bluuebunny/crossref_metadata_2025_split huggingface dataset:
On Sufficient Conditions for Chaotic Behavior of Multidimensional Discrete Time Dynamical System
Authors: Kamarudin Nor Syahmina , Dzul-Kifli Syahida Che 
Published: April 2021

AbstractIn this work, we look at the extension of classical discrete dynamical system to multidimensional discrete-time dynamical system by characterizing chaos notions on $${\mathbb {Z}}^d$$

Z

d

-action. The $${\mathbb {Z}}^d$$

Z

d

-action on a space X has been defined in a very general manner, and therefore we introduce a $${\mathbb {Z}}^d$$

Z

d

-action on X which is induced by a continuous map, $$f:{\mathbb {Z}}\times X \rightarrow X$$

f
:
Z
×
X
→
X

and denotes it as $$T_f:{\mathbb {Z}}^d \times X \rightarrow X$$

T
f

:

Z

d

×
X
→
X

. Basically, we wish to relate the behavior of origin discrete dynamical systems (X, f) and its induced multidimensional discrete-time $$(X,T_f)$$

(
X
,

T
f

)

. The chaotic behaviors that we emphasized are the transitivity and dense periodicity property. Analogues to these chaos notions, we consider k-type transitivity and k-type dense periodicity property in the multidimensional discrete-time dynamical system. In the process, we obtain some conditions on $$(X,T_f)$$

(
X
,

T
f

)

under which the chaotic behavior of $$(X,T_f)$$

(
X
,

T
f

)

is inherited from the original dynamical system (X, f). The conditions varies whenever f is open, totally transitive or mixing. Some examples are given to illustrate these conditions.
A Proactive Approach to Evaluating Intersection Safety Using Hard-Braking Data
Authors: Hunter Margaret , Saldivar-Carranza Enrique , Desai Jairaj , Mathew Jijo K. , Li Howell , Bullock Darcy M. 
Published: April 2021

AbstractTypical safety improvements at signalized intersections are identified and prioritized using crash data over 3–5 years. Enhanced probe data that provides date, time, heading, and location of hard-braking events has recently become available to agencies. In a typical month, over six million hard-braking events are logged in the state of Indiana. This study compared rear-end crash data over a period of 4.5 years at 8 signalized intersections with weekday hard-braking data from July 2019. Using Spearman’s rank-order correlation, results indicated a strong correlation between hard-braking events and rear-end crashes occurring more than 400 ft upstream of an intersection. The paper concludes that using a month or two of hard-braking events occurring upstream from the stop bar may be a useful tool to screen potential locations with elevated rear-end crashes. Using these techniques described in this paper, new commercially available hard-braking data sources will provide an opportunity for agencies to follow up with mitigation measures addressing emerging problems much quicker than typical practices that rely on 3–5 years of crash data.
Research on the viscosity of stabilized emulsions in different pipe diameters using pressure drop and phase inversion
Authors: Plasencia Jose , Inkson Nathanael , Nydal Ole Jørgen 
Published: April 2021

AbstractThis paper reports experimental research on the flow behavior of oil-water surfactant stabilized emulsions in different pipe diameters along with theoretical and computational fluid dynamics (CFD) modeling of the relative viscosity and inversion properties. The pipe flow of emulsions was studied in turbulent and laminar conditions in four pipe diameters (16, 32, 60, and 90 mm) at different mixture velocities and increasing water fractions. Salt water (3.5% NaCl w/v, pH = 7.3) and a mineral oil premixed with a lipophilic surfactant (Exxsol D80 + 0.25% v/v of Span 80) were used as the test fluids. The formation of water-in-oil emulsions was observed from low water fractions up to the inversion point. After inversion, unstable water-in-oil in water multiple emulsions were observed under different flow regimes. These regimes depend on the mixture velocity and the local water fraction of the water-in-oil emulsion. The eddy turbulent viscosity calculated using an elliptic-blending k-ε model and the relative viscosity in combination act to explain the enhanced pressure drop observed in the experiments. The inversion process occurred at a constant water fraction (90%) and was triggered by an increase of mixture velocity. No drag reduction effect was detected for the water-in-oil emulsions obtained before inversion.
IASI‐Derived Sea Surface Temperature Data Set for Climate Studies
Authors: Parracho Ana C. , Safieddine Sarah , Lezeaux Olivier , Clarisse Lieven , Whitburn Simon , George Maya , Prunet Pascal , Clerbaux Cathy 
Published: April 2021

AbstractSea surface temperature (SST) is an essential climate variable, that is directly used in climate monitoring. Although satellite measurements can offer continuous global coverage, obtaining a long‐term homogeneous satellite‐derived SST data set suitable for climate studies based on a single instrument is still a challenge. In this work, we assess a homogeneous SST data set derived from reprocessed Infrared Atmospheric Sounding Interferometer (IASI) level‐1 (L1C) radiance data. The SST is computed using Planck's Law and simple atmospheric corrections. We assess the data set using the ERA5 reanalysis and the EUMETSAT‐released IASI level‐2 SST product. Over the entire period, the reprocessed IASI SST shows a mean global difference with ERA5 close to zero, a mean absolute bias under 0.5°C, with a SD of difference around 0.3°C and a correlation coefficient over 0.99. In addition, the reprocessed data set shows a stable bias and SD, which is an advantage for climate studies. The interannual variability and trends were compared with other SST data sets: ERA5, Hadley Centre's SST (HadISST), and NOAA's Optimal Interpolation SST Analysis (OISSTv2). We found that the reprocessed SST data set is able to capture the patterns of interannual variability well, showing the same areas of high interannual variability (>1.5°C), including over the tropical Pacific in January corresponding to the El Niño Southern Oscillation. Although the period studied is relatively short, we demonstrate that the IASI data set reproduces the same trend patterns found in the other data sets (i.e., cooling trend in the North Atlantic, warming trend over the Mediterranean).
The TEC Enhancement Before Seismic Events Is an Artifact
Authors: Eisenbeis J. , Occhipinti G. 
Published: April 2021

AbstractSince 2011 there has been an ongoing debate about the possibility of short‐term earthquake prediction using total electron content (TEC) ionospheric monitoring by the Global Navigation Satellite System (GNSS). Heki (2011), https://doi.org/10.1029/2011gl047908 initiated this debate when he published results for the 2011 Tohoku event reporting a TEC enhancement 40 min before the earthquake; several later papers by Heki and coworkers have made similar claims for other earthquakes. If correct, Heki's methods might contribute to short‐term earthquake prediction. However, Heki's claims have been strongly criticized as being due to a decrease in the background TEC after earthquakes–the so called ionospheric hole–rather than an enhancement before. Depending on the choice of reference curve to be subtracted from the raw data to infer the “anomaly,” the data analysis can produce either a hole or an enhancement. We show that the choice of reference curve ‐calculated by Heki with a polynomial fit‐is strongly affected by the degree of the polynomial, as well as by the selection of the time window. We also show using synthetic examples that even if there is actually no signal before the event, Heki's methods can lead to spurious precursory signals (i.e., signals with non‐zero amplitude before the event) after the reference curve is subtracted. It thus appears likely that the reported TEC enhancements are artifacts.
A Comparison of Fabry–Perot Interferometer and Meteor Radar Wind Measurements Near the Polar Mesopause Region
Authors: Lee Changsup , Jee Geonhwa , Kam Hosik , Wu Qian , Ham Young‐Bae , Kim Yong Ha , Kim Jeong‐Han 
Published: April 2021

AbstractThe neutral winds in the Mesosphere and Lower Thermosphere (MLT) region have been observed at King Sejong Station, Antarctica using a meteor radar (MR) and a Fabry–Perot interferometer (FPI) simultaneously. These two independent MLT wind measurements are compared to each other to identify the characteristics of FPI measurement. Instead of using a fixed emission height for FPI winds, for the first time, we consider the temporal variations of airglow emission layer in association with corresponding meteor height distributions for more accurate comparison between the FPI and MR winds. The temporal variations of the airglow emission layers are examined from the inverse relationship between the height integrated emission rate and the peak emission height derived from the TIMED/SABER observations. It is found that FPI winds are consistently smaller than MR winds and the discrepancy becomes larger for OI emission at higher altitude, which may be related to large wind shear in the MLT region and variabilities of the emission layers. Finally, we found that the FPI can provide reliable height‐averaged winds in the MLT region where existing a strong wind shear from this simultaneous MR wind measurements.
Electrostatic Waves and Electron Heating Observed Over Lunar Crustal Magnetic Anomalies
Authors: Chu F. , Halekas J. S. , Cao X. , McFadden J. P. , Bonnell J. W. , Glassmeier K.‐H. 
Published: April 2021

AbstractAbove lunar crustal magnetic anomalies, large fractions of solar wind electrons and ions can be scattered and stream back toward the solar wind flow, leading to a number of interesting effects such as electrostatic instabilities and waves. These electrostatic structures can also interact with the background plasma, resulting in electron heating and scattering. We study the electrostatic waves and electron heating observed over the lunar magnetic anomalies by analyzing data from the Acceleration, Reconnection, Turbulence, and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS) spacecraft. Based on the analysis of two lunar flybys in 2011 and 2013, we find that the electron two‐stream instability (ETSI) and electron cyclotron drift instability (ECDI) may play an important role in driving the electrostatic waves. We also find that ECDI, along with the modified two‐stream instability (MTSI), may provide the mechanisms responsible for substantial isotropic electron heating over the lunar magnetic anomalies.
Quiet Night Arctic Ionospheric D Region Characteristics
Authors: Thomson Neil R. , Clilverd Mark A. , Brundell James B. , Rodger Craig J. 
Published: April 2021

AbstractVLF radio propagation recordings are used to determine the characteristics of the nighttime polar lower D region of the ionosphere. Recordings of both VLF phase and amplitude in the Arctic on days within ∼1–2 weeks of the equinoxes enable their day‐to‐night changes to be determined. These changes are then combined with previously measured daytime polar D region characteristics to find the nighttime characteristics. The previously determined daytime characteristics were measured in the Arctic summer; the NRLMSISE atmosphere model is used to help determine the height change from daytime summer to daytime equinox (∼5 km lower). The principal path used was from the 16.4 kHz Norwegian transmitter JXN (67°N, 14°E) 1,334 km northwards across the Arctic Ocean to Ny‐Ålesund (79°N, 12°E), Svalbard. Also used were the 2,014‐km path from NRK (37.5 kHz, Grindavik, 64°N, Iceland) to Ny‐Ålesund, the 1,655‐km path from JXN to Reykjavik (64°N, Iceland), and the 5,302‐km path from JXN across the Arctic Ocean to Fairbanks (65°N) in Alaska. The night values of (the Wait parameters) H′ and β were found to average from ∼79 km at equinox down to 77 km near winter solstice (lower than the 85 km at low and midlatitudes by ∼7 km) and 0.6 km−1, respectively. This lower height and its variability are shown to be consistent with the principal source of ionization being energetic electron precipitation.
Sustained Oxygen Spectral Gaps and Their Dynamic Evolution in the Inner Magnetosphere
Authors: Yue Chao , Zhou Xu‐Zhi , Bortnik Jacob , Zong Qiu‐Gang , Li Yuxuan , Ren Jie , Reeves Geoffrey D. , Spence Harlan E. 
Published: April 2021

AbstractVan Allen Probes observations of ion spectra often show a sustained gap within a very narrow energy range throughout the full orbit. To understand their formation mechanism, we statistically investigate the characteristics of the narrow gaps for oxygen ions and find that they are most frequently observed near the noon sector with a peak occurrence rate of over 30%. The magnetic moment (μ) of the oxygen ions in the gap shows a strong dependence on magnetic local time (MLT), with higher and lower μ values in the morning and afternoon sectors, respectively. Moreover, we find through superposed epoch analysis that the gap formation also depends on geomagnetic conditions. Those gaps formed at lower magnetic moments (μ < 3,000 keV/G) are associated with stable convection electric fields, which enable magnetospheric ions to follow a steady drift pattern that facilitates the gap formation by corotational drift resonance. On the other hand, gaps with higher μ values are statistically preceded by a gradual increase of geomagnetic activity. We suggest that ions within the gap were originally located inside the Alfven layer following closed drift paths, before they were transitioned into open drift paths as the convection electric field was enhanced. The sunward drift of these ions, with very low fluxes, forms a drainage void in the dayside magnetosphere manifested as the sustained gap in the oxygen spectrum. This scenario is supported by particle‐tracing simulations, which reproduce most of the observed characteristics and therefore provide new insights into inner magnetospheric dynamics.
Thermal Weakening Friction During Seismic Slip: Experiments and Models With Heat Sources and Sinks
Authors: Nielsen S. , Spagnuolo E. , Violay M. , Di Toro G. 
Published: April 2021

AbstractExperiments that systematically explore rock friction under crustal earthquake conditions reveal that faults undergo abrupt dynamic weakening. Processes related to heating and weakening of fault surfaces have been invoked to explain pronounced velocity weakening. Both contact asperity temperature Ta and background temperature T of the slip zone evolve significantly during high‐velocity slip due to heat sources (frictional work), heat sinks (e.g., latent heat of decomposition processes), and diffusion. Using carefully calibrated High‐Velocity Rotary Friction experiments, we test the compatibility of thermal weakening models: (1) a model of friction based only on T in an extremely simplified, Arrhenius‐like thermal dependence; (2) a flash heating model which accounts for the evolution of both V and T; (3) same but including heat sinks in the thermal balance; and (4) same but including the thermal dependence of diffusivity and heat capacity. All models reflect the experimental results but model (1) results in unrealistically low temperatures and model (2) reproduces the restrengthening phase only by modifying the parameters for each experimental condition. The presence of dissipative heat sinks in stage (3) significantly affects T and reflects on the friction, allowing a better joint fit of the initial weakening and final strength recovery across a range of experiments. Temperature is significantly altered by thermal dependence of (4). However, similar results can be obtained by (3) and (4) by adjusting the energy sinks. To compute temperature in this type of problem, we compare the efficiency of three different numerical approximations (finite difference, wavenumber summation, and discrete integral).
Cross‐Scale Seismic Anisotropy Analysis in Metamorphic Rocks From the COSC‐1 Borehole in the Scandinavian Caledonides
Authors: Kästner Felix , Pierdominici Simona , Zappone Alba , Morales Luiz F. G. , Schleicher Anja M. , Wilke Franziska D. H. , Berndt Christian 
Published: April 2021

AbstractMetamorphic and deformed rocks in thrust zones show particularly high seismic anisotropy causing challenges for seismic imaging and interpretation. A good example is the Seve Nappe Complex in central Sweden, an old exhumed orogenic thrust zone that is characterized by a strong but incoherent seismic reflectivity and considerable seismic anisotropy. However, only little is known about their origin in relation to composition and structural influences on measurements at different seismic scales. Here, we present a new integrative study of cross‐scale seismic anisotropy analyses combining mineralogical composition, microstructural analyses, and seismic laboratory experiments from the COSC‐1 borehole, which sampled a 2.5‐km‐deep section of metamorphic rocks deformed in an orogenic root now preserved in the Lower Seve Nappe. While there is strong crystallographic preferred orientation in most samples in general, variations in anisotropy depend mostly on bulk mineral composition and dominant core lithology as shown by a strong correlation between these. This relationship enables to identify three distinct seismic anisotropy facies providing a continuous anisotropy profile along the borehole. Moreover, comparison of laboratory seismic measurements and electron‐backscatter diffraction data reveals a strong scale dependence, which is more pronounced in the highly deformed, heterogeneous samples. This highlights the need for comprehensive cross‐validation of microscale anisotropy analyses with additional lithological data when integrating seismic anisotropy over seismic scales.
Nearshore Monitoring With X‐Band Radar: Maximizing Utility in Dynamic and Complex Environments
Authors: Atkinson J. , Esteves L. S. , Williams J. J. , Bell P. S. , McCann D. L. 
Published: April 2021

AbstractCoastal management and engineering applications require data that quantify the nature and magnitude of changes in nearshore bathymetry. However, bathymetric surveys are usually infrequent due to high costs and complex logistics. This study demonstrates that ground‐based X‐band radar offers a cost‐effective means to monitor nearshore changes at relatively high frequency and over large areas. A new data quality and processing framework was developed to reduce uncertainties in the estimates of radar‐derived bathymetry and tested using data from an 18‐months installation at Thorpeness (UK). In addition to data calibration and validation, two new elements are integrated to reduce the influence of data scatter and outliers: (a) an automated selection of periods of “good data” and (b) the application of a depth‐memory stabilization. For conditions when the wave height is >1 m, the accuracy of the radar‐derived depths is shown to be ±0.5 m (95% confidence interval) at 40 × 40‐m spatial resolution. At Thorpeness, radar‐derived bathymetry changes exceeding this error were observed at time scales ranging from 3 weeks to 6 months. These data enabled quantification of changes in nearshore sediment volume at frequencies and spatial cover that would be difficult and/or expensive to obtain by other methods. It is shown that the volume of nearshore sediment movement occurring at time scale as short as few weeks are comparable with the annual longshore transport rates reported in this area. The use of radar can provide an early warning of changes in offshore bathymetry likely to impact vulnerable coastal locations.
Wave Effects on Sediment Transport and Entrapment in a Channel‐Shoal Estuary: The Pearl River Estuary in the Dry Winter Season
Authors: Zhang Guang , Chen Yuren , Cheng Weicong , Zhang Heng , Gong Wenping 
Published: April 2021

AbstractSediment dynamics have great effects on the morphology of estuaries and deltas. As riverine sediment input has decreased in many estuaries in recent years, the removal and dispersion of sediments by currents and waves inside estuaries has assumed a more dominant role; however, the overall effects of waves are less well understood. In this study, we used the Coupled Ocean Atmosphere Wave Sediment Transport system to model the effects of waves on sediment transport in China's Pearl River Estuary. The results indicate that the presence of waves increased the landward current and sediment transport at the bottom of the channel and the seaward fluxes of water and sediment at the West Shoal, which is the main shallow area that accepts riverine sediment. Relative to the case without waves, the effects of waves increased the estuary's total sediment export by 45% to 9.14 megatons in one typical year, which even exceeded the annual riverine load in the year. The dry winter season shows the highest wave effects on sediment budget, and the sediment export was increased by 86% to 2.59 megatons with waves when compared with that without waves. This increase export was mainly concentrated at the surface near the western shore. Moreover, the waves increased lateral sediment entrapment in the Southwest Shoal, which explains the local geomorphologic evolution in recent decades. This study is of implication for the study on sediment exchange between shoal and channel in estuaries and on the fates of riverine sediment from source to sink.
Estimate of the D/H Ratio in the Martian Upper Atmosphere from the Low Spectral Resolution Mode of MAVEN/IUVS
Authors: Chaufray J‐Y. , Mayyasi M. , Chaffin M. , Deighan J. , Bhattacharyya D. , Clarke J. , Jain S. , Schneider N. , Jakosky B. 
Published: April 2021

AbstractRecent Mars Atmosphere and Volatile EvolutioN (MAVEN) observations have shown unexpectedly large deuterium Lyman‐α emissions near the Martian southern summer solstice. The deuterium Lyman‐α brightness can reach ∼10% of the hydrogen Lyman‐α brightness below 200 km. In this study, we propose a method to estimate the D/H ratio in the Martian upper atmosphere through analysis of the Lyman‐α vertical profiles without the ability to spectrally separate the two atomic emission lines. Lyman‐α vertical profiles measured by MAVEN/IUVS at four periods are analyzed. During southern summer, the derived D/H ratios at 200 km are larger than the HDO/H2O ratio measured in the lower atmosphere, yet the extrapolated D/H ratio from 200 to 80 km agrees with the HDO/H2O ratio. This larger D/H ratio at higher altitude is attributed to the more efficient escape of hydrogen atoms compared to deuterium atoms. The method we describe accounts for uncertainties related to constraining the temperature and density profiles of H and D in the lower thermosphere. Because spectrally resolved D and H Lyman‐α measurements are not always available, this method provides a way to estimate D/H variations in their absence. This method will be useful for analysis of relevant data sets from past and future Mars missions.