The dynamical characteristics of atmospheric aerosols over the Indo-Gangetic (IG) region are primarily dependent on the geographical settings and meteorological conditions. Detailed analysis of multi satellite data and ground observations have been carried out over three different cities i.e. Kanpur, Greater Noida and Amritsar during 2010-2013. Level-3 Moderate Resolution Imaging Spectroradiometer (MODIS) terra daily global grid product with spatial resolution of 1° × 1° shows the mean AOD at 500 nm wavelength value of 0.73, 0.70 and 0.67 with the standard deviation of 0.43, 0.39 and 0.36 respectively over Amritsar, Greater Noida and Kanpur. Our detailed analysis shows characteristic behavior of aerosols from west to east in the IG region depending upon the proximity of desert regions of Arabia. We have observed large influx of dusts from the Thar desert and Arabia peninsula during pre-monsoon season (April–June), highly affecting Amritsar which is close to the desert region.
An automatic and accurate technique
for angular positioning of mask with
respect to wafer is reported.. Alignment
marks are in the form of gratings and the
moire signal is obtained by the relative
displacement between the gratings. The
higher slope region of the moire signal
is used to obtain higher sensitivity and
better position control accuracy. The
experiments are performed with 25 micrometer pitch gratings and Piezo-
Electric Transducer is used for the
angular displacement. The angular
-7
accuracy of the order of 2 x 10 radian is
reported with a time constant of 0.2 sec.
In the recent years, use of moire
interference technique for mask to wafer
alignment has attracted much attention
especially in VLSI fabrication technology
where a highly accurate linear and
angular positioning is involved. In this
technique the alignment marks are in the
form of gratings.
A laser beam is passed normally
through a mask grating and reflected from
the wafer grating. Intensity variation in
the reflection mode due to relative
angular rotation is detected by a
photodetector and converted into the
electrical signal, known as moire signal.
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