Geometric Measurements Research Articles

Impact of the topology of urban streets on mobility optimization

Several natural and artificial structures and systems are somehow optimized for performing specific functionalities. The structure and topology of cities are no exception, as it is critically important to ensure effective access to the several resources as well as overall mobility. The present work addresses the important subject of improving the plan of a given city through the incorporation of avenues and other expressways such as bridges and tunnels. More specifically, we start with the topology of a real city and consider the incorporation of an expressway between any two locations in the city, keeping one location fixed and varying the angle of the other. The whole city area is covered in this manner, which allows us to derive a respective energy surface indicating the gain obtained regarding the average shortest path length for each of the possible situations. These surfaces therefore provide a complete picture of how much each city can be improved regarding minimal distances. Quite distinct surfaces have been obtained for 18 considered European cities. These surfaces are then characterized in terms of the number of local extrema and respective spatial complexity, expressed in terms of a raggedness measurement. Measurements are also obtained respectively to the geometry and topology of the considered cities. It is shown that the shortest path gain depends strongly on some of the considered measurements, especially lacunarity and transitivity. Interestingly, the intricacy of the energy surfaces resulted in relatively little correlation with the topological and geometrical measurements.

Evaluation of computed tomography dose profiler probe for computed tomography dose index and geometric efficiency measurements

The purpose of this study was to evaluate the performance of solid-state sensor based computed tomography dose profiler (CTDP) probe for measurement of standard computed tomography dose metric CTDI100 and free in air geometric efficiency for various beam widths available in a 128-slice CT scanner and also to estimate the efficiency of CTDI100 metric. The response accuracy of CTDP probe was verified using a standard 100 mm long ionization chamber. The geometric efficiency measurements performed by the CTDP probe were validated using XR-QA2 radiochromic film measurements. The efficiency of CTDI100 metric was assessed by calculating the ratio of CTDI100 measured in the center hole position to CTDI∞ measured in the same position of both head and body phantoms. The weighted CTDI values derived from CTDI100 measured by the CTDP probe showed an average difference of 8% from ionization chamber measured values. The efficiency of CTDI100 metric estimated using CTDP probe and 150 mm long phantoms was in the range of 82% to 86% and 76% to 80% for head and body phantom measurements respectively. The differences in the geometric efficiency values for various beam settings and tube voltages measured by the CTDP probe and films were within 7%. Taken together, the results of this study proved that unlike the 100 mm long ionization chamber, the CTDP probe can be efficiently used to determine CTDI for any length over which dose integration is desired and also measure geometric efficiency of MDCT scanners for various beam widths in helical mode of operation.

Machine-Learning-Inspired Workflow for Camera Calibration.

The performance of modern digital cameras approaches physical limits and enables high-precision measurements in optical metrology and in computer vision. All camera-assisted geometrical measurements are fundamentally limited by the quality of camera calibration. Unfortunately, this procedure is often effectively considered a nuisance: calibration data are collected in a non-systematic way and lack quality specifications; imaging models are selected in an ad hoc fashion without proper justification; and calibration results are evaluated, interpreted, and reported inconsistently. We outline an (arguably more) systematic and metrologically sound approach to calibrating cameras and characterizing the calibration outcomes that is inspired by typical machine learning workflows and practical requirements of camera-based measurements. Combining standard calibration tools and the technique of active targets with phase-shifted cosine patterns, we demonstrate that the imaging geometry of a typical industrial camera can be characterized with sub-mm uncertainty up to distances of a few meters even with simple parametric models, while the quality of data and resulting parameters can be known and controlled at all stages.

Local–flexural interactive buckling behaviour and resistance of press-braked stainless steel slender channel section columns

The present paper reports experimental and numerical studies of the local–flexural interactive buckling behaviour and resistance of press-braked stainless steel slender channel section columns. A testing programme was firstly performed, including tensile coupon tests, initial geometric imperfection measurements and ten pin-ended column tests. The pin-ended column test setup, procedures and results were fully reported and analysed. The progression of local buckling and flexural buckling was discussed in detail. Following the testing programme, a numerical modelling programme was conducted, where finite element models were developed to replicate the test responses 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 employed to assess the accuracy of the relevant design rules for press-braked stainless steel slender channel section columns, as set out in the European code, American specification and Australian/New Zealand standard. The assessment results revealed that the European code leads to conservative and scattered interactive buckling resistance predictions, while the American specification and Australian/New Zealand standard result in many unsafe and scattered interactive buckling resistance predictions. A new design approach was then developed, based on the Eurocode column buckling curve and the continuous strength method, and shown to lead to accurate, consistent and safe interactive buckling resistance predictions for press-braked stainless steel slender channel section columns. The reliability of the new design approach was confirmed by means of statical analyses. Besides, the relevant design rules for press-braked carbon steel slender channel section columns, as given in the North American specification, were assessed, and shown to result in unsafe though consistent interactive buckling resistance predictions, when used for their stainless steel counterparts.

Microstructure, Mechanical Properties and Cross‐sectional Behaviour of Additively Manufactured Stainless Steel Cylindrical Shells

AbstractPowder bed fusion (PBF) is an additive manufacturing method that enables complex metallic components to be manufactured with high precision. The microstructure, mechanical properties and cross‐sectional behaviour of PBF additively manufactured stainless steel circular hollow sections are investigated through experiments in this paper, with a view to applications in construction. The experimental programme included tensile coupon tests, microstructural characterisation, initial geometric imperfection measurements and compression tests on PBF 316L stainless steel cylindrical shells with large diameter‐to‐thickness (D/t) ratios. Advanced measurement methods – 3D laser scanning and digital image correlation, were employed to measure the specimen geometries prior to testing and deformation fields during testing, respectively. The possible anisotropy in mechanical properties was examined through tensile coupon tests and correlated with the underlying microstructural and textural features. Compression tests were performed to investigate the resistance against local buckling of thin‐walled cylindrical shells produced by PBF. All cylindrical shells buckled below their yield loads with a chequerboard failure mode and revealed the anticipated trend of reducing capacity relative to the yield load with increasing local slenderness, reflecting the increasing susceptibility to local buckling.

Behaviour of S960 Ultra‐high Strength Steel Press‐braked Channel Sections

AbstractThis paper reports a comprehensive experimental and numerical study of the cross‐sectional behaviour and resistances of press‐braked S960 ultra‐high strength steel (UHSS) channel section structural members. The experimental study was conducted on eight different ultra‐high strength steel plain channel sections, and comprised material testing, initial local geometric imperfection measurements, as well as a total of 10 stub column tests and 20 four‐point bending tests performed about the minor principal axes in both the ‘u’ and ‘n’ orientations. The experimental study was then supplemented by a finite element (FE) simulation programme, in which FE models were firstly developed to replicate the test structural responses and subsequently used to generate further numerical data over a wide variety of cross‐section sizes. On the basis of the experimental and numerical results, the assessment of the applicability of the codified provisions and formulations, established in the European code, to the design of S960 UHSS channel section stub columns and beams was conducted.

Automated Posture Positioning for High Precision 3D Scanning of a Freeform Design using Bayesian Optimization

Three-dimensional scanning is widely used for the dimension measurements of physical objects with freeform designs. The output point cloud is flexible enough to provide a detailed geometric description for these objects. However, geometric accuracy and precision are still debatable for this scanning process. Uncertainties are ubiquitous in geometric measurement due to many physical factors. One potential factor is the object’s posture in the scanning region. The posture of target positioning on the scanning platform could influence the normal of the scanning points, which could further affect the measurement variances. This paper first investigates the geometric and spatial factors that could potentially influence scanning variance. This functional relationship is modeled as a Bayesian extreme learning model, which is later utilized to find the object’s optimal posture for variance reduction. A Bayesian optimization approach is proposed to solve this minimization problem. Case studies are presented to validate the proposed methodology.

An approach for monitoring prefabricated building construction based on feature extraction and point cloud segmentation

PurposeConstruction schedule delays and quality problems caused by construction errors are common in the field of prefabricated buildings. The effective monitoring of the construction project process is one of the key factors for the success of a project. How to effectively monitor the construction process of prefabricated building construction projects is an urgent problem to be solved. Aiming at the problems existing in the monitoring of the construction process of prefabricated buildings, this paper proposes a monitoring method based on the feature extraction of point cloud model.Design/methodology/approachThis paper uses Trimble X7 3D laser scanner to complete field data collection experiments. The point cloud data are preprocessed, and the prefabricated component segmentation and geometric feature measurement are completed based on the PCL platform. Aiming at the problem of noisy points and large amount of data in the original point cloud data, the preprocessing is completed through the steps of constructing topological relations, thinning, and denoising. According to the spatial position relationship and geometric characteristics of prefabricated frame structure, the segmentation algorithm flow is designed in this paper. By processing the point cloud data of single column and beam members, the quality of precast column and beam members is measured. The as-built model and as-designed model are compared to realize the visual monitoring of construction progress.FindingsThe experimental results show that the dimensional measurement accuracy of beam and column proposed in this paper is more than 95%. This method can effectively detect the quality of prefabricated components. In the aspect of progress monitoring, the visualization of real-time progress monitoring is realized.Originality/valueThis paper proposed a new monitoring method based on feature extraction of the point cloud model, combined with three-dimensional laser scanning technology. This method allows for accurate monitoring of the construction process, rapid detection of construction information, and timely detection of construction quality errors and progress delays. The treatment process based on point cloud data has strong applicability, and the real-time point cloud data transfer treatment can guarantee the timeliness of monitoring.

Determination of as-built properties of fiber reinforced polymers in a wind turbine blade using scanning electron and high-resolution X-ray microscopy

The fiber volume fraction (FVF) and porosity in fiber reinforced polymers (FRPs) depends strongly on the manufacturing process. These parameters influence the mechanical properties and thus the performance of an FRP. For this research, an epoxy-pre-impregnated glass FRP was investigated to determine the FVF and matrix mass fraction taking into consideration all material constituents, including sizing, stitching thread, as well as the porosity, the area density and the fiber orientations of each lamina, the filament fiber diameter, and the inter-laminar void size and shape. Therefore, samples from a commercially manufactured wind turbine rotor blade were experimentally investigated using scanning electron (SEM) and high-resolution X-ray microscopy (micro-CT), as well as a standardized calcination method and geometric measurements. Post-processing techniques such as thresholding and edge detection were used to analyze the images. There was good FVF agreement between SEM and the method of calcination. Micro-void cross-sectional shapes were well captured by SEM while meso- and macro-voids were volumetrically resolved with a reproducible void size distribution for two sample volumes by micro-CT.

Experimental and numerical investigations of S960 ultra-high strength steel slender welded I-section columns failing by local–flexural interactive buckling

The present paper reports experimental and numerical investigations into the local–flexural interactive buckling behaviour and resistance of S960 ultra-high strength steel slender welded I-section columns. A testing programme was firstly conducted and included initial geometric imperfection measurements and ten pin-ended column tests. The pin-ended column test setup, procedures and results were fully reported and analysed. The progression of local buckling and flexural buckling was discussed. Following the testing programme, a numerical modelling programme was conducted, where finite element models were developed to replicate the test structural responses and then employed to perform parametric studies to generate further numerical data. It is worth noting that the current European code and American specification are only applicable to steel structures with material yield strengths up to 700 MPa (or 690 MPa). Regarding the design of slender welded I-section columns failing by local–flexural interactive buckling, both codes adopt the same concept — combined use of effective width method to account for local buckling and buckling curve to account for flexural buckling. The obtained test and numerical data were employed to assess the applicability of the codified design rules to S960 ultra-high strength steel slender welded I-section columns. The assessment results revealed that the European code leads to conservative interactive buckling resistance predictions, mainly due to the use of conservative buckling curve, while the American specification yields a good level of design accuracy and consistency. Finally, a revised Eurocode design approach was proposed and shown to result in more accurate and consistent interactive buckling resistance predictions for S960 ultra-high strength steel slender welded I-section columns.

Method for extrinsic parameters calibration of Pan-Tilt camera using intersecting lines from two images

Pan-Tilt (PT) cameras are widely used in video surveillance because of larger field of view. The camera’s intrinsic parameters remain unchanged and the extrinsic parameters calibration of the PT camera should be addressed when it comes to visual geometric measurement. In this paper, the unknown parameters of the PT camera are only reduced to the rotation angles in horizontal and vertical directions, and a method for extrinsic parameters calibration using intersecting lines from two images is presented. An improved feature point matching algorithm is proposed to obtain the natural feature point pairs between images acquired before and after rotation, and direct linear transformation method is employed to obtain the rough rotation angles by using the natural feature point pairs. Based on rotation constraint, the optimization function established by the projections of the intersections of the straight lines in natural scene is then used to calculate the refined extrinsic parameters. Computer simulations and real experiments prove the effectiveness of the improved feature point matching algorithm and the proposed calibration method. Experimental data reflects the extrinsic parameters estimated by our method are close to reference values from high-precision stepper motors, and the average deviation of Euler angles representing rotation matrix and translations from our method relative to reference values does not exceed 0.03° and 0.27 mm, respectively.

Atmospheric gaseous aromatic hydrocarbons in eastern China based on mobile measurements: Spatial distribution, secondary formation potential and source apportionment

Monocyclic aromatic hydrocarbons (MAHs) and polycyclic aromatic hydrocarbons (PAHs) are both well known as hazardous air pollutants and also important anthropogenic precursors of tropospheric ozone (O3) and secondary organic aerosols (SOA). In recent years, there have been intensive studies covering MAHs emission from various sources and their behavior under stimulated photochemical conditions. Yet in-situ measurements of PAHs presence and variations in ambient air are sparse. Herein we conducted large geometrical scale mobile measurements for 16 aromatic hydrocarbons (AHs, including 7 MAHs and 9 PAHs) in eastern China between October 27 and November 8, 2019. This unique dataset has allowed for some insights in terms of AHs concentration variations, accompanying chemical composition, source contributions and spatial distributions in eastern China. In general, AHs showed a clear concentration variability between the south and the north of the Yangtze River Delta (YRD). The concentrations of PAHs were approximately 9% of AHs, but contributed 23% of SOA formation potential. Source apportionment via positive matrix factorization (PMF) model revealed that industrial processes as the largest source (44%) of observed AHs, followed by solvent usage (21%), vehicle exhaust (19%), coal combustion (11%) and coking processes (6%). In the perspective of PAHs sources, coal combustion emissions were identified as the dominating factor of a share of 41%–52% in eastern China. Our findings complemented the simultaneously monitoring information of PAHs and MAHs in eastern China, revealed the importance of PAHs to SOA formation and highlighted the necessity of formulating strategies to reduce emissions from anthropogenic sources and reduce risks to human health.

Experimental and numerical investigations on stub column behaviour of cold-formed high strength steel irregular octagonal hollow sections

Comprehensive experimental and numerical investigations into the structural behaviour of cold-formed high-strength steel (HSS) irregular octagonal hollow sections (IOctHS) are presented in this paper. A total of 13 IOctHS stub columns were tested. Material properties measurements were conducted on the tensile coupons taken from both parent plates and within the cross-sections of HSS IOctHS stub columns. Initial local geometric imperfection measurements were also carried out. In conjunction with experimental tests on the stub columns, finite element (FE) models were developed to replicate the test results and failure modes. Afterwards, the validated FE models were employed to conduct parametric studies to supplement the experimental data by generating further structural performance data covering a broader range of cross-section slenderness. Cross-section slenderness limits set out in design codes such as EN 1993-1-1, ANSI/AISC 360-16, AS 4100 as well as ASCE/SEI 48, and design methods of DSM as well as CSM were evaluated against the experimental and numerical data. It was found that the current limits for internal compression plate elements of rectangular hollow sections set out in the design standards are not suitable for the design of cold-formed HSS IOctHS under compression load. Cross-section strength predictions obtained from EN 1993-1-12, ANSI/AISC 360-16, AS 4100, ASCE/SEI 48, DSM, CSM and modified design methods were also compared with the tests and numerical results. Relatively accurate predictions are provided by design codes. Non-conservative results are obtained from DSM and the CSM yields more consistent and precise results than DSM. The modified design approaches were also assessed and discussed.

Experimental and Numerical Study of Press-Braked S690 High-Strength Steel Channel–Section Columns Failing by Minor-Axis Flexural Buckling

This paper reports an experimental and numerical investigation into the minor-axis flexural buckling behavior and capacity of press-braked S690 high-strength steel channel–section columns. The experimental investigation comprised initial geometric imperfection measurements and 10 pin-ended column tests. This was accompanied by a numerical modeling program, in which finite-element models were developed and validated against the test results and then adopted to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions and member lengths. The obtained test and numerical data were adopted to assess the accuracy of the buckling curves, as given in the Eurocode, North American specification, and Australian/New Zealand standard, for press-braked S690 high-strength steel channel–section columns prone to minor-axis flexural buckling. Overall, it was found that the Eurocode buckling curve yields many conservative capacity predictions, whereas the buckling curves in the North American specification and the Australian/New Zealand standard lead to an overall good degree of design accuracy. A revised Eurocode buckling curve is proposed, and was shown to offer accurate capacity predictions for press-braked S690 high-strength steel channel–section columns prone to minor-axis flexural buckling.

Measurements of the Hubble Constant with a Two-rung Distance Ladder: Two Out of Three Ain’t Bad

The three-rung distance ladder, which calibrates Type Ia supernovae (SNe Ia) through stellar distances linked to geometric measurements, provides the highest precision direct measurement of the Hubble constant. In light of the Hubble tension, it is important to test the individual components of the distance ladder. For this purpose, we report a measurement of the Hubble constant from 35 extragalactic Cepheid hosts measured by the SH0ES team, using their distances and redshifts at cz ≤ 3300 km s−1, instead of any more distant SNe Ia, to measure the Hubble flow. The Cepheid distances are calibrated geometrically in the Milky Way, NGC 4258, and the Large Magellanic Cloud. Peculiar velocities are a significant source of systematic uncertainty at z ∼ 0.01, and we present a formalism for both mitigating and quantifying their effects, making use of external reconstructions of the density and velocity fields in the nearby universe. We identify a significant source of uncertainty originating from different assumptions about the selection criteria of this sample, whether distance or redshift limited, as it was assembled over three decades. Modeling these assumptions yields central values ranging from H 0 = 71.7 to 76.4 km s−1 Mpc−1. Combining the four best-fitting selection models yields as a fiducial result, at 2.4σ tension with Planck. While SNe Ia are essential for a precise measurement of H 0, unknown systematics in these supernovae are unlikely to be the source of the Hubble tension.

Stability improvement of large-scale power systems including offshore wind farms and MTDC grid aiming at compensation of time delay in sending robust damping signals

The main aim of this paper is to design a bi-level damping controller for compensating local and inter-area oscillating modes in the power system. Regarding the need for compensation of time delays in measuring the wide-area signals and transmitting them to the damping controllers, a method is required that can appropriately obtain the controllers’ gains in the presence of signal delays. A robust H∞-based criterion is employed in this paper to design a bi-level damping controller. In the proposed design, to reduce conservatism of linear matrix inequality (LMI), an auxiliary function is defined in Lyapunov function. In this function, by including triple adder, reinforced variables, and cross-terms, the conservatism reduction of LMI and preparation of appropriate gains for controllers using state-feedback is fulfilled. The second purpose is to apply the proposed approach on a large-scale power system in the presence of wind power units where transmission of their output power is carried out by multi-terminal DC (MTDC) grid. Regarding the large scale of the power system and control converters in each of the equipment, geometric measurements based on observability and controllability are utilized to acquire accurate damping signals for the input of each controller. Simulations are obtained in different uncertainty scenarios. The results clearly demonstrate robustness of the conducted approach.

Geometric error measurement of facing head and machining verification on large horizontal boring and milling machine tool

Geometric error measurement of facing head and machining verification on large horizontal boring and milling machine tool

Functional Impairment of Hip Joint and Activities of Daily Living Failure in Patients with Multiple Hereditary Exostoses.

In this study, we focused on the hip joints and examined pain and functional impairment, and their relationship with anatomical characteristics in MHE patients. Patients with MHE followed up in our hospital from January 2020 to December 2020 were enrolled. Clinical hip functional outcomes were evaluated using the Japanese Orthopedic Association (JOA) hip score and hip range of motion (ROM). Proximal femur geometric measurements were evaluated using radiography. A total of 39 patients (78 hips) with a median age of 25.6years and average JOA score of 94.0 ± 10.5 were included. Eight patients felt pain in their hip joints. The average ROM score was 18.2 ± 2.5, and 47.4% of the patients with MHE had ROM limitation. The average score of ability to walk was 19.6 ± 1.8, and three patients had some problems with walking. The average ADL score was 18.2 ± 2.5, and 51.3% of patients with MHE had some failures in ADL. The hip flexion and internal rotation were markedly restricted compared with the normal values. When patients were grouped according to their ADL scores, we found that the ADL failure group had a significantly lower ROM score than the no ADL failure group (p < 0.0001), and there were significant differences between the groups in terms of femoral neck widening (p = 0.0001). We found that half of MHE patients had some failures in their ADL due to hip functional impairment. The study results also suggest that femoral neck widening affected ADL failure and ROM limitation.

A low-cost open-source handheld LiDAR-based automated understory timber stand surveying device

Timber stand inventories are critical for making management decisions in both commercial and conservation related forestry applications. When taking these inventories, the most critical characteristics to record are diameter at breast height (DBH), stand density, tree height and tree species. As discovered in prior research, a relatively inexpensive device, which hereby will be referred to as AutoTSI (short for Automatic Timber Stand Inventory), can be assembled and deployed in the field to take accurate measurements of diameter at breast height (DBH) for timber stand sample plots in a short amount of time compared to the traditional method of manually measuring these trees. The specified range and angle of resolution of the sensor allows for estimation of stand density and basal area. Each element of both the hardware and software is modular by design allowing the user to customize according to whatever sensors may be readily available to the user. In silviculture research, methodical collection, and analysis of geometric measurements of trees is essential for developing land management plans that optimize biomass production, biodiversity, and other desired characteristics in a forest environment making this device useful to both tree farmers and researchers.

Flexural buckling of extruded high-strength aluminium alloy SHS columns

The structural performance and design of extruded high-strength aluminium alloy square hollow section (SHS) columns were presented in this paper. A total of 12 extruded 7A04-T6 aluminium alloy SHS column specimens were tested under axial compression, together with tensile coupon tests and initial global geometric imperfection measurements. The flexural buckling failure mode and axial load versus end shortening and mid-height lateral deflection curves were reported. Based on validated finite element (FE) models, 480 numerical results were generated by means of parametric studies over a broad range of cross-section dimensions, member lengths, proof strengths and strain hardening exponents of the aluminium alloy material. The applicability of current design rules used for normal-strength aluminium alloy columns in European, Chinese and American standards to extruded 7A04-T6 high-strength aluminium alloy SHS columns was evaluated through comparisons with the test and FE results. The analysis results showed that the three standards consistently yielded conservative axial compression resistance predictions by about 9% for extruded 7A04-T6 high-strength aluminium alloy SHS columns. New flexural buckling curves with linear and nonlinear imperfection terms for the Chinese code, as well as modifications to the American specification, were separately proposed, resulting in improved accuracy with significantly reduced scatter. Additionally, the continuous strength method (CSM) was further extended for the flexural buckling design of extruded 7A04-T6 high-strength aluminium alloy SHS columns, and was shown to provide accurate and consistent resistance predictions. Reliability analyses of the codified and the proposed design methods were performed, confirming that the design proposals meet the target reliability indices except the Eurocode approach.