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

In the present work, we estimate sensitive population mean at current occasion in presence of measurement error at both occasions in two occasion successive sampling. Compulsory and optional randomized response technique have been fused with calibration technique at both occasions. Responses are recorded with measurement error. Asymptotic properties of estimators are derived. The variances of the proposed estimators are also obtained upto first order of approximation under both the models. Mutual comparison of compulsory and optional randomized response technique is carried out in presence of measurement error. To show the impact of measurement error, the estimators are compared with similar direct estimators. A natural population related to COVID-19 infection has been considered to validate the theoretical findings. Further, simulation study is aided to show the practicability of the proposed estimators.

Graphene and graphene oxide (GO) have allured the interest of global scientists from diverse disciplines to explore the material in terms of all possible development owing to its essence of exceptional properties like electronic properties, adjustable structural properties, optical and mechanical properties. There have been immense efforts involved in the progress of advancement of technological development and fundamental research from chemically modified graphene in the form of GO, possessing several functionalities which can be tuned to obtain required structural modifications either covalently or non-covalently. This review is a complete carriage of GO, providing brief summary of its synthesis, routes of functionalization and various applications. The review begins with the structure and physicochemical properties of graphene and GO, followed by a brief history of GO synthesis. Subsequently, it comprehends covalent and non-covalent functionalization with their further classifications. Finally, it elucidates practical examples of multifarious applications in the fields of electrocatalysts, carbocatalysts, photocatalysts, drug delivery, water splitting, and biosensors. The role of GO in the impediment of the current epidemic of SARS-Cov-2 disease is encompassed as well. We anticipate that this review will deliver fundamentals of graphene and GO chemistry, as well as recent smart applications, allowing us to overcome current challenges.

Graphical Abstract

Herein, we report a controlled non-volatile bipolar resistive switching in nanostructured NiFe₂O₄ films using a capacitor like Al(aluminum)/NiFe₂O₄/FTO(fluorine-doped tin oxide) metal–insulator-metal device, which shows uniform resistive switching with a resistance ratio of high resistance state (HRS) to low resistance state (LRS) more than 3 × 10², accompanied with electroforming-free feature without any application of compliance current (ICC). The device can operate (read and switch) in small voltage and current ranges that makes it a low-power resistive switching device. The conduction mechanism in LRS was found to be Ohmic, whereas the HRS was governed by space charge-limited conduction mechanism. The current voltage and resistance temperature measurements indicate the presence of an interfacial AlO_x layer with oxygen-related defects near the top Al/NiFe₂O₄ interface. The device exhibits good program/erase endurance properties, acceptable memory window, and uniform resistive switching. In addition, different intermediate resistance states between HRS and LRS can be obtained in a controlled manner by choosing different stop voltages during the gradual RESET process, which makes the device a multilevel RS device and a potential candidate for future non-volatile resistive random access memory (RRAM).

Magnetic susceptibility (SI) measurements and mineralogical and petrographical studies were carried out on the alkaline potassium-rich Gölcük volcanic rocks, situated in the apex of the Isparta Angle in the southwest of Turkey. Magnetic susceptibility was measured on the pyroclastic rocks and outcrops using hand-held KT10-R Magnetic Susceptibility meter. The classification and SI values of the igneous rocks from the study area are as trachyte (SI between 0.45 × 10^–3 and 36.3 × 10^–3), trachyandesite (SI between 0.5 × 10^–3 and 5.7 × 10^–3), Clinopyroxene (Cpx)-phyric basaltic trachyandesite (SI: 36.3 × 10^–3), Clinopyroxene (Cpx)-phyric trachyandesite (SI: 0.63 × 10^–3), alkali feldspar syenite (SI: 20.9 × 10^–3 and 26.4 × 10^–3), syenite (SI: between 16 × 10^–3 and 35.6 × 10^–3), leucocratic monzosyenite (SI: 23.3 × 10^–3), monzosyenite (SI: 31.2 × 10^–3), mafic monzosyenite (SI: 15.4 × 10^–3 and 20.7 × 10^–3), pyroxene monzonite (SI: 0.56 × 10^–3), micaceous pyroxenite (SI: 0.42 × 10^–3), tephriphonolites (SI: between 11.3 × 10^–3 and 3.32 × 10^–3 but most of them between 17 × 10^–3 and 25 × 10^–3). Based on thin-section investigations, it is clearly seen that igneous rocks contain various amount of opaque minerals. X-ray data show that the opaque minerals are mainly magnetite minerals. Petrographical determinations and magnetic susceptibility SI measurements show that igneous rocks with the same composition and texture may have different magnetic susceptibility values and varying amount of magnetite minerals. On the other hand, some of the volcanic rocks with the same composition but different textures have also different magnetic susceptibility values. The presence of opaque minerals is the dominant factor controlling the magnetic susceptibility value of the Gölcük volcanites and the amount of magnetite mineral is directly proportional to the magnitude of the magnetic susceptibility. It is not plausible to suggest that rocks existing in the same classification should have the same magnetic susceptibility values.

We construct cosmological models for dark energy based on Lyra’s geometry for the Bianchi-I space-time to understand the evolution of the universe. The specific choice of the deceleration parameter (q=-frac{alpha _1}{t^2}+alpha _2-1) is used to determine the exact solutions of the field equations in Lyra geometry. The parameter (alpha _1) has a dimension equal to the square of time. Further, we have discussed two cosmological models depending on the parameter (alpha _2). Several physical parameters are obtained and the results in both the models are analyzed and presented graphically for the analysis of the results.

In uncertain environment, a sequence converges to a finite limit in different aspects. The aim of this article is to initiate three new types of convergence, namely convergence in metric, convergence in p-distance and completely convergence of complex uncertain double sequence and establish the interrelationships among these concepts, along with the existing ones. Thus, this study presents a more complete scenario of interconnections between the notions of convergences initiated in different directions.

In this paper, we present global norm of potential vector field in Ricci soliton. In particular, we deduce certain conditions so that the potential vector field has finite global norm in expanding Ricci soliton. In addition, we show that if the potential vector field has finite global norm in complete non-compact Ricci soliton having finite volume, then the scalar curvature becomes constant.

The present study describes the green synthesis of iron/titanium dioxide nanoparticles to enhance their photocatalytic applicability for degradation of commonly encountered pollutant Rhodamine B (RhB) dye. Iron-doped TiO₂ nanoparticles with the crystallite size 25 nm were successfully synthesized by a simple, eco-friendly synthesis route using Aegle marmelos leaf extract. Morphological and structural characterization of the product was done by the field emission scanning electron microscopy (FESEM), EDS, high-resolution X-ray diffraction (HRXRD) and Fourier transform infrared spectroscopy. SEM images reveal the circular morphology of TiO₂ nanoparticles with interparticle gaps. According to the result of particle size analyzer, the average particle size was 34 nm which concur well with the mean crystallite size 25 nm as obtained from HRXRD. The energy band gap of the sample was determined from the UV–visible spectrum, which unveiled better absorption of light in the visible region owing to noteworthy lowering of the energy band gap of TiO₂ after doping. Brunauer–Emmett–Teller (BET) characterization was also performed to analyze the specific surface area and mean pore diameter of the synthesized sample. Furthermore, the photocatalytic investigation indicates that the synthesized nanoparticles have exhibited catalytic performance in the degradation of Rhodamine B dye.

The domain wall (DW) motion in ferromagnetic nanostructures is of paramount importance for realizing high density magnetic data storage applications. In this work, we have investigated the vortex domain wall (VDW) motion in a ferromagnetic nanowire with a rectangular anti-dot using micromagnetic simulations. We found that the anti-dot acts as a pinning site resulting in either splitting or transformation of VDW to a transverse DW depending on the anti-dot width. The DW splitting and recombination result in the formation of a 360° DW from a single 180° VDW. The whole process follows the conservation of the topological charge associated with the DWs in the system. We found that energy distribution across the transverse domain wall (TDW) plays an important role in both the DW splitting and formation of 360° DW. The DW splitting field has shown a crossover as a function of anti-dot width which is attributed to the dependance of pinning field on the DW size as seen by the pinning site. This work reveals a novel method to stabilize 360° DW in a simple, compact and experimentally realizable ferromagnetic nanostructure under the application of a linear magnetic field.

The need for nano-sized memristive devices as synaptic emulators is increasing day-by-day to build neuromorphic devices on a chip with a large integration density. Therefore, nanoscale fabrication and subsequent device assessment are exigent to make further advancements in the field. In this report, by employing atomic force microscopy, we demonstrate highly dense electronic nano-synapses in filamentary metal oxide-based memristors, wherein the tip works as one of the electrodes. Different metal oxide-based memristors with varying defect concentrations have been studied to demonstrate the efficacy of atomic force microscopy-based local probe techniques in extracting the defect-dependent performance metrics of the same at nanoscale. Some of the basic biological synaptic characteristics such as potentiation/depression and spike’s property-dependent plasticities are accessed through different pulsed measurements in conductive atomic force microscopy mode. The current maps acquired using conductive atomic force microscopy measurements on the films confirm the filamentary resistive switching behaviour to prevail and point towards a possible decrease in the operating voltage with an increase in defects density. Kelvin probe force microscopic analyses, on the other hand, suggest that to improve the switching stability, resistivity of the active medium needs to be optimized. Overall, our results substantiate the efficacy of local probe microscopy-based methods to optimize the performance of memristive synapses at nanoscale for potential application in neuromorphic computing.