Oxygen trapped by rare earth tetrahedral clusters in Nd4FeOS6: Crystal structure, electronic structure, and magnetic properties

Abstract Single crystals of Nd4FeOS6 were grown from an Fe-S eutectic solution. Single crystal X-ray diffraction analysis revealed a Nd4MnOSe6-type structure (P63mc, a=9.2693(1) Å, c=6.6650(1)Å, V=495.94(1) Å3, Z=2), featuring parallel chains of face-sharing [FeS6×1/2]4- trigonal antiprisms and interlinked [Nd4OS3]4+ cubane-like clusters. Oxygen atoms were found to be trapped by Nd4 clusters in the [Nd4OS3]4+ chains. Structural differences among Nd4MnOSe6-type Nd4FeOS6 and the related La3CuSiS7- and Pr8CoGa3-type structures have been described. Magnetic susceptibility measurements on Nd4FeOS6 suggested the dominance of antiferromagnetic interactions at low temperature, but no magnetic ordering down to 2 K was observed. Spin-polarized electronic structure calculations revealed magnetic frustration with dominant antiferromagnetic interactions

Oxygen trapped by rare earth tetrahedral clusters in Nd4FeOS6: Crystal structure, electronic structure, and magnetic properties

Abstract Single crystals of Nd4FeOS6 were grown from an Fe-S eutectic solution. Single crystal X-ray diffraction analysis revealed a Nd4MnOSe6-type structure (P63mc, a=9.2693(1) Å, c=6.6650(1)Å, V=495.94(1) Å3, Z=2), featuring parallel chains of face-sharing [FeS6×1/2]4- trigonal antiprisms and interlinked [Nd4OS3]4+ cubane-like clusters. Oxygen atoms were found to be trapped by Nd4 clusters in the [Nd4OS3]4+ chains. Structural differences among Nd4MnOSe6-type Nd4FeOS6 and the related La3CuSiS7- and Pr8CoGa3-type structures have been described. Magnetic susceptibility measurements on Nd4FeOS6 suggested the dominance of antiferromagnetic interactions at low temperature, but no magnetic ordering down to 2 K was observed. Spin-polarized electronic structure calculations revealed magnetic frustration with dominant antiferromagnetic interactions

Cash flow signals and analysts' earnings forecast revisions

This study investigates the incorporation of cash flow information in forecasts of earnings made by security analysts. It extends and links two streams of research in accounting. One stream of research has been concerned with revisions in earnings forecasts made by analysts. What factors lead to forecast revisions? Prior research has concentrated on investigating revisions of earnings forecasts in response to earnings announcements. A critique of that literature notes that there is a lack of knowledge concerning other factors that lead to forecast revisions (Brown, et al., 1985, p. 130). This study extends that research by identifying accounting measures beyond earnings apparently deemed informative to analysts when predicting future earnings. The second stream of research has been concerned with the question of whether a decomposition of earnings into cash flow and accrual components provides incremental information beyond that contained in earnings alone.à ¢ Is such a decomposition informative? Is a dollar of accrual accounting earnings (worth) the same as a dollar of cash flow? Prior research has investigated this question through analysis of security returns. Findings have been somewhat contradictory. This study extends that research by addressing the question of the use of earnings component information in the previously unexamined context of the formation of analysts' earnings forecasts. In doing so, the study provides evidence on the signal conveyed by earnings components as perceived by one major group of users of accounting information

CFD based design of a 4.3MW Francis turbine for improved performance at design and off-design conditions

Hydraulic turbines are designed for the available head and flow rate of the hydroelectric power plant. Design point usually gives the best efficiency. However, when the turbine is used at off-design conditions where the flow rate and head change mostly because of seasonal fluctuations, efficiency significantly reduces. Therefore, the objective of hydraulic turbine design is not only satisfying the power requirements and maximum efficiency at the design point, but also improved characteristics at off-design conditions. In this work, a 4.3 MW Francis turbine is designed with the help of Computational fluid dynamics. All turbine components are designed separately, and then full turbine analyses are performed to confirm the design. Once an efficient design is obtained for the design head and flow rate, CFD simulations for off-design conditions are performed to confirm the high efficiency of the turbine at these flow rate-head combinations. The efficiency of the designed turbine is in the range of 90 to 92 % for a wide range of head and flow rates.This research is financially supported by Turkish Ministry of Development. Computations are performed using the computational cluster of TOBB ETU Hydro Energy Research Laboratory (ETU Hydro)