Two Ultraviolet Radiation Datasets that Cover China

Ultraviolet（UV） radiation has significant effects on ecosystems, environments, and human health, as well as atmospheric processes and climate change. Two ultraviolet radiation datasets are described in this paper. One contains hourly observations of UV radiation measured at 40 Chinese Ecosystem Research Network stations from 2005 to 2015. CUV3 broadband radiometers were used to observe the UV radiation, with an accuracy of 5%, which meets the World Meteorology Organization＇s measurement standards. The extremum method was used to control the quality of the measured datasets. The other dataset contains daily cumulative UV radiation estimates that were calculated using an all-sky estimation model combined with a hybrid model. The reconstructed daily UV radiation data span from 1961 to 2014. The mean absolute bias error and root-mean-square error are smaller than 30% at most stations, and most of the mean bias error values are negative, which indicates underestimation of the UV radiation intensity. These datasets can improve our basic knowledge of the spatial and temporal variations in UV radiation. Additionally, these datasets can be used in studies of potential ozone formation and atmospheric oxidation, as well as simulations of ecological processes.

Ecological role of physical dormancy in seeds of Oxytropis racemosa in a semiarid sandland with unpredictable rainfall

Aims Seed dormancy and the soil seed bank are crucial to plant regeneration strategy,especially in semiarid ecosystems with unpredictable precipi-tation.the aim of this study was to investigate how seed dormancy is controlled by environmental factors and how it is correlated with the soil seed bank and regeneration of the perennial legume Oxytropis race-mosa,a dominant perennial herb in Mu Us Sandland of semiarid China.Methods Germination and imbibition experiments on fresh intact and scarified seeds of O.racemosa were used to identify physical dormancy(PY)in seeds of this species.Soil seed bank dynamics,timing of seedling emer-gence and the fate of buried seeds in the natural habitat were investigated.Important Findings PY was broken by mechanical scarification or wet heat/ice water cycles but not solely by dry heat or wet heat treatment.the soil seed bank exhibited seasonal changes in the number of seeds,which was highest in September and lowest in July.Seeds buried at different sand depths gradually lost dormancy;20-42%of the seeds remained dormant after 20 months of burial.Dormancy break occurs grad-ually throughout the year.Our results indicate that O.racemosa exhibits hardcoatedness heterogeneity that spreads germination of a seed cohort between seasons and years in the semiarid environ-ment,where the amount of precipitation during the growing season is highly variable.

Ti2AlC triggered in-situ ultrafine TiC/Inconel 718 composites:Microstructure and enhanced properties

In situ ultrafine TiC dispersion reinforced Inconel 718 alloy with enhanced mechanical properties was fabricated by the technique of reactive hot-press sintering Ti2AlC and In718 powders.The effect of Ti2AlC precursor additions(5 vol.%,10 vol.%,15 vol.%)on microstructure and mechanical properties of TiC/In718 composites were investigated.A relationship of microstructural characteristics,room and elevated temperature mechanical performance,and underlying strengthening mechanisms were analyzed.The results show that initial Ti2AlC precursor transformed completely into ultrafine TiC particulate(~230 nm)and distributed uniformly in the matrix after sintering 5 and 10 vol.%Ti2AlC/In718.However,TiC particulates tended to aggregate to stripes with the addition of Ti2AlC up to 15 vol.%,which,in adverse,weaken the properties of In718.The 5 vol.%Ti2AlC/In718 sample showed a higher tensile strength of 1404±13 MPa with a noticeable elongation of 9.8%at room temperature compared to the pure In718(ultimate tensile strength(UTS)=1310 MPa,elongation=21.5%).At 600℃,700℃,800℃and 900℃,tensile strength of the as-sintered 5 vol.%Ti2AlC/In718 composite was determined to be 1333±13 MPa,1010±10 MPa,685±25 MPa and 276±3 MPa,increased by 9.2%,14.6%,14.2%and 55%,respectively,compared with that of monolithic In718 alloy.The excellent tensile properties of TiC/In718 composite can be ascribed to the combined mechanisms in term of increased dislocation density,dispersive Orowan and load transfer mechanisms.