Reflectivity Measurements Research Articles

The Technique for Manufacturing Flexible Electromagnetic Shields Based on Resistive Materials

The article introduces the technique for manufacturing flexible electromagnetic shields based on resistive materials ( powdered charcoals and sheet foil ), as well as the results of experimental justification of the use prospects of this technique in the development of new functional materials . This justification consisted of : 1) manufacturing of the experimental samples in accordance with the presented technique ; 2) carrying out the measurements of the electromagnetic radiation reflection and transmission coefficient values in the frequency range of 0.7–17.0 GHz of the manufactured experimental samples . It was discovered that flexible electromagnetic shields based on the powdered charcoals manufactured in accordance with the presented technique are characterized by the electromagnetic radiation reflection coefficient values in the frequency range of 0.7–17.0 GHz , reaching –10.0 dB , when electromagnetic radiation reflection coefficient values reach –20.0 dB . Due to this fact it is possible to r ecommend to use them in order to ensure electromagnetic compatibility of radioelectronic equipment and to protect people from exposure to radiation , emitted by such equipment , as well as to hide ground objects from detection in the radar wavelength range .

Effects of nonlinear internal gravity waves on normal-incident reflection measurements of seafloor sediments.

Sonar data acquired by sub-bottom profilers and echosounder systems are widely used to estimate geoacoustic properties of marine sediments. However, the uncertainty of the seabed property estimates caused by water-column variability may limit the application. In this paper, the acoustic focusing and defocusing effects of nonlinear internal gravity waves on normal-incident acoustic reflection measurements are studied. The experiment data were collected in the South China Sea from two transceiver moorings located at two different sites, one of which contained strong nonlinear internal waves (NIWs), while another site did not. The observed reflection intensity variation at the internal wave site varied up to 10 dB. On the other hand, the bottom reflections at the other site without internal waves were stable, and a seafloor sediment sample collected there was analyzed to validate the sediment type inferred from bottom loss. Numerical simulations using ray-tracing and parabolic equation models confirmed the cause of this intensity fluctuation by the acoustic focusing and defocusing of NIWs. This study eventually showed that NIWs may induce a significant bias for geoacoustic property estimates from seabed reflection coefficients.

Investigations on photovoltaic material absorptivity using hyperspectral photoluminescence excitation imaging

Photoluminescence imaging has become a standard method to characterize solar cells. However, performing some quantitative analysis of this technique requires the assumption of uniform local absorptivity, which cannot be directly measured using traditional methods. This study presents a novel approach to measure the local relative absorptivity over a broad spectral range for a perovskite absorber deposited on a charge extraction layer and an electrode. By analyzing the photoluminescence intensity as a function of the incident photon energy, we were able to determine the relative absorptivity of the incident light above the bandgap energy. Additionally, luminescence spectra allow us to accurately assess the absorptivity near the bandgap energy from the reciprocity between absorption and emission. Reflectivity measurements were also performed to further understand the possible limitations of our experiment and to discuss our results. Finally, this method was able to distinguish between variations in the photoluminescence response caused by slight differences in the local film thickness and changes in the local carrier lifetime.

Особенности и эффективность наносекундной лазерной абляции высокоуглеродистой стали сканирующим пучком импульсного излучения Yb:YAG лазера

The experiments results on the ablation of high-carbon (> 97 % Fe, 1.3 % C) and low-carbon (> 97 % Fe, 0.3 % C) steel targets by a nanosecond pulse laser radiation scanning beam are presented. The dependence of the depth and energy efficiency of ablation on the power density in the range q = 4·108 – 1010 W/cm2 has been determined. It has been established that the maximum efficiency of material removal is achieved at q = 4·109 W/cm2 for a high-carbon steel target and in the range q = 7·108 – 5·109 W/cm2 for a low-carbon steel target. The size distribution of ejected microparticles was determined. It has been established that a back flow of particles occurs upon irradiation of high-carbon steel and the flow origin mechanism is associated with nanosized condensate particles. Based on the reflectivity measurements and the electron microscopy microstructure study of the irradiated surface, it has been suggested that the mechanism for the higher efficiency of ablation of high-carbon steel compared to low-carbon steel is the condensation process of supersaturated carbon vapors on the target surface that increases the irradiated target surface absorptivity and, consequently, the material removal efficiency of the subsequent scanning pass is increased.

Design and Analysis of a Network Traffic Analysis Tool: NetFlow Analyzer

A network analyzer can often comprehend many protocols, which enables it to display talks taking place between hosts over a network. A network analyzer analyzes the device or network response and measures for the operator to keep an eye on the network’s or object’s performance in an RF circuit. The purpose of the following research includes analyzing the capabilities of NetFlow analyzer to measure various parts, including filters, mixers, frequency sensitive networks, transistors, and other RF-based instruments. NetFlow Analyzer is a network traffic analyzer that measures the network parameters of electrical networks. Although there are other types of network parameter sets including Y, Z, & H-parameters, these instruments are typically employed to measure S-parameters since transmission & reflection of electrical networks are simple to calculate at high frequencies. These analyzers are widely employed to distinguish between two-port networks, including filters and amplifiers. By allowing the user to view the actual data that is sent over a network, packet by packet, a network analyzer informs you of what is happening there. Also, this research will contain the design model of NetFlow Analyzer that Measurements involving transmission and reflection use. Gain, insertion loss, and transmission coefficient are measured in transmission measurements, whereas return loss, reflection coefficient, impedance, and other variables are measured in reflection measurements. These analyzers’ operational frequencies vary from 1 Hz to 1.5 THz. These analyzers can also be used to examine stability in measurements of open loops, audio components, and ultrasonics.

Uncertainties Caused by Noise for Microwave Interferometric and Reflection Measurements of Extreme Reflection Coefficients

This article concerns an uncertainty analysis of interferometric transmission measurements and standard reflection measurements of extreme impedances (extreme reflection coefficients) and broadens the scope of previously published works. Specifically, the paper focuses on revealing fundamental limits influencing achievable measurement accuracy and precision by means of the law of uncertainty propagation. The analysis considers sources of uncertainty influencing every measurement, in particular phase noise and thermal noise. The proportion of uncertainties of standard reflection measurements and interferometric measurements are derived theoretically and experimentally verified for two cases with dominant either the phase noise or the thermal noise. The values determined experimentally in a frequency band from 2 GHz to 4.5 GHz agree well with the values derived theoretically.

Switchable optics based on guided mode resonance in lithographically patterned vanadium dioxide with integrated heating layer

Vanadium dioxide (VO2) has promising applications in smart windows and active micro-optical devices due to its thermochromic properties. However, the successful fabrication and patterning of VO2 thin films with the correct stoichiometry and phase are challenging. In this study, we investigated lithographically patterned and non-patterned VO2 thin films fabricated by reactive ion beam deposition, using variable angle spectroscopic ellipsometry, Raman spectroscopy, and transmission and reflection measurements. The results show that the refractive index and extinction coefficient exhibit significant changes for near-infrared wavelengths when heated above 68 °C, confirming its thermochromic properties. The Raman spectroscopy results indicate the formation of the monoclinic phase VO2(M) after annealing, which was not changed by reactive ion etching. Lithographically structured VO2-layers were successfully realized demonstrating the potential of VO2 as a material for active micro-optical devices, such as guided mode resonance filters with switchable reflectance. The results suggest that VO2 has great potential as a promising material for actively switched optical elements and micro-optical devices.

TNO or Comet? The Search for Activity and Characterization of Distant Object 418993 (2009 MS9)

The perihelion of the trans-Neptunian object (TNO) 2009 MS9 brings it close to the distance where some long-period comets are seen to become active. Knowing this, and the fact that this object appears to brighten in excess of its predicted nucleus brightness, suggests that 2009 MS9 has a delayed onset of activity brought on by the sublimation of a species more volatile than water. In this paper, we characterize 2009 MS9's physical properties and investigate potential outgassing through composite images, sublimation models, and measurements of spectral reflectivity. We find that deep composite images of the object at various epochs along its orbit show no evidence of dust yet place sensitive limits to the dust production. We estimate the nucleus radius to be 11.5 ± 3.5 km using thermal IR modeling from NEOWISE data and use this and data pre-perihelion to estimate a geometric albedo of 0.25. We compare a CO sublimation activity model to its post-perihelion heliocentric light curve and find that these data support an active fractional area of 5 × 10−6 assuming 2 μm–sized grains and other typical comet parameters. The spectral reflectivity of the surface materials obtained with the Gemini Observatory and CFHT at different epochs shows a reddening spectral slope. We compare the physical properties of 2009 MS9 to both TNO and comet populations and speculate that 2009 MS9's reddening may be due to the buildup of a dust mantle on the surface and could be an explanation of why TNOs exhibit a color bimodality.

Microstructure and electrical transport properties of nanoscale [(CO40Fe40B20)34(SiO2)66/(In2O3)/C]46 multilayers

We investigated the role of microstructure and In2O3/C interlayer thickness on the electrical transport properties of [(Co40Fe40B20)34(SiO2)66/(In2O3)/C]46 multilayers prepared using ion-beam sputtering. These multilayers were characterized using an X-ray diffraction, X-ray reflectivity, impedance spectroscopy, and magnetoresistive measurements. The X-ray diffraction data showed that regardless of the layer thickness, all components of the multilayers are X-ray amorphous. Fitting X-ray reflectivity data, multilayer periodicities are extracted and layers thicknesses, densities and roughnesses are determined. Impedance spectroscopy has shown a resistive-capacitive coupling between electrically conductive ferromagnetic CoFeB clusters which corresponds to the model of a prepercolation composite. For the thinnest multilayer with nonmagnetic In2O3/C interlayer thickness of about 1.6 nm, we managed to achieve a magnetoresistance of about 0.8% at room temperature and 3.2% at cryogenic temperature.

MROX 2.0: a software tool to explore quantum heterostructures by combining X-ray reflectivity and diffraction

New software for the fitting of XRR measurements is developed. It is exemplified on 1 to 10 Si/Ge periods grown on Si template samples and on (001) substrates and one complex ZnO/Zn1−xMgxO superlattice grown on a m-ZnO substrate.

Extensive study of magneto-optical and optical properties of Cd1−xMnxTe between 675 and 1025 nm

We determine Faraday rotations and measure the optical reflection and transmission from magneto-optical Cd1−xMnxTe crystals with various stoichiometric ratios. For wavelengths between 675 and 1025 nm, we derive Verdet constants, optical loss coefficients, and the complex indices of reflection that are relevant measures to find suitable stoichiometric ratios of Cd1−xMnxTe for the realization of miniaturized optical isolators. By reflection and transmission measurements, we determine the stoichiometric ratios of several different Cd1−xMnxTe crystals and discuss the observed dependence of the optical properties on the stoichiometric ratio with respect to their use in optical isolators. Finally, we show the relevant figure of merit, i.e., the ratio of Verdet constants and optical loss coefficients for Cd1−xMnxTe crystals with Mn contents ranging from x = 0.14 to x = 0.50.

Impact of Crosstalk on Reflectivity and Doppler Measurements for the WIVERN Polarization Diversity Doppler Radar

Impact of Crosstalk on Reflectivity and Doppler Measurements for the WIVERN Polarization Diversity Doppler Radar

Reflectivity measurement technology of special high reflective mirrors and uncertainty analysis of measurement results

Reflectivity measurement technology of special high reflective mirrors and uncertainty analysis of measurement results

Probing the tightly bound layer in poly(vinyl alcohol) thin films using swelling measurements.

A strongly adsorbed, tightly bound polymer layer can exist at the polymer/substrate interface in polymer thin films and polymer nanocomposites. The characteristics of the tightly bound layer have long been of interest because of its effect on physical properties. However, direct investigations are challenging as the layer is buried deep within the sample. A common approach to access the tightly bound layer is by rinsing or washing away the loosely bound polymer using a good solvent. While this enables direct investigations of the tightly bound layer, it is unclear if the layer remains unperturbed by the preparation process. Therefore, in situ techniques that can probe the tightly bound layer without strongly perturbing it are preferable. In previous work (P. D. Lairenjam, S. K. Sukumaran and D. K. Satapathy, Macromolecules, 2021, 54, 10931-10942), we introduced an approach to estimate the thickness of the tightly bound layer at the chitosan/silicon interface using swelling of nanoscale thin films when exposed to solvent vapour. To determine the general validity of the approach, in this work we investigated the swelling of poly(vinyl alcohol) (PVA) thin films using two independent techniques: spectroscopic ellipsometry and X-ray reflectivity. We found that the swelling kinetics for thin films of initial thickness in the range 18-215 nm could be described by a single time-dependent swelling ratio, c(t), provided we account for a tightly bound layer of thickness 15 nm at the polymer/substrate interface. Consistent with the conclusions from the swelling measurements, electron density profiles determined by modeling X-ray reflectivity data clearly indicated the existence at the polymer/substrate interface of a 15 nm thick layer of a slightly higher density than the rest of the film. The early-time diffusion coefficient of H2O in PVA determined from the temporal evolution of the mass uptake of the solvent vapour was found to decrease by 3-4 orders of magnitude when the film thickness decreased by approximately an order of magnitude.

Maximum Likelihood Estimation of Debye Relaxation Parameters With Open-Ended Coaxial Probes

In this paper, we present a new method to measure the complex dielectric permittivity of materials-under-test with an open-ended coaxial probe. The method, which explicitly takes measurement noise into account to enhance the stability of the measurements, is formulated based on the maximum likelihood estimation of the Debye parameters from calibrated reflection measurements performed at the aperture of the probe. In particular, the measurement noises at different frequencies are approximated with independent Gaussian distributions. To estimate the mean and the standard deviation of the mentioned probability distributions at each frequency, the differences among repetitive measurements of a reference sample are analyzed. Later, these statistical distributions are enforced into a cost functional to derive an optimization scheme based on the maximum likelihood estimation. Finally, the cost functional is iteratively minimized with a second-order Newton-based technique to retrieve the Debye relaxation parameters of a material. We further experimentally verified the method with various liquid samples and the accuracy of the obtained results is compared with the previous works.

One-Way Optical Waveguide Realized by Edge Modes of Topological Photonic Crystals

A one-way optical waveguide was realized on the boundary between two types of photonic crystals with different topological properties, which were demonstrated by high-resolution infrared reflection measurements.

A Novel Liquid Water Content Retrieval Method Based on Mass Absorption for Single-Wavelength Cloud Radar

Low-level clouds (LLC), mainly composed of liquid water droplets, cool the climate system by strongly reflecting solar radiation back to space, and thus play an important role in the Earth energy budget. However, the LLC properties and their radiative effects are poorly represented in climate models, leading to the largest source of uncertainty in the climate prediction. Liquid water content (LWC) is a key property of LLC determining cloud extinction characteristics and is a fundamental parameter in the radiative transfer model. To improve the understanding of LWC properties, algorithms have been proposed to retrieve LWC based on millimeter-wavelength radar. However, the traditional retrieval relies on pre-constructed empirical relationship between reflectivity and LWC and have noticeable limitations. Particularly, the retrieval uncertainty is strongly depended on the assumed particle size distribution, the existence of drizzle particle; and on the accuracy of reflectivity measurement. In this study, we develop a new self-consistent algorithm to retrieve LWC by constraining radar reflectivity factor and attenuation in the whole liquid cloud layer. A relationship between the radar measured reflectivity, LWC, and the intrinsic reflectivity is first constructed based on the radiative transfer theory under Rayleigh scattering regime. A nonlinear least-square regression technique is then applied to derive the optimal parameters in the retrieval equations to obtain the LWC. Comparison with the microwave radiometer (MWR) derived liquid water path (LWP) indicates that our proposed method retrieves more accurate LWC products than that from the traditional empirical algorithms.

Compensation of noise floor distortion in long-range simplified optical correlation-domain reflectometry without the use of electrical spectrum analyzer

In simplified optical correlation-domain reflectometry (OCDR) without the use of an electrical spectrum analyzer (ESA), the noise floor of the reflectivity distribution is distorted in long-range measurement, which sometimes causes significant errors in the distributed reflectivity measurement. Herein, we experimentally analyze the distorted noise floor by high-speed ESA-free OCDR and clarify the origin of the noise floor. Then we show that this noise floor can be compensated by appropriate filtering. Consequently, distributed reflectivity measurement over a 1.1 km long sensing fiber is properly performed at a repetition rate of 100 Hz.

Body composition of female office workers compared with infrared reflection measurement, bioimpedance analysis and calipermetry

There are currently many different anthropometric methods for determining the individual body fat percentage, as well as almost as many variants of bioelectric impedance analysis (BIA) and only a single method of infrared reflection measurement (IR) as easily available methods of field research.
 The present study aims at a simultaneous comparison between calipermetry, IR and BIA. In particular, the question which measurement method could be used as an equivalent method in the event of failure of BIA or IR is investigated.
 The sample group consisted of 121 female office workers (average age 32.5 ± 9.4 years, average height 164.5 ± 6.3 cm and average weight 60.3 ± 6.8 kg), from the Rhine-Main area.
 The measurements were previously scheduled and mostly carried out during the lunch break. For anthropometry, 13 skin fat folds were measured with the Accu® Measure Caliper, thigh circumference with a measuring tape, the height with a height measuring device and the body mass on the weight scale. Subsequently, an IR measurement (Futrex®) and a BIA (InBody®) were performed on the same subjects.
 The parameters of body fat percentage and total body water (in L) were examined.
 Statistical methods were correlation coefficients, Bland-Altman comparison and paired t-test for equivalence.
 For the women studied, the highest correlation coefficients were in the comparisons between the formulas according to Parízková and Brožek et al. (r = 0.82), as well as for Parízková and Siri (r = 0.82).
 The correlation coefficient for the IR vs. BIA comparison was r = 0.92.
 A key result of the present study was the finding that the investigated methods in a female study group could not be substituted in an equivalent way.

Multiple Frequencies Five-Port Reflectometer (FPR) for Pure and Adulterated Honeys

Honey adulteration is one of the major health concerns among honey consumers, it is essential to inspect the quality of honey. One of the methods is to characterize the honey by using the microwave reflection technique. A Five-Port Reflectometer (FPR) is proposed in this work. The microstrip Five-Port ring junction circuit was designed for multiple frequencies of 0.60 GHz, 2.28 GHz, and 3.47 GHz. The fabricated circuit works with an analogue-digital converter, open-ended coaxial sensor, diode detectors and computer to form a complete FPR measurement system. The reflection measurements were conducted on Honey Gold and Trigona Honey for multiple frequencies. The performance of the FPR in s-parameter measurement was verified by Vector Network Analyzer (VNA). This study shown that the performance of FPR in term of reflection measurement has promising accuracy which is comparable with VNA. The FPR can be used as an alternative instrumentation system for characterizing pure and adulterated honey.