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472 results on '"Srivastava, Kumar Vaibhav"'

2. An Ontological Learning Management System

Author

Rani, Monika, Srivastava, Kumar Vaibhav, and Vyas, O. P.

Subjects
Computer Science - Computers and Society
Abstract

The current learning systems typically lack the level of metacognitive awareness, self-directed learning, and time management skills. Most of the ontologically based learning management systems are in the proposed phase and those which are developed do not provide the necessary path guidance for proper learning. The systems available are not as adaptive from the viewpoint of the learner as required. Ontology engineering has become an important pillar for knowledge management and representation in recent years. The design, approach, and implementation of ontology in e-learning and m-learning systems have made them more effective. In this paper, we have proposed a system for the betterment of knowledge management and representation of associated data as compared to the previously available learning management systems. Here, we have presented the application and implementation of ontological engineering methodology in the Computer Science domain. For knowledge management, we have created a domain associated ontology which represents knowledge of a single domain. Subsequently, ontology has been created to manage a learner profile so that a learner may be aligned to a proper path of learning. The learner ontology will use the VARK learning model which classifies what kind of learning does the learner requires so that necessary resources could be provided.

Published
2017

7. Application of Cross-correlation Greens Function along with FDTD for Fast Computation of Envelope Correlation Coefficient over Wideband for MIMO Antennas

Author

Sarkar, Debdeep and Srivastava, Kumar Vaibhav

Subjects
Physics - Classical Physics
Abstract

In this paper, the concept of cross-correlation Green's functions (CGF) is used in conjunction with the finite difference time domain (FDTD) technique for calculation of envelope correlation coefficient (ECC) of any arbitrary MIMO antenna system over wide frequency band. Both frequency-domain (FD) and time-domain (TD) post-processing techniques are proposed for possible application with this FDTD-CGF scheme. The FDTD-CGF time-domain (FDTD-CGF-TD) scheme utilizes time-domain signal processing methods and exhibits significant reduction in ECC computation time as compared to the FDTD-CGF frequency domain (FDTD-CGF-FD) scheme, for high frequency-resolution requirements. The proposed FDTD-CGF based schemes can be applied for accurate and fast prediction of wideband ECC response, instead of the conventional scattering parameter based techniques which have several limitations. Numerical examples of the proposed FDTD-CGF techniques are provided for two-element MIMO systems involving thin-wire half-wavelength dipoles in parallel side-by-side as well as orthogonal arrangements. The results obtained from the FDTD-CGF techniques are compared with results from commercial electromagnetic solver Ansys HFSS, to verify the validity of proposed approach., Comment: Accepted for publication in IEEE Transactions on Antennas and Propagation; IEEE Copyright Notice Added

Published
2016
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8. Analysis of antenna arrays using equivalent sources for increase in computational efficiency for 5G and beyond.

Author

Aakash, Bhattacharya, Sudeb, Jaiswal, Rahul Kumar, and Srivastava, Kumar Vaibhav

Subjects
ANTENNAS (Electronics), 5G networks, ANTENNA arrays
Abstract

The use of equivalent sources for the analysis of antenna arrays for high computational efficiency has been proposed. A single antenna element has been designed, and the fields have been saved on an enclosed geometry. The surface equivalence principle has been utilized to calculate the far‐field patterns from the fields saved on the enclosed geometry which has been termed as Huygens' box (HB). The antenna element has been used to design 2×1 $2\times 1$, 4×1 $4\times 1$, 8×1 $8\times 1$, and 16×1 $16\times 1$ array and the far‐fields have been calculated. For linear arrays of HBs far‐field patterns and computation time have been compared with that of the actual antenna array. As the number of elements increases from 4 to 16, the computation time has been found to reduce from 6% $6 \% $ to 47% $47 \% $. Further, the computation time has been found to reduce by 39% $39 \% $ and 75% $75 \% $ for 2×2 $2\times 2$ and 4×4 $4\times 4$ configurations, respectively. The method is suitable for analysis of complex geometry of antennas used in 5G technology and beyond. [ABSTRACT FROM AUTHOR]

Published
2024
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11. Flexible dielectric spacer with tunable dielectric properties for metamaterial absorber application.

Author

Chaudhary, Kajal, Malik, Sudha, Singh, Gaganpreet, Bhattacharya, Sudeb, Ramkumar, J, Ramakrishna, S Anantha, and Srivastava, Kumar Vaibhav

Subjects
DIELECTRIC properties, METAMATERIALS, DIELECTRICS, BARIUM titanate, MICROWAVE generation, POLYDIMETHYLSILOXANE
Abstract

The development of a flexible and robust metamaterial absorber is a great motivation for the new generation of microwave absorbers covering any conformal shape. Ceramic–polymer composites with variable dielectric constant within the microwave frequencies are proposed as a flexible middle dielectric spacer (MDS) layer to provide an additional degree of design freedom for metamaterial absorber applications. By varying the dielectric constant of the MDS layer, the resonance band of the metamaterial absorber can be tuned while retaining a low profile in addition to enhancing its electromagnetic performance for transverse magnetic (TM) polarized waves. To formulate these composites, tetragonal structured barium titanate (BaTiO3) powder is selected as an excellent candidate when mixed with elastomer polydimethylsiloxane (PDMS), resulting in high mechanical strength substrates. Experimentally, samples with a range of dielectric permittivity from 2.81 to 5.67 were obtained for a 0%–20% volume fill fraction of BaTiO3 in PDMS. The obtained dielectric permittivities are consistent with the Bruggeman effective medium theory. Utilizing an optimized composition (10% BaTiO3), resulting in ϵ r = 4 substrate, an X-band flexible absorber is designed and fabricated to absorb more than 90% of incident electromagnetic waves within a frequency band of 8.16–12.12 GHz. [ABSTRACT FROM AUTHOR]

Published
2024
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14. Wideband Low-Profile Endfire Antenna With Polarization Reconfigurability

Author

Jaiswal, Rahul Kumar, Aakash, Ojha, Anuj Kumar, Sim, Chow-Yen-Desmond, and Srivastava, Kumar Vaibhav

Abstract

A wideband, low-profile endfire antenna with polarization reconfiguration is proposed. The endfire antenna can be electronically switched among the left-hand circular polarization (LHCP), right-hand circular polarization (RHCP), and linear polarization (LP) using six PIN diodes in conjunction with biasing lines. The proposed antenna consists of a wideband half-mode substrate integrated waveguide (HMSIW) cavity (vertically polarized magnetic dipole) and tapered switchable electric dipole (horizontally polarized) with a feed line. The impedance bandwidth of the HMSIW cavity is increased by combining the resonance frequencies of quasi-TE1,0.5,0 mode with quasi-TE3,0.5,0 mode by placing the two slotted pairs at the null of quasi-TE3,0.5,0 mode. At LHCP/RHCP states, the proposed endfire antenna exhibited a stacked 10-dB impedance bandwidth (IBW) of 11.66% (6.54-7.35 GHz) and a 3-dB axial ratio bandwidth (ARBW) of 11.23% (6.515-7.29 GHz) with a peak gain of approximately 4.20 dBic. When switched to the LP state, it shows a 10-dB impedance bandwidth of 11.58% (6.87-7.715 GHz) with a peak gain of 5.35 dBi. Therefore, it can exhibit good effective bandwidths (stacked 10-dB IBW and 3-dB ARBW) of 5.93% (6.87-7.29 GHz) and 10.84% (6.54-7.29 GHz) across the three polarization states (LP/RHCP/LHCP) and two CP states (RHCP/LHCP), respectively.

Published
2024
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32. A Two-Stage Beamforming Antenna Using Butler Matrix and Reconfigurable Frequency Selective Surface for Wide Angle Beam Tilting

Author

Dutta, Ranjit Kumar, Jaiswal, Rahul Kumar, Saikia, Mondeep, and Srivastava, Kumar Vaibhav

Abstract

A two-stage beamforming technique for a wide tilt angle is proposed in this letter. The proposed structure has the potential to overcome the limitations of Butler matrix-based beamforming technique and reconfigurable frequency selective surfaces (FSS)-based beamforming technique, both of which normally lag behind in the present generation of wireless communication due to lesser number of radiating beams. The composite system comprises three parts: a 4 × 4 Butler matrix, an antenna array of 1 × 4 elements, and a reconfigurable FSS layer. Four semi-rigid coaxial cables are employed to connect the Butler matrix to the four-element antenna array. The reconfigurable FSS is mounted on top of antenna layer using air spacers. The FSS superstrate layer consists of 6 × 6 reconfigurable unit cells, which have been further divided into two equal sections to increase the number of radiating beams. Combining the four-port Butler matrix with reconfigurable FSS allows the system to generate 12 unique radiating beams in 12 distinct directions in 3-D space. The proposed system is designed, fabricated, and measured for operating frequency of 5.5 GHz. The proposed system attains a maximum tilt of 72$^\circ$ and a peak gain of 11.8 dBi.

Published
2023
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