Change In Reflection Coefficient Research Articles

Detection of adulterants in rice grains by the characteristics of reflection coefficient of the incident microwave signal

Detection of food quality by identifying different adulterants in food products is a grave requirement for the food industry. Various methods of food analysis have been evolved to identify the quality and quantity of impurities but those methods are time-consuming, expensive and laborious. Our research aims at reducing the challenges experienced in these existing methods. Our procedure is to detect food adulterants using a microwave signal and observe the change in reflection coefficient and resonant frequency of the reflected microwave signal. The property of modification of reflection coefficient and resonant frequency of reflected microwave signal from pure rice grains in the presence of adulterants like small stones/pebbles and broken rice is exploited. In this work, the detection and proportion of adulterants, such as stones and low-quality broken rice in fresh rice in varying proportions, have been determined. Adulterants as low as 2% weight of rice are highly detectable utilizing microwave.

Acoustic Design Parameter Change of a Pressurized Combustor Leading to Limit Cycle Oscillations

When aiming to cut down on the emission of nitric oxides by gas turbine engines, it is advantageous to have them operate at low combustion temperatures. This is achieved by lean premixed combustion. Although lean premixed combustion is a proven and promising technology, it is also very sensitive to thermoacoustic instabilities. These instabilities occur due to a coupling between the unsteady heat release rate of the flame and the acoustic field inside the combustion chamber. In this paper, this coupling is investigated in detail. Two acoustic design parameters of a swirl-stabilized pressurized preheated air (300 °C)/natural gas combustor are varied, and the occurrence of thermoacoustic limit cycle oscillations is explored. The sensitivity of the acoustic field as a function of combustion chamber length (0.9 m to 1.8 m) and reflection coefficient (0.7 and 0.9) at the exit of the combustor is investigated first using a hybrid numerical and analytical approach. ANSYS CFX is used for Unsteady Reynolds Averaged Navier-Stokes (URANS) numerical simulations, and a one-dimensional acoustic network model is used for the analytical investigation. Subsequently, the effects of a change in the reflection coefficient are validated on a pressurized combustor test rig at 125 kW and 1.5 bar. With the change in reflection coefficient, the combustor switched to limit cycle oscillation as predicted, and reached a sound pressure level of 150 dB.

ELECTRODYNAMIC ALGORITHM FOR CALCULATING AN ANTENNA ARRAY BASED ON AN INTEGRAL REPRESENTATION FOR A COMMON REGION FIELD

The article is devoted to the study of a new approach in the integral equation method. The solution of the electrodynamic problem is carried out based on conditional selection of the common region in the entire area of electromagnetic field definition. In our previous publications, we proposed an integral equation method based on the selection of a penetrating region for solving the problem of electromagnetic wave diffraction on a periodic structure. The legality of using the proposed approach and its equivalence with the previously proposed approach are shown. In this article, the calculation of an infinite antenna array scanning in the H-plane is carried out. The numerical convergence of the proposed approach for reflection coefficients R10 with increasing order of truncation of the system of linear algebraic equations was studied. It was found that the modulus of the reflection coefficient coincides with the exact solution at M = 1 and subsequently does not change with the growth of M. While the phase of the reflection coefficient changes with the growth of M and when M˃11, the difference between the phase value of the exact solution and the calculated value is less than 1%. That is, for the case of scanning in the H-plane, good convergence of the problem solution was obtained for all scanning angles. The aim of the work is to show that for a certain class of problems of applied electrodynamics, it is possible to apply the integral equation method based on the selection of a common region. The methodology consists in the conditional allocation of a common region in the entire area of electromagnetic field determination and the application of the integral equation method. The scientific novelty is that we have shown the correctness of using a new approach based on the selection of the field of the common region for the calculation of periodic structures in the H-plane. The conclusions can be formulated as follows. It is shown that two approaches can be used to calculate the antenna array in the H-plane: the first based on the selection of the integral representation for the full field of the penetrating region, the second based on the selection of the integral representation for the full field of the common region.

Design and analysis of an energy selective rasorber

Abstract By combining the technique of energy selective surface and frequency selective rasorber, an energy selective rasorber is proposed, which performs selective energy protection in the low communication frequency band (0.8–2 GHz) and wave-absorbing property in the high-frequency band (6–18 GHz). The design consists of two layers, of which the bottom one contains a lumped diode structure for energy selection function in the transmission band, while together with the top layer, they perform a wideband wave absorbing function. The simulated and measured results agree well with each other, and both show good absorption in 6–18 GHz and energy-selective property around 1.86 GHz. That is, when the incident power changes from −30 to 14 dBm, the reflection coefficient changes from below −22 dB to above −2 dB, while the transmission coefficient changes from above −3 dB to below −17 dB.

Longitudinal Hemodynamic Correlates of and Sex Differences in the Evolution of Blood Pressure Across the Adult Lifespan: The Framingham Heart Study.

Background Systolic blood pressure increases with age after midlife, particularly in women, and contributes to development of wide pulse pressure hypertension in middle-aged and older adults. Relative contributions of aortic stiffness and premature wave reflection to increases in pulse pressure remain controversial. Methods and Results We evaluated visit-specific values and change in key correlates of pulse pressure, aortic characteristic impedance, forward and backward wave amplitude, and global reflection coefficient, at 3 sequential examinations of the Framingham Generation 3 (N=4082), Omni-2 (N=410), and New Offspring Spouse (N=103) cohorts (53% women). Data were analyzed using repeated-measures linear mixed models adjusted for age, sex, and risk factor exposures. Pulse pressure increased markedly with age after midlife (age and age-squared terms, P<0.0001), particularly in women (age slope 3.1±0.2 mm Hg/decade higher in women, P<0.0001). In sex-specific models, change in pulse pressure was closely related (all P<0.0001) to baseline (6.7±0.2 and 7.3±0.2 mm Hg/SD in men and women, respectively) and change (11.8±0.1 and 11.7±0.1 mm Hg/SD) in forward wave amplitude, whereas relations with baseline (2.1±0.15 and 2.0±0.14 mm Hg/SD) and change (4.0±0.13 and 3.4±0.11 mm Hg/SD) in global reflection coefficient were weaker. Global reflection coefficient fell as aortic characteristic impedance increased (P<0.0001), consistent with the hypothesis that impedance matching reduces relative wave reflection in the arterial system. Conclusions Proximal aortic stiffening, as assessed by higher aortic characteristic impedance and larger forward wave amplitude, is strongly associated with longitudinal increase in pulse pressure, especially in women, whereas wave reflection has more modest relations.

Monitoring Wear of a Deep Groove Ball Bearing Using Ultrasonic Reflection

Abstract Wear changes the contact state and contact stiffness of the interface between the ball and the outer raceway under the operation of a deep groove ball bearing, resulting in the change of reflection coefficient of the interface. This paper describes a method based on ultrasonic reflection to assess the wear status of rolling element bearings. A deep groove ball bearing wear test was performed and the reflected pulses were collected with a linear ultrasonic probe mounted on the bearing outer ring. The results show as the wear intensity first increases and then decreases from running-in stage to steady wear period, the reflection coefficient of the interface between the outer raceway and ball shows the expected opposite trend. In addition, the ultrasonic measurement of wear state was verified by oil debris monitoring using on-line visual ferrography.

Generation and detection of sound at the effect of femtosecond pulses on a metal film on a dielectric substrate

The excitation of sound by a femtosecond laser pulse in a metal layer on a dielectric substrate has been studied. The modulations of the reflection coefficient of the metal, which arise due to the propagation of sound in it, are described in detail. It is shown that, in addition to oscillations corresponding to odd harmonics of sound waves, oscillations corresponding to even harmonics can be present on the profile of the Fourier image of the reflection coefficient change. The efficiency of even harmonic generation depends on the substrate material and the metal film thickness. The dependence of the reflection coefficient change on time has been studied. It has been established that if the electron heat flux reaches the metal–dielectric interface before the energy of the electrons is transferred to the lattice, then modulations are present both due to sound that occurs at the metal–vacuum interface and at the metal–dielectric interface. The wavelength of probe radiation also affects the reflection coefficient change. If real and imaginary parts of the permittivity at the wavelength of probing radiation are comparable in magnitude, then the Fourier image of the reflection coefficient change contains a smaller number of maxima, and the change in the reflection coefficient over time is accompanied by splitting of peaks.

Enhanced spin Hall effect of light in the PT-symmetric trilayer structure containing epsilon-near-zero materials

We systematically study the spin Hall effect of light (SHEL) in the parity-time (PT)-symmetric trilayer structure containing epsilon-near-zero (ENZ) materials, and design a high sensitivity refractive index sensor with an adjustable sensing range. It is revealed that the SHEL shift in the PT-symmetric trilayer structure is clearly enhanced, which is two orders of magnitude larger than that in the conventional sandwich structure containing ENZ materials. The enhancement of the SHEL shift is attributed to the fact that the change of reflection coefficient induced by the quasi-bound states in the continuum (quasi-BIC) in the former structure is smoother than that induced by the bound states in the continuum in the latter structure. It is further found that when the refractive index of the interlayer dielectric in the PT-symmetric structure is fixed, the SHEL shift is significantly enhanced near the quasi-BIC resonance angle determined by the gain-loss coefficient. Meanwhile, the SHEL shift enhanced by excitation of quasi-BIC is very sensitive to the gain-loss coefficient and the refractive index of the interlayer dielectric. Finally, we design a high sensitivity refractive index sensor with an adjustable sensing range based on the quasi-BIC-enhanced SHEL shift. These studies provide a pathway to enhance the SHEL and may open avenues for the application of optical sensors.

Novel tumor localization model and prediction of ablation zone using an intertwined helical antenna for the treatment of hepatocellular carcinoma.

Hepatocellular carcinoma has been the leading cause of death in recent centuries and with the advent of newer technologies, several thermal and cryo-ablation techniques have been introduced in the recent past. In this regard, microwave ablation has developed into a promising method for thermal ablation technique. However, due to clinical obligations, in-vivo analysis is not feasible and ex-vivo analysis is inaccurate due to changes in the electrical and thermal properties of the tissue. Therefore, in this study, temperature-dependent permittivity, electrical conductivity, and thermal conductivity along with phase change effect due to temperature reaching above 100°C are incorporated using finite element method model. Further, using an intertwined normal mode helical antenna ablation probe, a change in resonant frequency (Δf) and reflection coefficient (ΔS11 ) from the actual value (antenna parameter in the air at 5GHz) is modeled using second-order polynomial curve fitting to predict the surrounding permittivity in the range of 30-70. A maximum deviation of 0.8 value in permittivity from the actual value is observed. However, to obtain a generalized methodology, XG Boost and CAT Boost algorithms are used. Further, since ablation diameter plays a crucial role in achieving optimal tumor ablation, an artificial neural network (ANN) algorithm with three different optimizers is incorporated to predict ablation diameter using five critical parameters. Such an ANN algorithm which can predict the transversal and axial ablation zone may provide optimal ablation outcomes.

Effect of size, shape and scattering factors on electrical resistivity of metallic nanomaterials

In the present work, the author focussed on the electrical properties of nanostructures. A qualitative model is extended to obtain the expression of thermal conductivity of nanosolid. Using the Wiedemann-Franz law, electrical conductivity and then expression of electrical resistivity is obtained. The inclusion of scattering term in the calculation of electrical resistivity of nanosolid is essential. Incorporating the effect of surface scattering and grain boundary scattering, electrical resistivity is calculated for varied shapes and sizes of nanosolids. The electrical resistivity of nanomaterials is found to increase with decrease in size. The increment in electrical resistivity is found different for different shapes as surface atoms in nanosolid varies with shape and also with the change in surface roughness parameter and reflection coefficient. The present study explains the combined effect of shape, size and scattering factors on electrical resistivity of nanostructure. The proposed model results are depicted with available experimental results in figures for comparison. The study helps to identify the solids that possess high figure of merit and have plenty of applications in electronic devices.

Glasses frame‐based wearable antenna design for ultrahigh frequency radio frequency identification and Internet of Things applications using characteristic mode analysis

A novel ultra-high frequency (UHF) radio frequency identification (RFID) passive tag antenna based on a glasses frame is proposed for Internet of Things (IoT) applications. The glasses frame structure is exploited using characteristic mode analysis (CMA) to explore different modes for both 900 MHz and 2.4 GHz frequency bands. The proposed design consists of a glasses metallic frame and a loop for conjugate matching with an RFID chip (Alien Higgs H4). First of all, an already manufactured glasses metal frame structure is simulated in Computer Simulation Technology (CST) Microwave studio using CMA to get CM modes in the required RFID band. After that, a small loop is used along with the RFID chip as a capacitive coupling element to excite modes at 900 MHz by placing it at current minima. Moreover, the proposed tag antenna is also simulated with the voxel head model in CST and there is no significant change in impedance and reflection coefficient. The simulated specific absorption rate (SAR) is 0.5 W/Kg. Furthermore, the tag design is simulated with different glass materials and also with different frame structures to prove the robustness of the proposed solution. This tag design covers the entire US UHF RFID band (902–928 MHz) and features a read range of 2 m, measured using a UHF RFID reader setup with 4 W EIRP. Therefore, this antenna design can be a good candidate for future IoT technologies such as RFID, long range (LoRa), and other IoT applications.

Design of OCSRR-Based Differential Microwave Sensor for Microfluidic Applications

In this article, a high-sensitivity differential microwave sensor based on open comprehensive split-ring resonator (OCSRR) is proposed to extract the complex dielectric constant of liquid samples. An OCSRR structure is etched on the metal plate attached to the upper layer of the substrate. In addition, the outer ring of OCSRR adopts a hexagonal structure to reduce the original capacitance of OCSRR, and the inner ring of OCSRR adopts a rectangular structure to facilitate optimization and obtain the highest electric field intensity. The polydimethylsiloxane (PDMS) microfluidic channel is placed on the side of the outer ring with high electric field intensity and injects different concentrations of water–ethanol mixture. During resonance, the electric field is concentrated along the slit where the microfluidic channel is located. When the liquid sample is injected, the corresponding reflection coefficient changes. The designed sensor is fabricated and tested, and the experimental results are in good agreement with the simulation results. Compared with the previous similar sensors, the sensor can suppress the influence of environmental factors and has an average high sensitivity of 0.88%.

Design and analysis of a CPW ‐fed flexible ultrawideband antenna for microwave imaging of breast cancer

This article presents a novel CPW fed ultrawideband (UWB) antenna for detection of unwanted tumor cells in the human breast. Here, a compact and miniaturized UWB antenna employed with dodecagonal edges is proposed for broadening the bandwidth from 2.26 to 13.71 GHz (measured fractional bandwidth of about 143.39%). The antenna is designed on a durable RT 5880 substrate having 0.254 mm thickness, efficiency of 85% and gain of 3.84 dBi. For its flexibility characterization, the prototype of the fabricated antenna is analyzed in both the flat and bending configurations. The simulated testing is carried out by permitting the antenna to emit radiation in conjunction to the human breast phantom to obtain desired antenna characteristics for the microwave imaging (MI) applications. The changes in reflection coefficient with the variation of dielectric content of the breast phantom structure are analyzed. The suggested antenna for MI technique is apt for human exposure because the antenna bids the highest SAR value of 0.932 W/Kg at 10.6 GHz. Moreover, the proposed antenna is flexible, compact and low-profile with low SAR values that can be useful for breast cancer detection.

Detection of Metal Surface Cracks Based on Liquid Switch Controlled Spoof Surface Plasmon Polaritons

A spoof surface plasmon polaritons (SSPPs) sensor based on liquid switch control is proposed to detect metal surface cracks. The sensor consists of liquid switch controllers and power division structure. The liquid switch consists of a plastic pipe and syringe with water, which is fixed on the branch structure of SSPPs sensor. By filling the plastic pipe with water, the branch cannot transmit signal, which is called “ OFF” state. The branch retransmits signal by pumping water out of plastic pipe, which is called “ ON” state. By switching the “ ON” or “ OFF” state of sensor’s branches, it can control the transmission path of SSPPs sensor, that is, control the sensing area of SSPPs sensor. The detection method is based on the change of reflection coefficient of SSPPs sensor caused by cracks. By switching the states of branches in turn, it can detect whether there is a crack at each branch. The proposed sensor uses liquid switch instead of mechanical movement, which can realize rapid detection in the metallic materials with large surface area. The simulation and experimental results show that the SSPPs sensor can effectively detect metal surface crack with a width of 0.1mm.

Electromagnetic Insights Into Path Loss Modelling of IRS-Assisted SISO Links: Method-Of-Moment Based Analysis

In this paper, we demonstrate the usefulness of MoM (Method-of-Moments) based methods in efficient path-loss modelling for SISO (single-input single-output) communication links assisted by IRS (Intelligent Reflecting Surfaces). Being a full-wave computational electromagnetic tool, MoM is better equipped compared to high-frequency asymptotic methods like PO (Physical Optics), to handle the crucial electromagnetic (EM) effects like: mutual coupling between IRS unit-cells or interactions with spherical wave-front in antenna near-field. Furthermore, in terms of computational speed, accuracy and reproducibility, the MoM-based MATLAB Antenna Toolbox is significantly advantageous to emulate IRS-assisted wireless channels, as compared to the in-house FDTD (finite-difference time-domain) techniques. We consider a SISO system of two half-wavelength dipoles, and use a rectangular array of circular loops loaded with lumped circuit components as IRS. The lumped circuit loading enables us to control the reactance of individual unit-cells, resulting in alteration of IRS reflection coefficient and consequent changes in channel characteristics. Using numerous numerical simulations, we highlight the impacts of various IRS-parameters like: electrical size and number of unit-cells, distance of IRS from the transmitter/receiver as well as mutual coupling, on the path-loss models (both sub-6 GHz and mm-wave).

Study of reflection/transmission behavior of a planar nonlinear dielectric–NID interface

The manuscript is devoted to study the behavior of reflection and transmission from a planar interface of second order nonlinear–linear NID medium. Slowly varying amplitude approximation is used to simplify the solution of nonlinear wave equation. Analysis is conducted by considering imperfect matching case of permittivity for the nonlinear medium. It is noted that behavior of the reflection coefficient changes drastically when the angle of reflection for nonlinear polarization becomes complex. It is also observed that dimension of the NID medium is an effective parameter to control the behavior of coefficients.

DETERMINATION OF THE CHARACTERISTICS OF INVERSION REFLECTING LAYERS IN THE TROPOSPHERE ON CHANGES IN THE SIGNAL INTENSITY ON THE NEAR-EARTH OVER-THE-HORIZON ROUTES IN THE MIDDLE LATITUDES

The methodology for determining changes of altitude, elevation velocity, and reflection coefficient of the elevated inversion layer in the troposphere is examined based on the results of observation of VHF signals on over-the-horizon (OTH) routes. Estimations of the elevation velocity and reflection coefficient of the elevated inversion layers on the results of measuring of the levels of VHF signals in the zone of the near geometric shadow in the middle latitudes and the meteorological sounding data using balloons are obtained.

Total Internal Reflection in an Absorbing Medium

We report the results of a rigorous calculation on the total internal reflection when the second medium is absorbing. A complex dielectric constant given by, \(\hat{\varepsilon }^{\text{Re}} + i\hat{\varepsilon }^{\text{Im}}\) is introduced to represent the effect of the absorption. Starting from Maxwell’s equations, we show that the angle of refraction becomes progressively smaller than \(\frac{\pi }{2}\) with increasing \(\hat{\varepsilon }^{\text{Im}}\). The reflection and transmission coefficients for both of s- and p-polarized incident beams are calculated on the same footing. The absolute value of the reflection coefficient becomes smaller than unity and begins to depend on the incident angle φ with increasing \(\hat{\varepsilon }^{\text{Im}}\). When \(\hat{\varepsilon }^{\text{Im}} = 0\), the phase of the reflection coefficient changes from 0° at the critical angle to −180° at φ = 90°. With increasing \(\hat{\varepsilon }^{\text{Im}}\), the phase becomes less dependent on φ. From a calculation of the time average of the Poynting vector, we confirm that the law of conservation of energy holds at the boundary between the two media.

Coulsonite FeV2O4—A Rare Vanadium Spinel Group Mineral in Metamorphosed Massive Sulfide Ores of the Kola Region, Russia

This work presents new data on a rare vanadium spinel group mineral, i.e., coulsonite FeV2O4 established in massive sulfide ores of the Bragino occurrence in the Kola region, Russia. Coulsonite in massive sulfide ores of the Bragino occurrence is one of the most common vanadium minerals. Three varieties of coulsonite were established based on its chemical composition, some physical properties, and mineral association: coulsonite-I, coulsonite-II, and coulsonite-III. Coulsonite-I forms octahedral crystal clusters of up to 500 µm, and has a uniformly high content of Cr2O3 (20–30 wt.%), ZnO (up to 4.5 wt.%), and MnO (2.8 wt.%), high microhardness (743 kg/mm2) and coefficient of reflection. Coulsonite-II was found in relics of quartz–albite veins in association with other vanadium minerals. Its features are a thin tabular shape and enrichment in TiO2 of up to 18 wt.%. Coulsonite-III is the most common variety in massive sulfide ores of the Bragino occurrence. Coulsonite-III forms octahedral crystals of up to 150 µm, crystal clusters, and intergrowths with V-bearing ilmenite, W-V-bearing rutile, Sc-V-bearing senaite, etc. Chemical composition of coulsonite-III is characterized by wide variation of the major compounds—Fe, V, Cr. In some crystals of coulsonite-III, relics of chromite are observed. The microhardness of coulsonite-III is 577 kg/mm2, the reflection coefficient changes in relation to iron, vanadium, and chromium content.

Wideband microwave multiport-based system for low gas concentration sensing and its application for acetone detection

A microwave system dedicated to low gas concentrations sensing at room temperature is proposed. An optimized transmission line type sensor coated with a thin film, that changes electrical properties under target gas exposure is developed. The sensor’s response, namely its reflection coefficient is measured using a novel wideband multiport reflectometer. The instrument exhibits an advantageous measurement uncertainty, which can be adjusted to precisely measure small reflection coefficient changes over a wide bandwidth. Broadband data is used to extract the system’s response to gas defined as the reflection coefficient’s phase slope over frequency. The developed sensor covered with acetone-sensitive copper-oxide film together with a reflectometer operating over 1.5 GHz – 4.5 GHz band were incorporated in a gas measurement system to test its response to low acetone concentrations in the range of 0.5 ppm – 5 ppm. Due to high sensor’s sensitivity, optimum measurement conditions provided by the dedicated reflectometer and wideband analysis of the collected data, a robust and low-noise signal proportional to acetone concentration is achieved. The tested concentrations result in measured system’s response in the range of 0.02°/GHz – 0.29°/GHz @ 20 °C and 50 % of relative humidity derived with uncertainty of ±0.022°/GHz being 3 times lower than for a commercial instrument. Additionally, humidity dependence, stability, repeatability, reproducibility, and selectivity are investigated.