Extraction of thickness and water content gradients in hydrogel-based, water-backed corneal phantoms via submillimeter wave reflectometry
Absolute thickness and free water content gradients in gelatin-based corneal phantoms with physiologically accurate radii of curvature, and aqueous backing were extracted via coherent submillimeter wave reflectometry at 220 330 GHz. Fourier-domain based calibration methods, utilizing temporal and spatial gating, were developed and yielded peak-to-peak amplitude and phase clutter of 10-3 and 0.1, respectively for signal to noise ratios between 40 dB and 50 dB. Twelve phantoms were fabricated. Calibration methods enabled quantification of target sphericity that strongly correlated with optical coherence tomography-based sphericity metrics via image segmentation. Extracted free water volume fraction varied less than 5 % in the 5 phantoms whose fabrication yielded the most spherical geometry. Submillimeter wave-based thickness accuracy was better than 111 m (~/9) with average of 65 m (~/17) and standard deviation of 44 m (~/25) for phantoms with physiologically relevant geometry. Monte Carlo simulations of measurement noise and uncertainty limits agree with experimental data analysis and indicates a lower thickness accuracy limit of 33 m, and water content sensitivities of 0.5 % and 11.8 % for the anterior and posterior segments respectively. Numerical analysis suggests measurement fidelity was SNR limited and identified optical path length ambiguities within the cornea where a continuum of thickness/water gradient pairs produce statistically insignificant differences in complex reflection coefficient for finite SNR. This is the first known submillimeter-wave measurement technique able to extract both the thickness and water content gradients from a soft-tissue phantom, with a water backing, without the need for ancillary measurements.
We provide theoretical analysis of the reflectance of shock-compressed plasmas and warm dense matter for normal incidence of laser radiation as well as for the dependence of s- and p-polarized reflectivity on the incidence angle. The self-consistent approach for the calculation of the optical and electronic properties of warm dense matter and nonideal plasmas developed in our previous works is extended for the description of normal and polarized reflectivity from the broadened optically nonuniform medium. Two methods are applied for the calculation of the reflectivity from spatially broadened optically nonuniform medium. The first one is based on the solution of the Helmholtz equation for the amplitudes of the electromagnetic field. Another one is based on Drude theory of reflection. It allows us to calculate the ratio of the s- and p-polarized reflectivity if dependence of the dielectric function on distance is known. For the case of the polarized reflectivity, the particular attention is concentrated on the Brewster angle. The calculation results for the dielectric function, obtained within the framework of the density-functional theory with the longitudinal expression for the dielectric tensor, are applied for the calculation of the reflectivity. Comparison with the experimental data for shock-compressed xenon is performed.
Warm dense matter conductivity and reflectivity are investigated by means of density functional theory. Both one- and two-temperature cases are considered. One-temperature mode is related to equilibrium state where temperature of electrons and ions are equal. As an example of one-temperature system xenon plasma is studied. The reflectivity of shock-compressed dense xenon plasma is calculated and compared with experimental data. Two-temperature mode is associated with different temperature of electrons and ions. The thermal conductivity of aluminum and gold in such mode is examined. The comparison of obtained results with theoretical model based on Boltzmann equation is conducted.
An adequate water balance (hydration extent) is one of the basic factors of normal eye function, including its external shells: the cornea and the sclera. Adequate control of corneal and scleral hydration is very important for early diagnosis of a variety of eye diseases, stating indications for and contraindications against keratorefractive surgeries and the choice of contact lens correction solutions. THz systems of creating images in reflected beams are likely to become ideal instruments of noninvasive control of corneal and scleral hydration degrees. This paper reports on the results of a study involving transmittance and reflectance spectra for the cornea and the sclera of rabbit and human eyes, as well as those of the rabbit eye, in the frequency range of 0.13 to 0.32 THz. The dependence of the reflectance coefficient of these tissues on water mass percentage content was determined. The experiments were performed on three corneas, three rabbit scleras, two rabbit eyes, and three human scleras. The preliminary results demonstrate that the proposed technique, based on the use of a continuous THz radiation, may be utilized to create a device for noninvasive control of corneal and scleral hydration, which has clear potential of broad practical application. © 2016 Society of Photo-Optical Instrumentation Engineers (SPIE).
Generalized error-locating codes are discussed. An algorithm for calculation of the upper bound of the probability of erroneous decoding for known code parameters and the input error probability is given. Based on this algorithm, an algorithm for selection of the code parameters for a specified design and input and output error probabilities is constructed. The lower bound of the probability of erroneous decoding is given. Examples of the dependence of the probability of erroneous decoding on the input error probability are given and the behavior of the obtained curves is explained.
The dynamics of a two-component Davydov-Scott (DS) soliton with a small mismatch of the initial location or velocity of the high-frequency (HF) component was investigated within the framework of the Zakharov-type system of two coupled equations for the HF and low-frequency (LF) fields. In this system, the HF field is described by the linear Schrödinger equation with the potential generated by the LF component varying in time and space. The LF component in this system is described by the Korteweg-de Vries equation with a term of quadratic influence of the HF field on the LF field. The frequency of the DS soliton`s component oscillation was found analytically using the balance equation. The perturbed DS soliton was shown to be stable. The analytical results were confirmed by numerical simulations.
The conference “2021 Systems of signals generating and processing in the field of on board communications” is organized with technical sponsorship of Russian (Moscow) IEEE Circuits and Systems (CAS04) Chapter IEEE Region 8, Russian Section Chapter, MTT/ED and Institute of Radio and Information Systems Association (IRIS), Vienna, Austria. The conference featured invited researchers, educators, managers, and graduate students, whose research activity, case studies or best practices, are shedding light on the theory or practice of engineering, include modern digital transportation systems design and technical operation, radio waves propagation, transmitting, receiving and processing signals in television and radio broadcasting devices, information technologies in transport. The main areas of the conference “Systems of signals generating and processing in the field of on board communications” include modern digital transportation systems design and technical operation, radio waves propagation, transmitting, receiving and processing signals in television and radio broadcasting devices, information technologies in transport. FIELD OF INTEREST: Components, Circuits, Devices and Systems; General Topics for Engineers; Signal Processing and Analysis. Reports presented at the conference are grouped in 6 sections: 1. Antennas and Radio Waves Propagation. 2. Navigation and Mathematical Algorithms of an Object Space Orientation. 3. Radiofrequency Applications. 4. Wire and Optical Communication and Control Systems. 5. Intelligent Transport Systems (ITS): Sub-section 1: Use of digital ITS infrastructure in telematic control systems on urban passenger transport Sub-section 2: Peculiarities of data exchange in cooperative ITS Sub-section 3: Theoretical Aspects of Artificial Intelligence Systems Development for Transportation Engineering Sub-section 4: Test methods of motor vehicles integrated into an intelligent transport environment 6. Digital signal processing in on-board radio systems
Radiation conditions are described for various space regions, radiation-induced effects in spacecraft materials and equipment components are considered and information on theoretical, computational, and experimental methods for studying radiation effects are presented. The peculiarities of radiation effects on nanostructures and some problems related to modeling and radiation testing of such structures are considered.
This volume presents new results in the study and optimization of information transmission models in telecommunication networks using different approaches, mainly based on theiries of queueing systems and queueing networks .
The paper provides a number of proposed draft operational guidelines for technology measurement and includes a number of tentative technology definitions to be used for statistical purposes, principles for identification and classification of potentially growing technology areas, suggestions on the survey strategies and indicators. These are the key components of an internationally harmonized framework for collecting and interpreting technology data that would need to be further developed through a broader consultation process. A summary of definitions of technology already available in OECD manuals and the stocktaking results are provided in the Annex section.