Calculation Of Curvature Research Articles

Abstract 4121378: Non-invasive, Automated Approach to Estimate Septal Curvature as a Surrogate of Mean Pulmonary Arterial Pressure for Pediatric Pulmonary Hypertension Patients

Background: Pediatric pulmonary hypertension (PH) is diagnosed and monitored using echocardiography and right heart catheterization. Recently, non-invasive measurements using cardiac MRI have also been investigated for patient monitoring. A promising measurement is MRI-based septal curvature, which has excellent correlation with mean pulmonary arterial pressure (mPAP). However, this approach requires significant manual interaction and is subject to observer-dependent measurement variability. Hypothesis: Automated septal curvature computation can predict mPAP and is less observer-dependent than the manual approach. Aims: To develop an automated approach to measure septal curvature and compare its performance with a manual approach in pediatric PH patients. Methods: Pediatric PH patients (mPAP≥25mmHg) who had both a clinical cardiac MR exam and right heart catheterization were retrospectively enrolled. From the mid-slice of short-axis stack images for the ventricles, time-resolved contours for both ventricles were automatically generated with cvi42, and imported to a custom MATLAB tool to automatically compute normalized septal curvature (Fig.1). The minimum normalized curvature (a 7-point average around the minimum value in a cardiac cycle) was computed to investigate its association with mPAP and a composite outcome (death or referral for heart/lung transplant). The new and manual approaches were conducted by two observers to test interobserver agreement. Pearson correlation, univariable logistic regression, receiver-operating characteristic curve, area under the curve (AUC), and intraclass correlation coefficients (ICC) were conducted. P<0.05 was considered statistically significant. Results: Twenty-seven patients (14.3±5.4 years; mPAP, 44 [35.5–57] mmHg) were enrolled. Minimum normalized curvature was correlated with mPAP (r=0.78, p<0.001; Fig.2A). Logistic regression found significant association between outcomes and minimum curvature (AUC, 0.88; 95% CI, 0.74–1.00; p<0.001; Fig.3AC). The proposed approach found excellent interobserver agreement (ICC, 0.98; 95% CI, 0.96-0.99) and was similar or superior to the manual one in all performance metrics (manual: correlation with mPAP: r=0.67, p<0.001; AUC: 0.84, 95% CI, 0.69–0.99, p=0.004; ICC: 0.89, 95% CI, 0.81-0.94; Figs.2B,3BD). Conclusion: The proposed automated approach to compute septal curvature is less observer dependent than the manual approach and could be a robust tool to follow up pediatric PH patients.

Moduli dynamics in effective nested warped geometry in four dimensions and some cosmological implications

We analyze the effective four-dimensional dynamics of the extra-dimensional moduli fields in curved braneworlds having nested warping, with particular emphasis on the doubly warped model which is interesting in the light of current collider constraints on the mass of the Kaluza-Klein graviton. The presence of a non-zero brane cosmological constant (Ω) naturally induces an effective moduli potential in the four-dimensional action, which shows distinct features in dS (Ω > 0) and AdS (Ω < 0) branches. For the observationally interesting case of dS 4-branes, a metastable minimum in the potential arises along the first modulus, with no minima along the higher moduli. The underlying nested geometry also leads to interesting separable forms of the non-canonical kinetic terms in the Einstein frame, where the brane curvature directly impacts the kinetic properties of only the first modulus. The non-canonicity of the scenario has been illustrated via an explicit computation of the field space curvature. We subsequently explore the ability of curved multiply warped geometries to drive inflation with an in-built exit mechanism, by considering predominant slow roll along each modular direction on a case-by-case basis. We find slow roll on top of the metastable plateau along the first modular direction to be the most viable scenario, with the higher-dimensional moduli parametrically tuning the height of the potential without significant impact on the inflationary observables. On the other hand, while slow roll along the higher moduli can successfully inflate the background and eventually lead to an exit, consistency with observations seemingly requires unphysical hierarchies among the extra-dimensional radii, thus disfavouring such scenarios.

1D analytic and numerical analysis of thin film heat transfer gauges and infra-red cameras in non-planar applications

The impulse response method is widely used for heat transfer analysis in turbomachinery applications. Traditionally, the 1D method assumes a: linear time invariant, isotropic, semi-infinite block with planar surfaces and does not accurately model the true geometric behaviour. This paper evaluates the error introduced by the planar assumption and outlines the required modifications for accurate freeform surface analysis. Adapted cylindrical basis functions are defined for the impulse response method and used to evaluate the impact of the 1D planar assumption. The analytic solutions for both convex and concave surfaces are presented. A penta-diagonal algorithm, for a modified numerical Crank-Nicolson scheme, is also evaluated for fast stable implementation of curved geometry simulation. The scheme shows comparable performance to the impulse response, whilst removing the requirement for linear time invariance. The new methods are demonstrated in the case of aerothermal analysis for heat transfer in a turbine nozzle guide vane. A 3D ANSYS simulation is used as a benchmark and further highlights the importance of the curvature effects. The methods are extended using curvature mapping for infra-red camera data, enabling direct 3D thermal simulation or the fast calculation of freeform curvature. This paper defines the methodology to analyse heat transfer measurements on non-planar geometry.

Characterizing coal gas reservoirs: A multiparametric evaluation based on geological and geophysical methods

The gas content of coal seams is a key parameter to guide the development of coalbed methane (CBM). While most studies focused on geological features, geophysical methods provide a powerful tool for the analysis of the differential distribution of CBM. In this paper, we present a comprehensive model for the quantitative evaluation of gas content in coal seams based on the computation of multiple parameters including lithology coefficient, deformation coefficient, and ash content. Based on the results of industrial analysis and isothermal adsorption tests of 135 coal samples, logging data of 76 CBM wells, as well as 10 2D seismic lines, a geophysical evaluation method of lithology inversion, structural curvature calculation, and ash content identification was established. Our study reveals the differential distribution characteristics of gas content in coal seams under the coupling effect of the three parameters. The results from this method were applied in the southeastern margin area of the Ordos Basin where 5# coal seam with sandstone and mudstone is interbedded as the roof and floor, and the mudstone in the roof contributes more to the sealing ability of surrounding rock. For the 8# coal seam with stabilized limestone and thinly interbedded mudstones as the roof, the limestone contributes most to the sealing ability. The sealing ability of surrounding rock is poorer in the area with large sandstone content in the roof and floor of coal seams and large structural curvature. The lithological combination of the 5# coal seam is the most critical gas controlling factor, whereas deformation coefficient is found to be least significant. However, for the 8# coal seam with little change in the lithology of the roof, the effect of deformation coefficient on gas content increases, and the adsorption capacity is the most important factor influencing the differential distribution of CBM.

Local interface remapping based curvature computation on unstructured grids in volume of fluid methods using machine learning

Local interface remapping based curvature computation on unstructured grids in volume of fluid methods using machine learning

Measurement of body size parameters and body weight prediction in beef cattle based on image analysis

The body size parameter of cattle is an important index reflecting the growth and development and health condition of cattle. The traditional manual contact measurement is not only a large workload and difficult to measure, but also prone to problems such as affecting the normal life habits of cattle. In this paper, we address this problem by proposing a contactless body size measurement method for cattle based on machine vision. Firstly, the cattle is confined to a fixed space using a position-limiting device, and images of the body of the cattle are taken from three directions: top, left, and right, using multiple cameras. Secondly, the image is segmented using a fuzzy clustering algorithm based on neighborhood adaptive local spatial information improvement, and the image is processed to extract the contour images of the top view and side view. The key points of body measurements were extracted using interval division and curvature calculation for the side view images, and the key point information was extracted using skeleton extraction and pruning for the top view images, which realized the measurements of body height(BH), rump height(RH), body slanting length(BSL), and abdominal circumference(AC) parameters of the cattle. The correlation between body size and weight data obtained by contactless methods was investigated and the modeled using one-factor linear regression, one-factor nonlinear regression, multivariate stepwise regression, RBF network fitting, BP neural network fitting, support vector machine, and particle swarm optimization-based support vector machine methods, respectively. Information on body size parameters was collected from 137 cattles, and the results showed that the maximum errors between the measured and actual values of BH, RH, BSL and AC were 5.0%, 4.4%, 3.6%, and 5.5%, respectively. Correlation of BH, RH, BSL and AC with weight obtained by non-contact methods was &gt; 0.75. The BH parameter can be selected in the single-factor growth monitoring. The multi-body scale can reflect the growth status of cattle more comprehensively, in which RH, BSL and AC are important detection parameter; the multi-factor nonlinear model can reflect the growth characteristics of cattle more comprehensively. The contactless measurement method proposed in the paper can effectively improve the work efficiency and reduce the stress reaction of cattle, which is a long-term and effective monitoring method, and is of great significance in promoting accurate and welfare cattle rearing.

Morphological Reconstruction for Variable Wing Leading Edge Based on the Node Curvature Vectors.

Precise morphology acquisition for the variable wing leading edge is essential for its bio-inspired adaptive control. Therefore, this study proposes a morphological reconstruction method for the variable wing leading edge, utilizing the node curvature vectors-based curvature propagation method (NCV-CPM). By establishing a strain-arc curvature function, the method fundamentally mitigates the impact of surface curvature angle on curvature computation accuracy at sensing points. We introduce a technique that uses high-order curvature fitting functions to determine the curvature vectors of arc segment nodes. This method reduces cumulative errors in curvature computation linked to the linear interpolation-based curvature propagation method (LI-CPM) at unattached sensor positions. Integrating curvature-strain functions aids in wing leading-edge strain field reconstruction, supporting structural health monitoring. Additionally, a particle swarm algorithm optimizes the sensing point distribution, reducing network complexity. This study demonstrates significantly enhanced morphological reconstruction accuracy compared to those obtained with conventional LI-CPM.

Foundations of the wald space for phylogenetic trees

AbstractEvolutionary relationships between species are represented by phylogenetic trees, but these relationships are subject to uncertainty due to the random nature of evolution. A geometry for the space of phylogenetic trees is necessary in order to properly quantify this uncertainty during the statistical analysis of collections of possible evolutionary trees inferred from biological data. Recently, the wald space has been introduced: a length space for trees which is a certain subset of the manifold of symmetric positive definite matrices. In this work, the wald space is introduced formally and its topology and structure is studied in detail. In particular, we show that wald space has the topology of a disjoint union of open cubes, it is contractible, and by careful characterisation of cube boundaries, we demonstrate that wald space is a Whitney stratified space of type (A). Imposing the metric induced by the affine invariant metric on symmetric positive definite matrices, we prove that wald space is a geodesic Riemann stratified space. A new numerical method is proposed and investigated for construction of geodesics, computation of Fréchet means and calculation of curvature in wald space. This work is intended to serve as a mathematical foundation for further geometric and statistical research on this space.

Calculation of second-order bearing capacity of members subjected to axial load and biaxial bending

The second-order effects of biaxial bending members involve dual non-linear problems, namely material nonlinearity and geometric nonlinearity. These problems typically require iterative calculations and cannot be solved manually. To address this issue, this paper founded upon the strain-based resolution of stress and internal forces, deduces the formula for calculating the load-bearing capacity of the cross-section. The elastoplastic second-order deformation is then calculated at the member level, and the final result is presented in the form of a dimensionless nomogram for calculating the second-order biaxial bending members. In this paper, the limit range of section strain is determined based on the constitutive relationship of concrete and reinforcement. This range is divided into three limited strain areas, which enable the calculation of section bearing capacity and limit curvature, and subsequently the second-order bearing capacity of the member. The results are in good agreement with experimental data. The dimensionless nomogram in this paper considers the complete parabolic and rectangular of concrete stress-strain relationship and the ideal elastoplastic constitutive relationship of reinforcement and the second-order effect. It does not require iteration. It can quickly calculate the reinforcement or check the section bearing capacity by hand. It can be used to check the calculation results of engineering software and provides ideas for the design method of member subjected to axial load and biaxial bending based on seismic restoring force.

Two-Dimensional Os2Se3 Nanosheet: A Ferroelectric Metal with Room-Temperature Ferromagnetism.

Two-dimensional (2D) ferroelectric metals (FEMs) possess intriguing characteristics, such as unconventional superconductivity and the nonlinear anomalous Hall effect. However, their occurrence is exceedingly rare due to mutual repulsion between ferroelectricity and metallicity. In addition, further incorporating other features like ferromagnetism into FEMs to enhance their functionalities poses a significantly greater challenge. Here, via first-principles calculations, we demonstrate a case of an FEM that features a coexistence of room-temperature ferromagnetism, ferroelectricity, and metallicity in a thermodynamically stable 2D Os2Se3. It presents a vertical electric polarization of 3.00 pC/m that exceeds those of most FEMs and a moderate polarization switching barrier of 0.22 eV per formula unit. Moreover, 2D Os2Se3 exhibits robust ferromagnetism (Curie temperature TC ≈ 527 K) and a sizable magnetic anisotropy energy (-30.87 meV per formula unit). Furthermore, highly magnetization-dependent electrical conductivity is revealed, indicative of strong magnetoelectric coupling. Berry curvature calculation suggests that the FEM might exhibit nontrivial band topology.

Systematic Calculation of Yield and Failure Curvatures of Reinforced Concrete Cross-Sections

This paper examines and provides a robust solution to the problem of yield and failure curvatures of reinforced concrete (RC) cross-sections, taking into account cracking. At the same time, it calculates the corresponding necessary reinforcement or the moment of resistance in both yield and failure limit states. Computationally, the problem of determining the actual curvatures is reduced to the bending design problem of the cross-section in the yield and failure limit states. This study shows the researcher and the designer how to systematically calculate the strains for different concrete and steel grades and for standard or random cross-sections. This complex process is quite necessary to determine the respective curvatures. The main concept is presented with an emphasis on the “solution regions” as well as the critical cases of the “asymptotic regions”, both in yield and failure limit states. Our wide-ranging research on RC element design under biaxial bending with axial force for both yield and failure limit states has been completed and validated via sophisticated algorithms and is available for publication.

Piecewise circular interface construction using height functions

AbstractA piecewise circular interface construction (PCIC) method is described, where height functions based curvature estimates are directly utilised for accurate interface reconstruction under the framework of volume of fluid method. The present work is an attempt to develop a robust and accurate higher order interface reconstruction algorithm that is capable of accurate simulation of surface tension dominated flows. The proposed hybrid method (H‐PCIC) is thus able to take advantage of merits of both PCIC and HF methods, achieving at least second order convergence with respect to both interface reconstruction and curvature computation. This is in addition to the significantly superior quality of the reconstructed interface with respect to PLIC methods. This seamless blending of the HF and PCIC quantities is enabled by c0‐correction procedures applied to base PLIC and initial PCIC steps. More recent variants of the height function method with variable stencil size are used for calculation of radius of curvature. The capability of this proposed method towards simulation of flow problems within a well‐balanced two‐phase solver is established with help of multiple complex two‐phase flow problems. This validation exercise also demonstrates the capability of PCIC class of methods towards solutions of two‐phase flows with intricate physics.

Temperature deformation calculation of reinforced concrete parts in hot and dry climates

This paper presents a study on the temperature deformations of reinforced concrete elements in Uzbekistan’s arid and hot climate. The calculation of axis length and curvature for long-term alternating heating and cooling is essential for concrete and reinforced concrete elements in these conditions. The study’s findings can help engineers and construction professionals accurately calculate temperature changes in reinforced concrete elements in arid and hot climates, minimizing the risk of damage and reducing maintenance costs.

Identification and extraction of surface defects on composite workpieces based on Multilayer Perceptron‐Moth Flame algorithm two‐stage neural network

AbstractIn the aerospace sector, the identification and extraction of surface defects on composite parts is particularly important as they can have a very serious impact. This paper proposes a new extraction method for surface defects of composite materials, where 3D point clouds on the surface of composite workpieces are directly manipulated to finally extract a point cloud of defects containing both morphological and spatial location information. The specific operation explores the influencing factors in the formation and extraction process of composite surface defects and summarizes them into five categories: material type, fiber direction, curvature algorithm, neighborhood size, and filtering threshold. The Multilayer Perceptron‐Moth Flame algorithm two‐stage network model was constructed, which can reveal the relationship between these five types of influencing factors and the formation and extraction of surface defects in composites in the forward direction with an accuracy of 93.07%. It can also achieve optimal parameter recommendation in the reverse direction.Highlights Automatic identification and extraction of defects on the surface of composite workpieces is achieved based on 3D point cloud and curvature calculation. The forward direction reveals the relationship between the surface defect formation process and the material type and fabric direction. The reverse direction can automatically select the best curvature algorithm, neighborhood size, and filtering condition parameters. Build a Multilayer Perceptron‐Moth Flame Algorithm network structure based on multilayer perceptron and moth‐flame algorithm for model training of defect extraction, with an accuracy of 93.07%.

Free surface tension modelling using particle-grid hybrid method without considering gas particles

In particle method, the number of particles is an important factor affecting the computational efficiency. For the free-surface flow, gas particles are usually necessary for surface tension calculation, but they have little impact to the liquid flow with a large density. If the free surface tension can be modeled without considering gas particles, it is of great significance to improve the computational efficiency. The existing potential-based surface tension model and the stress-based surface tension model don't need gas particles, but they have the problems of instability or are difficult to implement. Therefore, in this study, another free surface tension calculation method by coupling particles and grids is proposed. In the method, background mesh is applied to the entire computational domain, where the boundary of grid is extended outward by 3.1 l0 on the basis of particle boundary for curvature calculation. The level-set function is adopted to mark different phases on background mesh, whose value is set according to the normal distance between the grid and the nearest free surface particle. After obtaining the curvature and the level-set function gradient on background mesh, these variables are interpolated to corresponding particles to calculate the surface tension. Through the comparative study of area-weighted and distance-weighted interpolation schemes, it is found that the accuracy of distance-weighted interpolation scheme is higher than that of area-weighted interpolation scheme. Finally, the performance of the particle-grid hybrid method is verified by simulating four benchmark cases, including droplet oscillations, droplet spreading, capillary jet breakup and droplet impinging onto plate.

Damage Identification in Cement-Based Structures: A Method Based on Modal Curvatures and Continuous Wavelet Transform.

Modal analysis is an effective tool in the context of Structural Health Monitoring (SHM) since the dynamic characteristics of cement-based structures reflect the structural health status of the material itself. The authors consider increasing level load tests on concrete beams and propose a methodology for damage identification relying on the computation of modal curvatures combined with continuous wavelet transform (CWT) to highlight damage-related changes. Unlike most literature studies, in the present work, no numerical models of the undamaged structure were exploited. Moreover, the authors defined synthetic damage indices depicting the status of a structure. The results show that the I mode shape is the most sensitive to damages; indeed, considering this mode, damages cause a decrease of natural vibration frequency (up to approximately -67%), an increase of loss factor (up to approximately fivefold), and changes in the mode shapes morphology (a cuspid appears). The proposed damage indices are promising, even if the level of damage is not clearly distinguishable, probably because tests were performed after the load removal. Further investigations are needed to scale the methodology to in-field applications.

TwoPhaseFlow: A Framework for Developing Two Phase Flow Solvers in OpenFOAM

We present a new OpenFOAM based open-source framework, TwoPhaseFlow, enabling fast implementation and testing of new phase change and surface tension force models for two-phase flows including interfacial heat and mass transfer. Capitalizing on the runtime-selection mechanism in OpenFOAM, the new models can easily be selected and benchmarked against analytical solutions and existing models. The framework currently includes the following three interface curvature calculation methods for surface tension: 1) the height function method, 2) the parabolic fit method and 3) the reconstructed distance function method. As for phase change, two models are available: 1) Interface heat resistance and 2) direct heat flux. These can be combined in three solvers: 1) InterFlow for isothermal, incompressible two-phase flow, 2) compressibleInterFlow for compressible, non-isothermal two-phase flow and 3) multiRegionPhaseChangeFlow for compressible, non-isothermal two-phase flow with conjugated heat transfer. By design, addition of new models and solvers is straightforward and users are encouraged to contribute their specific models, solvers, and validation cases to the library.

Physical modelling of climate-soil-infrastructure interactions of paved roadways constructed in expansive soil

Roadways founded on expansive soils are notorious for incurring damage in the months and years after construction. Soil swelling and shrinking manifest at the road surface as differential displacements of the pavement and eventually lead to linear cracks developing parallel with the direction of traffic flow. This climate-soil-infrastructure interaction occurs over daily, seasonal, and annual cycles that cause variations in moisture, temperature, relative humidity, and precipitation. Design recommendations often call for expansive soil to be compacted 1–2% wet of optimum to limit pavement damage regardless of the local climatic conditions or soil swell potential. Despite the prevalence of expansive soils found worldwide and the significant damage they cause to overlying infrastructure, very few studies appear in the literature that include field monitoring. To overcome this lack of physical data and examine the traditional design specification centrifuge modelling was undertaken to reproduce a stress-appropriate environment and control the moisture boundary conditions. These centrifuge experiments examine the effect of as-placed moisture content on the response of a two-lane paved road profile subjected to wetting–drying cycles. The centrifuge model results provide high temporal and spatial resolution displacement measurements using Digital Image Correlation. Cumulative subsurface strains are reflected at the road surface and cause detectable differential displacements of the model paved road. The relatively minor variation of initial moisture content in the three tests examined (varied from 29 to 34%) was found to have a significant impact on the hydraulic-mechanical response expressed in the isolated ground located beyond the influence of the road as well as the pavement-ground interface. The experimental results provide new insight into climate-soil-infrastructure interaction under a paved road, which would otherwise be unobservable using traditional discrete measurement techniques in the field. Interpretation of the high-density displacement measurements allowed for calculation of unique curvature / bending envelopes for the pavement under the different as-placed moisture conditions. The wet of optimum model displayed 5-times greater curvature / bending compared to the optimum and dry of optimum tests. Compacting wet of optimum may not be uniformly beneficial to limit pavement damage and construction specifications should consider local climate and swelling potential.

Planning and tracking control of full drive-by-wire electric vehicles in unstructured scenario

Full drive-by-wire electric vehicles (FDWEV) equipped with X-by-wire technology can enable independent driving, braking, and steering of each wheel, making them an ideal platform for developing autonomous driving technology. However, designing a robust control algorithm that comprehensively integrates vehicle path planning in a complex and unstructured scenario is a challenging task for FDWEV. To address this issue, this paper (1) proposes the artificial potential field (APF) method for path planning in the prescribed park with different static obstacles to generate the reference path information, where speed planning is incorporated considering kinematics and dynamic constraints; (2) designs curvature calculation (CC-based) and model predictive control (MPC-based) tracking methods with the lateral dynamics model to track the desired path under different driving conditions, in which a forward-looking behavior model of the driver with variable preview distance is designed based on the fuzzy control theory; (3) conducts CarSim-AMESim-Simulink co-simulation with the existence of obstacles. The simulation results show that the proposed two control approaches are practical for classical driving scenarios. Especially the MPC-based path-tracking controller enhances dynamic tracking performance and ensures good maneuverability under high-dynamic driving conditions.

Lorentz Force Distribution With Local Curvature and Near-Field Calculation of Racetrack Coil EMAT

Lorentz Force Distribution With Local Curvature and Near-Field Calculation of Racetrack Coil EMAT