Abstract: Artificial Neural Network (ANN)s are best suited for
prediction and optimization problems. Trained ANNs have found
wide spread acceptance in several antenna design systems. Four
parameters namely antenna radiation resistance, loss resistance, efficiency,
and inductance can be used to design an antenna layout though
there are several other parameters available. An ANN can be trained
to provide the best and worst case precisions of an antenna design
problem defined by these four parameters. This work describes the
use of an ANN to generate the four mentioned parameters for a loop
antenna for the specified frequency range. It also provides insights
to the prediction of best and worst-case design problems observed
in applications and thereby formulate a model for physical layout
design of a loop antenna.
Abstract: A group of Stellite alloys are studied in consideration
of temperature effects on their hardness and wear resistance. The
hardness test is conducted on a micro-hardness tester with a hot stage
equipped that allows heating the specimen up to 650°C. The wear
resistance of each alloy is evaluated using a pin-on-disc tribometer
with a heating furnace built-in that provides the temperature capacity
up to 450°C. The experimental results demonstrate that the hardness
and wear resistance of Stellite alloys behave differently at room
temperature and at high temperatures. The wear resistance of Stellite
alloys at room temperature mainly depends on their carbon content and
also influenced by the tungsten content in the alloys. However, at high
temperatures the wear mechanisms of Stellite alloys become more
complex, involving multiple factors. The relationships between
chemical composition, microstructure, hardness and wear resistance of
these alloys are studied, with focus on temperature effect on these
relations.
Abstract: The effect of different tempering temperatures and heat treatment times on the corrosion resistance of austenitic stainless steels in oxalic acid was studied in this work using conventional weight loss and electrochemical measurements. Typical 304 and 316 stainless steel samples were tempered at 150oC, 250oC and 350oC after being austenized at 1050oC for 10 minutes. These samples were then immersed in 1.0M oxalic acid and their weight losses were measured at every five days for 30 days. The results show that corrosion of both types of ASS samples increased with an increase in tempering temperature and time and this was due to the precipitation of chromium carbides at the grain boundaries of these metals. Electrochemical results also confirm that the 304 ASS is more susceptible to corrosion than 316 ASS in this medium. This is attributed to the molybdenum in the composition of the latter. The metallographic images of these samples showed non–uniform distribution of precipitated chromium carbides at the grain boundaries of these metals and unevenly distributed carbides and retained austenite phases which cause galvanic effects in the medium.
Abstract: The incessant discomfort for Voluntary Counselling and Testing (VCT) exhibited by students in some tertiary institutions in Kano State, Nigeria is capable of causing Psychological Resistance as well as jeopardizing the purpose of HIV intervention. This study investigated the Prevalence of Psychological Resistance to VCT of HIV/AIDS among students of tertiary institutions in the state. Two null hypotheses were postulated and tested. Cross- Sectional Survey Design was employed in which 1512 sample was selected from a student population of 104,841 following Stratified Random Sampling technique. A self-developed 20-item scale whose reliability coefficient is 0.83 was used for data collection. Data analyzed via Chi-square and t-test reveals a prevalence of 38% with males (Mean=0.34; SD=0.475) constituting 60% and females (Mean=0.45; SD=0.498) 40%. Also, the calculated chi-square and ttest were not significant at 0.05 as such the null hypotheses were upheld. Recommendation offered suggests the use of reinforcement and social support for students who patronize HIV/AIDS counselling.
Abstract: The major objective of this study is to understand the
potential of a newly fabricated equipment to study the thermal
properties of nonwoven textile fabrics treated with aerogel at subzero
temperatures. Thermal conductivity was calculated by using the
empirical relation Fourier’s law, The relationship between the
thermal conductivity and thermal resistance of the samples were
studied at various environmental temperatures (which was set in the
clima temperature system between +25oC to -25oC). The newly
fabricated equipment was found to be a suitable for measuring at
subzero temperatures. This field of measurements is being developed
and will be the subject of further research which will be more suitable
for measurement of the various thermal characteristics.
Abstract: The huge development of new technologies and the
apparition of open communication system more and more
sophisticated create a new challenge to protect digital content from
piracy. Digital watermarking is a recent research axis and a new
technique suggested as a solution to these problems. This technique
consists in inserting identification information (watermark) into
digital data (audio, video, image, databases...) in an invisible and
indelible manner and in such a way not to degrade original medium-s
quality. Moreover, we must be able to correctly extract the
watermark despite the deterioration of the watermarked medium (i.e
attacks). In this paper we propose a system for watermarking satellite
images. We chose to embed the watermark into frequency domain,
precisely the discrete wavelet transform (DWT). We applied our
algorithm on satellite images of Tunisian center. The experiments
show satisfying results. In addition, our algorithm showed an
important resistance facing different attacks, notably the compression
(JEPG, JPEG2000), the filtering, the histogram-s manipulation and
geometric distortions such as rotation, cropping, scaling.
Abstract: Martensitic stainless steels have been extensively used for their good corrosion resistance and better mechanical properties. Heat treatment was suggested as one of the most excellent ways to this regard; hence, it affects the microstructure, mechanical and corrosion properties of the steel. In the current research work the microstructural changes and corrosion behavior in an AISI 420A stainless steel exposed to temperatures in the 980-1035oC range were investigated. The heat treatment is carried out in vacuum furnace within the said temperature range. The quenching of the samples was carried out in oil, brine and water media. The formation and stability of passive film was studied by Open Circuit Potential, Potentiodynamic polarization and Electrochemical Scratch Tests. The Electrochemical Impedance Spectroscopy results simulated with Equivalent Electrical Circuit suggested bilayer structure of outer porous and inner barrier oxide films. The quantitative data showed thick inner barrier oxide film retarded electrochemical reactions. Micrographs of the quenched samples showed sigma and chromium carbide phases which prove the corrosion resistance of steel alloy.
Abstract: This research aims at modeling and simulating the effects of nanofluids on cylindrical heat pipes thermal performance using the ANSYS-FLUENT CFD commercial software. The heat pipe outer wall temperature distribution, thermal resistance, liquid pressure and axial velocity in presence of suspended nano-scaled solid particle (i.e. Cu, Al2O3 and TiO2) within the fluid (water) were investigated. The effect of particle concentration and size were explored and it is concluded that the thermal performance of the heat pipe is improved when using nanofluid as the system working fluid. Additionally, it was observed that the thermal resistance of the heat pipe drops as the particle concentration level increases and particle radius decreases.
Abstract: Coated tool inserts can be considered as the backbone
of machining processes due to their wear and heat resistance.
However, defects of coating can degrade the integrity of these inserts
and the number of these defects should be minimized or eliminated if
possible. Recently, the advancement of coating processes and
analytical tools open a new era for optimizing the coating tools.
First, an overview is given regarding coating technology for cutting
tool inserts. Testing techniques for coating layers properties, as well
as the various coating defects and their assessment are also surveyed.
Second, it is introduced an experimental approach to examine the
possible coating defects and flaws of worn multicoated carbide
inserts using two important techniques namely scanning electron
microscopy and atomic force microscopy. Finally, it is
recommended a simple procedure for investigating manufacturing
defects and flaws of worn inserts.
Abstract: This paper presents the impact study of GTO Controlled Series Capacitor (GCSC) parameters on measured impedance (Zseen) by MHO distance relays for single transmission line high voltage 220 kV in the presence of single phase to earth fault with fault resistance (RF). The study deals with a 220 kV single electrical transmission line of Eastern Algerian transmission networks at Group Sonelgaz (Algerian Company of Electrical and Gas) compensated by series Flexible AC Transmission System (FACTS) i.e. GCSC connected at midpoint of the transmission line. The transmitted active and reactive powers are controlled by three GCSC-s. The effects of maximum reactive power injected as well as injected maximum voltage by GCSC on distance relays measured impedance is treated. The simulations results investigate the effects of GCSC injected parameters: variable reactance (XGCSC), variable voltage (VGCSC) and reactive power injected (QGCSC) on measured resistance and reactance in the presence of earth fault with resistance fault varied between 5 to 50 Ω for three cases study.
Abstract: This paper presents two simplified models to
determine nodal voltages in power distribution networks. These
models allow estimating the impact of the installation of reactive
power compensations equipments like fixed or switched capacitor
banks. The procedure used to develop the models is similar to the
procedure used to develop linear power flow models of transmission
lines, which have been widely used in optimization problems of
operation planning and system expansion. The steady state non-linear
load flow equations are approximated by linear equations relating the
voltage amplitude and currents. The approximations of the linear
equations are based on the high relationship between line resistance
and line reactance (ratio R/X), which is valid for power distribution
networks. The performance and accuracy of the models are evaluated
through comparisons with the exact results obtained from the
solution of the load flow using two test networks: a hypothetical
network with 23 nodes and a real network with 217 nodes.
Abstract: Nowadays, engineering ceramics have significant
applications in different industries such as; automotive, aerospace,
electrical, electronics and even martial industries due to their
attractive physical and mechanical properties like very high hardness
and strength at elevated temperatures, chemical stability, low friction
and high wear resistance. However, these interesting properties plus
low heat conductivity make their machining processes too hard,
costly and time consuming. Many attempts have been made in order
to make the grinding process of engineering ceramics easier and
many scientists have tried to find proper techniques to economize
ceramics' machining processes. This paper proposes a new diamond
plunge grinding technique using ultrasonic vibration for grinding
Alumina ceramic (Al2O3). For this purpose, a set of laboratory
equipments have been designed and simulated using Finite Element
Method (FEM) and constructed in order to be used in various
measurements. The results obtained have been compared with the
conventional plunge grinding process without ultrasonic vibration
and indicated that the surface roughness and fracture strength
improved and the grinding forces decreased.
Abstract: This paper aims to discuss the influence of resistance
characteristic on the high conductive concrete considering the changes
of voltage and environment. The high conductive concrete with
appropriate proportion is produced to the press-electrode method. The
curve of resistivity with the changes of voltage and environment is
plotted and the changes of resistivity are explored.
Abstract: This investigation examines the effect of the sintering
temperature curve in manufactured nickel powder capillary structure
(wick) for a loop heat pipe (LHP). The sintering temperature curve is
composed of a region of increasing temperature; a region of constant
temperature and a region of declining temperature. The most important
region is that in which the temperature increases, as an index in the
stage in which the temperature increases. The wick of nickel powder is
manufactured in the stage of fixed sintering temperature and the time
between the stage of constant temperature and the stage of falling
temperature. When the slope of the curve in the region of increasing
temperature is unity (equivalent to 10 °C/min), the structure of the
wick is complete and the heat transfer performance is optimal. The
result of experiment test demonstrates that the heat transfer
performance is optimal at 320W; the minimal total thermal resistance
is approximately 0.18°C/W, and the heat flux is 17W/cm2; the internal
parameters of the wick are an effective pore radius of 3.1 μm, a
permeability of 3.25×10-13m2 and a porosity of 71%.
Abstract: Ultrathin (UTD) and Nanoscale (NSD) SOI-MOSFET devices, sharing a similar W/L but with a channel thickness of 46nm and 1.6nm respectively, were fabricated using a selective “gate recessed” process on the same silicon wafer. The electrical transport characterization at room temperature has shown a large difference between the two kinds of devices and has been interpreted in terms of a huge unexpected series resistance. Electrical characteristics of the Nanoscale device, taken in the linear region, can be analytically derived from the ultrathin device ones. A comparison of the structure and composition of the layers, using advanced techniques such as Focused Ion Beam (FIB) and High Resolution TEM (HRTEM) coupled with Energy Dispersive X-ray Spectroscopy (EDS), contributes an explanation as to the difference of transport between the devices.
Abstract: Candida spp. are common and aggressive pathogens.
Because of the growing resistance of Candida spp. to current
antifungals, novel targets, found in Candida spp. but not in humans
or other flora, have to be identified. The alternative oxidase (AOX)
is one such possibility. This enzyme is insensitive to cyanide, but is
sensitive to compounds such as salicylhydroxamic acid (SHAM),
disulfiram and n-alkyl gallates. The growth Candida albicans was
inhibited by SHAM (Ki = 9-15 mM) and cyanide (Ki = 2-4 mM),
albeit to differing extents. The rate of O2 uptake was inhibited by
less than 10% by 25 mM SHAM and by about 90% by 250 μM
KCN. Although SHAM substantially inhibited the growth of C.
albicans, it is unlikely that the inhibition of AOX was the cause.
Salicylhydroxamic acid is used therapeutically in the treatment of
urinary tract infections and urolithiasis, but it also has some potential
in the treatment of C. albicans infection.
Abstract: In this study, inhibition of Microcystis aeruginosa by
antialgal alleochemical gramine, was studied by analyzing algal
metabolic activity (represented by esterase and total dehydrogenase
activities) and cell ultrastructure (showing morphological and
ultrastructure alterations using transmission electron microscopy and
DNA ladder analysis). After gramine exposure, esterase and total
dehydrogenase activities were increased firstly but decreased later. In
contrast with the controls, the cells exposed to gramine showed
apparent ultrastructure alterations with thylakoids in breakage,
phycobilins in decrease, lipid and cyanophycin granules abundant
firstly but dissolved afterwards, DNA in fragementation. The
occurrence of increase of metabolic activity and specific granules
reflected that the resistance of cellular response to gramine was
initiated. DNA fragementation associated with the increase of
metabolic activity and specific granules hinted that gramine caused M.
aeruginosa cells to initiate some morphotype of programmed cell
death.
Abstract: The study and development of an innovative material
for building insulation is really important for a sustainable society in order to improve comfort and reducing energy consumption. The aim of this work is the development of insulating panels for
sustainable buildings based on an innovative material made by
cardboard and Phase Change Materials (PCMs).
The research has consisted in laboratory tests whose purpose has been the obtaining of the required properties for insulation panels: lightweight, porous structures and mechanical resistance. PCMs have been used for many years in the building industry as
smart insulation technology because of their properties of storage and release high quantity of latent heat at useful specific temperatures [1]- [2].
The integration of PCMs into cellulose matrix during the waste paper recycling process has been developed in order to obtain a
composite material.
Experiments on the productive process for the realization of insulating panels were done in order to make the new material
suitable for building application. The addition of rising agents
demonstrated the possibility to obtain a lighter structure with better
insulation properties.
Several tests were conducted to verify the new panel properties. The results obtained have shown the possibility to realize an
innovative and sustainable material suitable to replace insulating panels currently used.
Abstract: Speed sensorless systems are intensively studied during recent years; this is mainly due to their economical benefit and fragility of mechanical sensors and also the difficulty of installing this type of sensor in many applications. These systems suffer from instability problems and sensitivity to parameter mismatch at low speed operation. In this paper an analysis of adaptive observer stability with stator resistance estimation is given.
Abstract: The paper presents a part of the results obtained in a
complex research project on Romanian Grey Steppe breed, owner of
some remarkable qualities such as hardiness, longevity, adaptability,
special resistance to ban weather and diseases and included in the
genetic fund (G.D. no. 822/2008.) from Romania.
Following the researches effectuated, we identified alleles of six
loci, codifying the six types of major milk proteins: alpha-casein S1
(α S1-cz); beta-casein (β-cz); kappa-casein (K-cz); beta-lactoglobulin
(β-lg); alpha-lactalbumin (α-la) and alpha-casein S2 (α S2-cz). In
system αS1-cz allele αs1-Cn B has the highest frequency (0.700), in
system β-cz allele β-Cn A2 ( 0.550 ), in system K-cz allele k-CnA2 (
0.583 ) and heterozygote genotype AB ( 0.416 ) and BB (0.375), in
system β-lg allele β-lgA1 has the highest frequency (0.542 ) and
heterozygote genotype AB ( 0.500 ), in system α-la there is
monomorphism for allele α-la B and similarly in system αS2-cz for
allele αs2-Cn A.
The milk analysis by the isoelectric focalization technique (I.E.F.)
allowed the identification of a new allele for locus αS1-casein, for two
of the individuals under analysis, namely allele called αS1-casein
IRV. When experiments were repeated, we noticed that this is not a
proteolysis band and it really was a new allele that has not been
registered in the specialized literature so far. We identified two
heterozygote individuals, carriers of this allele, namely: BIRV and
CIRV. This discovery is extremely important if focus is laid on the
national genetic patrimony.