Browsing by Author "T. Tiwari"

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Analysis of H-plane sectoral dielectric horn antennas
(Publ by IEEE, 1993) T. Tiwari; S.P. Singh; A.R. Bayat; R.K. Jha; Banmali S. Rawat
The plane wave approach has been used to analyze the radiation from H-plane hollow sectoral dielectric horn antennas. Theoretical and experimental radiation patterns at x-band for 20°, 30°, and 40° flare angles, dielectric thickness of 0.30 cm and 0.44 cm and axial length of one γ have been obtained.
Analysis of various types of pierce electron guns by finite element method
(IEEE, 1995) T. Tiwari; R.K. Jha
Various types of Pierce electron guns are analyzed using finite element method (FEM) and iterative technique. They are first divided into two parts: electron trajectories in the first part and equipotential lines in the second. To apply EFM, the functional is calculated using Poisson's equation in the form of two dimensional rotationally symmetric and two dimensional axially symmetric spherical co-ordinates for parallel flow and conical convergent pierce electron guns respectively. The general form of nodal equations are found using the functional. These nodal equations are solved using band-matrix method and applying appropriate boundary conditions. Once the values potential are known at different nodal points, equipotential lines and electron trajectories can be determined.
Comparative studies of near field distributions of solid and hollow dielectric diagonal horn antennas
(IEEE, 1997) V.N. Tiwari; T. Tiwari; R.K. Jha
Near field distributions of solid and hollow dielectric diagonal horn antennas have been studied theoretically and experimentally. Solutions of the Helmholtz's equation are obtained for TE to x and TE to y modes using separation of variables technique for the horn. Transcendental equations for the transverse components of propagation constants are obtained by applying proper boundary conditions. These transcendental equations are solved for the transverse propagation constants for the fundamental mode for different horns each of axial length = 12.8 cm and flare angle = 8.5° and throat dimension = 4.7 cm at the frequency of 9.418 GHz in X - band. The theoretical aperture field distributions obtained for H11x and H11y modes propagating in these antennas are compared with corresponding experimental ones. Further, comparative studies are also done for aperture field distribution of solid and hollow dielectric diagonal horn antennas.
Comparative studies of radiation patterns of solid and hollow dielectric diagonal horn antennas
(IEEE, 1997) T. Tiwari; V.N. Tiwari
Radiation patterns of solid and hollow dielectric diagonal horn antennas have been studied theoretically and experimentally. The expressions for the near field components of the horn under study are used to obtain the expression for radiation pattern from Kirchoff's formula. The comparative studies of radiation patterns of these antennas have been done.
Computer aided design of various types of pierce electron guns
(IEEE, 1995) T. Tiwari; R.K. Jha
This paper deals with finite element and iterative techniques for the computer aided design of various types of Pierce electron guns. A computer program is developed on the basis of proposed scheme which is used for the determination of electrode shapes of various types of Pierce electron guns. The results obtained for some electron gun are shown which are the same as expected theoretically.
Effects of task load and cue validity on simultaneous sustained attention search task performance
(Indian Academy of Applied Psychology, 2018) Tarun Mishra; Naveen; T. Tiwari; Indramani L. Singh; Rakesh Pandey; Tara Singh; A.L. Singh
The present study aimed to examine the effect of task load on visual search sustained attention task performance. Cue works as a signal and may facilitate or deteriorate the performance. These effects depend on cue validity and its temporal properties. Present study used cue validity to observe the effect of cue on participant’s performance. Ninety participants were randomly assigned into different experimental conditions. A 2 (Task load: High and Low event rate) X3 (Cue validity: Valid, Invalid and Neutral) X4 (time block: 10 minutes each) mixed factorial design with repeated measure on the last two factors was used. Correct detection, incorrect detection and reaction time were recorded as performance measures to analyze sustained attention task performance. Results revealed that correct detection and perceptual sensitivity was higher under low task load condition in comparison to high task load condition. Moreover, response latency was found better under low task load condition than high task load. Ample evidences have proven that attentional tasks are resource demanding, when the temporal load of task increases it works as a catalyst to diminish our ability to perform on task. The present study holds promises to counter such decrement with the help of cue. © Journal of the Indian Academy of Applied Psychology.
Far field patterns of hollow dielectric wall diagonal horn antennas
(IEEE, 1995) V.N. Tiwari; T. Tiwari; S.P. Singh; R.K. Jha
In this paper, far field patterns of hollow dielectric wall diagonal horn antennas of various thicknesses (0.15, 0.15, 0.32 and 0.32 cm) and dielectric constants (ε′ = 2.54, 2.56, 2.56 and 3.03) are studied both theoretically and experimentally at 9.418 GHZ. Theoretical near field distribution at the aperture and at the side surfaces of a horn under study for TE to x and TE to y modes are obtained by solving the Helmholtz's equation using separation of variables technique. The expressions for the near field components of the horn under study are used to obtain the expression for radiation pattern from the Kirchoff's diffraction formula. The theoretical far field patterns obtained for these antennas are compared with corresponding experimental ones.
Near field analysis of solid dielectric diagonal horn antenna
(IEEE, 1995) V.N. Tiwari; T. Tiwari; S.P. Singh; R.K. Jha
The near field distributions of solid dielectric diagonal horn antennas are studied both theoretically and experimentally. Solution of Helmholtz's equation is obtained for TE to x and TE to y modes using separation of variables techniques. Transcendental equations for transverse components of propagation constants are obtained by applying proper boundary conditions. The theoretical near field distributions obtained for these antennas are compared with corresponding experimental results.