Journal of Engineering

This study aims to optimize the friction stir welding (FSW) parameters for joining 7075-T6 aluminum alloy using the Taguchi technique based on ultimate tensile test results. An orthogonal array of L9 (3^3) was used, considering three factors: tool shape (cylindrical thread flat end, cylindrical thread round end), thread pitch (0.8, 1, and 1.2 mm), and shoulder-workpiece interference depth (0.25 mm). The results showed that the optimal parameters were a cylindrical thread flat end pin shape, 1.2 mm thread pitch, and 0.25 mm shoulder-workpiece interference depth, achieving a welding efficiency of 93.3% based on the ultimate tensile stress. The study concluded that the Taguchi technique is effective in optimizing FSW parameters to achieve high welding efficiency.

Composite materials are widely used in engineered assets such as aerospace structures, marine, and air navigation due to their high strength-to-weight ratios. Detection and identification of damage in composite structures are crucial for monitoring and repairing structural systems during service to avoid instantaneous failure. Effective cost and reliability are essential during the detection process. The Lamb wave method is an effective and sensitive technique for detecting tiny damage and can be applied for structural health monitoring using low-energy sensors. It provides valuable information about the condition of the structure during its operation by analyzing the propagation of the wave in the plate. This paper presents the results and conclusions of a theoretical, numerical, and experimental study of this method used for damage detection in five-layer fiberglass/polyester composite laminated plates. The fiber layer type is plain woven (0°/90°). Numerical analysis was carried out using FEM with ABAQUS software for intact and cracked test specimens with various boundary conditions and excitation frequencies. The results obtained were confirmed experimentally using piezoelectric wafer transducers (PZT) as actuators and sensors for both cases of experiments, showing good agreement between experimental and numerical results.

To decrease the dependency of producing high octane number gasoline on the catalytic processes in petroleum refineries and to increase the gasoline pool, the effect of adding a suggested formula of composite blending octane number enhancer to motor gasoline composed of a mixture of oxygenated materials (ethanol and ether) and aromatic materials (toluene and xylene) was investigated by design of experiments made by Mini Tab 15 statistical software. The original gasoline before addition of the octane number blending enhancer has a value of 79 research octane number (RON). The design of experiments which study the optimum volumetric percentages of the four variables, ethanol, toluene, and ether and xylene materials leads to 30 experiments. The results obtained show that RON can reach a value of 103.1 (30.5% RON improvement) when a formula of composite octane number blending enhancer containing a volumetric percentage of 15, 25, 25 volumetric percent of ethanol, toluene and xylene respectively. The cost study in comparison with the price of high octane number gasoline sold in Iraq show that this formula has a high cost of 2050 Iraqi Dinar (IQD)/liter gasoline, while the formula of composite octane number blending enhancer containing 15% volumetric percentage of Ethanol only leading to gasoline of 89.6 RON (13.4 % ON improvement) gave minimum cost of 300 IQD / liter gasoline for the blend of octane number enhancer making the total price of the gasoline to be competitive with the high ON gasoline imported from outside Iraq. While the formula of 7.5, 12.5, 37.5 and 5% volumetric percentage of ethanol, toluene, xylene, and ether respectively have a maximum cost of 2525 IQD of produced gasoline of 101.3 RON (octane number improved by 28.23%).

The Fao region is characterized by weak soft silty clay to clayey silt thick layer which extends to a depth of about 20 m. The construction of some structures on such soils may need piles. During the installation of driven piles, the soil geotechnical properties are exposed to significant changes due to shearing under large shear strains. These changes significantly decrease the shear strength of the virgin soil due to the destruction of soil structure caused by remolding. The degradation of shear strength is usually followed by strength regaining, which is called “Thixotropy”. In this study, the thixotropic effect on Fao clay was investigated. Many disturbed and undisturbed soil samples were brought from the Fao region. Some of the soil samples were thoroughly remolded in the laboratory in their natural water content and molded as direct shear specimens. More than 180 specimens were prepared and tested over 36 weeks to accurately assess the percentage of strength regaining with time passing. The results show that soil remolding causes about a 45% reduction in shear strength compared to the shear strength of the intact soil. This reduced percentage in shear strength was almost fully regained after 25 weeks due to the thixotropic effect.

This study aims to find the effect of water-cement ratio on the compressive strength of concrete by using ultrasonic pulse velocity test (UPVT). Over 230 standard cube specimens were used in this study, with dimensions of 150mm, and concrete cubes were cured in water at 20 °C. Also, the specimens used in the study were made of concrete with varied water-cement ratio contents from 0.48 to 0.59. The specimens were taken from Diyarbakir-Turkey concrete centers and tested at the structure and material science lab, civil engineering, faculty of engineering from Dicle University. The UPV measurement and compressive strength tests were carried out at the concrete age of 28 days. Their UPV and compressive strength ranged between (3.89-4.66km/s) and (17.74-40.56MPa) respectively. The experimental results showed that although the UPV and the compressive strength of concrete are related, also, the UPV and compressive strength have a relation with the rate of the water-cement ratio of concrete.

In this paper, the computational complexity will be reduced using a revised version of the selected mapping (SLM) algorithm. Where a partial SLM is achieved to reduce the mathematical operations around 50%. Although the peak to average power ratio (PAPR) reduction gain has been slightly degraded, the dramatic reduction in the computational complexity is an outshining achievement. Matlab simulation is used to evaluate the results, where the PAPR result shows the capability of the proposed method.

Postmodern arguments formed a critical case of what modernity brought on several levels. Postmodern practice was considered a proactive case having amorphous concepts and features to what entailed as intellectual trends postmodern philosophically and intellectually. However, what postmodernism architecture brought in its essence was not isolation from the intellectual context and entrepreneurship case, and it was not disconnecting from the intellectual and philosophical era of that period. Literatures and philosophical arguments precede what Robert Venturi and Charles A. Jencks had brought, albeit it was closer to critics and correcting the path of modernity from crystallizing a direction that exceeds modernity to what follows. In this context, the research's aim was determined by investigating the philosophical depth and intellectual arguments for postmodernism, and their implications in architectural practice compared to the philosophical narratives, and then determining the reflection of that in the architectural technology practice. The research was initiated to discuss the intellectual foundations of postmodernism by discussing the philosophical propositions constitutive and crystallized, first. Then, it discussed the propositions of postmodernism in architecture, and the presence of thought in technological practice as influential and affected. The research reached the most important general and particular conclusions of the postmodern trends and their reflection in architecture, and then reached the comparative conclusions for each of the philosophical and architectural propositions, determining a reflection of all that in the architectural technological practice directions.