Level Set Strategy Research Articles

Multilevel thresholding image segmentation algorithm based on Mumford–Shah model

Abstract Image segmentation is one of the important tasks of computer vision and computer image processing, and the purpose of image segmentation is to achieve the extraction and recognition of the target image region. The classical Mumford–Shah (MSh) image segmentation model is used to achieve the segmentation of images. With the goal to get the best segmentation effect on images by minimizing the MSh energy generalization function, a level set strategy is developed, and a model with global information infinite curve evolution is utilized. However, considering the low efficiency of this model for processing level set curves and the general quality of image segmentation. A multi-layer threshold search scheme is proposed to achieve rapid convergence of the target image level set curve. The experimental results showed that the multi-level thresholding image segmentation algorithm based on the MSh model can significantly improve the segmentation effect of images and reduce the segmentation time. The suggested MSK method outperforms the MPO algorithm, SSA algorithm, and EMO algorithm in the picture segmentation convergence time test, respectively, in terms of runtime efficiency by 356, 289, and 71%. Additionally, it performs superbly in both threshold searches and picture quality tests. The research topic has significant reference value for the study of contemporary computer vision imaging technologies.

Influence of the spatial laser energy absorption on the molten pool dynamics in high-power laser beam welding

The spatial laser energy absorption inside the keyhole is decisive for the dynamic molten pool behaviors and the resultant weld properties in high-power laser beam welding (LBW). In this paper, a numerical simulation of the LBW process, considering the 3D transient heat transfer, fluid flow, and keyhole dynamics, is implemented, in which the free surface is tracked by the volume-of-fluid algorithm. The underlying laser-material interactions, i.e., the multiple reflections and Fresnel absorption, are considered by an advanced ray-tracing method based on a localized level-set strategy and a temperature-dependent absorption coefficient. The laser energy absorption is analyzed from a time-averaged point of view for a better statistical representation. It is found for the first time that a significant drop in the time-averaged laser energy absorption occurs at the focus position of the laser beam and that the rest of the keyhole region has relatively homogeneous absorbed energy. This unique absorption pattern may lead to a certain keyhole instability and have a strong correlation with the detrimental bulging and narrowing phenomena in the molten pool. The influence of different focus positions of the laser beam on the keyhole dynamics and molten pool profile is also analyzed. The obtained numerical results are compared with experimental measurements to ensure the validity of the proposed model.

Finite-Element Method for the Simulation of Lipid Vesicle/Fluid Interactions in a Quasi–Newtonian Fluid Flow

We present a computational framework for modeling an inextensible single vesicle driven by the Helfrich force in an incompressible, non-Newtonian extracellular Carreau fluid. The vesicle membrane is captured with a level set strategy. The local inextensibility constraint is relaxed by introducing a penalty which allows computational savings and facilitates implementation. A high-order Galerkin finite element approximation allows accurate calculations of the membrane force with high-order derivatives. The time discretization is based on the double composition of the one-step backward Euler scheme, while the time step size is flexibly controlled using a time integration error estimation. Numerical examples are presented with particular attention paid to the validation and assessment of the model’s relevance in terms of physiological significance. Optimal convergence rates of the time discretization are obtained.

Automatic detection of optic disc using distance regularized level-set segmentation for glaucoma screening system

PurposeThe abnormalities of glaucoma have high impact on deciding and representing the causes that effects severity of blindness in human beings. The simulation experimental results would help the ophthalmologist in diagnosing of glaucoma abnormality accurately. The significant effect of glaucoma has a huge impact on the quality of human life, and its growth rate in world population tremendously increases. Glaucoma is considered as second largest cause for the blindness in the world; hence identification of it marks the importance of its detection at the earliest.Design/methodology/approachThe prime objective of the work proposed is to build up a human intervention free image preparing framework for glaucoma screening. The disc calculation is assessed on retinal image dataset called retinal Image for glaucoma Analysis. The proposed method briefs a novel optic disc division calculation depending on applying a level-set strategy on a confined optic disc image. In the instance of low quality image, a twofold level set is designed, in which the principal level set is viewed as restriction for the optic disc. To keep the veins from meddling with the level-set procedure, an inpainting strategy has been applied. Also a significant commitment is to include the varieties in notion adopted by the ophthalmologists in distinguishing the disc localization and diagnosing the glaucoma. Most of the past investigations are prepared and tested depending on just a single feature, which can be thought to be one-sided for the ophthalmologist.FindingsIn continuation, the correctness has been determined depending on the quantity of image that matched with the investigation pattern adopted by the ophthalmologist. The 175 retinal images were utilized to test the results of proposed work with the manual markings of ophthalmologists. The error-free calculation in marking the optic disc region and centroid was 98.95% in comparison with the existing result of 87.34%.Originality/valueIn continuation, the correctness has been determined depending on the quantity of image that matched with the investigation pattern adopted by the ophthalmologist. The 175 retinal images were utilized to test the results of proposed work with the manual markings of ophthalmologists. The error-free calculation in marking the optic disc region and centroid was 98.95% in comparison with the existing result of 87.34%.

Optimization of the Interacting Stiffened Skins and Ribs Made of Composite Materials

A decomposition strategy for the structural optimization of a fiber-reinforced aircraft wing box is proposed. The proposed method decomposes the wing-box optimization into two levels: a system-level and a subsystem-level optimization. The ribs are the subsystems of the problem. Each rib has a local set of design variables and constraints. The loads on the ribs are the crushing loads caused by the bending of the wing. At the system level, the wing-box skins are optimized while accounting for the effect of the skin design on the loads applied to the ribs. The sensitivity of the rib mass to the applied loads is evaluated using the Lagrange multipliers of the optimized rib design. To enhance the numerical efficiency of the two-level optimization, the changes of the loads on the ribs are subjected to a reduction by principal component analysis (PCA). In both the wing-level and rib-level optimization problems, the level-set strategy for the optimization of composite structures, previously introduced by the authors, is employed. This method permits an advantageous use of coarse and fine finite element models employing a standard commercial finite element code. The proposed method is applied to the design of a composite horizontal tail plane. The accuracy of and the computational time savings by the proposed PCA-based reduction scheme are quantified.

Fuzzy c-means clustering based active contour model driven by edge scaled region information

This research article proposes a novel edge scaled method with local and global region based statistical information for inhomogeneous image segmentation. We coordinate region force (local and global) term with geodesic edge term in level set formulation. The vital energy of the proposed model utilizes both global and local terms fused with compacted geodesic edge term in an additive fashion, which uses image gradient information to segment feeble boundaries inside images. The initialization of the level set is always vulnerable and its execution is liable to suitable initialization, which requires manual intercession. In this regard, the proposed method is extended and automated by integrating the proposed method with FCM (fuzzy c-means) clustering. Modified active contour method gets suitable initialization from FCM clustering, which eliminates the initial contour problem existed in the traditional region-based active contour methods. A development in this paper is to interface FCM with level set strategy by morphological tasks. Moreover, the uninterrupted segmentation scheme confirms the effectiveness of the proposed method in modern intelligent and automatic systems. The experimental analysis is performed on synthetic and real inhomogeneous images. The visual and quantitative results confirm the proficiency of the proposed technique and show that proposed method achieves better accuracy results compared to previous methods.

Level-set strategy for inverse DSA-lithography

We introduce a level-set strategy to find the geometry of confinement that will guide the self-assembly of block copolymers to a given target design in the context of lithography. The methodology is based on a shape optimization algorithm, where the level-set normal velocity is defined as the pressure field computed through a self-consistent field theory simulation. We present numerical simulations that demonstrate that this methodology is capable of finding guiding templates for a variety of target arrangements of cylinders and thus is an effective approach to the inverse directed self-assembly problem.

Mobile Application for Emergency Navigation During Disaster Using Wireless Sensor Network

This Wireless Sensor Network (WSN) is gathering sensor hubs. A huge number of sensor hubs associated with each frame sensor arrange. Sensor hubs ordinarily comprise of radio handset, microcontroller and it is fueled with battery. In this Mobile Environment, the clients are furnished with Personal Digital Assistants (PDA) or advanced cells that can converse with the Sensors effectively. At the point when crisis happens, the WSN gives essential data to clients, So that guided to move out of an unsafe zone through connection with sensors. Remote system sensor joined with a route calculation could encourage securely control individuals to a building exit while helping them evade perilous range. We propose a plain route calculation for crisis circumstance. Clog Adaptive and little extend crisis Navigation calculation with WSNs (CANS) use level set strategy to track the development of the exit and the limit of the perilous territory, so that individuals close-by the risky region accomplish a gentle blockage at the cost of a slight reroute, while individuals inaccessible from the threat evade superfluous alternate routes. Firstly, the route of people looks for a safe-basic way, other than parcel misfortune or vitality productivity which is the primary need as in bundle directing. Besides, human route expends a great deal additional time than customary parcel directing procedure, because of the constrained development speed of individuals. Also, which are basic for a quick clearing, as they primarily concentrate on finding the briefest/most secure way for every individual, while other problematic (yet sheltered) ways are left unused all through a large portion of the departure procedure.

A Developed Numerical Method for Turbulent Unsteady Fluid Flow in Two-Phase Systems with Moving Interface

This paper presents the development of an accurate and robust numerical modeling of instability of an interface separating two-phase system, such as liquid–gas and/or solid–gas systems. The instability of the interface can be refereed to the buoyancy and capillary effects in liquid–gas system. The governing unsteady Navier–Stokes along with the stress balance and kinematic conditions at the interface are solved separately in each fluid using the finite-volume approach for the liquid–gas system and the Hamilton–Jacobi equation for the solid–gas phase. The developed numerical model represents the surface and the body forces as boundary value conditions on the interface. The adapted approaches enable accurate modeling of fluid flows driven by either body or surface forces. The moving interface is tracked and captured using the level set function that initially defined for both fluids in the computational domain. To asses the developed numerical model and its versatility, a selection of different unsteady test cases including oscillation of a capillary wave, sloshing in a rectangular tank, the broken-dam problem involving different density fluids, simulation of air/water flow, and finally the moving interface between the solid and gas phases of solid rocket propellant combustion were examined. The latter case model allowed for the complete coupling between the gas-phase physics, the condensed-phase physics, and the unsteady nonuniform regression of either liquid or the propellant solid surfaces. The propagation of the unsteady nonplanar regression surface is described, using the Essentially-Non-Oscillatory (ENO) scheme with the aid of the level set strategy. The computational results demonstrate a remarkable capability of the developed numerical model to predict the dynamical characteristics of the liquid–gas and solid–gas flows, which is of great importance in many civilian and military industrial and engineering applications.

SLEIPNNIR: A multiscale, particle level set method for Newtonian and non-Newtonian interface flows

We present in this paper a multiscale, micro–macro, particle level set method for Newtonian and non-Newtonian interface flows. The technique, termed SLEIPNNIR (‘Semi-Lagrangian Ensemble Implementation of Particle level set for Newtonian and non-Newtonian Interfacial Rheology’), uses the finite element method in a semi-Lagrangian framework for the discretization of the governing equations, capturing the free surface by means of a particle level set strategy where all involved magnitudes are computed sharply. Surface tension effects are considered via the Laplace–Beltrami operator using a fully-explicit or semi-implicit technique, with a second-order accurate reinitialization procedure to ensure the signed distance property. Non-Newtonian fluids are tackled by means of a stochastic, variance-reduced, kinetic modeling approach in which the polymer stress tensor is retrieved making use of Compactly-Supported Radial Basis Functions for randomly scattered data interpolation.We carry out numerical tests to highlight the versatility, robustness and accuracy of the proposed scheme through a series of bubble dynamics experiments in a 2D setup, for large density and viscosity ratios, and featuring strong, purely elastic effects relevant to Engineering applications.

Numerical modeling for the combustion of simulated solid rocket motor propellant

The numerical procedure for the burning of Ammonium Perchlorate (AP) with a Fuel-Binder (Hydroxyl Terminated Polybutadience HTPB) heterogeneous propellant is presented. This model accounts for the two-step reaction mechanism for the primary diffusion flame at the interface between Binder (B) and the oxidizer AP and the AP premixed flame. The complete coupling between the gas-phase, the condensed-phase, and the unsteady non-uniform regression of the propellant surface is considered. The parameters used in this model are chosen to fit experimental data for the burning of the composite AP/Binder. The propagation of the unsteady non-planer regression surface is described, using the Essentially-Non-Oscillatory (ENO) scheme with the aid of the level set strategy. The Alternating-Direction-Implicit (ADI) solver is employed to solve the full Navier–Stokes equations in the gas phase for the variable density model. The results show the effect of various parameters on the surface propagation speed, flame structure, and the burning surface geometry. A comparison between the computational and experimental results is presented.

Fully Eulerian finite element approximation of a fluid‐structure interaction problem in cardiac cells

SUMMARYWe propose in this paper an Eulerian finite element approximation of a coupled chemical fluid‐structure interaction problem arising in the study of mesoscopic cardiac biomechanics. We simulate the active response of a myocardial cell (here considered as an anisotropic, hyperelastic, and incompressible material), the propagation of calcium concentrations inside it, and the presence of a surrounding Newtonian fluid. An active strain approach is employed to account for the mechanical activation, and the deformation of the cell membrane is captured using a level set strategy. We address in detail the main features of the proposed method, and we report several numerical experiments aimed at model validation. Copyright © 2013 John Wiley & Sons, Ltd.

Implicit level set schemes for modeling hydraulic fractures using the XFEM

We describe two novel XFEM schemes for modeling fluid driven fractures both of which exploit an implicit level set algorithm (ILSA) for locating the singular free boundary that occurs when the fluid and fracture fronts coalesce. Both schemes use the mixed P&W XFEM formulation developed in Gordeliy and Peirce (2013) [1] to incorporate the singular asymptotic solution in the fracture tips. The proposed level set strategy also exploits the asymptotic solution to provide a robust procedure to locate the free boundary, which is not restricted to symmetric growth of the fracture geometry or to a particular mode of propagation. The versatility of the ILSA-XFEM scheme is demonstrated by sampling different asymptotic behaviors along the so-called MK edge of parameter space (Detournay, 2004) [2] by making use of a universal asymptote (Garagash, 1998 [3]; Garagash and Detournay, 2000 [4]). The two ILSA-XFEM schemes differ in the enrichment strategies that they use to represent the fracture tips: a scheme with full tip enrichment and a simpler, more efficient, scheme in which the tip asymptotic behavior is only imposed in a weak sense. Numerical experiments indicate that the XFEM-t scheme, with full tip enrichment, achieves an O(h2) asymptotic convergence rate, while the XFEM-s scheme, with only signum enrichment to represent the crack geometry, achieves an O(h) asymptotic convergence rate.

Spectrally resolved three-dimensional bioluminescence tomography with a level-set strategy

A reconstruction method is presented for spectrally resolved three-dimensional bioluminescence tomography (BLT) in heterogeneous media using a level-set strategy. In order to reconstruct internal bioluminescent sources, a level-set strategy is utilized to quantitatively localize the distribution of bioluminescent sources. The results in numerical phantom experiments clearly show that the proposed method can tolerate different initial values and noise levels and, furthermore, can work credibly even when the number of phases (levels) is not known a priori. In addition, a mouse atlas reconstruction is employed to demonstrate the effectiveness of the proposed method in turbid mouse geometry. Finally, the physical experiment further evaluates the method's potential in practical applications.

Shape based reconstruction of experimental data in 3D electrical capacitance tomography

Electrical capacitance tomography (ECT) is a non-invasive and non-destructive imaging technique that uses electrical capacitance measurement at the periphery of an object. The image reconstruction problem in ECT is an ill-posed inverse problem. This paper presents a level set based shape reconstruction method applied to 3D ECT using experimental data. The finite element models have been implemented based on a 32 electrode ECT system to formulate the forward problem. Development of the level set technique enables detection of smaller inclusions and improves the accuracy of boundary shapes of inclusions. The paper uses a shape based method rather than traditional image based methods. The shape-based approach offers several advantages compared with more traditional voxel-based approaches. The incorporation of an intrinsic regularization in the form of a-priori assumptions, regarding the general anatomical structures present in the medium, reduces the dimensionality of the inverse problem and thereby stabilizes the reconstruction. The level set strategy (which is an implicit representation of the shapes) can handle the topological during this reconstruction process. Additionally in this paper a new two-stage level set method has been developed, which shows significant improvement compared with the traditional level set reconstruction algorithm.

Detecting and imaging dielectric objects from real data: A shape-based approach

In this paper we investigate the performance of a shape-reconstruction technique as tested on the ‘Marseille data’. This approach, which is based on a level set technique, offers several advantages compared to other approaches, as for example well-defined boundaries and the incorporation of an intrinsic regularization in the form of a priori assumptions regarding the general structures in the medium. The level set strategy (which is an implicit representation of the shapes) frees us from topological restrictions during this reconstruction process. Our algorithm is aiming at, not only detecting the objects, but simultaneously determining their approximate locations, sizes and dielectric properties. The numerical experiments show the utility of this method.

Microwave Imaging for Early Breast Cancer Detection Using a Shape-based Strategy

In this paper, we propose and analyze a novel shape reconstruction technique for the early detection of breast cancer from microwave data, which is based on a level-set technique. The shape-based approach offers several advantages compared to more traditional pixel-based approaches when targeting the reconstruction of key characteristics of a hidden tumor such as its correct size, shape, and static permittivity value. In addition to these key characteristics of hidden tumors, we aim at estimating the correct interfaces between fatty and fibroglandular tissue in the breast and their internal permittivity profiles. The level set strategy (which is an implicit representation of the shapes) frees us from topological restrictions when reconstructing an a priori arbitrary number of tumors and the often quite complicated interfaces between fatty and fibroglandular regions. The presented strategy is able to detect and, in most cases, characterize tumors whose sizes (diameters) are much smaller than the wavelengths of the electromagnetic waves that are used for illuminating the breast. We present numerical results for a 2-D model with two distinct tissue types (fatty and fibroglandular) in the interior of the breast (in addition to a possible tumor and the surrounding skin). Our results demonstrate the performance and potential of our scheme in various simulated but realistic situations.

A level set evolution strategy in microwave imaging for early breast cancer detection

In this paper we propose and analyse a novel shape-reconstruction technique for the early detection of breast cancer from microwave data, which is based on a level-set technique. The shape-based approach offers several advantages compared to more traditional pixel-based approaches, as, for example, well-defined boundaries and the incorporation of an intrinsic regularization (in form of a-priori assumptions regarding the general anatomical structures present in the medium) that reduces the dimensionality of the inverse problem and thereby stabilizing the reconstruction. The level set strategy (which is an implicit representation of the shapes) frees us from topological restrictions during this reconstruction process. We present numerical results in 2D which demonstrate the performance of our scheme in various simulated realistic situations.

EFFECT OF AMMONIUM PERCHLORATE GRAIN SIZE ON COMBUSTION OF A SELECTED COMPOSITE SOLID PROPELLANT

The heterogeneous propellants consisting of Ammonium Perchlorate (AP) particles imbedded in a Hydroxyl Terminated Polybutadience (HTPB) are widely used in solid rocket industries. In this study, the effect of AP particles diameter and the random distribution with the HTPB on the burning of such propellant is presented. A mathematical model which describes the unsteady burning of a heterogeneous propellant by simultaneously solving the combustion fields in the gas phase and the thermal field in the solid phase with appropriate jump condition across the gas/solid interface is developed. The gas-phase kinetics is represented by a two-step reaction mechanism for the primary premixed flame and the primary diffusion flame between the decomposition products of the HTPB and the oxidizer AP. The propagation of the unsteady non-planer regression surface is described, using the Essentially-Non-Oscillatory (ENO) scheme with the aid of the level set strategy. The results show that the large AP particle diameter has a marked effect on the combustion surface deformation and on the burning rate as well. Therefore, modeling of the condensed phase process is mostly conducted on AP. Moreover, the effect of various parameters on the surface propagation speed, flame structure, and the burning surface geometry is obtained.

MODELING OF MICROSCALE SOLID PROPELLANT COMBUSTION

The numerical procedure for the burning of Ammonium Perchlorate (AP) with a Fuel-Binder (Hydroxyl Terminated Polybutadience HTPB) heterogeneous propellant is presented. This model accounts for the one-step reaction mechanism for the primary diffusion flame between the decomposition products of the Binder (B) and the oxidizer AP and allowed for the complete coupling between the gas-phase physics, the condensed-phase physics, and the unsteady non-uniform regression of the propellant surface. The parameters used in this model are fitted to experimental data for the combustion of AP/Binder. The propagation of the unsteady non-planer regression surface is described, using the Essentially-Non-Oscillatory (ENO) scheme with the aid of the level set strategy. The Alternating-Direction-Implicit (ADI) solver is employed to solve the full Navier-Stokes equations in the gas phase. The results show the effect of various parameters on the surface propagation speed, flame structure, and the burning surface geometry. A comparison between the computational and experimental results is presented.