Tikrit Journal of Engineering Sciences

High voltage insulators used in various overhead forms are exposed to leakage current and partial discharge. This work deals with different structure forms of insulator, such as (pin post, clamp top and tie top). These structures are applied in different tests, as covered and stripped states. The leakage current for these forms were measured by raising the insulator voltage to (5.25, 6.35, 7.57 kV) for covered and stripped state. Partial discharges were determined in covered and stripped state of these insulator forms using (straight and balanced detection method). Pin post insulators have a leakage current and electric field larger than both clamp top and tie top. The clamp top and tie top insulator show almost the same value of leakage current measurements. The stripped conductors always produce large partial discharge than covered conductor.

This paper describes the application of ac/ac/dc and ac/dc converters to control the speed of a separately excited DC motor. Artificial neural network and PI controller are trained to select the desired values of firing angles for triggering thyristors of the ac/ac/dc and ac/dc bridge converters in order to control the speed of the dc motor at a desired value with constant and different load torques in order to obtain the best speed response. Simulation results show that the rising time for ac/dc and ac/ac/dc converters at 250rpm are reduced about 79% and 89% respectively, while delay time it reduced about 69% and 64% respectively. Therefore, speed response of the dc motor is more efficient for closed loop system compared with open loop also the response of ac/ac/dc converter is better than ac/dc converter.

In this paper an electric field sensor based on the electro-optical effect in Lithium Niobate crystal is studied. The electro-optically induced polarization modification in crystal has been described and the response analyzed for different crystal lengths and light source wave lengths. The study shows that as the crystal length increased the required electric field to produce a phase-shift equal  is decreased. The responsivity of the sensor for different ranges of the electric field to be measured has been calculated and it is found that the rate of change of the half of the phase shift with respect to the electric field d(/2)/dE is equal to the responsivity of the sensor at the mid-point of the linear part of the light intensity response curve.

In the present work, Basrah crude oil, atmospheric distillate of 305-623 K boiling range, vacuum distillate of 623-823 K boiling range, and wide petroleum distillate of boiling range 305-823 K are hydrotreated in trickle bed reactor using Cobalt- Molybdenum alumina as a catalyst. Hydrotreating temperatures are 598-648K, 598- 673K, 648-673K and 648K respectively while LHSV are 0.7-2 hr-1, 1 hr-1, 0.7-2 hr-1 respectively. The operating pressure and H2/Oil ratio for all experiments are kept constant at 3 Mpa and 300 liter/liter. The results show that Sulphur and metal content decreased with increasing temperature and decreasing LHSV. Vacuum residue of boiling range above 823K is mixed with hydrotreated atmospheric distillate, vacuum distillate and with the hydrotreated wide petroleum distillate. The temperature for hydrotreating the mixed sample is 648K and LHSV is 1 hr-1. It was found that hydrotreating crude oil is the best choice since it gives the highest removal of sulphur, vanadium and cobalt removal..

The aim of this work is to study the effect of varying curing conditions, namely temperature ( 10o to 60odegrees Celsius) and curing period (2 to 90 days) on the unconfined compressive strength (UCS) and hydraulic conductivity of lime treated clayey soil selected from Mosul city. The soil was treated with (2,4 and 6%) hydrated lime. Test results showed that the UCS was increased with the increase of curing temperature especially at low curing period. On the other hand, hydraulic conductivity in treated soil has increased with temperature compared with that of untreated soil but not with a constant trend. Finally, leaching of treated soil has led to a decline in hydraulic conductivity with time, while the rate of decreasing was found to be more with samples exposed to higher temperature.

This research deal with an analytical study of a four titled pad bearing. These pads are arranged around the journal. A computer program has been used to solve Reynolds equation numerically using the finite difference technique. The results showed that, the non dimensional force is increased with the increase of the non dimensional load and the gradient of the curve is increased with the decrease of the ( cd / d ) ratio. while the gradient is decreased with the increase of the number of pads which gives less power absorption due to the decrease of the friction force. Also the results showed that the eccentricity ratio is in the range of (0.4-0.8) and the maximum attitude angle is (43o). The curve of the relation between the eccentricity ratio and the load number does not start from the zero. It has been noticed that the increase of the friction factor cause an increase in Summerfield number and the curve gradient is increase with the decrease of the ( cd / d ) ratio. Also the gradient is increased for a fixed value of the ( d cd / ) ratio with the decrease of external load, where as the decrease of the ( d cd / ) ratio cause a decrease of the oil film thickness and this cause an increase of the shearing rate. Finally, the oil flow rate is increased with the increase of the ( d cd / ) ratio and this would increased more with the increase of the number of pads for the same value of ( d cd / ) ratio which leads to a decrease of the bearing temperature and this maintain the same value of the oil film thickness due to maintaining the same viscosity for the lubricant.

A modern technique is presented to study the evaporation process which is considered as an important component of the hydrological cycle. The Pan Evaporation depth is estimated depending upon four metrological factors viz. (temperature, relative humidity, sunshine, and wind speed). Unsupervised Artificial Neural Network has been proposed to accomplish the study goal, specifically, a type called Linear Vector Quantitization, (LVQ). A step by step method is used to cope with difficulties that usually associated with computation procedures inherent in these kind of networks. Such systematic approach may close the gap between the hesitation of the user to make use of the capabilities of these type of neural networks and the relative complexity involving the computations procedures. The results reveal the possibility of using LVQ for of Pan Evaporation depth estimation where a good agreement has been noticed between the outputs of the proposed network and the observed values of the Pan Evaporation depth with a correlation coefficient of 0.986.

The present study is a theoretical investigation for the effects of several types of metal matrix for the rotary heat exchanger. Numerical analysis is used to analyze the parameters of the original matrix and compare them with those of the new three matrix: A metal matrix with a wave of (Corrugated Flat), a wave of ( Notched Flat ) , and tube matrix . The studied parameters included: temperature distribution of the combustion air , exhaust gases; heat transfer, pressure drop, heat elements, and surface area. It was seen that rate temperature of the burned air for the original matrix was 157.1 oC which is lower than that of TM and CF matrix by 14 % and 7.9 % respectively; and higher than that of the NF matrix by 1.6%. The temperatures of the exhaust gases increase during the cooling period with the increase of length of the heat exchanger. The mean temperature of exhaust gases for the original matrix was 296.6 oC which is higher than that of the TM and CF matrix by 3.7 % and 1.81 respectively; and lower than of the TM by 3.33%. The TM matrix has a heat transfer and pressure drop higher than the others. This is because the heat transfer coefficients of CF and NF matrix are lower than that of TM matrix by 8.2 % and 10.1 % respectively. The pressure drops for CF and NF matrix are lower by 45% and 53% respectively. The heat elements of TM matrix is higher than CF and NF by 65.4% and 76% respectively. The surface area decreases with the increase of cell number for all the types. TM matrix has the highest surface area. It is larger than that of CF and NF by 17.6% and 25% respectively.

Many sources play a significant role in changing the Tigris river water quality within Iraqi territory, such as the river’s tributaries receiving points, impounding like Mosul dam, the residential settlements as Mosul city, and the untreated discharge of agricultural activities. The First river tributary is Khabbor which confluences the Tigris River at Feshkhaboor village, near the Iraqi-Turkish borders. The second one is Upper Zab which meeting the river at Mishraq, 45 Km south of Mosul. Upper Zab Tributary is characterized by high discharges rates, and high pollution content. The study aim to evaluate its effect on the Tigris river water quality. The Study revealed that the Upper Zab river has buffering capacity that polishes or enhances the Tigris river water characteristics, with an adverse effect for the others. For example, the values increased by 6% for pH, 56% for Dissolved oxygen, and 134.5% for alkalinity, Whereas the other characteristics decreased by 27.7% for electrical conductivity, 23.6% for total solids, 40% for suspended solids,16.5% for calcium ion, 20% for chloride, 33% for sulfate, 50% for chemical oxygen demand, and 6% for biological oxygen demand.

Presented in this paper is a public service data base for Kirkuk city. The data base is based on dividing the town into a number of main districts and coding the zones and neighborhoods in each of the main distracted. This coding would help in constructing a comprehensive indexing system for the available services in the Nations zones of the city. The system may then be utilized in the plans of future expansion of the city in order to reduce discrepancies in the distribution of public services. It has been found that the block system is better and more suitable than other existing methods. It can be implemented easily by governmental establishments that are involved in such services uses geographical information system (GIS).