Daily variations ofE andF region drifts over Tiruchirapalli

Daily variations of the E-W and N-S components of ionospheric drifts, measured using closely spaced receiver method over Tiruchirapalli near magnetic equator, are described for the periods 1973–75 forE region and 1974–75 forF region. N-S component is not observed except for a few occasions during summer months for theE region. E-W component is generally eastward during night hours and westward during day hours. There is a large day-to-day variability in the magnitude as well as in the evening reversal time. Daily variations primarily consist of the diurnal component with average amplitude of about 90 m/sec forF region and of about 80 m/sec forE region. The drift speeds are found to decrease with magnetic activity. It is concluded that the abnormal electrojet region extends upto north of Tiruchirapalli in the Indian zone and drifts here can be used as a monitor of electric field.     

Geomagnetic disturbance effects on equatorial spreadF

Geomagnetic disturbance effects on the occurrence of range and frequency spread at Huancayo are studied for the period 1957–74. The occurrence of frequency spread is decreased on disturbed days forD-months andE-months while duringJ-months an increase is noted in the post-midnight period. The occurrence of range spread is decreased on disturbed days in the pre-midnight hours duringD andE-months. Post-midnight hours ofD andE-months and all hours of night duringJ-months show an increase of range spread on disturbed days, which is most prominent during low sunspot years. The mean occurrence of frequency spread (2300–0100 LT) and range spread (2000–2300 LT) decrease with increasing ΣKp. On the other hand, occurrence of range spread (0300–0500 LT) increases with increasing ΣKp, and is suggested as the consequence of the changes of the horizontal electric field in theF-region associated with the geomagnetic storms.     

Diffraction ofSH-waves originating from a moving point source by a rigid quarter space

Summary ApplyingWiener-Hopf techniques the diffraction ofSH-waves originating from a moving point source due to the presence of a step change in the elevation of the surface of a homogeneous half-space have been obtained. An interesting feature of resonance associated with the motion of a load at a velocityv ₀ ^–1 approachingv ₀ ^–1 has been observed.     

Thermal stresses in a finite cylinder having temperature varying linearly along the length prescribed on the curved surface

Summary The problem of a finite cylinder of isotropic material in which the temperature on the curved surface varies linearly along its length and has its ends in contact with smooth rigid insulating plates has been investigated in this paper.     

Photometric study of distant open clusters in the second quadrant: NGC 7245, King 9, King 13 and IC 166

We present a UBV CCD photometric study of four open clusters, NGC 7245, King 9, IC 166 and King 13, located between   l = 90°  and 135°. All are embedded in a rich Galactic field. NGC 7245 and King 9 are close together in the sky and have similar reddenings. The distances and ages are: NGC 7245, 3.8 ± 0.35 kpc and 400 Myr; King 9 (the most distant cluster in this quadrant), 7.9 ± 1.1 kpc and 3.0 Gyr. King 13 is 3.1 ± 0.3 kpc distant and 300 Myr old. King 9 and IC 166 (4.8 ± 0.5 kpc distant and 1 Gyr old) may be metal-poor clusters  ( Z = 0.008)  , as estimated from isochrone fitting. The average value of the distance of young clusters from the Galactic plane in the above longitude range and beyond 2 kpc (−47 ± 16 pc, for 64 clusters) indicates that the young disc bends towards the southern latitudes.     

Effect of nonlinear soil-structure interaction on seismic response of low-rise SMRF buildings

The nonlinear behavior of a soil-foundation system may alter the seismic response of a structure by providing additional flexibility to the system and dissipating hysteretic energy at the soil-foundation interface. However, the current design practice is still reluctant to consider the nonlinearity of the soil-foundation system, primarily due to lack of reliable modeling techniques. This study is motivated towards evaluating the effect of nonlinear soil-structure interaction (SSI) on the seismic responses of low-rise steel moment resisting frame (SMRF) structures. In order to achieve this, a Winkler-based approach is adopted, where the soil beneath the foundation is assumed to be a system of closely-spaced, independent, nonlinear spring elements. Static pushover analysis and nonlinear dynamic analyses are performed on a 3-story SMRF building and the performance of the structure is evaluated through a variety of force and displacement demand parameters. It is observed that incorporation of nonlinear SSI leads to an increase in story displacement demand and a significant reduction in base moment, base shear and inter-story drift demands, indicating the importance of its consideration towards achieving an economic, yet safe seismic design.     

Differences in tree species diversity and soil nutrient status in a tropical sacred forest ecosystem on Niyamgiri hill range, Eastern Ghats, India

We have quantitatively analyzed the tree species diversity with respect to soil nutrient status in three sites of a sacred forest ecosystem of Niyamgiri hill range,Eastern Ghats,India.Extensive field surveys and sampling were conducted in 3 sites of the hill range:Site 1 Pterocarpus dominated forest(PTF)(19°40’02.2" N and 83°21’23.1" E),Site 2 Mangifera dominated forest(MAF)(19°40’02.8" N and 83°21’40.8" E) and Site 3 Mixed forest(MIF)(19°36’47.1" N and 83°21’02.7" E).A total of 28 families,42 genera,46 tree species,and 286 individual trees were recorded on an area of 0.6 ha.Tree density varied between 470 and 490 individuals ha-1 and average basal area between 3.16 and 10.04 m2 ha-1.Shannon Index(H’) ranged from 2.34 to 4.53,Simpson’s Index ranged from 0.07 to 0.09,and equitability Index ranged from 0.7 to 1.34.The number of individuals was highest in the girth at breast height(GBH) class of 50-70 cm.The soil nutrient status of the three forest types was related to tree species diversity.The soil pH value of the three sites reflected the slightly acidic nature of the area.Species diversity was positively correlated with organic carbon and phosphorus and negatively with nitrogen,EC and pH.The results of the current study may be helpful to further develop a conservation planfor tree species in tropical sacred forest ecosystems.     

Investigating spatial contribution of land use types and land slope classes on soil erosion distribution under tropical environment

Natural Hazards - Increasing land occupancy for farming without conservation principles, particularly in the Indonesian island of Java, is resulting in a severe erosion problem. This study...     

Hook-shaped type-3 superposed fold in granulite,Badarama complex,Rengali province,India

International Journal of Earth Sciences -