Tikrit Journal of Engineering Sciences

Nano-refrigerant is announced to become an excellent refrigerant, which often improves heat transfer efficiency in the cooling systems. Different materials can be applied to be suspended in traditional coolants in the same way as nanoparticles. In this comprehensive research, mathematical modeling was used to investigate the effect of suspended nanoparticles (Al2O3, CuO, SiO2 and ZnO) on 1,1,1,2-Tetrafluoroethane, R-134a. The thermal conductivity, dynamic viscosity, density and specific heat capacity of the nano-refrigerant in an evaporator pipe were investigated. Compared to conventional refrigerants, the maximum increase in thermal conductivity was achieved by Al2O3/R-134a (96.23%) at a volume concentration of 0.04. At the same time, all nano-refrigerant types presented the same viscosity enhancement of(45.89%) at the same conditions. These types of complex thermophysical properties have enhanced the heat transfer tendencies in the pipe. Finally, the nano-refrigerant could be a likely working fluid generally used in the cooling unit to improve high-temperature transfer characteristics and save energy use.

Surface preparation of engineering materials is necessary for preventing corrosion and subsequent failure of materials in service. There are different methods of surface preparations that can affect engineering materials in different ways. This study investigated the effect of surface preparation on the corrosion behavior of zinc sprayed and unsprayed mild steel. Quantitative analysis and potentiodynamic polarization techniques were used to evaluate the immersed samples of different surface preparations. The results indicated that the least corrosion rate was observed for the uncoated sample prepared with CC1200 grit paper at 0.041 mpy and successive samples in the order of CC220 grit paper at 0.047 mpy < P60 grit paper at 0.052 mpy < filing at 0.064 mpy and grinding at 0.074 mpy after 42-days of immersion. The prepared samples that were further coated with zinc spray demonstrated a similar trend. The sample prepared with CC1200 grit paper and further coated with zinc spray exhibited the lowest corrosion rate of 1.35 x 10-9 mpy. Potentiodynamic polarization results further suggested that the same behavior was observed in the quantitative analysis.

The current study aims to create a computer program estimates the time required to complete the additional work due to the change command by evaluating the cost of these works. A set of mathematical formulas and arithmetic equations are utilized for programing purposes. Furthermore, the difference of time due to the change order (Y), which was calculated depending on the cost of these works (X). Furthermore these equations were developed by statistical analysis of the data collected from change orders for roads in Salah al-Din Governorate. Then the program was verified and valuated by a group of engineers through making a survey. Briefly the practical benefit of the program was very good, with a recurrence rate of (50%) based on the evaluation of these engineers. The benefit of using the program in future projects was good, with a recurrence rate of (49.8%).


Also, the most frequent works in change orders for road projects at Salah al-Din Governorate has specified and concluded. It was found that the works of operating and cleaning roads were repeated at a rate of (30%) in the change orders. Moreover, the earthworks were repeated at a rate of (20%), and the drainage works repeated at a rate of (20%). These results are used to focus on these works when preparing schedules of quantities for future projects to avoid errors in estimating quantities and the problem of increasing time and cost resulting from change orders of these projects.

The construction industry in Iraq faces many challenges, the most important of which is the lack of a performance measurement system for construction projects, thus showing the need to understand and identify performance areas that affect the performance of projects. Indicators were collected from and literature review. The Delphi technique was used in three rounds, the first is an open questionnaire and the second is to assess the importance of the indicators through the weighted average and the application of the Pareto principle to choose the most important indicators from the second round. The third round is a pairwise comparisons questionnaire and analyzed by the process of hierarchical analysis using Expert choice program. The most important indicators that are used to measure the success of the performance of construction projects (learning from the best practices and experiences of others) by obtaining (4.29) followed by (the organization's liquidity) by obtaining the importance (4.24) and the third indicator (the planned construction time) by obtaining (4.24). The indicators prioritize and set in a framework to help project managers and stakeholders remove weaknesses and take the necessary measures in a timely manner to reach a high-performing, successful facility therefore, it is preferable to pay attention to the importance of performance measurement for construction projects

This work introduces a new way to assess the condition of highways and classify them as congested or uncongested highways. This was done by recording a video and sorting the number of lane change orders instead of finding the traffic density, delay, and flow rate. Then extracting data from the video and performing a microscopic simulation for it to study the driver's behavior and create the statistical model. Thus, obtaining the mathematical relationships and coefficients that illustrate that process, after verifying the reliability and calibration of these variables. This research aims to facilitate the highway assessment process, as an alternative or supplementary method of highway evaluation by the Highway Capacity Manual 2010. It is adequate to record a video and count the number of vehicles that change their lanes and then compare them with the results that have been determined in the search to judge the highway is congested or not. The study area was achieved by choosing five segments of multilane arterial roads (six lanes divided) on the left coast of Mosul city. These segments were selected to be as similar as possible in the geometric configuration as well as like traffic flow. After that, cameras were installed according to criteria to record traffic movement and for a time not less than ten hours for each segment, and on the workdays for traffic movement. Then, the videos were uploaded using the Goodvision traffic data recognition program. These outputs were converted to be entered into the PTV-VISSIM traffic simulation program in addition to the other geometric information needed by the program to complete the analysis process and find traffic flow parameters. In the extraction process, the normal distribution and the uniform nature of the data representation of the observed event on the segments were examined using the Z-test and the K-S test, the results were normal and significant. Then the results were verified and the traffic parameters such as density and flow rate were checked to ensure the nature of the traffic flow. The process was also verified using the vehicle motion graphic representation method (Vehicle Trajectory), which is the initial examination to estimate the new variable. A new variable has been extracted, which is one of the traffic movement variables, which depends on the percentage of complete and proper lane change completion within the parameters imposed by the simulation program, it’s the Lane Change Occupancy factor (LnChOc.). Then the statistical model was derived using SPSS for the new variable. It describes traffic conditions on highways and the results are verified and calibrated in more than one way. It’s a simple statistical model was obtained to estimate the traffic movement from this variable and vice versa from the following equation:, Which gave results for critical traffic on multi-lane roads in the Mosul city as follows: -


-LnChOc=45.559 ≈One lane change per 46 Vehicle hour, -Max.flow rate =2558 pcphpl, -Critical Density =48.925 pcpkmpl, -Optimum Speed=52.28 kmphr.

The bond strength between the steel fiber and the ultra-high performance concrete (UHPC) matrix plays a significant role in improving the behavior of plain UHPC. This paper compiles the existing experimental research database on the pullout bond performance of steel fibers embedded in UHPC. The variations of key parameters in the database are the steel fiber type and geometry, fiber volume fractions, and fiber embedded length. The effects of these parameters are analyzed and discussed in detail. Based on the analysis of the results, it was found that the deformed steel fibers, i.e., the hooked-end, half-hooked-end, and twisted steel fibers clearly provided higher average bond strengths than that straight fibers. The average pullout bond strength was obtained by increasing of fiber volume fraction in the UHPC matrix up to 2% (11.21MPa) with an increment of 20.4%. When the steel fiber volume fractions increase beyond 2%, the average bond strength decreases. Additionally, it was also found that using smaller embedded lengths in deformed steel fibers could result in the improvement of bond strength. This could be due to the fact that the bond is controlled by the mechanical anchorage of the end-hook rather than the physio-chemical bond in the straight portion. Conversely, increasing the embedded length of steel fiber could greatly contribute to the enhancement of pullout resistance resulting in increased bond strength between the UHPC matrix and steel fibers.

This study investigates the flow of a semicircular labyrinth weir in an open channel by experimental and numerical methods. The experiments were carried out in a channel with a length of 3.5m and width of 0.25m and 0.3m height under five different flow rates. Five different discharge values over the weir were used. In each experiment, flow rate and flow depth were measured. Numerical processes solved using mathematical equations of fluid flow through the computational fluid dynamics using ANSYS FLUENT code. The Volume of Fluid (VOF) model is designed for the case of water and air-immiscible faces. Standard k-epsilon turbulence models were tested. A mass balance result indicates that the maximum error between the inlet and outlet discharges of the main channel does not exceed 12% for discharge values of 4.31 L/sec. The results indicate that by increasing the discharge flow rate, the percentage of error decreased to 0.4% for discharge, 14.6 L/sec. The findings show that the free water surface profile obtained from the numerical model compared to experimental values complies well with the experimental results.

The present study is about an experimental investigation of the strength and response of reinforced concrete tapered beams strengthened by near surface mounting (NSM)-CFRP technique. The influence of several parameters on the behavior of beams is investigated. And those parameters are: angle of inclination and strengthening patterns by NSM-CFRP technique. The experimental program involved testing nine specimens of reinforced concrete tapered beams and one prismatic beam. There were two groups in the experimental program; the first group included four unstrengthening reference beams to investigate the effect the angle of inclination, and the second group included six specimens were strengthened by NSM-CFRP strips with different strengthening patterns (U-strips) and (UL-strips) were used to strengthen the tapered beams against shear and flexural forces. The results of the experiments indicated that as the angle of inclination increased, from (0˚) to (7°), (14°) and (21°) decreases the ultimate load capacity (Pu) by about (4)%, (14)% and (41)% respectively for unstrengthen tapered beams, as well as the deflection at the ultimate load. Also, when compared unstrengthen with strengthened beams, the ultimate load capacity will increase with the angle of inclination increased, from (0˚) to (7°), (14°) and (21°), for (U-strips) patterns the percentages of increase were (7)%, (9)% and (33) % respectively, while (UL-strips) increased the ultimate load capacity by about (19)%, (19)% and (44)% respectively.

The visual elements play an essential role in E-learning utilisations that impact the effectiveness of the learning users. That requires highlighting the effect of new elements of E-learning on the learning outcomes of students as well as users. The study was carried out in two phases. In the first phase, a literature review was conducted to identify the most relevant studies on the subject. This paper investigates empirical identification and examines both E-learning text and non-text related to the category of visual materials. The user experience design perspective covers literature surveys, interviews, and questionnaires. Research has been done on the types and functions of the visual elements of E-learning. Therefore, based on the existing E-learning Levin visual model elements, including "organisational", "descriptive", "interpretative", "deformable", "decorative", and "social", distinguish the correlation degree of each element with learning content and persistence. The result shows better user satisfaction enhancement and promotion of E-learning's learning effectiveness and persistence. In addition, from the perspective of user experience, it is found that social elements are the potential needs of users, and sociality is one of the characteristics of digital learning.