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Search Results: 1 - 10 of 1616 matches for " Biplab Dutta "
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Length contraction in Very Special Relativity
Biplab Dutta,Kaushik Bhattacharya
Physics , 2011,
Abstract: Glashow and Cohen claim that many results of special theory of relativity (SR) like time dilation, relativistic velocity addition, etc, can be explained by using certain proper subgroups, of the Lorentz group, which collectively form the main body of Very special relativity (VSR). They did not mention about length contraction in VSR. Length contraction in VSR has not been studied at all. In this article we calculate how the length of a moving rod contracts in VSR, particularly in the HOM(2) version. The results are interesting in the sense that in general the length contraction formulas in VSR are different from SR but in many cases the two theories predict similar length contraction of moving rods.
Similarities between 2D and 3D convection for large Prandtl number
Ambrish Pandey,Mahendra K. Verma,Anando G. Chatterjee,Biplab Dutta
Physics , 2014,
Abstract: Using direct numerical simulations of Rayleigh-B\'{e}nard convection (RBC), we perform a comparative study of the spectra and fluxes of energy and entropy, and the scaling of large-scale quantities for large and infinite Prandtl numbers in two (2D) and three (3D) dimensions. We observe close similarities between the 2D and 3D RBC, in particular the kinetic energy spectrum $E_u(k) \sim k^{-13/3}$, and the entropy spectrum exhibits a dual branch with a dominant $k^{-2}$ spectrum. We showed that the dominant Fourier modes in the 2D and 3D flows are very close. Consequently, the 3D RBC is quasi two-dimensional, which is the reason for the similarities between the 2D and 3D RBC for large- and infinite Prandtl numbers.
A new first principles approach to calculate phonon spectra of disordered alloys
Oscar Gr? n?s,Biswanath Dutta,Subhradip Ghosh,Biplab Sanyal
Physics , 2012, DOI: 10.1088/0953-8984/24/1/015402
Abstract: The lattice dynamics in substitutional disordered alloys with constituents having large size differences is driven by strong disorder in masses, inter-atomic force constants and local environments. In this letter, a new first-principles approach based on special quasi random structures and itinerant coherent potential approximation to compute the phonon spectra of such alloys is proposed and applied to Ni$_{0.5}$Pt$_{0.5}$ alloy. The agreement between our results with the experiments is found to be much better than for previous models of disorder due to an accurate treatment of the interplay of inter-atomic forces among various pairs of chemical species. This new formalism serves as a potential solution to the longstanding problem of a proper microscopic understanding of lattice dynamical behavior of disordered alloys.
A first principles study of magnetism in Pd$_{3}$Fe under pressure
Biswanath Dutta,Sumanta Bhandary,Subhradip Ghosh,Biplab Sanyal
Physics , 2012, DOI: 10.1103/PhysRevB.86.024419
Abstract: Recent experiments on Pd$_{3}$Fe intermetallics [Phys. Rev. Lett. 102, 237202 (2009)] have revealed that the system behaves like a classical invar alloy under high pressure. The experimental pressure-volume relation suggests an anomalous volume collapse and a substantial increase in bulk modulus around the pressure where invar behavior is observed. With the help of first-principles density functional theory based calculations, we have explored various magnetic phases (ferromagnetic, fully and partially disordered local moment, spin spiral) in order to understand the effect of pressure on magnetism. Our calculations reveal that the system does not undergo a transition from a ferromagnetic to a spin-disordered state as was thought to be the possible mechanism to explain the invar behavior of this system. We rather suggest that the anomaly in the system could possibly be due to the transition from a collinear state to non-collinear magnetic states upon the application of pressure.
A Finite Element Study of Elastic-Plastic Hemispherical Contact Behavior against a Rigid Flat under Varying Modulus of Elasticity and Sphere Radius  [PDF]
Prasanta Sahoo, Biplab Chatterjee
Engineering (ENG) , 2010, DOI: 10.4236/eng.2010.24030
Abstract: The present study considers a finite element analysis of elastic-plastic axi-symmetric hemispherical contact for a frictionless deformable sphere pressed by a rigid flat. The material of the sphere is modeled as elastic perfectly plastic. Analysis is carried out to study the effect of varying modulus of elasticity and sphere radius in wide range of dimensionless interference until the inception of plasticity as well as in plastic range. Results are compared with previous elastic-plastic models. It is found that materials with Young’s modulus to yield strength (E/Y) ratio less than and greater than 300 show strikingly different contact phenomena. The dependency of E on dimensionless interference at which the plastic region fully covers the surface is observed. However with different radius, finite element study exhibits similar elastic-plastic phenomena.
Screening for Aphid Incidence on Some Potato Germplasm in Plains of West Bengal  [PDF]
Biplab Kahar, Amitava Konar
Agricultural Sciences (AS) , 2016, DOI: 10.4236/as.2016.76036
Abstract: A field trial was conducted to study the impact of various potato germplasm against aphids, Myzus persicae (Sulzer) and Aphis gossypii Glover (Aphididae: Hemiptera) during rabi season from November to March in 2012-2013 and 2013-2014, respectively at Adisaptagram Block Seed Farm, Hooghly, West Bengal. The population of aphids was started on potato crop in between third week of December and first week of January irrespective of various germplasms, except K. Chipsona-2, where its infestation was initiated during second and third week of January. Then, their population was gradually increased to reach its critical level (ETL) during first and second week of January in most of the potato germplasm, except in K. Anand, K. Chipsona-1, K. Chipsona-2 and Sailaja, where it was crossed in between fourth week of January and first week of February. The peak population of aphids was observed during third and fourth week of February in most of the potato germplasm. It was observed that K. Ashoka, K. Badshah, K. Chandramukhi, K. Jawahar, K. Jyoti and K. Pukhraj were highly susceptible to the pests, while K. Anand and K. Sutlez were moderately susceptible but K. Chipsona-1 , K. Chipsona-2 and K. Sailaja were less susceptible or tolerant to the pests. Maximum tuber yield (t/ha) of potato was recorded in K. Badshah (36.58 - 43.92) while it was lowest in K. Chandramukhi (22.08 - 22.12).
The Style of ‘Lokaabharan’ in Indian Proverbs
Biplab Chakraborty
Folklore : Electronic Journal of Folklore , 2007,
Abstract: The changing pattern of Indian proverbs is very much reflected invarious literary creations, especially in modern Indian poetry. Proverbs are used in poetry as a mode of creative process which entails change. Indeed, it is mostly expressed in a poetic style of narration which may be termed as the style of ‘lokaabharan’. Various types of folk elements are used in the creative process and amongst such folk elements proverbs assume a very important position in the making of the style of ‘lokaabharan’.The central message of a proverb is often conveyed with a subtle touch of language use as a linguistic device. Patterns of changes in language use need to be examined with a view to measure the mode of expression of the proverb concerned. In order to understand the style of ‘lokaabharan’, we must examine how proverbs have been used as fixative factors. In this process, we need to compare and contrast the original proverbs used and their changing patterns available in the text of the poems concerned. Fixative factors are what may be called the core of folk elements used in a poem. This may be either a conscious creative effort or an unconscious artistic measure. It plays a vital role in conveying the central theme or message, whatever the case may be.
GLOBAL WARMING AND PATTERN OF MAIN ECONOMY IN SUNDARBAN
Biplab Das
International Journal of Trends in Economics Management and Technology , 2013,
Abstract: In this article, the phrase “global warming” refers tothe change in the Earth's global average surfacetemperature. Measurements show a global temperatureincrease of 1.4 °F (0.78 °C) between the years 1900 and2005. Global warming is closely associated with a broadspectrum of other climate changes, such as increases inthe frequency of intense rainfall, decreases in snow coverand sea ice, more frequent and intense heat waves, risingsea levels, and widespread ocean acidification. TheIntergovernmental Panel on Climate Change (IPCC) hasproduced several reports where the economics literatureon climate change is assessed. In 1995, the IPCCproduced its second set of assessment reports on climatechange. Working Group III of the IPCC produced a reporton the "Economic and Social Dimensions of ClimateChange." In the later third and fourth IPCC assessments,published in 2001 and 2007 respectively, the assessmentof the economics literature is divided across two reportsproduced by IPCC Working Groups II and III. In 2011IPCC Working Group III published a Special Report onRenewable Energy Sources and Climate Change.
d-Wave Order Parameter in Bi2212 from a Phenomenological Model of High T$_c$ Cuprates
Biplab Chattopadhyay
Physics , 1996, DOI: 10.1016/S0375-9601(96)00887-0
Abstract: A phenomenological lattice model of high $T_c$ cuprates including order parameter phase fluctuations is considered within the BCS approximation, to interpret the experimental data from ARPES measurements on Bi2212 samples. A Kosterlitz-Thouless (KT) transition temperature $T_c^{KT}$ is estimated below the mean field transition $T_c^{MF}$, phase boundaries between competing order parameters of different symmetries are obtained and best model parameters, fitting the ARPES gap of $d_{x^2-y^2}$ symmetry, are determined. Variation of $T_c^{KT}$, as a function of the dopant concentration $\delta$, is in qualitative agreement with experiments.
Evolution of Intra-Cavity Fields at Non-Steady State in Dual Recycled Interferometer
Biplab Bhawal
Physics , 1995, DOI: 10.1364/AO.35.001041
Abstract: We describe how exactly the intra-cavity fields in a dual recycling cavity build up their power before achieving a steady state value. We restricted our analysis here to interferometers with lossless mirrors and beam-splitter. The complete series representation of the intra-cavity lights at any stage of evolution in non-steady state have been presented.
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