Journal of Engineering

Al-Si alloys, widely used in engineering applications due to their outstanding properties, can be modified for further enhancements. This study investigates the ability of these alloys to be modified by casting them with the addition of nanoparticles. Multi-wall carbon nanotubes (CNT) and titanium carbide ceramic particles (TIC) with a size of 20 nm were added in different amounts (0.5% to 3% by weight) to cast alloy A356, which served as the base metal matrix. The alloy was then stirred at different speeds (270, 800, 1500, 2150 rpm) at 520 °C for one minute. The results showed a change in the microstructure of the cast alloys from dendritic to spherical grains with increasing stirring speed. EDX analysis confirmed the presence of CNT and TIC additions in inter-dendritic locations. The enhancement in mechanical properties was most significant at a weight of 2.5% and a stirring speed of 1500 rpm.

This work presents the modeling of the electrical response of a monocrystalline photovoltaic module using a five-parameter model based on the manufacturer's data sheet of a solar module measured under standard test conditions (STC) at radiation 1000W/m² and cell temperature 25°C. The model accounts for the series and parallel (shunt) resistance of the module. The paper details the Matlab modeling of the solar module using a developed Simulink model and basic equations. The first approach estimates the parameters: photocurrent (I_ph), saturation current (I_s), shunt resistance (R_sh), series resistance (R_s), and ideality factor (A) at STC through an iteration process. A numerical approach based on the Newton-Raphson method is implemented and programmed in Matlab. The second mathematical model in Matlab/Simulink uses equations for each parameter to determine the parameters at all operating conditions. The Matlab program provides information about the behavior of the practical PV module under different atmospheric conditions. The model's accuracy is analyzed by comparing the practical and theoretical aspects at different solar radiation intensities (500, 750, and 1000 W/m²) by extracting error ratios. The results show differences between theoretical (modeled) and experimental data, with the best validation (less error) between the five-parameter model and experimental maximum power results at radiation levels of 500, 750, and 1000 W/m² and STC being 5.5%, 19%, 18%, and 12.3% in January, respectively. The decrease in ambient temperature and thus the temperature of the solar module in January led to an increase in maximum output power and produced the best validation between the model and experimental data in this month.

This paper presents an experimental study of the thermal performance of a hybrid solar air conditioning system to investigate its suitability for the hot climate in Iraq. The system consists of a vapor compression unit combined with an evacuated tube solar collector and a liquid storage tank. A three-way valve was installed after the compressor to control the direction flow of the refrigerant, either to the storage tank or directly to the condenser. The performance parameters were collected by a data logger and recorded using LabVIEW software. The results show that the average coefficient of performance of the hybrid solar air conditioning system (R=1) was about 2.42 to 2.77, and the average power consumption was about 1.1 to 1.12 kW when the ambient temperature was about 34.2 to 39.7°C. In contrast, the average coefficient of performance of the conventional system (R=0) was about 3.23, and the average power consumption was about 1 kW when the ambient temperature was about 30.8 to 34.3°C. The study concludes that the current form of the hybrid solar system in Iraq may not significantly save electricity.

Copper and its alloys and composites are broadly used in electronic and bearing materials due to their excellent thermal and electrical conductivities. This study used the powder metallurgy technique to produce copper-graphite composites with three volume percentages of graphite. The selected processing parameters were a sintering temperature of 900°C and a holding time of 90 minutes in an inert atmosphere (argon gas). The wear test results showed a significant improvement in wear resistance as the percentage of graphite increased, acting as a solid lubricant (wear rate decreased by about 88% compared to pure Cu). Microhardness and compressive strength increased (about 8% and 16%, respectively) and reached maximum values at 1% graphite percentage compared to pure Cu, then decreased after that critical graphite concentration. Microstructure tests indicated that the dark region in the copper matrix increased as the percentage of graphite increased, and the reinforcement particles were homogeneously distributed, demonstrating that the powder metallurgy technique is suitable for this task.

Magnetic nanoparticles (MNPs) of iron oxide (Fe₃O₄) represent the most promising materials in many applications. MNPs have been synthesized by co-precipitation of ferric and ferrous ions in alkaline solution. Two methods of synthesis were conducted with different parameters, such as temperature (25 and 80°C), adding a base to the reactants and the opposite process, and using nitrogen as an inert gas. The product of the first method (MNPs-1) and the second method (MNPs-2) were characterized by x-ray diffractometer (XRD), Zeta Potential, atomic force microscope (AFM) and scanning electron microscope (SEM). AFM results showed convergent particle size of (MNPs-1) and (MNPs-2) with (86.01) and (74.14) nm respectively. Also, the zeta potential values of (MNPs-1) and (MNPs-2) were (2.77) and (-12.48) mV, respectively, which indicates more stability of (MNP-2).

This study investigates the effect of increasing the value of coupled moment and increasing the rigidity of raft footing on the horizontal deflection using 3-D finite element analysis with the ABAQUS program. The results showed that increasing the coupled moment value leads to an increase in lateral deflection and rotational angle (α°). The rotational angle increases from (0.014, 0.15 to 0.19) at coupled moment (120 kN.m), (0.29, 0.31 and 0.49) at coupled moment (240 kN.m) and (0.57, 0.63 and 1.03) at coupled moment (480 kN.m) with decreasing the raft thickness from (1.5, 1.0 to 0.5m), respectively. The computed maximum lateral deflection decreases with increasing the rigidity of the raft. The maximum deflection decreases from (40 to 3mm) at coupled moment 120 kN.m, (150 to 60mm) at coupled moment 240 kN.m and (210 to 118mm) at coupled moment 480 kN.m with increased raft thickness from (t = 0.5 to 1.5m). The maximum reduction in maximum stress value and lateral deflection mobilized due to applied coupled moment is noticed when the width to thickness of footing ratio is less than (w/t<12). The failure of the footing is noticed when the rotational angle is more than 4° (α > 4°).

This study investigates the effect of using grinded rocks of quartzite and porcelanite as powder replacements (10% and 20% by weight of cement) for self-compacting concrete slabs. Five slabs with 15 concrete cubes were tested experimentally at 28 days to study the compressive strength, ultimate load, ultimate deflection, ductility, crack load, and steel strain. The test results showed that the compressive strength improved with the replacement of local rock powder, reaching 7.3% and 4.22% for 10% and 20% quartzite powder, and 11.3% and 16.1% for 10% and 20% porcelanite powder, respectively, compared to the reference specimen. The ultimate load percentage increase for slabs with 10% and 20% replacement of quartzite powder was 41.17% and 23.53%, while the slabs with 10% and 20% replacement of porcelanite powder were 23.53% and 35.3% compared to the reference slab, respectively. The ultimate deflection, ductility, spread cracks, and ultimate steel strain for slabs with replacement materials (quartzite and porcelanite) increased significantly compared to the reference slab.

This study aims to assess the performance of different GNSS receivers to provide reliable positions. Three different receivers from various manufacturers were fixed to form a triangle, and simultaneous observations were made in static mode for 2.5 to 3 hours. This observation technique was repeated three times, changing the location of receivers each time to ensure that each receiver observed each station three times. The performance of each receiver was evaluated using OPUS web-based processing software and TOPCON TOOLS to process the raw GNSS observations. The distances between adjacent stations were computed for each observation and compared to standard distances measured using a total station. Additionally, internal angles were computed and compared to those measured by Total Stations. The results showed that some calculated distances were closer to the corresponding distances measured by the total station, indicating that the receivers involved in these distances were the most accurate.