Wyniki wyszukiwania - Biblioteka Nauki

1

Modeling of direct and inverse problems in light scattering by rough surfaces

100%

Łukianowicz C.

Optica Applicata

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2003

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tom Vol. 33, nr 2-3

329-336

EN

The rough surface assessment by light scattering methods is mostly preceded by the solution to the so-called direct and inverse problem. It requires assuming the mutual theoretical model, describing the phenomenon of light scattering by rough surfaces, for both problems. In general, despite application of numerous simplifications, it is an intricate diffraction model. The description of the rough surface geometry is also quite often complicated. Therefore, in many cases experimental verification of analytical solutions to the direct and inverse problems is very difficult. Under such circumstances it is advisable to verify the correctness of the solutions obtained using the computer-modeling methods. The paper presents the process of the direct and inverse problem modeling and covers the results of the model tests on selected surfaces

2

Convergence of Monte Carlo algorithm for solving integral equations in light scattering simulations

80%

Kraszewski M. , Pluciński J.

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2020

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tom Vol. 50, nr 1

17--35

EN

The light scattering process can be modeled mathematically using the Fredholm integral equation. This equation is usually solved after its discretization and transformation into the system of algebraic equations. Volume integral equations can be also solved without discretization using the Monte Carlo algorithm, but its application to the light scattering simulations has not been sufficiently studied. Here we present the implementation of this algorithm for one and three-dimensional light scattering computations and discuss its applicability in this field. We show that the Monte Carlo algorithm can provide valid and accurate results but, due to its convergence properties, it might be difficult to apply for problems with large volumes or refractive indices of scattering objects.

3

Reciprocity relations for light wave scattered by a particulate collection

80%

Jiang Z. , Zhu Z. , Wang T.

Optica Applicata

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2018

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tom Vol. 48, nr 4

661--670

EN

Two Fourier relations of light waves scattered by a random-distributed particulate medium have been investigated. We find that the scattered field and the particulate collection satisfy two Fourier relations, i.e. the spectral density is directly proportional to a Fourier transform of a convolution of correlation coefficient of each particle and correlation coefficient of distribution function of the whole collection, and the spectral degree of coherence is directly proportional to a Fourier transform of a convolution of strength of the scattering potential of each particle and strength of the distribution function of the whole collection. To illustrate these relations, behaviors of the far-field generated by Gaussian-correlated particles with Gaussian-correlated distributions have been discussed.

4

Interference coloring of regularly scattered white light

80%

Angelsky O. V. , Bogatyryova H. V. , Polyanskii P. V.

Optica Applicata

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2008

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tom Vol. 38, nr 2

431-444

EN

Interference coloring of the regular component of a polychromatic light scattered by a colorlessdielectric slab with a rough surface is considered. To explain the observed alternation of colors as the depth of roughness grows, we apply the model of a transient layer associated with surfach roughness, which extends the well-known analogy between the layer and a light-scattering particle. It is shown that coloring of the forward-scattered component of a white light can be interpreted as the action of a peculiar quarter-wavelength (anti-reflecting) layer for some spectra component of a polychromatic probing beam. By applying the modern chromascopic technique, we compare the coloring of the forward-scattered and the specularly reflected radiation. As the demonstration, the effect of "a blue Moon" and "a red Moon" caused by the spectral changes induced by white-light scattering at the rough surface of a colorless glass is represented. - Natura simplex et fecunda, A. Fresnel.

5

Using the DDA (Discrete Dipole Approximation) Method in Determining the Extinction Cross Section of Black Carbon

80%

Skorupski K.

Metrology and Measurement Systems

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2015

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tom Vol. 22, nr 1

153--164

EN

BC (Black Carbon), which can be found in the atmosphere, is characterized by a large value of the imaginary part of the complex refractive index and, therefore, might have an impact on the global warming effect. To study the interaction of BC with light often computer simulations are used. One of the methods, which are capable of performing light scattering simulations by any shape, is DDA (Discrete Dipole Approximation). In this work its accuracy was estimated in respect to BC structures using the latest stable version of the ADDA (vr. 1.2) algorithm. As the reference algorithm the GMM (Generalized Multiparticle Mie-Solution) code was used. The study shows that the number of volume elements (dipoles) is the main parameter that defines the quality of results. However, they can be improved by a proper polarizability expression. The most accurate, and least time consuming, simulations were observed for IGT_SO. When an aggregate consists of particles composed of ca. 750 volume elements (dipoles), the averaged relative extinction error should not exceed ca. 4.5%.

6

Roughness characterization of well-polished surfaces by measurements of light scattering distribution

80%

Zhenrong Z. , Jing Z. , Peifu G.

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tom Vol. 40, nr 4

811--818

EN

According to vector scattering and scalar scattering theory, the relationship of BRDF (bidirectional reflectance distribution function) of light scattering from micro-rough surface with TIS (total integrated scattering) is analyzed. Roughness statistical characterization such as RMS (root mean square), PSD (power spectral density) function are deduced by TIS of polished surface. Based on the light scattering measurement theory, an automatic measure system of light scattering with one dimensional scanning method is built, BRDF of two kinds of polished surfaces (silica surface and Ag reflector) have been measured. PSD of two surfaces has been given by light scattering measurements, roughness characterization of two surfaces has been compared with the data tested by profile meter. The results show that the light scattering measurement method has great application prospects as regards nondestructive measurement for polishing surfaces.

7

Algorithm of irrespirable dust fraction suppression using an optical transducer of dust mass concentration

80%

Gmiterko A. , Zdravecká E.

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tom Vol. 45, nr 8-9

268-270

EN

An algorithm for processing information from an optical transducer of dust mass concentration is presented. It processes measurement results of electromagnetic radiation ranging from the visible to the infrared, which is scattered by the smaller respirable dust particles, but which is not similarly affected by the larger irrespirable dust particles of the same material. The algorithm is based on discretizing the wavelength of the radiation scattered by the dust into the finite number of the wavelength bands. The mass concentration of the respirable dust is obtained as the weighted sum of radiant fluxes occurring in the wavelength bands. The Mie theory [1] has been used for the description of the radiation scattering by the dust particles. Computational simulation results are presented to demonstrate the validity of this algorithm.

PL

W artykule zaprezentowano algorytm służący do przetwarzania informacji z optycznego przetwornika stężenia masowego pyłu. Przetwarzane są wyniki pomiarów promieniowania elektromagnetycznego mieszczącego się w zakresie widzialnym i podczerwieni. Promieniowanie jest rozpraszane przez mniejsze, wdychane cząstki pyłu, ale nie przez większe cząstki tego samego materiału, które nie są wdychane. Algorytm bazuje na dyskretyzacji długości fali promieniowania rozproszonego przez pył do skończonej liczby pasm długości fali. Stężenie masowe wdychanego pyłu wyznaczane jest jako suma ważona strumieni promieniujących, jakie pojawiają się w pasmach długości fali. Do opisu promieniowania rozproszonego przez cząstki pyłu wykorzystano teorię Mie'ego [1], a dla potwierdzenia poprawności algorytmu przedstawiono wyniki symulacji obliczeniowych.

8

Surface roughness assessment by light scattering

80%

Łukianowicz C.

Metrology and Measurement Systems

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2002

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tom Vol. 9, nr 3

247-260

EN

The paper presents the fundamental types of light scattering methods used to assess surface roughness. A brief review and classification of these methods are included. Their theoretical framework, properties and the most important metrological parameters were analysed. Methods of surface roughness assessment measure the intensity of the specular reflected light, the light scattered in one or several directions and the total integrated scattering. To some wider extent the methods based on an angular distribution of scattered light and those which make use of the optical Fourier transform are described.

PL

W artykule rozpatrzono podstawowe rodzaje metod rozpraszania światła stosowanych do oceny nierówności powierzchni. Metody te są przeznaczone przede wszystkim do oceny nierówności powierzchni elementów optycznych, krzemowych podłoży układów elektronicznych, precyzyjnie obrobionych części maszyn, itp. Mogą być one również wykorzystane do zautomatyzowanej kontroli, monitorowania i nadzorowania stanu powierzchni przdmiotów podczas procesu technologicznego. Na początku artykułu dokonano krótkiego przglądu, klasyfikacji i wstępnej charakterystyki metod rozpraszania światła. Następnie przeanalizowano ich podstawy teoretyczne, właściwości i najważniejsze parametry metrologiczne. Spośród metod rozpraszania światła najprostsze są te metody, ktre wykorzystują pomiar natężenia światła odbitego zwierciadlanie. Pozwalają one wyznaczać odchylenie standardowe wysokości nierówności powierzchni. Podstawą oceny nierówności jest w tym przypadku pomiar stosunku reflektancji zwierciadlanej do reflektancji całkowitej. W artykule przeanalizowano zakres pomiarowy tych metod oraz zależność błędu względnego mierzonego stosunkiem reflektancji od wysokości nierówności i długości fali światła. Odchylenie standardowe wysokości nierówności oceniane jest w podobny sposób w metodach integracyjnych. W przypadku tych metod, podstawę oceny nierówności powierzchni stanowi pomiar reflektancji dyfuzyjnej i reflektancji całkowitej. Nieco szerzej przedstawione są w artykule metody różniczkowe, w tym metody wykorzystujące optyczne przekształcenie Fouriera. Sa to metody oparte na pomiarze kątowego rozkładu natężenia światła rozproszonego. Pozwalają one oceniać gęstość widmową mocy nierówności powierzchni, a także określać anizotropię i kierunkowość struktury geometrycznej badanej powierzchni. Pokazano przykładowe wyniki uzyskane za pomocą niektórych metod różniczkowych. W części końcowej artykułu zamieszczono tabelę zawierającą zestawienie podstawowych właściwości charakteryzujących metody rozpraszania światła.

9

Infrared Sensor to Predict Atmospheric Visibility and Rainfall Rate

80%

Holejko K. , Czarnecki T. , Perlicki K.

International Journal of Electronics and Telecommunications

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2013

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tom Vol. 59, No. 2

109-112

EN

The presented paper describes an instrument called Aurometer which was designed for both atmospheric visibility and rainfall rate measurement. The principle of operation of Aurometer is based on determining the amount of light scatteredby particles in the air that passes through the sample volume. The achieved results show that simultaneous estimation of the atmospheric visibility.

10

Variability in the optical properties of a crude oil - seawater emulsion

80%

Król T. , Stelmaszewski A. , Freda W.

Oceanologia

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2006

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tom No. 48 (S)

203-211

EN

The paper analyses the optical properties of a crude oil - seawater emulsion, which is a form of petroleum pollution of the sea. These properties depend on the spillage concentration, the optical characteristics of the seawater and oil in question, and on the size distribution of the oil droplets. They may be described by the attenuation specific cross-sections and absorption specific cross-sections. Specific cross-sections and other optical parameters for droplets of a Baltic crude oil - Baltic seawater emulsion were calculated using Mie's solution. These characteristics were computed for fresh and weathered petroleum.

11

Optical properties of deposit of red blood cells suspended in dextran solutions

80%

Strzelecka J. , Bosek M. , Grzegorzewski B.

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tom Vol. 40, nr 1

177--185

EN

The optical properties of the deposit of red blood cells (RBCs) formed during sedimentation have been investigated. The human blood was obtained from healthy donors. RBCs were suspended in isotonic saline containing Dextran 70 of concentrations 2, 4 and 6 g/dl. Hematocrit of the samples was adjusted to 40%. The intensity of the light scattered by the samples of the RBC suspensions as a function of time and altitude from the bottom of a sample was measured. The region occupied by forming and sedimenting aggregates and the region occupied by deposit of the cells can be found in the sample and the temporal dependence of position of the interface separating both regions, called the deposit formation curve, can be determined. This curve exhibits the growth phase and the packing phase. We have obtained the mean intensity of light scattered by the deposit as a function of time. This intensity exhibits a monotonous decay with time over the growth as well as the packing phase, what shows that packing of the deposit occurs in the same way in both phases. The dependence from time of the mean hematocrit of the deposit was determined. We have introduced an empirical expression describing this dependence. Finally, using this dependence, we have obtained the mean intensity of light scattered by the deposit as a function of hematocrit. We have shown that this intensity follows an exponential decay. The values of an optical parameter of the deposit were found from this dependence.

12

Measurement and statistical modeling of BRDF of various samples

80%

Zhang H. , Wu Z. , Cao Y. , Zhang G.

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tom Vol. 40, nr 1

197--208

EN

Based on the Torrance-Sparrow model, a modified and simplified five-parameter model is obtained. Multi-angle bistatic reflectance data of surfaces of various materials are fitted using this model. Genetic algorithm is used to optimize the parameters for the model. The results of the five-parameter model are in good agreement with experimental data which do not take part in fitting, and are close to the results of two-dimensional bidirectional reflectance distribution function (BRDF) models. The five-parameter model shows a good applicability to various rough surfaces with different surface optical properties. The five-parameter model can be used to construct a three-dimensional BRDF distribution based on the spatial experimental data, which may provide more information on light scattering from rough surfaces.

13

Range dependent radiation leakage from thin scattering columns due to multiple small angle scatter

80%

Kravtsov Y. A. , Apresyan L. A. , Asatryan A. A. , Chrzanowski J. , Kirkiewicz J.

Optica Applicata

|

2003

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tom Vol. 33, nr 2-3

293-305

EN

The phenomenon of range dependent radiation leakage from thin random columns caused by small angle multiple scatter is analysed. On the basis of modified Born approximation (Ishimaru, 1978; Apresyan and Kravtsov, 1996), it is shown that extinction coefficient, describing energy leakage due to multiple scatter on large (as compared to wavelength) inhomogeneities, first increases proportionally to distance z1/2 and then saturates on the level which might significantly exceed conventional extinction coefficient, connected with large angle light scatter on small inhomogeneities. The effect might be observed in many physical systems, for example, in a tube filled with water emulsion or suspension, containing small and large particles. The phenomenon may be helpful in distinguishing the contribution of small and large inhomogeneities to total extinction

14

Inverse problem in scatterometry of rough surfaces

80%

Łukianowicz C.

Optica Applicata

|

2003

|

tom Vol. 33, nr 2-3

315-327

EN

The aim of the paper is to examine one of variant inverse problems constituting the basis for surface roughness measurements by light scattering methods. This problem consists in determining the scatterer form based on measured distribution of scattered light intensity. A solution of the inverse problem amounts to determination of the optical signal from a measured squared modulus of the Fourier transform of this signal. The paper presents methods for solving the inverse problem. For that purpose, the initial modification of the light wave on the surface measured was carried out so that the complex light amplitude was described by accordingly attenuated Hermitian function. The method presented can be used for analysis of other, similar problems

15

Light scattering in Baltic crude oil - seawater emulsion

80%

Stelmaszewski A. , Król T. , Toczek H.

Oceanologia

|

2009

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tom No. 51 (3)

405-414

EN

The paper discusses the scattering of radiation by a Baltic crude oil - seawater emulsion. The scattering spectrum calculated using the Mie solution in the spectral range from 380 nm to 730 nm is compared with the measured spectrum of light scattered through a right angle. Spectra in the wavelength range from 210 nm to 730 nm were measured using a spectrofluorimeter for fresh and stored samples of the Baltic crude oil emulsion. Scattering increases with wavelength in the UV range and then decreases slightly with the wavelength of visible light. The result of the calculation is similar to the measured spectra. Both the calculated and measured spectra display numerous relative extremes throughout the spectral area. Light scattering in the emulsion decreases during storage as the oil concentration in the medium diminishes. The results also demonstrate that the single scattering model describes the phenomenon correctly.

16

Spectral analysis of dynamic laser speckle patterns by using a full-field temporal modulation method

80%

Dake W. , Chasteen E. , Onyeuku C.

Optica Applicata

|

2013

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tom Vol. 43, nr 4

871--882

EN

We introduce an approach for analyzing the power spectrum of the time-varying intensity in the dynamic laser speckle patterns. The method is free from the limitation imposed by the Nyquist criterion on the minimum sampling rate. The temporal modulation shifts the intensity fluctuation spectrum by an amount that is equal to the modulation frequency. The subsequent integration of the intensity signal, performed at each detector pixel, acts effectively as a low-pass filter allowing the extraction of the spectral component at the modulation frequency. Within the speed range from 1 to 10 mm/s investigated in our experiment, the result demonstrates that the moving speed of the diffuse object can be determined with a good accuracy.

17

Lyapunov exponent of the optical radiation scattered by the Brownian particles

80%

Gavrylyak M. S. , Maksimyak O. P. , Maksimyak P. P.

Optica Applicata

|

2008

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tom Vol. 38, nr 3

539-548

EN

The computer and physical simulation of light scattering by the system of Brownian particles has been carried out. Temporary fluctuations of field intensity have been found to save chaotic properties of driving particles. Empirical diagnostic links have been retrieved of the largest Lyapunov exponent of fluctuations of field intensity with parameters of the dispersive media.

18

A device for light scatterometry on single levitated droplets

70%

Jakubczyk D. , Zientara M. , Bazhan W. , Kolwas M. , Kolwas K.

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tom Vol. 9, No. 4

423-430

EN

A compact device for measurements of levitated particles in humid atmosphere up tp 100% relative humidity and in temperature range from -30 to 60 C was built. The preliminary experiments were done using ethanediol and water microdroplets. Light scattered by the trapped particles on two perpendicular polarisations was recorder. On the basis of Mie theory information on the radius and refractive index of the droplets was extracted with FFT and T-matrix method combined with fitting procedure.

19

Insight into the kinetics and the mode of the interaction between smooth muscle calponin and F-actin.

70%

Kołakowski J. , Dąbrowska R.

Acta Biochimica Polonica

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2002

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tom 49

|

nr 2

471-479

EN

Kinetics of the smooth muscle calponin-F-actin interaction was studied by stopped- flow measurements of light scattering and fluorescence intensity of pyrene-labelled F-actin. The intensity and character of the changes in light scattering, and thus the mode of calponin binding to actin filaments leading to changes in their shape and bundling, depend on the molar ratio of the two proteins. Parallel measurements of pyrene-fluorescence quenching upon calponin binding revealed that intrinsic conformational changes in actin filaments are delayed relative to the binding process and are not markedly influenced by the mode of calponin binding. Bundling of actin filaments by calponin was not correlated with fluorescence changes and thus with alterations in the structure of actin filaments.

20

Calculation methods of interaction of electromagnetic waves with objects of complex geometries

70%

Shopa M.

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tom Vol. 20, No 2

231--240

EN

Modeling of the electromagnetic interaction with different homogeneous or inhomogeneous objects is a fundamental and important problem. It is relatively easy to solve Maxwell equations analytically when the scattering object is spherical or cylindrical, for example. However, when it loses these properties all that is left for us is to use approximation models, to acquire the solution we need. Modeling of complex, non-spherical, asymmetric particles is used to study cosmic, cometary dust, aerosols, atmospheric pollution etc. Few analytical, surface-based and volume-based methods of light scattering modeling, most commonly used by scientists, are reviewed here.