0.2 wt%. However, in the case of the alloys with carbon contents higher than 0.3 wt%, the single phase structure transformed into the dendrite structure. The inter-dendrite regions of these alloys were eutectic carbides containing lath M7C3 carbides and the FCC phase. The tensile yield strength of the CoCrFeNi alloy increased from 295 to 512 MPa with the addition of 0.9 wt% carbon. The strengthening mechanisms of the alloys were investigated, including the solid solution strengthening due to the interstitial carbon atoms and the precipitation strengthening due to the M7C3 carbides. In addition, the nanoindentation results revealed that the M7C3 carbides showed a high nanohardness of ~17.7 GPa, which is almost four times of that of the FCC phase. We also investigated the elasto-plastic relationships, plastic properties and wear resistance of the FCC phase, while elucidating the eutectic carbide regions and M7C3 carbides. The eutectic carbide regions exhibited brittle fracture, whereas the FCC phase showed plastic fracture.