Artykuły (CN-csci)

Permanent URI for this collectionhttps://repo.agh.edu.pl/handle/AGH/102784

Artykuły czasopisma Computer Science

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Access status: Open Access ,
Optimistic and pessimistic result of planning and scheduling dynamic processes
(Wydawnictwa AGH, 1999) Wajs, Wiesław
The combinatorial optimization is aimed at finding the optimum sequence for a given form of the performance index. This paper deals with the problems of combinatories optimization. Here are set forth three forms of the performance index for the optimization tasks. We can consider the scheduling problem. The loss of the profit depends on the resources volume. Special attention is paid at finding polynomial algorithms used for combinatories optimization tasks. Those optimization tasks may be solved for a large number of dynamic processes. The optimization algorithms set forth are based upon the sorting procedure. The performance index is assiimed to be additive. The performance index value, after having completed a number of dynamic processes, determines the initial condition for the successive dynamic problem under realization In real physical or economic processes it is necessary to know a determined time interval for carrying out the elementary technical, technological or economic operation.
Access status: Open Access ,
Problem integralności funkcjonalnej pewnej klasy systemów wieloagentowych
(Wydawnictwa AGH, 1999) Cetnarowicz, Krzysztof
Multi-agent systems have many advantages and give numerous new possibilities in creation of information systems. However many problems related to functioning of the systems are still unsolved. Functional integrity of multi-agent systems belongs to such problems. Functional integrity of multi-agent systems may be defined in general as preservation of basic functions of the system during its functioning. Functional integrity may be analyzed from the point of view of different functions of the system (the functions that should be preserved) and also from the point of view of various factors that may influence the loss or preservation of functional integrity of the system. The paper deals with examination of functional integrity of multi-agent system depending upon number of agents (global and of particular types). During system work, agents generate agents of the same or different type that depend on their possibilities and system needs. The process performed without use of appropriate control mechanisms may lead to excessive (blocking of the system) or too little number of agents and even lack of agents (disappearance of the functions of a system that are performed by a gents of a certain type). A proposal of functional integrity phenomenon analysis of multi-agent systems that is related to the number of agents in their population and a proposal of mechanisms that enable maintenance of functional integrity, in particular a concept of the so-call ed »free agents« have been presented in the paper. Consideration has been carried out on the basis of simulation examination of some elass of multi-agent systems. Results of simulation of proposed Solutions have been included in the work.
Access status: Open Access ,
Narzędzia do analizy jakości programów równoległych opartych na przesyłaniu komunikatów
(Wydawnictwa AGH, 1999) Funika, Włodzimierz
The article presents a number of issues of designing and implementing performance evaluation tools for message-passing parallel programs, e.g. MPI and PVM. There is a number of special techniques for investigating parallel programs, whose implementations are tools presented. A concept of performance observability is introduced. Although a number of interesting solutions of performace tools was developed in the course of last decade, there is a great demand for portable and integrated tools. Understanding the reason for this situation requires evaluating the state of art of existing tools, their advantages and drawbacks. Due to a complicated mechanism of interactions between a tool and operating system, computer architecture and application, evaluating the tool includes taking into account a large number of features. There is introduced a set of criteria, which enable a thorough evaluation of tools, based on the work of HPC standardizing organizations as well as the author's work. The second part of the article presents the review of features of the particular tools developed over last decade. The tools are being evaluated on the base of the criteria introduced. The features of the PARNAS performance tool project and its implementation are presented. The summary presents further avenues of inquiry in parallel performance evaluation tools.
Access status: Open Access ,
Inteligentny system w wybranej klasie dynamicznych środowisk decyzyjnych
(Wydawnictwa AGH, 1999) Święcicki, Mariusz
One of the trends in the information theory of recent years is a dynamic development of decentralized, intelligent information systems. The systems in question are so complex that the classical methods of describing their dynamics, prove to be insufficient. One of the possible ways of describing them is by applying the model of an agent which constitutes an independent entity existing in its own right. The agent has its own inventory of objectives and the ability to interact with the eivironment and adapt to the changes which take place in this environment. The paper presents the conception of autonomous agent as a cybernetic model of an autonomous system. It is based on psychological and biological phenomena which may be observed in living organisms. The description of the system distinguishes between three basic functional blocks: correlator, homeostasis and accumulator, it contains a detailed account of the functions and mutual correlations and interactions. Subsequently, the paper presents a elassification of interactions between correlator and homeostatis, as well as between homeostasis and accumulator. An analysis of the autonomous system from the point of view of the psychological and biological phenomena which take place in it, has allowed one to borrow certain educational methods from behavioural psychology (classical conditioning, instrumental conditioning) and apply them to the teaching of these type of systems. The paper presents the implementation of these type of systems in artificial neuron networks. Subsequently, the authors show how in practical terms these type of systems may be taught by means of the above-mentioned methods. Lastly, the paper presents the application of the above systems to the learning process together with the discussion of the accompanying phenomena.
Access status: Open Access ,
Animacja komputerowa oparta na symulacji metodą cząstek
(Wydawnictwa AGH, 1999) Wcisło, Rafał
The paper presents the main issues of a computer animation of a set of elastic macroscopic objects based on the particle method. The main assumption of the generated animations is to achieve very realistic movements in a scene observed on the computer display. The objects (solid bodies) interact mechanically with each other. The movements and deformations of solids are calculated using the particle method. Phenomena connected with the behaviour of solids in the gravitational field, their deformations caused by collisions and interactions with the optional liquid medium are simulated. The simulation of the Iiquid is performed using the cellular automata method. The paper presents both simulation schemes (particle method and cellular automata rules) and the method of combining them in the single animation program. In order to speed up the execution of the program the parallel version based on the network of workstation was developed. The paper describes the methods of the parallelization and it considers problems of load-balancing, collision detection, process synchronization and distributed control of the animation.
Access status: Open Access ,
Mostek bezpieczeństwa dla protokołu Internet Inter-ORB Protocol
(Wydawnictwa AGH, 1999) Pietras, Paweł; Słowikowski, Paweł
In this paper, we present a security bridge for the Internet protocol of interoperability amongst CORBA objects - the Internet Inter-ORB Protocol (HOP). The bridge helps in making accessible objects in the Internet and makes possible the access control to them. The bridge was realized in the popular request broker the Visigenic's VisiBroker under Windows 95/NT and Solaris 2.X operating systems. We describe two ways of locating the bridge in the request broker. The first means uses one name domain of broker and is not transparent for client. The second one uses two name domains and provides objects protection on the level of the Naming Service and is transparent for the client. We also describe the variant of the second means with using GateKeeper server to support HOP tunneling within HTTP. We emphasize the importance of a firewall, cooperating with a bridge, which is required for the purpose of providing object protection. The paper presents an original conception of security managing, basing on the ideas of users, groups and resources defined using the standard terms of CORBA, HOP and TCP/IP, that allows to control positively and negatively the access to classes (interfaces), objects and also to their individual methods. This conception was effectively implemented in a functioning bridge. Further chapters describe the foundations and some details of the bridge implementation such as the use of the Interface Repository, cache memory application, thread synchronization and the way of synchronization of the configuration applet with the bridge's objects. We discuss the influence of these solutions on the efficiency of the bridge and its source code portability. We also present the general structure of the component objects of the bridge with a scheme. In the next part we characterize the implementation foundations of the bridge manager, realized as an applet in Java, with the stress on the possibility of the bridge configuration through the network. Later, we describe the functionality of the bridge manager, which allows the configuration of all the important parameters of the bridge and of the security management. The next chapter discusses the conclusions from the efficiency tests of the two main bridge layers - the bridge manager and the bridge itself (proxy mechanism), the influence of the usage of memory caching on its efficiency. We provide there also an overall evaluation of the obtained results. The last chapter includes a summary and discusses the bridge advantages and limitations as well as its evolution possibilities.
Access status: Open Access ,
Metody transformacji prostującej i analizy zewnętrznych konturów obiektów w rozpoznawaniu obrazów medycznych
(Wydawnictwa AGH, 1999) Ogiela, Marek
The article presents an algorithm of the transformation straightening outer contours of objects, allowing to transform biological structures of interest, visible in medical images, from two-dimensional space of the image into two-dimensional graph, representing contours of the straightened object with its possible outer morphological changes, indicating the progress of pathological processes. The developed method is based on a sequence of geometrie transformations of the analyzed objects in the image, and its operation was described in detail and illustrated by exampIes of transformation of main pancreatie ducts, appearing in X-ray images acquired by ERCP, as well as by graphs showing outer morphology of blood vessels in the fundus of the eye. The proposed method is universal, and due to the fact that the transformation preserves and exposes pathologic morphological changes, such as abnormal lateral branches, Iocal dilatations or projections it can also be used in the recognition and analysis of other structure images acquired by va-rious techniques of computer tomography, e.g. cerebral vessels, bile ducts, coronary vessels or fragments of gastrointestinal tract. The graphs of the structures of interest obtained as a result of the transformation straightening outer contours of objects are a starting point for the recognition of morphological changes, important for diagnosis, using syntactic methods of pattern recognition.
Access status: Open Access ,
Formalna weryfikacja wymagań systemów czasu rzeczywistego
(Wydawnictwa AGH, 2000) Szpyrka, Marcin
The methodology of system requirements verification presented in this paper is a proposition of a practical procedure for reducing some negatives of the specification of requirements. The main problem that is considered is to create a complete description of the system requirements without any negatives. Verification of the initially defined requirements is based on the coloured Petri nets. Those nets are useful for testing some properties of system requirements such as completeness, consistency and optimality. An example of the lift controller is presented.
Access status: Open Access ,
Zastosowanie metod naturalnych w problemach poszukiwania optymalnego rozwiązania
(Wydawnictwa AGH, 2000) Jasińska-Suwada, Anna; Dzwinel, Witold; Rozmus, Krzysztof; Sołtysiak, Jacek
In the paper we present a new method, which can be used as a natural solver for searching the best solution in the multidimensional and multimodal parameter space. The method is based on a well-known simulation technique, i.e., molecular dynamics. To show advantages and disadvantages of the particle method in comparison to the standard genetic algorithm, we analyse efficiency of the methods in finding the global minimum of multi-dimensional and multi-modal test-bed functions and we calculate the evaluation indices. We analyse also the ways the solution space is explored and the parameters of algorithms adjusted. The optimal heuristics are proposed. The tests carried out show that the choice of the most appriopriate optimization method depends on type of a problem considered. We show that the particle method is more efficient for finding the optimal solution for multi-modal problems with distinct global extreme, while the genetic algorithm is better for deceptive functions with several locals extreme, which are placed far away from the global optimum. This comes from the different ways in which the particle method and genetic algorithm explore the solution space. The particle method can be used for initial analysis of functions, which character is unknown.
Access status: Open Access ,
Obliczenia metodą elementów skończonych na sieci stacji roboczych i na komputerze równoległym
(Wydawnictwa AGH, 2000) Chrobak, Renata
This paper presents three parallel algorithms for simulation of axisymmetrical metal forging processes. The algorithms are based on the non-overlapping domain decomposition method where a mesh of elements is divided into layers assigned to different processes. Parallel programs implementing these algorithms are written in C using PVM calls. The efficiency of the parallel programs is verified on networked IBM RS/6000, Sun SPARCstations and HP 9000 workstations as well as on HP/Convex Exemplar SPP1000.
Access status: Open Access ,
Dopasowanie krzywej tonalnej i równoważenie poziomów szarości przy kontrastowaniu i wstępnej wizualizacji struktur w analizie zdjęć medycznych
(Wydawnictwa AGH, 2000) Ogiela, Marek
The article presents a group of transformations which medical pictures can be subjected to, in the aim of enhancing their contrast and better distinguishing and diagnosis of organs shown in this pictures. In this work the analysis was based on images acquired by various techniques, such as roentgenography (RTG), magnetic resonance (MRI), classic computer tomography (CT) and ultrasonography (USG). Contrast expansion in these images was performed using the histogram method of balancing of gray levels and the method based on the modification of tonal curve. Such transformations were necessary during preliminary processing of these images, especially to adjust their quality for next steps of the analysis in case of automatic medical diagnosis, and also to enable their visual evaluation by specialists and diagnostic interpretation of images of organs and their structural features. The studies show that the method based on the modification of tonal curve yields better results in case of images acquired by roentgenography and magnetic resonance imaging. On the other hand, histogram method is more suitable for contrast expansion in CT and USG images.
Access status: Open Access ,
Wykorzystanie sieci neuronowych i analizy portfelowej w prognozowaniu kursów akcji na giełdzie papierów wartościowych
(Wydawnictwa AGH, 2000) Stochel, Przemysław
The article presents the use of neural networks in decision making process on the capital market. The author tried to show the efficiency of established solution in Polish reality which features different conditions in comparison with the markets of higher developed countries. The aim of the paper was to prove that neural networks are flexible tools which on one hand might be adjusted to investor's requirements and on the other, can reduce equirements to his experience. The article is based on the author's own research carried out by modelling neural network operation with a simulation program. The established solutions are input which employs stocks portfolio computed on the basis of Markowitz portfolio theory and Sharpe's model. According to the established propositions, the portfolio created in such a way is modified by neutral network in order to optimise a criterion which maximises the income of such a modified portfolio. A detailed genesis of the established input vector and network structure are presented. It allows the reader to carry out his own research and create his own attitude towards applied values. The research results based on a real stock market database with the use of one-output networks predicting the price of a single company - Agros as well as networks predicting the desirable structure of the whole portfolio are presented. The effect of the network structure learning parameters, input vector (not only as to the input quantity but also as to period of time they were collected) was examined. The dependence between the factors mentioned above such as input vector and network structure were discussed. It seems that the presented paper has proved that some not widely spread methods with neural networks can become a competitive tool to optimisation methods.
Access status: Open Access ,
Semantyczny parser języka polskiego
(Wydawnictwa AGH, 2000) Szostek, Grażyna; Grudzińska, Agnieszka
Amount of information transferred by computers grows very rapidly thus outgrowing the average man's capability of reception. It implies computer programs increase in the demand for which would be able to perform an introductory classification or even selection of information directed to a particular receiver. Due to the complexity of the problem, we restricted it to understanding short newspaper notes. Among many conceptions formulated so far, the conceptual dependency worked out by Roger Schank has been chosen. It is a formal language of description of the semantics of pronouncement integrated with a text understanding algorithm. Substantial part of each text transformation system is a semantic parser of the Polish language. It is a module, which as the first and the only one has an access to the text in the Polish language. It plays the role of an element, which finds relations between words of the Polish language and the formal registration. It translates sentences written in the language used by people into the language of theory. The presented structure of knowledge units and the shape of understanding process algorithms are universal by virtue of the theory. On the other hand the defined knowledge units and the rules used in the algorithms are only examples because they are constructed in order to understand short newspaper notes.
Access status: Open Access ,
Wykorzystanie łącza 12C oraz informacji lokalizacyjnej do personalizacji działania urządzeń
(Wydawnictwa AGH, 2000) Długopolski, Jacek
The article refers to the part of the hardware and software research which concerns the problem of personalization of a common used device operation. The proposed solution is based on the ABS system (Active Badge System) developed by ORL (Olivetti research Laboratories) in the United Kingdom, which delivers localization and identification information, and the universal communication interface I2C (Inter Integrated Circuit) developed by PHILIPS. The two above mentioned elements were used to create both the system of the automatic video signal flow control and the system to identify a TV program being currently viewed.
Access status: Open Access ,
Syntaktyczne metody rozstrzygania wieloznaczności form fleksyjnych
(Wydawnictwa AGH, 2001) Szostek, Grażyna
There are different types of ambiguity in natural language, which causes different problems in natural language processing. This paper describes the ambiguity of inflection form, eg. kamień (the stone), which is the form of Moninative Singular or Accusative Singular. The paper also proposes the constraint driven method for resolving that type of ambiguity.
Access status: Open Access ,
Metody sztucznej inteligencji w analizie morfologii wybranych narządów na obrazach medycznych
(Wydawnictwa AGH, 2001) Ogiela, Marek; Tadeusiewicz, Ryszard
The goal of this paper is the presentation of the possibilities of application of syntactic methods of computer image analysis for recognition of local stenoses of coronary arteries lumen and detection of pathological signs in upper parts of ureter ducts and renal calyxes. Analysis of correct morphology of these structures is possible thanks to the application of sequence and tree methods from the group of syntactic methods of pattern recognition. In the case of analysis of coronary arteries images the main objective is computer-aided early diagnosis of different forms of ischemic cardiovascular diseases. Such diseases may reveal in the form of stable or unstable disturbances of heart rhythm or infarction. In analysis of kidney radiograms the main goal is recognition of local irregularities in ureter lumens and examination of morphology of renal pelvis and calyxes.
Access status: Open Access ,
Finite-state methodology in natural language processing
(Wydawnictwa AGH, 2001) Korzycki, Michał
Recent mathematical and algorithmic results in thc field of finite-state technology, as well as the increase in computing power, have constructed the base for a new approach in natural language processing. However the task of creating an appropriate model that would describe the phenomena of the natural language is still to be achieved. In this paper I'm presenting some notions related to the finite-state modelling of syntax and morphology.
Access status: Open Access ,
Knowledge representation and inference for analysis and design of databases and tabular rule-based systems
(Wydawnictwa AGH, 2001) Ligęza, Antoni
Rule-based systems constitute a powerful tool for specification of knowledge in design and implementation of knowledge-based systems. They provide also a universal programming paradigm for domains such as intelligent control, decision support, situation classification and operational knowledge encoding. In order to assure safe and reliable performance, such systems should satisfy certain formal requirements, including completeness and consistency. This paper addresses the issue of analysis and verification of selected properties of a class of such systems in a systematic way. A uniform, tabular scheme of single-level rule-based systems is considered. Such systems can be applied as a generalized form of databases for specification of data patterns (unconditional knowledge), or can be used for defining attributive decision tables (conditional knowledge in form of rules). They can also serve as lower-level components of a hierarchical, multi-level control and decision support knowledge-based systems. An algebraic knowledge representation paradigm using extended tabular representation, similar to relational database tables is presented and algebraic bases for system analysis, verification and design support are outlined.
Access status: Open Access ,
Generation of triangular meshes for complex domains on the plane
(Wydawnictwa AGH, 2001) Jurczyk, Tomasz; Głut, Barbara
Many physical phenomena can be modeled by partial differential equations. The development of numerical methods based on the spatial subdivision of a domain into finite elements immediately extended interests to the tasks of generating a mesh. With the availability of versatile field solvers and powerful computers, the simulations of ever inereasing geometrical and physical complexity are attempted. At some point the main bottleneck becomes the mesh generation itself. The paper presents a detailed description of the triangular mesh generation scheme on the plane based upon the Delaunay triangulation. A mesh generator should be fully automatic and simplify input data as much as possible. It should offer rapid gradation from small to large sizes of elements. The generated mesh must be always valid and of good quality. All these requirements were taken into account during the selection and elaboration of utilized algorithms. Successive chapters describe procedures connected with the specification of a modeled domain, generation and triangulation of boundary vertices, introducing inner nodes, improving the quality of the created mesh, and renumbering of vertices.
Access status: Open Access ,
Fast automatic configuration of artificial neural networks used for binary patterns recognition
(Wydawnictwa AGH, 2001) Horzyk, Adrian
This paper presents a powerful method of an automatically generated architecture of neural networks used for binary patterns recognition, which can quickly and automatically reduce synapses in a way of minimally reducing a quality of recognition and a quality of generalization. Moreover, this method computes all weights in two runs over a learning sequence, what makes this method very fast. First, the method calculates all binary features for each pattern and then weights are computed. Furthermore, there is a quality of generalization considered because it is one of the most important factors of recognition while using neural networks.