Symmetric Morphology Research Articles

A skewed-Gaussian model for pulse decomposition analysis of photoplethysmography signals

Pulse Decomposition Analysis (PDA) has been proposed to extract reliable information from photoplethysmography (PPG) morphology by decomposing the signal in its physiological sub-waves. The Gaussian model has been widely used in the literature, even though it often underperforms because it is limited to symmetric morphologies. More advanced asymmetric models, such as the Gamma model, have been proposed to achieve improved accuracy. However, the physiological interpretation of the Gamma model is less effective than the Gaussian model, challenging the assessment of the clinical relevance of the outcomes. This paper aims to design an asymmetric PDA model with improved accuracy and effective physiological interpretability. We implemented a novel PDA model called the Skewed-Gaussian model and tested it on 8000 PPG pulses from the MIMIC-III Waveform Database. The performances were compared with the reference Gamma-Gaussian model. Models' accuracies were assessed using the residual sum of squares, while Bland-Altman plots were used to evaluate biases. Lastly, the sensitivity and robustness of the models to the initial values' choice were evaluated using random initial values. Our model achieved significantly higher accuracy than the reference model. The analysis with random initial values suggested that the model was less sensitive and consistently more robust. Finally, we highlighted the physiological interpretation of the model. The proposed model may help to establish a link between alterations in cardiovascular functions and variations detectable in the PPG signal, as well as opening up new avenues for PPG-based remote patient monitoring.

Heterostructure-induced anisotropy of tensile property in laser directed energy deposition TC11 titanium alloy

Grain structure is generally considered as an important factor to influence the anisotropy of mechanical properties of the additive manufactured metallic component. In this work, we revisit the mechanical anisotropy of a TC11 alloy with heterogeneous grain structure fabricated by laser directed energy deposition(L-DED) technology, and fully unravel the plastic deformation behavior with different types of heterogeneous grain morphology. It is found that the 0-BD specimens and 45-BD specimens exhibit desirable strength-ductility synergy with considerable YS, high UTS and prominent ductility. The synergistic increase in strength and plasticity is induced by the hetero-deformation of equiaxed grain and columnar grain induced. Specially, the optimum hetero-deformation induced (HDI) strengthening is obtained in 45-BD specimen due to the symmetric constraint morphology of heterostructure. The lower strength and elongation of the 90-BD specimens are associated with the fracture of α phases at grain boundaries perpendicular to the loading direction.

Effect of Impact Energy on the Interface Microstructure of Explosively Clad Mild Steel and Titanium

Effect of load ratio (R) on the interface microstructure and phase stability was investigated in mild steel/Grade-2 Ti explosive clads using experimental and JMatPro® computations. At low-impact-energy conditions (i.e., R = 1.07), the interface exhibited a symmetrical wavy morphology with molten metal entrapped in isolated regions within the vortices of the waves, while at high-impact loading conditions (R = 3) the interface had complex weld solidification structure consisting of planar interface, columnar and equiaxed dendrites. Based on the study, it was concluded that under high-impact loading conditions, the interface microstructure of the explosive clads will resemble fusion welded joints, but with relatively lower thickness of the interaction zones.

Ultranarrow Deep-Blue Luminescence of Perovskite Nanocrystals by A-Site Cation Control.

Metal-halide perovskite nanocrystals (NCs) are one of the most promising emitters for the application of display and nanolight sources. The full width at half-maximum (FWHM) of photoluminescence (PL) emission is essential for color purity, which however remains a difficulty to further reduce the FWHM of the perovskite NCs at room temperature. Here, we show the quasi-sphere perovskite NCs with narrow PL emission at a deep-blue wavelength of ∼430 nm; its PL FWHM reaches ∼11 nm at room temperature, owing to the monodispersion in size distribution as well as the symmetric quasi-sphere morphology of NCs releasing the fine structure splitting-induced inhomogeneous broadening. Through regulating A cations with respect to the ratio of FA (or MA)-to-Cs and Cs-to-Pb, the PL emission of the NCs could be tuned from ∼505 to ∼430 nm combined with varied morphologies from large cube to small quasi-sphere. Such spectroscopic and morphological discrepancies are supposed to be attributed to the different crystalline kinetics that is strongly dependent on the synthetic condition. To be specific, in the case of increasing FA (or MA)-to-Cs, the growth rate of CsPbBr3 and FAPbBr3 (or MAPbBr3) perovskites is determined by the reactivity of transient species, while in the case of decreasing the Cs-to-Pb ratio, the growth rate of perovskites is slowed down by the serious reduction of Cs+ in the precursor. This study provides an effective strategy to adjust the emission across from green to deep-blue color and promotes the perovskite NCs with a narrow FWHM, and tunable PL emission facilitates in application of optoelectronic devices.

Modeling Dust Production, Growth, and Destruction in Reionization-era Galaxies with the CROC Simulations. II. Predicting the Dust Content of High-redshift Galaxies

We model the interstellar dust content of the reionization era with a suite of cosmological, fluid-dynamical simulations of galaxies with stellar masses ranging from ∼105 to 109 M ⊙ in the first 1.2 Gyr of the Universe. We use a post-processing method that accounts for dust creation and destruction processes, allowing us to systematically vary the parameters of these processes to test whether dust-dependent observable quantities of galaxies at these epochs could be useful for placing constraints on dust physics. We then forward model observable properties of these galaxies to compare to existing data. We find that we are unable to simultaneously match existing observational constraints with any one set of model parameters. Specifically, the models that predict the largest dust masses D/Z ≳ 0.1 at z = 5—because of high assumed production yields and/or efficient growth via accretion in the interstellar medium—are preferred by constraints on total dust mass and infrared (IR) luminosities, but these models produce far too much attenuation in the ultraviolet (UV), preventing them from matching observations of β UV. To investigate this discrepancy, we analyze the relative spatial distribution of stars and dust as probed by IR and UV emission, which appear to exhibit overly symmetric morphologies compared to existing data, likely due to the limitations of the stellar feedback model used in the simulations. Our results indicate that the observable properties of the dust distribution in high redshift galaxies are a particularly strong test of stellar feedback.

A COMPLEX POST CARDIAC–ARREST SYNDROME: FROM UNCERTAIN NEUROLOGICAL OUTCOME TO HEMORRHAGIC COMPLICATION

Abstract A 49–years–old woman with type II diabetes mellitus, hypothyroidism and Churg–Strauss syndrome experienced chest pain with loss of consciousness. Emergency service was called and CPR promptly started. Cardiac arrest with shockable rhythm was documented, DC–shock performed with sign of anterior STEMI after ROSC, then refractory cardiac arrest appeared. The patient was centralized in our hospital and VA–ECMO was positioned through a percutaneous femoral access in cath–lab. Coronary angiography showed acute occlusion of the mid–proximal LAD and subocclusive stenosis of the dominant Cx for which PCI with DES was performed, then intra–aortic balloon pump (IABP) was implanted. At ICCU admission the patient was supported by ECMO and IABP with MAP 65 mmHg and lactates 3.5 mmol/L. Echocardiography and chest X–ray showed severe biventricular dysfunction and pulmonary overload (Fig 1). She was ventilated via ECMO circuit and mechanical ventilation setting protective TV values of 6 ml/kg. Diuresis was good with low dose of furosemide, lactates progressively decreased. Temperature control was set within 36°C with the cooling system of the ECMO circuit. Cardioaspirin, ticagrelor and bivalirudin were administered. At early neurological stratification EEG documented absence of epileptiform anomalies, responsiveness to painful stimuli, SSPE showed normal and symmetrical morphology, NSE at 48 h was 59 ng/mL, she opened eyes and performed simple orders. Levosimendan was administered with partial recovery of the right ventricular dysfunction leading to ECMO removal on 5th day. Due to poor consciousness recovery despite sedation reduction, percutaneous tracheostomy was performed on 8th day, IABP removed and the following day all vasopressors suspended. Neurological improvement allowed transition to spontaneous breathing and weaning from mechanical ventilation; on 19th day tracheostomy was removed. Massive enterorrhagia appeared after ECMO removal (figure 2). The colonoscopy showed ischemic pancolitis, therefore ticagrelor was suspended. On 18th day clopidogrel was reintroduced based on hemoglobin stability and endoscopic improvement. She was discharged from the cardiology department after a total length of stay of thirty days, with normal neurological status, no motor deficits, recovery of left and right ventricular function, stable hemoglobin levels.

Forming localized dust concentrations in a dust ring: DM Tau case study

Context. Previous high-angular-resolution 225 GHz (~1.3 mm) continuum observations of the transitional disk DM Tau have resolved an outer ring at 20–120 au radii that is weakly azimuthally asymmetric. Aims. We aim to examine dust growth and filtration in the outer ring of DM Tau. Methods. We performed ~0″.06 (~8.7 au) resolution Karl G. Jansky Very Large Array (JVLA) 40–48 GHz (~7 mm; Q band) continuum observations, along with complementary observations at lower frequencies. In addition, we analyzed the archival JVLA observations undertaken since 2010. Results. Intriguingly, the Q band image resolved the azimuthally highly asymmetric, knotty dust emission sources close to the inner edge of the outer ring. Fitting the 8–700 GHz spectral energy distribution (SED) with two dust components indicates that the maximum grain size (amax) in these knotty dust emission sources is likely ≳300 µm, whereas it is ≳50 µm in the rest of the ring. These results may be explained by a trapping of inwardly migrating “grown” dust close to the ring inner edge. The exact mechanism for developing the azimuthal asymmetry has not yet been identified, which may be due to planet-disk interaction that might also be responsible for the creation of the dust cavity and pressure bump. Otherwise, it may be due to the fluid instabilities and vortex formation as a result of shear motions. Finally, we remark that the asymmetries in DM Tau are difficult to diagnose from the ≳225 GHz observations, owing to a high optical depth at the ring. In other words, the apparent symmetric or asymmetric morphology of the transitional disks may be related to the optical depths of those disks at the observing frequency.

Robust inference of the Galactic Centre gamma-ray excess spatial properties

ABSTRACT The gamma-ray Fermi-LAT Galactic Centre excess (GCE) has puzzled scientists for over 15 yr. Despite ongoing debates about its properties, and especially its spatial distribution, its nature remains elusive. We scrutinize how the estimated spatial morphology of this excess depends on models for the Galactic diffuse emission, focusing particularly on the extent to which the Galactic plane and point sources are masked. Our main aim is to compare a spherically symmetric morphology – potentially arising from the annihilation of dark matter (DM) particles – with a boxy morphology – expected if faint unresolved sources in the Galactic bulge dominate the excess emission. Recent claims favouring a DM-motivated template for the GCE are shown to rely on a specific Galactic bulge template, which performs worse than other templates for the Galactic bulge. We find that a non-parametric model of the Galactic bulge derived from the VISTA Variables in the Via Lactea survey results in a significantly better fit for the GCE than DM-motivated templates. This result is independent of whether a galprop-based model or a more non-parametric ring-based model is used to describe the diffuse Galactic emission. This conclusion remains true even when additional freedom is added in the background models, allowing for non-parametric modulation of the model components and substantially improving the fit quality. When adopted, optimized background models provide robust results in terms of preference for a boxy bulge morphology for the GCE, regardless of the mask applied to the Galactic plane.

Three‐Dimensional Water Exchanges in the Shelf Circulation System of the Northern South China Sea Under Climatic Modulation From ENSO

AbstractUsing the numerical calculations of exposure time (), this study investigated the three‐dimensional characteristics of water exchanges associated with the coastal‐shelf circulations of the Northern South China Sea (NSCS). The circulation connectivity and its interannual variability under the modulation of El Niño Southern Oscillation (ENSO) were investigated. The gradually increased from approximately 50 days over the outer shelf to more than 150 days in the shallower coastal seas with the Beibu Gulf displaying a significantly longer (approximately 300 days). The Beibu Gulf played an influential role in the water exchange that had a contribution of over 30% to in the most regions. The results from sensitivity experiments indicate that the wind forcing is the primary controller of and the boundary flux plays a secondary role. Specifically, the wind enhances water exchange in western NSCS, particularly in the Beibu Gulf and Yuexi region. Conversely, boundary fluxes facilitate exchanges in the eastern shelf, such as Yuedong region. Analysis revealed a clear modulation from ENSO on water exchange, wherein El Niño and La Niña years displayed symmetrical morphologies in distribution anomalies, albeit with varying intensities. During El Niño years, the weakened southwestward shelf current increased and the shelf water was less likely to reach the Beibu Gulf, and once arrived, these waters were trapped inside to elongate . In contrast, during La Niña years, the strengthened southwestward shelf current shortened and more shelf waters were transported away from the NSCS by an intensified southwestward shelf current.

Serendipitous Archival Observations of a New Ultradistant Comet C/2019 E3 (ATLAS)

We identified a new ultradistant comet C/2019 E3 (ATLAS) exhibiting preperihelion cometary activity at heliocentric distances ≳20 au, making it the fourth member of this population after C/2010 U3 (Boattini), C/2014 UN271 (Bernardinelli–Bernstein), and C/2017 K2 (PANSTARRS). From serendipitous archival data, we conducted analyses of the comet, finding that the activity was consistent with steady-state behavior, suggestive of sublimation of supervolatiles; that the cross section of dust increased gradually on the inbound leg of the orbit, varying with heliocentric distances as rH−1.5±0.4 ; and that the dust was produced at a rate of ≳102 kg s−1 within the observed timespan. Our modeling of the largely symmetric morphology of the comet suggests that the dust environment was likely dominated by mm-scale dust grains ejected at speeds ≲0.4 m s−1 from the sunlit hemisphere of the nucleus. Assuming a typical geometric albedo of 0.05 and adopting several simplistic thermophysical models, we estimated the nucleus to be at least ∼3 km across. We also measured the color of the comet to be consistent with other long-period comets, except being slightly bluer in g − r. With our astrometric measurements, we determined an improved orbit of the comet, based upon which we derived that the comet is dynamically new and that its perihelion distance will further shrink due to the Galactic tide. We conclude the paper by comparing the known characteristics of the known ultradistant comets.

Exploring the formation of gold/silver nanoalloys with gas-phase synthesis and machine-learning assisted simulations.

While nanoalloys are of paramount scientific and practical interest, the main processes leading to their formation are still poorly understood. Key structural features in the alloy systems, including the crystal phase, chemical ordering, and morphology, are challenging to control at the nanoscale, making it difficult to extend their use to industrial applications. In this contribution, we focus on the gold/silver system that has two of the most prevalent noble metals and combine experiments with simulations to uncover the formation mechanisms at the atomic level. Nanoparticles were produced using a state-of-the-art inert-gas aggregation source and analyzed using transmission electron microscopy and energy-dispersive X-ray spectroscopy. Machine-learning-assisted molecular dynamics simulations were employed to model the crystallization process from liquid droplets to nanocrystals. Our study finds a preponderance of nanoparticles with five-fold symmetric morphology, including icosahedra and decahedra which is consistent with previous results on mono-metallic nanoparticles. However, we observed that gold atoms, rather than silver atoms, segregate at the surface of the obtained nanoparticles for all the considered alloy compositions. These segregation tendencies are in contrast to previous studies and have consequences on the crystallization dynamics and the subsequent crystal ordering. We finally showed that the underpinning of this surprising segregation dynamics is due to charge transfer and electrostatic interactions rather than surface energy considerations.

Morphological Investigation of Lamellae Patterns in Diblock Copolymers under Change of Thickness and Confinement in Polar Geometry

Mathematicians collaborate computationally with practical scientists to predict the novel morphologies soft materials, having potential applications in nanotechnology. This work presents the novel lamellae morphology that the confined diblock copolymer system displayed inside the polar geometry in order to achieve this, cell dynamics simulations (CDS) model is employed on a polar mesh to study the special impacts of confinement on the self-assembly behavior of diblock copolymer systems. Under the numerical formulation of the isotropic Laplacian with polar geometry employed in the CDS model, the set of 9-point stencil is considered to discretize the Laplacian operator on polar mesh system. FTCS finite difference mechanism is taken into consideration for discretization of Laplacian operator due to its computational efficiency and accuracy. Cell dynamics simulation is efficient simulation model for large-scale simulation as compared to the other models available in literature. In the simulation, evolutionary lamella morphology is presented with and without confinement for various sizes of the circular annular pores. A comparative review of lamella morphologies achieved by simulation in comparison of experimental study is presented, coupled with a thorough investigation of symmetric and asymmetric morphologies in captivity.

A Novel Method for one-Stage Repair of the lip Vermilion Defects in Progressive Hemifacial Atrophy

Background Progressive hemifacial atrophy often causes lip vermilion defects in patients. In this study, we described a one-stage repair method for lip defects in progressive hemifacial atrophy using a lip vermilion mucosal flap or combined dermal fat flap graft. Patients and Methods Patients diagnosed with progressive hemifacial atrophy with lip vermilion defects from 2010 to 2022 were included in this study. Based on the severity and location of the patient's lip defect, a lip vermilion mucosal flap was designed and transferred to the lip defect or combined with a hip dermal fat flap for one-stage repair of the lip morphology. Lip morphology and function of patients were followed up after surgery. Results A total of 22 patients were enrolled in this study, including 15 patients with lip defects on the upper lip alone and 7 patients with both upper and lower lip defects. Follow-up six months to two years postoperatively, all patients recovered uneventfully without complications. The repaired lips of the patient had a full and symmetrical morphology with no visible scarring. Two patients experienced transient dysesthesia of the lips postoperatively and both returned to normal after three months. All patients had good lip closure with normal dietary and speech function. Conclusions The method we described for repairing lip defects in progressive hemifacial atrophy can achieve satisfactory aesthetic and functional lip results. The distinct advantage of this approach is that the patients undergo only one-stage operation and it can be used to repair both upper and lower lip defects.

Spatial Integration of Cellular Shapes in Green Microalgae with Complex Morphology, the Genus Micrasterias (Desmidiales, Zygnematophyceae)

While ontogeny of multicellular organisms requires an interplay among tissues, morphogenesis of unicellular structures is typically organised with respect to differential growth of their cell covering. For example, shapes of various microalgae have often been emphasised as examples of symmetric fractal-like cellular morphology. Such a self-similar pattern is typical for the variability of a spatial fractal, with the shape variation remaining the same at different scales. This study investigated how these cells are integrated. A geometric morphometric analysis of spatial integration in the genus Micrasterias was used to assess the variation across scales by comparing the slopes of the linear fit of the log bending energy against the log variance of partial warps. Interestingly, the integration patterns were distinctly different from the notion of self-similarity. The variability consistently increased with decreasing scale, regardless of the cultivation temperature or the species examined. In addition, it was consistent after the adjustment of the slopes for the digitisation error. The developmental control over the final shape progressively declines with decreasing spatial scale, to the point that the terminal lobules are shaped almost independently of each other. These findings point to possible considerable differences in the generation of morphological complexity between free-living cells and multicellular organisms.

The magnetic field clock angle departure in the Venusian magnetosheath and its response to IMF rotation

We investigate the characteristics of interplanetary magnetic field (IMF) draping in the Venusian magnetosheath using both Venus Express (VEX) observations and magnetohydrodynamics simulations. The distributions of magnetosheath field clock angle illustrate the nearly symmetric morphology of draped magnetic field with respect to the solar wind electric field, and the departure of the IMF clock angle is larger at closer distances. Based on VEX data, the sheath field clock angle departures are found to be <45 degrees for 90% of the instances under steady IMF and this parameter can respond almost immediately to the unsteady IMF. We suggest the magnetosheath field just slips around the planet without significant pileup or bending. Our time-dependent simulations indicate that the response time of sheath field to IMF variation is not more than 1 min and it depends on the involved regions of magnetosheath: the timescale in the inner part of magnetosheath adjacent to the induced magnetosphere is longer than that in the outer part. We find this timescale is controlled by the convection velocity in the magnetosheath, emphasizing the magnetohydrodynamic characteristics of the behavior of the sheath field. The finite magnetosheath field clock angle departure and its quick response to IMF variation suggest that the magnetic field clock angle measured within the Venusian magnetosheath can be used as a reasonable proxy for the upstream IMF clock angle.

A Symmetry Concept for the Self-Assembly Synthesis of Mn-MIL-100 Using a Capping Agent and Its Adsorption Performance with Methylene Blue

In this study, a facile strategy of regulated self-assembly synthesis of Mn-MIL-100, using sodium acetate (CH3COONa) as a mono-dentate ligand capping agent (CA), was proposed. The as-prepared product is denoted Mn-MIL-100-CA. The coordination modulation of CH3COONa, led by its interference in the connectivity and symmetry of the metal centers and organic nodes, plays a vital role in the synthesis process. The crystallinity, morphology, topology, and properties of such MOF products were improved, since the self-assembly process of Mn-MIL-100-CA was promoted and regulated effectively. The materials were systematically characterized via XRD, SEM, N2 isotherms, XPS, and TGA in terms of crystallization behavior, morphology, topology, chemical composition, and thermal and water stability. The ability of Mn-MIL-100 and Mn-MIL-100-CA to remove methylene blue (MB) from an aqueous solution was investigated using a UV–vis spectrophotometer. The results indicate that with the addition of a molar ratio of 50% CH3COONa, Mn-MIL-100-CA particles developed a regularly symmetrical morphology, i.e., ‘spherical pyramid-like structure’ crystals with a dimension of 2~5 μm. Their specific surface area and pore volume increased by 59.2% and 56.7%, respectively. The increased proportion of Mn3+ implies reduced crystal defects and improved crystal structural order and integrity, and therefore an enhanced water stability. Mn-MIL-100-CA exhibited excellent adsorption performance towards MB from aqueous solution. The equilibrium adsorption value was as high as 1079.9 mg/g, which is 44.7% higher than that of Mn-MIL-100 without the addition of CA. The good adsorption capacity and excellent water stability mean that Mn-MIL-100-CA has great potential for the practical removal of MB dye pollutants from water.

Evaluation of Photocatalytic Activity and Electrochemical Properties of Hematite Nanoparticles

The symmetric nano morphologies, asymmetric electronic structures, and as well as the heterojunctions of the developed photocatalytic systems perform a vital role in promoting light absorption, separation of electron and hole pairs and charge carrier transport to the surface when exposed to near-infrared (NIR) light. In this present work, we synthesized hematite (α-Fe2O3) nanoparticles (NPs) by a facile hydrothermal method and studied their structural, optical, and photocatalytic properties. Powder X-ray diffraction (XRD) confirmed the rhombohedral phase of the α-Fe2O3 NPs, and Fourier transform infrared spectroscopy (FT-IR) was used to investigate symmetric and asymmetric stretching vibrations of the functional groups on the surface of the catalysts. The optical bandgap energy was estimated to be 2.25 eV using UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) and scanning electron microscopy (SEM) images indicated sphere like morphology. The oxidation and reduction properties of α-Fe2O3 NPs were analyzed by cyclic voltammetry (CV). The α-Fe2O3 NPs were utilized for the degradation of methylene blue (MB) dye under natural sunlight. The experimental results demonstrate that the degradation efficiency was achieved at 33% in 2 h, and the pseudo-first-order rate constant was calculated to be 0.0033 min−1.

Effects of aspect ratio and initial pressure on asymmetric flame and flame instability of premixed CO/air

Syngas is a promising alternative energy carrier with low carbon and pollutants emissions, and CO is the main component. The combustion characteristics of stoichiometric CO/air mixtures with varied initial pressure (0.5–1.5 atm) and aspect ratio (12–40) were examined through experiments in a rectangular closed duct. This experiment simulated the transport and storage conditions of CO to study its combustion characteristics at different aspect ratios and initial pressures. The flame images and overpressure dynamics were captured by high-speed camera and pressure sensor, respectively. Experiment results proved that the increase in aspect ratio had an important effect on flame shape evolution. The tilted flame for low aspect ratios was affected by buoyancy, while flames with high aspect ratios were influenced by competing buoyancy and intrinsic instability. The results showed that the flame morphology and dynamics were enhanced with increasing aspect ratio and initial pressure. The intrinsic instability of premixed CO/air combustion was investigated, and the formation mechanism of tilted flame and twisted flame were comprehensively analyzed. Qualitative distinctions were made between symmetric and asymmetric flame morphology regimes.

Global Distribution and Morphology of Small Seamounts

AbstractSeamounts are isolated elevations in the seafloor with circular or elliptical plans, comparatively steep slopes, and relatively small summit area (Menard, 1964). The vertical gravity gradient (VGG), which is the curvature of the ocean surface topography derived from satellite altimeter measurements, has been used to map the global distribution of seamounts (Kim & Wessel, 2011, https://doi.org/10.1111/j.1365-246x.2011.05076.x). We used the latest grid of VGG to update and refine the global seamount catalog; we identified 19,325 new seamounts, expanding a previously published catalog having 24,643 seamounts. Seven hundred thirty‐nine well‐surveyed seamounts, having heights ranging from 421 to 2,500 m, were used to estimate the typical radially symmetric seamount morphology. First, an Empirical Orthogonal Function (EOF) analysis was used to demonstrate that these small seamounts have a basal radius that is linearly related to their height—their shapes are scale invariant. Two methods were then used to compute this characteristic base to height ratio: an average Gaussian fit to the stack of all profiles and an individual Gaussian fit for each seamount in the sample. The first method combined the radial normalized height data from all 739 seamounts to form median and median‐absolute deviation. These data were fit by a 2‐parameter Gaussian model that explained 99.82% of the variance. The second method used the Gaussian function to individually model each seamount in the sample and further establish the Gaussian model. Using this characteristic Gaussian shape we show that VGG can be used to estimate the height of small seamounts to an accuracy of ∼270 m.

The propagation behavior of hydraulic fracture network in a reservoir with cemented natural fractures

AbstractThere are still some problems in the study of hydraulic fracture (HF) network evolution in cemented naturally fractured reservoirs, such as microseismic mapping showing exaggerated stimulated reservoir volume in some cases. In addition, the dominant role of natural fracture (NF) cementation strength, injection rate, in situ stress difference, NF distribution, and fracture initiation sequence of perforations in synthetically influencing fracture network formation needs to be further studied. For this purpose, a three‐dimensional matrix hexahedral element global coupled 0‐thickness cohesive element hydraulic fracturing model was developed. Results show that each interaction between HF and NF causes HF diameter shrinkage, which increases the propagation pressure of HF. When the cementation strength of the NF is low, the HF tends to deviate toward the tip of the NF to form a complex fracture network. Increasing the injection rate and the number of NFs can significantly enhance the complexity of the HF network, but does not change the HF and NF interaction pattern. The in situ stress differences dominate the morphology of the HF network when the cementation strength of NFs is constant. The stress interference of multiple fractures under segmented fracturing may form “S”‐shaped HFs, and the HFs are difficult to maintain a symmetrical morphology in the direction of the well axis. In addition, some NFs in inactivated damaged zones have developed a certain width geometrically due to the induced effect of HF, but they are still isolated by the low permeability matrix and might only generate some microseismic events.