IOSR-JAP   Volume-7 ~ Issue-2 ~ March-April 2015

ABSTRACT: In this work, an absolute method has been investigated to measure the 235U mass content in low and intermediate radioactive waste as a by-product in 99Mo production process, and at research labs. Destructive Assay (DA) using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) was used to perform elemental analysis for the collected samples. Absolute Non Destructive Assay (NDA) methods in collaboration with general Monte-Carlo N-transport Code MCNP5 (MC) were employed to fully characterizing the samples. ICP-OES was used to determine the sample composition and the Multi-Group Analysis software (MGAU) was also used for the determination of uranium enrichment. The obtained results from the absolute method were compared with those estimated based on MGAU and ICP-OES. An agreement between the two methods was found within an estimated maximum difference of about 3.5%.

Keywords: Low and intermediate radioactive waste,liquid waste characterization, Monte Carlo, Multi group gamma –ray analysis method (MGAU,) Non-destructive method, Bulk measurements,

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ABSTRACT: As devices shrink, there is a requirement to characterize the magnetic properties of individual inhomogeneous nanosized components. Here the site-specific giant magnetoresistance (GMR) of individual NiFe/Pt multilayer nanowires has been evaluated in the current perpendicular to plane (CPP) geometry using a new in-situ method directly inside a scanning electron microscope (SEM). In this method a controlled magnetic field is produced directly inside the SEM using a custom designed electromagnet. Two nanomanipulators equipped with sharp tips enable the site-specific measurement of the resistance of individual nanowires in the gap between the coils as the field is varied. The CPP-GMR measurement of ~70 nm diameter individual NiFe/Pt multilayer nanowires shows that, at 500 Oe, the nanowires have a magnetoresistance effect of up to 5.8 % dependant on the nanowire layer thicknesses and magnetic field orientation. This in-situ method of GMR measurement enables precise nanocharacterisation of magnetoresistance of nanowires as a function of local nanowire microstructure, geometry, length, and field orientation, whilst concurrently allowing the observation of any changes to the microstructure.

Keywords: Giant magnetoresistance (GMR), multilayer nanowires, in-situ SEM.

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ABSTRACT: In this paper, the attenuation of FSO communication systems operating at selected wvelengths of 650nm, 850nm, 950nm and 1550nm in fog models is theoretically analyzed, using 16-PPM and NRZ-OOK modulation techniques over fog channel. Four fog models are employed for optical beam propagation horizontally at different wavelengths. The received signal power, SNR is analyzed. The characteristics of bit error rate BER for 16-PPM and NRZ -OOK optical modulation techniques are studied. Simulation results show that the performance of 1550nm is more suited for an FSO communication system. On the other hand, we discuss the suitability of modulation techniques under these fog models.
Keywords: Fog models, modulation, FSO, 16-PPM, NRZ-OOK.

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