Abstract: A bauxite ore can be utilized in Bayer Process, if the
mass ratio of Al2O3 to SiO2 is greater than 10. Otherwise, its FexOy
and SiO2 content should be removed. On the other hand, removal of
TiO2 from the bauxite ore would be beneficial because of both
lowering the red mud residue and obtaining a valuable raw material
containing TiO2 mineral. In this study, the low grade diasporic
bauxite ore of Yalvaç, Isparta, Turkey was roasted under reducing
atmosphere and subjected to magnetic separation. According to the
experimental results, 800°C for reduction temperature and 20000
Gauss of magnetic intensity were found to be the optimum
parameters for removal of iron oxide and rutile from the nonmagnetic
ore. On the other hand, 600°C and 5000 Gauss were
determined to be the optimum parameters for removal of silica from
the non-magnetic ore.
Abstract: In recent years, honeycomb fiber reinforced plastic
(FRP) sandwich panels have been increasingly used in various
industries. Low weight, low price and high mechanical strength are
the benefits of these structures. However, their mechanical properties
and behavior have not been fully explored. The objective of this
study is to conduct a combined numerical-statistical investigation of
honeycomb FRP sandwich beams subject to torsion load. In this
paper, the effect of geometric parameters of sandwich panel on
maximum shear strain in both face and core and angle of torsion in a
honeycomb FRP sandwich structures in torsion is investigated. The
effect of Parameters including core thickness, face skin thickness,
cell shape, cell size, and cell thickness on mechanical behavior of the
structure were numerically investigated. Main effects of factors were
considered in this paper and regression equations were derived.
Taguchi method was employed as experimental design and an
optimum parameter combination for the maximum structure stiffness
has been obtained. The results showed that cell size and face skin
thickness have the most significant impacts on torsion angle,
maximum shear strain in face and core.
Abstract: Nanotechnology has become the world attention in
various applications including the solar cells devices due to the
uniqueness and benefits of achieving low cost and better
performances of devices. Recently, thin film solar cells such as
Cadmium Telluride (CdTe), Copper-Indium-Gallium-diSelenide
(CIGS), Copper-Zinc-Tin-Sulphide (CZTS), and Dye-Sensitized
Solar Cells (DSSC) enhanced by nanotechnology have attracted
much attention. Thus, a compilation of nanotechnology devices
giving the progress in the solar cells has been presented. It is much
related to nanoparticles or nanocrystallines, carbon nanotubes, and
nanowires or nanorods structures.
Abstract: In this paper, we present a new segmentation approach
for liver lesions in regions of interest within MRI (Magnetic
Resonance Imaging). This approach, based on a two-cluster Fuzzy CMeans
methodology, considers the parameter variable compactness
to handle uncertainty. Fine boundaries are detected by a local
recursive merging of ambiguous pixels with a sequential forward
floating selection with Zernike moments. The method has been tested
on both synthetic and real images. When applied on synthetic images,
the proposed approach provides good performance, segmentations
obtained are accurate, their shape is consistent with the ground truth,
and the extracted information is reliable. The results obtained on MR
images confirm such observations. Our approach allows, even for
difficult cases of MR images, to extract a segmentation with good
performance in terms of accuracy and shape, which implies that the
geometry of the tumor is preserved for further clinical activities (such
as automatic extraction of pharmaco-kinetics properties, lesion
characterization, etc.).
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: The effects of flame-holder position, the ratio of flame
holder diameter to combustion chamber diameter and injection angle
on fuel propulsive droplets sizing and effective mass fraction have
been studied by a cold flow. We named the mass of fuel vapor inside
the flammability limit as the effective mass fraction. An empty
cylinder as well as a flame-holder which are a simulator for duct
combustion has been considered. The airflow comes into the cylinder
from one side and injection operation will be done by four nozzles
which are located on the entrance of cylinder. To fulfill the
calculations a modified version of KIVA-3V code which is a
transient, three-dimensional, multiphase, multi component code for
the analysis of chemically reacting flows with sprays, is used.
Abstract: This paper is based on a large questionnaire study. The
paper presents how all participants and subgroups (upper- and
lower-level white-collar workers) answered the question, “Have you
had an ache, pain, or numbness, which you associate with desktop
computer use, in the different body parts during the last 12 months?’
14.6% of participants (19.4% of women and 8.2% of men) reported
that they had often or very often physical symptoms in the neck. Even
if our results cannot prove a causal relation of symptoms with
computer use, show that workers believe that computer use can
influence their wellbeing: this is important when devising treatment
modalities to decrease these physical symptoms.
Abstract: This work presents an improved single fiber pull-out
test for fiber/matrix interface characterization. This test has been
used to study the Inter-Facial Shear Strength ‘IFSS’ of hemp fibers
reinforced polypropylene (PP). For this aim, the fiber diameter
has been carefully measured using a tomography inspired method.
The fiber section contour can then be approximated by a circle
or a polygon. The results show that the IFSS is overestimated if
the circular approximation is used. The Influence of the molding
temperature on the IFSS has also been studied. We find that a molding
temperature of 183◦C leads to better interfacial properties. Above or
below this temperature the interface strength is reduced.
Abstract: In this study, to clarify the effectiveness of an
aluminum/chromium/tungsten-based-coated tool for cutting sintered
steel, tool wear was experimentally investigated. The sintered steel
was turned with the (Al60,Cr25,W15)N-, (Al60,Cr25,W15)(C,N)- and
(Al64,Cr28,W8)(C,N)-coated cemented carbide tools according to the
physical vapor deposition (PVD) method. Moreover, the tool wear of
the aluminum/chromium/tungsten-based-coated item was compared
with that of the (Al,Cr)N coated tool. Furthermore, to clarify the tool
wear mechanism of the aluminum/chromium/tungsten-coating film for
cutting sintered steel, Scanning Electron Microscope observation and
Energy Dispersive x-ray Spectroscopy mapping analysis were
conducted on the abraded surface. The following results were
obtained: (1) The wear progress of the (Al64,Cr28,W8)(C,N)-coated
tool was the slowest among that of the five coated tools. (2) Adding
carbon (C) to the aluminum/chromium/tungsten-based-coating film
was effective for improving the wear-resistance. (3) The main wear
mechanism of the (Al60,Cr25,W15)N-, the (Al60,Cr25,W15)(C,N)-
and the (Al64,Cr28,W8)(C,N)-coating films was abrasive wear.
Abstract: Bicycle Level of Service (BLOS) is a measure for
evaluating street conditions for cyclists. Currently, various methods
are proposed for BLOS. These analytical methods however have
some drawbacks: they usually assume cyclists as users that can share
street facilities with motorized vehicles, it is not easy to link them to
design process and they are not easy to follow. In addition, they only
support a narrow range of cycling facilities and may not be applicable
for all situations. Along this, the current paper introduces various
effective design factors for bicycle-friendly streets. This study
considers cyclists as users of streets who have special needs and
facilities. Therefore, the key factors that influence BLOS based on
different cycling facilities that are proposed by developed guidelines
and literature are identified. The combination of these factors
presents a complete set of effective design factors for bicycle-friendly
streets. In addition, the weight of each factor in existing BLOS
models is estimated and these effective factors are ranked based on
these weights. These factors and their weights can be used in further
studies to propose special bicycle-friendly street design model.
Abstract: The main parameters affecting the workability are the
water content, particle size, and the total surface of the grains, as long
as the mixing water begins by wetting the surface of the grains and
then fills the voids between the grains to form entrapped water, the
quantity of water remaining is called free water. The aim of this study is to undertake a fractal approach through
the relationship between the concrete formulation parameters and
workability. To develop this approach a series of concrete taken from
the literature was investigated by varying formulation parameters
such as G/S, the quantity of cement C and the quantity of water W. We also call another model as the model of water layer thickness
and model of paste layer thickness to judge their relevance, hence the
following results: the relevance of the water layer thickness model is
considered as a relevant when there is a variation in the water
quantity. The model of the paste layer thickness is only applicable if
we considered that the paste is made with the grain value Dmax =
2.85: value from which we see a stability of the model.
Abstract: Superabsorbent polymers received much attention and
are used in many fields because of their superior characters to
traditional absorbents, e.g., sponge and cotton. So, it is very
important but challenging to prepare highly and fast-swelling
superabsorbents. A reliable, efficient and low-cost technique for
removing heavy metal ions from wastewater is the adsorption using
bio-adsorbents obtained from biological materials, such as
polysaccharides-based hydrogels superabsorbents. In this study, novel multi-functional superabsorbent composites
type semi-interpenetrating polymer networks (Semi-IPNs) were
prepared via graft polymerization of acrylamide onto chitosan
backbone in presence of gelatin, CTS-g-PAAm/Ge, using potassium
persulfate and N,N’-methylene bisacrylamide as initiator and
crosslinker, respectively. These hydrogels were also partially
hydrolyzed to achieve superabsorbents with ampholytic properties
and uppermost swelling capacity. The formation of the grafted
network was evidenced by Fourier Transform Infrared Spectroscopy
(ATR-FTIR) and Thermogravimetric Analysis (TGA). The porous
structures were observed by Scanning Electron Microscope (SEM).
From TGA analysis, it was concluded that the incorporation of the Ge
in the CTS-g-PAAm network has marginally affected its thermal
stability. The effect of gelatin content on the swelling capacities of
these superabsorbent composites was examined in various media
(distilled water, saline and pH-solutions). The water absorbency was
enhanced by adding Ge in the network, where the optimum value was
reached at 2 wt. % of Ge. Their hydrolysis has not only greatly
optimized their absorption capacity but also improved the swelling
kinetic.These materials have also showed reswelling ability. We
believe that these super-absorbing materials would be very effective
for the adsorption of harmful metal ions from wastewater.
Abstract: Steepest descent method is a simple gradient method
for optimization. This method has a slow convergence in heading to
the optimal solution, which occurs because of the zigzag form of the
steps. Barzilai and Borwein modified this algorithm so that it
performs well for problems with large dimensions. Barzilai and
Borwein method results have sparked a lot of research on the method
of steepest descent, including alternate minimization gradient method
and Yuan method. Inspired by previous works, we modified the step
size of the steepest descent method. We then compare the
modification results against the Barzilai and Borwein method,
alternate minimization gradient method and Yuan method for
quadratic function cases in terms of the iterations number and the
running time. The average results indicate that the steepest descent
method with the new step sizes provide good results for small
dimensions and able to compete with the results of Barzilai and
Borwein method and the alternate minimization gradient method for
large dimensions. The new step sizes have faster convergence
compared to the other methods, especially for cases with large
dimensions.
Abstract: EEG correlates of mathematical and trait anxiety level
were studied in 52 healthy Russian-speakers during execution of
error-recognition tasks with lexical, arithmetic and algebraic
conditions. Event-related spectral perturbations were used as a
measure of brain activity. The ERSP plots revealed alpha/beta
desynchronizations within a 500-3000 ms interval after task onset
and slow-wave synchronization within an interval of 150-350 ms.
Amplitudes of these intervals reflected the accuracy of error
recognition, and were differently associated with the three conditions.
The correlates of anxiety were found in theta (4-8 Hz) and beta2 (16-
20 Hz) frequency bands. In theta band the effects of mathematical
anxiety were stronger expressed in lexical, than in arithmetic and
algebraic condition. The mathematical anxiety effects in theta band
were associated with differences between anterior and posterior
cortical areas, whereas the effects of trait anxiety were associated
with inter-hemispherical differences. In beta1 and beta2 bands effects
of trait and mathematical anxiety were directed oppositely. The trait
anxiety was associated with increase of amplitude of
desynchronization, whereas the mathematical anxiety was associated
with decrease of this amplitude. The effect of mathematical anxiety
in beta2 band was insignificant for lexical condition but was the
strongest in algebraic condition. EEG correlates of anxiety in theta
band could be interpreted as indexes of task emotionality, whereas
the reaction in beta2 band is related to tension of intellectual
resources.
Abstract: Aurèsregion is one of the arid and semi-arid areas that
have suffered climate crises and overexploitation of natural resources
they have led to significant land degradation. The use of remote sensing data allowed us to analyze the land and
its spatiotemporal changes in the Aurès between 1987 and 2013, for
this work, we adopted a method of analysis based on the exploitation
of the images satellite Landsat TM 1987 and Landsat OLI 2013, from
the supervised classification likelihood coupled with field surveys of
the mission of May and September of 2013. Using ENVI EX software by the superposition of the ground cover
maps from 1987 and 2013, one can extract a spatial map change of
different land cover units. The results show that between 1987 and
2013 vegetation has suffered negative changes are the significant
degradation of forests and steppe rangelands, and sandy soils and
bare land recorded a considerable increase. The spatial change map land cover units between 1987 and 2013
allows us to understand the extensive or regressive orientation of
vegetation and soil, this map shows that dense forests give his place
to clear forests and steppe vegetation develops from a degraded forest
vegetation and bare, sandy soils earn big steppe surfaces that explain
its remarkable extension.
The analysis of remote sensing data highlights the profound
changes in our environment over time and quantitative monitoring of
the risk of desertification.
Abstract: This paper presents a state-of-the-art survey of the
operations research models developed for internal audit planning.
Two alternative approaches have been followed in the literature for
audit planning: (1) identifying the optimal audit frequency; and (2)
determining the optimal audit resource allocation. The first approach
identifies the elapsed time between two successive audits, which can
be presented as the optimal number of audits in a given planning
horizon, or the optimal number of transactions after which an audit
should be performed. It also includes the optimal audit schedule. The
second approach determines the optimal allocation of audit frequency
among all auditable units in the firm. In our review, we discuss both
the deterministic and probabilistic models developed for audit
planning. In addition, game theory models are reviewed to find the
optimal auditing strategy based on the interactions between the
auditors and the clients.
Abstract: High Voltage Direct Current (HVDC) power
transmission is employed to move large amounts of electric power.
There are several possibilities to enhance the transient stability in a
power system. One adequate option is by using the high
controllability of the HVDC if HVDC is available in the system. This
paper presents a control technique for HVDC to enhance the transient
stability. The strategy controls the power through the HVDC to help
make the system more transient stable during disturbances. Loss of
synchronism is prevented by quickly producing sufficient
decelerating energy to counteract accelerating energy gained during.
In this study, the power flow in the HVDC link is modulated with the
addition of an auxiliary signal to the current reference of the rectifier
firing angle controller. This modulation control signal is derived from
speed deviation signal of the generator utilizing a PD controller; the
utilization of a PD controller is suitable because it has the property of
fast response. The effectiveness of the proposed controller is
demonstrated with a SMIB test system.
Abstract: In this paper, we present a four-step ortho-rectification
procedure for real-time geo-referencing of video data from a low-cost
UAV equipped with a multi-sensor system. The basic procedures for
the real-time ortho-rectification are: (1) decompilation of the video
stream into individual frames; (2) establishing the interior camera
orientation parameters; (3) determining the relative orientation
parameters for each video frame with respect to each other; (4)
finding the absolute orientation parameters, using a self-calibration
bundle and adjustment with the aid of a mathematical model. Each
ortho-rectified video frame is then mosaicked together to produce a
mosaic image of the test area, which is then merged with a well
referenced existing digital map for the purpose of geo-referencing
and aerial surveillance. A test field located in Abuja, Nigeria was
used to evaluate our method. Video and telemetry data were collected
for about fifteen minutes, and they were processed using the four-step
ortho-rectification procedure. The results demonstrated that the
geometric measurement of the control field from ortho-images is
more accurate when compared with those from original perspective
images when used to pin point the exact location of targets on the
video imagery acquired by the UAV. The 2-D planimetric accuracy
when compared with the 6 control points measured by a GPS receiver
is between 3 to 5 metres.
Abstract: In present global scenario, aluminum alloys are
coining the attention of many innovators as competing structural
materials for automotive and space applications. Comparing to other
challenging alloys, especially, 7xxx series aluminum alloys have
been studied seriously because of benefits such as moderate strength;
better deforming characteristics and affordable cost. It is expected
that substitution of aluminum alloys for steels will result in great
improvements in energy economy, durability and recyclability.
However, it is necessary to improve the strength and the formability
levels at low temperatures in aluminum alloys for still better
applications. Aluminum–Zinc–Magnesium with or without other
wetting agent denoted as 7XXX series alloys are medium strength
heat treatable alloys. In addition to Zn, Mg as major alloying
additions, Cu, Mn and Si are the other solute elements which
contribute for the improvement in mechanical properties by suitable
heat treatment process. Subjecting to suitable treatments like age
hardening or cold deformation assisted heat treatments; known as low
temperature thermomechanical treatments (LTMT) the challenging
properties might be incorporated. T6 is the age hardening or
precipitation hardening process with artificial aging cycle whereas T8
comprises of LTMT treatment aged artificially with X% cold
deformation. When the cold deformation is provided after solution
treatment, there is increase in hardness related properties such as
wear resistance, yield and ultimate strength, toughness with the
expense of ductility. During precipitation hardening both hardness
and strength of the samples are increasing. The hardness value may
further improve when room temperature deformation is positively
supported with age hardening known as thermomechanical treatment.
It is intended to perform heat treatment and evaluate hardness, tensile
strength, wear resistance and distribution pattern of reinforcement in
the matrix. 2 to 2.5 and 3 to 3.5 times increase in hardness is reported
in age hardening and LTMT treatments respectively as compared to
as-cast composite. There was better distribution of reinforcements in
the matrix, nearly two fold increase in strength levels and up to 5
times increase in wear resistance are also observed in the present
study.
Abstract: Numerical studies have been carried out using a
validated two-dimensional standard k-omega turbulence model for
the design optimization of a thrust vector control system using shock
induced self-impinging supersonic secondary double jet. Parametric
analytical studies have been carried out at different secondary
injection locations to identifying the highest unsymmetrical
distribution of the main gas flow due to shock waves, which produces
a desirable side force more lucratively for vectoring. The results from
the parametric studies of the case on hand reveal that the shock
induced self-impinging supersonic secondary double jet is more
efficient in certain locations at the divergent region of a CD nozzle
than a case with supersonic single jet with same mass flow rate. We
observed that the best axial location of the self-impinging supersonic
secondary double jet nozzle with a given jet interaction angle, built-in
to a CD nozzle having area ratio 1.797, is 0.991 times the primary
nozzle throat diameter from the throat location. We also observed
that the flexible steering is possible after invoking ON/OFF facility to
the secondary nozzles for meeting the onboard mission requirements.
Through our case studies we concluded that the supersonic self-impinging
secondary double jet at predesigned jet interaction angle
and location can provide more flexible steering options facilitating
with 8.81% higher thrust vectoring efficiency than the conventional
supersonic single secondary jet without compromising the payload
capability of any supersonic aerospace vehicle.