High Amplitude Research Articles

Frequency-dependent electrochemical breakdown of hydrogel ionotronics

When an ionic conductor meets an electronic conductor, ions and electrons couple at the interface between ionic and electronic circuits, enabling a class of devices: ionotronics. Such a coupling gives innovations but can cause electrochemical breakdown. Rapid advances in hydrogel ionotronics, in which hydrogel serves as stretchable, transparent, ionic conductor, highlight an urgent need: a general approach and criterion to study electrochemical breakdown under AC condition. Here we study the breakdown behavior of a metal-hydrogel-metal ionotronic system subject to alternating voltages of various frequencies and amplitudes. First, we apply a sinusoidal voltage to the ionotronic system which is connected in series to a load resistor, and compare the waveforms of the applied voltage and the output voltage between the two ends of the load resistor at various frequencies and amplitudes. Electrochemical breakdown tends to take place at low frequencies and high amplitudes, and causes distortion of waveform of the output voltage. Next, we develop an electric circuit model, in which each hydrogel-metal junction is modeled as a constant phase element in parallel with a leakage resistor and the hydrogel is modeled as a resistor. Our experiments show that the electrochemical window is insensitive to the frequency and amplitude of applied voltage, as well as to the concentration of ions in the hydrogel. Through a combination of experiment and theory, we further propose a frequency-amplitude phase diagram. Different from DC condition, the breakdown behavior under AC condition depends not only on the amplitude of applied voltage, but also on the frequency of applied voltage. We also show that electrochemical reaction can be retarded by stretching the hydrogel and by increasing the frequency. It is hoped that this work will guide the development of stable and reliable hydrogel ionotronic devices.

The effect of operating conditions on heat transfer for parallel plate heat exchangers of thermoacoustic standing wave systems

Thermoacoustic systems represent a promising technology for clean cooling and/or power generation. However, understanding of the behavior of oscillatory flow inside the system under high drive ratio operating conditions, at elevated mean pressures, range of frequencies, and high flow amplitudes, remains limited and poses challenges for designing efficient systems with minimal losses. This paper presents a numerical investigation into the flow and heat transfer characteristics across a coupled cold and hot parallel-plate heat exchanger operating under standing-wave type oscillatory flow conditions. The models were developed for various conditions, spanning frequencies from 13 Hz to 100 Hz and mean pressures between 1 and 20 bar, using both nitrogen and helium as working fluids. The study reveals significant phenomena such as heat accumulation and annular effects in both temperature and velocity/vorticity fields. These findings were discussed in the context of their impact on the heat transfer performance of the heat exchanger. Specifically, the emergence of vortices was examined in relation to mean pressure, alongside jet-like velocity profiles and natural convection effects. Furthermore, the paper includes a comparative analysis between the heat transfer model employed in this study and previous works, aiming to validate the findings. This research enhances the understanding of fluid dynamics and heat transfer phenomena within heat exchangers of thermoacoustic devices, thereby contributing to advancements in future design improvements.

A Low-Complexity Beamformer for Ultrasound Imaging Based on Sub-Beamformer and Multi-Apodization With Cross-Correlation

ObjectiveThis paper proposes an ultrasound imaging algorithm based on sub-beamformer and multi-apodization with cross-correlation (SUB-MAX), aiming to achieve high resolution close to the minimum variance (MV) beamforming with low complexity and to enhance image contrast while maintaining background quality. MethodsThe output of two (N/2)-element DAS beamformers with asymmetric phase centers is subtracted, resulting in a large drop in the main-lobe amplitude, while the sidelobe maintains a relatively high amplitude level. Inspired by this characteristic, the coefficients with opposite trends compared with the subtracted output are obtained and fused with the normalized cross-correlation (NCC) weighting matrix acquired by using multi-pair received apodization, the proposed SUB-MAX obtains a new weighting matrix to weight the output of the DAS beamformer. ResultsFor ats_wire point targets, the average full-width at half-maximum (FWHM) of SUB-MAX compared with DAS, DMAS, CF, and MAX decreases by 52.7%, 43.5%, 33.3%, and 52.7%, respectively. For geabr_0 cysts, the average contrast ratio (CR) of SUB-MAX compared with DAS, MV, DMAS, and CF increases by 57.7%, 86.8%, 2.5%, and 14.4%, respectively. Experiments on rat_tumor dataset also indicate that SUB-MAX has a superior comprehensive imaging performance. ConclusionThe experimental results indicate that the superior comprehensive imaging performance of the proposed SUB-MAX is expected to be suitable for real-time imaging systems due to its non-reliance on covariance matrix inversion.

Ultrasonic vibration-assisted single point incremental forming of hemispherical shaped component using AA3003 material

ABSTRACT Ultrasonic vibration-assisted single point incremental forming is a recent hybrid process variant of the single point incremental forming process. In this process, longitudinal ultrasonic vibration is used as an assistance in the conventional forming process. In this paper, the effect of amplitude of vibration in the ultrasonic vibration assisted single point incremental forming process have been researched. For the same, experimental work has been carried out by forming the hemispherical shaped components using multistage forming strategy. Moreover, numerical simulation work has been carried out using the LSDYNA solver and the results have been discussed in the light of depth of forming and strain distribution. The experimental fracture forming line is also developed for the AA3003 material for single point incremental forming process. High amplitude of vibration of 12 micron with 20 kHz frequency leads to poor formability; however, the lower amplitude of vibration of 8 micron with 30 kHz frequency leads to good formability.

Fatigue deformation behavior and fracture mechanism of high fatigue-resistant laser directed energy deposition fabricated titanium alloy: Effect of multi-scale microstructure

The application of the laser directed energy deposition (LDED) titanium (Ti) alloys has been severely impeded by their poor low cycle fatigue (LCF) properties in aerospace industry. Herein, we propose to improve the LCF properties of LDED-ed Ti6Al4V alloys via microstructure adjustment. A solid solution aging 850AA treatment is made to regulate the microstructure into a multi-scale composition dominated by discontinuous αGB and coarsened αP+(αS+β) phases. The LCF properties of LDED-ed Ti6Al4V with a multi-scale microstructure even outperform the wrought Ti6Al4V at high strain amplitudes. Furthermore, this multi-scale microstructure has special local plastic deformation behavior and dislocation activities under cyclic stress loading, which strongly affects the internal stress evolution and crack propagation. The fatigue softening behavior is attributed to the combined effect of back stress and friction stress. Fatigue cracks are deflected by the α/β boundary when the angle (φ) between the long axis of α lamellae and the crack direction is less than 35°. The transgranular fracture occurs when φ is close to 90° (70°–90°). Meanwhile, the fatigue crack usually propagates along the basal or prismatic planes with high Schmid factors. These findings provide novel insights into the microstructure design of LDED-ed Ti alloys with high fatigue damage tolerance.

Dislocation structures in micron-sized Ni single crystals produced via tension–compression cyclic loading

The strength and deformation characteristics of micron-sized metals under monotonic loading have long been investigated. In contrast, despite its practical significance, their fatigue behavior remains unexplored. To this end, tension–compression fatigue tests were conducted herein on micron-sized Ni single crystals to elucidate their fatigue behavior and internal dislocation structures. Specimens with square cross sections of 5 and 2 μm on a side were prepared and subjected to cyclic loading at low stress amplitudes, which did not induce fatigue cracking in bulk metals. Remarkably, fatigue cracks were not present in 5-μm-wide specimens, whereas intrusions/extrusions were observed in 2-μm-wide specimens, leading to crack initiation. Vein-like structures comprising edge dislocations were observed in 5-μm-wide specimens, which are commonly observed in bulk metals. Conversely, the dislocation structure in 2-μm-wide specimens resembled that associated with persistent slip bands, which cause intrusions/extrusions and fatigue cracking in bulk metals under high stress amplitudes. The experimental findings indicate that the fatigue behavior of small-sized metal single crystals is characterized by the absence of vein formation.

Dual-band tunable electromagnetically induced transparency in vanadium dioxide-based miniaturized terahertz metasurfaces

A dual-band electromagnetically induced transparency (EIT) effect with high transmission amplitudes and polarization-insensitive characteristic is realized in vanadium dioxide (VO2)-based miniaturized terahertz metasurfaces. The unit cell comprises a metallic spiral (MS) structure, a small square metal frame (SMF2) structure, and a large square metal frame (SMF1) structure. Two transparent windows with the transmission amplitudes of 0.84 and 0.82 are obtained. The surface current distributions reveal that the dual-band EIT effect is created by the bright-bright-quasi-dark coupling mode. The two transparent windows achieve modulation depths of 45.2% and 42.7%, with maximum group delays of 3.24 ps and 3.17 ps, respectively. The proposed EIT metasurfaces exhibit an electric size of only 0.25λ0, which is considerably smaller than that of other dual-band EIT metasurfaces. The present study offers a novel approach to investigating multi-band EIT metasurfaces, with considerable promise for the development of multi-band communication devices.

Parameterization of nonlinear aeroelastic reduced order models via direct interpolation of Taylor partial derivatives

The identification of optimally sparse Taylor partial derivatives presents a new opportunity in efficient nonlinear model reduction for complex aeroelastic systems. Unfortunately, for this class of reduced order model (ROM), the robustness that is observed in the linear regime to parameters including; dynamic pressure, control hinge linear stiffness, or even freeplay, can be quickly compromised in the nonlinear regime. In this paper, the nonlinear sensitivity of selected critical parameters is addressed by interpolating a library of nonlinear unsteady aerodynamic ROMs across a compact subspace in dynamic pressure and freeplay magnitude. The ROM, based on Lagrange interpolation of sparse higher-order Taylor partial derivatives, demonstrates excellent precision in modelling high amplitude transonic limit cycle oscillations for an all-movable wing with freeplay, capturing the LCO region (up to 96% of the linear flutter boundary), and for a range of freeplay values.

Surface degradation of epoxy resin exposed to corona discharge under bipolar square wave field: From phenomenon to the insights

The unavoidable corona discharge induced by distorted field is detrimental to the safety of power equipment, especially the equipment with high voltage magnitude and high frequency. In this paper, the degradation morphology, residual components, lifetime of endurance, partial discharge characteristics, and evolution of surface traps of epoxy insulation under bipolar square wave field is investigated. The results show that degraded zone exhibits as three layers with round pits and channel-like ravines on the surface of epoxy resin exposed to corona discharge. It is demonstrated that more oxygen element during corona discharge while more carbon element during breakdown appeared, and nano-Al2O3 fillers migrates to the discharged zone. The maximum temperature and number of emitted phonons increase with voltage amplitude and frequency in power law and exponential form, respectively, corresponding to the fitting function of endurance lifetime. The emitted light is concentrated on the near ultraviolet (UV) and infrared ray (IR) band, indicating the energy pooling and thermal effect of corona discharge, which interprets the distinct degradation behavior of samples under sinusoidal and bipolar square wave voltage. The effect of space charge and thermal conductivity should be considered simultaneously in the degradation of epoxy insulation under bipolar square wave field due to polarity reversal and high frequency, which is proved by the disparate behavior of EP/nano-Al2O3 composites resistance to corona discharge and the breakdown moment at falling edge of bipolar square wave voltage. This work may contribute to the advancement of resistance to corona discharge degradation in equipment with high power density, high voltage amplitude and high frequency.

Holocene Paleoclimate Changes around Qinghai Lake in the Northeastern Qinghai-Tibet Plateau: Insights from Isotope Geochemistry of Aeolian Sediment

The stable carbon isotope composition of total organic matter (δ13Corg) has been utilized in aeolian sediments, serving as an indicator for reconstructing terrestrial paleoenvironments. The Qinghai Lake (QHL) Basin is a climate-sensitive region of significant importance in paleoclimatic reconstruction. However, the reconstructed climatic variations based on δ13Corg in aeolian sediments in the QHL Basin in the northeastern Qinghai-Tibet Plateau (QTP) are lacking, and their paleoclimatic significance remains poorly understood. By conducting δ13Corg measurements on the Niaodao (ND) aeolian profile near QHL, we reconstructed the paleoclimate changes of 11 ka–present. The variation range of the δ13Corg values in the ND profile indicated the terrestrial ecosystems were not the sole contributor to lacustrine organic matter. The δ13Corg values are an indicator of historical temperature changes in the study area, exhibiting similar trends with the reconstruction of Chinese summer temperatures, East Asian air temperature, global temperature, and Northern Hemisphere summer insolation at 37° N. The temperature increased with high frequency and amplitude oscillations, with strong aeolian activity and low total organic carbon accumulation during the Early Holocene. The temperature was maintained at a high and stable level, with the weakest aeolian activity and intensified pedogenesis during the Middle Holocene. The temperature decreased at a high rate, with renewed aeolian activity and weak pedogenesis during the Late Holocene.

Study on Surfactant-Polymer Flooding after Polymer Flooding in High-Permeability Heterogeneous Offshore Oilfields: A Case Study of Bohai S Oilfield.

Polymer flooding is an effective development technology to enhance oil recovery, and it has been widely used all over the world. However, after long-term polymer flooding, a large number of oilfields have experienced a sharp decline in reservoir development efficiency. High water cut wells, serious dispersion of residual oil distribution and complex reservoir conditions all bring great challenges to enhance oil recovery. In this study, the method of enhancing oil recovery after polymer flooding was studied by taking the S Oilfield as an example. A surfactant-polymer system suitable for high-permeability heterogeneous oilfields was developed, comprising biogenic surfactants and polymers. Microscopic displacement experiments were conducted using cast thin sections from the S Oilfield, and nuclear magnetic resonance was employed for core displacement experiments. Numerical simulation experiments were also conducted on the S Oilfield. The results show that the enhanced oil recovery mechanism of the surfactant-polymer system is to adjust the flow direction, expand the swept volume, emulsify crude oil and reduce interfacial tension. Surfactant-polymer flooding proves to be effective in improving recovery efficiency, significantly reducing the time of flooding and further enhancing the strong swept area. The nuclear magnetic resonance results indicate a high amplitude of passive utilization of residual oil during the surfactant-polymer flooding stage, highlighting the enormous potential for an increased recovery ratio. Surfactant-polymer flooding emerges as a more suitable technique to enhance oil recovery in the post polymer-flooding stage in high-permeability heterogeneous oilfields.

Cyclic inelastic behaviour of a bonded patch repair system used for pipes with through-wall corrosion damage

Repairs of through-wall corrosion damage in pipes conveying liquids using bonded metallic patches are becoming common in the oil and gas industry. Usually, this kind of patch is used in association with a composite sleeve, and it is essential to assure that the repair wońt leak. The use of bonded metallic patches associated with the composite sleeve is not forbidden in the standards for the design of composite repair systems (such as ASME PCC-2 and ISO 24817). However, they do not address this very frequent practice adopted in industry. Since the patch is responsible for sustaining most of the pressure of the repair, it becomes necessary to further understand its behaviour. This paper investigates the cyclic inelastic behaviour of a metal patch/adhesive system and its effect on the failure pressure. Hydrostatic tests were performed regarding how pressure variations can generate cyclic inelastic strains in the adhesive layer that bonds the metal patch to the pipe, and how this cyclic loading–unloading process ultimately affects the failure pressure. The failure pressure in monotonic burst tests can be reasonably modelled using basic concepts of linear elastic fracture mechanics. Although the assumption of a brittle-elastic behaviour of the repair system seems adequate in the case of monotonic loading, it is not in the case of cyclic tests with high pressure amplitudes. Repairs in steel pipes under pressure with a 25 mm diameter hole failed after a very small number of cycles with pressure amplitude of 80% of the average failure pressure obtained in monotonic burst tests. To help understanding the behaviour of the system, single lap joints were studied. The patch and pipe are not subjected to significant permanent deformations, while the adhesive layer has an inelastic behaviour. Results show that the lap joints present a rate-dependent behaviour in tensile tests and may present highly different cyclic responses which are quite sensitive to very small perturbations in the manufacturing process.

Fatigue life prediction for high-speed railway bridges by reconstructing monitoring-based dynamic stress

Abstract Bridge responses that are excited by high-speed trains have the characteristics of high amplitude, high cycle, and large dynamic effects, which greatly affect the fatigue bearing capacity of affected bridges. To achieve reliable analysis of the fatigue performance of high-speed railway bridges, this study developed a bridge fatigue life prediction method based on the reconstruction of the train-induced dynamic stress time history. First, the equations for solving the static stress time history under influence line virtual loading are derived, and then the dynamic stress time history reconstruction method based on two types of dynamic correction factors is proposed. The statistical characteristics of the train loads and dynamic correction factors are fit according to monitoring data, and bridge fatigue life prediction is realized by use of the reliability theory. Finally, the applicability and effectiveness of the proposed method are verified by using a train-bridge interaction model and monitoring data from a long-span high-speed railway bridge. The results show that the proposed method can greatly improve the accuracy of fatigue performance analysis and can effectively predict the fatigue life of high-speed railway bridges under complex loads. These results can provide an important reference for fatigue evaluation of high-speed railway bridges.

SoftWind: Software-defined trajectory correction modelling of gust wind effects on internet of drone things using glowworm swarm optimization

The dynamic nature of the atmosphere, especially wind gust, poses a crucial challenge to efficient and real-time drone operations. This article presents a novel MQTT based software-defined drone network for trajectory correction of drone flights in gusty wind conditions using Glowworm Swarm Optimization (GSO). By imposing the GSO to the software-defined drone network, our proposed model SoftWind has optimized the navigation and control capabilities of drones by correcting the trajectories in a gusty wind environment. We have analyzed the trajectories and convergence of drones due to wind gusts. As wind disturbances affect the trajectories of drones, we have corrected it by our trajectory correction model and evaluated the direction of the drones must fly to mitigate the wind gust and the resultant velocity compared to the no-wind environment. This study analyzed the trajectories of 100 drone flights due to various wind gust lengths (i.e., 40 m, 10 m, 6 m, and 3 m) for a fixed gust amplitude of 15 m/s and various gust amplitude (i.e., 0 m/s, 5 m/s, 15 m/s, and 40 m/s) for a fixed gust length 5 m. We observed that all the drones are converged to a single point due to low gust length (≤ 5 m) and high gust amplitude (≥ 35 m/s). It is also found that the direction of the drone must fly 28.87°. East of South to mitigate the effect of wind gusts having 10 m gust length and 15 m/s gust amplitude and the resultant velocity of the drone is 22.38 m/s. The result shows that SoftWind reduces the convergence time by 26 %-54 % as compared to other existing models.

Harvesting vibration energy by quad-stable piezoelectric cantilever beam: Modeling, fabrication and testing

The combination of beams with piezoelectric patches has become a prevalent energy harvesting tool due to its ease of use. Typical energy harvesting systems are usually linear, and their efficiency is not satisfying due to low-frequency bandwidth. In this paper, a quad-stable piezoelectric vibration energy harvester is analyzed both numerically and experimentally. The primary purpose of this investigation is to analyze the static and dynamic characteristics of a proposed quad-stable system to consider its potential for application in broadband energy harvesting comprehensively. The harvester system consists of a slotted cantilever beam, a piezoelectric patch, a pair of tip-mass blocks, and a double-sided clip. The cantilever beam is subjected to pre-displacement constraints made by a mutual self-constraint at the free end of it. The nonlinear behaviors of the harvester system, including snap-through and softening phenomena, are analyzed using the assumed modes and finite element method (FEM). The harvester's vibration equation is solved numerically and through an FE model which is made by an in-house finite element software. A prototype is designed and fabricated to validate the mathematical model and FE simulation. The experimental force-displacement diagram of the harvester displays distinct discontinuities, reflecting abrupt transitions occurring while switching its stable states. The prototype dynamics are analyzed by harmonic base excitation with different amplitude levels in two conditions, including the presence and absence of the piezoelectric patch. The results obtained from the mathematical and FEM model demonstrate a satisfactory correlation with the experimental data. Furthermore, the experimental data reveal the occurrence of the snap-through phenomenon, accompanied by a significant widening of the frequency bandwidth at relatively high amplitude levels. The system has the ability to provide an average output electrical power of 0.288 mW for an electrical resistance of 3.262 kΩ at the excitation frequency of 12.695 Hz and base acceleration amplitude of 3g.

A simple numerical simulation model can elucidate the key factors for designing a miniaturized ion trap mass spectrometer

BackgroundMiniature ion trap mass spectrometer enables mass-to-charge ratio analysis of ions via quadrupole field in a low vacuum environment. It plays an important role in on-site detection due to its portability and specificity. In order to gain a deeper understanding of the analysis mechanism of miniature ion trap mass spectrometers, a quadrupole MS ion trajectory numerical simulation model (QITNS) is established in this paper for ions trajectory calculation under the action of quadrupole field, exciting field and neutral gas molecule collision. Compared with the existing methods, the model in this paper is simpler and more direct, which effectively explored the effects of dipole excitation and quadrupole excitation on ion manipulation under high background pressure. ResultsThe simulation results demonstrate that high RF amplitude, low auxiliary AC amplitude and quadrupole excitation can effectively improve the isolation resolution. Besides, it clarified the difference between the analysis mechanism of ion trap mass spectrometers under high background pressure (above 13.332 Pa) and absolute vacuum conditions. The relevant results are consistent with the conclusions of previous experiments and other theories, proving the applicability and accuracy of the proposed calculation model and solution method. SignificanceThis research bears the guiding significance for further understanding the mechanism of quadrupole mass spectrometry as well as designing and developing miniature mass spectrometers.

Is El Niño‐Southern Oscillation a Tipping Element in the Climate System?

AbstractObserved El Niño‐Southern Oscillation (ENSO) varies between decades with high ENSO amplitude and more extreme Eastern Pacific (EP) El Niño events and decades with low ENSO amplitude and mainly weak El Niño events. Based on experiments with the CESM1 model, ENSO may lock‐in into an extreme EP El Niño‐dominated state in a +3.7 K warmer climate, while in a −4.0 K cooler climate ENSO may lock‐in into a weak El Niño‐dominated state. The state shift of ENSO with global warming can be explained by the location and amplitude of the strongest warming over the eastern equatorial Pacific, which amplifies the Bjerknes feedback and allows a southward migration of the Intertropical Convergence Zone onto the equator, a prerequisite of extreme EP El Niños. In light of these results, we discuss to what extent the state of ENSO may be a tipping element in the climate system.

Side-Opened Hollow Fiber-Based SPR Sensor for High Refractive Index Detection.

To facilitate the sensor fabrication and sensing operation in microstructured optical fiber-based surface plasmon resonance (SPR) sensors for high refractive index (RI) detection, we propose a special hollow fiber-based SPR sensor that comprises an opening on its body side and a thin gold layer coated on its outer surface. The analyte is able to flow into the hollow core through the side-opening to form new fiber core, with the Gaussian-like mode propagating in it. We investigate the sensing performance of the proposed sensor in a higher RI range of 1.48 to 1.54 at two feasible schemes: one is to only fill the fiber core with analyte (Scheme A), and the other is to directly immerse the sensor in the analyte (Scheme B). The results demonstrate that our sensor exhibits higher wavelength sensitivity at Scheme A with a maximum wavelength sensitivity of 12,320 nm/RIU, while a greater amplitude sensitivity was found at Scheme B with a maximum amplitude sensitivity of 1146 RIU-1. Our proposed sensor features the advantages of simple fabrication, flexible operation, easy analyte filling and replacing, enhanced real-time detection capabilities, high RI detection, and very high wavelength sensitivity and amplitude sensitivity, which makes it more competitive in SPR sensing applications.

Advanced vibrant controller results of an energetic framework structure

Abstract This research shows the influence of a new active controller technique on a parametrically energized cantilever beam (PECB) with a tip mass model. This article remains primarily concerned with regulating the system’s response using a novel control mechanism. This study describes a novel control mechanism called the nonlinear proportional-derivative cubic velocity feedback controller (NPDCVFC). The motivation of this article is to design a novel control algorithm in order to mitigate the nonlinear vibrations of a parametrically energized cantilever beam with a tip mass model. The proposed controller NPDCVFC incorporates nonlinearly second- and first-order filters into the system. The system is governed by one nonlinear differential equation having both quadratic and cubic nonlinearities within the parametric force. The controller’s efficiency in reducing framework vibrations, managing nonlinear bifurcations, and calming unstable motion is evaluated using numerical simulations of instantaneous vibrations. The perturbation technique is beneficial for solving the current model under the proposed worst resonance case ( Ω ˆ p = 2 ω ˆ 0 ) \text{(}{\hat{{\Omega }}}_{\text{p}}=2{\hat{{\omega }}}_{0}) . In order to choose the optimal controller, we have also added three more controller approaches to the configuration. Integral resonant control, positive position feedback, and nonlinear integral positive position feedback are the three controller approaches that are applied to the structure under consideration. We determine that the NPDCVFC as a new controller is the most effective for lowering the high vibration amplitudes. Over the investigated model, all numerical results were performed using the MATLAB 18.0 programmer software. The stability analysis and the effects of various elements on the controlled structure have been investigated. A comparison with recently published works of a comparable model has also been prepared. Experiment capacities for a PECB with a tip mass are obtainable to validate the results, and they demonstrate good agreement with analytical and numerical results.

Diagnosis and Management of Knee Arthrofibrosis and Associated Pain-Related Fear Using Multidimensional Clinical Reasoning and Exposure In Vivo Concept: A Case Report

BACKGROUND: A plethora of treatment approaches are used to manage persistent pain, disability, and fear associated with restricted knee range of motion following knee surgery. We used the pain and disability driver model and exposure in vivo concepts to manage pain-related fear and disability. CASE PRESENTATION: A 68-year-old male who underwent arthroscopic partial meniscectomy presented to physical therapy with a medical diagnosis of Complex Regional Pain Syndrome Type I and knee range-of-motion restriction. Despite extensive medical care and physical therapy for 3 years (202 visits), he continued to experience debilitating knee pain and demonstrated a high level of fear. To ambulate, he wore a knee brace and used a trekking pole. OUTCOME AND FOLLOW UP: Interventions to address the knee stiffness included combined tibiofemoral joint mobilization and high-velocity low-amplitude thrust manipulation targeting tibial internal rotation and low-load long-duration sustained capsular stretching using total end range time principle for extension. His fear was managed using techniques inspired by in vivo exposure concepts. Total knee range of motion improved 110 degrees and the patient was able to ambulate for 30 minutes (0.5 mile) without an assistive device with <2/10 pain intensity. DISCUSSION: Outside-the-box clinical reasoning suggested that poor outcomes with previous interventions were likely due to hypervigilance and pain-related fear. This case delineates the value of nonreductionist clinical reasoning in diagnosis and management of musculoskeletal conditions. It also outlines how the exposure in vivo approach helped the patient overcome his long-established avoidance behaviors. JOSPT Cases 2024;4(3):121-132. Epub 2 July 2024. doi:10.2519/josptcases.2024.0034