Multiple Reflection Method Research Articles

Review of the Low-Temperature Acoustic Properties of Water, Aqueous Solutions, Lipids, and Soft Biological Tissues.

Existing data on the acoustic properties of low-temperature biological materials is limited and widely dispersed across fields. This makes it difficult to employ this information in the development of ultrasound applications in the medical field, such as cryosurgery and rewarming of cryopreserved tissues. In this review, the low-temperature acoustic properties of biological materials, and the measurement methods used to acquire them were collected from a range of scientific fields. The measurements were reviewed from the acoustic setup to thermal methodologies for samples preparation, temperature monitoring, and system insulation. The collected data contain the longitudinal and shear velocity, and attenuation coefficient of biological soft tissues and biologically relevant substances-water, aqueous solutions, and lipids-in the temperature range down to -50 °C and in the frequency range from 108 kHz to 25 MHz. The multiple reflection method (MRM) was found to be the preferred method for low-temperature samples, with a buffer rod inserted between the transducer and sample to avoid direct contact. Longitudinal velocity changes are observed through the phase transition zone, which is sharp in pure water, and occurs more slowly and at lower temperatures with added solutes. Lipids show longer transition zones with smaller sound velocity changes; with the longitudinal velocity changes observed during phase transition in tissues lying between these two extremes. More general conclusions on the shear velocity and attenuation coefficient at low-temperatures are restricted by the limited data. This review enhance knowledge guiding for further development of ultrasound applications in low-temperature biomedical fields, and may help to increase the precision and standardization of low-temperature acoustic property measurements.

Акустические свойства мартенситно-стареющей стали XM-12 после энергетических воздействий

The study of the acoustic properties of maraging steels operated under various energy force and temperature actions is a critical task, since it is the method of acoustic structuroscopy that provides the most reliable connection with the structure, stress-strain state and mechanical properties of steels. The paper is devoted to research of the acoustic properties of the 15-5 PH maraging steel samples under various types of heat treatment under the conditions of mechanical tensile and cyclic loads. Samples of the 15-5 PH maraging steel were studied in three structural states: solid solution annealing and subsequent aging at 470 and 565 °C; during tensile tests; during cyclic tension-compression loading. The research used a unique scientific installation “Information-measuring complex for investigation of acoustic properties of materials and products”. It implements the acoustic mirror-shadow multiple reflections method using electromagnetic-acoustic and piezoelectric transducers based on polyvinylidene fluoride film to excite and receive waves and allows determining the velocity of wave propagation with an error of no more than 2 m/s. The acoustic (wave velocity, elastic moduli, electromagnetic-acoustical (EMA) transformation coefficients, acoustic anisotropy coefficients, acoustoelastic coupling coefficients) and electromagnetic (coercive force and electrical conductivity) characteristics of the samples were examined. The samples were studied in the initial state (before loading); stepwise in the process of tensile loads and subsequent unloading; after tensile tests; during cyclic tension-compression loading. It was revealed that the following acoustic parameters of 15-5 PH steel samples are the greatest structural sensitivity to mechanical tensile load and cyclic loading: transverse wave velocity, Poisson’s ratio, double EMA-transformation coefficient, and acoustic anisotropy coefficient.

Upgraded Full multiple reflections method improves accuracy in Time-Domain dielectric spectroscopy

Automated measurements of the dielectric properties of matter, based on Time-Domain Dielectric Spectrometry, have been used for several decades. In this paper, we report and evaluate a novel Full Multiple Reflections algorithm for extracting the material-under-test complex dielectric permittivity, able to perform over a wide range of frequencies. The novel method is based on the analysis of multiple reflections due to non-idealities and unintended impedance mismatches in the transmission line, to extract their influence on the final result. The method is compared against two classic strategies and proves to be more accurate, while overriding the well-known drawbacks of using non-ideal transmission lines. Limitations of the method are discussed and tested through representative results using materials widely studied and researched in the literature.

Acoustic attenuation coefficient measurement in extreme environments: Experimental characterization of uncertainty in multiple-reflection method

Measuring acoustic properties in extreme environments, involving hazardous chemical samples or temperature above 50ºC or below 0ºC, is challenging yet crucial for understanding waveform interactions with materials, with applications in fields like non-destructive testing (NDT) and medical applications. Multiple-reflection methods (MRM), using a buffer-rod between transducer and sample, offer a solution. Yet, the impact of variables like contact force, buffer-rod size, and surface roughness on the accuracy and precision of MRM measurements remains unvalidated. To address this, we introduce a system and experiments to quantify the accuracy of measurements of acoustic attenuation coefficient. Results demonstrate the substantial impact of contact force on system accuracy and precision, reflected by a decrease in the measured attenuation coefficient at 0.5 MHz from 3.8 to 1.5dB/cm with increasing contact force. Effects of buffer-rod width were less pronounced and supported the theory that a cylindrical buffer-rod with twice the radius of the transducer is sufficient. Interestingly, surface roughness, despite being over 150 times smaller than the wavelength of the acoustic signal, influences measurement accuracy. This study illuminates the crucial role of system factors on measurement accuracy and uncertainty, which will aid optimization of measurements for diverse practical applications.

Mapping acoustic properties of tissues at low temperatures for ultrasound rewarming

Cryopreservation of large volumes of cells and tissues, followed by successful rewarming, promises to revolutionize organ transplantation by extending organ preservation times. This technology addresses a critical issue: over 6,000 individuals in the UK are awaiting organ transplants, yet an alarming 60% of donated organs go unused due to current preservation time limitations. A significant challenge lies in providing a rapid and uniform rewarming method for cryopreserved tissues. Ultrasound, capable of converting sound power into heat as it propagates through tissue, offers a promising solution. Nonetheless, before tapping into ultrasound’s potential for rewarming experiments, a fundamental understanding of the acoustic properties of tissues, which vary with temperature and during phase change, is essential. This study employs the multiple-reflection method (MRM), with buffer-rod positioned between the transducer and sample, to measure the acoustic attenuation coefficient and sound speed in biological relevant materials and the primary components of tissues, such as water and lipids, across a temperature range of 20 to −100ºC. Concurrently, the acoustic properties of commonly used cryopreservation solutions were assessed. These data will facilitate computational simulation of acoustic power delivery and the resulting temperature distributions, enabling planning and monitoring of tissue rewarming, which is critical to its success.

Synthesis of Elements in Compact Stars in Pycnonuclear Reactions with Carbon Isotopes: Quasibound States vs. States of Zero-Points Vibrations

(1) Purpose: Conditions of formation of compound nuclear systems needed for synthesis of heavy nuclei in pycnonuclear reactions in compact stars are studied on a quantum mechanical basis. (2) Methods: The method of multiple internal reflections is applied for pycnonuclear reactions in compact stars with new calculations of quasibound spectra and spectra of zero-point vibrations. (3) Results: Peculiarities of the method are analyzed for reaction with isotopes of Carbon. The developed method takes into account continuity and conservation of quantum flux (describing pycnonuclear reaction) inside the full spacial region of reaction, including the nuclear region. This gives the appearance of new states (called quasibound states) in which compound nuclear systems of Magnesium are formed with the largest probability. These states have not been studied yet in synthesis of elements in stars. Energy spectra of zero-point vibrations and spectra of quasibound states are estimated with high precision for reactions with isotopes of Carbon. For the first time, the influence of plasma screening on quasibound states and states of zero-point vibrations in pycnonuclear reactions has been studied. (4) Conclusions: The probability of formation of a compound nucleus in quasibound states in pycnonuclear reaction is essentially larger than the probability of formation of this system in states of zero-point vibrations studied by Zel’dovich and followers. Therefore, synthesis of Magnesium from isotopes of Carbon is more probable through the quasibound states than through the states of zero-point vibrations in compact stars. Energy spectra of zero-point vibrations are changed essentially after taking plasma screening into account. Analysis shows that from all studied isotopes of Magnesium, only 24Mg is stable after synthesis at an energy of relative motion of 4.881 MeV of the incident nuclei 12C.

Квантові ефекти пікноядерних реакцій у компактних зорях: Нові квазізв’язані стани та спектроскопія

Quantum effects in pycnonuclear reactions in compact stars at zero temperatures are studied with high precision. The reaction 16O + 16O was analyzed using the method of multiple internal reflections. The study of such reactions requires full consideration of quantum fluxes in the internal nuclear region. This reduces the rate and number of pycnonuclear reactions up to 1.8 times. This leads to the appearance of new states (which we call quasibound states) where the compound nuclear system is formed with maximal probability. As shown, the minimal energy of such a state is slightly higher than the energy of zero-mode oscillations in the lattice nodes in the pycnonuclear reaction, however, the probability of the formation of a compound system in a quasibound state is significantly greater than the corresponding probability in a state of zero-mode oscillations. It is reasonable to say that the frequency of reactions in quasi-bound states is more likely than in states of zero-mode oscillations. This can lead to significant changes in estimates of reaction rates in stars.

Stress evolution in plastically deformed austenitic and ferritic steels determined using angle- and energy-dispersive diffraction

In the presented research, the intergranular elastic interaction and the second-order plastic incompatibility stress in textured ferritic and austenitic steels were investigated by means of diffraction. The lattice strains were measured inside the samples by the multiple reflection method using high energy X-rays diffraction during uniaxial in situ tensile tests. Comparing experiment with various models of intergranular interaction, it was found that the Eshelby-Kröner model correctly approximates the X-ray stress factors (XSFs) for different reflections hkl and scattering vector orientations.The verified XSFs were used to investigate the evolution of the first and second-order stresses in both austenitic and ferritic steels. It was shown that considering only the elastic anisotropy, the non-linearity of sin2ψ plots cannot be explained by crystallographic texture. Therefore, a more advanced method based on elastic-plastic self-consistent modeling (EPSC) is required for the analysis. Using such methodology the non-linearities of cos2φ plots were explained, and the evolutions of the first and second-order stresses were determined. It was found that plastic deformation of about 1–2% can completely exchange the state of second-order plastic incompatibility stresses.

Acoustic and Electromagnetic Properties of Civilian Gun Blanks

The non-uniformity of acoustic properties of civilian gun barrel blanks has been studied. Four samples of civilian gun barrel blanks from the same batch, obtained after the first stage of the technological process, were subjected to the study. The blanks are of cylindrical shape with diameter of 34 mm, 210 mm in length and are made of high quality carbon steel 50A. In the research, a control echo-shadow method of multiple reflections was used with the application of an electromagnetic-acoustic transducer and a piezoelectric transducer based on a polyvinyl-dente-fluoride film for excitation and reception of waves. On the basis of the studies carried out using the echo-shadow method of multiple reflections on the samples of civilian gun barrel blanks, the following informative parameters were measured: the speed of the transverse, longitudinal and Rayleigh waves, and the elastic moduli and Poisson's ratio were calculated on their basis. The echo-shadow method of multiple reflections showed high sensitivity of the measured informative parameters of ultrasonic waves to material inhomogeneities in individual sections along the length of barrel blanks, which may be due to violations of machining processes. For transverse and Rayleigh waves, such parameters as the coefficient of detectability and dispersion are calculated, which also indicate the inhomogeneity of properties in individual sections with respect to length of the sample blanks. Using a micrometer, the diameters of the bars were measured at 17 points, and the minimum and maximum values were recorded at each point, which correlates with the results of measuring the wave velocities. The relative values of the electrical conductivity on each bar along the generatrix in 4 positions of the circle (0, 90, 180, and 270 degrees) were measured. Deviations of the obtained electric conductivity values up to 5% being the evidence of local inhomogeneities of electric properties revealing structural inhomogeneity is observed. Value inhomogeneity of coercitive force up to 0.7 A/cm along blank circumference.

Multiple Reflection Method in Problem of Constructive Synthesis of Polarizers and Phase Shifters Based on Three Non-dissipative Inhomogeneities in Waveguide

Multiple Reflection Method in Problem of Constructive Synthesis of Polarizers and Phase Shifters Based on Three Non-dissipative Inhomogeneities in Waveguide

Comparative Sensitivity of Informative Parameters of Electromagnetic-Acoustic Mirror-Shadow Multiple Reflections Method during Bar Stock Testing

Comparative Sensitivity of Informative Parameters of Electromagnetic-Acoustic Mirror-Shadow Multiple Reflections Method during Bar Stock Testing

Efficient Solution of Emissivity for the Area Blackbody Based on the Multiple Reflection Method

At present, the Monte Carlo method is the only method to evaluate the area blackbody emissivity, so it needs to be compared and verified with other calculation methods. In particular, the efficiency of Monte Carlo is low when the micro-cavity structure of the area blackbody is more complex for higher emissivity. An efficient algorithm for calculating emissivity of the area blackbody based on the multiple reflection method was put forward in this article. A multiple reflected light path that radiated into the inner micro-cavity structure of the area blackbody was simulated. The ratio of the outgoing light intensity to the incident light intensity was obtained by setting a threshold of the outgoing light intensity, and then the area blackbody emissivity was calculated. The simulation results showed that, compared with the Monte Carlo method, the results of the emissivity calculation were similar, and calculation efficiency was increased more than 100 times under the same micro-cavity structure. A practical area blackbody was made based on the simulation results from the proposed multiple reflection method, and the emissivity measurement experiments were carried out and compared to the cavity blackbody at the same temperature. The results showed that the emissivity was near one and stable for the NIR (Near Infrared) spectrum range when the temperature was higher than 280°C. Thus, the feasibility of the multiple reflection method for calculating the area blackbody emissivity was verified. The multiple reflection method proposed in this article provided one more design path for developing area blackbodies with more complex micro-cavity structures.

Расчет двузеркальной антенны по методу физической оптики с учетом многократных переотражений.

Calculation of a double reflector Cassegrain antenna by physical optics method with taking into account multiple reflections between the reflector and the subreflector was performed. It was shown that the convergence of antenna characteristics (gain, antenna efficiency, side-lobe level) with the increase of accounting reflections is observed. To check the method of multiple reflections the same Cassegrain antenna was calculated by the method of electric field integral equation with the unknown surface electric currents on the reflector and the sub-reflector. The comparison showed the coincidence of the result obtained by two different methods. The calculation of gain and efficiency of a Cassegrain antenna in frequency range from 1 to 10 GHz was performed by physical optics method with multiple reflections.

Retrieval of electrical and physical properties of dielectric samples using time‐domain multiple reflection method

In this study, a novel time-domain multiple reflection method for determining the electrical properties and thickness of the sample has been proposed. The unique advantage of this method is that it employs only reflection coefficient data for the reconstruction of the properties. The proposed scheme is validated by determining the permittivity, thickness, and loss tangent values of different samples of different thicknesses with high accuracy. The experimental characterisation has been carried out, incorporating the proposed scheme for its verification and thereby the electrical and physical properties of an unknown sample have been retrieved. The proposed method is simple, cost-effective and non-iterative in nature. The proposed technique is quite useful in applications like through-wall imaging, where the wall can be accessed from a single side only, monitoring the health of the building and ground-penetrating radar.

Acoustic Structural Analysis of Steel Samples Loaded with Rotational Bending During Fatigue Tests

С целью исследования влияния накопленной поврежденности металла на скорость ультразвуковых сдвиговых и рэлеевских волн образцы стального пруткового проката подвергли циклическому нагружению по схеме консольного изгиба с вращением. Представлены результаты измерения скорости ультразвуковых волн (сдвиговых и рэлеевских) в стальных прутках при малоцикловой усталости под воздействием циклических нагрузок. Исследованы образцы прутков марки стали 40Х в состоянии поставки и после отжига при температуре 700 оС в течение 30 мин. Длина прутков - 270 мм, диаметр - 10 и 19 мм. Циклические нагружения консольным изгибом обеспечивались с помощью специально разработанной установки для испытаний на усталость, в которой пруток одной стороной зажимался в патроне машины, обеспечивающей вращение, на другой стороне через подшипник подвешивался груз. Оценивались скорости сдвиговых волн в направлениях поперечного сечения прутка и рэлеевских волн по огибающей цилиндрической поверхности прутка в зоне максимальных напряжений. Возбуждение и прием волн осуществляли электромагнитно-акустическим способом. Для оценки скорости сдвиговых (поперечных) и рэлеевских волн использовался метод многократных отражений, соответственно, по сечению и огибающей прутка. Представлены результаты изменения скорости в прутках при увеличении консольной нагрузки и числа циклов. Найдено, что скорость сдвиговой волны в прутке максимально уменьшается в зоне максимальных напряжений. При нагрузках, составляющих 60 % от предела текучести, в образцах наблюдается резкое снижение скорости при 300000 циклах. Изменение структуры металла после отжига приводит к снижению числа циклов, после которого происходит резкое изменение скорости волн. Коэффициент Пуассона, рассчитанный по скоростям сдвиговых и рэлеевских волн, также изменяется с ростом числа циклов и позволяет учесть изменение диаметра прутка в процессе испытаний. Проведенные эксперименты по исследованию влияния циклических нагрузок прутков дают хорошие информативные данные по усталости в зависимости от термической обработки и структурных изменений материала. Возможность реализации электромагнитно-акустического метода контроля на многократных отражениях позволяет существенно повысить чувствительность к микродефектам при анализе сигнала на дальних отражениях и обеспечить высокую точность определения скорости волн.

Acoustic Field under Pulsed Transmission–Reception at the Surface of an Elliptic Cylinder

Longitudinal ultrasonic pulse propagation over the cross section of an elliptic cylinder is modeled for the case of transmission–reception of waves by a contactless electromagnetic acoustic transducer along the cylinder envelope. Modeling is based on ray approximation and finite-element method. Formation of series of multiple reflections within the cross section of an elliptic cylinder is studied both theoretically and experimentally. New informative parameters of determining the cylinder ellipticity by the mirror-shadow electromagnetic acoustic method of multiple reflections are justified: the modulation period of a series of multiple reflection pulses, the delay time of reflected pulses, and the probabilistic-statistical characteristics of the data array of multiple reflection series.

Acoustic Guided Wave Testing of Pipes of Small Diameters

Acoustic path is analyzed and main parameters of guided wave testing are substanti- ated applied to pipes of small diameters. The method is implemented using longitudinal L(0,1) and torsional T(0,1) waves based on electromagnetic-acoustic (EMA) transducers. The method of multiple reflections (MMR) combines echo-through, amplitude-shadow and time-shadow methods. Due to the effect of coherent amplification of echo-pulses from defects the sensitivity to the defects of small sizes at the signal analysis on the far reflections is increased. An oppor- tunity of detection of both local defects (dents, corrosion damages, rolling features, pitting, cracks) and defects extended along the pipe is shown.

Connection between the properties of 40kh-steel bar stock and the speed of bulk and rayleigh waves

Results of the research of dependence between the structural states of 40Kh-steel bar samples obtained with different modes of thermal processing and the velocity of longitudinal, transverse, and Rayleigh waves are presented. The mirror-shadow multiple reflection method with the use of dedicated pass-through and attachable electromagnetic–acoustic transducers was employed. A connection between the wave velocity and the ultimate strength, yield point, plasticity, and rigidity of the examined samples is demonstrated. Dependences of the acoustic wave velocity on mechanical tensile stresses are presented. The acoustoelastic coefficients are determined.

Non-invasive human extremely weak pulse wave measurement based on a high-precision laser self-mixing interferometer

In this paper, a technique based on laser self-mixing effect for acquiring pulse wave profile is proposed and demonstrated. For the characteristics of extremely weak vibration in human pulse waves, a method of multiple reflections with external cavity is designed to improve the measurement accuracy to λ/4. Based on the fringe counting algorithm, one period of pulse wave is successfully reconstructed. The measurement results show that the root mean square error (RMSE) of the reconstructed pulse wave is 0.912 μm at sampling rate of 8 kHz. Besides, the correlation coefficients and heart beats of this method and the traditional photoplethysmography (PPG) measurement are analyzed.

Investigation of orientational order in a nematic liquid crystal with semiconductor CdSe/Zns QDs by IR spectroscopy

The dichroic ratio and orientational-order parameter of fundamental bands have been studied in the IR spectrum for a nematic liquid crystal based on alkylcyanobiphenyls and its suspensions with semiconductor CdSe/ZnS QDs with a core size of 5 nm. Analyses have been performed by the method of multiple frustrated total internal reflection. It is shown that an increase in the nanoparticle concentration from 0.5 to 1.3 wt % improves the orientation uniformity of the liquid crystal near the interface with the orienting surface. The orientational order parameter in a suspension with 1.3 wt % QDs has increased in comparison with the initial liquid crystal by more than 10% for the fundamental bands in alkylcyanobiphenyl molecules, the stretching vibrations of which correspond to the direction of their long axes.