Search

The generation of terahertz (THz) waves by focusing a femtosecond pulsed laser beam at a distance is able to overcome the strong absorption properties of air and has rapidly attracted the attention of the industry. However, the poor directionality of the THz wave radiation generated by this method is not conducive to THz wave applications. By controlling the morphology of the ultrafast laser-excited plasma filament and its electron density distribution through coherent beam combining (CBC) technology, we achieve direct THz beam shaping and are able to obtain THz wave radiation of Gaussian or arbitrary transverse distribution. The novel experimental approach proposed in this paper opens up the research field of direct THz wave shaping using plasma. Moreover, it innovates multi-parameter convergence algorithms and, by doing so, has the potential to find beam patterns with higher energy conversion efficiency and break the energy limit of THz waves emitted by lasers at high power.

Actuated by the non-ionic heavy metal of antimony (Sb) contaminants with undesired toxicity to the environment and human health, capturing Sb is urgent to remedy contaminated water. Herein, the lamellar MnCo hydrotalcite was grown on catkin-derived biochar through the in situ etching of ZIF-L to construct a hierarchical microtube@nanosheet hybrid (CLMH) for Sb immobilization. The adsorption behaviour and mechanism of trivalent antimony (Sb (III)) on the CLMH were investigated. The CLMH shows good pH applicability for capturing Sb(III) at pH from 2 to 9. The excellent adsorption capacity of CLMH for Sb(III) is 247.62 mg g−1 at 303 K, and the endothermic process is proved by the positive value of Δ H 0 (10.54 kJ mol−1). The adsorption process is fitted with the intra-particle diffusion model, which can be described with external mass transfer, intraparticle diffusion in pores, and equilibrium stage. The adsorption mechanism is proved, which includes the bind of Metal–O–Sb bonds by inner-sphere complex, the embedding of Sb in the intercalation of hydrotalcite, redox between Mn and Sb, and functional groups dependent anchoring effect. The work benefits the understanding of the antimony removal behaviour over the hierarchical microtube@nanosheet hybrids.

The virtual pumped storage power station based on compressed air energy storage combines compressed air energy storage and pumped storage technology organically, complements each other’s advantages, and adopts efficient hydraulic equipment to compress air. In the process of power regulation, the head of high-pressure pool is controlled to be constant, the efficiency of pump-turbine unit is improved, and the power station is operated efficiently and steadily. In this paper, a 1 MW pumped storage power station is designed, and the power regulation strategy for stable operation of power generation and electric conditions is put forward. The mathematical model of each module of the power station is established. According to the power regulation instructions, the ideal values of the operation parameters of the power station are calculated, and the regulation instructions are given to the driving equipment of the hydraulic transformer. The running process of the hydraulic piston and the fluctuation of the head of the high-pressure pool are also simulated and analyzed, which verifies the feasibility of the strategy.

In the Tarim River Basin, water resources from the mountain areas play a key role due to the extremely arid climate of the lowlands. This study presents an analysis of future climate change impacts on glaciers and surface water availability for headwater catchments of the Aksu River, the most important tributary to the Tarim River. We applied a glacio-hydrological model that underwent a comprehensive multivariable and multiobjective model calibration and evaluation, based on daily and interannual discharge variations and glacier mass changes. Transient glacier geometry changes are simulated using the Δh-approach. For the ensemble-based projections, we considered three different emission scenarios, nine global climate models (GCMs) and two regional climate models, and different hydrological model parameters derived from the multiobjective calibration. The results show a decline in glacier area of −90% to −32% until 2099 (reference ~2008) (based on the 5–95 percentile range of the ensemble). Glacier melt is anticipated to further increase or stay at a high level during the first decades of the 21st century, but then declines because of decreased glacier extents. Overall discharge in the Aksu headwaters is expected to be increased in the period 2010–2039 (reference 1971–2000), but decreased in 2070–2099. Seasonally, projections show an increase in discharge in spring and early summer throughout the 21st century. Discharge changes in mid to late summer are more variable, with increases or decreases depending on the considered period and GCM. Uncertainties are largely caused by differences between the different GCMs, with further important contributions from different emission scenarios in the second half of the 21st century. Contributions from the hydrological model parameters to the ensemble uncertainty were generally found to be small.

Trivalent cerium-doped yttrium aluminum garnet (YAG:Ce3=) phosphors are synthesized by solid-state reaction method through using (Y1−xCex)2O3 solid solutions as precursors. Solid solubility limits of Ce3= replacing Y3= in Y2O3 and YAG are determined to be 40% and 7.5%, respectively, based on the relationship between the lattice parameter and chemical composition. Using (Y1−xCex)2O3 as precursors we synthesize YAG:Ce3= single phase at 1450 °C and N2 atmosphere. However, under the same conditions using CeO2 there exists a second phase YAlO3 as impurity. The photoluminescence intensity of YAG:Ce3= increases monotonically with the increase of Ce concentration until it reaches a maximum at solid solubility limits of Ce3= in YAG.

We present a set of inequalities based on mean values of quantum mechanical observables nonlinear entanglement witnesses for bipartite quantum systems. These inequalities give rise to sufficient and necessary conditions for separability of all bipartite pure states and even some mixed states. In terms of these mean values of quantum mechanical observables a measurable lower bound of the convex-roof extension of the negativity is derived., Comment: 8 pages, 1 figure

A many-body theoretical treatment of the Coulomb hole is presented. In contrast to the traditional density matrix approach, the interparticle separation distribution function is expressed in terms of the expectation value of the interparticle separation distribution operator. By introducing the second quantisation method, the Goldstone-type linked diagrammatic expansion of the distribution function is obtained, which provides a very clear and convenient frame for the discussion and calculation of the Coulomb hole. The effects of one-body excitation on the Coulomb hole are discussed in detail based on this formulation, and they imply that if the authors define the Coulomb hole with respect to Brueckner instead of Hartree-Fock (HF) orbitals, the Coulomb hole is expected to possess a well behaved form. To calculate the angular parts of the Coulomb hole Goldstone diagrams, the angular momentum graph-an elegant tool-is introduced. By using the formalism and techniques described above, the ground-state Coulomb hole of the beryllium atom is evaluated from a many-body wavefunction, and compared with those derived from CI wavefunctions. The formulation outlined here can be straightforwardly extended to discuss open-shell atoms.