Al-Qadisiyah Journal for Engineering Sciences

Visible light communication (VLC) has gained attraction for its use in high-speed wireless connectivity leveraging LED lighting elements. Orthogonal Frequency Division Multiplexing (OFDM) is an attractive modulation scheme due to its spectral efficiency and resilience to multipath distortion. However, the nonlinear electro-optic transfer characteristics of optical components introduce signal clipping and quantization noise which corrupt OFDM signals. This paper provides an in-depth analysis of clipping and quantization noise to quantify the impact of LED nonlinearities on OFDM-based VLC system performance. Detailed mathematical models are derived for clipping distortions caused by LED optical power saturation and quantization errors from ADC/DAC finite precision in the modulator and driver circuitry. This analysis is quantified through simulations of the degradations in terms of error vector magnitude (EVM), signal-to-noise ratio (SNR) loss, and bit error rate (BER) under varying clipping ratios and quantization bit-depths. The 16-QAM OFDM transmission shows that the LED driver should possess at least 12 dB signal linear dynamic range and 3-bit quantization to restrict SNR penalty within 3 dB. Adaptive tone mapping and digital pre-distortion techniques are examined to compensate for intensity distortions enabling high-speed OFDM transmission over VLC links.

Adsorption behavior can be determined using different essential studies such as adsorption isotherm, kinetics, and thermodynamics. In this study, adsorption isotherm models, and kinetic, and thermodynamics studies are used to describe the use of alumina as an effective adsorbent and a remover of vanadium (V+5) ions from aqueous solutions contaminated by this metal. The aqueous solutions used simulate the wastewater of most traditional oil refineries. Efficiency can be determined by comparing the correlation coefficients of the linear relationships used with each model. Using alumina, the perfect removal of vanadium ions was achieved. Vanadium removal increases with an increase in the operating conditions, which are time temperature, agitation speed, pH, and adsorbent’s media dose. However, it also increases with the elimination of the initial concentration. This study shows that the vanadium’s adsorption based on the Langmuir isotherm model gives a correlation coefficient of 0.9999, while when it is based on the Temkin and Freundlich isotherms the correlation coefficient is less. Hence, adsorption on the surface of alumina takes place in monolayer surfaces with a regular distribution of particle’s binding energy and a narrow quantity of identical sites on the surface of alumina. Subsequently, the kinetic study shows that the adsorption behavior matched the pseudo-second-order kinetic model with R2 equaling 0.9999. Also, thermodynamics studies approves that the adsorption is a spontaneous endothermic process of enthalpy change.

Load balancing in internet services acts as a reverse proxy to distribute network bandwidth or application traffic across multiple servers. To decrease the internet route cost and to make the network intermediate devices more intelligent distance, number of hops, bandwidth capacity, equipment maintenance, power consumption ...etc must be considered. .. The aim is for the devices to have self-decision: acting upon data found in the network and transport layer protocols (Internet Protocol IP, Transmission Control Protocol TCP, File Transfer Protocol FTP, User Datagram Protocol UDP), and delivering the services to the secondary internet (wireless or optical fibers) ISPs. To achieve this target, the use of an operation research algorithm, such as linear programming, has been proposed to solve the problem of minimizing transport and distribution costs by developing and overcoming the transmission load cost of the path selection. The proposed EWRRLB (Efficient Weighted Round Robin Load Balancer) will assign different costs to each internet connection based not only on its capacity or priority but also on the cost of transmission paths. This allows load balancers to allocate the best economic path and the share of the bandwidth to certain connections.

This work employs partial and non-OH models to mimic 2D steady-state spray combustion. The study examines the status of the partial OH model following the NOx forecast, comparing it to the non-model. It assumes that the O model is in equilibrium with the predicted NOx. The study assesses the numerical models by using data from Mao et al. (35). This study used n-pentane as the fuel and ambient air as the oxidant in a turbulent flame characterized by non-premixed combustion. The mixture fraction-probability density function model is used to solve chemical kinetics. Fluent 15.0 software performs numerical simulation of two-phase flow and combustion modeling for pollutant formation. The k−ε turbulence model was used to solve the conservation equations for mass, momentum, and energy in turbulent flow fields. A simulation was performed using a thermal NOx mechanism to compute NOx formation. This study investigated the velocity components in the gas phase, the mass fraction of NOx, the NOx rate, the turbulence kinetic energy, and the dissipation rate. Due to state stability, the instantaneous and partial OH models were equivalent, whereas the non-OH model was lower than the partial model. The NOx prediction predicted this temperature variation in response to NOx formation. The NOx mass fraction varies by 0.09% between the partial and non-OH models, and the NOx rates exhibit a 0.09% variation between these models. Across all tested domains, the non-OH model effectively decreased all variables, including NOx emissions.

This paper highlights the most significant recent developments in the scientific study of Heat sinks: thermal management components made of materials with sufficient thermal conductivity qualities. Due to the increase in operating power, speed, and the general reduction in system size, the issues of heat removal and temperature management have an increasing importance in these studies. Changing the geometry of extended surfaces, the material from which they were made, the working fluid that ran over them, and/or the dimensions of the channel, are some of the ways in which studies have been conducted. This review addresses the main recent findings in forced convection heat transfer that happens at laminar flow inside small-scale diameter channels. Recent studies indicate a remarkable enhancement through the change of Re, D, and internal geometry of the channel. The configuration of flow passages has also adopted a different passive technique to enhance thermal fluid flow.

Currently scientific research is searching for technological solutions that provide highly reliable building materials. Incorporating self-sealing agents into the design phase makes concrete more eco-friendly by reducing the maintenance processes and extending concrete\'s lifespan which decreasingthe need to produce cement and emits a lot of CO2. Consequently, this investigation describes an attempt to assess the performance of superabsorbent polymer (SAP) as a self-sealing agent. During the experimental work two different particle sizes were taken into consideration SAP1 (425–600μm) and SAP2 (> 600 μm), the ratios of SAP were 0.3%and 0.4% wt. to cementn respectively. Regular tests were performed for the pre-crack phase to generate the initial crack which started after 28 days. Two series of sealing periods wet-dry cycles ,Cy4th (8 days) and Cy10th (20 days), were taken to promote the sealing process. The DZM (Digital Zoom Microscope) system was used to detect the self-sealing phenomenon and the width of the sealing on the concrete cracks\' surface through the use of special software imaging processes. The outcomes demonstrated the positive effect of using SAP as a sealing agent as SAP2 was able to heal the crack up to 0.15mm depending on the particle’s size. Also, the percentage of partially at Cy4th was 64% compared to the other mixes.

Earthquakes are serious risks to human life and infrastructure. An earthquake\'s influence on human life and its socioeconomic consequences highlight the need to investigate and create the most efficient and easily adaptable ways for minimizing losses. The basic concept of different control mechanisms used for protecting structures from the destructive impacts of earthquakes is to dissipate the energy efficiently, therefore ensuring that the structure remains undamaged or sustains minimum damage. To achieve this purpose, the passive control mechanism is a particularly suitable and reliable technology as it doesn\'t rely on external power to actively dissipate energy. The present study proposes using a passive energy dissipation device called the Yielding Shear Panel Device (YSPD) for strengthening the current steel structures. The YSPD consists of a square hollow section (SHS) that houses a diaphragm plate. The fundamental concept of the YSPD involves harnessing the lateral deformation of a steel plate to absorb and disperse the seismic energy. The Bouc-Wen-Baber Noori (BWBN) material has been used for simulating the hysteresis force-deformation relationship of YSPDs by pinching. YSPDs are simulated as spring components that connect between the beam and the V-brace. A nonlinear time history dynamic analysis was performed to assess the alteration in the structural capacity with the setting up of YSPDs. The performance of the tested structure was assessed considering story drift, story displacement, story shear, column shear, and YSPD hysteresis loops. The results indicated that YSPD installation has improved the structure\'s capacity. However, the use of dampers resulted in significant drift in all stories, a reduction in total floor displacement, and a decrease in the shear force of the stories. However, the results demonstrated that the YSPD dampers effectively absorbed energy and exhibited stable hysteresis loops.

Induction motors (IMs) with varying torque-speed characteristics are widely employed in various industrial applications. However, designing an efficient induction motor requires some of the main parameters of the motor (torque, speed, and efficacy) to beinvestigated and optimized. Furthermore, due to the significant influence of the rotor slot configurations on the electromagnetic torque-speed envelope, a design optimization procedure is required to optimize the induction motor\'s dynamic characteristics. In this paper, the impact of rotor slots’ geometrical modifications on the behavior of 3-phase, four poles, 36 slots, and double-layer squirrel cage IM are presented and considered as examples of optimization. Moreover, the effect of the air gap dimensionand bore diameter of the stator and rotor parts are investigated. The predicted results demonstrate that the constructed geometry of the rotor slots has an observable effect on the performance of an (IM).

This work focuses on a numerical study of natural convection of a non-Newtonian viscoplastic fluid within a cubic enclosure. The viscoplastic behavior is described by the Bingham model. The considered three-dimensional convective flow is confined within a cavity, subjected to a horizontal temperature gradient, where the vertical walls have two imposed temperatures while the rest of the walls are adiabatic. The Navier-Stokes equations, along with the mass and energy conservation equations, are numerically solved. Fluid flow and heat transfer characteristics are systematically studied over a wide range of Rayleigh number Ra (103 - 106) and Bingham number Bn (0 - 20). Finally, comparisons were made with previous results obtained in two dimensions in order to analyze the existence of a three-dimensional effect on the flow of the Bingham fluid. The results shows that the Nusselt number decreases with the increase of the Bingham number, and for the large values of the latter the heat transfer is done by conduction. It is also noteworthy that the critical Bn of the 2D model is higher than that of the 3D model, which confirms the existence of the three-dimensional effect. This is attributed to the presence of a wall along the Z axis which hinders and limits the flow of fluid within the enclosure.

This study aims to assess the potential of water hyacinth (WH) in treating wastewater and its viability for co-digestion with municipal solid waste to achieve zero waste treatment by generating methane biogas. A batch flow reactor treated wastewater, evaluating nine parameters (NO3, PO4, BOD5, Turbidity, Chromium, Cadmium, Lead, Calcium, and Magnesium). The highest removal efficiencies were observed for NO3 (94.13%), PO4 (75.85%), BOD5 (100%), Turbidity (93.86%), Chromium (94.3%), Cadmium (94.93%), Lead (91.33%), Calcium (41.42%), and Magnesium (43.13%). The pH ranged from 7.82 to 7.44. Methane biogas production was examined using anaerobic digesters with varying ratios of carbon-based waste and WH, along with pH, temperature, and total solid content variations. The optimal methane biogas production ratio was found to be 1:3 for WH and solid waste at 35°C, 10% total solids, and a pH of 7.5, resulting in the highest cumulative methane generation of 1039.80 mL/gm vs. The Gompertz model accurately described methane biogas generation with a yield of 1083.088 mL/gm vs., supported by a coefficient of determination (R2) of 0.999. The kinetics of the biodegradation process were evaluated using a first-order kinetic model. The negative value of k (-0.2364) suggests a rapid solid waste biodegradation, with a high correlation coefficient (R2) of 0.9971. Numerous correlations were employed to enhance the production of methane, yielding a correlation coefficient of 91.36%.

This study investigated the lasting influence of British colonial architecture (129 years) on contemporary building design in Aden, Yemen. The initial focus was on the perception of British Neo-Classical architecture as a symbol of superiority, overshadowing Aden's rich architectural history. This research explored Aden's architectural transformation from pre-colonial to colonial periods, analyzing the impact of colonial-era building facades on modern design practices. Through observation and interviews with built environment professionals, the study examined the broader social, political, and economic effects of British colonialism. The findings reveal a significant influence of British colonial architecture on the design of building facades in Aden. This influence is evident in structures like the repurposed church on Crater Mountain, which now serves as a government building. The influx of British administrators, soldiers, and workers from diverse backgrounds (Indian, Somali, Jewish) during the colonial period contributed to Aden's architectural diversity by constructing churches, temples, and government buildings. Unfortunately, the ongoing war in Yemen has damaged or destroyed many of these structures. This study also found that classical architectural elements from British colonial buildings like the Military Museum in Crater, the Heritage Museum, and the Tax Office continue to influence modern design. These elements and the miniature Big Ben clock in Al-Tawahi stand as prominent symbols of British influence in Aden. However, the Yemeni government's restoration efforts for these colonial-era buildings have been slow and largely ineffective. The research further explored the enduring influence of Neo-classical architectural ideals in Aden. The study highlights the formal guidelines, specific modules, and proportions used in designing arches and columns, particularly in residential buildings. These elements contribute to the aesthetic qualities of these structures. While the British incorporated classical elements during their rule, architectural advancements and new materials have led to the incorporation of novel elements in contemporary design.