Scopus Research — Prof. Dr. Salwan Obaid Waheed Khafaji

This research examines the incorporation of thermoelectric generators (TEGs) into the exhaust systems of internal combustion engines to recover waste heat. The study employs a three-cylinder Yanmar diesel engine to evaluate the energy conversion efficiency of two layers of TEGs placed between a brass heat exchanger (HEX) and aluminum water coolers. As the author's knowledge is applied for the first time, a new zigzag HEX, new cooling blocks, and a new high-voltage Canadian (TEG1-24111-6.0) enhance thermal performance. Simultaneously, the cooling system maintains a consistent temperature gradient across the TEGs. Experiments were performed using thirty bismuth telluride-based TEGs connected electrically in series, yielding a peak gross power output of 259.01 W at 2400 rpm under steady-state conditions. The research analyzed five engine scenarios with varying running speeds (1900, 2000, 2125, 2250, and 2400 rpm) and load conditions. Results highlight the significant influence of engine speed, HEX design, and cooling efficiency on TEG performance. It was concluded that the engine brake specific fuel consumption with TEG integration is lower than that of the engine lacking TEGs, approximately 2.317 % at 2400 rpm. © 2025 Elsevier Ltd

In this paper, a method of controlling a MR fluid brake by simultaneously altering both the input current to the electric coil, and the MR fluid thickness between the stationary and rotating part of a single-disk brake was presented. In the development of the nonlinear torque-model for the brake, nondimensional analysis was used to generalize the problem for any brake configuration with similar attributes, while providing design guidance for making the energized and non-energized brake components comparable in strength. In order to control the brake speed, two saturating proportional-integral (PI) controllers were used in parallel: one for adjusting the MR fluid thickness, and the other for adjusting the input current to the electric coil. It was shown in this paper that the controller always achieves a steady-state output with zero error; however, the combination of fluid thickness and current is non-unique and depends upon initial conditions and saturation events that occur during the transient response. In conclusion, the control method proposed in this paper is shown to extend the range of torque capacity for the brake without increasing the radial envelope for the brake itself. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2025.

Integrating renewable energy with biomass valorization offers a scalable pathway toward circular and climate-resilient campus operations. This study presents a replicable model implemented at Alanya Alaaddin Keykubat University (ALKU, Türkiye), where post-consumer food waste from 30 cafeteria menus is converted into pet food and compost using a 150 L ECOAIR-150 thermal drying and grinding unit powered entirely by a 1.7 MW rooftop photovoltaic (PV) system. The PV infrastructure, established under Türkiye’s first public-sector Energy Performance Contract (EPC), ensures zero-electricity-cost operation. On average, 260 kg of organic waste are processed monthly, yielding 180 kg of pet food and 50 kg of compost, with an energy demand of 1.6 kWh h−1 and a conversion efficiency of 68.4%, resulting in approximately 17.5 t CO2 emissions avoided annually. Economic analysis indicates a monthly revenue of USD 55–65 and a payback period of ~36 months. Sensitivity analysis highlights the influence of input quality, seasonal waste composition, PV output variability, and operational continuity during academic breaks. Compared with similar initiatives in the literature, this model uniquely integrates EPC financing, renewable energy generation, and waste-to-product transformation within an academic setting, contributing directly to SDGs 7, 12, and 13. © 2025 by the authors.

Strengthening process of Al-Mg-Ag alloys after thermo-mechanical processing is important for enhancing the mechanical properties of alloys that used in automotive and aerospace and applications. Understanding how silver affect mechanism of strengthening allows for the development of stronger and lighter materials, enhancing the durability and performance in demanding environments. This study investigates the influence of silver content (0.75%, 1%, and 1.5%) and thermo-mechanical processing parameters on the mechanical properties and fracture behavior of Al-Mg-Ag alloys. Through systematic experimentation, the effects of cold rolling and aging treatments at various temperatures (150°C, 180°C, and 210°C) and durations (6h, 12h, and 24h), were examined. The results demonstrated that the optimal mechanical properties were achieved with 1.5% Ag content aged at 150°C for 24 hours, yielding an ultimate tensile strength of approximately 310 MPa while maintaining reasonable ductility. The fractographic analysis showed different failure mechanisms across different processing conditions: the rolled specimens showed characteristics of the predominantly brittle fracture, while aged specimens and solution-treated showed the main features of the ductile. The advancement in mechanical properties is attributed to the effective Orowan strengthening through the finely dispersed precipitates formation, whose morphology and distribution are significantly affected by both processing parameters and silver content. These results provided valuable insights into the optimization methodologies of Al-Mg-Ag alloys for structural applications that require high strength-to-weight ratios. © 2025 The Author(s). Published by Cefin Publishing House.

Latterly, a variety of researches have been concentrated on developing and utilizing leg exoskeletons to serve and assure recuperation for people with mobility challenges. Commonly, both linear and nonlinear techniques are applied to adhere to the intended trajectory. Alternatively, this work has advocated a new analytical approach to guide and refine patient movement using Fourier series function. The hip and knee joint angles are described by a combination of sine and cosine functions, each joint is described by 8 coefficients, leading to a total of 16 coefficients. The coefficients are computed to ensure the boundary conditions at the start, midpoint, and end of the run time. Next, the hip and knee torques are obtained using the proposed Fourier series function to steer the leg’s movement, guaranteeing it tracks the predefined references trajectories. The leg’s dynamic model is tested using Monte Carlo method under broad set of operational conditions. The knee joint displayed a maximum velocity of (1.92 rad/s) and a frequency of about 1.86 Hz while the hip joint recorded a maximum velocity of (0.82 rad/s) and a frequency of about (0.93 Hz). In addition, the observed maximum torque at the hip joint was determined as (89 N·m) while at the knee joint it was (39 N·m). These results illustrated that the proposed approach effectively directs the patient readily, reliably, and with high stability despite a broad range of patients features. © (2025), (Perm National Research Polytechnic University). All rights reserved.

In this study, experiments are used to evaluate the effectiveness of dynamic vibration absorbers (DVAs) in minimizing vibrations in beam structures. The dynamic vibration absorbers are modest additions to a structure that employ a mass-spring system tuned to the natural frequency of the structure to lower vibration levels. These absorbers were added to a beam construction as part of the experimental investigation, and the vibration levels under various conditions were measured. Under pinned-free boundary, the dynamic behavior of a beam is experimentally investigated with various combinations of the design parameters (mass and spring) and locations of the dynamic vibration absorbers. The beam is subjected to external vibrations, and both with and without the absorbers, its amplitude is measured. According to the results, adding DVAs to the beam structure significantly reduced vibration levels, particularly closer to the natural frequency of the beam. The dynamic response is greatly reduced by mass and stiffness (from, for example, 0.018m to 0.00052m). However, depending on the DVA location, this effect can change. The minimal requirements of the DVA parameters can better reduce the dynamic response if the DVA is positioned at the point of maximum displacement for each corresponding mode. © 2025 Penerbit UTM Press. All rights reserved.

The prolonged sitting for disabled patients can cause several health problems such as muscle wasting, bedsores, and pain. The majority of these disabled people are paraplegic patients that the activities of their muscles can effectively increase due to knee position training. In this work, a new analytical methodology for controlling the human knee position is emphasized. The knee angle profile is parameterized using seven-term exponential function. These seven coefficients are computed by fulfilling the initial and final states for knee angle, knee velocity, and electrical torque. Then, the analytical pulse width will be used to simulate the nonlinear knee dynamic system achieving the steady-state knee position with fast settling time (0.48 sec) and small overshoot (3.22%). Eventually, the introduced algorithm is confirmed in the presence of initial knee angle dispersions using Monte-Carlo simulation method. As a result, the nonlinear analytical control is successfully able to steer the human knee angle from the initial state to the desired state shortly with maximum overshoot of about 6.8% while including a wide range of initial knee angle deviations. © 2024, Cefin Publishing House. All rights reserved.

A new motion control system for a hydraulic rotary actuator was designed in this work. The hydraulic fluid that goes to the actuator was used in a variable displacement pump to control the actuator movement. A mathematical model was conducted and the stability and performance of the open loop system were studied. Routh–Hurwitz stability criterion was implemented to assess the system stability which showed that the system is stable as long as realistic parameters are chosen for the design. Since the open loop system showed poor performance, PID and H-infinity controllers were considered to improve the system overall performance. Multiplicative uncertainty was considered in the H-infinity design process to ensure that the system responds well when uncertainties in the system parameters exist within a specified range. The leakage and friction coefficients are the parameters that were considered uncertain due to their expected change with time. The uncertainty was considered in the viscous friction and the leakage coefficients within a range of ±3%. The results showed that the open system has about 20% percent overshoot, 10% steady state error for a unit step input signal and a poor disturbance rejection. The system with both H-infinity and PID controller has no steady state error and a low settling time which is about 7 time constants (6.3 ms). The H-infinity controller provides the least percent overshoot in response to the unit step input signal, 4% compared to 10% for the PID controller. In addition, the H-infinity controller provides faster response and better disturbance rejection characteristics. Finally, only the H-infinity controller meets the robustness requirements. © 2024, Cefin Publishing House. All rights reserved.

The efficiency of dynamic vibration absorbers (DVAs) in reducing vibrations in beam structures is experimentally assessed in this research. The dynamic vibration absorbers are small devices added to a structure, that use a mass-spring-damper system calibrated to the natural frequency of the structure to reduce vibration levels. The experimental examination included the addition of these absorbers to a beam structure and the measurement of the levels of vibrations under various circumstances. The dynamic behavior of a beam is examined experimentally under two boundary conditions (pinned-free, cantilever), with different configurations of the dynamic vibration absorbers' design parameters and placements along the beam. External vibrations are applied to the beam, and their amplitude is measured both with and without the absorbers. Investigations are conducted on the effects of the absorber's mass, stiffness, and locations. The findings demonstrated that adding DVAs to the beam structure greatly reduced vibration levels, especially at the beam natural frequency. Both mass and stiffness significantly reduce the dynamic response (from, for instance, 0.018m to 0.00052m). However, this effect changes based on the boundary conditions. If the DVA is situated at the point of maximum displacement, the minimal needs of the DVA parameters can better reduce the dynamic response. © 2024 Author(s).

The natural convection of nanofluid flow, which occurs between a sinusoidal-corrugated enclosure and a concentric inner cylinder has been numerically investigated. The two horizontal walls of this enclosure are considered adiabatic and two vertical corrugated walls are held at a constant value of the cold temperature while the inner concentric cylinder is heated isothermally. Different cylinder geometries (i.e, circular, square, rhombus, and triangular) located inside the enclosure are examined to find the best shape for optimum heat transfer. The physical and geometrical parameters influencing heat transfer are Rayleigh number (Ra=103-106), undulation numbers (N=0,1 and 2), aspect ratios (AR=5, 2.5 and 1.67) and two values for the volume fraction (φ=0 and 0.05). The numerical simulation was carried out using Comsol Multiphysics Software (5.3a). Galerkin approach along with the finite element method are used to solve equations of Navier-Stokes and energy with associated boundary conditions. In this study, validations of results between some available literatures and the present study found to be in an excellent agreement. Results indicate that the heat transfer and nanofluid flow characteristics in the sinusoidal-corrugated enclosure is significantly influenced by aspect ratio, undulation number, and Rayleigh number for all cylinder shapes. Thus, with the decrease in the aspect ratio, the intensity of streamlines becomes smaller, whereas, with rice in the Rayleigh number and undulation number, intensity increase is observed. Moreover, as the undulation number increases, the average value of the Nusselt number, including the hot surface of cylinders increases. At high Rayleigh numbers, the undulation number effect on the average value of the Nusselt number is more pronounced. Besides, the research showed that the circular cylinder shape inside the enclosure has the best heat transfer characteristics and flow than the others. © 2021, Global Digital Central. All rights reserved.