Attenuation Level Research Articles

Sound transmission loss enhancement through triple-peak coupled resonances acoustic metamaterials

Coupled resonances mechanisms combined with the notion of acoustic metamaterials offer exceptional sound insulation capabilities, even at the challenging low frequency ranges below 1000 Hz. In this context, the concept of Multiresonant Layered Acoustic Metamaterial (MLAM) emerged as a promising practical realization exploiting this phenomenon to produce a double-peak sound transmission loss (STL) response in a multilayer configuration that allows to overcome the challenge of manufacturing. This study proposes a novel enhanced MLAM-based design (MLAM+) that greatly improves the device’s STL response by allowing the coupling of a third additional peak, when compared to equivalent double-peak configurations. In contrast to existing metamaterial-based solutions, this third peak is not caused by local resonance effects, but through inducing a combined zero-stiffness response on the panel. Through analytical and numerical validation, it is demonstrated that the frequency of this third peak can be controlled through the geometrical features of the layered design, and it can be tuned to broaden the effective attenuation bandwidth and/or to increase the level of attenuation without necessarily increasing the overall mass and maintaining the load-bearing capabilities of the panel. This opens the path towards a metamaterial’s design methodology capable of tackling different functional outcomes depending on the application.

Electromagnetic Accessibility of Starlink User Terminals

The results of assessing the electromagnetic accessibility of radio emission sources of the Starlink satellite communication system are presented. The features of the organizational and technical structure of the system are considered. Its main technical capabilities for organizing the provision of telecommunications services to users of subscriber terminals are analyzed. The technical features of the infrastructure of the Starlink satellite communication system, which are essential for the electromagnetic accessibility of its sources, have been studied. The possibility of radio links for transmitting information content in the upstream and downstream channels of the Starlink satellite communication system was assessed. The main stages of the developed methodology for assessing the electromagnetic accessibility of sources are presented. Analytical expressions are given for calculating the probability of detection and attenuation of signals. The requirements for the sensitivity of the receiving equipment of monitoring equipment are substantiated. Dependences of the level of signal attenuation on the distance of control equipment were obtained.

Efficient Filter Design to Compensate Fabrication Imperfections in 6G Communication Systems.

In this paper, we present a consistent methodology for the reliable design of 6G-oriented filters with enhanced endurance to construction imperfections. The systematic formulation does not depend on the filter's operating frequency and employs a robust strategy for obtaining new roots and poles of the filtering function. Essentially, it requires that all the local maxima of the filtering function do not fluctuate beyond the design attenuation levels for a set of predefined roots/poles distortions. To this purpose, two novel algorithms for the derivation of the appropriate filtering functions are developed, in the prior basis, together with a versatile optimization criterion and a heuristic comparison approach that guarantee optimal outcomes. Specifically, the principal idea of the first technique is to accurately extract the roots of the new polynomial from a system of equations on condition that the maximum local peaks of the distorted (due to imperfections) initial polynomial are below a prefixed threshold, such as the unit. Conversely, the second method develops an alternative polynomial, compressed in the amplitude and frequency range, so that a similar prerequisite regarding the maximum local peaks, is satisfied. It is stressed that both methods are fully generalized and may be applied to any polynomial combination, without increasing the overall complexity. The proposed framework is successfully verified in terms of theoretical examples and the numerical simulation of realistic waveguide and mictrostrip line filters, operating at frequencies from 2GHz to 65GHz, which unveil its superiority over existing schemes and implementations.

Combined Radiation and Temperature Effects on Brillouin-Based Optical Fiber Sensors

The combined effects of temperature (from −80 °C to +80 °C) and 100 kV X-ray exposure (up to 108 kGy(SiO2)) on the physical properties of Brillouin scattering and losses in three differently doped silica-based optical fibers, with varying dopant type and concentration (4 wt%(Ge), 10 wt%(Ge) and 1 wt%(F)), are experimentally studied in this work. The dependencies of Brillouin Frequency Shifts (BFS), Radiation-Induced Attenuation (RIA) levels, Brillouin gain attenuation, Brillouin frequency temperature (CT) and strain (Cε) sensitivity coefficients are studied under X-rays in a wide temperature range [−80 °C; +80 °C]. Brillouin sensing capabilities are investigated using a Brillouin Optical Time Domain Analyzer (BOTDA), and several properties are reported: (i) similar behavior of the Brillouin gain amplitude decrease with the increase in the RIA; (ii) the F-doped and heavily Ge-doped fibers do not exhibit a temperature dependence under radiation for their responses in Brillouin gain losses. Increasing Ge dopant concentration also reduces the irradiation temperature effect on RIA. In addition, Radiation-Induced Brillouin Frequency Shift (RI-BFS) manifests a slightly different behavior for lower temperatures than RIA, presenting an opportunity for a comprehensive understanding of RI-BFS origins. Related temperature and strain sensors are designed for harsh environments over an extended irradiation temperature range, which is useful for a wide range of applications.

Приёмо-передающее устройство для исследования канала связи забой-устье

An ultrasonic receiving and transmitting communication system for the borehole bottom-wellhead channel inside the casing pipe based on PIC18F2455 has been designed. Combined receivers-transmitters TR60-10H0Z-01 were used as piezoelectric elements. The signal frequency was 60 kHz, the encoding was “Manchester-II”. The negative impact of interference is reduced at ultrasonic frequencies, and due to the heterogeneity of the medium, it is assumed to decrease the level of signal attenuation. The selected piezoelectric elements allow to increase the amplitude of the signal up to 140 V. The paper presents and describes in detail the basic electrical circuits of the transmitter and receiver. Developed devices operate from 12 V batteries without primary power supply. The signal to the piezoelectric emitter comes from a transformer. Two keyed-mode transistors opening one by one are connected with the transformer. Buffer amplifiers are used to open the keyed transistors. The developed system was tested on a tested, which is a pipe filled with water. As a result of the experiments, no significant attenuation of the signal was observed.

THE METHOD OF ADJUSTING THE MULTI-FREQUENCY PROBING RADAR SIGNAL PARAMETERS AND THE TROPOSPHERIC RADIO WAVEGUIDE CHARACTERISTICS

Peculiarities of air circulation in the coastal zone of large reservoirs (large lakes or inland seas such as the Black and Azov Seas) can lead to a significant departure from the standard spatial distribution of meteorological and, accordingly, radiophysical characteristics of air.
 As a result, it is possible for regions of space with an abnormally low attenuation level of radio waves of certain frequency ranges to appear – tropospheric radio waveguides (TWG). The appearance of TWG leads to multi-beam propagation of radio waves and fluctuations of radar signals. Fluctuations of the radar signal lead to a decrease in the range of detection of aerial objects by radars. For single-frequency radar signals, it is only possible to estimate the degree of distortion and the amount of radar detection range loss. A paradoxical situation arises when, due to TWG, it is possible to increase the range of detection of aerial objects, but due to the distortion of the radar signal in TWG, the detection performance decreases. For multi-frequency signals, it is potentially possible to adjust the parameters of the radar signal with the parameters of the radar channel (in this case, the tropospheric radio waveguide).
 The adjustable parameters of a multifrequency signal include: the number of frequency components; bandwidth of the frequency component; average frequency of the frequency component; signal duration; period.
 The characteristics of TWG, on which the parameters of the multifrequency signal depend, include: the lower transmission frequency of TWG; the upper transmission frequency of TWG; the delay time of the rays in the TWG.
 The bandwidth and beam delay values can be obtained directly by emitting and receiving a test multi- frequency pilot signal, but this method requires the presence of a reference reflector in space, which is difficult to implement in practice.
 The electrophysical characteristics of the tropospheric waveguide can be determined from the data of meteorological observations. The method developed in the article allows, based on the known characteristics of the tropospheric waveguide, to determine and adjust the parameters of a multi-frequency signal, which reduces the fluctuations of the sounding signal and increases the aerial objects detection rang.

Event-Triggered State and Disturbance Estimation for Lipschitz Nonlinear Systems With Unknown Time-Varying Delays.

We consider the event-triggered state and disturbance simultaneous estimation problem for Lipschitz nonlinear systems with an unknown time-varying delay in the state vector. For the first time, state and disturbance can be robustly estimated by using an event-triggered state observer. Our method uses only information of the output vector when an event-triggered condition is satisfied. This contrasts with previous methods of simultaneous state and disturbance estimation based on augmented state observers where the information of the output vector was assumed to be always continuously available. This salient feature, thus, lessens the stress on communication resources while can still maintain an acceptable estimation performance. First, to solve the new problem of event-triggered state and disturbance estimation, and to tackle unknown time-varying delays, we propose a novel event-triggered state observer and establish a sufficient condition for its existence. Then to overcome some technical difficulties in synthesizing observer parameters, we introduce some algebraic transformations and use inequalities, such as the Cauchy matrix inequality and the Schur complement lemma to establish a convex optimization problem in which observer parameters and optimal disturbance attenuation levels can be systematically derived. Finally, we demonstrate the applicability of the method by using two numerical examples.

Field measurement of ground effect for road traffic noises

In ASJ RTN-Model 2018, which was proposed by the Acoustical Society of Japan, a practical calculation method of the ground effect in A-weighted overall level for road traffic noise is specified by relatively simple formulae. The method is derived from the solution of the ground effect based on wave theory. By the practical calculation method, the attenuation level by the ground effect for a relatively long distance between the source and receivers tends to become larger on softer ground. Especially in the cases of lower sound source positions as specified in the ASJ RTN-Model 2018, the excess attenuation becomes large. To investigate the appropriate treatment of the ground condition in the case of road traffic noise propagation on soft ground, the authors have performed a field measurement of road traffic noise. The measurement results were compared with calculation results by both the ASJ RTN-Model 2018 and the theoretical solution based on the wave theory. From the comparison, the features of the propagation characteristics obtained by the ASJ RTN-Model 2018 were discussed.

Train Mitigation Measures in the Transmission Path: Seismic Metamaterial and Granular Barriers

The development of new mitigation measures is an effective solution to the annoyance generated by the induced vibration coming from the railway traffic to the residents of urban areas. This paper aims to give a brief comparison of two novel concepts of mitigation measures applied within the transmission path presented recently in the literature. In particular, the use of seismic metamaterial will be compared to the use of heterogeneous barriers, to evaluate to which extent these two mitigation measures can help to tackle the problem of ground-borne vibration and noise. These two cases will be related by considering the same railway environment based on a two-step approach, already validated in the past; in this study, the soil simulated in the second step is reproduced using the finite element method and spectral element method for the seismic metamaterial and heterogeneous barriers respectively. Finally, a parametric investigation is conducted to understand how the material and geometrical proprieties affect the attenuation levels of the two measures.

Adaptive analog and digital active noise control

Digital adaptive controllers are widely used for active noise control. The secondary path delay, including the anti-aliasing, sampling, and reconstruction effects, must be shorter than that in the primary path to maintain good broadband performance. To eliminate the added delay of the sampling, a mixed analog and digital adaptive feedforward controller is developed. The analog controller is based on a state-filtered adaptive linear combiner, while the digital one uses an adaptive finite-impulse-response filter. The adaptation of the analog controller is derived based on a sampled version of the normalized projection algorithm, while the digital controller adaptation is based on the filtered-reference least-mean-squares algorithm. Two configurations are considered for the analog combiner. One aims to minimize the electrical noise by introducing individual state filters, all driven by the same reference signal. The other gives a superior bandwidth by driving each component filter with the previous filter output. The performance of the proposed controller is assessed and compared with separate analog or digital controllers. The results highlight that the suggested controller obtains significant attenuation levels close to the causality limit using the analog controller but also allows long impulse responses using the sampled controller.

A memory state-feedback controller via random pocket dropouts for multi-agent systems with external disturbance

This study explores the challenge of achieving consensus in multi-agent systems (MASs) when facing the random packet dropouts and disturbances. It employs memory state-feedback control (MSFC) in the context of undirected graphs and specified leader agents. The analysis focuses on mean square consensus, considering MASs within strongly connected networks or networks with undirected spanning trees. The MSFC approach is developed to ensure asymptotic consensus despite packet dropouts and also to reduce the impact of disturbances. Specifically, the consensus analysis leverages the Lyapunov-Krasovskii functional (LKF) framework, and the necessary conditions for implementing the proposed MSFC are established using linear matrix inequalities (LMIs). The system, augmented with an H ∞ attenuation level is guaranteed to achieve asymptotic mean-square stability according to the provided criteria. In conclusion, two examples are provided to illustrate the effectiveness and practicality of the proposed control mechanism.

Nonlinear associations between computed tomography-measures of adiposity and long pentraxin-3 in the Multi-Ethnic Study of Atherosclerosis.

Long pentraxin-3 (PTX-3) is an acute phase protein associated with cardiovascular disease, lung injury, and mortality. We evaluated the association between computed tomography (CT)-measurements of adipose tissue and plasma levels of PTX-3. We performed a cross-sectional analysis of community-dwelling adults enrolled in the multi-center Multiethnic Study of Atherosclerosis who underwent cardiac or abdominal CT and had available PTX-3 measurements. There was a U-shaped association between pericardial adipose tissue volume (PAT), abdominal visceral adipose tissue area (VAT), hepatic attenuation, and PTX-3 levels, with extremes of adiposity associated with greater PTX-3 levels. Using multivariable-adjusted piecewise regression models, among participants with low PAT, every 1% increase in PAT volume was associated with a 13.8% decrease in PTX-3 (95% confidence interval [CI] -21.6 to -6.0); among participants with high PAT, every 1% increase in PAT volume was associated with a 6.0% increase in PTX-3 (95% CI -0.4 to 12.5). Results were similar for abdominal VAT and hepatic attenuation. In a cohort of community-dwelling adults, we demonstrated a "U-shaped" association between pericardial, abdominal visceral, and hepatic adiposity with PTX3 levels, suggesting that extreme adiposity is associated with greater circulating levels of PTX3. Further work is required to identify the mechanisms linking adiposity and PTX-3.

Abstract 14643: Coronary Spotty Calcification is Associated With a Higher Level of Plaque Vulnerability and Vascular Inflammation in Patients With Stable Angina

Background: There is controversy on clinical implication of spotty calcification in the coronary arteries. Optical coherence tomography (OCT) enables detailed plaque characterization including features of plaque vulnerability. Pericoronary adipose tissue (PCAT) attenuation is a recently developed marker for perivascular inflammation. Methods: Patients with stable angina pectoris (SAP) who had both computed tomography angiography (CTA) and OCT prior to coronary intervention were included. They were classified into two groups: spotty calcification group (calcification arc <90°, length <4mm) and macro calcification group. Non-calcified plaques or plaques with mixed spotty and macro calcification were excluded. The OCT findings of the culprit lesion and PCAT attenuation of the culprit vessel were compared between the two groups. Results: Among 316 patients, 62 had spotty calcifications and 66 had macro calcification in the culprit lesion. The spotty calcification group showed a significantly higher prevalence of lipid rich plaque (91.9% vs. 74.2%, p=0.008; Figure A), greater mean lipid arc (183.1 vs. 150.5°, p=0.01), and a higher level of PCAT attenuation (-71.7 ± 7.68 vs. -74.9 ± 9.17 HU, p=0.03; Figure B), compared with the macro calcification group. Conclusion: Plaques with spotty calcification are associated with a higher prevalence of lipid-rich plaques and a higher level of perivascular inflammation, compared to those with macro calcification.

Compact Quasi-Elliptic-Type Inline Waveguide Bandpass Filters With Nonlinear Frequency-Variant Couplings

This work presents the design techniques to synthesize a class of compact inline quasi-elliptic-type waveguide cavity bandpass filters based on novel nonlinear frequency-variant couplings (NFVCs). These highly dispersive frequency-variant couplings (FVCs) are realized by means of a pair of partial-height posts that are placed at the junctions between every two cavity resonators. Each NFVC produces a transmission pole in between a pair of independently adjustable transmission zeros (TZs). Although the pole is added to the overall filtering function to augment its order, the TZs can be placed at each side of the filter passband to attain sharp rejection capability and increase the stopband attenuation levels. To synthesize these filters, two coupling-routing-diagram (CRD) approaches for the NFVC are presented that either consider: 1) an arbitrary FVC (AFVC) or 2) two resonating nodes interacting with a zero-susceptance nonresonating node through constant inverters. An equivalent lumped-element circuit model associated with both CRD approaches is provided. It is demonstrated that both CRD models can be exploited for the theoretical synthesis of this type of filter, whereas the equivalent lumped-element circuit model can provide a deeper insight into the systematic dimensioning of the posts. For experimental validation purposes, three design examples are synthesized, and 10-GHz proof-of-concept filter prototypes of two of them are EM-simulated, fabricated, and characterized. The measured results agree well with the simulations and the design theory, thus verifying the concept of inline waveguide cavity filters with TZs using NFVCs.

Schisandrin A in Schisandra chinensis Upregulates the LDL Receptor by Inhibiting PCSK9 Protein Stabilization in Steatotic Model.

Schisandra chinensis extract (SCE) protects against hypocholesterolemia by inhibiting proprotein convertase subtilisin/kexin 9 (PCSK9) protein stabilization. We hypothesized that the hypocholesterolemic activity of SCE can be attributable to upregulation of the PCSK9 inhibition-associated low-density lipoprotein receptor (LDLR). Male mice were fed a low-fat diet or a Western diet (WD) containing SCE at 1% for 12 weeks. WD increased final body weight and blood LDL cholesterol levels as well as alanine transaminase and aspartate aminotransferase expression. However, SCE supplementation significantly attenuated the increase in blood markers caused by WD. SCE also attenuated WD-mediated increases in hepatic LDLR protein expression in the obese mice. In addition, SCE increased LDLR protein expression and attenuated cellular PCSK9 levels in HepG2 cells supplemented with delipidated serum (DLPS). Non-toxic concentrations of schisandrin A (SA), one of the active components of SCE, significantly increased LDLR expression and tended to decrease PCSK9 protein levels in DLPS-treated HepG2 cells. High levels of SA-mediated PCSK9 attenuation was not attributable to reduced PCSK9 gene expression, but was associated with free PCSK9 protein degradation in this cell model. Our findings show that PCSK9 secretion can be significantly reduced by SA treatment, contributing to reductions in free cholesterol levels.

T-S fuzzy model based event-triggered change control for product and supply chain systems

Product and supply chain systems are a class of complex nonlinear systems due to the uncertain demand fluctuation and unexpected events, and Takagi–Sugeno (T-S) fuzzy systems are suitable for modelling such product and supply chain systems with different production rates. According to the uncertainty customer demands, different subsystems which describe the corresponding production-inventory processes are orchestrated by the T-S fuzzy rule. Change control is designed to handle the supply chain blocking and event breaking caused by uncertain factors. Then, sufficient conditions are given such that the exponential stability with a prescribed bullwhip effect attenuation level can be guaranteed, and the control synthesis problem is transformed into the solvability of linear matrix inequalities for the product and supply chain systems. An example is introduced to verify the validness and efficiency of the proposed approach.

Vibration Event Recognition Using SST-Based Φ-OTDR System.

We propose a method based on Synchrosqueezing Transform (SST) for vibration event analysis and identification in Phase Sensitive Optical Time-Domain Reflectometry (Φ-OTDR) systems. SST has high time-frequency resolution and phase information, which can distinguish and enhance different vibration events. We use six tap events with different intensities and six other events as experimental data and test the effect of attenuation. We use Visual Geometry Group (VGG), Vision Transformer (ViT), and Residual Network (ResNet) as deep classifiers for the SST transformed data. The results show that our method outperforms the methods based on Continuous Wavelet Transform (CWT) and Short-Time Fourier Transform (STFT), while ResNet is the best classifier. Our method can achieve high recognition rate under different signal strengths, event types, and attenuation levels, which shows its value for Φ-OTDR system.

Acoustic signatures of porous rocks permeated by partially saturated, aligned planar fractures

AbstractThe presence of sets of vertical, parallel fractures is very common in the Earth's upper crust. Notably, open fractures exert critical control on the mechanical and hydraulic properties of the host formation. There is great interest in understanding how fractures interact with seismic waves, as this knowledge could be used to detect and characterize fractures from seismic data. When a seismic wave travels through a fractured formation, it induces oscillatory fluid pressure diffusion between the fractures and the embedding porous background, a physical process that produces attenuation and dispersion of the seismic wave. Although there are numerous studies on this topic, the case of parallel fractures saturated with different immiscible fluids, such as brine and CO2, remains rather unexplored. With these motivations, in this work, we propose an analytical approach to compute the phase velocity and attenuation of P‐waves travelling perpendicularly to a set of planar, parallel fractures. While we consider that the background is saturated with brine, the fractures can be saturated with brine or gas. Our numerical analysis shows for the first time that two manifestations of fluid pressure diffusion arise in these cases. One of them, associated with relatively high levels of attenuation, is due to fluid pressure diffusion occurring between consecutive fractures saturated with different fluids. In this case, the fluid pressure diffusion process is initiated at a fracture saturated with brine and reaches a consecutive fracture saturated with gas. The other fluid pressure diffusion manifestation, on the other hand, arises at higher frequencies, is characterized by lower levels of attenuation and results from the interaction in the background of fluid pressure diffusion processes initiated at consecutive fractures, irrespective of the fluid content. Finally, by considering a stochastic distribution of the two fluids and a classical frequency of interest in seismic experiments, we obtain P‐wave attenuation and phase velocity as functions of the fracture gas saturation. This approach could be of interest for the remote detection and quantification of pore fluids using seismic waves.

Design and analysis of highly selective ultrawide stopband lowpass filter using lumped and distributed equivalent circuit models

AbstractAn ultrawide stopband lowpass filter is reported using three stepped impedance resonators with high selectivity. The filter extends the stopband frequency range and attenuation, and two quarter‐wave open stubs and three circular ground slots are introduced. The lumped and distributed equivalent models are derived and analyzed. The corresponding results are validated experimentally in a fabricated prototype. The prototype lowpass filter has a 3 dB cutoff frequency (fc) of 2.9 GHz, and the stopband is extended up to 35 GHz (12.07fc), with an attenuation level better than 20 dB throughout. The passband‐to‐stopband transition (3 dB–20 dB) bandwidth is 0.18 GHz, and the roll‐off factor is 135 dB/GHz at 30 dB. The insertion loss is 0.3 dB at 1.6 GHz. The normalized circuit size of the proposed filter with respect to the guided wavelength is 0.04.

Coronary artery disease reporting and data system (CAD-RADS), vascular inflammation and plaque vulnerability

BackgroundCoronary artery disease reporting and data system (CAD-RADS) predicts future cardiovascular events in patients with coronary artery disease (CAD). However, information on vascular inflammation and vulnerability remains scarce. MethodsPatients who underwent coronary computed tomography angiography (CTA) and optical coherence tomography (OCT) prior to coronary intervention were enrolled. All three coronary arteries were evaluated for CAD-RADS score and pericoronary adipose tissue (PCAT) attenuation, while the culprit vessel was analyzed for plaque vulnerability by OCT. ResultsA total of 385 patients with 915 lesions were divided into two groups based on CAD-RADS score: 103 (26.8%) were categorized as CAD-RADS 4b/5 and 282 (73.2%) as CAD-RADS ≤4a. Patients with CAD-RADS 4b/5 had a higher level of PCAT attenuation (mean of 3 coronary arteries) than those with CAD-RADS ≤4a (−68.4 ​± ​6.7 HU vs. −70.1 ​± ​6.5, P ​= ​0.022). The prevalence of macrophage was higher, and lipid index was greater in patients with CAD-RADS 4b/5 than CAD-RADS ≤4a (94.2% vs. 83.0%, P ​= ​0.004, 1845 vs. 1477; P ​= ​0.003). These associations were significant in the culprit vessels of patients with chronic coronary syndrome but not in those with acute coronary syndromes. ConclusionsHigher CAD-RADS score was associated with higher levels of vascular inflammation and plaque vulnerability.