scholarly journals Comment on: “Interseismic Strain Accumulation near Lisbon (Portugal) from Space Geodesy” by Fonseca et al. (2021)

2021 ◽  
Author(s):  
Luis Matias
Keyword(s):  
Relative Velocity ◽  
Strain Accumulation ◽  
Geophysical Research ◽  
First Order ◽  
Crustal Block ◽  
Tectonic Lineament ◽  
The Moment ◽  
Gnss Data ◽  
Strain Rate Field ◽  
New Evidence

The paper by Fonseca et al. (2021), hereafter referred as FON21, published in Geophysical Research Letters2 make several conclusions that are not convincingly supported by the evidence of the data that is made available. In this comment we will address the following statements: 1) FON21 “provides new evidence of sinistral simple shear driven by a NNE-SSW first-order tectonic lineament; 2) “PSInSAR vertical velocities corroborate qualitatively the GNSS strain-rate field, showing uplift/subsidence where the GNSS data indicate contraction/extension”; 3) FON21 proposes “the presence of a small block to the W of Lisbon moving independently toward the SW with a relative velocity of 0.96 ± 0.20 mm/yr”; 4) FON21 shows “that the contribution of intraplate faults to the seismic hazard in the LMA is more important than currently assumed”. We conclude that more evidence needs to be collected to confirm or infirm FON21 statements and conclusions. For the moment the proposal of an autonomous crustal block moving with significant velocity in relation to the neighboring domain should be considered speculative and unproved.

Transfers with a rendezvous lasting no more than one orbit between close near-circular coplanar orbits

2020 ◽  
pp. 82-93
Author(s):  
Aleksandr F. BRAGAZIN ◽  
Alexey V. USKOV
Keyword(s):  
Key Words ◽  
Relative Velocity ◽  
Free Parameter ◽  
Space Station ◽  
Characteristic Velocity ◽  
Orbital Station ◽  
Orbit Transfer ◽  
Simulation Results ◽  
The Moment ◽  
Phase Differences

Consideration has been given to orbit transfers involving spacecraft rendezvous which belong to a class of coplanar non-intersecting near-circular orbits of a spacecraft and a space station. The duration of the transfer is assumed to be limited by one orbit. The feasibility of a rendezvous using an optimal two-burn orbit-to-orbit transfer is studied. To determine a single free parameter of the transfer, i.e. the time of its start, ensuring a rendezvous at a given time or at a given velocity at the end of transfer, appropriate equations have been obtained To implement in the guidance algorithms optimal three-burn correction programs are proposed to achieve a rendezvous at a given time with a specified relative velocity at the moment of spacecraft contact. A range of phase differences at the start of maneuvering is determined, within which the characteristic velocity of the rendezvous is equal to the minimum characteristic velocity of the orbit-to-orbit transfer. The paper presents simulation results for “quick" rendezvous profiles that use the proposed programs. Key words: spacecraft, orbital station, “quick” rendezvous, orbit transfer, rendezvous program.

Strain Rate Evolution in Aluminium Alloy Measured by ESPI during Tensile Test

2009 ◽  
Vol 614 ◽  
pp. 155-162 ◽  
Author(s):  
Johann Petit ◽  
Guillaume Montay ◽  
Manuel François
Keyword(s):  
Tensile Test ◽  
Strain Rate ◽  
Aluminium Alloy ◽  
Speckle Pattern ◽  
Local Strain ◽  
Plastic Instability ◽  
Electronic Speckle Pattern Interferometry ◽  
The Moment ◽  
The One ◽  
Strain Rate Field

The original and significant achievement of this work is to analyse strain rate field in aluminium alloy sheets during micro tensile test. In-plane Electronic Speckle Pattern Interferometry is used to follow the evolution of the local strain in real time. This paper is based on the detection of the localization on a relatively small area of the analysed specimen: less than 5mm × 4mm area. Moreover the speed of the tensile machine is very low, 0.2 to 0.1µm/s. The phase shifting technique is used to obtain the fringes representative of the material displacement. We can therefore get a very good accuracy in the material displacement. A heterogeneity in strain rate field can be noticed from a deformation stage which doesn’t coincide with the one calculated by the classic Considère’s criterion (dF=0) for the diffuse neck initiation (or plastic instability). We also show, the moment when one of the two slip bands systems becomes predominant, and even only one band continues to exist, this occurring widely before fracture. Finally, the fracture of the specimen occurs across this remaining band. The total strain is measured with a second camera, in white light, and is correlated together with the strain rate field to study the localization.

scholarly journals Slow strain waves in blocky geological media from GPS and seismological observations on the Amurian plate

2016 ◽  
Author(s):  
Victor G. Bykov ◽  
Sergei V. Trofimenko
Keyword(s):  
Active Faults ◽  
Periodic Variation ◽  
Observation Data ◽  
Strain Waves ◽  
Crustal Block ◽  
Amurian Plate ◽  
Block Movement ◽  
Observation Series ◽  
New Evidence ◽  
Gps Station

Abstract. Based on the statistical analysis of spatiotemporal distribution of earthquake epicenters and perennial geodetic observation series, new evidence is obtained for the existence of slow strain waves in the Earth. The results of our investigation allow us to identify the dynamics of seismicity along the northern boundary of the Amurian plate as a wave process. Migration of epicenters of weak earthquakes (2 ≤ М ≤ 4) is initiated by the east-west propagation of a strain wave front at an average velocity of 2.7 km/day. We have found a synchronous quasi-periodic variation of seismicity in equally spaced clusters with spatial periods of 3.5° and 7.26° comparable with the length of slow strain waves. The geodetic observations at GPS sites in proximity to local active faults show that in a number of cases, the GPS site coordinate seasonal variations exhibit a significant phase shift, whereas the time series of these GPS sites differ significantly from a sinusoid. Based on experimental observation data and the developed model of crustal block movement we have shown that there is one possible interpretation for this fact that the trajectory of GPS station position disturbance is induced by migrating of crustal deformation in the form of slow waves.

scholarly journals Timoshenko Beam Theory: Exact Solution for First-Order Analysis, Second-Order Analysis, and Stability

2021 ◽  
Author(s):  
Valentin Fogang
Keyword(s):  
Exact Solution ◽  
Closed Form ◽  
Timoshenko Beam ◽  
Beam Theory ◽  
Second Order ◽  
Bernoulli Beam ◽  
Order Analysis ◽  
First Order ◽  
The Moment ◽  
Relationship Of

This paper presents an exact solution to the Timoshenko beam theory (TBT) for first-order analysis, second-order analysis, and stability. The TBT covers cases associated with small deflections based on shear deformation considerations, whereas the Euler–Bernoulli beam theory (EBBT) neglects shear deformations. Thus, the Euler–Bernoulli beam is a special case of the Timoshenko beam. The moment-curvature relationship is one of the governing equations of the EBBT, and closed-form expressions of efforts and deformations are available in the literature. However, neither an equivalent to the moment-curvature relationship of EBBT nor closed-form expressions of efforts and deformations can be found in the TBT. In this paper, a moment-shear force-curvature relationship, the equivalent in TBT of the moment-curvature relationship of EBBT, was presented. Based on this relationship, first-order and second-order analyses were conducted, and closed-form expressions of efforts and deformations were derived for various load cases. Furthermore, beam stability was analyzed and buckling loads were calculated. Finally, first-order and second-order element stiffness matrices were determined.

scholarly journals Magnetic fields from cosmological bulk flows

2020 ◽  
Vol 497 (3) ◽  
pp. 3537-3541
Author(s):  
J A R Cembranos ◽  
A L Maroto ◽  
H Villarrubia-Rojo
Keyword(s):  
Magnetic Fields ◽  
Cosmic Microwave Background ◽  
Galaxy Formation ◽  
Relative Velocity ◽  
Background Level ◽  
Bulk Flow ◽  
Microwave Background ◽  
Boltzmann Equations ◽  
First Order ◽  
Dynamo Mechanism

ABSTRACT We explore the possibility that matter bulk flows could generate the required vorticity in the electron–proton–photon plasma to source cosmic magnetic fields through the Harrison mechanism. We analyse the coupled set of perturbed Maxwell and Boltzmann equations for a plasma in which the matter and radiation components exhibit relative bulk motions at the background level. These background bulk motions induce a relative velocity between the matter and cosmic microwave background rest frames at the present time, i.e. a bulk flow, with an amplitude β. We find that, to first order in cosmological perturbations, bulk flows with velocities compatible with current Planck limits (β < 8.5 × 10−4 at $95{{\ \rm per\ cent}}$ CL) could generate magnetic fields with an amplitude 10−21 G on 10 kpc comoving scales at the time of completed galaxy formation that could be sufficient to seed a galactic dynamo mechanism.

Ouder dan je zou denken

Lampas ◽  
2019 ◽  
Vol 52 (4) ◽  
pp. 395-415
Author(s):  
Willemijn Waal
Keyword(s):  
Administrative Records ◽  
Linguistic Data ◽  
Classical Studies ◽  
The Moment ◽  
New Evidence ◽  
Alphabetic Writing

Summary Though it is generally agreed upon that the Greeks borrowed (and modified) the alphabet from the Phoenicians, there is no consensus about the moment when this took place. Over the years, several dates have been proposed, ranging from the 14th to the 8th – 7th century BCE. In classical studies the prevalent opinion is that the alphabet was introduced in or shortly before the 8th century BCE, when the first attestations of Greek alphabetic writing appear. There are, however, quite a number of indications (from existing and new evidence) that plead for a much earlier date. In this article, an analysis of the presently available archaeological, epigraphic and linguistic data will be presented to argue the case for an introduction in the 11th century BCE at the latest. The earliest documents, which were in all likelihood economic and administrative records, have not come down to us, because they were written on perishable materials.

Anthropogenically induced subsidence in Thessaly, central Greece: new evidence from GNSS data

2020 ◽  
Vol 102 (1) ◽  
pp. 179-200 ◽  
Author(s):  
Panagiotis Argyrakis ◽  
Athanassios Ganas ◽  
Sotirios Valkaniotis ◽  
Vasilios Tsioumas ◽  
Nikolaos Sagias ◽  
...  
Keyword(s):  
Central Greece ◽  
Gnss Data ◽  
New Evidence

Stability of a Beddington–DeAngelis type predator–prey model with trichotomous noises

2016 ◽  
Vol 30 (17) ◽  
pp. 1650102 ◽  
Author(s):  
Yanfei Jin ◽  
Siyong Niu
Keyword(s):  
Correlation Time ◽  
Gaussian White Noise ◽  
Second Order ◽  
Predator Prey ◽  
First Order ◽  
Predator Prey Model ◽  
Order Solution ◽  
Prey Model ◽  
The Stability ◽  
The Moment

The stability analysis of a Beddington–DeAngelis (B–D) type predator–prey model driven by symmetric trichotomous noises is presented in this paper. Using the Shapiro–Loginov formula, the first-order and second-order solution moments of the system are obtained. The moment stability conditions of the B–D predator–prey model are given by using Routh–Hurwitz criterion. It is found that the stabilities of the first-order and second-order solution moments depend on the noise intensities and correlation time of noise. The first-order and second-order moments are stable when the correlation time of noise is increased. That is, the trichotomous noise plays a constructive role in stabilizing the solution moment with regard to Gaussian white noise. Finally, some numerical results are performed to support the theoretical analyses.

Application of the Method of Second Order Sign Behavior To the Study of Non-Spatial Delayed Response in Rhesus Monkeys

Behaviour ◽  
1969 ◽  
Vol 35 (1-2) ◽  
pp. 128-136 ◽  
Author(s):  
Bruno Cardu
Keyword(s):  
Rhesus Monkeys ◽  
Short Term Memory ◽  
Memory Span ◽  
Second Order ◽  
Delayed Response ◽  
Short Term ◽  
Term Memory ◽  
First Order ◽  
The Moment ◽  
Sign Behavior

AbstractThe behavior of seven rhesus monkeys on a test of non-spatial delayed response based on the method of second order sign behavior is reported. Four stimuli were used: two first order stimuli presented individually (two sounds or two lights) and two second order stimuli presented simultaneously (two objects). Subjects first learned to associate one of the objects to each of the two first order stimuli. An interval between the termination of the first signal and the moment of choice was then introduced; hence the subjects' short-term memory could be estimated. All subjects succeeded in this task; the limits of the memory span ranged from 20 to 45 seconds.

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