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Given the difficulty of explaining the unwrapping process through traditional teaching methodologies, this article presents the design, development, and validation of an immersive Virtual Reality (VR) serious game, named Unwrap 3D Virtual: Ready (UVR), aimed at facilitating the learning of unwrapping 3D models. The game incorporates animations to aid users in understanding the unwrapping process, following Mayer's Cognitive Theory of Multimedia Learning and Gamification principles. Structured into four levels of increasing complexity, users progress through different aspects of 3D model unwrapping, with the final level allowing for result review. A sample of 53 students with experience in 3D modeling was categorized based on device (PC or VR) and previous experience (XP) in VR, resulting in Low-XP, Mid-XP, and High-XP groups. Hierarchical clustering identified three clusters, reflecting varied user behaviors. Results from surveys assessing game experience, presence, and satisfaction show higher immersion reported by VR users despite greater satisfaction being observed in the PC group due to a bug in the VR version. Novice users exhibited higher satisfaction, which was attributed to the novelty effect, while experienced users demonstrated greater control and proficiency. [ABSTRACT FROM AUTHOR]

This brief article gathers several improvements to the LiCSBAS, an open-source python-based InSAR time series tool developed by the COMET UK group, focusing on improving quality of unwrapped interferograms that are the input to the time series inversion, therefore their quality is crucial. We add functionality of full re-unwrapping of the original wrapped interferograms using a procedure controlled by several key parameters. We then check the residuals of phase loop closure residuals and either nullify pixels in interferograms that probably contain unwrapping error, or attempt to correct the errors within connected components or pixel-wise using some basic assumptions, such as the minimal residue of the unwrapped data from a preliminary model estimate (whole time series velocity) is correct. All these approaches find their importance in different case studies and will be part of the next version of LiCSBAS. [ABSTRACT FROM AUTHOR]

This paper presents an innovative algorithm for unwrapping 2D phase maps with discontinuities. The method employs residue detection for identifying affected areas at a coarse scale. Unlike traditional techniques relying on subjective assessment, this algorithm automates threshold determination, ensuring precision without manual intervention. At the pixel level, it utilizes a bitmap mask based on second differences and the geometric mean formula to locate inconsistencies within the wrapped map precisely. This coarse-to-fine process establishes an optimal threshold for the second difference mask, resulting in highly accurate unwrapped outcomes while maintaining computational efficiency. Compared to conventional methods, this approach delivers superior unwrapped results, making it suitable for diverse applications. Experimental validation includes computer-simulated surfaces and practical fringe projection systems, accompanied by a thorough error analysis. [ABSTRACT FROM AUTHOR]

Interferometric synthetic aperture radar (InSAR) has been successfully used to map ground displacements associate with landslides. One challenge with InSAR is that the basic measurement of interferometric phase takes values between 0 and 2π instead of values representing total displacement relative to a stable reference frame. Phase unwrapping is necessary to reconstruct measurements of total displacement for use in quantitative analysis. Unwrapping approaches often assume that the absolute phase difference between two neighboring pixels should be smaller than π. In the presence of noise or high‐strain rates associated with fast‐moving landslides, aliasing of the phase (undersampling of the wrapped signal) can result in unwrapping errors and misinterpretation of total displacement. Here we use a pattern‐based strategy for phase unwrapping of InSAR observations of fast‐moving landslides, where we determine the unwrapped deformation field that is most similar to a scaled reference displacement map. We describe a range of metrics that we use to evaluate the most appropriate scaling for each interferogram. We also demonstrate the range of conditions where they perform well using synthetic data. For evaluation of the results, we generated UAVSAR wrapped interferograms over the Slumgullion landslide in Colorado where phase aliasing for interferograms with temporal baselines larger than 7 days is common. We compare the interferograms unwrapped with our approach against results from range offsets (pixel tracking). The comparison demonstrates that our approach can be used for time spans much larger than those where traditional phase unwrapping performs well. Plain Language Summary: InSAR allows measurement of surface displacement due to earthquakes, landslides, etc. However, InSAR requires a step known as "unwrapping" to convert the raw observations into quantitative measurements of displacement. Most unwrapping methods assume some degree of spatial and/or temporal continuity within the signal. In the presence of high‐strain rates, such as those observed on fast‐moving landslides, these unwrapping approaches are not reliable. We use a pattern‐based strategy for InSAR phase unwrapping that seeks the final model that best fits a scaled initial estimate of the deformation signal. We demonstrate this approach using synthetic data and UAVSAR observations over the Slumgullion landslide in Colorado, which has a displacement rate of up to 2 cm/day. With such a fast displacement rate, InSAR observations that span more than 7 days contain so much deformation that traditional unwrapping approaches almost always fail. We show that our approach can reliably unwrap interferograms spanning much larger time intervals and validate these results with independent measures of the displacement between each pair of images. Key Points: Here we use a pattern‐based approach for phase unwrapping of Interferometric synthetic aperture radar (InSAR) observations of fast‐moving landslidesWe define a similarity index and an error function to determine the most similar unwrapped phase to a scaled reference displacement mapWe show that our approach can be used for time spans much larger than those where traditional phase unwrapping performs well [ABSTRACT FROM AUTHOR]

Curators have developed preventive conservation strategies and usually try to control the temperature (T) and relative humidity (RH) variations in the museum rooms to stabilise the artworks. The control systems chosen by museums depend on the size and age of the building, the financial means and the strategies that can be adapted. However, there is a lack of methods that can monitor mechanical changes or chemical reactions of objects in real-time or regularly. It would therefore ideally be preferable to monitor each of them to alert them to preserve them. For this purpose, a non-destructive, non-contact, full-field technique, Digital Holographic Speckle Pattern Interferometry (DHSPI), has already been developed and allows direct tracking of changes on the surface of artworks. This technique is based on phase-shifting speckle interferometry and gives the deformation of the surface below the level of the micro-meter of the analysed object. In order to monitor the deformation continuously, a large number of images are acquired by DHSPI and have to be processed. The existing process consists of removing noise from the interferogram, unwrapping this image, and deriving and displaying a 2D or 3D deformation map. In order to improve the time and accuracy of processing the imaging data, a simpler and faster processing method is developed. Using Matlab®, a denoising methodology for the interference pattern generated during data acquisition is created, based on a stationary wavelet transform. The unwrapped image is calculated using the CPULSI (Calibrated Phase Unwrapping based on Least-Squares and Iterations) algorithm as it gives the fastest results among the tested methods. The unwrapped phase is then transformed into surface displacement. This process performs these steps for each interferogram automatically. It allows access to 2D or 3D deformation maps. [ABSTRACT FROM AUTHOR]

Quality assessment is one of the most common processes in the agri-food industry. Typically, this task involves the analysis of multiple views of the fruit. Generally speaking, analyzing these single views is a highly time-consuming operation. Moreover, there is usually significant overlap between consecutive views, so it might be necessary to provide a mechanism to cope with the redundancy and prevent the multiple counting of defect points. This paper presents a method to create surface maps of fruit from collections of views obtained when the piece is rotating. This single image map combines the information contained in the views, thus reducing the number of analysis operations and avoiding possible miscounts in the number of defects. After assigning each piece with a simple geometrical model, 3D rotation between consecutive views is estimated only from the captured images, without any further need for sensors or information about the conveyor. The fact that rotation is estimated directly from the views makes this novel methodology readily usable in high-throughput industrial inspection machines without any special hardware modification. As proof of this technique's usefulness, an application is shown where maps have been used as input to a CNN to classify oranges into different categories. [ABSTRACT FROM AUTHOR]

Quantitative susceptibility mapping (QSM) has gained broad interest in the field by extracting bulk tissue magnetic susceptibility, predominantly determined by myelin, iron and calcium from magnetic resonance imaging (MRI) phase measurements in vivo. Thereby, QSM can reveal pathological changes of these key components in a variety of diseases. QSM requires multiple processing steps such as phase unwrapping, background field removal and field‐to‐source inversion. Current state‐of‐the‐art techniques utilize iterative optimization procedures to solve the inversion and background field correction, which are computationally expensive and require a careful choice of regularization parameters. With the recent success of deep learning using convolutional neural networks for solving ill‐posed reconstruction problems, the QSM community also adapted these techniques and demonstrated that the QSM processing steps can be solved by efficient feed forward multiplications not requiring either iterative optimization or the choice of regularization parameters. Here, we review the current status of deep learning‐based approaches for processing QSM, highlighting limitations and potential pitfalls, and discuss the future directions the field may take to exploit the latest advances in deep learning for QSM. [ABSTRACT FROM AUTHOR]

Millimeter-wave radar interferometry is superior in detecting small displacement motions owing to its short wavelength. However, it is subject to phase ambiguity as the target displacement may often exceed a quarter wavelength. In this article, a modified differentiate and cross-multiply (MDACM) technique is proposed to tackle the phase ambiguity issue for accurate reconstruction of the phase history in millimeter-wave interferometry. In addition, to resolve the imperfections of the interferometric radar system, an MDACM-based integral phase reconstruction approach is presented, which seamlessly integrates alternating current (ac)-coupling-induced distortion correction, $I/Q$ mismatch correction, and direct current (dc) offsets’ calibration. Without causing any phase ambiguity, the proposed technique acts as a black box to take in the raw $I/Q$ signals and correct all the hardware imperfections, and it outputs the desired displacement motions with micrometer accuracy. The simulation results show that the proposed technique can not only linearly recover the displacement motions across a wide range in different noise conditions without any phase ambiguity but also improve the stability by 11 times under ac-coupling-induced distortion. With a custom-designed 120-GHz interferometric radar sensor, experiments were carried out to validate various scenarios including mechanical vibrations and gesture sensing. The experimental results show that the proposed technique can accurately track not only deep subwavelength motion of only $1~\mu \text{m}$ but also multiwavelength displacement of >40 times of the wavelength at 120 GHz. [ABSTRACT FROM AUTHOR]

Curators have developed preventive conservation strategies and usually try to control the temperature (T) and relative humidity (RH) variations in the museum rooms to stabilise the artworks. The control systems chosen by museums depend on the size and age of the building, the financial means and the strategies that can be adapted. However, there is a lack of methods that can monitor mechanical changes or chemical reactions of objects in real-time or regularly. It would therefore ideally be preferable to monitor each of them to alert them to preserve them. For this purpose, a non-destructive, non-contact, full-field technique, Digital Holographic Speckle Pattern Interferometry (DHSPI), has already been developed and allows direct tracking of changes on the surface of artworks. This technique is based on phase-shifting speckle interferometry and gives the deformation of the surface below the level of the micro-meter of the analysed object. In order to monitor the deformation continuously, a large number of images are acquired by DHSPI and have to be processed. The existing process consists of removing noise from the interferogram, unwrapping this image, and deriving and displaying a 2D or 3D deformation map. In order to improve the time and accuracy of processing the imaging data, a simpler and faster processing method is developed. Using Matlab®, a denoising methodology for the interference pattern generated during data acquisition is created, based on a stationary wavelet transform. The unwrapped image is calculated using the CPULSI (Calibrated Phase Unwrapping based on Least-Squares and Iterations) algorithm as it gives the fastest results among the tested methods. The unwrapped phase is then transformed into surface displacement. This process performs these steps for each interferogram automatically. It allows access to 2D or 3D deformation maps.

Quality assessment is one of the most common processes in the agri-food industry. Typically, this task involves the analysis of multiple views of the fruit. Generally speaking, analyzing these single views is a highly time-consuming operation. Moreover, there is usually significant overlap between consecutive views, so it might be necessary to provide a mechanism to cope with the redundancy and prevent the multiple counting of defect points. This paper presents a method to create surface maps of fruit from collections of views obtained when the piece is rotating. This single image map combines the information contained in the views, thus reducing the number of analysis operations and avoiding possible miscounts in the number of defects. After assigning each piece with a simple geometrical model, 3D rotation between consecutive views is estimated only from the captured images, without any further need for sensors or information about the conveyor. The fact that rotation is estimated directly from the views makes this novel methodology readily usable in high-throughput industrial inspection machines without any special hardware modification. As proof of this technique’s usefulness, an application is shown where maps have been used as input to a CNN to classify oranges into different categories.

Torsional stress has a significant impact on the structure and stability of the nucleosome. RNA polymerase imposes torsional stress on the DNA in chromatin and unwraps the DNA from the nucleosome to access the genetic information encoded in the DNA. To understand how the torsional stress affects the stability of the nucleosome, we examined the unwrapping of two half superhelical turns of nucleosomal DNA from either end of the DNA under torsional stress with all-atom molecular dynamics simulations. The free energies for unwrapping the DNA indicate that positive stress that overtwists DNA facilitates a large-scale asymmetric unwrapping of the DNA without a large extension of the DNA. During the unwrapping, one end of the DNA was dissociated from H3 and H2A-H2B, while the other end of the DNA stably remained wrapped. The detailed analysis indicates that this asymmetric dissociation is facilitated by the geometry and bendability of the DNA under positive stress. The geometry stabilized the interaction between the major groove of the twisted DNA and the H3 aN-helix, and the straightened DNA destabilized the interaction with H2AH2B. Under negative stress, the DNA became more bendable and flexible, which facilitated the binding of the unwrapped DNA to the octamer in a stable state. Consequently, we conclude that the torsional stress has a significant impact on the affinity of the DNA and the octamer through the inherent nature of the DNA and can change the accessibility of regulatory proteins. [ABSTRACT FROM AUTHOR]

There has been increasing interest in statistical analysis of data lying in manifolds. This paper generalizes a smoothing spline fitting method to Riemannian manifold data based on the technique of unrolling, unwrapping and wrapping originally proposed by Jupp and Kent for spherical data. In particular, we develop such a fitting procedure for shapes of configurations in general m‐dimensional Euclidean space, extending our previous work for two‐dimensional shapes. We show that parallel transport along a geodesic on Kendall shape space is linked to the solution of a homogeneous first‐order differential equation, some of whose coefficients are implicitly defined functions. This finding enables us to approximate the procedure of unrolling and unwrapping by simultaneously solving such equations numerically, and so to find numerical solutions for smoothing splines fitted to higher dimensional shape data. This fitting method is applied to the analysis of some dynamic 3D peptide data. [ABSTRACT FROM AUTHOR]

Eukaryotic genome is packaged in a nucleus in the form of chromatin. The fundamental structural unit of the chromatin is the protein-DNA complex, nucleosome, where DNA of about 150 bp is wrapped around a histone core almost twice. In cellular processes such as gene expression, DNA repair and duplication, the nucleosomal DNA has to be unwrapped. Histone proteins have their variants, indicating there are a variety of constitutions of nucleosomes. These different constitutions are observed in different cellular processes. To investigate differences among nucleosomes, we calculated free energy profiles for unwrapping the outer superhelical turn of CENP-A nucleosome and compared them with those of the canonical nucleosome. The free energy profiles for CENP-A nucleosome suggest that CENP-A nucleosome is the most stable when 16 to 22 bps are unwrapped in total whereas the canonical nucleosome is the most stable when it is fully wrapped. This indicates that the flexible conformation of CENP-A nucleosome is ready to provide binding sites for the structural integrity of the centromere.

Dual-VENC strategies have been proposed to improve the velocity-to-noise ratio in phase-contrast MRI. However, they are based on aliasing-free high-VENC data. The aim of this paper is to propose a dual-VENC velocity estimation method allowing high-VENC aliased data. For this purpose, we reformulate the phase-contrast velocity as a least squares estimator, providing a natural framework for including multiple encoding gradient measurements. By analyzing the mathematical properties of both single- and dual-VENC problems, we can justify theoretically high/low-VENC ratios such that the aliasing velocity can be minimized. The resulting reconstruction algorithm was assessed using three types of data: numerical, experimental, and volunteers. In clinical practice, this method would allow shorter examination times by avoiding tedious adaptation of VENC values by repeated scans. [ABSTRACT FROM AUTHOR]

Use of a color code to identify fringe orders has been in use in conventional photoelasticity. Phase shifting technology is the most widely used for isochromatic evaluation due to its simplicity and accuracy. The phase shifting method obtain isochromatic only in a wrapped form. On the one hand the colors tend to merge beyond fringe order three in white light photoelasticity,and on the other phase unwrapping is a challenging issue. Due to the fact that the isochromatic fringes are continuously varying in fringe patterns,the white light photoelasticity and the phase shifting technique are adapted to determine the isochromatic fringe orders. The advantage of new approach allows for determination of isochromatic fringe orders regardless whether the zero-order fringe is present or not. Experimental demonstration was performed on a disc under compressive loading.

Efficient and optimal design of radar-based Advanced Driver Assistant Systems (ADAS) needs the evaluation of many different electromagnetic solutions for evaluating the impact of the radome on the electromagnetic wave propagation. Because of the very high frequency at which these devices operate, with the associated extremely small wavelength, very fine meshes are needed to accurately discretize the electromagnetic equations. Thus, the computational cost of each numerical solution for a given choice of the design or operation parameters, is high (CPU time consuming and needing significant computational resources) compromising the efficiency of standard optimization algorithms. In order to alleviate the just referred difficulties the present paper proposes an approach based on the use of reduced order modeling, in particular the construction of a parametric solution by employing a non-intrusive formulation of the Proper Generalized Decomposition, combined with a powerful phase-angle unwrapping strategy for accurately addressing the electric and magnetic fields interpolation, contributing to improve the design, the calibration and the operational use of those systems.

In this work, a method which seeks to locate a radial-color mark attached to the object using the high sensitivity of the phase to determine the position spatial and angular with subpixel resolution due to movement of an object in a 2D scene is presented. The reference pattern is formed by a regular distribution with radially symmetrical of color-RGB fringes. The reconstruction of the absolute phase associated to the fringes allows the location the precise center of the mark and it finds position of the object with sub-pixel resolution. The reconstruction of absolute phase associated with the fringes using the phase shifting technique at three-frame and a development phase algorithm is calculated. A transformation of coordinates and a least squares adjustment is realized giving a function for to extract the center of the reference pattern. Experimental results of measurements of position, displacement and orientation with subpixel resolution is presented, as well as the description of the process for system optimization. [ABSTRACT FROM AUTHOR]

This research explains the methodology applied to the representation of the column shafts and capitals of the Temple C in the Selinunte Archaeological Site.Using mathematical auxiliary surfaces and NURBS modelling tools, textured highly-detailed meshes, produced with photogrammetry and laser scanner 3D data, was unwrapped onto a reference plane.The purpose of this unwrapping is to realize orthoimages that accurately describe the conic and toric surfaces of column shafts and echinus.Methodology gives a solution to the restoration and conservation specialists offering drawings on which to detect, map and quantify in these the damaged areas on complex curved surfaces.

Post translational modifications have a profound role in the regulation of several biological processes such as transcription, replication, and DNA repair. Acetylation and phosphorylation form a major class of post translational modifications involved in nucleosomal regulation by modifying its structure. The effect of post translational modifications on nucleosome structure could be better explored when the molecular trajectories explaining the time dependent structural evolution over a period of time is examined at the atomic level. The present study attempts to highlight the importance of acetylation, especially at entry-exit (Lys56) and dyad (Lys115 and Lys122) regions in regulating the nucleosome accessibility and mobility using all atom simulations. It is evident from this study that acetylation at Lys56, Lys115, and Lys122 introduces local changes in the electrostatic nature of the lateral surface and thereby weakens the histone-DNA interactions. In addition, simulations also reveal significant changes in the dynamics of superhelical DNA. The acetylation at Lys56 promotes a high amplitude out-of-planar movement of entry-exit termini. Whereas, acetylation at Lys115 and Lys122 increases the flexibility of the superhelical DNA to facilitate the rolling of the superhelical DNA around the octameric histone. In essence, the present study highlights the role of acetylation at Lys56, Lys115, and Lys122 in transcriptional regulation by promoting high amplitude dynamics of superhelical DNA for a possible unwrapping as well as mobility of nucleosome. [ABSTRACT FROM AUTHOR]

Electronic Speckle Pattern Interferometry (ESPI) is a sensitive optical method commonly used for making full-field measurements of surface displacements. It would be very desirable to be able to extend the technique also to determine surface strains. This would provide a full-field, non-contact strain measurement method that avoids the substantial installation burden of strain gauges. A mathematical approach is described where the ESPI data from an in-plane interferometer are numerically differentiated to determine surface strains. This is a challenging process because numerical differentiation is very sensitive to the presence of noise and ESPI data are inherently noisy. In addition, the phase information from ESPI data are wrapped modulo-2π. The resulting phase discontinuities make it difficult to use local averaging to smooth the data. A technique is described here where phasors are used to avoid the need for phase unwrapping. The effect of noise is reduced by a localized multiple smoothing technique that is effective in preserving spatial resolution, even near very high strain concentrations. Example measurements are shown and the effectiveness of the proposed method is illustrated. [ABSTRACT FROM AUTHOR]

The objective of this work is the application of an interferometric method for validating the result of wear in a cutting tool insert of hard metal. We describe in this paper the experimental setup for the application of Digital Holography technique, used with digital recording of holograms on a CCD camera. The cutting insert inspected with the optical technique was previously mounted on a support structure and slightly heated with a halogen lamp for evidence of defective regions. For image processing, the software used, ProITec. It was possible to detect, with high resolution and contactless defects that could compromise the structural integrity of the insert analyzed, no defect was found. Analysis of the images obtained, it is verified that the object is deformed as a whole, not to present any visible alteration in their pattern of fringes. [ABSTRACT FROM AUTHOR]

Depending upon the surface wave methods, the measured surface wave velocities are either normal mode velocities or apparent velocities. The "apparent" surface wave velocity corresponds to the superposed mode combining the available normal modes. The spectral-analysis-of-surface-waves (SASW) method measures the apparent surface wave velocities. However, these velocities render SASW analyses complicated because of the mode jumps induced by several wave groups. To alleviate such complications, this study introduced a beamforming technique and produced information on unwrapped wavenumber, which is vital in unwrapping the phase spectrum in SASW analyses. Additionally, incoming wave directions filtered out multiple reflections and irrelevant seismic events to retain only the surface waves directly propagating from the source. The proposed wavenumber unwrapping technique was verified using field applications, dynamic finite element analysis, and synthetic waveforms. Notably, an optimal beamforming technique was established using four geophones, making the proposed method highly practical and reducing the hardware requirements. Hopefully, the proposed analysis technique provides SASW practitioners with a more comfortable and more reliable environment in utilizing the SASW technique. • Unwrapped wavenumbers were proposed as a guide in SASW velocity calculations. • Wave directions were used as a filter for measured irrelevant stress waves. • Beamforming tests coupled with SASW analysis was optimized by using four receivers. • The proposed method was validated by seismograms, FEA and three field applications. [ABSTRACT FROM AUTHOR]

Phase map cross-correlation detection and quantification may produce highlighted signal at superparamagnetic iron oxide nanoparticles, and distinguish them from other hypointensities. The method may quantify susceptibility change by performing least squares analysis between a theoretically generated magnetic field template and an experimentally scanned phase image. Because characteristic phase recognition requires the removal of phase wrap and phase background, additional steps of phase unwrapping and filtering may increase the chance of computing error and enlarge the inconsistence among algorithms. To solve problem, phase gradient cross-correlation and quantification method is developed by recognizing characteristic phase gradient pattern instead of phase image because phase gradient operation inherently includes unwrapping and filtering functions. However, few studies have mentioned the detectable limit of currently used phase gradient calculation algorithms. The limit may lead to an underestimation of large magnetic susceptibility change caused by high-concentrated iron accumulation. In this study, mathematical derivation points out the value of maximum detectable phase gradient calculated by differential chain algorithm in both spatial and Fourier domain. To break through the limit, a modified quantification method is proposed by using unwrapped forward differentiation for phase gradient generation. The method enlarges the detectable range of phase gradient measurement and avoids the underestimation of magnetic susceptibility. Simulation and phantom experiments were used to quantitatively compare different methods. In vivo application performs MRI scanning on nude mice implanted by iron-labeled human cancer cells. Results validate the limit of detectable phase gradient and the consequent susceptibility underestimation. Results also demonstrate the advantage of unwrapped forward differentiation compared with differential chain algorithms for susceptibility quantification at high-concentrated iron accumulation. [ABSTRACT FROM AUTHOR]

It appears very interesting and particularly useful to perform DEM reconstruction with the configuration of multichannel bistatic SAR (BiSAR) because of its considerable advantages. In typical processing flow of multichannel interferometric synthetic aperture radar (InSAR), techniques based on statistical methods or iterative methods does not work very well with limits of specific BiSAR configurations. Moreover, the tradeoff between the correctness and precision of the reconstruction of different baselines needs to be overcome as well. Based on the advantages of multichannel BiSAR configuration, basic idea is the joint utilization of amplitude data, iterative reconstruction results and ML results to help the optimization of the total MRF energy function. Thus, a multichannel DEM reconstruction method based on Markov Random Fields (MRFs) for BiSAR, which concerns much about discontinuities and energy functions, is proposed to achieve not only correct but also more precise results. Afterward, the strategy to determine the weight parameter and processing flow is presented. Finally, simulated and real data experiments are given to validate the proposed method. [ABSTRACT FROM AUTHOR]

In order to realize the nondestructive, fast and accurate classification of batch of blood cells, a classification method using deep learning based on wrapped phases in polar coordinate is proposed. In this method, after the coordinate transformation, the wrapped phases of cells are obtained first, and then three characteristic parameters of symmetry, roundness and singularity are established to analyze the phases. Subsequently, the data set of wrapped phases is built with the data augmentation. Finally, the classification and identification of batch of blood cells are realized through the convolutional neural network training based on LeNet-5 and the stochastic gradient descent algorithm (SGDM). An excellent result of the classification accuracy rate of 100% is obtained, which proves that the method has good feasibility and high accuracy. This method only requires the wrapped phases of cells in polar coordinates, so the complex unwrapping procedure and the additional noise effects are avoided. [ABSTRACT FROM AUTHOR]

Objective Due to overlapping, temporal information is mostly lost in high rate steady-state pattern electroretinograms (PERG SS ). This study develops a deconvolution method and a display/recording system to “unwrap” PERG SS and obtain a transient, “per stimulus” response (PERG tr ) regardless of reversal rate. Methods Processing and instrumentation, including high temporal resolution display and acquisition were developed for deconvolving PERGs acquired at high rates by slight jittering of reversal onsets at a given mean rate. Results The system was successfully tested at eight rates from 2.2 to 78.1 rps. At medium rates (17.4–41.2 rps) recordings with conventional morphology (N35–P50–N95) but earlier peaks and higher amplitudes were extracted up to 40 rps. At higher rates, smaller triphasic responses were obtained, exhibiting similar peak latencies, but reversed polarity. Oscillating potentials (OPs) were also recorded at all rates after deconvolution. Conclusions Transient PERGs and OPs can be extracted from quasi steady-state PERG recordings obtained at high rates with a deconvolution algorithm using high temporal resolution display and acquisition systems. Significance The methodology to extract transient and oscillatory responses from steady-state PERGs could be useful in understanding high rate responses and diagnosis of various retinal diseases by revealing temporal information on waveform components which cannot be normally observed. [ABSTRACT FROM AUTHOR]

Purpose To develop a method of unwrapping phase images from multi-echo scans that works even where there are several wraps between echoes, and which generates unwrapped phase images in addition to phase difference (PD) images. Theory The difference between the echo spacings in an acquisition with three unevenly spaced echoes (an imposed delay) can be selected such that the phase evolution in that time is in the range −π to +π in all voxels of interest. Under this condition, an image of the difference between the phase evolutions in the two inter-echo periods, an estimate of ΔB0, is free of wraps. This ΔB0 estimate can be used to identify and remove receiver phase offsets and wraps in phase images. Methods The approach was tested on simulated data and high-resolution in vivo brain data acquired from six subjects at 7 Tesla. Results The method generated wrap-free phase images. It was able to remove more wraps than is possible with PD imaging and was faster and more reliable than spatial unwrapping. Conclusion Unwrapping Multi-echo Phase Images with iRregular Echo spacings (UMPIRE) is conceptually simple, fast, reliable, and requires no fitting, thresholds, or operator intervention. Magn Reson Med 72:80-92, 2014. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

In the traditional processing flow of interferometric synthetic aperture radar (SAR) technique, the processing of phase is conducted via two separated and successive steps, i.e., phase denoising and phase unwrapping. That is to say, first, wrapped phases without noise are generated, and then, the true phases without 2\pi-ambiguities are reconstructed (here and in the rest of this paper, true phase refers to the information-induced unwrapped phase without noise). Such separated steps will inevitably bring in extra estimation error because each step has necessary approximations and presumptions which do not always hold. On the contrary, in this paper, we treat phase denoising and unwrapping as a single problem of true phase recovery from observed ones. Following this methodology, an integrated phase denoising and unwrapping algorithm based upon Markov random fields (MRFs) is proposed. Taking a priori knowledge of interferometric phases into account, MRF is used to model the relationship between the elements in the random variable set including both true phases and their observations. After the model is built up, the energy function of this MRF is defined according to the local-independence property inferred from the MRF structure and then minimized to obtain the estimate of the true phase value. In the end of this paper, experiments on simulated and true phase data are conducted, and the comparison with several commonly used unwrapping methods is proposed to verify the efficiency of the proposed MRF algorithm. [ABSTRACT FROM AUTHOR]

This paper presents an improved non-data-aided algorithm for carrier frequency estimation for burst M-ary PSK signals when modulation order M and training symbols are unknown. Unlike data-aided estimation, a phase clustering algorithm is used first to estimate M and modulated information is removed by a variable interval linear phase unwrapping. Then, a high-order correlation algorithm with proper correction is present, which reduces the probability of phase ambiguity and promotes anti-noise capability of the estimation. Simulations are given to analyze the unbiased estimation range, and the asymptotic performance and symbol number are needed to compare with the former algorithms. The new algorithm has a large estimation range close to the theoretical maximum value for non-data-aided estimation and has a better performance than earlier non-data-aided techniques for large frequency offset, low signal-to-noise ratio, and limited symbol numbers. [ABSTRACT FROM AUTHOR]

Quantitative susceptibility mapping (QSM) opens the door for measuring tissue magnetic susceptibility properties that may be important biomarkers, and QSM is becoming an increasingly active area of scientific and clinical investigations. In practical applications, there are sources of errors for QSM including noise, phase unwrapping failures, and signal model inaccuracy. To improve the robustness of QSM quality, we propose a nonlinear data fidelity term for frequency map estimation and dipole inversion to reduce noise and effects of phase unwrapping failures, and a method for model error reduction through iterative tuning. Compared with the previous phase based linear QSM method, this nonlinear QSM method reduced salt and pepper noise or checkerboard pattern in high susceptibility regions in healthy subjects and markedly reduced artifacts in patients with intracerebral hemorrhages. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Purpose: To enhance image contrast in susceptibility phase imaging using a new method of background phase removal. Materials and Methods: A background phase removal method is proposed that uses the spatial gradient of the raw phase image to perform a moving window third-order local polynomial estimation and correction of the raw phase image followed by minimal high pass filtering. The method is demonstrated in simulation, 10 healthy volunteers, and 5 multiple sclerosis patients in comparison to a standard phase filtering approach. Results: Compared to standard phase filtering, the new method increased phase contrast with local background tissue in subcortical gray matter, cortical gray matter, and multiple sclerosis lesions by 67% ± 33%, 13% ± 7%, and 48% ± 19%, respectively (95% confidence interval). In addition, the new method removed more phase wraps in areas of rapidly changing background phase. Conclusion: Local phase gradient fitting combined with minimal high pass filtering provides better tissue depiction and more accurate phase quantification than standard filtering. J. Magn. Reson. Imaging 2012; 36:1460-1469. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Abstract: Positive contrast imaging methods produce enhanced signal at large magnetic field gradient in magnetic resonance imaging. Several postprocessing algorithms, such as susceptibility gradient mapping and phase gradient mapping methods, have been applied for positive contrast generation to detect the cells targeted by superparamagnetic iron oxide nanoparticles. In the phase gradient mapping methods, smoothness condition has to be satisfied to keep the phase gradient unwrapped. Moreover, there has been no discussion about the truncation artifact associated with the algorithm of differentiation that is performed in k-space by the multiplication with frequency value. In this work, phase gradient methods are discussed by considering the wrapping problem when the smoothness condition is not satisfied. A region-growing unwrapping algorithm is used in the phase gradient image to solve the problem. In order to reduce the truncation artifact, a cosine function is multiplied in the k-space to eliminate the abrupt change at the boundaries. Simulation, phantom and in vivo experimental results demonstrate that the modified phase gradient mapping methods may produce improved positive contrast effects by reducing truncation or wrapping artifacts. [Copyright &y& Elsevier]

Low-density parity-check (LDPC) convolutional codes are capable of achieving excellent performance with low encoding and decoding complexity. In this paper, we discuss several graph-cover-based methods for deriving families of time-invariant and time-varying LDPC convolutional codes from LDPC block codes and show how earlier proposed LDPC convolutional code constructions can be presented within this framework. Some of the constructed convolutional codes significantly outperform the underlying LDPC block codes. We investigate some possible reasons for this “convolutional gain,” and we also discuss the—mostly moderate—decoder cost increase that is incurred by going from LDPC block to LDPC convolutional codes. [ABSTRACT FROM AUTHOR]

Abstract: To enhance susceptibility-related contrast of magnetic resonance images, the phase of susceptibility weighted data needs to be corrected for background inhomogeneities and phase wraps caused by them. Current methods either use homodyne filtering or a combination of phase unwrapping and high pass filtering. The drawback of homodyne filtering is incomplete elimination of phase wraps in areas with steep phase topography produced by background inhomogeneities of the static magnetic field. The disadvantage of phase unwrapping is that it requires subsequent high pass filtering, which introduces artifacts in areas with very steep transitions, such as areas near interfaces between parenchyma and bone or air. A method is proposed that reduces the artifacts associated with high pass filtering without sacrificing the advantages of phase unwrapping. This technique is demonstrated with phantom data at 1.5 T and with human data at 1.5, 3 and 7 T. [Copyright &y& Elsevier]

Abstract: In photoelasticity, the method of obtaining the individual values of principal stresses/normal stresses separately is referred to as stress separation. Shear difference is one of the widely used techniques for stress separation in photoelasticity and one needs the value of fringe order and the isoclinic angle free of noise at every pixel over the domain. For accurate parameter determination, a ten-step phase shifting approach which uses a plane polariscope for isoclinic determination and a circular polariscope for isochromatic determination is proposed. A new quality guided approach for isoclinic unwrapping is developed. Isochromatic phasemap free of ambiguous zones is obtained by a new methodology and is unwrapped by a quality-guided approach. Whole field evaluation of stress components and its representation is then presented. The models used in this study are intentionally subjected to moderate loads showing a high level of isochromatic–isoclinic interaction. In view of this, the isoclinic data has several kinks which is found to cause streak formation in the whole field representation of separated stress components. An outlier smoothing algorithm is proposed for getting a smooth variation of the digital photoelastic parameters over the domain. Use of such smoothed data for stress separation has removed the streaks and has also greatly improved the accuracy of the separated stress components. [Copyright &y& Elsevier]

Abstract: In this work, the principle of interferometry is used to assess the surface roughness of the machined surfaces. Interferometry produces an interference fringe pattern when two or more light waves interact with each other. It is one of the important tool for precision optical metrology and testing. Well-known advantages of the phase shifting interferometry include high measurement accuracy, rapid measurement, good result even with low contrast fringes and that the polarity of the wave front can be determined. In fringe projection techniques, a known optical fringe pattern is projected onto the surface of interest. The fringe pattern on the surface is perturbed in accordance with the profile of the test surface, thereby enabling direct derivation of surface profile. In this work, an attempt has been made to assess the surface roughness using a speckle fringe analysis method of five frame phase shift algorithm for machined surface (ground surface). As these fringes are too noisy, advanced filtering technique has been used so as to reduce noise and to get improved wrapped phase map from the phase shifted fringes. A phase unwrapping software has been developed using discrete cosine transform (DCT) to generate the three-dimensional (3-D) profiles. Finally, it is compared with R a values measured using a mechanical stylus instrument, showing good agreement. [Copyright &y& Elsevier]

Photoelasticity is the only whole-field experimental technique which can analyse both 2-D and 3-D elasticity problems. In digital photoelasticity one gets two phase maps, one corresponding to principal stress direction (isoclinic) and the other corresponding to principal stress difference (isochromatic). The phase maps for both isoclinics and isochromatics are to be unwrapped differently for obtaining continuous phase values. Autonomous phase unwrapping is one of the challenging issues and this paper focuses on recent advances on isochromatic phase map unwrapping. A comparative study of different autonomous phase unwrapping algorithm is done by solving a bench mark problem and a stress frozen slice with cut-outs. The need for domain delimiting in addition to domain masking is brought out while using autonomous phase unwrapping algorithms. [ABSTRACT FROM AUTHOR]

Abstract: We present, for the first time to the best of our knowledge, a phase unwrapping method based on an algorithm which makes use of Green''s first identity. This method aims at recovering the correct phase information encoded in a fringe pattern after digital holography (DH) numerical processing. DH provides a quantitative measurement of the three-dimensional surface profile of objects. The information about the profile can be obtained in principle from the phase-map. However, the measured phase-map provides the actual phase values wrapped mod.2π so that an unwrapping process is required in order to reconstruct the object profile. [Copyright &y& Elsevier]

This paper presents an integrated approach to producing a two-dimensional decorative pattern for ceramic bone china cast ware components. The novelty of the approach is to integrate the approximate unwrapping of a generally non-developable surface with the constraints of the manufacturing process. The key components of the solution are an unwrapping algorithm to determine the shape of the pattern from the CAD model and an estimation of the scaling factors for the mould to compensate for shrinkage in drying and firing. The approach produces patterns that are at least as good as the traditional manual approach, which distort less when wrapped onto the final ceramic ware. Furthermore, because the unwrapping is produced from the CAD definition, the pattern design can be completed much earlier in the manufacturing process with a reduction in the lead time. [ABSTRACT FROM AUTHOR]

A novel approach is presented for obtaining the complete (integer and fractional) value of isochromatic parameters in digital imaging photoelasticity. This takes the form of a new variant on the existing technique of RGB photoelasticity, involving the matching of combinations of isochromatic fringe value measured on the three colour planes or channels rather than the usual RGB method of matching colour combinations directly. The new variant of RGB photoelasticity avoids the need for calibration for specific materials. This approach is demonstrated with real photoelastic data and compared with results from a conventional unwrapping process and from manual readings. [ABSTRACT FROM AUTHOR]