Browsing by Author "V.N. Tiwari"

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Assessment of Karmi Landslide Zone, Bageshwar, Uttarakhand, India
(Springer, 2020) V.N. Tiwari; V.H.R. Pandey; Ashutosh Kainthola; P.K. Singh; K.H. Singh; T.N. Singh
Slope instability is a big challenge for the population in mountainous regions. It poses a threat to life, economy, and infrastructure. For the safety of people, various prevention and precautions are taken and hence many scientific studies are going on. In the present study, the stability of the Karmi landslides zone, Bageshwar, Uttarakhand, India is assessed. Karmi village lies quite close to the northern border of India and the excavated roads are the only means of commute. The area lies in a tectonically active lesser Himalayan zone with high relief. Slope geometry was extracted using a total station, and seven different slope geometries were plotted. Soil and rock mass samples were taken and evaluated from various field and laboratory investigations. The direct shear test was performed to assess the friction angle and cohesion of the soil and rock mass. Numerical simulations viz., finite element analysis and probabilistic analysis have been applied on all seven slope sections and found that the mean and median safety factor of all the modeled slopes was 0.78 and 0.81, respectively. The study ascertains that the whole area to be quite vulnerable to failure, especially during rains, since the pore pressure build-up diminishes the shear strength of the slope forming material. Possible mitigation measures have been suggested based on the examined instability of the hill slopes. © 2020, Geological Society of India.
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.
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.