KUFA JOURNAL OF ENGINEERING

The present work investigated experimental and numerical the effect of internal radiate on the external tube on heat transfer coefficient and pressure drop in tube for range of Reynolds Number of (4000-16000). The study also discuss the different in results between the slot dimple tube and plain tube. Heat transfer and pressure drop for test tube were evaluated and presented as dimensionless value by Nusselt number and friction factor. Overall enhancement ratio of dimpled tube is discussed. Thermal and hydrodynamic results of CFD study are presented in form velocity vector and contour of local heat transfer coefficient. The results comparison of Nusselt number between plain tube and present slot dimples tube, shows that slot dimples tube enhance the heat transfer between 1.584 - 2 times the plain tube, and When compare between experimental and correlated Nusselt number for present slot dimple tube, the result show deviation in the test range of Reynolds number. The numerical results were in good agreement with the present experimental results. The deviation is within 6 - 22% higher for numerical at low and high Reynolds number, respectively. The overall enhancement ratio for present slot dimpled tube dependent on plain tube, the result depict that the slot dimple tube gave high enhancement in heat transfer relative to plain tube. The enhancement ratio is varied from (1.09 to 1.15) for range of Reynolds numbers between (4000 to16000).

This paper presents two methods used for three closed loop speed controller of Variable-Voltage Variable Frequency (VVVF) triple 3-phase Induction Motors (IMs) master/slaves system. A dynamic d-q model of a 3-phase IM in state space form and its computer simulation in MATLAB/SIMULINK software package are described. The two different methods of speed control which are used to improve the performance of three IMs drive system are named as conventional PI controller and PID controller. For PID speed controller, simulation results clearly show that the response of the system is superior compared to PI speed controller in terms of rise time, settling time, accuracy and steady state error. The design, analysis, and speed responses of the system obtained under both controllers have been simulated, studied and compared using MATLAB/Simulink environment for different operating conditions such as sudden change in reference speed and load torque. The simulation results showed good synchronization between the master and the slave IMs with suitable tracking error.

Tungsten Trioxide (WO3) thin films with a various crystal structure have been fabricated by a magnetron sputtering method. The effect of changing of crystal structure on the Electrochromic (EC) property was investigated. Atomic force microscopy (AFM) and X-ray diffraction (XRD) have been employed to investigate morphology and structure. For EC measurement, 0.1M LiClO4 aqueous solution was used as electrolyte, and Pt and Ag/AgCl were used for counter and reference electrodes respectively. WO3 thin film with a various structure has been obtained by changing reactive gas (Ar) gas and O2 flow rates. Fabricated WO3 thin films with 002 and 112 crystal structures have a high Electrochromic (EC) response.

The construction industry has a multifaceted relationship with most sectors of the economy in all nations, as well as playing a vital role in social and economic development. One of the main factors that affect the development of the construction industry is labour productivity. The aim of this paper is to identify and rank the importance of the factors perceived in the literature to influence labour productivity in the Iraqi construction industry using Basra city as a case study. From the literature a total of 59 main factors were identified that may affect labour productivity on construction sites. These factors were classified into ten primary groups: (1) Managerial; (2) Environmental; (3) Manpower; (4) materials and equipment; (5) Schedule; (6) Safety; (7) Quality; (8) Motivation; (9) Technical; (10) External. The statistical analysis of these factors was prepared by using the Relative Importance Index (RII) and SPSS 23 programme. The grades obtained made it possible to assess the comparative importance of the factors as perceived by respondents. The study provides comprehensive and explicit data for the construction contractors working in Iraq before providing the proposal for the bids taking in account the risks and the challenges mentioned in the study. Also it observed that the Iraqi government authority enforcement is essential to ensure that the construction labour productivity is fulfilled without losing in time and money. A structured questionnaire survey was sent to construction project managers, as a target group and the results showed in order to improve labour productivity in Basra city in particular and in Iraq in general. The results are show that the ten essential factors affect on construction labour productivity with different level of importance. In addition, all types of corruption must be considered to be serious problems affecting labour productivity. Enforcement, conduct education and training for manpower by using new techniques are decreasing the difference between estimated and actual labour productivity.

Water resources and hydraulic engineering projects have been upward rapidly in all over the world, accordingly the prediction of roughness coefficient is essential criteria to design open channels, and related hydraulic structures. The aims of this research are to find out the effect of changing beds materials and discharge on coefficient of roughness (n), the beds that used in the tests are smooth which represented by original channel bed (steel plate), rough bed material which is a gravel bed and waved bed .The experimental work was performed in a rectangular flume with dimension of (15 m* 0.3 m* 0.45 m) long, wide and deep, respectively with different value of slope (1:200 and 1:500) to analyze slope effect on coefficient of roughness in addition to the effect of channel bed material. The experimental work showed that The coefficient of roughness reduced when the discharge increases for specified slope and channel bed, The slope of the channel and bed roughness is the main factors affected on determining coefficient of roughness and when the channel slope increases the coefficient of roughness increases, the coefficient of roughness is decreased when using smooth bed and it is increased when channel bed is waved. The percentage change in the Manning coefficient due to changing in slope and channel bed is (112.6%) when slope equal to (1/200) and the channel bed changed from smooth to rough , (184%) when the bed changed from rough to waved, and (33.6%) when channel bed changed from rough to waved. And for (1/500) slope, the percentage change in the Manning coefficient equal to (33.5%) when the bed changed from smooth to rough, (80%) when changed from smooth to waved, and (33.1%) when changed from rough to waved.

The possibility to use fillet welds instead of complete joint penetration welds (CJP ) in directly- welded flange FR (fully restrained) connections is the main aim of this study. An experimental comparison has been made between these two types of welds. Fifteen specimens have been configured by welding plates to form butt, Tee and lap joint connections; three specimens with butt-joint, six with lap-joint, and six specimens were with T-joint. Fillet and CJP groove welds separately have been used to make these connections. After testing of all these specimens, the results indicated that the appropriately sized fillet weld is a good alternative to CJP groove weld when it is used for fully restrained FR moment connections.

This paper consists of experimental study on ability of use of wire mish strengthening and steel fiber to recover the flexural strength of the slab after configuring openings cut out with different shapes. 15 slabs (800*800*95 mm) made of high strength concrete were prepared and tested, these slabs were divided to gropes, the first group was with square openings, the second group with was rectangular openings. For each group, two different strengthening techniques were used wire mish (with different layers and widths) strips around openings and steel fibers (with four contents of 0, 0.5, 1.0 and 1% by volume fraction). The results showed that the two strengthening techniques increased the load-carrying capacities of the slabs with openings compared with the slabs without strengthening. The wire mish was more effective than the steel fibers technique. Wire mish and steel fiber reduced the cracks at the inside faces of opening and also wire mish prevent it at the inside corners.

In the last two decades, the communication and Internet industry has seen a rapid development, which caused an increase needed to develop an efficient compression image algorithm to reduce the volumes of the information transmitted through the communication system. In this work, the discrete multi wavelet transform is used to build an efficient image compression algorithm. The proposed algorithm is built under MATLAB environment and it is tested using two different images. The experimental results stated that the proposed algorithm has good result with very small loss of resolution when applied on the reconstructed images.

Preserve natural environmental resources and losing of land used as a graveyard for demolition waste concrete buildings, recycling concrete aggregate is one of the green sustainability practices and keep the land and reduce material losses. Investigation on mechanical properties of high performance concrete with polypropylene fiber reinforced. Coarse recycled concrete aggregate was replaced by natural coarse aggregate in three percent 25%, 50%, and 75%. Mechanical properties of high performance concrete are made from replacing natural coarse aggregate by 25% of recycled coarse aggregate, is considered the best among the other replacement ratios compared with the mixture of reference with slight reduction in compression strength by 8%, splitting tensile strength 8%, flexural strength by 9%, with increased total absorption by 4%, and no water under pressure permeable to the concrete specimen. In this study found that it can produce ultra-high performance fiber reinforced concrete using recycled concrete aggregate with high workability and low cement/water.

The effect of depth and location of the notch on the v-notched specimen on fatigue life of cantilever rotating beam of low carbon steel (ST37-2) is studied, by applying fully reversed cycle load of 150 N, and mean stress of Zero. The temperature variations during fatigue life were measured by infrared camera at three points in specimens. These points are the edge point, notch point and other specified points. Numerically, the finite element model of fatigue test was obtained using the ANSYS Workbench. The ANSYS model was based on the S/N curve measured experimentally.
From the results, there is a notch position that changed the fracture position from the notch position to the edge position. Also, fatigue life can be increased by putting the notch in appropriate position on the specimen. The temperature variation at different points in the specimen gave a good prediction to the fracture position before the fracture occurs. Also, from the comparison between experimental and numerical results, the two curves were similar but the ANSYS model based on the experimental S/N curve gave a good prediction for fatigue life.