Surface Measurements Research Articles

Accuracy analysis in determining the location of underground objects using GPR involving lidar data

Ground penetrating radar (GPR) is one of the most useful non-destructive techniques for locating underground objects. Advancements in this technology have facilitated the development of new sensors over the past decade. In this paper, an accuracy assessment of the location of underground objects using various GPR antennas is presented. To achieve the stated goals, measurements of 5 concrete slabs, reinforced with steel bars of various diameters and located at variable depths were taken. The experiment includes the usage of three GPR antennas to assess the format, characteristics, and differences of extracted data. This set of antennas from different manufacturers varied in terms of operating frequency. Additional lidar data from TLS (terrestrial laser scanning) was utilized in the methodology to provide precise surface measurements and therefore, external orientation of the surveyed data. The experiment allowed for the determination of vertical and horizontal accuracy for three tested antennas and the assessment of increasing errors value with greater depth of the measured items, which is important for surveying accuracy forecasting.

Sutureless Dehydrated Amniotic Membrane (Omnigen) Application Using a Specialised Bandage Contact Lens (OmniLenz) for the Treatment of Dry Eye Disease: A 6-Month Randomised Control Trial.

Background and Objectives: Dry Eye Disease (DED) is a chronic condition characterised by tear film instability and ocular surface disruption, significantly impacting patients' quality of life. This study aimed to provide top-level clinical evidence for the long-term efficacy of dehydrated amniotic membrane (dAM, Omnigen®) delivered via a specialised bandage contact lens (sBCL, OmniLenz) for managing moderate-to-severe DED. Materials and Methods: This randomised controlled trial (NCT04553432) involved 93 participants with moderate-to-severe DED, randomised to receive a 1-week bilateral treatment of either dAM (17 mm diameter with 6 mm central 'window') applied under a sBCL or sBCL alone. Participants were assessed at baseline and followed up at 1, 3, and 6 months post-treatment. Outcomes included changes in symptomatology, tear film and ocular surface measurements, and in vivo confocal microscopy imaging of corneal nerve parameters and corneal dendritic cell (CDC) counts. Results: The dAM-sBCL group demonstrated a 65% reduction in OSDI scores at 6 months (p < 0.001), with 88% of participants showing improvement at 1 month. Corneal staining was significantly reduced in both groups. dAM-sBCL provided significant improvements in corneal nerve parameters at 1 month, with sustained positive trends at 3 months. Additionally, dAM-sBCL significantly reduced mature CDC counts, suggesting an anti-inflammatory effect. Conclusions: Treatment with dAM-sBCL for just 1 week significantly and rapidly improved dry eye symptoms as well as ocular surface signs for at least 3 months. It also enhanced corneal nerve health while reducing activated/mature corneal inflammatory cell numbers, presenting a safe and promising new treatment for moderate-to-severe DED.

The set of intersections of several independent Brownian motions on Carnot group

In this paper the existence of intersections for functions of several Brownian motions on the Carnot group is studied. A condition is presented for the existence of such intersections with Probability 1, which is in the form of the asymptotics of a measure on a specific family of small balls. The measure is arbitrary but can be chosen as a surface measure on the manifold related to intersections, and the balls are constructed using the distances related to the processes. Additionally, if the same condition holds in a weaker form, it is shown that there is a Hausdorff measure, such that the value of this Hausdorff measure on the set of intersection points is finite with Probability 1.

A Multiscale Statistical Analysis of Rough Surfaces and Applications to Tribology

Mathematical modelling of surface roughness is of significant interest for a variety of modern applications, including, but not limited to, tribology and optics. The most popular approaches to modelling rough surfaces are reviewed and critically examined. By providing counterexamples, it is shown that approaches based solely on the use of the fractal geometry or power spectral density have many drawbacks. It is recommended to avoid these approaches. It is argued that the surfaces that cannot be distinguished from the original rough surfaces can be synthesised by employing the concept of the representative elementary pattern of roughness (REPR), i.e., the smallest interval (or area) of a rough surface that statistically represents the whole surface. The REPR may be extracted from surface measurement data by the use of the “moving window” technique in combination with the Kolmogorov–Smirnov statistic.

Accuracy improvement of a multi-ring beam structured inner surface measurement: via novel calibration methodology and light source optimization

Parts with a large depth-to-diameter ratio play a critical role in the military, aerospace, and automotive industries. However, accurately measuring their inner surface profile remains challenging owing to the lack of adequate and accurate sensors. We developed a multi-ring structured light system to obtain three-dimensional data of inner contours, such as inner diameters, which are crucial for ensuring component performance and safety. In this study, we proposed three simple yet effective techniques to improve the multi-ring beam structured measurement system. First, we designed a distortion correction method to calibrate the imaging system. Second, a two-step calibration approach was used to calibrate the multi-ring projection. Meanwhile, we benchmarked the effects of different light sources on image speckles. The calibration results demonstrated that the coefficient of determination (R-2) used for line fitting exceeded 0.999. Moreover, the measurement experimental results show that the uncertainty of less than 10 µm and the smallest measurable pipe inner diameter can reach 15 mm, demonstrating that our methods are promising for improving the accuracy of structured light optical sensing systems. This system satisfies the measurement requirements and can be immediately utilized to meet the high demand for inner contour measurements in industrial applications.

Exact surface measurement based on phase error insensitive method for white-light scanning interferometer

Phase error induced by the scanning error of piezoelectric transducer and vibration in white-light interference signal (WLIS) impose limitations on measurement accuracy. In this paper, two techniques are investigated to eliminate phase error cooperatively. A monochromatic interferometer owning the same optical path as the white-light scanning interferometer (WLSI) is employed to detect and compensate the phase error. Due to the incomplete consistency between the detected phase error and its actual distribution, an algorithm is introduced to further enhance the measurement accuracy. The simulation is given to prove the proposed method is available in different magnitude of noise. In the experiment, the front surface of wedged window is measured, whose maximum fluctuations are reduced to 28.8 nm and 3.0 nm from 62.7 nm with the gradual application of two technologies, and the repeatability reach 5.0 nm and 0.4 nm from 16.8 nm, respectively. The root mean square height S q and maximum height S z ultimately decrease to 1.3 nm and 1.6 nm. The measurement of step with height of about 3.0 μm also has the good accuracy and repeatability after phase error elimination. Since the different reflectivity of measured surfaces in the wavelength range of light source will also bring the measurement error, its influences are analyzed by simulation. The proposed techniques provide a phase error insensitive method for WLSI that has potential on measurement in the complex environment.

Study on temperature field distribution and leakage point localization of buried carbon dioxide pipeline leakage

Leakage from buried CO2 pipelines is a critical issue in the context of carbon capture and storage (CCS). Therefore, we developed a small-scale experimental system for buried CO2 pipeline leakage. to investigate the effects of leak pressure, leak aperture size, and soil type on the temperature distribution near the leak point. The results of the study showed that the lowest soil temperature appeared directly above the leak. The minimum temperature at the soil axial measurement point increased with increasing leak pressure, but the peak maximum temperature difference decreased. 3mm and 5mm leak pore sizes, the peak maximum temperature difference occurred at 10cm and 20cm, respectively. At all pressures, the maximum temperature difference peaked at 20cm. Soil surface temperature variations were mainly influenced by leak pressure. The maximum peak temperature difference at the soil surface measurement points also increased with increasing leak pressure. Smaller leakage apertures slowed down the decrease of soil surface temperature. In addition, based on the experimental results, we propose a new method to locate leaks based on the soil temperature gradient.

Error compensation for near optical coaxial phase measuring deflectometry with refraction error model

Phase measuring deflectometry (PMD) is a key measurement technology for specular surfaces form measurement. Compared with conventional PMD techniques, the near optical coaxial PMD (NCPMD) can achieve compact configuration, light weight and reducing measurement error caused by shadows of the surface structures through utilizing a plate beamsplitter. However, the introduction of the plate beamsplitter will affect the measurement accuracy of the NCPMD system. The refraction of the plate beamsplitter needs to be considered. In this work, a virtual system of NCPMD was established, and an error model of the NCPMD system by considering the refraction influence of the plate beamsplitter was presented to analyze the shape reconstruction error caused by the plate beamsplitter. Moreover, the calibration method of the beamsplitter and the ray tracing algorithm to achieve error compensation of the beamsplitter were proposed. The proposed error compensation method can effectively improve the measurement accuracy of NCPMD system which has been confirmed by surface measurement experiments.

Improved stiff string torque and drag prediction using a computationally efficient contact algorithm

ABSTRACT Due to the intermittent contact with the wellbore, determining torque and drag for deviated wells is difficult. Most models have ignored drill string stiffness and assumed continual contact to simplify derivation. However, the accuracy of these ‘soft-string’ models is restricted, especially at high dogleg severities. On the other hand, most ‘stiff-string’ models rely on computationally intensive approaches or continuous contact assumptions. To mitigate these issues, a computationally efficient penalty-based wellbore contact algorithm has been developed based on vector calculation, which at most requires two dot products and three arithmetic operations to determine contact locations. This algorithm is incorporated into a 3D multibody dynamics (MBD) model, which utilizes rigid drill-string segments based on the Newton-Euler formulation, connected via axial, shear, torsional, and bending springs to capture drill string flexibility. This model performs simulations faster than real-time and has been validated using surface measurements from a completed well.

Constraining effects of aerosol-cloud interaction by accounting for coupling between cloud and land surface.

Aerosol-cloud interactions (ACIs) are vital for regulating Earth's climate by influencing energy and water cycles. Yet, effects of ACI bear large uncertainties, evidenced by systematic discrepancies between observed and modeled estimates. This study quantifies a major bias in ACI determinations, stemming from conventional surface or space measurements that fail to capture aerosol at the cloud level unless the cloud is coupled with land surface. We introduce an advanced approach to determine radiative forcing of ACI by accounting for cloud-surface coupling. By integrating field observations, satellite data, and model simulations, this approach reveals a drastic alteration in aerosol vertical transport and ACI effects caused by cloud coupling. In coupled regimes, aerosols enhance cloud droplet number concentration across the boundary layer more homogeneously than in decoupled conditions, under which aerosols from the free atmosphere predominantly affect cloud properties, leading to marked cooling effects. Our findings spotlight cloud-surface coupling as a key factor for ACI quantification, hinting at potential underassessments in traditional estimates.

Utilization of Charcoal Obtained from Woody Biomass in Metallurgical Processes Based on Solid–Gas Reactions

The high demand for carbon-based products within pyrometallurgy is placing the industry in an increasingly challenging position to meet stringent requirements. To transition away from fossil carbon carriers, biochar emerges as a sustainable and CO2-neutral alternative, presenting a viable solution without necessitating fundamental adjustments to plant technology, unlike hydrogen as an alternative reducing agent. Prior investigations have underscored the potential of woody biomass pyrolysis products for CO2-neutral metallurgy. Nonetheless, it is imperative to recognize that biochar must meet distinct requirements across various metallurgical processes. This paper conducts a comparative analysis between biochar and petroleum coke using thermogravimetric analyses, surface measurements, reactivity assessments, and scanning electron microscopy. Furthermore, the performance in a furnace for simulating the Waelz process, specifically regarding ZnO reduction, is scrutinized. The results illustrate the optical differences between petroleum coke and biochar and the significantly higher reactivity and specific surface area of biochar. When used in solid–gas reactors, it is observed that due to its high reactivity, biochar reacts more vigorously and carbon is completely consumed. However, during the reduction of ZnO, only minor differences were monitored, making biochar comparable to petroleum coke. Therefore, under certain constraints, biochar can be considered a potential substitute for metallurgical solid–gas reactions.

Consistent Ground Surface Temperature Climatology Over China: 1956–2022

AbstractThe ground surface represents the land‐atmosphere interface and plays a crucial role in exchanging energy, matter, and biochemical fluxes. The ground surface temperature (Ts) is hence widely investigated as an indicator to understand the thermal state of soil in a warming world. However, regular and continuous Ts measurements are rare worldwide, and the early Ts records were derived from snow surface measurements and are not comparable with the measurements of modern automatic systems. In this study, we reconstruct the Ts records of the China Meteorological Administration (CMA) for 1956–2022 by numerical simulation. The results show that the mean annual ground surface temperature (MAGST) during 1981–2010 ranged from 0.4 to 30.8°C at 632 stations. The MAGST was mainly controlled by air temperature and refined by snow depth. The overall MAGST increased by 0.20 ± 0.02°C dec−1 across China during 1956–2022 and showed pronounced interdecadal variability corresponding to the surface air temperature (0.23 ± 0.03°C dec−1). At the snow‐covered sites, the Ts warming was amplified by increased snow depth, leading to about 0.24°C dec−1 (or 70.6%) faster warming for Ts in winter compared to that of surface air temperature. Many of the early reported ground surface temperature studies based on CMA measurements did not consider the measurement inconsistency and likely overestimated the warming trend of ground surface temperature over China.

Satellite-Based Estimation of Near-Surface NO2 Concentration in Cloudy and Rainy Areas

Satellite-based remote sensing enables the quantification of tropospheric NO2 concentrations, offering insights into their environmental and health impacts. However, remote sensing measurements are often impeded by extensive cloud cover and precipitation. The scarcity of valid NO2 observations in such meteorological conditions increases data gaps and thus hinders accurate characterization and variability of concentration across geographical regions. This study utilizes the Empirical Orthogonal Function interpolation in conjunction with the Extreme Gradient Boosting (XGBoost) algorithm and dense urban atmospheric observed station data to reconstruct continuous daily tropospheric NO2 column concentration data in cloudy and rainy areas and thereby improve the accuracy of NO2 concentration mapping in meteorologically obscured regions. Using Chengdu City as a case study, multiple datasets from satellite observations (TROPOspheric Monitoring Instrument, TROPOMI), near-surface NO2 measurements, meteorology, and ancillary data are leveraged to train models. The results showed that the integration of reconstructed satellite observations with provincial and municipal control surface measurements enables the XGBoost model to achieve heightened predictive accuracy (R2 = 0.87) and precision (RMSE = 5.36 μg/m3). Spatially, this approach effectively mitigates the problem of missing values in estimation results due to absent satellite data while simultaneously ensuring increased consistency with ground monitoring station data, yielding images with more continuous and refined details. These results underscore the potential for reconstructing satellite remote sensing information and combining it with dense ground observations to greatly improve NO2 mapping in cloudy and rainy areas.

Design and development of Rotational Magneto Abrasive Flow Finishing setup powered with machine learning tools for nanofinishing of cylindrical double camshaft followers

Surface finish and morphology play a vital role in the reliability and life of cam-roller or slider mechanisms, with improvement due to lesser contact pressure-based fatigue and failure as surface finish improves. An experimental setup using magnet-based abrasive finishing techniques is designed and developed to conduct studies on a double camshaft follower arrangement that resulted in less than 300 nm finish at an enhanced finishing rate. Finishing rate improves greatly as speed of rotation of the workpiece increases with relatively bigger abrasive particles while the best finish is obtained at lower speeds and particle sizes with progression of the finishing cycles. Subsequently, using the results as the training dataset, a machine learning system is developed to overcome the limitations of surface measurement techniques and human interventions, to predict outcomes like number of cycles, speed of rotation of workpiece, time to reach the desired finish and particle size to be used for the given material of workpiece, initial surface roughness and final desired surface finish. The predictions from the completely trained system are compared with the physics-based model and the real data and the error is found to be within 20 nm which has led to development of a highly reliable system.

Results of round robin form measurements of optical aspheres and freeform surfaces

High-quality aspherical and freeform surfaces are in high demand, and the high-accuracy form measurement of such surfaces is a challenging task. To explore the current status of form measurement systems for complex surfaces such as aspheres and freeforms, interlaboratory comparison measurements are performed. This study presents the pseudonymized results obtained using three different surfaces (metal asphere, glass asphere, toroidal surface) in a total of six different round robins. These results were taken from a total of 13 different measurement instruments based on 9 different measurement principles and operated at 12 different laboratories. They were analyzed using a sophisticated procedure that was first developed in 2018 and then refined and tested on simulated data in 2022 to address the challenges of such a comparison at this level of accuracy. In the current study, we applied these refined methods to data acquired from tactile and optical point measurements as well as from optical areal measurements. As there are no absolutely measured and very well characterized reference standard aspherical and freeform surfaces available at the accuracy level of a few tens of nanometers root-mean-square, the approximated true forms of the surfaces were derived from the measurements and indicate the manufacturing accuracy of the surface forms. Then, the measurement’s differences to the approximated true forms were analyzed, which directly indicate the systematic measurement errors of the instruments. By also comparing the approximated true forms from the two different round robins for each surface, additional insights into the reliability and stability of these so-called virtual reference topographies were gained.

Predicting ground surface deformation induced from CO2 plume movement using machine learning

Carbon capture and storage (CCS), which involves injecting carbon dioxide (CO2) into subsurface, is an increasingly popular process for mitigating human caused greenhouse gas emissions. In order to ensure the safety and efficacy of CCS implementation, it is necessary to possess a comprehensive understanding of the complex behaviour of CO2 plumes within geological formations and their potential impact on ground surface deformation. Therefore, conducting research and analysis on these critical aspects is of vital importance. This research provides a methodology to anticipate ground surface deformations, which result from the motion of CO2 plumes utilising an advanced machine learning (ML) technique. The ML surrogate model has been developed using conditional Generative Adversarial Networks (cGAN). The dataset used for the model training and testing comprises ground surface measurements (tiltmeters), reservoir properties, as well as pressure/volume data. The model has been trained and tested using a set of samples created using a forward finite element model. Results show that the surrogate model is capable of predicting reasonably accurate results while running much faster than the forward model.

Concept for improving the form measurement results of aspheres and freeform surfaces in a tilted-wave interferometer

Abstract. Accurate and flexible form measurements for aspherical and freeform surfaces are in high demand, and non-null-test interferometric methods such as tilted-wave interferometry have gained attention as a promising response to this need. Interferometric methods, however, display ambiguities between the measurement of certain form errors and the misalignment of the measured specimen. Therefore, improved knowledge of the absolute measurement position of the specimen in relation to the interferometer setup may improve the form measurement result. In this work, we propose a concept that uses a white light interferometer to measure the absolute distance between a transparent specimen's surface and the interferometer's objective and present preparatory data to qualify the white light interferometer for the improvement of tilted-wave interferometer measurements.

Development of Macrotexture Test Method for Dense-Graded Asphalt Mixtures

The design and construction of pavements necessitate careful consideration of longevity, cost-effectiveness, sustainability, and safety, with a focus on enhancing the durability and lifespan of dense-graded asphalt (DGA) surface mixtures. This paper discusses a research project the Federal Highway Administration (FHWA) initiated to assess the macrotexture characteristics of DGA mixture pavement—particularly concerning safety at higher speeds. The project aims to develop an efficient testing procedure for measuring macrotexture during mixture design and field-testing processes, striking a balance between longevity, cost-effectiveness, sustainability, and safety in pavement design and construction. The study began with a comprehensive review of existing practices, leading to the selection and testing of a unique laser texture scanner capable of noncontact macrotexture measurement. The subsequent phase involved validating the suggested macrotexture measurement system through data collected from State-sponsored projects under the FHWA Mobile Asphalt Technology Center program. Macrotexture measurements were collected from field cores and laboratory-compacted specimens from various State departments of transportation projects and analyzed. Preliminary analysis of the limited dataset to date revealed a positive correlation between average macrotexture measurements from gyratory specimens’ top surface and field core macrotexture measurements. The FHWA developed a draft test method for measuring macrotexture on laboratory specimens and field cores, thereby aiming to reduce procedural variability. Interlaboratory macrotexture test results demonstrated good reproducibility, with an average coefficient of variation of approximately 20%. Overall, this research project seeks to advance the understanding and measurement of macrotexture in DGA mixture pavements and thereby contribute to the development of safe pavements.

Vortex phase-based adaptive moiré technique accommodating micro displacement measurement of freeform surfaces.

The traditional displacement measurement interferometer (DMI) provides elegant performance by straight interference fringe movement counting to convert a phase calculation into an image motion calculation. However, it cannot be applied to a curve surface displacement measurement. The counting of the movement of irregular fringes is not achievable. We provide an adaptive moiré technique with a vortex phase to realize micro displacement measurement of a freeform surface with any continuous shape. The technique produces straight moiré fringes that rotate in a circle regardless of the shape of interference fringes and tested surface shapes. The vortex phase is used to record only one interferogram before the measurement for subsequent data processing, and then it no longer participates in the displacement measurement process. Therefore, this technology can be employed to remold traditional DMIs. Simulations and experiments validating the method are presented.

Stratospheric influence on surface ozone pollution in China

Events of stratospheric intrusions to the surface (SITS) can lead to severe ozone (O3) pollution. Still, to what extent SITS events impact surface O3 on a national scale over years remains a long-lasting question, mainly due to difficulty of resolving three key SITS metrics: frequency, duration and intensity. Here, we identify 27,616 SITS events over China during 2015-2022 based on spatiotemporally dense surface measurements of O3 and carbon monoxide, two effective indicators of SITS. An overview of the three metrics is presented, illustrating large influences of SITS on surface O3 in China. We find that SITS events occur preferentially in high-elevation regions, while those in plain regions are more intense. SITS enhances surface O3 by 20 ppbv on average, contributing to 30-45% of O3 during SITS periods. Nationally, SITS-induced O3 peaks in spring and autumn, while over 70% of SITS events during the warm months exacerbate O3 pollution. Over 2015-2022, SITS-induced O3 shows a declining trend. Our observation-based results can have implications for O3 mitigation policies in short and long terms.