Flatness Measurement Research Articles

Flatness Measurement of a Mosaic Focal Plane by using a Coaxial Multispectral Laser

The wide-field telescope will be an important tool in the discovery and birth of new theories of astronomy in future. The detectors in this kind of telescope mostly adopt a mosaic focal plane array. The focal depth of a large-F-number optical system is very small, and the flatness of the mosaic detector should be less than half the focal depth. In this paper, a new flatness measurement and data processing method is developed. A flatness measurement platform composed of a high-precision gantry platform and a coaxial multispectral displacement meter was built. The flatness of a single detector was measured under uncooled and cooled working conditions, and data processing was conducted, in which the root mean square (RMS) and the peak-valley (PV) values of the cooled detector were 0.0017 mm and 0.0112 mm, respectively. Next, a 2 × 6 mosaic model of the focal plane with a dimension of 148.5 mm × 168.5 mm was built using a metal detector model. The measurement platform was used to measure the flatness of the mosaic focal plane. According to the measurement results, the preliminary installation and mosaic adjustment were completed. The final RMS and PV values of the mosaic focal plane are 0.009 mm and 0.0808 mm, respectively. The experimental results show that the measurement and the data processing method can accurately reflect surface information on the detectors. This suggests that the method has great potential for use in ensuring the accuracy of wide-field telescope equipment in all applicable research areas.

Quantitative Analysis of Talar Dome Morphology

Category:Ankle; OtherIntroduction/Purpose:A flat-top talar dome deformity can alter ankle mechanics and impact daily activities. Radiographic determination of flatness is difficult using traditional measures. The purpose of this study is to describe a new method to quantify the talar dome morphology using lateral radiographs and a custom-written image processing algorithm.Methods:Skeletally mature patients previously treated for idiopathic clubfeet were identified from our institution’s clubfoot registry. All patients had weight-bearing lateral foot radiographs. Measurements included radius of curvature (ROC) of the talar dome and tibial plafond, talar length and height, and alpha angle. The ratio of the radii of the talar dome and tibial plafond (TD/TP Ratio) was determined. Custom-written, image processing MATLAB code was used to identify the talus from the lateral radiograph. Following manual identification of the articular surface, the average slope of the anterior, central, and posterior regions of the talar dome were calculated. Talar dome flatness was determined as the slope variance across all three regions.Higher variance indicated a rounder talar dome morphology, lower variance indicated a flatter dome. Inter-rater reliability of radiographic measures and the MATLAB based talar dome flatness were determined. Spearman’s rho was used to determine correlations between radiographic and MATLAB flatness measures.Results:For radiographic measures, the Inter-rater reliability (IRR) was determined for 52 feet. IRR was near perfect for the ROC of the talar dome (ICC=.985), talar length (ICC=.952), and alpha angle (ICC=.928). Measurement of the radius of the tibial plafond (ICC=.827) and talar height (ICC=.893) were reproduced with excellent reliability. The IRR of the TD/TP ratio was moderate (ICC=.608). Preliminary IRR for the MATLAB-based talar dome flatness (15 feet) was excellent (ICC=0.895). Flatness was strongly correlated with ROC of the talar dome (r=.621, p=.013), alpha angle (r=.557, p=.031) and TD/TP Ratio (r=-.589, p=.021).Conclusion:Flatness of the talar dome can be difficult to describe, as there lacks a single measure to accurately define its morphology. The method developed in this study was quick to apply (less than 5 to 10 minutes per foot) and had high inter-rater reliability.

Detection and evaluation of barely visible impact damage in woven glass fabric reinforced polyamide 6.6/6 composite using ultrasonic imaging, X-ray tomography and optical profilometry

The present experimental work investigates the response of woven glass fabric reinforced polyamide 6.6/6 subjected to drop weight impact loading. The main objective is the development and the introduction of a new experimental procedure/approach, based on different complementary detection techniques, that aims at investigating the damage induced by impact loading in thermoplastic woven fabric composites. The developed approach is intended to be generalized to other types of composite materials. The main idea is to assess all the experimental results obtained through the developed procedure with a direct investigation method. The latter consists in the Permanent Indentation (PI) measurement providing an indicator of the damage criticality in the composite sample. To this end, several non-destructive testing methods are carried-out and their experimental findings are analyzed and cross-linked. The identification of the different damage mechanisms, caused by the drop weight impact, is performed using X-Ray micro-computed tomography (µCT). C-scan ultrasonic investigation is conducted according to two types: transmission and reflection for the detection of the impact damage and the identification of the induced degradation area. B-scan imaging are then obtained through specific post-processing of the impacted surface to extract the permanent indentation (PI). The latter is validated through surface flatness measurement using the highly resolved 3D optical profilometry. The correlation between the X-Ray tomography results and the permanent indentation measurement is then established. It correlates the PI level with the damage mechanisms of a barely visible impact damage (BVID) in woven glass reinforced polyamide 6.6/6 composite.

From Self-Organization of Monoatomic Steps on the Silicon Surface to Subnanometer Metrology

The article presents how the understanding of the fundamental processes of self-organization and morphological transformations of the atomically clean Si(111) surface as a result of the study using in situ ultrahigh vacuum reflection electron microscopy can be applied to metrology. The method of high-resolution transmission electron microscopy is used to show that the native oxide formed on the Si(111) surface in atmospheric conditions replicates the atomic step height with high accuracy. The techniques for creating vertical measures in the range 0.31–31 nm with an error of less than 0.05 nm in the entire measurement range are developed on this basis. It is shown that it is possible to create extremely wide atomically smooth surfaces (up to 230 $$\mu$$ m) and use them as reference mirrors in interferometric microscopes. Crystal samples containing a certain number of monoatomic steps and atomically smooth surface areas are included in the State Secondary Reference Standard as a measure of angstrom height and angstrom flatness.

Prevalence of Corneal Astigmatism in Patients before Cataract Surgery in Western China.

Purpose To investigate the demographics and distribution of corneal astigmatism before cataract surgery in patients from western China and to compare and analyze these findings with those of patients in southern China. Setting. People's Hospital of Xinjiang Uygur Autonomous Region. Design Clinical-based cross-sectional study. Methods Patients undergoing cataract surgery in the People's Hospital of Xinjiang Uygur Autonomous Region from February 2012 to August 2019 were recruited. Preoperative keratometric data measured by performing preoperative bilateral partial coherence interferometry (IOLMaster), and patient demographics were recorded and analyzed. Results This study comprised 12,236 eyes of 7065 patients with a mean age of 64.75 ± 9.66 years, and 52.77% of the patients were female. The mean axial length was 23.14 ± 0.96 mm. Astigmatism ranged from 0 diopters (D) to 6.94 D, with a mean of 1.28 D. Corneal astigmatism was between 0.25 D and 1.25 D in 53.71% of eyes, 1.25 D or higher in 39.06% eyes, and less than 0.25 D in 7.23% of eyes. Astigmatism was with the rule (WTR) in 41.94% of the patients and against the rule (ATR) in 38.80% of patients. The mean flat and steep keratometry measurement was 43.19 ± 1.50 D and 44.24 ± 1.62 D, respectively. After matching, corneal astigmatism in western China was 1.30 ± 1.03 D, and it was significantly higher than that in southern China (0.98 ± 0.67 D, P < 0.001). After matching, the proportion of WTR astigmatism was 40.99% in western China, which was also significantly higher than the proportion (26.46%) in southern China (P < 0.001). Conclusion Corneal astigmatism in patients before cataract surgery in western China was mainly between 0.25 D and 1.25 D. Compared with patients in southern China, patients in western China are younger, have a much higher degree of astigmatism, and have a higher proportion of WTR astigmatism.

PERBANDINGAN HASIL BELAJAR MATEMATIKA SISWA KELAS IV YANG MENGIKUTI DENGAN YANG TIDAK MENGIKUTI BIMBINGAN BELAJAR

The purpose of this study is to compare the learning outcomes of fourth grade students in elementary schools who take tutoring with students who do not take tutoring and find out the motivation of students to follow guidance. Categories of student learning outcomes with the motivation of students who take tutoring are evaluated from the very low, low, medium, high, and very high categories. The method used in this research is quantitative descriptive. This research was conducted on 98 students from a public elementary school in Pekanbaru. The instruments used to collect data are objective test questions on the material of flat shapes, statistics and angle measurements as well as questionnaires about students' motivation to follow tutoring. The results of this study indicate that the learning outcomes of students who take tutoring are better than students who do not follow tutoring, and the motivation of students who take tutoring is motivated because students' desire to obtain learning outcomes is increased and better understand the science of mathematics learned. The implication of this research is that parents need to consider their children to attend tutoring and schools need to think and design learning that can improve student learning outcomes.

Planar Brownian motion and Gaussian multiplicative chaos

We construct the analogue of Gaussian multiplicative chaos measures for the local times of planar Brownian motion by exponentiating the square root of the local times of small circles. We also consider a flat measure supported on points whose local time is within a constant of the desired thickness level and show a simple relation between the two objects. Our results extend those of Bass, Burdzy and Khoshnevisan and in particular cover the entire $L^1$-phase or subcritical regime. These results allow us to obtain a nondegenerate limit for the appropriately rescaled size of thick points, thereby considerably refining estimates of Dembo, Peres, Rosen and Zeitouni.

Quantitative dispersion model for self-dispersion compensation and parameter optimization of interleavers

In this paper, we propose a theoretical model based on quantitative dispersion value to evaluate the influence of loss and transmission coefficient on the flatness of the interleaver. We use dispersion range (the difference between the maximum and the minimum) as the measure of flatness, and when the dispersion range is 0.352, the flatness of the interleaver is the highest. We can control the dispersion range around 0.352 by selecting appropriate parameters, achieving self-dispersion compensation. In addition, we can also utilize dispersion range as the index to guide the parameter optimization in the design stage. This method can quickly determine the optimum parameters without a large amount simulation and calculation attempts, thus saving a lot of time and cost. Not limited to the interleaver employing add–drop​ resonator Mach–Zehnder interferometer (ADR–MZI) demonstrated in this paper, our method can also apply for the parameter optimization in the fabrication of interleavers based on various infinite-impulse-response (IIR) filters. Our quantitative dispersion model can greatly reduce the cost of interleaver’s parameter design process and has practical application.

Brighter-fatter Effect in Near-infrared Detectors—III. Fourier-domain Treatment of Flat Field Correlations and Application to WFIRST

Weak gravitational lensing has emerged as a leading probe of the growth of cosmic structure. However, the shear signal is very small and accurate measurement depends critically on our ability to understand how non-ideal instrumental effects affect astronomical images. The Wide-Field Infrared Survey Telescope (WFIRST) will fly a focal plane containing 18 Teledyne H4RG-10 near-infrared detector arrays, which present different instrument calibration challenges from previous weak lensing observations. Previous work [Paper I: Hirata & Choi, PASP, 132, 014501 (2020); and Paper II: Choi & Hirata, PASP, 132, 014502 (2020)] has shown that correlation functions of flat field images, including cross-correlations between different time slices that are enabled by the non-destructive read capability of the infrared detectors, are effective tools for disentangling linear and nonlinear inter-pixel capacitance (IPC) and the brighter-fatter effect (BFE). Here we present a Fourier-domain treatment of the flat field correlations, which allows us to expand the previous formalism to all orders in IPC, BFE, and classical nonlinearity. We show that biases in simulated flat field analyses in Paper I are greatly reduced through the use of this formalism. We then apply this updated formalism to flat field data from three WFIRST flight candidate detectors, and explore the robustness to variations in the analysis. We find that the BFE is present in all three detectors, and that its contribution to the flat field correlations dominates over the nonlinear IPC, in accordance with the results from Paper II on a development detector. The magnitude of the BFE is such that the effective area of a pixel is increased by (3.54 ± 0.03) × 10−7 for every electron deposited in a neighboring pixel (sensor chip assembly [SCA] 20829, statistical error, not IPC-deconvolved). We compare IPC maps from flat field autocorrelation measurements to those obtained from the single pixel reset method and find a median difference of 0.113% for SCA 20829. After further diagnosis of this difference, we ascribe it largely to an additional source of cross-talk, the vertical trailing pixel effect, and recommend further work to develop a model for this effect. These results represent a significant step toward calibration of the non-ideal effects in WFIRST detectors.

Determination of silicon wafer site flatness using dual heterodyne interferometers with sub-nanometer precision.

Precise measurement of wafer flatness with high sensitivity and high spatial resolution is essential to realize high yields in nano-scale lithography because the depth of focus in this technology is relatively small. We report on a highly precise site flatness measurement system that employs a pair of heterodyne interferometers and achieves sub-nanometer precision for polished 300-mm silicon wafers. The determined overall mean standard deviation for the site flatness front-surface least-squares fit range is 0.21 nm. Furthermore, this system allows us to obtain images of the wafer flatness via scanning with a high spatial resolution of approximately 12 µm. These results suggest that the heterodyne interferometer-based system is a suited candidate for use at the next-generation 16-nm half-pitch technology node.

Flatness measurement primary measurement information processing

A methodology for measuring and processing the primary measurement information when estimating the deviation from flatness of significant large-scaled objects is considered. The laser measurement system used and the algorithms used to process the measurement information are described.

MoS2 “inorganic fullerenes” combined with TiO2 in water-methanol suspensions: Highly active hydrogen production photo catalysts operating via transfer of accumulated electrons

Water-methanol suspensions of size-tuned hollow MoS2 “inorganic fullerenes” (IF) combined with high surface area anatase TiO2 efficiently promote photo catalytic hydrogen evolution reaction (PHER). Despite low amount of the MoS2 slabs edges in the structure of closed-shell IF-MoS2 particles and relatively poor dispersion of co-catalyst, the best composite catalysts were nearly 50% as active as Pt/TiO2 benchmark and considerably more active than the reference MoS2–TiO2 catalysts containing highly dispersed MoS2 slabs. Straightforward experimental evidence is given that hydrogen can be formed due to transfer of stored (accumulated) electrons from TiO2 to the IF-MoS2 particles in liquid suspension. Electrochemical flat band potential measurements support the possibility of electrons transfer from TiO2 to IF-MoS2.

Methodology for Calculating Transport and Operational Parameters of Condition of Highways

This article is devoted to methodology of calculation of transport and operational parameters of condition of highways. The technique of determination of parameters of geometrical elements of the road is presented. The technique of definition of strength of road clothes according to statistical and dynamic methods is described. The specifics of measurement of coupling properties and longitudinal flatness of road carpet are presented. The methodology of inspection of engineering arrangement and assessment of parameters of structural elements of highways is concretized.

Machine vision system for key-cap flatness measurement of computer keyboards

Key-cap flatness detection after assembly is one of the basic quality control (QC) indexes in computer keyboard manufacturing. A modified machine vision system based on linear structured light imaging for measuring the key-cap flatness is proposed for keyboard QC automation. After a brief introduction of the system design and principle, the pipeline of light stripe image processing, especially the removal of printed letter interference, is studied. First, the staggered reprojection of dense multiline fringes is presented using the pattern editability of the digital light processing projector to replace the conventional three-dimensional (3-D) sensor mechanical scanning and avoid the movement and cumulative error. Second, an adaptive direction operator based on a Hough transform voting is proposed. This operator is used for directional morphological filtering to remove letter noise and solve the issue of printed letter interference on the key-cap surface, thus improving the accuracy and stability of stripe centerline extraction. Finally, the nonlinear least square method is used to fit the 3-D surface of the key-cap and evaluate its flatness efficiently based on the discrete globally distributed 3-D point cloud data. The experimental result demonstrates that the proposed machine vision system can quickly detect keyboard key-cap flatness and shows superior performance to that of the previous work.

Autoregressive Whitening Filtering of Phonocardiography Signals for Detection of Coronary Artery Disease

Background: Narrowing of the coronary arteries, which defines coronary artery disease (CAD), can be discovered through phonocardiography (PCG) analysis. Increased power of frequencies below 200 Hz in the diastole has been associated with CAD, and can be used to distinguish CAD from NonCAD patients. However, spectral roll off is steep (~40 dB/dec), and spectral leakage might mask the weak CAD-related signal.Methods: PCGs from 1168 subjects, 213 CAD and 955 NonCAD, were pooled from three studies. The average power spectral density (PSD) of diastole segments for NonCAD subjects was found, and an auto-regressive (AR) model of this PSD was constructed. The inverse of the corresponding filter was used for whitening.Results: A single iteration of whitening filtering was insufficient to make the PSD white for 5-1000 Hz. Two iterations of whitening filtering with an order of 6-10 were required to reach a plateau of maximal whitening with a spectral flatness measure close to 1 in the frequency band 5-1000 Hz. The whitening process revealed additional PSD differences between CAD and NonCAD subjects for the mid-diastole segment.Conclusion: Whitening of diastole PCG segments emphasized the difference between CAD and NonCAD patients.

Non-Catalytic Benefits of Ni(II) Binding to an Si(111)-PNP Construct for Photoelectrochemical Hydrogen Evolution Reaction: Metal Ion Induced Flat Band Potential Modulation.

We report here the remarkable and non-catalytic beneficial effects of a Ni(II) ion binding to a Si|PNP type surface as a result of significant thermodynamic band bending induced by ligand attachment and Ni(II) binding. We unambiguously deconvolute the thermodynamic flat band potentials (VFB) from the kinetic onset potentials (Von) by synthesizing a specialized bis-PNP macrochelate that enables one-step Ni(II) binding to a p-Si(111) substrate. XPS analysis and rigorous control experiments confirm covalent attachment of the designed ligand and its resulting Ni(II) complex. Illuminated J-V measurements under catalytic conditions show that the Si|BisPNP-Ni substrate exhibits the most positive onset potential for the hydrogen evolution reaction (HER) (-0.55 V vs Fc/Fc+) compared to other substrates herein. Thermodynamic flat band potential measurements in the dark reveal that Si|BisPNP-Ni also exhibits the most positive VFB value (-0.02 V vs Fc/Fc+) by a wide margin. Electrochemical impedance spectroscopy data generated under illuminated, catalytic conditions demonstrate a surprising lack of correlation evident between Von and equivalent circuit element parameters commonly associated with HER. Overall, the resulting paradigm comprises a system wherein the extent of band bending induced by metal ion binding is the primary driver of photoelectrochemical (PEC)-HER benefits, while the kinetic (catalytic) effects of the PNP-Ni(II) are minimal. This suggests that dipole and band-edge engineering must be a primary design consideration (not secondary to catalyst) in semiconductor|catalyst hybrids for PEC-HER.

Isoentangled Mutually Unbiased Bases, Symmetric Quantum Measurements, and Mixed-State Designs.

Discrete structures in Hilbert space play a crucial role in finding optimal schemes for quantum measurements. We solve the problem of whether a complete set of five isoentangled mutually unbiased bases exists in dimension four, providing an explicit analytical construction. The reduced density matrices of these 20 pure states forming this generalized quantum measurement form a regular dodecahedron inscribed in a sphere of radius sqrt[3/20] located inside the Bloch ball of radius 1/2. Such a set forms a mixed-state 2-design-a discrete set of quantum states with the property that the mean value of any quadratic function of density matrices is equal to the integral over the entire set of mixed states with respect to the flat Hilbert-Schmidt measure. We establish necessary and sufficient conditions mixed-state designs need to satisfy and present general methods to construct them. Furthermore, it is shown that partial traces of a projective design in a composite Hilbert space form a mixed-state design, while decoherence of elements of a projective design yields a design in the classical probability simplex. We identify a distinguished two-qubit orthogonal basis such that four reduced states are evenly distributed inside the Bloch ball and form a mixed-state 2-design.

Research on Flatness Rapid Measurement Technology of Large Deployable Antenna

The flatness of large deployable antenna needs to be measured several times during the deployment test, the theodolite measurement accuracy was low and the speed was slow, and the laser radar measurement range was limited. By building a flatness rapid measurement system for large deployable antenna, using autonomous navigation mobile technology to plan measuring path, and using digital photogrammetry technology to detect the flatness of antenna. It can realize rapid and automatic measurement for flatness of large antenna. The test results show that the accuracy of digital photogrammetry camera and laser tracker is no more than 0.05mm; the measurement accuracy of the flatness rapid measurement system shall not be more than 0.034mm away from the accuracy of laser radar, it can meet the requirements of flatness rapid measurement of large deployable antenna. This method can improve the efficiency and automation level of flatness measurement of large deployable antenna, and it lays a foundation for the plane measurement of large deployable antenna with larger size and more complex structure.

High-Accuracy Flatness Measurement of Large Structures using Range Images

High-Accuracy Flatness Measurement of Large Structures using Range Images

History state formalism for scalar particles

We present a covariant quantum formalism for scalar particles based on an enlarged Hilbert space. The particular physical theory can be introduced through a timeless Wheeler DeWitt-like equation, whose projection onto four-dimensional coordinates leads to the Klein Gordon equation. The standard quantum mechanical product in the enlarged space, which is invariant and positive definite, implies the usual Klein Gordon product when applied to its eigenstates. Moreover, the standard three-dimensional invariant measure emerges naturally from the flat measure in four dimensions when mass eigenstates are considered, allowing a rigorous identification between definite mass history states and the standard Wigner representation. Connections with the free propagator of scalar field theory and localized states are subsequently derived. The formalism also allows the superposition of different theories and remains valid in the presence of a fixed external field, revealing special orthogonality relations. Other details such as extended identities for the current density, the quantization of parameterized theories and the nonrelativistic limit, with its connection to the Page and Wootters formalism, are discussed. A related consistent second quantization formulation is also introduced.