Al-Qadisiyah Journal for Engineering Sciences

The flashover phenomena constitutes as one of the important high voltage insulators problems which may cause costly outage for power system. pollution is the most essential element in this phenomena at system working voltage.
In this paper, a research program is executed to investigate the pollution effect on flashover phenomena for south – west Iraqi (132kV) grid insulators routing through desert areas . In order to carryout the investigation, four typical sites have been selected, for each site one insulators string that suffering from deposition of contaminated substances has been select and brought to high voltage laboratory for checking flashover voltage values. From the present work it can be concluded that to a large extent, insulators show a significant changes in the electrical performance as exposed to desert environmental conditions like high temperature, humidity and sandstorms . A significant reduction in flashover voltage is observed as the pollution amount increases, these results have been compared with the new insulators

In this research a study effect of absorber surface shape for solar air collector
(Flat V-Corrugated, Sinusoidal Wave-Corrugated, Rectangular-Corrugated)(1 1 0.1m) titled to the horizontal by an angle(30o) on forced heat transfer and skin friction coefficient by Fluent Numerical Program at constant solar heat flax (530W/m2) with Reynold’s number (5000≤Re≤8000).
The government equation (mass, momentum and energy) are using Finite Volume by (Fluent 6.3) software for considering steady state, two dimensional and turbulent flow. The results show that the different between inlet and outlet air temperature is(13.65oC) and best heat transfer coefficient enhancement is(63%) for (V-Corrugated plate) compared with the flat plate at (Re=8000), Also the results show that the maximum skin friction coefficient is occured at (V-Corrugated) Cf=0.22 at (Re=8000).

The aim of this study is to improve the operation and performance Water Treatment Plant by
improving circular sedimentation tanks of Al-Gazaer Water Treatment Plants in Al-Dewanyia city
in Iraq which have been identified as operating poorly. A developed model of the circular settling
tanks for the Water Treatment Plant of Al-Gazaer was prepared using Computational Fluid
Dynamics (CFD). A three dimensional, multi-phase simulations with solids transport and removal
included is used, and reflected the state of the art in settling modeling. Computational Fluid
Dynamics simulations are employed to assess the effect of adding a vertical baffle at the feed
section of a full-scale sedimentation tank for the improvement of solids settling in potable water
treatment. Special attention was paid to the inlet baffle in the model setup. Apparently, there is a
good agreement between measured and predicted values. Results show, the overall solids removal
efficiency increased when using the baffle from 50 to 90.5% leading to a reduction of the effluent
solids concentration of approximately 86%.

In order to restore the strength of failed reinforced concrete columns, the cracked shell was replaced
by new materials of repair: plain concrete, fiber-reinforcement concrete and cement- mortar
alternatively. Three groups of reinforced concrete squared tied columns were tested concentrically.
The columns were short-columns reinforced with 2% longitudinal steel reinforcement ratio.
Behavior of repaired columns have been presented by measuring concrete surface strain with axial
load up to cracking load.
Effects of both concrete compressive strength of materials of repair and preloading on the restoring
column strength have been established. Test results have ,also, shown that the strength of failed
column can be restored by replacing the cracked shell with new shell having high compressive
strength. the strength of columns repaired by these materials can reach up to 136% of their original
strength depending on both the compressive strength and the condition of preloading.
Furthermore ,axial strength of repaired columns was derived by modifying the equation given by
ACI-Code for calculating design axial load strength of reinforced concrete column.

The main objective of this investigation is to study the effect of oil (kerosene, gas oil and crude
oil) on the compressive and tensile strengths of high performance concrete and to compare the
behavior with that of normal strength concrete. Four exposure periods were used for each specimen
and for each liquid, 30, 60, 90 and 120 days after 28 days water curing. To provide a basis for
comparison, reference specimens were cast and exposed to water for a
respective time of test.
The test results showed that the loss in mechanical properties (compressive and splitting tensile
strengths) resulting from exposure to oil was relatively smaller for high performance concrete
(HPC) compared with normal strength concrete (NSC). The difference was about 10 percent.
Furthermore, the reduction in compressive and splitting tensile strengths of NSC and HPC
increased with decrease in viscosity of oil in the entire period of exposure.

One dimensional advection-diffusion equation is numerically solved by using finite difference
method that may be simulated to describe transport of a pollutant in open channel. A generalized
Newton Raphson procedure is used to solve the system of equations. The validity of the numerical
model is obtained by comparing the experimental results and numerical solution under proper initial
and boundary conditions. The spatial variation of concentrations is also compared with the results
of experimental measurement. The application of the model revealed good agreement and
convincing between experimental and numerical results.

The mechanical properties of araldite matrix composites incorporated with hybrid carbon - kevlar fibers were evaluated . There are indications that the incorporation of both fibers into a single matrix which is araldite resin will stabilize mechanical properties and lowering manufacturing costs . In this research the impact strength , tensile strength ,flexural strength ,and hardness were studied for composite material reinforced with hybrid fibers as a woven roving (°90-°0) with density (225g/cm3) and (285g/cm3) for carbon and kevlar fibers respectively . These fibers were mixed with araldite resin in different reinforcement percentage (20%,40%,60%) and the effect on the above mechanical properties were studied , where we see Improves in these mechanical properties after reinforcement by fibers The value of mechanical properties will increase with increasing percentage of reinforcement .

This research uesd to compute the flow field variables of natural convection air flow based on
finite difference computational fluid dynamic methods. The problem considered deals with a two-
dimensional internal, laminer , isothermal flow over a vertical rectangular duct. In this work,
governing equations were solved using finite different forward explicit technique. The flow
characterstics are evaluated for Prandtl number at 0.7 and dimensionless inlet velocity equals to
0.005. The results explain that the heat transfer rate is a strong function of flow velocity also the
hydrodynamic properties such as pressure, temperature and velocity are increased when the flow
moves upward the duct.The results showed a good agreement with other published results.

In this research , the dynamics of the wind energy conversion system of a small wind turbine
is studied. The aerodynamic forces are estimated at any incoming wind speeds for turbine blade
which is known as airfoil section (NACA4412). The scheme is simulated by a program of
Fortran90 and results are presented . The torque and the productive power are estimated from this
program at each incoming wind speed, these results are compared with the extraction power from
Betz theorem . Also, the number of revs of the small turbine are estimated at each incoming wind
speed. From this model, we can specified the determinism of tip speed ratio and wind speed are a
more suiting . Because wind speed increase over the suitable value, causes increasing of vortices of
the hub and the tip and other losses .
The proposed model can further investigate for analysis, design and performance evaluation of
remote and off-grid wind energy conversion systems in hybrid applications.

The Field Programmable Gate Array (FPGA) approach is one of the most recent category, which
takes the place in the implementation of most Digital Signal Processing (DSP) applications. It had
proved its capability to handle such problems and supports all the necessary needs like scalability,
speed, size, cost, and efficiency.
In this paper a new circuit design is implemented for speech scrambling with an implemented
example using FPGA is provided. In this implementation the speech coefficients are evaluated on
both the scrambled and the De-scrambled sides.
This implementation was achieved using an FPGA Kit after building the logical circuits on the
specified kit that uses the Spartan-XL electronic library type implemented using the ISE-4.1
software which is one of the latest versions of the Xilinx Foundation Series 2.1I software.

Stream cipher is one of important branch of cryptography that can be implemented by using
software and hard ware components .this system is divided into two types :
1.linear stream cipher system .
2. Non- linear stream cipher system .
In this work, we deal with the two type of stream cipher system , the first type doesn’t have top
secret degree due to weakness of the linear complexity for the sequence generated from Linear
Feedback Shift Register (LFSR) .There are many algorithm ms that are designed by using the
process of non- linear combination for more than one linear shift register ,one of these algorithm
,that is called adder algorithm ,is used to generate a key sequence for encryption and deciphering
process .The data in form of speech or waveform have been recorded by using computer
microphone .these digital speech were encrypted .the encrypted speech has been sent via RS232
standard interface at a bit rate 19.6 kbps to another computer ,and then will be decrypted .
The encrypted data were transmitted through the optical system .a multi mode optical fiber is used
as a channel and PIN photo diode is used as an optical detector.

The capture and escape time constants are a small and finite capture and escape time of the
carriers between the separate confinement (SCH) region and the quantum well. These time
constants are in picosecond time scale and are important in the direct modulated quantum well
lasers which these small time constants are effected on the gain compression factor where the gain
compression factor is effected on the differential gain . The differential gain isone from the
important factors for the enhanced performance for the direct modulated quantum well lasers which
the output this lasers are depended on it.