93 research outputs found

    Reliability centered maintenance optimization for power distribution systems

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    a b s t r a c t Today's electricity distribution systems operate in a liberalized market. These systems should therefore be able to provide electricity to customers with a high degree of reliability and be cost-effective for suppliers. RCM (Reliability Centred Maintenance) was invented by the aircraft industry in the 1960s, to organize the increasing need for maintenance for reducing costs without reducing b safety. Today RCMmethods invented by ALADON [1] are seen as very complex and are not fully accepted by the Algerian power industry. The extensive need of human and capital resources in the introduction phase is also a negative factor that could be one of the reasons of why RCM methods are not used in our branch. This article provides a discussion of the two primary objectives of RCM: to ensure safety through preventive maintenance actions, and, when safety is not a concern, preserve functionality in the most economical manner. For the power distribution systems facilities, the mission should be considered at the same level as safety

    Investigation of the Switching Mechanism in TiO2-Based RRAM: A Two-Dimensional EDX Approach

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    The next generation of nonvolatile memory storage may well be based on resistive switching in metal oxides. TiO2 as transition metal oxide has been widely used as active layer for the fabrication of a variety of multistate memory nanostructure devices. However, progress in their technological development has been inhibited by the lack of a thorough understanding of the underlying switching mechanisms. Here, we employed high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) combined with two-dimensional energy dispersive X-ray spectroscopy (2D EDX) to provide a novel, nanoscale view of the mechanisms involved. Our results suggest that the switching mechanism involves redistribution of both Ti and O ions within the active layer combined with an overall loss of oxygen that effectively render conductive filaments. Our study shows evidence of titanium movement in a 10 nm TiO2 thin-film through direct EDX mapping that provides a viable starting point for the improvement of the robustness and lifetime of TiO2-based resistive random access memory (RRAM)

    Emulating long-term synaptic dynamics with memristive devices

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    The potential of memristive devices is often seeing in implementing neuromorphic architectures for achieving brain-like computation. However, the designing procedures do not allow for extended manipulation of the material, unlike CMOS technology, the properties of the memristive material should be harnessed in the context of such computation, under the view that biological synapses are memristors. Here we demonstrate that single solid-state TiO2 memristors can exhibit associative plasticity phenomena observed in biological cortical synapses, and are captured by a phenomenological plasticity model called triplet rule. This rule comprises of a spike-timing dependent plasticity regime and a classical hebbian associative regime, and is compatible with a large amount of electrophysiology data. Via a set of experiments with our artificial, memristive, synapses we show that, contrary to conventional uses of solid-state memory, the co-existence of field- and thermally-driven switching mechanisms that could render bipolar and/or unipolar programming modes is a salient feature for capturing long-term potentiation and depression synaptic dynamics. We further demonstrate that the non-linear accumulating nature of memristors promotes long-term potentiating or depressing memory transitions

    Comparative study between cases of previous one cesarean section delivered at Kafr El-Sheikh hospitals, versus those delivered at Tanta Uniersity Hospital

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    Background: Many factors have contributed to the increasing rates of CSs, including increases in maternal age, BMI, and changes in obstetric practices and technologies. CSs requested by the mother and fear of litigation among caregivers have now become one of the most common indications of CS. Aim of this study was to compare between conditions of previous one caesarean section subjects delivered at Kafr El-Sheikh general hospitals, versus those delivered at Tanta University hospital as regard integrity of the uterine scars, presence of adhesions, time of termination, and fetal outcomes.Methods: This study was an observational study that was carried out on 100 pregnant ladies with history of previous one caesarean section. Participants were divided into two groups: group I included 50 pregnant women selected from Tanta University hospitals, group II included 50 pregnant women selected from Kafr El-Sheikh General hospital.Results: The estimated blood loss was significantly higher in cases selected from Kafr El-Sheikh hospitals compared to that lost from cases selected from Tanta University hospitals. Furthermore, operation time was significantly longer in patients selected from Kafr El-Sheikh hospitals than those selected from Tanta University hospitals. Additionally, omental adhesion was observed in 5 cases (5%); 3 (6%) from those selected from Kafr El-sheikh hospitals and 2 (4%) from those selected from Tanta University hospitals. As regard post-operative blood transfusion, there were increase in the incidence of post-operative blood transfusion in pregnant women selected from Kafr El-Sheikh hospitals (8%) compared to those selected from Tanta University hospitals (4%), but without statistically significant difference (p=0.678).Conclusions: There is high rate of caesarean section in our country. But satisfactory results were present in both Tanta university hospitals and Kafr El-Sheikh general hospital with few complication rates found special in cases priory delivered at Tanta University hospitals including less adhesion finding and thus less intra and post-operative complications

    Role and optimization of the active oxide layer in TiO<sub>2</sub>-based RRAM

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    TiO2 is commonly used as the active switching layer in resistive random access memory. The electrical characteristics of these devices are directly related to the fundamental conditions inside the TiO2 layer and at the interfaces between it and the surrounding electrodes. However, it is complex to disentangle the effects of film “bulk” properties and interface phenomena. The present work uses hard X-ray photoemission spectroscopy (HAXPES) at different excitation energies to distinguish between these regimes. Changes are found to affect the entire thin film, but the most dramatic effects are confined to an interface. These changes are connected to oxygen ions moving and redistributing within the film. Based on the HAXPES results, post-deposition annealing of the TiO2 thin film was investigated as an optimisation pathway in order to reach an ideal compromise between device resistivity and lifetime. The structural and chemical changes upon annealing are investigated using X-ray absorption spectroscopy and are further supported by a range of bulk and surface sensitive characterisation methods. In summary, it is shown that the management of oxygen content and interface quality is intrinsically important to device behavior and that careful annealing procedures are a powerful device optimisation technique
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