Anbar Journal of Engineering Sciences

In this paper, a proposed model based on phase matrix rotation was suggested to
improve the performance of Multicarrier-Code Division Multiple Access (MC-CDMA) lies in
Fast Fourier Transform (FFT) algorithm under the Additive White Gaussian Noise (AWGN)
and frequency selective fading channel. This model is used to reduce the effect of multipath
fading. The results extracted by a computer simulation for a single user, then it compared with
the original technique for MC-CDMA based on FFT for both systems. As a result, it can be
seen from the proposed technique that a high performance improvement was obtained over the
conventional MC-CDMA, where the Bit Error Rate (BER) is widely reduced under different
channel characteristics for frequency selective fading and the AWGN channel.

This research presents an experimental and theoretical investigation of the effect of cutouts on
the stress and strain of composite laminate plates subjected to static loads. The experimental
program covers measurement of the normal strain at the edges of circular and square holes with
different number of layers and types of composite materials by using strain gages technique
under constant tensile loads. A numerical investigation has been achieved by using the
software package (ANSYS), involving static analysis of symmetric square plates with different
types of cutouts. The numerical results include the parametric effects of lamination angle, hole
dimensions, types of hole and the number of layers of a symmetric square plate. The
experimental results show good agreement compared with numerical results. It is found that
increasing the number of layers reduces the value of normal strain at the edges of circular and
square holes of a symmetric plate and the maximum value of stress occurs at a lamination
angle of (30o
) and the maximum value of strain occurs at a lamination angle of (50o
) for the
symmetric square plates subjected to uni-axial applied load. The hole dimensions to width of
plates ratio is found to increase the maximum value of stress and strain of a symmetric square
plate subjected to uniaxial applied load. Moreover, the value of maximum stress increases with
the order of type of circular, square, triangular and hexagonal cutout, whereas the value of
maximum strain increases with the order of type of circular, square, hexagonal and triangular
cutout.

Silica particles are directly introduced into polyurethane resin with different grain size
and different volume fractions to obtain a new composite. Hardness, impact strength (charpy)
and compression properties were studied with the conditions mentioned; Acid solutions and
UV- radiation were the main environments studied on the samples prepared. The results
showed that the acid affected the properties more than UV- radiation

Severe three phase trips are simulated on four arbitrary locations of an uncontrolled
power system transmission lines. The responses of three measurable state variables of the
system (rotor speed, stator direct axis current, and stator quadrature - axis current) are
recorded, and suitable ANNs are trained to detect and locate the positions of the
corresponding trips. The paper proves that this method is quick, active and accurate to
diagnose and find the locations of that kind of trips.

In this study, silicon and yttrium were simultaneously co-deposited by diffusion into
austenitic stainless steel (AISI 316L) substrates, by a single-step pack cementation process.
Cyclic oxidation tests were conducted on the siliconized coating and on the yttrium doped
siliconized coating of stainless steel in CO2 atmospheric pressure at temperatures 800° C and
900° C for 100h at 10h cyclic. The results show that the initial weight gain is rapid and
increased as the temperature increased. The oxidation resistance of the yttrium doped
siliconized of stainless steels was significantly improved as compared with the siliconized
stainless steels. The scale formed on coated stainless steel after oxidation in CO2 environment
was thick and consisted of Y2O3, SiO2, Fe2O3 and chromium oxide. Optical metallography
(LOM) and X-ray diffraction (XRD) were used to characterize the resulting coating and cyclic
oxidation structures.

In this study, yttrium and aluminum were simultaneously co-deposited by diffusion into
austenitic stainless steel (AISI 316L) substrates, by a single-step pack cementation process.
Cyclic oxidation tests were conducted on the aluminide coating and on the yttrium modified
aluminide coating of stainless steel in air under atmospheric pressure at temperatures 700 C°
and 800 C° for 100h at 10h cyclic. Optical metallography and X-ray diffraction (XRD)
techniques were used to characterize the changes in scale morphology and to identify the
phases and oxidation products. The yttrium modified aluminde coating showed very good
cyclic oxidation resistance compared to aluminide coating

This study is the second stage of the paper “Studying the Effect of Rubber- Silicone on
Physical Properties of Asphalt Cement”. The present study examines the effect of additives on
asphalt mixture performance. Asphalt mixture has been designed by Marshall Method for
determining the optimum asphalt content and geophysical properties of mix according to ASTM
(D-1559). Rubber-silicone at different percentages (1%, 2%, 3% and 5%) was added to asphalt
binder. Six specimens of asphalt rubber silicone mixture (ARSM) for each percentage are
prepared and evaluated according to Marshall method. Diametric tensile creep test ASTM (D-
1075) at 60 Co
was used to evaluate permanent deformation and modulus of elasticity for
ARSM. The study showed that the Rubber-Silicone has more effects on performance of asphalt
mixture by increasing the Marshal stability, air voids, and reducing the flow and bulk density
compared with the original mix. It also increases the flexibility properties of the mix and this
appears from reducing the permanent deformation at test temperature (60C), the reduction
percent is about (30 to 70) %

A numerical study regarding stress, strain, and deflection of a composite plate is presented.
The plate, consisting of three layers of Carbon-, Boron-, and Graphite-Epoxy, was fixed at
one end and loaded at the other end in a conventional cantilever configuration. Six
arrangements were examined and the spatial distribution of stress, strain, and deflection of the
upper surface were calculated. Generally, it was found that the order, by which the three
layers are arranged, has a great effect on the response of the plate and the maximum stiffness
(in terms of deflection) is achieved when using Epoxy with Graphite-Carbon-Boron as the
top-central-bottom layers of the plate.