Magnetic Field and Displacement sensor based on Giant Magneto-impedance effect

A two-core transducer assembly using a Fe73.5Nb3Cu1Si13.5B9 ribbon to detect a change of magnetic field is proposed and tested for displacement (linear and angular) and current sensor. Two identical inductors, with the ribbon as core, are a part of two series resonance network, and are in high impedance state when excited by a small a.c field of 1MHz in absence of d.c biasing field (Hdc). When the magnetic state of one inductor is altered by biasing field, produced by a bar magnet or current carrying coil, an ac signal proportional to Hdc is generated by transducer. The results for the sensitivity and linearity with displacement (linear and angular) of a magnet and with field from the current carrying coil are presented for two particular configurations of the transducer. High sensitivities of voltage response as much as 12micro-volt/micro-meter and 3mV/degree have been obtained for the transducer as a linear and angular displacement sensor respectively in the transverse configuration of exciting a.c and biasing d.c fields.Comment: 16 pages,7 figure

The star formation histories of early-type galaxies: insights from the rest-frame ultra-violet

Our current understanding of the star formation histories of early-type galaxies is reviewed, in the context of recent observational studies of their ultra-violet (UV) properties. Combination of UV and optical spectro-photometric data indicates that the bulk of the stellar mass in the early-type population forms at high redshift (z > 2), typically over short timescales (< 1 Gyr). Nevertheless, early-types of all luminosities form stars over the lifetime of the Universe, with most luminous (-23 < M(V) < -21) systems forming 10-15% of their stellar mass after z = 1 (with a scatter to higher value), while their less luminous (M(V) > -21) counterparts form 30-60% of their mass in the same redshift range. The large scatter in the (rest-frame) UV colours in the redshift range 0 < z < 0.7 indicates widespread low-level star formation in the early-type population over the last 8 billion years. The mass fraction of young (< 1 Gyr old) stars in luminous early-type galaxies varies between 1% and 6% at z~0 and is in the range 5-13% at z~0.7. The intensity of recent star formation and the bulk of the UV colour distribution is consistent with what might be expected from minor mergers (mass ratios < 1:6) in an LCDM cosmology.Comment: Brief Review, Mod. Phys. Lett.

Noise Correlations in Three-Terminal Diffusive Superconductor-Normal Metal-Superconductor Nanostructures

We present measurements of current noise and cross-correlations in three-terminal Superconductor-Normal metal-Superconductor (S-N-S) nanostructures that are potential solid-state entanglers thanks to Andreev reflections at the N-S interfaces. The noise correlation measurements spanned from the regime where electron-electron interactions are relevant to the regime of Incoherent Multiple Andreev Reflection (IMAR). In the latter regime, negative cross-correlations are observed in samples with closely-spaced junctions.Comment: Include Supplemental Materia

Anisotropic Dependence of Giant Magneto-Impedance of Amorphous Ferromagnetic Ribbon on Biasing Field

The magneto-impedance (MI) in amorphous ribbon of nominal composition Fe73.5Nb3Cu1Si13.5B9 has been measured at 1MHz and at room temperature for different configurations of exciting a.c and biasing d.c. fields. A large drop in both resistance and reactance is observed as a function of d.c magnetic field. When the d.c and a.c fields are parallel but normal to the axis of ribbon, smaller magnetic field is needed to reduce the impedance to its small saturated value compared to the situation when fields are along the axis of ribbon. Larger d.c. field is required to lower the impedance when the d.c field acts perpendicular to the plane of the ribbon. Such anisotropy in magneto-impedance is related to the anisotropic response of the magnetization of ribbon. The large change of impedance is attributed to large variation of a.c permeability on the direction and magnitude of the dc biasing field.Comment: 12 pages, 7 figures, to be published in "International Journal of Modern Physics B

Performances of a Newly High Sensitive Trilayer F/Cu/F GMI Sensor

We have selected stress-annealed nanocrystalline Fe-based ribbons for ferromagnetic/copper/ferromagnetic sensors exhibiting high magneto-impedance ratio. Longitudinal magneto-impedance reaches 400% at 60 kHz and longitudinal magneto-resistance increases up to 1300% around 200 kHz.Comment: 4 pages, 6 figures, Sensors and Actuators A (in review

Using ODL and ICT to develop the skills of the unreached: a contribution to the ADEA triennial of the Working Group on Distance Education and Open Learning

Innovation in technology is occurring at rapid pace thus shrinking the distances and making information and knowledge more than ever accessible to everyone irrespective of where the person resides. This paper consists of four main articles. The first one deals with technological trends. The second one focuses on the deployment and use of open and distance education mode in rural areas by documenting initiatives that embrace information and communication technologies (ICTs). Due to challenges faced in rural areas only a few success stories/cases currently exist and some of these are cited in this article. The challenges faced in the deployment of ICT enhanced ODL have been highlighted as well as the potential of developing and delivering effective and relevant ODL programmes in rural areas in order to ensure that issues of educational equity and social exclusion rural communities are adequately addressed. ICTs in ODL are perhaps the greatest tool to date for self-education and value addition to any community’s development efforts, yet poor rural communities particularly in Africa do not have the necessary awareness, skills or facilities to enable themselves to develop using ICTs. Inadequate ICT infrastructures in rural areas remain a major source for the digital divide in Africa and for under-performance of distance learners. The third one analyses the support provided to ODL learners who often encounter difficulties in completing their studies through the distance education mode due to loneliness, uncertainties and de-motivation. ICT has not been able to sufficiently support distance learners in overcoming those obstacles efficiently. An investigation regarding those learning supports has been conducted in ten distance learning institutions, along with an intensive literature review with the aim of understanding the high percentage of dropout rates of distant learners. The learners’ interactions have been scrutinized through content analysis of their synchronous exchanges, during a completely online course. After taking into account the limited technical and human resources in Africa, a technological virtual environment along with a pedagogical framework has been proposed with the aim of giving adequate educational support to them. The fourth article has explored The Open University (UK) and its efforts to use new technologies to deliver online courses to difficult-to- reach learners in prison environments. The case study analysed here is an international course (called, B201- Business Organisations and their environments) which also touches an African cohort of learners. The implications for designing and delivering online ODL to the complex unreachable environments of prisons anywhere, and particularly in Africa, have been discussed