Position Of Boundary Research Articles

Flexural Wave Bandgap Characteristics Analysis of Periodic Double-Span Beam Based on Spectral Geometry Method: A Unified Formulation

The bandgap characteristics of periodic double-span beams are analyzed using spectral geometry methods in this paper. The displacement function of the beam structure is represented in a unified form, supplemented by sine series in addition to Fourier cosine series to avoid discontinuities in displacement at the boundary positions. The introduction of artificial spring technology satisfies the strong coupling connection conditions between beams. Combining it with Bloch’s theorem allows the separation of boundary conditions and displacement functions, ensuring the convergence and accuracy of the method. The energy functional of the double-span beam under periodic boundary conditions is established. The bandgap characteristics of the double-span beam can be obtained using the Rayleigh–Ritz method. The bandgap characteristics calculated based on the proposed method are in good agreement with those obtained from the transfer matrix method, and the bandgap frequency range matches well with the vibration attenuation range obtained from the test results. The effectiveness of forced vibration analysis for finite periodic double-span beams is also validated through the finite element method. Additionally, the influence of material properties, geometric parameters and lattice constants on the bandgap characteristics of periodic double-span beams is presented, providing insights into the mechanisms for tuning bandgap characteristics.

Пространственное распределение авроральных высыпаний и сбоев в работе железнодорожной автоматики на севере европейской части России

We study the relationship between space weather disturbances and spatial distribution of failures in railway automatics at segments of Northern and October railways in 2001–2006. During the most intensive magnetic storms that caused numerous failures, latitude distribution of auroral electron precipitation and local geomagnetic disturbance, determined as mean absolute value of time derivative of the geomagnetic field horizontal component |dBH/dt|, are examined. We show that in magnetic storm main and recovery phases the segments, where the failures were recorded, correspond to the region of intense auroral precipitation and |dBH/dt| exceeded 5 nT/s. The relationship between position of auroral oval equatorial boundary and spatial distribution of failures is analyzed for individual magnetic storms and statistically for five years of observations. Both individual cases and statistic tests show that southward displacement of the auroral oval equatorial boundary correlates with increase in the proportion of failures at lower latitude railway segments.

Spatial distribution of auroral precipitation and failures in railway automatics at the north of European Russia

We study the relationship between space weather disturbances and spatial distribution of failures in railway automatics at segments of Northern and October railways in 2001–2006. During the most intensive magnetic storms that caused numerous failures, latitude distribution of auroral electron precipitation and local geomagnetic disturbance, determined as mean absolute value of time derivative of the geomagnetic field horizontal component |dBH/dt|, are examined. We show that in magnetic storm main and recovery phases the segments, where the failures were recorded, correspond to the region of intense auroral precipitation and |dBH/dt| exceeded 5 nT/s. The relationship between position of auroral oval equatorial boundary and spatial distribution of failures is analyzed for individual magnetic storms and statistically for five years of observations. Both individual cases and statistic tests show that southward displacement of the auroral oval equatorial boundary correlates with increase in the proportion of failures at lower latitude railway segments.

Correlation of the Upper Pliocene sediments of the Dnipro-Donetsk Depression based on palynological data

The problems of intra- and inter-regional correlations have always been the most difficult in stratigraphic studies. Particular difficulties arise when comparing same-age subaerial continental sediments that are depleted in palaeontological remains. The spore-pollen analysis, which is a component of the palynological method, is most effective in stratigraphic dissection and correlation of subaerial sediments, since pollen and spores, with few exceptions, are almost the only paleontological remains contained in fossil soils and intersoil clays and loess. The author has developed the methodological approaches to stratification and correlation of continental Pliocene and Pleistocene sediments of the Ukraine based on palynological data (Sirenko, 2017). These methods are applied in the presented work. Due to the changes in the International Stratigraphic Scale, including a change in the position of the lower boundary of the Quaternary period, it became necessary to modify the existing stratigraphic schemes of Cenozoic sediments. Therefore, there is a need to obtain new representative materials on sediment characteristics, as well as to solve the problems of intra- and interregional correlations. At the present stage of research on the Upper Cenozoic continental sediments of Ukraine, the least studied by the palynological and palaeopedological methods are Pliocene fossil soils and intersoil clays of the central and southeastern parts of the Dnipro-Donetsk depression. The presented paper is devoted to solving the issues of correlation of Upper Pliocene sediments of the Central Graben of the Dnipro-Donetsk Depression and its junction with the North-Western part of the Donetsk folded structure. Two sections (well 11 and the outcrop near Kamianka village) are located within these areas. The analysis of materials on the palynological characterization of the Kyzylyr and Bogdanivka climatoliths of these sections allowed us to identify the general patterns of the spore-pollen complexes that characterize them. The identified common patterns of the complexes from the Kyzylyr and Bogdanivka climatoliths can serve as a basis for comparing sediments of the same age located in different parts of the study area and for interregional correlations. The individual features of the described spore-pollen complexes are associated with different geomorphological and geographical locations of the compared sections. It is concluded that it is necessary to take into account the geographical and geomorphological location of the sections when performing stratigraphic and correlation constructions based on the palynological data. The efficiency of the palynological method for stratigraphic and correlation constructions is proved by comparing the sediments of two sections. The obtained conclusions on the correlation of the sediments of these sections are confirmed by the materials of palaeopedological studies. Key words: Upper Pliocene; fossil soils; stratigraphy; palynological method; spore-pollen complex; Ukraine.

Chitinozoan biostratigraphy through the Aeronian–Telychian boundary interval on Anticosti Island, Canada

Abstract. The well-preserved Llandovery (lower Silurian) succession of Anticosti Island (Quebec, eastern Canada) contains an expanded Aeronian–Telychian boundary interval when compared to other coeval basins. This boundary interval on Anticosti Island also includes two of the most important Llandovery biogeochemical events, the late Aeronian and Valgu events. These two events were previously documented in the Jupiter and Chicotte formations through the study of conodont, graptolite, and brachiopod biostratigraphy and δ13C chemostratigraphy. Despite these multiple investigations, the exact position of the Aeronian–Telychian stage boundary on Anticosti Island has not been firmly established. Here we locally define and globally correlate chitinozoan biozones to refine the position of this stage boundary. The Ancyrochitina ramosaspina biozone, recognized in the Ferrum Member of the Jupiter Formation, correlates with the global Conochitina alargada biozone and indicates an Aeronian age. The Eisenackitina dolioliformis biozone suggests mostly a Telychian age for the Pavillon Member of the Jupiter Formation and the Chicotte Formation. Three new species are defined, namely Conochitina asselinae sp. nov., Spinachitina glooscapi sp. nov., and Ancyrochitina wilsonae sp. nov. (registration date: 4 December 2024, publication LSID: urn:lsid:zoobank.org:pub:11184506-F273-4D7A-BC28-A1BB4BC8FCD8, asselinae LSID: D282DA9D-6A9C-4B9E-AA6C-9ADC4473E95B, glooscapi LSID: 5801DC12-4EA1-439F-B7C8-FAF7C1B9D2C7, wilsonae LSID: 549EEF2F-7F19-4E6D-9F8E-384594B2FE65). Our new chitinozoan data, combined with previous studies, allow a comparison with the well-studied Baltic succession, confirming that limited unconformities mark the Aeronian–Telychian boundary interval on Anticosti Island, in contrast to the less complete coeval location. Our refined age model for the Aeronian to Telychian succession of Anticosti Island provides a solid baseline to study further Llandovery biochemical events in the aftermath of the Late Ordovician mass extinction.

A class of free boundary problems describing the local-nonlocal cross-diffusion models with two species in ecology

We study a class of free boundary problems describing the local-nonlocal cross-diffusion models with two species in ecology. The first is a native species with nonlocal cross-diffusion, and the second is an invasion species with local cross-diffusion. Since the local and nonlocal cross-diffusions are taken into account, the models are described by the strongly coupled systems of integral and differential equations. In addition, the position of each free boundary is determined by the Stefan condition. By using the transformations of function and variable, various estimates and contraction mapping theorem, we show the global existence, uniqueness and regularity of solutions for the free boundary problems. Besides, the long time behavior of the solution for a special type of local-nonlocal cross-diffusion competition model is also obtained.

Road boundary extraction method from mobile laser scanning point clouds

Abstract With the rapid development of mobile laser scanning (MLS) technology, high-precision three-dimensional point cloud data has shown great potential in different fields such as topographic mapping, road asset management and smart city construc-tion. Three-dimensional point cloud data contains not only position information, but also the shape and attributes of the target, which is very convenient for obtaining road information. Accurate extraction of the road boundary is a basic task for obtaining road infrastructural data, which can support the generation of high-precision maps, vehicle navigation and auton-omous driving. However, road boundary extraction in urban environments is easily occluded such as vehicles and pedestri-ans on the road, which leads to problems such as difficulty and incomplete extraction of MLS point cloud road boundaries. To address this problem, this study proposes a road boundary extraction method that integrates pavement edge information, accurately considers the position of the road boundary from two dimensions, eliminates false boundaries, and completes the missing boundary through the extracted boundary spatial relationship. First, grid elevation filtering is used to remove high-level non-ground points. Then the pavement edges and curb stone points are extracted from the preprocessed point cloud, and they are superimposed to remove false boundary points to obtain accurate road boundaries. Finally, based on the spatial relationship of road boundaries, missing parts are detected and repaired to obtain complete road boundaries. Experimental results show that the accuracy on real road scenes exceeds 98%, the completeness rate is above 91%, and the extraction quality is above 90%, which verifies the effectiveness and accuracy of this method.

A collocation heat polynomials method for one-dimensional inverse Stefan problems

The inverse one-phase Stefan problem in one dimension, aimed at identifying the unknown time-dependent heat flux P(t) with a known moving boundary position s(t), is investigated. A previous study (Kassabek et al., 2021) attempted to reconstruct the unknown heat flux P(t) using the Variational Heat Polynomials Method (VHPM). In this paper, we develop the Collocation Heat Polynomials Method (CHPM) for the reconstruction of the time-dependent heat flux P(t). This method constructs an approximate solution as a linear combination of heat polynomials, which satisfies the heat equation, with the coefficients determined using the collocation method. To address the resulting ill-posed problem, Tikhonov regularization is applied. As an application, we demonstrate the effectiveness of the method on benchmark problems. Numerical results show that the proposed method accurately reconstructs the time-dependent heat flux P(t), even in the presence of significant noise. The results are also compared with those obtained in Kassabek et al. (2021) using the VHPM.

Mathematical model for heat transfer during underground coal gasification process

Purpose. To develop a mathematical model of the “coal-gas” medium heat transfer during underground coal gasification to predict the combustion face advance velocity and the duration of gasification column mining. Methodology. To detect the temperature fields in the coal seam and gas, depending on the displacement length of the phase transition boundary, a boundary-value problem of mathematical physics has been developed. To solve this boundary-value problem, Boltzmann transformations, as well as methods for solving ordinary differential equations, are used. Newton-Raphson method, which has quadratic convergence, is used to find the roots of the transcendental equation. Findings. Tendencies in the formation of mathematical models when studying temperature fields around an underground gasifier have been analyzed, with highlighting their disadvantages. A mathematical model of heat transfer during underground gasification has been developed, taking into account the phase transition boundaries of the “coal-gas” medium. A computational experiment was conducted to determine the temperature of the phase transition boundary based on the length of the gasification column and the duration of the process. Originality. A mathematical model for heat transfer during coal gasification in the form of a boundary-value problem of mathematical physics, which consists of parabolic heat-transfer equations, the Stefan condition at the phase transition boundary, and the Dirichlet boundary conditions, has been constructed. As a result of solving the boundary-value problem, a self-similar solution has been obtained for the distribution of the coal seam and gas temperature fields, as well as the position of the phase transition boundary depending on the gasification duration and on the medium density, thermal conductivity coefficients, specific heat capacity of gas and coal, specific calorific value and temperature of coal combustion, initial coal temperature and constant temperature of the gasification process. The conducted analysis of numerical calculations provides a deeper understanding of the dynamics of underground coal gasification process and makes necessary corrections to achieve the maximum process efficiency. Practical value. A methodology for determining the displacement length of the phase transition boundary of the “coal-gas” medium has been developed, taking into account the change in the combustion face temperature along the gasification zone length depending on the duration of this process. Application of the methodology makes it possible to predict the time of mining the gasified coal column for drawing up a calendar plan for mining operations.

Relocate the base of the Arundian? A re-evaluation from south Cumbrian sections and implications for British and Irish Lower Carboniferous successions

The largely ice-free world of the ‘Chadian’–Arundian (early Visean) is investigated in two successions in south Cumbria to better understand the relationships between transgression, hiatus and the position of the basal Arundian. A detailed foraminiferal biostratigraphy is used to age-constrain the transition from the late ‘Chadian’ to early Arundian. This demonstrates a good synchronous relationship between the sequence stratigraphy of the two successions and the first occurrence of key species (mostly primitive archaediscids, rapidly followed by more evolved forms of the same family), suggesting that there is no significant hiatus and that the record of faunal changes is closely comparable in the key successions. A synthesis of other ‘Chadian’–Arundian boundary successions in Britain and Ireland indicates some key problems with the current Arundian boundary stratotype in practical usage. We propose a stratigraphically higher position for the Arundian boundary in the stratotype, which is more easily correlated to the Bobrikian and Moliniacian substages of eastern Europe and Belgium, respectively, and tied to the first occurrences of foraminifera species, allowing more robust age assessments, free from the confounding factors of inferred lithological or sequence stratigraphic changes.

The Evolution of Earth's Outer Radiation Belt Over Geomagnetic Storm Phase in Van Allen Probe Era

AbstractEarth's outer radiation belts are highly dynamic during geomagnetic storms. Using electron flux data from 226 keV to 2.6 MeV measured by the Van Allen Probes, we statistically analyzed the peak flux position and inner boundary position of the outer radiation belt across different storm phases: pre‐storm quiet time, main phase, early recovery phase, and later recovery phase. This analysis covered 196 geomagnetic storm events from October 2012 to September 2019. Our results indicate that: (a) During the pre‐storm, decreases with increasing energy. From the pre‐storm to the early recovery phase, shifts inward for energies below 1 MeV and outward for energies above 1 MeV. For all energies, converges to approximately L = 4.3–4.6 in the early recovery phase. (b) Below approximately 1 MeV, generally move inward from the main phase to the early recovery phase. Above 1 MeV, remains nearly unchanged across different storm phases. (c) The half‐width (−) of the outer belt decreases during the main phase for energies below 1 MeV and increases during the recovery phase for energies above 1.5 MeV. (d) In the early recovery phase, and at 593–742 keV show a moderate correlation with storm intensity (CC 0.7–0.8), while and at energies greater than 1.1 MeV exhibit low correlations (CC0.4) during each phase. These results confirm the complex, energy‐dependent morphology of the outer radiation belt throughout geomagnetic storm phases.

The age and position of the southern boundary of prehistoric Polynesian dispersal

AbstractPrehistoric Polynesian voyaging into high latitudes with landfall in Antarctica remains a widely credited proposition. We examine it through archaeological and environmental evidence from the Subantarctic region of the southwest Pacific, focussing upon an extensive archaeological site at Sandy Bay on Enderby Island. Combining a new set of radiocarbon ages with former, older, ages we show that the site is now within the same rapid expansion phase in which South Polynesia was first colonised. Radiocarbon ages across the site indicate a single continuous settlement, probably of some decades. Consideration of limiting factors in Subantarctic settlement, including of seafaring capability and critical resources, suggests that the site was about as far south as prehistoric habitation could be sustained and was probably vacated at the onset of the Little Ice age (LIA) in the late 14th century. An absence of prehistoric remains on islands further south also suggests that Polynesian exploration reached a boundary 2000 km short of Antarctica. The southern case is discussed briefly in the wider context of Polynesian expansion.

Conservation of rib skeleton regionalization in the homoplastic evolution of the snake-like body form in squamates.

Squamates have independently evolved an elongate, limb-reduced body form numerous times. This transition has been proposed to involve either changes to regulatory gene expression or downstream modification of target enhancers to produce a homogeneous, deregionalized axial skeleton. Analysis of vertebral morphology has suggested that regionalization is maintained in snake-like body forms, but morphological variation in the other primary component of the axial skeleton, the dorsal ribs, has not been previously examined. We quantified rib morphology along the anterior-posterior axis in limbed and snake-like squamates to test different regionalization models. We find that the relative position of regional boundaries remains consistent across taxa of differing body types, including in the homoplastic evolution of snake-like body forms. The consistent retention of regional boundaries in this primaxial domain is uncorrelated with more plastic abaxial region markers. Rather than loss of regions, rib shape at the anterior and posterior of the axis converges on those in the middle, resulting in axial regions being distinguishable by allometric shape changes rather than by discrete morphologies. This complexity challenges notions of deregionalization, revealing a nuanced evolutionary history shaped by shared functions.

Position of the Precambrian-Cambrian boundary in the sections of Western Mongolia according to the malacological data

The Early Permian (275.3 ± 3.1 Ma) 40Ar/39Ar plateau age of detrital mica (Cr-phengite) from clasts in listvenite sandstones of the ophiolite-derived clastic sequence of the Rassokha Terrane of the Chersky Range probably corresponds (or is close) to the time of the formation of listvenites of the provenance (ophiolitic massifs of the range) and restricts the maximum deposition age of clastic rocks. A partial loss of Ar by mica as a result of deformations and postsedimentation transformation of rocks of the ophiolite-derived clastic sequence in the Early Permian is possible but it is less probable.

Hibiscus bullseyes reveal mechanisms controlling petal pattern proportions that influence plant-pollinator interactions.

Colorful flower patterns are key signals to attract pollinators. To produce such motifs, plants specify boundaries dividing petals into subdomains where cells develop distinctive pigmentations, shapes, and textures. While some transcription factors and biosynthetic pathways behind these characteristics are well studied, the upstream processes restricting their activities to specific petal regions remain enigmatic. Here, we unveil that the petal surface of Hibiscus trionum, an emerging model featuring a bullseye on its corolla, is prepatterned as the bullseye boundary position is specified long before it becomes visible. Using a computational model, we explore how pattern proportions are maintained while petals experience a 100-fold size increase. Exploiting transgenic lines and natural variants, we show that plants can regulate boundary position during the prepatterning phase or modulate growth on either side of this boundary later in development to vary bullseye proportions. Such modifications are functionally relevant, as buff-tailed bumblebees can reliably identify food sources based on bullseye size and prefer certain pattern proportions.

Integral BLF-Based Adaptive Dynamic Event-Triggered Boundary Control for a Flexible Riser System.

For the flexible riser systems modeled with partial differential equations (PDEs), this article explores the boundary control problem in depth for the first time using a dynamic event-triggered mechanism (DETM). Given the intrinsic time-space coupling characteristic inherent in PDE computations, implementing a state-dependent DETM for PDE-based flexible risers presents a significant challenge. To overcome this difficulty, a novel dynamic event-triggered control method is introduced for flexible riser systems, focusing on optimizing available control inputs. In order to save computational costs from the controller to the actuator, a dynamic event-triggered adaptive boundary controller is designed to effectively reduce boundary position vibrations. Additionally, considering external disturbances, an adaptive bounded compensation term is incorporated to counteract the influence of external disturbances on the system. Addressing boundary position constraints, a new integral barrier Lyapunov function (iBLF) tailored specifically for flexible riser systems is introduced, thereby alleviating conservatism in the controller design of flexible risers modeled by PDEs. At last, the validity of the proposed method is demonstrated through a simulation example.

A cochlear progenitor pool influences patterning of the mammalian sensory epithelium via MYBL2.

During embryonic development, Wnt signaling influences both proliferation and sensory formation in the cochlea. How this dual nature of Wnt signaling is coordinated is unknown. In this study, we define a novel role for a Wnt-regulated gene, Mybl2, which was already known to be important for proliferation, in determining the size and patterning of the sensory epithelium in the murine cochlea. Using a quantitative spatial analysis approach and analyzing Mybl2 loss-of-function, we show that Mybl2 promoted proliferation in the inner sulcus domain but limited the size of the sensory domain by influencing their adjoining boundary position via Jag1 regulation during development. Mybl2 loss-of-function simultaneously decreased proliferation in the inner sulcus and increased the size of the sensory domain, resulting in a wider sensory epithelium with ectopic inner hair cell formation during late embryonic stages. These data suggest that progenitor cells in the inner sulcus determine boundary formation and pattern the sensory epithelium via MYBL2.

Deep-learning-driven simulations of boundary layer clouds over the Southern Great Plains

Abstract. Based on long-term observations at the Southern Great Plains site by the Atmospheric Radiation Measurement (ARM) program for training and validation, a deep-learning model is developed to simulate the daytime evolution of boundary layer clouds (BLCs) from the perspective of land–atmosphere coupling. The model takes ARM measurements (including early-morning soundings and diurnally varying surface meteorological conditions and heat fluxes) as inputs and predicts hourly estimates (including cloud occurrence, the positions of cloud boundaries, and the vertical profile of the cloud fraction) as outputs. The deep-learning model offers good agreement with the observed cloud fields, especially in the accuracy with which cloud occurrence and base height are reproduced. When the inputs are substituted by reanalysis data from ERA5 and MERRA-2, the outputs of the deep-learning model provide a better agreement with observation than the cloud fields extracted from ERA5 and MERRA-2 themselves. Thus, the deep-learning model shows great potential to serve as a diagnostic tool for the performance of physics-based models in simulating stratiform and cumulus clouds. By quantifying biases in clouds and attributing them to the simulated atmospheric state variables versus the model-parameterized cloud processes, this observation-based deep-learning model may offer insights into the directions needed to improve the simulation of BLCs in physics-based models for weather forecasting and climate prediction.

Consensus of multi‐agent system with reaction‐diffusion terms and time delays via output‐feedback adaptive boundary control

SummaryMulti‐agent systems (MASs) are widely used in many necessary fields such as cybersecurity, precision agriculture, satellites, and smart grids. In many practical processes, a proportion of states cannot be obtained directly. Therefore, it is desired to design an observer. This article explores the utilization of output‐feedback adaptive control techniques to achieve consensus in MASs based on partial differential equations (PDEs) with reaction‐diffusion terms and time delays. First, in dealing with time‐invariant delays, an observer according to the Luenberger method is proposed to assess the state of agents. Convergence conditions of the estimated states are obtained by employing Lyapunov functions and Wirtinger inequality. Using the obtained estimated states, a boundary adaptive control strategy is proposed to make the error system consensus. The merit of this control method lies in the fact that communication between agents only occurs at the spatial boundary position, not throughout the entire spatial domain, and the parameters of the system can be constantly changed. Consensus criteria of MASs with time‐invariant delays are obtained by using the output‐feedback adaptive control, and the results are further generalized to the model with time‐varying delays. Lastly, two experimental scenarios are provided to show the practicality of the proposed theories.

Influence of aluminium in wetting characteristics of Zn-Al alloy

In this article, the effect of aluminium in Zn-5 wt%Al alloy is studied after heat treatment at 375 ⁰C focusing particularly on its effect at grain boundaries or grain boundary junctions. The understanding of such behaviour is crucial for microstructural controlling during alloy processing, ensuring better alloy performance for various applications. Using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD), the microstructural and crystallographic study of the alloy was carried out. The SEM results of the annealed sample show a lenticular-shaped wetting layer corresponding to the lower energy of the grain boundary. It was observed that Zn is distributed throughout the sample, while the concentration of Al is increased at the grain boundaries as evidenced by the elemental spectra. XRD result confirms that no new phases are formed thereby confirming the formation of an Al-rich solid solution at the grain boundary. The absence of new phases indicates that aluminium in the alloy tends to lower grain boundary energy by occupying grain boundary positions, rather than forming a new compound, thereby reaching thermodynamic equilibrium. This study is important for developing advanced engineering materials with solid-state lubrication capabilities, for diverse industrial applications.