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With memories continuing to dominate the area, power, cost and performance of a design, there is a critical need to provision reliable, high-performance memory bandwidth for emerging applications. Memories are susceptible to degradation and failures from a wide range of manufacturing, operational and environmental effects, requiring a multi-layer hardware/software approach that can tolerate, adapt and even opportunistically exploit such effects. The overall memory hierarchy is also highly vulnerable to the adverse effects of variability and operational stress. After reviewing the major memory degradation and failure modes, this paper describes the challenges for dependability across the memory hierarchy, and outlines research efforts to achieve multi-layer memory resilience using a hardware/software approach. Two specific exemplars are used to illustrate multilayer memory resilience: first we describe static and dynamic policies to achieve energy savings in caches using aggressive voltage scaling combined with disabling faulty blocks; and second we show how software characteristics can be exposed to the architecture in order to mitigate the aging of large register files in GPGPUs. These approaches can further benefit from semantic retention of application intent to enhance memory dependability across multiple abstraction levels, including applications, compilers, run-time systems, and hardware platforms. Copyright 2014 ACM.

In this study, Bi1-xSmxFe1-yCryO3 (x = 0.0, 0.05, 0.1, y = 0.0, 0.01, 0.02, 0.03) nanostructures were prepared by hydrothermal method at 220 °C using the KOH concentration of 4 M during 6 h. X-ray diffraction analysis showed that the samples have a distorted rhombohedral perovskite structure with the symmetry of an R3c space group. The FT-IR spectrums of BiFeO3 and Bi1-xSmxFe1-yCryO3 are confirmed by the metal-oxide absorption bands that appeared at 400 cm−1–600 cm−1, which are the characteristic bands of FeO6 octahedral groups in the perovskite structure. FESEM images showed that the particle size has been decreased by doping the elements Sm and Cr. The magnetic properties of Bi1-xSmxFe1-yCryO3 have been improved compared to the undoped BiFeO3. The results of the magnetic properties showed that a maximum magnetization at 15 k Oe of BiFeO3 (0.148 emu/g) to Bi0.9Sm0.1Fe0.97Cr0.03O3 (1.895 emu/g) has been increased. The optical properties showed that the optical bandgap energy of samples with co-doping of Sm and Cr has been reduced from 2.8 to 2.1 eV. The results of PL analysis showed that the electron–hole recombination with an increase of the doping of Sm and Cr contents has been decreased which result in an effect on the photocatalytic performance. The Congo red (CR) degradation efficiency under visible light irradiation with increased co-doped Sm and Cr consents has been increased and the Congo red degradation rate followed the first-order Langmuir–Hinshelwood kinetics model. [ABSTRACT FROM AUTHOR]

In this paper, spinel-strontium ferrite nanoparticles (SrFe2O4) were prepared by the sol-gel method. Structural, dielectric, and optical properties were characterized by the X-ray diffraction (XRD), LCR, UV-visible spectrophotometry, and photoluminescence spectroscopy (PL). The X-ray diffraction pattern shows that the single-phase cubic spinel structure for a sample at temperature of 700 °C has been formed. Also, studies of the field-scattering scanning electron microscope show that morphology synthesized samples are homogeneous, but since the samples have a magnetic property, thus the samples are aggregated. The dielectric parameters such as the dielectric constant (έ), dielectric loss (ἕ), and the ac electrical conductivity (σac) of the samples were investigated by using LCR-meter at room temperature in the frequency range of 20 Hz to 10 MHz. The results of the dielectric parameters show that by decreasing the frequency, the dielectric constant and the dielectric loss are increased, while the ac electrical conductivity increases in which these changes are justified by the Maxwell-Wegener model. The results of ultraviolet-light spectroscopy show that, by increasing temperature, the energy gap of SrFe2O4 nanoparticles decreases. Also, the results of photoluminescence spectroscopy of SrFe2O4 nanoparticles show that there is an emission peak in the ultraviolet region that is due to the recombination of free excitements arising from an exciton-exciton process which is known as the near band edge (NBE). [ABSTRACT FROM AUTHOR]

We study the magnetoresistance (MR) and spin transport in a graphene-based ferromagnetic/ferromagnetic barrier/s-wave superconductor (FFBS) junction for two regimes including retro-Andreev reflection (AR) (EF = 100Δ0) and retroreflection crossing over to specular Andreev reflection (EF = Δ0). We observed that the variation of exchange energy in the ferromagnetic region h1 has a stronger effect on the amplitude of the MR oscillations rather than length, exchange energy, and effective gate potential in the FB region in both regimes. In the EF = 100Δ0 regime, the higher values of exchange energy h1 approach EF, which decrease the amplitude of the MR oscillations with respect to FB length. By increasing the exchange energy up to h1 > EF, a phase shift occurs for the peaks of the MR curves and the amplitude of the MR oscillations reaches its maximum value at the exchange energy hc = 2EF + U0. Furthermore, in the EF = Δ0 regime, at the exchange energy h1 = eV, the amplitude of the MR oscillations approaches its maximum value. At this value of energy of carriers eV + h1 - EF (Dirac point), the sign of the energy will be reversed and a transition from the retroreflection to the specular Andreev reflection occurs. Thus, in this regime (EF = Δ0), by observing the maximum of the MR at specified values of eV and h1, we can measure the Fermi energy of the graphene. While in the EF = 100Δ0 regime, the MR versus bias energy can be tuned from the positive to negative values by varying h1, but in the EF = Δ0 regime, the MR shows only the positive values. In addition, we have investigated the spin conductance in both regimes. [ABSTRACT FROM AUTHOR]

We report the low-temperature preparation of WS2 nanosheets by chemical vapor deposition (CVD) method for photoelectrochemical (PEC) water splitting application. The WS2 nanosheets were synthesized onto the FTO, ITO, SiO2, and glass substrates at a relatively low temperature of 500 °C under pressure of 10−2 Torr. Compared to temperatures of conventional WS2 synthesis via CVD method, the deposition was performed at a sufficiently low temperature, which has not been reported for the layer deposition yet. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet–visible (UV–visible) spectroscopy. The results show that WS2 nanosheets were grown almost vertically and alike a single crystal. Based on the SEM images, the WS2 nanosheets grew homogenously on the FTO substrate and covered the entire surface of the substrate. Linear sweep voltammetry (LSV), applied bias photon to current efficiency (ABPE), photocurrent response, and electrochemical impedance spectroscopy (EIS) of the fabricated nanosheets were measured for the photoelectrochemical response. Because of no transferring to damage layer, the results showed that WS2 nanosheets on FTO substrate had good photoelectrochemical activity. The measured photocurrent of 32 µAcm−2 and ABPE efficiency of 0.84% at a 0.75 V bias (versus RHE) was considerably high compared to the other results reported for WS2 nanosheets. [ABSTRACT FROM AUTHOR]

Abstract: In this study, the microstructure, hardness, and dry sliding wear behavior of the hardfaced layers made by a cored wire Fe-B-C-Ti alloy were investigated. St37 steel was used as the substrate and the deposition of the hardfaced layers was conducted by the flux cored are welding(FCAW) process Under single-, two-, and three-pass conditions. Dry sliding wear tests were performed by a pin-on-disk apparatus, based on. ASTM-G99. at room temperature 25°i') at the normal applied loads of 50. 100. and 150 N with a constant speed of 0.08 m's for a sliding distance of 1000 m. The micurstructral and phase analyses were carried out by field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD), respectively. The results showed that the hardfaced layer produced by the single-pass process contains TiC rectangular phase distributed within a matrix containing ferrite and the eutectic of (a-FeB). But the hardfaced layers produced by the two- and three-pass process contain TiB, hexagonal phase in addition to TIC. winch prevents the formation of detrimental FeB phase around Fe2β and reduces the number of micro-cracks Moreover, the sample hardfaced by the three-pass process had the best wear resistance due to the greater hardness resulted from the higher amounts of TiC and TiB' phases. In addition increasing the number of passes has led to the reduction of wear rate at all the three applied loads At the applied load of 100 N. the wear mechanism for the all three hardfaced samples was an oxidation wear However, at the applied load of 150 N. the wear mechanism was a combination of oxidation and delamination. [ABSTRACT FROM AUTHOR]

Y3Ba5Cu8O18 superconductors were prepared through a standard solid-state reaction and the structural properties of the samples were studied through XRD and the Rietveld refinement method. The effect of silver nanoparticles doping on the Y3Ba5Cu8O18 superconductors was studied as well. It is known that the size of nanoparticles is increased during aging. Therefore, two batches of samples with 1 and 2 wt% of Ag nanoparticles and the size range of 30, 200, 500, 700, 800, and 1000 nm were prepared. After preparing the samples and observing the Meissner effect, the crystallography, critical current density, critical temperature, magnetic susceptibility, SEM, and EDX experiments of the samples were carried out. The results of the critical current density measurements showed that the sample with 2 wt% Ag nanoparticles and the size of 700 nm has the maximum current density. In both batches of samples, increasing the nanoparticle size to 700 nm led to an increase in the critical current density. The crystallography studies showed that silver nanoparticles do not insert into the superconductor’s frame. Actually, they are placed in the samples as a distinct phase. [ABSTRACT FROM AUTHOR]

The present study tries to investigate Wiedemann-Franz law near and far from the critical temperatures, given the tunneling between the grains in Cooper pair fluctuation propagator and impurity vertex. By means of Dyson’s equation, the Cooper pair fluctuation propagator, L(qkΩμ) and the Cooperon (impurity vertex), λ(q, k, ε1, ε2), are initially calculated in the presence of tunneling between the grains. Then, the three distinct contributions of density of states, Maki-Thompson, and Aslamazov-Larkin, are calculated in the frameworks of the Green’s functions formalism and the Kubo formula technique. The evaluation is conducted under the limited tunneling conductance between the grains. Findings show that although the tunneling is efficient near the critical temperature, it is not effective when it is far from the critical temperature Compared to that in high temperatures, moreover, the deviation from the Wiedemann-Franz law is much more evident in low temperatures. [ABSTRACT FROM AUTHOR]