Papers by Vassilios Chatzis
Lecture Notes in Computer Science, Dec 31, 2022
Proceedings of the 26th Pan-Hellenic Conference on Informatics, Nov 25, 2022
Sensors
The development of an effective agricultural robot presents various challenges in actuation, loca... more The development of an effective agricultural robot presents various challenges in actuation, localization, navigation, sensing, etc., depending on the prescribed task. Moreover, when multiple robots are engaged in an agricultural task, this requires appropriate coordination strategies to be developed to ensure safe, effective, and efficient operation. This paper presents a simulation study that demonstrates a robust coordination strategy for the navigation of two heterogeneous robots, where one robot is the expert and the second robot is the helper in a vineyard. The robots are equipped with localization and navigation capabilities so that they can navigate the environment and appropriately position themselves in the work area. A modular collaborative algorithm is proposed for the coordinated navigation of the two robots in the field via a communications module. Furthermore, the robots are also able to position themselves accurately relative to each other using a vision module in or...
This research concerns the modeling methods of System Dynamics and Simulation using the Anylogic ... more This research concerns the modeling methods of System Dynamics and Simulation using the Anylogic software. The purpose is to show how to use software to provide answers to supply chain issues, in particular inventory policy. We developed a supply chain simulation model that connects a retailer, a wholesaler and a factory. Using an optimization experiment we tried to find the optimal inventory policy for specific operating costs. Due to the interaction of the members of a supply chain, it is impossible to find a solution to the above problem without the use of modeling / simulation software. Based on this, we attempted to answer the problem using the Anylogic software. The supply chain model operates 24 hours a day and consists of four departments: customers, retailer, wholesaler, and factory. Using modeling and simulation of stock policy in a supply chain, it has become understandable that stock-related decisions are affected by all those involved in the chain. Our model showed that an agent’s stock policy cannot be taken in isolation because it is influenced by other supply chain agents. To solve the above problem, an optimization experiment was performed, which, considering the experimental stock policies of all agents, calculated the optimal stock policy solution. Using modeling and simulation have gave us the ability to study and improve our supply chain by providing us with information that we could not otherwise have. Our model is based on customer-based variables and their orders. The above method was chosen because there were no actual product’s demand data where we could base our simulation model. Using actual data will add more precision to the model and simulation. This feature can be achieved by linking the model to an ERP database with real-life data. In this way, the result of the optimization experiment will be even closer to the actual optimal stock policy value than now, where odds are being used.
Publication in the conference proceedings of EUSIPCO, Rhodes, Greece, 1998
2017 Panhellenic Conference on Electronics and Telecommunications (PACET), 2017
In offshore racing, sailboats with different potentialities compete to each other in the same rac... more In offshore racing, sailboats with different potentialities compete to each other in the same race field. The different potentialities are due to differences on geometrical and physical characteristics of the sailboats but also on their sailing equipment. In order to have fair rating, the Offshore Racing Congress (ORC) has established the International Measurement System (IMS) which is based on a velocity prediction model developed by the Massachusetts Institute of Technology [1] [2]. For this model, one of the key parameters which has to be calculated and may involve serious difficulties, is the definition of the waterline plane of the sailboat. Creating a 3d point cloud of the boat using a 3d laser scanner could help to overcome this problem, as it provides high accuracy in points measurements. And also a 3d point cloud processing algorithm can be developed to define the waterline plane accurately. In this paper a novel methodology on calculating the waterline plane is presented, which is based on the 3d point cloud that represents a sailing boat.
J. Inf. Hiding Multim. Signal Process., 2012
This paper presents a novel physics-based dual deformable model to detect objects in an image. Th... more This paper presents a novel physics-based dual deformable model to detect objects in an image. This model is more efficient than the known methods since it can detect objects whose boundaries are not necessarily defined by gradient. It minimizes an energy which can be seen as a particular case of a minimal partition problem. This energy is used as the model motivation power evolving the deformable model, which will stop on the desired object boundary. However, the stopping term does not depend on the gradient of the image, as most of the classical active and deformable contour models, but instead is related to the image color and spatial segments. Modal analysis is exploited to solve the deformation equation. Furthermore, the segmentation result produced depends on the physical characteristics of the model. Different physical characeristics lead to different segmentation results. The introduced deformable dual model composes of three interconnected deformable models. In most cases, ...
1996 8th European Signal Processing Conference (EUSIPCO 1996), 1996
In this paper a new variation of Hough Transform is proposed. It can be used to detect shapes or ... more In this paper a new variation of Hough Transform is proposed. It can be used to detect shapes or curves in an image, with better accuracy, especially in noisy images. It is based on a fuzzy split of the Hough Transform parameter space. The parameter space is split into fuzzy cells which are defined as fuzzy numbers. This fuzzy split of the parameter space provides the advantage to use the uncertainty of the contour points location, which is increased when noisy images have to be used. Moreover the computation time is slightly increased by this method, in comparison with classical Hough Transform.
2016 Digital Media Industry & Academic Forum (DMIAF), 2016
This paper presents a new geometrical feature based on iris geometry for automatic children detec... more This paper presents a new geometrical feature based on iris geometry for automatic children detection in digital images. The proposed feature is based on simple geometrical measures of face elements and especially iris. Iris outer boundary is approximated as a circle and the proposed feature is defined using the iris area and the distance of iris from mouth line. This approach is compared with two similar geometrical features. Experimental results show the superiority of the proposed feature over the existing ones. The proposed feature is more robust compared to the existing features that use geometrical information from human faces and gives better classification results, useful to digital forensics applications.
Proceedings of IEEE 5th International Fuzzy Systems
In this paper a new variation of Hough transform is proposed. The parameter space of Hough Transf... more In this paper a new variation of Hough transform is proposed. The parameter space of Hough Transform is iteratively split into fuzzy cells which are defined as fuzzy numbers. Each fuzzy cell corresponds to a fuzzy curve in the spatial domain. After each iteration the fuzziness of the cells is reduced and the curves are estimated with better accuracy. The
Lecture Notes in Computer Science, 2012
The continuing development of smaller electronic devices into the nanometer regime offers great p... more The continuing development of smaller electronic devices into the nanometer regime offers great possibilities of highly parallel computing systems, as it allows to reduce power consumption and device sizes and to increase operating speed. Quantum-dot Cellular Automata (QCA) has been proposed as an alternative for nanoelectronic devices and introduces a new opportunity for the design of highly parallel algorithms and architectures. Its benefits are the fast speed, very small size, high density and low energy consumption. These advantages can be very useful for various real time image processing applications. Complex image processing algorithms include in many cases the well-known binary median filter and mathematical morphology operations such as dilation and erosion. In this paper we propose and simulate two innovative QCA circuits which implement the dilation and the erosion.
In this paper the use of a fast algorithm for implementing shape decomposition of 3D binary objec... more In this paper the use of a fast algorithm for implementing shape decomposition of 3D binary objects is proposed. Shape decomposition is performed by successive 3D erosions and dilations, using 3D structuring elements of arbitrary size and shape. The proposed fast shape decomposition algorithm is based on a fast implementation of the basic morphological operation of Minkowski addition for the special case of binary 3D images (binary volumes). Experiments that evaluate the use of several structuring elements are also presented. The use of 2D and 1D structuring elements is also proposed to minimize the error of the reconstructed object. 1 Introduction Mathematical Morphology is a powerful image processing and analysis tool [1], [2], and plenty of implementations and applications in different fields have been presented in the literature [3], [4], [5], [6]. However, the application of mathematical morphology in 3D image processing and analysis is rather slow, since the 3D morphological o...
The main aim of this paper is the construction of a model, which involves the development of an a... more The main aim of this paper is the construction of a model, which involves the development of an application for estimating the real patient daily hospital expenses. These expenses concerns to the appropriate medicines, the necessary medical tests that along with all the requisite medical material for patient proper daily hospital treatment. According to the Daily Unified Closed Hospital Expense (DUCHE) defined by the state in Greek government gazette in February 1998, not all medicines or medical tests or even medical materials expenses are covered (paid by the state). The primary concern of the model that is proposed is the estimation of the mean daily expenses for each patient, treatment, clinic and total. An application has also been developed in order to implement the proposed model. A relational database has been created using MYSQL, capturing all the appropriate data concerning the supplies for medicines and medical materials. Data for each clinic in relation to the quantities...
This paper presents a new approach for the detection of image objects, based on active contours b... more This paper presents a new approach for the detection of image objects, based on active contours by exploiting techniques of curve evolution. The proposed model of active contours is based on the minimization of a fuzzy energy, which can be seen as a particular case of a minimal partition problem. Unlike to existing methods, the adopted fuzzy energy does not depend on the gradient of the image, but is related to the image color and spatial segments. The proposed fuzzy energy is used as the model motivation power evolving the active contour, which will stop on the desired object boundary. The fuzziness of the energy and the exploitation of both local gray-scale and spatial information provide a balanced technique with a strong ability to reject "weak", as well as, "strong" local minima. The proposed approach is faster comparing to existing active contour models, due to the fact that the fuzzy energy calculations are computed directly instead of solving the Euler-La...
Proceedings of Third International Conference on Electronics, Circuits, and Systems
Abstract This paper presents a simulation of an access control system that deals with the problem... more Abstract This paper presents a simulation of an access control system that deals with the problem of access control and copyright protection for broadcasted image-related services. The services that concentrate our interest include mainly Pay-TV, but also the existing and ...
Mathematical Methods in Pattern and Image Analysis, 2005
Industrial product quality is frequently assessed using up to second-order statistics of populati... more Industrial product quality is frequently assessed using up to second-order statistics of populations of measurements. Lately, a fuzzy interval number (FIN) was used for representing a whole population of samples. It turns out that a FIN can asymptotically capture statistics of all orders. The space F of FINs, including both conventional (fuzzy) numbers and conventional intervals, is studied here. A FIN is interpreted as a (linguistic) information granule that can capture industrial ambiguity. Based on generalized interval analysis it is shown rigorously that F is a metric mathematical lattice; moreover it is shown that F a cone in a linear space. An enhanced extension of Kohonen's Self-Organizing Map (KSOM), namely granular SOM or grSOM for short, is presented in FN for inducing a distribution of FINs from populations of measurements. The grSOM produces descriptive decision-making knowledge (i.e. rules) from the training data by expert attaching labels to induced n-tuples of FINs. Generalization is feasible beyond rule support. A positive valuation function, computable genetically, can introduce tunable nonlinearities. Preliminary results are demonstrated regarding industrial fertilizer quality assessment. Fuzzy-mathematical-morphology-based image processing techniques, which combine binary thresholding and object recognition, are used to automatically measure the geometry of fertilizer granules. Additional measurements are also considered. The far-reaching practical potential of the proposed techniques is discussed.
Proceedings IEEE International Conference on Multimedia Computing and Systems
In this papel; the Morphological Skeleton Interpolation (MSI) algorithm is presented. It is an ef... more In this papel; the Morphological Skeleton Interpolation (MSI) algorithm is presented. It is an eficient shape-based interpolation method used for interpolating slices between successive slices of a 3-0 object. It is based on the well known mathematical morphology procedure of morphological skeletonization, that is used as a representation of an object. The proposed morphological skeleton matching process provides translation, rotation and scaling information at the same time. The interpolated slices preserve the shape of the original object slices, when the slices have similar shapes. It can also modify the shape of an object when the successive slices have not similar shapes. Applications on artijicial and real data are also presented.
Studies in Fuzziness and Soft Computing, 2003
In this chapter, an overview of the applications of several fuzzy operators in image processing a... more In this chapter, an overview of the applications of several fuzzy operators in image processing and analysis is presented. First, the fuzzy location and scale estimators based on the extension principle, are presented. The definitions of the fuzzy nonlinear means, the fuzzy location and scale estimators based on fuzzy order statistics and other fuzzy scale estimators, e.g., fuzzy sample standard deviation, are also given. Equivalent relations that can be used to calculate the fuzzy estimators using classical arithmetic are derived. The Fuzzy Vector Median is defined as an extension of the classical Vector Median, based on a distance definition between fuzzy vectors. An application of Fuzzy Vector Median for filtering images corrupted by mixed Gaussian and impulsive noise is also given.
Noblesse Workshop on Non-Linear Model Based Image Analysis, 1998
In this paper the use of a fast algorithm for implementing shape decomposition of 3D binary objec... more In this paper the use of a fast algorithm for implementing shape decomposition of 3D binary objects is proposed. Shape decomposition is performed by successive 3D erosions and dilations, using 3D structuring elements of arbitrary size and shape. The proposed fast shape decomposition algorithm is based on a fast implementation of the basic morphological operation of Minkowski addition for the special case of binary 3D images (binary volumes). Experiments that evaluate the use of several structuring elements are also presented. The use of 2D and ID structuring elements is also proposed to minimize the error of the reconstructed object.
2011 17th International Conference on Digital Signal Processing (DSP), 2011
ABSTRACT A novel image clustering method based on the image histogram, which is processed by the ... more ABSTRACT A novel image clustering method based on the image histogram, which is processed by the empirical mode decomposition (EMD) is presented. An intermediate step derived from the EMD, which can decompose any nonlinear and non-stationary data into a number of intrinsic mode functions (IMFs) is exploited. The IMFs of the image histogram have interesting characteristics and provide a novel workspace that is utilized in order to automatically detect the different clusters into the image under examination. The proposed method was applied to several real and synthetic images and the obtained results show good image clustering robustness.
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Papers by Vassilios Chatzis