University of Thi-Qar Journal for Engineering Sciences

In this paper an Artificial Neural Networks (ANNS) model is designed to predict the Total Dissolved Solids (TDS) concentration in marsh water. A previous data set are selected from previous studies which done on analysis of marsh water quality, these data are arranged in a format of five input parameters to feed forword back-propagation including the acidity (pH), calcium concentration (C), Magnesium Concentration (M) , Chloride Concentration (Cl) and Sulphate Concentration (S), and one output parameter as Total Dissolved Solids concentration. Artificial Neural Network used to study the effect of each parameter on TDS concentration in marsh water. Several structures of ANNs model is examined with different transfer functions, activation functions, number of neurons in each hidden layer and number of hidden layers. Results show that the two hidden layer network with transfer function (trainscg) with (12 & 10) neurons in the first and second hidden layer respectively and (tansig-tansig-purelin) gives the best performance (Mean Square Error: 3.05e-5) network for this prediction.

Laboratory investigations were performed in order to assess the effectiveness of three types of inhibitors, calcium nitrite, ethanolamine and Sika ferro gard 901(commercial inhibitor) with 1%, 2% and 3%concentration by weight of cement for each inhibitor to retarding corrosion of steel embedded in concrete. Concrete specimens were used to assess the effects of corrosion inhibitors on the compressive and tensile strength of concrete and corrosion of reinforcement.Some of the specimens were subjected to wetting and drying cycles and reinforcement corrosion was evaluated by measuring corrosion potentials and corrosion current density. Other concrete specimens were immersed in the salt (Cl-+So3-2) solution and reinforcement corrosion was accelerated by impressing an anodic potential of +12 V from a DC power supply and measuring the time-to-cracking of the concrete specimens.The results indicated that the concrete specimens incorporated corrosion inhibitors of calcium nitrite and Sika ferro gard 901 did not adversely affect the compressive and tensile strength of concrete. Furthermore, the time-to-cracking in specimens contains those two inhibitors (calcium nitrite and Sika ferro gard 901) were higher. Two percent of calcium nitrite followed by three percent of Sika ferro gard 901 were efficient in delaying the initiation of reinforcement corrosion and reducing the rate of reinforcement corrosion current density in the concrete specimens, while all the percentages of ethanolamine corrosion inhibitor were ineffective to delay corrosion of the rebar under the conditions of the study and it's adversely affect the strength.

This paper presents an experimental investigation on the effect of silica fume on the mechanical properties of concrete obtained by replacing 50% of weight of stone aggregate by crushed clay-brick. The only variable considered in this study was the dosage of silica which it is a percent of cement weight, the percent values of replacement silica fume are (0%, 2%, 4%, 6%, and 8%) of cement weight. The comparative study is focus on the effect of the silica fume on this type of concrete not the effect of replacement of crushed brick. The added silica fume has active effect on the strength of crushed brick concrete. The effect of using silica fume on compressive strength is different for the different replacement of silica fume and it is more active for the 2% replacement at 7 days age, while the replacement that yield best enhancement at 28 days is 4%. The compressive strength for 28 days age is about 27.5 MPa,29.5 MPa, 38.5 MPa,31.4MPa, and 10MPa,for (0%, 2%,4%,6%, and8%) of replacement silica percent .Further more the best increasing in tensile strength is at 2%while there is a small gradually increasing in gain in modulus of rupture with using silica fume until 6%, which beyond the least value it starts to drop.The high level which is observed in this study beyond 6% reduces the gain in strength of compressive at 28 days and it gets a compressive strength less than the control value at 7 days. Furthermore it gets a reduction in tensile strength and modulus of rupturein at 28 days.

The cyclostationary based spectrum sensing algorithm is especially suitable for detection of orthogonal frequency division multiplexing (OFDM) signals that exhibit strong periodic correlation due to insertion of cyclic prefix between OFDM blocks.Normally, the cyclic prefix is used to remove the Intersymbol interference (ISI) and intercarrier interference (ICI) of the OFDM signal and so it eliminates a need for complex equalizer. In this paper, simulation results demonstrate the normalized spectrum correlation function of the primary OFDM signal used in cognitive radio systems with different values of cyclic frequency. Two techniques are assumed to be used as PAPR reduction of OFDM transmitted signal. The results show that only one of them has no apparent effect on the correlation performance of the cyclostationary detector. Finally, it is found that a reduction of 30% in the implementation complexity can be taken by suitable choice of detector cyclic frequency.

In this work the present a theoretical study for the free vibration of cylindrical, conical and helical springs. Circular cross sections, and non-circular cross section, namely elliptical, are considered as well for the investigating of the frequency characteristics of the springs. The equations of motion are derived mathematically for springs with different geometries. The mode shapes are numerically implemented by using COMSOL 4.2 software package for three dimensional solid elements. The mode shapes configurations are determined by applying different force loads and boundary conditions for different number of spring turns. The results show that increasing the number of turns leads to decrease the spring stiffness and vice versa. Also decreasing turn number is a good strategy to distinguish between different mode shapes. Springs stiffness is directly proportional to coil diameter. It is also shown that the configuration of cylindrical-elliptical spring is prone to the applied force where the stiffness is lower among all other spring types with the same number of turns.

A simply supported beam is used to calculate the critical buckling load. A common beam sections with constant cross sectional area are used to analyze the results using ANSYS11 program which gives a good results as comparing with the theoretical equation. The critical buckling load depends on the shape and dimensions of beam section which has constant cross sectional area. It observed that the critical buckling load is higher with a wide range of width for thinner hollow rectangular-section than the thicker section and lower for ( I, T & L-sections). Changing the width or thickness for U & Z-sections gave a small effect on the critical buckling load. Increasing the thickness of hollow circle beam section gives a decreasing in the critical buckling load. The last beam section gives a higher critical buckling load as comparing with solid circle section of the same cross sectional area. The same phenomenon is found for hollow rectangular-section as comparing with the solid section.

The film cooling effectiveness and local heat transfer coefficient for coolant jet holes direction (orientation angle), have been investigated. Experimental investigations were done on a flat plate by using a single test transient IR thermograph technique.Evaluation of the cooling performance is obtained by estimated both film cooling effectiveness and heat flux ratios. Threemodelsof coolant jet holes are investigated,each model consists of two rows of holes arranged in a staggered way with different orientation angles. Model (1) downstream row with acute angle and the upstream row with obtuse angle; model (2) both rows with obtuse angles, while model (3) both rows with acute angles.The holes diameter is 4mm, the longitudinal distance between the upstream and downstream rows (X/D) is 4D, and the span distance between two neighboring holes (S/D) is 3D. Three blowing ratios of (BR= 0.5, 1.0, and 1.5) were used in the investigation program.In order to predict the flow behavior numerically for the cases under investigation CFDcode is introduced.The numerical investigation shows two large vortices large counter rotating vortex pair and horseshoe vortices ,both vortices have major effects on cooling performance.The experimental results showed that the film cooling effectiveness increases as blowing ratio increases for models (1 and 2), while decreases for model(3), and model (1) provide better performance than the others at high blowing ratios.

The aim of this work is to study the possibility of joining the Aluminum alloy (2024T3) by the Manual Metal Arc Welding(MMAW) using the (E4043) electrode, and studying the microscopic structure in the joint area.A )V-Butt joint) were prepared before and after the heat treatment then thermally treated after welding (Solution treating and aging). It was clear that the molten zone (Fusion Zone) will be containing epitaxial growth, also it contains the phase (Al2Cu) what it called copper-rich phase, that was in case of not using heat treatment, but when using heat treatment before welding, the copper-rich phase will be less and the heat treatment after welding will result in distortion of that phase.

The purpose of this paper is to be familiarize with the microscopic structure of the welding specimen, before and after heat treatment in which the pure copper ( OFHC ) has been welded to the low carbon steel ( ASTMA36 ) by the method of fusion welding ( Arc Welding ) using covered welding electrode (SMAW) .A 12mm thick plates of the two metals were used.The plate have been prepared (Single Butt Joint ) where the dissimilar plates copper to steel were welded using ( Ecusu8 ) electrodes . The heat treatment has been carried out to the specimen at 600Co,700Co then cooled down in the oven . The microscopic test for the welded specimen has been carried out before and after the heat treatment .Before heat treatment It was clear that there exist a separating limit from the steel side with zigzag indicating that interaction was happened giving a ( Non-epitaxial ) structure with opening windows accompanied by diffusion of masses from the base metal inside the added metal ,while after heat treatment, it is found that more zigzag and opening cracks in the steel side filled with the added metal by the process of ( Brazing ) and excess clearness of diffusion process with diffused metal taking a tree shapes , While from the copper side, it showed ( Epitaxial Growth ) No existence to any cracks was noticed , but there was a granulated growth especially when heated up to 700Co