Geometry-based spherical JND modeling for 360∘^\circ display

360$^\circ$ videos have received widespread attention due to its realistic and immersive experiences for users. To date, how to accurately model the user perceptions on 360$^\circ$ display is still a challenging issue. In this paper, we exploit the visual characteristics of 360$^\circ$ projection and display and extend the popular just noticeable difference (JND) model to spherical JND (SJND). First, we propose a quantitative 2D-JND model by jointly considering spatial contrast sensitivity, luminance adaptation and texture masking effect. In particular, our model introduces an entropy-based region classification and utilizes different parameters for different types of regions for better modeling performance. Second, we extend our 2D-JND model to SJND by jointly exploiting latitude projection and field of view during 360$^\circ$ display. With this operation, SJND reflects both the characteristics of human vision system and the 360$^\circ$ display. Third, our SJND model is more consistent with user perceptions during subjective test and also shows more tolerance in distortions with fewer bit rates during 360$^\circ$ video compression. To further examine the effectiveness of our SJND model, we embed it in Versatile Video Coding (VVC) compression. Compared with the state-of-the-arts, our SJND-VVC framework significantly reduced the bit rate with negligible loss in visual quality

Investigation on the High-Temperature Oxidation Resistance of Ni-(3~10) Ta and Ni-(3~10) Y Alloys

Ni-(3~10) Ta and Ni-(3~10) Y alloys were fabricated by vacuum arc melting. The oxidation resistance of the alloys was studied by cyclic and isothermal oxidation tests at 800 °C in static air. The present work focused on the investigation of the effects of the alloying elements (Ta and Y) on the oxidation behavior of Ni-based alloys. The oxidation behavior of alloys was evaluated by mass gain, composition, as well as the microstructure of oxidized products. The experimental results indicated that Ta at a low content (3 wt %) had a positive role in enhancing oxidation resistance by decreasing the oxygen vacancy concentration of the oxide layer to prevent the inward diffusion of oxygen during oxidation, and the mass gain decreased from 2.9 mg·cm−2 to 1.7 mg·cm−2 (800 °C/200 h), while Y (3~10 wt %) degraded the oxidation resistance. However, it is worth mentioning that the pinning effect of Y2O3 increased the adhesion between the substrate and oxide layer by changing the growing patterns of the oxide layer from a plane growth to fibrous growth. Among the results, the bonding of the substrate and oxide layer was best in the Ni-3Y alloys

Photosynthetic and hydraulic changes caused by water deficit and flooding stress increase rice’s intrinsic water-use efficiency

Effects of water deficit and flooding stress on rice’s intrinsic water-use efficiency (iWUE) and how iWUE variations are linked to stress-induced physiological changes are poorly understood. Here, we proposed a model-based approach to analyze iWUE across datasets and its relationship with physiological changes, using only leaf gas exchange data and plant hydraulic vulnerability parameters. We applied this approach to a leaf gas exchange dataset of rice, measured during the post-stress period of water deficit and flooding experiments. Results show that water deficit and flooding stress decreased rice’s photosynthetic capacity (Vcmax25) and water transport capacity (Kmax) during the post-stress period, and that these physiological changes altered the relationship between photosynthetic rate and stomatal conductance, leading to an increase in iWUE. Nevertheless, improved iWUE cannot avoid the yield reduction. Interestingly, the stress-induced decrease in Vcmax25 was significantly correlated with the decline in Kmax. The Vcmax25-Kmax relationship was significantly different between the water deficit and flooding treatments, with the slope of the latter being closer to 1:1. Model predicts that stress-induced disproportionate Vcmax25-Kmax co-reduction improved iWUE while maintaining a relatively high intercellular to atmosphere CO2 concentration ratio; this may represent optimal coordination between photosynthetic and hydraulic traits in response to stress. Our work has important implications for using leaf gas exchange data to diagnose variations in iWUE, and for improving our understanding of crop physiological responses to environmental stresses

Improvement on water tree resistance and electrical properties of XLPE by adopting triallyl isocyanurate

The effect of TAIC (triallyl isocyanurate) on water tree resistance and electrical properties of XLPE (peroxide crosslinked polyethylene) was investigated in this paper. XLPE specimens with different content of TAIC were prepared for hot pressing method. Water blade method results showed that water tree ageing resistance of XLPE was improved obviously by adopting TAIC. The diameters of microvoids in specimens generated by water droplets would be reduced from micron scale to submicron scale due to the existence of TAIC. Contact angle test and Monte Carlo molecular simulation results revealed that water droplets would be disintegrated due to the presence of TAIC. Moreover, the addition of TAIC can also slightly improve the electrical properties of XLPE. The first-principles calculations revealed that an electron-bound state was generated in the band gap of XLPE for bonding with TAIC and formed a deep trap with 2.3eV. It can be concluded that low mixing energy of TAIC and water is an important reason for improving the water tree resistance of XLPE, and its improvement on electrical properties is attributed to the introduction of deep trap

Interactive Effects of Drought–Flood Abrupt Alternation on Morpho-Agronomic and Nutrient Use Traits in Rice

The frequent occurrence of drought–flood abrupt alternation (DFAA) in Huaibei Plain has shown a great impact on local rice production. Pot experiments were performed in 2016–2018 to investigate the effects of co-occurring drought and flooding stresses on dry weight (DW), grain yield, nitrogen (N), phosphorus (P) and potassium (K) uptake and use efficiencies (NUE, PUE and KUE) in rice. The results showed that DFAA changed the accumulation of biomass and nutrients among different organs in rice. Compared with control, DFAA significantly reduced the grain yield (−29.8%) and root DW (−30.0%), but increased the DW in stem and leaf (10.2% and 9.7%). The root/shoot ratio and morphological size of the root system in DFAA-treated plants was smaller than those of drought alone and flooding alone. Under DFAA stresses, the specific absorption rate of N, P and K increased significantly (47.9%, 31.8% and 32.8%, respectively), while NUE, PUE and KUE decreased significantly (−27.9%, −10.8% and −19.7%, respectively). The decrease of nutrient use efficiencies was mainly due to the redundant growth of branches and leaves, and the key factor limiting grain yield under DFAA conditions was the effective utilization of N. Compared with the earlier drought, the subsequent flooding might have more influence on rice growth, nutrient utilization and yield formation, but the interaction of the two weakened the cumulative effect of drought and flooding. These findings provide a scientific basis for establishing a nutrient and water management system of rice cultivation under transient soil moisture conditions

Large-Scale Synthesis of Silver Nanoparticles by Aqueous Reduction for Low-Temperature Sintering Bonding

Silver nanoparticles with average diameter of 22.4 nm were prepared by aqueous reduction method for low-temperature sintering bonding application. The reaction temperature and PVP concentration, which are the influential factors of nanoparticle characteristics, were investigated during reduction process. In our research, monodispersity of nanoparticles was remarkably improved while unfavorable agglomeration was avoided with the AgNO3/PVP mass ratio of 1 : 4 at the reaction temperature 30°C. Besides, copper pads were successfully bonded using sintering paste employing fresh silver nanoparticles with diameter of 20~35 nm at 200°C. In addition, after morphology of the bonding joint was analysed by scanning electron microscope (SEM), the porous sintering characteristics were confirmed

Inelastic Neutron Scattering Studies on the Crystal Field Excitations in Superconducting NdFeAsO0.85F0.15

Inelastic neutron scattering experiments were performed on polycrystalline samples of NdFeAsO0.85F0.15 over a wide temperature range (3 K–250 K). Based on the analysis of the experimental data, a Nd3+ CF energy level scheme is proposed to give a consistent explanation about the observed CF transitions. The observed extra ground-state CF transitions could not be simply explained by the transitions between five Kramers doublets split from the Nd3+   4I9/2 ground state in the C4v point symmetry. A reliable explanation would be a superposition of crystal fields due to different local symmetries around the Nd3+ ions induced by the fluorine doping