Abstract— Some measures of merit of an inverter system are the total harmonic distortion and the efficiency figures. On one hand, we have square wave and modified square wave inverters that have high efficiency and total harmonic distortion (THD) figures. On the other hand, there are the true sine wave inverters that have low THDs and relatively low efficiency figures at high output power levels. In this work, a five level waveform that can be synthesized efficiently was analysed for low distortion figures, and a THD figure of 1.25% was obtained. A microcontroller-based inverter circuit was designed to synthesize this waveform from a 12 volts d.c source. The microcontroller firmware and hardware were developed using MicroC® and Proteus® softwares respectively. The developed circuit generated a 50 Hz sinusoidal output waveform from a 12 volts battery source after filtering with an LC low pass filter.
As part of effort to examine the factors responsible for highway failure in the sedimentary terrain, geophysical survey involving Very Low Frequency Electromagnetic (VLF-EM), Schlumberger Vertical Electrical Sounding (VES), and dipole-dipole electrical resistivity techniques were carried out along Iruekpen-Ifon highway. This was aimed at using surface geophysics to characterize and identify the factors responsible the for road failures along Iruekpen-Ifon highway. ABEM WADI instrument was used to obtain electromagnetic-Very Low Frequency (VLF) field data, while ABEM resistivity meter was used to obtain electrical resistivity field data. The VLF-EM data were interpreted using the VLF Graphic software, VELFAN 1.0 double plot of filtered real and filtered imaginary against distance. The VES data obtained were interpreted using IP 2 Win software. Geoelectric parameters were used to generate the Dar Zarrouk second order parameters. 2-D inversion modeling of the dipole-dipole data was carried out using ZONDRES window software. VLF-EM result suggested varying degree of conductivity in the area and the wide spread of clay/metallic ore and water in the study area. Results show that the topsoil generally varies in composition from clay to clayey and laterite with resistivity values varying from 89 to 400 Ωm and thickness between 0.2 and 4.0 m. The fractured layers composed of clay and compacted clayey sand which represents the recent alluvial deposits with resistivity values of 2 to 89 Ωm and the thickness between 1.5 and 11 m. The fresh water zone is characterized by low resistivity ranging from 0.5 to 23 Ωm, which is diagnostic of saline water saturated with clay formation, fresh water ingression, and marls. The values of co-efficient of anisotropy () range from 1.03 to 2.19. The relatively higher values of λ (1.30 to 2.19) suggest that the subsurface rocks in these areas are likely to be more intensely fractured and more permeable. The saline water saturated with clay formation, fresh water ingression, fracture and marls clearly limit the lithological contacts and enhance high swelling potential which might be responsible for the road pavement failures in the studied area.
Electrical resistivity method has been performed using Vertical Electrical Sounding (VES) technique at a Bishop Smith Memorial College, Ilorin, Kwara State to examine the geophysical parameters that can be used to evaluate the subsurface competency. Eight VES stations were sounded, using Schlumberger configuration for data acquisition with current electrode spacing varying from 1.0 to 140.0 m. The VES data obtained were interpreted using ipi2win+ip Software. The field data acquired was presented as geoelectric sounding curves and geoelectric section. The interpretation of the field results revealed heterogeneous subsurface geologic sequence probed to 34.6 m and beyond. It also showed presence of near surface linear geologic structures of varying lengths, depths and attitude which suggest the competent zones for foundation laying. The major subsurface layers are the top soil which consists of interlocking and concretional lateritic stones and clayey sand, weathered basement, fractured basement and fresh basement. For building development in the study area, the topsoil must be excavated to at least the Fresh basement (competent layer) to avoid building deformation.
The determination of the thermodynamic properties of the Earth’s core requires the computation of acoustic Grüneisen parameter of solids at the prevailing pressure and temperature of the Earth’s core. The acoustic Grüneisen parameter, γa , of the Earth’s core were determined seismically from the velocity and density profiles. In this paper, the seismic data from the Preliminary Reference Earth Model (PREM) were used in computing the acoustic Grüneisen parameter γa at each depth of the Earth’s core. The thermal derivatives d ( I n V S ) d ( I n V ρ ) and d ( I n V P ) d ( I n V ρ ) which defines the modes from the velocity and density profiles were used to determine the values of the acoustic Grüneisen parameter. The result for the outer core showed that the average γa is 1.53 which is found to be consistent with result obtained from previous studies
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