Lei Wang

Bio: Lei Wang is an academic researcher from Chinese Academy of Sciences. The author has contributed to research in topics: Precipitation & Medicine. The author has an hindex of 50, co-authored 429 publications receiving 9543 citations. Previous affiliations of Lei Wang include Taizhou University & Peking University.

Carbon dioxide exchange processes over the grassland ecosystems in semiarid areas of China

Abstract: Based on the carbon fluxes measured over the grassland ecosystems in Inner Mongolia (UG79 site), Loess Plateau (SACOL site), and Tongyu, Jilin Province (TY site) in the semiarid areas from 2007 to 2008 with the eddy covariance method, we have investigated the carbon exchange processes over semiarid grassland ecosystem and its main affecting environmental variables. The precipitations at UG79 and TY sites in 2007 were below the historical average, especially for TY site, which was 50% below the historical average annual precipitation. The precipitation in SACOL site was close to average in 2007 but below average in 2008. The variation of monthly diurnal average NEE showed that the diurnal mean NEE decreased in the order of TY site, UG79 site, and SACOL site. However, a longer net carbon uptake period was observed at SACOL site. The diurnal course of NEE at UG79 site was similar between 2007 and 2008. The diurnal average NEE remained large during July and August in growing season (May to September) at UG79 site, with maximum values approaching 0.08 mg C m−2 s−1 in August of 2008. The diurnal average NEE of 2007 was larger than 2008 at SACOL site, with maximum values of 0.07 mg C m−2 s−1 in September of 2007. A shorter carbon uptake period was recorded in 2007 at TY site, lasting from July to August. A larger diurnal average NEE occurred in 2008 at TY site, with maximum values of 0.12 mg C m−2 s−1. The ecosystem respirations of three sites were controlled by both soil temperature and soil volumetric water content (at a depth of 5 cm below the land surface). Both UG79 site and SACOL site acted as a carbon sink during the growing periods of 2007 and 2008. Annual NEE in the growing seasons of 2007 and 2008 ranged from −68 to −50 g C m−2 at UG79 site and from −109 to −55 g C m−2 at SACOL site. Alternation between carbon source and carbon sink was found at TY site, with respective values of annual NEE in the growing seasons of 0.32 g C m−2 and −73 g C m−2 in 2007 and 2008. The magnitude and duration of carbon uptake depended mainly on the amount and timing of precipitation and the timing of the first effective rainfall during the growing season in semiarid grassland ecosystems.

Response of low flows under climate warming in high‐altitude permafrost regions in western China

Abstract: The increase in low flows (winter discharge and minimum monthly discharge), caused primarily by permafrost degradation, is common in high‐latitude permafrost regions, whereas the dynamics of low flows in high‐altitude permafrost regions remain largely unknown. Long‐term discharge data from 28 unregulated catchments in western China were analysed, and the findings showed that winter discharge/minimum monthly discharge significantly increased (p ≤ 0.1) in 82/82%, 55/64%, and 0/0% of the catchments in the higher‐latitude mountain permafrost regions (Tienshan Mountains), mid‐latitude mountain permafrost regions (Qilian Mountains), and mid‐ to low‐latitude plateau permafrost regions (the source regions of the Yangtze and Yellow rivers), respectively. The differences in permafrost type and the distribution of permafrost and alpine cold desert (which is similar to tundra) were found to be the main causes for the different responses in the low flows. The rate of change of low flows (winter discharge and minimum monthly discharge) was negatively and linearly correlated with permafrost coverage when coverage was less than 40% of the catchment area, whereas the low flows changed only slightly when the permafrost coverage exceeded 40%. A significant thickening of the active layer increased the low flows in the lower permafrost‐covered catchments, which are dominated by warm permafrost. However, in the higher permafrost‐covered catchments with cold permafrost and a cold climate, only an increase in permafrost temperature (without a notable thickening of the active layer) occurred, resulting in non‐significant changes in low flows.

Structural stability of multiferroic BiFeO3

Abstract: Multiferroic BiFeO3 was fabricated via a high pressure of 5GPa at 900 degrees C. The crystal structure of the BiFeO3 ceramic was determined by X-ray diffraction (XRD) to be a rhombohedral perovskite with a space group of R3c. The temperature dependence of XRDs was collected down to 5K under ambient pressure that showed no structure phase transition. The structural evolution of BiFeO3 under high pressures up to 56.6GPa was studied at room temperature using a diamond anvil cell combined with synchrotron radiation XRD. A possible phase transition was proposed at around 10GPa. The bulk modulus was estimated to be B0=97.3(7)GPa in the low-pressure range.

A facile approach to synthesize in situ functionalized graphene oxide/epoxy resin nanocomposites: mechanical and thermal properties

Abstract: The complex preparation processes of GO/polymer composites are a limitation for their application. In this study, epoxy composites filled with in situ functionalized graphene oxide (GO) were prepared by a facile wet mixing and solvent evaporation method. The structure and composition of 3′,4′-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (2021P)-functionalized GO (GO-2021P) were characterized. With surface modification, GO became more thermally stable and changed its nature from hydrophilic to hydrophobic. The influences of surface functionalization on the morphology of GO, its dispersion in the epoxy matrix, the mechanical and thermal behavior of the composites were fully investigated. With grafting of 2021P, the dispersion/exfoliation status of GO and interfacial interaction between GO and epoxy matrix were much improved. For epoxy composite with 1.0 wt% GO-2021P, the tensile strength and Young’s modulus increased by 34.0% and 25.9%, respectively. Increased glass transition temperature and thermal stability were also observed by dynamic mechanical analysis and thermogravimetric analysis. High-performance functionalized GO/epoxy composites can be produced using this technique.

Climate Change 2007: The Physical Science Basis.

Abstract: Cause, conseguenze e strategie di mitigazione Proponiamo il primo di una serie di articoli in cui affronteremo l’attuale problema dei mutamenti climatici. Presentiamo il documento redatto, votato e pubblicato dall’Ipcc - Comitato intergovernativo sui cambiamenti climatici - che illustra la sintesi delle ricerche svolte su questo tema rilevante.

Numerical study of convection observed during the Winter Monsoon Experiment using a mesoscale two-dimensional model [presentation]

Abstract: Abstract A two-dimensional version of the Pennsylvania State University mesoscale model has been applied to Winter Monsoon Experiment data in order to simulate the diurnally occurring convection observed over the South China Sea. The domain includes a representation of part of Borneo as well as the sea so that the model can simulate the initiation of convection. Also included in the model are parameterizations of mesoscale ice phase and moisture processes and longwave and shortwave radiation with a diurnal cycle. This allows use of the model to test the relative importance of various heating mechanisms to the stratiform cloud deck, which typically occupies several hundred kilometers of the domain. Frank and Cohen's cumulus parameterization scheme is employed to represent vital unresolved vertical transports in the convective area. The major conclusions are: Ice phase processes are important in determining the level of maximum large-scale heating and vertical motion because there is a strong anvil componen...

Carbon quantum dots and their applications

Abstract: Fluorescent carbon nanoparticles or carbon quantum dots (CQDs) are a new class of carbon nanomaterials that have emerged recently and have garnered much interest as potential competitors to conventional semiconductor quantum dots. In addition to their comparable optical properties, CQDs have the desired advantages of low toxicity, environmental friendliness low cost and simple synthetic routes. Moreover, surface passivation and functionalization of CQDs allow for the control of their physicochemical properties. Since their discovery, CQDs have found many applications in the fields of chemical sensing, biosensing, bioimaging, nanomedicine, photocatalysis and electrocatalysis. This article reviews the progress in the research and development of CQDs with an emphasis on their synthesis, functionalization and technical applications along with some discussion on challenges and perspectives in this exciting and promising field.