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Search Results: 1 - 10 of 786249 matches for " A. K. M. A. Islam "
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Structural, Elastic, Electronic and Optical Properties of a New Layered-Ternary Ta4SiC3 Compound
M. S. Islam,A. K. M. A. Islam
Physics , 2010, DOI: 10.1016/j.physb.2010.10.067
Abstract: We propose a new layered-ternary Ta4SiC3 with two different stacking sequences ({\alpha}- and {\beta}-phases) of the metal atoms along c axis and study their structural stability. The mechanical, electronic and optical properties are then calculated and compared with those of other compounds M4AX3 (M = V, Nb, Ta; A = Al, Si and X = C). The predicted compound in the {\alpha}-phase is found to possess higher hardness than any of these compounds. The independent elastic constants of the two phases are also evaluated and the results discussed. The electronic band structures for {\alpha}- and {\beta}-Ta4SiC3 show metallic conductivity. Ta 5d electrons are mainly contributing to the total density of states (DOS). We see that the hybridization peak of Ta 5d and C 2p lies lower in energy and the Ta 5d-C 2p bond is stronger than Ta 5d-Si 3p bond. Further an analysis of the different optical properties shows the compound to possess improved behavior compared to similar types of compounds.
Ab Initio Investigation of Nitride in Comparison with Carbide Phase of Superconducting InX (X = C, N)
M. Roknuzzaman,A. K. M. A. Islam
ISRN Condensed Matter Physics , 2013, DOI: 10.1155/2013/646042
Abstract:
Ab Initio Investigation of Nitride in Comparison with Carbide Phase of Superconducting InX (X?=?C, N)
M. Roknuzzaman,A. K. M. A. Islam
ISRN Condensed Matter Physics , 2013, DOI: 10.1155/2013/646042
Abstract: The structural, elastic, electronic, thermal, and optical properties of superconducting nanolaminates Ti2InX (X?=?C, N) are investigated by density functional theory (DFT). The results obtained from the least studied nitride phase are discussed in comparison with those of carbide phase having value half as that of the former. The carbide phase is found to be brittle in nature, while the nitride phase is less brittle. Elastic anisotropy demonstrates that the c-axis is stiffer in Ti2InN than in Ti2InC. The band structure and density of states show that these phases are conductors, with contribution predominantly from the Ti 3d states. The bulk modulus, Debye temperature, specific heats, and thermal expansion coefficient are obtained as a function of temperature and pressure for the first time through the quasiharmonic Debye model with phononic effects. The estimated values of electron-phonon coupling constants imply that Ti2InC and Ti2InN are moderately coupled superconductors. The calculated thermal expansion coefficient is in fair agreement with the only available measured value for Ti2InC. Further the first time calculated optical functions reveal that the reflectivity is high in the IR-visible-UV region up to?~10?eV and 12.8?eV for Ti2InC and Ti2InN, respectively, showing these to be promising coating materials. 1. Introduction The so-called nanolaminates (or MAX) phases since their discovery by Nowotny [1] have attracted a lot of interest among the research community due to their remarkable properties having attributes of both ceramic and metal [2–24]. Ceramic attributes include lightweight, elastically rigid, and high temperatures strength, whereas metallic attributes show the phases to be thermally and electrically conductive, quasiductile, and damage tolerant. Currently there are about 60 synthesized MAX phases [3]. Out of these only seven low- superconductors have so far been identified. These are Mo2GaC [4], Nb2SC [5], Nb2SnC [6], Nb2AsC [7], Ti2InC [8], Nb2InC [9], and Ti2InN [10]. The X-ray diffraction, magnetic, and resistivity measurements discovered that Ti2InX (X = C, N) are superconductors [8, 10] with superconducting temperatures of 3.1 and 7.3?K, respectively. In fact Bortolozo et al. [10] in 2010 showed unambiguously that Ti2InN is the first nitride superconductor belonging to the family. Among the ternary phases almost all the studies are concerned with carbide properties, but a very limited work on nitrides which was discovered in 1963 by Jeitschko et al. [12]. This nitride crystallizes in the same prototype structure as carbides
New Superconducting RbFe2As2: A First-principles Investigation
M. Aftabuzzaman,A. K. M. A. Islam
Physics , 2009, DOI: 10.1016/j.physc.2009.12.040
Abstract: RbFe2As2 has recently been reported to be a bulk superconductor with Tc = 2.6 K in the undoped state, in contrast to undoped BaFe2As2 with a magnetic ground state. We present here the results of the first-principles calculations of the structural, elastic and electronic properties for this newest superconductor and discuss its behaviour in relation to other related systems. Keywords: RbFe2As2, Electronic structure; Elastic constant; Superconductivity. PACS: 74.70.Dd, 74.10.+v, 74.20.Pq, 75.25.Ld
High pressure Ca-VI phase between 158-180 GPa: Stability, electronic structure and superconductivity
M. Aftabuzzaman,A. K. M. A. Islam
Physics , 2010, DOI: 10.1088/0953-8984/23/10/105701
Abstract: We have performed ab initio calculations for new high-pressure phase of Ca-VI between 158-180 GPa. The study includes elastic parameters of mono- and poly-crystalline aggregates, electronic band structure, lattice dynamics and superconductivity. The calculations show that the orthorhombic Pnma structure is mechanically and dynamically stable in the pressure range studied. The structure is superconducting in the entire pressure range and the calculated Tc (~25K) is maximum at ~172 GPa, where the transfer of charges from 4s to 3d may be thought to be completed.
Theoretical investigations of superconducting MAX phases Ti2InX (X = C, N)
M. Roknuzzaman,A. K. M. A. Islam
Physics , 2012,
Abstract: The structural, elastic, electronic, thermal and optical properties of superconducting MAX phases Ti2InX (X = C, N) are investigated by density functional theory (DFT). The results obtained from the least studied nitride phase are discussed in comparison with those of carbide phase having Tc-value half as that of the former. The band structure and density of states show that these phases are conductors, with contribution predominantly from the Ti 3d states. The bulk modulus, Debye temperature, specific heats, thermal expansion coefficient are all obtained as a function of temperature and pressure for the first time through the quasi-harmonic Debye model with phononic effects. Ti2InC and Ti2InN are indicated to be moderately coupled superconductors. The thermal expansion coefficients for both the phases are calculated, and the calculation is in fair agreement with the only available measured value for Ti2InC. Further the first time calculated optical functions reveal that the reflectivity is high in the IR-visible-UV region up to ~ 10 eV and 12.8 eV for Ti2InC and Ti2InN, respectively showing these to be promising coating materials. Keywords: Ti2InX superconductors; First-principles; Mechanical properties; Band structure; Thermodynamic properties; Optical properties
Efficacy and Economics of Different Need Based Nitrogen Management Approaches in Winter Rice  [PDF]
Nilufar Akhtar Jahan, Sabina Yeasmin, Md. Parvez Anwar, Md. Ariful Islam, Hamidur Rahman, A. K. M. Mominul Islam
American Journal of Plant Sciences (AJPS) , 2018, DOI: 10.4236/ajps.2018.913189
Abstract: This experiment aimed to study the efficacy of different nitrogen (N) management approaches in winter rice. The experiment consisted of two rice varieties: 1) BRRI (Bangladesh Rice Research Institute) dhan29-an inbred and 2) Dhanigold-a hybrid, and eight N management approaches: 1) BRRI recommended N (control), 2) Soil analysis based N management, 3) N application based on Agro-ecological zone, 4) 20 kg·N·ha-1 at ≤35 SPAD (Silicon photon activate diode) value, 5) 30 kg·N·ha-1 at ≤35 SPAD value, 6) 20 kg·N·ha-1 at ≤3.0 LCC (leaf colour chart) value, 7) 30 kg·N·ha-1 at ≤3.0 LCC value and 8) Urea Super Granule. Between two varieties, hybrid Dhani gold produced higher grain yield (6.67 t·ha-1) than the inbred BRRI dhan29. Application of 20 kg·N·ha-1 at ≤3.0 LCC value gave the highest grain yield (7.10 t·ha-1), whereas the lowest grain yield (5.92 t·ha-1) was found from the SPAD approach with 20 kg·N·ha-1 at ≤35 SPAD value. In case of treatment interaction highest grain yield (7.34 t·ha-1) was found in BRRI dhan29 coupled with 20 kg·N·ha-1 at ≤3.0 LCC value with 18 kg·N·savings·ha-1 over control, maximum gross income (146,800 BDT·ha-1) and net benefit (142,120 BDT·ha-1), which was statistically identical with the grain yield from the interaction of Dhani gold and 30 kg·N·ha-1 at ≤3.0 LCC value but required 42 kg·extra·N·ha-1 (over control). The lowest grain yield (5.19 t·ha-1) was found when Dhanigold was coupled with 30 kg·N·ha-1 at ≤35 SPAD value, while the 20 kg·N·application·ha-1 at ≤35 SPAD value gave moderate yield (6.87 t·ha-1) with considerable higher gross (139,600 BDT·ha-1) and net (136,090 BDT·ha-1) incomes than the control (gross: 121,000 and net: 115,600 BDT·ha-1). The results reveal that 20 kg·N·ha-1 at ≤3.0 LCC value appeared as the promising practice for inbred BRRI dhan29, and 30 kg·N·ha-1 at ≤35 SPAD value for hybrid Dhanigold in terms of yield, N use efficiency and economic benefit of winter rice.
Elastic and electronic properties of PbO-type FeSe1-xTex (x = 0 - 1.0): A first-principles study
S. Chandra,A. K. M. A. Islam
Physics , 2010,
Abstract: The effect of doping on electronic and other related properties of PbO-type FeSe1-xTex has been investigated theoretically using density functional method. The elastic properties for mono- and poly-crystalline FeSe1-xTex system are predicted for the first time and the results discussed. Analysis of doping dependent band characteristics in conjunction with previous studies reveal that favorable nesting of Fermi surface indicates a possible basis for understanding why Tc in FeSe1-xTex is maximum for x ~ 0.5. Keywords: FeSe superconductors, Substitution effect, Elastic properties, Electronic properties. PACS: 74.62.Dh, 74.70.Dd, 74.20.Pq, 74.25.Ld
Handwritten Signature Verification Using P-tree
A.K.M. Najmul Islam
Asian Journal of Information Technology , 2012,
Abstract: Handwritten signature recognition is a very complex task. At present many implementations are available for recognition of handwritten signatures. But none of them gives the hundred percent performances and their implementation is also very complex. This paper presents the implementation of handwritten signature verification system using the P-tree. The implementation of this system is very straightforward. This system takes a scanned image of the handwritten signature and tries to match it with already stored images in the database. This method uses the concept of P-tree. The signatures are converted into P-trees and then stored into the database. The signature, which needs to be verified, is also converted into a P-tree.
Synthesis, Spectral Characterization and Thermal Behavior of Newly Derived La(III), Co(III) and Mn(II) Complexes with Schiff Base Derived from Methionine and Salicylaldehyde  [PDF]
Shariful Islam, A. K. M. Nur Alam Siddiki, Shahida Begum, Md. Abdus Salam
Open Journal of Inorganic Chemistry (OJIC) , 2018, DOI: 10.4236/ojic.2018.82005
Abstract: Many metal complexes of Schiff base derived from different amino acids are widely employed as biologically active materials, especially as antibacterial agents. Three new metal [Co(III), Mn(II) and La(III)] complexes with the Schiff base (L) derived from salicylaldehyde and amino acid (methionine) were synthesized and investigated by using various physico-chemical techniques such as elemental analysis, FTIR, UV-visible spectroscopy, magnetic measurement, thermo gravimetric analysis (TGA) and X-ray powder diffraction (XRD) method. From spectral studies, it has been concluded that the synthesized ligand acts as a tetra-dentate molecule, coordinates metal through azomethine nitrogen, sulfur, phenolic oxygen and carboxylate oxygen. UV-visible spectrophotometry showed the characteristic absorption bands corresponding to a square planar geometry for La(III) and Mn(II) metal complexes and tetrahedral geometry for Co(III) complex. The XRD data demonstrated that the manganese and cobalt complexes were crystalline but the lanthanum complex was amorphous in nature. The empirical formula of the synthesized complexes based on analytical data were [Co(C12H13SNO3)]·(NO3), [La(C12H13SNO3)](Cl)(H2O) and [Mn (C12H13SNO3)].
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