3D hollow hybrid composites with ultrafine cobalt sulfide nanoparticles uniformly embedded within the well-graphitized porous carbon polyhedra/carbon nanotubes framework are rationally fabricated using a green and one-step method involving the simultaneous pyrolysis and sulfidation of ZIF-67. Because of the synergistic coupling effects favored by the unique nanohybridization, these composites exhibit high specific capacity, excellent cycle stability, and superior rate capability when evaluated as electrodes in lithium-ion batteries.
The development of a second-order integral model for a round turbulent buoyant
jet is reported based on new experimental data on turbulent mass and momentum
transport. The mean and turbulent characteristics of a round vertical buoyant jet
covering the full range from jets to plumes were investigated using a recently developed
combined digital particle image velocimetry (DPIV) and planar laser-induced
fluorescence (PLIF) system. The system couples the two well-known techniques to
enable synchronized planar measurements of flow velocities and concentrations in
a study area. The experimental results conserved the mass and momentum fluxes
introduced at the source accurately with closure errors of less than 5%. The momentum
flux contributed by turbulence and streamwise pressure gradient was determined
to be about 10% of the local mean momentum flux in both jets and plumes. The
turbulent mass flux, on the other hand, was measured to be about 7.6% and 15%
of the mean mass flux for jets and plumes respectively. While the velocity spread
rate was shown to be independent of the flow regime, the concentration-to-velocity
width ratio λ varied from 1.23 to 1.04 during the transition from jet to plume. Based
on the experimental results, a refined second-order integral model for buoyant jets
that achieves the conservation of total mass and momentum fluxes is proposed. The
model employs the widely used entrainment assumption with the entrainment coefficient
taken to be a function of the local Richardson number. Improved prediction
is achieved by taking into account the variation of turbulent mass and momentum
fluxes. The variation of turbulent mass flux is modelled as a function of the local
Richardson number. The turbulent momentum flux, on the other hand, is treated
as a fixed percentage of the local mean momentum flux. In addition, unlike most
existing integral models that assume a constant concentration-to-velocity width ratio,
the present model adopts a more accurate approach with the ratio expressed as a
function of the local Richardson number. As a result, smooth transition of all relevant
mean and turbulent characteristics from jet to plume is predicted, which is in line
with the underlying physical processes.
van der Waals heterostructures, obtained by stacking layers of isolated two-dimensional atomic crystals like graphene (GE) and silicene (SE), are one of emerging nanomaterials for the development of future multifunctional devices. Thermal transport behaviors at the interface of these heterostructures play a pivotal role in determining their thermal properties and functional performance. Using molecular dynamics simulations, the interfacial thermal conductance G of an SE/GE bilayer heterostructure is studied. Simulations show that G of a pristine SE/GE bilayer at room temperature is 11.74 MW/m(2)K when heat transfers from GE to SE, and is 9.52 MW/m(2)K for a reverse heat transfer, showing apparent thermal rectification effects. In addition, G increases monotonically with both the temperature and the interface coupling strength. Furthermore, hydrogenation of GE is efficient in enhancing G if an optimum hydrogenation pattern is adopted. By changing the hydrogen coverage f, G can be controllably manipulated and maximized up to five times larger than that of pristine SE/GE. This study is helpful for understanding the interface thermal transport behaviors of novel van der Waals heterostructures and provides guidance for the design and control of their thermal properties.
K. (2019). 3D printing of mixed matrix films based on metal-organic frameworks and thermoplastic polyamide 12 by selective laser sintering for water applications. ACS Applied Materials & Interfaces, 11(43), 40564-40574.
60 • inclined dense jets had been recommended for brine discharges from desalination plants to achieve a maximum mixing efficiency. However, the terminal rise associated with 60 • is relatively high and thus the angle may be too large for disposal in shallow coastal wasters. In this study, we investigate the mixing behavior of dense jets discharging at smaller angles of 30 • and 45 • in a stationary ambient. Combined Particle Image Velocimetry (PIV) and Planar Laser Induced Fluorescence (PLIF) were used as the measurement approaches that captured the velocity and concentration fields, respectively. Based on the experimental results, the characteristic geometrical features of the inclined dense jets, including the location of the centerline peak and the return point where the dense jet returns to the source level, etc., are quantified. The mixing and diluting behaviors are also revealed through the analysis of the axial and cross-sectional velocity and concentration profiles. In addition to the free inclined discharges, the present study also examines the effect of the proximity to the bed. Through the comparison of the results between two experimental series with distinct z 0 /D but overlapping z 0 /L M , the latter is identified as the deciding factor for the boundary influence.
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