Quantum Inspired Broadband Photonic Absorber: Potential Application as Solar Sail along with Mobility Analysis

Electromagnetic wideband absorption is still perceived as a critical and formidable challenge to address with an unambiguous photonic absorber. Subwavelength metamaterial (MM) unit cells with unique and controlled features have recently gained considerable interest. However, meta-atoms, generated using a quantum-inspired pattern distribution, are underwhelming in existing literature to design photonic absorbers and their potential application to manufacture solar sails is still quite uncommon. In this article, to create a flexible, polarization-insensitive, ultrathin, and broadband MM absorber, quantum interference pattern-inspired design is utilized. Herein, a novel approach to fabricating solar sails for the space exploration incorporates the proposed broadband photonic absorber rather than conventional reflectors. The quantum-inspired meta-absorber (QIMA) exhibits an absorption of over 91% for the visible domain, i.e., 380–800 nm under a conventional plane-polarized source. It is shown in the study that broadband absorbers are almost equivalent to excellent reflectors to design the solar sails in terms of the time-averaged force calculated by utilizing the Maxwell stress tensor method. Thus, the QIMA has the potential to be a viable alternative to reflectors in the design of futuristic solar sails for space exploration. The interference theory model is also utilized to assure the dependability of calculated data, and additionally, the standard AM1.5 solar spectrum is utilized to demonstrate the QIMA's solar-harvesting potentiality.     

Architectural design and FPGA implementation of radix-4 CORDIC processor

A new scaled radix-4 CORDIC architecture that incorporates pipelining and parallelism is presented. The latency of the architecture is n/2 clock cycles and throughput rate is one valid result per n/2 clocks for n bit precision. A 16 bit radix-4 CORDIC architecture is implemented on the available FPGA platform. The corresponding latency of the architecture is eight clock cycles and throughput rate is one valid result per eight clock cycles. The entire scaled architecture operates at 56.96 MHz of clock rate with a power consumption of 380 mW. The speed can be enhanced with the upgraded version of FPGA device. A speed-area optimized processor is obtained through this architecture and is suitable for real time applications.     

Fairness of Transitions in Diagnosability of Discrete Event Systems

Failure diagnosability has been widely studied for discrete event system (DES) models because of modeling simplicity and computational efficiency due to abstraction. In the literature it is often held that for diagnosability, such models can be used not only for systems that fall naturally in the class of DES but also for the ones traditionally treated as continuous variable dynamic systems. A class of algorithms for failure diagnosability of DES models has been successfully developed for systems where fairness is not a part of the model. These algorithms are based on detecting cycles in the normal and the failure model that look identical. However, there exist systems with all transitions fair where the diagnosability condition that hinges upon this feature renders many failures non-diagnosable although they may actually be diagnosable by transitions out of a cycle. Hence, the diagnosability conditions based on cycle detection need to be modified to hold for many real-world systems where all transitions are fair. In this work, however, it is shown by means of an example that a system may have some transitions fair and some unfair. A new failure diagnosability mechanism is proposed for DES models with both fair and unfair transitions. Time complexity for deciding diagnosability of DES models with fair and unfair transitions is analyzed and compared with the time complexities of other DES diagnosability analysis methods reported in the literature.     

Speech enhancement using Teager energy operated ERB-like perceptual wavelet packet decomposition

In recent past, wavelet packet (WP) based speech enhancement techniques have been gaining popularity due to their inherent nature of noise minimization. WP based techniques appeared as more robust and efficient than short-time Fourier transform based methods. In the present work, a speech enhancement method using Teager energy operated equal rectangular bandwidth (ERB)-like WP decomposition has been proposed. Twenty four sub-band perceptual wavelet packet decomposition (PWPD) structure is implemented according to the auditory ERB scale. ERB scale based decomposition structure is used because the central frequency of the ERB scale distribution is similar to the frequency response of the human cochlea. Teager energy operator is applied to estimate the threshold value for the PWPD coefficients. Lastly, Wiener filtering is applied to remove the low frequency noise before final reconstruction stage. The proposed method has been applied to evaluate the Hindi sentences database, corrupted with six noise conditions. The proposed method’s performance is analysed with respect to several speech quality parameters and output signal to noise ratio levels. Performance indicates that the proposed technique outperforms some traditional speech enhancement algorithms at all SNR levels.     

A more efficient and secure ID-based remote mutual authentication with key agreement scheme for mobile devices on elliptic curve cryptosystem

Recently, Yang and Chang proposed an identity-based remote login scheme using elliptic curve cryptography for the users of mobile devices. We have analyzed the security aspects of the Yang and Chang's scheme and identified some security flaws. Also two improvements of the Yang and Chang's scheme have been proposed recently, however, it has been found that the schemes have similar security flaws as in the Yang and Chang's scheme. In order to remove the security pitfalls of the Yang and Chang and the subsequent schemes, we proposed an enhanced remote user mutual authentication scheme that uses elliptic curve cryptography and identity-based cryptosystem with three-way challenge-response handshake technique. It supports flawless mutual authentication of participants, agreement of session key and the leaked key revocation capability. In addition, the proposed scheme possesses low power consumption, low computation cost and better security attributes. As a result, the proposed scheme seems to be more practical and suitable for mobile users for secure Internet banking, online shopping, online voting, etc.     

Initiation of air core in a swirl nozzle using time-independent power-law fluids

Summary Theoretical and experimental analyses have been carried out for determining the injection condition below which the formation of air core does not take place in the course of flow of a time-independent power-law fluid through a swirl nozzle. Analytical solution lends one distinct value of generalized Reynolds number at the inlet to a nozzle below which the air core is not formed. Experiments reveal that there exist two limiting values of such generalized Reynolds number regarding the formation of air core in a nozzle. One value being the upper limit below which steady flow occurs without air core, the other one is the lower limit above which steady flow with fully developed air core persists. In between these two limiting values, there prevails a transition zone through which fully developed air core is set up within the nozzle. For all the nozzles, theoretical results are in fair agreement with the experimental values of upper limit of generalized Reynolds numbers with respect to steady flow without air core. Amongst all the pertinent independent geometrical parameters of a nozzle, the orifice-to-swirl chamber-diameter ratio has the remarkable influence on generalized Reynolds number describing the initiation of air core.Nomenclature D ₁ Swirl chamber diameter - D ₂ Orifice diameter - D _s Diameter of tangential entry ports - E A non-dimensional parameter defined by Eq. (9) - E _R A non-dimensional parameter defined by Eq. (25) - K Flow consistency index - L ₁ Length of the swirl chamber - n Flow behaviour index - P Static pressure inside the nozzle - P _b Back-pressure of the nozzle - Q Volume flow rate - R Radius vector or longitudinal coordinate with respect to spherical coordinate system (Fig. 3) - R ₁ Radius of the swirl chamber - R ₂ Radius of the orifice - Generalized Reynolds number at the inlet to the nozzle - Limiting value of generalized Reynolds number describing initiation of air core - R _z Radius at any section - r Radial distance from the nozzle axis - r _a Air core radius - u Longitudinal component of velocity with respect to spherical coordinate system (Fig. 3) - V _r Radial velocity component - V _z Axial velocity component - V Tangential velocity component - Tangential velocity at inlet to the nozzle - v Component of velocity in the axial plane perpendicular toR (Fig. 3) - w Component of velocity perpendicular to axial plane with respect to the spherical coordinate system (Fig. 3) - z Distance along the nozzle axis from its inlet plane - Half of the spin chamber angle - Boundary layer thickness measured perpendicularly from the nozzle wall - ₂ Boundary layer thickness at the orifice - Angle, which a radius vector makes with the nozzle axis, in spherical coordinate system (Fig. 3) - Density of the fluid - Running coordinate in the azimuthal direction with respect to the cylindrical polar coordinate system as shown in Fig. 3 - Circulation constant With 8 Figures     

Evaluation of projection algorithms

A number of linear and nonlinear mapping algorithms for the projection of patterns from a high-dimensional space to two dimensions are available. These two-dimensional representations allow quick visual observation of a data set. A combination of two popular mapping algorithms-Sammon's mean-square error technique and the triangulation method-is proposed to overcome the limitations in the individual algorithms. Some factors which describe the goodness of a projection are described, and a comparison is made of six of these algorithms by running them on four data sets. The results obtained support the use of the proposed algorithm.     

Water Crisis

Abstract

Water crisis was not considered seriously at the Dublin and Rio conferences. It was put on the world agenda primarily by the Stockholm Water Symposia. Water management is likely to change more during the next twenty years compared to the past 2,000 years. The paper reviews the global water situtation based on the latest data available. In terms of water availability, it concludes that one can now be cautiously optimistic of the global water future. If there is to be a crisis, it is likely to be for two reasons: water quality and lack of investments. Neither of these two issues are receiving adquate attention at present. The roles IWRA can play in the future are briefly outlined.