Set Of Candidate Points Research Articles

Fully-automated tongue detection in ultrasound images

Tracking the tongue in ultrasound images provides information about its shape and kinematics during speech. Current methods for detecting/tracking the tongue require manual initialization or training using large amounts of labeled images. In this article, we propose a solution to convert a semi-automatic tongue contour tracking system to a fully-automatic one. This work introduces a new method for extracting tongue contours in ultrasound images that requires no training nor manual intervention. The method consists in an image enhancement step based on phase symmetry, followed by skeletonization and clustering steps, leading to a set of candidate points that can be used to fit an active contour to the image and subsequently initialize a tracking algorithm. Two novel quality measures were also developed that predict the reliability of the segmentation result so that an image with a reliable contour can be chosen to confidently initialize fully automated tongue tracking. This is achieved by automatically generating and choosing a set of points that can replace the manually segmented points for a semi-automated tracking approach. This paper also improves the accuracy of tracking by incorporating two criteria to reset the tracking algorithm from time to time. Experiments show that fully automated and semi-automated methods result in very similar mean sum of distances errors, respectively, indicating that the proposed automatic initialization does not significantly alter accuracy. Moreover, further results show that tracking accuracy is improved when using the new segmentation technique within the proposed re-initialization scheme.

Exploiting the structure of furthest neighbor search for fast approximate results

We present a novel strategy for approximate furthest neighbor search that selects a set of candidate points using the data distribution. This strategy leads to an algorithm, which we call DrusillaSelect, that is able to outperform existing approximate furthest neighbor strategies. Our strategy is motivated by a study of the behavior of the furthest neighbor search problem, which has significantly different structure than the nearest neighbor search problem, and can be understood with the help of an information-theoretic hardness measure that we introduce. We also present a variant of the algorithm that gives an absolute approximation guarantee; under some assumptions, the guaranteed approximation can be achieved in provably less time than brute-force search. Performance studies indicate that DrusillaSelect can achieve comparable levels of approximation to other algorithms, even on the hardest datasets, while giving up to an order of magnitude speedup. An implementation is available in the mlpack machine learning library (found at http://www.mlpack.org).

Advanced Topological Map Matching Algorithm Based on D–S Theory

Map matching combining vehicle Global Positioning System (GPS) with road attribute information has a significant impact on the traffic route guidance. In the current work, an advanced topological map matching algorithm based on the D–S (Dempster–Shafer) theory is proposed to improve the application for the high-density road network. Data cleaning is carried out to delete the apparent errors of original data and to reduce the data sources. Matching features of the GPS point stated four factors, namely the road speed limit, heading, proximity and spatial correlation. These factors are in line with the vehicle travel characteristics. The D–S theory is applied to dynamically estimate the weight of each factor and further to calculate the fusion result in order to increase the proposed algorithm flexibility. An optimization method based on trajectory shape matching is also proposed to filter the candidate point set to enhance the algorithm accuracy. The results established that the data cleaning can eliminate the invalid data up to more than 5% of the collected data; where using the four factors can guarantee the basic demand of the data matching, while the D–S theory and shape matching can effectively improve the matching accuracy. The proposed system achieved an overall algorithm matching accuracy up to 96.5%.

Finger-vein pattern restoration with Direction-Variance-Boundary Constraint Search

Finger-vein verification is an emerging biometrics technology. Its first task is extracting finger-vein patterns. Although existing algorithms can extract most finger-vein patterns robustly, some branch of these patterns always breaks, which leads to adverse effects for features extraction and matching. In this paper, a Direction-Variance-Boundary Constraint Search (DVBCS) model is presented to restore the broken finger-vein patterns. At the beginning, endpoints of broken finger-vein branches are located. Then, a direction constraint for searching candidate point set is demonstrated. Following the second stage, an optimal target point is selected from the candidate point set according to a minimum within-cluster variance criterion. Eventually, the boundary constraint and variance constraint are introduced as the termination conditions. Experimental results illustrate that, while maintaining low segmentation error, the proposed method can restore above 10% lost target points. Moreover, the equal error rate of finger-vein recognition is reduced from 0.57% to 0.29% when using the proposed method to restore finger-vein patterns.

Road detection from airborne LiDAR point clouds adaptive for variability of intensity data

This paper presents a novel algorithm of road detection from airborne LiDAR point clouds adaptive for variability of intensity data of road network. First, the point cloud topology is constructed using a grid index structure which facilitate spatial searching and preserves the accuracy of raw data without interpolation, and a LiDAR filtering algorithm is employed to distinguish the ground points from non-ground points. Second, road candidates are identified in the derived ground points by segmentation based on local intensity distribution histogram. Finally, the ultimate road point sets are verified by global inference based on the roughness and area of the road candidate point sets. The roughness of candidate point sets are calculated based on morphological gradients in consideration of the characteristics of roads compared to other non-road ground areas such as grass land and bare ground. The experimental results using practical data in complex environment demonstrate that this algorithm is able to automatically detect roads adaptive for the variability of intensity data of road network. Other non-road ground areas such as grass land and bare ground can be efficiently eliminated.

Complex Root Finding Algorithm Based on Delaunay Triangulation

A simple and flexible algorithm for finding zeros of a complex function is presented. An arbitrary-shaped search region can be considered and a very wide class of functions can be analyzed, including those containing singular points or even branch cuts. The proposed technique is based on sampling the function at nodes of a regular or a self-adaptive mesh and on the analysis of the function sign changes. As a result, a set of candidate points is created, where the signs of the real and imaginary parts of the function change simultaneously. To verify and refine the results, an iterative algorithm is applied. The validity of the presented technique is supported by the results obtained in numerical tests involving three different types of functions.

Dominance rules for the optimal placement of a finite-size facility in an existing layout

In this paper, we consider the problem of optimal placement of a single finite-size, rectangular facility in the presence of other rectangular facilities. There is a non-negative interaction between the new and existing facilities as well as pairs of existing facilities. All interactions are serviced through a finite number of input/output points located on the boundary of each facility. We assume that the travel occurs according to the rectilinear metric and the travel through the facilities is not permitted. It has been established in the previous works that the optimal placement of the new facility belongs to a finite set of candidate points, whose cardinality is polynomially bounded in the number of existing facilities. The optimal placement of the new facility can be found by evaluating the objective function value at each and every candidate point. This explicit enumeration guarantees the optimal solution, however it might become time consuming for a large number of existing facilities. We propose a new procedure based on the lower bounding technique, which can effectively cut down the number of candidate points that need to be evaluated, resulting in significant reduction in the computing time. The procedure was tested on a large number of randomly generated layouts with varying congestion factors (ratio of area occupied by the existing facilities to the total layout area). These extensive numerical tests reveal that, for a moderately congested layout, there is more than 70% reduction in both the number of evaluated candidates and the computing time.

Constructing space-filling designs using an adaptive WSP algorithm for spaces with constraints

Not all phenomena can be studied using standard experimental designs. Indeed, non-linear phenomena require experimental designs to cover the whole variable space in a reasonable number of experiments. Space-filling designs (SFD) propose a uniform distribution of points and are well adapted to numerical simulations. However, not all SFDs are equivalent in terms of uniformity of point distribution throughout the variable space, as assessed by quality criteria (such as MinDist, Coverage, etc.) and many algorithms which are powerful in low dimensional spaces (D<10) become difficult to use at higher dimensions (20D, 30D, etc.). The Wootton, Sergent, Phan-Tan-Luu's algorithm (WSP) was developed to select points from a set of candidate points and generate designs with good uniformity criteria whatever the number of dimensions. This study presents an adjustment of this algorithm, called adaptive WSP to obtain designs with specific experimental constraints, or when density is to be increased in a zone of particular interest. This adaptive WSP algorithm will be very useful as the number of dimensions increases and can solve the problem of the “hollow” center.

Geometric algorithm for dominant point extraction from shape contour

In this paper we propose a new algorithm for extracting dominant points from the real contour of a digital shape. A polygonal approximation of the shape can be obtained by the set of dominant points. In the proposed algorithm, in the first step before searching for dominant points, the real contour is made sparse using a geometric concept, named convex deficiency tree. This helps to select a set of candidate points from real contour. In comparison with break points (which are initial points in many algorithms), the set of candidate points is more heuristic and the ratio of them to the all points of the contour is lower. In the second step of the proposed algorithm, the less informative candidate points are removed in an iterative manner. After removing one candidate point, its adjacent positions are searched to find more stable position for its neighbors. The comparative result of the proposed algorithm with others shows its efficiency. The algorithm finds an effective polygonal approximation for digital shapes especially for the real contours, which makes the method more practical.

On the construction of experimental designs for a given task by jointly optimizing several quality criteria: Pareto-optimal experimental designs

Experimental designs for a given task should be selected on the base of the problem being solved and of some criteria that measure their quality. There are several such criteria because there are several aspects to be taken into account when making a choice. The most used criteria are probably the so-called alphabetical optimality criteria (for example, the A-, E-, and D-criteria related to the joint estimation of the coefficients, or the I- and G-criteria related to the prediction variance). Selecting a proper design to solve a problem implies finding a balance among these several criteria that measure the performance of the design in different aspects. Technically this is a problem of multi-criteria optimization, which can be tackled from different views.The approach presented here addresses the problem in its real vector nature, so that ad hoc experimental designs are generated with an algorithm based on evolutionary algorithms to find the Pareto-optimal front. There is not theoretical limit to the number of criteria that can be studied and, contrary to other approaches, no just one experimental design is computed but a set of experimental designs all of them with the property of being Pareto-optimal in the criteria needed by the user. Besides, the use of an evolutionary algorithm makes it possible to search in both continuous and discrete domains and avoid the need of having a set of candidate points, usual in exchange algorithms.

SCoBeP: Dense image registration using sparse coding and belief propagation

Image registration as a basic task in image processing has been studied widely in the literature. It is an important preprocessing step in various applications such as medical imaging, super resolution, and remote sensing. In this paper, we proposed a novel dense registration method based on sparse coding and belief propagation. We used image blocks as features, and then we employed sparse coding to find a set of candidate points. To select optimum matches, belief propagation was subsequently applied on these candidate points. Experimental results show that the proposed approach is able to robustly register scenes and is competitive as compared to high accuracy optical flow Brox et al. (2004) [1], and SIFT flow Liu et al. [2].

Automatic point correspondence using an artificial immune system optimization technique for medical image registration

In this paper, an automatic method for determining pairs of corresponding points between medical images is proposed. The method is based on the implementation of an artificial immune system (AIS). AIS is a relatively novel, population based category of algorithms, inspired by theoretical immunologic models. When used as function optimizers, AIS have the attractive property of locating the global optimum of a function as well as a large number of strong local optimum points. In this work, AIS has been applied both for the extraction of an optimal set of candidate points on the reference image and the definition of their corresponding ones on the second image. The performance of the proposed AIS algorithm is evaluated against the widely used Iterative Closest Point (ICP) algorithm in terms of the accuracy of the obtained correspondences and in terms of the accuracy of the point-based registration by the two correspondence algorithms and the Mutual Information criterion, as an intensity-based registration method. Qualitative and quantitative results involving 92 X-ray dental and 10 retinal image pairs subject to known and unknown transformations are presented. The results indicate a superior performance of the proposed AIS algorithm with respect to the ICP algorithm and the Mutual Information, in terms of both correct correspondence and registration accuracy.

Snakules: A Model-Based Active Contour Algorithm for the Annotation of Spicules on Mammography

We have developed a novel, model-based active contour algorithm, termed "snakules", for the annotation of spicules on mammography. At each suspect spiculated mass location that has been identified by either a radiologist or a computer-aided detection (CADe) algorithm, we deploy snakules that are converging open-ended active contours also known as snakes. The set of convergent snakules have the ability to deform, grow and adapt to the true spicules in the image, by an attractive process of curve evolution and motion that optimizes the local matching energy. Starting from a natural set of automatically detected candidate points, snakules are deployed in the region around a suspect spiculated mass location. Statistics of prior physical measurements of spiculated masses on mammography are used in the process of detecting the set of candidate points. Observer studies with experienced radiologists to evaluate the performance of snakules demonstrate the potential of the algorithm as an image analysis technique to improve the specificity of CADe algorithms and as a CADe prompting tool.

Generalized sparse MRF appearance models

Image segmentation or registration approaches that rely on a local search paradigm (e.g, Active Appearance Models, Active Contours) require an initialization that provides for considerable overlap or a coarse localization of the object to be segmented or localized. In this paper we propose an approach that does not need such an initialization, but localizes anatomical structures in a global manner by formulating the localization task as the solution of a Markov Random Field (MRF). During search Sparse MRF Appearance Models (SAMs) relate a priori information about the geometric configuration of landmarks and local appearance features to a set of candidate points in the target image. They encode the correspondence probabilities as an MRF, and the search in the target image is equivalent to solving the MRF. The resulting node labels define a mapping of the modeled object (e.g. a sequence of vertebrae) to the target image interest points. The local appearance information is captured by novel symmetry-based interest points and local descriptors derived from Gradient Vector Flow (GVF). Alternatively, arbitrary interest points can be used. Experimental results are reported for two data-sets showing the applicability to complex medical data. The approach does not require initialization and finds the most plausible match of the query structure in the entire image. It provides for precise, reliable and fast localization of the structure.

Shaft location selection at deep multiple orebody deposit by using fuzzy TOPSIS method and network optimization

A shaft is a vertical passageway connecting the surface to ore deposit located deep under surface. The decision on the shaft location is a critical element in the strategic planning for underground mine development system design. Ore deposit is often composed of few independent orebodies located in different places in the space that must be interconnected into one integrated system. In this paper, we examine the case when access points to orebodies lay in the Euclidean plane. We apply fuzzy techniques to incorporate data related to ore reserve and costs into shaft location problem. Fuzzy TOPSIS method is used for the multi-criteria evaluation of the location of the base of the shaft. To identify candidate points (alternatives), we use network optimization based on applying Kruskal’s algorithm and adding Steiner points. The set of candidate points is given by the union of access and Steiner points.

Pseudoreceptor-based pocket selection in a molecular dynamics simulation of the histamine H4 receptor

There is a renewed interest in pseudoreceptor models which enable computational chemists to bridge the gap of ligand- and receptor-based drug design. We developed a pseudoreceptor model for the histamine H4 receptor (H4R) based on five potent antagonists representing different chemotypes. Here we present the selection of potential ligand binding pockets that occur during molecular dynamics (MD) simulations of a homology-based receptor model. We present a method for prioritizing receptor models according to their match with the consensus ligand-binding mode represented by the pseudoreceptor. In this way, ligand information can be transferred to receptor-based modelling. We use Geometric Hashing to match three-dimensional points in Cartesion space. This allows for the rapid translation- and rotation-free comparison of atom coordinates, which also permits partial matching. The only prerequisite is a hash table, which uses distance triplets as hash keys. Each time a distance triplet occurring in the candidate point set which corresponds to an existing key, the match is represented by a vote of the respective key. Finally, the global match of both point sets can be easily extracted by selection of voted distance triplets. The results revealed a preferred ligand-binding pocket in H4R, which would not have been identified using an unrefined homology model of the protein. The key idea was to rely on ligand information by pseudoreceptor modelling.

Discrete approximation heuristics for the capacitated continuous location–allocation problem with probabilistic customer locations

The capacitated continuous location–allocation problem, also called capacitated multisource Weber problem (CMWP), is concerned with locating m facilities in the Euclidean plane, and allocating their capacity to n customers at minimum total cost. The deterministic version of the problem, which assumes that customer locations and demands are known with certainty, is a nonconvex optimization problem. In this work, we focus on a probabilistic extension referred to as the probabilistic CMWP (PCMWP), and consider the situation in which customer locations are randomly distributed according to a bivariate probability distribution. We first formulate the discrete approximation of the problem as a mixed-integer linear programming model in which facilities can be located on a set of candidate points. Then we present three heuristics to solve the problem. Since optimal solutions cannot be found, we assess the performance of the heuristics using the results obtained by an alternate location–allocation heuristic that is originally developed for the deterministic version of the problem and tailored by us for the PCMWP. The new heuristics depend on the evaluation of the expected distances between facilities and customers, which is possible only for a few number of distance function and probability distribution combinations. We therefore propose approximation methods which make the heuristics applicable for any distance function and probability distribution of customer coordinates.

Automatic correspondence using the enhanced hexagonal centre-based inner search algorithm for point-based dental image registration

In this paper, the enhanced hexagonal centre-based inner search (EHCBIS) algorithm, for automatic point correspondence, is proposed for dental image registration. The presented algorithm is incorporated within a general registration scheme, which is based on extracting a set of candidate points on the reference image, finding their corresponding points in the image to be transformed (float image) using the proposed algorithm and applying a suitable geometrical transformation towards automatic registration. The performance of the proposed algorithm is evaluated against three well-known methods for automatic correspondence, the self-organizing maps, the automatic extraction of corresponding points and the trimmed iterative closest point method, in terms of registration accuracy. Qualitative and quantitative results on registering 123 dental pairs show that the proposed algorithm outperforms the other methods for automatic correspondence with or without the presence of noise. The EHCBIS method is capable of defining automatically corresponding points in dental image pairs. It can be incorporated within a general scheme for point-based registration of dental radiographs acquired with or without rigorous a priori standardization. The applied projective transformation provides a reliable model for registering intraoral radiographs. The methodology does not require any segmentation prior to alignment providing subtraction radiographs and fused images for clinical evaluation regarding the evolution of a disease or the response to a therapeutic scheme.

Construction of a 21-Component Layered Mixture Experiment Design Using a New Mixture Coordinate-Exchange Algorithm

This article describes the solution to a unique and challenging mixture experiment design problem involving (1) 19 and 21 components for two different parts of the design, (2) many single-component and multicomponent constraints, (3) augmentation of existing data, (4) a layered design developed in stages, and (5) a no-candidate-point optimal design approach. The problem involved studying the liquidus temperature of spinel crystals as a function of nuclear waste glass composition. A D-optimal approach was used to augment existing glasses with new nonradioactive and radioactive glasses chosen to cover the designated nonradioactive and radioactive experimental regions. The traditional approach to building D-optimal mixture experiment designs is to generate a set of candidate points from which design points are D-optimally selected. The large number of mixture components (19 or 21) and many constraints defining each layer of the waste glass experimental region made it impossible to generate and store the huge number of vertices and other typical candidate points. A new coordinate-exchange algorithm applicable for constrained mixture experiments implemented in JMP® was used to D-optimally select design points without candidate points. The new coordinate-exchange algorithm for mixture experiments is described in this article.

Thep-facility ordered median problem on networks

In this paper we deal with the ordered median problem: a family of location prob- lems that allows us to deal with a large number of real situations which does not fit into the standard models of location analysis. Moreover, this family includes as particular instances many of the classical location models. Here, we analyze the p-facility version of this problem on networks and our goal is to study the structure of the set of candidate points to be optimal solutions.