Artykuły w czasopismach: „Compressive phase retrieval”

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Li, Yi, i Vasileios Nakos. "Sublinear-Time Algorithms for Compressive Phase Retrieval". IEEE Transactions on Information Theory 66, nr 11 (listopad 2020): 7302–10. http://dx.doi.org/10.1109/tit.2020.3020701.

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Zhang, Liang, Gang Wang, Georgios B. Giannakis i Jie Chen. "Compressive Phase Retrieval via Reweighted Amplitude Flow". IEEE Transactions on Signal Processing 66, nr 19 (1.10.2018): 5029–40. http://dx.doi.org/10.1109/tsp.2018.2862395.

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Schniter, Philip, i Sundeep Rangan. "Compressive Phase Retrieval via Generalized Approximate Message Passing". IEEE Transactions on Signal Processing 63, nr 4 (luty 2015): 1043–55. http://dx.doi.org/10.1109/tsp.2014.2386294.

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Peng, Tong, Runze Li, Junwei Min, Dan Dan, Meiling Zhou, Xianghua Yu, Chunmin Zhang, Chen Bai i Baoli Yao. "Quantitative Phase Retrieval Through Scattering Medium via Compressive Sensing". IEEE Photonics Journal 14, nr 1 (luty 2022): 1–8. http://dx.doi.org/10.1109/jphot.2021.3136509.

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Di, Hong, i Xin Zhang. "Compressive image encryption with customized key based on phase retrieval". Optical Engineering 56, nr 2 (10.02.2017): 023103. http://dx.doi.org/10.1117/1.oe.56.2.023103.

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Jerez, Andres, Samuel Pinilla i Henry Arguello. "Fast Target Detection via Template Matching in Compressive Phase Retrieval". IEEE Transactions on Computational Imaging 6 (2020): 934–44. http://dx.doi.org/10.1109/tci.2020.2995999.

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Ohlsson, Henrik, Allen Y. Yang, Roy Dong i S. Shankar Sastry. "Compressive Phase Retrieval From Squared Output Measurements Via Semidefinite Programming*". IFAC Proceedings Volumes 45, nr 16 (lipiec 2012): 89–94. http://dx.doi.org/10.3182/20120711-3-be-2027.00415.

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Li, Yingying, Jinchuan Zhou, Zhongfeng Sun i Jingyong Tang. "Heavy-Ball-Based Hard Thresholding Pursuit for Sparse Phase Retrieval Problems". Mathematics 11, nr 12 (16.06.2023): 2744. http://dx.doi.org/10.3390/math11122744.

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We introduce a novel iterative algorithm, termed the Heavy-Ball-Based Hard Thresholding Pursuit for sparse phase retrieval problem (SPR-HBHTP), to reconstruct a sparse signal from a small number of magnitude-only measurements. Our algorithm is obtained via a natural combination of the Hard Thresholding Pursuit for sparse phase retrieval (SPR-HTP) and the classical Heavy-Ball (HB) acceleration method. The robustness and convergence for the proposed algorithm were established with the help of the restricted isometry property. Furthermore, we prove that our algorithm can exactly recover a sparse signal with overwhelming probability in finite steps whenever the initialization is in the neighborhood of the underlying sparse signal, provided that the measurement is accurate. Extensive numerical tests show that SPR-HBHTP has a markedly improved recovery performance and runtime compared to existing alternatives, such as the Hard Thresholding Pursuit for sparse phase retrieval problem (SPR-HTP), the SPARse Truncated Amplitude Flow (SPARTA), and Compressive Phase Retrieval with Alternating Minimization (CoPRAM).

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Pedarsani, Ramtin, Dong Yin, Kangwook Lee i Kannan Ramchandran. "PhaseCode: Fast and Efficient Compressive Phase Retrieval Based on Sparse-Graph Codes". IEEE Transactions on Information Theory 63, nr 6 (czerwiec 2017): 3663–91. http://dx.doi.org/10.1109/tit.2017.2693287.

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Hu, Chen, Xiaodong Wang, Linglong Dai i Junjie Ma. "Partially Coherent Compressive Phase Retrieval for Millimeter-Wave Massive MIMO Channel Estimation". IEEE Transactions on Signal Processing 68 (2020): 1673–87. http://dx.doi.org/10.1109/tsp.2020.2975914.

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Yuan, Sheng, Yangrui Yang, Xuemei Liu, Xin Zhou i Zhenzhuo Wei. "Optical image transformation and encryption by phase-retrieval-based double random-phase encoding and compressive ghost imaging". Optics and Lasers in Engineering 100 (styczeń 2018): 105–10. http://dx.doi.org/10.1016/j.optlaseng.2017.07.015.

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SI, Jingjing, Jing XIANG, Yinbo CHENG i Kai LIU. "Compressive Phase Retrieval Realized by Combining Generalized Approximate Message Passing with Cartoon-Texture Model". IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences E101.A, nr 9 (1.09.2018): 1608–15. http://dx.doi.org/10.1587/transfun.e101.a.1608.

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Reddy, B. Lokesh, i Anith Nelleri. "Convex optimization for additive noise reduction in quantitative complex object wave retrieval using compressive off-axis digital holographic imaging". Journal of Intelligent Systems 31, nr 1 (1.01.2022): 706–15. http://dx.doi.org/10.1515/jisys-2022-0043.

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Abstract Image denoising is one of the important problems in the research field of computer vision, artificial intelligence, 3D vision, and image processing, where the fundamental aim is to recover the original image features from a noisy contaminated image. The camera sensor additive noise present in the holographic recording process reduces the quality of the retrieved image. Even though various techniques have been developed to minimize the noise in digital holography, the noise reduction still remains a challenging task. This article presents a compressive sensing (CS) technique to minimize the additive noise in the digital holographic reconstruction process. We demonstrate the reduction of additive noise using complex wave retrieval method as a sensing matrix in the CS model. The proposed CS method to suppress the noise during the reconstruction process is illustrated using numerical simulations. Only 50% of the pixel measurements are considered in the noisy hologram, which is far less than the original complex object pixels. The impact of additive gaussian noise in the recording plane on the reconstruction accuracy of both intensity and phase distribution is analysed. The CS method denoises and estimates the complex object information accurately. The numerical simulation results have shown that the proposed CS method has effectively minimized the noise in the reconstructed image and has greatly improved the quality of both intensity and phase information.

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Lokesh Reddy, B., Prakash Ramachandran i Anith Nelleri. "Compressive complex wave retrieval from a single off-axis digital Fresnel hologram for quantitative phase imaging and microlens characterization". Optics Communications 478 (styczeń 2021): 126371. http://dx.doi.org/10.1016/j.optcom.2020.126371.

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Li, Xianye, Xiangfeng Meng, Yurong Wang, Xiulun Yang, Yongkai Yin, Xiang Peng, Wenqi He, Guoyan Dong i Hongyi Chen. "Secret shared multiple-image encryption based on row scanning compressive ghost imaging and phase retrieval in the Fresnel domain". Optics and Lasers in Engineering 96 (wrzesień 2017): 7–16. http://dx.doi.org/10.1016/j.optlaseng.2017.04.005.

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Hua, Junlin, Karen M. Fischer, Nicholas J. Mancinelli i Tiezhao Bao. "Imaging with pre-stack migration based on Sp scattering kernels". Geophysical Journal International 220, nr 1 (10.10.2019): 428–49. http://dx.doi.org/10.1093/gji/ggz459.

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SUMMARY Sp receiver functions have been widely used to detect the lithosphere–asthenosphere boundary (LAB) and other mantle discontinuities. However, traditional common conversion point (CCP) stacking can be biased by the assumption of horizontal layers and this method typically underestimates scattering amplitudes from velocity boundaries with significant dips. A new pre-stack migration method based on recently developed Sp scattering kernels offers an alternative that more accurately captures the timing and amplitude of scattering. When calculating kernels, Sp-S times are estimated with the fast-marching method, and scattering amplitude versus direction, geometrical spreading and phase shifts are accounted for. To minimize imaging artefacts with larger station spacing, Sp receiver functions are interpolated to more closely spaced pseudo-stations using either compressive sampling or spatial averaging algorithms. To test the kernel-based stacking method, synthetic Sp phases were predicted using SPECFEM2D for velocity models with a flat Moho and a negative mantle velocity gradient with a ramp structure. The kernel-based stacking method resolves horizontal interfaces equally well as CCP stacking and outperforms CCP stacking when imaging boundaries with dips of more than 8°, although dip resolution is still limited. Use of more vertically incident phases such as SKSp improves retrieval of dipping discontinuity segments. A second approach is to down-weight the portions of the kernels that have the greatest positive interference among neighbouring stations, thus enhancing scattering from dipping structures where positive interference is lower. With this downweighting, the kernel-based stacking method applied to Sp data is able to continuously resolve LAB discontinuities with dips up to 15° and to partially resolve continuous LAB discontinuities with dips of ∼20°. The intrinsic properties of teleseismic Sp phase kernels limit their ability to resolve LAB structures with dips of ∼20–35°, but still larger dips of ∼40–50° are resolvable with dense and appropriately placed stations. Analysis of Sp scattering kernels also explains the effectiveness of CCP stacking for quasi-horizontal interfaces.

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Xu, Cong, i Hui Yu. "Compact system without moving parts for retrieving residuals from storage tanks". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 228, nr 13 (7.01.2014): 2372–82. http://dx.doi.org/10.1177/0954406213518909.

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A compact retrieval system without moving parts was designed to lift and transport residuals in storage tanks to a higher elevation. The key component of the retrieval system, a curve reverse flow diverter (CRFD) with a vortex diode, was machined into a stainless steel disk to enable the entire system to be compact. The compact retrieval system can be installed in storage tanks through an existing narrow mounting hole. The pumping performance of the retrieval system was examined in terms of the effects of curve reverse flow diverter configurations, lift height, compression pressure, and suction pressure. Results reveal that the vortex diode with higher swirl resistance does not enhance the pumping capacity of the retrieval system. The pumping capacity of the retrieval system increased with increasing compression pressure and decreased with increasing lift height and suction pressure. During the compression phase of the retrieval system, the empty factor qc was found to be linear with the Euler number Eu. The compact retrieval system can resolve the difficulty to retrieve high-level radioactive residuals in storage tanks without radioactive leak and frequent maintenance.

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Bakhshizadeh, Milad, Arian Maleki i Shirin Jalali. "Using Black-Box Compression Algorithms for Phase Retrieval". IEEE Transactions on Information Theory 66, nr 12 (grudzień 2020): 7978–8001. http://dx.doi.org/10.1109/tit.2020.3016183.

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Talmi, Amos, i Erez N. Ribak. "Compression of periodic images for faster phase retrieval". Applied Optics 49, nr 31 (28.10.2010): 6116. http://dx.doi.org/10.1364/ao.49.006116.

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Wegkamp, D., D. Brida, S. Bonora, G. Cerullo, J. Stähler, M. Wolf i S. Wall. "Phase retrieval and compression of low-power white-light pulses". Applied Physics Letters 99, nr 10 (5.09.2011): 101101. http://dx.doi.org/10.1063/1.3635396.

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Liu, Wei, Zhengjun Liu i Shutian Liu. "Simultaneous optical image compression and encryption using error-reduction phase retrieval algorithm". Journal of Optics 17, nr 12 (8.10.2015): 125701. http://dx.doi.org/10.1088/2040-8978/17/12/125701.

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Belarbi, Mohammed Amin, Saïd Mahmoudi, Ghalem Belalem, Sidi Ahmed Mahmoudi i Aurélie Cools. "A New Comparative Study of Dimensionality Reduction Methods in Large-Scale Image Retrieval". Big Data and Cognitive Computing 6, nr 2 (13.05.2022): 54. http://dx.doi.org/10.3390/bdcc6020054.

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Indexing images by content is one of the most used computer vision methods, where various techniques are used to extract visual characteristics from images. The deluge of data surrounding us, due the high use of social and diverse media acquisition systems, has created a major challenge for classical multimedia processing systems. This problem is referred to as the ‘curse of dimensionality’. In the literature, several methods have been used to decrease the high dimension of features, including principal component analysis (PCA) and locality sensitive hashing (LSH). Some methods, such as VA-File or binary tree, can be used to accelerate the search phase. In this paper, we propose an efficient approach that exploits three particular methods, those being PCA and LSH for dimensionality reduction, and the VA-File method to accelerate the search phase. This combined approach is fast and can be used for high dimensionality features. Indeed, our method consists of three phases: (1) image indexing within SIFT and SURF algorithms, (2) compressing the data using LSH and PCA, and (3) finally launching the image retrieval process, which is accelerated by using a VA-File approach.

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Hanafi, Idris, i Amal Abdel-Raouf. "P-Codec: Parallel Compressed File Decompression Algorithm for Hadoop". INTERNATIONAL JOURNAL OF COMPUTERS & TECHNOLOGY 15, nr 8 (24.05.2016): 6991–98. http://dx.doi.org/10.24297/ijct.v15i8.1500.

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The increasing amount and size of data being handled by data analytic applications running on Hadoop has created a need for faster data processing. One of the effective methods for handling big data sizes is compression. Data compression not only makes network I/O processing faster, but also provides better utilization of resources. However, this approach defeats one of Hadoopâ€™s main purposes, which is the parallelism of map and reduce tasks. The number of map tasks created is determined by the size of the file, so by compressing a large file, the number of mappers is reduced which in turn decreases parallelism. Consequently, standard Hadoop takes longer times to process. In this paper, we propose the design and implementation of a Parallel Compressed File Decompressor (P-Codec) that improves the performance of Hadoop when processing compressed data. P-Codec includes two modules; the first module decompresses data upon retrieval by a data node during the phase of uploading the data to the Hadoop Distributed File System (HDFS). This process reduces the runtime of a job by removing the burden of decompression during the MapReduce phase. The second P-Codec module is a decompressed map task divider that increases parallelism by dynamically changing the map task split sizes based on the size of the final decompressed block. Our experimental results using five different MapReduce benchmarks show an average improvement of approximately 80% compared to standard Hadoop.

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Li, Hai-Sheng, Qingxin Zhu, Ri-Gui zhou, Ming-Cui Li, lan Song i Hou Ian. "Multidimensional color image storage, retrieval, and compression based on quantum amplitudes and phases". Information Sciences 273 (lipiec 2014): 212–32. http://dx.doi.org/10.1016/j.ins.2014.03.035.

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Wang, Yujie, Praneeth Chakravarthula, Qi Sun i Baoquan Chen. "Joint neural phase retrieval and compression for energy- and computation-efficient holography on the edge". ACM Transactions on Graphics 41, nr 4 (lipiec 2022): 1–16. http://dx.doi.org/10.1145/3528223.3530070.

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Recent deep learning approaches have shown remarkable promise to enable high fidelity holographic displays. However, lightweight wearable display devices cannot afford the computation demand and energy consumption for hologram generation due to the limited onboard compute capability and battery life. On the other hand, if the computation is conducted entirely remotely on a cloud server, transmitting lossless hologram data is not only challenging but also result in prohibitively high latency and storage. In this work, by distributing the computation and optimizing the transmission, we propose the first framework that jointly generates and compresses high-quality phase-only holograms. Specifically, our framework asymmetrically separates the hologram generation process into high-compute remote encoding (on the server), and low-compute decoding (on the edge) stages. Our encoding enables light weight latent space data, thus faster and efficient transmission to the edge device. With our framework, we observed a reduction of 76% computation and consequently 83% in energy cost on edge devices, compared to the existing hologram generation methods. Our framework is robust to transmission and decoding errors, and approach high image fidelity for as low as 2 bits-per-pixel, and further reduced average bit-rates and decoding time for holographic videos.

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Shi, Hongyin, Ting Yang i Zhijun Qiao. "ISAR Autofocus Imaging Algorithm for Maneuvering Targets Based on Phase Retrieval and Gabor Wavelet Transform". Remote Sensing 10, nr 11 (15.11.2018): 1810. http://dx.doi.org/10.3390/rs10111810.

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The imaging issue of a rotating maneuvering target with a large angle and a high translational speed has been a challenging problem in the area of inverse synthetic aperture radar (ISAR) autofocus imaging, in particular when the target has both radial and angular accelerations. In this paper, on the basis of the phase retrieval algorithm and the Gabor wavelet transform (GWT), we propose a new method for phase error correction. The approach first performs the range compression on ISAR raw data to obtain range profiles, and then carries out the GWT transform as the time-frequency analysis tool for the rotational motion compensation (RMC) requirement. The time-varying terms, caused by rotational motion in the Doppler frequency shift, are able to be eliminated at the selected time frame. Furthermore, the processed backscattered signal is transformed to the one in the frequency domain while applying the phase retrieval to run the translational motion compensation (TMC). Phase retrieval plays an important role in range tracking, because the ISAR echo module is not affected by both radial velocity and the acceleration of the target. Finally, after the removal of both the rotational and translational motion errors, the time-invariant Doppler shift is generated, and radar returned signals from the same scatterer are always kept in the same range cell. Therefore, the unwanted motion effects can be removed by applying this approach to have an autofocused ISAR image of the maneuvering target. Furthermore, the method does not need to estimate any motion parameters of the maneuvering target, which has proven to be very effective for an ideal range–Doppler processing. Experimental and simulation results verify the feasibility of this approach.

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Wu, Zhenhua, Fafa Zhao, Man Zhang, Jun Qian i Lixia Yang. "Real-Time Phaseless Microwave Frequency-Diverse Imaging with Deep Prior Generative Neural Network". Remote Sensing 14, nr 22 (9.11.2022): 5665. http://dx.doi.org/10.3390/rs14225665.

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The millimeter-wave frequency-diverse imaging regime has recently received considerable attention in both the security screening and synthetic aperture radar imaging literature. Considering that the minor systematic errors and alignment errors could still produce heavily corrupted images, these complex-based imaging reconstructions rely heavily on the precise measurement of both phase and amplitude of radiation field patterns and echo signals. In the literature, it is shown that by leveraging phase-retrieval techniques, salient reconstruction images can still be acquired, even in the presence of significant phase errors, which could ease the phase error calibration pressure to a large extent in practical imaging applications. In this paper, in the regime of phaseless frequency-diverse imaging, with the powerful feature inference and generation power of unsupervised generative models, an end-to-end deep prior generative neural network is designed to achieve near real-time imaging. The harsh imaging reconstruction with both the high radiation mode correlations and extremely low scene compression sampling ratio, which are extremely troublesome to tackle for generally applied matched-filter and compressed sensing approach in the current frequency-diverse imaging literature, can still be preferably handled with our reconstruction network. The well-trained reconstruction network is constituted by prior inference and deep generative modules with excellent generative capabilities and significant prior inference abilities. Using simulation experiments with radiation field data, we verify that the integration of phase-free frequency-change imaging with deep learning networks can effectively improve reconstruction capabilities and improve robustness to systematic phase errors. Compared with existing imaging methods, our imaging method has high imaging performance and can even reconstruct targets under low compression ratio conditions, which is somewhat competitive with current state-of-the-art algorithms. Moreover, we find that the proposed method has good anti-noise and stability.

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Xu, Qing, Jiang Da He, Hong Qiang Xie, Ming Li Xiao i Jian Feng Liu. "Prefabricated Structures Surface Marble Rheological Tests and Constitutive Model Analysis". Applied Mechanics and Materials 501-504 (styczeń 2014): 419–25. http://dx.doi.org/10.4028/www.scientific.net/amm.501-504.419.

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The mechanical properties of intact rock and rock containing structural plane are very different. From the diversion tunnel of Jinping deep rock site to retrieve the complete block of marble, after a high confining pressure triaxial compression simulation tectonic movements, the formation of structural plane, it represents the mechanical properties of the original rock. On the surface of the marble structure containing triaxial compression creep tests, the results showed: at low confining pressure, the weak marble surface as micro-damage accumulation, the emergence of non-uniform partial destruction, while at high confining pressure, creep curve better continuity and integrity; different confining pressures, marble initial rheology and stability both appear rheological phase, accelerated phase rheological obvious; different confining pressures, the same stage of the axial stress steady flow rate compared with the confining pressure increases, the axial steady state flow rate becomes smaller; marble under test showed the rheological properties, the use of Nishihara model can better demonstrate the rheological properties and determine the rheological parameters for other practical engineering reference.

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Lo, Mor Diama, Matthieu Davy i Laurent Ferro-Famil. "Low-Complexity 3D InISAR Imaging Using a Compressive Hardware Device and a Single Receiver". Sensors 22, nr 15 (5.08.2022): 5870. http://dx.doi.org/10.3390/s22155870.

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An Interferometric Inverse SAR system is able to perform 3D imaging of non-cooperative targets by measuring their responses over time and through several receiving antennas. Phase differences between signals acquired with a spatial diversity in vertical or horizontal directions are used to localize moving scatterers in 3D. The use of several receiving channels generally results into a costly and complex hardware solution, and this paper proposes performing this multichannel acquisition using a single receiver and a hardware compressive device, based on a chaotic cavity which simultaneously multiplexes in the spectral domain signals acquired over different antennas. The radar responses of the scene are encoded in the spectral domain onto the single output of a leaky chaotic cavity, and can be retrieved by solving an inverse problem involving the random transfer matrix of the cavity. The applicability of this compressed sensing approach for the 3D imaging of a non-cooperative target using low-complexity hardware is demonstrated using both simulations and measurements. This study opens up new perspectives to reduce the hardware complexity of high-resolution ISAR systems.

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Arita, Masanori, Yasuhito Takahashi, Giuseppe Pezzotti, Takaaki Shishido, Toshinori Masaoka, Keiji Sano i Kengo Yamamoto. "Environmental Stability and Residual Stresses in Zirconia Femoral Head for Total Hip Arthroplasty:In VitroAging versus Retrieval Studies". BioMed Research International 2015 (2015): 1–9. http://dx.doi.org/10.1155/2015/638502.

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The objective of this study was to compare the low temperature degradation (LTD) behavior of femoral heads made of 3Y-TZP as observed on retrievals with that inducedin vitroupon prolonged exposures to a hydrothermal environment. The time-dependent evolution of tetragonal-to-monoclinic transformation and the related residual stresses were nondestructively monitored by Raman microspectroscopy. An increasing intensification of tensile and compressive stresses was detected with increasing hydrothermal aging duration in tetragonal and monoclinic phases, respectively. The dependence of monoclinic fraction upon exposure time was rationalized through the Mehl-Avrami-Johnson (MAJ) formalism in order to interpret the LTD process according to a two-step mechanism of formation and growth of monoclinic nuclei.In vitroresults were compared toin vivomonoclinic contents in the same type of 3Y-TZP head retrievals after implantation periods of 1.6–16.6 y, also including literature data previously reported by other authors. One-hour exposure under the selected aging condition is estimated to correspond toin vivoexposures of 4 and 2 years according to ISO and ASTM criteria, respectively. A critical review of these two criteria according to the present analyses revealed that the ASTM simulation predicts more closely thein vivoresults as compared to the ISO one.

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Marone, Federica, Jakob Vogel i Marco Stampanoni. "Impact of lossy compression of X-ray projections onto reconstructed tomographic slices". Journal of Synchrotron Radiation 27, nr 5 (28.07.2020): 1326–38. http://dx.doi.org/10.1107/s1600577520007353.

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Modern detectors used at synchrotron tomographic microscopy beamlines typically have sensors with more than 4–5 mega-pixels and are capable of acquiring 100–1000 frames per second at full frame. As a consequence, a data rate of a few TB per day can easily be exceeded, reaching peaks of a few tens of TB per day for time-resolved tomographic experiments. This data needs to be post-processed, analysed, stored and possibly transferred, imposing a significant burden onto the IT infrastructure. Compression of tomographic data, as routinely done for diffraction experiments, is therefore highly desirable. This study considers a set of representative datasets and investigates the effect of lossy compression of the original X-ray projections onto the final tomographic reconstructions. It demonstrates that a compression factor of at least three to four times does not generally impact the reconstruction quality. Potentially, compression with this factor could therefore be used in a transparent way to the user community, for instance, prior to data archiving. Higher factors (six to eight times) can be achieved for tomographic volumes with a high signal-to-noise ratio as it is the case for phase-retrieved datasets. Although a relationship between the dataset signal-to-noise ratio and a safe compression factor exists, this is not simple and, even considering additional dataset characteristics such as image entropy and high-frequency content variation, the automatic optimization of the compression factor for each single dataset, beyond the conservative factor of three to four, is not straightforward.

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Pascu, Ionuț-Silviu, Alexandru-Claudiu Dobre, Ovidiu Badea i Mihai Andrei Tanase. "Retrieval of Forest Structural Parameters From Terrestrial Laser Scanning: A Romanian Case Study". Forests 11, nr 4 (1.04.2020): 392. http://dx.doi.org/10.3390/f11040392.

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Research Highlights: The present study case investigates the differences occurring when tree’s biophysical parameters are extracted through single and multiple scans. Scan sessions covered mountainous and hill regions of the Carpathian forests. Background and Objectives: We focused on analyzing stems, as a function of diameter at breast height (DBH) and the total height (H), at sample plot level for natural forests, with the purpose of assessing the potential for transitioning available methodology to field work in Romania. Materials and Methods: We performed single and multiple scans using a FARO Focus 3D X130 phase shift terrestrial laser scanner at 122kpts and 0.3:0.15 mm noise compression ratio, resulting in an average point density of 6pts at 10m. The point cloud we obtained underpinned the DBH and heights analysis. In order to reach values similar to those measured in the field, we used both the original and the segmented point clouds, postprocessed in subsamples of different radii. Results: Pearson’s correlation coefficient above 0.8 for diameters showed high correlation with the field measurements. Diameter averages displayed differences within tolerances (0.02m) for 10 out of 12 plots. Height analysis led to poorer results. For both acquisition methods, the values of the correlation coefficient peaked at 0.6. The initial hypothesis that trees positioned at a distance equivalent to their height can be measured more precise, was not valid; no increase in correlation strength was visible for either heights or diameters as the distance from scanner varied (r = 0.52). Conclusions: With regard to tree biophysical parameters extraction, the acquisition method has no major influence upon visible trees. We emphasize the term “visible”, as an increase in the number of acquisitions led to an increased number of detected trees (16% in old stands and 29% in young stands).

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Liang, Ling, Jilan Lin, Zheng Qu, Ishtiyaque Ahmad, Fengbin Tu, Trinabh Gupta, Yufei Ding i Yuan Xie. "SPG: Structure-Private Graph Database via SqueezePIR". Proceedings of the VLDB Endowment 16, nr 7 (marzec 2023): 1615–28. http://dx.doi.org/10.14778/3587136.3587138.

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Many relational data in our daily life are represented as graphs, making graph application an important workload. Because of the large scale of graph datasets, moving graph data to the cloud becomes a popular option. To keep the confidential and private graph secure from an untrusted cloud server, many cryptographic techniques are leveraged to hide the content of the data. However, protecting only the data content is not enough for a graph database. Because the structural information of the graph can be revealed through the database accessing track. In this work, we study the graph neural network (GNN), an important graph workload to mine information from a graph database. We find that the server is able to infer which node is processing during the edge retrieving phase and also learn its neighbor indices during GNN's aggregation phase. This leads to the leakage of the information of graph structure data. In this work, we present SPG, a structure-private graph database with SqueezePIR. Our SPG is built on top of Private Information Retrieval (PIR), which securely hides which nodes/neighbors are accessed. In addition, we propose SqueezePIR, a compression technique to overcome the computation overhead of PIR. Based on our evaluation, our SqueezePIR achieves 11.85× speedup on average with less than 2% accuracy loss when compared to the state-of-the-art FastPIR protocol.

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Martín, C., R. Mulvaney, G. H. Gudmundsson i H. Corr. "Inferring paleo-accumulation records from ice-core data by an adjoint method: application to James Ross Island's ice core". Climate of the Past Discussions 10, nr 5 (24.09.2014): 3821–45. http://dx.doi.org/10.5194/cpd-10-3821-2014.

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Abstract. Ice cores contain a record of snow precipitation that includes information about past atmospheric circulation and mass imbalance in the polar regions. We present a novel adjoint method to reconstruct a climatic record by both optimally dating an ice-core and deriving from it a detailed accumulation history. The motivation of our work is the recent application of phase sensitive radar which measures the vertical velocity of an ice column. The velocity is dependent on the history of subsequent snow accumulation, compaction and compression; and in our inverse formulation of this problem, measured vertical velocity profiles can be utilized directly thereby reducing the uncertainty introduced by ice flow modelling. We first apply our method to synthetic data in order to study its capability and the effect of noise and gaps in the data on retrieved accumulation history. The method is then applied to the ice core retrieved from James Ross Island, Antarctica. We show that the method is robust and that the results depend on quality of the age-depth observations and the derived flow regime around the core site. The method facilitates the incorporation of increasing detail provided by ice-core analysis together with observed full-depth velocity in order to construct a complete climatic record of the polar regions.

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Rajasekhar, Anita, Hany Elmariah, Darwin Ang, Lawrence Lottenberg, Rebecca Beyth i Richard Lottenberg. "Inferior Vena Cava Filters in Trauma Patients: A National Practice Pattern Survey of U.S. Trauma Centers". Blood 120, nr 21 (16.11.2012): 4249. http://dx.doi.org/10.1182/blood.v120.21.4249.4249.

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Abstract Abstract 4249 Background: Despite the paucity of randomized controlled trials and strong observational studies supporting the efficacy of inferior vena cava filters (IVCFs) in venous thromboembolism (VTE) prevention, indications for placement of IVCFs have increased. Further, evidence-based guidelines for removal of retrievable filters do not exist. The purpose of this study was to characterize contemporary IVCF practices in the prevention and management of VTE, and clarify the stakeholders in IVCF placement and retrieval among trauma centers across the United States. Methods: In September 2011 a web-based survey was distributed to 1206 members of the Eastern Association for the Surgery of Trauma (EAST) in 3 waves over 3 weeks. This 31-question multiple choice and open-ended survey addressed: 1) provider and practice characteristics, 2) trauma patient population, 3) clinical practice of IVCF placement and retrieval, and 4) pharmacologic prophylaxis (PP). Results: Of the 1059 eligible providers that care for trauma patients on a routine basis, 281 completed the survey (27% response rate); 27% were identified as trauma directors. Seventy-two percent of all responents practiced in an academic setting and 74.7% in a level-1 trauma center. Sixty percent of trauma directors reported more than 1,000 trauma admissions per year. Familiarity with the 2002 EAST and 2008 American College of Chest Physicians guidelines for IVCF placement was noted by 84.3% and 63.0% of respondents, respectively. The majority of trauma centers placed IVCFs (98.9%), of which 3.6% placed only permanent IVCFs, 27.3% only retrievable IVCFs, and 67.3% both. Only 28.4% of centers had an institutional clinical protocol for IVCF placement and 25.5% for removal of IVCFs. The most common indication for IVCF placement was acute VTE and contraindication to therapeutic anticoagulation (32.4%). Prophylactic IVCFs (pIVCFs) in high-risk patients without known VTE were utilized by 97.6% of respondents. Indications for pIVCFs included inability to receive PP (26.5%), incomplete spinal cord injury (19.8%), and complex pelvic fracture with long bone fracture (19.6%). Filter insertion was performed by interventional radiologists (48.1%), vascular surgeons (35.6%), and/or trauma surgeons (15.5%) at each institution. Ultrasound guidance was used in 23.3% of IVCFs placed and 14.0% of insertions occured at the bedside. Acute and long-term complications encountered by providers included filter migration (21.0%), recurrent VTE (15.5%), hematoma (15.5%), and inferior vena cava thrombosis (13.8%). Surveillance for lower extremity deep vein thromboses in trauma patients was performed by 52% of centers. A registry to track patients with IVCFs was maintained by 38% of centers. Decisions to refer patients for IVCF removal were made by the proceduralist service (37.7%), ordering service (38.7%), and/or service following patients after discharge (12.7%). Only 2.5% of respondents removed IVCFs prior to hospital discharge. Screening for VTE prior to IVCF removal was performed with ultrasound (28%), venogram (14.4%), or computed tomography (2.5%), however 43.3% were uncertain of the screening method. In addition to IVCFs, adjunctive VTE prophylaxis indicated by respondents were sequential compression devices (26.7%), low molecular weight heparin (39.0%), unfractionated heparin (25.2%), fondaparinux (5.4%), or aspirin (2.0%). Only 1% of respondents indicated not using PP in trauma patients with IVCFs. Formal institutional PP guidelines existed in 92.9% of institutions. The most common reasons for contraindication to PP included pelvic or retroperitoneal hematoma requiring transfusion of blood products (20.0%), traumatic brain injury (18.3%), ocular injury with hemorrhage (16.3%), coagulopathy (13.6%), and solid intra-abdominal organ injury (11.4%). Sixty-one providers (7.1%) did not indicate any absolute contraindications for PP outside of acute phase of the above injuries. Conclusion: This study confirms the widespread use of IVCFs for both acute VTE and prophylactic indications. However, considerable variation in practice patterns with regards to institutional protocols for IVCF placement and retireval as well as utilization of adjunctive pharmacologic prophylaxis exists. These differences highlight the need for well-designed randomized controlled trials to address the efficacy and safety of IVCFs in trauma patients. Disclosures: No relevant conflicts of interest to declare.

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Philip, G., D. Crookes i Z. Juhasz. "QUIMaS (Queen's University Image Management System): a museum photographic database". Journal of Information Science 20, nr 3 (czerwiec 1994): 161–74. http://dx.doi.org/10.1177/016555159402000302.

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This paper reports on the construction of an interactive image management system. The system's operation is improved by image processing techniques and parallel processing technology. Although image processing is largely a well understood problem, the technology for supporting it is still immature. Basically, it is a highly computationally intensive activity, and the purpose of our project was to address this very problem using parallel processing technology in the form of transputers. More specifically, we will describe the use of a transputer network in the development of an image database consisting of a collection of historical museum photographs. During the first phase of the project, we developed a prototype system consisting of a small number of photographs using a simple hardware configuration. It made use of the hard disk of the PC to store the photographs and was implemented using a single transputer. During the second phase, the full hardware configuration was implemented, including the building up of the database of around 1,000 photographs. The final system consists of an IBM-compatible PC equipped with the necessary image processing and mass storage facilities (650 Mb hard disk) and linked to a network of six transputers. The user interface is provided through a serial mouse and a keyword menu. Users are able to retrieve images in three different modes: (i) a predefined keyword list, which is arranged in a hierarchical fashion to select images relating to a particular subject or geographical area; (ii) the Browse mode allows the user to display a set of up to twelve photographs in miniature ‘stub’ format at one go (this is similar to the turning of the pages of an album). Individual items can then be selected and displayed in full size, if necessary; (iii) if the museum reference number is known, the user can type in the number to retrieve the relevant item. Section 1 will provide a brief review of the background to the project and the use of transputer technology in image processing. The selection and documentation of the photographs are described in Section 2. Section 3 describes the hardware and software configuration of the single-transputer-based prototype, and the full image database system implemented on a network of transputers. The organisation of the database, both textual and image data, is explained in Section 4. This is followed by a description of the processing techniques for image enhancement and compression, and a discussion of the results of both compression and decompression processes. The final section will discuss the menu-based, mouse-driven user interface, including the various search facilities and display modes used to view images from the database.

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Meneghini, R., L. Liao i L. Tian. "A Feasibility Study for Simultaneous Estimates of Water Vapor and Precipitation Parameters Using a Three-Frequency Radar". Journal of Applied Meteorology 44, nr 10 (1.10.2005): 1511–25. http://dx.doi.org/10.1175/jam2302.1.

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Abstract The radar return powers from a three-frequency radar, with center frequency at 22.235 GHz and upper and lower frequencies chosen with equal water vapor absorption coefficients, can be used to estimate water vapor density and parameters of the precipitation. A linear combination of differential measurements between the center and lower frequencies on one hand and the upper and lower frequencies on the other provide an estimate of differential water vapor absorption. The coupling between the precipitation and water vapor estimates is generally weak but increases with bandwidth and the amount of non-Rayleigh scattering of the hydrometeors. The coupling leads to biases in the estimates of water vapor absorption that depend primarily on the phase state and the median mass diameter of the hydrometeors. For a down-looking radar, path-averaged estimates of water vapor absorption are possible under rain-free as well as raining conditions by using the surface returns at the three frequencies. Simulations of the water vapor attenuation retrieval show that the largest source of error typically arises from the variance in the measured radar return powers. Although the error can be mitigated by a combination of a high pulse repetition frequency, pulse compression, and averaging in range and time, the radar receiver must be stable over the averaging period. For fractional bandwidths of 20% or less, the potential exists for simultaneous measurements at the three frequencies with a single antenna and transceiver, thereby significantly reducing the cost and mass of the system.

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Martín, C., R. Mulvaney, G. H. Gudmundsson i H. Corr. "Inferring palaeo-accumulation records from ice-core data by an adjoint-based method: application to James Ross Island's ice core". Climate of the Past 11, nr 3 (27.03.2015): 547–57. http://dx.doi.org/10.5194/cp-11-547-2015.

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Abstract. Ice cores contain a record of snow precipitation that includes information about past atmospheric circulation and mass imbalance in the polar regions. We present a novel approach to reconstruct a climatic record – by both optimally dating an ice core and deriving from it a detailed accumulation history – that uses an adjoint-based method. The motivation of our work is the recent application of phase-sensitive radar which measures the vertical velocity of an ice column. The velocity is dependent on the history of subsequent snow accumulation, compaction and compression; in our inverse formulation of this problem, measured vertical velocity profiles can be utilized directly, thereby reducing the uncertainty introduced by ice-flow modelling. We first apply our method to synthetic data in order to study its capability and the effect of noise and gaps in the age–depth observations. The method is then applied to the ice core retrieved from James Ross Island, Antarctica. We show that the method is robust and that the results depend on the quality of the age–depth observations and the derived flow regime around the core site. The method facilitates the incorporation of increasing detail provided by ice-core analysis together with observed full-depth velocity in order to construct a complete climatic record of the polar regions.

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Nouioua, Nadhir, Ali Seddiki i Abdelkrim Ghaz. "Blind Digital Watermarking Framework Based on DTCWT and NSCT for Telemedicine Application". Traitement du Signal 37, nr 6 (31.12.2020): 955–64. http://dx.doi.org/10.18280/ts.370608.

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In this work, a blind watermarking framework for medical images based on Dual-Tree Complex Wavelet Transform (DTCWT) and Non-subsampled Contourlet Transform (NSCT) is proposed. The core idea of this technique is to embed the watermark in the appropriate NSCT sub-band obtained by decomposing the cover image low coefficients purchased from the DTCWT standing on a quantization embedding function, the extraction phase is done without the requirement of the original cover image, what makes it a fully blind process. As clarity and integrity of the retrieved watermark are mandatory, a series of tests were exerted to affirm the robustness of the proposed scheme. The effectiveness of the watermarking is validated by using the peak signal-to-noise ratio (PSNR) and the structural similarity index measure (SSIM) through experiments. Simulation results demonstrate the invisibility of the proposed method and its strong robustness against various attacks, including additive noise, image filtering, JPEG compression, amplitude scaling, rotation attack, and combinational attack. Furthermore, the method in hands outperformance within the quantitative comparisons with other techniques in the literature in terms of rapid execution time, and quality extraction of hidden information, and appropriateness to be integrated for secure exchange in the healthcare sector.

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Zhang, Qingjun, Cheng Hu, Lixin Wu, Tao Zeng i Teng Long. "Imaging Formation Algorithm of the Ground and Space-Borne Hybrid BiSAR Based on Parameters Estimation from Direct Signal". Mathematical Problems in Engineering 2014 (2014): 1–11. http://dx.doi.org/10.1155/2014/294306.

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This paper proposes a novel image formation algorithm for the bistatic synthetic aperture radar (BiSAR) with the configuration of a noncooperative transmitter and a stationary receiver in which the traditional imaging algorithm failed because the necessary imaging parameters cannot be estimated from the limited information from the noncooperative data provider. In the new algorithm, the essential parameters for imaging, such as squint angle, Doppler centroid, and Doppler chirp-rate, will be estimated by full exploration of the recorded direct signal (direct signal is the echo from satellite to stationary receiver directly) from the transmitter. The Doppler chirp-rate is retrieved by modeling the peak phase of direct signal as a quadratic polynomial. The Doppler centroid frequency and the squint angle can be derived from the image contrast optimization. Then the range focusing, the range cell migration correction (RCMC), and the azimuth focusing are implemented by secondary range compression (SRC) and the range cell migration, respectively. At last, the proposed algorithm is validated by imaging of the BiSAR experiment configured with china YAOGAN 10 SAR as the transmitter and the receiver platform located on a building at a height of 109 m in Jiangsu province. The experiment image with geometric correction shows good accordance with local Google images.

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Kong, Lijiao, i Ailing Yan. "Robust amplitude method with $ L_{1/2} $-regularization for compressive phase retrieval". Journal of Industrial and Management Optimization, 2023, 0. http://dx.doi.org/10.3934/jimo.2023014.

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Li, Peng, Wen Gu Chen i Qi Yu Sun. "Inertial Proximal ADMM for Separable Multi-Block Convex Optimizations and Compressive Affine Phase Retrieval". Acta Mathematica Sinica, English Series, 10.05.2023. http://dx.doi.org/10.1007/s10114-023-1401-x.

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Shujia Wan, Qiong Gong, Hongjuan Wang, Shibang Ma i Yi Qin. "Compressed optical image encryption in the diffractive-imaging-based scheme by input plane and output plane random sampling". Optica Applicata 52, nr 1 (2022). http://dx.doi.org/10.37190/oa220104.

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The successful recovery of the plaintext in the simplified diffractive-imaging-based encryption (S-DIBE) scheme needs to record one intact axial intensity map as the ciphertext. By aid of compressive sensing, we propose here a new image encryption approach, referred to as compressed DIBE (C-DIBE), which allows further compression of the intensity map. The plaintext is sampled before being sent to DIBE. Afterwards, the intensity map recorded by the CCD camera is also processed by such sampling operation to generate the ciphertext. For decryption, we first obtain the sparse plaintext using the proposed phase retrieval algorithm, and then reobtain the primary plaintext from it via compressive sensing. Numerical results show that a proper proportion of the intensity map (e.g. 50%) is enough to totally recover a grayscale image. We achieve multiple-image encryption by space multiplexing without enlarging the size of the ciphertext. The robustness of C-DIBE against brute-force attack evidently outperforms S-DIBE due to the extended key space. Numerical simulation has been presented to confirm the proposal.

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Jafari, Mahin, Mahtab Aflaki, Zahra Mousavi, Andrea Walpersdorf i Khalil Motaghi. "Coseismic and postseismic characteristics of the 2021 Ganaveh earthquake along the Zagros foredeep fault based on InSAR data". Geophysical Journal International, 23.03.2023. http://dx.doi.org/10.1093/gji/ggad127.

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Summary The Ganaveh earthquake on 2021 April 18 (Mw 5.8) occurred in the southwest of the Dezful embayment of the Zagros Mountain belt, Iran, as a mainly compressive event. The InSAR coseismic displacement maps reveal a maximum of 17 cm of surface displacement in the satellite line of sight direction. InSAR inversion indicates a low-angle NE-dipping causative fault plane with a maximum slip of 95 cm at ∼6 km depth. It highlights the occurrence of the Ganaveh earthquake within the competent layers of the Zagros sedimentary cover, beneath the Gachsaran formation. A slight sinistral slip component (2.9 cm) is retrieved which is compatible with the USGS focal mechanism. Time series analysis of SAR images after the mainshock until the end of 2021 indicates a maximum of 7 cm of postseismic surface displacement with a similar strike and pattern as the coseismic phase. This similarity and the distribution of aftershocks suggest an afterslip mechanism for the postseismic phase. The inversion of postseismic cumulative displacement evaluates a maximum of 30 cm slip at a depth of ∼5 km along the coseismic causative fault. A regional compressional stress regime (N041° E for the direction of the σ1 stress axis) is constrained by using the focal mechanisms of 39 earthquakes occurring between 1968 and 2021, including the Ganaveh mainshock and its five larger aftershocks. Applying this direction of compression on the Ganaveh fault plane also results in a minor sinistral movement, consistent with the geodetic results. The relocated mainshock and aftershocks as well as our InSAR coseismic displacement situations on the hanging wall of the Zagros Foredeep fault highlight it as the causative fault of the Ganaveh earthquake. To fit the geometry of the Ganaveh rupture plane with the Zagros Foredeep fault, we modeled a listric fault plane and its slip distribution using the available geological data. The retrieved slip variation on the listric plane is in close agreement with the slip pattern on the modeled planar geometry. The low dip angle of the rupture plane combined with a listric geometry highlights the thin-skin characteristics of the Zagros Foredeep fault as the causative fault of the Ganaveh earthquake. The occurrence of this moderate magnitude earthquake on the Zagros Foredeep fault underlines its role as the western structural boundary for the recurrence of Mb > 5 events in the Dezful embayment.

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"CBIR : Color Feature Extraction using CIELAB Color Space with Compact Color Signature". International Journal of Innovative Technology and Exploring Engineering 9, nr 6 (10.04.2020): 470–76. http://dx.doi.org/10.35940/ijitee.f3770.049620.

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The immense progress of new technology we have been created an enormous number of digital images by using such devices as a digital camera, scanner, and mobile phones so on. All the images which are taken by the devices to keep in Image Database. For retrieving the desire images which were given in an input image has compared with the large database according to the visual content used by the technique as referred to as the Content Based Image Retrieval (CBIR) system. There are two phases for retrieving images in the CBIR system, as the first one is feature extraction and the second one is similarity size. Thus, the feature extraction consists of every image has produced symbolic content in the form of the function. The visual contents of an image in the CBIR system contain the features which have represented as shape, texture, spatial region and color of the images. In our paper tries to design the images’ color features as in the steps to focus color representation in the k-d tree, CIELAB color space of color signature compression along with categories of Human’s color for Content-based image retrieval and also acquire the results using MATLAB.

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Nishimoto, Yuji, Masanao Toma, Kohei Iwasa i Yukihito Sato. "Successful staged management of a spontaneous iliac vein rupture associated with May–Thurner syndrome: a case report". European Heart Journal - Case Reports 5, nr 8 (1.08.2021). http://dx.doi.org/10.1093/ehjcr/ytab316.

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Abstract Background Spontaneous iliac vein ruptures have only been reported in approximately 50 cases. An accurate preoperative diagnosis is difficult even with contrast-enhanced computed tomography (CT), and the operative mortality and morbidity rates are quite high. The cause of spontaneous iliac vein ruptures and their optimal diagnosis and management remain unclear. Case summary A 69-year-old woman without a history of prior trauma presented with low back pain, left lower limb swelling, and hypovolaemic shock. An initial contrast-enhanced CT revealed a large retroperitoneal haematoma without arterial extravasation. Her blood pressure dropped again under a noradrenaline administration. A second venous phase contrast-enhanced CT revealed venous extravasation in the external iliac vein with a suspected compression of the common iliac vein (May–Thurner syndrome) and deep vein thrombosis (DVT). Her haemodynamics were stabilized whilst a laparotomy was arranged. An inferior vena cava (IVC) filter was placed due to concerns about rebleeding with initiating anticoagulation therapy. Given the failed conservative management, elective endovascular treatment (EVT) was performed including percutaneous Fogarty venous thrombectomy and placement of self-expanding and covered stents. After the intervention, the lower limb swelling significantly improved under oral anticoagulation therapy, and the IVC filter was retrieved. At the 3-month follow-up, the lower limb swelling completely disappeared, and the contrast-enhanced CT demonstrated the complete disappearance of the retroperitoneal haematoma and DVT. Discussion This case provided not only the potential value of the venous phase contrast-enhanced CT in diagnosing a spontaneous iliac vein rupture but also the potential benefit of conservative management followed by elective EVT.

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