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 $\pm 0.8$ with F10.7 compared to Rz ($\pm 0.3$). 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