Distortion Parameters Research Articles

Supersonic jet microwave rotational spectrum of 2,3-difluorophenol

The microwave rotational spectrum of the aromatic 2,3-difluorophenol (2,3-DFP) has been recorded and analyzed in the frequency range of 5–25 GHz using a pulsed-jet Fourier transform microwave spectrometer. Rotational transitions were measured for the parent, the 18O, and all six 13C singly substituted isotopologues in natural abundance as well as the deuterium enriched 2HO-species. In addition to the rotational and quartic centrifugal distortion parameters, the quadrupole coupling constants of the deuterium species were determined. The rotational constants for the parent species are obtained as A = 2313.37516(14) MHz, B = 1797.935693(62) MHz, C = 1011.695171(36) MHz. For the deuterated species, the 2H quadrupole coupling constants are χaa = −0.11693(80) MHz and (χbb−χcc) = 0.4112(14) MHz. The partial rs substitution structure as well as a semi-experimental r0 structure was determined from the rotational constants of the observed isotopologues. Both rs and r0 structures agree well with each other and with MP2/6-311++g(2d, 2p) and B3LYP/6-311++g(2d, 2p) predicted equilibrium structures with the biggest deviation in heavy atom bond lengths being 0.008 Å.

Millimeter-wave detection of doubly excited bending mode in the CO–N2 van der Waals complex

A millimeter-wave intracavity OROTRON spectrometer in combination with a pulsed supersonic pin-hole jet expansion has been used to record a new subband of the CO–N2 weakly bound van der Waals complex in the 100–150 GHz region. Seven lines were assigned to the K = 0–0, (jCO, jN2) = (2, 0)–(1, 0) “hot band” transitions to a thus far unobserved K = 0 state at 9.336 cm−1 above the ground state. This is the highest in energy van der Waals mode detected so far, and this mode may be interpreted as a doubly excited bending vibration of the CO–orthoN2 nuclear spin isomer. Hyperfine structure caused by two 14N nuclei was partly resolved for the measured lines, and the quadrupole coupling constant, associated with the N2 subunit, together with rotational and centrifugal distortion parameters were precisely determined for the new K = 0, (jCO, jN2) = (2,0) state. The high lying energy levels of this state provided a sensitive test for the recent ab initio potential energy surfaces.

In situ SEM-DIC technique and its application to characterize the high-temperature fatigue crack closure effect

In situ high-temperature (maximum: 650°C) experiments for fatigue crack growth on single edge-notched GH4169 superalloy specimens have been performed in scanning electron microscopy (SEM). In order to investigate the crack closure behavior, digital image correlation (DIC) method was applied to measure the full-field displacement and strain fields around the crack tip. The deformation carrier (speckle) was fabricated on the polished specimen surface with ZrO2 powders having a good high-temperature resistance, and the speckle patterns were recorded during the fatigue test by SEM. In consideration of the distortion of SEM images, the unabridged model and the bicubic model were used to correct the spatial distortion, and the distortion parameters can be determined by a calibration test. It is shown that the unabridged model makes a better contribution towards improving SEM-DIC measurement accuracy. Based on the deformation field, the mode Ι stress intensity factor range ∆K and the crack opening displacement (COD) can be calculated for evaluating the crack closure effect. Additionally, the crack propagation was monitored using SEM and optical microscope. It indicates that the cracks grew initially in trans-granular mode at room temperature and 650°C, then propagated in both trans-granular and inter-granular modes.

Robust Multibit Image Watermarking Based on Contrast Modulation and Affine Rectification

In this paper, we present a robust multibit image watermarking scheme to undertake the common image-processing attacks as well as affine distortions. This scheme combines contrast modulation and effective synchronization for large payload and high robustness. We analyze the robustness, payload, and the lower bound of fidelity. Regarding watermark resynchronization under affine distortions, we develop a self-referencing rectification method to detect the distortion parameters for reconstruction by the center of mass in affine covariant regions. The effectiveness and advantages of the proposed scheme are confirmed by experimental results, which show the superior performance as comparing against several state-of-the-art watermarking methods.

A 1-MHz Relaxation Oscillator Core Employing a Self-Compensating Chopped Comparator Pair

An improved relaxation oscillator core is designed and fabricated in 0.35– $\mu \text{m}$ CMOS process, occupying the area of 0.032 mm2 and consuming around 160 $\mu \text{W}$ while running at 1 MHz. Employing a self-compensating chopped comparator structure, the designed oscillator exhibits a significant improvement in the frequency stability and control linearity, at the same time retaining a fast start-up and having a minimal overhead in the power consumption and area. Measured on 8 test chips, the frequency variation against temperature is ±0.26% in the temperature range from −40 to 125 °C, and the line sensitivity is ±0.08 %/V with the supply voltage changing from 3.0 to 4.5 V. The typical distortion parameters of the control characteristic are HD2 = −61.7 dB and HD3 = −93.2 dB at $\Delta f_{\text {osc}}=500 $ kHz. The measured jitter and phase noise at 10 kHz carrier offset are 235 ppm and −92 dBc/Hz, respectively, while the Allan deviation floor is 15 ppm.

Pendekatan Kaedah Taguchi untuk Mengurangkan Penyimpangan Angular pada Penyambung Kimpalan

Welding process is joining method which is extensively utilized in shipbuilding and automotive industry. Distortion is a classic problem encountered during the welding process which always occurs in welding processes. Distortion on weld joint involves many parameters that influence such as properties of materials and welding parameters. The objective of this work is to investigate effect of various processes of Shielded Metal Arc Welding (SMAW) on angular distortion in low carbon steel weld joints. To obtain optimum parameters of angular distortion, the effect various welding parameter is analysed using Taguchi Method. In this work, the effect of groove type, welding current and root opening are investigated for determining angular distortion. Taguchi method with L9 orthogonal array is utilized to analysed contribution for each parameter. ANOVA results revealed that the welding current the significant contribution parameter, on the other hand root opening shows minimum contribution to determine angular distortion value. Optimum parameter is obtained with groove type, welding current and root opening is X, 75A and 3 mm, respectively. Welding current parameter is considered the most significant contribution to determine for angular distortion effect due to has the highest contribution (50.04 %) than the other parameters groove type and root opening, with contribution value 21.76 %, 2.38%, respectively. Moreover, hardness test result on weld joint shows that X type groove has maximum hardness number than the other groove type.

Spectral method for stable estimating the distortion parameters in inverse problem of image restoration

Spectral method for stable estimating the distortion parameters in inverse problem of image restoration

A Pre-Processing Method Based on Self-Scoring Restoration and Self-Calibration for Image in Pressure Flow Pipes

The appearance of the inside of a running pressure flow pipe, when viewed through a photo-lens, is often blurred and deformed by the influence of fluid pressure, temperature and type. This study proposes an image pre-processing method based on self-scoring restoration and self-calibration to solve the problems and make it adaptable to the complicated environments inside the pipe. The method consists of two stages, in the first stage, a restoration method based on Wiener filter is used to work with the defined merit functions to deal with the degenerated images, in the second stage, two images taken from different depths inside the pipe are used to calculate the distortion parameters according to the matching points obtained from those two pictures. The experiment results show the proposed method performs well in clarity and contrast and removes the distortion effectively.

Quantum Rate-Distortion Coding of Relevant Information

Rate-distortion theory provides bounds for compressing data produced by an information source to a specified encoding rate that is strictly less than the source's entropy. This necessarily entails some loss, or distortion, between the original source data and the best approximation after decompression. The so-called Information Bottleneck Method is designed to compress only `relevant' information. Which information is relevant is determined by the correlation between the data being compressed and a variable of interest, so-called side information. In this paper, an Information Bottleneck Method is introduced for the compression of quantum data. The channel communication picture is used for compression and decompression. The rate of compression is derived using an entanglement assisted protocol with classical communication, and under an unproved conjecture that the rate function is convex in the distortion parameter. The optimum channel achieving this rate for a given input state is characterised. The conceptual difficulties arising due to differences in the mathematical formalism between quantum and classical probability theory are discussed and solutions are presented.

Incorporation of Mn2+ into cobalt ferrite via sol–gel method: insights on induced changes in the structural, thermal, dielectric, and magnetic properties

Precise tailoring of nanostructured cobalt ferrite paves the way to design and develop devices for stress and noncontact torque sensors. Herein, Mn2+ ions are inserted into cobalt ferrite with different ratios using a facile sol–gel method. The as-synthesized ferrites are characterized via energy dispersive X-ray (EDX), Fourier transforms infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), high resolution transmission electron microscope (HR-TEM), thermogravimetric analysis (TGA), electrochemical impedance spectroscopy (EIS), and vibrating sample magnetometer (VSM). EDX analyses affirm the stoichiometry of the synthesized samples with the intended ratios. The FTIR and XRD prove the presence of a single-phase cubic spinel structure for all as-synthesized samples. The dislocation, the inter-chain distance and the distortion parameter values decrease with increasing Mn2+ content, which outweigh the improvement of the crystal structure of the doped CFO samples. SEM micrographs illustrate that the incorporation of Mn2+ significantly soars the porosity of the samples. TEM images reveal that the samples comprise particles in the nanometer range with spherical shape and porous nature. Thermal analyses show that the weight loss is dependent on Mn2+ content in the sample. For instance, at x = 0, a slight variation in the weight loss estimated by 8% is observed while at x = 0.25 the weight loss has reached up to 40%. The dielectric losses (8 × 105) of Co0.5Mn0.5 Fe2O4 is enough to meet the demands of microwave applications. Finally, a reduction in the magnetization of the pure CFO from 68.419 emu g−1 to 50.307 emu g−1 is achieved at x = 0.25.

Analysis of Fish-Eye Lens Camera Self-Calibration

The fish-eye lens camera offers the advantage of efficient acquisition of image data through a wide field of view. However, unlike the popular perspective projection camera, a strong distortion effect appears as the periphery of the image is compressed. Such characteristics must be precisely analyzed through camera self-calibration. In this study, we carried out a fish-eye lens camera self-calibration while considering different types of test objects and projection models. Self-calibration was performed using the V-, A-, Plane-, and Room-type test objects. In the fish-eye lens camera, the V-type test object was the most advantageous for ensuring the accuracy of the principal point coordinates and focal length, because the correlations between parameters were relatively low. On the other hand, the other test objects were advantageous for ensuring the accuracy of distortion parameters because of the well-distributed image points. Based on the above analysis, we proposed, an accurate fish-eye lens camera self-calibration method that applies the V-type test object. The RMS-residuals of the proposed method were less than 1 pixel.

Delaunay simplices in diagonally distorted lattices

Delaunay protection is a measure of how far is a Delaunay triangulation from being degenerate. In this short paper we study the protection properties and other quality measures of the Delaunay triangulations of a family of lattices that is obtained by distorting the integer grid in Rd. We show that the quality measures of this family are maximized for a certain distortion parameter, and that for this parameter, the lattice is isometric to the permutahedral lattice, which is a well-known object in discrete geometry.

Baryon acoustic oscillation methods for generic curvature: application to the SDSS-III Baryon Oscillation Spectroscopic Survey

We develop methods for investigating baryon acoustic oscillation (BAO) features in cosmological models with non-trivial (but slowly varying) averaged spatial curvature: models that are not necessarily flat, close to flat, nor with constant spatial curvature. The class of models to which our methods apply include Lemaître-Tolman-Bondi models, modified gravity cosmologies, and inhomogeneous cosmologies with backreaction—in which we do not have a prediction of the shape of the spatial 2-point correlation function, but where we nevertheless expect to see a BAO feature in the present-day galaxy distribution, in form of an excess in the galaxy 2-point correlation function. We apply our methods to the Baryon Oscillation Spectroscopic Survey (BOSS) dataset, investigating both the Lambda Cold Dark Matter (ΛCDM) and timescape cosmological models as case studies. The correlation functions measured in the two fiducial models contain a similarly-pronounced BAO feature. We use the relative tangential and radial BAO scales to measure the anisotropic Alcock-Paczy'nski distortion parameter, ϵ, which is independent of the underlying BAO preferred scale. We find that ϵ is consistent with zero in both fiducial cosmologies, indicating that models with a different spatial curvature evolution can account for the relative positions of the tangential and radial BAO scale. We validate our methods using ΛCDM mocks.

The magnetotelluric impedance tensor through Clifford algebras: part I — theory

ABSTRACTThe magnetotelluric impedance tensor is analysed in the context of Clifford algebras. In this framework, the tensor is broken down into different parts, each one with a particular geometric algebra meaning, the simplicity of which allows us to deduce a number of known properties and opens up many other possibilities. As examples to show its capabilities, some of the algebraic relationships involving the impedance tensor, such as rotations, Mohr diagrams and phase tensor, are shown under this theory. Rotations are analysed in Clifford algebra and Mohr diagrams, and phase tensor are expressed in Clifford algebra . The galvanic distortion matrix and its transformations are also seen in Clifford algebra , where a number of relationships allow us to recognize the galvanic distortion in a measured two‐dimensional/three‐dimensional impedance tensor. These relationships are useful as constraints to determine the galvanic distortion parameters.

The magnetotelluric impedance tensor through Clifford algebras: part II — a constrained stochastic heuristic method for recovering the magnetotelluric regional impedance tensor in 2D/3D case

ABSTRACTA method for obtaining the galvanic distortion matrix is presented so that the regional impedance tensor (free of distortion) is recovered. The method is a constrained stochastic heuristic method, which consists in randomly exploring the space of the distortion parameters. Constraints are imposed on the shortest periods of the regional impedance tensor that, at these short periods, tends to be two dimensional (or one dimensional). Depending on the constraints used, two different methods to recover the regional impedance tensor in this 2D/3D case are presented. Method 1 needs to find the strike of the short periods and Method 2 applies to the measurement directions. Twist, shear and anisotropy parameters are obtained. Thus, the regional impedance tensor is recovered with the only exception being the vertical shift due to the gain, which is equal for all the components of the tensor. Examples with synthetic impedance tensors from 2D/3D models perturbed with galvanic distortion are presented to illustrate how the algorithm works. The presence of noise in data is considered and rules for proceeding are provided. The same examples perturbed by Gaussian noise together with experimental data illustrate the capabilities of the algorithm.

DR-GAN: Automatic Radial Distortion Rectification Using Conditional GAN in Real-Time

Radial distortion, which severely hinders object detection and semantic recognition, frequently exists in images captured using a wide-angle lens. Correction of this distortion of images is crucial in many computer vision applications. In this paper, we present distortion rectification generative adversarial network (DR-GAN), a conditional generative adversarial network (GAN) for automatic radial DR. To the best of our knowledge, this is the first end-to-end trainable adversarial framework for radial distortion rectification. The DR-GAN trained using the proposed low-to-high perceptual loss learns the mapping relation between different structural images rather than estimating multifarious distortion parameters, while also realizing label-free training and one-stage rectification. As a benefit of one-stage rectification, the proposed method is extremely fast with the completion of rectification in real time. This is approximately 22 times faster than the state-of-the-art methods. The experimental results show that the DR-GAN achieves an excellent performance in both quantitative measure (PSNR and SSIM) and visual qualitative appearance.

Image intensifier distortion influences a surgeon's ability to aim guidewires during orthopaedic procedures.

Accurate insertion of a guidewire under image intensifier guidance is a fundamental skill required by orthopaedic surgeons. This study investigated how image intensifier distortion, which is composed of pin-cushion and sigmoidal components, changed the apparent trajectory of a guidewire, and the resulting deviation between the intended and actual guidewire tip position. Intraoperative image intensifier images for 220 consecutive patients with hip fractures were retrospectively corrected for distortion using a global polynomial method. The deviation between the intended and actual guidewire tip positions was calculated. Additional distortion parameters were tested using an image intensifier produced by a different manufacturer, and a flat-panel c-arm. Deviation was approximately 1cm if the guidewire was aimed from the extremity of the image and almost 0 if the entry point was only 20% from the centre (p < 0.001). The direction of deviation was different for left and right hips, with average deviations measuring 3mm proximal and 5mm distal respectively (p < 0.001). The flat-panel c-arm almost completely eliminated distortion. Image intensifier distortion significantly altered the intended trajectory of a guidewire, with guidewires aimed from the image periphery more affected than guidewires aimed from the centre. Furthermore, for right hips, guidewires should be aimed distal to their intended position, and for left hips they should be aimed proximal to achieve their desired position. The flat-panel c-arm eliminated the effect of distortion; hence, it may be preferable if precision in guidewire positioning is vital.

Large-scale redshift space distortions in modified gravity theories

Measurements of redshift space distortions (RSD) provide a means to test models of gravity on large-scales. We use mock galaxy catalogues constructed from large N-body simulations of standard and modified gravity models to measure galaxy clustering in redshift space. We focus our attention on two of the most representative and popular families of modified gravity models: the Hu \& Sawicki $f(R)$ gravity and the normal branch of the DGP model. The galaxy catalogues are built using a halo occupation distribution (HOD) prescription with the HOD parameters in the modified gravity models tuned to match with the number density and the real-space clustering of {\sc boss-cmass} galaxies. We employ two approaches to model RSD: the first is based on linear perturbation theory and the second models non-linear effects on small-scales by assuming standard gravity and including biasing and RSD effects. We measure the monopole to real-space correlation function ratio, the quadrupole to monopole ratio, clustering wedges and multipoles of the correlation function and use these statistics to find the constraints on the distortion parameter, $\beta$. We find that the linear model fails to reproduce the N-body simulation results and the true value of $\beta$ on scales $s < 40\Mpch$, while the non-linear modelling of RSD recovers the value of $\beta$ on the scales of interest for all models. RSD on large scales ($s\gtrsim20$-$40\Mpch$) have been found to show significant deviations from the prediction of standard gravity in the DGP models. However, the potential to use RSD to constrain $f(R)$ models is less promising, due to the different screening mechanism in this model.

Simulation Study on Noise Reduction Performance of Thickness of Sound Absorber Films in Industrial Gas Turbine Muffler

The simulated model of industrial gas turbine muffle is established to study the influence of sound absorber films for noise reduction performance. By the analysis of the Finite Element Model, the results show when the thickness of sound absorbing films increases to a certain extent, the flow pressure increases, the flow space decreases, and the flow velocity in the muffler increases, which reduces the distortion parameters and enhances the flow uniformity.

Robust Line-Based Radial Distortion Estimation From a Single Image

The pinhole model utilized in most computer vision algorithms becomes unfeasible because of lens distortion. Thus it is a must to compensate lens distortion to make the pinhole model available. In this paper, we propose a new robust line-based distortion estimation method to correct radial distortion. Our method works from a single image and is able to estimate the distortion center rather than assuming it is at the image center. Distortion parameters are estimated from parameters of circulars arcs, on the basis that straight lines are imaged as circular arcs under one-parameter division model. A new feature selection scheme by refining circular arcs is introduced to make the process of distortion estimation fully automatic and more robust. Moreover, a linear optimization algorithm is applied to calculating parameters in each selection run, making our feature selection scheme more efficient. Experiments on synthetic images and real images show that our method performs well in radial distortion estimation even with severely distorted images.