University of Thi-Qar Journal for Engineering Sciences

This paper presents a new approach to improve the performance of power system by enhancing the voltage profile and reducing the real power losses based on two stages fuzzy controller which is used to select the appropriate size and location of capacitor banks required to minimize the power losses and maintain the voltage profile in permissible limits.The first stage of fuzzy controller is used to specify the optimal location of capacitors installation, while the optimal size is specified by the second stage . The proposed method is tested on a 34-bus, 74-transmission lines from Iraqi Northern power system with multilevel ofloads. The load levels are represented by 50%, 75%, 100% and 125% of peak load and satisfied results are obtained to show the feasibility and flexibility of the proposed method.

Laminar, natural convection heat transfer of air filling horizontal space between isothermal (cold) square enclosure and four isothermal (hot) cylindrical rods has been theoretically studied. Finite element method has been used to solve the conservation of governing equations by using software package (FlexPDE).Parametric study has been conducted for the range of Rayliegh number 103Ra105,Aspect ratio 0.11AR0.28. Results are presented in the form of streamlines, isotherms contours and Nusselt numbers. Results showed that the overall heat transfer increases with increasing of both Ra and AR. The values of mean Nusselt numbers are compared with data reported in Ref.[6] and[15], and good agreement has been achieved.

In this paper two spreading schemes and their detection methods were proposed and compared. The comparison depends on the performance of each scheme in Rayleigh flat fading channel. Space Time Spreading (STS) codes are used with Layered Space Time Codes(LST), with Vertical Bell Laboratories Space Time codes (V-BLAST) in particular. Also,Direct Sequence Code Division Multiple Access system (DS-CDMA) was used as a multi-user criterion. As a result of this spreading, a simple decoding algorithm was used. The simulation shows that STS-LST-DS-CDMA system with 3TX-3RX (3 transmitting antennas-3 receiving antennas) using all paths between transmitter and receiver was better than LST-DS-CDMA system by about 4dB in SNR at BER of 10-4. More detailed results are shown in Table 1. Also, the proposed scheme (may be partially) solves the problem of the code reuse.

This paper investigates the performance of stone columns in soft soil of Al-Nassiriya city (one of Iraqi cities in the south). A geotechnical study of physical and mechanical properties of the soil has been carried out for a selected areas from Al-Nassiriya city. A finite difference Matlab program has been employed in simulation of installing stone columns in the aforementioned soil. Results of the study illustrate using stone columns reduces the settlement of the soil for different values of the modular ratio and replacement ratio, thus the Wmax maximum settlement ratio changes from 30% to 16% of the modular ratios (Ec-/Es)=10 and 50 respectively. The effect of spacing and column width is taken into consideration.All results are reasonable and harmonic with most last studies

To evaluate the environmental impact of pollution, mathematical models play a major role in predicting the pollution level in the regions under consideration. Computer models are becoming increasingly important tools in every environmental management aspects.A general one dimensional water quality model (Advection-diffusion Equation ADE) has been developed the dissolved oxygen in Abu-Zirig marsh water. The general one-dimensional model equation was solved using the numerical solution by finite difference discritization and procedure was prepared by writing a computer program in MATLAB program (version 7.6).

New method for inhibition CO2 corrosion in Iraqi oilfield was used in this work. This new method included using combination of heat treatment of steel and added Aromatic(Tetrahydronaphthalene) compounds as corrosion inhibitor in different concentration (0.05%,0.1%, 0.2%, 0.5% and 1%). The results referred that the weight loss was reduced as inhibitor concentration increased for all conditions of specimens whether, there were heat treated or not. The combination of annealing heat treatment of samples and using Aromatic compounds inhibitor offered a better corrosion resistance than the combination of quenching + tempering(Q+T) samples. The presence of inhibitor improves the corrosion resistance for annealed samples. For fully annealing, the weight loss was 5 times lesser than that for (Q+T) samples,while the weight loss of steel (as received condition) was 3 times lesser than that for (Q+T)samples.

This paper includes a study of the performance of Al-Nassiriyah thermal power plant condenser. Which includes a calculations of the main variables of condenser (heat transfer,condensation rate, overall heat transfer coefficient and vapour pressure) by applying two dimensional mathematical model and depending on the empirical equations of heat transfer.Comparison was made between the theoretical results for Al-Nassiriyah thermal power plant condenser before operation it (standard power plant) with practical data which taken from the plant for the second unit in year 2007. The comparison showed that there was a large difference between theoretical results and the values taken from the plant as a result to the effect of operation conditions.

The study aimed towards developing a computer model to be used for evaluating the effect of water distribution uniformity of deficit irrigation with saline water on field crop production. The development of the model is based on the concept of water balance in the field. For the application of the model, corn crop (yellow maize) autumn season is selected using ready data on reference evapotranspiration at the selected field site (North Jazirah Project – Nineva). Moreover, published data on field sprinkler water distribution around sprinkler head of stationary system are used. The main assumption upon which the model is based is that, for a given case, irrigation water distribution and salinity are fixed for all irrigations during the season. The results of the study revealed that the deficit in the yield ratio increases with the increase in moisture depletion ration and water salinity, but decreases with the increase in the degree of irrigation uniformity. Furthermore, the effect of salinity on production is greater with deficit irrigation, therefore a balance should be sought between deficit irrigation level and water salinity on production under each case of irrigation non-uniformity. Finally, the study showed that the leaching fraction increases as the degree of irrigation uniformity deteriorates because deep percolation losses increase with the reduction in uniformity.