Vorticity from Line-of-Sight Lidar Velocity Scans

2009 ◽  
Vol 26 (12) ◽  
pp. 2683-2690 ◽  
Author(s):  
Martin Weissmann ◽  
Andreas Dörnbrack ◽  
James D. Doyle
Keyword(s):  
High Resolution ◽  
Numerical Simulations ◽  
Cross Sections ◽  
Polar Coordinates ◽  
Line Of Sight ◽  
Rotor Experiment ◽  
Vorticity Component ◽  
Wind Lidar ◽  
Spanwise Vorticity ◽  
Lidar Observations

Abstract A method is presented to compute the spanwise vorticity in polar coordinates from 2D vertical cross sections of high-resolution line-of-sight Doppler wind lidar observations. The method uses the continuity equation to derive the velocity component perpendicular to the observed line-of-sight velocity, which then yields the spanwise vorticity component. The results of the method are tested using a ground-based Doppler lidar, which was deployed during the Terrain-Induced Rotor Experiment (T-REX). The resulting fields can be used to identify and quantify the strength and size of vortices, such as those associated with atmospheric rotors. Furthermore, they may serve to investigate the dynamics and evolution of vortices and to evaluate numerical simulations. A demonstration of the method and comparison with high-resolution numerical simulations reveals that the derived vorticity can explain 66% of the mean-square vorticity fluctuations, has a reasonably skillful magnitude, exhibits no significant bias, and is in qualitative agreement with model-derived vorticity.

scholarly journals High-Resolution Simulations of Lee Waves and Downslope Winds over the Sierra Nevada during T-REX IOP 6

2012 ◽  
Vol 51 (7) ◽  
pp. 1333-1352 ◽  
Author(s):  
Peter Sheridan ◽  
Simon Vosper
Keyword(s):  
High Resolution ◽  
Sierra Nevada ◽  
Cross Sections ◽  
Weather Prediction ◽  
Vertical Motion ◽  
Owens Valley ◽  
Downslope Winds ◽  
Lee Waves ◽  
Rotor Experiment ◽  
Intensive Observation

AbstractThe downslope windstorm during intensive observation period (IOP) 6 was the most severe that was detected during the Terrain-Induced Rotor Experiment (T-REX) in Owens Valley in the Sierra Nevada of California. Cross sections of vertical motion in the form of a composite constructed from aircraft data spanning the depth of the troposphere are used to link the winds experienced at the surface to the changing structure of the mountain-wave field aloft. Detailed analysis of other observations allows the role played by a passing occluded front, associated with the rapid intensification (and subsequent cessation) of the windstorm, to be studied. High-resolution, nested modeling using the Met Office Unified Model (MetUM) is used to study qualitative aspects of the flow and the influence of the front, and this modeling suggests that accurate forecasting of the timing and position of both the front and strong mountaintop winds is crucial to capture the wave dynamics and accompanying windstorm. Meanwhile, far ahead of the front, simulated downslope winds are shallow and foehnlike, driven by the thermal contrast between the upstream and valley air mass. The study also highlights the difficulties of capturing the detailed interaction of weather systems with large and complex orography in numerical weather prediction.

Simultaneous Dual-Doppler and Mobile Mesonet Observations of Streamwise Vorticity Currents in Three Supercells

2020 ◽  
Vol 148 (12) ◽  
pp. 4859-4874
Author(s):  
Shawn S. Murdzek ◽  
Paul M. Markowski ◽  
Yvette P. Richardson
Keyword(s):  
High Resolution ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Numerical Simulations ◽  
Cross Sections ◽  
The Other ◽  
Streamwise Vorticity ◽  
Vorticity Generation ◽  
Southern Fringe

AbstractRecent high-resolution numerical simulations of supercells have identified a feature referred to as the streamwise vorticity current (SVC). Some have presumed the SVC to play a role in tornadogenesis and maintenance, though observations of such a feature have been limited. To this end, 125-m dual-Doppler wind syntheses and mobile mesonet observations are used to examine three observed supercells for evidence of an SVC. Two of the three supercells are found to contain a feature similar to an SVC, while the other supercell contains an antistreamwise vorticity ribbon on the southern fringe of the forward flank. A closer examination of the two supercells with SVCs reveals that the SVCs are located on the cool side of boundaries within the forward flank that separate colder, more turbulent flow from warmer, more laminar flow, similar to numerical simulations. Furthermore, the observed SVCs are similar to those in simulations in that they appear to be associated with baroclinic vorticity generation and have similar appearances in vertical cross sections. Aside from some apparent differences in the location of the maximum streamwise vorticity between simulated and observed SVCs, the SVCs seen in numerical simulations are indeed similar to reality. The SVC, however, may not be essential for tornadogenesis, at least for weak tornadoes, because the supercell that did not have a well-defined SVC produced at least one brief, weak tornado during the analysis period.

An Analysis of Dissociation of Molecules in a High Resolution Electron Microscope

1973 ◽  
Vol 31 ◽  
pp. 486-487
Author(s):  
Mihir Parikh
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Cross Sections ◽  
Resolving Power ◽  
Peak Intensity ◽  
Molecular Film ◽  
Resolution Electron ◽  
Dissociation Cross Section ◽  
High Resolution Electron Microscope ◽  
The Stability

It is well known that the resolution of bio-molecules in a high resolution electron microscope depends not just on the physical resolving power of the instrument, but also on the stability of these molecules under the electron beam. Experimentally, the damage to the bio-molecules is commo ly monitored by the decrease in the intensity of the diffraction pattern, or more quantitatively by the decrease in the peaks of an energy loss spectrum. In the latter case the exposure, EC, to decrease the peak intensity from IO to I’O can be related to the molecular dissociation cross-section, σD, by EC = ℓn(IO /I’O) /ℓD. Qu ntitative data on damage cross-sections are just being reported, However, the microscopist needs to know the explicit dependence of damage on: (1) the molecular properties, (2) the density and characteristics of the molecular film and that of the support film, if any, (3) the temperature of the molecular film and (4) certain characteristics of the electron microscope used

Comparison of ultra high resolution immersion lens CFESEM and TEM for imaging of semiconductor devices

1990 ◽  
Vol 48 (4) ◽  
pp. 622-623
Author(s):  
Terrence Reilly ◽  
Al Pelillo ◽  
Barbara Miner
Keyword(s):  
High Resolution ◽  
Sample Preparation ◽  
Cross Sections ◽  
Semiconductor Devices ◽  
Ion Milling ◽  
Observation Area ◽  
Transmission Electron ◽  
Milling Machines ◽  
Resolution Imaging ◽  
Electron Microscopes

The use of transmission electron microscopes (TEM) has proven to be very valuable in the observation of semiconductor devices. The need for high resolution imaging becomes more important as the devices become smaller and more complex. However, the sample preparation for TEM observation of semiconductor devices have generally proven to be complex and time consuming. The use of ion milling machines usually require a certain degree of expertise and allow a very limited viewing area. Recently, the use of an ultra high resolution "immersion lens" cold cathode field emission scanning electron microscope (CFESEM) has proven to be very useful in the observation of semiconductor devices. Particularly at low accelerating voltages where compositional contrast is increased. The Hitachi S-900 has provided comparable resolution to a 300kV TEM on semiconductor cross sections. Using the CFESEM to supplement work currently being done with high voltage TEMs provides many advantages: sample preparation time is greatly reduced and the observation area has also been increased to 7mm. The larger viewing area provides the operator a much greater area to search for a particular feature of interest. More samples can be imaged on the CFESEM, leaving the TEM for analyses requiring diffraction work and/or detecting the nature of the crystallinity.

FIB Enhancement of Mechanically Polished Cross-sections

2019 ◽  
Author(s):  
Becky Holdford
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Scanning Electron Microscope ◽  
Cross Sections ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
High Resolution Imaging ◽  
Chemical Attack ◽  
Resolution Imaging ◽  
Scanning Electron

Abstract On mechanically polished cross-sections, getting a surface adequate for high-resolution imaging is sometimes beyond the analyst’s ability, due to material smearing, chipping, polishing media chemical attack, etc.. A method has been developed to enable the focused ion beam (FIB) to re-face the section block and achieve a surface that can be imaged at high resolution in the scanning electron microscope (SEM).

Cross Section Analysis of Cu Filled TSVs Based on High Throughput Plasma-FIB Milling

2012 ◽  
Author(s):  
Frank Altmann ◽  
Jens Beyersdorfer ◽  
Jan Schischka ◽  
Michael Krause ◽  
German Franz ◽  
...  
Keyword(s):  
High Resolution ◽  
Cross Section ◽  
High Throughput ◽  
Cross Sections ◽  
Electron Backscatter Diffraction ◽  
Grain Structure ◽  
Electron Backscatter ◽  
Section Surface ◽  
Backscatter Diffraction ◽  
Section Analysis

Abstract In this paper the new Vion™ Plasma-FIB system, developed by FEI, is evaluated for cross sectioning of Cu filled Through Silicon Via (TSV) interconnects. The aim of the study presented in this paper is to evaluate and optimise different Plasma-FIB (P-FIB) milling strategies in terms of performance and cross section surface quality. The sufficient preservation of microstructures within cross sections is crucial for subsequent Electron Backscatter Diffraction (EBSD) grain structure analyses and a high resolution interface characterisation by TEM.

scholarly journals High-resolution 2D Raman mapping of mono- and bicomponent filament cross-sections

Polymer ◽  
2021 ◽  
pp. 124011 ◽  
Author(s):  
E. Perret ◽  
O. Braun ◽  
K. Sharma ◽  
S. Tritsch ◽  
R. Muff ◽  
...  
Keyword(s):  
High Resolution ◽  
Cross Sections ◽  
Raman Mapping

scholarly journals Photoionization Cross-Sections of Carbon-Like N+ Near the K-Edge (390–440 eV)

Atoms ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 27
Author(s):  
Jean-Paul Mosnier ◽  
Eugene T. Kennedy ◽  
Jean-Marc Bizau ◽  
Denis Cubaynes ◽  
Ségolène Guilbaud ◽  
...  
Keyword(s):  
High Resolution ◽  
Cross Section ◽  
Cross Sections ◽  
Experimental Studies ◽  
Photoionization Cross Section ◽  
Theoretical Work ◽  
Rydberg Series ◽  
R Matrix ◽  
Resonance Strengths ◽  
Nitrogen Ion

High-resolution K-shell photoionization cross-sections for the C-like atomic nitrogen ion (N+) are reported in the 398 eV (31.15 Å) to 450 eV (27.55 Å) energy (wavelength) range. The results were obtained from absolute ion-yield measurements using the SOLEIL synchrotron radiation facility for spectral bandpasses of 65 meV or 250 meV. In the photon energy region 398–403 eV, 1s⟶2p autoionizing resonance states dominated the cross section spectrum. Analyses of the experimental profiles yielded resonance strengths and Auger widths. In the 415–440 eV photon region 1s⟶(1s2s22p2 4P)np and 1s⟶(1s2s22p2 2P)np resonances forming well-developed Rydberg series up n=7 and n=8 , respectively, were identified in both the single and double ionization spectra. Theoretical photoionization cross-section calculations, performed using the R-matrix plus pseudo-states (RMPS) method and the multiconfiguration Dirac-Fock (MCDF) approach were bench marked against these high-resolution experimental results. Comparison of the state-of-the-art theoretical work with the experimental studies allowed the identification of new resonance features. Resonance strengths, energies and Auger widths (where available) are compared quantitatively with the theoretical values. Contributions from excited metastable states of the N+ ions were carefully considered throughout.

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