Flat Segment Research Articles

Dynamic subsidence in the Colorado basin, offshore Argentina, South Atlantic

The Colorado basin in the SW Atlantic is one of the key exploratory frontier basins along the Argentine shelf. The stratigraphy shows a typical rift basin, divided into two major seismic successions, a Jurassic-Lower Cretaceous synrift followed by an Upper Cretaceous to Cenozoic postrift. They represent, respectively, the breakup of Gondwana and passive margin evolution. While the synrift basin formation was associated with the development of structural grabens, the preservation of thick (thousands of meters) postrift sequences are still debated because they cannot be accounted for only by thermal subsidence. In this work, we conducted a multimethodological subsidence analysis across the Colorado basin, including part of the continental slope. We performed a 1D backstripping analysis on 10 hydrocarbon exploration wells and 32 pseudo-wells, covering the whole basin area and a uniform stretching model, which were supported using dynamic topography data from the study region. From the backstripping analyses, considering the six major postrift sedimentary successions described in the literature, we could recognize three subsidence stages. An initial rapid subsidence stage during the post-rift (125–83 Ma), which is restricted to the main depocenters, followed by a stage of generalized and low subsidence focused on the main axis of the basin (83–33 Ma), with an increase in the last 33 my (33–0 Ma). The stretching models exhibit a typical asymptotic curve, depicting significant subsidence at the onset of the postrift stage, gradually diminishing to minimal values within a few tens of millions of years. Upon comparing the backstripping curves with the stretching subsidence models, particularly during the final flat segments, a residual negative value emerges over time (locally exceeding −500 m), indicating considerable residual subsidence during the Cenozoic postrift evolution along the Colorado Basin. This could be interpreted as dynamic subsidence. This residual sinking in the Argentina shelf matches with dynamic topography numerical models in the study region as well as the occurrence of accumulated slabs in the mantle detected by seismic tomography studies. We propose that the accumulation of slabs along this segment of the South American subduction zone might be the drivers of dynamic subsidence, which assisted to the preservation of a large thickness of post-rift strata along the SW Atlantic margin.

Theoretical Substantiation of the Dependence of Spring Deformation of an Improved Opener

The article presents factors influencing the germination and development of plants after seeding with disk seeders. Schemes of improved two-disk seeders are proposed, forces acting on the improved seeder during operation, determination of the maximum distance between the seeder disks at the field surface level, and calculation schemes for determining the draft resistance of the serial and improved seeders, the area of the flat disk segment of the seeder, determination of the deformer, and tailstock area of the pressing plate. During the theoretical study of the seeding process, the following parameters and observations were obtained: analytical dependencies of soil density created by the pressing plate; geometric parameters of the pressing plate with a curvature radius r = 52…57 mm, plate section thickness of 2.5 mm; installation of the pressing plate insignificantly increases the draft resistance of the seeder; and the depth of the seeder’s travel has the greatest influence on spring deformation. Experimental studies reveal that the stiffness of the pressing plate is 7500…7600 N/m, ensuring an optimal furrow bottom density of 1.1–1.3 g/cm3; in the range of seed embedding depth of 0.05…0.07 m, 89% of the total number of seeds are placed compared to 76% of seeds embedded by the serial seeder.

Thermal modeling of subduction zones with prescribed and evolving 2D and 3D slab geometries

The determination of the temperature in and above the slab in subduction zones, using models where the top of the slab is precisely known, is important to test hypotheses regarding the causes of arc volcanism and intermediate-depth seismicity. While 2D and 3D models can predict the thermal structure with high precision for fixed slab geometries, a number of regions are characterized by relatively large geometrical changes over time. Examples include the flat slab segments in South America that evolved from more steeply dipping geometries to the present day flat slab geometry. We devise, implement, and test a numerical approach to model the thermal evolution of a subduction zone with prescribed changes in slab geometry over time. Our numerical model approximates the subduction zone geometry by employing time dependent deformation of a Bézier spline that is used as the slab interface in a finite element discretization of the Stokes and heat equations. We implement the numerical model using the FEniCS open source finite element suite and describe the means by which we compute approximations of the subduction zone velocity, temperature, and pressure fields. We compute and compare the 3D time evolving numerical model with its 2D analogy at cross-sections for slabs that evolve to the present-day structure of a flat segment of the subducting Nazca plate.

Vibration-assisted vat photopolymerization for pixelated-aliasing-free surface fabrication

Mask image projection-based vat photopolymerization (MIP-VPP) offers advantages like low cost, high resolution, and a wide material range, making it popular in industry and education. Recently, MIP-VPP employing liquid crystal displays (LCDs) has gained traction, increasingly replacing digital micromirror devices, particularly among hobbyists and in educational settings, and is now beginning to be used in industrial environments. However, LCD-based MIP-VPP suffers from pronounced pixelated aliasing arising from LCD’s discrete image pixels and its direct-contact configuration in MIP-VPP machines, leading to rough surfaces on the 3D-printed parts. Here, we propose a vibration-assisted MIP-VPP method that utilizes a microscale vibration to uniformize the light intensity distribution of the LCD-based mask image on VPP’s building platform. By maintaining the same fabrication speed, our technique generates a smoother, non-pixelated mask image, reducing the roughness on flat surfaces and boundary segments of 3D-printed parts. Through light intensity modeling and simulation, we derived an optimal vibration pattern for LCD mask images, subsequently validated by experiments. We assessed the surface texture, boundary integrity, and dimensional accuracy of components produced using the vibration-assisted approach. The notably smoother surfaces and improved boundary roughness enhance the printing quality of MIP-VPP, enabling its promising applications in sectors like the production of 3D-printed optical devices and others.

An efficient algorithm for areal morphological filter

This article discusses morphological filtering for assessing a areal parameters of a texture of engineering products. A data organization structure has been proposed that makes it possible to increase the efficiency of an iterative algorithm for enumerating a surface coordinates. Morphological filters complement the standard Gaussian filter to evaluate the functional properties of a surface. The widespread use of the areal morphological filtering in metrological practice is currently hampered by the lack of an effective algorithm. An algorithm based on a matrix representation of morphological operations on the surface coordinates is presented. For this purpose, different indexing of points on a primary surface and a structuring element has been introduced. A sphere or flat segment is used as the structuring element. The high performance of the developed algorithm is ensured due to the fact that all calculations are carried out by enumerating the surface coordinates in one pass, without nested loops, as in some other algorithms. Algorithms for morphological operations of dilation and erosion are presented, on the basis of which a closing and opening filters are constructed. Simulations carried out for various data sets and comparison with known morphological filtering algorithms confirmed the high efficiency of the designed algorithm. The results obtained can be used to analyze the functional properties of product surfaces.

Geodynamic models of Indian continental flat slab subduction with implications for the topography of the Himalaya-Tibet region

The slab structure and high elevation of the Himalaya-Tibet region and their underlying mechanisms have been widely discussed. Many studies interpret a flat slab segment of Indian continental lithosphere located below the overriding plate, but interpretations of the northward extent of the flat slab differ substantially, with minimum estimates placing the boundary at the northern margin of the Himalaya (Indus-Yarlung Tsangpo suture), and maximum estimates placing it at the northern boundary of Tibet. In this study, we investigate for the first time if a flat slab segment of subducted buoyant Indian continental lithosphere below the Himalaya-Tibet region is geodynamically feasible and we quantify its northward extent, as well as its contribution to the high topography of the region. We conduct three large-scale fully-dynamic (buoyancy-driven) analogue experiments to simulate the subduction of the Indian continent. Our preferred, and geodynamically most feasible, model shows a continental flat slab extending northward up to ~ 320 km from the Himalayan thrust front, in agreement with recent estimates. Furthermore, it suggests that the positively buoyant flat slab segment of the Indian continent contributes some ~ 1.5–2 km to the high topography of the Himalaya-Southern Tibet region by providing an upward force to elevate the overriding Eurasian plate.

Badania przyczyn niepożądanej synchronizacji prędkości obrotowej silnika z częstotliwością modulacji PWM w układzie napędowym PM BLDC

In a drive system comprising a high-speed PM BLDC motor and an inverter implementing motor phases commutation and phase voltages PWM modulation, a spontaneous synchronisation between the PWM modulation frequency and the motor rotational speed may occur. The drive behaves like an unintended phase-locked loop. The effect distorts mechanical characteristic of the drive by introducing flat segments where the rotational speed remains constant despite changing load torque. It makes the speed-torque relationship discontinuous, nonlinear, and non-unique. The phenomenon is closely related to the problem of phase current and motor torque ripples. The paper presents experimental results recorded with a laboratory test bench for drives for electric power tools where the phenomenon of the parasitic speed locking has been observed. A root cause of this effect is discussed, and the mechanism of unwanted synchronisation is investigated. Several mitigation techniques are proposed and verified with computer simulations.

AS-Parser: Log Parsing Based on Adaptive Segmentation

System logs have long been recognized as valuable data for analyzing and diagnosing system failures. One fundamental task of log processing is to convert unstructured logs into structured logs through log parsing. All previous log parsing approaches follow a general framework that first segments each log into a token sequence and then computes similarity between two sequences. However, all existing approaches share the common drawback: the flat segmentation with fixed delimiters fails to understand the structural information of logs, which causes low parsing accuracy. To address this problem, we propose a novel log parsing approach, AS-Parser. Our approach introduces a hierarchical log segmentation mechanism that can adaptively segment logs into a tree structure. It can automatically recognize the appropriate delimiters and capture the common structural information. Moreover, we propose three improvements that enhance both the effectiveness and efficiency of our approach. On the public benchmark, AS-Parser performs best on 14 out of 16 datasets, with an average parsing accuracy of 0.943, far exceeding existing approaches.

Anisotropic structure of the normally-dipping and flat slab segments of the Alaska subduction zone: Insights from receiver function analysis

The complex tectonic setting of south-central Alaska is characterized by a transition from normally-dipping subduction of the Pacific plate in the west to near-flat slab subduction of the overthickened Yakutat microplate in the east. Many previous studies have characterized both the isotropic and anisotropic subsurface structure of this region, but only a few studies have characterized anisotropy using receiver functions. Here, we present anisotropy-aware receiver function analysis for two transects of permanent seismic stations in south-central Alaska, one covering a normally-dipping segment of the subduction zone, and one covering the adjacent flat slab segment. Beneath the normally-dipping segment, there is evidence for shearing and possibly serpentinization at the top of the slab in the shallow forearc, and for variation in mantle flow geometry with depth, possibly a result of oblique subduction and/or the adjacent flat slab segment, or an arc magmatism-related process. Additionally, there appears to be significant crustal deformation associated with the volcanic arc. We also identify significant crustal deformation and anisotropy along the flat slab segment, likely a result of the subducting Yakutat microplate, with crustal deformation geometry appearing to vary along the transect. There also appears to be evidence for water-rich conditions at the top of the flat slab, shedding light on the distribution of volatiles in a flat slab setting that lacks an active volcanic arc.

3D Crustal Structure of the Jammu and Kashmir Himalaya: Signatures of Mid‐Crustal Ramp and Lesser Himalayan Duplex

AbstractThe NW Himalayan “seismic gap” lies between the 1905 and 2005 earthquake rupture zones and straddles the meisoseismal zone of the 1555‐Kashmir earthquake. Sufficient elastic strain has now accumulated across this region to drive a mega‐thrust earthquake. We model the crustal structure and geometry of the Main Himalayan Thrust (MHT) using Jammu and Kashmir Seismological NETwork data. P‐wave receiver‐function spatial and common‐conversion‐point (CCP) stacks, and joint inversion with Rayleigh‐wave group‐velocities are used to construct 3D Vs model of the region. This model reveals increasing crustal thickness from foreland‐to‐hinterland, and an under‐thrust Indian crust beneath NW Himalaya. The Moho is at ∼45 km depth beneath Sub‐Himalaya deepening to ∼70 km beneath Higher‐to‐Tethyan Himalaya with a gentle NE dip. The MHT forms a low‐velocity layer and has a flat–ramp geometry. The flat segment is beneath Sub‐to‐Lesser Himalaya at 6–10 km depth, and dips ∼4°. The mid‐crustal (frontal) ramp is beneath Kishtwar Higher‐Himalaya and Zanskar Range at 10–16 km depth, and dips ∼13–17°. Crustal structure varies along‐arc between east (Kishtwar) and west (Kashmir Valley) segments. A Lesser Himalayan duplex (LHD) lies beneath the Kishtwar Window and is bound by MHT and Main Central Thrust. The LHD high‐angle imbricate structures are illuminated by moderate seismicity. Beneath Kashmir Valley, the underthrust crust is ∼10 km thicker, has higher crustal Vs, and a shallower MHT at ∼10 km depth. The westward shallowing of MHT occurs through a lateral ramp. Aftershocks of the 2013‐Kishtwar earthquake concentrate on the frontal–lateral ramp intersection and mark the MHT down‐dip locked‐to‐creep transition.

Mechanization of a scalar field theory in 1+1 dimensions: Bogomol'nyi-Prasad-Sommerfeld mechanical kinks and their scattering.

We present an updated version of a general-purpose collective coordinate model that aims to fully map out the dynamics of a single scalar field in 1+1 dimensions. This is achieved by a procedure that we call a mechanization, in which we reduce the infinite number of degrees of freedom down to a finite and controllable number by chopping the field into flat segments connected via joints. In this paper we introduce two new ingredients to our procedure. The first is a manifestly Bogomol'nyi-Prasad-Sommerfeld (BPS) mechanization in which BPS mechanical kinks saturate the same bound on energy as their field-theoretic progenitors. The second is allowing the joints to switch, leading to an extended concept of the effective Lagrangian, through which we describe direct collisions of mechanical kinks and antikinks.

Revealing flat bands and hybridization gaps in a twisted bilayer graphene device with microARPES

Controlling the electronic structure of two-dimensional materials using the combination of twist angle and electrostatic doping is an effective means to induce emergent phenomena. In bilayer graphene with an interlayer twist angle near the magic angle, the electronic dispersion is strongly modified by a manifold of hybridizing moiré Dirac cones leading to flat band segments with strong electronic correlations. Numerous technical challenges arising from spatial inhomogeneity of interlayer interactions, twist angle and device functionality have so far limited momentum-resolved electronic structure measurements of these systems to static conditions. Here, we present a detailed characterization of the electronic structure exhibiting miniband dispersions for twisted bilayer graphene, near the magic angle, integrated in a functional device architecture using micro-focused angle-resolved photoemission spectroscopy. The optimum conditions for visualizing the miniband dispersion are determined by exploiting the spatial resolution and photon energy tunability of the light source and applied to extract a hybridization gap size of eV and flat band segments extending across a moiré mini Brillouin zone. In situ electrostatic gating of the sample enables significant electron-doping, causing the conduction band states to shift below the Fermi energy. Our work emphasizes key challenges in probing the electronic structure of magic angle bilayer graphene devices and outlines conditions for exploring the doping-dependent evolution of the dispersion that underpins the ability to control many-body interactions in the material.

Forward Modeling and Model Test of Ground-Penetrating Radar toward Typical Asphalt Pavement Distresses

As the total mileage of roads with asphalt concrete pavement is increasing rapidly, using ground-penetrating radar (GPR) to estimate the dimension of internal distresses of the asphalt pavement is of great significance for pavement maintenance. However, the relationship between the dimension of road distress and the characteristics of road distress’s radar echo has not been quantified. Therefore, in this paper, a GPR forward modeling toward base cracks and interlayer voids is conducted to investigate the relationship, and a model test is conducted to verify the forward modeling. The results indicate that it is feasible to use a GPR image to estimate the dimension of interlayer voids and base cracks. For vertical dimension estimation, the vertical dimension of the distressed area has a positive relationship with the difference in the return time of radar echoes from the top and bottom of the distressed area. However, the area’s vertical dimension must be at least a quarter of the length of the electromagnetic wave used in the GPR to be correctly identified. Otherwise, it is not easy to distinguish the overlapping echoes from each other. For horizontal dimension estimation, the base crack’s horizontal dimension has a quadratic correlation with the echo’s amplitude, and the horizontal dimension of an interlayer void is approximately equal to the length of its echo’s flat segment.

Constraining the Gravitational Potential from the Projected Morphology of Extragalactic Tidal Streams

The positions and velocities of stellar streams have been used to constrain the mass and shape of the Milky Way's dark matter halo. Several extragalactic streams have already been detected, though it has remained unclear what can be inferred about the gravitational potential from only 2D photometric data of a stream. We present a fast method to infer halo shapes from the curvature of 2D projected stream tracks. We show that the stream curvature vector must point within 90° of the projected acceleration vector, in the absence of recent time-dependent perturbations. While insensitive to the total magnitude of the acceleration, and therefore the total mass, applying this constraint along a stream can determine halo shape parameters and place limits on disk-to-halo mass ratios. The most informative streams are those with sharp turns or flat segments, since these streams sample a wide range of curvature vectors over a small area (sharp turns) or have a vanishing projected acceleration component (flat segments). We apply our method to low surface brightness imaging of NGC 5907, and find that its dark matter halo is oblate. Our analytic approach is significantly faster than other stream modeling techniques, and indicates which parts of a stream contribute to constraints on the potential. The method enables a measurement of dark matter halo shapes for thousands of systems using stellar stream detections expected from upcoming facilities like Rubin and Roman.

1.5-m flat imaging system aligned and phased in real time

Flat optics has been considered promising for constructions of spaceborne imaging systems with apertures in excess of 10 m. Despite recent advances, there are long-existing challenges to perform in-phase stitching of multiple flat optical elements. Phasing the segmented planar instrument has remained at the proof of concept. Here, we achieve autonomous system-level cophasing of a 1.5-m stitching flat device, bridging the gap between the concept and engineering implementation. To do so, we propose a flat element stitching scheme, by manipulating the point spread function, which enables our demonstration of automatically bringing seven flat segments’ tip/tilt and piston errors within the tolerance. With phasing done, the 1.5-m system has become the largest phased planar instrument ever built in the world, to our knowledge. The first demonstration of phasing the large practical flat imaging system marks a significant step towards fielding a 10-m class one in space, also paving the way for ultrathin flat imaging in various remote applications.

A robust bathtub-shaped failure time model for a two-component system with applications to complete and censored reliability data

ABSTRACT This article proposes a flexible additive model that adequately describes complex reliability and survival data. The proposed methodology, referred to as the flexible exponential power-Gompertz (FEPG4) distribution, is able to characterize the behavior of a complex system whose failure times have bathtub-shaped, with clear burn-in and wear-out change points and a low, yet lengthy, flat middle segment as its underlying failure rate distribution. We discuss some properties of the model. Parameter inferences are proposed under maximum likelihood and Bayesian techniques. We determine the Bayes estimators of the FEPG4 parameters and used Hamiltonian Monte Carlo for posterior simulations. Extensive simulation experiments are performed to validate the proposed estimators. For assessing the potential of the FEPG4, the model is compared with other recent bathtub distributions constructed via the same approach on devices’ failure and running times (censored and non-censored case) and failure times of some devices, each with the bathtub failure rate. Seven parametric and non-parametric selection criteria and other supporting plots are utilized for comparison purposes. Findings indicate that the FEPG4 model might be the best alternative for representing device failure times, particularly when the bathtub-shaped failure rate of the available data clearly illustrates its three phases.

Genome-wide measurement of DNA replication fork directionality and quantification of DNA replication initiation and termination with Okazaki fragment sequencing.

Studying the dynamics of genome replication in mammalian cells has been historically challenging. To reveal the location of replication initiation and termination in the human genome, we developed Okazaki fragment sequencing (OK-seq), a quantitative approach based on the isolation and strand-specific sequencing of Okazaki fragments, the lagging strand replication intermediates. OK-seq quantitates the proportion of leftward- and rightward-oriented forks at every genomic locus and reveals the location and efficiency of replication initiation and termination events. Here we provide the detailed experimental procedures for performing OK-seq in unperturbed cultured human cells and budding yeast and the bioinformatics pipelines for data processing and computation of replication fork directionality. Furthermore, we present the analytical approach based on a hidden Markov model, which allows automated detection of ascending, descending and flat replication fork directionality segments revealing the zones of replication initiation, termination and unidirectional fork movement across the entire genome. These tools are essential for the accurate interpretation of human and yeast replication programs. The experiments and the data processing can be accomplished within six days. Besides revealing the genome replication program in fine detail, OK-seq has been instrumental in numerous studies unravelling mechanisms of genome stability, epigenome maintenance and genome evolution.

Elucidating the fine-scale structural morphology of nanocellulose by nano infrared spectroscopy

Nanoscale infrared (IR) spectroscopy and microscopy, enabling the acquisition of IR spectra and images with a lateral resolution of 20 nm, is employed to chemically characterize individual cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) to elucidate if the CNCs and CNFs consist of alternating crystalline and amorphous domains along the CNF/CNC. The high lateral resolution enables studies of the nanoscale morphology at different domains of the CNFs/CNCs: flat segments, kinks, twisted areas, and end points. The types of nanocellulose investigated are CNFs from tunicate, CNCs from cotton, and anionic and cationic wood-derived CNFs. All nano-FTIR spectra acquired from the different samples and different domains of the individual nanocellulose particles resemble a spectrum of crystalline cellulose, suggesting that the non-crystalline cellulose signal observed in macroscopic measurements of nanocellulose most likely originate from cellulose chains present at the surface of the nanocellulose particles.

The distinct morphologic signature of underplating and seamounts in accretionary prisms, insights from thermomechanical modeling applied to Coastal Iranian Makran

The active structures of the Iranian Makran, especially the presence of normal faults, vary laterally in the upper plate of the subduction zone, and their relationship with the deep duplexes and seamounts at depth remains unknown due to poor coverage of data onshore. In this paper, we investigate the relationship between deep structures and the topographic slope using thermo-mechanical simulations. The initial and boundary conditions of the models, including basal heat flux and convergence rate, are calibrated using the depth of the seafloor, bottom seafloor reflectors and the few available well temperature. We specifically test the influence of seamount subduction and thermally controlled changes in rock strength and décollement on the relationship between topography and deep tectonic structures. The inclusion of the brittle-ductile transition and dehydration reactions like the smectite-illite transition produce the three slope segments observed in the Makran accretionary prism. The three segments correspond to a regular accretionary prism, a flat segment that marks the smectite-illite transition, and a rise in topography located above the zone where the tegument reaches its temperature-controlled brittle-ductile transition causing underplating. Nevertheless, the models show that neither the decrease in friction associated with dehydration nor the onset of underplating is sufficient for the observed normal faults to arise in a self-consistent manner from the simulations. Crustal-scale normal faults only emerge in simulations that include subduction of a large seamount. These simulations also produce a large-thrust-slice that is the scar of former subducting seamount and serves as a buttress for the formation of a new imbricated zone. Using offshore seismic reflection data, the published onshore tomographic profiles, and our thermo-mechanical simulations, we propose two onshore-offshore cross-sections of the Iranian Makran accretionary prism.

Convergence of perturbation series for unbounded monotone quasiperiodic operators

We consider a class of unbounded quasiperiodic Schrödinger-type operators on ℓ2(Zd) with monotone potentials (akin to the Maryland model) and show that the Rayleigh–Schrödinger perturbation series for these operators converges in the regime of small kinetic energies, uniformly in the spectrum. As a consequence, we obtain a new proof of Anderson localization in a more general than before class of such operators, with explicit convergent series expansions for eigenvalues and eigenvectors. This result can be restricted to an energy window if the potential is only locally monotone and one-to-one. A modification of this approach also allows the potential to be non-strictly monotone and have a flat segment, under additional restrictions on the frequencies.