Exploring the Room-Temperature Ferromagnetism and Temperature-Dependent Dielectric Properties of Sr/Ni-Doped LaFeO<Subscript>3</Subscript> Nanoparticles Synthesized by Reverse Micelle Method

This paper reports the thermal, microstructural, dielectric and magnetic properties of La_0.75Sr_0.25Fe_0.65Ni_0.35O₃ nanoparticles (NPs) synthesized via reverse micelle technique. The thermogravimetric analysis of as-prepared NPs confirmed a good thermal stability of the sample. Powder x-ray diffraction data analyzed with a Rietveld refinement technique revealed single-phase and orthorhombic distorted perovskite crystal structure of the NPs having Pbnm space group. The transmission electron microscopy images show the crystalline nature and formation of nanostructures with a fairly uniform distribution of particles throughout the sample. Temperature-dependent dielectric properties of the NPs in accordance with the Kramers–Kronig transformation (KKT) model, universal dielectric response model and jump relaxation model have been discussed. Electrode or interface polarization is likely the cause of the observed dielectric behavior. Due to grain boundaries and Schottky barriers of the metallic electrodes of semiconductors, the depletion region is observed, which gives rise to Maxwell–Wagner relaxation and hence high dielectric constants. Magnetic studies revealed the ferromagnetic nature of the prepared NPs upon Sr and Ni doping in LaFeO₃ perovskite at room temperature. Therefore, these NPs could be a potential candidate as electrode material in solid oxide fuel cells.     

高负荷轴流压气机内以氦-氙混合气为工作介质的评估（英文）

本文评价了分子量为15g/mole的氦-氙双项混合气体作为流动工质在核电厂轴流压气机的应用。由于纯氦具有普遍的传输特性,在很多情况下很难被压缩,因此是一种最佳的冷却剂。同时,纯氦工质在高温气冷堆(HTGR)的应用引起了涡轮机械的尺寸更大、质量越来越大、成本更高及叶轮机械的动力问题。为此,本文设计了一台高负荷氦氙压气机,并对其性能进行了分析。结果显示,只有18%的氦气压气机级需要在高负荷氦气-氙气压气机中将气体压缩至所需压力。通过设计分析,工作在闭式布雷顿循环(CBC)中高温气冷堆(HTGR)压气机,可由16级减少到2级。因此,在高温气冷堆电厂的涡轮压压气中,氦氙比纯氦更有优势。     

Influence of Nd-Co Substitution on Structural,Electrical, and Dielectric Properties of X-Type Hexagonal Nanoferrites

A series of single phase X-type hexagonal ferrites with concentration Sr_2?x Nd _x Ni₂Fe_28?y Co _y O₄₆ (x = 0.02, 0.04, 0.06, 0.08, 0.10 and y = 0.1, 0.2, 0.3, 0.4, 0.5) has been prepared by sol-gel method sintered at 1250 °C for 6 h. The x-ray diffraction analysis reveals the single phase of X-type hexagonal ferrites. The particle size was calculated by using SEM and TEM. The ferrite substituted with Nd³⁺ and Co²⁺ has average particle size in the range of 40-50 nm. The room temperature electrical resistivity experiences the significant enhancement from a value of 1.1 × 10⁷ to 2.03 × 10⁸ Ωcm with the increase in Nd³⁺ and Co²⁺ concentration. The dielectric constant exhibits high value at low frequencies and decreases with the increase of frequency. The tangent dielectric loss shows the abnormal behavior which can be explained on the basis of hopping between the Fe²⁺ and Fe³⁺ ions on octahedral sites. The maximum value of tangent loss at low frequencies reflects the application of these materials in medium frequency devices (MF).     

The effects of hydrogen on aluminum-induced crystallization of sputtered hydrogenated amorphous silicon

The effects of hydrogen on aluminum-induced crystallization (AIC) of sputtered hydrogenated amorphous silicon (a-Si:H) were investigated by controlling the hydrogen content of a-SiH films. Nonhydrogenated (a-Si) and hydrogenated (a-Si:H) samples were deposited by sputtering and plasma-enhanced chemical vapor deposition (PECVD). All aluminum films were deposited by sputtering. Hydrogen was introduced into the sputter-deposited a-Si films during the deposition. After deposition, the samples were annealed at temperatures from 200°C to 400°C for different periods of time. X-ray diffraction (XRD) patterns were used to confirm the presence and degree of crystallization in the a-Si:H films. For nonhydrogenated films, crystallization initiates at a temperature of 350°C. The crystallization of sputter-deposited a-Si:H initiates at 225°C when 14% hydrogen is present in the film. As the hydrogen content is decreased, the crystallization temperature increases. On the other hand, the crystallization initiation temperature for PECVD a-Si:H containing 11at.%H is 200°C. Further study revealed that the crystallization initiation temperature is a function, not only of the total atomic percent hydrogen in the film, but also a function of the way in which the hydrogen is bonded in the film. Models are developed for crystallization initiation temperature dependence on hydrogen concentration in a-Si:H thin films.     

Practical verification of embedded software

Using a new verification algorithm called the compositional backward technique, the authors demonstrate that they can exhaustively verify even the largest industrial applications-comprising more than 1,000 components-in a few minutes on a standard PC     

Repelling the young and attracting the old: Examining age-related differences in saccade trajectory deviations.

In the present study, the authors examined age-related differences in saccade curvature as older and younger adults looked to an X target that appeared concurrently with an O distractor. They used a fixation gap procedure to introduce variance into the saccadic latencies of both groups. Consistent with earlier findings, younger adults' early onset saccades curved toward the distractor (as the distractor competed with the target for response selection), while late-onset saccades curved away from the distractor (as the distractor location became inhibited over time). In contrast, older adults' saccades gradually decreased in curvature toward the distractor, but at no point along the latency continuum did they show deviations away. These results suggest that while the local inhibitory mechanisms responsible for decreases in curvature toward distractors may be preserved with age, aging may lead to a selective decline in the frontal inhibitory mechanisms responsible for deviations away from distractors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Arsenic-implanted thin film PECVD semi-insulating polysilicon (SIPOS) resistors

Thin film (2000&#x00C5;) PECVD SIPOS resistors were fabricated using arsenic implantation and rapid thermal annealing. The current-voltage characteristics are symmetrical and field-dependent. The resistivity (as low as 0.2 ohm-cm) is shown to be a function of the oxygen content of the as-deposited material, the implant dose, and the annealing temperature. The variation of resistance with operating temperature also decreases with increasing dose and annealing temperature. As expected, the lowest resistivity is obtained for films with high refractive indices or alternatively, low oxygen content. *This work was supported by a research contract from Sandia National Lab.