Bridge-Site Extreme Wind Prediction

2018 ◽  
pp. 27-43
Author(s):  
Yang Deng ◽  
Aiqun Li
Keyword(s):  
Bridge Site ◽  
Extreme Wind

Coverage and Stability of NHx Terminated Cobalt and Ruthenium Surfaces: a First Principles Investigation

2019 ◽  
Author(s):  
Ji Liu ◽  
Michael Nolan
Keyword(s):  
Metal Surfaces ◽  
High Vacuum ◽  
Atomic Layer ◽  
Nitrogen Plasma ◽  
Operating Conditions ◽  
Ultra High Vacuum ◽  
Bridge Site ◽  
Stable Surface ◽  
Saturation Coverage ◽  
The Stability

<div>In the atomic layer deposition (ALD) of Cobalt (Co) and Ruthenium (Ru) metal using nitrogen plasma, the structure and composition of the post N-plasma NHx terminated (x = 1 or 2) metal surfaces are not well known but are important in the subsequent metal containing pulse. In this paper, we use the low-index (001) and (100) surfaces of Co and Ru as models of the metal polycrystalline thin films. The (001) surface with a hexagonal surface structure is the most stable surface and the (100) surface with a zigzag structure is the least stable surface but has high reactivity. We investigate the stability of NH and NH2 terminations on these surfaces to determine the saturation coverage of NHx on Co and Ru. NH is most stable in the hollow hcp site on (001) surface and the bridge site on the (100) surface, while NH2 prefers the bridge site on both (001) and (100) surfaces. The differential energy is calculated to find the saturation coverage of NH and NH2. We also present results on mixed NH/NH2-terminations. The results are analyzed by thermodynamics using Gibbs free energies (ΔG) to reveal temperature effects on the stability of NH and NH2 terminations. Ultra-high vacuum (UHV) and standard ALD</div><div>operating conditions are considered. Under typical ALD operating conditions we find that the most stable NHx terminated metal surfaces are 1 ML NH on Ru (001) surface (350K-550K), 5/9 ML NH on Co (001) surface (400K-650K) and a mixture of NH and NH2 on both Ru (100) and Co (100) surfaces.</div>

Forecasting of Tornadoes and Downbursts

2020 ◽  
Author(s):  
Djordje Romanic
Keyword(s):  
Chaos Theory ◽  
Prediction Models ◽  
Weather Prediction ◽  
Small Scale ◽  
Weather Forecasts ◽  
Wind Speeds ◽  
The Past ◽  
Extreme Wind ◽  
Extreme Wind Speeds ◽  
Numerical Weather Prediction Models

Tornadoes and downbursts cause extreme wind speeds that often present a threat to human safety, structures, and the environment. While the accuracy of weather forecasts has increased manifold over the past several decades, the current numerical weather prediction models are still not capable of explicitly resolving tornadoes and small-scale downbursts in their operational applications. This chapter describes some of the physical (e.g., tornadogenesis and downburst formation), mathematical (e.g., chaos theory), and computational (e.g., grid resolution) challenges that meteorologists currently face in tornado and downburst forecasting.

scholarly journals Antecedent lake conditions shape resistance and resilience of a shallow lake ecosystem following extreme wind storms

2021 ◽  
Author(s):  
Michael W. Thayne ◽  
Benjamin M. Kraemer ◽  
Jorrit P. Mesman ◽  
Bastiaan W. Ibelings ◽  
Rita Adrian
Keyword(s):  
Shallow Lake ◽  
Lake Ecosystem ◽  
Extreme Wind ◽  
Wind Storms

scholarly journals A Novel Sea Surface Roughness Parameterization Based on Wave State and Sea Foam

2021 ◽  
Vol 9 (3) ◽  
pp. 246
Author(s):  
Difu Sun ◽  
Junqiang Song ◽  
Xiaoyong Li ◽  
Kaijun Ren ◽  
Hongze Leng
Keyword(s):  
Surface Roughness ◽  
Wind Speed ◽  
Drag Coefficient ◽  
Sea Surface ◽  
High Wind Speed ◽  
Wave State ◽  
Wind Speeds ◽  
Sea Surface Roughness ◽  
Extreme Wind ◽  
The Impact

A wave state related sea surface roughness parameterization scheme that takes into account the impact of sea foam is proposed in this study. Using eight observational datasets, the performances of two most widely used wave state related parameterizations are examined under various wave conditions. Based on the different performances of two wave state related parameterizations under different wave state, and by introducing the effect of sea foam, a new sea surface roughness parameterization suitable for low to extreme wind conditions is proposed. The behaviors of drag coefficient predicted by the proposed parameterization match the field and laboratory measurements well. It is shown that the drag coefficient increases with the increasing wind speed under low and moderate wind speed conditions, and then decreases with increasing wind speed, due to the effect of sea foam under high wind speed conditions. The maximum values of the drag coefficient are reached when the 10 m wind speeds are in the range of 30–35 m/s.

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