Optimal Contour Research Articles

Numerical solution of generalized fractional Volterra integro-differential equations via approximation the Bromwich integral

In this paper, we consider the generalized fractional Volterra integro-differential equations with the regularized Prabhakar derivative and represent the solution of this type of equations in the form of Bromwich integral in the complex plane. Then we select the hyperbolic contour as an optimal contour to approximate the Bromwich integral. Further, an example to show absolute errors for various parameters by using our numerical scheme on hyperbolic contour is given.

Non-axisymmetric endwall contour optimization and performance assessment as affected by simulated swirl purge flow and backward hole injection

A shape optimization system was constructed using the kriging model, NSGA-II algorithm and CFD simulation, and the endwall contour was optimized targeting on balancing the endwall cooling and blade phantom cooling performances. Off-design conditions of simulated swirl purge flow and backward hole injection were introduced to evaluate the aero-thermal performances of the optimal non-axisymmetric endwall. The results show that two optimal contours are able to increase the endwall adiabatic effectiveness separately by 3.518% and 2.177%, but the flat endwall achieves the best phantom cooling performance. Under both design and off-design condition, the slot coolant coverage on pressure side endwall is enlarge by contours. The swirled slot leakage is able to weaken the tendency for the hole coolant to cover the suction side hot ring on both contoured and flat endwall. With the increase of SR, the averaged phantom cooling effectiveness is decreased when slot MFR = 1.0% but increased when MFR = 1.5%. When MFR = 1.0%, the averaged endwall Nu between 0.4 < z/Cax < 0.8 is decreased by 15% in optimal_2. When MFR = 1.5%, the averaged Nu for the upstream part endwall is increased by approximately 20% when SR = 0.6 compared with SR = 1.0. The net heat flux reduction of the pressure side endwall is increased by contouring, but the swirled purge flow dramatically decreases this protection effect. This research provides insights into the designing of non-axisymmetric endwall in off-design film cooling condition.

Infrared and visible image fusion based on optimal segmenting and contour extraction

Image fusion is the combining process of complementary information of multiple same scene images into an output image. The resultant output image that is named fused image, produces more precise description of the scene than any of the individual input images. In this paper, we propose a novel simple and fast strategy for infrared (IR) and visible images based on local important areas of IR image. The fusion method is completed in three step approach. Firstly, only the segmented regions in the infrared image is extracted. Next, the image fusion is applied on segmented area and finally, contour lines are also used to improve the quality of the results of the second step of fusion method. Using a publicly available database, the proposed method is evaluated and compared to the other fusion methods. The experimental results show the effectiveness of the proposed method compared to the state of the art methods.

Selection of the optimal contour of the open pit in mining the lead and zinc ore deposit with the increased mercury content

Mining processes are complex and complicated, with many different economic, technical, environmental and other parameters that must be planned before the project gets its practical value. Many of these parameters are evaluated independently of others, due to the expediency and difficulties in predictting values for variables under consideration. Costs, prices, reserves, mining and processing of ore, as well as many social aspects, such as issuing permits for works, are absolutely crucial for the project evaluation. Each ore body is different, but the main steps in the open pit planning, when the main goal is to maximize NPV, follow the same principle. These steps are presented as the linear for simplicity. The actual planning process is an iterative process, in which some steps or a combination of steps are repeated many times with the sensitivity analysis.

Periodontal plastic surgery for the management of an ankylosed permanent maxillary lateral incisor: A clinical report with 5-year follow-up

Anterior maxillary tooth ankylosis disturbs the development of the alveolar bone process, leading to discrepancies between the cervical gingival margin and incisal edge position of the affected tooth, and therefore, the esthetics is compromised. Proposed treatments in adults and growing patients have been used successfully, but they have disadvantages and are contraindicated in some circumstances. This article proposes an alternative treatment for an ankylosed permanent maxillary anterior tooth with a slow replacement resorption rate in an adult patient, for whom a combination of a periodontal plastic surgery procedure and a fixed dental prosthesis was used to correct the esthetics. This treatment has less risk of complications, preserves the ankylosed tooth as long as possible, creates an optimal gingival contour, and maintains the alveolar bone for further treatment should the tooth be lost.

Internal Shocks in Supersonic Flows past the Contours of Optimal Bodies and Nozzles

The problems of designing the contours of two-dimensional and axisymmetric bodies of minimum wave drag and maximum-thrust nozzles, such that flow past them can contain internal shocks, are considered within the ideal (inviscid and non-heat-conducting) gas model. These shocks may occur in flows past internal breaks in the optimal contours or on intersection of characteristics of the same family proceeding from these breaks. The submerged shocks occurring in the latter case are named internal, if their initial points lie within the domain of determinacy of the flowed-over optimal contour region. Further downstream the domain of determinacy is bounded by the characteristic coming to the end point of this contour. The internal submerged shocks can appear, when the optimal contour includes an interval of an isobaric streamline. The appearance of internal breaks in the optimal contours is possible due to the reflection of the pressure waves induced by them from the bow shock (for body noses) or, as might be expected, from tangential discontinuities (for afterbodies). In the case of supersonic freestreams having a tangential discontinuity the search for optimal two-dimensional afterbodies with an internal concave break flowed-over with an oblique shock is performed using the direct method with the representation of the required contours by the Bernstein—Bezier curves, a genetic algorithm, and a rapid and accurate marching scheme for calculating steady supersonic flows. While the optimal two-dimensional afterbodies with a convex internal break designed earlier using the general method of Lagrange multipliers could be reliably reproduced using the above-mentioned method, the expected optimal configurations with a concave break and an internal shock were not found. Instead, optimal contours with centered compression and expansion waves with the common focus on a tangential discontinuity and an “external” oblique shock proceeding from it were discovered. Then the new “discontinuous shock-free” solutions were constructed in the exact formulation, within the framework of the method of indefinite control contours and the method of characteristics. The solutions are generalized to include the contours of the afterbodies of revolution and supersonic parts of nozzles. In the case of a uniform freestream the flow past optimal afterbodies never includes internal shocks.

Grabber: A tool to improve convergence in interactive image segmentation

Abstract Interactive image segmentation has considerably evolved from techniques that do not learn the parameters of the model to methods that pre-train a model and adapt it from user inputs during the process. However, user control over segmentation still requires significant improvements to avoid that corrections in one part of the object cause errors in other parts. We address this problem by presenting Grabber — a tool to improve convergence (user control) in interactive image segmentation. Grabber is thought to complete segmentation of some other initial method. From a given segmentation mask, Grabber quickly estimates anchor points in one orientation along the boundary of the mask and delineates an optimum contour constrained to pass through those points. The user can control the process by adding, removing, and moving anchor points. Grabber can also explore object properties from the initial coarse segmentation to improve boundary delineation. We integrate Grabber with two recent methods, a region-based approach and a pixel classification method based on deep neural networks. Extensive experiments with robot users on two datasets show in both cases that Grabber can significantly improve convergence, with faster delineation, higher effectiveness, and less user effort. The code of Grabber is available at https://github.com/LIDS-UNICAMP/grabber .

Editorial of the special issue DLHI: Deep learning in medical imaging and healthinformatics

Interactive image segmentation has considerably evolved from techniques that do not learn the parameters of the model to methods that pre-train a model and adapt it from user inputs during the process. However, user control over segmentation still requires significant improvements to avoid that corrections in one part of the object cause errors in other parts. We address this problem by presenting Grabber — a tool to improve convergence (user control) in interactive image segmentation. Grabber is thought to complete segmentation of some other initial method. From a given segmentation mask, Grabber quickly estimates anchor points in one orientation along the boundary of the mask and delineates an optimum contour constrained to pass through those points. The user can control the process by adding, removing, and moving anchor points. Grabber can also explore object properties from the initial coarse segmentation to improve boundary delineation. We integrate Grabber with two recent methods, a region-based approach and a pixel classification method based on deep neural networks. Extensive experiments with robot users on two datasets show in both cases that Grabber can significantly improve convergence, with faster delineation, higher effectiveness, and less user effort. The code of Grabber is available at https://github.com/LIDS-UNICAMP/grabber.

Genetic algorithm-based initial contour optimization for skin lesion border detection

Automated segmentation has an essential role in detecting several diseases, such as skin lesions. In segmentation, the active contour (AC) is an efficient method based on energy forces and constraints in an image to separate the region of interest (ROI) by defining a curvature or contour. It outlines an initial contour to fit the ROI, which changed iteratively by minimizing the energy function. If the contour is improperly initialized, the AC may trap in local minima. In this work, the initial contour of the AC without edge ‘Chan-Vese’ model is optimized using the genetic algorithm (GA) to find the optimal initial circular area percentage of the skin lesion image from the whole image area. This optimal optimized value drives the AC and enhances the performance of the traditional AC while detecting the skin lesion boundaries. Various evaluation metrics were measured to compare the performance of the proposed optimized IAC (initial active contour), graph-cut, and the k-means, in dermoscopic image segmentation. The results show the dominance of the proposed method indicating that the optimal initial circular contour of 30.86% from the original image area. The results proved 96.2% detection accuracy best results achieved using this optimal value.

On the numerical approximation of Volterra integro-differential equation using Laplace transform

In this work we constructed a numerical scheme to approximate the Volterra integro- differential equations of convolution type using Laplace transform. The solution of the problem is recovered using inverse Laplace transform as contour integral in the complex plane. The integral is then approximated along a suitable contour using the trapezoidal rule with equal step size. The solution accuracy depends on optimal contour of integrations to compute accurately the inverse Laplace transform. For better accuracy two types of contour parabolic and hyperbolic are used which are available in the literature. The performance of the numerical scheme is tested for different examples. The actual error well agree with the corresponding error estimates of the proposed numerical scheme for both parabolic as well as hyperbolic contours.

An algorithm for line matching in an image by mapping into an n-dimensional vector space

This paper proposes a minimal length difference algorithm for construction of a line in an image by solving the problem of optimal contour approximation. In this algorithm, a method for finding interest points is proposed, and the object matching (classification) is done by mapping interest points onto a vector space. In cases where the lines in the representation of the images are not smooth, the algorithm converges rapidly. The results of the experiments showed that for convergence of the contour simplification, there were 5-6 iterations for $n = 13$. To check how close the curve approximation calculated by the algorithm above, the researchers have calculated the length of the curve simplification manually. This length was then compared to the length of the original curve. The results showed that the length of the simplified curve grew rapidly to 92 % - 95 % of the original curve length. The further increase in the number of points does not affect this indicator. According to the obtained results, the relative difference and the relative difference distance are good metrics to match objects.

К ВОПРОСУ ТЕРМОДИНАМИЧЕСКОГО ПРОЕКТИРОВАНИЯ КАМЕРЫ ЖРД

Analysis of the thermodynamic and thermophysical properties of combustion products (CP) in the liquid rocket engine (LRE) chamber shows that their dissociation degree depends on temperature T, gas expansion degree ε, etc. Practically, CP’s are always chemically active working fluid, therefore the number of moles N of the products varies along the length of the LRE chamber in the entire reaction mixture. The local values of the parameters T and N depend on the specific physical conditions. Therefore, the distribution of local numbers of moles of the components of the gas mixture and its heat capacities can be represented as dependencies N~f(T) and c~g(T). For this purpose based on the numerical values of the moles and the heat capacities of the gas mixture components in the main sections of the LRE chamber are formed as corresponding empirical functions through interpolation. Analysis of changes in moles and weight fractions of gaseous and condensed СP’s components shows that, depending on the specific conditions (α, Km, pc, ε), the number of moles of one group of individual substances increases, while these parameters of the other group decrease. These changes are alternating in nature and lead to the formation of new centers -sources of chemical and thermal energy along the length of the LRE nozzle. Thus, for different conditions (α, Km, pc, ε), the design of the LRE chamber should be carried out taking into account the nature of the change in N, cp, cv, and γ. Therefore, from energy conversion, the number of moles of the i-th CP component can be represented as a function Ni = f(Ti) or Ni = f(x,y). Numerical studies show that, based on the Ni values in the main sections of the LRE chamber with a given length, it is possible to form linear or nonlinear empirical functions in the form Ni= f(x) by interpolation. Depending on the specific tasks, one of the interpolation functions can be taken into account in the formulas for calculating the specific heats of CP. In this case, to form the refined geometry of the LRE chamber, the thermo-gas-dynamic calculation is repeated taking into account new indicated dependencies. Consequently, the system of equations for the thermodynamic calculation of an LRE is solved taking into account new functions. This approach allows forming the optimal contour of the LRE chamber at the preliminary stage of engine design and improving the results of gas-dynamic calculation and profiling of the nozzle using a modified method of characteristics. In the framework of the presented studies, to obtain an optimal geometry for the LRE nozzle, are compared values of the velocities, which obtained using the solutions of the direct and inverse problems. Thus, the correct consideration of changes in the basic parameters along the nozzle length allows us to organize the correct operation of the LRE chamber by changing the thermal properties of CP along the nozzle length in all flight conditions of the flight vehicle. This circumstance requires some improvement of the principles and schemes of regulation systems of the LRE operation, which leads to the conduct of extensive researches in this direction.

Functional Recording of Maxillo-mandibular Relationship Using Neutral Zone Technique- a Case Report

One of the most challenging cases dentists face is the rehabilitation of atrophic mandibular residual alveolar ridges. Such ridges present with a multitude of problems such as decrease in the denture foundation, retention and stability. Instability of denture bases can also give rise to an error in the maxillo-mandibular registrations. The neutral zone concept aims at the construction of complete dentures in the potential denture space, which ensures optimal denture contours and physiological arrangement of denture teeth as determined by the patient’s oral musculature, to enhance the stability and function of the prosthesis. This article presents a classical technique of recording the patient’s neutral zone with an improvised clinical step to record the patient’s maxillo-mandibular relation functionally. This technique can be practised routinely in cases of atrophied mandibular residual ridges to provide the patients with optimal complete denture therapy. Key Words: Neutral zone, resorbed mandibular ridges, maxillo-mandibular records, denture stability

A Revision Mandibuloplasty: Causes, Indications, Surgical Methods and Treatment Outcomes.

This paper aims to propose a classification system to categorize patients undergoing revision mandibuloplasty according to their dissatisfaction types. This paper also introduces various appropriate revision techniques and evaluates their outcomes. Through this classification system and suggested surgical techniques, surgeons can settle the disappointments experienced by patients after their primary mandibuloplasty, by realizing more natural-looking results. The study subjects consisted of 184 patients who underwent a revision mandibuloplasty from October 2010 to March 2016, conducted by a single surgeon at a single institution. The authors were able to classify the dissatisfaction into two primary types-(1) lack of an overall slender frontal facial contour and (2) unnatural and asymmetrical overall facial appearance due to over- or inaccurate resection of the bone. A self-evaluation of patient's subjective satisfaction based on the scale from 1 to 5, both after the primary operation and after revision surgery, was compared. Dissatisfaction type I accounted for 145 patients (78.8 percent). The number of patients classified into dissatisfaction type II was 39 (21.2 percent). Of the patients categorized into type I, those undergoing revision surgeries due to an under-corrected mandibular tubercle and parasymphysis showed the most remarkable improvement in self-satisfaction score after reoperation-from 2.3 to 4.0. To realize a natural-looking outcome in facial look through mandibular contouring, it is important not only to carefully consider the ratio and shape essential for an optimal slender facial contour, but also to minimize unnecessary resection of the bone. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Screening Inattentive Agents

Information plays a crucial role in mechanism design problems. A potential complication is that agents may be inattentive, and so information may endogenously and flexibly depend on what options are offered. I show that it is without loss to look at contour mechanisms, which comprise triplets of allocation probabilities, prices, and beliefs, and are uniquely determined by a single such point. The mechanism design problem then reduces to Bayesian persuasion along the optimal contour. The reduction to contour mechanisms has significant implications for both implementation of the optimal mechanism, and the revenues that can be achieved.

Regenerative surgical flap to maintain interdental papilla around dental implant

The modified surgical flap technique for placement of implant in the anterior maxilla has been described. The flap design has been used to achieve optimal soft-tissue contour for implant restoration. A modification in the surgical technique has been employed with the intention to preserve the interdental papilla, which is the key to the maintenance of hygiene and esthetics around anterior implants. This, in turn, prevents black triangles and improves soft-tissue contours. The modified surgical flap method maintains both functional and esthetic values.

Methodological approach to creation of the 3D model of an oval-shaped open pit mine

A 3D model of optimal contours phased development of oval-shaped open pit mines is proposed in the article. It is assumed that with enough accuracy the volumetric contour of the open pit mine is interpolated by an elongated elliptic hyperboloid. The calculation formulas for mineral resources are derived and optimal volumes of overburden are determined depending on the mining phase. In this case, the total number of mining phases is set in advance. The stripping ratio is used as a quality criterion of the optimization task. The problem of optimal control is solved using the Bellman function in dynamic programming. All the necessary calculation formulas are obtained in the final form by solving the optimization problem. Their simplicity and substantiation of each conclusion ensure that the results of this study can be successfully applied in practical calculations of the design and planning of mining operations in open pit mining.

Intelligent Process Planning for Additive Manufacturing

Abstract This paper introduces an intelligent approach for process planning of additive manufacturing (AM) in digital environment. A global adaptive slicing algorithm is developed and embedded in the introduced concept, which determines the layer thicknesses and widths based on the minimization of the deviations between the CAD model boundary and its stepped approximation. It is discussed that there are different metrics to measure the deviations such as cusp height, cusp volume and surface roughness criteria. A new criterion is developed to globally minimize the overall volumetric deviations of the final product from the desired geometric model. The proposed methodology uses the locally optimized layer thicknesses as the inputs to calculate the globally optimized layer thicknesses and the optimal contour for each layer. The global optimization problem is highly nonlinear that can be solved with a metaheuristic algorithm such as Simulated Annealing.

Geodesic distance framework for contour-based consistent stereo image segmentation

This study concentrates on consistent object contour extraction method for stereo image segmentation after the object regions in the left image have been obtained. By taking advantage of the epipolar geometry, our approach introduces an energy optimization framework that incorporates both the stereo correspondence term and patch-based object contour probability term. The contour map is generated by integrating the terms of stereo correspondence and patch-based object contour probability; then, the optimal contours are obtained using geodesic distance technology. The core of the proposed method is to build upon an energy optimization framework with two key contributions: first, it incorporates the patch-based object contour probability term that introduces two search strategies to efficiently find the joint nearest neighbor patch pairs for the stereo image pair. The patch-based object contour probability term provides consistent and reliable priors for the contour extraction. Second, previous methods encounter missing pixels in the extracted contour in the occluded regions. Our approach overcomes this limit by introducing the geodesic distance technology to search the optimal contours. Experimental evaluation on Middlebury dataset and Adobe open dataset indicates that the results of our stereo image segmentation are comparable with or of higher quality than state-of-the-art methods.

Quantitative characterization of carotid plaque components using MR apparent diffusion coefficients and longitudinal relaxation rates at 3T: A comparison with histology

There is limited evidence of parametric MR mapping to characterize carotid plaques associated with cerebral ischemic events. To explore the apparent diffusion coefficients (ADCs) and longitudinal relaxation rates (R1 ) of carotid plaques, including areas of hemorrhage, lipid-rich/necrotic core (LR/NC) without hemorrhage, and fibrous tissue (Fbr) STUDY TYPE: Prospective. Twelve patients who underwent carotid endarterectomy. R1 was measured using double angle Look-Locker acquisition on 3T systems. Single-shot spin-echo echo-planar imaging with fat suppression and outer-volume suppression (OVS-DWEPI) with b values of 10 and 500 s/mm2 was used for diffusion-weighted imaging. A phantom study using diluted gadolinium solutions and polyvinyl alcohol solutions was used to validate the two protocols. Regions of interest (ROIs) were manually outlined on MR images for areas of LR/NC, hemorrhage, and Fbr based on histological cross-sections. Pixel-based R1 and ADC values in the ROIs were plotted for each component. The probability density function of the plots determined the optimum contours to separate the three components in the ADC-R1 plane. The LR/NC, hemorrhage, and Fbr regions were mapped on MR images based on the above results and compared to histological results. The R1 values of the phantom measurements were tested using Bland-Altman analysis. The accuracies of the MRI classification were calculated. R1 values <8 s-1 calculated using our method agreed with those calculated using an inversion-recovery fast-spin-echo sequence (error, ≤0.1 s-1 ). ADC values obtained using OVS-DWEPI were 4.1% higher than those obtained using standard echo-planar imaging. LR/NC (R1 , 0.4-1.2 s-1 ; ADC, 0-1.5 μm2 /ms), hemorrhage (R1 ≥ 1.5 s-1 ; ADC, 0.5-1.5 μm2 /ms), and Fbr (R1 , 0.2-0.8 s-1 ; ADC, 1.5-2.9 μm2 /ms) were separated on the plots. The accuracies of MRI classification were LR/NC, 0.86; hemorrhage, 0.79; and Fbr, 0.77. The combination of ADC and R1 values measured using our method enabled differentiation among LR/NC, hemorrhage, and Fbr. 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;48:1657-1667.