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1
Paterova, Anna V., Dmitry A. Kalashnikov, Egor Khaidarov, Hongzhi Yang, Tobias W. W. Mass, Ramón Paniagua-Domínguez, Arseniy I. Kuznetsov e Leonid A. Krivitsky. "Non-linear interferometry with infrared metasurfaces". Nanophotonics 10, n. 6 (22 marzo 2021): 1775–84. http://dx.doi.org/10.1515/nanoph-2021-0011.
Testo completoAbstract (sommario):
Abstract The optical elements comprised of sub-diffractive light scatterers, or metasurfaces, hold a promise to reduce the footprint and unfold new functionalities of optical devices. A particular interest is focused on metasurfaces for manipulation of phase and amplitude of light beams. Characterisation of metasurfaces can be performed using interferometry, which, however, may be cumbersome, specifically in the infrared (IR) range. Here, we realise a new method for characterising metasurfaces operating in the telecom IR range using accessible components for visible light. Correlated IR and visible photons are launched into a non-linear interferometer so that the phase profile, imposed by the metasurface on the IR photons, modifies the interference at the visible photon wavelength. Furthermore, we show that this concept can be used for broadband manipulation of the intensity profile of a visible beam using a single IR metasurface. Our method unfolds the potential of quantum interferometry for the characterization of advanced optical elements.
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Bakon, Matus, Daniele Perissin, Milan Lazecky e Juraj Papco. "Infrastructure Non-linear Deformation Monitoring Via Satellite Radar Interferometry". Procedia Technology 16 (2014): 294–300. http://dx.doi.org/10.1016/j.protcy.2014.10.095.
Testo completo
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Jundt, G., G. T. Purves, C. S. Adams e I. G. Hughes. "Non-linear Sagnac interferometry for pump-probe dispersion spectroscopy". European Physical Journal D - Atomic, Molecular and Optical Physics 27, n. 3 (1 dicembre 2003): 273–76. http://dx.doi.org/10.1140/epjd/e2003-00275-5.
Testo completo
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Ogushi, Fumitaka, Masashi Matsuoka, Marco Defilippi e Paolo Pasquali. "Implementation of Non-Linear Non-Parametric Persistent Scatterer Interferometry and Its Robustness for Displacement Monitoring". Sensors 21, n. 3 (2 febbraio 2021): 1004. http://dx.doi.org/10.3390/s21031004.
Testo completoAbstract (sommario):
To derive surface displacement, interferometric stacking with synthetic aperture radar (SAR) data is commonly used, and this technique is now in the implementation phase in the real world. Persistent scatterer interferometry (PSI) is one of the most universal approaches among in- terferometric stacking techniques, and non-linear non-parametric PSI (NN-PSI) was proposed to overcome the drawbacks of PSI approaches. The estimation of the non-linear displacements was successfully conducted using NN-PSI. However, the estimation of NN-PSI is not always stable with certain displacements because wider range of the velocity spectrum is used in NN-PSI than the conventional approaches; therefore, a calculation procedure and parameter optimization are needed to consider. In this paper, optimized parameters and procedures of NN-PSI are proposed, and real data processing with Sentinel-1 in the Kanto region in Japan was conducted. We confirmed that the displacement estimation was comparable to the measurement of the permanent global positioning system (GPS) stations, and the root mean square error between the GPS measurement and NN-PSI estimation was less than 3 mm in two years. The displacement over 2π ambiguity, which the conventional PSI approach wrongly reconstructed, was also quantitatively validated and successfully estimated by NN-PSI. As a result of the real data processing, periodical displacements were also reconstructed through NN-PSI. We concluded that the NN-PSI approach with the proposed parameters and method enabled the estimation of several types of surface displacements that conventional PSI approaches could not reconstruct.
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Corcoran, T. C., L. L. Connell, G. V. Hartland, B. F. Henson e P. M. Felker. "Down-shifting of high frequency components in non-linear interferometry". Chemical Physics Letters 147, n. 6 (giugno 1988): 517–24. http://dx.doi.org/10.1016/0009-2614(88)80260-4.
Testo completo
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Bedding, T. R., J. G. Robertson e R. G. Marson. "MAPPIT: Optical Interferometry with Non-Redundant Masks". Symposium - International Astronomical Union 158 (1994): 327–30. http://dx.doi.org/10.1017/s007418090010782x.
Testo completoAbstract (sommario):
MAPPIT (Masked APerture-Plane Interference Telescope) is an optical interferometer mounted at the coudé focus of the 3.9 m Anglo-Australian Telescope. The instrument, shown schematically in Fig. 1, uses a pupil mask with five apertures of diameter ≲r0. The apertures are arranged in a linear non-redundant array, with the spacings chosen to optimize the spatial frequency coverage (R. G. Marson, these Proceedings).
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Lendiel, Vasyl, Iryna Stepakhno e Leonid Yarovoi. "APPLICATION OF THREE-WAVE HETERODINE INTERFEROMETRY FOR NANORIZED LAYERS THICKNESS MEASUREMENT IN THE PROCESS OF THEIR DEPOSITION". Bulletin of Kyiv Polytechnic Institute. Series Instrument Making, n. 63(1) (4 luglio 2022): 39–45. http://dx.doi.org/10.20535/1970.63(1).2022.260636.
Testo completoAbstract (sommario):
The paper proposes a new method of current measurement of the layer thickness of optical films in the process of their forming, in particular, by the method of vacuum deposition. Such films, among other things, are used to create a variety of optoelectronic devices and optical nanosensors for laboratory research in the chemical and pharmaceutical industries, for environmental monitoring.
We propose a method for measuring the phase of a laser beam, which is based on heterodyne interferometry. The method of heterodyne interferometry in comparison with ordinary interference methods provides better S/N ration results due to the transfer of the investigated signal from the low frequency domain to heterodyne frequency. Our proposed approach is the three-wave heterodyne interferometry (TGI), otherwise - TWI (three waves interference). The TGI method is designed to critically increase the sensitivity to small amplitudes of laser Doppler vibrometers and increase their noise resistance. In interference gauges of optical film thickness, in refractometers, and in many other film thickness gauges as well as in laser Doppler vibrometers the investigated parameter is the phase shift of probing optical radiation. Therefore, the developments of TGI in laser Doppler vibrometers can be used to measure the phase shift.
The analysis of the new method on mathematical model of TGI was provided. We have got the relations of the output signal of a three-wave heterodyne interferometer dependence on the phase shift , as well as on the thickness of optical films and on their refractive index. The simulation results show that for the optoelectronic equipment that provides with an error of up to 10 %, the absolute error of phase shift measurement, compared to the classical heterodyne interferometer, can be reduced to 103 times. The same results applies to the thickness of the optical coating layer.
The paper also analyzes the results of experiments on the use of TGI in laser vibrometers and shows that they indicate the possibility of measuring the phase of optical radiation up to 10-5. The disadvantage of the proposed method is its non-linearity and, as a result, a limited linear range. Ways of extending the linear range are discussed.
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Gerberding, Oliver, e Katharina-Sophie Isleif. "Ghost Beam Suppression in Deep Frequency Modulation Interferometry for Compact On-Axis Optical Heads". Sensors 21, n. 5 (2 marzo 2021): 1708. http://dx.doi.org/10.3390/s21051708.
Testo completoAbstract (sommario):
We present a compact optical head design for wide-range and low noise displacement sensing using deep frequency modulation interferometry (DFMI). The on-axis beam topology is realised in a quasi-monolithic component and relies on cube beamsplitters and beam transmission through perpendicular surfaces to keep angular alignment constant when operating in air or in a vacuum, which leads to the generation of ghost beams that can limit the phase readout linearity. We investigated the coupling of these beams into the non-linear phase readout scheme of DFMI and implemented adjustments of the phase estimation algorithm to reduce this effect. This was done through a combination of balanced detection and the inherent orthogonality of beat signals with different relative time-delays in deep frequency modulation interferometry, which is a unique feature not available for heterodyne, quadrature or homodyne interferometry.
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Martínez-Tapia, Áulide, Samuel Corona-Aquino, Freiman Triana-Arango, Chenglong You, Rui-Bo Jin, Omar S. Magaña-Loaiza, Shi-Hai Dong, Alfred B. U’Ren e Roberto de J. León-Montiel. "Witnessing entangled two-photon absorption via quantum interferometry". APL Photonics 8, n. 3 (1 marzo 2023): 036104. http://dx.doi.org/10.1063/5.0128249.
Testo completoAbstract (sommario):
Recent investigations have suggested that the use of non-classical states of light, such as entangled photon pairs, may open new and exciting avenues in experimental two-photon absorption spectroscopy. Despite several experimental studies of entangled two-photon absorption (eTPA), there is still a heated debate on whether eTPA has truly been observed. This interesting debate has arisen mainly because it has recently been argued that single-photon-loss mechanisms, such as scattering or hot-band absorption, may mimic the expected entangled-photon linear absorption behavior. In this work, we focus on transmission measurements of eTPA and explore three different two-photon quantum interferometers in the context of assessing eTPA. We demonstrate that the so-called N00N-state configuration is the only one among those considered insensitive to linear (single-photon) losses. Remarkably, our results show that N00N states may become a potentially powerful tool for quantum spectroscopy, placing them as a strong candidate for the certification of eTPA in an arbitrary sample.
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Zou, Lilong, Weike Feng, Olimpia Masci, Giovanni Nico, Amir M. Alani e Motoyuki Sato. "Bridge Monitoring Strategies for Sustainable Development with Microwave Radar Interferometry". Sustainability 16, n. 7 (22 marzo 2024): 2607. http://dx.doi.org/10.3390/su16072607.
Testo completoAbstract (sommario):
The potential of a coherent microwave radar for infrastructure health monitoring has been investigated over the past decade. Microwave radar measuring based on interferometry processing is a non-invasive technique that can measure the line-of-sight (LOS) displacements of large infrastructure with sub-millimeter precision and provide the corresponding frequency spectrum. It has the capability to estimate infrastructure vibration simultaneously and remotely with high accuracy and repeatability, which serves the long-term serviceability of bridge structures within the context of the long-term sustainability of civil engineering infrastructure management. In this paper, we present three types of microwave radar systems employed to monitor the displacement of bridges in Japan and Italy. A technique that fuses polarimetric analysis and the interferometry technique for bridge monitoring is proposed. Monitoring results achieved with full polarimetric real aperture radar (RAR), step-frequency continuous-wave (SFCW)-based linear synthetic aperture, and multi-input multi-output (MIMO) array sensors are also presented. The results reveal bridge dynamic responses under different loading conditions, including wind, vehicular traffic, and passing trains, and show that microwave sensor interferometry can be utilized to monitor the dynamics of bridge structures with unprecedented spatial and temporal resolution. This paper demonstrates that microwave sensor interferometry with efficient, cost-effective, and non-destructive properties is a serious contender to employment as a sustainable infrastructure monitoring technology serving the sustainable development agenda.
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Mirmazloumi, S. M., Á. F. Gambin, Y. Wassie, A. Barra, R. Palamà, M. Crosetto, O. Monserrat e B. Crippa. "INSAR DEFORMATION TIME SERIES CLASSIFICATION USING A CONVOLUTIONAL NEURAL NETWORK". International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLIII-B3-2022 (30 maggio 2022): 307–12. http://dx.doi.org/10.5194/isprs-archives-xliii-b3-2022-307-2022.
Testo completoAbstract (sommario):
Abstract. Temporal analysis of deformations Time Series (TS) provides detailed information of various natural and humanmade displacements. Interferometric Synthetic Aperture Radar (InSAR) generates millimetre-scale products, indicating the chronicle behaviour of detected targets via TS products. Deep Learning (DL) can handle a massive load of InSAR TS to categorize significant movements from non-moving targets. To this end, we employed a supervised Convolutional Neural Network (CNN) model to distinguish five deformations trends, including Stable, Linear, Quadratic, Bilinear, and Phase Unwrapping Error (PUE). Considering several arguments in a CNN model, we trained numerous combinations to explore the most accurate combination from 5000 samples extracted from a Persistent Scatterer Interferometry (PSI) technique and Sentinel-1 images over the Granada region, Spain. The model overall accuracy exceeds 92%. Deformations of three cases of landslides were also detected over the same area, including the Cortijo de Lorenzo, El Arrecife, and Rules Viaduct areas.
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Berti, M., A. Corsini, S. Franceschini e J. P. Iannacone. "Automated classification of Persistent Scatterers Interferometry time-series". Natural Hazards and Earth System Sciences Discussions 1, n. 1 (15 febbraio 2013): 207–46. http://dx.doi.org/10.5194/nhessd-1-207-2013.
Testo completoAbstract (sommario):
Abstract. We present a new method for the automatic classification of Persistent Scatters Interferometry (PSI) time series based on a conditional sequence of statistical tests. Time series are classified into distinctive predefined target trends (such as uncorrelated, linear, quadratic, bilinear and discontinuous) that describe different styles of ground deformation. Our automatic analysis overcomes limits related to the visual classification of PSI time series, which cannot be carried out systematically for large datasets. The method has been tested with reference to landslides using PSI datasets covering the northern Apennines of Italy. The clear distinction between the relative frequency of uncorrelated, linear and non-linear time series with respect to mean velocity distribution suggests that different target trends are related to different physical processes that are likely to control slope movements. The spatial distribution of classified time series is also consistent with respect the known distribution of flat areas, slopes and landslides in the tests area. Classified time series enhances the radar interpretation of slope movements at the site scale, pointing out significant advantages in comparison with the conventional analysis based solely on the mean velocity. The test application also warns against potentially misleading classification outputs in case of datasets affected by systematic errors. Although the method was developed and tested to investigate landslides, it should be also useful for the analysis of other ground deformation processes such as subsidence, swelling/shrinkage of soils, uplifts due to deep injections in reservoirs.
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Berti, M., A. Corsini, S. Franceschini e J. P. Iannacone. "Automated classification of Persistent Scatterers Interferometry time series". Natural Hazards and Earth System Sciences 13, n. 8 (6 agosto 2013): 1945–58. http://dx.doi.org/10.5194/nhess-13-1945-2013.
Testo completoAbstract (sommario):
Abstract. We present a new method for the automatic classification of Persistent Scatters Interferometry (PSI) time series based on a conditional sequence of statistical tests. Time series are classified into distinctive predefined target trends, such as uncorrelated, linear, quadratic, bilinear and discontinuous, that describe different styles of ground deformation. Our automatic analysis overcomes limits related to the visual classification of PSI time series, which cannot be carried out systematically for large datasets. The method has been tested with reference to landslides using PSI datasets covering the northern Apennines of Italy. The clear distinction between the relative frequency of uncorrelated, linear and non-linear time series with respect to mean velocity distribution suggests that different target trends are related to different physical processes that are likely to control slope movements. The spatial distribution of classified time series is also consistent with respect the known distribution of flat areas, slopes and landslides in the tests area. Classified time series enhances the radar interpretation of slope movements at the site scale, pointing out significant advantages in comparison with the conventional analysis based solely on the mean velocity. The test application also warns against potentially misleading classification outputs in case of datasets affected by systematic errors. Although the method was developed and tested to investigate landslides, it should be also useful for the analysis of other ground deformation processes such as subsidence, swelling/shrinkage of soils, or uplifts due to deep injections in reservoirs.
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Ogushi, Matsuoka, Defilippi e Pasquali. "Improvement of Persistent Scatterer Interferometry to Detect Large Non-Linear Displacements with the 2π Ambiguity by a Non-Parametric Approach". Remote Sensing 11, n. 21 (23 ottobre 2019): 2467. http://dx.doi.org/10.3390/rs11212467.
Testo completoAbstract (sommario):
Persistent scatterer interferometry (PSI) is commonly applied to monitor surface displacements with millimetric precision. However, this technique still has trouble estimating non-linear displacements because the algorithm is designed for the slow and linear displacements. Additionally, there is a variety of non-linear displacement types, and finding an appropriate displacement model for PSI is still assumed to be a fairly large task. In this paper, the conventional PSI technique is extended using a non-parametric non-linear approach (NN-PSI), and the performance of the extended method is investigated by simulations and actual observation data processing with TerraSAR-X. In the simulation, non-linear displacements are modeled by the magnitudes and periods of the displacement, and the evaluation of NN-PSI is conducted. According to the simulation results, the maximum magnitude of the displacement that can be estimated by NN-PSI is two and a half times the magnitude of the SAR sensor’s wavelength (2.5λ that is roughly equivalent to 8 cm for X-band, 14 cm for C-band, and 60 cm for L-band), and the period of the displacement is about three months. However, this displacement cannot be reconstructed by the conventional PSI due to the limitation, known as the 2π displacement ambiguity. The result of the observation data processing shows that a large displacement with the 2π ambiguity can be estimated by NN-PSI as the simulation results show, but the conventional PSI cannot reconstruct it. In addition, a different approach, Small BAseline Subset (SBAS), is applied to the same data to ensure the accuracy of results, and the correlation between NN-PSI and SBAS is 0.95, while that between the conventional PSI and SBAS is –0.66. It is concluded that NN-PSI enables the reconstruction of non-linear displacements by the non-parametric approach and the expansion of applications to measure surface displacements that could not be measured due to the limitations of the traditional PSI methods.
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Mana, G., F. Vattaneo e G. Zosi. "Non-Linear Analysis of the Elastic Behaviour of a Translation Device for X-Ray Interferometry". Metrologia 26, n. 4 (1 gennaio 1989): 219–27. http://dx.doi.org/10.1088/0026-1394/26/4/002.
Testo completo
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Nilson, Alec, e Kurt Wick. "Picometer measurements of strain coefficients by quadrature interferometry and lock-in amplification". American Journal of Physics 91, n. 2 (febbraio 2023): 142–52. http://dx.doi.org/10.1119/5.0102091.
Testo completoAbstract (sommario):
Modulated strain displacements were measured with a quadrature Michelson–Morley interferometer employing polarization optics and two lock-in amplifiers to filter noise and thermal drift. The advantages of the technique, its limitations, and estimates on the accuracy are discussed, including an algorithm to correct for non-ideal components and non-linear effects. Instructions for the construction and setup of the quadrature interferometer are provided. To test the interferometer, the dynamic converse piezoelectric effect was used, and by modulating the electric field across the sample, the [Formula: see text] strain coefficient for x-cut quartz was determined to be [Formula: see text], which is within 1.5 standard deviations of the accepted standard. The measurements had a standard deviation of 4.1 pm, resulting in standard errors as low as 5 fm/V after fitting.
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Belsten, Nicholas, Mary Knapp, Rebecca Masterson, Cadence Payne, Kristen Ammons, Frank D. Lind e Kerri Cahoy. "Verification and calibration of a commercial anisotropic magnetoresistive magnetometer by multivariate non-linear regression". Geoscientific Instrumentation, Methods and Data Systems 12, n. 2 (15 settembre 2023): 201–13. http://dx.doi.org/10.5194/gi-12-201-2023.
Testo completoAbstract (sommario):
Abstract. Commercially available anisotropic magnetoresistive (AMR) magnetometers exhibit on the order of 1 nanotesla (nT) sensitivity in small size, weight, and power (SWaP) packages. However, AMR magnetometer accuracy is diminished by properties such as static offsets, gain uncertainty, off-axis coupling, and temperature effects. This work presents a measurement of the magnitude of these effects for a Honeywell HMC1053 magnetometer and evaluates a method for calibrating the observed effects by multivariate non-linear regression using a 24-parameter measurement equation. The presented calibration method has reduced the vector norm of the root mean square error from 4300 to 72 nT for the data acquired in this experiment. This calibration method has been developed for use on the AERO (Auroral Emissions Radio Observer) and VISTA (Vector Interferometry Space Technology using AERO) CubeSat missions, but the methods and results may be applicable to other resource-constrained magnetometers whose accuracies are limited by the offset, gain, off-axis, and thermal effects that are similar to the HMC1053 AMR magnetometer.
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Tao, Nan, Yinhang Ma, Hanyang Jiang, Meiling Dai e Fujun Yang. "Investigation on Non-Linear Vibration Response of Cantilevered Thin Plates with Crack Using Electronic Speckle Pattern Interferometry". Proceedings 2, n. 8 (19 luglio 2018): 539. http://dx.doi.org/10.3390/icem18-05456.
Testo completoAbstract (sommario):
The time-averaged electronic speckle pattern interferometry (ESPI) is employed to measure the frequencies and mode shapes of thin, cantilevered plates with root-slit. The first 12 order linear resonance frequency and mode shape of an intact cantilevered plate is determined by using FEM calculation. The dynamic response of the intact specimen forced by a PZT actuator is measured and its super-harmonic resonance of forced response is investigated experimentally. The results show that the principal mode shape of super-harmonic vibration is similar to its natural modal. In contrast to linear forcing vibration, the threshold of force for super-harmonic resonance is much higher than that of the former. In addition, linear free response of four cantilevered root-slit plates with variation length of slit are analyzed by applying the FEM calculation, and their responses of forcing vibration were measured by using the ESPI method. The validity and accuracy of the numerical prediction are confirmed through experimental studies. The present work shows that the ESPI technique can provide whole-field and real-time measurement for vibration analysis and can also be employed for validation of the FEM calculation.
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Rizzieri, Nicola, e Alessio Facchin. "Comparison of Eye Axial Length Measurements Taken Using Partial Coherence Interferometry and OCT Biometry". Vision 8, n. 3 (26 luglio 2024): 46. http://dx.doi.org/10.3390/vision8030046.
Testo completoAbstract (sommario):
This study evaluates the inter-device measurement properties of partial coherence interferometry (PCI) and spectral domain optical coherence tomography (SD-OCT) in measuring axial length, particularly for myopia management. We recruited 82 eyes from 41 adult participants with a mean age of 31.0 ± 17.6 years and a mean spherical equivalent of −2.20 ± 2.28 D. Axial length was measured using SD-OCT and PCI for both the right and left eyes. Agreement between the two measurements was assessed using Bland–Altman analysis, and graphs and values were compared with linear mixed models. The results show a near-to-zero and non-significant bias between measurements. The 95% limits of agreement showed a value of 0.06 mm. Both devices can accurately measure the axial length. OCT biometry performed with SD-OCT can be successfully interchanged with partial coherence interferometry, but they should be cautiously interchanged when performing longitudinal comparisons.
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KOK, PIETER, e SAMUEL L. BRAUNSTEIN. "RELATIVISTIC QUANTUM INFORMATION PROCESSING WITH BOSONIC AND FERMIONIC INTERFEROMETERS". International Journal of Quantum Information 04, n. 01 (febbraio 2006): 119–30. http://dx.doi.org/10.1142/s0219749906001736.
Testo completoAbstract (sommario):
We derive the relativistic transformation laws for the annihilation operators of the scalar field, the massive spin-1 vector field, the electromagnetic field and the spinor field. The technique developed here involves straightforward mathematical techniques based on fundamental quantum field theory, and is applicable to the study of entanglement in arbitrary coordinate transformations. In particular, it predicts particle creation for non-inertial motion. Furthermore, we present a unified description of relativistic transformations and multi-particle interferometry with bosons and fermions, which encompasses linear optical quantum computing.
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Infante, D., D. Di Martire, P. Confuorto, S. Tessitore, M. Ramondini e D. Calcaterra. "DIFFERENTIAL SAR INTERFEROMETRY TECHNIQUE FOR CONTROL OF LINEAR INFRASTRUCTURES AFFECTED BY GROUND INSTABILITY PHENOMENA". ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-3/W4 (6 marzo 2018): 251–58. http://dx.doi.org/10.5194/isprs-archives-xlii-3-w4-251-2018.
Testo completoAbstract (sommario):
<p><strong>Abstract.</strong> The Italian territory is strongly affected by ground instability phenomena and the occurrence of geological events, such as landslides and subsidence, is one of the main causes of damage to linear infrastructures, such as roads, bridges, railways and retaining walls, resulting in important socio-economic and human losses. To this aim, the frequent and accurate monitoring of surface displacements plays a key role in risk prevention and mitigation activities. In the last decade, a considerable interest towards innovative approaches has grown among the scientific community and land management institutions. In particular, Differential Interferometry Synthetic Aperture Radar (DInSAR) technique represents a useful tool to provide information on temporal and spatial evolution both of ground instability phenomena and of their interaction with man-made facilities, thanks to its accuracy, high spatial resolution, non-invasiveness and long-term temporal coverage, at reasonable costs. In this work, a GIS-semiautomatic approach, using Synthetic Aperture Radar data acquired by COSMO-SkyMed sensor, has been successfully applied to detect landslide-induced effects in terms of deformations of a linear infrastructure interested by slow-moving landslides in Campania Region (Italy).</p>
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Donati, Silvano. "Vibration Measurements by Self-Mixing Interferometry: An Overview of Configurations and Benchmark Performances". Vibration 6, n. 3 (2 agosto 2023): 625–44. http://dx.doi.org/10.3390/vibration6030039.
Testo completoAbstract (sommario):
Self-mixing interferometry (SMI) is suitable to sense and measure vibrations of amplitudes ranging from picometers to millimeters at frequencies from sub-Hz to MHz’s. As an optical probe, SMI has the advantage of being non-invasive with the ability to measure without any treatment of the target surface and operate from a substantial standoff distance from the target. As an additional advantage, the SMI configuration is much simpler than that of conventional interferometers as it does not require any optical part external to the laser source. After a short introduction to the basics of SMI, we review the development of configurations of SMI instruments for vibration measurements, based on both analog and digital processing, with record performance to cover the range of vibration amplitudes from 0.1 nm to 1 mm, frequencies up to MHz, and stand-off distances up to 100 m. These performances set a benchmark that is unequaled by other approaches reported so far in the literature. The configurations we describe are (i) a simple MEMS-response testing instrument based on fringe counting, (ii) a half-fringe locking vibrometer for mechanical mode analysis and transfer function measurements, with a wide linear response on six decades of amplitude, (iii) a vibrometer with analog switching cancellation for μm-to-mm amplitude of vibrations, and (iv) a long standoff distance vibrometer for testing large structures at distances up to 100 m and with nm sensitivity. Lastly, as the vibrometer will almost invariably operate on untreated, diffusing surfaces, we provide an evaluation of phase-induced speckle pattern errors affecting the SMI measurement.
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Singh, Amandeep, Pawan Kumar, Sriya Yeleswarapu, Falguni Pati e Renu John. "Surface wave elastography using high speed full-field optical interferometry". Biomedical Physics & Engineering Express 8, n. 2 (10 febbraio 2022): 025013. http://dx.doi.org/10.1088/2057-1976/ac50be.
Testo completoAbstract (sommario):
Abstract The assessment of mechanical stiffness is an essential diagnostic tool for investigating the biomechanical properties of biological tissues. Surface wave elastography (SWE) is an emerging technique to quantify elastic properties of tissues in clinical diagnosis. High-speed optical imaging combined with SWE has enormous potential in quantifying the elastic properties of tissues at microscale resolutions. In this study, we implement surface wave elastography using high-speed optical interferometry to characterize the elastic properties of tissue-mimicking phantoms and ex-vivo native caprine liver tissue by imaging the surface wave induced by an electromechanical actuator. The sinusoidal mechanical excitations ranging from 120 Hz to 1.2 kHz on the surface of tissues are captured using a high-speed camera with a frame rate of 4 kHz at micrometer resolutions. The surface wavefront reconstruction is performed using a phase-shifting algorithm and linear regression is used to calculate the surface wave velocity. The mechanical stiffness estimated from the optical system is compared with the results of mechanical compression testing measurements. The results from this multimodal platform combining optical interferometry and vibrational spectroscopy using SWE are highly promising towards a non-invasive or minimally invasive imaging for in-vivo and ex-vivo mechanical characterization of tissues with future clinical applications.
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Li, Yinan, Markus Kästner e Eduard Reithmeier. "Optimization of the GPU-based data evaluation for the low coherence interferometry". tm - Technisches Messen 85, n. 11 (27 novembre 2018): 680–90. http://dx.doi.org/10.1515/teme-2017-0091.
Testo completoAbstract (sommario):
Abstract Optical interferometers as non-contact measurement devices are very desirable for the measurement of surface roughness and topography. Compared to phase shifting interferometers (PSIs) with a limited measurement range and a scan step of maximum λ/4, the optical interferometers like low coherence interferometers (LCIs) evaluating the degree of fringe coherence allow a larger vertical measurement range. Their vertical measurement range is only limited by the scan length allowed by the linear piezo stage and the coherence length of the light source. To evaluate the obtained data for a large range, the common LCIs require much computation time. To overcome this drawback, we present an evaluation algorithm based on the Hilbert-Transform and curve fitting (Levenberg–Marquardt algorithm) using Compute Unified Device Architecture (CUDA) technology, which allows parallel and independent data evaluation on General Purpose Graphics Processing Unit (GPGPU). Firstly, the evaluation algorithm is implemented and tested on an in-house developed LCI, which is based on Michelson configurations. Furthermore, we focus on the performance optimization of the GPU-based program using the different approaches to further achieve efficient and accurate massive parallel computing. Finally, the performance comparison for evaluating measurement data using different approaches is discussed in this paper.
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Diewald, Fabian, Niklas Epple, Thomas Kraenkel, Christoph Gehlen e Ernst Niederleithinger. "Impact of External Mechanical Loads on Coda Waves in Concrete". Materials 15, n. 16 (9 agosto 2022): 5482. http://dx.doi.org/10.3390/ma15165482.
Testo completoAbstract (sommario):
During their life span, concrete structures interact with many kinds of external mechanical loads. Most of these loads are considered in advance and result in reversible deformations. Nevertheless, some of the loads cause irreversible, sometimes unnoticed changes below the macroscopic scale depending on the type and dimension of the impact. As the functionality of concrete structures is often relevant to safety and society, their condition must be known and, therefore, assessed on a regular basis. Out of the spectrum of non-destructive monitoring methods, Coda Wave Interferometry using embedded ultrasonic sensors is one particularly sensitive technique to evaluate changes to heterogeneous media. However, there are various influences on Coda waves in concrete, and the interpretation of their superimposed effect is ambiguous. In this study, we quantify the relations of uniaxial compression and uniaxial tension on Coda waves propagating in normal concrete. We found that both the signal correlation of ultrasonic signals as well as their velocity variation directly reflect the stress change in concrete structures in a laboratory environment. For the linear elastic range up to 30% of the strength, we calculated a velocity variation of −0.97‰/MPa for compression and 0.33%/MPa for tension using linear regression. In addition, these parameters revealed even weak irreversible changes after removal of the load. Furthermore, we show the time-dependent effects of shrinkage and creep on Coda waves by providing the development of the signal parameters over time during half a year together with creep recovery. Our observations showed that time-dependent material changes must be taken into account for any comparison of ultrasonic signals that are far apart in time. The study’s results demonstrate how Coda Wave Interferometry is capable of monitoring stress changes and detecting even small-size microstructural changes. By indicating the stated relations and their separation from further impacts, e.g., temperature and moisture, we anticipate our study to contribute to the qualification of Coda Wave Interferometry for its application as an early-warning system for concrete structures.
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Bock, Stefan, Franziska Marie Herrmann, Thomas Püschel, Uwe Helbig, René Gebhardt, Jakob Johannes Lötfering, Richard Pausch et al. "Characterization of Accumulated B-Integral of Regenerative Amplifier Based CPA Systems". Crystals 10, n. 9 (22 settembre 2020): 847. http://dx.doi.org/10.3390/cryst10090847.
Testo completoAbstract (sommario):
We report on a new approach to measure the accumulated B-integral in the regenerative and multipass amplifier stages of ultrashort-pulse high-power laser systems by B-integral-induced coupling between delayed test post-pulses and the main pulse. A numerical model for such non-linear pulse coupling is presented and compared to data taken at the high-power laser Draco with self-referenced spectral interferometry (SRSI). The dependence of the B-integral accumulated in the regenerative amplifier on its operation mode enables optimization strategies for extracted energy vs. collected B-integral. The technique presented here can, in principle, be applied to characterize any type of ultrashort pulse laser system and is essential for pre-pulse reduction.
27
Petrov, M. A., D. A. Romashov e V. V. Isakov. "Estimation of Sheet Deformation of Aluminium Blank using Non-Contact Methods on the Example of Erichsen Cupping Test". Scientific Visualization 15, n. 4 (novembre 2023): 124–39. http://dx.doi.org/10.26583/sv.15.4.10.
Testo completoAbstract (sommario):
In the present study, non-contact techniques for estimating the deformation of a sheet specimen of aluminium alloy AA5051 (AMg2) subjected to Erichsen cupping test are considered. It is shown that it is possible to get reliable information by numerical simulation, however, for the case when the coefficients of the yield and fracture equations of the material are well-known and validated. This requires the application of confirmatory techniques based on the results of real experiments, for example, through optical 3D-scanning. The realization of the techniques requires preparing the blank prior the experimental stage. The combined technique of speckle interferometry and digital image correlation allows estimating deformations on the outer linear surfaces, but does not indicate deformations of products with curved surfaces and inside the specimen, which requires performing an additional numerical simulation.
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Pawluszek-Filipiak, K., e A. Borkowski. "COMPARISON OF PSI AND DINSAR APPROACH FOR THE SUBSIDENCE MONITORING CAUSED BY COAL MINING EXPLOITATION". ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLIII-B3-2020 (21 agosto 2020): 333–37. http://dx.doi.org/10.5194/isprs-archives-xliii-b3-2020-333-2020.
Testo completoAbstract (sommario):
Abstract. Underground coal exploitation has its reflection in ground movements such as subsidence, sinking or shaking. These cause buildings and infrastructure damage, therefore it is important to measure the magnitude of deformation. Last decades, Differential Interferometric Synthetic Aperture Radar (DInSAR) captured considerable attention as a tool for deformation monitoring. The results of conventional DInSAR, which utilizes two SAR images, are degraded due to atmospheric, topographic and orbital errors. To overcome these limitations, various stacking-based methods have been introduced. Therefore, the goal of presented study is to compare Persistent Scatterer Interferometry (PSI) as stacking-based method with classical DInSAR for monitoring of subsidence caused by underground coal exploitation. Deformations in the areas of active mining exploitation are characterised typically by rapid non-linear movement. The comparison has been performed for the area of active exploitation in Rydułtowy mine located in Upper Silesian Coal Basin (USCB) in Poland. Results from two separate PSI and DInSAR processing portray similar deformation pattern over the study area. Unfortunately, due to the temporal decorrelation, PSI clearly demonstrate smaller information coverage in respect to DInSAR results. Additionally, due to the applied linear deformation model, PSI failed in displacement estimation with magnitude higher than 12 cm. In contrast, DInSAR thanks 6-day temporal baseline and no assumption for a deformation model, was able to capture the maximum magnitude of subsidence reaching 86 cm/year. However, these results are affected by atmospheric artefacts which in presented case study can reach even 14 cm/year. To achieve few cm level of accuracy and to estimate high deformation magnitude such as in presented study case (1m/year), integrated use of both InSAR techniques seems to be the reasonable solution.
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Skripal An.V., Добдин C.Ю., Inkin M.G. e Dzhafarov A.V. "Measurement of distance by the maximum frequency of the interference signal with harmonic deviation of the wavelength of the self-mixing laser". Technical Physics 68, n. 4 (2023): 484. http://dx.doi.org/10.21883/tp.2023.04.55940.282-22.
Testo completoAbstract (sommario):
A method is proposed for measuring absolute distances from the low-frequency spectrum of the interference signal of a frequency-modulated laser diode. The method of modulation of the self-mixing laser signal according to the harmonic law is used, in the spectrum of which a wide range of frequency components is observed. The connection between the maximum frequency of change of the interference signal and the absolute distance to the reflector is shown. A linear dependence of the frequency corresponding to the inflection region of the decay envelope of the interference signal spectrum on the distance is shown, which can be used to implement a non-contact distance measurement method with harmonic modulation of the self-mixing laser supply current. Keywords: laser interferometry, self-mixing laser, semiconductor laser, laser radiation modulation, distance measurement, signal spectral analysis.
30
Oliveira, V., N. I. Polushkin, O. Conde e R. Vilar. "SEM characterization of two-dimensional patterns generated in titanium by femtosecond laser interferometry". Microscopy and Microanalysis 19, S4 (agosto 2013): 143–44. http://dx.doi.org/10.1017/s1431927613001335.
Testo completoAbstract (sommario):
Laser ablation using ultrafast femtosecond lasers and holographic schemes has proven to be a powerful and versatile tool for surface and volume structuring. The principle of operation of this technique is simple: when two or more pulses overlap in time and space, an interference pattern is generated that can be used to create periodic surface structures. In addition, due to the extremely short pulse duration, a very high peak power is achieved leading to intense non-linear effects. As a result, almost any type of material can be processed without undesirable collateral thermal effects.In this paper, characterization of two-dimensional (2D) patterns generated in titanium using femtosecond laser radiation has been carried out using scanning electron microscopy (SEM). The laser source is a commercial Yb:KYW laser system providing pulses with a duration of 560 fs at a central wavelength of >= 1030 nm. The surface topography was characterized using a Hitachi S2400 scanning electron microscope operated at an electron acceleration voltage of 25.0 kV. Laser processing was performed in air on polished grade 2 titanium samples, a material typically used in low load bearing medical devices.One-dimensional (1D) gratings were created using a modified Michelson interferometer described in detail elsewhere (Oliveira et al., 2012). To create 2D gratings a double exposure method was used. First, 1D gratings were produced in linear tracks by translating the sample relatively to the stationary interfering laser beams with a fixed scanning velocity of 0.1 mm/s. As an example, Figure 1 depicts SEM pictures of horizontal and vertical 1D gratings with period of about 3.9 m, generated using a pulse energy and pulse repetition rate of 0.35 mJ and 100 Hz, respectively. The peak to valley distance of these patterns can be controlled either by changing the scanning velocity or the pulse repetition rate. By overlapping two linear tracks, different kinds of 2D structures can be created. Figure 2 depicts a square pattern obtained by overlapping two 1D gratings rotated by 90°. The dimensions of the squares depend on the one-dimensional gratings period, which in turn can be easily controlled by varying the distance between the interfering beams. Figure 3 depicts two other possibilities: i) trapezium-like patterns obtained by rotating the 1D gratings by 45°, and ii) rectangular patterns obtained using 1D gratings with different periods and rotated by 90°.The proposed optical setup offers a simple method of texturing the surface of materials and, hence, to control surface properties such as wettability. In the case of titanium, this is particularly important because surface texturing enhances its osseointegration ability. For this purpose, when compared with the columns spontaneously formed on titanium surfaces treated with femtosecond laser radiation, these 2D gratings present the major advantage of being size and shape-controllable.
31
Pringkasemchai, A., J. Wongsaroj e K. Mongkolsuttirat. "Determination of probe non-linearity and error due to measurement position for direct measurement type of gauge block comparator and its measurement uncertainty". Journal of Physics: Conference Series 2145, n. 1 (1 dicembre 2021): 012060. http://dx.doi.org/10.1088/1742-6596/2145/1/012060.
Testo completoAbstract (sommario):
Abstract The non-linearity of probes is one of the important components in gauge block calibration by the mechanical comparative method of two gauges blocks at the same nominal length. However, an advanced method for gauge block calibration is a mechanical direct measurement method of two gauge blocks showing the greatest difference in nominal length of 25 mm. This method uses a special probe based on the interferential scanning principle to produce the signals to measure the displacement. In this paper, non-linearity and error due to measurement position were investigated as they related to the accuracy of measurement results. The differences in central length of pairs of standard gauge blocks made of steel were measured by optical interferometry with the measurement uncertainty (k=2) 23 nm. Length in the range of 5 μm to 25 mm was used in the experiment. Non-linearity of the probe was evaluated by the simple linear regression model. Various factors such as origin setting point, temperature, and vibration have been analysed. In the preliminary experiment, the non-linearity, position error, repeatability and retrace error over the measuring range 25 mm are 13 nm, -18 nm, 15 nm, and 10 nm respectively. The standard uncertainty of direct measurement type caused by non-linearity is 4 nm.
32
CHIADRONI, E., M. CASTELLANO, A. CIANCHI, K. HONKAVAARA e G. KUBE. "NEW EXPERIMENTAL RESULTS WITH OPTICAL DIFFRACTION RADIATION DIAGNOSTICS". International Journal of Modern Physics A 25, supp01 (giugno 2010): 189–200. http://dx.doi.org/10.1142/s0217751x10050032.
Testo completoAbstract (sommario):
The characterization of the transverse phase space for high charge density and high energy electron beams is demanding for the successful development of the next generation light sources and linear colliders. Due to its non-invasive and non-intercepting features, Optical Diffraction Radiation (ODR) is considered as one of the most promising candidates to measure the transverse beam size and angular divergence. The recent results of our experiment, based on the detection of the ODR angular distribution to measure the electron beam transverse parameters and set up at FLASH (DESY), are presented. A thin stainless steel mask has been installed at 45° with respect to the DR target and normally to the beam propagation to reduce the contribution of synchrotron radiation (SR) background. In addition, interference between the ODR emitted on the shielding mask in the forward direction and the radiation from the DR target in the backward direction is observed. This is what we call Optical Diffraction Interferometry (ODRI). The contribution of this interference effect to the ODR angular distribution pattern and, consequently, its impact on the beam transverse parameters is discussed.
33
Zimmermann, G., U. Müller e S. H. Davis. "Bénard convection in binary mixtures with Soret effects and solidification". Journal of Fluid Mechanics 238 (maggio 1992): 657–82. http://dx.doi.org/10.1017/s002211209200185x.
Testo completoAbstract (sommario):
Bénard convection of a two-component liquid is considered. The liquid displays Soret effects and the boundary temperatures are fixed to span the solidification temperature of the mixture. Near the lower, heated plate the material is liquid and near the upper cooled plate there is a layer of pure solid solvent; all the solute is rejected during freezing. Linear stability theory is used to determine the effects on the critical conditions for Soret convection in the presence of the solidified layer and the interface between solid and liquid.Experiments on mixtures of ethyl alcohol and water are performed using interferometry, photography and thermocouple measurements. The measured onset of instability to travelling waves at negative Soret coefficient compares well with those predicted by our linear theory. In the absence of ice the waves develop at finite amplitude to a fixed-amplitude state. However, when ice is present, these waves fail to persist but evolve to a state of steady finite-amplitude (overturning) convection. These differences are attributed to the presence of the ice and the nonlinear density profile of the basic state, both of which act as sources of non-Boussinesq effects.
34
Struhár, Juraj, Petr Rapant, Michal Kačmařík, Ivana Hlaváčová e Milan Lazecký. "Monitoring Non-Linear Ground Motion above Underground Gas Storage Using GNSS and PSInSAR Based on Sentinel-1 Data". Remote Sensing 14, n. 19 (30 settembre 2022): 4898. http://dx.doi.org/10.3390/rs14194898.
Testo completoAbstract (sommario):
Several methods allow accurate measurement of terrain surface motions. Global navigation satellite systems (GNSSes) and interferometry with synthetic aperture radar (InSAR) stand out in terms of measurement accuracy among them. In principle, both methods make it possible to evaluate a three-dimensional vector of the motion of points on the terrain surface. In this work, we dealt with the evaluation of motions in the up–down (U–D) and east–west direction (E–W) over underground gas storage (UGS) from InSAR. One crucial step in breaking down PSInSAR line of sight (LOS) measurements to U–D and E–W components is getting time series derived from individual tracks to the same time frame. This is usually performed by interpolation, but we used an innovative approach: we analyzed individual time series using the Lomb–Scargle periodogram (LSP), which is suitable for periodic noisy and irregularly sampled data; we selected the most significant period, created LSP models, and used them instead of the original time series. Then, it was possible to derive time series values for any arbitrary time step. To validate the results, we installed one GNSS receiver in the Tvrdonice UGS test area to perform independent measurements. The results show a good agreement in the evaluation of motions by both methods. The correlation coefficient between horizontal components from both PSInSAR and GNSS was 0.95 in the case of the E–W component, with an RMSE of 1.75 mm; for U–D they were 0.78 and 2.35 mm, respectively. In addition to comparing the motions in the U–D and E–W directions, we also created a comparison by converting GNSS measurements to a line of sight of the Sentinel-1 satellite to evaluate the conformity of InSAR and GNSS measurements. Based on descending track, the correlation coefficient between LOS from both methods is, on average, 0.97, with an RMSE of 2.70 mm.
35
Salykina, Dariya, e Farid Khalili. "Sensitivity of Quantum-Enhanced Interferometers". Symmetry 15, n. 3 (22 marzo 2023): 774. http://dx.doi.org/10.3390/sym15030774.
Testo completoAbstract (sommario):
We review various schemes of quantum-enhanced optical interferometers, both linear (SU(2)) and non-linear (SU(1,1)) ones, as well as hybrid SU(2)/SU(1,1) options, using the unified modular approach based on the Quantum Cramèr–Rao bound (QCRB), and taking into account the practical limitations pertinent to all real-world highly-sensitive interferometers. We focus on three important cases defined by the interferometer symmetry: (i) the asymmetric single-arm interferometer; (ii) the symmetric two-arm interferometer with the antisymmetric phase shifts in the arms; and (iii) the symmetric two-arm interferometer with the symmetric phase shifts in the arms. We show that while the optimal regimes for these cases differ significantly, their QCRBs asymptotically correspond to the same squeezing-enhanced shot noise limit (2), which first appeared in the pioneering work by C. Caves in 1981.We show also that in all considered cases the QCRB can be asymptotically saturated by the standard (direct or homodyne) detection schemes.
36
Zechel, Fabian, Julia Jasovski e Robert H. Schmitt. "Dynamic, Adaptive Inline Process Monitoring for Laser Material Processing by Means of Low Coherence Interferometry". Applied Sciences 11, n. 16 (18 agosto 2021): 7556. http://dx.doi.org/10.3390/app11167556.
Testo completoAbstract (sommario):
Surface laser structuring of electrical steel sheets can be used to manipulate their magnetic properties, such as energy losses and contribute to a more efficient use. This requires a technology such as low coherence interferometry, which makes it possible to be coupled directly into the existing beam path of the process laser and enables the possibility for an 100% inspection during the process. It opens the possibility of measuring directly in the machine, without removing the workpiece, as well as during the machining process. One of the biggest challenges in integrating an LCI measurement system into an existing machine is the need to use a different wavelength than the one for which the optical components were designed. This results in an offset between the measurement and processing spot. By integrating an additional scanning system exclusively for the measuring beam and developing a compensation model for the non-linear spot offset, this can be adaptively corrected by up to 98.9% so that the ablation point can be measured. The simulation model can also be easily applied to other systems with different components and at the same time allows further options for in-line quality assurance.
37
Zhang, Yanqi, Adam S. Hines, Guillermo Valdes e Felipe Guzman. "Investigation and Mitigation of Noise Contributions in a Compact Heterodyne Interferometer". Sensors 21, n. 17 (28 agosto 2021): 5788. http://dx.doi.org/10.3390/s21175788.
Testo completoAbstract (sommario):
We present a noise estimation and subtraction algorithm capable of increasing the sensitivity of heterodyne laser interferometers by one order of magnitude. The heterodyne interferometer is specially designed for dynamic measurements of a test mass in the application of sub-Hz inertial sensing. A noise floor of 3.31×10−11m/Hz at 100 mHz is achieved after applying our noise subtraction algorithm to a benchtop prototype interferometer that showed a noise level of 2.76×10−10m/Hz at 100 mHz when tested in vacuum at levels of 3×10−5 Torr. Based on the previous results, we investigated noise estimation and subtraction techniques of non-linear optical pathlength noise, laser frequency noise, and temperature fluctuations in heterodyne laser interferometers. For each noise source, we identified its contribution and removed it from the measurement by linear fitting or a spectral analysis algorithm. The noise correction algorithm we present in this article can be generally applied to heterodyne laser interferometers.
38
Birdi, Jasleen, Audrey Repetti e Yves Wiaux. "Sparse interferometric Stokes imaging under the polarization constraint (Polarized SARA)". Monthly Notices of the Royal Astronomical Society 478, n. 4 (4 luglio 2018): 4442–63. http://dx.doi.org/10.1093/mnras/sty1182.
Testo completoAbstract (sommario):
ABSTRACT We develop a novel algorithm for sparse imaging of Stokes parameters in radio interferometry under the polarization constraint. The latter is a physical non-linear relation between the Stokes parameters, imposing the polarization intensity as a lower bound on the total intensity. To solve the joint inverse Stokes imaging problem including this bound, we leverage epigraphical projection techniques in convex optimization and we design a primal–dual method offering a highly flexible and parallelizable structure. In addition, we propose to regularize each Stokes parameter map through an average sparsity prior in the context of a reweighted analysis approach (SARA). The resulting method is dubbed Polarized SARA. Using simulated observations of M87 with the Event Horizon Telescope, we demonstrate that imposing the polarization constraint leads to superior image quality. For the considered data sets, the results also indicate better performance of the average sparsity prior in comparison with the widely used Cotton–Schwab clean algorithm and other total variation based priors for polarimetric imaging. Our matlab code is available online on GitHub.
39
Yukalov, V. I., E. P. Yukalova e V. S. Bagnato. "Trapped Bose–Einstein condensates with nonlinear coherent modes". Laser Physics 33, n. 12 (31 ottobre 2023): 123001. http://dx.doi.org/10.1088/1555-6611/ad04c1.
Testo completoAbstract (sommario):
Abstract The review presents the methods of generation of nonlinear coherent excitations in strongly nonequilibrium Bose-condensed systems of trapped atoms and their properties. Non-ground-state Bose–Einstein condensates are represented by nonlinear coherent modes. The principal difference of nonlinear coherent modes from linear collective excitations is emphasized. Methods of generating nonlinear modes and the properties of the latter are described. Matter-wave interferometry with coherent modes is discussed, including such effects as interference patterns, internal Josephson current, Rabi oscillations, Ramsey fringes, harmonic generation, and parametric conversion. Dynamic transition between mode-locked and mode-unlocked regimes is shown to be analogous to a phase transition. Atomic squeezing and entanglement in a lattice of condensed atomic clouds with coherent modes are considered. Nonequilibrium states of trapped Bose-condensed systems, starting from weakly nonequilibrium state, vortex state, vortex turbulence, droplet or grain turbulence, and wave turbulence, are classified by means of effective Fresnel and Mach numbers. The inverse Kibble–Zurek scenario is described. A method for the formation of directed beams from atom lasers is reported.
40
Marsh, O. J., W. Rack, D. Floricioiu, N. R. Golledge e W. Lawson. "Tidally-induced velocity variations of the Beardmore Glacier, Antarctica, and their representation in satellite measurements of ice velocity". Cryosphere Discussions 7, n. 2 (29 aprile 2013): 1761–85. http://dx.doi.org/10.5194/tcd-7-1761-2013.
Testo completoAbstract (sommario):
Abstract. Ocean tides close to the grounding line of outlet glaciers around Antarctica have been shown to directly influence ice velocity, in both linear and non-linear patterns. These fluctuations can be significant and have the potential to affect satellite measurements of ice discharge which assume displacement between satellite passes to be consistent and representative of annual means. Satellite observations of horizontal velocity variation in the grounding zone are also contaminated by vertical tidal effects, shown here to be present in speckle tracking measurements. Eight TerraSAR-X scenes from the grounding zone of the Beardmore Glacier are analysed in conjunction with GPS measurements to determine short-term and decadal trends in ice velocity. Diurnal tides produce horizontal velocity fluctuations of >50% on the ice shelf, recorded in the GPS data 4 km downstream of the grounding line. This decreases rapidly to <5% only 15 km upstream of the grounding line. Daily fluctuations are smoothed to <1% in the 11 day repeat pass TerraSAR-X imagery but fortnightly variations over this period are still visible and show that satellite-velocity measurements can be affected by tides over longer periods. The measured tidal displacement observed in radar look direction over floating ice also allows a~new method of grounding line identification to be demonstrated, using differential speckle tracking where phase coherence is too poor for SAR interferometry.
41
Stepanova, L. V., D. A. Semenov e G. S. Anisimov. "APPLICATION OF HOLOGRAPHY METHOD FOR THE RESTORATION OF THE WILLIAMS SERIES NEAR THE CRACK TIP". Vestnik of Samara University. Natural Science Series 29, n. 1 (27 giugno 2023): 15–46. http://dx.doi.org/10.18287/2541-7525-2023-29-1-15-46.
Testo completoAbstract (sommario):
The article describes the processing of the results of a series of experiments performed by the interference-optical method of holographic interferometry (holographic photoelasticity) aimed at computing the amplitude coefficients of the M. Williams series constituting the stress and displacement fields at the crack tip for several cracked configurations. The main objective of this study is the experimental and computational determination of the coefficients of the M. Williams series for the stress, strain and displacement fields associated with the crack tip in an isotropic linearly elastic medium taking into account regular (non-singular) terms in the multiparameter Williams series. These coefficients are named generalized stress intensity factors. The method of holographic interferometry is shown to be a convenient and efficacious tool for reconstructingthe stress field near the tip of the crack, because during the experiment it is possible to obtain two families of interference fringe patterns: absolute retardation fringes (isodromics) for vertical and horizontal polarizations. Experimental outcomes were thoroughly processed using the developed digital application allowing us to accumulate the isodromics orders and coordinates of points belonging to absolute retardations. In this work, absolute retardation fringes in a plate with a central horizontal crack and a crack inclined at different angles are obtained. For each type of experimental sample, the coefficients of the Williams series were calculated taking into account non-singular terms (in the representation of M. Williams, fifteen terms were preserved). A procedure for linearization of nonlinear algebraic equations following from the relations of Favres law is proposed. By solving the obtained overdeterministic system of linear algebraic equations, the generalized stress intensity factors (coefficients of the M. Williams series) are estimated. Conjointly, the finite element analysis of the specimens with same geometry was effectuated. The experimentally determined values of the Williams series are compared with the results of the finite element calculation of the stress-strain state performed in the SIMULIA Abaqus software.The results of the numerical and experimental studies were found to be quite consistent. It is lucidly shown that it is imperative to keep the higher order terms in the Williams seriesexpansions for the fields associated with the crack tip.
42
Konovalov, Yuri V. "Inversion for basal friction coefficients with a two-dimensional flow line model using Tikhonov regularization". Research in Geophysics 2, n. 2 (17 settembre 2012): 11. http://dx.doi.org/10.4081/rg.2012.e11.
Testo completoAbstract (sommario):
We present results of basal friction coefficient inversion. The inversion was performed by a 2D flow line model for one of the four fast flowing ice streams on the southern side of the Academy of Sciences Ice Cap in the Komsomolets Island, Severnaya Zemlya archipelago. The input data for the performance of both the forward and the inverse problems included synthetic aperture radar interferometry ice surface velocities, ice surface elevations and ice thicknesses obtained by airborne measurements (all were taken from Dowdeswell <em>et al.</em>, 2002). Numerical experiments with: i) different sea level shifts; and ii) randomly perturbed friction coefficient have been carried out in the forward problem. The impact of sea level changes on vertical distribution of horizontal velocity and on shear stress distribution near the ice front has been investigated in experiments with different sea level shifts. The experiments with randomly perturbed friction coefficient have revealed that the modeled surface velocity is weakly sensitive to the perturbations and, therefore, the inverse problem should be considered ill posed. To mitigate ill posedness of the inverse problem, Tikhonov’s regularization was applied. The regularization parameter was determined from the relation of the discrepancy between observed and modeled velocities to the regularization parameter. The inversion was performed for both linear and non-linear sliding laws. The inverted spatial distributions of the basal friction coefficient are similar for both sliding laws. The similarity between these inverted distributions suggests that the changes in the friction coefficient are accompanied by appropriate water content variations at the glacier base.
43
Xing, Xuemin, Tengfei Zhang, Lifu Chen, Zefa Yang, Xiangbin Liu, Wei Peng e Zhihui Yuan. "InSAR Modeling and Deformation Prediction for Salt Solution Mining Using a Novel CT-PIM Function". Remote Sensing 14, n. 4 (10 febbraio 2022): 842. http://dx.doi.org/10.3390/rs14040842.
Testo completoAbstract (sommario):
Deformation prediction for a salt solution mining area is essential to mining environmental protection. The combination of Synthetic Aperture Radar Interferometry (InSAR) technique with Probability Integral Method (PIM) has proven to be powerful in predicting mining-induced subsidence. However, traditional mathematical empirical models (such as linear model or linear model combined with periodical function) are mostly used in InSAR approaches, ignoring the underground mining mechanisms, which may limit the accuracy of the retrieved deformations. Inaccurate InSAR deformations will transmit an unavoidable error to the estimated PIM parameters and the forward predicted subsidence, which may induce more significant errors. Besides, theoretical contradictory and non-consistency between InSAR deformation model and future prediction model is another limitation. This paper introduces the Coordinate-Time (CT) function into InSAR deformation modeling. A novel time-series InSAR model (namely, CT-PIM) is proposed as a substitute for traditional InSAR mathematical empirical models and directly applied for future dynamic prediction. The unknown CT-PIM parameters can be estimated directly via InSAR phase observations, which can avoid the error propagation from the InSAR-generated deformations. The new approach has been tested by both simulated and real data experiments over a salt mine in China. The root mean square error (RMSE) is determined as ±10.9 mm, with an improvement of 37.2% compared to traditional static PIM prediction method. The new approach provides a more robust tool for the forecasting of mining-induced hazards in salt solution mining areas, as well as a reference for ensuring the environment protection and safety management.
44
Kent, James, Adam P. Beardsley, Landman Bester, Steve F. Gull, Bojan Nikolic, Jayce Dowell, Nithyanandan Thyagarajan, Greg B. Taylor e Judd Bowman. "Direct wide-field radio imaging in real-time at high time resolution using antenna electric fields". Monthly Notices of the Royal Astronomical Society 491, n. 1 (30 ottobre 2019): 254–63. http://dx.doi.org/10.1093/mnras/stz3028.
Testo completoAbstract (sommario):
ABSTRACT The recent demonstration of a real-time direct imaging radio interferometry correlator represents a new capability in radio astronomy. However, wide-field imaging with this method is challenging since wide-field effects and array non-coplanarity degrade image quality if not compensated for. Here, we present an alternative direct imaging correlation strategy using a direct Fourier transform (DFT), modelled as a linear operator facilitating a matrix multiplication between the DFT matrix and a vector of the electric fields from each antenna. This offers perfect correction for wide field and non-coplanarity effects. When implemented with data from the Long Wavelength Array (LWA), it offers comparable computational performance to previously demonstrated direct imaging techniques, despite having a theoretically higher floating point cost. It also has additional benefits, such as imaging sparse arrays and control over which sky coordinates are imaged, allowing variable pixel placement across an image. It is in practice a highly flexible and efficient method of direct radio imaging when implemented on suitable arrays. A functioning electric field direct imaging architecture using the DFT is presented, alongside an exploration of techniques for wide-field imaging similar to those in visibility-based imaging, and an explanation of why they do not fit well to imaging directly with the digitized electric field data. The DFT imaging method is demonstrated on real data from the LWA telescope, alongside a detailed performance analysis, as well as an exploration of its applicability to other arrays.
45
Auffarth, Gerd U., Tadas Naujokaitis, Louise Blöck, Anna Daghbashyan, Jan Meis, Victor A. Augustin, Ramin Khoramnia e Timur M. Yildirim. "Development and Verification of an Adjustment Factor for Determining the Axial Length Using Optical Biometry in Silicone Oil-Filled Eyes". Diagnostics 12, n. 1 (11 gennaio 2022): 163. http://dx.doi.org/10.3390/diagnostics12010163.
Testo completoAbstract (sommario):
The aim of this prospective clinical study was to establish and verify an adaptation for axial length (AL) measurement in silicone oil (SO)-filled pseudophakic eyes with a Scheimpflug and partial coherence interferometry (PCI)-based biometer. The AL was measured with a Pentacam AXL (OCULUS Optikgeräte GmbH, Wetzler, Germany) and IOLMaster 700 (Carl Zeiss Meditec, Jena, Germany). The coefficients of variation (CoV) and the mean systematic difference (95% confidence interval (CI)) between the devices were calculated. After implementing a setting for measuring AL in tamponaded eyes with a Pentacam based on data of 29 eyes, another 12 eyes were examined for verification. The mean AL obtained with the Pentacam was 25.53 ± 1.94 mm (range: 21.70 to 30.76 mm), and with IOLMaster, 24.73 ± 1.97 mm (ranged 20.84 to 29.92 mm), resulting in a mean offset of 0.80 ± 0.08 mm (95% CI: 0.77, 0.83 mm), p < 0.001. The AL values of both devices showed a strong linear correlation (r = 0.999). Verification data confirmed good agreement, with a statistically and clinically non-significant mean difference of 0.02 ± 0.04 (95% CI: −0.01, 0.05) mm, p = 0.134. We implemented a specific adaptation for obtaining reliable AL values in SO-filled eyes with the Pentacam AXL.
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Famiglietti, Nicola Angelo, Pietro Miele, Marco Defilippi, Alessio Cantone, Paolo Riccardi, Giulia Tessari e Annamaria Vicari. "Landslide Mapping in Calitri (Southern Italy) Using New Multi-Temporal InSAR Algorithms Based on Permanent and Distributed Scatterers". Remote Sensing 16, n. 9 (30 aprile 2024): 1610. http://dx.doi.org/10.3390/rs16091610.
Testo completoAbstract (sommario):
Landslides play a significant role in the morpho-evolutional processes of slopes, affecting them globally under various geological conditions. Often unnoticed due to low velocities, they cause diffuse damage and loss of economic resources to the infrastructure or villages built on them. Recognizing and mapping mass movements is crucial for mitigating economic and social impacts. Conventional monitoring techniques prove challenging for large areas, necessitating resource-intensive ground-based networks. Leveraging abundant synthetic aperture radar (SAR) sensors, satellite techniques offer cost-effective solutions. Among the various methods based on SAR products for detecting landslides, multi-temporal differential interferometry SAR techniques (MTInSAR) stand out for their precise measurement capabilities and spatiotemporal evolution analysis. They have been widely used in several works in the last decades. Using information from the official Italian landslide database (IFFI), this study employs Sentinel-1 imagery and two new processing chains, E-PS and E-SBAS algorithms, to detect deformation areas on the slopes of Calitri, a small town in Southern Italy; these algorithms assess the cumulated displacements and their state of activity. Taking into account the non-linear trends of the scatterers, these innovative algorithms have helped to identify a dozen clusters of points that correspond well with IFFI polygons.
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Bovenga, Fabio, Ilenia Argentiero, Alberto Refice, Raffaele Nutricato, Davide O. Nitti, Guido Pasquariello e Giuseppe Spilotro. "Assessing the Potential of Long, Multi-Temporal SAR Interferometry Time Series for Slope Instability Monitoring: Two Case Studies in Southern Italy". Remote Sensing 14, n. 7 (31 marzo 2022): 1677. http://dx.doi.org/10.3390/rs14071677.
Testo completoAbstract (sommario):
Multi-temporal SAR interferometry (MTInSAR), by providing both mean displacement maps and displacement time series over coherent objects on the Earth’s surface, allows analyzing wide areas, identifying ground displacements, and studying the phenomenon evolution at a long time scale. This technique has also been proven to be very useful for detecting and monitoring slope instabilities. For this type of hazard, detection of velocity variations over short time intervals should be useful for early warning of damaging events. In this work, we present the results obtained by using both COSMO-SkyMed (CSK) and Sentinel-1 (S1) data for investigating the ground stability of two hilly villages located in the Southern Italian Apennines (Basilicata region), namely the towns of Montescaglioso and Pomarico. In these two municipalities, landslides occurred in the recent past (in Montescaglioso in 2013) and more recently (in Pomarico in 2019), causing damage to houses, commercial buildings, and infrastructures. SAR datasets acquired by CSK and S1 from both ascending and descending orbits were processed using the SPINUA MTInSAR algorithm. Mean velocity maps and displacement time series were analyzed, also by means of innovative ad hoc procedures, looking, in particular, for non-linear trends. Results evidenced the presence of nonlinear displacements in correspondence of some key infrastructures. In particular, the analysis of accelerations and decelerations of PS objects corresponding to structures affected by recent stabilization measures helps to shed new light in relation to known events that occurred in the area of interest.
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Naimark, O. B., A. S. Nikityuk, V. O. Nebogatikov e V. V. Grishko. "Evaluation of nonlinear dynamics of the cell structure damage as a promising method for personalized cancer diagnostics". Almanac of Clinical Medicine 46, n. 8 (31 dicembre 2018): 742–47. http://dx.doi.org/10.18786/2072-0505-201846-8-742-747.
Testo completoAbstract (sommario):
Background:Modulation interference microscopy is one of the promising technologies for early personalized cancer diagnostics, while it gives the possibility to obtain real-time images of living functioning cells at a nanometer resolution, as well as to assess spatio-temporal changes of their intracellular structures.Aim:To identify the markers of malignant transformation of cells based on a multiple scale spatio-temporal of the data obtained by lase interferometry duringin situregistration of changes in intracellular structures.Materials and methods:The study was performed with the breast adenocarcinoma MCF-7 cell line and human kidney epithelial cells HEK 293 provided by the N.N. Blokhin National Medical Research Centre of Oncology (Moscow, Russia). Changes in fluctuation of the living cell phase thickness were measured with a laser modulation interference microscope MIM-340 (PA UOMZ, Russia). The multifractal detrended fluctuation analysis (MF-DFA) was used to assess the results obtained.Results:By comparison of the scaling exponential spectra and corresponding spectra of the singular fluctuations in the minimal and maximal diameters of the phase pictures of HEK 293 cells and MCF-7 cells, it was shown that the cancer cell dynamics has definite monofractal properties: a linear dependency of the scaling exponentsτfrom the actualqparameter and “dotted” singularity spectrum (the spectral width does not exceed 0.1). The dynamics of healthy cell demonstrated multifractal properties, such as a non-linear dependencyτ(q)and a bell shaped singularity spectrum (the spectral width over 0.1).Conclusion:We have proposed a new approach to assess the intracellular structural damage during oncogenesis. The signs of monofractality are objective criteria of malignization. The results obtained seems promising as early diagnostic markers of cancer transformation (damage) of cells and determination of tumor cell sensitivity / resistance to anti-tumor agents in an individual patient.
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Seleznev, Mikhail, e Alexei Vinogradov. "Shear Bands Topology in the Deformed Bulk Metallic Glasses". Metals 10, n. 3 (14 marzo 2020): 374. http://dx.doi.org/10.3390/met10030374.
Testo completoAbstract (sommario):
Recent experimental studies revealed the presence of Volterra dislocation-type long-range elastic strain/stress field around a shear band (SB) terminated in a bulk metallic glass (BMG). The corollary from this finding is that shear bands can interact with these stress fields. In other words, the mutual behaviour of SBs should be affected by their stress fields superimposed with the external stresses. In order to verify this suggestion, the topography of the regions surrounding SBs terminated in the BMGs was carefully analysed. The surfaces of several BMGs, deformed by compression and indentation, were investigated with a high spatial resolution by means of scanning white-light interferometry (SWLI). Along with the evidence for the interaction between SBs, different scenarios of the SB propagation have been observed. Specifically, the SB path deviation, mutual blocking, and deflection of SBs were revealed along with the significant differences between the topologies of the mode II (in-plane) and mode III (out of plane) SBs. While the type II shear manifests a linear propagation path and a monotonically increasing shear offset, the type III shear is associated with a curved, segmented path and a non-monotonically varying shear offset. The systematic application of the “classic” elastic Volterra’s theory of dislocations to the behaviour of SBs in BMGs provides new insight into the widely reported experimental phenomena concerning the SB morphology, which is further detailed in the present work.
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Li, Kan, Richard H. C. Huntwork, Gillian Q. Horn, S. Munir Alam, Georgia D. Tomaras e S. Moses Dennison. "TitrationAnalysis: a tool for high throughput binding kinetics data analysis for multiple label-free platforms". Gates Open Research 7 (4 luglio 2023): 107. http://dx.doi.org/10.12688/gatesopenres.14743.1.
Testo completoAbstract (sommario):
Label-free techniques including Surface Plasmon Resonance (SPR) and Biolayer Interferometry (BLI) are biophysical tools widely used to collect binding kinetics data of bimolecular interactions. To efficiently analyze SPR and BLI binding kinetics data, we have built a new high throughput analysis tool named the TitrationAnalysis. It can be used as a package in the Mathematica scripting environment and ultilize the non-linear curve-fitting module of Mathematica for its core function. This tool can fit the binding time course data and estimate association and dissociation rate constants (ka and kd respectively) for determining apparent dissociation constant (KD) values. The high throughput fitting process is automatic, requires minimal knowledge on Mathematica scripting and can be applied to data from multiple label-free platforms. We demonstrate that the TitrationAnalysis is optimal to analyze antibody-antigen binding data acquired on Biacore T200 (SPR), Carterra LSA (SPR imaging) and ForteBio Octet Red384 (BLI) platforms. The ka, kd and KD values derived using TitrationAnalysis very closely matched the results from the commercial analysis software provided specifically for these instruments. Additionally, the TitrationAnalysis tool generates user-directed customizable results output that can be readily used in downstream Data Quality Control associated with Good Clinical Laboratory Practice operations. With the versatility in source of data input source and options of analysis result output, the TitrationAnalysis high throughput analysis tool offers investigators a powerful alternative in biomolecular interaction characterization.