University of Thi-Qar Journal for Engineering Sciences

The aim of this paper is to improve thermal performance of a counter flow microchannel heat exchanger (CFMCHE) by using microencapsulated phase change material slurry (MEPCM suspension) as a cooling fluid instead of pure fluid. The MEPCM suspension used in this paper consists of microcapsules constructed from n-octadecane as a phase change material (PCM) and the shell material is Polymethylmethacrylat, these capsules are suspended in water in a concentration of (0 – 20) %. From the results, using of MEPCM suspensions as a cooling fluid leads to modify thermal performance of a CFMCHE by increasing its effectiveness but it also leads to increase the pressure drop. From heat transfer (thermal performance) point of view it is better to use this type of fluid to increase cooling efficiency of a CFMCHE, but due to extra increase in pressure drop it leads to reduce the overall performance compared with pure fluids. Therefore its application depends on the conditions at which this heat exchanger is used.

The use of central receiver (or Power-Tower type) of heliostat as concentrators on absorber plate (target), used practically as boiler, proved convenient and favorable both in performance and cost. In this work a model of solar thermal power plant field was designed, analyzed, fabricated and studied in details using central receiver type. The model is constructed on flat, smooth, rigid and strong plywood board used as a base for the model fixed on an inclined base at an angle of 20º. The field area was set on quarter circle to arrange the heliostats; and at the centre of a circle the tower is carrying a copper plate target was fixed. Two sets of heliostat field [(540) and (1097) mirror] were tested experimentally. Experimental data and results obtained showed that the use of solar energy in power generation is a very promising application .The temperatures achieved for target were in the range of steam boilers operation temperatures (268- 578)C ̊. The number of heliostat has a major effect on the target temperature; the power concentration factor and the overall efficiency of the system.

Orthogonal frequency division multiplexing (OFDM) is a form of multi-carrier modulation technique with high spectral efficiency, robustness to channel fading and immunity to impulse interference. Recently, it is being used for both wireless and wired high data rate communications. Despite of its many advantages, OFDM has a main drawback, namely high Peak to Average Power Ratio (PAPR).High PAPR causes saturation in power amplifiers, and leads to inter-modulation products among the sub carriers and disturbing out of band energy. Therefore, it is desirable to reduce the PAPR. In this paper we used Inverse Discrete Cosine Transform (IDCT) technique in the transmitter side to reduce PAPR problem. The use of this technique in the output of Inverse Fast Fourier Transform (IFFT) stage gave good results toward reduction PAPR. The receiver side includes Discrete Cosine Transform to achieve correct detection. Computer simulation tests have been applied on IEEE 802.11a standard as OFDM practical system with the proposed method .The results exhibit the ability of such techniques to reduce the PAPR with no major effect on the system performance as compared with the conventional OFDM technique

In this paper a scheme is proposed to improve the Bit Error Rate (BER) performance for Discrete Multi-Tone (DMT) system in wireless channel. The conventional DMT system is based on Fast Fourier Transform (FFT). The proposed system is based on Hybrid Multi-Wavelet Transform (HMWT). The HMWT is mixed between FFT and Multi-Wavelet Transform (MWT). The Inter-Carrier Interference (ICI) in DMT system due to Doppler spread is reduced by using Polynomial Cancellation Coding (PCC). Simulation results are done in three different types of channels: Additive White Gaussian Noise (AWGN) channel, flat fading channel and selective fading channel. The results show that the PCC-DMT system based on HMWT achieves better performance than the PCC-DMT system based on FFT and the PCC-DMT system based on MWT in all channels types.

n this study, the kinematic equations are derived to describe the angles, velocities, and accelerations of the leg of bike rider when changing the height and angle of seat tube. These equations are useful to get the optimum seat position, (in separated study), for best performance and efficiency. The pedaling motion model was simulated as four-bar mechanism (the foot was not considered), and by using polar form of complex number notation to get the kinematic equations. These equations are agreed with MATLAB/Simulink/SimMechanics/Four-Bar Model, as well as, the graphical method. The derived equations (kinematic equations) can describe the crossed and open four-bar mechanism.

In this study, a numerical investigation of heat transfer and fluid flow a cross circular and elliptical tube bank has been made then comparisons made between these two types. The study focus on the effect of Reynolds number and ellipse eccentricity on the Nusselt number and pressure drop through the tube bank for two arrangements (in-line and staggered). The results are reported for air and for Reynolds number range of 20≤Re≤500. The results of the study shows that Nusselt number increased as Reynolds number increased for all cases. The values of Nusselt number for elliptical tube are higher than for circular tube for Reynolds number range of 100≤Re≤500.The pressure drop for the two arrangements increased as the Reynolds number increases. The elliptical tube array has batter thermal performance and lower pressure drop than circular tube array .

This paper presents a novel method for identification of the Weiner and Hammerstein models and the model's parameters by the application of genetic algorithm optimization method and an iterative search through a lock up Table. The coefficient values of both linear and nonlinear parts are estimated by the GA while the type of nonlinearity and degree of delay of the linear part are determined by the iterative search through the lock up Table. The simulation results show the effectiveness and ability of the proposed algorithm for identification and realization of the Weiner and Hammerstein models that describe the real system.

Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) offer many advantages due to their low noise and high associated gain at microwave frequencies. Therefore, they are well suited to the amplifier requirements of broadband light-wave receivers, through providing a high dynamic range and wide bandwidths. In this work, the performance of integrated optical receiver consisting of PIN-photodiode and MOSFET-based transimpedence type amplifier is analyzed. The effect of various device parameters on receiver performance is investigated in details. The simulation results show that the sensitivity (Psen) of an optical receiver is approximately constant if it is based on well-designed MOSFET.

Occasionally, the state organizations and many private companies in Thi Qar Governorate request some spare parts that must be manufactured locally because they are unavailable in Iraq .Since these parts have complex shapes, and the Engineering College Workshop's machines are unable to cut them, thus it was necessary to develop the existing Oxy Estelline cutting machine to control its motion by computer. The main idea of this research is to make the machine cutter movement in two dimensions according to a path drawn by (Autodesk Land Desktop) program which necessitates addition of an electric circuit (Interface) between the machine and the computer to convert the path into two dimensional motions .This requires replacement of some unnecessary parts from the machine by others. The major added parts are:1.Servo Motors.2.Controller.3.Drive.4.Power Supply.5.Power Cables.6.Data Cables.7.Lead Screws.8.Brackets.9.Bases to fix the motors and brackets. After welding processes of the bases and mounting the motors, brackets, and electric circuits, the machine was tested by fixing a pen instead of the cutter and drawing many graphs such as circle, rose, gear, and gasket on a paper .The drawings are completed successfully and accurately, then the machine was used to cut rose and gasket by the flame .Satisfactory results are obtained .Now, the user can use the machine easily to cut any complex shape.

The following study is considered as a part of the requests of reconstructing a strategy to develop Al-Hamza city (urban center)and to put to a plan to renew the basic design of the city center, this will participate in establishing a primary data base beside the urban planning to assist for the base imagination about the capabilities and limitations of the development in order to establish a strategy of development of Al-Hamza city in the hands of the wanted basic planning . This study depended on different references, historical academic and statistics in addition to number of field-visits to the region and listening to the points of views of the local peoples and establishing interviews to the local habitants of the area especially those heads of the tribes and the city- center gentlemen in order to add the documentary and scientific interests and to discover some of the service needs that can be depended to start the stage of preparing the requests of plan of the development and reconstruction of renewing urban planning of land uses. In this level of study it has been worked to discover the planning signs via specifying the capabilities and chances on which the city-planning strategy can be built in addition to prepare substitutes for the new basic design ,of the most important results are studying the population statistics and its expected population numbers under the balance between the people on our side and what the city needs of the services according to the present and expected offer and the available need and defect in the services .

The marshes are very important areas in iraq , in spite of that ,the geotechnical studies are still very limited . Two locations which have been selected for study in this research ; al fohod and al hammar region . The engineering properties of the soil have been studied and focused on the collapse properties and strength of soil , the tests performed on the soaked soil that the water reflowing away from it during the summer time, we expect these regions to develop in the construction and tourism sides.The results reveal that the soil of the two regions contains high percentage of salts ,although the soil soaked with water along the winter. also, it was found that the soil is soft and it is collapse soil and the degree of collapse ranging from severe to moderate.