Abstract: In recent years, the use of the aluminum based alloys
in the industry and technology are increasing. Alloying elements in
aluminum have further been improving the strength and stiffness
properties that provide superior compared to other metals. In this
study, investigation of physical properties (microstructure,
microhardness, tensile strength, electrical conductivity and thermal
properties) in the Al-12.6wt.%Si-%2wt.Ni ternary alloy were
investigated. Al-Si-Ni alloy was prepared in vacuum atmosphere. The
samples were directionally solidified upwards with different growth
rate V (8.3−165.45 μm/s) at constant temperature gradient G (7.73
K/mm). The flake spacings (λ), microhardness (HV), ultimate tensile
strength (σ), electrical resistivity (ρ) and thermal properties (H, Cp,
Tm) of the samples were measured. Influence of the growth rate and
spacings on microhardness, ultimate tensile strength and electrical
resistivity were investigated and relationships between them were
obtained. According to results, λ values decrease with increasing V,
but HV, σ and ρ values increase with increasing V. Variations of
electrical resistivity (ρ) of solidified samples were also measured.
The enthalpy of fusion (H) and specific heat (Cp) for the alloy was
also determined by differential scanning calorimeter (DSC) from
heating trace during the transformation from liquid to solid. The
results in this work were compared with the previous similar
experimental results.
Abstract: In insulation and cooling of power transformers
various liquids are used. Mineral oils have wide availability and low
cost. However, they have a poor biodegradability potential and lower
fire point in comparison with other insulating liquids. Use of a liquid
having high biodegradability is important due to environmental
consideration. This paper investigates edible corn oil as an alternative
to mineral oil. Various properties of mineral and corn oil like
breakdown voltage, dissipation factor, relative dielectric constant,
power loss and resistivity were measured according to different
standards.
Abstract: Polyaniline is an indispensible component in lightemitting
devices (LEDs), televisions, cellular telephones, automotive,
corrosion-resistant coatings, actuators etc. The electrical conductivity
properties was found be increased by introduction of metal nano
particles. In the present study, an attempt has been made to utilize
platinum nano particles to achieve the improved electrical properties.
Polyaniline and Pt-polyaniline composite are synthesized by
electrochemical routes. X-ray diffractometer confirms the amorphous
nature of polyaniline. The Bragg’s diffraction peaks correspond to
platinum nanoparticles in Pt-polyaniline composite and
thermogravimetric analyzer indicates its decomposition at certain
temperature. The Scanning Electron Micrographs of colloidal
platinum nanoparticles were spherical, uniform shape in the
composite. The current-voltage (I-V) characteristics of the PANI and
composites were also studied which indicate a significant decreasing
resistivity than PANI-Platinum after introduction of pt nanoparticles
in the matrix of polyaniline (PANI).
Abstract: RF magnetron sputtering is used on the ceramic targets,
each of which contains zinc oxide (ZnO), zinc oxide doped with
aluminum (AZO) and zinc oxide doped with gallium (GZO). The XRD
analysis showed a preferred orientation along the (002) plane for ZnO,
AZO, and GZO films. The AZO film had the best electrical properties;
it had the lowest resistivity of 6.6 × 10-4 cm, the best sheet resistance of
2.2 × 10-1 Ω/square, and the highest carrier concentration of 4.3 × 1020
cm-3, as compared to the ZnO and GZO films.
Abstract: While choosing insulating oil, characteristic features
such as thermal cooling, endurance, efficiency and being
environment-friendly should be considered. Mineral oils are referred
as petroleum-based oil. In this study, vegetable oils investigated as an
alternative insulating liquid to mineral oil. Dissipation factor,
breakdown voltage, relative dielectric constant and resistivity
changes with the frequency and voltage of mineral, rapeseed and nut
oils were measured. Experimental studies were performed according
to ASTM D924 and IEC 60156 standards.
Abstract: The effect of partially substitution of magnetic
impurity Fe for Cu to the magnetic and transport properties in
electron-doped superconducting cuprates of
Eu1.85+yCe0.15-yCu1-yFeyO4+α-δ (ECCFO) with y = 0, 0.010, 0.020, and
0.050 has been studied, in order to investigate the mechanism of
magnetic and transport properties of ECCFO in normal-state.
Magnetic properties are investigated by DC magnetic-susceptibility
measurements that carried out at low temperatures down to 2 K using a
standard SQUID magnetometer in a magnetic field of 5 Oe on field
cooling. Transport properties addressed to electron mobility, are
extracted from radius of electron localization calculated from
temperature dependence of resistivity. For y = 0, temperature
dependence of dc magnetic-susceptibility (χ) indicated the change of
magnetic behavior from paramagnetic to diamagnetic below 15 K.
Above 15 K, all samples show paramagnetic behavior with the values
of magnetic moment in every volume unit increased with increasing y.
Electron mobility decreased with increasing y.
Abstract: High density electrical prospecting has been widely
used in groundwater investigation, civil engineering and
environmental survey. For efficient inversion, the forward modeling
routine, sensitivity calculation, and inversion algorithm must be
efficient. This paper attempts to provide a brief summary of the past
and ongoing developments of the method. It includes reviews of the
procedures used for data acquisition, processing and inversion of
electrical resistivity data based on compilation of academic literature.
In recent times there had been a significant evolution in field survey
designs and data inversion techniques for the resistivity method. In
general 2-D inversion for resistivity data is carried out using the
linearized least-square method with the local optimization technique
.Multi-electrode and multi-channel systems have made it possible to
conduct large 2-D, 3-D and even 4-D surveys efficiently to resolve
complex geological structures that were not possible with traditional
1-D surveys. 3-D surveys play an increasingly important role in very
complex areas where 2-D models suffer from artifacts due to off-line
structures. Continued developments in computation technology, as
well as fast data inversion techniques and software, have made it
possible to use optimization techniques to obtain model parameters to
a higher accuracy. A brief discussion on the limitations of the
electrical resistivity method has also been presented.
Abstract: Ibeno, Nigeria hosts the operational base of Mobil
Producing Nigeria Unlimited (MPNU), a subsidiary of ExxonMobil
and the current highest oil & condensate producer in Nigeria. Besides
MPNU, other oil companies operate onshore, on the continental shelf
and deep offshore of the Atlantic Ocean in Ibeno, Nigeria. This study
was designed to delineate oil polluted sites in Ibeno, Nigeria using
geophysical methods of electrical resistivity (ER) and ground
penetrating radar (GPR). Results obtained revealed that there have
been hydrocarbon contaminations of this environment by past crude
oil spills as observed from high resistivity values and GPR profiles
which clearly show the distribution, thickness and lateral extent of
hydrocarbon contamination as represented on the radargram reflector
tones. Contaminations were of varying degrees, ranging from slight
to high, indicating levels of substantial attenuation of crude oil
contamination over time. Moreover, the display of relatively lower
resistivities of locations outside the impacted areas compared to
resistivity values within the impacted areas and the 3-D Cartesian
images of oil contaminant plume depicted by red, light brown and
magenta for high, low and very low oil impacted areas, respectively
confirmed significant recent pollution of the study area with crude
oil.
Abstract: Considering palm oil as non-drying oil owing to its
low iodine value, an attempt was taken to increase the unsaturation in
the fatty acid chains of palm oil for the preparation of alkyds. To
increase the unsaturation in the palm oil, sulphuric acid (SA) and
para-toluene sulphonic acid (PTSA) was used prior to alcoholysis for
the dehydration process. The iodine number of the oil samples was
checked for the unsaturation measurement by Wijs method. Alkyd
resin was prepared using the dehydrated palm oil by following
alcoholysis and esterification reaction. To improve the film properties
0.5wt.% multi-wall carbon nano tubes (MWCNTs) were used to
manufacture polymeric film. The properties of the resins were
characterized by various physico-chemical properties such as density,
viscosity, iodine value, saponification value, etc. Structural
elucidation was confirmed by Fourier transform of infrared
spectroscopy and proton nuclear magnetic resonance; surfaces of the
films were examined by field-emission scanning electron microscope.
In addition, pencil hardness and chemical resistivity was also
measured by using standard methods. The effect of enhancement of
the unsaturation in the fatty acid chain found significant and
motivational. The resin prepared with dehydrated palm oil showed
improved properties regarding hardness and chemical resistivity
testing. The incorporation of MWCNTs enhanced the thermal
stability and hardness of the films as well.
Abstract: In this study, several crossplots of the P-impedance
with the lithology logs (gamma ray, neutron porosity, deep resistivity,
water saturation and Vp/Vs curves) were made in three available
wells, which were drilled in central part of the Blue Nile basin in
depths varies from 1460m to 1600m. These crossplots were
successful to discriminate between sand and shale when using PImpedance
values, and between the wet sand and the pay sand when
using both P-impedance and Vp/Vs together. Also some impedance
sections were converted to porosity sections using linear formula to
characterize the reservoir in terms of porosity. The used crossplots
were created on log resolution, while the seismic resolution can
identify only the reservoir, unless a 3D seismic angle stacks were
available; then it would be easier to identify the pay sand with great
confidence; through high resolution seismic inversion and
geostatistical approach when using P-impedance and Vp/Vs volumes.
Abstract: Composite material based on Fe3Si micro-particles
and Mn-Zn nano-ferrite was prepared using powder metallurgy
technology. The sol-gel followed by autocombustion process was
used for synthesis of Mn0.8Zn0.2Fe2O4 ferrite. 3 wt.% of mechanically
milled ferrite was mixed with Fe3Si powder alloy. Mixed micro-nano
powder system was homogenized by the Resonant Acoustic Mixing
using ResodynLabRAM Mixer. This non-invasive homogenization
technique was used to preserve spherical morphology of Fe3Si
powder particles. Uniaxial cold pressing in the closed die at pressure
600 MPa was applied to obtain a compact sample. Microwave
sintering of green compact was realized at 800°C, 20 minutes, in air.
Density of the powders and composite was measured by
Hepycnometry. Impulse excitation method was used to measure
elastic properties of sintered composite. Mechanical properties were
evaluated by measurement of transverse rupture strength (TRS) and
Vickers hardness (HV). Resistivity was measured by 4 point probe
method. Ferrite phase distribution in volume of the composite was
documented by metallographic analysis.
It has been found that nano-ferrite particle distributed among
micro- particles of Fe3Si powder alloy led to high relative density
(~93%) and suitable mechanical properties (TRS >100 MPa, HV
~1GPa, E-modulus ~140 GPa) of the composite. High electric
resistivity (R~6.7 ohm.cm) of prepared composite indicate their
potential application as soft magnetic material at medium and high
frequencies.
Abstract: This paper presents a novel statistical description of
the counterpoise effective length due to lightning surges, where the
(impulse) effective length had been obtained by means of regressive
formulas applied to the transient simulation results. The effective
length is described in terms of a statistical distribution function, from
which median, mean, variance, and other parameters of interest could
be readily obtained. The influence of lightning current amplitude,
lightning front duration, and soil resistivity on the effective length has
been accounted for, assuming statistical nature of these parameters. A
method for determining the optimal counterpoise length, in terms of
the statistical impulse effective length, is also presented. It is based on
estimating the number of dangerous events associated with lightning
strikes. Proposed statistical description and the associated method
provide valuable information which could aid the design engineer in
optimising physical lengths of counterpoises in different grounding
arrangements and soil resistivity situations.
Abstract: The parameters of a two-layer soil can be determined by
processing resistivity data obtained from resistivity measurements
carried out on the soil of interest. The processing usually entails
applying the resistivity data as inputs to an optimisation function.
This paper proposes an algorithm which utilises the square error as an
optimisation function. Resistivity data from previous works were
applied to test the accuracy of the new algorithm developed and the
result obtained conforms significantly to results from previous works.
Abstract: The study area is Zaria, located in the basement
complex of northern Nigeria. The rock type forming the major part of
the Zaria batholith is granite. This research work was carried out to
compare the responses of seismic refraction tomography and
resistivity tomography in the same geologic environment and under
the same conditions. Hence, the choice of the site that has a visible
granitic outcrop that extends across a narrow stream channel and is
flanked by unconsolidated overburden, a neutral profile that was
covered by plain overburden and a site with thick lateritic cover
became necessary. The results of the seismic and resistivity
tomography models reveals that seismic velocity and resistivity does
not always simultaneously increase with depth, but their responses in
any geologic environment are determined by changes in the
mechanical and chemical content of the rock types rather than depth.
Abstract: In this study, the Mo-electrode thin films were deposited using two-stepped process and the high purity copper indium selenide-based powder (CuInSe2, CIS) was fabricated by using hydrothermal process by Nanowin Technology Co. Ltd. Because the CIS powder was aggregated into microscale particles, the CIS power was ground into nano-scale particles. 6 wt% CIS particles were mixed and dispersed into isopropyl alcohol (IPA). A new non-vacuum thin-film deposition process, spray coating method (SPM), was investigated to deposit the high-densified CIS absorber layers. 0.1 ml CIS solution was sprayed on the 20 mm×10 mm Mo/glass substrates and then the CuInSe2 thin films were annealed in a selenization furnace using N2 as atmosphere. The annealing temperature and time were set at 550oC and 5 min, and 0.0g~0.6g extra Se content was added in the furnace. The influences of extra Se content on the densification, crystallization, resistivity (ρ), hall mobility (μ), and carrier concentration of the CIS absorber layers were well investigated in this study.
Abstract: In this study, we investigated (In,Ga,Zn)Ox (IGZO) thin films and examined their characteristics of using Ga2O3-2 ZnO (GZO) co-sputtered In2O3 prepared by dual target radio frequency magnetron sputtering at room temperature in a pure Ar atmosphere. RF powers of 80 W and 70 W were used for GZO and pure In2O3, room temperature (RT) was used as deposition temperature, and the deposition time was changed from 15 min to 60 min. Structural, surface, electrical, and optical properties of IGZO thin films were investigated as a function of deposition time. Furthermore, the GZO co-sputtered In2O3 thin films showed a very smooth and featureless surface and an amorphous structure regardless of the deposition time due to the room temperature sputtering process. We would show that the co-sputtered IGZO thin films exhibited transparent electrode properties with high transmittance ratio and low resistivity.
Abstract: The factors necessary to obtain an optimal heat treatment that influence the hardness and resistivity of Al-6Si-0.5Mg casting alloys with Cu or/and Ni additions were investigated. The alloys were homogenised (24hr at 500oC), solutionized (2hr at 540oC) and artificially ageing at various times and temperatures. The alloys were aged isochronally for 60 minutes at temperatures up to 400oC and isothermally at 150, 175, 200, 225, 250 & 300oC for different periods in the range 15 to 360 minutes. The hardness and electrical resistivity of the alloys were measured for various artificial ageing times and temperatures. From the isochronal ageing treatment, hardness found maximum ageing at 225oC. And from the isothermal ageing treatment, hardness found maximum for 60 minutes at 225oC. So the optimal heat treatment consists of 60 minutes ageing at 225oC.
Abstract: In this paper, steady-state ampacity (current carrying capacity) evaluation of underground power cable system by using analytical and numerical methods for different conditions (depth of cable, spacing between phases, soil thermal resistivity, ambient temperature, wind speed), for two system voltage level were used 132 and 380 kV. The analytical method or traditional method that was used is based on the thermal analysis method developed by Neher-McGrath and further enhanced by International Electrotechnical Commission (IEC) and published in standard IEC 60287. The numerical method that was used is finite element method and it was recourse commercial software based on finite element method.
Abstract: The prologue of new High Voltage (HV) transmission mains into the community necessitates earthing design to ensure safety compliance of the system. Concrete poles are widely used within HV transmission mains; many retired transmission mains with timber poles are being replaced with concrete ones, green transmission mains are deploying concrete poles. The earthing arrangement of the concrete poles could have an impact on the earth grid impedance also on the input impedance of the system from the fault point of view. This paper endeavors to provide information on the soil resistivity of the area and the deployments of concrete poles. It introduce the cut off soil resistivity value ρSC, this value aid in determine the impact of deploying the concrete poles on the earthing system. Multiple cases were discussed in this paper.
Abstract: Ageing of 75% cold rolled Al-6Mg alloy with ternary 0.4 wt% scandium and quaternary zirconium and titanium has been carried out. Alloy samples are naturally, isochronally and isothermally aged for different time and temperatures. Hardness values of the differently processed alloys have been measured to understand the ageing behavior of Al-6Mg alloy with scandium and quaternary zirconium and titanium addition. Resistivity changes with annealing time and temperature were measured to understand the precipitation behavior and recovery of strain of the alloy. Attempts were also made to understand the grain refining effect of scandium in Al-6Mg alloy. It is observed that significant hardening takes place in the aged alloys due to the precipitation of scandium aluminides and the dendrites of the Al-6Mg alloy have been refined significantly due to addition of scandium.