Geometric Measurements Research Articles

A graph autoencoder network to measure the geometric similarity of drainage networks in scaling transformation

ABSTRACT Similarity measurement has been a prevailing research topic in geographic information science. Geometric similarity measurement in scaling transformation (GSM_ST) is critical to ensure spatial data quality while balancing detailed information with distinctive features. However, GSM_ST is an uncertain problem due to subjective spatial cognition, global and local concerns, and geometric complexity. Traditional rule-based methods considering multiple consistent conditions require subjective adjustments to characteristics and weights, leading to poor robustness in addressing GSM_ST. This study proposes an unsupervised representation learning framework for automated GSM_ST, using a Graph Autoencoder Network (GAE) and drainage networks as an example. The framework involves constructing a drainage graph, designing the GAE architecture for GSM_ST, and using Cosine similarity to measure similarity based on the GAE-derived drainage embeddings in different scales. We perform extensive experiments and compare methods across 71 drainage networks during five scaling transformations. The results show that the proposed GAE method outperforms other methods with a satisfaction ratio of around 88% and has strong robustness. Moreover, our proposed method also can be applied to other scenarios, such as measuring similarity between geographical entities at different times and data from different datasets.

Magnitude of formative flows in stream potholes

Although it is generally recognized that geomorphic work is tied to bedrock channel reshaping, the importance of low vs. high flow stages that cause the most geomorphic impact remains unclear. The objective of the research is to study the concept of “formative flow” in bedrock channels and determine, through morphological studies, if those flows have any impact on sculpted features such as potholes and how this relationship relates to various inputs such as flow stages (magnitude and frequency), shear stress, and sediment size. Here, we studied the distribution of the main pothole typologies and tried to understand why potholes are found along bedrock river channels. Specifically, we examined stream potholes from three locations along the Spanish Central System: Alberche, Tietar, and Manzanares rivers. We conducted the research by taking precise geometric measurements, classifying potholes, analyzing flow magnitude and frequency, and using a two-dimensional (2D) hydrodynamic model to assess key variables in Manzanares river. This research demonstrated that bankfull depths completely cover all pothole typologies in all the analyzed sites but are not sufficient to achieve its formative flow depth (FFD). Using a detailed 2D hydrodynamic model in Manzanares river, we discovered that dimensions of cylindrical potholes are closely related to bankfull discharge and that this depth is connected to FFD. Other potholes, such as erosive-compound and erosive-lateral, are historical remnants, and their shapes are not related to any particular FFD and are likely associated with rare events and catastrophic breaks. A collection of laterals that exhibit FFD near bankfull flows appear to represent a part of the recent evolution of a knickpoint. To summarize, it can be inferred from the findings that the utility of morphological analysis in conjunction with the 2D hydrodynamic model is to examine the fraction of erosional/active features to determine the degree of senescence and/or change in natural conditions in a river reach.

Genetic basis of ecologically relevant body shape variation among four genera of cichlid fishes.

Divergence in body shape is one of the most widespread and repeated patterns of morphological variation in fishes and is associated with habitat specification and swimming mechanics. Such ecological diversification is the first stage of the explosive adaptive radiation of cichlid fishes in the East African Rift Lakes. We use two hybrid crosses of cichlids (Metriaclima sp. × Aulonocara sp. and Labidochromis sp. × Labeotropheus sp., >975 animals total) to determine the genetic basis of body shape diversification that is similar to benthic-pelagic divergence across fishes. Using a series of both linear and geometric shape measurements, we identified 34 quantitative trait loci (QTL) that underlie various aspects of body shape variation. These QTL are spread throughout the genome, each explaining 3.2-8.6% of phenotypic variation, and are largely modular. Further, QTL are distinct both between these two crosses of Lake Malawi cichlids and compared to previously identified QTL for body shape in fishes such as sticklebacks. We find that body shape is controlled by many genes of small effect. In all, we find that convergent body shape phenotypes commonly observed across fish clades are most likely due to distinct genetic and molecular mechanisms.

Testing, FE modelling and design of pin-ended stainless steel equal-leg angle section columns and beam–columns

The behaviour and design of pin-ended stainless steel equal-leg angle section members under compression and compression plus minor-axis bending are investigated herein. The studied members are cylindrically pinned about the minor axis. An experimental investigation, including material testing, initial geometric imperfection measurements and physical tests on hot-rolled stainless steel equal-leg angle section members is first presented. Numerical models are developed and validated against the new experimental data. A numerical parametric study is then presented considering both hot-rolled and cold-formed stainless steel angle section columns alongside beam–columns with a wide range of slenderness values. Finally, new design proposals for pin-ended stainless steel equal-leg angle section members under compression and combined compression and minor-axis bending are developed and verified against the results of existing physical experiments, as well as the newly-generated test and numerical results. The proposed design rules are shown to offer substantially more accurate and consistent resistance predictions compared to existing codified design rules. The reliability of the new design provisions, with a recommended partial safety factor γM1=1.1, is verified following the EN 1990 procedure.

Cross-section behaviour and design of press-braked ferritic stainless steel channel sections under combined compression and major-axis bending moment

This paper presents experimental and numerical investigations into the cross-section behaviour and resistance of press-braked ferritic stainless steel channel sections under combined compression and major-axis bending moment. An experimental programme, including initial local geometric imperfection measurements and ten major-axis eccentric compression tests, was firstly conducted, with the test setup, procedures and results reported in detail. This was followed by a numerical modelling programme, where finite element models were developed and validated against the major-axis eccentric compression test results and then adopted to conduct parametric studies to expand the test data pool over a wider range of cross-section dimensions and loading combinations. Based on the obtained test and numerical data, the design interaction curves for press-braked ferritic stainless steel channel sections under combined compression and major-axis bending moment, as given in the American specification and European code, were evaluated. The evaluation results revealed that the American specification resulted in a good level of design accuracy, while the European code led to conservative resistance predictions, due to the conservative bending end point and inefficient linear shape of the design interaction curve. New design interaction curves were also developed and shown to offer more accurate and consistent resistance predictions for press-braked ferritic stainless steel channel sections under combined compression and major-axis bending moment than the codified design interaction curves.

A new method for determining loess particle size distribution based on ‘core + clothes’ structure

AbstractThe particle size distribution (PSD) of loess particles and agglomerates is the key factor determining the microstructure of loess. The PSD largely determines many physical and mechanical properties such as mechanical strength, deformation characteristics and permeability of loess. In this paper, we combined image processing, geometric measurements and statistical methods to quantitatively characterize the scanning electron microscopy (SEM) images of loess. A new method based on the ‘core + clothes’ structure is proposed to determine the PSD. The developed Gaussian mixture model is applicable to describe the overall distribution of the image pixel density. Determining pixel density distribution and particle boundary allows for the measurement of various geometric parameters. The comparison analyses suggest that the sieve‐hydrometer method has a well‐developed test procedure; however, the measured particle size is limited to 0.075 mm. The laser diffraction method is simple and fast, yet only weak agglomerates can be dispersed, and very fine particles are influenced by size data conversion theory and light source parameters. X‐ray microtomography has the advantage of a non‐destructive sample preparation and intuitive process. However, the results are greatly affected by the parameter settings and segmentation algorithm, and the segmentation effect is poor for particles with a size smaller than 12 μm. The new image processing technique developed in this study improves the limitation of the measurement results via changes in the loess state (water content, stress level). Moreover, different PSDs can be determined according to the variation of functional units. This work is of great significance for the study of numerous properties related to the loess state.

Research on the Estimation Method of Target Motion Parameters Based on Ternary Array

The ternary array passive positioning technique performs the estimation of target distance and bearing by measuring the time delay difference between array elements. The estimates are limited by the geometric model and time delay measurement errors, and the positioning accuracy and reliability are poor. In this paper, we propose an orientation matching-based motion target localization model. By introducing the target motion model, and establish a matching objective function for the time delay difference obtained by calculating the predefined target motion trajectory and the actual received data of the ternary array separately. The matching objective function is optimally solved by using Burg algorithm in the AR spectrum estimation method, and a highly accurate and reliable target parameter estimation can be obtained in a short time. The results of computer simulation experiments verify the effectiveness of the method.

Udo Krüger Charts TechnoTeam's Journey

Udo Krüger Charts TechnoTeam's Journey

Usability of Road Infrastructure for Persons with Mobility Impairment

Globally, there have been sustained efforts at addressing inclusion by providing access to safe, accessible, reliable, and affordable transport systems for all, including persons with mobility impairment. Individuals or groups such as children, the elderly, and people with disabilities, whose capacities to travel are restricted by some permanent or temporary frailties have been generally referred to as Persons With Mobility Impairment (PWMI). While many city dwellers take mobility for granted, it is not the case for PWMI as their travel experiences are marked by exclusion and frustrations due to inherent barriers in transport infrastructure and services. This study examined usability of road infrastructure for persons with mobility impairment. The study was centred on six randomly selected cities in Nigeria. Survey research design was employed by which primary data were collected through geometric measurement, observation, and the use of structured questionnaire. We adopted the Safety, Accessibility, Reliability and Affordability (SARA) analytical framework for data analysis. Statistical analyses of data were done using descriptive statistics, Analysis of Variants (ANOVA), and the Kruskal-Wallis H test. The study found insignificant numbers, and (in some cases), complete non-existence of pedestrian infrastructure and universal design facilities on major roads in the investigated cities. Most of the roads examined have facilities in less than 20% of the required locations. There was no statistically significant difference between the mean number of facilities across the selected roads and across the six cities studied. More than 90% of respondents rated each of the usability indices (safety, accessibility, reliability, and affordability) low. Generally, roads in Nigerian cities are characterised by structural barriers which impede safety and accessibility for people with mobility impairment thereby making them experience unreliable and less-affordable journeys, reflecting the low usability of road infrastructure across the cities.

Geometric shape measurement and its application in bridge construction based on UAV and terrestrial laser scanner

Oblique photography and laser scanning techniques are increasingly being used to measure the geometric shapes of structures. Optimizing the flight path of unmanned aerial vehicles (UAVs) in data acquisition can make the collected image data more complete with muti-view details and improve the utilization of image data in 3D reconstruction. This paper proposed a convenient UAV flight planning approach for oblique photography based on feature waypoints along with an efficient framework for automatically extracting bridge alignment from point cloud data. The application on an under-construction long multi-span girder bridge demonstrated the effectiveness of the optimized UAV flight planning method for collecting multi-view bridge images and the superiority of the rebuilt 3D model compared to commonly used flight strategies. Taking the total station data as references, the errors of the bridge alignment obtained from the point cloud collected by the frequently adopted terrestrial laser scanners (TLS) and UAV devices, respectively, achieve 4.41 mm and 10.97 mm in 142 m measured length. The analysis of the original and eliminated-slope bridge alignments illustrates the potential for using the suggested method in general large-scale bridge constructions.

Femur reconstruction in 3D ultrasound for orthopedic surgery planning.

Derotation varisation osteotomy of the proximal femur in pediatric patients usually relies on 2-dimensional X-ray imaging, as CT and MRI still are disadvantageous when applied in small children either due to a high radiation exposure or the need of anesthesia. This work presents a radiation-free non-invasive tool to 3D-reconstruct the femur surface and measure relevant angles for orthopedic diagnosis and surgery planning from 3D ultrasound scans instead. Multiple tracked ultrasound recordings are segmented, registered and reconstructed to a 3D femur model allowing for manual measurements of caput-collum-diaphyseal (CCD) and femoral anteversion (FA) angles. Novel contributions include the design of a dedicated phantom model to mimic the application ex vivo, an iterative registration scheme to overcome movements of a relative tracker only attached to the skin, and a technique to obtain the angle measurements. We obtained sub-millimetric surface reconstruction accuracy from 3D ultrasound on a custom 3D-printed phantom model. On a pre-clinical pediatric patient cohort, angular measurement errors were [Formula: see text] and eventually [Formula: see text] for CCD and FA angles, respectively, both within the clinically acceptable range. To obtain these results, multiple refinements of the acquisition protocol were necessary, ultimately reaching success rates of up to 67% for achieving sufficient surface coverage and femur reconstructions that allow for geometric measurements. Given sufficient surface coverage of the femur, clinically acceptable characterization of femoral anatomy is feasible from non-invasive 3D ultrasound. The acquisition protocol requires leg repositioning, which can be overcome using the presented algorithm. In the future, improvements of the image processing pipeline and more extensive surface reconstruction error assessments could enable more personalized orthopedic surgery planning using cutting templates.

Evaluating the damage content of Karbandi using frequency domain analysis (Case Study: Timche Haj-Mohammad-Qoli of Tabriz Historic Bazaar)

In this study, an alternate method to evaluate structural systems, especially those with historical importance has introduced by applying Fourier Transform (FT) to the damage ratio of time history outcome in the frequency domain. The concept of damage content (DC) regarding the mechanical characteristics of the used material, including plastic strain, failure plane, and ultimate load-bearing capacity, along with drift value, record selection criteria, and architectural aspects, have employed. Due to its valuable aesthetic and architectural view, Timche Haj-Mohammad-Qoli of Tabriz Historic Bazaar, one of the traditional covered spaces with the complicated configuration of spatial masonry intersecting arches, selected for further assessment in the current research program. The required experimental samples for obtaining the mechanical properties and relevant geometrical measurements to prepare the numerical model of the structure obtained. The strong ground motions according to seismological and geological characteristics of the construction site selected. The records with different durations were merged by Fourier Transform (FT) and Damage Content (DC) analysis. According to the outcomes, the damage state of the structure due to the imposed strong motion at every stage of the lateral loading from the failure initiation to the final collapse was traceable. As a straightforward outcome, the vulnerability of the near-field earthquakes is more tangible than that of the far-field earthquakes. The provided methodology could have proper use in future similar studies for evaluating the performance of the structures.

EXPERIMENTAL AND COMPUTATIONAL MODELLING ASSESSMENT OF EDGE-LOADED TOTAL HIP ARTHROPLASTY POLYETHYLENE LINERS

Non-optimal clinical alignment of components in total hip replacements (THRs) may lead to edge loading of the acetabular cup liner. This has the potential to cause changes to the liner rim not accounted for in standard wear models. A greater understanding of the material behaviours could be beneficial to design and surgical guidance for THR devices. The aim of this research was to combine finite element (FE) modelling and experimental simulation with microstructural assessment to examine material behaviour changes during edge loading.A dynamic deformable FE model, matching the experimental conditions, was created to simulate the stress strain environment within liners. Five liners were tested for 4Mc (million cycles) of standard loading (ISO14242:1) followed by 3Mc of edge loading with dynamic separation (ISO14242:4) in a hip simulator. Microstructural measurements by Raman spectroscopy were taken at unloaded and highly loaded rim locations informed by FE results. Gravimetric and geometric measurements were taken every 1Mc cycles.Under edge loading, peak Mises stress and plastic deformation occur below the surface of the rim during heel strike. After 7Mc, microstructural analysis determined edge loaded regions had an increased crystalline mass fraction compared to unloaded regions (p<0.05). Gravimetric wear rates of 12.5mm3/Mc and 22.3mm3/Mc were measured for standard and edge loading respectively. A liner penetration of 0.37mm was measured after 7Mc.Edge loading led to an increase in gravimetric wear rate indicating a different wear mechanism is occurring. FE and Raman results suggest that changes to material behaviour at the rim could be possible. These methods will now be used to assess more liners and over a larger number of cycles. They have potential to explore the impact of edge loading on different surgical and patient variables.

Accuracy Assessment of the Positioning of a Swarm of Underwater Vehicles in Relation to Four Surface Vehicles Using the TDOA Method

This paper presents the results of research on the accuracy assessment of the positioning of a swarm of underwater vehicles based on hydroacoustic measurements made with respect to four surface vehicles under the time difference of arrival (TDOA) method. The assessment consisted of the estimation of accuracy parameters for determining the position of an underwater vehicle in relation to surface vehicles forming a so-called moving geometrical measurement structure (MGMS) in the following shapes: square, rectilinear, triangular, and three-pointed. This demonstrated that MGMS makes it possible to estimate the relative position of underwater vehicles in a swarm with an accuracy of 2.1 m (RMS) over an area of approx. 1000 m2 and approx. 3.0 m (RMS) over an area of approx. 1600 m2. The most favourable MGMS shapes include three-pointedwhile maximising the size of the positioning area, where the positioning accuracy should not exceed 3.0 m (RMS)—and rectilinear—while maximising the size of the positioning area, where the positioning accuracy should not exceed 10.0 m (RMS).

Accurate cavity volume testing based on micropressure differential gas inflation and deflation

For cavity volume testing, conventional optical or acoustic direct test methods are not only limited in terms of measurement efficiency, but also have difficulty avoiding errors due to complex cavity structures. In this paper, we present a cavity volume test based on micropressure differential gas inflation and deflation. The principle of the method is to charge and deflate the test cavity and obtain a mapping between the microbe difference and the inflating flow rate. Variability curves of the pressure difference inside and outside the cavity are measured during the deflating process and the cavity volume is calculated using parameters such as the intake flow rate and differential pressure. The heat and mass transfer equations are formulated for the gas in the cavity under inflation and deflation conditions. Numerical simulations of the variability of the gas state parameters and their impact factors are performed to verify the feasibility of the volumetric measurements. An experimental setup for volume measurements is constructed and a cockpit is used as an application object for volume measurement experiments under different micropressure differential inflation and deflation conditions. It shown that, as a complement to geometrical physical measurements, this method can better characterize the gas volume of the cavity.

A handsewn pericardial valved pulmonary conduit: pulsatile flow loop in vitro and acute porcine in vivo evaluation.

Right ventricle to pulmonary artery anatomic discontinuity is common in complex congenital heart malformations. Handsewn conduits are a practised method of repair. In a proof-of-concept study, we evaluated pulmonary valve replacement with a handsewn pericardial valved pulmonary conduit in vitro and in vivo. A pulsatile flow-loop model (in vitro) and an acute 60-kg porcine model (in vivo) were used. With echocardiography and pressure catheters, baseline geometry and fluid dynamics were measured. The pulmonary valve was replaced with a handsewn glutaraldehyde-treated pericardial valved pulmonary conduit corresponding to a 21-mm prosthetic valve, after which geometric measurements and fluid dynamics were reassessed. In vitro, 15 pulmonary trunks at 4 l/min and 13 trunks at 7 l/min, and in vivo, 11 animals were investigated. The valved pulmonary conduit was straightforward to produce at the operating table and easy to suture in place. All valves were clinically sufficient in vitro and in vivo. The mean transvalvular pressure gradient in the native valve and the conduit was 8 mmHg [standard deviation (SD): 2] and 7 mmHg (SD: 2) at 4 l/min in vitro, 19 mmHg (SD: 3) and 17 mmHg (SD: 4) at 7 l/min in vitro and 3 mmHg (SD: 2) and 6 mmHg (SD: 3) in vivo. Our proof-of-concept demonstrates no early evidence of structural damage to the conduit, and the fluid dynamic data were acceptable. The handsewn conduit can be produced at the operating table.

Monocular spatial geometrical measurement method based on local geometric elements associated with out-of-view datum

In the field of industrial inspection, visual non-contact measurement of the radial dimension of the extension end of the long pole structure is a difficult problem. Utilizing the principle of telecentric vision measurement, we propose a monocular spatial geometrical measurement method based on local geometric elements associated with out-of-view datum, focusing on key techniques such as visual calibration and global unification of separate dimensions. Firstly, the designed associated target is used to establish the conversion relationship between the measurement reference space and the camera FOV space. Singular Value Decomposition (SVD) is used to obtain the initial values R0 and T0 of the rotation matrix and translation vector during the three-dimensional coordinate system conversion. Then the initial values are linearized based on the Rodrigues iterative transformation to obtain the optimized R and T, thereby achieving the high-precision conversion of the coordinate system, realizing the global unification of the coordinates of the separated size elements. In order to verify the effectiveness of the method, an experimental measurement device was constructed. The experimental results show that the measurement uncertainty (95% confidence level) of the space radial dimension is ±10.37 µm, and the %R&R index is 12.91%. This method is suitable for applications such as rapid and precise measurement of narrow and long workpieces such as partial visible elements in vitro or cross-scale measurement.

Applications of Chromatic Confocal Technology in Precision Geometric Measurement of Workpieces

Chromatic confocal technology is increasingly applied in industries that require high-precision geometric measurements such as aerospace, naval ordnance, and medical electronics owing to its advantages in testing accuracy, real-time performance, anti-interference, and no damage to tested workpieces. This paper introduces the measurement principle of chromatic confocal technology and the structure of chromatic confocal sensors, and enumerates several typical application scenarios of the technology from the aspects of thickness measurement, profile, 3D topography scanning, roughness measurement, and wafer comprehensive parameter measurement. It also looks into potential development directions of chromatic confocal technology.

Armed to the teeth: The underestimated diversity in tooth shape in snakes and its relation to feeding behavior and diet.

The structure, composition, and shape of teeth have been related to dietary specialization in many vertebrate species, but comparative studies on snakes' teeth are lacking. Yet, snakes have diverse dietary habits that may impact the shape of their teeth. We hypothesize that prey properties, such as hardness and shape, as well as feeding behavior, such as aquatic or arboreal predation, or holding vigorous prey, impose constraints on the evolution of tooth shape in snakes. We compared the morphology of the dentary teeth of 63 species that cover the phylogenetic and dietary diversity of snakes, using 3D geometric morphometrics and linear measurements. Our results show that prey hardness, foraging substrate, and the main feeding mechanical challenge are important drivers of tooth shape, size, and curvature. Overall, long, slender, curved teeth with a thin layer of hard tissue are observed in species that need to maintain a grip on their prey. Short, stout, less curved teeth are associated with species that undergo high or repeated loads. Our study demonstrates the diversity of tooth morphology in snakes and the need to investigate its underlying functional implications to better understand the evolution of teeth in vertebrates.

Weld Cross-Section Profile Fitting and Geometric Dimension Measurement Method Based on Machine Vision

A visual measurement method based on a key point detection network is proposed for the difficulty of fitting the cross-sectional profile of ultra-narrow gap welds and the low efficiency and accuracy of manual measurement of geometric parameters. First, the HRnet (High-Resolution Net) key point detection algorithm was used to train the feature point detection model, and 18 profile feature points in a “measurement unit” were extracted. Secondly, the feature point coordinates are transformed from the image coordinate system to the weld coordinate system, and the weld profiles are fitted by the least squares method. Finally, the measurement system is calibrated with a coplanar linear calibration algorithm to perform pixel distance to actual distance conversion for quantitative detection of geometric dimensions. The experimental results show that the accuracy of the proposed method for key point localization is 95.6%, the mean value of the coefficient of determination R-square for curve fitting is greater than 94%, the absolute error of measurement is between 0.06 and 0.15 mm, and the relative error is between 1.27% and 3.12%. The measurement results are more reliable, and the efficiency is significantly improved compared to manual measurement.