University of Thi-Qar Journal for Engineering Sciences

In this research, the deep drawing dies are designed by using a "computer-aided designed calculating system" to save time and facilitate the design process. Also finite elements method (FEM) is used to simulate the drawing process to select the best die design .A programming language (VISUAL BASIC 6.0) was used to build the computer–aided design system, which was linked to drafting package (AutoCAD) to plot the deep drawing dies. A commercially available finite elements program code (ANSYS) was used to perform the numerical simulation. Finite elements results is compared with experimental results.Though the compression between the experimental and FEM, it has concluded that finite elements method is more accurate than the experimental method in predicting the best die design, and a good match between the two methods was found.

One of the promising techniques in communication systems is the Multiple Input –Multiple Output (MIMO) systems. The aim of these systems is increasing channel capacity, and the main problem in these systems is the required separation distance between antennas which must be greater than or equal to half wavelength. Satisfying this separation distance is difficult especially at low frequencies. In this paper we study the ability to reduce the total separation distance by using polarization diversity. Each two adjacent antenna are replaced by one dual polarized antenna. The obtained results show that the use of polarization diversity will reduce the required separation distance and the performance of the system will be better than that of classical system (without polarization diversity). This improvement is more useful at the system with greater number of antennas. Increasing the correlation between antennas due to the separation angle will reduce the channel capacity. The results also show that increasing the cross polarization discrimination XPD will increase channel capacity at low level of signal to noise ratio (SNR) and decrease it at high level of it if the attenuation for horizontally polarized signal is the same as that for vertically polarized signal (CPF=0), but if (CPF 0) then low values of XPD will improve channel capacity especially at high level of SNR. The results also prove that channel capacity inversely proportional with CPF at rural area (XPD 0), and when XPD=0 (urban area) the channel capacity linearly proportion with CPF at high level of SNR, and inversely proportional with CPF at low level of it.

Predicting the shape function of a pre-tensioned spherical dome is very important for the safety of a dome structures design and performance under cyclic loading. This paper presents a new shape function mathematical model which is proposed for use with three dimensional pre-tensioned spherical dome that should provide for a more accurate stresses. The new model is proposed based on an improved Airy stress function principle; to retain objectivity of the results for three dimensional pre-tensioned spherical dome. This model is adopted in this study for its simplicity and computational efficiency. The objective of this work is to analyze the response and to describe the behavior of pre-tensioning dome structure under loading. The model provides a very powerful tool for the solution of many problems in elasticity; such applications include tensor analysis of the stresses and strains. Correlation between the proposed model with experimental studies results of pre-tensioned specimens are conducted and show a reasonable agreement. The results are drawn as to the applicability of this approach. Stresses within dome surface are constant and the shear stress is zero when subjected to a hoop stress. The maximum stress occurs at the boundary of the dome intersecting the y-axis and is decreased along the boundary of the disc as it nears the x-axis. The maximum compressive stress occurs at the boundary intersecting with the x-axis and decreases as it nears the z-axis along the interfacing boundary.

In this paper an Artificial Neural Networks (ANNs) model is developed to predict the shear strength of concrete beams reinforced with fiber reinforced polymer (FRP) bars. An experimented data set collected from the experimental studies on concrete beams reinforce with FRP bars are used in the artificial neural network. They are arranged in a format of six input parameters including the width and depth of beams, compressive strength of concrete, modulus of elasticity, reinforcement ratio of FRP and the shear span to depth ratio and one output parameter which is shear strength. A parametric study is carried out using ANN to study the influence of each parameter on the shear strength of concrete beams reinforced with fiber reinforced polymers; the results showed that the shear strength increases with increasing all parameters used in ANN model except the shear span to depth ratio. In this case, as the shear span to depth ratio decreases, the shear strength increase. The results of this study indicate that the ANN provides good prediction as compared to the experimental data and the empirical equations.

In this paper, 6063-T4 Al-alloy sheets with dimensions(6x90x200) mm were joined via friction stir welding (FSW). Tow sheets were but welded with square mating edges. The rotating welding tool made of tool steel heat-treated to HRC 60.The temperature distribution had been investigated experimentally with constant revolution speed and constant linear speed. A digital reader of twelve channels was used to read and record the temperature with time at each channel as an excel table. Nine K-type thermocouples were positioned along the weld length. The mechanical properties were evaluated (such as tensile strength ,microhardness, and microstructure tests) at room temperature in several positions along the length of the joint. The results show that the max. temperature was conducted at the end of the weld to be 375C ̊. The relationships between the peak temperature and the time, distance from start, microhardness, tensile strength, and microstructure were discussed. The hardness of the stirred zone was more than the base metal hardness due to refinement of grains by friction stir process. The strength and hardness of the FSW were as min. at the end of the weld due to increasing in heat input to the joint at this region which lead to grain growth at the microstructure of last region.

In this work, Genetic Algorithm (GA) models have been built to design a microstrip antennas in various forms such as rectangular, equilateral triangle and hexagon patch antenna. The design problem can be defined to obtain the resonant frequency for a given the thickness of dielectric material and dimension of geometrical structure. This approach has a few advantages: giving a clearer and simpler representation of the problem, simplifying chromosome construction, and totally avoiding binary encoding and decoding to simplify software programming. The antenna designed using GA is implemented using MATLAB program and the analysis of antenna is implemented using Microwave Office software 7.1 produced in 2007.

The analysis of voltage series multistage feedback amplifier network is achieved by evaluating the nodal admittance matrix of the equivalent circuit representing the replacing of each transistor in a stage by its high frequency small-signal model and the performing of the high order voltage transfer function of the system. The main reasons of treating such a wide-band amplifier network are of its stabilized voltage gain and its ability to amplify the pulses occurring in a television signal. The frequency response of the system is calculated and confirmed. System dynamics and variation of input signal are obtained by calculating the response of a continuous time system. The discrete-time equivalent to the analogue system allows the system designer to choose an appropriate pulse transfer function to investigate the performance of the system suitable for a given specifications and requirements. The software powerful MAT-LAB version 7.2 techniques is used for treating the single expression transfer function obtained by assigning numerical values and the response of the system in time and frequency domain.

Estimation of quantity of flow through earth dams by using finite elements method mainly depends on the magnitudes of permeability for the earth dam. The permeability of soil medium may be included in the solution as constant permeability or non homogeneous, anisotropic or may be distributed as random field. Simulation of properties of soil by using random fields’ generators has great interest nowadays. This paper includes studying of the effect of anisotropy of scale of fluctuation of the permeability through the stochastic finite elements analysis for case of flow through earth dam. Permeability has been simulated by random field and mapped into finite element methods according to the most recent studies. The results have shown that (1) quantity of seepage through stochastic earth dam is always less than that calculated for deterministic state. (2) As horizontal to vertical scale of fluctuation (anisotropy of scale of fluctuation) increases, quantity of seepage increases but it still less than that for deterministic state. The seepage elevation is also reduced at random field state compared to deterministic solution.

This paper is an attempt to study the case that a new type of curves through rolling (not sliding) of the geometric shape on the path to, a specific research was to study the composition of a special case of rounded shapes-circle by making them in contact permanently with the surface of rounded surface of the R-Cone based as a case study especially to search for study a current research, the paper continues with the new curves resulting from the fixed point on the circumference of a circle which was plotter curves of"cycloids" and its derivatives, which uses it in this study purpose to renew the designs of bulbar form domes, especially in Islamic architecture dome in shapes in past and present .The paper aimed to develop these cases, as a standard curves over the study status of the three coordinates not in two as previously studied by the extraction of a new type of curve which can generate for its ratio a new architecture domes or roofs of three-dimensional curves in new formations provided by the researcher as models of past forms that was researched in depth.The paper is focused for the first time the formation of this type of curves within the three-dimensional space by using the cone surface-based path of the movement of a circular situation of complete contact with the surface of the cone existing at any moment of his side induced in this research to be adopted to configure circular shape ,the status of the inter section of ball perpendicular (i.e. the case of the search) and tangent to complete each point with three-dimensional surface as the surface of the cone has been studied from a specified paths with the base of the cone, to consist of the intersection curve is closed symmetrical circular where all the points surrounding in contact permanently with surface of the cone-based,,which makes a circle plotter in the special case where flattens all points around the surface of the cone from the two sides parallel with the base (horizontal), and axis inclination surface of the cone (angle-slop surface of the cone with the line of the horizon of its base=(u), which gives the distinctive shape of the area intersection in the Departments of the plotter flat,perfectly with the points of angle-slop surface of the cone of any situation of complete contact with the points in which case that have been studied in 3d-space, relying on the case of the intersection of a sphere or cylinder (the case outside the field of research), the spiral new curve based is the shop geometric closed to all points of intersection cylinder or ball and perpendicular with them so there is only one point at the base of the cone.