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Due to the significant weight reduction advantage, aerospace composite tanks have become the focus of international competition of spacecraft. However, the permeation of small molecules at low temperature caused by the internal voids of composites is one of the key technical problems which restrict the engineering application of composite tanks. In this study, a combination of theoretical research and experimental research was adopted. By changing the curing pressures of the composites’ autoclave process, laminates with different porosities were prepared and tested for low-temperature permeability. Based on the grayscale processing and median filtering methods, a permeability prediction model with the true voids morphology of composite materials was established. Based on the random medium theory, the random voids model of composites was built to study the effect of void size and shape on the permeability of laminates. The results showed that the finite element analysis of composites, permeability based on the real voids morphology model was in good agreement with the experimental results, which proved the feasibility of this method. The permeation rate of laminates increased with the raised of porosity, and the internal porosity of the laminates could be diminished by improving the curing pressure so as to reduce the permeation of the composite components. Under the condition of a certain porosity, the laminates with small, stripe voids had a higher permeation rate than the laminates with large, circular voids.

Multiple optical scattering occurs when light propagates in a non-uniform medium. During the multiple scattering, images were distorted and the spatial information they carried became scrambled. However, the image information is not lost but presents in the form of speckle patterns (SPs). In this study, we built up an optical random scattering system based on an liquid crystal display (LCD) and an RGB laser source. We found that the image classification can be improved by the help of random scattering which is considered as a feedforward neural network to extracts features from image. Along with the ridge classification deployed on computer, we achieved excellent classification accuracy higher than 94%, for a variety of data sets covering medical, agricultural, environmental protection and other fields. In addition, the proposed optical scattering system has the advantages of high speed, low power consumption, and miniaturization, which is suitable for deploying in edge computing applications.

We extend the scalar elliptical multi-Gaussian Schell-model (EMGSM) beams with twist phase to the electromagnetic domain and obtain the analytical expression for the propagation of the electromagnetic twisted EMGSM beams through random media. The twist phase-induced changes of the spectral density and degree of polarization of such beams on propagation are studied numerically. Results show that by adjusting the twist factor and the correlated parameters of the source, both the spectral density and degree of polarization not only rotate around the propagation axis but also exhibit diverse shapes. The flattopped ellipse-like and diamond-like shape maintain over a relatively long propagation distance and finally involve into Gaussian-like shape due to stronger atmospheric turbulence. The results will be useful in optical trapping and optical communication.

We present a class of diffraction-free partially coherent beams each member of which is comprised of a finite power, non-accelerating Airy bump residing on a statistically homogeneous, Gaussian-correlated background. We examine free-space propagation of soft apertured realizations of the proposed beams and show that their evolution is governed by two spatial scales: the coherence width of the background and aperture size. A relative magnitude of these factors determines the practical range of propagation distances over which the novel beams can withstand diffraction. The proposed beams can find applications to imaging and optical communications through random media., 5 pages, 5 figures

Properties of vortex beams are significantly affected upon interaction with random phase screens. We provide a quantitative description of the measurable vorticity as a function of variance and spatial correlation properties of distorting media.

In this paper, wavefield storage optimization strategies are discussed with respect to reverse-time migration (RTM) imaging in reflection-acoustic logging, considering the problem of massive wavefield data storage in RTM itself. In doing so, two optimization methods are proposed and implemented to avoid wavefield storage. Firstly, the RTM based on the excitation-amplitude imaging condition uses the excitation time to judge the imaging time, and accordingly, we only need to store a small part of wavefield, such as the wavefield data of dozens of time points, the instances prove that they can even be imaged by only two time points. The traditional RTM usually needs to store the wavefield data of thousands of time points, compared with which the data storage can be reduced by tens or even thousands of times. Secondly, the RTM based on the random boundary uses the idea that the wavefield scatters rather than reflects in a random medium to reconstruct the wavefield source and thereby directly avoid storing the forward wavefield data. Numerical examples show that compared with other migration algorithms and the traditional RTM, both methods can effectively reduce wavefield data storage as well as improve data-processing efficiency while ensuring imaging accuracy, thereby providing the means for high-efficiency and high-precision imaging of fractures and caves by boreholes.

A novel class of random media with designed correlation functions are introduced. When light waves are scattered by this kind of media, the spectral density distributions of the scattered field present concentric rings-like profiles. By adjusting different parameters of the media, the number and the size of concentric rings can be modulated properly. Besides, it is found that the spectral density function of the scattered field and the non-negative definiteness function of the media belong to the same kind of functions. Our results have potential applications in optical trapping and particle manipulation.

Adopting an effective top coal caving method is the key to enhancing coal recovery and reducing gangue content for the fully mechanized top coal caving working face with extra-thick coal seams. In this study, the movement of coal particles generated during top coal caving is considered to follow a normal distribution. Then, the caving body and coal-rock settlement along the working face during the caving process are studied based on both the random media theory and probability theory. Accordingly, the optimal caving interval and caving sequences are determined, and a novel interval symmetrical coal caving method is proposed. The proposed method is systematically verified with results from physical similarity tests, and different caving methods are assessed by field tests. The results show the following: (1) The coal-rock settlement and the caving body demonstrate clear axial symmetrical features along the working face; the size of the caving body increases as the caving height grows and its shape turns progressively from semicircular to semielliptical with a lower foot of the coal-rock settlement. (2) The caving interval is derived using the sum of the radii of the coal-rock settlement curves formed by the two largest caving bodies. (3) The symmetrical caving approach provides a symmetrical space for the subsequent movement of the broken top coal, which enables a uniform development of the caving body. (4) Compared with the traditional sequential coal caving method with the same number of supports, the interval symmetrical caving method results in a 21.7% of coal production increase, 17% caving rate promotion, and a shortened caving time by 23.4%. (5) The interval symmetrical caving method is found to improve the controllability of the caving process at the fully mechanized top coal caving working face. In general, this work presents a theoretical approach to select the optimal caving methods for the fully mechanized caving working face in extra-thick coal seams for an improved production efficiency of the work face. The results of this study can also provide theoretical significance and referencing value for quantitative analyses of the coal caving methods for work faces with similar geological conditions.

Far-subwavelength spatial resolution based on relative motion between a struc- tured field and an object with far-field intensity measurements is proposed, supported with numerical simulations, and demonstrated with speckle from random media to sense mi- crostructure.

This paper considers wave-based imaging through a heterogeneous (random) scattering medium. The goal is to estimate the support of the reflectivity function of a remote scene from measurements of the backscattered wave field. The proposed imaging methodology is based on the coherent interferometric (CINT) approach that exploits the local empirical cross correlations of the measurements of the wave field. The standard CINT images are known to be robust (statistically stable) with respect to the random medium, but the stability comes at the expense of a loss of resolution. This paper shows that a two-point CINT function contains the information needed to obtain statistically stable and high-resolution images. Different methods to build such images are presented, theoretically analyzed and compared with the standard imaging approaches using numerical simulations. The first method involves a phase-retrieval step to extract the reflectivity function from the modulus of its Fourier transform. The second method involves the evaluation of the leading eigenvector of the two-point CINT imaging function seen as the kernel of a linear operator. The third method uses an optimization step to extract the reflectivity function from some cross products of its Fourier transform. The presentation is for the synthetic aperture radar data acquisition setup, where a moving sensor probes the scene with signals emitted periodically and records the resulting backscattered wave. The generalization to other imaging setups, with passive or active arrays of sensors, is discussed briefly., Comment: 31 pages, 5 figures

We study wave propagation in materials in which the refractive index varies in time. We compare the situations in which the variations are periodic and random. If the modulation period (in the peri...

Çevrimiçi ortamların etkili bir iletişim aracı olarak yükselişi, habere ulaşma, tüketme ve paylaşma şeklini kökten değiştirdi. Haber platformu olarak sosyal medyanın yükselişi, bilgiye erişim ve katılım deneyimlerimizi de zenginleştirmiştir. Bu çalışma, genç kullanıcıların sosyal medyada haber tüketim sürecini Eveland’in Bilişsel Arabuluculuk modeli ile incelemektedir. Sosyal medyada habere rastlantısal maruz kalınması, paylaşılan haber içeriğine katılım, bilişsel ayrıntılandırma ve güncel olaylar bilgisi arasındaki ilişkileri ortaya çıkarmayı amaçlayan bu araştırma, 402 kişiyle veri toplama aracı kullanılarak gerçekleştirilmiştir. Araştırmadan elde edilen sonuçlara göre, genç kullanıcıların çoğu, çevrimiçi erişim gerektiren dijital ortamlarla bağlantılarının bir parçası olarak sosyal medyada rastladıkları haberlere dikkat etmektedir. Ayrıca sonuçlar, pasif olarak habere maruz kalan genç kullanıcıları da dahil etme becerisine sahip sosyal medyanın, haber ve bilgi kullanımı arasındaki ilişkiye aracılık ettiğini ortaya koymaktadır. The rise of online environments as an effective means of communication has radically changed the way in which news is accessed, consumed and shared. The rise of social media as a news-platform enriches our experiences of access to information and participation. This study examines the news consumption process of young users on social media with Eveland's Cognitive Mediation Model. This study aimed to reveal the relationship between random media exposure, participation in shared news content, cognitive refinement, and current affairs information and this research was carried out using 402 data collection tool. According to the results of the research, most young users pay attention to the news they encounter on social media as a part of their connection to digital environments that require online access. The results also show that social media capable of involving young users who are passively exposed to news mediate the relationship between news and information use.

The authors provide an statistical treatment of speckle intensity correlations as a function of the position of an obscured moving object and perform experiments to compare with their theory

Random lasing is a lasing phenomenon realized in random media, and it has attracted a great deal of attention in recent years. An essential requirement for strong random lasing is to achieve strong and recurrent scattering among grain boundaries of a disordered structure. Herein, we report a random laser (RL) based on individual polycrystalline GaTe microflakes (MFs) with a lasing threshold of 4.15 kW cm

A 2D modelling study is presented on the transmission enhancement by iterative optical phase conjugation through diffusive random media. Factors affecting coherent control for enhancing the total transmission is discussed.

We demonstrate theoretically that the average spatial intensity profile of any partially coherent optical beam, composed of a finite-power bright intensity bump atop a fluctuating background, evolves into a universal self-similar Gaussian shape upon long-term propagation in a statistically homogeneous, isotropic linear random medium. The result depends neither on the degree of the background spatial coherence nor on the strength of the medium turbulence. To our knowledge, this is the first demonstration of universal self-similar asymptotics in linear random media.

We consider the problem of localizing one or more sources in a two-dimensional waveguide with horizontal flat boundaries and random sound speed fluctuations. Our data are the acoustic press...

We present a survey of recent results on the acousto-optic effect in random media with applications to biomedical imaging. Related inverse problems are described, including those of coherent and incoherent acousto-optic imaging in both the diffusion and transport regimes.

We highlight the impact of Emil Wolf's work on coherence and polarization on an ever increasing amount of applications in the 21st century. We present a brief review of how partial coherence at the level of increasing order of coherence functions is leading to evolution in the better methods for microscopy, imaging, optical coherence tomography, speckle imaging, and propagation through random media. This evolution in our capabilities is expected to have wide ramifications in Science and Engineering.

We discuss the problem of tomographic reconstruction of fluorescent objects hidden behind random media. To accomplish this, we focus on the properties of the autocorrelation, relying on phase retrieval algorithms to perform 3D reconstruction.

[EN] The time that waves spend inside 1D random media with the possibility of performing Lévy walks is experimentally and theoretically studied. The dynamics of quantum and classical wave diffusion has been investigated in canonical disordered systems via the delay time. We show that a wide class of disorder¿Lévy disorder¿leads to strong random fluctuations of the delay time; nevertheless, some statistical properties such as the tail of the distribution and the average of the delay time are insensitive to Lévy walks. Our results reveal a universal character of wave propagation that goes beyond standard Brownian wave-diffusion., A. A. F.-M. thanks the hospitality of the Laboratoire d'Acoustique de l'Universite du Mans, France, where part of this work was done. J. A. M.-B, gratefully acknowledges to Departamento de Matematica Aplicada e Estatistica, Instituto de Ciencias Matematicas e de Computacao, Universidade de Sao Paulo during which this work was completed. J.A.M.-B. was supported by FAPESP (Grant No. 2019/06931-2), Brazil. A. A. F.-M. thanks partial support by RFI Le Mans Acoustique and by the project HYPERMETA funded under the program Etoiles Montantes of the Region Pays de la Loire. V. A. G. acknowledges support by MCIU (Spain) under the Project number PGC2018-094684-B-C22.

When waves propagate through a strongly scattering medium the energy is transferred to the incoherent wave part by scattering. The wave intensity then forms a random speckle pattern seemingly witho...

This work addresses the range in which the accuracy of object identification is enhanced regardless of radar parameters. We compute the radar cross-section (RCS) of conducting objects in free space and random media. We use beam wave incidence and postulate its coherency with a finite width around an object located in the far field. Accordingly, we examine the impact of radar parameters on the RCS, where these parameters include the incident angle, target size and complexity, medium fluctuation intensity and the beam size of the incident waves. H-wave polarization is assumed for the waves’ incidence.

This feature issue presents original work on light-matter interaction in complex photonics systems, which has been a continuously growing area of optics and photonics, in terms of both importance and breadth. From disordered systems to highly controlled micro- and nanostructures, recent decades have witnessed the onset of random media, photonic crystals, metamaterials, plasmonics, and, more recently, metasurfaces.

We experimentally investigate random laser (RL) emission from dye-doped polymer random media with inhomogeneously distributed scatterers. A random structure, which we call a bubble structure (BS), is realized by using nonscattering spacer particles randomly distributed in a gain medium. The experimental results show that the bubble-structured RL that incorporates an appropriate amount of spacer particles exhibits a higher spectral peak and a larger slope efficiency than conventional RLs. The highest peak intensity is observed when the size variation of spacer particles is maximized. Furthermore, an analysis of laser modes reveals that an increase in the spectral peak intensity can be partly attributed to the mode selection properties of the BS.

A Design, simulation and optimal selection of non-linear frequency modulation waveforms (NLFM) based on correlated ambiguity function (AF) quality analysis for the purpose of Synthetic Aperture Radar (SAR) is done in this article. The selected optimum CNLFM waveform in contribution with other waveforms are applied directly into a SAR image formation algorithm (IFA) and their quality metrics in comparison to other waveforms are derived and analyzed in a complex random media (CRM). The total quality performance analysis includes both the qualitative AF diagrams and the objective image quality metrics assessments. The simulation results not only verify the robustness of the proposed NLFM waveforms as a suitable alternative for LFM waveform but also introduce NLFM as a proper method of modulation for SAR in CRM.

Post-print (lokagerð höfundar), In conventional Stokes polarimetry, where the polarimetric information is obtained from a series of intensity measurements, stable and accurate measurements typically require the optical elements to be carefully designed. Here, we propose a paradigm shift where deep neural network assisted polarimeters based on disordered photonic structures perform high quality polarimetric measurements while completely removing the need for specially designed polarization analyzers, demonstrating how disordered photonic structures fabricated without the use of any nanolithography techniques can enable accurate analysis of optical signals. We implement this concept with disorder- engineered nano-scatterers that allow for analyzing varying degrees of disorder and cellophane film that demonstrate the cost-saving potential of the concept. We demonstrate polarimetric performances, calibrated using deep neural networks, that are comparable to commercial polarimeters, does not require prior knowledge of the input wavelength and show a high degree of mechanical stability., This work was supported in part by the Icelandic Research Fund under Grant 187043-0611 and in part by the Air Force O ce for Scienti c Research under MURI Grant FA9550-14-1-0389. The authors thank J.P. Balthasar Mueller, Einar B. Magnusson and Noah Rubin for valuable help and advice. The processing of gold metasurfaces was performed at the nanofabrication facility at the University of Iceland.

Transmission matrices are one of the most useful tools to address the transport of light in random media. For example, they have been used for focusing [1], reconstruction of images [2], imaging through optical fibers [3], maximal energy transport [4], and control in photo-acoustics [5].

In this paper, we investigate the domain where the radar detection accuracy is maximized. In doing this, we study the effect of the illumination region of a conducting concave-to-convex object on the laser radar cross-section (LRCS) in random medium. Beam wave incidence is considered and assumed to be coherent with limited size around the target in the far field. H-wave polarization of the incident waves is considered.

The Oguchi method is an important tool for characterizing the transmission characteristics of polarized electromagnetic waves in precipitation. In this paper, the forward scattering matrix of chaff is calculated for the special random medium of chaff cloud. Then the transmission characteristics of polarized electromagnetic wave, including attenuation, (specific) differential phase, are studied by using Oguchi method. The obtained characteristics are consistent with the physical laws, and the feasibility of the Oguchi method in chaff characteristic analysis is preliminarily verified.

Time‐resolved nonlinear optical sum‐frequency generation (SFG) of two differently colored, infrared (sub‐)picosecond laser pulses is studied by means of nonlinear diffuse femtosecond‐pulse reflectometry using lithium niobate nanoparticle pellets. The visible SFG emission exhibits an asymmetric pulse shape in the time domain which is explained within the framework of light propagation in random media. The analysis of the spectro‐temporal data set indicates that LiNbO3 nanoparticle pellets can be used for an alternative type of an optical correlator, e.g., for the determination of a pulse's chirp parameter. This finding is generalized by means of numerical simulations. As a result, ultrashort pulse shapes can now be predicted inside nanoscaled, densely packed media with a nonlinear optical response on a comprehensive basis, giving rise to a number of prospective fields of applications.

We study the energy density of shaped waves inside a quasi-1D disordered waveguide. We find that the spatial energy density of optimally shaped waves, when expanded in the complete set of eigenfunctions of the diffusion equation, is well described by considering only a few of the lowest eigenfunctions. Taking into account only the fundamental eigenfunction, the total internal energy inside the sample is underestimated by only 2%. The spatial distribution of the shaped energy density is very similar to the fundamental eigenfunction, up to a cosine distance of about 0.01. We obtain the energy density of transmission eigenchannels inside the sample by numerical simulation of the scattering matrix. Computing the transmission-averaged energy density over all transmission channels yields the ensemble averaged energy density of shaped waves. From the averaged energy density, we reconstruct its spatial distribution using the eigenfunctions of the diffusion equation. The results of our study have exciting applications in controlled biomedical imaging, efficient light harvesting in solar cells, enhanced energy conversion in solid-state lighting, and low threshold random lasers.

This work is to select precisely the proper frequency range that reduces the dependence of the laser radar cross-section (LRCS) on the incident wave parameters. In doing this, we investigate the effect of these parameters including incident angle and the beam width on the LRCS. We present a numerical analysis of the effect of the H-wave polarization on the radar detection capability in random medium and hence compare it with the freespace case. In doing this, our calculations use a boundary value method considering surface current on the whole contour of the object. As a result, the performance of the LRCS is studied with the target configuration assuming the creeping waves that have remarkable influence especially in the resonance range.

The possibility for different media to generate scattered field with identical spectral coherence is discussed. It is shown that two random media, with different characters of correlation function, may generate scattered field with identical spectral coherence property. An example of light waves on scattering from Gaussian-Schell model media is discussed, and a condition for identical spectral coherence of the far-zone scattered field is obtained.

When lidar is used to detect the microphysical properties of clouds and aerosols, it is a spot when the laser reaches the clouds. This is because the lidar has a certain divergence angle, and the location of the lidar is at a certain distance from the clouds. In this paper, a Monte Carlo method for simulating multiple scattering in clouds by lidar is presented, and the influence of the size and shape of the spot on the backscattering of polarized light in clouds is analyzed. From the calculation results, it can be seen that the spot will increase the depolarization ratio of lidar, and the larger of the size of the spot, the larger the depolarization ratio. In addition, depolarization ratio increases with the increase of optical thickness and field of view angle. The methods and conclusions in this paper are of great significance for long-distance detection of discrete random media by laser.

We show that the “intensity bump” cross-spectral density used in Opt. Lett. 45, 698 (2020)OPLEDP0146-959210.1364/OL.385246 does not satisfy the non-negative definiteness requirement and cannot be used as a cross-spectral density model.

Non-invasive optical focusing inside scattering media is still a big challenge because inhomogeneous media scatter both incoming photons for focusing and outgoing photons for observation. Various approaches, utilizing non-linear fluorescence or ultrasound, have been reported to address this difficulty. However, implementation of these methods is complicated and highly expensive, as ultrafast laser systems or photo-acoustic equipment must be employed. Here, we demonstrate a wavefront shaping technique to achieve non-invasive focusing (NiF) inside scattering media using only a linear fluorescent signal. Contrast and mean of incoherent speckles, produced by the linear fluorescence, are utilized as feedback signals to optimize the input wavefront. While increasing speckle contrast makes the focus tighter, and increasing the speckle mean enhances the intensity, fine-tuning the contribution of these two factors in our two-step optimization is essential. An optimal wavefront is found to achieve simultaneously both a micrometer focal spot size (down to 20 um diameter) and high intensity (more than a 100-fold enhancement) inside the scattering media. Our method promises a new route in life science towards focusing, imaging or manipulating deep into biological tissues with linear fluorescent agents., 9 pages

We consider the theory of radiative transport in quasi-homogeneous random media. We derive the radiative transport equation that governs the propagation of light in such media. This result provides conditions under which it is justified to apply radiative transport theory to spatially inhomogeneous media.

Beams carrying C-point polarization singularity (lemon and star) are experimentally shown to maintain robust intensity profile on passing through a random medium compared to beams carrying V-points polarization singularity (radially and azimuthally polarized).

Diffusion is the result of repeated random scattering. It governs a wide range of phenomena from Brownian motion, to heat flow through window panes, neutron flux in fuel rods, dispersion of light in human tissue, and electronic conduction. It is universally acknowledged that the diffusion approach to describing wave transport fails in translucent samples thinner than the distance between scattering events such as are encountered in meteorology, astronomy, biomedicine, and communications. Here we show in optical measurements and numerical simulations that the scaling of transmission and the intensity profiles of transmission eigenchannels have the same form in translucent as in opaque media. Paradoxically, the similarities in transport across translucent and opaque samples explain the puzzling observations of suppressed optical and ultrasonic delay times relative to predictions of diffusion theory well into the diffusive regime., Despite the universal nature of diffusion, the behavior of light transport in optically thin media has remained unclear. Here the authors show that the description of this behavior in translucent media has the same form as in opaque media, even at length scales far below the mean free path.

This book is timely summarization of recent advances in the multiscale theory of composites and random media. The theories in the book can be used in many disciplines, including geophysics, materia...

We experimentally show that the non-separability of polarization and orbital angular momentum present in a light beam remains preserved under scattering through a random medium like rotating ground glass. We verify this by measuring the degree of polarization and observing the intensity distribution of the beam when projected to different polarization states, before as well as after the scattering. We extend our study to the non-maximally non-separable states also.

Light transport and the physical phenomena related to light propagation in random media are very intriguing, they also provide scope for new paradigms of device functionality, most of which remain unexplored. Here we demonstrate, experimentally and by simulation, a novel kind of asymmetric light transmission (diffusion) in a stack of random media (SRM) with graded transport mean free path. The structure is studied in terms of transmission, of photons propagated through and photons generated within the SRM. It is observed that the SRM exhibits asymmetric transmission property with a transmission contrast of 0.25. In addition, it is shown that the SRM works as a perfect optical low-pass filter with a well-defined cutoff wavelength at 580 nm. Further, the photons generated within the SRM found to exhibit functionality similar to an optical diode with a transmission contrast of 0.62. The basis of this functionality is explained in terms of wavelength dependent photon randomization and the graded transport mean free path of SRM. MOE (Min. of Education, S’pore) Accepted version