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Load flow analysis is an essential tool for the reliable planning and operation of interconnected power systems. The constant increase in power demand, apart from the increased intermittency in power generation due to renewable energy sources without proportionate augmentation in transmission system infrastructure, has driven the power systems to function nearer to their limits. Though the power flow (PF) solution may exist in such circumstances, the traditional Newton–Raphson based PF techniques may fail due to computational difficulties owing to the singularity of the Jacobian Matrix during critical conditions and faces difficulties in solving ill-conditioned systems. To address these problems and to assess the impact of large-scale photovoltaic generator (PVG) integration in power systems on power flow studies, a derivative-free quasi-oppositional heap-based optimization (HBO) (QOHBO) technique is proposed in the present paper. In the proposed approach, the concept of quasi-oppositional learning is applied to HBO to enhance the convergence speed. The efficacy and effectiveness of the proposed QOHBO-PF technique are verified by applying it to the standard IEEE and ill-conditioned systems. The robustness of the algorithm is validated under the maximum loadability limits and high R/X ratios, comparing the results with other well-known methods suggested in the literature. The results thus obtained show that the proposed QOHBO-PF technique has less computation time, further enhancement of reliability in the presence of PVG, and has the ability to provide multiple PF solutions that can be utilized for voltage stability analysis.

The hybrid nanofluid has sparked new significance in the industrial and engineering sectors because of their applications like water heating in solar and analysis of heat exchanger surfaces. As a result, the current study emphasizes the analysis of heat transfer and Agrawal axisymmetric flow towards a rotational stagnation point incorporated via hybrid nanofluids imposing on a radially permeable shrinking/stretching rotating disk. The leading partial differential equations are refined into ordinary differential equations by using appropriate similarity variables. The bvp4c solver in MATLAB is then employed to solve the simplified system numerically. The current numerical procedure is adequate of generating double solutions when excellent initial guesses are implemented. The results show that the features of fluid flow along with heat transfer rate induced by hybrid nanofluid are significantly influenced. The Nusselt number and the tendency of the wall drag force can be improved as the concentration of nanoparticles and the suction factor are increased. Moreover, the results of the model have been discussed in detail for both solution branches due to the cases of rotating disk parameter as well as non-rotating disk parameter. Therefore, an extraordinary behavior is observed for the branch of lower solutions in the case of rotating disk parameter. In addition, the shear stress in the radial direction upsurges for the first solution but declines for the second solution with higher values of suction. Moreover, the rotating parameter slows down the separation of the boundary layer.

The main purpose of this study is to present dual solutions for the problem of magneto-hydrodynamic Jeffery-Hamel nano-fluid flow in non-parallel walls. To do so, we employ a new analytical technique, Predictor Homotopy Analysis Method (PHAM). This effective method is capable to calculate all branches of the multiple solutions simultaneously. Moreover, comparison of the PHAM results with numerical results obtained by the shooting method coupled with a Runge-Kutta integration method illustrates the high accuracy for this technique. For the current problem, it is found that the multiple (dual) solutions exist for some values of governing parameters especially for the convergent channel cases ([alpha]=-1). The fluid in the non-parallel walls, divergent and convergent channels, is the drinking water containing different nanoparticles; Copper oxide (CuO), Copper (Cu) and Silver (Ag). The effects of nanoparticle volume fraction parameter [phi] Reynolds number (Re), magnetic parameter (Mn), and angle of the channel ([alpha]) as well as different types of nanoparticles on the flow characteristics are discussed.

In this paper, we develop two new fourth-order integrable equations represented by nonlinear PDEs of second-order derivative in time t . The new equations model both right- and left-going waves in a like manner to the Boussinesq equation. We will employ the Painlevé analysis to formally show the complete integrability of each equation. The simplified Hirota’s method is used to derive multiple soliton solutions for this equation. We introduce a complex form of the simplified Hirota’s method to develop multiple complex soliton solutions. More exact traveling wave solutions for each equation will be derived as well.

This paper presents the results of numerical simulations of a non-linear, tristable system for harvesting energy from vibrating mechanical devices. Detailed model tests were carried out in relation to the system consisting of a beam and three permanent magnets. Based on the derived mathematical model and assuming a range of control parameter variability, a three-dimensional image of the distribution of the largest Lyapunov exponent was plotted. On its basis, the regions of chaotic and predictable movement of the considered system exist have been established. With reference to selected plane of the largest Lyapunov exponent cross-sections, possible co-existing solutions were identified. To identify multiple solutions, a diagram of solutions (DS) diagram was used to illustrate the number of existing solutions and their periodicity. The proposed calculation tool is based on the so-called fixed points of Poincaré cross-section. In relation to selected values of the control parameter ω, coexisting periodic solutions were identified for which phase trajectories and basins of attraction were presented. Based on the model tests carried out, it was found that in order to efficiently harvest energy, appropriate transducer adjustment is required. Calibration of the transducer is necessary to obtain the greatest amplitude of vibration of the beam, which corresponds to the phase trajectory limited by external energy potential barriers. As expected, the average voltage induced on the electrodes of the piezoelectric transducer and the average electrical power recorded on the resistive element are directly proportional to the amplitude and average kinetic energy of the beam.

This study investigates the precise solutions of the (2+1)-dimensional modified KdV–KP equation. Resonant multiple soliton solutions are examined by first discussing the linear superposition principle and then exploring two scenarios to illustrate the wave profiles and behaviors using various graphical representations. Utilizing the (3-2-4) bilinear neural network model, numerous rogue-type multiple lump wave solutions are generated, including 1-lump wave, 3-lump wave, and 6-lump wave results through symbolic computation. Additionally, the physical structure and dynamical features of these solutions are elucidated through three-dimensional plots and density graphs.

In this paper, we develop a new extended Kadomtsev–Petviashvili (eKP) equation. We use the Painlevé analysis to confirm the integrability of the eKP equation. We derive the bilinear form, multiple soliton solutions and lump solutions via using the Hirota’s direct method. Moreover, the soliton, breather and lump interaction solutions for this model are also obtained as well. Graphs are drawn to illustrate the abundant dynamical behaviors of the obtained solutions.

In this paper, the combination resonance characteristics of a high-dimensional dual-rotor-bearing-casing system with bearing nonlinearities are presented. All the periodic solution branches, including the unstable solutions of the system, are obtained by the semi-analytical harmonic balance method. Two primary and two combination resonance regions are found in the amplitude–frequency responses, with the vibration jump and multiple solutions phenomena being observed. Furthermore, the amplitude–frequency responses with separated frequencies are analyzed; it is shown that the vibration responses of the combination resonance regions are dominated by the combination frequencies of the rotating speeds of the high- and low-pressure rotors. Moreover, parametric analysis shows that the combination resonances are sensitive to the change in the inter-shaft bearing clearance. With the increase in clearance, the combination resonance regions are widened. The results in this paper provide a better understanding of the combination resonances in high-dimensional dual-rotor-bearing-casing systems.

In this paper, we study the existence of at least two non-trivial solutions for a class of p(x)-Laplacian equations with perturbation in the whole space. Using Ekeland’s variational principle and the mountain pass theorem, under appropriate assumptions, we prove the existence of two solutions for the equations.