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Depth of closure (DOC) is defined as the most landward depth seaward of which there is no significant change in bed elevation and no significant net sediment exchange between the nearshore and the offshore over a certain period of time, such as 5 to 20 years. DOC is an essential parameter used in beach and shore protection, sediment management, and many other aspects of coastal studies. Taking advantage of advancements in wave hindcast and bathymetry measurement in the past 20 years (2000-2019), this study determined the DOC at 12 locations along the Florida coast, including three from the northwest Gulf coast, three from the west Gulf coast, and six from the east Atlantic coast. The 12 sites covered a wide range of coastal morphodynamic conditions, with considerable difference in tidal ranges, incident wave heights, as well as nearshore and offshore morphology. Hindcast wave data from WAVEWATCHIII, available since 2005, were analyzed and applied to calculate the closure depth using various empirical formulas. At all the 12 study sites, time-series profiles demonstrated an apparent convergence point indicating the presences of a DOC. The bed-level change at DOC, as quantified by the standard deviation of elevation variation, ranged from 0.05 m to 0.19 m. Along the studied northwest Florida Gulf coast the DOC ranged from 9.12 m to 9.76 m. The DOC along the studied west Florida Gulf coast ranged from 1.59 m to 4.06 m and is influenced by the shallow flat inner continental shelf. Along the studied east Florida Atlantic coast, the DOC ranged from 4.35 m to 8.20 m, with considerable alongshore variation. The Birkemeier formula yielded the closest predictions to the measured values. A linear relationship between the seaward slope of the outer bar and DOC was identified. Incorporating the seaward slope of the outer bar into the Birkemeier formula improved the accuracy of DOC prediction. 

One of the most challenging aspects of developing high-energy lithium-based batteries is the structural and (electro)chemical stability of Ni-rich active cathode materials at thermally-abused and prolonged cell cycling conditions. Here, we report in situ physicochemical characterizations to improve the fundamental understanding of the degradation mechanism of charged polycrystalline Ni-rich cathodes at elevated temperatures (e.g., ≥ 40 °C). Using multiple microscopy, scattering, thermal, and electrochemical probes, we decouple the major contributors for the thermal instability from intertwined factors. Our research work demonstrates that the grain microstructures play an essential role in the thermal stability of polycrystalline lithium-based positive battery electrodes. We also show that the oxygen release, a crucial process during battery thermal runaway, can be regulated by engineering grain arrangements. Furthermore, the grain arrangements can also modulate the macroscopic crystallographic transformation pattern and oxygen diffusion length in layered oxide cathode materials.

 

Using quantum Monte Carlo, exact diagonalization, and perturbation theory, we study the spectrum of theS = 1/2 antiferromagnetic Heisenberg trimer chain by varying the ratiog = J₂/J₁of the intertrimer and intratrimer coupling strengths. The doublet ground states of trimers form effective interactingS = 1/2 degrees of freedom described by a Heisenberg chain. Therefore, the conventional two-spinon continuum of width ∝ J₁wheng = 1 evolves into to a similar continuum of width ∝ J₂wheng → 0. The intermediate-energy and high-energy modes are termeddoublonsandquartonswhich fractionalize with increasinggto form the conventional spinon continuum. In particular, atg ≈ 0.716, the gap between the low-energy spinon branch and the high-energy band with mixed doublons, quartons, and spinons closes. These features should be observable in inelastic neutron scattering experiments if a quasi-one-dimensional quantum magnet with the linear trimer structure andJ₂ < J₁can be identified. Our results may open a window for exploring the high-energy fractional excitations.

 

Tropical Storm Eta impacted the coast of west-central Florida from 11 November to 12 November 2020 and generated high waves over elevated water levels for over 20 hours. A total of 148 beach and nearshore profiles, spaced about 300 m (984 ft) apart, were surveyed one to two weeks before and one to eight days after the storm to examine the beach changes along four barrier islands, including Sand Key, Treasure Island, Long Key, and Mullet Key. The high storm waves superimposed on elevated water level reached the toe of dunes or seawalls and caused dune erosion and overwash at various places. Throughout most of the coast, the dune, dry beach, and nearshore area was eroded and most of the sediment was deposited on the seaward slope of the nearshore bar, resulting in a roughly conserved sand volume above closure depth. The longshore variation of beach-profile volume loss demonstrates an overall southward decreasing trend, mainly due to a southward decreasing nearshore wave height as controlled by offshore bathymetry and shoreline configurations. The Storm Erosion Index (SEI) developed by Miller and Livermont (2008) captured the longshore variation of beach-profile volume loss reasonably well. The longshore variation of breaking wave height is the dominant factor controlling the longshore changes of SEI and beach erosion. Temporal variation of water level also played a significant role, while beach berm elevation was a minor factor. Although wider beaches tended to experience more volume loss from TS Eta due to the availability of sediment, they were effective in protecting the back beach and dune area from erosion. On the other hand, smaller profile-volume loss from narrow beach did not necessarily relate to less dune/ structure damage. The opposite is often true. Accurate evaluation of a storm’s severity in terms of erosion potential would benefit beach management especially under the circumstance of increasing storm activities due to climate change.