Current Issue : April - June Volume : 2013 Issue Number : 2 Articles : 5 Articles
The use of carbon nanotubes for piezoresistive strain sensors has acquired significant attention due to its unique electromechanical\r\nproperties. In this comprehensive review paper, we discussed some important aspects of carbon nanotubes for strain sensing at\r\nboth the nanoscale and macroscale. Carbon nanotubes undergo changes in their band structures when subjected to mechanical\r\ndeformations. This phenomenon makes them applicable for strain sensing applications. This paper signifies the type of carbon\r\nnanotubes best suitable for piezoresistive strain sensors. The electrical resistivities of carbon nanotube thin film increase linearly\r\nwith strain, making it an ideal material for a piezoresistive strain sensor. Carbon nanotube composite films, which are usually fabricated\r\nby mixing small amounts of single-walled or multiwalled carbon nanotubes with selected polymers, have shown promising\r\ncharacteristics of piezoresistive strain sensors. Studies also show that carbon nanotubes display a stable and predictable voltage response\r\nas a function of temperature....
The paper describes a new transducer dedicated for evaluation of a duplex stainless steel (DSS). Different phases which exist in\r\nDSS have influence on mechanical as well as on electrical properties. Therefore, an eddy current transducer was utilized. In order\r\nto achieve high sensitivity, a differential type of the transducer was selected. The performance of the transducer was verified by\r\nutilizing the samples which had a different amount of sigma phase....
This paper presents a method of health monitoring for coated steel belts in an elevator system by measuring the electrical resistance\r\nof the ropes embedded in the belt. A model on resistance change caused by fretting wear and stress fatigue has been established.\r\nTemperature and reciprocating cycles are also taken into consideration when determining the potential strength degradation of the\r\nbelts. It is proved by experiments that the method could effectively estimate the health degradation of the most dangerous section\r\nas well as other ones along the whole belts....
Photonic crystal fibers are a kind of fiber optics that present a diversity of new and improved features beyond what conventional\r\noptical fibers can offer. Due to their unique geometric structure, photonic crystal fibers present special properties and capabilities\r\nthat lead to an outstanding potential for sensing applications. A review of photonic crystal fiber sensors is presented. Two different\r\ngroups of sensors are detailed separately: physical and biochemical sensors, based on the sensor measured parameter. Several\r\nsensors have been reported until the date, and more are expected to be developed due to the remarkable characteristics such fibers\r\ncan offer....
Leaf area index (LAI) is a key biophysical variable for environmental process modelling. Remotely sensed data have become the\r\nprimary source for estimation of LAI at the scales from local to global. A summary of existing LAI data sets and a discussion\r\nof their appropriateness for the formerly Soviet Central Asia, especially Kazakhstan, which is known for its huge grassland area\r\n(about 2 million km2), are valuable for environmental modelling in this region. The paper gives a brief review of existing global\r\nLAI products, such as AVHRR LAI, MODIS LAI, and SPOT-VEGETATION LAI, and shows that validation of these products in\r\nKazakhstan as well as in other countries of the formerly Soviet Central Asia has not been carried out yet. Apart from the global\r\nLAI products, there are just a few data sets retrieved by remote sensing methods at subregional and regional scales in Kazakhstan.\r\nMore research activities are needed to focus on the validation of the available global LAI products over the formerly Soviet Central\r\nAsia and developing new LAI data sets suitable for application in environmental modelling at different scales in this region....
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