7,427 research outputs found
Increased Water Storage in the Qaidam Basin, the North Tibet Plateau from GRACE Gravity Data
published_or_final_versio
More severe hydrological drought events emerge at different warming levels over the Wudinghe watershed in northern China
Assessment of changes in hydrological droughts at specific warming levels is
important for an adaptive water resources management with consideration of
the 2015Ā Paris Agreement. However, most studies focused on the response of
drought frequency to the warming and neglected other drought characteristics,
including severity. By using a semiarid watershed in northern China (i.e.,
Wudinghe) as an example, here we show less frequent but more severe
hydrological drought events emerge atĀ 1.5, 2Ā and 3 āC warming levels.
We used meteorological forcings from eight Coupled Model Intercomparison
Project PhaseĀ 5 climate models under four representative concentration
pathways, to drive a newly developed land surface hydrological model to
simulate streamflow, and analyzed historical and future hydrological drought
characteristics based on the standardized streamflow index. The Wudinghe
watershed will reach the 1.5, 2 and 3 āC warming levels around
2015ā2034, 2032ā2051 and 2060ā2079, with an increase in precipitation of
8 %, 9 % and 18 % and runoff of 27 %, 19 % and 44 %, and a drop
in hydrological drought frequency of 11 %, 26 % and 23 % as compared to the
baseline periodĀ (1986ā2005). However, the drought severity will rise
dramatically by 184 %, 116 % and 184 %, which is mainly caused by the
increased variability in precipitation and evapotranspiration. The climate
models and the land surface hydrological model contribute to more than 80 %
of total uncertainties in the future projection of precipitation and
hydrological droughts. This study suggests that different aspects of
hydrological droughts should be carefully investigated when assessing the
impact ofĀ 1.5, 2Ā and 3 āC global warming.</p
Group Sparse Recovery via the ā0(ā2) Penalty: Theory and Algorithm
In this work we propose and analyze a novel approach for recovering group sparse signals, which arise naturally in a number of practical applications. It is based on regularized least squares with an ā0(ā2) penalty. One distinct feature of the new approach is that it has the built-in decorrelation mechanism within each group, and thus can handle the challenging strong inner-group correlation. We provide a complete analysis of the regularized model, e.g., the existence of global minimizers, invariance property, support recovery, and characterization and properties of block coordinatewise minimizers. Further, the regularized functional can be minimized efficiently and accurately by a primal dual active set algorithm with provable global convergence. In particular, at each iteration, it involves solving least squares problems on the active set only, and merits fast local convergence, which makes the method extremely efficient for recovering group sparse signals. Extensive numerical experiments are presented to illustrate salient features of the model and the efficiency and accuracy of the algorithm. A comparative experimental study indicates that it is competitive with existing approaches
Approximate perturbed direct homotopy reduction method: infinite series reductions to two perturbed mKdV equations
An approximate perturbed direct homotopy reduction method is proposed and
applied to two perturbed modified Korteweg-de Vries (mKdV) equations with
fourth order dispersion and second order dissipation. The similarity reduction
equations are derived to arbitrary orders. The method is valid not only for
single soliton solution but also for the Painlev\'e II waves and periodic waves
expressed by Jacobi elliptic functions for both fourth order dispersion and
second order dissipation. The method is valid also for strong perturbations.Comment: 8 pages, 1 figur
Genome-wide profiling of uncapped mRNA
Gene transcripts are under extensive posttranscriptional regulation, including the regulation of their
stability. A major route for mRNA degradation produces uncapped mRNAs, which can be generated by
decapping enzymes, endonucleases, and small RNAs. Profiling uncapped mRNA molecules is important for
the understanding of the transcriptome, whose composition is determined by a balance between mRNA
synthesis and degradation. In this chapter, we describe a method to profile these uncapped mRNAs at the
genome scale
Oxidation and mechanical properties of in situ hybrid (TiCp+TiBw)/Ti6Al4V composites with tailored network microstructure
Synergy of Ag and AgBr in a Pressurized Flow Reactor for Selective Photocatalytic Oxidative Coupling of Methane
Oxidation of methane into valuable chemicals, such as C2+ molecules, has been long sought after but the dilemma between high yield and high selectivity of desired products remains. Herein, methane is upgraded through the photocatalytic oxidative coupling of methane (OCM) over a ternary Ag-AgBr/TiO2 catalyst in a pressurized flow reactor. The ethane yield of 35.4 Ī¼mol/h with a high C2+ selectivity of 79% has been obtained under 6 bar pressure. These are much better than most of the previous benchmark performance in photocatalytic OCM processes. These results are attributed to the synergy between Ag and AgBr, where Ag serves as an electron acceptor and promotes the charge transfer and AgBr forms a heterostructure with TiO2 not only to facilitate charge separation but also to avoid the overoxidation process. This work thus demonstrates an efficient strategy for photocatalytic methane conversion by both the rational design of the catalyst for the high selectivity and reactor engineering for the high conversion
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