Change In Reflection Coefficient Research Articles

Reflection of Light from a Layer of a Hyperbolic Metamaterial

We have investigated specific features of reflection of a plane elliptically polarized electromagnetic wave that is incident from an isotropic nonabsorbing medium onto a plane-parallel layer of a hyperbolic metamaterial the optical axis of which is parallel to the interface, while the diagonal values of the dielectric permittivity are smaller than the dielectric permittivity of the isotropic medium. Depending on the angle of incidence and the angle between the plane of incidence and the optical axis of the hyperbolic metamaterial, regimes are possible in which either an ordinary wave or an extraordinary wave, or both waves decay outward from the interface, and, in the latter case, for some values of these angles, the decay may be nonexponential. For these three regimes, the reflection coefficient from a layer of an ITO/Ag nanostructure has been calculated numerically. Upon variation in the polarization of the incident wave, the energy reflection coefficient changes from minimum to maximum values, which depend on the layer thickness. As distinct from conventional anisotropic media, in all cases, the maximum value of the reflection coefficient tends to unity with increasing layer thickness. If the amplitude of an ordinary or extraordinary wave does not decrease outward from the interface boundary, the minimal reflection coefficient periodically turns to zero with increasing layer thickness due to interference. In the case in which both waves decay, with this decay being nonexponential under certain incidence conditions, the minimum reflection coefficient turns to zero at a certain layer thickness, and then tends to unity.

Investigating changes in wave reflection coefficient and upward coefficients and wave force in lattice breaker using Flow 3D numerical model

Investigating changes in wave reflection coefficient and upward coefficients and wave force in lattice breaker using Flow 3D numerical model

Effects of added Secondary Dielectric material on the Performance of a Microstrip patch Antenna

Micro strip patch antennas are normally fabricated on the surface of a dielectric material. Due to various reasons, the replacement of the surface material and modifications in area are not possible, once the antenna is fabricated. In some cases, the operating frequency and bandwidth of the antenna needs to be altered without changing the substrate. This paper investigates a dual dielectric patch antenna and analyses the performances of the antenna under the combined dielectric layers inside the cavity. Initially, a patch antenna is designed for a resonant frequency with a widely used dielectric material, FR4 and after which another dielectric layer is added. The performance of the antenna is evaluated using Method of moments solver in ADS software. The thickness sharing percentage of the secondary dielectric material was linearly increased from 10% to 90% in simulation. The analysis shows an emergence of another band due to the introduction of secondary dielectric layer. Measurements also confirm the simulation results and notable change in reflection coefficient with bandwidth enhancement is observed.

Unidirectional Invisibility Induced by Complex Anti-Parity–Time Symmetric Periodic Lattices

Complex anti-parity-time symmetric periodic lattices, in a wide frequency band, can act as unidirectional invisible media. The reflection from one end is suppressed while it is enhanced from the other. Furthermore, unidirectional laser points (ULPs) which correspond to the poles of reflection from one end, arise in the parameter space composed of the permittivity and angular frequency. The phase of the reflection coefficient changes sharply near the ULPs. Subsequently, large lateral shift which is proportional to the slope of phase could be induced for the reflected beam. The study may find great applications in unidirectional invisibility, unidirectional lasers and highly sensitive sensors.

Hydrodynamic performance of a novel oscillating-water-column breakwater with a horizontal bottom-plate: Experimental and numerical study

Abstract In this study, the hydrodynamic characteristics of a novel oscillating water column (OWC) breakwater with a horizontal bottom-plate is numerically and experimentally investigated. A viscous fully nonlinear numerical wave tank (NWT) solved by the open source package OpenFOAM is established under laminar flow conditions. After comparing the numerical results with the experimental ones, the well-validated numerical model is further employed to investigate the effects of the length of horizontal bottom-plate (D), the immersion depth of back-plate ( d 2 ), the water depth (h) and the wave height (H) on the reflection ( C r ) and transmission ( C t ) coefficients, dissipation coefficient ( C d ) and column-confined energy coefficient ( C e ) of the breakwater. The results show that lengthening the bottom-plate can effectively increase the energy dissipation and then lead to lower reflection and transmission coefficients, and a smaller draught of the back-plate can also increase energy dissipation. The water depth has insignificant influence on the hydrodynamic coefficient of long waves, but influences the breakwater performance in short waves. The variation of wave height mainly contributes to the change of reflection coefficient.

The Study of 4D Converted-Wave Seismic Interpretation Methods for CO2 Sequestration

CCUS technology is currently the most effective way to slow greenhouse gas emissions. CO2 geological storage technology is the core of CCUS technology. Combining 4D seismic technology with CCUS (Carbon Capture, Utilization and Storage) technology is the most effective way to confirm security of CO2 sequestration in CO2 geological storage project. However, conventional 4D seismic method mainly study on time-lapse PP reflection information which could not separate fluid saturation and pressure. The potential of using PS wave to monitor CO2-EOR and security of CO2 sequestration has not been explored. Our study focuses on 4D PS-wave. In order to improve our understanding of converted wave in utilization during CO2-EOR and CO2 sequestration. We built two-layer based models in both porous and fracture mediums before and after CO2 injection, and combining with rock physics data and well log data, we got the change rules of elastic parameters of mix fluids changing with injecting pressure before and after CO2 injection. We analyze the changes of PS1 and PS2 AVA curves, and we studied the relationship between time-lapse seismic data with pore pressure and CO2 saturation, then we could confirm the influence of pore pressure and CO2 saturation on 4D multicomponent seismic data. And then, we combined 4D converted wave forward models and 4D PP wave forward models. We studied the effect of pore pressure and fluid saturation on the change of PP-wave reflection coefficients and PS-wave reflection coefficients separately. Combined with the results of fluid substations in different pore pressure and fluid saturation, we could explore the effect of pore pressure and fluid saturation on P-wave velocity, S-wave velocity and density separately. We could establish the relationship between change of PP-wave reflection coefficients and PSwave reflection coefficients and change of pore pressure and fluid saturation. Thus, we computed the change of pore pressure and fluid saturation with 4D PP and PS seismic data.

Applying full-azimuth depth processing in the Local Angle Domain for Frequency Absorption versus Azimuth) (FAVAz) analysis to predict permeable, oil-saturated fractures

Predicting the permeability of fractured reservoirs is valuable for both reservoir assessment and drilling planning. Characterization of such systems requires advanced amplitude analysis, mainly based on seismic imaging results of the recorded wavefield. A significant amount of work has been done on the subject over the past few decades. Thomsen (1995) showed the effect of seismic amplitude variations for different fractured media. Pisetsky and Fedorov (1998) showed the influence of the size of cracks and the seismic wave length on the change of reflection coefficient. Ruger (1998) used the Zoeppritz equation to formalize the reflection coefficient variation as a function of the wavefront azimuthal direction with respect to the fracture azimuth. An approximation of the latter by Tsvankin and Grechka (1998) became the basis for AVAz inversion analysis. Studies have also been performed on frequency absorption properties of fluid-saturated and dry fractured layers. Goloshubin (2002) observed that reflections are stronger for fluid-saturated fractured layers than for dry fractured layers at low-frequency ranges. Geek (2008) studied high-frequency absorption vs. wavefront azimuth for dry fractures in the acoustic frequency range for P-waves, and showed that the absorption is insensitive to the azimuth for S-waves. Kozlov (2006) made a comprehensive generalization of the physics of frequency absorption effects in the case of dry and fluid-saturated fractures. In his study he showed that in fractured reservoirs, high fluid permeability has an observable effect of absorption of the low-frequency spectral range for reflected P-waves. This observation was also noted in several exploration areas of Western Siberia (Upper and Middle Jurassic deposits, Davydova, 2004). Despite the research detailed above, predicting and delineating oil-saturated fracture systems using low-frequency absorption analysis has not yet become a standard practice in the industry. This is in large part due to the approximation made by standard processing and imaging methods in creating azimuthal data. To make this process more effective, a true amplitude full-azimuth imaging procedure that decomposes the fully recorded seismic wavefield in the local angle domain is required. This procedure is carried out in-situ, in the depth migrated domain, preserving both reflection azimuth and structural azimuth. Such a technology is the ideal solution for extracting the main faults, building the Structural Tectonic Skeleton (STS), exposing the main fracture orientation, and eventually measuring anisotropic frequency absorption effects. This paper presents a study of carbonate reservoirs in an oilfield in the Middle Volga region of Russia, and suggests a workflow based on imaging and processing in the Local Angle Domain to predict prospective areas of oil-saturated permeable fractured reservoirs.

Отражение света от слоя гиперболического метаматериала

In this paper, we study the features of reflection of a plane elliptically polarized electromagnetic wave falling from an isotropic non-absorbing medium on a layer of hyperbolic metamaterial (HMM) the optical axis of which is parallel to the interface and the diagonal values ​​of the dielectric constant are less than the dielectric constant of an isotropic medium. It is shown that changing the values of the angle of incidence and the angle between the plane of incidence and the optical axis of the HMM one can realize different regimes of refrection: when ordinary ( or extraodinary) wave or both waves decay from the interface. Meanwhile, in the latter case, for some values ​​of the angles the decaying can be nonexponential. For these three cases, numerical calculations of the reflection coefficient from the ITO / Ag nanostructure layer are performed. When the polarization of the incident wave varies, the energetic reflection coefficient changes from minimum to maximum values which depend on the layer thickness. Unlike usual anisotropic media, in all cases the maximum value of the reflection coefficient tends to unity with increasing the layer thickness. When the amplitude of the ordinary or extraordinary wave does not decrease from the interface, the minimum reflection coefficient periodically vanishes with increasing layer thickness due to the interference. In the case when both waves decay, and under some conditions the incidence is not exponential, the minimum reflection coefficient vanishes at a certain layer thickness, and then tends to unity.

Calculation of Peak Particle Velocity Caused by Blasting Vibration in Step Topography

High ground vibrations not only adversely affect the integrity of the structures in a mine area but also create inconvenience for the nearby population. In order to protect the Sanyou Mine slope in Tangshan, China from blasting vibration, the peak particle velocity in step topography must be accurately calculated. At present, the reflection coefficient of the stress wave at free interface is not considered in the equation for calculating the peak particle velocity in step topography. Therefore the accuracy of the peak particle velocity calculation is decreased in the side direction when the reflection coefficient changes. In this study, a 3D finite element analysis was employed for modeling of the blasting vibration. A series of field-testing experiments was conducted to measure the peak particle velocity. Then the reflection coefficient of the stress wave was calculated. Based on this, the principle of the peak particle velocity in step topography was explained. In addition, the application range of the equation in step topography was determined and a new equation for peak particle velocity calculation in step topography is proposed based on the numerical simulation analysis and field-testing experiment.

Mathematical Model for Diagnosing Strains by an Optical Fiber Sensor with a Distributed Bragg Grating According to the Solution of a Fredholm Integral Equation

A mathematical model for the diagnostics of strain distribution along a optical fiber sensor (light guide) with a base distributed weakly reflecting fiber Bragg grating is developed. In the initial, undeformed state, the base Bragg grating has a constant period along the light guide. The base uniform Bragg grating is transformed to a nonuniform one as a result of emergence of nonuniform axial strains along the light guide. These changes in the period of Bragg grating lead to corresponding informative changes in reflection coefficients for various lengths of the waves entering into the optical fiber. As a result, the problem on finding the required density distribution function of axial strains along the optical fiber is reduced to solution of the Fredholm integral equation of the 1st kind by using the measured values of derivatives of reflection coefficients at the exit of the light guide. The results of numerical modeling of the spectra of coefficients of reflection from the nonuniform deformed Bragg grating are presented for various model and real distribution laws of diagnosed strains along the light guide.

Microwave Imaging for Breast Tumor Detection Using Uniplanar AMC Based CPW-Fed Microstrip Antenna

A novel, low cost, and comprehensive microwave imaging (MWI) system is presented for the detection of unwanted tumorous cells into the human breast. A compact metamaterials (MTM) artificial magnetic conductor (AMC) surface-inspired coplanar waveguide fed (CPW-fed) microstrip antenna is developed for MWI applications. The initial wideband CPW antenna is designed by the modified oval shape patch and half cycle copper stripe line ground. The antenna is incorporated with two layers uniplanar AMC structure which is composed of a $5\times 5$ array of square modified split ring resonator unit cells to obtain the desired antenna characteristics for the MWI applications like breast imaging. The metamaterial-based AMC structure improves the gain about 5 dB and produces stronger directive radiation characteristics. The enhancement of CPW performance proofs the effectiveness of the double layer MTM-AMC structure and its suitability for MWI. A microcontroller-based PC controlled alternative mechanical imaging system is designed to collect the scattering signal from the CPW-fed antenna. The changes of reflection and transmission coefficient with the variation of dielectric content into the breast phantom structure are analyzed. The remarkable deviation of scattered field is processed by image processing program using Matlab. By using these AMC inspired CPW-fed antenna based microwave imaging, the system can clearly detect the tumor inside the breast phantom.

Changes in the multilayer dielectric coating reflection coefficient change under variations in the medium humidity

Changes in the multilayer dielectric coating reflection coefficient change under variations in the medium humidity

Transverse magnetooptic effect in multilayers applied to mapping of microwave currents

A sensor capable of mapping microwave (mw) currents in semiconductor circuits can be realized by exploiting magneto-optic effects (MO) at transverse magnetization (M⊥) in ultrathin ferromagnetic or ferrimagnetic films. In the sensor, M⊥would be induced in the magnetic film by the fringing fields of mw currents flowing in the semiconductor circuit along the plane of incidence. In this work, an evaluation of MO sensor performance was made for nanostructures consisting of ultrathin Fe layers sandwiched between AlN dielectric layers. The multilayer thin film stacks were grown on Si wafer substrates. The performance of the sensor systems is characterized in terms of magnetization-induced changes in the MO multilayer reflection coefficients, expressed analytically. Sensor configurations which optimize the operation at the laser wavelength of 410 nm, and which are still easy to fabricate, are proposed. Modeling predicts the strongest MO enhancement in a sensor incorporating two Fe nanolayers, each of a different thickness, formed by the layer sequence AlN/Fe/AlN/Fe/AlN/Au/Si. The use of ferrimagnetic hexagonal ferrite films with the in-plane c-axis as an alternative sensor material is also discussed.

A defected ground split ring resonator for an ultra-fast, selective sensing of glucose content in blood plasma

Compact antenna-coupled split-ring resonator-based sensors have been designed, fabricated, and tested for sensing glucose concentration in blood plasma. Both circular and square type metallic ring is integrated along with two monopole antennas upon a dielectric substrate, which exhibits a resonance frequency of 1.9 GHz and 8.3 GHz, respectively. The effect of defected ground plane is also investigated which is observed to produce a deep rejection frequency band with sharp cutoff resonant frequency. The SRRs exhibit a shift in resonant frequency with change in reflection coefficient when subjected to blood plasma with different concentration of glucose.

Six-port microwave system for volatile organic compounds detection

An interdigital capacitor with resonant frequency fres ≈ 8.6GHz coated by comb polymer Pc-based thin film as a sensitive layer was investigated under exposure to different concentrations of various VOCs, such as: acetone, ethanol, methanol, isopropanol, butanol and ethylbenzene in a 0–25ppm concentration range. The measurement system has been significantly simplified due to measurement of the reflection coefficient at a single frequency f0=8GHz, at which the sensor exhibits the largest change in reflection coefficient's magnitude. For the reflection coefficient's measurement a new six-port reflectometer has been developed, which provides an enhanced measurement accuracy for the measurements of reflection coefficients having small magnitudes. The developed detector based on microwave measurements can be utilized in a portable exhaled breath analyzers.

Monitoring of bitumen hardening with a non-destructive ultrasonic shear wave reflection technique

The article presents a possibility of using a non-destructive ultrasonic shear wave reflection technique for monitoring hardening process of bitumen. The technique relies on the use of a new measuring instrument called USWR-4 Hardening meter, which was developed to be applicable directly in situ and has been effectively used for cement-based materials so far. It works on the principle of continuous measurement of change of a shear wave reflection coefficient. Three different types of paving grade and two polymer-modified bitumens were used. Results show that the presented ultrasound technique can effectively track a temperature-dependent hardening process of bitumen.

In-line femtosecond common-path interferometer in reflection mode.

An innovative method to perform femtosecond time-resolved interferometry in reflection mode is proposed. The experiment consists in the combined use of a pump-probe setup and of a fully passive in-line femtosecond common-path interferometer. The originality of this interferometer relies on the use of a single birefringent crystal first to generate a pair of phase-locked pulses and second to recombine them to interfere. As predicted by analytical modeling, this interferometer measures the temporal derivative of the ultrafast changes of the complex optical reflection coefficient of the sample. Working conditions are illustrated through picosecond opto-acoustic experiments on a thin film.

Acoustic Characterization of Patterning Degradation during Wet Etching

Wet etching in photoresist presence is commonly used in MEMS or integrated circuits manufacturing: metal gates [1], or gate oxides patterning [2]. Nonetheless the resist can’t stand a too long exposure to wet chemicals. Indeed, the liquids diffuse through the resist. Then the polymer enters a plasticizing sequence. It swells under the action of polar water and etchant molecules that break the cohesive hydrogen bonds between the polymer chains. The resist stress increases till fractures and blisters appears (figure 1). Hence these phenomena have been characterized by various acoustic means described hereby. First method consists in using a high-frequency echography principle [3]. A ZnO transducer, sputtered on the backside of the silicon wafer emits a 2GHz acoustic wave. The longitudinal wave reflection occurs at the interface between the silicon and the medium on the wafer frontside enabling its characterization by monitoring the transducer electrical impedance (figure 3). In the case of a silicon / air interface, the acoustic wave reflection is total. When air is replaced by water, the reflection is partial and the reflection coefficient value is 0.86. These reflection properties will be modified in the presence of a thin TiN layer coated with a 248nm deep UV resist. As the resist thickness (210 nm) is thin compared with the acoustic wavelengths in the different materials (micrometer range), reflections at each interface cannot be separated (silicon / resist and resist / upper medium) so only one total reflection occurs in the presence of air. Then, the reflection coefficient is measured with water on the resist. Without any resist damage, the reflection coefficient changes from 0.86 to 0.765. This latter value is then modulated by the resist blisters amount due to the modification of the mechanical properties of the silicon / resist interface. Measurements are performed on wafers exposed to SC1 (Standard Clean 1) solutions for different durations (figure 1). The reflection coefficient increases with the blisters apparition (figure 4). By determining the ratio of blisters area on optical microscope images of the resist, the reflection coefficient is theoretically calculated for different blisters mechanical properties (solids, liquids and gas). Experimental and theoretical values perfectly match in the case of gas. This result let us think that gas pockets appeared in the resist during blisters formation. The method sensitivity is excellent and mainly depends on the high contrast between gas and water acoustic impedances. A comparison with two other complementary technics will be made. First, picosecond acoustic will characterize the resist adhesion loss. Its principle is similar to a sonar. The acoustic wave into the sample is supplied by a tunable laser [4], and an echo is generated at each interface enabling its characterization. Finally the scanning acoustic microscopy will monitor the resist blister apparition with a thicker resist. This technic is commonly used to monitor wafer bonding voids in 3D integrated circuits assembly [5]. Conclusion Photoresist degradation occurs during long exposure to wet etching. Resist delamination from substrate and blisters appear after a certain contact duration. This latter is shorter with thin resist, which occurs more and more along the integrated circuits node evolution to maintain photolithography optical requirements. Three acoustic methods have been compared to monitor this degradation. Results show these methods are far better than optical microscopy to detect the resist degradation starting point.

A normalized wave number variation parameter for acoustic black hole design.

In recent years, the concept of the Acoustic Black Hole has been developed as an efficient passive, lightweight absorber of bending waves in plates and beams. Theory predicts greater absorption for a higher thickness taper power. However, a higher taper power also increases the violation of an underlying theory smoothness assumption. This paper explores the effects of high taper power on the reflection coefficient and spatial change in wave number and discusses the normalized wave number variation as a spatial design parameter for performance, assessment, and optimization.

Dielectric and Microwave Properties of Natural Rubber Based Composites Containing Fullerene Black

It is expected that filling a rubber with a small amount of fullerene could lead to a new set of properties, bringing to the composite advantages over the rubbers in use. In the present work, the dielectric and microwave properties of natural rubber (SMR10) based composites containing various concentration of fullerene black (0-7,5 phr), rich in fullerenes (7,5%) were investigated in the 1-12 GHz frequency range. It has been established that within the range used for the experiments the increasing frequency and fullerene filler amount lead to an increase in the values of relative dielectric permittivity, dielectric loss angle tangent, reflection coefficient and attenuation of electromagnetic waves, while the values for shielding effectiveness get lower. That is due to the fact that under the experimental conditions the change in the reflection coefficient is greater than that in the attenuation of electromagnetic waves. The dielectric properties of the composites (especially the dielectric loss angle tangent) are more affected by fullerene black filler than their microwave properties. Further change in the properties could also occur at higher concentrations of fullerene black but the cost of rubber compound would be much higher