Error In Thickness Measurement Research Articles

Ultrasonic non-destructive inspection method for glass fibre reinforcement polymer (GFRP) hull plates considering design and construction characteristics

The design and construction characteristics, including glass fibre weight fraction ( Gc), number of single-ply layers, fabric combination, and fabrication quality, of glass fibre reinforcement polymer (GFRP) hull plates affect ultrasound propagation characteristics, such as ultrasonic velocity and attenuation, thereby influencing the accuracy of ultrasonic non-destructive test results. Therefore, this study is to propose a method to decrease the ultrasonic test errors of GFRP hull plate by using statistical method. The GFRP specimens with Gc of approximately 30–50 wt%, thicknesses of approximately 5–20 mm, and different fabric combinations were prepared using the hand lay-up method, considering the general design–construction characteristics. Further, an ultrasonic velocity decision method for ultrasonic inspection was proposed considering the GFRP hull design-construction characteristics, such as Gc and number of single-ply layers of hull plate by multiple linear regression method. The results show that the proposed method can reduce the thickness measurement error from approximately 20%–30% to 1%–2%, compared to an existing ultrasonic inspection method, only considering the Gc effect on ultrasonic velocity, which indicates that the proposed test method is suitable for practical applications.

Fringe Projection Profilometry for Three-Dimensional Measurement of Aerospace Blades

The aero-engine serves as the “heart” of an aircraft and is a primary factor determining the aircraft’s performance. Among the crucial components in the core of aero-engines, aero-engine compressor blades stand out as extremely important. They are not only numerous but also characterized by a multitude of parameters, making them the most complex parts in an aero-engine. This paper aims to address the trade-off between accuracy and efficiency in the existing measurement methods for asymmetric blades. Non-contact measurements were conducted using a structured light system composed of a stereo camera and a DLC projector. The point cloud data of the blades are processed using methods such as the PCA (Principal Component Analysis) algorithm, binary search, and least squares fitting. This paper established a fringe-projection profilometry light sensor system for the multi-view measurement of the blades. High-precision rotary tables are utilized to rotate and extract complete spatial point cloud data of aviation blades. Finally, measurements and comparative experiments on the blade body are conducted. The obtained blade point cloud data undergo sorting and denoising processes, resulting in improved measurement accuracy. The measurement error of the blade chord length is 0.001%, the measurement error of blade maximum thickness is 0.895%, compared to CMM (Coordinate Measuring Machine), where the measurement error of chord is 0.06%.

Accuracy-improved ultrasonic phase algorithm for measuring lubricant film thickness

The reflected ultrasonic waves are generally used for the determination of the lubricant film thickness, which consist of a directly reflected wave at the first solid-lubricant interface and the other reflected waves passing through the oil layer. The whole reflected waves are generally utilized in current available ultrasonic algorithms. However, the directly reflected wave is independent on the lubricant film, which can be ignored for improving the measurement accuracy. In the present work, an accuracy-improved ultrasonic phase algorithm is proposed based on the reflection coefficient phase of the other reflected waves passing through the oil layer, rather than that of the whole reflected waves. Both experimental and finite element analysis results show that the proposed new algorithm possesses a high sensitivity and a robust anti-noise interference ability, which effectively improves the measurement accuracy, especially for thin films. With comparison to the current available phase algorithm, the maximum measurement error of lubricant film thickness decreased from 45 % to 6 %.

Reliability analysis of the impact of thickness measurement accuracy on the longitudinal strength assessment of CAP

The reliability analysis of the longitudinal bending strength of ships is conducted using the total probability method, taking into account and analyzing the accuracy error in thickness measurement of transverse section members on existing servicing ships. A mathematical model for calculating failure probability CAP ratings is established. By calculating the CAP rating of an aged LPG carrier, it is observed that when the deterministic method reaches the target rating, the failure probability in rating calculation by the reliability analysis method is high. This indicates a significant influence of thickness measurement accuracy on CAP rating accuracy.

A method for measuring and adaptively correcting lens center thickness based on the chromatic confocal principle

Optical systems are widely used in aerospace, life sciences, civil livelihood and other fields. The lens is one of the most common components in optical systems, and its centre thickness is an important parameter in material characterization and manufacturing process, which directly affects the performance and function of optical components. In this paper, based on the chromatic confocal principle and laser interference technology, we propose a method applied to the measurement and adaptive correction of lens centre thickness, aiming to solve the problem of lens centre thickness measurement error. We successfully built an adaptive error correction system and proposed a translation correction algorithm and a tilt correction algorithm. This method not only can accurately measure the lens thickness but also can adaptively compensate for the measurement error caused by the lack of accuracy of mechanical elements or motion mechanisms through the spatial attitude correction of the element to be measured. The experimental results show that this method has obvious advantages in the translation error correction and tilt error correction of the lens. After the translation correction, the measurement accuracy of the lens is improved by about 75.21%; after the tilt correction, the measurement accuracy of the lens is improved by about 71.48%.

Combination of a Nondestructive Testing Method with Artificial Neural Network for Determining Thickness of Aluminum Sheets Regardless of Alloy’s Type

Non-destructive and reliable radiation-based gauges have been routinely used in industry to determine the thickness of metal layers. When the material’s composition is understood in advance, only then can the standard radiation thickness meter be relied upon. Errors in thickness measurements are to be expected in settings where the actual composition of the material may deviate significantly from the nominal composition, such as rolled metal manufacturers. In this research, an X-ray-based system is proposed to determine the thickness of an aluminum sheet regardless of its alloy type. In the presented detection system, an X-ray tube with a voltage of 150 kV and two sodium iodide detectors, a transmission detector and a backscattering detector, were used. Between the X-ray tube and the transmission detector, an aluminum plate with different thicknesses, ranging from 2 to 45 mm, and with four alloys named 1050, 3050, 5052, and 6061 were simulated. The MCNP code was used as a very powerful platform in the implementation of radiation-based systems in this research to simulate the detection structure and the spectra recorded using the detectors. From the spectra recorded using two detectors, three features of the total count of both detectors and the maximum value of the transmission detector were extracted. These characteristics were applied to the inputs of an RBF neural network to obtain the relationship between the inputs and the thickness of the aluminum plate. The trained neural network was able to determine the thickness of the aluminum with an MRE of 2.11%. Although the presented methodology is used to determine the thickness of the aluminum plate independent of the type of alloy, it can be used to determine the thickness of other metals as well.

Reproducibility of subscapularis muscle thickness measurement using ultrasound imaging. -Relationship between subscapularis muscle thickness and internal rotation torque of the shoulder joint-

BackgroundFew studies have reported on the morphometry of the subscapularis muscle using ultrasound imaging (USI); and their reproducibility has not been verified. ObjectivesThis study aimed to clarify the relative and absolute reproducibility of USI measurements of subscapularis muscle thickness at rest and during isometric contraction as well as the degree of change in muscle thickness caused by the amount of internal rotational torque in the shoulder joint. DesignTwo-group repeated-measures study. MethodsThe subjects were the inferior fibers of the subscapularis muscle of 40 healthy adult males. Muscle thickness was measured at rest and at 10%–30% of the maximum isometric internal rotation torque. Intraclass correlation coefficients (ICC) and Brand Altman analysis were used for reproducibility measurement. The degree of change in muscle thickness at each torque was also calculated. ResultsIntra- and inter-rater ICCs (ranged from 0.69 to 0.91) were good. A proportional error was observed in intra-rater measurements. Both minimal detectable change 95 (ranged from 2.33 to 6.47) were high. The subscapularis muscle thickness was significantly increased at 10% torque (25.49 ± 3.80 mm), 20% torque (26.07 ± 3.90 mm), and 30% torque (25.96 ± 3.82 mm) as compared to that in resting conditions (24.53 ± 4.46 mm) (p < 0.05). ConclusionThe reproducibility and error of the subscapularis muscle thickness measurement using USI used in this study were clarified when repeated measurements were made in the same limb position and under the same probe installation conditions, suggesting that the contraction of the subscapularis muscle can be estimated by muscle thickness measurement.

Segmentation Errors and Off-Center Artifacts in SS-OCT: Insight from a Population-Based Imaging Study

Purpose To evaluate the frequency and associated factors of artifacts in swept-source optical coherence tomography (SS-OCT) imaging. Methods This was a population-based cross-sectional study. Individuals aged 35 years or older, residing in the Yuexiu district of Guangzhou, China, were recruited by random cluster sampling. Nearly half of the participants were randomly selected for SS-OCT imaging centered on the optic nerve head. Six types of artifacts in the peripapillary choroidal layer and retinal nerve fiber layer (RNFL) were graded and identified. Univariate and multivariate logistic regression analyses were used to investigate the association between the presence of artifacts and clinical characteristics. Results Out of the 616 eligible individuals who underwent SS-OCT imaging, 18.3% and 13.6% of subjects exhibited at least one artifact in peripapillary RNFL (pRNFL) and peripapillary choroidal thickness (pCT) measurements, respectively, with posterior segmentation error and off-center artifact ranked as the most common artifacts. The presence of artifacts was significantly associated with age (odds ratio [OR], 1.03; 95% confidence interval [CI], 1.01–1.06; p = .003), refractive error (OR, 0.80; 95% CI, 0.71–0.89; p < .001), and signal strength (OR, 0.95; 95% CI, 0.90–0.997; p = .039) in pRNFL thickness measurement. Similarly, the presence of artifacts in pCT measurement was significantly associated with age (OR, 1.05; 95% CI, 1.03–1.08; p < .001), and refractive error (OR, 0.76; 95% CI, 0.68–0.86; p < .001). Conclusion Nearly one-fifth of the eyes were noted with at least one artifact in the population-scale SS-OCT study. Age was a risk factor for the presence of artifacts and should be considered in clinical settings.

At-line porosity sensing for non-destructive disintegration testing in immediate release tablets

Fully automated at-line terahertz time-domain spectroscopy in transmission mode is used to measure tablet porosity for thousands of immediate release tablets. The measurements are rapid and non-destructive. Both laboratory prepared tablets and commercial samples are studied. Multiple measurements on individual tablets quantify the random errors in the terahertz results. These show that the measurements of refractive index are precise, with the standard deviation on a single tablet being about 0.002, with variation between measurements being due to small errors in thickness measurement and from the resolution of the instrument. Six batches of 1000 tablets each were directly compressed using a rotary press. The tabletting turret speed (10 and 30 rpm) and compaction pressure (50, 100 and 200 MPa) were varied between the batches. As expected, the tablets compacted at the highest pressure have far lower porosity than those compacted at the lowest pressure. The turret rotation speed also has a significant effect on porosity. This variation in process parameters resulted in batches of tablets with an average porosity between 5.5 and 26.5%. Within each batch, there is a distribution of porosity values, the standard deviation of which is in the range 1.1 to 1.9%. Destructive measurements of disintegration time were performed in order to develop a predictive model correlating disintegration time and tablet porosity. Testing of the model suggested it was reasonable though there may be some small systematic errors in disintegration time measurement. The terahertz measurements further showed that there are changes in tablet properties after storage for nine months in ambient conditions.

Extraction of LIF features using sweep-frequency eddy current for conductivity and thickness evaluation of non-magnetic metallic plates

Sweep-frequency eddy current testing(ECT) is an efficient tool in nondestructive testing and evaluation due to its characteristics of non-contact, high sensitivity and abundant frequency information. In fact, the lift-off fluctuation is the main influencing factor to introduce the measurement errors. In this paper, the response signal feature, i.e. lift-off irrelevant frequency (LIF), has been found, which is immune to the effect of lift-off. Based on the characteristics, the sensor including two pairs of T-R coils is designed to obtain the feature point of LIF. Related analytical solutions and experiments are conducted to investigate the properties of LIF for non-magnetic materials, and the performance of LIF is also analyzed along with the conductivity and thickness of the tested piece. Hence, the LIF can provide the effective measurement of non-magnetic materials and immune to the lift-off fluctuation. The errors of thickness and conductivity measurement are 3.7% and 3.8% respectively.

Validade, confiabilidade e erro da medida da espessura muscular do quadríceps femoral obtida pela ultrassonografia em adultos saudáveis: uma revisão sistemática

Abstract Due to its low cost and operational simplicity, ultrasound has been used to monitor muscle thickness in laboratory environments, rehabilitation clinics, and sports clubs. However, it is necessary to determine the measurement's quality to infer whether the possible changes observed are derived from the treatment or the measurement error. Therefore, we performed a systematic review to determine the validity, reliability, and measurement error of quadriceps femoris muscle thickness obtained by ultrasound in healthy adults. A search was conducted in the Pubmed, Scopus, and Web of Science databases until April 2022. The study selection process was carried out by two independent researchers, with the presence of a third researcher in case of disagreements. Twenty-six studies were eligible for the review, being 4 of validity, 4 of reliability only, and 18 of reliability and measurement error. The intraclass correlation coefficient ranged from 0.60 to 0.99 in validity studies and from 0.44 to 0.99 in reliability studies. The typical error of measurement ranged from 0.01 to 0.47 cm, and the coefficient of variation was from 0.5 to 17.9%. Four studies received “very good” classification in all the risk of bias analysis criteria. Therefore, it is concluded that the quadriceps femoris muscle thickness obtained by ultrasound was shown to be valid, reliable, and to have low measurement errors in healthy adults. The weighted average of the relative error was 6.5%, less than typical increases in resistance training studies. The raters' experience and methodological care for repeated measurements were necessary to observe low measurement errors.

Dielectric constant of ice in natural rivers

Ground-penetrating radar (GPR) is a non-contact measurement method widely used to determine ice thickness, which is an important hydrological parameter of rivers in winter. The accuracy of GPR measurements of ice thicknesses is highly dependent on the dielectric constant value of ice. Research on the dielectric constant of ice has mainly focused on pure ice; however, pure ice is not commonly found in natural rivers. In fact, hydrodynamic and meteorological factors, as well as boundary conditions, affect ice in natural rivers, which can be treated as a mixture of pure ice, air bubbles, sediment, and pure water. Therefore, the dielectric constant of ice in natural rivers often differs from the theoretical value of pure ice, a fact that has often been neglected in prototype measurements. During eight years of prototype monitoring in the Heilong River and Yellow River (China), it was found that variations in the dielectric constants of ice in the two rivers produced errors in the GPR ice thickness measurements. In this study, we measure the dielectric constant of ice at 158 measurement points across more than 20 river sections, and we present a recommended range of values for the dielectric constant. Regarding media, such as air bubbles, sediment, and water in natural river ice, we analyze sand (both dry and wet) in ice-bound sediment and the effects of air bubbles, sediment, and water upon the ice's dielectric constant. Using temperature and voltage measuring rods installed in the ice, we demonstrate that the water content in the ice differs significantly according to the freeze-up and breakup periods. The present study recommends guidelines including suitable timing, ice-condition, and dielectric-constant reference values for GPR-based ice thickness measurements to improve the measurement accuracy. Thus, this work can serve as a reference for future applications in similar rivers.

Cereal grain 3D point cloud analysis method for shape extraction and filled/unfilled grain identification based on structured light imaging

Cereals are the main food for mankind. The grain shape extraction and filled/unfilled grain recognition are meaningful for crop breeding and genetic analysis. The conventional measuring method is mainly manual, which is inefficient, labor-intensive and subjective. Therefore, a novel method was proposed to extract the phenotypic traits of cereal grains based on point clouds. First, a structured light scanner was used to obtain the grains point cloud data. Then, the single grain segmentation was accomplished by image preprocessing, plane fitting, region growth clustering. The length, width, thickness, surface area and volume was calculated by the specified analysis algorithms for grain point cloud. To demonstrate this method, experimental materials included rice, wheat and corn were tested. Compared with manual measurement results, the average measurement error of grain length, width and thickness was 2.07%, 0.97%, 1.13%, and the average measurement efficiency was about 9.6 s per grain. In addition, the grain identification model was conducted with 25 grain phenotypic traits, using 6 machine learning methods. The results showed that the best accuracy for filled/unfilled grain classification was 90.184%.The best accuracy for indica and japonica identification was 99.950%, while for different varieties identification was only 47.252%. Therefore, this method was proved to be an efficient and effective way for crop research.

New method for the calibration of a road condition sensor

PurposeThis study aims to improve the calibration accquracy of the road condition sensor. A road condition sensor is widely used to detect water or ice deposits on the road to assess associated driving risks. Its quantitative calibration is central to the thickness measurement accuracy and conventionally performed using the single fitting method-based calibration method. One existing limitation is that the distribution characteristics of calibration data of different road conditions are diversified, which leads to the fitting error can not be minimized when using the conventional calibration method. Thus, the multiple fitting methods-based calibration method is developed to realize an optimal calibration for the road condition sensor.Design/methodology/approachA fitting method assignment for the calibration data of different road conditions was introduced to realize an optimal combination for fitting method and calibration data. In the experiments, the calibration methods were tested in the absence of measurement errors, then tested with calibration data, and finally, in the covering thickness measurement.FindingsThe comparison results indicate that compared with the conventional calibration method, the multiple fitting methods-based calibration method cuts the fitting error in the quantitative calibration by 13.3% and contributes to reducing the thickness measurement error by 8.11% for different road conditions.Originality/valueThe multiple fitting methods-based calibration method has been successfully applied for quantitative calibration and shown to reduce calibration errors. The comparison between different calibration methods demonstrates the superior performance of the new calibration method.

Risk factors for carotid plaque progression after optimising the risk factor treatment: substudy results of the Atherosclerotic Plaque Characteristics Associated with a Progression Rate of the Plaque and a Risk of Stroke in Patients with the carotid Bifurcation Plaque Study (ANTIQUE)

Background and aimCarotid plaque progression contributes to increasing stroke risk. The study aims to identify factors influencing carotid plaque thickness progression after changing the preventive treatment to the ‘treating arteries...

Accuracy of Intraocular Lens Calculation Formulas in Patients Undergoing Combined Phakic Intraocular Lens Removal and Cataract Surgery

To investigate the prediction accuracy of intraocular lens (IOL) calculation formulas, and the impact of anterior chamber depth (ACD) and lens thickness (LT) measurement errors on IOL power calculation in patients undergoing combined phakic IOL (PIOL) removal and cataract surgery. Retrospective, consecutive case series study. Thirty-six PIOL implanted eyes (12 anterior chamber PIOLs and 24 posterior chamber PIOLs [PC-PIOL]) undergoing cataract surgery were included. The prediction accuracy of new formulas (Barrett universal II, Emmetropia verifying optical, Kane, and Ladas super formula) and traditional formulas (Haigis, Hoffer Q, Holladay 1 and SRK/T) with or without Wang-Koch (WK) axial length (AL) adjustment was evaluated. The influence of ACD and LT measurement errors of IOLMaster 700 on refractive outcomes was also investigated. The Kane and traditional formulas with WK AL adjustment had no significant systematic prediction error and displayed a smaller median absolute error, whereas the other formulas showed significant hyperopia shift (P < .05) and relatively lower prediction accuracy. The accuracy rate of IOLMaster 700 in measuring the ACD and LT was 100% in eyes with anterior chamber PIOL implantation, and 37.50% in the PC-PIOL subgroup. No significant difference was observed in refractive outcomes of formulas using correct and wrong parameters in the PC-PIOL subgroup (P > .05). The Kane and traditional formulas with WK AL adjustment exhibited relatively higher prediction accuracy in patients who underwent combined PIOL removal and cataract surgery. The IOLMaster 700 displayed low accuracy in ACD and LT measurements for PC-PIOL implanted eyes, but showed negligible impact on IOL prediction accuracy.

Influence of eccentricity and tilt of radial GRIN lens on its thickness measurement by chromatic confocal technology

The chromatic confocal technology (CCT) has ultra-high distance measurement resolution and the characteristics of multi-surface tomography. Based on the principle of optical dispersion and confocal, the technology achieves accurate axial position or micro-displacement measurement. The radial gradient index (GRIN) lens is a typical important inhomogeneous material. Its refractive index gradually decreases from the center to the edge along the radial direction. We propose to measure the thickness of the radial GRIN lens based on CCT. The thickness measurement model is established by the ray-tracing method, the optical Lagrange function, and the ray arc differential in the Cartesian coordinate system. The refractive index distribution makes the eccentric tilt of the lens change the propagation of the probe light and affects the extraction of the peak of the spectral response causing the thickness measurement error. The influence of eccentricity and tilt of the radial GRIN lens on its thickness measurement is studied. The precision shift table drives the radial GRIN lens movement to simulate the eccentric tilt state of the lens under the dispersion probe. According to the comparative analysis between the experimental and simulation results, it is concluded that the greater the eccentric distance and inclination degree of the radial GRIN lens is, the greater the influence on the thickness measurement is. The larger the lens thickness is, the greater the measurement error is. For the radial GRIN lens with a thickness of 2.36 mm, the measurement error is about 20 μm when the eccentricity is 0.1 mm and the tilt is 6 deg. The research results have significance for optimizing the system structure and further improving the system performance for the application of the CCT in measuring non-homogeneous materials or optical thin film. And the research will encourage the development of GRIN lens instrument preparation and application technology by improving the thickness measurement accuracy and precision of the GRIN lens.

A method for measuring ice thickness of wind turbine blades based on edge detection

In recent years, with the successive development of mountain wind power resources in the high humidity regions, the problem of ice covering on wind turbine blades has become increasingly prominent. Wind turbine blade icing will affect blade aerodynamic performance and reduce power generation. In this paper, a method for measuring the ice thickness of wind turbine blades based on edge detection was proposed. As the icing images of blades have characteristics like low contrast, unclearness and blurred edges, the images were preprocessed by methods like defogging, gray-scale transformation, histogram correction, Gaussian filtering, and Laplace edge enhancement. Aiming at the characteristics of wind turbine icing images with many noises and many small edges, a multiscale wavelet edge detection algorithm was used to detect the blade icing images. Based on the pixel coordinates of the ice edge and the edge of the blade, through the pre-calibration, a method for calculating the ice thickness of the leading edge of the blade based on the pixel coordinate difference /real length ratio was proposed. Multiple measurement tests were performed in the natural icing environment. The average ice thickness measurement error value of short distance (0.5 m)/long distance (35 m) is 0.31 mm/8.9 mm, and the average ice thickness measurement error rate is 2.62% /6.0%.

Shape measurement of large thickness glass plates with a white-light scanning interferometer using a compensation glass and a fixed reference surface

Conventional white-light scanning interferometers cannot measure exactly large thickness of glass plates because of a great dispersion effect. In this paper a compensation glass plate is used to reduce the dispersion effect. Moreover, a fixed reference surface is added behind the object and four-step measurements are performed. By this method a front surface profile and a thickness distribution of the object can be measured exactly without knowing the refractive index of the object, the thickness of the compensation glass, and dispersion effect containing in the interferometer. Due to the difficulty in scanning the reference surface at a constant speed over a long distance for a large thickness of the object, a piezoelectric transducer stage with a high positioning resolution are utilized together with an additional interferometer which measures the movement of this stage. Experimental results show that the error in thickness measurement is less than 60 nm and 170 nm for 1 mm and 5 mm-thickness glass plates, respectively.

Interscan measurement error of knee cartilage thickness and projected cartilage area ratio at 9 regions and 45 subregions by fully automatic three-dimensional MRI analysis

BackgroundWe have developed a fully automatic three-dimensional MRI analysis software program for automatic segmentation of knee cartilage using a deep neural network. The purpose of this study was to use this software to clarify the interscan measurement error of the knee cartilage thickness and projected cartilage area ratio at 9 regions and 45 subregions in the knee. MethodsTen healthy volunteers underwent MRI twice in the same day. The software provided cartilage thickness and projected cartilage area ratio (thickness ≥ 1.5 mm) at 9 regions and 45 subregions of the knee without any manual correction. The interscan measurement error was calculated at each region and subregion from the data of nine donors, except for one donor who had body motion during the MRI examination. ResultsThe interscan measurement error of cartilage thickness was less than 0.10 mm at all 9 regions and at 39 subregions among 45 subregions. The measurement errors ranged from 0.03 to 0.21 mm. The intraclass correlation coefficients (ICC) of cartilage thickness were higher than 0.75 at all 9 regions and 41 subregions. The interscan measurement error of the projected cartilage area ratio ranged from 0.01 to 0.03 for all 9 regions. ConclusionsThis study clarified the interscan measurement error of the knee cartilage thickness and projected cartilage area ratio.