Displacement Range Research Articles

How Linear Elastic Material Properties Affect Lung Tumor Motion and Deformation: A Finite Element Analysis

Radiation therapy (RT) is a common method for treating lung cancer; however, targeting the moving tumor while sparing the surrounding healthy lung tissue is challenging. One of the methods proposed is tracking the tumor at the time of treatment and using multi leaf collimators (MLCs) to precisely target the tumor shape. One of the most accurate ways to predict the position and shape of the tumor is simulating the respiratory process at the time of RT delivery. However, an efficient and accurate way to find patient-specific material characteristics of lung and tumor as input for the simulation is still to be found. In this work, we have i) studied the effect that lung and tumor material properties have on tumor displacement and deformation and ii) found out that a simple, linear, elastic model may be sufficient for examining the effect of the material properties on the tumor displacement and deformation. A model was constructed in a simulation environment. STL meshes of a lung and a tumor were imported and set up to have separate material property values assigned for elastic modulus, Poisson's ratio, and density. Boundary conditions on the lung included a fixed surface located at the top of the lung and a distributed boundary load on the lower surfaces of the lung. The boundary load provided a 2.5cm displacement of the lower surfaces to imitate the diaphragm motion during the inhalation phase of the breathing cycle. Lung density showed no effect on tumor movement or deformation. Tumor displacement differences as a function of material property values ranged from 0.0043-1.53cm. The lung elastic modulus had the greatest effect on tumor displacement, with displacements ranging from 0.041- 1.53cm, or a range of approximately 1.5cm. Lung Poisson's ratio values affected displacement with a maximum displacement range of 0.1942cm. Tumor elastic modulus showed an insignificant effect on displacement of the tumor, with displacement ranges up to 0.0043cm. Tumor displacement was also insensitive to tumor Poisson's ratio values with a maximum range of displacement of 0.0005cm. We found out that a simple, linear, elastic model was useful for examining the effect of the material properties on the tumor displacement and deformation. Tumor properties and Poisson's ratio of the lung did not affect the tumor displacement and deformation significantly; however, having a patient-specific approximated value for the lung elastic modulus is required for optimal modeling of the process. Implementation of MLC-based tracking in RT, although an effective technique, is complex and time-consuming. Finding simplifications that make this more cost- and time-efficient can potentially increase the accuracy of delivery techniques, especially for lung cancer. Improvements that can be easily adopted to the RT workflow can improve overall therapy outcomes and quality of life for more patients.

The Effects of Fatigue on the Lower Limb Biomechanics of Amateur Athletes during a Y-Balance Test.

The Y-Balance Test (YBT) is a reliable tool for assessing the dynamic balance of athletes' lower limbs. This study aimed to compare the effects of the YBT on lower limb biomechanics before and after fatigue. Sixteen adult male recreational athletes were recruited for the study, and motion capture in combination with a force plate was used to collect kinematic, dynamics, and center of pressure (COP) data of the dominant leg during YBT testing before and after fatigue. Based on the research findings, there were significant statistical differences in the distances reached during the YBT in three directions before and after fatigue. After fatigue, there is a significant decrease in the ROM of the hip and knee joints in all three directions. Also, there is a significant increase in hip joint torque in the anterior- and posterior-lateral directions, while a significant decrease in hip and ankle joint torque is observed in the posterior-medial direction. Moreover, there is an increasing trend in positive and negative joint work for the hip, knee, and ankle joints in all three directions after fatigue. The range of COP displacement also increases following fatigue. The decline in YBT scores demonstrates the detrimental impact of fatigue on the dynamic balance of the lower limbs of adult male amateur athletes. We hope that these results can provide information for athletes and coaches to better understand the effects of fatigue on the dynamic balance of lower limbs, so as to carry out targeted lower limb balance training and prevent sports injuries.

Roles of ageing on the physical, chemical and mechanical parameters of a prototype municipal solid waste

ABSTRACT This study is mainly aimed at exploring effects of the aging-induced chemical decomposition of Municipal Solid Waste (MSW) on the shear response and physical properties of locally available MSW of Fars province, Iran, at its in-situ condition. To this end, a large direct shear device (1×1×1.1 m3) is designed, fabricated and employed to evaluate the parameters of the failure envelop at plane strain condition representing slopes of engineered landfills. Bulk disturbed samples of fresh MSW are exhumed from an operational disposal site to be implemented into the study and subsequently remolded in the large-scale shear box. Four drained shear tests are performed under a variety of vertical stresses. Next, intact components of MSW are landfilled over a period of 3, 6, and 9 months. Similar shear experiments are conducted at the end of each mentioned time interval. Mechanical behavior of MSW is completely frictional and internal friction angle of the studied MSW non-linearly increases with time from 44.2º to 55.7º. The stress-strain response is almost bilinear over a wide range of displacement. The decomposition process is further clarified in light of results of pH tests conducted on the leachate of the MSW at the end of various landfilling time intervals.

A Highly Accurate and Sensitive mmWave Displacement-Sensing Doppler Radar With a Quadrature-Less Edge-Driven Phase Demodulator

A 110-mW 39-GHz Doppler radar front end in 65-nm CMOS for displacement and vibration sensing is proposed. Conventional Doppler radar suffers from detection nulls, at which the receiver detection gain drops to zero. Quadrature demodulation for either carrier frequency or intermediate frequency (IF) is necessary to alleviate nulls but still induces nonlinear detection gain that needs to be compensated through digital signal processing (DSP). In this article, a Doppler radar topology is proposed to achieve ultrahigh displacement range accuracy and sensitivity and to eliminate detection nulls without using quadrature demodulation. An edge-driven phase demodulator (EDPD) processes the rectified square-wave intermediate signal and converts displacement/vibration to a true-dc/baseband signal with a constant gain. Coherent demodulation and signal generation through common-referenced subsampling phase-locked loops (SSPLLs) allow the radar to achieve 4- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> m static range accuracy and 39-nm vibrational (at 10 kHz) range sensitivity in measurement.

Point-of-care ultrasound for monitoring catheter tip location during umbilical vein catheterization in neonates: a prospective study.

Point-of-care ultrasound (POCUS) can guide umbilical vein catheter placement in real time and monitor catheter tip position, allowing avoidance of severe complications due to catheter malposition. This study aims to explore the effectiveness of POCUS in guiding venous catheter insertion and monitoring complications. Sixty-eight neonates with ultrasound-guided venous catheter insertion at the Neonatal Department of Dongguan Children's Hospital between December 2020 and February 2022 were included. POCUS was applied to monitor catheter tip location daily until catheter removal. A displacement range exceeding the intersection of the inferior vena cava and right atrium by ±0.5 cm was considered misalignment. Sixty-four neonates had a displaced catheter tip (94.1%, 64/68), with a median displacement distance of 0.4 cm (minimum -0.2 cm, maximum 1.2 cm). Ten neonates had a misalignment (14.7%, 10/68) caused by displacement. Displacement usually occurs within 2-4 days after placement, with displacement rates of 94.1% (64/68), 90.6% (58/64), and 98.3% (59/60) on days 2, 3, and 4, respectively, and could still occur on day 9 post-placement. In addition, misalignment mainly occurs on the second day after placement. During the monitoring process, 58 neonates had catheter tip displacement ≥2 times, resulting in 252 displacement and 22 misalignment incidents. Among them, the catheter tip migrated outward from the inferior vena cava seven times, all of which were removed in time. Ultrasound was used for positioning 486 times, and x-ray was indirectly avoided 486 times. The catheter tip is prone to displacement and misalignment after umbilical vein catheterization, which most commonly occurs on days 2-4. POCUS is recommended for daily monitoring of the tip location during umbilical vein catheterization until catheter removal.

On topology design of compliant constant output/input force mechanisms with contact interactions

We seek monolithic topologies for constant output (CoFM) and input (CiFM) force mechanisms using topology optimization. We capture large displacements, buckling, contact interaction between members and external surfaces, and importantly, interaction of the mechanism with flexible workpieces to accurately simulate force transfer. Features of constant force characteristics, e.g., magnitude(s) of the desired force(s), range of input displacement over which slope of the force–displacement curve is near zero, and distance between workpiece and the mechanism are controlled individually. Two constant output and constant input force mechanisms each, are synthesized using stochastic optimization ensuring ready manufacturability. We observe that (a) accurate modeling of the mechanism-workpiece interaction is important. (b) Fixed external surfaces may not necessarily contribute to contact force characteristics though interesting alternative solutions are possible in their presence. (c) It behooves to model self contact between members than to reject viable solutions wherein members intersect in intermediate configurations. We finally fabricate the synthesized mechanisms and find that the desired constant force characteristics are by-and-large retained qualitatively, even when the mechanisms may undergo plastic deformation.

Dielectric elastomer actuator biased by magnetorheological elastomer with permanent magnet

Dielectric elastomer actuators have become one of the most important smart material transducers in recent times. One of the crucial aspects in this field is the application of bias to find the best operating conditions. The basic task is to find the proper bias configuration to obtain a wide range of displacements in the actuator. In the literature, various biases, such as mechanical springs, permanent magnets (PMs), or pneumatic springs, are studied. In our work, the magnetorheological elastomer (MRE) is applied to build a novel bias that ensures a wide range of displacement. Because of the softness and the compliant chemical structure, the MRE can be easily integrated with the dielectric elastomer actuator. The MRE as a bias for a dielectric elastomer actuator is verified in the series of experiments. Finally, the discussion on the advantages and disadvantages of the new bias type is performed.

Comparison Between the Effects of Transfer Energy Capacitive and Resistive Therapy and Therapeutic Ultrasound on Hamstring Muscle Shortness in Male Athletes: A Single-Blind Randomized Controlled Trial.

Transfer energy capacitive and resistive (TECAR) therapy (TT) is a newly developed deep heating therapy that can generate heat within tissues through high-frequency wave stimulation. Compared to conventional physiotherapy methods, the application of TT especially in sports rehabilitation is becoming more popular. This study aimed to investigate the comparative effect of TT and therapeutic ultrasound (US) on hamstring muscle shortness. Additionally, the effects of TT with static stretching (SS) were compared with US combined with SS. Totally, 39 male athletes with hamstring shortness were randomly assigned into three groups: A, B, and C. Group A received 15 minutes of TT plus SS, while Group B received 15 minutes of US with SS, and Group C only performed SS. Hamstring flexibility was measured by active knee extension (AKE), passive knee extension (PKE), and the sit and Reach (SR) tests before the intervention, and following the first, and third treatment sessions. The range of motion of the AKE and PKE, and displacement range in the SR test improved significantly after the first and third sessions in all three groups (P0.0001). The improvement of the three flexibility indices in the TT group was greater than in the other two groups. The present study showed that TT could increase the flexibility of hamstring muscles more than US therapy. However, TT in combination with SS had a similar effect to SS alone.

Design of Novel Artificial Anal Sphincter

ObjectivesArtificial anal sphincter is considered to be a good method for the treatment of severe fecal incontinence, but there are problems of low biomechanical compatibility in clinical application. The purpose of this study is to design a novel artificial anal sphincter that can output stable loading force to solve the mechanical mismatch between artificial anal sphincter and intestinal tissue caused by excessive or too small local pressure on the intestine. Material and methodsAiming at the shortcomings of the existing artificial anal sphincter, a novel artificial anal sphincter with constant force mechanism is designed based on the C-shaped SMA sheet of Ti-55.9at%Ni and combined with the normal defecation mechanism of human body. In this paper, the chord length l of C-shaped SMA sheet is used as the design variable, and the artificial anal sphincter is optimized and verified initially by using finite element analysis method. ResultsThe results show that the artificial anal sphincter can achieve a constant force to clamp the intestine in a large displacement range when the chord length l of the C-shaped SMA is 13 mm, the chord height h is 1.5 mm, the width w is 2 mm, and the thickness δ is 0.2 mm. ConclusionThe design of artificial anal sphincter with constant force loading mechanism has a good effect in solving the biomechanical compatibility problem between the implant device and the intestinal tissue. In addition, the designed artificial anal sphincter occupies a small space, which provides a new idea for future clinical application.

Bending performance of the AuxOcta multi-cellular beam structure

Auxetic cellular tubes are potential candidates for several engineering applications requiring resistance to bending due to the enormous demand for lightweight and high mechanical performance. Interestingly, we found that the preferential buckling mode can change the direction of deformation in the beam cross-section by applying negative Poisson's ratio cells in the lateral direction and is an effective modifying region. The bending response and energy absorption of multi-cellular tube with auxetic cells (Aux) and novel design tubes with auxetic and octagonal cells (AuxOcta) have been investigated with numerical and experimental systematically. These unique auxetic structures are produced by direct metal laser sintering (DMLS) with 316L stainless steel. The bending results show that the Aux tube indicates gradual local deformation in the loading region, while the cells of the AuxOcta tube beam are homogeneously deformed in the loading region. Moreover, AuxOcta structure is optimized to improve load-carrying and energy-absorbing capacities. This optimized AuxOcta structure (AuxOcta-G) offers superior bending performance from the test results. Compared to the Aux structure, the improvement in the specific load carrying (SLC) capacity of the AuxOcta-G structure above is 15% for 5 mm displacement, while the improvement in the specific energy absorption (SEA) approximately reaches 16%. The Finite Element Method (FEM) results showed that AuxOcta and AuxOcta-G structures offer a preferred behavior with a wide displacement range. This study provides a baseline for future investigation of hybrid beam design with a negative Poisson cross-section.

A Small-Scale Hopper Design Using a Power Spring-Based Linear Actuator.

Hopping locomotion has the potential to enable small-scale robots to maneuver lands quickly while overcoming obstacles bigger than themselves. To make this possible, in this paper, we propose a novel design of a high-power linear actuator for a small-scale hopper. The key design principle of the linear actuator is to use a power spring and an active clutch. The power spring provides a near constant torque along the wide range of output displacement. The active clutch controls the moving direction and operation timing of the linear actuator, which enables the hopper to take off at the right timing. As a result, the hopper has a size of 143 mm, a mass of 45.9 g, and hops up to 0.58 m.

Micro-Mesh Construction

Micro-meshes (μ-meshes) are a new structured graphics primitive supporting a large increase in geometric fidelity, without commensurate memory and run-time processing costs, consisting of a base mesh enriched by a displacement map. A new generation of GPUs supports this structure with native hardware μ-mesh ray-tracing, that leverages a self-bounding, compressed displacement mapping scheme to achieve these efficiencies. In this paper, we present anautomatic method to convert an existing multi-million triangle mesh into this compact format, unlocking the advantages of the data representation for a large number of scenarios. We identify the requirements for high-quality μ-meshes, and show how existing re-meshing and displacement-map baking tools are ill-suited for their generation. Our method is based on a simplification scheme tailored to the generation of high-quality base meshes , optimized for tessellation and displacement sampling, in conjunction with algorithms for determining displacement vectors to control the direction and range of displacements. We also explore the optimization of μ-meshes for texture maps and the representation of boundaries. We demonstrate our method with extensive batch processing, converting an existing collection of high-resolution scanned models to the micro-mesh representation, providing an open-source reference implementation, and, as additional material, the data and an inspection tool.

Self‐Diffusion of a Chemical Warfare Agent Simulant and Water in Nafion by Pulsed Field Gradient NMR

AbstractPulsed field gradient (PFG) NMR at high magnetic field was used to study microscopic diffusion of dimethyl methyl phosphonate (DMMP), a common chemical warfare agent (CWA) simulant, and water in Nafion membranes. PFG NMR measurements were performed for a broad range of molecular displacements. The self‐diffusivities were measured as a function of the DMMP concentration for several fixed water concentrations. The measured data suggest that DMMP and water diffuse in different regions of Nafion. While water mostly diffuses in hydrophilic regions of the membrane, viz. water channels, DMMP diffusion is mostly limited to interfacial perfluoroether regions between these water channels and the semi‐crystalline matrix.

Load Bearing Capacity of Lateral Loaded Piles in Watered Carpathian Flysch

In this paper, flysch is presented as a representative material of a wide section of the Carpathian Mountains, with some areas in Poland highlighted. The geological structure of this area is complex due to the alternating layers of blocky rock masses and soil (Vessia et al., 2017). Such a complex pattern is seen in some Alpine flysch slopes, such as the Ingelsberg landslide area (Romeo et al., 2015). Many authors are monitored, predicted landslides (Allasia et al., 2013; Bertacchini et al., 2009; Casagli et al., 2010) by sophisticated sensors. The rock-soil flysch successions have become intensively fissured as a result of their geological history, weathering (precipitation and snowmelt), and long-term water retention, especially on the surface layers. These complex materials are characterised by heterogeneous lithologies, whose mechanical properties are largely uncertain. These geological structures have also been confirmed by monitoring and control studies performed on a large number of landslides (Bednarczyk, 2014). One of the most striking phenomena is the sudden decrease in the strength parameters in the studied rocks in the direction parallel to the layers due to watering. The process is made possible by heterogeneous fractured strong rock layers with high permeability coefficients for water. This study precisely describes the phenomena occurring at the contact area between the component layers of flysch under the wet conditions of a weak plane. An elastic-plastic analysis method that considers the developed strength model at the surfaces of the contact areas (Biernatowski & Pula, 1988; Pula, 1997) has been used to estimate the load capacity for piles working under a horizontal load. The piles are part of a reliability chain (Pula, 1997) in a given construction and are the first element of concern for monitoring (Muszynski & Rybak, 2017). A particular device intended to study the dependence of the shear stress on a fixed failure surface in a controlled consolidation condition was utilized. The study was conducted for a wide range of displacements and for different values of stabilized vertical stresses of consolidation. The complexity of the processes occurring in the shear zone, presented as a detailed study of the material crack mechanics, is highlighted. The laboratory results were used to construct the mechanical model of the slip surface between the soil and rock with the description supported by a neural network (NN) approximation. The artificial NN was created as a multi-layered, easy to use approach for interpreting results and for quick reconstruction of approximated values useful for the calculations presented in laterally loaded piles. For the calculations, long, sheared strips of material were considered in a semi-analytical procedure to solve a differential equation of stability. The calculations are intended to reveal the safety indexes for a wide range of boundary tasks as the most significant indicator for design decisions.

Dynamic Response of a Long-Span Double-Deck Suspension Bridge and Its Vibration Reduction

This paper presents a dynamic analysis of a long-span double-deck suspension bridge subjected to random traffic loading using a Finite Element (FE) model. During this study, the influence of various traffic parameters, such as vehicle speed, traffic volume, traffic weight, and the location of the passing girder, on the longitudinal movement of the girders was investigated. The results reveal that schemes with double girders passing can lead to greater longitudinal displacement of the girder as compared to a long-span bridge with a single passing girder. However, the incorporation of fluid-viscous dampers at the ends of the girders significantly reduces the displacement range of each node. For instance, at the left end of the bridge, the original model (without dampers) exhibits a displacement range of approximately 0.01–0.056 m, whereas the constrained model (with dampers) shows a range of 0.025–0.033 m. A quantitative analysis demonstrates that higher damping coefficients (or smaller damping exponents) can further mitigate the girder’s movement.

The Effect of Non-Newtonian Fluid Midsole Footwear on Lower Limb Biomechanics after 5 km of Running in High Temperature

This study’s aim was to examine the effect of non-Newtonian fluid (NN) shoe and ethylene vinyl acetate (EVA) shoe on human lower limb biomechanics and muscle activation during running in hot temperatures. Thirty-five men utilizing a rearfoot strike ran 5 km at a self-selected tempo at an average summer temperature of 41.7 ± 1.0 °C and relative humidity of 80.7 ± 3.5%. The kinematics, kinetics, and muscle activation of the right leg were monitored from landing until the pedal was off the ground. A two-way repeated-measures ANOVA was conducted to investigate the main effects of the shoe condition, temperature, and interaction effect. Wearing NN at high temperature resulted in increased hip range of motion (ROM) (p = 0.001). The knee torque increased significantly when wearing EVA and NN shoes after the temperature increased (p = 0.006). When wearing EVA and NN, the ground reaction force (GRF) and loading rate (LR) increased significantly after the temperature increased (p = 0.001; p = 0.009). When wearing NN after running for 5 km at a high temperature, the displacement range of center of pressure (COP) was significantly reduced (p &lt; 0.001), while the EVA was significantly increased (p &lt; 0.001). Neither pair of shoes substantially altered muscle activity. After excluding the factor of fatigue, the increase in temperature not only changed the properties of the material inside the shoe, but also changed the parameters of the biomechanics of the human lower limbs. After the temperature increases, the shoes made of non-Newtonian fluid materials can quickly stabilize under the condition of increased shear stress and reduce the displacement of the human body. Thus, it indicated that non-Newtonian fluid shoes may lower the risk of injury when running in extremely hot conditions.

Tests and Micro–Macro Cross-Scale Model of High-Performance Acrylate Viscoelastic Dampers Used in Structural Resistance

This study aims to develop a high-performance acrylate viscoelastic damper (HAVED), which is suitable for the low-frequency vibration control of building structures. To reveal the influence of ambient temperature, excitation frequency, and displacement amplitude on the dynamic mechanical performance and energy dissipation capacity of a HAVED, a series of dynamic mechanical performance tests were performed on a HAVED within the extensive temperature (10°C–50°C), frequency (0.1–3 Hz), and displacement (0.5–4 mm) range. The analysis results show that a HAVED has excellent energy dissipation capacity and good adaptability to the external environment. The loss factor of a HAVED can reach up to 1.85, and it remains above 0.28 even in a high-temperature environment of 50°C. The dynamic mechanical properties and energy dissipation capacity of a HAVED show strong dependences and obvious coupling effects on temperature, frequency, and displacement amplitude. Based on the experimental research of a HAVED, the micromechanical properties of viscoelastic materials are analyzed, and the high-order fractional derivative model is used to comprehensively describe the mechanical characterization of microscopic molecular chains. The Kraus theory is introduced to consider the influence of filler particles, and the high-order fractional derivative micro–macro cross-scale mathematical model is proposed by combining with the temperature-frequency equivalence principle. Through the experimental results, the prediction capabilities of the model that have been established have been verified. The analysis results show that the proposed model can comprehensively describe the influence of ambient temperature, excitation frequency, displacement amplitude, microscopic molecular chain structure, and filler particles on the mechanical properties of a HAVED.

Early Postoperative Activities of Daily Living Do Not Adversely Affect Joint Torques or Translation Regardless of Capsular Condition: A Cadaveric Study

To evaluate the impact of capsular management on joint constraint and femoral head translations during simulated activities of daily living (ADL). Using 6 (n= 6) cadaveric hip specimens, the effect of capsulotomies and repair was then evaluated during simulated ADL. Joint forces and rotational kinematics associated with gait and sitting, adopted from telemeterized implant studies, were applied to the hip using a 6-degrees of freedom (DOF) joint motion simulator. Testing occurred after creation of portals, interportal capsulotomy (IPC), IPC repair, T-capsulotomy (T-Cap), partial T-Cap repair, and full T-Cap repair. The anterior-posterior (AP), medial-lateral (ML), and axial compression DOFs were operated in force control, whereas flexion-extension, adduction-abduction, and internal-external rotation were manipulated in displacement control. Resulting femoral head translations and joint reaction torques were recorded and evaluated. Subsequently, the mean-centered range of femoral head displacements and peak signed joint restraint torques were calculated and compared. During simulated gait and sitting, the mean range of AP femoral head displacements with respect to intact exceeded 1% of the femoral head diameter after creating portals, T-Caps, and partial T-Cap repair (Wilcoxon signed rank P < .05); the mean ranges of ML displacements did not. Deviations in femoral head kinematics varied by capsule stage but were never very large. No consistent trends with respect to alterations in peak joint restrain torques were observed. In this cadaveric biomechanical study, capsulotomy and repair minimally affected resultant femoral head translation and joint torques during simulated ADLs. The tested ADLs appear safe to perform after surgery, regardless of capsular status, because adverse kinematics were not observed. However, further study is required to determine the importance of capsular repair beyond time-zero biomechanics and the resultant effect on patient-reported outcomes.

Piezoelectric small scale generator: towards near-Joule output energy generation

Research on piezoelectric microgenerators harvesting energy from vibrations led to an abundant literature, with various strategies to optimize the frequency range and output power. In contrast, for very low frequency range (<10 Hz) and/or for non-harmonic mechanical source, the large majority of the strategies are not adapted. This work deals with a small scale piezoelectric generator where the input mechanical source consists of a single force application in the range of hundreds of Newtons (i.e. typical human weight). Contrary to harmonic mechanical sources, such an application context necessitates harvesting as much as energy as possible in a single cycle. This was achieved by assembling several piezoelectric stacks within a mechanical amplification system, and to use the electric field and stress levels close to the limits of the piezoelectric elements. Ericsson cycle (i.e. thermodynamic cycle comprising two iso-electric field and two iso-stress steps) was applied to the piezoelectric material and later two device prototypes were developed in order to quantify the harvesting capabilities. Finally, in a realistic application point of view, a passive electrical interface based on Bennet’s doubler was implemented and compared to the Ericsson cycles in terms of output energy. This electrical energy management strategy successfully allowed working at ultra-high electric field (>2 kV mm−1) enabling a converted energy density close to the ultimate value. An maximal energy density of 320 mJ cm−3 was reached using Ericsson cycles, and 130 mJ cm−3 using Bennet’s doubler (∼40% of the ultimate energy density). The device comprising ∼2.4 cm3 of piezoelectric material, the net output energy converted and stored per cycle reached 320 mJ. Still, the work presented here can be adapted to other range of forces and displacements for maximizing energy harvesting.

Design of an adjustable constant-force mechanism using a geared Sarrus linkage and spring

This paper presents the design of a novel adjustable constant-force mechanism (CFM) using a geared Sarrus linkage and a linear spring. The uniqueness of this design is that it provides a constant force over a wide range of displacement and the constant-force level can be adjusted energy-freely by varying the spring position without a preload. In this work, the construction, geometric constraints, and constant-force design of the CFM are expressed. The desired parameters of the mechanism, with consideration of gear friction, are also determined. A numerical example is then given to illustrate the constant-force performance and the effect of gear friction. This paper also shows a prototype of a CFM and experimental studies on it. It was found that the CFM delivered a constant force of up to 20 N within a stroke of 140 mm, and the force error was less than 6%. Moreover, the CFM compensated for masses of 1 and 2 kg with a torque reduction of more than 90%.