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In this Paper, a low-profile circularly polarized (CP) chamfered rectangular dielectric resonator antenna (RDRA) is designed and investigated for radio frequency energy harvesting (RFEH) applications. The proposed modified RDRA comprises of dielectric resonator (DR) made up of Alumina material (εr = 9.9) mounted on the PEC ground plane. Dual unequal triangular-shaped vertical slits are engraved on the rectangular DR for generating the orthogonal modes with CP characteristics. The optimized antenna offers an impedance bandwidth (IBW) of 51.4% (2.25–3.81 GHz) and axial ratio bandwidth (ARBW) of 14.8% (3.25–3.77 GHz), respectively. The peak realized gain and maximum radiation efficiency are 7.18 dBi and 97.8% in desired frequency bands. Due to the wide impedance and AR bandwidths with realized gain and radiation efficiency, the optimized antenna is suitable for integration with a rectifier circuit for RF energy harvesting applications. A rectifier circuit with a single shunt diode topology is also designed for rectification purposes. The rectifier achieved 67.16% RF-DC power conversion efficiency (PCE) at 3.5 GHz and 5dBm input power. At 0dBm input power, the rectifier achieved 60.26% PCE. The effective input power range, during which the PCE maintains above 50%, is calculated to be 15.2 dBm from −3.5 to 11.7 dBm. [ABSTRACT FROM AUTHOR]

This review article outlines research on nanoantennas in infrared bands and visible bands over the last one and half decades. The objective of this survey is to highlight basic insights and state-of-the-art developments based on applications. Besides, characterization and fabrication methods are also presented. The authors also proposed a dipole nanoantenna of multi-layer geometry which provides better efficiency and wider bandwidth. It offers an impedance bandwidth of 312 THz with maximum radiation efficiency and peak realized gain of 82.1% and 2.95 dBi, respectively. This proposed antenna provides an omnidirectional radiation pattern, which is a suitable candidate for energy harvesting and other photonic applications. [ABSTRACT FROM AUTHOR]

Vertically polarized omnidirectional antenna system (VPOAS) and horizontally polarized omnidirectional antenna system (HPOAS) are designed and theoretically analyzed at 2.2 GHz for NAG-Missile telemetry. Theoretical formulations of far-zone field patterns are derived using the cavity model in conjunction with array theory, equivalence theorem, and image theory. The derived radiation patterns are plotted using MATLAB software. The proposed antenna is simulated using CST software and fabricated to validate the derived results. The proposed antenna systems are resonating at 2.22 GHz with 32 MHz impedance bandwidth and peak gain of 4.15 and 5.37 dBi for VPOAS and HPOAS, respectively. [ABSTRACT FROM AUTHOR]

Due to the widespread use of low-power embedded devices in both industrial and consumer applications, research into the use of alternate energy sources has been sparked by the requirement for continuous power. Due to its accessibility and ability to be implanted, RF energy is always taken into consideration among the traditional energy sources that are currently available. There is a significant necessity for efficient RF front-ends, which must provide effective circular polarization (CP) features, effectiveness, feasibility from a design standpoint, and optimal usage of ambient RF signals accessible in the environment. So, for understanding their utilization in RF energy harvesting, a metasurface reflector-inspired CP-printed reconfigurable antenna integrated with a Greinacher voltage divider (GVD) rectifier circuit is reported. It offers broadband CP with fractional bandwidth > 25%, CP gain > 8.35 dBic, and directional radiation with the 3 dB angular beamwidth > 100° in the 3.5/5 GHz bands. With the integration of the rectifier circuit, a theoretical DC output > 4.8 V at 12 dBm is obtained. The acceptable impedance bandwidth, axial ratio bandwidth, antenna gain, antenna efficiency, and directional radiation with a 3 dB angular beamwidth value are studied and subsequently matched with the trade-offs (usage of diodes, complexity of DC biasing circuits, and attainment of polarization reconfigurability) obtained from the state of the art. A comprehensive study of the reconfigurable antennas is reported to highlight the findings as a widespread solution for these limitations in RF energy harvesting application. [ABSTRACT FROM AUTHOR]

In this research article, a metasurface (MTS)-loaded high-gain and broadband circularly polarized (CP) monopole antenna is reported. The proposed antenna configuration consists of a symmetric Y-shaped radiating monopole over a partial ground plane with extended twin parasitic conducting strips (PCS) loaded with a MTS reflector. To achieve left-hand circular polarization characteristics, a metallic copper strip is utilized to short the partial ground plane with one of the twin PCS [PCS(L)]. By using the grid-slotted sub patches on a rectangular MTS a reflector of 2λ fa × 1.65λ fa × 0.02λ fa is placed just below the monopole radiator at a height of 0.33λ fa , which provides broadened impedance (IBW) and 3 dB axial ratio bandwidth (ARBW) responses with high gain. The proposed prototype with an volumetric dimension of 1.33λ fa × 0.9λ fa × 0.02λ fa at f a = 5 GHz is designed and characterized. It exhibits a measured IBW of 48.45% (3.57–5.89 GHz), ARBW of 25.25% (4.21–5.42 GHz), and CP gain of > 8.35 dBic with the antenna efficiency of > 75% in the desired operating frequency bands. The obtained performances of the proposed MTS antenna confirm its suitability for RF energy harvesting application. [ABSTRACT FROM AUTHOR]

Chemical ordering through two microscopic functions namely concentration-concentration fluctuation as k tends to zero, S CC (0) and the Warren-Cowley ordering parameter, α ′ have been theoretically investigated in Fe–Al melts as function of Al concentration under pair wise square-well (SW) potential function. In view of ordering phenomena in melts, partial and total structure functions, g(r) and self and mutual diffusion coefficients have been theoretically formulated and computed at different compositions of Al in Fe–Al melts. Total structure factor obtained using SW potential function at four compositions of Al are in good agreement with X-ray data obtained by Roik et al. Excess entropy in melts has been determined using computed values of transport coefficients and Dzugutov scaling law. Stokes–Einstein (SE) relation is modified by substituting hydrodynamic radius by nearest neighbor distance in pair correlation function. Validity of the SE relation was examined by comparing theoretically obtained data of viscosity coefficients with experimental values and correlated with excess entropy of the melts obtained through two body approximation. Various physico-chemical properties of industrially important Fe–Al alloys have been reported to establish their correlation with microscopic structure functions. [ABSTRACT FROM AUTHOR]

This letter presents a novel approach to design metasurface-based dual-band dual-polarized monopole antennas at 2.4 GHz ISM and 3.5 GHz WiMAX-band for off-body communications. The behavior is modeled with an array of unit-cells excited by a truncated monopole structure. A rectangular via-free unit-cell (RVU) is theoretically developed using a transmission-line model to exhibit an AMC-like characteristic. Following that, by controlling the RVU dispersion curve, two distinct unit-cells, UC $_{1}$ and UC $_{2}$ , are optimized to construct the metasurfaces of size 3 × 3 (MS $_{1}$) and 2 × 2 (MS $_{2}$), respectively, which generate TM $_{10}$ mode in the lower band (LB) and TM $_{20}$ mode in the higher band (HB). Then, these metasurfaces are excited by four variant truncated monopole structures to design four dual-band dual-polarized antennas (A $_{1}$ , A $_{2}$ , A $_{3}$ , and A $_{4}$). A $_{1}$ and A $_{3}$ are MS $_{1}$ -based, whereas A $_{2}$ and A $_{4}$ are MS $_{2}$ -based. A $_{1}$ and A $_{2}$ are designed to produce circular-polarization (CP) in the LB, whereas A $_{3}$ and A $_{4}$ are designed to produce CP in the HB. In A $_{1}$ and A $_{2}$ , additional 0.25 ${\lambda _{g}}$ diagonal slots are used to enhance impedance-bandwidth in the LB. All the antennas produce a wide impedance-bandwidth and high gain with low SAR. A $_{1}$ is fabricated using a felt substrate and measured, which shows good agreement with simulations. [ABSTRACT FROM AUTHOR]

This article presents a chronological overview of circularly polarized dielectric resonator antennas (CPDRAs). This article provides a comprehensive review about innovation and rapid developments of CPDRAs over the last three and half decades since 1986s. The objective of this article is to highlight the basic concept of CP mechanism in DRA and state‐of‐the‐art developments of CPDRAs in terms of single and multi‐point feed for unmodified and modified DR geometries considering different types of excitation mechanism such as microstrip line, coaxial probe, and aperture coupled feed. To give insights into circular polarization, Authors proposed a compact modified CPDRA. It offers simulated bandwidth of 47.5% (2.34‐3.80 GHz), measured impedance bandwidth of 50.8% (2.26‐3.78), and simulated axial bandwidth of 13% (3.29‐3.75 GHz) respectively. Other antenna parameters such as peak realized gain and radiation efficiency are 7.7 dBi and 98% within operating frequency bands, respectively. The proposed outcomes confirm that the proposed CPDRA can be used as a suitable candidate for wireless body area network applications. [ABSTRACT FROM AUTHOR]

In this article, a broadband circularly polarized rectangular dielectric resonator antenna (CP‐RDRA) is explored and reported. The proposed antenna comprises of rectangular dielectric resonator (DR) made up of aluminum oxide placed on a Rogers RT‐5880 substrate and fed by a 50‐Ω microstrip line with a partial ground plane. Microstrip line feed is placed at the right edge of rectangular DR to excite orthogonal fields, which achieves circular polarization (CP). The proposed antenna is fabricated and characterized. The measured −10 dB impedance bandwidth and 3 dB axial bandwidth are obtained as 5.44 GHz (5.79‐11.23 GHz) and 2.93 GHz (6.08‐9.01 GHz), respectively. The peak realized gain and antenna efficiency are obtained to be 4.62 dBi and 94%, respectively, in the desired frequency band. In addition, the proposed CP‐RDRA is also realized using a new technique of glueless concept to achieve mechanical stability that also enhances the axial bandwidth without affecting the radiation characteristics. It is observed from the results that the proposed antenna can be a potential candidate for C‐band and X‐band in satellite communication systems. [ABSTRACT FROM AUTHOR]

Summary: Accurate estimation and tracking of power quality (PQ) disturbances requires efficient adaptive model‐based techniques, which should have elegant structures to be applicable in practical systems. Though extended Kalman filter (EKF) has been used as a popular estimator to track the time‐varying PQ events, the performance is limited due to higher‐order nonlinearity exists in system dynamics. Moreover, the computational complexity and sensitivity to the measurement noise affect the estimation accuracy and error convergence properties. If the underlying sparse behavior of adaptive filters can be exploited through norm penalty, then significant improvement can be achieved in terms of convergence speed, stability, and steady state excess mean square error performance. In this paper, a modification to EKF is proposed by using sparse model to estimate PQ disturbances with better estimation accuracy and faster convergence speed. A thorough comparison is presented in terms of simulation results by using a family of existing algorithms like least mean square, recursive least square, and EKF. Adaptive estimation model incorporates real and complex state space representations to represent discrete time PQ disturbances. The convergence of the proposed sparse model–based filter is also mathematically proved considering the mean square error performance. [ABSTRACT FROM AUTHOR]

Introduction: In order to maintain a strict control over the results generated in clinical chemistry laboratories, a number of procedures are followed to maintain the quality of results. The procedures followed in order to compare the performances between different laboratories are known as External Quality Assessment (EQA). Separate EQA programmes for different analysers are recommended as the methods and principles may be different for them. Aim: To compare the performance of EQA results from Dimension EXL 200 and VITROS® 4600 analysers from two consecutive years and to analyse differences, if any. Materials and Methods: The clinical chemistry laboratory of this tertiary care hospital is enrolled in EQA with CMC Vellore. The lab has Dimension EXL 200 and VITROS® 4600 analysers. The results from two different EQA cycles of 2016 (Dimension EXL 200) and 2017 (VITROS® 4600) have been for analysed and compared. The Variable Index Score (VIS) and Standard Deviation Index (SDI) from these reports were analysed. Results: The data for 2016 for Dimension EXL 200 had 15 parameters in the EQA while VITROS® 4600 had 20 parameters in the EQA list. There were some parameters that were not common and hence have not been compared. The overall VIS for the Dimension had 07 parameters (46.7%) VIS (<100) 'very good', 05 (33%) VIS (100-150) 'good category', 02 (13%) VIS (151-200) in 'satisfactory' and 01 (07%) parameter had VIS (>200) 'not acceptable' category. The overall VIS for the VITROS® 4600 had 15 parameters (75%) with VIS (<100) 'very good', 04 (20%) with VIS (100-150) 'good category', 01 (13%) with' VIS (151-200) in 'satisfactory' category. The SDI of the same parameters on both the equipments were similar with DIMENSION having 12 (86%) and VITROS 4600 having 11 (79%) results in the 'excellent' category while each had a single parameter in the 'accept with caution' category with no parameter requiring any corrective action. Conclusion: The VIS results from the VITROS® 4600 as compared to Dimension EXL 200 showed marked improvement with 71.4% parameters undergoing a reduction in the VIS values while the SDI results were mostly similar. [ABSTRACT FROM AUTHOR]

Correct estimation of harmonics and sequence components is essential to monitor the overall performance of three phase power systems. Least mean square (LMS) based adaptive models have simpler structures to estimate the required parameters for a given power quality (PQ) event. However, these models are not very much effective in case of time-varying and short duration disturbances. Least mean fourth (LMF) is comparatively a better approach than LMS to deal with different PQ problems, but high computational complexity limits the filter performance in case of practical applications. LMS/fourth (LMS/F) filter is a compromise between LMS and LMF to improve the error convergence properties. The proposed model explained in this paper is based on the concept of LMS/F with Volterra expansions of input samples. The proposed Volterrra LMS/F filter is tested in case of distorted power signals to estimate harmonics, decaying dc, and sequence components in presence of white Gaussian noise. The detail comparison results are presented using MATLAB simulations to verify the performance of the adaptive model. [ABSTRACT FROM AUTHOR]

A person's self-concept is motivating force in his behavior. The individual acts in accordance with how he sees himself at the moment. If he feels that he is misunderstood or discriminated against, he will act like a martyr. If he feels that people accept him, he will act in a friendly cooperative way. The self- concept is the dominant elements in the personality pattern; it governs the individual's characteristics reaction to people and situations and determines the quality of his behavior. In this research paper, the researcher focused on the meaning of self- concept with its components, theories and categories i.e., the term self- concept refers to the correlation of the cluster of the most personal meanings, a person attributes of self, upon which he places the highest value of himself. [ABSTRACT FROM AUTHOR]

In this article, a parallel metal-plated split U-shaped omnidirectional ultra wideband (UWB) antenna fed by a novel 1×3 microstrip line is proposed. Printed monopole antennas fabricated on a substrate offer impedance bandwidth which can cover UWB. However, radiation pattern varies significantly over the bandwidth. The cross polar component increases with frequency and the pattern degrades from the desired omnidirectional characteristics. Omnidirectional radiation bandwidth can be increased significantly by decreasing the substrate thickness and using substrate material of low dielectric constant. With the use of the proposed feeding arrangement, parallel metal-plated split U-shaped monopole antenna shows omnidirectional radiation pattern. The proposed metal-plated structure using foam as dielectric is designed, fabricated, and tested. The measured VSWR is <2 over 3.1 to 10.6 GHz frequency band. The antenna offers high efficiency, stable gain, small group delay variation, and its radiation patterns indicate its suitability for UWB applications. [ABSTRACT FROM AUTHOR]

In this article, a novel printed ultra-wideband (UWB) antenna with band stop characteristics is proposed. The proposed antenna is a simple U-shaped monopole structure where a rectangular strip is placed on both sides at the top of semi annular ring monopole structure. The band rejection characteristic is achieved by introducing a pair of L-shaped slots in the ground plane to prevent interference due to wireless local area network (WLAN) systems operating within ultra-wideband. To achieve the desired UWB response with WLAN band notched characteristics, the dimensions of rectangular strip, L-shaped slot, symmetrical step slot on the both edge of ground plane, a single slot in the center of the ground plane and the gap between the ground plane and the radiating structure are optimized. Frequency rejection characteristics depend on the dimension of L-shaped slot and can be fine controlled using other parameters. The antenna structure is designed, fabricated and tested. The simulation and measurement results show that the return loss = −10 dB from 3.09 to 10.6 GHz with band stop characteristics in 5.11-6.14 GHz frequency band. The radiation characteristics show its suitability for indoor wireless communication. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26091 [ABSTRACT FROM AUTHOR]