Journal of Engineering and Sustainable Development (JEASD)

Beams in two configurations; uniform and non-uniform, are common structural components utilized for several engineering applications. Thus, the studies dealing with their behavior under dynamic and vibrations have been increased. In this research, the transverse vibration phenomena of pre-twisted beams were experimentally and theoretically studied by investigating the effect of twisting angles on the first three transverse natural frequencies. In the present experimental part, the pre-twisted beams are manufactured using a 3D printer, and the fundamental frequencies of manufactured pre-twisted beams are measured by a suitable rig. In the theoretical work, the finite element method is used to simulate the transverse vibration behavior of the pre-twisted beams. The accuracy of the simulation process is checked by comparison of the first natural frequencies calculated by the finite element method (using ANSYS Workbench Software) with those measured experimentally. The results show that there is an excellent agreement between the experimental results and finite element outputs. For the clamped-free pre-twisted beam, there is no critical twisting angle. The critical twisting angle is equal to the mode number for simply – simply and clamped simple pre-twisted beam. While there is more than one value of critical twisting angle for the clamped-clamped pre-twisted beam.

Air impact processes have diverse applications in engineering, including backflow welding, textile drying, and gas turbine blade and combustion liner cooling. This research examines the influence of experimental methodologies and measurement tools on convective heat transfer in adjustable air jet assemblies. The experiment involves the use of heated targets made of thin stainless steel foil with constant heat flux boundary conditions. Thermography measures target surface temperatures by analyzing how internal passage cross-flow affects convective heat transfer via outflow adjustments. The experiments involve two arrays of jet nozzles: inline and staggering, each comprising 44 impingement jet nozzles arranged in 4 rows with 11 jet holes in each row. The study presents unsteady time average local and spatial Nusselt numbers as functions of jet Reynolds number (4630-14000) and explores their dependence on the jet nozzle diameter. Cross-flow levels significantly affect spatial and local Nusselt numbers in both local and span-wise averaged values, regardless of the Reynolds number. Strong cross-flow (single configuration) distributes flow causing turbulence and uneven heat distribution, reducing Nusselt numbers. In contrast, moderate cross-flow (double configuration) improves heat transfer and increases Nusselt numbers. The study emphasizes the crucial role of experimental techniques in heat transfer evaluation and demonstrates agreement with prior studies within a standard error below 5%.

Natural woods as a raw material have been taking a considerable interest topic by industries such as the forest industry, furniture manufacturing, and nowadays suitable electronics. One of the most essential steps of manufacturing for those industry purposes is RF heating/drying of raw wood material nowadays. However, knowing the electrical properties, such as the dielectric constant of wood-based material before processing is tremendously important. It is well-known that the moisture content and density levels of material directly affect the dielectric properties. Moisture and density conditions are different in each material because it’s related directly to the absorption and affection of material towards moisture sources. Therefore, in this study of wood material under varying conditions, proper empiric models have been generated to express this relationship. This study is based on three different softwood specimens widely used in the forest industry. The dielectric properties were determined in the frequency range of 2.17 GHz-6.0 GHz as a function of moisture content and density for wood species. Each measurement contains 500 raw data points; a vector network analyzer collected 49,500 S-parameter data. Each wood specimen consists of six samples; the average of data obtained from these samples was considered as a dielectric measure for the examined wood specimen. The proposed empiric models have RMSE better than 0.05 for the relation between loss tangent and density, while the proposed empiric models for dielectric permittivity have better than 0.90 with density relation, which is considered an acceptable ratio for model generation.

As non-linear weirs with a high flow rate, Piano Key Weirs (PKWs) have attracted the attention of water engineers in recent years. Given the limited information available on the energy losses of these weirs, it is important to investigate the energy losses and discharge capacity of these weirs. In this research, two trapezoidal PKWs, i.e., type-B and -C, with a height of 0.2 m were used. The studied flow rates were 0.025, 0.03, 0.035, and 0.04 m3/s. The results showed that energy loss decreased by increasing the flow velocity and upstream depth. The average energy loss in the type-B trapezoidal PKW was about 10.9% lower than that in the type-C PKW. The type-B weir had a higher discharge coefficient of about 5.6% compared to that of the type-C weir. Finally, an equation was presented to calculate the energy loss of these two weirs with a correlation coefficient of 97.42%.

In this article, a triple-band patch antenna using a circular patch microstrip antenna is constructed with a low-profile patch antenna using a 1.5 mm thick FR4 substrate (εr= 4.3). As mobile devices like smartphones and laptops become more common, the usage of tiny, triple-band antennas has also become more common. The objective of this research is to design a circular patch antenna with a 3–11 GHz dipole-like radiation pattern, which may be used for industrial, scientific, and medical reasons. For the suggested triple-band antenna design, the slotted radiator with six arches and the reduction of the ground plane are among the components. In addition, the standard 50 Ω RF transmission line stimulates the patch antenna; this transmission line is attached to the microstrip line by an impedance-compliant SMA connection. Data from the experiments are obtained, evaluated, and compared; to the patch\'s surface current distributions, gain, and radiation patterns. According to the measurements, S11 has an impedance bandwidth in the 5.5 GHz band of less than -10 dB, 6.6 GHz band, and 10.4 GHz band at all frequencies. The superb radiation pattern performance, relatively consistent gain throughout the bands, and practical bandwidths of this antenna make it a good choice for C-band and dual X-band applications.

Epoxy resins have been the subject of many studies as a consequence of their extensive usage in recent years. The brittleness and low resistance to propagation and crack initiation of epoxy resins are well-recognized characteristics. Therefore, in recent years, experts have concentrated on increasing epoxy resin's fracture resistance. Adding inorganic nanoparticles like titanium dioxide (TiO2) TiO2, silica (SiO2), carbon black, alumina (Al2O3), and others to the polymer matrix is one of the most investigated techniques in polymer science. Despite having a modest nanofiller content, the resulting nanocomposites may enhance their thermal, mechanical, rheological, electrical, and optical characteristics. These nanocomposites are an alternative to metal-based materials. They have great promise as multifunctional materials in a range of applications, including optoelectronic devices, semiconductor devices, civil engineering, automotive, and aerospace. To show potential future directions and market prospects for polymer nanocomposites reinforced with TiO2 nanoparticles, current results, and trends have been examined and highlighted. In addition, the current review surveys many studies that highlighted using nanoparticles as reinforcement, their different structure, the interface, and the geometry and structure of the resulting nano-materials reinforced resin.

Several studies aim to reduce surface temperatures and improve the performance of hot mix asphalt. These studies have occurred to reduce the global warming phenomena and economic concerns. We're researching how organic materials affect the viscosity of modified asphalt. Asphaltan A, Asphaltan B, Asphaltan C, and T-grade are organic additives. temperatures with the asphalt binder were employed in the current study. These organic additives were used to improve the characteristics of hot-mix asphalt. In addition, it increases the durability, and lifespan of pavement and reduces mixing and compaction temperatures. A penetration grade bitumen of 40/50 was used in this study. Then, pure bitumen was added to the organic additives to modify binders containing varying concentrations of each additive. Physical properties were performance at different levels of additives. In the research, conventional bitumen/asphalt should be adjusted due to climate conditions, strong traffic loads, and growing axial loads. As a result, asphalt mixtures comprehending bitumen with a high penetration index are less prone to low-temperature cracking and irreversible deformation. Traditional asphalt studies found that bitumen samples with the softening point of warm mix asphalt additives were greater rate, and were less susceptible to temperature changes. The introduction of organic compounds increased the penetration and softening point of the asphalt substantially. This indicated that the stiffness and thermal expansion of the binder had gotten better.

Because of developments in high-power converters, it has become crucial to investigate how effective inverter performance is. consequently, via being aware of the temperature value of the junction for the inverter switch. The rise in the switching frequency of the inverter, as well as the kind of control technique used, all have an impact on the value of junction temperature. The traditional methods for determining the junction temperature are imprecise and challenging to use. Therefore, a novel approach was used in this study to compute the junction temperature in a simple manner utilizing the MATLAB/Simulation SIMSCAPE environment. The junction temperature of the inverter's switches is easily estimated, where the heat conveyed over the layers of the IGBT can be indicated by using the simple thermal model of Foster. Because the semiconductors within the SIMSCAPE environment exhibit boosted design together with a direct thermal port. As a result, the estimation of the junction temperature is more precise and direct. This feature is only openable in the newest categories of the MATLAB program (2019-2023) This paper presents the losses formed in an Insulated Gate Bipolar Transistors, and thermal behavior analysis to represent IGBT's layers. The simulation included the influence of various operating switching frequencies on the temperature value of the junction. The results show that the temperature value of the junction increases as the switching frequency value increases and the Space Vector pulse width modulation technique has a value of junction temperature lower than the Sinusoidal pulse width modulation technique at the same switching frequency.

In recent years, Fiber Reinforced Polymer (FRP) rebar has been adopted to reinforce structural concrete elements such as slabs. FRP strips are also increasingly used to reinforce or strengthen concrete members that require higher carrying capacity or to restore damaged structural elements. Therefore, the reinforcement of concrete structures with this material is increasing but the effect of variables on CFRP-reinforced concrete slabs and externally bonded with CFRP laminates has not been evaluated in detail. This study presents a numerical analysis of the structural performance of concrete slabs reinforced by CFRP bars and strengthened by CFRP laminates using a finite element approach with ANSYS software. Six models with the same geometry (1550x1550x100 mm) were analyzed. Four models were reinforced with CFRP bars and externally strengthened with CFRP laminates, one model was reinforced with CFRP bars without external strength, and one reference model with traditional reinforcing bars (control specimen). Different parameters were adopted, such as amounts of FRP bars and CFRP laminates layout in which some models contained both CFRP bars and CFRP laminates. A uniformly distributed load that was calculated by plastic analysis was applied at the top surface area of each model. The plastic load considers the contribution of the laminated CFRP strips that increased the strength of the slab. Analysis results in the maximum strength carrying capacity in equivalent CFRP bars exhibit higher strength percentages of 5.07% of load capacity but differed in mode of failure than conventional reinforcements control slab.

The present work provides an experimental study for preparing eco-friendly geopolymer mortar based on ground granulated blasted furnace slags with good mechanical properties and durability. This work studied the effect of silica fume reactive powder as a replacement material for slag weight with constant weight ratios of 20% on geopolymer mortar’s mechanical tests. The geopolymer mixtures were prepared with (15M) NaOH solution and a (2.5:1) ratio of (Na2SiO3/NaOH). The samples were cured at ambient conditions at different times of 7 and 28 days and a high temperature of 70°C in a furnace for three hours. It was found from the obtained results that silica fume played a vital role in improving all these properties by enhancing the degree of the silicate ion geopolymerization reaction in the alkaline solution. In addition, the curing process greatly impacted the geopolymers’ features. The properties improve significantly with increasing the curing time and temperature, especially when cured at high temperatures, compared to ambient curing.