Load Resistance Research Articles

Utilization of Stochastic P-bifurcation for Simultaneous Energy Harvesting and Vibration Suppression: An Experimental Investigation

Abstract This research focuses on the prediction and experimental verification of P-bifurcation as well as the effectiveness in reducing vibrations and harvesting energy with the use of an inertially nonlinear energy harvesting device attached to a single-degree-of-freedom structure subjected to Gaussian broadband base excitation, modeled as white noise. Four experimental scenarios were tested, including three with different resistive loads and one with an open circuit. Frequency domain optimization involved an optimization routine that was designed to minimize the mean squared error in the pendulum velocity's frequency content below two cycles per second while constraining the RMS velocity discrepancy between the simulations and actual experiments to be below 3%. This facilitated accurate predictions of power, vibration suppression, and P-bifurcation. Using the fitted model, an analytically derived P-bifurcation boundary in the noise intensity versus electrical damping plane was presented and experimentally verified. Additionally, power spectral densities for electric power and relative suspended mass velocity were determined for the IPVA system and compared with a top-performing linear system. Results indicated that the monomodal system was the least effective in energy harvesting, while the bimodal and rotational systems significantly enhanced mean and resonant peak power by up to four and two times, respectively. Near the resonant frequency, the peak relative velocity power spectral density decreased by a factor of four, and the mean square relative velocity improved by a factor of two.

Vibration characteristics of piezoelectric pipe conveying fluid subjected to fluid-structure-electrical interaction

This paper mainly investigates the vibration characteristics of piezoelectric pipe conveying fluid subjected to fluid-structure-electrical interaction. Based on the Hamilton’s principle, the dynamic equations of the cantilever piezoelectric pipe subjected to the weight and fluid-structure-electrical interaction are established and solved by using the Galerkin method. Ultimately, complex frequency and critical flow velocity are obtained. The main discussion focused on the influence of electromechanical coupling, resistive load, and dimensionless capacitance on the critical flow velocity under different lengths of piezoelectric materials. It also examined the dynamic trajectories of the real and imaginary parts of the complex frequency under various mass ratios and resistive loads. Furthermore, it explored the impact of parameters representing voltage on the stability of the system. The results indicate various stability evolutions under different lengths of piezoelectric materials, flow velocities, and parameters representing voltage. The stability of the system pipe is influenced by factors such as the length of the piezoelectric material and resistive load.

Quantum Marine Predator Algorithm: A Quantum Leap in Photovoltaic Efficiency Under Dynamic Conditions

The Quantum Marine Predator Algorithm (QMPA) presents a groundbreaking solution to the inherent limitations of conventional Maximum Power Point Tracking (MPPT) techniques in photovoltaic systems. These limitations, such as sluggish response times and inadequate adaptability to environmental fluctuations, are particularly pronounced in regions with challenging weather patterns like Sunderland. QMPA emerges as a formidable contender by seamlessly integrating the sophisticated hunting tactics of marine predators with the principles of quantum mechanics. This amalgamation not only enhances operational efficiency but also addresses the need for real-time adaptability. One of the most striking advantages of QMPA is its remarkable improvement in response time and adaptability. Compared to traditional MPPT methods, which often struggle to keep pace with rapidly changing environmental factors, QMPA demonstrates a significant reduction in response time, resulting in up to a 30% increase in efficiency under fluctuating irradiance conditions for a resistive load of 100 Ω. These findings are derived from extensive experimentation using NASA’s worldwide power prediction data. Through a detailed comparative analysis with existing MPPT methodologies, QMPA consistently outperforms its counterparts, exhibiting superior operational efficiency and stability across varying environmental scenarios. By substantiating its claims with concrete data and measurable improvements, this research transcends generic assertions and establishes QMPA as a tangible advancement in MPPT technology.

Accentuated Eccentric Loading and Alternative Set Structures: A Narrative Review for Potential Synergies in Resistance Training.

Chae, S, McDowell, KW, Baur, ML, Long, SA, Tufano, JJ, and Stone, MH. Accentuated eccentric loading and alternative set structures: A narrative review for potential synergies in resistance training. J Strength Cond Res 38(11): 1987-2000, 2024-As athletes become adapted to training over time, it becomes more difficult to develop their strength and power. In a conventional resistance training strategy, volume or load may be increased to provide novel stimuli to break through a plateau. However, physiological stress markers increase with increased volume or load, which is an innate shortcoming. In that case, practitioners strive to develop unconventional strategies that could increase training stimuli while adjusting fatigue. Two programming tactics, accentuated eccentric loading (AEL) using eccentric overload and alternative set structures (AS) using intraset rests, have been reported to increase training stimuli and alleviate fatigue, respectively. Importantly, when merging AEL and AS in various contexts, the 2 benefits could be accomplished together. Because AEL and AS cause different outcomes, it is important to deal with when and how they may be integrated into periodization. Moreover, prescribing eccentric overload and intraset rests requires logistical considerations that need to be addressed. This review discusses the scientific and practical aspects of AEL and AS to further optimize strength and power adaptations. This review discusses (a) scientific evidence as to which tactic is effective for a certain block, (b) potential practical applications, and (c) related discussions and future research directions.

Swelling problems in immobilized filler: an improvement method and comparative study of the effect of different fillers on biotrickling filters.

Immobilized fillers have been increasingly utilized in biotrickling filters (BTFs) due to their positive impact on shock load resistance and recovery performance. However, due to the inherent characteristics of its immobilized carrier, the immobilized filler is prone to swelling during the long-term operation of the system, resulting in increased pressure drop. Polyurethane (PU) sponge was used as the cross-linked skeleton of immobilized filler and compared with direct emulsified cross-linked immobilized filler for treating ethylbenzene gas. In the early stage, both fillers can maintain good performance despite changes in the inlet concentration and short-term stagnation. However, on the 107th day of operation, the immobilized filler experienced swelling, and the pressure drop sharply increased to 137.2 Pa, while the PU immobilized filler was still able to maintain a low-pressure drop level. The results of the microbial diversity analysis revealed that the microbial community structure of PU immobilized fillers remained relatively stable when responding to the fluctuations in operating conditions. PU sponges as the skeleton can effectively prolong the service life of the immobilized filler and improve the performance of the biotrickling filter.

Inspiratory Muscle Training Using Tapered Flow Resistive Loading to Enhance Pulmonary Function in Smokers: A Randomized Controlled Trial

Inspiratory Muscle Training Using Tapered Flow Resistive Loading to Enhance Pulmonary Function in Smokers: A Randomized Controlled Trial

High-efficiency quad-band RF energy harvesting system with improved cross-coupled differential-drive rectifier

Abstract RF energy harvesting technology has garnered significant attention from researchers in recent years. This paper presents a high-efficiency quad-band RF energy harvesting (RFEH) system. It introduces an improved cross-coupled differential-drive rectifier designed for ambient wireless powering, capable of harnessing power from four distinct ambient RF sources: FM-100, DTV-600, GSM-1800, and WiFi-2400 frequency bands. The proposed RFEH system demonstrates notable advancements, achieving a high RF to DC conversion efficiency of over 80 % within an input power range of −5 dB m to +13 dB m, with a 5 kΩ resistance load. This power output is deemed sufficient for energizing low-power micro-devices autonomously, without reliance on external power sources. Notably, the DC output voltage of the proposed RFEH system exhibits a high level of stability against variations in input power, a characteristic not adequately addressed in existing systems.

Triboelectric nanogenerator based on silane-coupled LTA/PDMS for physiological monitoring and biomechanical energy harvesting

Energy harvesting from ambient sources present in the environment is essential to replace traditional energy sources. These strategies can diversify the energy sources, reduce maintenance, lower costs, and provide near-perpetual operation of the devices. In this work, a triboelectric nanogenerator (TENG) based on silane-coupled Linde type A/polydimethylsiloxane (LTA/PDMS) is developed for harsh environmental conditions. The silane-coupled LTA/PDMS-based TENG can produce a high output power density of 42.6 µW/cm2 at a load resistance of 10 MΩ and operates at an open-circuit voltage of 120 V and a short-circuit current of 15 µA under a damping frequency of 14 Hz. Furthermore, the device shows ultra-robust and stable cyclic repeatability for more than 30 k cycles. The fabricated TENG is used for the physiological monitoring and charging of commercial capacitors to drive low-power electronic devices. Hence, these results suggest that the silane-coupled LTA/PDMS approach can be used to fabricate ultra-robust TENGs for harsh environmental conditions and also provides an effective path toward wearable self-powered microelectronic devices.

Evaluation of a motor generator adapted to biogas

With the need to reduce the environmental impacts caused by fossil fuels and minimize the problems caused by a possible crisis arising from price increases or even energy shortages, alternative and renewable ways to replace such non-renewable sources are sought. them. Among the various forms, there is biogas, which can be used as fuel in internal combustion engines. In this context, the present work aimed to evaluate a motor generator adapted to biogas. A 4-stroke, single-cylinder, gasoline-powered motor generator was used, with a nominal power of 6.5 HP. The tests were carried out, taking 6 times with an interval of 10 minutes each, where the rotations and energy consumption of the motor were measured, in addition to the voltage and electric current generated to supply the resistive load. The resistive load used in the motor generator was provided by lighting seven incandescent lamps of 100W nominal each, resulting in a verified measurement of 510W, which was maintained throughout the test. The motor-generator set consumed an average volumetric flow of 1.97m³ h-¹ and an average mass flow of 1.228 kg h-¹ for a generator power of 501 W and a set efficiency of 7.53%.

Experimental and numerical investigation on composite beam–column joint connection behavior using different types of connection schemes

Abstract Over the past few decades, composite joints have been regarded as one of the most promising approaches. After reviewing the research articles dealing with composite beam-column joints, it can be withdrawn that few researchers studied and developed different types of composite beam-column joints. The objectives of this paper to study the effect and behavior of different connection types on the composite beam – column joint under repeated loading as well as to investigate new forms of slab connection with column flange in composite connection joints, aiming to enhance the behaviors of the joints and make the slab endure a part of the load in a more efficient way. Five specimens with various connection types were tested to failure; the composite model number two (CM2) was considered the control specimen. Regarding the ultimate moment, the result found that CM5 has moment 50.47% more than control specimen, the lowest rotation value was in CM5. The general behaviours of the FEM were in good accordance with the experiment results. According to the parametric a higher yield strength is more rigid stiffer, the effect of web thickness on the load is too small and increase in load resistance with an increase in beam flange thickness.

A Wearable Multichannel Electrical Stimulator for Tremor Suppression

Abstract Pathological wrist and finger tremors can be mitigated by out-of-phase stimulation of the sensory nerves in the flexor and extensor muscles. This study endeavors to develop a portable, multichannel electrical stimulator designed to deliver high-frequency, low-intensity, biphasic charge-balanced current pulses within a practical load range to effectively suppress wrist and finger tremors. The circuit architecture integrates an Arduino Nanomicrocontroller, a four-channel digital potentiometer, and four Howland current pumps. The Howland current pump, employing an operational amplifier, generates bipolar currents by accepting bipolar voltages, whereas the digital potentiometer offers programmable bipolar voltages via its wiper terminals. Experimental results indicate that the pulse frequency can be adjusted between 50 Hz and 200 Hz, and the current level can be modulated within a range of −10 mA to +10 mA, with load resistance spanning 100 Ω to 1.3 kΩ. This portable and multichannel device is effective in delivering high-frequency, low-intensity sensory nerve stimulation through programmable biphasic charge-balanced current pulses. The proposed stimulator has the potential to enable adaptive muscle activation, thereby initiating, promoting, and generating movements, and facilitating interactive in-home neurorehabilitation for disabled patients. The portability and programmability of this device make it a promising tool for personalized tremor management and rehabilitation, enhancing the quality of life for individuals with motor impairments.

Fabrication of Cu-Infiltrated Journal Bearing by Binder Jetting Additive Manufacturing

In this study, considering the economic feasibility of products that can be produced through the binder jetting additive manufacturing process, 316L stainless steel, a widely used material with a wide particle size ranging from 15 to 106 μm, was used. The lubrication effect was increased by internal patterning through design for additive manufacturing, and journal bearing parts with excellent load resistance and wear resistance were implemented by using wear-resistant Cu as an infiltration material. In addition, to investigate the amount of Cu infiltrated as a function of porosity, the parts were pre-sintered from 1423 K to 1573 K, and the best performance was obtained when Cu was infiltrated after pre-sintering at 1473 K. As a result of rig testing of Cu-infiltrated journal bearings, mechanical properties were obtained that were more than 50% improved compared to those of mass products.

Inhalable cyclodextrin metal-organic framework dry powder enhanced direct pulmonary delivery of paclitaxel for the treatment of lung cancer

Inhalation dry powders are in great demand for the treatment of lung diseases due to their unique advantages such as excellent direct delivery, rapid onset of action, and reduced systemic side effects. Herein, this work highlights the successful development of an inhalable paclitaxel dry powder, which is facilely constructed through the optimization of the formulation between chemotherapy components (paclitaxel) and a metal-organic framework (MOF) carrier (γ-cyclodextrin and KOH). Moderate pore and particle size distribution, as well as low hygroscopicity endow the dry powder with excellent loading efficiency and resistance to degradation. All ingredients and their interactions confer favorable emptying rates, flowability, and pulmonary deposition, as well as direct lung drug delivery and release. These attractive characteristics enable the dry powder to effectively enhance cytotoxicity, improve pharmacokinetics, promote lung accumulation, and reduce the side effects of paclitaxel. Thus, this paclitaxel dry powder may open a new avenue for the inhalation treatment of diseases, greatly advancing its clinical application.

Analytical parametric analysis of profiled composite walls reinforced with embedded tubes subjected to axial loading

This paper presents analytical analysis of the axial load behavior of a profiled composite wall (PCW) consisting of two profiled steel sheets (PSSs) filled with concrete and reinforced with/without embedded cold-formed steel tubes (CFSTs). This type of composite wall was designed to resist in-plane axial loading (bearing wall). Three experimental samples were tested and its results were presented in this research. The ultimate axial loads of 42 PCW FE models were calculated based on a published work done by the authors earlier. Comparisons between the results of the FE models via the proposed methods and those of Eurocode 4, BS5400, AISC, Hossain (2000), and Wright (1998) were made. Applied calculation formulas for the ultimate axial load were presented via regression analysis theory on the basis of the verified FE results. Comparisons were made between the developed formulas and existing experimental tests, such as those of Hossain (2000) and Wright (1998) and an experimental study performed by the author, and perfect accuracy was achieved. The results of this study proved that the effects of the embedded CFSTs reduced local buckling of the PSS and increased ductility with increasing axial load resistance of the PCW. The provided formulas accurately predict the axial load of the PCWs.

Experimental and analytical investigations on bond–slip behavior of steel reinforcement in UHPFRC considering yielding

AbstractThe bond behavior between ultra‐high‐performance fibre‐reinforced concrete (UHPFRC) and steel rebars plays an important role in the load‐bearing capacity and serviceability of structural members. A suitable bond–slip model is essential for predicting the load resistance and deformation capacity of members, after cracking of the UHPFRC. This paper studies the bond strength between ribbed steel bars and the surrounding UHPFRC before and after yielding of the steel reinforcement. To determine the corresponding bond–slip relationship, pull‐out tests, with varying embedment lengths of the reinforcement, namely 2 times and 10 times the rebar diameter, and diameter of reinforcing bars ranging from 10 mm to 16 mm were conducted. The bond stress, strain and slip along the embedment length of the steel rebars were measured by strain gauges and displacement transducers. Based on the test data, a bond stress–slip model was derived before (elastic stage) and after (inelastic stage) yielding of the reinforcement. The slip at the yield point is suggested through theoretical equations. The post‐yield bond–slip model is based on yield bond stress and frictional bond stress. The two‐part model was validated through iterative procedures and is able to predict the applied force, bond stress and strain distribution along the reinforcing bar. A comparison between the test data and analytical results demonstrates a good predictive capacity on the bond behavior of reinforcement in UHPFRC both before and after yielding of the reinforcement.

Fabrication of Vanadium Oxide-encapsulated Hybrid Carbon Nanospheres for Enhanced Tribological Performance.

A new sulfur-containing carbon nanospheres encapsulated with vanadium oxide (V@SCN) is synthesized through a one-pot oxidation polymerization and then carbonization method. The prepared V@SCNs exhibit good dispersibility as a lubricant additive, which is owing to the inherited lipophilic organic functional groups in the sulfur-containing carbon shell derived from the carbonization of polythiophene. The agglomeration and precipitation of metals in the base oil are also avoided through the encapsulation of lipophilic carbon shells. The stress and thermal simulation results show that the vanadium oxide core bestows upon the carbon nanospheres enhanced load resistance and superior thermal conductivity, which contributes to their excellent tribological properties. Introducing 0.04M-V@SCN to the base oil leads to favorable tribological characteristics, such as a fourfold rise in extreme pressure capacity from 250 to 1050N, a reduction in friction coefficient from 0.2 to ≈0.1, and a substantial decrease in wear by 90.2%. The lubrication mechanism of V@SCNs as lubricant additive involves the formation of a robust protective film on the friction pair, which is formed via complex physical and chemical reactions with the friction pair during friction.

A nonlinear and asymmetric monostable compliant ortho-planar spring piezoelectric vibrational energy harvester using a H-I structure

This paper proposes a compliant ortho-planar spring piezoelectric vibrational energy harvester (COPS-PVEH) using a H-I structure that exploits a nonlinearity and an asymmetric mono-stability to enhance the bandwidth of the device. The main structure is based on a double clamped beam (I-structure) coupled with four cantilever beams (H-structure) and an ortho-planar spring in the centre of the I-structure. Finite element analysis (FEA), analytical modelling, and experimentation were performed to analyse the dynamical and electrical behaviour of the harvester. The device was fabricated using polylactide (PLA). Six bimorph PZT-5H piezoelectric materials, electrically connected in parallel, were used as piezoelectric generators. The device was tested using an optimum load resistor of 90 kΩ under sinusoidal and sine sweep excitation in the gravity (vertical) direction. The pre-load (due to gravitation) causes a softening nonlinearity and an asymmetric mono-stability in the potential energy function. The results show that multiple peaks are observed in the output voltage of the harvester in the FEA, analytical modelling, and experimentation under harmonic excitation in the sub 15 Hz frequency range. Furthermore, analytical modelling and experimentation exhibit softening nonlinearity and chaotic behaviour, reaching a maximum amplitude power of 1.01 mW (at 8.3 Hz) and 1.07 mW (at 9.5 Hz) respectively under sine sweep excitation (amplitude of 0.6 g (g = 9.81 m/s2)). Experimentally, the harvester also generates an average power greater than 46 µW with a 6.8 Hz bandwidth under the same excitation. The softening nonlinearity and asymmetric mono-stability enhance the bandwidth of the harvester in the low frequency region where most broadband ambient vibrations are available in practical environments.

Numerical Investigation of Polymer-based Biomaterials for Artificial Hip Joint with Diverse Boundary Conditions

Background: Hip suffering is a serious concern for human health, which may be caused by arthritis, accidents, and childhood disorders; hence, man-made joints are the only option for restoring the function of natural hips and ensuring a comfortable life. To design an effective hip joint is a challenging task; there are myriads of novel designs continuously patented over the last two decades. Methods: The finite element approach was utilized in this extensive investigation to assess selfmated polymer-based biomaterials (PTFE, UHMWPE, and PEEK) with different boundary conditions. The numerical analysis was performed to find the stress intensity and deflection of the femoral head and the acetabular components; the evaluation was done critically with a 10-node quadratic tetrahedron element and different mesh intensities. Results: The detailed outcome showcases that the bare PEEK mated GO-PEEK has good load resistance and is affected by minimum stress and deflection, which is quantified at 20.89% less than the PTFE with GO-PEEK (M3) combination. This stress and deflection are quite higher than those of metal implants (Ti6Al4V) but comparatively more prominent materials for human cortical bone. Conclusion: This investigation proved the polymer-on-polymer combination effectively eliminates stress shielding and metal ion emission, reducing revision surgery and elevating implant longevity. Therefore, it was identified that PEEK-based polymer composites are the best-suited alternative substance for hip repair applications.

Cumulative optimization of magnetoelectric composite-based wireless energy transfer

Abstract Magnetoelectric composite-based wireless energy transfer (WET) comprising omnidirectional ring-shaped transmitter and laminated plate receiver elements have been studied experimentally and theoretically. The objective is to reveal the conditions conducive to achieving optimal power based on the device geometries, the relative orientations, and the operating conditions, including the vibrational frequency, applied electric field, bias magnetic field, and the corresponding resistive load. The reformulated physics-based model establishes the dependence of the output power on the load resistance, elucidating a strong interrelationship between the transferred power, vibrational displacement, and strain transduction coefficient based on relaxing all previous simplifying assumptions. The model ascertained the non-monotonic variation of the output power as a function of the interface coupling factor, emphasizing the crucial influence of gradual change in material properties within the strain-mediated magnetoelectric transmitter and receiver devices, i.e., an agile design framework for multiferroics-based power transfer devices.

Differential neuromotor control of the vertical and longitudinal genioglossus muscle fibers: An overlooked tongue retractor

IntroductionThe genioglossus (GG) is known to be the main tongue protrusor, and therefore plays a major role in breathing. However, due to the fan shape of the GG fibers, it could be assumed that contraction of the anterior fibers of the GG do not cause tongue protrusion. In this study, we examined the effect of contraction of the anterior-vertical fibers of the GG (GGV) on the tongue and their EMG activity during wakefulness and sleep. The findings were compared to those of the longitudinal fibers (GGL), which, based on their orientation, are responsible for tongue protrusion. MethodsFine-wire electrode pairs were placed into the GGV and GGL in 11 patients with untreated OSA. Movement of the tongue during electrical stimulation at each site was videoed. The same electrodes were used to record EMG from both sites during respiratory stimulation by inspiratory loading and CO2 rebreathing during wakefulness. During sleep, repetitive flow limitation events were induced with low-level CPAP to augment GG activity. ResultsIn all participants, electrical stimulation of GGL and GGV protruded and retracted the tongue, respectively. Respiratory stimulation increased GG activity, but GGV reached only 39 % and 23 % of peak GGL activity during high resistive loading and PCO2 of 65 mmHg, respectively. Flow limitation during sleep increased GGL to levels that were considerably higher than awake baseline, but GGV activity remained tonic or with minimal phasic activity, reaching on average 15 % of GGL peak activity. ConclusionsOur electrical stimulation findings indicate that GGV is a tongue retractor and depressor. Tongue stimulation for OSA should avoid this area. The EMG results demonstrate that the anterior part of the GG is controlled very differently from the longitudinal protrusive fibers. The GGV responses are similar to those previously found in tongue retractors and peri-pharyngeal muscles other than the GG, in which diminished activation during sleep is likely to be involved in the failure of increasing GGL activity to alleviate flow limitation.