Robust inversion of vegetation structure parameters from low-frequency, polarimetric interferometric SAR

2002 ◽  
Author(s):  
M. Tabb ◽  
R. Carande
Keyword(s):  
Vegetation Structure ◽  
Low Frequency ◽  
Structure Parameters ◽  
Interferometric Sar

Influence of Structure Parameters on the Permanent Magnetic Planetary Gear Forced Vibration Frequency Response

2014 ◽  
Vol 635-637 ◽  
pp. 168-171
Author(s):  
Xue Jun Zhu ◽  
Li Zhong Xu
Keyword(s):  
Dynamic Performance ◽  
Low Frequency ◽  
Planetary Gear ◽  
System Structure ◽  
Structure Parameters ◽  
Magnetic Parameters ◽  
Low Frequency Vibration ◽  
Magnetization Intensity ◽  
Pair Number ◽  
Forced Responses

The time and frequency forced responses for the permanent magnetic planetary gear drive were computed and analyzed. The influence of magnetization intensity and pole pair number to frequency forced responses is discussed. Results show that the dynamic displacement when only considering output excitation is larger than that when only considering input excitation,and magnetic parameters have obvious effects on the low frequency vibration amplitude of elements. When magnetization intensity and pole pair number are too large or too small, they will seriously affect the dynamic performance of the system. So, selecting rational system structure parameters is very important, which can avoid system elements generating larger vibration.

scholarly journals Estimation of Vegetation Structure Parameters From SMAP Radar Intensity Observations

2020 ◽  
pp. 1-17
Author(s):  
Thomas Jagdhuber ◽  
Carsten Montzka ◽  
Carlos Lopez-Martinez ◽  
Martin J. Baur ◽  
Moritz Link ◽  
...  
Keyword(s):  
Vegetation Structure ◽  
Structure Parameters

ULTRACOMPACT DIRECTION AND FREQUENCY FILTER CONSISTING OF ALTERNATING METAL LAYERS AND AIR LAYERS

2009 ◽  
Vol 23 (25) ◽  
pp. 2963-2970
Author(s):  
FEI XU ◽  
MING WEI
Keyword(s):  
Low Frequency ◽  
Evanescent Waves ◽  
Structure Parameters ◽  
Frequency Filtering ◽  
Frequency Filter ◽  
Frequency Range ◽  
Transmission Frequency ◽  
Transmission Properties ◽  
Air Layers ◽  
Metal Layers

The transmission properties of a periodic structure consisting of alternating metal layers and air layers are studied by numeric methods. The metal layers are the epsilon-negative (ENG) materials. The interaction of the evanescent waves in metal layers and propagation waves in air layers forms some special transmission bands. Given proper structure parameters, one transmission frequency only allows one incident direction in the low frequency range. This structure can simultaneously achieve frequency filtering and direction filtering.

scholarly journals Forest Canopy Height and Gaps from Multiangular BRDF, Assessed with Airborne LiDAR Data

2019 ◽  
Vol 11 (21) ◽  
pp. 2566 ◽  
Author(s):  
Qiang Wang ◽  
Wenge Ni-Meister
Keyword(s):  
Remote Sensing ◽  
Vegetation Structure ◽  
Near Infrared ◽  
Structural Parameters ◽  
Remote Sensing Data ◽  
Tree Height ◽  
Lidar Data ◽  
Structure Parameters ◽  
Infrared Band ◽  
Gap Fraction

Both vegetation multi-angular and LiDAR (light detection and ranging) remote sensing data are indirectly and directly linked with 3D vegetation structure parameters, such as the tree height and vegetation gap fraction, which are critical elements in above-ground biomass and light profiles for photosynthesis estimation. LiDAR, particularly LiDAR using waveform data, provides accurate estimates of these structural parameters but suffers from not enough spatial samplings. Structural parameters retrieved from multiangular imaging data through the inversion of physical models have larger uncertainties. This study searches for an analytical approach to fuse LiDAR and multiangular data. We explore the relationships between vegetation structure parameters derived from airborne vegetation LiDAR data and multiangular data and present a new potential angle vegetation index to retrieve the tree height and gap fraction using multi-angular data in Howland Forest, Maine. The BRDF (bidirectional reflectance distribution factor) index named NDMM (normalized difference between the maximum and minimum reflectance) linearly increases with the tree height and decreases with the gap fraction. In addition, these relationships are also dependent on the wavelength, tree species, and stand density. The NDMM index performs better in conifer (R = 0.451 for tree height and R = 0.472 for the gap fraction using the near infrared band) than in deciduous and mixed forests. It is superior in sparse (R = 0.569 for tree height and R = 0.604 for the gap fraction using the near infrared band) compared to dense forest. Moreover, the NDMM index is more strongly related to tree height and the gap fraction at the near infrared band than at the three visible bands. This study sheds light on the possibility of using multiangular data to map vegetation’s structural parameters in larger regions for carbon cycle studies through the fusion of LiDAR and multiangular remote sensing data.

Subsurface imaging with electrokinetically-induced seismoelectric signals generated by low-frequency seismic waves

2020 ◽  
Author(s):  
Dmitry Alekseev ◽  
Mikhail Gokhberg ◽  
Aleksandra Pliss ◽  
Aleksey Goncharov ◽  
Ilya Veklich
Keyword(s):  
Rayleigh Waves ◽  
Seismic Waves ◽  
Low Frequency ◽  
Basic Research ◽  
Structure Parameters ◽  
Subsurface Imaging ◽  
Subsurface Structure ◽  
Macroscopic Description ◽  
Basic Research Project

<p>In this study we focus on the coupled macroscopic description of the second-kind seismo-electric (SE) effect in the subsurface structure arising due to low-frequency seismic waves. Starting with the Biot poroelasticity model, we derive the equations of the coupled geomechanical-electromagnetic problem assuming mechanical excitation in the form of seismic waves (primarily Rayleigh waves), and create code for seismoelectric field simulation. We present the results of the feasibility study showing the promising possibilities for determination of non-uniform subsurface structure parameters and allowing a subsurface imaging in terms of rock elastic constants, conductivity and permeability.</p><p>The study was supported by the Russian Foundation for Basic Research (Project No. 20-05-00691).</p>

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