Experimental studies on sloshing behavior due to horizontal movement of liquids in baffled tanks     

P.K. Panigrahy  U.K. Saha  D. Maity 《Ocean Engineering》2009,36(3-4):213-222

A series of experiments have been carried out in a developed liquid sloshing setup to estimate the pressure developed on the tank walls and the free surface displacement of water from the mean static level. The square tank attached to a shaking table can be moved to and fro by a cam arrangement driven by a DC motor. Pressure and displacement studies are done on the basis of changing excitation frequency of the shaking table and fill level in the tank. Experiments were carried out without and with baffles, and the consequent changes in the parameters are observed.  相似文献   

Low-latitude infrasonics associated with geomagnetic activity     

B. J. Srivastava  R. Venkatachari  A. K. Saha 《Geophysical Journal International》1982,71(1):241-245

Summary. Certain associated fluctuations in geomagnetic records and infrasonic pressure variations at ground level noted at Hyderabad and Delhi are discussed with the help of simultaneous records taken during 1980. Typical infrasound signals are noted, apparently generated by the magnetic substorms in the auroral zones and travelling down to near tropical latitudes with speeds in the range of 400–500m s^-1. Characteristic signatures in infrasound records, corresponding to SSCs and storm time fluctuations are also noted, but only when substorms are associated with the storms.  相似文献   

Parameters Optimization of Geotechnical Problem Using Different Optimization Algorithm     

Sukanta Nama  Apu Kumar Saha  Sima Ghosh 《Geotechnical and Geological Engineering》2015,33(5):1235-1253

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Paleoenvironment of deposition of the Dupi Tila Formation,Lalmai Hills,Comilla, Bangladesh     

Mrinal Kanti Roy  Syed Samsuddin Ahmed  Tapas Kumar Bhattacharjee  Sultan Mahmud  Md. Moniruzzaman  Md. Masidul Haque  Sudip Saha  Md. Ismail Molla  Pulin Chandra Roy 《Journal of the Geological Society of India》2012,80(3):409-419

The Dupi Tila Formation is composed of yellow to light brown medium to very fine moderately hard to loose sandstone, siltstone, silty clay, mudstone and shale with some conglomerates with clasts of petrified wood. The lithofacies of matrix supported conglomerate, trough cross bedded conglomerate, massive sandstone, trough cross bedded sandstone, planar cross bedded sandstone, ripple cross laminated sandstone-siltstone, flaser laminated sandstone-shale, lenticular laminated sandstone-siltstone-shale, parallel laminated sandstone-siltstone, wavy laminated shale, parallel laminated blue shale, and mudstone are delineated within this formation. Based on the grain size, sedimentary structures, water depth and genesis of individual facies, facies are grouped into three types of facies associations like (i) coarse-grained conglomerate facies association in relation to tractive current deposits of alluvial fan set up at the base of litho-succession (FAC), (ii) medium to fine-grained sandstone-siltstone-mudstone facies association or facies association in relation to strong tide (FAT) characterizing the middle part of litho-succession, (iii) very fine-grained sandstone-siltstone-mudstone facies association in relation to less frequent weak tide or heterolithic facies association (FAHL) characterizing upper part of litho-succession and shallow marine facies association (FASM) composing the uppermost litho-succession. Presence of gluconite indicates that the depositional environment was shallow to deep marine. The dominant paleoflow direction during the deposition of Dupi Tila Formation was toward southeast to southwestern direction. The rivers were of braided type at the piedmont alluvial depositional set up at the lower part, which later changed to estuarine-tidal flat type environmental set up in the middle part to upper part and paleo-environment was shallow marine in the uppermost part.  相似文献   

Simple statistical and mineralogical studies as petrogenetic indicator for neoproterozoic mylliem porphyritic granites of east Khasi Hills,Meghalaya, Northeastern India     

Sampa Hazra  Pritam Saha  Jyotisankar Ray  Avijit Podder 《Journal of the Geological Society of India》2010,75(5):760-768

The porphyritic granite body (∼ 600 Ma) around Mylliem (25°32′N: 91°52′E), east Khasi hills district, Meghalaya occurs as a distinct intrusive body into the host rock of low- grade meta-sediments belonging to Proterozoic Shillong Group. The porphyritic granite body manifests prominent lath- shaped feldspar phenocrysts giving rise to dominant porphyritic texture. Further, this porphyritic granite body is characterized by primary foliation (defined by parallely arranged feldspar laths), tongues and appophyses and xenoliths of older metamorphics. Petrographically, the Mylliem porphyritic granite is grey leucocratic, coarse grained, phanerocrystalline with modal variants ranging from granite to granodiorite tending to tonalite. Simple statistical studies based on correlation coefficient values involving modal variables of the Mylliem porphyritic granite bodies appear significant in majority of the cases indicating magmatic crystallization. Use of relevant thermometric method indicates temperature of equilibration of the body in the range of 369°C to 507°C. The crystallization of the Mylliem porphyritic granite pluton initiated at an average lithostatic pressure in the tune of ∼11 Kb followed by dominant P_H2O controlled milieu. Spatially projected mineralogical parameters suggest a general trend of the magmatic cooling of the body from margin inward with sudden influx of volatile matters that occasionally offsets mineralogical trends.  相似文献   

Intracontinental thrusts and inclined transpression along eastern margin of the East Dharwar craton, India     

Dilip Saha  S. Chakraborti  V. Tripathy 《Journal of the Geological Society of India》2010,75(1):323-337

Recent works suggest Proterozoic plate convergence along the southeastern margin of India which led to amalgamation of the high grade Eastern Ghats belt (EGB) and adjoining fold-and-thrust belts to the East Dhrawar craton. Two major thrusts namely the Vellikonda thrust at the western margin of the Nellore Schist belt (NSB) and the Maidukuru thrust at the western margin of the Nallamalai fold belt (NFB) accommodate significant upper crustal shortening, which is indicated by juxtaposition of geological terranes with distinct tectonostratigraphy, varying deformation intensity, structural styles and metamorphic grade. Kinematic analysis of structures and fabric of the fault zone rocks in these intracontinental thrust zones and the hanging wall and footwall rocks suggest spatially heterogeneous partitioning of strain into various combinations of E-W shortening, top-to-west shear on stratum parallel subhorizontal detachments or on easterly dipping thrusts, and a strike slip component. Although relatively less prominent than the other two components of the strain triangle, non-orthogonal slickenfibres associated with flexural slip folds and mylonitic foliation-stretching lineation orientation geometry within the arcuate NSB and NFB indicate left lateral strike slip subparallel to the overall N-S trend. On the whole an inclined transpression is inferred to have controlled the spatially heterogeneous development of thrust related fabric in the terrane between the Eastern Ghats belt south of the Godavari graben and the East Dharwar craton.  相似文献   

HS 1216+5032: a physical quasar pair with one radio-loud broad absorption line quasar     

P. J. Green  Thomas L. Aldcroft  Warren R. Brown  Olga Kuhn  Abhijit Saha 《Monthly notices of the Royal Astronomical Society》2004,349(4):1261-1266

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Non-circular beam correction to the CMB power spectrum     

Tarun Souradeep  Sanjit Mitra  Anand Sengupta  Subharthi Ray  Rajib Saha   《New Astronomy Reviews》2006,50(11-12):1030

In the era of high precision CMB measurements, systematic effects are beginning to limit the ability to extract subtler cosmological information. The non-circularity of the experimental beam has become progressively important as CMB experiments strive to attain higher angular resolution and sensitivity. The effect of non-circular beam on the power spectrum is important at multipoles larger than the beam-width. For recent experiments with high angular resolution, optimal methods of power spectrum estimation are computationally prohibitive and sub-optimal approaches, such as the Pseudo-C_l method are used. We provide an analytic framework for correcting the power spectrum for the effect of beam non-circularity and non-uniform sky coverage (including incomplete/masked sky maps). The approach is perturbative in the distortion of the beam from non-circularity allowing for rapid computations when the beam is mildly non-circular. We advocate that when the non-circular beams are important, it is computationally advantageous to employ ‘soft’ azimuthally apodized masks whose spherical harmonic transforms die down fast with m.  相似文献   

Arc‐nascent back‐arc signature in metabasalts from the Neoarchaean Jonnagiri greenstone terrane,Eastern Dharwar Craton,India     

C. Manikyamba  Sohini Ganguly  M. Santosh  M. Rajanikanta Singh  Abhishek Saha 《Geological Journal》2015,50(5):651-669

The Neoarchaean Jonnagiri greenstone terrane (JGT) is located at the centre of the arcuate Hutti–Jonnagiri–Kadiri–Kolar composite greenstone belt in the eastern Dharwar Craton. High MgO (MgO = ~14 wt.%; Nb = 0.2 ppm), low Nb (LNB) (MgO = 7.8–12 wt.%; Nb = 0.1–5.1 ppm) and high Nb basalts (HNB) (MgO = 5.6–10.1 wt.%; Nb = 9.0–10.6 ppm) metamorphosed to lower amphibolite facies are identified based on their geochemical compositions. These metabasalts exhibit depleted HFSE (Nb–Ta, Zr–Hf), pronounced LREE and LILE enrichments suggesting contribution from subduction‐related components during their genesis. Th and U enrichment over Nb–Ta indicates influx of fluids dehydrated from subducted oceanic lithosphere. The high MgO basalts with higher Mg# (51) than that of the associated LNB and HNB (Mg# = 34–47) represent early fractionated melts of subduction‐modified mantle peridotite. The LNB were produced by partial melting of mantle wedge metasomatized by slab‐dehydrated fluids, whereas the HNB represents melts of subducted oceanic crust and hybridized mantle wedge. Lower Dy/Yb and variable La/Yb ratios suggest their generation at shallower depth within spinel peridotite stability field. The low Ce–Yb trend of these metabasalts reflects intraoceanic type subduction which straddles the fields of arc and back‐arc basin basalts, resembling the Mariana‐type arc basalts. The Jonnagiri metabasalts were derived in a paired arc‐back‐arc setting marked by nascent back‐arc rift system that developed in the proximity of an intraoceanic arc. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Anisotropic Cosmological Models with a Perfect Fluid and a Λ Term     

Dr. Bijan Saha PhD 《Astrophysics and Space Science》2006,302(1-4):83-91

We consider a self-consistent system of Bianchi type-I (BI) gravitational field and a binary mixture of perfect fluid and dark energy given by a cosmological constant. The perfect fluid is chosen to be the one obeying either the usual equation of state, i.e., p = ζ, with ζ ∊ [0, 1] or a van der Waals equation of state. Role of the Λ term in the evolution of the BI Universe has been studied.  相似文献