Displacement produced in an elastic half-space by the impulsive torsional motion of a circular ring source

Summary In this paper the problem of disturbance in an elastic semi-infinite medium due to the torsional motion of a circular ring source on the free surface of a medium are studied. Two cases, when the medium is either homogeneous or inhomogeneous, are treated. In order to solve the problem, the Laplace transform and the Hankel transform and the Laplace inversion by Cagniard's method as modified byDe Hoop (1959) are applied. Finally, the integrals for displacement are evaluated numerically. The displacement on the free surface as a function of time is shown by means of graphs, in the case of both a homogeneous and an inhomogeneous medium, indicating clearly the variation in displacement due to the presence of an inhomogeneity.     

Distortion of planar structures around rigid spherical bodies

Theoretical and experimental results show that determination of sense of rigid rotation from drag-patterns of foliation around a rigid spherical inclusion (such as a porphyroblast of garnet) is not as simple as was previously thought. An asymmetric drag-pattern can develop even when the bulk deformation is non-rotational, provided a pre-existing foliation was initially at an angle to the principal axes of strain.In simple shear, the drag-pattern of a pre-existing foliation around the rigid inclusion may belong to any one of the following four types:

1. (1) asymmetric pattern, with the same sense of drag all over the contact.

2. (2) more or less symmetrical pattern, with different senses of drag at different parts of the contact.

3. (3) asymmetrical pattern, with different senses of drag.

4. (4) pattern with inward bowing of foliation (i.e. convex toward the rigid inclusion).

The geometry of the distorted foliation will depend on the amount of simple shear and the initial angle between the pre-existing foliation and the direction of simple shear.If the development of schistosity and the subsequent development of drag around a rigid porphyroblast are results of the same continuous simple-shear movement, a wellpreserved drag-pattern may be utilized to confirm that the schistosity initially developed perpendicular to the maximum finite compressive strain, provided the total deformation is not very large.     

Disturbance produced in an elastic half-space by impulsive normal pressure

Summary The displacement produced in the half-space by uniform impulsive pressure acting over a circular portion of the surface has been obtained in terms of definite integrals. FollowingCagniard andGarvin, the displacement at an interior point on the axis of symmetry has been calculated. The approximate displacement at points far off from the axis of symmetry has been obtained by using saddle point method and Tauberian limit theorem.     

Petrography and metamorphism of the lower Gondwana (Permian) coal of Rangit Valley, eastern Himalays, India

A triangular outlier of coal-bearing lower Gondwana rocks comprises a tectonic window within the Precambrian metamorphic terrain of the Rangit Valley, in the eastern Himalays of India. Due to a series of tectonic events which took place during the Mesozoic and Tertiary the succession has become reversed and the coal has undergone severe physical, chemical, microstructural and optical changes. Studies reveal that (1) the rank of the coal prior to tectonism was low, (2) the coal underwent oxidation in the peat forming stage and during subsequent orogenic stages but effect of oxidation on the properties of coal was insignificant, (3) the coal reached its present abnormally high rank mainly due to heating under tectonic pressure and (4) the heat which was generated due to tectonic pressure, affected all the coal seams of this belt.     

Fractal-based dimensionality reduction of hyperspectral images

The spectral reflectance of any pixel in a remote sensing image depends on the characteristics of the particular land cover (LC) present in the Instantaneous Field of View (IFOV) of the sensor. The fractal dimension of the spectral reflectance curve (SRC) of any pixel can thus be visualized as a representation of the characteristics of the LC. Based on this, a fractalbased method for reduction of the dimensionality of Hyperspectral (HS) images has been investigated. The fractal dimension (FD) of SRC has been calculated by adopting a method based on Hausdorff metric that reduces the dimensionality from N HS bands to a single feature incorporating the characteristics associated with each of the bands. Further, it has been established that FD values can be used as a feature to identify anomaly in water cover.     

Impact of climate on tea production: a study of the Dooars region in India

Theoretical and Applied Climatology - The Dooars region of West Bengal in India is a major tea producing region that contributes around 25% of the national tea yield. Changes in weather patterns...     

Flare-like activity in Be stars HR 7403 and .8762

Rapid spectrophotometric observations of two Be stars were carried out on several nights between November 1984 and December 1985. During the interval of our observations we could not detect any ultra-rapid variations in the spectra of the studied stars except a few flare-like events. The flare-like event of HR 7403 was recorded only at H and that for HR 8762 (o And) was observed (two events) from H photometric observations. Time-scales of these emission events were around few minutes and the total energy liberated by the events were of the order of 10³⁴ to 10³⁷ ergs.     

Influence of strong motion characteristics on permanent displacement of slopes

Landslides triggered by moderate to major earthquakes are a recognized seismic hazard. Arias Intensity (I _a) is a key intensity measure of the ground motion, but significant duration is widely used to define strong motion duration. We calculate Newmark’s displacements using earthquake records bracketing a broad range of Arias Intensity and significant duration employing Newmark’s rigid block method and a number of yield accelerations. Total landslide displacement increases with the increase in the energy content of the ground motion (I _a) above a threshold. Such threshold may be expressed as a function of yield acceleration of the slope regardless of the ground motion characteristics. Newmark displacement decreases with increasing duration for earthquakes with similar energy content. The wide scatter in the results converges when using formal dimensional analysis. Self-similar symmetry may facilitate the assessment of the performance of slopes during earthquakes. The mathematical framework for probabilistic determination of landslides displacement may be a useful aid to estimate the likelihood of landslide hazards provided that the geotechnical properties of the slopes are known.     

Temporal MODIS data for identification of wheat crop using noise clustering soft classification approach

In this study, temporal MODIS-Terra MOD13Q1 data have been used for identification of wheat crop uniquely, using the noise clustering (NC) soft classification approach. This research also optimises the selection of date combination and vegetation index for classification of wheat crop. First, a separability analysis is used to optimise the date combination for each case of number of dates and vegetation index. Then, these scenes have undergone for NC soft classification. The resolution parameter (δ) was optimised for the NC classifier and found to be a value of 1.6 × 10⁴ for wheat crop identification. Classified outputs were analysed by receiver operating characteristics (ROC) analysis for sub-pixel detection. Highest area under the ROC curve was found for soil-adjusted vegetation index corresponding to the three different phenological stages data sets. From this study, the data sets corresponding to the Sowing, Flowering and Maturity phenological stages of wheat crop were found more suitable to identify it uniquely.