AL-Rafidain Engineering Journal (AREJ)

In this Paper, a neural network image recognition system is used. The
Neocognitron[8] in that system is used as feature extractor, then the feature are
classified by using a multilayered feedforward network to generate recognition
codes. Many neural learning algorithms are used to extract the feature, then
comparison among them is presented. Finally a comparison between most active
algorithms among them with respect to the whole performance of the of the
designed system is presented. The biases used in MBCL (Modified Bias
Competitive Learning) played an important role to improve the performance of
competitive learning algorithms. Using SOFM (Self Organizing Feature Map) to
extract features gave better recognition rate than MBCL and other algorithms

Airborne imaging radar systems are known by their ability to produce high
resolution images of ground targets using microwave region of electromagnetic
waves. There are many military and civilian applications of imaging radar
systems. The high resolution images achieved by transmitting a number of
electromagnetic pulses to the earth surface then integrating them coherently at the
receiver. A study have been achieved to show the effect of changing speed or
height or both of the airplane carrying the focused synthetic aperture radar upon
the azimuth resolution. The simulation results showed that increasing the speed or
decreasing the height of the airplane will improve the azimuth resolution, and it
can be noted for practical parameters that decreasing the speed and the height of
the airplane leads to degraded azimuth resolution. The results of azimuth
resolution obtained from simulations and those from theoretical calculations are
nearly identical for targets of point reflectors.

Security problems take an important part of computer network study in
which several techniques were developed for this purpose. Virtual Private
Networks (VPNs) are considered as an active form for providing secure networks.
The key feature of VPNs is that they are able to use public networks like the
Internet rather than rely on expensive private lines.
The aim of this paper is to design a VPN switch with the help of simulink
software provided by MATLAB 6.5. The VPN switch is a single hardware device,
it has the ability to support firewall, encryption, authentication, and data integrity
for secure tunneling across managed IP networks and Internet.
Introducing scrambling code within a VPN switch for encryption is
something new. The basic advantage of this method is to eliminate long headers,
which are usually dedicated for authentication and encapsulation in IPSec.
Therefore an increase in the bandwidth efficiency of the channel is expected.
Larger values of spreading factor show better probability of error and data
integrity in spite of the decrement in the bandwidth of the channel in some cases

This work involves a numerical two-dimensional study on the effect of the
variation in heat transfer coefficient on the performance of annular fins. The
object was to study the effect of varying the heat transfer coefficient on the fin
efficiency. , Fin effectiveness, optimum length and the heat flow for fins of
different cross-section, namely, constant thickness, and trapezoidal assuming a
two dimensional flow inside the fin (radial and axial).
The results were obtained through setting up the governing equations and
solving them by a finite difference technique employing the method of grid
generation and coordinate transformation with the aid of the Gauss-Siedel
method.
A power relationship was used to describe the variation of the heat transfer
coefficient as a function of the fin length.
It was found that the variation in heat transfer coefficient reduces the fin
efficiency, effectiveness, optimum length and the temperature gradient at the root
of the fin and consequently the amount of heat transfer. Further more this
variation led to an increase in the volume required to dissipate a known quantity
of heat as compared to the constant coefficient case It was also found that heat
dissipation increased with the increase in fin length to a certain limit and then
begins to drop

The present investigation considers the effect of steel fibers content and
the combined effect of rice husk ash (RHA) and high range water reducing agent
(HRWRA) on the mechanical properties of the produced matrix. The
experimental results showed the using steel fibers in High-performance concrete
led to a considerable improvement in mechanical properties of concrete. The
results exhibited that the addition of steel fibers to high performance concrete up
to 1% with 6% (HRWRA) and 8% (RHA) as a partial replacement by weight of
cement, increases the compressive strength significantly. Also, the results showed
that the addition of 1.5% steel fibers with 6% (HRWRA) and 8% (RHA) increases
the splitting and flexural strengths significant. At 28 days, the compressive,
splitting and flexural strengths were increased to 11.57%, 63.86%, and 32.93%
more than High performance concrete without steel fibers, respectively

The aim of this investigation is to study the effect of cyclic heating and cooling on
the nonlinear analysis of the reinforced concrete plate at different load conditions
before and after cracking up to failure, and it`s effect on cracking and crushing of
concrete and yielding of steel.Also to calculate the stresses and strains due to the
applied load under the effect of cyclic heating and cooling .
The study also present the mathematical mode for the behavior of the
reinforced concrete plate under cyclic heating with different variables , such as
temperatures , duration of heating, and number of cyclic heating ,The relation
between load and deflection .is presented .
Ressiner`s theory has been used to represent the behavior of thick plate . The Finite
Difference method and Dynamic Relaxation have been used in the solution of the
differential equations ..

A thermodynamic simulation of the power generation gas turbine of the
Mosul gas turbine power station was carried out, and its performance was
observed. The simulation included detailed modeling of the compressor, the
combustion chamber and the turbine based on the physics as well as the common
practice in the field. Comparison of the simulation code results with the field
collected data indicated agreement to within 2% of the compared parameters. The
developed code then used to study the effect of varying the ambient temperature
on the performance of the system. The results showed a decrease of up to 21% in
the power output when the ambient temperature increases from its ISO value of
15 ˚C to 45 ˚C. Comparison between running the system under constant turbine
inlet temperature and constant turbine power output were also conducted

In this investigation, scour in long contractions phenomenon was studied
experimentally. For this purpose, forty laboratory experiments were carried out in
a laboratory channel .Two different river sand sizes of 0.653 mm, 1.040 mm were
used to conduct the experiments with standard deviations of 2.151 and 3.474
respectively. Three different ratios of contraction (B1/B2 =4,3 and 2) and three
different angles of contraction (????=10,15 and 20 degrees) were tested. For each
case, the discharge was changed four times from 10.4 Liter/sec to 47.6 Liter/sec.
Data analysis showed that depth of scour (ds) depends mainly on contraction
ratio (B1/B2), densimetric particle Froude number (Fr????) and geometric standard
deviation (????g). Results of this study showed that there is a strong linear direct
relation between the ratio of the contraction channel width and the depth of scour.
Also a direct relationship was found to describe the effect of discharge on depth of
scour. The results showed that there is no effect of contraction angle on the scour
depth in long contractions. Also, an empirical non-dimensional relationship was
obtained to determine depth ratio (Y2/Y1) in long contraction with correlation
coefficient (R2) = 0.9343.
The results of the present investigation were compared with those of other
investigators showing a good agreement among them.

The study defines the research problem as a reconsideration or
reformulation of a scientific approach to study of the dimensions of rhythm
in Islamic Architecture, depending on rhythmic polyphonic and harmonic
relations in Islamic architecture, as well as on rhythmic in Arabic poetry
and music. To fulfill such as objective a scale for rhythmic dimension is being
laid down. The hypothesis postulates that the aesthetic taste constituting the
dimensions of rhythm in Islamic architecture is itself the force behind Arabic
poetry and music.
So that the characteristics of rhythm in Arabic poetry and music are
defined and clarified going back to their roots as they were founded by Al-
Khalil Bin Ahmad, Al-Farabi, Ekhwan Al-Safa and Al-Armani. A graphic
model for musical and poetic rhythm is devised so as to project the distinctive
features descriptive of the Islamic character and how they may apply to
Islamic architecture in eclectic samples. Periods, beats and paces between
music and poetry on the hand and their architectural counterparts on the
others are being rigorously compared. The results project similarity and
continuity of the expressive aspects in Islamic architecture and Arabic music
and poetry for both reflect the slow, monotonous and infinite nature of the
Muslim mind. The groupings, spaces and modulation in both arts are almost
identical. In both arts the shape and the rhythm are but reflections and an
embodiment of the same cultural tempo and spirit… infinite, colorless and
monotonous.