Tikrit Journal of Engineering Sciences

The aim of this paper is to analyze the influence of adding serial inductance in AC side of the 3ph -6 pulse bridge rectifier on the reduction of harmonic distortion rate. A simulated model with serial inductance was analyzed. The 3-phase 6-pulse diode bridge rectifier was chosen because it corresponds to the operation of the 6-pulse thyristor bridge rectifier at maximum load (while keeping the angle α = 0). Both the total harmonic distortion (THDi) and the power factor (PF) for the circuit have been measured. The results obtained of the THDi has been recorded for four values of serial inductance and results was compared with the (IEEE 519-1992) standard. Comparison results indicates that for values of inductive reactance (Xi) up to 67% cause a reduction of THDi which is above the standard values, while for (Xi) more than 67% cause a reduction in THDi within the acceptable standard level. Analyzing of results prove that the adding of serial inductance at the AC side leads to good reduction in harmonic distortion rate, but with some reduction in power factor value, which results in some energy losses.

Due to its attractive features, the utilization of fiber optics as a transmission medium with various applications is increased rapidly. In despite, when signals are transmitted with high data rates through ultra-long haul distances of single-mode fiber (SMF), which is usually used at wide area networks (WANs), the nonlinear dispersion of signals is raised. This phenomenon leads digital pulses to interfere with the adjacent pulses. In this paper, an optical orthogonal frequency division multiplexing based T-transform (T-OOFDM) system is proposed to mitigate the effect of fiber dispersion significantly and reduce the peak-to-average power ratio (PAPR) of the transmitted signal when compared with conventional optical OFDM (OOFDM) system. Simulations results confirmed by the analytical analysis demonstrated that the detrimental effects arising from fiber channel dispersion on the subcarrier orthogonality of the transmitted signals can be efficiently minimized by using T-OOFDM system. Moreover, the peak of the transmitted signal will be considerably reduced whilst preserving the average power of signals.

Huffman coding is very important technique in information theory. Compression technique is the technology for reducing the amount of data used to denote any content without decreasing the quality. Furthermore, Clock gating is an effective method for decreasing power consumption in a sequence design. It saves more power by dividing the main clock and distributing the clock to the logic blocks only when there is a need for those blocks to be activated. This paper aim to design Huffman coding and decoding process with proposing a novel method of clock gating to achieve low power consumption. Huffman design is executed by expending ASIC design procedures. With the purpose of executing the encoder and decoder structures, 130 nm typical cell technology libraries are utilized for ASIC implementation. The simulations are completed by utilizing Modelsim tool. The design of coding and decoding process has been made using Verilog HDL language. Moreover, it carried out using Quartus II 14.1 Web Edition (64-Bit).

The design and analysis of the power distribution and supply system on a chip is a complex issue. The ideal network consists of millions of transistors, which act as energy consumers. This large number makes them complex in terms of design and analysis. Building typical algorithms with logical gates and working automatically is the best way to solve the problem of power grid complexity. In this research, it was proposed to design a new model for consumers on the basis of effective resistance. passive elements were used only in this model and based on the actual resistance and capacity of the logical gates. Consumers and power grids can adopt computational physics methods and consider each group of consumers in each subnet as within total circuits. Emphasis is placed on the interaction between consumers for energy distribution network and energy supply. Using Matlab/ Simulink, accuracy of the system is verified to determine the technical issues related to the operation of the system for power networks.

The use of solar cells as photodetectors in Optical Wireless Communications (OWC) systems, is acquiring an increasing attention. This is due to the fact that a solar cell can detect an incident optical signal without the need to be biased by an external dc source, unlike traditional photodetectors. Basically, solar cells are designed to be used in solar energy harvesting systems. However, the solar cells are used during the day time and they remain idle at night. Then, they can be used in other applications, such as optical signal detection during night hours. Moreover, the efficiency of solar systems and solar receivers can be maximized by using dual axis light source tracking, to keep the cell orientation at the direction that results in the maximum electrical output. Therefore, in this paper, a solar cell positioning algorithm is proposed to track the maximum power point of both of the sun at day time and the optical communication signal at night. The proposed system can automatically distinguish between its two operation modes and then provides the necessary control. The proposed system is implemented and tested under realistic outdoor environment. It showed an accurate detection of the operation situation and also an accurate and smooth positioning during the specific operation mode. The measurement of the generated and consumed power by the designed system has emphasized it feasibility.

In this investigation the effect of large web opening on the on the behaver of beams made by normal concrete (NC) and reactive powder concrete (RPC) have been studied. The experimental work consists of casting and testing in flexure 12 rectangular simply supported reinforced concrete beams. The main parameters of this test are opening locations and normal concrete and RPC location with is the section. The ultimate loads, cracking loads, load -deflection behavior, skew of the openings (deflection at the two opposite corners of openings) and ductility were discussed. These results showed that increase ultimate loads (Pu) and stiffness by increase RPC layers. The using RPC layers increase ultimate load about (1-30) %. Using RPC in compression fiber is found to be more effective than using RPC in tension fiber. The cracking load of hybrid beam with one layer of RPC in compression fiber (having one opening) higher than NC beams by 48.5%. The ultimate strength was decreases with increases opening about (4-21)%, thus indicating that the stiffness decreases accordingly. Hybrid beams with RPC in tension fiber failed with less crack than those for hybrid beams with RPC in compression fiber at the same number of openings. The skew at opening of flexural zone show greater values than the skew at opening in shear zone for each beam until failure. The increase in the number of openings leads to increase in the ductility because it reduces the strength of beams.

In this study, the strong and weak forms of Darcy flow equation has been derived. The final obtained equation is Laplace partial differential equation. For total head evaluation, Laplace equation is solved using exact solution depending on Fourier series and numerical solution depending on finite element method. A computer program has been developed in MATLAB program to solve the Laplace equation using both exact and finite element solutions and the seepage of water under sheet pile is taken as a case study. Different number of points and nodes has been selected for the two methods. It is shown that both exact and finite element solutions have a good match in distribution for the study area especially when the Fourier points are increased.

The mass flow rate and Rayleigh number has been investigated experimentally on the passive solar using Trombe wall consist of (industrial wax) used as phase change material (PCM). A test rig of a cubicle was made of PVC sandwich panel except the south wall, Trombe wall; covered with a clear glass of 6 mm thickness. The six experiments were carried out during the winter season in Kirkuk city with six different widths of the air gap channel (10, 15, 20, 25, 30, and 35) cm. The experimental resultts show that the mass flow rate proportional directly to a width of the channel and inversely with Rayleigh number. Moreover, the highest efficiency was obtained at a depth of 30 cm, where it was about 2.45 times the efficiency of 10 cm.

In this tribological study, we highlight the effect of lubricating oil viscosity in the Multi-pads hydrodynamic journal bearings generate important improvement in characteristics of stiffness and stability in the high speed turbomachines. Depending on viscosity of oil film (three values) variation for five tilted pads bearing, each pad is pivoted and is facilitated to be tilted with small angles, by using Matlab program, we calculate the oil film thickness for convergence layer. We applied Reynold's equation and solved it's numerically by using finite difference method with 5 nodes technique to find the pressure distributed on each node in the mesh of tilted pad, then calculate stiffness coefficients. Results show that there is clear effect on stiffens with viscosity change. The increase in value of Krr (for n = 0.3) between viscosity (0.04 Pas. s) and viscosity (0.058 Pas. s) is14.33 MN/m, while the increase in Krr value between viscosity (0.058 Pas. s) and viscosity (0.087 Pas. s) is 11.37 MN/m. the increase in value the of Kss (for n = 0.3) between viscosity (0.04 Pas. s) and viscosity (0.058 Pas. s) is5.921 MN/m, while increase in Kss value between viscosity (0.058 Pas. s) and viscosity (0.087 Pas. s) is9.55 MN/m respectively. the increase in value of Ksr (for n = 0.3) between viscosity (0.04 Pas. s) and viscosity (0.058 Pas. s) is 8.95 MN/m, while the increase in Ksr value between viscosity (0.058 Pas. s) and viscosity (0.087 Pas. s) is 14.41 MN/m respectively. the increase in value of Krs (for n = 0.3) between viscosity (0.04 Pas. s) and viscosity (0.058 Pas. s) are 5.08 MN/m, while the increase in Krs value between viscosity (0.058 Pas. s) and viscosity (0.087 Pas. s) is8.19 MN/m respectively. The values of the dominate principal coefficients Krr is greater than that of Ksr, also The values of the principal coefficients Kss is greater than that of cross coupling Krs for all values of viscosity that studied. From this result, we can conclude the side effect of cross coupling coefficients (Ksr ,Krs) can be overcome by great values for principal coefficient (Krr, Kss) respectively, so we can get good improvement instability for this bearing by variation the viscosity. After that, we regarded to use high viscosity lubricant in multi-pad journal bearing to improve the performance and stability by controlling the stiffness coefficients.

Ducting system is an effective way to potentially augment the performance of wind turbine for applications in building architectures. This paper is aimed to study one of the possible enhancement method of the vertical axis wind turbine performance. It is characterized by adding divergent duct to facilitate imparting more flow rate. The divergent duct was designed and adapted with wind turbine. The system was modelled and simulated analytically and numerically. A computer program built in MATLAB 16 to simulate the performance of system. The performance and flow are also solved numerically using ANSYS-FLUENT 17.2. Two opening angles of the divergent -duct were employed to study the behavior of air flow through divergent duct and results were compared with base vertical axis wind turbine. The duct turbine with a straight wall type diffuser demonstrate power coefficient augmentation by 24.2% and 9.09% for opening angle 20° and 12° respectively. The optimum half opening angle was attained for the diffuser. The diffuser’s length of a half of the throat opening is recommended, and its angle of opening is 20°. The diffuser was located in a stream-was direction that adequately aligned with the center of the vertical axis wind turbine. Results showed a reasonable influence on the performance of wind turbine. This technology may be used in gates and in urban areas with a relatively low wind speed regime.