Shape Measurement Research Articles

Electron density distribution in bis(guanidinium) disodium hypodiphosphate heptahydrate, (CH6N3)2Na2(P2O6)·7H2O.

X-ray structural analysis of bis(guanidinium) disodium hypodiphosphate heptahydrate, (CH6N3)2Na2(P2O6)·7H2O revealed close Na+...guanidinium [Na...N 3.0366 (6) Å] and water...guanidinium O-H...N [H...N 2.07 Å, O...N 3.0401 (9) Å] contacts, the nature of which is explored with the use of electron density distribution and Hirshfeld surface analysis. The crystal structure is governed by coordination interactions to Na+ cations and an extensive network of hydrogen bonds, in which guanidinium cations, hypodiphosphate ions and water molecules are involved. Na+ cations are in tetragonal pyramidal or octahedral environment, which was proved by continuous shape measures. From ∇2ρ(rc) and bond degree values, the character of P-P bonds are classified as shared shell or covalent bond types, whereas P-O bonds are of transit closed shell or polarized covalent types. Despite the lack of a lone electron pair on the N atom and positive charge of the guanidinium cation, the existence of an O-H...N hydrogen bond was confirmed by electron density studies.

Euclid preparation: LXVII. Deep learning true galaxy morphologies for weak lensing shear bias calibration

To date, galaxy image simulations for weak lensing surveys usually approximate the light profiles of all galaxies as a single or double Sérsic profile, neglecting the influence of galaxy substructures and morphologies deviating from such a simplified parametric characterisation. While this approximation may be sufficient for previous data sets, the stringent cosmic shear calibration requirements and the high quality of the data in the upcoming survey demand a consideration of the effects that realistic galaxy substructures and irregular shapes have on shear measurement biases. Here we present a novel deep learning-based method to create such simulated galaxies directly from Hubble Space Telescope (HST) data. We first build and validate a convolutional neural network based on the wavelet scattering transform to learn noise-free representations independent of the point-spread function (PSF) of HST galaxy images. These can be injected into simulations of images from optical instrument VIS without introducing noise correlations during PSF convolution or shearing. Then, we demonstrate the generation of new galaxy images by sampling from the model randomly as well as conditionally. In the latter case, we fine-tune the interpolation between latent space vectors of sample galaxies to directly obtain new realistic objects following a specific Sérsic index and half-light radius distribution. Furthermore, we show that the distribution of galaxy structural and morphological parameters of our generative model matches the distribution of the input HST training data, proving the capability of the model to produce realistic shapes. Next, we quantify the cosmic shear bias from complex galaxy shapes in simulations by comparing the shear measurement biases between a sample of model objects and their best-fit double-Sérsic counterparts, thereby creating two separate branches that only differ in the complexity of their shapes. Using the Kaiser, Squires, and Broadhurst shape measurement algorithm, we find a multiplicative bias difference between these branches with realistic morphologies and parametric profiles on the order of $(6.9± 0.6) $ for a realistic magnitude-Sérsic index distribution. Moreover, we find clear detection bias differences between full image scenes simulated with parametric and realistic galaxies, leading to a bias difference of $(4.0± 0.9) $ independent of the shape measurement method. This makes complex morphology relevant for stage IV weak lensing surveys, exceeding the full error budget of the Euclid Wide Survey (Δμ_

Single-shot Digital Image Correlation-assisted Digital Holography for Simultaneous 3D Shape and Displacement Measurement

Single-shot Digital Image Correlation-assisted Digital Holography for Simultaneous 3D Shape and Displacement Measurement

Three-dimensional shape measurement method and system calibration for an annular inner-wall.

In the field of industrial measurement, capturing a three-dimensional (3D) profile of an annular inner-wall has been a significant challenge. Current methods typically require multiple scans using a 3D scanner or circular structured light technique, which are inefficient and inconvenient to use. To address this issue, an off-axis measurement method and corresponding system has been proposed in this paper based on circular fringe projection. It can be used to reconstruct the 360° profile of an annular inner-wall in a single scan without any movement. Additionally, a full-field calibration method using ray-tracing for this system has also been presented. Compared to the traditional methods, this method features a simple calibration structure, convenient operation and no need for strict coaxial alignment, which enhances the flexibility of the proposed measurement system and contributes to its high efficiency and the integrity of its output data. Simulation and experimental results confirm the effectiveness and practicality of this measuring approach and system calibration method, providing an alternative solution for automated 3D profile measurement of annular inner-wall.

Characteristics of Ra-226 particles from legacy contamination and implications for radiological protection.

Radioactive particles are physically discrete sources of radioactivity that have been released into the environment as result of past accidents, incidents, and practices, and can present a hazard to members of the public. The historical use of radium in the luminising of aircraft components, and the subsequent decommissioning of those aircraft and associated waste disposal practices, has left a legacy of contamination, such as the radioactive particles containing Ra-226 at Dalgety Bay, Scotland. The aim of this research was to physically, chemically, and radiologically characterise Ra-226 particles from Dalgety Bay and consider the implications for radiological protection of the public. Physical characterisation measured particle size and shape using optical macroscopy with image analysis, measured particle mass, and calculated particle density, as well as general observations on their physical appearance. Chemical characterisation used scanning electron microscopy with energy dispersive X-ray spectroscopy to measure surface elemental composition, and gamma spectrometry was used to measure the activities of Ra-226 and its gamma-emitting daughter radionuclides. Qualitative observations on visual appearance indicated there were five distinct subpopulations, and measurements of size, shape and density varied widely. A wide range of surface chemical compositions were observed, and evidence of their estuarine origin was visible in the form of sand grains and salt deposits. Ra-226, Pb-214, Bi-214 and Pb-210 were detected in all samples with activities over several orders of magnitude and varying degrees of secular equilibrium. Two original aircraft artefacts were also included in the investigation, comparison with which showed the particles and artefacts differed in their characteristics, indicating that the source material has undergone alteration. The diversity of particle characteristics has implications for the radiological protection of the public from Ra-226 particles including pathways of exposure, assessment of radiation dose, and longevity in the environment.

Identification of global main cable line shape parameters of suspension bridges based on local 3D point cloud

Main cable line shape measurement and parameter identification are a critical task in the construction monitoring and service maintenance of suspension bridges. 3D LiDAR scanning can simultaneously obtain the coordinates of multiple points on the target, offering high accuracy and efficiency. As a result, it is expected to be used in applications requiring rapid, large-scale measurements, such as main cable line shape measurement for suspension bridges. However, due to the large span and tall main towers of suspension bridges, the LiDAR field of view often encounters obstructions, making it difficult to obtain high-quality point clouds for the entire bridge. The collected point clouds are typically unevenly distributed and of poor quality. Therefore, LiDAR is used to monitor the local cable line shape. This paper proposes an innovative non-uniform sampling method that adjusts the sampling density based on the main cable’s rate of change. Additionally, the Random Sample Consensus (RANSAC) algorithm, the ordinary least squares, and center-of-mass calibration are applied to identify and optimize the geometric parameters of the cross-section point cloud of the main cable. Given the strong design prior information available during suspension bridge construction, Bayesian theory is applied to predict and adjust the global line shape of the main cable. The study shows that using LiDAR for cable point cloud measurement enables rapid acquisition of high-precision point cloud data, significantly enhancing data collection efficiency. The method proposed in this paper offers advantages such as highly automated, low risk, low cost, and sustainability, making it suitable for green monitoring throughout the entire main cable construction process.

A rare case of a zero-field single-ion magnet in a cerium(III) pseudo-icosahedral complex.

The synthesis and structural characterisation of [Ln(Tp2-Fu)2]I (1-Ln; Ln = La, Ce, Pr, Nd) (Tp2-Fu = hydrotris(3-(2'-furyl)-pyrazol-1-yl)borate) have been reported as an isomorphous series adopting pseudo-icosahedral ligand field geometries. Continuous shape measurement (CShM) analyses on the crystal field environments of 1-Ln show the smallest values yet reported for complexes employing two hexadentate ligands (e.g. bis-scorpionate environments), with the smallest belonging to 1-La. Single-ion magnetism for 1-Ce, 1-Pr and 1-Nd was probed with ac magnetic susceptibility studies revealing slow magnetic relaxation for 1-Nd in applied magnetic fields and in zero-applied field for 1-Ce, which is a rare observation for Ce(III)-based single-ion magnets. The energy barrier to magnetic relaxation for 1-Ce was experimentally determined to be Ueff = 30(5) cm-1, which is comparable to that of other cerium-based single-molecule magnets in the literature, where these systems stablise the mJ = ±5/2 state and possess large energy gaps between the ground and first excited state that do not agree with the experimentally determined barrier.

Accelerating the measurement of time-resolved emission line shapes with a denoising neural network

Accelerating the measurement of time-resolved emission line shapes with a denoising neural network

Multi-Color Channel Gamma Correction in Fringe Projection Profilometry

Three-dimensional shape measurement plays an important role in various fields. As a way of three-dimensional measurement, fringe projection profilometry (FPP) is widely used because of its non-contact, simple structure, and high stability. One of the key challenges affecting measurement accuracy is the gamma effect. With the development of FPP technology, multi-color channels are gradually applied to the measurement, and the response of different colors in the projector-camera system (pro-cam system) is not exactly the same. Therefore, more accurate gamma correction for different color channels is required. To solve this problem, a model of joint gamma correction for different color channels is proposed. In this model, the light is subdivided into three channels: red; green; and blue (RGB). In the pro-cam system, the different responses of different colors and the influence of background light intensity on gamma correction are comprehensively considered, and some error compensation is made for color crosstalk. Compared with the traditional gamma correction methods, the gamma correction method proposed in this paper is more accurate and has a larger effective working range after correction. This method is particularly beneficial in scenarios where multiple color channels are used for measurement, as it more accurately reflects the true measurement results for each channel. The effectiveness and accuracy of the method are validated through experiments.

Non-Stationary Wind Loading Identification for Large Transmission Tower Based on Dynamic Finite-Element Model Updating

An effective approach to deal with the structural failures of transmission towers in tornadic events is to develop good structural health monitoring (SHM) systems for them. However, the strategy for SHM of transmission towers against tornados should be different from the conventional atmospheric boundary layer (ABL) winds oriented ones, as the non-stationary nature of the tornados significantly differentiates them from the ABL winds. To satisfy the need of obtaining the highly time-varying whole-field stress on the structure in the course of the tornadic event for effective SHM, an innovative transient tornadic load distribution identification method is proposed for use, which is based on the field structural mode shape measurement and dynamic finite-element (FE) model updating. Via a numerical case study, it is noted that good effectiveness is achieved for the new load distribution identification method. Employing the Modal Assurance Criteria based FE model updating technique, the new method has the advantage of being easily embraced in practical SHM systems. It is found that when the transient tornadic velocity profile to be identified is noticeably different from the mode shape of the structure without undertaking external loads, the identified load pattern is very accurate for the new approach.

Deep 3D-DIC using a coarse-to-fine network for robust and accurate 3D shape and displacement measurements.

Deep learning has become an attractive tool for addressing the limitations of traditional digital image correlation (DIC). However, extending learning-based DIC methods to three-dimensional (3D-DIC) measurements is challenging due to the limited displacement estimation range, which cannot handle the large displacements caused by stereo-matching disparities. Besides, most of the existing learning-based DIC architectures lack prior information to guide displacement estimation, resulting in insufficient accuracy. To solve these problems, we proposed a learning-based 3D-DIC (i.e., Deep 3D-DIC) using a coarse-to-fine network called G-RAFT for large and accurate image displacement estimation. Specifically, the large displacement estimation network GMA is adopted to calculate the large coarse displacement field, which is further warped on the deformed image to eliminate the main displacement component. The residual small deformation between the reference image and the warped image is further extracted using the recently proposed RAFT-DIC with high accuracy. By subtracting small displacement from large displacement, the refined displacement field is obtained. In contrast to standard subset-based 3D-DIC, Deep 3D-DIC achieves full-automatic pixel-wise 3D shape and displacement reconstruction without manual parameter input. Experimental results demonstrate that Deep 3D-DIC achieves accuracy comparable to subset-based 3D-DIC, with strong generalization ability and remarkable advantages in scenarios with complex surfaces.

EMT-Induced Morphological Variations on Living Cell Membrane Surface.

Epithelial-mesenchymal transition (EMT) is a drastic and important cellular process by which epithelial cells acquire a mesenchymal phenotype. Herein, we evaluated EMT-induced membrane variations using scanning ion conductance microscopy (SICM), which allows noninvasive nanoscale visualization. The results showed that the number and size of ruffles on the living cell surface decreased as the EMT progressed. It was also shown that the overall cell shape change occurred first rather than the nanoscale morphological variations. Time-lapse imaging using SICM showed that the small ruffles still moved actively after EMT induction. This study indicates that surface shape measurements using SICM may be useful indicators for assessing EMT progression.

Estimation of Sensitivity Coefficients for Rockwell Indenters Using Finite Element Simulation for Uncertainty Evaluation

Abstract Rockwell hardness testing is a widely used hardness test, and there are many scales depending on the indenter shape and test force for corresponding to various materials. The common Rockwell indenters are the diamond sphero-conical indenter and the tungsten carbide ball indenter. The influence of indenter shape error on Rockwell hardness has been acknowledged, as this shape impacts test results. To accurately estimate this uncertainty, it is essential to understand the sensitivity coefficient, which delineates the relationship between indenter shape and Rockwell hardness. Traditionally, this coefficient has been derived experimentally, but this approach faces challenges that are attributable to the nonuniformity of hardness test blocks and indenter shape measurement errors. This study introduces the estimation of sensitivity coefficients for Rockwell indenters using finite element analysis (FEA). The FEA method offers the advantage of being unaffected by the nonuniformity of test blocks and indenter shape measurement errors. We calculated the sensitivity coefficients by assessing the influence of variations in indenter angle and tip radius for diamond indenters, and indenter diameter for ball indenters, on hardness results through FEA. The sensitivity coefficients obtained via FEA for specific scales aligned with those from previous experimental studies, affirming the validity of FEA-derived coefficients for other scales. This study demonstrates that FEA is a useful tool for estimating the sensitivity coefficients of Rockwell indenters.

Structured light surface shape measurement method for highly reflective surfaces

Structured light surface shape measurement method for highly reflective surfaces

Laser Differential Confocal Freeform Surface Shape Measurement Based on Monitoring and Compensation of Translational Motion Error

Laser Differential Confocal Freeform Surface Shape Measurement Based on Monitoring and Compensation of Translational Motion Error

Analysis of high-temperature exposure to physical changes in Valplast®-based denture with acrylic element for human identification purpose

BackgroundIdentification of victims will be difficult due to exposure to high temperatures when fires occur. In some cases of fire, small pieces, such as teeth, can be detached and ignored as necessary evidence. Destroyed body parts or the number of victims in a disaster makes the identification of victims more complicated, and forensic odontology is hoped to help the identification process. In a fire disaster, it is possible that a victim used dentures. One of them is a Valplast®-based denture with an acrylic element. If a victim wearing dentures caught fire and was exposed to high-temperature flames, there may be remains of dentures that can be identified. This study aimed to determine the physical changes in Valplast®-based dentures with acrylic elements in shape, color, and weight due to high exposure temperature. In this article, Valplast®-based dentures with acrylic element samples of four groups (P1: 32–288 °C; P2: 32–319 °C; P3: 32–412 °C; P4: 32–800 °C) were observed in shape, weight, and color measurements before and after heating using an oven.ResultsThe result is a change in shape and weight after heating that is shown by the results of the Kruskal–Wallis and Mann–Whitney tests with a p-value < 0.05, that is, the results of the one-way ANOVA test show that the average color change is not significantly different (p > 0.05).ConclusionValplast®-based dentures with acrylic elements experience changes in shape and weight after being heated at high temperatures. So, these results can be used as a reference in the forensic identification process for burn victims who use dentures.

Effects of underweight, overweight, and obesity on the body growth of preschoolers.

This study aimed to investigate the impact of underweight, overweight, and obesity on the growth and development of preschoolers by comparing body shape characteristics across different weight statuses. A total of 729 preschoolers (5.2 ± 0.83 years, 53.8% boys) from three kindergartens were assessed for 11 different body shape measurements. Two-way ANOVA was employed to examine BMI variations across different ages and sexes. Discriminant analysis was utilized to identify body shape measurements correlated with BMI, and one-way ANOVA was conducted to compare the body shape differences among preschoolers with varying BMI. (1) There was no significant interaction effect of gender and age on BMI (F = 1.602, p = 0.173). Additionally, neither the main effect of age (F = 1.461, p = 0.228) nor the main effect of sex (F = 0.905, p = 0.345) was significant. (2) The results of the stepwise discriminant analysis showed that chest circumference, calf length, calf circumference, foot length, and width between greater trochanters entered the discriminant model, with the three discriminant functions explaining 95.8, 3.1, and 1.1% of variance, respectively. (3) Compared to their normal-weight counterparts, obese preschoolers displayed significantly larger measurements in chest circumference, width between greater trochanters, calf circumference, calf length, and foot length (p < 0.05). Overweight preschoolers also exhibited larger chest and calf circumferences, and width between greater trochanters (p < 0.05), while underweight children showed lagging development in various body shape measurements (p < 0.05). Variations in BMI were significantly correlated with preschoolers' body shape which included chest circumference, calf length, calf circumference, foot length, and the distance between the greater trochanters. Overweight and obese preschoolers experienced faster body growth; conversely, underweight preschoolers often showed delayed growth. This underscores that the underweight group also merits attention and concern.

Evaluation of hyoid bone position, shape, area, volume, and tongue volume.

Our study aims to determine the position and types of the hyoid bone and to evaluate the morphometry of the hyoid bone and tongue according to sex. Our study included cervical Computed Tomography (CT) images of 200 individuals (100 females, 100 males) between the ages of 18 and 84. Using the 3D Slicer software package, hyoid bone position, shape, area, volume and tongue volume measurements were made on these images. In our study, the position of the hyoid bone was found to be proportionally at the C3 vertebral level in both sexes. The most common hyoid bone was type B, while the least common was type V. Type B rate was statistically higher in females, and type H rate was higher in males (p < 0.05). Participants with type H had statistically higher bone volumes and areas than those with type B (p < 0.05). Differences between bone volumes and areas of other bone types were not statistically significant (p > 0.05). Average hyoid bone volume (females 1575.9mm3; males 2609.6mm3), hyoid bone area (females 1519.8mm2; males 2406.4mm2), tongue volume (females 66,659.5mm3; males 83,085.5mm3) were measured in females and males. A statistically weak negative correlation was found between the participants' ages and hyoid bone areas (rho = -0.162; p = 0.022). A statistically moderate positive correlation was found between tongue volume and hyoid bone volume/area (respectively p < 0.001; rho1 = 0.658, rho2 = 0.546). Hyoid bone volume, hyoid bone area and tongue volume were higher in males than females. As tongue volume increased, hyoid bone volume and hyoid bone area increased. The connection between tongue volume and hyoid bone volume will contribute to dentomaxillary development and surgical procedures, and bone morphology will also be important in different disciplines.

Distortion correction algorithm based on absolute phase image in structured light 3D reconstruction

Abstract This paper proposes a distortion correction algorithm based on absolute phase maps for a dual-projector, single-camera structured light 3D shape measurement system. Distortion correction is performed separately for the projector-camera pairs on the left and right. By projecting a ninth-order complementary Gray code combined with the eight-step phase-shifting method onto a white board, absolute phase maps are obtained, solving the impact of radial and tangential lens distortion. A sub-pixel level distortion error lookup table is introduced to address the influence of residual error after distortion correction on measurement accuracy, improving the overall precision by at least 95.7%. Experiments demonstrate that the dual-projector, single-camera structured light 3D shape measurement system expands the system’s measurement range while reducing shadowing issues caused by single-projector illumination. The proposed distortion correction and error compensation algorithms effectively enhance the overall measurement accuracy of the system and significantly improve issues like warping caused by distortion.

MORPHOLOGICAL AND MORPHOMETRIC VARIATIONS OF SPLEEN: A CADAVERIC STUDY IN NORTH INDIAN POPULATION

Objective: The aim of study is to study morphological and morphometric analysis of spleen and its clinical importance. Spleen consists of a large encapsulated vascular organ and important lymphatic tissue in the human body. Its immunological functions are being well realized. The weight, size, and shape of the spleen vary in human being with age, sex, and under different conditions in the same individual. The morphological variations are important for physicians, surgeons, and radiologists to avoid misinterpretation of the splenic variants. Methods: A cross-sectional study of a total of 50 adult human cadaveric spleens was done in the Department of Anatomy Government Medical College, Amritsar, Punjab. The study observed the morphological features such as shape, anomalous fissures, and morphometric measurements such as length, breadth, thickness, and weight of all the spleen specimens. Results: The wedge-shaped spleen constituted 62%, tetrahedral (30%), triangular (4%), and irregular (4%), shaped spleens. Out of 50, 60% displayed notches on the superior border of spleen and 10% on inferior border of spleen. There was no notch in 30% of the specimens. Mean length of spleen was 9.2 cm, mean breadth was 6.2 cm, and thickness was 3.08 cm, respectively. The mean weight of the spleens was 140.008 g. Anomalous fissures were 2% found on the diaphragmatic surface. Conclusion: The findings of the present study will be of fundamental importance to the physicians, surgeons, and radiologists and give clues for various clinical diseases.