bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Two-sample Nonparametric Test for Circular Data– its Exact Distribution and Performance
Authors: Jammalamadaka S. Rao , Guerrier Stéphane , Mangalam Vasudevan 
Published: February 2021

AbstractA nonparametric test labelled ‘Rao Spacing-frequencies test’ is explored and developed for testing whether two circular samples come from the same population. Its exact distribution and performance relative to comparable tests such as the Wheeler-Watson test and the Dixon test in small samples, are discussed. Although this test statistic is shown to be asymptotically normal, as one would expect, this large sample distribution does not provide satisfactory approximations for small to moderate samples. Exact critical values for small samples are obtained and tables provided here, using combinatorial techniques, and asymptotic critical regions are assessed against these. For moderate sample sizes in-between i.e. when the samples are too large making combinatorial techniques computationally prohibitive but yet asymptotic regions do not provide a good approximation, we provide a simple Monte Carlo procedure that gives very accurate critical values. As is well-known, the large number of usual rank-based tests are not applicable in the context of circular data since the values of such ranks depend on the arbitrary choice of origin and the sense of rotation used (clockwise or anti-clockwise). Tests that are invariant under the group of rotations, depend on the data through the so-called ‘spacing frequencies’, the frequencies of one sample that fall in between the spacings (or gaps) made by the other. The Wheeler-Watson, Dixon, and the proposed Rao tests are of this form and are explicitly useful for circular data, but they also have the added advantage of being valid and useful for comparing any two samples on the real line. Our study and simulations establish the ‘Rao spacing-frequencies test’ as a desirable, and indeed preferable test in a wide variety of contexts for comparing two circular samples, and as a viable competitor even for data on the real line. Computational help for implementing any of these tests, is made available online “” R package and is part of this paper.
Patterns of multimorbidity and risk of disability in community-dwelling older persons
Authors: Marengoni Alessandra , Akugizibwe Roselyne , Vetrano Davide L. , Roso-Llorach Albert , Onder Graziano , Welmer Anna-Karin , Calderón-Larrañaga Amaia 
Published: February 2021

AbstractThe aim was to analyze the association between specific patterns of multimorbidity and risk of disability in older persons. Data were gathered from the Swedish National Study on Aging and Care in Kungsholmen (SNAC-K); 2066 60 + year-old participants living in the community and free from disability at baseline were grouped according to their multimorbidity patterns and followed-up for six years. The association between multimorbidity patterns and disability in basic (ADL) and instrumental (IADL) activities of daily living was examined through multinomial models. Throughout the follow-up, 434 (21.0%) participants developed at least one ADL and 310 (15.0%) at least one IADL. Compared to the unspecific pattern, which included diseases not exceeding their expected prevalence in the total sample, belonging to the cardiovascular/anemia/dementia, the sensory impairment/cancer and the musculoskeletal/respiratory/gastrointestinal patterns was associated with a higher risk of developing both ADL and IADL, whereas subjects in the metabolic/sleep disorders pattern showed a higher risk of developing only IADL. Multimorbidity patterns are differentially associated with incident disability, which is important for the design of future prevention strategies aimed at delaying functional impairment in old age, and for a better healthcare resource planning.
Profiling the Self in Mobile Online Dating Apps: a Serial Picture Analysis
Authors: Degen Johanna Lisa , Kleeberg-Niepage Andrea 
Published: February 2021

AbstractProfiles in the widely used phenomenon of mobile online dating applications are characteristically reduced to condensed information mostly containing one or a few pictures. Thus, these picture(s) play a significant role for the decision-making processes and success, supposedly holding vital meaning for the subjects. While profile pictures in social media are omnipresent and some research has already focused on these pictures, especially selfies, there has been little attention with regards to the actual self-presentation when mobile online dating. In this paper, we show the results of a reconstructive serial analysis of 524 mobile online dating profile pictures investigating how subjects present themselves in the context of a mobile online dating app. This context is highly specific and characterized by continuous and dichotomous judgments by (unknown) others, unseen competition, and permanent validation of the self. Despite the conceivable multitude of possible self-presentations, our analysis led to eight clear types of self-presentation. Contemplating on subject’s good reasons for presenting the self as one of many and not as varied and unique when mobile online dating, we refer to the discourse of the private self (Gergen, The saturated self: Dilemmas of identity in contemporary life, Basic Books, New York, 1991; Rose, Governing the soul: Shaping of the private self, Free Association Books, London, 2006) and to (Holzkamp, 1983. Grundlagen der Psychologie. Frankfurt a.M.: Campus.) concept of restrictive and generalized agency in a context of socially constituted norms.
Complex Human Action Recognition Using a Hierarchical Feature Reduction and Deep Learning-Based Method
Authors: Serpush Fatemeh , Rezaei Mahdi 
Published: February 2021

AbstractAutomated human action recognition is one of the most attractive and practical research fields in computer vision. In such systems, the human action labelling is based on the appearance and patterns of the motions in the video sequences; however, majority of the existing research and most of the conventional methodologies and classic neural networks either neglect or are not able to use temporal information for action recognition prediction in a video sequence. On the other hand, the computational cost of a proper and accurate human action recognition is high. In this paper, we address the challenges of the preprocessing phase, by an automated selection of representative frames from the input sequences. We extract the key features of the representative frame rather than the entire features. We propose a hierarchical technique using background subtraction and HOG, followed by application of a deep neural network and skeletal modelling method. The combination of a CNN and the LSTM recursive network is considered for feature selection and maintaining the previous information; and finally, a Softmax-KNN classifier is used for labelling the human activities. We name our model as “Hierarchical Feature Reduction & Deep Learning”-based action recognition method, or HFR-DL in short. To evaluate the proposed method, we use the UCF101 dataset for the benchmarking which is widely used among researchers in the action recognition research field. The dataset includes 101 complicated activities in the wild. Experimental results show a significant improvement in terms of accuracy and speed in comparison with eight state-of-the-art methods.
Observations of Density Cavities and Associated Warm Ion Flux Enhancements in the Inner Magnetosphere
Authors: Ferradas C. P. , Boardsen S. A. , Fok M.‐C. , Buzulukova N. , Reeves G. D. , Larsen B. A. 
Published: February 2021

AbstractWe present a statistical study of density cavities observed in the inner magnetosphere by the Van Allen Probes during four one‐month periods: February 2013, July 2013, January 2014, and June 2014. These periods were chosen to allow the survey of all magnetic local times. We find that density cavities are a recurrent feature of the density profiles of in situ measurements in the inner magnetosphere. We further investigate the correlation between the density cavities and the enhancement of fluxes of warm ions with energies of 10–100 eV. The results show that warm ion flux enhancements associated with the density cavities were observed more frequently for H+, then for He+ and the least frequently for O+. The occurrences of the associated flux enhancements were increased when considering only the cavities inside the plasmasphere. Possible mechanisms responsible for the observed warm ion flux enhancements and the role of density cavities on these ion flux enhancements are discussed.
RBSP‐ECT Combined Pitch Angle Resolved Electron Flux Data Product
Authors: Boyd A. J. , Spence H. E. , Reeves G. D. , Funsten H. O. , Skoug R. M. , Larsen B. A. , Blake J. B. , Fennell J. F. , Claudepierre S. G. , Baker D. N. , Kanekal S. G. , Jaynes A. N. 
Published: February 2021

AbstractWe describe a new data product combining pitch angle resolved electron flux measurements from the Radiation Belt Storm Probes (RBSP) Energetic Particle Composition and Thermal Plasma (ECT) suite on the National Aeronautics and Space Administration’s Van Allen Probes. We describe the methodology used to combine each of the data sets and produce a consistent set of pitch‐angle‐resolved spectra for the entire Van Allen Probes mission. Three‐minute‐averaged flux spectra are provided spanning energies from 15 eV up to 20 MeV. This new data product offers researchers a consistent cross calibrated data set to explore the particle dynamics of the inner magnetosphere across a wide range of energies.
On the Effects of Mesospheric and Lower Thermospheric Oxygen Chemistry on the Thermosphere and Ionosphere Semiannual Oscillation
Authors: Jones M. , Sutton E. K. , Emmert J. T. , Siskind D. E. , Drob D. P. 
Published: February 2021

AbstractThis study quantifies mesosphere/lower thermosphere (MLT) oxygen chemical contributions to the global thermosphere‐ionosphere (T‐I) semiannual oscillation (SAO) using a series of numerical experiments from the National Center for Atmospheric Research (NCAR) thermosphere‐ionosphere‐mesosphere‐electrodynamics general circulation model (TIME‐GCM) that isolate essential chemical processes affecting O and O2 in the MLT region. We track the vertical dynamical, diffusive, and chemical fluxes of O and O2 in and out of two control volumes between ∼80 and 130 km using a finite volume approach to the individual species continuity equation to investigate their relative importance on the global T‐I SAO. TIME‐GCM results indicate that the global T‐I SAO amplitude and phase is fairly insensitive to significant changes in odd oxygen chemical reaction rates in the MLT. While chemistry has an appreciable effect on O in the MLT region, sensitivity to changes in odd oxygen and odd hydrogen chemical rates appear to be offset by a consequent adjustment in the vertical bulk wind and eddy diffusive transport of O locally, rendering their effects inconsequential to the global T‐I SAO aloft. The implications of our findings for reproducing a self‐consistent global T‐I SAO in the NCAR thermosphere‐ionosphere‐electrodynamics general circulation model (TIE‐GCM) with a lower boundary near ∼100 km are discussed. Specifically, including latitude‐season variations in O, O2, and N2 from NRLMSIS® 2.0 at the lower boundary of the TIE‐GCM near ∼100 km improves its representation of the climatological T‐I SAO. However, reformulating the TIE‐GCM temperature lower boundary condition could further improve its ability to simulate the T‐I SAO from first‐principles.
Near Trench 3D Seismic Attenuation Offshore Northern Hikurangi Subduction Margin, North Island, New Zealand
Authors: Nakai Jenny S. , Sheehan Anne F. , Abercrombie Rachel E. , Eberhart‐Phillips Donna 
Published: February 2021

AbstractWe image seismic attenuation near the Hikurangi trench offshore New Zealand, using ocean bottom and land‐based seismometers, revealing high attenuation above a recurring shallow slow‐slip event and within the subducting Hikurangi Plateau. The Hikurangi subduction margin east of the North Island, New Zealand is the site of frequent shallow slow slip events. Overpressured fluids are hypothesized to lead to slow slip at shallow depths close to the oceanic trench. Seismic attenuation, energy loss of seismic waves, can be used to detect high temperatures, melt, the presence of fluids, and fractures. We use local earthquake P‐ and S‐waves from 180 earthquakes to invert for t*, and subsequently invert for Qp and Qs, offshore the North Island directly above the area of slow slip. We image Qp and Qs to ∼25 km depth, increasing resolution of previously identified coastal low Q (100–300), and finding a new region of even higher attenuation (Qp and Qs < 50–100) directly above the shallow slow slip event of 2014–2015, beneath the offshore seismic array. This highest attenuation is downdip of a subducting seamount, and is spatially correlated with a high seismic reflectivity zone and Vp/Vs > 1.85, all of which provide evidence for the presence of fluids. The Qp and Qs is low at the trench (<50–100) and in the subducting plate (100–200), suggesting that seismic wave scattering due to faults, fractures, and the inherent heterogeneous composition of the Hikurangi Plateau, a large igneous province, plays a role in seismic attenuation.
Vorticity Recirculation and Asymmetric Generation at a Small Headland With Broadband Currents
Authors: Kovatch Michael , Feddersen Falk , Grimes Derek J. , MacMahan Jamie H. 
Published: February 2021

AbstractFixed acoustic Doppler current profiler (ADCP) velocity measurements are used to investigate headland vorticity generation and recirculation in ∼20 m depth around the small (∼1 km) central California headland Pt. Sal. To reduce vorticity estimation noise, velocities are reconstructed from the first two Empirical Orthogonal Function modes representing ≈73% of the variance. Using fixed ADCPs, depth‐averaged vorticity is estimated west and south of Pt. Sal. Only one west‐location vorticity component is estimated, leading to negative vorticity bias for northward flow. The south location vorticity is consistent with estimates from parallel vessel transects on one day. The observed depth‐averaged flow V was primarily along‐bathymetric contours and varied ±0.2 ms−1 across subtidal and tidal frequency bands. The depth‐averaged normalized vorticity varied ±8 across all frequency bands. Vorticity distributions are skewed with opposite sign at west and south locations, and is more likely at the west location. At both locations, depth‐averaged vorticity and velocity are inversely related, with relationship asymmetric with sign of V, indicating headland and farther upstream vorticity generation. Binned‐mean depends on both V and its time‐derivative, and indicates vorticity recirculation across the headland. The ∼2 h vorticity adjustment timescale and the associated short excursion distances indicate vorticity generation between south and west locations. Potential vorticity changes across the headland are different for positive and negative V indicating headland asymmetric vorticity generation. Pt. Sal occupies a nondimensional parameter space that is unique relative to other well studied headlands.
Four Types of Baroclinic Instability Waves in the Global Oceans and the Implications for the Vertical Structure of Mesoscale Eddies
Authors: Feng Ling , Liu Chuanyu , Köhl Armin , Stammer Detlef , Wang Fan 
Published: February 2021

AbstractLinear stability analysis is re‐conducted to fully understand the geostrophic distribution of the different types of baroclinic instability (BCI) in the global oceans, their correspondence to the different vertical structures of the observed mesoscale eddies, and the properties and formation mechanisms of the instability waves. Four principal vertical types of BCI are identified, which are found to exhibit large‐scale patterns in the global ocean. The surface‐ and bottom‐intensified type (called the Eady type hereafter) is mainly located in the Antarctic Circumpolar Current (ACC) region, locations of the bottom‐intensified type (Charney_b type) are scattered around the Eady type, the surface‐intensified type (Charney_s type) primarily occurs in the subtropics (10°–35°), and the interior‐intensified type (Phillips type) occurs primarily between 5° and 20° in both hemispheres. More specifically, both geostrophic locations and the depths of the maximum perturbation velocities of the Phillips type BCIs match those of observed subsurface eddies. Moreover, the BCI waves show regions of uniform propagation properties: eastward in the ACC and the mid‐latitudes (25°–45°), and westward in the low latitudes (30°S–30°N) of both hemispheres and in the high latitudes of the Northern Hemisphere (>50°N). These waves resemble normal mode Rossby waves in structure (i.e., first baroclinic, second baroclinic, and topographic Rossby waves), but their propagation speeds are found to be Doppler shifted by the mean flows relevant for the corresponding BCI type. Propagating signals with the same dispersion relationships as the BCI waves are captured with numerical ocean general circulation models.
The Role of Climate and Lake Size in Regulating the Ice Phenology of Boreal Lakes
Authors: Higgins S. N. , Desjardins C. M. , Drouin H. , Hrenchuk L. E. , van der Sanden J. J. 
Published: February 2021

AbstractWe quantified the relationships between seasonal air temperatures and ice phenology for a 0.54 km2 boreal lake in Northwestern Ontario, Canada using a 50‐year time series (1970–2019). Significant temporal trends in the duration of ice cover (−4.0 days decade−1) occurred over the study period and both ice‐on and ice‐off dates were highly predictable from seasonal air temperatures. While temporal trends in ice‐off dates were not significant, ice‐on dates trended later by 2.2 days decade−1, and both ice‐off dates and the duration of ice‐cover became increasingly variable over the study period. For three consecutive winter seasons, we also evaluated regional variations of ice‐phenology and snow and ice‐thickness from 9 to 30 boreal lakes across a lake size gradient (0.02–26 km2) using ground based and satellite observations. Regional variation of ice‐on dates (30–45 days), ice‐off dates (10–21 days), and total duration of ice‐cover (22–38 days) between lakes displayed significant nonlinear relationships to lake size across all years. Regional variation of ice‐off dates was structured according to lake size, and appeared driven by relationships between lake size, snow thickness, and ice thickness. Multiple linear regression and generalized additive modeling approaches to predict ice‐on and ice‐off dates at the regional scale by integrating the effects of air temperature and lake size had similar performance, explaining >90% of the variance of observed.
Reliable intermittent extended dissipative control for uncertain fuzzy flexible spacecraft systems with Bernoulli stochastic distribution
Authors: Ding Kui , Zhu Quanxin 
Published: February 2021

AbstractThis paper addresses the problem of uncertain fuzzy intermittent extended dissipative control to stabilize the flexible spacecraft (FS). However, to the systems with actuator random failures, input saturation and Bernoulli stochastic distribution by utilizing a novel switching Lyapunov function method. Compared with the existing common Lyapuonv function, the proposed approach is convenient for us to exploit more information of switching interval. Especially, the condition that control length and control period must be a certain proportion in the previous works of intermittent control strategy is removed in this work, which promotes the obtained criterion to be less conservative. Numerical simulations are finally given to demonstrate the validity and superiority of the theoretical results.
Performance‐enhanced iterative learning control using a model‐free disturbance observer
Authors: Li Min , Yan Tingjian , Mao Caohui , Wen Long , Zhang Xinxin , Huang Tao 
Published: February 2021

AbstractThis paper proposes a novel performance‐enhanced iterative learning control (ILC) scheme using a model‐free disturbance observer (DOB) to achieve high performance for precision motion systems that encounter non‐repetitive disturbances. As is well known, the performance of the standard ILC (SILC) is severely degraded by the non‐repetitive disturbances. By introducing DOB into SILC, this paper improves the robustness of the ILC system against non‐repetitive disturbances. In the proposed enhanced ILC (EILC), SILC aims at learning the feedforward signals for a specific reference, while DOB is to compensate for external disturbances. Little or no plant model knowledge is required for SILC. To maintain this advantage after introducing DOB, a model‐free design method for DOB is proposed to release the need for the plant model. Based only on a specific reference and the corresponding feedforward signals learned by SILC, the filter of DOB is optimized via an instrumental‐variable estimate method. Numerical simulation is performed to illustrate the effectiveness and enhanced performance of the proposed control approach.
The robust multi‐innovation estimation algorithm for Hammerstein non‐linear systems with non‐Gaussian noise
Authors: Wang Xuehai , Ding Feng 
Published: February 2021

AbstractThe characteristic of the external noise has significant influences on system modelling and identification, and the assumption that the noise follows the Gaussian distribution may be invalid due to realistic reasons. This paper discusses the identification issue of Hammerstein non‐linear systems with non‐Gaussian noise and presents a robust gradient algorithm. The algorithm is derived based on the logarithmic cost function of continuous mixed ‐norm of prediction errors, which takes into account each ‐norm of errors for . The gain at each recursive step adapts to the data quality so that the algorithm has good robustness to non‐Gaussian noise. To improve the estimation accuracy, a robust multi‐innovation gradient algorithm is proposed by using the multi‐innovation identification theory. Two examples are provided to exhibit the validity of the proposed algorithms.
Optimal mean‐square consensus for heterogeneous multi‐agent system with probabilistic time delay
Authors: Sun Fenglan , Li Hao , Zhu Wei , Kurths Jürgen 
Published: February 2021

AbstractThis paper studies the mean‐square consensus for heterogeneous multi‐agent systems with probabilistic time delay. Each agent in the system has an objective function and only knows its own objective function. Control protocols for the system both over the fixed and the switched weighted‐balanced topologies are designed. The consensus state of agents' position can make the sum of objective functions minimum. By adopting probability statistics, stochastic process, matrix theory and some stability method, sufficient conditions for the consensus protocol are given. Several simulations are presented to illustrate the potential correctness of the results.