DIYALA JOURNAL OF ENGINEERING SCIENCES

Until now many regions around the world are still uncovered by cellular terrestrial mobile system services due to the lack of economic feasibility as well as the difficulty of introducing such services. Conversely, a large geographic region can be covered by using only a single satellite, so it is worthwhile to extend the actual terrestrial services using satellite system. The new hybrid integrated “terrestrial-satellite” cellular system, known under the name of Non-Terrestrial Networks (NTN), will see the light with the support of future 6G technology. It is expected that 6G cellular mobile system will play the role of integrating terrestrial, aerial, maritime, and space communications into a universal network that could support a massive number of terminals with ultra-low latency. For the realization of the NTN system, new technologies should be introduced at the level of terrestrial cellular network, arial network, and satellite network. One of these promising technologies is represented by an efficient multiplexing technique known under the name of non-orthogonal multiple access (NOMA). With this technique, multiple users can be served on a single time-frequency resource block by using the concepts of superposition coding at the transmitter and successive interference cancellation (SIC) at the receiver. Moreover, NOMA has an achievable performance gain in terms of spectral efficiency over the traditional orthogonal multiple access (OMA) technique. Evaluation of a NOMA-based NTN system supported by 6G technologies in terms of system parameters and channel capacity represent the main objective of this paper.

The study explores the feasibility of using a photovoltaic (PV) energy system to produce hydrogen for off-site hydrogen refueling stations (HRS) in three Iraqi cities (Karbala, Maysan, and Nineveh), focusing on a comprehensive system model consisting of a 558 MWp off-grid photovoltaic system, a 157.5 MWp proton exchange membrane (PEM) electrolyzer, a converter, and a hydrogen storage tank. Utilizing HOMER Pro software for system simulation and MATLAB, with consedaring 28 years from 2022 to 2050 life span, incorporating hourly weather data for 2022 to optimize system performance. The outcomes identify that the Karbala city as the most cost-effective for green hydrogen production, highlighting the economic benefits of PV technology, which presents the most economical option with a levelized energy cost of $5,010/GWh. The project is projected to produce 10.61 million kg of hydrogen annually at a production cost of $2.75/kg, with an overall project cost estimated at $372.77 million. The results are of strategic significance for Iraq transportation sector, supporting the development of a robust green hydrogen infrastructure for HRS. This infrastructure is expected to promote sustainable transportation practices and reduce reliance on fossil fuels, contributing significantly to the energy transition in Iraq. This techno-economic analysis provides a foundational assessment for stakeholders considering investments in renewable hydrogen production and infrastructure development.

Reactive powder concrete (RPC) is a new kind of concrete technique that has been enhanced and improved in recent decades which showing superior performance on structural systems. This paper shows experimental research to study the structural performance of reactive powder reinforced concrete one-way slabs in static loading by applying two symmetric loads and simply support type. In the present investigation, five RPC one-way slabs designed, casted and tested. All the slabs were similar in the length and the width (980x400mm), also in the properties of materials and their proportions, but different in thickness and the ratios of main reinforcement. They were cast into two groups; the first group had three values of longitudinal reinforcement proportions (ρw): 0.0036, 0.0048, and 0.0060, respectively, and the second group included three values of slab thickness: 40 mm, 60 mm, and 80 mm, respectively. Experimentally, it has been noticed that the ductility and flexural behaviour of RPC one-way slabs are considerably affected by increasing slab thickness but influence of longitudinal reinforcement less significant. The results of specimen testing indicated that increasing main steel reinforcement proportion from 0.0036 to 0.0048 and to 0.0060 led to an increase in the first cracking load test with a value of (19.05%, 42.86%), respectively, an increase in the ultimate load test with a value of (21%, 40.91%) respectively, and the value of ultimate mid-span deflection increased from 17.78% to 28.98%. The test results also revealed that the increase in thickness of slabs from 40mm to 60mm and then to 80mm led to an increase in the first cracking load test with a value of (166%, 240%), respectively, increase the ultimate load by (104.06%, 234.71%), respectively, and the value of ultimate mid-span deflection decreased from 36.82% to 58.26.

This paper presents the lateral static and cyclic response of a group of piles. The experimental program included this on a small scale using hollow piles of aluminium, and the sand rain method was employed to prepare the sandy soil with a 70% relative density. The case study is a laboratory model of a pile group 2x2 with spacing (i.e., 3D,5D, and 7D), and the proportion of embedded length to circular pile diameter (L/D) = 43. Different lateral cyclic loading ratios CLR of 60%, 80%, and 100% from pile group capacity are used. According to the experiments' results, the vertical and lateral piles' capacity and displacement are greatly impacted by the cyclic-loading variables, which include the number of cycles and the cyclic-load ratio. It can be concluded that when increases in CLR usually influence on pile group performance, and the lateral displacement increasing up to 66% for closely spaced piles. The pile group spacing affects the uplift displacement; the highest reach value (4.7mm) upward is 7D.

A natural convection heat transfer inside rhombic square cavity partially filled with porous material have been numerically investigated. A constant heat flux has been applied to the left wall with a right wall kept in constant cold temperature while thermally insulated the top and bottom walls. Finite volume technique with Simple algorithm have been used to simulate the governing equations of fluid flow and heat transfer coupled with Darcy-Brinkman model to simulate the flow of the air inside the main cavity and the open cells of the porous media. Three factors were chosen to study their effects on the natural air velocity and the mechanism of the free convection inside the enclosure. The inclined angle of the sidewall of the rhombic (q = 90o, 80o and 70o), the thickness of the metal foam (t = 5 cm, 10 cm, and 15 cm) and the amount of heat flux (q = 150 to 600 w/m2). Copper metal foam with 0.9 porosity was chosen as porous media with open cell filled by air (Prandtl number =0.7) and 10 as pore density. The results showed that using a layer of porous metal foam with open cells will increase the heat transfer rate. It was 41.3% enhancement when use 5 cm of porous media and 68% for 15 cm. Acute inclined angle will decrease local Nusselt number and led to form vorticities. Furthermore, high heat flux increased the average Nusselt number and improved the heat transfer rate.

A retaining wall was practically developed to provide lateral support for soil, and it is widely used in underground projects, highway barriers, and mines as well as for aesthetic considerations and slope stabilization. This type of earth structure member can carry machine foundation load simultaneously with traditional static load. This study carried out using the finite element program PLAXIS 3D. The linear elastic model for retaining walls and the Mohr-Coulomb model for soil layers were used in this numerical analysis. The study included three layers of soils under the wall with dry condition. The high of the wall was 4m and the dimensions of machine foundation were 3x3m. It can be concluded that the vertical settlement, horizontal displacement and velocity increased when the duration of the machine load increases. Usually, the horizontal displacement increases to highest value and reached to 10 times the original static value when the machine was closed to the wall with 0.5m and 75Hz. This can be taken into account in the design for such geotechnical system in the design stages.

Concrete dams are the strongest dams, designed for flood control, electricity generation, and water management. They can become unstable due to ground shaking and earthquake impacts, resulting in stability loss due to embankment and foundation materials or severe deformations like slumping, settlement, cracking, and slope collapse. Where consider an earthquake one of the factors that pose a major threat to dams, especially if the earthquake is strong and if the soil under the dam is sandy soil, so that geotechnical designers should consider more than any other disaster when developing construction in seismically active areas. Therefore, a laboratory study was conducted on a model of concrete dam with dimensions (width =15 cm, high = 20 cm, and thick = 5cm) on fine sand soil. In order to study the stability of the concrete dam subjected to earthquake vibration, the model of the dam was subjected to different types of earthquakes (Halabja and El Centro). The main goal of the study is understanding the behavior and performance of concrete dam subjected to seismic load. It can be concluded that the stability of the concrete dam subjected to earthquake depends on the intensity of the earthquake. Thickness and width of the dam. According to the results, the El-Centro earthquake effect on concrete dams is 60% greater than the Halabja earthquake.

Hybrid composite materials combining polymers and reinforcements are gaining interest for enhanced engineering properties. The main goal of this study was to create the best hybrid composite using carbon fibers, zinc oxide micro- and nanoparticles, epoxy, phenol-formaldehyde resin, and more. Samples with varying ratios of epoxy resin (50–100%) and phenol-formaldehyde resin (0–50%) were fabricated. Mechanical and water absorption testing evaluated the effects of the zinc oxide particles and carbon fibers on tensile strength, elasticity, and liquid resistance. Results showed improved tensile strength and minimized water absorption at 10% phenol resin content. Further, zinc oxide nanoparticles offered better reinforcement than microparticles, attributed to higher surface area-to-volume ratios. However, carbon fiber addition increased water absorption despite improving tensile properties. In the end, the best composite was made up of carbon fibers, zinc oxide nanoparticles, 90% epoxy resin, and 10% phenol-formaldehyde resin. This affordable hybrid composite has potential applications in sewage system piping. Further work should focus on improved mixing methods to leverage synergies between the composite constituents. The study provides valuable insights into tuning hybrid composites with nanoparticles and fibers for advanced functionality.

The conventional methods follow in designing piles adopt the assumption of saturated condition of soil depending on soil parameters at saturated condition while at most cases the whole piles or part of them lays in unsaturated soil zone, thus the estimated pile capacity will be far of the real. This issue made the need to study the pile capacity at unsaturated condition and compare it with saturated condition. This study is performed to investigate the behavior of single pile inserted in clay soil at different degrees of saturation. The test was performed under axial compression loads by using different degrees of saturation (100,80,60,40%). A pile of 14x14 mm cross section with different slenderness ratios (L/D) (24,30,36) employed in the study. The impact of saturation degree, matric suction and slenderness ratio on pile load capacity is examined. The results illustrate that pile capacity influenced considerably by the saturation degree, matric suction, and slenderness ratio. The results showed that when saturation degree reduced from 100% to (80,60,40%), bearing capacity of pile increased for all L/D used. An example ultimate capacity of pile with L/D (24) increased (380, 512, 63%) by de-creasing degree of saturation from 100 % to(80 ,60 ,40%) respectively, this means the pile capacity increased about four times by decreasing Sr. from 100 % to 80 % , five times by decrease Sr. from 100% to 60 % and little increase (63 %) in pile capacity by decreasing Sr. to 40 %.A close results had been observed at L/D 30 and 36. The effect of increasing slenderness ratio had been studied at different saturation degrees, an ex-ample by increasing L/D from 24 to 30 pile capacity increased (11.45, 10.2, 25, 32.5%) at Sr.(100 ,80 ,60 ,40%) respectively.

A maximum power point tracking (MPPT) control procedure constructed based on the Artificial intelligence optimization algorithm is proposed. A mathematical model of photovoltaic cells was established under varying light intensity and ambient temperature. Maximal power tracking control for iterative search using an artificial intelligence (AI) optimization technique Excellent, the artificial intelligence-based MPPT algorithm's principle is presented. Simulation results it shows that the artificial intelligence algorithm can faster and exactly track the maximum power point and remains stable, and compared to Perturb and Observe algorithm under dynamic shadow conditions and artificial intelligence MPPT control method, which has higher tracking accuracy and faster convergence speed. Faster and smaller oscillation amplitude, which is the best response to sunlight conditions for photovoltaic maximum power point tracking technology Flexibility. Using Matlab/Simulink software to build a simulation model of an independent photovoltaic system. It controls variables by keeping the temperature continuous and changes the light intensity to simulate different lighting environments. The identical comparison was conducted between all based MPPT methods such as the fuzzy control approach, demonstrating that the fuzzy control based technique exhibits higher results in terms of efficiency.

This study focuses on creating and analyzing pentagonal microstrip patch antenna arrays with one, two, and three elements for use in the 10 GHz X-band range, utilizing a metamaterial (MTM) superstrate technique. The MTM superstrate, composed of open circular ring cells, is tailored for a 1×2 array with a 10×8 cell arrangement covering an area of 45×36 mm². A 1×3 array has a 14×12 cell configuration spanning 63×54 mm². Positioned beneath the radiating elements and optimized with a quarter-wave transformer for impedance matching, the superstrate significantly enhances antenna performance. The MTM superstrate alters the radiation pattern and increases the gain by approximately 2 dB, demonstrating a gain improvement of around 27% for high-gain applications in the X-band frequency range. For the 1×2 array, the gain increases from 7.52 dB to 9.58 dB, representing a 27.38% improvement, while the input reflection coefficient improves from -48.6 dB to -58.068 dB, reflecting a 19.5% enhancement. Similarly, for the 1×3 array, the gain rises from 9.69 dB to 11.6 dB, showing a 19.73% increase, and the input reflection coefficient improves from -57.46 dB to -60.64 dB, indicating a 5.54% improvement and a good radiation efficiency of about 79.11%. This work involves designing and simulating the proposed antenna arrays using the Computer Simulation Technology (CST) software.

The main goal of this study is to improve the mechanical properties of low-alloy steels using an austempering heat treatment that involves combined molten bismuth and gallium (Bi-Ga) alloys. The cooling media is an alternative to the salt media, which is commonly used for austampering heat treatment. The steel was maintained at a constant temperature of 500 °C by immersing it in a cooling medium containing gallium and bismuth. The steel achieved an improvement of 229% in hardness and a 50% increase in tensile strength. Some slight decreases in thermal conductivity and diffusivity occurred as a result of the development of bainite in austempered steel, which affected the thermal behavior of the material. Through the process of bismuth diffusion into the steel grains, phase hardening was improved. To accomplish this, maintaining carbide stability and encouraging uniform carbon distribution were key. 500 °C was the best choice for austempering, where improved mechanical qualities were equally balanced. With its enhanced tensile strength, lightweight applications are now within reach, and the steel's enhanced hardness makes it perfect for uses requiring high durability and resistance to wear. This research emphasizes the potential of molten Bi-Ga austempering to enhance the performance of low-alloy steel across several industrial applications.