Al-Nahrain Journal for Engineering Sciences

IR UWB system has been proposed as a
promising physical layer candidate for indoor
wireless communications, because it offers very
fine time resolution and multipath resolvability.
Inter pulse interference (IPI) is one important
challenge related to the transmit reference (TR)
IR UWB receiver. In this paper, an attempt to
completely remove the IPI problem in TR with
increasing the data rate. This is achieved by
using orthogonal codes generated from modified
version of Hadamard matrix via the application
of the reference sign technique, i.e., by
modulating the reference pulse besides the
already data modulated.

The effect of reduction area for flat and
conical dies in forward-backward extrusion
process was investigated experimentally
using flat punches with three reduction areas
(0.305,0.444,0.605), 0.444 with cone angles
(60o,90o,120o) and polygonal punches
(hexagonal and square).Three reduction
areas of dies (0.395, 0.555, 0.691) are used.
The results show that the extrusion load is
effected with reduction area of flat dies more
than conical dies when using cone and flat
punches while the reduction area of conical
dies affected with square punch more than
hexagonal punch and this result was inversed
with flat dies. The relative extrusion pressure
P/ increases when the reduction area of
conical and flat dies increases too for all
punches, but this result contrasts with the
square punch at conical dies.The less value
of max. stress was found with cone punch of
prism angle 120o among cone punches for
conical dies except the die of reduction area
(0.555) and the cone punch of 90o prism angle
gave less max. stress with all flat dies. Flat
punch of reduction area (0.444) among the
flat punches gave less value of max. stress
with all conical dies and flat die of
reduction area (0.691).

In this research a theoretical study was
presented to find the performance of the offset
halves bearing which used in applications of
high velocities ,like centrifugal machines,
dentist tools and high precession machines.
In studying the elastic deformation,
three types of alloys have been used for coating
the bearing surface. These alloys Cu-alloy, Alalloy
and Mg-alloy. And these show that the
bearing material has a considerable effect on the
essential bearing characteristics. The bearing
made of soft material has lower performance
than that made of harder material.
In this work the bearing performance
was investigated under the following conditions :
1-Elastohydrodynamic lubrication at a rotational
velocity of 2000rpm and L/D ratios
Of(0.5.)and (1)
2-Elastohydrodynamic lubrication at a rotational
velocity of 15000rpm and L/D ratios of 0.5and
(1).
The results of analysis show that the offset
bearing deformation (elastic deformation) has a
considerable influence on the performance at a
high eccentricity values (n>0.9) i.e. under high
loa

Buckling analysis of laminated conical
shells under axial compressive load are
investigated analytically using high order and
Love ,s shell theories. Power series are used to
solve the developed equations of motion for
conical shells with different semi vertex
angles, length- to radius ratio, number of
layers and boundary conditions. The validity
of the presented procedure is confirmed.

In order to investigate the alumina
effect on the low frequency dielectric constant
of fire clay manufacture from Iraqi clay. Fire
clay products have been powder pressed with
different alumina content ,sintered ,then
dielectric constant and dielectric loss( tan )
has been measured at low frequencies which
extend from 30 kHz to 100kHz.There is a
significant difference in their properties were
observed between samples made with different
alumina content added to the fire clay product
where these differences were measured as a
function of alumina content. This confirm that
the insulating properties of the fire specimen
from the electrical view point was affected by
the crystallization of mullite and cristobolite .

In this work it has been attempted to study
the kinetic of vanadium recovery from fly ash
by leaching with NaOH solution from previous
work of Mosa (1999).
The selected data were chosen at particle
size of scale between 125 to 200 μm,
temperature 343 to 373 K, reaction (leaching)
time up to 8 hours and at about fixed NaOH
solution molarity (3 to 4 M).The results show
that vanadium recovery increased with time
and temperature and mostly decreased with
particle size.A second order polynomial
mathematical correlation was employed to
describe vanadium recovery response. The
correlation coefficient of the obtained
correlation was 0.9990 and variance of 0.9981
with confidence levels of 95 %.Kinetic study
shows that the chemical reaction is the
controlling step which has the highest
resistance among other steps. A chemical
reaction order was found equals to -3 with
activation energy of 1080 J/ mole and
frequency factor of about 2.6884.

In this paper, the crack propagation in
opening mode (Mode I) for three kinds of cast
iron rotating disc: Flake graphite cast iron disc,
Compacted Vermicular cast iron disc, and
Spheroidal graphite cast iron disc are analysed
by using Boundary Element Method (BEM) and
Finite Element Method (FEM). Weibull uniaxial
and multi-axial distribution function is
developed and applied to evaluate the reliability
of the fracture strength of rotating cast iron disc
have inner surface crack. As a result the stress
intensity factor (KI) for Flake graphite disc
(FGD) is smallest, while (KI) for Spheroidal
graphite disc (SGD) was the larger, the value of
(KI) for Compacted Vermicular disc (CVD) has
intermediate between the two cast iron discs. It is
found that there is a convergence between
results obtained from uni-axial and multi-axial
distribution function, but multi-axial
distribution function give high values compared
to uni-axial distribution function.

This research deals with the effect of type and
concentration of different polymer solutions on
rheological behavior and apparent viscosity. All
polymers studied in this work are water soluble,
which are: XC-polymer, Carboxymethyl
cellulose (two types), Hydroxyethyl cellulose and
Polyvinyl alcohol. 55 experiments were
performed with different polymer types and
concentrations at 30 C ( 1 C). By using the
Solver Add-in in Microsoft Excel®, the power
law flow model was found to be the best fits the
experimental results. The apparent viscosity of
each polymer used at different concentrations
was decreased with shear rates. It was found
that XC-polymer solutions have higher shear
stresses than other polymers. Also it was found
that XC-polymer solutions have a higher
viscosity, and its viscosity decreases much more
than other polymer solutions used in this study.

The aim of this paper is to study the possibility
of using laser technique for blood flow velocity
measurement using the fiber optics to deliver
the laser light and receive the scattered light
from the blood flowing in different types of
vessels. The measuring technique is based on
utilizing the Doppler effect in light by using a
He-Ne laser source. The correlation function has
been used to consider the scattering light from
different erythrocytes. Different angles of
transmitted laser inside the vessel were used. It
was found that the best angle for all vessels is
45 degrees between the light direction and the
direction of blood flow.