113 research outputs found
Effect of using vegetable oils as quenching media for pure commercial aluminium
This paper presents the effects of rate of heat extraction by groundnut, melon, palm kernel, shea butter
and palm oils on the mechanical properties of various samples of pure commercial aluminium heat
treated at 200°C, 250°C, 300°C and 350°C. Muffle furnace equipped with digital thermometer and
thermocouple was used for the heat treatment. Tensile strength and hardness tests were carried out
using Instron Universal Tester and Vickers hardness methods, respectively. Results obtained from the
experiment were presented graphically. The results showed that palm kernel oil cools faster at 200°C and
250°C, while palm oil and shea butter oil quench faster at 300°C and 350°C, respectively. Palm kernel oil
offers the highest elongation at 200°C, while at 350°C shea butter oil gave the best result. The best
among the bio-quenching oils in providing good ductility is shea butter oil at 200°C, while at 300°C and
350°C groundnut oil give the best result. Highest hardness values were obtained from samples quenched
in melon oil between 200°C-300°C. However, these values decreased with increased heating
temperature probably due to density and viscosity variation with temperature rise. Similar observations
were made on most of other samples quenched in other bio-quenching oils used in this experiment. This
study shows that these locally available vegetable oils have promising potentials to serve as a possible
replacement for non-biodegradable mineral oils in many applications
Spatio-temporal influence of solar activity on global air temperature
Previous studies on the impact and influence of solar activity on terrestrial
weather has yielded contradictory results in literature. Present study
presents, on a global scale, the correlation between surface air temperature
and two solar activity indices (Sunspot number, 'Rz', and solar radio flux at
10.7, 'F10.7' ) at different time scales during solar cycle 23. Global air
temperature has higher correlation values of with F10.7 compared to
Rz (). Our results showed hemispheric delineation of the correlation
between air temperature and solar activity with negative correlation in the
southern hemisphere and positive correlation in the northern hemisphere. At the
onset of the solar cycle, this hemispheric delineation pattern was prevalent,
however, an inverse hemispheric delineation was observed at the recession of
the solar cycle.Comment: To appear in Sun and Geospher
Radiation hazard in soil from Ajaokuta North-central Nigeria
Background: Measurement of the radia�on dose distribu�on is important in
assessing the health risk a popula�on and serve as reference in documen�ng
changes to environmental radioac�vity in soil due to man-made ac�vi�es.
Materials and Methods: The ac�vity concentra�on of 238U, 232Th and 40K in
soil samples obtained from different loca�ons in Ajaokuta Local Government
area was measured using Hyper Pure germanium Detec�on System (HPGe).
Results: The calculated average concentra�on of the radionuclides ranged
from 12 ± 1 Bqkg-1 to 59 ± 2 Bqkg-1 for 238U, 14 ± 1 Bqkg-1 to 78 ± 5 Bqkg-1 for
232Th and 49 ± 2 Bqkg-1 to 1272 ± 23 Bqkg-1 for 40K. In order to evaluate the
radiological hazards due to natural radionuclides within Ajaokuta, the
absorbed dose rate, gamma index, radium equivalent and excess life�me
cancer risk were es�mated. According to measured data from the top soil
(0-10 cm), the es�mated radium equivalent (Raeq) ranges from 55.7 Bqkg-1 at
Steel Complex to 253.3 Bqkg-1 obtained from Forest samples. Conclusion: The
mean absorbed dose rate, annual effec�ve dose and gamma radia�on index
evaluated were 66.2 nGyh-1, 81.2 μSvy-1 and 1.05 respec�vely which are
higher than the recommended limit for normal background radia�on. Thus,
we conclude that people living in these loca�ons may be exposed to higher
radia�on
Dynamics of vertical profile of Radio Refractivity in Akure South-Western Nigeria.
This research investigated fractal and chaotic dynamics in the vertical profile radio refractivity in the atmosphere using Tsallis Entropy, Hurst Exponent and Largest Lyapunov Exponent (LLE). Daily temperature, relative humidity and radio refractivity data obtained from the European Centre for Medium Range Weather Forecasts (ECMWF) Re-Analysis Project at thirty seven (37) different atmospheric pressure level from 1979-2014 were used in this study. The Hurst Exponent parameter obtained, using the method of Detrended Fluctuation Analysis, in the radio refractivity profile studied showed that there is persistence across all levels. Tsallis entropy did not reveal any structure or significant variations from the tropopause to the surface. To determine if any of the radio refractivity is chaotic at any of the studied level, the Largest Lyapunov Exponent (LLE) was computed. Positive values were obtained at all levels for radio refractivity, indicating deterministic chaos in the profile of radio refractivity
Study of Ionospheric Amplitude Scintillation during Geomagnetic Activities of 2012 at Low Latitude Region
The impact of scintillation on radio communications, geodesy, radar system and navigation
cannot be underemphasized. The first evident effect of space weather in the phase of radio signals
and amplitude that passes over ionosphere is fluctuations. If there are intense fluctuations in the
quality of the signals received, such signals might degrade or attenuate in quality. This phenomenon
is referred to as scintillations. To study the effects of magnetic activity on scintillations, the percentage
occurrence of scintillations has been separated for the five international quiet (Q) days and five
international disturbed (D) days over Ilorin for the year 2012 which was obtained from world data
centre Kyoto. The occurrences of S4 were recorded during quiet days than the disturbed days in the
study area. Generally, occurrence of S4 was enhanced during pre-midnight hours but was suppressed
during post-midnight hour both at quiet and disturbed days in Ilorin, Kwara State, Nigeria
Occurrence of Similar Periods in Geomagnetic Field Variations and Solar Activity
The periodicities associated with some geomagnetic field parameters under quiet and disturbed solar conditions have been examined using a set of data spanning through five years obtained courtesy of INTERMAGNET network. Hourly values of the Horizontal component of the geomagnetic field simultaneously obtained at seven INTERMAGNET stations were engaged in the study. The stations were well distributed across the latitudes, viz: Bangui, 4.4°N; Kourou, 5.1°N; Alibag, 18.6°N; San Juan18.1°N; Crozet, 46.4°S; Barrow, 71.3°N; Scott Base, 77.9°S). Solar quiet daily variation Sq, Superposed Magnetic field SPMF and Solar disturbance daily variation SD in the horizontal magnetic field component were evaluated and studied for their spectral characteristics. The spectral analysis revealed the periods of 6 hours, 12 hours, 24 hours, 3 months, 6 months, 12 months and 16 months in the geomagnetic field variations. The observed periodicities were explained in terms of associated solar terrestrial processes. This clearly shows the influence of an extra terrestrial source (the Sun) on terrestrial processes. Sun is the undisputable driver of space weathe
Radiological assessment of natural radionuclide contents in soils from Omala, Kogi State, Nigeria.
High purity germanium detector (HPGe) was employed to assess radionuclide contents of 238U, 40K and 232Th in soils obtained from Omala, Kogi State, Nigeria. The activities measured vary from 9.0 to 82.2, 12.3 to 114.86 and below detector limit (BDL) and 349.0 Bq Kg-1 in 238U, 232Th and 40K respectively. Highest activities for the three radionuclides were consistently obtained from soil samples got from Igaliwu. The measured activities were engaged to estimate the absorbed dose, annual outdoor effective dose and gamma index. It was observed from the absorbed dose, annual equivalent dose and the gamma index estimated that soils from Igaliwu, Ijeke-ogene and Bagana were found to be higher than the recommended safe limit for normal background. This suggests that those living or using the soil for construction purposes are exposed to high radiation burden from natural radionuclides
Influence of Agronomic Practices on Crop Production
The ultimate goal of any farmer is to get maximum yield per unit area. To obtain high yield, effective crop management practices, appeared to be of paramount value. Crop production in Nigeria is faced with many challenges among which are: untimely planting, incorrect plant spacing, wrong method of planting, poor sowing depth, delayed weeding
The longitudinal variability of equatorial electrojet and vertical drift velocity in the African and American sectors
While the formation of equatorial electrojet (EEJ) and its temporal
variation is believed to be fairly well understood, the longitudinal
variability at all local times is still unknown. This paper presents a case
and statistical study of the longitudinal variability of dayside EEJ for all
local times using ground-based observations. We found EEJ is stronger in the
west American sector and decreases from west to east longitudinal sectors.
We also confirm the presence of significant longitudinal difference in the
dusk sector pre-reversal drift, using the ion velocity meter (IVM)
instrument onboard the C/NOFS satellite, with stronger pre-reversal drift in
the west American sector compared to the African sector. Previous satellite
observations have shown that the African sector is home to stronger and
year-round ionospheric bubbles/irregularities compared to the American and
Asian sectors. This study's results raises the question if the vertical
drift, which is believed to be the main cause for the enhancement of
Rayleigh–Taylor (RT) instability growth rate, is stronger in the American
sector and weaker in the African sector – why are the occurrence and
amplitude of equatorial irregularities stronger in the African sector
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