AL-Rafidain Engineering Journal (AREJ)

In this research, the effect of intermittent feeding on the efficiency of plug flow
activated sludge reactors has been studied. An experimental plant has been constructed
and operated. The plant consists of five identical reactors with the volume of (15) liter
working in parallel under the same operating conditions for each of discharge; sludge
recycling ratio; hydraulic detention time and the organic load. Four of these reactors
had been worked at the intermittent (ON/OFF) feeding mode with the ratios of (1/1),
(2/2), (4/4) and (6/6) for the first, second, third, and fourth reactor respectively, while the
fifth reactor worked at continuous feeding mode. The results showed that, removal
efficiencies for each of ammonia (NH3) and phosphorus (PO4) were close in both of
intermittent and continuous feeding system, while the concentrations of (COD) in
effluent were less in the intermittent reactors. Removal efficiencies of (COD), (NH3), and
(PO4) decreased with reducing the hydraulic retention, whereas nitrate removal
efficiency increased with decreasing of hydraulic retention time.

In this research, an experimental laboratory plant was constructed in order to
evaluate the effect of organic, nitrogenous and phosphorus loads on the removal
efficiency and behavior of duckweed based wastewater stabilization ponds. The results
of the study showed that; covering the oxidation ponds with duckweed improve their
ability to treat higher organic and nitrogenous loads. In addition, covering the oxidation
ponds with duckweed improve their ability to treat higher organic and nitrogenous
loads. Organic and nitrogen load can be increased from (65 kg/ ha. day) to (158 kg/ ha.
day) and from (49 kg. ha. day) to (111 kg/ ha. day) by covering the ponds by duckweed.
On the other hand, the results of research also showed that; increasing nitrogen and
phosphor load leads to decrease removal efficiency of nitrate, nitrite, and increases
removal efficiency of ammonia and phosphate at the same hydraulic retention time.

Human Eye’s detection is one of the significant difficulties in computer vision. Eye
detection utilized in medical applications and computer control system for people with
special needs. In this paper, an efficient algorithm for eye detection is proposed. The
algorithm utilized both luminesce and chrominance components to detect face region
and later with geometrical characteristics to fine detection for pupil center. The
experiments results show that the algorithm is works with 93% of images database used
for testing with small computation time means the algorithm is usable in real time
applications.

The present research deals with preparing (11) samples of composite materials
with metal matrix represented by Aluminum alloy (AA3003)cast and particulate
reinforced by (SiC) having particles volume fractions (5,10,15 Vol.%). The alloy matrix
and composite materials were prepared by stir casting method. Stir casting technique
was used to increase the homogeneity distribution of the particles in alloy matrix.
Average particle sizes of (75,106,150μm) were used. The aim of this study is to
investigate the relationships between ultrasonic attenuation and stirrer speed
,reinforcement contents of SiC reinforced Al-alloy (AA3003)composites .Attenuation
(longitudinal and shear) were measured using the pulse-echo amplitude technique with
normal and angle probes of (45°,60°,and70°) and frequencies of (2 and 4 MHz) . The
results show an increase in volume fraction of particles causes an increase in
attenuation. It was also found, that the ultrasonic attenuation decreases with increasing particle size. It was observed that an increases in stirrer speed, increases in the longitudinal ultrasonic attenuation

The aim of the present research was to study the effect of friction stir welding
parameters such as ( tool rotation and tool transverse speeds) on the joint efficiency of
(6.1 mm) thick weldments of aluminum alloys (7075-T651,2024-T351) , which are used
in aircraft industries and are poorly weldable by fusion welding such as (TIG,MIG and
Laser) welding . Friction stir welding welds were carried out on a traditional milling
machine .Tow tool rotation speeds (900 and 1120 rpm) and three travel speeds (28,40
and 56 mm/min) were selected for the friction stir welding of each alloy. The strength of
the weldments has been investigated using the tensile test with standard specimens at
room temperature. It was observed that the strength and joint efficiency of the
weldments decreased with increasing the tool rotation speed and decreasing travel speed
with improvement in ductility. The best weldments joint efficiency of the (2024-T351)
alloy is (86.41%) and for (7075-T651) is (73.5%) these were obtained at tool rotation
speed (900 rpm) and travel speed (56 mm/min).

The work concerns a laboratory study to investigate the effect of changing the bed
roughness of the main channel on the branching discharge and separation zone formed
in the main channel as a result of discharging flow through a branch channel. The ratio
of main channel roughness to the roughness of the branch channel bed has been changed
between (1.7 – 3.9) for two branching angles (30˚ , 90˚ ) and for different values of main
channel discharge ranged between (7 – 17) L/sec. Laboratory result shows that
branching discharge ratio increases by the increasing the total discharge through the
main channel at roughness ratio less than (2), where\'s the branching discharge decreases
at roughness ratio greater than (2), and stay constant at roughness ratio about (2) for all
discharge passing through the main channel. The result shows that the length of the
separation zone decrease with the increasing in the roughness ratio and total discharge
through the main channel.

In this research, a series of laboratory experiments were carried out to estimate
the removing sediment amount from upstream weirs using bottom outlets. The
experiments were conducted in a laboratory channel (24.6 m) in length and (0.81 m)
wide, in middle of which a weir was fixed. Six discharges were allowed to flow with,
three different sediment concentration for each. The results showed that there is a direct
relation between the area of the holes, Froude number and the amount of sediment
removed, the depth of aggradation near weir location decreases with increasing the
number of holes. A dimensionless equation was created to compute the amount of
sediment removed in terms of area of the holes with a coefficient of determination
(0.895) and the percentage of the highest and lowest difference between the measured
and calculated sediment amount were (15.7, 0.2), respectively.

It is well known that airport elevation with respect to sea level has a considerable effect on the
jet engine thrust. In this study an airplane type (Viper jet, Learjet) with jet engine type (J85-
CJ610 ) was selected and tested at different elevations to show the effect of elevation on the
engine thrust . The study includes theoretical background about turbojet engines, thrust,
atmosphere and the change of some parameters and the relation between the thrust and
altitude. According to the values of engine thrust in this study at different airports in the world
for the selected engine mathematical calculation shows that the thrust decreases as altitude
increases during maintaining the same speed, and as result of that the fuel consumption
decreases also. Mathematical calculations shows that at 11 km a jet engine develops 41% of
the thrust at sea level .So the turbojet engine performance is more efficient at a higher
altitude ،but that requires a longer runway to attain the take-off speed.

A boundary layer analysis is presented for the interaction of non-Darcy mixed
convection with thermal radiation along a non-isothermal vertical flat plate embedded in a
saturated porous medium with thermal dispersion and viscous dissipation. The governing
partial differential equations are transformed into a nonsimilar boundary layer equations.
These equations are solved numerically by a finite difference method. The obtained results are
checked against previously published work on special case of the problem and is found to be
in excellent agreement. A parametric study illustrating the influence of the various physical
parameters on velocity and temperature profiles as well as the local Nusselt number are
conducted. It is obtained that as the value of the power law index, thermal dispersion
parameter, and radiation parameter increases the value of the local Nusselt number increases.
As the value of inertia parameter and viscous dissipation parameter increases the value of the
local Nusselt number decreases.

Fluid flow and heat transfer in a square enclosure diagonally divided by a
conductive thin plate has been numerically investigated. The upper diagonal zone of the
enclosure filled with a saturated porous medium while the subdiagonal zone of the
enclosure filled with air as working fluids. The enclosure was heated partially from
below and cold from upper surface isothermally while the two vertical surface are
insulated. The governing equations are solved using finite difference methods. Results
were obtained for different value of Rayleigh number (103 ≤ Ra ≤ 105) for air and
different value of modified Rayleigh number (100 ≤ Ra* ≤ 500) for porous medium as
well as different dimensionless length of the heated surface (0.2 , 0.4 , 0.5 and 0.6 ). The
results show that the increasing in Rayleigh number in both sides of the enclosure (Ra*
& Ra) causes increasing in the Nusselt number. The percentage increasing is
approximately is (92% at Ra*=100, 1000≤ Ra≤105 and 71% at Ra*=500, 1000≤ Ra≤105
for S=1 ) and ( 90% at Ra*=100 , Ra=104 and 0.2≤S≤0.6 and 80% at Ra*=500 , Ra=104
for 0.2≤S≤0.6 ). The flow become multi-cellular in porous media side also the increasing
in dimensionless length of the heated surface causes increasing in the Nusselt number.
Keywords: natural convection; enclosure; thin plate; two fluids

In the current study, stir and centrifugal casting apparatus have been designed
and constructed for the preparation of cast functionally graded aluminium alloy
(AA4043) based composites containing Silicon Carbide (SiC) reinforcement particles.
Hardness of different cast functionally graded composites (FGCs.) processed with
different rotating speeds have been investigated. Unreinforced base alloy and cast
gravity composite corresponding to the composition of matrix alloy of cast FGCs have
also been cast and characterized for the purpose of comparison. The present study aims
to understand the influence of rotating speed of mould on the reinforcing particles
distribution and hardness of the resulting cast FGCs. It was found that increasing the
processing speed of mould increases the level of distribution of reinforcing particles
from the inner to the outer region. At a given processing speed, hardness increases
significantly with increasing the radial distance for the both top and bottom surfaces
and could be attributed to the segregation of the reinforcing particles at the outer
region.

Ultrasonic metal welding (USMW) has become an efficient technique covers a wide
range of applications of metals. Because of recent light weight of the parts, an efficient
technique like (USMW) has become more applicable, because it considers more
accurate, more minimised welding method than before. Welding horn must be designed
on satisfying many criteria: vibrate longitudinally at operating frequency, isolated the
axial mode from other nearest vibration frequencies, uniformity of vibration amplitude
at the working surface and high amplitude of the operating mode. This research
presents an approach to the design and simulate of the horn configuration which
satisfies these criteria. The simulation and vibration mode shape characterisation of the
horn is discussed and the analysis is accomplished using FE-package (ABAQUS), whilst
the vibration modes are classified using experimental data from 3D laser Doppler
vibrometer measurements. Modal and harmonic analysis are completed successfully to
examine the frequency for the welding tuned horn.

The focus of this paper is to implement a simulator for the Direct Sequence - Code Division
Multiple Access (DS-CDMA) communication system and test its performance against certain
parameters using the VisSim/Comm Version 6.0.03 software. In this paper, the
communication system is considered to consist of a number of users each of which generating
binary data of specified rate and is assigned a unique code. There are many major system
aspects that associated with the design of a spread spectrum system need to be considered.
One of these very important concepts is how to evaluate the performance of the system. The
main evaluation method in the simulator for system evaluation is the measurement of the Bit-
Error-Rate (BER) for various conditions that are essential in the DS-CDMA design and
implementation.

In this paper design of a broadband printed microstrip patch antenna suitable for wireless communication (WLAN/WiMAX) applications is presented. The antenna occupies small size of 50×40×1.6 mm3 . Parallel slots and corner notch are employed in a rectangular patch to achieve broadband characteristics. Two parasitic elements are printed on the bottom surface of the substrate to give good performance. The proposed
antenna has return losses of -32 dB and -30.8 dB at 2.4 GHz and 3.5 GHz respectively.
The bandwidth is 1.768 GHz (from 1.985 GHz - 3.753 GHz) at S11< -10 dB. The
maximum gain is 2.8 dBi for 2.4 GHz and 3.3 dBi for 3.5 GHz. The simulated results are obtained using the software computer simulation technology CST. The designed antenna is printed at a low cost on FR-4 substrate and simple feeding using microstrip line feed.

Optical wavelength converters are very important devices in optical
Dense Wavelength Division Multiplexing (DWDM) Systems. Among numerous
wavelength technologies Four-Wave Mixing (FWM) in optical fibers is attractive
because it offers strict transparency to amplitude, frequency and phase. They also
have the ability to convert multiple wavelengths simultaneously and to invert optical
spectra. Four-wave mixing conversion efficiency depends upon fiber nonlinearity.
The effects of fiber nonlinearity play a decisive role in the design and
performance of modem optical communication links. So it is important to measure
the nonlinear promising technique for determining fiber nonlinearity (γ). This paper investigates a way of estimating fiber nonlinearity through four-wave mixing process