Positioning and Surveying Requirements for Exploration and Exploitation of Ocean Wealth

Deep sea mining, such as is now being planned to be carried out in the Indian Ocean, requires an accurate positioning system for navigation and for the control of the equipment. Short range systems using electromagnetic principles cover only a limited area while the longer range systems which can be used for offshore, deep ocean work although covering large areas, have limited accuracy. This paper reviews the requirements for position fixing systems for deep ocean mining and the ways to reach the best solution at the most reasonable cost

Increased low field magnetoresistance in electron doped system Sr0.4Ba1.6−xLaxFeMoO6

Magnetotransport properties of electron doped polycrystalline system Sr0.4Ba1.6−xLaxFeMoO6 are presented in this paper. We have observed increased low field magnetoresistance values with significant Curie temperature increase in the electron doped system Sr0.4Ba1.6−xLaxFeMoO6. The low field magnetoresistance value (at 1000 Oe) in 20% La3+ doped sample is observed to be 2.17% at 300 K. At 0.64 T and 80 K, the magnetoresistance change measured in this sample is 21.4%. This sample also showed 50 K increase in Curie temperature over the pristine sample. The increased low field magnetoresistance values are associated with modified grain boundary barriers of the system. The results confirm the fact that the modification of grain boundary barriers has enough potential to possess high low field magnetoresistance values even in the systems with lower spin polarization values. The role of grain to grain connectivity is observed to be dominantly determining the low field magnetoresistance values in grain to grain tunnel type magnetoresistance

Study of electrical properties and the magnetoelectric effect in Ni0.2Co0.8Fe2O4 + PbZr0.8Ti0.2O3 particulate composites

The electric properties and magnetoelectric effect in magnetoelectric (ME) composites with composition (x) Ni0.2Co0.8Fe2O4 + (1 − x)PbZr0.8Ti0.2O3 (PZT—lead zirconate titanate) were studied. The presence of single- (x = 0 and 1) and bi-phases (x = 0.15, 0.30 and 0.45) in the composites was confirmed by x-ray diffraction (XRD) measurements. A structural analysis of the composites was carried out by scanning electron microscopy (SEM) measurements. Electric resistivity measurement as a function of temperature shows the semiconducting nature of the samples. The dielectric constant (ε') and loss tangent (tanδ) decrease rapidly at lower frequencies and remain constant at higher frequencies for all the samples. An AC conductivity measurement was used to discuss the conduction mechanism in all the samples. The ME voltage coefficient (dE/dH)H measured as a function of DC magnetic field gives the maximum ME output of 778 µV cm−1 Oe−1 for 15% of ferrite in the composites

Study of electric, magnetic properties and improvements in ME effects of NMFO plus BZT particulate composites

ME composite materials with the general formula (x) Ni0.9Mg0.1Fe2O4 + (1 - x) BaZr0.2Ti0.8O3 (x = 0.1, 0.2, 0.3, 0.4 and 0.5) were synthesized by solid state reaction method. X-ray diffraction (XRD) study reveals the coexistence of piezomagnetic and piezoelectric phases without interacting with each other. The cubic spinel structure of Ni0.9Mg0.1Fe2O4 (NMFO) piezomagnetic phase and tetragonal perovskite structure of BaZr0.2Ti0.8O3 (BZT) piezoelectric phase for synthesized composites were confirmed by XRD measurements. The lattice constant of piezomagnetic and piezoelectric phases increases with increase in composition of the substituent. The dielectric constant and dielectric loss tangent of the composites measured as a function of frequency in the range 10 Hz-1 MHz at room temperature are found to decrease rapidly in low frequency regime and remain constant in high frequency regime shows the dielectric dispersion behavior. The magnetic properties of the composites have been studied using M-H hysteresis loops to see the response of the magnetic field on the NMFO phase in the composites. The saturation magnetization increases with increase in the mole% of piezomagnetic phase in the composites. The ME voltage coefficient measured as a function of the applied DC magnetic field; shows maximum value (8.622 mV cm (1) Oe) for (50%) NMFO + (50%) BZT bulk composites. The addition of NMFO and BZT enhances the ME properties of the composites

Study of electric, magnetic properties and improvements in ME effects of NMFO + BZT particulate composites

ME composite materials with the general formula (x) Ni0.9Mg0.1Fe2O4 + (1 - x) BaZr0.2Ti0.8O3 (x = 0.1, 0.2, 0.3, 0.4 and 0.5) were synthesized by solid state reaction method. X-ray diffraction (XRD) study reveals the coexistence of piezomagnetic and piezoelectric phases without interacting with each other. The cubic spinel structure of Ni0.9Mg0.1Fe2O4 (NMFO) piezomagnetic phase and tetragonal perovskite structure of BaZr0.2Ti0.8O3 (BZT) piezoelectric phase for synthesized composites were confirmed by XRD measurements. The lattice constant of piezomagnetic and piezoelectric phases increases with increase in composition of the substituent. The dielectric constant and dielectric loss tangent of the composites measured as a function of frequency in the range 10 Hz-1 MHz at room temperature are found to decrease rapidly in low frequency regime and remain constant in high frequency regime shows the dielectric dispersion behavior. The magnetic properties of the composites have been studied using M-H hysteresis loops to see the response of the magnetic field on the NMFO phase in the composites. The saturation magnetization increases with increase in the mole% of piezomagnetic phase in the composites. The ME voltage coefficient measured as a function of the applied DC magnetic field; shows maximum value (8.622 mV cm (1) Oe) for (50%) NMFO + (50%) BZT bulk composites. The addition of NMFO and BZT enhances the ME properties of the composites

Wave refraction studies off Agonda beach (Goa)

52-55Analysis of wave refraction and longshore current has been carried out for a narrow strip off the shores of Agonda. Zones with high wave energy and rip currents have been demarcated. It is found from the analysis that the southern part of the beach is hazardous for water sport activities

Dielectric, magnetic and magnetoelectric properties of ferrite-ferroelectric based particulate composites

Particulate composites based on ferrite and ferroelectric phase viz. cobalt zinc ferrite (Co0.8Zn 0.2Fe2O4 ) and bismuth sodium titanate (Bi0.5Na0.5TiO3) were synthesized using solid state reaction method. The formation of diphase composite was established using x-ray diffraction. Field emission scanning electron microscopy was used to study the microstructure of the composites, exhibiting fine blending of constituent phases in the composites. Dielectric behaviour of the composites was studied as a function of temperature and frequency. Variation of dielectric constant with temperature exhibits a shift in Curie temperature with increase in ferrite content. Usual dielectric dispersion is observed for the composites with increase in frequency. The consequence of addition of ferrite phase on ferroelectric and magnetic properties of composites was studied. All composites exhibit typical ferromagnetic hysteresis loops. Magnetoelctric coupling in the composites was confirmed by measuring magnetoelctric voltage coefficient (alpha(ME)). The maximum a ME of 7.11 mV cm(-1) -Oe was obtained for 10% Co0.8Zn0.2Fe2O4-90% Bi0.5Na0.5TiO3 composite

Structural, dielectric, magnetic and magnetoelectric properties of (x) Bi0.5Na0.5TiO3-(1-x) Ni0.2Co0.8Fe2O4 composites

Magnetoelectric composites (x) Bi0.5Na0.5TiO3-(1 - x) Ni0.2Co0.8Fe2O4 (x = 0.0, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, and 1.0) were synthesized using a solid-state reaction method. The x-ray diffraction studies confirm the existence of rhombohedral Bi0.5Na0.5TiO3 (BNT) and mixed spinel Ni0.2Co0.8Fe2O4 (NCFO) phases without any intermediate phase. The microstructure and surface morphology were studied using a field-emission scanning electron microscope. The relative permittivity (epsilon') and dielectric loss (tan delta) are measured as a function of frequency in the frequency range 100 Hz-1 MHzat room temperature and found to decrease rapidly in low-frequency regime and remain nearly constant in high-frequency regime. The magnetization-magnetic field (M-H) hysteresis loops have been measured to see the response of the magnetic field on the NCFO phase in the composites. The saturation and remnant magnetization are observed to decrease with increasing BNT content in the composite. The magnetoelectric (ME) voltage coefficient, alpha(ME) was measured as a function of the applied DC magnetic field. The highest value of alpha(ME) = 7.538 mV cm(-1) Oe was obtained for the 60% BNT-40% NCFO bulk composite, which is attributed to the enhanced mechanical coupling between the phases. This is a promising result compared to other BNT-based composites. The addition of BNT and NCFO enhances the ME properties of these composites

Nickel substituted oxygen deficient nanoporous lithium ferrite based green energy device hydroelectric cell

In green energy generation, recently Hydroelectric cell (HEC) by dissociating the water molecules at room temperature has taken a big stride among other alternative green energy sources. In this work, another unique novel material Ni substituted lithium ferrite (LNFO) for the fabrication of hydroelectric cell to generate green electricity has been reported. Oxygen deficient nanoporous LNFO has been synthesised by the Solid-State reaction method. Special processing steps were taken to control oxygen defect's concentration in the ferrite by varying pre-sintering temperature during its synthesis to deliver more power output. Phase formation of nickel substituted lithium ferrite has been confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The porous microstructure of LNFO has been analysed by Field-emission scanning electron microscope (FESEM) micrographs, BET and DFT techniques. The presence of defects and decrease in their concentration with the increase in pre-sintering temperature has been confirmed by analysing X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) measurements. Hydroelectric cell fabricated using LNFO pellets pre-sintered at 750 degrees C and 800 degrees C, delivered output current densities of 3.8 mA/cm(2) and 3.6 mA/cm(2) respectively. The decrease in output current is attributed to reduction in defect concentration as confirmed by PL and XPS spectrum. Generated current densities are two times higher than reported in lithium substituted magnesium ferrite based hydroelectric cell (1.7 mA/cm(2))