Diffusing Wave Spectroscopy: The Dynamics of Multiply Scattering Media

1991 ◽  
Vol 253 ◽  
Author(s):  
D. A. Weitz ◽  
D. J. Pine ◽  
D. J. Durian ◽  
J. X. Zhu
Keyword(s):  
Hydrodynamic Interaction ◽  
Colloidal Particles ◽  
Mean Free Path ◽  
Diffusing Wave Spectroscopy ◽  
Scattering Medium ◽  
Scattering Media ◽  
Physical Processes ◽  
Total Light ◽  
Path Lengths ◽  
Physical Phenomena

ABSTRACTWhen light is very strongly multiply scattered by a medium, its propagation can be well described by a diffusion approximation. This allows important, measurable quantities to be calculated theoretically and interpreted. Thus, for example the total light transmitted through a sample can be used to determine the transport mean free path which characterizes the diffusive transport of the light. In addition, the distribution of path lengths followed by the diffusing light can be determined. This distribution can in turn be used to interpret the temporal fluctuations of the scattered intensity that arise due to the motion of the scattering medium. Therefore, traditional quasielastic, or dynamic, light scattering can be extended to the strongly multiple scattering limit. This technique is called Diffusing Wave Spectroscopy (DWS), and allows useful information about the dynamics of the medium to be determined. Furthermore, new physical processes can be studiedusing DWS. For example, DWS is sensitive to very small motions of colloidal particles: motion of 1 pm diameter particles can be resolved on lengths of∼ 5 Å using light with a wavelength of 0.5 μm. New physical phenomena are probed when motion on these length scales is observed. In particular, the time evolution of the hydrodynamic interaction between concentrated colloidal particles can be resolved. In addition, DWScan also probe spatially rare events since the light paths sample a large volume of the sample. This allows DWS to probe very slow dynamics, making it useful for the study of materials such as foams. This talk reviews the fundamentals of DWS and highlights some ofits unique applications.

scholarly journals Wide-field multiphoton imaging through scattering media without correction

2018 ◽  
Vol 4 (10) ◽  
pp. eaau1338 ◽  
Author(s):  
Adrià Escobet-Montalbán ◽  
Roman Spesyvtsev ◽  
Mingzhou Chen ◽  
Wardiya Afshar Saber ◽  
Melissa Andrews ◽  
...  
Keyword(s):  
A Priori ◽  
Super Resolution ◽  
Mean Free Path ◽  
Wide Field ◽  
Biomedical Sciences ◽  
Scattering Media ◽  
Multiphoton Imaging ◽  
Two Photon ◽  
Temporal Focusing ◽  
Path Lengths

Optical approaches to fluorescent, spectroscopic, and morphological imaging have made exceptional advances in the last decade. Super-resolution imaging and wide-field multiphoton imaging are now underpinning major advances across the biomedical sciences. While the advances have been startling, the key unmet challenge to date in all forms of optical imaging is to penetrate deeper. A number of schemes implement aberration correction or the use of complex photonics to address this need. In contrast, we approach this challenge by implementing a scheme that requires no a priori information about the medium nor its properties. Exploiting temporal focusing and single-pixel detection in our innovative scheme, we obtain wide-field two-photon images through various turbid media including a scattering phantom and tissue reaching a depth of up to seven scattering mean free path lengths. Our results show that it competes favorably with standard point-scanning two-photon imaging, with up to a fivefold improvement in signal-to-background ratio while showing significantly lower photobleaching.

scholarly journals Locating and Imaging through Scattering Medium in a Large Depth

Sensors ◽  
2020 ◽  
Vol 21 (1) ◽  
pp. 90
Author(s):  
Shuo Zhu ◽  
Enlai Guo ◽  
Qianying Cui ◽  
Lianfa Bai ◽  
Jing Han ◽  
...  
Keyword(s):  
Phase Space ◽  
Signal To Noise Ratio ◽  
Speckle Pattern ◽  
Heuristic Method ◽  
Scattering Medium ◽  
Scattering Media ◽  
Signal To Noise ◽  
Practical Applications ◽  
Large Depth ◽  
Strong Scattering

Scattering medium brings great difficulties to locate and reconstruct objects especially when the objects are distributed in different positions. In this paper, a novel physics and learning-heuristic method is presented to locate and image the object through a strong scattering medium. A novel physics-informed framework, named DINet, is constructed to predict the depth and the image of the hidden object from the captured speckle pattern. With the phase-space constraint and the efficient network structure, the proposed method enables to locate the object with a depth mean error less than 0.05 mm, and image the object with an average peak signal-to-noise ratio (PSNR) above 24 dB, ranging from 350 mm to 1150 mm. The constructed DINet firstly solves the problem of quantitative locating and imaging via a single speckle pattern in a large depth. Comparing with the traditional methods, it paves the way to the practical applications requiring multi-physics through scattering media.

Fluid-structure Interactions

1998 ◽  
Vol 120 (04) ◽  
pp. 66-68 ◽  
Author(s):  
Klaus-Ju¨rgen Bathe
Keyword(s):  
Finite Element ◽  
Fluid Structure Interactions ◽  
Physical Processes ◽  
Fluid Structure ◽  
Modeling And Analysis ◽  
Structure Interaction ◽  
Design And Manufacturing ◽  
Physical Phenomena ◽  
Acoustic Fluid ◽  
Made In

This article reviews finite element methods that are widely used in the analysis of solids and structures, and they provide great benefits in product design. In fact, with today’s highly competitive design and manufacturing markets, it is nearly impossible to ignore the advances that have been made in the computer analysis of structures without losing an edge in innovation and productivity. Various commercial finite-element programs are widely used and have proven to be indispensable in designing safer, more economical products. Applications of acoustic-fluid/structure interactions are found whenever the fluid can be modeled to be inviscid and to undergo only relatively small particle motions. The interplay between finite-element modeling and analysis with the recognition and understanding of new physical phenomena will advance the understanding of physical processes. This will lead to increasingly better simulations. Based on current technology and realistic expectations of further hardware and software developments, a tremendous future for fluid–structure interaction applications lies ahead.

scholarly journals Size-dependent thermodynamic structural selection in colloidal crystallization

2019 ◽  
Vol 5 (9) ◽  
pp. eaaw5912 ◽  
Author(s):  
Evan Pretti ◽  
Hasan Zerze ◽  
Minseok Song ◽  
Yajun Ding ◽  
Runfang Mao ◽  
...  
Keyword(s):  
Self Assembly ◽  
Colloidal Particles ◽  
Size Dependence ◽  
Fluid Phase ◽  
Two Dimensions ◽  
Size Dependent ◽  
Colloidal Crystallization ◽  
Kinetic Effects ◽  
Physical Phenomena ◽  
Surrounding Fluid

Nucleation and growth of crystalline phases play an important role in a variety of physical phenomena, ranging from freezing of liquids to assembly of colloidal particles. Understanding these processes in the context of colloidal crystallization is of great importance for predicting and controlling the structures produced. In many systems, crystallites that nucleate have structures differing from those expected from bulk equilibrium thermodynamic considerations, and this is often attributed to kinetic effects. In this work, we consider the self-assembly of a binary mixture of colloids in two dimensions, which exhibits a structural transformation from a non–close-packed to a close-packed lattice during crystal growth. We show that this transformation is thermodynamically driven, resulting from size dependence of the relative free energy between the two structures. We demonstrate that structural selection can be entirely thermodynamic, in contrast to previously considered effects involving growth kinetics or interaction with the surrounding fluid phase.

scholarly journals The behaviour of scattering media in fully diffused light

1918 ◽  
Vol 94 (659) ◽  
pp. 222-237 ◽  
Keyword(s):  
Experimental Data ◽  
Finite Thickness ◽  
Scattering Medium ◽  
Scattering Media ◽  
Present Communication ◽  
Practical Standpoint ◽  
The Subject ◽  
American Society ◽  
Diffused Light ◽  
Complex Subject

The present paper is the outcome of a discussion which arose between the authors after the publication of a paper by O. Bloch and F. F. Renwick,* which dealt with the subject of the opacity of diffusing media, chiefly from the practical standpoint, and included also lengthy extracts from the Reports of a Committee of the American Society of Illuminating Engineers. On finding that we were unable to reconcile the experimental data with the theory included in the above paper, we were gradually led into the attempt to find solutions of some of the problems involved in this complex subject, starting only with the indisputable fact that when light falls upon a finite thickness of a scattering medium, part is rejected, part extinguished, and part transmitted. In the present communication we have confined ourselves to a study of the action of such media upon light which is assumed to be already completely diffused.

scholarly journals Spatiotemporal functional modeling of postseismic deformations after the 2011 Tohoku-Oki earthquake

2022 ◽  
Vol 74 (1) ◽  
Author(s):  
Satoshi Fujiwara ◽  
Mikio Tobita ◽  
Shinzaburo Ozawa
Keyword(s):  
Standard Deviation ◽  
Statistical Data ◽  
Functional Model ◽  
Satellite System ◽  
Physical Processes ◽  
Linear Deformation ◽  
Practical Applications ◽  
Long Period ◽  
Global Navigation Satellite ◽  
Physical Phenomena

AbstractPostseismic deformations continue to occur for a long period after major earthquakes. Temporal changes in postseismic deformations can be approximated using simple functions. Since the 2011 Tohoku-Oki earthquake, operating global navigation satellite system stations have been continuously accumulating a remarkable amount of relevant data. To verify the functional model, we performed statistical data processing on postseismic deformations due to this earthquake and obtained their spatiotemporal distribution. Moreover, we approximated the postseismic deformations over a relatively wide area with a standard deviation of residuals of 1 cm for approximately 10 years using a combined functional model of two logarithmic and one exponential functions; however, the residuals from the functional model exhibited a marked deviation since 2015. Although the pattern of postseismic deformations remained unaltered after the earthquake, a change in the linear deformation occurred from 2015 to date. We reduced the overall standard deviation of the residuals of > 200 stations distributed over > 1000 km to < 0.4 cm in the horizontal component by enhancing the functional model to incorporate this linear deformation. Notably, time constants of the functions were similarly applicable for all stations and components. Furthermore, the spatial distribution of the coefficients of each time constant were nonrandom, and the distribution was spatially smooth, with minute changes in the short wavelengths in space. Thus, it is possible to obtain a gridded model in terms of a spatial function. The spatial distributions of short- and long-period components of the functional model and afterslip and viscoelastic relaxation calculated using the physical model were similar to each other, respectively. Each time function revealed a connotation regarding the physical processes, which provided an understanding of the physical phenomena involved in seismogenesis. The functional model can be used to practical applications, such as discerning small variations and modeling for precise positioning. Graphical Abstract

Field-driven ion migration against dead-stop collisional braking

1988 ◽  
Vol 39 (1) ◽  
pp. 53-60
Author(s):  
J. A. Grzesik
Keyword(s):  
Mean Free Path ◽  
Plasma Sheath ◽  
Metal Corrosion ◽  
Space Distribution ◽  
Uniform Electric Field ◽  
Average Kinetic Energy ◽  
Ion Density ◽  
Ion Migration ◽  
Explicit Recognition ◽  
Path Lengths

The steady-state migration of ions, driven by a uniform electric field against full-stop collisions, is investigated in some detail. The required phase-space distribution is obtained very easily from Boltzmann's equation together with explicit recognition of energy conservation and population balance for the stagnant ion pool. We go on to decompose this aggregate solution into ion tiers classified by the number of background impacts previously endured. Such a decomposition permits us to detect the presence of Poisson statistics (as to collision number) lurking within the composite, thermalized Maxwellian, and likewise also a multiple-scattering hierarchy having the maiden, first-flight distribution for its natural kernel. Scattering-sequence accounting, in particular, allows a quantitative (even though unwieldy) distinction to be made between ions of varying residence times. A model of this sort is motivated by the technique of ion implantation through sample immersion within a plasma at higher electric potential. Numerical consequences of the solution obtained here reveal that both ion density and average kinetic energy relax to their terminal values within just a few mean free-path lengths. Such modest scaling of plasma-sheath extent evidently carries a beneficial implication for the technological ease with which surface properties (such as metal corrosion resistance and hardness) remain open to improvement via ion bombardment.

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