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Search Results: 1 - 10 of 7380 matches for " Diptasikha Das "
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Magnetoresistive property study of direct and indirect band gap thermoelectric Bi-Sb alloys
Diptasikha Das,K. Malik,S. Bandyopadhyay,D. Das,S. Chatterjee,Aritra Banerjee
Physics , 2014, DOI: 10.1063/1.4894095
Abstract: We report magnetoresistive properties of direct and indirect band gap Bismuth-Antimony (Bi-Sb) alloys. Band gap increases with magnetic field. Large positive magnetoresistance (MR) approaching to 400 % is observed. Low field MR experiences quadratic growth and at high field it follows a nearly linear behavior without sign of saturation. Carrier mobility extracted from low field MR data, depicts remarkable high value. Correlation between MR and mobility is revealed. We demonstrate that the strong nearly linear MR at high field can be well understood by classical method, co-build by Parish and Littlewood.
The effect of quenching from different temperatures on Bi 0.88 Sb 0.12 alloy
K. Malik,Diptasikha Das,S. K. Neogi,A. K. Deb,Arup Dasgupta,S. Bandyopadhyay,Aritra Banerjee
Physics , 2015, DOI: 10.1016/j.jpcs.2015.11.017
Abstract: Structural, thermal, resistive and magnetic properties of melt quenched Bi 0.88 Sb 0.12 alloys are reported. The samples are heated at three different temperatures, followed by rapid quenching in liquid nitrogen. Large temperature difference between liquidus and solidus lines, led to microscopic in-homogeneity in the alloy. The effect of quenching from different temperatures in polycrystalline Bi 0.88 Sb 0.12 alloy has been studied. The parameters such as strain, unit cell volume, and resistivity are found to increase with temperature. Thermal variation of resistivity depicts non monotonic temperature dependence. The total negative susceptibility increases and band gap of semiconducting Bi 0.88 Sb 0.12 samples decreases with increasing temperature.
Temperature-dependent structural property and power factor of n type thermoelectric Bi0.90Sb0.10 and Bi0.86Sb0.14 alloys
K. Malik,Diptasikha Das,S. Bandyopadhyay,P. Mandal,A. K. Deb,Velaga Srihari,Aritra Banerjee
Physics , 2013, DOI: 10.1063/1.4844635
Abstract: Thermal variation of structural property, linear thermal expansion coefficient, resistivity, thermopower and power factor of polycrystalline Bi1-xSbx (x=0.10, 0.14) samples are reported. Temperature-dependent powder diffraction experiments indicate that samples do not undergo any structural phase transition. Rietveld refinement technique has been used to perform detailed structural analysis. Temperature dependence of thermal expansion coefficient is found to be stronger for Bi0.90Sb0.10. Also, power factor for direct band gap Bi0.90Sb0.10 is higher as compared to that for indirect band gap Bi0.86Sb0.14. Role of electron-electron and electron-phonon scattering on resistivity, thermopower and power factor have been discussed.
Sb concentration dependent structural and resistive properties of polycrystalline Bi-Sb alloys
K. Malik,Diptasikha Das,D. Mondal,D. Chattopadhyay,A. K. Deb,S. Bandyopadhyay,Aritra Banerjee
Physics , 2012, DOI: 10.1063/1.4759137
Abstract: Polycrystalline Bi-Sb alloys have been synthesized over a wide range of antimony concentration (8 at% to 20 at%) by solid state reaction method. In depth structural analysis using X-Ray diffraction (XRD) and temperature dependent resistivity measurement of synthesized samples have been performed. XRD data confirmed single phase nature of polycrystalline samples and revealed that complete solid solution is formed between bismuth and antimony. Rietveld refinement technique, utilizing MAUD software, has been used to perform detail structural analysis of the samples and lattice parameters of synthesized Bi-Sb alloys have been estimated. Lattice parameter and unit cell volume decreases monotonically with increasing antimony content. The variation of lattice parameters with antimony concentration depicts a distinct slope change beyond 12 at% Sb content sample. Band gap has been estimated from the thermal variation of resistivity data, with the 12% Sb content sample showing maximum value. It has been observed that, with increasing antimony concentration the transition from direct to indirect gap semiconductor is intimately related to the variation of the estimated lattice parameters. Band diagram for the polycrystalline Bi-Sb alloy system has also been proposed.
Defect induced structural and thermoelectric properties of Sb2Te3 alloy
Diptasikha Das,K. Malik,A. K. Deb,Sandip Dhara,S. Bandyopadhyay,Aritra Banerjee
Physics , 2015,
Abstract: Structural and thermoelectric properties of metallic and semiconducting Sb2Te3 are reported. X-Ray diffraction and Raman spectroscopy studies reveal that semiconducting sample have higher defect density. Nature and origin of possible defects are highlighted. Semiconducting Sb2Te3 hosts larger numbers of defects, which act as scattering center and give rise to the increased value of resistivity, thermopower and power factor. Thermopower data indicates p-type nature of the synthesized samples. It is evidenced that the surface states are often mixed with the bulk state, giving rise to metallicity in Sb2Te3. Role of different scattering mechanism on the thermoelectric property of Sb2Te3 is discussed.
In Vitro Somatic Embryogenesis in Some Oil Yielding Tropical Tree Species  [PDF]
Premananda Das
American Journal of Plant Sciences (AJPS) , 2011, DOI: 10.4236/ajps.2011.22023
Abstract: Somatic embryogenesis was achieved in two oil yielding tropical tree species i.e. Simarouba glauca & Azadirachta indica using immature zygotic embryos as explants on Murashige and Skoog (MS) medium supplemented with 0.5 – 1.5 mg/l benzylaminopurine (BA) and 2.0 - 3.0 mg/l NAA (1-napthaleneacetic acid) or 2, 4-D (2,4-dichlorophenoxyacetic acid) and 3% sucrose. MS medium containing 1.0 mg/l BA and 2.0 mg/l NAA was noted to be the most effective in inducing friable embryogenic callus (FEC) in Simarouba glauca; the number of somatic embryos per culture varied in MS medium supplemented with 1.0 – 1.5 mg/l BA and 1.0 mg/l NAA. In Azadirachta indica, somatic embryos developed on MS medium supplemented with 0.5 mg/l BA and 1.5 – 2.0 mg/l 2,4-D which were in various shapes and sizes after the first subculture on MS medium supplemented with 0.25 mg/l abscisic acid. The somatic embryos which developed shoots were isolated and rooted in 1/2 strength MS medium supplemented with 0.25 mg/l abscisic acid and 2% sucrose. About 25% of embryos germinated within 20 days of culture in case of Simarouba glauca and 62% in Azadirachta indica. The somatic embryo-derived plantlets were transferred to the field after being hardened in the climate controlled hardening chamber.
Besicovitch-Eggleston Function  [PDF]
Manav Das
Advances in Pure Mathematics (APM) , 2011, DOI: 10.4236/apm.2011.15048
Abstract: In this work we introduce a function based on the well-known Besicovitch-Eggleston sets, and prove that the Hausdorff dimension of its graph is 2.
Quantized Energy Momentum and Wave for an Electromagnetic Pulse—A Single Photon inside Negative Refractive Indexed Media  [PDF]
Shantanu Das
Journal of Modern Physics (JMP) , 2011, DOI: 10.4236/jmp.2011.212183
Abstract: An Electromagnetic (EM) radiation in dispersion less free space vacuum is represented by a photon, with corpuscular and wave nature. The discussions, for the past century aimed at the nature of photon inside a media having dispersion in the refraction property, other than free space. What about its nature if the space be of refractive index which is negative, is discussed in this paper. We call mechanical momentum, wave-momentum, and try to match our present theories with intriguing property of this ‘photon’ or pulse carrying EM energy packet, and more so we try to find its property energy, momentum inside a media a positive refractive media, and if the media show a negative refractive index behavior, then these queries are profound, and suitable explanations to these classical concepts of corpuscular-wave nature of photon inside these media are quest for the scientists dealing with these materials having negative index of refraction. Here some of this counterintuitive nature of corpuscular-wave nature of photon inside negative indexed material is brought out, with possible ‘new definition’ of its ‘wave-momentum’, the concept of ‘reactive energy’ inside negative indexed material, along with possible ‘new wave equation’. These definitions and expressions of ‘wave-momentum’ and ‘reactive energy’ pertaining to negative indexed material are new and discussed and derived by classical means.
Is There Chaos in Inflation Data?  [PDF]
Pritha Das
Journal of Applied Mathematics and Physics (JAMP) , 2014, DOI: 10.4236/jamp.2014.25026
Abstract: Economic indicators are snippets of financial and economic data published regularly by governmental agencies and the private sector. An exchange rate represents the value of one currency in another and it fluctuates over time. ForEx rates are affected by many highly correlated economic, political and even psychological factors. It was observed that changes in the exchange rate are related to news in the fundamentals which cover Inflation for the country concerned. In a series of work, we investigated and confirmed the chaotic property of ForEx Rates of several countries. In this perspective, we concentrate on nonlinear data analysis of inflation data of nine countries. We find existence of chaos in inflation data for some countries.
Revisiting the Curie-Von Schweidler Law for Dielectric Relaxation and Derivation of Distribution Function for Relaxation Rates as Zipf’s Power Law and Manifestation of Fractional Differential Equation for Capacitor  [PDF]
Shantanu Das
Journal of Modern Physics (JMP) , 2017, DOI: 10.4236/jmp.2017.812120
Abstract: The classical power law relaxation, i.e. relaxation of current with inverse of power of time for a step-voltage excitation to dielectric—as popularly known as Curie-von Schweidler law is empirically derived and is observed in several relaxation experiments on various dielectrics studies since late 19th Century. This relaxation law is also regarded as “universal-law” for dielectric relaxations; and is also termed as power law. This empirical Curie-von Schewidler relaxation law is then used to derive fractional differential equations describing constituent expression for capacitor. In this paper, we give simple mathematical treatment to derive the distribution of relaxation rates of this Curie-von Schweidler law, and show that the relaxation rate follows Zipf’s power law distribution. We also show the method developed here give Zipfian power law distribution for relaxing time constants. Then we will show however mathematically correct this may be, but physical interpretation from the obtained time constants distribution are contradictory to the Zipfian rate relaxation distribution. In this paper, we develop possible explanation that as to why Zipfian distribution of relaxation rates appears for Curie-von Schweidler Law, and relate this law to time variant rate of relaxation. In this paper, we derive appearance of fractional derivative while using Zipfian power law distribution that gives notion of scale dependent relaxation rate function for Curie-von Schweidler relaxation phenomena. This paper gives analytical approach to get insight of a non-Debye relaxation and gives a new treatment to especially much used empirical Curie-von Schweidler (universal) relaxation law.
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