scholarly journals Analysis of the Double-Bounce Interaction between a Random Volume and an Underlying Ground, Using a Controlled High-Resolution PolTomoSAR Experiment

2021 ◽  
Vol 13 (4) ◽  
pp. 636
Author(s):  
Ray Abdo ◽  
Laurent Ferro-Famil ◽  
Frederic Boutet ◽  
Sophie Allain-Bailhache
Keyword(s):  
3D Imaging ◽  
Full Rank ◽  
Ground Level ◽  
Ground Response ◽  
Soil Response ◽  
Classical Characterization ◽  
Forested Areas ◽  
Imaging Mode ◽  
Specific Contribution ◽  
Arbitrary Volume

The radar response of vegetated environments, and forested areas in particular, are usually modeled using a very simple structure made of a random volume, representing a cloud of vegetation particles, lying over a semi-infinite medium with a rough interface, associated with the underlying ground. This Random Volume over Ground model can efficiently handle double-bounce scattering mechanisms, or arbitrary volume reflectivity profiles. This paper proposes to analyze a specific component of the Random Volume over Ground simplified scattering model, which concerns the double-bounce interaction between the ground and the volume. This specific contribution is not considered by classical characterization techniques and is studied in this work using a controlled experiment involving a Synthetic Aperture Radar operated in a Polarimetric and Tomographic configuration in order to image in 3D a controlled miniaturized scene composed of volume lying over a ground. It is shown that ground/volume double-bounce scattering, which remains focused at the ground level even in 3D imaging mode, and has polarimetric patterns that differ largely from those usually expected from double-bounce reflections, with volume-like features, such as a strong cross-polarized reflectivity or decorrelation between co-polarized channels. Moreover, it is shown that the full rank polarimetric patterns of the ground-volume mechanism are tightly linked to the reflectivity of the volume and may mask the ground response. As a consequence, isolating the ground response using 3D imaging does not permit to avoid a generally very strong distortion of the soil response by the double-bounce reflection, and the estimation of different geophysical parameters of the ground, such as its humidity or roughness are significantly altered.

scholarly journals THE DIVERSITY OF HERBACEOUS VEGETATION AFTER FOREST FIRE

2018 ◽  
Author(s):  
Jolita ABRAITIENĖ ◽  
Gerda ŠILINGIENĖ ◽  
Rasa VAITKEVIČIŪTĖ ◽  
Regina VASINAUSKIENĖ
Keyword(s):  
New Species ◽  
Plant Species ◽  
Forest Fire ◽  
Forest Fires ◽  
Ground Level ◽  
Herbaceous Plants ◽  
Coniferous Forests ◽  
First Year ◽  
Herbaceous Plant ◽  
Forested Areas

Forest fire is an uncontrolled combustion of flammable materials in forested and non-forested areas. In Lithuania forest fires mainly occur in late spring and summer, mostly in young coniferous forests (Forest ..., 1987). The studies of herbaceous plants in fireplaces were carried out in 2016 in Jurbarkas SFE. Ground-level forest fire increased the projection coverage of herbaceous plants and their species composition in the fireplaces. According to the average data of the survey, 18 herbaceous plant species were ascertained in the fireplace and 14 species in the control stand. During the first year after fire, 9 new species were recorded in the fireplace and 5 species have disappeared, while in the seventh year - 7 new species were recorded and 1 disappeared, as compared with the control stand. Summarizing the obtained data it can be stated that low-intensity ground-level forest fire in pine forest increased the number of herbaceous plant species, however, the number of new and extinct species has been gradually decreasing, suggesting that in the fireplaces the diversity of herbaceous plant species will be like in the control stand.

Influence of Epistemic Uncertainty in Shear Wave Velocity on Seismic Ground Response Analyses

2019 ◽  
Vol 35 (2) ◽  
pp. 929-954 ◽  
Author(s):  
Federico Passeri ◽  
Sebastiano Foti ◽  
Brady R. Cox ◽  
Adrian Rodriguez-Marek
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Site Response ◽  
Epistemic Uncertainty ◽  
Ground Response ◽  
Soil Response ◽  
Linear Elastic ◽  
Seismic Ground Response ◽  
Study Sites

This study aims to evaluate the influence of epistemic uncertainties in shear wave velocity ( VS) on seismic ground response analyses (GRAs). A number of alternative VS profiles obtained from both invasive (i.e., borehole) and noninvasive (i.e., surface waves) testing methods are available for two blind study sites. These profiles are used to estimate epistemic uncertainties in VS, which are then propagated through equivalent linear-elastic GRAs, allowing for the quantification of intramethod uncertainty and intermethod variability in terms of spectral accelerations, amplification functions, and damage parameters (i.e., Arias and Housner intensities). This study demonstrates that nonlinearity of soil response plays a fundamental role in increasing the propagated uncertainty in GRA. Additionally, GRAs were also performed by means of VS upper/lower-range profiles developed from assumptions commonly used to account for epistemic uncertainties. These VS profiles were found to yield unrealistic site response estimates for both low strain (i.e., linear-elastic) and high strain (i.e., nonlinear) levels.

Electronic Cone Illumination with the Conventional Transmission Electron Microscope

1977 ◽  
Vol 35 ◽  
pp. 72-73
Author(s):  
William Krakow
Keyword(s):  
Electronic Device ◽  
Chromatic Aberration ◽  
Objective Lens ◽  
Hollow Cone ◽  
Transmission Electron ◽  
Lissajous Figures ◽  
High Resolution Images ◽  
Imaging Mode ◽  
Diffraction Patterns ◽  
Transmission Microscope

An electronic device has been constructed which manipulates the primary beam in the conventional transmission microscope to illuminate a specimen under a variety of virtual condenser aperture conditions. The device uses the existing tilt coils of the microscope, and modulates the D.C. signals to both x and y tilt directions simultaneously with various waveforms to produce Lissajous figures in the back-focal plane of the objective lens. Electron diffraction patterns can be recorded which reflect the manner in which the direct beam is tilted during exposure of a micrograph. The device has been utilized mainly for the hollow cone imaging mode where the device provides a microscope transfer function without zeros in all spatial directions and has produced high resolution images which are also free from the effect of chromatic aberration. A standard second condenser aperture is employed and the width of the cone annulus is readily controlled by defocusing the second condenser lens.

Effects of Vibration on the Preparation of Ultrathin Sections

1973 ◽  
Vol 31 ◽  
pp. 358-359
Author(s):  
Joseph M. Blum ◽  
Edward P. Gargiulo ◽  
J. R. Sawers
Keyword(s):  
Cutting Speed ◽  
Ground Level ◽  
Environmental Vibration ◽  
Block Face ◽  
Ultrathin Sections ◽  
Embedding Medium ◽  
Thickness Variations ◽  
Building Walls ◽  
Cutting Direction ◽  
Diamond Knife

It is now well-known that chatter (Figure 1) is caused by vibration between the microtome arm and the diamond knife. It is usually observed as a cyclical variation in “optical” density of an electron micrograph due to sample thickness variations perpendicular to the cutting direction. This vibration might be induced by using too large a block face, too large a clearance angle, excessive cutting speed, non-uniform embedding medium or microtome vibration. Another prominent cause is environmental vibration caused by inadequate building construction. Microtomes should be installed on firm, solid floors. The best floors are thick, ground-level concrete pads poured over a sand bed and isolated from the building walls. Even when these precautions are followed, we recommend an additional isolation pad placed on the top of a sturdy table.

Design and calibration of an IVEM for general 3-dimensional imaging of non-diffracting materials

1992 ◽  
Vol 50 (2) ◽  
pp. 1040-1041
Author(s):  
Neil Rowlands ◽  
Jeff Price ◽  
Michael Kersker ◽  
Seichi Suzuki ◽  
Steve Young ◽  
...  
Keyword(s):  
3D Imaging ◽  
Tomographic Reconstruction ◽  
Three Dimensional ◽  
3 Dimensional ◽  
3D Microstructure ◽  
Image Translation ◽  
Digital Correlation ◽  
On Line ◽  
Mechanical Stage ◽  
Projection Angle

Three-dimensional (3D) microstructure visualization on the electron microscope requires that the sample be tilted to different positions to collect a series of projections. This tilting should be performed rapidly for on-line stereo viewing and precisely for off-line tomographic reconstruction. Usually a projection series is collected using mechanical stage tilt alone. The stereo pairs must be viewed off-line and the 60 to 120 tomographic projections must be aligned with fiduciary markers or digital correlation methods. The delay in viewing stereo pairs and the alignment problems in tomographic reconstruction could be eliminated or improved by tilting the beam if such tilt could be accomplished without image translation.A microscope capable of beam tilt with simultaneous image shift to eliminate tilt-induced translation has been investigated for 3D imaging of thick (1 μm) biologic specimens. By tilting the beam above and through the specimen and bringing it back below the specimen, a brightfield image with a projection angle corresponding to the beam tilt angle can be recorded (Fig. 1a).

Ultra high resolution SEM at high voltage images individual fab fragments applied as molecular label to cell surface receptors

1989 ◽  
Vol 47 ◽  
pp. 70-71
Author(s):  
Klaus-Ruediger Peters
Keyword(s):  
High Resolution ◽  
High Energy ◽  
Metal Coating ◽  
Beam Diameter ◽  
Surface Receptors ◽  
Surface Mobility ◽  
Metal Atoms ◽  
Shadowing Effect ◽  
Imaging Mode ◽  
Deposition Techniques

Topographic ultra high resolution can now routinely be established on bulk samples in cold field emission scanning electron microscopy with a second generation of microscopes (FSEM) designed to provide 0.5 nm probe diameters. If such small probes are used for high magnification imaging, topographic contrast is so high that remarkably fine details can be imaged on 2DMSO/osmium-impregnated specimens at ribosome surfaces even without a metal coating. On TCH/osmium-impregnated specimens topographic resolution can be increased further if the SE-I imaging mode is applied. This requires that beam diameter and metal coating thickness be made smaller than the SE range of ~1 nm and background signal contributions be reduced. Subnanometer small probes can be obtained (only) at high accelerating voltages. Subnanometer thin continuous metal films can be produced under the following conditions: self-shadowing effect between metal atoms must be reduced through appropriate deposition techniques and surface mobility of metal atoms must be diminished through high energy sputtering and/or specimen cooling.

Quantification of gold labeled cell surface antigens by SEM: Current progress and remaining problems

1990 ◽  
Vol 48 (3) ◽  
pp. 34-35
Author(s):  
Etienne de Harven ◽  
Davide Soligo ◽  
Roy McGroarty ◽  
Hilary Christensen ◽  
Richard Leung ◽  
...  
Keyword(s):  
Cell Surface ◽  
Immunogold Labeling ◽  
Target Antigen ◽  
Facs Analysis ◽  
Becton Dickinson ◽  
Cell Surface Antigens ◽  
Human T Lymphocyte ◽  
Backscattered Electron ◽  
Imaging Mode ◽  
Electron Imaging

Taking advantage of the high elemental contrast of particles of colloidal gold observed in the backscattered electron imaging(BEI) mode of the SEM (1,2), the human T lymphocyte was chosen as a model system to study the potential value of immunogold labeling for the quantification of cell surface expressed molecules. The CD3 antigen which is expressed on all human T lymphocytes and is readily identified by the LEU-4 murine monoclonal antibody (Becton Dickinson, Mountain View, CA) followed by a gold conjugated goat anti-mouse Ig polyclonal antibody was chosen as a model target antigen. When quantified by non-EM methods, using radio-iodinated probes or FACS analysis, approximately 30,000 to 50,000 copies of this antigen per cell are enumerated.The following observations were made while attempting to quantify the same molecule by SEM after specific immunogold labeling:Imaging in the SE vs BE mode: The numbers of gold markers counted in the secondary electron (SE) imaging mode are considerably lower than those counted on the same cells in the backscattered electron (BE) imaging mode.

Optical characteristics of the hitachi HF-2000 cold field-emission TEM

1993 ◽  
Vol 51 ◽  
pp. 1076-1077
Author(s):  
L. F. Allard ◽  
E. Völkl ◽  
T. A. Nolan
Keyword(s):  
Field Emission ◽  
Recent Literature ◽  
Electron Gun ◽  
High Brightness ◽  
Condenser Lens ◽  
Illumination System ◽  
High Resolution Images ◽  
Imaging Mode ◽  
Better Than ◽  
Illuminating System

The illumination system of the cold field emission (CFE) Hitachi HF-2000 TEM operates with a single condenser lens in normal imaging mode, and with a second condenser lens excited to give the ultra-fine 1 nm probe for microanalysis. The electron gun provides a guaranteed high brightness of better than 7×l08 A/cm2/sr, more than twice the guaranteed brightness of Schottky emission guns. There have been several articles in the recent literature (e.g. refs.) which claim that the geometry of this illumination system yields a total current which is so low that when the beam is spread at low magnifications (say 10 kX), the operator must “keep his eyes glued to the binoculars” in order to see the image. It is also claimed that this illuminating system produces an isoplanatic patch (the area over which image character does not vary significantly) at high magnification which is so small that the instrument is ineffective for recording high resolution images.

A global perspective of ground level, 'ambient' carbon dioxide for assessing the response of plants to atmospheric CO2

2001 ◽  
Vol 7 (7) ◽  
pp. 789-796 ◽  
Author(s):  
L. H. Ziska ◽  
O. Ghannoum ◽  
J. T. Baker ◽  
J. Conroy ◽  
J. A. Bunce ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Ground Level ◽  
Global Perspective ◽  
Atmospheric Co2
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