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In this paper, we consider a limited-aperture inverse scattering problem for a fast identification of small dielectric objects from two-dimensional Fresnel experimental dataset. To this end, we apply the Kirchhoff migration (KM) imaging technique and design an imaging function from the generated multi-static response matrix. Using the integral equation-based representation formula for the scattered field, we theoretically investigate the applicability of the KM by formulating the imaging function as a uniformly convergent infinite series of integer-order Bessel functions of the first kind. Numerical simulation results using the experimental Fresnel dataset are presented to support the theoretical result. [ABSTRACT FROM AUTHOR]

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This paper investigates the dynamics of mmWave at the free space-human skin interface. The four Fresnel equations tailored for parallel and perpendicular polarizations, are employed in the analysis. The research reveals that for human tissue with relative permittivities (18.99, 15.51, 13.35, 11.69, 10.40) and conductivities (22.48, 27.09, 29.76, 31.79, 33.38) S/m, when exposed to 5G mmWave frequencies (24, 30, 35, 40, 45) GHz, respectively, exhibits Brewster angles of (79°, 78°, 77°, 76°, 75°), respectively. Additionally, it is shown that Brewster angles exist between 60° and 80°, which aligns with existing literature using Gabriel's skin model. To further validate obtained results, use is made of the results of the Gabriel's skin model at (40, 60, 80, 100) GHz with the respective permittivities and conductivities, to generate new power reflection coefficients for the parallel and perpendicular polarizations for the sake of comparative analysis. First, comparisons of the curves for the Gabriel's skin model reported in the literature with this work, show fairly good agreements. Second, the Brewster angles of (78°, 76°, 74°, 73°) obtained from this work, for the respective frequencies compare favorably with (75°, 74°, 70°, 69°) extracted from Gabriel's skin model curves reported in the literature, with all values falling within the expected range of 60° to 80°. [ABSTRACT FROM AUTHOR]

In linear Fresnel reflectors, field arrangement has a significant effect on optical efficiency. Three constant, optimal, and variable distance layouts are proposed for Fresdemo solar power plant. The study was carried out by simulation and experiment. The small-scale Fresnel concentrator was designed and built with the capability to implement these three arrangements. The optical efficiency of the solar power plant with optimal variable and constant gap between mirrors were compared, considering fixed conditions for all layouts, including overall dimensions of the plant, width, and number of mirrors and dimensions of the receiver. It was observed that the arrangement with the optimal variable, and fixed distance had the highest to the lowest energy efficiency. Besides, the mirrors farther from the center entail more losses due to the sharper tilt angles, hence more spaces between these mirrors is required to reduce the losses. Meanwhile, the last mirrors in fixed distance arrangement have severe losses of shading and blocking while, they produce almost the same energy as central mirrors in the optimal and variable distance arrangement. The experimental results of the developed prototype showed that the thermal efficiency for the optimal distance was the highest, while it was followed closely by variable distance arrangement. The fixed distance arrangement had the lowest thermal efficiency. In addition, the variable and optimal distance arrangements exhibited an efficiency of 54% and 55%, respectively. [ABSTRACT FROM AUTHOR]

The Linear Canonical Transform (LCT) is a mathematical transform that generalizes several well-known transforms, including the Fourier transform, the fractional Fourier transform, and the Fresnel transform. It provides a unified framework for understanding and representing a wide range of linear and linear-like transforms, allowing for the analysis and manipulation of signals in various domains. Recently, Gao et al. extended the notion of LCT to octonion domains and showed its efficacy in precisely representing the non-transient octonion-valued signals. However, the octonion LCT exhibits limitations in effectively localizing the frequency characteristics of non-transient octonion-valued signals. As such, it is imperative to introduce the Octonion Windowed Linear Canonical Transform (OCWLCT) and explore its fundamental characteristics. We delve into the inversion formula and the orthogonality relation for the onedimensional OCWLCT. Additionally, we derive the inversion formula for the three-dimensional Octonion Windowed Linear Canonical Transform (OCWLCT). [ABSTRACT FROM AUTHOR]

In this paper, the Hermite-Hadamard inequality and its generalization for quasi p-convex functions are provided. Also several new inequalities are established for the functions whose first derivative in absolute value is quasi p-convex, which states some bounds for sides of the Hermite-Hadamard inequalities. In the context of the applications of results, we presented some relations involving special means and some inequalities for special functions including digamma function and Fresnel integral for sinus. In addiditon, an upper bound for error in numerical integration of quasi p-convex functions via composite trapezoid rule is given. [ABSTRACT FROM AUTHOR]

The surface morphology of metal influences its optical absorptivity. Recent experiments have demonstrated that the femtosecond laser induced surface structures on metals could be dynamically controlled by the fluence of laser and the number of pulses. In this paper, we formulate an analytical model to calculate the optical absorption of a rough metallic surface by modeling the roughness as a fractal slab. For a given experimental image of the surface roughness, we characterize the roughness with a fractal parameter by using the box-counting method. With this parameter as an input, we calculate the absorption of an 800 nm laser pulse impinging on gold, copper, and platinum, and the calculated results show excellent agreements. In terms of physics, our model can be viewed as a fractional version of the Fresnel coefficients, and it will be useful for designing suitable surface structures to tune the light absorption on metals from purely reflective to highly absorptive based on different applications. [ABSTRACT FROM AUTHOR]

We report an optical asymmetric scheme for double-image encryption and authentication based on interference using sparse representation. We employ sparse representation and interference to process the Fresnel spectra related with the two original images, and then respectively acquire two ciphertexts and two pairs of private keys. Each original image possesses its corresponding two private keys. Furthermore, the decrypted image is compared with its corresponding plaintext with the aid of a nonlinear correlation for authentication. In the proposed scheme, any information concerning each primary image and comprising its silhouette cannot be recognized even though one, two, or even three masks of the two ciphertexts and two private keys are utilized for decryption. The Fresnel spectrum functions which have different diffraction distances enhance the security of the proposal significantly. Moreover, the proposal also avoids the crosstalk problem. The effectiveness and security of this proposed method are demonstrated via numerical simulations. [ABSTRACT FROM AUTHOR]

Bu çalışmada, Sınır Kırınım Dalgası Teorisi (SKDT) yaklaşımı kullanılarak opak bir yüzey üzerindeki dairesel açıklıktan saçılan alanların hesabı incelenmiştir. İlk olarak, Miyamoto ve Wolf tarafından ortaya konulan vektör potansiyelinin sembolik ifadesi, SKD Teorisi integralinde kullanılmıştır. Bu ifade probleme uygulanmış, bulunan düzgün olmayan (non-uniform) alan ifadesi Detour parametresi kullanılarak, Fresnel fonksiyonunun asimptotik ilişkilendirmesi yardımıyla düzgün (uniform) hale getirilmiştir. Bu problemi, benzer şekilde kırınan alanlar için inceleyen Umul Y.Z.’nin, SKD'nin Uniform Teorisi ile sonuçlar grafiksel olarak karşılaştırılmış ve saçılan alanlar için genişletilmiştir. Sonuç olarak, saçılan düzgün (uniform) alanlar hesap edilmiş, elde edilen alan ifadeleri, farklı açıklık yarıçapları ve gözlem mesafeleri için grafikler ile değerlendirilerek yorumlanmıştır. Böylece, opak bir yüzey üzerindeki dairesel açıklıktan saçılan düzgün (uniform) alanlar SKD Teorisi yaklaşımı ile ilk kez hesaplanmıştır.

The article focuses on designing of Fresnel zone plate optics for photon energies and demonstrates X-ray holography limited by the numerical aperture of probing beam. Topics discussed include attempts of x-ray microscopes based on concept of optical imaging system, propagation of x-ray wave fields using finite-differences propagation method, and showing holographic X-ray imaging based on illumination of cone-beam.

The diffraction of plane electromagnetic waves by a perfect electromagnetic conductor (PEMC) semi-infinite sheet which is embedded in an anisotropic medium is examined. The anisotropic region is modeled by a dielectric matrix. The external uniform magnetic field is taken as parallel to the edge of the semi-infinite sheet. Upon considering the $H$ -polarized incident wave, the total scattered fields are obtained with the diffracted waves by using an integral theory which is associated with the scattered fields. The results are expressed in terms of the Fresnel functions. Thus, the wave behaviors at the transition boundaries are uniform. The solutions are compared numerically with the literature including limit values. [ABSTRACT FROM AUTHOR]

In this study, diffraction of waves by a planar junction between impedance and perfect electromagnetic conductor half-planes is investigated. The method of transition boundary is used for the solution of the problem. The diffracted wave expressions are expressed in terms of the Fresnel functions by using the uniform theory of diffraction method. Thus, finite magnitudes are obtained at the transition regions and the results are analyzed numerically for different set of parameters. [ABSTRACT FROM AUTHOR]

Currently, human sensing draws much attention in the field of ubiquitous computing, and human sensing based on WiFi CSI (channel state information) becomes a hot research topic due to the easy deployment and availability of WiFi devices. Although various human sensing applications based on the CSI signal model are emerging, the model-based approach has not been studied thoroughly. This paper provides a comprehensive survey of the latest model-based human sensing methods and their applications. First, the CSI signal and framework of model-based human sensing methods are introduced. Then, related models and fundamental signal preprocessing techniques are described. Next, typical human sensing applications are investigated, and the crucial characteristics are summarized. Finally, the advantages, limitations, and future research trends of model-based human sensing methods are concluded in this paper. [ABSTRACT FROM AUTHOR]

An integral theory that is associated with the scattered fields is considered for the solution of H‐polarized line source diffraction by a conductive half‐plane, which is surrounded by an anisotropic plasma. As the anisotropy does not affect an E‐polarized incident wave, only one polarization case is considered. The cold plasma medium is characterized by the dielectric tensor. The constant external magnetic field producing the anisotropy in a cold plasma is applied parallel to the edge of the half‐plane. The total, scattered, and diffracted waves are derived in terms of the Fresnel functions. Therefore, finite magnitude values at the transition boundaries are obtained. The wave behaviours are investigated numerically for different quantities of the medium. [ABSTRACT FROM AUTHOR]

In this paper, a novel small-decentralized desalination device is presented for increasing the temperature difference between brackish water and glass cover, so as to enhance the solar still's freshwater productivity. This novel solar still device is based on installing a lens in front of the single slope solar still, and two lenses on still's both sides, and a reflector over the back side of the solar still. The main objective of such novel still is to concentrate sunrays at the still's bottom basin, through the refraction function of Fresnel lens. Furthermore, this novel still makes the reflector transferring its reflected sunrays to the solar still's basin. Experiments are conducted under the climate conditions in Hangzhou city, China, for testing the novel still's operational performance, and internal heat and mass transfer characteristics. Assessment of the novel still's feasibility is performed based on energy, exergy, exergoeconomic, and enviroeconomic methodologies, as well as energy payback time. Results show that the productivity of novel still is 32% higher than that of conventional still, and novel solar still enhances the average hourly energy efficiency by 97.73%, compared to conventional solar still. While, the corresponding value of hourly exergy efficiency is also enhanced by 43.713%. Due to the higher energy and exergy outputs of novel still throughout its lifetime, the novel solar still proposed in this study mitigates more CO 2 compared to the conventional still. Overall, incorporation three lenses and one reflector with the still is found promising in terms of freshwater yield, cost, and energy payback time compared to conventional one. Exergoeconomic and environmental parameters of the novel solar still are found more effective compared to the conventional one. • A novel solar still with lenses and reflector is developed and evaluated. • Using lenses and reflector increases still's productivity by about 32%. • Novel solar still enhances the average hourly energy efficiency by 97.73%. • Novel still mitigates more CO 2 compared to conventional one based on energy & exergy. • Novel solar still's enviroeconomic and exergoenvironmental are 324.317 $ and 22.148 $. [ABSTRACT FROM AUTHOR]

In this paper, we describe an improved technique for using the backscattered phase from meteor radar echo measurements just prior to the specular point (t0) to calculate meteor speeds and their uncertainty. Our method, which builds on earlier work of Cervera et al. (1997, https://doi.org/10.1029/96RS03638), scans possible speeds in the Fresnel distance‐time domain with a dynamic, sliding window and derives a best‐speed estimate from the resultant speed distribution. We test the performance of our method, called pre‐t0 speeds by sliding‐slopes technique (PSSST), on transverse scattered meteor echoes observed by the Middle Atmosphere Alomar Radar System (MAARSY) and the Canadian Meteor Orbit Radar (CMOR) and compare the results to time‐of‐flight and Fresnel transform speed estimates. Our novel technique is shown to produce good results when compared to both model and speed measurements using other techniques. We show that our speed precision is ±5% at speeds less than 40 km/s, and we find that more than 90% of all CMOR multistation echoes have PSSST solutions. For CMOR data, PSSST is robust against the selection of critical phase value and poor phase unwrapping. Pick errors of up to ±6 pulses for meteor speeds less than about 50 km/s produce errors of less than ±5% of the meteoroid speed. In addition, the width of the PSSST speed Kernel density estimate (KDE) is used as a natural measure of uncertainty that captures both noise and t0 pick uncertainties. Key Points: Meteor speed determination by novel meansOur algorithm allows to determine the meteor speed with 5% uncertainty for >90% echoes using only a single radar stationWe tested our method for two different radar systems with more than 10 million unique events [ABSTRACT FROM AUTHOR]

Advanced digital holography attracts a lot of attentions for 3D visualization nowadays. The representation of high-resolution digital holographic 3D human images suffers from computational inefficiency on the mobile devices due to the limited hardware for digital holographic processing. Specifically, to reconstruct the high-quality holographic image needs to compensate for the phase aberration, which needs lots of expensive optical hardware components to acquire measurements such as different axial distances, illumination angles, wavelengths, polarization states, and so on. To reduce computational complexity in digital holographic 3D human image reconstruction, we propose an efficient and effective algorithm to simplify Fresnel transforms for the mobile devices. Our algorithm reduces the number of FFTs and fastens the calculation of the exponential function in the Fresnel integral for the digital holography image reconstruction. Specifically, we reformulate the Fresnel integral and use a polynomial approximation to approximate the exponential function. In the holographic image quality improvement, we modify a maximum a posteriori (MAP) estimation to improve the quality of the reconstructed holographic 3D image restoration. Our algorithm outperforms previous approaches in not only smaller running time but also the better quality of the digital holographic 3D human image representation for the mobile devices. [ABSTRACT FROM AUTHOR]

In this study, a beam steering antenna was presented, comprising patch antenna and two layers of Fresnel zone plate (FZP). One of the FZP was a fixed structure, the other was a 1‐D collapsible radome with alternately deployed metal strips covering and non‐covering regions. The two sets of FZP were arranged in order in front of the patch antenna. First, the beam was compressed vertically by the fixed FZP. Subsequently, the beam steering was achieved with the use of the collapsible radome by setting the folding status in the respective region. To assess the effectiveness of the method, a 1‐D beam steering antenna working at 3 GHz was designed by applying linear polarized patch antenna as the feeding source. The collapsible FZP structure was developed using a low‐loss fiberglass cloth that was covered with copper strips. Based on the simulation and the experiment, the beam was focused to a beam width of 30° vertically and 10° horizontally. Moreover, 60° of beam steering in the horizontal direction could be achieved by regulating the folding angles in the respective region. This antenna design was found to be light weight and flexible, which has promising applications in 5G cell coverage and satellite communication. [ABSTRACT FROM AUTHOR]

Dawson's integral and related functions in mathematical physics that include the complex error function (Faddeeva's integral), Fried–Conte (plasma dispersion) function, Jackson function, Fresnel function and Gordeyev's integral are analytically evaluated in terms of the confluent hypergeometric function. And hence, the asymptotic expansions of these functions on the complex plane ℂ {\mathbb{C}} are derived by using the asymptotic expansion of the confluent hypergeometric function. [ABSTRACT FROM AUTHOR]

Abstract In lensless digital holography the resolving power is limited by factors such as the finite size of recorded area, pixel dimensions and sampling rate of digital acquisition system. These factors acts as a filter that discards high-frequency components with useful information about the analyzed object. In the present work, we propose a method to overcome these limitations to proving the resolution recovery in digital in-line holography by utilizing adjustable magnification in a compressive sensing framework. Here, we model the sensed field as low-pass filtered and projected on a Fresnel base with adjustable magnification and use sparse regularization in an inverse problem approach to image reconstruction. Our method enhances image reconstruction resolution from a single recorded hologram with magnification independent of parameters such as propagation distance and wavelength of light, which enables to be used in applications like multi-wavelength digital holography. In addition, this technique offers high noise immunity and eliminates typical problems of holographically reconstructed images such as twin image and speckle. Therefore, we demonstrate by simulations and experimentally results that our approach significantly improves the quality of reconstructed images when compared with conventional techniques. Highlights • An approach for holographic magnification using compressive sensing is proposed. • The technique enables holographic reconstruction even from very noisy holograms. • Improves resolution on magnified image reconstructed from a single hologram. • Reduces typical holography problems such as speckle, twin image and aliasing. [ABSTRACT FROM AUTHOR]

In this paper, a novel image encryption scheme based on quick response code and interference in Fresnel domain is proposed. The framework is asymmetric in nature due to amplitude- and phase-truncation operation of encoded spectrum. The input image is scrambled using Arnold cat map and divided into pixel blocks. Each block is encoded into a quick response code, which are then multiplexed to generate a binary matrix. The phase-truncated binary matrix is encoded into analytically generated two phase-only masks. During decryption the phase-only masks are recombined to yield the binary matrix, which is grouped into quick response codes and decoded into pixel blocks. The pixel blocks are recombined and descrambled to retrieve the original image. Numerical simulations have been carried out to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

A simple scheme to synthesize non-uniform patterns of polarization across the transverse section of a beam is proposed with the standard materials in an undergraduate optics laboratory. The experiment is based on the superposition of two orthogonally polarized fields obtained by using a Fresnel biprism and dichroic polarizers. Although no interference pattern appears in the superposition area, a non-uniformly totally polarized field is synthesized. Analytic expressions for the Jones vector and Stokes parameters of the output beam are calculated and, in the process, students can cement their knowledge about the representation of polarized light with these formalisms. The experimental polarization pattern is either obtained from intensity measurements with a CCD camera or measured directly with a commercial polarimeter modified with a pinhole. This experiment will help students discover an easy way to vary the state of polarization across the transverse section of a light field. [ABSTRACT FROM AUTHOR]

Abstract Interband-transition-induced absorption of gold films limits its color rendering in the blue part of the visible spectrum. In this work, we investigate extending the color of ultra-thin gold film to the blue region via Fabry-Pérot-Cavity-Resonance-Enhanced reflection. Systematic experiments and simulations were conducted to demonstrate the color variation of the Fabry-Pérot cavities. By choosing the appropriate dielectric thickness, colors covering the whole visible range including blue color were realized. The electronic field and absorbed power distribution were analyzed to understand the origin of the blue color. A multi-layer Fresnel reflection equation was employed to explain the whole color variation of this structure and the theoretical calculations were in agreement with both simulations and experimental results. Our work provides an approach to achieve blue color for gold and may have potential applications in surface decoration and functional optical elements. [ABSTRACT FROM AUTHOR]

A new method is proposed for the antenna aperture illumination design on microwave wireless power transmission. Bezier curves are used to describe the aperture amplitude distributions. By optimizing the coordinates of the associated Bezier points, an aperture distribution yielding the maximum beam collection efficiency (BCE) can be achieved. Moreover, edge tapers can be easily controlled by the Bezier curves. The proposed method shows its effectiveness from carrying out extensive numerical experiments on different Fresnel parameters as well as edge taper constraints. The results show that larger aperture power coefficients obtain with a little sacrifice of BCEs when larger edge taper constraints are considered. Besides, the peak lobe irradiated outside the rectenna can be suppressed as well. [ABSTRACT FROM AUTHOR]

This work demonstrates an interferometric technique to estimate the reflected powers from dielectric interfaces and the reflection coefficient using the Fresnel equation for measurement of the refractive index (RI) of liquid samples. It uses low-coherence common-path optical interferometry that is commonly used for optical imaging. A uniquely designed optical fiber tip generating a high-quality non-diffractive Bessel beam probes liquid samples in a glass container non-invasively. The light reflected from different interfaces of the container is recollected by the same optical fiber tip. The reflected beams interfere with the reference beam generated at the fiber tip itself. This interference spectrum is further processed using fast-Fourier transform to measure reflected powers from the respective interfaces. The acquired powers are used to solve the Fresnel equation to find RI of liquid samples. As a proof of concept, experiments have been performed on several liquid samples including turbid media such as blood. This non-invasive interferometric technique could also be an ideal example confirming the Fresnel equation for reflection of light. Unlike other optical fiber-based RI sensors, this technique does not require temperature compensation. The method can be employed for inspection of the production process in terms of RI in pharmaceutical and chemical process plants, etc. [ABSTRACT FROM AUTHOR]

Water surface visualization is an important research topic in computer graphics. This paper presents a novel method of water surface simulation by Secondary Distorted Textures (SDT), which realistically simulates and visualizes the reflection and refraction of calm water in real-time using current consumer-level hardware. The proposed method renders water surface using two stages of texture maps. 1. The first texture map stores the 3D geometries’ perspective reflection with respect to 3D perspective view; 2. The second texture map stores the distortion results of the first reflection map with lighting effects. Perlin noise is used to generate random height map. Reflection and refraction are obtained and stored in the secondary distorted texture map with Fresnel effects for each frame. At rendering pass, the SDT is directly tiled on water surface. This paper also discussed the rendering of transparent geometry, which have view-dependent of lighting effects features. Experimental results demonstrated that our method can render realistic geometry nearby dynamic water surface at the frame rates of 70-100 FPS by NVIDIA Quadro k5000 graphic card. The existing texture mapping and bump mapping methods were compared for illustrating that our method produced high realistic water surface without aliasing reflection. [ABSTRACT FROM AUTHOR]

The objective of this paper is to investigate theoretically a solar driven 60 kW absorption cooling system. The system is constituted of a combined ejector single-effect absorption cycle coupled with a linear Fresnel solar concentrator and using water/lithium bromide as working fluid. The combined ejector single-effect absorption cycle exhibits high performances, almost equal to that of double-effect absorption device. However, higher driving heat temperatures are required than in the case of conventional single-effect machines. A mathematical model is set up to analyze the optical performance of the linear Fresnel concentrator. Simulations are carried out to study the overall system performance COPsystem and the performances of the combined absorption machine COPcycle for generator driving temperatures and pressures in the ranges 180°C – 210°C and 198 kPa – 270 kPa, respectively. Further, the effect of operating parameters such as the cooling medium and chilled water temperatures is investigated. A maximum cycle performance of 1.03 is found for a generator pressure of 272 kPa and chilled and cooling water temperatures of 7°C and 25°C, respectively. A case study is investigated for a typical summer Tunisian day, from 8:00 to 18:00. The effect of ambient temperature and solar radiation on cycle and system performances is simulated. The optical performances of the concentrator are also analyzed. Simulation results show that between 11:00 and 14:00 the collector efficiency is 0.61 and that the COPcycle reaches values always higher than 0.9 and the COPsystem is larger than 0.55. Globally the performances of the investigated cycle are similar to those of double-effect conventional absorption system. [ABSTRACT FROM AUTHOR]

Based on the extended Huygens–Fresnel principle, an analytical expression for the cross-spectral density of optical coherence lattices (OCL) in oceanic turbulence is derived. With the help of this expression, we investigate the propagation of OCL in oceanic turbulence. In order to increase underwater optical communication distance, we investigated the effects of source parameters, such as lattices constant, wavelength and beam width, on intensity distribution of OCL in oceanic turbulence. Results indicate that the light intensity received by receiver increases with the increase of lattice constant, the increase of beam width and the decrease of wavelength, which may have some potential applications in underwater optical communication. [ABSTRACT FROM AUTHOR]

Highlights • The incident angle modifiers of a linear Fresnel collector are calculated. • Analytical and simple expressions are suggested and validated. • Six different collectors are used for validating the developed model. • The deviations are generally low and up to 5%. • The developed formulas can be used also for optimization procedures. Abstract Linear Fresnel reflector is one promising solar concentrating technology for medium and high temperatures (200–400 °C) because of its simple design and its low cost. However, the greatest drawback of this collector is the increased optical losses and thus the emphasis is usually given to this issue. In this direction, the objective of this work is the development of analytical expressions for the incident angle modifiers of a linear Fresnel reflector for the longitudinal and the transversal directions. The goal is to create a simple and accurate formula for all the possible solar angles ranges. The developed equations are based on reasonable assumptions and on the geometric analysis of a simple collector with flat primary mirrors. The developed equations are tested with literature data from other studies and from commercial collectors. It is found that the developed equations lead to accurate results with mean deviations up to 5%. The developed analytical expressions can be used for the quick calculation of the optical performance of a linear Fresnel reflector, as well as they can be used for the geometry optimization of the collector. [ABSTRACT FROM AUTHOR]

Highlights • A linear Fresnel reflector is examined on daily, monthly and yearly basis. • The collector is examined thermally and optically with SolidWorks Flow Simulation. • The mean yearly incident angle modifier is found to be 37%. • The optimum operating temperature level is close to 450 K exergetically. • This collector operates efficiently from March up to September. Abstract The main objective of this study is to investigate the daily performance of a linear Fresnel reflector in energetic and exergetic terms. The collector is designed and examined in SolidWorks Flow Simulation in order to obtain the optical and thermal efficiency curves. These data are inserted in a developed numerical dynamic model for the prediction of the daily performance of the solar collector which is coupled to a storage tank. The collector has total aperture 27 m2, concentration ratio 20.46 and the storage tank volume is 3 m3. The system is investigated for twelve typical days, one for each month, and its yearly performance is determined by taking into consideration only the sunny days of every month. According to the final results, the mean yearly incident angle modifier is found to be 37% while the maximum yearly exergy efficiency is 8.0% when the system starts with 450 K inlet temperature at the morning. For this case, the mean yearly thermal efficiency is found to be 18.5% and also June is the month with the highest thermal and exergy outputs. Furthermore, it is important to state that the mean daily incident angle modifier is found to be the 81% of the maximum daily incident angle modifier for all the months. [ABSTRACT FROM AUTHOR]

We have developed a new, fast, and simple 3-D imaging approach referred to as Simultaneous Azimuth and Fresnel Elevation (SAFE) compounding using a bias-sensitive crossed-electrode array. The principle behind this technique is to perform conventional plane-wave compounding with a back set of electrodes, while implementing a reconfigurable Fresnel elevation lens with an orthogonal set of front electrodes. While a Fresnel lens would usually result in unacceptable secondary lobe levels, these lobes can be suppressed by compounding different Fresnel patterns. The azimuthal and elevational planes can be simultaneously compounded to increase the beam quality with no loss in frame rate. A 10-MHz, $64 \times 64$ element crossed-electrode relaxor array was fabricated on an electrostrictive one-to-three composite substrate to demonstrate the SAFE compounding approach. The electrostrictive composite array has a measured electromechanical coupling coefficient ($k_{t}$) of 0.62 with a bias voltage of 90 V and a measured two-way pulse bandwidth of 60%. The electrical impedance magnitude of array elements on resonance was measured to be $90~\Omega$ with a phase angle of −35°. Radiation patterns were simulated showing a −6-dB beamwidth of $330~\mu \text{m}$ with secondary lobe levels suppressed more than −60 dB in the azimuth dimension, and a −6-dB beamwidth of $450~\mu \text{m}$ with secondary lobe levels suppressed to −50 dB in the elevation dimension after 64 compounds. Experimental radiation patterns were collected and found to be in good agreement with simulations. Experimental 3-D images of wire phantoms were collected using a Verasonics experimental ultrasound system. [ABSTRACT FROM AUTHOR]

A tensor approach to simulate and predict the transverse intensity and distribution of a two-point correlation of beams of arbitrary shape and coherence through atmospheric turbulence has been derived on the basis of the extended Huygens–Fresnel principle. The validity of this approach is verified by comparing the reconstructed intensity and second-order correlation of symmetric points in the output plane of a Gaussian Schell-model beam with calculated results from analytic formulae. An example illustrates how this tensor approach can be applied to beams blocked by finite apertures in the atmospheric propagation. Our approach provides an efficient and universal numerical model to manage the turbulent propagation of various optical sources. This approach can be useful in long-distance imaging and optical communication. [ABSTRACT FROM AUTHOR]

In this paper, closed-form (Cf.) expressions for the backscattered radar cross section of cylindrically curved perfect electrically conducting plates have been derived. These Cf. expressions have been validated using full-wave integral equation-based solver for several radii (angles) of curvature of the curved plates. Here, the plane wave is incident symmetric with respect to the edges of the curved plate for both convex and concave side incidence cases. Cf. expressions include the contributions due to the reflected rays and the single edge diffracted rays for the convex side incidence case. In addition, the double edge diffracted rays have also been considered for the concave side incidence. The Cf. expressions have been demonstrated to be valid for all angles of curvature for the case of convex side incidence, whereas for the concave side incidence case, they are applicable up to 90° curvature, beyond which the higher order and surface diffracted rays become significant due to the concave nature of the curved plate. [ABSTRACT FROM AUTHOR]

A novel optical image encryption method is proposed by using Dammann grating and biometric array keys. Dammann grating is utilized to create a 2D finite uniform-intensity spot array. In encryption, a fingerprint array is used as private encryption keys. An original image can be encrypted by a scanning Fresnel zone plate array. Encrypted signals are processed by an optical coherent heterodyne detection system. Biometric array keys and optical scanning cryptography are integrated with each other to enhance information security greatly. Numerical simulations are performed to demonstrate the feasibility and validity of this method. Analyses on key sensitivity and the resistance against to possible attacks are provided. [ABSTRACT FROM AUTHOR]

Abstract: We study the chiroptical properties of one‐dimensional photonic crystals supporting superchiral surface waves by introducing a simple formalism based on the Fresnel reflection matrix. We show that the proposed framework provides useful insights on the behavior of all the relevant chiroptical quantities, allowing for a deeper understanding of surface‐enhanced chiral sensing platforms based on one‐dimensional photonic crystals. Finally, we analyze and discuss the limitations of such platforms as the surface concentration of the target chiral analytes is gradually increased. [ABSTRACT FROM AUTHOR]

Theoretical analysis of a linear Fresnel reflector solar concentrator powered Rankine thermodynamic cycle utilizing supercritical CO2 as a working fluid is presented. The system model consists of a linear Fresnel reflector solar concentrator with trapezoidal cavity absorber, a power generating turbine, a heat recovery system and a feed pump. The effects of the principal parameters of the supercritical CO2 on the performance of the system are investigated numerically by means of MATLAB simulation program under the assumed design conditions. It is shown that the key performance parameters, such as concentrator area, concentrated power reached to the absorber, CO2 flow rate have significant effects on the thermal performance of the supercritical CO2 in the trapezoidal cavity absorber. Analytical simulations show that the proposed system may have 0.3-0.38 kW power generation and 2.0-2.14 kW heat output for the various mass flow rates of the CO2. The results recommend the potential of this new system for applications to electricity power and heat power generation. [ABSTRACT FROM AUTHOR]

Solar collectors—especially Linear Fresnel Reflectors—are one of the main implements to utilize the energy of sun light. The receiver cavity of the collector is recognized as an important component of each concentrating solar power plant. In this study, the heat transfer rate and heat loss in a trapezoidal cavity of the linear Fresnel reflector are analyzed. The calculations are performed for steady-state, laminar model in which temperature-dependent density is assumed for the air inside the cavity. The effects of the cavity angle and the effect of the tube size are evaluated, in various models. DTRM radiation model is employed for the simulation, while considering radiation, conduction and convection heat transfers are as the boundary conditions. Finally, it will be observed that by increasing the cavity angle, the total value for heat transfer rate is increased, but the heat absorbed by each tube is decreased. The results also show that the tube size is less effective on heat transfer rate compared to the cavity angle. [ABSTRACT FROM AUTHOR]

In this paper, a current density convolution finite-difference time-domain method is extended to study the electromagnetic wave propagation and absorption in inhomogeneous magnetized plasmas. First of all, we analyze the wave propagation in homogeneous magnetized plasmas for arbitrary magnetic inclination angle. Then, we studied three types of plasma absorption, including plasma resonance, electron cyclotron resonance, and upper hybrid resonance in homogeneous and inhomogeneous magnetized plasmas. This model is applied to simulate the heating mechanism during ionospheric modification experiments by high-power high-frequency radio waves. These results have important implications for the interpretation of physical mechanisms for the interaction of high power radio waves with magnetized ionospheric plasmas and design of future experiments. [ABSTRACT FROM AUTHOR]

A Cauchy problem for the time-dependent radiative transfer equation in a three-dimensional multicomponent medium with generalized matching conditions describing Fresnel reflection and refraction at the interface of the media is considered. The unique solvability of the problem is proven, a Monte Carlo method for solving the initial-boundary value problem is developed, and computational experiments for different implementations of the algorithm are conducted. [ABSTRACT FROM AUTHOR]

A numerical study is carried out to determine the heat losses caused by natural and forced convection as well as radiation from the parabolic secondary receiver of a Solar Linear Fresnel Reflector system. The geometric configuration considered corresponds to an absorber tube placed in an open aperture. Thermal performance of the receiver with the acceptance angle θ a = 45°, truncation point H/W = 0.6, focal position of the absorber f = 7.9 m and gap between the secondary reflector and absorber tube (G) to the height of the secondary reflector (H) at G/H = 0.14 are considered for the thermal analysis. Thermal losses from the reflector over a wide range of temperature ( 373 K − 773 K ) , diameter ratio ( 0.14 − 0.27 ) and emissivity ( 0.01 − 1 ) are analysed. Realistic conditions including the effects of wind and commerically available absorber diameter and emissivity values are considered to assess the performance of the receiver. Investigation is carried out to determine the heat losses at wind velocities up to 10  m/s. Nusselt number correlations are proposed for determining the heat losses from a solar cavity open aperture with CPC profile. The proposed correlations are functions of the temperature ratio ( T h / T ∞ ) , diameter ratio, emissivity, Grashof number and Reynolds number and they are very useful for predicting the heat losses from the linear receiver of a typical solar LFR system. [ABSTRACT FROM AUTHOR]

Fresnel coefficients obtained when solving the problem of wave propagation through the interface of two elastic media and expressions for components of the elastic-distortion tensor allow one to study the character of dynamic deformations at the interface. Deformation modes different from zero at the interface of the elastic media under the slip-contact condition have been determined. Dependences of deformation amplitudes at the interface on the wave incidence angle and parameters of the adjacent media for incident longitudinal and transverse waves have been constructed and analyzed. [ABSTRACT FROM AUTHOR]

In this paper, we have calculated the band structure of an instance of one-dimensional photonic crystal (1DPC) composed of double-layered dielectrics via the Fresnel coefficients method. Then, we supposed the addition of a thin layer of graphene to each dielectric layer and the given photonic crystal (PC) composed of dielectric-graphene composites. The effects of graphene layers on the PC band structure were evaluated. We found out that according to the effective medium theory unlike the TE polarization, the electric permittivity of the dielectric layers changed at TM polarization. As such, the band structure of PC for TM polarization changed, too. Moreover, instead of bandgap related to 'zero averaged refractive index' an approximately omnidirectional bandgap appeared and a related bandgap to ' = 0' disappeared. In addition, a new angular gap branch appeared at a new frequency at TM polarization in which the width of gap increased as the angle increased. [ABSTRACT FROM AUTHOR]

For a ТМ or ТЕ quasiplane wave normally incident on a tangentially magnetized dielectric layer, the application of an external static electric field along the normal to the layer plane results in the appearance of the spatial and angular Goos-Hänchen effects for a beam transmitted through the layer, as well the angular Goos-Hänchen effect for a reflected highly directional wave beam. [ABSTRACT FROM AUTHOR]

In this paper a modified composite zone plate (MCZP) based on the Thue-Morse and Fresnel zone plates is proposed. The focusing properties of the MCZPs are studied theoretically and experimentally. Along the propagation direction the MCZP generates three main foci with approximately equal intensity. The point spread functions (PSFs) at the separate focal planes of the three foci have almost the same ratio between the energy in the diffraction limit region of the PSF plane and the energy in the entire PSF plane. The MCZPs have potential applications in the fields of three-dimensional optical tweezers and multi-plane lithography. [ABSTRACT FROM AUTHOR]

A novel cascade organic Rankine cycle (ORC) configuration involving ejector refrigeration loops is introduced to produce liquefied natural gas (LNG) and power. Linear Fresnel solar collectors are utilized to supply the required energy of the system. Exergy, exergoeconomic and exergoenvironmental concepts are undertaken upon the concerned system during a year. A multi-objective optimization procedure based on a fast and elitist non-dominated sorting genetic algorithm (NSGA-II) is conducted and three decision makers, i.e. Shannon Entropy, LINMAP and TOPSIS methods are employed to find the ultimate optimum thermodynamic, economic and environmental impact performances from Pareto frontier obtained by NSGA-II with corresponding design variables of the system. As a result, the solar radiation increment affects the efficiencies negatively and the lowest total product cost and EI rates are obtained within 78.588 $/h in May and 77.544 Pts/h in December, respectively. The optimum energy and exergy efficiencies are achieved respectively by about 7.3% and 12.6% in relation to the base point using Shannon Entropy decision maker. Moreover, the economic and EI performances of the system are improved respectively within 1.2% and 1.1% through the LINMAP method so that the highest reduction may be obtained for the cost and EI per unit exergies of LNG within 0.4200 $/GJ and 7.36 Pts/GJ, respectively. [ABSTRACT FROM AUTHOR]

In this paper, a three-dimensional powder bed model, considering Fresnel absorption of S and P polarization and multiple reflections, has been reasonably proposed. The coupled interaction of the powder bed particles and laser beam energy, mainly focusing on the laser absorptivity and irradiance distribution on powder particles surface and the influence of particle size distribution on the single track molten pool, during selective laser melting additive manufacturing of AlSi12 material using the ray-tracing calculation have been thoroughly evaluated. The results indicated that the energy absorbed on the powder bed was significantly larger than that on the dense flat material and, the distribution of the irradiance was gradually decreasing from the center to the edge of the interaction region. Meanwhile, the powder bed absorptivity and the irradiance of central powder particle of powder bed were found to be sensitive to the powder particle sizes. The absorptivity of the AlSi12 powder bed decreased from 0.222 to 0.123 for the particle size ranging from 10 μm to 60 μm, respectively. The contour of the irradiance distribution continuously changed from the uniform pattern to the double peak and terminally to the single peak for the increase in the particle size. The influence of the particle size on the cross section of the single-track morphology was experimentally studied, having a good agreement with the results predicted by the simulation. [ABSTRACT FROM AUTHOR]