Wet tropospheric range corrections for radar altimeter over Indian Ocean

A relation between wet tropospheric range correction and precipitable water has been proposed for correcting satellite-borne radar altimeter data over the Indian Ocean region for south-west monsoon months (May-July). The proposed regional relation, which used data from May-July 1979, gave an rms error of 1·53 mm as compared to rms error of 4·54mm for Liu and Mock's relation using global data. The precipitable water values ranged from 30 mm to 75 mm with larger concentration of data points between 40 to 65 mm. The wet tropospheric range correction could be useful for analysing ERS-1 radar altimeter data over Indian oceans whose dual angle split thermal IR channels and/or microwave channels could be used for estimating total precipitable water with an accuracy of 2 to 4 mm.

We have also investigated the variability of equivalent temperature with precipitable water and air temperature and found that they are not strongly correlated with each other.     

Iron-substituted AB5-type MH electrode

The present investigation is aimed to study MmNi₅-type (Mm = Mischmetal) hydrogen storage alloys with composition, Mm_0·8La_0·2Ni_3·7Al_0·38Co_0·3Mn_0·6?x Mo_0·02Fe _x (x = 0, 0·1, 0·2 and 0·3). The alloys are synthesized by radio-frequency induction melting. To study their electrochemical properties via measurements of discharge capacity, activation process, rate capability and cyclic stability, electrodes are fabricated using as-synthesized and annealed version of the alloys. The maximum discharge capacity is recorded as 288 mAhg^?1 for the iron concentration, x = 0·1, as compared to 270 mAhg^?1 for the alloy electrode without iron. Similarly, 99% cyclic stability is observed in annealed alloy electrode (x = 0·1) as compared to 78% in the alloy electrode without iron. Hence, small amount of iron-substitution (x = 0·1) in the alloy is found to improve the electrochemical properties. This improvement is thought to be due to less pulverization of the alloy in electrochemically-cycled alloy, as confirmed through structural and microstructural characterizations carried out by X-ray diffraction phase analysis and scanning electron microscopy of as-fabricated and electrochemically-cycled electrodes.     

Fast response time alcohol gas sensor using nanocrystalline F-doped SnO2 films derived via sol–gel method

Pure and fluorine-modified tin oxide (SnO₂) thin films (250–300 nm) were uniformly deposited on corning glass substrate using sol–gel technique to fabricate SnO₂-based resistive sensors for ethanol detection. The characteristic properties of the multicoatings have been investigated, including their electrical conductivity and optical transparency in visible IR range. Pure SnO₂ films exhibited a visible transmission of 90% compared with F-doped films (80% for low doping and 60% for high doping). F-doped SnO₂ films exhibited lower resistivity (0· 12 × 10^???4 Ω  cm) compared with the pure (14·16 × 10^???4 Ω  cm) one. X-ray diffraction and scanning electron microscopy techniques were used to analyse the structure and surface morphology of the prepared films. Resistance change was studied at different temperatures (523–623 K) with metallic contacts of silver in air and in presence of different ethanol vapour concentrations. Comparative gas-sensing results revealed that the prepared F-doped SnO₂ sensor exhibited the lowest response and recovery times of 10 and 13 s, respectively whereas that of pure SnO₂ gas sensor, 32 and 65 s, respectively. The maximum sensitivities of both gas sensors were obtained at 623 K.     

Correlation between optical emission spectra and the process parameters of a 915 MHz microwave plasma CVD reactor used for depositing polycrystalline diamond coatings

In this paper, the hydrogen and hydrogen-methane mixed plasma have been generated inside a 33 cm diameter quartz bell jar with a low power (9 KW) and lower frequency 915 MHz microwave plasma chemical vapor deposition system. The reactor is being used for growing polycrystalline diamond (PCD) over large area (100 mm). The generated plasma is diagnosed by in situ optical emission spectroscopy method with wave length ranging from 200 to 900 nm. The effects of microwave power, chamber pressure and gas concentration on plasma characteristics have been studied in this work. Within the optical range, Balmer H _α , H _β , C₂swan band and CH lines have been detected at the wavelengths of 655.95, 485.7, 515.82 and 430.17 nm, respectively. It has been observed that for hydrogen plasma, the amount of transition from hydrogen atom inner shell 3 to 2 (H _α ) is almost constant with increasing microwave (MW) power (from 2000 to 2800 W) and pressure (from 15 to 30 Torr) initially, after that it increases with further increase of MW power and pressure, whereas, the transition from 4 to 2 (H _β ) is slowly increased with increasing MW power and pressure. For hydrogen-methane plasma, intensities of C₂ swan band, i.e., the transitions from D³π _g to A³π _μ energy levels, are also increased with the increasing microwave power and reactor pressure. It has been observed that the radicals present in the plasma are affected by variation of different reactor parameters like pressure, MW power, CH₄ concentration, etc.