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REVIEW OF AVAILABLE PRODUCTS OF LEAF AREA INDEX AND THEIR SUITABILITY OVER THE FORMERLY SOVIET CENTRAL ASIA
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M W Kappas, P A Propastin
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Leaf area index (LAI) is a key biophysical variable for environmental process modelling. Remotely sensed data have become the
primary source for estimation of LAI at the scales from local to global. A summary of existing LAI data sets and a discussion
of their appropriateness for the formerly Soviet Central Asia, especially Kazakhstan, which is known for its huge grassland area
(about 2 million km2), are valuable for environmental modelling in this region. The paper gives a brief review of existing global
LAI products, such as AVHRR LAI, MODIS LAI, and SPOT-VEGETATION LAI, and shows that validation of these products in
Kazakhstan as well as in other countries of the formerly Soviet Central Asia has not been carried out yet. Apart from the global
LAI products, there are just a few data sets retrieved by remote sensing methods at subregional and regional scales in Kazakhstan.
More research activities are needed to focus on the validation of the available global LAI products over the formerly Soviet Central
Asia and developing new LAI data sets suitable for application in environmental modelling at different scales in this region....
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PHOTONIC CRYSTAL FIBERS FOR SENSING APPLICATIONS
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Ana M R Pinto, Manuel Lopez-Amo
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Photonic crystal fibers are a kind of fiber optics that present a diversity of new and improved features beyond what conventional
optical fibers can offer. Due to their unique geometric structure, photonic crystal fibers present special properties and capabilities
that lead to an outstanding potential for sensing applications. A review of photonic crystal fiber sensors is presented. Two different
groups of sensors are detailed separately: physical and biochemical sensors, based on the sensor measured parameter. Several
sensors have been reported until the date, and more are expected to be developed due to the remarkable characteristics such fibers
can offer....
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A REVIEW: CARBON NANOTUBE-BASED PIEZORESISTIVE STRAIN SENSORS
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Waris Obitayo, Tao Liu
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The use of carbon nanotubes for piezoresistive strain sensors has acquired significant attention due to its unique electromechanical
properties. In this comprehensive review paper, we discussed some important aspects of carbon nanotubes for strain sensing at
both the nanoscale and macroscale. Carbon nanotubes undergo changes in their band structures when subjected to mechanical
deformations. This phenomenon makes them applicable for strain sensing applications. This paper signifies the type of carbon
nanotubes best suitable for piezoresistive strain sensors. The electrical resistivities of carbon nanotube thin film increase linearly
with strain, making it an ideal material for a piezoresistive strain sensor. Carbon nanotube composite films, which are usually fabricated
by mixing small amounts of single-walled or multiwalled carbon nanotubes with selected polymers, have shown promising
characteristics of piezoresistive strain sensors. Studies also show that carbon nanotubes display a stable and predictable voltage response
as a function of temperature....
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