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Journal articles on the topic 'Unwrapping'

Author: Grafiati

Published: 4 June 2021

Last updated: 1 February 2022

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1

Kang, Y., C. Y. Zhao, Q. Zhang, and C. S. Yang. "INSAR UNWRAPPING ERROR CORRECTION BASED ON QUASI-ACCURATE DETECTION OF GROSS ERRORS (QUAD)." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-3 (April 30, 2018): 723–28. http://dx.doi.org/10.5194/isprs-archives-xlii-3-723-2018.

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Unwrapping error is a common error in the InSAR processing, which will seriously degrade the accuracy of the monitoring results. Based on a gross error correction method, Quasi-accurate detection (QUAD), the method for unwrapping errors automatic correction is established in this paper. This method identifies and corrects the unwrapping errors by establishing a functional model between the true errors and interferograms. The basic principle and processing steps are presented. Then this method is compared with the L1-norm method with simulated data. Results show that both methods can effectively suppress the unwrapping error when the ratio of the unwrapping errors is low, and the two methods can complement each other when the ratio of the unwrapping errors is relatively high. At last the real SAR data is tested for the phase unwrapping error correction. Results show that this new method can correct the phase unwrapping errors successfully in the practical application.

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2

Santino, Jack, and Daniel Miller. "Unwrapping Christmas." Contemporary Sociology 24, no. 2 (March 1995): 262. http://dx.doi.org/10.2307/2076909.

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3

Young, Kevin D. "Unwrapping Bacteria." PLoS Genetics 10, no. 1 (January 2, 2014): e1004054. http://dx.doi.org/10.1371/journal.pgen.1004054.

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4

Podell, Richard N. "Unwrapping urticaria." Postgraduate Medicine 78, no. 8 (December 1985): 83–97. http://dx.doi.org/10.1080/00325481.1985.11699221.

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5

Lewis, Anne C. "Unwrapping Teaching." Phi Delta Kappan 85, no. 6 (February 2004): 419–20. http://dx.doi.org/10.1177/003172170408500602.

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6

Maddox, Richard, and Daniel Miller. "Unwrapping Christmas." Sociology of Religion 55, no. 4 (1994): 496. http://dx.doi.org/10.2307/3711993.

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7

Tauxe, Caroline S., and Daniel Miller. "Unwrapping Christmas." Man 29, no. 3 (September 1994): 744. http://dx.doi.org/10.2307/2804387.

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8

Talbot, Nicholas J. "Unwrapping theLaccariagenome." New Phytologist 180, no. 2 (October 2008): 259–60. http://dx.doi.org/10.1111/j.1469-8137.2008.02636.x.

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9

Lemke, Greg. "Unwrapping myelination." Nature 383, no. 6599 (October 1996): 395–96. http://dx.doi.org/10.1038/383395a0.

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10

He, Guo Tian, Ying Chun Ran, Li Song, and Zhong Xun Wang. "Study on a Rotary Self-Check Phase Unwrapping Algorithm." Applied Mechanics and Materials 246-247 (December 2012): 204–7. http://dx.doi.org/10.4028/www.scientific.net/amm.246-247.204.

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This article presented a rotary self-check phase unwrapping algorithm. The algorithm was mainly to process phase unwrapping for the phase main value got from Interferometer in accurately measuring object surface topography, and then accurately restored the object surface topography. The object surface topography measured by Interferometer generally tended to be smooth, the phase unwrapping was not difficult without noise interference. The algorithm processed phase unwrapping by the path of gradually rotational diffusion from the middle to the around in the wrapped phase map, at the same time the check for the error was carried out. It used the median filter technology to process the phase unwrapping error, and avoided the transmission of phase unwrapping error, had a greater inhibitory effect on the noises. This method did not identify the residuals, had small amount of operations, and Unwrapping velocity was several times faster than the fastest traditional branch blocking algorithm.

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11

Zhang, Yao Ting, and Min Jui Huang. "Surface Crack Search and Marking on Materials with Regional Phase Unwrapping Technology." Advanced Materials Research 291-294 (July 2011): 1074–81. http://dx.doi.org/10.4028/www.scientific.net/amr.291-294.1074.

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Depending on the size of sets, a wrapped phase map is unwrapped by either region or pixel. In region phase unwrapping, the jump point threshold value is adjusted to search the region boundary after filtering a wrapped map with higher noise and then phase unwrapping ±2nπ in each region without filtering. The latter compares if the phase difference of adjacent pixels is greater than π as a reference for determining pixel point ±2π to perform phase unwrapping point by point. Although the former unwraps phase by means of boundary search and the latter with the phase difference of adjacent pixels, phase unwrapping errors occur in both cases in detecting surface cracks on materials as data on both sides of a crack are discontinuous. This paper proposes a solution for phase unwrapping on discontinuous surfaces by means of crack search and marking with region assembly phase unwrapping technology to locate boundaries in both region splits and crack splits and further extends the scope of application of region assembly phase unwrapping.

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12

Gao, Yue Hua, Bing Luo, Zhong Yu Sun, and Su Fang Zhao. "Combined Phase Unwrapping Method Using 2D Image Information in PMP 3D Measurement." Advanced Materials Research 765-767 (September 2013): 2148–52. http://dx.doi.org/10.4028/www.scientific.net/amr.765-767.2148.

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In SMT solder paste deposit 3D measurement based on PMP, conventional phase unwrapping method suffered from shadow, noise and holes. Considering practical engineering condition, phase unwrapping method can be improved using 2D image information: basic principle method was applied to smooth area, quality-guided unwrapping and least-square method were taken in shadow or break area for phase unwrapping respectively. Experimental results show that desired phases can be correctly and quickly unwrapped in proposed method.

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13

Wu, Xinming, and Guangfa Zhong. "Generating a relative geologic time volume by 3D graph-cut phase unwrapping method with horizon and unconformity constraints." GEOPHYSICS 77, no. 4 (July 1, 2012): O21—O34. http://dx.doi.org/10.1190/geo2011-0351.1.

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Construction of a relative geologic time (RGT) volume is vital to seismic geomorphological and sedimentological interpretation. Seismic instantaneous phase unwrapping provides an excellent approach for generating an RGT volume. Although several 2D or 3D seismic phase unwrapping results have been published, there is a clear need for discussions on concrete methods for seismic phase unwrapping. We have developed the graph-cut phase unwrapping method, which performs well in the interferometric synthetic aperture radar image processing. It has advantages of strong discontinuity-preserving ability and high computing efficiency. To make it suitable for 3D seismic phase unwrapping, the method is improved by extending it from 2D to 3D, and by introducing the seismic horizon and unconformity constraints. The strong and continuous conformable seismic events, which can be easily tracked by certain autopicking methods, are introduced as horizon constraints for guiding the phase unwrapping to ensure a constant unwrapped phase on a constraining horizon. This idea is based on the fact that continuous seismic horizons are of time-stratigraphic significance. The horizon constraints can promise a correct unwrapped result on the constraining horizons and avoid the possible phase unwrapping errors propagating across a horizon. An unconformity represents a geologic time discontinuity, which is difficult to recover in an RGT volume by phase unwrapping. What’s worse, incorrect phase unwrapping on an unconformity will result in some discontinuities of unwrapped phase in the conformable data areas outside the unconformity. Interpreted unconformities are used as unconformity constraints to recover the discontinuities of the unwrapped phase at the constraining unconformities. As a test, our improved 3D graph-cut phase unwrapping method is successfully applied to the late Permian to early Triassic carbonate reservoirs in northern Sichuan Basin, southwest China. The results match well with the regional geologic background.

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14

Spagnolini, Umberto. "2-D phase unwrapping and phase aliasing." GEOPHYSICS 58, no. 9 (September 1993): 1324–34. http://dx.doi.org/10.1190/1.1443515.

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The phase of complex signals is measured modulo-2π (wrapped phase); continuous‐phase information is obtained by adding properly chosen multiples of 2π shift to the wrapped phase. Unwrapping searches for the 2π combinations that minimize the discontinuity of the unwrapped phase as only the unwrapped phase can be analyzed and interpreted by further processing. The key problem of phase unwrapping is phase aliasing, a condition mainly caused by rapid phase variations. The extension of the one‐dimensional (1-D) phase unwrapping algorithms to a two‐dimensional (2-D) domain by 1-D slicing gives unsatisfactory results even in the presence of low‐phase aliasing, whereas 2-D phase unwrapping deals with the complete problem, overcoming the limitations of 1-D unwrapping. The 2-D unwrapped phase is obtained as the solution of a variational problem that minimizes the differences between the gradients of the wrapped and unwrapped phase. The Euler equation is then integrated using the boundary conditions obtained from the wrapped phase. In addition to determining a unique unwrapped phase, this approach has the advantage that it limits the influence of phase aliasing. It is also more attractive than iterative 1-D unwrapping since it limits the propagation of unwrapping errors. Error propagation in phase unwrapping can strongly influence the result of any phase processing. Examples in this paper apply 2-D phase unwrapping to problems of refraction statics and interferometrical imaging using a remote system (SAR) and demonstrate how limited error propagation allows phase processing.

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15

Tavakkoli Estahbanat, A., and M. Dehghani. "APPLICATION OF EXTENDED KALMAN FILTER IN PERSISTANT SCATTERER INTERFEROMETRY TO ENHACE THE ACCURACY OF UNWRAPPING PROCESS." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-4/W4 (September 27, 2017): 287–91. http://dx.doi.org/10.5194/isprs-archives-xlii-4-w4-287-2017.

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In interferometry technique, phases have been modulated between 0-2π. Finding the number of integer phases missed when they were wrapped is the main goal of unwrapping algorithms. Although the density of points in conventional interferometry is high, this is not effective in some cases such as large temporal baselines or noisy interferograms. Due to existing noisy pixels, not only it does not improve results, but also it leads to some unwrapping errors during interferogram unwrapping. In PS technique, because of the sparse PS pixels, scientists are confronted with a problem to unwrap phases. Due to the irregular data separation, conventional methods are sterile. Unwrapping techniques are divided in to path-independent and path-dependent in the case of unwrapping paths. A region-growing method which is a path-dependent technique has been used to unwrap PS data. In this paper an idea of EKF has been generalized on PS data. This algorithm is applied to consider the nonlinearity of PS unwrapping problem as well as conventional unwrapping problem. A pulse-pair method enhanced with singular value decomposition (SVD) has been used to estimate spectral shift from interferometric power spectral density in 7*7 local windows. Furthermore, a hybrid cost-map is used to manage the unwrapping path. This algorithm has been implemented on simulated PS data. To form a sparse dataset, A few points from regular grid are randomly selected and the RMSE of results and true unambiguous phases in presented to validate presented approach. The results of this algorithm and true unwrapped phases were completely identical.

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16

Wen, Zengqi, Liwei Zhang, Haihe Ruan, and Guohong Li. "Histone variant H2A.Z regulates nucleosome unwrapping and CTCF binding in mouse ES cells." Nucleic Acids Research 48, no. 11 (May 11, 2020): 5939–52. http://dx.doi.org/10.1093/nar/gkaa360.

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Abstract Nucleosome is the basic structural unit of chromatin, and its dynamics plays critical roles in the regulation of genome functions. However, how the nucleosome structure is regulated by histone variants in vivo is still largely uncharacterized. Here, by employing Micrococcal nuclease (MNase) digestion of crosslinked chromatin followed by chromatin immunoprecipitation (ChIP) and paired-end sequencing (MNase-X-ChIP-seq), we mapped unwrapping states of nucleosomes containing histone variant H2A.Z in mouse embryonic stem (ES) cells. We found that H2A.Z nucleosomes are more enriched with unwrapping states compared with canonical nucleosomes. Interestingly, +1 H2A.Z nucleosomes with 30–80 bp DNA is correlated with less active genes compared with +1 H2A.Z nucleosomes with 120–140 bp DNA. We confirmed the unwrapping of H2A.Z nucleosomes under native condition by re-ChIP of H2A.Z and H2A after CTCF CUT&RUN in mouse ES cells. Importantly, we found that depletion of H2A.Z results in decreased unwrapping of H3.3 nucleosomes and increased CTCF binding. Taken together, through MNase-X-ChIP-seq, we showed that histone variant H2A.Z regulates nucleosome unwrapping in vivo and that its function in regulating transcription or CTCF binding is correlated with unwrapping states of H2A.Z nucleosomes.

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17

Wang, Li Fen, and Man Yan. "Weighted Kalman Filter Phase Unwrapping Algorithm Based on the Phase Derivative Variance Map." Applied Mechanics and Materials 475-476 (December 2013): 991–95. http://dx.doi.org/10.4028/www.scientific.net/amm.475-476.991.

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The kalman filtering phase unwrapping is a state estimation problem. It can realize phase unwrapping and noise elimination at the same time, and calculate the real phase by establishing the state space model and vector observation model. In the steep terrain, the conventional kalman filtering algorithm unwrapping results are often not accurate, easy to cause the error transfer. Aiming at this problem, the weighted kalman filter phase unwrapping algorithm based on the phase derivative variance map is proposed. The values of the phase derivative variance maps are applied to determine the noise variance in the observation equation, then the weighted kalman filter is used to unwrap phase, this can increase the accuracy of the results. Finally, experiments are carried out in the InSAR data application under the condition of steep terrain, and with the conventional kalman filtering phase unwrapping algorithm are compared, the effectiveness of the proposed method is verified.

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18

Soille, Pierre. "Morphological phase unwrapping." Optics and Lasers in Engineering 32, no. 4 (October 1999): 339–52. http://dx.doi.org/10.1016/s0143-8166(00)00006-3.

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19

Freeman, Marc R., Jeffrey Delrow, Junhyong Kim, Eric Johnson, and Chris Q. Doe. "Unwrapping Glial Biology." Neuron 38, no. 4 (May 2003): 567–80. http://dx.doi.org/10.1016/s0896-6273(03)00289-7.

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20

Leslie, Mitch. "Unwrapping new histones." Journal of Cell Biology 190, no. 5 (September 6, 2010): 708. http://dx.doi.org/10.1083/jcb.1905iti1.

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21

Flight, Monica Hoyos. "Unwrapping glial differentiation." Nature Reviews Neuroscience 11, no. 5 (March 31, 2010): 299. http://dx.doi.org/10.1038/nrn2838.

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22

Turner, Barnard. "Unwrapping the Reichstag." Thesis Eleven 63, no. 1 (November 2000): 80–88. http://dx.doi.org/10.1177/0725513600063000007.

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23

Lyuboshenko, Igor. "Unwrapping circular interferograms." Applied Optics 39, no. 26 (September 10, 2000): 4817. http://dx.doi.org/10.1364/ao.39.004817.

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24

Pang, Jiayin, Megan H. Ryan, Kadambot H. M. Siddique, and Richard J. Simpson. "Unwrapping the rhizosheath." Plant and Soil 418, no. 1-2 (July 27, 2017): 129–39. http://dx.doi.org/10.1007/s11104-017-3358-y.

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25

Finn, Douglas. "Unwrapping the Spectacle." Augustinian Studies 52, no. 1 (2021): 43–70. http://dx.doi.org/10.5840/augstudies20213564.

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In this article, I explore how Augustine uses sermonic rhetoric to bring about the transfiguration of Babylon, the city of humankind, into Jerusalem, the city of God. Focusing on Enarratio in Psalmum 147, I show how Augustine situates his audience between two spectacles, the Roman theater and games and the eschatological vision of God. Augustine seeks to turn his hearers’ eyes and hearts from the one spectacle to the other, from the love of this world to love of the next. In the process, Augustine wages battle on two fronts: he criticizes pagan Roman culture, on the one hand, and Donatist Christian separatism and perfectionism, on the other. Through his preaching, Augustine stages yet another spectacle, the history of God’s mercy and love, whereby God affirmed the world’s goodness by using it as the means of healing and transfiguration. Indeed, Augustine does not simply depict the spectacle of salvation; he seeks to make his hearers into that spectacle by exhorting them to practice mercy, thereby inscribing them into the history of God’s love and helping gradually transfigure them into the heavenly Jerusalem.

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Salfity, M. F., J. M. Huntley, M. J. Graves, O. Marklund, R. Cusack, and D. A. Beauregard. "Extending the dynamic range of phase contrast magnetic resonance velocity imaging using advanced higher-dimensional phase unwrapping algorithms." Journal of The Royal Society Interface 3, no. 8 (December 5, 2005): 415–27. http://dx.doi.org/10.1098/rsif.2005.0096.

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Phase contrast magnetic resonance velocity imaging is a powerful technique for quantitative in vivo blood flow measurement. Current practice normally involves restricting the sensitivity of the technique so as to avoid the problem of the measured phase being ‘wrapped’ onto the range − π to + π . However, as a result, dynamic range and signal-to-noise ratio are sacrificed. Alternatively, the true phase values can be estimated by a phase unwrapping process which consists of adding integral multiples of 2 π to the measured wrapped phase values. In the presence of noise and data undersampling, the phase unwrapping problem becomes non-trivial. In this paper, we investigate the performance of three different phase unwrapping algorithms when applied to three-dimensional (two spatial axes and one time axis) phase contrast datasets. A simple one-dimensional temporal unwrapping algorithm, a more complex and robust three-dimensional unwrapping algorithm and a novel velocity encoding unwrapping algorithm which involves unwrapping along a fourth dimension (the ‘velocity encoding’ direction) are discussed, and results from the three are presented and compared. It is shown that compared to the traditional approach, both dynamic range and signal-to-noise ratio can be increased by a factor of up to five times, which demonstrates considerable promise for a possible eventual clinical implementation. The results are also of direct relevance to users of any other technique delivering time-varying two-dimensional phase images, such as dynamic speckle interferometry and synthetic aperture radar.

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27

Huntley, J. M., and H. O. Saldner. "Shape measurement by temporal phase unwrapping: comparison of unwrapping algorithms." Measurement Science and Technology 8, no. 9 (September 1, 1997): 986–92. http://dx.doi.org/10.1088/0957-0233/8/9/005.

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28

Zhang, Shu Bi, and Tuo Fu. "Analysis and Evaluation of InSAR Phase Unwrapping Approaches." Advanced Materials Research 301-303 (July 2011): 1029–35. http://dx.doi.org/10.4028/www.scientific.net/amr.301-303.1029.

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In recent years SAR interferometry has become a widely used technique for measuring altitude and displacement of the surface of the earth. Phase unwrapping of the interferometric SAR is a very important step to obtain an accurate DEM(Digital Elevation Model)[1,2,3],and phase unwrapping is not only crucial in InSAR but also a major source in InSAR errors. Therefore, with GAMMA software, VC++ and MATLAB coding implementing six kinds of phase unwrapping approaches ,this paper presents the best method for different situations through two sets of experimental results used for analysing and comparing run time and precision. In the plain and alpine area, the best phase unwrapping methods are separately Goldstein branch-cut method and Minimum Cost Network Flow method.

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29

Liu, Wei Ke, Gou Lin Liu, and Xiao Qing Zhang. "Least Squares Phase Unwrapping Algorithm Based on Topographic Factors." Applied Mechanics and Materials 105-107 (September 2011): 1876–79. http://dx.doi.org/10.4028/www.scientific.net/amm.105-107.1876.

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The phase of complex signals is wrapped since it can only be measured modulo-2; unwrapping searches for the 2-combinations that minimize the discontinuity of the unwrapped phase, as only the unwrapped phase can be analyzed and interpreted by further processing. Weighted least squares phase unwrapping algorithm could avoid errors transmission in the whole phase images, but it could not avoid defect and overlay of interference fringes caused by topographic factors. Therefore, a new phase unwrapping and weights choosing method based on local phase frequency estimate of topographic factors was presented. Experiments show it is an efficient phase unwrapping method which well overcome the defect of under-estimate slopes by least squares algorithm, and has higher accuracy and stability than other methods.

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30

Kemao, Qian, and Seah Hock Soon. "A Simple Phase Unwrapping Approach Based on Filtering by Windowed Fourier Transform (II)." Key Engineering Materials 326-328 (December 2006): 67–70. http://dx.doi.org/10.4028/www.scientific.net/kem.326-328.67.

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Phase unwrapping is an important and challenging process in optical interferometry. Difficulties in phase unwrapping are usually caused by either noise (“bad” pixels) or invalid areas (“bad” regions). If the “bad” pixels can be removed, the problems due to the noise are solved. Further, if the “bad” regions can be identified, they can be avoided in phase unwrapping. In our previous work the noise can be successfully removed using a windowed Fourier transform [Optics and Lasers Technology, 37:458-462 (2005)]. In this paper we will show that the invalid areas can be identified by the same windowed Fourier transform. Thus a single windowed Fourier transform is able to process both “bad” pixels and “bad” regions simultaneously, which makes the phase unwrapping simple and effective.

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Takahashi, Yoshitaka, and Fuyuki Sahara. "Surface Measurement by Digital Holography with New Unwrapping Method." Key Engineering Materials 643 (May 2015): 179–83. http://dx.doi.org/10.4028/www.scientific.net/kem.643.179.

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Digital holography can record 3-D image of the object by using one CCD camera. Surface shape can be measured by changing angles of the object-illuminating mirror. But the measured signals are wrapped because of the periodicity of a sinusoidal function, and then phase unwrapping is needed. We have developed a new modified phase unwrapping method and applied it to surface measurement. Unwrapping errors were significantly reduced in comparison to application of the previous method.

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32

Hao, Hua Dong, Ting Yi Bai, and Guo Lin Liu. "InSAR Adaptive Extended Kalman Filter Phase Unwrapping Algorithm." Advanced Materials Research 798-799 (September 2013): 493–96. http://dx.doi.org/10.4028/www.scientific.net/amr.798-799.493.

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Phase Unwrapping (PU) is the key step in the image processing for Interferometric Synthetic Aperture Radar (InSAR). In the Extended Kalman Filter (EKF) model of PU, due to the state space model is not taken into account the terrain factors, it is often resulted in unwrapping error delivery as the pixel to the next when the state changes rapidly in steep terrain. The observation equation is nonlinear and usually applied in PU through linear processing, requiring the system model and noise statistics known. But in fact the mathematical model or statistical noise is completely or partially unknown; the results have been inevitably lead to the declining of valuation accuracy and filter divergence. If directly applied in phase unwrapping, it is made impossible to retrieve surface deformation. In order to solve this problem and fully consider the terrain effect and model error, an adaptive EKF PU algorithm (AEKFPU) for InSAR is presented. On the one hand, it is achieved local adaptive estimation of image fringe frequency through 2D FFT and Chirp-Z Transform (CZT) joint method, by considering the impact of terrain factors on unwrapping results; On the one hand, the fading factor is calculated by innovation covariance and adaptively adjusted with the error covariance so as to suppress the memory length of the filter, compensating the effect of incomplete information on unwrapping. The experimental results are proved the proposed method is effective, it can be dealt with phase unwrapping and filtering simultaneously, and can be adaptively considered terrain factors in state space model and compensated for model error in observation equation model, ultimately improving the accuracy of phase unwrapping.

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33

Li, Wen Guo, and Shao Jun Duan. "Phase Unwrapping for 3D Shape Measurement of Discontinous Surface." Applied Mechanics and Materials 530-531 (February 2014): 109–12. http://dx.doi.org/10.4028/www.scientific.net/amm.530-531.109.

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A phase unwrapping algorithm for 3D shape measurement of discontinous surface is presented. The proposed phase unwrapping algorithm can overcome the phase discontinuous problem.Three channel values in HSV space are completely employed to calculate the pattern color information intensity, the relative position relationship between adjacent pixels hue channel value is used to decide absolute phase fringe order. The proposed unwrapping algorithm can be applied to the measurement for 3d object with large height steps and/or spatially isolated surfaces. The correctness of the proposed algorithm is validated by our simulated experiment.

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34

Cheng, Nai-Jen, and Wei-Hung Su. "Phase-Shifting Projected Fringe Profilometry Using Binary-Encoded Patterns." Photonics 8, no. 9 (August 29, 2021): 362. http://dx.doi.org/10.3390/photonics8090362.

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A phase unwrapping method for phase-shifting projected fringe profilometry is presented. It did not require additional projections to identify the fringe orders. The pattern used for the phase extraction could be used for phase unwrapping directly. By spatially encoding the fringe patterns that were used to perform the phase-shifting technique with binary contrasts, fringe orders could be discerned. For spatially isolated objects or surfaces with large depth discontinuities, unwrapping could be identified without ambiguity. Even though the surface color or reflectivity varied periodically with position, it distinguished the fringe order very well.

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35

Yu, Zihao, Jin Liu, Haima Yang, Bo Huang, and Yumei Jian. "A Multifrequency Heterodyne Phase Error Compensation Method for 3D Reconstruction." Journal of Sensors 2020 (August 8, 2020): 1–10. http://dx.doi.org/10.1155/2020/8833305.

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In view of the problem of “jumping points” in the phase unwrapping of the multifrequency heterodyne principle, this paper proposes a novel method to improve the multifrequency heterodyne. By solving the root-mean-square error of the original frequency function, it includes the relationship between the error and the adjacent phase in the condition of constrained phase unwrapping, and it compensates phase ±2π of the skip point. To ensure the accuracy of phase unwrapping, the function with a “jump point” after each phase unwrapping and the absolute phase curve of the principal value function are used to establish the threshold judgment model of the least square method, and the initial phase unwrapping of the principal value function with different frequencies is carried out continuously. The simulation analysis of phase compensation with the four-step phase-shifting method shows that the error is reduced to 36% under the set environment. The experimental result of 3D reconstruction by measuring the flatness of the plate shows that the error decreases by 41% after phase compensation compared with before phase compensation. The three-dimensional reconstruction experiment of pitch measurement with a nut shows that the nut after phase compensation is smooth without noise, and the pitch error is 0.033 mm, which verified the method is workable and effective.

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36

He, Wei, Ling Xia, and Feng Liu. "Sparse-Representation-Based Direct MinimumLp-Norm Algorithm for MRI Phase Unwrapping." Computational and Mathematical Methods in Medicine 2014 (2014): 1–11. http://dx.doi.org/10.1155/2014/134058.

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A sparse-representation-based direct minimumLp-norm algorithm is proposed for a two-dimensional MRI phase unwrapping. First, the algorithm converts the weighted-Lp-norm-minimization-based phase unwrapping problem into a linear system problem whose system (coefficient) matrix is a large, symmetric one. Then, the coefficient-matrix is represented in the sparse structure. Finally, standard direct solvers are employed to solve this linear system. Several wrapped phase datasets, including simulated and MR data, were used to evaluate this algorithm’s performance. The results demonstrated that the proposed algorithm for unwrapping MRI phase data is reliable and robust.

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37

He, Yan Bin, Xin Zhong Li, Wei Min Chen, and Jun Song Wen. "Phase Unwrapping Method Based on Windowed Fourier Transform." Applied Mechanics and Materials 307 (February 2013): 321–26. http://dx.doi.org/10.4028/www.scientific.net/amm.307.321.

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Phase unwrapping is one of the key technologies in electronic speckle pattern interferometry. A new phase unwrapping algorithm, based on windowed Fourier transform is proposed. The high noisy phase map is denoised by the window Fourier transform approach and then is uwrapped by the discrete cosine transform. The method is tested in this paper using a circumferentially fixed circular plate with a point load at the centre and compared with not denoised wrapped phase map and unwrapped phase map. The result shows the new proposed phase unwrapping method in denoising and improving image quality has obvious superiority.

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38

Kono, Hidetoshi, and Hisashi Ishida. "Nucleosome unwrapping and unstacking." Current Opinion in Structural Biology 64 (October 2020): 119–25. http://dx.doi.org/10.1016/j.sbi.2020.06.020.

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Roy, Sajal, Habib Zafarullah, and Arunima Kishore Das. "Unwrapping the Memory Box." Asian Journal of Social Science 48, no. 3-4 (September 24, 2020): 375–94. http://dx.doi.org/10.1163/15685314-04803010.

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Abstract The Sundarbans, the largest mangrove forest in the world, has been undergoing significant ecological changes due to climate change-related weather events since the late 1990s. This forest, situated in south-west Bangladesh, provides livelihood services to 3.5 million people. The livelihood provision of the Sundarbans forest has been invented due to climate-induced disasters, such as cyclones, sea-level rise, salinisation, heat waves, and flooding. Considering the impacts of cyclones Aila and Sidr, this autoethnographic study closely examines the long-established perceptions of women and men about the resources of the Sundarbans. While doing so, this study uses feminist political ecology as a theoretical framework. This study examines how these two cyclones transformed lives and gendered livelihoods of the villagers of Shora in the Sundarbans forest.

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Wang, Boxiong, Yuqing Shi, T. Pfeifer, and H. Mischo. "Phase unwrapping by blocks." Measurement 25, no. 4 (June 1999): 285–90. http://dx.doi.org/10.1016/s0263-2241(99)00012-3.

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Xu, Z., B. Huang, and S. Xu. "Robust phase unwrapping algorithm." Electronics Letters 49, no. 24 (November 2013): 1565–67. http://dx.doi.org/10.1049/el.2013.2909.

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Freeman, J., and C. M. Ziemba. "Unwrapping the Ventral Stream." Journal of Neuroscience 31, no. 7 (February 16, 2011): 2349–51. http://dx.doi.org/10.1523/jneurosci.6191-10.2011.

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Carruthers, William. "Unwrapping Ancient Egypt (Riggs)." Museum Anthropology Review 9, no. 1-2 (February 13, 2015): 130–31. http://dx.doi.org/10.14434/mar.v9i1-2.13667.

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Lewis, Marilyn. "Unwrapping the Serials Package." Serials Review 26, no. 3 (October 2000): 79–80. http://dx.doi.org/10.1080/00987913.2000.10764610.

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Yamaki, R., and A. Hirose. "Singularity-Spreading Phase Unwrapping." IEEE Transactions on Geoscience and Remote Sensing 45, no. 10 (October 2007): 3240–51. http://dx.doi.org/10.1109/tgrs.2007.906973.

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He, Xuelian, Yang Yu, Rajeshwar Awatramani, and Q. Richard Lu. "Unwrapping Myelination by MicroRNAs." Neuroscientist 18, no. 1 (May 2, 2011): 45–55. http://dx.doi.org/10.1177/1073858410392382.

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Slobodov, Sergei. "Unwrapping Closed Timelike Curves." Foundations of Physics 38, no. 12 (October 30, 2008): 1082–109. http://dx.doi.org/10.1007/s10701-008-9253-x.

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Yan, Man, and Li Fen Wang. "Extended Kalman Filter Phase Unwrapping Smooth Algorithm in InSAR Image." Applied Mechanics and Materials 701-702 (December 2014): 449–52. http://dx.doi.org/10.4028/www.scientific.net/amm.701-702.449.

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InSAR phase unwrapping is one of the key technologies in precise differential interferometry measurement. However, when the noise is more, wrapped phase easily make the unwrapping result’s errors more. To solve this problem, phase error is compensated, and extended Kalman filter gain is limited within a certain range, error is suppressed in a relatively small area. Finally, extended Kalman filter smooth reduce the errors’ spread. Using interference data of ESA ERS-1 satellite to do experiments, it show that this method is superior to least squares method, quality guided method and original Kalman filter method in unwrapping precision and quality, it has higher stability.

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Benoit, Angélique, Béatrice Pinel-Puysségur, Romain Jolivet, and Cécile Lasserre. "CorPhU: an algorithm based on phase closure for the correction of unwrapping errors in SAR interferometry." Geophysical Journal International 221, no. 3 (March 18, 2020): 1959–70. http://dx.doi.org/10.1093/gji/ggaa120.

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SUMMARY Interferometric Synthetic Aperture Radar (InSAR) is commonly used in Earth Sciences to study surface displacements or construct high resolution topographic maps. Recent satellites such as those of the Sentinel-1 constellation allow to derive dense deformation maps with millimetric precision with high revisit frequency. However, InSAR is still limited by interferometric coherence. Interferometric phase noise resulting from a loss of coherence, due to changes in scattering properties between repeated SAR acquisitions, may lead to unwrapping errors, which then in turn lead to centimetric errors in time-series reconstruction. We present an algorithm based on interferometric phase closure to automatically correct unwrapping errors. We describe the algorithm and highlight its performances with two case studies, in Lebanon with Envisat satellite data and in Central Turkey with Sentinel-1 data. The first data set is particularly affected by unwrapping errors because of long spatial (500 m) and temporal baseline interferograms (6 yr) and decorrelation due, in particular, to vegetation. The second data set contains unwrapping errors because of temporal changes in the scattering properties of the ground. For these two examples, the algorithm allows the correction of almost all detectable unwrapping errors, without requiring visual inspection or manual deletions. Our algorithm is efficient especially on large data sets, such as with Sentinel-1 constellation, where interferometric phase is redundant and improves eventually the reconstruction of time-series.

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Reddy, Govardhan, and D. Thirumalai. "Asymmetry in histone rotation in forced unwrapping and force quench rewrapping in a nucleosome." Nucleic Acids Research 49, no. 9 (April 20, 2021): 4907–18. http://dx.doi.org/10.1093/nar/gkab263.

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Abstract Single molecule pulling experiments have shown that DNA in the nucleosomes unwraps in two stages from the histone protein core (HPC). The first stage, attributed to the rupture of the outer DNA turn, occurs between 3 and 5 pNs, and is reversible. The inner DNA turn ruptures irreversibly at forces between 9 and 15 pNs (or higher) in the second stage. Molecular simulations using the Self-Organized Polymer model capture the experimental findings. The unwrapping of the outer DNA turn is independent of the pulling direction. The rupture of the DNA inner turn depends on the pulling direction and involves overcoming substantial energetic (most likely electrostatic in origin) and kinetic barriers. They arise because the mechanical force has to generate sufficient torque to rotate the HPC by 180°. On the other hand, during the rewrapping process, HPC rotation is stochastic, with force playing no role. The assembly of the outer DNA wrap upon force quench nearly coincides with the unwrapping process, confirming the reversibility of the outer turn rupture. The asymmetry in HPC rotation during unwrapping and rewrapping explains the observed hysteresis in the stretch-release cycles in experiments. We propose experiments to test the prediction that HPC rotation produces kinetic barriers in the unwrapping process.

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