Absolute Displacement Research Articles

A novel restrainer device for acquistion of brain images in awake rats

Functional neuroimaging methods like fMRI and PET are vital in neuroscience research, but require that subjects remain still throughout the scan. In animal research, anesthetic agents are typically applied to facilitate the acquisition of high-quality data with minimal motion artifact. However, anesthesia can have profound effects on brain metabolism, selectively altering dynamic neural networks and confounding the acquired data. To overcome the challenge, we have developed a novel head fixation device designed to support awake rat brain imaging. A validation experiment demonstrated that the device effectively minimizes animal motion throughout the scan, with mean absolute displacement and mean relative displacement of 0.0256 (SD: 0.001) and 0.009 (SD: 0.002), across eight evaluated subjects throughout fMRI image acquisition (total scanning time per subject: 31 min, 12 s). Furthermore, the awake scans did not induce discernable stress to the animals, with stable physiological parameters throughout the scan (Mean HR: 344, Mean RR: 56, Mean SpO2: 94 %) and unaltered serum corticosterone levels (p = 0.159). In conclusion, the device presented in this paper offers an effective and safe method of acquiring functional brain images in rats, allowing researchers to minimize the confounding effects of anesthetic use.

Proportional-retarded control of a quasi-zero-stiffness vibration isolator

This paper explores the control design and performance analysis of an active quasi-zero-stiffness vibration isolator utilizing the proportional-retarded (PR) control architecture. The PR architecture replaces the conventional “derivative” term in the proportional-derivative (or displacement-velocity) controller with the novel “retarded (time-delayed)” term, which is a new and effective way of active vibration suppression. Comprehensive gain-delay conjoint regulation strategies are developed for the strengthened isolation performance. For impact excitations, a complete stability analysis is conducted near the equilibrium position. Furthermore, a parameterized dominant pole placement algorithm is proposed to optimize the transient response of the PR-actuated isolator. Focusing on the rectangular pulse and long-duration step impacts, the algorithm adjusts the dominant poles to optimize the transient performance metrics, including the maximum displacement overshoot, steady-state displacement overshoot, and settling time. Regarding harmonic excitations, the delay-coupled effect is scrutinized for better low-frequency isolation performance, including the resonance frequency, nonlinear steady-state amplitude, multiple steady-state bands and nonlinearity elimination, equivalent active damping and stiffness, and absolute displacement transmissibility. In the case of random excitations, we demonstrate the superiority of the PR structure over the passive system.

Nonreciprocal vibration transmission using dislocated displacement feedback

This paper examines absolute displacement feedback using dislocated sensor-actuator pairs to design and implement an active metamaterial cell for nonreciprocal vibration transmission. Comprehensive stability and performance analyses are carried out, both theoretically and experimentally. The theoretical analysis yields a simple condition on parameters of the example two-degree-of-freedom metamaterial cell to guarantee the stability. If the condition is respected, very large feedback gains can be implemented so that the difference in vibration transmission in the two opposite directions may be substantial. This is confirmed experimentally: the nonreciprocity measured in terms of the amplitudes of two characteristic transfer mobilities of the cell amounts to about 30 dB in the frequency range between 30 and 1000 Hz. As shown in the Appendix to the paper, the cell could be used as a prefabricated and pre-tuned modular building block to form a functional active metamaterial for nonreciprocal vibration transmission.

Between a rock and a hard place: how does the tourist crowding perception affect the decision of absolute displacement?

ABSTRACT This study investigates the mechanism of tourist crowding perception on their decisions of absolute displacement based on the conservation of resource theory and social influence theory. We collected 455 valid questionnaires from a tourism destination (West Street in Quanzhou city) in China. Results show that both physical crowding and human crowding motivate tourists to select absolute displacement. Perceived wait time partly mediates the effect of physical crowding on absolute displacement, while it fully mediates the effect of human crowding on absolute displacement. Travel group size negatively moderates the effect of tourist crowding perception on absolute displacement. Theoretically, this paper enriches the literature and theories on understanding the mechanism of crowding perception on tourist behavior and expands insights into how tourists respond to crowded situations. Practically, this paper provides implications for destination marketing organizations to use various tourism services to solve over-tourism issues and achieve sustainable tourism development.

New advanced monitoring systems of Bridges with Actionable Real Time Sensor Data

The reliability of structures and the preservation of the built environment are issues with a decisive role in the field of civil engineering as well as in the public eye. The existing heritage surrounding human beings is varied and fragile because of its inherent characteristics and the environment in which it is inscribed. These elements are found and emphasized when dealing with special facilities, by constitution and by public utility. This case study analyzes innovative approaches and IoT tools for defining an operational procedure for the proper Life-Cycle management of infrastructure works through a Digital Twin approach. This methodology provides key elements for the proper planning of structural rehabilitation and reinforcement strategies and techniques with innovative interventions and methods, starting with a careful investigation/monitoring campaign to assess its safety condition. This monitoring activity involves the assessment of the real robustness and safety of large structures by acquiring the general principles of signal analysis and the traditional technologies currently available for diagnostics and monitoring (accelerometers, inclinometers, deformometers, strain gauges, etc.). The case study under consideration monitoring activities go through a static type of monitoring that involves the acquisition of absolute and relative displacements, and through a dynamic structural monitoring that is based on the analysis of natural and traffic- induced vibrations using triaxial accelerometer transducers. The latter case of structural monitoring makes it possible to derive the dynamic properties of the structure and ensure the reliability of the finite element model; in addition, the variation in dynamic characteristics over time is an indicator of ongoing degradation in the structure due to damage phenomena. By means of a dense network of sensors (IoT devices) operating completely wirelessly that are able to communicate in real time through a LoRaWAN telecommunication technology, it is possible to create a digital, living and interactive copy in constant update of the physical object. In addition, the system includes implementation of a Real Time notification system called "recognized call," which consists of automatically making a phone call, to numbers specified by the managing body of the work, whose content includes indication of the location, type of alarm threshold, actions to be taken. The objective of this study is to investigate the possibility of using Digital Twin-based systems associated with structural health monitoring of infrastructure works through real-time data analysis.

AUTOMATED DESIGN OF KORSCH ORTHOSCOPIC ASPHERICAL MIRROR TELESCOPES FOR NANOSATELLITES

This study presents the results of an automated parametric synthesis of a series of orthoscopic aspheric optical systems of mirror telescopes with different focal lengths, built according to the Korsch scheme. In order to ensure compactness of the design, these systems consist of three second-order aspheric mirrors and three folded flat mirrors. The obtained optical systems have a focal length ranging from 480 mm to 960 mm, an angular field of view ranging from 1.2° to 2.4°, an aperture number ranging from 6 to 12, an entrance aperture with a diameter of 80 mm, and an axial length of no more than 170 mm, which is within the dimensions of a 2U CubeSat. The maximum linear size of the image detector's sensitive area is 20 mm in all considered systems. The mirror telescopes do not have chromatic aberrations, enabling the capture of images within the visible spectrum and multiple infrared sub-bands. The provided aberration analysis demonstrates the high image quality of the considered optical systems. Specifically, for a wavelength of 0.546 μm, thediffraction modulation transfer function values both in the meridional and sagittal planes across the entire field exceed 0.53 for a spatial frequency of 30 mm-1, and 0.3 for a spatial frequency of 50 mm-1. The maximum relative distortion in the designed systems is 0.005%, corresponding to an absolute displacement of 0.5 μm. The presented telescopes are capable of covering an observation band of Earth's surface with linear dimensions ranging from 12.6 km to 25.1 km when a satellite track height is 600 km. By applying multi-element image detectors with a pixel size of 5 μm and achieving diffraction-limited image quality in the optical systems, both the geometric and diffraction resolution limits on Earth's surface will not exceed 10 m.

Quasi-Zero Stiffness Vibration Sensing and Energy Harvesting Integration Based on Buckled Piezoelectric Euler Beam.

This paper presents a novel quasi-zero stiffness vibration sensing and energy harvesting integration system for absolute displacement measurements based on a buckled piezoelectric Euler beam (BPEB) with quasi-zero stiffness (QZS) characteristics. On one hand, BPEB provides negative stiffness to the system, thus creating a vibration-free point within the system and transforming the absolute displacement measurement problem into a relative motion sensing problem. On the other hand, during the measurement process, the BPEB collects the vibration energy from the system, which can provide electrical energy for low-power relative motion sensing devices and remarkably suppress the frequency range of the jump phenomenon, thereby further expanding the frequency domain measurement range of the sensing system. The research results have shown that this system can measure the absolute motion signal of the tested object in low-frequency vibration with small excitation. By adjusting parameters such as the force-electric coupling coefficient and damping ratio, the measurement accuracy of the sensing system can be improved. Furthermore, the system can convert the mechanical energy of vibrations into electrical energy to power the surrounding low-power sensors or provide partial power. This could potentially achieve self-powering integrated quasi-zero stiffness vibration sensing, offering another approach and possibility for the automation development in wireless sensing systems and the Internet of Things field.

An enhanced chromatic dispersion probe for simultaneous measurement of dual-axis absolute and relative displacement with nanometric resolutions

This paper presents an enhanced chromatic dispersion probe for simultaneous measurement of dual-axis absolute and relative displacement with nanometric resolutions based on a 4f optical system and a signal processing algorithm. In the 4f optical system, a light source is generated by a pinhole in such a way that the employed pinhole is placed on the focal planes of the two achromatic lenses, aimed at generating a low-pass filter in the frequency domain. With a smaller pinhole, side lobes of the measured spectra are effectively suppressed and the signal-to-noise ratio is optimized, resulting in an expanded absolute measurement range and improved resolution of the two axes, and an enhanced relative measurement resolution of the dual-axis. A signal processing algorithm is proposed in such a way that in the spectral curvature region of the dual-axis output spectra, the original fitted spectrum is replaced by a linear fitting line and a newly-intersected wavelength can be obtained, resulting in an expanded measurement range of the relative displacement of the dual-axis. Numerical simulation and experiments have indicated that the absolute measurement range has been expanded to 225 μm with an enhanced resolution of 40 nm, and the measurement range of the relative displacement of the dual-axis has been expanded to 370 μm with an enhanced relative measurement resolution of 90 nm.

The use of a Mamdani-type fuzzy model for assessing the performance of a boom stabilization systems in a field sprayer

Fuzzy logic models are increasingly used to control simple and complex devices, as well as entire operating systems. In this study, a fuzzy logic model was applied to assess the performance a boom stabilization system in a field sprayer. The model was tested on a field sprayer with a trapezoid system for stabilizing the sprayer boom with a length of 21 m. Measuring cables for registering the displacement of the boom's terminal segments (right and left) in the vertical and horizontal plane were installed on the sprayer. The field sprayer was connected to a tractor. The model was based on two linguistic variables: "absolute displacement of the boom's terminal segments" and "boom stability index". It was assumed that the sprayer boom was stable when the displacement of the boom's terminal segments did not exceed 0.25% of boom length. The study demonstrated that the proposed model can be reliably used to assess boom stability in real time (during field operations). The time required to achieve boom stability was more than 2.5 times shorter in the vertical than in the horizontal plane, which can be attributed mainly to the structure of the stabilization system. The proposed model is universal, and it can be applied to evaluate other boom stabilization systems in field sprayers.

Displacement Calibration of Optical Tweezers With Gravitational Acceleration

In recent years, levitated particles of optical traps in vacuum have shown the enormous potential for precision sensor development and new physics exploration. However, the accuracy of the sensor is still hampered by the uncertainty of the calibration factor relating the detected signal to the absolute displacement of the trapped particle. In this paper, we suggest and experimentally demonstrate a novel calibration method for optical tweezers based on free-falling particles in vacuum, where the gravitational acceleration is introduced as an absolute reference. Our work provides a calibration protocol with a great certainty and traceability, which is significant in improving the accuracy of precision sensing based on levitated optomechanical systems.

Three-dimensional microanalysis of tooth movement during the first 6 months of orthodontic double retention

This study performed a 3-dimensional analysis of tooth movement during orthodontic retention to assess the effectiveness of double retention (fixed and removable) in preventing undesired tooth movement. One hundred randomly selected patients were included at the initiation of double orthodontic retention with fixed retainers and vacuum-formed splints (recommended to be worn 22 h/d) in both arches. Intraoral scans were performed directly (T0), 1 month (n= 88), 3 months (T2) (n= 78), and 6 months (T3) (n= 66) after retainer bonding. Nine reference points were marked on each tooth in every patient. Subsequent scans were superimposed, and point displacement was calculated. Statistical analysis was performed using the R statistical software (version 4.2.2; R Core Team, Vienna, Austria). Sample size calculation determined at least 55 patients were needed. The total dropout between T0 and T3 was 34 patients (did not show up for appointment). The median absolute displacement value of a single point between T0 and T3 was 0.015 mm. The most stable teeth were mandibular central incisors, whereas the least stable were mandibular molars. Most tooth displacements occurred between T0 and T2, then slowed down significantly. Double orthodontic retention prevents major tooth displacements in most patients during the first 6 months of retention; however, larger, unpredictable single-tooth displacement may occur in individual patients.

Assessing Displacement of Plastic Interstitial Catheters in Image-Guided Gynecological HDR Brachytherapy

Interstitial HDR brachytherapy involves precise, localized delivery to targets with high dose gradients, sparing adjacent organs at risk. Due to the proximity of the rectum and bladder to the target, deviations in the catheters with respect to patient anatomy can change dose to those structures. While utilizing plastic interstitial catheters allows the patient to receive hyperthermia therapy during their course of interstitial treatment, the plastic catheters were observed to show significant deflection when the metal stylets are removed for treatment. The hyperthermia electrodes and the HDR source cable are both wires of approximately the same thickness. The purpose of this study is to assess the magnitude and deflection of the plastic catheters for gynecologic interstitial plans and determine whether using flexible wires for visualization on pre-treatment imaging is suitable for reconstructing the actual treatment received. Pre-treatment CT images where the stylets were utilized for catheter visualization were registered to a subsequent CT scan with the metal stylets removed. The original treatment dwell positions were adjusted to the second CT to evaluate 3D catheter displacement and dose distributions calculated for the bladder, rectum, and target. The plans were subsequently reconstructed on a pre-planning CT with flexible 20-gauge wires instead of metal stylets to determine their suitability as a surrogate for stylets. Absolute 3D displacement for all patients was 3.5 ± 5.4 mm (n = 3433 catheter dwell positions, mean ± SD, p < 0.001) comparing plans with the stylet in versus out. Absolute catheter deflection for interstitial treatments increased with the removal of the metal stylets with a difference of 0.75 ± 0.49° (n = 313 catheters, mean ± SD, p < 0.01). The plans utilizing flexible wire instead of stylets are observed to correlate with the plans with no stylets with absolute 3D displacement and angular deflection of 1.1 ± 0.6 mm and 0.35° ± 0.3° respectively (n = 39 catheters, mean ± SD, p > 0.2). While the average target EQD2 D90 reduced by 5% ± 5% by planning without the stylets, four patients would have experienced a deviation from the prescription by >10%. There was an overall decrease in bladder D2cc and overall increase in rectal D2cc in the plans with the stylets utilized vs removed. Bladder D2cc, rectal D2cc, and target coverage showed no appreciable difference between utilizing flexible wires and the plans without. The difference in HU between the metal stylets and flexible wires was negligible. Catheter reconstruction in interstitial gynecological treatments with CT imaging revealed significant changes in catheter positioning with respect to the target volume once the stylets are removed for treatment. Using flexible wires of similar thickness to the source cable allow for more accurate tracking during planning without distorting the patient's anatomy or the treatment images, preserving the integrity of the treatment plan.

Retrospective Assessment of Surface Imaging Set up Accuracy for Intensity Modulated Proton Therapy of Comprehensive Breast Irradiation

The purpose of this work is to retrospectively assess differences in pretreatment set-up between x-ray-based alignment (kV pair and/or CBCT) and the CatalystPT Surface Imaging System (C-RAD) to quantify accuracy and determine maximum deviation of intra-fractional motion in breast patients treated with proton therapy. Breast patient setup differences were evaluated for ninety-seven patients (n = 97) treated by proton therapy between 2019 and 2022 at our institution. Each patient was initially aligned using C-RAD followed by orthogonal planar x-rays and/or CBCT to finalize pre-treatment localization. The couch coordinates from C-RAD immediately after patient positioning were captured and compared with the finalized couch coordinates using x-ray-based alignment. Additionally, the maximum 6D deviation of patient position recorded by C-RAD during the course of treatment was captured. Patient BMI and age were correlated with setup differences between C-RAD and x-ray imaging and evaluated using Pearson Correlation Coefficients (PCC) and Analysis of Variance (ANOVA) test. The absolute mean displacement was calculated over the entire course of treatment and reported by comparing the absolute difference between C-RAD and x-ray setups for each patient. The absolute mean displacement difference calculated by the mean of all the patients was found to be 2.5±1.1 mm (lateral), 2.8±1.2 mm (longitudinal), 2.5±1.0 mm (vertical), 1.2±0.5° (Yaw), 1.0±0.5°(Pitch) and 1.0±0.5°(Roll). The relative mean displacement difference with respect to the couch coordinate finalized by x-ray imaging was calculated by the mean of all the patients and was found to be 3.9±1.8 mm (lateral), 4.8±1.7 mm (longitudinal), 3.1±1.6 mm (vertical), 1.2±0.7° (Yaw), 1.6±0.7°(Pitch) and 1.3±0.6°(Roll). The mean maximum deviation for the entire course of treatment reported by C-RAD for all the patients was calculated to be 3.3±0.9 mm. Statistically, there are no significant correlations between BMI or age for mean displacement difference (BMI: PCC = 0.18, p-value = 0.075, Age: PCC = 0.004, p-value = 0.80705) and maximum deviation (BMI: PCC = 0.023, p-value = 0.72, Age: PCC = -0.089, p-value = 0.37). C-RAD was able to position breast patients to within 3 mm of the isocenter and monitor the intra-fractional motion of patients which was found to be 3.3±0.9 mm.

CBCT Guided Interfraction Absolute Displacement and Setup Error Assessment during Breast Prone Radiotherapy

To calculate interfraction absolute displacement/shift and setup error using cone beam computed tomography (CBCT) during breast prone radiotherapy. Fifty-nine patients undergoing prone whole breast-irradiation after breast-conserving surgery (BCS) were studied as part of an institutional review board- approved prospective trial. Setup precision was monitored using a daily online CBCT. Translational shifts in 3 axes (AP: anterior posterior; LR: left right; and SI: superior inferior) and 3 rotations (pitch, roll, and rtn) after CBCT were analyzed for 1062 treatment fractions. The random and systematic setup errors (SE) were calculated and were analyzed for time trends during the course of radiotherapy. For absolute inter-fractional shifts, the numbers of fractions exceeding 10 mm in the AP, LR, and SI directions were 6.5%, 17.42% and 8.92%, respectively; 0%, 0% and 1.31% fractions exceeded 3°for pitch, roll, and Rtn, respectively. The population systematic errors were 1.89/2.91/1.98 mm in AP/SI/LR directions, while the random error were 2.72/3.99/3.31 mm. In pitch, roll, rtn rotations, the population systematic error were 0.64°/0.49°/0.46°, and 0.89°/0.90°/0.93° for the random error. Without correction these would correspond to a clinical to planning target volume margin of 6.64/10.08/7.26 mm in AP/SI/LR directions and 2.22°/1.79°/1.8° in pitch, roll, rtn rotations. The magnitude of inter-fraction motion was not correlated with patient treatment time accept in AP direction (P = 0.000). SE was larger in prone position in breast cancer patients, attributable mostly to random errors, which emphasize the need for on-line imaging guidance in breast prone radiotherapy. 10mm margins would adequately cover the target volume and account for setup errors in the absence of IGRT.

Lumbar dorsal root ganglion displacement between supine and prone positions evaluated with 3D MRI

ObjectivePre-operative lumbar spine MRI is usually acquired with the patient supine, whereas lumbar spine surgery is most commonly performed prone. For MRI to be used reliably and safely for intra-operative navigation for foraminal and extraforaminal decompression, the magnitude of dorsal root ganglion (DRG) displacement between supine and prone positions needs to be understood. MethodsA prospective study of a degenerative lumbar spine cohort of 18 subjects indicated for lumbar spine surgery. Three-dimensional T2-weighted fast spin echo and T1-weighted spoiled gradient echo sequences were acquired at 3 T. Displacement and cross-sectional area (CSA) of the bilateral DRGs at 5 motion levels (L1–2 to L5-S1) were determined via 3D segmentation by 2 independent evaluators. Wilcoxon rank-sum tests without correction for multiple comparison were performed against hypothesized 1-mm absolute displacement and corresponding 24% CSA change. ResultsDRG mean absolute displacement was <1 mm (p > 0.99, mean = 0.707 mm, 95% confidence interval (CI) = 0.659 to 0.755 mm), with the largest directional displacement in the dorsal-to-ventral direction from supine to prone (mean = 0.141 mm, 95% CI = 0.082 to 0.200 mm). Directional displacements caudal-to-cephalad were 0.087 mm (95% CI = 0.022 to 0.151 mm), and left-right were −0.030 mm (95%CI = −0.059 to −0.001 mm). Mean CSA change was within 24% (p > 0.99, mean = −8.30%, 95% CI = −10.5 to −6.09%). Mean absolute displacement was largest for the L1 (mean = 0.811 mm) and L2 (mean = 0.829 mm) DRGs. ConclusionsMinimal, non-statistically significant soft tissue displacement and morphological area differences were demonstrated between supine and prone positions during 3D lumbar spine MRI.

Structural stiffness and equivalent viscous damping in a supercritical carbon dioxide lubricated hybrid journal bearing under hydrostatic status

PurposeThe purpose of this paper is to propose a type of hybrid bearing lubricated with supercritical carbon dioxide (S-CO2) and to investigate the stiffness and damping characteristics of the bearing under hydrostatic status.Design/methodology/approachEstablished a test rig for radial bearings lubricated with S-CO2 and used it to measure the dynamic coefficients by recording the relative and absolute displacements of bearing. Test bearing is mounted on a nonrotating, stiff shaft. Using static loading experiments to obtain structural stiffness. The dynamic coefficient regularities of the test bearing under hydrostatic status were revealed through dynamic loading experiments.FindingsExperiment results indicate that test bearing displayed increased stiffness when subjected to high excitation frequencies and low excitation forces, as well as elevated damping when exposed to low excitation frequencies and low excitation forces. Additionally, an increase in either environmental pressure or hydrostatic recess pressure can elevate the dynamic coefficient. The effect of temperature on the dynamic coefficient is more pronounced around the critical temperature of S-CO2.Originality/valueDesigned a type of hybrid bearing for use in the Brayton cycle that is lubricated with S-CO2 and uses hydrostatic lubrication during start-stop and hydrodynamic lubrication during high-speed operation. The hybrid bearing reduces the wear and friction power consumption of gas bearing. However, few experimental analyses have been conducted by researchers in this field.

Study on the pier bottom self-centering seismic isolation structure of the high-pier continuous rigid frame bridges

Four seismic isolation specimens were designed, fabricated, and subjected to physical loading tests to enhance the seismic performance of a high-pier continuous rigid-frame bridge. A finite element model of the seismic isolation structure of the high-pier was established using numerical simulation software. The entire bridge model was established based on the multi-scale modeling method to investigate the seismic response of the high-pier continuous rigid frame bridge under different seismic waves. The results indicate that the seismic isolation pier has self-centering and energy dissipation capabilities. The seismic isolation pier has satisfactory energy dissipation capacity and ductility when the ratio of the long-axis and short-axis radii is 1.5. The results of the finite-element simulation corresponded well with the experimental results. Significant damage occurred to the concrete at the bottom and corner of the pier, and the reinforcement did not reach its yield strength throughout the loading process. Therefore, measures must be implemented to ensure the seismic performance of the structure. The pier bottom self-centering seismic isolation structure effectively absorbs shocks, as evidenced by reduced absolute acceleration and relative displacement at the pier top, decreased shear force and bending moment at the pier bottom, and minimized girder displacement. It was recommended that the ratio of the long-axis and short-axis radii be adopted as 1.5–2.0 and that the pier height be selected as 60 m–100 m. These results provide a reference for the research and applications of this type of structure.

Measurement of absolute three-dimensional displacement gradients using tri-color quad-beam digital shearography

Measurement of absolute three-dimensional displacement gradients using tri-color quad-beam digital shearography

Assessment of pediatric shoulder range of motion and loading response to evaluate the biofidelity of the Large Omni-directional Child (LODC) anthropomorphic test device (ATD) shoulder design

The shoulder girdle complex, through engagement with the seat belt, influences motor vehicle occupant upper body movement during frontal impacts, affecting the movement of the head and spine. The recently developed Large Omni-directional Child (LODC) anthropomorphic test device (ATD) was designed with flexible shoulder girdle structures that capture the unique kinematics in pediatric occupants. However, the LODC shoulder has not been evaluated for biofidelity due to the lack of biomechanical data available on pediatric shoulder responses. This study evaluated quasi-static pediatric shoulder girdle complex responses through non-invasive displacement measurements. These data were obtained to evaluate, and, if necessary, improve the biofidelity of the LODC ATD. Shoulder range of motion and anthropometric measurements were obtained from 25 pediatric volunteers, ages 8–12 years old. Loads were applied bilaterally exclusively to the shoulder complexes in increments of 25 N up to 150 N per shoulder at 90 and 135 degrees of shoulder flexion. Still photos were used to determine shoulder displacement in the sagittal plane from images captured prior to and following the load applications. Data analysis consisted of motion tracking to evaluate the absolute and relative displacement of the right acromion and T1. The displacements for each volunteer were normalized based on the volunteer’s shoulder width compared to the shoulder width of the LODC ATD. For the 90° load, the acromion moved relative to T1 an average of 28.1 mm forward and 3.1 mm downward at maximum displacement. For the 135° load, the acromion moved relative to T1 an average of 15.5 mm forward and 42.7 mm upward at maximum displacement. Similar displacements at higher loads indicated that the volunteers achieved their maximum range of motion. The results of this study will be compared to the LODC ATD, assessing the biofidelity of the shoulder complex.

Compact flexible actuator based on a shape memory alloy for shaping surgical instruments

Abstract Conventional flexible actuators for minimally invasive interventions come with complex and bulky actuation infrastructure. We present a proof-of-concept study of a compact flexible actuator with variable shape change featuring shape memory alloy wire loops in active-antagonist configurations for a bending and S-shape. The actuator was fabricated using heat-treated wire loops. The evaluation using optical marker tracking revealed a mean maximum absolute displacement at the distal tip of 19 mm and a force of 90 mN reached in under 15 s. For control, a closed-loop regime was evaluated with steady-state errors below 2°.