Karnaugh map extended to six or more variables

Inclusion of up to four minterms in each of the sixteen cells enables a Karnaugh map to be extended for the minimisation of six-variable logical functions. The columns of minterms of the map have been so designed as to alternate as even minterm and odd minterm columns. This distinctive separation of columns would facilitate the plotting of function minterms on the map as well as the generation of prime implicants. An example illustrates the application of the extended map in the easy minimisation of a six-variable function.     

Rician noise removal in magnitude MRI images using efficient anisotropic diffusion filtering

In this article, a new methodology for denoising of Rician noise in Magnetic Resonance Images (MRI) is presented. MRI imaging creates a distinctive view into the interior of a human body and has become an essential tool of clinical diagnosis. However, Rician noise is a type of artifact inherent to the acquisition process of the magnitude MRI image, making diagnosis difficult. We proposed a moment‐based Rician noise reduction technique in anisotropic diffusion filtering. We extend the work of the classical anisotropic diffusion filter and have customized it to remove Rician noise in the magnitude MRI image in 3D domain space. Our proposed scheme shows better results against various quality measures in terms of noise removal and edge preservation while retaining fine textures.     

Overcoming Zinc Oxide Interface Instability with a Methylammonium‐Free Perovskite for High‐Performance Solar Cells

Perovskite solar cells have achieved the highest power conversion efficiencies on metal oxide n‐type layers, including SnO₂ and TiO₂. Despite ZnO having superior optoelectronic properties to these metal oxides, such as improved transmittance, higher conductivity, and closer conduction band alignment to methylammonium (MA)PbI₃, ZnO is largely overlooked due to a chemical instability when in contact with metal halide perovskites, which leads to rapid decomposition of the perovskite. While surface passivation techniques have somewhat mitigated this instability, investigations as to whether all metal halide perovskites exhibit this instability with ZnO are yet to be undertaken. Experimental methods to elucidate the degradation mechanisms at ZnO–MAPbI₃ interfaces are developed. By substituting MA with formamidinium (FA) and cesium (Cs), the stability of the perovskite–ZnO interface is greatly enhanced and it is found that stability compares favorably with SnO₂‐based devices after high‐intensity UV irradiation and 85 °C thermal stressing. For devices comprising FA‐ and Cs‐based metal halide perovskite absorber layers on ZnO, a 21.1% scanned power conversion efficiency and 18% steady‐state power output are achieved. This work demonstrates that ZnO appears to be as feasible an n‐type charge extraction layer as SnO₂, with many foreseeable advantages, provided that MA cations are avoided.     

Effect of temporal pH variation of the reaction mixture on Mg(OH)2 morphology precipitated from an aqueous Mg(NO3)2-NaOH system

To understand the impact of temporal pH variation on the crystallisation process, Mg(OH)₂ was synthesized via wet precipitation route from an aqueous Mg(NO₃)₂-NaOH system. A detailed analysis of morphological evolution and the nano-structural transformation was carried out to model the crystallisation process. Interestingly, low supersaturation at low pH level lying between 9.2 and 9.4 of the reaction mixture, was found to promote the growth of nanorod like 1-D structures. On the contrary, enhanced supersaturation created a chemical driving force favouring an edgewise growth of the nucleated primary nanocrystals along (101) and (110) crystallographic planes, which resulted in lamellar hexagonal nanostructures. The lamellar growth demonstrated an increment in the particle size and reduction in anisotropic strain and dislocation density due to proper nucleation in the samples. Such controlled growth and nucleation of the Mg(OH)₂ morphology presents a great scope of potential applications of this material.     

A survey on mobile anchor assisted localization techniques in wireless sensor networks

Identifying locations of sensor nodes in wireless sensor networks (WSNs) is significant for both network operations and most application level tasks. Although, geographical positioning system (GPS) based localization schemes are used for determining node locations but the cost of GPS devices and non-availability of GPS signals in indoor environments prevent their use in large scale WSNs. A substantial amount of research work exist that intend at obtaining precise and relative spatial locations of sensor nodes without requiring large amount of specialized hardware. Mobile anchor assisted localization is one typical approach that significantly reduces the implementation cost by using limited number of mobile anchors. In this survey, we present key issues and inherent challenges faced by the mobile anchor assisted localization techniques in WSNs. We take a closer look at the algorithmic approaches of various important fine-grained mobile anchor assisted localization techniques applicable in WSNs. In addition, we highlight the error refinement mechanisms adopted by the state-of-the-art works associated with their approaches. Well known mobile anchor trajectories presented in existing works are also reviewed. Finally, open research issues are discussed for future research scope in this field.     

RVCloud: a routing protocol for vehicular ad hoc network in city environment using cloud computing

Routing in Vehicular Ad hoc Network (VANET) is a challenging task due to high mobility of vehicles. In this paper, a RVCloud routing protocol is proposed for VANET to send the data efficiently to the destination vehicle using cloud computing technology. In this protocol, vehicle beacon information is send to the cloud storage through the Road Side Unit (RSU). As vehicles have less storage and computing facility, the information of all the vehicles moving in the city is maintained by the cloud. Source vehicle sends the data to the destination by sending the data to the nearby RSU. After receiving the data, RSU sends a request to the cloud for an optimal RSU information, that takes minimum packet forwarding delay to send the data to the destination. Cloud provides location service by providing destination location and optimal RSU information. Then RSU sends the data to the optimal RSU using internet. By using the internet facility, packet forwarding delay and link disruption problem are reduced. Simulation results show that, RVCloud performs better than VehiCloud, P-GEDIR, GyTAR, A-STAR, and GSR routing protocols.     

Dielectric Relaxation and Collective Vibrational Modes of Double‐Perovskites A2SmTaO6 (A = Ba,Sr and Ca)

The crystal structures of the double‐perovskite oxide A₂SmTaO₆ series (AST, A = Ba, Sr, Ca) synthesized by solid‐state reaction technique are determined from X‐ray powder diffraction data. Rietveld refinements of the X‐ray diffraction data of the samples show that Ba₂SmTaO₆ (BST) crystallizes in cubic phase and Sr₂SmTaO₆ (SST) and Ca₂SmTaO₆ (CST) crystallize in monoclinic phase. Fourier transform infrared spectra show two primary modes of the samples at around 370 and 600 cm^?1. The vibrational properties of the samples are studied by Raman spectroscopy taken at 488‐nm wavelength. Group‐theoretical study is performed to assign the different vibrational modes of the samples in accordance with structural symmetry. The observed shifts of some vibrations in the SST and CST w.r.t. BST upon changing the A cation are tentatively explained. Dielectric spectroscopy is applied to investigate the ac electrical conductivity of AST in different temperatures between 303 and 673 K and in a frequency range of 42 Hz–1 MHz. The complex impedance plane plots show that the relaxation (conduction) mechanism in these materials is purely a bulk effect arising from the semiconductive grains. The relaxation mechanism of the samples is modeled by Cole–Cole equation. The frequency‐dependent conductivity spectra are found to follow the power law.