Static Force Research Articles

Heat Influence on Different Hyaluronic Acid Fillers

Facial volume deficits, providing long-term facial aesthetic enhancement outcomes for the signs of aging and/or facial contouring. Numerous hyaluronic acid (HA) fillers seem to have similar characteristics, although their properties regarding rheology, viscoelasticity, heat resistance are different in many ways. The resistance heat degradation is important when hyaluronic acid fillers and energy-based devices are going to be used sequentially. Our objective was to determine the characteristics of HA gels in terms of heat resistance. Degradation of the gels was measured as a change of surface area of the sample. Five types of HA fillers, chosen from most common products on the market for temporary correction of congenital and acquired soft tissue deficits of the face via intradermal or subcutaneous injection: 20mg/ml HA-BDDE, 20mg/ml HA-BDDE, 20mg/ml HA-BDDE, 25 mg/ml HA-BDDE, 28mg/ml HA-PEG were tested in this study. Even though the three dermal fillers contained the same concentration of HA and were cross-linked with the same cross-linking agent, they were produced by different manufacturers using different technologies developed by individual companies. We tested in vitro resistance to heat degradation using Celltibator GT (Medikan Co., LTD, Seoul, Rep. of Korea) and Autoclave (Medotti 22L PRO, Poland). All of the HA fillers samples (0,3 ml) were placed on the petri dishes and put into the autoclave for 10 minutes (temp. 72,4°C). Three of the gels samples (20mg/ml HA-BDDE, 25mg/ml HA-BDDE, 28mg/ml HA-PEG) each 0,3ml were placed into Celltibator for 10 min, temp. 55,2°C degree, centrifugation: 30 RPM. Centrifugation was used to imitate the behaviour of the fillers under the conditions of forces acting on it in the tissue (stress under the influence of facial expressions, exercises, etc.). The temperatures used during this test correspond with commonly used heat-based devices, such as radio-frequency devices (about 45°C), infrared (about 55-65°C) and HiFU (about 70-75°C). Before and after each test pictures of the samples were taken. Heat degradation of the HA samples was measured by comparing (before and after) the changes of the surface area of samples on the petri dishes (on the graph paper). The 28-mg/ml HA-PEG gel filler demonstrated greater resistance to heat versus the 20- mg/ml and 25-mg/ml BDDE gel fillers. The 28-mg/ml HA-PEG, demonstrated in both test (celltibator with/without rotation and autoclave) greater resistance to heat in terms of deformation / thermal degradation and change of surface area. Selection of dermal filler with the right rheological properties is a key factor in achieving a natural-looking long-lasting desired aesthetic outcome. Hyaluronic acid fillers combined with energy-based devices are frequently used sequentially during the same session, however, in some cases it might cause thermal damage of HA. Caution is advised in using IR over recently injected filler (selection of dermal fillers is crucial in this case). Study limitations include use of in vitro model and lack of inflammatory response in an ex-vivo model.

Hydrography, inorganic nutrients and chlorophyll a linked to sea ice cover in the Atlantic Water inflow region north of Svalbard

Changes in the inflow of Atlantic Water (AW) and its properties to the Arctic Ocean bring more warm water, contribute to sea ice decline, promote borealisation of marine ecosystems, and affect biological and particularly primary productivity in the Eurasian Arctic Ocean. One of the two branches of AW inflow follows the shelf break north of Svalbard, where it dominates oceanographic conditions, bringing in heat, salt, nutrients and organisms. However, the interplay with sea ice and Polar Surface Water (PSW) determines the supply of nutrients to the euphotic layer especially northeast of Svalbard where AW subducts below PSW. In an effort to build up a time series monitoring the key characteristics of the AW inflow, repeat sampling of hydrography, macronutrients (nitrate, phosphate and silicate), and chlorophyll a (chl a) was undertaken along a transect across the AW inflow at 31°E, 81.5°N since 2012 — first during late summer and in later years during early winter. Such time series are scarce but invaluable for investigating the range of variability in hydrography and nutrient concentrations. We investigate linkages between late summer hydrographic conditions and nutrient concentrations along the transect and the preceding seasonal dynamics of surface chl a and sea ice cover in the region north of Svalbard. We find large interannual variability in hydrography, nutrients and chl a, indicating varying levels of nutrient drawdown by primary producers over summer. Sea ice conditions varied considerably between the years, impacting upper ocean stratification, light availability and potential wind-driven mixing, with a strong potential for steering chl a concentration over the productive season. Early winter measurements show variable efficiency of nutrient re-supply through vertical mixing when stratification was low, related to autumn wind forcing and sea ice conditions. While this re-supply elevates nutrient levels sufficiently for primary production, it likely happens too late in the season when light levels are already low, limiting the potential for autumn blooms. Such multidisciplinary observations provide insight into the interplay between physical, chemical and biological drivers in the marine environment and are key to understanding ongoing and future changes, especially at this entrance to the central Arctic Ocean.

Transformational deformation models of continuous thin‐walled structural elements with support elements of finite sizes: Theoretical foundations, computational, and physical experiments

AbstractA method of experimental study of forced bending vibrations of unfixed spans of continuous thin‐walled structural element fixed on rigid support elements of finite dimensions has been developed using instrumental means for registration of vibration acceleration amplitudes. The technique is realized on beams with different types of their fixing under the loading of one of the beam section with an external force that varies in time according to a harmonic law. Experimental dependences of amplitude values of vibration accelerations in specific points of certain spans of the beam on the frequency of external load have been obtained. These results indicate the passage of vibrations through the fixed sections due to the transformation of bending vibration modes of the loaded section into longitudinal transverse‐shift vibrations of the fixed sections during the transition across the boundary from the unfixed section to the fixed one (from the fixed to the unfixed section). For the theoretical study of the described phenomenon a transformational model of the flat beam deformation is constructed on the basis of the refined Timoshenko model with additional account of the deformability of the section with fixation to a rigid support element of finite length on one of its face surfaces. The corresponding equations of motion of the unfixed and fixed sections are derived. The corresponding kinematic and force conditions of their conjugation are formulated. On their basis, analytical solutions of two specific problems are found in the linear approximation. One‐dimensional finite elements for modeling the dynamic response of continuous beam of the considered class are also constructed. Numerical experiments have been carried out for a flat beam made of aluminum alloys D16AT, AMg‐6 and unidirectional fiber reinforced plastic. The presence of a significant transformation of the stress‐strain state parameters of the considered beams at the transition across the boundary from unfixed to fixed sections and a significant increase in the level of transverse tangential stresses on the fixed section of the beam in the vicinity of the interface of the unfixed section with the fixed one have been revealed.

Force plate coverings significantly affect measurement of ground reaction forces.

The purpose of this study was to carry out a material test to investigate the effect of different force plate coverings on vertical and horizontal ground reaction force and derived parameters. Four surface conditions were analysed; bare plate, vinyl, sportflex, and astroturf on a Kistler force plate. Vertical data were collected by dropping a 2 kg rigid, textured medicine ball from a low (61 cm) and a high (139 cm) height. Horizontal data were collected using a custom-built, rigid, metal pendulum device. A one-way ANOVA revealed a significant main effect of surface on peak force and rate of force development for high height, low height, and horizontal force conditions (all p<0.001), with effect sizes in the post-hoc analysis being mostly large to very large. Interestingly, sportflex yielded the highest vertical but the lowest horizontal ground reaction forces. This study showed the use of current force platform coverings had a significant effect on peak force and rate of force development measurements during a standardised testing procedure. Future research should try to obtain rate of force development values that more closely replicate aspects of human performance during standardised testing procedures. Also further investigate the effect of the different surfaces on ground reaction forces during human movement.

Mass estimation of a simple hydraulic crane using discrete extended Kalman filter and inverse dynamics for online identification

Automatization of hydraulic machinery requires accurate information of the current dynamic state of the machinery but also information of the underlying dynamic model characterized by a set of parameters. Some of the parameters can be considered static and well defined, such as machinery dimensions, whereas a part of the parameter set is time varying and needs to be identified based on observations. Particularly, difficult parameters to estimate are the ones, from which no prior knowledge is available. Consequently, the parameter corrections cannot be assumed to be small, which is commonly required for the existing parameter estimation algorithms. This study creates an online capable identification algorithm for estimation of a load mass operated by a hydraulic crane. In the case of load mass estimation, the unknown parameter can be practically any positive value, which implies the parameter corrections to be large. In this study, the estimation problem is divided in two parts: First, the dynamical states of the system are estimated based on the system kinematic relationships and dynamics of the hydraulic circuit. Secondly, the unknown load mass is estimated based on the known hydraulic forces and kinematics using the inverse dynamics of the mechanical structure. The proposed algorithm is tested with both artificially created measurements and with an experimental setup. The results show that both the kinematics of the structure and hydraulic pressures can be accurately estimated using the proposed method. Moreover, the method can be used to further estimate the payload mass. A drawback related to inverse dynamics is that it produces biased estimates in static equilibrium because of the discontinuous nature of static friction force. However, this drawback can be avoided, in part, by not updating the payload estimate in the low-velocity region. The proposed estimation methodology is capable for online identification, and as such, it can be used to adapt the control laws of automated machinery. Moreover, the methodology can be useful to record and document the amount of payload being handled during a work cycle.

Metoda eksperymentalnego badania charakterystyki siła-odkszałcenie sprężyn Beleville w zespole odcinającym zasuwy klinowej

The article presents research methods and appropriate equipment for conducting experiments, as well as the analysis of the results. Studies on the hardness of the microstructure, elastic deformation and parts and samples were carried out using hardness testers, microscopes PMT-3, MIM-8 and devices for measuring the “force-strain” characteristic. The results of the study wer used to establish the dependence of the elastic properties of Belleville springs on the heat treatment modes, while also determining the microstructure and layer depth using various research methods. Every work studying the elastic properties and measurement of the static compressive force of a spring at a given strain value has been studied theoretically. Depending on the operating conditions, disc springs can be installed singly or assembled into packages, forming an elastic element working under compression. The research materials will be used in the work to improve the tightness of straight-through valves and the durability of the shut-off assembly parts. The dependence of the spring compression force and its deformation on the geometrical parameters of the disc springs has been established. Comparison of experimental and theoretical dependences has been made. It has been established that the residual deformation of the Belleville spring after captivity has a negative effect on the tightness of the shut-off valve assembly. The influence of various technological processes and modes of thermal treatment of disc springs on their elastic properties has been studied. Practical recommendations for improving the technological process of thermal treatment of Belleville springs have been proposed. The tasks of further research and implementation of the obtained results have been determined. Search work has been carried out to improve the technology of hardening processing of parts of the shut-off unit (gate and seat) of direct-flow valves. The possibility of using accelerated nitrocarburizing in a triethanolamine medium with induction heating by high-frequency currents at a temperature range of 950°С for boriding and borochroming has been established. Samples were made from standard steel grades 40, 40Kh and 38Kh2MYuA, subjected to hardening by the considered methods, and a study was made of the hardness, depth and microstructure of the hardened layer. Research in this direction should be continued in order to study the tribological characteristics (friction coefficient and wear resistance) of hardened parts. Each operation of the spring manufacturing technology has been studied, and deviations that have a significant impact on the operation of the spring and the sealing of the shut-off valve assembly have been identified.

On the issue of evaluating the effectiveness of the anti-slip profile of machine structures

Profiles with anti-slip grooves can be used for the design and modernization of machines, but the magnitude of the anti-slip effect for such profiles has not yet been fully studied. At the same time, among the causes of injuries to transport passengers, slipping on bearing contact surfaces is not uncommon. The existing scientific literature gives some idea of the factors influencing tribocontact with the macro-dimensions of surfaces. This served as the basis for the mathematical description in the article of the factorial effect on the anti-slip efficiency of the grooved profile. For this purpose, two indicators were identified that take into account the influence of the shape and number of profile irregularities. With the help of modeling tribocontact with profiles of different corrugation in the SolidWorks Motion environment, calculated values of the maximum static friction force were obtained. These values were compared with the calculated values of performance indicators, as a result of which a conclusion was made about the adequacy of the mathematical description of the factors. Keywords: machine structures, grooved profile, anti-slip surface properties, anti-slip efficiency, tribocontact, coefficient of friction, macro-dimensions

Improving the Grasping Force Behavior of a Robotic Gripper: Model, Simulations, and Experiments

Robotic grippers allow industrial robots to interact with the surrounding environment. However, control architectures of the grasping force are still rare in common industrial grippers. In this context, one or more sensors (e.g., force or torque sensors) are necessary. However, the incorporation of such sensors might heavily affect the cost of the gripper, regardless of its type (e.g., pneumatic or electric). An alternative approach could be open-loop force control strategies. Hence, this work proposes an approach for optimizing the open-loop grasping force behavior of a robotic gripper. For this purpose, a specialized robotic gripper was built, as well as its mathematical model. The model was employed to predict the gripper performance during both static and dynamic force characterization, simulating grasping tasks under different experimental conditions. Both simulated and experimental results showed that by managing the mechanical properties of the finger–object contact interface (e.g., stiffness), the steady-state force variability could be greatly reduced, as well as undesired effects such as finger bouncing. Further, the object’s size is not required unlike most of the grasping approaches for industrial rigid grippers, which often involve high finger velocities. These results may pave the way toward conceiving cheaper and more reliable open-loop force control techniques for use in robotic grippers.

Analysis of the Braking System in the Gardapati Prototype Energy Saving Car

The braking system is one of the crucial components in a vehicle because braking is a vital safety feature of the vehicle. The braking system functions to reduce or slow down the speed and stop the vehicle, as well as to enable the possibility of parking the vehicle on a downward slope. The braking system under investigation is examined in the prototype vehicle called Gardapati, which employs a hydraulic brake system. Gardapati is a vehicle created by students from the University of Riau's Mechanical Engineering Department, affiliated with the UKM Selembayung, following the standard references provided by the Energy-Efficient Vehicle Competition organized by BPTI.&#x0D; This final project will involve several calculations related to the braking system, following the specifications used in the Gardapati vehicle. First, calculations will determine the dynamic braking force required (Fb) when the vehicle is moving at a speed of 50 km/h with a distance of 20 meters, as well as the static braking force (Fb) required when the vehicle is on an incline of 11.2 degrees, adjusted to the requirements and regulations of the 2023 Energy-Efficient Vehicle Competition (KMHE). Then, the braking distance will be calculated for speeds of 30, 40, and 50 km/h on dry and wet asphalt road conditions.&#x0D; From the calculation results and data analysis, it is found that the required dynamic braking force (Fb) is 510,76 N, and the static braking force (Fb) is 830,31 N. Meanwhile, the minimum braking distance is observed on dry asphalt road conditions at a speed of 30 km/h with a percentage error of 1,59 %, where the theoretical value is 5.67 m and the actual value is 5,76 m. On the other hand, the highest braking distance is observed on wet asphalt road conditions at a speed of 50 km/h with a percentage error of 7,39%, where the theoretical value is 14.47 m and the actual value is 15.54 m. Of the two road conditions, the largest percentage error occurs when testing the vehicle at speeds of 30, 40, and 50 km/h on wet asphalt conditions, amounting to 4,61%. With this level of percentage error, it can be concluded that the variation in the obtained data is relatively small, which is less than 10%.

Impaired Lumbar Extensor Force Control Is Associated with Increased Lifting Knee Velocity in People with Chronic Low-Back Pain

The ability of the lumbar extensor muscles to accurately control static and dynamic forces is important during daily activities such as lifting. Lumbar extensor force control is impaired in low-back pain patients and may therefore explain the variances in lifting kinematics. Thirty-three chronic low-back pain participants were instructed to lift weight using a self-selected technique. Participants also performed an isometric lumbar extension task where they increased and decreased their lumbar extensor force output to match a variable target force within 20–50% lumbar extensor maximal voluntary contraction. Lifting trunk and lower limb range of motion and angular velocity variables derived from phase plane analysis in all planes were calculated. Lumbar extensor force control was analyzed by calculating the Root-Mean-Square Error (RMSE) between the participants’ force and the target force during the increasing (RMSEA), decreasing (RMSED) force portions and for the overall force error (RMSET) of the test. The relationship between lifting kinematics and RMSE variables was analyzed using multiple linear regression. Knee angular velocity in the sagittal and coronal planes were positively associated with RMSEA (R2 = 0.10, β = 0.35, p = 0.046 and R2 = 0.21, β = 0.48, p = 0.004, respectively). Impaired lumbar extensor force control is associated with increased multiplanar knee movement velocity during lifting. The study findings suggest a potential relationship between lumbar and lower limb neuromuscular function in people with chronic low-back pain.

Strength Evaluation of Welded Aluminum T-joints, as a Function of Its Welding Process, Execution, Filler Material, and Weld Root Penetration

Essential requirements for weld seams are the long-term transmission of static and time-varying forces. Requirements for the verification of laser welded fillet weld T-joints are proposed in this paper, since there is no established procedure in this field for laser welding. More precisely, the strength of laser MIG hybrid welded AlMg3Mn T-joints, made from 3.5 mm thick sheet metal are determined, depending on the penetration of their weld root gap. This allowed the unwelded root gap to be related to the decrease in strength, even though this is more apparent with dynamic than with static loading. In addition, the influence of filler material, single and mutual-sided MIG welds have been added to this comparison. Filler materials used are the related AlMg2.7Mn or the extraneous AlSi5.

The effect of temperature-dependent interfacial interaction on the stick–slip behavior of polyamide-66/zinc-coated steel

The stick–slip behavior of polymer/metal is a complex frictional issue since the properties of polymers are highly temperature-sensitive. The present study aimed to shed light on the key factors influencing the stick–slip behavior of polyamide-66/zinc-coated steel by conducting experiments at varying temperatures. The results revealed that the stick–slip behavior and interfacial interaction are temperature-dependent. The friction behavior transitioned from stick-slip to smooth sliding at 40 °C. The transition in the interfacial interaction from adhesion to plastic deformation with increased temperature was responsible for the reduction in stick–slip intensity. The reductions in both the potential energy and static friction force were believed to cause the decreased stick–slip intensity, as evidenced by the in-situ observation of the friction pairs through the digital image correlation (DIC) method. The present study could provide a comprehensive and targeted approach to suppressing the stick–slip behavior of polymer/metal over a wide range of temperatures.

Development of potentiometric immunosensor for determination of live attenuated Varicella Vaccine: Potency and stability studies

Determination of Varicella vaccine's potency; containing live attenuated strain (Oka) of Varicella Zoster virus, has been limited to in vitro cell culture methods. In this study, a label free potentiometric biosensor has been developed for the first time and optimized to determine the content of varicella zoster virus. A passive ion-flux sensing platform has been developed using an anti-varicella monoclonal antibody and tetrabutyl ammonium bromide as a marker ion. The immunosensor has been optimized with respect to membrane diameter and concentration of the immobilized antibody. Linearity was achieved over a concentration range of 2.5–3.2 log PFU/dose with a LOD of 1.9 log PFU/dose. Potentiometric results were compared to the plaque-forming assay using the cell culture technique. The developed immunosensor was superior with respect to analysis time and cost without affecting critical analytical performance characteristics. Furthermore, in order to evaluate the stability indicating ability of the immunosensor, the effect of pH and temperature was investigated. Vaccine samples were subjected to forced degradation conditions; pH and elevated temperatures. Stability results showed the ability of immunosensor to differentiate between intact and degraded viral content. This would demonstrate the reliability of the immunosensor for evaluating the efficacy and stability of the vaccine.

Effect of Atmospheric Conditions on the Tightening Behaviour of HV Galvanised Bolts in Structural Bolt Sets

The aim of this article is to investigate the effect of atmospheric conditions on the tightening behaviour of HV bolts in structural bolt sets. The article describes the results of experimental tests carried out for bolt sets of a selected type. The parts of the joined sets were stored according to the specified six different conditions for four weeks before assembly. Paper, cardboard boxes and anticorrosion foils were used as protection against atmospheric conditions. The behaviour of unassembled and assembled bolt sets was also taken into account. The variation in the friction coefficient depending on the clamping force and storage conditions of the bolt sets was demonstrated. This applies both to the contact between the joining elements on the threaded surfaces and to the area between the bolt head and the bearing surface of the nut and washer.

Complex gravity-acoustic impact on V-flame structure

Development of efficient and safe energy systems for space objects includes ensuring fire safety. This problem requires a deep understanding of influence of gravitational forces on combustion processes, which explains the importance of studying this issue. The paper analyzes the dynamics of inverted conical methane-air flame under conditions of normal and reverse gravitational force with external acoustic excitation. Applied frequencies of acoustic excitation could be parasitic or be produced during proper work of different technical systems of aircraft. High speed recording of flame chemiluminescence and PIV analysis were conducted. Decomposition of flow vector pictures into the modes was calculated using POD method. Energy contribution into the flow was analyzed for its separate elements at the different frequencies of excitation. At the high excitation frequencies vortex generation intensity in the shear layer with reverse gravity is about the same as it was observed in the experiments with normal gravity direction, that could indicate dominance of acoustic mechanism of the vortexes stimulation over the mechanism of shear instability. At external excitation frequency equals 240 Hz significant growth of shear vortex diameters and increasing of perpendicular oscillations amplitude of flame branches were obtained. Thereby in such experiment with 240 Hz external acoustic excitation the most intensive large scale instability of flow was observed.

Low-Speed Impact and Residual Mechanical Performance of the BR1200HS/AA6082 Self-Piercing Riveted Joints

To investigate the low-speed impact response of the BR1200HS steel and AA6082 aluminum alloy self-piercing riveted (SPR) joint, low-speed impact tests with impact energies of 2.5 J, 5.0 J, 7.5 J, 10.0 J, 12.5 J, 15.0 J, 20.0 J, and 30.0 J were conducted utilizing a drop hammer impact tester. The results show that with the increased impact energy, the visual breakages of the SPR joints become more severe. The maximum impact energy the joints can sustain ranges from 10.0 J to 12.5 J. When the impact energy is less than 12.5 J, the contact force/energy–time curves show similar variations. Moreover, as the impact energy increases, total uptake energy value (Et), maximum uptake energy value (Ef), and maximum contact force (Fm) of the joints increase gradually. The low-speed impact energy has little effect on the maximum static tensile force of the impacted joints. However, the residual energy values decrease with the increase in impact energy. The tensile failure form of the joints is the pulling out of the rivets from the lower plates, and the low-speed impacts have no significant effect on the tensile failure form of the joints.

Evaluation of Fracture Strength after Repair of Cervical External Resorption Cavities with Different Materials

IntroductionThe aim was to evaluate the stress distributions on dentin and repair materials caused by static force applied to teeth, with cervical external root resorption (CER) after repair with different materials using finite element analysis. MethodsThis study was performed with the 3-dimensional finite element analysis method. Access cavity, root canal cavity dimensions, and supporting tissues other than cementum were modeled in the maxillary central tooth. The CER cavity was created on the labial side of the tooth model. The coronal side of the resorption cavity was restored with composite, and the radicular side with different materials (MTA, Biodentine, BioAggregate, calcium-enriched cement [CEM], glass ionomer cement [GIC], and resin-modified glass ionomer cement [RMGIC]). A static force of 300 N was applied to the palatal surface of the crown at an angle of 135° to the long axis of the tooth. The stress distributions in dentin and repair materials were analyzed. ResultsThe highest stress in dentin was seen in the fFigmodel with unrepaired CER. In the models repaired with MTA, GIC, and RMGIC, von Mises stress values in dentin were greater than for repairs with Biodentine, BioAggregate, and CEM materials. The von Mises stress on the repair materials applied to the root were highest for the BioAggregate material. This was followed by CEM, Biodentine, MTA, RMGIC, and GIC materials, respectively. ConclusionThe repair of CER in the tooth significantly decreased the stress values in dentin. Biodentine, BioAggregate, and CEM absorbed more force and caused less stress to be transmitted to dentin compared to MTA, GIC, and RMGIC.

A peak time shifting phenomenon in transformer axial short‐circuit electromagnetic force due to the coupling of electromagnetic‐axial vibration

AbstractAccurately calculating axial electromagnetic force is essential to analyse transformer winding axial stability. Prior research has mainly focused on the effect of winding structure on static axial electromagnetic force and studying vibration by substituting the static force in a time‐varying function. However, the coupling effect between axial electromagnetic force and winding vibration has not been addressed, and no calculation method for the axial electromagnetic force that considers both winding meso‐structures and vibration coupling effects has been proposed. Previously the authors presented an electromagnetic force calculation model that considers winding structure characteristics, and an iterative algorithm for magnetic‐structure coupling calculation. Currently, the winding vibration model was first proposed and the dynamic calculation method was formulated. By applying the method to a typical 110kV transformer, the spatial‐temporal distribution of winding axial short‐circuit electromagnetic force was obtained. It was found that the peak value of the axial short‐circuit electromagnetic force of some windings appears at the second or third peak moment of the short‐circuit current, which is called as peak time shift phenomenon. Further stress analysis indicates that existing evaluation methods may overestimate the short‐circuit resistance of windings by only considering short‐circuit electromagnetic force under maximum peak of short‐circuit current.

A hybrid energy harvesting framework and graphene‐based supercapacitor for 6G and smart grid networks

SummaryThis paper proposes a novel hybrid energy harvesting framework integrated with a graphene‐based supercapacitor to address the energy demands of 6G communication systems and smart grid networks. To ensure consistent power generation, the proposed framework combines diverse energy harvesting mechanisms, including acoustic, vibration, and radio frequency (RF) energy sources. These harvested energies are then efficiently managed and stored in a proposed graphene‐based supercapacitor compared with existing Li‐ion batteries, due to its high energy density and rapid charge‐discharge capabilities. Smart grids and 6G networks can utilize the energy that hybrid systems harvest. This paper examines the analysis of RF energy extracted from various antenna configurations. In the acoustic energy harvesting system, energy extraction has been achieved by subjecting it to acoustic pressure and impedance. Notably, the inclusion of acoustic impedance has resulted in a greater amount of harvested energy. The vibration energy harvesting analysis with angular frequencies under various force conditions is employed. The magnitude of force applied to the harvesting system significantly influences the efficiency of the harvested energy. The three‐dimensional structure and voltage levels of the graphene‐based supercapacitor have been examined for various electrodes. For maximizing the harvested hybrid energy, convex optimization is formulated due to its ability to efficiently navigate complex design spaces while ensuring reliable and globally optimal solutions. CVX tool in MATLAB is used for validation. The results improve the energy harvesting efficiency and enhance the power availability of all the harvesting sources. Furthermore, the compatibility of the proposed framework with existing network infrastructure highlights its potential for seamless integration into real‐world communication and energy distribution systems.

The harmonic resonance and singularity analysis of bifurcation for the magnetized elastic plate with action of time-varying magnetic potential

This paper deals with the superharmonic resonance of a ferromagnetic thin rectangular plate in the air-gap magnetic field excited by armature magnetic potential. Electromagnetic forces applied on the plate by the air-gap magnetic field cause the plate to transversal vibrate, which affects the air-gap magnetic field in turn, resulting the vibration and magnetic field coupling. According to the basic electromagnetic field theory and considering the magnetoelastic coupling effect, the air-gap magnetic field intensity is obtained by solving the Laplace's equation satisfied the air-gap magnetic boundary conditions. The electromagnetic force model of soft ferromagnetic plates is determined based on theories of electromagnetic and elasticity. According to the large deflection theory of plates, basic energy relationships and variational equations of the elastic plate are given. Eventually, the nonlinear magnetoelastic vibration equation of ferromagnetic thin plates is derived using Hamilton's principle and Galerkin method. The multi-scale method is used to solve the superharmonic resonance to obtain the amplitude-frequency response equation and the stability discriminant of solutions. The topological analysis of amplitude-frequency equation is carried out using singularity theory, and the bifurcation characteristics of systems on physical parameter planes in different regions are obtained according to the transition set. The correctness of analytical solutions is verified by comparison with numerical solutions. Through numerical calculations, curves of the static deflection and equivalent magnetic force of plate with parameters are given, and the amplitude curves, dynamic phase plane trajectories and time history diagrams of system response with changes in electromagnetic and structural parameters are plotted. Results show that both the decrease of armature magnetic potential amplitude and the increases of plate thickness and initial air-gap thickness reduce the static deflection. The increase of armature magnetic potential amplitude increases the equivalent magnetic force. As the decrease of initial air-gap thickness and the increases of armature magnetic potential amplitude and excitation force amplitude, the amplitudes of the upper branch and lower branch curves representing stable solutions decrease and increase, respectively, and the single-value solution region increases.