This study investigates the flow and heat transfer characteristics of copper (Cu) and silver (Ag) nanofluids over a permeable, moving flat plate embedded in a porous medium under the influence of a uniform magnetic field. Key effects such as thermal radiation, viscous dissipation, nanoparticle volume fraction, and suction/injection are incorporated into the model. The governing partial differential equations are reduced to ordinary differential equations using similarity transformations and solved numerically via the Runge-Kutta fourth-order method with a shooting technique. Results reveal that Ag-water nanofluid exhibits a higher temperature profile, whereas Cu-water shows greater skin friction and heat transfer rates. Velocity decreases with increasing magnetic field strength, porosity, volume fraction, and suction/injection parameters. Thermal boundary layer thickness increases with magnetic and porosity parameters but decreases with stronger suction. The Nusselt number increases with nanoparticle concentration, and temperature rises with higher viscous dissipation but decreases with thermal radiation.

Tool-path smoothing is essential for ensuring continuous motion at transition corners between linear segments, since kinematic discontinuities degrade both machining efficiency and surface quality. Most existing spline-based methods achieve only G2 or C2 continuity and therefore produce discontinuous jerk, which can excite high-order structural resonances. Achieving true C3 continuity remains challenging, particularly because synchronizing tool-tip position and orientation is complicated by the nonlinear relationship between arc length and spline parameterization. This study presents an analytical Catmull–Rom (CR) spline–based method for C3-continuous tool-path smoothing in five-axis CNC milling. Transition corners are replaced by adjustable Catmull–Rom (ACR) splines, whose control points and tuning parameters are designed or optimized to constrain the deviation from the original path. The remaining linear segments are also substituted with ACR splines to enforce position–orientation synchronization, with control points that can be chosen analytically to guarantee zero synchronization error. The proposed method is fully analytical and non-iterative. Numerical simulations demonstrate that the generated tool paths satisfy prescribed geometric tolerances, produce smooth and continuous jerk profiles, and achieve exact synchronization between tool-tip position and orientation.

This study investigates the theoretical energy intensity of ammonia production via sonochemical reactions in non-Newtonian test fluids. A single, freely oscillating microbubble containing nitrogen and hydrogen is modelled using the Keller–Miksis equation, the first law of thermodynamics, and a detailed reaction mechanism. The goal is to assess whether modifying fluid properties can improve the energy intensity compared to conventional methods. Key parameters—including bubble size, ambient pressure, gas composition, and rheological properties—are varied systematically. The total energy input includes bubble expansion work, hydrogen production via electrolysis, and gas compression energy. The lowest energy intensity achieved is 682.6 GJ/t, which is 17.5 times higher than the Haber–Bosch process using renewable hydrogen. Compared to previous studies in water, a 5.3% improvement is observed, attributed primarily to the increased sound speed. The non-Newtonian rheology had only minor influence, suggesting that future efforts should focus on optimizing acoustic parameters and fluid compressibility rather than rheological properties.

This paper presents a control framework that integrates fixed-time sliding mode control (FxTSMC) with a radial basis function neural network (RBF-NN). The novelty of the proposed approach lies in the synergy between the two techniques, leveraging their respective strengths to enhance overall system performance. The FxTSMC component guarantees fast system response within a predefined time, while the RBF-NN offers adaptive capabilities to handle model uncertainties, thereby improving robustness. The stability of the combined approach is theoretically established and validated through its application to a nonlinear system, specifically a 2-DoF robotic manipulator. Comparative simulations with existing methods are conducted, accompanied by discussions on the results.

This work presents the thermophoretic migration of a solid cylinder, whose direction is normal to its axis and situated in a concentric cylindrical cavity. The space between the particle and the cavity is filled with isotropic porous medium. The Kundsen number is considered to be small, so that the fluid flow through the porous medium is in continuum regime. The continuity of heat flux, temperature jump, viscous slip, thermal creep and thermal stress slip conditions are employed to solve the thermal transport and fluid flow equations. We have obtained analytical expressions for thermophoretic velocity, thermophoretic mobilities and drag force. The effects of the permeability, frictional slip parameter, particle-to-cavity radii ratio, and thermal conductivity ratio of particle to medium on thermoosmotic velocity, thermophoretic mobility and net normalized velocity are presented in graphical form. We have found that the thermoosmotic and thermophoretic mobility have maximum for the high permeability, and for the low radii ratio of particle to cavity. Reduction cases for the unbounded medium are also obtained. The present study has significant applications in industrial and engineering fields, such as manufacturing of precipitators, sampling of soot particles, air cleaning, etc.

The present work deals with the identification of speed-dependent misalignment parameters in a multi-disk coupled rotor system supported on Tilting pad journal bearings (TPJB) and Active magnetic bearings (AMB). The stiffness matrix of misaligned coupling is modelled as the sum of static coupling stiffness (SCS) and additive coupling stiffness (ACS) matrices. The presence of parallel and/or angular misalignments gives rise to ACS matrix and its coefficients represent misalignment in/about a given direction. ACS coefficients are time dependent and a suitable mathematical function has been chosen to define the time varying nature of these coefficients. The global equations of motion (EOMs) are assembled and solved in time domain to obtain rotor vibration and AMB current data. This data is processed by full spectrum Fast Fourier Transform, and subsequently input to the identification algorithm. The stiffness and damping of TPJBs, stiffness of AMBs and ACS coefficients that correspond to misalignment are estimated at six different speeds along with speed-invariant disc unbalances, and SCS coefficients. The robustness of algorithm is tested against measurement noise and modelling bias. ACS coefficients have been identified within reasonable error margins. Finally, the method of application of the algorithm to real rotors is presented. The novelty of the work is the development of an inverse problem for the identification of parallel and angular misalignments in real rotors.

Exoskeletons of lower extremities are used mainly for gait treatment in physical rehabilitation. However, they are also capable of being involved in other types of exercises. Nevertheless, their structure needs to be adequately adjusted for such applications. To analyse approaches to that, this review paper investigates the mechanical designs of rehabilitation exoskeletons for lower extremities. The study seeks to identify best practices in designing and implementing these devices by analysing fifty-two articles. It covers aspects such as kinematic structures, materials used, types of drives, and the range of exercises. Standard design features include multiple degrees of freedom, primarily at the hip, knee, and ankle joints, and using lightweight materials to enhance mobility and reduce power consumption. The review also discusses the advantages of different driving systems. The findings provide valuable insights for developing effective and safe rehabilitation exoskeletons, contributing to improved patient outcomes in physiotherapy and rehabilitation settings.

Flow control is studied to improve the aerodynamic performance of an aerofoil. A strategy for maintaining the near-wall flow structure with a given spatial scale, developed within the framework of interdisciplinary research, is used. The proposed active flow control method is based on the application of spanwise arrays of mechanical, thermal, or plasma vortex generators. The latter are found most versatile and efficient for the formulated goal. Aerodynamic coefficients measured in the specified wind tunnel are discussed for the 12.5% supercritical airfoil model. The model is controlled by the spanwise array of pulsating high-voltage plasma discharges. This multi-actuator system provides a sufficient number of control parameters such as pulse duration and repetition rate, the distance between the neighboring actuators (space scale of generated disturbances), and the plasma array location along the airfoil chord. Measurements in a range of Reynolds numbers of Rec=(3-7)x105 showed growth of a maximal lift coefficient CLmax up to 10% and the stall angle by 1.5°-3.5° accompanied by drag reduction up to 7%.

This paper investigates on developing a novel model-based identification technique for the simultaneous identification of severe faults such as the unbalance in the rotor and transverse crack in the shaft supported on foil bearings. With plenty of advantages over rolling element bearings or fluid film bearings, foil bearings have been used as the supported bearings in rotating machines such as fuel cell-electric air compressors, blowers, expanders, air cycle machines, etc. In the present article, a rotor model consisting of a cracked and unbalanced rotor with a disc in the middle supported by foil bearings has been considered for easier understanding of online identification of faults in high-speed rotating machines. Dynamic equations of motion of the rotor-foil bearing system have been derived based on the equivalent stiffness concept of shaft-foil bearing, inertia force, unbalance force, and crack force relying on the switching crack concept. The solutions of the equations, i.e., time domain displacement responses, orbit plots, etc. have been obtained numerically using the Simulink inbuilt Runge-Kutta method for different values of spin speed of the rotor and ramp-up speeds. The shaft centreline orbit is found to have eight shaped and asymmetric about the axes due to presence of crack and unbalance faults. The force due to unbalance fault gets dominated over the crack force at the higher speeds. Moreover, the orbit line is also observed to be thicker at higher level of noise addition in the responses. As the switching crack force contains multiple harmonics, a full spectrum analysis has been done to investigate both the forward and backward rotor whirls. The frequency-based rotor displacement is utilized to illustrate an identification algorithm for the estimation of the dynamic coefficients of foil bearings, additive crack stiffness, and magnitude as well as phase of disc unbalance. The identification algorithm is found to be quite suitable for the estimation of system and faults parameters even with addition of different levels of noise signal and modelling errors.

This paper investigates the effect of friction on the buckling behavior of a thin, shallow, elastic spherical shell under uniform external pressure based on an axisymmetric model of the finite element method. The study examines a combination of different geometric parameters with three different types of boundary conditions: clamped, hinged, and frictional ends with a wide range of friction coefficients. Friction has a significant influence on the buckling response of the spherical shell for all geometric parameters. In general, the critical pressure decreases as the friction coefficient or geometric parameter decreases. The buckling behavior of the frictional end with small friction coefficients presents an obvious difference compared to the results of high coefficients. For certain geometric parameters, the buckling mode of the spherical shell is transited because of changing the friction coefficient. A buckling map that describes the dependence of critical pressure on both friction coefficient and geometric parameter combined with buckling mode is generated. This map can be applied to the design of the spherical shell against buckling.