International Journal of Engineering
Volume:35 Issue: 12, Dec 2022

This paper presents a acomprehensive design and control strategy for a photovoltaic (PV) energy storage system. The system consists of a 2kW photovoltaic system, two converter circuits, a resistive load of 6 Ohm and a lithium-ion battery storage integrated with DC Bus applying constant power to the resistive load. This scheme offered two converter topologies, one is a boost converter and another is a DC/DC bidirectional converter. The boost converter is directly connected in series to the PV array whereas the bidirectional DC/DC converter (BDC) is connected to the battery. The boost converter is used to regulate the maximum power point tracking (MPPT) of the PV array. Closed-loop control of the bidirectional controller is implemented with Takagi-Sugeno Fuzzy (TS-Fuzzy) controller to regulate the battery charging and discharging power flow. The proposed scheme provides a good stabilization in the DC bus volatge. Simulation results of the proposed control schema under MATLAB/Simulink are presented and compared with the Proportional Integral (PI) controller. The simulation results obtained from MATLAB are verified on Real Time Digital Simulator (RTDS).

The effect of installation depth and height of the incident wave on the hydrodynamic and economic performance of an oscillating wave surge converter (OWSC) wave energy converter is crucial. In this study, an OWSC by considering 1:8 scale has been studied under Caspian Sea wave conditions for 8 water depths from the semi-submerged to fully submerged. The study has been conducted to achieve the best draft ratio and evaluate the systems performance imposed to Caspian waves condition by experimantal method.The results are presented in three parts. The first part studied the converter's flow, power, and sensitivity to the installation depth on a laboratory scale. In the second part, the system results were converted to the main scale 1:8 by using Froude scaling method, and finally, the performance from an economic view evaluated. Results showed that the draft depth has a non-linear effect on the power. System’s power in the dimensionless draft depth of 0.59 is better, and can produce 61 kW. Also, it can pump up to 50 l/s of water. Likewise, suppose the system is used for electricity generation, In that case, it sells $22500 of electricity to the grid annually, and if it is used as a pump, it can supply water to 4710 households on average.

This study investigated the effect of temperature changes on different logarithmic surfaces. One-dimensional heat transfer was considered. The heat generation source term is added to the governing equations. Most scientific problems and phenomena such as heat transfer occur nonlinearly, and it is not easy to find exact analytical solutions. Using the appropriate similarity transformation for temperature and the generation components causes the basic equations governing flow and heat transfer to be reduced to a set of ordinary differential equations. These equations have been solved approximately subject to the relevant boundary conditions with numerical and analytical techniques. According to the given boundary conditions, Collocation, Galerkin, and least squares methods were used to find an answer to the governing differential equations. The validation of the present techniques has been done with the fourth-order Runge-Kutta method as a numerical method. The temperature profiles for different values of β and α have been obtained. The results showed that the proposed methods could consider nonlinear equations in heat transfer. Therefore, the results accepted by current analytical methods are very close to those of numerical methods. Comparing the results provides a more realistic solution and reinforces the conclusions regarding the efficiency of these methods. Furthermore, changes in temperature profiles occur with decreasing and increasing β and α numbers.

Continuous improvement in the friction stir welding process (FSW) is still growing to improve the process capabilities and overcome certain drawbacks encountered in the process. Low welding speeds, high welding loads, and high torque needed are the main limitations of this process. Applying ultrasonic vibration is one of the versatile approaches that was proposed to tackle these issues. In this paper, a comparative study between the conventional friction stir welding process (CFSW) and the ultrasonic-assisted friction stir welding process (UAFSW) was conducted. The objective is to evaluate quantitively and qualitatively the influence of ultrasonic vibration waves on the weld surface quality, tensile strength, micro-hardness, microstructure, and weld formation of the joints. The results have demonstrated that ultrasonic vibration waves cause grain refinement action by 23.6% at the stirring zone (SZ) as well as its desirable role in enhancing the mechanical properties by a percentage up to 15% for ultimate tensile strength and eliminating weld defects, especially at high welding speed (120 mm/min). However, no profound effect was found for ultrasonic waves on the grain size in the thermomechanical affected zone (TMAZ) or the heat-affected zone (HAZ). A considerable reduction in the elongation % whether in CFSW or UAFSW compared to that of base metal was detected.

The way a wave behaves, while propagating across a medium, varies with the wave type and the medium. So, knowledge of the behaviour of a wave in a system with a different form of damage, and behaviour of different types of waves in a particular system is an essential prerequisite for almost all activities in structural system identification and mainly for damage detection and localization of damage. This paper presents a comparative study of various wave propagations, that has been done by researchers in various structural systems. Further, a numerical model of an isotropic plate using finite element is created both with and without damage. The behaviour of waves has been studied. Finally, the comparative result is shown. This paper offers a new perspective for ongoing research by providing the most recent developments, difficulties, and prospects of wave propagation behaviours for damage detection and localization in the commonly used structural systems and structural elements. While propagating through different structural systems and components, the most used waves, which are (a) Shear wave, (b) Rayleigh wave, (c) Ultrasonic wave and (d) Lamb wave, have been thoroughly investigated. Along with several difficult problems for future growth, the summarized observations are provided.

Drag is one of the main factors in improving fuel efficiency. Various study in regards to improve drag performance of a planing hull amongst them is a stern flap. The main parameters to design a stern flap are span length and angle of stern flap. The stern flap works by changing pressure distribution over the ship's bottom and creating a lift force on the stern transom part. This study aims to analyze the behavior of stern flap in variations of span length and angle of stern flap towards drag performance of Fridsma hull form. Finite Volume Method (FVM) and Reynolds-Averaged Navier - Stokes (RANS) are used to predict the hull resistance during simulations. Results show that shear drag is very sensitive towards the total drag value, proving that shear drag valued at least 60% of the total drag in each planing hull multi-phase characteristics phase. Stern flap with 58% of hull breadth span length installed at 0° is considered the most optimal, reducing 10.2% of total drag, followed by 18% displacement reduction. In conclusion, the stern flap effectively improves the Fridsma hull’s total drag and its components on 0.89 < Fr < 1.89.

The main goal of this work is the mitigation of inrush current in a three-phase transformer. This inrush current appears when energizing a no-load or lightly loaded transformer. It can reach very high values and can cause failures in the electrical system. The control strategy is achieved by considering the value of the residual flux when the transformer is de-energized as well as by respecting the phase shifting between the three phases. To measure the inrush current, an experimental configuration with a data acquisition system using dSPACE 1104 card was developed and is presented in this paper. A technique to control the circuit breaker for energizing a 2 kVA three-phase transformer without the appearance of inrush current was also tested and applied in the experimental setup. The specific contribution of this work is that this technique is applied in the measurements with a thorough investigation of the residual flux. The proposed technique achieved complete elimination of the inrush current.

Pedestrian safety at signalized intersections is a major cause of concern all over the world. Properly marked crosswalk enhances the safety of pedestrians as it is a well recognized crossing location by drivers. However a large number of accidents are reported at intersections predominantly due to the violation behavior of pedestrians. This study aims at understanding the crosswalk utilization behavior of pedestrians at urban signalized intersections. Data was collected through video recording and a questionnaire survey. Significant variables were identified and modelled using binomial logistic regression. Pedestrian personal level factors were found to significantly affect crosswalk compliance. Discrepancies were identified between perception and reality, suggesting that variation exists between what people say and what they practice in reality. The findings from this study suggest that a perception based study may not be as reliable as an observational study. The findings have both theoretical as well as practical implications and would certainly help the policy makers and designers in enhanced understanding of pedestrian behavior at urban signalized intersections.

In the present paper, the numerical modelling to predict the interface damage of weld defect in a steel pipeline was studied. This work focused on determination of the maximum operating pressure and the characterisation of mechanical behaviour at a weld-base metal interface. The operating pressure can fluctuate leading to the phenomenon of fatigue and consequently to the failure of pipeline. Experimental investigations were carried out using non-destructive test (NDT) in order to locate and determine size of defects. A bilinear interface decohesion model is used to simulate the damage behaviour considering a stress-relative displacement laws. Numerical simulations based on the finite element method were used to study the influence of size defects and young's moduli ratio on the operating pressure as well as interfacial damage between the weld and base metal. The obtained results showed that the interface damage depending on shape and material properties of defects has an impact on pipeline safety and integrity.

Bismuth-doped zinc oxide (ZnO) nanoparticles can serve as efficient photocatalysts for various reactions. Herein, we synthesized and discussed the growth mechanisms of Bi-doped ZnO nanoflakes using co-precipitation with Bi concentrations ranging from 0 to 3 %. The resulting ZnO were hexagonal nanosheets with diameters ranging from 80 nm (ZnO) to 200 nm (ZnO: Bi 3%). The dominant crystal structure matches hexagonal wurtzite with a small presence of Bi2O3 diffraction peaks. The estimated crystallite sizes range from ~ 33 nm to ~ 45 nm, indicating multiple crystalline regions in each nanoflake. Nevertheless, as sheet resistance monotonically decreases with the Bi concentration, the higher number of grain boundaries likely has a lower effect on the conductivity compared to an increase in free carriers and larger grain size in the samples with higher Bi concentration. The bandgap decreases from ~ 3.13 eV to ~ 2.96 eV, likely due to the shrinkage effect from electron-electron or electron-impurity interaction that lowers the conduction band of ZnO.

Soft robotics using Pneumatic Network actuators (Pneu-Net) is a developing field that has a promising future for variety of applications involving delicate operations such as biomedical assistance. The interaction between geometry and the performance of the actuator is an important topic which has been studied by many researchers in this field. However, there is a lack of investigation on the relationship between gripping capability and geometrical parameters of soft actuators. Especially, there is a need to shed more light on the effects of wall thicknesses on the gripping force developed. In the present study, a semi-cylindrical chambered PneuNet soft actuator is numerically investigated to evaluate the effects of pressure and wall thickness variations on its performance characteristics. The results revealed that increasing the restraining layer thickness (RLT) aids the bending capability of the actuator whereas increasing the chamber wall thickness reduces it. Therefore, maximum bending of the actuator is achieved at the combinations of minimum wall thickness and maximum RLT. At these geometrical configurations of maximum bending, the deformation-pressure relationships followed a sigmoidal function and tended towards linearity with increasing wall thickness and decreasing RLT. The gripping force showed an exponential increase with increasing working pressures and wall thicknesses. The maximum gripping force increased cubically with increasing wall thicknesses at their respective maximum working pressures, which was modeled using a polynomial regression model (R2=99.79%).

The vehicle routing problem as a challenging decision problem has been studied extensively. More specifically, solving it for a mixed fleet requires realistic calculation of the performance of electric and combustion vehicles. This study addresses a new variant of the vehicle routing problem for a mixed fleet of electric and combustion vehicles under the presence of time windows and charging stations. A bi-objective mixed-integer programming model is developed which aims at minimizing cost and pollution level concurrently. To accurately quantify travel quantities, such as fuel consumption, emission, and battery charge level, a set of realistic mathematical formulas are used. The model is first converted to a single-objective counterpart using the epsilon-constraint method and a simulated annealing algorithm is tailored to obtain Pareto optimal solutions. A discussion is also made on how the final solution can be selected from the Pareto frontier according to the design objectives. The presented framework can find a set of Pareto optimal solutions as a trade-off between cost and pollution objectives by considering different combinations of electric and combustion vehicles. It was shown that those solutions that involve more electric fleet than combustion fleet, lead to higher total costs and smaller emissions and vice versa.

In this study the factors that are affecting the copper nodular growth on the cathode edge were investigated from metallurgical and operation point of view. Statistical analysis was performed to evaluate the effect of operational conditions on the nodular copper growth by characterization of the nodule-containing cathodes. Besides, the effects of defects on polymer edge strips as well as changes in weight and thickness of anodes on the formation of nodules were investigated. Electrochemical galvanostatic experiments were employed to study the effect of electrolyte additives and the distance between the anode and cathode on cathode surface quality. A relatively large porosities of about 50 µm were observed in the microstructure of the cathode edge nodules. In addition, few nodule samples that were taken was observed to have a higher concentration of Fe, Cd and Pb, up to 25 ppm. Low probability (1%) in the repeatability of the nodule formation over the same position on the edge strip was approved the insignificant effect of possible edge strip defects on nodulation. The large weight variation of anodes can cause the anode thickness variation by 10 mm and consequently alter the distance between the anode and the cathode. This was shown to cause formation of nodules at the cathode edge. The peaks that were observed in the cathodic potential curves in galvanostatic tests, were believed to be the sign of nodulation and therefore was investigated further using the optical microscopic images.

In multilevel inverters, unused energies are created due to the asynchronous use of the input DC sources. when the input DC sources are replaced by renewable systems such as photovoltaic arrays, some of the input energies remain unused. This paper presents a new multilevel inverter topology that can harvest the unused energies and return them to another output which leads to the harvest of the maximum input energy. The harvest of maximum energy (HME) based multilevel inverter structure consists of two terminals. One is connected to AC-load and another is joined to DC-load or rechargeable batteries. Another merit of the proposed multilevel inverter is that the number of its switches is comparable to other structures where unused energies cannot be harvested. Selective harmonic elimination (SHE) has been used as the switching strategy in the proposed multilevel structure. To verify the performance of the HME-based multilevel inverter topology, the experimental results for a type seven-level inverter were performed by the TMS320F28379D DSP.

Oil spills in the seas and oceans cause pollution and have many destructive environmental effects. The diffusion (parabolic) equations are the most reasonable option to model the propagation of this leakage and contamination. These equations allow statistics regarding the amount of oil that has outreached the ocean outlet, to be used as initial and boundary conditions for a mathematical model of oil diffusion and alteration in seas. As it involves the hyperbolic (advection/wave) component of the equation, the most reasonable choices are diffusion and Allen–Cahn (AC) equations, which are difficult to solve numerically. Equations of diffusion and Allen-Cahn were solved with different degrees of fractional derivatives (α= 0.25, α=0.5, α=0.75 and α=0.75), and the oil pollution concentration was obtained at a specific time and place. This study adopts the homotopy perturbation method (HPM) for nonlinear Allen–Cahn (AC) equation and time fractional diffusion equation to express oil pollution in the water. Fractional derivatives are portrayed in the sense of Caputo. Two presented examples illustrate the applicability and validity of the proposed method. Pollution concentrations in flow field over an interval of time and space for different degrees of fractional derivation are shown. At lower fraction derivative degrees, the pollution concentration behavior is nonlinear, and as the degree of fraction derivation increases to one, the nonlinear behavior of the pollution concentration decreases. The results produced by the suggested technique compared to the exact solutions shows that it is efficient and convenient; it is also reduces computational time.

This paper presents the design of an Magnetorheological (MR) damper that includes an arrangement of a piston and cylinder. This study developed a 3-D  model based on the finite element method (FEM) concept on the COMSOL  Multiphysics to analyze and investigate the MR damper characteristics. A  prototype of the MR damper is being fabricated based on the FEM model and is put through a series of experiments using the Servo-Hydraulic material testing machine (MTS). Maximum and minimum forces, 171.5235N and 249.2749N, were measured at 0.1Hz and 1Hz, respectively, for the FEM model. The fabricated model obtained similar results at 0.1Hz and 1Hz, with maximum and minimum forces of 175.9103N and 252.7765N, respectively. Comparing these two model analyses reveals that the FEM-based model accurately depicts the experimental behaviour of the MR damper in terms of its damping force, although there is minor variation. The findings of this paper will be helpful for designers in creating MR dampers that are more efficient and reliable, as well as in predicting the characteristics of their damping force.