Geometric Measurements Research Articles

Noise reduction method in both time and frequency domains for envelope peak position extraction of pulse-train interferometry measuring distance between interference fringes

Multi-pulse train interferometry is used to measure distance for meter-scale/nanometer-resolution geometric measurements. The core of multi-pulse train interferometry is object positioning accuracy, which is limited by the ability to position the interference fringe envelope peak. The Fourier fringe analysis method, optical Hilbert transform method, and other methods are used in the envelope demodulation of multi-pulse train interferometry. The matched filter, which provides good noise reduction capability in the time domain, is widely used in radar signal processing. In this study, a matched filter is combined with the Fourier fringe analysis method and used to demodulate the envelopes of a fringe in a multi-pulse train interferometry because the proposed combined method performs noise reduction in both the time and frequency domains for fringe envelope signal processing. Compared with two conventional methods, the proposed combined method was proven to be feasible for envelope demodulation of multi-pulse train interferometry.

Ultrahigh Carrier Mobilities in Ferroelectric Domain Wall Corbino Cones at Room Temperature.

Recently, electrically conducting heterointerfaces between dissimilar band insulators (such as lanthanum aluminate and strontium titanate) have attracted considerable research interest. Charge transport and fundamental aspects of conduction have been thoroughly explored. Perhaps surprisingly, similar studies on conceptually much simpler conducting homointerfaces, such as domain walls, are not nearly so well developed. Addressing this disparity, magnetoresistance is herein reported in approximately conical 180° charged domain walls, in partially switched ferroelectric thin-film single-crystal lithium niobate. This system is ideal for such measurements: first, the conductivity difference between domains and domain walls is unusually large (a factor of 1013 ) and hence currents driven through the thin film, between planar top and bottom electrodes, are overwhelmingly channeled along the walls; second, when electrical contact is made to the top and bottom of the domain walls and a magnetic field is applied along their cone axes, then the test geometry mirrors that of a Corbino disk: a textbook arrangement for geometric magnetoresistance measurement. Data imply carriers with extremely high room-temperature Hall mobilities of up to ≈3700 cm2 V-1 s-1 . This is an unparalleled value for oxide interfaces (and for bulk oxides) comparable to mobilities in other systems seen at cryogenic, rather than at room, temperature.

Geometrical aberration measurement by experimental ray-tracing based on fiber point diffraction interferometry

The geometrical aberration of an optical system is usually measured through wavefront aberration. We propose a very direct experimental ray-tracing measurement method in this paper. Two fiber point-light-sources are used to simulate an arbitrary incident ray in space, the diffracting wavefronts of the two fibers pass through the lens under test and interfere on two photographic planes. The outgoing ray intersects the photographic planes at the extrema of their phase maps, thus can be traced by connecting the two intersections. We measure four kinds of geometrical aberrations of the lens and compare them with Zemax simulation results. This method provides a new solution for the geometrical aberration measurement of an optical system.

Poster 242: Deep Learning for Identifying Patellofemoral Measurements Associated with Cartilage Lesions on MRI

Poster 242: Deep Learning for Identifying Patellofemoral Measurements Associated with Cartilage Lesions on MRI

Flexural buckling of high-strength aluminium alloy CHS columns

High-strength aluminium alloys are increasingly popular and gaining more prominence in structural engineering. The global buckling behaviour and design of high-strength aluminium alloy circular hollow section (CHS) columns subjected to axial compression are investigated in this study. Ten experiments on CHS specimens with two extruded 7A04-T6 CHS profiles – 165 × 15 and 165 × 7.5 (in mm), were conducted. The material tests and initial geometric imperfection measurements were carried out prior to column tests. The test setup, procedure and results, including failure modes, ultimate resistances and load–displacement curves were comprehensively reported and analysed. Based on the developed and validated finite element (FE) models, an extensive parametric study, over a broad range of member and cross-section slenderness as well as the strain hardening exponents and proof strengths of the high-strength aluminium alloy material, was performed to complement the test data pool. The applicability of current buckling design provisions used for normal-strength aluminium alloy columns in the European, Chinese, American, Australian & New Zealand standards and the proposal of Rasmussen and Rondal to 7A04-T6 high-strength aluminium alloy CHS columns was evaluated through comparisons with the test and FE results. The results show that the European, Chinese and American standards provide conservative buckling resistance predictions, while the Australian & New Zealand standard and Rasmussen’s proposal generally yield unsafe capacity predictions. Finally, two flexural buckling curves within the framework of the EN 1999-1-1:2007 design method, featuring a revised linear imperfection term and a newly developed hybrid linear-nonlinear imperfection term, were proposed accordingly, and were shown to provide more accurate and consistent buckling resistance predictions.

Prediction and Control of Product Shape Quality for Wire and Arc Additive Manufacturing

Abstract Wire and arc additive manufacturing (WAAM) has become an economically viable option for fast fabrication of large near-net shape parts using high-value materials in the aerospace and petroleum industries. However, wide adoption of WAAM technologies has been limited by low shape accuracy, high surface roughness, and poor reproducibility. Since WAAM part quality is affected by a multitude of factors related to part geometries, materials, and process parameters, experimental characterization or physics-based simulation for WAAM process optimization can be cost prohibitive, particularly for new part designs. As an effective alternative, data-analytical approaches have been developed for prescriptive modeling and compensation of shape deviations in 3D printed parts. However, WAAM faces a unique challenge of large shape deviation and high surface roughness at the same time. Accurate prediction and control of WAAM part quality require process-meaningful error decomposition under geometric measurement uncertainties. We propose a generalized additive modeling approach to separate global geometric shape deformation from surface roughness. Under this statistical framework, tensor product basis expansion is adopted to learn both the low-order shape deformation and high-order roughness patterns. The established predictive model enables optimal geometric compensation for product redesign to reduce shape deformation from the target geometry without altering process parameters. Experimental validation on WAAM manufactured cylindrical walls of various radii shows the effectiveness of the proposed framework.

The study of the b-choromatic number of some classes of fractal graphs

In graph coloring, labels are assigned to graph elements according to certain constraints. Colors are a special case of graph labeling as well as in practical applications, graph coloring also poses some theoretical challenges. A topic related to graph coloring will be discussed in this study, i.e., b-chromatic number. In proper coloring, edges, vertices, or both of them are colored so that they are distinct from one another. A b-coloring of m colors of a graph G is similar to proper coloring in which at least one vertex from each color class is connected to (m-1) other colors. The b-chromatic number of a graph G is the greatest positive number k such that G admits a b-coloring with k colors and is represented by ϕ(G). Fractals are geometric objects that are self-similar at multiple scales and their geometric measurements are different from fractal measurements. In this paper, we will evaluate the b-chromatic number of Fractal type graphs, i.e., Sierpinski network S(n; Kk) (where Kk is a complete graph of order k) and Sierpinski gasket network S(n). Firstly, we will compute the b-chromatic number of S(n; K3), S(n; K4) and S(n; K5) for n ≥ 2. After that, we will generalize the result for the Sierpinski network of complete graph Kk. In addition, we will also determine the b-choromatic number of Sierpinski gasket graph S(n). As an application, we will also determine the b-chromatic number of Sierpinski graph of house graph.

AlphaFold2 and RoseTTAFold predict posttranslational modifications. Chromophore formation in GFP-like proteins.

AlphaFold2 and RoseTTAfold are able to predict, based solely on their sequence whether GFP-like proteins will post-translationally form a chromophore (the part of the protein responsible for fluorescence) or not. Their training has not only taught them protein structure and folding, but also chemistry. The structures of 21 sequences of GFP-like fluorescent proteins that will post-translationally form a chromophore and of 23 GFP-like non-fluorescent proteins that do not have the residues required to form a chromophore were determined by AlphaFold2 and RoseTTAfold. The resultant structures were mined for a series of geometric measurements that are crucial to chromophore formation. Statistical analysis of these measurements showed that both programs conclusively distinguished between chromophore forming and non-chromophore forming proteins. A clear distinction between sequences capable of forming a chromophore and those that do not have the residues required for chromophore formation can be obtained by examining a single measurement-the RMSD of the overlap of the central alpha helices of the crystal structure of S65T GFP and the AlphaFold2 determined structure. Only 10 of the 578 GFP-like proteins in the pdb have no chromophore, yet when AlphaFold2 and RoseTTAFold are presented with the sequences of 44 GFP-like proteins that are not in the pdb they fold the proteins in such a way that one can unequivocally distinguish between those that can and cannot form a chromophore.

Inverse analysis of material parameters in coupled multi-physics biofilm models

In this article we propose an inverse analysis algorithm to find the best fit of multiple material parameters in different coupled multi-physics biofilm models. We use a nonlinear continuum mechanical approach to model biofilm deformation that occurs in flow cell experiments. The objective function is based on a simple geometrical measurement of the distance of the fluid biofilm interface between model and experiments. A Levenberg-Marquardt algorithm based on finite difference approximation is used as an optimizer. The proposed method uses a moderate to low amount of model evaluations. For a first presentation and evaluation the algorithm is applied and tested on different numerical examples based on generated numerical results and the addition of Gaussian noise. Achieved numerical results show that the proposed method serves well for different physical effects investigated and numerical approaches chosen for the model. Presented examples show the inverse analysis for multiple parameters in biofilm models including fluid-solid interaction effects, poroelasticity, heterogeneous material properties and growth.

A framework of tolerance specification for freeform point clouds and capability analysis for reverse engineering processes

The combination of reverse engineering (RE) with additive manufacturing (AM) is widely used for solid freeform fabrication and overcomes limitations with the current capabilities of designers and CAD packages that are restricted to classical model shapes. The shape flexibility offered by RE typically leads to the generated CAD models being represented in point cloud formats or stereolithography files. One resulting challenge is the difficulty with tolerance specification for the RE-generated models, especially for freeform shapes. Geometric metrology for the AM-produced parts to determine their geometric conformation can also be involved. Furthermore, conventional process analyses cannot be performed directly after RE because of the complex geometric data structure. We propose to address all these issues with a new tolerance specification and process analysis framework based on volumetric data analysis. The tolerance zone constructed under our framework, and the corresponding geometric measurements, are consistent with the profile tolerance in geometric dimensioning and tolerancing standards. Reverse engineering's process capability is assessed under our methodology via a parametric bootstrap procedure in the size-and-shape space. The performance and utility of the proposed framework are validated via a process capability study on RE-generated CAD models of multiple, additively manufactured freeform objects.

Local buckling and capacity of press-braked ferritic stainless steel channel sections under minor-axis combined loading

This paper presents experimental and numerical studies of the local buckling behaviour and cross-section resistances of press-braked ferritic stainless steel channel sections under combined compression and minor-axis bending. An experimental programme was firstly conducted and included material testing, initial local geometric imperfection measurements and ten eccentric compression tests. Following the experimental programme, a numerical modelling programme was conducted, where finite element models were developed to replicate the test observations and then used to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions and loading combinations. The obtained test and numerical data were then used to assess the relevant design interaction curves for press-braked ferritic stainless steel channel sections under minor-axis combined loading, as set out in the European code and American specification. The assessment results revealed that the codified design interaction curves result in conservative and scattered resistance predictions, mainly owing to the conservative bending end point and inefficient linear shape. Finally, new design interaction curves were developed and shown to provide a higher level of design accuracy and consistency than the codified design interaction curves.

Full-Scale Highway Bridge Deformation Tracking via Photogrammetry and Remote Sensing

Recent improvements in remote sensing technologies have shown that techniques such as photogrammetry and laser scanning can resolve geometric details at the millimeter scale. This is significant because it has expanded the range of structural health monitoring scenarios where these techniques can be used. In this work, we explore how 3D geometric measurements extracted from photogrammetric point clouds can be used to evaluate the performance of a highway bridge during a static load test. Various point cloud registration and deformation tracking algorithms are explored. Included is an introduction to a novel deformation tracking algorithm that uses the interpolation technique of kriging as the basis for measuring the geometric changes. The challenging nature of 3D point cloud data means that statistical methods must be employed to adequately evaluate the deformation field of the bridge. The results demonstrate a pathway from the collection of digital photographs to a mechanical analysis with results that capture the bridge deformation within one standard deviation of the mean reported value. These results are promising given that the midspan bridge deformation for the load test is only a few millimeters. Ultimately, the approaches evaluated in this work yielded errors on the order of 1 mm or less for ground truth deflections as small as 3.5 mm. Future work for this method will investigate using these results for updating finite element models.

S960 ultra-high strength steel slender welded I-section beam–columns: Testing, numerical modelling and design

This paper presents experimental and numerical investigations of the buckling behaviour and resistance of S960 ultra-high strength steel slender welded I-section beam–columns under combined compression and minor-axis bending moment. An experimental programme, including initial geometric imperfection measurements and eight beam–column tests, was firstly conducted. The test procedures, setups and results were fully reported. Following the experimental programme, a numerical modelling programme was carried out, with finite element models initially developed and validated against the test results and then employed to conduct parametric studies to generate further numerical data. On the basis of the test and numerical data, the relevant design interaction curves, as provided in the European code, Australian standard and American specification, were evaluated for their applicability to S960 ultra-high strength steel slender welded I-section beam–columns. The evaluation results revealed that all three codified design interaction curves lead to conservative resistance predictions, mainly owing to the conservative end points (i.e. column buckling strength and cross-section minor-axis bending resistance). Finally, a revised Eurocode design interaction curve, with improved compression end point determined from more accurate column buckling curve and bending end point determined from the direct strength method, was finally proposed, and shown to result in more accurate resistance predictions for S960 ultra-high strength steel slender welded I-section beam–columns than the codified design interaction curves.

Rachis detection and three-dimensional localization of cut off point for vision-based banana robot

For the operation and visual positioning of a banana robot, it is important to accurately position the rachis and cut off point. However, the main factors that affect the three-dimensional (3D) positioning accuracy of the point of cutting off male flower clusters are the image detection algorithm and positioning errors in the depth direction. In this study, a new YOLOv5-B model was constructed using the InvolutionBottleneck module in the network structures of YOLOv5 and improving the loss function to improve the accuracy and speed of small target detection. Then, the contour of the rachis is segmented using an edge detection algorithm, and the optimal cut off point is obtained as a scalar. Finally, a robot experiment platform with stereo vision for cutting off male flower clusters of bananas is built to obtain the 3D space coordinates of the cutoff point of the rachis through visual inspection and analyze positioning errors in the depth direction. The experiments show that the overall mean average position (mAP) of the YOLOv5-B model for multi-target recognition of bananas is 93.2%, which is higher than that of the YOLOv5 and PP-YOLOv2 models. Among these, the small-target detection accuracy of the proposed model is better than that of the others. Additionally, the YOLOv5-B model shows excellent speed, with an average image processing time of only 0.009 s/piece. An accurate relation model for the geometric measurement between the depth camera and laser measurement was established, and positioning errors were analyzed. The median error (MEDE) of the depth coordinates was 8 mm and the median absolute deviation (MAD) was 2 mm. If the depth error is within the control range of the compensation, the requirements of rachis segmentation by robots can be met.

Research on 3D face measurement for facial virtual plastic surgery

Calculating the key data of human face through three-dimensional face model can help doctors predict the surgical results before plastic surgery, guide the formulation of surgical plan and reduce the surgical risk. In this paper, 3D face measurement technology is studied, and the area of plastic area is calculated by slice method. A large number of experimental tests show that the average errors of facial geometric feature measurement, area measurement are 0.458mm and 0.65mm2 respectively. The rating of simulation results provided by plastic surgeons shows that facial measurement technology can effectively improve the success rate of plastic surgery. Compared with the original face, the edited 3D face is more attractive in respecting the following beauty standards: “three courts and five eyes”, golden section, etc.

Experimental and numerical study of press-braked S690 high strength steel slender channel section columns prone to local–flexural interactive buckling

This paper reports an experimental and numerical investigation into the local–flexural interactive buckling behaviour and resistance of press-braked S690 high strength steel slender channel section columns. An experimental programme was firstly conducted and included initial geometric imperfection measurements and twelve pin-ended column tests. Interaction between local buckling and flexural buckling was observed for all specimens upon testing and discussed in detail. The experimental programme was accompanied by a numerical modelling programme, where finite element models were developed and validated against the test results and then employed to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions and member effective lengths. The obtained test and numerical data were used to assess the accuracy of the codified design rules for press-braked S690 high strength steel slender channel section columns failing by local–flexural interactive buckling, as set out in the European code, North American specification and Australian/New Zealand standard. The assessment results revealed that the European code leads to excessively conservative and scattered resistance predictions, while the North American specification and Australian/New Zealand standard result in a higher level of design accuracy and consistency, but still with many conservative resistance predictions for columns with short to intermediate lengths. Finally, a new design approach was proposed and shown to yield substantially more accurate and consistent resistance predictions for press-braked S690 high strength steel slender channel section columns over the design codes.

Fostering Geometrical Measurement Skills to Enhance Geometrical Measurement Performance in Primary Schools

Geometrical measurement becomes one of the most critical topics in primary mathematics which require the understanding of the underlying concepts and not just focusing solely on formulas. Unfortunately, the teaching and learning of geometrical measurement is usually based on rules, procedures and formulas. Besides, research have also shown that the scarcity of the conceptual understanding significantly contributes to the poor geometrical measurement understanding. Thus, the focus of this study is to clarify the specific types of geometrical measurement skills that contribute to the geometrical measurement conceptual understanding. The research method was based on literature review search strategy through online database such as Google Scholar and Scopus. The results of this study indicate that in order to grasp the conceptual understanding of geometrical measurement, pupils need to be proficient in geometrical measurement skills. From the literature, it can be concluded that geometrical measurement skills involve the integration of spatial skills and numerical skills. Thus, the findings of this study led us to draw conclusions on the skills that guide primary-level pupils to grasp conceptual understanding in geometrical measurement. Subsequently, the findings may also provide guidance for potential researchers and teachers to evaluate the performance of pupils in geometrical measurement such as developing an alternative assessment tool.

UAV-based bridge geometric shape measurement using automatic bridge component detection and distributed multi-view reconstruction

UAV cameras combined with image-based reconstruction are promising non-contact tools for bridge shape inspection while computational efficiency is low, particularly on large-scale image sets. This paper describes an efficient image-based reconstruction pipeline for bridge geometry measurements. A full bridge three-dimensional reconstruction task is decomposed into multiple distributed tasks of reconstructing bridge sub-models using sub-image sets. A deep learning-based object detection method combined with Euclidean clustering is proposed to automatically generate cropped sub-image sets. An image mask generation technique based on 3D-to-2D mesh projection is used to keep valid pixels for camera pose estimation. The proposed method was validated in a laboratory test for arch shape measurement and in a field test for suspension cable shape measurement. The results show significant improvement about computational efficiency without accuracy reduction, compared with conventional image reconstruction methods.

Experimental and numerical investigations of hybrid high strength steel welded T-section stub columns with Q690 flange and Q460 web

Comprehensive experimental and numerical investigations on mechanical properties of Q690 and Q460 high strength steel (HSS) sections and stub column behaviour of the 14 hybrid HSS welded T-section stub column specimens are presented in this paper. A total of six coupon specimens were longitudinally and transversely machined from HSS Q690 and Q460 steel parent plates respectively. Furthermore, initial local geometric imperfections measurements were also carried out. In parallel with the experimental investigation on stub column behaviour, extensive numerical studies were carried out by developing finite element (FE) models to replicate the experimental tests results. The validation of the FE models was confirmed against the obtained experimental data. To supplement the experimental data, validated FE models were used in the parametric studies, by which numerical specimens with a larger range of cross-section dimensions can be generated. Subsequently, cross-section classification slenderness limits for outstand plate elements under compressive load set out in structural steel design codes of EN 1993-1-12, ANSI/AISC 360-16, AS 4100 were evaluated against the experimental and numerical data. In addition to the design codes, design methods such as direct strength method (DSM) and continuous strength method (CSM) were also assessed to evaluate the applicability and suitability for hybrid HSS welded T-section stub columns. It was found that the current codified slenderness limits in EN 1993-1-12, ANSI/AISC 360-16 as well as AS 4100 for slender/non-slender outstand flat elements can generally be adopted for hybrid HSS welded T-section under compression. CSM provide under-estimated compressive resistance in comparison to the design codes and DSM for slender sections.

Research on non-linear visual matching model under inherent constraints of images

Abstract Visual matching of plane images has promoted the development of artificial intelligence and digital vision. High-precision visual matching can promote the innovation of geometric measurement, visual navigation and other fields. Therefore, a non-linear visual matching model with inherent constraints is established in this paper. First, according to the principle of visual imaging, a non-linear conversion model of visual point coordinates is proposed, and the deviation of coordinate points is proofread. Then, inherent boundary constraints are introduced into the model to improve the accuracy of visual matching. Finally, through analysis and evaluation of error, results are generated showing that the visual matching model can effectively solve the shortcoming of low-matching accuracy in feature points, and provide more accurate data support for 3D calculation of images.