Papers by Keyword: Stability

Abstract: This study examines the fabrication and performance of hydrophobic copper and nickel foams produced via a two-step immersion coating method using silver nitrate and stearic acid, targeting oil–water separation and corrosion protection in marine-related environments. In both substrates, silver deposition generated hierarchical surface roughness, while stearic acid functionalization reduced surface energy. Surface morphology and coating integrity were analyzed using scanning electron microscopy (SEM), and wettability was evaluated through water contact angle measurements. Copper foams exhibited water contact angles approaching 180°, demonstrated improved coating adhesion and separation efficiency remained above 95 % over repeated use. Copper-based superhydrophobic foams also showed excellent thermal and chemical stability, maintaining hydrophobicity after prolonged exposure to harsh conditions. Nickel foams developed a strongly adhered hydrophobic silver coating with water contact angles of approximately 147°. The coatings maintained high hydrophobicity across a wide temperature range and exhibited excellent reusability, achieving oil–water separation efficiencies higher than 95 % after multiple cycles. Potentiodynamic polarization was employed to evaluate corrosion behavior of both coated substrates in 3.5 % NaCl solution. Overall, the results indicate that while the same coating effectively provides hydrophobicity and durability to both copper and nickel foams, differences in wettability and coating stability are determined by their intrinsic microstructures.

Abstract: Some composite preforms lose dimensional stability after mandrel removal during tube winding, leading to pronounced longitudinal expansion and radial contraction for specific layup configurations. This work presents an experimental method for tracking the reorganization of individual wound tapes during mandrel release and uses these measurements to validate a finite element (FE) model designed to capture the underlying deformation mechanisms. The experiments reveal a nonlinear dependence of ribbon elongation on the initial winding angle. Complementary FE parametric studies investigate the effects of tape geometry and mechanical properties, demonstrating that increased mechanical anisotropy amplifies the elongation response. The study also introduces a layer-equivalent stiffness formulation and concludes with FE simulations of multi-tape preforms. Together, these results support the development of improved winding strategies aimed at reducing defects, lowering production costs, and enhancing the structural performance of tubular composite components.

Abstract: This research developed a performance improvement of power transmission system to enhance performance during line disturbance using model Predictive control (MPC) control scheme. This research work was implemented using MATLAB 2023a. However, the parameters of these controllers are usually adjusted based on a linearized model of the power system, which typically depends on the system's operating point or state. To assess the performance of the developed scheme, multiple simulation studies were carried out under conditions where the voltage magnitude of the infinite bus and the transmission line reactance changed due to faults at the infinite bus and sending terminals. The results from the waveform analyses indicate that the dynamic characteristics of the system under investigation have significantly improved. settling time, at post fault of the transmission and from fault recovery settled time to its stable state value of 1.8sec compared to 2.8sec with minimal control effort that fluctuated between faults and system stability before settling time at the shortest time value of 2. 6305s in 2.42s compared to 4.28, in 1.92s compared, and 3.32s.

Abstract: This paper presents the design, modeling, and analysis of a solar-powered geared tricycle intended to provide an efficient, eco-friendly alternative for personal mobility. The work integrates mechanical, electrical, and structural engineering principles to ensure dynamic performance, structural integrity, and overall stability under varying operational conditions. A lightweight chassis, optimized using finite element analysis (FEA), is designed to withstand dynamic loads while maintaining low energy consumption. The drive system incorporates a multi-speed gear mechanism coupled with a high-efficiency brushless DC motor powered by a photovoltaic (PV) array and battery storage system, enabling hybrid propulsion. The dynamic behaviour of the tricycle, including acceleration, turning, and braking responses, is simulated using MATLAB/Simulink to evaluate performance across urban terrains. Stability is assessed through center-of-gravity analysis, roll-over threshold calculations, and tilt angle monitoring to prevent tipping during sharp maneuvers. The integration of solar technology not only extends operational range but also reduces environmental impact, making the design suitable for sustainable transportation in developing and urban regions.

Abstract: The use of hybrid nanofluids aimed to improve the exceptional qualities of fluids, including adsorption, viscosity, stability, and interfacial tension. Although several surfactant changes utilizing hybrid nanomaterials have been documented, their wider application has been hindered by the material's stability and processing challenges. The purpose of this study is to use the liquid phase exfoliation technique and examine the properties of the recently created hybrid nanofluids. This paper investigates the mechanisms of how hybrid nanofluids (HNF) composed of Graphene nanoplatelet (GNP) & SiO₂ with various surfactants such as Gum Arabic (GA) and Sodium Carboxymethyl Cellulose (SCMC) could improve EOR through adsorption of nanoparticles, improve viscosity, Interfacial tension (IFT), and wettability contact angle. Based on the results, using the hybrid nanoparticles decreases the IFT between oil-water interface from 39.700 mN/m for brine to 38.466, 37.582, 35.609 mN/m, for Control HNF, GA HNF, and SCMC HNF respectively. The adsorption of nanoparticles mechanism occurs and peaks during a 12-hour to 24hour period. Furthermore, the findings on the performance of hybrid nanofluid have increased the viscosity from 0.317cP (brine) to 3.638cP (GA) and 3.556cP (SCMC) nanofluid. When nanoparticles are introduced into reservoirs, they interact with rocks and crude oil via rock absorption, potentially improving the recovery rate of oil by changing wettability and influencing the efficiency of water-transfer to oil in several improved oil recovery methods. The contact between the rock surface, nanofluid, and oil was shown to be reduced by 29.47% and 59.12%, as seen by the contact angle of the oil droplet on the rock surfaces. The phenomenon occurs because nanoparticles are attached to the interface of rock, oil, and brine.

Abstract: The article is devoted to the analysis of the operational suitability of the aircraft shelter structure under the action of an explosion, taking into account the nature of their spread through the soil backfills. The intensity of the decrease in the bearing capacity of the covering structure, which depends on the content of reinforcement in the structural element, is considered. Including, preventive measures are proposed for the progressive collapse of the hangar roof slabs in the event of a possible missile hit. The article considers various scenarios of explosive effects, under which the worst-case conditions for ensuring the reliability of the hangar structure during emergency effects were checked. Wave propagation during a ground explosion was analyzed. An example of calculating the arched hangar structure for a blast wave in the LIRA-FEM PC under the action of a surface explosive effect is provided. The results of the nonlinear calculation of the arch and the roofing slabs with an additional impact load of up to 20 tf/m² are presented. The modeling of the nonlinear loading process was carried out taking into account the damping of the soil base of up to 10% on an area of up to 80 m² with a dynamic coefficient of 1.2 in the PC LIRA-FEM, the calculation of the emergency load was performed with the specified TR (type of reinforcement).

Abstract: Stabilization of steel structure has always been a key concern in the engineering world. The phoenix shape of the upper station house in the ropeway project of Shaohuashan National Forest Park in Shaanxi Province consists of 5 groups of tube truss structures forming an overall space tube truss structure form through connecting rods. The finite element method was used to analyze its stability, and the overall structural eigenvalue buckling analysis and nonlinear instability analysis were carried out. It is shown that the factor of safety of the structure is inversely related to the initial defects under the consideration of the influencing factors of the initial defects. The instability modes of the structure are instability of the connecting rods connecting the five groups of tube trusses, instability of the bottom rods of the structure, and instability of the head rods of the skeleton.

Abstract: The assessment of bridge structures is not only relevant, but also an integral part of effective infrastructure management aimed at ensuring safety, convenience and comfort for citizens. Many bridges have been destroyed due to imperfect design, the use of low-quality materials, and inappropriate construction methods. Consideration of natural and human factors in the design, construction and operation of bridge structures is key to ensuring their safety, durability and long-term performance. Any defects require careful monitoring, assessment and timely repair to ensure the safety and reliability of bridges. Various methods are used to inspect bridge structures. Inspection methods can be used individually or in combination to obtain comprehensive information on the condition of bridge structures and take the necessary measures for their maintenance and repair. In work to determine the stresses in a bridge, we use the finite element method (LIRA 9.4 R3). The inspection of the bridge's structures revealed a number of defects resulting from corrosion processes, operational factors and certain structural deficiencies. To ensure the durability of the bridge structures, it is necessary to reconstruct the bridge.

Abstract: The article is devoted to the issues of modeling and analysis of the protective structures’ designs under the influence of explosive loads. An analysis of shock waves is carried out, the nature of their propagation and impact on buildings, as well as methods for their modeling in the LIRA-SAPR software. Some proposals for preventing the collapse failure of the structure due to the impact of missile fragments are given. The article discusses different types of point explosions - air and ground. The diagram of the formation of waves during an air explosion and a characteristic wave pattern during a ground explosion is given. The propagation of waves during a ground explosion is analyzed. A mathematical model for determining shock wave parameters is given. An example of the calculation of the protective structure constructions against a blast wave in PC LIRA-SAPR (LIRA-FEM) under the action of a surface blast effect is provided. The results of the non-linear calculation of the roof slab for resistance to collapse failure in the case of an emergency explosive impact on an area up to 80 m² are presented.

Abstract: The two aspect ratios 1.0 and 0.5 analysed comparatively to perform a stability study of a 120° partial arc journal bearing have lubricated with a fluid of couple stresses. Reynold’s equation in modified form is obtained for couple stresses and coupled with elasticity equation to predict the impact of deformation in bearing liner on stability characteristics of journal bearing to know its performance. The results quoted here are in terms of attitude angle, somerfeld number, critical mass, whirl frequency and threshold speed. The conclusion made shows that the bearings with high aspect ratio (1.0) are more stable than aspect ratio 0.5 for the fluid of couple stresses and its stability is improved by the use of fluid with couple stresses. Threshold speed is reduced with an increase in the factor of liner deformation and shows that the region of stability is reduced on increasing deformation of bearing liner.