Improvement of vector compensation method for vehicle magnetic distortion field

International Nuclear Information System (INIS)

Pang, Hongfeng; Zhang, Qi; Li, Ji; Luo, Shitu; Chen, Dixiang; Pan, Mengchun; Luo, Feilu

2014-01-01

Magnetic distortions such as eddy-current field and low frequency magnetic field have not been considered in vector compensation methods. A new compensation method is proposed to suppress these magnetic distortions and improve compensation performance, in which the magnetic distortions related to measurement vectors and time are considered. The experimental system mainly consists of a three-axis fluxgate magnetometer (DM-050), an underwater vehicle and a proton magnetometer, in which the scalar value of magnetic field is obtained with the proton magnetometer and considered to be the true value. Comparing with traditional compensation methods, experimental results show that the magnetic distortions can be further reduced by two times. After compensation, error intensity and RMS error are reduced from 11684.013 nT and 7794.604 nT to 16.219 nT and 5.907 nT respectively. It suggests an effective way to improve the compensation performance of magnetic distortions. - Highlights: • A new vector compensation method is proposed for vehicle magnetic distortion. • The proposed model not only includes magnetometer error but also considers magnetic distortion. • Compensation parameters are computed directly by solving nonlinear equations. • Compared with traditional methods, the proposed method is not related with rotation angle rate. • Error intensity and RMS error can be reduced to 1/2 of the error with traditional methods

Color correction for chromatic distortion in a multi-wavelength digital holographic system

International Nuclear Information System (INIS)

Lin, Li-Chien; Huang, Yi-Lun; Tu, Han-Yen; Lai, Xin-Ji; Cheng, Chau-Jern

2011-01-01

A multi-wavelength digital holographic (MWDH) system has been developed to record and reconstruct color images. In comparison to working with digital cameras, however, high-quality color reproduction is difficult to achieve, because of the imperfections from the light sources, optical components, optical recording devices and recording processes. Thus, we face the problem of correcting the colors altered during the digital holographic process. We therefore propose a color correction scheme to correct the chromatic distortion caused by the MWDH system. The scheme consists of two steps: (1) creating a color correction profile and (2) applying it to the correction of the distorted colors. To create the color correction profile, we generate two algorithms: the sequential algorithm and the integrated algorithm. The ColorChecker is used to generate the distorted colors and their desired corrected colors. The relationship between these two color patches is fixed into a specific mathematical model, the parameters of which are estimated, creating the profile. Next, the profile is used to correct the color distortion of images, capturing and preserving the original vibrancy of the reproduced colors for different reconstructed images

Effects of Field-Map Distortion Correction on Resting State Functional Connectivity MRI

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Hiroki Togo

2017-12-01

Full Text Available Magnetic field inhomogeneities cause geometric distortions of echo planar images used for functional magnetic resonance imaging (fMRI. To reduce this problem, distortion correction (DC with field map is widely used for both task and resting-state fMRI (rs-fMRI. Although DC with field map has been reported to improve the quality of task fMRI, little is known about its effects on rs-fMRI. Here, we tested the influence of field-map DC on rs-fMRI results using two rs-fMRI datasets derived from 40 healthy subjects: one with DC (DC+ and the other without correction (DC−. Independent component analysis followed by the dual regression approach was used for evaluation of resting-state functional connectivity networks (RSN. We also obtained the ratio of low-frequency to high-frequency signal power (0.01–0.1 Hz and above 0.1 Hz, respectively; LFHF ratio to assess the quality of rs-fMRI signals. For comparison of RSN between DC+ and DC− datasets, the default mode network showed more robust functional connectivity in the DC+ dataset than the DC− dataset. Basal ganglia RSN showed some decreases in functional connectivity primarily in white matter, indicating imperfect registration/normalization without DC. Supplementary seed-based and simulation analyses supported the utility of DC. Furthermore, we found a higher LFHF ratio after field map correction in the anterior cingulate cortex, posterior cingulate cortex, ventral striatum, and cerebellum. In conclusion, field map DC improved detection of functional connectivity derived from low-frequency rs-fMRI signals. We encourage researchers to include a DC step in the preprocessing pipeline of rs-fMRI analysis.

Multiview Trajectory Mapping Using Homography with Lens Distortion Correction

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Andrea Cavallaro

2008-11-01

Full Text Available We present a trajectory mapping algorithm for a distributed camera setting that is based on statistical homography estimation accounting for the distortion introduced by camera lenses. Unlike traditional approaches based on the direct linear transformation (DLT algorithm and singular value decomposition (SVD, the planar homography estimation is derived from renormalization. In addition to this, the algorithm explicitly introduces a correction parameter to account for the nonlinear radial lens distortion, thus improving the accuracy of the transformation. We demonstrate the proposed algorithm by generating mosaics of the observed scenes and by registering the spatial locations of moving objects (trajectories from multiple cameras on the mosaics. Moreover, we objectively compare the transformed trajectories with those obtained by SVD and least mean square (LMS methods on standard datasets and demonstrate the advantages of the renormalization and the lens distortion correction.

Multiview Trajectory Mapping Using Homography with Lens Distortion Correction

Directory of Open Access Journals (Sweden)

Kayumbi Gabin

2008-01-01

Full Text Available Abstract We present a trajectory mapping algorithm for a distributed camera setting that is based on statistical homography estimation accounting for the distortion introduced by camera lenses. Unlike traditional approaches based on the direct linear transformation (DLT algorithm and singular value decomposition (SVD, the planar homography estimation is derived from renormalization. In addition to this, the algorithm explicitly introduces a correction parameter to account for the nonlinear radial lens distortion, thus improving the accuracy of the transformation. We demonstrate the proposed algorithm by generating mosaics of the observed scenes and by registering the spatial locations of moving objects (trajectories from multiple cameras on the mosaics. Moreover, we objectively compare the transformed trajectories with those obtained by SVD and least mean square (LMS methods on standard datasets and demonstrate the advantages of the renormalization and the lens distortion correction.

Harmonic analysis for the characterization and correction of geometric distortion in MRI.

Science.gov (United States)

Tadic, Tony; Jaffray, David A; Stanescu, Teodor

2014-11-01

Magnetic resonance imaging (MRI) is gaining widespread use in radiation therapy planning, patient setup verification, and real-time guidance of radiation delivery. Successful implementation of these technologies relies on the development of simple and efficient methods to characterize and monitor the geometric distortions arising due to system imperfections and gradient nonlinearities. To this end, the authors present the theory and validation of a novel harmonic approach to the quantification of system-related distortions in MRI. The theory of spatial encoding in MRI is applied to demonstrate that the 3D distortion vector field (DVF) is given by the solution of a second-order boundary value problem (BVP). This BVP is comprised of Laplace's equation and a limited measurement of the distortion on the boundary of a specified region of interest (ROI). An analytical series expansion solving this BVP within a spherical ROI is obtained, and a statistical uncertainty analysis is performed to determine how random errors in the boundary measurements propagate to the ROI interior. This series expansion is then evaluated to obtain volumetric DVF mappings that are compared to reference data obtained on a 3 T full-body scanner. This validation is performed within two spheres of 20 cm diameter (one centered at the scanner origin and the other offset +3 cm along each of the transverse directions). Initially, a high-order mapping requiring measurements at 5810 boundary points is used. Then, after exploring the impact of the boundary sampling density and the effect of series truncation, a reduced-order mapping requiring measurements at 302 boundary points is evaluated. The volumetric DVF mappings obtained from the harmonic analysis are in good agreement with the reference data. Following distortion correction using the high-order mapping, the authors estimate a reduction in the mean distortion magnitude from 0.86 to 0.42 mm and from 0.93 to 0.39 mm within the central and offset

A high precision recipe for correcting images distorted by a tapered fiber optic

International Nuclear Information System (INIS)

Islam, M Sirajul; Kitchen, M J; Lewis, R A; Uesugi, K

2010-01-01

Images captured with a tapered fiber optic camera show significant spatial distortion mainly because the spatial orientation of the fiber bundles is not identical at each end of the taper. We present three different techniques for the automatic distortion correction of images acquired with a charge-coupled device (CCD) camera bonded to a tapered optical fiber. In this paper we report - (i) comparison of various methods for distortion correction (ii) extensive quantitative analysis of the techniques and (iii) experiments carried out using a high resolution fiber optic camera. A pinhole array was used to find control points in the distorted image space. These control points were then associated with their known true coordinates. To apply geometric correction, three different approaches were investigated - global polynomial fitting, local polynomial fitting and triangulated interpolation. Sub-pixel accuracy was achieved in all approaches, but the experimental results reveal that the triangulated interpolation gave the most satisfactory result for the distortion correction. The effect of proper alignment of the mask with the fiber optic taper (FOT) camera was also investigated. It was found that the overall dewarping error is minimal when the mask is almost parallel to the CCD.

Characterization of tissue magnetic susceptibility-induced distortions for MRIgRT

International Nuclear Information System (INIS)

Stanescu, T.; Wachowicz, K.; Jaffray, D. A.

2012-01-01

Purpose: MR image geometric integrity is one of the building blocks of MRI-guided radiotherapy. In particular, tissue magnetic susceptibility-induced effects are patient-dependent and their behavior is difficult to assess and predict. In this study, the authors investigated in detail the characteristics of susceptibility (χ) distortions in the context of MRIgRT, including the case of two common MR-linac system configurations. Methods: The magnetic field distortions were numerically simulated for several imaging parameters and anatomical sites, i.e., brain, lung, pelvis (with air pockets), and prostate. The simulation process consisted of (a) segmentation of patient CT data into susceptibility relevant anatomical volumes (i.e., soft-tissue, bone and air/lung), (b) conversion of CT data into susceptibility masks by assigning bulk χ values to the structures defined at (a), (c) numerical computations of the local magnetic fields by using a finite difference algorithm, and (d) generation of the geometric distortion maps from the magnetic field distributions. For each patient anatomy, the distortions were quantified at the interfaces of anatomical structures with significantly different χ values. The analysis was performed for two specific orientations of the external main magnetic field (B 0 ) characteristic to the MR-linac systems, specifically along the z-axis for a bore MR scanner and in the (x,y)-plane for a biplanner magnet. The magnetic field local perturbations were reported in ppm. The metrics used to quantify the geometric distortions were the maximum, mean, and range of distortions. The numerical simulation algorithm was validated using phantom data measurements. Results: Susceptibility-induced distortions were determined for both quadratic and patient specific geometries. The numerical simulations showed a good agreement with the experimental data. The measurements were acquired at 1.5 and 3 T and with an encoding gradient varying between 3 and 20 mT/m by

Characterization of tissue magnetic susceptibility-induced distortions for MRIgRT.

Science.gov (United States)

Stanescu, T; Wachowicz, K; Jaffray, D A

2012-12-01

MR image geometric integrity is one of the building blocks of MRI-guided radiotherapy. In particular, tissue magnetic susceptibility-induced effects are patient-dependent and their behavior is difficult to assess and predict. In this study, the authors investigated in detail the characteristics of susceptibility (χ) distortions in the context of MRIgRT, including the case of two common MR-linac system configurations. The magnetic field distortions were numerically simulated for several imaging parameters and anatomical sites, i.e., brain, lung, pelvis (with air pockets), and prostate. The simulation process consisted of (a) segmentation of patient CT data into susceptibility relevant anatomical volumes (i.e., soft-tissue, bone and air∕lung), (b) conversion of CT data into susceptibility masks by assigning bulk χ values to the structures defined at (a), (c) numerical computations of the local magnetic fields by using a finite difference algorithm, and (d) generation of the geometric distortion maps from the magnetic field distributions. For each patient anatomy, the distortions were quantified at the interfaces of anatomical structures with significantly different χ values. The analysis was performed for two specific orientations of the external main magnetic field (B(0)) characteristic to the MR-linac systems, specifically along the z-axis for a bore MR scanner and in the (x,y)-plane for a biplanner magnet. The magnetic field local perturbations were reported in ppm. The metrics used to quantify the geometric distortions were the maximum, mean, and range of distortions. The numerical simulation algorithm was validated using phantom data measurements. Susceptibility-induced distortions were determined for both quadratic and patient specific geometries. The numerical simulations showed a good agreement with the experimental data. The measurements were acquired at 1.5 and 3 T and with an encoding gradient varying between 3 and 20 mT∕m by using an annular

Harmonic analysis for the characterization and correction of geometric distortion in MRI

International Nuclear Information System (INIS)

Tadic, Tony; Stanescu, Teodor; Jaffray, David A.

2014-01-01

Purpose: Magnetic resonance imaging (MRI) is gaining widespread use in radiation therapy planning, patient setup verification, and real-time guidance of radiation delivery. Successful implementation of these technologies relies on the development of simple and efficient methods to characterize and monitor the geometric distortions arising due to system imperfections and gradient nonlinearities. To this end, the authors present the theory and validation of a novel harmonic approach to the quantification of system-related distortions in MRI. Methods: The theory of spatial encoding in MRI is applied to demonstrate that the 3D distortion vector field (DVF) is given by the solution of a second-order boundary value problem (BVP). This BVP is comprised of Laplace’s equation and a limited measurement of the distortion on the boundary of a specified region of interest (ROI). An analytical series expansion solving this BVP within a spherical ROI is obtained, and a statistical uncertainty analysis is performed to determine how random errors in the boundary measurements propagate to the ROI interior. This series expansion is then evaluated to obtain volumetric DVF mappings that are compared to reference data obtained on a 3 T full-body scanner. This validation is performed within two spheres of 20 cm diameter (one centered at the scanner origin and the other offset +3 cm along each of the transverse directions). Initially, a high-order mapping requiring measurements at 5810 boundary points is used. Then, after exploring the impact of the boundary sampling density and the effect of series truncation, a reduced-order mapping requiring measurements at 302 boundary points is evaluated. Results: The volumetric DVF mappings obtained from the harmonic analysis are in good agreement with the reference data. Following distortion correction using the high-order mapping, the authors estimate a reduction in the mean distortion magnitude from 0.86 to 0.42 mm and from 0.93 to 0.39 mm

Distortion correction algorithm for UAV remote sensing image based on CUDA

International Nuclear Information System (INIS)

Wenhao, Zhang; Yingcheng, Li; Delong, Li; Changsheng, Teng; Jin, Liu

2014-01-01

In China, natural disasters are characterized by wide distribution, severe destruction and high impact range, and they cause significant property damage and casualties every year. Following a disaster, timely and accurate acquisition of geospatial information can provide an important basis for disaster assessment, emergency relief, and reconstruction. In recent years, Unmanned Aerial Vehicle (UAV) remote sensing systems have played an important role in major natural disasters, with UAVs becoming an important technique of obtaining disaster information. UAV is equipped with a non-metric digital camera with lens distortion, resulting in larger geometric deformation for acquired images, and affecting the accuracy of subsequent processing. The slow speed of the traditional CPU-based distortion correction algorithm cannot meet the requirements of disaster emergencies. Therefore, we propose a Compute Unified Device Architecture (CUDA)-based image distortion correction algorithm for UAV remote sensing, which takes advantage of the powerful parallel processing capability of the GPU, greatly improving the efficiency of distortion correction. Our experiments show that, compared with traditional CPU algorithms and regardless of image loading and saving times, the maximum acceleration ratio using our proposed algorithm reaches 58 times that using the traditional algorithm. Thus, data processing time can be reduced by one to two hours, thereby considerably improving disaster emergency response capability

Correcting geometric and photometric distortion of document images on a smartphone

Science.gov (United States)

Simon, Christian; Williem; Park, In Kyu

2015-01-01

A set of document image processing algorithms for improving the optical character recognition (OCR) capability of smartphone applications is presented. The scope of the problem covers the geometric and photometric distortion correction of document images. The proposed framework was developed to satisfy industrial requirements. It is implemented on an off-the-shelf smartphone with limited resources in terms of speed and memory. Geometric distortions, i.e., skew and perspective distortion, are corrected by sending horizontal and vertical vanishing points toward infinity in a downsampled image. Photometric distortion includes image degradation from moiré pattern noise and specular highlights. Moiré pattern noise is removed using low-pass filters with different sizes independently applied to the background and text region. The contrast of the text in a specular highlighted area is enhanced by locally enlarging the intensity difference between the background and text while the noise is suppressed. Intensive experiments indicate that the proposed methods show a consistent and robust performance on a smartphone with a runtime of less than 1 s.

Correction for polychromatic X-ray image distortion in computer tomography images

International Nuclear Information System (INIS)

1979-01-01

A method and apparatus are described which correct the polychromatic distortion of CT images that is produced by the non-linear interaction of body constituents with a polychromatic X-ray beam. A CT image is processed to estimate the proportion of the attenuation coefficients of the constituents in each pixel element. A multiplicity of projections for each constituent are generated from the original image and are combined utilizing a multidimensional polynomial which approximates the non-linear interaction involved. An error image is then generated from the combined projections and is subtracted from the original image to correct for the polychromatic distortion. (Auth.)

Radial lens distortion correction with sub-pixel accuracy for X-ray micro-tomography.

Science.gov (United States)

Vo, Nghia T; Atwood, Robert C; Drakopoulos, Michael

2015-12-14

Distortion correction or camera calibration for an imaging system which is highly configurable and requires frequent disassembly for maintenance or replacement of parts needs a speedy method for recalibration. Here we present direct techniques for calculating distortion parameters of a non-linear model based on the correct determination of the center of distortion. These techniques are fast, very easy to implement, and accurate at sub-pixel level. The implementation at the X-ray tomography system of the I12 beamline, Diamond Light Source, which strictly requires sub-pixel accuracy, shows excellent performance in the calibration image and in the reconstructed images.

Magnetic distortion in motion labs, implications for validating inertial magnetic sensors

NARCIS (Netherlands)

de Vries, W.H.; Veeger, H.E.J.; Baten, C.T.M.; Helm, F.C.

2009-01-01

Background: Ambulatory 3D orientation estimation with Inertial Magnetic Sensor Units (IMU's) use the earth magnetic field. The magnitude of distortion in orientation in a standard equipped motion lab and its effect on the accuracy of the orientation estimation with IMU's is addressed. Methods:

Magnetic distortion in motion labs, implications for validating inertial magnetic sensors.

NARCIS (Netherlands)

Vries, W.H. de; Veeger, H.E.; Baten, C.T.; Helm, F.C.T. van der

2009-01-01

BACKGROUND: Ambulatory 3D orientation estimation with Inertial Magnetic Sensor Units (IMU's) use the earth magnetic field. The magnitude of distortion in orientation in a standard equipped motion lab and its effect on the accuracy of the orientation estimation with IMU's is addressed. METHODS:

Reducing Field Distortion in Magnetic Resonance Imaging

Science.gov (United States)

Eom, Byeong Ho; Penanen, Konstantin; Hahn, Inseob

2010-01-01

A concept for a magnetic resonance imaging (MRI) system that would utilize a relatively weak magnetic field provides for several design features that differ significantly from the corresponding features of conventional MRI systems. Notable among these features are a magnetic-field configuration that reduces (relative to the conventional configuration) distortion and blurring of the image, the use of a superconducting quantum interference device (SQUID) magnetometer as the detector, and an imaging procedure suited for the unconventional field configuration and sensor. In a typical application of MRI, a radio-frequency pulse is used to excite precession of the magnetic moments of protons in an applied magnetic field, and the decaying precession is detected for a short time following the pulse. The precession occurs at a resonance frequency proportional to the strengths of the magnetic field and the proton magnetic moment. The magnetic field is configured to vary with position in a known way; hence, by virtue of the aforesaid proportionality, the resonance frequency varies with position in a known way. In other words, position is encoded as resonance frequency. MRI using magnetic fields weaker than those of conventional MRI offers several advantages, including cheaper and smaller equipment, greater compatibility with metallic objects, and higher image quality because of low susceptibility distortion and enhanced spin-lattice-relaxation- time contrast. SQUID MRI is being developed into a practical MRI method for applied magnetic flux densities of the order of only 100 T

[Signal analysis and spectrum distortion correction for tunable diode laser absorption spectroscopy system].

Science.gov (United States)

Bao, Wei-Yi; Zhu, Yong; Chen, Jun; Chen, Jun-Qing; Liang, Bo

2011-04-01

In the present paper, the signal of a tunable diode laser absorption spectroscopy (TDLAS) trace gas sensing system, which has a wavelength modulation with a wide range of modulation amplitudes, is studied based on Fourier analysis method. Theory explanation of spectrum distortion induced by laser intensity amplitude modulation is given. In order to rectify the spectrum distortion, a method of synchronous amplitude modulation suppression by a variable optical attenuator is proposed. To validate the method, an experimental setup is designed. Absorption spectrum measurement experiments on CO2 gas were carried out. The results show that the residual laser intensity modulation amplitude of the experimental system is reduced to -0.1% of its original value and the spectrum distortion improvement is 92% with the synchronous amplitude modulation suppression. The modulation amplitude of laser intensity can be effectively reduced and the spectrum distortion can be well corrected by using the given correction method and system. By using a variable optical attenuator in the TDLAS (tunable diode laser absorption spectroscopy) system, the dynamic range requirements of photoelectric detector, digital to analog converter, filters and other aspects of the TDLAS system are reduced. This spectrum distortion correction method can be used for online trace gas analyzing in process industry.

An Iterative Optimization Algorithm for Lens Distortion Correction Using Two-Parameter Models

Directory of Open Access Journals (Sweden)

Daniel Santana-Cedrés

2016-12-01

Full Text Available We present a method for the automatic estimation of two-parameter radial distortion models, considering polynomial as well as division models. The method first detects the longest distorted lines within the image by applying the Hough transform enriched with a radial distortion parameter. From these lines, the first distortion parameter is estimated, then we initialize the second distortion parameter to zero and the two-parameter model is embedded into an iterative nonlinear optimization process to improve the estimation. This optimization aims at reducing the distance from the edge points to the lines, adjusting two distortion parameters as well as the coordinates of the center of distortion. Furthermore, this allows detecting more points belonging to the distorted lines, so that the Hough transform is iteratively repeated to extract a better set of lines until no improvement is achieved. We present some experiments on real images with significant distortion to show the ability of the proposed approach to automatically correct this type of distortion as well as a comparison between the polynomial and division models.

Correction of distortion of MR pictures for MR-guided robotic sterotactic procedures

International Nuclear Information System (INIS)

Jonckheere, E.A.; Kwoh, Y.S.

1988-01-01

Ever since magnetic resonance (MR) invaded the medical imaging field, it has played an increasingly important role and is even currently being considered for stereotactic guidance of probes in the brain. While MR pictures indeed convey more clinical information than CT, the geometry of MR pictures is, unfortunately, not as accurate as the geometry of CT pictures. In other words, if a square grid phantom is scanned, then the CT picture will show a square grid, while the MR picture will rather reveal a distorted grid. This distortion is primarily due to small variations in the static magnetic field. This small distortion does not impede radiological diagnosis; however, it is a source of concern if one contemplates utilizing the MR pictures for accurate stereotactic positioning of a probe at a very precise point in the brain. Another area of application where the distortion of the MR picture should be compensated for is the superposition of CT and MR pictures so that both informations could be used for diagnosis or stereotactic purposes. This paper essentially addresses the nonlinear distortion of MR pictures and how it could be compensated for through software manipulation of the MR picture

Diffusion tensor imaging of the brain. Effects of distortion correction with correspondence to numbers of encoding directions

International Nuclear Information System (INIS)

Yoshikawa, Takeharu; Aoki, Shigeki; Abe, Osamu; Hayashi, Naoto; Masutani, Yoshitaka; Masumoto, Tomohiko; Mori, Harushi; Satake, Yoshiroh; Ohtomo, Kuni

2008-01-01

The aim of the study was to estimate the effect of distortion correction with correspondence to numbers of encoding directions to acquire diffusion tensor imaging (DTI) of improved quality. Ten volunteers underwent DTI of the head using echo planar imaging with 6, 13, 27, and 55 encoding directions. Fractional anisotropy (FA) maps and apparent diffusion coefficient (ADC) maps were created before and after distortion correction. Regions of interest were placed in the corpus callosum on each map, and standard deviations of FA and ADC were calculated. FA maps were also evaluated visually by experienced neuroradiologists. Dispersion of standard deviations tended to be reduced after distortion correction, with significant differences found in FA maps with 6 encoding directions, ADC maps with 6 directions, and ADC maps with 13 directions (P<0.001, P<0.005, and P<0.05, respectively). Visual image quality was improved after distortion correction (P<0.01 for all of the visual comparisons). Distortion correction is effective in providing DTI of enhanced quality, notwithstanding the number of encoding directions. (author)

Quantitative studies with the gamma-camera: correction for spatial and energy distortion

International Nuclear Information System (INIS)

Soussaline, F.; Todd-Pokropek, A.E.; Raynaud, C.

1977-01-01

The gamma camera sensitivity distribution is an important source of error in quantitative studies. In addition, spatial distortion produces apparent variations in count density which degrades quantitative studies. The flood field image takes into account both effects and is influenced by the pile-up of the tail distribution. It is essential to measure separately each of these parameters. These were investigated using a point source displaced by a special scanning table with two X, Y stepping motors of 10 micron precision. The spatial distribution of the sensitivity, spatial distortion and photopeak in the field of view were measured and compared for different setting-up of the camera and PM gains. For well-tuned cameras, the sensitivity is fairly constant, while the variations appearing in the flood field image are primarily due to spatial distortion, the former more dependent than the latter on the energy window setting. This indicates why conventional flood field uniformity correction must not be applied. A correction technique to improve the results in quantitative studies has been tested using a continuously matched energy window at every point within the field. A method for correcting spatial distortion is also proposed, where, after an adequately sampled measurement of this error, a transformation can be applied to calculate the true position of events. The knowledge of the magnitude of these parameters is essential in the routine use and design of detector systems

Implementation and Application of PSF-Based EPI Distortion Correction to High Field Animal Imaging

Directory of Open Access Journals (Sweden)

Dominik Paul

2009-01-01

Full Text Available The purpose of this work is to demonstrate the functionality and performance of a PSF-based geometric distortion correction for high-field functional animal EPI. The EPI method was extended to measure the PSF and a postprocessing chain was implemented in Matlab for offline distortion correction. The correction procedure was applied to phantom and in vivo imaging of mice and rats at 9.4T using different SE-EPI and DWI-EPI protocols. Results show the significant improvement in image quality for single- and multishot EPI. Using a reduced FOV in the PSF encoding direction clearly reduced the acquisition time for PSF data by an acceleration factor of 2 or 4, without affecting the correction quality.

The magnetic-distortion probe: velocimetry in conducting fluids.

Science.gov (United States)

Miralles, Sophie; Verhille, Gautier; Plihon, Nicolas; Pinton, Jean-François

2011-09-01

A new type of velocimeter, capable of local velocity measurements in conducting fluids, is introduced. The principle of the "magnetic-distortion probe" is based on the measurement of the induced magnetic field by the flow of a conducting fluid in the vicinity of a localized magnetic field. The new velocimeter has no moving parts, and can be enclosed in a sealed cap, easing the implementation in harsh environments, such as liquid metals. The proposed method allows one to probe both the continuous part and fluctuations of the velocity, the temporal and spatial resolution being linked to the actual geometric configuration of the probe. A prototype probe has been tested in a gallinstan pipe flow and in a fully turbulent flow of liquid gallium generated by the counter rotation of two coaxial impellers in a cylinder. The signals have been compared to a reference potential probe and show very good agreement both for time-averaged velocities and turbulent fluctuations. The prototype is shown to detect motion from a few cm s(-1) to a few m s(-1). Moreover, the use of the magnetic-distortion probe with large-scale applied magnetic field is discussed. © 2011 American Institute of Physics

Experimental evaluation of indoor magnetic distortion effects on gait analysis performed with wearable inertial sensors

International Nuclear Information System (INIS)

Palermo, E; Patanè, F; Cappa, P; Rossi, S

2014-01-01

Magnetic inertial measurement unit systems (MIMU) offer the potential to perform joint kinematics evaluation as an alternative to optoelectronic systems (OS). Several studies have reported the effect of indoor magnetic field disturbances on the MIMU's heading output, even though the overall effect on the evaluation of lower limb joint kinematics is not yet fully explored. The aim of the study is to assess the influence of indoor magnetic field distortion on gait analysis trials conducted with a commercial MIMU system. A healthy adult performed gait analysis sessions both indoors and outdoors. Data collected indoors were post-processed with and without a heading correction methodology performed with OS at the start of the gait trial. The performance of the MIMU system is characterized in terms of indices, based on the mean value of lower limb joint angles and the associated ROM, quantifying the system repeatability. We find that the effects of magnetic field distortion, such as the one we experienced in our lab, were limited to the transverse plane of each joint and to the frontal plane of the ankle. Sagittal plane values, instead, showed sufficient repeatability moving from outdoors to indoors. Our findings provide indications to clinicians on MIMU performance in the measurement of lower limb kinematics. (paper)

Self-consistent EXAFS PDF Projection Method by Matched Correction of Fourier Filter Signal Distortion

International Nuclear Information System (INIS)

Lee, Jay Min; Yang, Dong-Seok

2007-01-01

Inverse problem solving computation was performed for solving PDF (pair distribution function) from simulated data EXAFS based on data FEFF. For a realistic comparison with experimental data, we chose a model of the first sub-shell Mn-0 pair showing the Jahn Teller distortion in crystalline LaMnO3. To restore the Fourier filtering signal distortion, involved in the first sub-shell information isolated from higher shell contents, relevant distortion matching function was computed initially from the proximity model, and iteratively from the prior-guess during consecutive regularization computation. Adaptive computation of EXAFS background correction is an issue of algorithm development, but our preliminary test was performed under the simulated background correction perfectly excluding the higher shell interference. In our numerical result, efficient convergence of iterative solution indicates a self-consistent tendency that a true PDF solution is convinced as a counterpart of genuine chi-data, provided that a background correction function is iteratively solved using an extended algorithm of MEPP (Matched EXAFS PDF Projection) under development

Spatial Distortion in MRI-Guided Stereotactic Procedures: Evaluation in 1.5-, 3- and 7-Tesla MRI Scanners.

Science.gov (United States)

Neumann, Jan-Oliver; Giese, Henrik; Biller, Armin; Nagel, Armin M; Kiening, Karl

2015-01-01

Magnetic resonance imaging (MRI) is replacing computed tomography (CT) as the main imaging modality for stereotactic transformations. MRI is prone to spatial distortion artifacts, which can lead to inaccuracy in stereotactic procedures. Modern MRI systems provide distortion correction algorithms that may ameliorate this problem. This study investigates the different options of distortion correction using standard 1.5-, 3- and 7-tesla MRI scanners. A phantom was mounted on a stereotactic frame. One CT scan and three MRI scans were performed. At all three field strengths, two 3-dimensional sequences, volumetric interpolated breath-hold examination (VIBE) and magnetization-prepared rapid acquisition with gradient echo, were acquired, and automatic distortion correction was performed. Global stereotactic transformation of all 13 datasets was performed and two stereotactic planning workflows (MRI only vs. CT/MR image fusion) were subsequently analysed. Distortion correction on the 1.5- and 3-tesla scanners caused a considerable reduction in positional error. The effect was more pronounced when using the VIBE sequences. By using co-registration (CT/MR image fusion), even a lower positional error could be obtained. In ultra-high-field (7 T) MR imaging, distortion correction introduced even higher errors. However, the accuracy of non-corrected 7-tesla sequences was comparable to CT/MR image fusion 3-tesla imaging. MRI distortion correction algorithms can reduce positional errors by up to 60%. For stereotactic applications of utmost precision, we recommend a co-registration to an additional CT dataset. © 2015 S. Karger AG, Basel.

A distortion correction method for image intensifier and electronic portal images used in radiotherapy

Energy Technology Data Exchange (ETDEWEB)

Ioannidis, G T; Geramani, K N; Zamboglou, N [Strahlenklinik, Stadtische Kliniken Offenbach, Offenbach (Germany); Uzunoglu, N [Department of Electrical and Computer Engineering, National Technical University of Athens, Athens (Greece)

1999-12-31

At the most of radiation departments a simulator and an `on line` verification system of the treated volume, in form of an electronic portal imaging device (EPID), are available. Networking and digital handling (saving, archiving etc.) of the image information is a necessity in the image processing procedures in order to evaluate verification and simulation recordings at the computer screen. Distortion is on the other hand prerequisite for quantitative comparison of both image modalities. Another limitation factor, in order to make quantitative assertions, is the fact that the irradiation fields in radiotherapy are usually bigger than the field of view of an image intensifier. Several segments of the irradiation field must therefore be acquired. Using pattern recognition techniques these segments can be composed into a single image. In this paper a distortion correction method will be presented. The method is based upon a well defined Grid which is embedded during the registration process on the image. The video signal from the image intensifier is acquired and processed. The grid is then recognised using image processing techniques. Ideally if all grid points are recognised, various methods can be applied in order to correct the distortion. But in practice this is not the case. Overlapping structures (bones etc.) have as a consequence that not all of the grid points can be recognised. Mathematical models from the Graph theory are applied in order to reconstruct the whole grid. The deviation of the grid points positions from the rated value is then used to calculate correction coefficients. This method (well defined grid, grid recognition, correction factors) can also be applied in verification images from the EPID or in other image modalities, and therefore a quantitative comparison in radiation treatment is possible. The distortion correction method and the application on simulator images will be presented. (authors)

Effect of Jahn-Teller distortion on the short range magnetic order in copper ferrite

Energy Technology Data Exchange (ETDEWEB)

Abdellatif, M.H., E-mail: Mohamed.abdellatif@iit.it [Nanostrctures Department, Istituto Italiano di Tecnologia, via Morego 30, I-16163 Genova (Italy); Innocenti, Claudia [INSTM—Department of Chemistry, University of Florence, via della Lastruccia 3, I-50019 Sesto Fiorentino, FI (Italy); Liakos, Ioannis [Nanostrctures Department, Istituto Italiano di Tecnologia, via Morego 30, I-16163 Genova (Italy); Scarpellini, Alice; Marras, Sergio [Nanochemistry Department, Istituto Italiano di Tecnologia, via Morego 30, I-16163 Genova (Italy); Salerno, Marco [Nanostrctures Department, Istituto Italiano di Tecnologia, via Morego 30, I-16163 Genova (Italy)

2017-02-15

Copper ferrite of spinel crystal structure was synthesized in the form of nano-particles using citrate-gel auto-combustion method. The sample morphology and composition were identified using scanning electron microscopy, X-ray diffraction, and X-ray spectroscopy. The latter technique reveals an inverse spinel structure with Jahn-Teller tetragonal distortion. The static magnetization was measured using vibrating sample magnetometer. Magnetic force microscopy was used in combination with the magnetization data to demonstrate the finite size effect of the magnetic spins and their casting behavior due to the introduction of copper ions in the tetrahedral magnetic sub-lattices, which results in tetragonal distorting the spinel structure of the copper ferrite. The magnetic properties of materials are a result of the collective behavior of the magnetic spins, and magnetic force microscopy can probe the collective behavior of the magnetic spins in copper ferrite, yet providing a sufficient resolution to map the effects below the micrometer size scale, such as the magnetic spin canting. A theoretical study was done to clarify the finite size effect of Jahn-Teller distortion on the magnetic properties of the material. When the particles are in the nano-scale, below the single domain size, their magnetic properties are very sensitive to their size change. - Highlights: • The spin canting due to Jahn-Teller distortion in Copper ferrite can be detected using magnetic force microscope. • The contrast in the magnetic AFM image can be analyzed to give information not only about the surface spins but also about the canting of the core spins inside the aggregated cluster of magnetic nanoparticle.

Correction of projective distortion in long-image-sequence mosaics without prior information

Science.gov (United States)

Yang, Chenhui; Mao, Hongwei; Abousleman, Glen; Si, Jennie

2010-04-01

Image mosaicking is the process of piecing together multiple video frames or still images from a moving camera to form a wide-area or panoramic view of the scene being imaged. Mosaics have widespread applications in many areas such as security surveillance, remote sensing, geographical exploration, agricultural field surveillance, virtual reality, digital video, and medical image analysis, among others. When mosaicking a large number of still images or video frames, the quality of the resulting mosaic is compromised by projective distortion. That is, during the mosaicking process, the image frames that are transformed and pasted to the mosaic become significantly scaled down and appear out of proportion with respect to the mosaic. As more frames continue to be transformed, important target information in the frames can be lost since the transformed frames become too small, which eventually leads to the inability to continue further. Some projective distortion correction techniques make use of prior information such as GPS information embedded within the image, or camera internal and external parameters. Alternatively, this paper proposes a new algorithm to reduce the projective distortion without using any prior information whatsoever. Based on the analysis of the projective distortion, we approximate the projective matrix that describes the transformation between image frames using an affine model. Using singular value decomposition, we can deduce the affine model scaling factor that is usually very close to 1. By resetting the image scale of the affine model to 1, the transformed image size remains unchanged. Even though the proposed correction introduces some error in the image matching, this error is typically acceptable and more importantly, the final mosaic preserves the original image size after transformation. We demonstrate the effectiveness of this new correction algorithm on two real-world unmanned air vehicle (UAV) sequences. The proposed method is

Distortion Correction for a Brewster Angle Microscope Using an Optical Grating.

Science.gov (United States)

Sun, Zhe; Zheng, Desheng; Baldelli, Steven

2017-02-21

A distortion-corrected Brewster angle microscope (DC-BAM) is designed, constructed, and tested based on the combination of an optical grating and a relay lens. Avoiding the drawbacks of most conventional BAM instruments, this configuration corrects the image propagation direction and consequently provides an image in focus over the entire field of view without any beam scanning or imaging reconstruction. This new BAM can be applied to both liquid and solid subphases with good spatial resolution in static and dynamic studies.

Image Registration to Compensate for EPI Distortion in Patients with Brain Tumors: An Evaluation of Tract-Specific Effects.

Science.gov (United States)

Albi, Angela; Meola, Antonio; Zhang, Fan; Kahali, Pegah; Rigolo, Laura; Tax, Chantal M W; Ciris, Pelin Aksit; Essayed, Walid I; Unadkat, Prashin; Norton, Isaiah; Rathi, Yogesh; Olubiyi, Olutayo; Golby, Alexandra J; O'Donnell, Lauren J

2018-03-01

Diffusion magnetic resonance imaging (dMRI) provides preoperative maps of neurosurgical patients' white matter tracts, but these maps suffer from echo-planar imaging (EPI) distortions caused by magnetic field inhomogeneities. In clinical neurosurgical planning, these distortions are generally not corrected and thus contribute to the uncertainty of fiber tracking. Multiple image processing pipelines have been proposed for image-registration-based EPI distortion correction in healthy subjects. In this article, we perform the first comparison of such pipelines in neurosurgical patient data. Five pipelines were tested in a retrospective clinical dMRI dataset of 9 patients with brain tumors. Pipelines differed in the choice of fixed and moving images and the similarity metric for image registration. Distortions were measured in two important tracts for neurosurgery, the arcuate fasciculus and corticospinal tracts. Significant differences in distortion estimates were found across processing pipelines. The most successful pipeline used dMRI baseline and T2-weighted images as inputs for distortion correction. This pipeline gave the most consistent distortion estimates across image resolutions and brain hemispheres. Quantitative results of mean tract distortions on the order of 1-2 mm are in line with other recent studies, supporting the potential need for distortion correction in neurosurgical planning. Novel results include significantly higher distortion estimates in the tumor hemisphere and greater effect of image resolution choice on results in the tumor hemisphere. Overall, this study demonstrates possible pitfalls and indicates that care should be taken when implementing EPI distortion correction in clinical settings. Copyright © 2018 by the American Society of Neuroimaging.

TPC track distortions III: fiat lux

CERN Document Server

Boyko, I; Dydak, F; Elagin, A; Gostkin, M; Guskov, A; Koreshev, V; Nefedov, Y; Nikolaev, K; Veenhof, R; Wotschack, J; Zhemchugov, A

2005-01-01

We present a comprehensive overview and final summary of all four types of static track distortions seen in the HARP TPC, in terms of physical origins, mathematical modelling, and correction algorithms. 'Static'™ distortions are defined as not depending on the event time within the 400 ms long accelerator spill. Calculated static distortions are compared with measurements from cosmic-muon tracks. We characterize track distortions by the r phi residuals of cluster positions with respect to the transverse projection of a helical trajectory constrained by hits in the RPC overlap regions. This method provides a fixed TPC-external reference system (by contrast to the co-moving coordinate system associated with a fit) which solely permits to identify individually, and measure quantitatively, the static TPC track distortions arising from (i) the inhomogeneity of the solenoidal magnetic field, (ii) the inhomogeneity of the electric field from the high-voltage mismatch between the inner and outer TPC field cages, (...

A method based on moving least squares for XRII image distortion correction

International Nuclear Information System (INIS)

Yan Shiju; Wang Chengtao; Ye Ming

2007-01-01

This paper presents a novel integrated method to correct geometric distortions of XRII (x-ray image intensifier) images. The method has been compared, in terms of mean-squared residual error measured at control and intermediate points, with two traditional local methods and a traditional global methods. The proposed method is based on the methods of moving least squares (MLS) and polynomial fitting. Extensive experiments were performed on simulated and real XRII images. In simulation, the effect of pincushion distortion, sigmoidal distortion, local distortion, noise, and the number of control points was tested. The traditional local methods were sensitive to pincushion and sigmoidal distortion. The traditional global method was only sensitive to sigmoidal distortion. The proposed method was found neither sensitive to pincushion distortion nor sensitive to sigmoidal distortion. The sensitivity of the proposed method to local distortion was lower than or comparable with that of the traditional global method. The sensitivity of the proposed method to noise was higher than that of all three traditional methods. Nevertheless, provided the standard deviation of noise was not greater than 0.1 pixels, accuracy of the proposed method is still higher than the traditional methods. The sensitivity of the proposed method to the number of control points was greatly lower than that of the traditional methods. Provided that a proper cutoff radius is chosen, accuracy of the proposed method is higher than that of the traditional methods. Experiments on real images, carried out by using a 9 in. XRII, showed that residual error of the proposed method (0.2544±0.2479 pixels) is lower than that of the traditional global method (0.4223±0.3879 pixels) and local methods (0.4555±0.3518 pixels and 0.3696±0.4019 pixels, respectively)

Correction of distortions in a discontinuous image

International Nuclear Information System (INIS)

Geagan, M.J.; Chase, B.B.; Muehllehner, G.

1994-01-01

Large area position-sensitive NaI detectors have been successfully applied to positron emission tomography (PET). Typical PET studies involve detector singles rates in excess of 500 kcps, which can lead to pile-up and image degradation as a function of countrate. Better high countrate performance can be achieved with a local centroid algorithm, in which the position of each event is calculated from a small group of photomultipliers (PMTs) immediately surrounding the PMT with the highest signal (the peak PMT). The local centroid contains most of the light from the scintillation. If a local centroid of only seven PMTs is used, the position resolution becomes quite stable at high countrates, however, discontinuities appear in the detector flood image as events cluster around each PMT. We therefore developed a method for distortion correction of a discontinuous flood image. For each PMT on the detector, a peak PMT domain is defined. The peak PMT domain is the area on the detector where that PMT could have the highest signal. The peak PMT domains overlap slightly, so that all combinations of peak PMT and position are represented. A collimated source is moved through a regular grid of points - a template - over each peak PMT region. A short collection is performed at each point, and the real and measured position data are recorded. For each point in the spatial range of a given PMT, distortion correction offsets are computed by interpolating between the data points which correspond to that PMT. This new method has been implemented and evaluated. System resolution has been measured at low and high countrates. The high countrate resolution is better with the new method, with no degradation in low countrate resolution. The axial sensitivity profile is also more stable at high countrates, compared to the previously developed method. 3-D brain phantom images show a clear improvement in image quality at high countrates. ((orig.))

Reproducing Electric Field Observations during Magnetic Storms by means of Rigorous 3-D Modelling and Distortion Matrix Co-estimation

Science.gov (United States)

Püthe, Christoph; Manoj, Chandrasekharan; Kuvshinov, Alexey

2015-04-01

Electric fields induced in the conducting Earth during magnetic storms drive currents in power transmission grids, telecommunication lines or buried pipelines. These geomagnetically induced currents (GIC) can cause severe service disruptions. The prediction of GIC is thus of great importance for public and industry. A key step in the prediction of the hazard to technological systems during magnetic storms is the calculation of the geoelectric field. To address this issue for mid-latitude regions, we developed a method that involves 3-D modelling of induction processes in a heterogeneous Earth and the construction of a model of the magnetospheric source. The latter is described by low-degree spherical harmonics; its temporal evolution is derived from observatory magnetic data. Time series of the electric field can be computed for every location on Earth's surface. The actual electric field however is known to be perturbed by galvanic effects, arising from very local near-surface heterogeneities or topography, which cannot be included in the conductivity model. Galvanic effects are commonly accounted for with a real-valued time-independent distortion matrix, which linearly relates measured and computed electric fields. Using data of various magnetic storms that occurred between 2000 and 2003, we estimated distortion matrices for observatory sites onshore and on the ocean bottom. Strong correlations between modellings and measurements validate our method. The distortion matrix estimates prove to be reliable, as they are accurately reproduced for different magnetic storms. We further show that 3-D modelling is crucial for a correct separation of galvanic and inductive effects and a precise prediction of electric field time series during magnetic storms. Since the required computational resources are negligible, our approach is suitable for a real-time prediction of GIC. For this purpose, a reliable forecast of the source field, e.g. based on data from satellites

Concurrent correction of geometric distortion and motion using the map-slice-to-volume method in echo-planar imaging.

Science.gov (United States)

Yeo, Desmond T B; Fessler, Jeffrey A; Kim, Boklye

2008-06-01

The accuracy of measuring voxel intensity changes between stimulus and rest images in fMRI echo-planar imaging (EPI) data is severely degraded in the presence of head motion. In addition, EPI is sensitive to susceptibility-induced geometric distortions. Head motion causes image shifts and associated field map changes that induce different geometric distortion at different time points. Conventionally, geometric distortion is "corrected" with a static field map independently of image registration. That approach ignores all field map changes induced by head motion. This work evaluates the improved motion correction capability of mapping slice to volume with concurrent iterative field corrected reconstruction using updated field maps derived from an initial static field map that has been spatially transformed and resampled. It accounts for motion-induced field map changes for translational and in-plane rotation motion. The results from simulated EPI time series data, in which motion, image intensity and activation ground truths are available, show improved accuracy in image registration, field corrected image reconstruction and activation detection.

Concurrent correction of geometric distortion and motion using the map-slice-to-volume method in EPI

Science.gov (United States)

Yeo, Desmond T. B.; Fessler, Jeffrey A.; Kim, Boklye

2014-01-01

The accuracy of measuring voxel intensity changes between stimulus and rest images in fMRI echo-planar imaging (EPI) data is severely degraded in the presence of head motion. In addition, EPI is sensitive to susceptibility-induced geometric distortions. Head motion causes image shifts and associated field map changes that induce different geometric distortion at different time points. Conventionally, geometric distortion is “corrected” with a static field map independently of image registration. That approach ignores all field map changes induced by head motion. This work evaluates the improved motion correction capability of mapping slice to volume (MSV) registration with concurrent iterative field corrected reconstruction using updated field maps derived from an initial static field map that has been spatially transformed and resampled. It accounts for motion-induced field map changes for translational and in-plane rotation motion. The results from simulated EPI time series data, in which motion, image intensity and activation ground truths are available, show improved accuracy in image registration, field corrected image reconstruction and activation detection. PMID:18280077

Probing correlations of early magnetic fields using mu-distortion

DEFF Research Database (Denmark)

Ganc, Jonathan; Sloth, Martin Snoager

2014-01-01

the perturbations which produce the $\\mu$-distortion will be much smaller scale than the relevant density perturbations, the observation of this correlation is sensitive to the squeezed limit of $\\langle B^2\\zeta\\rangle$, which is naturally parameterized by $b_{\\text{NL}}$ (a parameter defined analogously to $f_{\\text......{NL}}$). We find that a PIXIE-like CMB experiments has a signal to noise $S/N\\approx 1.0 \\times b_{\\text{NL}} (\\tilde B_\\mu/10\\text{ nG})^2$, where $\\tilde B_\\mu$ is the magnetic field's strength on $\\mu$-distortion scales normalized to today's redshift; thus, a 10 nG field would be detectable with $b_{\\text...

Research and implementation of the algorithm for unwrapped and distortion correction basing on CORDIC for panoramic image

Science.gov (United States)

Zhang, Zhenhai; Li, Kejie; Wu, Xiaobing; Zhang, Shujiang

2008-03-01

The unwrapped and correcting algorithm based on Coordinate Rotation Digital Computer (CORDIC) and bilinear interpolation algorithm was presented in this paper, with the purpose of processing dynamic panoramic annular image. An original annular panoramic image captured by panoramic annular lens (PAL) can be unwrapped and corrected to conventional rectangular image without distortion, which is much more coincident with people's vision. The algorithm for panoramic image processing is modeled by VHDL and implemented in FPGA. The experimental results show that the proposed panoramic image algorithm for unwrapped and distortion correction has the lower computation complexity and the architecture for dynamic panoramic image processing has lower hardware cost and power consumption. And the proposed algorithm is valid.

Perovskite LaPbMSbO6 (M=Co, Ni): Structural distortion, magnetic and dielectric properties

International Nuclear Information System (INIS)

Bai, Yijia; Han, Lin; Liu, Xiaojuan; Deng, Xiaolong; Wu, Xiaojie; Yao, Chuangang; Liang, Qingshuang; Meng, Junling; Meng, Jian

2014-01-01

The B-site ordered double perovskite oxides LaPbMSbO 6 (M=Co, Ni) have been synthesized via the modified Sol–Gel precursor two-step route. Rietveld refinements reveal strong abnormal structural distortion and BO 6 octahedral deformation appearing along the ab plane. Owing to the cooperative Jahn–Teller effect of Co 2+ and Pb 2+ ions, the Co-related compound exhibits almost complete Co 2+ –Sb 5+ order. For magnetic properties, spin-canted antiferromagnetic state with high extent of magnetic frustration is confirmed. The Ni-related compound presents heavier magnetic frustration for introducing tiny disorder on site occupation accompanied with valence state and further enhancing the complexity of magnetic competition. Dielectric measurements present a considerable temperature dependent dielectric relaxation with great dc-like loss feature in the LaPbCoSbO 6 . For LaPbNiSbO 6 , however, the permittivity with low dielectric loss is shown to be insensitive to either temperature or frequency. The corresponding electronic active energy manifests that the weakly bounded 3d-electron is prone to hop in a more distorted Co–Sb sublattice. - Graphical abstract: XRD Rietveld refinement result of LaPbCoSbO 6 presented a large BO 6 octahedral distortion along the ab plane. Based upon the variations from Co–O–Sb bond angles, a fierce competition from many extended magnetic coupling routes (M–O–O–M) would induce a considerably large magnetic frustration and electron hopping restriction. - Highlights: • Highly ordered LaPbMSbO 6 (M=Co, Ni) were synthesized. • Abnormal structural distortion appeared in the ab plane. • Strong magnetic frustration was confirmed via M 2+ –O–O–M 2+ route. • Dielectric measurements presented a large difference between Co and Ni samples. • 3d-electronic structure determines lattice distortion and physical properties

Correction of rotational distortion for catheter-based en face OCT and OCT angiography

Science.gov (United States)

Ahsen, Osman O.; Lee, Hsiang-Chieh; Giacomelli, Michael G.; Wang, Zhao; Liang, Kaicheng; Tsai, Tsung-Han; Potsaid, Benjamin; Mashimo, Hiroshi; Fujimoto, James G.

2015-01-01

We demonstrate a computationally efficient method for correcting the nonuniform rotational distortion (NURD) in catheter-based imaging systems to improve endoscopic en face optical coherence tomography (OCT) and OCT angiography. The method performs nonrigid registration using fiducial markers on the catheter to correct rotational speed variations. Algorithm performance is investigated with an ultrahigh-speed endoscopic OCT system and micromotor catheter. Scan nonuniformity is quantitatively characterized, and artifacts from rotational speed variations are significantly reduced. Furthermore, we present endoscopic en face OCT and OCT angiography images of human gastrointestinal tract in vivo to demonstrate the image quality improvement using the correction algorithm. PMID:25361133

Numerical correction of distorted images in full-field optical coherence tomography

Science.gov (United States)

Min, Gihyeon; Kim, Ju Wan; Choi, Woo June; Lee, Byeong Ha

2012-03-01

We propose a numerical method which can numerically correct the distorted en face images obtained with a full field optical coherence tomography (FF-OCT) system. It is shown that the FF-OCT image of the deep region of a biological sample is easily blurred or degraded because the sample has a refractive index (RI) much higher than its surrounding medium in general. It is analyzed that the focal plane of the imaging system is segregated from the imaging plane of the coherence-gated system due to the RI mismatch. This image-blurring phenomenon is experimentally confirmed by imaging the chrome pattern of a resolution test target through its glass substrate in water. Moreover, we demonstrate that the blurred image can be appreciably corrected by using the numerical correction process based on the Fresnel-Kirchhoff diffraction theory. The proposed correction method is applied to enhance the image of a human hair, which permits the distinct identification of the melanin granules inside the cortex layer of the hair shaft.

Correction magnet power supplies for APS machine

International Nuclear Information System (INIS)

Kang, Y.G.

1991-04-01

A number of correction magnets are required for the advanced photon source (APS) machine to correct the beam. There are five kinds of correction magnets for the storage ring, two for the injector synchrotron, and two for the positron accumulator ring (PAR). Table I shoes a summary of the correction magnet power supplies for the APS machine. For the storage ring, the displacement of the quadrupole magnets due to the low frequency vibration below 25 Hz has the most significant effect on the stability of the positron closed orbit. The primary external source of the low frequency vibration is the ground motion of approximately 20 μm amplitude, with frequency components concentrated below 10 Hz. These low frequency vibrations can be corrected by using the correction magnets, whose field strengths are controlled individually through the feedback loop comprising the beam position monitoring system. The correction field require could be either positive or negative. Thus for all the correction magnets, bipolar power supplies (BPSs) are required to produce both polarities of correction fields. Three different types of BPS are used for all the correction magnets. Type I BPSs cover all the correction magnets for the storage ring, except for the trim dipoles. The maximum output current of the Type I BPS is 140 Adc. A Type II BPS powers a trim dipole, and its maximum output current is 60 Adc. The injector synchrotron and PAR correction magnets are powered form Type III BPSs, whose maximum output current is 25 Adc

Correction method and software for image distortion and nonuniform response in charge-coupled device-based x-ray detectors utilizing x-ray image intensifier

International Nuclear Information System (INIS)

Ito, Kazuki; Kamikubo, Hironari; Yagi, Naoto; Amemiya, Yoshiyuki

2005-01-01

An on-site method of correcting the image distortion and nonuniform response of a charge-coupled device (CCD)-based X-ray detector was developed using the response of the imaging plate as a reference. The CCD-based X-ray detector consists of a beryllium-windowed X-ray image intensifier (Be-XRII) and a CCD as the image sensor. An image distortion of 29% was improved to less than 1% after the correction. In the correction of nonuniform response due to image distortion, subpixel approximation was performed for the redistribution of pixel values. The optimal number of subpixels was also discussed. In an experiment with polystyrene (PS) latex, it was verified that the correction of both image distortion and nonuniform response worked properly. The correction for the 'contrast reduction' problem was also demonstrated for an isotropic X-ray scattering pattern from the PS latex. (author)

The main postulates of adaptive correction of distortions of the wave front in large-size optical systems

Directory of Open Access Journals (Sweden)

V. V. Sychev

2014-01-01

medium on the transmitted radiation WF;•  the lack of a reference source at the wavelength of trasnmitted laser radiation, which is required to implement methods for adaptive correction of the distorted WF;•  the unique to laser systems additional distorting factors available in transmission systems.These distorting factors include:• length of the optical path due to need in spatial diversity of high power laser source with a large number of matching optical elements;• thermal self-action of power laser radiation in the transport path of the radiation before its entry into forming optical system;• instability of spatio-temporal characteristics of the laser radiation source itself to take a turn for the worse conditions of radiation transmission both inside the optical path, and in the free atmosphere;• thermal irregularities and thermal deformation.It is shown that the adaptive systems differ from the active optics in that radiation wave front distortion is corrected in real time per totality of distorting factors (not only on the effect of the atmosphere with the speed ten times exceeding the effect of distortion itself. Here, the correction quality is estimated by criterion of the primary image quality.In this case, the correction continuously takes into account data about optical system parameters such as current space, temperature, time, and adjusting, thereby supporting the high quality of images under the action of distorting factors.The paper formulates and proposes the basic postulates of adaptive correction.Postulates are a set of statements and assertions, allowing us to implement effective means of adaptive correction of distortions.The paper also shows the real capabilities the methods and means of adaptive optics offer in case of efficient use of laser radiation power and what ways are possible to solve these tasks. First of all, these are:- forming a system of assumptions and minimization of distortions in the optical path, which includes a

Field-dependent spin chirality and frustration in V3 and Cu3 nanomagnets in transverse magnetic field. 2. Spin configurations, chirality and intermediate spin magnetization in distorted trimers

International Nuclear Information System (INIS)

Belinsky, Moisey I.

2014-01-01

Highlights: • Distorted spin configurations determine field behavior of the variable chiralities. • Distortions change spin chiralities, intermediate M 12 ± and staggered magnetization. • Magnetizations, distorted vector and scalar chiralities are strongly correlated. • Distorted V 3 , Cu 3 nanomagnets possess large vector chirality in the ground state in B ⊥ . • Chiralities and distortions in EPR, INS and NMR spectra were considered. - Abstract: Correlated spin configurations, magnetizations, frustration, vector κ ¯ z and scalar χ ¯ chiralities are considered for distorted V ‾ 3 , /Cu 3 / anisotropic DM nanomagnets in transverse B x ‖X and longitudinal B‖Z fields. Different planar configurations in the ground and excited states of distorted nanomagnets in B x determine different field behavior of the vector chiralities and the degenerate frustration in these states correlated with the M ~ 12 ± (B x ) intermediate spin (IS) magnetization which describes the S 12 characteristics, χ=0. Distortion results in the reduced κ ¯ z <1 chirality in the ground distorted configuration and in the maximum κ z =±1 in the excited states with the planar 120° configurations at avoided level crossing. In B‖Z, distorted longitudinal spin-collinear configurations are characterized by the reduced degenerate frustration, out-of-plane staggered and IS M ~ 12 ± (B z ) magnetizations, and in-plane toroidal moments, correlated with the κ ¯ z , χ ¯ chiralities, χ ¯ =±|κ ¯ z |. The chiralities and IS magnetization in EPR, INS and NMR spectra are considered. The quantitative correlations describe variable spin chirality, frustration and field manipulation of chiralities in nanomagnets

Centi-pixel accurate real-time inverse distortion correction

CSIR Research Space (South Africa)

De Villiers, Johan P

2008-11-01

Full Text Available Inverse distortion is used to create an undistorted image from a distorted image. For each pixel in the undistorted image it is required to determine which pixel in the distorted image should be used. However the process of characterizing a lens...

Perovskite LaPbMSbO{sub 6} (M=Co, Ni): Structural distortion, magnetic and dielectric properties

Energy Technology Data Exchange (ETDEWEB)

Bai, Yijia [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, 5625 Renmin Street, Changchun 130022 (China); Chemical Engineering College, Inner Mongolia University of Technology, 49 Aimin Street, Hohhot 010051 (China); Han, Lin [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, 5625 Renmin Street, Changchun 130022 (China); University of Chinese Academy of Sciences, Beijing 10049 (China); Liu, Xiaojuan, E-mail: lxjuan@ciac.jl.cn [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, 5625 Renmin Street, Changchun 130022 (China); Deng, Xiaolong [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, 5625 Renmin Street, Changchun 130022 (China); University of Chinese Academy of Sciences, Beijing 10049 (China); Wu, Xiaojie [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, 5625 Renmin Street, Changchun 130022 (China); Yao, Chuangang; Liang, Qingshuang; Meng, Junling [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, 5625 Renmin Street, Changchun 130022 (China); University of Chinese Academy of Sciences, Beijing 10049 (China); Meng, Jian, E-mail: jmeng@ciac.jl.cn [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, 5625 Renmin Street, Changchun 130022 (China)

2014-09-15

The B-site ordered double perovskite oxides LaPbMSbO{sub 6} (M=Co, Ni) have been synthesized via the modified Sol–Gel precursor two-step route. Rietveld refinements reveal strong abnormal structural distortion and BO{sub 6} octahedral deformation appearing along the ab plane. Owing to the cooperative Jahn–Teller effect of Co{sup 2+} and Pb{sup 2+} ions, the Co-related compound exhibits almost complete Co{sup 2+}–Sb{sup 5+} order. For magnetic properties, spin-canted antiferromagnetic state with high extent of magnetic frustration is confirmed. The Ni-related compound presents heavier magnetic frustration for introducing tiny disorder on site occupation accompanied with valence state and further enhancing the complexity of magnetic competition. Dielectric measurements present a considerable temperature dependent dielectric relaxation with great dc-like loss feature in the LaPbCoSbO{sub 6}. For LaPbNiSbO{sub 6}, however, the permittivity with low dielectric loss is shown to be insensitive to either temperature or frequency. The corresponding electronic active energy manifests that the weakly bounded 3d-electron is prone to hop in a more distorted Co–Sb sublattice. - Graphical abstract: XRD Rietveld refinement result of LaPbCoSbO{sub 6} presented a large BO{sub 6} octahedral distortion along the ab plane. Based upon the variations from Co–O–Sb bond angles, a fierce competition from many extended magnetic coupling routes (M–O–O–M) would induce a considerably large magnetic frustration and electron hopping restriction. - Highlights: • Highly ordered LaPbMSbO{sub 6} (M=Co, Ni) were synthesized. • Abnormal structural distortion appeared in the ab plane. • Strong magnetic frustration was confirmed via M{sup 2+}–O–O–M{sup 2+} route. • Dielectric measurements presented a large difference between Co and Ni samples. • 3d-electronic structure determines lattice distortion and physical properties.

MATLAB based beam orbit correction system of HLS storage ring

International Nuclear Information System (INIS)

Ding Shichuan; Liu Gongfa; Xuan Ke; Li Weimin; Wang Lin; Wang Jigang; Li Chuan; Bao Xun; Guo Weiqun

2006-01-01

The distortion of closed orbit usually causes much side effect which is harmful to synchrotron radiation source such as HLS, so it is necessary to correct the distortion of closed orbit. In this paper, the correction principle, development procedure and test of MATLAB based on beam orbit correction system of HLS storage ring are described. The correction system is consisted of the beam orbit measure system, corrector magnet system and the control system, and the beam orbit correction code based on MATLAB is working on the operation interface. The data of the beam orbit are analyzed and calculated firstly, and then the orbit is corrected by changing corrector strength via control system. The test shows that the distortion of closed orbit is from max 4.468 mm before correction to max 0.299 mm after correction as well as SDEV is from 2.986 mm to 0.087 mm. So the correction system reaches the design goal. (authors)

Correction magnet power supplies for APS machine

International Nuclear Information System (INIS)

Kang, Y.G.

1991-01-01

The Advanced Photon Source machine requires a number of correction magnets; five kinds for the storage ring, two for the injector synchrotron, and two for the positron accumulator ring. Three types of bipolar power supply will be used for all the correction magnets. This paper describes the design aspects and considerations for correction magnet power supplies for the APS machine. 3 refs., 3 figs., 1 tab

Prediction of d^0 magnetism in self-interaction corrected density functional theory

Science.gov (United States)

Das Pemmaraju, Chaitanya

2010-03-01

-LSDA approaches that are either self-interaction free or effectively correct for it overcome such failures to produce a more accurate description of acceptor defects in Oxides. Typically, correcting for the SIE, leads to an enhanced localization of the holes responsible for the magnetism. Additionally, the ground state becomes insulating driven by polaronic distortions around the defect site and the magnetic coupling between the impurities becomes weak [4,5,6].[4pt] [1] J.M.D. Coey, Solid State Sci., 7, 660 (2005). [0pt] [2] I.S. Elfimov et al, PRL 89, 216403 (2002).[0pt] [3] C. D. Pemmaraju and S. Sanvito, PRL 94,217205 (2005)[0pt] [4] A. Droghetti et al, PRB 78, 140404(R) (2008)[0pt] [5] J.A. Chan et al, PRL 103, 016404, (2009).[0pt] [6] V. Pardo et al, PRB 78, 134427 (2008)

TPC track distortions IV: post tenebras lux

CERN Document Server

Ammosov, V; Boyko, I; Chelkov, G; Dedovitch, D; Dydak, F; Elagin, A; Gostkin, M; Guskov, A; Koreshev, V; Krumshtein, Z; Nefedov, Y; Nikolaev, K; Wotschack, J; Zhemchugov, A

2007-01-01

We present a comprehensive discussion and summary of static and dynamic track distortions in the HARP TPC in terms of physical origin, mathematical modelling and correction algorithms. `Static' distortions are constant with time, while `dynamic' distortions are distortions that occur only during the 400 ms long accelerator spill. The measurement of dynamic distortions, their mathematical modelling and the correction algorithms build on our understanding of static distortions. In the course of corroborating the validity of our static distortion corrections, their reliability and precision was further improved. Dynamic TPC distortions originate dominantly from the `stalactite' effect: a column of positive-ion charge starts growing at the begin of the accelerator spill, and continues growing with nearly constant velocity out from the sense-wire plane into the active TPC volume. However, the `stalactite' effect is not able to describe the distortions that are present already at the start of the spill and which ha...

Relativistic Scott correction in self-generated magnetic fields

DEFF Research Database (Denmark)

Erdos, Laszlo; Fournais, Søren; Solovej, Jan Philip

2012-01-01

/3}$ and it is unchanged by including the self-generated magnetic field. We prove the first correction term to this energy, the so-called Scott correction of the form $S(\\alpha Z) Z^2$. The current paper extends the result of \\cite{SSS} on the Scott correction for relativistic molecules to include a self......-generated magnetic field. Furthermore, we show that the corresponding Scott correction function $S$, first identified in \\cite{SSS}, is unchanged by including a magnetic field. We also prove new Lieb-Thirring inequalities for the relativistic kinetic energy with magnetic fields....

Combined prospective and retrospective correction to reduce motion-induced image misalignment and geometric distortions in EPI.

Science.gov (United States)

Ooi, Melvyn B; Muraskin, Jordan; Zou, Xiaowei; Thomas, William J; Krueger, Sascha; Aksoy, Murat; Bammer, Roland; Brown, Truman R

2013-03-01

Despite rigid-body realignment to compensate for head motion during an echo-planar imaging time-series scan, nonrigid image deformations remain due to changes in the effective shim within the brain as the head moves through the B(0) field. The current work presents a combined prospective/retrospective solution to reduce both rigid and nonrigid components of this motion-related image misalignment. Prospective rigid-body correction, where the scan-plane orientation is dynamically updated to track with the subject's head, is performed using an active marker setup. Retrospective distortion correction is then applied to unwarp the remaining nonrigid image deformations caused by motion-induced field changes. Distortion correction relative to a reference time-frame does not require any additional field mapping scans or models, but rather uses the phase information from the echo-planar imaging time-series itself. This combined method is applied to compensate echo-planar imaging scans of volunteers performing in-plane and through-plane head motions, resulting in increased image stability beyond what either prospective or retrospective rigid-body correction alone can achieve. The combined method is also assessed in a blood oxygen level dependent functional MRI task, resulting in improved Z-score statistics. Copyright © 2012 Wiley Periodicals, Inc.

Novel grid combined with peripheral distortion correction for ultra-widefield image grading of age-related macular degeneration

Directory of Open Access Journals (Sweden)

Oellers P

2017-11-01

Full Text Available Patrick Oellers,1,* Inês Laíns,1,2,* Steven Mach,1 Shady Garas,1 Ivana K Kim,1 Demetrios G Vavvas,1 Joan W Miller,1 Deeba Husain,1 John B Miller1 1Retina Service, Department of Ophthalmology, Massachusetts Eye and Ear, Harvard Medical School, Boston, MA, USA; 2Faculty of Medicine, University of Coimbra, Coimbra, Portugal *These authors contributed equally to this work Purpose: Eyes with age-related macular degeneration (AMD often harbor pathological changes in the retinal periphery and perimacular region. These extramacular changes have not been well classified, but may be phenotypically and functionally relevant. The purpose of this study was to demonstrate a novel grid to systematically study peripheral retinal abnormalities in AMD using geometric distortion-corrected ultra-widefield (UWF imaging.Methods: This is a cross-sectional observational case series. Consecutive patients with AMD without any other coexisting vitreoretinal disease and control patients over age 50 without AMD or any other vitreoretinal disease were imaged using Optos 200 Tx. Captured 200° UWF images were corrected for peripheral geometric distortion using Optos transformation software. A newly developed grid to study perimacular and peripheral abnormalities in AMD was then projected onto the images.Results: Peripheral and perimacular changes such as drusen, retinal pigment epithelium changes and atrophy were found in patients with AMD. The presented grid in conjunction with geometric distortion-corrected UWF images allowed for systematic study of these peripheral changes in AMD.Conclusion: We present a novel grid to study peripheral and posterior pole changes in AMD. The grid is unique in that it adds a perimacular zone, which may be important in characterizing certain phenotypes in AMD. Our UWF images were corrected for geometric peripheral distortion to accurately reflect the anatomical dimensions of the retina. This grid offers a reliable and reproducible foundation

Distortion definition and correction in off-axis systems

Science.gov (United States)

Da Deppo, Vania; Simioni, Emanuele; Naletto, Giampiero; Cremonese, Gabriele

2015-09-01

Off-axis optical configurations are becoming more and more used in a variety of applications, in particular they are the most preferred solution for cameras devoted to Solar System planets and small bodies (i.e. asteroids and comets) study. Off-axis designs, being devoid of central obstruction, are able to guarantee better PSF and MTF performance, and thus higher contrast imaging capabilities with respect to classical on-axis designs. In particular they are suitable for observing extended targets with intrinsic low contrast features, or scenes where a high dynamical signal range is present. Classical distortion theory is able to well describe the performance of the on-axis systems, but it has to be adapted for the off-axis case. A proper way to deal with off-axis distortion definition is thus needed together with dedicated techniques to accurately measure and hence remove the distortion effects present in the acquired images. In this paper, a review of the distortion definition for off-axis systems will be given. In particular the method adopted by the authors to deal with the distortion related issues (definition, measure, removal) in some off-axis instruments will be described in detail.

Correction of magnetization sextupole in one-meter long dipole magnets using passing superconductor

International Nuclear Information System (INIS)

Green, M.A.; Althaus, R.F.; Barale, P.J.; Benjegerdes, R.W.; Gilbert, W.S.; Green, M.I.; Scanlan, R.M.

1990-03-01

The generation of higher multipoles due to the magnetization of the superconductor in the dipoles of the SSC is a problem during injection of the beam into the machine. The use of passive superconductor was proposed some years ago to correct the magnetization sextupole in the dipole magnet. This paper presents the LBL test results in which the magnetization sextupole was greatly reduced in two one-meter long dipole magnets by the use of passive superconductor mounted on the magnet bore tube. The magnetization sextupole was reduced a factor of five on one magnet and a factor of eight on the other magnet using this technique. Magnetization decapole was also reduced by the passive superconductor. The passive superconductor method of correction also reduced the temperature dependence of the magnetization multipoles. In addition, the drift in the magnetization sextupole due to flux creep was also reduced. Passive superconductor correction appears to be a promising method of correcting out the effects of superconductor magnetization in SSC dipoles and quadrupoles. 10 refs., 6 figs

Correction of a Depth-Dependent Lateral Distortion in 3D Super-Resolution Imaging.

Directory of Open Access Journals (Sweden)

Lina Carlini

Full Text Available Three-dimensional (3D localization-based super-resolution microscopy (SR requires correction of aberrations to accurately represent 3D structure. Here we show how a depth-dependent lateral shift in the apparent position of a fluorescent point source, which we term `wobble`, results in warped 3D SR images and provide a software tool to correct this distortion. This system-specific, lateral shift is typically > 80 nm across an axial range of ~ 1 μm. A theoretical analysis based on phase retrieval data from our microscope suggests that the wobble is caused by non-rotationally symmetric phase and amplitude aberrations in the microscope's pupil function. We then apply our correction to the bacterial cytoskeletal protein FtsZ in live bacteria and demonstrate that the corrected data more accurately represent the true shape of this vertically-oriented ring-like structure. We also include this correction method in a registration procedure for dual-color, 3D SR data and show that it improves target registration error (TRE at the axial limits over an imaging depth of 1 μm, yielding TRE values of < 20 nm. This work highlights the importance of correcting aberrations in 3D SR to achieve high fidelity between the measurements and the sample.

Magnetic measurements of the correction and adjustment magnets of the main ring

International Nuclear Information System (INIS)

Trbojevic, D.

1986-07-01

Correction magnets correct the field imperfections and alignment errors of the main quadrupole and bend magnets. For reducing and controlling chromaticity there are 186 sextupoles and 78 octupoles, while for suppressing various resonances there are 12 normal and 18 skew sextupoles and 24 normal and 19 skew quadrupoles. Beam positions are individually controlled by 108 horizontal and 108 skew dipoles. This report includes results of the all Main Ring correction and adjustment magnet harmonic measurements. The measurement principle and basic equations are described

Magnetic field perturbation in proton MR imaging - A study of a contrast agent and of distortions due to metallic implants

International Nuclear Information System (INIS)

Olsson, M.

1992-01-01

Perturbations of the static magnetic field in proton MR imaging (NMR imaging, MRI, MRT) result in image distortion and/or signal loss. An investigation of a superparamagnetic contrast agent for MR imaging has been performed. Magnetite particles were embedded in biodegradable starch spheres with a diameter of one micrometer. Animal experiments showed that the agent was quickly accumulated in the reticulo-endothelial system (RES), causing a decrease in signal intensity in this region. Diffusion within the locally generated magnetic field perturbation is responsible for signal loss in spin-echo images. Furthermore, the magnetic properties of various aneurysm clips were investigated to determine which clips could be used safely in a clinical MR investigation. MR artifacts caused by the metallic clips were studied using a geometric phantom. Non-ferromagnetic clips were concluded to be safe for examinations with medium field (0.3 tesla) MR imaging systems. A comparison study between MR and CT was performed on patients harbouring intracranial, nonferromagnetic aneurysm clips. The artifacts close to the clips were equally serve for MR and CT, but at some distance, the MR images were much less affected than the CT images. Finally, a computer program capable of simulating any realistic MR imaging situation has been developed. Raw data matrices are obtained by solving the Bloch equations. Corrections for intravascular spin behaviour have been implemented together with efficient algorithms. A quantitative investigation of signal displacement and signal loss, caused by small metallic implants, has been performed by computer simulation. An exact expression for the magnetic field outside a homogeneous ellipsoid in an external magnetic field has been derived. Distortions in MR images, caused by perturbing ellipsoids of different shapes and orientations, were studied. (30 refs.) (au)

Lattice Distortion Mediated Paramagnetic Relaxation in High-Spin High-Symmetry Molecular Magnets

Science.gov (United States)

Garg, Anupam

1998-08-01

Field-dependent maxima in the relaxation rate of the magnetic molecules Mn12-Ac and Fe8-tacn have commonly been ascribed to some resonant tunneling phenomena. We argue instead that the relaxation is purely due to phonons. The rate maxima arise because of a Jahn-Teller-like distortion caused by the coupling of phonons to degenerate Zeeman levels of the molecule at the top of the barrier. The binding energy of the distorted intermediate states lowers the barrier height and increases the relaxation rate. A nonperturbative calculation of this effect is carried out for a model system. An approximate result for the field variation near a maximum is found to agree reasonably with experiment.

Doppler distortion correction based on microphone array and matching pursuit algorithm for a wayside train bearing monitoring system

International Nuclear Information System (INIS)

Liu, Xingchen; Hu, Zhiyong; He, Qingbo; Zhang, Shangbin; Zhu, Jun

2017-01-01

Doppler distortion and background noise can reduce the effectiveness of wayside acoustic train bearing monitoring and fault diagnosis. This paper proposes a method of combining a microphone array and matching pursuit algorithm to overcome these difficulties. First, a dictionary is constructed based on the characteristics and mechanism of a far-field assumption. Then, the angle of arrival of the train bearing is acquired when applying matching pursuit to analyze the acoustic array signals. Finally, after obtaining the resampling time series, the Doppler distortion can be corrected, which is convenient for further diagnostic work. Compared with traditional single-microphone Doppler correction methods, the advantages of the presented array method are its robustness to background noise and its barely requiring pre-measuring parameters. Simulation and experimental study show that the proposed method is effective in performing wayside acoustic bearing fault diagnosis. (paper)

Doppler distortion correction based on microphone array and matching pursuit algorithm for a wayside train bearing monitoring system

Science.gov (United States)

Liu, Xingchen; Hu, Zhiyong; He, Qingbo; Zhang, Shangbin; Zhu, Jun

2017-10-01

Doppler distortion and background noise can reduce the effectiveness of wayside acoustic train bearing monitoring and fault diagnosis. This paper proposes a method of combining a microphone array and matching pursuit algorithm to overcome these difficulties. First, a dictionary is constructed based on the characteristics and mechanism of a far-field assumption. Then, the angle of arrival of the train bearing is acquired when applying matching pursuit to analyze the acoustic array signals. Finally, after obtaining the resampling time series, the Doppler distortion can be corrected, which is convenient for further diagnostic work. Compared with traditional single-microphone Doppler correction methods, the advantages of the presented array method are its robustness to background noise and its barely requiring pre-measuring parameters. Simulation and experimental study show that the proposed method is effective in performing wayside acoustic bearing fault diagnosis.

METHOD OF RADIOMETRIC DISTORTION CORRECTION OF MULTISPECTRAL DATA FOR THE EARTH REMOTE SENSING

Directory of Open Access Journals (Sweden)

A. N. Grigoriev

2015-07-01

Full Text Available The paper deals with technologies of ground secondary processing of heterogeneous multispectral data. The factors of heterogeneous data include uneven illumination of objects on the Earth surface caused by different properties of the relief. A procedure for the image restoration of spectral channels by means of terrain distortion compensation is developed. The object matter of this paper is to improve the quality of the results during image restoration of areas with large and medium landforms. Methods. Researches are based on the elements of the digital image processing theory, statistical processing of the observation results and the theory of multi-dimensional arrays. Main Results. The author has introduced operations on multidimensional arrays: concatenation and elementwise division. Extended model description for input data about the area is given. The model contains all necessary data for image restoration. Correction method for multispectral data radiometric distortions of the Earth remote sensing has been developed. The method consists of two phases: construction of empirical dependences for spectral reflectance on the relief properties and restoration of spectral images according to semiempirical data. Practical Relevance. Research novelty lies in developme nt of the application theory of multidimensional arrays with respect to the processing of multispectral data, together with data on the topography and terrain objects. The results are usable for development of radiometric data correction tools. Processing is performed on the basis of a digital terrain model without carrying out ground works connected with research of the objects reflective properties.

Generic distortion model for metrology under optical microscopes

Science.gov (United States)

Liu, Xingjian; Li, Zhongwei; Zhong, Kai; Chao, YuhJin; Miraldo, Pedro; Shi, Yusheng

2018-04-01

For metrology under optical microscopes, lens distortion is the dominant source of error. Previous distortion models and correction methods mostly rely on the assumption that parametric distortion models require a priori knowledge of the microscopes' lens systems. However, because of the numerous optical elements in a microscope, distortions can be hardly represented by a simple parametric model. In this paper, a generic distortion model considering both symmetric and asymmetric distortions is developed. Such a model is obtained by using radial basis functions (RBFs) to interpolate the radius and distortion values of symmetric distortions (image coordinates and distortion rays for asymmetric distortions). An accurate and easy to implement distortion correction method is presented. With the proposed approach, quantitative measurement with better accuracy can be achieved, such as in Digital Image Correlation for deformation measurement when used with an optical microscope. The proposed technique is verified by both synthetic and real data experiments.

Effect of magnet sorting using a simple resonance cancellation method on the RMS orbit distortion at the APS injector synchrotron

International Nuclear Information System (INIS)

Lopez, F.; Koul, R.; Mills, F.E.

1993-01-01

The Advanced Photon Source injector synchrotron is a 7-GeV positron machine with a standard alternating gradient lattice. The calculated effect of dipole magnet strength errors on the orbit distortion, simulated by Monte Carlo, was reduced by sorting pairs of magnets having the closest simulated measured strengths to reduce the driving the term of the integer resonance nearest the operating point. This method resulted in a factor of four average reduction in the rms orbit distortion when all 68 magnets were sorted at once. The simulated effect of magnet measurement experimental resolution was found to limit the actual improvement. The Β-beat factors were similarly reduced by sorting the quadrupole magnets according to their gradients

Analysis of dynamical corrections to baryon magnetic moments

International Nuclear Information System (INIS)

Ha, Phuoc; Durand, Loyal

2003-01-01

We present and analyze QCD corrections to the baryon magnetic moments in terms of the one-, two-, and three-body operators which appear in the effective field theory developed in our recent papers. The main corrections are extended Thomas-type corrections associated with the confining interactions in the baryon. We investigate the contributions of low-lying angular excitations to the baryon magnetic moments quantitatively and show that they are completely negligible. When the QCD corrections are combined with the nonquark model contributions of the meson loops, we obtain a model which describes the baryon magnetic moments within a mean deviation of 0.04 μ N . The nontrivial interplay of the two types of corrections to the quark-model magnetic moments is analyzed in detail, and explains why the quark model is so successful. In the course of these calculations, we parametrize the general spin structure of the j=(1/2) + baryon wave functions in a form which clearly displays the symmetry properties and the internal angular momentum content of the wave functions, and allows us to use spin-trace methods to calculate the many spin matrix elements which appear in the expressions for the baryon magnetic moments. This representation may be useful elsewhere

A GENERALIZED NON-LINEAR METHOD FOR DISTORTION CORRECTION AND TOP-DOWN VIEW CONVERSION OF FISH EYE IMAGES

Directory of Open Access Journals (Sweden)

Vivek Singh Bawa

2017-06-01

Full Text Available Advanced driver assistance systems (ADAS have been developed to automate and modify vehicles for safety and better driving experience. Among all computer vision modules in ADAS, 360-degree surround view generation of immediate surroundings of the vehicle is very important, due to application in on-road traffic assistance, parking assistance etc. This paper presents a novel algorithm for fast and computationally efficient transformation of input fisheye images into required top down view. This paper also presents a generalized framework for generating top down view of images captured by cameras with fish-eye lenses mounted on vehicles, irrespective of pitch or tilt angle. The proposed approach comprises of two major steps, viz. correcting the fish-eye lens images to rectilinear images, and generating top-view perspective of the corrected images. The images captured by the fish-eye lens possess barrel distortion, for which a nonlinear and non-iterative method is used. Thereafter, homography is used to obtain top-down view of corrected images. This paper also targets to develop surroundings of the vehicle for wider distortion less field of view and camera perspective independent top down view, with minimum computation cost which is essential due to limited computation power on vehicles.

Higher magnetic field multipoles generated by superconductor magnetization within a set of nested superconducting correction coils

International Nuclear Information System (INIS)

Green, M.A.

1990-01-01

Correction elements in colliding beam accelerators such as the Superconducting Super Collider (SSC) can be the source of undesirable higher magnetic field multipoles due to magnetization of the superconductor within the corrector. Quadrupole and sextupole correctors located within the main dipole will produce sextupole and decapole due to magnetization of the superconductor within the correction coils. Lumped nested correction coils can produce a large number of skew and normal magnetization multipoles which may have an adverse effect on a stored beam at injection into a high energy colliding beam machine such as the SSC. Multipole magnetization field components have been measured within the HERA storage ring dipole magnets. Calculations of these components using the SCMAG04 code, which agree substantially with the measured multipoles, are presented in the report. As a result, in the proposed continuous correction winding for the SSC, dipoles have been replaced with lumped correction elements every six dipole magnets (about 120 meters apart). Nested lumped correction elements will also produce undesirable higher magnetization multipoles. This report shows a method by which the higher multipole generated by nested correction elements can be identified. (author)

Correcting coils in end magnets of accelerators

Directory of Open Access Journals (Sweden)

L. R. P. Kassab

1998-05-01

Full Text Available We present an empirical investigation of the correcting coils behavior used to homogenize the field distribution of the race-track microtron accelerator end magnets. These end magnets belong to the second stage of the 30.0 MeV cw electron accelerator under construction at IFUSP, the race-track microtron booster, in which the beam energy is raised from 1.97 to 5.1 MeV. The correcting coils are attached to the pole faces and are based on the inhomogeneities of the magnetic field measured. The performance of these coils, when operating the end magnets with currents that differ by ±10% from the one used in the mappings that originated the coils copper leads, is presented. For one of the magnets, adjusting conveniently the current of the correcting coils makes it possible to homogenize field distributions of different intensities, once their shapes are practically identical to those that originated the coils. For the other one, the shapes are changed and the coils are less efficient. This is related to intrinsic factors that determine the inhomogeneities. However, we obtained uniformity of 0.001% in both cases.

Spatial distortion in MRI with application to stereotactic neurosurgery

International Nuclear Information System (INIS)

Morgan, P.S.

1999-05-01

The aim of this work was to implement a thorough method for quantifying the errors introduced to frame-based neurosurgical stereotactic procedures by the use of MRI. Chang and Fitzpatrick's reversed gradient distortion correction method was used, in combination with a phantom, to measure these errors. Spatial distortion in MR images of between 1 mm and 2 mm was measured. Further analysis showed that this typically introduced an additional error in the coordinate of the actual treatment point of 0.7 mm. The implications of this are discussed. The main source of distortion in the MR images used for stereotaxis was found to be the head ring. A comparison between imaging sequences and MR scanners revealed that the spatial distortion depends mainly on the bandwidth per pixel of the sequence rather than other differences in the imaging sequences. By comparison with a phase map distortion correction technique, the imaging parameters required to allow successful distortion correction with the reversed gradient method were identified. The most important was the use of full Fourier spin echo acquisitions. The reversed gradient correction method was applied to two contemporary EPI techniques. Considerable improvement was seen in the production of ADC maps after the images had been corrected for distortion. The method also was shown to be valid in application to BOLD fMRl data. (author)

Correction of distortions in distressed mothers' ratings of their preschool children's psychopathology.

Science.gov (United States)

Müller, Jörg M; Furniss, Tilman

2013-11-30

The often-reported low informant agreement about child psychopathology between multiple informants has lead to various suggestions about how to address discrepant ratings. Among the factors that may lower agreement that have been discussed is informant credibility, reliability, or psychopathology, which is of interest in this paper. We tested three different models, namely, the accuracy, the distortion, and an integrated so-called combined model, that conceptualize parental ratings to assess child psychopathology. The data comprise ratings of child psychopathology from multiple informants (mother, therapist and kindergarten teacher) and ratings of maternal psychopathology. The children were patients in a preschool psychiatry unit (N=247). The results from structural equation modeling show that maternal ratings of child psychopathology were biased by maternal psychopathology (distortion model). Based on this statistical background, we suggest a method to adjust biased maternal ratings. We illustrate the maternal bias by comparing the ratings of mother to expert ratings (combined kindergarten teacher and therapist ratings) and show that the correction equation increases the agreement between maternal and expert ratings. We conclude that this approach may help to reduce misclassification of preschool children as 'clinical' on the basis of biased maternal ratings. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Deep subcritical levels measurements dependents upon kinetic distortion factors

International Nuclear Information System (INIS)

Pan Shibiao; Li Xiang; Fu Guo'en; Huang Liyuan; Mu Keliang

2013-01-01

The measurement of deep subcritical levels, with the increase of subcriticality, showed that the results impact on the kinetic distortion effect, along with neutron flux strongly deteriorated. Using the diffusion theory, calculations have been carried out to quantify the kinetic distortion correction factors in subcritical systems, and these indicate that epithermal neutron distributions are strongly affected by kinetic distortion. Subcriticality measurements in four different rod-state combination at the zero power device was carried out. The test data analysis shows that, with increasing subcriticality, kinetic distortion effect correction factor gradually increases from 1.052 to 1.065, corresponding reactive correction amount of 0.78β eff ∼ 3.01β eff . Thus, it is necessary to consider the kinetic distortion effect in the deep subcritical reactivity measurements. (authors)

Design of self-correction coils in a superferric dipole magnet

Indian Academy of Sciences (India)

Design of self-correction coils in a superferric dipole magnet is carried out. By adopting the self-correction coil (SCC) scheme, we can do online correction of unwanted fields inside the magnet aperture during the whole operating cycle irrespective of their origin. The self-correction coils are short-circuited superconducting ...

Studies of field distortions in a time projection chamber for the International Linear Collider

International Nuclear Information System (INIS)

Zenker, Klaus

2014-12-01

The International Linear Collider (ILC) will allow to do precision measurements of Standard Model parameter and to search for new physics. The ILD detector concept, which is developed for the ILC, uses a Time Projection Chamber (TPC) as central tracking device. The momentum resolution goal for the ILD TPC is δ(1/p t ) ≅ 10 -4 (GeV/c) -1 at a magnetic field of B=3.5 T. Field distortions of the magnetic or electric field inside the sensitive volume of the TPC distort the momentum measurements. Therefore, one needs to keep them under control and correct them with high precision. In this thesis the main sources of field distortions in the TPC are identified and their effects are determined. Furthermore, possibilities to reduce the identified field distortions are presented. One known source of distortions of the electric field are ions, produced by the gas amplification in the TPC anode, that drift into the sensitive volume of the TPC. In the first part of this work the creation of these ions in Gas Electron Multiplier (GEM), which are used for the gas amplification, is studied. It will be shown that the resulting field distortions are not acceptable at the ILD TPC. By tuning the parameters of the gas amplification at the anode the field distortion can be reduced, which is shown in measurements and simulations. In addition measurements using a modified GEM show that it is possible to further reduce the field distortions with such a GEM. In the second part of this work field distortions arising at boundaries between individual readout modules are investigated using simulation studies. It will be shown in simulations, which are verified by measurement results, that these field distortions significantly influence the readout module performance. Based on the simulation results the GEM based readout module developed at DESY is optimised and the field distortions are reduced. These performance improvements could also be verified in measurements. Finally, a laser

Distortion of Magnetic Fields in a Starless Core: Near-infrared Polarimetry of FeSt 1–457

Energy Technology Data Exchange (ETDEWEB)

Kandori, Ryo; Tamura, Motohide; Kusakabe, Nobuhiko [Department of Astronomy, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Nakajima, Yasushi [Hitotsubashi University, 2-1 Naka, Kunitachi, Tokyo 186-8601 (Japan); Kwon, Jungmi [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Nagayama, Takahiro [Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065 (Japan); Nagata, Tetsuya [Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan); Tomisaka, Kohji; Tatematsu, Ken’ichi, E-mail: r.kandori@nao.ac.jp [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)

2017-08-10

Magnetic fields are believed to play an important role in controlling the stability and contraction of the dense condensations of gas and dust that lead to the formation of stars and planetary systems. In the present study, the magnetic field of FeSt 1–457, a cold starless molecular cloud core, was mapped on the basis of the polarized near-infrared light from 185 background stars after being dichroically absorbed by dust aligned with the magnetic field in the core. A distinct “hourglass-shaped” magnetic field was identified in the region of the core, and was interpreted as the first evidence of a magnetic field structure distorted by mass condensation in a starless core. The steep curvature of the magnetic field lines obtained in the present study indicates that the distortion was mainly created during the formation phase of the dense core. The derived mass-to-magnetic flux ratio indicates that the core is in a magnetically supercritical state. However, the stability of the core can be considered to be in a nearly critical state if the additional contributions from the thermal and turbulent support are included. Further diffusion of the magnetic field and/or turbulent dissipation would cause the onset of the dynamical collapse of the core. The geometrical relationship between the direction of the magnetic field lines and the elongation of the core was found to be in good agreement with theoretical predictions for the formation of Sun-like stars under the influence of a magnetic field.

Correcting PSP electron measurements for the effects of spacecraft electrostatic and magnetic fields

Science.gov (United States)

McGinnis, D.; Halekas, J. S.; Larson, D. E.; Whittlesey, P. L.; Kasper, J. C.

2017-12-01

The near-Sun environment which the Parker Solar Probe will investigate presents a unique challenge for the measurement of thermal and suprathermal electrons. Over one orbital period, the ionizing photon flux and charged particle densities vary to such an extent that the spacecraft could charge to electrostatic potentials ranging from a few volts to tens of volts or more, and it may even develop negative electrostatic potentials near closest approach. In addition, significant permanent magnetic fields from spacecraft components will perturb thermal electron trajectories. Given these effects, electron distribution function (EDF) measurements made by the SWEAP/SPAN electron sensors will be significantly affected. It is thus important to try to understand the extent and nature of such effects, and to remediate them as much as possible. To this end, we have incorporated magnetic fields and a model electrostatic potential field into particle tracing simulations to predict particle trajectories through the near spacecraft environment. These simulations allow us to estimate how the solid angle elements measured by SPAN deflect and stretch in the presence of these fields and therefore how and to what extent EDF measurements will be distorted. In this work, we demonstrate how this technique can be used to produce a `dewarping' correction factor. Further, we show that this factor can correct synthetic datasets simulating the warped EDFs that the SPAN instruments are likely to measure over a wide range of spacecraft potentials and plasma Debye lengths.

S.C. correction coils and magnets for the HERA proton ring

International Nuclear Information System (INIS)

Daum, C.; Geerinck, J.; Schmueser, P.

1986-05-01

The quadrupole and sextupole correction coils of the HERA proton ring are mounted on the cold beam pipe inside the main dipole magnets. Superferric dipole magnets for orbit correction are located adjacent to the main quadrupole magnets in a common cryostat which also contains the beam monitor. The design, manufacture and performance of both types of correction elements are described. (orig.)

Quality Evaluation and Nonuniform Compression of Geometrically Distorted Images Using the Quadtree Distortion Map

Directory of Open Access Journals (Sweden)

Cristina Costa

2004-09-01

Full Text Available The paper presents an analysis of the effects of lossy compression algorithms applied to images affected by geometrical distortion. It will be shown that the encoding-decoding process results in a nonhomogeneous image degradation in the geometrically corrected image, due to the different amount of information associated to each pixel. A distortion measure named quadtree distortion map (QDM able to quantify this aspect is proposed. Furthermore, QDM is exploited to achieve adaptive compression of geometrically distorted pictures, in order to ensure a uniform quality on the final image. Tests are performed using JPEG and JPEG2000 coding standards in order to quantitatively and qualitatively assess the performance of the proposed method.

Multi-layer universal correction magnet

International Nuclear Information System (INIS)

Parzen, G.

1981-08-01

This paper presents an approach for constructing a universal correction magnet in which the return currents play an active role in determining the field. The return currents are not hidden by the iron shield. The coil is wound in many layers, instead of just one layer. Each layer has a particular symmetry, and generates a particular class of field multipoles such that the location of the return current for each independently excited current block is clear. Three layers may be sufficient in many cases. This approach is applied to the ISABELLE storage accelerator correction system

High magnetic field multipoles generated by superconductor magnetization within a set of nested superconducting correction coils

International Nuclear Information System (INIS)

Green, M.A.

1990-04-01

Correction elements in colliding beam accelerators such as the SSC can be the source of undesirable higher magnetic field multipoles due to magnetization of the superconductor within the corrector. Quadrupole and sextupole correctors located within the main dipole will produce sextupole and decapole due to magnetization of the superconductor within the correction coils. Lumped nested correction coils can produce a large number of skew and normal magnetization multipoles which may have an adverse effect on a stored beam at injection into a high energy colliding beam machine such as the SSC. 6 refs., 2 figs., 2 tabs

Measurement of 2D vector magnetic properties under the distorted flux density conditions

International Nuclear Information System (INIS)

Urata, Shinya; Todaka, Takashi; Enokizono, Masato; Maeda, Yoshitaka; Shimoji, Hiroyasu

2006-01-01

Under distorted flux density condition, it is very difficult to evaluate the field intensity, because there is no criterion for the measurement. In the linear approximation, the measured field intensity waveform (MFI) is compared with the linear synthesis of field intensity waveform (LSFI) in each frequency, and it is shown that they are not in good agreement at higher induction. In this paper, we examined the 2D vector magnetic properties excited by distorted flux density, which consists of the 1st (fundamental frequency: 50 Hz), 3rd, and 5th harmonics. Improved linear synthesis of the field intensity waveform (ILSFI) is proposed as a new estimation method of the field intensity, instead of the conventional linear synthesis of field intensity waveform (LSFI). The usefulness of the proposed ILSFI is demonstrated in the comparison with the measured results

Measurement of 2D vector magnetic properties under the distorted flux density conditions

Energy Technology Data Exchange (ETDEWEB)

Urata, Shinya [Department of Electrical and Electronic Engineering, Faculty of Engineering, Oita University, 700 Dannoharu, Oita 870-1192 (Japan)]. E-mail: urata@mag.eee.oita-u.ac.jp; Todaka, Takashi [Department of Electrical and Electronic Engineering, Faculty of Engineering, Oita University, 700 Dannoharu, Oita 870-1192 (Japan); Enokizono, Masato [Department of Electrical and Electronic Engineering, Faculty of Engineering, Oita University, 700 Dannoharu, Oita 870-1192 (Japan); Maeda, Yoshitaka [Department of Electrical and Electronic Engineering, Faculty of Engineering, Oita University, 700 Dannoharu, Oita 870-1192 (Japan); Shimoji, Hiroyasu [Department of Electrical and Electronic Engineering, Faculty of Engineering, Oita University, 700 Dannoharu, Oita 870-1192 (Japan)

2006-09-15

Under distorted flux density condition, it is very difficult to evaluate the field intensity, because there is no criterion for the measurement. In the linear approximation, the measured field intensity waveform (MFI) is compared with the linear synthesis of field intensity waveform (LSFI) in each frequency, and it is shown that they are not in good agreement at higher induction. In this paper, we examined the 2D vector magnetic properties excited by distorted flux density, which consists of the 1st (fundamental frequency: 50 Hz), 3rd, and 5th harmonics. Improved linear synthesis of the field intensity waveform (ILSFI) is proposed as a new estimation method of the field intensity, instead of the conventional linear synthesis of field intensity waveform (LSFI). The usefulness of the proposed ILSFI is demonstrated in the comparison with the measured results.

Magnetic field measurement and correction of VECC K500 superconducting cyclotron

International Nuclear Information System (INIS)

Dey, M.K.; Debnath, J.; Bhunia, U.; Pradhan, J.; Rashid, H.; Paul, S.; Dutta, A.; Naser, Z.A.; Singh, V.; Pal, G.; Nandi, C.; Dasgupta, S.; Bhattacharya, S.; Pal, S.; Roy, A.; Bhattacharya, T.; Bhole, R.B.; Bhale, D.; Chatterjee, M.; Prasad, R.; Nabhiraj, P.Y.; Hazra, D.P.; Mallik, C.; Bhandari, R.K.

2006-01-01

The VECC K500 superconducting cyclotron magnet is commissioned and magnetic field measurement and correction program was successfully completed in March 2006. Here we report the analysis of the measured field data and subsequent correction of the magnet to improve the field quality. (author)

SU-G-JeP2-10: On the Need for a Dynamic Model for Patient-Specific Distortion Corrections for MR-Only Pelvis Treatment Planning

Energy Technology Data Exchange (ETDEWEB)

Glide-Hurst, C; Zheng, W [Henry Ford Health System, Detroit, MI (United States); Stehning, C; Weiss, S; Renisch, S [Philips Research Laboratories, Hamburg (Germany)

2016-06-15

Purpose: Patient-specific distortions, particularly near tissue/air interfaces, require assessment and possible corrections for MRI-only radiation treatment planning (RTP). However, patients are dynamic due to changes in physiological status and motion during imaging sessions. This work investigated the need for dynamic patient-specific distortion corrections to support pelvis MR-only RTP. Methods: The pelvises of healthy volunteers were imaged at 1.0T, 1.5T, and 3.0T. Patient-specific distortion field maps were generated using a dual-echo gradient-recalled echo (GRE) sequence with B0 field maps obtained from the phase difference between the two echoes acquired at two timepoints: empty and full bladders. To quantify changes arising from respiratory state, end-inhalation and end-expiration data were acquired. Distortion map differences were computed between the empty/full bladder and inhalation/expiration to characterize local changes. The normalized frequency distortion distributions in T2-weighted TSE images were characterized, particularly for simulated prostate planning target volumes (PTVs). Results: Changes in rectal and bowel air location were observed, likely due to changes in bladder filling. Within the PTVs, displacement differences (mean ± stdev, range) were −0.02 ± 0.02 mm (−0.13 to 0.07 mm) for 1.0T, −0.1 ± 0.2 mm (−0.92 to 0.74 mm) for 1.5T, and −0.20 ± 0.03 mm (−0.61 to 0.38 mm) for 3.0T. Local changes of ∼1 mm at the prostate-rectal interface were observed for an extreme case at 1.5T. For end-inhale and end-exhale scans at 3.0T, 99% of the voxels had Δx differences within ±0.25mm, thus the displacement differences due to respiratory state appear negligible in the pelvis. Conclusion: Our work suggests that transient bowel/rectal gas due to bladder filling may yield non-negligible patient-specific distortion differences near the prostate/rectal interface, whereas respiration had minimal effect. A temporal patient model for patient

A methodology to investigate the impact of image distortions on the radiation dose when using magnetic resonance images for planning

Science.gov (United States)

Yan, Yue; Yang, Jinzhong; Beddar, Sam; Ibbott, Geoffrey; Wen, Zhifei; Court, Laurence E.; Hwang, Ken-Pin; Kadbi, Mo; Krishnan, Sunil; Fuller, Clifton D.; Frank, Steven J.; Yang, James; Balter, Peter; Kudchadker, Rajat J.; Wang, Jihong

2018-04-01

We developed a novel technique to study the impact of geometric distortion of magnetic resonance imaging (MRI) on intensity-modulated radiation therapy treatment planning. The measured 3D datasets of residual geometric distortion (a 1.5 T MRI component of an MRI linear accelerator system) was fitted with a second-order polynomial model to map the spatial dependence of geometric distortions. Then the geometric distortion model was applied to computed tomography (CT) image and structure data to simulate the distortion of MRI data and structures. Fourteen CT-based treatment plans were selected from patients treated for gastrointestinal, genitourinary, thoracic, head and neck, or spinal tumors. Plans based on the distorted CT and structure data were generated (as the distorted plans). Dose deviations of the distorted plans were calculated and compared with the original plans to study the dosimetric impact of MRI distortion. The MRI geometric distortion led to notable dose deviations in five of the 14 patients, causing loss of target coverage of up to 3.68% and dose deviations to organs at risk in three patients, increasing the mean dose to the chest wall by up to 6.19 Gy in a gastrointestinal patient, and increases the maximum dose to the lung by 5.17 Gy in a thoracic patient.

Anisotropic extinction distortion of the galaxy correlation function

International Nuclear Information System (INIS)

Fang Wenjuan; Hui Lam; Menard, Brice; May, Morgan; Scranton, Ryan

2011-01-01

Similar to the magnification of the galaxies' fluxes by gravitational lensing, the extinction of the fluxes by comic dust, whose existence is recently detected by [B. Menard, R. Scranton, M. Fukugita, and G. Richards, Mon. Not. R. Astron. Soc. 405, 1025 (2010).], also modifies the distribution of a flux-selected galaxy sample. We study the anisotropic distortion by dust extinction to the 3D galaxy correlation function, including magnification bias and redshift distortion at the same time. We find the extinction distortion is most significant along the line of sight and at large separations, similar to that by magnification bias. The correction from dust extinction is negative except at sufficiently large transverse separations, which is almost always opposite to that from magnification bias (we consider a number count slope s>0.4). Hence, the distortions from these two effects tend to reduce each other. At low z (< or approx. 1), the distortion by extinction is stronger than that by magnification bias, but at high z, the reverse holds. We also study how dust extinction affects probes in real space of the baryon acoustic oscillations (BAO) and the linear redshift distortion parameter β. We find its effect on BAO is negligible. However, it introduces a positive scale-dependent correction to β that can be as large as a few percent. At the same time, we also find a negative scale-dependent correction from magnification bias, which is up to percent level at low z, but to ∼40% at high z. These corrections are non-negligible for precision cosmology, and should be considered when testing General Relativity through the scale-dependence of β.

Single-shot imaging with higher-dimensional encoding using magnetic field monitoring and concomitant field correction.

Science.gov (United States)

Testud, Frederik; Gallichan, Daniel; Layton, Kelvin J; Barmet, Christoph; Welz, Anna M; Dewdney, Andrew; Cocosco, Chris A; Pruessmann, Klaas P; Hennig, Jürgen; Zaitsev, Maxim

2015-03-01

PatLoc (Parallel Imaging Technique using Localized Gradients) accelerates imaging and introduces a resolution variation across the field-of-view. Higher-dimensional encoding employs more spatial encoding magnetic fields (SEMs) than the corresponding image dimensionality requires, e.g. by applying two quadratic and two linear spatial encoding magnetic fields to reconstruct a 2D image. Images acquired with higher-dimensional single-shot trajectories can exhibit strong artifacts and geometric distortions. In this work, the source of these artifacts is analyzed and a reliable correction strategy is derived. A dynamic field camera was built for encoding field calibration. Concomitant fields of linear and nonlinear spatial encoding magnetic fields were analyzed. A combined basis consisting of spherical harmonics and concomitant terms was proposed and used for encoding field calibration and image reconstruction. A good agreement between the analytical solution for the concomitant fields and the magnetic field simulations of the custom-built PatLoc SEM coil was observed. Substantial image quality improvements were obtained using a dynamic field camera for encoding field calibration combined with the proposed combined basis. The importance of trajectory calibration for single-shot higher-dimensional encoding is demonstrated using the combined basis including spherical harmonics and concomitant terms, which treats the concomitant fields as an integral part of the encoding. © 2014 Wiley Periodicals, Inc.

Interplay between magnetic order at Mn and Tm sites alongside the structural distortion in multiferroic films of o -TmMn O3

Science.gov (United States)

Windsor, Y. W.; Ramakrishnan, M.; Rettig, L.; Alberca, A.; Bothschafter, E. M.; Staub, U.; Shimamoto, K.; Hu, Y.; Lippert, T.; Schneider, C. W.

2015-06-01

We employ resonant soft x-ray diffraction to individually study the magnetic ordering of the Mn and the Tm sublattices in single-crystalline films of orthorhombic (o -) TmMn O3 . The same magnetic ordering wave vector of (0 q 0 ) with q ≈0.46 is found for both ionic species, suggesting that the familiar antiferromagnetic order of the Mn ions induces a magnetic order on the Tm unpaired 4 f electrons. Indeed, intensity variations of magnetic reflections with temperature corroborate this scenario. Calculated magnetic fields at the Tm sites are used as a model magnetic structure for the Tm, which correctly predicts intensity variations at the Tm resonance upon azimuthal rotation of the sample. The model allows ruling out a b c -cycloid modulation of the Mn ions as the cause for the incommensurate ordering, as found in TbMn O3 . The structural distortion, which occurs in the ferroelectric phase below TC, was followed through nonresonant diffraction of structural reflections forbidden by the high-temperature crystal symmetry. The (0 q 0 ) magnetic reflection appears at the Mn resonance well above TC, indicating that this reflection is sensitive also to the intermediate sinusoidal magnetic phase. The model presented suggests that the Tm 4 f electrons are polarized well above the ferroelectric transition and are possibly not affected by the transition at TC. The successful description of the induced order observed at the Tm resonance is a promising example for future element-selective studies in which "spectator" ions may allow access to previously unobtainable information about other constituent ions.

SU-G-IeP1-15: Towards Accurate Cerebral Blood Flow Quantification with Distortion- Corrected Pseudo-Continuous Arterial Spin Labeling

Energy Technology Data Exchange (ETDEWEB)

Hoff, M; Rane-Levandovsky, S; Andre, J [University of Washington, Seattle, WA (United States)

2016-06-15

Purpose: Traditional arterial spin labeling (ASL) acquisitions with echo planar imaging (EPI) readouts suffer from image distortion due to susceptibility effects, compromising ASL’s ability to accurately quantify cerebral blood flow (CBF) and assess disease-specific patterns associated with CBF abnormalities. Phase labeling for additional coordinate encoding (PLACE) can remove image distortion; our goal is to apply PLACE to improve the quantitative accuracy of ASL CBF in humans. Methods: Four subjects were imaged on a 3T Philips Ingenia scanner using a 16-channel receive coil with a 21/21/10cm (frequency/phase/slice direction) field-of-view. An ASL sequence with a pseudo-continuous ASL (pCASL) labeling scheme was employed to acquire thirty dynamics of single-shot EPI data, with control and label datasets for all dynamics, and PLACE gradients applied on odd dynamics. Parameters included a post-labeling delay = 2s, label duration = 1.8s, flip angle = 90°, TR/TE = 5000/23.5ms, and 2.9/2.9/5.0mm (frequency/phase/slice direction) voxel size. “M0” EPI-reference images and T1-weighted spin-echo images with 0.8/1.0/3.3mm (frequency/phase/slice directions) voxel size were also acquired. Complex conjugate image products of pCASL odd and even dynamics were formed, a linear phase ramp applied, and data expanded and smoothed. Data phase was extracted to map control, label, and M0 magnitude image pixels to their undistorted locations, and images were rebinned to original size. All images were corrected for motion artifacts in FSL 5.0. pCASL images were registered to M0 images, and control and label images were subtracted to compute quantitative CBF maps. Results: pCASL image and CBF map distortions were removed by PLACE in all subjects. Corrected images conformed well to the anatomical T1-weighted reference image, and deviations in corrected CBF maps were evident. Conclusion: Eliminating pCASL distortion with PLACE can improve CBF quantification accuracy using minimal

SU-G-IeP1-15: Towards Accurate Cerebral Blood Flow Quantification with Distortion- Corrected Pseudo-Continuous Arterial Spin Labeling

International Nuclear Information System (INIS)

Hoff, M; Rane-Levandovsky, S; Andre, J

2016-01-01

Purpose: Traditional arterial spin labeling (ASL) acquisitions with echo planar imaging (EPI) readouts suffer from image distortion due to susceptibility effects, compromising ASL’s ability to accurately quantify cerebral blood flow (CBF) and assess disease-specific patterns associated with CBF abnormalities. Phase labeling for additional coordinate encoding (PLACE) can remove image distortion; our goal is to apply PLACE to improve the quantitative accuracy of ASL CBF in humans. Methods: Four subjects were imaged on a 3T Philips Ingenia scanner using a 16-channel receive coil with a 21/21/10cm (frequency/phase/slice direction) field-of-view. An ASL sequence with a pseudo-continuous ASL (pCASL) labeling scheme was employed to acquire thirty dynamics of single-shot EPI data, with control and label datasets for all dynamics, and PLACE gradients applied on odd dynamics. Parameters included a post-labeling delay = 2s, label duration = 1.8s, flip angle = 90°, TR/TE = 5000/23.5ms, and 2.9/2.9/5.0mm (frequency/phase/slice direction) voxel size. “M0” EPI-reference images and T1-weighted spin-echo images with 0.8/1.0/3.3mm (frequency/phase/slice directions) voxel size were also acquired. Complex conjugate image products of pCASL odd and even dynamics were formed, a linear phase ramp applied, and data expanded and smoothed. Data phase was extracted to map control, label, and M0 magnitude image pixels to their undistorted locations, and images were rebinned to original size. All images were corrected for motion artifacts in FSL 5.0. pCASL images were registered to M0 images, and control and label images were subtracted to compute quantitative CBF maps. Results: pCASL image and CBF map distortions were removed by PLACE in all subjects. Corrected images conformed well to the anatomical T1-weighted reference image, and deviations in corrected CBF maps were evident. Conclusion: Eliminating pCASL distortion with PLACE can improve CBF quantification accuracy using minimal

Meson-exchange-current corrections to magnetic moments in quantum hadrodynamics

International Nuclear Information System (INIS)

Morse, T.M.

1990-01-01

Corrections to the magnetic moments of the non-relativistic shell model (Schmidt lines) have a long history. In the early fifties calculations of pion exchange and core polarization contributions to nuclear magnetic moments were initiated. These calculations matured by the early eighties to include other mesons and the delta isobar. Relativistic nuclear shell model calculations are relatively recent. Meson exchange and the delta isobar current contributions to the magnetic moments of the relativistic shell model have remained largely unexplored. The disagreement between the valence values of spherical relativistic mean-field models and experiment was a major problem with early (1975-1985) quantum hydrodynamics (QHD) calculations of magnetic moments. Core polarization calculations (1986-1988) have been found to resolve the large discrepancy, predicting isoscalar magnetic moments to within typically five percent of experiment. The isovector magnetic moments, however, are about twice as far from experiment with an average discrepancy of about ten percent. The pion, being the lightest of the mesons, has historically been expected to dominate isovector corrections. Because this has been found to be true in non-relativistic calculations, the author calculated the pion corrections in the framework of QHD. The seagull and in-flight pion exchange current diagram corrections to the magnetic moments of eight finite nuclei (plus or minus one valence nucleon from the magic A = 16 and A = 40 doubly closed shell systems) are calculated in the framework of QHD, and compared with earlier non-relativistic calculations and experiment

Study and distortion correction in a selective dissemination of information system

International Nuclear Information System (INIS)

Freitas Queiroz, I.O. de.

1978-03-01

The Selective Dissemination of Information (S D I) system of the Nuclear Information Center (Brazil) was presented, and some parameters, for the evaluation of performance and distortion were defined. These parameters were quantified for a sample of 35 user's profiles and 25.818 documents. Possible distortion factors were analysed, and some were selected, so that they could be automatically processed. The 35 profiles were up-dated by use of two algorithms developed for this purpose. For the up-dated profiles new values of the parameters were determined and showed that distortion decreased and efficiency improved. Critical points of the system were identified and new studies, on topics investigated superficially, were proposed. (Author) [pt

Heisenberg coupling constant predicted for molecular magnets with pairwise spin-contamination correction

Energy Technology Data Exchange (ETDEWEB)

Masunov, Artëm E., E-mail: amasunov@ucf.edu [NanoScience Technology Center, Department of Chemistry, and Department of Physics, University of Central Florida, Orlando, FL 32826 (United States); Photochemistry Center RAS, ul. Novatorov 7a, Moscow 119421 (Russian Federation); Gangopadhyay, Shruba [Department of Physics, University of California, Davis, CA 95616 (United States); IBM Almaden Research Center, 650 Harry Road, San Jose, CA 95120 (United States)

2015-12-15

New method to eliminate the spin-contamination in broken symmetry density functional theory (BS DFT) calculations is introduced. Unlike conventional spin-purification correction, this method is based on canonical Natural Orbitals (NO) for each high/low spin coupled electron pair. We derive an expression to extract the energy of the pure singlet state given in terms of energy of BS DFT solution, the occupation number of the bonding NO, and the energy of the higher spin state built on these bonding and antibonding NOs (not self-consistent Kohn–Sham orbitals of the high spin state). Compared to the other spin-contamination correction schemes, spin-correction is applied to each correlated electron pair individually. We investigate two binuclear Mn(IV) molecular magnets using this pairwise correction. While one of the molecules is described by magnetic orbitals strongly localized on the metal centers, and spin gap is accurately predicted by Noodleman and Yamaguchi schemes, for the other one the gap is predicted poorly by these schemes due to strong delocalization of the magnetic orbitals onto the ligands. We show our new correction to yield more accurate results in both cases. - Highlights: • Magnetic orbitails obtained for high and low spin states are not related. • Spin-purification correction becomes inaccurate for delocalized magnetic orbitals. • We use the natural orbitals of the broken symmetry state to build high spin state. • This new correction is made separately for each electron pair. • Our spin-purification correction is more accurate for delocalised magnetic orbitals.

Modifications in the rhombohedral degree of distortion and magnetic properties of Ba-doped BiFeO3 as a function of synthesis methodology

International Nuclear Information System (INIS)

Rojas-George, G.; Silva, J.; Castañeda, R.; Lardizábal, D.; Graeve, O.A.; Fuentes, L.; Reyes-Rojas, A.

2014-01-01

We present an analysis of crystallographic symmetry and the origin of the pseudo-cubic character of doped BiFeO 3 . Specifically, barium-doped bismuth ferrite, Bi 1−x Ba x FeO 3 (x = 0.05, 0.075, 0.1, 0.125), perovskite-type nanoparticles have been synthesized by implementing five modifications to the sol–gel technique (citric acid-assisted sol–gel method, ethylene glycol method, tartaric acid-assisted sol–gel method, polyvinyl alcohol–ethylene glycol method, and EDTA complexing sol–gel method) and their final pseudo-cubic character is discussed. The effect of the carboxylic groups and hydroxyl groups during synthesis is critical to obtain single phase BBFO. Fourier transform infrared spectroscopy and thermogravimetric analysis is used to study the decomposition and thermal behavior of the precursors and their relation to the final nanoparticle characteristics. X-ray diffraction analysis shows a single phase with symmetry changes for four of the five synthesis methodologies employed. Only the EDTA complexing sol–gel method, where EDTA is used as dissolver and chelating agent, is not satisfactory in all concentration ranges. Rietveld results suggest that the degree of distortion of the rhombohedral symmetry in the crystallized BiFeO 3 powders decreases 12% as a result of progressive substitution of Bi 3+ by Ba 2+ and that there is no shift from rhombohedral to tetragonal symmetry. Magnetization properties of samples with a low-distortion rhombohedral structure show higher magnetic saturation and remanent magnetization than samples with high-distortion rhombohedral structure. - Highlights: • Ba–BiFeO 3 : rhombohedral distortion degree is highly affected by the chemical method. • Rietveld results show no shift in BBFO from rhombohedral to tetragonal symmetry. • The low-distortion rhombohedral structure show higher magnetic saturation. • To stabilize a metal complex is necessary a balance between COOH − and OH − groups

Electrical and magnetic properties of the energy-saver correction elements

International Nuclear Information System (INIS)

Johnson, M.; McInturff, A.; Raja, R.; Mantsch, P.

1983-08-01

The lattice of the Fermi National Accelerator Laboratory's Energy Saver/Doubler contains a group of superconducting correction windings associated with each quadrupole. These are housed in an element referred to as a spool. There are 192 spools in the ring plus 12 special power spools which contain the main buss 5000 ampere power input as well as correction elements. There will be constructed and tested 290 spools, including spares of each of the eight different types. There have been 266 individual spools tested to date. The spools were tested for (a) magnetic field quality, harmonic moments, transfer constants and coil angles, (b) high voltage integrity, (c) critical transport current, and (d) cryogenic operating characteristics (i.e., heatloads, thermometry calibration checks, etc.). Data are summarized for 318 cryogenic tests and magnetic field quality of the 266 different spools, which contain 1614 correction magnet coils

Diagnostics of vector magnetic fields

Science.gov (United States)

Stenflo, J. O.

1985-01-01

It is shown that the vector magnetic fields derived from observations with a filter magnetograph will be severely distorted if the spatially unresolved magnetic structure is not properly accounted for. Thus the apparent vector field will appear much more horizontal than it really is, but this distortion is strongly dependent on the area factor and the temperature line weakenings. As the available fluxtube models are not sufficiently well determined, it is not possible to correct the filter magnetograph observations for these effects in a reliable way, although a crude correction is of course much better than no correction at all. The solution to this diagnostic problem is to observe simultaneously in suitable combinations of spectral lines, and/or use Stokes line profiles recorded with very high spectral resolution. The diagnostic power of using a Fourier transform spectrometer for polarimetry is shown and some results from I and V spectra are illustrated. The line asymmetries caused by mass motions inside the fluxtubes adds an extra complication to the diagnostic problem, in particular as there are indications that the motions are nonstationary in nature. The temperature structure appears to be a function of fluxtube diameter, as a clear difference between plage and network fluxtubes was revealed. The divergence of the magnetic field with height plays an essential role in the explanation of the Stokes V asymmetries (in combination with the mass motions). A self consistent treatment of the subarcsec field geometry may be required to allow an accurate derivation of the spatially averaged vector magnetic field from spectrally resolved data.

Corrections for hysteresis curves for rare earth magnet materials measured by open magnetic circuit methods

International Nuclear Information System (INIS)

Nakagawa, Yasuaki

1996-01-01

The methods for testing permanent magnets stipulated in the usual industrial standards are so-called closed magnetic circuit methods which employ a loop tracer using an iron-core electromagnet. If the coercivity exceeds the highest magnetic field generated by the electromagnet, full hysteresis curves cannot be obtained. In the present work, magnetic fields up to 15 T were generated by a high-power water-cooled magnet, and the magnetization was measured by an induction method with an open magnetic circuit, in which the effect of a demagnetizing field should be taken into account. Various rare earth magnets materials such as sintered or bonded Sm-Co and Nd-Fe-B were provided by a number of manufacturers. Hysteresis curves for cylindrical samples with 10 nm in diameter and 2 mm, 3.5 mm, 5 mm, 14 mm or 28 mm in length were measured. Correction for the demagnetizing field is rather difficult because of its non-uniformity. Roughly speaking, a mean demagnetizing factor for soft magnetic materials can be used for the correction, although the application of this factor to hard magnetic material is hardly justified. Thus the dimensions of the sample should be specified when the data obtained by the open magnetic circuit method are used as industrial standards. (author)

Lattice effects in La1-xCaxMnO3 (x=0→1): Relationships between distortions, charge distribution, and magnetism

International Nuclear Information System (INIS)

Booth, C.H.; Bridges, F.; Kwei, G.H.; Lawrence, J.M.; Cornelius, A.L.; Neumeier, J.J.

1998-01-01

X-ray-absorption fine-structure measurements from the Mn and La K edges of samples of La 1-x Ca x MnO 3 (x=0→1) are presented as a function of temperature. In the insulating state, distortions of the Mn-O environment are found to be linear with calcium concentration x. These distortions are consistent with a model where individual Mn 3+ sites have strong Jahn-Teller (JT) distortions while Mn 4+ sites do not, although intermediate distortions are also possible. Comparisons to simulations of various possible bond length distributions show that these distortions are best modeled as a JT distortion, as opposed to charge disproportionation or other models. In the metallic state, at least ∼70% of the distortion is removed. A similar effect is seen in the Mn-Mn bond length distribution. The La-O bond length distribution does not change significantly through the ferromagnetic transition, constraining possible changes in the Mn-O-Mn bond angle to less than 0.5 degree. The changes in the MnO 6 distortion that occur near T c are also present (to a lesser degree) in an insulating sample with x=0.12. The functional relation between the MnO 6 distortions and the magnetization is determined, and compared to transport measurements. copyright 1998 The American Physical Society

Arbitrary function generator for APS injector synchrotron correction magnets

International Nuclear Information System (INIS)

Despe, O.D.

1991-01-01

The APS injector synchrotron has eighty correction magnets around its circumference to provide the vernier field changes required for beam orbit correction during acceleration. The arbitrary function generator (AFG) design is based on scanning out encoded data from a semi-conductor memory, a first-in-first-out (FIFO) device. The data input consists of a maximum of 20 correction values specified within the acceleration window. Additional points between these values are then linearly interpolated to create a uniformly spaced 1000 data-point function stored in the FIFO. Each point, encoded as a 3-bit value is scanned out in synchronism with the injection pulse and used to clock the up/down counter driving the DAC. The DAC produces the analog reference voltage used to control the magnet current. 1 ref., 4 figs

Magnetic corrections to π -π scattering lengths in the linear sigma model

Science.gov (United States)

Loewe, M.; Monje, L.; Zamora, R.

2018-03-01

In this article, we consider the magnetic corrections to π -π scattering lengths in the frame of the linear sigma model. For this, we consider all the one-loop corrections in the s , t , and u channels, associated to the insertion of a Schwinger propagator for charged pions, working in the region of small values of the magnetic field. Our calculation relies on an appropriate expansion for the propagator. It turns out that the leading scattering length, l =0 in the S channel, increases for an increasing value of the magnetic field, in the isospin I =2 case, whereas the opposite effect is found for the I =0 case. The isospin symmetry is valid because the insertion of the magnetic field occurs through the absolute value of the electric charges. The channel I =1 does not receive any corrections. These results, for the channels I =0 and I =2 , are opposite with respect to the thermal corrections found previously in the literature.

Memory Distortion and Its Avoidance: An Event-Related Potentials Study on False Recognition and Correct Rejection.

Science.gov (United States)

Cadavid, Sara; Beato, Maria Soledad

2016-01-01

Memory researchers have long been captivated by the nature of memory distortions and have made efforts to identify the neural correlates of true and false memories. However, the underlying mechanisms of avoiding false memories by correctly rejecting related lures remains underexplored. In this study, we employed a variant of the Deese/Roediger-McDermott paradigm to explore neural signatures of committing and avoiding false memories. ERP were obtained for True recognition, False recognition, Correct rejection of new items, and, more importantly, Correct rejection of related lures. With these ERP data, early-frontal, left-parietal, and late right-frontal old/new effects (associated with familiarity, recollection, and monitoring processes, respectively) were analysed. Results indicated that there were similar patterns for True and False recognition in all three old/new effects analysed in our study. Also, False recognition and Correct rejection of related lures activities seemed to share common underlying familiarity-based processes. The ERP similarities between False recognition and Correct rejection of related lures disappeared when recollection processes were examined because only False recognition presented a parietal old/new effect. This finding supported the view that actual false recollections underlie false memories, providing evidence consistent with previous behavioural research and with most ERP and neuroimaging studies. Later, with the onset of monitoring processes, False recognition and Correct rejection of related lures waveforms presented, again, clearly dissociated patterns. Specifically, False recognition and True recognition showed more positive going patterns than Correct rejection of related lures signal and Correct rejection of new items signature. Since False recognition and Correct rejection of related lures triggered familiarity-recognition processes, our results suggest that deciding which items are studied is based more on recollection

Memory Distortion and Its Avoidance: An Event-Related Potentials Study on False Recognition and Correct Rejection.

Directory of Open Access Journals (Sweden)

Sara Cadavid

Full Text Available Memory researchers have long been captivated by the nature of memory distortions and have made efforts to identify the neural correlates of true and false memories. However, the underlying mechanisms of avoiding false memories by correctly rejecting related lures remains underexplored. In this study, we employed a variant of the Deese/Roediger-McDermott paradigm to explore neural signatures of committing and avoiding false memories. ERP were obtained for True recognition, False recognition, Correct rejection of new items, and, more importantly, Correct rejection of related lures. With these ERP data, early-frontal, left-parietal, and late right-frontal old/new effects (associated with familiarity, recollection, and monitoring processes, respectively were analysed. Results indicated that there were similar patterns for True and False recognition in all three old/new effects analysed in our study. Also, False recognition and Correct rejection of related lures activities seemed to share common underlying familiarity-based processes. The ERP similarities between False recognition and Correct rejection of related lures disappeared when recollection processes were examined because only False recognition presented a parietal old/new effect. This finding supported the view that actual false recollections underlie false memories, providing evidence consistent with previous behavioural research and with most ERP and neuroimaging studies. Later, with the onset of monitoring processes, False recognition and Correct rejection of related lures waveforms presented, again, clearly dissociated patterns. Specifically, False recognition and True recognition showed more positive going patterns than Correct rejection of related lures signal and Correct rejection of new items signature. Since False recognition and Correct rejection of related lures triggered familiarity-recognition processes, our results suggest that deciding which items are studied is based more on

Line voltage distortions due to operation of the power supply devices required for plasma heating and magnetic field generation in the W7X thermonuclear fusion experiment

International Nuclear Information System (INIS)

Werner, F.

1997-03-01

The operation of the W7-X plasma heating devices requires high voltage DC power supplies with a total electrical power of 40 MVA. For this purpose twelve-pulse AC/DC converters are projected. These converters enforce a non sinusoidal line current, whose harmonics are causing corresponding line voltage distortions. To evaluate the extent of these distortions, the reaction of the harmonic currents on the AC line, is investigated by numerical network analysis. This is done for both, the 20 kV-junction point of the converters and the 110 kV-line terminal of the electricity supply company. Furthermore the design of LC series-resonant circuits, projected for power factor correction and damping of the harmonic content of the line voltage, has been verified. The additional operation of the 1.5 MVA magnet power supplies also contributes, even though to a much smaller extent, to the line voltage distortion. The influence of these twelve-pulse AC/DC converters was investigated too. The numerical calculations have been done with the aid of the network simulation program 'Pspice'. In an equivalent circuit the transmission line network and the transformers are represented by their inductances respectively equivalent inductances. The rectifier units are simulated by a number of current sources, producing the current harmonics in amplitude, frequency and phase. The harmonics amplitudes of the plasma heating power supplies are frequency and phase. The harmonics amplitudes of the plasma heating power supplies are measured values given by the manufacturer. For the magnet power supplies, the harmonics are derived from the theoretical step like I(t) current shape by Fourier series decomposition. Due to the action of the LC circuits the achieved characteristic voltage quality values are far below the permissible values corresponding to the recommendations of VDE 0160. (orig.) [de

Tidally distorted exoplanets: Density corrections for short-period hot-Jupiters based solely on observable parameters

Energy Technology Data Exchange (ETDEWEB)

Burton, J. R.; Watson, C. A.; Fitzsimmons, A.; Moulds, V. [Astrophysics Research Centre, Queen' s University Belfast, Belfast BT7 1NN (United Kingdom); Pollacco, D.; Wheatley, P. J. [Department of Physics and Astronomy, University of Warwick, Coventry CV4 7AL (United Kingdom); Littlefair, S. P., E-mail: jburton04@qub.ac.uk [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom)

2014-07-10

The close proximity of short-period hot-Jupiters to their parent star means they are subject to extreme tidal forces. This has a profound effect on their structure and, as a result, density measurements that assume that the planet is spherical can be incorrect. We have simulated the tidally distorted surface for 34 known short-period hot-Jupiters, assuming surfaces of constant gravitational equipotential for the planet, and the resulting densities have been calculated based only on observed parameters of the exoplanet systems. Comparing these results to the density values, assuming the planets are spherical, shows that there is an appreciable change in the measured density for planets with very short periods (typically less than two days). For one of the shortest-period systems, WASP-19b, we determine a decrease in bulk density of 12% from the spherical case and, for the majority of systems in this study, this value is in the range of 1%-5%. On the other hand, we also find cases where the distortion is negligible (relative to the measurement errors on the planetary parameters) even in the cases of some very short period systems, depending on the mass ratio and planetary radius. For high-density gas planets requiring apparently anomalously large core masses, density corrections due to tidal deformation could become important for the shortest-period systems.

Magnetized Reverse Shock: Density-fluctuation-induced Field Distortion, Polarization Degree Reduction, and Application to GRBs

Energy Technology Data Exchange (ETDEWEB)

Deng Wei; Zhang Bing [Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, NV 89154 (United States); Li Hui [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Stone, James M., E-mail: deng@physics.unlv.edu, E-mail: zhang@physics.unlv.edu, E-mail: hli@lanl.gov, E-mail: jstone@astro.princeton.edu [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544-1001 (United States)

2017-08-10

The early optical afterglow emission of several gamma-ray bursts (GRBs) shows a high linear polarization degree (PD) of tens of percent, suggesting an ordered magnetic field in the emission region. The light curves are consistent with being of a reverse shock (RS) origin. However, the magnetization parameter, σ , of the outflow is unknown. If σ is too small, an ordered field in the RS may be quickly randomized due to turbulence driven by various perturbations so that the PD may not be as high as observed. Here we use the “Athena++” relativistic MHD code to simulate a relativistic jet with an ordered magnetic field propagating into a clumpy ambient medium, with a focus on how density fluctuations may distort the ordered magnetic field and reduce PD in the RS emission for different σ values. For a given density fluctuation, we discover a clear power-law relationship between the relative PD reduction and the σ value of the outflow. Such a relation may be applied to estimate σ of the GRB outflows using the polarization data of early afterglows.

Modifications in the rhombohedral degree of distortion and magnetic properties of Ba-doped BiFeO{sub 3} as a function of synthesis methodology

Energy Technology Data Exchange (ETDEWEB)

Rojas-George, G. [Centro de Investigación en Materiales Avanzados S.C., Miguel de Cervantes 120, Complejo Industrial Chihuahua, Chihuahua, Chih. 31109 (Mexico); Silva, J. [Universidad Autónoma de Ciudad Juárez, Ave. del Charro 450 Norte, Cd. Juárez, Chih. 32310 (Mexico); Castañeda, R.; Lardizábal, D. [Centro de Investigación en Materiales Avanzados S.C., Miguel de Cervantes 120, Complejo Industrial Chihuahua, Chihuahua, Chih. 31109 (Mexico); Graeve, O.A. [Department of Mechanical and Aerospace Engineering, University of California, San Diego, 9500 Gilman Dr. – MC 0411, La Jolla, CA 92093-0411 (United States); Fuentes, L. [Centro de Investigación en Materiales Avanzados S.C., Miguel de Cervantes 120, Complejo Industrial Chihuahua, Chihuahua, Chih. 31109 (Mexico); Reyes-Rojas, A., E-mail: armando.reyes@cimav.edu.mx [Centro de Investigación en Materiales Avanzados S.C., Miguel de Cervantes 120, Complejo Industrial Chihuahua, Chihuahua, Chih. 31109 (Mexico)

2014-07-01

We present an analysis of crystallographic symmetry and the origin of the pseudo-cubic character of doped BiFeO{sub 3}. Specifically, barium-doped bismuth ferrite, Bi{sub 1−x}Ba{sub x}FeO{sub 3} (x = 0.05, 0.075, 0.1, 0.125), perovskite-type nanoparticles have been synthesized by implementing five modifications to the sol–gel technique (citric acid-assisted sol–gel method, ethylene glycol method, tartaric acid-assisted sol–gel method, polyvinyl alcohol–ethylene glycol method, and EDTA complexing sol–gel method) and their final pseudo-cubic character is discussed. The effect of the carboxylic groups and hydroxyl groups during synthesis is critical to obtain single phase BBFO. Fourier transform infrared spectroscopy and thermogravimetric analysis is used to study the decomposition and thermal behavior of the precursors and their relation to the final nanoparticle characteristics. X-ray diffraction analysis shows a single phase with symmetry changes for four of the five synthesis methodologies employed. Only the EDTA complexing sol–gel method, where EDTA is used as dissolver and chelating agent, is not satisfactory in all concentration ranges. Rietveld results suggest that the degree of distortion of the rhombohedral symmetry in the crystallized BiFeO{sub 3} powders decreases 12% as a result of progressive substitution of Bi{sup 3+} by Ba{sup 2+} and that there is no shift from rhombohedral to tetragonal symmetry. Magnetization properties of samples with a low-distortion rhombohedral structure show higher magnetic saturation and remanent magnetization than samples with high-distortion rhombohedral structure. - Highlights: • Ba–BiFeO{sub 3}: rhombohedral distortion degree is highly affected by the chemical method. • Rietveld results show no shift in BBFO from rhombohedral to tetragonal symmetry. • The low-distortion rhombohedral structure show higher magnetic saturation. • To stabilize a metal complex is necessary a balance between COOH{sup �

Distortion correction for x-ray image intensifiers: Local unwarping polynomials and RBF neural networks

International Nuclear Information System (INIS)

Cerveri, P.; Forlani, C.; Borghese, N.A.; Ferrigno, G.

2002-01-01

In this paper we present two novel techniques, namely a local unwarping polynomial (LUP) and a hierarchical radial basis function (HRBF) network, to correct geometric distortions in XRII images. The two techniques have been implemented and compared, in terms of residual error measured at control and intermediate points, with local and global methods reported in the previous literature. In particular, LUP rests on a locally optimized 3rd degree polynomial applied within each quadrilateral cell on the rectilinear calibration grid of points. HRBF, based on a feed-forward neural network paradigm, is constituted by a set of hierarchical layers at increasing cut-off frequency, each characterized by a set of Gaussian functions. Extensive experiments have been performed both on simulated and real data. In simulation, we tested the effect of pincushion, sigmoidal and local distortions, along with the number of calibration points. Provided that a sufficient number of cells of the calibration grid is available, the obtained accuracy for both LUP and HRBF is comparable to or better than that of global polynomial technique. Tests on real data, carried out by using two different (12 in. and 16 in.) XRIIs, showed that the global polynomial accuracy (0.16±0.08 pixels) is slightly worse than that of LUP (0.07±0.05 pixels) and HRBF (0.08±0.04 pixels). The effects of the discontinuity at the border of the local areas and the decreased accuracy at intermediate points, typical of local techniques, have been proved to be smoothed for both LUP and HRBF

FPGA Based Compensation Method for Correcting Distortion in Voltage Inverters

National Research Council Canada - National Science Library

Williamson, Kenya D

2007-01-01

...) voltage source inverters. Blanking time distortion is caused by the delay inserted to prevent the short circuit that would occur if the two transistors in the same inverter leg are both on at the same time...

Magnetic branes in Gauss-Bonnet gravity with nonlinear electrodynamics: correction of magnetic branes in Einstein-Maxwell gravity

Energy Technology Data Exchange (ETDEWEB)

Hendi, Seyed Hossein [Shiraz University, Physics Department and Biruni Observatory, College of Sciences, Shiraz (Iran, Islamic Republic of); Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), Maragha (Iran, Islamic Republic of); Panahiyan, Shahram; Panah, Behzad Eslam [Shiraz University, Physics Department and Biruni Observatory, College of Sciences, Shiraz (Iran, Islamic Republic of)

2015-06-15

In this paper, we consider two first order corrections to both the gravity and the gauge sides of the Einstein-Maxwell gravity: Gauss-Bonnet gravity and quadratic Maxwell invariant as corrections. We obtain horizonless magnetic solutions by implying a metric representing a topological defect. We analyze the geometric properties of the solutions and investigate the effects of both corrections, and find that these solutions may be interpreted as magnetic branes. We study the singularity condition and find a nonsingular spacetime with a conical geometry. We also investigate the effects of different parameters on the deficit angle of spacetime near the origin. (orig.)

Magnetic branes in Gauss-Bonnet gravity with nonlinear electrodynamics: correction of magnetic branes in Einstein-Maxwell gravity

International Nuclear Information System (INIS)

Hendi, Seyed Hossein; Panahiyan, Shahram; Panah, Behzad Eslam

2015-01-01

In this paper, we consider two first order corrections to both the gravity and the gauge sides of the Einstein-Maxwell gravity: Gauss-Bonnet gravity and quadratic Maxwell invariant as corrections. We obtain horizonless magnetic solutions by implying a metric representing a topological defect. We analyze the geometric properties of the solutions and investigate the effects of both corrections, and find that these solutions may be interpreted as magnetic branes. We study the singularity condition and find a nonsingular spacetime with a conical geometry. We also investigate the effects of different parameters on the deficit angle of spacetime near the origin. (orig.)

Effects and Correction of Closed Orbit Magnet Errors in the SNS Ring

Energy Technology Data Exchange (ETDEWEB)

Bunch, S.C.; Holmes, J.

2004-01-01

We consider the effect and correction of three types of orbit errors in SNS: quadrupole displacement errors, dipole displacement errors, and dipole field errors. Using the ORBIT beam dynamics code, we focus on orbit deflection of a standard pencil beam and on beam losses in a high intensity injection simulation. We study the correction of these orbit errors using the proposed system of 88 (44 horizontal and 44 vertical) ring beam position monitors (BPMs) and 52 (24 horizontal and 28 vertical) dipole corrector magnets. Correction is carried out numerically by adjusting the kick strengths of the dipole corrector magnets to minimize the sum of the squares of the BPM signals for the pencil beam. In addition to using the exact BPM signals as input to the correction algorithm, we also consider the effect of random BPM signal errors. For all three types of error and for perturbations of individual magnets, the correction algorithm always chooses the three-bump method to localize the orbit displacement to the region between the magnet and its adjacent correctors. The values of the BPM signals resulting from specified settings of the dipole corrector kick strengths can be used to set up the orbit response matrix, which can then be applied to the correction in the limit that the signals from the separate errors add linearly. When high intensity calculations are carried out to study beam losses, it is seen that the SNS orbit correction system, even with BPM uncertainties, is sufficient to correct losses to less than 10-4 in nearly all cases, even those for which uncorrected losses constitute a large portion of the beam.

A New Quaternion-Based Kalman Filter for Real-Time Attitude Estimation Using the Two-Step Geometrically-Intuitive Correction Algorithm.

Science.gov (United States)

Feng, Kaiqiang; Li, Jie; Zhang, Xiaoming; Shen, Chong; Bi, Yu; Zheng, Tao; Liu, Jun

2017-09-19

In order to reduce the computational complexity, and improve the pitch/roll estimation accuracy of the low-cost attitude heading reference system (AHRS) under conditions of magnetic-distortion, a novel linear Kalman filter, suitable for nonlinear attitude estimation, is proposed in this paper. The new algorithm is the combination of two-step geometrically-intuitive correction (TGIC) and the Kalman filter. In the proposed algorithm, the sequential two-step geometrically-intuitive correction scheme is used to make the current estimation of pitch/roll immune to magnetic distortion. Meanwhile, the TGIC produces a computed quaternion input for the Kalman filter, which avoids the linearization error of measurement equations and reduces the computational complexity. Several experiments have been carried out to validate the performance of the filter design. The results demonstrate that the mean time consumption and the root mean square error (RMSE) of pitch/roll estimation under magnetic disturbances are reduced by 45.9% and 33.8%, respectively, when compared with a standard filter. In addition, the proposed filter is applicable for attitude estimation under various dynamic conditions.

Emittance and beam size distortion due to linear coupling

International Nuclear Information System (INIS)

Parzen, G.

1993-01-01

At injection, the presence of linear coupling may result in an increased beam emittance and in increased beam dimensions. Results for the emittance in the presence of linear coupling will be found. These results for the emittance distortion show that the harmonics of the skew quadrupole field close to ν x + ν y are the important harmonics. Results will be found for the important driving terms for the emittance distortion. It will be shown that if these driving terms are corrected, then the total emittance is unchanged, var-epsilon x + var-epsilon y = var-epsilon 1 + var-epsilon 2 . Also, the increase in the beam dimensions will be limited to a factor which is less than 1.414. If the correction is good enough, see below for details, one can achieve var-epsilon 1 = var-epsilon x , var-epsilon 2 = var-epsilon where var-epsilon 1 , var-epsilon 2 are the emittances in the presence of coupling, and the beam dimensions are unchanged. Global correction of the emittance and beam size distortion appears possible

Models of brachial to finger pulse wave distortion and pressure decrement

NARCIS (Netherlands)

Gizdulich, P.; Prentza, A.; Wesseling, K.H.

1997-01-01

Objective: To model the pulse wave distortion and pressure decrement occurring between brachial and finger arteries. Distortion reversion and decrement correction were also our aims. Methods: Brachial artery pressure was recorded intra-arterially and finger pressure was recorded non-invasively by

A variational image-based approach to the correction of susceptibility artifacts in the alignment of diffusion weighted and structural MRI.

Science.gov (United States)

Tao, Ran; Fletcher, P Thomas; Gerber, Samuel; Whitaker, Ross T

2009-01-01

This paper presents a method for correcting the geometric and greyscale distortions in diffusion-weighted MRI that result from inhomogeneities in the static magnetic field. These inhomogeneities may due to imperfections in the magnet or to spatial variations in the magnetic susceptibility of the object being imaged--so called susceptibility artifacts. Echo-planar imaging (EPI), used in virtually all diffusion weighted acquisition protocols, assumes a homogeneous static field, which generally does not hold for head MRI. The resulting distortions are significant, sometimes more than ten millimeters. These artifacts impede accurate alignment of diffusion images with structural MRI, and are generally considered an obstacle to the joint analysis of connectivity and structure in head MRI. In principle, susceptibility artifacts can be corrected by acquiring (and applying) a field map. However, as shown in the literature and demonstrated in this paper, field map corrections of susceptibility artifacts are not entirely accurate and reliable, and thus field maps do not produce reliable alignment of EPIs with corresponding structural images. This paper presents a new, image-based method for correcting susceptibility artifacts. The method relies on a variational formulation of the match between an EPI baseline image and a corresponding T2-weighted structural image but also specifically accounts for the physics of susceptibility artifacts. We derive a set of partial differential equations associated with the optimization, describe the numerical methods for solving these equations, and present results that demonstrate the effectiveness of the proposed method compared with field-map correction.

Effect of lattice distortion on uranium magnetic moments in U4Ru7Ge6 studied by polarized neutron diffraction

Science.gov (United States)

Vališka, Michal; Klicpera, Milan; Doležal, Petr; Fabelo, Oscar; Stunault, Anne; Diviš, Martin; Sechovský, Vladimír

2018-03-01

In a cubic ferromagnet, small spontaneous lattice distortions are expected below the Curie temperature, but the phenomenon is usually neglected. This study focuses on such an effect in the U4Ru7Ge6 compound. Based on DFT calculations, we propose a lattice distortion from the cubic I m -3 m space group to a lower, rhombohedral, symmetry described by the R -3 m space group. The strong spin-orbit coupling of the uranium ions plays an essential role in lowering the symmetry, giving rise to two different U sites (U1 and U2). Using polarized neutron diffraction in applied magnetic fields of 1 and 9 T in the ordered state (1.9 K ) and in the paramagnetic state (20 K ), we bring convincing experimental evidence of this splitting of the U sites, with different magnetic moments. The data have been analyzed both by maximum entropy calculations and by a direct fit in the dipolar approximation. In the ordered phase, the μL/μS ratio of the orbital and spin moments on the U2 site is remarkably lower than for the free U3 + or U4 + ion, which points to a strong hybridization of the U 5 f wave functions with the 4 d wave functions of the surrounding Ru. On the U1 site, the μL/μS ratio exhibits an unexpectedly low value: the orbital moment is almost quenched, like in metallic α -uranium. As a further evidence of the 5 f -4 d hybridization in the U4Ru7Ge6 system, we observe the absence of a magnetic moment on the Ru1 site, but a rather large induced moment on the Ru2 site, which is in closer coordination with both U positions. Very similar results are obtained at 20 K in the ferromagnetic regime induced by the magnetic field of 9 T . This shows that applying a strong magnetic field above the Curie temperature also leads to the splitting of the uranium sites, which further demonstrates the intimate coupling of the magnetic ordering and structural distortion. We propose that the difference between the magnetic moment on the U1 and U2 sites results from the strong spin

Touchless attitude correction for satellite with constant magnetic moment

Science.gov (United States)

Ao, Hou-jun; Yang, Le-ping; Zhu, Yan-wei; Zhang, Yuan-wen; Huang, Huan

2017-09-01

Rescue of satellite with attitude fault is of great value. Satellite with improper injection attitude may lose contact with ground as the antenna points to the wrong direction, or encounter energy problems as solar arrays are not facing the sun. Improper uploaded command may set the attitude out of control, exemplified by Japanese Hitomi spacecraft. In engineering practice, traditional physical contact approaches have been applied, yet with a potential risk of collision and a lack of versatility since the mechanical systems are mission-specific. This paper puts forward a touchless attitude correction approach, in which three satellites are considered, one having constant dipole and two having magnetic coils to control attitude of the first. Particular correction configurations are designed and analyzed to maintain the target's orbit during the attitude correction process. A reference coordinate system is introduced to simplify the control process and avoid the singular value problem of Euler angles. Based on the spherical triangle basic relations, the accurate varying geomagnetic field is considered in the attitude dynamic mode. Sliding mode control method is utilized to design the correction law. Finally, numerical simulation is conducted to verify the theoretical derivation. It can be safely concluded that the no-contact attitude correction approach for the satellite with uniaxial constant magnetic moment is feasible and potentially applicable to on-orbit operations.

Comparitive study of the influence of harmonic voltage distortion on the efficiency of induction machines versus line start permanent magnet machines

OpenAIRE

Debruyne, Colin; Derammelaere, Stijn; Desmet, Jan; Vandevelde, Lieven

2012-01-01

Induction machines have nearly reached their maximal efficiency. In order to further increase the efficiency the use of permanent magnets in combination with the robust design of the induction machine is being extensively researched. These so-called line start permanent magnet machines have an increased efficiency in sine wave conditions in respect to standard induction machines, however the efficiency of these machines is less researched under distorted voltage conditions. This paper compare...

Accuracy evaluation of optical distortion calibration by digital image correlation

Science.gov (United States)

Gao, Zeren; Zhang, Qingchuan; Su, Yong; Wu, Shangquan

2017-11-01

Due to its convenience of operation, the camera calibration algorithm, which is based on the plane template, is widely used in image measurement, computer vision and other fields. How to select a suitable distortion model is always a problem to be solved. Therefore, there is an urgent need for an experimental evaluation of the accuracy of camera distortion calibrations. This paper presents an experimental method for evaluating camera distortion calibration accuracy, which is easy to implement, has high precision, and is suitable for a variety of commonly used lens. First, we use the digital image correlation method to calculate the in-plane rigid body displacement field of an image displayed on a liquid crystal display before and after translation, as captured with a camera. Next, we use a calibration board to calibrate the camera to obtain calibration parameters which are used to correct calculation points of the image before and after deformation. The displacement field before and after correction is compared to analyze the distortion calibration results. Experiments were carried out to evaluate the performance of two commonly used industrial camera lenses for four commonly used distortion models.

Large crystal structure distortion in DyB6 studied by X-ray diffraction

International Nuclear Information System (INIS)

Granovsky, S.A.; Markosyan, A.S.

2003-01-01

A large magnetoelastic coupling induces a lattice distortion of a rhombohedral type in DyB 6 . Below the quadrupolar ordering temperature T Q =31 K the cubic and the distorted phases coexist. The cubic phase disappears at 23 K, which was identified as the magnetic ordering point T N . In the magnetic phase the distortion (dl/l) 111 increases monotonically with decreasing temperature and reaches the value of 9x10 -3 at 8 K, which is one of the largest value known for cubic compounds

Impact of the MLC on the MRI field distortion of a prototype MRI-linac

International Nuclear Information System (INIS)

Kolling, Stefan; Keall, Paul; Oborn, Brad

2013-01-01

Purpose: To cope with intrafraction tumor motion, integrated MRI-linac systems for real-time image guidance are currently under development. The multileaf collimator (MLC) is a key component in every state-of-the-art radiotherapy treatment system, allowing for accurate field shaping and tumor tracking. This work quantifies the magnetic impact of a widely used MLC on the MRI field homogeneity for such a modality.Methods: The finite element method was employed to model a MRI-linac assembly comprised of a 1.0 T split-bore MRI magnet and the key ferromagnetic components of a Varian Millennium 120 MLC, namely, the leaves and motors. Full 3D magnetic field maps of the system were generated. From these field maps, the peak-to-peak distortion within the MRI imaging volume was evaluated over a 30 cm diameter sphere volume (DSV) around the isocenter and compared to a maximum preshim inhomogeneity of 300 μT. Five parametric studies were performed: (1) The source-to-isocenter distance (SID) was varied from 100 to 200 cm, to span the range of a compact system to that with lower magnetic coupling. (2) The MLC model was changed from leaves only to leaves with motors, to determine the contribution to the total distortion caused by MLC leaves and motors separately. (3) The system was configured in the inline or perpendicular orientation, i.e., the linac treatment beam was oriented parallel or perpendicular to the magnetic field direction. (4) The treatment field size was varied from 0 × 0 to 20×20 cm 2 , to span the range of clinical treatment fields. (5) The coil currents were scaled linearly to produce magnetic field strengths B 0 of 0.5, 1.0, and 1.5 T, to estimate how the MLC impact changes with B 0 .Results: (1) The MLC-induced MRI field distortion fell continuously with increasing SID. (2) MLC leaves and motors were found to contribute to the distortion in approximately equal measure. (3) Due to faster falloff of the fringe field, the field distortion was

Corrections of residual fluorescence distortions for a glancing-emergence-angle x-ray-absorption technique

International Nuclear Information System (INIS)

Brewe, D.L.; Pease, D.M.; Budnick, J.I.

1994-01-01

Distortions appear in x-ray-absorption spectra obtained by monitoring the fluorescence from thick samples with concentrated absorbing species. The glancing-emergence-angle technique for obtaining spectra from this type of sample eliminates distortions from the measured spectra by monitoring the fluorescence leaving the sample at a small angle relative to the sample surface. This technique is limited by the small signal available from the inherently limited detector solid angle. In addition, no precise estimate of the required restriction on maximum emergent angle θ max has been available. We have calculated residual extended x-ray-absorption fine structure distortions as a function of θ max , and performed experimental tests of the calculations. These calculations provide a means to estimate the required detector geometry for negligible distortions, or alternatively, allow the use of a larger θ max , increasing the available signal, with the remaining residual distortions removed by application of the calculations. The calculations are also applicable to other detector geometries, and account for detectors subtending a large solid angle by an integration over the subtended angle. This represents an improvement over previous calculations. The application to more general detector configurations is also discussed

Superconducting self-correcting harmonic coils for pulsed superconducting dipole or multipole magnets

International Nuclear Information System (INIS)

Dael, A.; Kircher, F.; Perot, J.

1975-01-01

Due to the zero resistance of a superconducting wire, an induced current in a closed superconducting circuit is continuously exactly opposed to its cause. This phenomenon was applied to the correction of the field harmonics of a pulsed magnet by putting short-circuited superconducting coils of particular symmetry in the useful aperture of the magnet. After a review of the main characteristics of such devices, the construction of two correcting coils (quadrupole and sextupole) is described. Experimental results of magnetic efficiency and time behavior are given; they are quite encouraging, since the field harmonics were reduced by one or two orders of magnitude

Development and validation of a novel large field of view phantom and a software module for the quality assurance of geometric distortion in magnetic resonance imaging.

Science.gov (United States)

Torfeh, Tarraf; Hammoud, Rabih; McGarry, Maeve; Al-Hammadi, Noora; Perkins, Gregory

2015-09-01

To develop and validate a large field of view phantom and quality assurance software tool for the assessment and characterization of geometric distortion in MRI scanners commissioned for radiation therapy planning. A purpose built phantom was developed consisting of 357 rods (6mm in diameter) of polymethyl-methacrylat separated by 20mm intervals, providing a three dimensional array of control points at known spatial locations covering a large field of view up to a diameter of 420mm. An in-house software module was developed to allow automatic geometric distortion assessment. This software module was validated against a virtual dataset of the phantom that reproduced the exact geometry of the physical phantom, but with known translational and rotational displacements and warping. For validation experiments, clinical MRI sequences were acquired with and without the application of a commercial 3D distortion correction algorithm (Gradwarp™). The software module was used to characterize and assess system-related geometric distortion in the sequences relative to a benchmark CT dataset, and the efficacy of the vendor geometric distortion correction algorithms (GDC) was also assessed. Results issued from the validation of the software against virtual images demonstrate the algorithm's ability to accurately calculate geometric distortion with sub-pixel precision by the extraction of rods and quantization of displacements. Geometric distortion was assessed for the typical sequences used in radiotherapy applications and over a clinically relevant 420mm field of view (FOV). As expected and towards the edges of the field of view (FOV), distortion increased with increasing FOV. For all assessed sequences, the vendor GDC was able to reduce the mean distortion to below 1mm over a field of view of 5, 10, 15 and 20cm radius respectively. Results issued from the application of the developed phantoms and algorithms demonstrate a high level of precision. The results indicate that this

Correction of distortions in optical coherence tomography imaging of the eye

Energy Technology Data Exchange (ETDEWEB)

Podoleanu, Adrian [Applied Optics Group, University of Kent, Canterbury (United Kingdom); Charalambous, Ismini [Applied Optics Group, University of Kent, Canterbury (United Kingdom); Plesea, Lucian [Applied Optics Group, University of Kent, Canterbury (United Kingdom); Dogariu, Aristide [School of Optics, CREOL, University of Central Florida, Orlando, FL (United States); Rosen, Richard [Advanced Retinal Imaging Center, New York Eye and Ear Infirmary, NY (United States)

2004-04-07

Optical coherence tomography (OCT) images are affected by artefacts. These artefacts are the result of different factors such as refraction, curvature of the intermediate layers up to the depth of interest and the scanning procedure. The effect of such errors is different, depending on the way the image is acquired, either en-face or longitudinal OCT. We quantify the distortions by evaluating a lateral and an axial error. These measure the lateral and axial deviations of each image point from the object point inside the tissue. We show that the axial distortion can be larger than the achievable depth resolution in modern OCT systems. We have investigated these errors in imaging different tissue: cornea and retina in vivo and an intraocular lens in vitro.

Efficient bias correction for magnetic resonance image denoising.

Science.gov (United States)

Mukherjee, Partha Sarathi; Qiu, Peihua

2013-05-30

Magnetic resonance imaging (MRI) is a popular radiology technique that is used for visualizing detailed internal structure of the body. Observed MRI images are generated by the inverse Fourier transformation from received frequency signals of a magnetic resonance scanner system. Previous research has demonstrated that random noise involved in the observed MRI images can be described adequately by the so-called Rician noise model. Under that model, the observed image intensity at a given pixel is a nonlinear function of the true image intensity and of two independent zero-mean random variables with the same normal distribution. Because of such a complicated noise structure in the observed MRI images, denoised images by conventional denoising methods are usually biased, and the bias could reduce image contrast and negatively affect subsequent image analysis. Therefore, it is important to address the bias issue properly. To this end, several bias-correction procedures have been proposed in the literature. In this paper, we study the Rician noise model and the corresponding bias-correction problem systematically and propose a new and more effective bias-correction formula based on the regression analysis and Monte Carlo simulation. Numerical studies show that our proposed method works well in various applications. Copyright © 2012 John Wiley & Sons, Ltd.

Slice profile and B1 corrections in 2D magnetic resonance fingerprinting.

Science.gov (United States)

Ma, Dan; Coppo, Simone; Chen, Yong; McGivney, Debra F; Jiang, Yun; Pahwa, Shivani; Gulani, Vikas; Griswold, Mark A

2017-11-01

The goal of this study is to characterize and improve the accuracy of 2D magnetic resonance fingerprinting (MRF) scans in the presence of slice profile (SP) and B 1 imperfections, which are two main factors that affect quantitative results in MRF. The SP and B 1 imperfections are characterized and corrected separately. The SP effect is corrected by simulating the radiofrequency pulse in the dictionary, and the B 1 is corrected by acquiring a B 1 map using the Bloch-Siegert method before each scan. The accuracy, precision, and repeatability of the proposed method are evaluated in phantom studies. The effects of both SP and B 1 imperfections are also illustrated and corrected in the in vivo studies. The SP and B 1 corrections improve the accuracy of the T 1 and T 2 values, independent of the shape of the radiofrequency pulse. The T 1 and T 2 values obtained from different excitation patterns become more consistent after corrections, which leads to an improvement of the robustness of the MRF design. This study demonstrates that MRF is sensitive to both SP and B 1 effects, and that corrections can be made to improve the accuracy of MRF with only a 2-s increase in acquisition time. Magn Reson Med 78:1781-1789, 2017. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Localization of Electrical Insulation Failures in Superconducting Collared Coils by Analysis of the Distortion of a Pulsed Magnetic Field

CERN Document Server

Komorowski, P A

2000-01-01

The localization of possible electrical faults in superconducting accelerator magnets may, in most cases, be a complex, expensive and time-consuming process. In particular, inter-turn short circuits and failures of the ground insulation are well detectable when the magnet is collared, but often disappear after disassembly for repair due to the release of the pre-stress in the coils. The fault localization method presented in this paper is based on the measurement and analysis of the magnetic field generated inside the magnet aperture by a high voltage pulse. The presence of the fault modifies the distribution of the current in the coils and produces a distortion of the magnetic field. The described method aims at locating both the longitudinal and azimuthal position of the fault-affected area. The test method, the transient case FEM models and the implemented experimental set-up are presented and discussed for the LHC dipole models.

Three dimensional topography correction applied to magnetotelluric data from Sikkim Himalayas

Science.gov (United States)

Kumar, Sushil; Patro, Prasanta K.; Chaudhary, B. S.

2018-06-01

Magnetotelluric (MT) method is one of the powerful tools to investigate the deep crustal image of mountainous regions such as Himalayas. Topographic variations due to irregular surface terrain distort the resistivity curves and hence may not give accurate interpretation of magnetotelluric data. The two-dimensional (2-D) topographic effects in Transverse Magnetic (TM) mode is only galvanic whereas inductive in Transverse Electric (TE) mode, thus TM mode responses is much more important than TE mode responses in 2-D. In three-dimensional (3-D), the topography effect is both galvanic and inductive in each element of impedance tensor and hence the interpretation is complicated. In the present work, we investigate the effects of three-dimensional (3-D) topography for a hill model. This paper presents the impedance tensor correction algorithm to reduce the topographic effects in MT data. The distortion caused by surface topography effectively decreases by using homogeneous background resistivity in impedance correction method. In this study, we analyze the response of ramp, distance from topographic edges, conductive and resistive dykes. The new correction method is applied to the real data from Sikkim Himalayas, which brought out the true nature of the basement in this region.

Evidence of two-channel distortion effects in positronium formation reactions

International Nuclear Information System (INIS)

Macri, P A; Miraglia, J E; Hanssen, J; Fojon, O A; Rivarola, R D

2004-01-01

The formation of ground-state positronium in collisions of positrons on hydrogen-like atoms is considered. In previous theoretical works, two-centre distorted wavefunctions were employed to approximate either the initial or the final channel. Here we report results obtained by means of the eikonal final state continuum distorted wave approximation for which asymptotically correct distorted wavefunctions are used for both the initial and final states of the scattering system. Comparison of the present theoretical total cross sections with experimental data reveals that distortion effects become important in both channels as the impact energy decreases. This work also shows that distorted-wave theories may be extended from their usual domain of high impact energies to lower ones. (letter to the editor)

Evidence of two-channel distortion effects in positronium formation reactions

Energy Technology Data Exchange (ETDEWEB)

Macri, P A [Instituto de AstronomIa y FIsica del Espacio, Consejo Nacional de Investigaciones CientIficas y Tecnicas-Universidad de Buenos Aires, Casilla de Correo 67, Suc. 28, 1428 Buenos Aires (Argentina); Miraglia, J E [Instituto de AstronomIa y FIsica del Espacio, Consejo Nacional de Investigaciones CientIficas y Tecnicas-Universidad de Buenos Aires, Casilla de Correo 67, Suc. 28, 1428 Buenos Aires (Argentina); Hanssen, J [Laboratoire de Physique Moleculaire et des Collisions, Institute de Physique Rue Arago, Tecnopole 2000, Metz (France); Fojon, O A [Instituto de FIsica de Rosario, Consejo Nacional de Investigaciones CientIficas y Tecnicas-Universidad Nacional de Rosario, Av. Pellegrini 250, 2000 Rosario (Argentina); Rivarola, R D [Instituto de FIsica de Rosario, Consejo Nacional de Investigaciones CientIficas y Tecnicas-Universidad Nacional de Rosario, Av. Pellegrini 250, 2000 Rosario (Argentina)

2004-03-28

The formation of ground-state positronium in collisions of positrons on hydrogen-like atoms is considered. In previous theoretical works, two-centre distorted wavefunctions were employed to approximate either the initial or the final channel. Here we report results obtained by means of the eikonal final state continuum distorted wave approximation for which asymptotically correct distorted wavefunctions are used for both the initial and final states of the scattering system. Comparison of the present theoretical total cross sections with experimental data reveals that distortion effects become important in both channels as the impact energy decreases. This work also shows that distorted-wave theories may be extended from their usual domain of high impact energies to lower ones. (letter to the editor)

Investigation of the 4D composite MR image distortion field associated with tumor motion for MR-guided radiotherapy.

Science.gov (United States)

Stanescu, T; Jaffray, D

2016-03-01

Magnetic resonance (MR) images are affected by geometric distortions due to the specifics of the MR scanner and patient anatomy. Quantifying the distortions associated with mobile tumors is particularly challenging due to real anatomical changes in the tumor's volume, shape, and relative location within the MR imaging volume. In this study, the authors investigate the 4D composite distortion field, which combines the effects of the susceptibility-induced and system-related distortion fields, experienced by mobile lung tumors. The susceptibility (χ) effects were numerically simulated for two specific scenarios: (a) a full motion cycle of a lung tumor due to breathing as depicted on ten phases of a 4D CBCT data set and (b) varying the tumor size and location in lung tissue via a synthetically generated sphere with variable diameter (4-80 mm). The χ simulation procedure relied on the segmentation and generation of 3D susceptibility (χ) masks and computation of the magnetic field by means of finite difference methods. A system-related distortion field, determined with a phantom and image processing algorithm, was used as a reference. The 4D composite distortion field was generated as the vector summation of the χ-induced and system-related fields. The analysis was performed for two orientations of the main magnetic field (B0), which correspond to several MRIgRT system configurations. Specifically, B0 was set along the z-axis as in the case of a cylindrical-bore scanner and in the (x,y)-plane as for a biplanar MR. Computations were also performed for a full revolution at 15° increments in the case of a rotating biplanar magnet. Histograms and metrics such as maximum, mean, and range were used to evaluate the characteristics of the 4D distortion field. The χ-induced field depends on the change in volume and shape of the moving tumor as well as the local surrounding anatomy. In the case of system-related distortions, the tumor experiences increased field

Intraoperative magnetic tracker calibration using a magneto-optic hybrid tracker for 3-D ultrasound-based navigation in laparoscopic surgery.

Science.gov (United States)

Nakamoto, Masahiko; Nakada, Kazuhisa; Sato, Yoshinobu; Konishi, Kozo; Hashizume, Makoto; Tamura, Shinichi

2008-02-01

This paper describes a ultrasound (3-D US) system that aims to achieve augmented reality (AR) visualization during laparoscopic surgery, especially for the liver. To acquire 3-D US data of the liver, the tip of a laparoscopic ultrasound probe is tracked inside the abdominal cavity using a magnetic tracker. The accuracy of magnetic trackers, however, is greatly affected by magnetic field distortion that results from the close proximity of metal objects and electronic equipment, which is usually unavoidable in the operating room. In this paper, we describe a calibration method for intraoperative magnetic distortion that can be applied to laparoscopic 3-D US data acquisition; we evaluate the accuracy and feasibility of the method by in vitro and in vivo experiments. Although calibration data can be acquired freehand using a magneto-optic hybrid tracker, there are two problems associated with this method--error caused by the time delay between measurements of the optical and magnetic trackers, and instability of the calibration accuracy that results from the uniformity and density of calibration data. A temporal calibration procedure is developed to estimate the time delay, which is then integrated into the calibration, and a distortion model is formulated by zeroth-degree to fourth-degree polynomial fitting to the calibration data. In the in vivo experiment using a pig, the positional error caused by magnetic distortion was reduced from 44.1 to 2.9 mm. The standard deviation of corrected target positions was less than 1.0 mm. Freehand acquisition of calibration data was performed smoothly using a magneto-optic hybrid sampling tool through a trocar under guidance by realtime 3-D monitoring of the tool trajectory; data acquisition time was less than 2 min. The present study suggests that our proposed method could correct for magnetic field distortion inside the patient's abdomen during a laparoscopic procedure within a clinically permissible period of time, as well as

Investigation of image distortion due to MCP electronic readout misalignment and correction via customized GUI application

Science.gov (United States)

Vitucci, G.; Minniti, T.; Tremsin, A. S.; Kockelmann, W.; Gorini, G.

2018-04-01

The MCP-based neutron counting detector is a novel device that allows high spatial resolution and time-resolved neutron radiography and tomography with epithermal, thermal and cold neutrons. Time resolution is possible by the high readout speeds of ~ 1200 frames/sec, allowing high resolution event counting with relatively high rates without spatial resolution degradation due to event overlaps. The electronic readout is based on a Timepix sensor, a CMOS pixel readout chip developed at CERN. Currently, a geometry of a quad Timepix detector is used with an active format of 28 × 28 mm2 limited by the size of the Timepix quad (2 × 2 chips) readout. Measurements of a set of high-precision micrometers test samples have been performed at the Imaging and Materials Science & Engineering (IMAT) beamline operating at the ISIS spallation neutron source (U.K.). The aim of these experiments was the full characterization of the chip misalignment and of the gaps between each pad in the quad Timepix sensor. Such misalignment causes distortions of the recorded shape of the sample analyzed. We present in this work a post-processing image procedure that considers and corrects these effects. Results of the correction will be discussed and the efficacy of this method evaluated.

Periodic seasonal variation of magnets level of the STB ring

International Nuclear Information System (INIS)

Takahashi, Shigenobu

2003-01-01

The Stretcher-Booster (STB) ring, a 1.2 GeV electron synchrotron, was completed in December, 1997 at the Laboratory of Nuclear Sciences (LNS), Tohoku University. The total weight more than 400 tons were placed near the STB ring, such as concrete blocks for radiation shielding and a spectrometer magnet for nuclear physics experiments after the completion of the STB ring. Re-surveying of magnets alignment was started after 2000. Very recently a new building of an experimental hall was constructed close to the building of the STB ring for use of high energy γ-ray from the electron beam. The building will give rise the changes of magnet levels due to its seasonal distortion. The measurements of the magnet level after construction are continued as well as an expected change of the closed orbit distortion (COD) in the STB ring. The serious influence of the variation of the magnet level may be a change of the beam orbit of extracted beam in the stretcher operation. Difference of the orbit distortion reaches more than 5 mm. Correlation between the COD and the seasonal change of the magnet position is not clear at the moment. However, the machine operation and the beam diagnostics are getting better recently. Continuous surveying of the magnet level will be a useful data for a feed forward correction of the beam orbit. Future subjects and prospects are discussed on surveying. (Y. Tanaka)

Large crystal structure distortion in DyB{sub 6} studied by X-ray diffraction

Energy Technology Data Exchange (ETDEWEB)

Granovsky, S.A. E-mail: ser@plms.phys.msu.su; Markosyan, A.S

2003-03-01

A large magnetoelastic coupling induces a lattice distortion of a rhombohedral type in DyB{sub 6}. Below the quadrupolar ordering temperature T{sub Q}=31 K the cubic and the distorted phases coexist. The cubic phase disappears at 23 K, which was identified as the magnetic ordering point T{sub N}. In the magnetic phase the distortion (dl/l){sub 111} increases monotonically with decreasing temperature and reaches the value of 9x10{sup -3} at 8 K, which is one of the largest value known for cubic compounds.

Safe and sensible preprocessing and baseline correction of pupil-size data.

Science.gov (United States)

Mathôt, Sebastiaan; Fabius, Jasper; Van Heusden, Elle; Van der Stigchel, Stefan

2018-02-01

Measurement of pupil size (pupillometry) has recently gained renewed interest from psychologists, but there is little agreement on how pupil-size data is best analyzed. Here we focus on one aspect of pupillometric analyses: baseline correction, i.e., analyzing changes in pupil size relative to a baseline period. Baseline correction is useful in experiments that investigate the effect of some experimental manipulation on pupil size. In such experiments, baseline correction improves statistical power by taking into account random fluctuations in pupil size over time. However, we show that baseline correction can also distort data if unrealistically small pupil sizes are recorded during the baseline period, which can easily occur due to eye blinks, data loss, or other distortions. Divisive baseline correction (corrected pupil size = pupil size/baseline) is affected more strongly by such distortions than subtractive baseline correction (corrected pupil size = pupil size - baseline). We discuss the role of baseline correction as a part of preprocessing of pupillometric data, and make five recommendations: (1) before baseline correction, perform data preprocessing to mark missing and invalid data, but assume that some distortions will remain in the data; (2) use subtractive baseline correction; (3) visually compare your corrected and uncorrected data; (4) be wary of pupil-size effects that emerge faster than the latency of the pupillary response allows (within ±220 ms after the manipulation that induces the effect); and (5) remove trials on which baseline pupil size is unrealistically small (indicative of blinks and other distortions).

Distortion

OpenAIRE

Schultz, Isabella Odorico; Zmylon, Nanna Nielsen; Britze, Juliane

2014-01-01

This paper investigates the audience’s perception of the music festival Distortion. By conducting a field-study focusing on the subject’s perception of Distortion, their perception of the Distortion-attendants, and their perception on the promotion of Distortion, the paper will relate the audience perception to the promotion of the event. Using the group’s own research on the promotion of Distortion, the paper points out both the consistencies and the inconsistencies between the promotion and...

Influence of static Jahn-Teller distortion on the magnetic excitation spectrum of PrO2: A synchrotron x-ray and neutron inelastic scattering study

International Nuclear Information System (INIS)

Webster, C. H.; Helme, L. M.; Boothroyd, A. T.; McMorrow, D. F.; Wilkins, S. B.; Detlefs, C.; Detlefs, B.; Bewley, R. I.; McKelvy, M. J.

2007-01-01

A synchrotron x-ray diffraction study of the crystallographic structure of PrO 2 in the Jahn-Teller distorted phase is reported. The distortion of the oxygen sublattice, which was previously ambiguous, is shown to be a chiral structure in which neighboring oxygen chains have opposite chiralities. A temperature dependent study of the magnetic excitation spectrum, probed by neutron inelastic scattering, is also reported. Changes in the energies and relative intensities of the crystal field transitions provide an insight into the interplay between the static and dynamic Jahn-Teller effects

Magnet design and test of positron emission tomography cyclotron

International Nuclear Information System (INIS)

Wei Tao; Yang Guojun; He Xiaozhong; Pang Jian; Zhao Liangchao; Zhang Kaizhi

2012-01-01

An 11 MeV H - compact cyclotron used for medical radioactive isotope production is under construction in Institute of Fluid Physics, CAEP. The cyclotron magnet adopts the design of small valley gaps and coulee structure which can provide high average magnetic field and strong focus ability. To achieve 5 × 10 -4 measuring accuracy, a magnetic field mapping system has been developed. After iterative correction using field measurement data, the total phase excursion of the cyclotron is within ± 9° and the first harmonic is less than 10 -3 T, which are all acceptable. Furthermore, the beam testing declares the successful construction of the cyclotron magnet. Besides, some magnetic field influence factors were discussed, including the magnetic field distortion and measurement error. (authors)

Effects of Visual Feedback Distortion on Gait Adaptation: Comparison of Implicit Visual Distortion Versus Conscious Modulation on Retention of Motor Learning.

Science.gov (United States)

Kim, Seung-Jae; Ogilvie, Mitchell; Shimabukuro, Nathan; Stewart, Trevor; Shin, Joon-Ho

2015-09-01

Visual feedback can be used during gait rehabilitation to improve the efficacy of training. We presented a paradigm called visual feedback distortion; the visual representation of step length was manipulated during treadmill walking. Our prior work demonstrated that an implicit distortion of visual feedback of step length entails an unintentional adaptive process in the subjects' spatial gait pattern. Here, we investigated whether the implicit visual feedback distortion, versus conscious correction, promotes efficient locomotor adaptation that relates to greater retention of a task. Thirteen healthy subjects were studied under two conditions: (1) we implicitly distorted the visual representation of their gait symmetry over 14 min, and (2) with help of visual feedback, subjects were told to walk on the treadmill with the intent of attaining the gait asymmetry observed during the first implicit trial. After adaptation, the visual feedback was removed while subjects continued walking normally. Over this 6-min period, retention of preserved asymmetric pattern was assessed. We found that there was a greater retention rate during the implicit distortion trial than that of the visually guided conscious modulation trial. This study highlights the important role of implicit learning in the context of gait rehabilitation by demonstrating that training with implicit visual feedback distortion may produce longer lasting effects. This suggests that using visual feedback distortion could improve the effectiveness of treadmill rehabilitation processes by influencing the retention of motor skills.

One-pion exchange current corrections for nuclear magnetic moments in relativistic mean field theory

International Nuclear Information System (INIS)

Li Jian; Yao, J.M.; Meng Jie; Arima, Akito

2011-01-01

The one-pion exchange current corrections to isoscalar and isovector magnetic moments of double-closed shell nuclei plus and minus one nucleon with A = 15, 17, 39 and 41 have been studied in the relativistic mean field (RMF) theory and compared with previous relativistic and non-relativistic results. It has been found that the one-pion exchange current gives a negligible contribution to the isoscalar magnetic moments but a significant correction to the isovector ones. However, the one-pion exchange current enhances the isovector magnetic moments further and does not improve the corresponding description for the concerned nuclei in the present work. (author)

Meson exchange current corrections to magnetic moments in quantum hadro-dynamics

Energy Technology Data Exchange (ETDEWEB)

Morse, T M; Price, C E; Shepard, J R [Colorado Univ., Boulder (USA). Dept. of Physics

1990-11-15

We have calculated pion exchange current corrections to the magnetic moments of closed shell {plus minus}1 particle nuclei near A=16 and 40 within the framework of quantum hadro-dynamics (QHD). We find that the correction is significant and that, in general, the agreement of the QHD isovector moments with experiment is worsened. Comparisons to previous non-relativistic calculations are also made. (orig.).

Distortion of depth perception in virtual environments using stereoscopic displays: quantitative assessment and corrective measures

Science.gov (United States)

Kleiber, Michael; Winkelholz, Carsten

2008-02-01

The aim of the presented research was to quantify the distortion of depth perception when using stereoscopic displays. The visualization parameters of the used virtual reality system such as perspective, haploscopic separation and width of stereoscopic separation were varied. The experiment was designed to measure distortion in depth perception according to allocentric frames of reference. The results of the experiments indicate that some of the parameters have an antithetic effect which allows to compensate the distortion of depth perception for a range of depths. In contrast to earlier research which reported underestimation of depth perception we found that depth was overestimated when using true projection parameters according to the position of the eyes of the user and display geometry.

The effect of the observer vantage point on perceived distortions in linear perspective images.

Science.gov (United States)

Todorović, Dejan

2009-01-01

Some features of linear perspective images may look distorted. Such distortions appear in two drawings by Jan Vredeman de Vries involving perceived elliptical, instead of circular, pillars and tilted, instead of upright, columns. Distortions may be due to factors intrinsic to the images, such as violations of the so-called Perkins's laws, or factors extrinsic to them, such as observing the images from positions different from their center of projection. When the correct projection centers for the two drawings were reconstructed, it was found that they were very close to the images and, therefore, practically unattainable in normal observation. In two experiments, enlarged versions of images were used as stimuli, making the positions of the projection centers attainable for observers. When observed from the correct positions, the perceived distortions disappeared or were greatly diminished. Distortions perceived from other positions were smaller than would be predicted by geometrical analyses, possibly due to flatness cues in the images. The results are relevant for the practical purposes of creating faithful impressions of 3-D spaces using 2-D images.

Modeling susceptibility difference artifacts produced by metallic implants in magnetic resonance imaging with point-based thin-plate spline image registration.

Science.gov (United States)

Pauchard, Y; Smith, M; Mintchev, M

2004-01-01

Magnetic resonance imaging (MRI) suffers from geometric distortions arising from various sources. One such source are the non-linearities associated with the presence of metallic implants, which can profoundly distort the obtained images. These non-linearities result in pixel shifts and intensity changes in the vicinity of the implant, often precluding any meaningful assessment of the entire image. This paper presents a method for correcting these distortions based on non-rigid image registration techniques. Two images from a modelled three-dimensional (3D) grid phantom were subjected to point-based thin-plate spline registration. The reference image (without distortions) was obtained from a grid model including a spherical implant, and the corresponding test image containing the distortions was obtained using previously reported technique for spatial modelling of magnetic susceptibility artifacts. After identifying the nonrecoverable area in the distorted image, the calculated spline model was able to quantitatively account for the distortions, thus facilitating their compensation. Upon the completion of the compensation procedure, the non-recoverable area was removed from the reference image and the latter was compared to the compensated image. Quantitative assessment of the goodness of the proposed compensation technique is presented.

Electromagnetic hammer removes weld distortions from aluminum tanks

Science.gov (United States)

Schwinghamer, R. J.

1965-01-01

Distortions around weld areas on sheet-aluminum tanks and other structures are removed with a portable electromagnetic hammer. The hammer incorporates a coil that generates a controlled high-energy pulsed magnetic field over localized areas on the metal surface.

Effects of galvanic distortions on magnetotelluric data: Interpretation ...

Indian Academy of Sciences (India)

R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

But in the case of field data the problem is ... The distorted data set is corrected using the MT response for DRS model and further ... ments, the apparent resistivity and phase at differ- ... from the telluric field, which is of galvanic or inductive ...

Method of correcting eddy current magnetic fields in particle accelerator vacuum chambers

Science.gov (United States)

Danby, Gordon T.; Jackson, John W.

1991-01-01

A method for correcting magnetic field aberrations produced by eddy currents induced in a particle accelerator vacuum chamber housing is provided wherein correction windings are attached to selected positions on the housing and the windings are energized by transformer action from secondary coils, which coils are inductively coupled to the poles of electro-magnets that are powered to confine the charged particle beam within a desired orbit as the charged particles are accelerated through the vacuum chamber by a particle-driving rf field. The power inductively coupled to the secondary coils varies as a function of variations in the power supplied by the particle-accelerating rf field to a beam of particles accelerated through the vacuum chamber, so the current in the energized correction coils is effective to cancel eddy current flux fields that would otherwise be induced in the vacuum chamber by power variations in the particle beam.

Hologram production and representation for corrected image

Science.gov (United States)

Jiao, Gui Chao; Zhang, Rui; Su, Xue Mei

2015-12-01

In this paper, a CCD sensor device is used to record the distorted homemade grid images which are taken by a wide angle camera. The distorted images are corrected by using methods of position calibration and correction of gray with vc++ 6.0 and opencv software. Holography graphes for the corrected pictures are produced. The clearly reproduced images are obtained where Fresnel algorithm is used in graph processing by reducing the object and reference light from Fresnel diffraction to delete zero-order part of the reproduced images. The investigation is useful in optical information processing and image encryption transmission.

Bipolar power sources for the correction magnets of AmPS

International Nuclear Information System (INIS)

Es, J.T. van; Luigjes, G.; Trigt, J.H. van.

1992-01-01

AmPS consists of many correction magnets which must provide the currents. These currents serve continuously between -3 Amp and +3 Amp. The adjusted current must be stable inside 0,1%. The copper resistance of magnet coils and their wires are ≤ 8 ohm and the self induction is 200 mH. An extended market research on power supplies has enabled the authors to decide to develop it themselves. This development has led to a module system with Bitbus control. (authors). 14 figs., 4 tabs

A magnetic focusing channel for VEC at Calcutta

International Nuclear Information System (INIS)

Mallik, C.

1986-01-01

The extent of the useful aperture of a beam handling quadrupole magnet of the variable energy cyclotron at Calcutta is about 6 cms, but the extent of the beam in radial plane near the entrance to the quadrupole is at least 10 cm i.e. it exceeds the size of the useful aperture. This creates the problem of phase space distortion decreasing the efficiency of the beam transport line and the usable beam. To correct this problem, a triplet bar has been used as a magnetic focusing channel. The magnetic field induced due to this bar in the median plane is shown in a figure and advantages of its use are described. (M.G.B.)

Chromatic aberration correction: an enhancement to the calibration of low-cost digital dermoscopes.

Science.gov (United States)

Wighton, Paul; Lee, Tim K; Lui, Harvey; McLean, David; Atkins, M Stella

2011-08-01

We present a method for calibrating low-cost digital dermoscopes that corrects for color and inconsistent lighting and also corrects for chromatic aberration. Chromatic aberration is a form of radial distortion that often occurs in inexpensive digital dermoscopes and creates red and blue halo-like effects on edges. Being radial in nature, distortions due to chromatic aberration are not constant across the image, but rather vary in both magnitude and direction. As a result, distortions are not only visually distracting but could also mislead automated characterization techniques. Two low-cost dermoscopes, based on different consumer-grade cameras, were tested. Color is corrected by imaging a reference and applying singular value decomposition to determine the transformation required to ensure accurate color reproduction. Lighting is corrected by imaging a uniform surface and creating lighting correction maps. Chromatic aberration is corrected using a second-order radial distortion model. Our results for color and lighting calibration are consistent with previously published results, while distortions due to chromatic aberration can be reduced by 42-47% in the two systems considered. The disadvantages of inexpensive dermoscopy can be quickly substantially mitigated with a suitable calibration procedure. © 2011 John Wiley & Sons A/S.

Continuous table acquisition MRI for radiotherapy treatment planning: Distortion assessment with a new extended 3D volumetric phantom

Energy Technology Data Exchange (ETDEWEB)

Walker, Amy, E-mail: aw554@uowmail.edu.au; Metcalfe, Peter [Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW 2522, Australia and Liverpool and Macarthur Cancer Therapy Centres and Ingham Institute for Applied Medical Research, Liverpool, NSW 2170 (Australia); Liney, Gary [Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW 2522 (Australia); Liverpool and Macarthur Cancer Therapy Centres and Ingham Institute for Applied Medical Research, Liverpool, NSW 2170 (Australia); South West Clinical School, University of New South Wales, Sydney, NSW 2170 (Australia); Holloway, Lois [Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW 2522 (Australia); Liverpool and Macarthur Cancer Therapy Centres and Ingham Institute for Applied Medical Research, Liverpool, NSW 2170 (Australia); South West Clinical School, University of New South Wales, Sydney, NSW 2170 (Australia); Institute of Medical Physics, School of Physics, University of Sydney, Sydney, NSW 2006 (Australia); Dowling, Jason; Rivest-Henault, David [Commonwealth Scientific and Industrial Research Organisation, Australian E-Health Research Centre, Herston, QLD 4029 (Australia)

2015-04-15

Purpose: Accurate geometry is required for radiotherapy treatment planning (RTP). When considering the use of magnetic resonance imaging (MRI) for RTP, geometric distortions observed in the acquired images should be considered. While scanner technology and vendor supplied correction algorithms provide some correction, large distortions are still present in images, even when considering considerably smaller scan lengths than those typically acquired with CT in conventional RTP. This study investigates MRI acquisition with a moving table compared with static scans for potential geometric benefits for RTP. Methods: A full field of view (FOV) phantom (diameter 500 mm; length 513 mm) was developed for measuring geometric distortions in MR images over volumes pertinent to RTP. The phantom consisted of layers of refined plastic within which vitamin E capsules were inserted. The phantom was scanned on CT to provide the geometric gold standard and on MRI, with differences in capsule location determining the distortion. MRI images were acquired with two techniques. For the first method, standard static table acquisitions were considered. Both 2D and 3D acquisition techniques were investigated. With the second technique, images were acquired with a moving table. The same sequence was acquired with a static table and then with table speeds of 1.1 mm/s and 2 mm/s. All of the MR images acquired were registered to the CT dataset using a deformable B-spline registration with the resulting deformation fields providing the distortion information for each acquisition. Results: MR images acquired with the moving table enabled imaging of the whole phantom length while images acquired with a static table were only able to image 50%–70% of the phantom length of 513 mm. Maximum distortion values were reduced across a larger volume when imaging with a moving table. Increased table speed resulted in a larger contribution of distortion from gradient nonlinearities in the through

Imaging and assessment of diffusion coefficients by magnetic resonance

International Nuclear Information System (INIS)

Tintera, J.; Dezortova, M.; Hajek, M.; Fitzek, C.

1999-01-01

The problem of assessment of molecular diffusion by magnetic resonance is highlighted and some typical applications of diffusion imaging in the diagnosis, e.g., of cerebral ischemia, changes in patients with phenylketonuria or multiple sclerosis are discussed. The images were obtained by using diffusion weighted spin echo Echo-Planar Imaging sequence with subsequent correction of the geometrical distortion of the images and calculation of the Apparent Diffusion Coefficient map

Anomalous Schottky specific heat and structural distortion in ferromagnetic PrAl2.

Science.gov (United States)

Pathak, Arjun K; Paudyal, D; Mudryk, Y; Gschneidner, K A; Pecharsky, V K

2013-05-03

Unique from other rare earth dialuminides, PrAl(2) undergoes a cubic to tetragonal distortion below T = 30 K in a zero magnetic field, but the system recovers its cubic symmetry upon the application of an external magnetic field of 10 kOe via a lifting of the 4f crystal field splitting. The nuclear Schottky specific heat in PrAl(2) is anomalously high compared to that of pure Pr metal. First principles calculations reveal that the 4f crystal field splitting in the tetragonally distorted phase of PrAl(2) underpins the observed unusual low temperature phenomena.

Monte Carlo study of the double and super-exchange model with lattice distortion

Energy Technology Data Exchange (ETDEWEB)

Suarez, J R; Vallejo, E; Navarro, O [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-360, 04510 Mexico D. F. (Mexico); Avignon, M, E-mail: jrsuarez@iim.unam.m [Institut Neel, Centre National de la Recherche Scientifique (CNRS) and Universite Joseph Fourier, BP 166, 38042 Grenoble Cedex 9 (France)

2009-05-01

In this work a magneto-elastic phase transition was obtained in a linear chain due to the interplay between magnetism and lattice distortion in a double and super-exchange model. It is considered a linear chain consisting of localized classical spins interacting with itinerant electrons. Due to the double exchange interaction, localized spins tend to align ferromagnetically. This ferromagnetic tendency is expected to be frustrated by anti-ferromagnetic super-exchange interactions between neighbor localized spins. Additionally, lattice parameter is allowed to have small changes, which contributes harmonically to the energy of the system. Phase diagram is obtained as a function of the electron density and the super-exchange interaction using a Monte Carlo minimization. At low super-exchange interaction energy phase transition between electron-full ferromagnetic distorted and electron-empty anti-ferromagnetic undistorted phases occurs. In this case all electrons and lattice distortions were found within the ferromagnetic domain. For high super-exchange interaction energy, phase transition between two site distorted periodic arrangement of independent magnetic polarons ordered anti-ferromagnetically and the electron-empty anti-ferromagnetic undistorted phase was found. For this high interaction energy, Wigner crystallization, lattice distortion and charge distribution inside two-site polarons were obtained.

Simulation of 3D-treatment plans in head and neck tumors aided by matching of digitally reconstructed radiographs (DRR) and on-line distortion corrected simulator images

International Nuclear Information System (INIS)

Lohr, Frank; Schramm, Oliver; Schraube, Peter; Sroka-Perez, Gabriele; Seeber, Steffen; Schlepple, Gerd; Schlegel, Wolfgang; Wannenmacher, Michael

1997-01-01

Background and purpose: Simulation of 3D-treatment plans for head and neck malignancy is difficult due to complex anatomy. Therefore, CT-simulation and stereotactic techniques are becoming more common in the treatment preparation, overcoming the need for simulation. However, if simulation is still performed, it is an important step in the treatment preparation/execution chain, since simulation errors, if not detected immediately, can compromise the success of treatment. A recently developed PC-based system for on-line image matching and comparison of digitally reconstructed radiographs (DRR) and distortion corrected simulator monitor images that enables instant correction of field placement errors during the simulation process was evaluated. The range of field placement errors with noncomputer aided simulation is reported. Materials and methods: For 14 patients either a primary 3D-treatment plan or a 3D-boost plan after initial treatment with opposing laterals for head and neck malignancy with a coplanar or non-coplanar two- or three-field technique was simulated. After determining the robustness of the matching process and the accuracy of field placement error detection with phantom measurements, DRRs were generated from the treatment planning CT-dataset of each patient and were interactively matched with on-line simulator images that had undergone correction for geometrical distortion, using a landmark algorithm. Translational field placement errors in all three planes as well as in-plane rotational errors were studied and were corrected immediately. Results: The interactive matching process is very robust with a tolerance of <2 mm when suitable anatomical landmarks are chosen. The accuracy for detection of translational errors in phantom measurements was <1 mm and for in-plane rotational errors the accuracy had a maximum of only 1.5 deg.. For patient simulation, the mean absolute distance of the planned versus simulated isocenter was 6.4 ± 3.9 mm. The in

Correction of magnetization sextupole and decapole in a 5 centimeter bore SSC dipole using passive superconductor

International Nuclear Information System (INIS)

Green, M.A.

1991-05-01

Higher multipoles due to magnetization of the superconductor in four and five centimeter bore Superconducting Super Collider (SSC) superconducting dipole magnets have been observed. The use of passive superconductor to correct out the magnetization sextupole has been demonstrated on two dipoles built by the Lawrence Berkeley Laboratory (LBL). This reports shows how passive correction can be applied to the five centimeter SSC dipoles to remove sextupole and decapole caused by magnetization of the dipole superconductor. Two passive superconductor corrector options will be presented. The change in magnetization sextupole and decapole due to flux creep decay of the superconductor during injection can be partially compensated for using the passive superconductor. 9 refs; 5 figs

Orbit Correction for the Newly Developed Polarization-Switching Undulator

Science.gov (United States)

Obina, Takashi; Honda, Tohru; Shioya, Tatsuro; Kobayashi, Yukinori; Tsuchiya, Kimichika; Yamamoto, Shigeru

2007-01-01

A new scheme of undulator magnet arrangements has been proposed and developed as a polarization-switching radiation source, and its test-stand was installed in the 2.5-GeV Photon Factory storage ring (PF ring) in order to investigate the effects on the beam orbit. The closed orbit distortion (COD) over 200 μm was produced in a vertical direction when we switched the polarization of the radiation from the test-stand. In a horizontal direction, the COD was less than 50μm. The results agreed well with the predictions from the magnetic-field measurement on the bench. In order to suppress the CODs and realize a stable operation of the ring with the polarization-switching, we developed an orbit correction system which consists of an encoder to detect motion of magnets, a pair of beam position monitors (BPMs), signal processing parts, and a pair of steering magnets. We succeeded in suppressing the CODs to the level below 3μm using the system even when we switch the polarization at a maximum frequency of 0.8 Hz.

Models of brachial to finger pulse wave distortion and pressure decrement.

Science.gov (United States)

Gizdulich, P; Prentza, A; Wesseling, K H

1997-03-01

To model the pulse wave distortion and pressure decrement occurring between brachial and finger arteries. Distortion reversion and decrement correction were also our aims. Brachial artery pressure was recorded intra-arterially and finger pressure was recorded non-invasively by the Finapres technique in 53 adult human subjects. Mean pressure was subtracted from each pressure waveform and Fourier analysis applied to the pulsations. A distortion model was estimated for each subject and averaged over the group. The average inverse model was applied to the full finger pressure waveform. The pressure decrement was modelled by multiple regression on finger systolic and diastolic levels. Waveform distortion could be described by a general, frequency dependent model having a resonance at 7.3 Hz. The general inverse model has an anti-resonance at this frequency. It converts finger to brachial pulsations thereby reducing average waveform distortion from 9.7 (s.d. 3.2) mmHg per sample for the finger pulse to 3.7 (1.7) mmHg for the converted pulse. Systolic and diastolic level differences between finger and brachial arterial pressures changed from -4 (15) and -8 (11) to +8 (14) and +8 (12) mmHg, respectively, after inverse modelling, with pulse pressures correct on average. The pressure decrement model reduced both the mean and the standard deviation of systolic and diastolic level differences to 0 (13) and 0 (8) mmHg. Diastolic differences were thus reduced most. Brachial to finger pulse wave distortion due to wave reflection in arteries is almost identical in all subjects and can be modelled by a single resonance. The pressure decrement due to flow in arteries is greatest for high pulse pressures superimposed on low means.

Time-resolved magnetic imaging in an aberration-corrected, energy-filtered photoemission electron microscope

International Nuclear Information System (INIS)

Nickel, F.; Gottlob, D.M.; Krug, I.P.; Doganay, H.; Cramm, S.; Kaiser, A.M.; Lin, G.; Makarov, D.; Schmidt, O.G.

2013-01-01

We report on the implementation and usage of a synchrotron-based time-resolving operation mode in an aberration-corrected, energy-filtered photoemission electron microscope. The setup consists of a new type of sample holder, which enables fast magnetization reversal of the sample by sub-ns pulses of up to 10 mT. Within the sample holder current pulses are generated by a fast avalanche photo diode and transformed into magnetic fields by means of a microstrip line. For more efficient use of the synchrotron time structure, we developed an electrostatic deflection gating mechanism capable of beam blanking within a few nanoseconds. This allows us to operate the setup in the hybrid bunch mode of the storage ring facility, selecting one or several bright singular light pulses which are temporally well-separated from the normal high-intensity multibunch pulse pattern. - Highlights: • A new time-resolving operation mode in photoemission electron microscopy is shown. • Our setup works within an energy-filtered, aberration-corrected PEEM. • A new gating system for bunch selection using synchrotron radiation is developed. • An alternative magnetic excitation system is developed. • First tr-imaging using an energy-filtered, aberration-corrected PEEM is shown

Vertical dispersion produced by random closed orbit distortions and sextupoles

International Nuclear Information System (INIS)

Suzuki, Toshio.

1977-01-01

Vertical dispersion appears even in a machine designed with plane symmetry because of vertical closed orbit distortions, linear coupling and coupling due to sextupoles. This gives rise to several undesirable effects in an electron-positron storage ring such as PEP. Vertical dispersion at the interaction point will increase beam height and reduce luminosity. Vertical dispersion around the ring will modify vertical emittance and partition numbers for synchrotron radiation damping. It will also induce betatron-synchrotron resonance and affect chromaticity correction. Vertical dispersion due to random closed orbit distortions and sextupoles has been studied by Piwinski, and he has indicated that correction of chromaticity and chromatic change of β-function is important. However, he has assumed one error element and evaluated the dispersion at the position of the element. We generalize his argument to a more realistic case and derive more precise criteria for the correction of vertical dispersion. Horizontal dispersion due to perturbations is also studied. Vertical dispersion due to linear coupling is neglected in this note, since it has been studied by other authors. 7 refs

Systems analysis determining critical items, critical assembly processes, primary failure modes and corrective actions on ASST magnets

International Nuclear Information System (INIS)

Arden, C.S.

1993-04-01

During the assembly process through the completion of the Accelerator Surface String Test (ASST) phase one test, Magnet Systems Division Reliability Engineering has tracked all the known discrepancies utilizing the Failure Reporting, Analysis and Corrective Action System (FRACAS) and data base. This paper discusses the critical items, critical assembly processes, primary failure modes and corrective actions (lessons learned) based on actual data for the ASST magnets. The ASST magnets include seven Brookhaven Lab Dipoles (DCA-207 through 213), fourteen Fermi Lab Dipoles (DCA-310 through 323) and five Lawrence Berkeley Lab Quadrupoles (QCC-402 through 406). Between all the ASST magnets built there were one hundred eighty six (186) class one discrepancies reported out of approximately eleven hundred total discrepancy reports. The class one or critical discrepancies are defined as form, fit, function, safety or reliability problem. Each and every ASST magnet is considered a success, as they all achieved the quench performance requirements and were capable of being incorporated into the string test. This paper also discuss some specific magnet discrepancies, including failure cause(s), corrective action and possible open issues

Systems analysis determining critical items, critical assembly processes, primary failure modes and corrective actions on ASST magnets

International Nuclear Information System (INIS)

Arden, C.S.

1994-01-01

During the assembly process through the completion of the Accelerator Surface String Test (ASST) phase one test, Magnet Systems Division Reliability Engineering has tracked all the known discrepancies utilizing the Failure Reporting, Analysis and Corrective Action System (FRACAS) and data base. This paper discusses the critical items, critical assembly processes, primary failure modes and corrective actions (lessons learned) based on actual data for the ASST magnets. The ASST magnets include seven Brookhaven Lab Dipoles (DCA-207 through 213), fourteen Fermi Lab Dipoles (DCA-310 through 323) and five Lawrence Berkeley Lab Quadrupoles (QCC-402 through 406). Between all the ASST magnets built there were one hundred eighty six (186) class one discrepancies reported out of approximately eleven hundred total discrepancy reports. The class one or critical discrepancies are defined as form, fit, function, safety or reliability problem. Each and every ASST magnet is considered a success, as they all achieved the quench performance requirements and were capable of being incorporated into the string test. This paper will also discuss some specific magnet discrepancies, including failure cause(s), corrective action and possible open issues

Cognitive distortions as a component and treatment focus of pathological gambling: a review.

Science.gov (United States)

Fortune, Erica E; Goodie, Adam S

2012-06-01

The literature on the role of cognitive distortions in the understanding and treatment of pathological gambling (PG) is reviewed, with sections focusing on (a) conceptual underpinnings of cognitive distortions, (b) cognitive distortions related to PG, (c) PG therapies that target cognitive distortions, (d) methodological factors and outcome variations, and (e) conclusions and prescriptive recommendations. The conceptual background for distortions related to PG lies in the program of heuristics and biases (Kahneman & Tversky, 1974) as well as other errors identified in basic psychology. The literature has focused on distortions arising from the representativeness heuristic (gambler's fallacy, overconfidence, and trends in number picking), the availability heuristic (illusory correlation, other individuals' wins, and inherent memory bias), and other sources (the illusion of control and double switching). Some therapies have incorporated cognitive restructuring within broader cognitive-behavioral therapies, with success. Other therapies have focused more narrowly on correcting distorted beliefs, more often with limited success. It is concluded that the literature establishes the role of cognitive distortions in PG and suggests therapies with particularly good promise, but is in need of further enrichment.

Measurements of passive correction of magnetization higher multipoles in one meter long dipoles

International Nuclear Information System (INIS)

Green, M.A.; Althaus, R.F.; Barale, P.J.; Benjegerdes, R.W.; Gilbert, W.S.; Green, M.I.; Scanlan, R.M.; Taylor, C.E.

1990-09-01

The use of passive superconductor to correct the magnetization sextupole and decapole in SSC dipoles appears to be promising. This paper presents the results of a series of experiments of passive superconductor correctors in one meter long dipole magnets. Reduction of the magnetization sextupole by a factor of five to ten has been achieved using the passive superconductor correctors. The magnetization decapole was also reduced. The passive superconductor correctors reduced the sextupole temperature sensitivity by an order of magnitude. Flux creep decay was partially compensated for by the correctors. 13 refs., 7 figs

Tomosynthesis-detected Architectural Distortion: Management Algorithm with Radiologic-Pathologic Correlation.

Science.gov (United States)

Durand, Melissa A; Wang, Steven; Hooley, Regina J; Raghu, Madhavi; Philpotts, Liane E

2016-01-01

As use of digital breast tomosynthesis becomes increasingly widespread, new management challenges are inevitable because tomosynthesis may reveal suspicious lesions not visible at conventional two-dimensional (2D) full-field digital mammography. Architectural distortion is a mammographic finding associated with a high positive predictive value for malignancy. It is detected more frequently at tomosynthesis than at 2D digital mammography and may even be occult at conventional 2D imaging. Few studies have focused on tomosynthesis-detected architectural distortions to date, and optimal management of these distortions has yet to be well defined. Since implementing tomosynthesis at our institution in 2011, we have learned some practical ways to assess architectural distortion. Because distortions may be subtle, tomosynthesis localization tools plus improved visualization of adjacent landmarks are crucial elements in guiding mammographic identification of elusive distortions. These same tools can guide more focused ultrasonography (US) of the breast, which facilitates detection and permits US-guided tissue sampling. Some distortions may be sonographically occult, in which case magnetic resonance imaging may be a reasonable option, both to increase diagnostic confidence and to provide a means for image-guided biopsy. As an alternative, tomosynthesis-guided biopsy, conventional stereotactic biopsy (when possible), or tomosynthesis-guided needle localization may be used to achieve tissue diagnosis. Practical uses for tomosynthesis in evaluation of architectural distortion are highlighted, potential complications are identified, and a working algorithm for management of tomosynthesis-detected architectural distortion is proposed. (©)RSNA, 2016.

Local probe studies on lattice distortions and electronic correlations in manganites

CERN Document Server

lopes, Armandina; Correia, João Guilherme

This thesis presents an experimental study on lattice distortions and electronic correlations in colossal magnetoresistive magnetic oxides. The Perturbed Angular Correlation local probe technique is used to study selected manganite systems in order to obtain relevant insight into microscopic phenomena responsible for their macroscopic pr operties. Complementary structural, magnetic and electric characterization was performed. The work is focused on the following aspects: \\\\Lattice distortions and polaron clusters in LaMnO$_{3+ \\Delta}$ system. A study of the electric field gradi ent and magnetic hyperfine field was performed in representative samples of the LaMnO$_{3+ \\Delta}$ system, and correlated with macroscopic information obtained in the same samples. Particular attention was given to the LaMnO$_{3.12}$ sample since this compound is a prototype of a ferromagnetic-insulat or manganite, presenting a rhombohedric- orthorhombic structural phase transition near room temperature. We found that random distribu...

Analytical model for relativistic corrections to the nuclear magnetic shielding constant in atoms

International Nuclear Information System (INIS)

Romero, Rodolfo H.; Gomez, Sergio S.

2006-01-01

We present a simple analytical model for calculating and rationalizing the main relativistic corrections to the nuclear magnetic shielding constant in atoms. It provides good estimates for those corrections and their trends, in reasonable agreement with accurate four-component calculations and perturbation methods. The origin of the effects in deep core atomic orbitals is manifestly shown

Analytical model for relativistic corrections to the nuclear magnetic shielding constant in atoms

Energy Technology Data Exchange (ETDEWEB)

Romero, Rodolfo H. [Facultad de Ciencias Exactas, Universidad Nacional del Nordeste, Avenida Libertad 5500 (3400), Corrientes (Argentina)]. E-mail: rhromero@exa.unne.edu.ar; Gomez, Sergio S. [Facultad de Ciencias Exactas, Universidad Nacional del Nordeste, Avenida Libertad 5500 (3400), Corrientes (Argentina)

2006-04-24

We present a simple analytical model for calculating and rationalizing the main relativistic corrections to the nuclear magnetic shielding constant in atoms. It provides good estimates for those corrections and their trends, in reasonable agreement with accurate four-component calculations and perturbation methods. The origin of the effects in deep core atomic orbitals is manifestly shown.

Asymmetry of the Ion Diffusion Region Hall Electric and Magnetic Fields during Guide Field Reconnection: Observations and Comparison with Simulations

International Nuclear Information System (INIS)

Eastwood, J. P.; Shay, M. A.; Phan, T. D.; Oieroset, M.

2010-01-01

In situ measurements of magnetic reconnection in the Earth's magnetotail are presented showing that even a moderate guide field (20% of the reconnecting field) considerably distorts ion diffusion region structure. The Hall magnetic and electric fields are asymmetric and shunted away from the current sheet; an appropriately scaled particle-in-cell simulation is found to be in excellent agreement with the data. The results show the importance of correctly accounting for the effects of the magnetic shear when attempting to identify and study magnetic reconnection diffusion regions in nature.

MAGNETIC SYMPATHICUS CORRECTION IN TREATMENT ENURESIS IN CHILDREN

Directory of Open Access Journals (Sweden)

T. V. Otpuschennikova

2014-01-01

Full Text Available Based on a investigation 92 children aged 6 to 15 years with enuresis shown to be effective use of physiotherapy in combination with a minimum dose of oxybutynin (2.5 mg at night. Physiotherapy is a combination of two types of magnetic therapy – transcranial method for bitemporal and cervical sympathetic ganglia on the neck-collar method. Therapeutic effect as reliever enuresis achieved in 76.6% of children. Positive dynamics of enuresis associated with the correction and improvement of adaptation hypersympathicotonia and autonomic nervous system.

Coil extensions improve line shapes by removing field distortions

Science.gov (United States)

Conradi, Mark S.; Altobelli, Stephen A.; McDowell, Andrew F.

2018-06-01

The static magnetic susceptibility of the rf coil can substantially distort the field B0 and be a dominant source of line broadening. A scaling argument shows that this may be a particular problem in microcoil NMR. We propose coil extensions to reduce the distortion. The actual rf coil is extended to a much longer overall length by abutted coil segments that do not carry rf current. The result is a long and nearly uniform sheath of copper wire, in terms of the static susceptibility. The line shape improvement is demonstrated at 43.9 MHz and in simulation calculations.

Flat-field response and geometric distortion measurements of optical streak cameras

International Nuclear Information System (INIS)

Montgomery, D.S.; Drake, R.P.; Jones, B.A.; Wiedwald, J.D.

1987-01-01

To accurately measure pulse amplitude, shape, and relative time histories of optical signals with an optical streak camera, it is necessary to correct each recorded image for spatially-dependent gain nonuniformity and geometric distortion. Gain nonuniformities arise from sensitivity variations in the streak-tube photocathode, phosphor screen, image-intensifier tube, and image recording system. By using a 1.053-μm, long-pulse, high-power laser to generate a spatially and temporally uniform source as input to the streak camera, the combined effects of flat-field response and geometric distortion can be measured under the normal dynamic operation of cameras with S-1 photocathodes. Additionally, by using the same laser system to generate a train of short pulses that can be spatially modulated at the input of the streak camera, the authors can create a two-dimensional grid of equally-spaced pulses. This allows a dynamic measurement of the geometric distortion of the streak camera. The author discusses the techniques involved in performing these calibrations, present some of the measured results for LLNL optical streak cameras, and will discuss software methods to correct for these effects

Magnetic-distortion-induced Ellipticity and Gravitational Wave Radiation of Neutron Stars: Millisecond Magnetars in Short GRBs, Galactic Pulsars, and Magnetars

Energy Technology Data Exchange (ETDEWEB)

Gao, He; Cao, Zhoujian [Department of Astronomy, Beijing Normal University, Beijing 100875 (China); Zhang, Bing, E-mail: gaohe@bnu.edu.cn [Department of Physics and Astronomy, University of Nevada Las Vegas, NV 89154 (United States)

2017-08-01

Neutron stars may sustain a non-axisymmetric deformation due to magnetic distortion and are potential sources of continuous gravitational waves (GWs) for ground-based interferometric detectors. With decades of searches using available GW detectors, no evidence of a GW signal from any pulsar has been observed. Progressively stringent upper limits of ellipticity have been placed on Galactic pulsars. In this work, we use the ellipticity inferred from the putative millisecond magnetars in short gamma-ray bursts (SGRBs) to estimate their detectability by current and future GW detectors. For ∼1 ms magnetars inferred from the SGRB data, the detection horizon is ∼30 Mpc and ∼600 Mpc for the advanced LIGO (aLIGO) and Einstein Telescope (ET), respectively. Using the ellipticity of SGRB millisecond magnetars as calibration, we estimate the ellipticity and GW strain of Galactic pulsars and magnetars assuming that the ellipticity is magnetic-distortion-induced. We find that the results are consistent with the null detection results of Galactic pulsars and magnetars with the aLIGO O1. We further predict that the GW signals from these pulsars/magnetars may not be detectable by the currently designed aLIGO detector. The ET detector may be able to detect some relatively low-frequency signals (<50 Hz) from some of these pulsars. Limited by its design sensitivity, the eLISA detector seems to not be suitable for detecting the signals from Galactic pulsars and magnetars.

Improved distorted wave theory with the localized virial conditions

Science.gov (United States)

Hahn, Y. K.; Zerrad, E.

2009-12-01

The distorted wave theory is operationally improved to treat the full collision amplitude, such that the corrections to the distorted wave Born amplitude can be systematically calculated. The localized virial conditions provide the tools necessary to test the quality of successive approximations at each stage and to optimize the solution. The details of the theoretical procedure are explained in concrete terms using a collisional ionization model and variational trial functions. For the first time, adjustable parameters associated with an approximate scattering solution can be fully determined by the theory. A small number of linear parameters are introduced to examine the convergence property and the effectiveness of the new approach.

Distortions of the magnetic field by storm-time current systems in Earth's magnetosphere

Directory of Open Access Journals (Sweden)

N. Yu. Ganushkina

2010-01-01

Full Text Available Magnetic field and current system changes in Earth's inner magnetosphere during storm times are studied using two principally different modeling approaches: on one hand, the event-oriented empirical magnetic field model, and, on the other, the Space Weather Modeling Framework (SWMF built around a global MHD simulation. Two storm events, one moderate storm on 6–7 November 1997 with Dst minimum about −120 nT and one intense storm on 21–23 October 1999 with Dst minimum about −250 nT were modeled. Both modeling approaches predicted a large ring current (first partial, later symmetric contribution to the magnetic field perturbation for the intense storm. For the moderate storm, the tail current plays a dominant role in the event-oriented model results, while the SWMF results showed no strong tail current in the main phase, which resulted in a poorly timed storm peak relative to the observations. These results imply that the the development of a ring current depends on a strong force to inject the particles deep into the inner magnetosphere, and that the tail current is an important external source for the distortions of the inner magnetospheric magnetic field for both storms. Neither modeling approach was able to reproduce all the variations in the B_x and B_y components observed at geostationary orbit by GOES satellites during these two storms: the magnetopause current intensifications are inadequate, and the field-aligned currents are not sufficiently represented. While the event-oriented model reproduces rather well the B_z component at geostationary orbit, including the substorm-associated changes, the SWMF field is too dipolar at these locations. The empirical model is a useful tool for validation of the first-principle based models such as the SWMF.

A locally adaptive algorithm for shadow correction in color images

Science.gov (United States)

Karnaukhov, Victor; Kober, Vitaly

2017-09-01

The paper deals with correction of color images distorted by spatially nonuniform illumination. A serious distortion occurs in real conditions when a part of the scene containing 3D objects close to a directed light source is illuminated much brighter than the rest of the scene. A locally-adaptive algorithm for correction of shadow regions in color images is proposed. The algorithm consists of segmentation of shadow areas with rank-order statistics followed by correction of nonuniform illumination with human visual perception approach. The performance of the proposed algorithm is compared to that of common algorithms for correction of color images containing shadow regions.

Flat-field response and geometric distortion measurements of optical streak cameras

International Nuclear Information System (INIS)

Montgomery, D.S.; Drake, R.P.; Jones, B.A.; Wiedwald, J.D.

1987-08-01

To accurately measure pulse amplitude, shape, and relative time histories of optical signals with an optical streak camera, it is necessary to correct each recorded image for spatially-dependent gain nonuniformity and geometric distortion. Gain nonuniformities arise from sensitivity variations in the streak-tube photocathode, phosphor screen, image-intensifier tube, and image recording system. These nonuniformities may be severe, and have been observed to be on the order of 100% for some LLNL optical streak cameras. Geometric distortion due to optical couplings, electron-optics, and sweep nonlinearity not only affects pulse position and timing measurements, but affects pulse amplitude and shape measurements as well. By using a 1.053-μm, long-pulse, high-power laser to generate a spatially and temporally uniform source as input to the streak camera, the combined effects of flat-field response and geometric distortion can be measured under the normal dynamic operation of cameras with S-1 photocathodes. Additionally, by using the same laser system to generate a train of short pulses that can be spatially modulated at the input of the streak camera, we can effectively create a two-dimensional grid of equally-spaced pulses. This allows a dynamic measurement of the geometric distortion of the streak camera. We will discuss the techniques involved in performing these calibrations, will present some of the measured results for LLNL optical streak cameras, and will discuss software methods to correct for these effects. 6 refs., 6 figs

Time-dependent phase error correction using digital waveform synthesis

Science.gov (United States)

Doerry, Armin W.; Buskirk, Stephen

2017-10-10

The various technologies presented herein relate to correcting a time-dependent phase error generated as part of the formation of a radar waveform. A waveform can be pre-distorted to facilitate correction of an error induced into the waveform by a downstream operation/component in a radar system. For example, amplifier power droop effect can engender a time-dependent phase error in a waveform as part of a radar signal generating operation. The error can be quantified and an according complimentary distortion can be applied to the waveform to facilitate negation of the error during the subsequent processing of the waveform. A time domain correction can be applied by a phase error correction look up table incorporated into a waveform phase generator.

Hitchhiker'S Guide to Voxel Segmentation for Partial Volume Correction of in Vivo Magnetic Resonance Spectroscopy

Directory of Open Access Journals (Sweden)

Scott Quadrelli

2016-01-01

Full Text Available Partial volume effects have the potential to cause inaccuracies when quantifying metabolites using proton magnetic resonance spectroscopy (MRS. In order to correct for cerebrospinal fluid content, a spectroscopic voxel needs to be segmented according to different tissue contents. This article aims to detail how automated partial volume segmentation can be undertaken and provides a software framework for researchers to develop their own tools. While many studies have detailed the impact of partial volume correction on proton magnetic resonance spectroscopy quantification, there is a paucity of literature explaining how voxel segmentation can be achieved using freely available neuroimaging packages.

Practical estimate of gradient nonlinearity for implementation of apparent diffusion coefficient bias correction.

Science.gov (United States)

Malkyarenko, Dariya I; Chenevert, Thomas L

2014-12-01

To describe an efficient procedure to empirically characterize gradient nonlinearity and correct for the corresponding apparent diffusion coefficient (ADC) bias on a clinical magnetic resonance imaging (MRI) scanner. Spatial nonlinearity scalars for individual gradient coils along superior and right directions were estimated via diffusion measurements of an isotropicic e-water phantom. Digital nonlinearity model from an independent scanner, described in the literature, was rescaled by system-specific scalars to approximate 3D bias correction maps. Correction efficacy was assessed by comparison to unbiased ADC values measured at isocenter. Empirically estimated nonlinearity scalars were confirmed by geometric distortion measurements of a regular grid phantom. The applied nonlinearity correction for arbitrarily oriented diffusion gradients reduced ADC bias from 20% down to 2% at clinically relevant offsets both for isotropic and anisotropic media. Identical performance was achieved using either corrected diffusion-weighted imaging (DWI) intensities or corrected b-values for each direction in brain and ice-water. Direction-average trace image correction was adequate only for isotropic medium. Empiric scalar adjustment of an independent gradient nonlinearity model adequately described DWI bias for a clinical scanner. Observed efficiency of implemented ADC bias correction quantitatively agreed with previous theoretical predictions and numerical simulations. The described procedure provides an independent benchmark for nonlinearity bias correction of clinical MRI scanners.

Vibrating wire apparatus for periodic magnetic structure measurement

International Nuclear Information System (INIS)

Temnykh, A.B.

2003-01-01

Devices with periodic magnetic structures such as wigglers and undulators are often key elements in synchrotron radiation sources. In applications where the coherence of the emitted radiation is important, magnetic field errors distorting the periodicity of the field can significantly reduce the performance of the devices. Thus, the measurement, localization, and correction of the field errors can be a critical issue. This article presents a new method for magnetic field measurements in periodic magnetic structures. The method uses a vibrating taut wire passing through the magnetic structure, and it involves measurements of the amplitudes and phases of the standing waves excited on the wire by the Lorentz force between an AC current in the wire and the surrounding magnetic field. For certain arrangements of the wire, vibrations in the wire will be excited by only non-periodic magnetic field component, i.e., by the error field. By measuring the phase and amplitude of these waves, one can reconstruct the error field distribution and then correct it. The method was tested on a permanent magnet wiggler with 19.8 cm period and a peak field of ∼7000G. It demonstrated ∼0.6G RMS sensitivity, δB rms /B rms ∼1.2x10 -4 and spatial resolution sufficient to identify poles generating the field error. Good agreement was found between field error measurements obtained with the vibrating wire method and with traditional Hall probe field mapping

Partial fourier and parallel MR image reconstruction with integrated gradient nonlinearity correction.

Science.gov (United States)

Tao, Shengzhen; Trzasko, Joshua D; Shu, Yunhong; Weavers, Paul T; Huston, John; Gray, Erin M; Bernstein, Matt A

2016-06-01

To describe how integrated gradient nonlinearity (GNL) correction can be used within noniterative partial Fourier (homodyne) and parallel (SENSE and GRAPPA) MR image reconstruction strategies, and demonstrate that performing GNL correction during, rather than after, these routines mitigates the image blurring and resolution loss caused by postreconstruction image domain based GNL correction. Starting from partial Fourier and parallel magnetic resonance imaging signal models that explicitly account for GNL, noniterative image reconstruction strategies for each accelerated acquisition technique are derived under the same core mathematical assumptions as their standard counterparts. A series of phantom and in vivo experiments on retrospectively undersampled data were performed to investigate the spatial resolution benefit of integrated GNL correction over conventional postreconstruction correction. Phantom and in vivo results demonstrate that the integrated GNL correction reduces the image blurring introduced by the conventional GNL correction, while still correcting GNL-induced coarse-scale geometrical distortion. Images generated from undersampled data using the proposed integrated GNL strategies offer superior depiction of fine image detail, for example, phantom resolution inserts and anatomical tissue boundaries. Noniterative partial Fourier and parallel imaging reconstruction methods with integrated GNL correction reduce the resolution loss that occurs during conventional postreconstruction GNL correction while preserving the computational efficiency of standard reconstruction techniques. Magn Reson Med 75:2534-2544, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Grids in topographic maps reduce distortions in the recall of learned object locations.

Science.gov (United States)

Edler, Dennis; Bestgen, Anne-Kathrin; Kuchinke, Lars; Dickmann, Frank

2014-01-01

To date, it has been shown that cognitive map representations based on cartographic visualisations are systematically distorted. The grid is a traditional element of map graphics that has rarely been considered in research on perception-based spatial distortions. Grids do not only support the map reader in finding coordinates or locations of objects, they also provide a systematic structure for clustering visual map information ("spatial chunks"). The aim of this study was to examine whether different cartographic kinds of grids reduce spatial distortions and improve recall memory for object locations. Recall performance was measured as both the percentage of correctly recalled objects (hit rate) and the mean distance errors of correctly recalled objects (spatial accuracy). Different kinds of grids (continuous lines, dashed lines, crosses) were applied to topographic maps. These maps were also varied in their type of characteristic areas (LANDSCAPE) and different information layer compositions (DENSITY) to examine the effects of map complexity. The study involving 144 participants shows that all experimental cartographic factors (GRID, LANDSCAPE, DENSITY) improve recall performance and spatial accuracy of learned object locations. Overlaying a topographic map with a grid significantly reduces the mean distance errors of correctly recalled map objects. The paper includes a discussion of a square grid's usefulness concerning object location memory, independent of whether the grid is clearly visible (continuous or dashed lines) or only indicated by crosses.

Bending Distortion Analysis of a Steel Shaft Manufacturing Chain from Cold Drawing to Grinding

Science.gov (United States)

Dias, Vinicius Waechter; da Silva Rocha, Alexandre; Zottis, Juliana; Dong, Juan; Epp, Jérémy; Zoch, Hans Werner

2017-04-01

Shafts are usually manufactured from bars that are cold drawn, cut machined, induction hardened, straightened, and finally ground. The main distortion is characterized by bending that appears after induction hardening and is corrected by straightening and/or grinding. In this work, the consequence of the variation of manufacturing parameters on the distortion was analyzed for a complete manufacturing route for production of induction hardened shafts made of Grade 1045 steel. A DoE plan was implemented varying the drawing angle, cutting method, induction hardening layer depth, and grinding penetration depth. The distortion was determined by calculating curvature vectors from dimensional analysis by 3D coordinate measurements. Optical microscopy, microhardness testing, residual stress analysis, and FEM process simulation were used to evaluate and understand effects of the main carriers of distortion potential. The drawing process was identified as the most significant influence on the final distortion of the shafts.

Impedance Based Analysis of DFIG Stator Current Unbalance and Distortion Suppression Strategies

DEFF Research Database (Denmark)

Song, Yipeng; Zhou, Dao; Blaabjerg, Frede

2016-01-01

The control strategies of Doubly Fed Induction Generator (DFIG) system output current unbalance and distortion suppression have been well investigated in detail, with the implementation of two kinds of resonant regulators, i.e., conventional Resonance (R) regulator or Vector Proportional Integral...... reshaping though the introduction of R and VPI regulator. It is pointed out that, when implemented in the DFIG system output current unbalance and distortion suppression, the VPI regulator (equivalent to the combination of virtual positive inductor and virtual positive resistor) has two advantages over R...... regulator (equivalent to the combination of virtual positive resistor and virtual negative inductor), i.e., better high order harmonic distortion suppression. The theoretical analysis and MATLAB simulation results have validated the correctness of this conclusion....

[Study on phase correction method of spatial heterodyne spectrometer].

Science.gov (United States)

Wang, Xin-Qiang; Ye, Song; Zhang, Li-Juan; Xiong, Wei

2013-05-01

Phase distortion exists in collected interferogram because of a variety of measure reasons when spatial heterodyne spectrometers are used in practice. So an improved phase correction method is presented. The phase curve of interferogram was obtained through Fourier inverse transform to extract single side transform spectrum, based on which, the phase distortions were attained by fitting phase slope, so were the phase correction functions, and the convolution was processed between transform spectrum and phase correction function to implement spectrum phase correction. The method was applied to phase correction of actually measured monochromatic spectrum and emulational water vapor spectrum. Experimental results show that the low-frequency false signals in monochromatic spectrum fringe would be eliminated effectively to increase the periodicity and the symmetry of interferogram, in addition when the continuous spectrum imposed phase error was corrected, the standard deviation between it and the original spectrum would be reduced form 0.47 to 0.20, and thus the accuracy of spectrum could be improved.

Distorted images of one's own body activates the prefrontal cortex and limbic/paralimbic system in young women: a functional magnetic resonance imaging study.

Science.gov (United States)

Kurosaki, Mitsuhaya; Shirao, Naoko; Yamashita, Hidehisa; Okamoto, Yasumasa; Yamawaki, Shigeto

2006-02-15

Our aim was to study the gender differences in brain activation upon viewing visual stimuli of distorted images of one's own body. We performed functional magnetic resonance imaging on 11 healthy young men and 11 healthy young women using the "body image tasks" which consisted of fat, real, and thin shapes of the subject's own body. Comparison of the brain activation upon performing the fat-image task versus real-image task showed significant activation of the bilateral prefrontal cortex and left parahippocampal area including the amygdala in the women, and significant activation of the right occipital lobe including the primary and secondary visual cortices in the men. Comparison of brain activation upon performing the thin-image task versus real-image task showed significant activation of the left prefrontal cortex, left limbic area including the cingulate gyrus and paralimbic area including the insula in women, and significant activation of the occipital lobe including the left primary and secondary visual cortices in men. These results suggest that women tend to perceive distorted images of their own bodies by complex cognitive processing of emotion, whereas men tend to perceive distorted images of their own bodies by object visual processing and spatial visual processing.

Simulation and experimental study on distortion of butt and T-joints using WELD PLANNER

International Nuclear Information System (INIS)

Sulaiman, Mohd Shahar; Manurung, Yupiter HP; Rahim, Mohammad Ridzwan Abdul Mohd; Redza, Ridhwan; Lidam, Robert Ngendang Ak.; Abas, Sunhaji Kiyai; Tham, Ghalib; Haruman, Esa; Chau, Chan Yin

2011-01-01

This paper investigates the capability of linear thermal elastic numerical analysis to predict the welding distortion that occurs due to GMAW process. Distortion is considered as the major stumbling block that can adversely affect the dimensional accuracy and thus lead to expensive corrective work. Hence, forecast of distortion is crucially needed and ought to be determined in advance in order to minimize the negative effects, improve the quality of welded parts and finally to reduce the production costs. In this study, the welding deformation was simulated by using relatively new FEM software WELD PLANNER developed by ESI Group. This novel Welding Simulation Solution was employed to predict welding distortion induced in butt and T-joints with thickness of 4 mm. Low carbon steel material was used for the simulation and experimental study. A series of experiments using fully automated welding process were conducted for verification purpose to measure the distortion. By comparing between the simulation and experimental results, it was found out that this program code offered fast solution analysis time in estimating weld induced distortion within acceptable accuracy

Simulation and experimental study on distortion of butt and T-joints using WELD PLANNER

Energy Technology Data Exchange (ETDEWEB)

Sulaiman, Mohd Shahar; Manurung, Yupiter HP; Rahim, Mohammad Ridzwan Abdul Mohd; Redza, Ridhwan; Lidam, Robert Ngendang Ak.; Abas, Sunhaji Kiyai; Tham, Ghalib [Universiti Teknologi MARA, Kuala Lumpur (Malaysia); Haruman, Esa [Bakrie University, Jakarta (Indonesia); Chau, Chan Yin [ESI Group, Kuala Lumpur (Malaysia)

2011-10-15

This paper investigates the capability of linear thermal elastic numerical analysis to predict the welding distortion that occurs due to GMAW process. Distortion is considered as the major stumbling block that can adversely affect the dimensional accuracy and thus lead to expensive corrective work. Hence, forecast of distortion is crucially needed and ought to be determined in advance in order to minimize the negative effects, improve the quality of welded parts and finally to reduce the production costs. In this study, the welding deformation was simulated by using relatively new FEM software WELD PLANNER developed by ESI Group. This novel Welding Simulation Solution was employed to predict welding distortion induced in butt and T-joints with thickness of 4 mm. Low carbon steel material was used for the simulation and experimental study. A series of experiments using fully automated welding process were conducted for verification purpose to measure the distortion. By comparing between the simulation and experimental results, it was found out that this program code offered fast solution analysis time in estimating weld induced distortion within acceptable accuracy.

Sextupole correction for a ring with large chromaticity and the influence of magnetic errors on its parameters

International Nuclear Information System (INIS)

Kamiya, Y.; Katoh, M.; Honjo, I.

1987-01-01

A future ring with a low emittance and large circumference, specifically dedicated to a synchrotron light source, will have a large chromaticity, so that it is important to employ a sophisticated sextupole correction as well as the design of linear lattice to obtain the stable beam. The authors tried a method of sextupole correction for a lattice with a large chromaticity and small dispersion function. In such a lattice the sextupole magnets are obliged to become large in strength to compensate the chromaticity. Then the nonlinear effects of the sextupole magnets will become more serious than their chromatic effects. Furthermore, a ring with strong quadrupole magnets to get a very small emittance and with strong sextupole magnets to compensate the generated chromaticity will be very sensitive to their magnetic errors. The authors also present simple formulae to evaluate the effects on the beam parameters. The details will appear in a KEK Report

Measurement, analysis and correction of the closed orbit distortion ...

Indian Academy of Sciences (India)

2013-02-01

Feb 1, 2013 ... quency (RF), linear coupling are being carried out. ..... Its guide tool is used to develop GUI for COD correction software. In addition ... rection software also has a feature to save all the parameters such as predicted/measured.

Distortions Imposed By Inflation on Historical-Cost Depreciation

OpenAIRE

Bravo-Ureta, Boris E.

1983-01-01

The use of historical-cost depreciation in periods of persistent inflation decreases the present value of depreciation deductions, thus understating the true economic cost of capital and increasing the real after-tax rate of return required by potential investors. Efforts to correct these problems by adopting depreciation methods that allow for artificially short recovery periods or accelerated rates do not provide an adequate solution. Distortions imposed by inflation on historical-cost depr...

Intermediate magnetization state and competing orders in Dy2Ti2O7 and Ho2Ti2O7

Science.gov (United States)

Borzi, R. A.; Gómez Albarracín, F. A.; Rosales, H. D.; Rossini, G. L.; Steppke, A.; Prabhakaran, D.; Mackenzie, A. P.; Cabra, D. C.; Grigera, S. A.

2016-01-01

Among the frustrated magnetic materials, spin-ice stands out as a particularly interesting system. Residual entropy, freezing and glassiness, Kasteleyn transitions and fractionalization of excitations in three dimensions all stem from a simple classical Hamiltonian. But is the usual spin-ice Hamiltonian a correct description of the experimental systems? Here we address this issue by measuring magnetic susceptibility in the two most studied spin-ice compounds, Dy2Ti2O7 and Ho2Ti2O7, using a vector magnet. Using these results, and guided by a theoretical analysis of possible distortions to the pyrochlore lattice, we construct an effective Hamiltonian and explore it using Monte Carlo simulations. We show how this Hamiltonian reproduces the experimental results, including the formation of a phase of intermediate polarization, and gives important information about the possible ground state of real spin-ice systems. Our work suggests an unusual situation in which distortions might contribute to the preservation rather than relief of the effects of frustration. PMID:27558021

Rate-distortion analysis of steganography for conveying stereovision disparity maps

Science.gov (United States)

Umeda, Toshiyuki; Batolomeu, Ana B. D. T.; Francob, Filipe A. L.; Delannay, Damien; Macq, Benoit M. M.

2004-06-01

3-D images transmission in a way which is compliant with traditional 2-D representations can be done through the embedding of disparity maps within the 2-D signal. This approach enables the transmission of stereoscopic video sequences or images on traditional analogue TV channels (PAL or NTSC) or printed photographic images. The aim of this work is to study the achievable performances of such a technique. The embedding of disparity maps has to be seen as a global rate-distortion problem. The embedding capacity through steganography is determined by the transmission channel noise and by the bearable distortion on the watermarked image. The distortion of the 3-D image displayed as two stereo views depends on the rate allocated to the complementary information required to build those two views from one reference 2-D image. Results from the works on the scalar Costa scheme are used to optimize the embedding of the disparity map compressed bit stream into the reference image. A method for computing the optimal trade off between the disparity map distortion and embedding distortion as a function of the channel impairments is proposed. The goal is to get a similar distortion on the left (the reference image) and the right (the disparity compensated image) images. We show that in typical situations the embedding of 2 bits/pixels in the left image, while the disparity map is compressed at 1 bit per pixel leads to a good trade-off. The disparity map is encoded with a strong error correcting code, including synchronisation bits.

Correction of errors in scale values for magnetic elements for Helsinki

Directory of Open Access Journals (Sweden)

L. Svalgaard

2014-06-01

Full Text Available Using several lines of evidence we show that the scale values of the geomagnetic variometers operating in Helsinki in the 19th century were not constant throughout the years of operation 1844–1897. Specifically, the adopted scale value of the horizontal force variometer appears to be too low by ~ 30% during the years 1866–1874.5 and the adopted scale value of the declination variometer appears to be too low by a factor of ~ 2 during the interval 1885.8–1887.5. Reconstructing the heliospheric magnetic field strength from geomagnetic data has reached a stage where a reliable reconstruction is possible using even just a single geomagnetic data set of hourly or daily values. Before such reconstructions can be accepted as reliable, the underlying data must be calibrated correctly. It is thus mandatory that the Helsinki data be corrected. Such correction has been satisfactorily carried out and the HMF strength is now well constrained back to 1845.

Magnet sorting algorithms

International Nuclear Information System (INIS)

Dinev, D.

1996-01-01

Several new algorithms for sorting of dipole and/or quadrupole magnets in synchrotrons and storage rings are described. The algorithms make use of a combinatorial approach to the problem and belong to the class of random search algorithms. They use an appropriate metrization of the state space. The phase-space distortion (smear) is used as a goal function. Computational experiments for the case of the JINR-Dubna superconducting heavy ion synchrotron NUCLOTRON have shown a significant reduction of the phase-space distortion after the magnet sorting. (orig.)

Rigid-body motion correction of the liver in image reconstruction for golden-angle stack-of-stars DCE MRI.

Science.gov (United States)

Johansson, Adam; Balter, James; Cao, Yue

2018-03-01

Respiratory motion can affect pharmacokinetic perfusion parameters quantified from liver dynamic contrast-enhanced MRI. Image registration can be used to align dynamic images after reconstruction. However, intra-image motion blur remains after alignment and can alter the shape of contrast-agent uptake curves. We introduce a method to correct for inter- and intra-image motion during image reconstruction. Sixteen liver dynamic contrast-enhanced MRI examinations of nine subjects were performed using a golden-angle stack-of-stars sequence. For each examination, an image time series with high temporal resolution but severe streak artifacts was reconstructed. Images were aligned using region-limited rigid image registration within a region of interest covering the liver. The transformations resulting from alignment were used to correct raw data for motion by modulating and rotating acquired lines in k-space. The corrected data were then reconstructed using view sharing. Portal-venous input functions extracted from motion-corrected images had significantly greater peak signal enhancements (mean increase: 16%, t-test, P <  0.001) than those from images aligned using image registration after reconstruction. In addition, portal-venous perfusion maps estimated from motion-corrected images showed fewer artifacts close to the edge of the liver. Motion-corrected image reconstruction restores uptake curves distorted by motion. Motion correction also reduces motion artifacts in estimated perfusion parameter maps. Magn Reson Med 79:1345-1353, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

An Investigation on the Efficiency Correction Method of the Turbocharger at Low Speed

Directory of Open Access Journals (Sweden)

Jin Eun Chung

2018-01-01

Full Text Available The heat transfer in the turbocharger occurs due to the temperature difference between the exhaust gas and intake air, coolant, and oil. This heat transfer causes the efficiency of the compressor and turbine to be distorted, which is known to be exacerbated during low rotational speeds. Thus, this study proposes a method to mitigate the distortion of the test result data caused by heat transfer in the turbocharger. With this method, the representative compressor temperature is defined and the heat transfer rate of the compressor is calculated by considering the effect of the oil and turbine inlet temperatures at low rotation speeds, when the cold and the hot gas test are simultaneously performed. The correction of compressor efficiency, depending on the turbine inlet temperature, was performed through both hot and cold gas tests and the results showed a maximum of 16% error prior to correction and a maximum of 3% error after the correction. In addition, it shows that it is possible to correct the efficiency distortion of the turbocharger by heat transfer by correcting to the combined turbine efficiency based on the corrected compressor efficiency.

Quadratic Regression-based Non-uniform Response Correction for Radiochromic Film Scanners

International Nuclear Information System (INIS)

Jeong, Hae Sun; Kim, Chan Hyeong; Han, Young Yih; Kum, O Yeon

2009-01-01

In recent years, several types of radiochromic films have been extensively used for two-dimensional dose measurements such as dosimetry in radiotherapy as well as imaging and radiation protection applications. One of the critical aspects in radiochromic film dosimetry is the accurate readout of the scanner without dose distortion. However, most of charge-coupled device (CCD) scanners used for the optical density readout of the film employ a fluorescent lamp or a coldcathode lamp as a light source, which leads to a significant amount of light scattering on the active layer of the film. Due to the effect of the light scattering, dose distortions are produced with non-uniform responses, although the dose is uniformly irradiated to the film. In order to correct the distorted doses, a method based on correction factors (CF) has been reported and used. However, the prediction of the real incident doses is difficult when the indiscreet doses are delivered to the film, since the dose correction with the CF-based method is restrictively used in case that the incident doses are already known. In a previous study, therefore, a pixel-based algorithm with linear regression was developed to correct the dose distortion of a flatbed scanner, and to estimate the initial doses. The result, however, was not very good for some cases especially when the incident dose is under approximately 100 cGy. In the present study, the problem was addressed by replacing the linear regression with the quadratic regression. The corrected doses using this method were also compared with the results of other conventional methods

'Distorted structure modelling' - a more physical approach to Rapid Distortion Theory

International Nuclear Information System (INIS)

Savill, A.M.

1979-11-01

Rapid Distortion Theory is reviewed in the light of the modern mechanistic approach to turbulent motion. The apparent failure of current models, based on this theory, to predict stress intensity ratios accurately in distorted shear flows is attributed to their oversimplistic assumptions concerning the inherent turbulence structure of such flows. A more realistic picture of this structure and the manner in which it responds to distortion is presented in terms of interactions between the mean flow and three principal types of eddies. If Rapid Distortion Theory is modified to account for this it is shown that the stress intensity ratios can be accurately predicted in three test flows. It is concluded that a computational scheme based on Rapid Distortion Theory might ultimately be capable of predicting turbulence parameters in the highly complex geometries of reactor cooling systems. (author)

Two-flavor QCD correction to lepton magnetic moments at leading-order in the electromagnetic coupling

Energy Technology Data Exchange (ETDEWEB)

Dru Renner, Xu Feng, Karl Jansen, Marcus Petschlies

2011-08-01

We present a reliable nonperturbative calculation of the QCD correction, at leading-order in the electromagnetic coupling, to the anomalous magnetic moment of the electron, muon and tau leptons using two-flavor lattice QCD. We use multiple lattice spacings, multiple volumes and a broad range of quark masses to control the continuum, infinite-volume and chiral limits. We examine the impact of the commonly ignored disconnected diagrams and introduce a modification to the previously used method that results in a well-controlled lattice calculation. We obtain 1.513 (43) 10^-12, 5.72 (16) 10^-8 and 2.650 (54) 10^-6 for the leading-order QCD correction to the anomalous magnetic moment of the electron, muon and tau respectively, each accurate to better than 3%.

Multi-frequency interpolation in spiral magnetic resonance fingerprinting for correction of off-resonance blurring.

Science.gov (United States)

Ostenson, Jason; Robison, Ryan K; Zwart, Nicholas R; Welch, E Brian

2017-09-01

Magnetic resonance fingerprinting (MRF) pulse sequences often employ spiral trajectories for data readout. Spiral k-space acquisitions are vulnerable to blurring in the spatial domain in the presence of static field off-resonance. This work describes a blurring correction algorithm for use in spiral MRF and demonstrates its effectiveness in phantom and in vivo experiments. Results show that image quality of T1 and T2 parametric maps is improved by application of this correction. This MRF correction has negligible effect on the concordance correlation coefficient and improves coefficient of variation in regions of off-resonance relative to uncorrected measurements. Copyright © 2017 Elsevier Inc. All rights reserved.

Bias correction for magnetic resonance images via joint entropy regularization.

Science.gov (United States)

Wang, Shanshan; Xia, Yong; Dong, Pei; Luo, Jianhua; Huang, Qiu; Feng, Dagan; Li, Yuanxiang

2014-01-01

Due to the imperfections of the radio frequency (RF) coil or object-dependent electrodynamic interactions, magnetic resonance (MR) images often suffer from a smooth and biologically meaningless bias field, which causes severe troubles for subsequent processing and quantitative analysis. To effectively restore the original signal, this paper simultaneously exploits the spatial and gradient features of the corrupted MR images for bias correction via the joint entropy regularization. With both isotropic and anisotropic total variation (TV) considered, two nonparametric bias correction algorithms have been proposed, namely IsoTVBiasC and AniTVBiasC. These two methods have been applied to simulated images under various noise levels and bias field corruption and also tested on real MR data. The test results show that the proposed two methods can effectively remove the bias field and also present comparable performance compared to the state-of-the-art methods.

Optimal transformation for correcting partial volume averaging effects in magnetic resonance imaging

International Nuclear Information System (INIS)

Soltanian-Zadeh, H.; Windham, J.P.; Yagle, A.E.

1993-01-01

Segmentation of a feature of interest while correcting for partial volume averaging effects is a major tool for identification of hidden abnormalities, fast and accurate volume calculation, and three-dimensional visualization in the field of magnetic resonance imaging (MRI). The authors present the optimal transformation for simultaneous segmentation of a desired feature and correction of partial volume averaging effects, while maximizing the signal-to-noise ratio (SNR) of the desired feature. It is proved that correction of partial volume averaging effects requires the removal of the interfering features from the scene. It is also proved that correction of partial volume averaging effects can be achieved merely by a linear transformation. It is finally shown that the optimal transformation matrix is easily obtained using the Gram-Schmidt orthogonalization procedure, which is numerically stable. Applications of the technique to MRI simulation, phantom, and brain images are shown. They show that in all cases the desired feature is segmented from the interfering features and partial volume information is visualized in the resulting transformed images

Wide aperture multipole magnets of the kinematic separator COMBAS. Correcting pair of multipole magnets M3M4 (M5M6) with compensation for higher order aberrations

International Nuclear Information System (INIS)

Artyukh, A.G.; Gridnev, G.F.; Teterev, Yu.G.

1999-01-01

The high-resolving large aperture separator COMBAS has been created and commissioned. The magneto-optical structure of the separator is based on the strong focusing principle. The separator consists of eight wide aperture multipole magnets M1-M8. The magnets M1, M2, M7, M8 forming the 1 st order optics together with some higher order optical corrections and M3-M6 being dedicated to higher order corrections of the chromatic and spherical aberrations at the intermediate and exit foci of the separator. The multipole correctors M3-M6 contain the dipolar, sextupole and octupole components in their magnetic field distributions. It was the use of the rectangular dipoles M3-M6 as carriers of sextupole and octupole field components that let achieve high values of the separator angular and momentum acceptances. Measurements of the magnetic field distributions in the median planes of the pairs of magnets M3M6 (M4M5) have been performed. These measurements allowed one to analyze the magnets manufacturing quality. Based on the analysis, shimming of pole pieces of the pair of magnets M3M6 have been done. Pole surface correcting coils for the magnets M4M5 have been foreseen to compensate for small deviations (within a few percents) of the 2 nd and 3 rd order field components from the design values, which are probable due to manufacturing errors in all the magnets M1-M8. The measured magnetic field distributions are supposed to be used for particle trajectory simulations throughout the entire separator

Real-space post-processing correction of thermal drift and piezoelectric actuator nonlinearities in scanning tunneling microscope images

Science.gov (United States)

Yothers, Mitchell P.; Browder, Aaron E.; Bumm, Lloyd A.

2017-01-01

We have developed a real-space method to correct distortion due to thermal drift and piezoelectric actuator nonlinearities on scanning tunneling microscope images using Matlab. The method uses the known structures typically present in high-resolution atomic and molecularly resolved images as an internal standard. Each image feature (atom or molecule) is first identified in the image. The locations of each feature's nearest neighbors are used to measure the local distortion at that location. The local distortion map across the image is simultaneously fit to our distortion model, which includes thermal drift in addition to piezoelectric actuator hysteresis and creep. The image coordinates of the features and image pixels are corrected using an inverse transform from the distortion model. We call this technique the thermal-drift, hysteresis, and creep transform. Performing the correction in real space allows defects, domain boundaries, and step edges to be excluded with a spatial mask. Additional real-space image analyses are now possible with these corrected images. Using graphite(0001) as a model system, we show lattice fitting to the corrected image, averaged unit cell images, and symmetry-averaged unit cell images. Statistical analysis of the distribution of the image features around their best-fit lattice sites measures the aggregate noise in the image, which can be expressed as feature confidence ellipsoids.

Real-space post-processing correction of thermal drift and piezoelectric actuator nonlinearities in scanning tunneling microscope images.

Science.gov (United States)

Yothers, Mitchell P; Browder, Aaron E; Bumm, Lloyd A

2017-01-01

We have developed a real-space method to correct distortion due to thermal drift and piezoelectric actuator nonlinearities on scanning tunneling microscope images using Matlab. The method uses the known structures typically present in high-resolution atomic and molecularly resolved images as an internal standard. Each image feature (atom or molecule) is first identified in the image. The locations of each feature's nearest neighbors are used to measure the local distortion at that location. The local distortion map across the image is simultaneously fit to our distortion model, which includes thermal drift in addition to piezoelectric actuator hysteresis and creep. The image coordinates of the features and image pixels are corrected using an inverse transform from the distortion model. We call this technique the thermal-drift, hysteresis, and creep transform. Performing the correction in real space allows defects, domain boundaries, and step edges to be excluded with a spatial mask. Additional real-space image analyses are now possible with these corrected images. Using graphite(0001) as a model system, we show lattice fitting to the corrected image, averaged unit cell images, and symmetry-averaged unit cell images. Statistical analysis of the distribution of the image features around their best-fit lattice sites measures the aggregate noise in the image, which can be expressed as feature confidence ellipsoids.

Neutron lifetime experiments using magnetically trapped neutrons: optimal background correction strategies

International Nuclear Information System (INIS)

Coakley, K.J.

2001-01-01

In the first stage of each run of a neutron lifetime experiment, a magnetic trap is filled with neutrons. In the second stage of each run, decay events plus background events are observed. In a separate experiment, background is measured. The mean lifetime is estimated by fitting a two parameter exponential model to the background-corrected data. For two models of the background signal, I determine the optimal ratio of the number of 'background-only' measurements to the number of primary 'neutron decay plus background' measurements. Further, for each run, I determine the optimal allocation of time for filling and for observing decay events. For the case where the background consists of an activated material (aluminum) plus a stationary Poisson process, the asymptotic standard error of the lifetime estimate computed from the background-corrected data is lower than the asymptotic standard error computed from the uncorrected data. For the case where the background is a stationary Poisson process, background correction is desirable provided that the background intensity is sufficiently small compared to the rate at which neutrons enter the trap

Two-flavor QCD correction to lepton magnetic moments at leading-order in the electromagnetic coupling

Energy Technology Data Exchange (ETDEWEB)

Feng, Xu [DESY, Zeuthen (Germany). NIC; Muenster Univ. (Germany). Inst. fuer Theoretische Physik; Jansen, Karl; Renner, Dru B. [DESY, Zeuthen (Germany). NIC; Petschlies, Marcus [Humboldt Univ. Berlin (Germany). Inst. fuer Physik

2011-03-15

We present a reliable nonperturbative calculation of the QCD correction, at leading-order in the electromagnetic coupling, to the anomalous magnetic moment of the electron, muon and tau leptons using two-flavor lattice QCD. We use multiple lattice spacings, multiple volumes and a broad range of quark masses to control the continuum, in nite-volume and chiral limits. We examine the impact of the commonly ignored disconnected diagrams and introduce a modi cation to the previously used method that results in a well-controlled lattice calculation. We obtain 1.513(43).10{sup -12}, 5.72(16).10{sup -8} and 2.650(54).10{sup -6} for the leading-order QCD correction to the anomalous magnetic moment of the electron, muon and tau respectively, each accurate to better than 3%. (orig.)

Holographic measurement of distortion during laser melting: Additive distortion from overlapping pulses

Science.gov (United States)

Haglund, Peter; Frostevarg, Jan; Powell, John; Eriksson, Ingemar; Kaplan, Alexander F. H.

2018-03-01

Laser - material interactions such as welding, heat treatment and thermal bending generate thermal gradients which give rise to thermal stresses and strains which often result in a permanent distortion of the heated object. This paper investigates the thermal distortion response which results from pulsed laser surface melting of a stainless steel sheet. Pulsed holography has been used to accurately monitor, in real time, the out-of-plane distortion of stainless steel samples melted on one face by with both single and multiple laser pulses. It has been shown that surface melting by additional laser pulses increases the out of plane distortion of the sample without significantly increasing the melt depth. The distortion differences between the primary pulse and subsequent pulses has also been analysed for fully and partially overlapping laser pulses.

SU-G-JeP2-13: Spatial Accuracy Evaluation for Real-Time MR Guided Radiation Therapy Using a Novel Large-Field MRI Distortion Phantom

International Nuclear Information System (INIS)

Antolak, A; Bayouth, J; Bosca, R; Jackson, E

2016-01-01

Purpose: Evaluate a large-field MRI phantom for assessment of geometric distortion in whole-body MRI for real-time MR guided radiation therapy. Methods: A prototype CIRS large-field MRI distortion phantom consisting of a PMMA cylinder (33 cm diameter, 30 cm length) containing a 3D-printed orthogonal grid (3 mm diameter rods, 20 mm apart), was filled with 6 mM NiCl_2 and 30 mM NaCl solution. The phantom was scanned at 1.5T and 3.0T on a GE HDxt and Discovery MR750, respectively, and at 0.35T on a ViewRay system. Scans were obtained with and without 3D distortion correction to demonstrate the impact of such corrections. CT images were used as a reference standard for analysis of geometric distortion, as determined by a fully automated gradient-search method developed in Matlab. Results: 1,116 grid points distributed throughout a cylindrical volume 28 cm in diameter and 16 cm in length were identified and analyzed. With 3D distortion correction, average/maximum displacements for the 1.5, 3.0, and 0.35T systems were 0.84/2.91, 1.00/2.97, and 0.95/2.37 mm, respectively. The percentage of points with less than (1.0, 1.5, 2.0 mm) total displacement were (73%, 92%, 97%), (54%, 85%, 97%), and (55%, 90%, 99%), respectively. A reduced scan volume of 20 × 20 × 10 cm"3 (representative of a head and neck scan volume) consisting of 420 points was also analyzed. In this volume, the percentage of points with less than (1.0, 1.5, 2.0 mm) total displacement were (90%, 99%, 100%), (63%, 95%, 100%), and (75%, 96%, 100%), respectively. Without 3D distortion correction, average/maximum displacements were 1.35/3.67, 1.67/4.46, and 1.51/3.89 mm, respectively. Conclusion: The prototype large-field MRI distortion phantom and developed software provide a thorough assessment of 3D spatial distortions in MRI. The distortions measured were acceptable for RT applications, both for the high field strengths and the system configuration developed by ViewRay.

Chemical short range order and magnetic correction in liquid manganese–gallium zero alloy

Energy Technology Data Exchange (ETDEWEB)

Grosdidier, B. [Laboratoire de Chimie Physique – Approche Multi-Echelle des Milieux Complexes, Institut Jean Bariol, Université de Lorraine, Institut de Chimie, Physique et Matériaux, 1 Bd Arago, 57078 Metz Cedex 3 (France); Ben Abdellah, A. [Laboratoire de Chimie Physique – Approche Multi-Echelle des Milieux Complexes, Institut Jean Bariol, Université de Lorraine, Institut de Chimie, Physique et Matériaux, 1 Bd Arago, 57078 Metz Cedex 3 (France); Innovation and Management of Industrial Systems, Abdelmalek Essaadi University, College of Sciences and Techniques of Tangier , P.O. Box 416, Postal code 90000, Tangier (Morocco); Université Internationale de Rabat, Parc Technopolis Rabat-Shore, 11100 Sala El Jadida (Morocco); Osman, S.M., E-mail: osm@squ.edu.om [Physics Department, College of Science, Sultan Qaboos University, P.O. Box 36, Postal Code 123, Al-Khod, Muscat (Oman); Ataati, J. [Innovation and Management of Industrial Systems, Abdelmalek Essaadi University, College of Sciences and Techniques of Tangier, P.O. Box 416, Postal code 90000, Tangier (Morocco); Gasser, J.G. [Laboratoire de Chimie Physique – Approche Multi-Echelle des Milieux Complexes, Institut Jean Bariol, Université de Lorraine, Institut de Chimie, Physique et Matériaux, 1 Bd Arago, 57078 Metz Cedex 3 (France)

2015-12-15

The Mn{sub 66}Ga{sub 34} alloy at this particular composition is known to be zero alloy in which the linear combination of the two neutron scattering lengths weighted by the atomic compositions vanish. Thus for this specific concentration, the effect of the partial structure factors S{sub NN} and S{sub NC} is cancelled by a weighted term, which value is zero. Then the measured total structure factor S(q) gives directly the concentration–concentration structure factor S{sub CC}(q). We present here the first experimental results of neutron diffraction on the Mn{sub 66}Ga{sub 34} “null matrix alloy” at 1050 °C. The main peak of the experimental S{sub CC}(q) gives a strong evidence of a hetero-atomic chemical order in this coordinated alloy. This order also appears in real space radial distribution function which is calculated by the Fourier transform of the structure factor. The degree of hetero-coordination is discussed together with other manganese-polyvalent alloys. However manganese also shows abnormal magnetic scattering in the alloy structure factor which must be corrected. This correction gives an experimental information on the mean effective spin of manganese in this liquid alloy. We present the first critical theoretical calculations of the magnetic correction factor in Mn–Ga zero-alloy based on our accurate experimental measurements of S{sub CC}(q).

Internal process: what is abstraction and distortion process?

Science.gov (United States)

Fiantika, F. R.; Budayasa, I. K.; Lukito, A.

2018-03-01

Geometry is one of the branch of mathematics that plays a major role in the development of science and technology. Thus, knowing the geometry concept is needed for students from their early basic level of thinking. A preliminary study showed that the elementary students have difficulty in perceiving parallelogram shape in a 2-dimention of a cube drawing as a square shape. This difficulty makes the students can not solve geometrical problems correctly. This problem is related to the internal thinking process in geometry. We conducted the exploration of students’ internal thinking processes in geometry particularly in distinguishing the square and parallelogram shape. How the students process their internal thinking through distortion and abstraction is the main aim of this study. Analysis of the geometrical test and deep interview are used in this study to obtain the data. The result of this study is there are two types of distortion and abstraction respectively in which the student used in their internal thinking processes.

Observation of distorted Maxwell-Boltzmann distribution of epithermal ions in LHD

Science.gov (United States)

Ida, K.; Kobayashi, T.; Yoshinuma, M.; Akiyama, T.; Tokuzawa, T.; Tsuchiya, H.; Itoh, K.; LHD Experiment Group

2017-12-01

A distorted Maxwell-Boltzmann distribution of epithermal ions is observed associated with the collapse of energetic ions triggered by the tongue shaped deformation. The tongue shaped deformation is characterized by the plasma displacement localized in the toroidal, poloidal, and radial directions at the non-rational magnetic flux surface in toroidal plasma. Moment analysis of the ion velocity distribution measured with charge exchange spectroscopy is studied in order to investigate the impact of tongue event on ion distribution. A clear non-zero skewness (3rd moment) and kurtosis (4th moment -3) of ion velocity distribution in the epithermal region (within three times of thermal velocity) is observed after the tongue event. This observation indicates the clear evidence of the distortion of ion velocity distribution from Maxwell-Boltzmann distribution. This distortion from Maxwell-Boltzmann distribution is observed in one-third of plasma minor radius region near the plasma edge and disappears in the ion-ion collision time scale.

Three isostructural one-dimensional Ln(III) chains with distorted cubane motifs showing dual fluorescence and slow magnetic relaxation/magnetocaloric effect.

Science.gov (United States)

Li, Yan; Yu, Jia-Wen; Liu, Zhong-Yi; Yang, En-Cui; Zhao, Xiao-Jun

2015-01-05

Three new homometallic lanthanide complexes with mixed carboxylate-modified rigid ligands, [Ln(μ3-OH)(na)(pyzc)]n (na(-) = 1-naphtholate, pyzc(-) = 2-pyrazinecarboxylate, Ln = Dy (1), Yb (2), and Gd (3)), were solvothermally synthesized, and their structures and magnetic as well as photophysical properties were completely investigated. Complexes 1-3 are crystallographically isostructural, exhibiting linear chains with four bidentate bridging μ-COO(-) moieties encapsulated cubic {Ln4(μ3-OH)4}(8+) clusters repeatedly extended by 4-fold chelating-bridging-pyzc(-) connectors. Magnetically, the former two complexes with highly anisotropic Dy(III) and weak anisotropic Yb(III) ions in the distorted NO7 triangular dodecahedron coordination environment display field-induced slow relaxation of magnetization. Fitting the dynamic magnetic data to the Arrhenius law gives energy barrier ΔE/kB = 39.6 K and pre-exponential factor τo = 1.52 × 10(-8) s for 1 and ΔE/kB = 14.1 K and τo = 2.13 × 10(-7) s for 2. By contrast, complex 3 with isotropic Gd(III) ion and weak intracluster antiferromagnetic coupling shows a significant cryogenic magnetocaloric effect, with a maximum -ΔSm value of 30.0 J kg(-1) K(-1) at 2.5 K and 70 kOe. Additionally, the chromophoric na(-) and pyzc(-) ligands can serve as antenna groups, selectively sensitizing the Dy(III)- and Yb(III)-based luminescence of 1 and 2 in the UV-visible region by an intramolecular energy transfer process. Thus, complexes 1-3, incorporating field-induced slow magnetic magnetization and interesting luminescence together, can be used as composite magneto-optical materials. More importantly, these interesting results further demonstrate that the mixed-ligand system with rigid carboxylate-functionalized chromophores can be excellent candidates for the preparations of new bifunctional magneto-optical materials.

Magnetic flux density in the heliosphere through several solar cycles

Energy Technology Data Exchange (ETDEWEB)

Erdős, G. [Wigner Research Centre for Physics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest (Hungary); Balogh, A., E-mail: erdos.geza@wigner.mta.hu [The Blackett Laboratory, Imperial College London, London SW7 2BZ (United Kingdom)

2014-01-20

We studied the magnetic flux density carried by solar wind to various locations in the heliosphere, covering a heliospheric distance range of 0.3-5.4 AU and a heliolatitudinal range from 80° south to 80° north. Distributions of the radial component of the magnetic field, B{sub R} , were determined over long intervals from the Helios, ACE, STEREO, and Ulysses missions, as well as from using the 1 AU OMNI data set. We show that at larger distances from the Sun, the fluctuations of the magnetic field around the average Parker field line distort the distribution of B{sub R} to such an extent that the determination of the unsigned, open solar magnetic flux density from the average (|B{sub R} |) is no longer justified. We analyze in detail two methods for reducing the effect of fluctuations. The two methods are tested using magnetic field and plasma velocity measurements in the OMNI database and in the Ulysses observations, normalized to 1 AU. It is shown that without such corrections for the fluctuations, the magnetic flux density measured by Ulysses around the aphelion phase of the orbit is significantly overestimated. However, the matching between the in-ecliptic magnetic flux density at 1 AU (OMNI data) and the off-ecliptic, more distant, normalized flux density by Ulysses is remarkably good if corrections are made for the fluctuations using either method. The main finding of the analysis is that the magnetic flux density in the heliosphere is fairly uniform, with no significant variations having been observed either in heliocentric distance or heliographic latitude.

Distortions of the statistical distribution of Barkhausen noise measured by magneto-optical Kerr effect

International Nuclear Information System (INIS)

Pinotti, E.; Brenna, M.; Puppin, E.

2008-01-01

In magneto-optical Kerr measurements of the Barkhausen noise, a magnetization jump ΔM due to a domain reversal produces a variation ΔI of the intensity of a laser beam reflected by the sample, which is the physical quantity actually measured. Due to the non-uniform beam intensity profile, the magnitude of ΔI depends both on ΔM and on its position on the laser spot. This could distort the statistical distribution p(ΔI) of the measured ΔI with respect to the true distribution p(ΔM) of the magnetization jumps ΔM. In this work the exact relationship between the two distributions is derived in a general form, which will be applied to some possible beam profiles. It will be shown that in most cases the usual Gaussian beam produces a negligible statistical distortion. Moreover, for small ΔI the noise of the experimental setup can also distort the statistical distribution p(ΔI), by erroneously rejecting small ΔI as noise. This effect has been calculated for white noise, and it will be shown that it is relatively small but not totally negligible as the measured ΔI approaches the detection limit

Effect of structural distortion on the electronic band structure of NaOsO3 studied within density functional theory and a three-orbital model

Science.gov (United States)

Mohapatra, Shubhajyoti; Bhandari, Churna; Satpathy, Sashi; Singh, Avinash

2018-04-01

Effects of the structural distortion associated with the OsO6 octahedral rotation and tilting on the electronic band structure and magnetic anisotropy energy for the 5 d3 compound NaOsO3 are investigated using the density functional theory (DFT) and within a three-orbital model. Comparison of the essential features of the DFT band structures with the three-orbital model for both the undistorted and distorted structures provides insight into the orbital and directional asymmetry in the electron hopping terms resulting from the structural distortion. The orbital mixing terms obtained in the transformed hopping Hamiltonian resulting from the octahedral rotations are shown to account for the fine features in the DFT band structure. Staggered magnetization and the magnetic character of states near the Fermi energy indicate weak coupling behavior.

Oceanic Loading and Local Distortions at the Baksan, Russia, and Gran Sasso, Italy, Strain Stations

Science.gov (United States)

Milyukov, V. K.; Amoruso, A.; Crescentini, L.; Mironov, A. P.; Myasnikov, A. V.; Lagutkina, A. V.

2018-03-01

Reliable use of strain data in geophysical studies requires their preliminary correction for ocean loading and various local distortions. These effects, in turn, can be estimated from the tidal records which are contributed by solid and oceanic loading. In this work, we estimate the oceanic tidal loading at two European strain stations (Baksan, Russia, and Gran Sasso, Italy) by analyzing the results obtained with the different Earth and ocean models. The influence of local distortions on the strain measurements at the two stations is estimated.

Weak correction to the muon magnetic moment in a gauge model

International Nuclear Information System (INIS)

Darby, D.; Grammer, G. Jr.

1976-01-01

The weak correction, asub(μ)sup(W), to the anomalous magnetic moment of the muon is calculated in an SU(2) x U(1) x U(1) gauge model of weak and electromagnetic interactions. The Rsub(xi) gauge is used and Ward-Takahashi identities are utilized in eliminating all xi-dependence before the loop integration is performed. asub(μ)sup(W,expt) places no constraint on the mass of one of the neutral vector mesons, which may be arbitrarily small. (Auth.)

Flow distortion on boom mounted cup anemometers

DEFF Research Database (Denmark)

Lindelöw, Per Jonas Petter; Friis Pedersen, Troels; Gottschall, Julia

In this report we investigate on wind direction dependent errors in the measurement of the horizontal wind speed by boom mounted cup anemometers. The boom mounting on the studied lattice tower is performed according to IEC standard design rules, yet, larger deviations than predicted by flow models...... are observed. The errors on the measurements are likely caused by an underestimation of the flow distortions around the tower. In this paper an experimental method for deriving a correction formula and an in-field calibration is suggested. The method is based on measurements with two cup anemometers mounted...

Correction of vertical dispersion and betatron coupling for the CLIC damping ring

CERN Document Server

Korostelev, M S

2006-01-01

The sensitivity of the CLIC damping ring to various kinds of alignment errors has been studied. Without any correction, fairly small vertical misalignments of the quadrupoles and, in particular, the sextupoles, introduce unacceptable distortions of the closed orbit as well as intolerable spurious vertical dispersion and coupling due to the strong focusing optics of the damping ring. A sophisticated beam-based correction scheme has been developed to bring the design target emittances and the dynamic aperture back to the ideal value. The correction using dipolar correctors and several skew quadrupole correctors allows a minimization of the closed-orbit distortion, the cross-talk between vertical and horizontal closed orbits, the residual vertical dispersion and the betatron coupling.

Time-stamp correction of magnetic observatory data acquired during unavailability of time-synchronization services

Science.gov (United States)

Coïsson, Pierdavide; Telali, Kader; Heumez, Benoit; Lesur, Vincent; Lalanne, Xavier; Jiang Xin, Chang

2017-09-01

During magnetic observatory data acquisition, the data time stamp is kept synchronized with a precise source of time. This is usually done using a GPS-controlled pulse per second (PPS) signal. For some observatories located in remote areas or where internet restrictions are enforced, only the magnetometer data are transmitted, limiting the capabilities of monitoring the acquisition operations. The magnetic observatory in Lanzhou (LZH), China, experienced an unnoticed interruption of the GPS PPS starting 7 March 2013. The data logger clock drifted slowly in time: in 6 months a lag of 27 s was accumulated. After a reboot on 2 April 2014 the drift became faster, -2 s per day, before the GPS PPS could be restored on 8 July 2014. To estimate the time lags that LZH time series had accumulated, we compared it with data from other observatories located in East Asia. A synchronization algorithm was developed. Natural sources providing synchronous events could be used as markers to obtain the time lag between the observatories. The analysis of slices of 1 h of 1 s data at arbitrary UTC allowed estimating time lags with an uncertainty of ˜ 11 s, revealing the correct trends of LZH time drift. A precise estimation of the time lag was obtained by comparing data from co-located instruments controlled by an independent PPS. In this case, it was possible to take advantage of spikes and local noise that constituted precise time markers. It was therefore possible to determine a correction to apply to LZH time stamps to correct the data files and produce reliable 1 min averaged definitive magnetic data.

Compensation of the flux modulation distortion using an additional coil in a loudspeaker unit

DEFF Research Database (Denmark)

Antonello, Niccoló; Agerkvist, Finn T.

2014-01-01

the compensation coil is derived. The compensation technique consists on feeding the compensation coil and voice coil with filtered versions of the wanted audio signal. Simulations show that a significant reduction in flux modulation distortion can be achieved with this technique. A simple magnetic circuit has......Flux modulation is one of the main causes of distortion in electrodynamic loudspeaker units. A new compensation technique that eliminates this type of non-linearity using an additional compensation coil in the speaker unit is presented. An equivalent circuit model of the device including...

Multi-shape pulse pile-up correction: The MCPPU code

International Nuclear Information System (INIS)

Sabbatucci, Lorenzo; Scot, Viviana; Fernandez, Jorge E.

2014-01-01

In spectroscopic measurements with high counting rate, pulse pile-up (PPU) is a common distortion of the spectrum. It is fully ascribable to the pulse handling circuitry of the detector and it is not comprised in the detector response function which is well explained by a purely physical model. Since PPU occurs after the transport inside the detector, this is the first correction to perform in case of spectrum unfolding. Many producers include electronic rejection circuits to limit the appearance of PPU, but it is never suppressed completely. Therefore, it is always necessary to correct PPU distortions after the measurement. In the present work, it is described the post-processing tool MCPPU (Monte Carlo Pulse Pile-Up), based on the MC algorithm developed by Guo et al. (2004, 2005). MCPPU automatically determines the dead time of the counting system and corrects for PPU effects even in the presence of electronic suppression. The capability of allowing a user defined pulse shape makes the code suitable to be used with any kind of detector. The features of MCPPU are illustrated with some examples. - Highlights: • Pulse pile-up (PPU) is a common distortion in radiation detection. • MCPPU is a Monte Carlo code to perform post-processing PPU correction. • MCPPU evaluates automatically the dead time to use in the pile-up recovery. • The measured pulse shape can be introduced as a normalized discrete distribution. • MCPPU is compatible with detectors using electronic rejection circuitry

The magnetic field for the ZEUS central detector - analysis and correction of the field measurement

International Nuclear Information System (INIS)

Mengel, S.

1992-06-01

The magnetic field in the central tracking region of the ZEUS-detector - a facility to investigate highly energetic electron-proton-collisions at the HERA-collider at DESY Hamburg - is generated by a superconducting coil and reaches 18 kG (1.8 T). Some of the tracking devices particularly the drift chambers in the proton forward and rear direction (FTD1-3 and RTD) are not fully contained within the coil and therefore situated in a highly inhomogeneous magnetic field: The radial component B r is up to 6.6 kG, maximum gradients are found to be 300 G/cm for δB r /δr. Evaluating the space drifttime relation necessitates a detailed knowledge of the magnetic field. To reach this goal we analysed the field measurements and corrected them for systematic errors. The corrected data were compared with the field calculations (TOSCA-maps). Measurements and calculations are confirmed by studying consistency with Maxwell's equations. The accuracy reached is better than 100 G throughout the forward and central drift chambers (FTD1-3, CTD) and better than 150 G in the RTD. (orig.) [de

Logarithmic corrections to entropy of magnetically charged AdS4 black holes

Directory of Open Access Journals (Sweden)

Imtak Jeon

2017-11-01

Full Text Available Logarithmic terms are quantum corrections to black hole entropy determined completely from classical data, thus providing a strong check for candidate theories of quantum gravity purely from physics in the infrared. We compute these terms in the entropy associated to the horizon of a magnetically charged extremal black hole in AdS×4S7 using the quantum entropy function and discuss the possibility of matching against recently derived microscopic expressions.

Calculation of gravity and magnetic anomalies along profiles with end corrections and inverse solutions for density and magnetization

Science.gov (United States)

Cady, John W.

1977-01-01

An equation derived for the vertical gravity field due to a body with polygonal cross section and finite strike length.  The equations consists of the 2-dimensional equation of Talwani, Worzel, and Landisman (1959), with the addition of end corrections.  Equations for the magnetic field due to a similar body were derived by Shuey and Pasquale (1973).  They coined the term "2 1/2-dimensional" to describe the geometry.

Hybrid wavefront sensing and image correction algorithm for imaging through turbulent media

Science.gov (United States)

Wu, Chensheng; Robertson Rzasa, John; Ko, Jonathan; Davis, Christopher C.

2017-09-01

It is well known that passive image correction of turbulence distortions often involves using geometry-dependent deconvolution algorithms. On the other hand, active imaging techniques using adaptive optic correction should use the distorted wavefront information for guidance. Our work shows that a hybrid hardware-software approach is possible to obtain accurate and highly detailed images through turbulent media. The processing algorithm also takes much fewer iteration steps in comparison with conventional image processing algorithms. In our proposed approach, a plenoptic sensor is used as a wavefront sensor to guide post-stage image correction on a high-definition zoomable camera. Conversely, we show that given the ground truth of the highly detailed image and the plenoptic imaging result, we can generate an accurate prediction of the blurred image on a traditional zoomable camera. Similarly, the ground truth combined with the blurred image from the zoomable camera would provide the wavefront conditions. In application, our hybrid approach can be used as an effective way to conduct object recognition in a turbulent environment where the target has been significantly distorted or is even unrecognizable.

Beam loss reduction by magnetic shielding using beam pipes and bellows of soft magnetic materials

Science.gov (United States)

Kamiya, J.; Ogiwara, N.; Hotchi, H.; Hayashi, N.; Kinsho, M.

2014-11-01

One of the main sources of beam loss in high power accelerators is unwanted stray magnetic fields from magnets near the beam line, which can distort the beam orbit. The most effective way to shield such magnetic fields is to perfectly surround the beam region without any gaps with a soft magnetic high permeability material. This leads to the manufacture of vacuum chambers (beam pipes and bellows) with soft magnetic materials. A Ni-Fe alloy (permalloy) was selected for the material of the pipe parts and outer bellows parts, while a ferritic stainless steel was selected for the flanges. An austenitic stainless steel, which is non-magnetic material, was used for the inner bellows for vacuum tightness. To achieve good magnetic shielding and vacuum performances, a heat treatment under high vacuum was applied during the manufacturing process of the vacuum chambers. Using this heat treatment, the ratio of the integrated magnetic flux density along the beam orbit between the inside and outside of the beam pipe and bellows became small enough to suppress beam orbit distortion. The outgassing rate of the materials with this heat treatment was reduced by one order magnitude compared to that without heat treatment. By installing the beam pipes and bellows of soft magnetic materials as part of the Japan Proton Accelerator Research Complex 3 GeV rapid cycling synchrotron beam line, the closed orbit distortion (COD) was reduced by more than 80%. In addition, a 95.5% beam survival ratio was achieved by this COD improvement.

Limited distortion in LSB steganography

Science.gov (United States)

Kim, Younhee; Duric, Zoran; Richards, Dana

2006-02-01

It is well known that all information hiding methods that modify the least significant bits introduce distortions into the cover objects. Those distortions have been utilized by steganalysis algorithms to detect that the objects had been modified. It has been proposed that only coefficients whose modification does not introduce large distortions should be used for embedding. In this paper we propose an effcient algorithm for information hiding in the LSBs of JPEG coefficients. Our algorithm uses parity coding to choose the coefficients whose modifications introduce minimal additional distortion. We derive the expected value of the additional distortion as a function of the message length and the probability distribution of the JPEG quantization errors of cover images. Our experiments show close agreement between the theoretical prediction and the actual additional distortion.

Reinterpretation of the ''relativistic mass'' correction to the spin magnetic moment of a moving particle

International Nuclear Information System (INIS)

Hegstrom, R.A.; Lhuillier, C.

1977-01-01

Starting from a classical covariant equation of motion for the spin of a particle moving in a homogeneous electromagnetic field (the Bargmann-Michel-Telegdi equation), we show that the ''relativistic mass'' correction to the electron spin magnetic moment, which has been obtained previously from relativistic quantum-mechanical treatments of the Zeeman effect, may be reinterpreted as the combination of three classical effects: (i) the difference in time scales in the electron rest frame vis-a-vis the lab frame, (ii) the Lorentz transformation of the magnetic field between the two frames, and (iii) the Thomas precession of the electron spin due to the acceleration of the electron produced by the magnetic field

Synthesis, structure and magnetic properties of distorted Y{sub x}La{sub 1-x}FeO{sub 3}: Effects of mechanochemical activation and composition

Energy Technology Data Exchange (ETDEWEB)

Cristobal, A.A. [Instituto de Investigaciones en Ciencia y Tecnologia de Materiales, INTEMA (CONICET-UNMdP), J.B. Justo 4302 B7608FDQ, Mar del Plata (Argentina); Botta, P.M., E-mail: pbotta@fi.mdp.edu.ar [Instituto de Investigaciones en Ciencia y Tecnologia de Materiales, INTEMA (CONICET-UNMdP), J.B. Justo 4302 B7608FDQ, Mar del Plata (Argentina); Aglietti, E.F.; Conconi, M.S. [Centro de Tecnologia de Recursos Minerales y Ceramica, CETMIC (CIC-CONICET), Camino P. Centenario y 506 B1897ZCA, Gonnet (Argentina); Bercoff, P.G. [Facultad de Matematica, Astronomia y Fisica, FaMAF UNC and IFEG (CONICET), Ciudad Universitaria (5000), Cordoba (Argentina); Porto Lopez, J.M. [Instituto de Investigaciones en Ciencia y Tecnologia de Materiales, INTEMA (CONICET-UNMdP), J.B. Justo 4302 B7608FDQ, Mar del Plata (Argentina)

2011-11-01

Highlights: {yields} Y{sub x}La{sub 1-x}FeO{sub 3} phases (0 {<=} x {<=} 1) were prepared at RT by mechanochemical treatment. {yields} The obtained materials showed an anisotropic distortion of its crystal structure. {yields} Combination of Y-doping and mechanochemistry produced weak ferromagnetic materials. {yields} Thermal treatments improved the structural order, leading to antiferromagnetic solids. {yields} Neel temperature decreased with x due to less stable magnetic structures. - Abstract: The influence of mechanochemical treatment on the synthesis and properties of Y{sub x}La{sub 1-x}FeO{sub 3} (0 {<=} x {<=} 1) orthoferrites is studied. Solid mixtures of the corresponding metal oxides were treated in a high-energy ball-mill. X-ray diffraction revealed that during the milling the disappearance of the reactants and a fast conversion to orthoferrite phase take place. Magnetic measurements showed a weak ferromagnetic behavior of the obtained materials, observing higher magnetization for larger x. The activated powders heated at 600 and 800 deg. C showed a progressive crystalline ordering together with a significant drop of magnetization. Thermal treatments at 1000 deg. C produced the formation of the phase Y{sub 3}Fe{sub 5}O{sub 12} for the samples richer in yttrium, increasing the magnetization. Rietveld refinements of the diffraction patterns and dynamical scanning calorimetry were used respectively to determine the lattice parameters and Neel temperatures for the formed orthoferrites. The effect of the composition on the structure and magnetic behavior is discussed.

Light-by-light-type corrections to the muon anomalous magnetic moment at four-loop order

International Nuclear Information System (INIS)

Kurz, Alexander; Smirnov, Alexander V.; Smirnov, Vladimir A.

2015-08-01

The numerically dominant QED contributions to the anomalous magnetic moment of the muon stem from Feynman diagrams with internal electron loops. We consider such corrections and present a calculation of the four-loop light-by-light-type corrections where the external photon couples to a closed electron or muon loop. We perform an asymptotic expansion in the ratio of electron and muon mass and reduce the resulting integrals to master integrals which we evaluate using analytical and numerical methods. We confirm the results present in the literature which are based on different computational methods.

Magnetic reconnection during eruptive magnetic flux ropes

Science.gov (United States)

Mei, Z. X.; Keppens, R.; Roussev, I. I.; Lin, J.

2017-08-01

Aims: We perform a three-dimensional (3D) high resolution numerical simulation in isothermal magnetohydrodynamics to study the magnetic reconnection process in a current sheet (CS) formed during an eruption of a twisted magnetic flux rope (MFR). Because the twist distribution violates the Kruskal-Shafranov condition, the kink instability occurs, and the MFR is distorted. The centre part of the MFR loses its equilibrium and erupts upward, which leads to the formation of a 3D CS underneath it. Methods: In order to study the magnetic reconnection inside the CS in detail, mesh refinement has been used to reduce the numerical diffusion and we estimate a Lundquist number S = 104 in the vicinity of the CS. Results: The refined mesh allows us to resolve fine structures inside the 3D CS: a bifurcating sheet structure signaling the 3D generalization of Petschek slow shocks, some distorted-cylindrical substructures due to the tearing mode instabilities, and two turbulence regions near the upper and the lower tips of the CS. The topological characteristics of the MFR depend sensitively on the observer's viewing angle: it presents as a sigmoid structure, an outwardly expanding MFR with helical distortion, or a flare-CS-coronal mass ejection symbiosis as in 2D flux-rope models when observed from the top, the front, or the side. The movie associated to Fig. 2 is available at http://www.aanda.org

MRI, geometric distortion of the image and stereotaxy

International Nuclear Information System (INIS)

Derosier, C.; Delegue, G.; Munier, T.; Pharaboz, C.; Cosnard, G.

1991-01-01

The MRI technology may be the starting-point of geometric distortion. The mathematical preciseness of a spatial location may be disturbed and alter the guidance of a MRI interventional act, especially in stereotactic brain biopsy. A review of the literature shows errors of 1 to 1.5 mm. Our results show an error of 0.16±0.66. The control of quality: homogeneity and calibration of magnetic-field gradients, permit an improve of the ballistic preciseness and give permission to realize the guidance of a stereotactic brain biopsy with the alone MRI

Sustained spheromak coaxial gun operation in the presence of an n=1 magnetic distortion

International Nuclear Information System (INIS)

Holcomb, C.T.; Jarboe, T.R.; Hill, D.N.; Woodruff, S.; Wood, R.D.

2006-01-01

The Sustained Spheromak Physics Experiment (SSPX) [E. B. Hooper, L. D. Pearlstein, and R. H. Bulmer, Nucl. Fusion 39, 863 (1999)] uses a magnetized coaxial gun to form and sustain spheromaks by helicity injection. Internal probes give the magnetic profile within the gun. An analysis of these data show that a number of commonly applied assumptions are not completely correct, and some previously unrecognized processes may be at work. Specifically, the fraction of the available vacuum flux spanning the gun that is stretched out of the gun is variable and not usually 100%. The n=1 mode that is present during sustained discharges has its largest value of δB/B within the gun, so that instantaneously B within the gun is not axisymmetric. By applying a rigid-rotor model to account for the mode, the instantaneous field and current structure within the gun are determined. The current density is also highly nonaxisymmetric and the local value of λ≡μ 0 j parallel /B is not constant, although the global value λ g ≡μ 0 I g /ψ g closely matches that expected by axisymmetric models. The current distribution near the gun muzzle suggests a cross-field current exists, and this is explained as a line-tying reaction to plasma rotation

The Dark Side of Context: Context Reinstatement Can Distort Memory.

Science.gov (United States)

Doss, Manoj K; Picart, Jamila K; Gallo, David A

2018-04-01

It is widely assumed that context reinstatement benefits memory, but our experiments revealed that context reinstatement can systematically distort memory. Participants viewed pictures of objects superimposed over scenes, and we later tested their ability to differentiate these old objects from similar new objects. Context reinstatement was manipulated by presenting objects on the reinstated or switched scene at test. Not only did context reinstatement increase correct recognition of old objects, but it also consistently increased incorrect recognition of similar objects as old ones. This false recognition effect was robust, as it was found in several experiments, occurred after both immediate and delayed testing, and persisted with high confidence even after participants were warned to avoid the distorting effects of context. To explain this memory illusion, we propose that context reinstatement increases the likelihood of confusing conceptual and perceptual information, potentially in medial temporal brain regions that integrate this information.

Lifting the geometric frustration through a monoclinic distortion in “114” YBaFe4O7.0: Magnetism and transport

International Nuclear Information System (INIS)

Duffort, V.; Sarkar, T.; Caignaert, V.; Pralong, V.; Raveau, B.; Avdeev, M.; Cervellino, A.; Waerenborgh, J.C.; Tsipis, E.V.

2013-01-01

The possibility to lift the geometric frustration in the “114” stoichiomeric tetragonal oxide YBaFe 4 O 7.0 by decreasing the temperature has been investigated using neutron and synchrotron powder diffraction techniques. Besides the structural transition from tetragonal to monoclinic symmetry that appears at T S =180 K, a magnetic transition is observed below T N =95 K. The latter corresponds to a lifting of the 3D geometric frustration toward an antiferromagnetic long range ordering, never observed to date in a cubic based “114’” oxide. The magnetic structure, characterized by the propagation vector k 1 =(0,0,½), shows that one iron Fe2 exhibits a larger magnetic moment than the three others, suggesting a possible charge ordering according to the formula YBaFe 3+ Fe 3 2+ O 7.0 . The magnetic M(T) and χ′(T) curves, in agreement with neutron data, confirm the structural and magnetic transitions and evidence the coexistence of residual magnetic frustration. Moreover, the transport measurements show a resistive transition from a thermally activated conduction mechanism to a variable range hopping mechanism at T S =180 K, with a significant increase of the dependence of the resistivity vs. temperature. Mössbauer spectroscopy clearly evidences a change in the electronic configuration of the iron framework at the structural transition as well as coexistence of several oxidation states. The role of barium underbonding in these transitions is discussed. - Graphical abstract: Atomic displacements at the tetragonal-monoclinic transition in YBaFe 4 O 7 . Display Omitted - Highlights: • The structural and magnetic phase transitions of YBaFe 4 O 7 were studied below room temperature. • The tetragonal to monoclinic transition, characterized by NPD and SXRD, was studied using mode crystallography approach. • Monoclinic distortion allows the lifting of the geometrical frustration on the iron sublattice, leading to AF order at T=95 K

On-line implant reconstruction in HDR brachytherapy

International Nuclear Information System (INIS)

Kolkman-Deurloo, Inger-Karine K.; Kruijf, Wilhelmus J.M. de; Levendag, Peter C.

2006-01-01

Background and purpose: To evaluate the accuracy of on-line planning in an Integrated Brachytherapy Unit (IBU) using dedicated image distortion correction algorithms, correcting the geometric distortion and magnetic distortion separately, and to determine the effect of the reconstruction accuracy on clinical treatment plans in terms of deviations in treatment time and dose. Patients and methods: The reconstruction accuracy has been measured using 20 markers, positioned at well known locations in a QA phantom. Treatment plans of two phantoms representing clinical implant geometries, have been compared with reference plans to determine the effect of the reconstruction accuracy on the treatment plan. Before clinical introduction, treatment plans of three representative patients, based on on-line reconstruction, have been compared with reference plans. Results: The average reconstruction error for 10 in. images reduces from -0.6 mm (range -2.6 to +1.0 mm) to -0.2 mm (range -1.2 to +0.6 mm) after image distortion correction and for 15 in. images from 0.8 mm (range -0.5 to +3.0 mm) to 0.0 mm (range -0.8 to +0.8 mm). The error in case of eccentric positioning of the phantom, i.e. 0.8 mm (range -1.0 to +3.3 mm), reduces to 0.1 mm (range -0.5 to +0.9 mm). Correction of the image distortions reduces the deviation in the calculated treatment time of maximally 2.7% to less than 0.8% in case of eccentrically positioned clinical phantoms. The deviation in the treatment time or reference dose in the plans based on on-line reconstruction with image distortion correction of the three patient examples is smaller than 0.3%. Conclusions: Accurate on-line implant reconstruction using the IBU localiser and dedicated correction algorithms separating the geometric distortion and the magnetic distortion is possible. The results fulfill the minimum requirements as imposed by the Netherlands Commission on Radiation Dosimetry (NCS) without limitations regarding the usable range of the field

Nonperturbative QCD corrections to electroweak observables

Energy Technology Data Exchange (ETDEWEB)

Dru B Renner, Xu Feng, Karl Jansen, Marcus Petschlies

2011-12-01

Nonperturbative QCD corrections are important to many low-energy electroweak observables, for example the muon magnetic moment. However, hadronic corrections also play a significant role at much higher energies due to their impact on the running of standard model parameters, such as the electromagnetic coupling. Currently, these hadronic contributions are accounted for by a combination of experimental measurements and phenomenological modeling but ideally should be calculated from first principles. Recent developments indicate that many of the most important hadronic corrections may be feasibly calculated using lattice QCD methods. To illustrate this, we will examine the lattice computation of the leading-order QCD corrections to the muon magnetic moment, paying particular attention to a recently developed method but also reviewing the results from other calculations. We will then continue with several examples that demonstrate the potential impact of the new approach: the leading-order corrections to the electron and tau magnetic moments, the running of the electromagnetic coupling, and a class of the next-to-leading-order corrections for the muon magnetic moment. Along the way, we will mention applications to the Adler function, the determination of the strong coupling constant and QCD corrections to muonic-hydrogen.

Applying image quality in cell phone cameras: lens distortion

Science.gov (United States)

Baxter, Donald; Goma, Sergio R.; Aleksic, Milivoje

2009-01-01

This paper describes the framework used in one of the pilot studies run under the I3A CPIQ initiative to quantify overall image quality in cell-phone cameras. The framework is based on a multivariate formalism which tries to predict overall image quality from individual image quality attributes and was validated in a CPIQ pilot program. The pilot study focuses on image quality distortions introduced in the optical path of a cell-phone camera, which may or may not be corrected in the image processing path. The assumption is that the captured image used is JPEG compressed and the cellphone camera is set to 'auto' mode. As the used framework requires that the individual attributes to be relatively perceptually orthogonal, in the pilot study, the attributes used are lens geometric distortion (LGD) and lateral chromatic aberrations (LCA). The goal of this paper is to present the framework of this pilot project starting with the definition of the individual attributes, up to their quantification in JNDs of quality, a requirement of the multivariate formalism, therefore both objective and subjective evaluations were used. A major distinction in the objective part from the 'DSC imaging world' is that the LCA/LGD distortions found in cell-phone cameras, rarely exhibit radial behavior, therefore a radial mapping/modeling cannot be used in this case.

Magnetic anisotropy of a Co-II single ion magnet with distorted trigonal prismatic coordination

DEFF Research Database (Denmark)

Peng, Yan; Bodenstein, Tilmann; Fink, Karin

2016-01-01

calculations. Though the complex shows a slight deviation from an ideal trigonal prismatic coordination, the zero-field splitting as well as the g-tensor are strongly axial with D = -41 cm(-1) and E ... with a spin Hamiltonian of the form H = D(S-z(2) - S(S + 1)/3) + E(S-x(2) - S-y(2)) + mu(B)gS.B using an effective spin S = 3/2. Calculations on model complexes show the influence of the coordinating atoms and the deviation from the ideal trigonal prismatic coordination. As the distortion is reduced towards...... idealised D-3h, the zero field splitting increases and the g-tensor of the second Kramers doublet also becomes axial....

The main injector chromaticity correction sextupole magnets: Measurements and operating schemes

International Nuclear Information System (INIS)

Bhat, C.M.; Bogacz, A.; Brown, B.C.; Harding, D.J.; Fang, S.J.; Martin, P.S.; Glass, H.D.; Sim, J.

1995-05-01

The Fermilab Main Injector (FMI) is a high intensity proton synchrotron which will be used to accelerate protons and antiprotons from 8.9 GeV/c to 150 GeV/c. The natural chromaticities of the machine for the horizontal and the vertical Planes are -33.6 and -33.9 respectively. The Δp/p of the beam at injection is about 0.002. The chromaticity requirements of the FMI, are primarily decided by the Δp/p = 0.002 of the beam at injection. This limits the final chromaticity of the FMI to be ±5 units. To correct the chromaticity in the FMI two families of sextupole magnets will be installed in the lattice, one for each plane. A sextupole magnet suitable for the FMI needs has been designed and a number of them are being built. New chromaticity compensation schemes have been worked out in the light of recently proposed faster acceleration ramps. On an R/D sextupole magnet the low current measurements have been carried out to determine the electrical properties. Also, using a Morgan coil, measurements have been performed to determine the higher ordered multipole components up to 18-poles. An overview of these result are presented here

Magnetic tension and gravitational collapse

International Nuclear Information System (INIS)

Tsagas, Christos G

2006-01-01

The gravitational collapse of a magnetized medium is investigated by studying qualitatively the convergence of a timelike family of non-geodesic worldlines in the presence of a magnetic field. Focusing on the field's tension, we illustrate how the winding of the magnetic forcelines due to the fluid's rotation assists the collapse, while shear-like distortions in the distribution of the field's gradients resist contraction. We also show that the relativistic coupling between magnetism and geometry, together with the tension properties of the field, lead to a magneto-curvature stress that opposes the collapse. This tension stress grows stronger with increasing curvature distortion, which means that it could potentially dominate over the gravitational pull of the matter. If this happens, a converging family of non-geodesic worldlines can be prevented from focusing without violating the standard energy conditions

The effect of band Jahn-Teller distortion on the magnetoresistivity of manganites: a model study

International Nuclear Information System (INIS)

Rout, G C; Panda, Saswati; Behera, S N

2011-01-01

We present a model study of magnetoresistance through the interplay of magnetisation, structural distortion and external magnetic field for the manganite systems. The manganite system is described by the Hamiltonian which consists of the s-d type double exchange interaction, Heisenberg spin-spin interaction among the core electrons, and the static and dynamic band Jahn-Teller (JT) interaction in the e g band. The relaxation time of the e g electron is found from the imaginary part of the Green's function using the total Hamiltonian consisting of the interactions due to the electron and phonon. The calculated resistivity exhibits a peak in the pure JT distorted insulating phase separating the low temperature metallic ferromagnetic phase and the high temperature paramagnetic phase. The resistivity is suppressed with the increase of the external magnetic field. The e g electron band splitting and its effect on magnetoresistivity is reported here. (paper)

Corrections for a constant radial magnetic field in the muon g - 2 and electric-dipole-moment experiments in storage rings

Energy Technology Data Exchange (ETDEWEB)

Silenko, Alexander J. [Belarusian State University, Research Institute for Nuclear Problems, Minsk (Belarus); Joint Institute for Nuclear Research, Bogoliubov Laboratory of Theoretical Physics, Dubna (Russian Federation)

2017-10-15

We calculate the corrections for constant radial magnetic field in muon g - 2 and electric-dipole-moment experiments in storage rings. While the correction is negligible for the current generation of g - 2 experiments, it affects the upcoming muon electric-dipole-moment experiment at Fermilab. (orig.)

Analysis of slippery droplet on tilted plate by development of optical correction method

Science.gov (United States)

Ko, Han Seo; Gim, Yeonghyeon; Choi, Sung Ho; Jang, Dong Kyu; Sohn, Dong Kee

2017-11-01

Because of distortion effects on a surface of a sessile droplet, the inner flow field of the droplet is measured by a PIV (particle image velocimetry) method with low reliability. In order to solve this problem, many researchers have studied and developed the optical correction method. However, the method cannot be applied for various cases such as the tilted droplet or other asymmetric shaped droplets since most methods were considered only for the axisymmetric shaped droplets. For the optical correction of the asymmetric shaped droplet, the surface function was calculated by the three-dimensional reconstruction using the ellipse curve fitting method. Also, the optical correction using the surface function was verified by the numerical simulation. Then, the developed method was applied to reconstruct the inner flow field of the droplet on the tilted plate. The colloidal droplet of water on the tilted surface was used, and the distorted effect on the surface of the droplet was calculated. Using the obtained results and the PIV method, the corrected flow field for the inner and interface parts of the droplet was reconstructed. Consequently, the error caused by the distortion effect of the velocity vector located on the apex of the droplet was removed. National Research Foundation (NRF) of Korea, (2016R1A2B4011087).

Analysis of Brown camera distortion model

Science.gov (United States)

Nowakowski, Artur; Skarbek, Władysław

2013-10-01

Contemporary image acquisition devices introduce optical distortion into image. It results in pixel displacement and therefore needs to be compensated for many computer vision applications. The distortion is usually modeled by the Brown distortion model, which parameters can be included in camera calibration task. In this paper we describe original model, its dependencies and analyze orthogonality with regard to radius for its decentering distortion component. We also report experiments with camera calibration algorithm included in OpenCV library, especially a stability of distortion parameters estimation is evaluated.

Observation of Anomalous Properties associated with the Low Temperature Structural Distortion in β-FeSe and Related Superconductorsa

Directory of Open Access Journals (Sweden)

Wu M. K.

2012-03-01

Full Text Available The discovery of Superconductivity in the tetragonal phase FeSe provides a unique platform for the detailed investigation of the correlation between the physical properties and crystal structure to better understand the possible origin of superconductivity in the new iron-based superconductors. We have carried out a series of properties characterizations by measuring magnetic susceptibility, Raman, NMR and femtosecond spectroscopy on single crystals and epitaxial thin films of the FeSe and Te-doped Fe(SeTe samples. Our results show clearly the presence of anomalies in all the characterized properties at the temperature where a structural distortion from tetragonal to orthorhombic (or monoclinic appears for all superconducting samples, but not in the non-superconducting ones. This structural distortion was observed not accompanied by a magnetic ordering as commonly occurs in the parent compounds of FeAs-based superconductors. All the observations suggest that the low temperature structural distortion is essential for the occurrence of superconductivity in the FeSe and related compounds. Details of the experimental results will be presented and discussed.

Predicting thermal distortion of synchrotron radiation mirrors with finite element analysis

International Nuclear Information System (INIS)

DiGennaro, R.; Edwards, W.R.; Hoyer, E.

1985-10-01

High power and high power densities due to absorbed radiation are significant design considerations which can limit performance of mirrors receiving highly collimated synchrotron radiation from insertion devices and bending magnet sources. Although the grazing incidence angles needed for x-ray optics spread the thermal load, localized, non-uniform heating can cause distortions which exceed allowable surface figure errors and limit focusing resolution. This paper discusses the suitability of numerical approximations using finite element methods for heat transfer, deformation, and stress analysis of optical elements. The primary analysis objectives are (1) to estimate optical surface figure under maximum heat loads, (2) to correctly predict thermal stresses in order to select suitable materials and mechanical design configurations, and (3) to minimize fabrication costs by specifying appropriate tolerances for surface figure. Important factors which determine accuracy of results include finite element model mesh refinement, accuracy of boundary condition modeling, and reliability of material property data. Some methods to verify accuracy are suggested. Design analysis for an x-ray mirror is presented. Some specific configurations for internal water-cooling are evaluated in order to determine design sensitivity with respect to structural geometry, material properties, fabrication tolerances, absorbed heat magnitude and distribution, and heat transfer approximations. Estimated accuracy of these results is discussed

Cardiovascular magnetic resonance in the follow-up of patients with corrected tetralogy of Fallot: a review

NARCIS (Netherlands)

Oosterhof, Thomas; Mulder, Barbara J. M.; Vliegen, Hubert W.; de Roos, Albert

2006-01-01

Cardiovascular magnetic resonance (CMR) is becoming an important tool in the clinical management of patients with congenital heart disease. Because of the diverse problems patients may face after initial correction for tetralogy of Fallot and the large amount of CMR techniques that can be applied,

The data correction algorithms in sup 6 sup 0 Co train inspection system

CERN Document Server

Yuan Ya Ding; LiuXiMing; Miao Ji Cheng

2002-01-01

Because of the physical characteristics of the sup 6 sup 0 Co train inspection system and the application of high-speed data collection system based on current integral, the original images have been distorted in a certain degree. Authors investigate into the reasons why the distortion comes into being, and accordingly present the data correction algorithm

Neural mechanisms of reactivation-induced updating that enhance and distort memory

OpenAIRE

St. Jacques, Peggy L.; Olm, Christopher; Schacter, Daniel L.

2013-01-01

We remember a considerable number of personal experiences because we are frequently reminded of them, a process known as memory reactivation. Although memory reactivation helps to stabilize and update memories, reactivation may also introduce distortions if novel information becomes incorporated with memory. Here we used functional magnetic resonance imaging (fMRI) to investigate the neural mechanisms mediating reactivation-induced updating in memory for events experienced during a museum tou...

Baseline distortion effect on gamma-ray pulse-height spectra in neutron capture experiments

International Nuclear Information System (INIS)

Laptev, A.; Harada, H.; Nakamura, S.; Hori, J.; Igashira, M.; Ohsaki, T.; Ohgama, K.

2005-01-01

A baseline distortion effect due to gamma-flash at neutron time-of-flight measurement using a pulse neutron source has been investigated. Pulses from C 6 D 6 detectors accumulated by flash-ADC were processed with both standard analog-to-digital converter (ADC) and flash-ADC operational modes. A correction factor of gamma-ray yields, due to baseline shift, was quantitatively obtained by comparing the pulse height spectra of the two data-taking modes. The magnitude of the correction factor depends on the time after gamma-flash and has complex time dependence with a changing sign

Nonperturbative QCD corrections to electroweak observables

Energy Technology Data Exchange (ETDEWEB)

Renner, Dru B. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Feng, Xu [High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki (Japan); Jansen, Karl [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Petschlies, Marcus [The Cyprus Institute, Nicosia (Cyprus)

2012-06-15

Nonperturbative QCD corrections are important to many low-energy electroweak observables, for example the muon magnetic moment. However, hadronic corrections also play a significant role at much higher energies due to their impact on the running of standard model parameters, such as the electromagnetic coupling. Currently, these hadronic contributions are accounted for by a combination of experimental measurements, effective field theory techniques and phenomenological modeling but ideally should be calculated from first principles. Recent developments indicate that many of the most important hadronic corrections may be feasibly calculated using lattice QCD methods. To illustrate this, we examine the lattice computation of the leading-order QCD corrections to the muon magnetic moment, paying particular attention to a recently developed method but also reviewing the results from other calculations. We then continue with several examples that demonstrate the potential impact of the new approach: the leading-order corrections to the electron and tau magnetic moments, the running of the electromagnetic coupling, and a class of the next-to-leading-order corrections for the muon magnetic moment. Along the way, we mention applications to the Adler function, which can be used to determine the strong coupling constant, and QCD corrections to muonic-hydrogen.

Cognitive Distortions, Humor Styles, and Depression.

Science.gov (United States)

Rnic, Katerina; Dozois, David J A; Martin, Rod A

2016-08-01

Cognitive distortions are negative biases in thinking that are theorized to represent vulnerability factors for depression and dysphoria. Despite the emphasis placed on cognitive distortions in the context of cognitive behavioural theory and practice, a paucity of research has examined the mechanisms through which they impact depressive symptomatology. Both adaptive and maladaptive styles of humor represent coping strategies that may mediate the relation between cognitive distortions and depressive symptoms. The current study examined the correlations between the frequency and impact of cognitive distortions across both social and achievement-related contexts and types of humor. Cognitive distortions were associated with reduced use of adaptive Affiliative and Self-Enhancing humor styles and increased use of maladaptive Aggressive and Self-Defeating humor. Reduced use of Self-Enhancing humor mediated the relationship between most types of cognitive distortions and depressed mood, indicating that distorted negative thinking may interfere with an individual's ability to adopt a humorous and cheerful outlook on life (i.e., use Self-Enhancing humor) as a way of regulating emotions and coping with stress, thereby resulting in elevated depressive symptoms. Similarly, Self-Defeating humor mediated the association of the social impact of cognitive distortions with depression, such that this humor style may be used as a coping strategy for dealing with distorted thinking that ultimately backfires and results in increased dysphoria.

Distortion of magnetic field lines caused by radial displacements of ITER toroidal field coils

Energy Technology Data Exchange (ETDEWEB)

Amoskov, V.M., E-mail: sytch@niiefa.spb.su [D.V. Efremov Scientific Research Institute of Electrophysical Apparatus, St. Petersburg (Russian Federation); Gribov, Y.V. [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St Paul Lez Durance Cedex (France); Lamzin, E.A.; Sytchevsky, S.E. [D.V. Efremov Scientific Research Institute of Electrophysical Apparatus, St. Petersburg (Russian Federation)

2017-05-15

An assessment of distortions of ideal (circle) field lines caused by random radial displacements of the TF coils by |∆R| ≤ 5 mm has been performed from the statistical analysis assuming a uniform probability density function for displacements.

Distortion Control during Welding

NARCIS (Netherlands)

Akbari Pazooki, A.M.

2014-01-01

The local material expansion and contraction involved in welding result in permanent deformations or instability i.e., welding distortion. Considerable efforts have been made in controlling welding distortion prior to, during or after welding. Thermal Tensioning (TT) describes a group of in-situ

Magnetic field influences on the lateral dose response functions of photon-beam detectors: MC study of wall-less water-filled detectors with various densities.

Science.gov (United States)

Looe, Hui Khee; Delfs, Björn; Poppinga, Daniela; Harder, Dietrich; Poppe, Björn

2017-06-21

The distortion of detector reading profiles across photon beams in the presence of magnetic fields is a developing subject of clinical photon-beam dosimetry. The underlying modification by the Lorentz force of a detector's lateral dose response function-the convolution kernel transforming the true cross-beam dose profile in water into the detector reading profile-is here studied for the first time. The three basic convolution kernels, the photon fluence response function, the dose deposition kernel, and the lateral dose response function, of wall-less cylindrical detectors filled with water of low, normal and enhanced density are shown by Monte Carlo simulation to be distorted in the prevailing direction of the Lorentz force. The asymmetric shape changes of these convolution kernels in a water medium and in magnetic fields of up to 1.5 T are confined to the lower millimetre range, and they depend on the photon beam quality, the magnetic flux density and the detector's density. The impact of this distortion on detector reading profiles is demonstrated using a narrow photon beam profile. For clinical applications it appears as favourable that the magnetic flux density dependent distortion of the lateral dose response function, as far as secondary electron transport is concerned, vanishes in the case of water-equivalent detectors of normal water density. By means of secondary electron history backtracing, the spatial distribution of the photon interactions giving rise either directly to secondary electrons or to scattered photons further downstream producing secondary electrons which contribute to the detector's signal, and their lateral shift due to the Lorentz force is elucidated. Electron history backtracing also serves to illustrate the correct treatment of the influences of the Lorentz force in the EGSnrc Monte Carlo code applied in this study.

Equation-Method for correcting clipping errors in OFDM signals.

Science.gov (United States)

Bibi, Nargis; Kleerekoper, Anthony; Muhammad, Nazeer; Cheetham, Barry

2016-01-01

Orthogonal frequency division multiplexing (OFDM) is the digital modulation technique used by 4G and many other wireless communication systems. OFDM signals have significant amplitude fluctuations resulting in high peak to average power ratios which can make an OFDM transmitter susceptible to non-linear distortion produced by its high power amplifiers (HPA). A simple and popular solution to this problem is to clip the peaks before an OFDM signal is applied to the HPA but this causes in-band distortion and introduces bit-errors at the receiver. In this paper we discuss a novel technique, which we call the Equation-Method, for correcting these errors. The Equation-Method uses the Fast Fourier Transform to create a set of simultaneous equations which, when solved, return the amplitudes of the peaks before they were clipped. We show analytically and through simulations that this method can, correct all clipping errors over a wide range of clipping thresholds. We show that numerical instability can be avoided and new techniques are needed to enable the receiver to differentiate between correctly and incorrectly received frequency-domain constellation symbols.

Corrections for a constant radial magnetic field in the muon \\varvec{g}-2 and electric-dipole-moment experiments in storage rings

Science.gov (United States)

Silenko, Alexander J.

2017-10-01

We calculate the corrections for constant radial magnetic field in muon {g}-2 and electric-dipole-moment experiments in storage rings. While the correction is negligible for the current generation of {g}-2 experiments, it affects the upcoming muon electric-dipole-moment experiment at Fermilab.

The effect of band Jahn-Teller distortion on the magnetoresistivity of manganites: a model study

Energy Technology Data Exchange (ETDEWEB)

Rout, G C [Condensed Matter Physics Group, P G Department of Applied Physics and Ballistics, F M University, Balasore 756 019 (India); Panda, Saswati [Trident Academy of Technology, F2/A, Chandaka Industrial Estate, Bhubaneswar 751 024 (India); Behera, S N, E-mail: gcr@iopb.res.in, E-mail: saswatip7@gmail.com [National Institute of Science and Technology, Palur Hills, Berhampur 761 008 (India)

2011-10-05

We present a model study of magnetoresistance through the interplay of magnetisation, structural distortion and external magnetic field for the manganite systems. The manganite system is described by the Hamiltonian which consists of the s-d type double exchange interaction, Heisenberg spin-spin interaction among the core electrons, and the static and dynamic band Jahn-Teller (JT) interaction in the e{sub g} band. The relaxation time of the e{sub g} electron is found from the imaginary part of the Green's function using the total Hamiltonian consisting of the interactions due to the electron and phonon. The calculated resistivity exhibits a peak in the pure JT distorted insulating phase separating the low temperature metallic ferromagnetic phase and the high temperature paramagnetic phase. The resistivity is suppressed with the increase of the external magnetic field. The e{sub g} electron band splitting and its effect on magnetoresistivity is reported here. (paper)

Correction between B and H, and the analysis of the magnetization into uniaxial superconductor in the limit at large values of B

International Nuclear Information System (INIS)

Oliveira, I.G. de.

1994-04-01

Using the London theory, a correction is obtained between the direction of the magnetic induction B and the applied magnetic field H in superconductors with uniaxial anisotropy when the Ginsburg-Landau constant is not so large. One analysis of the magnetization as function of angle α is made. (author). 5 refs, 2 figs

Correction between B and H, and the analysis of the magnetization into uniaxial superconductor in the limit at large values of B

Energy Technology Data Exchange (ETDEWEB)

Oliveira, I.G. de

1994-04-01

Using the London theory, a correction is obtained between the direction of the magnetic induction B and the applied magnetic field H in superconductors with uniaxial anisotropy when the Ginsburg-Landau constant is not so large. One analysis of the magnetization as function of angle {alpha} is made. (author). 5 refs, 2 figs.

Consideration of possible mass and velocity corrections to magnetic cluster experiments

International Nuclear Information System (INIS)

Liu, Z.Y.; Dowben, P.A.; Popov, A.P.; Pappas, David P.

2003-01-01

Gadolinium occurs, in natural abundance, as several isotopes. The possible combinations of different gadolinium isotopes dictates that even for a fixed number of atoms in the cluster, clusters of gadolinium atoms will exhibit a range of masses. This and the expected consequence of the translation energy distributions are explored as possible corrections to Stern-Gerlach cluster beam-deflection experiments. Upon closer inspection of the experimental data, we find that the translation energy plus the vibrational temperature distribution may be inhomogeneous. This could be the origin of a long tail to high deflections in the experimental deflection profiles, at low cluster temperatures, in the magnetic cluster Stern-Gerlach experiments

Correction magnets for the Fermilab Recycler Ring

International Nuclear Information System (INIS)

James T Volk et al.

2003-01-01

In the commissioning of the Fermilab Recycler ring the need for higher order corrector magnets in the regions near beam transfers was discovered. Three types of permanent magnet skew quadrupoles, and two types of permanent magnet sextupoles were designed and built. This paper describes the need for these magnets, the design, assembly, and magnetic measurements

Variational-integral perturbation corrections of some lower excited states for hydrogen atoms in magnetic fields

International Nuclear Information System (INIS)

Yuan Lin; Zhou Ben-Hu; Zhao Yun-Hui; Xu Jun; Hai Wen-Hua

2012-01-01

A variational-integral perturbation method (VIPM) is established by combining the variational perturbation with the integral perturbation. The first-order corrected wave functions are constructed, and the second-order energy corrections for the ground state and several lower excited states are calculated by applying the VIPM to the hydrogen atom in a strong uniform magnetic field. Our calculations demonstrated that the energy calculated by the VIPM only shows a negative value, which indicates that the VIPM method is more accurate than the other methods. Our study indicated that the VIPM can not only increase the accuracy of the results but also keep the convergence of the wave functions

Frequency modulation television analysis: Distortion analysis

Science.gov (United States)

Hodge, W. H.; Wong, W. H.

1973-01-01

Computer simulation is used to calculate the time-domain waveform of standard T-pulse-and-bar test signal distorted in passing through an FM television system. The simulator includes flat or preemphasized systems and requires specification of the RF predetection filter characteristics. The predetection filters are modeled with frequency-symmetric Chebyshev (0.1-db ripple) and Butterworth filters. The computer was used to calculate distorted output signals for sixty-four different specified systems, and the output waveforms are plotted for all sixty-four. Comparison of the plotted graphs indicates that a Chebyshev predetection filter of four poles causes slightly more signal distortion than a corresponding Butterworth filter and the signal distortion increases as the number of poles increases. An increase in the peak deviation also increases signal distortion. Distortion also increases with the addition of preemphasis.

Quantum corrections to conductivity observed at intermediate magnetic fields in a high mobility GaAs/AlGaAs 2-dimensional electron gas

International Nuclear Information System (INIS)

Taboryski, R.; Veje, E.; Lindelof, P.E.

1990-01-01

Magnetoresistance with the field perpendicular to the 2-dimensional electron gas in a high mobility GaAs/AlGaAs heterostructure at low temperatures is studied. At the lowest magnetic field we observe the weak localization. At magnetic fields, where the product of the mobility and the magnetic field is of the order of unity, the quantum correction to conductivity due to the electron-electron interaction is as a source of magnetoresistance. A consistent analysis of experiments in this regime is for the first time performed. In addition to the well known electron-electron term with the expected temperature dependence, we find a new type of temperature independent quantum correction, which varies logarithmically with mobility. (orig.)

A simulation study of linear coupling effects and their correction in RHIC

International Nuclear Information System (INIS)

Parzen, G.

1992-11-01

This paper describes a possible skew quadrupole correction system for linear coupling for the RHIC92 lattice. A simulation study has been done for the correction system. Results are given for the performance of the correction system, and the required strength of the skew quadruple correctors. An important effect of linear coupling in RHIC is to shift the tune ν x ν y , sometimes called tune splitting. Most of this tune splitting can be corrected with a two family skew quadrupole correction system. For RHIC92, the same 2 family correction system will work for all likely choices of β*. This was not the case for the RHIC91 lattice where different families of correctors were needed for different β*. The tune splitting described above which is corrected with a 2 family correction system is driven primarily by the ν x - ν y harmonic of the skew quadrupole field given by the field multipole αl. There are several other effects of linear coupling present which are driven primarily by the ν x + ν y harmonics of the skew quadrupole field, αl. These include the following: (1) A higher order residual tune shift that remains after correction with the 2 family correction system. This tune shift is roughly quadratic in αl; (2) Possible large changes in the beta functions; (3) Possible increase in the beam size at injection due to the beta function distortion and the emittance distortion at injection

Volterra Filtering for ADC Error Correction

Directory of Open Access Journals (Sweden)

J. Saliga

2001-09-01

Full Text Available Dynamic non-linearity of analog-to-digital converters (ADCcontributes significantly to the distortion of digitized signals. Thispaper introduces a new effective method for compensation such adistortion based on application of Volterra filtering. Considering ana-priori error model of ADC allows finding an efficient inverseVolterra model for error correction. Efficiency of proposed method isdemonstrated on experimental results.

Effect of Phase-Encoding Reduction on Geometric Distortion and BOLD Signal Changes in fMRI

Directory of Open Access Journals (Sweden)

Golestan karami

2013-03-01

Full Text Available Introduction Echo-planar imaging (EPI is a group of fast data acquisition methods commonly used in fMRI studies. It acquires multiple image lines in k-space after a single excitation, which leads to a very short scan time. A well-known problem with EPI is that it is more sensitive to distortions due to the used encoding scheme. Source of distortion is inhomogeneity in the static B0 field that causes more geometric distortion in phase encoding direction. This inhomogeneity is induced mainly by the magnetic susceptibility differences between various structures within the object placed inside the scanner, often at air-tissue or bone-tissue interfaces. Methods of reducing EPI distortion are mainly based on decreasing steps of the phase encoding. Reducing steps of phase encoding can be applied by reducing field of view, slice thickness, and/or the use of parallel acquisition technique. Materials and Methods We obtained three data acquisitions with different FOVs including: conventional low resolution, conventional high resolution, and zoomed high resolution EPIs. Moreover we used SENSE technique for phase encoding reduction. All experiments were carried out on three Tesla scanners (Siemens, TIM, and Germany equipped with 12 channel head coil. Ten subjects participated in the experiments. Results The data were processed by FSL software and were evaluated by ANOVA. Distortion was assessed by obtaining low displacement voxels map, and calculated from a field map image. Conclusion We showed that image distortion can be reduced by decreasing slice thickness and phase encoding steps. Distortion reduction in zoomed technique resulted the lowest level, but at the cost of signal-to-noise loss. Moreover, the SENSE technique was shown to decrease the amount of image distortion, efficiently.

Magnetic resonance imaging-guided attenuation and scatter corrections in three-dimensional brain positron emission tomography

CERN Document Server

Zaidi, H; Slosman, D O

2003-01-01

Reliable attenuation correction represents an essential component of the long chain of modules required for the reconstruction of artifact-free, quantitative brain positron emission tomography (PET) images. In this work we demonstrate the proof of principle of segmented magnetic resonance imaging (MRI)-guided attenuation and scatter corrections in 3D brain PET. We have developed a method for attenuation correction based on registered T1-weighted MRI, eliminating the need of an additional transmission (TX) scan. The MR images were realigned to preliminary reconstructions of PET data using an automatic algorithm and then segmented by means of a fuzzy clustering technique which identifies tissues of significantly different density and composition. The voxels belonging to different regions were classified into air, skull, brain tissue and nasal sinuses. These voxels were then assigned theoretical tissue-dependent attenuation coefficients as reported in the ICRU 44 report followed by Gaussian smoothing and additio...

Mechanical design and construction qualification program on ITER correction coils structures

Energy Technology Data Exchange (ETDEWEB)

Foussat, A., E-mail: arnaud.foussat@iter.org [ITER Organization, Route de Vinon sur Verdon, 13115 Saint Paul Lez Durance (France); Weiyue, Wu; Jing, Wei; Shuangsong, Du [Academy of Science Institute of Plasma Physics, PO 1126, Hefei, Anhui 230031 (China); Sgobba, S. [European Center for Nuclear Research, CH-1211 Geneva 23 (Switzerland); Hongwei, Li [China International Nuclear Fusion Energy Program Execution Center, Ministry of Science and Technology, 15B Fuxing Rd., Beijing 100862 (China); Libeyre, Paul; Jong, Cornelis; Klofac, Kamil; Mitchell, Neil [ITER Organization, Route de Vinon sur Verdon, 13115 Saint Paul Lez Durance (France)

2014-04-01

The ITER Magnet system consists of 4 main coils sub-systems, i.e. 18 toroidal field coils (TFC), a central solenoid (CS), 6 poloidal field coils (PF) and 3 sets of correction coils (CC). The ITER fusion project has selected the stainless steel 316LN as main material for the magnet structure. The CC contribute to reducing the range of magnetic error fields created by imperfections in the location and geometry of the other coils used to confine, heat, and shape the plasma. During plasma operation, a large number of loading condition scenarios have been considered and structural analysis performed on key items like Cable-In-Conduit Conductor and the coil case. The results obtained are used for both static and fatigue structural assessment defining the present baseline design. For the construction of the structural cases, welding techniques such as GTAW (Gas Tungsten Arc Welding) and techniques resulting in low distortion and shrinkage like EBW (Electron Beam Welding) or Laser Beam Welding (LBW) with filler metal wire have been selected. Those methods are considered for future qualifications to guarantee proper weld parameters and specified weld properties. In order to determine the strength and fracture toughness of 316LN stainless steel welds with respect to design criteria, some mechanical tests have been carried out at 7 K (or 77 K), and room temperature.

Latency and distortion of electromagnetic trackers for augmented reality systems

CERN Document Server

Himberg, Henry

2014-01-01

Augmented reality (AR) systems are often used to superimpose virtual objects or information on a scene to improve situational awareness. Delays in the display system or inaccurate registration of objects destroy the sense of immersion a user experiences when using AR systems. AC electromagnetic trackers are ideal for these applications when combined with head orientation prediction to compensate for display system delays. Unfortunately, these trackers do not perform well in environments that contain conductive or ferrous materials due to magnetic field distortion without expensive calibration

Fen (n=1–6) clusters chemisorbed on vacancy defects in graphene: Stability, spin-dipole moment, and magnetic anisotropy

KAUST Repository

Haldar, Soumyajyoti

2014-05-09

In this work, we have studied the chemical and magnetic interactions of Fen (n=1–6) clusters with vacancy defects (monovacancy to correlated vacancies with six missing C atoms) in a graphene sheet by ab initio density functional calculations combined with Hubbard U corrections for correlated Fe-d electrons. It is found that the vacancy formation energies are lowered in the presence of Fe, indicating an easier destruction of the graphene sheet. Due to strong chemical interactions between Fe clusters and vacancies, a complex distribution of magnetic moments appear on the distorted Fe clusters which results in reduced averaged magnetic moments compared to the free clusters. In addition to that, we have calculated spin-dipole moments and magnetic anisotropy energies. The calculated spin-dipole moments arising from anisotropic spin density distributions vary between positive and negative values, yielding increased or decreased effective moments. Depending on the cluster geometry, the easy axis of magnetization of the Fe clusters shows in-plane or out-of-plane behavior.

Possible bicollinear nematic state with monoclinic lattice distortions in iron telluride compounds

Energy Technology Data Exchange (ETDEWEB)

Bishop, Christopher B. [Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Herbrych, Jacek W. [Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Dagotto, Elbio R. [Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Moreo, Adriana [Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2017-07-15

Here, iron telluride (FeTe) is known to display bicollinear magnetic order at low temperatures together with a monoclinic lattice distortion. Because the bicollinear order can involve two different wave vectors (π/2,π/2) and (π/2,–π/2), symmetry considerations allow for the possible stabilization of a nematic state with short-range bicollinear order coupled to monoclinic lattice distortions at a T_S higher than the temperature T_N where long-range bicollinear order fully develops. As a concrete example, the three-orbital spin-fermion model for iron telluride is studied with an additional coupling ˜λ₁₂ between the monoclinic lattice strain and an orbital-nematic order parameter with B_2g symmetry. Monte Carlo simulations show that with increasing ˜λ₁₂ the first-order transition characteristic of FeTe splits and bicollinear nematicity is stabilized in a (narrow) temperature range. In this new regime, the lattice is monoclinically distorted and short-range spin and orbital order breaks rotational invariance. A discussion of possible realizations of this exotic state is provided.

Magnetic resonance imaging-guided attenuation correction of positron emission tomography data in PET/MRI

Science.gov (United States)

Izquierdo-Garcia, David; Catana, Ciprian

2018-01-01

Synopsis Attenuation correction (AC) is one of the most important challenges in the recently introduced combined positron emission tomography/magnetic resonance imaging (PET/MR) scanners. PET/MR AC (MR-AC) approaches aim to develop methods that allow accurate estimation of the linear attenuation coefficients (LACs) of the tissues and other components located in the PET field of view (FoV). MR-AC methods can be divided into three main categories: segmentation-, atlas- and PET-based. This review aims to provide a comprehensive list of the state of the art MR-AC approaches as well as their pros and cons. The main sources of artifacts such as body-truncation, metallic implants and hardware correction will be presented. Finally, this review will discuss the current status of MR-AC approaches for clinical applications. PMID:26952727

The reliability of identifying the Omega sign using axial T2-weighted magnetic resonance imaging.

Science.gov (United States)

Zakaria, Hesham Mostafa; Massa, Peter Joseph; Smith, Richard L; Moharram, Tarek Hazem; Corrigan, John; Lee, Ian; Schultz, Lonni; Hu, Jianhui; Patel, Suresh; Griffith, Brent

2018-01-01

Preoperative identification of the eloquent brain is important for neurosurgical planning. One common method of finding the motor cortex is by localizing "the Omega sign." No studies have tested the reliability of imaging to identify the Omega sign. We identified 40 recent and consecutive patients who had undergone preoperative functional magnetic resonance imaging for identification of the hand motor area prior to tumor resection. We recruited 11 neurosurgical residents of various levels of training and one board-certified neurosurgeon to identify the hand motor cortex Omega. Testees were given axial images of T2-weighted MRI and placed marks where they expected to find the Omega. Two board-certified radiologists graded and quantified the localization attempts. Inter-rater reliability was assessed using the kappa statistic, and Rao-Scott chi-square tests were used to examine the relationship between clinical factors and testees' experience with correct identification of the Omega sign. The overall correct identification rate was 69.9% (95% CI = 63.4-75.7), ranging from 36.6% to 92.7% among all raters for the tumor side and from 46.2% to 97.4% for the non-tumor side. Anatomic distortion greatly affected correct identification ( p Omega than junior residents ( p Omega sign is poor, with a Fleiss kappa of 0.23. We concluded that correct identification of the Omega sign is affected by tumor distortion and experience but overall is not reliable. This underscores the limitations of anatomic landmarks and the importance of utilizing multiple scanning planes and preoperative fMRI for appropriate localization.

Guessing and compression subject to distortion

OpenAIRE

Hanawal, Manjesh Kumar; Sundaresan, Rajesh

2010-01-01

The problem of guessing a random string is revisited. The relation-ship between guessing without distortion and compression is extended to the case when source alphabet size is countably in¯nite. Further, similar relationship is established for the case when distortion allowed by establishing a tight relationship between rate distortion codes and guessing strategies.

An Improved Distortion Operator for Insurance Risks

Institute of Scientific and Technical Information of China (English)

GAO Jian-wei; QIU Wan-hua

2002-01-01

This paper reviews the distortion function approach developed in the actuarial literature for insurance risks. The main aim of this paper is to derive an extensive distortion operator, and to propose a new premium principle based on this extensive distortion operator. Furthermore, the non-robustness of general distortion operator is also discussed. Examples are provided using Bernoulli, Pareto, Lognormal and Gamma distribution assumptions.

Numerical Study of Electrostatic Field Distortion on LPTPC End-Plates based on Bulk Micromegas Modules

Directory of Open Access Journals (Sweden)

Bhattacharya Purba

2018-01-01

Full Text Available The R&D activities for the linear collider TPC (LC-TPC are currently working on the adoption of the micro pattern devices for the gaseous amplification stage. Several beam tests have been carried out at DESY with a 5 GeV electron beam in a 1 T superconducting magnet. We worked on a large prototype TPC with an end-plate that was built, for the first time, using seven resistive bulk Micromegas modules. During experiments, reduced signal sensitivity was observed at the boundary of these modules. Electrostatic field distortion near the module boundaries was considered to be the possible major reason behind these observations. In the present work, we will explore this hypothesis through numerical simulation. Our aim has been to understand the origin of distortions observed close to the edges of the test beam modules and to explore the possibility of using the Garfield simulation framework for investigating a phenomenon as complex as distortion.

Magnetic resonance imaging-guided attenuation correction of positron emission tomography data in PET/MRI

OpenAIRE

Izquierdo-Garcia, David; Catana, Ciprian

2016-01-01

Attenuation correction (AC) is one of the most important challenges in the recently introduced combined positron emission tomography/magnetic resonance imaging (PET/MR) scanners. PET/MR AC (MR-AC) approaches aim to develop methods that allow accurate estimation of the linear attenuation coefficients (LACs) of the tissues and other components located in the PET field of view (FoV). MR-AC methods can be divided into three main categories: segmentation-, atlas- and PET-based. This review aims to...

Isotropic resolution diffusion tensor imaging of lumbosacral and sciatic nerves using a phase-corrected diffusion-prepared 3D turbo spin echo.

Science.gov (United States)

Cervantes, Barbara; Van, Anh T; Weidlich, Dominik; Kooijman, Hendrick; Hock, Andreas; Rummeny, Ernst J; Gersing, Alexandra; Kirschke, Jan S; Karampinos, Dimitrios C

2018-08-01

To perform in vivo isotropic-resolution diffusion tensor imaging (DTI) of lumbosacral and sciatic nerves with a phase-navigated diffusion-prepared (DP) 3D turbo spin echo (TSE) acquisition and modified reconstruction incorporating intershot phase-error correction and to investigate the improvement on image quality and diffusion quantification with the proposed phase correction. Phase-navigated DP 3D TSE included magnitude stabilizers to minimize motion and eddy-current effects on the signal magnitude. Phase navigation of motion-induced phase errors was introduced before readout in 3D TSE. DTI of lower back nerves was performed in vivo using 3D TSE and single-shot echo planar imaging (ss-EPI) in 13 subjects. Diffusion data were phase-corrected per k z plane with respect to T 2 -weighted data. The effects of motion-induced phase errors on DTI quantification was assessed for 3D TSE and compared with ss-EPI. Non-phase-corrected 3D TSE resulted in artifacts in diffusion-weighted images and overestimated DTI parameters in the sciatic nerve (mean diffusivity [MD] = 2.06 ± 0.45). Phase correction of 3D TSE DTI data resulted in reductions in all DTI parameters (MD = 1.73 ± 0.26) of statistical significance (P ≤ 0.001) and in closer agreement with ss-EPI DTI parameters (MD = 1.62 ± 0.21). DP 3D TSE with phase correction allows distortion-free isotropic diffusion imaging of lower back nerves with robustness to motion-induced artifacts and DTI quantification errors. Magn Reson Med 80:609-618, 2018. © 2018 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. © 2018 The Authors Magnetic Resonance

Volterra Series Based Distortion Effect

DEFF Research Database (Denmark)

Agerkvist, Finn T.

2010-01-01

A large part of the characteristic sound of the electric guitar comes from nonlinearities in the signal path. Such nonlinearities may come from the input- or output-stage of the amplier, which is often equipped with vacuum tubes or a dedicated distortion pedal. In this paper the Volterra series...... expansion for non linear systems is investigated with respect to generating good distortion. The Volterra series allows for unlimited adjustment of the level and frequency dependency of each distortion component. Subjectively relevant ways of linking the dierent orders are discussed....

Orbit and optics distortion in fixed field alternating gradient muon accelerators

Directory of Open Access Journals (Sweden)

Shinji Machida

2007-11-01

Full Text Available In a linear nonscaling fixed field alternating gradient (FFAG accelerator, betatron tunes vary over a wide range and a beam has to cross integer and half-integer tunes several times. Although it is plausible to say that integer and half-integer resonances are not harmful if the crossing speed is fast, no quantitative argument exists. With tracking simulation, we studied orbit and optics distortion due to alignment and magnet errors. It was found that the concept of integer and half-integer resonance crossing is irrelevant to explain beam behavior in a nonscaling FFAG when acceleration is fast and betatron tunes change quickly. In a muon FFAG accelerator, it takes 17 turns for acceleration and the betatron tunes change more than 10, for example. Instead, the orbit and optics distortion is excited by random dipole and quadrupole kicks. The latter causes beam size growth because the beam starts tumbling in phase space, but not necessarily with emittance growth.

An X-ray wave theory for heavily distorted crystals. 1

International Nuclear Information System (INIS)

Ohkawa, T.; Hashimoto, H.

1985-01-01

An X-ray diffraction theory is developed of monochromatic waves having spherical wave front, which is applicable to an interpretation of divergent X-ray diffraction images of crystals containing arbitral types of strain field. The theory is divided into two parts. In part I, Takagi's theory is expanded by introducing amplitude and phase correction functions and a new improved representation for the X-ray diffraction theory is given. In part II dispersion surfaces in heavily distorted crystals are discussed, and in the discussion the resonance shift functions are introduced. These formulations can lead to a complete understanding of the extinction phenomena. (author)

[Application of an Adaptive Inertia Weight Particle Swarm Algorithm in the Magnetic Resonance Bias Field Correction].

Science.gov (United States)

Wang, Chang; Qin, Xin; Liu, Yan; Zhang, Wenchao

2016-06-01

An adaptive inertia weight particle swarm algorithm is proposed in this study to solve the local optimal problem with the method of traditional particle swarm optimization in the process of estimating magnetic resonance(MR)image bias field.An indicator measuring the degree of premature convergence was designed for the defect of traditional particle swarm optimization algorithm.The inertia weight was adjusted adaptively based on this indicator to ensure particle swarm to be optimized globally and to avoid it from falling into local optimum.The Legendre polynomial was used to fit bias field,the polynomial parameters were optimized globally,and finally the bias field was estimated and corrected.Compared to those with the improved entropy minimum algorithm,the entropy of corrected image was smaller and the estimated bias field was more accurate in this study.Then the corrected image was segmented and the segmentation accuracy obtained in this research was 10% higher than that with improved entropy minimum algorithm.This algorithm can be applied to the correction of MR image bias field.

Spectral Distortion in Lossy Compression of Hyperspectral Data

Directory of Open Access Journals (Sweden)

Bruno Aiazzi

2012-01-01

Full Text Available Distortion allocation varying with wavelength in lossy compression of hyperspectral imagery is investigated, with the aim of minimizing the spectral distortion between original and decompressed data. The absolute angular error, or spectral angle mapper (SAM, is used to quantify spectral distortion, while radiometric distortions are measured by maximum absolute deviation (MAD for near-lossless methods, for example, differential pulse code modulation (DPCM, or mean-squared error (MSE for lossy methods, for example, spectral decorrelation followed by JPEG 2000. Two strategies of interband distortion allocation are compared: given a target average bit rate, distortion may be set to be constant with wavelength. Otherwise, it may be allocated proportionally to the noise level of each band, according to the virtually lossless protocol. Comparisons with the uncompressed originals show that the average SAM of radiance spectra is minimized by constant distortion allocation to radiance data. However, variable distortion allocation according to the virtually lossless protocol yields significantly lower SAM in case of reflectance spectra obtained from compressed radiance data, if compared with the constant distortion allocation at the same compression ratio.

Profile distortion by beam space-charge in Ionization Profile Monitors

CERN Document Server

Vilsmeier, D; Wettig, T

Measuring the transverse beam size in the Large Hadron Collider by using Ionization Profile Monitors is a difficult task for energies above injection during the energy ramp from 450 GeV to 6.5TeV. The beam size decreases from around 1mm to 200um and the brightness of the beam is high enough to destroy the structure of any form of interacting matter. While the electron trajectories are confined by an external electro-magnetic field which forces the electrons accordingly on helix paths with certain gyroradii, this gyration is heavily increased under the influence of the electric field of the beam. Smaller beam sizes, which go hand in hand with increased bunch electric fields, lead to larger gyroradii of the ionized electrons, which results in strongly distorted profiles. In addition, this distortion becomes more visible for smaller beam sizes as the extent of gyration grows compared to the actual beam size. Depending on the initial momentum distribution of the electrons, emerging from the ionization process wit...

Structural distortion and electronic properties of NiO under high pressure: an ab initio GGA+U study

International Nuclear Information System (INIS)

Zhang Weibing; Hu Yulin; Han Keli; Tang Biyu

2006-01-01

The structural distortion and electronic properties of NiO under high pressure are investigated by means of first-principles calculations within the density functional theory (DFT) in the generalized gradient approximation (GGA). The strong electronic correlations are also taken into account in the form of GGA+U. Recent experiments implied that previous local density approximation (LDA) calculations incorrectly predicted structural distortion under high pressure, especially above 60 GPa. The present results show that even GGA calculations do not give a proper description of structural distortion under high pressure, although much improved structural and bulk properties are obtained. When strong correlations are included, overall agreement of the structural distortions of NiO under high pressure is obtained. The lattice constants a and c as well as the axial ratio c/a are in good agreement with experiment over the entire experimental pressure range. The successful prediction of the structural distortion of GGA+U can be attributed to the reasonable description of nearest-neighbour magnetic exchange interactions. In addition, we also analyse the density of states under different pressures. Present results indicate that, with increasing pressure, the bandwidth increases and the bandgap transits from being a mixture of charge-transfer and Mott-Hubbard type towards solely Mott-Hubbard type

Magnetoelastic couplings in the distorted diamond-chain compound azurite

Science.gov (United States)

Cong, Pham Thanh; Wolf, Bernd; Manna, Rudra Sekhar; Tutsch, Ulrich; de Souza, Mariano; Brühl, Andreas; Lang, Michael

2014-05-01

We present results of ultrasonic measurements on a single crystal of the distorted diamond-chain compound azurite Cu3(CO3)2(OH)2. Pronounced elastic anomalies are observed in the temperature dependence of the longitudinal elastic mode c22 which can be assigned to the relevant magnetic interactions in the system and their couplings to the lattice degrees of freedom. From a semiquantitative analysis of the magnetic contribution to c22 the magnetoelastic coupling G =∂J2/∂ɛb can be estimated, where J2 is the intradimer coupling constant and ɛb the strain along the intrachain b axis. We find an exceptionally large coupling constant of |G |˜ 3650 K highlighting an extraordinarily strong sensitivity of J2 against changes of the b-axis lattice parameter. These results are complemented by measurements of the hydrostatic pressure dependence of J2 by means of thermal expansion and magnetic susceptibility measurements performed both at ambient and finite hydrostatic pressure. We propose that a structural peculiarity of this compound, in which Cu2O6 dimer units are incorporated in an unusually stretched manner, is responsible for the anomalously large magnetoelastic coupling.

Twisted molecular magnets

DEFF Research Database (Denmark)

Inglis, Ross; Milios, Constantinos J.; Jones, Leigh F.

2012-01-01

The use of derivatised salicylaldoximes in manganese chemistry has led to the synthesis of a family of approximately fifty hexanuclear ([Mn(III)(6)]) and thirty trinuclear ([Mn(III)(3)]) Single-Molecule Magnets (SMMs). Deliberate, targeted structural distortion of the metallic core afforded family...

Rigidity spectrum of Forbush decrease calculated by neutron monitors data corrected and uncorrected for geomagnetic disturbances

International Nuclear Information System (INIS)

Alania, M V; Wawrzynczak, A; Sdobnov, V E; Kravtsova, M V

2013-01-01

Forbush decreases (Fd) of the galactic cosmic ray (GCR) intensity and geomagnetic storms are observed almost at the same time. Geomagnetic storm is a reason of significant disturbances of the magnetic cut off rigidity causing the distortion of the time profile of the Fd of the GCR intensity. We show some differences in the temporal changes of the rigidity spectra of Fd calculated by neutron monitors experimental data corrected and uncorrected for the changes of the geomagnetic cut off rigidity. Nevertheless, the general features of the temporal changes of the rigidity spectrum of Fd maintain as it was found in our previous investigations. Namely, at the beginning phase of Fd rigidity spectrum is relatively soft and gradually becomes hard up to reaching the minimum level of the GCR intensity; then the rigidity spectrum gradually becomes soft during the recovery phase of Fd. We also confirm that for the established temporal profiles of the rigidity spectrum of Fd a structural changes of the interplanetary magnetic field turbulence in the range of frequencies, 10 −-6 ÷10 −-5 Hz are responsible.

Relativistic correction to the deuteron magnetic moment and angular condition

International Nuclear Information System (INIS)

Kondratyuk, L.A.; Strikman, M.I.

1983-01-01

The relativistic correction (RC) to the deuteron magnetic moment μsub(d) is investigated using the light-cone dynamics. The restrictions imposed by the angular condition on the electromagnetic current operator of deuteron are discussed in detail. It is shown that the additive model for the current operator of interacting consistuencies is consistent with the angular condition only for the two first terms of expansion of the ''good'' electromagnetic current component jsub(+) in powers of the momentum transfer q. The RC into μsub(d) is calculated using the mattix element of the ''good'' component. The account of RC decreases essentially the discrepancy between the theoretical and experimental values. The value of Δsub(μ) is determined for the Hamada-Johnston potential hard core potential (0.93x10 -2 ) for the Reid soft core potential (0.71x10 -2 ) and for the Paris potential (0.63x10 -2 )

Distortions in Judged Spatial Relations.

Science.gov (United States)

Stevens, Albert

1978-01-01

Distortions in judgments of relative geographical relations were observed, particularly when the locations were in different geographical or political units. Subjects distorted the judged relation to conform with the relation of the superordinate political unit. A model for the hierachical storage of spatial information is presented. (Author/RD)

Pile-up correction by Genetic Algorithm and Artificial Neural Network

Science.gov (United States)

Kafaee, M.; Saramad, S.

2009-08-01

Pile-up distortion is a common problem for high counting rates radiation spectroscopy in many fields such as industrial, nuclear and medical applications. It is possible to reduce pulse pile-up using hardware-based pile-up rejections. However, this phenomenon may not be eliminated completely by this approach and the spectrum distortion caused by pile-up rejection can be increased as well. In addition, inaccurate correction or rejection of pile-up artifacts in applications such as energy dispersive X-ray (EDX) spectrometers can lead to losses of counts, will give poor quantitative results and even false element identification. Therefore, it is highly desirable to use software-based models to predict and correct any recognized pile-up signals in data acquisition systems. The present paper describes two new intelligent approaches for pile-up correction; the Genetic Algorithm (GA) and Artificial Neural Networks (ANNs). The validation and testing results of these new methods have been compared, which shows excellent agreement with the measured data with 60Co source and NaI detector. The Monte Carlo simulation of these new intelligent algorithms also shows their advantages over hardware-based pulse pile-up rejection methods.

INTERSTELLAR MAGNETIC FIELD SURROUNDING THE HELIOPAUSE

International Nuclear Information System (INIS)

Whang, Y. C.

2010-01-01

This paper presents a three-dimensional analytical solution, in the limit of very low plasma β-ratio, for the distortion of the interstellar magnetic field surrounding the heliopause. The solution is obtained using a line dipole method that is the integration of point dipole along a semi-infinite line; it represents the magnetic field caused by the presence of the heliopause. The solution allows the variation of the undisturbed magnetic field at any inclination angle. The heliosphere is considered as having blunt-nosed geometry on the upwind side and it asymptotically approaches a cylindrical geometry having an open exit for the continuous outflow of the solar wind on the downwind side. The heliopause is treated as a magnetohydrodynamic tangential discontinuity; the interstellar magnetic field lines at the boundary are tangential to the heliopause. The interstellar magnetic field is substantially distorted due to the presence of the heliopause. The solution shows the draping of the field lines around the heliopause. The magnetic field strength varies substantially near the surface of the heliopause. The effect on the magnetic field due to the presence of the heliopause penetrates very deep into the interstellar space; the depth of penetration is of the same order of magnitude as the scale length of the heliosphere.

Correction of echo shift in reconstruction processing for ultra-short TE pulse sequence

International Nuclear Information System (INIS)

Takizawa, Masahiro; Ootsuka, Takehiro; Abe, Takayuki; Takahashi, Tetsuhiko

2010-01-01

An ultra-short echo time (TE) pulse sequence is composed of a radial sampling that acquires echo signals radially in the K-space and a half-echo acquisition that acquires only half of the echo signal. The shift in the position of the echo signal (echo shift) caused by the timing errors in the gradient magnetic field pulses affects the image quality in the radial sampling with the half-echo acquisition. To improve image quality, we have developed a signal correction algorithm that detects and eliminates this echo shift during reconstruction by performing a pre-scan within 10 seconds. The results showed that image quality is improved under oblique and/or off-centering conditions that frequently cause image distortion due to hardware error. In conclusion, we have developed a robust ultra-short TE pulse sequence that allows wide latitude in the scan parameters, including oblique and off-centering conditions. (author)

Alternating-gradient canted cosine theta superconducting magnets for future compact proton gantries

Directory of Open Access Journals (Sweden)

Weishi Wan

2015-10-01

Full Text Available We present a design of superconducting magnets, optimized for application in a gantry for proton therapy. We have introduced a new magnet design concept, called an alternating-gradient canted cosine theta (AG-CCT concept, which is compatible with an achromatic layout. This layout allows a large momentum acceptance. The 15 cm radius of the bore aperture enables the application of pencil beam scanning in front of the SC-magnet. The optical and dynamic performance of a gantry based on these magnets has been analyzed using the fields derived (via Biot-Savart law from the actual windings of the AG-CCT combined with the full equations of motion. The results show that with appropriate higher order correction, a large 3D volume can be rapidly scanned with little beam shape distortion. A very big advantage is that all this can be done while keeping the AG-CCT fields fixed. This reduces the need for fast field ramping of the superconducting magnets between the successive beam energies used for the scanning in depth and it is important for medical application since this reduces the technical risk (e.g., a quench associated with fast field changes in superconducting magnets. For proton gantries the corresponding superconducting magnet system holds promise of dramatic reduction in weight. For heavier ion gantries there may furthermore be a significant reduction in size.

JET ENGINE INLET DISTORTION SCREEN AND DESCRIPTOR EVALUATION

Directory of Open Access Journals (Sweden)

Jiří Pečinka

2017-02-01

Full Text Available Total pressure distortion is one of the three basic flow distortions (total pressure, total temperature and swirl distortion that might appear at the inlet of a gas turbine engine (GTE during operation. Different numerical parameters are used for assessing the total pressure distortion intensity and extent. These summary descriptors are based on the distribution of total pressure in the aerodynamic interface plane. There are two descriptors largely spread around the world, however, three or four others are still in use and can be found in current references. The staff at the University of Defence decided to compare the most common descriptors using basic flow distortion patterns in order to select the most appropriate descriptor for future department research. The most common descriptors were identified based on their prevalence in widely accessible publications. The construction and use of these descriptors are reviewed in the paper. Subsequently, they are applied to radial, angular, and combined distortion patterns of different intensities and with varied mass flow rates. The tests were performed on a specially designed test bench using an electrically driven standalone industrial centrifugal compressor, sucking air through the inlet of a TJ100 small turbojet engine. Distortion screens were placed into the inlet channel to create the desired total pressure distortions. Of the three basic distortions, only the total pressure distortion descriptors were evaluated. However, both total and static pressures were collected using a multi probe rotational measurement system.

Distortional Modes of Thin-Walled Beams

DEFF Research Database (Denmark)

Jönsson, Jeppe; Andreassen, Michael Joachim

2009-01-01

The classic thin-walled beam theory for open and closed cross-sections can be generalized by including distortional displacement modes. The introduction of additional displacement modes leads to coupled differential equations, which seems to have prohibited the use of exact shape functions...... in the modelling of coupled torsion and distortion. However, if the distortional displacement modes are chosen as those which decouple the differential equations as in non proportionally damped modal dynamic analysis then it may be possible to use exact shape functions and perform analysis on a reduced problem....... In the recently developed generalized beam theory (GBT) the natural distortional displacement modes are determined on the basis of a quadratic eigenvalue problem. However, as in linear modal dynamic analysis of proportionally damped structures this problem has been solved approximately using linear eigenvalue...

Removing Distortion of Periapical Radiographs in Dental Digital Radiography Using Embedded Markers in an External frame.

Science.gov (United States)

Kafieh, Rahele; Shahamoradi, Mahdi; Hekmatian, Ehsan; Foroohandeh, Mehrdad; Emamidoost, Mostafa

2012-10-01

To carry out in vivo and in vitro comparative pilot study to evaluate the preciseness of a newly proposed digital dental radiography setup. This setup was based on markers placed on an external frame to eliminate the measurement errors due to incorrect geometry in relative positioning of cone, teeth and the sensor. Five patients with previous panoramic images were selected to undergo the proposed periapical digital imaging for in vivo phase. For in vitro phase, 40 extracted teeth were replanted in dry mandibular sockets and periapical digital images were prepared. The standard reference for real scales of the teeth were obtained through extracted teeth measurements for in vitro application and were calculated through panoramic imaging for in vivo phases. The proposed image processing thechnique was applied on periapical digital images to distinguish the incorrect geometry. The recognized error was inversely applied on the image and the modified images were compared to the correct values. The measurement findings after the distortion removal were compared to our gold standards (results of panoramic imaging or measurements from extracted teeth) and showed the accuracy of 96.45% through in vivo examinations and 96.0% through in vitro tests. The proposed distortion removal method is perfectly able to identify the possible inaccurate geometry during image acquisition and is capable of applying the inverse transform to the distorted radiograph to obtain the correctly modified image. This can be really helpful in applications like root canal therapy, implant surgical procedures and digital subtraction radiography, which are essentially dependent on precise measurements.

Virtual phantom magnetic resonance imaging (ViP MRI) on a clinical MRI platform.

Science.gov (United States)

Saint-Jalmes, Hervé; Bordelois, Alejandro; Gambarota, Giulio

2018-01-01

The purpose of this study was to implement Virtual Phantom Magnetic Resonance Imaging (ViP MRI), a technique that allows for generating reference signals in MR images using radiofrequency (RF) signals, on a clinical MR system and to test newly designed virtual phantoms. MRI experiments were conducted on a 1.5 T MRI scanner. Electromagnetic modelling of the ViP system was done using the principle of reciprocity. The ViP RF signals were generated using a compact waveform generator (dimensions of 26 cm × 18 cm × 16 cm), connected to a homebuilt 25 mm-diameter RF coil. The ViP RF signals were transmitted to the MRI scanner bore, simultaneously with the acquisition of the signal from the object of interest. Different types of MRI data acquisition (2D and 3D gradient-echo) as well as different phantoms, including the Shepp-Logan phantom, were tested. Furthermore, a uniquely designed virtual phantom - in the shape of a grid - was generated; this newly proposed phantom allows for the investigations of the vendor distortion correction field. High quality MR images of virtual phantoms were obtained. An excellent agreement was found between the experimental data and the inverse cube law, which was the expected functional dependence obtained from the electromagnetic modelling of the ViP system. Short-term time stability measurements yielded a coefficient of variation in the signal intensity over time equal to 0.23% and 0.13% for virtual and physical phantom, respectively. MR images of the virtual grid-shaped phantom were reconstructed with the vendor distortion correction; this allowed for a direct visualization of the vendor distortion correction field. Furthermore, as expected from the electromagnetic modelling of the ViP system, a very compact coil (diameter ~ cm) and very small currents (intensity ~ mA) were sufficient to generate a signal comparable to that of physical phantoms in MRI experiments. The ViP MRI technique was successfully implemented on a clinical MR

Growth rate of matter perturbations as a probe of large-scale magnetism

CERN Document Server

Giovannini, Massimo

2011-01-01

The growth rate of matter perturbations is computed in a magnetized environment for the LambdaCDM and wCDM paradigms. It is argued that the baryons do not necessarily follow into the dark matter potential wells after they are released from the drag of the photons. The baryonic evolution equations inherit a forcing term whose explicit form depends on the plasma description and can be deduced, for instance, in the resistive magnetohydrodynamical approximation. After deriving an analytical expression for the growth rate applicable when dark energy does not cluster, the effects of relativistic corrections and of the inhomogeneities associated with the other species of the plasma are taken into account numerically. The spectral amplitudes and slopes of the stochastic magnetic background are selected to avoid appreciable distortions in the measured temperature and polarization anisotropies of the Cosmic Microwave Background. The growth of structures in the current paradigms of structure formation represents a compl...

The clinical utility of reduced-distortion readout-segmented echo-planar imaging in the head and neck region: initial experience

Energy Technology Data Exchange (ETDEWEB)

Koyasu, Sho; Iima, Mami; Umeoka, Shigeaki; Morisawa, Nobuko; Togashi, Kaori [Kyoto University, Department of Diagnostic Imaging and Nuclear Medicine, Graduate School of Medicine, Sakyo-Ku, Kyoto (Japan); Porter, David A. [Siemens AG, MED MR PLM AW Neurology, Allee am Roethelheimpark 2, Erlangen (Germany); Ito, Juichi [Kyoto University, Department of Otolaryngology, Head and Neck Surgery, Graduate School of Medicine, Sakyo-Ku, Kyoto (Japan); Le Bihan, Denis [Kyoto University, Human Brain Research Center, Graduate School of Medicine, Sakyo-Ku, Kyoto (Japan); Neurospin, CEA-Saclay Center, Gif-sur-Yvette Cedex (France)

2014-12-15

To evaluate whether readout-segmented echo-planar imaging (RS-EPI) diffusion weighted image (DWI) can diminish image distortion in the head and neck area, compared with single-shot (SS)-EPI DWI. We conducted phantom and patient studies using 3 T magnetic resonance imaging (MRI) with a 16-channel coil. For the phantom study, we evaluated distortion and signal homogeneity in gel phantoms. For the patient study, 29 consecutive patients with clinically suspicious parotid lesions were prospectively enrolled. RS-EPI and SS-EPI DWI were evaluated by two independent readers for identification of organ/lesion and distortion, using semiquantitative scales and quantitative scores. Apparent diffusion coefficient (ADC) values and contrast-noise ratios of parotid tumours (if present; n = 15) were also compared. The phantom experiments showed that RS-EPI provided less distorted and more homogeneous ADC maps than SS-EPI. In the patient study, RS-EPI was found to provide significantly less distortion in almost all organs/lesions (p < 0.05), according to both semiquantitative scales and quantitative scores. There was no significant difference in ADC values and contrast-noise ratios between the two DWI techniques. The distortion in DWI was significantly reduced with RS-EPI in both phantom and patient studies. The RS-EPI technique provided more homogenous images than SS-EPI, and can potentially offer higher image quality in the head and neck area. (orig.)

Photoacoustic signal and noise analysis for Si thin plate: signal correction in frequency domain.

Science.gov (United States)

Markushev, D D; Rabasović, M D; Todorović, D M; Galović, S; Bialkowski, S E

2015-03-01

Methods for photoacoustic signal measurement, rectification, and analysis for 85 μm thin Si samples in the 20-20 000 Hz modulation frequency range are presented. Methods for frequency-dependent amplitude and phase signal rectification in the presence of coherent and incoherent noise as well as distortion due to microphone characteristics are presented. Signal correction is accomplished using inverse system response functions deduced by comparing real to ideal signals for a sample with well-known bulk parameters and dimensions. The system response is a piece-wise construction, each component being due to a particular effect of the measurement system. Heat transfer and elastic effects are modeled using standard Rosencweig-Gersho and elastic-bending theories. Thermal diffusion, thermoelastic, and plasmaelastic signal components are calculated and compared to measurements. The differences between theory and experiment are used to detect and correct signal distortion and to determine detector and sound-card characteristics. Corrected signal analysis is found to faithfully reflect known sample parameters.

Detection of chromatic and luminance distortions in natural scenes.

Science.gov (United States)

Jennings, Ben J; Wang, Karen; Menzies, Samantha; Kingdom, Frederick A A

2015-09-01

A number of studies have measured visual thresholds for detecting spatial distortions applied to images of natural scenes. In one study, Bex [J. Vis.10(2), 1 (2010)10.1167/10.2.231534-7362] measured sensitivity to sinusoidal spatial modulations of image scale. Here, we measure sensitivity to sinusoidal scale distortions applied to the chromatic, luminance, or both layers of natural scene images. We first established that sensitivity does not depend on whether the undistorted comparison image was of the same or of a different scene. Next, we found that, when the luminance but not chromatic layer was distorted, performance was the same regardless of whether the chromatic layer was present, absent, or phase-scrambled; in other words, the chromatic layer, in whatever form, did not affect sensitivity to the luminance layer distortion. However, when the chromatic layer was distorted, sensitivity was higher when the luminance layer was intact compared to when absent or phase-scrambled. These detection threshold results complement the appearance of periodic distortions of the image scale: when the luminance layer is distorted visibly, the scene appears distorted, but when the chromatic layer is distorted visibly, there is little apparent scene distortion. We conclude that (a) observers have a built-in sense of how a normal image of a natural scene should appear, and (b) the detection of distortion in, as well as the apparent distortion of, natural scene images is mediated predominantly by the luminance layer and not chromatic layer.

Prediction of transmission distortion for wireless video communication: analysis.

Science.gov (United States)

Chen, Zhifeng; Wu, Dapeng

2012-03-01

Transmitting video over wireless is a challenging problem since video may be seriously distorted due to packet errors caused by wireless channels. The capability of predicting transmission distortion (i.e., video distortion caused by packet errors) can assist in designing video encoding and transmission schemes that achieve maximum video quality or minimum end-to-end video distortion. This paper is aimed at deriving formulas for predicting transmission distortion. The contribution of this paper is twofold. First, we identify the governing law that describes how the transmission distortion process evolves over time and analytically derive the transmission distortion formula as a closed-form function of video frame statistics, channel error statistics, and system parameters. Second, we identify, for the first time, two important properties of transmission distortion. The first property is that the clipping noise, which is produced by nonlinear clipping, causes decay of propagated error. The second property is that the correlation between motion-vector concealment error and propagated error is negative and has dominant impact on transmission distortion, compared with other correlations. Due to these two properties and elegant error/distortion decomposition, our formula provides not only more accurate prediction but also lower complexity than the existing methods.

A ferrofluid based artificial tactile sensor with magnetic field control

Energy Technology Data Exchange (ETDEWEB)

Volkova, T.I., E-mail: tatiana.volkova@tu-ilmenau.de [Technical Mechanics Group, Faculty of Mechanical Engineering, Technische Universität Ilmenau, Ilmenau D-98684 (Germany); Böhm, V., E-mail: valter.boehm@tu-ilmenau.de [Technical Mechanics Group, Faculty of Mechanical Engineering, Technische Universität Ilmenau, Ilmenau D-98684 (Germany); Naletova, V.A., E-mail: naletova@imec.msu.ru [Faculty of Mechanics and Mathematics, Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Kaufhold, T., E-mail: tobias.kaufhold@tu-ilmenau.de [Technical Mechanics Group, Faculty of Mechanical Engineering, Technische Universität Ilmenau, Ilmenau D-98684 (Germany); Becker, F., E-mail: felix.becker@tu-ilmenau.de [Technical Mechanics Group, Faculty of Mechanical Engineering, Technische Universität Ilmenau, Ilmenau D-98684 (Germany); Zeidis, I., E-mail: igor.zeidis@tu-ilmenau.de [Technical Mechanics Group, Faculty of Mechanical Engineering, Technische Universität Ilmenau, Ilmenau D-98684 (Germany); Zimmermann, K., E-mail: klaus.zimmermann@tu-ilmenau.de [Technical Mechanics Group, Faculty of Mechanical Engineering, Technische Universität Ilmenau, Ilmenau D-98684 (Germany)

2017-06-01

The paper deals with a tactile sensor inspired by biological hairs of mammals. The working principle is based on the effect of the magnetic force exerted on a paramagnetic body submerged into a ferrofluid volume under the influence of a nonuniform magnetic field. The deflection of the sensor's rod caused by external mechanical stimuli may be unambiguously identified by the distortion of the magnetic field, which occurs due to the motion of the attached body in the ferrofluid. The magnetic force acting on the body is evaluated experimentally and theoretically for the nonuniform magnetic field of a permanent magnet. The controlled oscillations of the rod are realised by applying a nonuniform magnetic field of periodically altering direction. - Highlights: • A design approach of a tactile sensor inspired by special mammalian hairs is presented. • The working principle is based on magnetic properties of a ferrofluid in magnetic fields. • The magnetic force acting on a body submerged into a ferrofluid volume is evaluated. • External mechanical stimuli may be identified by the distortion of the magnetic field. • The controlled whisking-like oscillations of the sensor's rod are realised experimentally.

A ferrofluid based artificial tactile sensor with magnetic field control

International Nuclear Information System (INIS)

Volkova, T.I.; Böhm, V.; Naletova, V.A.; Kaufhold, T.; Becker, F.; Zeidis, I.; Zimmermann, K.

2017-01-01

The paper deals with a tactile sensor inspired by biological hairs of mammals. The working principle is based on the effect of the magnetic force exerted on a paramagnetic body submerged into a ferrofluid volume under the influence of a nonuniform magnetic field. The deflection of the sensor's rod caused by external mechanical stimuli may be unambiguously identified by the distortion of the magnetic field, which occurs due to the motion of the attached body in the ferrofluid. The magnetic force acting on the body is evaluated experimentally and theoretically for the nonuniform magnetic field of a permanent magnet. The controlled oscillations of the rod are realised by applying a nonuniform magnetic field of periodically altering direction. - Highlights: • A design approach of a tactile sensor inspired by special mammalian hairs is presented. • The working principle is based on magnetic properties of a ferrofluid in magnetic fields. • The magnetic force acting on a body submerged into a ferrofluid volume is evaluated. • External mechanical stimuli may be identified by the distortion of the magnetic field. • The controlled whisking-like oscillations of the sensor's rod are realised experimentally.

Radiative corrections to the Coulomb law and model of dense quantum plasmas: Dispersion of longitudinal waves in magnetized quantum plasmas

Science.gov (United States)

Andreev, Pavel A.

2018-04-01

Two kinds of quantum electrodynamic radiative corrections to electromagnetic interactions and their influence on the properties of highly dense quantum plasmas are considered. Linear radiative correction to the Coulomb interaction is considered. Its contribution in the spectrum of the Langmuir waves is presented. The second kind of radiative corrections are related to the nonlinearity of the Maxwell equations for the strong electromagnetic field. Their contribution in the spectrum of transverse waves of magnetized plasmas is briefly discussed. At the consideration of the Langmuir wave spectrum, we included the effect of different distributions of the spin-up and spin-down electrons revealing in the Fermi pressure shift.

Ultrasonographic Findings of Mammographic Architectural Distortion

International Nuclear Information System (INIS)

Ma, Jeong Hyun; Kang, Bong Joo; Cha, Eun Suk; Hwangbo, Seol; Kim, Hyeon Sook; Park, Chang Suk; Kim, Sung Hun; Choi, Jae Jeong; Chung, Yong An

2008-01-01

To review the sonographic findings of various diseases showing architectural distortion depicted under mammography. We collected and reviewed architectural distortions observed under mammography at our health institution between 1 March 2004, and 28 February 2007. We collected 23 cases of sonographically-detected mammographic architectural distortions that confirmed lesions after surgical resection. The sonographic findings of mammographic architectural distortion were analyzed by use of the BI-RADS lexicon for shape, margin, lesion boundary, echo pattern, posterior acoustic feature and orientation. There were variable diseases that showed architectural distortion depicted under mammography. Fibrocystic disease was the most common presentation (n = 6), followed by adenosis (n = 2), stromal fibrosis (n = 2), radial scar (n = 3), usual ductal hyperplasia (n = 1), atypical ductal hyperplasia (n = 1) and mild fibrosis with microcalcification (n = 1). Malignant lesions such as ductal carcinoma in situ (DCIS) (n = 2), lobular carcinoma in situ (LCIS) (n = 2), invasive ductal carcinoma (n = 2) and invasive lobular carcinoma (n = 1) were observed. As observed by sonography, shape was divided as irregular (n = 22) and round (n = 1). Margin was divided as circumscribed (n = 1), indistinct (n = 7), angular (n = 1), microlobulated (n = 1) and sipculated (n = 13). Lesion boundary was divided as abrupt interface (n = 11) and echogenic halo (n = 12). Echo pattern was divided as hypoechoic (n = 20), anechoic (n = 1), hyperechoic (n = 1) and isoechoic (n = 1). Posterior acoustic feature was divided as posterior acoustic feature (n = 7), posterior acoustic shadow (n = 15) and complex posterior acoustic feature (n = 1). Orientation was divided as parallel (n = 12) and not parallel (n = 11). There were no differential sonographic findings between benign and malignant lesions. This study presented various sonographic findings of mammographic architectural distortion and that it is

New Geometric-distortion Solution for STIS FUV-MAMA

Science.gov (United States)

Sohn, S. Tony

2018-04-01

We derived a new geometric distortion solution for the STIS FUV-MAMA detector. To do this, positions of stars in 89 FUV-MAMA observations of NGC 6681 were compared to an astrometric standard catalog created using WFC3/UVIS imaging data to derive a fourth-order polynomial solution that transforms raw (x, y) positions to geometrically- corrected (x, y) positions. When compared to astrometric catalog positions, the FUV- MAMA position measurements based on the IDCTAB showed residuals with an RMS of ∼ 30 mas in each coordinate. Using the new IDCTAB, the RMS is reduced to ∼ 4 mas, or 0.16 FUV-MAMA pixels, in each coordinate. The updated IDCTAB is now being used in the HST STIS pipeline to process all STIS FUV-MAMA images.

Corrections in clinical Magnetic Resonance Spectroscopy and SPECT

DEFF Research Database (Denmark)

de Nijs, Robin

infants. In Iodine-123 SPECT the problem of downscatter was addressed. This thesis is based on two papers. Paper I deals with the problem of motion in Single Voxel Spectroscopy. Two novel methods for the identification of outliers in the set of repeated measurements were implemented and compared...... a detrimental effect of the extra-uterine environment on brain development. Paper II describes a method to correct for downscatter in low count Iodine-123 SPECT with a broad energy window above the normal imaging window. Both spatial dependency and weight factors were measured. As expected, the implicitly...... be performed by the subtraction of an energy window, a method was developed to perform scatter and downscatter correction simultaneously. A phantom study has been performed, where the in paper II described downscatter correction was extended with scatter correction. This new combined correction was compared...

Cubic Dresselhaus interaction parameter from quantum corrections to the conductivity in the presence of an in-plane magnetic field

Science.gov (United States)

Marinescu, D. C.

2017-09-01

We evaluate the quantum corrections to the conductivity of a two-dimensional electron system with competing Rashba (R) and linear and cubic Dresselhaus (D) spin-orbit interactions in the presence of an in-plane magnetic field B . Within a perturbative approximation, we investigate the interplay between the spin-orbit coupling and the magnetic field in determining the transport regime in two different limiting scenarios: when only one of the linear terms, either Rashba or Dresselhaus, dominates, and at equal linear couplings, when the cubic Dresselhaus breaks the spin symmetry. In each instance, we find that for B higher than a critical value, the antilocalization correction is suppressed and the effective dephasing time saturates to a constant value determined only by the spin-orbit interaction. At equal R-D linear couplings, this value is directly proportional with the cubic Dresselhaus contribution. In the same regime, the magnetoconductivity is expressed as a simple logarithmic function dependent only on the cubic Dresselhaus constant.

Intrinsic Local Distortions and charge carrier behavior in CMR manganites and cobaltites

Science.gov (United States)

Bridges, Frank

2010-03-01

We compare and contrast the local structure and electronic configurations in two oxide systems La1-xSrxCoO3 (LSCO) and La1-yCayMnO3 (LCMO). Although these oxides may appear quite similar they have rather different properties. At x=0, LaCoO3 (LCO) has unusual magnetic properties - diamagnetic at low T but developing a moment near 100K. The Sr doped LSCO materials show ferromagnetism for x > 0.2. For LCO, one of the possible spin state configurations called the intermediate spin (IS) state (S=1), should be Jahn-Teller (JT) active, while the low spin (S=0) and high spin (S=2) states have no JT distortion. Early local structure measurements suggested a JT distortion was present in LCO and therefore supported an IS spin model. However we find no evidence for any significant JT distortion (and hence no support for the IS model) for a range of bulk and nanoparticle cobaltites La1-xSrxCoO3, x = 0 - 0.35. In contrast there are large JT distortions in the manganites LCMO, 0.2 K-edge XANES data that shown no significant shift of the edge for the cobaltites as the Sr concentration increases from x =0 to 0.35 indicating essentially no change in the electronic configuration about Co; consequently, the holes introduced via Sr doping appear to go primarily into the O bands. In contrast there is a large shift of the Mn K-edge with Ca doping indicating a change in the average Mn valence, and a corresponding change in the Mn electronic configuration. We briefly discuss some possible models.

Relativistic energy correction of the hydrogen atom with an anomalous magnetic moment

International Nuclear Information System (INIS)

Ambogo, David Otieno

2015-07-01

The electron is known to possess an anomalous magnetic moment, which interacts with the gradient of the electric field. This makes it necessary to compute its effects on the energy spectrum. Even though the Coulomb Dirac equation can be solved in closed form, this is no longer possible when the anomalous magnetic moment is included. In fact the interaction due to this term is so strong that it changes the domain of the Hamiltonian. From a differential equation point of view, the anomalous magnetic moment term is strongly singular near the origin. As usual, one has to resort to perturbation theory. This, however, only makes sense if the eigenvalues are stable. To prove stability is therefore a challenge one has to face before actually computing the energy shifts. The first stability results in this line were shown by Behncke for angular momenta κ≥3, because the eigenfunctions of the unperturbed Hamiltonian decay fast enough near the origin. He achieved this by decoupling the system and then using the techniques available for second order differential equations. Later, Kalf and Schmidt extended Behncke's results basing their analysis on the Pruefer angle technique and a comparison result for first order differential equations. The Pruefer angle method is particularly useful because it shows a better stability and because it obeys a first order differential equation. Nonetheless, Kalf and Schmidt had to exclude some coupling constants for κ>0. This I believe is an artefact of their method. In this study, I make increasing use of asymptotic integration, a method which is rather well adapted to perturbation theory and is known to give stability results to any level of accuracy. Together with the Pruefer angle technique, this lead to a more general stability result and even allows for an energy shifts estimate. Hamiltonians traditionally treated in physics to describe the spin-orbit effect are not self adjoint i.e. they are not proper observables in quantum

Relativistic energy correction of the hydrogen atom with an anomalous magnetic moment

Energy Technology Data Exchange (ETDEWEB)

Ambogo, David Otieno

2015-07-15

The electron is known to possess an anomalous magnetic moment, which interacts with the gradient of the electric field. This makes it necessary to compute its effects on the energy spectrum. Even though the Coulomb Dirac equation can be solved in closed form, this is no longer possible when the anomalous magnetic moment is included. In fact the interaction due to this term is so strong that it changes the domain of the Hamiltonian. From a differential equation point of view, the anomalous magnetic moment term is strongly singular near the origin. As usual, one has to resort to perturbation theory. This, however, only makes sense if the eigenvalues are stable. To prove stability is therefore a challenge one has to face before actually computing the energy shifts. The first stability results in this line were shown by Behncke for angular momenta κ≥3, because the eigenfunctions of the unperturbed Hamiltonian decay fast enough near the origin. He achieved this by decoupling the system and then using the techniques available for second order differential equations. Later, Kalf and Schmidt extended Behncke's results basing their analysis on the Pruefer angle technique and a comparison result for first order differential equations. The Pruefer angle method is particularly useful because it shows a better stability and because it obeys a first order differential equation. Nonetheless, Kalf and Schmidt had to exclude some coupling constants for κ>0. This I believe is an artefact of their method. In this study, I make increasing use of asymptotic integration, a method which is rather well adapted to perturbation theory and is known to give stability results to any level of accuracy. Together with the Pruefer angle technique, this lead to a more general stability result and even allows for an energy shifts estimate. Hamiltonians traditionally treated in physics to describe the spin-orbit effect are not self adjoint i.e. they are not proper observables in quantum

Components of segregation distortion in Drosophila melanogaster

International Nuclear Information System (INIS)

Ganetzky, B.

1977-01-01

The segregation distorter (SD) complex is a naturally occurring meiotic drive system with the property that males heterozygous for an SD-bearing chromosome 2 and an SD+-bearing homolog transmit the SD-bearing chromosome almost exclusively. This distorted segregation is the consequence of an induced dysfunction of those sperm that receive the SD+ homolog. From previous studies, two loci have been implicated in this phenomenon: the Sd locus which is required to produce distortion, and the Responder (Rsp) locus that is the site at which Sd acts. There are two allelic alternatives of Rsp-sensitive (Rsp/sup sens/) and insensitive (Rsp/sup ins/); a chromosome carrying Rsp/sup ins/ is not distorted by SD. In the present study, the function and location of each of these elements was examined by a genetic and cytological characterization of x-ray-induced mutations at each locus. The results indicate the following: the Rsp locus is located in the proximal heterochromatin of 2R; a deletion for the Rsp locus renders a chromosome insensitive to distortion; the Sd locus is located to the left of pr (2-54.5), in the region from 37D2-D7 to 38A6-B2 of the salivary chromosome map; an SD chromosome deleted for Sd loses its ability to distort; there is another important component of the SD system, E(SD), in or near the proximal heterochromatin of 2L, that behaves as a strong enhancer of distortion. The results of these studies allow a reinterpretation of results from earlier analyses of the SD system and serve to limit the possible mechanisms to account for segregation distortion

Analysis and correction of intrinsic non-axisymmetric magnetic fields in high-β DIII-D plasmas

International Nuclear Information System (INIS)

Garofalo, A.M.; La Haye, R.J.; Scoville, J.T.

2002-01-01

Rapid plasma toroidal rotation, sufficient for stabilization of the n=1 resistive wall mode, can be sustained by improving the axisymmetry of the toroidal magnetic field geometry of DIII-D. The required symmetrization is determined experimentally both by optimizing currents in external n=1 correction coils with respect to the plasma rotation, and by use of the n=1 magnetic feedback to detect and minimize the plasma response to non-axisymmetric fields as β increases. Both methods point to an intrinsic ∼7 G (0.03% of the toroidal field), m/n=2/1 resonant helical field at the q=2 surface as the cause of the plasma rotation slowdown above the no-wall β limit. The drag exerted by this field on the plasma rotation is consistent with the behaviour of 'slipping' in a simple induction motor model. (author)

Attenuation correction for flexible magnetic resonance coils in combined magnetic resonance/positron emission tomography imaging.

Science.gov (United States)

Eldib, Mootaz; Bini, Jason; Calcagno, Claudia; Robson, Philip M; Mani, Venkatesh; Fayad, Zahi A

2014-02-01

Attenuation correction for magnetic resonance (MR) coils is a new challenge that came about with the development of combined MR and positron emission tomography (PET) imaging. This task is difficult because such coils are not directly visible on either PET or MR acquisitions with current combined scanners and are therefore not easily localized in the field of view. This issue becomes more evident when trying to localize flexible MR coils (eg, cardiac or body matrix coil) that change position and shape from patient to patient and from one imaging session to another. In this study, we proposed a novel method to localize and correct for the attenuation and scatter of a flexible MR cardiac coil, using MR fiducial markers placed on the surface of the coil to allow for accurate registration of a template computed tomography (CT)-based attenuation map. To quantify the attenuation properties of the cardiac coil, a uniform cylindrical water phantom injected with 18F-fluorodeoxyglucose (18F-FDG) was imaged on a sequential MR/PET system with and without the flexible cardiac coil. After establishing the need to correct for the attenuation of the coil, we tested the feasibility of several methods to register a precomputed attenuation map to correct for the attenuation. To accomplish this, MR and CT visible markers were placed on the surface of the cardiac flexible coil. Using only the markers as a driver for registration, the CT image was registered to the reference image through a combination of rigid and deformable registration. The accuracy of several methods was compared for the deformable registration, including B-spline, thin-plate spline, elastic body spline, and volume spline. Finally, we validated our novel approach both in phantom and patient studies. The findings from the phantom experiments indicated that the presence of the coil resulted in a 10% reduction in measured 18F-FDG activity when compared with the phantom-only scan. Local underestimation reached 22% in

Magnetic Resonance Imaging (MRI) -- Head

Medline Plus

Full Text Available ... distort images of the facial area or brain, so you should let the radiologist know about them. ... MRI units, called short-bore systems , are designed so that the magnet does not completely surround you. ...

Children's (Pediatric) Magnetic Resonance Imaging

Medline Plus

Full Text Available ... distort images of the facial area or brain, so the radiologist should be aware of them. Parents ... MRI units, called short-bore systems , are designed so that the magnet does not completely surround you. ...

Electron capture by alpha particles from helium atoms in a Coulomb-Born distorted-wave approximation

International Nuclear Information System (INIS)

Ghanbari-Adivi, E; Ghavaminia, H

2012-01-01

A three-body Coulomb-Born continuum distorted-wave approximation is applied to calculate the differential and total cross sections for single-electron exchange in the collision of fast alpha particles with helium atoms in their ground states. The applied first-order distorted wave theory satisfies correct Coulomb boundary conditions. Both post and prior forms of the transition amplitude are calculated. The nuclear-screening effect of the passive electron on the differential and total cross sections is investigated. The results are compared with those of other theories and with the available experimental data. For differential cross sections, the comparisons show a reasonable agreement with empirical measurements at higher impact energies. The agreement between experimental data and the present calculations for total cross sections with the average of the post and prior forms of the transition amplitude is reasonable at all the specified energies.

Sonographic ally Detected Architectural Distortion: Clinical Significance

Energy Technology Data Exchange (ETDEWEB)

Kim, Shin Kee; Seo, Bo Kyoung; Yi, Ann; Cha, Sang Hoon; Kim, Baek Hyun; Cho, Kyu Ran; Kim, Young Sik; Son, Gil Soo; Kim, Young Soo; Kim, Hee Young [Korea University Ansan Hospital, Ansan (Korea, Republic of)

2008-12-15

Architectural distortion is a suspicious abnormality for the diagnosis of breast cancer. The aim of this study was to investigate the clinical significance of sonographic ally detected architectural distortion. From January 2006 to June 2008, 20 patients were identified who had sonographic ally detected architectural distortions without a history of trauma or surgery and abnormal mammographic findings related to an architectural distortion. All of the lesions were pathologically verified. We evaluated the clinical and pathological findings and then assessed the clinical significance of the sonographic ally detected architectural distortions. Based on the clinical findings, one (5%) of the 20 patients had a palpable lump and the remaining 19 patients had no symptoms. No patient had a family history of breast cancer. Based on the pathological findings, three (15%) patients had malignancies. The malignant lesions included invasive ductal carcinomas (n = 2) and ductal carcinoma in situ (n = 1). Four (20%) patients had high-risk lesions: atypical ductal hyperplasia (n = 3) and lobular carcinoma in situ (n = 1). The remaining 13 (65%) patients had benign lesions, however, seven (35%) out of 13 patients had mild-risk lesions (three intraductal papillomas, three moderate or florid epithelial hyperplasia and one sclerosing adenosis). Of the sonographic ally detected architectural distortions, 35% were breast cancers or high-risk lesions and 35% were mild-risk lesions. Thus, a biopsy might be needed for an architectural distortion without an associated mass as depicted on breast ultrasound, even though the mammographic findings are normal

Sonographic ally Detected Architectural Distortion: Clinical Significance

International Nuclear Information System (INIS)

Kim, Shin Kee; Seo, Bo Kyoung; Yi, Ann; Cha, Sang Hoon; Kim, Baek Hyun; Cho, Kyu Ran; Kim, Young Sik; Son, Gil Soo; Kim, Young Soo; Kim, Hee Young

2008-01-01

Architectural distortion is a suspicious abnormality for the diagnosis of breast cancer. The aim of this study was to investigate the clinical significance of sonographic ally detected architectural distortion. From January 2006 to June 2008, 20 patients were identified who had sonographic ally detected architectural distortions without a history of trauma or surgery and abnormal mammographic findings related to an architectural distortion. All of the lesions were pathologically verified. We evaluated the clinical and pathological findings and then assessed the clinical significance of the sonographic ally detected architectural distortions. Based on the clinical findings, one (5%) of the 20 patients had a palpable lump and the remaining 19 patients had no symptoms. No patient had a family history of breast cancer. Based on the pathological findings, three (15%) patients had malignancies. The malignant lesions included invasive ductal carcinomas (n = 2) and ductal carcinoma in situ (n = 1). Four (20%) patients had high-risk lesions: atypical ductal hyperplasia (n = 3) and lobular carcinoma in situ (n = 1). The remaining 13 (65%) patients had benign lesions, however, seven (35%) out of 13 patients had mild-risk lesions (three intraductal papillomas, three moderate or florid epithelial hyperplasia and one sclerosing adenosis). Of the sonographic ally detected architectural distortions, 35% were breast cancers or high-risk lesions and 35% were mild-risk lesions. Thus, a biopsy might be needed for an architectural distortion without an associated mass as depicted on breast ultrasound, even though the mammographic findings are normal

Can journalistic "false balance" distort public perception of consensus in expert opinion?

Science.gov (United States)

Koehler, Derek J

2016-03-01

Media critics have expressed concern that journalistic "false balance" can distort the public's perceptions of what ought to be noncontroversial subjects (e.g., climate change). I report several experiments testing the influence of presenting conflicting comments from 2 experts who disagree on an issue (balance condition) in addition to a complete count of the number of experts on a panel who favor either side. Compared with a control condition, who received only the complete count, participants in the balance condition gave ratings of the perceived agreement among the experts that did not discriminate as clearly between issues with and without strong expert consensus. Participants in the balance condition also perceived less agreement among the experts in general, and were less likely to think that there was enough agreement among experts on the high-consensus issues to guide government policy. Evidently, "false balance" can distort perceptions of expert opinion even when participants would seem to have all the information needed to correct for its influence. (c) 2016 APA, all rights reserved).

Magnetic Resonance Imaging (MRI) -- Head

Medline Plus

Full Text Available ... an MRI scan, but this is rare. Tooth fillings and braces usually are not affected by the magnetic field, but they may distort images of the facial area or brain, so you should let the ...

Children's (Pediatric) Magnetic Resonance Imaging

Medline Plus

Full Text Available ... lodged in the eyes are particularly important. Tooth fillings and braces usually are not affected by the magnetic field, but they may distort images of the facial area or brain, so the radiologist should be ...

[Magnetic resonance compatibility research for coronary mental stents].

Science.gov (United States)

Wang, Ying; Liu, Li; Wang, Shuo; Shang, Ruyao; Wang, Chunren

2015-01-01

The objective of this article is to research magnetic resonance compatibility for coronary mental stents, and to evaluate the magnetic resonance compatibility based on laboratory testing results. Coronary stents magnetic resonance compatibility test includes magnetically induced displacement force test, magnetically induced torque test, radio frequency induced heating and evaluation of MR image. By magnetic displacement force and torque values, temperature, and image distortion values to determine metal coronary stent demagnetization effect. The methods can be applied to test magnetic resonance compatibility for coronary mental stents and evaluate its demagnetization effect.

Centimeter-order view for magnetic domain imaging with local magnetization direction by longitudinal Kerr effect

Directory of Open Access Journals (Sweden)

Sakae Meguro

2016-05-01

Full Text Available An observation system of centimeter-order of view of magnetic domain with local magnetization direction was developed by designing a telecentric optical system of finite design through the extension of microscope technology. The field of view realized in the developed system was 1.40 × 1.05 cm as suppressing defocus and distortion. Detection of the local magnetization direction has become possible by longitudinal Kerr observation from the orthogonal two directions. This system can be applied to the domain observation of rough surface samples and time resolved analysis for soft magnetic materials such as amorphous foil strips and soft magnetic thin films.

FSD: Frequency Space Differential measurement of CMB spectral distortions

Science.gov (United States)

Mukherjee, Suvodip; Silk, Joseph; Wandelt, Benjamin D.

2018-04-01

Although the Cosmic Microwave Background agrees with a perfect blackbody spectrum within the current experimental limits, it is expected to exhibit certain spectral distortions with known spectral properties. We propose a new method, Frequency Space Differential (FSD) to measure the spectral distortions in the CMB spectrum by using the inter-frequency differences of the brightness temperature. The difference between the observed CMB temperature at different frequencies must agree with the frequency derivative of the blackbody spectrum, in the absence of any distortion. However, in the presence of spectral distortions, the measured inter-frequency differences would also exhibit deviations from blackbody which can be modeled for known sources of spectral distortions like y & μ. Our technique uses FSD information for the CMB blackbody, y, μ or any other sources of spectral distortions to model the observed signal. Successful application of this method in future CMB missions can provide an alternative method to extract spectral distortion signals and can potentially make it feasible to measure spectral distortions without an internal blackbody calibrator.

Establishment of a tolerance budget for the advanced photon source storage ring

International Nuclear Information System (INIS)

Bizek, H.; Crosbie, E.; Lessner, E.; Teng, L.

1993-01-01

The limitations on the dynamic aperture of the Advanced Photon Source storage ring due to magnet misalignments and fabrication errors are presented. The reduction of the dynamic aperture is analyzed first for each error considered individually, and then for combined error multipole fields in dipole, quadrupole, and sextupole magnets, excluding and including magnet misalignments. Since misalignments of the strong quadrupoles in the ring induce large orbit distortions, the effects on the dynamic aperture are investigated before and after orbit correction. Effects of off-momentum particles and the tune dependence with momentum are also presented. This extensive analysis leads to the establishment of a tolerance budget. With all the errors set at the tolerance level, and with the orbit distortions corrected, the dynamic aperture reduction is no greater than 50% of that of the ideal machine

Establishment of a tolerance budget for the Advanced Photon Source storage ring

International Nuclear Information System (INIS)

Bizek, H.; Crosbie, E.; Lessner, E.; Teng, L.

1993-01-01

The limitations on the dynamic aperture of the Advanced Photon Source storage ring due to magnet misalignments and fabrication errors are presented. The reduction of the dynamic aperture is analyzed first for each error considered individually, and then for combined error multipole fields in dipole, quadrupole, and sextupole magnets, excluding and including magnet misalignments. Since misalignments of the strong quadrupoles in the ring induce large orbit distortions, the effects on the dynamic aperture are investigated before and after orbit correction. Effects of off-momentum particles and the tune dependence with momentum are also presented. This extensive analysis leads to the establishment of a tolerance budget. With all the errors set at the tolerance level and with the orbit distortions corrected, the dynamic aperture reduction is no greater than 50% of that of the ideal machine

Photometric correction for an optical CCD-based system based on the sparsity of an eight-neighborhood gray gradient.

Science.gov (United States)

Zhang, Yuzhong; Zhang, Yan

2016-07-01

In an optical measurement and analysis system based on a CCD, due to the existence of optical vignetting and natural vignetting, photometric distortion, in which the intensity falls off away from the image center, affects the subsequent processing and measuring precision severely. To deal with this problem, an easy and straightforward method used for photometric distortion correction is presented in this paper. This method introduces a simple polynomial fitting model of the photometric distortion function and employs a particle swarm optimization algorithm to get these model parameters by means of a minimizing eight-neighborhood gray gradient. Compared with conventional calibration methods, this method can obtain the profile information of photometric distortion from only a single common image captured by the optical CCD-based system, with no need for a uniform luminance area source used as a standard reference source and relevant optical and geometric parameters in advance. To illustrate the applicability of this method, numerical simulations and photometric distortions with different lens parameters are evaluated using this method in this paper. Moreover, the application example of temperature field correction for casting billets also demonstrates the effectiveness of this method. The experimental results show that the proposed method is able to achieve the maximum absolute error for vignetting estimation of 0.0765 and the relative error for vignetting estimation from different background images of 3.86%.

Rabi oscillations and quantum beats in a qubit in distorted magnetic field

International Nuclear Information System (INIS)

Ivanchenko, E.A.; Tolstoluzhsky, A.P.

2007-01-01

In a two-level system the time-periodic modulation of the magnetic field stabilizing the magnetic resonance position has been investigated. It was shown that the fundamental resonance is stable with respect to consistent variation of the longitudinal and transverse magnetic fields. The time-dependency of the Rabi oscillations and quantum beats of the spin flip probably was numerically researched in different parameter regimes taking into account dissipation and decoherence in the Lindblad form. The present study may be useful in the analysis of interference experiments and for manipulation of quantum bits

The psychological analysis of distortions of a behaviour of schoolboys living in various regions

International Nuclear Information System (INIS)

Furmanov, I.A.

1995-01-01

The necessity of compelled living on contaminated territory and the state social psychological disadaptation, connected with expectation of a remove to other regions, is the reason that the children are in a situation of a prolongation stress, destroying motivational, emotional, strong-willed and moral components of a behaviour regulation. It results to inadequate behaviour reactions to effects of social environment and varying conditions of activity. For the explanation of the reasons of a distortion of behaviour in a critical situation a psychological diagnostics of school teenagers living in the contamination and 'clear' regions was conducted, inter regional distinctions in the behaviour sphere of schoolboys are determined, psychological analysis of the main components of a regulation of a behaviour of teenagers with a various level of an aggressive is conducted. A psychological portrait of schoolboys with various types of behaviour distortions is received. Main directions of a correction work with various categories schoolboys are offered. 8 refs., 1 tab

Impact of loudspeaker nonlinear distortion on personal sound zones

DEFF Research Database (Denmark)

Ma, Xiaohui; J. Hegarty, Patrick; Abildgaard Pedersen, Jan

2018-01-01

Personal sound zone systems aim at creating multiple listening zones within a shared space with minimum interference between zones, but the performance is often poorer than simulations predict and effects of nonlinear distortion are sometimes audible. This paper assesses the impact of nonlinear...... distortion on sound zones through simulations and measurements performed under anechoic conditions. Two sound zones, one bright and one dark, are created with acoustic contrast control using two loudspeaker arrays driven at 250 Hz. Nonlinear distortion is modelled using second or third order nonlinearities....... Simulations show that nonlinear distortion degrades the acoustic contrast, which is confirmed by experimental measurements. The harmonic distortion is audible in the dark zone. Frequency resolved measurements reveal that harmonic distortion contributes to contrast loss, but nonlinear effects...

Correcting and coating thin walled X-ray Optics via a combination of controlled film deposition and magnetic smart materials

Science.gov (United States)

Ulmer, Melville

The project goal is to demonstrate that thin walled (price. Since the desired surface area for the next generation X-ray telescope is >10x that of Chandra, the >10x requirement is then for >200 m^2 of surface area with a surface finish of better than 0.5 nm. Therefore, replication of some sort is called for. Because no replication technology has been shown to achieve ≤1" angular resolution, post fabrication figure corrections are likely going to be necessary. Some have proposed to do this in orbit and others prelaunch including us. Our prelaunch approach is to apply in-plane stresses to the thin walled mirror shells via a magnetic field. The field will be held in by some magnetically hard material such as NiCo. By use of a so called magnetic smart material (MSM) such as Terfenol-D, we already shown that strong enough stresses can be generated. Preliminary work has also shown that the magnetic field can be held in well enough to apply the figure correcting stresses pre-launch. What we call "set-it and forget-it." However, what is unique about our approach is that at the cost of complexity and some areal coverage, our concept will also accommodate in-orbit adjustments. Furthermore, to the best of our knowledge ours is one of two known stress modification processes that are bi-axial. Our plan is first to validate set-it and forget-it first on cantilevers and then to expand this to working on 5 cm x 5 cm pieces. We will work both with NiCo and glass or Si coated with Terfenol-D. Except for the NiCo, substrates we will also coat the samples with NiCo in order to have a film that will hold in the magnetic field. As part of the coating process, we will control the stress of the film by varying the voltage bias while coating. The bias stress control can be used to apply films with minimal stress such as Terfenol-D and X-ray reflecting coatings such as Ir. Ir is a highly desirable coating for soft X-ray astronomy mirrors that can have significant built in stress unless

Magnetic properties of nano-multiferroic materials

Science.gov (United States)

Ramam, Koduri; Diwakar, Bhagavathula S.; Varaprasad, Kokkarachedu; Swaminadham, Veluri; Reddy, Venu

2017-11-01

Latent magnetization in the multiferroics can be achieved via the structural distortion with respect to particle size and destroying the spiral spin structure, which plays the vital role in high-performance applications. In this investigation, multifunctional single phase Bi1-xLaxFe1-yCoyO3 nanomaterials were synthesized by co-precipitation technique. The chemical composition, phase genesis, morphology and thermal characteristics of the Bi1-xLaxFe1-yCoyO3 were studied by FTIR, XRD, SEM/EDS, TEM and TGA. XRD studies confirmed single phase distorted rhombohedral structure in Bi1-xLaxFe1-yCoyO3. The novelty in magnetic behavior of the Bi0.85La0.15Fe0.75Co0.25O3 multiferroic at room temperature showed both ferro and anti-ferromagnetic nature with higher order remanent magnetization among other nanocomposites in this study. This magnetic anomaly in Bi0.85La0.15Fe0.75Co0.25O3 is due to doping and size effects on the crystal structure that leads to spin-orbit interactions. Besides, Bi0.85La0.15Fe0.75Co0.25O3 integrated graphene oxide (GO) nanocomposite has shown the change in the magnetic hysteresis that indicates the effect of the semiconducting behavior of GO on the ordered magnetic moments in the multiferroic. This kind of magnetic anomaly could form advanced multiferroic devices.

Invisible magnetic sensors

Science.gov (United States)

Mach-Batlle, Rosa; Navau, Carles; Sanchez, Alvaro

2018-04-01

Sensing magnetic fields is essential in many applications in biomedicine, transportation, or smart cities. The distortion magnetic sensors create in response to the field they are detecting may hinder their use, for example, in applications requiring dense packaging of sensors or accurately shaped field distributions. For sensing electromagnetic waves, cloaking shells that reduce the scattering of sensors have been introduced. However, the problem of making a magnetic sensor undetectable remains unsolved. Here, we present a general strategy on how to make a sensor magnetically invisible while keeping its ability to sense. The sensor is rendered undetectable by surrounding it with a spherical shell having a tailored magnetic permeability. Our method can be applied to arbitrary shaped magnetic sensors in arbitrary magnetic fields. The invisibility can be made exact when the sensor is spherical and the probed field is uniform. A metasurface composed of superconducting pieces is presented as a practical realization of the ideal invisibility shell.

Correction of Visual Perception Based on Neuro-Fuzzy Learning for the Humanoid Robot TEO

Directory of Open Access Journals (Sweden)

Juan Hernandez-Vicen

2018-03-01

Full Text Available New applications related to robotic manipulation or transportation tasks, with or without physical grasping, are continuously being developed. To perform these activities, the robot takes advantage of different kinds of perceptions. One of the key perceptions in robotics is vision. However, some problems related to image processing makes the application of visual information within robot control algorithms difficult. Camera-based systems have inherent errors that affect the quality and reliability of the information obtained. The need of correcting image distortion slows down image parameter computing, which decreases performance of control algorithms. In this paper, a new approach to correcting several sources of visual distortions on images in only one computing step is proposed. The goal of this system/algorithm is the computation of the tilt angle of an object transported by a robot, minimizing image inherent errors and increasing computing speed. After capturing the image, the computer system extracts the angle using a Fuzzy filter that corrects at the same time all possible distortions, obtaining the real angle in only one processing step. This filter has been developed by the means of Neuro-Fuzzy learning techniques, using datasets with information obtained from real experiments. In this way, the computing time has been decreased and the performance of the application has been improved. The resulting algorithm has been tried out experimentally in robot transportation tasks in the humanoid robot TEO (Task Environment Operator from the University Carlos III of Madrid.

Structural Change Accounting with Labor Market Distortions

OpenAIRE

Wenbiao Cai

2014-01-01

This paper quantifies the relative importance of sectoral productivity and labor market distortions for structural change. I use a model in which labor productivity is the product of TFP and human capital in each sector, but distortions generate wedges in wage per efficiency worker across sectors. I calculate human capital by sector using micro census data, and use the model to infer TFP and distortions such that it replicates structural change in the US, India, Mexico and Brazil between 1960...

Influence of initial state distortion in ion-atom collisions

Energy Technology Data Exchange (ETDEWEB)

Ciappina, M F [CONICET and Departamento de FIsica, Universidad Nacional del Sur, 8000 BahIa Blanca (Argentina); Cravero, W R [CONICET and Departamento de FIsica, Universidad Nacional del Sur, 8000 BahIa Blanca (Argentina); Garibotti, C R [CONICET and Division Colisiones Atomicas, Centro Atomico Bariloche, 8400 Bariloche (Argentina)

2004-05-28

We have studied the influence of initial state distortion in a single ionization by ion impact. We have taken a continuum distorted wave type distortion and by taking up to the first order in its asymptotic series expansion we build an eikonal-spherical distortion. In this way the influence of each term in the transition amplitude can be stated. This approximation can be considered an intermediate one between the eikonal initial state and the continuum distorted wave approaches for initial state distortion. We have computed doubly differential cross sections for helium ionization by protons and highly charged ions at high and intermediate impact energy. We have also discussed the contribution of the different terms in electron energy spectra, specially in the vicinity of ECC peak. Very good agreement is found with the available experimental data.

Influence of initial state distortion in ion-atom collisions

International Nuclear Information System (INIS)

Ciappina, M F; Cravero, W R; Garibotti, C R

2004-01-01

We have studied the influence of initial state distortion in a single ionization by ion impact. We have taken a continuum distorted wave type distortion and by taking up to the first order in its asymptotic series expansion we build an eikonal-spherical distortion. In this way the influence of each term in the transition amplitude can be stated. This approximation can be considered an intermediate one between the eikonal initial state and the continuum distorted wave approaches for initial state distortion. We have computed doubly differential cross sections for helium ionization by protons and highly charged ions at high and intermediate impact energy. We have also discussed the contribution of the different terms in electron energy spectra, specially in the vicinity of ECC peak. Very good agreement is found with the available experimental data

Observation of helix associations for insertion of a retinal molecule and distortions of helix structures in bacteriorhodopsin

Science.gov (United States)

Urano, Ryo; Okamoto, Yuko

2015-12-01

We applied a newly proposed prediction method for membrane protein structures to bacteriorhodopsin that has distorted transmembrane helices in the native structure. This method uses an implicit membrane model, which restricts sampling space during folding in a membrane region, and includes helix bending. Replica-exchange simulations were performed with seven transmembrane helices only without a retinal molecule. Obtained structures were classified into clusters of similar structures, which correspond to local-minimum free energy states. The two lowest free energy states corresponded to a native-like structure with the correct empty space for retinal and a structure with this empty space filled with a helix. Previous experiments of bacteriorhodopsin suggested that association of transmembrane helices enables them to make a room for insertion of a retinal. Our results are consistent with these results. Moreover, distortions of helices in the native-like structures were successfully reproduced. In the distortions, whereas the locations of kinks for all helices were similar to those of Protein Data Bank's data, the amount of bends was more similar for helices away from the retinal than for those close to the retinal in the native structure. This suggests a hypothesis that the amino-acid sequence specifies the location of kinks in transmembrane helices and that the amount of distortions depends on the interactions with the surrounding molecules such as neighboring helices, lipids, and retinal.

Density distortion within a rotating body

International Nuclear Information System (INIS)

Lanzano, P.

1975-01-01

This paper ascertains the distortion of the density distribution within a self-gravitating body in hydrostatic equilibrium under the influence of rotation. For this purpose, the Poisson equation has been solved by using the undistorted density profile within the Laplacian to obtain the distorted density. The Laplacian has been expressed in terms of a system of curvilinear coordinates for which the equipotential surfaces constitute a family of fundamental surfaces. In performing the requisite algebraic manipulations, the Clairaut and Radau equations developed in a previous paper (Lanzano,1974) were utilized to eliminate the derivatives of the elements pertaining to the equipotential surfaces. The density distortion has been obtained up to third-order terms in a small rotational parameter. (Auth.)

Cognitive Distortions in Depressed Women: Trait, or State Dependent?

Directory of Open Access Journals (Sweden)

Sedat BATMAZ

2015-12-01

Conclusion: The results have revealed that self-criticism, helplessness, hopelessness and preoccupation with danger related distortions had trait-like features, whereas self-blame related distortions were state dependent. This has clinical implications for the psychotherapeutic treatment of cognitive distortions in depression. Specifically, self-criticism related distortions should be managed during cognitive therapy for depression since the other subscales seem rather problematic. [JCBPR 2015; 4(3.000: 147-152

Advanced Machining Toolpath for Low Distortion

Science.gov (United States)

2017-02-28

Advanced Machining Toolpath for Low Distortion FINAL STATUS REPORT Prepared by Brian Becker R&D Technology Manager Third Wave Systems, Inc... Machining Toolpath for Low Distortion December 2016 Contract No.: W911W6-16-P-0044 2 Table of Contents 1.0 EXECUTIVE SUMMARY...2 2.1 Task 1: Collect Details of Machining Lab to Support

An update on passive correctors for the SSC dipole magnets

International Nuclear Information System (INIS)

Green, M.A.

1991-05-01

The concept of correction of the magnetization sextupole became a topic of discussion as soon as it was realized that superconductor magnetization could have a serious effect on the SSC beam during injection. Several methods of correction were proposed. These included (1) correction with active bore tube windings like those on the HERA machine which correct out magnetization sextupole and the sextupole due to iron saturation, (2) correction with persistent sextupole windings mounted on the bore tube (3) correction using passive superconductor (4) correction using ferromagnetic material, and (5) correction using oriented magnetized materials. This report deals with the use of passive superconductor to correct the magnetization sextupole. Two basic methods are explored in this report: (1) One can correct the magnetization sextupole by changing the diameter of the superconductor filaments in one or more blocks of the SSC dipole. (2) One can correct the magnetization sextupole and decapole by mounting passive superconducting wires on the inside of the SSC dipole coil bore. In addition, an assessment of the contribution of each conductor in the dipole to the magnetization sextupole and decapole is shown. 38 refs, 25 figs., 15 tabs

Motion-Corrected Real-Time Cine Magnetic Resonance Imaging of the Heart: Initial Clinical Experience.

Science.gov (United States)

Rahsepar, Amir Ali; Saybasili, Haris; Ghasemiesfe, Ahmadreza; Dolan, Ryan S; Shehata, Monda L; Botelho, Marcos P; Markl, Michael; Spottiswoode, Bruce; Collins, Jeremy D; Carr, James C

2018-01-01

Free-breathing real-time (RT) imaging can be used in patients with difficulty in breath-holding; however, RT cine imaging typically experiences poor image quality compared with segmented cine imaging because of low resolution. Here, we validate a novel unsupervised motion-corrected (MOCO) reconstruction technique for free-breathing RT cardiac images, called MOCO-RT. Motion-corrected RT uses elastic image registration to generate a single heartbeat of high-quality data from a free-breathing RT acquisition. Segmented balanced steady-state free precession (bSSFP) cine images and free-breathing RT images (Cartesian, TGRAPPA factor 4) were acquired with the same spatial/temporal resolution in 40 patients using clinical 1.5 T magnetic resonance scanners. The respiratory cycle was estimated using the reconstructed RT images, and nonrigid unsupervised motion correction was applied to eliminate breathing motion. Conventional segmented RT and MOCO-RT single-heartbeat cine images were analyzed to evaluate left ventricular (LV) function and volume measurements. Two radiologists scored images for overall image quality, artifact, noise, and wall motion abnormalities. Intraclass correlation coefficient was used to assess the reliability of MOCO-RT measurement. Intraclass correlation coefficient showed excellent reliability (intraclass correlation coefficient ≥ 0.95) of MOCO-RT with segmented cine in measuring LV function, mass, and volume. Comparison of the qualitative ratings indicated comparable image quality for MOCO-RT (4.80 ± 0.35) with segmented cine (4.45 ± 0.88, P = 0.215) and significantly higher than conventional RT techniques (3.51 ± 0.41, P cine (1.51 ± 0.90, P = 0.088 and 1.23 ± 0.45, P = 0.182) were not different. Wall motion abnormality ratings were comparable among different techniques (P = 0.96). The MOCO-RT technique can be used to process conventional free-breathing RT cine images and provides comparable quantitative assessment of LV function and volume

Measurement, correction, and analysis of the equilibrium orbit in the electron stretcher facility ELSA

International Nuclear Information System (INIS)

Keil, J.

2000-07-01

The electron stretcher accelerator ELSA provides an electron beam in the energy range between 0.5 and 3.5 GeV with a high duty factor for medium energy physics experiments. The acceleration of polarized electrons and demands by synchrotron radiation users for a high beam quality require a good correction of the closed orbit. For its measurement a precise beam position monitor (BPM) system based on narrow band RF-receivers with a resolution of some micrometers was developed and installed. 28 stations are connected by a fieldbus with a VME multiprocessor system, which is used for control of the BPM stations and for data acquisition. BPM offsets relative to the quadrupole centers were determined with an accuracy better than 100 μm using the method of beam-based alignment. Based on these measurements the closed orbit distortions were reduced from approx. 3 mm to 140 μm (rms) in both planes. Furthermore elements with dipole field errors were located by means of the uncorrected orbit. Orbit response matrices were analyzed to determine errors of quadrupole magnets and calibration factors of BPMs and corrector magnets. Predicted optics functions and tunes based on the improved optics model are in good agreement with the measurements. (orig.)

Sextupole correction magnets for the Large Hadron Collider

CERN Document Server

Meinke, R B; Senti, M; Op de Beeck, W J; De Ryck, C; MacKay, W W

1999-01-01

About 2500 superconducting sextupole corrector magnets (MCS) are needed for the Large Hadron Collider (LHC) at CERN to compensate persistent current sextupole fields of the main dipoles. The MCS is a cold bore magnet with iron yoke. The coils are made from a NbTi conductor, which is cooled to 1.9 K. In the original CERN design 6 individual sub-coils, made from a monolithic composite conductor, are assembled and spliced together to form the sextupole. The coils are individually wound around precision-machined central islands and stabilized with matching saddle pieces at both ends. The Advanced Magnet Lab, Inc. (AML) has produced an alternative design, which gives improved performance and reliability at reduced manufacturing cost. In the AML design, the magnet consists of three splice-free sub-coils, which are placed with an automated winding process into pockets of prefabricated G-11 support cylinders. Any assembly process of sub-coils with potential misalignment is eliminated. The AML magnet uses a Kapton-wra...

Determination of microturbulence enhanced electron collisionality in magnetized coaxial accelerator channels by direct magnetic field measurement

International Nuclear Information System (INIS)

Black, D.C.; Mayo, R.M.; Caress, R.W.

1997-01-01

A miniature magnetic probe array, consisting of 10 spatially separated coils, has been used to obtain profile information on the time varying magnetic field within the 2.54 cm wide flow channel of the coaxial plasma source experiment (CPS-1) [R. M. Mayo et al., Plasma Sources Sci. Technol. 4, 47 (1995)]. The magnetic field data have been used, together with a resistive, Hall magnetohydrodynamic (MHD) model of applied field distortion by the flowing plasma, to obtain estimates of the microturbulent enhancement to electron collisionality within the CPS-1 flow channel. These measurements provide direct experimental evidence of anomalous electron collisionality, a previously predicted effect in these devices. The anomaly parameter, a=ν an /ν cl , determined both from the distortion of contours of constant magnetic flux, and from local B θ and B z measurements scales with the classical electron magnetization parameter (Ω cl =ω ce /ν e cl ), indicating that collisionality plays a strong role in determining the level of anomalous transport in the plasma. When this anomaly parameter scaling is cast in terms of the ratio ν e cl /ω lh , it is found that the resistivity enhancement scales with ν e cl /ω lh , and becomes significant at ν e cl /ω lh ≤1, suggesting that a lower hybrid drift instability may be the responsible mechanism for enhanced transport. copyright 1997 American Institute of Physics

How does relativity affect magnetically induced currents?

Science.gov (United States)

Berger, R J F; Repisky, M; Komorovsky, S

2015-09-21

Magnetically induced probability currents in molecules are studied in relativistic theory. Spin-orbit coupling (SOC) enhances the curvature and gives rise to a previously unobserved current cusp in AuH or small bulge-like distortions in HgH2 at the proton positions. The origin of this curvature is magnetically induced spin-density arising from SOC in the relativistic description.

Disturbed Intracardiac Flow Organization After Atrioventricular Septal Defect Correction as Assessed With 4D Flow Magnetic Resonance Imaging and Quantitative Particle Tracing

NARCIS (Netherlands)

Calkoen, Emmeline E.; de Koning, Patrick J. H.; Blom, Nico A.; Kroft, Lucia J. M.; de Roos, Albert; Wolterbeek, Ron; Roest, Arno A. W.; Westenberg, Jos J. M.

2015-01-01

Objectives Four-dimensional (3 spatial directions and time) velocity-encoded flow magnetic resonance imaging with quantitative particle tracing analysis allows assessment of left ventricular (LV) blood flow organization. Corrected atrioventricular septal defect (AVSD) patients have an abnormal left

TU-H-206-07: Assessment of Geometric Distortion in EPI with a SPAMM Tagged Acquisition

Energy Technology Data Exchange (ETDEWEB)

Hwang, K; Meier, J; Yung, J; Stafford, R [The University of Texas MD Anderson Cancer Center, Houston, TX (United States)

2016-06-15

Purpose: Echo planar imaging (EPI) is known to exhibit gross geometric distortion caused by multiple factors, including B0 inhomgeneity and transient eddy currents. However, diffusion weighted (DW) EPI has become indispensable for diagnosis and therapy assessment. We propose a methodology for quantifying distortion in EPI sequences that does not require the use of dedicated spatial accuracy phantoms, enabling flexibility in phantom design for QA of distortion effects in EPI protocols. Methods: The proposed methodology utilizes a saturation technique known as Spatial Modulation of Magnetization (SPAMM) that tags the imaging subject with saturated grid lines. Originally intended for tracking cardiac motion, these grids are applied to assess differences between diffusion weighting directions and b-values, or against a more geometrically robust sequence such as fast spin echo (FSE). The saturation preparation sequence consists of binomially weighted (e.g. 1-3-3-1) pulses interleaved with gradient blips along the frequency encode direction, followed by the same sequence with gradient blips in the phase encode direction. Three phantoms were assessed with these sequences: a spherical head-sized phantom, a large shimming phantom, and a modified PET ACR phantom that included compartments of water, air, oil, and Teflon. Each phantom was acquired with three sequences using parameters from a clinically appropriate protocol (22 cm head or 46 cm abdomen): a conventional DW-EPI sequence (3 DW directions), and both the DW-EPI and FSE sequences with tagging. Differences in grid locations were visualized with minimum intensity projection between images, and measured using intersecting locations on the grids. Results: Grid lines were clearly visualized on tagged images and enabled quantification of distortions. Maximum eddy current induced errors of 10.8 to 14.8 mm were observed in areas away from isocenter with DW gradients applied in various directions. Conclusion: SPAMM tagging

Magnetic field errors tolerances of Nuclotron booster

Science.gov (United States)

Butenko, Andrey; Kazinova, Olha; Kostromin, Sergey; Mikhaylov, Vladimir; Tuzikov, Alexey; Khodzhibagiyan, Hamlet

2018-04-01

Generation of magnetic field in units of booster synchrotron for the NICA project is one of the most important conditions for getting the required parameters and qualitative accelerator operation. Research of linear and nonlinear dynamics of ion beam 197Au31+ in the booster have carried out with MADX program. Analytical estimation of magnetic field errors tolerance and numerical computation of dynamic aperture of booster DFO-magnetic lattice are presented. Closed orbit distortion with random errors of magnetic fields and errors in layout of booster units was evaluated.

On the wavelength dependence of the reflectivity of one-dimensionally distorted crystals

International Nuclear Information System (INIS)

Guigay, J.P.

1986-01-01

Scaling properties of the integrated reflectivity of non-absorbing perfect or ideally imperfect crystals as a function of wavelength, in the symmetrical Laue and Bragg cases, are shown also to be valid for distorted crystals where the gradient of the lattice phase factor is perpendicular to the crystal surfaces. This result is obtained by an analysis of the Taupin-Takagi equations. Some previous experiments (test of a proposal for extinction-free measurements of F M /F N in polarized neutron scattering by magnetic crystals, and neutron diffraction from curved and non-curved crystals) are discussed from this point of view. (orig.)

Profile correction to electron temperature and enhancement factor in soft-x-ray pulse-height-analysis measurements in tokamaks

International Nuclear Information System (INIS)

Sesnic, S.; Diesso, M.; Hill, K.; Holland, A.; Pohl, F.

1988-01-01

Because soft-x-ray pulse-height-analysis spectra contain chordal information, the electron temperature and the radiation intensity (enhancement factor) measurements do not represent the local values. The correction factors for the electron temperature and the enhancement factor as a function of the temperature and density profile parameters and the energy are obtained. The spectrum distortion due to pulse pileup effects is also evaluated. A set of curves is given from which the distortion of the spectrum can be obtained if the electron temperature, the Be filter thickness, and the electronic parameters of the acquisition system are known. PG 1810,1812 ID 131801CON N X-ray diagnostics TT Profile correction to electron temperature and enhancement factor in soft-x-ray pulse-height-analysis measurements in tokamaks AU S. Sesnic, M. Diesso, K. Hill, and A. Holland LO Princeton University, Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543 AU F. Pohl LO Max-Planck Institut fuer Plasmaphysik, 8046-Garching, Federal Republic of Germany SD (Presented on 16 March 1988) AB Because soft-x-ray pulse-height-analysis spectra contain chordal information, the electron temperature and the radiation intensity (enhancement factor) measurements do not represent the local values. The correction factors for the electron temperature and the enhancement factor as a function of the temperature and density profile parameters and the energy are obtained. The spectrum distortion due to pulse pileup effects is also evaluated. A set of curves is given from which the distortion of the spectrum can be obtained if the electron tempe

Design and implementation of a 3D-MR/CT geometric image distortion phantom/analysis system for stereotactic radiosurgery

Science.gov (United States)

Damyanovich, A. Z.; Rieker, M.; Zhang, B.; Bissonnette, J.-P.; Jaffray, D. A.

2018-04-01

The design, construction and application of a multimodality, 3D magnetic resonance/computed tomography (MR/CT) image distortion phantom and analysis system for stereotactic radiosurgery (SRS) is presented. The phantom is characterized by (1) a 1 × 1 × 1 (cm)3 MRI/CT-visible 3D-Cartesian grid; (2) 2002 grid vertices that are 3D-intersections of MR-/CT-visible ‘lines’ in all three orthogonal planes; (3) a 3D-grid that is MR-signal positive/CT-signal negative; (4) a vertex distribution sufficiently ‘dense’ to characterize geometrical parameters properly, and (5) a grid/vertex resolution consistent with SRS localization accuracy. When positioned correctly, successive 3D-vertex planes along any orthogonal axis of the phantom appear as 1 × 1 (cm)2-2D grids, whereas between vertex planes, images are defined by 1 × 1 (cm)2-2D arrays of signal points. Image distortion is evaluated using a centroid algorithm that automatically identifies the center of each 3D-intersection and then calculates the deviations dx, dy, dz and dr for each vertex point; the results are presented as a color-coded 2D or 3D distribution of deviations. The phantom components and 3D-grid are machined to sub-millimeter accuracy, making the device uniquely suited to SRS applications; as such, we present it here in a form adapted for use with a Leksell stereotactic frame. Imaging reproducibility was assessed via repeated phantom imaging across ten back-to-back scans; 80%–90% of the differences in vertex deviations dx, dy, dz and dr between successive 3 T MRI scans were found to be  ⩽0.05 mm for both axial and coronal acquisitions, and over  >95% of the differences were observed to be  ⩽0.05 mm for repeated CT scans, clearly demonstrating excellent reproducibility. Applications of the 3D-phantom/analysis system are presented, using a 32-month time-course assessment of image distortion/gradient stability and statistical control chart for 1.5 T and 3 T GE TwinSpeed MRI

Finite-Q22 Corrections to Parity-Violating DIS

International Nuclear Information System (INIS)

T. Hobbs; W. Melnitchouk

2008-01-01

Parity-violating deep inelastic scattering (PVDIS) has been proposed as an important new tool to extract the flavor and isospin dependence of parton distributions in the nucleon. We discuss finite-Q 2 effects in PVDIS asymmetries arising from subleading kinematical corrections and longitudinal contributions to the gamma Z interference. For the proton, these need to be accounted for when extracting the d/u ratio at large x. For the deuteron, the finite-Q 2 corrections can distort the effects of charge symmetry violation in parton distributions, or signals for physics beyond the standard model. We further explore the dependence of PVDIS asymmetries for polarized targets on the u and d helicity distributions at large x

A Cognitive Distortions and Deficits Model of Suicide Ideation

Directory of Open Access Journals (Sweden)

Laura L. Fazakas-DeHoog

2017-05-01

Full Text Available Although cognitive distortions and deficits are known risk factors for the development and escalation of suicide ideation and behaviour, no empirical work has examined how these variables interact to predict suicide ideation. The current study proposes an integrative model of cognitive distortions (hopelessness and negative evaluations of self and future and deficits (problem solving deficits, problem solving avoidance, and cognitive rigidity. To test the integrity of this model, a sample of 397 undergraduate students completed measures of deficits, distortions, and current suicide ideation. A structural equation model demonstrated excellent fit, and findings indicated that only distortions have a direct effect on suicidal thinking, whereas cognitive deficits may exert their effects on suicide ideation via their reciprocal relation with distortions. Findings underscore the importance of both cognitive distortions and deficits for understanding suicidality, which may have implications for preventative efforts and treatment.

Doping effects on structural and magnetic properties of Heusler alloys Fe2Cr1-xCoxSi

Science.gov (United States)

Liu, Yifan; Ren, Lizhu; Zheng, Yuhong; He, Shikun; Liu, Yang; Yang, Ping; Yang, Hyunsoo; Teo, Kie Leong

2018-05-01

In this work, 30nm Fe2Cr1-xCoxSi (FCCS) magnetic films were deposited on Cr buffered MgO (100) substrates by sputtering. Fe2Cr0.5Co0.5Si exhibits the largest magnetization and optimal ordered L21 cubic structure at in-situ annealing temperature (Tia) of 450°C. The Co composition dependence of crystalline structures, surface morphology, defects, lattice distortions and their correlation with the magnetic properties are analyzed in detail. The Co-doped samples show in-plane M-H loops with magnetic squareness ratio of 1 and increasing anisotropy energy density with Co composition. Appropriate Co doping composition promotes L21 phase but higher Co composition converts L21 to B2 phase. Doping effect and lattice mismatch both are proved to increase the defect density. In addition, distortions of the FCCS lattice are found to be approximately linear with Co composition. The largest lattice distortion (c/a) is 0.969 for Fe2Cr0.25Co0.75Si and the smallest is 0.983 for Fe2CrSi. Our analyses suggest that these tetragonal distortions mainly induced by an elastic stress from Cr buffer account for the large in-plane anisotropy energy. This work paves the way for further tailoring the magnetic and structural properties of quaternary Heusler alloys.

SU-E-J-209: Geometric Distortion at 3T in a Commercial 4D MRI-Compatible Phantom

International Nuclear Information System (INIS)

Fatemi-Ardekani, A; Wronski, M; Kim, A; Stanisz, G; Sarfehnia, A; Keller, B

2015-01-01

Purpose: There are very few commercial 4D phantoms that are marketed as MRI compatible. We are evaluating one such commercial phantom, made to be used with an MRI-Linear accelerator. The focus of this work is to characterize the geometric distortions produced in this phantom at 3T using 3 clinical MR pulse sequences. Methods: The CIRS MRI-Linac Dynamic Phantom (CIRSTM) under investigation in this study consists of a softwaredriven moving tumour volume within a thorax phantom body and enables dose accumulation by placing a dosimeter within the tumour volume. Our initial investigation is to evaluate the phantom in static mode prior to examining its 4D capability. The water-filled thorax phantom was scanned using a wide-bore Philips 3T Achieva MRI scanner employing a Thoracic xl coil and clinical 2D T1W FFE, 2D T1W TSE and 3D T1W TFE pulse sequences. Each of the MR image sets was rigidly fused with a reference CT image of the phantom employing a rigid registration with 6 degrees of freedom. Geometric distortions between the MR and CT image sets were measured in 3 dimensions at selected points along the periphery of the distortion grid embedded within the phantom body (11.5, 7.5 and 3 cm laterally, ant/post and sup/inf of magnetic isocenter respectively). Results: The maximal measured geometric distortions between the MR and reference CT points of interest were 0.9, 1.8 and 1.3 mm in the lateral, anteriorposterior and cranio-caudal directions, respectively. For all 3 spatial dimensions, the maximal distortions occurred for the FFE pulse sequence. Maximal distortions for the 2D FFE, 2D TSE and 3D TFE sequences were 1, 0.7 and 1.8 mm, respectively. Conclusion: Our initial static investigation of this phantom shows minimal geometric distortions at 3T along the periphery of the embedded grid. CIRS has provided us with a phantom at no charge for evaluation at 3 Tesla

Bilateral Symmetry of Distortions of Tactile Size Perception.

Science.gov (United States)

Longo, Matthew R; Ghosh, Arko; Yahya, Tasneem

2015-01-01

The perceived distance between touches on the limbs is generally bigger for distances oriented across the width of the limb than for distances oriented along the length of the limb. The present study aimed to investigate the coherence of such distortions of tactile size perception across different skin surfaces. We investigated distortions of tactile size perception on the dorsal and palmar surfaces of both the left and right hands as well as the forehead. Participants judged which of two tactile distances felt larger. One distance was aligned with the proximodistal axis (along the body), the other with the mediolateral axis (across the body). Clear distortions were found on all five skin surfaces, with stimuli oriented across the width of the body being perceived as farther apart than those oriented along the length of the body. Consistent with previous results, distortions were smaller on the palmar than on the dorsal hand surface. Distortion on the forehead was intermediate between the dorsal and palmar surfaces. There were clear correlations between distortion on the left and right hands, for both the dorsal and palmar skin surfaces. In contrast, within each hand, there was no significant correlation between the two skin surfaces. Distortion on the forehead was not significantly correlated with that on any of the other skin surfaces. These results provide evidence for bilaterally symmetric representations underlying tactile size perception. © The Author(s) 2015.

Thermodynamically constrained correction to ab initio equations of state

International Nuclear Information System (INIS)

French, Martin; Mattsson, Thomas R.

2014-01-01

We show how equations of state generated by density functional theory methods can be augmented to match experimental data without distorting the correct behavior in the high- and low-density limits. The technique is thermodynamically consistent and relies on knowledge of the density and bulk modulus at a reference state and an estimation of the critical density of the liquid phase. We apply the method to four materials representing different classes of solids: carbon, molybdenum, lithium, and lithium fluoride. It is demonstrated that the corrected equations of state for both the liquid and solid phases show a significantly reduced dependence of the exchange-correlation functional used.

Vision 20/20: Magnetic resonance imaging-guided attenuation correction in PET/MRI: Challenges, solutions, and opportunities

Energy Technology Data Exchange (ETDEWEB)

Mehranian, Abolfazl; Arabi, Hossein [Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva CH-1211 (Switzerland); Zaidi, Habib, E-mail: habib.zaidi@hcuge.ch [Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva CH-1211 (Switzerland); Geneva Neuroscience Centre, University of Geneva, Geneva CH-1205 (Switzerland); Department of Nuclear Medicine and Molecular Imaging, University of Groningen, Groningen 9700 RB (Netherlands)

2016-03-15

Attenuation correction is an essential component of the long chain of data correction techniques required to achieve the full potential of quantitative positron emission tomography (PET) imaging. The development of combined PET/magnetic resonance imaging (MRI) systems mandated the widespread interest in developing novel strategies for deriving accurate attenuation maps with the aim to improve the quantitative accuracy of these emerging hybrid imaging systems. The attenuation map in PET/MRI should ideally be derived from anatomical MR images; however, MRI intensities reflect proton density and relaxation time properties of biological tissues rather than their electron density and photon attenuation properties. Therefore, in contrast to PET/computed tomography, there is a lack of standardized global mapping between the intensities of MRI signal and linear attenuation coefficients at 511 keV. Moreover, in standard MRI sequences, bones and lung tissues do not produce measurable signals owing to their low proton density and short transverse relaxation times. MR images are also inevitably subject to artifacts that degrade their quality, thus compromising their applicability for the task of attenuation correction in PET/MRI. MRI-guided attenuation correction strategies can be classified in three broad categories: (i) segmentation-based approaches, (ii) atlas-registration and machine learning methods, and (iii) emission/transmission-based approaches. This paper summarizes past and current state-of-the-art developments and latest advances in PET/MRI attenuation correction. The advantages and drawbacks of each approach for addressing the challenges of MR-based attenuation correction are comprehensively described. The opportunities brought by both MRI and PET imaging modalities for deriving accurate attenuation maps and improving PET quantification will be elaborated. Future prospects and potential clinical applications of these techniques and their integration in commercial

Superconducting Accelerator Magnets

CERN Document Server

Mess, K H; Wolff, S

1996-01-01

The main topic of the book are the superconducting dipole and quadrupole magnets needed in high-energy accelerators and storage rings for protons, antiprotons or heavy ions. The basic principles of low-temperature superconductivity are outlined with special emphasis on the effects which are relevant for accelerator magnets. Properties and fabrication methods of practical superconductors are described. Analytical methods for field calculation and multipole expansion are presented for coils without and with iron yoke. The effect of yoke saturation and geometric distortions on field quality is studied. Persistent magnetization currents in the superconductor and eddy currents the copper part of the cable are analyzed in detail and their influence on field quality and magnet performance is investigated. Superconductor stability, quench origins and propagation and magnet protection are addressed. Some important concepts of accelerator physics are introduced which are needed to appreciate the demanding requirements ...

Spatial Distortion of Vibration Modes via Magnetic Correlation of Impurities

Science.gov (United States)

Krasniqi, F. S.; Zhong, Y.; Epp, S. W.; Foucar, L.; Trigo, M.; Chen, J.; Reis, D. A.; Wang, H. L.; Zhao, J. H.; Lemke, H. T.; Zhu, D.; Chollet, M.; Fritz, D. M.; Hartmann, R.; Englert, L.; Strüder, L.; Schlichting, I.; Ullrich, J.

2018-03-01

Long wavelength vibrational modes in the ferromagnetic semiconductor Ga0.91 Mn0.09 As are investigated using time resolved x-ray diffraction. At room temperature, we measure oscillations in the x-ray diffraction intensity corresponding to coherent vibrational modes with well-defined wavelengths. When the correlation of magnetic impurities sets in, we observe the transition of the lattice into a disordered state that does not support coherent modes at large wavelengths. Our measurements point toward a magnetically induced broadening of long wavelength vibrational modes in momentum space and their quasilocalization in the real space. More specifically, long wavelength vibrational modes cannot be assigned to a single wavelength but rather should be represented as a superposition of plane waves with different wavelengths. Our findings have strong implications for the phonon-related processes, especially carrier-phonon and phonon-phonon scattering, which govern the electrical conductivity and thermal management of semiconductor-based devices.

Magnetic chicane for terahertz management

Science.gov (United States)

Benson, Stephen; Biallas, George Herman; Douglas, David; Jordan, Kevin Carl; Neil, George R.; Michelle D. Shinn; Willams, Gwyn P.

2010-12-28

The introduction of a magnetic electron beam orbit chicane between the wiggler and the downstream initial bending dipole in an energy recovering Linac alleviates the effects of radiation propagated from the downstream bending dipole that tend to distort the proximate downstream mirror of the optical cavity resonator.

Study of the magnetic spectrograph BIG KARL on image errors and their causes

International Nuclear Information System (INIS)

Paul, D.

1987-12-01

The ionoptical aberrations of the QQDDQ spectrograph BIG KARL are measured and analyzed in order to improve resolution and transmission at large acceptance. The entrance phasespace is scanned in a cartesian grid by means of a narrow collimated beam of scattered deuterons. The distortions due to the nonlinear transformation by the system are measured in the detector plane. A model is developed which describes the measured distortions. The model allows to locate nonlinearities in the system responsible for the observed distortions. It gives a good understanding of geometrical nonlinearities up to the fifth order and chromatical nonlinearities up to the third order. To confirm the model, the magnetic field in the quadrupoles is measured including the fringe field region. Furthermore, nonlinearities appearing in ideal magnets are discussed and compared to experimental data. (orig.) [de

Systems and methods for mirror mounting with minimized distortion

Science.gov (United States)

Antonille, Scott R. (Inventor); Wallace, Thomas E. (Inventor); Content, David A. (Inventor); Wake, Shane W. (Inventor)

2012-01-01

A method for mounting a mirror for use in a telescope includes attaching the mirror to a plurality of adjustable mounts; determining a distortion in the mirror caused by the plurality adjustable mounts, and, if the distortion is determined to be above a predetermined level: adjusting one or more of the adjustable mounts; and determining the distortion in the mirror caused by the adjustable mounts; and in the event the determined distortion is determined to be at or below the predetermined level, rigidizing the adjustable mounts.

Simulation of Distortion and Residual Stress Development During Heat Treatment of Steel Castings

Energy Technology Data Exchange (ETDEWEB)

Beckermann, Christoph; Carlson, Kent

2011-07-22

Heat treatment and associated processing, such as quenching, are critical during high strength steel casting production. These processes must be managed closely to prevent thermal and residual stresses that may result in distortion, cracking (particularly after machining), re-work, and weld repair. The risk of casting distortion limits aggressive quenching that can be beneficial to the process and yield an improved outcome. As a result of these distortions, adjustments must be made to the casting or pattern design, or tie bars must be added. Straightening castings after heat treatments can be both time-consuming and expensive. Residual stresses may reduce a casting's overall service performance, possibly resulting in catastrophic failure. Stress relieving may help, but expends additional energy in the process. Casting software is very limited in predicting distortions during heat treatment, so corrective measures most often involve a tedious trial-and-error procedure. An extensive review of existing heat treatment residual stress and distortion modeling revealed that it is vital to predict the phase transformations and microstructure of the steel along with the thermal stress development during heat treatment. After reviewing the state-of-the-art in heat treatment residual stress and distortion modeling, an existing commercial code was selected because of its advanced capabilities in predicting phase transformations, the evolving microstructure and related properties along with thermal stress development during heat treatment. However, this software was developed for small parts created from forgings or machined stock, and not for steel castings. Therefore, its predictive capabilities for heat treatment of steel castings were investigated. Available experimental steel casting heat treatment data was determined to be of insufficient detail and breadth, and so new heat treatment experiments were designed and performed, casting and heat treating modified versions

Modelling the Perceptual Components of Loudspeaker Distortion

DEFF Research Database (Denmark)

Olsen, Sune L.; Agerkvist, Finn T.; MacDonald, Ewen

2016-01-01

While non-linear distortion in loudspeakers decreases audio quality, the perceptual consequences can vary substantially. This paper investigates the metric Rnonlin [1] which was developed to predict subjective measurements of sound quality in nonlinear systems. The generalisability of the metric...... the perceptual consequences of non-linear distortion....

Off-shell distortions of multichannel atomic processes

Science.gov (United States)

Barrachina, R. O.; Clauser, C. F.

2017-10-01

Any multichannel problem can be reduced to a succession of two-body events. However, these basic building blocks of many-body theories do not correspond to elastic processes but are off-the-energy-shell. In view of this difficulty, the great majority of the Distorted-Wave models includes a subsidiary approximation where these off-shell terms are arbitrarily forced to lie on the energy shell. At a first glance, since the energy deficiency is negligible for high enough velocities, the on-shell assumption seems to be completely justified. However, for the case of Coulomb interactions, the two-body off-shell distortions have branch-point singularities on the on-shell limit. In this article we demonstrate that these singularities might produce sizeable distortions of multiple scattering amplitudes, mainly when dealing with ion-ion collisions. Finally, we propose a method of including these distortions that might lead to better results that removing them completely.

Attenuation correction for SPECT

International Nuclear Information System (INIS)

Hosoba, Minoru

1986-01-01

Attenuation correction is required for the reconstruction of a quantitative SPECT image. A new method for detecting body contours, which are important for the correction of tissue attenuation, is presented. The effect of body contours, detected by the newly developed method, on the reconstructed images was evaluated using various techniques for attenuation correction. The count rates in the specified region of interest in the phantom image by the Radial Post Correction (RPC) method, the Weighted Back Projection (WBP) method, Chang's method were strongly affected by the accuracy of the contours, as compared to those by Sorenson's method. To evaluate the effect of non-uniform attenuators on the cardiac SPECT, computer simulation experiments were performed using two types of models, the uniform attenuator model (UAM) and the non-uniform attenuator model (NUAM). The RPC method showed the lowest relative percent error (%ERROR) in UAM (11 %). However, 20 to 30 percent increase in %ERROR was observed for NUAM reconstructed with the RPC, WBP, and Chang's methods. Introducing an average attenuation coefficient (0.12/cm for Tc-99m and 0.14/cm for Tl-201) in the RPC method decreased %ERROR to the levels for UAM. Finally, a comparison between images, which were obtained by 180 deg and 360 deg scans and reconstructed from the RPC method, showed that the degree of the distortion of the contour of the simulated ventricles in the 180 deg scan was 15 % higher than that in the 360 deg scan. (Namekawa, K.)

Modeling Kinetics of Distortion in Porous Bi-layered Structures

DEFF Research Database (Denmark)

Tadesse Molla, Tesfaye; Frandsen, Henrik Lund; Bjørk, Rasmus

2013-01-01

because of different sintering rates of the materials resulting in undesired distortions of the component. An analytical model based on the continuum theory of sintering has been developed to describe the kinetics of densification and distortion in the sintering processes. A new approach is used...... to extract the material parameters controlling shape distortion through optimizing the model to experimental data of free shrinkage strains. The significant influence of weight of the sample (gravity) on the kinetics of distortion is taken in to consideration. The modeling predictions indicate good agreement...

Harmonic distortion in microwave photonic filters.

Science.gov (United States)

Rius, Manuel; Mora, José; Bolea, Mario; Capmany, José

2012-04-09

We present a theoretical and experimental analysis of nonlinear microwave photonic filters. Far from the conventional condition of low modulation index commonly used to neglect high-order terms, we have analyzed the harmonic distortion involved in microwave photonic structures with periodic and non-periodic frequency responses. We show that it is possible to design microwave photonic filters with reduced harmonic distortion and high linearity even under large signal operation.

CMB spectral distortions as solutions to the Boltzmann equations

Energy Technology Data Exchange (ETDEWEB)

Ota, Atsuhisa, E-mail: a.ota@th.phys.titech.ac.jp [Department of Physics, Tokyo Institute of Technology, Tokyo 152-8551 (Japan)

2017-01-01

We propose to re-interpret the cosmic microwave background spectral distortions as solutions to the Boltzmann equation. This approach makes it possible to solve the second order Boltzmann equation explicitly, with the spectral y distortion and the momentum independent second order temperature perturbation, while generation of μ distortion cannot be explained even at second order in this framework. We also extend our method to higher order Boltzmann equations systematically and find new type spectral distortions, assuming that the collision term is linear in the photon distribution functions, namely, in the Thomson scattering limit. As an example, we concretely construct solutions to the cubic order Boltzmann equation and show that the equations are closed with additional three parameters composed of a cubic order temperature perturbation and two cubic order spectral distortions. The linear Sunyaev-Zel'dovich effect whose momentum dependence is different from the usual y distortion is also discussed in the presence of the next leading order Kompaneets terms, and we show that higher order spectral distortions are also generated as a result of the diffusion process in a framework of higher order Boltzmann equations. The method may be applicable to a wider class of problems and has potential to give a general prescription to non-equilibrium physics.

Correction of Magnetic Optics and Beam Trajectory Using LOCO Based Algorithm with Expanded Experimental Data Sets

Energy Technology Data Exchange (ETDEWEB)

Romanov, A.; Edstrom, D.; Emanov, F. A.; Koop, I. A.; Perevedentsev, E. A.; Rogovsky, Yu. A.; Shwartz, D. B.; Valishev, A.

2017-03-28

Precise beam based measurement and correction of magnetic optics is essential for the successful operation of accelerators. The LOCO algorithm is a proven and reliable tool, which in some situations can be improved by using a broader class of experimental data. The standard data sets for LOCO include the closed orbit responses to dipole corrector variation, dispersion, and betatron tunes. This paper discusses the benefits from augmenting the data with four additional classes of experimental data: the beam shape measured with beam profile monitors; responses of closed orbit bumps to focusing field variations; betatron tune responses to focusing field variations; BPM-to-BPM betatron phase advances and beta functions in BPMs from turn-by-turn coordinates of kicked beam. All of the described features were implemented in the Sixdsimulation software that was used to correct the optics of the VEPP-2000 collider, the VEPP-5 injector booster ring, and the FAST linac.

Distortional solutions for loaded semi-discretized thin-walled beams

DEFF Research Database (Denmark)

Andreassen, Michael Joachim; Jönsson, Jeppe

2012-01-01

distortional displacement fields which decouple the reduced order differential equations. In this process the cross section is discretized into finite cross-section elements, and the natural distortional modes as well as the related axial variations are found as solutions to the established coupled fourth...... order homogeneous differential equations of GBT.In this paper the non-homogeneous distortional differential equations of GBT are formulated using this novel semi-discretization process. Transforming these non-homogeneous distortional differential equations into the natural eigenmode space by using...... the distortional modal matrix found for the homogeneous system, we get the uncoupled set of differential equations including the distributed loads. This uncoupling is very important in GBT, since the shear stiffness contribution from St. Venant torsional shear stress as well as “Bredt's shear flow” cannot...

Lattice shear distortions in fluorite structure oxides

International Nuclear Information System (INIS)

Faber, J. Jr.; Mueller, M.H.; Hitterman, R.L.

1979-01-01

Crystallographic shear distortions have been observed in fluorite structure, single crystals of UO 2 and Zr(Ca)O 2 /sub-x/ by neutron-diffraction techniques. These distortions localize on the oxygen sublattice and do not require the presence of an external strain. The internal rearrangement mode in UO 2 is a transverse, zone boundary q vector = 2π/a (0.5, 0.0) deformation with amplitude 0.014 A. In Zr(Ca)O/sub 2-x/, the mode is a longitudinal, q vector = 2-/a (0,0,0.5) deformation with amplitude 0.23 A. Cation-anion elastic interactions dominate in selecting the nature of the internal distortion

Analysis and optimization of hybrid excitation permanent magnet synchronous generator for stand-alone power system

Energy Technology Data Exchange (ETDEWEB)

Wang, Huijun, E-mail: huijun024@gmail.com [School of Instrumentation Science and Opto-electronics Engineering, Beihang University (China); Qu, Zheng; Tang, Shaofei; Pang, Mingqi [School of Instrumentation Science and Opto-electronics Engineering, Beihang University (China); Zhang, Mingju [Shanghai Aerospace Control Technology Institute, Shanghai (China)

2017-08-15

Highlights: • One novel permanent magnet generator structure has been proposed to reduce voltage regulation ratio. • Finite element method and equivalent circuit methods are both employed to realize rapid generator design. • Design of experiment (DOE) method is used to optimize permanent magnet shape for reduce voltage waveform distortion. • The obtained analysis and experiment results verify the proposed design methods. - Abstract: In this paper, electromagnetic design and permanent magnet shape optimization for permanent magnet synchronous generator with hybrid excitation are investigated. Based on generator structure and principle, design outline is presented for obtaining high efficiency and low voltage fluctuation. In order to realize rapid design, equivalent magnetic circuits for permanent magnet and iron poles are developed. At the same time, finite element analysis is employed. Furthermore, by means of design of experiment (DOE) method, permanent magnet is optimized to reduce voltage waveform distortion. Finally, the validity of proposed design methods is validated by the analytical and experimental results.

Analysis and optimization of hybrid excitation permanent magnet synchronous generator for stand-alone power system

International Nuclear Information System (INIS)

Wang, Huijun; Qu, Zheng; Tang, Shaofei; Pang, Mingqi; Zhang, Mingju

2017-01-01

Highlights: • One novel permanent magnet generator structure has been proposed to reduce voltage regulation ratio. • Finite element method and equivalent circuit methods are both employed to realize rapid generator design. • Design of experiment (DOE) method is used to optimize permanent magnet shape for reduce voltage waveform distortion. • The obtained analysis and experiment results verify the proposed design methods. - Abstract: In this paper, electromagnetic design and permanent magnet shape optimization for permanent magnet synchronous generator with hybrid excitation are investigated. Based on generator structure and principle, design outline is presented for obtaining high efficiency and low voltage fluctuation. In order to realize rapid design, equivalent magnetic circuits for permanent magnet and iron poles are developed. At the same time, finite element analysis is employed. Furthermore, by means of design of experiment (DOE) method, permanent magnet is optimized to reduce voltage waveform distortion. Finally, the validity of proposed design methods is validated by the analytical and experimental results.

Passive correction of persistent current multipoles in superconducting accelerator dipoles

International Nuclear Information System (INIS)

Fisk, H.E.; Hanft, R.A.; Kuchnir, M.; McInturff, A.D.

1986-07-01

Correction of the magnetization sextupole and decapole fields with strips of superconductor placed just inside the coil winding is discussed. Calculations have been carried out for such a scheme, and tests have been conducted on a 4 cm aperture magnet. The calculated sextupole correction at the injection excitation of 330 A, 5% of full field, was expected to be 77% effective, while the measured correction is 83%, thus suggesting the scheme may be useful for future accelerators such as SSC and LHC

Coulomb Distortion in the Inelastic Regime

Energy Technology Data Exchange (ETDEWEB)

Patricia Solvignon, Dave Gaskell, John Arrington

2009-09-01

The Coulomb distortion effects have been for a long time neglected in deep inelastic scattering for the good reason that the incident energies were very high. But for energies in the range of earlier data from SLAC or at JLab, the Coulomb distortion could have the potential consequence of affecting the A-dependence of the EMC effect and of the longitudinal to transverse virtual photon absorption cross section ratio $R(x,Q^2)$.

Compensation of the ux modulation distortion using an additional coil in a loudspeaker unit

DEFF Research Database (Denmark)

Antonello, Niccoló; Agerkvist, Finn T.

2014-01-01

Flux modulation is one of the main causes of distortion in electrodynamic loudspeaker units. A new com- pensation technique that eliminates this type of non-linearity using an additional compensation coil in the speaker unit is presented. An equivalent circuit model of the device including...... the compensation coil is de- rived. The compensation technique consists on feeding the compensation coil and voice coil with ltered versions of the wanted audio signal. Simulations show that a signicant reduction in ux modulation distor- tion can be achieved with this technique. A simple magnetic circuit has been...

Studies for a silicon telescope to extend the magnet facility at the DESY test beam

Energy Technology Data Exchange (ETDEWEB)

Tsionou, Dimitra [Deutsches Elektronen-Synchrotron (DESY), Notkestrasse 85, 22607 Hamburg (Germany)

2016-07-01

The International Large Detector is a detector concept for the International Linear Collider (ILC) which uses a Time Projection Chamber (TPC) as its main tracking detector. Within the framework of the LCTPC collaboration, a large prototype (LP) TPC has been built as a demonstrator. The LP has been equipped with Micro-Pattern Gas Detector modules and studied with an electron beam (1-6 GeV) in a 1 Tesla magnetic field at DESY. To extend the capabilities of the test beam setup, an external silicon tracker to be installed inside the magnet will be discussed. The silicon detector will provide high precision space points in front and behind the TPC inside the magnet. It will provide reference tracks that will allow to determine the momentum of the tracks passing the TPC, and which will help in correcting for field distortion effects in the LPTPC volume. In order to meet these requirements, simulation studies have been performed to determine the layout of the system and have placed stringent requirements on the sensor spatial resolution of better than 10 μ m. These studies will be presented along with the hardware options under evaluation.

Field correction for a one meter long permanent-magnet wiggler

International Nuclear Information System (INIS)

Fortgang, C.M.

1992-01-01

Field errors in wigglers are usually measured and corrected on-axis only, thus ignoring field error gradients. We find that gradient scale lengths are of the same order as electron beam size and therefore can be important. We report measurements of wiggler field errors in three dimensions and expansion of these errors out to first order (including two dipole and two quadrupole components). Conventional techniques for correcting on-axis errors (order zero) create new off-axis (first order) errors. We present a new approach to correcting wiggler fields out to first order. By correcting quadrupole errors in addition to the usual dipole correction, we minimize growth in electron beam size. Correction to first order yields better overlap between the electron and optical beams and should improve laser gain. (Author) 2 refs., 5 figs

COD correction for laser cooling at S-LSR

International Nuclear Information System (INIS)

Souda, Hikaru; Fujimoto, Shinji; Tongu, Hiromu; Shirai, Toshiyuki; Tanabe, Mikio; Ishikawa, Takehiro; Nakao, Masao; Ikegami, Masahiro; Wakita, Akihisa; Iwata, Soma; Fujimoto, Tetsuya; Takeuchi, Takeshi; Noda, Koji; Noda, Akira

2008-01-01

A closed orbit is corrected for single-turn injection to perform laser cooling experiments of 40 keV 24 Mg + beam at the small laser-equipped storage ring (S-LSR). Closed orbit distortion (COD) corrections have been carried out using a downhill simplex method, and CODs of less than ±0.5mm have been achieved throughout the whole circumference. The injection orbit and the CODs are optimized to pass through the two aperture holes in the alignment targets located in the laser cooling section with an algorithm to maximize beam lifetime. The CODs at the aperture holes are reduced to be less than ±0.2mm, assuring an overlap between the laser and the 24 Mg + ion beam.

Tactile sensor of hardness recognition based on magnetic anomaly detection

Science.gov (United States)

Xue, Lingyun; Zhang, Dongfang; Chen, Qingguang; Rao, Huanle; Xu, Ping

2018-03-01

Hardness, as one kind of tactile sensing, plays an important role in the field of intelligent robot application such as gripping, agricultural harvesting, prosthetic hand and so on. Recently, with the rapid development of magnetic field sensing technology with high performance, a number of magnetic sensors have been developed for intelligent application. The tunnel Magnetoresistance(TMR) based on magnetoresistance principal works as the sensitive element to detect the magnetic field and it has proven its excellent ability of weak magnetic detection. In the paper, a new method based on magnetic anomaly detection was proposed to detect the hardness in the tactile way. The sensor is composed of elastic body, ferrous probe, TMR element, permanent magnet. When the elastic body embedded with ferrous probe touches the object under the certain size of force, deformation of elastic body will produce. Correspondingly, the ferrous probe will be forced to displace and the background magnetic field will be distorted. The distorted magnetic field was detected by TMR elements and the output signal at different time can be sampled. The slope of magnetic signal with the sampling time is different for object with different hardness. The result indicated that the magnetic anomaly sensor can recognize the hardness rapidly within 150ms after the tactile moment. The hardness sensor based on magnetic anomaly detection principal proposed in the paper has the advantages of simple structure, low cost, rapid response and it has shown great application potential in the field of intelligent robot.

Correcting for static shift of magnetotelluric data with airborne electromagnetic measurements: a case study from Rathlin Basin, Northern Ireland

Directory of Open Access Journals (Sweden)

R. Delhaye

2017-05-01

Full Text Available Galvanic distortions of magnetotelluric (MT data, such as the static-shift effect, are a known problem that can lead to incorrect estimation of resistivities and erroneous modelling of geometries with resulting misinterpretation of subsurface electrical resistivity structure. A wide variety of approaches have been proposed to account for these galvanic distortions, some depending on the target area, with varying degrees of success. The natural laboratory for our study is a hydraulically permeable volume of conductive sediment at depth, the internal resistivity structure of which can be used to estimate reservoir viability for geothermal purposes; however, static-shift correction is required in order to ensure robust and precise modelling accuracy.We present here a possible method to employ frequency–domain electromagnetic data in order to correct static-shift effects, illustrated by a case study from Northern Ireland. In our survey area, airborne frequency domain electromagnetic (FDEM data are regionally available with high spatial density. The spatial distributions of the derived static-shift corrections are analysed and applied to the uncorrected MT data prior to inversion. Two comparative inversion models are derived, one with and one without static-shift corrections, with instructive results. As expected from the one-dimensional analogy of static-shift correction, at shallow model depths, where the structure is controlled by a single local MT site, the correction of static-shift effects leads to vertical scaling of resistivity–thickness products in the model, with the corrected model showing improved correlation to existing borehole wireline resistivity data. In turn, as these vertical scalings are effectively independent of adjacent sites, lateral resistivity distributions are also affected, with up to half a decade of resistivity variation between the models estimated at depths down to 2000 m. Simple estimation of differences in bulk