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The internal mono-standard relative method has been used for compositional analysis of prompt gamma activation analysis (PGAA). PGAA is very useful for the analysis of boron elements in various sample matrices, especially in the uranium samples, which attenuates neutron intensity significantly. The concentration ratio of boron is determined relative to the uranium as internal mono-standard. The concentration of uranium is well traceable when the sample was fabricated and also measured by a relative method using certified reference material. The uranium dioxide powder samples were prepared by crushing the fuel pellets and then mixed with the adjuvant compounds to improve the combustion characteristics of the nuclear fuel. The first adjuvant compound is boron compound like boron nitride and hafnium diboride. The second adjuvant is manganese oxide, which is considered to enhance the thermal stability of the boron compounds. The elemental concentrations of the samples were measured by a thermal neutron PGAA facility at the HANARO research reactor and analyzed using a KAERI-PGAA code including a Doppler-broadened boron peak analysis (DBPA) routine for boron analysis. [ABSTRACT FROM AUTHOR]

A spin valve is a microelectronic device in which high- and low-resistance states are realized by using both the charge and spin of carriers. Spin-valve structures used in modern hard-drive read heads and magnetic random access memoriescomprise two ferromagnetic electrodes whose relative magnetization orientations can be switched between parallel and antiparallel configurations, yielding the desired giant or tunnelling magnetoresistance effect. Here we demonstrate more than 100% spin-valve-like signal in a NiFe/IrMn/MgO/Pt stack with an antiferromagnet on one side and a non-magnetic metal on the other side of the tunnel barrier. Ferromagneticmoments in NiFe are reversed by external fields of approximately50 mT or less, and the exchange-spring effect of NiFe on IrMn induces rotation of antiferromagnetic moments in IrMn, which is detected by the measured tunnelling anisotropic magnetoresistance. Our work demonstrates a spintronic element whose transport characteristics are governed by an antiferromagnet. It demonstrates that sensitivity to low magnetic fields can be combined with large, spin-orbit-coupling-induced magnetotransport anisotropy using a single magnetic electrode. The antiferromagnetic tunnelling anisotropic magnetoresistance provides a means to study magnetic characteristics of antiferromagnetic films by an electronic-transport measurement. [ABSTRACT FROM AUTHOR]

This paper describes ongoing research into the multi-physics model development of an electrorefining process for the treatment of spent nuclear fuel. A forced convection of molten eutectic (LiCl–KCl) electrolyte in an electrorefining cell is considered to establish an appropriate electro-fluid model within the 3-dimensional framework of a conventional computational fluid dynamic model. This computational platform includes the electrochemical reaction rate of charge transfer kinetics which is described by a Butler–Volmer equation, while mass transport is considered using an ionic transport equation. The coupling of the local overpotential distribution and uranium concentration gradient makes it possible to predict the local current density distribution at the electrode surfaces. [ABSTRACT FROM AUTHOR]

Electrical detection of spin-polarized transport in semiconductors is one of the key prerequisites for successful incorporation of spin in semiconductor microelectronics. The present schemes are based on spin-dependent transport effects within the spin generation region in the semiconductor, or on non-local detection outside the spin-injection area using a ferromagnet attached to the semiconductor. Here, we report that polarized injection of carriers can be detected by transverse electrical signals directly along the semiconducting channel, both inside and outside the injection area, without disturbing the spin-polarized current or using magnetic elements. Our planar p–n diode microdevices enable us to demonstrate Hall effect symmetries and large magnitudes of the measured effect. Supported by microscopic calculations, we infer that the observed spin-injection Hall effect reflects spin dynamics induced by an internal spin–orbit field and is closely related to the anomalous and spin Hall effects. The spin-injection Hall effect is observed up to high temperatures and our devices represent a realization of a non-magnetic spin-photovoltaic polarimeter that directly converts polarization of light into transverse voltage signals. [ABSTRACT FROM AUTHOR]

A pyrochemical processing has become one of the potential technologies for a future nuclear fuel cycle. An integrated multi-physics simulation and electrotransport model of a molten-salt electrolytic process are proposed and discussed with respect to the recovery of pure uranium when using thermochemical data. This study has been performed to provide information for diffusion boundary layers between the molten salt (KCl-LiCl) and electrode. The diffusion-controlled electrochemical model demonstrate a prediction of the electrotransport behaviors of LWR spent fuel as a function of the time up to the corresponding electrotransport satisfying a given applied current based on a galvanostatic electrolysis. [ABSTRACT FROM AUTHOR]

We present the preliminary results of more than 160 h of time-series photometry on the subdwarf B pulsating star PG 1325+101 (Teff = 34 500 K log g = 6.1), obtained in March-April 2003 at nine different sites. The amplitude spectrum confirms the presence of the four frequencies found in the discovery run at the NOT in July 2001 (but with significantly lower amplitudes in two of them) and also shows at least two new low amplitude signals. Moreover, there is no sign of frequency splitting near the main peak at 7256 μHz, suggesting that this mode might be actually radial as indicated by the time-resolved spectroscopy (Østensen and Telting, 2004). [ABSTRACT FROM AUTHOR]

The mechanical properties of metal matrix composites (MMCs) are critical to their potential application as structural materials. A systematic examination of the effect of particulate volume fraction on the mechanical properties of an Al2O3-Al MMC has been undertaken. The material used was a powder metallurgy processed AA 6061 matrix alloy reinforced with MICRAL-20™, a polycrystalline microsphere reinforcement consisting of a mixture of alumina and mullite. The volume fraction of the reinforcement was varied systematically from 5 to 30% in 5% intervals. The powder metallurgy composites were extruded then heat treated to the T6 condition. Extruded liquid metallurgy processed AA 6061 was used to establish the properties of the unreinforced material. [ABSTRACT FROM AUTHOR]

An internal membrane-filtration bioreactor system with periodic fouling removal and on-line cell measurement was employed for long-term continuous ethanol production from glucose in order to prove its performance and practicality. The bioreactor system developed in this study was successfully operated for 2 months with no problems in the maintenance of filtration flux. The maximum productivity obtained in this study was about 13 g/l-h which was ca. 3.3 times higher than that obtained in a conventional chemostat without cell retention by membrane. In another run of continuous culture, the laser turbidimeter used for the on-line monitoring of cell concentration showed a stable performance for 45 days without sensitivity loss due to fouling. [ABSTRACT FROM AUTHOR]

Filtration of ethanol fermentation medium and broth by using symmetric and asymmetric ceramic membranes has been studied in an internal filter bioreactor. Factors studied included membrane structure and pore size, medium sterilization, and concentrations of glucose, yeast extract in the medium, yeast cell and protein in broth. The aim was to determine the main factors responsible for the decline in filtration performance during ethanol fermentation by Saccharomyces cerevisiae. Flux index (Fi) of a new concept has been developed to evaluate the degree of flux decline during the membrane fouling process. Fi was defined as the ratio of the membrane flux at certain filtration time ( t = t) to the initial ( t = −0) flux of pure water, not the initial ( t = +0) flux of the test fluid. Flux with sterilized medium was approximately two-fold higher than that with unsterilized medium although the reason could not be explained clearly. Glucose, interaction between glucose and yeast extract, yeast cells, and proteins in fermentation broth were found to play an important part in membrane fouling. Fi of the symmetric membrane decreased to a less extent than that of the asymmetric membrane with increasing glucose concentration. But, the result with various yeast cell concentrations turned out to be contrary. Fouling was more serious for asymmetric membrane during the filtration of fermentation supernatant. This was thought to be due to different fouling mechanisms for the two types of membrane. [ABSTRACT FROM AUTHOR]

Periodic backflushing of tubular ceramic membrane filters with filtrate was employed to alleviate membrane fouling in a bioreactor with internal-filtration. As the model system, yeast fermentation was dealt with in this study. There existed optimum backflushing interval and time to give a maximum flux recovery. At 16 g/l of yeast cell concentration, the mean flux increased about 2.5 times by using such repeated operation cycles as consisted of 4.53 minutes for filtration, 4.5 seconds for intermission, and 40 seconds for backflushing. Effects of aeration, agitation speed, and yeast cell concentration were also investigated. [ABSTRACT FROM AUTHOR]