Proceedings of the National Academy of Sciences, India Section A: Physical Sciences最新文献

Multi-level switching memristor devices are becoming a need of the hour to implement the synaptic behaviour for brain-inspired in-memory computing. In that regard, out of all the available memory candidates, Phase Change Memory (PCM) is an attractive option as it is technologically mature, and its physical mechanism is well understood. However, the current generation of PCM materials suffers from stochasticity in their multi-level switching. In this communication, nitrogen alloyed GaSb (N-GaSb) material is proposed as a multi-level switching PCM material to redress stochasticity. Interestingly, N-GaSb exhibits well-defined three states, and it is found to reduce the threshold switching power of GaSb from 16 mW to 17.2 μW. The reason behind multi-level switching and the reduction in required power for threshold switching in N-GaSb has been revealed by synchrotron-based grazing-incidence X-ray diffraction and photoelectron spectroscopy.

Domain walls in cylindrical nanowires exhibit several intriguing properties making them suitable for spintronic applications. Here, we report the microwave response of domain walls in cylindrical nanowires using micromagnetic simulations. The domain walls exhibit two kinds of reversal modes, namely vortex reversal mode and transverse reversal mode. The present study is confined to the sub-50-nm-diameter cylindrical nanowires, where the transverse domain wall is a stable configuration. The microwave properties are highly dependent on demagnetizing fields that exist along the nanowire. Two well distinguishable modes are observed in the nanowires, one that arises from the domain wall and the other due to the inhomogeneities at the edges. Both modes are found to be sensitive to the diameter of the cylindrical nanowire. The results reveal additional functionality of the DWs in cylindrical nanowires based on high-frequency spin dynamics for microwave applications.

In the present article, we present the notions of fuzzy multiset interior and closure operator and study their basic characterizations and properties. Furthermore, using the fuzzy multiset closure operator we introduce the notion of fuzzy multiset closure space and present its related properties. Finally, the notion of connectedness in the context of fuzzy multiset topology is discussed and some properties are investigated.

The development in electronic sector has brought a remarkable change in the lifestyle of mankind. At the same time, this technological advancement results in adverse effect on environment due to the use of toxic and non-degradable materials in various electronic devices. With the emergence of environmental problems, the green, reprogrammable, biodegradable, sustainable and environmental-friendly electronic devices have become one of the best solutions for protecting our environment from hazardous materials without compromising the growth of the electronic industry. Natural material has emerged as the promising candidate for the next generation of electronic devices due to its easy processing, transparency, flexibility, abundant resources, sustainability, recyclability, and simple extraction. This review targets the characteristics, advancements, role, limitations, and prospects of using natural materials as the functional layer of a resistive switching memory device with a primary focus on the switching/memory properties. Among the available memory devices, resistive random access memory, write once read many unipolar memory, etc., devices have a huge potential to become the nonvolatile memory of the next generation owing to their simple structure, high scalability, and low power consumption. The motivation behind this work is to promote the use of natural materials in electronic devices and attract researchers toward a green solution of hazardous problems associated with the electronic devices.

A numerical study has been made on free convection in the anisotropic porous enclosure. By nonuniform sinusoidal heating, flow is induced on the right side wall along with three adiabatic walls. The principal directions of the gravity vector have been taken obliquely to the permeability tensor. The performed study is conducted by using the Brinkman-extended non-Darcy model. The vorticity–streamfunction approach of the spectral element method is applied to solve the governing equations. The significance is specified on the impact of the periodicity parameter (N), local heat transfer rate (Nu(_{y})) along with the flow mechanism in the enclosure with reference to orientation angle ((phi)), permeability ratio (K(^{*})) and anisotropic parameters. The outcome for odd N shows that a particular heat transfer at (y=1.5) is pointed extreme. Additionally, the increase in the permeability media while switching K(^{*}) from 1 to 0.2 increases the heat transfer rate. This increment occurs at the right corner, below the enclosure’s right. Moreover, considering every N, the profiles of Nu(_{y}) in both media (isotropic and anisotropic) are similar. However, it varies slightly for N(=2). Remarkably, this analysis shows that the flow pattern has been affected by distinct N via boundary conditions of temperatures. Consequently, the local heat transfer phenomena have also been affected.

In this paper, problem of estimation of ratio of two population means has been discussed in presence of non-response. A wider two-phase class of estimators has been suggested using ratio and ordinal auxiliary variables under incomplete data due to non-response. Expressions of bias and mean square error of the suggested class of estimators have been derived, and minimum value of mean square error has been obtained under optimum conditions. The properties of the suggested class of estimators have been studied under fixed budget as well as precision. The increase in efficiency of the suggested class of estimators over the relevant estimators has been demonstrated by real data analysis. On the ground of theoretical and empirical studies, it has been explained that suggested class of estimators is efficient than existing conventional estimators.

This article is an overview of emerging memory materials and their role in advanced brain-inspired computing technologies. It starts with the progress of memory technologies over the last 50 years along with emergence and dominance of NAND flash in the memory market. Though flash is currently leading the memory market due to its high volume manufacturing and low cost, it has a latency gap with dynamic random access memory. To address this, various nonvolatile memories have been explored across the world potentially to replace flash. Here, an overview of various major emerging nonvolatile memory (NVM) technologies is presented. Along with the global view of NVMs as their current status as a storage solution, the research of NVMs in India is discussed briefly with a focus on resistance random access memory and phase change memory. Further, the need of brain-inspired advanced computing technologies like neuromorphic computing, in-memory computing are discussed along with the utility of the NVMs for such brain-inspired computing technologies. Finally, various NVMs are presented for their unique characteristic to mimic synapse, neuron functionalities as required for neuromorphic computing and for in-memory computing solutions.

Recent developments in the field of topological quantum materials have stimulated the search for materials that could serve as the building blocks for next-generation memory applications. Due to their intriguing topological properties, such as flat bands, Dirac nodes, and Weyl points, kagome magnets are anticipated to be the leading materials for this application. In this mini review, we discuss some of the recent advancements in binary kagome magnets, both ferromagnetic and anti-ferromagnetic, for use as emerging memory devices. First, we discuss ferromagnetic kagome magnets, specifically Fe(_3)Sn(_2), and then we discuss non-collinear antiferromagnetic kagome magnets, Mn(_3)Sn and Mn(_3)Ir. Finally, we discuss collinear antiferromagnetic kagome magnet, FeSn. In each of the aforementioned sections, we begin with a discussion of their topological, structural, and magnetic properties, followed by application-specific studies such as spin-orbit torques (SOT). In the final section, we discuss the current state of kagome magnets for efficient, faster, denser, and reliable memory technologies with focus on the SOT switching and observation/manipulation of skyrmions.

Lignosulfonate was extracted from jute sticks by acid sulfite pulping and purified by two alternative chemical processes. The lignosulfonate from jute was compared with commercially available products by infrared spectroscopy and X-ray diffraction techniques. The jute sourced lignosulfonates showed crystalline peaks and higher solubility in water. The characteristic FTIR peaks of lignosulfonate were observed. The jute sourced lignosulfonate was used to construct the negative active mass (NAM) of lead–acid battery (LAB). The constructed LAB was subjected to standard charging and discharging cycles at 20 h, 10 h and 5 h. The normalized capacity of the constructed cells at different discharge rate was used to compare the performance of lignosulfonates from jute with a commercial sample. It showed better performance at lower discharge rates of 20 h and 10 h, while under faster discharge cycles of 5 h, the performance of the NAM plates containing jute sourced lignosulfonate showed slightly lower specific charge capacity in comparison with standard commercial product. The performance studies indicated that jute sticks could serve as a competitive source of sodium lignosulfonate for application in LAB involving lower rate discharge cycles as in solar power battery. As an alternative to conventionally used wood for commercial manufacture of lignosulfonates, lignosulfonate extracted from an inexpensive, annually renewable agro-waste, jute stick, could open new manufacturing stations and contribute to conservation of the environment.

NavIC is a regional navigation system developed by India; NavIC signal is available in the central/primary service area covering the Indian landmass and 1500 km around India, and for the areas falling in the extended/secondary service region laying between latitude 30° S to 50° N and longitude 30° E to 130° E. Advantages and quality of NavIC-based position solution has been reported for the secondary service area based on simulated data. In this manuscript, real-time NMEA data are collected from NSSTC, Al Ain, UAE, NIMT, Pathum Thani, Thailand, falling within the extended/secondary service region and from TUMSAT, Tokyo, Japan, situated just outside the extended service region using compact, low-cost NavIC modules. Spread of the of position solution in 2-dimension, and its correspondence with rank defect satellite geometry is presented. The precision of solution and North-East-Up error plots are also estimated for those locations. Real-time data from the locations points towards the advantage of having NavIC satellites placed in GEO or IGSO from high elevation angles have been discussed towards seamless navigation operation in GNSS + NavIC hybrid operation within the constrained or degraded GNSS satellite visibility situations.