Journal articles on the topic 'CRIM (Complex Refractive Index Model)'
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1
Zadhoush, Hossain, Antonios Giannopoulos, and Iraklis Giannakis. "Optimising the Complex Refractive Index Model for Estimating the Permittivity of Heterogeneous Concrete Models." Remote Sensing 13, no. 4 (February 16, 2021): 723. http://dx.doi.org/10.3390/rs13040723.
Abstract:
Estimating the permittivity of heterogeneous mixtures based on the permittivity of their components is of high importance with many applications in ground penetrating radar (GPR) and in electrodynamics-based sensing in general. Complex Refractive Index Model (CRIM) is the most mainstream approach for estimating the bulk permittivity of heterogeneous materials and has been widely applied for GPR applications. The popularity of CRIM is primarily based on its simplicity while its accuracy has never been rigorously tested. In the current study, an optimised shape factor is derived that is fine-tuned for modelling the dielectric properties of concrete. The bulk permittivity of concrete is expressed with respect to its components i.e., aggregate particles, cement particles, air-voids and volumetric water fraction. Different combinations of the above materials are accurately modelled using the Finite-Difference Time-Domain (FDTD) method. The numerically estimated bulk permittivity is then used to fine-tune the shape factor of the CRIM model. Then, using laboratory measurements it is shown that the revised CRIM model over-performs the default shape factor and provides with more accurate estimations of the bulk permittivity of concrete.
2
Hu, Jun, Xinbin Wang, Fujun Zhang, and Yuanke Zhao. "Experimental Study on the Variation of Soil Dielectric Permittivity under the Influence of Soil Compaction and Water Content." Geofluids 2022 (November 18, 2022): 1–9. http://dx.doi.org/10.1155/2022/3575541.
Abstract:
The dielectric permittivity of common soils is mainly controlled by water content and porosity, while the latter is closely related to the characteristics of compaction. By studying the changes in dielectric permittivity of soil samples with different soil water content and compaction levels, the influence of the controlling factors on the relationship model between soil water content and dielectric permittivity can be evaluated. In this paper, network analyzer was used to measure the dielectric permittivity of 7 groups of soil samples with gravimetric water content ranging from 8.09% to 14.52% and dry density ranging from 1.61 g/cm3 to 1.96 g/cm3. The results show that the dielectric permittivity increases with the increase of water content and dry density, and the effect of water content on permittivity is more significant for soils with higher dry density. Furthermore, when the water content is less than or equal to the optimal water content, Topp formula and the complex refractive index model (CRIM) can better predict the soil dry density. When the water content approaches the saturated state of soil, there is a deviation between the predicted value and the actual value. At last, the modified Topp formula and the complex refractive index model (CRIM) can accurately predict soil compactness. This provides an important basis for rapid detection of water content and compactness of highway subgrade soil by ground penetrating radar.
3
Zhong, Yanhui, Yanlong Gao, Bei Zhang, Songtao Li, Hongchuan Cui, Xiaolong Li, and Han Zhao. "Experimental Study on the Dielectric Model of Common Asphalt Pavement Surface Materials Based on the L-R Model." Advances in Civil Engineering 2021 (May 26, 2021): 1–8. http://dx.doi.org/10.1155/2021/6667101.
Abstract:
The establishment of a dielectric model of the asphalt pavement surface material is the premise and key to applying the electromagnetic wave technology to asphalt pavement nondestructive testing. Asphalt pavement can be made of different materials, including various types of asphalt mixtures. Therefore, in order to study and analyze the dielectric properties of different types of asphalt mixtures and establish a dielectric model of the asphalt pavement surface material, this paper studies four types of asphalt mixtures commonly used in the asphalt pavement surface course. Based on the comparative analysis of three classical models, the complex refractive index method (CRIM), Brown, and Looyenga; based on the L-R model, the linear regression analysis was conducted on the test data. The dielectric models which are suitable for the interpretation of four types of asphalt mixtures were established, and the dielectric model database of asphalt pavement surface materials was extended, which provides theoretical and technical support for nondestructive testing of the asphalt pavement.
4
Du, Erji, Lin Zhao, Defu Zou, Ren Li, Zhiwei Wang, Xiaodong Wu, Guojie Hu, Yonghua Zhao, Guangyue Liu, and Zhe Sun. "Soil Moisture Calibration Equations for Active Layer GPR Detection—a Case Study Specially for the Qinghai–Tibet Plateau Permafrost Regions." Remote Sensing 12, no. 4 (February 11, 2020): 605. http://dx.doi.org/10.3390/rs12040605.
Abstract:
Ground-penetrating radar (GPR) is a convenient geophysical technique for active-layer soil moisture detection in permafrost regions, which is theoretically based on the petrophysical relationship between soil moisture (θ) and the soil dielectric constant (ε). The θ–ε relationship varies with soil type and thus must be calibrated for a specific region or soil type. At present, there is lack of such a relationship for active-layer soil moisture estimation for the Qinghai–Tibet plateau permafrost regions. In this paper, we utilize the Complex Refractive Index Model to establish such a calibration equation that is suitable for active-layer soil moisture estimation with GPR velocity. Based on the relationship between liquid water, temperature, and salinity, the soil water dielectric constant was determined, which varied from 84 to 88, with an average value of 86 within the active layer for our research regions. Based on the calculated soil-water dielectric constant variation range, and the exponent value range within the Complex Refractive Index Model, the exponent value was determined as 0.26 with our field-investigated active-layer soil moisture and dielectric data set. By neglecting the influence of the soil matrix dielectric constant and soil porosity variations on soil moisture estimation at the regional scale, a simple active-layer soil moisture calibration curve, named CRIM, which is suitable for the Qinghai–Tibet plateau permafrost regions, was established. The main shortage of the CRIM calibration equation is that its calculated soil-moisture error will gradually increase with a decreasing GPR velocity and an increasing GPR velocity interpretation error. To avoid this shortage, a direct linear fitting calibration equation, named as υ-fitting, was acquired based on the statistical relationship between the active-layer soil moisture and GPR velocity with our field-investigated data set. When the GPR velocity interpretation error is within ±0.004 m/ns, the maximum moisture error calculated by CRIM is within 0.08 m3/m3. While when the GPR velocity interpretation error is larger than ±0.004 m/ns, a piecewise formula calculation method, combined with the υ-fitting equation when the GPR velocity is lower than 0.07 m/ns and the CRIM equation when the GPR velocity is larger than 0.07 m/ns, was recommended for the active-layer moisture estimation with GPR detection in the Qinghai–Tibet plateau permafrost regions.
5
Berg, Charles R. "A simple, effective‐medium model for water saturation in porous rocks." GEOPHYSICS 60, no. 4 (July 1995): 1070–80. http://dx.doi.org/10.1190/1.1443835.
Abstract:
A general equation for water saturation is derived from effective‐medium theory. A simpler low‐frequency equation is also derived. Both equations are directly solvable for water saturation. The model should be applicable to any granular, water‐wet formation. Additional relationships are derived specifically for application to shaly sandstones, but the model should be applicable to a wide range of rock types, water conductivities, and tool frequencies. In the derivation, hydrocarbons are included in the matrix component of the equation and the combined “matrix” elements are treated as resistors in parallel. The low‐frequency equation is compared to various approaches to calculation of water saturation, such as Dual‐Water, Waxman‐Smits, and Bussian. The general equation is compared to three‐component effective medium, porosity index, and complex refractive index models (CRIM). The model is proven to work on experimental data under a wide range of frequencies and water conductivities. It is recommended that the new saturation model be used for nearly all types of electrical saturation calculation, whether the measurements are from standard resistivity tools or from dielectric tools.
6
Liu, Zonghui, Yinghao Lan, Xiaolei Zhang, Fanzheng Zeng, and Chuanghui Li. "A rapid detection method for diesel content in diesel-contaminated soil based on dielectric measurement and oven-drying tests." IOP Conference Series: Earth and Environmental Science 1335, no. 1 (May 1, 2024): 012036. http://dx.doi.org/10.1088/1755-1315/1335/1/012036.
Abstract:
Abstract Geophysical testing techniques have been successfully applied to identify light non-aqueous phase liquids in soils, but challenges remain in rapidly detecting contaminant content. Detection of contaminants in soil using geophysical testing techniques relies on sensors sensitive to electrical and electromagnetic parameter changes. In this study, the complex permittivity of silty clay contaminated with 0# diesel was measured using an open-ended coaxial probe at frequencies from 200–3000 MHz, and the four-phase dielectric mixing models were evaluated. The measurement results showed that the complex refractive index method (CRIM) model provided a better match with the real permittivity of the four-phase system between 500–3000 MHz with relative errors within an acceptable range of 4%. To eliminate the unknown variable in the CRIM model, an improved equation for the relationship between water content and diesel content of the watery diesel-contaminated silty clay was established by the oven-drying method. Thus, a method for the rapid quantitative detection of the diesel content in contaminated soil has been developed based on dielectric measurement and oven-drying tests. The relative error between the calculated and actual set diesel content for ten manually configured diesel-contaminated soil samples was within 10%, with a maximum error of 15.75%.
7
Bumberger, Jan, Juliane Mai, Felix Schmidt, Peter Lünenschloß, Norman Wagner, and Hannes Töpfer. "Spatial Retrieval of Broadband Dielectric Spectra." Sensors 18, no. 9 (August 23, 2018): 2780. http://dx.doi.org/10.3390/s18092780.
Abstract:
A broadband soil dielectric spectra retrieval approach ( 1 MHz– 2 GHz) has been implemented for a layered half space. The inversion kernel consists of a two-port transmission line forward model in the frequency domain and a constitutive material equation based on a power law soil mixture rule (Complex Refractive Index Model - CRIM). The spatially-distributed retrieval of broadband dielectric spectra was achieved with a global optimization approach based on a Shuffled Complex Evolution (SCE) algorithm using the full set of the scattering parameters. For each layer, the broadband dielectric spectra were retrieved with the corresponding parameters thickness, porosity, water saturation and electrical conductivity of the aqueous pore solution. For the validation of the approach, a coaxial transmission line cell measured with a network analyzer was used. The possibilities and limitations of the inverse parameter estimation were numerically analyzed in four scenarios. Expected and retrieved layer thicknesses, soil properties and broadband dielectric spectra in each scenario were in reasonable agreement. Hence, the model is suitable for an estimation of in-homogeneous material parameter distributions. Moreover, the proposed frequency domain approach allows an automatic adaptation of layer number and thickness or regular grids in time and/or space.
8
Abdorahimi, Danial, and Ali M. Sadeghioon. "Comparison of Radio Frequency Path Loss Models in Soil for Wireless Underground Sensor Networks." Journal of Sensor and Actuator Networks 8, no. 2 (June 22, 2019): 35. http://dx.doi.org/10.3390/jsan8020035.
Abstract:
A wireless Underground Sensor Network (WUSN) is a group of sensors that collectively communicate through the underground medium. Radio Frequency (RF) signal transmission of the sensors through the ground is the most challenging aspects of a WUSN due to the high attenuation of the electromagnetic (EM) signal in the soil. Signals are often required to travel through soils with a high density or water content and generally through a non-isotropic and non-homogenous soil mixture with different boundaries, both of which can attenuate the signal sharply. The variability of the these conditions and complexity of the behaviour of signal attenuation with respect to these parameters makes accurate estimation of EM signal attenuation in soil challenging. Two main EM signal attenuation models exist to estimate attenuation (modified-Friis and Complex Refractive Index Model-Fresnel (CRIM-Fresnel). These were reviewed and a methodology was developed in order to measure the attenuation of the EM signals in the laboratory. Results from the laboratory measurements were compared with the estimation values calculated from the attenuation models. These comparisons showed a large difference between the estimated values by the models. In addition, analysis of the comparison tests showed that the CRIM-Fresnel model provides a better estimation of attenuation in samples with lower permittivity values while the modified-Friis model had a higher accuracy in samples with higher clay/water content which have higher permittivity values.
9
Chen, Huangye, and Zoya Heidari. "Pore-Scale Joint Evaluation of Dielectric Permittivity and Electrical Resistivity for Assessment of Hydrocarbon Saturation Using Numerical Simulations." SPE Journal 21, no. 06 (May 19, 2016): 1930–42. http://dx.doi.org/10.2118/170973-pa.
Abstract:
Summary Complex pore geometry and composition, as well as anisotropic behavior and heterogeneity, can affect physical properties of rocks such as electrical resistivity and dielectric permittivity. The aforementioned physical properties are used to estimate in-situ petrophysical properties of the formation such as hydrocarbon saturation. In the application of conventional methods for interpretation of electrical-resistivity (e.g., Archie's equation and the dual-water model) and dielectric-permittivity measurements [e.g., complex refractive index model (CRIM)], the impacts of complex pore structure (e.g., kerogen porosity and intergranular pores), pyrite, and conductive mature kerogen have not been taken into account. These limitations cause significant uncertainty in estimates of water saturation. In this paper, we introduce a new method that combines interpretation of dielectric-permittivity and electrical-resistivity measurements to improve assessment of hydrocarbon saturation. The combined interpretation of dielectric-permittivity and electrical-resistivity measurements enables assimilating spatial distribution of rock components (e.g., pore, kerogen, and pyrite networks) in conventional models. We start with pore-scale numerical simulations of electrical resistivity and dielectric permittivity of fluid-bearing porous media to investigate the structure of pore and matrix constituents in these measurements. The inputs to these simulators are 3D pore-scale images. We then introduce an analytical model that combines resistivity and permittivity measurements to assess water-filled porosity and hydrocarbon saturation. We apply the new method to actual digital sandstones and synthetic digital organic-rich mudrock samples. The relative errors (compared with actual values estimated from image processing) in the estimate of water-filled porosity through our new method are all within the 10% range. In the case of digital sandstone samples, CRIM provided reasonable estimates of water-filled porosity, with only four out of twenty-one estimates beyond 10% relative error, with the maximum error of 30%. However, in the case of synthetic digital organic-rich mudrocks, six out of ten estimates for water-filled porosity were beyond 10% with CRIM, with the maximum error of 40%. Therefore, the improvement was more significant in the case of organic-rich mudrocks with complex pore structure. In the case of synthetic digital organic-rich mudrock samples, our simulation results confirm that not only the pore structure but also spatial distribution and tortuosity of water, kerogen, and pyrite networks affect the measurements of dielectric permittivity and electrical resistivity. Taking into account these parameters through the joint interpretation of dielectric-permittivity and electrical-resistivity measurements significantly improves assessment of hydrocarbon saturation.
10
Manning, Michael J., and Kumud A. Athavale. "Dielectric properties of pyrite samples at 1 100 MHz." GEOPHYSICS 51, no. 1 (January 1986): 172–82. http://dx.doi.org/10.1190/1.1442030.
Abstract:
Pyrite occurs in many petroleum reservoirs and significantly affects density and electric well logs even in low concentrations. Ultrahigh‐frequency dielectric measurements also are significantly affected by pyrite. Dielectric properties of core samples containing approximately 50 percent pyrite by volume were measured from 800 to 1 200 MHz ([Formula: see text]). These measurements demonstrate the high, complex dielectric permittivity of pyrite and provide data for calculation of pyrite permittivity at ultrahigh frequencies. The measured complex‐permittivity of water‐saturated pyrite nodules is approximately [Formula: see text] at 1 100 MHz and 25 °C. The measured permittivity of pyrite nodules depends upon the concentration of pyrite and only slightly on saturating‐water salinity. Two geometric mixing models, the complex refractive‐index method (CRIM) and a modified Hanai‐Bruggeman‐Sen (HBS) model, are used to analyze the data. CRIM analysis of water‐saturated and oil‐saturated core data gives inconsistent results because the porosity is poorly connected. HBS, with a variable dielectric exponent, provides more consistent results. [Formula: see text] is the complex permittivity of pyrite at 1 100 MHz and 25 °C determined by applying HBS to laboratory measurements. CRIM‐determined pyrite permittivity is about 50 percent greater in both real and imaginary parts. This high [Formula: see text] has important implications for high‐frequency dielectric well‐logging tools. Signal amplitudes are highly attenuated in formations with large concentrations of pyrite. Where pyrite nodules occur, wave scattering may cause inconsistent data indicative of formation heterogeneity. Low concentration, disseminated pyrite increases the rock “matrix” permittivity. Mineralogical variations, particularly in trace quantities of heavy minerals, are a likely explanation for significant variations in measured matrix permittivities for sandstones. Comparison of pyrite permittivity with available values for the permittivity of rutile, another heavy mineral found in sedimentary rocks, suggests employing pyrite and rutile in artificial sandpack experiments. The real parts of pyrite and rutile permittivities are nearly equal, but the imaginary part of the permittivity of rutile is lower than pyrite by about [Formula: see text]. Experiments with both minerals could test mixing models and the effects of distribution in mixtures of conductive minerals.
11
Wang, Zhi-Hang, Jin-Yu Xu, Er-Lei Bai, and Liang-Xue Nie. "Dielectric Model of Carbon Nanofiber Reinforced Concrete." Materials 13, no. 21 (October 30, 2020): 4869. http://dx.doi.org/10.3390/ma13214869.
Abstract:
The formula describing the relationship between the dielectric constant of a composite and the dielectric constants or volume rates of its components is called a dielectric model. The establishment of a cement concrete dielectric model is the basic and key technique for applying electromagnetic wave technology to concrete structure quality testing and internal damage detection. To construct the dielectric model of carbon nanofiber reinforced concrete, the carbon nanofiber reinforced concrete was measured by the transmission and reflection method for dielectric constant ε, and ε,, in the frequency range of 1.7~2.6 GHz as the fiber content was 0, 0.1%, 0.2%, 0.3% and 0.5%. Meanwhile, concrete was considered as a composite material composed of three phases, matrix (mortar), coarse aggregate (limestone gravel) and air, and the dielectric constants and volume rates of each component phase were tested. The Brown model, CRIM (Complex Refractive Index Model) model and Looyenga model commonly used in composite materials were modified based on the experimental data, suitable dielectric models of carbon nanofiber reinforced concrete were constructed, and a reliability check and error analysis of the modified models were carried out. The results showed that the goodness of fit between the calculated curves based on the three modified models and the measured curves was very high, the accuracy and applicability were very strong and the variation rule for the dielectric constant of carbon nanofiber concrete with the frequency of electromagnetic wave could be described accurately. For ε, and ε,,, the error between the dielectric constant calculated by the three modified models and the corresponding measured values was very small. For the dielectric constant ε,, the average error was maintained below 1.2%, and the minimum error was only 0.35%; for the dielectric constant ε,,, the average error was maintained below 3.55%.
12
Gkortsas, Vasileios-Marios, Lalitha Venkataramanan, Kamilla Fellah, David Ramsdell, Chang-Yu Hou, and Nikita Seleznev. "Comparison of different dielectric models to calculate water saturation and estimate textural parameters in partially saturated cores." GEOPHYSICS 83, no. 5 (September 1, 2018): E303—E318. http://dx.doi.org/10.1190/geo2018-0100.1.
Abstract:
Accurate estimation of water saturation is central in predicting capillary pressure and relative permeability, under special core analysis in the laboratory. We have explored the use of dielectric measurements at different frequencies to estimate water saturation. In addition to water saturation, dielectric measurements are sensitive to the distribution of water and oil in a porous system, reflected by the apparent cementation factor [Formula: see text], which describes the water phase tortuosity. We have performed an experimental study to benchmark water saturation from dielectric measurements on eight carbonate cores and estimated their cementation exponent [Formula: see text] and saturation exponent [Formula: see text] in Archie’s equation from dielectric data. All cores went through a series of drainage/imbibition steps, creating varying saturations of brine/fluorocarbon. Fluorocarbon was chosen because it is invisible to proton nuclear magnetic resonance (NMR). Therefore,NMR porosity represents only the water-filled porosity and can be used to benchmark dielectric water-filled porosity. Three dielectric models were used for the comparison of the dielectric water-filled porosity with the one from NMR, i.e., the complex refractive index model (CRIM), bimodal model, and Stroud-Milton-De (SMD) model, and very good agreement of 1.5 porosity units on average is found. Despite its simplicity, CRIM predicted well the water-filled porosity in this experiment. However, it cannot provide information about the texture, which is captured by bimodal and SMD models. We also estimated [Formula: see text] and [Formula: see text] based on [Formula: see text] found from bimodal and SMD models, and good agreement with [Formula: see text] from resistivity data was shown. This is the first time to our knowledge that such a rich set of dielectric and NMR measurements was acquired at different saturation stages in a surface laboratory. This study is useful in benchmarking the water saturation from dielectrics, comparing different dielectric models, and demonstrating feasibility of estimating textural parameters.
13
Iravani, Mohammad Ali, Jacques Deparis, Hossein Davarzani, Stéfan Colombano, Roger Guérin, and Alexis Maineult. "Complex Electrical Resistivity and Dielectric Permittivity Responses to Dense Non-aqueous Phase Liquids' Imbibition and Drainage in Porous Media: A Laboratory Study." Journal of Environmental and Engineering Geophysics 25, no. 4 (December 2020): 557–67. http://dx.doi.org/10.32389/jeeg20-050.
Abstract:
The effective techniques for remediation of sites polluted by dense non-aqueous phase liquids (DNAPLs) remains a challenge. Among the various technical monitoring methods, there is an increasing interest in studying the geophysical characteristics of contaminated soils, as indicators of the progress in clean-up programs. This work sought to investigate the variation of the electrical complex resistivity and the relative permittivity by analyzing the results obtained from spectral induced polarization (SIP) and time domain reflectometry (TDR). Different series of measurements during drainage and imbibition of DNAPLs in porous media were done to validate the clean-up process on sites polluted by DNAPLs. Therefore, a methodology based on laboratory work was designed and carried out to study the electrical complex resistivity (both in magnitude and phase) in the frequency range 0.183 Hz to 20 kHz, and the relative dielectric permittivity at 70 MHz. The experiments were done on small 1D cells. In these cells, glass beads were used as a porous medium. Two different fluid couples, i.e., coal tar (CT)/water and canola oil (CO)/salty ethanol (SE), were used to produce two-phase flow. Our findings highlight that due to the high resistivity of CO and CT, an increase in water saturation led to decrease in amplitude and phase. Saturation change of SE had the same effect on resistivity but no relationship was found for phase and saturation for the mixture CO and SE. It is also showed that the complex resistivity and relative permittivity measurements were compatible with generalized Archie's law and complete complex refractive index method (CRIM) model as two empirical models for defining the correlation between the electrical resistivity, relative permittivity, and saturation of each phase in the multiphase porous medium.
14
Lai, W. L., W. F. Tsang, H. Fang, and D. Xiao. "Experimental determination of bulk dielectric properties and porosity of porous asphalt and soils using GPR and a cyclic moisture variation technique." GEOPHYSICS 71, no. 4 (July 2006): K93—K102. http://dx.doi.org/10.1190/1.2217730.
Abstract:
This paper describes a new method for determining porosities in two porous construction and geologic materials (asphalt and soil) by using ground-penetrating radar (GPR) over a wide range of controlled degrees of water saturation [Formula: see text]. We call this method a cyclic moisture variation technique (CMVT). Freshwater is used as an enhancer or a tracer to allow GPR to easily detect and differentiate amounts of water or other moisture in these materials. The CMVT is based on measuring the changes of real permittivity [Formula: see text] and [Formula: see text] in the test materials as they transition from partially saturated states to a fully saturated state via cycles of water permeation and dewatering. This method does not disturb the test materials, as do the methods associated with traditional laboratory testing on cored samples. It also tests a large mass of in situ material, compared with the small mass tested by the conventional or electromagnetic coaxial transmission line (EMCTL) method (also known as a dielectric cell) and the time-domain reflectometry (TDR) method. Porosity values of asphalt [Formula: see text] and of soils [Formula: see text] were determined by fitting the data into the complex refractive index model (CRIM). Dielectric hysteresis of both soils and asphalt also is observable during the tests and shows that the pathways of water-ingress and water-egress processes are not identical in the plot of [Formula: see text] versus degrees of water saturation [Formula: see text].
15
Jaumann, Stefan, and Kurt Roth. "Soil hydraulic material properties and layered architecture from time-lapse GPR." Hydrology and Earth System Sciences 22, no. 4 (April 25, 2018): 2551–73. http://dx.doi.org/10.5194/hess-22-2551-2018.
Abstract:
Abstract. Quantitative knowledge of the subsurface material distribution and its effective soil hydraulic material properties is essential to predict soil water movement. Ground-penetrating radar (GPR) is a noninvasive and nondestructive geophysical measurement method that is suitable to monitor hydraulic processes. Previous studies showed that the GPR signal from a fluctuating groundwater table is sensitive to the soil water characteristic and the hydraulic conductivity function. In this work, we show that the GPR signal originating from both the subsurface architecture and the fluctuating groundwater table is suitable to estimate the position of layers within the subsurface architecture together with the associated effective soil hydraulic material properties with inversion methods. To that end, we parameterize the subsurface architecture, solve the Richards equation, convert the resulting water content to relative permittivity with the complex refractive index model (CRIM), and solve Maxwell's equations numerically. In order to analyze the GPR signal, we implemented a new heuristic algorithm that detects relevant signals in the radargram (events) and extracts the corresponding signal travel time and amplitude. This algorithm is applied to simulated as well as measured radargrams and the detected events are associated automatically. Using events instead of the full wave regularizes the inversion focussing on the relevant measurement signal. For optimization, we use a global–local approach with preconditioning. Starting from an ensemble of initial parameter sets drawn with a Latin hypercube algorithm, we sequentially couple a simulated annealing algorithm with a Levenberg–Marquardt algorithm. The method is applied to synthetic as well as measured data from the ASSESS test site. We show that the method yields reasonable estimates for the position of the layers as well as for the soil hydraulic material properties by comparing the results to references derived from ground truth data as well as from time domain reflectometry (TDR).
16
Velasco Davoise, Lara, Rafael Peña Capilla, and Ana M. Díez-Pascual. "Isotropic and Anisotropic Complex Refractive Index of PEDOT:PSS." Polymers 15, no. 15 (August 4, 2023): 3298. http://dx.doi.org/10.3390/polym15153298.
Abstract:
In this work, the complex refractive indexes of seven PEDOT:PSS samples, three with isotropic behavior and four with optical anisotropy, were determined. For the anisotropic samples, the ordinary and extraordinary components of the refractive index were described. The effect of the film thickness, measurement technique and preparation method on the extinction coefficient (k) and refractive index (n) of each sample was also discussed. Important differences (up to 20% in the average n) were found among the samples investigated. In most anisotropic films, the mean value of the extraordinary component was between 7 and 10% higher than that of the ordinary. In the three isotropic films, the average k rose when the film thickness increased. Moreover, the different sets of refractive index data were fitted to three different models: the original Forouhi–Bloomer model, the Liu (2007) model and the revised version of the Forouhi–Bloomer model (2019). In general, Liu’s model gave better results, with small errors in n and k (<7.81 and 4.68%, respectively, in all the cases). However, this model had seven fitting parameters, which led to significantly longer computation time than the other two models. The influence of the differences in the measurement of the complex refractive index on the simulation of the optical properties of PEDOT:PSS multilayers was discussed. The results showed that n must be known precisely to accurately calculate the light absorption in a multilayer, without ignoring the isotropic or anisotropic behavior of the material or the influence of the layer thickness on its optical properties. This study aids in the development of simulation and optimization tools that allow understanding the optical properties of PEDOT:PSS films for their potential applications in organic optoelectronic devices, such as organic solar cells.
17
Chen, Hui, Céline Montanari, Max Yan, Sergei Popov, Yuanyuan Li, Ilya Sychugov, and Lars A. Berglund. "Refractive index of delignified wood for transparent biocomposites." RSC Advances 10, no. 67 (2020): 40719–24. http://dx.doi.org/10.1039/d0ra07409h.
18
Brissinger, Damien. "Modeling the Impact of Dye Concentration on Polymer Optical Properties via the Complex Refractive Index: A Pathway to Optical Engineering." Polymers 16, no. 5 (February 29, 2024): 660. http://dx.doi.org/10.3390/polym16050660.
Abstract:
This work investigates the potential to rely on the complex refractive index to correlate the chemical composition of polymers with their optical properties, including transmittance, reflectance and absorbance. The optical properties of polycarbonate slabs with various controlled concentrations of two dyes were initially measured and analyzed. The reflection and transmission measurements obtained were used to determine the corresponding complex refractive index over a wide range of wavelengths. Comparing it with that of a clear material provided the spectral deviation of the complex refractive index induced by the dye concentrations and resulted in assigning a spectral efficiency to both of them. A modification function of the complex refractive index was established based on this spectral efficiency, which acts as a spectral fingerprint related to each dye. Finally, two samples doped with the two dyes mixed were studied to assess the model’s capabilities. On the one hand, based on the measured transmittance, the dye concentrations were determined within a deviation below 8% in comparison with the values provided by the manufacturer. On the other hand, when the dye concentrations were known, the model reproduced the optical properties with good accuracy beyond the limitations of the experimental setup. The model’s effectiveness in correlating the chemical composition of polymer with its optical properties through the complex refractive index makes it a valuable asset in analyzing and formulating plastics with intended optical properties.
19
Zhang, Ji Yan, Wen Li Liu, Lei Yang, and Ming Liang Gao. "Analysis on Refractive Property of Complex Optometry System." Applied Mechanics and Materials 668-669 (October 2014): 1565–68. http://dx.doi.org/10.4028/www.scientific.net/amm.668-669.1565.
Abstract:
In optometry, simplified models are usually used to analyze refractive property of optometry system on the assumption that lenses are thin and close enough to each other. However, in fact those lenses do have stated center thickness and lens space between them. The simplified models are not suitable for accurate analysis and system design. In this paper, first, accurate mathematic model for refractive property of single spherical and cylindrical lens is established. Next, accurate model is established for complex optometry system with different kinds of lenses combination. Then, influence factors such as lens structural parameter, lens space and lens position are analyzed for refractive property. Results show that correct lens position is very important for complex optometry system. Parallel light should pass lower power lens first and then higher power lens. When lens power and lens space gets bigger the influence of lens space will be more significant on refractive property. For uncertainty component, uncertainty from front and back surface radii are the biggest, secondary is the refractive index and lens space, and uncertainty from lens thickness is the least.
20
Blahut, Marek. "Model of the broadband interferometric optical biosensor in a planar configuration." Photonics Letters of Poland 12, no. 2 (July 1, 2020): 28. http://dx.doi.org/10.4302/plp.v12i2.987.
Abstract:
The paper presents numerical studies of the model of an optical sensor based on interference of modes in planar one-dimensional step-index configuration, excited by a broadband light source from a selected spectral range. The refractive index variation of measured external surrounding affects the modal properties of multimode waveguide and the spectral field distribution at the output of the structure. The optical system described is designed to the analysis of biological substances. Full Text: PDF ReferencesM. Blahut, "Optical sensor in planar configuration based on multimode interference" Proc. SPIE, 10455, (2017). CrossRef K. Misiakos, et al, "Broad-band Mach-Zehnder interferometers as high performance refractive index sensors: Theory and monolithic implementation", Opt. Express, 22, 8856, (2014). CrossRef K. Gut, "Study of a Broadband Difference Interferometer Based on Low-Cost Polymer Slab Waveguides", Nanomaterials, 9, 729 (2019). CrossRef M. Nordstrom, et al, "Single-Mode Waveguides With SU-8 Polymer Core and Cladding for MOEMS Applications", J. Light. Techn., 25, 1284, (2007). CrossRef D. Segelstein, "The complex refractive index of water", M.S. Thesis, University of Missouri, (1981). DirectLink https://www.yokogawa.com/pl/solutions/products-platforms/ DirectLink
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Keaney, Erin, John Shearer, Artee Panwar, and Joey Mead. "Refractive index matching for high light transmission composite systems." Journal of Composite Materials 52, no. 24 (March 22, 2018): 3299–307. http://dx.doi.org/10.1177/0021998318764787.
Abstract:
Transparent optical polymer/filler systems can be produced into complex shapes for a range of applications, such as lenses, shields, and containers. This work used refractive index liquids as a model for polymer matrices to investigate the degree of refractive index match required to maintain high transmission in an inorganic-filled polymer system (cubic calcium fluoride with particle size of 1 to 5 µm) over the visible spectrum. It was determined that in order to achieve a transparent composite (>85% transmission with 10 mm pathlength) with this filler (using literature reported dispersion data), the materials must have a refractive index match within ±0.007 for 1.6 vol.% loading. With a loading of 3.1 vol.%, the matching range required was reduced to approximately ±0.002.
22
Pistore, Valentino, Osman Balci, Jincan Zhang, Sachin M. Schinde, Adil Meersha, Andrea C. Ferrari, and Miriam S. Vitiello. "Mapping the complex refractive index of single layer graphene on semiconductor or polymeric substrates at terahertz frequencies." 2D Materials 9, no. 2 (March 16, 2022): 025018. http://dx.doi.org/10.1088/2053-1583/ac57c9.
Abstract:
Abstract Assessing experimentally the main optical parameters of graphene (e.g. complex refractive index, carrier density, mobility) in the far-infrared (0.1–10 THz) is important for quantum science, due to the possibility to devise miniaturized devices (frequency combs, random lasers), components (optical switches, spatial light modulators, metamaterial mirrors and modulators) or photonic circuits, in which graphene can be integrated with existing semiconductor technologies to manipulate their optical properties and induce novel functionalities. Here, we combine time domain terahertz (THz) spectroscopy and Fourier transform infrared spectroscopy to extract the complex refractive index of large (∼1cm2) area single layer graphene on thin (∼0.1-1 µm) polymeric suspended substrates, flexible and transparent films, and high reflectivity Si substrates in the 0.4–1.8 THz range. We model our data to extract the relevant optical (refractive index, absorption coefficient, penetration length) electronic (Fermi velocity) and electrical (carrier density, mobility) properties of the different graphene samples.
23
Bilyk, V. R., and K. A. Grishunin. "Complex Refractive Index of Strontium Titanate in the Terahertz Frequency Range." Russian Technological Journal 7, no. 4 (August 11, 2019): 71–80. http://dx.doi.org/10.32362/2500-316x-2019-7-4-71-80.
Abstract:
The recent progress in terahertz time-domain spectroscopy enables the accurate and reliable measurements of dielectric properties in comparison with the traditional far-infrared spectroscopy using an incoherent light source. The broadband THz-TDS is a powerful tool to determine the real and imaginary parts of a complex dielectric constant by the transmission which allows to detect the parameters of the soft modes in ferroelectrics. In this work, the terahertz time-domain spectroscopy was used to investigate the dependence of the complex refractive index of a single-crystal quantum paraelectric strontium titanate in the terahertz frequency range from 0.3 to 2 THz. It was shown that the low-frequency terahertz response of the material is determined by the soft phonon mode TO1. The measured experimental dependences showed a good agreement with the theoretical curves obtained from the analysis of the Lorentz oscillator model for the complex dielectric constant of strontium titanate. The obtained results are necessary for understanding the principle of possibility to manipulate the order parameter in ferroelectric materials and can be used to create energy-efficient memory devices with a speed of recording information close to the theoretical limit.
24
Sun Du-Juan, Hu Yi-Hua, Gu You-Lin, Wang Yong, and Li Le. "Determination and model construction of microbes' complex refractive index in far infrared band." Acta Physica Sinica 62, no. 9 (2013): 094218. http://dx.doi.org/10.7498/aps.62.094218.
25
Stathopoulos, N. A., S. P. Savaidis, and M. Rangoussi. "Propagation characteristics of nonlinear waveguides with complex refractive index using a transmission line model." Optical and Quantum Electronics 38, no. 8 (September 27, 2006): 683–99. http://dx.doi.org/10.1007/s11082-006-9005-0.
26
Brovelli, Alessandro, and Giorgio Cassiani. "Effective permittivity of porous media: a critical analysis of the complex refractive index model." Geophysical Prospecting 56, no. 5 (September 2008): 715–27. http://dx.doi.org/10.1111/j.1365-2478.2008.00724.x.
27
Wang, Jiayu, Haodong Shi, Yingchao Li, Qiang Fu, Yingjie Zhao, and Huilin Jiang. "Multi-Parameter Model-Based Polarimetric Calibration for Dual-Coded Spectral Polarization Imaging System." Photonics 10, no. 8 (August 13, 2023): 929. http://dx.doi.org/10.3390/photonics10080929.
Abstract:
A polarization analysis method based on a multi-parameter model is proposed to address the polarization effect analysis and calibration requirements of a dual-coded snapshot spectral polarization imaging system. A full-link polarization effect model for a spectral polarization imaging system is established that includes a digital micromirror array (DMD), prism grating prism (PGP), micro-polarizer array detector (MPA), and multi-film. The influence of parameters such as the refractive index, incident angle, grating refractive index, constant, prism refractive index, vertex angle, multi-layer film complex refractive index, and film thickness on the optical transmittance of the system are analyzed. Using a dynamic data exchange mechanism to perform full-link, full-FOV, and full-pupil ray tracing on the optical system, the polarization effect distribution of the system under different degrees of polarization (DOP) and wavelengths is obtained. A calibration experiment for the controllable incident wavelength and DOP using narrowband filters and glass stacks is established. The experimental results show that in the 420 nm, 532 nm, and 635 nm wavelength bands, the MSEs of the calibrated values are 1.3924 × 10−4, 1.6852 × 10−4, and 1.6735 × 10−4, respectively. It is proven that the calibration method based on a multi-parameter model is feasible. Finally, the spectral polarization image at 532 nm is calibrated. The contrast ratio of metallic aluminum is calibrated from 7.13 to 15.33. This study provides a theoretical basis for the analysis and calibration of polarization effects in a dual-coded snapshot spectral polarization imaging system.
28
Herguedas, Natalia, and Enrique Carretero. "Optical Properties in Mid-Infrared Range of Silicon Oxide Thin Films with Different Stoichiometries." Nanomaterials 13, no. 20 (October 12, 2023): 2749. http://dx.doi.org/10.3390/nano13202749.
Abstract:
SiOx thin films were prepared using magnetron sputtering with different O2 flow rates on a silicon substrate. The samples were characterized using Fourier transform infrared spectroscopy in transmission and reflection, covering a spectral range of 5 to 25 μm. By employing a multilayer model, the values of the complex refractive index that best fit the experimental transmission and reflection results were optimized using the Brendel–Bormann oscillator model. The results demonstrate the significance of selecting an appropriate range of O2 flow rates to modify the SiOx stoichiometry, as well as how the refractive index values can be altered between those of Si and SiO2 in the mid-infrared range.
29
Ivanov, Oleg V., Kaushal Bhavsar, Oliver Morgan-Clague, and James M. Gilbert. "Monitoring of Curing Process of Epoxy Resin by Long-Period Fiber Gratings." Sensors 24, no. 11 (May 25, 2024): 3397. http://dx.doi.org/10.3390/s24113397.
Abstract:
The curing of epoxy resin is a complex thermo-chemical process that is difficult to monitor using existing sensing systems. We monitored the curing process of an epoxy resin by using long-period fiber gratings. The refractive index of the epoxy resin increases during the curing process and can be measured to determine the degree of curing. We employed long-period fiber gratings that are sensitive to the refractive index of an external medium for the measurement of refractive index changes in the resin. We observed that the resonances of long-period fiber gratings increased their depth with the increased refractive index of the resin, which was well described by our simulation taking the coupling to radiation modes into account. We demonstrated that the degree of cure can be estimated from the depth of the grating resonances using a phenomenological model. At the same time, long-period fiber gratings are sensitive to temperature variations and internal strains that are induced during curing. These factors may affect the measurements of curing degree and should also be addressed.
30
Miffre, Alain, Danaël Cholleton, Clément Noël, and Patrick Rairoux. "Investigating the dependence of mineral dust depolarization on complex refractive index and size with a laboratory polarimeter at 180.0° lidar backscattering angle." Atmospheric Measurement Techniques 16, no. 2 (January 24, 2023): 403–17. http://dx.doi.org/10.5194/amt-16-403-2023.
Abstract:
Abstract. In this paper, the dependence of the particles' depolarization ratio (PDR) of mineral dust on the complex refractive index and size is for the first time investigated through a laboratory π-polarimeter operating at 180.0∘ backscattering angle and at (355, 532) nm wavelengths for lidar purposes. The dust PDR is indeed an important input parameter in polarization lidar experiments involving mineral dust. Our π-polarimeter provides 16 accurate (<1 %) values of the dust lidar PDR at 180.0∘ corresponding to four different complex refractive indices, studied at two size distributions (fine, coarse) ranging from 10 nm to more than 10 µm and at (355, 532) nm wavelengths while accounting for the highly irregular shape of mineral dust, which is difficult to model numerically. At 355 nm, the lidar PDR of coarser silica, the main oxide in mineral dust, is equal to (33±1) %, while that of coarser hematite, the main light absorbent in mineral dust, is (10±1) %. This huge difference is here explained by accounting for the high imaginary part of the hematite complex refractive index. In turn, Arizona dust exhibits higher depolarization than Asian dust, due to the higher proportion in hematite in the latter. As a result, when the strong light-absorbent hematite is involved, the dust lidar PDR primarily depends on the particles' complex refractive index, and its variations with size and shape are less pronounced. When hematite is less or not involved, the dust lidar PDR increases with increasing sizes, though the shape dependence may then also play a role. The (355, 532) nm wavelength dependence of the dust lidar PDR then allows discussing on the involved particle sizes, thus highlighting the importance of dual-wavelength (or more) polarization lidar instruments. We believe these laboratory findings will help improve our understanding of the challenging dependence of the dust lidar PDR with complex refractive index and size to help interpret the complexity and the wealth of polarization lidar signals.
31
Savaidis, S. P., and N. A. Stathopoulos. "Propagation characteristics of nonlinear optical fibers with complex refractive index. A transmission line model approach." Optics Communications 260, no. 2 (April 2006): 427–33. http://dx.doi.org/10.1016/j.optcom.2005.11.040.
32
Zhou, Zhen, Siqi Zhang, Jia Qi, and Xu Yang. "Extension of complex refractive index model and analysis of scattering properties of charged submicron spheres." Journal of Quantitative Spectroscopy and Radiative Transfer 242 (February 2020): 106735. http://dx.doi.org/10.1016/j.jqsrt.2019.106735.
33
Wagner, R., T. Ajtai, K. Kandler, K. Lieke, C. Linke, T. Müller, M. Schnaiter, and M. Vragel. "Complex refractive indices of Saharan dust samples at visible and near UV wavelengths: a laboratory study." Atmospheric Chemistry and Physics Discussions 11, no. 7 (July 28, 2011): 21363–427. http://dx.doi.org/10.5194/acpd-11-21363-2011.
Abstract:
Abstract. We have retrieved the wavelength-dependent imaginary parts of the complex refractive index for five different Saharan dust aerosol particles of variable mineralogical composition at wavelengths between 305 and 955 nm. The dust particles were generated by re-dispersing soil samples into a laboratory aerosol chamber, typically yielding particle sizes with mean diameters ranging from 0.3 to 0.4 μm and maximum diameters from 2 to 4 μm. The extinction and absorption coefficients as well as the number size distribution of the dust particles were simultaneously measured by various established techniques. An inversion scheme based on a spheroidal dust model was employed to deduce the refractive indices. The retrieved imaginary parts of the complex refractive index were in the range from 0.003 to 0.005, 0.005 to 0.011, and 0.016 to 0.050 at the wavelengths 955, 505, and 305 nm. The hematite content of the dust particles was determined by electron-microscopical single particle analysis. Hematite volume fractions in the range from 1.1 to 2.7 % were found for the different dusts, a range typical for atmospheric mineral dust. We have performed a sensitivity study to assess how accurately the retrieved imaginary refractive indices could be reproduced by calculations with mixing rule approximations using the experimentally determined hematite contents as input.
34
Wagner, R., T. Ajtai, K. Kandler, K. Lieke, C. Linke, T. Müller, M. Schnaiter, and M. Vragel. "Complex refractive indices of Saharan dust samples at visible and near UV wavelengths: a laboratory study." Atmospheric Chemistry and Physics 12, no. 5 (March 5, 2012): 2491–512. http://dx.doi.org/10.5194/acp-12-2491-2012.
Abstract:
Abstract. We have retrieved the wavelength-dependent imaginary parts of the complex refractive index for five different Saharan dust aerosol particles of variable mineralogical composition at wavelengths between 305 and 955 nm. The dust particles were generated by dispersing soil samples into a laboratory aerosol chamber, typically yielding particle sizes with mean diameters ranging from 0.3 to 0.4 μm and maximum diameters from 2 to 4 μm. The extinction and absorption coefficients as well as the number size distribution of the dust particles were simultaneously measured by various established techniques. An inversion scheme based on a spheroidal dust model was employed to deduce the refractive indices. The retrieved imaginary parts of the complex refractive index were in the range from 0.003 to 0.005, 0.005 to 0.011, and 0.016 to 0.050 at the wavelengths 955, 505, and 305 nm. The hematite content of the dust particles was determined by electron-microscopical single particle analysis. Hematite volume fractions in the range from 1.1 to 2.7% were found for the different dusts, a range typical for atmospheric mineral dust. We have performed a sensitivity study to assess how accurately the retrieved imaginary refractive indices could be reproduced by calculations with mixing rule approximations using the experimentally determined hematite contents as input.
35
ARENAS, M. C., HAILIN HU, R. NAVA, and J. A. DEL RÍO. "DETERMINATION OF THE COMPLEX REFRACTIVE INDEX OF POROUS SILICON LAYERS ON CRYSTALLINE SILICON SUBSTRATES." International Journal of Modern Physics B 24, no. 24 (September 30, 2010): 4835–50. http://dx.doi.org/10.1142/s0217979210054932.
Abstract:
In this work, we show an algorithm to calculate the complex refractive index of porous silicon (PS) on its crystalline silicon (c-Si) substrate in UV-NIR range by means of the reflectance spectra only. The algorithm is based on the analytical relations established by Heavens to obtain both complex refractive index and thickness of an absorbing thin film on an absorbing substrate. Based on this model, some simplification is introduced at different wavelengths. We start with the NIR range (1000–2500 nm), where the c-Si substrate has a low extinction coefficient. Then, we continue with the near infrared to the optical range (300–1000 nm), where PS has a strong extinction coefficient and dispersion. The calculated n and k values are in agreement with those reported in the literature obtained from separated measurements of a free standing PS film. We consider that the algorithm can be applied to any thin film on a substrate with similar optical properties.
36
Rybin, Oleg, and Sergey Shulga. "Feedback magnetization of ultra-low index irradiative structure." Modern Physics Letters B 29, no. 29 (October 25, 2015): 1550179. http://dx.doi.org/10.1142/s0217984915501791.
Abstract:
Ultra-low refractive index irradiative structure is considered. The structure consists of a patch antenna with the metamaterial slab located on top of the antenna, as superstrate. In this study, ultra-low index phenomenon of the irradiative system is associated with improving the directivity of the patch antenna by putting the metamaterial slab on top of the antenna. The last phenomenon, in turn, is associated with the feedback partial magnetization of Iron inclusions of the slab caused by the radiation from the antenna. Mathematical model for evaluating the complex effective relative permittivity of the irradiative structure is developed. Numerical calculations for complex effective relative permittivity of the irradiative structure and real part of the complex effective relative permeability of the metamaterial slab are done in the study.
37
Ghanipour, Mahshad, and Davoud Dorranian. "Effect of Ag-Nanoparticles Doped in Polyvinyl Alcohol on the Structural and Optical Properties of PVA Films." Journal of Nanomaterials 2013 (2013): 1–10. http://dx.doi.org/10.1155/2013/897043.
Abstract:
The effect of silver nanoparticles doped in PVA on the structural and optical properties of composite films is studied experimentally. Samples are PVA films of 0.14 mm thickness doped with different sizes and concentrations of silver nanoparticles. Structural properties are studied using X-ray diffraction and FTIR spectrum. Using the reflectance and transmittance of samples, the effect of doped nanoparticles and their concentration on optical parameters of PVA films include absorption coefficient, optical bandgap energy, complex refractive index, complex dielectric function, complex optical conductivity, and relaxation time is extracted and discussed. The dispersion of the refractive index of films in terms of the single oscillator Wemple-DiDomenico (WD) model is investigated and the dispersion parameters are calculated. Results show that by doping silver nanoparticles in PVA, number of Bragg’s planes in the structure of polymer and its crystallinity are increased noticeably. Ag–O bonds are formed in the films and the bandgap energy of samples is decreased. Calculations based on WD model confirm that by doping nanoparticles, the anion strength of PVA as a dielectric medium is decreased.
38
Bernard, S., T. A. Probyn, and A. Quirantes. "Simulating the optical properties of phytoplankton cells using a two-layered spherical geometry." Biogeosciences Discussions 6, no. 1 (January 30, 2009): 1497–563. http://dx.doi.org/10.5194/bgd-6-1497-2009.
Abstract:
Abstract. Effective use of ocean colour and other bio-optical observations is dependent upon an ability to understand and characterise the angular scattering properties of phytoplankton populations. The two-layered sphere appears to offer the simplest heterogeneous geometry capable of simulating the observed angular scattering of phytoplankton cells. A study is made of the twolayered spherical model for the simulation of the inherent optical properties of algal populations, with a particular focus on backscattering as causal to ocean colour. Homogenous and two-layered volume-equivalent single particle models are used to examine the effects of varying cellular geometry, chloroplast volume, and complex refractive index on optical efficiency factors. A morphology with a chloroplast layer surrounding the cytoplasm is shown to be optimal for algal cell simulation. Appropriate chloroplast volume and refractive index ranges, and means of determining complex refractive indices for cellular chloroplast and cytoplasm material, are discussed with regard to available literature. The approach is expanded to polydispersed populations using equivalent size distribution models: to demonstrate variability in simulated inherent optical properties for phytoplankton assemblages of changing dominant cell size and functional type. Finally, a preliminary validation is conducted of inherent optical properties determined for natural phytoplankton populations with the two-layered model, using the reflectance approximation. The study demonstrates the validity of the two-layered geometry and refractive index structure, and indicates that the combined use of equivalent size distributions with the heterogeneous geometry can be used to establish a quantitative formulation between single particle optics, size and assemblage-specific inherent optical properties, and ocean colour.
39
Giuliano, B. M., A. A. Gavdush, B. Müller, K. I. Zaytsev, T. Grassi, A. V. Ivlev, M. E. Palumbo, et al. "Broadband spectroscopy of astrophysical ice analogues." Astronomy & Astrophysics 629 (September 2019): A112. http://dx.doi.org/10.1051/0004-6361/201935619.
Abstract:
Context. Reliable, directly measured optical properties of astrophysical ice analogues in the infrared and terahertz (THz) range are missing from the literature. These parameters are of great importance to model the dust continuum radiative transfer in dense and cold regions, where thick ice mantles are present, and are necessary for the interpretation of future observations planned in the far-infrared region. Aims. Coherent THz radiation allows for direct measurement of the complex dielectric function (refractive index) of astrophysically relevant ice species in the THz range. Methods. We recorded the time-domain waveforms and the frequency-domain spectra of reference samples of CO ice, deposited at a temperature of 28.5 K and annealed to 33 K at different thicknesses. We developed a new algorithm to reconstruct the real and imaginary parts of the refractive index from the time-domain THz data. Results. The complex refractive index in the wavelength range 1 mm–150 μm (0.3–2.0 THz) was determined for the studied ice samples, and this index was compared with available data found in the literature. Conclusions. The developed algorithm of reconstructing the real and imaginary parts of the refractive index from the time-domain THz data enables us, for the first time, to determine the optical properties of astrophysical ice analogues without using the Kramers–Kronig relations. The obtained data provide a benchmark to interpret the observational data from current ground-based facilities as well as future space telescope missions, and we used these data to estimate the opacities of the dust grains in presence of CO ice mantles.
40
Vargas-Rodriguez, Everardo, Ana Dinora Guzman-Chavez, Roberto Baeza-Serrato, and Mario Alberto Garcia-Ramirez. "Optical Fiber FP Sensor for Simultaneous Measurement of Refractive Index and Temperature Based on the Empirical Mode Decomposition Algorithm." Sensors 20, no. 3 (January 24, 2020): 664. http://dx.doi.org/10.3390/s20030664.
Abstract:
In this work, a dual refractive index and temperature sensor based on an interferometric system and on the empirical mode decomposition (EMD) algorithm is presented. Here, it is shown that the EMD provides a comprehensive way to analyze and decompose complex reflection spectra produced by an interferometric filter build at the tip of an optical fiber. By applying the EMD algorithm, the spectrum can be decomposed into a set of intrinsic mode functions (IMF) from which the temperature and the refractive index can be easily extracted. Moreover, the proposed methodology provides a detailed insight of the behavior of this type of interferometric sensors and allows widening of the dynamic measurement ranges of both variables. Here, for proof of principle purposes, a filter based on a stack of three layers (two of them were thermo-sensitive) was fabricated. Finally, it is shown that the proposed methodology can decompose the experimental measured spectra and to determine the refractive index and the temperature, supporting the mathematical model.
41
Cui, Xiaohan, Kun Ding, Jian-Wen Dong, and C. T. Chan. "Realization of complex conjugate media using non-PT-symmetric photonic crystals." Nanophotonics 9, no. 1 (December 5, 2019): 195–203. http://dx.doi.org/10.1515/nanoph-2019-0389.
Abstract:
AbstractAlthough parity-time (PT)-symmetric systems can exhibit real spectra in the exact PT-symmetry regime, PT-symmetry is actually not a necessary condition for the real spectra. Here, we show that non-PT-symmetric photonic crystals (PCs) carrying Dirac-like cone dispersions can always exhibit real spectra as long as the average non-Hermiticity strength within the unit cell for the eigenstates is zero. By building a non-Hermitian Hamiltonian model, we find that the real spectra of the non-PT-symmetric system can be explained using the concept of pseudo-Hermiticity. We demonstrate using effective medium theories that, in the long-wavelength limit, such non-PT-symmetric PCs behave like the so-called complex conjugate medium (CCM) whose refractive index is real but whose permittivity and permeability are complex numbers. The real refractive index for this effective CCM is guaranteed by the real spectrum of the PCs, and the complex permittivity and permeability come from non-PT-symmetric loss-gain distributions. We show some interesting phenomena associated with CCM, such as the lasing effect.
42
Huang, Chung-Hsuan, Yun-Ju Lai, Li-Nian Chen, Yu-Hsuan Hung, Han-Yen Tu, and Chau-Jern Cheng. "Label-Free Three-Dimensional Morphological Characterization of Cell Death Using Holographic Tomography." Sensors 24, no. 11 (May 26, 2024): 3435. http://dx.doi.org/10.3390/s24113435.
Abstract:
This study presents a novel label-free approach for characterizing cell death states, eliminating the need for complex molecular labeling that may yield artificial or ambiguous results due to technical limitations in microscope resolution. The proposed holographic tomography technique offers a label-free avenue for capturing precise three-dimensional (3D) refractive index morphologies of cells and directly analyzing cellular parameters like area, height, volume, and nucleus/cytoplasm ratio within the 3D cellular model. We showcase holographic tomography results illustrating various cell death types and elucidate distinctive refractive index correlations with specific cell morphologies complemented by biochemical assays to verify cell death states. These findings hold promise for advancing in situ single cell state identification and diagnosis applications.
43
Yao, Gang, Khian-Hooi Chew, Yan Wu, Yuhua Li, and Rui-Pin Chen. "Propagation dynamics of vector vortex beams in a strongly nonlocal nonlinear medium with parity-time-symmetric potentials." Journal of Optics 24, no. 3 (February 4, 2022): 035606. http://dx.doi.org/10.1088/2040-8986/ac4e5f.
Abstract:
Abstract We demonstrate the dynamical properties of a vector vortex optical field (VVOF) in a strongly nonlocal nonlinear medium (SNNM) with sine and cosine parity-time-symmetric potentials (SCPT) by using the coupled vector Snyder-Mitchell model. Our study shows that the shape of the optical field is chaotically distorted in different propagation distances due to the modulation of complex refractive index. Despite the distorted optical field, the VVOF reciprocally evolves in a periodic stretch and shrink behavior during propagation in the SNNM-SCPT. The reciprocal conversions between the linear and circular polarizations periodically occur during propagation. The evolution of VVOF and the linear and circular polarization conversions are strongly dependent on the modulation of the complex refractive index, the initial powers and the vortex topological charge numbers. These results can provide a new way to complexly manipulate the VVOF in a SNNM-SCPT.
44
Kumar, A. R., Z. M. Zhang, V. A. Boychev, D. B. Tanner, L. R. Vale, and D. A. Rudman. "Far-Infrared Transmittance and Reflectance of YBa2Cu3O7-δ Films on Si Substrates." Journal of Heat Transfer 121, no. 4 (November 1, 1999): 844–51. http://dx.doi.org/10.1115/1.2826074.
Abstract:
The transmittance and reflectance of superconductive YBa2Cu307-δ (YBCO) thin films deposited on Si substrates have been measured in the far-infrared frequency region from 10 to 100 cm−1 (wavelength from 1000 to 100 μm) at temperatures between 10 and 300 K. The effects of interference, optical resonance, and antireflection on the radiative properties of high-temperature superconducting (HTSC) films are observed and quantitatively analyzed. Furthermore, we have measured the reflectance of the HTSC film-substrate composites for radiation incident on the substrate side (backside reflectance) for the first time. The backside reflectance increases significantly from the normal state to the superconducting state at certain frequencies; this experimentally demonstrates that HTSC films can be used to build far-infrared intensity modulators. The complex refractive index of the YBCO films is determined from the measured transmittance using the Drude model in the normal state and a two-fluid model in the superconducting state. The complex refractive index obtained from this study is useful for various applications of YBCO films, including radiation modulators, detectors, and Fabry-Perot resonators.
45
Holoubek, Jaroslav, and Miroslav Raab. "Stress Whitening in Polypropylene. I. Light Scattering Theory and Model Experiments." Collection of Czechoslovak Chemical Communications 60, no. 11 (1995): 1875–87. http://dx.doi.org/10.1135/cccc19951875.
Abstract:
Theoretical background for an optical method is presented which makes it possible to distinguish unambiguously between voids and particles as light scattering sites in polymeric materials. Typical dependences of turbidity as a function of diameter of scattering elements, their volume fractions and also turbidity curves as a function of the wavelength of the incident light were calculated, based both on the Lorenz-Mie theory and the fluctuation theory. Such dependences calculated for polypropylene-containing voids on the one hand and particles, differing only slightly from the surrounding matrix in their refractive index, on the other hand, are markedly different. The most significant results are: (i) Turbidity is at least by two orders of magnitude larger for voids in comparison to embedded particles of ethylene-propylene (EPDM) rubber of the same size, concentration and at the same wavelength. (ii) The wavelength dependence of turbidity for EPDM particles and the inherent refractive index fluctuations in the polypropylene matrix is much steeper as compared to voids for all considered diameters (0.1-10 μm). Thus, the nature of stress whitening in complex polymeric materials can be determined from turbidity measurements.
46
Barnett, Sasha, Joseph Blau, Paul Frederickson, and Keith Cohn. "Measurements and Modeling of Optical Turbulence in the Coastal Environment." Applied Sciences 12, no. 10 (May 12, 2022): 4892. http://dx.doi.org/10.3390/app12104892.
Abstract:
The goal of this study was to characterize optical turbulence in the near-coastal environment. Measurements to obtain the refractive index structure parameter and other meteorological data were taken over the course of a month along the shore of Monterey Bay. The results were compared to a new version of the Navy Vertical Surface Layer Model (NAVSLaM), a model of turbulence originally developed for maritime environments but now extended to terrestrial environments. The new version has not been previously validated by comparisons to experiments, particularly in a complex environment such as near the coastline. Our experimental results showed generally good agreement between measured and modeled levels of turbulence. Specifically, the differences between experimental and modeled values of the refractive index structure parameter were less than an order of magnitude in most conditions and followed the same diurnal trend. There were some greater differences during near-neutral conditions, but this is a known limitation of the model. Overall, this extended model appears to do a good job of predicting turbulence in this environment for the observed time period.
47
HATTORI, Yasuhisa. "Consideration on the Optical Model in Measuring Complex Refractive Index for the Purpose of Judging Real Contact." Proceedings of Mechanical Engineering Congress, Japan 2022 (2022): S114–03. http://dx.doi.org/10.1299/jsmemecj.2022.s114-03.
48
SORAYA, M. M., E. R. SHAABAN, M. I. EMAN, A. QASEM, S. A. MAHMOUD, and E. YOUSEF. "INDIUM INCORPORATION EFFECTS ON OPTICAL PROPERTIES OF QUATERNARY CHALCOGNIDE Se-Zn-Te-In FILMS." Chalcogenide Letters 17, no. 3 (March 2020): 133–45. http://dx.doi.org/10.15251/cl.2020.173.133.
Abstract:
Amorphous semiconducting thin films of Se90-xZn5Te5Inx (x=0, 2, 4, 6, 8 and 10 at. %) are deposited on glass substrates by thermal evaporating technique with thickness about of 1000 nm. The transmittance spectra are investigated by Swanepoel method to compute the optical coefficients and parameters in the spectral region of (400–2500) nm, such as absorption coefficient α, extinction coefficient k, optical band gap, Eg and refractive index, n. The optical absorption edge is described by using the non-direct transition model in terms of Tauc relation. The obtained values of both n and k were found to be dependent of the In content in the investigated samples. Also, other parameters have been computed like the real, (εr) and imaginary (εi) parts of complex dielectric constants. The dispersion parameters (dispersion energy, Ed, oscillation energy Eo) were discussed according to the single oscillator Wemple–DiDomenico model. The non-linear refractive index, n2 was computed by using Tichy-Ticha and Fourier-Snitzer relationships.
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Liu, Chao, Chul Eddy Chung, Yan Yin, and Martin Schnaiter. "The absorption Ångström exponent of black carbon: from numerical aspects." Atmospheric Chemistry and Physics 18, no. 9 (May 4, 2018): 6259–73. http://dx.doi.org/10.5194/acp-18-6259-2018.
Abstract:
Abstract. The absorption Ångström exponent (AAE) is an important aerosol optical parameter used for aerosol characterization and apportionment studies. The AAE of black carbon (BC) particles is widely accepted to be 1.0, although observational estimates give quite a wide range of 0.6–1.3. With considerable uncertainties related to observations, a numerical study is a powerful method, if not the only one, to provide a better and more accurate understanding on BC AAE. This study calculates BC AAE using realistic particle geometries based on fractal aggregate and an accurate numerical optical model (namely the multiple-sphere T-matrix method), and considers bulk properties of an ensemble of BC particles following lognormal size distributions. At odds with the expectations, BC AAE is not 1.0, even when BC is assumed to have small sizes and a wavelength-independent refractive index. With a wavelength-independent refractive index, the AAE of fresh BC is approximately 1.05 and relatively insensitive to particle size. For BC with geometric mean diameters larger than 0.12 µm, BC AAE becomes smaller when BC particles are aged (compact structures or coated by other non-absorptive materials). For coated BC, we prescribe the coating fraction variation based on a laboratory study, where smaller BC cores are shown to develop larger coating fractions than those of bigger BC cores. For both compact and coated BC, the AAE is highly sensitive to particle size distribution, ranging from approximately 0.8 to even over 1.4 with wavelength-independent refractive index. When the refractive index is allowed to vary with wavelength, a feature with observational backing, the BC AAE may show an even wider range. For different BC morphologies, we derive simple empirical equations on BC AAE based on our numerical results, which can serve as a guide for the response of BC AAE to BC size and refractive index. Due to its complex influences, the effects of BC geometry is better to be discussed at certain BC properties, i.e., known size and refractive index.
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Ryu, Meguya, Soon Hock Ng, Vijayakumar Anand, Stefan Lundgaard, Jingwen Hu, Tomas Katkus, Dominique Appadoo, et al. "Attenuated Total Reflection at THz Wavelengths: Prospective Use of Total Internal Reflection and Polariscopy." Applied Sciences 11, no. 16 (August 19, 2021): 7632. http://dx.doi.org/10.3390/app11167632.
Abstract:
Capabilities of the attenuated total reflection (ATR) at THz wavelengths for increased sub-surface depth characterisation of (bio-)materials are presented. The penetration depth of a THz evanescent wave in biological samples is dependent on the wavelength and temperature and can reach 0.1–0.5 mm depth, due to the strong refractive index change ∼0.4 of the ice-water transition; this is quite significant and important when studying biological samples. Technical challenges are discussed when using ATR for uneven, heterogeneous, high refractive index samples with the possibility of frustrated total internal reflection (a breakdown of the ATR reflection mode into transmission mode). Local field enhancements at the interface are discussed with numerical/analytical examples. Maxwell’s scaling is used to model the behaviour of absorber–scatterer inside the materials at the interface with the ATR prism for realistic complex refractive indices of bio-materials. The modality of ATR with a polarisation analysis is proposed, and its principle is illustrated, opening an invitation for its experimental validation. The sensitivity of the polarised ATR mode to the refractive index between the sample and ATR prism is numerically modelled and experimentally verified for background (air) spectra. The design principles of polarisation active optical elements and spectral filters are outlined. The results and proposed concepts are based on experimental conditions at the THz beamline of the Australian Synchrotron.