Papers by Md Akther Hossain
Developing a virtual sensor (VS) for mapping soil moisture at high spatial and temporal resolution
Mapping soil moisture at both high spatial and temporal resolution has not been possible due to l... more Mapping soil moisture at both high spatial and temporal resolution has not been possible due to lack of sensors with these combined capabilities. We transformed the Moderate Resolution Imaging Spectroradiometer (MODIS) into a virtual sensor (VS) for quantitative soil moisture mapping and monitoring at 1 km and 250 m resolution daily. The Vegetation Index (VI) - Land Surface Temperature (LST) triangle model was used as the governing algorithm for VS. We used a time series of 13 data sets from August 01, 2006 to November 06, 2006 of MODIS reflective and thermal imagery and AMSR-E Level 3 soil moisture imagery to develop the VS in the semi-arid environment of southeastern New Mexico. We used Synthetic Aperture Radar (SAR) derived soil moisture imagery for five corresponding dates of the MODIS/AMSR-E imagery to evaluate the performance of VS for soil moisture estimation along with near real time in situ soil moisture measurements. In situ soil moisture measurements, vegetation density/d...
Testing the Potential of Next Generation VIIRS Satellite Data to Monitor Food Security: A Case of Mesoamerica
In the past more than two decades, Normalized Difference Vegetation Index (NDVI) derived from the... more In the past more than two decades, Normalized Difference Vegetation Index (NDVI) derived from the Advanced Very High Resolution Radiometer (AVHRR) has been successfully used to monitor crop conditions over large areas of the globe. In recent years the use of the Moderate Resolution and Imaging Spectrometer (MODIS) data, with improved resolution, has increased. As the end of the MODIS
Materials Sciences and Applications, 2013
Mn 0.50-x Zn 0.50 Cu x Fe 2 O 4 (where x = 0.0 -0.3) ferrites have been synthesized by auto combu... more Mn 0.50-x Zn 0.50 Cu x Fe 2 O 4 (where x = 0.0 -0.3) ferrites have been synthesized by auto combustion method. X-ray diffraction patterns reveal that all compositions are of single phase cubic spinel structure. The lattice parameter decreases with the increase in Cu 2+ content obeying the Vegard's law. The bulk density, average grain size, initial permeability, Néel temperature and saturation magnetic induction of Mn 0.50-x Zn 0.50 Cu x Fe 2 O 4 increased with increasing Cu 2+ content. It is observed that both density and initial permeability increase with increasing sintering temperature. The maximum initial permeability is found to be 1061 which is almost four times greater than that of the parent composition. The resonance frequency of all the samples shifts towards the lower frequency as the permeability increases with Cu 2+ content. It is observed from B-H loops of Mn 0.50-x Zn 0.50 Cu x Fe 2 O 4 that coercivity decreases and retentivity increases with Cu 2+ content. Possible explanations for the observed magnetic properties with various Cu 2+ contents are discussed.
Journal of Magnetism and Magnetic Materials, 2014
Cu 2+ substituted cobalt ferrite represented chemically as Co 1-x Cu x Fe 2 O 4 (x = 0.00, 0.05, ... more Cu 2+ substituted cobalt ferrite represented chemically as Co 1-x Cu x Fe 2 O 4 (x = 0.00, 0.05, 0.10, 0.15, 0.20 and 0.25) was prepared by the sol-gel assisted auto-combustion process using malic acid as a complexing agent. The auto-combusted sample was investigated using thermal analyzer, and accordingly, thermal treatments were given to the samples. The concentration of metal ions present was estimated using ICP-AES technique. Evaluation of transmission electron microscopy and scanning electron microscopy results indicate the homogenous distribution of particles along with agglomeration. X-ray photoelectron spectroscopy studies confirm the existence of elements in their respective oxidation states. Raman and Infrared spectroscopy were employed to shed light on the vibrational modes of the spinel ferrites. Magnetic properties determined from vibrating sample magnetometer at 50 K shows a significant increase in saturation magnetization (M s ) and coercivity (H c ) as compared to 300 K. While, the substitution of Cu 2+ ions showed a marginal decrease in M s and H c at individual temperatures. The drop in Curie temperature (T c ) with Cu 2+ content indicates the weakening in the strength of the overall A-B super-exchange interaction. The dielectric properties have been determined as a function of frequency and temperature. Antimicrobial tests performed, indicated that the Cu 2+ content in CoFe 2 O 4 significantly influenced the activity against both Gram-positive and Gram-negative pathogenic microbes.
Relaxation mechanism of (x)Mn0.45Ni0.05Zn0.50Fe2O4+ (1 − x)BaZr0.52Ti0.48O3multiferroic materials
Physica Scripta, 2014
ABSTRACT Polycrystalline (x)Mn0.45Ni0.05Zn0.50Fe2O4 + (1 − x)BaZr0.52Ti0.48O3 (with 0.2 ≤ x ≤ 0.8... more ABSTRACT Polycrystalline (x)Mn0.45Ni0.05Zn0.50Fe2O4 + (1 − x)BaZr0.52Ti0.48O3 (with 0.2 ≤ x ≤ 0.8) multiferroic materials were prepared by the standard solid state reaction technique and samples prepared from these composites were sintered at 1200 °C. The impedance, electrical modulus, ac conductivity and dielectric permittivity were investigated over a wide range of frequencies (20 Hz–1 MHz) and at various temperatures (room temperature to 600 °C) to understand the relaxation phenomenon in these materials. X-ray diffraction patterns confirm the presence of a simple cubic spinel structure for the ferromagnetic phase and tetragonal peroveskite for the ferroelectric phase. Frequency-independent conductivity was observed in the low frequency region, which shifts to a higher frequency and dominates over a wide range of frequency (up to 1 MHZ) at higher temperature (600 °C). The transition temperature (~675 °C) of these composites is higher than that of ferrite and ferroelectric phases. The frequency response electric modulus graphs for some composites show two maxima in the relaxation process. The first relaxation process appears at lower temperature and higher frequency with a lower value of activation energy for the composites containing more than 20% ferrimagnetic phase. This relaxation process is due to the first ionization energy of oxygen vacancies. The second relaxation process appears at all temperatures and at lower frequency, which shifts to higher frequency with increasing temperature, possessing a comparatively higher value of activation energy. This relaxation process is attributed to the Maxwell–Wagner–Sillars relaxation phenomenon. The frequency-dependent impedance and modulus plots exhibit a non-coincidence of relaxation peaks, indicating the deviation from the Debye-type relaxation process.
Journal of Superconductivity and Novel Magnetism, 2014
Polycrystalline Ba 4 Ni 2-x Zn x Fe 36 O 60 (0.0 ≤ x ≤ 1.4) hexagonal ferrite samples have been p... more Polycrystalline Ba 4 Ni 2-x Zn x Fe 36 O 60 (0.0 ≤ x ≤ 1.4) hexagonal ferrite samples have been prepared by conventional solid-state reaction method. Structural and magnetic properties of the prepared samples were then analyzed by the X-ray diffraction technique and with superconducting quantum interface device (SQUID) magnetometer, respectively. Variations of lattice parameters, density, and porosity with Zn content were measured. Magnetic properties such as complex permeability, relative quality factor, loss factor, and saturation magnetization have been investigated as a function of Zn content. The study revealed that Zn content has a significant effect on structural and magnetic properties of the Ba 4 Ni 2 Fe 36 O 60 hexaferrites.
Network coverage of wireless sensor network (WSN) means how well an area of interest is being mon... more Network coverage of wireless sensor network (WSN) means how well an area of interest is being monitored by the deployed network. It depends mainly on sensing model of nodes. In this paper, we present three types of sensing models viz. Boolean sensing model, shadow-fading sensing model and Elfes sensing model. We investigate the impact of sensing models on network coverage. We also investigate network coverage based on Poisson node distribution. A comparative study between regular and random node placement has also been presented in this paper. This study will be useful for coverage analysis of WSN.
On the impact of node failure on network coverage in wireless sensor network
Network coverage of wireless sensor network (WSN) means how well the entire area of interest is b... more Network coverage of wireless sensor network (WSN) means how well the entire area of interest is being monitored by a deployed network. It depends on several factors including sensing model of a node. Node failure is an important issue in WSN. The sensor nodes are prone to be non-functional due to noise and battery energy depletion. In the literature, node failure has not been considered while studying coverage. In this paper, we investigate the impact of node failure on network coverage. The network coverage has been derived for three sensing models in the event of node failure.
In this paper we investigate the dependency of characteristic distance on energy dissipation mode... more In this paper we investigate the dependency of characteristic distance on energy dissipation model. Both the many-to-one and any-to-any communication paradigm have been presented for performance analysis. Characteristic distance has been derived for three different cases. This study will be useful for designing an energy-efficient wireless network where nodes are energy-constrained.
World Journal of Condensed Matter Physics, 2012
Y-type hexagonal ferrites with the nominal chemical composition Ba 2 Ni 2-x Zn x Fe 12 O 22 (0.0 ... more Y-type hexagonal ferrites with the nominal chemical composition Ba 2 Ni 2-x Zn x Fe 12 O 22 (0.0 ≤ x ≤ 0.6 with a step of 0.1) have been synthesized by the conventional solid state reaction method and sintered in the temperature range 1150˚C -1250˚C to study their structural and magnetic properties. The aim of the present work is to increase the magnetic properties of Y-type hexaferrites by Zn substitution. X-ray diffraction analysis confirms the formation of the hexagonal phase. The effect of chemical composition on the lattice parameter, density and porosity is studied. The lattice parameter increases with Zn substitution. The density increases with Zn substitution up to a certain level and after that density decreases. The ac magnetic properties of the hexaferrites sintered at temperature 1200˚C are characterized within the frequency range 100 kHz -120 MHz. The real part (μ i ') of the complex initial permeability for different compositions indicates that μ i ' decreases with increase in frequency. The permeability increases with the increase in Zn content, reaches a maximum value and then decreases with further increase in Zn content. Magnetization has been measured using the Superconducting Quantum Interference Device (SQUID) magnetometer. The saturation magnetization is observed to be maximum at x = 0.1 and then decreases with Zn content for x > 0.1. From the M-H curve it is clear that at room temperature the polycrystalline Ba 2 Ni 2-x Zn x Fe 12 O 22 compositions are in ferrimagnetic state.
Solid State Communications, 2005
Thin films of (111)-oriented spinel ferrite Al 0.5 Fe 2.5 O 4 have been prepared by a pulsed-lase... more Thin films of (111)-oriented spinel ferrite Al 0.5 Fe 2.5 O 4 have been prepared by a pulsed-laser deposition (PLD) technique on a-Al 2 O 3 (0001) substrates. The films exhibit cluster-glass behaviors with a spin-freezing temperature, T g , near or above room temperature. The magnetization was found to increase following light irradiation below T g , which indicates the photoinduced melting of cluster-glass states. An analysis comparing the dynamic behavior of magnetic response to light irradiation between zero-field-cooled (ZFC) states and field-cooled (FC) states at 10 K under various light intensities, I, revealed that the direct photoexcitation of spins occurs when I%0.78 mW/mm 2 , while the thermal heating effect following the light absorption of the samples also contributes to the enhancement of magnetization when IR1.22 mW/mm 2 . The magnetization of the films could be controlled by light irradiation even at room temperature. This suggests the possibility of utilizing these films in the development of novel magneto-optical memory devices.
Materials Science and Engineering: B, 2001
Thick films of La 0.63 Y 0.07 Ca o.30 MnO 3 were fabricated on (100) oriented single crystal LaAl... more Thick films of La 0.63 Y 0.07 Ca o.30 MnO 3 were fabricated on (100) oriented single crystal LaAlO 3 (LAO) and on polycrystalline Al 2 O 3 substrates by a screen printing technique. The films were sintered at 1200°C in air and oxygen atmosphere. All these thick films show a metal-insulator (M-I) transition at T p1 220 K. For both substrates, the films sintered in oxygen flow have slightly higher T p1 . The film on polycrystalline Al 2 O 3 sintered in oxygen flow shows 71% magnetoresistance (MR) at 220 K in the presence of an 8 T applied field. The salient feature of the colossal magnetoresistance observed in these thick films is that low-temperature low-field MR is highly sensitive than only Ca doped manganites.
Materials Science and Engineering: B, 2000
Thick films of La 0.67 Ca 0.33 MnO 3 were fabricated on (100) oriented single crystal LaAlO 3 (LA... more Thick films of La 0.67 Ca 0.33 MnO 3 were fabricated on (100) oriented single crystal LaAlO 3 (LAO), yttria stabilized zirconia (YSZ) and on polycrystalline Al 2 O 3 by a screen printing technique. A range of sintering conditions were explored with temperature of 1200, 1300 and 1400°C, and in air, oxygen and nitrogen atmospheres. Magnetic and DC resistance properties were measured on all films. The so-called 'colossal magnetoresistance' (CMR) behaviour was found to occur for films on all substrates but for specific preparation conditions. The salient feature of the CMR observed in these thick films is that MR is not limited to a small temperature window near the metal-insulator transition (M -I), T p1 . The MR peak is very broad and for some films a temperature independent CMR is observed at temperatures below T p1 . Several repeat films were made and the reproducibility of the results obtained in the first batch was confirmed.
Journal of Mechanical Engineering, 2009
A 2D analytical turbulent diffusion model for particle dispersion and deposition at different hei... more A 2D analytical turbulent diffusion model for particle dispersion and deposition at different heights across the pipe flow and circumferential deposition has been developed. This liquid-solid turbulent diffusion model presented in this paper has emanated from an existing gas-liquid turbulent diffusion model. Simultaneously a comprehensive 3D numerical investigation has been carried out to study the above making of multiphase mixture model available in Fluent 6.1. In both studies different particles sizes and densities were used. The deposition was studied as a function of particle diameter, density and fluid velocity. The deposition of particles, along the periphery of the wall and at different depths, was also investigated. Both studies showed that the deposition of heavier particles at the bottom of the pipe wall was found to be higher at lower velocities and lower at higher velocities. The lighter particles were found mostly suspended with homogeneous distribution. Smaller partic...
Structure and Magnetic Properties of La0.7Ca0.3MnO3??for (3 ? ?) < 3.0
Journal of the American Ceramic Society, 2001
Page 1. Structure and Magnetic Properties of La0.7Ca0.3MnO3 for (3 ) < 3.0 Ying Hai Li, Franç... more Page 1. Structure and Magnetic Properties of La0.7Ca0.3MnO3 for (3 ) < 3.0 Ying Hai Li, Françoise Damay, Lesley F. Cohen, Kodenkandath A. Thomas, Akther KM Hossain, and Judith L. MacManus-Driscoll,§ Department ...
Journal of Physics and Chemistry of Solids, 2007
Structural, AC and DC magnetic properties of polycrystalline Zn 1Àx Co x Fe 2 O 4 (x ¼ 0.2, 0.4) ... more Structural, AC and DC magnetic properties of polycrystalline Zn 1Àx Co x Fe 2 O 4 (x ¼ 0.2, 0.4) samples sintered at various temperatures (1100-1300 1C), and various dwell times (0.2-15 h) have been investigated thoroughly. The bulk density of the Zn 0.60 Co 0.40 Fe 2 O 4 samples increases as the sintering temperature (T s ) increases from 1100 to 1250 1C, and above 1250 1C the bulk density decreases slightly. The Zn 0.80 Co 0.20 Fe 2 O 4 samples show similar behavior of changes to that of Zn 0.60 Co 0.40 Fe 2 O 4 samples except that the bulk density is found to be highest at 1200 1C. The DC magnetization as a function of temperature curves show that the Zn 0.60 Co 0.40 Fe 2 O 4 sample is ferrimagnetic at room temperature while the Zn 0.80 Co 0.20 Fe 2 O 4 sample is paramagnetic at room temperature. The T c of Zn 0.80 Co 0.20 Fe 2 O 4 sample is found to be 170 K from DC magnetization measurement. Separate measurement (AC magnetization), initial permeability as a function of temperature shows that the T c of the Zn 0.60 Co 0.40 Fe 2 O 4 sample is 353 K. Slight variation of T c is observed depending on sintering condition. The initial permeability for the Zn 0.60 Co 0.40 Fe 2 O 4 composition sintered at 1250 1C is found to be maximum.
Structural, Dielectric and Complex Impedance Spectroscopy Studies of Lead Free Ca0.5+xNd0.5−x(Ti0.5Fe0.5)O3
Journal of Materials Science & Technology, 2013
ABSTRACT Structural and various electrical properties of polycrystalline Ca0.5+xNd0.5−x(Ti0.5Fe0.... more ABSTRACT Structural and various electrical properties of polycrystalline Ca0.5+xNd0.5−x(Ti0.5Fe0.5)O3, prepared by standard solid state reaction technique, were studied. Formation of single phase orthorhombic structure of the compositions was confirmed by X-ray diffraction study. The composition dependence of lattice parameters, density and microstructural study show that they vary significantly with Ca content. The dielectric measurements were carried out at room temperature as function of frequency and composition. The experimental results reveal that the dielectric constant (ε′) increases with increasing Ca content. Similar behavior is observed for the dielectric loss (tanδ) and ac conductivity (σac). In complex impedance analysis it is observed that the real part (Z′) vs imaginary part (Z″) graph exhibits a tendency of formation of a single semicircular arc for each composition of samples. Different parameters were determined by fitting the experimental data in Cole–Cole empirical formula. A dominance of grain boundary resistance (Rgb) is observed. The Rgb decreases with increasing Ca content. The high ε′ observed in present samples are suitable for fabrication of devices.
Magnetoresistive properties of Zn1−xCoxFe2O4 ferrites
Journal of Magnetism and Magnetic Materials, 2008
The magnetic and magnetoresistive properties of spinel-type Zn 1− x Co x Fe 2 O 4 (x=0, 0.2 and 0... more The magnetic and magnetoresistive properties of spinel-type Zn 1− x Co x Fe 2 O 4 (x=0, 0.2 and 0.4) ferrites are extensively investigated in this study. A large negative magnetoresistance (MR) effect is observed in Zn 1− x Co x Fe 2 O 4 ferrites of spinel structure. These ...
Influence of grain size on magnetoresistance properties of bulk La0.67Ca0.33MnO3−δ
Journal of Magnetism and Magnetic Materials, 1999
The magnetic and magnetoresistive properties of six polycrystalline bulk samples of nominal chemi... more The magnetic and magnetoresistive properties of six polycrystalline bulk samples of nominal chemical composition La 0.67 Ca 0.33 MnO 3−δ and varying grain size (3.3 μm20.4 μm), were investigated. Although the Curie temperature, T c , is independent of grain size, the ...
The electrical transport properties of Zn x Li 0.45-x/2 Fe 2.55-x/2 O 4 (where, x=0.0, 0.3, 0.5) ... more The electrical transport properties of Zn x Li 0.45-x/2 Fe 2.55-x/2 O 4 (where, x=0.0, 0.3, 0.5) synthesized by conventional ceramic method have been investigated as a function of Zn content. The X-ray analysis confirms the formation of single phase cubic spinel structure . The ac resistivity and dielectric constant show opposite trend with increase in Zn content. The ac resistivity and dielectric constant of the samples are found to decreases with increase in frequency, exhibiting normal ferromagnetic behaviour. Dielectric constant of the samples decreases rapidly at lower frequencies and slower at higher frequencies which may be due to the Maxwell-Wagner interfacial polarization. The electrical properties can be explained on the basis of Fe 2+ /Fe 3+ ionic concentration.
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Papers by Md Akther Hossain