Results 281 to 290 of about 4,461,069 (318)

On the correct estimation of gap fraction: How to remove scattered radiation in gap fraction measurements?

Agricultural and Forest Meteorology, 2013
Abstract Correct estimates of gap fraction are essential for quantifying canopy architectural variables, such as leaf area and clumping indices, which modify land–atmosphere interactions. However, gap fraction measurements from optical sensors are contaminated by radiation that is scattered by plant elements and ground surfaces.
Hideki Kobayashi, Hideki Kobayashi, Y. Ryu, Y. Ryu, D. Baldocchi, J. Welles, J. Norman   +6 more
semanticscholar   +2 more sources

Canopy Gap Fraction

Encyclopedia of Wildfires and Wildland-Urban Interface (WUI) Fires, 2020

semanticscholar   +2 more sources

Bias in lidar-based canopy gap fraction estimates

Remote Sensing Letters, 2013
Leaf area index and canopy gap fraction (GF) provide important information to forest managers regarding the ecological functioning and productivity of forest resources. Traditional measurements such as those obtained from hemispherical photography (HP) measure solar irradiation, penetrating the forest canopy, but do not provide information regarding ...
S. Vaccari, M. van Leeuwen, K. Calders, N. Coops, M. Herold   +4 more
semanticscholar   +2 more sources

Estimating 3D canopy's gap fraction using photographic method

2011 19th International Conference on Geoinformatics, 2011
Gap fraction, which is the probability that a light penetrates through the canopy unintercepted and reaches the surface under the canopy, is characteristic geometric parameter of canopy's structure, and has great influence on radiative transfer of the vegetation.
Jiangeng Wang, Xuezhi Feng, P. Xiao
semanticscholar   +2 more sources

Retrieval of Canopy Gap Fraction From Terrestrial Laser Scanning Data Based on the Monte Carlo Method

IEEE Geoscience and Remote Sensing Letters, 2022
Canopy gaps affect the spatial distribution of radiation in the canopy. The estimation of gap fraction (GF) is important for the study of leaf area index (LAI).
Yifan Xu, Shihua Li, Han You, Ze He, Zhonghua Su   +4 more
semanticscholar   +1 more source

A new method to estimate clumping index integrating gap fraction averaging with the analysis of gap size distribution

Canadian Journal of Forest Research, 2019
Estimates of clumping index (Ω) are required to improve the indirect estimation of leaf area index (L) from optical field-based instruments such as digital hemispherical photography (DHP). A widely used method allows estimation of Ω from DHP using simple
F. Chianucci, Jie Zou, Peng Leng, Yinguo Zhuang, C. Ferrara   +4 more
semanticscholar   +1 more source

Beware of “Gaps” in Students’ Fraction Conceptions

Mathematics Teacher: Learning and Teaching PK-12, 2023
Many students have a dominant part-whole conception of fractions. We examine why this is problematic and explore strategies to move students beyond this limitation.
Patrick L. Sullivan, Joann E. Barnett, Kurt Killion   +2 more
openaire   +1 more source

Grating structures with symmetric fractionally organized gaps

Microwave and Optical Technology Letters, 2001
AbstractIt is well known that grating structures with subgratings separated by small identical gaps (for example, quarter‐wavelength gaps) create a transmission window in the middle of the reflectivity spectrum. In this paper, we analyze structures with mirror symmetry with respect to their centers, but with gaps at both ends that continuously decrease
Carmem L. Barbosa, Rogério M. Cazo, Haroldo T. Hattori   +2 more
openaire   +1 more source

Collective-Excitation Gap in the Fractional Quantum Hall Effect

Physical Review Letters, 1985
We present a theory of the collective excitation spectrum in the fractional quantum Hall-effect regimes, in analogy with Feynman's theory for helium. The spectrum is in excellent quantitative agreement with the numerical results of Haldane. Within this approximation we prove that a finite gap is generic to any liquid state in the extreme quantum limit ...
, Girvin, , MacDonald, , Platzman
openaire   +2 more sources

Excitation gap in the fractionally quantized Hall effect

Physical Review B, 1987
It is shown that due to disorder the excitation gap in the fractionally quantized Hall effect is reduced and goes to zero at a critical magnetic field ${B}_{c}$. Impurity scattering defines a lower critical field ${B}_{c1}$ and surface roughness scattering an upper critical field ${B}_{c2}$.
openaire   +2 more sources