Currently, 2D nanomaterials-based resistive random access memory (RRAMs) are explored on account of their tunable material properties enabling fabrication of low power and flexible RRAM devices. In ...this work, hybrid MoS2-GO based active layer RRAM devices are investigated. A facile hydrothermal co-synthesis approach is used to obtain the hybrid materials and a cost-effective spin coating method adopted for the fabrication of Ag/MoS2-GO/ITO RRAM devices. The performance of the fabricated hybrid active layer RRAM device is analysed with respect to change in material properties of the synthesized hybrid material. The progressive addition of 0.5, 1.5, 2.5 and 4.5 weight % of GO to MoS2, results in a hybrid active layer with higher intermolecular interaction, in the case of Ag/MoS2-GO4.5/ITO RRAM device, resulting in a unipolar resistive switching RRAM behavior with low SET voltage of 1.37 V and highIon/Ioffof 200 with multilevel resistance states. A space charge limited conduction mechanism is obtained during switching, which may be attributed to the trap states present due to functional groups of GO. The increased number of conduction pathways on account of both Ag+ions and oxygen vacancies (Vo2+), participating in the formation of conducting filament, results in higherIon/Ioff. This is the first report of unipolar Ag/MoS2-GO/ITO RRAM devices, which are particularly important in realizing high density crossbar memories for neuromorphic and in-memory computing as well as enabling flexible 2D nanomaterials-based memristor applications.Currently, 2D nanomaterials-based resistive random access memory (RRAMs) are explored on account of their tunable material properties enabling fabrication of low power and flexible RRAM devices. In this work, hybrid MoS2-GO based active layer RRAM devices are investigated. A facile hydrothermal co-synthesis approach is used to obtain the hybrid materials and a cost-effective spin coating method adopted for the fabrication of Ag/MoS2-GO/ITO RRAM devices. The performance of the fabricated hybrid active layer RRAM device is analysed with respect to change in material properties of the synthesized hybrid material. The progressive addition of 0.5, 1.5, 2.5 and 4.5 weight % of GO to MoS2, results in a hybrid active layer with higher intermolecular interaction, in the case of Ag/MoS2-GO4.5/ITO RRAM device, resulting in a unipolar resistive switching RRAM behavior with low SET voltage of 1.37 V and highIon/Ioffof 200 with multilevel resistance states. A space charge limited conduction mechanism is obtained during switching, which may be attributed to the trap states present due to functional groups of GO. The increased number of conduction pathways on account of both Ag+ions and oxygen vacancies (Vo2+), participating in the formation of conducting filament, results in higherIon/Ioff. This is the first report of unipolar Ag/MoS2-GO/ITO RRAM devices, which are particularly important in realizing high density crossbar memories for neuromorphic and in-memory computing as well as enabling flexible 2D nanomaterials-based memristor applications.
This study examines the effect of cobalt on the crystallographic texture and grain boundary evolution of hot-press sintered tungsten heavy alloy (W-4.9Ni-2.1Cu). Traditional tungsten heavy alloy with ...a Ni:Cu ratio of 7:3 has cobalt added (i.e., cobalt content increased from 0 to 1 wt% with a 0.25 wt% interval). The samples were produced using the hot press sintering method with the following parameters: 50 MPa pressure, 10 °C/min heating rate, 1450 °C temperature, and a 20-min hold time. The unalloyed cobalt WHA compact has a fibre texture in the (001) plane that is aligned in the 〈111〉 orientation. In addition, the cobalt-alloyed WHAs compacts exhibit a lower proportion of grain boundaries with low angles. Enhanced solid solution formation between cobalt and WHAs during liquid phase sintering led to increased compacts densification and randomised weak fibre development in cobalt-alloyed compacts. Texture deterioration (001) in cobalt-added WHAs is caused predominantly by substructural recovery during liquid phase sintering. This study indicates that the addition of cobalt to the stoichiometry of WHAs resulted in the homogenous distribution of binder matrix within the compact during sintering. As a result, the W-4.9Ni-2.1Cu-1Co alloy exhibited improved microhardness (429.5 HV0.5), electrical conductivity (23.34% of IACS), and relative density (98.10%).
•The use of ball milling results in higher densification, faster solution re-precipitation kinetics during sintering.•Weakness in (001) texture was attributed from the increase of cobalt stoichiometry in WHAs (W-4.9Ni-2.1Cu).•Enrichment of cobalt at the tungsten-binder matrix interface results in textural anisotropy in cobalt added WHAs.•Cobalt is an effective alloying addition for strengthening the WHA as evidenced by an increase of hardness and conductivity.
In the present scenario, conducting and lightweight flexible polymer nanocomposites rival metallic and inorganic semiconducting materials as highly sensitive piezoresistive force sensors. Herein, we ...explore the feasibility of vertically aligned carbon nanotube (VACNT) nanocomposites impregnated in different polymer matrixes, envisioned as highly efficient piezoresistors in sensor applications. Polymer nanocomposites are selectively designed and fabricated using three different polymer matrixes, i.e., polydimethylsiloxane (PDMS), polyurethane (PU), and epoxy resins with ideal reinforcement of VACNTs to enhance the thermal stability, conductivity, compressibility, piezoresistivity, and sensitivity of these nanocomposites. To predict the best piezoresistive force sensor, we evaluated the structural, optical, thermal, electrical, mechanical, and piezoresistive properties of the nanocomposites using field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Raman spectroscopy, thermogravimetric analysis (TGA), I–V measurements, compressive stress–strain measurements, hysteresis, sensitivity, and force studies. The results demonstrate that the PDMS/VACNT nanocomposite is capable of sustaining large force with almost complete recovery and enhanced sensitivity, thereby fulfilling the desirable need for a highly efficient conductive and flexible force sensor as compared to PU/VACNT and epoxy/VACNT nanocomposites.
A production-inventory system with the item produced being admitted (added to the inventory) with probability δ as well as an item from the inventory supplied to the customer with probability γ at ...the end of a service, is considered in this paper. The (s, S) control policy is followed. We obtain the joint distribution of the number of customers and the number of items in the inventory as the product of their marginals under the assumption that customers do not join when the inventory level is zero. Performance measures that impact the system are obtained. A few level-crossing results are derived. In particular optimal pairs (s, S) are obtained through numerical procedures for values of (γ, δ) on the set {0.1, 0.2, . . . , 1} × {0.1, 0.2, . . . , 1} . A comparison of the performance measures for a few (γ, δ) pair values is provided. Finally, we discuss the first emptiness time distribution for the M/M/1/1 production-inventory system.
In this article, we investigate the dynamic control problem of a production-inventory system. Here, demands arrive at the production unit according to a Poisson process and are processed in an FCFS ...manner. The processing time of the customer’s demand is exponentially distributed. Production manufacturers produce items on a make-to-order basis to meet customer demands. The production is run until the inventory level becomes sufficiently large. We assume that the production time of an item follows an exponential distribution and that the amount of time for the produced item to reach the retail shop is negligible. In addition, we assume that no new customer joins the queue when there is void inventory. Moreover, when a customer is waiting in an infinite FIFO queue for service, he/she does not leave the queue even if the inventory is exhausted. This yields an explicit product-form solution for the steady-state probability vector of the system. The optimal policy that minimizes the discounted/average/pathwise average total cost per production is derived using a Markov decision process approach. We find an optimal policy using value/policy iteration algorithms. Numerical examples are discussed to verify the proposed algorithms.
This study focuses on fabricating aluminium hybrid metal matrix with eco-friendly agro waste, cow dung ash and boron carbide by two stage stir casting. Weight percentage of cow dung ash and boron ...carbide were reinforced in ratios of 2.5:7.5, 5:5, and 7.5:2.5. The fabricated samples were subjected to optical microscope, scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX) to identify micro structural analysis and phase identification of the reinforcements respectively. The effects on mechanical properties like density, hardness, tensile strength, impact strength and flexural strength properties were studied, and the results are compared to the base alloy (Al 7075). Fracture mechanisms for tensile and impact specimens were analysed through SEM and EDX. Micro structural and SEM images reveal uniform distribution of particles in the matrix. Increasing CDA particles has reduced the density of the hybrid composite up to 8%. A maximum increase in hardness and tensile strength was up to 30% and 56% respectively, and then a slight decrease was found in increasing the CDA particles. The flexural strength has increased to a maximum of 12% at 7.5% CDA and decrement in impact strength was inferred in all the hybrid composites when compared with base alloy. Dimples, transgranular cleavage facets and cracks are revealed from the fractured specimens of tensile and impact specimens.
Graphic Abstract
In this current study, the impact of manganese addition to 93 W-4.9Ni-2.1Cu-xMn (where x = 1, 2, 3, and 4 Wt%) on the microstructure, texture development, and grain boundary character distribution of ...tungsten heavy alloy (WHAs) was examined. The samples were produced through a vacuum hot press sintering, with parameters 50 MPa pressure, 10 °C/min heating rate, and 1450 °C sintering temperature for 20 min holding duration. To study the influence of manganese on the texture development and microstructure in conventional WHAs, electron backscatter diffraction (EBSD) was employed. The important findings from the EBSD analysis reveal that fibre texture (001) 〈111〉 and a higher fraction of low-angle grain boundaries in the Mn unalloyed compact resulted from extensive atomic jumps between the particles at elevated temperatures. Further texture analysis on the Mn-added compacts reveals that manganese oxide (MnO) formation during liquid phase sintering led to lower densification and randomized weak fibre texture development in manganese-alloyed compacts. In addition, the texture degradation in Mn-added compacts is mainly caused by recrystallization followed by sub-structural recovery during liquid phase sintering. This study indicates that increasing manganese content in WHAs stoichiometry led to a heterogeneous distribution of binder matrix (NiCu) in the sintered compact. As a result, W-4.9Ni-2.1Cu-4Mn alloy revealed decreased relative density (90.70%), microhardness (389.5 HV0.5), and electrical conductivity (15.74% of IACS).
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•The formation of manganese oxide in Mn-added WHAs leads to a reduction in density and properties.•The addition of Mn into WHAs induces alterations in the texture orientation of Ʃ3 CSL and HAGBs.•The {111} 〈001〉 texture became weaker as the manganese stoichiometry in WHAs increased.•Hardness and conductivity showed the W-Ni-Cu alloy does not benefit from Mn.
Antioxidants and cataract Thiagarajan, R.; Manikandan, R.
Free radical research,
05/2013, Letnik:
47, Številka:
5
Journal Article
Recenzirano
Abstract
The major causes for cataract formation are free radicals, and these free radicals are neutralized by the presence of endogenous antioxidants in the eye. Using xenobiotics, it has been ...confirmed that free radicals mediate the formation of cataract. Two cataract model-selenite model and the diabetic cataract model-have been developed to study the pathophysiology of cataract formation due to free radicals and the role of antioxidants during the process of cataractogenesis. This review focuses on natural compounds with antioxidant properties that could actually be applied as an interventional strategy on a large scale and are also relatively inexpensive. A brief overview of plants with antioxidant properties that in addition possess potential anti-cataract properties has been discussed. In addition to plants, three natural compounds (curcumin, vitamin C and vitamin E), on which a lot of data exist showing anti-cataract and antioxidant activities, have also been discussed. These antioxidants can be supplemented in the diet for a better defence against free radicals. Studies on vitamin C and vitamin E have proved that they are capable of preventing lipid peroxidation, thereby preventing the generation of free radicals, but their efficacy as anti-cataract agent is questionable. Unlike vitamins C and E, curcumin is well established as an anti-cataract agent, but the issue of curcumin bioavailability is yet to be addressed. Nanotechnology proves to be a promising area in increasing the curcumin bioavailability, but still a lot more research needs to be done before the use of curcumin as an effective anti-cataract agent for humans.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Diagnostics of defective leg and switch faults in 3-ph voltage source inverter (VSI) powered induction motor drive system is the primary stage to design the fault-tolerant operation. The ...preponderance of fault detection techniques largely relies on threshold value-tuning for identifying defective switches. And, using the current component as a variable to determine open circuit switch failure. From this perspective, the paper presents an open circuit switch fault diagnosis strategy for 3-ph 2-level VSI. The strategy is based on the estimated phase voltages, which are immune to false alarms caused by transient conditions and parameter fluctuation. An average objective function from the established model predictive current (MPC) control scheme is selected as the fault diagnosis variable to identify the fault in the 3-ph VSI. The polarities of the estimated normalized mean value of inverter voltages are utilized to localize the open circuit switch fault. With the aid of the aforementioned variables, the developed fault diagnosis technique accurately identifies and locates the faulty switches. The voltage signature for the 18 possible combination faults is developed and realized. To assure the reliability of the established fault identification approach, the IM with 2-level VSI is operated with the open fault in different operating conditions in Matlab/Simulink environment and experimentally validated. The hardware experimentation is performed with 2-level VSI and 3.7 kW three-phase IMD.
