Current Acceleration Research Articles

Syn‐rift sequence development in a fault‐controlled embayment (Early Permian Irwin River Coal Measures, Northern Perth Basin, Western Australia)

AbstractStratigraphic patterns and sequence development in tectonically active extensional basins remain poorly documented in comparison with passive‐margin settings. Rift basin fills are generally characterized by coarsening‐upward trends in response to the rapid creation of accommodation by extensional faulting, and the progressive filling of graben during more quiescent periods. The Early Permian Irwin River Coal Measures in the Northern Perth Basin (Western Australia) record a complex stratigraphic arrangement of conglomerate, sandstone, mudstone and coal, and have been attributed to delta plain depositional environments that developed in a cool–temperate climatic setting during syn‐rift activity. Sedimentary analysis of outcrop and core data from the fault‐bounded Irwin Terrace is used to distinguish nine facies associations reflecting deposition in braided rivers, fixed‐anastomosed channel belts, tide‐influenced coastal environments and storm‐affected distal bays. The broader depositional system is interpreted as a morphologically asymmetrical tide‐dominated embayment with a fluvial and wave influence. The stratigraphic architecture of the Irwin River Coal Measures was strongly influenced by the evolving rift basin margin. Fault reactivation of the major basin‐bounding Darling Fault in the early syn‐rift phase caused footwall uplift and the inception of transverse palaeo‐valleys occupied by braided fluvial systems. Fault block subsidence during the subsequent balanced, backstepping and drowning phases resulted in a dominantly retrogradational stacking pattern indicating progressive flooding of marginal‐marine areas and culminating in deposition of distal marine elements. In the active rift basin, it is proposed that preservation of a shallow‐marine syn‐rift sequence was promoted by the geomorphological confinement of the embayed system increasing tidal current acceleration and hampering transgressive ravinement. The proposed sequence model demonstrates that transgressive successions can develop in the early syn‐rift phase in response to footwall uplift and tectonic subsidence. The syn‐rift sequence recording the filling of an embayment on a rift basin margin may be applied in similar tectonic and/or depositional contexts worldwide.

Sensor Systems for FRP Lightweight Structures: Automotive Features Based on Serial Sensor Products.

To achieve resource efficiency and an increased performance, as well as a higher safety and more features for vehicles, lightweight composites are a central sphere of activity for automotive innovations. This becomes particularly striking if the focus is not only a reduced vehicle weight but also an efficient overall concept. In addition to compatible material technologies and component design, new electronic solutions are of interest. A research contribution at the Robert Bosch Company deals with the direct integration of a current automotive acceleration sensor in fiber-reinforced polymer (FRP) parts. The sensor is part of the passive vehicle safety. Primarily, the principal application of the currently mounted sensor as an integrated part of the vehicle structure was proven. Sensor-integrated parts were evaluated on their sensing functionality as well as their structural performance. The present research is done to use the integrated sensor for a secondary feature. The study shows that the sensor can also be an indicator for the condition of its surrounding FRP structure. Hence, the sensor integration makes it possible to derive a secondary feature for automobiles by using the current sensor for future functionalized lightweight structures.

Covert Spoofing Algorithm of UAV Based on GPS/INS-Integrated Navigation

A covert spoofing algorithm of an unmanned aerial vehicle (UAV) based on GPS/inertial-navigation-system-integrated navigation is analyzed in this paper. The proposed algorithm theoretically proves the fact that when the acceleration component of the counterfeit GPS signal is the difference between the UAV's current acceleration and the spoofing control input, the UAV can be covert spoofed. To avoid adverse consequences (detection or crash) caused by frequent changes in UAV flight during the GPS spoofing attacks, the proposed algorithm requires that the deception trajectory planned by the GPS spoofer is slowly changing relative to the reference trajectory, which is pre-set by the UAV. Simulation results have verified the correctness of the proposed covert spoofing algorithm of UAV. Moreover, the spoofing effect is more distinct when the deception trajectory planning is considered.

Exploring the dark universe: Constraints on dynamical dark energy models from CMB, BAO and growth rate measurements

In order to explain the current acceleration of the universe, the fine-tuning problem of the cosmological constant [Formula: see text] and the cosmic coincidence problem, different alternative models have been proposed in the literature. We use the most recent observational data from CMB (Planck 2018 final data release) and LSS (SDSS, WiggleZ, VIPERS) to constrain dynamical dark energy (DE) models. The CMB shift parameter, which traditionally has been used to determine the main cosmological parameters of the standard model [Formula: see text], is employed in addition to data from redshift-space distortions through the growth parameter [Formula: see text] to constrain the mass variance [Formula: see text]. BAO data are also used to study the history of the cosmological expansion and the main properties of DE. From the evolution of [Formula: see text], we found a slowdown of acceleration behavior at low redshifts, and by using the Akaike and Bayesian Information Criteria (AIC, BIC), we discriminate different models to find those that are better suited to the observational data, finding that the interacting dark energy (IDE) model is the most favored by observational data, including information from SNIa and Hz. The analysis shows that the IDE model is followed closely by EDE and [Formula: see text] models, which in some cases fit better the observational data with individual probes.

ExPRES: an Exoplanetary and Planetary Radio Emissions Simulator

Context. Earth and outer planets are known to produce intense non-thermal radio emissions through a mechanism known as cyclotron maser instability (CMI), requiring the presence of accelerated electrons generally arising from magnetospheric current systems. In return, radio emissions are a good probe of these current systems and acceleration processes. The CMI generates highly anisotropic emissions and leads to important visibility effects, which have to be taken into account when interpreting the data. Several studies have shown that modelling the radio source anisotropic beaming pattern can reveal a wealth of physical information about the planetary or exoplanetary magnetospheres that produce these emissions. Aims. We present a numerical tool, called ExPRES (Exoplanetary and Planetary Radio Emission Simulator), which is able to reproduce the occurrence in a time-frequency plane of R−X CMI-generated radio emissions from planetary magnetospheres, exoplanets, or star–planet interacting systems. Special attention is given to the computation of the radio emission beaming at and near its source. Methods. We explain what physical information about the system can be drawn from such radio observations, and how it is obtained. This information may include the location and dynamics of the radio sources, the type of current system leading to electron acceleration and their energy, and, for exoplanetary systems, the orbital period of the emitting body and the strength, rotation period, tilt, and the offset of the planetary magnetic field. Most of these parameters can only be remotely measured via radio observations. Results. The ExPRES code provides the proper framework of analysis and interpretation for past, current, and future observations of planetary radio emissions, as well as for future detection of radio emissions from exoplanetary systems (or magnetic, white dwarf–planet or white dwarf–brown dwarf systems). Our methodology can be easily adapted to simulate specific observations once effective detection is achieved.

Turbulence and Particle Acceleration in Collisionless Magnetic Reconnection: Effects of Temperature Inhomogeneity across Pre-reconnection Current Sheet

Abstract Magnetic reconnection is an important process in various collisionless plasma environments because it reconfigures the magnetic field and releases magnetic energy to accelerate charged particles. Its dynamics depend critically on the properties of the pre-reconnection current sheet. One property in particular, cross-sheet temperature inhomogeneity, which is ubiquitous throughout the heliosphere, has been shown to increase reconnection outflow speed, energy conversion efficiency, and secondary island formation rate using two-dimensional particle-in-cell simulations. Here we expand upon these findings, considering two cases with a long, thin current sheet, one with homogeneous temperature and one with inhomogeneous temperature across the current sheet. In the inhomogeneous temperature case, numerous secondary islands form continuously, which increases current sheet turbulence (well-developed cascade power spectra) at large wavenumbers. Current density, energy conversion, dissipation, and acceleration of high-energy particles are also enhanced relative to the homogenous temperature case. Our results suggest that inhomogeneous temperature profiles, which are realistic, need to be incorporated into studies of turbulence and particle acceleration in collisionless magnetic reconnection.

Ultralight massive photons in Stueckelberg QED cosmology with self- and curvature non-minimal couplings

In this communication, we study non-minimal massive Stueckelberg QED for the evolution of the universe in the presence of non-minimal kinetic coupling to itself and to the curvature and where massive photons in the theory are of the order of the Hubble parameter or ultralight mass. By adopting the idea that the gauge vector field depends on the Hubble parameter, we observe that the universe is undergoing accelerated expansion with time and is dominated by quintessence, a decaying scalar field, and ultra-light massive photons. The existence of massive photons or massive particles of light is therefore able to explain the current acceleration of the quintessential universe in the absence of a cosmological constant.

Stability evaluation of the acceleration and energy response spectra

Seismic design codes commonly use the acceleration response spectrum to determine the seismic force. It is based on the maximum elastic response at a specific time according to the equation of motion for a single-degree-of-freedom system. The seismic effect is evaluated as the load effect by the response spectrum. However, there is no close correlation between the seismic input energy and acceleration response spectrum. Structural damage is not necessarily proportional to the maximum response of acceleration/displacement and is also significantly affected by the accumulative inelastic deformation during an earthquake. In addition, real structures have multiple stories with various distributions of the strength, stiffness and mass alongside P-Delta and torsional effects, so the current acceleration spectrum is very different from real behavior. In this study, the stability of the acceleration response spectrum according to structural characteristics mentioned above was verified by numerical analysis and compared to the stability of the energy response spectrum. The adequacy of the current design spectrum was evaluated to develop suggestions for improving the accuracy of seismic design for the ground motions with the predominant period of less than 1.00 s.

Research on Test Method of Satellite Navigation Signal Simulator

The method of the current acceleration range navigation satellite signal simulator detection theoretically analyzed, but in the actual test work, how to set the satellite navigation signal simulator motion scenes and satellite receivers, a smaller level of the RF test signal navigation As well as implementing automated testing, there is a lack of practical and feasible testing methods. This paper simulates the RF signals received by receivers in different dynamic environments in real time, builds a dynamic range test staging, forms a specific test plan, and carries out the validity, practicability and effectiveness of the test verification test method. This test method is simple and reliable. The dynamic range of the satellite navigation signal simulator in the simulation environment can be accurately detected by this method.

Greybody factor for black string in dRGT massive gravity

The greybody factor from the black string in the de Rham–Gabadadze–Tolley (dRGT) massive gravity theory is investigated in this study. The dRGT massive gravity theory is one of the modified gravity theories used in explaining the current acceleration in the expansion of the universe. Through the use of cylindrical symmetry, black strings in dRGT massive gravity are shown to exist. When quantum effects are taken into account, black strings can emit thermal radiation, called Hawking radiation. The Hawking radiation at spatial infinity differs from that at the source by the so-called greybody factor. In this paper, we examine the rigorous bounds on the greybody factors from the dRGT black strings. The results show that the greybody factor crucially depends on the shape of the potential, which is characterised by the model parameters. The results agree with ones in quantum mechanics; the higher the potential, the harder it is for the waves to penetrate, and also the lower the bound for the rigorous bounds.

IKs ion-channel pore conductance can result from individual voltage sensor movements

The IKs current has an established role in cardiac action potential repolarization, and provides a repolarization reserve at times of stress. The underlying channels are formed from tetramers of KCNQ1 along with one to four KCNE1 accessory subunits, but how these components together gate the IKs complex to open the pore is controversial. Currently, either a concerted movement involving all four subunits of the tetramer or allosteric regulation of open probability through voltage-dependent subunit activation is thought to precede opening. Here, by using the E160R mutation in KCNQ1 or the F57W mutation in KCNE1 to prevent or impede, respectively, voltage sensors from moving into activated conformations, we demonstrate that a concerted transition of all four subunits after voltage sensor activation is not required for the opening of IKs channels. Tracking voltage sensor movement, via [2-(trimethylammonium)ethyl]methanethiosulfonate bromide (MTSET) modification and fluorescence recordings, shows that E160R-containing voltage sensors do not translocate upon depolarization. E160R, when expressed in all four KCNQ1 subunits, is nonconducting, but if one, two, or three voltage sensors contain the E160R mutation, whole-cell and single-channel currents are still observed in both the presence and absence of KCNE1, and average conductance is reduced proportional to the number of E160R voltage sensors. The data suggest that KCNQ1 + KCNE1 channels gate like KCNQ1 alone. A model of independent voltage sensors directly coupled to open states can simulate experimental changes in IKs current kinetics, including the nonlinear depolarization of the conductance-voltage (G-V) relationship, and tail current acceleration as the number of nonactivatable E160R subunits is increased.

Contour current imprints and contourite drifts in the Bahamian archipelago

AbstractNew data collected along the slopes of Little and Great Bahama Bank and the abyssal plain of the Bahama Escarpment provides new insights about contour current‐related erosive structures and associated deposits. The Bahamian slope shows abundant evidence of bottom current activity such as furrows, comet‐like structures, sediment waves and drifts. At a seismic scale, large erosion surfaces and main periods of drift growth resulted from current acceleration related to plate tectonic processes and progressive opening and closure of gateways and long‐term palaeoclimate evolution. At present‐day, erosion features and contourite drifts are either related to relatively shallow currents (<1000 m water depth) or to deep currents (>2500 m water depth). It appears that the carbonate nature of the drifts does not impact the drift morphology at the resolution addressed in the present study. Classical drift morphologies defined in siliciclastic environments are found, such as mounded, plastered and separated drifts. In core, contourite sequences show a bi‐gradational trend that resembles classical contourite sequences in siliciclastic deposits showing a direct relationship with a change in current velocity at the sea floor. However, in a carbonate system the peak in grain size is associated with increased winnowing rather than increased sediment supply as in siliciclastic environments. In addition, the carbonate contourite sequence is usually thinner than in siliciclastics because of lower sediment supply rates. Little Bahama Bank and Great Bahama Bank contourites contain open‐ocean input and slope‐derived debris from glacial episodes. Inner platform, platform edge and open ocean pelagic input characterize the classical periplatform ooze during interglacials. In all studied examples, the drift composition depends on the sea floor topography surrounding the drift location and the type of sediment supply. Carbonate particles are derived from either the slope or the platform in slope and toe of slope drifts, very deep contourites have distant siliciclastic sources of sediment supply. The recent discovery of the importance of a large downslope gravitary system along Bahamian slopes suggests frequent interactions between downslope and along‐slope (contour currents) processes. The interlayering of mass flow deposits and contourites at a seismic scale or the presence of surface structures associated with both contour currents and mass flow processes shows that both processes act at the same location. Finally, contour currents have an important impact on the repartition of deep‐water coral mounds. Currents can actively interact with mounds as a nutrient and oxygen supplier or have a passive interaction, with mounds solely being obstacles orienting erosion and deposition.

Neogene palaeoceanographic changes recorded in a carbonate contourite drift (Santaren Channel, Bahamas)

AbstractThe Santaren Drift between the Great Bahama Bank and Cay Sal Bank (Bahamas) is closely linked to the development of the Gulf Stream and its shape and geometry record the local to global oceanographic, climatic and tectonic events since the Miocene. High‐resolution multichannel seismic data from the Santaren Channel allow detailed insight into the growth phases of the contourite drift, and by using the stratigraphic information from Ocean Drilling Program Site 1006 to infer its sedimentation rates. The results bring new understanding to this region and to interpretation of carbonate drifts. The data document that the signatures of a bottom current flow in the Santaren Channel initiated about 12·3 Ma, as indicated by the first occurrence of sheeted drifts and moat development at the northern part of the Santaren Channel. Narrowing and steepening of moat flanks as well as the pronounced upslope migration of the moat reflects a sustained current acceleration of the bottom currents until 5·5 Ma, associated with a transformation into mounded elongated drifts. Between 5·5 Ma and 3·1 Ma, bottom current intensity reached its maximum probably caused by the final closure of the Central American Seaway. The last 3·1 Myr were characterized by a marked increase in volume through flow reaching a maximum during the past 900 kyr. Drift growth was driven by the combined sources of export from the shallow‐water carbonate factory and by pelagic rain. The Middle Miocene channel‐related sheeted drift of the inner Santaren Channel is characterized by low accumulation rates, but a rapid increase of accumulation rates occurred during the Early Pliocene. The contourite drift buildup was disturbed by minor erosional phases with narrow moats in the Late Pliocene due to increasing bottom‐current velocities forced by strengthened Atlantic Ocean ventilation. The Early Pleistocene was dominated by increased periplatform sedimentation and margin progradation facilitated by a reduction in along‐slope current flow speed and a concurrent widening and flattening of the moats.

Deep learning hardware acceleration based on general vector DSP

As deep learning (DL) plays an increasingly significant role in several fields, designing a high performance, low power, low-latency hardware accelerator for DL has become a topic of interest in the field of architecture. Based on the structure and optimization method of DL algorithms, this study aims to analyze the difficulties and challenges in DL hardware design. In comparison with the current mainstream DL hardware acceleration platform, advantages of the DL hardware acceleration based on general vector DSP are discussed. Besides, acceleration techniques, such as vector broadcasting and matrix conversion, are described. From the viewpoint of the shortcomings of the general vector DSP discussed herein, optimization techniques such as reconfigurable computing arrays that take into account the general vector calculations as well as specific DL acceleration are discussed in depth.

Gravity and cosmology with ghost condensate

Dark energy indicated by the current acceleration of our universe is one of the greatest mysteries in modern cosmology. Although more than 70% of our universe is thought to be dark energy, we do not know what it really is. In this situation, it seems natural to ask whether we can modify gravity at long distances to address the mystery. Ghost condensation is an analog of Higgs mechanism in general relativity, and modifies gravity at long distances without pathologies like ghost instability or strong coupling. In this presentation I discuss gravity and cosmology with ghost condensate.

Transitioning Scenario of Bianchi-I Universe Within f (R,T) Formalism

In this paper, we report the existence of transitioning scenario of Bianchi type I universe in the context of $f\left(R,T\right)$ gravity with special case $f\left(R,T\right) = f_{1}(R) + f_{2}(R)f_{3}(T)$ and it's functional forms $f_{1}(R) = f_{2}(R) = R$ and $f_{3}(T) = \alpha T$ with $\alpha$ being constant. The exact solution of the Einstein's field equations are derived by using the generalized hybrid expansion law that yields the model of transitioning universe from early deceleration phase to current acceleration phase. Under this specification, we obtain the singular as well as non singular solution of Bianchi type I model depending upon the particular choice of the value of problem parameters. We also notice that the validation of weak energy condition and dominant energy condition and violation of strong energy condition occurs for these values of problem parameters. The deceleration parameter is found to be negative at present (z = 0) in the derived model which is supported by recent observations.

Reheating in quintessential inflation via gravitational production of heavy massive particles: a detailed analysis

An improved version of the well-known Peebles-Vilenkin model unifying early inflationary era to current cosmic acceleration, is introduced in order to match with the theoretical values of the spectral quantities provided by it with the recent observational data about the early universe. Since the model presents a sudden phase transition, we consider the simplest way to reheat the universe—via the gravitational production of heavy massive particles—which assuming that inflation starts at GUT scales ∼ 1016 GeV, allows us to use the Wentzel-Kramers-Brillouin (WKB) approximation and consequently this enables us to perform all the calculations in an analytic way. Our results show that the model leads to a maximum temperature at the TeV regime, and passes the bounds to ensure the success of the Big Bang Nucleosynthesis. Finally, we have constrained the quintessence piece of the proposed improved version of the Peebles-Vilenkin model using various astronomical datasets available at present.

Visualization of cosmological density fluctuations with phase space analysis: case study: Brans\u2013Dicke theory

Cosmological perturbation theory is a powerful tool to understanding the large-scale structure of the Universe. However, the set of field equations describes the general linear perturbations for the cosmological models is highly nonlinear and coupled where no analytical solution can be found. It is only after some simplification and numerical computation that we obtain limited solutions. On way around is to employ the phase space analysis and investigate the asymptotic stability of the model. The advantage of using this approach is that the system of field equations become simpler to solve numerically. The algorithm also determines the stability of the system. Here, we apply this approach in Brans–Dicke cosmology and study the attractor solutions after fitting the model with the SNeIa observational data. As a result, the model confirms small fluctuations of energy density. The model also predicts current universe acceleration confirmed by observation and benefits from phase space analysis that the new dynamical variables are independent of the model initial conditions.

Holographic Ricci Dark Energy with Constant Bulk Viscosity in f(R,T) Gravity

The holographic Ricci dark energy (HRDE) model is studied with bulk viscosity in modified f(R, T) gravity theory. We consider a universe filled with bulk viscous HRDE and pressureless dark matter. We obtain exact solutions and study the evolution of the scale factor and deceleration parameter and their transition from decelerated to accelerated expansion of the universe. The bulk viscosity coefficient is assumed to be constant. The behaviors concerning the cosmic expansion depend on the coupling parameter of f(R, T) and bulk viscous term. We apply two geometric diagnostics, the statefinder {r, s} and Om(z), to discriminate HRDE model from the ΛCDM model. We plot the evolution trajectories in the statefinder plane and Om(z) plane. We find that the viscous HRDE model behaves like quintessence at small values of the bulk-viscous term and like a Chaplygin gas at large values of the bulk-viscous term. However, the model approaches ΛCDM at late times of the evolution of the universe. We explore the obvious violation of energy-momentum conservation in f(R, T) gravity and provide a thermodynamic interpretation of extra terms generated by the nonminimal geometry-matter coupling describing particle production. We observe that the current acceleration of our universe is well explained with bulk viscosity.

The Reasons for Additional Growth Limit of Consumer Non-Purpose Loans in the Banking Sector of Bosnia and Herzegovina

The growth in consumer non-purpose loans leads to the reduction in BiH current account balance and amplifies the current account deficit. According to regression models, the commercial loan has the same effect on the current account. However, in dynamic VAR models, a commercial loan has, either neutral influence on the current account balance, or contributes to its mild growth. A commercial loan is necessary for BiH economy, because the private sector is the main factor of the economic growth, while a consumer non-purpose loan generates mainly demand for import. When a credit growth is very low, the credit is economic and not free good and additional need for the direct regulation of credit appears, especially in countries with underdeveloped financial market. The share of private companies in the credit distribution is reduced and from the economic point of view, redistribution of loans can be made only at the expense of consumer loans. Additional growth limit on the consumer non-purpose loan, which is composed of 74.2% of total consumer loans, and 34.9% of all bank’s loans (10/2016), is one of the preconditions for the decrease of current account deficit, economic growth and economic development acceleration.