138 research outputs found
Thermodynamics and kinetics of reactions in protective coating systems
A study of the aluminization of Ni from packs containing various percentages of unalloyed Al confirmed that the surface aluminum content of specimens aluminized tends to decrease with time and consequently a simple parabolic law for the weight-gain vs. time relationship is not obeyed. The diffusivity-composition relationship in NiAl was examined, and a set of curves is presented. A numerical method for the calculation of coating dissolution rates was developed and applied to NiAl-Ni3Al type of coatings
Martian M2 peak behaviour in the dayside near-terminator ionosphere during ICMEs
The interplanetary coronal mass ejections (ICMEs) can pose significant
impacts on the Martian ionosphere, resulting in plasma depletion, variability,
and escape to space. However, the connections between the ICMEs and the
associated responses of the dayside near-terminator Martian ionospheric M2 peak
are not well understood. The present study primarily investigates the behaviour
of the ionospheric peak density (Nm) and height (hm) during the passage of
ICMEs using observations from the Radio Occultation Science Experiment (ROSE)
aboard MAVEN spacecraft. We have selected 8 such ICMEs (during 2017-2022) at
Mars from the existing catalogs and studied the ROSE electron density profiles
during quiet and disturbed time (ICMEs) for identical solar zenith angle range.
We observed the elevation of the M2 peak (hm ~4-16 km) during disturbed time
(ICMEs) with a decrease in Nm (0.41-2.8 * 10^10 m-3) in comparison to the quiet
time. The present study, for the first time, addressed the influence of ICMEs
on the M2 peak parameters (Nm and hm). We have proposed that the development of
large vertical pressure gradient and electron temperature enhancement are
plausible causes for ionospheric variability. Therefore, the present study
provides new insights to understand the peak plasma behaviour in the dayside
near-terminator ionosphere during ICMEs
Salvaging the values from the rejects of a by-product recovery plant
Two samples of table tailings (-147 pm and -74 pm in size) from refracÂŹtory linings of the precious metal recovery (PMR) plant of Indian Copper Complex (ICC), Ghatshila were received to study the possbility to reÂŹcover residual values of precious metals from them. Analyses, as reported by ICC, were 0.021% Au and 0.39% Ag for the -147 pm sample and 0.023% Au and 0.47%Ag for the -74 pm sample. Multi-Gravity Separator (MGS) studies, with varying design and operating variables, showed three fold upgradation - assay of Au improved from 0.023% to 0.076% and assay of Ag improved from 0.47% to 1.53%. The -74 pm sample yielded better results with MGS than the -147 pm sample
Gravity separation at variable 'g' for management of mineral wastes and pollution
The treatment of mineral wastes in the form of slimes and its utilisation, for management of pollution and conservation of mineral wealth, have become very important now-a-days. Multi Gravity Separator (MGS) is the latest inclusion to various gravity separation machines developed far the treatment offines and ultrafines. In this paper, results of recent studies carried out at NML with MGS using slimes of chromite ore, iron ore, phosphatic soil etc. are discussed to evaluate the effectiveness of the equipment for the treatment of slimes. In most of the cases, three to four fold upgradations have been achieved even at very fine sizes
Delivery of Subterranean Arsenic Removal in West Bengal
Environment and Developmen
Modified hydrocycloning for effective elimination of stubborn slimes
The present paper deals with the skillful exploitation of the extremely high shear fields inside a hydrocyclone to effectively eliminate a sticky slime from a phosphate ore before beneficiating the coarser fraction using conÂŹventional mineral processing techniques. Earlier studies on samples of the same ore at NML and abroad established that it was necessary to pass the ore through a series of three stages of desliming, each consisting of a step of rigorous attrition scrubbing followed by hydrocycloning, for effective elimination of the slime. With the new approach,by innovative modificaÂŹtions on the standard hydrocyclone design, it was possible to eliminate all the stages of attrition scrubbing while minimising the stages of hydrocycloning. It could be established that the modified technique not only yielded concentrate of grade comparable to that obtained by employÂŹing the earlier more complex flowsheet, it also improved the P205 recovery
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Evidence for the InâSitu Generation of Plasma Depletion Structures Over the Transition Region of Geomagnetic LowâMid Latitude
On a geomagnetic quiet night of October 29, 2018, we captured an observational evidence of the onset of dark band structures within the field-of-view of an all-sky airglow imager operating at 630.0 nm over a geomagnetic low-mid latitude transition region, Hanle, Leh Ladakh. Simultaneous ionosonde observations over New Delhi shows the occurrence of spread-F in the ionograms. Additionally, virtual and peak height indicate vertical upliftment in the F layer altitude and reduction in the ionospheric peak frequency were also observed when the dark band pass through the ionosonde location. All these results confirmed that the observed depletions are indeed associated with ionospheric F region plasma irregularities. The rate of total electron content index (ROTI) indicates the absence of plasma bubble activities over the equatorial/low latitude region which confirms that the observed event is a mid-latitude plasma depletion. Our calculations reveal that the growth time of the plasma depletion is âŒ2 h if one considers only the Perkins instability mechanism. This is not consistent with the present observations as the plasma depletion developed within âŒ25 min. By invoking possible Es layer instabilities and associated E-F region coupling, we show that the growth rate increases roughly by an order of magnitude. This strongly suggests that the Cosgrove and Tsunoda mechanism may be simultaneously operational in this case. Furthermore, it is also suggested that reduced F region flux-tube integrated conductivity in the southern part of onset region created conducive background conditions for the growth of the plasma depletion on this night
On the Long Lasting âCâTypeâ Structures in the Sodium Lidargram: The Lifetime of KelvinâHelmholtz Billows in the Mesosphere and Lower Thermosphere Region
In order to understand the characteristics of longâlasting âCâtypeâ structure in the Sodium (Na) lidargram, six cases from different observational locations have been analyzed. The Na lidargram, collected from lowâ, middleâ, and highâlatitude sites, show long lifetime of the Câtype structures which is believed to be the manifestation of KelvinâHelmholtz (KH) billows in the Mesosphere and Lower Thermosphere (MLT) region. In order to explore the characteristics of the longâlasting Câtype structures, the altitude profile of square of BruntâVĂ€isĂ€lĂ€ frequency in the MLT region has been derived using the temperature profile collected from the Na lidar instruments and the SABER instrument onboard TIMED satellite. It is found to be positive in the Câtype structure region for all the six cases which indicates that the regions are convectively stable. Simultaneous wind measurements, which allowed us to calculate the Richardson numbers and Reynolds numbers for three cases, suggest that the regions where the Câtype structure appeared were dynamically stable and nonturbulent. This paper brings out a hypothesis wherein the low temperature can increase the magnitude of the Prandtl number and convectively stable atmospheric region can cause the magnitude of Reynolds number to decrease. As a consequence, the remnant of previously generated KH billows in nearly âfrozenâinâ condition can be advected through this conducive region to a different location by the background wind where they can sustain for a long time without much deformation. These longâlived KH billows in the MLT region will eventually manifest the longâlasting Câtype structures in the Na lidargram
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