Cation distribution in oxide fuels — a neutron scattering study

We use diffuse neutron scattering techniques to investigate cation ordering in the mixed oxide U/CeO_2?x — a model system for the oxide U/PuO_2?x. Our results show that there is little deviation from a random cation distribution at 10 or 20 mol% dopant concentration. Significant short-range order appears, however, to be present at 30 mol%. Experiments on samples prepared under reducing conditions suggest that vacancies have little effect on the cation short-range order, and thus cast doubt on the validity of models which assume dopant aggregation around vacancies.     

Separation of a Nonstationary Component from the EEG by a Nonlinear Digital Filter

A new nonlinear digital filter which separates nonstationary waves such as spikes from stationary background waves of the EEG is proposed. This filter is composed of a prediction filter and a simple nonlinear function. Some examples showing the separation of spikes from EEG data of epileptic patients are given.     

Adenovirus 3 penton dodecahedron exhibits structural changes of the base on fibre binding

It was recently shown that co-expression of adenovirus type 3 (Ad3) penton base and fibre in the baculovirus system produces dodecahedral particles, as does the expression of the penton base alone. The structure of both of these dodecahedral particles, with and without fibre, has been determined by cryoelectron microscopy and 3-dimensional reconstruction techniques to a resolution of 25 and 20 A, respectively. The general form of the penton base resembles that of the base protein in the recent reconstruction of adenovirus type 2. There is a remarkable difference in the penton base structure with and without the fibre. The five small protuberances on the outer surface of each base move away from the 5-fold axis by approximately 15 A when the fibre is present. These protuberances are of relatively low density and most probably represent a flexible loop possibly containing the RGD site involved in integrin binding. The fibre is apparently bound to the outer surface of the penton base, rather than inserted into it. The fibre is flexible and the shaft contains two distinct globular regions 26 A in diameter. The volume of the inner cavity of the dodecahedron is 350 +/- 100 nm3. This small volume precludes the use of the inner cavity to house genetic information for gene therapy; however, the possibility remains of linking the gene to the dodecahedron surface in the hope that it will be internalized with the dodecahedron.     

Eye movements and neural remapping during fusion of misaligned random-dot stereograms

Fender and Julesz [J. Opt. Soc. Am. 57, 819 (1967)] found that fused retinally stabilized binocular line targets could be misaligned on the two retinas in the temporalward direction by at least 30 min of arc without loss of fusion and stereopsis and that random-dot stereograms could be misaligned 2 deg before fusion was lost. To test these results in normal vision, we recorded eye motions of four observers while they viewed a random-dot stereogram that subtended about 10 deg. The observers misaligned overlaid vectograph stereo images by moving them apart in a temporalward direction until fusion was lost. They then returned the vectographs to the overlaid position. Throughout this cycle the observers reported at frequent intervals if they could perceive strong or weak depth, loss of depth, or loss of fusion. For some observers the image separation could be increased to 5 deg beyond parallel before fusion was lost. The visual axes diverged to follow the image centers and varied from overconverged to overdiverged with respect to the image centers while the observers still reported depth and fusion. We call the difference between the image separation and eye vergence the vergence error. If a vergence error persisted for at least 10 sec without loss of the percepts of fusion and depth, we postulate that neutral remapping occurred that compensated for the retinal misalignment. We found that the average maximum neural remapping was 3.0 deg.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dynamic two-axis curvature measurement using multicore fiber Bragg gratings interrogated by arrayed waveguide gratings

We describe the use of arrayed waveguide gratings (AWGs) in the interrogation of fiber Bragg gratings (FBGs) for dynamic strain measurement. The ratiometric AWG output was calibrated in a static deflection experiment over a +/-200 microepsilon range. Dynamic strain measurement was demonstrated with a FBG in a conventional single-mode fiber mounted on the surface of a vibrating cantilever and on a piezoelectric actuator, giving a resolution of 0.5 microepsilon at 2.4 kHz. We present results of this technique extended to measure the dynamic differential strain between two FBG pairs within a multicore fiber. An arbitrary cantilever oscillation of the multicore fiber was determined from curvature measurements in two orthogonal axes at 1125 Hz with a resolution of 0.05 m(-1).     

Direct computation of solution spaces

In engineering, it is often desirable to find a subset of the set of feasible designs, a solution space, rather than a single solution. A feasible design is defined as a design which does not violate any constraints and has a performance value below a desired threshold. Performance measure, threshold value and constraints depend on the specific problem. For evaluation of a design with respect to feasibility, a model is required which maps the design parameters from the input space onto the performance measures in the output space. In state-of-the-art methodology, iterative sampling is used to generate an estimate of the frontier between feasible and infeasible regions in the input space. By evaluating each sample point with respect to feasibility, areas which contain a large fraction of feasible designs are identified and subsequently resampled. The largest hypercube containing only feasible designs is sought, because this results in independent intervals for each design parameter. Estimating this hypercube with sufficient precision may require a large number of model evaluations, depending on the dimensionality of the input space. In this paper, a novel approach is proposed for modeling the inequality constraints and an objective function in a way for which a linear formulation can be used, independently of the dimensionality of the problem. Thereby the exact solution for the largest feasible hypercube can be calculated at much lower cost than with stochastic sampling as described above, as the problem is reduced to solving a linear system of equations. The method is applied to structural design with respect to the US-NCAP frontal impact. The obtained solution is compared to numerical solutions of an identical system, which are computed using reduced order models and stochastic methods. By this example, the high potential of the new direct method for solution space computation is shown.     

Unbalance protection of fuseless, split-wye, grounded, shunt capacitor banks

In recent years, a large number of electric utilities have been implementing fuseless split-wye grounded capacitor banks in lieu of the traditional externally fused bank. This change in philosophy has forced many protection engineers to research new methods of calculating the quantities needed to apply unbalance protection. This paper presents a novel method of calculating the unbalance current produced by fuseless capacitor unit failures as well as some general background information regarding fuseless split-wye grounded capacitor bank technology and unbalanced protection.     

The SrFeO2.5 | SrFeO3.0 system. Evidence of a new phase Sr4Fe4O11 (SrFeO2.75)

Evidence is presented for a new phase of ideal composition SrFeO_2.75 in the system SrFeO_3?x (0.5 ? x ? 0). Electron diffraction evidence suggests orthorhombic or body-centred tetragonal symmetry with lattice parameters related to the cubic perovskite lattice parameter a_c by $\text{a}\text{? 2√2}\text{a}{}_{\mathrm{c}}$, $\text{b}\text{? 2}\text{a}{}_{\mathrm{c}}$. $\text{c}\text{? 2√2}\text{a}{}_{\mathrm{c}}$. A plausible model for the structure is presented which is related to that of SrFeO_2.5. Powder x-ray diffraction photographs reveal only a simple cubic perovskite cell for SrFeO_2.75, presumably because the ordered domains giving rise to the superstructure observed in electron diffraction are small in extent. At other intermediate compositions slow cooling gives mixtures of the new phase and either SrFeO_2.5 or SrFeO₃. The two-phase regions narrow at high temperatures and thermogravimetric studies at 1 atm pressure of oxygen indicate a single phase between SrFeO_2.5 and SrFeO_2.75 between 500°C and 950°C.