Deformation Measurement Research Articles

Simultaneous three-dimensional deformation measurement using tri-wavelength and monochrome camera imaging with a pyramid prism.

What we believe to be a new electronic speckle pattern interferometry (ESPI) configuration is being developed for simultaneous three-dimensional deformation measurements. In this ESPI system, two pairs of symmetrical illuminating arrangement with dual-wavelength lights were used to independently sense two in-plane deformation components, one Michelson interferometer-based set illuminating with the other wavelength light was utilized to measure out-of-plane deformation. The color speckle interferogram was split into four sub-patterns by a prism, three of them were filtered by three different bandpass dichroic filters and recorded by one monochrome camera. Micro-rotation testing work firstly verifies the validation of the proposed phase-shifting device. Three-dimensional deformation information was simultaneous obtained by using temporal phase-shift method. All strain components related to the specimen surface deformation were further determined by numerical differential. The experimental results of a tested specimen were excellently consistent with those of FEM simulation, which verified the validation and feasibility of the proposed ESPI system for measuring 3D deformation.

Association between Postoperative Medial: Middle Intercuneiform Joint Gapping and Recurrence Rates in Hallux Valgus

Category: Bunion; Midfoot/Forefoot Introduction/Purpose: Hallux valgus (HV) is a triplanar deformity of the first metatarsal, which may extend beyond the first ray. Compared with normal feet, previous studies have found that HV patients have an increase in hypermobility of the joints along the medial column and at the medial – middle (MM) intercuneiform joint. Despite increased instability at the MM intercuneiform joint, no study has investigated its clinical significance. The primary purpose of this study was to determine if postoperative widening of the MM intercuneiform joint was associated with recurrence in HV patients who undergo a first tarsometatarsal fusion (modified Lapidus procedure). A secondary purpose was to investigate whether other HV imaging parameters were associated with a widening of the MM intercuneiform joint. Methods: This study included 52 consecutive HV patients who underwent a modified Lapidus procedure and had preoperative and at least 5-month postoperative weightbearing CT (WBCT) scans. Preoperative and postoperative measurements of HV deformity, including the intermetatarsal angle and hallux valgus angle (HVA) on plain radiographs and triplanar pronation angle and sesamoid station from WBCTs, were performed as previously described. MM intercuneiform distance was measured on the coronal multiplanar reconstructed WBCT scans after reorienting the axial and sagittal planes such that the coronal cuts were orthogonal to the intercuneiform joint (Figure 1A). Recurrence of the HV deformity was defined as a postoperative HVA ≥ 20°. Paired t-tests were used to compare preoperative and postoperative imaging parameters, and Mann-Whitney U tests were used to compare measurements between patients with and without HV recurrence. Pearson correlation coefficients were used to explore associations between preoperative and postoperative measurements and the change in MM intercuneiform distance. Results: Nine of 52 patients (17.3%) had recurrence of their HV deformity. For the entire cohort, the mean preoperative and postoperative MM intercuneiform distances were 0.73 mm (standard deviation (SD) 0.3) and 1.08 mm (SD 0.5), respectively. In patients with and without HV recurrence, the mean widening at the MM intercuneiform joint was 0.69 mm (95% confidence interval (CI) 0.52-0.86) and 0.27 mm (95% CI 0.17-0.38, P< 0.001), respectively. Patients with recurrence had significantly greater widening of the MM intercuneiform joint than patients without recurrence (P=0.001, Figure 1B and Table 1). While no preoperative imaging parameters were associated with a change in the MM intercuneiform distance, increasing postoperative sesamoid position (r=0.32, P=0.022) and HVA (r=0.28, P=0.046) were correlated with a greater change MM intercuneiform joint gapping. Conclusion: In patients undergoing a modified Lapidus procedure for correction of their HV deformity, postoperative widening of the MM intercuneiform joint was associated with recurrence of the HV deformity. As understanding of the HV deformity continues to evolve, our study suggests that there is a complex interplay between deformity at the hallux metatarsophalangeal (MP) joint, reduction of the metatarsosesamoid joint complex, and the instability at the tarsometatarsal and intercuneiform joints. This may guide surgical correction as surgeons may need to address both intercuneiform instability and correction at the hallux MP joint in order to decrease HV recurrence rates.

WarpPINN: Cine-MR image registration with physics-informed neural networks.

The diagnosis of heart failure usually includes a global functional assessment, such as ejection fraction measured by magnetic resonance imaging. However, these metrics have low discriminate power to distinguish different cardiomyopathies, which may not affect the global function of the heart. Quantifying local deformations in the form of cardiac strain can provide helpful information, but it remains a challenge. In this work, we introduce WarpPINN, a physics-informed neural network to perform image registration to obtain local metrics of heart deformation. We apply this method to cine magnetic resonance images to estimate the motion during the cardiac cycle. We inform our neural network of the near-incompressibility of cardiac tissue by penalizing the Jacobian of the deformation field. The loss function has two components: an intensity-based similarity term between the reference and the warped template images, and a regularizer that represents the hyperelastic behavior of the tissue. The architecture of the neural network allows us to easily compute the strain via automatic differentiation to assess cardiac activity. We use Fourier feature mappings to overcome the spectral bias of neural networks, allowing us to capture discontinuities in the strain field. The algorithm is tested on synthetic examples and on a cine SSFP MRI benchmark of 15 healthy volunteers, where it is trained to learn the deformation mapping of each case. We outperform current methodologies in landmark tracking and provide physiological strain estimations in the radial and circumferential directions. WarpPINN provides precise measurements of local cardiac deformations that can be used for a better diagnosis of heart failure and can be used for general image registration tasks. Source code is available at https://github.com/fsahli/WarpPINN.

Outcomes of Hindfoot Joint-Sparing Reconstructive Procedures for Flexible Progressive Collapsing Foot Deformity: A Prospective Cohort Study

Category: Hindfoot; Other Introduction/Purpose: Treatment of Progressive Collapsing Foot Deformity (PCFD) is controversial and surgical procedures utilized usually depend on the type and rigidity of deformities present (PCFD classes and stages), degree of soft tissue involvement, and surgeon’s preference. Multiple surgical procedures are usually performed concomitantly to achieve adequate correction. Prospective data regarding the utilization of hindfoot joint-sparing reconstructive procedures in the treatment of flexible PCFD is scarce, and little is known about the influence of the different procedures utilized to treat PCFD in deformity correction and patient-reported outcomes (PROs). The objective of this prospective study was to evaluate the most used hindfoot joint-sparing procedures utilized by a single-surgeon to treat flexible PCFD, and the influence of the utilized procedures in deformity pattern corrections, and PROs. Methods: IRB-approved, prospective, and comparative cohort study. Adult PCFD patients with flexible deformity (stage 1), no history of surgical treatment, and that failed conservative treatment for >3-months were enrolled. Patients underwent surgical treatment by a single-surgeon. Patients were excluded if a hindfoot fusion procedure was needed intra-operatively to achieve correction. Types, numbers, and sizes of surgical procedures utilized were recorded. Weight-bearing CT (WBCT) measurements of overall 3D deformity, Classes A (hindfoot valgus), B (abduction), C (medial column instability), D (peritalar subluxation), and E (ankle valgus tilt) were assessed preoperatively, and at first 3-months WBCT. PROs were recorded preoperatively and at the most recent follow-up. Descriptive statistics were used to report the frequency of deformity and procedures utilized. Pre and postoperative measurements and PROs were compared with paired T-tests/Wilcoxon. Multivariate regression analysis was used to correlate procedures utilized with deformity correction and PROs. P-values of >0.05 were considered significant. Results: A total of 29 patients included (28 feet, 79%F, 21%M), mean age and BMI of respectively 47.6-years and 34kg/m2. Average number of procedures performed was five and mean follow-up was 19.1 months (range, 3 to 40). Frequency and sizes of medial displacement calcaneal osteotomy (MDCO), first ray plantarflexion procedure (Cotton/LapiCoton), and lateral column lengthening (LCL) procedures were, respectively: 100% (8.9mm displacement), 100% (66% Lapicotton/34% Cotton, 8.3mm wedge-opening) and 39% (6.8mm wedge-opening). Soft-tissue procedures performed: 83% Posterior tibial tendon (re-tensioning/FDL transfer/allograft reconstruction), 34% peroneal tendon (brevis-to-longus and brevis lengthening), 76% gastrocnemius-recession, 38% spring ligament (re-tensioning/reconstruction/augmentation) and 31% deltoid ligament (re- tensioning/reconstruction/augmentation). Significant improvement postoperatively was observed in all PCFD measurements performed and PROs (Figure). However, no direct correlation was found between procedures performed/measurement improvements and PROs. Conclusion: In this prospective comparative cohort study of flexible PCFD patients undergoing surgical treatment with hindfoot joint sparing surgical procedures, we observed significant postoperative improvement in all deformity patterns assessed (Classes A, B, C, and D) as well as PROs. MDCO and first ray plantarflexion procedures (Cotton or LapiCotton) were the most commonly utilized procedures and were performed in all cases. Even though deformity correction and PRO improvements were observed postoperatively, no direct correlation was observed between PROs and specific surgical procedures performed or deformity pattern corrections (PCFD classes).

Comparing Symptomatic and Asymptomatic Flatfeet Using Known Markers of Progressive Collapsing Foot Deformity (PCFD): A Case Control Study

Category: Midfoot/Forefoot; Hindfoot Introduction/Purpose: Flattening of the longitudinal arch of the foot (Flatfoot) can represent a normal spectrum of foot morphology and alignment. The issue comes when the foot is collapsing progressively, what is now termed Progressive Collapsing Foot Deformity (PCFD). Literature on asymptomatic flatfoot is scarce since asymptomatic patients do not seek medical attention. Alignment differences between asymptomatic flatfoot and PCFD have not been established and might represent a key-step in understanding predictors of PCFD. The objective of this prospective study was to compare established PCFD measures in a cohort of asymptomatic flatfoot, PCFD patients and healthy controls. We hypothesized that asymptomatic flatfeet alignment would differ from both symptomatic PCFD patients and healthy controls. Methods: In this prospective comparative study, patients with asymptomatic flatfeet were recruited to undergo a weight-bearing CT (WBCT) scan. This cohort (22 feet, 10 males, 12 females) was compared to two other prospective cohorts (22 symptomatic PCFD and 22 healthy controls). Along with demographic data, PCFD measurements performed include Foot and Ankle Offset (FAO), Forefoot Arch Angle (FAA), Middle Facet Uncoverage, and the Transverse Arch Plantar (TAP) angle. Normality of variables was assessed using the Shapiro-Wilk test. Chi-squared or analysis of variance (ANOVA) test was performed to compare each parameter between the three groups. A post-hoc Bonferroni test was then performed to assess significance between each group pairing. P-values of >0.05 were considered significant. Results: All three groups were comparable on BMI (p=0.10), Age (p=0.75) and Gender (p=0.78). All measurements taken differed significantly between the symptomatic PCFD and healthy controls (Table 1). FAO was significantly different between controls vs asymptomatic (p < 0.001) and asymptomatic vs symptomatic (p < 0.001). FAA was also significantly different between asymptomatic and both symptomatic (p=0.001) and control groups (p=0.001). Middle facet uncoverage differed between the asymptomatic and control group (p=0.001) but the asymptomatic and symptomatic group were similar (p=0.106). While the TAP angle was significantly different between asymptotic and symptomatic groups (p=0.013), the asymptomatic and control groups failed to reach significance (p=0.061) (Table 1). On average, deformity measurements for asymptomatic flatfeet were in between the values for healthy controls and symptomatic PCFD (Figures 1-3). Conclusion: To our knowledge this is the first prospective study to compare healthy controls, asymptomatic flatfoot and symptomatic PCFD patients. We observed that asymptomatic flatfoot patients usually had measurements of PCFD that would fall in between normal alignment asymptomatic controls and symptomatic PCFD patients. Further, the asymptomatic group differed significantly from both other groups on every measure but two. Our data supports the idea that asymptomatic flatfoot should be considered a risk factor for Progressive Collapsing Foot Deformity. Our data can hopefully shine light in finding predictive markers for the development of PCFD.

Making use of Digital Image Correlation to identify the true character of the applied load

Digital Image Correlation became one of the dominant optical full-field techniques used in experimental mechanics. It does not require sophisticated equipment to evaluate the full displacement vector field of the specimen under test with great accuracy. In this paper, we would like to put the reader's attention to the DIC technique as a solution that may identify the genuine character of the load applied to the object under test. Our experience with testing wind turbine blades using DIC proves that possibility. Full Text: PDF References E.M.C Jones, M.A. Iadicola, "A good practises guide for digital image correlation" International Digital Image Correlation Society, (2018), CrossRef B. Pan, "Digital image correlation for surface deformation measurement: historical developments, recent advances and future goals", Meas. Sci. Technol. 29, 082001 (2018), CrossRef B. Pan, L.P. Yu, Q.B. Zhang, "Review of single-camera stereo-digital image correlation techniques for full-field 3D shape and deformation measurement", Sci. China Technol. Sci. 61, 2 (2018), CrossRef S. Sharma, N. Iniyan Thiruselvam, S.J. Subramanian, G.S. Kumar, "Computation of strains from stereo digital image correlation using principal component analysis", Meas. Sci. Technol. 32, 105201 (2021), CrossRef IEC 61400-5:2020 Wind energy generation systems - Part 5: Wind turbine, DirectLink IEC 61400-23:2014 Wind turbines - Part 23: Full-scale structural testing of rotor blades, DirectLink

Validation of an electro-hydraulic press for dynamic measurement of elastic deformations in agricultural tires

Tests with agricultural tires and wheelsets allow for mitigating the machinery traffic limitations to crop productivity, as it shows the tire-surface interaction under different suitability conditions, optimizing farming processes with the use of technology. Thus, this paper aims to develop an electro-hydraulic press for dynamically measuring elastic deformations occurring in agricultural tires. The experiment used a completely randomized design, evaluating two pneumatic wheelsets, bias-ply and radial, and six vertical loads, 4.9033, 9.8066, 14.71, 19.6133, 24.5166, and 29.4199 kN, on the tire, totalizing 12 treatments with five repetitions. The analyzed parameters are contact area, horizontal and vertical deflection. The collected data underwent an analysis of variance F-test and a polynomial regression analysis. The results showed continuous replicability of the data obtained with the electro-hydraulic press. That demonstrates the efficiency of the developed device for evaluating agricultural tires in a controlled environment. The bias-ply tire presented a smaller contact area than the radial with the increase of incident loads, and the 14.71 kN load achieved a higher amplitude, generating a difference of 40 %. The maximum load resulted in 27 % more horizontal deflections for the radial tire. However, the vertical deflection values were 8 % higher with the bias-ply tires.

Optical mapping of cardiac electromechanics in beating in vivo hearts

Optical mapping has been widely used in the study of cardiac electrophysiology in motion-arrested, ex vivo heart preparations. Recent developments in motion artifact mitigation techniques have made it possible to optically map beating ex vivo hearts, enabling the study of cardiac electromechanics using optical mapping. However, the ex vivo setting imposes limitations on optical mapping such as altered metabolic states, oversimplified mechanical loads, and the absence of neurohormonal regulation. In this study, we demonstrate optical electromechanical mapping in an in vivo heart preparation. Swine hearts were exposed via median sternotomy. Voltage-sensitive dye, either di-4-ANEQ(F)PTEA or di-5-ANEQ(F)PTEA, was injected into the left anterior descending artery. Fluorescence was excited by alternating green and amber light for excitation ratiometry. Cardiac motion during sinus and paced rhythm was tracked using a marker-based method. Motion tracking and excitation ratiometry successfully corrected most motion artifact in the membrane potential signal. Marker-based motion tracking also allowed simultaneous measurement of epicardial deformation. Reconstructed membrane potential and mechanical deformation measurements were validated using monophasic action potentials and sonomicrometry, respectively. Di-5-ANEQ(F)PTEA produced longer working time and higher signal/noise ratio than di-4-ANEQ(F)PTEA. In addition, we demonstrate potential applications of the new optical mapping system including electromechanical mapping during vagal nerve stimulation, fibrillation/defibrillation. and acute regional ischemia. In conclusion, although some technical limitations remain, optical mapping experiments that simultaneously image electrical and mechanical function can be conducted in beating, in vivo hearts.

Experimental investigation of steel beam-to-column end-plate joints under static and impact loading

Events like blasts, vehicle impacts, gas explosions, or terrorist attacks can induce dynamic structural responses. Traditional design practices focus on structures' static or quasi-static behavior, neglecting dynamic effects. However, the response of structural members and joints under dynamic loading can differ significantly from that under static loading. For instance, the mechanical properties of steel, such as yield strength and tensile strength, exhibit variations depending on the strain rate. Experimental impact load tests of members and connections are needed to validate FEM models, but a very limited number of such tests have been presented in the literature. This article presents experimental static and impact tests of double-sided extended steel bolted end-plate joints. The tests were carried out on three identical steel specimens of a beam-to-column system, with static tests on one specimen and impact tests on two other specimens. A free-falling concrete-steel package was used as the impact load, with varying values of its weight and the height of the fall. The structural responses of the joints and selected components were measured using advanced measuring equipment for experimental static and dynamic tests. In both static and impact tests, significant deformation of the connection elements, especially the column and end-plate, was observed. Moreover, local buckling appeared in the compression zone of the column web as well as fracture of the end plate below the lower flange of the beam. Based on the results of the deformation measurements, the actual strain rate and dynamic increase factor (DIF) were obtained.

A deformability-based biochip for precise label-free stratification of metastatic subtypes using deep learning

Cellular deformability is a promising biomarker for evaluating the physiological state of cells in medical applications. Microfluidics has emerged as a powerful technique for measuring cellular deformability. However, existing microfluidic-based assays for measuring cellular deformability rely heavily on image analysis, which can limit their scalability for high-throughput applications. Here, we develop a parallel constriction-based microfluidic flow cytometry device and an integrated computational framework (ATMQcD). The ATMQcD framework includes automatic training set generation, multiple object tracking, segmentation, and cellular deformability quantification. The system was validated using cancer cell lines of varying metastatic potential, achieving a classification accuracy of 92.4% for invasiveness assessment and stratifying cancer cells before and after hypoxia treatment. The ATMQcD system also demonstrated excellent performance in distinguishing cancer cells from leukocytes (accuracy = 89.5%). We developed a mechanical model based on power-law rheology to quantify stiffness, which was fitted with measured data directly. The model evaluated metastatic potentials for multiple cancer types and mixed cell populations, even under real-world clinical conditions. Our study presents a highly robust and transferable computational framework for multiobject tracking and deformation measurement tasks in microfluidics. We believe that this platform has the potential to pave the way for high-throughput analysis in clinical applications, providing a powerful tool for evaluating cellular deformability and assessing the physiological state of cells.

Remote Surveillance of Differential Deformation for Kazakhstan Offshore Kashagan Oilfield Using Microwave Satellite Remote Sensing

The primary objective of this study was to assess differential vertical and horizontal deformations for the offshore Kashagan oilfield located in the Northern Caspian Sea. Sentinel-1 (SNT1) and COSMO-SkyMed (CSK) synthetic-aperture radar (SAR) images (9 January 2018–6 April 2022) were processed using persistent scatterer interferometric SAR (PS-InSAR) technique with further 2D decomposition of line-of-sight (LOS) measurements to differential vertical and horizontal deformations. Differential vertical deformation velocity was observed to be between −4 mm/y and 4 mm/y, whereas horizontal was between −4 mm/y and 5 mm/y during 2018–2022. However, it was possible to observe the spatial deformation patterns with the subsidence hotspots reaching differential cumulative vertical displacement of −20 mm from both satellite missions. PS-InSAR differential vertical deformation measurements derived from SNT1 and CSK satellite images showed identical spatial patterns with moderate agreement, whereas poor agreement was observed for differential horizontal deformations. The differential vertical deformation hotspots were observed for the oilfield areas installed on piles with obviously higher vulnerability to dynamic movements. Through this study, based on the interferometric measurements, marine geotechnical expert feedback, and no reported deformation-related incidents since 2013, it was possible to conclude that the Kashagan oilfield had not been impacted by significant differential vertical and horizontal deformations on the oilfield. However, since long-term GPS measurements were not accessible from the oilfield to be used as the reference for PS-InSAR measurements, we were not able to judge the long-term displacements of the entire oilfield or possible oscillations, even though it is built on the artificial island. Considering the broad range of PS-InSAR measurements using time-series radar images, the interferometric measurements could play a significant role in the prioritization of insitu risk assessment activities, operational cost reduction, strengthening of safety factors, and planning of further targeted insitu measurements.

Optimal Pair Selection Applied to Sentinel-2 Images for Mapping Ground Deformation Using Pixel Offset Tracking: A Case Study of the 2022 Menyuan Earthquake (Mw 6.9), China

Pixel Offset Tracking (POT) for optical imagery is a widely used method for extracting large-scale ground deformation. However, the influence of imaging parameters on the measurement accuracy of POT is still unclear. In this study, based on 16 pairs of Sentinel-2 images covering the period before and after the Ms6.9 Menyuan earthquake in 2022, we quantitatively assessed the effects of imaging bands, time intervals between image pairs, and differences in solar zenith angles on the measurement accuracy of optical POT. The results showed that the quality of ground deformation extracted using the near-infrared band was superior to other bands. The accuracy of optical POT measurements exhibited a negative correlation with both the time interval between image pairs and the differences in solar zenith angles. The maximum difference in optical POT measurement accuracy for the near-infrared band between image pairs with different time intervals (5/10/15 days) reached 30.3%, while the maximum difference in deformation measurement accuracy for pairs with different solar zenith angle differences was 30.56%. Utilizing the optimal POT image pair, the accuracy of co-seismic deformation measurement for the Menyuan earthquake improved by 48.3% compared to the worst image pair. The maximum co-seismic horizontal displacement caused by the earthquake was estimated to be 3.00 ± 0.51 m.

Impact-dynamic properties of aromatic hyperbranched polyester/RTM6 epoxy nanocomposites

Present study investigates the influence of aromatic hyperbranched polyester (AHBP) nanofillers on the impact-dynamic properties of RTM6 epoxy. The strain rate dependence of the energy absorption capacity of neat RTM6 epoxy and RTM6 nanocomposites with filler weight ratios of 0.1%, 1%, and 5% was determined through compression testing. Additionally, static and dynamic tensile tests were performed on these materials. Universal testing machines were used for the quasi-static tests, split Hopkinson bar setups for the high-strain rate experiments. Furthermore, dynamic single-edge notch bending (SENB) tests were conducted to measure fracture toughness using an adapted split Hopkinson compression bar setup. In addition to global deformation measurements, full-field deformation measurements were also performed in all experiments using the digital image correlation (DIC) technique. The results indicate that the energy absorption capacity, tensile strength, fracture strain, and toughness are significantly influenced by both strain rate and filler content of the RTM6 epoxy.

Kinematic inventory of rock glaciers in the Nyainqêntanglha Range using the MT-InSAR method

ABSTRACT Rock glaciers are typical periglacial landforms with tongue or lobate morphological shapes and characterized by the distinct front, lateral margins, and often by ridge-and-furrow surface topography textures as well as kinematic characteristics, widely distributed in alpine environments. Multitemporal Synthetic aperture radar interferometry (MT-InSAR), is a remote sensing technique with demonstrated effectiveness for detecting landform kinematics. However, its application to rock glaciers is challenged by temporal decorrelation and atmospheric phase noises due to complex topography and snow cover. We designed a quadtree segmentation and parallel computing-based MT-InSAR method to improve the quality and efficiency of deformation measurement of rock glaciers. We applied the method to a rock glacier inventory of the Nyainqêntanglha Range, China, derived from high-resolution Gaofen-2 images, to quantify the activity rate of each rock glacier. Results showed that 32.1% (6,389) of the identified rock glaciers exhibited slope-parallel deformation rates exceeding 100 mm/y. The activities of the rock glaciers exhibited strong correlations with their distance to glaciers, precipitation, freeze–thaw magnitude, and permafrost occurrence probability. The results demonstrate the effectiveness of the developed segmentation-parallel MT-InSAR method for monitoring rock glacier deformation over a large region.

Integrating shallow head measurements and InSAR data to quantify groundwater-storage change in San Joaquin Valley, California (USA)

Monitoring groundwater storage is essential for sustainable groundwater management. Storage can be quantified by considering the two main components through which storage change is expressed: saturation changes and deformation of aquifer materials. Here, these components were quantified using a selected area in California’s San Joaquin Valley (USA). First, this involved following existing observational approaches: quantifying the component expressed through saturation changes by identifying head measurements from shallow wells and scaling by specific yield. In the San Joaquin Valley, existing approaches to estimate the deformation component are to ignore it or approximate it with a simple linear relation to measured head. However, head and deformation measurements made at extensometers revealed that assuming a linear relationship between deformation and head might provide a poor estimate, particularly during periods in which measured head is rising. Instead, InSAR-derived surface deformation measurements were used to quantify the deformation component of storage changes. This showed that the two components—saturation and deformation—accounted for storage declines of equal magnitude over 2015–2021, suggesting that the deformation component should not be neglected when estimating storage changes in regions with subsidence. Summing the two calculated components gave a new estimate of the total storage change that captured the major trends seen in independent estimates, while better accounting for the deformation component. An additional benefit is that this method accounts for the deformation component in the unconfined aquifer. This method to quantify total storage change can be a practical and effective tool to support groundwater management.

Image feature based quality assessment of speckle patterns for digital image correlation measurement

A novel method is proposed to assess the quality of speckle patterns for deformation measurement using the digital image correlation (DIC) technique. Different from existing methods that focused on the characteristics of individual speckle or frequency of grayscale values, our approach explores the usage of the image features essential for image registration, which is the basis of DIC. An indicator called density and evenness of features (DEF) is defined, combining the distribution density and evenness of image features. Numerical and real experiments demonstrate that the DEF is sensitive to the quality of various speckle patterns. It can detect the subtle difference between good speckle images leading to small gap in measurement accuracy. The DEF can also provide reliable guidelines to design high-quality transferable speckle patterns, as it shows clear relation to the main controllable parameters in generation of speckle patterns, including speckle duty ratio, image contrast, speckle radius and its dispersion, as well as speckle edge sharpness.

Limitations of the Check Calculation for Tooth Deformation of Plastic Gears According to Gear Design Guideline VDI 2736.

An in situ gear test rig has been developed at the Institute of Polymer Technology (LKT) to characterize the deformation of plastic gears during operation. It analyses timing differences between following index pulses of rotary encoders on the input and output shaft. This measurement principle enables the continuous measurement of the elastic tooth deformation and permanent deformations and wear at operating speed by switching between a high and low torque. Gear tests using a steel-polybutylene terephthalate (PBT) gear set were performed at different rotational speeds and tooth temperatures to analyze the tooth deformation during operation. The results were compared to the calculated deformation according to gear design guideline VDI 2736. Moreover, the results of the gear tests were correlated with the results of a dynamomechanical analysis (DMA). Both, the DMA and the in situ gear tests show that the effect of temperature on deformation is much higher than the effect of frequency or rotational speed. However, the experimentally measured tooth deformation is significantly higher (up to 50%) than the calculated at lower speed. Thus, the check calculation according to VDI 2736 underestimates the actual tooth deformation at lower speeds. Therefore, the guideline should be adjusted in the future.

A full-field warpage characterization measurement method coupled with infrared information

The thermomechanical properties of microelectronic packages can serve as important indicators of reliability. Indeed, it is of great interest in dynamic warpage measurement of deformation and temperature of the local package structure to explore the evolutionary mechanism. In this paper, a full-field warpage characterization measurement method coupled with the infrared information is proposed to quantitatively evaluate the thermomechanical properties of microelectronic devices. A heat source is used to illuminate the calibration board of the infrared image to facilitate multi-camera calibration. After performing a series of image processing procedures, a clear grayscale infrared image of the calibration board was easily obtained, and the calibration between the infrared camera and the optical camera was realized. The thermomechanical properties of the copper thermoelectric cooler were explored after fully verifying the accuracy and error of the measurement. There is an obvious positive correlation between the full-field temperature and warpage of the cooler. The feasibility and validity of the measurement system were validated.

Shape-Morphing Dynamics of Soft Compliant Membranes for Drag and Turbulence Modulation.

We study the kinematics and dynamics of a highly compliant membrane disk placed head-on in a uniform flow. With increasing flow velocity, the membrane deforms nonlinearly into increasingly parachutelike shapes. These aerodynamically elongated materials exhibit a modified drag law, which is linked to the elastohydrodynamic interactions. We predict the unsteady structural response of the membranes using a nonlinear, aeroelastic model-in excellent agreement with experimental measurements of deformations and force fluctuations. With simultaneous membrane interface tracking, force measurements and flow tracing, we reveal that a peculiar skewness in the membrane's oscillations triggers turbulence production in the wake, thereby modulating the drag. The present work provides a demonstration of the complex interplay between soft materials and fluid turbulence, leading to new, emergent system properties.

Fluorescence imaging deformability cytometry: integrating nuclear structure with mechanical phenotyping

Mechanical measurements of cells can provide unique insights into cell state and disease processes. The overall mechanical properties of cells can be heavily affected by the stiffest organelle, the nucleus. However, it is challenging to fully characterize internal nuclear structures in most cell mechanical measurement platforms. Here, we demonstrate single-cell deformability measurements of whole cells and stained nuclei in a fluorescence imaging flow cytometry platform. We also introduce bending energy derived metrics as a way to normalize measurements of cytoskeletal cortex and nuclear shape changes of cells and demonstrate the utility of relative deformability distributions to characterize populations of cells. We apply the platform to measure changes in cell biophysical properties during the process of NETosis, whereby neutrophils undergo drastic nuclear restructuring. We characterize cell size, deformability, and nuclear structure changes and their correlations in thousands of neutrophils undergoing NETosis, a process implicated in development of critical disease states, such as sepsis. This platform can aid in understanding heterogeneity in deformability in cell populations and how this may be influenced by nuclear or internal structure changes.Graphical