Apparent Propagation Velocity Research Articles

Propagation velocity measurements of substrate phonon bursts using MKIDs for superconducting circuits

High-energy bursts in superconducting quantum circuits from various radiation sources have recently become a practical concern due to induced errors and their propagation in the chip. The speed and distance of these disturbances have practical implications. We used a linear array of multiplexed MKIDs on a single silicon chip to measure the propagation velocity of a localized high-energy burst, introduced by driving a normal metal-insulator-superconductor (NIS) junction. We observed a reduction in the apparent propagation velocity with NIS power, which is due to the combined effect of reduced phonon flux with distance and the existence of a minimum detectable QP density in the MKIDs. A simple theoretical model is fitted to extract the longitudinal phonon velocity in the substrate and the conversion efficiency of phonons to QPs in the superconductor.

О возможности импульсного сверхпроводящего индуктивного накопителя энергии без внешнего коммутатора, использующего явление сверхбыстрого перехода

The phenomenon of ultrafast transition (fast quench) to the normal state is known for some types of multistrand superconducting cables. The apparent velocity of propagation of the normal zone in such cables exceeds 100 km/s. Based on the application of the phenomenon of ultrafast transition, a possible concept of a pulsed superconducting inductive energy storage without an external switch is discussed. The strengths and weaknesses of such a storage device are considered and preliminary estimates of a system with an energy of ~ 1 MJ are made.

Seismic Phenomena Associated with the Eruption of a Volcano in the Area of the Tonga Archipelago on January 15, 2022

The study of changes in the seismic process associated with the eruption and the assessment of the energy parameters and structure of the wave field from seismic data is the subject of this work. Three types of disturbances are distinguished in the structure of the wave field. First of all, these are Rayleigh surface waves with an average oscillation period of 23 s, well traceable at distances up to 100 degrees. The group velocity of Rayleigh waves is 3.6–3.8 km/s. The magnitude calculated from them at stations mainly with oceanic propagation paths is Ms = 5.52 ± 0.18, and the corresponding seismic energy was on the order of Ec = (1–7) × 1013 J, and the scalar seismic moment M0 =2.4 × 1017 J. Two other types of oscillations were detected on seismic channels with a frequency band from 0.0003 to 0.1 Hz of the stations. For the first, the apparent velocity of propagation of the disturbance lies in the range of 0.28–0.37 km/s with a characteristic period of 268 s. This type of disturbance is associated with the gravitational response of the seismometer to an acoustic disturbance in the atmosphere. For the second type of seismic disturbances, the propagation velocity is 0.21–0.28 km/s with characteristic periods of 450 s on the horizontal components of seismic receivers. This type of seismic disturbance is probably caused by the interaction of the gravitational wave in the hydrosphere with the coast of the islands on which the seismic stations are located.

Near‐Real‐Time Analysis of the Ionospheric Response to the 15 January 2022 Hunga Tonga‐Hunga Ha'apai Volcanic Eruption

AbstractWe present a near‐real‐time (NRT) scenario of analysis of ionospheric response to the 15 January 2022 Hunga Tonga‐Hunga Ha'apai eruption by using Global Navigation Satellite Systems data in the near‐field (in the vicinity of the volcano), and in the far‐field (Japan, North America, and South America). We introduce a new method to determine instantaneous velocities using an interferometric approach and using the time derivative of the total electron content (TEC). Moreover, for the first time, we propose a novel method that automatically estimates the apparent propagation velocity of ionospheric disturbances from NRT travel‐time diagrams. By using our new methods, we analyzed the dynamics of co‐volcanic ionospheric disturbances generated by the Hunga‐Tonga eruption, and we estimated the first propagation velocity in the near‐field to be ∼800–950 m/s, subsequently decreasing to ∼600 m/s. Based on these values, we conclude that in the near‐field, we detect ionospheric signatures of acoustic waves. In the far field, the apparent velocity of ionospheric disturbances was estimated to be between 277 and 365 m/s, which corresponds to the propagation of the Lamb wave. It is important to note that our new methods can successfully perform at low spatial resolution networks and with 30‐s cadence data. Also, they enable NRT spatio‐temporal analysis of ionospheric TEC response to smaller‐amplitude events.

Why Ablation of Sites With Purkinje Activation Is Antiarrhythmic: The Interplay Between Fast Activation and Arrhythmogenesis.

Ablation of sites showing Purkinje activity is antiarrhythmic in some patients with idiopathic ventricular fibrillation (iVF). The mechanism for the therapeutic success of ablation is not fully understood. We propose that deeper penetrance of the Purkinje network allows faster activation of the ventricles and is proarrhythmic in the presence of steep repolarization gradients. Reduction of Purkinje penetrance, or its indirect reducing effect on apparent propagation velocity may be a therapeutic target in patients with iVF.

Geomechanical characterization of carbonates of the Sete Lagoas Formation (Bambuí Group)

Abstract The geomechanical properties of rock masses must be identified to assess their quality and employability; however, the methodologies may differ depending on the lithotype and analytical purposes. The present study aimed to estimate the not-well-known physical-mechanical properties of three types of carbonate rocks (calcarenite, calcilutite, and marble) of Sete Lagoas Formation, which are not recognized in scientific literature, southeast Brazil. These are important rocks from an economic point of view, as they comprise an important input for cement, fertilizers and construction material. Both physical indexes (apparent porosity, apparently dry and saturated specific mass, apparent absorption capacity and wave propagation velocity) and mechanical properties (uniaxial compression, point load and slake durability) were determined. Mechanical tests for these three rock types were correlated to those of other carbonate rocks from other countries, for comparisons. The results showed that the lithotypes under study are peculiar in terms of porosity, wave propagation velocity and strength. Also found were a very high durability and a very good correlation between specific mass and uniaxial compressive strength.

Assessment of seismic vulnerability of continuous bridges considering soil-structure interaction and wave passage effects

Identical ground motion excitations at all supports are typically assumed in practice for the design and seismic analysis of structures. Such assumption is customarily made despite the fact that ground motions do vary among supports especially for extended-in-plan structures such as long continuous bridges, tunnels, dams, pipelines, etc. This paper focuses on studying the effects of non-synchronized motion (due to the difference in the ground motion arrival time at different bridge supports) on the seismic performance of continuous box girder bridges, and the severity of such effects whether soil-structure interaction, SSI, is ignored or considered in the analysis. The study is carried out on a nine-span bridge with a total length of 430 m supported on deep (piled) foundation embedded in sandy soils. Three different sand soil profiles are investigated representing medium to stiff soil. Eighteen real bedrock earthquakes are extracted from PEER database and incremental nonlinear dynamic analyses are conducted for different apparent wave propagation velocities (namely, 100, 420, 1000 m/s, and ∞). Fragility curves are hence generated for three pre-selected performance levels (namely, Operational, Life Safety, and Complete Collapse) considering some modeling and capacity uncertainties. The fragility curves are finally compared to examine the joint effect and severity of non-synchronized support motions and soil-structure interaction on the seismic performance and vulnerability of investigated bridges. Results demonstrate that the wave passage effect and SSI significantly affect the bridge response and the probability of exceeding various pre-selected performance levels, especially for scenarios with low apparent velocity and schemes with soft soil.

Young’s Modulus of Corundum Ceramics Sintered from Powders with a Core-Shell Structure Synthesized by Iodine Transport

The paper presents an experimental study of the effect that preliminary synthesis by iodine transport of ceramic powders with a core-shell structure has on apparent density, open porosity, elastic modulus, and sound propagation velocity of corundum ceramics sintered at various temperatures.

Young's modulus of corundum ceramics sintered from powders with a core-shell structure synthesized by iodine transport

An experimental study of the effect of preliminary synthesis by the iodine transport method of ceramic powders having a core-shell structure on apparent density, open porosity, elastic modulus, and sound propagation velocity of corundum ceramics sintered at various temperatures. was made. Ill. 1. Ref. 7. Tab. 3.

A configuration with several linear subarrays for the joint estimation of the apparent velocity & direction of propagation of a seismic wave

In this paper we propose a processing method with several linear subarrays for the joint estimation of the apparent velocity and the direction of propagation of a seismic wave. This method estimates the parallel velocities along the directions of the considered linear subarrays, followed by a geometrical based procedure to compute the apparent velocity and the direction of propagation of the wave. Examples, using synthetic as well as field data, are presented to verify the suggested method. The proposed method can be used to determine the properties and sources of the microseism and microtremor signals acquired by seismic array data.

Investigation on focal ignition and combustion of aluminum-air suspension

The paper provides a numerical investigation on focal ignition and flame propagation in an aluminum-air suspension. The aim of the research was to determine the apparent flame propagation velocity in the aluminum-air suspension depending on the size and mass concentration of the aluminum particles. Numerical simulation showed that the smaller the particle radius the stronger the apparent burning velocity of the suspension depends on the initial mass concentration of the aluminum powder. The obtained results qualitatively correspond to the experimental data described in the scientific papers.

Two uncertainties in simulating spatially varying seismic ground motions: incoherency coefficient and apparent propagation velocity

The main focus of this paper is on uncertainties associated with the selection of the incoherency coefficient and apparent propagation velocity in the simulation of asynchronous seismic excitations based on the provisions of CEN [Comite Europeen de Normalisation] (Eurocode 8: Design of structures for earthquake resistance—part 2: bridges, BS EN 1998-2:2005, Brussels, Belgium 2005). To this effect, the importance of utilizing appropriate values of these two parameters in the simulation of spatially varying seismic excitations is highlighted, and practice-oriented recommendations are provided for their selection. In addition, preliminary probability distributions are proposed for the consideration of the effect of uncertainty in the selection of the apparent propagation velocity for reliability (fragility) analyses. The effect of multi-support input motions on the seismic response of bridges is also discussed.

Detailed Analysis of the Far‐Regional Seismic Coda in Kazakhstan Using Array Processing

Abstract An analysis of seismic coda phases recorded by five small aperture arrays in Kazakhstan and Russia is performed. The characteristics of the coda phases are obtained using array processing providing estimates of direction of propagation, frequency content, and apparent propagation velocity of coherent arrivals propagating through the arrays. A statistical analysis, using the coda characteristics of the whole dataset (far‐regional earthquakes) recorded by the arrays, is performed leading to a time‐azimuth distribution of the detected waves. Long Lg ‐coda wavetrains clearly dominate the far‐regional seismic records. The later part of an Lg ‐coda wavefield is generally expected to consist of omnidirectional and multiple scattered waves; still, in the present study, preferential propagation directions of scattered waves are identified in seismic signals, even for a lapse time larger than 1200 s. The comparison of the Lg ‐coda characteristics for two different groups of earthquakes and for the different arrays shows that the geometrical configuration of the event array strongly influences the back‐azimuthal distribution of detected waves. More precisely, temporal variations of the Lg ‐coda characteristics are identified: (1) as a transitory regime in the early part of the coda where arrival directions deviate from the epicenter back azimuth (eastward or westward); (2) as a final regime where the later part of the Lg coda observed by the two northern arrays exhibits incoherent phases with random propagation directions; and (3) as a final regime for the three southern arrays, which reveals coherent arrivals propagating from array‐specific back azimuths not related to the epicenter back azimuth. Electronic Supplement: Figures showing frequency content of detections.

Assessment of bridge vulnerability due to seismic excitations considering wave passage effects

Uniform ground motion excitation at different supports is typically assumed in practice while performing seismic response analysis of structures with somehow limited footprints. In essence, design of bridges is customarily performed assuming identical signal at all bridge supports. In fact, ground motions may vary at the different supports, especially, for long extended structures, such as long bridges, dams and pipelines. This paper illustrates the impact of the difference in the arrival time of the ground motions on the seismic performance of continuous box girder bridges in both bridge orthogonal directions (longitudinal and transverse). For illustration purposes, a nine-span case-study bridge with a total length of 430m is considered. Non-linear time history analyses are carried out using opensees software and the “out-of-phase ground motions at different supports” phenomenon is examined using a set of 20 real records originally extracted from the peer (Pacific Earthquake Engineering Center) Strong Motion Database. The analyses are repeated for different apparent wave propagation velocities (namely, 100, 200, 400m/s, and ∞ designating synchronized arrival time of the signal at all supports) along the bridge longitudinal direction. Results of the non-linear time history analyses performed in an incremental dynamic analysis context are hence manipulated through a probabilistic analysis framework to generate fragility curves associated with various performance levels for the case study bridge. Fragility curves giving the conditional probability of exceeding various performance levels are then integrated with generated hazard curves defining the expected seismic hazard in a specific zone. The outcome of this integration process results in values of mean annual frequency of exceeding pre-defined performance levels.

Interconnection of ion current with carbon concentration in fuel and the apparent propagation velocity of flame

The article experimentally proves the interconnection of ion current with a carbon concentration in fuel and apparent propagation velocity of the flame. This confirms the hypothesis about the strong influence of rate of radical CH + formation on ion current and allows the use of its amplitude to determine characteristics of flame propagation, which greatly simplifies and reduces the cost of existing research methods using ionization probes of combustion process in piston engines.

Earthquake performance assessment of concrete gravity dams subjected to spatially varying seismic ground motions

This paper investigates the earthquake performance of concrete gravity dams under spatially variable seismic excitations. A nonlinear finite element model is developed and validated using shake table experimental results. The model is then subjected to spatially varying earthquake ground motions incorporating the wave passage effect, with values for apparent propagation velocities consistent with the source-site geometry and the shear wave velocity in the foundation rock. The evaluation reveals that different response patterns occur when spatially non-uniform and uniform seismic ground motions are applied as input excitations to the model, because spatially non-uniform excitations induce the quasi-static response, whereas uniform excitations do not, and, in addition, the dynamic response caused by different input motions varies. Notably, spatially non-uniform excitations produce larger opening at the heel of the dam and severer slipping at its toe; this latter observation can have a significant effect on the global equilibrium and stability of the dam during an earthquake.

A note on autoregressive spectral estimates for frequency-wavenumber analysis of strong-motion array data

Frequency-wavenumber (f-k) spectra of seismic strong-motion array data are useful in estimating back-azimuth and apparent propagation velocity of seismic waves arriving at the array. Such estimates are required to model wave passage effects while studying spatial variability of strong ground motion. Although periodogram-based spectral estimates are commonly used, practical applications based on them encounter limitations, such as, lack of objective criteria for selecting a proper smoothing window and its associated bandwidth, and relatively large variance of the estimated spectral quantities. We present an alternative spectral estimate based on parametric time series modelling approach. The well-known autoregressive (AR) time series model is used in a system-based approach to estimate the spectral matrix of auto- and cross-spectral densities. Such spectral estimates are found to be smoother than the windowed periodogram estimates, and can directly be used in f-k spectral analysis. We present an example application of the proposed technique using strong-motion data recorded by the SMART-1 array in Taiwan during the January 29 1981 \(M_{L}\) 6.3 earthquake. Our results, in terms of back azimuth and apparent propagation velocity, are found to be in excellent agreement with those reported in the literature.

Infrasound oscillations in the ionosphere affected by high-power radio waves

We present the results of filtering in the range of periods 5.6–6.7 min of temporal variations in the Doppler frequency shift of the ionosphere-reflected radio signals from the high-frequency vertical ionospheric-sounding radar located near the city of Kharkov during ionospheric plasma modification by high-power periodic (with 6-min period) radio waves of the Sura facility. It is found that switching on and off a series of pulses with 3-min duration and the same pause launched a damped wave process with 6-min period, a delay time of about 30–50 min, and an apparent propagation velocity of about 320–530 m/s. The quasi-periodic variation amplitude of the Doppler frequency shift was 10–40 MHz. The corresponding relative-perturbation amplitude of the electron number density was about 0.1–0.3%. Detected oscillations is evidence that damped infrasound density waves can be generated in the upper atmosphere.

Automated analysis of investigational near-infrared fluorescence lymphatic imaging in humans

ALFIA (Automated Lymphatic Function Imaging Analysis), an algorithm providing quantitative analysis of investigational near-infrared fluorescence lymphatic images, is described. Images from nine human subjects were analyzed for apparent lymphatic propagation velocities and propulsion periods using manual analysis and ALFIA. While lymphatic propulsion was more easily detected using ALFIA than with manual analysis, statistical analyses indicate no significant difference in the apparent lymphatic velocities although ALFIA tended to calculate longer propulsion periods. With the base ALFIA algorithms validated, further automation can now proceed to provide a clinically relevant analytic tool for quantitatively assessing lymphatic function in humans.

Ionospheric response to Kuril undersea earthquakes according to GPS satellite data

The effects that the two Kuril undersea earthquakes of November 15, 2006, and January 13, 2007, had on the ionosphere are considered on the basis of the results of measurements of variations in the ionosphere’s total electron content obtained from the network of Russian GPS stations. Owing to a favorable location of the stations, the ionosphere’s response to these earthquakes is studied in the vicinity of and far (up to distances on the order of 1000 km) from their epicenters. It is found that the apparent velocity of propagation of ionospheric disturbances (1–3 km/s) significantly exceeds the velocity of propagation of tsunami waves caused by earthquakes; this fact can be used in forecasting tsunamis. It is shown that, in parallel with the known type of ionospheric response to earthquakes in the form of an N-wave, there is also its response in the form of an inverted N-wave in the vicinity of and far from their epicenters. The causes of occurrence of the response in the form of an inverted N-wave are interpreted.