Density Inversion Research Articles

A GGIW-PHD Filter for Multiple Non-Ellipsoidal Extended Targets Tracking With Varying Number of Sub-Objects

When the extension state of the non-ellipsoidal extended target (NET) changes, the performance of traditional multiple target tracking algorithms based on the constant number of sub-objects will decrease. To solve this problem, this paper proposes a gamma Gaussian inverse Wishart probability hypothesis density filter for non-ellipsoidal extended targets with varying number of sub-objects, called VN-NET-GGIW-PHD filter. In the proposed filter, each NET is considered as a combination of multiple spatially close sub-objects, and the label management is introduced to realize the association between the NET and corresponding sub-objects. Then, by target spawning and combination, the number of sub-objects for approximating the extension state of each NET can be adjusted automatically. Furthermore, to obtain the partition of the measurement set, an approach based on the clustering by fast search and find of density peaks (CFSFDP) algorithm and expectation maximization (EM) algorithm is proposed. Simulation results show that the proposed filter can adaptively adjust the number of sub-objects and has better performance when the extension state of the NET changes.

Supercritical convective flows of melt water in an open horizontal rectangular cavity with a prescribed vertical heat flux

The influence of the intensity of heating, expressed by the Grashof number, on supercritical regimes of thermal convection of melt water in a horizontal rectangular cavity with an aspect ratio of two is investigated. On the lateral solid boundaries, the thermal insulation conditions are satisfied, and a constant vertical heat flux is set on the lower solid and upper free horizontal and non-deformable edges. Under conditions when the cavity-average temperature is close to the temperature of water density inversion in the cavity, a state of mechanical equilibrium is possible, when a stably stratified layer is located on top of an unstable stratified layer. For two cases of the position of the horizontal boundary between these layers, the structure of stationary planar supercritical thermal convection is investigated. The calculations were carried out by the finite-difference method on a square grid with 128 nodes along the horizontal coordinate and 64 along the vertical one. Calculations have shown that, with an equal thickness of unstable and stably stratified layers, supercritical convection in the region up to about six supercriticalities has a two-cell structure in the horizontal direction with two (large at the bottom and weaker at the top) vortices in each of the cells. With an increase in supercriticality, this two-cell structure turns into a four-cell structure in a hysteresis manner. For the case when the thickness of the stably stratified layer is three times less than the thickness of the unstable stratified layer, the supercritical convective flow has the general form of a single-vortex cell elongated horizontally. With an increase in the Grashof number up to about a hundredfold supercriticality, it remains generally single-vortex and does not experience bifurcations.

Water Vapor Retrieval Using Commercial Microwave Links Based on the LSTM Network

In this article, a water vapor density inversion model based on the long short-term memory network is proposed for E-band commercial microwave links (CMLs). A full-duplex E-band microwave link located in Prague (two sublinks with frequencies of 73.5 and 83.5 GHz, both vertically polarized) was used to verify the performance of the model. The results show that the model inversion results are in good agreement with the water vapor density calculated by temperature and humidity sensors. Compared with previous water vapor inversion methods based on CMLs, this model has a higher temporal resolution and can realize real-time monitoring.

Characteristics of gravity and magnetic fields and deep structural responses in the southern part of the Kyushu-Palau Ridge

The southern part of the Kyushu-Palau Ridge (KPR) is located at the conjunction of the West Philippine Basin, the Parece Vela Basin, the Palau Basin, and the Caroline Basin. This area has extremely complex structures and is critical for the research on the tectonic evolution of marginal seas in the Western Pacific Ocean. However, only few studies have been completed on the southern part, and the geophysical fields and deep structures in this part are not well understood. Given this, this study finely depicts the characteristics of the gravity and magnetic anomalies and extracts information on deep structures in the southern part of the KPR based on the gravity and magnetic data obtained from the 11th expedition of the deep-sea geological survey of the Western Pacific Ocean conducted by the Guangzhou Marine Geological Survey, China Geological Survey using the R/V Haiyangdizhi 6. Furthermore, with the data collected on the water depth, sediment thickness, and multichannel seismic transects as constraints, a 3D density model and Moho depths of the study area were obtained using 3D density inversion. The results are as follows. (1) The gravity and magnetic anomalies in the study area show distinct zoning and segmentation. In detail, the gravity and magnetic anomalies to the south of 11°N of the KPR transition from high-amplitude continuous linear positive anomalies into low-amplitude intermittent linear positive anomalies. In contrast, the gravity and magnetic anomalies to the north of 11°N of the KPR are discontinuous and show alternating positive and negative anomalies. These anomalies can be divided into four sections, of which the separation points correspond well to the locations of deep faults, thus, revealing different field-source attributes and tectonic genesis of the KPR. (2) The Moho depth in the basins in the study area is 6–12 km. The Moho depth in the southern part of KPR show segmentation. Specifically, the depth is 10–12 km to the north of 11°N, 12–14 km from 9.5°N to 11°N, 14–16 km from 8.5°N to 9.5°N, and 16–25 km in the Palau Islands. (3) The KPR is a remnant intra-oceanic arc with the oceanic-crust basement.which shows noticeably discontinuous from north to south in geological structure and is intersected by NEE-trending lithospheric-scale deep faults. With large and deep faults F3 and F1 (the Mindanao fault) as boundaries overall, the southern part of the KPR can be divided into three zones. In detail, the portion to the south of 8.5°N (F3) is a tectonically active zone, the KPR portion between 8.5°N and 11°N is a tectonically active transition zone, and the portion to the north of 11°N is a tectonically inactive zone. (4) The oceanic crust in the KPR is slightly thicker than that in the basins on both sides of the ridge, and it is inferred that the KPR formed from the thickening of the oceanic crust induced by the upwelling of deep magma in the process of rifting of remnant arcs during the Middle Oligocene. In addition, it is inferred that the thick oceanic crust under the Palau Islands is related to the constant upwelling of deep magma induced by the continuous northwestward subduction of the Caroline Plate toward the Palau Trench since the Late Oligocene. This study provides a scientific basis for systematically understanding the crustal attributes, deep structures, and evolution of the KPR.©2021 China Geology Editorial Office.

A ternary mixture at the border of Soret separation stability.

Ternary mixtures with the Soret effect are prone to triple-diffusive convection in a thermal field. The Soret coefficients of the toluene-methanol-cyclohexane mixture, measured in microgravity at a given composition [0.62-0.31-0.07] in mass fractions, showed that the net separation ratio, Ψ, the parameter responsible for the hydrodynamic stability in a gravity field is close to zero. Furthermore, the large cross-diffusion of toluene leads to a curious situation: the Soret coefficient ST1 is positive while the thermodiffusion coefficient DT1 is negative. The behavior of this ternary mixture on the border of stability, when Ψ is slightly negative or positive, is examined experimentally and numerically. The mixture is placed in an elongated cell between the differently heated walls. Depending on Ψ and the initial temperature of the liquid (mean temperature, linear profile or cold one), the evolution of concentration patterns are classified by four regimes. We observe the emergence of motionless, metastable, and convective patterns. In the case of Ψ > 0, it was found that cross-diffusion fluxes cause a temporarily unstable density pattern. The initially cold mixture at either Ψ sign shows dissimilar Soret separation in the upper and lower parts of the cell. It leads to the formation of a long-lived inverse density gradient at the upper part of the cell, which finally results in a motionless (Ψ > 0) or convective (Ψ < 0) pattern.

Point cloud analysis model combining inverse density function and relation-shape convolution neural network

Point cloud analysis model combining inverse density function and relation-shape convolution neural network

AVO inversion using pseudoisotropic elastic properties

Amplitude variation with offset (AVO) inversion of an anisotropic data set is a challenging task. Nonnegligible differences in the anisotropy parameters between the various lithologies make the seismic data AVO response completely different from the isotropic synthetic seismogram. In this case, it is difficult to invert for VP/VSand density consistent with well-log data. AVO inversion using pseudoisotropic elastic properties is a practical solution to this problem. Verification of this method was performed using data from an offshore Western Australia field. It was found that wavelet extraction and density inversion are improved significantly by replacing the isotropic elastic properties with the pseudoisotropic properties. Inverted density shows reasonable quality and therefore can be included in the reservoir characterization study. Postinversion analyses can be performed effectively on the pseudoisotropic elastic properties because crossplot analysis shows the increased separation of different lithofacies due to contrasts in anisotropy parameters. This result could have significant implications for other fields, as shale constitutes most of the overburden in conventional oil and gas fields and often shows strong elastic anisotropy.

Estimation of weak anisotropy parameters and fracture density of asymmetric fractures in monoclinic medium

Abstract One of the typical anisotropic media is the monoclinic anisotropy (MA) medium, which is formed by embedding two sets of non-orthogonal fracture sets into an isotropic or vertical transverse isotropic (VTI) background medium. Weak anisotropy (WA) parameters and fracture density provide important in situ stress and high-porosity zone information. Estimation of WA parameters and fracture density of MA medium by prestack seismic amplitude inversion is important for shale reservoir characterisation. We derive the expression of generalised WA parameters in a basic reflection coefficients formula of MA medium by incorporating a stiffness matrix of VTI background and disturbance compliance matrix of asymmetric fracture. We then re-express the P-wave reflection coefficients in terms of WA parameters and fracture compliance tensors. To achieve the direct inversion of fracture density, we rewrite the linearised expression of P-wave reflection coefficients related to WA parameters and fracture density. Finally, under the Bayesian framework, the WA parameters and fracture density are estimated by using the amplitude versus offset and azimuth (AVOA) inversion parameters. We use a Monte Carlo simulation to test the effect of uncertainties in the priori information about fracture property parameters. The application of synthetic seismic gathers show that the proposed inversion strategy is reliable within moderate noise. Compared with the results obtained by using inversion based on a rotationally invariant fracture, the test indicates that a fracture model with a simplified shape or wrong assumption will increase calculation error and reduce the inversion accuracy.

Simulated tempering with irreversible Gibbs sampling techniques.

We present here two novel algorithms for simulated tempering simulations, which break the detailed balance condition (DBC) but satisfy the skewed detailed balance to ensure invariance of the target distribution. The irreversible methods we present here are based on Gibbs sampling and concern breaking DBC at the update scheme of the temperature swaps. We utilize three systems as a test bed for our methods: a Markov chain Monte Carlo simulation on a simple system described by a one-dimensional double well potential, the Ising model, and molecular dynamics simulations on alanine pentapeptide (ALA5). The relaxation times of inverse temperature, magnetic susceptibility, and energy density for the Ising model indicate clear gains in sampling efficiency over conventional Gibbs sampling techniques with DBC and also over the conventionally used simulated tempering with the Metropolis-Hastings (MH) scheme. Simulations on ALA5 with a large number of temperatures indicate distinct gains in mixing times for inverse temperature and consequently the energy of the system compared to conventional MH. With no additional computational overhead, our methods were found to be more efficient alternatives to the conventionally used simulated tempering methods with DBC. Our algorithms should be particularly advantageous in simulations of large systems with many temperature ladders, as our algorithms showed a more favorable constant scaling in Ising spin systems as compared with both reversible and irreversible MH algorithms. In future applications, our irreversible methods can also be easily tailored to utilize a given dynamical variable other than temperature to flatten rugged free energy landscapes.

Evolution Model for the Absheron Mud Volcano: From Stratified Sediments to Fluid Mud Generation

AbstractSubmarine mud volcanoes (MVs) are one of the most spectacular methane expulsion features at the seafloor and they represent a significant geohazard worldwide. In this work, we focus on the physical processes controlling the initiation and early evolution of the Absheron mud volcano (AMV). Our analyses were carried out based on basin modeling calibrated thanks to existing seismic interpretation of the AMV, analysis of sediment samples from seabed, and data from two exploration wells. Acquired laboratory geotechnical data allowed us to derive laws considering the impact of gas exsolution on host sediment behaviors. In this study, we identified key geological and physical conditions that led to MV formation: by coupling diffusion processes with hydrofracturing and fluid advection, we were able to simulate the conditions required to generate mud 3.5 km below the AMV. Mud remobilization up to the seabed was reproduced by using Navier‐Stokes equations modified to account for the impact of gas expansion on mud density. Considering density inversion only, simulations indicate that mud would be extruded at the seabed 100 years after its generation, an ascent rate similar to extrusion rates measured at the active Kotyrdag MV in Azerbaijan.

Study on gravity inversion and seismogenic environment of density in Tibetan Plateau and its adjacent areas

Study on gravity inversion and seismogenic environment of density in Tibetan Plateau and its adjacent areas

Crustal Density Inversion and Its Tectonic Structure in Badong-Zigui Area

Objectives The Badong-Zigui Basin is located in the west of the Three Gorges area, and it is surrounded by four different tectonic units: With the Xuefengshan thick-soil tectonic belt on the south, the Qinling orogenic belt on the north, the Huangling anticline on the east, and the eastern extension of the Sichuan Basin in the west. The Badong-Zigui basin is a north-south syncline structure, the sediments in the basin are dominated by Late Triassic-Late Turassic argillaceous rocks, and the special tectonic setting causes strong tectonic activities in the basin. Methods Using a three-dimensional gravity inversion algorithm based on Lagrangian multiplier constraints, the local Bouguer gravity anomaly in Badong-Zigui area is inverted, and the underground three-dimensional density structure of Badong-Zigui and adjacent areas is obtained. Results The inversion results show that the Zigui Basin is a low-density area compared with the surrounding area. The sedimentation thickness in the east is deeper than that in the west, and the sediment density is lower than that in the west. The small and medium earthquakes in the area are basically 4-12 km underground. Conclusions The north-south and north-east ancient water flows in the northern edge of the Zigui Basin successively provide sources for the sedimentation and filling of the basin, forming a structure with lower material density and deeper deposits in the eastern part of the basin; low-density materials in the east are transported and accumulated to the west in the basin. At the same time, it is squeezed by the eastward extension of the Sichuan Basin, and it is speculated that there is a tendency of east-west movement and compression in the basin.

Study on vascular remodeling, inflammatory response, and their correlations in acute spinal cord injury in rats

To study the local vascular remodeling, inflammatory response, and their correlations following acute spinal cord injury (SCI) with different grades, and to assess the histological changes in SCI rats. One hundred and sixteen adult female Sprague Dawley rats were randomly divided into 4 groups ( n=29). The rats in sham group were received laminectomy only. A standard MASCIS spinal cord compactor was applied with drop height of 12.5, 25.0, or 50.0 mm to establish the mild, moderate, or severe SCI model, respectively. Quantitative rat endothelial cell antigen 1 (RECA1) and CD68 positive areas and the correlations were studied by double immunofluorescent (DIF) staining at 12 hours, 24 hours, 3 days, 7 days, and 28 days following SCI. Moreover, qualitative neurofilament-H (NF-H) and glial fibrillary acidic protein (GFAP) positive glial cells were studied by DIF staining at 28 days. ELISA was used to detect the levels of tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), and IL-6 in spinal cord homogenates at 12 hours, 24 hours, and 3 days, and the correlations between TNF-α, IL-1β, or IL-6 levels and microvascular density (RECA1) were accordingly studied. Moreover, the neural tissue integrity and neuron damage were assessed by HE staining at 12 hours, 24 hours, 3 days, 7 days, and 28 days, and Nissl's staining at 28 days following SCI, respectively. DIF staining revealed that the ratio of RECA1 positive area was the highest in moderate group, higher in mild and severe groups, and the lowest in sham group with significant differences between groups ( P<0.05). The ratio of CD68 positive area was the highest in severe group, higher in moderate and mild groups, and the lowest in sham group with significant differences between groups ( P<0.05), except the comparisons between mild and moderate groups at 24 hours and 28 days after SCI ( P>0.05). There was no significant correlation between the RECA1 and CD68 expressions in sham group at different time points ( P>0.05). At 12 and 24 hours after SCI, the RECA1 and CD68 expressions in mild and moderate groups showed significant positive correlations ( P<0.05), while no significant correlation was found in severe group ( P>0.05). No significant correlations between the RECA1 and CD68 expressions was shown in all SCI groups at 3 days and in severe group at 7 days ( P>0.05), while the negative correlations were shown in mild and moderate groups at 7 days, and in all SCI groups at 28 days ( P<0.05). In mild, moderate, and severe groups, the axons became disrupted, shorter and thicker rods-like, or even merged blocks with increased injury, while the astrocytes decreased in number, unorganized and condensed in appearance. ELISA studies showed that TNF-α, IL-1β, and IL-6 levels in sham group were significantly lower than those in other 3 groups at different time points ( P>0.05). The differences in TNF-α, IL-1β, and IL-6 levels between SCI groups at different time points were sinificant ( P<0.05), except IL-1β levels between the mild and moderate groups at 12 hours ( P>0.05). Three inflammatory factors were all significantly correlated with the microvascular density grades ( P<0.05). Histological analysis indicated that the damage to spinal cord tissue structure correlated with the extent of SCI. In severe group, local hemorrhage, edema, and infiltration of inflammatory cells were found the most drastic, the grey/white matter boundary was disappeared concurrently with the formation of cavity and shortage of normal neurons. In the acute stage following mild or moderate SCI, progressively aggravated injury result in higher microvessel density and increased inflammation. However, at the SCI region, the relation between microvessel density and inflammation inverse with time in the different grades of SCI. Accordingly, the destruction of neural structures positively relate to the grades of SCI and severity of inflammation.

Non-Linear Pharmacokinetics of Oral Roscovitine (Seliciclib) in Cystic Fibrosis Patients Chronically Infected with Pseudomonas aeruginosa: A Study on Population Pharmacokinetics with Monte Carlo Simulations.

Roscovitine (Seliciclib), a new protein kinase inhibitor, was administered orally to adult patients with cystic fibrosis for the first time in the ROSCO-CF trial, a dose-escalation, phase IIa, randomized, controlled trial. Extensive pharmacokinetic sampling was performed up to 12 h after the first oral dose. Roscovitine and its main metabolite M3 were quantified by liquid chromatography coupled with tandem mass spectrometry. The pharmacokinetics analyses were performed by non-linear mixed effects modelling. Monte Carlo simulations were performed to assess the impact of dose on the pharmacokinetics of oral roscovitine. Twenty-three patients received oral doses ranging from 200 to 800 mg of roscovitine and 138 data points were available for both roscovitine and M3 concentrations. The pharmacokinetics was best described by a two-compartment parent-metabolite model, with a complex saturable absorption process modelled as the sum of Gaussian inverse density functions. The Monte Carlo simulations showed a dose-dependent and saturable first-pass effect leading to pre-systemic formation of M3. The treatment with proton-pump inhibitors reduced the rate of absorption of oral roscovitine. The pharmacokinetics of oral roscovitine in adult patients with cystic fibrosis was non-linear and showed significant inter-individual variability. A repeat-dose study will be required to assess the inter-occasional variability of its pharmacokinetics.

A Poisson Multi-Bernoulli Mixture Filter for Coexisting Point and Extended Targets

This paper proposes a Poisson multi-Bernoulli mixture (PMBM) filter for coexisting point and extended targets, i.e., for scenarios where there may be simultaneous point and extended targets. The PMBM filter provides a recursion to compute the multi-target filtering posterior based on probabilistic information on data associations, and single-target predictions and updates. In this paper, we first derive the PMBM filter update for a generalised measurement model, which can include measurements originated from point and extended targets. Second, we propose a single-target space that accommodates both point and extended targets and derive the filtering recursion that propagates Gaussian densities for point targets and gamma Gaussian inverse Wishart densities for extended targets. As a computationally efficient approximation of the PMBM filter, we also develop a Poisson multi-Bernoulli (PMB) filter for coexisting point and extended targets. The resulting filters are analysed via numerical simulations.

Interannual summer mixing processes in the Ilulissat Icefjord, Greenland

In the stratified water column inside the Ilulissat ice fjord, oceanic mixing processes can promote an upward transport of heat and salt from the subsurface to the surface mixed layer. Our objective was to map the temporal variation of vertical mixing inside the fjord by estimating the diapycnal mixing rates derived from oceanographic data collected during summer research cruises between 2009 and 2017. We applied the Thorpe scale method based on local density inversions. We found enhanced mixing in the deep water at 400 m sill depth inside the fjord, with diapycnal diffusivity reaching a maximum value of 1× 10 –3.5 m 2 s −1 . The strongest mixing rates in 2013, and the weakest during 2016, were mainly due to the Glacier's melting conditions and melange. The highest values of diapycnal diffusivity values occurred during years when low melange concentrations inside the ice fjord increased ventilation, which favored the intrusion of Polar and Irminger waters that perturbed the water structure. These years were also associated with a decrease in diffusive convection processes. Our results give insight into how the intrusion of waters from Disko Bay to the Ilulissat ice fjord may affect the stability of the Jakobshavn Isbræ Glacier. • · Water mixing interaction in the Ilulissat Ice Fjord, increase diapycnal diffusivities by more than one order of magnitude. • We used the Thorpe method to estimate mixing rates in the IIF system. • A warm water intrusion in 2013 lifted the isopycnals reducing the ice melange leading to the retreat of the glacier front.

Reynolds number scaling of burning rates in spherical turbulent premixed flames

Abstract

Bayesian Inference of Mantle Viscosity From Whole‐Mantle Density Models

AbstractThe long‐wavelength geoid is sensitive to Earth's mantle density structure as well as radial variations in mantle viscosity. We present a suite of inversions for the radial viscosity profile using whole‐mantle models that jointly constrain the variations in density, shear‐ and compressional‐wavespeeds using full‐spectrum tomography. We use a Bayesian approach to identify a collection of viscosity profiles compatible with the geoid, while enabling uncertainties to be quantified. Depending on tomographic model parameterization and data weighting, it is possible to obtain models with either positive‐ or negative‐buoyancy in the large low shear velocity provinces. We demonstrate that whole‐mantle density models in which density and VS variations are correlated imply an increase in viscosity below the transition zone, often near 1,000 km. Many solutions also contain a low‐viscosity channel below 650 km. Alternatively, models in which density is less‐correlated with VS—which better fit normal mode data—require a reduced viscosity region in the lower mantle. This feature appears in solutions because it reduces the sensitivity of the geoid to buoyancy variations in the lowermost mantle. The variability among the viscosity profiles obtained using different density models is indicative of the strong nonlinearities in modeling the geoid and the limited resolving power of the geoid kernels. We demonstrate that linearized analyses of model resolution do not adequately capture the posterior uncertainty on viscosity. Joint and iterative inversions of viscosity, wavespeeds, and density using seismic and geodynamic observations are required to reduce bias from prior assumptions on viscosity variation and scalings between material properties.

Impact of braconid wasps on larval performance of longhorned borer Coptocercus rubripes Boisduval (Coleoptera: Cerambycidae) in Eucalyptus forest of southwestern Australia

AbstractIn southwestern Australia, outbreaks of cerambycids have been associated with infestation of drying and stressed trees. Felled timber provides an abundant habitat for a variety of subcortical beetles where their development can be modified by attack from natural enemies, including parasitoids. There are a variety of parasitoid wasps of cerambycids native to Australia, yet their effectiveness in controlling the larval performance of borers has been little studied. Approximately 700 Eucalyptus trees felled to realign a forest road provided an opportunity to determine how a mass of drying logs influences borer infestation rates and whether parasitoid wasps were effective in controlling borer survival. The native borer Coptocercus rubripes (Coleoptera: Cerambycidae) caused an extensive infestation of fallen trees at the clearfell site. These infestations were subsequently limited by the direct effect of parasitism from the native braconid wasps Callibracon limbatus and Syngaster lepidus emerging from a single hole in a white cocoon. The effects of parasitism showed inverse density dependency where high borer larval densities increased the chances of borer larval survival. The absence of parasitism in caged logs promoted high borer larval densities and greatly improved adult borer survival, and while this increased the demand for sapwood resources, it promoted early adult borer emergence. Control by native braconid wasps of high infestations of Co. rubripes borers attacking drying and stressed trees limits adult borer emergence and has the potential to partially regulate borer populations.

Weak Integrability Breaking: Chaos with Integrability Signature in Coherent Diffusion.

We study how perturbations affect dynamics of integrable many-body quantum systems, causing transition from integrability to chaos. Looking at spin transport in the Heisenberg chain with impurities we find that in the thermodynamic limit transport gets diffusive already at an infinitesimal perturbation. Small extensive perturbations therefore cause an immediate transition from integrability to chaos. Nevertheless, there is a remnant of integrability encoded in the dependence of the diffusion constant on the impurity density, namely, at small densities it is proportional to the square root of the inverse density, instead of to the inverse density as would follow from Matthiessen's rule. We show that Matthiessen's rule has to be modified in nonballistic systems. Results also highlight a nontrivial role of interacting scattering on a single impurity, and that there is a regime where adding more impurities can actually increase transport.