Minutes of the extraordinary general body meeting of the Indian society of photo-interpretation and remote sensing held on 20th October, 1982     

H. S. Iyer 《Journal of the Indian Society of Remote Sensing》1982,10(3):69-70

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Problem area inventory of parts of Hoshiarpur district through photo-interpretation     

H. S. Iyer  A. N. Singh  Ram Kumar 《Journal of the Indian Society of Remote Sensing》1975,3(2):79-85

A systematic air-photo-interpretation procedure employing physiographic analysis has been used in preparing a quick inventory of the problem areas of parts of Hoshiarpur district of Punjab. The inventory has been prepared in respect of two selected areas viz. Hoshiarpur and Nangal on the basis of the study of photo-mosaic of Hoshiarpur district. The soil conservation needs of the predominant problem land units of both the areas are indicated.  相似文献   

A discussion on the lead isotope geochemistry of galenas from the Bambui group,Minas Gerais — Brazil     

S. S. Iyer 《Mineralium Deposita》1984,19(2):132-137

Lead isotope data on galenas from the Bambui group, Minas Gerais have been assembled and discussed. The isotope data, when plotted on the Single Stage Model III lead isotope development curve of Cumming and Richards (1975), yield 207/206 ages of 650±50 m.y and a linear array of data points with negative model ages, which intercept the growth curve at 650±60 m.y and 1850±150 m.y. The radiometric dates coincide with the two major orogenic episodes, the Brazilian and the Transamazonian. The data are interpreted in terms of a two stage model, where the source of lead for galenas, formed during Brazilian orogeny, is the basement rocks of Transamazonian age. The calculated Th/U value for the source rock is 2.9±0.3. The geographical distribution of lead isotope ratios shows a zonation in Vazante Paracatu region, an area containing large deposits of zinc. The implication of the distribution on the ore formation is discussed.  相似文献   

Use of aerial photographs for soil erosion studies     

H. S. Iyer 《Journal of the Indian Society of Remote Sensing》1974,2(2):33-45

Using air photos soil loss from agricultural fields has been estimated in respect of the Rana and granitic areas of south-west of Merida, Spain, applying the universal soil-loss equation. The results of soil-loss have been shown as soil erosion susceptibility and soil erosion hazard classes. This study has shown that large scale aerial photographs (1:12500) are quite useful in evaluating many of the parameters of the universal soil loss equation with limited field checks.  相似文献   

Characteristics of VHF scintillations in the equatorial anomaly crest region in India     

K. N. Pathak  R. D. Jivrajani  H. P. Joshi  K. N. Iyer 《Annales Geophysicae》1995,13(7):730-739

The characteristics of ionospheric scintillations at Rajkot in the equatorial anomaly crest region in India are described for the years 1987–1991 by monitoring the 244-MHz transmission from the satellite FLEETSAT. This period covers the ascending phase of solar cycle 22. Scintillations occur predominantly in the pre-midnight period during equinoxes and winter seasons and in the post-midnight period during summer season. During equinoxes and winter, scintillation occurrence increases with solar activity, whilst in summer it is found to decrease with solar activity. Statistically, scintillation occurrence is suppressed by magnetic activity. The characteristics observed during winter and equinoxes are similar to those seen at the equatorial station, Trivandrum. This, coupled with the nature of the post-sunset equatorial F-region drift and h‘F variations, supports the view that at the anomaly crest station, scintillations are of equatorial origin during equinox and winter, whilst in summer they may be of mid-latitude type. The variations in scintillation intensity (in dB) with season and solar activity are also reported.  相似文献   

Morphotectonic and petrological variations along the southern Central Indian Ridge     

Ranadhir Mukhopadhyay  Sridhar D. Iyer  Dwijesh Ray  S. M. Karisiddaiah  Rajendra K. Drolia 《International Journal of Earth Sciences》2016,105(3):905-920

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Distribution and Origin of Seamounts in the Central Indian Ocean Basin     

Pranab Das  Sridhar D. Iyer  V. N. Kodagali  K. S. Krishna 《Marine Geodesy》2005,28(3):259-269

Approximately 200 seamounts of different dimensions have been identified, from multibeam bathymetry maps of the Central Indian Ocean Basin (CIOB) (9°S to 16°S and 72°E to 80°E), of which 61% form eight chains that trend N-S. The seamounts are clustered above and below 12°S latitude. Area II (9°-12°S) shows a concentration of smaller seamounts (≤400 m height), and area I (12°-15°S) has a mixed population (including both less and more than 400 m height). Inspite of the differences in their height, the seamounts of these eight chains are morphologically (slope angle, flatness, basal width) corelatable. Furthermore, we suggest that height-width ratio could be useful in identifying the style of seamount eruption. The seamount chains in the CIOB probably originated from propagative fractures and were produced between 61 and 52 Ma (chrons A26 to A23) as a result of the interaction between the conjugate crusts of the Central Indian and Southeast Indian Ridges during the Indo-Eurasian collision event.  相似文献   

Comparison of internal features and microchemistry of ferromanganese crusts from the Central Indian Basin     

S. D. Iyer 《Geo-Marine Letters》1991,11(1):44-50

SEM/probe analyses of two ferromanganese crusts from the Central Indian Basin, formed on basalt substrate, reveal botryoids and cusps. The botryoids composed of δ-MnO₂, are enriched in Co, and the cusps and laminations with todorokite are enriched in Ni and Cu. Microstructural and elemental variations, from the ferromanganese crust outer surface to the basalt substrate, probably reflect changes in the accretion or in the source of metals. The major source of the crust metals is the seawater, as indicated by the Mn/Fe ratio of unity and by the microstructures.  相似文献   

Some investigations to quantify hysteresis associated with water retention behaviour of fine-grained soils     

Kannan K. R. Iyer  Jeevan Joseph  Rakshith Shetty 《Geomechanics and Geoengineering》2018,13(4):264-275

The soil water retention characteristics curve (SWRC) has been reported to be quite useful for estimation of unsaturated soil properties. However, the uniqueness of SWRC is questionable due to hysteresis associated with the drying- and wetting-path SWRCs and this poses great challenge in utilising the SWRC for reliable estimation of unsaturated soil properties. Although hysteresis associated with SWRCs has been extensively studied for coarse-grained soils, due to limited studies on wetting-path SWRC for fine-grained soils, the hysteresis for fine-grained soils is not well understood. The present work attempts to address this gap, by studying the drying- and wetting-path SWRCs for eight different fine-grained soils by employing Dew point Potentiameter (WP4C®), Environmental Chamber and Controlled Water Sprinkling method. The study employs the concept of ‘Suction Hysteresis’, ψ_h, for quantification of hysteresis. Further, the influence of various soil-specific properties on the variation of ψ_h-water content relationship (viz., slope of variation of suction hysteresis, S_ψh) has also been studied and demonstrated. The findings of the study are quite encouraging and it has been realised that extensive studies on soils of different characteristics would be quite useful in quantifying the variation of SWRC during drying and wetting cycles.  相似文献   

Water retention characteristics of swelling clays in different compaction states     

Kannan K. R. Iyer  Jeevan Joseph  Bruna C. F. L. Lopes  D. N. Singh  Alessandro Tarantino 《Geomechanics and Geoengineering》2018,13(2):88-103

The soil–water retention (SWR) characteristics of the clays play an important role in controlling their engineering behaviour, particularly, in the unsaturated state. Although, researchers have attempted to understand the water retention characteristics of the clays in their reconstituted or remoulded state, such studies are rare for the clays in their intact state. In this context, it becomes important to understand the influence of initial state of compaction, which would create different pore and fabric structure (viz., microstructure), on the water retention characteristics of the clays. With this in view, SWR behaviour was experimentally determined for the swelling clays (dried from different compaction states, viz., intact, reconstituted and remoulded) by employing Dewpoint PotentiaMeter (WP4C®). The changes in the pore size distribution of the clays at different stages of drying cycle were also studied by employing the Mercury Intrusion Porosimetry. The study reveals that the SWR curves for the intact and reconstituted specimens of the clays converge beyond a certain stage of drying. Also, a critical analysis of changes in the pore structure of the swelling clay specimens, during drying, indicates that the progressively deforming pore structure plays an important role in controlling its water retention characteristics to a great extent.  相似文献